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Biomedical subjects

M Tobita

Publications and source records attributed to M Tobita.

At least 19 recordsLinked to original sources
PubMed1992

Retrograde filling of the anterior choroidal artery: vertebral angiographic sign of obstruction in the carotid system.

Retrograde filling of seven anterior choroidal arteries from the posterior circulation was observed on a vertebral angiogram in six patients with occlusion of the proximal anterior choroidal artery or of the internal carotid artery. In one patient with thrombotic occlusion of the internal carotid artery, the enlarged anterior choroidal artery functioned as a major collateral pathway from the posterior circulation to the territory of the middle cerebral artery. Retrograde filling of the anterior choroidal artery is a sign of obstruction changes in the ipsilateral carotid artery at or proximal to the origin of the anterior choroidal artery.

Adolescent↗
PubMed1991

[Microbiological characterization of clinical isolates of Staphylococcus epidermidis].

As a result of recent development in medical practice including use of new antimicrobial agents, coagulase-negative Staphylococci (CNS) that were once considered nonpathogenic contaminants have captured attention as causes of disease. The 43 clinical isolates of Staphylococcus epidermidis sensu stricto and 7 isolates of S. epidermidis from the medical staffs were characterized with regard to (1) their biochemical profiles, (2) slime productivity, (3) beta-lactamase productivity and (4) plasmid patterns. Most of the isolates have an identical biochemical profile code. The slime production was observed in the 9 strains isolated from pleural effusions or the tubes used for pleural drainage. These strains had a similar antimicrobial susceptibility profile that are commonly seen in multi-resistant strains of methicillin-resistant Staphylococcus aureus (MRSA). In addition, most of these strains produced beta-lactamase. For the plasmid profiling, we selected 12 isolates that possessed 5 distinct antimicrobial susceptibility profiles. Upon agarose gel electrophoresis, 8 isolates were shown to possess a 1.9 kb plasmid. These 8 isolates had resistance against tobramycin (TOB) and erythromycin (EM). Emergence of S. epidermidis as causes of disease will increasingly necessitate the detailed microbiological characterization of the clinical isolates.

DNA, Bacterial↗
PubMed1989

Identification and characterization of receptors for granulocyte colony-stimulating factor on human placenta and trophoblastic cells.

Since radioiodination of human granulocyte colony-stimulating factor (G-CSF) is difficult, we synthesized a mutein of human G-CSF that retains full biological activity and receptor-binding capacity for at least 2 weeks after radioiodination. Receptors for human G-CSF were characterized in the plasma membrane fraction from the human term placenta (human placental membranes) and trophoblastic cells by using the 125I-labeled mutein of human G-CSF (KW-2228). The specific binding of 125I-labeled KW-2228 to placental membranes was pH-dependent, with maximal specific binding at pH 7.8; it increased linearly with protein to 3.7 mg of protein per ml and was both time- and temperature-dependent, with maximal binding at 4 degrees C after a 24-hr incubation. When we examined the ability of hematopoietic growth factors to inhibit 125I-labeled KW-2228 binding, we found that KW-2228 and intact human G-CSF inhibited 125I-labeled KW-2228 binding, whereas erythropoietin or granulocyte-macrophage colony-stimulating factor did not. Scatchard analysis revealed a single receptor type with a Bmax of 210 fmol/mg of protein and a Kd of 480 pM. The human G-CSF receptors on human placental membranes were shown to consist of two molecular species of 150 kDa and 120 kDa that could be specifically cross-linked to 125I-labeled KW-2228. Human trophoblastic cells, T3M-3, also possessed a single receptor for G-CSF with a Bmax of 533 receptors per cell and a Kd of 390 pM. Thus we have identified the receptor for human G-CSF on human placental membranes and trophoblastic cells, and the presence of this receptor in these membranes suggests that human G-CSF plays some role in the feto-placental unit during human development.

Binding, Competitive↗
PubMed1989

[Nosocomial infections and clinical microbiology].

Hospital-acquired infection with strains of methicillin-resistant Staphylococcus aureus (MRSA) have considerably increased in recent years. In addition to being resistant to methicillin, these strains are resistant to practically all forms beta-lactams, aminoglycosides and many other antibiotics. There appears no cost-effective control and preventive measures for this common but also potentially life-threatening disease. Although not clearly presented, the overall cost for the treatment of patients infected with MRSA should be enormous. Can laboratory medicine (or clinical microbiology) contribute to this global medical problem? Multiple strains of MRSA circulate within a hospital and some strains are even localized within specific wards. These facts suggest yet undisclosed routes of transmission and/or foci of infection. Triumph over these versatile organisms may have to await the development of new antibiotics effective for MRSA.

