Littérature scientifique sur le sujet « Membrana cellulare »
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Articles de revues sur le sujet "Membrana cellulare"
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Boatti, Leonardo. « Dalla mentalitŕ talebana alla democrazia degli affetti in un gruppo di bambini ». GRUPPI, no 1 (octobre 2010) : 63–73. http://dx.doi.org/10.3280/gru2010-001006.
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La psicoterapia analitica dell'etŕ evolutiva viene a trovarsi in questi ultimi anni in una fase di profondo rinnovamento dal punto di vista metodologico e operativo. Viviamo in una societŕ "narcisistica", improntata sulla soddisfazione immediata del bisogno e delle mete pulsionali. Ciň comporta un'ipotrofia dell'area preconscia-transizionale, dello sviluppo della capacitŕ di pensiero e del mantenimento dei legami. Kaës sottolinea l'importanza di un buon sviluppo dell'area transizionale o preconscia, indispensabile per tollerare l'attesa, la frustrazione, necessaria per lo sviluppo della capacitŕ riflessiva. Lebovici afferma che «molti adolescenti della generazione attuale non sanno che agire e sono condannati a non elaborare le loro emozioni, che non sanno rappresentare». In parallelo sempre piů bambini non sanno giocare: "presentano" piů che rappresentano i propri vissuti. Il terapeuta dell'etŕ evolutiva si trova ad affrontare gruppi di bambini la cui modalitŕ di comunicare le proprie emozioni č prevalentemente sensoriale-corporea. Viene messa a dura prova la capacitŕ contenitiva e conservativa il pensare. Il faticoso lavoro del terapeuta consiste nel permanere in una situazione bioniana di K- e nel tradurre in parole e pensieri, attraverso rappresentazioni e gioco (play), espressione di ciň che sta avvenendo in quel momento nel gruppo, le comunicazioni affettive ed emotive espresse con la sensorialitŕ e il corpo. Ciň permette nel tempo la creazione di una membrana preconscia (membrana di contatto bioniana) capace, come la membrana cellulare, di favorire lo scambio fra dentro e fuori, fra conscio e inconscio. Nell'abstract la esemplificazione clinica tratta un gruppo di bambini il cui cambiamento della composizione ha determinato lo scontro anche violento fra i rappresentanti delle due modalitŕ di comunicazione degli affetti. In particolare l'arrivo di due femmine favorisce il faticoso e doloroso cambiamento della struttura e soprattutto della mentalitŕ del gruppo: da una mentalitŕ talebana a una mentalitŕ democratica degli affetti. Si assiste a un conflitto fra una modalitŕ maschile improntata sull'azione e sul gioco (game) come veicolo delle emozioni e una modalitŕ femminile improntata sulla parola e sul pensiero.
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Masola, V., S. Granata, M. Proglio, G. Gambaro, A. Lupo et G. Zaza. « Eparanasi : un nuovo biomarker di fibrosi e un potenziale target farmacologico per ridurre la progressione del danno renale cronico ». Giornale di Clinica Nefrologica e Dialisi 24, no 2 (26 janvier 2018) : 10–15. http://dx.doi.org/10.33393/gcnd.2012.1131.
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Il trattamento poli-farmacologico ha determinato, nel corso degli anni, un significativo rallentamento della progressione della malattia renale cronica verso lo stadio di uremia terminale, ma siamo ancora distanti dallo sviluppo di interventi terapeutici in grado di bloccare questo inesorabile e irreversibile processo. Studi clinico-patologici hanno chiaramente dimostrato che il principale elemento coinvolto nel danno renale è la fibrosi tubulo-interstiziale e che il meccanismo patogenetico alla base di questa condizione ha inizio in larga parte nel compartimento tubulare. In particolare, il processo di transizione epitelio-mesenchimale gioca un ruolo importante nella genesi del danno cronico. Durante questo processo, le cellule epiteliali tubulari subiscono un incremento significativo di markers di superficie di natura mesenchimale e, grazie al rimodellamento del citoscheletro e alla degradazione della membrana basale, sono in grado di migrare nell'interstizio dove svolgono un ruolo chiave nel processo patogenetico. In questo contesto, sembra avere un ruolo chiave l'enzima eparanasi, una endo-β-D-glucuronidasi che taglia le catene dell'eparan-solfato a livello di siti specifici intracatena, e partecipa attivamente alla degradazione e al rimodellamento della matrice extracellulare. La degradazione dei vari costituenti dell'ECM, inclusi i proteoglicani eparan-solfato fa-vorisce il rilascio di fattori trofici quali il FGF-2 che induce l'espressione dei marcatori mesenchimali alfa-SMA, VIM e FN, porta alla degradazione della membrana basale mediante la secrezione di metalloproteinasi della matrice ed aumenta la motilità cellulare. L'epressione dell'eparanasi è regolata da fattori di trascrizione, dalla metilazione del DNA e da varie molecole endogene. L'importanza di questo enzima è stata confermata clinicamente dal riscontro di una sua iperespressione in preparati istologici di biopsie effettuate in soggetti affetti da nefropatie croniche (per esempio, nefropatia diabetica). Pertanto visto l'importante ruolo dell'eparanasi sono in fase di standardizzazione numerose strategie per inibire la sua espressione genica e/o la sua attività enzimatica. Infine, è stato proposto il suo possibile utilizzo come biomarker di progressione del danno tubulo-interstiziale da utilizzare routinariamente in ambito nefrologico.
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Matarrese, Paola, et Giuseppe Marano. « Modulazione dei recettori β-adrenergici e differenze di genere ». CARDIOLOGIA AMBULATORIALE 30, no 1 (31 mai 2022) : 20–24. http://dx.doi.org/10.17473/1971-6818-2022-1-5.
Texte intégralRésumé :
Lo scompenso cardiaco (SC), processo evolutivo comune di più malattie cardiovascolari a differente eziologia (ad es. infarto del miocardio, ipertensione, cardiomiopatie, disturbi valvolari e altre), è diventato sempre più comune nella popolazione anziana, influenzando drasticamente il tasso di sopravvivenza e la qualità della vita. L’iperattività del sistema nervoso simpatico (SNS) che si associa allo SC determina un aumento delle catecolamine circolanti epinefrina e norepinefrina che, attraverso l’attivazione dei recettori beta-adrenergici (β-AR), svolgono un ruolo critico nella regolazione della funzione del sistema cardiovascolare. Una caratteristica distintiva dello SC è la diminuzione o la desensibilizzazione dei recettori β1-adrenergici (β1-AR) sulla membrana delle cellule cardiache. Le catecolamine e lo stress ossidativo sono coinvolti nella regolazione della densità dei β-AR. Lo stress ossidativo associato alla disfunzione mitocondriale sembra giocare un ruolo importante nella fisiopatologia dello SC. Infatti, una condizione di stress ossidativo è stata osservata sia in pazienti con SC che in modelli animali, e un’eccessiva esposizione a specie reattive dell’ossigeno (ROS) diminuisce l’espressione di β1-AR in cardiomiociti murini, sebbene i meccanismi sottostanti rimangano ancora non chiari. Recentemente, è stato scoperto che il recettore periferico delle benzodiazepine (PBR) svolge un ruolo chiave oltre che nell’energetica cellulare, nella regolazione della fisiologia mitocondriale e dell’equilibrio redox nei cardiomiociti. Nel presente studio, abbiamo valutato gli effetti delle catecolamine e dei ligandi del PBR sulla densità dei β1- e β2-AR nei monociti umani isolati da sangue periferico, che sono noti per esprimere entrambi i β-AR. La densità dei β-AR è stata misurata mediante citometria a flusso utilizzando anticorpi selettivi diretti contro un epitopo extracellulare di β1-AR o β2-AR. Il trattamento dei monociti con benzodiazepine induceva una riduzione della densità del β1-AR, ma non del β2-AR, sulla membrana dei monociti che veniva ripristinata utilizzando [1-(2-chlorophenyl)-N-methyl-(1-meth-ylpropyl)-3 isoquinolinecarboxamide] (PK11195), un antagonista del PBR. Questi risultati suggeriscono un possibile ruolo del PBR nella regolazione della densità del β1-AR proponendo i monociti isolati dal sangue periferico sia come modello in vitro utile per lo studio del sistema recettoriale β-adrenergico che come potenziali biomarcatori di progressione della malattia e risposta alla terapia.
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Wang, Jing, Jennifer B. Ptacek, Karla Kirkegaard et Esther Bullitt. « Double-membraned Liposomes Sculpted by Poliovirus 3AB Protein ». Journal of Biological Chemistry 288, no 38 (1 août 2013) : 27287–98. http://dx.doi.org/10.1074/jbc.m113.498899.
Texte intégralRésumé :
Infection with many positive-strand RNA viruses dramatically remodels cellular membranes, resulting in the accumulation of double-membraned vesicles that resemble cellular autophagosomes. In this study, a single protein encoded by poliovirus, 3AB, is shown to be sufficient to induce the formation of double-membraned liposomes via the invagination of single-membraned liposomes. Poliovirus 3AB is a 109-amino acid protein with a natively unstructured N-terminal domain. HeLa cells transduced with 3AB protein displayed intracellular membrane disruption; specifically, the formation of cytoplasmic invaginations. The ability of a single viral protein to produce structures of similar topology to cellular autophagosomes should facilitate the understanding of both cellular and viral mechanisms for membrane remodeling.
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Putri, Venesa Thalia, Ayu Pramita et Theresia Evila Purwanti Sri Rahayu. « Sintesis Selulosa Asetat dari Tanaman Lidah Mertua (Sansevieria trifasciata) sebagai Membran Pereduksi CO (Karbon Monoksida) pada Asap Rokok ». Jurnal Rekayasa Hijau 5, no 3 (14 mars 2022) : 281–90. http://dx.doi.org/10.26760/jrh.v5i3.281-290.
