Artículos de revistas: "Cellules en cycle"

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Savatier, Pierre y Marielle Afanassieff. "Cycle cellulaire et contrôle de l’autorenouvellement des cellules embryonnaires souches". Journal de la Société de Biologie 196, n.º 1 (2002): 117–23. http://dx.doi.org/10.1051/jbio/2002196010117.

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Garbay, Sandrine y Aline Lonvaud-Funel. "Etude de la lyse de Leuconostoc oenos". OENO One 24, n.º 4 (31 de diciembre de 1990): 157. http://dx.doi.org/10.20870/oeno-one.1990.24.4.1234.

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La lyse de Leuconostoc oenos a été étudiée en suspension dans l'eau et dans une solution synthétique (pH 3,5; alcool 11 % v/v, acide tartrique 4 g/l). Elle a été mesurée par deux méthodes basées sur la libération de constituants cellulaires (mesure à 210 mm) et sur la diminution de l'opacité de la solution (mesure à 600 nm). Les cellules en phase de croissance exponentielle se lysent plus facilement que les cellules prélevées pendant les autres phases du cycle cellulaire.L'éthanol dans le milieu de suspension augmente la lyse de cellules cultivées dans le milieu standard. Par contre, le phénomène est plus limité dans la solution acide et alcoolisée que dans l'eau, sauf pour les cellules cultivées en présence d'acides gras insaturés où l'on observe le résultat inverse.La désorganisation des membranes et l'activité autolytique des cellules dépendent à la fois des conditions de culture des bactéries et du milieu dans lequel elles sont mises en suspension.

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3

Basso, F., B. Ragazzon, J. Bertherat y M. Rizk-Rabin. "Corrélation entre la stéroidogenèse et le cycle cellulaire dans les cellules corticosurrénaliennes tumorales". Annales d'Endocrinologie 75, n.º 5-6 (octubre de 2014): 274. http://dx.doi.org/10.1016/j.ando.2014.07.072.

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4

Rizk-Rabin, M., B. Ragazzon y J. Bertherat. "Corrélation entre cycle cellulaire, stéroidogenèse et pka dans les cellules corticosurrénaliennes tumorales h295r". Annales d'Endocrinologie 77, n.º 4 (septiembre de 2016): 427–28. http://dx.doi.org/10.1016/j.ando.2016.07.966.

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5

ROBELIN, J. "Différenciation, croissance et développement cellulaire du tissu musculaire". INRAE Productions Animales 3, n.º 4 (10 de octubre de 1990): 253–63. http://dx.doi.org/10.20870/productions-animales.1990.3.4.4384.

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Le tissu musculaire est constitué de fibres allongées, cylindriques, plurinucléées et organisées en faisceaux entourés par une gaine de tissu conjonctif. On distingue différents types de fibres musculaires, selon qu’elles sont alimentées en énergie par la glycolyse en milieu anaérobie, ou par le cycle de Krebs et la chaîne respiratoire en milieu aérobie. On distingue aussi les fibres à contraction lente de celles à contraction rapide. Les cellules musculaires se développent chez l’embryon à partir de la région somitique. Les cellules myogéniques, non encore différenciées se multiplient au cours du cycle de prolifération. Les cellules qui quittent ce cycle entrent ensuite dans la phase de différenciation pour se transformer en myoblastes. Ces derniers fusionnent pour donner des myotubes qui évoluent enfin en fibres musculaires. La différenciation métabolique et fonctionnelle est sous le contrôle de l’innervation et des hormones. La différenciation musculaire chez les bovins se produit en totalité durant la vie foetale. Le premier tiers de la vie foetale est caractérisé par la présence de myotubes, par une multiplication très rapide des noyaux et une augmentation du nombre des myotubes. Au cours du deuxième tiers de la vie foetale, les myotubes évoluent en fibres musculaires. La multiplication des noyaux est encore très intense, mais l’augmentation du nombre de fibres se ralentit. C’est à ce stade qu’apparaissent les différents types contractiles de fibres. A partir du troisième tiers de la vie foetale, le nombre de fibres reste stable, alors que le nombre de noyaux continue de s’accroître, et cela presque jusqu’au stade adulte, grâce à l’incorporation de nouveaux noyaux issus des cellules satellites. La synthèse protéique est très intense chez le foetus, et reste à un niveau élevé après la naissance. La croissance foetale représente une phase primordiale de la croissance musculaire, avec un accroissement important du nombre de fibres et surtout du nombre de noyaux, et aussi une synthèse protéique très rapide. La croissance postnatale est surtout caractérisée par la maturation des fibres juste après la naissance, et par l’accroissement de leur diamètre jusqu’au stade adulte.

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6

Prozesky, L., A. Hart y M. S. Brett. "Une étude in vitro du cycle de vie de Cowdria ruminantium". Revue d’élevage et de médecine vétérinaire des pays tropicaux 46, n.º 1-2 (1 de enero de 1993): 247. http://dx.doi.org/10.19182/remvt.9373.

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Le cycle de vie de Cowdria ruminantium a été étudié dans des cellules SBE 189 par microscopie classique et électronique. Des cultures ont été infectées avec un inoculum synchronisé et fixées et préparées entre 15 min et 111 h post-inoculation (PI). Après 12 h, de grands corps réticulaires seuls ou en petits groupes ont été identifiés dans des vacuoles intracytoplasmatiques entourées de membranes. Ils se développaient graduellement dans des corps réticulaires plus petits avec une structure interne plus granuleuse. De 66 à 75 h PI, il y avait une augmentation importante de la taille des colonies. La plupart des colonies contenaient des corps réticulaires, bien que quelques corps intermédiaires et opaques aux électrons aient été visibles. Des corps réticulaires solitaires extracellulaires avec une couche ressemblant au peptidoglycan ont été observés 84 h PI. Après 90 h, des corps intermédiaires et opaques aux électrons fussent présents en abondance et cela coïncidait avec la lyse des cellules de culture. Le cycle de développement de Cowdria ruminantium durait donc environ 4 jours, dans cette étude.

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7

Boubekri, A., T. Gernigon, N. Kaci, F. Khammar y J. Exbrayat. "Plasticité des cellules lactotropes au cours du cycle de reproduction du rat des sables". Annales d'Endocrinologie 74, n.º 4 (septiembre de 2013): 432. http://dx.doi.org/10.1016/j.ando.2013.07.692.

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8

Gromada, Xavier, Nabil Rabhi, Julie Kerr-Conte, Fraçois Pattou, Philippe Froguel y Jean-Sebastien Annicotte. "Le régulateur du cycle cellulaire E2F1 maintient l’identité et la fonction des cellules β pancréatiques". Diabetes & Metabolism 43, n.º 2 (marzo de 2017): A85. http://dx.doi.org/10.1016/s1262-3636(17)30346-4.

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9

Burgaud, Mathilde, Betty Bretin, Arnaud Reignier, John De Vos y Laurent David. "Du nouveau dans les modèles d’étude de l’embryon humain". médecine/sciences 39, n.º 2 (febrero de 2023): 129–36. http://dx.doi.org/10.1051/medsci/2023018.

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Depuis 2021, l’assistance médicale à la procréation (AMP) est accessible aux couples infertiles, mais aussi aux femmes seules et aux couples de femmes. Le processus de fécondation in vitro (FIV) a permis de franchir le seuil de cinq millions de naissances dans le monde, entre 1978 et 2013. Cependant, le taux d’échec à chaque cycle est évalué à environ 75 %. Il est donc nécessaire de mieux comprendre le développement embryonnaire humain afin d’améliorer le taux de succès des FIV. Les modèles d’étude ont beaucoup évolué ces dernières années : mise au point de la culture embryonnaire, séquençage du transcriptome de cellules individualisées, découverte des conditions de culture de cellules souches pluripotentes naïves et génération de blastoïdes. Nous revenons dans cette revue sur ces avancées récentes concernant la modélisation de l’embryon humain, qui établissent un nouveau socle de connaissances pour améliorer l’AMP.

