Biomedical subjects

C Bellido

Publications and source records attributed to C Bellido.

At least 37 records · Page 2Linked to original sources

PubMed2001

Luteolytic effect of prolactin is dependent on the degree of differentiation of luteal cells in the rat.

We studied the morphological and quantitative changes in cyclic corpora lutea (CCL) and in CL of pregnancy (CLP) during structural luteolysis. Elimination of CCL takes several cycles, and cell death occurs as successive apoptotic bursts, from 2100 h in proestrus to 1300 h in estrus. Each apoptotic burst determined a 60% decrease in the CL volume and an 80% decrease in the number of steroidogenic cells (SC). All these changes were inhibited by blocking the preovulatory prolactin (PRL) surge with bromocryptine (CB154). Neither apoptotic cells nor changes in the number of SC were found in regressing CLP from Day 21 of pregnancy to Day 2 postpartum, although there was a 50% decrease in the CLP volume and a 30% decrease in the mean cross-sectional area of SC. Treatment with CB154 on the day of parturition did not modify these regressive changes. On Day 5 postpartum, the volume of the CLP and the number of SC were equivalent in lactating rats (showing high PRL concentrations induced by pup suckling) and nonlactating noncycling rats (in which cyclicity and, therefore PRL surges, were blocked by treatment with LHRH antagonist). However, on Day 10 postpartum, the CLP volume and the number of SC were significantly decreased in lactating rats, and apoptotic cells were frequent. In postpartum cycling rats, the CLP did not show apoptotic cells on the day of the second postpartum estrus (on Day 5 postpartum), whereas on the day of the third postpartum estrus (on Day 9 postpartum), apoptotic cells were abundant. These results indicate that PRL does not induce apoptosis in the CLP before Day 5 postpartum and strongly suggest that the proapoptotic effect of PRL is dependent on the degree of differentiation of luteal cells.

Animals↗

PubMed2001

Effects of systemic blockade of nitric oxide synthases on pulsatile LH, prolactin, and GH secretion in adult male rats.

BACKGROUND: Nitric oxide (NO) has emerged as an important neurotransmitter involved in the control of the neuroendocrine function. NO acts at hypothalamic, pituitary, and gonadal levels. Previous data from our laboratory showed that blockade of NO generation, after systemic administration of a NO synthase inhibitor (Nomega-nitro-arginine methyl ester, NAME), increased the luteinizing hormone (LH) secretion in intact and ovariectomized females, whereas a blockade of spontaneous and steroid-induced LH and prolactin surges after NO synthase inhibition has been also described. METHODS AND RESULTS: Adult male rats were implanted with chronic intra-auricular cannulae and 5 days later sampled at 15-min intervals during 6 h (10.00-16.00 h). Administration of NAME (40 mg/kg at 08.00 and 13.00 h) stimulated significantly (p < or = 0.01) the LH secretion, increasing LH pulse amplitude (0.58 +/- 0.14 vs. 0.08 +/- 0.01 ng/ml in controls), mean LH levels (0.64 +/- 0.15 vs. 0.15 +/- 0.03 ng/ml in controls), and area under curve (239 +/- 56 vs. 57 +/- 13 in controls). This effect was blocked by coadministration of sodium nitroprusside (SNP), a NO donor (0.5 mg/kg). The action of NAME was observed 3 h after administration, in contrast to the earlier response detected in female rats, and it appeared selective for LH, as prolactin and growth hormone secretion remained unchanged. Further analysis was carried out to determine whether the effect of NAME on the LH secretion was indirect and mediated by changes in testosterone release. To this end, adult male rats were decapitated 2 h after administration of NAME (40 mg/kg), SNP (0.5 mg/kg), or L-nitro-arginine methyl ester (L-AME), a substrate for NOS (1 g/kg). The serum testosterone concentrations were unchanged after NAME administration, but inhibited by SNP and L-AME. Finally, the effect of NAME and SNP on in vitro testosterone secretion was analyzed. NAME (10 mM) did not affect basal testosterone production, but inhibited the human chorionic gonadotropin stimulated testosterone secretion. CONCLUSIONS: These data strongly suggest that the stimulatory effect of NAME on LH secretion is not due to an inhibition of testosterone release and is exerted at the hypothalamic-pituitary level.

