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Biomedical subjects

B J Martin

Publications and source records attributed to B J Martin.

At least 145 records · Page 8Linked to original sources
PubMed1984

Spinal reflex alterations as a function of intensity and frequency of vibration applied to the feet of seated subjects.

Sensorimotor system performance is known to be altered by vibration applied locally to tendons and muscles or to the whole body. The present study is an attempt to determine the influence of vibration amplitude, acceleration, and frequency on the excitability of the motoneurons as evaluated by the amplitude of electrically induced spinal reflex response in man. The results show that a vibration applied to the legs of a seated subject (S) decreased the reflex response. The effect is directly related to the vibration intensity. The reflex amplitude is minimal in the 10-30 Hz range. At constant acceleration, the depressive effect decreased beyond 20-30 Hz while, at constant displacement amplitude, the reflex inhibition was almost constant throughout the frequency range of 20-60 Hz. These observations suggest that the diminution of the reflex response is mainly related to the amplitude of the vibration, regardless of the frequency. The results are interpreted in light of current knowledge of the effect of locally applied vibration on muscle tendons. The marked inhibition observed in the 10-30 Hz range, even with moderate intensity, suggests that particular attention should be devoted to avoid vibration in that frequency range in vehicles in order to prevent alteration of the performance of sensorimotor systems.

Adolescent↗
PubMed1984

Anaerobic metabolism of the respiratory muscles during exercise.

Although minute ventilation (VE) exhibits marked increases during heavy rhythmic exercise utilizing a large muscle mass, the extent to which this hyperpnea stresses the respiratory muscles remains controversial. In an attempt to resolve this matter, we measured arterial blood lactate concentration during seated isocapnic reproduction of peak exercise ventilation. This level of ventilation had previously been identified during a maximal 2-min treadmill run. We found that maintenance of peak exercise ventilation raised blood lactate 50% in subjects otherwise at rest (N = 8, P less than 0.01). This lactate rise occurred despite addition of CO2 to inspired gas in amounts sufficient to maintain arterial blood pH and PCO2 at resting levels, which suggests that achieving the high exercise ventilation associated with VO2max may require significant anaerobic metabolism by respiratory muscles.

Adult↗
PubMed1984

Primary cell cultures from the teleost, Cyprinodon variegatus: culture establishment and application in carcinogen exposure studies.

Methods were developed for aseptic maintenance of Cyprinodon variegatus fry for extended periods. Preliminary studies indicated that under optimum conditions sterile embryos develop normally for a sufficient time to function as carcinogen-teratogen assay systems. An embryo-primary cell culture technique was developed that incorporates, in a single system, certain characteristics of both intact embryos and primary cell cultures and allows simultaneous observation of the effects of carcinogens on the whole organism and primary cell monolayers. The effective use of these systems provides one the opportunity to study the effects of carcinogens on teleosts at the cellular and organismic level.

Animals↗
PubMed1984

Serological alterations in carcinogen-exposed teleosts: procedures for preparation and analysis of samples from small fish.

To study the effects of environmental carcinogens on the immune system of Cyprinodon variegatus, we had to miniaturize or modify standard immunological procedures due to the small size of the fish. Modifications in standard bleeding procedures allowed collection of sufficient serum for most serological procedures. Serum electrophoresis showed considerable variation between exposed and unexposed fish as did qualitative immunoelectrophoresis techniques. We successfully adapted a bacteriophage neutralization procedure for use with the C. variegatus system to measure antiviral antibodies. The presence of antibody-forming cells in spleen suspensions from fish immunized with human type O erythrocytes was demonstrated by a modified immune rosette procedure. A capillary tube procedure was developed for separation of leukocytes from erythrocytes in blood from C. variegatus.

Animals↗
PubMed1982

Ventilatory endurance in athletes: a family study.

