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Biomedical subjects

H Shindo

Publications and source records attributed to H Shindo.

At least 181 records · Page 10Linked to original sources
PubMed1980

Products of reaction catalyzed by purified rat liver guanylate cyclase determined by 31p NMR spectroscopy.

Products of the reactions catalyzed by highly purified preparations of soluble guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] from rat liver were identified and quantified with 31P NMR spectroscopy. Utilization of this technique necessitated modification of the standard assay conditions; higher concentrations of enzyme and substrate (2 mM), Mg2+ instead of Mn2+, and longer incubation times (up to 46 hr) at 30 degrees C were used. Revision of our reported procedure for purificaton of guanylate cyclase [Tsai, S-C., Manganiello, V. C. & Vaughan, M. (1978) J. Biol. Chem. 253, 8452-8457] to include chromatography on Ultrogel AcA34 and agarose-hexane-GTP provided an enzyme with specific activity higher than in our earlier preparations. 31P NMR spectra obtained during incubation of this enzyme showed that the rates of GTP disappearance and cyclic GMP (cGMP) accumulation were constant for approximately 16 hr. They indicated, however, that the preparations were contaminated with inorganic pyrophosphatase. This was removed by preparative electrophoresis, yielding enzyme with specific activities (900-1300 nmol/min per mg of protein) higher than those reported for guanylate cyclases from rat liver or lung. With this preparation, cGMP and PPi were the only products of GTP detected, consistent with the assumption that the guanylate and adenylate cyclase reactions are analogous.

Animals↗
PubMed1980

Autoradiographic studies on distribution of L-3,4-dihydroxyphenylalanine (L-DOPA)-14C and L-5-hydroxytryptophan (L-5-HTP)-14C in the cat brain.

The distribution and metabolism of L-DOPA-14C and L-5-HTP-14C in the cat brain were examined by means of autoradiography and chromatography. The results revealed that an appreciable amount of radioactivity in the gray matter, but not the white, and that the localization of radioactivity of L-DOPA and L-5-HTP significantly differed. After L-DOPA-14C administration, a high accumulation was found in the caudate nucleus, putamen and pallidum. With L-5-HTP-14C administration, high radioactivity was observed in the hypothalamus, raphe nucleus, substantia nigra, inferior olivalis and caudate nucleus. An analysis of the main metabolites of both amino acids in various regions of the brain was also made. When L-DOPA was given, a high concentration of dopamine was detected in the caudate nucleus, followed by the hypothalamus. In the case of L-5-HTP, a high concentration of serotonin was detected in the hypothalamus and the medulla oblongata. These results suggest that amines derived from exogenously administered L-DOPA and L-5-HTP accumulate in the brain regions known as the corresponding amine rich regions, under physiological conditions.

5-Hydroxytryptophan↗
PubMed1980

Ultrastructral changes induced by 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosourea in L1210 lymphocytic leukemia cells in mice.

Ultrastructural changes in L1210 leukemic cells infiltrated in the sinusoid of mouse liver after treatment with a single dose of a newly developed antitumor agent, 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosourea hydrochloride, were observed by electron microscopy. In the earliest stage after injection of 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosourea hydrochloride in tumor-bearing mice, marked changes were observed in both nucleolar and cytoplasmic ultrastructures. At 48 hr after administration, numerous Golgi complexes were observed in the cytoplasm, and lysosome-like granules also increased. The most striking change after treatment with 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosourea hydrochloride, however, occurred in the nucleolus. The chromatin was condensed, tending to collect near the nuclear membrane. Segregation of the nucleolar constituents was observed in the nucleus. Many necrobiotic cells were also observed within the liver sinusoid at this stage.

Animals↗
PubMed1979

Conformation of ribonuclease S-protein.

Ribonuclease S-protein exhibits a pH-dependent conformational transition between folded and unfolded states, and some unfolded S-protein persists up to pH 8. The histidine C2 proton resonance of the unfolded species was erroneously assigned by Bradbury et al. to histidine residue 119 of the folded species.

Histidine↗
PubMed1979

Conformation of DNA in chromatin core particles containing poly(dAdT)-poly(dAdT) studied by 31 P NMR spectroscopy.

