Biomedical subjects

C Bellido

Publications and source records attributed to C Bellido.

At least 73 records · Page 4Linked to original sources

PubMed1994

Decreased number and size and the defective function of testicular macrophages in long-term hypophysectomized rats are reversed by treatment with human gonadotrophins.

Macrophages are a common cell type in the testicular interstitium of the rat and are morphologically and functionally related to Leydig cells. We investigated the number of macrophages and Leydig cells in long-term (24 weeks) hypophysectomized (LTHX) or sham-operated rats. LTHX rats showed a 76% decrease in the number of macrophages, whereas the number of Leydig cells was only slightly decreased (by 18%). The profile areas of both macrophages and Leydig cells were very much decreased (46% and 66% respectively). Sham-operated and LTHX rats were treated with vehicle or human FSH and LH (hFSH/hLH; 75 IU/kg body weight per day) for 1 week. This treatment induced a 286% increase in the number of macrophages and a 32% increase in the number of Leydig cells in LTHX rats. The profile areas of macrophages and Leydig cells were also increased (212% and 184% respectively). About 80% of macrophages showed vacuolization of the cytoplasm. Gonadotrophin treatment did not induce changes in cell numbers in sham-operated animals but about 30% of macrophages showed large cytoplasmic vacuoles. Vehicle- or hormone-treated LTHX rats were given a single injection of ethylene dimethane sulphonate (EDS) and killed 72 h later. Leydig cells were absent from the testicular interstitium of sham-operated rats but there were large numbers of dead Leydig cells (about 40% of the pre-existing population) in the testicular interstitium of LTHX rats 3 days after EDS treatment. Complete clearance of the testicular interstitium from EDS-killed Leydig cells was found in LTHX rats treated with hFSH/hLH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Periovulatory LHRH, LH and FSH secretion in cyclic rats treated with RU486: effects of exogenous LHRH and LHRH antagonist on LH and FSH secretion at early oestrus.

The antiprogesterone RU486 injected on the morning of pro-oestrus blunts the preovulatory secretion of LH and FSH and abolishes the secondary secretion of FSH during oestrus without affecting ovulation in the rat. To ascertain whether the secretion of LHRH is involved in these effects, we studied the effects of RU486 (4 mg/0.2 ml oil), given s.c. at 0800 h on pro-oestrus, on LHRH secretion into the pituitary stalk blood vessels and on peripheral plasma concentrations of LH and FSH at 1800 h on pro-oestrus and 0200 h on oestrus. Furthermore, we determined the effects of an s.c. injection of 1 mg of an LHRH antagonist (LHRH-A; ORG30276) at 2000 h on pro-oestrus and those of an i.p. injection of 100 ng LHRH (Peninsula 7201) at 0100 h on oestrus on serum concentrations of LH, FSH and oestradiol at 0200 h on oestrus in oil- and RU486-treated rats. RU486 decreased LHRH secretion at 1800 h on pro-oestrus while this was increased at 0200 h on oestrus. While the reduction of preovulatory LHRH secretion in RU486-treated rats coincided with a reduction in both LH and FSH surges during the evening of pro-oestrus, the increased LHRH secretion during the early hours of oestrus was only accompanied by an increased concentration of LH. An injection of LHRH stimulated, while that of LHRH-A inhibited serum concentrations of LH at 0200 h on oestrus in both oil- and RU486-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Hypothalamus-pituitary-ovarian axis in cyclic rats lacking progesterone actions.

