Search PubMed⌕ Search

Biomedical subjects

J A Fischer

Publications and source records attributed to J A Fischer.

At least 109 records · Page 6Linked to original sources
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

Substance P and calcitonin gene-related peptide: immunohistochemical localisation and microvascular effects in rabbit skeletal muscle.

1. The distribution and microvascular effects of substance P (SP) and calcitonin gene-related peptide (CGRP) were studied in the rabbit tenuissimus muscle using immunohistochemistry and intravital microscopy. 2. Individual fibers within nerve bundles and along blood vessels in the muscle were found to be immunoreactive (IR) for both SP and CGRP, thus showing an apparently complete coexistence for these peptides. In dorsal root ganglia most SP-positive cells were also CGRP-IR, but the latter cells were somewhat more numerous than SP-IR cells. 3. When applied topically to the muscle, both SP and CGRP increased blood flow in a dose-dependent manner, but CGRP was more potent and caused responses of longer duration. Both SP and CGRP dilated transverse arterioles, but they had little or no effect on the smaller terminal arterioles. This resulted in a redistribution of blood flow to the connective tissue adjacent to the muscle. 4. SP, but not CGRP, elicited vigorous vasomotion in larger arterioles and caused the formation of aggregates of platelets and leukocytes in the venules. Neither flow increase, nor vasomotion or aggregate formation were influenced by pretreatment of the animals with mepyramine, cimetidine or indomethacin. Capsaicin (1 microM) had a powerful effect on transverse arterioles resembling that of both SP and CGRP. 5. It is concluded that some of the vascular effects hitherto ascribed to SP on the basis of nerve stimulation and application of capsaicin might, at least in part, be due to release of CGRP.

Animals↗
PubMed1987

Primary sensory neurons of the rat showing calcitonin gene-related peptide immunoreactivity and their relation to substance P-, somatostatin-, galanin-, vasoactive intestinal polypeptide- and cholecystokinin-immunoreactive ganglion cells.

By use of the indirect immunofluorescence technique the distribution of calcitonin gene-related peptide (CGRP)-like immunoreactivity (LI) has been analyzed in cervical and lumbar dorsal root ganglia of untreated and colchicine-treated rats. In addition, lumbar ganglia were examined 2 weeks after transection of the sciatic nerve. The occurrence of CGRP-positive cells in relation to ganglion cells containing substance P-, somatostatin-, galanin-, cholecystokinin (CCK)-, and vasoactive intestinal polypeptide (VIP)/peptide histidine isoleucin (PHI)-LI has been evaluated on consecutive sections as well as using elution-restaining and double-staining techniques. CGRP-LI was observed in many ganglion cells of all sizes ranging in diameter from 15 microns to 65 microns. Thus, this peptide occurs also in the large primary sensory neurons. In contrast to the sensory peptides described to date, CGRP-positive cells constituted up to 50% of all and 70% of the medium-sized neurons, thus being the most frequently occurring peptide in sensory neurons so far encountered. Subpulations of CGRP-positive neurons were shown to contain substance P-, somatostatin-, or galanin-LI and some CGRP-positive neurons contained both substance P- and galanin-LI. In fact, most substance P-, somatostatin- and galanin-positive cell bodies were CGRP-immunoreactive. The coexistence analysis further revealed that galanin and substance P often coexisted and that some cells contained both substance P- and somatostatin-LI, whereas no coexistence between galanin and somatostatin has as yet been seen. VIP/PHI-LI was only shown in a few cells in untreated or colchicine-treated rats. However, after transection of the sciatic nerve numerous VIP/PHI-positive cells were observed, some of which also contained CGRP-LI. The present results indicate that a CGRP-like peptide is present in a wide range of primary sensory neurons probably not related to specific sensory modalities. Often this peptide coexists with other biologically active peptides. Taken together these findings suggest that CGRP may have a generalized function.

Animals↗
PubMed1987

Vasodilatory effects and coexistence of calcitonin gene-related peptide (CGRP) and substance P in sensory nerves of cat dental pulp.

Substance P (SP)- and calcitonin gene-related peptide (CGRP)-immunoreactivity (-IR) were localized by immunohistochemistry in the same nerve cell bodies in the trigeminal ganglia as well as in nerve terminals of the dental pulp. The distribution of SP- and CGRP-IR nerves were identical in the dental pulp and mainly associated with blood vessels. The level of CGRP-IR in the dental pulp, as measured by radio-immunoassay (RIA), was 1.4 +/- 0.2 pmol g-1 wet wt, which is in the same range as that found for substance P. Local intra-arterial infusion of synthetic CGRP and substance P produced vasodilatation in the dental pulp as measured by both laser Doppler flowmetry and an 125I clearance technique. The CGRP was effective as a vasodilator when infused in the femtomole per minute range, and SP in the picomole range. The effect of CGRP (50 fmol min-1) was 10 times larger when given after SP (15 pmol min-1) than before it. Since the two peptides coexist in the same neurons, it is suggested that they both contribute to the vasodilation seen upon antidromic stimulation of sensory nerves.

