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Biomedical subjects

A Miyata

Publications and source records attributed to A Miyata.

At least 181 records · Page 10Linked to original sources
PubMed1986

Molecular forms of atrial natriuretic peptides in rat tissues and plasma.

By using the sensitive radio-immunoassay specific for rat atrial natriuretic peptide (rANP) combined with chromatographic separation, we have determined molecular forms of rANP in rat tissues and plasma. Gamma-rat atrial natriuretic peptide is a major component of rANP in rat atria and ventricles, while alpha-rANP is a predominant form in the plasma, brain and submaxillary gland. Although molecular patterns in the adrenal and thyroid glands were very similar to that in the brain, a major immunoreactive (ir) alpha-rANP peak was accompanied by two minor peaks due to gamma-rANP and another unidentified ir-rANP. This variety in molecular forms suggests that the processing system for rANP precursors differs from tissue to tissue.

Animals↗
PubMed1985

Second lytic target of beta-lactam compounds that have a terminal D-amino acid residue.

A new biochemical mechanism of lysing bacterial cells by treatment with certain beta-lactam compounds that possess a terminal D-amino acid moiety in their side chain was demonstrated. The two functions of the molecule, the beta-lactam and terminal D-amino acid moiety, are both involved in the activity of lysing gram-negative bacteria, which is characterized by very rapid lysis of the cells in the first few hours after their contact with the compound. This mechanism was proved by studies on one such compound, named MT-141, which contains a terminal D-cysteine moiety with free amino and carboxyl groups in the 7 beta-side chain of the 7 alpha-methoxy-cephalosporin skeleton. This compound bound to the cell-wall peptidoglycan of Escherichia coli through the D-amino group of its terminal D-amino acid moiety and this seemed to cause rapid cell lysis. Both activities, of binding to peptidoglycan and of causing rapid cell lysis, were inhibited by certain D-amino acids, but not by L-amino acids. Mutants were isolated that had simultaneously gained decreased sensitivity to this kind of beta-lactam compound and supersensitivity to globomycin, an inhibitor of formation of lipoproteins which function in linking the peptidoglycan to the outer membrane. These results suggest that binding of the terminal D-amino acid moiety of the beta-lactam compound to peptidoglycan somehow influences formation of the linkage between the outer membrane and the peptidoglycan and consequently enhances the cell lytic activity of the beta-lactam portion of the molecule.

Amino Acid Sequence↗
PubMed1985

Molecular forms of atrial natriuretic polypeptides in mammalian tissues and plasma.

A highly sensitive radioimmunoassay detecting for all the atrial natriuretic polypeptides isolated so far from human and rat (hANPs and rANPs) has been established by using an antiserum raised against alpha-hANP, since the antiserum recognizes the subsequence flanked by two cysteine residues (positions 7 and 23) in alpha-hANP and crossreacts with human as well as rat ANPs. By using the radioimmunoassay combined with gel chromatography or high performance liquid chromatography, it was revealed that ANP immunoreactivity in human atria is composed of alpha-(28 residues), beta-(56 residues: alpha-hANP dimer) and gamma-hANP(126 residues) in various ratios. In rat, porcine and bovine atrial tissues, however, gamma-rANP(126 residues) was found to be a major component. In contrast with atrial ANP, plasma ANP was found to be predominantly alpha-form in rat.

Animals↗
PubMed1985

Adrenorphin immunoreactivity in rat brain.

Adrenorphin is the first C-terminally amidated form of opioid peptides isolated from human pheochromocytoma tumor and is considered to be generated out of proenkephalin A by unique processing. By the highly specific and sensitive radioimmunoassay (RIA) procedure utilizing the antiserum against adrenorphin, combined with high performance liquid chromatography (HPLC), immunoreactive adrenorphin in rat brain was verified to be identical with its authentic peptide. It has been revealed that adrenorphin immunoreactivity distributes widely in rat brain but in the unique pattern distinct from those of other endogenous opioid peptides. Note that immunoreactive adrenorphin was most concentrated in the olfactory bulb, and appreciably in the hypothalamus and striatum. Furthermore, immunohistochemical study has revealed that adrenorphin-immunoreactive structures in hypothalamic region of rat were localized in the neurones of the arcuate nucleus. In addition, adrenorphin-immunoreactive fibre plexus was found in the various regions of the hypothalamus, such as median eminence, periventricular zone and paraventricular nucleus. These indicate that adrenorphin may have a unique physiological function.

Animals↗
PubMed1985

The bacteriolytic action of MT-141, a new cephamycin antibiotic, on gram-negative bacteria.

MT-141, a new cephamycin (7 alpha-methoxy-cephalosporin) antibiotic with a D-cysteine moiety in its 7 beta-side chain, has binding affinities to penicillin-binding proteins of Escherichia coli and an inhibitory action on their transpeptidase activity similar to those of other structurally related cephamycins. Yet this antibiotic was found to exert an exceedingly strong and rapid lytic action on sensitive Gram-negative bacteria such as E. coli, Klebsiella pneumoniae, Serratia marcescens and Salmonella enteritidis. Not only rapidly growing cells, but also slowly growing dense cells of the above bacteria could be lysed by this antibiotic at low concentrations. In the presence of 20% sucrose, low concentrations of MT-141 induced smooth-surfaced single and twin bulges of the putative growth zone of the cells and irregularly orientated rough-surfaced bulges. Probably the 7 beta-side chain structure of this antibiotic is involved in its rapid and strong bacteriolytic action.

