Biomedical subjects

A Hurwitz

Publications and source records attributed to A Hurwitz.

At least 73 records · Page 4Linked to original sources

PubMed1991

Cytokine-mediated regulation of ovarian function: interleukin-1 inhibits gonadotropin-induced androgen biosynthesis.

Resident ovarian macrophages have long been recognized as potential in situ regulators of ovarian function, presumably through local paracrine secretion of regulatory molecules (i.e. cytokines). One such macrophage product, interleukin-1 (IL-1) has recently been shown to exert profound regulatory effects at the level of the ovarian granulosa cell. In this report, we examine the possibility that the adjacent theca-interstitial (androgen-producing) cell may also be a site of IL-1 reception and action. The basal accumulation of androsterone, the major androgenic steroid synthesized by whole ovarian dispersates from immature rats, in the presence of insulin (1 microgram/ml), increased 8- to 9-fold after treatment with human CG (1 ng/ml). Although IL-1 alpha or IL-1 beta (10 ng/ml) by themselves were without effect on basal androsterone accumulation, both cytokines (IL-1 beta greater than IL-1 alpha) inhibited human CG hormonal action (in the presence of insulin) in a dose-dependent manner, the maximal inhibitory effect being 75%. Similar results were obtained when using highly purified theca-interstitial cells derived from the same animal model suggesting that IL-1-attenuated androgen biosynthesis is due, at least in part, to IL-1 acting directly at the level of the theca-interstitial cells. The IL-1 effect proved relatively specific since all other known interleukins (IL-1, IL-3, IL-4, IL-5, and IL-6) were without effect. Moreover, IL-1 beta action was effectively immunoneutralized when concurrently applied with anti-IL-1 beta (but not nonimmune) sera. Significantly, the antigonadotropic action of IL-1 could not be accounted for by a decrease in the viable cell mass. Tracer studies with radiolabeled steroid substrates suggested that IL-1-attenuated ovarian androsterone accumulation is due, if only in part, to inhibition of transformations catalyzed by (theca-interstitial) 17 alpha-hydroxylase/17:20 lyase, stimulation of theca-interstitial (or granulosa 20 alpha-hydroxysteroid dehydrogenase-mediated conversions, or both. Taken together, these findings indicate that relatively low concentrations of IL-1, possibly originating from somatic ovarian cells or resident ovarian macrophages, are capable of exerting an inhibitory effect upon gonadotropin-supported androgen production. As such, these and previous observations suggest that intraovarian IL-1 may play a dual regulatory role in the developing ovarian follicle by targeting both the granulosa and theca-interstitial cells as its sites of action.

Androsterone↗

PubMed1991

The ovarian expression of the antigonadotropic insulin-like growth factor binding protein-2 is theca-interstitial cell-selective: evidence for hormonal regulation.

