Human soleus H-reflex gain was measured in supine lying and in standing vertically while stabilised by a backboard. H-reflex amplitude was less in stabilised standing than in supine lying. The reduction was partly due to the effect of gravitational load. When the same load was applied (by compression of the body between shoulders and feet) while lying supine the corresponding reduction was 70%. The results are discussed in relation to possible gravitational load receptors. In a second series of experiments a collapsible landing platform was used to differentiate between reflex and programmed contributions to EMG activity in landing from a jump. Post-landing activity of the calf muscles was a short latency spinal reflex triggered by ankle rotation. In the rectus femoris muscle, activity was programmed for short falls and had a reflex component in longer falls. When the collapsible platform caused a landing to occur at a time later than anticipated, reflex gain was increased in the gastrocnemius, biceps femoris and rectus femoris muscles. Experimental results were consistent with the time that would be required for descending pathways to modulate the reflex gain and an appropriate model is proposed.

No description available.

L’objectif de ce projet est d’étudier une nouvelle voie de thérapie basée sur l’échographie de contraste. Les agents de contraste utilisés sont capables de vectoriser différentes molécules chimiques et de les libérer lorsqu’ils sont détruits par le biais des ultrasons. Cette méthode permet donc un traitement ciblé et contrôlé ce qui a pour avantages de réduire la quantité de principe actif (donc des effets de secondaires). De plus, les microbulles augmentent la perméabilité cellulaire ou tissulaire donc améliore leur incorporation cellulaire. Cependant le mécanisme n’est pas connu. In vitro, nous avons utilisé un ensemble de techniques dont le patch clamp pour visualiser les échanges trans-membranaires et la TEER pour les modifications de la perméabilité trans-endothéliales. In vivo, nous avons effectué des ECG pour observer et comprendre les effets secondaires afin de mieux les prévenir. Le but de la thèse est d’aboutir à la connaissance du phénomène d’augmentation de la perméabilité induite par les ultrasons et les microbulles afin de pouvoir l’optimiser. / The aim of this work is to study a new way of therapy based on the contrast ultrasonography. The used contrast agents are able of transport different chemical molecules and to liberate them when they are destroyed by means of ultrasounds. This method allows a controlled and targeted treatment therefore what has as advantages to reduce drugs quantity (therefore side effects). Moreover, microbubbles augment cell or tissue permeability therefore ameliorates their cell uptake. However, the mechanism is not known. In vitro, we used the whole technology of which the patch clamp to show exchanges through the cell membrane and TEER for modification of trans-endothelial permeability. In vivo, we have performed ECG to notice and understand side effects to their apparition. The purpose of PhD work is to succeed to the knowledge of the phenomenon of increase of the permeability led by ultrasounds and microbubbles to be able to optimise it.

The focus of this work was to develop a deeper understanding of the mechanisms of flame stabilization and extinction for shear layer stabilized, premixed flames. Planar experimental studies were performed in the attachment point region of an inner shear layer stabilized flame in an annular, swirl combustor. Through high resolution, simultaneous PIV & CH-PLIF measurements, the instantaneous flow field and flame position was captured enabling the characterization of 2D flame stretch and velocity conditions in the attachment point region. In addition, measurements performed at various equivalence ratios and premixer velocities provided insight into the physics governing blowoff. Most notably, these studies showed that as lean blowoff conditions are approached by decreasing equivalence ratio, the mean stretch rates near the attachment point decrease but remain positive throughout the measurement domain. In fact, compared to numerically calculated extinction stretch rates, the flame becomes less critically stretched as equivalence ratio is decreased. Also, investigation of the flame structure at the leading edge of the flame showed strong evidence that the flame is edge flame stabilized. This was supported by inspection of the CH-PLIF images, which showed the CH-layer oriented tangent to the flow field and terminating abruptly at the leading edge. Lastly, the flame anchoring location was observed to be highly robust as the mean flame edge flow conditions and mean location of leading edge of the flame were insensitive to changes in equivalence ratio, remaining nearly constant for values ranging from 0.9 to 1.1. However, at the leanest equivalence ratio of 0.8, the flame leading edge was located farther downstream and subject to much higher flow velocities. These results thus suggest that blowoff is the result of a kinematic balance and not directly from stretch induced flame extinction.

