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R Patiño

Publications and source records attributed to R Patiño.

At least 37 records · Page 2Linked to original sources
PubMed1993

Inhibitory effects of n-alkanols on the hormonal induction of maturation in follicle-enclosed Xenopus oocytes: implications for gap junctional transport of maturation-inducing steroid.

In fishes and amphibians, the induction of oocyte maturation by gonadotropin is mediated by follicle cell production of maturation-inducing steroid. This steroid appears to be progesterone in the frog Xenopus laevis. It is also known that full-grown oocytes of X. laevis are cytoplasmically linked to follicle (granulosa) cells via gap junctions, and that these gap junctions are enhanced by whole-animal injections of gonadotropin (human chorionic gonadotropin, hCG). However, the specific role of this heterocellular gap junctional communication is unclear, especially in regard to its possible involvement in the regulation of oocyte maturation. Therefore, the objective of this study is to examine the role of follicle cell-oocyte gap junctional coupling during maturation of the ovarian follicle of X. laevis. For this purpose, we determined the in vitro effects on oocyte maturation of the known gap junction uncouplers 1-heptanol and 1-octanol, alone or in combination with maturational concentrations of hCG or progesterone. The n-alkanols alone did not have any effect on maturation. However, both heptanol and octanol at 1 mM blocked the hCG and progesterone induction of maturation in follicle-enclosed Xenopus oocytes. At least in the case of heptanol, the inhibition of hormone-induced maturation was not accompanied by changes in the steroidogenic response of intact follicles to hCG or in the responsiveness of defolliculated oocytes to exogenous progesterone. These latter observations seem to rule out non-specific effects of the alcohols on follicle cell or oocyte function. Therefore, our results suggest that gap junctional coupling between follicle cells and the oocyte is required for maturational steroid signaling in amphibian ovaries.

1-Octanol↗
PubMed1993

Ultrastructural changes in follicle cell-oocyte associations during development and maturation of the ovarian follicle in Atlantic croaker.

Full-grown ovarian follicles of the marine teleost Atlantic croaker (Micropogonias undulatus) are unresponsive to steroidal maturation-inducing substance (MIS). However, responsiveness to MIS (maturational competence) can be induced in vivo or in vitro by brief stimulation with gonadotropin (e.g., human chorionic gonadotropin, hCG). The objective of this study was to examine ultrastructural changes in follicle cell-oocyte associations related to the acquisition of maturational competence and maturation in croaker ovarian follicles. Ultrathin sections of lanthanum-infiltrated samples were observed by transmission electron microscopy at various points during follicular development and hormone-induced maturation: vitellogenic oocytes (< 350 microns), full-grown oocytes (350-400 microns), hCG-stimulated (maturationally competent) oocytes, hCG/MIS-stimulated (early-maturation, hydrating) oocytes, and ovulated oocytes. In general, prior to ovulation, oocyte microvilli made contact with granulosa cells, and gap junction-like structures were seen at these points of contact. Midvitellogenic follicles (< 350 microns) had relatively high levels of follicle cell-oocyte associations and gap junctional contacts, but by late vitellogenesis (350-400 microns) these levels had declined markedly. However, high levels of intercellular associations and gap junctional contacts were reestablished upon induction of maturational competence with hCG, and these levels remained high in early-maturation oocytes. These changes seemed to be mainly due to alterations in oocyte microvilli length and surface contact with granulosa cells rather than to alterations in the numbers of microvilli. However, retraction and disappearance of microvilli occurred during ovulation. Therefore, the appearance of maturational competence coincided with the reestablishment of heterocellular gap junctional contacts in full-grown follicles. One function of these contacts may be to allow transfer of maturational signals between the granulosa cells and the oocyte during the early stages of follicular maturation.

Animals↗
PubMed1993

High-affinity binding of progesterone to the plasma membrane of Xenopus oocytes: characteristics of binding and hormonal and developmental control.

