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Biomedical subjects

A Okabe

Publications and source records attributed to A Okabe.

At least 91 records · Page 5Linked to original sources
PubMed1986

Lincomycin stimulates synthesis of TEM-2 beta-lactamase by Escherichia coli.

Lincomycin increased the TEM-2 beta-lactamase activity of Escherichia coli K-12 cells carrying plasmid RP4 at a concentration which slightly inhibited cell growth. In a control culture beta-lactamase activity reached its maximal level in late log phase, whereas when lincomycin was present beta-lactamase activity continued to increase into the stationary phase. Lincomycin (100 micrograms/ml) inhibited both cell growth and protein synthesis by about 35% but stimulated beta-lactamase activity 2.5-fold per ml of culture and about 4-fold per cell after 20 h of growth. The amount of beta-lactamase produced in each culture was also compared by densitophotometry of a stained sodium dodecyl sulfate-polyacrylamide gel. The relative values were in good agreement with the relative enzyme activities, indicating that the stimulatory effect of lincomycin was due to an increase in the amount of beta-lactamase protein. Inactivation of beta-lactamase appeared to be faster when lincomycin was present. This was determined by measuring the decrease in beta-lactamase activity when phenethyl alcohol was present to prevent maturation of the enzyme. There was no significant difference in plasmid copy number between the cells grown in the presence or absence of lincomycin. These results indicate that lincomycin stimulates transcription, translation, or translocation of beta-lactamase.

Electrophoresis, Polyacrylamide Gel↗
PubMed1986

[Quantitation of regional left ventricular wall motion by curvature: two-dimensional echocardiographic analysis].

Echocardiographically abnormal regional configuration of the left ventricle is one of the clues in detecting asynergy of the left ventricular wall. For the quantitative assessment, regional left ventricular configuration was expressed quantitatively using a new index, relative curvature. To obtain the end-systolic curvature, end-systolic echocardiograms were digitized and divided into eight segments. Then end-systolic curvature was determined as the reciprocal of the circumradius of a triangle determined by three consecutive dividing points. Relative curvature was defined as the product of end-systolic curvature multiplied by end-diastolic circumference. To assess the accuracy of quantitative analysis of regional left ventricular wall motion by relative curvature, short-axis images of the left ventricle at the level of the chordae tendineae were analyzed in 20 patients with myocardial infarction and 20 normal subjects by three different indices: segmental area change using a fixed reference system, segmental wall thickness change, and relative curvature. Groups of 10 patients with anteroseptal infarction, 10 patients with inferoposterior infarction, and 10 normal subjects could be differentiated from each other by these three indices. With the 95 per cent confidence intervals obtained from 10 other normal subjects, asynergic segments were detected objectively. By segmental area change, the sensitivity was 100 per cent and the specificity was 90 per cent on the anterior wall; the sensitivity was 90 per cent and the specificity was 95 per cent on the posterior wall. By segmental wall thickness change, the sensitivity was 70 per cent and the specificity was 75 per cent on the anterior wall; and those were 80 per cent and 90 per cent, respectively, on the posterior wall. By relative curvature, the sensitivity was 100 per cent and the specificity was 85 per cent on the anterior wall; and those were 90 per cent and 90 per cent, respectively, on the posterior wall. It was concluded that left ventricular regional contraction could be assessed quantitatively by relative curvature which quantitatively expresses regional left ventricular configuration. This index is independent of any reference systems, so it is expected to be used for quantitative analysis of regional wall motion, even though the cardiac motion within the thorax is not disregarded.

Adult↗
PubMed1985

Axonal transport of glycoconjugates in the rat visual system.

Long-Evans rats at 45 days of age were injected intraocularly with 25 mu Ci of [3H]glucosamine. Incorporation of radioactivity into retinal gangliosides, glycoproteins, and glycosaminoglycans (GAGs) was determined at various times after injection. Portions of all three classes of radioactive macromolecules were committed to rapid axonal transport in the retinal ganglion cells. With respect to gangliosides about 60% of those synthesized in the retina were retained in that structure, 30% were committed to transport to regions containing the nerve terminal structures (lateral geniculate body and superior colliculus), and about 10% were deposited in stationary structures of the axons (optic nerve and tract). With the exception of ganglioside GD3 the molecular species distribution of gangliosides synthesized in the retina matched that committed to transport. In contrast to gangliosides a smaller fraction of newly synthesized retinal glycoprotein (less than 12% of that synthesized in the retina) was committed to rapid transport to nerve ending regions and only about 0.5% was retained in the nerve and tract. The molecular-weight distribution of glycoproteins committed to transport differed quantitatively from that of the retina. With respect to GAGs an even smaller portion (1-2%) of that synthesized in the retina was committed to rapid transport; of this portion almost all was recovered in nerve terminal-containing structures. A constant proportion of each retinal GAG species was transported to the superior colliculus. We suggest that most of the retinal gangliosides are synthesized in neurons and preferentially in ganglion cells (possibly a function of the large surface membrane area supported by these cells). Subcellular fractionation experiments indicated that transported gangliosides, glycoproteins, and GAGs may be preferentially distributed into different subcellular compartments.

Animals↗
PubMed1984

Quantitative analysis of the production of heat-labile enterotoxin by enterotoxigenic Escherichia coli.

