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Biomedical subjects

L E Hart

Publications and source records attributed to L E Hart.

At least 19 recordsLinked to original sources
PubMed1992

Ionic and endocrine characteristics of reproductive failure in calcium-deficient and vitamin D-deficient laying hens.

Whole blood ionized calcium and plasma total calcium, inorganic phosphorus, estradiol-17 beta, progesterone, and 1,25-di-hydroxycholecalciferol concentrations were measured in calcium- or vitamin D-deficient Single Comb White Leghorn hens. Control birds were serially sampled every 2 h for 26 h immediately following oviposition until the next oviposition. Deficient birds, which had ceased laying 10 to 14 days prior to sampling, were sampled at the same times. The control birds had significantly higher mean total and bound plasma calcium and inorganic phosphorus concentrations than the deficient hens. Control and vitamin D-deficient hens had similar mean ionized calcium concentrations. Control hens exhibited a cyclic pattern in ionized calcium and inorganic phosphorus concentrations over the sampling period that was related to shell calcification. Deficient hens showed no changes in ionized calcium concentration during this time. Plasma 1,25-dihydroxycholecalciferol concentrations were significantly higher in the calcium-deficient birds than the control or vitamin D-deficient hens. Mean plasma estradiol-17 beta and progesterone concentrations were consistently higher in the control hens than the deficient hens. Consistent with this observation were decreases in ovary and oviduct weights, which occurred in the nonlaying deficient hens.

Animals↗
PubMed1992

Aerobic fitness and hormonal responses to prolonged sleep deprivation and sustained mental work.

This study examined the influence of aerobic fitness on the responses of selected hormones to the combined stressors of sleep deprivation (SD) and sustained mental work. Six aerobically high fit (HF) (VO2max greater than 50 ml.kg-1.min-1) and six average fit (AF) (VO2max less than 40 ml.kg-1.min-1) female subjects were subjected to a period of sleep loss of 60 h during which time they performed sustained mental tasks with no physical activity component. Venous blood samples were drawn every 12 h at 1330 hours and 0130 hours and plasmas analyzed for cortisol, growth hormone (hGH), prolactin, thyroxine (T4), triiodothyronine (T3), and reverse-triiodothyronine (rT3). For cortisol, both the HF and AF groups exhibited the normal high-daytime and low-nighttime pattern of secretion, with levels increasing significantly as the duration of SD increased. The normal elevations of hGH and prolactin levels during normal sleep were suppressed during SD. No significant fitness effects were found for cortisol, hGH, and prolactin responses. Plasma levels of T4, T3, and rT3 increased significantly during SD, with highly fit subjects exhibiting higher levels of these hormones than those of average fitness. We suggest that aerobic fitness may influence the peripheral metabolism of T4 during SD, but that aerobic fitness does not influence the regulation of the classical stress hormones during SD.

Adult↗
PubMed1991

Dioxin contamination and growth and development in great blue heron embryos.

A great blue heron colony located near a pulp mill in British Columbia failed to fledge young in 1987, with a concurrent sharp increase in polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) levels in their eggs. In 1988 we tested the hypothesis that the PCDD and PCDF contamination caused reproductive failure by increasing mortality of the heron embryos in ovo. Pairs of great blue heron eggs were collected from three British Columbia colonies with low, intermediate, and high levels of dioxin contamination: Nicomekl, Vancouver, and Crofton, respectively. One egg of each pair was incubated under laboratory conditions at the University of British Columbia (UBC) while the other egg was analyzed for PCDDs and PCDFs. All incubated eggs were fertile. All eggs from the Nicomekl colony hatched, while 13 of 14 eggs from Vancouver and 12 of 13 eggs from Crofton hatched. Subcutaneous edema was observed in 4 of 12 chicks from Crofton and 2 of 13 chicks from Vancouver. No edema was seen in the chicks from Nicomekl. There was a small, but significant, negative regression of plasma calcium concentration, yolk-free body weight, tibia length, wet, dry, and ash weight, beak length, and kidney and stomach weight of the hatched chicks on the tetrachlorodibenzo-p-dioxin (TCDD) level of the paired eggs. Fewer down follicles were present on the heads of TCDD-contaminated chicks. Hence while dioxins did not cause mortality of the heron embryos in ovo, the depression of growth and the presence of edema are suggestive that dioxins at the levels found in the environment have an adverse effect on the development of great blue heron embryos.

