bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bradykinin stimulates phosphoinositide metabolism and prolactin secretion in rat anterior pituitary cells
Authors: Jones T.H. , Brown B. L. , Dobson P. R. M. 
Published: December 2008

ABSTRACT
Bradykinin stimulated prolactin secretion from monolayer cultures of rat anterior pituitary cells, the stimulation being greater from the cells of male rats. This stimulated secretion was accompanied by a rise in total inositol phosphate accumulation, suggesting that the action of bradykinin is mediated by phosphoinositide hydrolysis. The increase in inositol phosphate accumulation was biphasic; a further sharp rise occurred when the concentration of bradykinin exceeded 1 μmol/l. This may indicate that bradykinin acts on other cell types in the pituitary gland. Bradykinin had no effect on growth hormone secretion from cells of normal pituitary glands, or on prolactin secretion and phosphoinositide metabolism in GH3 rat pituitary tumour cells. Bradykinin receptor antagonists (both B1 and B2) had no effect on either bradykinin-stimulated inositol phosphate accumulation or prolactin secretion. Kallikreins, the enzymes responsible for the generation of kinins, are known to be present in the adenohypophysis. Therefore, the results presented here would suggest that kinins may have a role as paracrine agents in the pituitary gland.
Nuclear proteins from the rat pituitary gland bind to regulatory sequences of the thyrotrophin-β gene
Authors: Ahlquist J. A. O. , Franklyn J. A. , Ramsden D. B. , Sheppard M. C. 
Published: December 2008

ABSTRACT
Interactions between DNA sequences and nuclear proteins are important in the regulation of gene expression. We have applied a gel retardation method to examine the binding of nuclear proteins from the rat pituitary gland to regulatory sequences of the rat TSH β-subunit gene. Binding between nuclear protein and DNA is demonstrated by an alteration in electrophoretic mobility of the DNA. A 0·4 m NaCl fraction of pituitary nuclear proteins bound to a fragment of DNA containing the promoter region of the TSH-β gene, but not to plasmid DNA or insulin cDNA of comparable size. This nuclear protein fraction also bound to fragments of DNA containing sequences from the 5′-flanking region of the gene; binding of nuclear proteins was evident as far as 1 kb 5′ to the structural gene. Each of these regions of the TSH-β gene formed a number of distinct complexes with the nuclear protein extract, distinguished by their differing binding affinities in the presence of poly(dI-dC), and by their electrophoretic mobility. These findings suggest that transcriptional regulation of the rat TSH-β gene may be mediated by interaction of a number of nuclear proteins with regulatory sequences of DNA up to 1 kb upstream of the transcriptional start site of the gene.
Effects of benextramine on the adrenergic inhibition of insulin secretion in isolated rat pancreatic islets
Authors: Hurst R. D. , Chan S. L. F. , Morgan N. G. 
Published: December 2008

ABSTRACT
Insulin secretion from isolated rat islets of Langerhans in the presence of 4 mm glucose averaged 2·26 ± 0·20 (s.e.m.) ng/islet per 90 min and was significantly (P<0·001; n=30) increased to 3·28 ± 0·21 ng/islet per 90 min by the covalent α-adrenoceptor antagonist benextramine (10 μm). Glucose (20 mm) also increased the secretion rate (to 6·24 ± 6·0 ng/islet per 90 min) but, under these conditions, the response was not further enhanced by benextramine. Clonidine and noradrenaline (1 nm–10 μm) each caused dose-dependent inhibition of glucose-induced insulin secretion which was maximal at 1 μm. Benextramine, when added simultaneously with the agonist, relieved, in a dosedependent manner, the inhibition of secretion induced by either clonidine or noradrenaline with similar sensitivity. Even after a 30-min preincubation with benextramine the antagonist failed to differentiate between noradrenaline, adrenaline and clonidine with respect to inhibition of insulin secretion. In contrast to its effects on adrenergic responses, short-term treatment with benextramine did not significantly affect muscarinic—cholinergic receptor-mediated 45Ca2+ efflux from rat islets of Langerhans perifused in Ca2+-depleted medium. These data suggest that benextramine does not differentiate between clonidine and noradrenaline in rat islets of Langerhans but that it does show preference for α-adrenoceptors in this tissue.
In-vitro biosynthesis of multiple preproglucagons results from acetylation of the primary translation products
Authors: Okun M. M. , Warren T. G. , Shields D. 
Published: December 2008