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ABSTRAKPenelitian ini bertujuan untuk mengetahui proses pembuatann membran selulosa dari tanaman Lidah mertua (Sansevieria trifasciata) yang mampu menurunkan kadar gas CO (karbon monoksida). Terdapat beberapa tahapan diantaranya persiapan alat dan bahan; proses ekstraksi yang terdiri dari delignifikasi dan bleaching; proses sintesis yang terdiri dari swelling-up, asetilasi, dan hidrolisis; uji kadar asetil selulosa; pembuatan membran selulosa, serta tahap pengujian dan analisis data yang dilakukan secara kuantitatif dan instrumentasi. Hasil penelitian ini adalah lidah mertua dapat diolah menjadi filter berbentuk membran yang mampu mereduksi karbon monoksida melalui proses sintesis selulosa asetat. Efektivitas membran selulosa Sansevieria trifasciata dalam menurunkan kandungan karbon monoksida pada rokok yang dibakar selama 5 menit adalah sebesar 70% ketika berada di dalam ruangan dan 87% ketika berada di luar ruangan. Pembuatan membran harus dilakukan dengan mengamati jenis bahan, kondisi CH3COOH, perlakuan setelah asetilasi, suhu oven, kadar asetil, dan homogenitas.Kata kunci: efektivitas, karbon monoksida, Lidah mertua, membran selulosa, merokok.ABSTRACTThis study aims to determine the process of making cellulose membranes from the mother-in-law's tongue plant (Sansevieria trifasciata) which is able to reduce CO (carbon monoxide) gas levels. There are several stages including the preparation of tools and materials; extraction process consisting of delignification and bleaching; synthesis process consisting of swelling-up, acetylation, and hydrolysis; test for acetyl cellulose content; manufacture of cellulose membranes, as well as the stages of testing and data analysis carried out quantitatively and instrumentation. The result of this research is that mother-in-law's tongue can be processed into a membrane-shaped filter that is able to reduce carbon monoxide through the synthesis of cellulose acetate. The effectiveness of Sansevieria trifasciata cellulose membrane in reducing the carbon monoxide content in cigarettes burned for 5 minutes was 70% when indoors and 87% when outdoors. The manufacture of membranes must be carried out by observing the type of material, CH3COOH conditions, treatment after acetylation, oven temperature, acetyl content, and homogeneity.Keywords: carbon monoxide, cellulose membrane, effectiveness, Sansevieria trifasciata, smoking.
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Sirolli, V., E. Ballone, S. Di Stante, L. Amoroso et M. Bonomini. « Cell Activation and Cellular-Cellular Interactions during Hemodialysis : Effect of Dialyzer Membrane ». International Journal of Artificial Organs 25, no 6 (juin 2002) : 529–37. http://dx.doi.org/10.1177/039139880202500607.
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During hemodialysis (HD), circulating blood cells can be activated and also engage in dynamic interplay. These phenomena may be important factors behind dialysis membrane bio(in)compatibility. In the present prospective cross-over study, we have used flow cytometry to evaluate the influence of different dialysis membranes on the activation of circulating blood cells (leukocytes, platelets) and their dynamic interactions (formation of circulating platelet-leukocyte and platelet-erythrocyte aggregates) during in vivo HD. Each patient (n = 10) was treated with dialyzers containing membranes of cellulose diacetate, polysulfone and ethylenevinylalcohol (EVAL) in a randomized order. Upregulation of adhesion receptor expression (CD15s, CD11b/CD18) occurred mainly with the cellulosic membrane, though an increase in CD11b/CD18 circulating on neutrophils was also found with both synthetic membranes. Circulating activated platelets (P-selectin/CD63-positive platelets) increased during HD sessions with cellulose diacetate and polysulfone. An increased formation of platelet-neutrophil aggregates was found at 15 and 30 min during dialysis with cellulose diacetate and polysulfone but not with EVAL. Platelet-erythrocyte aggregates also increased with cellulose diacetate and at 15 min with polysulfone as well. Generally in concomitance with the increase in platelet-neutrophil coaggregates, there was an increased hydrogen peroxide production by neutrophils. The results of this study indicate that cellular mechanisms can be activated during HD largely depending on the membrane material, EVAL causing less reactivity than the other two membranes. It appears that each dialysis membrane has multiple and different characteristics that may contribute to interactions with blood components. Our results also indicate that derivatizing cellulose (cellulose diacetate) may be a useful way to improve the biocompatibility of the cellulose polymer and that there may be great variability in the biocompatibility profile of synthetic membranes, dialysis with polysulfone being in general associated with a higher degree of cell activation than EVAL membrane.
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Wang, Yue, et Yangfang Chen. « The Role of Cellular Membrane Microvesicles in Acute Myelogenous Leukemia ». ISP Medicine 2, no 1 (1 janvier 2020) : 1–6. http://dx.doi.org/10.52274/ispmed20200213.
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Little is known about the role of cellular membrance microvesicles (MVs) in hematological malignancies, especially acute myelogenous leukemia (AML), a malignant disease characterized by uncontrolled proliferation of hematopoietic stem or progenitor cells, which can lead to bone marrow failure and eventually to death. The role of MVs in the pathogenesis of cancer has been reported previously. In this review, we summarized the current progress of MVs in AML, and their roles as potential biomarkers and therapeutically targets for this research area. In summary, we found that MVs may represent a novel biomarker for disease diagnosis and response to treatment, indicators of disease status and severity, as well as potential active modulator for driving drug resistance. Further studies are needed to better understanding deeply about the role of MVs in AML.
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Ariyanti, Dhita, Nurul Widiastuti et Nourma Safarina. « Kinerja Membran Plat Berpori Berbasis Selulosa Asetat yang Disintesis Secara Inversi Fasa untuk Ultrafiltrasi Bakteri E.coli di PDAM Surabaya ». Jurnal Teknologi Lingkungan 21, no 2 (30 juillet 2020) : 165–73. http://dx.doi.org/10.29122/jtl.v21i2.3945.
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ABSTRACTThe lack of consumable water in urban and industrial-dense areas encourages research on clean water treatment methods. Some current treatment methods, such as precipitation, adsorption, and UV light irradiation are ineffective for water with high levels of suspended solids, organic matter, and turbidity. Therefore, alternative approaches are required to support the availability of clean and consumable water. The membrane technology is an alternative filtration method proposed in the East Surabaya's municipal waterworks area. The membrane filtration method is quite simple and easy to operate. This study aimed to determine the performance of cellulose acetate-based porous plate membranes synthesized by phase inversion for E. coli bacteria's ultrafiltration. As a raw material, cellulose acetate is preferred because of its high hydrophilicity and good biocompatibility. Membrane synthesis was carried out through the phase inversion method with acetone solvents and non-solvent water in the coagulation bath. The positive test for E. coli bacteria was carried out through the MPN (Most Probable Number) method on the municipal waterworks water samples before and after filtering with membranes. The results showed that the synthesis of cellulose acetate membrane had good homogeneity. This result was supported by the results of ANOVA single factor statistical data analysis. Also, cellulose acetate membrane had good permeability and flux performance as ultrafiltration of E. coli bacteria with a flux of 37.25 L/m2.hour.bar at a sufficient pressure of 5 bar. Test results for the presence of E. coli bacteria in PDAM water samples using the MPN method gave an initial indication that the water sample after filtration with cellulose acetate membrane was negative. Keywords: membrane, cellulose acetate, permeability, water fluxABSTRAKMinimnya air bersih yang layak konsumsi di daerah perkotaan dan padat industri mendorong penelitian tentang metode pengolahan air bersih. Kurangnya efektivitas metode pengolahan sebelumnya seperti pengendapan, adsorbsi, dan penyinaran dengan sinar UV untuk air dengan kadar suspended solids, zat organik, dan kekeruhan yang tinggi, diperlukan metode alternatif untuk mendukung ketersediaan air bersih layak konsumsi. Metode filtrasi alternatif yang ditawarkan di PDAM di kawasan Surabaya Timur. Metode filtrasi dengan membran sangat sederhana dan mudah dalam operasionalnya. Penelitian ini bertujuan untuk mengetahui kinerja membran plat berpori berbasis selulosa asetat yang disintesis secara inversi fasa untuk ultrafiltrasi bakteri E.coli. Selulosa asetat dipilih sebagai bahan baku membran karena selulosa asetat merupakan bahan polimer yang memiliki hidrofilitas tinggi dan biokompatibilitas yang baik. Sintesis membran dilakukan melalui metode inversi fasa dengan pelarut aseton dan nonpelarut air dalam bak koagulasi. Uji positif bakteri E.coli dilakukan melalui metode MPN (Most Probable Number) pada sampel air PDAM sebelum dan sesudah difiltrasi dengan membran. Hasil penelitian menunjukkan bahwa sintesis membran selulosa asetat memiliki homogenitas baik yang ditunjukkan oleh hasil analisis data statistika ANOVA single factor. Selain itu, membran selulosa asetat memiliki kinerja permeabilitas dan fluks yang baik sebagai ultrafiltrasi bakteri E.coli dengan ketercapaian fluks sebesar 37,25 L/m2.jam.bar pada tekanan efektif sebesar 5 bar. Hasil uji keberadaan bakteri E.coli pada sampel air PDAM dengan metode MPN memberikan indikasi awal bahwa sampel air setelah filtrasi dengan membran selulosa asetat adalah negatif.Kata kunci: membran, selulosa asetat, permeabilitas, fluks air
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Ali, Asmadi, Rosli Mohd Yunus, Mohamad Awang, Anwar Johari et Ramli Mat. « Effect of Cellulose Acetate Phthalate (CAP) on Characteristics and Morphology of Polysulfone/Cellulose Acetate Phthalate (PSf/CAP) Blend Membranes ». Applied Mechanics and Materials 493 (janvier 2014) : 640–44. http://dx.doi.org/10.4028/www.scientific.net/amm.493.640.
Texte intégralRésumé :
Polysulfone (PSf) membrane is catogorized as hydrophobic membrane that easily fouled during membrane operation process. The presence of second hydrophilic polymer which added into membrane casting solutions plays a crucial role in adjusting the membrane properties. This hydrophilic polymer was employed in hydrophobic polymer membranes in order to improve hydrophilicity and performance as well as formed antifouling ultrafiltration (UF) membranes. In this study, a hydrophilic polymer, cellulose acetate phthalate (CAP) was added into polysulfone (PSf) membrane casting solutions by blending technique to produce PSf/CAP blend membranes. Flat sheet asymmetric PSf/CAP blend membranes were prepared by wet phase inversion method. The results revealed that an increase in CAP increased the hydrophilicity properties of PSf/CAP blend membranes compared to pure PSf membrane. The significant changes in size and numbers of microvoids and macrovoids in the morphological structures of PSf/CAP blend membranes were due to CAP promote the instantaneous liquid-liquid demixing during phase inversion process.
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Singh, Amit Kant, et Reena Rani Verma. « Role of Resting Membrane Potential in the Regulation of Cellular Functions ». International Physiology 5, no 2 (2017) : 131–34. http://dx.doi.org/10.21088/ip.2347.1506.5217.17.
