Follistatin suppresses steroid-enhanced follicle-stimulating hormone release in vitro in rats

Previous in vitro and in vivo studies from our laboratory showed that progesterone (P(4)), corticosterone (B), and testosterone (T) increase intracellular content and release of FSH in the anterior pituitary. Activin (Act) and inhibin (Inh) are structurally related proteins with antagonistic actions, as Act stimulates and Inh inhibits FSH secretion from the anterior pituitary. Together with follistatin (FS), a protein that bioneutralizes Act, they form an autocrine-paracrine loop in the anterior pituitary that tightly regulates FSH secretion. The objective of the present study was to test the hypothesis that P(4), B, and T modulate this autocrine-paracrine loop to favor increased FSH secretion. If Act were to mediate steroid-induced FSH release, FS would be expected to block these effects. To test this interaction, cell cultures were prepared from anterior pituitaries of male and female rats, and treated with Act, B, P(4), or T in the absence or presence of FS. Act, B, P(4), and T increased FSH release; FS suppressed both basal and Act- and steroid-stimulated FSH release to approximately 50% below basal levels. Cell cultures from anterior pituitary of female rats were used to compare the interaction of incremental concentrations of FS on dose-related Act- and P(4)-stimulated FSH release. With increasing concentrations of Act, the FS-induced suppression of FSH release was attenuated and eventually abolished; in contrast, maximally stimulatory concentrations of P(4) did not fully overcome the FS-induced suppression of FSH release. The effects of P(4), B, and Act in the presence and absence of estradiol on steady-state mRNA levels of FSHbeta, Actbeta(B), and FS were determined in primary pituitary cell cultures from metestrous female rats by reverse transcription-polymerase chain reaction. Whereas Act, P(4), B increased FSHbeta mRNA levels, only Act raised the level of FS mRNA, and neither steroid increased Actbeta(B) mRNA. The results support the hypothesis that endogenous Act is a common mediator of the action of P(4), B, and T in the rat primary anterior pituitary cell culture. We conclude that the stimulation of FSH release and intracellular content in the gonadotroph by P(4), B, and T is mediated, in part, by Act and involves modulation of a tightly regulated Act/FS autocrine-paracrine loop.

Progesterone receptor A and B messenger ribonucleic acid levels in the anterior pituitary of rats are regulated by estrogen

In target tissues of most mammalian and avian species, progesterone receptors (PR) are expressed as structurally related, but functionally distinct, isoforms A and B, and they are regulated by estrogen (E) as well as by their cognate ligand, progesterone (P(4)). The objectives of the present work were to identify mRNA expression for the A and B isoforms of PR in the anterior pituitary of the rat, to examine its regulation by gonadal steroids, and to compare this regulation with that in the primary target organ, the uterus. Messenger RNAs for the PR isoforms, determined by two separate reverse transcription-polymerase chain reaction protocols, one that detects PR A and PR B equally and the other specific for PR B, were identified in anterior pituitary of female and male rats. In anterior pituitary of cycling female rats, steady-state mRNA levels for both PR A+B and PR B were highest at 0900 h on proestrus, declined rapidly to nadir values at 0900 h on metestrus (PR A+B) or 0900 h on estrus (PR B), and remained below proestrous values through 2100 h on diestrus. Administration of E to intact proestrous female rats caused significant increases in mRNA for both PR A+B and PR B on estrus and metestrus. Blockade of P(4) action by administration of the antiprogestins RU-486 and ZK-98299 on proestrus had no effect on PR mRNA levels on the morning of estrus. Ovariectomy two and ten days after surgery markedly reduced mRNA levels for both PR A+B and PR B. Whereas treatment of 10-day-ovariectomized rats with E led to marked induction of mRNA for PR A+B and PR B two days later, treatment with P(4) one day after treatment had no effect on basal or E-stimulated PR mRNA. Regulation of PR mRNA expression in the pituitary differed from that in the uterus, in which P(4) treatment of ovariectomized rats antagonized the E-induced rise in mRNA for PR B, and antiprogestins increased mRNA for both isoforms. In addition to induction of PR mRNA in the pituitary of female rats by E in vivo, we also demonstrated induction by E in primary culture of anterior pituitary cells in vitro. We conclude that in the anterior pituitary of female rats, both the A and B isoforms of PR are expressed and regulated by E.