Antagonizing diestrous progesterone actions in cyclic rats by s.c. injections of the antiprogesterone RU486 (2 mg twice a day from metestrus through proestrus) increased LH and decreased FSH basal serum concentrations. Ovariectomy at metestrus (0800 h) increased serum levels of both gonadotropins in controls and reversed the RU486-induced dissociation of basal gonadotropin secretion. RU486-dissociated gonadotropin secretion is also dependent upon LHRH, since treatment (s.c.) with 1 mg GnRH antagonist (ORG 30276) twice a day on metestrus and diestrus completely prevented both the RU486-induced increase in LH and the decrease in FSH serum concentrations. The LHRH content in the medial basal hypothalamus and median eminence increased on proestrous morning in RU486-treated rats. The LH pituitary response to an exogenous i.v. bolus of 25 ng LHRH (Peninsula 7201; Peninsula Laboratory, Inc., Merseyside, UK) at 1700 h on diestrus was enhanced in rats treated with RU486. No differences in pituitary FSH response were noted with respect to oil-injected rats. The pituitary content of both gonadotropins decreased in RU486-treated rats on proestrous morning. All these effects due to RU486 in cyclic rats were reversed by ovariectomy. Testosterone serum levels increased significantly from diestrus onward, and the estradiol concentration increased on proestrous morning in RU486-treated rats. Ovariectomy as well as LHRH antagonist treatment eliminated the effects of RU486 on ovarian steroid production. Moreover, antiestrogen tamoxifen treatment reversed RU486-dissociated gonadotropin secretion, while antiandrogen flutamide treatment had no effect. The results of this experiment have confirmed previous findings that RU486 treatment dissociates basal gonadotropin secretion in cyclic rats. In addition, the present results show that: (1) this effect of RU486 is not due to a direct effect of this compound or to the blockade of progesterone action at a central level; (2) the effect of RU486 on pituitary gonadotropin secretion depends on ovarian substances other than progesterone and LHRH, since it is reversed by ovariectomy and completely abolished by LHRH antagonist treatment; (3) the reduction in FSH serum levels in rats treated with RU486 seems to be exerted by inhibin and estradiol at the pituitary level by reducing FSH synthesis and secretion; and (4) the hypersecretion of LH in rats treated with RU486, as compared to that resulting from ovariectomy, seems to be the consequence of, first, a lack of progesterone inhibitory action on LH secretion, and, second, an inappropriate feedback system involving increased hypothalamic LHRH activity and pituitary sensitivity to LHRH of moderately high levels of estradiol in the presence of abnormally high levels of testosterone.

Amino Acid Sequence↗

PubMed1993

Changes in pituitary secretion during the early postnatal period and anovulatory syndrome induced by neonatal oestrogen or androgen in rats.

The following experiments were performed: (i) concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin in plasma were measured at 2, 5, 8, 10 and 15 days in female Wistar rats treated on the first day of life with 100 micrograms oestradiol benzoate or vehicle; (ii) females injected on day 1 with 100 micrograms of oestradiol benzoate or 1 mg of testosterone propionate and from day 1 to day 10 or 15 with FSH and LH were killed on day 90; (iii) females injected from day 1 to day 10 or 15 with prolactin or vehicle were killed on day 90; (iv) females injected on day 1 with oestradiol benzoate and from day 1 to day 15 with a luteinizing-hormone-releasing hormone (LHRH) agonist were killed on day 90; (v) groups of females injected on days 1, 4, 7, 10, 13 and 16 with an LHRH antagonist were killed on day 90. Onset of puberty, vaginal cycles, organ weights and hormonal plasma concentrations were measured. Females treated on the first day of life with 100 micrograms oestradiol showed inhibition of gonadotrophin secretion and stimulation of prolactin secretion during the neonatal period. Females injected on the first day of life with oestradiol benzoate or testosterone propionate showed, in adulthood, anovulation, ovarian atrophy, reduced FSH plasma concentrations, increased prolactin plasma concentrations and reduced pituitary prolactin content.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗

PubMed1992

Changes in follicle-stimulating hormone secretion in spontaneously hypertensive rats.

FSH and testosterone plasma levels, pituitary FSH content and concentration and the weight of testis, seminal vesicles and ventral prostate have been studied at the ages of 30, 60 and 90 days in spontaneously hypertensive rats (SHR) and normotensive control (WKY) rats. In vitro FSH secretion by pituitaries, and the response to orchidectomy and to exogenous administration of either LHRH (1 microgram) or LHRH agonist (0.05, 0.1, 1, and 5 micrograms/kg) were analyzed in 90-day-old SHR and WKY male rats. Ventral prostate weight and FSH plasma levels were determined in other groups of adult male rats castrated and castrated and implanted for 15 days with silastic capsules containing testosterone, dihydrotestosterone or estradiol. Also FSH plasma levels and pituitary FSH concentration were determined at the ages of 30, 60 and 90 days in SHR and WKY female rats. Male SHR showed increased plasma FSH levels and high testicular weight in all the cases, and enhanced testosterone levels in plasma and pituitary FSH content on days 60 and 90. Weight of seminal vesicles and ventral prostate was normal or reduced, depending on the animal age. Adult SHR had increased FSH secretion in vitro, normal response to orchidectomy and did not exhibit FSH increases after LHRH administration. The efficiency of testosterone to stimulate ventral prostate growth and the ability of estradiol to reduce FSH plasma levels were decreased in SHR. Female SHR showed a significant increase in the pituitary content of FSH on day 30 and on proestrus at the ages of days 60 and 90.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Antiprogesterone RU486 induces dissociation of LH and FSH secretion in the cyclic rat: effect of anti-inhibin serum.

