bluuebunny/crossref_metadata_2025_split huggingface dataset:
The peroxisome proliferator-activated receptor:retinoid X receptor heterodimer is activated by fatty acids and fibrate hypolipidaemic drugs
Authors: Issemann I , Prince R A , Tugwood J D , Green S 
Published: December 2008

ABSTRACT
The peroxisome proliferator-activated receptor (PPAR) is a member of the steroid hormone receptor superfamily and is activated by a variety of fibrate hypolipidaemic drugs and non-genotoxic rodent hepatocarcinogens that are collectively termed peroxisome proliferators. A key marker of peroxisome proliferator action is the peroxisomal enzyme acyl CoA oxidase, which is elevated about tenfold in the livers of treated rodents. We have previously shown that a peroxisome proliferator response element (PPRE) is located 570 bp upstream of the rat peroxisomal acyl CoA oxidase gene and that PPAR binds to it. We show here that the retinoid X receptor (RXR) is required for PPAR to bind to the PPRE, and that the RXR ligand, 9-cis retinoic acid, enhances PPAR action. Retinoids may therefore modulate the action of peroxisome proliferators and PPAR may interfere with retinoid action, perhaps providing one mechanism to explain the toxicity of peroxisome proliferators. We have also shown that a variety of hypolipidaemic drugs and fatty acids can activate PPAR. This supports the suggestion that the physiological role of PPAR is to regulate fatty acid homeostasis, and provides further evidence that PPAR is the target of the fibrate class of hypolipidaemic drugs. Finally, we have demonstrated that a metabolically stabilized fatty acid is a potent PPAR activator, suggesting that fatty acids, or their acyl CoA derivatives, may be the natural ligands of PPAR.
Hormonal study of a human mixed follicular and medullary thyroid carcinoma
Authors: Massart C , Gibassier J , Lucas C , Le Gall F , Giscard-Dartevelle S , Bourdinière J , Moukhtar M S , Nicol M 
Published: December 2008

ABSTRACT
We studied the hormonal secretion of a human mixed follicular and medullary carcinoma. Thyroglobulin (Tg) secretion, especially by large cells and sometimes by small ones, was visualized with immunoenzymatic staining. Calcitonin (CT) was produced by small spindle-shaped cells. Moreover, immunofluorescence double staining performed on the resected thyroid tissue showed the secretion of both Tg and CT in a small number of cells. The cells lost their hormonal secretion after 2 months of culture. Hormonal secretion was modulated by different additives in the medium. Tg secretion was induced when TSH was added to the culture medium; the maximal effect was produced with the addition of 1 mU TSH/ml and 1 μm cortisol, which potentiated the effect of TSH on Tg production. A durable Tg secretion was obtained by embedding the cells in Engelbretch—Hohn—Swarn (EHS) tumour matrix. The CT production was reinduced by the addition of 4 mm Ca2+, 1 μm glucagon and 1 μm cortisol to the culture medium. These findings show that different cells are found in a mixed follicular and medullary carcinoma, some of which can secrete both CT and Tg. They can remain differentiated for a long period after being embedded in EHS tumour matrix with Ca2+ and hormonal components.
Role of oestradiol-17β in the regulation of synthesis and secretion of human chorionic gonadotrophin by first trimester human placenta
Authors: Sharma S C , Purohit P , Rao A J 
Published: December 2008

ABSTRACT
Inhibition of aromatase, a key enzyme in the biosynthesis of oestradiol-17β, by the addition of 1,4,6-androstatrien-3,17-dione resulted in a significant increase in the levels of immunoreactive human chorionic gonadotrophin (hCG) in the medium and tissue. This increase was partially reversed by the simultaneous addition of oestradiol-17β. These effects on the levels of immunoreactive hCG were also reflected by the increased levels of mRNA specific for the α and β subunits of hCG following the addition of the aromatase inhibitor. However, addition of tamoxifen resulted in a drastic decrease in the levels of both the messages. Based on these results, it is suggested that the synthesis of hCG is negatively modulated by oestradiol-17β in the human placenta.
Pit-1/GHF-1 expression in pituitary adenomas: further analogy between human adenomas and rat SMtTW tumours
Authors: Delhase M , Vergani P , Malur A , Velkeniers B , Teugels E , Trouillas J , Hooghe-Peters E L 
Published: December 2008