Animals↗
PubMed1991

The effect of taurine transport antagonists on cardiac taurine concentration and the incidence of sudden death syndrome in male broiler chickens.

Two experiments were conducted in which 540 day-old male broiler chickens were raised in heated battery brooders to 4 wk of age. Diets contained taurine antagonists to test effects on cardiac taurine content and the incidence of Sudden Death Syndrome (SDS). In Experiment 1 treatments during Weeks 2 to 4 were A) basal diet; B) basal diet supplemented with .25% guanidinoethyl sulfonate (GES) in Week 2 and 1.5% GES in Weeks 3 and 4; and C) basal diet supplemented with .5% GES in Weeks 2 to 4. The taurine content of heart was significantly reduced (P less than .05) with GES supplementation, but no effects on SDS mortality rates were noted. In Experiment 2 birds received diets containing 0. 2.5, or 5% beta-alanine. Supplementation with this compound decreased cardiac taurine concentration to extremely low levels (P less than .05). No significant effects on SDS mortality rates were noted. The results are interpreted as suggesting that taurine does not play a major role in the etiology of SDS.

Animals↗
PubMed1991

Comparison of four articular indices for use in clinical trials in rheumatoid arthritis: patient, order and observer variation.

Using a Latin square design, 4 patients were examined by 4 rheumatologists. Joints were scored for tenderness and inflammation. The Ritchie, the index of the American Rheumatism Association (ARA), the Hart modified Ritchie and a simplified Lansbury index were calculated from the raw data. The results suggest that an articular index consisting of a simple count of tender joints (Hart modified Ritchie) or a simple count of tender or swollen joints (ARA index) are the most reproducible with multiple observers. We suggest that these indices would be most appropriate for multicenter clinical trials.

Arthritis, Rheumatoid↗
PubMed1990

Comparison of polychlorinated dibenzodioxin levels with hepatic mixed-function oxidase induction in great blue herons.

As part of the Canadian Wildlife Service monitoring of great blue herons in British Columbia, eggs were collected from three colonies with low, intermediate, and high levels of PCDD and PCDF contamination: Nicomekl, Vancouver, and Crofton, respectively. One egg from each nest was used for chemical analysis by GC-MS; the others were hatched. Liver microsomes were prepared from the heron chicks and used for determination of cytochrome P-450-dependent activities. No erythromycin N-demethylase activity was found in any sample. Ethoxyresorufin O-dealkylase activity in the Nicomekl group was similar to that in pigeons, a control altricial species. The ethoxyresorufin activity in the herons from the Crofton colony was 2.6-fold higher than in the Nicomekl group. The Vancouver colony was intermediate. No difference among the three heron colonies was found in pentoxyresorufin O-dealkylase activity, although levels were 20-33 times that in the pigeon. Chemical analysis was carried out on paired heron eggs. Vancouver and Crofton eggs contained 13.5 and 21 times the levels of 2,3,7,8-TCDD compared to the Nicomekl group. The Crofton eggs contained higher levels of several other contaminants also. A highly significant correlation (p less than .001) was found between ethoxyresorufin O-dealkylase and 2,3,7,8-TCDD concentrations. The correlation coefficient did not change when ethoxyresorufin O-dealkylase was compared to total chemical contamination using several toxic equivalency factors. Multiple regression analysis resulted in only one predictor variable for ethoxyresorufin O-dealkylase: 2,3,7,8-TCDD.

Animals↗
PubMed1990

Moderate exercise and hemodilution during sleep deprivation.