Hypothalamic-pituitary-gonadal axis in the mutant weaver mouse

The weaver (wv) mutant mouse manifests severe locomotor defects, a deficiency in granule cells of the cerebellum, and cellular deficits in the midbrain dopaminergic system. The wv phenotype is associated with a missense mutation in the pore region of the G-protein-gated inwardly rectifying potassium channel, GIRK2. The homozygous male wv mouse is essentially infertile due to an inadequate level of sperm production. Females are fertile although they also manifest the neurological phenotype. Homozygotes of both sexes have reduced body weight. We have evaluated the hypothalamic-pituitary-gonadal axis in heterozygote and homozygote male and female wv mutants in comparison with wild-type controls. Testicular weight was significantly reduced in the homozygous males, due to degenerative changes of seminiferous epithelium. Serum and pituitary content of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were normal in all groups, and the normal sex differences were noted (FSH and LH higher in males, prolactin higher in females). Pituitary growth hormone (GH) concentration was normal, with control and mutant males showing higher GH than females. Serum testosterone levels were normal in the mutants, as was testicular testosterone. Testicular alpha-inhibin content was mildly reduced, but high in proportion to testicular weight. The defect in spermatogenesis appeared predominantly in the postmeiotic stages. In situ hybridization was consistent with expression of some GIRK2 mRNA isoforms in seminiferous epithelium. There were no significant differences between genotypes in the levels of dopamine, dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in the mediobasal and preoptic hypothalamic regions. Homovanillic acid levels in these two areas were, however, reduced in wv homozygotes compared to wild-type animals. In the light of normal pituitary hormone levels, normal hypothalamic monoamine concentrations and normal sex differences in gonadotropins, we conclude that the infertility in the male homozygote wv mouse lies within the tubule and is probably a primary defect in the germ cells. The hormonal data suggest that Leydig cell function, and at least some aspects of Sertoli cell function, are normal in the mutant mice.

125I-labeled fasciculin 2: a new tool for quantitation of acetylcholinesterase densities at synaptic sites by EM-autoradiography

Radio-iodinated fasciculin 2 (Fas2), a polypeptide anticholinesterase toxin from Mamba venom, was used as a new probe for localizing and quantifying acetylcholinesterase (AChE) at mouse neuromuscular junctions (NMJs) by quantitative electron microscope autoradiography. We demonstrate that 125I-Fas2 binds very specifically to the NMJs of mouse sternomastoid muscles, with very little binding to other regions in the muscles. Junctional AChE-site densities obtained from the autoradiograms were similar to those previously obtained for the same muscles using 3H-DFP. The use of 125I-Fas2 with EM-autoradiography is simpler and provides higher resolution and sensitivity, as well as considerably lower non-specific binding than previously attainable with 3H-DFP. The advantages and limitations of this procedure are discussed.

Antiprogestins suppress basal and activin-stimulated follicle-stimulating hormone secretion in an estrogen-dependent manner

Previous studies from our laboratory, demonstrating that suppression of serum FSH by RU486 requires a high estrogen (E) background, suggested that E-inducible progesterone receptors play a role in the regulation of FSH secretion. We demonstrated further that the type II antiprogestin RU486 and the type I antiprogestin ZK98299 both suppressed the elevated serum FSH and FSHbeta messenger RNA levels similarly on the evening of proestrus, but had divergent effects on the morning of estrus, when only RU486, but not ZK98299, lowered the elevated serum FSH level (secondary FSH surge). In the present work we used primary anterior pituitary cell culture to examine whether RU486 caused direct, E-dependent suppression of basal and recombinant human activin A (activin)-induced FSH secretion in the gonadotrope and to compare this direct effect, if any, with that of ZK98299. Primary cell cultures were prepared from anterior pituitaries collected from cycling female rats either on metestrous or proestrous morning and cultured in DMEM, supplemented with charcoal-stripped serum without or with 10 nM estradiol (E2) for 96 h; exposure to test agents occurred during the last 48 h of culture. FSH released into the medium and intracellular FSH content were determined by RIA. In cells from the anterior pituitary of metestrous rats cultured in E2-free medium, neither antiprogestin (10 nM) affected FSH release; in contrast, when cells were cultured in medium to which E2 had been added, both antiprogestins caused profound suppression of both basal and activin (10 ng/ml)-stimulated FSH release. In cell cultures from proestrous rats, both antiprogestins caused a slight, but significant, suppression of basal FSH release even in the absence of added E2; activin-stimulated FSH release, however, was not affected. Upon exposure of the cells from proestrous rats to E2, the antiprogestins potently suppressed both basal and activin-stimulated FSH secretion. Because the foregoing incubations were performed in culture medium devoid of progesterone (P4), the actions of the antiprogestins on FSH secretion were independent of the natural ligand. Addition of P4 (10 nM) to the cell cultures stimulated basal and activin-induced FSH release more in the presence than in the absence of E2. The FSH response to P4 was completely blocked by both antiprogestins in both the absence and presence of E2. Finally, both RU486 and ZK98299 blocked the stimulatory effect of corticosterone (1 microM) on FSH secretion. The observed effects of P4 and antiprogestins were specific for FSH secretion; LH secretion was not similarly suppressed by either antiprogestin, but was, in fact, stimulated by ZK98299 in E2-treated cells. We conclude that 1) E2-inducible progesterone receptors interact with activin-mediated signal transduction to regulate FSH secretion, and 2) unlike on the morning of estrus in vivo, RU486 and ZK98299 affect FSH secretion similarly in the gonadotrope in vitro.