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10

Éraud, Chantal, Monique Loiseau y Maryse Tort. "Évolution des cellules à tannins dans les bourgeons végétatifs de Pêcher au cours d'un cycle annuel". Acta Botanica Gallica 147, n.º 2 (enero de 2000): 199–208. http://dx.doi.org/10.1080/12538078.2000.10515409.

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11

Munuswamy, N. y T. Subramoniam. "Neuro-Endocrine Activity During Ovarian Maturation in the Fairy Shrimp Streptocephal Us Dichotomus Baird, 1860 (Anostraca)". Crustaceana 52, n.º 3 (1987): 303–15. http://dx.doi.org/10.1163/156854087x00547.

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AbstractLes centres neurosécréteurs, tels que le cerveau et le pédoncule oculaire de S. dichotomus possèdent trois types de NSCs, se distinguant par la taille, la forme et les propriétés tinctoriales. Le pédoncule oculaire montre la présence d'un complexe organe X-glande du sinus au dessus de la région du pédoncule optique. Le NSM de la glande du sinus montre des variations cycliques pendant la reproduction. L'histologie des organes frontaux et leur inclusion dans le système neurosécréteur sont discutées. Les études cytologiques faites au cours des présentes recherches montrent une corrélation définie entre l'activité secrétrice des cellules du cerveau et le développement de l'ovaire. Les NSCs A et B du cerveau par exemple ont montré une intense NSM pendant le développement des oocytes. Ceci suggérerait que les cellules cérébrales A et B secrètent une hormone stimulatrice de l'ovaire. Dans le pédoncule oculaire les NSCs de type B et C ont montré une activité intense chez les femelles quiescentes sur le plan de la reproduction, ce qui suggère la production d'une hormone inhibitrice dans les NSCs du pédoncule oculaire. Chez S. dichotomus, en raison du chevauchement du cycle de reproduction, sans interphase importante il peut y avoir une production continue par les NSCs d'hormones destinées à la glande du sinus, et ainsi une phase distincte d'accumulation/liberation peut ne pas être évidente. Cependant, des expériences de ligature du pédoncule oculaire effectuées chez S. dichotomus à différentes phases du cycle de reproduction dénotent clairement l'analogie fonctionelle de la glande du sinus avec celle des Crustacés supérieurs.

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12

Gressens, P., B. Paindaveine, JM Hill, DE Brenneman y P. Evrard. "Le peptide vasoactif intestinal : un modulateur physiologique des phases S et G1 du cycle mitotique des cellules neurales". Archives de Pédiatrie 3, n.º 12 (diciembre de 1996): 1293–94. http://dx.doi.org/10.1016/s0929-693x(97)85972-6.

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13

Girard, F., N. Lamb y A. Fernandez. "Le cycle cellulaire analysé par micro-injection dans les cellules somatiques de mammifères : rôle distinct des cyclines A et B". médecine/sciences 8, n.º 4 (1992): 375. http://dx.doi.org/10.4267/10608/3143.

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14

Ourouda, R., H. Rahabi-Layachi, Z. A. Massy, A. Boullier y C. Amant. "Le phosphate inorganique bloque le cycle cellulaire des cellules endothéliales en phase G1 en augmentant l’expression de p16 et p27". Néphrologie & Thérapeutique 12, n.º 5 (septiembre de 2016): 415. http://dx.doi.org/10.1016/j.nephro.2016.07.271.

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15

Basso, F., S. Chaoui, B. Ragazzon, J. Bertherat y M. Rizk-Rabin. "L’activation de la stéroïdogenèse est sous contrôle du cycle cellulaire, et de la PRKARIA dans les cellules corticosurrénaliennes tumorales H295R". Annales d'Endocrinologie 76, n.º 4 (septiembre de 2015): 360. http://dx.doi.org/10.1016/j.ando.2015.07.192.

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16

Basso, M. F., M. B. Ragazzon, J. Bertherat y M. Rizk-Rabin. "Corrélation entre la stéroidogenèse, le cycle cellulaire, l’inactivation du gène PRKARIA, et les voies de signalisation, dans les cellules H295R". Annales d'Endocrinologie 73, n.º 4 (septiembre de 2012): 345. http://dx.doi.org/10.1016/j.ando.2012.07.814.

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17

Jouvenot, M., I. Pellerin, G. Maréchal, M. Royez, C. Ordener, M. Alkhalaf y GL Adessi. "REGULATION DE L'EXPRESSION DES ONCOGENES c-FOS ET c-MYC AU COURS DU CYCLE CELLULAIRE DANS LES CELLULES EPITHELIALES DE L'ENDOMETRE". Reproduction Nutrition Développement 29, Suppl. 1 (1989): 49. http://dx.doi.org/10.1051/rnd:19890786.

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18

Bourass, Mohamed y Mohammed Bouachrine. "Étude structurale des systèmes dissymétriques de structure D-π-A à base de thiénopyrazine destinés aux cellules solaires organiques de type « bulk heterojunction » (BHJ)". Canadian Journal of Chemistry 97, n.º 10 (octubre de 2019): 745–55. http://dx.doi.org/10.1139/cjc-2019-0053.

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Onze nouvelles molécules organiques de structure donneurs-espaceur-accepteurs (D-π-A) utilisées pour les cellules solaires organiques (OSC) basées sur la thiénopyrazine et le thiophène ont été étudiées par la théorie de la densité fonctionnelle (DFT) et la théorie de la densité fonctionnelle dépendante de temps DFT (TD-DFT), pour expliquer comment l’ordre de conjugaison influe sur les performances des cellules solaires. Le groupe accepteur d’électrons (ancrage) était composé de 2-cyanoacrylique pour tous les composés, tandis que l’unité donneuse d’électrons était variée et que son influence fut étudiée. Les résultats théoriques ont montré que les calculs TD-DFT, avec une fonction hybride d’échange – corrélation utilisant la méthode d’atténuation de Coulomb (CAM-B3LYP) en conjonction avec un modèle de solvatation à cycle continu polarisable (modèle de continuum polarisable, PCM) combinée avec la base 6-31G(d,p), était raisonnablement capable de prédire les énergies d’excitation, les spectres d’absorption et d’émission des molécules étudiées. Les niveaux d’énergie des orbitales moléculaires frontières (orbitale moléculaire occupée de plus haute énergie (HOMO) et orbitale moléculaire inoccupée de plus basse énergie (LUMO) de ces composés peuvent avoir un effet positif sur le processus d’injection et de régénération d’électrons. La tendance des lacunes calculées HOMO-LUMO se compare bien avec les données spectrales. En outre, les valeurs estimées de photovoltage en circuit ouvert (Voc) pour ces composés ont été présentées. L’étude des propriétés structurelles, électroniques et optiques de ces composés pourrait aider à concevoir des matériaux organiques photovoltaïques fonctionnels plus efficaces.

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19

Mwamengele, G. L. M. y S. Larsen. "L’ultrastructure de lamicrovasculature cérébrale de chèvres infectées expérimentalement avec Cowdria ruminantium". Revue d’élevage et de médecine vétérinaire des pays tropicaux 46, n.º 1-2 (1 de enero de 1993): 245. http://dx.doi.org/10.19182/remvt.9372.