The American alligator (Alligator mississippiensis) is an aquatic diving reptile with a periodic breathing pattern. Previous work has identified pulmonary stretch receptors (PSR), both rapidly- and slowly-adapting, and intrapulmonary chemoreceptors (IPCs) that modulate breathing patterns in alligators. The purpose of the present study was to identify the effects of prolonged lung inflation and deflation (simulated dives) on PSR and/or IPC firing characteristics in the alligator. The effects of airway pressure, hypercapnia, and hypoxia on dynamic and static responses of pulmonary stretch receptors (PSR) were studied in juvenile alligators (mean mass = 246 g) at 24°C. Receptor activity appeared to be a mixture of slowly-adapting PSRs (SARs) and rapidly-adapting PSRs (RARs) with varying thresholds and degrees of adaptation, but no CO2 sensitivity. Dives were simulated in order to character receptor activity before, during, and after prolonged periods of lung inflation and deflation. Some stretch receptors showed a change in dynamic response, exhibiting inhibition for several breaths after 1 min of lung inflation, but were unaffected by prolonged deflation. For SAR, the post-dive inhibition was inhibited by CO2 and hypoxia alone. These airway stretch receptors may be involved in recovery of breathing patterns and lung volume during pre- and post-diving behavior and apneic periods in diving reptiles. These results suggest that inhibition of PSR firing following prolonged inflation may promote post-dive ventilation in alligators.

"Mechanical loads play a pivotal role in the growth, maintenance, remodeling, and disease onset in connective tissues. Harnessing the relationship between mechanical signals and how cells remodel their surrounding extracellular matrix would provide new insights into the fundamental processes of wound healing and fibrosis and also assist in the creation of custom-tailored tissue equivalents for use in regenerative medicine. In 3D tissue models, uniaxial cyclic stretch has been shown to stimulate the synthesis and crosslinking of collagen while increasing the matrix density, fiber alignment, stiffness, and tensile strength in the direction of principal stretch. Unfortunately, the profound fiber realignment in these systems render it difficult to differentiate between passive effects and cell-mediated remodeling. Further, these previous studies generally focus on a single level of stretch magnitude and duration, and they also investigate matrix remodeling under a homogeneous strain conditions. Therefore, these studies are not sufficient to establish key information regarding stretch-dependent remodeling for use in tissue engineering and also do not simulate the complex mechanical environment of connective tissue. We first developed a novel in vitro model system using equibiaxial stretch on fibrin gels (early models of wound healing) that enabled the isolation of mechanical effects on cell-mediated matrix remodeling. Using this system we demonstrated that in the absence of in-plane alignment, stretch stimulates fibroblasts to produce a stronger tissue by synthesizing collagen and condensing their surrounding matrix. We then developed dose-response curves for multiple aspects of tissue remodeling as a function of stretch magnitude and duration (intermittent versus continuous stretch). Our results indicate that both the magnitude and the duration per day of stretch are important factors in mechanically induced cell activity, as evidenced by dose-dependent responses of several remodeling metrics in response to these two parameters (UTS, matrix stiffness, collagen content, cell number). In addition, we found that cellularity, collagen content, and resistance to tension increased when the tissues were mechanically loaded intermittently as opposed to continuously. Finally, we developed a novel model system that produces non-homogeneous strain distribution, allowing for the simultaneous study of strain gradients, strain anisotropy, and strain magnitude in 2D and 3D. Establishing a system that produces complex strain distributions provides a more accurate model of the mechanical conditions found in connective tissue, and also allows for the investigation of cellular adaptations to a changing mechanical environment. "

Polyethylene Terephthalate (PET) has become the preferred material of choice for many packaging applications. A preference over glass due to its low weight, similar transparency to glass and cost consideration, including the availability of recycled PET feedstock via kerbside collection has provided newer opportunities for hot-fill applications. Ostensibly, this material is used for beverage markets requiring cold and hot filling (85 oC) of liquid foods. However due to the poor thermal stability of PET - due to its low glass transition temperature - an increase in elevated temperatures limits the number of market segments the material can be utilised. Current practices incorporate the heat-set process, aimed at improving the crystallisation kinetics within the amorphous and crystalline region. This body of work incorporates a single stage Injection Stretch Blow Moulding machine (ISBM). Modifications to conventional carbonated soft drink (CSD) beverage containers to include heat-set capabilities are incorporated. The current research study investigates the potential benefits of RPET blends for improving thermal stability at elevated temperatures. This study investigates changes in mechanical properties which include • Youngs modulus, • top load strength, • burst strength, • Thermal analysis specifically investigating changes in • Glass transition temperature, • enthalpy changes due to heat-set conditions • Percentage crystallinity changes as a function of heat-set conditions Rheological characteristics to all materials used were investigates. Furthermore, changes in the physical properties to each PET beverage container were investigated which include; • process shrinkage (S1), • hot-fill shrinkage (S2) • Density changes via optimised DoE parameters. A combination of cold (80 oC) and hot moulds (150 oC) as measured via Forward Looking Infrared (FLIR) at the exterior to the blow mould and their affect on percentage crystallinity was studied. Preform surface temperature (PST) and strain induced crystallinity, assisting in molecular relaxation is analysed. Upon completion to an exhaustive experimental ISBM trial, a DoE software package - in this case Echip - was used to analyse and predict optimised hot-fill shrinkage values of 2.5 percent with a maximum constrained RPET blend value totalling 40 percent. ISBM optimised conditions demonstrated advantages when combining an increased preform surface temperature, RPET blends and optimised ISBM process conditions as indicated via the DoE at low heat-set temperatures.