Administration of the antiprogesterone RU486 to 4-day cyclic rats from metoestrus to pro-oestrus increases serum levels of LH while decreasing levels of FSH. If it is assumed that there is only one gonadotrophin-releasing hormone, there is no direct explanation for the decrease in FSH concentrations. The purpose of these experiments was to investigate the effect of RU486 on gonadotrophin secretion in cyclic rats during periods when the secretion of LH and FSH diverges. RU486 blunted the transient increase in FSH concentration on the afternoon of metoestrus and the compensatory ovarian hypertrophy on the next day of oestrus in unilaterally ovariectomized 4-day cyclic rats. In addition, bilateral ovariectomy reversed the effect of RU486 on the basal secretion of FSH. RU486 induced an increase in basal LH concentrations. Since ovarian inhibin decreases the basal release of FSH, and decreases in peripheral inhibin seem to be responsible for the transient rise in FSH during the oestrus cycle, the effect of RU486 on serum levels of LH and FSH during dioestrus in rats injected with a sheep anti-inhibin serum (AIS) were further evaluated. Treatment with AIS increased FSH levels in oil-treated rats without altering the levels of LH. In contrast, the effects of AIS on FSH secretion were blunted in RU486-treated rats. The results suggest that inhibin might be involved in the RU486-induced decrease of FSH secretion in cyclic rats.

Animals↗

PubMed1991

Estrous cycle-related changes in mast cell numbers in several ovarian compartments in the rat.

The absolute number of mast cells in several ovarian compartments was studied during the estrous cycle of the rat. The number of mast cells significantly increased on proestrus (either in the morning or in the evening) in the ovarian medulla and cortex, whereas no significant changes were found in the ovarian bursa. During proestrus, abundant mast cells were present in the bursal cavity along with eosinophil and mononuclear leucocytes. Mast cells in the different ovarian compartments corresponded to mature mast cells, and degranulated or immature cells were only rarely found. These results seem to indicate that migration from an extraovarian source could be the mechanism underlying cyclic changes in ovarian mast cells.

Animals↗

PubMed1990

Differentiation of mast cells during postnatal development of neonatally estrogen-treated rats.

The accumulation of mast cells in the testicular interstitium of neonatally estrogen-treated rats was studied from 15 to 90 days of age. The maturation of these cells was assessed by ultrastructural analysis and their histochemical properties were examined with the sequential alcian blue-safranin staining method. The first identifiable mast cells appeared in the testis at 17-20 days of age, as immature cells with proliferative capacity. The density of mast cells increased up to 45 days of age, showing a slight decrease from 45 to 90 days of age. Before 45 days of age, most mast cells showed alcian blue-stained granules, whereas at 45 days of age, most cells presented a mixture of alcian blue and safranin-stained granules. From this age onward, most cells were stained with safranin. These maturational changes were well-correlated with their ultrastructural features. Mast cells presented few and heterogeneous immature granules up to 45 days of age, and many uniform electron-dense granules at 90 days of age. These results indicate that the testicular interstitium of neonatally estrogen-treated rats provides an advantageous environment for the recruitment, proliferation and maturation of connective tissue mast cells.

Aging↗

PubMed1990

Leydig cell involvement in the paracrine regulation of mast cells in the testicular interstitium of the rat.

The accumulation of mast cells in the rat testicular interstitium was studied under different experimental conditions in order to correlate this accumulation with the alterations of specific testicular tissue compartments or cell types. Estrogen treatment was effective in inducing mast cell proliferation when administered on Day 1 or at higher doses at 10 days of age. Estrogens were ineffective beyond 20 days of age. Postnatal treatment of neonatal-estrogen-treated rats with FSH and LH prevented the appearance of mast cells. In contrast, treatment with the Leydig cell cytotoxic ethylene dimethane sulphonate (EDS) was effective in inducing mast cell accumulation only when administered to adult rats, inducing small numbers of mast cells at 45 days of age; it was ineffective on 30-day-old rats. Hypophysectomy alone did not determine the appearance of mast cells. However, when atrophic Leydig cells were destroyed with EDS, high numbers of mast cells accumulated in the testis. These results support the existence of Leydig cell-related inhibitory factors for mast cells in the rat testicular interstitium.