Animals↗
PubMed1987

Cardiovascular effects of calcitonin gene-related peptides I and II in man.

Calcitonin gene-related peptide (CGRP) is present in sensory nerve fibers in the heart and around peripheral arteries. On interaction with specific CGRP binding sites and activation of adenylate cyclase, CGRP causes vasodilation and has positive inotropic and chronotropic effects on the heart. In the present study, human CGRP I and II exerted positive inotropic effects on isolated human right auricles and relaxed small arteries from human skeletal muscle precontracted with norepinephrine (EC50 for CGRP I 0.59 nM and for CGRP II 0.37 nM). CGRP I and II (3.2 nmol) administered i.v. to 6 normal subjects exerted positive inotropic actions on the human heart concomitant with positive chronotropic effects, hypotension, and vasodilation. CGRP may, therefore, be of importance for cardiovascular control in man.

Blood Pressure↗
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↗
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↗
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

Parathyroid hormone secretion does not respond to changes of free calcium in electropermeabilized bovine parathyroid cells, but is stimulated with phorbol ester and cyclic AMP.

The secretion of parathyroid hormone (PTH) is suppressed in bovine parathyroid cells by raised extracellular [Ca2+], and 12-0-tetradecanoyl-phorbol-13-acetate (TPA) stimulates the release of PTH from cells suppressed by high extracellular [Ca2+]. Extracellular and cytosolic free [Ca2+] are proportionally related in intact cells. To assess the role of cytosolic free [Ca2+] on PTH secretion, bovine parathyroid cells were rendered permeable by brief exposure to an intense electric field. PTH secretion was comparable at 40 nM, 500 nM, 5 microM, 28 microM, 0.5 mM and 2 mM [Ca2+] (release of total cellular PTH 3.7 +/- 0.5%, 3.9 +/- 0.4%, 3.4% +/- 0.3%, 3.9 +/- 0.4%, 3.1 +/- 0.3%, 3.5 +/- 0.7%, respectively), but the secretion was stimulated twofold (P less than 0.05 vs. control) in a dose and ATP dependent manner with TPA (100 nM) and cyclic AMP (1 mM). As a result, free [Ca2+] in the range of those observed in intact cells during regulation of PTH secretion by changes of extracellular [Ca2+] did not affect the release of PTH in permeabilized cells. The [Ca2+] independent stimulation of PTH release by TPA and cyclic AMP indicates that changes of cytosolic free [Ca2+] may represent a secondary event not related to the regulation of PTH secretion.

Adenosine Triphosphate↗
PubMed1986

Does cholecystokinin-like immunoreactivity in rat primary sensory neurons represent calcitonin gene-related peptide?

Using immunohistochemistry, calcitonin gene-related peptide (CGRP)- and cholecystokinin (CCK)-like immunoreactivity (LI) were found in many of the same spinal and trigeminal ganglion cells and motoneurons in the spinal cord and hypoglossal nucleus, as well as in fibers with an overlapping distribution in the spinal cord (dorsal horn, bundle ventral to the central canal) and in the spinal trigeminal nucleus. CCK-LI in all these structures disappeared after preadsorption of CCK antisera with CGRP at 10(-4) M and almost completely at 10(-5) M. CCK peptide in concentrations up to 10(-4) M, on the other hand, did not influence CGRP staining. The present findings raise the possibility that some CCK-LI in primary sensory neurons in rat may represent CGRP or a similar peptide.

Animals↗
PubMed1986

Simultaneous release of several tachykinins and calcitonin gene-related peptide from rat spinal cord slices.

Superfusion of slices of the dorsal half of rat spinal cord in vitro with 10 microM capsaicin or 60 mM potassium lead to the simultaneous release of substance P (SP)-, neurokinin A (NKA)- and calcitonin gene-related peptide (CGRP)-like immunoreactivities (LI). The ratio between capsaicin-stimulated and basal release was higher for CGRP-LI than for SP-LI, indicating that relatively more CGRP is released from sensory nerves, whereas SP is not only released from afferent neurons. High-performance liquid chromatography of NKA-LI revealed several immunoreactive components. One major peak had the retention time of synthetic NKA. A second peak eluted close to the position of synthetic eledoisin. In conclusion, capsaicin releases several bioactive peptides from sensory neurons which may mediate the acute algetic effect of chemical irritants.

Animals↗
PubMed1986

Stimulation of parathyroid hormone secretion by phorbol esters is associated with a decrease of cytosolic calcium.