Progesterone induces maturation of the amphibian oocyte through its action on the plasma membrane. However, whether or not this action requires high-affinity binding to a specific receptor is unclear. In this study, the binding activity of progesterone was characterized in plasma membranes from whole ovaries or defolliculated oocytes of Xenopus laevis. Membrane-bound, radiolabeled progesterone was isolated by filtration of membrane suspensions and quantified by liquid scintillation. The association of progesterone to membrane preparations reached equilibrium within 15 min. Progesterone binding activity was directly proportional to the sample concentration, was significantly reduced by trypsin digestion, and was pH-dependent and temperature-sensitive. Also, binding activity was observed in membrane preparations from whole ovaries and defolliculated oocytes but not in those from somatic cells, indicating that progesterone binding is restricted to the oocyte membrane. Scatchard analysis indicated a single class of high-affinity (average KD, 10(-9) M), low-capacity (average concentration, 10(-12) mol/mg protein) binding sites for progesterone in all oocyte membrane preparations tested. Progesterone binding activity was also detected in preparations from albino frog ovaries, indicating that the binding activity is not an artifact of melanin contamination. Competition studies showed the following order of affinities: progesterone > pregnenolone > 17 alpha, 20 beta, 21-trihydroxy-4-pregnen-3-one > 11-deoxycorticosterone > 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one > 11-deoxycortisol > estradiol > R5020 > corticosterone > aldosterone > cortisol > androstenedione > ouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Induction of maturation of Atlantic croaker oocytes by 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one in vitro: consideration of some biological and experimental variables.

We characterized the in vitro control of germinal vesicle breakdown (GVBD) by 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one (20 beta-S) in intact ovarian follicles of gonadotropin-primed Atlantic croaker. 20 beta-S-induced GVBD was determined in relation to ovarian (oocyte) morphology, duration of incubation, steroid metabolism, and interaction with other steroids. The rate of GVBD in vitro in the absence of exogenous steroid was positively correlated with initial stage of ovarian morphological development. Maximal responsiveness to 20 beta-S was seen in ovaries with oocytes showing the first signs of morphological maturation. Dose-response experiments with 20 beta-S and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-P) over a range of incubation times yielded similar results for both steroids, suggesting that conversion of 17 alpha,20 beta-P to 20 beta-S is not required for 17 alpha,20 beta-P-induced GVBD. The ED50 of these steroids markedly decreased with increasing incubation times. Comparisons between patterns of follicular transformation of various radiolabelled steroids to 20 beta-S and their respective activities (using unlabelled steroids) in the GVBD bioassay suggested that, in addition to 17 alpha,20 beta-P, progesterone has some intrinsic maturational activity. However, the maturational effects of 11-deoxycortisol and pregnenolone may be explained by their conversion to 20 beta-S. For the first time in any vertebrate, we showed that the proposed maturation-inducing steroid (20 beta-S) is not significantly transformed to any extractable, potentially active metabolite by intact, maturing ovarian follicles. These findings strongly suggest that 20 beta-S is the terminal product of the MIS biosynthetic pathway in Atlantic croaker ovaries. Estradiol had no acute effects on 20 beta-S-induced GVBD. However, testosterone decreased and cortisol augmented the maturational activity of 20 beta-S. Excess progesterone reduced the activity of a maximally effective dose of 20 beta-S, but pregnenolone was without effect. The effects of these steroids on 20 beta-S-induced GVBD are discussed in relation to their possible interactions with 20 beta-S at the MIS receptor level.

17-Hydroxycorticosteroids↗
PubMed1990

Characterization of membrane receptor activity for 17 alpha, 20 beta, 21-trihydroxy-4-pregnen-3-one in ovaries of spotted seatrout (Cynoscion nebulosus).