To begin the process of identification and charactization of rat ovarian insulin-like growth factor binding proteins, we have undertaken to explore the ovarian expression, cellular localization, and hormonal regulation of the insulin-like growth factor binding protein-2 (IGFBP-2) gene for which an antigonadotropic potential has recently been demonstrated. To this end, a solution hybridization/RNase protection assay was employed wherein total ovarian RNA (20 micrograms) from immature (21-23 days old) female rats was hybridized with a [32P]-labeled IGFBP-2 riboprobe. As in liver, a single protected fragment (550 bases long) corresponding to IGFBP-2 transcripts was identified in whole ovarian material. Cellular localization studies revealed the IGFBP-2 gene to be exclusively expressed in the theca-interstitial rather than the granulosa cell compartment. To confirm the cellular distribution of the IGFBP-2 protein, media conditioned by cultured granulosa or theca-interstitial cells were subjected to immunoprecipitation using two IGFBP-2-directed polyclonal antisera. Expectedly, both antibodies (but not non-immune rabbit serum) readily immunoprecipitated the 28 kDa rat IGFBP-2 species generated by hepatic BRL-3A cells. Similarly, both antibodies effectively immunoprecipitated an IGFBP the size of rat IGFBP-2 elaborated by theca-interstitial cells. In contrast, neither antibody immunoprecipitated the 28-29 kDa IGFBP species elaborated by granulosa cells otherwise readily apparent in conventional Western ligand blots. Hypophysectomy resulted in a 3-fold decrease (P less than 0.05) in the relative (densitometrically-quantified) abundance of ovarian IGFBP-2 transcripts, a diametrically opposed effect (P less than 0.05) being noted at the level of the liver. In contrast, treatment of immature hypophysectomized rats with a diethylstilbestrol-containing subcutaneous silastic implant for a total of 5 days resulted in a concordant 3-fold increase (P less than 0.05) in the relative abundance of IGFBP-2 transcripts in both ovary and liver when compared with untreated hypophysectomized controls. Taken together, these findings document rat ovarian IGFPB-2 gene expression to be theca-interstitial (rather than granulosa) cell-selective, and subject to upregulatory control by pituitary principle(s) and/or by estrogens. Although equally estrogen-dependent, hepatic IGFBP-2 gene expression proved constitutive in nature and subject to (diametrically opposed) inhibitory control by (potentially distinct) pituitary principle(s).

Animals↗

PubMed1991

Endocrine- and autocrine-mediated regulation of rat ovarian (theca-interstitial) interleukin-1 beta gene expression: gonadotropin-dependent preovulatory acquisition.

We, and others have recently demonstrated the ovary to be a site of interleukin-1 (IL-1) reception and action. Since IL-1 is an established mediator of inflammation and since ovulation may constitute an inflammatory-like reaction, consideration was given to the possibility that IL-1 may play an intermediary role in the ovulatory process. To begin to evaluate the above hypothesis, we have set out to evaluate rat ovarian IL-1 beta gene expression, to determine its cellular localization, and to study its modulation by key endocrine and autocrine regulatory signals. To this end, use was made of a solution hybridization/RNase protection assay in which rat ovarian total RNA (20 micrograms) was hybridized with a [32P]-labeled 272 base rat IL-1 beta antisense riboprobe. To assess rat ovarian IL-1 beta gene expression under in vivo circumstances, use was made of an established experimental model capable of simulating naturally-occurring follicular maturation, ovulation, and corpus luteum formation. Specifically, a single subcutaneous injection of PMSG (15IU/rat) was followed (48h) later by an ovulatory dose (15IU) of human chorionic gonadotropin (hCG). A faint protected fragment 222 bases long corresponding to the IL-1 beta message was detectable in whole ovarian material prior to gonadotropic stimulation. Treatment with PMSG for 48h resulted in a modest, albeit measurable increase in the densitometrically-quantified steady state levels of the ovarian IL-1 beta message. Most striking, however, were the increments noted in the relative abundance of ovarian IL-1 beta transcripts following a 6h exposure to hCG producing a 4 to 5-fold increase (P less than 0.05) over the untreated state at a time point approximately 6h prior to projected follicular rupture. Subsequent evaluation of ovarian IL-1 beta transcripts, 24 and 48h following hCG administration, revealed significant (P less than 0.05) decrements (relative to the 6h peak) to a level comparable to that seen at the conclusion of 48h of treatment with PMSG. Cellular localization studies revealed the gonadotropin-dependent IL-1 beta mRNA to be theca-interstitial cell-exclusive. To assess rat ovarian IL-1 beta gene expression under in vitro circumstances, we have set out to determine whether IL-1 itself may influence the relative level of its own message. Treatment of whole ovarian dispersates with rhIL-1 beta (10ng/ml) for 4 and 24h resulted in a marked (P less than 0.05) time-dependent increase (up to 12-fold) in the relative abundance of IL-1 beta transcripts when compared with untreated controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1991

Insulin-like growth factor receptor gene expression in the rat ovary: divergent regulation of distinct receptor species.