ABSTRACT
In-vitro translation of anglerfish islet mRNA revealed three glucagon precursors (preproglucagons): one with Mr 16 000 and two with Mr 14 000. The two Mr 14 000 precursors were well separated upon isoelectric focusing gels (pI values of 7·2 and 7·3), but had identical peptide maps. Translation of hybrid-selected Mr 14 000 preproglucagon mRNA in the presence of microsomal vesicles revealed that both precursors were processed to the same proglucagon. Northern blot analysis detected two mRNA species encoding Mr 14 000 precursor. A full-length Mr 14 000 preproglucagon cDNA was subcloned into a transcription vector, and coupled in-vitro transcription—translation was performed; surprisingly, both Mr 14 000 precursors were synthesized. To test whether acetylation of the free amino terminus generated the more acidic precursor, acetylase activity was partially inactivated with the inhibitor S-acetonyl-CoA, and acetyl-CoA was depleted by addition of oxaloacetate and citrate synthetase. Under these conditions, the level of the most basic preproglucagon was greatly enhanced, but when exogenous acetyl-CoA was added, the acidic form predominated. We conclude that acetylation generates the acidic precursor, and we discuss the implications of our findings for the biogenesis of other peptide hormones.
Immune induction of major histocompatibility complex antigens on a human thyroid cell line (SGHTL-34)
Authors: King S. L. , Whitley G. St J. , Page S. , Nussey S. S. , Johnstone A. P. 
Published: December 2008

ABSTRACT
Expression of major histocompatibility complex antigens by epithelial cells may play a role in the aetiology of autoimmune disorders. We have studied the effect of γ-interferon on SGHTL-34, a human thyroid cell line which constitutively expresses class I but not class II antigens. γ-Interferon induced the expression of class II and increased the expression of class I molecules (assessed by flow cytofluorimetry) in a dose-dependent manner. Thyrotrophin or phytohaemagglutinin had no effect on either class I or class II expression. However, a supernatant from phytohaemagglutinin-stimulated peripheral blood mononuclear cells, containing 6400 U γ-interferon/ml, was an effective inducer of both class I and class II antigens. These data clarify earlier studies using primary thyroid cultures, which are contaminated with cells of the immune system.
Thyrotrophin, forskolin and ionomycin increase cathepsin B mRNA concentrations in rat thyroid cells in culture
Authors: Phillips I. D. , Black E. G. , Sheppard M. C. , Docherty K. 
Published: December 2008

ABSTRACT
In order to study the regulation of cathepsin B expression in the thyroid, cathepsin B mRNA concentrations were measured in rat thyroid cells (FRTL5) in culture. Northern blot analysis demonstrated that cathepsin B mRNA concentrations were increased in FRTL5 cells cultured for up to 6 days in TSH. The effect of TSH on cathepsin B mRNA concentrations was dose dependent over the range 25–150 μunits/ml. Cytoplasmic dot-blot analysis was used to characterize this effect further. The TSH-induced increase in cathepsin B mRNA concentrations (approximately fivefold over that in untreated cells) was partially mimicked by forskolin (approximately threefold) and ionomycin, while phorbol ester decreased cathepsin B mRNA concentrations. Similar changes were observed for thyroglobulin and actin mRNA concentrations. TSH had no effect on cathepsin B enzymatic activity or immunoreactive protein concentration. These results demonstrate (1) that cathepsin B expression in the thyroid is regulated in parallel with that of thyroglobulin and actin, and (2) that cyclic AMP- and Ca2+-dependent processes stimulate gene expression, while phorbol ester treatment inhibits gene expression in FRTL5 cells.
Effects of antioestrogens on the proliferation of MCF-7 human breast cancer cells
Authors: Wakeling A. E. , Newboult E. , Peters S. W. 
Published: December 2008

