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Biomedical subjects

A R Morton

Publications and source records attributed to A R Morton.

At least 73 records · Page 4Linked to original sources
PubMed1991

Monitoring exercise stress by changes in metabolic and hormonal responses over a 24-h period.

Metabolic and endocrine responses of 14 subjects of varying levels of fitness to an intensive anaerobic interval training session were assessed before exercise and at 2 h, 4 h, 8 h and 24 h postexercise. The endocrine response of the same subjects to a control day, where they were required not to exercise, was also assessed and compared with the values obtained on the interval training day. Uric acid, urea, and creatine phosphokinase concentrations still remained elevated above pre-exercise values 24 h postexercise. Lactate, creatinine, testosterone and cortisol concentrations were significantly elevated above pre-exercise values immediately postexercise but these had reversed by 2 h postexercise. Over the remainder of the recovery period testosterone concentrations remained significantly lower than values measured at similar times on the control day. This was shown to be due directly to a change in testosterone as sex hormone binding globulin concentration remained constant throughout the recovery period. The data indicate that when comparisons of data were made to control (rest) days, imbalances in homeostasis, due to intensive training, are not totally reversed within the next 24-h. The data also demonstrate that the parameters measured undergo the same variations in subjects with a wide range of physical fitness, indicating that these parameters could be used to monitor exercise stress and recovery in athletes of a wide range of abilities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Parathyroid hormone-related protein(50-69) and response to pamidronate therapy for tumour-induced hypercalcaemia.

A region-specific radioimmunoassay has been employed to measure levels of immunoreactive parathyroid hormone-related protein(50-69) (iPTHrP(50-69)) in patients with tumour-induced hypercalcaemia (TIH). This assay is based on an antiserum raised against synthetic human PTHrP(50-69). The assay showed no cross-reactivity with human or bovine parathyroid hormone(1-84). The effect of a single dose (60 mg) of pamidronate was studied in 25 consecutive patients with TIH. All were rehydrated prior to treatment. All but 2 patients (8%) became normocalcaemic after treatment; both of these had very high levels of iPTHrP(50-69). Time to achieve normocalcaemia, as an index of relative resistance to pamidronate, correlated positively with pretreatment level of iPTHrP(50-69). Absence of radiological evidence of bone metastases also predicted relative resistance to pamidronate. In this study, iPTHrP(50-69)-induced osteoclastic bone resorption was a more important mechanism in the causation of TIH than PTHrP-induced renal reabsorption of calcium as assessed by the renal thresholds for calcium and phosphate.

Adult↗
PubMed1991

Medical and social outcome in adolescents with end-stage renal failure.

Clinical information was collected on 118 adolescents who developed ESRF at age 143 months or older and were treated between 1966 and 1986 at the Toronto Hospital for Sick Children. The cumulative survival rate in transplanted patients (N = 109) was 80.1% after 15 years. Survival rates after four years were 93.9% in transplanted and 46.9% in nontransplanted patients (P less than 0.001). No patient receiving dialysis alone (N = 9) was followed longer than four years. Nine patients received three transplants and had an 89% survival rate. Six of these had a functioning graft at end of the follow-up. The cumulative survival of the entire group was 76.4% at eighteen years. Forty-two (35.6%) patients had a height below the third percentile. Functional status obtained by a structure telephone interview with a member of the present treating nephrology service was good (G) or excellent (E) for 66.7% of all patients (73.5% of transplant patients (N = 68) and 45% of dialysis patients (N = 20). Hemodialysis patients functioned less well [25% G/E (N = 12)] than peritoneal dialysis patients [75% G/E (N = 8)]. Most patients achieved an appropriate level of formal education although more slowly than normal adolescents. Only 11 patients were neither enrolled in an educational institution nor employed. We conclude that aggressive treatment for adolescents with ESRF is an appropriate application of health care resources.

