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Biomedical subjects

T Ogata

Publications and source records attributed to T Ogata.

At least 19 recordsLinked to original sources
PubMed1992

Secondary aminoglycoside resistance in aminoglycoside-producing strains of Streptomyces.

The role of aminoglycoside (AG) acetyltransferases (AACs) and of the corresponding genes in resistance to foreign AGs in AG-producing strains of Streptomyces were studied. The research focussed on (i) the activation mechanism of the cryptic kanamycin(Km)-resistance-encoding gene that encodes an AAC(3) in streptomycin-producing S. griseus SS-1198, and (ii) an AAC(2') with novel activity and substrate specificity in kasugamycin-producing S. kasugaensis MB273. Activation of the cryptic kan gene in S. griseus SS-1198 is probably due to a single base substitution at the putative -10 promoter region, leading to the enhancement of transcription, resulting in resistance to AG. The coding region of the kan gene was highly homologous to that of the aacC7 gene of paromomycin-producing S. rimosus forma paromomycinus. On the other hand, resistance in S. kasugaensis MB273 was found to be due to an AAC(2') capable of acetylating astromicin group AGs at two different sites (1-NH2 with istamycin B, and 2'-NH2 with astromicin and istamycin A). These additional antibiotic resistances that are independent of a self-resistance basis may be regarded as 'secondary' resistances, so as to distinguish them from 'primary' resistances arising from a self-resistance basis.

Aminoglycosides↗
PubMed1992

Determination of platelet monoamine oxidase activity by high-performance liquid chromatography with electrochemical detection.

A procedure for determining human platelet monoamine oxidase (MAO) with dopamine (DA) as substrate is described. High-performance liquid chromatography (HPLC) with electrochemical detection (ED) was used to separate and detect components of the reaction mixture. The method for platelet preparation was also improved and only 2 ml of blood were required. Following a 10-min incubation of the platelet preparation with DA in 0.1 M Tris buffer (pH 9.0), excess DA substrate was removed by adsorption on a cation-exchange resin. The reaction product, 3,4-dihydroxyphenylacetaldehyde, was adsorbed on acid-washed alumina, eluted with 0.1 M perchloric acid and analyzed by HPLC. Simple, clean chromatograms were obtained with good reproducibility using 3,4-dihydroxybenzylamine as an internal standard. The within-sample, between-samples and between-day relative standard deviations were 0.9, 3.7 and 6.1%, respectively. The apparent Michaelis constant and maximum velocity were 0.10 mM and 0.37 nmol/min.mg protein, respectively. This HPLC-ED method offers a good alternative to methods using radioactivity.

Blood Platelets↗
PubMed1992

Central nervous system changes in mitochondrial encephalomyopathy: light and electron microscopic study.

An autopsy case of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is reported. It presented with generalized muscle atrophy, stroke-like episodes, schizophrenia-like mental disorder and progressive dementia. Serum lactate and pyruvate levels were high. In the biopsied muscles, ragged-red fibers were observed by light microscopy and aggregation of abnormal mitochondria with paracrystaline formation by electron microscopy. The most characteristic neuropathological findings were infarct-like lesions widespread in the cerebral cortex. In addition, this case showed some unusual pathological features: (1) diffuse moderate fibrillary gliosis in the whole cerebral and cerebellar white matter, which might have been due to metabolic disturbances; (2) several focal lesions with demyelination and numerous spheroids in the pontocerebellar fibers; and (3) marked degeneration of the posterior columns and spinocerebellar tracts. Electron microscopic examination revealed that abnormal mitochondria were markedly aggregated in smooth muscle cells and endothelium of the cerebral and cerebellar blood vessels. These fine structural findings suggest a "mitochondrial angiopathy".

Acidosis, Lactic↗
PubMed1992

A pathological and immunohistological case report of fatal infectious mononucleosis, Epstein-Barr virus infection, demonstrated by in situ and Southern blot hybridization.

We present an autopsy case of 20-month-old boy who had a fulminant course of infectious mononucleosis, with severe hepatic failure. Autopsy revealed marked infiltration of immunoblasts in the lymph nodes, liver, spleen, thymus and kidneys. We identified a large number of Epstein-Barr virus (EBV) genomes in the immunoblasts of the lymph nodes, liver and spleen by in situ hybridization. EBV genomes were also detected in the liver and spleen by Southern blot hybridization. Histology of the liver revealed diffuse feathery degeneration of the hepatocytes. However, EBV genomes were not detected in the hepatocytes by in situ hybridization and monoclonal antibody studies. Immunostaining of the autopsy liver specimen revealed a large number of suppressor/cytotoxic T cells (Leu2a positive) in the portal areas and of natural killer (NK) cells (Leu7 positive) in the portal areas and sinusoids of the liver. We therefore suggest that the hepatocellular damage was not caused by the viral replication in the hepatocytes but was mainly caused by the abnormal killer cell activity of the suppressor/cytotoxic T cells and NK cells.

