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Biomedical subjects

W Born

Publications and source records attributed to W Born.

At least 91 records · Page 5Linked to original sources
PubMed1988

Identification of a receptor for calcitonin gene-related peptides I and II in human cerebellum.

Receptor proteins for human calcitonin gene-related peptide (CGRP) have been demonstrated in the human cerebellum. Membrane homogenates were incubated with [125I] iodo CGRP-I and -II ([125I]CGRP). The bound radioligands were cross-linked to membrane proteins. Solubilized membrane proteins were separated by gel-electrophoresis. Autoradiography of the gels revealed specifically labeled ligand-protein complexes of Mr 17,500 and 54,000 for human CGRP-I and -II. Specific binding of [125I]CGRP-I and -II was only minimally affected by up to 0.5 microM salmon and human calcitonin. The affinity and specificity of CGRP-I and -II binding were the same in crude homogenates and in the purified binding proteins. In conclusion, indistinguishable binding proteins for [125I]CGRP-I and -II of 13,700 and 50,000 Da have been identified in the human cerebellum.

Autoradiography↗
PubMed1988

Diversity of the mouse T cell receptor C gamma 1 gene: structural analysis in C57BL/Ka.

We have isolated an unusual T cell receptor gamma chain cDNA clone (gamma 7.1) from a library made from RNA derived from adult thymus of C57BL/Ka mice. This cDNA clone corresponds to the appropriately processed C gamma 1 constant region exons preceded by 1.5 kb of J-C gamma 1 intron. The gamma 7.1 coding region is extremely homologous to the C gamma 1 gene of BALB/c mice, differing at the protein level by a single deletion (alanine 139) and a single substitution. This latter change eliminates the sole N-linked sugar attachment site, providing a basis for strain-specific glycosylation patterns. The J-C gamma 1 intronic region contains two DNA segments (termed psi J gamma 1 and psi J gamma 2) that are highly reminiscent of joining (J) segments; both have potentially functional recombination and donor splice sequences flanking an open reading frame. Northern analysis suggests that gamma 7.1 may be derived from a large, variable region-containing precursor.

Amino Acid Sequence↗
PubMed1988

Calcitonin gene-related peptides I and II and calcitonin: distinct effects on gastric acid secretion in humans.

The human calcitonin gene-related peptides I and II (CGRP I and CGRP II) are two neuropeptides that have been recognized throughout the gastrointestinal system including the stomach. The present study was undertaken to compare in healthy volunteers the effects of intravenous infusions of CGRP I and CGRP II (79 pmol/kg.h) on pentagastrin-stimulated acid secretion to those of calcitonin (88 pmol/kg.h). Calcitonin gene-related peptide I did not inhibit basal or pentagastrin-stimulated acid secretion. However, CGRP II and calcitonin inhibited pentagastrin-stimulated acid responses by 20% and 28%, respectively (p less than 0.05 and p less than 0.01), whereas basal acid output was only reduced with calcitonin (p less than 0.05). These effects were recognized with low doses of pentagastrin, and absent with high doses suggesting competitive inhibition. Furthermore, step-doses of CGRP I and CGRP II (79-320 pmol/kg.h) were given intravenously on continuous pentagastrin stimulation and compared with calcitonin (88-352 pmol/kg.h). Calcitonin gene-related peptide II and calcitonin induced a dose-dependent decrease of acid output, whereas CGRP I was ineffective. The inhibitory effects of CGRP II and calcitonin are not due to increased gastric alkaline secretion or to somatostatin release, as neither peptide stimulated gastric bicarbonate secretion or induced an increase in circulating somatostatin. In conclusion, CGRP II, unlike CGRP I, inhibits gastric acid secretion in humans. Inhibitory effects of CGRP II and of calcitonin were comparable. The results imply that CGRP I and II, at the level of the stomach, have distinct biological properties in humans.

Adult↗
PubMed1988

Effect of calcitonin and calcitonin gene-related peptide on pancreatic functions in man.

