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Biomedical subjects

K Ohtsuki

Publications and source records attributed to K Ohtsuki.

At least 127 records · Page 7Linked to original sources
PubMed1984

Nucleosidediphosphate kinase in Escherichia coli: its polypeptide structure and reaction intermediate.

A nucleosidediphosphate kinase (NDP-kinase) has been highly purified from E. coli. The purified enzyme was found to have a molecular weight of approximately 64,000 daltons and be a 16,000 dalton polypeptide tetramer. The enzyme rapidly formed a phosphoenzyme when incubated with ATP in the presence of divalent cations such as Mg2+ and Ca2+ (1 mM) even at low temperatures (below 4 degrees C). The available evidence suggests that the phosphoenzyme is an enzyme-bound high energy phosphate intermediate, which functions as an intermediary in NDP-kinase action.

Amino Acids↗
PubMed1984

Apparent accommodation in pseudophakic eyes after implantation of posterior chamber intraocular lenses: optical analysis.

The authors measured apparent accommodation in 39 pseudophakic eyes (31 patients) after implantation of posterior chamber intraocular lenses. The mean apparent accommodation was 2.01 +/- 0.95 D. The authors also measured each patient's pupillary diameter, anterior chamber depth, and corneal refractive power to calculate the factor that represents the depth of field. The authors found a significant correlation between apparent accommodation and depth of field. The correlation between apparent accommodation and calculated depth of field is statistically significant (r = 0.48, P less than 0.005).

Accommodation, Ocular↗
PubMed1984

[Reduction of cisplatin toxicity by fosfomycin in animal models].

The protective effect of fosfomycin against cisplatin-induced toxicities was studied in rats. A total of 64 Fischer rats were injected intravenously with daily doses of 1, 2, 5 and 10 mg/kg of cisplatin with or without 300 mg/kg of fosfomycin for a period varying from 1 to 10 days. The same total dose of 10 mg/kg of cisplatin was given to all animals. Cisplatin-induced toxic side-effects of body weight loss, nephrotoxicity and ototoxicity were significantly reduced functionally or histopathologically by the combined administration of cisplatin and fosfomycin. A comparison of different dosage schedules with a total dose of 10 mg/kg of cisplatin showed that a higher daily dose for a shorter time period produced more marked toxicities.

Alanine Transaminase↗
PubMed1983

Mouse submaxillary renin has a protease activity and converts human plasma inactive prorenin to an active form.

The activation of inactive prorenin by active renin was investigated. Inactive prorenin extensively purified from human plasma was activated by active renin which had been purified from mouse submaxillary glands by multiple chromatographic steps. The apparent lack of protease activity in renin was puzzling in view of the close similarity of its active site structure with that of acid proteases. After a series of affinity chromatographic steps designed to eliminate minute contaminants, renin was found to contain a very low but finite level of a neutral protease activity which was equivalent to 1/40,000 of that of cathepsin D tested by hemoglobinolytic activity. The protease activity was considered as intrinsic to renin since it co-purified with renin persistently at a constant ratio to the renin activity, was precipitated by a monoclonal antibody specific for renin, showed a neutral pH optimum of the enzyme activity in the same pH range as that of renin, and was inhibited by pepstatin. The neutral protease activity is likely to mediate the activation of inactive prorenin.

Animals↗
PubMed1983

Apparent accommodation in pseudophakic eyes after implantation of posterior chamber intraocular lenses.

We measured apparent accommodation in 42 pseudophakic eyes (34 patients) after implantation of posterior chamber intraocular lenses. The mean apparent accommodation was 2.03 +/- 1.03 diopters. The mean accommodative power of 16 phakic eyes used as controls was 2.91 +/- 1.29 diopters. The diameter of the pupil appeared to be the most important factor in apparent accommodation--the smaller the pupil, the greater the apparent accommodation. Apparent accommodation was inversely proportional to the pupillary diameter. There was no correlation, however, between apparent accommodation and corrected visual acuity, refractive error, corneal astigmatism, or axial length. There was a negative correlation between apparent accommodation and anterior chamber depth.

Accommodation, Ocular↗
PubMed1982

Biochemical characterization of a specific phosphate acceptor of nuclear cyclic AMP-independent protein kinase.

The regulatory mechanism of transcription involved in the phosphorylation of a 13 kDa non-histone chromatin protein from calf thymus, which is the most effective phosphate acceptor for cyclic AMP-independent protein kinase purified from the nuclei of mouse spleen cells, by the kinase has been studied in vitro. An analytical study of the circular dichroism (CD) spectra of the 13 kDa protein under different conditions showed that it underwent a major conformational change when incubated with DNA. The presented data suggest that the DNA-induced conformational change may result in a great increase of the 13 kDa protein phosphorylation by the kinase in vitro. Mg2+ (8-10 mM) enhanced the binding of the protein to DNA. Furthermore, the phosphorylated 13 kDa protein stimulated elongation of RNA synthesis by RNA polymerase II from calf thymus. However, neither the 13 kDa protein nor the phosphorylated 13 kDa protein had any affect on DNA synthesis. The available evidence suggests that the 13 kDa protein may play a role in the regulation of transcription through its phosphorylation by the kinase in vitro.

Animals↗
PubMed1982

Evaluation of ototoxicity of amino-glycoside antibiotics in rabbits.