ABSTRACT
Non-steroidal antioestrogens, such as tamoxifen, inhibit the growth of human breast cancer cells. The experiments described here compare and contrast the efficacy of tamoxifen and the 'pure' antioestrogen, ICI 164384, on the inhibition of proliferation of MCF-7 cells.
Previous studies have shown that ICI 164384 has a greater maximal inhibitory effect than conventional antioestrogens on the growth of MCF-7 cells. Both types of compound block progression of cells through the cell cycle in the early G1 phase. These studies have been extended to measure the population distribution of antioestrogen-treated cells by the use of two-parameter flow cytometry. ICI 164384 proved to be more effective than tamoxifen in decreasing the proportion of actively growing cells in an asynchronous population.
In cells grown in the complete absence of exogenous oestrogens, growth was stimulated by oestradiol, insulin, insulin-like growth factor-I (IGF-I) or transforming growth factor-α (TGF-α). The potent metabolite of tamoxifen, trans 4′-hydroxytamoxifen (4′-OHT), alone also stimulated growth, whereas ICI 164384 did not. Oestradiol and insulin added together demonstrated a clear synergistic enhancement of cell growth. Correspondingly, the stimulatory effect of 4′-OHT on growth was magnified in the presence of insulin, and a combination of ICI 164384 with insulin revealed a much weaker stimulatory action of the 'pure' antagonist. For both compounds the interaction with insulin was complex and characterized by a bell-shaped dose—response curve. However, for 4′-OHT at all concentrations in the range 1 pm–1 μm in the presence of insulin, cell numbers were greater than in cultures exposed to insulin alone. This was not the case for ICI 164384 which suggested that differences in efficacy may be due to interactions between oestrogen and growth factor-mediated mechanisms. Furthermore, ICI 164384 was more effective in inhibiting the action of IGF-I and TGF-α alone or in combination, although both antioestrogens produced a partial blockade of growth factor responses in the complete absence of oestradiol.
It is concluded that the difference in efficacy between partial agonist and 'pure' antagonist antioestrogens to inhibit growth in vitro is consistent with the difference in the pharmacological profile of these compounds. The absence of stimulatory activity of ICI 164384 is of particular significance in reducing to a minimum the synergistic interaction between oestrogens and insulin. In addition, the partial blockade of the effect of IGF-I and/or TGF-α by antioestrogens in the complete absence of oestradiol, where ICI 164384 is also more effective than 4′-OHT, suggests that novel mechanisms of growth inhibition may be involved.
Interleukin-1 induces a pertussis toxin-sensitive increase in diacylglycerol accumulation in mouse thymoma cells.
Authors: Dobson P.R.M. , Plested C.P. , Jones D.R. , Barks T. , Brown B.L. 
Published: December 2008

ABSTRACT
The mechanism of action of the cytokine, interleukin-l (IL-1), has been investigated. Mouse thymoma (EL4 6.1) cells were preincubated with [3H]-glycerol and then incubated with recombinant IL-1β for varying periods. Interleukin-1 caused a rapid increase in diacylglycerol production (approx. 2 fold at 30 sees). This reproducible enhancement of diacylglycerol accumulation was abolished by pretreatment of the cells with pertussis toxin. Interestingly, a similar IL-1 induced increase in diacylglycerol was observed when the cells were preincubated with [3H]-myristic acid. These results appear to suggest a novel mode of action of interleukin-1 which involves a G-protein mediated breakdown of a membrane lipid resulting in the production of diacylglycerol. It is suggested that one possible candidate for this parent lipid may be a phosphatidylinositol glycan.
Early regulation of c-myc mRNA by 1,25-dihydroxyvitamin D3 in human myelomonocytic U937 cells
Authors: Karmali R. , Bhalla A. K. , Farrow S. M. , Williams M. M. , Lal S. , Lydyard P. M. , O'Riordan J. L. H. 
Published: December 2008

ABSTRACT
The effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3; 10 nmol/1) on the human monomyelocytic cell line U937 were investigated. Addition of 1,25-(OH)2D3 led to a decrease in cell proliferation which fell at 72 h to 67·8 ± 4·3 % (mean±s.e.m.) of control values. The presence of CD14, a surface marker found on mature monocytes/macrophages but not on U937 cells, was detectable as early as 18 h and peaked at 48 h, when 63·6 ± 4·2% of the cells were positive. However, changes in c-myc mRNA levels were detected earlier, starting within 4 h of exposure to the hormone and being reduced to 38±8·2% of control values of 24 h. These effects were reversible after removal of the hormone, with the same sequence of events seen following addition of the hormone. There was first an increase in c-myc mRNA levels, starting within 2 h and reaching control values by 24 h. These changes were followed by loss of CD14 which became undetectable after 72 h. Proliferation recovered slowly and incompletely, since it was 81·7 ± 0·7% of control after 72 h. A constant reciprocal relationship between c-myc mRNA and CD14 levels was found both in the presence and after removal of 1,25-(OH)2D3.
Regulation of U937 cell proliferation and maturation by 1,25-(OH)2D3 is thus preceded by early modulation of c-myc mRNA.
Decreased expression of hepatic epidermal growth factor receptor gene in diabetic mice
Authors: Kasayama S. , Yoshimura M. , Oka T. 
Published: December 2008

