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W Born

Publications and source records attributed to W Born.

At least 109 records · Page 6Linked to original sources
PubMed1986

Biosynthesis of calcitonin gene-related peptide and calcitonin by a human medullary thyroid carcinoma cell line.

cDNA analyses predict that the human calcitonin gene encodes the two precursor proteins of calcitonin and calcitonin gene-related peptide (CGRP). The mRNAs for the putative precursors of these peptides are derived from alternative processing of the primary transcript of this gene. The 75 amino-terminal residues of each preprohormone are predicted to be identical. We have developed the TT human medullary thyroid carcinoma cell line as a model to study human calcitonin gene expression. Mature calcitonin and CGRP are major secretory products of this cell line. Extracts of TT cells radiolabeled with amino acids for 1 h contained only one peak of either immunoprecipitable calcitonin or CGRP on reverse-phase high-pressure liquid chromatography. Each of these species had an Mr = 12,800 as estimated by gel filtration chromatography. The results of partial amino-terminal microsequencing of these two precursors were identical. Residues 2, 11, and 14 of each precursor were proline, and residues 7, 17, 24, 25, 26, and 29 were leucine. The unique alignment of the positions of these amino acids with the cDNA-predicted sequence for the common region of preprocalcitonin and preproCGRP suggests that the site of signal sequence cleavage occurs after residue 25 of both preprophormones. These studies represent the first identification of procalcitonin (116 amino acids) from a human cell line and of proCGRP (103 amino acids) from any tissue.

Amino Acid Sequence↗
PubMed1986

Synchronized rearrangement of T-cell gamma and beta chain genes in fetal thymocyte development.

Kinetics of mouse T-cell gamma gene rearrangements in ontogeny were determined as an approach to understanding the possible role of these genes in the development of fetal thymocytes. Two of these genes (C gamma 1 and C gamma 2) rearranged rapidly during days 14 to 17 of the gestational period in BALB/c mice. Moreover, these rearrangements seemed to be tightly synchronized with rearrangements of T-cell receptor beta chain genes in the same cells. It is suggested that the early transcriptional activity of gamma genes, which precedes that of beta chain genes, may not reflect the functional activation of these genes. Nevertheless, productive and therefore potentially functional gamma gene rearrangements precede surface expression of T-cell receptors in the thymus by 2 to 3 days, which is compatible with a role for gamma gene products in thymocyte development prior to antigen-specific stages.

Age Factors↗
PubMed1986

The role of the T-cell receptor in thymocyte maturation: effects in vivo of anti-receptor antibody.

The T-cell receptor, which recognizes antigen plus a product of the major histocompatibility complex, has been postulated to drive T-cell maturation in the thymus by engaging major histocompatibility complex proteins expressed on thymic stromal cells. We tested this idea by injecting neonatal animals with an anti-receptor antibody, KJ16, that binds to about 20% of T cells and is capable of blocking receptor function. In the presence of this antibody, mature T cells bearing the KJ16 epitope failed to develop. On the other hand, although the antibody could be shown to bind to receptors on cortical thymocytes, it did not prevent the rapid expansion or survival of the bulk of the KJ16+ cells in this population. These results are consistent with the hypothesis that most cortical thymocytes arise by a receptor-independent mechanism and that only a small proportion of these cells mature by a process dependent on receptor-major histocompatibility complex interactions.

Animals↗
PubMed1985

Novel peptides from the calcitonin gene: expression, receptors and biological function.

