Anaplastic Myeloma with Deposits in Three Different Sites: Case report and literature review

Anaplastic myeloma is a rare aggressive disease that is resistant to most chemotherapeutic agents and radiotherapy. It develops usually after a diagnosis of classical multiple myeloma and is associated with at least one extramedullary plasmacytoma site. We report a case of this rare disease in a patient who had no previous illness and presented to us with more than one extramedullary plasmacytoma site: a mass in the right anterior chest wall, a swollen scrotum and multiple nodular skin lesions mainly in the legs.

Absorption of the cholic acid-conjugated peptide hormone cholylsecretin from the rat ileum in vivo

AIMS

Previously, we demonstrated that gastrin peptides as long as 34 amino acids were absorbed from the ileum of rat after conjugation to the C24 position of cholic acid and that these peptides retained full biological activity. As absorption was specific to the ileum, it was inferred that the conjugated hormone was taken up by the bile salt transporters. We have now extended these experiments to a member of a different family of hormones, viz. secretin, a 27-amino acid hormone that stimulates serous secretions from the exocrine pancreas.

METHODS

After conjugation to cholic acid, the degree of cholylsecretin absorption from the ileum of anaesthetized rats was assessed from the increase in pancreatic secretions.

RESULTS

A complication to the study was that intra-ileal infusion of native secretin caused a transient increase in the levels of pancreatic secretions. This was in contrast to the effects of intra-ileal infusion of cholylsecretin which did not cause this transient increase but, instead, gave rise to a delayed increase in pancreatic secretions which was sustained over several hours during which cholylsecretin was detected in plasma in high concentration by mass spectrometry. The pancreatic response to cholylsecretin was abolished by co-infusion of 50 mm taurocholate, employed to compete with the bile salt transporters, although a transient increase in pancreatic secretions similar to that caused by secretin was now generated. This was shown to arise from an action of taurocholate per se causing the release of endogenous secretin which is present in rat ileum.

CONCLUSIONS

We, therefore, concluded that cholylsecretin had been absorbed from the rat ileum by uptake by bile salt transporters.

[Local necrosis of finger following stab with needle used to pump terbutaline sulfate (Bricalin)]

Terbutaline sulfate (Bricalin) is a widely used medication for asthma. It works mostly, but not only, on beta-adrenergic receptors. In this case study we describe a 50-year-old nurse referred to the emergency department after she was stabbed by needle that was used to draw bricalin for inhalation. She arrived at the emergency room with an inflamed necrotic area at the point of the stab. Later, she developed acute infection that was treated with antibiotics. Following the acute phase there was still a necrotic area, that required surgical debridement. It seems that this is the result of the vasoconstrictive influence of terbutaline sulfate via alpha adrenergic receptors. In the medical literature there is scarce data regarding this side effect.

Gonadotropin-releasing hormone regulation of gonadotropin subunit gene expression in female rats: actions on follicle-stimulating hormone beta messenger ribonucleic acid (mRNA) involve differential expression of pituitary activin (beta-B) and follistatin mRNAs

GnRH is the primary stimulus in the regulation of gonadotropin subunit mRNA expression. Additionally, local (pituitary) production of activin and follistatin appear to modulate the expression of FSH beta mRNA. The current studies aimed to determine whether GnRH regulation of pituitary activin (beta-B) and follistatin mRNAs could play a role in the differential actions of GnRH pulse pattern on gonadotropin mRNA expression in female rats. In response to altered GnRH pulse amplitude, the expression of FSH beta and follistatin mRNAs followed an inverse pattern. Only high dose GnRH increased expression of follistatin whereas, in contrast, beta-B and FSH beta expression were increased following lower doses of GnRH. To determine whether increased follistatin mRNA expression was correlated with FSH beta mRNA responses, we examined their temporal relationship following high dose GnRH. Both FSH beta and follistatin mRNAs were increased within 2 h and remained increased through 6 h. However, by 12 h FSH beta mRNA levels returned to values seen in controls, suggesting that increased follistatin requires 6-12 h to reduce FSH beta mRNA. In response to altered GnRH pulse frequency, FSH beta expression was increased at all pulse intervals (8-240 min) examined. Rapid GnRH pulse frequencies (8-min intervals) increased follistatin expression, whereas beta-B mRNA was only increased after 30-min pulse intervals, which also resulted in maximal FSH beta mRNA concentrations. These results suggest that changes in pituitary activin (beta-B) and follistatin mRNA expression may be important components of gonadotrope responses to pulsatile GnRH, and potentially imply that GnRH stimulation of activin and follistatin peptide production provides regulatory control over the production of FSH.

