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Biomedical subjects

M Ohtsuki

Publications and source records attributed to M Ohtsuki.

At least 109 records · Page 6Linked to original sources

Preferential inhibition of the activity of a stimulatory protein of eukaryotic transcription by platinum (II) complexes.

The effect of platinum(II) complexes on RNA polymerase II was studied. (D-Glucuronato)(1R,2R-cyclohexanediamine)platinum(II) nitrate (II-GHP) preferentially inhibited RNA synthesis in the presence of S-II, an essential component of eukaryotic transcription. When DNA was pretreated with I-GHP, its template activity decreased significantly, especially when assayed in the presence of S-II. The target of platinum(II) complexes is probably DNA. When DNA is modified, regulatory proteins of transcription, such as S-II, seem to lose their function preferentially on such a template, resulting in the inhibition of RNA synthesis.

HeLa Cells↗

Computed tomography in the diagnosis of fatty liver: total lipid content and computed tomography number.

Fifty-three histologically proved cases of various diffuse liver disease were studied for their computed tomography numbers (CTN). The machine used was Ohio Nuclear's Delta Scanner 50FS type and CTN was expressed by the Hounsfield unit (H). Mean CTN in each group was as follows: 66.6 +/- 2.6 H in normal control (N), 63.3 +/- 6.0 H in chronic hepatitis (CH). 61.8 +/- 7.0 H in liver cirrhosis (LC), and 44.4 +/- 10.6 H in fatty infiltration (FI). There were no significant differences among them except FI group. As N group were all above 60 H and CH and LC groups were all above 50 H, CTN below 60 H suggests chronic liver disease or fatty infiltration and CTN below 50 H strongly suggests fatty infiltration. In eleven cases where total lipid content of the liver could be be biochemically determined by the sulfo-phospho-vanillin reagent, a relation of total lipid content to CTN was studied. As a result, a significant correlation existed between them (r = -0.89; p less than 0.001). If the diagnostic criterion of fatty liver was set at total lipid content above 100 mg/g wet liver, CT criterion was estimated at CTN below 48 H from the regression formula.

Chronic Disease↗

Observation of unstained biological macromolecules with the STEM.

We discuss the observation of an unstained single biological macromoilecule of human serum low density lipoprotein in a scanning transmission electron microscope (STEM). Using a carbon substrate with 16 A average thickness and an electron dose of 19 electrons/A2 the image obtained from the unstained molecule shows a similar surface substructure as that seen in a negatively stained conventional transmission electron microscope (CTEM) micrograph.

Freeze Drying↗

Optimal imaging techniques in the scanning transmission electron microscope: applications to biological macromolecules.

We show applications of the optimal imaging method to stained biological macromolecules. This optimal imaging method involves the following basic procedures: (i) for any given resolution, which is represented by the electron probe size in the scanning transmission electron microscope, a preferred magnification is used; (ii) the micrographs taken at the condition described above are then spatially filtered by using a low-pass filter (nu < 1/2d, in which d is the space between scan lines) to optically reconstruct the final optimal image. It is found that the micrographs obtained by using the optimal imaging method clearly show an improvement in contrast.

Animals↗

Membrane-bound fructose 1,6-bisphosphate aldolase: catalytic activity and mechanisms of desorption.

Fructose 1,6-bisphosphate aldolase [EC 4.1.2.13] in rat liver was found to be bound to the intracellular membraneous structures such as microsomes and nuclear membranes when the animals were fasted for 48 hr or administered tryptophan. Upon refeeding the rats the aldolase was released into the cytosol. The membrane-bound aldolase was almost inactive, showing about 50-fold larger Km and a smaller Vmax (37%) as compared with those of the free enzyme. The enzyme was released cooperatively from the membrane by exposure to fructose 1,6-bisphosphate, glyceraldehyde 3-phosphate or dihydroxyacetone phosphate at low concentrations. Apparent desorption constants (Kd, concentrations necessary for 50% desorption of enzyme) for fructose 1,6-bisphosphate of the enzymes bound to microsomes, mitochondria and nuclei were estimated to be 8 X 10(-5), 6.1 X 10(-6), and 4.8 X 10(-6)M, respectively, at pH 7.3. With the microsome-bound enzyme Kd values of 3.9 X 10(-4), 4.1 X 10(-4), 2.7 X 10(-3), 1.1 X 10(-2) and 2.0 X 10(-2) M were obtained for glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, fructose 1-phosphate, fumarate, and KCl, respectively. Strong cooperativities were observed in the enzyme desorption by the substances which showed large Kd values.