Animals↗

PubMed2001

Cyclic changes in the responsiveness of regressing corpora lutea to the luteolytic effects of prolactin in rats.

In cyclic rats, apoptosis of luteal cells during structural luteolysis occurs cyclically at the transition from pro-oestrus to oestrus in response to the preovulatory prolactin surge. This finding indicates that cyclic changes in apoptosis during luteolysis are dependent on prolactin surge cyclicity. In this study, the effects of prolactin on structural luteolysis were studied under different experimental conditions in relation to the phase of the oestrous cycle. In rats treated with prolactin at metoestrus and dioestrus, apoptosis did not occur in regressing corpora lutea, whereas in rats treated with prolactin on the morning of pro-oestrus, a 12.3-fold and 3.4-fold increase were observed in the number of apoptotic cells in regressing corpora lutea of the current and previous oestrous cycles, respectively. However, when the preovulatory prolactin surge and hence the subsequent apoptotic burst were blocked, prolactin treatment at the dioestrus phase induced a 13-fold increase in the number of apoptotic cells and significant changes in the volume of the corpus luteum (38% decrease) and the number of steroidogenic cells per corpus luteum (70% decrease). The results of this study indicate that the responsiveness of the regressing corpus luteum to the pro-apoptotic effects of prolactin are dependent on the phase of the oestrous cycle and on the presence or absence of an apoptotic burst in response to the preovulatory prolactin surge on the evening of pro-oestrus. Steroidogenic cells surviving to the apoptotic burst during the transition from pro-oestrus to oestrus became refractory to the lytic effect of prolactin. Furthermore, these cells also responded to the luteotrophic effects of prolactin, reaching full morphological luteinization, as indicated by the rescue of regressing cyclic corpora lutea during pregnancy.

Animals↗

PubMed2000

Luteinizing hormone secretion elicited in a ligand-independent activation of progesterone receptor manner at pituitary level in the rat: differential effect of two selective estrogen receptor modulators.

In the absence of progesterone, RU486 reduced basal and luteinizing hormone-releasing hormone (LHRH)-stimulated LH secretion in pituitaries from proestrous rats, a fact which evidences a ligand-independent activation of progesterone receptors (LIAPR) at pituitary level. This was also observed in pituitaries from rats treated with tamoxifen, and absent in glands from either ovariectomized or raloxifene-treated animals. Both ovariectomy or raloxifene treatment reduced the stimulatory effect of LHRH on LH secretion, while tamoxifen induced an even higher response. Prolactin (PRL) secretion was unaffected by either RU486 or LHRH, nor it was influenced by ovariectomy or raloxifene treatment. However, treatment with tamoxifen elevated PRL in all groups. These findings indicate that LIAPR is an estrogen-dependent phenomenon at the anterior pituitary of the female rat, and that tamoxifen and raloxifene present agonist and antagonist estrogen activity, respectively, at this level.

Animals↗

PubMed2000

Comparison of the effects of antiprogestins RU38486, ZK98299 and ORG31710 on periovulatory hypophysial, ovarian and adrenal hormone secretion in the rat.

The antiprogestin (AP) RU38486 (RU) blocks progesterone (P) and glucocorticoid (G) actions. Administration of 4 mg RU on proestrous morning to cyclic rats dissociates LH and FSH secretion on proestrous afternoon, early estrus and on estrous afternoon. In order to ascertain which action blocked by RU is predominant in the control of periovulatory LH and FSH secretion, a study was made on the effects of: a) 1 or 4 mg of ZK98299 (ZK) (type I P antagonist; Schering), b) 2 or 8 mg of Org31710 (OR) (type II P antagonist lacking anti-G actions; Organon) or c) 1 or 4 mg of RU (type II P antagonist; Exelgyn) to 4-day cyclic rats on proestrous morning on serum concentrations of LH, FSH, inhibin-alpha (I), estradiol-17beta (E), progesterone (P) and corticosterone (B) at 18:30 h on proestrus and at 02:00 and 18:30 h on estrus. Controls, receiving 0.2 ml oil, had elevated serum concentrations of all six hormones on proestrous afternoon; at early estrus, only serum concentrations of FSH and P remained elevated, and, on estrous afternoon, all hormones but I and B, that peaked again, had reached their lowest serum levels. All AP treatments except 1 mg ZK had the same effects. On proestrous afternoon serum LH concentrations were reduced and serum FSH concentrations were suppressed whereas serum levels of I, E, P and B were unaffected. At early estrus, basal serum concentrations of LH and E increased while FSH secretion was abolished. Serum levels of I, P and B did not differ from controls. AP treatments increased basal LH concentration, hyperstimulated FSH secretion and reduced serum I concentration on the afternoon of estrus. E, P and B serum levels did not differ from controls at this stage. Treatment with 1 mg ZK was less effective in reducing serum FSH on proestrous afternoon and at early estrus, and had no effect on serum concentrations of any hormone on estrous afternoon. These results indicate that blockade of P receptor activation by P is, predominantly, the mechanism of AP action on periovulatory gonadotropin secretion in rats.