ABSTRACT
The expression of hepatic epidermal growth factor (EGF) receptor gene was studied in genetically diabetic (C57BL/KsJ db/db) mice and streptozotocininduced diabetic mice. The binding of 125I-labelled EGF to hepatic membrane preparations of genetically diabetic mice was only 35% of that of non-diabetic mice. Levels of EGF receptor messenger RNAs (10 and 6 kb) in the liver of the diabetic animals were also reduced by about 75%. In streptozotocin-induced diabetic mice, levels of hepatic EGF binding and messenger RNAs for EGF receptor were decreased to 27 and 30% of control levels respectively, at 5 weeks after injection of the drug. There were, however, no significant differences in levels of messenger RNAs for the structural protein β-actin in the liver. In addition, levels of EGF receptor messenger RNAs in the kidney were similar between control and the two kinds of diabetic mice. Daily administration of insulin to the streptozotocin-induced diabetic mice increased the hepatic levels of EGF receptor messenger RNAs to almost normal levels. These results indicate that EGF binding to its receptor decreases in the liver of diabetic mice, involving alterations in the level of EGF receptor messenger RNAs, and that insulin is important for the regulation of EGF receptor gene expression in the liver but not in the kidney.
Pro-opiomelanocortin gene expression and peptide secretion in human small-cell lung cancer cell lines
Authors: White A. , Stewart M. F. , Farrell W. E. , Crosby S. R. , Lavender P. M. , Twentyman P. R. , Rees L. H. , Clark A. J. L. 
Published: December 2008

ABSTRACT
Expression of the RNA coding for the ACTH—β-lipotrophin precursor, pro-opiomelanocortin (POMC), has been demonstrated in five human small-cell lung cancer (SCLC) cell lines. Using Northern and slot-blot hybridization analysis of RNA and a bovine POMC cDNA as probe, the processed POMC RNA from SCLC cells was found to be approximately 1350 nucleotides in length, which is larger than that found in the normal human pituitary. Expression of the POMC gene was confirmed by measurement of ACTH precursors secreted by the cells, using a novel two-site immunoradiometric assay based on monoclonal antibodies, which directly quantifies both POMC and pro-ACTH but does not recognize ACTH. Levels of POMC in medium accumulated throughout the growth of the cells, in contrast to POMC RNA which showed a relatively constant level of expression. We conclude that human SCLC cell lines are valuable models for studying the aberrant expression and regulation of the human POMC gene.
The androgen-dependent rat prostatic binding protein: comparison of the sequences in the 5′ part and upstream region of the Cl and C2 genes and analysis of their transcripts
Authors: Claessens F. , Dirckx L. , Delaey B. , Decourt J.-L. , Hemschoote K. , Peeters B. , Rombauts W. 
Published: December 2008

ABSTRACT
The complete gene encoding the polypeptide Cl of the complex androgen-controlled prostatic binding protein was isolated from a rat genomic library. A new genomic fragment (C2B) containing only the 5′ part of a C2-related gene was also purified. The segments containing exon 1 and a large part of the adjacent sequences were analysed and compared with the corresponding region of the C2A gene which has been completely sequenced previously. The high structural similarity extending over a large part of all three genomic fragments suggests the duplication of a common ancestral gene, followed by a more recent duplication of the C2-coding region. However, since the structural similarity upstream of position − 150 between C2A and C2B abruptly disappears and no transcripts specific for the C2B region can be detected in prostate RNA, we propose that at a later stage in evolution the C2B region was disrupted and inactivated. Despite the common origin and the similar regulation of the two active genes, Cl and C2A, the only obvious conserved structural element is the homopurine stretch located at position −400, although sequence motifs resembling steroid hormone response elements are present at several locations.
Expression and partial purification of human pro-opiomelanocortin in Escherichia coli
Authors: Grewal T. S. , Lowry P. J. , Savva D. 
Published: December 2008

