Pituitary gland: one site of ultrashort-feedback regulation for control of thyrotropin

Studies from our laboratory have previously demonstrated sensitive and specific autoregulatory control systems for thyrotropin (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in the rabbit. Because our studies of LH autoregulation showed the feedback regulation acted directly at a pituitary level, the current studies were designed to investigate whether the TSH control system also acted at the pituitary level. Two species-specific TSH assays were employed; a rabbit TSH radioimmunoassay which showed little or no reaction to human TSH, and a human TSH radioimmunoassay which showed little or no reaction to rabbit TSH. Both in vivo and in vitro studies were performed. TRH (thyrotropin-releasing hormone) in doses of 2, 10, and 50 micrograms was injected as an intravenous bolus into thyroidectomized hypothyroid rabbits during continuous perfusion with highly purified human TSH (hTSH) or with saline. In these in vivo studies, TRH-stimulated rabbit TSH (rTSH) secretion was suppressed by hTSH perfusion compared with control saline perfusion. The effect of hTSH was studied in vitro by employing short-term cultured rabbit pituitary cells. When hTSH was added to the incubation medium, TRH-stimulated rTSH secretion was inhibited. From these studies, we conclude that one site of the autoregulatory control for TSH in the rabbit is at the pituitary level. These studies do not exclude a possible additional short-loop feedback control at an hypothalamic level, but such a site of action is not required to explain the autoregulatory phenomenon.

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Pan-American Lancehead Pit-Vipers: Coagulotoxic Venom Effects and Antivenom Neutralisation of Bothrops asper and B. atrox Geographical Variants

Toxins ◽

10.3390/toxins13020078 ◽

2021 ◽

Vol 13 (2) ◽

pp. 78

Author(s):

Lachlan A. Bourke ◽

Christina N. Zdenek ◽

Edgar Neri-Castro ◽

Melisa Bénard-Valle ◽

Alejandro Alagón ◽

...

Keyword(s):

Evolutionary Biology ◽

Current Knowledge ◽

Clinical Manifestations ◽

In Vivo Studies ◽

Factor X ◽

Clotting Factors ◽

Bothrops Asper ◽

Species Specific

The toxin composition of snake venoms and, thus, their functional activity, can vary between and within species. Intraspecific venom variation across a species’ geographic range is a major concern for antivenom treatment of envenomations, particularly for countries like French Guiana that lack a locally produced antivenom. Bothrops asper and Bothrops atrox are the most medically significant species of snakes in Latin America, both producing a variety of clinical manifestations, including systemic bleeding. These pathophysiological actions are due to the activation by the venom of the blood clotting factors Factor X and prothrombin, thereby causing severe consumptive coagulopathy. Both species are extremely wide-ranging, and previous studies have shown their venoms to exhibit regional venom variation. In this study, we investigate the differential coagulotoxic effects on human plasma of six venoms (four B. asper and two B. atrox samples) from different geographic locations, spanning from Mexico to Peru. We assessed how the venom variation of these venom samples affects neutralisation by five regionally available antivenoms: Antivipmyn, Antivipmyn-Tri, PoliVal-ICP, Bothrofav, and Soro Antibotrópico (SAB). The results revealed both inter- and intraspecific variations in the clotting activity of the venoms. These variations in turn resulted in significant variation in antivenom efficacy against the coagulotoxic effects of these venoms. Due to variations in the venoms used in the antivenom production process, antivenoms differed in their species-specific or geographical neutralisation capacity. Some antivenoms (PoliVal-ICP, Bothrofav, and SAB) showed species-specific patterns of neutralisation, while another antivenom (Antivipmyn) showed geographic-specific patterns of neutralisation. This study adds to current knowledge of Bothrops venoms and also illustrates the importance of considering evolutionary biology when developing antivenoms. Therefore, these results have tangible, real-world implications by aiding evidence-based design of antivenoms for treatment of the envenomed patient. We stress that these in vitro studies must be backed by future in vivo studies and clinical trials before therapeutic guidelines are issued regarding specific antivenom use in a clinical setting.

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In vitro processing at the 3'-terminal region of pre-18S rRNA by a nucleolar endoribonuclease.

