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Biomedical subjects

J Vriend

Publications and source records attributed to J Vriend.

9 recordsLinked to original sources
PubMed1992

Changes in hippocampal monoamine concentration following halothane anesthesia and concussion.

The concentration of norepinephrine in the hippocampus of rats anesthetized with halothane (Wyeth-Ayerst, Philadelphia, Pa) is found to be markedly increased, presumably due to the stress of handling and administering the anesthetic. This increased norepinephrine concentration persists for about 50 minutes but is obliterated when the anesthetized rat is concussed. This 50-minute period corresponds to the time it takes for a rat (or human), comatose for 1-2 seconds following concussion, to regain normal memory. No changes in 3,4-dihydroxybenzene-acetic acid (DOPAC), 3-(3,4-dihydroxyphenyl) alanine (L-DOPA), and 3,4-dihydroxybenzylamine (DHBA) were noted. 5-Hydroxy indole acetic acid (HIAA) showed a depression at 5 minutes and again at 30 minutes, changes that were consistent but not considered statistically significant.

Anesthesia, Inhalation↗
PubMed1990

Melatonin increases serum growth hormone and insulin-like growth factor I (IGF-I) levels in male Syrian hamsters via hypothalamic neurotransmitters.

In male Syrian hamsters daily evening melatonin injections resulted in increased circulating levels of growth hormone (GH), as well as a modest increase in body weight. A substantial increase in serum levels of insulin-like growth factor I (IGF-I) was observed in all hamsters receiving evening injections of melatonin for 10 weeks. The melatonin-induced increase in serum IGF-I levels was interpreted as a result of increased release of GH during the 10 week period of melatonin administration. The increase in serum GH and IGF-I was associated with significantly decreased hypothalamic turnover of norepinephrine (NE). Since blocking NE synthesis with alpha methyl-p-tyrosine reduced serum GH, the melatonin-induced increase in GH could not readily be attributed to decreased NE turnover. Highly significant increases in 5-hydroxyindole acetic acid (5HIAA) concentrations and in ratios of 5HIAA to serotonin (5HT) were noted in extracts of hypothalamus and in extracts of brain stem, suggesting a serotonergic component to melatonin-induced increase in GH-induced IGF secretion and subsequent growth.

Animals↗
PubMed1978

An animal model for childhood convoluted T-cell lymphoma.

The light microscopic and ultrastructural characteristics of the AKR-J mouse lymphoma are described in detail. Clinical and histologic facets of convoluted T-cell lymphoma of childhood and AKR-J mouse lymphoma are reviewed. The remarkably close correlation between these two entities is demonstrated. The possibility that this mouse tumor should be utilized as a model for convoluted T-cell lymphoma of childhood is emphasized.

Animals↗
PubMed1977

Free thyroxin index in normal, melatonin-treated and blind hamsters.

The administration of melatonin to young male hamsters depressed thyroxin levels, as measured by radioimmunoassay, by 38.5% of saline controls. Free thyroxin index was also signficantly depressed by melatonin injections. The depression of thyroxin and free thyroxin index by melatonin injections was more effective in intact than in pinealectomized animals. Blinding of hamsters also reduced both thyroxin and free thyroxin index.

Animals↗
PubMed1977

Effects of blinding, pinealectomy and superior cervical ganglionectomy on free thyroxine index of male golden hamsters.

Blinding young male golden hamsters led to a depression of the plasma free thyroxine index after an 8 week period. Removal of either the pineal gland or the superior cervical ganglia of blind hamsters reversed the effects of blinding on free thyroxine index. No significant effects were observed 2 weeks after treatment. Previously reported effects of blinking, and removal of the pineal gland or the superior cervical ganglia on testicular weight were confirmed. A similar mechanism of pineal inhibition of thyroid function and gonadal function is suggested.

Animals↗
PubMed1975

Effects of light environment on the weight of bursa of Fabricius in White Rock chicks.

The weight of the bursa of Fabricius of White Rock chicks reared under two photoperiods was studied in relation to body weight, weight of the endocrine organs, and spleen using a multiple correlation method. At the 95% level of confidence the coefficient of determination suggested that the weight of the bursa could be predicted with 77% plus or minus 7.8% accuracy from the organs weighed for a period from 2-24 weeks, the weight of the pituitary being the most stable contributor to this prediction. The weight of the spleen, similarly, could be predicted with a 92% plus or minus 3.8% accuracy. Correlations of testes and thyroid weight with bursa weight suggested possible influence of testosterone and thyroxin on bursa-spleen relationships during the period of bursal growth and involution.

Adrenal Glands↗
PubMedDate not supplied

Testing the TRH hypothesis of pineal function.

In the Syrian hamster gonadal involution may be induced by exposure of the animal to darkness, short photoperiod, or blindness for several weeks. These conditions also influence body metabolism by inducing a substantial decrease in thyroxin concentrations. The role of the pineal gland in these phenomena has been demonstrated by experiments showing that if pinealectomized hamsters are subjected to darkness, short photoperiod, or blindness, their gonads do not involute and plasma thyroxin levels remain normal. Since thyrotrophin releasing hormone (TRH) causes the release of both prolactin and thyrotrophin from the pituitary we can predict on theoretical grounds that TRH mediates both pineal-gonad and pineal-thyroid phenomena. Melatonin may be the pineal hormone regulating hypothalamic TRH levels.

Animals↗
PubMedDate not supplied

Genetic, endocrine, and viral aspects of AKR leukemogenesis.

In the AKR strain of mice a high incidence of spontaneous lymphoid leukemia develops before 12 months of age. Genetic, viral, and endocrine factors interact during development to produce the syndrome. Many of the deficiencies of AKR mice are associated with gene action in chromosome 17, at or near the major histocompatibility locus. It is suggested that low steroid levels and high thyroxin levels during an early period of development are an essential part of the syndrome. Specifically, induction of a polymerase enzyme and regulation of the extent of its action by hormones are postulated to favor appearance of C-type particles and accumulation of a population of undifferentiated lymphoid stem cells. Immunodeficiency and leukemic transformation result.

Animals↗