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Biomedical subjects

H Shimada

Publications and source records attributed to H Shimada.

At least 829 records · Page 46Linked to original sources
PubMed1986

The significance of myocardial bridge upon atherosclerosis in the left anterior descending coronary artery.

The relation between myocardial bridges (MB) and atherosclerosis in the left anterior descending coronary artery (LAD) was explored using morphometric methods in 642 hearts. The location of myocardial bridges in the LAD was classified according to distribution as proximal, middle and distal. Myocardial bridges were found in 48 per cent of males and 36 per cent of females. When proximal myocardial bridging was present intimal thickening and macroscopic raised lesion were increased just before the bridge as compared with the corresponding site in the other two categories. Underneath bridges eccentric plaques and raised lesions are absent although there is often concentric intimal thickening. The overall frequency of myocardial infarction was the same in patients with and without myocardial bridges. However, when infarction occurred in the patients having bridges, it was almost confined to those in the proximal group despite this being infrequent in the general distribution of myocardial bridges in the left anterior descending artery. It is postulated that hypertension may enhance infarction in the case of myocardial bridges in the very proximal left anterior descending artery. It is concluded that the location of myocardial bridges greatly alters the distribution of physical force against the arterial wall and influences the extent of atherosclerosis.

Aged↗
PubMed1986

Kinetic studies of sulfate transport in basolateral membrane vesicles from rat renal cortex.

The kinetics of sulfate uptake were studied in basolateral membrane vesicles from rat renal cortex. Sulfate uptake exhibits a DIDS-sensitive, saturable component, and a DIDS-insensitive component, which does not saturate in the tested sulfate concentration range (up to 10 mM). Intravesicular (= trans) sulfate strongly stimulates sulfate uptake by increasing Jmax and--to a lesser degree--by decreasing apparent Km. The marked dependence of Jmax on trans-sulfate indicates that the transport system operates as an anion exchanger. Half-maximal sulfate uptake occurs at 0.08-0.14 mmol/l extravesicular sulfate. Half-maximal trans-stimulation is observed at 11 mmol/l intravesicular sulfate indicating that the sulfate transporter is highly asymmetric. Lowering extravesicular pH stimulates sulfate uptake, suggesting that external protons are essential for sulfate uptake. This stimulation is mainly due to a decrease in Km. An inside positive membrane potential stimulates sulfate uptake at pHout = 8.8, but not at pHout = 6.4. These results are compatible with electrogenic sulfate transport at higher and electroneutral 2H+ -SO4(2-) cotransport at lower pH.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1986

Nuclear AP4A-binding activity of sea urchin embryos changes in relation to the initiation of S phase.

The AP4A-binding activity of sea urchin embryos was studied using radioactively labelled diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A). Among various subcellular components that can bind [3H]AP4A, nuclei alone showed the highly specific Ap4A-binding activity which was not influenced by the presence of AP4A, AP5A and GP4G. The addition of an excess amount of ATP only slightly reduced the binding of [3H]AP4A to the nuclei. It was found that AP4A binds to the residual proteinaceous structure of nuclei which was resistant to the extraction with 2 M NaCl. The nuclear AP4A-binding activity fluctuated cyclically during each cell cycle, with a transient increase at the beginning of S phase followed by an abrupt decrease within 10 min. When the initiation of S phase was blocked, the increase in the AP4A-binding activity was also prevented. It seems that the binding of AP4A to the nuclear structural protein is involved in the initiation of S phase.

Adenine Nucleotides↗
PubMed1986

Carbonic anhydrase activity in developing sea urchin embryos with special reference to calcification of spicules.

Eggs and embryos of the sea urchins Anthocidaris crassispina and Hemicentrotus pulcherrimus did not exhibit significant changes in carbonic anhydrase activity during early development. Acetazolamide inhibited enzyme activity in homogenates of embryos and inhibited the formation of calcified spicules in a culture of micromeres at concentrations between 40 and 100 microM. Acetazolamide allowed intact embryos to develop to quasi-normal plutei but inhibited calcium deposition in the spicules. It is suggested that carbonic anhydrase contributes to CaCO3 deposition in the spicule.

Acetazolamide↗
PubMed1986

A Zn2+-dependent and histone H1-specific protease in sea urchin sperm.