[Anesthesiologic characteristics of isolated hyperthermic liver perfusion with mitomycin C]

The isolated hyperthermic liver perfusion with mitomycin C presents a new technique of regional therapy for irresectable liver tumours. The advantage is a high local concentration of the antitumour agent with reduced systemic side-effects. Isolated hyperthermic liver perfusion is an extensive surgical procedure requiring a veno-venous bypass and a heart-lung machine. Disturbances affecting the base-acid hemostasis, the coagulation system and the cardiocirculatory function can occur. To date, there has been little experience with this technique. The intraoperative changes during the isolated hyperthermic liver perfusion in our series were similar to those seen during orthotopic liver transplantation. In contrast to orthotopic liver transplantation, heparin is given during the anhepatic phase. The reperfusion after isolated hyperthermic liver perfusion was not complicated by severe cardiocirculatory changes. A decrease in body temperature was not observed probably due to the absence of cold, potassium-rich perfusate flowing into the systemic circulation. Two patients developed signs of a reperfusion syndrome within the first hour after reperfusion (decrease in peripheral systemic resistance).

The antiprogestins RU486 and ZK98299 affect follicle-stimulating hormone secretion differentially on estrus, but not on proestrus

Previous in vivo studies from our laboratory indicated that administration of the antiprogestin RU486 on proestrus suppresses both the preovulatory gonadotropin surges and the secondary FSH surge, suggesting a role for the progesterone receptor (PR) in the generation of these surges. The present study was designed to test the effects of another antiprogestin, ZK98299, which has been reported to block the PR through a mechanism different from that of RU486, on gonadotropin secretion in vivo. RU486 and ZK98299 (2 and 6 mg/kg) were administered s.c. at 1230 h on proestrus; uterine intraluminal fluid content, serum gonadotropins, and gonadotropin subunit messenger RNAs (mRNAs) were determined at 1830 h on proestrus and at 0900 h on estrus. At 1830 h on proestrus, both RU486 and ZK98299 at both doses caused equal suppression of the preovulatory FSH surge and FSHbeta mRNA. Both antiprogestins also equally attenuated the preovulatory LH surge at this time, with the higher doses causing greater suppression. In contrast, at 0900 h on estrus, the antiprogestins affected serum FSH differentially; only RU486 suppressed the secondary FSH surge despite the fact that both drugs prevented the release of uterine intraluminal fluid, confirming blockade of progesterone action at the level of the uterus. Neither drug had a significant effect on FSHbeta mRNA at 0900 h on estrus. ZK98299 at the higher dose caused a small, but significant, increase in serum LH. In a subsequent experiment, we compared the effects of RU486 and ZK98299 (6 mg/kg, s.c.), administered at 1230 h on proestrus, on serum FSH raised above the natural secondary FSH surge on the morning of estrus by passive immunization with an antiserum to inhibin-alpha (anti-I) at 1700 h on proestrus. Consistent with the results of the first experiment, both antiprogestins blocked the release of uterine intraluminal fluid, but only RU486 lowered serum FSH in both the normal sheep serum-treated controls and anti-I-treated rats; in contrast, ZK98299 actually increased serum FSH in the normal sheep serum-treated control animals. ZK98299 also increased FSHbeta mRNA in the control group; RU486, on the other hand, reduced FSHbeta mRNA only in the anti-I group. The results demonstrate unequivocally that whereas the effects of the two antiprogestins on serum FSH and FSHbeta mRNA are similar on proestrus, they are divergent on estrus. The data suggest that the functional state of the PR/transcriptional activation complex in the gonadotrope on the morning of estrus is different from that on the evening of proestrus.