Adolescent↗
PubMed1991

A controlled study of the effects of aerobic exercise on antihypertensive drug requirements of essential hypertensive patients in the general practice setting.

1. To investigate the effect of an exercise training programme on antihypertensive drug requirements, 19 sedentary subjects (14 men and five women) with mild essential hypertension (systolic blood pressure greater than 140 mmHg but less than 180 mmHg), aged 29-55 years, were randomly assigned to 16 weeks of moderate intensity exercise or light intensity exercise (control), and titrated on antihypertensive drug therapy (captopril and hydrochlorothiazide) until resting systolic blood pressure (sitting) of less than 140 mmHg was achieved. 2. The moderate exercise group (n = 11) followed a graded walk-jog programme to greater than 60% age-predicted maximum heart rate (HRmax), attending 45 min sessions, three times each week. The light exercise group (n = 8) followed a programme of flexibility (stretching exercises) and walking to less than 60% age-predicted HRmax, attending 45 min sessions, three times each week. 3. There was no difference between treatment groups for the level of reduction in both resting systolic and diastolic blood pressure over the 16 weeks (15.64 +/- 10.6/12.81 +/- 9.97 mmHg in the moderate intensity group and 15.31 +/- 10.9/7.7 +/- 7.1 mmHg in the light intensity group). The change in 24 h ambulatory blood pressure profile was also similar in both treatment groups. The final antihypertensive drug requirements to achieve these changes in blood pressure was not significantly different between the two treatment groups. This was despite a significant improvement in submaximal exercise performance in the moderate intensity exercise group (P less than 0.001). 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Overtraining in athletes. An update.

Overtraining appears to be caused by too much high intensity training and/or too little regeneration (recovery) time often combined with other training and nontraining stressors. There are a multitude of symptoms of overtraining, the expression of which vary depending upon the athlete's physical and physiological makeup, type of exercise undertaken and other factors. The aetiology of overtraining may therefore be different in different people suggesting the need to be aware of a wide variety of parameters as markers of overtraining. At present there is no one single diagnostic test that can define overtraining. The recognition of overtraining requires the identification of stress indicators which do not return to baseline following a period of regeneration. Possible indicators include an imbalance of the neuroendocrine system, suppression of the immune system, indicators of muscle damage, depressed muscle glycogen reserves, deteriorating aerobic, ventilatory and cardiac efficiency, a depressed psychological profile, and poor performance in sport specific tests, e.g. time trials. Screening for changes in parameters indicative of overtraining needs to be a routine component of the training programme and must be incorporated into the programme in such a way that the short term fatigue associated with overload training is not confused with the chronic fatigue characteristic of overtraining. An in-depth knowledge of periodisation of training theory may be necessary to promote optimal performance improvements, prevent overtraining, and develop a system for incorporating a screening system into the training programme. Screening for overtraining and performance improvements must occur at the culmination of regeneration periods.

Adaptation, Physiological↗
PubMed1991

Physiological and kinanthropometric attributes of elite flatwater kayakists.

Physical and physiological factors accounting for the variability of performance in 500, 1000, 10,000, and 42,000 m flatwater kayaking were investigated using linear regression. Times achieved for each distance were used as the dependent variable for analysis while the independent variables were the parameters derived from the test battery. The 38 kayakists who participated were categorized as either state team members or nonselected paddlers, based on an objective selection policy. Several of the participant subjects were Australian international representatives. All selected paddlers were grouped together and Student's t-tests performed to determine which variables could distinguish between selected and nonselected paddlers. Simple regression was used to determine the strength of association of each parameter with performance time over each race distance, and multiple regression was used to generate equations for the prediction of performance times. Aerobic power and variables related to the aerobic-anaerobic transition were examined using gas analysis during an incremental workload test on a kayak ergometer. A 1-min all-out test also on a kayak ergometer was used to obtain an indication of anaerobic capacity and power. Muscular strength and fatigue were assessed using a simulated kayak stroke on a Cybex isokinetic dynamometer. Physical characteristics were determined using kinanthropometric tests. Aerobic power, anaerobic power and capacity, muscular strength, resistance to muscular fatigue, and measures of body size were significantly greater in more successful kayakists. All of the parameters measured correlated significantly with performance time over at least one of the four race distances.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1990

Controlled comparison of effects of exercise and alcohol on blood pressure and serum high density lipoprotein cholesterol in sedentary males.