Adrenal Glands↗

PubMed2000

The in vitro inhibitory action of antiprogestin RU486 on LH and FSH secretion in the absence of progesterone in rats is estrogen-dependent.

Previous in vivo findings show that in the virtual absence of progesterone (P), the antiprogestin RU486 reduces LH and FSH secretion in proestrous rats, indicating that activation of P receptor (PR) can occur in the absence of the cognate ligand. The present study investigates, in vitro, whether or not the inhibitory effect of antiprogestin RU486 on gonadotropin secretion in the absence of P is estrous cycle dependent, and whether its specific expression in proestrus mirrors the high estrogen (E2) background. In the first experiment we investigated the effect of RU486 (10 nM) and/or LHRH (10 nM) on LH and FSH secretion in incubated pituitaries collected on each day of the estrous cycle of the rat. In the second experiment, we determined the effect of RU486 and/or LHRH on preovulatory LH and FSH release by pituitaries from female rats that were ovariectomized (OVX), treated with the antiestrogen LY117018-HCL (Eli Lilly & Co.), or injected with 20 micrograms of estradiol benzoate (EB). The third experiment investigated the effect of RU486 and/or LHRH on LH and FSH release by pituitaries collected from intact or EB-treated (0.1 mg/kg over three consecutive days) male rats. RU486 reduced both basal and LHRH-stimulated LH and FSH secretion in proestrous pituitaries from normal 4-day cyclic rats. By contrast, in diestrous pituitaries, RU486 increased both parameters of LH secretion but was without effect on FSH release. RU486 was also without effect in pituitaries collected from rats in estrus or metestrus, or from OVX or antiestrogen-treated rats. Moreover, EB injection or treatment induced the full inhibitory effect of RU486 in pituitaries from female and male rats, respectively. The above results suggested that P occupancy of the receptor is not required for the formation or function of the active receptor and hence for preovulatory LH and FSH secretion, and that this form of PR activation at pituitary level is E2-dependent and not genetically determined.

Animals↗

PubMed2000

Different patterns of structural luteolysis in the human corpus luteum of menstruation.

Structural luteolysis is a complex process responsible for the elimination of the corpus luteum (CL). The aim of this study was to analyse the luteolytic process of the CL of menstruation. For this, we have morphologically studied 654 ovaries from 340 cycling women. Apoptotic cells were observed almost exclusively during the perimenstrual period and were extremely scarce at advanced stages of involution. Steroidogenic luteal cells surviving to the perimenstrual apoptotic wave underwent characteristic degenerative changes, consisting of intense cytoplasmic vacuolation, expression of macrophage markers and accumulation of lipofuscin pigment, and they persisted for long periods of time. Accumulation of corpora albicantia (CA) was observed in only 25% of a subset of 168 women, whereas 28% showed involuting CL without hyalinization, consisting of clusters of pigment-filled cells, and 46.4% showed ovaries with a mixture of CA and involuting CL without hyalinization or involuting CL with intermediate features. Evolution of the CL towards CA seemed to be related to the presence of a large, blood-filled cavity. The data from this study suggested that different patterns of structural luteolysis exist during CL involution, and that the final fate of the involuting CL is dependent on the presence of a large, central, blood-filled cavity.

Adult↗

PubMed2000

Progesterone on an oestrogen background enhances prolactin-induced apoptosis in regressing corpora lutea in the cyclic rat: possible involvement of luteal endothelial cell progesterone receptors.

