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Biomedical subjects

J Gilchrist

Publications and source records attributed to J Gilchrist.

70 records · Page 4Linked to original sources

Coordination of Ca2+ regulating and Ca2+ regulated processes in the study of muscle function.

The self-organization of biological systems is, in part, described by dynamical order and cooperativity of system elements. Consideration of this, therefore, should form the infrastructure of future Exercise/Sport Biochemistry Research in Canada since a solely elemental focus, in its' interpretation, may not be meaningful if the synergy among system elements is not appreciated. This approach is illustrated through a description of the central role of Ca2+ metabolism in coordinating subcellular events associated with muscle contraction. The decline in force generating capabilities associated with extreme muscle use (e.g. endurance type exercise) is, in our view, due to an uncoupling of excitation-contraction coupling leading a Ca2+ imbalance. The observed dissolution of the myofibril ultrastructure and altered SR function reflect a loss of normal order and synergy amongst Ca2+ regulated and Ca2+ regulating processes which will lead to an upcoupling of oxidative phosphorylation. These apparently catastrophic events may, paradoxically, establish a new order in which energy utilizing systems attempt to keep pace with the abbreviated energy production system.

Animals↗

Biochemical basis of muscular fatigue associated with repetitious contractions of skeletal muscle.

The decline in force generating capabilities of skeletal muscle associated with prolonged, repetitive low force producing contractions does have a biochemical basis. It is our view that an alteration in neuromuscular transmission results in an uncoupling of excitation-contraction via disturbances in Ca2+ imbalance, an uncoupling of energy utilization and production may result, which affect a favourable cellular environment for the initiation of myofilament degradation. The myofilament dissolution may be the last stage in this fatigue process and associated with only extreme conditions of muscle use.

Action Potentials↗

Fechner's paradox in binocular contrast sensitivity.

It is generally accepted that binocular spatial contrast sensitivity in normal observers is higher than monocular sensitivity by some 42% across all spatial frequencies, an amount predictable on the basis of neural summation of the two monocular responses. Such summation predicts that a reduction of sensitivity in one eye would result in a fall in binocular sensitivity to a level approaching, but never lower than, that of the other eye. We present evidence that reduction in monocular sensitivity caused by reduced luminance can, in some subjects, lower binocular sensitivity to a level below that of the other eye, an analogue of Fechner's brightness paradox. In other subjects the expected summation occurs and binocular sensitivity always remains at or above the monocular level.

Form Perception↗

Hemispheric asymmetry in use of semantic category information.

When two pictures of common objects were presented sequentially, the second was named more quickly if both were members of the same semantic category. This semantic priming effect occurred only when both pictures went directly to the left hemisphere. If the target or prime stimulus was presented to the left visual field--right hemisphere, no priming effect was observed. These results suggest that semantic category information is activated and used by the left hemisphere of the brain.

Adult↗

Effect of tunicamycin on rotavirus assembly and infectivity.

Bovine rotavirus grown in the presence or absence of tunicamycin was analyzed with respect to yield of infectious virus, the ratio of complete to incomplete particles, and polypeptide composition. Tunicamycin at a concentration of 1 microgram/ml reduced virus yields by 4 logs and completely prevented the incorporation of [3H]uridine into complete rotavirus particles, as determined by cesium chloride gradient analysis. Concomitant with a reduction in complete particles, three rotavirus polypeptides shifted in their relative position on polyacrylamide gels from 41,900-molecular-weight position (41.9K), 29.3K, and 16.1K to migrate at 35.5K, 22.7K, and 15.5K, respectively. Limited proteolysis indicated that the lower-molecular-weight polypeptides possessed the same constituent peptides as the larger polypeptides, suggesting that they represented the unglycosylated equivalents. These results suggest that interference with glycosylation prevents proper assembly of the outer coat proteins in bovine rotavirus.

Animals↗

Operative biopsy of the pancreas.

A review has been undertaken of the 47 patients who have had open pancreatic biopsy performed at the Royal Free Hospital between 1967 and 1972. It is concluded that not only is the procedure safe when using the technique described but also it is a valuable and accurate diagnostic procedure.

Aged↗

The prevention of ankle sprains in sports. A systematic review of the literature.

To assess the published evidence on the effectiveness of various approaches to the prevention of ankle sprains in athletes, we used textbooks, journals, and experts in the field of sports medicine to identify citations. We identified 113 studies reporting the risk of ankle sprains in sports, methods to provide support, the effect of these interventions on performance, and comparison of prevention efforts. The most common risk factor for ankle sprain in sports is history of a previous sprain. Ten citations of studies involving athletes in basketball, football, soccer, or volleyball compared alternative methods of prevention. Methods tested included wrapping the ankle with tape or cloth, orthoses, high-top shoes, or some combination of these methods. Most studies indicate that appropriately applied braces, tape, or orthoses do not adversely affect performance. Based on our review, we recommend that athletes with a sprained ankle complete supervised rehabilitation before returning to practice or competition, and those athletes suffering a moderate or severe sprain should wear an appropriate orthosis for at least 6 months. Both coaches and players must assume responsibility for prevention of injuries in sports. Methodologic limitations of published studies suggested several areas for future research.

Ankle Injuries↗

Legislative and regulatory strategies to reduce childhood unintentional injuries.

Laws and regulations are among the most effective mechanisms for getting large segments of the population to adopt safety behaviors. These have been applied at both the state and federal levels for diverse injury issues. Certain legal actions are taken to prevent the occurrence of an otherwise injury-producing event, while other legal actions are designed to prevent injury once an event has occurred. At the federal level, effective laws and regulations have been directed at dangers posed by unsafe manufactured products or motor vehicle design. At the state level, effective safety laws and regulations have been directed at encouraging safety behaviors and regulating the use of motor vehicles or other forms of transportation. In this article, six legislative efforts are described to point out pros and cons of the legislative approach to promoting safety. Three such efforts are aimed at preventing injury-producing events from occurring: mandating child-resistant packaging for prescription drugs and other hazardous substances, regulating tap water temperature by presetting a safe hot-water heater temperature at the factory, and graduated licensing. Three other examples illustrate the value and complexities of laws designed to prevent injuries once an injury-producing event does occur: mandatory bicycle helmet use, sleep-wear standards, and child safety seat use. This article concludes with specific recommendations, which include assessing the value of laws and regulations, preventing the rescission of laws and regulations known to work, refining existing laws to eliminate gaps in coverage, developing regulations to adapt to changing technology, exploring new legal means to encourage safe behavior, and increasing funding for basic and applied research and community programs. Further reductions in childhood injury rates will require that leaders working in the field of injury prevention together provide the creativity to devise new safety devices and programs, incentives to persuade the public to adopt a "culture of safety" as a social norm, training and education to develop new leaders and workers, and the political will to challenge the status quo and engage the public interest.

Adolescent↗