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Biomedical subjects

B L Metzger

Publications and source records attributed to B L Metzger.

14 recordsLinked to original sources
PubMed2001

Effect of genetic obesity on thermoregulatory activity responses to inversion of the light/dark cycle.

In this pilot work, the authors compared the circadian rhythm responses of 3-month-old female fatty Zucker rats with those of lean Zucker rats and Sprague-Dawley rats to reversal of the light/dark (LD) cycle. Core temperature and spontaneous cage activity were continuously monitored by implanted microtelemetry devices prior to and for 5 days following complete LD cycle reversal. By the 5th day after LD reversal, temperature rhythm nadir had phase-advanced 10.5 hours in the lean Zucker rats, 10.8 hours in the Sprague-Dawley rats, and only 3.8 hours in the fatty Zucker rats. Similarly, total activity increased in lean Zucker rats and Sprague-Dawley rats after LD reversal but declined in the fatty Zucker rat during the same time. Results of this study show that obese Zucker rats displayed an impaired ability to reentrain circadian rhythms for temperature and activity when compared to lean Zucker rats and Sprague-Dawley rats. These findings suggest that dysfunction in the circadian pacemaker previously shown to manifest itself by 43 weeks of age in fatty Zucker rats may already be present at 3 months of age and suggest that altered thermoregulation may play a role in the development of obesity in this animal model of genetic obesity.

Animals↗
PubMed2001

Effects of exercise conditioning on thermoregulatory response to anticholinesterase insecticide toxicity.

Chronic exercise conditioning has been shown to alter basal thermoregulatory processes (change in thermoregulatory set point) as well as the response to infectious fever Chlorpyrifos (CHP), an organophosphate insecticide, also affects thermoregulation, causing an acute period of hypothermia followed by a delayed fever. This study examined whether chronic exercise training in the rat alters the thermoregulatory response to CHP. Core temperature and motor activity were monitored by radiotelemetry in female Sprague-Dawley rats housed individually at an ambient temperature of 22 degrees C. The rats were either given continuous access to running wheels or housed in standard cages without wheels. The exercise group ran predominately at night. After 8 weeks, the rats were gavaged with corn oil or 15 mg/kg CHP. CHP induced a transient hypothermic response followed by a delayed fever, beginning 1 day after exposure. Relative to controls, T7 decreases were not significantly different between the exercise (1.6 degrees C) group and the sedentary (0.5 degrees C) group given CHP. The sedentary and exercise group administered CHP developed a fever the day after CHP treatment. The fever response was greater in the sedentary group and persisted for approximately 3 days post-injection. Fever of the exercise group persisted for just one-half of 1 day after CHP. It is well known that chronic exercise training improves aerobic capacity; however, trained rats were not protected from the hypothermic effects of CHP. Training did ameliorate the febrile effects of CHP. Thus, exercise training may afford protection to the toxic effects of organophosphate insecticides.

Animals↗
PubMed2000

The effect of a high-fat diet and exercise on the expression of genetic obesity.

In the United States, there are 300,000 obesity-related premature deaths each year. Furthermore, no current obesity treatment program results in consistent weight reductions. Obesity is thought to be caused by complex genetic-environmental interactions. We studied the effect of two environmental factors, high-fat diet and non-weight-bearing exercise, on obesity expression. Young adult, female, genetically obese (fa/fa) rats (n = 52) and their lean (Fa/fa) littermates (n = 24) were studied using an experimental 2 x 2 x 2 factorial design (diet type, genetics, and exercise). Repeated measures ANOVA and secondarily stepwise regressions were used to analyze the data. The authors discovered that the effect of appetite on obesity expression is more limited than expected, and there may be critical stages when obesity expression is amenable to environmental modification.

Analysis of Variance↗
PubMed1990

Ethnic differences in physiological responses associated with the Valsalva maneuver.

Ethnic differences in cardiovascular indices at rest and across the Valsalva maneuver (VM) were studied in 30 Asian, 86 Caucasian, and 12 Black healthy men and women aged 30 to 55 years. Subjects simulated the VM by blowing into an aneroid pressure-gauge meter to 40 mmHg for 10 seconds. Resting systolic blood pressure (SBP) was significantly higher in Blacks than in Asians or Caucasians. During the strain phase of the VM, the fall in SBP from baseline was significantly greater in Asians and Blacks than in Caucasians. Further, Asians had the greatest overshoot of SBP above baseline. Although resting heart rate was significantly higher in Asians compared to Caucasians, there were no differences in heart rate responses to the VM. Reduction in carotid artery blood flow velocity during strain was significantly less in Blacks. We conclude that there are ethnic differences in cardiovascular indices at rest and across the VM.

Adult↗
PubMed1989

Exercise and functional capacity after myocardial infarction.