ABSTRACT
Adenomas can develop from each cell type of the anterior pituitary. In the normal pituitary, three of these cell types, the GH-, prolactin- and TSH-secreting cells, express the transcription factor Pit-1/GHF-1 which is responsible for prolactin and GH (and probably TSH) cell commitment, differentiation, probably proliferation and gene expression. We have analysed the expression of Pit-1/GHF-1 in a panel of human pituitary adenomas. All GH-, prolactin- and TSH-expressing adenomas studied expressed the Pit-1/GHF-1 factor, as demonstrated by in-situ hybridization and immunocytochemistry. The expression was higher in adenomas than in normal human pituitary. In contrast, ACTH- and LH—FSH-secreting and non-secreting adenomas were negative. Seven transplants of the spontaneous rat prolactinoma SMtTW were also investigated and all were found to be positive.
This further stresses the analogy between these tumours and human prolactinomas. Taken together, the data confirm that Pit-1/GHF-1 expression is restricted to GH-, prolactin- and TSH-expressing cells, and the increased expression in adenomas is compatible with a role of Pit-1/GHF-1 in cell proliferation.
Characterization of the mouse thyrotrophin-releasing hormone receptor gene: an exon corresponds to a deletion in the rat cDNA
Authors: Duthie S M , Taylor P L , Eidne K A 
Published: December 2008

ABSTRACT
The cloning and characterization of the mouse TRH receptor (TRH-R) gene revealed an untranslated exon (exon 1), a single intron and an upstream dinucleotide repeat sequence (d(TG)16.d(AG)21) in the 5′ untranslated region (UTR). The coding region was contained almost entirely on a second exon (exon 2), with the final amino acid and stop codon at the COOH terminus of the gene encoded by a third exon (exon 3) flanked by two introns. The 3′ UTR was contained on the remainder of exon 3 and on the final exon (exon 4). Exon 3 (228 bp) corresponds exactly to a 228 bp deletion that exists in the rat TRH-R cDNA, but not in the mouse cDNA.
The mouse TRH-R cDNA encodes a protein of 393 amino acids which is 96% homologous to the rat TRH-R protein of 412 amino acids, but is 19 amino acids shorter at its COOH terminus. The coding sequence for these 19 amino acids (plus 1 extra amino acid) does exist in the mouse TRH-R gene, but the sequence is encoded by exon 4, separated from the rest of the coding region by the stop codon and 223 bp of 3′ UTR on exon 3. Splicing of exon 3 in the mouse TRH-R gene would remove the last amino acid, the stop codon and the 223 bp of 3′ UTR, allowing transcription to continue into the 3′ UTR on exon 4, which encodes the 19 extra amino acids found in the rat cDNA. This would then result in an alternative 412 amino acid version of the mouse TRH-R protein, with 95% homology to the rat TRH-R. This study focused on the structural differences in the intracellular COOH-terminal tail of the receptor, which is known to be a functionally important domain in other members of the G protein-coupled receptor family. We have also recently characterized the human TRH-R cDNA, which revealed a third variant at the COOH terminus. Comparisons between mouse, rat and human TRH-Rs show that the amino acid sequences are virtually identical. However, significant differences between these species exist at the COOH terminus, with each TRH-R having a unique form of the COOH-terminal tail, beginning at exactly the same site and encoding 1, 20 and 6 amino acids in the mouse, rat and human respectively.
Expression of a functional thyroglobulin fragment in a baculovirus system
Authors: den Hartog M T , Sijmons C C , Kristel P M P , Bakker O , de Vijlder J J M 
Published: December 2008

ABSTRACT
The synthesis is described of an N-terminal thyroglobulin (Tg) polypeptide of 27 kDa, which is capable of hormonogenesis, in a baculovirus system. This polypeptide was made using a 657 bp Tg cDNA cloned from human thyroid RNA by a polymerase chain reaction method. The cDNA contained the information for the Tg signal peptide, the N-terminally located site for thyroid hormone formation and, at the 3′ end, a sequence coding for six histidine residues. The fragments produced were purified using a nickel—nitrilotriacetic acid column using these six histidine residues. The products were analysed by sodium dodecyl sulphatepolyacrylamide gel electrophoresis and showed two glycosylated fragments of 32 and 34 kDa, both of which started with asparagine. Iodination of the fragments with lactoperoxidase in vitro resulted in the formation of thyroxine (T4). The formation rate of T4 in the fragments was about five times lower than that of the mature Tg dimer of 660 kDa, but ten times more rapid than in bovine serum albumin under the same conditions.
Isolation- and dehydration-induced changes in neuropeptide gene expression in the sheep hypothalamus
Authors: Matthews S G , Parrott R F , Sirinathsinghji D J S 
Published: December 2008

