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Biomedical subjects

D Richter

Publications and source records attributed to D Richter.

At least 289 records · Page 16Linked to original sources
PubMed1988

Expression of the vasopressin and oxytocin genes in rats occurs in mutually exclusive sets of hypothalamic neurons.

The genes for the hypothalamic hormones vasopressin and oxytocin are located in close proximity to each other within the rat genome. They are separated by only approx. 11 kbp of DNA sequence and oriented in such a way that their transcription occurs on opposite DNA strands. Although the two genes are structurally very similar including common potential regulatory elements in their putative promotor regions, they are expressed in discrete populations of magnocellular neurons of the hypothalamus. In rats placed under osmotic stress, the vasopressin gene is upregulated; concomitantly transcription of the oxytocin gene is also stimulated. To address the question of whether this coordinated rise in oxytocin-encoding mRNA is the result of switching on oxytocin gene transcription in vasopressinergic neurons, in situ hybridization with double labelled cRNA probes was carried out. Biotinylated and [alpha-35S]CTP labelled antisense cRNA probes specific for either vasopressin or oxytocin mRNA were constructed and hybridized to hypothalamic sections from salt-loaded rats. The results demonstrate that upregulation of oxytocin gene transcription is restricted solely to oxytocinergic cells; no oxytocin gene transcripts can be detected in vasopressinergic neurons.

Animals↗
PubMed1988

Processing of the oxytocin precursor: isolation of an exopeptidase from neurosecretory granules of bovine pituitaries.

The bovine pro-oxytocin precursor consists of the nonapeptide hormone and its neurophysin carrier protein that contains at its C-terminus a rudimentary processing signal, the single basic amino acid residue histidine. An exopeptidase has been isolated from neurosecretory granules of the bovine posterior pituitary that releases the supernumary histidine residue from the pro-hormone precursor. Based on its sensitivity to inhibitors and activators the enzyme has carboxypeptidase B-like properties with a pH optimum between 5.0 and 5.5.

Animals↗
PubMed1988

Expression and electrophysiological identification of the receptor for bombesin and gastrin-releasing peptide in Xenopus laevis oocytes injected with polyA+ RNA from rat brain.

The receptor for bombesin and the related peptide, gastrin-releasing peptide (GRP) has been induced in frog oocytes by injection of polyA+ RNA from rat brain. The primed oocytes responded to peptides of the bombesin family (GRP, neuromedin C of bombesin) by showing dose-dependent oscillations in membrane currents as recorded by the voltage-clamp method. The induced membrane changes were suppressed when oocytes were pretreated with a bombesin-receptor antagonist.

Animals↗
PubMed1988

Rapidly adapting pulmonary receptor afferents: I. Arborization in the nucleus of the tractus solitarius.

The organization of axon collaterals, preterminal processes, and presumptive synaptic boutons of single physiologically identified rapidly adapting receptor (RAR) pulmonary afferent fibers was examined following the intraaxonal application of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP). The RAR axons were injected 200-300 microns lateral to the nucleus of the tractus solitarius (nTS) at a number of different rostrocaudal levels in seven individual experiments. The trajectories of the stained axons were reconstructed from individual 50-microns-thick serial sections. The rostrocaudal extent, as well as the distribution of the trajectory of each RAR afferent, was reconstructed from every section by using a camera lucida attachment. In this first of two papers, we describe the pattern of organization of bouton terminals of RAR afferents related to cytoarchitectonically distinct subnuclei of the nTS. In the companion paper, morphological details of the fine structure of these synaptic boutons and axonal branches are described in different subnuclei in order to illustrate morphological differences in these functionally distinct regions. A number of significant findings have resulted from this light microscopic study. The central process of a single RAR afferent fiber arborized in the medulla oblongata over a considerable distance in the rostrocaudal plane (2.5 mm rostral to 1.4 mm caudal to the obex). A single RAR afferent fiber terminated in numerous bouton terminals (range 500-1,050), and these terminals arose from over 400 segments of branches of the parent injected axon. A small number of en passant bouton terminals were found. There appeared to be a remarkable degree of consistency in the subnuclei of the nTS where these terminals arborized. The dorsal and dorsolateral subnuclei of the nTS received 144-647 bouton terminals. The second-largest concentration of bouton terminals of RAR afferents was found in the intermediate (nI) subnucleus of the nTS. No labeled bouton terminal was found in the ventral and ventrolateral subnuclei of the nTS. This finding is in sharp contrast to the terminations of SAR afferents which terminated predominantly in the ventral and ventrolateral nuclei of the nTS, the interstitial nucleus of the nTS, and the nI. The parent RAR axon could be traced as far rostrally as 2.5 mm, even though the region of terminal arborization could not be followed beyond 0.8 mm. The destination of this rostrally projecting RAR afferent could not be determined in this study.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1988