This paper summarizes the literature on the effects of both inpatient and outpatient exercise programs on functional capacity in patients categorized as having mild, moderate, severe and very severe left ventricular damage after myocardial infarction (MI). Current evidence suggests that inpatient activities of daily living programs do not improve functional capacity as measured by a predischarge exercise stress test. In contrast, outpatient exercise training programs can improve functional capacity through augmentation of skeletal muscle arteriovenous oxygen difference (oxygen extraction) in nearly all patients with mild left ventricular damage, in most patients with moderate damage and in a few patients with severe damage. The recently developed conceptual model of functional capacity in post-MI patients presented in this paper underscores the need for assessment of the level of structural and functional impairment of the left ventricle before the nurse prescribes any type of exercise program. It also enables the nurse to begin to explain why post-MI patients differ in their response to exercise. Further research is needed, however, before the model can be used for predicting exercise outcomes in the clinical setting.

Activities of Daily Living↗
PubMed1989

Hepatic glucose production and insulin sensitivity preceding diabetes in monkeys.

The purpose of this study was to identify the relationship between basal hepatic glucose production (HGP) and peripheral insulin sensitivity as assessed by the hyperinsulinemic euglycemic clamp prior to and during the development of non-insulin-dependent (type 2) diabetes mellitus in rhesus monkeys. Twenty-six male monkeys (Macaca mulatta), including normal animals and monkeys in various phases of the development of spontaneous obesity-associated type 2 diabetes were studied. Fasting plasma glucose (FPG) and insulin (FIRI), basal HGP using a [3H]glucose infusion, and peripheral insulin sensitivity (as determined by the euglycemic clamp technique) were examined. The earliest change that could be detected was a significant reduction in peripheral insulin sensitivity accompanied by increased FIRI. These changes preceded a significant deterioration of glucose tolerance. Basal HGP changed in parallel with FPG (r = 0.90, P less than 0.001), becoming significantly elevated only when FPG rose to levels diagnostic of diabetes (greater than 140 mg/dl). Thus basal HGP and fasting glucose levels showed no significant changes early in the development of type 2 diabetes. We conclude that the early serial decreases in insulin sensitivity and progressive increases in FIRI, with or without decreased glucose tolerance, are prognostic of the future development of diabetes in obese monkeys, a longitudinal process that is also likely to be observed in most if not all obese humans progressing to diabetes.

Animals↗
PubMed1985

Nutrient composition: effects on appetite in monkeys with oral factors held constant.

The effects of macronutrients on appetite and total caloric intake in monkeys (Macaca mulatta) was studied using a new feeding and infusion system which yoked intragastric infusion of various nutrients to oral ad lib intake and removed the confounding factor of palatability from the assessment of nutrient effects on feeding behavior. A suction-activated liquid diet feeding system provided free access to a nutritionally complete diet, with 1 ml of diet delivered orally by pump with each discrete suck by the monkey. A second pump was yoked to the oral feeding pump and delivered various nutrients directly into the stomach via an implanted intragastric cannula. Thus, while oral diet composition remained constant, the net diet reaching the stomach varied over ranges of 28 to 77% carbohydrate, 16 to 65% fat and 7 to 36% protein. No significant differences in total caloric intake were observed between intakes of diets with net composition of high carbohydrate or high fat. When protein was increased to 36%, total caloric intake was generally reduced, and this effect was sustained for at least 3 weeks. Therefore, protein appears to have an increased specific satiating effect beyond the caloric content, when compared to carbohydrate or fat.

Animals↗
PubMed1985

Adiposity, anthropometric measures, and plasma insulin levels of rhesus monkeys.

In order to characterize spontaneous adult-onset obesity in a non-human primate model, we have studied a group of twenty-four obese and non-obese male rhesus monkeys (Macaca mulatta). The monkeys, ranging in age from 12 to 27 years, were defined as obese on the basis of tritiated water estimates of body fat content exceeding 25 percent of body weight. Although the obese and non-obese monkeys had similar crown-rump lengths, they differed significantly not only in body weight (17.0 +/- 3.2 vs 11.7 +/- 1.8 kg, X +/- s.d., P less than 0.001), and average body fat content (37.8 +/- 6.6 vs 13.2 +/- 5.4 percent, P less than 0.001) but also in midgirth circumferences (57.5 +/- 8.4 vs 34.8 +/- 6.2 cm, P less than 0.001) and abdominal (but not triceps or scapular) skinfold thicknesses (22.74 +/- 5.8 vs 9.82 +/- 1.82 mm, P less than 0.001), thus, indicating the predominantly abdominal distribution of the fat mass. A new Obesity Index Rh, for rhesus monkeys, defined as body weight divided by the square of the crown-rump length, was developed as an adaptation of obesity indices used for humans and rats. The high correlation of the Obesity Index Rh with percent body fat and its relative independence of height make possible future identification of obese rhesus monkeys on the basis of anthropometric measurements. There were slight, but not significant, differences between the obese and the non-obese groups in lean body mass (10.9 +/- 2.8 vs 8.8 +/- 1.8 kg) and in fasting plasma glucose levels (87.1 +/- 31.8 vs 63.2 +/- 7.5 mg/dl). Obese monkeys had significantly larger average fat cell sizes (1.29 +/- 0.54 vs 0.61 +/- 0.29 microgram lipid/cell, P less than 0.05) and significantly greater fat cell numbers (6.1 X 10(9) vs 2.2 X 10(9), P less than 0.01). Fat cell numbers were better correlated with body weight and total body fat parameters than fat cell size, while fat cell size was more closely associated with the log of fasting plasma insulin levels than was fat cell number. The similarities to studies in humans indicate the importance of the spontaneously obese adult rhesus monkey as an animal model in the study of obesity.

