Characterization of the "giant precursors" (70-80K) of vasopressin and oxytocin in the rat hypothalamus.
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Biomedical subjects
Publications and source records attributed to G J Moore.
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Properties of the neurohypophysial hormones and neurophysins are presented and historical events contributing to our present understanding of the biosynthesis of these molecules are reviewed. Recent findings, including cloning of mRNA and identification of putative giant precursors, are discussed in the context of precursor processing systems and possible biochemical and physiological mechanisms.
Nude mice (nu/nu on BALB/cAn background), maintained under conventional conditions, developed an acute moist dermatitis of the nose and occasionally the ears, with heavy contamination with Staphylococcus pyogenes. Only homozygotes over 10 weeks old were affected. Treatment with parenteral ampicillin or oral oxytetracycline was ineffective. Other conditions associated with the same organism were conjunctivitis and periorbital abscesses.
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Reversed phase HPLC has wide applications in studies on neuropeptides. It provides a fast and effective technique for assessing the purity of synthetic peptides and for purifying mg amounts of synthetic peptides (examples: angiotensins II and III and analogues; neurohypophysial hormones). Due to the very small quantities of peptides which can usually be safely recovered after HPLC, the method is also useful in the isolation, purification and sequencing of peptides from biological sources (examples: urotensin I and II), and in the identification of neuropeptides in tissues when coupled with radioligand-binding displacement assays (example: [arginine 8]vasotocin in the anterior ganglia of Aplysia californica.
The amino acid sequence (residues 4-34) of urotensin I, a 41 residue peptide from the urophysis of the Alberta white sucker Catastomus Commersoni, has been determined by a solid phase method. Based on the structure elucidated a peptide comprising residues 4-28 of urotensin I, Pro-Pro-Ile-Ser-Ile-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Met-Ile-Glu-Met- Asn-Arg-Ile-Leu-Asn-Glu-Arg, was synthesized by a solid phase method. The synthetic peptide demonstrated no blood pressure lowering activity and did not block the hypotensive effect of native urotensin I in the rat. It appears that almost the entire sequence of urotensin I is required for binding to vascular receptors and that no "active region" is available in this regard.
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Analogs of [arginine8]vasopressin (AVP) in which the peptide chain was elongated from the N-terminus by the addition of Ala-Arg-Arg-, Ala-Ala-Phe-, Pro-Arg-Val-, Pro-Ala-Arg-Arg, and Pro-Ala-Ala-Phe-, and from the C-terminus by the addition of -Ala-Met-Ala-NH2 and -Gly-Arg-Arg-Ala-NH2 were synthesized by the solid phase method and purified by Sephadex G-15 chromatography. At the final step of the synthesis, the extent of formation of the intramolecular disulfide bond was found to be sequence dependent. These peptides were incubated with extracts of the rat hypothalamus (supraoptic region) and neural lobe and with isolated neurosecretory granules from the neural lobe, and the release of vasopressin was measured by the rat pressor assay. All peptides resisted conversion to the hormone in the presence of tissue extracts, except (Ala-Ala-Phe)-AVP which was converted to AVP in the presence of all three tissue extracts at pH 4.7 but not at pH 8.0. When these peptides were treated with trypsin, chymotrypsin, or leucine aminopeptidase at pH 8.0, only the action of chymotrypsin on [Ala-Ala-Phe]AVP resulted in AVP formation. Evidence obtained using lysosomal enzyme markers suggested that the converting enzyme activity in neurosecretory granule preparations was not of lysosomal origin.
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Radioimmunoassays and high pressure liquid chromatography have been used to demonstrate the presence of an arginine-vasotocin-like peptide (AVT) in the anterior ganglia of Aplysia. Previously, AVT, using similar methods, was found to be present only in vertebrates. AVT when perfused over the abdominal ganglion (10(-6)-10(-12)M) was found to increase the bursting activity of R15, to decrease the bursting activity of L3-L6 and to increase the CNS's suppressive influence over the gill withdrawal reflex evoked by siphon stimulation. The AVT present in the nervous system of Aplysia may mediate long-term suppression of gill reflex behaviors induced by factors such as satiation and, as well, regulate the activity of certain neurosecretory neurons.