Calcitonin gene-related peptide (CGRP) has recently been identified in central and peripheral nerve fibres, including those of blood vessels supplying the exocrine pancreas, and in pancreatic islet cells. Moreover, receptors have been characterised in the same tissue. The present study examined the effects of human CGRP and of calcitonin on exocrine pancreatic secretion and on islet cell function in nine healthy volunteers. CGRP (300 ng/kg/h) caused, respectively, a 25% and 31% inhibition of caerulein stimulated trypsin and amylase output which was similar to that seen with calcitonin (300 ng/kg/h). Arginine stimulated insulin and glucagon release was unaffected by either CGRP, or calcitonin. Calcitonin gene-related peptide caused cutaneous flushing, but did not affect the pulse rate or arterial blood pressure in the doses tested. Calcitonin gene-related peptide inhibits exocrine pancreatic secretion in vivo in man, but does not affect islet cell hormone release.

Adult↗
PubMed1988

Calcitonin gene-related peptide is a stimulator of renin secretion.

Calcitonin gene-related peptide (CGRP) was found to stimulate renin secretion in vivo in normal human volunteers. Moreover, CGRP stimulated the release of renin in vitro from isolated rat renal juxtaglomerular cells (half-maximal effective concentration [EC50] 100 nM) concomitant with stimulation of cAMP production (EC50 60 nM). Immunoreactive CGRP was recognized in rat renal cortical nerve fibers, and intact rat CGRP was identified in extracts of the rat renal cortex. Because CGRP containing sensory nerve fibers are seen in the region of the juxtaglomerular apparatus, it would seem that the release of CGRP from these afferent nerves may be involved in the physiological control of renin secretion.

Animals↗
PubMed1988

Inhibition of parathyroid hormone bioactivity by human parathyroid hormone (PTH)-(3-84) and PTH-(8-84) synthesized in Escherichia coli.

Human PTH (hPTH)-(3-84) and hPTH-(8-84) were synthesized in Escherichia (E.) coli when the cells were transformed with a multicopy plasmid in which the transcription of human preproPTH cDNA is directed by the E. coli lac promoter. PTH fragments were extracted from cells and purified by reverse phase HPLC. PTH bioactivity and PTH antagonist activity were estimated in a renal cytochemical bioassay. hPTH-(3-84) and hPTH-(8-84) exhibited less than 1% and less than 0.1%, respectively, of the biological activity of synthetic hPTH-(1-84). hPTH-(8-84) had 1% of the PTH inhibitory activity of synthetic [Nle8,18,Tyr34]bovine PTH-(3-34)amide, whereas hPTH-(3-84) was 100 times more active as a PTH inhibitor than the synthetic bovine PTH-(3-34) analog. The latter has so far been recognized as the most potent PTH antagonist in vitro. A 5-fold molar excess of hPTH-(3-84) over hPTH-(1-84) completely blocked the biological action of intact hPTH-(1-84) in the renal cytochemical bioassay. These findings suggest that the carboxyl-terminal portion of the intact hPTH-(1-84) molecule contributes importantly to inhibitor potency.

Animals↗
PubMed1987

Expression and role of the T cell receptor in early thymocyte differentiation in vitro.

Fetal thymus organ culture was used to study the expression and function of antigen-specific, major histocompatibility complex-restricted receptors on thymocytes. Receptor gene rearrangement and expression occurred de novo in organ culture indicating that these events are induced in the thymus itself, presumably in response to thymus-derived stimuli. During organ culture a population of immature thymocytes expressing low levels of receptors developed first, and then diminished as mature thymocytes with high levels of receptor expression appeared. Continuous culture with antireceptor antibody modulated receptor from the surfaces of immature thymocytes, but did not prevent their appearance or accumulation. By contrast, appearance of receptor-bearing mature thymocytes was prevented in the presence of antireceptor antibody. These results indicate that the receptor is not essential for the generation of immature thymocytes but is involved in the selection or maintenance of mature cells from this pool.

Animals↗
PubMed1987

Identification in the human central nervous system, pituitary, and thyroid of a novel calcitonin gene-related peptide, and partial amino acid sequence in the spinal cord.