It is generally accepted that the ototoxicity of aminoglycoside antibiotics is gentamicin (GM) greater than dibekacin (DKB) greater than kanamycin (KM) greater than amikacin (AMK) based on the results of animal experiments. However, clinical data reveals that the ototoxicity caused by each of the aminoglycoside antibiotics does not coincide with the ototoxicity in the animals. The present study was intended histopathologically for comparative evaluation of above-mentioned antibiotics using rabbits. The ototoxicity was GM greater than DKB greater than KM greater than AMK with the dose of 100 mg/kg, which coincide with many of the conventional reports on animal experiments. However, with the dose of 50 mg/kg, the order was GM greater than AMK greater than KM greater than DKB. With the dose of 30 mg/kg, hardly any differences were noted between the ototoxicity of GM and that of AMK. It was found out that the evaluation of the ototoxicity of drugs in high doses does not always correspond to that of lower doses. Therefore, the ototoxicity should be evaluated in strict consideration of dose of drugs. Usually, the doses of drugs used in the ototoxicity studies with animals are more than 10 times higher than those used clinically. Consequently, problems still exist in infering the ototoxicity of drugs in humans directly from the results obtained from animal experiments.

Amikacin↗
PubMed1982

Interferon gamma-induced Ca-dependent protein kinase in mouse L cells.

Treatment of mouse L cells with mouse IFN gamma induced a cytoplasmic Ca-dependent protein kinase, which highly phosphorylated cellular enzymes such as phosphodiesterase and RNase in vitro. The kinase partially purified from IFN gamma-treated cells (100 units/ml, 12 h at 37 degrees C) was different from IFN-induced dsRNA-dependent protein kinase since it was dsRNA independent. The kinase may have played an important role in mediating IFN-induced biological effects, since cellular enzymes were found to alter enzyme activity after phosphorylation by the kinase in vitro.

Animals↗
PubMed1982

Ototoxicity of aminoglycoside antibiotics by rapid intravenous injection.

The ototoxicity and nephrotoxicity of aminoglycoside antibiotics (dibekacin, gentamicin and kanamycin) administered to rabbits by rapid intravenous or intramuscular injections were histopathologically compared. Comparative evaluations between the two routes were further made concerning the levels of the antibiotics in serum and in perilymph. The results revealed that, although the peak serum level after a rapid intravenous injection was significantly higher than that observed after an intramuscular injection, no differences in the transfer into the perilymph, and in inner ear or renal damage were seen between the two different routes. In other words, the results of the present study did not support the conventional idea that the higher the peak blood levels of the aminoglycoside antibiotics, the greater the risk of damage to the inner ear or kidney.

Aminoglycosides↗
PubMed1982

Human plasma inactive renin: purification and activation by proteases.

A new affinity chromatographic procedure was devised to purify inactive renin by using a selective hydrophobic interaction of inactive renin to octyl-Sepharose. Additional extensive purification was accomplished by immunoaffinity chromatography on antihuman renin immunoglobulin G-Sepharose. A trace amount of active renin was removed by chromatography on pepstatin-Sepharose. Human plasma inactive renin purified by this method was free from protease inhibitors and permitted the investigation of protease-mediated activation without the acid treatment which was used previously to remove inhibitors. Human plasma kallikrein, human plasmin, cathepsin B1, and arginine esteropeptidases associated with mouse epidermis growth factor and nerve growth factor were effective activators. Human urinary kallikrein, hog pancreatic kallikrein, and rat urinary esterase A were inefficient activators of low potency. Thrombin, factor Xa, factor XIIa, and urokinase did not activate inactive renin. The in vitro activation of 56,000-dalton inactive renin by these proteases was not accompanied by a recognizable reduction in molecular weight. Activation required plasma albumin, presumably as a protecting substance. These results suggest that human inactive renin can be activated by a minimum change in its molecular size.

Cathepsin B↗
PubMed1981

Totally inactive renin zymogen and different forms of active renin in hog brain tissues.

The nature of the activable form of renin in the kidney and other tissues has not been clear. Its identification and isolation from kidney have been hampered by rapid activation due to high levels of proteases. Using a pepstatin-Sepharose column, which distinguishes inactive renin from the active enzyme, evidence was obtained for the presence of a totally inactive zymogenic precursor of renin in the pituitary, pineal, and other regions of hog brain. The precursor has an approximate molecular weight of 50,000 and conversion to the active enzyme causes reduction in molecular weight to 43,000. Conversion of this active enzyme to an active but high molecular weight form (60,000) was also observed when the pituitary extract was treated with thiol-blocking reagents. This result was interpreted to indicate the presence of a binding protein. This study has demonstrated that inactive renin zymogen is different from so-called active big renin, which is a complex of active renin and the binding protein.

Animals↗
PubMed1981

The inhibitory mechanism of in vitro protein phosphorylation by a nonprotein chromophore removed from neocarzinostatin.

The inhibitory effect of a nonprotein chromophore removed from neocarzinostatin on protein phosphorylation by nuclear protein kinase in vitro has been studied. Low levels of the chromophore greatly inhibited protein phosphorylation in vitro. This inhibition, however, was not selectively dependent on the indicated kinases and their different phosphate acceptors (histones and non-histone protein). In contrast, the protein component (apoprotein) of neocarzinostatin did not affect the phosphorylation even at a concentration of 400-times higher than that of the chromophore. Moreover, apoprotein suppressed the chromophore-induced inhibition of protein phosphorylation in vitro in proportion to the apoprotein concentrations. Kinetic and analytical experiments suggest that the chromophore-induced inhibition of protein phosphorylation seems to be due to the binding of the chromophore to the kinases. In addition, we found that ultraviolet irradiation as well as methanol extraction can release the chromophore from neocarzinostatin, but it exhibits no inhibitory activity of DNA synthesis in growing cells. The fact that the chromophore-induced inhibition of protein phosphorylation in vitro was not sensitive to ultraviolet irradiation, which rapidly inactivated the ability of the chromophore to induce DNA degradation in vitro, suggests that there are different actions involved in the two inhibitions induced by the chromophore which is removed from neocarzinostatin.

Animals↗