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Biomedical subjects

Z V Kendrick

Publications and source records attributed to Z V Kendrick.

29 records · Page 2Linked to original sources
PubMed1986

A reappraisal of caloric requirements in healthy women.

The caloric expenditure of 44 healthy, lean and obese women, 8 of whom were trained athletes, was measured by indirect calorimetry. Body composition was determined. Ages ranged from 18-65 yr and body weights from 43-143 kg. Stepwise, multiple-regression analysis was used to determine whether one or several variables best predicted the resting metabolic rate (RMR) of the women. The RMR and the thermic effect of food (TEF) were measured before and after the women consumed a mixed breakfast meal. The results showed that the currently available tables and regression equations overestimate the RMR of healthy women by 7-14%. Body weight was highly related to the RMR, and stepwise inclusions of various variables did not improve predictions of RMR. The slopes of the regression lines for nonathletes and athletes were significantly different. Regression equations for predicting RMR of women were developed: Nonathletes RMR = 795 + 7.18 kg WT; Athletes RMR = 50.4 + 21.1 kg WT. The range of RMR per kilogram body weight was wide for nonathletic, but narrow for athletic women. The metabolism of some lean and obese, nonathletic women was highly efficient, predisposing these women for developing and maintaining body fat. The TEFs were indistinguishable between nonathletic and athletic women, and formed a continuum from the lightest to the heaviest woman.

Adolescent↗
PubMed1984

Exercise activation of myocardial lipoprotein lipase in male and estrogen-treated female rats.

Lipoprotein lipase (LPL) is the rate-limiting enzyme in the utilization of plasma triglycerides by extrahepatic tissues. The present study examined the effect of estrogen upon the circadian rhythm of rat myocardial LPL and upon the endothelial-bound and tissue components of rat myocardial LPL immediately after exhaustive exercise. Female rats were ovariectomized at 28 days. Estrogen replaced female rats (ER) received 17-beta-estradiol in sunflower oil (200 micrograms/100 g body weight/week for 4 weeks). Oil-injected female rats (OI) received sunflower oil (0.1 mL/100 g body weight/week for 4 weeks). Normal male rats (M) were studied for comparison. ER, OI, and M animals were killed every four hours starting at 8 AM. Estrogen treatment did not alter the circadian rhythm of LPL activity. A second group of animals were run to exhaustion on a motorized treadmill, starting at 9 AM. ER animals performed significantly more work (P less than 0.05) than OI or M rats. Liver glycogen concentration was reduced 96.8% to 97.8% from control in all three groups after exercise. Both the tissue and endothelial fractions of LPL activity were elevated after exercise in all three groups. Exercised ER females (116.3 +/- 9.0 units) had significantly higher cardiac tissue enzyme activity than exercised males (85.0 +/- 9.4 units). Heparin-releasable LPL activity in exercised ER rats (65.3 +/- 5.7 units) was 43% higher than in exercised M rats (45.5 +/- 5.6 units) and 53% higher than in OI female rats (42.6 +/- 8.1 units).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effect of sexual maturation and exhaustive exercise on myocardial glycogen metabolism.

Prepubertal, pubertal, and postpubertal (28, 45, and 60 days old, respectively) rats of both sexes were run to exhaustion on a motor-driven treadmill to determine whether sexual maturation was involved in the glycogen sparing phenomenon previously reported in the myocardium of female rats receiving high doses of estrogen. Positive work was calculated and was not different in the male and female age-paired rats. Liver glycogen was significantly depleted by 92-98% in male and 96-97% in female exercising rats of all ages. The exercise bout resulted in significant depletion of glycogen in the red and white portions of the vastus lateralis muscle of male and female animals. At 45 and 60 days of age female animals had significantly more glycogen in the red muscle at exhaustion than age-paired males. Myocardial glycogen was significantly depleted by 32, 38, and 41% in prepubertal and pubertal males and prepubertal females, respectively. Pubertal females depleted myocardial glycogen by 19% (P less than 0.05). Postpubertal male animals exhibited a 46% depletion of myocardial glycogen (P less than 0.01), while myocardial glycogen in sexually mature females was not decreased at exhaustion. These data indicate that a myocardial glycogen sparing phenomenon exists in vivo in sexually mature female rats. These data further suggest that the glycogen sparing phenomenon develops in association with sexual maturation.

Animals↗
PubMed1981

Effect of an exercise run to exhaustion on cAMP in the rat heart.