Texte intégralThèses sur le sujet "Membrana cellulare"
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Rimoldi, V. « Recettore dell’ossitocina e regolazione della proliferazione cellulare : ruolo della localizzazione in microdomini di membrana ». Doctoral thesis, Università degli Studi di Milano, 2004. http://hdl.handle.net/2434/46512.
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D'Alessandro, Margherita. « Meccanismi di risposta genici di Lactobacillus acidophilus 08 a seguito dell'applicazione di alte pressioni di omogeneizzazione ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16839/.
Texte intégralRésumé :
Al fine di aumentare il benessere dell’individuo, la ricerca nelle ultime decadi si è incentrata nell’individuazione di specifiche strategie alimentari, diete, alimenti funzionali. In particolare, particolarmente apprezzati, sono gli alimenti contenenti microrganismi probiotici. Tra questi, Lactobacillus acidophilus 08 risulta una coltura probiotica riconosciuta e commercialmente distribuita. Studi recenti hanno dimostrato come le alte pressioni di omogenizzazione (HPH) su Lb. acidophilus, siano in grado di modularne l’idrofobicità di membrana, la capacità di autoaggregazione nonché la resistenza a stress gastrico-duodenali simulati; proprietà che influiscono direttamente sulla capacità di adesione e colonizzazione del ceppo con gli epiteli intestinali. Tuttavia, ancora poco studiati sono i meccanismi genici microbici messi in atto a seguito dello stress iperbarico. Obiettivo della mia tesi è stato, quindi, quello di valutare gli effetti dei trattamenti HPH sulla vitalità, idrofobicità, ed espressione genica di Lb. acidophilus 08, quando sottoposto a 50 MPa. I risultati ottenuti, evidenziano, oltre alla barotolleranza del ceppo di Lb.acidophilus 08, anche un sensibile incremento della sua idrofobicità di membrana. Ciò potrebbe influenzare positivamente l’eventuale interazione stabilita tra il microrganismo e l’epitelio intestinale. Il cambiamento riscontrato non è esclusivamente di tipo meccanico, il trattamento induce infatti la modulazione di una serie di geni coinvolti nei fenomeni di adesione cellulare e di risposta agli stress quali groEL, efTU, slp e clpP. I risultati di questa tesi risultano funzionali per la messa appunto di nuove strategie al fine di migliorare le performance probiotiche del ceppo considerato, individuando nel trattamento HPH un ottimo sistema per stimolare la risposta adattiva di Lb. acidophilus.
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Ibanez, Sébastien. « Caractérisation physicochimique des membranes cellulaires lors de la cancérogénèse : application à la plasticité cellulaire ». Electronic Thesis or Diss., Lyon, 2021. https://n2t.net/ark:/47881/m6tt4qsz.
Texte intégralRésumé :
Le tissu mammaire est intrinsèquement hétérogène et son développement ainsi que son homéostasie impliquent des mécanismes génétiques et épigénétiques permettant des modifications contrôlées de l’identité cellulaire tout au long de la vie d’une femme. Dans un contexte tumoral, les mécanismes liés à cette modulation de l’identité cellulaire peuvent être en revanche perturbés. Ceci facilite une grande dynamique épigénétique et l’acquisition d’une plasticité phénotypique située au cœur du développement et de la progression tumorale. La plasticité phénotypique décrit la capacité d’un système biologique à s’adapter et exprimer différents phénotypes en réponse à des conditions environnementales changeantes. Les cellules perdent dans ce contexte leur identité cellulaire et subissent des modifications profondes de leur métabolisme. L’une des conséquences de ces dérégulations métaboliques est le remodelage des lipides lors de l’acquisition d’un phénotype plastique. Nous avons pu corréler ce remodelage lipidique à une modification de la fluidité membranaire des membranes cellulaires. Cette mesure de fluidité membranaire s’effectue à l’aide d’une sonde de fluorescence ratiométrique synthétisée pour la première fois dans notre équipe. La première partie de cette thèse a concerné la validation dans un contexte biologique de la capacité de cette sonde fluorescente, le Dioll, à rendre compte de l’alignement des chaînes lipidiques directement au sein des membranes d’une cellule. L’analyse des propriétés physicochimiques de la sonde de fluorescence lors du marquage des membranes cellulaires a mis en avant les avantages de cette molécule par rapport aux sondes préexistantes, notamment un meilleur rapport quantique, une meilleure répartition au sein des phases liquides désordonnées permettant ainsi une meilleure discrimination des endomembranes et un marquage des membranes cellulaires avec une résolution sans précédent. Lors de la deuxième partie de cette thèse, nous avons utilisé les propriétés du Dioll pour mettre en évidence la corrélation existant entre fluidité membranaire et des variations phénotypiques à l’origine de la plasticité cellulaire. L’analyse d’un ensemble de lignées cellulaires cancéreuses mammaires a montré que nous pouvions discriminer les différents sous-types cellulaires à partir de ces mesures corrélées le plus souvent à une plus grande fluidité membranaire. Dans un second temps, nous avons utilisé un modèle isogénique de modulation de la plasticité cellulaire par induction d’un processus de perte des caractéristiques épithéliales au sein de cellules mammaires humaines immortalisées initialement épithéliales (HMEC). À partir de ce modèle, nous avons pu observer une diminution de l’alignement des chaînes lipidiques membranaires lors de l’acquisition d’un phénotype plus indifférencié. Finalement en modulant l’environnement hormono-nutritif de la cellule, il a été possible de créer un modèle permettant l’acquisition et la stabilisation d’un phénotype très indifférencié, hybride en termes de composante épithéliale et mésenchymateuse et multipotent. Ce phénotype dit « métastable » permet de rediriger de façon très efficace ces cellules dans les différentes voies de différenciation mammaire luminale ou myoépithéliale. Nous avons pu ainsi corréler les variations phénotypiques dans ce modèle à des variations biophysiques associées à une plus grande fluidité membranaire, les cellules métastables possédant un désordre très important au niveau de leurs chaînes lipidiques membranaires en comparaison de leur descendance ayant acquis une identité cellulaire luminale ou myoépithéliale. L’ensemble de ces résultats est discuté dans la perspective d’utiliser ces mesures indirectes de fluidité membranaire pour déterminer un indice de plasticité phénotypique ou de dynamique épigénétique qui servirait alors d’outil diagnostic et d’aide à la mise en place de stratégies thérapeutiques plus efficaces et personnaliséesThe mammary tissue is inherently heterogeneous and its development as well as homeostasis involve genetic and epigenetic mechanism allowing controlled switches of cell identity during woman’s lifetime. During tumoral context, the mechanisms linked to this cell identity modulation can be disturbed. This facilitates a large epigenetic dynamic and the acquisition of phenotypic plasticity essential for tumour development and progression. Phenotypic plasticity describes the ability of a biological system to adapt and express different phenotypes in response to variations of environmental conditions. In this context, the cells lose their cell identity and undergo profound changes in their metabolism. One of the consequences of these metabolic dysregulation is the remodelling of cell lipid composition during the acquisition of a plastic phenotype. We were able to correlate this lipid remodelling with a change in lipid chains arrangement within cell membranes, a phenomenon known to modify the membrane fluidity. The membrane fluidity is measured by a ratiometric fluorescent probe synthesized for the first time in our team. The first part of this thesis concerned the validation in a biological context of this probe, Dioll, to report its capacity of following the membrane fluidity of cell membranes. The analysis of the physicochemical properties of the fluorescent probe during the labeling of cell membranes has highlighted the advantages of this molecule compared to pre-existing probes (better quantum ratio, better distribution within disordered liquid phase and better discrimination of endomembranes). The second part of this thesis, we used the properties of Dioll to highlight the correlation between membrane fluidity and phenotypic variations at the origin of cell plasticity. Analysis of a set of breast cancer cell lines showed that we could discriminate different cell subtypes. Secondly, we used an isogenic model of modulation of cellular plasticity by inducing a process of loss of epithelial characteristics within initially epithelial immortalized human mammary cells (HMEC). From this model, we were able to observe an increase of membrane fluidity during the acquisition of a more undifferentiated phenotype. Finally, by modulating the hormonal-nutritive environment of the cell, it was possible to create a model allowing the acquisition and stabilization of a much undifferentiated phenotype, hybrid in terms of epithelial and mesenchymal component and multipotent. This so-called “metastable” phenotype makes it possible to redirect these cells into the various luminal or myoepithelial mammary differentiation pathways. We were thus able to correlate the phenotypic variations in this model with biophysical variations associated with greater membrane fluidity, the metastable cells having a very significant disorder at the level of their membrane lipid chains in comparison with their progeny having acquired a luminal cell identity or myoepithelial. All of these results are discussed with a view to using these measurements of membrane fluidity to determine an index of phenotypic plasticity or epigenetic dynamics which would then serve as a diagnostic tool and aid in the implementation of therapeutic strategies more efficient and personalized
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Tremblay, André Y. « The role of structural forces in membrane transport : Cellulose membranes ». Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5886.
Texte intégralRésumé :
The phenomena governing Transition RO/UF (nanofiltration) membrane transport have been critically studied. The residuals and predicted pore sizes of 965 individual permeation runs performed on 70 cellulose membranes were used to discriminate between several restricted transport models and various solute-solvent-membrane material interactions. Solute-membrane interactions were found to be mediated by the presence of structured solvent at the surface of the membrane. Two new interaction parameters, $\Psi\sb{DP}$ and $\kappa\sp\prime$ describing structural solvent forces at the surface of a membrane have been quantified. For solvent mediated interactions, the potential energy of a solute molecule $\phi\sbsp{DP}{\prime}(\underline d$) at a distance $\underline d$ from the membrane surface can be obtained by combining $\Psi\sb{DP}$ and $\kappa\sp\prime$ and the Stokes-Einstein radius a$\sb{s}$ of the solute as follows:$$\phi\sbsp{DP}{\prime}(\underline d) = -\Psi\sb{DP}\ a\sb{s}\ e\sp{-\kappa\sp\prime(\underline{d}-a\sb{s})}$$ A method to evaluate $\Psi\sb{DP}$ from simple permeation experiments and $\kappa\sp\prime$ from direct force measurements is given. This approach permits the decoupling of solute size and solute-membrane material interactions in predicting separation. The inverse of $\kappa\sp\prime$ was found to be approximately equal to the diameter of a solvent molecule. A linear correlation was obtained between the square root of $\Psi\sb{DP}$ and the solubility parameter $\delta\sb{SP}$ for all solutes tested in this work. The slope of this correlation reflects the ability of the membrane material to structure water dipoles at a solid-liquid interface. The ordinate's intercept of this correlation was equal to the solubility parameter of the solvent which implies that steric solute interactions $(\Psi\sb{DP}\to 0)$ occur when $\delta\sb{SP}$ of the solute approaches that of the solvent. The results of this study indicate that a solute molecule can penetrate hydrated layers of solvent at the surface of a material to different extents depending on its size and solvent compatibility. These findings are assumed to be applicable to reverse osmosis transport and indicate that if a membrane material is to be used in RO it must be capable of structuring solvent molecules at its surface. Several parametric studies were performed using the surface force pore flow (SFPF) model to determine the exact shape of the velocity profile in the membrane pore under conditions of solute adsorption and rejection. These studies were performed at various feed concentrations and values of $\lambda$ for polyethylene glycol, of molecular weight 1000, and casein. The shape of the solute separation vs. solute radius curve was studied parametrically as a function of pressure for four restricted transport models. The shape of this curve was also determined, using a radially dependent pore model (RDPM), for adsorptive and repulsive van der Waals interactions, electrical double layer (DLVO) interactions, increased viscosity in the membrane pore and effects of chain permeability and the shape of the interacting surface. Morphological reasons are given for the general inability to reduce the pore radius of cellulose membranes below 1.5 nm. Viscometric measurements performed on cellulose casting solutions indicate that the dissolved elements of the solution exist as rigid, rod-like structures. It is proposed, that the pore size of cellulose membranes be limited by the regular occurrence of indentations on the protofibril surface and by stacking limitations, enhanced by the geometry of the protofibrils. This interpretation is conform with the folded ribbon model of a cellulose protofibril described in the literature.