1. Seventy-two sedentary male drinkers, aged 20-45 years, and with mean blood pressure (BP) at entry of 132 +/- 1.2/73 +/- 0.9 mmHg, completed a 4 week study during which they were assigned randomly to either drink a low alcohol beer (effectively reducing their weekly alcohol intake from 481 +/- 47 mL to 52 +/- 5 mL) or to continue their normal drinking habits. 2. Within these two groups subjects were further assigned to either a moderate exercise programme of three 30 min sessions per week of stationary cycling at 60-70% maximum workload or to a control light exercise programme where they pedalled against zero or minimal resistance. 3. Both alcohol restriction and moderate exercise were associated with mean falls in bodyweight of 0.5 kg. After adjustment for bodyweight a significant main effect of alcohol restriction on systolic BP (-4.1 +/- 1.7 mmHg, P less than 0.05) and diastolic BP (-1.6 +/- 0.8 mmHg, P = 0.05) was demonstrated. There was no significant main effect of moderate exercise on systolic or diastolic blood pressure despite a significant improvement in physical fitness (maximal oxygen uptake increasing from 33.2 +/- 0.8 mL/kg per min to 35.5 +/- 0.1 mL/kg per min). 4. Significant falls in high density lipoprotein cholesterol (HDLC) and triglyceride levels seen with alcohol restriction were unaffected by the increase in fitness, the magnitude of the fall being similar in both the moderate and light exercise groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The effects of theophylline on the physical performance and work capacity of well-trained athletes.

Theophylline, a pharmacologic agent presently permitted during international sporting competition, has come under scrutiny because of the suggestion that it may be ergogenic. This study examined the effects of serum theophylline levels of 10 to 20 mg/L and the administration of a placebo on selected measures of physical performance and work capacity to determine any ergogenic outcomes. Seven male and three female elite athletes from a variety of team sports and aged 18 to 30 years participated in the study. The variables measured were height, mass, maximal oxygen consumption, muscular endurance, muscular power, muscular strength, FVC, FEV1, and reaction time. When the scores obtained after ingestion of theophylline and a placebo with a double-blind, crossover technique were compared, no significant difference was found for any of these variables. A two-way analysis of variance of FEV1 scores obtained before and after maximal exercise revealed no significant "F" ratios. This indicated that none of these trained athletes demonstrated exercise-induced asthma and that there was no difference in airway resistance after maximal exercise while they were under the influence of theophylline or placebo. We conclude that no ergogenic effects were attributable to theophylline therapy which should therefore remain an acceptable means of management of athletes with asthma participating in international sporting events.

Adolescent↗
PubMed1989

Rimiterol and the prevention of exercise-induced asthma.

The potential for rimiterol to protect athletes from exercise-induced asthma (EIA) has not been fully established. Ten athletes with asthma (15 to 30 years of age) undertook 8 minutes of submaximal exercise (80% of anaerobic threshold) on the treadmill ergometer, once after inhaling rimiterol and once after inhaling a placebo. Treatment with all bronchodilator drugs was stopped for the 12 hours preceding each exercise test. Two puffs (400 micrograms) of rimiterol or placebo were administered in a double-blind crossover manner 2 minutes before each exercise test. Lung function measurements were made before exercise and immediately, 5, 10, 15, 20, 25, and 30 minutes after completion of exercise. The results of a two-way analysis of variance revealed significant (p less than 0.01) difference in the FEV1 scores obtained after rimiterol inhalation and placebo inhalation, 5, 10, 15, 20, 25, and 30 minutes after cessation of exercise. After inhalation of rimiterol, there were no significant changes in FEV1. After inhaling the placebo, significant reductions (p less than 0.01) in FEV1 occurred after cessation of exercise (5, 10, 15, and 20 minutes). All subjects exhibited EIA after placebo, and none after rimiterol. The mean maximum drop after exercise in FEV1 after inhalation of rimiterol (2.807 +/- 5.55) and placebo (24.54 +/- 8.4) was significantly different (t = 6.849). It was concluded that inhalation of rimiterol 2 minutes before exercise afforded significant protection from EIA in all subjects tested.