The effect of 52 h of sleep deprivation (SD) upon blood constituents was studied in 12 young women aged 21.5 +/- 0.4 years. Subjects were individually isolated without time cues, performing a sequence of cognitive tasks. Significant decreases in hematocrit (p less than 0.002) and red cell count (p less than 0.04) developed, mainly over the first 28 h of SD, reaching a subsequent plateau or partial recovery. The calculated plasma volume also increased by 10.7 +/- 3.1% at 52 h, with recovery to a 6.9 +/- 3.2% increase the following day. About 1 L of water was retained over the first 30 h of SD, with a subsequent partial elimination of this excess. Plasma albumin and total protein concentrations were largely sustained in the face of the plasma expansion. The plasma pH showed a progressive fall from a baseline value of 7.381 +/- 0.014 to 7.332 +/- 0.006 at 52 h, while plasma bicarbonate decreased from a baseline figure of 31.2 +/- 0.7 to 26-27 mM/L (p less than 0.05). After 8 weeks, all subjects repeated the experiment, with the introduction of 30 min of exercise in the 40th h of wakefulness. Hematocrit and plasma volume changes were similar to those of the first experiment up to the time of exercise, but hematocrit decreased and plasma volume increased after the exercise bout, rather than reaching a plateau. Plasma pH increased with exercise, but returned to the previous low level at 52 h. Any arousing effect of the exercise bout was transient. The plasma expansion reflects metabolic and/or respiratory acidosis, plus possible effects of a prolonged period without recumbency.

Adult↗
PubMed1989

Effects of sexual and physical abuse: a comparison of adolescent inpatients.

The present study was designed to collect descriptive data on a sample of hospitalized adolescents who were victims of sexual and/or physical abuse and to compare these groups to patients without a history of abuse. A questionnaire was administered to 51 inpatient teenagers at Fort Logan Mental Health Center, a state psychiatric hospital in Denver, Colorado. Information was obtained about family background, type, extent and duration of abuse, drug and alcohol abuse and self-reported mental health and general adjustment problems. In addition, clinical staff completed the Revised Behavior Problem Checklist (1) for the subjects. The results indicated statistically significant differences (p less than .05) between groups with adolescents who were both physically and sexually abused reporting the most problems. The implications for the findings for treatment are discussed.

Adolescent↗
PubMed1989

The Ontario cohort study of running-related injuries.

A cohort of 1680 runners was enrolled through two community road race events and monitored during a 12-month follow-up period for the occurrence of musculoskeletal injuries. Forty-eight percent of the runners experienced at least one injury, and 54% of these injuries were new; the remainder were recurrences of previous injuries. The risk of injury was associated with increased running mileage but was relatively unassociated with other aspects of training, such as usual pace, usual running surface, hill running, or intense training. Injury rates were equal for all age-sex groups and were independent of years of running experience. Runners injured in the previous year had approximately a 50% higher risk for a new injury during follow-up.

Adolescent↗
PubMed1987

Endocrinology of the avian embryo: an overview.

The full endocrine system is developed during the embryonic stages of the domestic fowl and probably in all avian species. This involves the genesis and differentiation of endocrine cells and progressive acquisition of interactions between endocrine tissues leading to integrated series of control systems. The embryonic endocrine organs produce hormones with a variety of physiological roles (including homeostatic, homeorhetic, and anticipatory). The present chapter provides an overview of the recent advances in the endocrinology of the avian embryo. Particular attention is focused on the general phenomenon of endocrine development and on the ontogeny of the hypothalamo-pituitary (growth hormone)-somatomedin-growth axis, the hypothalamo-pituitary-thyroid axis, and the hormones of calcium homeostasis.

Animals↗
PubMed1987

DNA quaternary structure in the radiation sensitivity of human lymphocytes--a proposed role of copper.