Protease activity was extracted from sea urchin sperm with 1% Triton X-100 and partially purified by DEAE-cellulose and Sephadex G-100 chromatography. The enzyme preferentially degraded histone H1, while showing only a weak activity toward other histones. Heat-denatured casein and bovine serum albumin were not digested by this enzyme under the present experimental conditions. This protease hydrolyzed only Boc-Val-Leu-Lys-MCA among various peptidyl-MCAs. The optimal pH ranged from 7 to 11. Its molecular weight was about 41,000. Among various known inhibitors of proteases, only omicron-phenanthroline effectively inhibited the activity. The enzyme was stimulated by Zn2+ or Co2+. It was inactivated by omicron-phenanthroline but could be reactivated by the addition of Zn2+ or Co2+. Therefore, this protease seems to be a metalloprotease dependent on Zn2+ or Co2+. The insensitivity of this enzyme to phosphoramidon and its very restricted substrate specificity suggest that this enzyme is very different from other metalloproteases described hitherto.

Animals↗
PubMed1986

Hypercalcemia due to spontaneous hemorrhage in a parathyroid adenoma during recovery from acute renal failure.

A 89-year-old woman showed transient and mild hypercalcemia (11.0 mg/dl) at the phase of recovery from acute renal failure. Serum PTH level elevated to 2.1 ng/ml when hypercalcemia was observed, and decreased to 1.1 ng/ml. Autopsy study revealed the bleeding within parathyroid adenoma. The transient and mild hypercalcemia seen in the patient was considered as the result of the bleeding within parathyroid adenoma. This unusual manifestation of parathyroid adenoma, bleeding, usually causes hypercalcemic crisis. The mild hypercalcemia observed in this patient despite of bleeding into parathyroid adenoma might be due to old age of the patient and the existence of renal failure in the patient.

Acute Kidney Injury↗
PubMed1986

Monacolin M, a new inhibitor of cholesterol biosynthesis.

Monacolin M, a new specific inhibitor of cholesterol biosynthesis structurally related to monacolin K (mevinolin), was isolated from cultures of a strain of Monascus ruber. The structure of monacolin M was determined to be beta-hydroxybutyryl ester of monacolin J by a combination of physical techniques. It was suggested that monacolin M is derived from monacolin J via a synthetic pathway distinct from that for the synthesis of monacolin K, alpha-methylbutyryl ester of monacolin J. The inhibitory effect of monacolin M on beta-hydroxy-beta-methylglutaryl-CoA reductase was slightly lower than that of monacolin K.

Anti-Bacterial Agents↗
PubMed1986

[A case of Pick's disease with long duration--an extraordinary cerebral change in the fore part of cerebrum].

An autopsied case of Pick's disease, having an extraordinary cerebral change in the anterior portion of Lobus frontalis and temporalis, was reported. Our case is a 71 year-old woman at death with a fourteen year history of chronic progressive dementia and mental deterioration, and it may be stressed that the existence lasted 8 years, over the latter half of clinical course, was depended on the tube feeding. The first symptoms suddenly appeared in 1964, 2 months after her husband's death of illness, when she was 57. She prepared the table for breakfast late at night, calculated wrongly in her domestic account book, and stole foods in the grocery. Two years later, her illness was diagnosed as presenile dementia by characteristic personality change and marked dilatation of anterior horn of lateral ventriculus. On admission to National Musashi Sanatorium, three years after the first symptoms' appearance, she presented restless walking, insomnia, memory loss, weakness of concentration, and high degree of disorientation. Particularly, it was noticeable that she behaved with bizzare contact. After 1970, tube feeding was introduced continuously, because of swallowing difficulty. Death occurred in July 1978 from a general weakness and a broncho-pneumonia, 14 years after the onset of the first symptoms. Autopsy revealed small and atrophied brain weighed 820 g. Cerebral cortical atrophy extended to frontal, temporal, insular, and parietal lobes, but right T-1 was relatively well preserved. On section, frontal and temporal ventriculus were remarkably enlarged and caudate nuclei were extremely atrophic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Flash photolysis studies on the CO complexes of ferrous cytochrome P-450scc and cytochrome P-45011 beta. Effects of steroid binding on the photochemical and ligand binding properties.

