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Biomedical subjects

T Aoki

Publications and source records attributed to T Aoki.

At least 829 records · Page 46Linked to original sources
PubMed1991

Expression of a restricted fragment of staphylococcal tetracycline resistance determinant as a fused product in Escherichia coli.

Tetracycline resistance (TcR) plasmid pNS1, a deletion derivative constructed from staphylococcal plasmid pTP5, carries a tet determinant which specifies a TcR protein (TET) with a molecular weight of 50 kilodaltons (kDa). In order to express the pNS1-encoded TET as a fused product, a 0.8 kilobase pairs fragment containing 57.1% of tet determinant was inserted into a chloramphenicol resistance determinant. From the nucleotide sequence, it is deduced that the fusion protein (designated CAT'-TET') is a 53 kDa protein composed of 472 amino acids in which the 199 and 262 amino acids are derived from CAT and TET, respectively. Although the molecular weight of CAT'-TET' obtained from the result of sodium dodecyl sulfate polyacrylamide gel electrophoresis (42 kDa) was not in agreement with its predicted weight (53 kDa), the ratio of TET' segment to the fusion protein (22 kDa/42 kDa) corresponded almost exactly to that deduced from the nucleotide sequence (29 kDa/53 kDa). The expression of CAT'-TET' in Escherichia coli caused a rapid decrease in growth rate and in the number of viable cells. This result is thought to be due to the toxic effect of CAT'-TET' on the cell membrane.

Escherichia coli↗
PubMed1991

[Long-lasting changes in motoneuron discharges following 50 Hz tetanization of afferent nerves in cats].

The effects of 50 Hz tetanization on motoneuron discharges were studied in non-immobilized, non-anesthetized, decerebrate cats. Motoneuron discharges were monitored by recording either muscle (hamstring muscles or foot extensors) action potentials or ventral root (L7 or S1) discharges. In the latter case both ventral and dorsal roots were cut and corresponding dorsal roots were stimulated. It was found that in 13 out of 32 cases the tetanization of the sciatic nerve at 4.0T for 5 s produced enhancement of monosynaptically evoked muscle action potentials (H-wave) for 20-25 min. Three categories of potentials were distinguished in ventral root discharge according to latencies and thresholds: monosynaptic, polysynaptic and late potentials. When the dorsal root was tetanized at 2.5-5.0T for 5 s, all of these 3 categories of potentials exhibited an enhancement of the potential lasting for more than 30 min. The late potential, which was the longest-latency polysynaptic potential (4.7-6.5 ms), was the most sensitive to the tetanization. Its enhancement could develop slowly, yet the degree of the enhancement was the greatest, as compared with other two categories of potentials. In contrast, the enhancement of these potentials were always immediate. In 15 out of 46 cases at least one of the 3 categories of potentials exhibited the enhancement. Since the long-lasting changes were induced only with the strength enough to activate polysynaptic pathways, interneurons were considered to be responsible for these plastic changes. The monosynaptic potential could show a long-lasting depression following the tetanization.

Action Potentials↗
PubMed1991

Radiographic evidence of cholecystokinin octapeptide receptors in the hamster gallbladder.

The distribution of cholecystokinin receptors in the hamster gallbladder was investigated by 125I-labeled Bolton-Hunter-cholecystokinin octapeptide autoradiography. Light microscopic examination showed a marked accumulation of radiolabeled cholecystokinin within the domain of the muscle layer of the gallbladder. The electron microscopic study further disclosed the presence of radiolabeling mostly in those areas corresponding to cell-to-cell junctions of smooth-muscle cells. Our results suggest that contraction of the gallbladder may primarily be induced by cholecystokinin interacting with its specific receptor in smooth-muscle cells. That cholecystokinin receptors were more abundant in the junctional complexes of smooth-muscle cells suggests that cholecystokinin may have a major role in muscle contraction of the gallbladder, which eventually produces an effective bile emptying.

Animals↗
PubMed1991

[Developmental changes and sex differences in judging weights addition between 5th and 6th graders].

The purpose of the present study is to examined developmental changes and sex differences in judging weights. Experimental groups were engaged in weights addition tasks and then given correct answers (correctional feedback). Four to six months later, both experimental and control groups were subjected to the same tasks. The individual range of reaction time in 6th graders is much wider than that in 5th graders and that the presentation of correctional feedback is more effective in 6th graders. These results suggest that 6th graders make more efforts in judging weights addition with logical and overall criteria. Both 6th male and 5th female students judge weight with more consistent confidence than both 5th male and 6th female students. These results suggest that male students come to judge weight with consistent confidence with age while female students do not, and that the social desirability, that is, "male will always hold their own opinion" seems to affect judging process.

Child↗
PubMed1991

A comparative study of the effects of phebrol on the respiratory chains of rat liver, Biomphalaria glabrata and Oncomelania nosophora.

