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Biomedical subjects

A J Carrillo

Publications and source records attributed to A J Carrillo.

At least 37 records · Page 2Linked to original sources
PubMed1986

Hyperprolactinemia attenuates ovarian steroid stimulation of region-specific hypothalamic serotonin synthesis and luteinizing hormone release in ovariectomized rats.

Hyperprolactinemia adversely affects reproductive functions, presumably through an effect at the hypothalamic level. Given the numerous published reports linking hypothalamic serotonin (5-hydroxytryptamine, 5HT) mechanisms to the regulation of gonadotrophin secretion, we sought to determine the effects of experimentally induced hyperprolactinemia on ovarian steroid-induced increases in serum LH levels and region-specific hypothalamic 5HT synthesis in ovariectomized rats. In the first study, bilaterally ovariectomized Sprague-Dawley rats either received two pituitary homografts implanted beneath the left kidney capsule or were sham-grafted. Both groups of rats were injected subcutaneously with 5 micrograms/100 g of estradiol benzoate (E2) in corn oil vehicle at 08.00 h, 1 and 2 days before serum collection and 5 mg/100 g of progesterone (P) in corn oil vehicle at 07.00 h on the day of serum collection. Blood samples were collected via chronic indwelling jugular cannulae from each rat at 10.00, 12.00, 13.00, 14.00, 16.00 and 18.00 h. A statistically significant elevation in serum LH levels was detected at 13.00, 14.00 and 16.00 h. This increase in serum LH levels was significantly attenuated in rats bearing pituitary homografts, an effect attributed to the high serum PRL levels measured in these animals. In the second study, bilaterally ovariectomized Sprague-Dawley rats were divided into three experimental groups: (1) rats bearing two pituitary homografts and injected with E2 and P on the schedule and at the dosages previously described, (2) sham-grafted rats injected with E2 and P on the schedule and at dosages previously described and (3) sham-grafted rats injected with corn oil vehicle only.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Vasoactive intestinal peptide increases prolactin messenger ribonucleic acid content in GH3 cells.

The influence of vasoactive intestinal peptide (VIP), TRH, and dexamethasone (Dex) on PRL mRNA was investigated in PRL-producing GH3 cells using cytoplasmic dot hybridization and RNA blot analysis. Total cytoplasmic RNA was transferred to nitrocellulose filter paper and quantitated by hybridization to PRL recombinant DNA probes labeled with 32P. Incubation of GH3 cells with VIP for 25 h increased the content of cytoplasmic PRL mRNA. This increase was dose dependent, being significant at 2 X 10(-8) M and reaching a maximum at 2 X 10(-7) M. VIP at 2 X 10(-9) M had no effect on cytoplasmic PRL mRNA content. TRH (2 X 10(-7) M) also increased whereas Dex (2 X 10(-7) M) decreased the content of PRL mRNA. The inhibitory effect of Dex (2 X 10(-7) M) on cytoplasmic PRL mRNA was reversed by VIP (2 X 10(-7) M). Changes in medium PRL levels after these various hormone treatments paralleled those changes observed in PRL mRNA content. Examination of total poly(A)+ RNA demonstrated that incubation with VIP (2 X 10(-7) M) for 6 h increased the content of the mature PRL mRNA and its processing intermediates. Dex (2 X 10(-7) M) decreased the content of all species of PRL mRNA. These data suggest that VIP-stimulated PRL release is the result of an increase in the content of PRL mRNA and its precursors.

Animals↗
PubMed1985

Estrogen induced prolactin mRNA accumulation in adult male rat pituitary as revealed by in situ hybridization.

Adult male rats were injected with different doses (1, 10, and 100 micrograms) of 17 beta-estradiol daily for 5 days, and the changes in prolactin (PRL) mRNA levels were examined by in situ hybridization and cytoplasmic dot blot hybridization using cloned cDNA for rat prolactin mRNA. An increase in cytoplasmic PRL mRNA content was evident in all the animals treated with estrogen as revealed with cytoplasmic dot blot analysis. There were however, no significant differences in PRL mRNA content among the three estradiol treated groups. Cytoplasmic PRL mRNA was also demonstrated by in situ hybridization on the frozen pituitary sections using a 3H-labeled PRL cDNA probe. The number of grains per cell was increased after estrogen treatment. 3H-thymidine uptake into pituitary cells was also examined in vivo using combined techniques of immunocytochemistry and autoradiography. Although the percentage of immunoreactive PRL cells which took up thymidine in their nuclei increased to more than double after estrogen treatment, the increase in the total number of immunoreactive PRL cells was small. These results suggest that the major effect of estrogen on PRL cells is an increase in the accumulation of PRL mRNA in the individual PRL cells. The number of grains per cell was found to vary from cell to cell, both in control and estrogen treated animals. This variability is discussed in relation to the functional heterogeneity within the PRL cell population.

