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Biomedical subjects

A Pépin

Publications and source records attributed to A Pépin.

10 recordsLinked to original sources
PubMed2006

Distribution of SPARC during neovascularisation of degenerative aortic stenosis.

OBJECTIVE: To examine the hypothesis that degenerative aortic stenosis (AS) is associated with the development of blood vessels and the expression of the secreted protein, acidic and rich in cysteine/osteonectin (SPARC), a matricellular protein that is involved in ossification, the modulation of angiogenesis and the production of metalloproteinases. METHODS: 30 surgically excised AS valves and 20 normal aortic valves were studied. RESULTS: Blood vessels were detected in the aortic valves from patients with degenerative AS, whereas normal valves were avascular structures. Blood vessels in AS valves expressed endothelial nitric oxide synthase, CD34 and von Willebrand factor (vWF). Blood vessels were located in three distinct regions: near calcified nodules, under the leaflet border and in rich cellular areas forming cell islands. Blood vessels were predominantly present in early and intermediate grades of calcification. Cell islands were densely populated by CD45-positive cells where endothelial cells (CD34+, vWF+) forming cord-like structures were present. Immunoblotting detected SPARC only in AS valves and immunohistological analysis located SPARC in mature blood vessels. The proportion of blood vessels positive for SPARC was higher in valves with a lower grade of calcification. In cell islands, SPARC was distributed to mature blood vessels and to macrophages, where it co-located with matrix metalloproteinase-9, whereas no expression was detected in endothelial cells forming cord-like structures. CONCLUSION: The localisation of SPARC to mature blood vessels and its predominant expression in AS valves with a lower calcification grade suggest that the spatial and temporal distribution of this matricellular protein is tightly controlled to participate in the neovascularisation of AS valves.

Aged↗
PubMed2003

Treadmill walking in incomplete spinal-cord-injured subjects: 1. Adaptation to changes in speed.

UNLABELLED: Walking in spinal-cord-injured (SCI) subjects is usually achieved at a lower speed than in normal subjects. STUDY DESIGN/METHODS: Time and distance parameters, angular displacements of lower limbs and electromyographic (EMG) activity were measured for seven normal and seven SCI subjects at several walking speeds. Analyses of variance were used for comparing groups and speeds. OBJECTIVES: First, to measure the adaptability of SCI subjects' walking pattern to different speeds (0.1-1.0 m/s), and to compare it to that of normal subjects. Second, to characterize SCI subjects' walking pattern as compared to that of normal subjects at a matched treadmill speed (0.3 m/s). SETTING: University-Based Human Gait Laboratory, Montreal, Canada. RESULTS: SCI subjects' pattern adapted to a limited range of speeds. Longer cycle duration, flexed knee at foot contact, increased hip joint flexion at foot contact and during swing, and altered coordination of hip and knee joints were found for the SCI group. At all speeds, duration of muscle activity was longer in the SCI group and the increase in amplitude of soleus EMG activity at higher speeds was not specific to push-off. The importance of matching the walking speed of SCI and normal subjects in order to differentiate the features that are a consequence of SCI subjects' reduced walking speed rather than a direct consequence of the injury is demonstrated. CONCLUSIONS: All SCI subjects could adapt to a narrow range of speeds and only three could reach the maximal tested speed. This limited maximal speed seems to be a consequence of SCI subjects having reached their limit in increasing stride length and not being able to increase stride frequency further. This limitation in increasing stride frequency is likely because of the altered neural drive. SPONSORSHIP: Neuroscience Network of the Canadian Centre of Excellence.

Adaptation, Physiological↗
PubMed2003

Treadmill walking in incomplete spinal-cord-injured subjects: 2. Factors limiting the maximal speed.