We have prepared semi-synthetic chromatin core particles from a complex of chicken erythrocyte inner histones (H2A, H2B, H3 and H4) with double-stranded poly(dAdT).poly(dAdT) and studied the conformation of the phosphodiester backbone using 31P NMR at 109.3 MHz. At 20 degrees C, the core particle spectrum is fit well by a single Lorenzian distribution with a line width of 110 Hz. This signal is significantly broader than that for the 145 base pair poly(dAdT).poly(dAdT) alone; the latter consists of two resonances, approximately equal in intensity, with average line width 41 Hz. Major changes in the spectrum ensue on heating the core particle preparation. In conjunction with other results (1) these data suggest four states for the core particle at increasing temperatures. Additionally, analysis of the spectrum of the unmelted core particle and its differences from protein-free DNA of the same length suggests that the conformation of the phosphodiester backbone and/or its interactions with histones along the length of the core particle DNA segment may not be uniform.

Animals↗
PubMed1979

An alternating conformation characterizes the phosphodiester backbone of poly(dA-dT) in solution.

A highly homogeneous 145-base-pair fragment of double helical poly(dA-dT) . poly(dA-dT) was obtained by micrococcal nuclease digestion of a semisynthetic chromatin prepared from the nucleosome core histones (H2A, H2B, H3, H4) and the synthetic polydeoxyribonucleotide. In contrast to higher molecular weight alternating copolymers, this fragment displayed two resolved 31P NMR signals, separated by 24 Hz at 10.93 MHz. The two signals were of equal intensity at all temperatures less than the Tm for the fragment. Analyses of the possible origins for the two reasonances leads to the conclusion that the phosphodiester backbone of this DNA contains two distinct phosphorus environments, probably in an alternating array. We suggest that this may indicate the presence of sequence-dependent local variation in the helical structure of DNA in general.

DNA↗
PubMed1979

Cross-peptide bond 13C--15N coupling constants by 13C and J cross-polarization 15N NMR.

Comparative 13C--15N coupling constants are reported for the linear dipeptide tBoc-L-[U-13C]Ala-[15N]GlyOMe and the corresponding cyclic diketopiperazine, both in dimethylsulfoxide (DMSO) and, upon removal of the tBoc group, in water solutions. Spectra were obtained by 13C NMR and by the first application of J cross-polarization (JCP) 15N NMR, which greatly reduces the time required to accumulate 15N NMR spectra. In DMSO there was evidence for the formation of complexed species which were not present in water. The values obtained for the cross-peptide bond coupling constant 2J13C alpha--15N were consistently less (by 2.2 Hz in DMSO, 4.3 Hz in water) for the cyclic than for the linear peptide, which may be related to the cross-peptide bond conformation. The 15N resonance for the cyclic peptide was shifted only 2 ppm downfield from the linear peptide chemical shift value in both solvents.

Alanine↗
PubMed1979

Whole-body autoradiography of bumetanide-14C in dogs by round saw method.--A combined method of autoradiography and tissue radioassay--.

The distribution of a new potent diuretic, Bumetanide, in dogs was studied by means of a combined method of whole-body autoradiography and tissue radioassay, after oral administration of Bumetanide-14C to five young beagle dogs (ca. 1.2 kg). A round saw method developed by Kalberer was applied to obtain frozen slices of dog whole-body with a thickness of 3 mm. After exposure to X-ray films from both sides of the slices at -60 degrees C, frozen samples of the main tissues as well as the blood, urine, bile and intestinal contents were obtained to be assayed for radioactivity and to be analyzed for metabolites by TLC. The advantages of the round saw method (thick slices) in larger animals as dogs and monkeys as compared to the conventional microtome method (thin sections) were pointed out and discussed.

Administration, Oral↗
PubMed1978

On the tyrosine residues of ribonuclease A.

The six 13Czeta resonances of the 6 tyrosine residues of ribonuclease A have been resolved by high field 13C Fourier transform nuclear magnetic resonance spect=oscopy. Titration studies of these resonances reveal 1 nontitrating or buried tyrosine residue, 1 partially buried residue, and 4 normally titrating residues, which are tentatively identified.

Magnetic Resonance Spectroscopy↗