Animals↗
PubMed1984

Hypothalamic deafferentation inhibits the stimulatory influence of prolactin on follicle-stimulating hormone release in the golden hamster.

We have examined the effects of PRL-producing ectopic pituitary grafts on plasma FSH and LH levels in male golden hamsters with anterior (AHD) and anteolateral hypothalamic deafferentation (ALHD). After hypothalamic deafferentation or sham deafferentation, hamsters received pituitary transplants under the kidney capsule. In the first experiment, the animals were unilaterally nephrectomized 5-6 weeks after transplantation to remove the ectopic pituitaries. In a second experiment the ectopic pituitaries remained under the kidney capsule for the duration of the experiment. Serial blood samples were collected before and after pituitary transplantation and after transplant removal. In the first experiment, ALHD resulted in a significant (P less than 0.01) suppression of plasma LH levels that lasted through the entire study, but had no significant effect on plasma FSH levels or on testicular and seminal vesicle weight. The presence of pituitary grafts resulted in a significant (P less than 0.01) elevation in plasma FSH levels in the sham-deafferented hamsters but had no effect on plasma FSH levels in those with ALHD. After transplant removal there was a significant (P less than 0.01) drop in plasma FSH levels in the hamsters that had been sham deafferented but not in those with a deafferented hypothalamus. Plasma LH levels were not affected by the pituitary transplants or their removal in either group. In the second experiment, ALHD but not AHD significantly (P less than 0.05) reduced testicular and seminal vesicle weights. Transplantation of an anterior pituitary elevated plasma FSH levels in the control group but not in the AHD and ALHD groups. Both types of deafferentations suppressed plasma LH levels below the limit of sensitivity of the assay for the duration of the experiment. Plasma PRL levels were markedly elevated only in the groups with an ectopic pituitary transplant. These results suggest that the anterior connections of the medial basal hypothalamus are necessary in order for PRL-producing pituitary transplants to influence FSH secretion from the in situ pituitary.

Afferent Pathways↗
PubMed1983

Dopaminergic stimulation of pituitary but not hypothalamic estrogen receptors in ovariectomized rats.

This study was designed to examine the role of catecholamines and serotonin in the regulation of estrogen receptors (ER) in the medial basal hypothalamus (MBH) and anterior pituitary gland (AP) of adult ovariectomized rats. Plasma PRL and LH were also determined. Injection of alpha-methyl tyrosine (alpha-MT) resulted in the significant reduction of norepinephrine and dopamine (DA) content in the MBH, and of plasma LH levels as well as in the significant elevation of plasma PRL levels. This treatment also resulted in the significant reduction of ER concentration in the AP. The elevation in plasma PRL by alpha-MT was reversed by the simultaneous injection of bromocriptine (BC), a DA agonist, which also partially reversed the alpha-MT reduction of ER concentrations in the AP. BC had no effect on plasma LH levels. The ER concentration in the MBH was not significantly changed by any of these treatments. The reduction of serotonin content in the MBH by the injection of p-chlorophenylalanine had no effect on the ER concentration in either the MBH or AP, nor did it have any effect on plasma PRL levels. However, p-chlorophenylalanine treatment did decrease plasma LH levels. Neonatal treatment of female rats with monosodium glutamate which has been reported to destroy part of the MBH, resulted in a significant reduction in body and pituitary weight and in a significant elevation of plasma PRL levels in adults (2 months old). This treatment also resulted in a significant reduction in the AP and MBH ER concentration. Injection of BC to adults reversed the effects of neonatal monosodium glutamate treatment on plasma PRL levels and on the pituitary ER concentration, but had no effect on the ER concentration in the MBH. BC had no effect on the AP or MBH ER concentration in control rats, although it did as expected reduce the plasma PRL levels in these animals. Plasma LH levels were not significantly changed by any of these treatments. Injection of the DA antagonist, haloperidol, to adult rats resulted in a significant elevation of plasma PRL and in a significant reduction of ER concentration in the AP. Haloperidol treatment did not affect the binding affinity of these receptors. Overall, these data suggest that DA is involved with the regulation of ER in the AP.