STUDY DESIGN/METHODS: Five SCI subjects referred to the laboratory and a convenience sample of five normal volunteer individuals was selected. Stride length and frequency were measured at different walking speeds under three different conditions: preferred, highest possible and lowest possible stepping frequencies. OBJECTIVE: To determine which factors are limiting the maximal walking speed in spinal-cord-injured (SCI) individuals. SETTING: University-Based Human Gait Laboratory, Montreal, Canada. RESULTS: It is shown that maximal stride frequency was the predominant limiting factor of the maximal treadmill-walking speed in SCI subjects. These results were explained in the light of the forced hybrid mass-spring pendulum model. At all speeds, SCI subjects spent longer time in stance, swing and double support phases. The relative time spent in single support is greater at higher walking speed and the difficulty to reduce double support time is a limiting factor. CONCLUSIONS: A better understanding of the factors limiting the maximal speed in SCI subjects should help developing rehabilitation interventions oriented towards increasing the control and the capacity of walking. Rehabilitation strategies should put the emphasis on improving the capacity to produce rapid alternate rhythmical stepping movements of the lower limbs. SPONSORSHIP: Neuroscience Network of the Canadian Centre of Excellence.

Adult↗
PubMed2001

Nanofabrication: conventional and nonconventional methods.

Nanofabrication is playing an ever increasing role in science and technology on the nanometer scale and will soon allow us to build systems of the same complexity as found in nature. Conventional methods that emerged from microelectronics are now used for the fabrication of structures for integrated circuits, microelectro-mechanical systems, microoptics and microanalytical devices. Nonconventional or alternative approaches have changed the way we pattern very fine structures and have brought about a new appreciation of simple and low-cost techniques. We present an overview of some of these methods, paying particular attention to those which enable large-scale production of lithographic patterns. We preface the review with a brief primer on lithography and pattern transfer concepts. After reviewing the various patterning techniques, we discuss some recent application issues in the fields of microelectronics, optoelectronics, magnetism as well as in biology and biochemistry.

Biomedical Technology↗
PubMed1999

Walking after spinal cord injury: evaluation, treatment, and functional recovery.

OBJECTIVE: To present some recent developments and concepts emerging from both animal and human studies aimed at enhancing recovery of walking after spinal cord injury (SCI). DATA SOURCES: Researchers in the field of restoration of walking after SCI, as well as references extracted from searches in the Medline computerized database. STUDY SELECTION: Studies that reported outcome measures of walking for spinal cord injured persons with an incomplete motor function loss or cats with either a complete or incomplete spinal section. DATA EXTRACTION: Data were extracted and validity was assessed by the authors. DATA SYNTHESIS: This review shows that a multitude of interventions--mechanical, electrical, or pharmacologic--can increase the walking abilities of persons with SCI who have incomplete motor function loss. CONCLUSIONS: A comprehensive evaluation of walking behavior requires tasks involving the different control variables. This comprehensive evaluation can be used to characterize the process of recovery of walking as well as the effectiveness of various treatments.

Animals↗
PubMed1998

Effects of drugs on walking after spinal cord injury.

Clonidine, a noradrenergic agonist, and cyproheptadine, a serotonergic antagonist, have each been associated with improved walking in SCI subjects. Baclofen, a GABA agonist, is frequently prescribed for spasticity but its effects on walking have not been well quantified. The objective of this study was to compare the effects of clonidine, cyproheptadine and baclofen on walking in SCI subjects with incomplete injuries. A motorized treadmill was used and harness support provided when necessary. A repeated single-subject design was employed for the twelve subjects. The greatest effects were found in more severely disabled subjects. Cyproheptadine was associated with greatly reduced need for assistance, increases in maximum treadmill speed (MTS) and reduced clonus. Clonidine was associated with increases in MTS and a generally more upright posture. Baclofen was associated with minor changes in walking. In many cases of drug effects, MTS increases and other changes were retained following washout of drugs. The significance and implications of the drug effects and the retention of effects during washout periods are discussed. It is concluded that clonidine and cyproheptadine have different effects but both appear useful for severely disabled SCI subjects. The effects of baclofen on walking after spinal cord injury remains unclear.