Regulation of pituitary follistatin and inhibin/activin subunit messenger ribonucleic acids (mRNAs) in male and female rats: evidence for inhibin regulation of follistatin mRNA in females

The regulation of FSHbeta messenger RNA (mRNA) expression is complex and involves signals from the hypothalamus and gonads. Additionally, the local (pituitary) production of activin and follistatin appears to serve as an important modulator of endocrine signals for FSHbeta regulation. The purpose of these studies was to identify factors controlling pituitary activin/inhibin subunit and follistatin mRNA production in male and female rats. Both males and females expressed the follistatin, inhibin alpha, and betaB mRNAs, whereas the betaA mRNA was not detected. In males, levels of FSHbeta and follistatin were higher than those in females. After gonadectomy, levels of FSHbeta and follistatin increased in both sexes, whereas betaB rose only in females. In males, blockade of GnRH action from the time of castration prevented the increase in FSHbeta and follistatin, suggesting that GnRH is the primary stimulus for these gene products. In females, treatment with a GnRH antagonist only partially prevented the rise in FSHbeta, follistatin, and betaB expression, suggesting that other factors were also important. Passive immunoneutralization of circulating inhibin increased FSHbeta and follistatin (but not betaB), providing evidence that inhibin is a physiological regulator of follistatin. Replacement of estradiol at the time of ovariectomy prevented the increase in betaB mRNA, suggesting that gonadal steroids may also act via local factors to regulate FSHbeta. In summary, these studies provide evidence that GnRH, gonadal steroids, and gonadal peptides probably regulate FSHbeta expression at least in part via the intrapituitary activin/follistatin system.

Gonadotropin subunit and gonadotropin-releasing hormone receptor gene expression are regulated by alterations in the frequency of calcium pulsatile signals

Previously, we have shown that intermittent calcium (Ca2+) stimuli increase alpha, LHbeta, and FSHbeta messenger RNAs (mRNAs), and only LHbeta mRNA was increased by continuous Ca2+. As gonadotropin subunit and GnRH receptor (GnRH-R) mRNAs are differentially regulated by alterations in GnRH pulse interval, we aimed to determine whether changes in the frequency of Ca2+ signals play a role in this effect. Cultured adult female rat pituitary cells in perifusion were given pulses of the Ca2+ channel activator BayK 8644 (10 microM; with 10 mM KCl in the injectate), at intervals of 16, 60, or 180 min for 24 h (vehicle pulses or 100 pM GnRH to controls). Pulsatile Ca2+ influx stimulated a rise in all mRNAs examined (P < 0.05 vs. vehicle controls); however, optimal pulse intervals differed. Alpha and LHbeta mRNAs were maximally stimulated by 16- or 60-min pulses (57% and 74% increases, respectively), with 180-min pulses being less effective. In contrast, FSHbeta and GnRH-R mRNAs were selectively stimulated by 180-min pulses (51% and 41% increases, respectively). Pulsatile GnRH produced similar increases in GnRH-R and subunit mRNAs (53-78% vs. controls). These results reveal that alterations in the frequency of Ca2+ signals can regulate gonadotrope gene expression in a differential manner, producing effects similar to previous findings for GnRH. Thus, intermittent increases in intracellular Ca2+ may be an important step in the transmission of GnRH pulse signals from the plasma membrane to the gene.

Primary hepatic lymphoma: unusual presentation and clinical course

Although primary hepatic lymphoma is rare, it should be considered in the differential diagnosis of a hepatic tumor, because it is usually associated with a favorable prognosis. This report describes an unusual case of primary hepatic lymphoma with an atypical presentation (only mild, right upper quadrant pain and no hepatomegaly) followed by acute fulminating hepatic failure, metabolic acidosis, followed by a rapidly fatal course. A review of the literature and discussion of the disease are also presented.

Ovarian activin receptor subtype and follistatin gene expression in rats: reciprocal regulation by gonadotropins

The production of activin, follistatin (FS), and inhibin, proteins present in the ovary and involved in mammalian reproduction, is regulated by gonadotropins and estradiol. We report here gonadotropin regulation of ovarian activin receptor (ActR) subtype and FS mRNAs. Expression of ActRI, ActRIIA, ActRIIB, and FS mRNA was measured on the afternoon of proestrus (1800 h) and the morning of estrus (0800 h). ActRI and ActIIA subtype mRNA concentrations fell by approximately 50% (p < 0.05) following the proestrous gonadotropin surge (ActRIIB mRNA was undetectable), while FS mRNA was unchanged. To define the contribution of gonadotropins, hypophysectomized (HYPOX) female rats were given recombinant human (rh) FSH and hCG, which decreased both ActR mRNAs (by approximately 70% and aproximately 50% for ActRI and IIA, respectively) and increased FS mRNA by 2-fold. As gonadotropins could act via estradiol (E2), HYPOX rats were given E2; ActRI was decreased, but ActRIIA mRNA was increased. The actions of gonadotropins were preferential, as the combination of rhFSH and hCG with E2 reduced ActRIIA mRNA. FS mRNA was increased to a similar degree by E2 and/or gonadotropins. These data suggest that gonadotropins regulate ActR and FS gene expression via multiple mechanisms. Both a direct action on ActRIIA (inhibition) and an indirect action through E2 on ActRI (inhibition) and FS (stimulation) suggest potential physiologic mechanisms for the reciprocal regulation of ActR subtype and FS mRNAs.