Animals↗

[Experimental studies on administration method of chemotherapeutic agents. 16. Effect of polymyxin B against Pseudomonas aeruginosa (author's transl)].

The most effective administration method of polymyxin B (PL-B), a peptide antibiotic, has been studied in the experimental mice infection with Pseudomonas aeruginosa. 1) Pseudomonas aeruginosa damaged by PL-B, when the drug was free, immediately began to regrow in vitro. 2) the therapeutic efficacy of PL-B on multiple administration was less effective than its single administration. 3) An important factor to decide the therapeutic efficacy of PL-B was the high drug concentration in plasma and peritoneal fluid.

Animals↗

Dark field imaging of biological macromolecules with the scanning transmission electron microscope.

A scanning transmission electron microscope (STEM) equipped with a field emission gun has been employed for the examination of biological macromolecules at high resolution. The quality of micrographs obtained with the STEM is dependent upon the quality of the substrate used to support biological objects because the image contrast in dark field is proportional to the mass density of the specimen. In order to reduce deleterious effects of the substrates on the image quality, we have developed a method of fabricating substrates consisting of very thin, very clean carbon films supported on very clean fenestrated plastic films. These films are approximately 15 A thick. Well-known biological macromolecules such as glutamine synthetase and tobacco mosaic virus (both stained) and low-density lipoprotein and ferritin (both unstained were placed on these substrates and examined with the STEM by using various modes of contrast. The micrographs obtained by using the dark field mode of contrast employing an annular detector were free from phase contrast, as expected. Using this contrast mode, we have been able to directly observe (in-focus) 2.5- to 4.4-A lattice spacings in the ferritin core. The effect of electron radiation damage on the helical structure of tobacco mosaic virus was also examined. Micrographs as well as corresponding optical diffraction patterns obtained with moderately low doses showed very clear helical structure from both sides of the virus. In addition, the (11.5 A)(-1) layer lines indicated the effective resolution attained on these particles.

Ferritins↗

Mechanisms of desorption and adsorption of liver cytosolic fumarase to cellular membranous components.

The cytosolic fumarase [EC 4.2.1.2[ of rat liver was bound, after dialysis, to the microsomal membrane in vitro. Binding of the enzyme was dependent on pH, and was facilitated in the pH range below 7.5. The binding reaction was completely inhibited by 0.5 mM fumarate, aurintricarboxylate or colchicine. The bound fumarase was released from the membrane by the substrates, isocitrate, citrate or 2,3-diphosphoglycerate at low concentrations. Desorption of the enzyme by metabolites was also dependent on pH, and was more rapid in the alkaline pH range. The enzyme desorption curves were sigmoidal, and kinetic studies suggested a biphasic cooperative mechanism for the action of the metabolites. The apparent desorption constants (concentrations necessary for 50% desorption of the enzyme) estimated at pH 7.3 for isocitrate, 2,3-diphosphoglycerate, L-malate, oxalacetate, fumarate, citrate, succinate, and KCl were 0.073, 0.074, 0.22, 0.39, 0.56, 2.9, and 19 mM, respectively. The bound fumarase showed little enzymatic activity, and its Km and Vmax values were fivefold and 31%, respectively, of those of the free enzyme.

Adsorption↗

The lipid-chemical features of the metastatic tissues into the liver from the human gastric cancer, large intestinal cancer and malignant insulinoma.

