Дисертації з теми "Biophysical stimulation"

Healthy bone is bombarded with many different mechanical strain derived signals during normal daily activities. One of these signals is present as a direct connective tissue strain on the cells. However, there is also the presence of an electrically charged streaming potential during this straining. The electrical potential is created from the movement of charged fluid through the small bone porosities. To date, little focus has been applied to elucidating the possible synergistic effects of these two stimulants. The aim of this project was to evaluate the effects of mechanical strain and indirect electrical stimulation upon the development of bone forming osteoblast cells and any possible synergistic effects of the two stimulants. This aim was achieved by using a novel device, designed and developed with the capability of creating a cell substrate surface strain along with an exogenous electrical stimulant individually or at the same time. Proliferation and differentiation were determined as a measure of cellular development. The indirect electrical stimulation was achieved through the use of a pulsed electromagnetic field (PEMF) while the mechanical strain was produced from dynamic stretching of a deformable cell substrate. Strain and strain rate were modelled from recent studies proposing that relatively high frequency, low strain osteogenic mechanical stimulants are more indicative of what healthy bone would be experiencing during normal activities. The PEMF signal mimicked a clinically available bone growth stimulator signal. Results showed a PEMF stimulus on monolayers of SaOS-2 and MG-63 osteoblast-like cells leads to a depression in proliferation. A concomitant increase in alkaline phosphatase production was also observed for the SaOS-2 cultures, but not for the MG-63 cell line. It was hypothesised that this was due to the MG-63's lack of phenotypic maturity compared to the SaOS-2 cells. Mechanical strain of the cell substrate alone, at a relatively high frequency (5Hz) but small strain, did not significantly effect either cell proliferation or differentiation for the MG-63 cells. However, when the electrical and mechanical stimulants were combined a significant increase in cellular differentiation occurred with MG-63 cultures, revealing a possible synergistic effect of these two stimulants on the development of bone cells.

Healthy bone is bombarded with many different mechanical strain derived signals during normal daily activities. One of these signals is present as a direct connective tissue strain on the cells. However, there is also the presence of an electrically charged streaming potential during this straining. The electrical potential is created from the movement of charged fluid through the small bone porosities. To date, little focus has been applied to elucidating the possible synergistic effects of these two stimulants. The aim of this project was to evaluate the effects of mechanical strain and indirect electrical stimulation upon the development of bone forming osteoblast cells and any possible synergistic effects of the two stimulants. This aim was achieved by using a novel device, designed and developed with the capability of creating a cell substrate surface strain along with an exogenous electrical stimulant individually or at the same time. Proliferation and differentiation were determined as a measure of cellular development. The indirect electrical stimulation was achieved through the use of a pulsed electromagnetic field (PEMF) while the mechanical strain was produced from dynamic stretching of a deformable cell substrate. Strain and strain rate were modelled from recent studies proposing that relatively high frequency, low strain osteogenic mechanical stimulants are more indicative of what healthy bone would be experiencing during normal activities. The PEMF signal mimicked a clinically available bone growth stimulator signal. Results showed a PEMF stimulus on monolayers of SaOS-2 and MG-63 osteoblast-like cells leads to a depression in proliferation. A concomitant increase in alkaline phosphatase production was also observed for the SaOS-2 cultures, but not for the MG-63 cell line. It was hypothesised that this was due to the MG-63's lack of phenotypic maturity compared to the SaOS-2 cells. Mechanical strain of the cell substrate alone, at a relatively high frequency (5Hz) but small strain, did not significantly effect either cell proliferation or differentiation for the MG-63 cells. However, when the electrical and mechanical stimulants were combined a significant increase in cellular differentiation occurred with MG-63 cultures, revealing a possible synergistic effect of these two stimulants on the development of bone cells.

Mechanical loading is crucial in modulating the physiology and architecture of bone. Previous experiments indicated intercellular communication among osteoblasts upon mechanical stimulation, suggesting the involvement of a soluble signal mediator. Extracellular adenosine triphosphate (ATP) functions as signaling molecules in many cell regulation processes, therefore appears to be a prone candidate. ATP acts on osteoblasts through multiple P2 receptors. To provide insights on the roles of individual receptors, we modeled ATP concentration dependence for different P2 receptors. Next, the process of ATP degradation and the diffusion of ATP, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) are modeled. To confirm the predictions of the model, we initiated experiments to measure ATP release from mechanically stimulated osteoblasts. Firefly luciferase assay successfully measures ATP using a luminometer and a charge coupled device (CCD) camera. Local indentation with a AFM cantilever is applied to mechanically stimulate an osteoblast. Preliminary results on real time imaging of ATP release from osteoblasts are reported.
Le chargement mécanique est crucial dans la modulation de la physiologie et de l'architecture de l'os. Des expériences antérieures ont indiqué la communication intercellulaire entre les ostéoblastes lors de la stimulation mécanique. Ces résultats suggèrent l'implication d'un médiateur soluble. L'adénosine triphosphate (ATP) extracellulaire fonctionne comme des molécules de signalisation dans de nombreux processus de régulation cellulaire. Celle-ci semble être un candidat à risque. L'ATP agit sur les ostéoblastes via les récepteurs P2. Ici, la concentration d'ATP pour chacun de ces récepteurs P2 a été modélisée mathématiquement pour mieux comprendre leur rôle. Le processus de dégradation de l'ATP et la diffusion de l'ATP, adénosine diphosphate (ADP) et adénosine monophosphate (AMP) ont aussi été modélisés. Avec le luminomètre, nous étions capables de mesurer avec succès l'ATP par dosage de la luciférase de luciole. Des images de haute résolution de la détection d'ATP ont été obtenues avec un dispositif à transfert de charge (CCD). Enfin, l'indentification locale avec une pointe de microscopie à force atomique (MFA) est appliquée mécaniquement pour stimuler un ostéoblaste. Les résultats préliminaires sur l'imagerie en temps réel de la libération d'ATP à partir d'ostéoblastes sont présentés.