GnRH regulates steroidogenic factor-1 (SF-1) gene expression in the rat pituitary

Recent studies have demonstrated that the nuclear receptor, steroidogenic factor 1 (SF-1) plays a role in the regulation of pituitary gonadotropin gene expression. As GnRH is critical to stimulating LH and FSH gene expression, the present study was conducted to determine whether GnRH also regulates pituitary SF-1 mRNA. Pituitary SF-1 mRNA levels were measured in individual animals by RNase protection assay. In the first study, adult male and female rats were gonadectomized (GDX) for 7 days and some received testosterone (T) to prevent the post-GDX rise in GnRH, and compared to intact animals. Pituitary SF-1 mRNA levels increased significantly (3 fold in males, 2 fold in females; p < 0.05 vs intacts) after gonadectomy, which was blocked by exogenous T. Similar changes were observed in serum LH. To directly test whether GnRH stimulates SF-1 mRNA, we used a GnRH-deficient rat model (phenoxybenzamine-treated, ovariectomized females) and administered GnRH pulses for 6h (5ng at 30 min intervals; saline pulses to controls). Pulsatile GnRH stimulated a 51-64% increase in SF-1 mRNA levels (p < 0.05 vs controls). These results show that GnRH stimulates SF-1 gene expression, which may be a critical component in GnRH stimulation of gonadotropin subunit transcription.

Testosterone is required for gonadotropin-releasing hormone stimulation of luteinizing hormone-beta messenger ribonucleic acid expression in female rats

Pulsatile GnRH stimulates the synthesis and secretion of LH and FSH in both male and female rats. In the male rat, exogenous GnRH pulses increase alpha, LH and FSH beta messenger RNAs (mRNAs) 3-fold within 24 h. In contrast, the results of recent in vivo and in vitro studies have shown that GnRH stimulates an increase in alpha and FSH beta mRNAs, but not LHbeta. However, during the estrous cycle, LHbeta mRNA increases during the GnRH-induced LH surge on proestrus afternoon. This increase in LHbeta mRNA appears to be coincident with a transient rise in serum testosterone (T). Therefore, the present study was conducted to determine whether T has a role in facilitating GnRH stimulation of LHbeta mRNA expression. In the first group of studies, adult female rats were ovariectomized, and T implants were inserted sc 7 days before the study (serum T, 1.86 ng/ml). Animals received iv pulses of GnRH (25 ng; 30-min interval) for 6-24 h (saline pulses to controls). The data showed that in the presence of T, GnRH stimulated a significant increase in LHbeta (as well as alpha and FSH beta) mRNAs within 6 h (P < 0.05 vs. saline-pulsed controls). Other results revealed that T treatment was critical to the stimulatory effect of GnRH on LH beta mRNA. A second group of studies examined the time course and dose effects of T on LH beta mRNA expression. Maximal LH beta mRNA responses to GnRH (3-fold increase vs. saline controls; P < 0.05) were seen after pretreatment with the lowest dose of T examined (serum T, 0.42 ng/ml), which is similar to T concentrations on proestrus. Higher doses of T suppressed LH release, as well as LH mRNA responses to GnRH. The T-induced LHbeta mRNA response to pulsatile GnRH was seen within 24 h of exposure to T and was the result of an androgenic action, as similar results were observed in rats that received dihydrotestosterone. These findings suggest that T is required to facilitate GnRH stimulation of LHbeta mRNA in the female rat. Moreover, in the presence of the concentrations of T seen on proestrus, LHbeta mRNA increases within 6 h, which is similar to the time course seen during the LH surge. Thus, the present results also suggest that the combined effects of the rise in serum T and increased GnRH secretion induce the rapid rise in LHbeta mRNA expression on the afternoon of proestrus.

Pituitary activin receptor subtypes and follistatin gene expression in female rats: differential regulation by activin and follistatin