The proposed maturation-inducing substance (MIS) of spotted seatrout (Cynoscion nebulosus) is 17 alpha, 20 beta, 21-trihydroxy-4-pregnen-3-one (20 beta-S). In this study, we characterized the binding of radioactive 20 beta-S to plasma membranes from the ovaries of spotted seatrout. Bound 20 beta-S was isolated by filtration of membrane suspensions and quantified by measurement of the radioactivity content of the filters. The saturable component of 20 beta-S binding reached equilibrium within 5 min at 0 degree, showed linearity with membrane concentration, and was pH dependent (optimum, 7.5-7.8). Scatchard analyses suggested a single class of high-affinity (KD, 10(-9) M), low-capacity (10(-13)-10(-12) mol/g ovary) binding sites for 20 beta-S. High levels of saturable binding were found in membrane preparations from the ovary, testis, and liver, but not from the gills. 17 alpha, 20 beta-Dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-P) showed relatively little affinity for the 20 beta-S binding site. However, this steroid was converted to a compound immunologically and chromatographically similar to 20 beta-S by intact ovarian follicles, a finding which may explain its previously reported high potency in an in vitro oocyte maturation bioassay. Conversely, although reportedly a weak inducer of oocyte maturation, progesterone readily displaced 20 beta-S from its binding site. Thus, progesterone appears to be a relatively inactive ligand with high affinity for the 20 beta-S receptor. The concentration of 20 beta-S binding sites in ovaries was significantly higher during final oocyte maturation (germinal vesicle migration) than at earlier stages of development. These results strongly suggest that the 20 beta-S binding activity characterized in our study represents authentic MIS receptors. A distinct, soluble binding site for 17 alpha, 20 beta-P was also identified in seatrout ovaries, but its biological function remains unclear. A hypothesis is presented for the significance of this 17 alpha,20 beta-P binding site.

17-Hydroxycorticosteroids↗
PubMed1990

Effects of gonadotropin on ovarian intrafollicular processes during the development of oocyte maturational competence in a teleost, the Atlantic croaker: evidence for two distinct stages of gonadotropin control of final oocyte maturation.

Full-grown oocytes of Atlantic croaker are insensitive to maturation-inducing steroid (MIS) unless they are primed with gonadotropin (GtH). The objective of this study was to examine the mechanism of GtH-induced maturational competence in croaker oocytes. Specifically, we determined the in vitro secretion of steroids by intact ovarian follicles of unprimed or hCG-primed fish, the direct effects of steroids on maturational competence, and the effects of steroid (cyanoketone), protein (cycloheximide), and RNA (actinomycin D) synthesis inhibitors on hCG-induced maturational competence and steroidogenesis in vitro. The steroid content of the incubation medium after hCG treatment was measured by RIA. The effects of hCG or exogenous steroid treatment on maturational competence were determined by recording the incidence of germinal vesicle breakdown (GVBD) after MIS-induced GVBD in a standard bioassay. Our major findings were: (1) induction of maturational competence occurred after exposure of ovarian follicles to hCG either in vivo or in vitro; (2) MIS secretion was detected in follicles of hCG-primed fish but not unprimed fish, and no MIS secretion was observed during hCG induction of maturational competence in vitro; (3) treatment with cyanoketone blocked the hCG-dependent secretion of testosterone and estradiol but not the development of maturational competence; (4) treatment with MIS or various other exogenous steroids in the absence of hCG did not induce maturational competence; and (5) hCG-induced maturational competence was inhibited by cycloheximide and actinomycin D. Therefore, the mechanisms of GtH induction of oocyte maturation in Atlantic croaker can be described in two distinct stages: a delta-4 steroid-(including MIS) and estrogen-independent priming stage followed by a MIS-mediated GVBD stage. The priming stage may involve mechanisms requiring RNA as well as protein synthesis.

Animals↗
PubMed1988

Spontaneous and ACTH-induced interrenal steroidogenesis in juvenile coho salmon (Oncorhynchus kisutch): effects of monovalent ions and osmolality in vitro.

We determined the in vitro effects of changes in extracellular monovalent ion levels and osmotic pressure on the spontaneous and adrenocorticotropin (ACTH)-stimulated interrenal activity of coho salmon (Oncorhynchus kisutch). We used a perifusion system of incubation and monitored interrenal activity by measuring the effluent cortisol content with a radioimmunoassay. An increase in the medium osmolality with mannitol, from 206 to 290 or 353 mosmol, caused an increase in the spontaneous release of cortisol only slightly (compared with the much greater increase induced by porcine-ACTH). A similar minor increase was observed when NaCl was elevated from 130 to 180 mM. On the other hand, the spontaneous release of cortisol was not affected by increasing the KCl level from 3.2 to 9.6 mM, but was clearly increased when KCl was raised from 3.2 mM to a supraphysiological level of 27.2 mM. Ionic or osmolality changes, within the physiological range observed in coho salmon plasma, did not affect the characteristics of interrenal secretion of cortisol in response to porcine-ACTH. If our results with interrenal cells in vitro are representative of the basic functioning of the cells in vivo, then one would have to conclude that changes in concentrations of plasma monovalent ions or in osmotic pressure may not play a significant physiological role in the regulation of interrenal steroidogenesis or corticosteroid release in coho salmon.