Administration, Inhalation↗
PubMed1989

Improvements in heat tolerance induced by interval running training in the heat and in sweat clothing in cool conditions.

To compare the effectiveness of training in heat and in sweat clothing in cool conditions on improving heat tolerance, two groups of active subjects (n = 6 in each) performed an interval running heat-tolerance test before and after a 7-day experimental treatment. On each treatment day the subjects attempted to complete 4 x 15 min interval treadmill running periods (a 7.5 s effort every 30 s, on 15 km h-1, 15% grade; the same exercise format as the heat-tolerance test), which were interspersed with 5-min recovery periods (total time each day = 80 min). Group 1 (heat) ran in shorts, socks and shoes in hot humid conditions, and Group 2 (sweat clothing) ran in cool conditions dressed in shorts, socks and T-shirt covered by a polyester-cotton tracksuit, over which was worn 100% nylon spray-proof pants and jacket (cotton lined) with an acrylic cloth bobble hat (beanie) on the head. Both groups displayed changes typical of heat acclimatization over the 7-day period, with significant decreases in final rectal temperature (Tr) and heart rate (HR) being evident, but no change in sweat loss. Mean skin temperature (Tsk) was similar in both groups during the training sessions (heat group: 34.8-35.7 degrees C; sweat clothing group 34.9-35.5 degrees C). After the heat-tolerance test, both groups had significantly lower Tr, Tsk and HR values than before, and sweating sensitivity (g m-2 h-1 degrees C rise in Tr) was significantly increased. There was only one significant difference between the two groups (Tsk, 20th min value). It was concluded that training in sweat clothing in cool conditions can provide the same improvements in heat tolerance as training in hot humid conditions where a fixed exercise intensity and duration are used.

Acclimatization↗
PubMed1989

CO2 sensitivity changes during the menstrual cycle.

A study of the changes in CO2 sensitivity at rest was undertaken in 20 regularly menstruating females in an attempt to determine the influence of the menstrual cycle on this variable. A biphasic oral temperature graph was used to signify fertility and demarcate three phases of the cycle. A CO2-rebreathing test was conducted 3 times/wk for 6 wk to obtain CO2 sensitivity and CO2 threshold measures. An analysis of variance was used to compare the results collected in each phase of the cycle for each of the variables. A significant increase was found in the sensitivity to CO2 between the follicular and luteal phases, a significant decrease between the luteal and menstrual phases, and no significant difference between the follicular and menstrual phases. The change between follicular and luteal phases was attributed to the effect of progesterone, which is elevated during the luteal phase. No significant change was found in the CO2 threshold level.

Adolescent↗
PubMed1989

Tuberculosis surveillance in a state prison system.

After four inmates at two New Mexico prisons converted their tuberculosis skin tests, a mass screening program was carried out at all the State's adult correctional facilities (2,240 inmates). Previously unknown converters were found with a disproportionally high per cent of converters (6.8 per cent and 6.3 per cent) and reactors (14.4 per cent and 12.2 per cent) at the first two prisons. No index cases were found. State policy has been revised to include two-stage skin testing of new inmates, annual testing thereafter, and screening of all new correctional staff.