Molecular and Cellular Biology ◽

10.1128/mcb.10.8.3868 ◽

1990 ◽

Vol 10 (8) ◽

pp. 3868-3872 ◽

Cited By ~ 15

Author(s):

C M Shumard ◽

C Torres ◽

D C Eichler

Keyword(s):

18S Rrna ◽

Precise Determination ◽

In Vivo Studies ◽

Rrna Sequence ◽

S1 Nuclease ◽

In Vitro Processing ◽

Rrna Maturation ◽

A Site

In an investigation of the possible involvement of a highly purified nucleolar endoribonuclease in processing of pre-rRNA at the 3' end of the 18S rRNA sequence, an in vitro synthesized pre-18S rRNA transcript containing the 3' end region of 18S rRNA and the 5' region of the first internal transcribed spacer (ITS1) was used as a substrate for the enzyme. Cleavages generated by the nucleolar RNase were localized by S1 nuclease protection analysis and by the direct release of labeled rRNA products. Precise determination of the specificity of cleavage was achieved by RNA sequence analysis with end-labeled rRNA transcripts. These data demonstrated that the purified nucleolar RNase cleaved the pre-18S rRNA transcript at three specific sites relative to the 3' region of 18S rRNA. The first two sites included the mature 3'-end 18S rRNA sequence and a site approximately 55 nucleotides downstream of the 3'-end 18S rRNA sequence, both of which corresponded directly to recent results (Raziuddin, R. D. Little, T. Labella, and D. Schlessinger, Mol. Cell. Biol. 9:1667-1671, 1989) obtained with transfected mouse rDNA in hamster cells. The other cleavage occurred approximately 35 nucleotides upstream from the mature 3' end in the 18S rRNA sequence. The results from this study mimic the results obtained from in vivo studies for processing in the 3' region of pre-18S rRNA, supporting the proposed involvement of this nucleolar endoribonuclease in rRNA maturation.

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Inhibin, a member of a new peptide family

Reproduction Fertility and Development ◽

10.1071/rd9890001 ◽

1989 ◽

Vol 1 (1) ◽

pp. 1 ◽

Cited By ~ 9

Author(s):

HG Burger

Keyword(s):

Feedback System ◽

Suppressive Effect ◽

Commercial Application ◽

Pituitary Cells ◽

Cell Content ◽

Peptide Family ◽

Normal Menstrual Cycle ◽

Loop Feedback

There is considerable experimental evidence that follicle stimulating hormone (FSH) and luteinizing hormone (LH) are regulated by separate mechanisms in some circumstances. Part of this differential regulation involves the gonadal factor inhibin, which preferentially affects FSH. A sensitive and specific bioassay based on suppression of FSH cell content in dispersed cultured pituitary cells was used to monitor the purification of inhibin to homogeneity. The two subunits were cloned and the full amino acid sequence of the molecule established. Much evidence has been gathered to support the hypothesis that FSH and inhibin form a classic endocrine closed-loop feedback system in which FSH stimulates inhibin secretion both in vivo and in vitro and inhibin in turn exerts a significant suppressive effect on FSH secretion. The establishment of an inhibin radioimmunoassay has allowed the description of its concentrations in various physiological states such as in the normal menstrual cycle, during puberty and in pregnancy. Inhibin levels were shown to be within the normal range in the polycystic ovarian syndrome. A potential commercial application of inhibin is as a vaccine to increase fertility in domestic animals.

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Heterozygous Disruption of the TATA-Binding Protein Gene in DT40 Cells Causes Reduced cdc25B Phosphatase Expression and Delayed Mitosis

Molecular and Cellular Biology ◽

10.1128/mcb.21.7.2435-2448.2001 ◽

2001 ◽

Vol 21 (7) ◽

pp. 2435-2448 ◽

Cited By ~ 31

Author(s):

Moonkyoung Um ◽

Jun Yamauchi ◽

Shigeaki Kato ◽

James L. Manley

Keyword(s):

Binding Protein ◽

Tata Binding Protein ◽

In Vivo Studies ◽

Mutant Form ◽

Lower Growth ◽

Protein Levels ◽

Species Specific ◽

Dt40 Cells

ABSTRACT TATA-binding protein (TBP) is a key general transcription factor required for transcription by all three nuclear RNA polymerases. Although it has been intensively analyzed in vitro and inSaccharomyces cerevisiae, in vivo studies of vertebrate TBP have been limited. We applied gene-targeting techniques using chicken DT40 cells to generate heterozygous cells with one copy of theTBP gene disrupted. Such TBP-heterozygous (TBP-Het) cells showed unexpected phenotypic abnormalities, resembling those of cells with delayed mitosis: a significantly lower growth rate, larger size, more G2/-M- than G1-phase cells, and a high proportion of sub-G1, presumably apoptotic, cells. Further evidence for delayed mitosis in TBP-Het cells was provided by the differential effects of several cell cycle-arresting drugs. To determine the cause of these defects, we first examined the status of cdc2 kinase, which regulates the G2/M transition, and unexpectedly observed more hyperphosphorylated, inactive cdc2 in TBP-Het cells. Providing an explanation for this, mRNA and protein levels of cdc25B, the trigger cdc2 phosphatase, were significantly and specifically reduced. These properties were all due to decreased TBP levels, as they could be rescued by expression of exogeneous TBP, including, in most but not all cases, a mutant form lacking the species-specific N-terminal domain. Our results indicate that small changes in TBP concentration can have profound effects on cell growth in vertebrate cells.