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Afin d’étudier les lésions de la microvasculature cérébrale dans la cowdriose, 14 chèvres tanzaniennes ont été infectées par inoculation intraveineuse avec le stock Ball-3 de Cowdria ruminantium. Elles ont été suivies sur le plan clinique pendant la période d’incubation et la réaction fébrile, et sacrifiées lorsque les températures ont commencé à baisser. Cinq chèvres saines ont été utilisées pour déterminer la meilleure procédure pour la fixation du cerveau par perfusion et pour servir de témoins. La perfusion a été effectuée par l’artère carotide sous anesthésie générale au pentobarbitone, utilisant du glutaraldehyde de pH 7,4 à 3 p.100, à 500 mOsm. Des prélèvements de tissu cérébral ont été pris pour microscopie classique et électronique. Des signes variables de désordres du système nerveux central et un hydropéricarde peu important se sont développés chez toutes les chèvres infectées. Deux changements neuropathologiques différents ont été observés : des colonies de Cowdria dans des cellules endothéliales vasculaires, sans autres changements, et des petites infiltrations périvasculaires de cellules mononucléaires. Aucun signe de vasculite ou d’une perméabilité vasculaire anormale n’a été observé. Plusieurs phagocytes périvasculaires renfermaient des inclusions cytoplasmiques inhabituelles, se présentant comme des agrégations de particules irrégulièrement arrondies, associées à une membrane, de 0,25 à 0,4 µm de diamètre, ayant dans quelques cas une structure interne évocatrice de mitochondries partiellement dégradées. Néanmoins, ces agrégations ne semblaient pas enfermées de façon convaincante à l’intérieur de membranes, comme il est à à prévoir en cas d’autophagocytose. Une autre interprétation hypothétique est qu’elles représentent des stades abortifs de C. ruminantium qui tentent de se développer en dehors des vaisseaux et qu’une réponse immunitaire cellulaire, développée pendant et après la période d’incubation, limite ce deuxième cycle dans l’hôte et provoque des infiltrations périvasculaires mononucléaires.

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Maji, Poulami, Megha Maji, Paramita Ghosh y Prashant Shukla. "Cellulase-producing Microorganisms from Diverse Ecosystem: A Review". UTTAR PRADESH JOURNAL OF ZOOLOGY 46, n.º 2 (16 de enero de 2025): 25–38. https://doi.org/10.56557/upjoz/2025/v46i24760.

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Cellulose is the most abundant organic matter present on the planet. It is made up of glucose molecules which is the ultimate energy currency. Still, cellulose is utilized by most the animals as energy source as they lack necessary enzymes for degradation of the molecule. The animals who are able to utilize cellulose based materials as source of energy are able to do so due to cellulase producing gut microflora. Cellulases are enzymes which are used by certain organisms to breakdown the cellulose. Very small number of organisms are able to produce different types of cellulases which can break the bonds present in cellulose molecules. Only few bacteria, fungi and protozoa have necessary genes for cellulase. It has been found that certain herbivorous insects are also able to synthesize their own cellulase but again this property is very limited in few insect types. The microorganisms who are able to synthesize cellulase are present in soil and water along with certain mammalian and insect guts. In soil and water such microorganisms decompose the dead plant matter containing cellulose and help in maintaining the carbon cycle along with getting energy from the molecule. Apart from ecological activity the cellulases are utilized for various industrial purposes. In the current review we have discussed different types of microorganisms which are able to produce cellulases. The source of such microorganisms are also discussed briefly to place them in the right context.

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Revathi, D. y S. Ramalingam. "A study on critical associations of media components on enhanced cellulase production from wild Trichoderma viride and cellulase immobilization on iron-oxide magnetic nanoparticles". Journal of Environmental Biology 44, n.º 1 (23 de enero de 2023): 27–33. http://dx.doi.org/10.22438/jeb/44/1/mrn-5048.

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Aim: The current study is a preliminary step towards enhancing the cellulase productivity in wild Trichoderma viride which will enable robust valorization of non-edible lignocellulosic biomass through co-generative enzymatic saccharification, specifically concentrating on influence of individual media components on biomass growth and cellulase productivity. Further, cellulase immobilization on iron-oxide magnetic nanoparticles was also achieved that can increase the shelf life of the enzyme. Methodology: The cellulase production in the wild Trichoderma viride was enhanced using media design and formulation. EDC {1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide} functionalized iron-oxide nanoparticles were chosen to act as carriers for cellulase immobilization. The binding efficiency and relative activity were measured in addition to optimal pH and temperature for cellulase bound iron-oxide nanoparticles. Further, the hydrolysis efficiency of immobilized cellulases was also measured after which it was subjected to consecutive hydrolytic cycles to calculate the recycle rate. Results: A maximum growth rate of 60 PCV (Packed cell volume) and total cellulase activity of 7.4 U ml-1 was obtained on media design and formulation. 82.5% binding efficiency was achieved on EDC functionalized iron-oxide magnetic nanoparticles which showed good stability at 5pH and 500C. There was 44.4% activity loss after 5 consecutive hydrolytic cycles which showed steady decline with increased cycle number and finally at the end of the 10th hydrolytic cycle, 22.2% of total relative activity was retained. Interpretation: Unprecedented total cellulase activity from a wild strain was obtained through media design. The stability of cellulases was further enhanced using iron-oxide magnetic nanoparticle immobilization. Key words: Cellulases, Immobilization, Iron-oxide magnetic nanoparticles, Submerged fermentation, Trichoderma viride

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Després, Merlin y Simon Gaudin. "Le monoxyde d’azote: Une arme du système immunitaire pour brouiller les communications entre bactéries". médecine/sciences 36, n.º 11 (noviembre de 2020): 1074–77. http://dx.doi.org/10.1051/medsci/2020214.

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Le dossier thématique suivant a été rédigé par les étudiantes et étudiants de Master 1 de Biologie de l’École Normale Supérieure de Lyon à l’issue de l’UE Microbiologie Moléculaire et Structurale (2019-2020). Le Master de Biologie de l’ENS de Lyon, cohabilité par l’université Claude Bernard Lyon 1, accueille chaque année environ 50 étudiants en M1 et en M2 et propose une formation de haut niveau à la recherche en biosciences. Chaque étudiant y construit son parcours à la carte, en choisissant ses options parmi un large panel de modules, favorisant ainsi une approche pluridisciplinaire des sciences du vivant, et ce en relation étroite avec les laboratoires de recherche du tissu local, national et international. En participant à diverses activités scientifiques connexes aux UE de leur formation, les étudiants préparent également l’obtention du Diplôme de l’ENS de Lyon, qui valide leur scolarité à l’ENS. La rédaction du présent dossier, qui vise à transmettre de façon claire les messages issus d’une sélection d’articles scientifiques publiés récemment dans le domaine de la microbiologie, constitue l’une de ces activités connexes proposées aux étudiants. Les bactéries peuvent vivre en communautés dont la structure est régulée par de nombreuses interactions abiotiques et biotiques. Les interactions biotiques reposent sur des communications inter-bactériennes qui participent à la mise en place de relations de collaboration, de compétition ou de prédation. Ces communautés bactériennes peuvent en outre être en interaction avec des hôtes animaux, dans le cas des bactéries du microbiote ou des bactéries pathogènes par exemple, ou avec des virus parasites, les bactériophages. Le présent dossier illustre quelques aspects nouveaux de cette communication bactérienne, et de la façon dont les interactions bactéries/hôte ou bactéries/phages peuvent impacter cette communication. Deux nouvelles s’attardent sur des découvertes récentes autour du quorum sensing, une modalité de communication bactérienne permettant l’expression coordonnée des gènes à l’échelle de la population, en fonction de la densité de la population. La nouvelle intitulée « Le monoxyde d’azote : une arme du système immunitaire pour brouiller les communications entre bactéries » illustre comment le quorum sensing chez Staphylococcus aureus, une bactérie opportuniste, peut être affecté par un médiateur du système immunitaire de la souris. La nouvelle intitulée « Un bactériophage exploite le système de communication de son hôte bactérien pour entrer en cycle lytique » montre une stratégie étonnante par laquelle le phage VP882 décrypte des signaux issus du quorum sensing de la bactérie qu’il infecte pour réguler son propre cycle de réplication. Au-delà du quorum sensing, deux nouvelles décrivent de nouvelles modalités de communication inter-bactérienne. La nouvelle intitulée « Les nanotubes bactériens, acteurs de la compétition entre Bacillus subtilis et Bacillus megaterium » met en lumière le rôle des nanotubes, des structures de communication intercellulaire insoupçonnées jusque récemment chez les bactéries. La nouvelle intitulée « La bactérie Vibrio cholerae lyse les bactéries environnantes et assimile leur ADN qu’elle intègre dans son propre génome » illustre comment un système de sécrétion, qui permet l’injection d’effecteurs bactériens dans des cellules cibles, peut être exploité pour faciliter les transferts horizontaux de gènes chez les bactéries. Enfin, pour élargir la réflexion au monde des virus eucaryotes, deux nouvelles montrent comment l’infection virale peut interférer avec la communication entre cellules eucaryotes, sur l’exemple de la communication s’effectuant par l’intermédiaire de vésicules extracellulaires. La nouvelle intitulée « La sécrétion de vésicules extracellulaires par les plaquettes activées à l’origine de la létalité de la dengue ? » discute des mécanismes par lesquels le virus de la dengue déclenche la sécrétion de vésicules extracellulaires par les plaquettes, et des conséquences que cela peut avoir sur l’inflammation et le déclenchement de chocs hémorragiques. La nouvelle intitulée « Le coccolithovirus et Emiliania huxleyi : le détournement viral des vésicules extracellulaires » montre enfin comment ce virus d’algue unicellulaire exploite la communication intercellulaire de son hôte pour augmenter son pouvoir de diffusion au sein de la population, et des conséquences écologiques et géochimiques que cela peut entraîner à grande échelle.