The purpose of this research was to evaluate the effects of a long-term static stretching program on flexibility and spinal reflexes in the human soleus muscle. Day-to-day reliability over two days of H-reflex gain (Hslp/Mslp) and pre-synaptic inhibition of spinal reflexes in the human soleus was measured in an initial study. Thirty subjects (age=23.4 ± 3.9 yr, height=175.64 ± 10.87 cm, weight=84.5 ± 24.18 kg) with no history of lower leg pathology and/or injury within the previous 12 months volunteered. The slopes of the ascending portions of the H-reflex and M-wave recruitment curves were used to evaluate H-reflex gain (Hslp/Mslp). The mean soleus H-reflex from 10 conditioning stimulations and 10 unconditioned stimulations was used to calculate the amount of pre-synaptic inhibition. Measurements of H-reflex gain and pre-synaptic inhibition yielded test-retest reliability of R=.95 and R=.91, respectively. The contribution of pre-synaptic and post-synaptic reciprocal mechanisms in flexibility adaptations has not been measured during the same study. A long-term static stretching program (5 times per week for 6 weeks) of the soleus implemented within an experimental group of 20 subjects was used as an intervention to measure both spinal control flexibility changes. Additionally, 20 control subjects were measured that did not participate in the stretching program. Passive ankle dorsiflexion, Hmax/Mmax, H-reflex gain (Hslp/Mslp), pre-synaptic and post-synaptic reciprocal mechanisms were measured at baseline, 3 weeks, and 6 weeks for all 40 subjects. A 2 (Group) X 2 (Sex) X 3 (Time) mixed MANOVA with Tukey HSD with (a<0.05) was used. Only ROM had a significant interaction between Group and Time, whereas, a significant difference was not detected in the other dependent variables. The experimental group demonstrated significantly improved dorsiflexion ROM from baseline to 3 weeks (mean=6.2 ± .88, P<0.001), 3 weeks to 6 weeks (mean=4.9 ± .84, P<0.001), and baseline to 6 weeks (mean=11.2 ± .91, P<0.001). Consequently, the increase in flexibility by 42% after 30 stretching sessions was not the result of spinal reflex changes. / Graduation date: 2006

The increase in tissue extensibility and joint range of motion through stretching has often been demonstrated. However, the existence of an optimal stretch duration has not been proven and the identification of an ideal number of repetitions of a stretch has received little attention in the literature. The purpose of this study was to examine and clarify the relationship of duration and number of repetitions of a stretch and their effect on changes in hamstring extensibility (HE) resulting from a stretching program. The HE of 33 subjects who were randomly assigned to a control group or one of three treatment groups was assessed before and after a three-week stretching program. The subjects in the three treatment groups stretched once a day, five times a week, and either once for 15 seconds (1 X 15), twice for 15 seconds (2 X 15), or once for 30 seconds (1 X 30). A repeated measures ANOVA showed no statistically significant effect for treatment group (P=0.181) or for treatment by pre- and post-treatment measurements (P=0.140), but indicated a significant difference between pre- and post-treatment measurements (P<0.001). The HE of the control group (which did not stretch) changed only slightly (0.9��, SD 5.7), the 1 X 15 and 1 X 30 groups improved more clearly (4.2��, SD 3.1 and 3.8��, SD 6.7, respectively), and the 2 X 15 group's HE increased the most (6.8��, SD 3.9). The results suggest that varying durations and repetitions of a stretch may influence the magnitude of improvement of HE. However, with the relatively low power (0.46) in the present study, no statistically significant difference between stretching protocols of 1 X 15 seconds, 2 X 15 seconds, and 1 X 30 seconds could be found. / Graduation date: 1997

名古屋大学博士学位論文 学位の種類:博士（医療技術学）（課程）学位授与年月日:平成21年3月25日