The intraovarian insulin-like growth factor (IGF) system constitutes a triad composed of ligands, receptors, and binding proteins. Although conventional radioligand receptor assays have documented the presence of specific receptors for insulin and insulin-like peptides in some rat somatic ovarian cell types, the exact cellular localization and hormonal regulation of the receptors in question remain matters of inquiry. To reevaluate the very presence, cellular localization, and hormonal regulation of the IGF receptor gene family in the rat ovary, solution hybridization/RNase protection assays were used wherein ovarian total RNA (20 micrograms) from immature (21-23 days old) rats was hybridized with 32P-labeled type I IGF receptor, type II IGF/mannose-6-phosphate receptor, and insulin receptor riboprobes. Single protected fragments 261 (type I IGF receptor), 500 (type II IGF/mannose-6-phosphate receptor), and 478 (insulin receptor) bases long were evident in whole ovary, granulosa, and theca-interstitial cells. Hypophysectomy of immature rats led to significant (P less than 0.05) albeit variable decrements in the relative (densitometrically quantified) ovarian abundance of transcripts corresponding to the type I IGF (but not insulin or type II IGF/mannose-6-phosphate) receptor. Treatment of immature hypophysectomized rats with FSH (10 micrograms/rat.day x 2.5 days) resulted in a significant (P less than 0.05) increase (4-fold) in transcripts corresponding to the type I IGF receptor in both whole ovarian material and freshly isolated granulosa cells. Similar (3.7-fold) increments (P less than 0.05) were noted after treatment with a diethylstilbestrol-containing sc silastic implant applied for a total of 5 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Ovarian granulosa cell-derived insulin-like growth factor (IGF) binding proteins: release of low molecular weight, high-affinity IGF-selective species.

The ovarian granulosa cell has previously been shown to be a site of insulin-like growth factor (IGF) I production, reception, and action. It is the objective of this study to characterize in greater detail the soluble IGF binding activity released by this cell type. To this end, use was made of granulosa cells from immature diethylstilbestrol-treated rats. Serum-free media conditioned for 72 h by cultured untreated cells acquired polyethylene glycol (PEG)-precipitable [125I]IGF-I binding activity. The latter proved cell density-dependent, displaying a minimal inoculum requirement of less than or equal to 3 x 10(5) cells/culture. The daily elaboration of IGF-I binding activity appeared constant throughout the 72 h experimental period, the overall time-dependent accumulation of binding activity (over the same time period) proving virtually additive. Scatchard analysis of detailed competition studies with IGF-I suggests that the latter ligand binds to granulosa cell-derived IGF binding protein(s) (IGFBPs) with an apparent affinity of 3 x 10(-10) M. Qualitatively similar results were obtained when using [125I]IGF-II suggesting that the IGFBPs in question are not IGF-I-selective. In fact, specificity studies using either [125I]IGF-I or [125I]IGF-II revealed a rank order of competitive potencies compatible with that observed in other tissues so studied (IGF-II greater than IGF-I much greater than insulin). The proteinacious nature of the acid-stable IGF binding activity under study was indicated by its sensitivity to relatively low concentrations of cycloheximide, its apparent deactivation following repeated cycles of freezing and thawing, and its virtual elimination when subjected to boiling or trypsin treatment. Cycloheximide-induced blockade of protein biosynthesis also revealed that the IGF binding activity is subject to measurable turnover thereby suggesting that its accumulation represents the balance struck between synthetic and degradative processes. Western ligand blotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis-fractionated media revealed a non-glycosylated major band doublet of 28-29 kDa. A single minor IGFBP species represented by a 23 kDa band was also appreciated in some but not all experiments. Taken together, these findings document the ability of ovarian granulosa cells to secrete a heterogenous mix of low molecular weight, high-affinity IGF-selective binding species. As such, these observations are in keeping with the concept of a complete intraovarian IGF system replete with ligands, receptors, and soluble binding activity.