Bacterial Proteins↗
PubMed1985

Cardiac content and plasma concentration of atrial natriuretic polypeptide (ANP) in spontaneously hypertensive rats (SHR).

The cardiac content and plasma concentration of atrial natriuretic polypeptide (ANP) in hypertensive rats were measured by using radioimmunoassay for ANP. The animals used in this study were young (5-week-old) and adult (12- to 14-week-old) spontaneously hypertensive rats (SHR), stroke-prone SHR (SHR-SP) and normotensive control Wistar-Kyoto rats (WKY). Most immunoreactive ANP in the cardiac extract of the hypertensive rats (both SHR and SHR-SP) was found to be predominantly gamma-form as well as that of WKY. Cardiac ANP content in adult SHR and SHR-SP was significantly lower than in adult WKY (p less than 0.01), although there were no differences among three groups in young rats. Similar tendencies were also observed for plasma ANP concentration. The level of plasma in adult hypertensive rats was significantly lower or tended to be lower than in adult normotensive rats. Furthermore, a high negative correlation was present between blood pressure and cardiac ANP content (r = 0.748, p less than 0.01) and between blood pressure and plasma ANP concentration (r = 0.608, p less than 0.01) in all adult rats but there were no such relationships in young rats. The present study suggests that atrial natriuretic polypeptide may contribute to the pathogenesis or maintenance of high blood pressure in the genetic hypertensive rats.

Animals↗
PubMed1985

Small cell carcinoma of the skin "non-Merkel cell type".

An 81-year-old Japanese woman developed small cell carcinoma of the skin, which was different from trabecular carcinoma or neuroendocrine carcinoma of the skin. The tumor was composed of spindle-shaped or fusiform cells with scanty cytoplasm and numerous mitoses. The tumor cells were arranged in a streaming pattern and not in anastomosing trabecular fashion at all. No granules were detected by Grimelius' stain either. Immunoperoxidase staining for neuron specific enolase (NSE) did not reveal any activity. Ultrastructural study showed scanty organelles in the cytoplasm which contained a few round mitochondria, rough endoplasmic reticulum, and free polysomes. Occasionally, filamentous bundles, desmosomes, and intracytoplasmic canaliculi were recognized in the cytoplasm, but neurosecretory granules were not found throughout the cytoplasm. Electron microscopic features suggest that this tumor originated from the embryonal stratum germinativum. The present tumor can be distinguished from trabecular carcinoma or neuroendocrine carcinoma of the skin, and may be regarded as "small cell carcinoma" of the skin.

Aged↗
PubMed1984

Regional distribution of adrenorphin in rat brain: comparative study with PH-8P.

Adrenorphin is the first C-terminally amidated form of opioid peptide isolated from human pheochromocytoma tumor and is considered to be generated out of proenkephalin A by unique processing. We have developed a highly specific and sensitive radioimmunoassay for adrenorphin as well as for PH- 8P , whose structure and processing are similar to adrenorphin . Prior to the measurement of both peptides in rat brain, immunoreactive adrenorphin and PH- 8P were verified to be identical with their individual authentic peptides by high performance liquid chromatography. Here we have determined the distribution of adrenorphin in rat brain by radioimmunoassay, and compared it with that of PH- 8P . The regional distribution of adrenorphin was found to be quite different from that of other endogenous opioid peptides including PH- 8P . The highest concentration of adrenorphin was found in the olfactory bulb. These results suggest that adrenorphin is generated by a specific processing mechanism and may have a unique physiological function distinct from that of known opioid peptides. In addition, we identified adrenorphin also in human and bovine adrenal medullas.

Animals↗
PubMed1984

Penicillin-insensitive incorporation of D-amino acids into cell wall peptidoglycan influences the amount of bound lipoprotein in Escherichia coli.

Certain D-amino acids, such as D-methionine and D-cystine, were incorporated into cells of Escherichia coli under conditions inhibiting protein and cell wall synthesis. Part of the radioactivity of D-14C-amino acids incorporated into the cells was found in the isolated cell wall peptidoglycan. A covalent linkage between the amino group of the D-amino acids and the peptidoglycan was presumed to be the main cause of the binding of the D-amino acids to peptidoglycan, because the amino group of the D-amino acids in the incorporation product was substituted. Whether the carboxyl terminus was substituted was unknown. The formation of the D-amino acid-peptidoglycan linkage was insensitive to beta-lactam antibiotics such as benzylpenicillin and ampicillin (500 micrograms/ml) and therefore was not due to the reaction of DD-transpeptidation which is involved in the biosynthesis of peptidoglycan. The D-amino acids also strongly inhibited the formation of peptidoglycan-bound lipoprotein in the E. coli cells. The results may suggest the correlation between binding of D-amino acid to peptidoglycan and inhibition of formation of the bound form of lipoprotein.

Amino Acids↗