Corticosterone selectively increases follicle-stimulating hormone beta-subunit messenger ribonucleic acid in primary anterior pituitary cell culture without affecting its half-life

We demonstrated previously that glucocorticoids differentially affect the levels of the two pituitary gonadotropins, LH and FSH, both in vivo and in vitro. In vivo, the effect of glucocorticoids is GnRH independent, indicating a direct action on the gonadotrope, and it leads to selective up-regulation of the pituitary content of FSH and FSH beta-subunit messenger RNA (mRNA). The objective of the present study was to confirm the direct action of corticosterone (B) on FSH beta-subunit mRNA in primary anterior pituitary cell culture and to assess whether the selective B-induced rise in FSH beta mRNA is mediated through altered stability of the FSH beta transcript. Anterior pituitary glands collected from randomly cycling female rats were dissociated with trypsin. Cells were incubated at 37 C for 48 h and subsequently exposed to vehicle or B (1.7 microM) for an additional 42 h. At the end of the incubation, media were sampled for FSH and LH, cells were lysed, and total RNA was isolated for Northern blot analysis. Exposure to B for 42 h caused direct and selective upregulation of FSH release, FSH content, and FSH beta mRNA; decreased alpha-subunit mRNA; and had no significant effect on LH release, LH content, or LH beta mRNA. To evaluate the mRNA stability of the three subunits, cells were exposed to the transcription blocker actinomycin D (act D; 5 micrograms/ml) for an additional 6 h. The combined 6-h treatment with B and act D slightly, but significantly, suppressed alpha-subunit mRNA and did not change LH beta mRNA, confirming a long half-life of the two gonadotropin subunit mRNAs. In contrast, FSH beta mRNA was significantly suppressed by act D to the same level in vehicle- and B-treated cells. The posttranscriptional decay rate was examined by sampling at 0, 1, 2, 3, and 6 h during the 6-h act D treatment period. Decay curves for FSH beta mRNA were parallel in vehicle- and B-treated cells, indicating that B did not alter FSH beta mRNA stability. We conclude that the selective B-induced rise in FSH beta mRNA is mediated at the level of transcription rather than mRNA stabilization.

RU486 on an estrogen background blocks the rise in serum follicle-stimulating hormone induced by antiserum to inhibin or ovariectomy

We used passive immunization with an antiserum to the alpha-subunit of inhibin (anti-I) or acute ovariectomy to investigate the relationship between serum inhibin levels and FSH secretion in the presence of the progesterone/glucocorticoid antagonist RU486. We demonstrated previously that 1) anti-I administered at 1700 h causes serum FSH to rise on the morning of estrus, even in the presence of a GnRH antagonist, when the two treatments are delivered on proestrus; and that 2) RU486 given on proestrus (1230 h), a time when serum estradiol levels are high, not only blocks the natural secondary FSH surge, but also suppresses the anti-I-induced rise in serum FSH on the morning of estrus. We have now extended our studies of the relationship between inhibin and RU486 to investigate treatment with RU486 and anti-I on a different day of the cycle, estrus, when serum estradiol levels are low. When both RU486 and anti-I were given on estrus (1230 and 1700 h, respectively), RU486 failed to block the anti-I-induced rise in serum FSH on the next morning of metestrus, in contrast to the blockade seen with RU486 treatment on the day of proestrus. However, pretreatment with estradiol benzoate (50 microgram) on the evening of proestrus, before the RU486 and anti-I treatment on estrus, caused RU486 to suppress the effects of anti-I on serum FSH, as it does when given on proestrus. We then repeated the study, using ovariectomy on proestrus or estrus (1700 h) to raise serum FSH, and assessed the effects of RU486 treatment at proestrus and estrus and estradiol benzoate treatment on proestrus. Our results indicate that treatment with RU486 can block the postovariectomy rise in serum FSH only in the presence of high circulating estradiol levels. We conclude that the inhibitory action of RU486 on FSH secretion after a fall in serum inhibin depends on a precedent estradiol background, probably due to induction of progesterone receptors by estradiol.