Upon irradiation by a light flash (100-J), the carbon monoxide complex of cytochrome P-450scc was fully photodissociated in both the presence and absence of cholesterol, while less than 20% of the CO complex was photodissociable with those of deoxycorticosterone-bound and -free forms of cytochrome P-45011 beta. When the quantum yield of the reaction was measured for each photodissociable portion, the values were 0.5 and 1.0 for the substrate-free and -bound forms of cytochrome P-450scc, and 0.03 and 0.8 for the substrate-free and -bound forms of cytochrome P-45011 beta, respectively. Thus, CO complexes of these enzymes become more photosensitive upon binding with the specific substrates. Steroid binding also affected kinetic constants of reactions between the ferrous enzymes and CO. The rate constants for the CO recombination at 15 degrees C were 2.7 X 10(6) and 2.3 X 10(5) M-1 s-1 for the substrate-free and -bound forms of cytochrome P-450scc, and were 7.0 X 10(5) and 5.4 X 10(3) M-1 s-1 for the substrate-free and -bound forms of cytochrome P-45011 beta, respectively. The rate constants for the CO dissociation also decreased upon the steroid bindings. The products of the enzyme reactions, pregnenolone and corticosterone, had similar effects on the kinetic constants. From these findings, we postulate that the binding of a steroid to the substrate site of each enzyme alters the bonding character of CO with the heme-iron, thereby affecting both photochemical and kinetic properties of the CO complex. The nature of the photoindissociable portion of the CO complex of cytochrome P-45011 beta is also discussed.

Adrenal Cortex↗
PubMed1985

Lysis of platelets and erythrocytes by the incorporation of a unique oxygenated sterol: 22R-hydroxycholesterol.

We have found that an oxygenated sterol, 22R-hydroxycholesterol [(22R)-5-cholestene-3 beta, 22-diol], lyses not only platelets but also erythrocytes in a dose-dependent manner. The lysis of platelets and erythrocytes were evidenced by the release of intracellular proteins, lactate dehydrogenase and hemoglobin, respectively. Their morphological change was shown by scanning electron microscopy. Elevated temperature was required for the lysis, probably to redistribute the sterol in the lipid bilayers in the plasma membranes. When the sterol was incorporated at low temperature, the temperature had to be raised to readily lyse cells. This lytic effect was, surprisingly enough, restricted to the R-isomer; the S-isomer was only marginally effective. Furthermore, sitosterol and other oxygenated sterols, with a hydroxyl group at different positions in the side chain of cholesterol, were much less lytic, regardless of the configuration of the hydroxyl group introduced. A possible mechanism for this interesting phenomenon will be discussed in relation with a structural alteration in lipid bilayers in plasma membranes brought about by the incorporation of this unique oxygenated sterol.

Animals↗
PubMed1985

The submucosal island flap in the closure of oro-antral fistula.

A submucosal island palatal flap technique was used successfully in seven patients for closure of large oro-antral fistulae. The technique provides not only an island flap of submucosal connective tissue to close the fistula, but a flap of mucosa to cover the raw area of palatal bone. The advantages of the technique are that healing is satisfactory without denuded bone, the island flap has excellent mobility and does not produce bunching of the mucosa of the hard palate and recipient site, and dentures may be fitted early following the excellent healing of the wound.

Adult↗
PubMed1985

Controlled transcription of the yeast regulatory gene GAL80.

Transcription of the tightly linked genes GAL7-GAL10-GAL1 encoding three galactose-metabolizing enzymes in Saccharomyces cerevisiae is regulated by an interplay of the positive regulatory gene GAL4 and the negative regulatory gene GAL80. The concentration of GAL80 mRNA (determined by a quantitative blot hybridization) was nearly comparable to that of URA3 mRNA, in the wild-type yeast grown in medium with glucose or glycerol. The intracellular concentration of GAL80 mRNA increased by changing the carbon source to galactose by a factor of more than 5, in contrast to a GAL4 mRNA concentration which is essentially unaffected by galactose [Laughon and Gesteland, Proc. Natl. Acad. Sci. USA 79 (1982) 6827-6831]. The inducible expression of the GAL80 gene was suggested to involve its own product and also the product of GAL4 by using various mutations in those genes.

DNA, Fungal↗