Animals↗
PubMed1982

Plasma LH levels in the long term ovariectomized rat after anterolateral deafferentation of the medial basal hypothalamus and lesions in the medial preoptic area.

This study was designed to investigate the effect of anterolateral hypothalamic deafferentiation (ALHD) and medial preoptic area (MPOA) lesions on plasma LH levels in the long term ovariectomized rat. The deafferentations were carried out with a Halasz-Pupp knife (radius of 1.5 mm and height of 2.0 mm) and the MPOA lesions with a platinum electrode. Sham treated and an intact group served as controls. Blood samples were obtained from the jugular vein under light ether anesthesia before and at 1, 2, 4 and 6 weeks after brain surgery. After the sixth week sample all rats were treated with 50 micrograms of estradiol benzoate (EB) and two days later blood samples were collected during the morning and afternoon. Hypothalamic deafferentation resulted in a more significant (p less than 0.01) drop in plasma LH levels in one half of the group (ALHD-1) than in the other half (p less than 0.05) (ALHD-2) when compared to the controls. Treatment of the controls with EB resulted in a significant (p less than 0.01) depression of LH levels in the morning and an LH surge during the afternoon. EB also resulted in a suppression (p less than 0.01) of LH levels during the morning in all of the ALDH rats; however, only the ALHD-1 group had an LH surge during the afternoon following EB. Plasma LH levels in the ALHD-2 remained suppressed during the afternoon after EB treatment. Lesions in the MPOA had no effect on plasma LH levels at 1 to 6 weeks when compared to controls. Treatment of the MPOA lesion group with EB resulted in a significant (p less than 0.01) drop in plasma LH levels during the morning as well as the afternoon. These data suggest that the fibers that are critical for the control of tonic and phasic LH secretion enter the medial basal hypothalamus laterally and that the deafferentations carried out here were selective in interrupting fibers involved with tonic LH secretion in some rats and those involved with the phasic secretion in others. These data also suggest that the MOPA components involved with tonic LH secretion are separate from those controlling phasic LH secretion.

Afferent Pathways↗
PubMed1982

The hypophyseal-adrenal axis in the protein-calorie malnourished rat.

Male rats were fed an 8% low protein diet for 30 consecutive days beginning at 20 days of age. On day 50, the effect of the diet was evaluated on the hypophyseal-adrenal axis and the observations compared with those noted in age-matched controls fed a standard laboratory diet. The malnourished animals had significantly larger adrenal gland weights, relative to body size, and higher levels of serum corticosterone. Additionally, the number of ACTH-secreting cells in the pituitary glands of these rats was 63.8% greater than that present in the controls. These results suggest that ACTH secretion and adrenocortical physiology are stimulated under conditions of experimentally induced protein-calorie malnutrition.

Adrenal Glands↗
PubMed1981

Stimulation of the hippocampus and ovulation in the rat: specific or nonspecific effects.

Bilateral electrochemical stimulation (ECS) of the ventral hippocampus (VHPC) or dorsal hippocampus (DHPC) under acute condition at 10.00, 12.00 or 13.00 h on proestrus did no interfere with ovulation. When the same ECS of the VHPC was repeated at 12.00 h proestrus followed by the taking of blood samples at 14.00, 16.00 and 18.00 h under ether anesthesia from the jugular vein, the LH surge and ovulation were significantly (p less than 0.05) inhibited. Acute unilateral ECS of the VHPC or passing the same current through a platinum electrode had no effect on the LH surge. When large electrolytic lesions were bilaterally made in the VHPC with a platinum electrode at 12.00 h of proestrus followed by blood samples, the LH surge and ovulation were also inhibited (p less than 0.05). Large lesions in the caudate putamen also resulted in a significant (p less than 0.05) suppression of the LH surge and the number of ova. These data suggest that (1) electrochemical stimulation of the hippocampus is not inhibitory to ovulation, and (2) acute procedures on the day of proestrus can inhibit LH secretion.

Animals↗
PubMed1980

Episodic corticosterone secretion in the female rat.