The activins, hormones produced in the gonads and extragonadal tissues (including the pituitary), rapidly increase FSH beta messenger RNA (mRNA) and FSH secretion. In the rat, activin acts via a family of activin receptor (ActR) subunits that includes at least one type I (ActRI or ALK-2) and two homologous type II (IIA and IIB) subunits. We have previously reported that ActRIIA mRNA rises after ovariectomy (OVX). Potentially, the OVX-induced increases in ActR mRNAs could result from altered activin or the activin-binding protein follistatin. It was the purpose of the current studies to determine whether activin and/or follistatin regulated activin receptor subunit mRNAs. Adult female rat pituitaries were dissociated and plated for 48 h, transferred to wells containing follistatin or activin for 2 or 24 h, then RNA extracted for measurement of ActRI, IIA, and IIB and follistatin mRNAs. All three ActR mRNAs were easily detectable in pituitary RNA, with the relative abundance of ActRI > IIA >> IIB (18:9:1). Between 2-24 h, levels of all three ActR mRNAs increased 2- to 3-fold in wells containing medium alone, whereas levels of follistatin mRNA were unchanged. Follistatin significantly reduced FSH secretion and follistatin mRNA, but not the ActR mRNAs. Activin increased ActRI (4-fold, at 2 h), ActRIIB (2-fold, at 24 h), and follistatin (2-fold, at 24 h) mRNAs and FSH release (2-fold, at 24 h), but did not alter ActRIIA mRNA levels. We conclude that 1) pituitary ActR mRNA expression is under inhibitory tone in vivo, as suggested by the effect of pituitary removal and cell dispersion and an earlier report after OVX. 2) Pituitary-derived activin stimulates follistatin (but not ActR) mRNA production, and additional increases in follistatin mRNA can be induced by exogenous activin. 3) Higher concentrations of activin differentially regulate pituitary ActR mRNA expression, suggesting that activin exerts a positive feedback effect on its own receptor.

Are immediate early genes involved in gonadotropin-releasing hormone receptor gene regulation? Characterization of changes in GnRH receptor (GnRH-R), c-fos, and c-jun messenger ribonucleic acids during the ovine estrous cycle

GnRH regulates the secretion and synthesis of gonadotropins by binding to specific receptors located in the plasma membrane of the pituitary gonadotroph. Like the concentration of the signaling ligand GnRH, the number of GnRH receptors (GnRH-R) varies dynamically with the changing endocrine milieu during the ovine estrous cycle. With the recent success in cloning of the mammalian GnRH-R gene, it is becoming increasingly evident that some of the changes in GnRH-R numbers may be mediated at least in part via changes in GnRH-R gene transcription. However, the regulatory steps involved in the GnRH-R transcription are unknown. The present studies were conducted to 1) characterize in detail the changes in GnRH-R gene expression during the 16-day ovine estrous cycle, 2) determine whether or not changes in GnRH-R gene expression during the estrous cycle are paralleled by alterations in the expression of c-fos and c-jun mRNAs, and 3) determine whether GnRH can induce expression of c-fos and c-jun mRNAs. Results revealed that concentrations of GnRH-R mRNA were highest on the day before estrus, when circulating LH concentrations were still low. GnRH-R mRNA concentrations declined steadily starting at 5 h postestrus, the time of the preovulatory LH surge, reaching their lowest levels by 24 h after estrus. Changes in c-jun mRNA levels, in general, paralleled changes in GnRH-R mRNA concentrations, being highest on the day before estrus and declining thereafter. c-Fos mRNA followed a different time course than c-jun mRNA, remaining elevated from Day 8 prior to estrus until the onset of estrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of gonadotropin subunit messenger ribonucleic acid expression in gonadotropin-releasing hormone (GnRH)-deficient female rats: effects of GnRH, galanin, GnRH-associated peptide, neuropeptide-Y, and thyrotropin-releasing hormone

Gonadotropin subunit mRNA expression is differentially regulated during the 4-day estrous cycle in rats, with LH-beta and FSH-beta mRNA expression rapidly increasing on proestrus. Studies in an ovariectomized (OVX) GnRH-deficient female rat model have shown that GnRH pulses can increase alpha and FSH-beta mRNA concentrations, but LH-beta mRNA is unchanged. Thus, the factors required for physiologic regulation of the LH-beta gene are not fully understood. To determine whether or not the proestrous ovarian hormone environment is required to allow increased expression of the LH-beta gene, GnRH pulses were administered to GnRH-deficient (phenoxybenzamine-treated) intact female rats on proestrus. Both LH and FSH secretion and alpha and FSH-beta mRNA concentrations were increased, but LH-beta mRNA expression was unaltered. The effect of co-administration of GnRH and specific neurohormones (GnRH-associated peptide [GAP], galanin, neuropeptide-Y [NPY], and thyrotropin-releasing hormone [TRH] was also examined in OVX rats receiving estradiol (E2) and progesterone (P) replacement. Alpha and FSH-beta mRNA concentrations increased 2-fold in response to pulsatile GnRH, and no further increase was seen after the addition of GAP, galanin, or TRH. It was of interest that NPY blocked the GnRH-induced rise in alpha and FSH-beta mRNA. LH-beta mRNA expression was not increased by GnRH pulses alone or by addition of any of the neuropeptides. Further studies determined that continuous GnRH was no more effective than pulsatile GnRH in stimulating a rise in LH-beta mRNA. The results indicate that GnRH pulses are not sufficient to enhance LH-beta mRNA expression in the GnRH-deficient female rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotropin-releasing hormone (GnRH) pulse pattern regulates GnRH receptor gene expression: augmentation by estradiol