Differential desensitization response of the neonatal and adult rat somatotroph to growth hormone-releasing hormone and phorbol ester

Elevated levels of circulating growth hormone (GH) in the perinatal animal may be caused in part by relative resistance to the desensitizing effects of GH secretagogues. We compared the effects of 4-day exposure of primary pituitary cell cultures from adult male and 2-day-old rats to GH-releasing hormone (GHRH; 10 nM) or 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 1 microM) on subsequent acute GH response to these secretagogues. Prolonged exposure to GHRH reduced subsequent GHRH-induced GH release from pituitary cells of both age groups, but the reduction in GH response was significantly less in neonates than adults. In addition, GH secretion from neonatal pituitaries rose progressively during each day of GHRH exposure, to reach levels almost 7 times basal; by contrast, GH secretion from adult pituitaries increased only transiently and then declined. Prolonged exposure to TPA reduced the subsequent GH response to TPA equally in neonates and adults, but differentially affected the GH response to GHRH; TPA exposure reduced the GH response to GHRH in neonates, but not in adults. These data suggest a fundamental difference between the GH regulatory processes of neonatal and adult pituitaries. The ability of the somatotroph to exhibit attenuated GH response on exposure to secretagogue is developmentally regulated, and relative resistance of the immature somatotroph to homologous desensitization by GHRH may contribute to elevated serum GH levels during the perinatal period.

Mechanism of the inhibitory action of RU486 on the secondary follicle-stimulating hormone surge

Recent evidence utilizing RU486 has implicated progesterone (P) and glucocorticoids, in addition to a drop in serum inhibin, in the development of the secondary FSH surge on the morning of estrus. To assess the role of these steroids, we treated proestrous female rats with the antiprogestin/antiglucocorticoid RU486 (6 mg/kg sc) at 1230 h, and with dexamethasone (dex; 8.4 or 16.2 mg/kg sc), or with the steroid biosynthesis inhibitor aminoglutethimide (AG; 150 mg/kg ip) at 1030 h, alone or in combination with RU486. The effects of these treatments on uterine ballooning and intraluminal fluid content (an index of P action), ovulation, and serum levels of P, corticosterone (B), FSH, LH, and inhibin-alpha at 1830 h proestrus and 0900 h estrus were examined. In accord with previous work from our laboratory, RU 486 caused uterine intraluminal fluid retention on the morning of estrus and significantly suppressed the preovulatory surges of both FSH and LH, and the secondary surge of FSH without affecting the fall in inhibin-alpha. Treatment with dex alone raised serum FSH at both 1830 h proestrus and 0900 h estrus, coincident with suppression of serum inhibin-alpha. When administered in combination with RU486, dex partially reversed the increased uterine intraluminal fluid retention at 0900 h estrus, but did not modify the inhibitory effect of RU486 on the primary gonadotropin surges or the secondary surge of FSH. AG alone significantly suppressed serum P, B, and gonadotropins (LH to a greater extent than FSH) at 1830 h proestrus and blocked ovulation and uterine intraluminal fluid release at 0900 h estrus; it did not, however, suppress the secondary FSH surge or prevent the fall in serum inhibin-alpha. When administered 2 h before RU486, AG did not prevent the RU486-induced inhibition of the primary gonadotropin surges or the secondary FSH surge. We conclude from these results that development of the secondary FSH surge does not require P or glucocorticoid action and that RU486 suppression of the secondary FSH surge does not involve blockade of binding of these steroids to their receptors. Our data are compatible with ligand-independent activation of the P receptor, susceptible to blockade by RU486, as the mechanism underlying the enhanced secretion of FSH from the gonadotrope on the morning of estrus.