ABSTRACT
A large portion of the human pro-opiomelanocortin (POMC) peptide corresponding to amino acid residues 59–241 has been cloned and expressed in Escherichia coli. A 1·0 kb DNA fragment encoding this peptide was cloned into the expression vectors pUC8 and pUR291. Plasmid pJMBG51 (a pUC8 recombinant) was found to direct the expression of a 24 kDa peptide. The recombinant pUR291 (pJMBG52) was shown to produce a β-galactosidase fusion protein of 140 kDa. Western blot analysis showed that both the 24 kDa and 140 kDa peptides are recognized by antibodies raised against POMC-derived peptides. The β-galactosidase fusion protein has been partially purified from crude E. coli cell lysates using affinity chromatography on p-aminobenzyl-1-thio-β-d-galactopyranoside agarose.
Growth hormone regulates the rodent hepatic epidermal growth factor receptor at a pretranslational level
Authors: Johansson S. , Husman B. , Norstedt G. , Andersson G. 
Published: December 2008

ABSTRACT
Recent studies have implicated the involvement of pituitary factor(s) in the regulation of hepatic epidermal growth factor receptor (EGF-R) levels. In the present study the possible role of GH as a regulator of EGF-R has been examined by measuring hepatic EGF-R mRNA and EGF binding in intact and GH-deficient rats and mice before and after administration of GH. Using a human EGF-R probe, 10·5 and 6·0 kb transcripts were detected in mouse and rat liver by Northern gel analysis. EGF-R mRNA was quantified by solution hybridization, and EGF binding determined by incubation of 125I-labelled EGF with a low-density membrane fraction.
Levels of hepatic EGF-R mRNA and binding of EGF in female rats were about two-thirds of those in male rats. GH-deficient (lit/lit) male and female mice had approximately 10 and 25% respectively of the levels of EGF-R mRNA and EGF binding of intact male and female mice. Furthermore, hypophysectomized rats exhibited a reduced level of EGF-R mRNA and EGF binding, corresponding to about 20% of the levels detected in intact male rats. When hypophysectomized male and female rats received recombinant human GH (hGH) either as intermittent injections or by continuous infusion using osmotic minipumps, the EGF-R mRNA and EGF binding levels increased to about half those of the intact male animals. No differences between intermittent or continuous administration of hGH on the induction of EGF-R mRNA or EGF binding could be seen. The correlation between mRNA and binding levels suggests regulation at a pretranslational level.
There was a reduction of EGF-R mRNA to female levels when intact male rats were given hGH. An additional reduction of EGF binding levels was seen in both intact male and female rats exposed continuously to GH. This may indicate additional translational and/or post-translational regulatory mechanisms.
Dual effects of thyrotrophin-releasing hormone (TRH) on K+ conductance in frog pituitary melanotrophs. TRH-induced α-melanocyte-stimulating hormone release is not mediated through voltage-sensitive K+ channels
Authors: Louiset E. , Cazin L. , Lamacz M. , Tonon M.-C. , Vaudry H. 
Published: December 2008

ABSTRACT
Modulation of the activity of K+ channels by TRH and the possible involvement of this modulation in TRH-induced release of α-MSH were studied in cultured frog melanotrophs, using patch-clamp and perifusion techniques. Pars intermedia cells were enzymatically dispersed and cultured in Leibovitz medium. In order to test the viability of cultured cells, the amount of α-MSH released into the medium was measured by radioimmunoassay every day for 1 week of culture. The total amount of α-MSH released during the first 4 days of culture was 8·6 times higher than the intracellular content of α-MSH on day 1. Melanotrophs were identified by an indirect immunofluorescence technique using a specific antiserum to α-MSH. Recordings obtained in whole-cell, cell-attached and excised patch-clamp configurations showed that TRH induced a transient polarization concomitant with an increase in the probability of opening of Ca2+-activated K+ channels. This transient response was followed by a depolarization accompanied by an enhanced frequency of action potential discharge. TRH also induced a decrease in voltage-dependent K+ conductance. Application of tetraethylammonium, a K+ channel blocker, depolarized the cells and increased the basal secretory level without noticeable changes in TRH-evoked α-MSH release.
These results demonstrate that the neuropeptide TRH both stimulates Ca2+-sensitive K+ channels and inhibits voltage-dependent K+ current in pituitary melanotrophs. Our data indicate that TRH-induced secretion of α-MSH is not a direct consequence of the lowering of K+ conductance. It thus appears that basal and TRH-induced α-MSH release occur through distinct pathways; the spontaneous release of α-MSH is probably linked to membrane potential, while modulation of the electrical activity is not directly involved in TRH-induced activation of the secretory process.