Rapidly adapting pulmonary receptor afferents: II. Fine structure and synaptic organization of central terminal processes in the nucleus of the tractus solitarius.

The nucleus of the tractus solitarius (nTS) is a site for termination of primary afferents originating from a variety of different visceral sensory endings (Kalia and Mesulam: J. Comp. Neurol. 193:523-553, '80). The light and electron microscopic evaluation of bouton terminals of slowly adapting lung stretch (SAR) afferent fibers originating from the tracheobronchial tree has been described previously (Kalia and Richter: J. Comp. Neurol. 241:503-520, 521-535, '85). The companion article (Kalia and Richter: J. Comp. Neurol. 273:000-000, '88) describes details of the light microscopic organization of a second group of pulmonary afferents, the rapidly adapting receptors (RARs), that are known to signal transient volume changes in airways (Sellick and Widdicombe: J. Physiol. (Lond.) 203: 359-381, '69; Q.J. Exp. Physiol. 55:153-163, '70). Terminals from RAR afferents are concentrated within two specific subnuclear groups of the nTS (dnTS and nI) and are distributed over 4 mm of the medulla oblongata rostrocaudally. Within the nTS, axon collaterals of RAR afferents remain myelinated up to a diameter of 0.4-1.0 microns. Preterminal processes are always unmyelinated and range in diameter from 0.15 to 0.3 microns. Bouton terminals (1.0-2.0 microns) are of both the en passant and end terminal varieties. The synaptic profiles formed by 143 bouton terminals of RAR afferents, were examined in uninterrupted sequential sections and are described in this paper. All the bouton terminals examined under the electron microscope were found to contain clear, round synaptic vesicles. Boutons made synaptic contact with different profiles in each of the two subnuclei (dnTS and nI) examined. Contacts were usually asymmetrical (type I) containing clear, round synaptic vesicles 35-50 nm in diameter. In the dorsal subnucleus of the nTS (dnTS), the synaptic arrangement of RAR boutons did not appear to be complex. The RAR bouton terminal was usually located in juxtaposition to unlabeled axon terminals of similar morphological characteristics. Typically, the RAR bouton terminal made synaptic contact with a medium-sized spiny dendrite. No axosomatic contacts involving RAR afferents were observed in this subnucleus. In the intermediate subnucleus of the nTS (nI), the most common synaptic arrangement of RAR bouton terminals was in the form of a "glomerulus," which was formed by five to seven different types of neuronal profiles surrounding the labeled RAR bouton terminal.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1988

Expression of the bovine hypothalamic hormone oxytocin precursor in Escherichia coli.

The bovine oxytocin precursor was expressed in Escherichia coli as a fusion protein by cloning the hormone encoding cDNA in frame behind the replicase gene of the RNA phage MS2. By step-wise extraction with different urea concentrations, the fusion protein was enriched in the 7 M urea fraction and further purified by Sephacryl S-300 chromatography. The oxytocin precursor was cleaved off the fusion protein by cyanogen bromide treatment, chromatographed on FPLC columns and identified by Western blot analysis, using antibodies raised against neurophysin.

Amino Acid Sequence↗
PubMed1988

Cloning and sequence analysis of cDNA for corticotropin-releasing factor precursor from the teleost fish Catostomus commersoni.

The sequence of a cDNA encoding the corticotropin-releasing factor precursor has been identified by screening lambda gt11 libraries constructed from poly(A)+ RNA of the hypothalamic region of the white sucker Catostomus commersoni brain with synthetic oligonucleotide probes deduced from the sequence of the rat corticotropin-releasing factor. The amino acid sequence of corticotropin-releasing factor of the sucker is strikingly conserved when compared to its counterpart from rat and differs only in two positions at the carboxyl terminus; in contrast, there is little similarity between their cryptic regions.