ABSTRACT
Changes in neuropeptide gene expression in the hypothalami of sheep subjected to psychological stress (isolation, 1 h; n=3) or dehydration (48 h; n=3) were examined using in-situ hybridization histochemistry. Compared with non-stressed euhydrated control animals (n=3), isolation induced significant accumulation of mRNA for corticotrophin-releasing hormone, pro-enkephalin and pro-dynorphin (DYN) in the paraventricular nucleus (PVN), but no change in mRNA content within the supraoptic nucleus (SON). By contrast, dehydration significantly increased DYN mRNA in the magnocellular neurones of the PVN and SON. However, neither isolation nor dehydration altered the expression of mRNA for vasopressin (AVP) in either the PVN or the SON. These results indicate that in the ovine hypothalamus (1) stress represents a powerful stimulus to co-ordinated neuropeptide synthesis and (2) expression of DYN mRNA and AVP mRNA may be independently regulated during changes in plasma osmolality.
The porcine insulin-like growth factor-I gene: characterization and expression of alternate transcription sites
Authors: Weller P A , Dickson M C , Huskisson N S , Dauncey M J , Buttery P J , Gilmour R S 
Published: December 2008

ABSTRACT
Genomic DNA encoding the 5′ region of the porcine IGF-I gene was cloned and sequenced and shown to be highly homologous to that of man, rats and sheep. Two leader exons (exons 1 and 2), which are alternately spliced to exon 3 (encoding part of the mature IGF-I molecule), were identified by RNase protection analysis. In both cases, transcription initiates upstream from exons 1 and 2 at multiple dispersed start sites to yield two distinct IGF-I mRNA transcript classes (1 and 2) which differ in the precursor peptides predicted from their individual leader sequences.
The expression of class 1 and 2 transcripts was measured in liver and muscle RNA from two groups of 2-month-old pigs whose energy status had been manipulated within physiological limits to produce marked differences in plasma IGF-I levels and growth rates. For this purpose, RNase protection probes were developed that contained the individual leader exons 1 and 2 linked separately to the common exon 3, so that class-specific and total IGF-I gene expression could be determined in a single assay. At normal plasma IGF-I concentrations (200 ng/ml), class 1 and 2 transcripts comprised 81 and 19% respectively of total liver IGF-I mRNA, while at a lower plasma concentration (90 ng/ml) the corresponding values were 95 and 5% respectively. Although both classes of transcript declined with the decrease in plasma IGF-I, the relative drop in levels of class 2 transcripts (84%) was substantially greater than that of class 1 (54%). In longissimus dorsi, cardiac and soleus muscles IGF-I mRNA was predominantly of class 1 and did not change in response to decreased plasma IGF-I. This suggests that liver-derived endocrine IGF-I has an important function in the regulation of muscle growth and that class 2 IGF-I transcripts are more sensitive to conditions that promote optimal growth.
A trans-acting locus regulates transcriptional repression of the female-specific steroid 15α-hydroxylase gene in male mice
Authors: Aida K , Negishi M 
Published: December 2008

ABSTRACT
Steroid 15α-hydroxylase (P45015α) is a female-specific enzyme in the livers of many inbred mice including DBA/2J. Run-on assays using liver nuclei from GH-deficient Little mice indicated that the P45015α gene is transcriptionally repressed by GH in male mice. BALB/cJ is a variant strain in which the gene is expressed in the males as well as in the females. Genetic crosses between DBA/2J and BALB/cJ indicated that expression of the P45015α gene in BALB/cJ males is inherited as a recessive trait and is regulated by a single locus. The parental origin of the P45015α genes, determined using restriction site polymorphism in the exons of the P45015α genes, divided the F2 males expressing the P45015α gene into three phenotypes at a ratio of 1:1:2, the individuals expressing the gene from only BALB/cJ or DBA/2J and the individuals expressing the genes from both parents respectively. The results indicate that the repression of the P45015α gene in male mice is regulated by a trans-acting regulatory locus between the DBA/2J and BALB/cJ pairs. Because hypophysectomy derepressed the P45015α gene in Fl males and GH repressed the gene in hypophysectomized Fl males, the hormone appears to regulate gene repression through a trans-acting locus, named GH-dependent repression, GDR.
A monoclonal antibody to a conserved sequence in the extracellular domain recognizes the angiotensin II AT1 receptor in mammalian target tissues
Authors: Barker S , Marchant W , Ho M M , Puddefoot J R , Hinson J P , Clark A J L , Vinson G P 
Published: December 2008