Living cells, depending on their physiological functions, are subjected to a variety of mechanical stimulation. The magnitude and frequency of such mechanical stimulation varies dramatically in different organs. Oscillatory mechanical stimulation at relatively high frequancies, as occurs in walking, respiration and circulation, is one of the most extensively studied schemes. However, the stimulation at extremely low frequencies is rarely examined. This research investigates the effects of relatively low frequency mechanical stimulation in molecular scale, on different cell types. Throughout the work presented in this document, the emphasis was on the stem cells differentiation, and primary cells dedifferentiation. The results suggested that performing extremely slow activities, namely low frequency movements, significantly affects the differentiation pathways of stem cells. In addition, it was found that slow movement of surface culture area enhances phenotypical characteristics of primary cells.
Toutes les cellules vivantes, selon leur fonctions physiologiques, sont soumises à différentes stimulations mécaniques. L'ampleur et la fréquence de ces stimulations mécaniques varies considérablement d'un organe à un autre. Les stimulations oscillantes dues notamment à la marche, la respiration et la circulation sanguine sont largement étudiées. Par contre, les travaux concernant les stimulations a très faibles fréquences sont rare. Cette recherche examine les effets sur différents types de molécules, des stimulations mécaniques à relativement basse fréquence, à l'échelle moléculaire. Tout au long du travail présenté ici, l'accent a été mis sur la différenciation des cellules souches et la dedifférenciation des cellules primaires. Les résultats suggèrent que la pratique d'activités extrêmement lentes, à savoir les mouvements à basse fréquence, affectent, de manière significative, le mécanisme de différentiation des cellules souches. En outre, il a été constaté que les mouvements lents à la surface des cultures améliorent les caractéristiques phénotypiques des cellules primaires.