Blotting, Southern↗
PubMed1992

Enhanced expression of stomach cancer antigen derived from malignantly transformed bloom syndrome cells previously labeled with bromodeoxyuridine.

Bromodeoxyuridine (BrdU) greatly enhanced expression of stomach (ST) cancer antigen (CA) that originated from a malignantly transformed Bloom syndrome (BS) cell line (BS-SHI-4M), although the expression was suppressed with a decrease in sister chromatid exchange (SCE) in the presence of deoxythymidine (dT) or deoxycytidine (dC) and enhanced with an increase in SCE with deoxyguanosine (dG) or deoxyadenosine (dA). Although the exact mechanisms for enhancing CA by BrdU treatment are unknown, these findings appeared to be of special interest because of the parallelism of CA expression and SCE alterations. The finding that BrdU enhancement of the ST CA was effective not only in the immunofluorescence (IF) protocol but also in the band appearance of Western blotting would be worthwhile as a sensitive serodiagnosis of cancer. The 118-kd band obtained from proteins of ST CA cells previously labeled with BrdU was clearly more darkly stained than that from nonlabeled cells and enabled eight weak-positive ST CA to show strong-positive levels retaining complete negativity to nonmalignant sera. Some ST cancer sera (advanced cancer), which originally gave a negative reaction in the nonlabeled condition, still inhibited negative reaction even in BrdU-labeled ST CA cells, however. The inability to detect cancer antibody in our assay might be due to immunocomplexes. Acid dissociation and ultrafiltration of sera from six of seven advanced ST cancers (originally IF negative) have allowed detection of antibody responses to ST CA by Western blot assay with enhanced reactivity as compared with the negativity under native serum conditions. This technique provides a reasonable avenue for study of the mechanisms of CA expression and serodiagnosis.

Antibodies, Neoplasm↗
PubMed1992

An ESR-CT imaging of the head of a living rat receiving an administration of a nitroxide radical.

Three-dimensional ESR imaging of a living rat has been performed by an L-band ESR system, which is composed of an L-band ESR spectrometer, a field gradient coil, and a data processor. The imaging was carried out by Lauterbur's method. A nitroxide, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (Carbamoyl-PROXYL), was used as an imaging agent in saline solution at a concentration of 0.2 M and administered intraperitoneally to obtain a constant concentration in the head for about an hour. It took about 40 min to obtain one set of ESR-CT images. The cross-sectional images were made, both as coronal and horizontal images. In the images of the rat head the nitroxide-rich region was clearly distinguished from the deficient region. The nitroxide-deficient areas corresponded well to the brain of the rat.

Animals↗
PubMed1992

HIV-1 reverse transcriptase inhibitor from Phyllanthus niruri.

An aqueous extract of Phyllanthus niruri (Euphorbiaceae) inhibited human immunodeficiency virus type-1 reverse transcriptase (HIV-1-RT). The inhibitor against HIV-1-RT in this plant was purified by combination of three column chromatographies, Sephadex LH-20, cellulose, and reverse-phase high-performance liquid chromatography. The inhibitor was then identified by nuclear magnetic resonance (NMR) spectra as repandusinic acid A monosodium salt (RA) which was originally isolated from Mallotus repandus. The 50% inhibitory doses (ID50) of RA on HIV-1-RT and DNA polymerase alpha (from HeLa cells) were 0.05 microM and 0.6 microM, respectively, representing approximately a 10-fold more sensitivity of HIV-1-RT compared with DNA polymerase alpha. RA was shown to be a competitive inhibitor with respect to the template-primer while it was a noncompetitive inhibitor with respect to the substrate. RA as low as 10.1 microM inhibited HIV-1-induced cytopathogenicity in MT-4 cells. In addition, 4.5 microM of RA inhibited HIV-1-induced giant cell formation of SUP-T1 approximately 50%. RA (2.5 microM) inhibited up to 90% of HIV-1 specific p24 antigen production in a Clone H9 cell system.

