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Biomedical subjects

G D Marsh

Publications and source records attributed to G D Marsh.

31 records · Page 2Linked to original sources
PubMed1993

Metabolic adaptations to endurance training in older individuals.

The purpose of this study was to describe the effects of moderate intensity exercise training on the muscle energy utilization, blood flow, and exercise performance of four sedentary older individuals (58 +/- 4 yrs). Subjects trained the dominant forearm each day for 12 weeks. The nondominant arm was not trained and served as a within-subject control. 31P nuclear magnetic resonance spectroscopy (31P NMRS) was used to identify the power output in watts (W) at the onset, or threshold, of intracellular acidosis (IT) in the exercising muscle during progressive exercise tests to fatigue. After 6 weeks of training, power output at the IT increased by 14% (p < 0.05) in the dominant arm; however, an additional 6 weeks of the same exercise program failed to produce a further increase in IT power. IT power of the nondominant forearm was not changed. In the dominant forearm, endurance time for a submaximal wrist flexion test was increased 34% and 58% at 6 and 12 weeks, respectively. Maximal voluntary strength was not affected by training, nor was resting or exercising blood flow. The training program delayed the onset of intracellular acidosis during progressive exercise and increased the capacity for submaximal work. These effects did not appear to depend on an increase in muscle blood flow.

Acidosis↗
PubMed1993

Transient changes in muscle high-energy phosphates during moderate exercise.

The purpose of this study was to use 31P-nuclear magnetic resonance spectroscopy to examine changes in wrist flexor muscle metabolism during the transitions from rest to steady-state exercise (on-transient) and back to rest (off-transient). Five healthy young males (mean age 25 +/- 2 yr) performed a series of square-wave exercise tests, each consisting of 5 min of moderate-intensity work followed by a 5-min recovery period. The subjects repeated this protocol six times, and each individual's results were pooled before analysis. ATP and intracellular pH did not change significantly during exercise or recovery. Phosphocreatine (PCr) declined progressively at the onset of exercise, reaching a plateau after approximately 2 min. A reciprocal increase in Pi occurred during the onset of exercise. During the recovery period PCr was resynthesized, whereas Pi returned to resting levels. The data were plotted as a function of time and fit with both first- and second-order exponential growth or decay models; however, the second-order model did not significantly improve the fit of the data. Time constants for the first-order model of the on- and off-transient responses for both PCr and Pi were approximately 30 s. These values are nearly identical to the time constants for oxygen consumption during submaximal exercise that have been reported previously by several authors. The results of this study show that the metabolism of muscle PCr during steady-state exercise and recovery can be accurately described by a monoexponential model and, further, suggest that a first-order proportionality exists between metabolic substrate utilization and oxygen consumption.

Adenosine Triphosphate↗
PubMed1993

Theophylline delays skeletal muscle fatigue during progressive exercise.

In this study, 31P nuclear magnetic resonance spectroscopy (NMRS) was used to examine the effect of theophylline on human forearm muscle metabolism during progressive exercise. Six healthy men (37 +/- 14 yr of age) were assigned to either a control (CTRL) group (n = 3), or a theophylline treatment (THEO) group (n = 3). Each subject performed two dynamic wrist flexion exercise tests to fatigue, with at least 72 h separating each trial. The THEO group repeated the protocol after receiving 300 mg of sustained-release theophylline every 12 h. 31P spectra were acquired every 36 s throughout exercise, and the relative contributions of the phosphate metabolites and pH were determined. Power output at the onset, or threshold of intracellular acidosis (IT), was identified for each subject from changes in phosphocreatine (PCr) metabolism and pH. Power at maximal exercise and at the IT was found to be reproducible in the CTRL group. After theophylline administration, the maximal power attained by the THEO group increased significantly by 19% (p < 0.05), from 2.25 +/- 0.2 to 2.68 +/- 0.15 W. A similar trend occurred in the onset of the IT, which was also prolonged by 19%, from 1.33 +/- 0.18 to 1.58 +/- 0.22 W. Therapeutic concentrations of theophylline significantly increased the endurance of the forearm musculature, apparently by delaying the onset of intracellular metabolic acidosis. These findings suggest an enhancement of oxidative capacity of the muscle.

Adult↗
PubMed1993

Bupivacaine infiltration after haemorrhoidectomy.

The effect of a locally infiltrated solution of bupivacaine was studied in 30 patients undergoing haemorrhoidectomy. A standard Milligan-Morgan haemorrhoidectomy, with preoperative infiltration of adrenaline solution (1:200,000), was performed. The patients were randomized to receive local four quadrant perianal infiltration of 20 ml of 0.5% bupivacaine or normal saline. Analgesia was available on demand postoperatively. There was no significant difference between the groups with respect to visual analogue pain scores, analgesic requirement, time to first bowel action or duration of hospital stay. Bupivacaine as a local infiltration in this situation does not confer analgesic effect into the postoperative period.

Adult↗
PubMed1991

Coincident thresholds in intracellular phosphorylation potential and pH during progressive exercise.