Two human genes encoding precursors for two calcitonin gene-related peptides (CGRP) I (or alpha) and II (or beta) have been identified (Steenbergh, P. H., Höppener, J. W. M., Zandberg, J., Lips, C. J. M., and Jansz, H. S. (1985) FEBS Lett. 183, 403-407). The amino acid sequence of CGRP-I was obtained in medullary thyroid carcinoma extracts (Morris, H. R., Panico, M., Etienne, T., Tippins, J., Girgis, S. I., and MacIntyre, I. (1984) Nature 308, 746-748), but not in normal human tissues. The human CGRP-II peptide remained to be discovered. Here we have determined in the human spinal cord the amino acid composition and the partial amino acid sequence of the DNA-predicted CGRP-I and -II. The data indicate for the first time the existence of a second CGRP different from the known CGRP-I. CGRP-II has been identified in the central nervous system, pituitary, thyroid, and in medullary thyroid carcinoma as a major CGRP form together with CGRP-I.

Amino Acid Sequence↗
PubMed1987

Signal sequence of human preproparathyroid hormone is inactive in yeast.

The biosynthesis of human preproparathyroid hormone (hpreproPTH) and the processing to mature parathyroid hormone (hPTH) was investigated in yeast. Cells were transformed with a plasmid that carried a fusion gene made of the yeast pyruvate kinase promoter, complementary DNA (cDNA) encoding a slightly modified form of hpreproPTH and the transcription termination signal from yeast triosephosphate-isomerase. In transformed yeast cells we identified a protein that was recognized by a PTH antiserum and, on gel electrophoresis, comigrated with hpreproPTH marker. The amino-terminal sequence of the protein was consistent with that of hpreproPTH, indicating that the hormone precursor is not processed. It was localized inside the cell, when analyzed in pulse-chase experiments by trypsin accessibility in intact and lysed spheroplasts. In contrast, when mRNA from these yeast cells and from human parathyroid tissue was translated into preproPTH in a reticulocyte lysate supplemented with canine pancreatic microsomes, the preproPTHs from both mRNAs were transported and cleaved with identical efficiencies. We conclude that hpreproPTH is synthesized in yeast but not recognized and processed like a precursor of a secreted protein by the yeast secretory apparatus.

Animals↗
PubMed1987

Role of cytosolic free calcium concentration in the secretion of calcitonin gene-related peptide and calcitonin from medullary thyroid carcinoma cells.

Calcitonin gene-related peptide (CGRP) and calcitonin (CT) are secreted by medullary thyroid carcinoma (MTC). Relationships between extracellular calcium ([Ca2+]e), cytosolic free calcium ([Ca2+]i) (as measured with fura-2), and secretion of immunoreactive CGRP and CT have been investigated in rat and human MTC cell lines. Rat MTC 6-23 cells responded to a rise in [Ca2+]e from 0.5 to 3.0 mM with a transient increase of [Ca2+]i, and the secretion of CGRP and CT was raised from 19 +/- 2 (mean +/- SE) to 122 +/- 28 pg rat CGRP/mg protein . min and from 33 +/- 8 to 155 +/- 42 pg rat CT/mg protein . min (P less than 0.01). In the human MTC (TT) cell line, a rise of [Ca2+]e from 0.5 to 3.0 mM did not affect [Ca2+]i, and the secretion of CGRP and CT remained unchanged at 7.0 +/- 1.1 ng CGRP/mg protein . min and 1.0 +/- 0.1 ng CT/mg protein . min. However, when the plasma membrane was bypassed by electropermeabilization, the release of CGRP and CT was stimulated by calcium with an ED50 of 0.5 microM and 0.3 microM, respectively. With ionomycin, the secretion of CGRP and CT was also stimulated up to 17-fold in [Ca2+]i-dependent manner. The results indicate a role of [Ca2+]i in the secretion of CGRP and CT and provide evidence for a defect in Ca2+ signal transduction in the human MTC cell line.

Animals↗
PubMed1987

Expression of the second calcitonin/calcitonin gene-related peptide gene in Ewing sarcoma cell lines.