ABSTRACT
We have generated hybridomas which secrete monoclonal antibodies to the AT1 subtype of the angiotensin II receptor (AT1 receptor). These were obtained after immunization of Balb C/c mice with synthetic peptides representing sequences from either the extracellular domain (residues 8-17) or the intracellular domain (residues 229-237) of the AT1 receptor.
Hybridoma populations were first screened for the production of antibodies which bound to rat liver cells. Further selection, and cloning by limiting dilution, was carried out for antibodies which bound specifically to rat adrenal glomerulosa cells. Confirmation that the antibody designated 6313/G2 interacted with the angiotensin II receptor was obtained using COS-7 cells transfected with AT1A receptor cDNA. In particular, the initial characterization of 6313/G2 showed specific immunofluorescence of vascular endothelium.
The hepatic receptor for sex steroid-binding protein: study on a non-malignant cell line (Chang liver)
Authors: Fortunati N , Becchis M , Fissore F , Berta L , Catalano M G , Orsello M , Gaidano G , Frairia R 
Published: December 2008

ABSTRACT
The binding of human sex steroid-binding protein (SBP), labelled with 125I, was studied on whole cultured liver cells (Chang liver cells). SBP was shown to bind to a receptor site on normal hepatocytes. The binding was time- and temperature-dependent, highly specific and of high affinity. The liver receptor recognizing SBP was demonstrated to be different from the asialoglyco-protein receptor; in addition, laminin, which is structurally related to SBP, could not bind to the receptor. SBP was shown to recognize two binding sites with different affinities; the low affinity site was shown to possess a remarkably high capacity. This characteristic, which until now has been described only for hepatocytes, could be related to the unique role of the liver with regard to both SBP and sex steroids.
Differential expression of non-allelic insulin genes in rodent islet tumour cells
Authors: Lund K , Blume N , Michelsen B K , Bucchini D , Madsen O D 
Published: December 2008

ABSTRACT
We have compared the expression patterns of the non-allelic insulin 1 and 2 genes during prolonged in-vitro culture of the mouse islet cell line β-TC3, where transformation by the SV40 T oncoprotein is targeted to the differentiated β-cell phenotype, and the rat islet cell line NHI-6F, in which the β-cell phenotype is induced by transient in-vivo passage. The NHI-6F clone carries, in addition, a single copy of a transfected silent human insulin gene which contains 3 kb of regulatory sequences known to confer β-cell-specific expression. Insulin gene expression was measured by an assay based on a reverse transcription-polymerase chain reaction, to determine whether the ancestral rodent insulin 2 genes (and the human homologue in the NHI-6F cells) are regulated differently from the duplicated rat and mouse insulin 1 genes.
We have shown that activation of insulin gene expression in the NHI-6F cells includes transcriptional activation of all three genes, but that extended propagation of tumour cells in vitro leads to a selective and equal decline in the quantities of transcripts from the rat 2 and human genes relative to transcripts from the rat 1 gene. In the later passages, insulin transcripts were derived almost exclusively from the rat 1 gene. In early in-vitro passages of the mouse endocrine cell line β-TC3, the expression pattern of the mouse 1 and 2 insulin genes resembled that seen in isolated mouse islets. After more than 45 in-vitro passages, expression of the duplicated mouse 1 gene decreased tenfold when compared with the ancestral mouse 2 gene. As previously shown for NHI-6F cells, the differential expression of non-allelic insulin genes in the β-TC3 line was also clearly evident at the cellular level, where a subpopulation of cells selectively expressed readily detectable levels of mouse C-peptide 2 immunoreactivity while devoid of C-peptide 1. Our results suggest that the maintenance of insulin gene expression in rodent tumour cells is influenced by enhancer sequences which are not shared by the ancestral and duplicated insulin genes, and that either species-specific conditions or transformation-related differences exist between the rat and mouse cell lines that govern which gene remains active during prolonged in-vitro propagation.
Direct effect of adenosine on prolactin secretion at the level of the single rat lactotroph: involvement of pertussis toxin-sensitive and -insensitive transducing mechanisms
Authors: Scorziello A , Landolfi E , Grimaldi M , Meucci O , Ventra C , Avallone A , Postiglione A , Schettini G 
Published: December 2008