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23

Wang, Lunji, Yishen Zhao, Siqiao Chen, Xian Wen, Wilfred Mabeche Anjago, Tianchi Tian, Yajuan Chen et al. "Growth, Enzymatic, and Transcriptomic Analysis of xyr1 Deletion Reveals a Major Regulator of Plant Biomass-Degrading Enzymes in Trichoderma harzianum". Biomolecules 14, n.º 2 (24 de enero de 2024): 148. http://dx.doi.org/10.3390/biom14020148.

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The regulation of plant biomass degradation by fungi is critical to the carbon cycle, and applications in bioproducts and biocontrol. Trichoderma harzianum is an important plant biomass degrader, enzyme producer, and biocontrol agent, but few putative major transcriptional regulators have been deleted in this species. The T. harzianum ortholog of the transcriptional activator XYR1/XlnR/XLR-1 was deleted, and the mutant strains were analyzed through growth profiling, enzymatic activities, and transcriptomics on cellulose. From plate cultures, the Δxyr1 mutant had reduced growth on D-xylose, xylan, and cellulose, and from shake-flask cultures with cellulose, the Δxyr1 mutant had ~90% lower β-glucosidase activity, and no detectable β-xylosidase or cellulase activity. The comparison of the transcriptomes from 18 h shake-flask cultures on D-fructose, without a carbon source, and cellulose, showed major effects of XYR1 deletion whereby the Δxyr1 mutant on cellulose was transcriptionally most similar to the cultures without a carbon source. The cellulose induced 43 plant biomass-degrading CAZymes including xylanases as well as cellulases, and most of these had massively lower expression in the Δxyr1 mutant. The expression of a subset of carbon catabolic enzymes, other transcription factors, and sugar transporters was also lower in the Δxyr1 mutant on cellulose. In summary, T. harzianum XYR1 is the master regulator of cellulases and xylanases, as well as regulating carbon catabolic enzymes.

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24

Wolgemuth, DJ, K. Rhee, S. Wu y SE Ravnik. "Genetic control of mitosis, meiosis and cellular differentiation during mammalian spermatogenesis". Reproduction, Fertility and Development 7, n.º 4 (1995): 669. http://dx.doi.org/10.1071/rd9950669.

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Gametogenesis in both the male and female mammal represents a specialized and highly regulated series of cell cycle events, involving both mitosis and meiosis as well as subsequent differentiation. Recent advances in our understanding of the genetic control of the eukaryotic cell cycle have underscored the evolutionarily-conserved nature of these regulatory processes. However, most of the data have been obtained from yeast model systems and mammalian cell lines. Furthermore, most of the observations focus on regulation of mitotic cell cycles. In the present paper: (i) aspects of gametogenesis in mammals that represent unique cell-cycle control points are highlighted; (ii) current knowledge on the regulation of the germ cell cycle, in the context of what is known in yeast and other model eukaryotic systems, is summarized; and (iii) strategies that can be used to identify additional cell cycle regulating genes are outlined.

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25

MELNIK, RODERICK V. N., XILIN WEI y GABRIEL MORENO–HAGELSIEB. "NONLINEAR DYNAMICS OF CELL CYCLES WITH STOCHASTIC MATHEMATICAL MODELS". Journal of Biological Systems 17, n.º 03 (septiembre de 2009): 425–60. http://dx.doi.org/10.1142/s0218339009002879.

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Cell cycles are fundamental components of all living organisms and their systematic studies extend our knowledge about the interconnection between regulatory, metabolic, and signaling networks, and therefore open new opportunities for our ultimate efficient control of cellular processes for disease treatments, as well as for a wide variety of biomedical and biotechnological applications. In the study of cell cycles, nonlinear phenomena play a paramount role, in particular in those cases where the cellular dynamics is in the focus of attention. Quantification of this dynamics is a challenging task due to a wide range of parameters that require estimations and the presence of many stochastic effects. Based on the originally deterministic model, in this paper we develop a hierarchy of models that allow us to describe the nonlinear dynamics accounting for special events of cell cycles. First, we develop a model that takes into account fluctuations of relative concentrations of proteins during special events of cell cycles. Such fluctuations are induced by varying rates of relative concentrations of proteins and/or by relative concentrations of proteins themselves. As such fluctuations may be responsible for qualitative changes in the cell, we develop a new model that accounts for the effect of cellular dynamics on the cell cycle. Finally, we analyze numerically nonlinear effects in the cell cycle by constructing phase portraits based on the newly developed model and carry out a parametric sensitivity analysis in order to identify parameters for an efficient cell cycle control. The results of computational experiments demonstrate that the metabolic events in gene regulatory networks can qualitatively influence the dynamics of the cell cycle.

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26

Immonen, Kirsi, Sini Metsä-Kortelainen, Juha Nurmio, Amélie Tribot, Tuomas Turpeinen, Atte Mikkelson, Tomi Kalpio, Otto-Ville Kaukoniemi y Heli Kangas. "Recycling of 3D Printable Thermoplastic Cellulose-Composite". Sustainability 14, n.º 5 (25 de febrero de 2022): 2734. http://dx.doi.org/10.3390/su14052734.

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3D printing enables sustainable product innovations through novel design, reduced use of materials, and local manufacturing. Sustainable 3D printing can further be realized using recyclable materials. Cellulose is an abundantly available renewable material. Modified celluloses, such as thermoplastic cellulose esters, are widely used in injection molding applications. The aim of this research was to study the properties of a cellulose-based composite (cellulose acetate propionate (CAP) polymer matrix with 20 wt. % microcellulose) in injection molding and granular extrusion-based 3D printing processes over multiple recycles. The impact of the processing methods on the composite’s properties were investigated. Both injection molded and 3D printed samples were ground with plastic grinding mill to particle sizes below 3 mm after each preparation stage and reused as such in the next process cycle. Morphology, mechanical and thermal properties, and material degradation were analyzed. The thermoplastic cellulose-based compound was found to be directly recyclable for both processes without the need for any additional compounding steps. The polymer matrix was able to withstand at least seven processing cycles without degradation. However, microcellulose was found to be more sensitive to thermal stress. The mechanical and thermal properties of the cellulose-based composites remained close to initial levels throughout.

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27

West, Thomas P. "Pullulan Production by Aureobasidium pullulans ATCC 201253 Cells Adsorbed onto Cellulose Anion and Cation Exchangers". ISRN Microbiology 2012 (23 de septiembre de 2012): 1–4. http://dx.doi.org/10.5402/2012/140951.

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The anion exchanger phosphocellulose and the cation exchanger triethylaminoethyl cellulose were used to immobilize cells of the fungus Aureobasidium pullulans ATCC 201253 and the adsorbed cells were subsequently investigated for their ability to produce the polysaccharide pullulan using batch fermentation. The cells adsorbed on the triethylaminoethyl cellulose at pH 7.5 produced higher pullulan levels than those cells immobilized on phosphocellulose at pH 4.0 for 2 cycles of 168 h at 30 °C. Relative to the initial cycle of 168 h, pullulan production by the cells immobilized on the triethylaminoethyl cellulose decreased slightly after 168 h of the second production cycle while pullulan production by the phosphocellulose-immobilized cells remained about the same after 168 h of the second production cycle.