Animals↗

PubMed1990

Secondary biosynthetic defects in women with late-onset congenital adrenal hyperplasia.

BACKGROUND AND METHODS: Late-onset (non-classic) congenital adrenal hyperplasia is a cause of hirsutism, menstrual disorders, and infertility, but its frequency and the patterns of abnormalities in adrenal hormone secretion are not well understood. We investigated the frequency and ethnic distribution of nonclassic congenital adrenal hyperplasia due to deficiencies of 3 beta-hydroxy-delta 5-steroid dehydrogenase, 21-hydroxylase, or 11 beta-hydroxylase among 170 Israeli Jewish women with these clinical problems. All enzyme defects were identified by comparing the patients' hormonal responses to a 0.25-mg intravenous bolus dose of alpha 1-24-ACTH with those of 26 age-matched normal women. RESULTS: Twenty women (12 percent) had 3 beta-hydroxy-delta 5-steroid dehydrogenase deficiency, 18 (10 percent) 21-hydroxylase deficiency (14 homozygous), and 14 (8 percent) 11 beta-hydroxylase deficiency. All the homozygous women with 21-hydroxylase deficiency also had evidence of a partial deficiency in 11 beta-hydroxylase activity. Similarly, most of the women with 11 beta-hydroxylase deficiency also had evidence of a deficiency in 3 beta-hydroxy-delta 5-steroid dehydrogenase. Among the 118 women with no adrenal biosynthetic defect, 38 had high plasma androgen concentrations, and 80 had normal concentrations. CONCLUSIONS: About one third of Israeli Jewish women with hirsutism, menstrual disorders, or unexplained infertility had nonclassic congenital adrenal hyperplasia. Secondary adrenal biosynthetic defects were frequent in these women and were probably caused by intra-adrenal androgen excess rather than by dual inherited enzymatic deficiencies.

3-Hydroxysteroid Dehydrogenases↗

PubMed1990

Hepatobiliary effects of morphine are mediated in the brain.

Morphine slows hepatobiliary elimination of sulfobromophthalein in rodents, raising dye levels in plasma and liver. Earlier studies showed these effects to be independent of other opiate effects such as bile duct spasm, hypothermia or blood gas changes resulting from respiratory depression. Because opiate receptors are distributed throughout the body, within the central nervous system and at peripheral sites including the gastrointestinal tract, experiments were performed to ascertain whether central or peripheral sites mediate the hepatobiliary effects of morphine. Sulfobromophthalein was administered intravenously to mice and its levels were measured in plasma and liver. Tail-flick latency indicated centrally mediated analgesia. Inhibited intestinal transit of India ink reflected an opiate effect with a significant peripheral component. When injected into a cerebral ventricle morphine was much more potent in producing analgesia and raising sulfobromophthalein levels than when administered intravenously or intraperitoneally. An intravenous dose of naloxone that reversed morphine analgesia also prevented sulfobromophthalein elevation but did not prevent gut slowing. Naltrexone injected in a cerebral ventricle also reversed analgesia and sulfobromophthalein elevation but not intestinal slowing. The polar opiate agonist N-methylmorphine did not cause analgesia or raise sulfobromophthalein levels at peripheral intraperitoneal doses to 100 mg/kg. When given in a central ventricle at 4 x 10(-3) mg/kg, this agent produced analgesia and raised sulfobromophthalein but did not slow intestinal transit. After spinal cord transection, intravenous morphine did not retard the tail-flick response or affect sulfobromophthalein disposition, but peripherally mediated intestinal transit was slowed as it was in intact mice. These experiments demonstrate parallel opiate effects on analgesia and on BSP disposition but not on intestinal transit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Cytokine-mediated regulation of ovarian function: tumor necrosis factor alpha inhibits gonadotropin-supported progesterone accumulation by differentiating and luteinized murine granulosa cells.