Clinical treatments based on electrical stimulation of excitable cells have been efficacious for a variety of diseases. However, these devices are often limited by their bulkiness, need for wiring electrodes and inability to target specific cells. Implantable devices that can directly convert optical or magnetic energy to localized electrical output to actuate cells are promising alternatives. This thesis focused on the development of opto-electric and magneto-opto-electric nanomaterials for wireless cell stimulation. Currently, the opto-electric stimulators usually require low penetration visible light and high intensities, the magneto-electric stimulators usually provide poor spatial and temporal precision. In this thesis, two types of nanomaterials have been developed to overcome these challenges. The first nanomaterial was based on Si/Au nanopillars to achieve opto-electric stimulation in the first and second NIR biological windows with ultralow light intensities. We started with the rational design and analysis, the FDTD simulations predicted that Si nanopillars capped by Au nanodiscs exhibited 6-fold enhancement of the light absorption compared with the plain Si wafer, such enhancement is due to the excitation of novel hybrid metal/dielectric resonances. Next, an exhaustive experimental opto-electric-chemical analysis of Si/Au nanostructures was presented. In particular, the short Si/Au nanopillars gave the highest opto-electric performance, achieving a photovoltage of 80 mV at ultralow light intensity of 0.44 µW/mm2, showing a frequency window of 50-200 Hz to maximize the photovoltage and photocurrent. Finally, the biocompatibility of the Si/Au nanostructures was validated by cell viability assays. The second nanomaterial was composed of arrays of hollow FeGa/ZnO nanodomes integrated onto soft, flexible and biocompatible elastomeric film. The proposed magneto-electric stimulation is based on the magnetostriction of FeGa and the piezoelectricity of ZnO, the opto-electric stimulation is based on the NIR light absorption of FeGa and the pyroelectric response of ZnO. The magnetic behaviour results revealed that the hexagonal-close-packed arrays with 400 nm diameter provided the lowest saturation magnetic field and minimal remanence. The photothermal test showed intense optical heating for light wavelengths of 808 nm and 1064 nm. The biocompatibility was proved by evaluating the bone Saos-2 cells viability. Therefore, the Si/Au and FeGa/ZnO nanoactuators present new platforms for wireless cell modulation through NIR light and magnetic field, which may be broadly applicable to both fundamental biological studies and clinical therapeutics.
Los tratamientos clínicos basados en la estimulación eléctrica de células excitables han sido eficaces y ampliamente utilizados para una variedad de enfermedades. Sin embargo, estos dispositivos a menudo están limitados por su volumen, la necesidad de electrodos con cableado externo y la incapacidad de actuar en células específicas. Los dispositivos implantables que pueden convertir la energía óptica o magnética en estímulos localizados eléctricos o térmicos para activar las células, son alternativas prometedoras. Esta tesis se centró en el desarrollo de nanomateriales opto-eléctricos y magneto-opto-eléctricos para la estimulación celular inalámbrica. Actualmente, los estimuladores opto-eléctricos generalmente requieren luz visible de baja penetración y altas intensidades, y los estimuladores magnetoeléctricos generalmente proporcionan una precisión espacial y temporal deficiente. En esta tesis, se han desarrollado dos tipos de nanomateriales para superar estos desafíos. El primer nanomaterial se basó en nanopilares Si/Au para lograr la estimulación opto-eléctrica en la primera y segunda ventanas biológicas del infrarrojo cercano con intensidades de luz ultrabajas. Las simulaciones teóricas predijeron que los nanopilares de Si coronados por nanodiscos Au exhiben una mejora de 6 veces en la absorción de luz en comparación con la oblea de Si simple. Tal mejora se debe a la excitación de nuevas resonancias híbridas de metal/dieléctrico. A continuación, se presentó un exhaustivo análisis experimental opto-eléctrico-químico de los nanopilares de Si/Au. Los nanopilares cortos de Si/Au dieron el mayor rendimiento opto-eléctrico, logrando un fotovoltaje de 80 mV a una intensidad de luz ultrabaja de 0,44 µW/mm2, que fue 11 veces mayor que la oblea p-n Si simple. La fotocorriente también mostró una mejora sustancial de 2.5 veces, mostrando una combinación de corrientes capacitivas y faradaicas inducidas por la luz que pueden ajustarse con la densidad de los nanopilares Si/Au. Además, los nanopilares cortos de Si/Au mostraron una ventana de frecuencia de 50-200 Hz para maximizar la fotovoltaje y la fotocorriente. Finalmente, la biocompatibilidad de las nanoestructuras Si/Au fue validada por ensayos de viabilidad celular. El segundo nanomaterial estaba compuesto por matrices de nanocúpulas huecas de FeGa/ZnO integradas en una película elastomérica flexible y biocompatible. La estimulación magnetoeléctrica propuesta se basa en la magnetostricción del FeGa y la piezoelectricidad del ZnO. La estimulación optoeléctrica se basa en la absorción de luz infrarroja por el FeGa y la respuesta piroeléctrica del ZnO. Los resultados del comportamiento magnético revelaron que las matrices hexagonales empaquetadas con un diámetro de 400 nm proporcionaron el campo magnético de saturación más bajo y una remanencia mínima. El análisis fototérmico mostró un intenso calentamiento óptico para longitudes de onda de luz de 808 nm y 1064 nm. La biocompatibilidad se demostró evaluando la viabilidad de las células Saos-2 óseas. En conclusión, los actuadores celulares nanoestructurados de Si/Au y FeGa/ZnO constituyen nuevas plataformas para la modulación electrofisiológica inalámbrica mediante luz infrarroja y campo magnético. Mirando hacia el futuro, son prometedores como nanoactuadores inyectables e implantables in vivo debido a las posibles optimizaciones, como la fabricación en sustratos flexibles y la funcionalización de su superficie para su unión a tipos celulares específicos, que podrían ser ampliamente aplicables tanto a los estudios biológicos fundamentales como a terapias clínicas.