Preovulatory surges of both prolactin (PRL) and progesterone have been suggested to be necessary for the induction of apoptosis in the regressing corpus luteum of the cyclic rat. The aim of these experiments was to study whether the administration of PRL and/or progesterone on the morning of pro-oestrus reproduces the regressive changes that happen in the cyclic corpus luteum (CL) during the transition from pro-oestrus to oestrus, and to analyse the temporal relationships between two characteristic features of structural luteolysis (luteal cell apoptosis and accumulation of macrophages). Cyclic rats (treated at 0900 h with an LHRH antagonist to block LH secretion) were injected at 1000 h with PRL and progesterone and killed at 0, 30, 60, 90 and 180 min after treatment. The number of apoptotic cells increased progressively from 60 min after treatment onward in hormone-treated rats, whereas the number of macrophages did not change throughout the period of time considered. Rats injected with PRL plus progesterone showed significantly greater numbers of apoptotic cells than those injected with PRL alone. The luteolytic effects of progesterone were in keeping with the presence of luteal endothelial cells showing progesterone receptor (PR) immunoreactivity in pro-oestrus. Treatment of rats during dioestrus and pro-oestrus with the specific antioestrogens LY117018 and RU58668 decreased the luteolytic effects of PRL and progesterone and the number of luteal endothelial cells immunostained for PR. These results strongly suggest that the preovulatory PRL surge and the preovulatory increase in progesterone together trigger structural regression of the corpus luteum. This seems to be dependent on oestrogen-driven cyclic changes in PRs in luteal endothelial cells.

Animals↗

PubMed1999

A quantitative study of changes in the human corpus luteum microvasculature during the menstrual cycle.

Endothelial cells are the most abundant cell type in the corpus luteum (CL), and changes in blood vessels have been proposed to play a pivotal role in CL regression. We have studied quantitatively the changes in the human granulosa-luteal microvasculature in CL of various ages: young (Days 17-19 of the cycle), mature (Days 20-24), old (Days 25-27), early regressing (follicular phase of the following cycle), and late regressing (luteal phase of the following cycle). Blood vessels were identified by immunohistochemical staining for the endothelial cell marker CD34. Because of the anisotropy of blood vessels, both vertical and transverse sections of the granulosa-lutein layer (GLL) were used to estimate relative (volume, surface, and length densities) and absolute (mean cross-sectional area) vascular variables. Full luteinization from young to mature CL was accompanied by a 61% increase in the mean cross-sectional area of vascular profiles and a 52% increase in the mean volume of granulosa-lutein cells, as an estimator of changes in the volume of the GLL. In old and early regressing CL, there was a progressive increase in relative structural vascular variables, due to the shrinkage of the GLL, whereas the mean cross-sectional area of capillaries showed a 53% decrease from mature to old CL. Finally, in late regressing CL, there was a decrease in most relative structural variables, in spite of the increasingly shrunken GLL. The decrease in the capillary diameter found at the late luteal phase most likely leads to a decreased blood flow, and early changes in blood vessels could initiate and/or accelerate CL regression.

Corpus Luteum↗

PubMed1999

The antiprogestin RU486 dissociates LH and FSH secretion in male rats: evidence for direct action at the pituitary level.