The existence of two closely related calcitonin (CT)/CT gene-related peptide (CGRP) genes has been recognized in rat and man. In man, expression of the CALC-I gene produces CT and/or CGRP-I mRNA, whereas CGRP-II mRNA is transcribed from the CALC-II gene. Until recently, expression of the CALC-II gene had been detected only in a metastasis of medullary thyroid carcinoma. In this study, expression of the CALC-II gene was demonstrated by Northern blot hybridization analysis in four of six cell lines established from different Ewing sarcomas, a malignant neoplasm of bone. Expression of the CALC-I gene was not detected in any of the six cell lines. A presumed large mol wt immunoreactive precursor of CGRP-II and small amounts of mature CGRP-II, but no CT, were found in medium from IARC/EW 1 cells. Nucleotide sequence analysis of cloned cDNA from this cell line confirmed the production of CGRP-II mRNA. CALC-II gene expression in Ewing sarcoma might be useful for studies concerning regulation of gene expression in the CALC gene family and possibly for tumor classification.

Base Sequence↗
PubMed1987

Human preproparathyroid hormone synthesized in Escherichia coli is transported to the surface of the bacterial inner membrane but not processed to the mature hormone.

cDNA encoding human preproPTH (hpreproPTH) was expressed in Escherichia coli to study the processing of the precursor to hPTH and its secretion by the bacterial secretory apparatus. We first constructed hybrid genes that differed randomly in the distance between the E. coli lac promoter's ribosomal binding site and DNA encoding a fusion protein with beta-galactosidase activity and the prepro sequence of hpreproPTH on the aminoterminus. Starting with clones identified as efficient producers of beta-galactosidase on indicator agar plates, the coding sequence for hpreproPTH was reconstituted intact. In a different construction we placed the hpreproPTH coding sequence downstream from the lac promoter at a distance of 12 base pairs from the ribosomal binding site. PTH immunoreactive proteins from multiple clones were identified by protein gel electrophoresis and by protein microsequencing. PTH-related proteins encoded by different plasmids were shown to be hpreproPTH with amino-terminal extensions of either two or four amino acids and as authentic hpreproPTH. Two hPTH fragments, hPTH(3-84) and hPTH(8-84), were also observed. The trypsin accessibility of hpreproPTH and of the two hPTH fragments in pulse-chase, cell-fractionation experiments using intact and lysed spheroplasts lets us conclude that the mammalian signal sequence directs hpreproPTH to the surface of the spheroplast membrane but is not appropriately cleaved by the signal peptidase.

Animals↗
PubMed1987

Replicative and repair DNA synthesis after solar damage.

It is possible to enhance the individually maximal spontaneous extent of unscheduled DNA synthesis after ultraviolet light damage in human skin by 40% using topical pretreatment with bifidus fraction compounds (7,8,9). This new and biological method of active radiation protection (4,5,7), has been shown to be unaffected by any artificially produced findings due to hydroxyurea, butyrates of misinterpreted thymidine labels from replicative SDS and repair UDS. The original experimental results could be reproduced also by others, even using completely different test methods. Obviously, the results are dependent on an appropriate topical compound allowing sufficient release and penetration.

DNA Repair↗
PubMed1986

Separation of inhibitory activity from biologically active parathyroid hormone in patients with pseudohypoparathyroidism type I.

Patients with pseudohypoparathyroidism type I have the symptoms of hypoparathyroidism despite elevated levels of immunoreactive parathyroid hormone (PTH). However, the circulating levels of bioactive PTH, as measured in a cytochemical bioassay, are generally within the normal range suggesting that the high levels of immunoreactive PTH are either due to the presence of biologically inactive fragments of parathyroid hormone or to the presence of an 'inhibitor' of PTH bioactivity. Gel-permeation chromatography has been used to fractionate plasma from patients with pseudohypoparathyroidism type I and revealed the presence of high levels of bioactive PTH and of an 'inhibitor'. This inhibitory activity was absent or much lower in plasma from control subjects. These results indicate, therefore, that in pseudohypoparathyroidism type I the expression of the biological activity of PTH at the level of the kidney is affected by the presence of a circulating inhibitor which can be separated from intact PTH by gel-permeation chromatography.

Adolescent↗