Search PubMed⌕ Search

Biomedical subjects

J A McCubbin

Publications and source records attributed to J A McCubbin.

At least 37 records · Page 2Linked to original sources
PubMed1993

Stress and endogenous opioids: behavioral and circulatory interactions.

Endogenous opioid peptides are the basis of a diverse system of complex neuroregulatory and endocrine mechanisms. While relatively quiescent in the resting state, these peptides are released during intense stimulation and modify, in a number of ways, circulatory homeostatic mechanisms. The endogenous opioids, primarily via endorphins and enkephalins, are capable of influencing circulatory responses to stress at the behavioral, the endocrinological, and the neural level. Recent research in humans and animals has described several roles for opioids in regulation of the circulatory stress response, and has also provided clues about the significance of opioid dysregulation in the pathophysiology of stress. Increased understanding of the basic mechanisms of stress and endogenous opioids will clarify the potential roles of opioids in important pharmacologic and behaviorally based therapeutics.

Animals↗
PubMed1992

Aerobic fitness and opioidergic inhibition of cardiovascular stress reactivity.

The role of endogenous opioids in aerobic fitness-induced decrements in cardiovascular stress reactivity was examined by comparing the effects of opioid antagonism with naltrexone on responses to stress in young adults with high versus low levels of aerobic fitness. Two hundred forty subjects were given an activity questionnaire and males with the highest (Fit) and lowest (Nonfit) aerobic activity profiles were recruited for maximal oxygen consumption (VO2max) treadmill testing and psychological stress testing (final sample N = 28). Heart rate and blood pressures were measured during performance on a computer-controlled arithmetic task after pretreatment with either naltrexone (Trexan, DuPont) or a placebo. During placebo challenges, Fit subjects, compared with Nonfit, showed lower heart rate reactivity during stress and lower mean arterial blood pressures immediately before and during recovery from stress. Naltrexone eliminated these reactivity differences by increasing heart rate reactivity and raising mean arterial blood pressure in Fit subjects. These data suggest that aerobic fitness is associated with enhanced opioidergic inhibition of circulatory stress reactivity. Opioidergic modulatory effects on stress reactivity may comprise an important mechanism in fitness-associated risk reduction for cardiovascular disease.

Adult↗
PubMed1992

Validity of a cardiorespiratory fitness test for men with mental retardation.

The purpose of this study was to validate a field test of cardiorespiratory fitness for men with mental retardation. The subjects were 19 healthy young men (26 +/- 6 yr) with moderate mental retardation (IQ = 48 +/- 11). Each subject underwent a maximal treadmill test after a three-phase familiarization process. Each subject also completed a 1-mile walk test twice (Rockport Fitness Walking Test = RFWT). The correlation coefficients between peak VO2 on the treadmill and the two 1-mile walks varied from 0.78 to 0.83. When weight, height, age, heart rates of 1-mile walks, and their combinations were held constant, the correlations were strengthened. Using multiple correlation analysis the best equation for predicting peak VO2 was: Peak VO2 = 101.92 - 2.356(mile-1 time) - 0.42(weight). This model accounted for 85% of total variance. The standard error of estimate was 4.06 ml.kg-1.min-1. The test-retest reliability of the RFWT for the 19 subjects used in this study was very high (R = 0.97). This finding suggests that the RFWT is a valid and reliable field test for this population and appears to be a valid indicator of cardiorespiratory fitness for these men with mental retardation.

Adult↗
PubMed1990

Resistance exercise training for persons with arthritis.

This article reviews the benefits of resistance exercise training in the rehabilitation of persons with arthritis. Without question, the person with arthritis has a need to develop muscular strength and endurance in order to maintain functional movement. Deficits in muscular strength, muscular endurance, range of motion, and other physical fitness indices have been identified clearly in the literature. Research studies have indicated that the effect of training persons with arthritis is promising; however, deficits exist in the literature on the types of specific exercise protocol that are most effective in training persons with arthritis. Guidelines for program development are provided with suggestions for alternative types of resistance exercise programs. It is hoped that the reader will look closely at resistance exercise programs as an important component in the rehabilitation of a person with arthritis.

Arthritis↗
PubMed1989

Differential glycemic effects of morphine in diabetic and normal mice.

C57BL/6J ob/ob mice, C57BL/6J+/? lean mice and A/J mice were given injections of 10 mg/kg of morphine or an equal volume of saline, and then blood was sampled by retroorbital sinus puncture. In addition, animals from each strain were exposed to a brief experimental stress ten minutes after the administration of morphine or saline. While morphine produced significant increases in serum glucose in albino mice, morphine lowered blood insulin in both C57BL/6J ob/ob and C57BL/6J+/? mice. Morphine significantly lowered blood insulin in A/J mice, but effects in C57BL/6J mice were not significant. In contrast, morphine attenuated blood glucose and insulin during stress in C57BL/6J ob/ob but did not significantly affect either glucose or insulin during stress in lean C57BL/6J or A/J mice. These results are interpreted in the light of other data suggesting that endogenous opiates modulate the effects of sympathetic nervous system activity in type II diabetes.

Animals↗
PubMed1989

Altered pituitary hormone response to naloxone in hypertension development.

Endogenous opioid regulation of blood pressure is altered during stress in young adults at risk for hypertension. We studied the effects of the opioid antagonist naloxone on the secretion of corticotropin and beta-endorphin during psychological stress in young adults with mildly elevated casual arterial pressures. Naloxone-induced secretion of both corticotropin and beta-endorphin was significantly diminished in persons at enhanced risk for hypertension compared with the low blood pressure control group. Results suggest that opioidergic inhibition of anterior pituitary function is altered in hypertension development.