Transcranial magnetic stimulation (TMS) is a modern non invasive method of drug resistant psychiatric disorder treatment. TMS physiology research is hindered by variable, often controversial results. In most studies main attention is being focused on immediate effects after single TMS procedure rather than the influence of a complete therapy course. It is considered that variability of results in TMS practice is caused by different stimulation parameters and imprecision of stimulated area placement in the brain. Although TMS therapy is often viewed as a milder alternative to electroconvulsive therapy (ECT), comparative physiological studies of these two methods are very rare. The aim of this study was to evaluate the effect of rTMS therapy course on bioelectrical brain activity and compare it to an ECT effect. Research included the effect of high and low frequency (10 Hz and 1 Hz) TMS on EEG band power spectrum and auditory evoked potential P300, using both standard and neuronavigated target positioning. TMS evoked EEG changes were also compared to the changes of ECT. Change dynamics after several months of TMS therapy were also measured. Results showed that after TMS therapy the most notable change in the brain occurs in the form of delta power increase. When using standard positioning 10 Hz TMS evokes more diverse and intense EEG band power spectrum changes than the 1 Hz TMS. Application of neuronavigation system decreases theta and alpha band power changes in 10 Hz TMS... [to full text]
Transkranijinė magnetinė stimuliacija (TMS) – tai modernus neinvazinis vaistams rezistentiškų psichiatrinių sutrikimų gydymo būdas. Fiziologiniai TMS tyrimai pasižymi įvairiais, dažnai prieštaringais rezultatais, daugeliu atvejų didžiausias dėmesys skiriamas betarpiškiems poveikiams po vienos TMS procedūros, bet ne po pilno terapinio kurso. Manoma, kad rezultatų įvairovę TMS praktikoje įtakoja skirtingi stimuliacijos parametrai ir netikslumai parenkant stimuliuojamą zoną smegenyse. Nors TMS terapija dažnai traktuojama kaip švelnesnė alternatyva elektros impulsų terapijai (EIT), palyginamųjų fiziologinių šių metodikų tyrimų labai trūksta. Darbo tikslas buvo įvertinti TMS terapijos kurso poveikį bioelektriniam galvos smegenų aktyvumui ir palyginti jį su EIT terapijos poveikiu. Buvo tirta aukšto ir žemo dažnių (10 Hz ir 1 Hz) TMS terapijos įtaka EEG dažnių galios spektrui bei sukeltiniam klausos potencialui P300, naudojant standartinį ir neuronavigacinį taikinio pozicionavimą. TMS sukelti EEG pokyčiai palyginti su EIT terapijos sukeltais EEG pokyčiais, išmatuota TMS terapijos sąlygotų pokyčių dinamika kelių mėnesių bėgyje. Rezultatai parodė, kad TMS terapijos pasekoje smegenyse ryškiausiai padidėja delta dažnio galia. Naudojant standartinį pozicionavimą 10 Hz TMS sukėlė įvairesnius ir intensyvesnius EEG galios spektro pokyčius nei 1 Hz TMS. Pritaikius neuronavigacinę sistemą 10 Hz TMS atveju sumažėjo teta ir alfa dažnių galios pokyčiai. Praėjus keliems mėnesiams nuo TMS... [toliau žr. visą tekstą]

Nipah belongs to the family of paramyxoviruses that cause numerous fatal diseases in humans and farm animals. There are no FDA approved drugs for Nipah or any of the paramyxoviruses. Designing antiviral therapies that are more resistant to viral mutations require understanding of molecular details underlying infection. This dissertation focuses on obtaining molecular insights into the very first step of infection by Nipah. Such details, in fact, remain unknown for all paramyxoviruses. Infection begins with the allosteric stimulation of Nipah virus host binding protein by host cell receptors. Understanding molecular details of this stimulation process have been challenging mainly because, just as in many eukaryotic proteins, including GPCRs, PDZ domains and T-cell receptors, host receptors induce only minor structural changes (< 2 Å) and, consequently, thermal fluctuations or dynamics play a key role. This work utilizes a powerful molecular dynamics based approach, which yields information on both structure and dynamics, laying the foundation for its future applications to other paramyxoviruses. It proposes a new model for the initial phase of stimulation of Nipah’s host binding protein, and in general, highlights that (a) interfacial waters can play a crucial role in the inception and propagation of allosteric signals; (b) extensive inter-domain rearrangements can be triggered by minor changes in the structures of individual domains; and (c) mutations in dynamically stimulated proteins can induce non-local changes that spread across entire domains.

The principle calcium regulator in the muscle cell is the calcium ion release channel (RyR). Improper calcium homeostasis in the muscle cell is the foundation of many pathological states and has been targeted as a contributing factor to ventricular tachycardia, which is known to precede sudden cardiac arrest. Numerous endogenous and exogenous compounds can affect the way RyR regulates calcium. In this study the anthocyanidin Pelargonidin (Pg), an important natural colorant and dietary antioxidant, is evaluated for its effect on regulating the transport of calcium through the RyR1 of skeletal muscle sarcoplasmic reticulum. Pelargonidin undergoes time dependent structural changes in aqueous solutions at physiological pH and a mixture of up to seven forms of Pelargonidin are present in solution simultaneously. Pelargonidin is a unique RyR1 modulator. It can both stimulate and inhibit the RyR1 depending on the experimental conditions. In addition, when Pelargonidin is irradiated with white light, its inhibition properties on the RyR1 are essentially nullified. Proposed mechanisms include excited state charge shift within RyR1-Pg complexes.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xv, 192 p.; also includes graphics (some col.). Includes bibliographical references (p. 183-192). Available online via OhioLINK's ETD Center