Adult↗
PubMed1989

[Experiences of postoperative staphylococcal enteritis caused by methicillin-cephem resistant Staphylococcus aureus (MRSA) and the state of the isolation of MRSA].

During the last 12 months, three cases of postoperative staphylococcal enteritis were experienced in our surgical ward. Kanamycin, Clindamycin and Latamoxef were given prophylactically in all cases. They developed dehydration with severe diarrhea and paralytic ileus in three to ten days after abdominal surgery. MRSA was cultured from the intestinal fluid or feces and Minocycline, sensitive anti-microbial agent to the organism, was administered intravenously and their conditions improved dramatically. Since the nosocomial infections of MRSA are believed to be the cause of these cases, following items were investigated; 1) the frequency of MRSA among Staphylococcus aureus clinically isolated from patients in surgical ward, 2) the state of nasal carriage of MRSA in medical staffs and inpatients without infections in surgical ward, 3) drug sensitivity of MRSA to ten kinds of antibiotics. The results were as follows; 1) the frequency of MRSA was 83% of all the strains of Staphylococcus aureus, 2) the nasal carrier status was 2 in 46 medical staffs and 4 in 17 inpatients, 3) 124 strains of MRSA, 114 isolated from patients and 10 from nasal carriers, showed the identical drug sensitivity, that is, MRSA is sensitive to Minocycline and resistant to every other antibiotics. It is believed that these three cases were due to nosocomial infections of MRSA, and early diagnosis of MRSA enteritis should lead to early antibiotic therapy and to a cure of this serious postoperative complication.

Adult↗
PubMed1988

The effect of transient ischemia on 2-[14C]deoxyglucose metabolism in the rat hippocampus pretreated with kainic acid.

CA1 pyramidal neurons are selectively vulnerable to ischemia. 2-[14C]Deoxyglucose (2-DG) autoradiography was employed to measure local glucose utilization in the rat hippocampus after transient ischemia, under the condition of unilateral prevention of ischemic CA1 pyramidal cell necrosis by unilateral lesioning of Schaffer collaterals (left side). Columnar 2-DG uptake patterns in the CA1 region with intact Schaffer collaterals (right side) was observed 19-22 h after recirculation, though no laterality was noted 3 and 8 h after recirculation. In the right subiculum, higher 2-DG uptake was observed 19-22 h after recirculation in 5 out of 8 animals. These results suggest that Schaffer collaterals play a role in modulating glucose metabolism in the CA1 and subiculum during recirculation.

Animals↗
PubMed1987

[Effects of S-adenosyl-L-methionine on the cerebral energy metabolism and microcirculation in the rats subjected to transient forebrain ischemia].

Effects of S-adenosyl-L-methionine (SAM) on the improvement of cerebral energy metabolism and microcirculation were examined in postischemic rat brain. Male Wistar rats, whose vertebral arteries were electrically cauterized last day, were subjected to forebrain ischemia by temporary clipping of both common carotid arteries. After 60 min of ischemic insult, they were intravenously administered with SAM at doses of 30 or 100 mg/kg; this was followed by recirculation for 60 min. To determine cerebral concentrations of energy metabolites, the brain was frozen in situ. Adenine nucleotides (ATP, ADP, AMP) were assayed by anion-exchange HPLC system, and other metabolites (PCr, glucose, lactate, pyruvate) were analyzed by enzymatic fluorometry. In order to estimate regional cerebral blood flow (rCBF) and glucose utilization, double-tracer autoradiography was undertaken using 14C-iodoantipyrine (14C-IAP) and 18F-fluorodeoxyglucose (18F-FDG). In animals without SAM treatment (60-60 group), energy metabolites did not recover and neither CBF nor glucose uptake restored during 60 min of recirculation. In contrast, in SAM-treated animals (60-60 SAM group), values of the energy metabolites improved significantly and both CBF and glucose uptake recovered, though incompletely. These results indicate that SAM is able to improve postischemic cerebral microcirculation and energy metabolism. For mechanisms of the effects, it is suggested to the enhancement of erythrocyte deformability by phospholipid methylation, the stabilization of mitochondria, and the normalization of injured metabolic reactions. Therefore, we conclude that SAM is able to be effective clinically as a drug treated for the acute phase of cerebrovascular diseases.

Animals↗
PubMed1986

Gene structure of calcium-dependent protease retains the ancestral organization of the calcium-binding protein gene.

