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Biomedical subjects

A Hirata

Publications and source records attributed to A Hirata.

At least 217 records · Page 12Linked to original sources
PubMed1989

Cytochemical studies on pathological Müller cells after argon laser photocoagulation.

The cytochemical localization of G6Pase activity, which is specific to the endoplasmic reticulum (ER) of Müller cells, was studied after argon laser photocoagulation in the guinea pig retina. After argon laser radiation, Müller cells exhibited enlargement of the cytoplasm, an increase of reactive ER and the nuclei, dislocation of the nuclei and diagonal stretching of the cytoplasm. However, cell attachment between Müller cells and the proliferated pigment epithelial cells or Bruch's membrane differed with the degree of retinal coagulation. This histo- and cytochemical method may be useful for examining Müller cells under various pathological conditions.

Animals↗
PubMed1988

Thermosensitive omsA mutation of Escherichia coli that causes thermoregulated release of periplasmic proteins.

A mutant of Escherichia coli with a thermosensitive defect, possibly in the outer membrane (omsA mutant), was isolated from E. coli K-12 by mutagenization and selection for thermosensitivity and beta-lactam supersensitivity of growth. The mutant also showed very high sensitivity to other antibiotics, such as macarbomycin, midecamycin, rifampin, and bacitracin. The mutation was recessive to the wild type and was mapped at about 4 min on the E. coli chromosome between fhuA and metD. The mutation caused rapid release into the medium of periplasmic enzymes such as RTEM penicillinase but practically no cytoplasmic enzyme when cells grown at 30 degrees C were transferred to 37 or 42 degrees C. Electron microscopic observations showed many large double-layered vesicles attached to the surface of cells incubated at 42 degrees C. We conclude that the mutant had a mutation that caused a temperature-dependent defect in the outer membrane structure or its assembly (named an oms mutation). The omsA mutant may be useful for production of periplasmic proteins, which it releases into the culture medium on shift up of temperature.

Bacterial Outer Membrane Proteins↗
PubMed1987

Inhibition of microtubule polymerization by synthetic estrogens: formation of a ribbon structure.

Dienestrol, meso-hexestrol, and dl-hexestrol, synthetic nonsteroidal estrogens, were shown to be inhibitors of microtubule assembly in vitro using microtubule proteins isolated from porcine brains. The order of activity of the synthetic estrogens as inhibitors of microtubule assembly is: dienestrol greater than diethylstilbestrol greater than meso-hexestrol greater than dl-hexestrol greater than isodienestrol. The activity of dienestrol as an inhibitor was of the same order as that of (+)-griseofulvin, as determined by turbidity measurement. Electron microscopic observation revealed that twisted ribbon structures are formed from microtubule proteins in the presence of some synthetic estrogens (dienestrol, meso-hexestrol, and dl-hexestrol).

Animals↗
PubMed1986

Hypokalemia modulates alpha- and beta-adrenoceptor bindings in rat skeletal muscle.

Changes in the population of adrenergic alpha- and beta-receptors were examined in rat soleus muscles during hypokalemia by their direct determination using radiolabeled ligands. Only beta-adrenoceptors were detected in the normal rat muscles. Hypokalemia led to a pronounced decrease in beta-adrenoceptors, the number of [3H]DHA binding sites, by 50%, as compared with that in the normal rats. There was a genesis of alpha 1-adrenoceptors in hypokalemic rat muscles, since the competitive potency of adrenergic drugs against [3H]prazosin binding was in the order prazosin much greater than phentolamine greater than (+/-)-noradrenaline greater than yohimbine much greater than (+/-)-isoproterenol. The reduction of [3H]DHA binding sites was accompanied by an increase of an approximately equal amount in high-affinity [3H]prazosin binding sites. The Kd determined by kinetic analysis of [3H]prazosin binding was calculated from the ratio K-1/K1 that gave a value of 3.05 nM, which generally agreed with the 1.83 nM determined by saturation experiments (Scatchard plot). This phenomenon of a reduction in the beta-adrenoceptors and the occurrence of alpha 1-adrenoceptors in muscles during hypokalemia is discussed. alpha- and beta-adrenoceptors on soleus muscle membrane may play important but opposite roles in modulating potassium release from the muscle cells.

Animals↗
PubMed1986

[A clinical observation on aged patients subjected to urological surgery].

A clinical analysis was made on 44 inpatients over 80 years old at our department from 1980 to 1984. Forty-three urological surgeries were performed on 36 out of the 44 patients, accounting for 3.4% of all the inpatients. Benign prostatic hypertrophy, which was the most popular disease in our study, was seen in 20 patients. Preoperative examinations revealed one or more complications besides urological disorders in 35 patients (97.5%), 11 patients of which needed some prophylactic treatments prior to urological surgery. Although major postoperative complications consisted of heart disease in 4 patients, gastrointestinal tract disease in 3 patients, and pulmonary disease in 2 patients, there was no operative death. Postoperative laboratory test results revealed hypoproteinemia in 16 patients (44.4%). Postoperative urological complications such as wound dehiscence, urinary fistula, or acute epididymitis occurred in 9 patients, all of whom had urinary tract infections. These results suggest that aged patients have fewer problems if extensive preoperative examinations and active treatments for any abnormality are made and careful attention is paid to postoperative complications.

Aged↗
PubMed1986

[Clinical effect of buprenorphine in ureteral colic].