Current views favor the notion that resident ovarian macrophages play an in situ role in the regulation of ovarian function through the local secretion of regulatory molecule(s) (i.e., cytokines). Herein we report on the potential ovarian relevance of one such macrophage product, tumor necrosis factor (TNF) alpha, a polypeptide capable of oncolytic as well as pleiotropic noncytotoxic biologic activities. Our findings suggest that the ability of TNF alpha to diminish the gonadotropin-supported accumulation of progesterone by granulosa/luteal cells is largely due to attenuation of key biosynthetic steps leading to progesterone production. These findings are in keeping with the notion that TNF alpha, possibly of intraovarian (e.g., macrophage or granulosa cell) origin, may comprise the centerpiece of a regulatory loop designed to attenuate gonadotropin hormonal action. Acting at or adjacent to its site of synthesis, TNF alpha may thus partake in the modulation of ovarian progestin economy, possibly in connection with the death of the corpus luteum.

Animals↗

PubMed1990

Prolongation of the latent period in patients with premature rupture of the membranes by avoiding digital examination.

Fifty three women with PROM between 26 and 34 weeks of gestation were examined. Twenty five women (group A) underwent one digital examination for cervical assessment while in 28 women (group B) the cervix was evaluated by speculum. No pelvic examinations were performed throughout the latent period. The latent period increased from 3.1 days in group A to 9.5 days in group B (P less than 0.005). Chorioamnionitis developed in 24% in group A and in 18% in group B (N.S.).

Adolescent↗

PubMed1990

Sinusoidal fetal heart rate pattern due to massive feto-maternal transfusion.

A 30-year-old woman presented with mild abdominal discomfort and decreased fetal movements in the 34th week of her third pregnancy. Fetal monitoring revealed a sinusoidal heart rate pattern, and abdominal delivery was promptly performed, with the newborn having a hematocrit of 7% due to massive fetomaternal transfusion. Fetal resuscitation was followed by a favorable outcome. The sinusoidal heart rate is discussed, with emphasis on the need for proper and prompt recognition of its significance.

Adult↗

PubMed1990

Bioavailability of phenylalanine and aspartate from aspartame (20 mg/kg) in capsules and solution.

Aspartame (L-aspartyl-L-phenylalanine methyl ester) was given in capsules or solution to compare the bioavailability of its constituent amino acids, aspartate and phenylalanine. Twenty healthy subjects received a single 20 mg/kg dose of aspartame in capsules or solution in a randomized, crossover design. Plasma amino acid concentrations and the phenylalanine to large neutral amino acid ratios (Phe/LNAA) were determined. Plasma aspartate concentrations did not increase with either treatment. For plasma phenylalanine following capsule ingestion, there was a smaller peak plasma concentration (Cmax; 103.3 v 126.6 mumol/L), a longer time to peak concentration (tmax; 108.6 v 36.6 minutes), but no significant difference in the area under the plasma concentration-time curve (AUC) (7,656 v 7,200 mumol.min/L) when compared with solution ingestion. The maximum plasma Phe/LNAA ratio was smaller (0.16 v 0.19) with capsules. The changes for plasma tyrosine were similar to those seen with phenylalanine. There were no significant differences in the plasma concentrations of the other LNAAs between capsule and solution ingestion. Thus, given the small effect on phenylalanine Cmax and Phe/LNAA and no effect on the extent of absorption of phenylalanine, aspartame ingested in capsules at doses up to 20 mg/kg is a suitable dosage form for blinded clinical studies, provided that the slower rate of absorption of phenylalanine from capsules is taken into account.

Adolescent↗

PubMed1990

Chronic use of hypnotics in a family practice--patients' reluctance to stop treatment.