On challenging with 2M NaCl, the nuclei of human lymphocytes yield an aggregate of DNA-protein material. The density of the material is less when isolated from irradiated cells than when isolated from unirradiated cells. The density of this material, designated histone-free-DNA (HF-DNA), from irradiated cells returns to that from unirradiated cells if the irradiated cells are allowed time at 37 degrees C in nutrient conditions. Lymphocyte HF-DNA from patients who have exhibited hypersensitivity to radiotherapy exhibit slower repair characteristics than lymphocyte HF-DNA from the average normal subjects. Neutrons are more effective than X-rays in producing density changes. Misonidazole and the ADPRT inhibitor 3-AAB substantially inhibit return to unirradiated densities. The oer for the initial effect is between 2 and 3. These properties of this DNA material from human lymphocytes suggest that alterations in the configuration of such material by the loss and re-establishment of relatively weak cellular bonds are closely related to the well-known changes observed in classical cell survival experiments. Where the proliferation of human lymphocytes has been observed by concanavalin A stimulation, oer, RBE and chemical modification has been of the same order as the measured density changes. Additionally, we have found that the density of HF-DNA is heavily dependent upon Cu content. This has led us to propose that cell killing or malfunction at the nuclear level caused by ionizing radiation is caused by the conversion CuII----CuI and also by specific .OH attack on DNA or proteins at a Cu site.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Survival↗
PubMed1987

Environmental considerations for exercise.

Physical activity, whether at a competitive or a recreational level, is frequently affected by environmental conditions. With changes in the natural environment, the exercising individual invokes a series of complex physiologic responses that are directed at maintaining homeostasis. This article will focus on the nature of these responses, with special reference to their influence on cardiorespiratory function. Because alterations in ambient temperature and ascent to altitude are the most common and are the most extensively studied of man's adaptational abilities, these will provide the basis for this discussion.

Altitude Sickness↗
PubMed1986

Studies on the role of 1,25-dihydroxyvitamin D in chick embryonic development.

Vitamin D-deficient laying hens were repleted with 25-hydroxy[26,27-3H]vitamin D3 or 1,25-dihydroxy[26,27-3H]vitamin D3. Egg production returned to normal for both groups of hens by the third week. Eggs from hens fed either 25-hydroxy[26,27-3H]vitamin D3 or 1,25-dihydroxy[26,27-3H]vitamin D3 contained 1,25-dihydroxy[26,27-3H]vitamin D3. Eggs from hens fed 25-hydroxy[26,27-3H]vitamin D3 contained substantial amounts of 25-hydroxy[26,27-3H]vitamin D3, while those from hens fed 1,25-dihydroxy[26,27-3H]vitamin D3 contained none. Plasma from 18-day embryos from hens fed 1,25-dihydroxy[26,27-3H]vitamin D3 contained little or no 1,25-dihydroxy[26,27-3H]vitamin D3, while that from 18-day embryos from hens given 25-hydroxy[26,27-3H]vitamin D3 had normal levels of 1,25-dihydroxy[26,27-3H]vitamin D3. No eggs from hens fed 1,25-dihydroxy[26,27-3H]vitamin D3 hatched, while eggs from hens fed 25-hydroxy[26,27-3H]vitamin D3 achieved a hatchability of 90%. It appears that embryos from hens maintained on 1,25-dihydroxyvitamin D3 as their sole source of vitamin D are essentially vitamin D deficient.

Animals↗
PubMed1986

The action of various vitamin D3 metabolites on calcium and phosphorus metabolism in chick embryo calvariae.

Chick embryos from vitamin D-deficient hens given physiological doses of 1,25-dihydroxyvitamin D3 or 24,25-dihydroxyvitamin D3 or both become severely hypocalcemic, hyperphosphatemic and fail to hatch as compared to those derived from hens given 25-hydroxyvitamin D3 or 24,25-difluoro-25-hydroxyvitamin D3. Calvariae from the former contain less mineral and on incubation in vitro produce significantly lower calcium and higher phosphate concentration in the medium than do the calvariae derived from the embryos of hens supported on 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3.

24,25-Dihydroxyvitamin D 3↗