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Ledauphin, Valérie. « Simulation par dynamique moléculaire d'une bicouche lipidique : développement d'une stratégie de calcul des interactions non liées : potentiel tronqué adapté aux systèmes non sphériques ». Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-473.pdf.
Texte intégralRésumé :
Les membranes biologiques sont le siège de nombreux échanges entre milieux intra- et extra- cellulaires. Comprendre et prédire ses propriétés fonctionnelles est un enjeu primordial qui passe nécessairement par la compréhension de l'organisation structurale des bicouches phospholipidiques. En terme de modélisation et de simulation moléculaires, ceci se traduit par l'étude de la structure tridimensionnelle de ces bicouches à la fois dans son aspect statique mais également dans son aspect dynamique. Ce travail concerne donc dans un premier temps, la modélisation moléculaire d'un modèle de bicouche lipidique. La difficulté essentielle réside dans le manque ou l'imprécision des données expérimentales d'ordre structural, en particulier au niveau atomique. La seconde partie de cette étude consiste en l'étude par dynamique moléculaire de la flexibilité de ce modèle de bicouche. Au travers de l'examen de la littérature, la nécessité d'établir une méthodologie de simulation spécifique aux bicouches lipidiques est apparue indispensable. Plus précisément, nous avons élaboré une nouvelle méthode de calcul des interactions non liées adaptée aux systèmes non sphériques, en général, et aux bicouches lipidiques, en particulier. Les performances de cette méthode, basée sur le principe des potentiels tronqués, ont été comparées à la méthode classique du potentiel tronqué de type sphérique. Une étude préliminaire consistant en l'étude de la solvatation d'un cation sodium, nous a permis de vérifier la faisabilité et la fiabilité des modifications apportées. Enfin, à partir des trajectoires de dynamique moléculaire, une étude comparatives des deux méthodes a porté sur l'analyse structurale et conformationnelle des monomères lipidiques. Par la conservation de l'intégrité de la structure de la bicouche lipidique, notre nouvelle méthode s'est montrée performante et parfaitement adaptée.
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Lasserre, Rémi [Jacques Alain]. « Etude du rôle des microdomaines lipidiques dans le recrutement à la membrane et l'activation de PKB/Akt ». Aix-Marseille 2, 2005. http://theses.univ-amu.fr.lama.univ-amu.fr/2005AIX22076.pdf.
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Daste, Frédéric. « Function and regulation of coiled‐coil domains in intracellular membrane fusion ». Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015PA05T001.
Texte intégralRésumé :
Les mécanismes moléculaires impliqués dans la fusion membranaire ont été amplement étudiés au cours des trente dernières années. Notre compréhension actuelle de ce phénomène est principalement basée sur des résultats obtenus par (1) le développement de modèles physiques décrivant la fusion des membranes biologiques, (2) l’étude mécanistique et structurale des protéines de fusion membranaire des virus à enveloppe et (3) l’étude des évènements de fusion intracellulaire médiés par les protéines SNARES dans les cellules eucaryotes. La découverte du complexe SNARE fut l’aboutissement de travaux interdisciplinaires qui ont exigés un large éventail de techniques tel que la génétique de la levure, l’électrophysiologie, la biologie moléculaire, la biochimie cellulaire, la biophysique expérimentale et l’imagerie. Tirant parti des paradigmes et techniques biophysiques qui ont émergés de ces études, nous avons examiné les fonctions et mécanismes de régulation des domaines « coiled-coil » dans les processus de fusion intracellulaire impliquant des protéines de la famille des Longin-SNAREs ou des Mitofusines, deux machineries protéiques de fusion dont le mode d’action exact reste encore peu clair. La conception exacte des mécanismes moléculaires de la fusion membranaire requiert la reconstitution in vitro des protéines de fusion dans un large spectre d’environnement membranaire avec des propriétés biophysiques définies et facilement modulables. Idéalement, ces systèmes membranaires devraient permettre à l’expérimentateur de contrôler la composition lipidique et protéique, ainsi que la topologie membranaire, afin de rendre compte de l’importante variabilité observée entre les différents compartiments de fusion cellulaire. La reconstitution dans des liposomes offre une incroyable flexibilité avec la possibilité de faire varier la plupart des paramètres clefs et de créer un environnement minimal dans lequel les facteurs solubles et/ou membranaires peuvent être ajoutés, seuls ou en combinaison, pour dévoiler leur rôle avec clarté. Nous avons mis au point des systèmes in vitro de reconstitution de protéines dans des plateformes membranaires artificielles pour nos deux systèmes d’études (les deux protéines Longin-SNAREs TI-VAMP et Sec 22b, ainsi que les domaines « coiled-coil » des Mitofusines) et nous avons réalisé des expériences biochimiques pour caractériser le mode d’action de ces protéines. L’objectif à long-terme de ce projet est de comparer les mécanismes moléculaires des machineries de fusion associés aux protéines SNAREs et Mitofusines, et ainsi de dévoiler des similitudes structurelles et fonctionnelles entre (1) leur protéines de fusion principales et (2) leur facteurs régulateursThe molecular mechanisms involved in membrane fusion have been extensively studied for the past thirty years. Our current understanding of this phenomenon is mainly based on results obtained by (i) the development of physical models describing the fusion of membranes, (ii) structural and mechanistic investigations on fusion proteins of enveloped viruses and (iii) studies of SNARE protein-mediated intracellular fusion events of eukaryotic cells. Discovery of the SNARE complex was the outcome of interdisciplinary works which involved a wide range of techniques including yeast genetics, electrophysiology, molecular biology, cell-free biochemistry, adhesion/fusion biophysics and imaging. Taking advantage of the paradigms and biophysical techniques that emerged from these studies, we investigated the function and regulation of coiled-coil domains in intracellular fusion processes involving Longin-SNAREs or Mitofusins, two fusion protein machineries whose exact mode of action still remains unclear. A comprehensive understanding of the molecular mechanisms of membrane fusion requires the in vitro reconstitution of fusion proteins into a wide variety of membrane environments with defined and tunable biophysical properties. Ideally, these membrane systems should allow the experimentalists to control the lipid and protein composition as well as the membrane topology, to account for the variability observed across cellular fusing compartments. Reconstitution into liposomes offers amazing flexibility with the capacity to vary most of these relevant parameters, and to create a minimal environment in which membrane and/or soluble factors can be added, one at a time or in combination, to reveal their role with clarity. We have set up the in vitro reconstitution of proteins into various artificial membrane platforms for both systems (the Longin-SNAREs TI-VAMP and Sec22b and the coiled-coil domains of Mitofusins) and performed biochemical assays to gain insight into how these proteins execute their functions. The long-term goal of this project is to compare the molecular mechanisms of SNARE and Mitofusin fusion machineries and thus reveal structural and functional similitudes between (i) their core fusion proteins, and (ii) their regulatory factors
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Bories, Florent. « Interaction entre inclusions transmembranaires transmise par la membrane cellulaire ». Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC224.
Texte intégralRésumé :
L'objet de cette thèse est d'étudier les interactions entre inclusions transmembranaires imposant un excès d'épaisseur en utilisant un modèle élastique décrivant les membranes au niveau de leur épaisseur. Dans un premier temps, je montre que ce modèle généralise bien les précédents en prenant en compte toutes les constantes physiques possibles. J'ajoute ensuite une condition d'ancrage au bord de l'inclusion qui peut induire ou non une pente préférentielle. Je m'assure que les résultats trouvés dans le cadre de mon modèle rejoignent le précédent pour une seule inclusion dans deux cas limites. Dans un deuxième temps, je développe une méthode de calcul multipolaire me permettant d'envisager des calculs de la forme d'une membrane où plusieurs inclusions sont présentes. Je donne les solutions générales de ce modèle et donne une manière de déterminer la solution dans le cas où deux inclusions sont présentes dans une membrane de taille infinie. Enfin, je donne pour une bicouche lipidique typique certaines courbes de profil et d'énergie d'interaction attendues. Je compare mes résultats à des expériences de Constantin à l'aide d'un algorithme de traitement reposant sur l'équation d'Ornstein-Zernike et une relation de fermeture. Le premier système "C12E5 + gramicidine", dont la membrane est constituée de surfactants, me permet de faire concorder le modèle théorique avec les expériences et je donne ainsi pour celui-ci les premières mesures de paramètres physiques nouveaux. Le deuxième système "DLPC + gramicidine" donne un moins bon accord entre la théorie et les expériences mais je donne une nouvelle piste de traitement afin de donner des estimations pour ce systèmeThe present thesis is a study of interactions between transmembrane proteins inducing a hydrophobic mismatch with an elastic model describing the membranes at the scale of their thickness. I begin by showing that this model generalizes the precedent ones found in litterature by taking in account every possible physical constants. I add also an anchoring term at the edge of the inclusion that can induce a preferential slope. I verify that the results found with this addition is what was found previously with one inclusion in a membrane in two différent cases. Next, I develop a multipolar computation method that allows me to compute the shape of a membrane where several inclusions are presents. I give the general solutions of this model and gives an algorithm in the case where two inclusions are present in an infinite membrane. Then, I give the expected profile and the interaction energies for a typical lipidic bilayer. I compare my results to experiments performed by Constantin with an algorithm using Omstein-Zernike equation and closure relations. The first system "C12E5 + gramicidin", where the membrane is made of surfactant, gives good agreement between the theory and the experiments and allows me to give a first measurement for new physical parameters. The second system "DLPC + gramicidin" does not allow such an agreement between the theory and the experiments but I give a new lead which may give a measurement for this system
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Morlot, Sandrine. « Dynamin-Mediated Membrane Fission ». Paris 7, 2012. http://www.theses.fr/2012PA077136.