Calcitonin gene products include calcitonin and its carboxyl-terminal flanking peptide (in man PDN-21), and calcitonin gene-related peptide (CGRP). Alternative splicing of the initial gene transcripts results in the production of two distinct messenger RNA encoding precursors of CGRP and of calcitonin. CGRP messenger RNA is the predominant transcription product of the calcitonin gene in neural tissues, but it is also present in the pituitary and the C-cells of normal thyroid glands and in medullary thyroid carcinoma. Immunoreactive CGRP has, moreover, been recognized around blood vessels of the heart. Calcitonin and PDN-21 are cosecreted from thyroid C-cells, but they are also found in the brain and pituitary. CGRP receptors are present in the brain and the heart, and calcitonin receptors in bone and kidney cells and in the hypothalamus. Calcitonin administered peripherally and in vitro inhibits bone resorption and stimulates renal 1.25-dihydroxycholecalciferol production. CGRP used in the same manner has potent cardiovascular effects (vasodilation, hypotension, positive chronotropic and inotropic action in the heart). Intracerebroventricular administration of CGRP raises the blood pressure, and both CGRP and calcitonin inhibit gastric acid secretion and food intake. The distinct but overlapping effects of calcitonin and CGRP raise important regulatory and functional issues.

Amino Acid Sequence↗
PubMed1985

Rearrangement of T-cell receptor beta-chain genes during T-cell development.

The kinetics and order of rearrangements in the gene complex encoding T-cell-receptor beta chains were studied by Southern blot hybridization in a collection of hybridomas derived from fetal thymocytes at various stages of ontogeny (day 14 to day 17). Our results show a steady increase in the frequency of rearranged beta complexes during this period and suggest that these rearrangements occur within the thymus. beta-chain diversity region (D beta) to beta-chain joining region (J beta) joining preceded other types of rearrangements. More complex hybridization patterns consistent with fully rearranged functional beta-chain genes did not begin to accumulate until day 16, 1 day prior to significant surface expression of the receptor protein.

Age Factors↗
PubMed1985

Diagnostic evaluation of measurements of carboxyl-terminal flanking peptide (PDN-21) of the human calcitonin gene in human serum.

Calcitonin and its carboxyl-terminal flanking peptide (PDN-21), also encoded by the calcitonin gene, were measured by RIA in unextracted serum of normal subjects and patients with primary hyperparathyroidism and surgically verified and suspected medullary thyroid carcinoma. Serum PDN-21 was detectable (greater than 0.005 ngeq/ml) in the large majority of normal subjects (92%), and the values increased significantly more in men than women (4.8- and 2.0-fold, respectively; P less than 0.01) in response to 1-min iv calcium injections. Calcitonin was detectable (greater than 0.025 ngeq/ml) in only 25% of normal subjects before iv calcium and became measurable after iv calcium in 88% of men and 41% of women. In patients with chronic hypercalcemia due to primary hyperparathyroidism, PDN-21 and calcitonin were within normal limits. In normal subjects, iv pentagastrin (0.5 microgram/kg BW) did not increase PDN-21, and calcitonin remained undetectable. In 41 medullary thyroid carcinoma patients, basal PDN-21 and calcitonin levels were increased similarly, and they were stimulated in response to iv calcium or iv pentagastrin. In 5 siblings of medullary thyroid carcinoma patients, PDN-21 and calcitonin were increased in response to iv pentagastrin, and we suspect C-cell hyperplasia or medullary thyroid carcinoma. In conclusion, a diagnostically useful RIA for the measurement of PDN-21 in unextracted serum which complements calcitonin measurements has been developed.

Adolescent↗
PubMed1983

Killer-cell lines derived from mouse thymus, resembling large granular lymphocytes and expressing natural killer-like cytotoxicity.

Murine thymus cells were maintained in vitro with supernatant-factors derived from Concanavalin-A-stimulated spleen cells. After an initial phase of vigorous proliferation, large granular cells (GC), which were not observed in fresh thymus cell preparations, appeared in these cultures. GC, derived from C3Hf/Tif-, BALB/c-, and C57BL/10-thymus cultures, could be slowly expanded and have been maintained as increasingly homogeneous (oligoclonal) lines for up to six months. During this time, other types of thymus cells died or were diluted out. Thymic GC differ functionally and histochemically from macrophages and mast cells. They do not phagocytize zymosan particles, bind opsonized SRBC, express nonspecific esterases or contain detectable amounts of histamine. GC share many features with natural killer (NK) cells and large granular lymphocytes (LGL). One morphologically representative line (C3Hf/Tif) had the following surface phenotype: Thy-1+, Lyt-1-, Lyt-2-, H-2K+, I-A-, asialo Gm1+. GC bind peanut agglutinin (PNA) on their surface and contain azurophilic granules. These cytoplasmic granules are considerably larger than those in LGL. Cells of a GC line derived from mouse strain C3Hf/Tif (H-2k) lysed the NK-sensitive YAC-1 (H-2a) and EL-4 (H-2b), but not the NK-insensitive P815 cells.