Insomnia is a common symptom in family practice, and hypnotics are frequently prescribed for its treatment. A survey was performed in an urban clinic serving 1900 persons in order to detect the prevalence of this disorder and to reassess the need for hypnotics. Sixty-one patients were identified who were taking prescribed hypnotic drugs, mainly benzodiazepines. All were over the age of 40, and they comprised 8.1% of this age group. Forty-five were chronic users, taking hypnotics for more than 4 months during a 6-month study period. Eighty-nine percent of these chronic users were above 60 years of age. Seventy-seven percent had difficulty initiating sleep and 23% had problems maintaining sleep. Information was given to these patients on the side effects and possible addictive nature of chronic hypnotic use. Different kinds of psychological support were offered as alternatives to drug treatment, but these were refused by all. We conclude that in view of the addiction associated with chronic use and the difficulty of weaning patients off the sleeping pill, there is a place for more careful evaluation and management before hypnotics are prescribed.

Adult↗

PubMed1990

Follicle-stimulating hormone inhibits the constitutive release of insulin-like growth factor binding proteins by cultured rat ovarian granulosa cells.

The ovarian granulosa cell has previously been shown to be a site of insulin-like growth factor (IGF)-I production, reception, and action. It is the purpose of this communication to explore the possibility that this cell type is also capable of hormonally-regulatable elaboration of IGF binding proteins (BPs). To this end, granulosa cells from immature, diethylstilbestrol-primed rats were cultured for up to 72 h under serum-free conditions in the absence or presence of FSH (100 ng/ml). Media conditioned by untreated granulosa cells revealed constitutively released polyethylene glycol (PEG)-precipitable [125I] IGF-I binding activity the daily elaboration of which proved constant throughout the 72 h experimental period. However, treatment of granulosa cells, with FSH resulted in dramatic inhibition of the accumulation of IGF-I binding activity (89% at the 100 ng/ml dose level). Systemic provision of FSH (10 micrograms/rat/day for 2 days) revealed that this gonadotropic action is not strictly an in vitro phenomenon but that it can be fully reproduced under in vivo circumstances. Western ligand blotting of SDS-PAGE-fractionated media conditioned by untreated granulosa cells revealed three IGF-BP species comprising a major band doublet (28-29 kDa) as well as a single minor band (23 kDa). Treatment with FSH virtually eliminated the 23 kDa species and substantially reduced the relative representation of the 28 and 29 kDa IGF-BP species (82 and 74% inhibition, respectively). Taken together, these observations disclose the multiplicity of granulosa cell-derived IGF-BPs and reveal the striking ability of FSH to suppress their constitutive release under both in vitro and in vivo circumstances. This FSH action is all the more noteworthy in light of the generally stimulatory effect exerted by FSH at the level of the granulosa cell. Inasmuch as FSH may be concerned with the promotion of granulosa cell development, its ability to attenuate the release of (presumptively inhibitory) IGF-BPs may enhance the access of endogenously-produced IGF-1 to its cognate cell surface receptors and hence its cellular hormonal action.

Animals↗

PubMed1990

Basic fibroblast growth factor inhibits gonadotropin-supported ovarian androgen biosynthesis: mechanism(s) and site(s) of action.

