Search PubMed⌕ Search

Biomedical subjects

H Morimoto

Publications and source records attributed to H Morimoto.

At least 217 records · Page 12Linked to original sources
PubMed1979

Effects of thio-group modification and Ca2+ on agonist-specific state transitions of a central nicotinic acetylcholine receptor.

Agonist-binding affinities of central nervous system nicotinic acetylcholine receptors (nAcChR) are sensitive to the duration of exposure to agonist. These agonist-induced changes in receptor state may be mimicked by appropriate modification of receptor thio groups and/or by manipulation of solvent ionic composition. In the absence of Ca2+, the concentration of acetylcholine (AcCh) necessary to prevent half of specific 3H-labeled alpha-bungarotoxin binding is approximately 1 mM for nAcChR treated with dithiothreitol (DTT) or DTT-N-ethylmaleimide (low-affinity states) and approximately 40 microM for nAcChR treated with DTT-5,5'-dithiobis(2-nitrobenzoic acid) or for native nAcChR pretreated with AcCh (high-affinity states). Addition of Ca2+ results in an increase in the effectiveness of AcCh toward blocking toxin binding. None of these treatments alters toxin or antagonist binding nor are there observed differences in Hill numbers for agonist binding. Agonists competitively inhibit toxin binding to low-affinity states, but noncompetitive inhibition is observed for binding to high-affinity states. Values of AcCh dissociation constants estimated from these data fall within the range of values determined physiologically with nAcChR from other systems. The data indicate that the redox state of brain nAcChR thio groups and Ca2+ may mediate physiologically important changes in the receptor state during activation and desensitization.

Acetylcholine↗
PubMed1978

Social grouping cannot account for cerebral effects of enriched environments.

Several experiments were conducted to test whether, as suggested by Welch et al. in this journal, mere group living (social stimulation) can account for the significant differences in measures of brain anatomy and brain chemistry that develop between rodents housed in groups in enriched environments and rodents housed singly in restricted environments; the alternative hypothesis was that features of the inanimate environment can significantly affect brain measures of animals living in a social group. Groups of 12 male rats were assigned for 30 days to several types of environment: (a) large cage without stimulus objects, (b) large cage containing varied stimulus objects, (c) large cage containing a maze whose pattern of barriers was changed daily, and (d) a seminatural outdoor environment; in each experiment, littermates of rats in the social conditions were housed in isolation in small colony cages. At the end of the 30-day period, measures were taken of weights of brain regions, RNA and DNA contents of regions of cerebral cortex, and acetylcholinesterase activities of brain regions. Although the number of rats housed together was constant for conditions a--d and cage size was constant for conditions a--c, the magnitudes of the cerebral measures varied significantly as a function of the inanimate stimulus conditions. The differences from isola;ion-housed littermates was greatest in condition d and smallest in condition a. Thus, social grouping alone is inadequate to explain the cerebral effects of enriched environments and the inanimate stimulus conditions must be taken into account.

Acetylcholinesterase↗
PubMed1978

The effect of quaternary structure on the state of the alpha and beta subunits within nitrosyl haemoglobin. Low temperature photodissociation and the ESR spectra.

Photodissociation of nitrosyl haemoglobin and nitrosyl hybrids, in which either the alpha or beta subunit is in the nitrosyl form has been stidued at liquid helium temperature (4.2 degrees K) by electron spin resonance and optical absorption spectroscopy. In the presence of inositol hexaphosphate, the photodissociated form of nitrosyl haemoglobin showed an anomalous absorption spectrum in the near infrared region. The experiments with nitrosyl hybrids showed that the alphaNO subunit within the T state haemoglobin is predominantly responsible for the anomalous photodissociated form and the ESR spectrum with three distinct hypefines. The ESR spectrum of alphaNO2betadeoxy2 with inositol hexaphosphate appeared to be very similar to that of the 5-coordinated NO-haem complexes but the absorption spectrum of its photodissociated form was similar to none of protoporphyrin Fe(II) derivatives so far reported. This result suggests that the anomalous photodissociated form may be attributable to some structural distortion of porphyrin or a new electronic state of the haem with different spin state from that of deoxyhaemoglobin.

Electron Spin Resonance Spectroscopy↗
PubMed1978

Fluorescent staining of fungal nuclei with a benzimidazol derivative.

A direct staining procedure is described for fluorescence microscopy of fungal nuclei, chromosomes and mitochondria. The fluorochrome is a benzimidazol derivative (33258 Hoechst) known to bind selectively to deoxyribonucleic acid at neutral pH. The advantages of 33258 Hoechst relative to Feulgen compounds used previously to stain these structures include a greater intensity of fluorescence, the absence of fading or rapid quenching of the fluorescence, and the omission of acid hydrolysis from the procedure for removal of ribonucleic acid. 33258 Hoechst has been evaluated as a nuclear stain with a yeast (Saccharomyces cerevisiae) and a filamentous fungus (Agaricus bisporus) and appears to penetrate easily vegetative cells and spores of both fungi.

Basidiomycota↗
PubMed1978

The effect of ubiquinone-7 and its metabolites on the immune response. IV. Chemical structure-adjuvant activity relationship of quinonyl derivatives on humoral immune response.

The effects of the emulsion of quinonyl acids (QS-n, ES-n, KS-n) and related compounds (QSA-n) in Freund's incomplete adjuvant on the humoral immune response to bacterial alpha-amylase were assayed, and their structure-adjuvant activity relationships were discussed. All the quinonyl acids tested (500 microgram/mouse) enhanced the humoral immune response two to seven times as much as that of the control group, five weeks after immunization. 3'-Methyl and 2', 3'-double bond in the carboxy side chains of ubiquinone metabolites (Q acid-I, -II) were not essential for the adjuvant activity. The conversion of methoxyls on the quinone ring into methyls, and that of benzoquinone into phenol also did not affect the activity, but the activity seemed to depend on the carbon number of the carboxy side chain, and the prominent adjuvant activity was observed in the carboxylates having the carboxyalkyl chain of five to seven carbons. High doses (1 or 5 mg/mouse) of ubiquinone-7 and -2 enhanced the humoral immune response two to three times as much as that of the control group, and quinonyl alcohols (QSA-n) enhanced that with low dose (500 microgram/mouse).

Adjuvants, Immunologic↗