GnRH acts via a single cell surface receptor (GnRH-R), and the number of pituitary GnRH-R increases on proestrus, after gonadectomy, or in response to pulsatile GnRH in the rat. Estradiol (E2) is known to exert a transient positive action to increase GnRH-R number, and the rise in plasma E2 contributes to initiation of the midcycle LH surge. The present study was designed to determine the effect of GnRH pulse amplitude and frequency on GnRH-R messenger RNA (mRNA) levels and to assess the relative contributions of GnRH and gonadal steroids to increasing GnRH-R gene expression. These studies were conducted in vivo using previously characterized GnRH-deficient male (castrate testosterone-replaced) and ovariectomized phenoxybenzamine-treated female models. To investigate the effect of GnRH pulse amplitude, adult male and female rats received GnRH iv (5-250 ng/pulse at 30-min intervals; saline pulses to controls) for 12 or 24 h. In males, GnRH-R mRNA was increased by all pulse doses, with maximal effects (3-fold) at 5-25 ng/pulse. In contrast, only lower doses (5-10 ng/pulse) were effective in females (2-fold increase). In a subsequent study, GnRH pulses (25 ng for males; 10 ng for females) were given at 8-, 30-, or 240-min intervals for 12 or 24 h. Some animals received a continuous GnRH infusion (200 ng/h). In males, GnRH-R mRNA levels were stimulated by all GnRH pulse intervals (maximal after 30-min pulses), whereas continuous GnRH was ineffective. In females, only 30- and 240-min pulse intervals increased GnRH-R mRNA levels, with faster (8-min) pulses or continuous GnRH being ineffective. To determine the relative roles of ovarian steroids and GnRH, ovariectomized phenoxybenzamine-treated female animals received GnRH (10 ng/pulse, 30-min interval), E2 (via sc implants; plasma E2 levels, approximately 50 pg/ml), or their combination for 12-24 h (saline pulses to controls). In the absence of E2, GnRH-R concentrations fell by 70% between 12-24 h. E2 alone tended to increase GnRH-R mRNA at 12 h, with a 2-fold rise observed after 24 h. Pulsatile GnRH alone increased GnRH-R mRNA by 50% at 12 h (compared to saline-pulsed controls; P < 0.05) and by 6-fold after 24 h. When GnRH and E2 were combined, the magnitude of the increase (vs. saline controls) was greater than that seen for either GnRH or E2 alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Ovarian inhibin subunit gene expression: regulation by gonadotropins and estradiol

Inhibin and FSH maintain a dynamic inverse relationship throughout the rat estrous cycle. In particular, inhibin alpha- and beta A-subunit messenger RNAs (mRNAs) have been shown to be maximally expressed immediately after the midcycle gonadotropin surge, when both circulating estradiol (E2) and inhibin are also elevated. The current study was designed to investigate the regulation of inhibin subunit gene expression and secretion in vivo by recombinant human FSH (rhFSH) and estradiol. Initially, we determined if physiological levels of rhFSH regulated ovarian inhibin subunit gene expression and secretion. Hypophysectomized (HYPOX) adult female rats received hCG (10 IU, sc) and were then treated for 24 h with either rhFSH (0.5-20 IU every 6 h, i.v.) or saline. Hypophysectomy reduced inhibin subunit mRNAs as well as serum inhibin and estradiol. Although 0.5 IU rhFSH was ineffective in increasing inhibin subunit mRNAs, all doses between 2.5-20 IU increased inhibin subunit gene expression and inhibin secretion. Inhibin alpha-, beta A-, and beta B-subunit mRNAs were increased to a similar degree (3- to 5-fold) by all rhFSH doses of 5 IU or more. Similarly, serum E2 and inhibin were increased 2- and 3-fold, respectively, above HYPOX values after all doses of rhFSH of 5 IU or more. To investigate the role of a pure FSH signal in a physiological dose on inhibin subunit gene expression, HYPOX rats were given either rhFSH (5 IU, i.v., every 6 h for 24 or 48 h), hCG (10 IU, sc), or their combination. Neither gonadotropin when given alone altered inhibin subunit gene expression or serum E2 concentrations. Inhibin secretion rose in response to rhFSH alone, but not to hCG. The combination of hCG and rhFSH resulted in increased inhibin subunit mRNAs (3- to 5-fold) as well as circulating E2 and inhibin concentrations. We next studied the effects of E2 replacement in HYPOX rats at both physiological (serum approximately equal to 40 pg/ml) and higher doses (serum approximately equal to 800 pg/ml, to mimic intraovarian concentrations) in the presence or absence of exogenous gonadotropins (for 24 and 48 h). Although not as effective as gonadotropins, both E2 regimens increased inhibin alpha to a similar degree (2-fold), whereas beta-subunit mRNAs were unchanged at 24 h. Serum inhibin concentrations were increased only 48 h after high dose E2 treatments. As the actions of E2 and gonadotropins on alpha-subunit mRNA were not additive, E2 appears to mediate gonadotropin regulation of alpha-subunit gene expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of gonadotropin, thyrotropin subunit, and prolactin messenger ribonucleic acid expression by pulsatile or continuous protein kinase-C stimulation