Texte intégralRésumé :
La cellule eukaryote est organisée en plusieurs compartiments, appelés organelles, délimités par des membranes; La fission des membranes est nécessaire pour le transport intracellulaire entre organelles. L'endocytose est un mécanisme de transport depuis la membrane plasmique vers les autres organelles. La Dynamine est une guanosine triphosphatase (GTPase) impliquée dans la fission des vésicules pendant l'endocytose médiée par la Clathrine. Elle polymerise en hélice au coup des bourgeons endocytiques. Après hydrolyse du GTP, la structure de l'hélice est modifiée : le rayon interne diminue de 10 à 5 nm et le pas hélical de 13 à 9 nm. Ces modifications indiquent un mécanisme de constriction. La dynamique de constriction est étudiée en suivant la rotation de microbilles attachées à des tubes lipidiques recouverts de Dynamine. La déformation des hélices de Dynamine est concertée et amortie par la friction entre membrane et Dynamine. Cependant la constriction ne suffit pas pour la fission. Pour comprendre davantage son mécanisme, la fission par la Dynamine est étudiée à l'aide de tubes lipidiques extraits de vésicules unilamellaires géantes. La fission se produit au bord de l'hélice, où la membrane est fortement courbée. D'après l'analyse statistique des temps de fission, la réaction de fission peut être modélisée par une unique barrière énergétique. La dépendance du temps de fission en rigidité de membrane, en tension de membrane et en couple est établie théoriquement et validée expérimentalement. Ce travail établit le profil énergétique de la réaction de fission membranaire et évalue à 70 KBT la barrière énergétiqueThe eukaryotic cell is organized in several compartments, named organelles, delimited by lipid membranes. The fission of these membranes is required for vesicular traffic between organelles. Endocytosis is the mechanism of vesicular traffic from the plasma membrane towards other organelles inside the cell. Dynamin is a guanosise triphosphatase (GTPase) implicated in vesicle scission during Clathrin-mediated endocytosis. It polymerizes into a helix at the neck of endocytic buds. Upon GTP hydrolysis, conformational changes modify the helical structure : the inner radius decreases from 10 to 5 nm and the helical pitch reduces from 13 to 9 nm. These modifications show that fission proceeds through a constriction mechanism. The dynamics of constriction is investigated by monitoring the rotations of microbeads attached along Dynamin-coated tubes after GTP addition. The deformation of Dynamic helices is highly concerted and damped by the friction between membrane and Dynamin. However constriction is not enough to trigger fission. To further understand fission, Dynamin polymerization and fission are studied on lipid tubes extruded from Giant Unilamellar Vesicles. It is shown that fission occurs at the edge of the helix, where the membrane is strongly curved. A statistical analysis of fission time reveals that the fission reaction can be modeledby a single step energy barrier. The fission time dependence on membrane tension, membrane rigidity and torque is established theoretically and validated experimentally. This work gives a quantitative picture of the energy landscape of Dynamin-mediated fission : the height of the energy barrier of fission is estimated around 70 KBT
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Conchonaud, Fabien. « Dynamique de l'organisation de la membrane plasmique et incidence fonctionnelle ». Aix-Marseille 2, 2008. http://www.theses.fr/2008AIX22026.
Texte intégralRésumé :
L’extraordinaire cohérence de la membrane plasmique est la résultante des interactions moléculaires de faible énergie existant entre les différents constituants qui la composent. De fait, les molécules s'organisent et ségrégent en fonction de leurs affinités respectives, formant des hétérogénéités locales au sein de la membrane. En regard de cette organisation, les questions fondamentales sont de comprendre sur quelles échelles spatio-temporelles ses hétérogénéités prennent place et d’identifier en quoi une telle organisation contribue-t-elle à réguler les grandes fonctions d’une cellule. Afin d’apporter une réponse à ces questions, il nous fallait dans une premier temps établir et valider une approche expérimentale robuste permettant d’identifier et de décrire les hétérogénéités locales de la membrane plasmique. Une utilisation systématique de la FCS à rayons variables a permis d’établir notamment le rôle fondamental de certains lipides dans la génération de ces hétérogénéités. Le second volet de cette étude a été essentiellement consacré à explorer l’impact d’une telle organisation membranaire sur différentes fonctions fondamentales de la physiologie d’une cellule. Ainsi, les partitionnements observés ont un effet important dans la signalisation en modulant l'intensité du signal provenant d'un stimulus externe. En d'autres termes, si les molécules conservent leur capacité de signaler, il apparaît clairement que cette microorganisation dynamique de la membrane en contrôle l’amplitude. En conclusion, nos résultats ont permis d'éclaircir certains points fortement débattus et de soulever plusieurs questions qui feront l'objet d'analyses ultérieures comme : le couplage entre les deux feuillets membranaires, l'impact des échanges membrane/cytoplasme de constituants ou le recyclage membranaire sur la régulation des fonctions cellulairesThe extraordinary coherence of the plasma membrane results from molecular interactions of weak energy between the membrane components. In fact, the molecules organize and segregate according to their respective affinities, creating local heterogeneities within the plasma membrane. Regarding this organisation, fundamental questions are to understand on which spatio-temporal scales these heterogeneities take place and to identify to what extent such dynamic organization contributes to control basic cellular functions. In order to answer these questions, it was necessary in the first time to establish and validate a robust experimental approach making possible the identification and description of the plasma membrane heterogeneities. A systematic use of the FCS performed at variable wait of observation has made possible to establish the fundamental implication of certain classes of lipids in the generation of these heterogeneities. The second focus of this study was primarily devoted to explore the impact of such membrane organization on various fundamental cellular functions. Thus, molecular partitioning has an important effect signal delivery by modulating the intensity of the outcome signal. In other terms, if the molecules preserve their capacity to signal, it clearly appears that this dynamic micro-organization of the membrane controls the amplitude of the signal. In conclusion, our results have allowed us to clarify debated points but also to raise several news questions which will the subject of future studies like the coupling between the two membrane leaflets, the impact of the membrane component exchanges/cytoplasm or membrane recycling on the regulation of cellular functions
Livres sur le sujet "Membrana cellulare"
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Harris, Maddy Alun, et Harris James R, dir. Subcellular Biochemistry. New York : Plenum, 1994.
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H, Maddy A., et Harris J. R, dir. Membrane biogenesis. New York : Plenum Press, 1994.
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The membranes of cells. 2e éd. San Diego : Academic Press, 1993.
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The membranes of cells. Orlando : Academic Press, 1987.
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Graham, J. M. Membrane structure and function. Oxford : I.R.L. Press, 1989.
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1933-, Kuo J. F., dir. Phospholipids and cellular regulation. Boca Raton, Fla : CRC Press, 1985.
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J, Hilderson Herwig, et Ralston Gregory B, dir. Physicochemical methods in the study of biomembranes. New York : Plenum Press, 1994.
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J, Quinn P., dir. Membrane dynamics and domains. Dordrecht : Kluwer Academic/Plenum, 2004.
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Cellular domains. Hoboken, N.J : Wiley-Blackwell, 2011.
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Gheorghe, Benga, et Tager J. M, dir. Biomembranes : Basic and medical research. Berlin : Springer-Verlag, 1988.
Trouver le texte intégralChapitres de livres sur le sujet "Membrana cellulare"
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Hoffmann, H., M. Grabosh et K. Schügrel. « Ethanol Production by Coupled Enzyme Fermentation and Continuous Saccharification of Cellulose, Using Membrane Cell-Recycling Systems ». Dans Membranes and Membrane Processes, 533–42. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_52.
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Macknight, Anthony D. C., et Alexander Leaf. « Regulation of Cellular Volume ». Dans Membrane Physiology, 311–28. Boston, MA : Springer US, 1987. http://dx.doi.org/10.1007/978-1-4613-1943-6_19.
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Coombs, Daniel, Raibatak Das et Jennifer S. Morrison. « Modeling Membrane Domains ». Dans Cellular Domains, 71–84. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118015759.ch5.
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Bazzarelli, Fabio, Rosalinda Mazzei et Lidietta Giorno. « Cellular Membranes ». Dans Encyclopedia of Membranes, 345–47. Berlin, Heidelberg : Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-44324-8_2200.
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Bazzarelli, Fabio, Rosalinda Mazzei et Lidietta Giorno. « Cellular Membranes ». Dans Encyclopedia of Membranes, 1–3. Berlin, Heidelberg : Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-40872-4_2200-1.
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Zerbini, Gianpaolo, et Livio Luzi. « Le membrane cellulari ». Dans Biologia cellulare nell’esercizio fisico, 17–22. Milano : Springer Milan, 2010. http://dx.doi.org/10.1007/978-88-470-1535-7_3.
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Kirkilionis, Markus, Mirela Domijan, Martin Eigel, Erwin George, Mike Li et Luca Sbano. « A Definition of Cellular Interface Problems ». Dans Membrane Computing, 36–62. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-95885-7_4.
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Cavaliere, Matteo, et Alvaro Sanchez. « The Evolutionary Resilience of Distributed Cellular Computing ». Dans Membrane Computing, 3–15. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-54072-6_1.
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Papahadjopoulos, Demetrios, Paul R. Meers, Keelung Hong, Joel D. Ernst, Ira M. Goldstein et Nejat Düzgünes. « Calcium-Induced Membrane Fusion : From Liposomes to Cellular Membranes ». Dans Molecular Mechanisms of Membrane Fusion, 1–16. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1659-6_1.
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Macknight, Anthony D. C., et Alexander Leaf. « Regulation of Cellular Volume ». Dans Physiology of Membrane Disorders, 311–28. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2097-5_19.
Texte intégralActes de conférences sur le sujet "Membrana cellulare"
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Schumacher, Kristopher, Aleksander Popel, Bahman Anvari, William Brownell et Alexander Spector. « Computational Analysis of the Tether Pulling Experiment to Probe Cellular Membranes ». Dans ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206324.