1. Phebrol (sodium 2,5-dichloro-4-bromophenol), a synthetic molluscicide against Oncomelania nosophora, showed a dual effect on rat liver submitochondria, acting as an uncoupler at low concentrations (approximately 10 microM) and an inhibitor of succinate-cytochrome c reductase at high concentrations. 2. Phebrol also inhibited the enzymes responsible for succinate-fumarate conversion, i.e. the succinate-cytochrome c reductase, fumarate reductase and NADH-cytochrome c reductase of the mitochondrial fraction from Biomphalaria glabrata. 3. Kinetic inhibition studies showed succinate-cytochrome c reductase of B. glabrata and O. nosophora to be more sensitive than that of rat liver toward phebrol. 4. Phebrol accumulated in whole tissues of B. glabrata and O. nosophora and had significant effects on the production of succinate, fumarate and malate by these snails. 5. On the basis of these results, the possible sites of inhibition by phebrol of snail respiratory chains are proposed.

Animals↗
PubMed1991

Distribution of substance P and vasoactive intestinal peptide in the human liver: light and electron immunoperoxidase methods of observation.

The localization of substance P (SP) and vasoactive intestinal peptide (VIP) in 12 normal human liver tissues was examined by light and electron immunohistochemistry using immunoperoxidase methods. SP and VIP immunoreactive nerve fibers were observed around portal veins, bile ducts, and hepatic arteries in portal areas, along sinusoids and hepatocytes in hepatic lobules, and around central veins. More SP and VIP immunoreactive nerve fibers were present in the portal areas than in other regions. Moreover, SP and VIP containing nerve endings were localized close to myofibroblasts, Ito cells, fibroblasts and endothelial cells of blood vessels, and sinusoids. The results suggested that part of the innervation of the human liver may be related to the contraction and relaxation of the cells close to nerve endings, and to the regulation of hemodynamic processes by the neurotransmitters such as SP and VIP at the hepatic lobular level.

Adult↗
PubMed1991

[Asbestos concentration and fiber size in lungs of the urban residents].

Asbestos fiber concentrations and fiber size distribution in lung tissues of 53 urban residents (males: 34, female: 19) were analyzed by low temperature ashing-analytical transmission electronmicroscopy. The following findings were obtained. 1. Pulmonary asbestos fibers were found in 51 out of 53 patients. The types of asbestos fibers were chrysotile, amosite, crocidolite, actinolite and tremolite. 2. Thirty-six of 53 patients had no history of occupational asbestos exposure, and their geometric mean concentration of asbestos fibers was 1.67 x 10(6) fibers/g dry lung. Most of these asbestos fibers are probably attributable to general environmental contamination. Thirteen patients who had a history of occupational asbestos exposure showed a geometric mean of their pulmonary asbestos concentrations (5.82 x 10(6) fibers/g dry lung) which was significantly higher than that of patients without occupational asbestos exposure (p less than 0.01). 3. The geometric mean concentration of asbestos fiber in males (2.70 x 10(6)) was higher than in females (1.59 x 10(6)), probably due to a difference in the occupational asbestos exposure between males and females. 4. Regardless of the patient's sex, the geometric mean concentration of asbestos fibers in patients without a history of smoking (male: 4.91 x 10(6), female: 1.78 x 10(6)) was higher than that in patients with a smoking history (male: 2.76 x 10(6), female: 1.37 x 10(6)). The difference, however, was not statistically significant, and no correlation was seen between the concentration of asbestos fibers and smoking history. 5. Although most asbestos fiber utilized in Japan is chrysotile, the geometric mean concentration of chrysotile (0.87 x 10(6)) was almost identical to that of amphibole asbestos fiber (0.90 x 10(6)). 6. Of the asbestos fibers observed, 95% of chrysotile and 85% of amphibole asbestos were less than 5 microns in length and 93% of the total asbestos fibers were too small to be visible by light microscopy.

Adult↗
PubMed1991

[Immunomodulatory effects of interferons on target human gliosarcoma cells in the tumor-specific CTL- and LAK-mediated cytolysis].

We compared the regulatory effects of interferon (IFN)-beta and IFN-gamma on the susceptibility of a human gliosarcoma line GI-1 to the attack of autologous cloned tumor-specific cytotoxic T-lymphocytes (CTL) and lymphokine-activated killer (LAK) cells. Preincubation of GI-1 cells with IFN-gamma caused augmented susceptibility to the cytotoxic attack of two autologous CTL clones, whereas IFN-beta exhibited no such marked effect. On the other hand, preincubation with either IFN-beta or IFN-gamma made the GI-1 cells resistant to the attack of autologous LAK cells. Both IFNs augmented the surface expression of HLA class-I molecules on GI-1 cells. A monoclonal anti-HLA class-I antibody blocked the cytolysis by one CTL clone, but not by the other one. These results suggest that IFN-gamma exerts some different effect (s) from that of IFN-beta on the target GI-1 cells in their susceptibility to the CTL-mediated cytolysis, and that recognition mechanisms of target cells by the CTL are different from those by LAK cells. This draws our attention to IFN administration in adoptive immunotherapy against brain tumors using CTLs and LAK cells.