Antigens, Viral↗
PubMed1992

Comparing postgraduate medical education at university and non-university hospitals in Japan.

In 1988 the authors surveyed all the teaching hospitals in Japan to evaluate the present status of postgraduate medical education (PGME); they received responses from 67 (84%) of the university and 172 (89%) of the non-university teaching hospitals. It was found that a large proportion of residents had spent two years in a residency without having had a single experience of some of the basic clinical skills. Consequently the residents' confidence in their abilities to perform these skills was low. The residents at the university hospitals, in particular, had had fewer experiences and were less confident about their clinical skills than were the residents at the non-university hospitals. The lack of standard and minimum requirements for PGME in Japan may be the cause of the poor level of acquisition of clinical skills of residents during PGME. Other possible causes are the tendency in Japanese medical society to attach greater importance to academic attainment than to clinical competence and the excessive gravitation of residents toward university hospitals. The authors suggest their results show the necessity to improve the training in basic clinical skills in PGME in Japan, especially in university hospitals.

Clinical Competence↗
PubMed1992

An autopsied case of dentatorubropallidoluysian atrophy with atypical pathological features.

This is a report of an autopsied case of dentatorubropallidoluysian atrophy (DRPLA) with atypical neuropathological findings. The patients was a 31-year-old female. Her clinical symptoms were epileptic seizures, cerebellar ataxia, choreoathetosis and dementia. A neuropathological examination revealed the fibrillary gliosis in various areas of the CNS and severe degeneration in the cerebellar cortex and nucleus fasciculi dorsalis in addition to a marked degeneration of the dentatorubropallidoluysian systems. The present case is diagnosed neuropathologically as DRPLA associated with the findings of chronic diphenylhydantoin intoxication and epileptic brain damage.

Atrophy↗
PubMed1992

Release of excitatory amino acids from cultured hippocampal astrocytes induced by a hypoxic-hypoglycemic stimulation.

An excess release of excitatory amino acids (EAA) is an important factor for postischemic brain damage. In the present communication, we demonstrate that cultured hippocampal cells release EAA after hypoxic-hypoglycemic treatment. The amounts of EAA released from astrocytes were appreciably above those released from neurons. Furthermore, the amount of aspartate released from astrocytes was comparable to that of glutamate, although the endogenous content of aspartate was one-fifth that of glutamate. The endogenous content of aspartate in astrocytes increased even after hypoxic-hypoglycemic treatment. These results suggests that ischemic neuronal death is due, at least in part, to the excitotoxicity of aspartate and glutamate derived from surrounding astrocytes.

Amino Acids↗
PubMed1992

Sex reversal in a child with a 46,X,Yp+ karyotype: support for the existence of a gene(s), located in distal Xp, involved in testis formation.

We report on a sex reversed Japanese child with a 46,X,Yp+ karyotype, minor dysmorphic features, and no testicular development. The Yp+ chromosome was derived by translocation of an Xp fragment (Xp21-Xp22.3) to Yp11.3. This has resulted in deletion of distal part of the Y chromosome pseudoautosomal region (DXYS15-telomere) and duplication of the X specific region (DXS84-PABX) and proximal part of the pseudoautosomal region (MIC2-DXYS17). No deletion of the Y specific region was detected nor was any mutation found in SRY. Cytogenetic analysis suggests that the proximal part of the Xp fragment is the most distal part of the short arm of the Yp+ chromosome (Xp21----Xp 22.3::Yp11.3----Yqter). No chromosomal mosaicism was detected. These results are similar to previous reports of sex reversal in four subjects with a 46,Y,Xp+ karyotype. We conclude that the sex reversal is a direct, or indirect, consequence of having two active copies of the distal part of Xp and may indicate the presence of a gene(s) which acts in the testis determination or differentiation pathway.

Base Sequence↗
PubMed1992

Comparison of adult height between patients with XX and XY gonadal dysgenesis: support for a Y specific growth gene(s).

Adult height was compared between published cases of patients with XX gonadal dysgenesis (XXGD) and those with XY gonadal dysgenesis (XYGD). The mean adult height of XYGD patients (171.0 cm (SD 7.8), n = 27) was significantly greater than that of XXGD patients (164.4 cm (7.7), n = 27) (p less than 0.01). This finding supports the existence of a Y specific growth gene(s) which promotes statural growth independently of the effects of gonadal sex steroids.

Adult↗
PubMed1992

Chromosomal localisation of a pseudoautosomal growth gene(s).