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28

Xu, Yiwei, Zhuo Shen, Eleni Gentekaki, Jiahui Xu y Zhenzhen Yi. "Comparative Transcriptome Analyses during the Vegetative Cell Cycle in the Mono-Cellular Organism Pseudokeronopsis erythrina (Alveolata, Ciliophora)". Microorganisms 8, n.º 1 (12 de enero de 2020): 108. http://dx.doi.org/10.3390/microorganisms8010108.

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Studies focusing on molecular mechanisms of cell cycles have been lagging in unicellular eukaryotes compared to other groups. Ciliates, a group of unicellular eukaryotes, have complex cell division cycles characterized by multiple events. During their vegetative cell cycle, ciliates undergo macronuclear amitosis, micronuclear mitosis, stomatogenesis and somatic cortex morphogenesis, and cytokinesis. Herein, we used the hypotrich ciliate Pseudokeronopsis erythrina, whose morphogenesis has been well studied, to examine molecular mechanisms of ciliate vegetative cell cycles. Single-cell transcriptomes of the growth (G) and cell division (D) stages were compared. The results showed that (i) More than 2051 significantly differentially expressed genes (DEGs) were detected, among which 1545 were up-regulated, while 256 were down-regulated at the D stage. Of these, 11 randomly picked DEGs were validated by reverse transcription quantitative polymerase chain reaction (RT-qPCR); (ii) Enriched DEGs during the D stage of the vegetative cell cycle of P. erythrina were involved in development, cortex modifications, and several organelle-related biological processes, showing correspondence of molecular evidence to morphogenetic changes for the first time; (iii) Several individual components of molecular mechanisms of ciliate vegetative division, the sexual cell cycle and cellular regeneration overlap; and (iv) The P. erythrina cell cycle and division have the same essential components as other eukaryotes, including cyclin-dependent kinases (CDKs), cyclins, and genes closely related to cell proliferation, indicating the conserved nature of this biological process. Further studies are needed focusing on detailed inventory and gene interactions that regulate specific ciliated cell-phase events.

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Vermaas, Josh V., Riin Kont, Gregg T. Beckham, Michael F. Crowley, Mikael Gudmundsson, Mats Sandgren, Jerry Ståhlberg, Priit Väljamäe y Brandon C. Knott. "The dissociation mechanism of processive cellulases". Proceedings of the National Academy of Sciences 116, n.º 46 (30 de octubre de 2019): 23061–67. http://dx.doi.org/10.1073/pnas.1913398116.

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Cellulase enzymes deconstruct recalcitrant cellulose into soluble sugars, making them a biocatalyst of biotechnological interest for use in the nascent lignocellulosic bioeconomy. Cellobiohydrolases (CBHs) are cellulases capable of liberating many sugar molecules in a processive manner without dissociating from the substrate. Within the complete processive cycle of CBHs, dissociation from the cellulose substrate is rate limiting, but the molecular mechanism of this step is unknown. Here, we present a direct comparison of potential molecular mechanisms for dissociation via Hamiltonian replica exchange molecular dynamics of the model fungal CBH, Trichoderma reesei Cel7A. Computational rate estimates indicate that stepwise cellulose dethreading from the binding tunnel is 4 orders of magnitude faster than a clamshell mechanism, in which the substrate-enclosing loops open and release the substrate without reversing. We also present the crystal structure of a disulfide variant that covalently links substrate-enclosing loops on either side of the substrate-binding tunnel, which constitutes a CBH that can only dissociate via stepwise dethreading. Biochemical measurements indicate that this variant has a dissociation rate constant essentially equivalent to the wild type, implying that dethreading is likely the predominant mechanism for dissociation.

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30

Fitri, Lenni, Yurnita Yurnita y Suhartono Suhartono. "Isolation and Celulolytic Activity Assay of Actinobacteria Isolated from Palm Oil Wastewater". Trends in Sciences 20, n.º 6 (10 de marzo de 2023): 6715. http://dx.doi.org/10.48048/tis.2023.6715.

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Cellulose plays an important role in the carbon cycle in nature and is the largest compound. This study aimed to isolate, to characterize and to determine actinobacteria that capable of producing cellulases. The sampling method in this study was carried out by purposive sampling at the outlet point of aeration pond of the wastewater treatment plant (IPAL) from palm oil waste station of PT. Teupin Lada. Isolation of actinobacteria was carried out on Humic Acid Vitamin b Agar (HVA), morphological characterization was carried out on Yeast Malt Agar (YMA), Yeast Starch Agar (YSA), Oatmeal Agar (OA), and microscopic characterization of actinobacteria and measuring the diameter of the clear zone formed on Carboxymethyl Cellulose (CMC) medium using the indicator Congo Red. Eight isolates were obtained from the isolation. Of the 8 isolates obtained, 7 of them were able to produce cellulase enzymes which were measured based on the clear zone formed in the test Congo Red on Carboxymethil Cellulose (CMC), and one isolate did not show any clear zones. The highest value of Cellulolytic Index (IS) was obtained from isolate ATLS-05, namely 8.38 mm. HIGHLIGHTS Cellulose plays an important role in the carbon cycle in nature and is the largest compound The high waste load especially palm oil mill effluent (Elaeis guineensis) or known as Palm Oil Mill Effluent(POME) could cause various problems for the environment and society. POME is wastewater from the palm oil industry, which is one of the most polluting agro-industrial wastes Actinobacteria are one of the soil microbes which have the greatest abundance and play an important role in the decomposition process. One of the roles of soil microbes is too degrading cellulose GRAPHICAL ABSTRACT

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31

Royou, Anne, William Sullivan y Roger Karess. "Cortical recruitment of nonmuscle myosin II in early syncytial Drosophila embryos". Journal of Cell Biology 158, n.º 1 (8 de julio de 2002): 127–37. http://dx.doi.org/10.1083/jcb.200203148.

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The nuclei of early syncytial Drosophila embryos migrate dramatically toward the poles. The cellular mechanisms driving this process, called axial expansion, are unclear, but myosin II activity is required. By following regulatory myosin light chain (RLC)–green fluorescent protein dynamics in living embryos, we observed cycles of myosin recruitment to the cortex synchronized with mitotic cycles. Cortical myosin is first seen in a patch at the anterocentral part of the embryo at cycle 4. With each succeeding cycle, the patch expands poleward, dispersing at the beginning of each mitosis and reassembling at the end of telophase. Each cycle of actin and myosin recruitment is accompanied by a cortical contraction. The cortical myosin cycle does not require microtubules but correlates inversely with Cdc2/cyclinB (mitosis-promoting factor) activity. A mutant RLC lacking inhibitory phosphorylation sites was fully functional with no effect on the cortical myosin cycle, indicating that Cdc2 must be modulating myosin activity by some other mechanism. An inhibitor of Rho kinase blocks the cortical myosin recruitment cycles and provokes a concomitant failure of axial expansion. These studies suggest a model in which cycles of myosin-mediated contraction and relaxation, tightly linked to Cdc2 and Rho kinase activity, are directly responsible for the axial expansion of the syncytial nuclei.

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32

Omasta, Bozena y Jana Tomaskova. "Cellular Lipids—Hijacked Victims of Viruses". Viruses 14, n.º 9 (27 de agosto de 2022): 1896. http://dx.doi.org/10.3390/v14091896.

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Over the millions of years-long co-evolution with their hosts, viruses have evolved plenty of mechanisms through which they are able to escape cellular anti-viral defenses and utilize cellular pathways and organelles for replication and production of infectious virions. In recent years, it has become clear that lipids play an important role during viral replication. Viruses use cellular lipids in a variety of ways throughout their life cycle. They not only physically interact with cellular membranes but also alter cellular lipid metabolic pathways and lipid composition to create an optimal replication environment. This review focuses on examples of how different viruses exploit cellular lipids in different cellular compartments during their life cycles.