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Eplerenone Prevents Atrial Fibrosis via the TGF-β Signaling Pathway

Cardiology ◽

10.1159/000471918 ◽

2017 ◽

Vol 138 (1) ◽

pp. 55-62 ◽

Cited By ~ 4

Author(s):

Lili Du ◽

Mu Qin ◽

Yi Yi ◽

Xiaoqing Chen ◽

Weifeng Jiang ◽

...

Keyword(s):

Protein Expression ◽

Western Blotting ◽

Feedback Regulation ◽

Underlying Mechanism ◽

In Vivo Studies ◽

Atrial Fibrosis ◽

Qrt Pcr ◽

Tgf Β1

Objectives: Eplerenone (EPL), an antagonist of the mineralocorticoid receptor, is beneficial for atrial fibrillation and atrial fibrosis. However, the underlying mechanism remains less well known. We aimed to investigate the effect of EPL on atrial fibrosis using a mouse with selective atrial fibrosis and to explore the underlying mechanisms. Methods: EPL-treated MHC-TGFcys33ser transgenic mice that have selective atrial fibrosis (Tx+EPL mice), as well as control mice, were used for in vivo studies including histological analyses, Western blotting, and qRT-PCR studies. TGF-β1-stimulated atrial fibroblasts were treated with EPL or vehicle for the in vitro studies including Western blotting and qRT-PCR studies. In addition, Smad7 siRNA was used to knock down Smad7. Results: EPL inhibited atrial fibrosis in the Tx mice. In addition, EPL suppressed the expression of fibrosis-related molecules induced by TGF-β1 in vivo and in vitro. This occurred in concert with a downregulation of Smad7 protein expression and an upregulation of p-Smad2/3 protein expression. In addition, knockdown of Smad7 by siRNA abolished the protective roles of EPL. Conclusions: EPL inhibited atrial fibrosis in Tx mice. The underlying mechanism may involve increased protein expression of Smad7, which enhances the inhibitory feedback regulation of TGF-β1/Smad signaling.

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In vitro processing at the 3'-terminal region of pre-18S rRNA by a nucleolar endoribonuclease

Molecular and Cellular Biology ◽

10.1128/mcb.10.8.3868-3872.1990 ◽

1990 ◽

Vol 10 (8) ◽

pp. 3868-3872

Author(s):

C M Shumard ◽

C Torres ◽

D C Eichler

Keyword(s):

18S Rrna ◽

Precise Determination ◽

In Vivo Studies ◽

Rrna Sequence ◽

S1 Nuclease ◽

In Vitro Processing ◽

Rrna Maturation ◽

A Site

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Possible site of action of CGRP antagonists in migraine

Cephalalgia ◽

10.1177/0333102411398403 ◽

2011 ◽

Vol 31 (6) ◽

pp. 748-750 ◽

Cited By ~ 41

Author(s):

Peer Tfelt-Hansen ◽

Jes Olesen

Keyword(s):

In Vivo Studies ◽

Cgrp Receptor ◽

Receptor Antagonists ◽

Calcitonin Gene ◽

Site Of Action ◽

Cgrp Receptor Antagonists ◽

The Central Nervous System ◽

High Doses

Background: The calcitonin gene-related peptide (CGRP) receptor antagonists olcegepant and telcagepant are very potent drugs. Both are effective in migraine but in doses much higher than would be predicted from receptor binding and other in vitro results. This could perhaps suggest an effect of CGRP antagonists behind the blood-brain barrier (BBB), i.e. in the central nervous system (CNS). Methods: Comparison of doses needed for CGRP blocking effect in vitro with dose needed in vivo in man and monkeys. Discussion of these doses in relation to doses needed for anti-migraine activity. Results: In vivo studies in monkeys and man showed that high doses compared to doses needed in vitro are needed to block capsaicin-induced in skin blood flow, a CGRP-mediated reaction. These doses are close to those needed for anti-migraine activity. Conclusion: The apparently high doses of CGRP receptor antagonists, olcegepant and telcagepant needed for anti-migraine effect are not so high after all. They do not allow a conclusion as to whether CGRP antagonists act on peripheral sites or central sites in migraine.

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