Adult↗
PubMed1989

Alterations in plasma lipids consequent to endurance training and beta-blockade.

Alterations in plasma lipids consequent to endurance training and beta-blockade. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 288-292, 1989. The chronic use of beta adrenergic blockers (BAB) has been associated with reductions in HDL-cholesterol (HDL-C) and increases in triglycerides (TG). This study evaluated the impact of concurrent endurance exercise training and chronic medication with BAB on plasma lipid and lipoprotein profiles in healthy young adult males. Changes in plasma lipids and lipoproteins were investigated while exercise training under the influence of one of two nonselective BAB [sotalol (320 mg.d-1) and propranolol (160 mg.d-1)], one beta 1 selective BAB [atenolol (100 mg.d-1)], or a placebo control. Total cholesterol (TC), HDL-C, LDL-cholesterol (LDL-C), TG, and the ratios of TC/HDL and LDL/HDL were determined before and after endurance training programs of either 14 (N = 27, sotalol) or 15 (N = 47, propranolol/atenolol) wk duration. The subjects exhibited increases in maximal oxygen uptake of 12-20%. Despite increased endurance capacity, the subjects in both BAB and placebo control groups failed to demonstrate the expected increase in HDL-C and decrease in TG. In fact, HDL-C was significantly decreased post-training in the propranolol group. The placebo groups did decrease TC, LDL-C and the TC/HDL and LDL/HDL ratios, improving their CHD risk profile. Similar changes were not observed in the groups on BAB. Thus, with respect to the present population, BAB does appear to interfere with the usual training-induced improvements in the lipid profile. Endurance training may, however, reduce the deterioration in the lipid profile known to occur with BAB.

Adrenergic beta-Antagonists↗
PubMed1988

Single dose versus daily intravenous aminohydroxypropylidene biphosphonate (APD) for the hypercalcaemia of malignancy.

Thirty patients with hypercalcaemia and known malignant disease were randomly allocated to receive 60 mg 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (APD) intravenously as a single dose or as consecutive daily doses of 30 mg (two days) or 15 mg (four days). The rate of infusion was the same for each regimen (7.5 mg/hour). Calcium concentrations fell in all patients and returned to normal in all but two. Relapse of hypercalcaemia occurred after a mean of 21 days in each group. Urinary calcium excretion fell in all groups and symptoms were greatly improved. After relapse patients were retreated with APD (30 mg as a single infusion) and normocalcaemia maintained by regular infusions at two to three week intervals. APD given as a single 60 mg infusion over eight hours together with rehydration is recommended as the initial management of the hypercalcaemia of malignancy, followed by 30 mg APD roughly every two to three weeks to maintain normal or near normal serum calcium concentrations.

Calcium↗
PubMed1988

Exercise and the immune response.

A growing number of reports have become available which implicate infectious disease with reduced performance in athletes. The immune system consists of both nonspecific and specific components geared to control infections. Adaptive immunity functions through both antibody-mediated and cell-mediated compartments to establish and maintain long term immunity to infectious agents. Evidence is accumulating to support the view that physical exercise can lead to modification of the cells of the immune system. However, studies have often not been well designed to control exercise protocols when examining the effects of exercise on the immune system. Large numbers of peripheral blood lymphocytes are mobilised with exercise and in vitro tests indicate that temporarily these cells may not be capable of responding normally to mitogens. These reactions appear to be influenced by hormones to some degree and there are reports that the cells of the immune system are extremely active biochemically and may depend on products from muscles to maintain their activity. Specific populations within the circulating leucocyte pool vary significantly with exercise and there is some evidence that the T4/T8 lymphocyte ratio may become significantly reduced. This reduction in ratio may be related to the variable responses to T and B cell mitogens recorded in vitro which overall suggests that a temporary immune suppression may exist following certain training or performance schedules. It is argued that this may lead to a temporary susceptibility to infection and could result from overtraining.

Antibody Formation↗