The gene structure of calcium-dependent protease (Ca2+-protease) was determined. It comprises at least 21 exons, and these were assigned to the 4 functional domains of the protease. The protease domain does not show clear correlation between exons and functional units, but the calmodulin-like calcium-binding domain shows strong correlation. Each of the 4 consecutive calcium-binding regions in the C-terminal part of Ca2+-protease is encoded by one exon. This gene structure supports the idea that the 4 calcium-binding regions of calcium-binding proteins such as calmodulin arose by 2 steps of gene duplication.

Animals↗
PubMed1986

Characterization of experimental ischemic brain edema utilizing proton nuclear magnetic resonance imaging.

Correlations between T1 and T2 relaxation times and water and electrolyte content in the normal and ischemic rat and gerbil brains were studied by means of both nuclear magnetic resonance (NMR) spectroscopic and imaging methods. In the spectroscopic experiment on excised rat brains, T1 was linearly dependent on tissue water content and T2 was prolonged in edematous tissue to a greater extent than expected by an increase in water content, showing that T2 possesses a greater sensitivity for edema identification and localization. Changes in Na+ and K+ content of the tissue mattered little in the prolongation of relaxation times. Serial NMR imaging of gerbil brains insulted with permanent hemispheric ischemia offered early lesion detection in T1- and especially T2-weighted images (detection as soon as 30 min after insult). The progressive nature of lesions was also imaged. Calculated T1 and T2 relaxation times in regions of interest correlated excellently with tissue water content (r = 0.892 and 0.744 for T1 and T2, respectively). As a result, detection of cerebral ischemia utilizing NMR imaging was strongly dependent on a change in tissue water content. The different nature of T1 and T2 relaxation times was also observed.

Animals↗
PubMed1986

Sequential cerebral blood flow study by chrono-autoradiography.

A novel chrono-autoradiographic technique (sequential double label autoradiography) was established in order to evaluate regional cerebral blood flow (CBF) changes utilizing N-isopropyl-p-123I-iodoamphetamine (123I-IMP) and 14C-iodoantipyrine (14C-IAP). With sequential administration of 123I-IMP and 14C-IAP, two CBF images were obtained from the same brain section. By applying this method to focal cerebral ischemia, two sequential CBF images, one during ischemia and one after recirculation, were obtained. These results show that this method is useful in topographical evaluation of CBF changes. From a pathophysiological point of view, the result demonstrates a heterogeneous tissue perfusion after a transient ischemic insult.

Amphetamines↗
PubMed1986

[Basic study on human interferon-beta: Part III. The mechanisms of its antitumor effect].

The mechanisms of the direct and indirect antitumor effects of human interferon-beta (IFN-beta, MR-21) were examined. IFN-beta suppressed DNA, RNA and protein synthesis in cells derived from human tumor. The expression of cellular oncogenes (c-Ha-ras and c-myc) in tumor-originated cells was also suppressed by IFN-beta. These results suggest that such suppression is one possible mechanism of the direct anticellular effect induced by IFN-beta. IFN-beta augmented NK cell activity and the ADCC activity of human peripheral blood lymphocytes. It is also suggested that these are two of the immune system-mediated mechanisms responsible for the indirect antitumor effect of IFN-beta in vivo.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1986

[Magnetic resonance imaging of experimental cerebral ischemia: correlations between NMR parameters and water content].

Recent studies on proton NMR imaging revealed its remarkable sensitivity for detecting cerebral ischemia. Since proton NMR reflects the distribution and state of water in the brain, an NMR imager becomes a sensitive in vivo detector of brain edema developing soon after the energy state is compromized by ischemia. To further clarify the usefulness of NMR imaging to characterize the ischemia-induced changes, correlations between T1 and T2 relaxation times and water content of the normal and ischemic rat and gerbil brain were studied by means of both spectroscopic and in vivo imaging methods. In the spectroscopic experiment on excised rat brain (cortex, white matter, hippocampus and thalamus for normal and ischemia-laden brain), T1 and T2 relaxation times and water content were determined. The ischemic insult was induced for 60 min by the method of Pulsinelli followed by 60 min of reperfusion. All of the T1, T2 and water content significantly increased in the ischemic tissue. Gray-white difference was evident in T1 and T1 was linearly correlated with the water content of the tissue. T2 was by far prolonged in the ischemic tissue compared with the increase in the water content, showing greater sensitivity of T2 for detection of ischemia. In the imaging experiment, coronal NMR imaging at 0.5 tesla was performed employing proton density-weighted saturation recovery (TR = 1.6 s, TE = 14 ms), T1-weighted inversion recovery (TR = 1.6 s, TI = 300 ms, TE = 14 ms) and T2-weighted spin echo (TR = 1.6 s, TE = 106 ms) pulse sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