The biosynthesis of [arginine8]vasopressin (AVP) and oxytocin (OT) was studied, and the results obtained have been compared with a study of their associated neurophysins (NP), AVP-NP and OT-NP. Rat hypothalamic extracts obtained at acid pH were subjected to Sephadex G-75 gel filtration chromatography and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Fractions of gel chromatography effluent and extract of SDS-PAGE gel slices were subjected to RIA for immunoreactive precursors of AVP, AVP-NP, OT, and OT-NP using specific antisera fro each molecule. Tritiated bovine serum albumin, ovalbumin, and cytochrome c were used as internal standards during gel filtration chromatography and SDS-PAGE. Molecular weight estimates obtained for precursors of AVP were more than 70K, 31K, 13K, 5K, and less than 5K (AVP) by G-75 chromatography and more than 70K, 39K, 15K, and less than 5K (AVP) by SDS-PAGE. Molecular weight estimates obtained for precursors of AVP-NP were more than 70K, 35K, 24K, and 12K (AVP-NP) by G-75 chromatography and 19K and 10K (AVP-NP) by SDS-PAGE. Molecular weight estimates of OT were more than 70K, 35K, 19K, 8K, and less than 5K (OT) by G-75 chromatography and 60K, 35K, 19K, 9K, and less than 5K (OT) by SDS-PAGE. Precursors of OT-NP were estimated to be more than 70K, 17-18K, and 10K (OT-NP) by G-75 chromatography and 28K, 18K and 10K (Ot-NP) by SDS-PAGE. These studies show that there are small differences in precursor processing among AVP, AVP-NP, and OT, OT-NP, but allow for the existence of common precursors for AVP and AVP-NP and for OT and OT-NP.
The nature of the protected amino acid or peptide attached to the Merrifield resin influences the rate of KCN-catalyzed transesterification in benzyl alcohol. Although crown ether complexes of KCN do not expedite the reaction, sterically hindered amino acids are readily transesterified in the presence of saturating concentrations of KCN at elevated temperatures.
Des-aspartyl1-[sarcosine7-isoleucine8]-angiotensin II was found to be a more potent antagonist of the angiotensin II mediated contraction of the isolated rat uterus than of the angiotensin III mediated response. The data suggest that at least two types of angiotensin receptors exist in uterine smooth muscle.
The effects of several paired analogs of angiotensin II and angiotensin III, designed as antagonists, have been compared in isolated smooth muscle (rat uterus) and by in vivo rat blood pressure assay. These analogs were (1) the angiotensin II series: (1-sarcosine, 7-X, 8-isoleucine-) angiotensin II, and (2) the angiotensin III series: (1-despartyl, 7-X, 8-isoleucine)angiotensin II, where X=sarcosine, N-methyl-L-alanine or DL-nipecotic acid. All of these analogs had very low pressor and myotropic activities in the vagotomized, ganglion-blocked rat and the isolated rat uterus, respectively, although the angiotensin II analogs had significantly higher intrinsic pressor activity than the angiotensin III analogs. In addition, the angiotensin II analogs were potent antagonists of the contractile response to angiotensin II in the rat uterus whereas the angiotensin III analogs were weak inhibitors. These observations demonstrate the existence of functional differences for the proline residue in angiotensin II and angiotensin III analogs and may reflect differences in conformation and modes of binding to smooth muscle receptors between the two classes of peptides.
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Two cats, inoculated with a street rabies virus strain, survived with only some progressive debility and atrophy of musculature in the injected limb for 136 weeks. They had continuously increasing titers of neutralizing antibody in serum and in cerebrospinal fluid, and terminally they had high antibody titers in the brain. Virus was isolated from two brain specimens of one cat obtained at necropsy; isolation was successful only by explant culture and inoculation of explanted tissue into mice. Virus antigen was detected in eight sites in the brain and spinal cord of the same cat by frozen-section immunofluorescence. Lesions in the central nervous system consisted of neuronal degeneration and neuronophagia, associated with the prescence of inclusion bodies and widespread inflammatory cell inflitration into brain and spinal cord parenchyma, perineuronal sites, and perivascular spaces. The inflitrates contained lymphocytes, monocytes-macrophages, and a high proportion of plasma cells. These experimental cases of chronic progressive rabies resembled more closely subacute sclerosing panecephalitis of man than the usual subacute fatal rabies encephalitis of man and other mammalian species.
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