Transkranijinė magnetinė stimuliacija (TMS) – tai modernus neinvazinis vaistams rezistentiškų psichiatrinių sutrikimų gydymo būdas. Fiziologiniai TMS tyrimai pasižymi įvairiais, dažnai prieštaringais rezultatais, daugeliu atvejų didžiausias dėmesys skiriamas betarpiškiems poveikiams po vienos TMS procedūros, bet ne po pilno terapinio kurso. Manoma, kad rezultatų įvairovę TMS praktikoje įtakoja skirtingi stimuliacijos parametrai ir netikslumai parenkant stimuliuojamą zoną smegenyse. Nors TMS terapija dažnai traktuojama kaip švelnesnė alternatyva elektros impulsų terapijai (EIT), palyginamųjų fiziologinių šių metodikų tyrimų labai trūksta. Darbo tikslas buvo įvertinti TMS terapijos kurso poveikį bioelektriniam galvos smegenų aktyvumui ir palyginti jį su EIT terapijos poveikiu. Buvo tirta aukšto ir žemo dažnių (10 Hz ir 1 Hz) TMS terapijos įtaka EEG dažnių galios spektrui bei sukeltiniam klausos potencialui P300, naudojant standartinį ir neuronavigacinį taikinio pozicionavimą. TMS sukelti EEG pokyčiai palyginti su EIT terapijos sukeltais EEG pokyčiais, išmatuota TMS terapijos sąlygotų pokyčių dinamika kelių mėnesių bėgyje. Rezultatai parodė, kad TMS terapijos pasekoje smegenyse ryškiausiai padidėja delta dažnio galia. Naudojant standartinį pozicionavimą 10 Hz TMS sukėlė įvairesnius ir intensyvesnius EEG galios spektro pokyčius nei 1 Hz TMS. Pritaikius neuronavigacinę sistemą 10 Hz TMS atveju sumažėjo teta ir alfa dažnių galios pokyčiai. Praėjus keliems mėnesiams nuo TMS... [toliau žr. visą tekstą]
Transcranial magnetic stimulation (TMS) is a modern non invasive method of drug resistant psychiatric disorder treatment. TMS physiology research is hindered by variable, often controversial results. In most studies main attention is being focused on immediate effects after single TMS procedure rather than the influence of a complete therapy course. It is considered that variability of results in TMS practice is caused by different stimulation parameters and imprecision of stimulated area placement in the brain. Although TMS therapy is often viewed as a milder alternative to electroconvulsive therapy (ECT), comparative physiological studies of these two methods are very rare. The aim of this study was to evaluate the effect of rTMS therapy course on bioelectrical brain activity and compare it to an ECT effect. Research included the effect of high and low frequency (10 Hz and 1 Hz) TMS on EEG band power spectrum and auditory evoked potential P300, using both standard and neuronavigated target positioning. TMS evoked EEG changes were also compared to the changes of ECT. Change dynamics after several months of TMS therapy were also measured. Results showed that after TMS therapy the most notable change in the brain occurs in the form of delta power increase. When using standard positioning 10 Hz TMS evokes more diverse and intense EEG band power spectrum changes than the 1 Hz TMS. Application of neuronavigation system decreases theta and alpha band power changes in 10 Hz TMS... [to full text]

En réponse à une stimulation sonore, la cellule ciliée interne libère du glutamate qui va activer des récepteurs distribués sur le bouton post-synaptique. Les courants post-synaptiques vont ensuite dépolariser la terminaison périphérique des neurones auditifs primaires, et initier le déclenchement d'un potentiel d'action. Tandis que la connaissance des mécanismes pré-synaptiques a considérablement progressé ces 10 dernières années, les mécanismes responsables de l'initiation des potentiels d'action sont encore méconnus. Dans cette étude, nous avons déterminé les conductances ioniques nécessaires au déclenchement des potentiels d'action. Les paramètres biophysiques des conductances (Na et K) ont été identifiés (algorithme d'identification trace entière) à partir d'enregistrements de patch clamp acquis sur les corps cellulaires. Un modèle mathématique de nœud de Ranvier a ensuite été développé en faisant l'hypothèse que les canaux présents sur le corps cellulaire et sur un nœud de Ranvier étaient de même nature mais en densités différentes. Les paramètres de ce modèle ont été identifiés pour reproduire les potentiels d'action extracellulaire au moyen d'un algorithme de descente du gradient. Nous avons identifié i) un courant Na entrant rapide (GNa activation: V1/2=-33 mV, act< 0.5 ms; inactivation: V1/2=-61 mV, inact < 2 ms) et deux courants K sortants, un rectifiant retardé activé à haut seuil (GKH, activation: V1/2=-41 mV; act < 2.5 ms) et un activé à bas seuil (GKL, activation: V1/2=-56 mV; act < 5 ms). Le modèle de nœud de Ranvier génère des potentiels d'action extracellulaire similaires à ceux enregistrés in vivo. La différence de durée du potentiel d'action observée le long de l'axe tonotopique (i.e. 450 µs de durée pic à pic à 1 kHz contre 250 µs à 20 kHz) s'explique parfaitement par un gradient de densité en canaux ioniques le long de la cochlée (GNa~78 nS, GKL~9 nS, GKH~3 nS à 1 kHz contre GNa~90 nS, GKL~12 nS, GKH ~6 nS à 20 kHz). Cette étude a permis d'identifier les conductances ioniques et les densités de canaux responsables de l'initiation des potentiels d'action dans les neurones auditifs primaires. Elle suggère que la coopération entre le courant Na et des 2 courants K est probablement à l'origine de la haute fréquence de décharge de ces neurones. Le modèle de nœud de Ranvier permet en outre de tester de nouvelles stratégies de stimulation électrique dans le contexte de l'implant cochléaire.