Autofeedback suppression of growth hormone (GH) secretion in transgenic mice expressing a human GH reporter targeted by tyrosine hydroxylase 5'-flanking sequences to the hypothalamus

Transgenic mice expressing a tyrosine hydroxylase-human (h) GH fusion gene in the hypothalamus exhibit a dwarf phenotype. The GH feedback mechanism(s) underlying the growth retardation in these animals was investigated by assessing peptide and messenger RNA (mRNA) levels of the hormones of the hypothalamic-GH-IGF-I axis. Pituitary GH content, hypothalamic GH-releasing hormone (GHRH) and somatostatin (SRIH) content, and serum IGF-I levels were measured by RIA. mRNA levels of hypothalamic GHRH and SRIH and of pituitary GH and the GHRH receptor were measured by Northern blot hybridization. Transgenic mice of both sexes and their wild-type littermates were studied at 2-4 months of age. The pituitary GH content was markedly reduced by 85% in male and by 87% in female transgenic mice compared to that in wild-type controls (P < 0.01 for both). The pituitary GH mRNA content was also decreased by 73% (P = 0.002) in transgenic male mice. Circulating IGF-I levels were significantly reduced by 66% and 68% in male and female transgenic mice, respectively (P = 0.001). The hypothalamic GHRH content was significantly reduced by 19% and 33% (P < 0.05) in male and female transgenic mice, respectively. No significant difference was detected, however, in the hypothalamic SRIH content between wild-type and transgenic mice. Hypothalamic GHRH mRNA levels were significantly decreased by 35% (P = 0.002) in transgenic male mice compared to those in wild-type littermates. In contrast, SRIH mRNA was not significantly changed. An even greater reduction (61%; P = 0.003) was observed in pituitary GHRH receptor mRNA in transgenic mice. These data indicate that the GH deficiency and dwarf phenotype of the tyrosine hydroxylase-hGH transgenic mouse can be attributed primarily to impaired hypothalamic GHRH production. The mechanism of GH feedback inhibition appears to involve direct suppression of GHRH gene expression by locally produced hGH in the hypothalamus.

Ontogeny of the GH response to phorbol ester and phospholipase C in rat pituitary cells

GH secretory patterns undergo marked change during early mammalian development. The factors that underlie these changes and the major components of signal transduction in the immature somatotrophs are not fully understood. Increasing evidence suggests that protein kinase C (PKC) plays a central role in perinatal organ differentiation and function. To evaluate the possible role of PKC as a mediator of GH secretion from immature pituitaries, we tested the effects of the PKC activating phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), alone or together with GH-releasing factor (GRF), somatostatin (SRIF), and Ca2+ modifying agents; an inactive phorbol analogue (4 alpha-12-13-didecanoate; 4 alpha-PDD), and phospholipase C on GH release from pituitary cell cultures from perinatal and mature rats. Pituitary primary cell cultures were prepared from fetal (day 20 of 21.5 days of gestation), 2-day-old, 12-day-old, and adult male (2- to 4-month-old) rats. Each experiment was performed on at least three separate occasions. The magnitude of TPA (0.15-150 nM)-induced GH release was markedly age-dependent, fractional GH release being greatest from pituitaries of fetal and newborn rats, and least from those of adults (P < 0.001). Further, the minimum dose of TPA required to stimulate GH release over basal levels was tenfold higher for adult pituitaries (15 nM) than for perinatal pituitaries (1.5 nM). Phospholipase C (1 and 10 U/ml) also caused greater fractional GH release from neonatal pituitaries than from adult pituitaries (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between rfb gene clusters required for biosynthesis of identical D-galactose-containing O antigens in Klebsiella pneumoniae serotype O1 and Serratia marcescens serotype O16

The lipopolysaccharide O antigens of Klebsiella pneumoniae serotype O1 and Serratia marcescens serotype O16 both contain a repeating unit disaccharide of [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]; the resulting polymer is known as D-galactan I. In K. pneumoniae serotype O1, the genes responsible for the synthesis of D-galactan I are found in the rfb gene cluster (rfbKpO1). We report here the cloning and analysis of the rfb cluster from S. marcescens serotype O16 (rfbSmO16). This is the first rfb gene cluster examined for the genus Serratia. Synthesis of D-galactan I is an rfe-dependent process for both K. pneumoniae serotype O1 and S. marcescens serotype O16. Hybridization experiments with probes derived from each of the six rfbKpO1 genes indicate that the cloned rfbSmO16 cluster contains homologous genes arranged in the same order. However, the degree of homology at the nucleotide sequence level was sufficiently low that hybridization was detected only under low-stringency conditions. rfbABSmO16 genes were subcloned and shown to encode an ABC-2 (ATP-binding cassette) transporter which is functionally identical to the one encoded by the corresponding rfb genes from K. pneumoniae serotype O1. The amino acid sequences of the predicted RfbA and RfbB homologs showed identities of 75.7% (87.9% total similarity) and 78.0% (86.5% total similarity), respectively. The last gene of the rfbKpO1 cluster, rfbFKpO1, encodes a bifunctional galactosyltransferase which initiates the formation of D-galactan I. RfbFKpO1 and RfbFSmO16 are 57.6% identical (with 71.1% total similarity), and both show similarity with RfpB, the galactosyltransferase involved in the synthesis of Shigella dysenteriae type I O-polysaccharide. The G+C contents of the rfbAB genes from each organism are quite similar, and values are lower than those typical for the species. However, the G+C content of rfbFSmO16 (47.6%) was much higher than that of rfbFKpO1 (37.3%), despite the fact that the average for each species (52 to 60%) falls within the same range.