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33

Gaikwad, Swapnil, Avinash P. Ingle, Silvio Silverio da Silva y Mahendra Rai. "Immobilized Nanoparticles-Mediated Enzymatic Hydrolysis of Cellulose for Clean Sugar Production: A Novel Approach". Current Nanoscience 15, n.º 3 (19 de febrero de 2019): 296–303. http://dx.doi.org/10.2174/1573413714666180611081759.

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Background: Enzymatic hydrolysis of cellulose is an expensive approach due to the high cost of an enzyme involved in the process. The goal of the current study was to apply magnetic nanomaterials as a support for immobilization of enzyme, which helps in the repeated use of immobilized enzyme for hydrolysis to make the process cost-effective. In addition, it will also provide stability to enzyme and increase its catalytic activity. Objective: The main aim of the present study is to immobilize cellulase enzyme on Magnetic Nanoparticles (MNPs) in order to enable the enzyme to be re-used for clean sugar production from cellulose. Methods: MNPs were synthesized using chemical precipitation methods and characterized by different techniques. Further, cellulase enzyme was immobilized on MNPs and efficacy of free and immobilized cellulase for hydrolysis of cellulose was evaluated. Results: Enzymatic hydrolysis of cellulose by immobilized enzyme showed enhanced catalytic activity after 48 hours compared to free enzyme. In first cycle of hydrolysis, immobilized enzyme hydrolyzed the cellulose and produced 19.5 ± 0.15 gm/L of glucose after 48 hours. On the contrary, free enzyme produced only 13.7 ± 0.25 gm/L of glucose in 48 hours. Immobilized enzyme maintained its stability and produced 6.15 ± 0.15 and 3.03 ± 0.25 gm/L of glucose in second and third cycle, respectively after 48 hours. Conclusion: This study will be very useful for sugar production because of enzyme binding efficiency and admirable reusability of immobilized enzyme, which leads to the significant increase in production of sugar from cellulosic materials.

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Takahashi, Tadanobu y Takashi Suzuki. "Function of Membrane Rafts in Viral Lifecycles and Host Cellular Response". Biochemistry Research International 2011 (2011): 1–23. http://dx.doi.org/10.1155/2011/245090.

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Membrane rafts are small (10–200 nm) sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process) and the late stage (assembly, budding, and release processes of virus particles). In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction.

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35

Chen, Bokun, Jihua Liu, Ge Xu y Gang Li. "Lowering pO2 Interacts with Photoperiod to Alter Physiological Performance of the Coastal Diatom Thalassiosira pseudonana". Microorganisms 9, n.º 12 (9 de diciembre de 2021): 2541. http://dx.doi.org/10.3390/microorganisms9122541.

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Exacerbating deoxygenation is extensively affecting marine organisms, with no exception for phytoplankton. To probe these effects, we comparably explored the growth, cell compositions, photosynthesis, and transcriptome of a diatom Thalassiosira pseudonana under a matrix of pO2 levels and Light:Dark cycles at an optimal growth light. The growth rate (μ) of T. pseudonana under a 8:16 L:D cycle was enhanced by 34% by low pO2 but reduced by 22% by hypoxia. Under a 16:8 L:D cycle, however, the μ decreased with decreasing pO2 level. The cellular Chl a content decreased with decreasing pO2 under a 8:16 L:D cycle, whereas the protein content decreased under a 16:8 L:D cycle. The prolonged photoperiod reduced the Chl a but enhanced the protein contents. The lowered pO2 reduced the maximal PSII photochemical quantum yield (FV/FM), photosynthetic oxygen evolution rate (Pn), and respiration rate (Rd) under the 8:16 or 16:8 L:D cycles. Cellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were higher under low pO2 than ambient pO2 or hypoxia. Moreover, the prolonged photoperiod reduced the FV/FM and Pn among all three pO2 levels but enhanced the Rd, MDA, and SOD activity. Transcriptome data showed that most of 26 differentially expressed genes (DEGs) that mainly relate to photosynthesis, respiration, and metabolism were down-regulated by hypoxia, with varying expression degrees between the 8:16 and 16:8 L:D cycles. In addition, our results demonstrated that the positive or negative effect of lowering pO2 upon the growth of diatoms depends on the pO2 level and is mediated by the photoperiod.

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Ahmad Khorairi, Ain Nadiah Sofiah, Noor-Soffalina Sofian-Seng, Rizafizah Othaman, Noorul Syuhada Mohd Razali y Khairul Farihan Kasim. "Assessment of Natural Cellulosic Powder from Pepper Pericarp Waste (Piper nigrum L.) after Alkalization and Bleaching Treatment: Effect of Alkali Concentration and Treatment Cycle". Sains Malaysiana 51, n.º 4 (30 de abril de 2022): 1061–74. http://dx.doi.org/10.17576/jsm-2022-5104-09.

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Pepper (Piper nigrum L.) pericarp is an agriculture waste in the production of white pepper. It is underutilised agro-industrial waste which could be a promising natural source of cellulose. Hence, finding an optimum way to remove the non cellulose components without degrading the cellulose structure is essential. In this work, the effects of alkaline concentration (4, 5, and 6% NaOH) and number of soaking cycle (3 & 4 cycles) on the characteristics of cellulose from pepper pericarp were investigated. The obtained cellulose powder was characterized for its yield, α-cellulose content, particle size, zeta potential, morphology, whiteness index, crystallinity degree and thermal stability. The white powder cellulose after 4th cycle treatment with 4% NaOH appeared to have the highest yield (23.63%), α-cellulose (65.97%), crystallinity structure (51%) and better thermal stability at 334 °C. FTIR spectrum at band around 1732 cm-1 indicates a partial removal of non-cellulosic material at all alkalization condition due to the presence of remaining lignin and hemicellulose. These may contribute to formation of negative surface charge on all cellulose samples which may potentially enhance the functionality of the material as emulsifier. Based on two-way ANOVA test, concentration and cycle of alkaline treatment significantly (p<0.05) influenced the yield, particle size and zeta potential, meanwhile α-cellulose significantly influence by NaOH concentration only (p<0.05). The findings showed that manipulating the synthesis condition of cellulose powder influenced its properties which could be further used in various applications.

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de Figueirêdo, Maria Cléa Brito, Morsyleide de Freitas Rosa, Cássia Maria Lie Ugaya, Men de Sá Moreira de Souza Filho, Ana Cláudia Carneiro da Silva Braid y Luiz Flávio Luciano de Melo. "Life cycle assessment of cellulose nanowhiskers". Journal of Cleaner Production 35 (noviembre de 2012): 130–39. http://dx.doi.org/10.1016/j.jclepro.2012.05.033.

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38

Diaz Vivancos, Pedro, Tonja Wolff, Jelena Markovic, Federico V. Pallardó y Christine H. Foyer. "A nuclear glutathione cycle within the cell cycle". Biochemical Journal 431, n.º 2 (28 de septiembre de 2010): 169–78. http://dx.doi.org/10.1042/bj20100409.

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The complex antioxidant network of plant and animal cells has the thiol tripeptide GSH at its centre to buffer ROS (reactive oxygen species) and facilitate cellular redox signalling which controls growth, development and defence. GSH is found in nearly every compartment of the cell, including the nucleus. Transport between the different intracellular compartments is pivotal to the regulation of cell proliferation. GSH co-localizes with nuclear DNA at the early stages of proliferation in plant and animal cells. Moreover, GSH recruitment and sequestration in the nucleus during the G1- and S-phases of the cell cycle has a profound impact on cellular redox homoeostasis and on gene expression. For example, the abundance of transcripts encoding stress and defence proteins is decreased when GSH is sequestered in the nucleus. The functions of GSHn (nuclear GSH) are considered in the present review in the context of whole-cell redox homoeostasis and signalling, as well as potential mechanisms for GSH transport into the nucleus. We also discuss the possible role of GSHn as a regulator of nuclear proteins such as histones and PARP [poly(ADP-ribose) polymerase] that control genetic and epigenetic events. In this way, a high level of GSH in the nucleus may not only have an immediate effect on gene expression patterns, but also contribute to how cells retain a memory of the cellular redox environment that is transferred through generations.