Adolescent↗
PubMed1988

Diet-induced type II diabetes in C57BL/6J mice.

We investigated the effects of diet-induced obesity on glucose metabolism in two strains of mice, C57BL/6J and A/J. Twenty animals from each strain received ad libitum exposure to a high-fat high-simple-carbohydrate diet or standard Purina Rodent Chow for 6 mo. Exposure to the high-fat, high-simple-carbohydrate, low-fiber diet produced obesity in both A/J and C57BL/6J mice. Whereas obesity was associated with only moderate glucose intolerance and insulin resistance in A/J mice, obese C57BL/6J mice showed clear-cut diabetes with fasting blood glucose levels of greater than 240 mg/dl and blood insulin levels of greater than 150 microU/ml. C57BL/6J mice showed larger glycemic responses to stress and epinephrine in the lean state than AJ mice, and these responses were exaggerated by obesity. These data suggest that the C57BL/6J mouse carries a genetic predisposition to develop non-insulin-dependent (type II) diabetes. Furthermore, altered glycemic response to adrenergic stimulation may be a biologic marker for this genetic predisposition to develop type II diabetes.

Animals↗
PubMed1984

Naltrexone prevents footshock-induced performance deficit in rats.

Three experiments demonstrate that inescapable footshock delivered to unrestrained rats produces analgesia as well as performance deficits in subsequent one-way shuttle acquisition. Both the performance and the antinociceptive effects are prevented by pretreatment with as little as 0.1 mg/kg i.p. of the opiate antagonist, naltrexone. These studies suggest that both effects are mediated through opiate receptors with similar underlying naltrexone pharmaco-dynamics.

Analgesia↗
PubMed1984

Behavioral manipulation of the diabetic phenotype in ob/ob mice.

The genetically obese mouse (C57BL/6J ob/ob) is a commonly used model of non-insulin-dependent diabetes mellitus. However, our studies demonstrate that, while the animal is significantly hyperinsulinemic, it in fact does not show consistent hyperglycemia in the resting state. During stress, both obese animals and their lean littermates become hyperglycemic, but the magnitude of the hyperglycemia is exaggerated in the obese mice. Obese animals also show an exaggerated plasma glucose increase in response to epinephrine injection. This increase in plasma glucose is accompanied by a decrease in plasma insulin in response to both stress and epinephrine. Our findings suggest that environmental stimuli influence the expression of diabetes in the C57BL/6J obese mouse and therefore must be considered in studies of this animal model of diabetes.

Animals↗
PubMed1980

The value of no-touch isolation technique for resection of cancer. The eye as a model.

The role of the no-touch technique was examined using retinoblastoma and primary choroidal malignant melanoma of the eye as a model. Choroidal invasion, tumor friability, and tumor vascularity are important factors that render these two tumors susceptible to metastasis secondary to intraorgan pressure increases. Animal studies on no-touch enucleation procedures show that increased intraocular pressure during enucleation decreases survival rates considerably providing the tumor has invaded the choroid but has not yet metastasized. This "critical stage" correlates well with earlier data on the no-touch technique studied in noneye models. In humans, standard enucleations create intraocular pressures measured up to 500 mm Hg. The no-touch technique is applicable to the therapy of retinoblastoma and primary choroidal malignant melanomas, but long-term clinical studies are needed to establish the true benefit.

Animals↗
PubMed1979

Hemodynamic and metabolic adjustments during exercise and shock avoidance in dogs.

The purpose of this study was to examine whether the hemodynamic and metabolic consequences of a physical (treadmill excercise) and behavioral (signaled shock-avoidance) stressor could be differentiated. To do this, direct continuous recordings of cardiac output, systolic and diastolic blood pressure, and discrete determinations of the arterial-mixed venous oxygen ((a-v)O2) content difference were analyzed in six dogs during exposure to three grades of treadmill exercise and when working on a shock-avoidance task. The results indicated that in five animals the relationship between cardiac output and the (a-v)O2 difference during shock-avoidance conditioning was significantly different from the corresponding pattern observed during exercise. In four animals the data suggested that avoidance conditioning, relative to exercise stress, elicited overperfusion. Behavioral stress also produced reliable elevations in diastolic and systolic blood pressure. These results suggest that, when compared to physical stress, behavioral stress can produce a dissociation of cardiovascular and metabolic processes in the presence of acute pressor responses.

Animals↗
PubMed1979

Infant heart rate response to trigeminal airstream stimulation: determination of normal and deviant values.

In this study, trigeminal airstream stimulation is used on a group of normal, sleeping infants to screen for reflex bradycardia. Infants were tested at 1--3 days and at 4, 8, 12, and 16 weeks of age. The usual heart rate response was acceleration above the prestimulus level. The amount of heart rate change was seen to depend on prestimulus rate and, to a lesser extent, postconceptional age. Multiple regression analysis of the data provided estimates of expected responses, given postconceptional age and prestimulus heart rate. From these, ranges were established for classification of normal or abnormal responses. Six deviant data points over 2 SDs from expected values were identified. Two of these represented heart rate increases and four were heart rate decreases. One deviant heart rate decrease was over 3 SDs from the mean. Although the deviant increases were thought to represent exaggerated startles, the more severe heart rate decreases were believed to be a reflex resembling the diving reflex.

Heart Rate↗