The present study investigated the importance of pulsatile vs. continuous protein kinase-C (PKC) stimulation in regulating pituitary gene expression. Adult female rat pituitaries were dissociated, and cells were plated for 48 h, then inserted into perifusion chambers (n = 5-8/group). Chambers received pulses of GnRH (100 pM) plus TRH (4 nM) or sn-1,2-dioctanoylglycerol (DOG; peak chamber concentration, 0.2, 1, or 5 mM; vehicle pulses to controls) every 60 min or a continuous infusion of phorbol 12-myristate 13-acetate (PMA; 20 nM). Secretory responses were determined in perifusate fractions collected after 2 and 22 h of perifusion. After 24 h of treatment, the cells were recovered, total RNA was extracted, and messenger RNAs (mRNAs) were measured by dot blot hybridization. The data revealed that GnRH plus TRH and both pulsatile (DOG) and continuous (PMA) PKC stimulation increased LH, FSH, TSH, and PRL secretory activity. Pulses of GnRH plus TRH increased PRL, alpha, TSH beta, and FSH beta mRNAs, but not LH beta mRNA. Pulsatile DOG only increased LH beta and PRL mRNAs, with maximal responses seen after the 1-mM dose for LH beta and the 0.2-mM dose for PRL. In contrast, PMA stimulated significant increases in alpha, LH beta, and TSH beta, but not PRL or FSH beta. These data show that alpha, TSH beta, LH beta, and PRL mRNA expression are regulated by PKC. Maximal increases are seen after continuous stimulation (via PMA), with the exception of PRL, which requires a pulsatile signal pattern. Thus, intermittent activation of PKC does not appear to play a major role in regulating pituitary gene expression.

Gonadotropin-releasing hormone pulse frequency regulates expression of pituitary follistatin messenger ribonucleic acid: a mechanism for differential gonadotrope function

Follistatin (FS) is a monomeric glycoprotein that selectively inhibits both secretion of FSH and expression of FSH beta messenger RNA (mRNA), presumably via its ability to bind activin. FS mRNA and protein are present in the gonadotrope, suggesting a local action in regulating FSH beta. Pituitary FS mRNA increases after gonadectomy and at the midcycle gonadotropin surge of the estrous cycle, times of increased GnRH secretion. Thus, the purpose of the present studies was to assess the role of GnRH secretion on the regulation of pituitary FS. To confirm GnRH regulation of FS and to study the role of gonadal steroids, adult male rats were gonadectomized (2-36 h), with some animals receiving either testosterone (T) replacement, LRF-147 (a GnRH antagonist, AC-DTrp1-pCl-DPhe2-DTrp3-Ser4-Tyr5-DArg6-L eu7-Arg8-Pro9-DAla10), or both for 36 h (from the time of castration). Pituitary FS mRNA increased rapidly after castration, with levels rising 3-fold by 12 h and 4-fold by 36 h when compared to intact animals (P < 0.05). This rise was completely abolished by administration of LRF-147 and prevented by T replacement. Because GnRH pulse frequency can selectively regulate FSH beta mRNA expression, we next examined the effect of GnRH pulse interval (8-480 min) on FS mRNA expression. Fast frequency GnRH pulses (8 min), which did not increase FSH beta mRNA, were associated with an increase in FS mRNA (2.5-fold). The 30-min interval increased FS and gonadotropin subunit mRNAs. Slower pulse frequencies (> or = 120 min), which selectively stimulated a rise in FSH beta mRNA, did not increase FS mRNA. These results indicate that pituitary FS mRNA is regulated by GnRH. In addition, GnRH frequency modulation of pituitary FS provides a mechanism whereby a single hypothalamic GnRH can differentially regulate the gonadotropins, LH and FSH.

Failure of gonadotropin-releasing hormone (GnRH) pulses to increase luteinizing hormone beta messenger ribonucleic acid in GnRH-deficient female rats