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Mukherjee, Sukanya, Kamalika Bhattacharjee y Sukanta Das. "Clustering Using Cyclic Spaces of Reversible Cellular Automata". Complex Systems 30, n.º 2 (15 de junio de 2021): 205–37. http://dx.doi.org/10.25088/complexsystems.30.2.205.

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This paper introduces a cycle-based clustering technique using the cyclic spaces of reversible cellular automata (CAs). Traditionally, a cluster consists of close objects, which in the case of CAs necessarily means that the objects belong to the same cycle; that is, they are reachable from each other. Each of the cyclic spaces of a cellular automaton (CA) forms a unique cluster. This paper identifies CA properties based on “reachability” that make the clustering effective. To do that, we first figure out which CA rules contribute to maintaining the minimum intracluster distance. Our CA is then designed with such rules to ensure that a limited number of cycles exist in the configuration space. An iterative strategy is also introduced that can generate a desired number of clusters by merging objects of closely reachable clusters from a previous level in the present level using a unique auxiliary CA. Finally, the performance of our algorithm is measured using some standard benchmark validation indices and compared with existing well-known clustering techniques. It is found that our algorithm is at least on a par with the best algorithms existing today on the metric of these standard validation indices.

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40

Zhang, Shouan y George W. Sundin. "Long-Term Effect of Mutagenic DNA Repair on Accumulation of Mutations in Pseudomonas syringae B86-17". Journal of Bacteriology 186, n.º 22 (15 de noviembre de 2004): 7807–10. http://dx.doi.org/10.1128/jb.186.22.7807-7810.2004.

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ABSTRACT Forty replicate lineages of Pseudomonas syringae B86-17 cells expressing the rulAB mutagenic DNA repair (MDR) determinant or the rulB::Km MDR-deficient mutant GWS242 were passaged through single-cell bottlenecks (60 cycles), with a UV radiation (UVR) exposure given to half of the lineages at the beginning of each cycle. After every 10th bottleneck cycle, single-colony isolates from all 80 lineages were subjected to 39 phenotypic screens, with newly arising mutations detected in 60 and 0% of UVR-exposed or non-UVR-exposed B86-17 lineages, respectively, by the 60th cycle. Cellular fitness, measured as growth rate in a minimal medium, of UVR-exposed lineages of both B86-17 and GWS242 after 60 cycles was not significantly different from that of the ancestral strains. Although UVR exposure and MDR activity increased the occurrence of mutations in cells, a significant reduction in overall fitness was not observed.

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41

Paula, Ronaldo Damião de y Sivanilza Teixeira Machado. "The rentability of the second and third production cycle of the eucalyptus (corymbia angophora) in alto Tietê community". Independent Journal of Management & Production 11, n.º 5 (1 de septiembre de 2020): 1594. http://dx.doi.org/10.14807/ijmp.v11i5.1292.

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Over the years, the paper and cellulose industry in Alto Tietê community kept the eucalypt production system in partners with local farmers. However, the costs of the integrated systems were very higher, and contribute to the industry adopted the new strategy like investment in production mechanization in areas plains and most far. This hit the local market with eucalyptus devaluation. Thus, this paper aims to analyze the strategy applied by local farmers to reduce eucalypt production costs. The case study was carried out in the Salesópolis community, São Paulo, as an exploratory research to comprehend the impact of paper and cellulose industry change made in the local community. The results showed that the total cost estimated to first production cycle was 1.8 most than the second cycle and the rentability in 6.5 years was de 1,92% less than other cycles. The third production cycle showed downs in land rentability, almost 18.5% less than the second cycle and 16.5% less than the first cycle. Therefore, the eucalypt production in the Alto Tietê community already was a big business and income source to local farmers and with eucalypt market devaluation and the cost increase of production and operation, the farmers had opted by the maintenance of the third cycle of production even not being the most profitable.

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Brownstein, Alexandra J., Michaela Veliova, Rebeca Acin-Perez, Marc Liesa y Orian S. Shirihai. "ATP-consuming futile cycles as energy dissipating mechanisms to counteract obesity". Reviews in Endocrine and Metabolic Disorders 23, n.º 1 (6 de noviembre de 2021): 121–31. http://dx.doi.org/10.1007/s11154-021-09690-w.

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AbstractObesity results from an imbalance in energy homeostasis, whereby excessive energy intake exceeds caloric expenditure. Energy can be dissipated out of an organism by producing heat (thermogenesis), explaining the long-standing interest in exploiting thermogenic processes to counteract obesity. Mitochondrial uncoupling is a process that expends energy by oxidizing nutrients to produce heat, instead of ATP synthesis. Energy can also be dissipated through mechanisms that do not involve mitochondrial uncoupling. Such mechanisms include futile cycles described as metabolic reactions that consume ATP to produce a product from a substrate but then converting the product back into the original substrate, releasing the energy as heat. Energy dissipation driven by cellular ATP demand can be regulated by adjusting the speed and number of futile cycles. Energy consuming futile cycles that are reviewed here are lipolysis/fatty acid re-esterification cycle, creatine/phosphocreatine cycle, and the SERCA-mediated calcium import and export cycle. Their reliance on ATP emphasizes that mitochondrial oxidative function coupled to ATP synthesis, and not just uncoupling, can play a role in thermogenic energy dissipation. Here, we review ATP consuming futile cycles, the evidence for their function in humans, and their potential employment as a strategy to dissipate energy and counteract obesity.

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Xiao, Lu, Renjie Liao y Jia Guo. "Highly Multiplexed Single-Cell In Situ RNA and DNA Analysis by Consecutive Hybridization". Molecules 25, n.º 21 (23 de octubre de 2020): 4900. http://dx.doi.org/10.3390/molecules25214900.

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The ability to comprehensively profile nucleic acids in individual cells in their natural spatial contexts is essential to advance our understanding of biology and medicine. Here, we report a novel method for spatial transcriptomics and genomics analysis. In this method, every nucleic acid molecule is detected as a fluorescent spot at its natural cellular location throughout the cycles of consecutive fluorescence in situ hybridization (C-FISH). In each C-FISH cycle, fluorescent oligonucleotide probes hybridize to the probes applied in the previous cycle, and also introduce the binding sites for the next cycle probes. With reiterative cycles of hybridization, imaging and photobleaching, the identities of the varied nucleic acids are determined by their unique color sequences. To demonstrate the feasibility of this method, we show that transcripts or genomic loci in single cells can be unambiguously quantified with 2 fluorophores and 16 C-FISH cycles or with 3 fluorophores and 9 C-FISH cycles. Without any error correction, the error rates obtained using the raw data are close to zero. These results indicate that C-FISH potentially enables tens of thousands (216 = 65,536 or 39 = 19,683) of different transcripts or genomic loci to be precisely profiled in individual cells in situ.

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Gribble, Daniel A. y Vilas G. Pol. "Polydopamine-Modified Carboxymethyl Cellulose as Advanced Polysulfide Trapping Binder". Batteries 9, n.º 11 (24 de octubre de 2023): 525. http://dx.doi.org/10.3390/batteries9110525.

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The search for a high-energy-density alternative to lithium-ion batteries has led to great interest in the lithium sulfur battery (LSB). However, poor cycle lifetimes and coulombic efficiencies (CEs) due to detrimental lithium polysulfide (LiPS) shuttling has hindered its widespread adoption. To address this challenge, a modified sodium carboxymethyl cellulose (CMC) polymer with integrated dopamine moieties and polydopamine nanoparticles was created through a facile one-pot dopamine (DOP) amidation reaction to strengthen noncovalent interactions with LiPSs and mitigate the shuttling effect. The resulting CMC-DOP binder improved electrode wettability, adhesion, and electrochemical performance. Compared to LSBs with a standard CMC binder, CMC-DOP 5:1 (with a 5:1 weight ratio of CMC to dopamine precursor) improves the specific capacity at cycle 100 by 38% to 552 mAh g−1 and CE from 96.8 to 98.9%. LSBs show good stability, even after 500 cycles. Post-mortem electrochemical impedance spectroscopy (EIS) and energy-dispersive spectroscopy (EDS) studies confirmed the effectiveness of the CMC-DOP in confining LiPS in the cathode. This simple but effective nature-inspired strategy promises to enhance the viability of LSBs without using harmful chemicals or adding excess bulk.