Studies conducted in several laboratories have shown primate glucocorticoid secretion to occur episodically. In light of the methodological, as well as physiological importance of this finding, the present study was undertaken to determine whether the rat corticosteroid secretion also occurs episodically. Female rats were outfitted with chronic intravenous cannulas, and 1 week later 200 units of heparin were injected through the implanted cannula and blood samples (0.3-0.4 ml) were collected from each rat every 10 min for 3 h during the morning (06.00-10.00 h) or during the afternoon (16.00-19.00 h) (lights on from 05.00 to 19.00 h). Plasma corticosterone levels in cannulated rats showed fluctuations indicative of episodic secretion. The pattern of plasma corticosterone levels was characterized by periodic rapid increases in hormone concentration during both the morning and afternoon sampling periods; the occurrence of these hormonal fluctuations did not have a characteristic frequency. When the data were grouped to obtain single morning and afternoon values, the AM-PM difference was significant (p < 0.005). Collectively, these data suggest that in the rat, adrenal corticosteroids are secreted episodically.

Adrenocorticotropic Hormone↗
PubMed1980

The effect of amygdaloid and hippocampal lesions on compensatory ovulation and pro-oestrous gonadotropin levels in the rat.

The purpose of this study was to examine the effects of limbic forebrain lesions in conjunction with unilateral ovariectomy (ULO) on compensatory ovulation. At metoestrus, cyclic rats were ULO and bilateral brain lesions were placed in either the cerebral cortex (CTX), dorsal hippocampus (DHPC), amygdaloid nucleus (ACO) or stria terminalis (ST). In addition, two control groups consisted of intact and ULO only rats. Plasma samples were obtained at the subsequent pro-oestrus and analyzed by radioimmunoassay for FSH and LH. All animals were killed at the next metoestrus and the number of eggs shed were determined. After ULO alone, twice as many ova as normal were shed from the remaining ovary. Ovulation was inhibited in 30% of the ACO- and ST-ULO animals and damage to either the DHPC, ACO or ST caused a delay in time to the post-lesioned ovulation. However, all animals in the four brain lesioned-ULO groups that did ovulate doubled the number of eggs shed. Pro-oestrus plasma levels of FSH and LH did not differ between animals in the six groups. Thus, while amygdaloid lesions may alter certain parameters of pituitary ovarian function, the limbic forebrain is not involved in the mechanism of compensatory ovulation.

Amygdala↗
PubMed1978

Changes in diurnal fluctuations of plasma thyroid stimulating hormone and corticosterone following anterior hypothalamic deafferentation in the rat.

Systemic thyroid stimulating hormone (TSH) and corticosterone (B) levels were measured in serial plasma samples withdrawn from 8 adult female rats before and for several weeks after anterior hypothalamic cuts (FC), made with a modified Halász knife (1.5 mm radius). With lights on from 5:00 to 19:00 h the rats were bled by rapid venipuncture at 9:00 and 20:00 h 14 days before and 5 days after FC and by chronic intra-atrial cannulas at 9:00, 13:00, 17:00 and 20:00 h on days 25, 30 and 40 or 50 post-FC. The frontal cuts, localized later by histology to sites just rostral to the suprachiasmatic nucleus in 3 rats and just caudal to the nucleus in the other 5 brains, altered the charactersitic diurnal drop in plasma TSH and rise in B but did not eliminate marked fluctuations in hormone levels. The new hormonal platterns could not be related specifically to FC loci and appeared to be a dynamic process for each rat. At 5 days after FC the diurnal patterns were either obscured or shifted in phase. The most consistent finding at subsequent sampling intervals was that TSH and B plasma levels in each animal showed parallel fluctuations (during 9:00--20:00 h) as though synchronized in phase. The data suggest that interruption of anterior hypothalamic connections in the female rat is compatible with fluctuations in plasma TSH and B which are unique to a particular animal and may be obscured by group analysis.

Afferent Pathways↗
PubMed1978

Circadian variation in the sensitivity of the pituitary-adrenal system to dexamethasone suppression.

Intact female rats were injected with 100 microgram dexamethasone/kg body weight or saline at 12.00, 24.00 or 04.00 h. Four hours later, i.e. 16.00, 04.00 or 08.00 h respectively, a double bleeding procedure was used to obtain blood samples from stressed and unstressed rats for subsequent fluorometric determination of corticosterone levels in the plasma. The difference between the level of corticosterone is stressed and unstressed rats (the stress increment) was determined and used as an index of the response of corticosterone in the plasma to stress. Increments in the levels of corticosterone in the plasma evoked by stress in rats injected at 12.00 h with dexamethasone and bled 4 h later were significantly (P less than 0.05) less than those in rats given dexamethasone at 24.00 or 04.00 and bled at 04.00 or 08.00 h respectively. In contrast, stress-induced increments in the level of corticosterone in the plasma of rats treated with saline did not vary with the time of day.

Animals↗