Gonadotropin subunit gene transcription and messenger RNA (mRNA) levels are differentially regulated by GnRH pulse frequency and amplitude in the male rat. The rapid changes of subunit mRNA levels and LH and FSH secretion during the estrous cycle, particularly the rapid rise in LH-beta subunit mRNA on proestrus afternoon, suggest that physiological changes in the pattern of GnRH action may also be important in female rats. However, in the absence of a GnRH-deficient female model the role of varying GnRH stimulation remains to be determined. We have characterized a GnRH-deficient model by administering the alpha-adrenergic antagonist phenoxybenzamine (PBZ) to ovariectomized (OVX) rats. Initial experiments showed that PBZ given 24 h earlier abolished the afternoon LH surge in OVX estradiol (E2) replaced rats whereas LH responses to exogenous GnRH were preserved. A PBZ regimen of 15 mg/kg ip at OVX followed by 10 mg/kg at 24 h and 5 mg/kg at 48 h prevented the increase in alpha, LH-beta, and FSH-beta mRNAs and LH and FSH secretion for 72 h post-OVX. LH and FSH responses to GnRH pulses were preserved suggesting that PBZ blocked the post-OVX increase in hypothalamic GnRH secretion. The suppressive effect of PBZ appeared to be specific to the hypothalamic-pituitary-ovarian axis as plasma PRL, TSH, and corticosterone were not decreased compared to controls. We have used this GnRH-deficient OVX female model to investigate the effects of exogenous GnRH pulses on subunit mRNA expression. GnRH pulses (5-250 ng/30 min for 12-24 h) were administered via an intraatrial catheter beginning 24 h after OVX and the first PBZ injection (OVX+PBZ+saline pulses to controls). Expression of alpha and FSH-beta mRNAs and LH and FSH secretion were increased by GnRH pulse doses of 5-25 ng to values similar to or greater than those in OVX controls though the higher doses of GnRH/pulse did not increase FSH-beta mRNA or plasma FSH. However, LH-beta mRNA levels were not increased by GnRH pulses. GnRH pulses were also given to rats replaced with proestrus concentrations of estradiol alone or in combination with progesterone (P). Again, no demonstrable increases in LH-beta mRNA expression were observed. alpha-mRNA concentrations were further increased in the presence of E2 alone, and P in combination with E2, produced an augmented response of FSH-beta subunit mRNA. These data suggest that ovarian steroid hormones act directly on the gonadotrope to augment alpha and FSH-beta mRNA responses to GnRH.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of prolactin, thyrotropin subunit, and gonadotropin subunit gene expression by pulsatile or continuous calcium signals

We investigated the importance of calcium (Ca2+) influx in increasing the steady state concentrations of mRNAs coding for the pituitary peptides PRL, alpha, and TSH, LH, and FSH beta-subunits. Adult female rat pituitaries were dissociated, plated for 48 h, then inserted into perifusion chambers. Secretory responses were measured after 2 and 22 h of perifusion, and after 24 h, the cells were recovered, total RNA was extracted, and mRNAs were assayed by dot blot hybridization. The first experiment examined the effect of the Ca2+ channel blocker verapamil (100 microM) on the stimulatory action of pulsatile TRH (4 nM; 60-min interval) or GnRH (100 pM; 60-min interval) on pituitary mRNAs. TRH pulses induced a significant increase (49-56%) in PRL, alpha, and TSH beta mRNAs. Similarly, GnRH pulses stimulated a rise in alpha (64%) and FSH beta (50%) mRNAs, but not LH beta. The effects of pulsatile TRH or GnRH were eliminated when verapamil was added to the medium, suggesting that Ca2+ influx is critical to the stimulatory action of TRH or GnRH. The second experiment examined the effect of pulsatile vs. continuous increases in intracellular Ca2+ on pituitary mRNA expression. Pulsatile Ca2+ signals were produced by giving 60-min pulses of 50 mM KCl, Bay K 8644 (10 microM), or Bay K 8644 (10 microM; in the presence of 10 mM KCl in the injectate) and vehicle pulses to controls. Continuous increases in intracellular Ca2+ were induced by perifusion with medium containing the Ca2+ ionophore A23187 (20 microM), and these groups were compared to that receiving continuous verapamil. Pulsatile increases in Ca2+ influx (KCl or Bay K 8644) stimulated significant elevations in all mRNAs studied (36-74% increase vs. controls), with the exception of TSH beta. The magnitude of the mRNA responses to pulsatile Ca2+ (vs. controls) was similar to that observed after TRH and GnRH pulses. In contrast, only LH beta was increased by A23187 (42% increase vs. controls; P < 0.05). PRL and alpha mRNAs were selectively diminished by A23187 (57% and 83% decreases vs. controls, respectively; P < 0.05) and verapamil (67% and 60%; P < 0.05). The data show that expression of these pituitary genes is regulated by Ca2+ and that a pulsatile Ca2+ signal is required to stimulate PRL, alpha, and FSH beta (but not LH beta).(ABSTRACT TRUNCATED AT 400 WORDS)

L(+)-Mandelate dehydrogenase from Rhodotorula graminis: purification, partial characterization and identification as a flavocytochrome b