In summary, the biomechanical stimulations can augment osteotendinous healing processes by facilitating better fibrocartilagious transitional zone regeneration as well as the restoration of proprioceptions, and the early application showed the more beneficial effects. However, further experimental and clinical studies are still needed to explore the optimal timing, intensity, frequency, and duration of the proposed postoperative biomechanical stimulation protocols.
LIPUS is a "non-contact" biomechanical stimulation, which can provide a direct mechanical stimulation through cavitation and acoustic microstreaming effects to improve tissue healing in a less-than-rigid biomechanical environment. So the mechanical stimulation induced from LIPUS could be applied immediately after surgery without worrying about the mechanical strain exceed the structural property at the osteotendinous healing interface in the early phase of repair. In this part of study, we also examined the effects of the regime of biomechanical stimulations applying immediately after repair on the osteotendinous healing interface. By using the same healing junction model, forty-two female New Zealand white rabbits were randomly divided into two groups; daily mechanical stimulation was applied immediately after surgery lasting up to post-operative 12 weeks on the healing interface in the treatment group. The regime of mechanical stimulations included by LIPUS was 20 minutes, 5 days per week for 4 weeks, followed by cyclic mechanical stimulation generated from quadriceps muscles induced by FES for 8 weeks. Results showed that early application of biomechanical stimulations on the osteotendinous healing interface were significantly better radiologically, histologically and biomechanically than that of not any or later application of the biomechanical stimulations during the osteotendinous healing processes when assessing at the same healing time point. In addition, the early application of biomechanical stimulations showed the better functional recovery in terms of the restoration of the proprioceptions, which an increased numbers of sensory nerve endings labeled by calcitonin gene-relate peptide (CGRP) was detected in the whole osteotendinous healing complex.
Sports or trauma injuries around osteotendinous junctions are common; treatments usually require surgical reattachment of the involved tendon to bone. Restoration of osteotendinous junction after repair is slow and difficult due to regenerating the intermitted fibrocartilage zone to connect two different characteristic tissues, tendon to bone. Although the factors influencing fibrocartilage zone regeneration and remodeling during osteotendinous repair are poorly understood, however, is believed that the mechanical environment plays an important role in such healing process. In present study, the effects of mechanical stimulation on osteotendinous healing process were examined, in the way of mechanical stimulations induced by biophysical stimulations, surface functional electric stimulation (FES) and low intensity pulsed ultrasound (LIPUS), applying on the patellar tendon to patellar bone healing interface in an established partial patellectomy model in rabbits.
The mechanotransductive stimulation linked to the transmission of forces across osteotendinous junction can be generated from its muscle contraction induced by FES. In the partial patellectomy model, thirty-five female New Zealand white rabbits were randomly divided into two groups with initial immobilization for 6 weeks, daily FES was applied to quadriceps muscles for 30 minutes, 5 days per week for 6 weeks in treatment group and compared with non-treatment control group at postoperative week 6, 12 and 18, radiologically, histologically and biomechanically. Results showed that FES-induced cyclic mechanical stimulation significantly increased new bone formation and its bone mineral density. An elevated expression of tenascin C and TGFbeta1; an increased proteoglycant stainability; mature fibrocartilage zone formation with better resumptions of biomechanical properties also observed on the osteotendinous healing interface, indicating that the post-operative programmed cyclic mechanical stimulation generated from its muscle contraction has beneficial effects on osteotendinous healing processes by facilitating the fibrocartilagious transitional zone regeneration.
by Wang Wen.
Advisers: Kai Ming Chan; Ling Qin.
Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1550.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 159-175).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.

World health organization (WHO) has recognized multiple degenerative diseases as the leading causes of mortality, globally. The drugs-based clinical treatment of chronic degenerative diseases such as multiple sclerosis, Parkinson’s disease, osteoarthritis, muscular dystrophy, etc., has been accomplished with limited success. In this perspective, “stem cell-based regenerative engineering” provides a new treatment option to repair and regenerate the damaged tissue or organ. Stem cells have the unique capability to replicate themselves (self-renewal) unless they are provided with specific external factors (i.e., biochemical, and biophysical). Among various biophysical signals, the efficacy of electrical stimulation, substrate stiffness, and conductivity have been demonstrated to direct stem cell differentiation. In the present thesis, cellular differentiation has been regulated using biophysical signals on multifunctional biomaterials. The multifunctional biomaterials provide a ‘smart’ platform to deliver biophysical cues to direct stem cell differentiation. The electrical stimulation on conducting polymer (polyvinylidene difluoride, PVDF reinforced with multiwall carbon nanotubes) guided the stem cells towards neuron-like and glial-like cells. The strategy to differentiate stem cells towards functional neurons has future implications in stem cell therapy to treat neurodegenerative diseases. Also, the conducting polymeric biomaterials, developed in the present dissertation, can be further developed into an artificial nerve conduit and nerve patch to repair the damaged nerve tissues. To address the osteoarthritis-related clinical challenges, bone and cartilage mimicking polymer composites have been developed in this thesis. The electrical stimulation on a bone-mimicking polymeric platform (PVDF reinforced with Barium Titanate) induced the differentiation of stem cells towards bone-like cells. The continuous electrical signal generated higher stresses in stem cells, while the non-continuous alternative electrical signal exhibited differentiation without causing cellular stress. The bone-mimicking PVDF composite has the potential to be used as an acetabular liner in total-hip-joint replacement. The electrical stimulation technology can be translated to induce a faster bone healing with an upregulated ability of osseointegration of synthetic polymer implant. Furthermore, a novel hybrid bilayer composite with elastically stiff and compliant (soft) polymeric matrices has been fabricated to mimic the osteochondral tissue (interfacial tissue of bone and cartilage). The upregulated activity of bone cells on the elastically stiff layer and maturation of cartilage cells on the elastically compliant layer demonstrates the efficacy of the bilayer construct to repair the osteochondral defect. The modulated osteochondral functionalities on the elastically stiff and compliant substrate also revealed the role of substrate stiffness to direct cellular differentiation. Taken together, the present thesis conclusively establishes the efficacy of external biophysical signals to direct cellular differentiation using multifunctional biomaterial platforms for neural and osteochondral regeneration.