Administration of 4 mg of the antisteroid RU486 over 8 consecutive days to adult male rats dissociated in vivo and in vitro gonadotrophin secretion, increasing FSH and decreasing LH secretion. In subsequent experiments we evaluated the involvement of testicular or adrenal secretory products, as well as hypothalamic LHRH, in the effects of 4 consecutive days of RU486 treatment on the secretion of gonadotrophins. The first day of RU486 injection was designated day 1, subsequent days being numbered consecutively. Groups of rats injected with oil (0.2 ml) or RU486 (4 mg) were: (i) injected s.c. from day 1 to day 4 with the antiandrogen flutamide (10 mg/kg); (ii) bilateral orchidectomized (ORCH) on day 1; and (iii) bilateral adrenalectomized (ADX) on day 1. Controls were given flutamide vehicle or were sham operated. To ascertain whether the secretion of LHRH is involved in the effects of RU486 on gonadotrophin secretion, we measured the LHRH secretion into the pituitary stalk blood vessels at 1100 h on day 5 in oil- or RU486-treated rats. Additional oil- and RU486-treated rats were injected i.p. with 100 ng LHRH at 1000 h on day 5, or s.c. with 1 mg LHRH antagonist (LHRH-ANT) at 1000 h on days 2 and 4. Controls were given saline. All animals were decapitated at 1100 h on day 5, trunk blood collected and serum stored frozen until FSH, LH and testosterone assays.%While ADX had no effect on FSH and LH secretion in either oil- or RU486-treated rats, the removal of androgen negative feedback with flutamide treatment or by ORCH substantially increased serum levels of FSH and LH in both oil- and RU486-treated rats, and thus annulled the effects of RU486. No differences in pituitary stalk plasma LHRH concentrations were found between oil- and RU486-treated rats. Injection of LHRH increased serum FSH and LH concentrations in oil-treated rats but only, and to a lesser extent, LH concentrations in RU486-treated rats. Treatment with LHRH-ANT decreased serum concentrations of FSH and LH in both oil- and RU486-treated rats. These results suggest that RU486 inhibited LHRH-stimulated LH secretion at the pituitary level, and that FSH secretion increased in response to a reduction in the negative feedback of androgen.

Adrenalectomy↗

PubMed1999

Antiprogestins RU486 and ZK299 suppress basal and LHRH-stimulated FSH and LH secretion at pituitary level in the rat in an oestrous cycle stage-dependent manner.

We have previously shown that administration of antiprogestin (AP) type II RU486 to ovariectomized (OVX) rats on the morning of pro-oestrus decreases the magnitude of preovulatory gonadotrophin surge. This suggests that the effect of RU486 on LHRH-dependent gonadotrophin release may be independent of its ability to block progesterone actions. The aim of the present research was to study the possible site of RU486 action and to determine whether the gonadotrophin suppressive effect of APs RU486 and ZK299 is dependent on the oestrogen background. Intact or OVX rats in the morning of pro-oestrus were injected s.c. with 4 mg of RU486 or ZK299 (AP type I) at 0900 h on pro-oestrus. At 1830 h, serum concentration of FSH and LH and median eminence (ME) content of LHRH were determined. In the second experiment, the effect of RU486 and ZK299 on pituitary responsiveness to LHRH (100 ng, i.p.) and ME content of LHRH at 1830 h pentobarbital-blocked intact or OVX rats was evaluated. In the last study, the anterior pituitary release of FSH and LH from pro-oestrus or metoestrus donors incubated with or without LHRH (1, 10 or 100 nM) in the presence or absence of APs (20 nM) was evaluated. Both APs reduced serum FSH and LH levels at 1830 h on pro-oestrus in intact and OVX rats. The suppressive effect on gonadotrophin release brought about by AP treatment was also evidenced in PB-blocked intact and OVX rats. This suggested that the inhibitory effect of APs occurred, at least in part, at pituitary level. Furthermore, in the absence of the natural ligand, APs significantly reduced basal and LHRH-stimulated FSH and LH release from pro-oestrous but not from metoestrus pituitaries. In conclusion, these experiments have shown, both 'in vivo' and 'in vitro', that APs RU486 and ZK299 have suppressive effects at pituitary level on basal and LHRH-stimulated FSH and LH secretion, regardless of their antiprogestagenic activity, in pro-oestrus but not in metoestrus.

Analysis of Variance↗

PubMed1998

Ovarian follicle macrophages: is follicular atresia in the immature rat a macrophage-mediated event?

Macrophages have recently been found to play roles in most ovarian events through cytokine release and/or cell-cell communication. We studied the presence of macrophages in the ovaries of neonatal (0-7 days of age), juvenile (10-20 days of age), and prepubertal (25-30 days of age) rats, as well as adult cycling rats, in relation to follicular development and atresia. Macrophages were extremely scarce in the ovarian stroma up to 30 days of age. However, at 10 days of age, about 13% of small growing healthy follicles contained macrophages among granulosa cells. The percentage of macrophage-containing follicles at 15 days of age was about 60%, and the vast majority of these follicles also had pyknotic granulosa cells, which increased in number from 15 to 20 days of age. This type of atresia showed distinctive morphological and functional features in comparison with the atretic process observed in adult cycling rats. At 25 and 30 days of age, atretic follicles in advanced stages of atresia, together with atretic follicles similar to those present in adult rats, were observed. In adult rats, only a small proportion of healthy growing follicles contained macrophages. These cells were absent from early atretic follicles, and invasion by macrophages occurred at advanced stages of atresia. These data indicate that a different type of atresia occurred during early postnatal development, probably related to the special endocrine environment in immature rats. The close association between the presence of macrophages inside the follicles and of apoptotic granulosa cells strongly supports the hypothesis that macrophages mediate follicular atresia in immature rats.