Current evidence favors the hypothesis that granulosa cell-derived basic fibroblast growth factor (bFGF) may be the centerpiece of an intraovarian autocrine loop. In this report we examine the possibility that bFGF may also be involved in paracrine interactions at the level of the ovarian theca-interstitial cell. To this end, whole ovarian dispersates obtained from immature rats were cultured for 96 h under serum-free conditions. The accumulation of androsterone, the major androgenic steroid detected, increased 3- to 5-fold over baseline in response to treatment with hCG (1 ng/ml), an effect further optimized (2- to 4-fold) by supplementation with insulin-like growth factor-I (10 ng/ml), insulin (1 microgram/ml), terbutaline (10(-6) M), or high density lipoprotein (100 micrograms/ml). In the absence of these optimizing supplements, bFGF was without effect on basal androsterone accumulation, but produced a relatively modest (20%) inhibition of hCG hormonal action. In contrast, bFGF proved a highly potent inhibitor (80%) of hCG-stimulated androgen biosynthesis in supplement-enriched cultures. This reversible bFGF action proved to be time and dose dependent, with a minimal time requirement of 48 h and a median inhibitory dose of 2 ng/ml. Unaccounted for by altered (hCG-stimulated) cAMP generation or a diminution in the viable cell mass, the antigonadotropic effect of bFGF may by inference be assumed to involve a site(s) of action distal to or independent of cAMP generation. In this connection, cellular radiolabeling with [3H] pregnanolone (3 alpha-hydroxy-5 alpha-pregnane-20-one) revealed bFGF to be a potent inhibitor of the steroidogenic enzyme 17 alpha-hydroxylase/17-20-lyase. As such, these findings are in keeping with the possibility that locally derived bFGF may exert a dual inhibitory action on (mature) ovarian estrogen production by reducing androgen substrate provision as well as by exercising its now established ability to attenuate granulosa cell aromatase activity.

Aldehyde-Lyases↗

PubMed1990

Transforming growth factor-beta 1 inhibits ovarian androgen production: gene expression, cellular localization, mechanisms(s), and site(s) of action.

It is the aim of this study to establish ovarian transforming growth factor-beta 1 (TGF beta 1) gene expression, to reevaluate its cellular localization, and to explore potential interactions of this regulatory peptide on ovarian androgen biosynthesis. Northern analysis of whole ovarian polyadenylated RNA revealed a single 2.5-kilobase transcript corresponding to the TGF beta 1 precursor. Immunohistochemical staining localized the protein to the thecal-interstitial (interfollicular) compartment. To explore potential autocrine effects of TGF beta 1, use was made of whole ovarian dispersates from immature rats the differentiation of which was monitored by the acquisition of androgen biosynthetic capacity. The accumulation of androsterone, the major androgenic steroid detectable in this culture system, increased 5.4-fold over baseline in response to treatment with hCG (1 ng/ml). This effect was further optimized (2- to 4-fold) by supplementation with insulin (1 microgram/ml) and insulin-like growth factor-I (50 ng/ml). In the absence of these optimizing supplements, TGF beta 1 (10 ng/ml) was without effect on basal androsterone accumulation, producing distinct, albeit relatively limited (25%), inhibition of hCG hormonal action. In contrast, supplement-mediated optimization of ovarian androgen biosynthesis revealed TGF beta 1 to be a highly potent inhibitor (greater than 80%) of hCG hormonal action. This reversible TGF beta 1 action proved time and dose dependent, with a minimal time requirement of 72 h and a median inhibitory dose of 2.6 ng/ml. TGF beta 1 action was not due to diminution in the viable cell mass or altered cAMP generation and, therefore, most likely involved a site(s) of action distal to or independent of cAMP generation. Cellular radiolabeling studies of TGF beta 1-treated ovarian cells disclosed the accumulation of steroid intermediates proximal to the 17 alpha-hydroxylation step, suggesting TGF beta 1-mediated blockade at the level of the steroidogenic enzyme 17 alpha-hydroxylase/17-20-lyase. Taken together, these observations are in keeping with the view that TGF beta 1, possibly of thecal-interstitial origin, may not only play a positive paracrine role at the level of the adjacent granulosa cell (as previously reported), but may also constitute one of several autocrine signals concerned with the regulation of ovarian androgen economy. As such, these findings reaffirm the polyfunctional nature of TGF beta 1 action, as manifested by its diametrically opposed effects in different ovarian compartments.

Androgens↗

PubMed1990

Rat ovarian insulin-like growth factor II gene expression is theca-interstitial cell-exclusive: hormonal regulation and receptor distribution.