A modified method of passive immune hemolysis (PIH) was applied to the quantitative assay of heat-labile enterotoxin (LT) produced by enterotoxigenic Escherichia coli. The method enabled the measurement of 0.2 to 1.2 ng LT. The production of LT by enterotoxigenic E. coli under various conditions was analyzed using the modified method. LT production was intense during the logarithmic growth phase and decreased during the stationary growth phase. Lincomycin (50 to 100 micrograms/ml) affected cell growth slightly, but enhanced production of LT until the late-stationary growth phase. About 90% of the LT produced was retained in the cell, and the rest was excreted into the culture medium. The initial pH of the culture medium affected LT production. Alkaline pH enhanced LT production, though growth was depressed. Aeration enhanced both growth and LT production.

Aerobiosis↗
PubMed1984

[Computerized processing of two-dimensional echo-cardiograms: its application for quantitating left ventricular regional contractility and three-dimensional echocardiography].

This study assessed the computerized processing of two-dimensional echocardiograms for quantitating left ventricular regional contractility and for computer reconstruction of the left ventricle; so-called three-dimensional echocardiography. Computer analysis of two-dimensional echocardiograms for quantitative evaluations of the left ventricular regional contractility in myocardial infarction: A new practical method for computer digital image processing of two-dimensional echocardiograms was developed for quantitating left ventricular regional contractility. Short-axis cross-sectional images of the left ventricle at the levels of the mitral valve (MV), papillary muscles (PM) and the apex (AP) were recorded using a phased array sector scanner in thirty patients with healed myocardial infarction and fifteen normal control subjects. The echocardiographic data were recorded on the video tape and transferred to a minicomputer via interface circuits, digitized, and processed automatically. Each digitized image consisted of 256 X 256 pixels with a gray scale of 256 values. The edges of the endocardial and epicardial walls were detected by applying sequential steps including smoothing, dynamic thresholding, region growing, and filling of small holes. The rationale of edge detection depended on assuming that abrupt changes in gray levels occurred at the boundary, and that the points with maximum gradient values were boundaries of the left ventricular wall. Best-fit contours of endocardial and epicardial edges were drawn by fitting a spline. Besides this automatic edge tracing, endocardial and epicardial edges were also manually traced using a digi-pen system, whose results coincided well with automatic tracings. After detection of edges of endocardial and epicardial walls, the short-axis cross sectional left ventricular wall at each level was divided into eight segments. The geometric center of the end-diastolic left ventricular cavity and the axis connecting this with the posterior end of the right side of the septum was used as the reference point and line (fixed reference system). End-diastolic and end-systolic segmental hemiaxes, segmental area, segmental wall thickness and changes during the cardiac cycle were measured and calculated automatically in each segment using a computer. Regional contractility of the left ventricle was evaluated by percent systolic changes of the segmental hemiaxis, area and wall thickness. These values were significantly reduced in the infarcted left ventricular wall as defined by left ventriculography and coronary angiography.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

The effects of acid etching on the in-vivo permeability of dentine in the dog.

Cavities were cut in both lower molars of 11 anaesthetized dogs. Dentine permeability was quantitated in these teeth using a filtration technique before and after acid etching to remove the smear layer. Acid-etching increased 5-fold the ease with which fluid could flow across dentine. Under conditions of high fluid filtration, an opening into the pulp chamber from the opposite side of the tooth produced only slight increases in filtration rate, indicating that the rate-limiting step is filtration of fluid across dentine, rather than removal of the fluid by the pulp circulation.

Acid Etching, Dental↗
PubMed1983

Progressive decrease in dentine permeability following cavity preparation.

Dentine permeability determinations were made longitudinally in cavities prepared in dog teeth in vivo, using two different techniques: isotope clearance and fluid filtration. Measurements made with both techniques indicate that there is a large reduction in dentine-permeability within the first week following cavity preparation. The phenomenon requires an intact pulp and is not the result of microleakage of temporary restorations.

Animals↗
PubMed1983

Coronary angiographic findings in various types of unstable angina--study on the pathophysiology of unstable angina.

Coronary angiographic findings were studied in 129 patients with various types of unstable angina in order to clarify the pathophysiology of unstable angina. The subjects were divided into 3 types: effort angina (E), rest angina (R), and effort and rest angina (E+R), and each of these 3 types was subdivided into group I (new onset), II (recurrent) and III (changing pattern). 1) R had less severe coronary lesions than E or E+R. 2) Severity and distribution of coronary atherosclerotic lesions in unstable angina were similar to those in stable angina. 3) Incidence of coronary spasm is higher in unstable R and E+R than in stable R and E+R, respectively. 4) Unstable R and E+R with frequent attacks were associated with a higher frequency of coronary spasm and severe proximal coronary stenosis than those without frequent attacks, respectively. 5) Among unstable E+R-III (changing pattern), the patients who developed E+R from E showed significantly higher incidence of multiple vessel disease than those who developed E+R from R and significantly lower incidence of spontaneous spasm than those with E+R, who remained with the same pattern but in whom the frequency and/or the intensity of the attack increased, without any significant difference in the severity of coronary stenosis from other 2 subgroups. It is concluded that coronary spasm as well as severe coronary atherosclerotic lesions may be responsible for the unstable state of angina. Especially in R and E+R, coronary spasm is the most important factor responsible for the unstabilization of angina.

Adult↗