Animals↗

PubMed1990

Are eosinophil leucocytes involved in the oestrogenic response of the postnatal rat epididymis?

The effects of oestrogens and androgens, alone or in combination, on several epididymal parameters have been studied in 15-day-old rats after neonatal treatment. Oestrogens induced several responses, such as increased growth of the fibromuscular stroma and eosinophil leucocyte accumulation, whereas the proliferative activity of the epithelium was decreased significantly. Otherwise, the density of intra-epithelial leucocytes was not modified. Different oestrogen-induced responses, such as the increase in volume of the fibromuscular stroma and eosinophil leucocyte accumulation were inhibited by treatment with testosterone, whereas dihydrotestosterone had no appreciable effect. This study raises the possibility that eosinophils are mediators of some of the oestrogenic responses in the early postnatal rat epididymis.

Animals↗

PubMed1990

Changes in growth hormone secretion in spontaneously hypertensive rats.

Secretion of the growth hormone (GH) in spontaneously hypertensive (SH) male rats has been determined and compared with that of normotensive Wistar-Kyoto (WKY) controls. In a first set of experiments, plasma GH concentration and pituitary GH content were measured in SH rats 30, 60 and 90 days old. 30-day rats showed reduced GH plasma and pituitary levels, whereas in 60- and 90-day-old rat no differences in GH plasma concentration and increased GH pituitary content were observed. In a second set of experiments, 90-day-old SH male rats anesthetized with sodium pentobarbital and intravenously injected with growth hormone-releasing factor (GRF) showed an amplitude and duration of response to injected hormone higher than WKY controls. In a third set of experiments, hemipituitaries of 90-day-old SH males were incubated for 2 h in Krebs-Ringer-bicarbonate either in the presence or in the absence of GRF. In the absence of GRF stimulation, the in vitro release of GH was higher than in WKY controls, whereas in the presence of GRF the sensitivity and the maximum response to GRF was reduced in comparison with normotensive male rats. These results indicate that SH rats have decreased pituitary content and plasma GH concentration before puberty. Besides, they showed increased pituitary GH content in adulthood and opposite changes in the in vivo and in vitro response to GRF.

Animals↗

PubMed1990

Possible role of changes in post-natal gonadotrophin concentrations on permanent impairment of the reproductive system in neonatally oestrogenized male rats.

Rats were treated neonatally with oestrogen (500 micrograms oestradiol benzoate injected on Day 1 of life). Treatment with FSH and LH (80 micrograms/100 g body wt and 40 micrograms/100 g body wt respectively) during the early post-natal period (Days 1-10) abolished the effects of oestradiol on the morphological and functional development of the testes and on the regulation of prolactin secretion, but had no action on the effects of oestradiol on the development of the sex accessory glands. Treatment with prolactin (100 micrograms/100 g body wt) during the early post-natal period did not affect the integrity of the reproductive system in adult life. These results suggest that neonatal oestradiol acts indirectly, through an inhibition of gonadotrophin secretion on testicular development, and directly on the development of the sex accessory glands.

Animals↗

PubMed1988

Age-related changes of norepinephrine content in kidneys of spontaneously hypertensive and Wistar-Kyoto rats.

Renal norepinephrine (NE) content was determined during the development of spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) rats in an attempt to correlate biochemical changes with the reported functional changes occurring in hypertension development in the SHR. In contrast to WKY rats, in which the levels of NE remained relatively constant with age, renal NE content in the SHR was highest at the 4th week of age, decreasing transiently during the 5th, 6th, and 7th weeks, and then again reaching a plateau during the 8th week. The fall in NE content in the kidney is associated with a rise in blood pressure with age in SHR and suggests a relationship between NE levels and hypertension.

Aging↗

PubMed1988

Mechanisms of precocious puberty induced in male rats by pituitary grafts.