Animals↗
PubMed1983

Rapidity of plasma 1,25-dihydroxyvitamin D responses to hypo- and hypercalcemia in steers.

Experiments were designed to study the rapidity of changes in plasma 1,25-dihydroxyvitamin D [1,25-(OH)2D] levels in response to hypercalcemia and hypocalcemia induced by 10-h infusions of CaCl2 or EGTA in steers. In response to CaCl2 infusions, 1,25-(OH)2D was decreased within 4 h (P less than 0.05) and remained lower (P less than 0.05) than preinfusion concentrations for up to 14 h after termination of the infusions. PTH and inorganic phosphate (Pin) transiently decreased in response to the CaCl2 infusions, whereas total magnesium (Mg) continuously fell for up to 24 h after the start of the infusions. In response to infusions with EGTA, on the other hand, 1,25-(OH)2D continuously increased and was raised significantly (P less than 0.05) between 12 and 24 h after the start of the infusions. PTH increased within 2 h (P less than 0.05) and remained elevated (P less than 0.05) for up to 2 h after the end of the EGTA infusions, whereas Pin and Mg were not significantly changed. During and after 10-h control infusions of sodium chloride, the levels of 1,25-(OH)2D, PTH, Ca, Ca++, Pin, and Mg remained unaltered. In conclusion, plasma levels of 1,25-(OH)2D were lowered in response to hypercalcemia within 4 h and increased in response to hypocalcemia within 12 h. After termination of the infusions with CaCl2 or EGTA, levels of 1,25-(OH)2D remained decreased or elevated for at least 14 h, even though Ca, Ca++, and PTH levels were normalized. The slow changes in 1,25-(OH)2D contrast with the rapid responses of PTH to hyper- and hypocalcemia.

Animals↗
PubMed1983

Identification and characterization of calcitonin forms in plasma and urine of normal subjects and medullary carcinoma patients.

Different immunoreactive calcitonin (CT) forms were identified by a reversed phase high performance liquid chromatography gradient system in plasma and urine of normal subjects. The separated CT components were characterized by chemical and enzymatic methods and found to be identical in normal subjects and medullary thyroid carcinoma patients. Of seven major CT forms we identified monomeric human CT-(1-32), its sulfoxide form, and dimeric CT in plasma. The monomeric, but not the dimeric form, was also detected in urine. A predominant CT component in plasma with a molecular weight of about 12,000 may correspond to a biosynthetic precursor of the hormone.

Calcitonin↗
PubMed1983

A new bioactive form of human calcitonin.

Distinct immunoreactive forms of calcitonin (CT), extracted with 2 M acetic acid from two pancreatic tumors, were characterized and identified by gel permeation chromatography and by reverse-phase high-performance liquid chromatography. The extracted CT forms were compared to CT obtained from medullary thyroid carcinoma and from normal thyroid glands, and were, furthermore, analyzed in a rat hypocalcemic bioassay. On gel filtration analysis, two broad peaks coeluting with synthetic human CT-(1-32) and extracted dimeric CT, respectively, were found in variable amounts. An acetonitrile gradient high-performance liquid chromatography system revealed two to three predominant CT peaks. Biologically active monomeric and dimeric CT and the biologically inactive sulfoxide form of human CT-(1-32) have been identified. Moreover, we have detected for the first time a new biologically active CT-like component which was most prominently recognized in a benign pancreatic tumor.

Aged↗
PubMed1982

Identity of calcitonin extracted from normal human thyroid glands with synthetic human calcitonin-(1-32).