Adipose Tissue↗
PubMed1983

Cholecystokinin effects on feeding, glucose, and pancreatic hormones in rhesus monkeys.

The effects of cholecystokinin on feeding, and on plasma glucose and pancreatic hormone responses to a mixed-meal were determined in lean rhesus monkeys. Following an overnight fast the octapeptide of cholecystokinin (CCK-8) was administered intravenously over a 6 minute period coincident with the initiation of free feeding or an intragastric infusion of a mixed liquid diet. CCK-8 inhibited feeding and delayed the plasma glucose and insulin response to a mixed-meal. The threshold for the feeding effect ranged from 30 to 120 ng/kg/min across monkeys and did not extend beyond 15 minutes of the start of the CCK infusion. The delays in plasma glucose and insulin were not dependent on rate or amount of food entering the stomach. Further, there were no alterations from basal levels in plasma glucose or insulin prior to the onset of CCK-induced feeding inhibition. There was no evidence that CCK-8 stimulated insulin release, nor was the usual close relationship between plasma glucose and insulin levels in response to a mixed-meal changed by CCK-8.

Animals↗
PubMedDate not supplied

Effect of position on cardiovascular response during the Valsalva maneuver.

Sudden cardiac death (SCD) has frequently been associated with the Valsalva maneuver (VM), which is characterized by sudden intense changes in systolic blood pressure (SBP) and heart rate (HR). The purpose of this study was to examine the effect of manipulating body position on the intensity of SBP and HR changes during the VM. Thirty-two men and 32 women (35-55 years) without a history or signs of cardiovascular disease (CVD) were studied. Subjects produced a VM of 40 mmHg for 10 seconds in each of five randomly assigned bed (flat, sidelying, 30 degrees elevated, 70 degrees elevated) and chair positions. Age covaried with SBP and HR responses to the VM. When age relationships were factored out, the most intense changes in SBP during the VM occurred in the 30 degrees and 70 degrees elevated and chair positions. Persons with a history of atherosclerotic CVD, on bedrest, should be positioned with head of the bed flat to reduce cardiovascular risks associated with the VM.

Adult↗
PubMedDate not supplied

Effects of age on autonomic cardiovascular responsiveness in healthy men and women.

Blood pressure and heart rate responses to the Valsalva maneuver (straining) were used to quantify the effects of age on autonomic cardiovascular responsiveness in 110 healthy men and women, 30 to 76 years. In general, aging was associated with diminished sympathetic responsiveness during strain. In women, however, the predominant age effect was a significant reduction in bradycardic response to systolic blood pressure overshoot following release of strain. When present, age-related differences in cardiovascular responses to the Valsalva maneuver were manifest by age 45. These findings are consistent with an age-related diminution of autonomic cardiovascular responsiveness in healthy adults. Moreover, they suggest that interventions to reduce the frequency and intensity of straining may be especially important in older adults in order to minimize health risks associated with rapid, abrupt changes in blood pressure.

Adult↗
PubMedDate not supplied

Preexisting physical activity level and cardiovascular responses across the Valsalva maneuver.

To determine the effect of preexisting physical activity level on resting cardiovascular measures and the intensity of cardiovascular responses across the Valsalva Maneuver (VM), 131 young (30-55 years) and 67 older (greater than 55 years) healthy adults, classified into sedentary, active, semitrained, or trained groups, were studied. Resting heart rate (HR) was lower in all trained subjects. In contrast, resting diastolic blood pressure was lower in young but not older trained subjects. During the VM, the expected fall in systolic blood pressure (SBP) from baseline during strain was less in young trained but not older trained subjects. Physical training significantly lessened the intensity of SBP and HR responses during the overshoot phase of the VM only in young subjects, most often in young males.

Adult↗