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Membrane tethers can form naturally such as during leukocyte rolling (pre-adhesion) stage. Tethers can also be experimentally pulled from cellular membranes to estimate membrane mechanical and electromechanical properties, including bending modulus, adhesion energy of the membrane-cytoskeleton interaction, tension, and electromechanical forces produced by membranes. This technique has been effectively applied to a variety of cells such as red blood cells [1], neutrophils [2], and cochlear outer hair cells [3,4]. Fig. 1 presents the experiment where tethers are pulled from cellular membranes using optically trapped beads.
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Freeman, Eric C., Michael K. Philen et Donald J. Leo. « Combined Modeling of Bilayer Networks for Sensing Applications ». Dans ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8115.
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The bilayer lipid membrane (BLM) is a naturally occurring thin layer of phospholipid molecules that surrounds cellular systems. The membrane operates as a near-impermeable barrier allowing for the generation of membrane potentials across the layer through changes in ionic concentrations. This membrane is required for regular cell function ranging from storing energy to passing signals. Engineering advancements have allowed for the rapid creation of artificial bilayer membranes, and these membranes are currently considered for many biomimetic applications. The application of interest for this paper is the further development of these cellular systems for sensing applications. This will be accomplished through a combined fluid-bilayer model, allowing for study of the bilayer transduction properties at both high and low frequencies. Several approaches are discussed and applied to multiple cell systems with or without embedded voltage-dependent ion pores. Finally the results are studied and evidence is presented for the development of a new molecular model for cellular systems combining chemical, electrical, and mechanical stimuli.
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Wang, Qian, Bongsu Kim, Xu Zhang et Yi Zhao. « Fabrication and Characterization of a Microscale Cellular Loading Device for Cellular Biomechanical Study ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65188.
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Mechanical stimuli interfere with cellular behaviors under many physiological conditions. To understand the role of mechanical stimuli, engineered devices are developed to apply mechanical loads to cells in vitro. Despite of their usefulness, these devices are limited since they often lack the capacity of spatial load control, which is essential for intercellular study. Moreover, application of both compressive and tensile loads using a single loading device is challenging. Here, we fabricate and characterize a microdevice for applying programmable compressive/tensile loads to live cells. The device consists of two PDMS substrates. The top substrate consists of nine circular membranes with patterned microdots array on the top surfaces. Each membrane is connected with a microfluidic channel built in the bottom substrate. Upon actuation, the fluid in the channels deforms the membranes and applies controllable strain to cells cultured on the membranes. In this design, each membrane can be individually controlled to apply desired strain levels. The surface strain of the PDMS membranes is characterized by mapping the displacement of the dot array. The result of strain analysis shows that, the radial strain at the center of a circular membrane upon deformation ranges from about 5% compressive strain to about 20% tensile strain, validating the capacity of the device in applying both tensile and compressive stresses. Cell testing is performed using trabecular meshwork endothelial cells. Cells on different membranes are subjected to 0.5Hz of compressive or tensile stresses. The result shows that compressive and tensile stresses have different effects on the cells, indicating the device a promising solution for cellular biomechanical study.
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Brahmbhatt, Khushboo, Wujun Zhao, Zhaojie Deng, Leidong Mao et Eric Freeman. « Magnetically Responsive Droplet Interface Bilayer Networks ». Dans ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/smasis2015-9029.
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This work explores incorporating ferrofluids with droplet interface bilayer (DIB) membranes. Ferrofluids contain magnetic nanoparticles in solution with a stabilizing surfactant, providing a magnetically-responsive fluid. These fluids allow for remote mechanical manipulation of ferrofluid droplets through magnetic fields, and will allow for better control over the characteristics of networks of stimuli-responsive cellular membranes created through by DIB technique. This work involves several phases. First, a suitable biocompatible ferrofluid is synthesized, containing a neutral pH and a biocompatible surfactant. Once a proper ferrofluid is identified, it is tested as the aqueous phase for the creation of DIB membranes. Interfacial membranes between ferrofluid droplets are created and compared to non-ferrofluid DIB membranes. The interfacial membrane between two ferrofluid droplets was tested for leakage and stability, and the electrical characteristics of the interfacial membrane were studied and compared to non-ferrofluid DIB membranes. Once it is confirmed that the ferrofluid droplets do not negatively interfere with the formation of the artificial cellular membranes through the electrical measurements, the magnetically-responsive nature of the ferrofluid droplets are used to form large networks of DIB membranes through a simple magnetic field. These networks are easy to assemble and may be remotely manipulated, providing a significant step towards the rapid and simple assembly of DIB networks advancing towards the tissue scale.
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Rosengarten, Gary. « Can We Learn From Nature to Design Membranes ? The Intricate Pore Structure of the Diatom ». Dans ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82148.
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Membranes are ubiquitous functional elements used in separation processes. An ideal membrane will stop certain species penetrating it while having excellent transport properties for others. Membranes are used in synthetic systems such as fuel cells and desalination plants, but are also formed naturally in biological systems. For example all cells use a membrane to contain the cellular contents, while allowing transport of nutrients though the cell wall. I will present our recent work on examining diatoms, which are unicellular algae that grow in water. They have a self assembled silica membrane wall with a regular array of nanopores whose function is very poorly understood. I will outline the unique structure of the pores and our experimental work on understanding their structure to help develop membranes with better performance.
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Arena, Christopher B., Michael B. Sano, Marissa Nichole Rylander et Rafael V. Davalos. « High Frequency Electroporation for Cancer Therapy ». Dans ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53626.
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Electroporation is a non-linear biophysical mechanism in which the application of an external pulsed electric field leads to an increase in the permeability of cellular membranes. The extent of electroporation is attributed to the induced buildup of charge across the membrane, and consequently, transmembrane potential (TMP). Increasing the TMP has been described to produce various permeabilizing effects, wherein the formation of hydrophilic, aqueous pores becomes energetically favorable [1]. If the pulse parameters are tuned such that the membrane defects are only temporary, and the cell remains viable, the process is termed reversible electroporation. As a cancer therapy, reversible electroporation has been employed to increase the cellular uptake of chemotherapeutic drugs. Irreversible electroporation (IRE) results when membrane defects are permanent, leading to cell death. Recently, IRE has been recognized as an independent means to destroy tumors without the use of adjuvant drugs and prior to the onset of thermal injury [2].
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Nguyen, Mary-Anne, Graham Taylor et Stephen A. Sarles. « A Microfluidic Assembly and Simultaneous Interrogation of Networks of Asymmetric Biomimetic Membranes ». Dans ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3878.
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In this study, we utilize a novel microfluidic device to perform simultaneous electrical interrogation of an array of droplet interface bilayers (DIB) that feature asymmetric phospholipid leaflet compositions. While asymmetry is vital to many cellular functions, it is has received very little attention in membrane-based engineered material systems for sensing, energy conversion, or actuation. This gap is due to challenges in constructing and interrogating networks of asymmetric membranes, limiting our understanding of how lipid asymmetry affects membrane active peptides, and vice versa. Our system overcomes these difficulties by enabling asymmetric membrane formation between many pairs of lipid-coated droplets in oil. We demonstrate its use in probing the interactions between alamethicin, a membrane-active peptide that forms voltage-induced ion channels, and asymmetric DPhPC:DOPhPC membranes, a choice that creates an intrinsic intramembrane potential of |137 mV| due to differences in their respective dipole potentials. Our experiments show that adding alamethicin peptides to one side of the membrane causes this inherent membrane potential to decrease over time, and it alters the value of external voltage that must be applied to drive alamethicin insertion for ion channel formation. These effects take place over the course of 1 to 5 hours after membrane formation, and both results are consistent with translocation and mixing of lipids across the leaflets of the membrane.
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Ma, Jeff, Joshua David Summers et Paul F. Joseph. « Numerical Investigation of Effect of Membrane Thickness on the Performance of Cellular Shear Band Based Non-Pneumatic Tire ». Dans ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47045.
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Several treaded cellular shear bands have been investigated and it is found that the shear band with cellular geometry of (θ = −65°, h = 21) is the most promising to give us best contact pressure profile. To further optimize the design of the pneumatic tire made with this cellular geometry for NASA’s new moon mission, the Finite Element Method is used to investigate the effect of the thickness of membranes on the performance of the cellular shear band based non-pneumatic tire. In this research, we use the Lebanon sand found in New Hampshire and employ the Drucker-Prager/Cap plasticity constitutive law with hardening to model the sand. Penalty contact algorithm is used to model the tangential behavior of the contact between the tread and sand and Coulomb’s law is considered for the friction between tire and sand. The tires and tread are treated as deformable elastic bodies. Numerical results show the deformation of sand and tire, the stress (strain) distribution in sand, tire, and along the interface between them for different thickness of the membranes and hub. The effect of membrane thickness on the contact pressure between tire and sand is explored and it reveals that the tire with thickness t = 0.2mm for inner and outer membranes is not acceptable in terms of the elastic deformation of tire and contact pressure profile and the tire with thickness t = 1.0mm gives us best contact pressure profile.
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Hsieh, Yi-Cheng, Huinan Liang et Jeffrey D. Zahn. « Microdevices for Microdialysis and Membrane Separations ». Dans ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-55052.
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Microdialysis is a commonly used technique for separating small biomolecules within a complex biological mixture for continuous biochemical monitoring. Microdialysis is based upon controlling the mass transfer rate of small biomolecules diffusing across a semipermeable membrane into a dialysis fluid while excluding larger molecules such as proteins. These small molecules are subsequently sensed using a biosensor. Since many biosensors are extremely susceptible to fouling, their stability and lifetime can be extended if metabolites are filtered through a microdialysis membrane before the dialysis fluid is moved into the sensor. Dialysis is also used commonly in biological laboratories to desalt high ionic strength protein solutions. As biochemical analysis systems become more integrated for μTAS systems there is a need to automate this process. Thus, an on-chip dialysis system is useful for biochemical reaction engineering where very tight control of ionic conditions must be maintained for effective enzymatic activity. This work demonstrates the ability to integrate polymer microdialysis membranes with microfluidic systems. Microchannels are bonded with a regenerated cellulose membrane. After microchannels are produced using standard processing techniques, they are integrated with these membranes. The cellulose is activated in an oxygen plasma followed by a lamination bond to the microchannels at moderate pressure and elevated temperature. Devices were placed in a solution of rhodamine dye, and dialysis fluid was allowed to flow through the microchannels. The outlet dye concentration was measured by fluorescence intensity as a function of flow rate and follows analytically predicted results.