Adrenal Glands↗
PubMed1987

Interrenal secretion of corticosteroids and plasma cortisol and cortisone concentrations after acute stress and during seawater acclimation in juvenile coho salmon (Oncorhynchus kisutch).

We determined the major corticosteroids secreted by interrenal tissue and those present in plasma of juvenile coho salmon (Oncorhynchus kisutch). Incubation medium of interrenal tissue, unstimulated or stimulated with exogenous ACTH in vitro, and plasma of resting or acutely stressed salmon were extracted and qualitatively analyzed for steroid composition using high-performance liquid chromatography. Concentrations of plasma cortisone and cortisol following an acute handling stress or exposure to seawater were quantitatively measured by radioimmunoassay (RIA). Cortisol was the only corticosteroid detected by HPLC in media after incubation of interrenal tissue in the absence or presence of ACTH in vitro. However, both cortisone and cortisol were detected by HPLC in plasma sampled 1 hr after fish were acutely stressed by handling. Stress and seawater acclimation produced marked elevations in plasma levels of both steroids as determined by RIA and also resulted in long-lasting changes in the plasma cortisone:cortisol ratios. In resting fish, cortisone concentrations were similar or higher than cortisol levels. We concluded that cortisol is the primary steroid secreted by the interrenal tissue of coho salmon, and that plasma cortisone arises primarily from the peripheral conversion of cortisol to cortisone. The relatively high levels of cortisone in resting fish and its increase following stress and seawater acclimation suggest the possibility of a biologically significant role for this hormone.

Acclimatization↗
PubMed1986

Adenylate cyclase activators and inhibitors, cyclic nucleotide analogs, and phosphatidylinositol: effects on interrenal function of coho salmon (Oncorhynchus kisutch) in vitro.

The role of cyclic AMP (cAMP) as mediator of ACTH action on interrenal steroidogenesis was evaluated in juvenile coho salmon (Oncorhynchus kisutch). Head kidneys (containing the interrenal cells) were incubated in the absence or presence of putative adenylate cyclase activators (forskolin and cholera toxin), ACTH combined with putative adenylate cyclase inhibitors (hydrolysis-resistant ATP analogs), dibutyryl cyclic (dbc) AMP, dbcGMP, or phosphatidylinositol. The cortisol content of the incubation medium was subsequently determined by radioimmunoassay. Forskolin markedly stimulated cortisol secretion by interrenal cells. Adenylate cyclase inhibitors depressed the steroidogenic response to ACTH. Dibutyryl cAMP, but not dbcGMP, enhanced steroid secretion. Thus, cAMP seems to be an important "second messenger" for ACTH action on salmon interrenal cells. In contrast to findings in mammalian adrenocortical cells, exogenous phosphatidylinositol and cholera toxin failed to stimulate corticosteroid secretion in salmon interrenal cells. However, it was unclear whether these negative findings were an artifact resulting from the use of kidney tissue fragments instead of isolated interrenal cells.

Adenylyl Cyclases↗
PubMed1986

Sexual dimorphism of plasma sex steroid levels in juvenile coho salmon, Oncorhynchus kisutch, during smoltification.

Concentrations of plasma sex steroids, cortisol, and thyroxine were measured by radioimmunoassay in hatchery coho salmon (Oncorhynchus kisutch during winter and early spring. Mean plasma 11-ketotestosterone (11-KT) and estradiol levels fell into two distinct categories: 11-KT was 181-373% higher in males than in females, and estradiol was 109-143% higher in females than in males. No changes in plasma levels of estradiol in fish of both sexes, or in levels of 11-KT in males, were evident during spring when plasma thyroxine and cortisol were markedly elevated, indicating that the fish were undergoing smoltification. Although plasma 11-KT in females appeared to be lower in late April than in February, it showed no correlation with plasma thyroxine or cortisol in these individuals. Our finding of sexual dimorphism in 17 alpha-20 beta-dihydroxy-4-pregnen-3-one was inconsistent between stocks of fish and among sampling dates, thus making interpretation of the results difficult. However, no relationship between this steroid and plasma thyroxine or cortisol was observed. Therefore, plasma levels of sex steroids do not seem to be related to the changes in plasma thyroxine or cortisol observed during smoltification of coho salmon.