In order to clarify the biochemical features of metastatic tissues into the liver of human cancerous cells, 12 of primary cancerous tissues and 3 of metastatic tissues of the large intestinal cancer, 6 of primary cancerous tissues and 2 of metastatic tissues of the gastric cancer, and 3 of primary cancerous tissues and 3 of metastatic tissues of malignant insulinoma were studied lipid-chemically. Cancerous tissues and metastatic tissues into the liver were collected by biopsy or surgical operation. From each tissue, the total lipid was extracted and one part of the total lipid was separated into phospholipid and triglyceride by TLC. Then, the fatty acid composition and the fatty acid content of each lipid fraction were measured by GLC. The most remarkable findings were recognized in the phospholipid fatty acid composition of the tissues. Namely, the percentage values of C14:0 and C16:1 were larger and that of C20:4 was smaller in metastatic tissues than those of gastric primary lesions. As for the large intestinal cancer, the percentage value of C18:1 was smaller and that of C18:2 larger in metastatic tissues than those of primary lesions. In the malignant insulinoma, the percentage value of C18:0 was larger in metastatic tissues than that of the primary lesions.

Adenoma, Islet Cell↗

Electron microscopy of negatively stained and freeze-etched high density lipoprotein-3 from human serum.

High density lipoproteins of d = 1.12 to 1.21 g/ml from human serum (HDL3) were studied by electron microscopy with both negative staining and freeze-etching techniques. For the negatively stained specimens, a modified conventional transmission electron microscope as well as a scanning transmission electron microscope were used. The freeze-etched specimens were examined by a conventional transmission electron microscope. The diameter of HDL3 was found to be 105 +/- 4 A by freeze-etching and 94 +/- 6 A by negative staining. The surface of the HDL3 particles exhibited about 12 discrete domains, 28 +/- 3 A (freeze-etched) and 28 +/- 4 A (negatively stained) in diameter, of undefined chemical composition. Moreover, the freeze-etched specimens revealed an inner core 40 +/- 2 A in diameter, corresponding to estimated values reported previously. All information is consistent with the HDL3 model proposed by B. W. Shen, F. J. Kézdy, and A. M. Scanu [(1977) Proc. Natl. Acad. Sci. USA 74, 837-841], with additional evidence for well-defined surface substructure. The consistency of the images obtained with the various electron microscopy techniques and the marked change in the appearance of the surface in the HDL3 preparations that were digested by phospholipase A2 (EC 3.1.1.4) support the validity of the interpretation.

Freeze Etching↗

Electron microscopy of fibers and discs of hemoglobin S having sixfold symmetry.

Aggregated forms of deoxyhemoglobin S were examined with a field emission transmission electron microscope. Images of isolated helical fibers were obtained from sickled cell lysates stained directly on the electron microscope grid. Optical and digital analyses of the electron micrographs showed that the fibers are similar to those characterized by J. T. Finch, M. F. Perutz, J. F. Bertles, and J. Döbler [(1973) Proc. Natl. Acad. Sci. USA 70, 718-722] in that they consist of stacked discs each composed of six hemoglobin molecules. The fibers exhibit an outer diameter of 160-170 A and an inner diameter of about 60 A with an axial spacing of 58 A per disc. The fiber can be described as a helix consisting of 56 discs per helical turn. We observed discs of six hemoglobin molecules, which may be stable substructural components of the fibers. They were observed in preparations of hemoglobin fibers and exhibited 6-fold symmetry by power spectrum analysis. A reconstructed image of a disc digitally filtered for 6-fold symmetry has a maximum external diameter of approximately 170 A and a central hole of 60 A diameter and is similar to the axial projection of a single disc from a low-resolution, three-dimensional reconstructed model of a fiber.

Computers↗

[Bacteriological evaluation of clindamycin-2-phosphate (author's transl)].

Clindamycin-2-phosphate, a newly developed injectable antibiotic, was bacteriologically evaluated in comparison with the parent compound, clindamycin. Clindamycin-2-phosphate has a rather weak antibacterial activity. However, it is metabolized into clindamycin in vivo. And this parent compound shows strong activity against both gram-positive bacteria and gram-negative cocci. In vitro studies demonstrated that clindamycin-2-phosphate and clindamycin are affected by the pH of the medium used--the antibacterial activity becomes stronger as the medium is made more alkaline--while they are little affected by the size of the inoculum. In mice with experimental infections, clindamycin-2-phosphate showed about the same therapeutical effect as clindamycin in contrast with the former's inferior in vitro activity as compared with the latter.