Adrenergic alpha-Agonists↗
PubMed1993

Idiotype and anti-anti-idiotype antibodies to Neisseria gonorrhoeae lipooligosaccharides with bactericidal activity but no cross-reactivity with red blood cell antigens.

A panel of murine mAb against three different epitopes of Neisseria gonorrhoeae lipooligosaccharides (LOS) was developed. Only one of these, 3G5, displays bactericidal activity against all in vitro serum-resistant strains of N. gonorrhoeae. Evidence suggests that sialylation, which could occur in vivo, modifies some LOS epitopes in such a way that the strains become resistant to bactericidal activity and are no longer recognized by specific antibodies. The epitope recognized by our bactericidal mAb is not affected by sialylation as shown by immunoblot analysis. We also provided evidence that the 3G5 epitope is different from RBC precursor Ag, since our mAb did not induce RBC agglutination. Since LOS induce an immune response in a T cell-independent fashion and are highly toxic, they cannot be used for immunization. Use of anti-idiotypic antibodies (aId) could be a way to bypass these difficulties. Therefore, in the present study, aId were produced in rabbits and rendered idiotype-specific by appropriate adsorption. These aId specifically bind to the relevant Id but not to LOS, and inhibit only the binding of anti-LOS mAb (3G5) to LOS preparations from N. gonorrhoeae in a dose-response fashion. The specificity of our aId for the binding site of anti-LOS mAb is suggested by the binding inhibition of affinity-purified aId to Id by LOS. In addition, the capacity of aId to inhibit bactericidal activity of this anti-LOS mAb and the idiotypic cross-reactivity between rat and mouse anti-LOS antibodies support this point. Finally, the elicitation of anti-LOS activity with bactericidal activity upon immunization of naive mice with aId confirms the internal image properties of the aId. These data suggest that a bactericidal mAb suitable for immunoprotection was obtained, and the production of aId opens the door for development of a vaccine.

Animals↗
PubMedDate not supplied

Quadriceps femoris muscle activity in patellofemoral pain syndrome.

To elucidate and attempt to dissociate the two mechanisms, neuromuscular and mechanical, underlying patellofemoral pain syndrome, 18 subjects, divided into two groups based on a diagnosis of patellofemoral pain syndrome and the knee Q angle, were studied. The control group was asymptomatic and exhibited a normal Q angle (mean, 8.25 degrees), whereas the other group, diagnosed as patellofemoral pain syndrome patients, reported knee pain and had an above-normal Q angle (mean, 21.05 degrees). All subjects were tested for isometric maximum knee extension at 90 degrees, 30 degrees, and 15 degrees of knee flexion while they were seated in a special restraining chair. During testing, surface electromyography at the oblique and long fibers of the vastus medialis, and at the vastus lateralis were recorded along with the knee moment of force. The integrated electromyographic signals associated with the peak torque for all of the vastus muscles, along with the vastus medialis obliquus:vastus lateralis and vastus medialis longus:vastus lateralis activity ratios showed no significant differences between groups nor between the three angles, suggesting that all vasti measured were consistently active throughout the studied range of motion. This suggests that the neural drive was not affected in the patellofemoral pain syndrome patients. However, when the five patients showing the largest Q angles were isolated, they revealed a significantly smaller vastus medialis obliquus:vastus lateralis ratio when compared to the other group. The same ratio was also significantly smaller at 15 degrees compared to 90 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

The effect of molecular structure in a series of merocyanines on the in vitro cytotoxicity for adenocarcinoma cells.

Preliminary results have shown that merocyanines were cytotoxic for human adenocarcinoma cells in vitro. We report the synthesis of a series of new merocyanines and the structure-effect relationship as cytotoxic agents on human adenocarcinoma cells in vitro. Some of these new derivatives were found very cytotoxic for tumor cells in vitro, whereas their systemic toxicity in vivo was very low.

Adenocarcinoma↗