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Jiang, Yanfei, Guy M. Genin, Srikanth Singamaneni et Elliot L. Elson. « Interfacial Phases on Giant Unilamellar Vesicles ». Dans ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80942.
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Lipid nanodomains in cell membranes are believed to play a significant role in a number of critical cellular processes (Elson, et al., 2010). These include, for example, replication processes in enveloped viruses such as bird flu and HIV and signaling mechanisms underlying pathological conditions such as cancer. Due to the potential for developing new disease treatments through the control of these membrane rafts, the biophysics underlying their formation has been the subject of intense study, much of this focused on domain formation in giant unilamellar lipid vesicles (GUVs), a simplified model system.
Rapports d'organisations sur le sujet "Membrana cellulare"
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Fang, I.-Ju. Cellular membrane trafficking of mesoporous silica nanoparticles. Office of Scientific and Technical Information (OSTI), janvier 2012. http://dx.doi.org/10.2172/1048532.
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Jensen, Robert. Conference Macromolecular Transport Across Cellular Membranes"". Fort Belvoir, VA : Defense Technical Information Center, septembre 2000. http://dx.doi.org/10.21236/ada390726.
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Delmer, Deborah P., et Prem S. Chourey. The Importance of the Enzyme Sucrose Synthase for Cell Wall Synthesis in Plants. United States Department of Agriculture, octobre 1994. http://dx.doi.org/10.32747/1994.7568771.bard.
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The goal of this work was to understand the role of the enzyme sucrose synthase (SuSy) in synthesis of cellulose and callose in plants. The work resulting from the this grant leads to a number of conclusions. SuSy clearly plays diverse roles in carbon metabolism. It can associate with the plasma membrane of cells undergoing rapid cellulose deposition, such as cotton fibers, developing maize endosperm, gravistimulated pulvini, and transfer cells of the cotton seed. It is also concentrated at sites of high callose deposition (tapetal cells; cell plates). When SuSy levels are lowered by mutation or by anti-sense technology, cell walls undergo degeneration (maize endosperm) and show reduced levels of cellulose (potato tubers). In sum, our evidence has very much strengthened the concept that SuSy does function in the plasma membrane to channel carbon from sucrose via UDP-glucose to glucan synthase complexes. Soluble SuSy also clearly plays a role in providing carbon for starch synthesis and respiration. Surprisingly, we found that the cotton seed is one unique case where SuSy apparently does not play a role in starch synthesis. Current evidence in sum suggests that no specific SuSy gene encodes the membrane-associated form, although in maize the SS 1 form of SuSy may be most important for cell wall synthesis in the early stages of endosperm development. Work is still in progress to determine what does control membrane localization - and the current evidence we have favors a role for Ca2+, and possibly also protein phosphorylation by differentially regulated protein kinases. Finally, we have discovered for the first time, a major new family of genes that encode the catalytic subunit of the cellulose synthase of plants - a result that has been widely cited and opens many new approaches for the study of this important plant function.
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Staiger, Christopher. Regulation of Cell Wall Assembly : Myosin and Exocyst Involvement in Cellulose Synthase Delivery to the Plasma Membrane. Office of Scientific and Technical Information (OSTI), janvier 2022. http://dx.doi.org/10.2172/1840725.
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Philosoph-Hadas, Sonia, Peter B. Kaufman, Shimon Meir et Abraham H. Halevy. Inhibition of the Gravitropic Shoot Bending in Stored Cut Flowers Through Control of Their Graviperception : Involvement of the Cytoskeleton and Cytosolic Calcium. United States Department of Agriculture, décembre 2005. http://dx.doi.org/10.32747/2005.7586533.bard.
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Original objectives: The basic goal of the present project was to study the mechanism involved in shoot graviperception and early transduction, in order to determine the sequence of events operating in this process. This will enable to control the entire process of gravity-induced differential growth without affecting vertical growth processes essential for development. Thus, several new postulated interactions, operating at the perception and early transduction stages of the signaling cascade leading to auxin-mediated bending, were proposed to be examined in snapdragon spikes and oat shoot pulvini, according to the following research goals: 1) Establish the role of amyloplasts as gravireceptors in shoots; 2) Investigate gravity-induced changes in the integrity of shoot actin cytoskeleton (CK); 3) Study the cellular interactions among actin CK, statoliths and cell membranes (endoplasmic reticulum - ER, plasma membrane - PM) during shoot graviperception; 4) Examine mediation of graviperception by modulations of cytosolic calcium - [Ca2+]cyt, and other second messengers (protein phosphorylation, inositol 1,4,5-trisphosphate - IP3). Revisions: 1) Model system: in addition to snapdragon (Antirrhinum majus L.) spikes and oat (Avena sativa) shoot pulvini, the model system of maize (Zea mays) primary roots was targeted to confirm a more general mechanism for graviperception. 2) Research topic: brassinolide, which were not included in the original plan, were examined for their regulatory role in gravity perception and signal transduction in roots, in relation to auxin and ethylene. Background to the topic: The negative gravitropic response of shoots is a complex multi-step process that requires the participation of various cellular components acting in succession or in parallel. Most of the long-lasting studies regarding the link between graviperception and cellular components were focused mainly on roots, and there are relatively few reports on shoot graviperception. Our previous project has successfully characterized several key events occurring during shoot bending of cut flowers and oat pulvini, including amyloplast displacement, hormonal interactions and differential growth analysis. Based on this evidence, the present project has focused on studying the initial graviperception process in flowering stems and cereal shoots. Major conclusions and achievements: 1) The actin and not the microtubule (MT) CK is involved in the graviperception of snapdragon shoots. 2) Gravisensing, exhibited by amyloplast displacement, and early transduction events (auxin redistribution) in the gravitropic response of snapdragon spikes are mediated by the acto-myosin complex. 3) MTs are involved in stem directional growth, which occurs during gravitropism of cut snapdragon spikes, but they are not necessary for the gravity-induced differential growth. 4) The role of amyloplasts as gravisensors in the shoot endodermis was demonstrated for both plant systems. 5) A gravity-induced increase in IP.
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Naim, Michael, Andrew Spielman, Shlomo Nir et Ann Noble. Bitter Taste Transduction : Cellular Pathways, Inhibition and Implications for Human Acceptance of Agricultural Food Products. United States Department of Agriculture, février 2000. http://dx.doi.org/10.32747/2000.7695839.bard.
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Historically, the aversive response of humans and other mammals to bitter-taste substances has been useful for survival, since many toxic constituents taste bitter. Today, the range of foods available is more diverse. Many bitter foods are not only safe for consumption but contain bitter constituents that provide nutritional benefits. Despite this, these foods are often eliminated from our current diets because of their unacceptable bitterness. Extensive technology has been developed to remove or mask bitterness in foods, but a lack of understanding of the mechanisms of bitterness perception at the taste receptor level has prevented the development of inhibitors or efficient methods for reducing bitterness. In our original application we proposed to: (a) investigate the time course and effect of selected bitter tastants relevant to agricultural products on the formation of intracellular signal molecules (cAMP, IP3, Ca2+) in intact taste cells, in model cells and in membranes derived therefrom; (b) study the effect of specific bitter taste inhibitors on messenger formation and identify G-proteins that may be involved in tastant-induced bitter sensation; (c) investigate interactions and self-aggregation of bitter tastants within membranes; (d) study human sensory responses over time to these bitter-taste stimuli and inhibitors in order to validate the biochemical data. Quench-flow module (QFM) and fast pipetting system (FPS) allowed us to monitor fast release of the aforementioned signal molecules (cGMP, as a putative initial signal was substituted for Ca2+ ions) - using taste membranes and intact taste cells in a time range below 500 ms (real time of taste sensation) - in response to bitter-taste stimulation. Limonin (citrus) and catechin (wine) were found to reduce cellular cAMP and increase IP3 contents. Naringin (citrus) stimulated an IP3 increase whereas the cheese-derived bitter peptide cyclo(leu-Trp) reduced IP3 but significantly increased cAMP levels. Thus, specific transduction pathways were identified, the results support the notion of multiple transduction pathways for bitter taste and cross-talk between a few of those transduction pathways. Furthermore, amphipathic tastants permeate rapidly (within seconds) into liposomes and taste cells suggesting their availability for direct activation of signal transduction components by means of receptor-independent mechanisms within the time course of taste sensation. The activation of pigment movement and transduction pathways in frog melanophores by these tastants supports such mechanisms. Some bitter tastants, due to their amphipathic properties, permeated (or interacted with) into a bitter tastant inhibitor (specific phospholipid mixture) which apparently forms micelles. Thus, a mechanism via which this bitter taste inhibitor acts is proposed. Human sensory evaluation experiments humans performed according to their 6-n-propyl thiouracil (PROP) status (non-tasters, tasters, super-tasters), indicated differential perception of bitterness threshold and intensity of these bitter compounds by different individuals independent of PROP status. This suggests that natural products containing bitter compounds (e.g., naringin and limonin in citrus), are perceived very differently, and are in line with multiple transduction pathways suggested in the biochemical experiments. This project provides the first comprehensive effort to explore the molecular basis of bitter taste at the taste-cell level induced by economically important and agriculturally relevant food products. The findings, proposing a mechanism for bitter-taste inhibition by a bitter taste inhibitor (made up of food components) pave the way for the development of new, and perhaps more potent bitter-taste inhibitors which may eventually become economically relevant.
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Epel, Bernard, et Roger Beachy. Mechanisms of intra- and intercellular targeting and movement of tobacco mosaic virus. United States Department of Agriculture, novembre 2005. http://dx.doi.org/10.32747/2005.7695874.bard.