Brain Neoplasms↗
PubMed1991

[A case of what was regarded as isolated benign cerebral vasculitis].

A 55-year-old man came to us with dysarthria and right hemiparesis. The cerebral angiography showed segmental narrowing and irregularity of the left anterior cerebral artery. The patient responded well to corticosteroid therapy and there was later angiographic evidence of healing. After systemic angiitis and central nervous system infection were excluded, the diagnosis of isolated benign cerebral vasculitis was made. According to past reports, at least 13 patients have been described as having isolated benign cerebral vasculitis. The common features of isolated benign cerebral vasculitis are as follows: 1) benign evolution, 2) sensitiveness to corticosteroids, 3) absence or minimal change of CSF findings, 4) angiographic pattern of arteritis, 5) the most common symptom is headache. We suggest that early corticosteroid therapy is necessary in any case of cerebral vasculitis.

Administration, Oral↗
PubMed1991

[Exercise-induced ST segment shift in vasospastic angina with special reference to comparisons between treadmill and bicycle ergometer exercise testings].

To assess the difference between cardiovascular responses to treadmill exercise (TM) and those to bicycle ergometer exercise (EM) in provoking coronary spasm, we compared the ST segment shifts (elevation or depression) during TM and EM in 67 patients with vasospastic angina. Coronary artery spasm was demonstrated on angiography. Both TM and EM were performed on the same day during a medication-free period. For both tests, multistage, symptom-limited exercise protocols were used; EM in the morning and TM in the afternoon. The results obtained were as follows: 1. Rate-pressure products at peak exercise during TM and EM were similar. Systolic blood pressure levels at peak exercise were higher during EM than during TM (p < 0.01). The patients' heart rates at peak exercise were higher during TM than during EM (p < 0.01). Diastolic blood pressure levels at peak exercise were higher during EM than during TM (p < 0.05). 2. Exercise-induced ST elevation occurred more frequently with TM than with EM (19% vs 9%, p < 0.05). 3. Exercise-induced ST depression was provided in 27 patients during TM and in 13 during EM (40% vs 19%, p < 0.01). Among 45 patients without significant lesions, ST depression occurred in 19 during TM, but in only 7 during EM (42% vs 16%, p < 0.01). In conclusion, coronary spasm seemed to occur more frequently with TM than with EM. The mechanism causing such difference remains to be elucidated, however, we speculate that the difference between TM and EM as to enhanced autonomous nervous system activity and coronary perfusion exercise may be related to the difference in the incidence of coronary spasm.

Aged↗
PubMed1991

[Evaluation of maintenance of cardiac output during DDD and VVI pacing by exercise Doppler echocardiography].

To evaluate the efficacy of DDD pacing for cardiac reserve, we assessed increases in the stroke volume and cardiac output during randomized treadmill exercise in 16 patients by DDD and fixed-rate ventricular (VVI) pacing. The stroke volume index and cardiac index were determined using suprasternal Doppler measurements. Ten patients who showed sinus rhythm during exercise were excluded from this study. Compared with the findings during VVI pacing, those during DDD pacing showed: 1) a greater exercise-induced positive chronotropic response (mean maximum heart rate 122 +/- 22 beats/min vs 70 beats/min, p < 0.01), 2) a lesser increase in the stroke volume index (34 +/- 7 to 39 +/- 9 ml/m2 vs 31 +/- 7 to 49 +/- 11 ml/m2, p < 0.05), 3) a greater increase in the cardiac index (2.43 +/- 0.45 to 4.48 +/- 1.36 L/min/m2 vs 2.22 +/- 0.47 to 3.43 +/- 0.45 L/min/m2, p < 0.05), and 4) prolongation of exercise duration (6.35 +/- 2.00 min vs 5.97 +/- 1.81 min, NS). These findings indicated that VVI pacing promoted a greater stroke volume than DDD pacing, which provides a compensatory increase in contractility and the preload in cases without an increase in heart rate during exercise, however, the increase in cardiac output was insufficient due to the absence of a chronotropic response. In conclusion, a DDD pacemaker could effectively increase heart rate, causing a significant increase in cardiac output and extending exercise duration.

Adult↗
PubMed1991

Effects of serum-isolated vs synthetic bilirubin-albumin complexes on dye-binding methods for estimating serum albumin.

Bush and Reed reported (Clin Chem 1987;33:821-3) that the reaction of albumin with bromcresol purple but not with bromcresol green underestimated the concentration of albumin in synthetically obtained bilirubin-albumin (Bd) by 29%. Their unproven assumption was that chemically synthesized Bd behaved in a manner indistinguishable from the natural Bd in icteric serum. Here we verify that Bd, whether synthetically obtained or isolated from serum, causes an underestimation of albumin in the bromcresol purple but not in the bromcresol green method. The molar ratio of Bd from either source to underestimated albumin approximates 1.0, suggesting that one molecule of Bd would react equivalently to a molecule of albumin in the bromcresol purple method. This underestimation might falsely suggest hypoalbuminemia in patients with increased serum Bd.

Adult↗