Although recent molecular studies in patients with sex chromosome aberrations are consistent with a growth gene(s) being present in the pseudoautosomal region (PAR), the precise location has not been determined. In this report, we describe a Japanese boy and his mother with an interstitial deletion in Xp22.3 and review the correlation between genotype and stature in six cases of partial monosomy of the PAR. The results indicate that the region from DXYS20 to DXYS15 is the critical region for the putative growth gene(s).

Abnormalities, Multiple↗
PubMed1992

Giant air cell of the petrous apex: a possible cause of facial hypalgesia.

A giant air cell of the left petrous apex was found in a 23-year-old man with ipsilateral facial hypalgesia. The size of the giant air cell depicted on computed tomography was 1.5 x 2.0 x 2.0 cm. A coronal T1-weighted magnetic resonance image showed that the trigeminal nerve was compressed superomedially by a large signal void area that was probably a result of excessive pneumatization of the petrous apex. It is suggested that the facial hypalgesia was caused by the compression by the giant air cell of the petrous apex on the trigeminal nerve.

Adult↗
PubMed1992

Scanning electron microscopic study on the three-dimensional structure of the collagen fibrillar framework in the chronic active hepatitis and liver cirrhosis.

The three-dimensional collagen framework of human liver parenchyma in surgical specimens from patients with chronic active hepatitis (CAH), viral or alcoholic cirrhoses (LC) was observed by scanning electron microscopy after cell-maceration by the method of Ohtani (1988). In control livers, the tubular sheaths of collagen fibers housing the sinusoid were shown to form a labyrinthine network, which we called the perisinusoidal collagen sheaths (PSCSs), and a loose band-like collagen sheath was seen embracing each hepatocyte, which we called the perihepatocellular collagen sheath (PHCS). In CAH, thin septa partially surrounded the lobules, but the PHCS and PSCS appeared almost unchanged. In viral LC, thick collagen septa surrounded pseudolobules of various sizes. In these conditions, the collagen density was slight in PSCSs, while in PHCSs, it was prominent and associated with an enlargement of sheaths themselves. In alcoholic LC of mixed type, the basic structure of the collagen framework closely imitated that of viral LC.

Collagen↗
PubMed1992

Ultra-high-resolution scanning electron microscopic studies on the sarcoplasmic reticulum and mitochondria of the rat intrafusal muscle fibers. Part II: The extracapsular region.

The three-dimensional structure of the transverse-axial tubular system, sarcoplasmic reticulum (SR) and mitochondria in the extracapsular region of the intrafusal muscle fibers of the rat lumbrical muscle was observed by ultra-high-resolution scanning electron microscopy after removal of the cytoplasmic matrix by the osmium-DMSO-osmium procedure. Nuclear chain fibers possessed thick to moderately sized column-forming mitochondria with occasional I-band branches. The transverse tubules (T-tubules) running at the level of the A-band side of the A-I junction were sandwiched between two large terminal cisternae for most of their length, forming triads. The sarcotubules arising from the terminal cisternae formed single-layered networks at the A-band level, and well developed, double-layered, three-dimensional networks at the I-band level. Nuclear bag1 fibers possessed slender column-forming mitochondria devoid of I-band branches. The T-tubules were located at the level of the A-I junction. Both the T- and the axial-tubules were occasionally coupled with small terminal cisternae, forming dyads or triads. At the I-band level, the SR was well developed and formed single layered networks, but at the A-band level only a few longitudinally arranged sarcotubules and axial tubules were observed. Nuclear bag2 fibers contained medium to large diameter column-forming mitochondria without I-band branches. The T-tubules ran at the level of the A-band adjacent to the A-I junction, and were coupled at some intervals with terminal cisternae of various lengths. Swollen, large terminal cisternae were frequently seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Quantitative DNA image cytometry by color image analyzer].

We developed a new method to analyze DNA quantitatively by a color image analyzer. A microscopic image of the nucleus stained with Feulgen's reaction, is taken by a CCD color camera and inputted in a color image analyzer. DNA quantity can be calculated directly from the RGB components of the color image instead of the monochrome image taken through band-pass filter, which is specific for the absorption of Feulgen's stain. It takes about 10 minutes to measure 500 nuclei by this method and its accuracy is almost the same as flow cytometry (CV = 3%). The nuclear color image can also be analyzed morphometrically. This method can select tumor cells in a usual cytologic specimen and measure their DNA contents.

Cytophotometry↗