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To cause disease, plant viruses must replicate and spread locally and systemically within the host. Cell-to-cell virus spread is mediated by virus-encoded movement proteins (MPs), which modify the structure and function of plasmodesmata (Pd), trans-wall co-axial membranous tunnels that interconnect the cytoplasm of neighboring cells. Tobacco mosaic virus (TMV) employ a single MP for cell- cell spread and for which CP is not required. The PIs, Beachy (USA) and Epel (Israel) and co-workers, developed new tools and approaches for study of the mechanism of spread of TMV that lead to a partial identification and molecular characterization of the cellular machinery involved in the trafficking process. Original research objectives: Based on our data and those of others, we proposed a working model of plant viral spread. Our model stated that MPᵀᴹⱽ, an integral ER membrane protein with its C-terminus exposed to the cytoplasm (Reichel and Beachy, 1998), alters the Pd SEL, causes the Pd cytoplasmic annulus to dilate (Wolf et al., 1989), allowing ER to glide through Pd and that this gliding is cytoskeleton mediated. The model claimed that in absence of MP, the ER in Pd (the desmotubule) is stationary, i.e. does not move through the Pd. Based on this model we designed a series of experiments to test the following questions: -Does MP potentiate ER movement through the Pd? - In the presence of MP, is there communication between adjacent cells via ER lumen? -Does MP potentiate the movement of cytoskeletal elements cell to cell? -Is MP required for cell-to-cell movement of ER membranes between cells in sink tissue? -Is the binding in situ of MP to RNA specific to vRNA sequences or is it nonspecific as measured in vitro? And if specific: -What sequences of RNA are involved in binding to MP? And finally, what host proteins are associated with MP during intracellular targeting to various subcellular targets and what if any post-translational modifications occur to MP, other than phosphorylation (Kawakami et al., 1999)? Major conclusions, solutions and achievements. A new quantitative tool was developed to measure the "coefficient of conductivity" of Pd to cytoplasmic soluble proteins. Employing this tool, we measured changes in Pd conductivity in epidermal cells of sink and source leaves of wild-type and transgenic Nicotiana benthamiana (N. benthamiana) plants expressing MPᵀᴹⱽ incubated both in dark and light and at 16 and 25 ᵒC (Liarzi and Epel, 2005 (appendix 1). To test our model we measured the effect of the presence of MP on cell-to-cell spread of a cytoplasmic fluorescent probe, of two ER intrinsic membrane protein-probes and two ER lumen protein-probes fused to GFP. The effect of a mutant virus that is incapable of cell-to-cell spread on the spread of these probes was also determined. Our data shows that MP reduces SEL for cytoplasmic molecules, dilates the desmotubule allowing cell-cell diffusion of proteins via the desmotubule lumen and reduces the rate of spread of the ER membrane probes. Replicase was shown to enhance cell-cell spread. The data are not in support of the proposed model and have led us to propose a new model for virus cell-cell spread: this model proposes that MP, an integral ER membrane protein, forms a MP:vRNAER complex and that this ER-membrane complex diffuses in the lipid milieu of the ER into the desmotubule (the ER within the Pd), and spreads cell to cell by simple diffusion in the ER/desmotubule membrane; the driving force for spread is the chemical potential gradient between an infected cell and contingent non-infected neighbors. Our data also suggests that the virus replicase has a function in altering the Pd conductivity. Transgenic plant lines that express the MP gene of the Cg tobamovirus fused to YFP under the control the ecdysone receptor and methoxyfenocide ligand were generated by the Beachy group and the expression pattern and the timing and targeting patterns were determined. A vector expressing this MPs was also developed for use by the Epel lab . The transgenic lines are being used to identify and isolate host genes that are required for cell-to-cell movement of TMV/tobamoviruses. This line is now being grown and to be employed in proteomic studies which will commence November 2005. T-DNA insertion mutagenesis is being developed to identify and isolate host genes required for cell-to-cell movement of TMV.
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Eldar, Avigdor, et Donald L. Evans. Streptococcus iniae Infections in Trout and Tilapia : Host-Pathogen Interactions, the Immune Response Toward the Pathogen and Vaccine Formulation. United States Department of Agriculture, décembre 2000. http://dx.doi.org/10.32747/2000.7575286.bard.
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In Israel and in the U.S., Streptococcus iniae is responsible for considerable losses in various fish species. Poor understanding of its virulence factors and limited know-how-to of vaccine formulation and administration are the main reasons for the limited efficacy of vaccines. Our strategy was that in order to Improve control measures, both aspects should be equally addressed. Our proposal included the following objectives: (i) construction of host-pathogen interaction models; (ii) characterization of virulence factors and immunodominant antigens, with assessment of their relative importance in terms of protection and (iii) genetic identification of virulence factors and genes, with evaluation of the protective effect of recombinant proteins. We have shown that two different serotypes are involved. Their capsular polysaccharides (CPS) were characterized, and proved to play an important role in immune evasion and in other consequences of the infection. This is an innovative finding in fish bacteriology and resembles what, in other fields, has become apparent in the recent years: S. iniae alters surface antigens. By so doing, the pathogen escapes immune destruction. Immunological assays (agar-gel immunodiffusion and antibody titers) confirmed that only limited cross recognition between the two types occurs and that capsular polysaccharides are immunodominant. Vaccination with purified CPS (as an acellular vaccine) results in protection. In vitro and ex-vivo models have allowed us to unravel additional insights of the host-pathogen interactions. S. iniae 173 (type II) produced DNA fragmentation of TMB-8 cells characteristic of cellular necrosis; the same isolate also prevented the development of apoptosis in NCC. This was determined by finding reduced expression of phosphotidylserine (PS) on the outer membrane leaflet of NCC. NCC treated with this isolate had very high levels of cellular necrosis compared to all other isolates. This cellular pathology was confirmed by observing reduced DNA laddering in these same treated cells. Transmission EM also showed characteristic necrotic cellular changes in treated cells. To determine if the (in vitro) PCD/apoptosis protective effects of #173 correlated with any in vivo activity, tilapia were injected IV with #173 and #164 (an Israeli type I strain). Following injection, purified NCC were tested (in vitro) for cytotoxicity against HL-60 target cells. Four significant observations were made : (i) fish injected with #173 had 100-400% increased cytotoxicity compared to #164 (ii) in vivo activation occurred within 5 minutes of injection; (iii) activation occurred only within the peripheral blood compartment; and (iv) the isolate that protected NCC from apoptosis in vitro caused in vivo activation of cytotoxicity. The levels of in vivo cytotoxicity responses are associated with certain pathogens (pathogen associated molecular patterns/PAMP) and with the tissue of origin of NCC. NCC from different tissue (i.e. PBL, anterior kidney, spleen) exist in different states of differentiation. Random amplified polymorphic DNA (RAPD) analysis revealed the "adaptation" of the bacterium to the vaccinated environment, suggesting a "Darwinian-like" evolution of any bacterium. Due to the selective pressure which has occurred in the vaccinated environment, type II strains, able to evade the protective response elicited by the vaccine, have evolved from type I strains. The increased virulence through the appropriation of a novel antigenic composition conforms with pathogenic mechanisms described for other streptococci. Vaccine efficacy was improved: water-in-oil formulations were found effective in inducing protection that lasted for a period of (at least) 6 months. Protection was evaluated by functional tests - the protective effect, and immunological parameters - elicitation of T- and B-cells proliferation. Vaccinated fish were found to be resistant to the disease for (at least) six months; protection was accompanied by activation of the cellular and the humoral branches.
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Seetala, Naidu, et Upali Siriwardane. Development of Low Cost Membranes (Ta, Nb & ; Cellulose Acetate) for H2/CO2 Separation in WGS Reactors. Office of Scientific and Technical Information (OSTI), décembre 2011. http://dx.doi.org/10.2172/1043820.
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Christopher, David A., et Avihai Danon. Plant Adaptation to Light Stress : Genetic Regulatory Mechanisms. United States Department of Agriculture, mai 2004. http://dx.doi.org/10.32747/2004.7586534.bard.
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Original Objectives: 1. Purify and biochemically characterize RB60 orthologs in higher plant chloroplasts; 2. Clone the gene(s) encoding plant RB60 orthologs and determine their structure and expression; 3. Manipulate the expression of RB60; 4. Assay the effects of altered RB60 expression on thylakoid biogenesis and photosynthetic function in plants exposed to different light conditions. In addition, we also examined the gene structure and expression of RB60 orthologs in the non-vascular plant, Physcomitrella patens and cloned the poly(A)-binding protein orthologue (43 kDa RB47-like protein). This protein is believed to a partner that interacts with RB60 to bind to the psbA5' UTR. Thus, to obtain a comprehensive view of RB60 function requires analysis of its biochemical partners such as RB43. Background & Achievements: High levels of sunlight reduce photosynthesis in plants by damaging the photo system II reaction center (PSII) subunits, such as D1 (encoded by the chloroplast tpsbAgene). When the rate of D1 synthesis is less than the rate of photo damage, photo inhibition occurs and plant growth is decreased. Plants use light-activated translation and enhanced psbAmRNA stability to maintain D1 synthesis and replace the photo damaged 01. Despite the importance to photosynthetic capacity, these mechanisms are poorly understood in plants. One intriguing model derived from the algal chloroplast system, Chlamydomonas, implicates the role of three proteins (RB60, RB47, RB38) that bind to the psbAmRNA 5' untranslated leader (5' UTR) in the light to activate translation or enhance mRNA stability. RB60 is the key enzyme, protein D1sulfide isomerase (Pill), that regulates the psbA-RN :Binding proteins (RB's) by way of light-mediated redox potentials generated by the photosystems. However, proteins with these functions have not been described from higher plants. We provided compelling evidence for the existence of RB60, RB47 and RB38 orthologs in the vascular plant, Arabidopsis. Using gel mobility shift, Rnase protection and UV-crosslinking assays, we have shown that a dithiol redox mechanism which resembles a Pill (RB60) activity regulates the interaction of 43- and 30-kDa proteins with a thermolabile stem-loop in the 5' UTR of the psbAmRNA from Arabidopsis. We discovered, in Arabidopsis, the PD1 gene family consists of II members that differ in polypeptide length from 361 to 566 amino acids, presence of signal peptides, KDEL motifs, and the number and positions of thioredoxin domains. PD1's catalyze the reversible formation an disomerization of disulfide bonds necessary for the proper folding, assembly, activity, and secretion of numerous enzymes and structural proteins. PD1's have also evolved novel cellular redox functions, as single enzymes and as subunits of protein complexes in organelles. We provide evidence that at least one Pill is localized to the chloroplast. We have used PDI-specific polyclonal and monoclonal antisera to characterize the PD1 (55 kDa) in the chloroplast that is unevenly distributed between the stroma and pellet (containing membranes, DNA, polysomes, starch), being three-fold more abundant in the pellet phase. PD1-55 levels increase with light intensity and it assembles into a high molecular weight complex of ~230 kDa as determined on native blue gels. In vitro translation of all 11 different Pill's followed by microsomal membrane processing reactions were used to differentiate among PD1's localized in the endoplasmic reticulum or other organelles. These results will provide.1e insights into redox regulatory mechanisms involved in adaptation of the photosynthetic apparatus to light stress. Elucidating the genetic mechanisms and factors regulating chloroplast photosynthetic genes is important for developing strategies to improve photosynthetic efficiency, crop productivity and adaptation to high light environments.