ABSTRACT
We studied the effect of adenosine on prolactin secretion by the anterior pituitary, and the transduction mechanisms whereby the purine exerts its action. Adenosine inhibited prolactin release in basal and in vasoactive intestinal peptide (VIP)- or TRH-stimulated conditions. Pertussis toxin pretreatment reduced the inhibition of VIP-stimulated prolactin secretion which was induced by adenosine, while it completely abolished the effect of the purine on TRH-evoked prolactin release. In membrane preparations of anterior pituitary cells, adenosine reduced the adenylate cyclase activity stimulated by VIP. Such an inhibition was not blocked by pertussis toxin pretreatment.
Furthermore, the purine reduced TRH-stimulated inositol phosphate production in cultured anterior pituitary cells, an effect that was reversed by pretreatment with pertussis toxin. In addition, the nucleoside did not significantly affect the TRH-induced rise in intracellular calcium.
In conclusion, our data show that adenosine inhibits prolactin secretion, acting on purinergic receptors coupled to the adenylate cyclase enzyme and phospholipase C. The effect of the nucleoside on adenylate cyclase seems to be achieved either by the involvement of an adenosine receptor coupled to the catalytic subunit of the enzyme via a pertussis toxin-sensitive G protein, or by the activation of a site directly coupled to the catalytic subunit of the adenylate cyclase (the P site). Its effect on phospholipase C seems to be mediated by a purinergic receptor coupled to the intracellular effector via a pertussis toxin-sensitive G protein.
Insulin delivery by somatic cell gene therapy
Authors: Stewart C , Taylor N A , Docherty K , Bailey C J 
Published: December 2008

ABSTRACT
The feasibility of somatic cell gene therapy as a method of insulin delivery has been studied in mice. Murine pituitary AtT20 cells were transfected with a human preproinsulin DNA in a plasmid containing a metallothionein promoter and a gene conferring resistance to the antibiotic G418. The AtT20MtIns-1·4 clone of cells was selected because of its higher insulin-releasing activity compared with other clones. After culturing for 24 h in Dulbecco's medium containing 10 mM glucose, the AtT20MtIns-1·4 cells released human insulin at about 5 ng/106 cells per 24 h. Insulin release was not significantly altered by raised concentrations of glucose, potassium or calcium, but insulin release was increased by 20 mm arginine, 5 mm isomethylbutylxanthine and 90 μm zinc.
AtT20MtIns-1·4 cells (2 × 106) were implanted intraperitoneally into non-diabetic athymic nude (nu/nu) mice, and the mice were made diabetic by injection of streptozotocin after 7 days. Release of human insulin in vivo was assessed using a specific plasma human C-peptide assay. Human C-peptide concentrations were maintained at about 01 pmol/ml throughout the 29 days of the study. The development of streptozotocin-induced hyperglycaemia was delayed in recipients of the cells releasing human insulin, compared with a control group receiving an implant of non-transfected cells. At autopsy the implanted AtT20MtIns-1·4 cells in each recipient had formed a tumour-like aggregation, with an outer region of insulin-containing cells. The study suggests that somatic cell gene therapy offers a feasible approach to insulin delivery.
Cloning of a toad prolactin cDNA: expression of prolactin mRNA in larval and adult pituitaries
Authors: Takahashi N , Yamamoto K , Kikuyama S 
Published: December 2008

ABSTRACT
A toad (Bufo japonicus) prolactin cDNA was specifically amplified from cDNAs constructed from the total RNA of adenohypophyses, employing the DNA polymerase chain reaction. Sequencing analysis revealed that the cDNA clone thus obtained was 602 bp in length, and encoded the C-terminal 134 amino acid residues of the toad prolactin molecule. The length of the toad prolactin mRNA was estimated to be about 1·0 kb by Northern blot analysis. The partial amino acid sequence deduced from the nucleotide sequence showed the following homologies between toad prolactin and the prolactins of other vertebrates: 69% with man, 80% with chicken, 81% with sea turtle, 91% with bullfrog and 38% with salmon. Using the cDNA as a probe, developmental and seasonal changes in prolactin mRNA levels in the pituitaries of toads were studied. Prolactin mRNA in the pituitary rose as metamorphosis progressed and declined at the end of metamorphosis. During the breeding season the pituitary content of prolactin mRNA was relatively high. This finding suggests that the increases in plasma and pituitary prolactin levels in larvae at metamorphic climax and in adults that remain in or migrate into water, as reported previously, accompany the increase in prolactin synthesis.