Prolonged effects of tumor necrosis factor-alpha on anterior pituitary hormone release

We examined the chronic (72 h) effects of 30 ng/ml recombinant murine tumor necrosis factor (TNF)-alpha on release of immunoreactive growth hormone (GH), prolactin (PRL), thyrotropin (TSH), and TSH glycosylation, as assessed by lectin binding, in cultured rat anterior pituitary cells. In cultured cells from adult female rats, TNF-alpha significantly suppressed basal and GH-releasing hormone (GRH)-stimulated GH release. TNF-alpha also suppressed basal PRL release and completely abolished the PRL response to TRH (0.1-10 nM). Whereas TNF-alpha reduced basal TSH release, it significantly enhanced the maximal TSH response to TRH. TNF-alpha did not affect the concanavalin A and lentil lectin binding of TSH accumulated in the medium during the 4-day culture, but significantly decreased the lentil lectin binding of TSH released in response to acute TRH stimulation. TNF-alpha significantly enhanced the inhibitory effect of somatostatin on stimulated PRL release, but not on GH or TSH release. Compared to cell cultures from adult female rats, in anterior pituitary cell cultures from 12-day-old rats the effects of prolonged exposure to TNF-alpha on hormone release were diminished or absent. Pituitary hormone release was unaffected by acute (3 h) exposure to TNF-alpha. These results demonstrate a direct effect of TNF-alpha on anterior pituitary hormone release, which is cell-type specific and age dependent.

DNA regulatory sequences of the rat tyrosine hydroxylase gene direct correct catecholaminergic cell-type specificity of a human growth hormone reporter in the CNS of transgenic mice causing a dwarf phenotype

Transgenic mice bearing 4.8 kilobases (kb) of upstream rat tyrosine hydroxylase (TH) sequences linked to a human growth hormone gene (hGH) exhibited cell-specific expression of hGH in all the appropriate catecholaminergic neurons in the central nervous system (CNS), although with different penetrance in two different mouse lineages. No ectopic expression was observed in any brain or peripheral region in one founder and its progeny. In another founder there was some ectopic expression in addition to appropriate and high levels of tissue-specific expression in all catecholaminergic areas. These results identify regulatory sequences that are sufficient for targeting expression to all catecholaminergic CNS neurons. Also, expression of exogenous hGH in the hypothalamus caused a dwarf phenotype, generating a novel genetic model for GH deficiency of hypothalamic origin.

The effect of isobutylmethylxanthine, forskolin, and cholera toxin on growth hormone release from pituitary cell cultures of perinatal and mature rats