Aging↗

PubMed1998

Macrophages, cell proliferation, and cell death in the human menstrual corpus luteum.

We studied the presence and numbers of macrophages in the different compartments of the human menstrual corpus luteum (CL) in relation to the proliferative activity and apoptosis in luteal cells. Macrophages were recognized by immunohistochemical demonstration of the lysosome-associated glycoprotein CD68, and proliferating cells by immunohistochemical detection of the cell cycle-related protein Ki67 and by counting mitotic cells. In general, changes in the number of macrophages were parallel to the functional activity of the CL. Macrophage numbers increased up to the end of the early luteal phase, remained relatively unchanged during the midluteal phase, and decreased at the late luteal phase. Furthermore, macrophages showed prominent morphological changes during the cycle. They showed round or elongated cytoplasm during the early and late luteal phases, and dendritic features in the midluteal phase. Proliferating cells were very abundant on Days 15-16 and showed a significant decrease thereafter. Most proliferating cells corresponded to stromal (mainly vascular) cells. However, about 5% of granulosa-lutein cells and about 15% of theca-lutein cells were proliferating during the early and midluteal phases. Regression of the CL at the late luteal phase was associated with both a decrease in the number of proliferating cells and an increase in the number of apoptotic cells, which were highly increased on Days 25-27 of the cycle. The number of macrophages was not related to cell proliferation nor to cell death during the luteal phase. The observed changes in both macrophage number and morphology suggest the existence of a bidirectional communication between macrophages and steroidogenic cells in the human CL, or regulation of both cell populations by similar mechanisms.

Apoptosis↗

PubMed1998

Both prolactin and progesterone in proestrus are necessary for the induction of apoptosis in the regressing corpus luteum of the rat.

This study was conducted to analyze the roles of prolactin (PRL) and progesterone in the induction of luteal cell apoptosis and accumulation of macrophages in the regressing corpus luteum. We studied the number of apoptotic cells and macrophages in regressing corpora lutea in estrus 1) in cycling rats or after blocking PRL secretion with the dopaminergic agonist CB154, and 2) after blocking progesterone actions with the progesterone receptor antagonists RU-486 or ZK98299. Cells showing the morphological features characteristic of apoptosis contained fragmented DNA as indicated by in situ 3' end labeling. In cycling rats, a 100-fold increase in the number of apoptotic cells and a 4-fold increase in the number of macrophages was found from the evening (1600 h) of proestrus to the morning (1100 h) of estrus. Both increases were blocked by PRL suppression with CB154. Furthermore, blocking progesterone actions with progesterone receptor antagonists RU-486 or ZK98299 without affecting PRL secretion inhibited apoptosis but did not affect the accumulation of macrophages, whether treatment was started on the morning of metestrus (blocking diestrous and proestrous progesterone) or on proestrus (blocking only proestrous progesterone). Otherwise, exogenous progesterone was not effective in inducing apoptosis in the absence of PRL. These results indicate that both PRL and progesterone in proestrus are necessary for the induction of apoptosis in the regressing corpora lutea, whereas the accumulation of macrophages seemed to be dependent exclusively on the PRL surge.

Animals↗

PubMed1998

A comparative study of mast cells and eosinophil leukocytes in the mammalian testis.

The existence of a physiological integration between the immune and endocrine systems has long been recognized. In spite of the abundant literature data on the presence of cells of the immune system in the testis, mast cells and eosinophil leukocytes have received little attention. We have studied the presence, distribution and numbers of mast cells and eosinophils in the testes of 12 mammalian species. Mast cells were frequently found in equine (stallion, ass and mule) and human testis, whereas eosinophils were nearly absent. On the contrary, eosinophils were abundant in the hare testis, while mast cells were lacking. Both cells types were present in high numbers in swine (wild and domestic boar) testis. Otherwise, mast cells and eosinophils were absent from the testicular parenchyma of several species (rat, dog, cat, bull and deer), although they were present, in most cases, around blood vessels in the tunica albuginea. The presence of high numbers of mast cells and/or eosinophil leukocytes in the testicular parenchyma of some species suggest a role for these cells in local regulatory pathways.