Calcitonin in human thyroid glands obtained at autopsy from normal subjects were extracted with 2 M acetic acid. The extracts were additionally purified by adsorption to Sep-Pak C18 cartridges, and calcitonin was identified after gel filtration analysis, reverse-phase high-performance liquid chromatography (HPLC), thin-layer chromatography and isoelectric focusing. The purification steps were monitored by radioimmunoassay, and partially purified calcitonin was used for biological and physicochemical comparison with synthetic human calcitonin-(1-32) and its Met8-sulfoxide form. On gel filtration analysis a predominant peak coeluted with the synthetic hormone, and on HPLC two discrete peaks with the retention times of monomeric and dimeric human calcitonin were found. Thin-layer chromatography allowed the detection of two peaks with the Rf of human calcitonin-(1-32) and of its sulfoxide, respectively. The pI (7.9) of the predominant peaks of synthetic calcitonin were identical. Our findings provide strong evidence that the predominant forms of human calcitonin extracted from normal thyroid glands correspond to synthetic calcitonin-(1-32) and to dimeric calcitonin.

Calcitonin↗
PubMed1982

Leydig cells nonspecifically suppress lymphoproliferation in vitro: implications for the testis as an immunologically privileged site.

We have studied the influence of mouse testis cells on unstimulated lymphoproliferation; on allogeneic mixed lymphocyte reaction; and on concanavalin A-stimulated, phytohemagglutinin-stimulated, or lipopolysaccaride-stimulated responses in vitro. Co-culture with highly enriched irradiated (2000 R) Leydig cells (LC) led in each case to a considerable reduction of 3H TdR uptake. Prolonged tissue graft survival times suggest that the testis is an immunologically privileged site. This may be explained by an immune-suppressive function of LC in vivo. LC are also capable of selectively binding lymphoid and myeloid cells to their surface. This capacity, accompanied by a suppression of immune reactivity in situ, may play a role in cases of testicular relapse observed in acute leukemia.

Animals↗
PubMed1982

Potassium stimulates parathyroid hormone release from perifused parathyroid cells.

A method for perifusing dispersed bovine parathyroid cells is described. Using this approach, we have studied the effects of raised extracellular potassium and ouabain on calcium-regulated parathyroid hormone (PTH) secretion in vitro. Decreasing calcium from 1.5 to 0.5 mM stimulated PTH release within 5-10 min, and the increased secretory rate was maintained for the duration of the low calcium administration. High potassium (60 mM) promptly stimulated PTH secretion at 1.5 mM calcium. The effect of high potassium was more transient than that of low calcium. Raised potassium significantly enhanced the response to 0.5 mM calcium. Ouabain (10(-3) M) had no significant effect at 1.5 mM calcium, but depressed the secretory response to 0.5 mM calcium. In conclusion, the effect of raised potassium on parathyroid cells is qualitatively similar to its effect on other endocrine and exocrine systems.

Animals↗
PubMed1981

[The differential diagnosis of hypercalcitoninism].

Plasma levels of calcitonin (CT) are highest in patients with medullary thyroid carcinoma (MTC). Plasma CT is also raised in some patients with carcinoma such as that of the breast, the lung or the pancreas, and in pheochromocytoma. It must be kept in mind, however, that plasma CT can be similarly raised in patients with renal failure, non-tumoral pulmonary disease or acute pancreatitis. In hypercalcemia patients with primary hyperparathyroidism the plasma CT is normal or only marginally elevated. It is speculated that the raised levels in pregnant and lactating women and in new-born infants prevent excessive bone destruction at times of greater physiological need for calcium. Larger molecular weight forms than monomeric CT (1--32) are circulating at least in plasma of patients with calcitonin-producing tumors and in renal insufficiency. The biological function of these larger molecular weight forms is not yet known. The discrepancies among the results of different laboratories can in part be explained by the immunoheterogeneity of the hormone and the different antigenic recognition sites of the antisera used. The measurement of plasma CT levels is nevertheless important for the diagnosis of MTC and may prove useful in some patients with malignant tumors unrelated to the C-cells of the thyroid gland. CT-radioimmunoassay may be improved by using antibodies specific to the different forms of circulating calcitonin.

Adult↗