Buprenorphine, a new analgesic, was administered at a dose of 0.2 mg by intramuscular injection to 21 patients with acute ureteral colic. The patients consisted of 14 males and 7 females with a mean age of 42. In all cases, the diagnosis was confirmed based on intravenous urography performed after the treatment. In 19 of the 21 patients, colicky pain was reduced at least within one hour after the administration of buprenorphine. No significant changes in the pulse or blood pressure were observed. In 6 patients, mild dizziness or nausea was observed, and none of the patients required withdrawal of the treatment. Clinical use of buprenorphine was considered to the effective and safe in patients with ureteral colic.

Adolescent↗
PubMed1986

[Photodynamic therapy of superficial bladder tumors].

Photodynamic therapy (PDT), using hematoporphyrin derivative (HPD) and the red light (wavelength 630 nm) of an argon-dye laser as the source of excitation energy was performed on 46 patients with superficial bladder tumors. Two methods of laser irradiation, (1) focal PDT using a 400 micron quartz fiber through a cystourethroscope in 22 patients with superficial bladder tumors and (2) whole bladder wall total PDT using a motor-driven laser light scattering device in 24 patients with multifocal carcinoma in situ and/or dysplasia of bladder mucosa associated with multicentric concurrent superficial tumors, were used. The patients in (2) had been referred for total cystectomy, and 19 of these 24 patients had a history of several transurethral resections, hyperthermia and/or instillation therapy. HPD 2-4 mg/kg was i.v. injected 48 to 72 hours before PDT. Judging from the results of 60 protrusions treated by focal PDT, the light power should be 200 mW/cm2 for 5-10 minutes or more and the total light energy should be 100 J/cm2 or more in tumors up to 2 cm in size. With focal PDT, 4 of the 22 patients had no recurrence with the mean tumor free time of 20.8 months. In 6 of the 24 patients treated with total PDT using 10, 20 or 30 J/cm2 of light energy, there was no recurrence with a mean tumor-free time of 7.5 months and there was no significant relationship between the recurrence rate and total light energy used.

Adult↗
PubMed1985

Characterization of meiosis-deficient mutants by electron microscopy and mapping of four essential genes in the fission yeast Schizosaccharomyces pombe.

Meiosis-deficient mutants of the fission yeast Schizosaccharomyces pombe carrying mei1, mei2, mei3, mei4 and mes1 mutant alleles were characterized by electron microscopy and staining of the nucleus with 4', 6-diamidino-2-phenylindole. Zygotes of either mei1, mei2 or mei3 mutants contained one round nucleus with a single spindle pole body (SPB). These mutants were arrested before premeiotic DNA synthesis. Zygotes of mei4 mutants had one elongated nucleus containing thick electron-dense filaments (linear elements). In the mes1 mutant, the first meiotic division was completed but the SBPs did not duplicate. Modification of the SPB (outer plaque formation) was also blocked and the forespore membrane was not assembled. By haploidization, random spore and tetrad analyses, four essential genes for meiosis (mei2, mei3, mei4 and mes1) were mapped. Gene mei2 was located on chromosome I 14.2 cM distant from ura2. Gene mei3 was linked to ade7 (45.4 cM) on chromosome II. Gene mei4 was linked to cdc2 (0.6 cM) on chromosome II. Gene mes1 was linked to ura3 (25.3 cM) on chromosome I.

Ascomycota↗
PubMed1985

Outer plaque assembly and spore encapsulation are defective during sporulation of adenylate cyclase-deficient mutants of Saccharomyces cerevisiae.

Sporulation in diploid cells homozygous for the cyr1-2 mutation of the yeast Saccharomyces cerevisiae was examined. This mutation causes a defect in adenylate cyclase and temperature-sensitive arrest in the G1 phase of the mitotic cell cycle. The cyr1-2/cyr1-2 diploid cells were able to initiate meiotic divisions, but produced predominantly two-spored asci at the restrictive temperature. Temperature-sensitive period for production of two-spored asci was approximately 12 h after the transfer of cells to the sporulation medium. The levels of cAMP increased during this period in the wild type and cyr1-2/cyr1-2 diploid cells incubated at the permissive temperature, but remained at an extremely low level in the cyr1-2/cyr1-2 diploid cells incubated at the restrictive temperature. Dyad analysis of the cyr1-2 strain indicated that meiotic products were randomly included into ascospores. Fluorescent microscopy of the cyr1-2/cyr1-2 diploid cells incubated at the restrictive temperature revealed that individual haploid nuclei were enclosed in each of the two spores after meiosis. About half of the cyr1-2/cyr1-2 diploid cells entered normal meiosis 1 producing two normal spindle pole bodies with inner and outer plaques, and the other half entered abnormal meiosis 1 producing one normal spindle pole body and one defective spindle pole body without out plaque. At meiosis II, some cells contained a pair of normal spindle pole bodies and other cells contained pairs of normal and abnormal spindle pole bodies.

Adenylyl Cyclases↗
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↗
PubMed1984

Blocking effect of verapamil on conduction over a catecholamine-sensitive bypass tract in exercise-induced Wolff-Parkinson-White syndrome.

By intravenous administration of isoproterenol, 0.5 micrograms/min, a catecholamine-sensitive bypass tract was confirmed in two patients with exercise-induced Wolff-Parkinson-White syndrome. In a 24 year old woman, an intravenous bolus injection of 5 mg of verapamil suddenly blocked conduction over a catecholamine-sensitive bypass tract. In a 62 year old man, the exercise-induced Wolff-Parkinson-White syndrome disappeared after 3 days of oral administration of verapamil (120 mg/day). These observations suggest that a slow inward calcium current plays an important role in conduction over a catecholamine-sensitive bypass tract in exercise-induced Wolff-Parkinson-White syndrome.

Adult↗