Σκοπός της παρούσας διατριβής ήταν να μελετηθεί η επίδραση του μηχανικού-ακουστικού ερεθισμού στη βιοφυσική εικόνα του εμβρύου με μια προοπτική τυχαιοποιημένη μελέτη Το υλικό της μελέτης απετέλεσαν γυναίκες με μονήρεις κυήσεις, ηλικία κύησης 30 + 0 εβδομάδες και βιοφυσική εικόνα ≤ 8/10. Οι γυναίκες με τυχαίο τρόπο κατατάσσονταν σε μια από δύο ομάδες. Στην ομάδα Α εφαρμοζόταν ακουστικός ερεθισμός διάρκειας 3 δευτερολέπτων με ένα τεχνητό λάρυγγα. Αν η βιοφυσική εικόνα παρέμενε μη φυσιολογική για 30 λεπτά, ακολουθούσε η εφαρμογή ενός δεύτερου ερεθίσματος, ίδιου με το πρώτο και εκτίμηση της βιοφυσικής εικόνας για ακόμη 30 λεπτά. Στην ομάδα Β ο χρόνος παρατήρησης παρατάθηκε για 60 λεπτά (δύο διαστήματα των 30 λεπτών) , ώστε να συμφωνεί με το χρόνο εξέτασης των γυναικών της ομάδας Α. Οι κυήσεις αντιμετωπίστηκαν με βάση την τελική βαθμολογία της βιοφυσικής εικόνας. Όσες γυναίκες γέννησαν περισσότερο από 24 ώρες από την τελευταία εξέταση δεν περιελήφθησαν στη μελέτη. Τα κριτήρια αξιολόγησης ήταν ενδομήτριος θάνατος, καισαρική τομή για εμβρυϊκή δυσπραγία, βαθμολογία Apgar < 7 στα 5 λεπτά από τον τοκετό, κεχρωσμένο αμνιακό υγρό (από μηκώνιο) και εισαγωγή στη ΜΕΘ νεογνών. Η μηδενική υπόθεση ήταν ότι η εφαρμογή του ακουστικού ερεθισμού δεν μεταβάλλει τις στατιστικές παραμέτρους της δοκιμασίας. Συνολικά 2,833 γυναίκες εισήλθαν στη μελέτη και συγκεκριμένα 1,349 στην ομάδα Α και 1,484 στην ομάδα Β. Η εφαρμογή του ακουστικού ερεθισμού μείωσε σημαντικά τον αριθμό των θετικών δοκιμασιών στην ομάδα Α σε σχέση με την ομάδα Β (4.74% vs. 6.67%, p < 0.05) και αύξησε την επίπτωση των κριτηρίων αξιολόγησης στην υποομάδα των γυναικών με θετική τελική δοκιμασία (positive likelihood ratio: 24.1-CI 95%: 11.12-52.46 vs. 7.52-CI 95%: 4.93-11.46), χωρίς να τροποποιεί το περιγεννητικό αποτέλεσμα. Επιπλέον, η ειδικότητα, η θετική προγνωστική αξία και η ακρίβεια της μεθόδου βελτιώθηκαν σημαντικά στην ομάδα Α,όπως επίσης και η αρνητική προγνωστική αξία για τους ενδομήτριους θανάτους. Συμπερασματικά, η εφαρμογή του μηχανικού-ακουστικού ερεθισμού σε περιπτώσεις που υπάρχει υποψία για εμβρυϊκή δυσπραγία, βελτιώνει την αποτελεσματικότητα της μεθόδου (βιοφυσικής εικόνας), μειώνοντας τις ψευδώς θετικές δοκιμασίες και βελτιώνοντας την ακρίβεια της μεθόδου. Θα πρέπει δε να θεωρείται ως μέσο μιας πιο ενδελεχούς εμβρυϊκής εκτίμησης σε αυτές τις περιπτώσεις.
OBJECTIVES: To verify the effect of vibroacoustic stimulation on biophysical profile score, with a prospective randomised study. STUDY DESIGN: All women with singleton pregnancy, gestational age ≥ 30 weeks, intact membranes and biophysical profile score ≤ 8/10 entered the study, after giving written consent, and were randomised to two groups. In group A, a 3-second stimulus with an artificial larynx was applied; if biophysical profile remained abnormal for 30 minutes, a second stimulus was applied, and it was assessed again. In group B the observation time was extended for 60 minutes to match the time periods of group A. Pregnancies were managed by final test score and patients delivering more than 24 hours apart from last examination were disregarded from the study. Outcome criteria were intrauterine deaths, caesarean sections for fetal distress, Apgar score < 7 at 5 minutes postpartum, meconium-stained amniotic fluid and neonatal intensive care unit admissions. Our null hypothesis was that application of vibroacoustic stimulation does not alter test’s statistical parameters. RESULTS: 1,349 patients were randomised in group A, and 1,484 in group B (2,833 in total). When comparing group A to B, application of vibroacoustic stimulation significantly decreased the number of positive tests (4.74% vs. 6.67%, p < 0.05) and increased the prevalence of outcome criteria in this subgroup (positive likelihood ratio: 24.1-CI 95%: 11.12-52.46 vs. 7.52-CI 95%: 4.93-11.46), without altering perinatal outcome. Furthermore, specificity, positive predictive value and test accuracy were significantly improved, as well as negative predictive value for intrauterine death. CONCLUSION: Vibroacoustic stimulation improves the efficiency of biophysical profile score by decreasing false positive tests and improving test accuracy and should be considered as a means of a more thorough fetal evaluation when fetal compromise is suspected.