Animals↗

[In vitro antibacterial effects of spectinomycin and penicillin G on Neisseria gonorrhoeae singly and in combination (author's transl)].

The antibacterial effects of spectinomycin and penicillin G on clinical isolates of Neisseria gonorrhoeae were studied. The concentrations of penicillin G at which the isolates showed drug sensitivity ranged widely from 0.011 to 6.25 mug/ml. Some of the isolates were resistant to penicillin G. Sensitivity to spectinomycin was observed at the drug concentrations ranging from 3.13 to 12.5 mug/ml. About 60% of the isolates were sensitive to 6.25 mug/ml of spectinomycin, and those isolates which were resistant to penicillin G showed good sensitivity to spectinomycin. No correlation in sensitivity was noted between the two drugs. Tests for their bactericidal activities on bouillon media revealed that the addition of spectinomycin at the concentration of 12.5 mug/ml or over produced a marked bactericidal effect in a short time while penicillin G exhibited a bactericidal or bacteriostatic effect depending upon the concentration used. A synergistic effect of a penicillin and an aminoglycoside antibiotic was observed in these isolates of N. gonorrhoea as was in the isolates of Pseudomonas aeruginosa. Where penicillin G and spectinomycin were used in combination, a simultaneous addition of both the drugs produced the most marked synergistic effect. Morphology of N. gonorrhoeae cells exposed to either of these drugs was examined under a scanning electron microscope. Exposure to spectinomycin at the level of 6.25 mug/ml resulted in almost no morphological change. At 6.25 mug/ml of the drug, however, a roughened cell surface, a bleb-like structure or a state suggesting the loosening of such a bleb-like structure was noted. The addition of penicillin G at 0.19 mug/ml led to an impairment of cell division at one hour of exposure and to cell swelling and lysis with further exposure. At 1.19 mug/ml of the drug, these processes of cell swelling and lysis took place early.

Drug Combinations↗

Hepatic steatosis and the elevated plasma insulin level in patients with endogenous hypertriglyceridemia.

Among 31 nonobese or obese patients with endogenous hypertriglyceridemia, hepatic steatosis was found by histologic examination of the biopsied specimen in 17 patients, and it was severe in six patients, They had no history of excessive alcohol intake. Chemical analysis revealed that the lipid accumulated in the liver was triglyceride. The hypertriglyceridemic patients, with or without histologic steatosis, showed significantly increased responses of both plasma insulin and blood glucose to oral glucose load compared with control subjects. The responses were more exaggerated in the hypertriglyceridemic patients with steatosis than in the hypertriglyceridemic patients without steatosis. Analysis of correlations between five variables (liver triglyceride, plasma insulin, blood glucose, body weight index, and serum triglyceride) was done on 15 subjects whose liver triglyceride values were quantified, and highly significant correlations were found between liver triglyceride and plasma insulin, blood glucose, or body weight index. A step wise multiple regression analysis performed on the five variables with liver triglyceride as the dependent variable revealed that the plasma insulin level was the most closely related variable, and the blood glucose level the next. The prediction equation for liver triglyceride as a function of plasma insulin and blood glucose levels (r = 0.91, p greater than 0.001) accounted for 84 percent of the total variance of liver triglyceride. It was shown that the decay of intravenously injected insulin in plasma was not delayed in the hypertriglyceridemic patients with steatosis, while the insulin sensitivity examined after intravenous insulin injection significantly decreased in the hypertriglyceridemic patients with or without steatosis, thus suggesting that the hyperinsulinemia in the hypertriglyceridemic patients was due to an increased insulin secretion associated with the decrease in the insulin sensitivity. Therefore, the elevated plasma insulin and blood glucose levels--or the insulin insensitivity by itself--might be the essential abnormalities in patients with endogenous hypertriglyceridemia, which, in extreme cases, might lead to massive triglyceride accumulation in the liver.

Adult↗