Animals↗

PubMed1998

Design and calibration of unicapillary pneumotachographs.

This study presents a method for design and calibration of unicapillary pneumotachographs for small-animal experiments. The design, based on Poiseuille's law, defines a set of internal radius and length values that allows for laminar flow, measurable pressure differences, and minimal interference with animal's respiratory mechanics and gas exchange. A third-order polynomial calibration (Pol) of the pressure-flow relationship was employed and compared with linear calibration (Lin). Tests were done for conditions of ambient pressure (Pam) and positive pressure (Ppos) ventilation at different flow ranges. A physical model designed to match normal and low compliance in rats was used. At normal compliance, Pol provided lower errors than Lin for mixed (1-12 ml/s), mean (4-10 ml/s), and high (8-12 ml/s) flow rate calibrations for both Pam and Ppos inspiratory tests (P < 0.001 for all conditions) and expiratory tests (P < 0.001 for all conditions). At low compliance, they differed significantly with 8.6 +/- 4.1% underestimation when Lin at Pam was used in Ppos tests. Ppos calibration, preferably in combination with Pol, should be used in this case to minimize errors (Pol = 0.8 +/- 0.5%, Lin = 6.5 +/- 4.0%, P < 0.0005). Nonlinear calibration may be useful for improvement of flow and volume measurements in small animals during both Pam and Ppos ventilation.

Animals↗

PubMed1997

Proliferative activity of preovulatory follicles and newly formed corpora lutea in cycling rats from late prooestrus to early oestrus.

Ovaries from adult cycling rats were studied from 1600 h on the day of prooestrus to 0700 h on the day of oestrus in order to relate the cyclic hormonal changes to the proliferative activity of preovulatory and postovulatory (i.e. newly-formed corpora lutea) follicles. Proliferative activity was studied by the immunohistochemical demonstration of DNA-incorporated 5-bromodeoxyuridine (BrdU). The proliferative activity of granulosa cells (GC) in large preovulatory follicles showed a centripetal pattern and decreased during prooestrus, reaching a minimum at 2100 h. However, a proliferative wave was found in the GC of preovulatory follicles at 0200 h on the day of oestrus and in those of newly-formed corpora lutea at 0700 h on the day of oestrus. These results suggest that the granulosa cells of preovulatory follicles show maturational changes that followed a different pattern, depending on their location within the follicle, and that the proliferative wave found from 0200 to 0700 h on oestrus is important for the establishment of the number of steroidogenic cells in the cyclic corpus luteum.

Animals↗

PubMed1997

Role of prolactin in the regulation of macrophages and in the proliferative activity of vascular cells in newly formed and regressing rat corpora lutea.

The proliferative activity of vascular cells and the number of macrophages were studied in corpora lutea of cycling and pregnant rats after prolactin (PRL) administration or depletion with the dopaminergic agonist CB154. Pregnant rats showed a higher proliferative activity of the vascular cells in newly formed corpora lutea than did cycling rats in metestrus. When cycling rats were treated with PRL, the proliferative activity was equivalent to that of pregnant rats. Treatment of pregnant rats with CB154 decreased the proliferative activity of vascular cells to the level in cycling rats. Otherwise, the proliferative activity was not modified in cycling rats after CB154 treatment. This indicates that the increase in the proliferative activity of vascular cells in the corpus luteum of pregnancy was due to the twice-daily PRL surges induced by mating. Treatment of cycling rats with CB154 decreased the number of macrophages in both newly formed and regressing corpora lutea, whereas PRL treatment increased the number of macrophages in regressing corpora lutea. In pregnant rats, treatment with CB154 decreased the number of macrophages in both newly formed and regressing corpora lutea. These results suggest that both the preovulatory and the twice-daily PRL surges regulate the macrophage population in newly formed and regressing corpora lutea.

Animals↗