Animals↗
PubMed1985

Changes in plasma cortisol during stress and smoltification in coho salmon, Oncorhynchus kisutch.

The cortisol stress response in juvenile coho salmon, Oncorhynchus kisutch, considered as the difference between resting and peak poststress cortisol levels, increased from 80 ng/ml in March to 166 ng/ml in July, the period when smoltification normally occurs. Resting plasma cortisol levels also continually increased from 4 ng/ml in March to a maximum of 39 ng/ml in May, but then declined again to 3 ng/ml in July. The results indicate that there is an increased interrenal responsiveness to stress during the period of smoltification in coho salmon.

Analysis of Variance↗
PubMed1985

Clearance of plasma corticosteroids during smoltification of coho salmon, Oncorhynchus kisutch.

The plasma clearance rate (PCR) of radioactivity after a single intracardial injection of 3H-cortisol was elevated during the spring in yearling coho salmon, Oncorhynchus kisutch. Graphical analysis suggested a seasonal correlation between PCR and gill Na/K-ATPase activity. An explanation for this correlation is suggested. The major metabolite of 3H-cortisol in plasma was 3H-cortisone. It appeared rapidly following injection of the original radiotracer.

Adrenal Cortex Hormones↗
PubMed1984

Clearance of corticosteroids in yearling coho salmon, Oncorhynchus kisutch, in fresh water and seawater and after stress.

The metabolic clearance rate of corticosteroids determined after a single injection of [3H]cortisol was higher in fish acclimated to seawater (SW) than in those acclimated to fresh water (FW). Uptake and retention of corticosteroids in liver, gill filaments, and gall bladder bile were greater in SW than in FW fish. The stress of long-term (5 days), but not short-term (12 hr), continuous confinement apparently increased the clearance rate of corticosteroids in both FW and SW fish. Chronic, but not acute, administration of exogenous cortisol, yielding cortisol titers close to the physiological range, appeared to increase the clearance rate of corticosteroids in FW fish.

Acclimatization↗
PubMed1979

The role of growth hormone in the pathogenesis of postmenopausal osteoporosis.

The secretory response of somatotropic hormone (STH) to arginine hydrochloride stimulation (0.5 g/kg) was studied in 13 postmenopausal women. Eight showed evidence of osteoporosis, based on clinical and morphoradiological data and on metacarpal cortical thickness measurement, and five had normal bone mass. In addition, the response to levodopa (500 mg) was determined in four of the osteoporotic patients. Baseline STH concentrations in the osteoporotic subjects did not differ from those in the nonosteoporotic group, but the latter showed a significant increase over the former at 45, 60, 90, and 120 minutes after stimulation. Similar findings were obtained with levodopa stimulation. Without necessarily implying a cause-effect relationship, our data appear to support the hypothesis that the poor secretory response of STH may be to some degree responsible for the osteopenia observed during the climateric.

Adult↗
PubMed1975

Treatment of tumors of the third ventricle: a new and simple technique.

A new surgical technique is described for the treatment of benign cystic tumors of the third ventricle. It basically consist of: 1) introduction of a catheter to the third ventricle, therefore to the cyst; 2) suction of all the material of the cyst; 3) connection of the catheter to a ventriculoatrial shunt. A report of five patients with a possible colloid cyst in the third ventricle treated with this technique and the satisfactory results obtained in all the cases, with lack of morbidity and mortality, is presented. A comparison between the traditional surgical procedure and ours, as far as the technique itself and the results are concerned, is made. The simplicity of the technique is emphasized and it is proposed as another solution for the treatment of cystic tumors of the third ventricle.

Brain Diseases↗