The factors that regulate growth hormone (GH) release during the perinatal period are not well understood. Circulating GH levels are markedly elevated in mammalian fetuses and newborns compared with mature animals, and the immature pituitary is highly responsive to the GH-stimulatory effect of GH-releasing factor (GHRF). The etiology of these developmental changes in GH secretion is not known. In order to investigate the mechanisms underlying GH release from immature pituitaries, we tested the effects of agents that increase intracellular cyclic adenosine 3',5' monophosphate (cAMP) production independent of the GHRF receptor on GH release from pituitaries of developing and mature rats. Pituitary cell cultures from fetal (day 20 of gestation), newborn (postnatal day 2), juvenile (postnatal day 12-15), adult male (3-4 months), and adult female (3-4 months) rats were tested with isobutylmethylxanthine (IBMX; 0.001-1.0 mM), forskolin (0.01-10 microM), and cholera toxin (0.025-25 ng/ml). IBMX, forskolin, and cholera toxin stimulated GH release in a dose-dependent manner from pituitary cultures of all age groups. However, the magnitude of the GH responses to these agents was highly age-dependent. Perinatal pituitaries exhibited markedly greater GH responses to IBMX, forskolin, and cholera toxin than did those of mature animals (P < 0.001 for age effect with each agent). GH release in response to the highest dose of IBMX (1 mM) was 301 +/- 8, 389 +/- 37, 296 +/- 33, 198 +/- 14, and 187 +/- 19% of control values from pituitary cell cultures of fetal, newborn, juvenile, adult male, and adult female rats, respectively (P < 0.001). In response to the highest dose of forskolin (10 microM) GH release was 537 +/- 46, 601 +/- 75, 274 +/- 22, 270 +/- 37, and 248 +/- 35% of control values in the same respective age groups (P < 0.001). Similarly, the highest dose of cholera toxin (25 ng/ml) stimulated GH release to 407 +/- 55, 365 +/- 43, 249 +/- 26, 186 +/- 11, and 186 +/- 1% of controls in these respective age groups (P < 0.003). The marked stimulation of GH release from perinatal pituitaries by IBMX, forskolin, and cholera toxin is consistent with the concept that cAMP is a potent mediator of GH release from immature as well as mature somatotrophs. The developmental changes in the GH secretory response to these agents further suggest that signal transduction pathways mediating GH release may undergo maturation, at least in part, at intrasomatotroph loci distal to the GHRF receptor.

PCR amplification of DNA sequences from nitrocellulose-bound, immunostained bacterial colonies

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Use of chromosomal gene fusions to investigate the role of repetitive DNA in regulation of genes involved in lipopolysaccharide biosynthesis in Haemophilus influenzae

The lic3 locus of Haemophilus influenzae consists of four open reading frames. The derived amino acid sequences of orf2 and orf4 exhibit homology to Escherichia coli GalE and AdK, respectively. The functions of orf1 and orf3 remain unknown. orf1 contains multiple tandem repeats of the tetrameric DNA sequence CAAT near the 5' end. Two possible translational starts (ATG1 and ATG2) lie upstream. We have used lacZ fusions to investigate whether changes in the number of CAAT repeats in conjunction with differential usage of the upstream frames control the expression of lic3-orf1. Phase-variable expression of lacZ was observed for individual colonies and could be related to variable numbers of CAAT repeats. Of the three possible upstream frames, only one, containing the more downstream of the two possible ATG start codons (ATG2), is used for strong expression of lacZ. Utilization of the more upstream ATG (ATG1) or ATG2 was observed with medium-level expression, while utilization of any of the three possible frames was observed when lacZ was expressed at low to undetectable levels, indicating that other mechanisms may affect expression. To investigate this, lacZ was fused in frame with ATG2 of lic3-orf1, with concomitant deletion of the repeats. Phase-variable expression was still observed, supporting the view that an alternative level of control operates in conjunction with the repeat mechanism.

Inhibition of tumor induction in tobacco by Agrobacterium tumefaciens and nodulation induced by Rhizobium meliloti in the presence of phenothiazines and structurally related compounds

Plasmids of Agrobacterium tumefaciens and Rhizobium meliloti carrying Kanamycin resistance genes were eliminated from 1.4 to 0.2% of the growing bacterial cultures by promethazine and imipramine. As a result of plasmid elimination, the A. tumefaciens plasmidless isolate was not able to induce crown gall tumor on tobacco plants. The plasmidless R. meliloti strain failed to induce nodule formation on alfalfa plants. The efficiency of nodulation was decreased when the bacteria were grown in the presence of the drugs. The antiplasmid effects of the drugs were not prevented by opines, (nopaline and octopine) in Escherichia coli F'lac cells.

In vitro cytotoxicity of Haemophilus influenzae lipopolysaccharides for bovine aortal endothelial cells

The cytotoxicity of purified lipopolysaccharide (LPS) from a prototype Haemophilus influenzae type b (Hib) strain (Eagan) and three transformants, differing in their LPS phenotype, for bovine aortal endothelial cells (BAOEC) was investigated. All LPS preparations caused cell disruption and release of lactate dehydrogenase (LDH), an indicator of cytotoxicity, from BAOEC monolayers but to differing extents. There was no correlation between the cytotoxicity of purified Hib LPS to BAOEC monolayers and potential to cause bacteraemia in experimental animals.