While the potential role of insulin-like growth factor (IGF)-I in ovarian physiology has been extensively studied, relatively limited attention has been paid to IGF-II the very presence of which in the mature rat ovary has been questioned. In the present study, we have reevaluated rat ovarian IGF-II gene expression, its cellular localization, hormonal regulation, and site(s) of receptor interaction. IGF-II mRNA was detected in whole ovaries from immature as well as mature intact rats. Cellular localization studies revealed IGF-II transcripts in theca-interstitial but not granulosa cells (a site of IGF-I gene expression). In contrast, no cellular selectivity was noted for Type I and Type II IGF receptor gene expression, both of which were clearly detectable in both granulosa and theca-interstitial cells. In vivo treatment of immature hypophysectomized rats with diethylstilbestrol reduced ovarian IGF-II mRNA levels while increasing IGF-I mRNA levels. Taken together, these and previous observations reveal fundamental differences in the cellular localization and hormonal regulation of ovarian IGF gene expression in that IGF-II gene expression (unlike IGF-I) is theca-interstitial (rather than granulosa) cell-specific, and is subject to down (as opposed to up) regulation in response to estrogenic stimulation. In contrast, Type I and Type II IGF receptors exist on both somatic cell types of the rat ovary. These observations are consistent with the view that IGF-II of theca-interstitial cell origin may not only play an autocrine role but may also serve as one of several signals through which this androgen-producing cell may communicate in a paracrine fashion with the adjacent granulosa cell compartment.

Animals↗

PubMed1989

Impaired bowel motility following small intestinal transplantation.

Little information is available concerning motility following bowel transplantation and the appropriate timing of offering enteral feedings. Eight Lewis rats (300 g) underwent small bowel transplant as described by R. P. Harmel, Jr., and H. Stanley (J. Pediatr. Surg. 21:214, 1986). Silver oxide electrodes were placed in the native proximal ileum and in the distal segment of the homograft. Four control rats underwent laparotomy and placement of silver oxide electrodes in the jejunum and proximal ileum. Leads were brought out through a stab wound and the abdominal incision was closed. The electrodes were connected to a continuous recorder. Basal electrical rhythm (BER) was recorded periodically and was evaluated daily as the average of three readings per animal per day. Homograft electrical activity was not observed until at least 40 hr post-transplant and never attained the level of BER of the native intestine (P less than 0.05). Myoelectric complex potentials were not observed in the transplanted rats until post-operative day 11. These data suggest that basal electrical activity is significantly impaired following bowel transplantation. This study indicates that intestinal activity can be monitored for extended periods of time and may be a useful method of evaluating recovery of motility post bowel transplant prior to initiating enteral intake.

Animals↗

PubMed1989

Interaction of clonidine and morphine with lidocaine in mice and rats.

Morphine and clonidine both elevated plasma levels of lidocaine to the same extent in mice while slowing lidocaine metabolism to deethylated products. The effects of clonidine on lidocaine disposition were reversed by yohimbine. Mice given morphine, 20 mg/kg sc, or clonidine, 0.2 mg/kg sc, had similar, 30-50%, elevation of plasma lidocaine levels at 15 min after lidocaine, 15 mg/kg iv, when compared to saline-treated animals. Despite similarity of effect on plasma lidocaine, mice treated with morphine were much more susceptible to lethal effects of lidocaine than were mice given clonidine. At iv doses of 22 mg/kg or higher, lidocaine caused death in nearly all morphine-treated mice, while even 32 mg/kg lidocaine caused only 11% mortality after saline or clonidine. Clonidine, 0.5 mg/kg sc, and morphine, 20 mg/kg sc, both raised plasma lidocaine levels in rats, but only morphine depressed respiration, causing hypoxia, hypercapnia, and acidosis and increasing lidocaine lethality. These data suggest that potentiation of lidocaine toxicity by morphine is due primarily to changes in blood gases rather than to elevation in lidocaine levels.

Animals↗