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Biomedical subjects

V D Ramirez

Publications and source records attributed to V D Ramirez.

At least 127 records · Page 7Linked to original sources
PubMed1978

Monoamines, estrogen and female sexual behavior in the golden hamster.

In the golden hamster drugs which inhibit monoaminergic function (including p-chlorophenylalanine (PCPA), methysergide and a-methyl-p-tyrosine (a-MPT) facilitated lordosis in ovariectomized female hamsters as a function of the duration of estradiol benzoate (EB) priming. a-MPT (200 mg/kg), methysergide (6 mg/animal) or PCPA (150 or 360 mg/kg) potentiated lordosis if 6 days of EB priming preceded drug treatment. However, if female hamsters were primed with EB for only 2 days, a-MPT and methysergide were ineffective. PCPA (360 mg/kg) was less effective after 2 days of EB than after 6 days of EB priming. alpha-MPT produced a three-fold elevation in progesterone levels in ovariectomized females but methysergide and PCPA did not influence serum progesterone. PCPA (360 mg/kg) facilitated lordosis in adrenalectomized, ovariectomized females, eliminating the possibility that adrenal progesterone is essential for the behavioral effects of the drug. Luteinizing hormone-releasing hormone levels in the preoptic/anterior hypothalamic area and the medial basal hypothalamus were also not significantly altered at 1 h after PCPA injection. Pimozide (1.5 mg/kg) and pimozide (1.5 mg/kg) and amphetamine (2.5 mg/kg) did not potentiate lordosis in ovariectomized hamsters after either 2 or 6 days of EB priming. Pargyline, a monoamine oxidase inhibitor, inhibited female sexual behavior in females in estrogen alone-induced estrus. Lordosis in the female rat is more readily elicited both by drugs and estrogen. It is proposed with regard to female sexual behavior that species differences in estrogen sensitivity may underlie apparent differences in drug sensitivity.

Adrenalectomy↗
PubMed1978

Compulsive, abnormal walking caused by anticholinergics in akinetic, 6-hydroxydopamine-treated rats.

In otherwise profoundly akinetic rats that had been severely depleted of brain catecholamines, anticholinergic drugs caused excessive walking. The effect did not appear until 10 days after surgery and then increased with time, suggesting that a phenomenon analogous to denervation supersensitivity may be involved. If the animals walked into corners, they were unable to turn around or back out. Their gait (extremely short steps) was reminiscent of that of patients with Parkinson's disease. The results are consistent with a mutually antagonistic interaction between cholinergic and dopaminergic brain systems and emphasize certain complexities in this interaction.

Animals↗
PubMed1978

Prolactin receptors: a comparison between chloramine-T and lactoperoxidase iodination.

The binding properties of chloramine-T iodinated oPRL (using a modified iodination procedure) to prolactin receptors of female rat liver membrane particles were compared with those of lactoperoxidase iodinated oPRL. The results indicated that both iodination methods provided 125I-oPRLs which were suitable for receptor binding studies. Our results suggested that chloramine-T 125I-oPRL was even better than lactoperoxidase 125I-oPRL in terms of lower nonspecific binding. The chloramine-T iodinated oPRL was used to study the prolactin receptors in rat ovaries and DMBA induced rat mammary tumors. The results showed that the amount of prolactin receptors in rat ovaries was related to the plasma level of prolactin as it had been reported in liver by other investigators. The study of prolactin receptors in rat mammary tumors indicated that the prolactin receptor content of hormone dependent mammary tumors was much higher than that of hormone independent mammary tumors.

Animals↗
PubMed1975

Distribution of LH-RH in subcellular fractions of the basomedial hypothalamus.

Subcellular fractionation of the mediobasal hypothalamus (MBH) and other brain structures was achieved by differential and sucrose gradient centrifugation. The fractions were monitored by measuring lactate dehydrogenase (LDH) activity (a marker for the soluble cytoplasmic fraction) and by electron microscopic examination. The luteinizing-hormone-releasing-hormone (LH-RH) content of the fractions was evaluated both by bioassay and radioimmunoassay. Significant amounts of LH-RH were found only in the MBH and in an anterobasal location corresponding to the organum vasculosum of the lamina terminalis. Within these areas, LH-RH activity was present in the first supernatant (homogenate with the exclusion of the nuclear pellet). Seventy percent of the LH-RH activity was recovered in the crude mitochondrial fraction. After further fractionation on a sucrose gradient, the distribution of LH-RH was parallel with that of LDH activity. Since LDH is predominantly located in the synaptosomal soluble fraction, it is concluded that the vast majority of LH-RH is contained within nerve endings. This finding is consistent with cyto-immunological data on the distribution of the neuropeptide in the rat hypothalamus.

Animals↗
PubMed1975

Ultrastructure of the mammary gland in lactating rats after local implantation of oestrogen.

Cannulae containing oestrogen were implanted in the mammary glands of rats on the first day after parturition and lactation assessed by daily measurements of the litter weight. Sham-implanted and intact lactating rats were used as controls. A clear-cut inhibition of the milk yield was observed in the oestrogen-implanted group. Mammary tissue was processed for fine structural study after 4, 8 or 10 days. The initial phase showed milk stasis and secretion of colostrum progressively involving the alveoli and culminating in regression of the mammary tissue. Disappearance of myofilaments from the myoepithelial cells was consistently observed. Secretion of colostrum and mammary regression could be the result of the stasis produced by an abnormal dynamic state of the myoepithelial cell elicited by the steroid.

Animals↗