L(+)-Mandelate dehydrogenase was purified to homogeneity from the yeast Rhodotorula graminis KGX 39 by a combination of (NH4)2SO4 fractionation, ion-exchange and hydrophobic-interaction chromatography and gel filtration. The amino-acid composition and the N-terminal sequence of the enzyme were determined. Comprehensive details of the sequence determinations have been deposited as Supplementary Publication SUP 50172 (4 pages) at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1993) 289, 9. The enzyme is a tetramer as judged by comparison of its subunit M(r) value of 59,100 and native M(r) of 239,900, estimated by SDS/PAGE and gel filtration respectively. There is one molecule of haem and approx. one molecule of non-covalently bound FMN per subunit. 2,6-Dichloroindophenol, cytochrome c and ferricyanide can all serve as electron acceptors. L(+)-Mandelate dehydrogenase is stereospecific for its substrate. D(-)-Mandelate and L(+)-hexahydromandelate are competitive inhibitors. The enzyme has maximum activity at pH 7.9 and it has a pI value of 4.4. HgCl2 and 4-chloromercuribenzoate are potent inhibitors, but there is no evidence that the enzyme is subject to feedback inhibition by potential metabolic effectors. The evidence suggests that L(+)-mandelate dehydrogenase from R. graminis is a flavocytochrome b which is very similar to, and probably (at least so far as the haem domain is concerned) homologous with, certain well-characterized yeast L(+)-lactate dehydrogenases, and that the chief difference between them is their mutually exclusive substrate specificities.

Relationships amongst some bacterial and yeast lactate and mandelate dehydrogenases

Five yeast strains were isolated by enrichment culture on the basis of their ability to grow on mandelate and two of these strains were identified as Rhodotorula glutinis. In addition, a range of yeasts from culture collections was screened for growth on mandelate. The results suggest that mandelate utilization is a widespread but not universal characteristic within the genus Rhodotorula. Several of the yeasts contained an inducible NAD-dependent D(-)-mandelate dehydrogenase and an inducible dye-linked (presumably flavoprotein) L(+)-mandelate dehydrogenase. All the D(-)-mandelate dehydrogenases from the yeasts showed immunological cross-reactivity with each other (as judged by both immunoinhibition and immunoblotting), as did all the yeast L(+)-mandelate dehydrogenases that were tested. Determination of N-terminal amino acid sequences of several bacterial and yeast lactate and mandelate dehydrogenases, together with the evidence from the immunological studies, confirmed and extended previous proposals that there are several major groups of such dehydrogenases: FMN-dependent, membrane-bound L(+)-lactate and L(+)-mandelate dehydrogenases (M(r) = approx. 44,000) in bacteria, mitochondrial flavocytochrome b2 L(+)-lactate and L(+)-mandelate dehydrogenases (M(r) = approx. 59,000) in yeasts, FAD-dependent, membrane-bound D(-)-lactate and D(-)-mandelate dehydrogenases in bacteria, and soluble NAD-dependent D(-)-mandelate dehydrogenases in both bacteria and yeasts.

Ovariectomy and inhibin immunoneutralization acutely increase follicle-stimulating hormone-beta messenger ribonucleic acid concentrations: evidence for a nontranscriptional mechanism

After ovariectomy (ovx), FSH beta mRNA levels and serum FSH increase 2- to 3-fold within 12 h, and this persists in the presence of a GnRH antagonist. As a fall in plasma estradiol and progesterone appears to regulate FSH beta via increased GnRH secretion, it is thought that the acute (by 2 h) changes in FSH beta mRNA after ovx reflect falling levels of plasma inhibin. The current study addressed the following questions. 1) Does a reduction of circulating inhibin (via passive immunoneutralization or gonadectomy) increase FSH beta mRNA levels? 2) If so, are the acute increases in FSH beta mRNA associated with changes in the transcription rate? Adult male and female rats received 0.5 ml antiinhibin antiserum, iv, and were killed 2 or 12 h later. A second group of rats was gonadectomized; some received a GnRH antagonist and were killed at various intervals between 2 h and 7 days later. In adult males, no change in gonadotropin mRNA levels was observed after either addition of inhibin antiserum or removal of the testes. In contrast, in adult female rats, both ovx and inhibin antiserum increased FSH beta mRNA levels (2-fold) within 2 h, and a similar increase occurred in the presence of a GnRH antagonist. To determine if the increase in FSH beta resulted from increased mRNA synthesis, adult female rats were ovx, and half received a GnRH antagonist. Animals were killed 2 or 12 h later, and transcription rates were measured by nuclear run-off assay in pituitaries pooled from three rats. The transcription rate of the alpha-subunit, although not altered by ovx, was decreased in animals receiving the GnRH antagonist. Transcription of the LH beta gene was increased within 2 h after ovx, a change that was abolished by the GnRH antagonist. mRNA concentrations of either alpha or LH beta do not increase acutely after ovx, suggesting that GnRH regulates alpha and LH beta gene transcription and 12 h or more of mRNA synthesis are required to increase cytoplasmic concentrations. The FSH beta gene transcription rate was unchanged in both ovx and GnRH antagonist-treated animals, but serum FSH increased at 12 h. These data indicate that the rapid GnRH-independent increase in FSH beta mRNA levels seen immediately after ovx is not associated with altered mRNA synthesis and suggest that inhibin may also regulate FSH beta gene expression through nontranscriptional mechanisms.