The purpose of this investigation was to determine whether adenosine 3',5'-cyclic monophosphate (cAMP) content is increased in vivo in the heart as a result of exercise at a time when there is rapid cardiac glycogen utilization. Rats were run to exhaustion on a treadmill for a period of 164.5 +/- 9.5 min. Blood norepinephrine and epinephrine were significantly elevated approximately 2.5-fold above resting levels at the end of the treadmill run. Myocardial glycogen was reduced by 54.7% at exhaustion compared with control values. Myocardial cAMP was significantly elevated 88% above control levels as a result of the run. Associated with the depletion of myocardial glycogen and the elevation of cAMP was an activation of phosphorylase to its a form. These data suggest that myocardial glycogen metabolism during exercise is, in part, mediated by hormonal influences that are associated with increases in cAMP.

Animals↗
PubMed1980

Pharmacokinetic studies of taurine in bovine Purkinje fibers.

Taurine (2-aminoethane sulfonic acid) is found in high concentrations in the heart, particularly in Purkinje fibers. We studied the transport of taurine in Purkinje fibers that were excised rapidly from the heart and placed in a vessel containing oxygenated Krebs-Henseleit solution (37 degrees C). After equilibration, 4.4 x 10(-6)M radiolabeled taurine[14C] was added to the bath. A computer compartmental analysis of the uptake and efflux indicated the presence of two pools for uptake--a pool with a rapid kinetics K1 (t1/2 = 0.80 min) and K2 (t1/2 = 176.30 min). These studies suggest that Purkinje fibers have the capacity to transport taurine rapidly. Michaelis-Menten procedures showed the presence of a high affinity and a low affinity transport process. Guanidinotaurine, at a 10:1 ratio, had no appreciable effect on taurine uptake, but 3-aminopropane phosphonic acid decreased taurine uptake by 42.7%. Ouabain and acetylstrophanthidin (10(-5) M) inhibited taurine uptake (K1) by 34% and 73%, respectively. The inhibition of the rapid component of taurine uptake suggests that K1 is an energy-linked process possibly requiring Na+,K+-ATPase. Taurine uptake in a calcium-free medium was decreased by 58%. Verapamil (6 x 10(-6) M) decreased taurine uptake by 42%. Tetrodotoxin (3.4 x 10(-5) M) decreased taurine uptake by 51%. The requirement of calcium and sodium for taurine uptake suggests an important relationship between taurine, calcium, and sodium in the function of fibers in the cardiac conducting system.

Animals↗
PubMed1979

Blood levels following intravenous and endotracheal epinephrine administration.

The blood levels of epinephrine and its metabolites which were obtained when the drug was given by both the intravenous (IV) and endotracheal (ET) routes were compared. Anesthetized dogs were subjected to radioactive epinephrine in doses of 0.005, 0.03, 0.06, and 0.09 mg/kg administered both intravenously and endotracheally. Blood levels were obtained at 0.25, 0.75, 1.5, 3, 5, 10 and 30 minutes following injection and analyzed by thin layer chromatography. The maximum measured concentration following IV injection was observed at 15 seconds. Epinephrine was rapidly metabolized with 20% of the original concentration detected at 5 minutes following IV injection. When the drug was given by the ET route, the maximum measured concentration was similarly observed at 15 seconds. Following ET installation, initial blood concentrations are sustained over a much longer period of time and 80% of the initial concentration was detected at 5 minutes. Maximum concentrations are approximately one-tenth of those achieved with an equal IV dosage. It is concluded that endotracheally and intravenously administered epinephrine rapidly reach maximum blood levels although there are differences in kinetics between the two routes.

Animals↗
PubMedDate not supplied

Correlation of platelet taurine levels with thyroid function.

Changes in neurotransmitter or neuromodular activity and levels have been thought to be responsible for some of the behavioral characteristics observed in patients with thyroid disease. To investigate these relationships, taurine, a proposed inhibitory neurotransmitter or modulator, was measured in platelets, which may serve as biochemical model for synaptosomes. Blood of euthyroid, hypothyroid and hyperthyroid patients was collected. Thyroxine was determined by RIA. Platelets were separated using differential centrifugation techniques. The taurine in platelets was separated by ion exchange chromatography and was assayed spectrophotometrically as a product produced by coupling with dinitrofluorobenzene. In hypothyroid, untreated hyperthyroid and euthyroid individuals, taurine/platelet and number of platelets/ml of blood were inversely related. In propranolol-treated hyperthyroid patients, such a relation was not found. Following initial treatment with either antithyroid drugs (i.e. methimazole or propylthiouracil) and/or propranolol, taurine/platelet returned to euthyroid levels while plasma thyroxine levels remained elevated. These data implicate a relationship between taurine in platelets and the thyroid state in man.

Blood Platelets↗