Amino Acid Sequence↗
PubMed1988

Receptors for neuropeptides are induced by exogenous poly(A)+ RNA in oocytes from Xenopus laevis.

Receptors for the hormones vasopressin, angiotensin II, and thyrotropin-releasing hormone have been studied electrophysiologically in Xenopus laevis oocytes previously injected with poly(A)+ RNA from the respective receptor-containing tissues. The injected oocytes responded to the hormones by demonstrating oscillations in membrane currents as recorded by the voltage-clamp method. The response was dependent on the hormone concentrations and detectable between 5 and 1000 nM concentrations. Size fractionation of poly(A)+ RNA from the respective tissues showed that the mRNAs encoding the three hormone receptors were larger than 18S rRNA, suggesting a length of at least 2 kilobases. When vasopressin was added to the oocyte bath, an inward membrane current was generated in oocytes injected with rat poly(A)+ RNA from liver but not from kidney. This suggests that the V1-type (liver), not the V2-type (kidney), vasopressin receptor can be expressed and electrophysiologically identified in the oocyte. A V1-specific, but not a V2-specific, antagonist suppressed the vasopressin-dependent effect. Application of angiotensin II to liver poly(A)+ RNA-injected oocytes elicited oscillations in membrane current, indicating that these oocytes also expressed receptors for angiotension II; the antagonist [Sar1, O-methionyl-Tyr4]angiotensin II blocked this effect. Poly(A)+ RNA from tumor-derived GH3B6 cells, known to contain receptors for thyrotropin-releasing hormone, injected into oocytes induced receptors responding to thyrotropin-releasing hormone; the drug chlordiazepoxide suppressed the thyrotropin-releasing hormone response.

Action Potentials↗
PubMed1988

Molecular events in expression of vasopressin and oxytocin and their cognate receptors.

This article focuses on some aspects of neuropeptide gene expression using as examples the hypothalamic hormones vasopressin and oxytocin. Their transcriptional and translational expressions as polyproteins have been outlined, including the analysis of the genetic defect in the expression of vasopressin by the Brattleboro gene. The interaction of neuropeptide hormones with their target organs is discussed. A molecular approach toward the identification of the respective neuropeptide hormone receptors is described.

Amino Acid Sequence↗
PubMed1988

Functional expression of the oxytocin receptor in Xenopus laevis oocytes primed with mRNA from bovine endometrium.

Synthesis of the uterine receptor for the hypothalamic hormone oxytocin has been induced in oocytes from Xenopus laevis previously primed with bovine endometrium mRNA. The injected oocytes responded to oxytocin by showing dose-dependent oscillations in membrane currents as recorded by the voltage-clamp method. The response was specific in that it was not elicited by several other peptides tested. The oxytocin-induced membrane changes were suppressed when oocytes were pretreated with an oxytocin receptor antagonist.

Animals↗
PubMed1988

Clinical evidence of secretory IgA and Schwangerschaftsprotein 1 in pleural effusions of lung cancer patients.

Secretory immunoglobulin A, alpha 1-fetoprotein, orosomucoid and alpha 2-macroglobulin have been estimated in pleural effusions of 11 lung cancer patients. Secretory immunoglobulin could be detected in all cancer patients except one with a secondary embolism. Levels could be found between 0.19 and 0.73 g/l. No SIgA could be detected in a control group of 7 patients with pleural effusions of other origin.

Enzyme-Linked Immunosorbent Assay↗
PubMed1988

[Placental protein 5 and pregnancy zone protein in ovarian cysts and benign cystic ovarian tumors].

Placental protein 5 (PP 5), a serine protease inhibitor, was measured by radioimmunoassay in benign ovarian cyst fluids, especially in follicular and luteal fluids. PP 5 was detectable in 12 out of 29 cystic fluids; the levels ranging from greater than 1.0 to less than 100 micrograms/l. PP 5 was not detectable in the corresponding serum samples. Protein of the "pregnancy zone" (PZ) was found in 3 out of 11 follicular fluids (9-38 mg/l). Local production of PP 5 and PZ in cystic epithelia of the ovary was taken into consideration.

Female↗