Unlike in other endocrine systems calcium inhibits parathyroid hormone (PTH) secretion and this inhibition is paralleled by a rise of cytosolic calcium concentration ([Ca]i). Because of evidence that diglyceride levels and protein kinase C activity are also decreased by high extracellular calcium we have investigated the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, on [Ca]i and PTH secretion using dispersed bovine parathyroid cells. At 1.5 mM medium calcium TPA enhanced PTH secretion and caused reduction of [Ca]i from 639 +/- 36 nM (SE) to 335 +/- 21 nM (P less than 0.001); at 0.5 mM calcium TPA was ineffective. Moreover, TPA suppressed the rise of [Ca]i evoked by high extracellular calcium. Thus TPA presumably stimulates PTH secretion via activation of protein kinase C, and the lowering of [Ca]i may TPA presumably stimulates PTH secretion via activation of protein kinase C, and the lowering of [Ca]i may be a secondary event related to diglyceride availability.

Animals↗
PubMed1986

Regulatory elements involved in Drosophila Adh gene expression are conserved in divergent species and separate elements mediate expression in different tissues.

Alcohol dehydrogenase (ADH) is expressed in a complex temporal and spatial pattern from tandem promoters (proximal and distal) in Drosophila melanogaster, and from two closely linked genes (Adh-1 and Adh-2) in D. mulleri. The expression patterns of Adh-1 and the proximal promoter, and Adh-2 and the distal promoter are similar, but not identical. We show that the mulleri Adh genes are appropriately expressed when introduced into the melanogaster genome, indicating that the cis- and trans-acting elements which regulate the corresponding promoters are functionally equivalent in the two species. By analyzing the expression of in vitro generated mutants of the mulleri Adh locus, we define at least three regulatory regions of the mulleri Adh genes and show that different control elements mediate the expression of Adh in different tissues.

Alcohol Dehydrogenase↗
PubMed1986

Kenny syndrome: evidence for idiopathic hypoparathyroidism in two patients and for abnormal parathyroid hormone in one.

We report three unrelated patients with Kenny syndrome. Clinical symptoms included severe dwarfism, with internal cortical thickening and medullary stenosis of the tubular bones, normal bone age, macrocephaly, absent diploic space, delayed closure of the anterior fontanel, and normal intelligence; two of the patients had hyperopia and papillary edema. The patients also had episodic hypocalcemic tetany and low serum levels of magnesium. In two patients the diagnosis of idiopathic hypoparathyroidism was established on the basis of undetectable serum parathyroid hormone (PTH) levels (N- and C-terminal RIAs); one of these had normal urinary cyclic adenosine monophosphate (cAMP) response to exogenous PTH. Circulating calcitonin was undetectable in either patient. In a third patient, who had abnormal body proportions, serum levels of PTH were increased in an RIA detecting predominantly intact PTH (N-RIA) and undetectable in another RIA recognizing carboxy-terminal fragments (C-RIA). Administration of PTH promptly increased urinary cAMP excretion. In this patient, serum levels of calcitonin were increased, whereas values for 25-OHD and 1,25(OH)2D were normal.

Abnormalities, Multiple↗
PubMed1986

Suppression of parathyroid hormone inhibitory activity of plasma in pseudohypoparathyroidism type I by i.v. calcium.

The biological response, as measured in the cytochemical bioassay, to the high circulating levels of immunoreactive parathyroid hormone (iPTH) in patients with pseudohypoparathyroidism type I (PSPI) is affected by the presence of an endogenous inhibitor. This is evidenced by the reduced recovery of the biological activity of PTH added to the plasma. Here we have used i.v. calcium infusion to inhibit the release of PTH and studied endogenous PTH bioactivity and immunoreactivity as well as the recovery of the bioactivity of added PTH in a normal subject and two patients with PSPI. In the control subject both bioactive PTH (bioPTH) and iPTH fell in response to the increased levels of plasma calcium and the recovery of the biological activity of PTH added to the plasma remained unchanged. In the PSPI patients, although the level of iPTH fell, the level of bioPTH remained unchanged. However, the level of inhibitory activity of the plasma, as determined by the recovery of added PTH, was transiently normalized in response to the rise in plasma calcium. Thus i.v. calcium infusions not only suppress the release of endogenous iPTH but also the inhibitory activity present in the plasma of PSPI patients.

Adult↗
PubMed1986

Evaluation of the in vivo and in vitro calcium-regulating actions of noncalcitonin peptides produced via calcitonin gene expression.

Recent studies of rat and human calcitonin (CT) gene expression have uncovered a diversity of secretory peptides. Here we report the results of testing two such non-CT secretory peptides for CT-like action in live rats and in cultured fetal rat long bone. One peptide, the carboxyl-terminal CT-adjacent peptide that is cosynthesized with CT, has no hypocalcemic effect and no inhibitory action on bone resorption in vitro. The other peptide, CT gene-related peptide, lowers blood calcium and inhibits bone resorption. In vitro experiments are consistent with the idea that CT gene-related peptide is acting at CT receptors in bone.

Animals↗