The adaptation of bone to mechanical loading is very poorly understood at the molecular genetic level. Little is known of gene expression in bone following mechanical stimulation primarily because of a lack of in vivo data. While the calcified extracellular matrix provides bone with its mechanical strength, it also makes the analysis of genetic information difficult. A new method has been developed which can extract high quality RNA from intact bone. This new technique enables the use of the Sprague Dawley rat to study the in vivo regulation of skeletal gene expression The tibia of fifteen skeletally mature female rats were subjected to either a dynamic four point bending stimulation or parathyroid hormone (PTH) stimulation. The animals were sacrificed within a twenty-four hour period following stimulation. The RNA within the tibia was extracted with the novel method and examined by Northern blot analysis. The constitutive expression of mRNA transcripts coding for transforming growth factor-beta 1 (TGF-$\beta$1) and $\alpha$-1 collagen I (COL I $\alpha$-1) were observed. Densitometric examinations demonstrated that over the first 24 hours, there was down regulation of TGF-$\beta$1 mRNA following mechanical stimulation (p = 0. 005). The TGF-$\beta$1 mRNA was maximally depressed at 1 hour and increased gradually over the remaining twenty-four hours. PTH seemed to cause a similar down regulation of TGF-$\beta$1 mRNA but no significance was reached (p = 0.097) To better quantify transcriptional differences, an internal control gene, ribosomal protein S3 (RPS3), was selected. RPS3 is transcribed at a steady state rate and can therefore be used to normalize other mRNA levels. With this technique, a six fold increase in COL I $\alpha$-1 mRNA transcripts was observed twelve hours following stimulation with PTH (p =.006) The constitutive expression of TGF-$\beta$1 and COL I $\alpha$-1 in bone in vivo are significant new pieces of molecular genetic information. TGF-$\beta$1 and COL I $\alpha$-1 are factors known to be involved in the process of bone formation. The fact that they are always present indicates that their in vivo regulated expression may prove helpful in our understanding of the mechanisms of human bone formation
acase@tulane.edu

The Deep Brain Stimulation (DBS) is a successful clinic technique in reducing symptoms of Parkinson's disease. However the underlying mechanisms of action are still largely unknown. In order to evaluate an accurate calculation of the electric quantities induced by the stimulation inside the brain structures, we have developed an 2-D and an 3-D dosimetric model, encompassing the anatomic structures affected by neural stimulation, the surrounding environment, and the stimulating electrode. The dosimetric model has been used to predict the effect of the stimulation on neuronal fibers and for an exact quantification of the fundamental electrical quantities inside the anatomical target. This exogenous quantities become an input for the biophysical neuronal model in order to evaluate the neuronal response. Moreover, a bi-compartimental biophysical model has been developed, exhibiting a good match with the experimental recordings of a sub-thalamic neuron (STN). In conclusion, dosimetric and biophysical models have been able to reproduce both experimental data of STN soma inhibition and STN axon excitation induced by DBS.

The Deep Brain Stimulation (DBS) is a successful clinic technique in reducing symptoms of Parkinson's disease. However the underlying mechanisms of action are still largely unknown. In order to evaluate an accurate calculation of the electric quantities induced by the stimulation inside the brain structures, we have developed an 2-D and an 3-D dosimetric model, encompassing the anatomic structures affected by neural stimulation, the surrounding environment, and the stimulating electrode. The dosimetric model has been used to predict the effect of the stimulation on neuronal fibers and for an exact quantification of the fundamental electrical quantities inside the anatomical target. This exogenous quantities become an input for the biophysical neuronal model in order to evaluate the neuronal response. Moreover, a bi-compartimental biophysical model has been developed, exhibiting a good match with the experimental recordings of a sub-thalamic neuron (STN). In conclusion, dosimetric and biophysical models have been able to reproduce both experimental data of STN soma inhibition and STN axon excitation induced by DBS.