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45

Skehan, Philip. "Control models of cell cycle transit, exit, and arrest". Biochemistry and Cell Biology 66, n.º 6 (1 de junio de 1988): 467–77. http://dx.doi.org/10.1139/o88-059.

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Several distinct cycles mediate the events which occur between one cell division and the next. In micro-organisms there are generally two cycles. One governs biomass growth, the other DNA synthesis and cell division. In higher eukaryotes there can be as many as four distinct cycles, with growth, DNA synthesis, cell division, and nuclear division each possessing its own functional sequence of events. These cycles are controlled and coordinated by several different regulatory mechanisms. Restriction points are specific steps in the cycle whose completion is governed by external regulatory agents. One set of restriction points requires nutrients and growth hormones for step completion. Another set serves as receptors for differentiating factors which cause cycle arrest and initiate cellular differentiation. There is currently a debate as to whether restriction point inhibition involves permanent arrest or temporary arrest with a stochastic arrested-state residence time controlled by a transition probability mechanism. Tissue sizing is a process of negative feedback inhibition mediated by intercellular communication via cell surface contact and the extracellular matrix. Sizers commonly operate throughout broad portions of the cycle and appear to cause a slowing of cycle transit velocity rather than arrest. Sizers are probably the major regulatory mechanism for cell growth under conditions of nutrient and growth factor excess. They also generate compensatory proliferation following wounding or cell death. A growing body of evidence suggests that both the transit velocity, with which cells move through their several cycles, and the coordination of the cycles are controlled by intracellular regulatory mechanisms which behave as biological oscillators. These oscillators trigger complex sequences of events such as DNA synthesis and cell division.

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46

Sevim, Volkan, Xinwei Gong y Joshua E. S. Socolar. "Reliability of Transcriptional Cycles and the Yeast Cell-Cycle Oscillator". PLoS Computational Biology 6, n.º 7 (8 de julio de 2010): e1000842. http://dx.doi.org/10.1371/journal.pcbi.1000842.

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47

Ouyang, Yang, Na Yin, Shi Yan Chen, Lian Tang y Hua Ping Wang. "Synthesis and Characterization of Bacterial Cellulose/Calcium Silicate Composites". Advanced Materials Research 476-478 (febrero de 2012): 863–66. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.863.

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A novel composites material consisting of calcium silicate deposited in bacterial cellulose membrane was synthesized by immersing BC membrane in the calcium and silicate solutions by turns with different cycle times and characterized. The results indicated that the CaSiO3 particles were homogeneously dispersed on the surface of nanofibers with the effect of BC template when two cycles of soaking proceed, during which the fabrication of most CaSiO3 particles took place. The FT-IR reveals the strong interaction between the two parts of the BC/CaSiO3 composite. The XRD pattern demonstrated a crystal structure disruption of the cellulose aroused by CaSiO3 particle. BC/ CaSiO3 is considered to have a potential application in bone tissue field.

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48

LIN, SONG-SUN, WEN-WEI LIN y TING-HUI YANG. "BIFURCATIONS AND CHAOS IN TWO-CELL CELLULAR NEURAL NETWORKS WITH PERIODIC INPUTS". International Journal of Bifurcation and Chaos 14, n.º 09 (septiembre de 2004): 3179–204. http://dx.doi.org/10.1142/s021812740401134x.

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This study investigates bifurcations and chaos in two-cell Cellular Neural Networks (CNN) with periodic inputs. Without the inputs, the time periodic solutions are obtained for template A=[r,p,s] with p>1, r>p-1 and -s>p-1. The number of periodic solutions can be proven to be no more than two in exterior regions. The input is b sin 2πt/T with period T>0 and amplitude b>0. The typical trajectories Γ(b,T,A) and their ω-limit set ω(b,T,A) vary with b, T and A are also considered. The asymptotic limit cycles Λ∞(T,A) with period T of Γ(b,T,A) are obtained as b→∞. When [Formula: see text] (given in (67)), Λ∞and -Λ∞can be separated. The onset of chaos can be induced by crises of ω(b,T,A) and -ω(b,T,A) for suitable T and b. The ratio [Formula: see text], of largest amplitude a1(b) except for T-mode and amplitude of the T-mode of the Fast Fourier Transform (FFT) of Γ(b,T,A), can be used to compare the strength of sustained periodic cycle Λ0(A) and the inputs. When [Formula: see text], Λ0(A) dominates and the attractor ω(b,T,A) is either a quasi-periodic or a periodic. Moreover, the range b of the window of periodic cycles constitutes a devil's staircase. When [Formula: see text], finitely many chaotic regions and window regions exist and interweave with each other. In each window, the basic periodic cycle can be identified. A sequence of period-doubling is observed to the left of the basic periodic cycle and a quasi-periodic region is observed to the right of it. For large b, the input dominates, ω(b,T,A) becomes simpler, from quasi-periodic to periodic as b increases.

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49

Coutant, Anthony, Katherine Roper, Daniel Trejo-Banos, Dominique Bouthinon, Martin Carpenter, Jacek Grzebyta, Guillaume Santini et al. "Closed-loop cycles of experiment design, execution, and learning accelerate systems biology model development in yeast". Proceedings of the National Academy of Sciences 116, n.º 36 (16 de agosto de 2019): 18142–47. http://dx.doi.org/10.1073/pnas.1900548116.

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One of the most challenging tasks in modern science is the development of systems biology models: Existing models are often very complex but generally have low predictive performance. The construction of high-fidelity models will require hundreds/thousands of cycles of model improvement, yet few current systems biology research studies complete even a single cycle. We combined multiple software tools with integrated laboratory robotics to execute three cycles of model improvement of the prototypical eukaryotic cellular transformation, the yeast (Saccharomyces cerevisiae) diauxic shift. In the first cycle, a model outperforming the best previous diauxic shift model was developed using bioinformatic and systems biology tools. In the second cycle, the model was further improved using automatically planned experiments. In the third cycle, hypothesis-led experiments improved the model to a greater extent than achieved using high-throughput experiments. All of the experiments were formalized and communicated to a cloud laboratory automation system (Eve) for automatic execution, and the results stored on the semantic web for reuse. The final model adds a substantial amount of knowledge about the yeast diauxic shift: 92 genes (+45%), and 1,048 interactions (+147%). This knowledge is also relevant to understanding cancer, the immune system, and aging. We conclude that systems biology software tools can be combined and integrated with laboratory robots in closed-loop cycles.

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50

Wheeler, Richard John. "Analyzing the dynamics of cell cycle processes from fixed samples through ergodic principles". Molecular Biology of the Cell 26, n.º 22 (5 de noviembre de 2015): 3898–903. http://dx.doi.org/10.1091/mbc.e15-03-0151.

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Tools to analyze cyclical cellular processes, particularly the cell cycle, are of broad value for cell biology. Cell cycle synchronization and live-cell time-lapse observation are widely used to analyze these processes but are not available for many systems. Simple mathematical methods built on the ergodic principle are a well-established, widely applicable, and powerful alternative analysis approach, although they are less widely used. These methods extract data about the dynamics of a cyclical process from a single time-point “snapshot” of a population of cells progressing through the cycle asynchronously. Here, I demonstrate application of these simple mathematical methods to analysis of basic cyclical processes—cycles including a division event, cell populations undergoing unicellular aging, and cell cycles with multiple fission (schizogony)—as well as recent advances that allow detailed mapping of the cell cycle from continuously changing properties of the cell such as size and DNA content. This includes examples using existing data from mammalian, yeast, and unicellular eukaryotic parasite cell biology. Through the ongoing advances in high-throughput cell analysis by light microscopy, electron microscopy, and flow cytometry, these mathematical methods are becoming ever more important and are a powerful complementary method to traditional synchronization and time-lapse cell cycle analysis methods.

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