Endurance athletes possess superior ability to sustain high ventilation. However, it remains unknown if this high ventilatory endurance is an effect of training. As one approach to this question, we compared the breathing endurance of eight distance runners with that of eight of their siblings who were untrained. In two separate tests involving seated isocapnic hyperpnea, the athletes had greater ability to sustain high VE than did their brothers and sisters. In the first test, VE was voluntarily incremented by 30 l/min each 4 min. Before exhaustion, the athletes reached a VE that was a significantly greater fraction of their 12-s maximal voluntary ventilation than did the untrained siblings (75 vs. 62%; P less than 0.01). In the second test, 80% of the 12-s MVV was sustained until exhaustion. Endurance times for the athletes doubled those of the untrained siblings (7 vs. 3 min; P less than 0.05). The failure of elevated ventilatory endurance to occur in family clusters suggests that it may primarily result from training.

Adolescent↗
PubMed1982

Variation among normal persons in short-term ventilatory capacity.

Among individuals of comparable size with normal lungs, short-term breathing capacity varies widely for unknown reasons. If the velocity of ventilatory muscle contraction limits airflow, then persons with a high proportion of fast twitch fibers in the ventilatory muscles should have large ventilatory capacities. As one test of this hypothesis, we correlated ventilatory capacity with vertical jump, an index of leg and thus of diaphragmatic muscle fiber composition. We found significant positive correlations between vertical jump and the 12-second maximal voluntary ventilation in both women (n = 19, r = 0.6; p less than 0.01) and men (n = 25; r = + 0.4; p = 0.06). Both correlations were independent of body weight or vital capacity. These results are consistent with the hypothesis that short-term ventilatory capacity is influenced by the contractile characteristics of the ventilatory muscles.

Adult↗
PubMed1982

Altered myosin isozyme patterns from pressure-overloaded and thyrotoxic hypertrophied rabbit hearts.

Cardiac hypertrophy, induced by pressure overload, leads to a depression in the rate of force development, velocity of shortening, tension-dependent heat generation, and myosin ATPase activity, whereas cardiac hypertrophy, induced by thyroxine administration, leads to an increase in these parameters. These changes have been attributed, in part, to structural changes in myosin. In this study, we have investigated changes in the relative content of myosin isozymes and differences in primary structure of the isozymes in pressure-overloaded and thyrotoxic cardiac hypertrophy in the rabbit. Three myosin isozymic forms (V1 = fastest, V2 = intermediate, V3 = slowest mobility) were observed in pyrophosphate polyacrylamide gels from normal hearts with the V3 component being the predominant species. In the pressure-overloaded model, the V1 and V2 components disappeared or were present in reduced amounts leaving the V3 more predominant. The most striking difference was the isozymic profile produced in thyrotoxic hearts where the V1 became the predominant component and V2 and V3 the minor components. alpha-Chymotryptic digestion of myosin heavy chains produced characteristic, reproducible peptide patterns for each of the animal models, as did fluorographic analyses of alpha-chymotryptic digests of 14C-iodoacetamide (IAA)-labeled SH1 peptides of myosin. Our results suggest that altered proportions of myosin isozymes may be responsible for altered cardiac performance.

Adenosine Triphosphatases↗
PubMed1981

Effect of sleep deprivation on tolerance of prolonged exercise.

Acute loss of sleep produces few apparent physiological effects at rest. Nevertheless, many anecdotes suggest that adequate sleep is essential for optimum endurance athletic performance. To investigate this question, heavy exercise performance after 36 h without sleep was compared with that after normal sleep in eight subjects. During prolonged treadmill walking at about 80% of the VO2 max, sleep loss reduced work time to exhaustion by an average of 11% (p = 0.05). This decrease occurred despite doubling monetary incentives for subjects during work after sleeplessness. Subjects appeared to fall into "resistant" and "susceptible" categories: four showed less than a 5% change in performance after sleep loss, while four others showed decrements in exercise tolerance ranging from 15 to 40%. During the walk, sleep loss resulted in significantly greater perceived exertion (p less than 0.05), even though exercise heart rate and metabolic rate (VO2 and VCO2) were unchanged. Minute ventilation was significantly elevated during exercise after sleep loss ( p less than 0.05). Sleep loss failed to alter the continuous slow rises in VE and heart rate that occurred as work was prolonged. These findings suggest that the psychological effects of acute sleep loss may contribute to decreased tolerance of prolonged heavy exercise.

Adult↗