Male rats were grafted on Day 21 of age with 'young' (21 days old) or 'adult' (90 days old) pituitary glands and then treated daily with 4 mg bromocriptine/kg or vehicle. Plasma samples were obtained on Days 21, 25 and 35 and when balano-preputial separation occurred. Both types of grafts advanced the age at which balano-preputial separation occurred and increased prolactin concentrations. Bromocriptine treatment reduced the prolactin values in both grafted groups, but did not block the advancement of puberty in rats treated with 'young' pituitary grafts. These results suggest the existence of two possible mechanisms in precocious puberty induced by pituitary grafts: one is prolactin-dependent (when 'adult' pituitary glands were used) and the other not directly related to prolactin (when 'young' pituitary glands were used).

Animals↗

PubMed1988

[Body development and puberty in spontaneously hypertensive rats].

The body growth and the onset of puberty in spontaneously hypertensive rats (SHR) and in normotensive controls (WKY) have been studied. In female rats the onset of puberty was determined by both the age and the body weight at which the vaginal opening and first estrus appeared, as well as the ability of estradiol and progesterone to induce pituitary LH release. For this purpose females were injected with estradiol benzoate (0.1 mg/kg) and progesterone (1 mg/rat). Control animals received only oil vehicle. In male rats, puberty was assessed by studying the age and body weight at the time of balano-preputial separation. In another experiment, SH and WKY rats were decapitated on day 30 to determine FSH, LH, PRL, GH and testosterone plasma levels in males and FSH and LH in females. The results obtained show: a) A greater body weight, at all the ages studied (every 4 days between days 28 and 92) in SHR animals. b) A delay in vaginal opening and first estrus presentation in SHR females. c) Absence of spontaneous LH peaks in WKY females. d) Advancement in balano-preputial separation in SHR males and e) Higher plasma FSH levels in SHR males than in WKY males, without differences in other hormones.

Animals↗

PubMed1987

Secretion of LH in spontaneously hypertensive rats.

Weights of testes, seminal vesicles, ventral prostate and pituitary, plasma testosterone and LH concentrations, pituitary LH content and concentration, the LH in-vivo response after LHRH administration (1 microgram), and basal and LHRH-stimulated secretion in vitro were analysed in adult male spontaneously hypertensive (SH) and normotensive control (WKY) rats. Spontaneously hypertensive rats showed: testis and pituitary hypertrophy; seminal vesicle and ventral prostate atrophy; increased plasma testosterone and LH concentrations; increased pituitary LH content and concentration; unchanged net increase of plasma concentrations of LH 15 and 45 min after administration of 1 microgram LHRH; and increased basal LH secretion in vitro with a normal response to LHRH stimulation. These results provide evidence that SH rats show increased LH secretion with a normal response to LHRH stimulation. The coexistence of high plasma concentrations of testosterone with seminal vesicle and ventral prostate atrophy suggest a reduction in the effectiveness of testosterone in these structures.

Animals↗

PubMed1986

Morphometric analysis of the rat ventral prostate and seminal vesicles during prepubertal development: effects of neonatal treatment with estrogen.

In a morphometric study on the ventral prostate and seminal vesicles in the rat, we investigated the changes in fibromuscular stroma, glandular epithelium, and glandular lumen. Animals were studied at 15, 30 and 45 days of age. The rapid prepubertal growth started earlier in the ventral prostate than in seminal vesicles. In addition, the effects of neonatal administration of estrogens on the different tissue compartments were studied, comparing rats that had been castrated and/or treated with estrogen at birth to intact animals at 15 days of age. Estrogens caused a decrease in the volume of the glandular epithelium and increased the volume of the fibromuscular stroma in both ventral prostate and seminal vesicles. Castration partially abolished the estrogen-induced growth of the stroma, which suggests that the growth is dependent on testicular factors. The difference in proportion of the fibromuscular stroma between the two glands is evidence that the size of the whole seminal vesicles has increased whereas the size of the ventral prostate has decreased.

Aging↗

PubMed1986

Increased number of mast cells in the testis of neonatally estrogenized rats.

The presence of increased numbers of mast cells in the testis of adult neonatally estrogenized rats is reported. The histometric study revealed significant differences between control and estrogenized animals for two ages considered (45 and 90 days). This increase might be related with the development of connective tissue in estrogenized rats.

Animals↗