Dynamic changes in intracellular phosphocreatine (PCr), inorganic phosphate (Pi), and pH in human forearm muscle were studied from rest through heavy exercise by means of a ramp exercise protocol and 31P nuclear magnetic resonance spectroscopy. Eighteen healthy volunteers performed an isotonic wrist flexion exercise of repeated contractions at a frequency of 0.5 Hz. Work rate was increased continuously (ramped) at approximately 0.13 W each minute from 0.34 to 1.5 W or until fatigue. Pi/PCr was used as an estimate of the cellular phosphorylation potential of the muscle. Exercise caused a progressive increase in Pi/PCr with an initial slow and later fast component. The transition between these components was distinct and corresponded to the onset of pH decline in all subjects. These changes in Pi/PCr and pH were best fit (P less than 0.05) by a piecewise linear regression model with a break point or threshold. Repeated ramp testing of six subjects showed that the threshold was reproducible (r = 0.98). The results of this study demonstrate the existence of an intracellular metabolic threshold and suggest that indirect threshold measures (lactate and ventilatory thresholds) may reflect events at the cellular level.

Adult↗
PubMed1991

Post-polio fatigue: a 31P magnetic resonance spectroscopy investigation.

Changes in high energy phosphates (HEP) and intramuscular pH during exercise were measured in 17 patients with post-polio fatigue and in 28 healthy controls using 31P magnetic resonance spectroscopy (MRS). Subjects performed a dynamic hand grip exercise at low and high intensity. Mean changes in the HEP and pH showed no significant differences between the groups, although the post-polio group's response was highly variable. Six patients showed evidence of a lower lactate accumulation during the high intensity exercise when compared with controls. These data suggest that the whole body fatigue experienced by polio survivors is not related to any systemic metabolic abnormality.

Adult↗
PubMed1991

Procurement for a comprehensive cancer center.

The director of materials management services at M.D. Anderson is a position of endless opportunities, as well as continual challenges. The procurement process provides the opportunity to be an integral part of a team that has made a significant difference to many of the patients in the areas of cancer prevention, education, detection, diagnosis, treatment, cure, and rehabilitation. All involved in health care purchasing derive a personal fulfillment not available to purchasers in other industries. At MDA, however, this goes even one step further, as our department supports a team in the battle against cancer--a battle that affects nearly every household in America today. MDA can state that more than half of all patients treated are considered cured, and that is certainly a great team with which to be associated. But even more exciting are the years to come, as materiel management services supports the M.D. Anderson mission of eliminating cancer and allied diseases as significant health problems throughout the world.

Cancer Care Facilities↗
PubMed1991

Spectroscopy of the isolated rabbit heart: effects of perfusion with oxygenated crystalloid cardioplegia at 4 degrees C and 20 degrees C.

Factors that limit survival of explanted cardiac allografts include intracellular acidosis and loss of high energy phosphates. This study was undertaken to determine if these processes could be retarded by specific interventions during organ storage and to determine the capabilities of phosphorus-31 (31P) nuclear magnetic resonance spectroscopy to monitor these intracellular changes noninvasively. Thirty-six excised rabbit hearts were studied in six groups according to the storage temperature and conditions of their perfusion: nonperfused, aerated perfusate or oxygenated perfusate, each at 4 degrees C and 20 degrees C. 31P spectra were continuously obtained starting 20 mins post explanation and continuing for at least 5 h. The resulting data were analyzed to determine metabolite concentration and intracellular pH. The phosphodiesters, inorganic phosphates and phosphomonoesters, as well as the phosphocreatine and adenosine triphosphate peaks, could be reproducibly resolved. Comparisons at 0.5, 1, 2, 3, 4, and 5 h indicated that high energy phosphates were the most quickly degraded, and intracellular acidosis progressed most rapidly in nonperfused hearts at 20 degrees C. Hearts perfused with oxygenated cardioplegic solution at 4 degrees C showed significantly prolonged preservation of high energy phosphates and delayed development of intracellular acidosis. It was concluded that continuous infusion of oxygenated cardioplegic solution improves preservation of high energy phosphates at low temperatures, and that 31P magnetic resonance spectroscopy can be used to monitor these important intracellular changes rapidly and nonivasively, permitting serial studies on the same heart. This technique substantially reduced the number of animals needed for the study (36 were used in this study rather than the 216 required by traditional techniques).

Adenosine Triphosphate↗
PubMedDate not supplied

A model for in vivo serial investigation of hepatic metabolism using 31P nuclear magnetic resonance spectroscopy.

We have developed an animal model which allows serial, in vivo, evaluation of high energy phosphate metabolism in rat liver, using 31P nuclear magnetic resonance spectroscopy (MRS). In seven rats, the left lobe of the was surgically relocated into a subcutaneous position. The animals recovered quickly from the surgery and continued to thrive. Localization of the liver was obtained using simple surface coil technology. Typical MRS data acquisition times were less than 45 minutes. After the 28 days, the livers showed both normal histology and 31P metabolic measures.

Aging↗
PubMedDate not supplied

An in vivo animal model to study chronic adriamycin cardiotoxicity: a P-31 nuclear magnetic resonance spectroscopy investigation.

The mechanism responsible for adriamycin induced cardiotoxicity is unknown. We have developed an in vivo rabbit model for use with P-31 nuclear magnetic resonance spectroscopy which allows serial investigations of the drug's effects on myocardial metabolism. Eleven animals were studied over a 10 week period and changes in intracellular pH and phosphate metabolites were observed. The magnitude of changes in pH and inorganic phosphate were the best indicators of the severity of the cardiomyopathy. The results are consistent with an adriamycin induced degeneration of myofibrils rather than a severe metabolic impairment.

Adenosine Triphosphate↗