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Biomedical subjects

N Kasai

Publications and source records attributed to N Kasai.

At least 55 records · Page 3Linked to original sources
PubMed1997

A wide spectrum of collagen vascular and autoimmune diseases in transgenic rats carrying the env-pX gene of human T lymphocyte virus type I.

To investigate the pathogenesis of human T lymphocyte virus type I (HTLV-I)- related diseases, the env-pX gene of HTLV-I was introduced into the germline of inbred Wistar-King-Aptekman-Hokudai rats. A wide spectrum of collagen vascular diseases was evident in the transgenic rats, including chronic destructive arthritis similar to rheumatoid arthritis, necrotizing arteritis mimicking polyarteritis nodosa, polymyositis, myocarditis, dermatitis, and chronic sialoadenitis and dacryoadenitis resembling Sjögren's syndrome in humans. Thymic atrophy with the depletion of CD4 and CD8 double-positive thymocytes was also observed. In these animals, a number of autoantibodies, including high titers of rheumatoid factor, were present in the serum. We propose that the HTLV-I env-pX gene region may play a pathogenetic role in the development of collagen vascular and autoimmune diseases associated with autoimmune phenomenon.

Animals↗
PubMed1997

Structure of the zinc endoprotease from Streptomyces caespitosus.

A zinc endoprotease produced by Streptomyces caespitosus (ScNP) specifically hydrolyzes the peptide bond at the imino side of aromatic residues and is the smallest protease found to date. Although ScNP carries the zinc-binding sequence HEXXH, its primary structure of 132 amino acid residues differs from those of other known zinc metalloendoproteases. X-ray structural analysis of ScNP at 1.6 A resolution revealed that despite a lack of sequence homology, the common topological feature of main-chain folding and a beta-turn containing methionine, which is a feature of the zinc metalloendoprotease superfamily of metzincins, is conserved in ScNP. The zinc atom of ScNP is tetrahedrally ligated by the two histidines in the HEXXH sequence, an aspartate residue and a water molecule. Thus, ScNP represents a novel subfamily of metzincins with a HEXXHXXGXXD zinc-binding sequence. A plausible substrate recognition pocket to which aromatic residues bind is located near the catalytic zinc ion.

Amino Acid Sequence↗
PubMed1997

Novel selection method for engineered antibodies using the mechanism of Fv fragment stabilization in the presence of antigen.

Although the heavy and light chain domains of some antibody variable region fragments (Fvs) readily dissociate under physiological conditions, the Fvs are stable in the presence of antigen. This 'antigen-driven Fv stabilization mechanism' was applied to the selection of clones with specificity toward target antigens. The results can be summarized as follows. (i) Some of the residues in the heavy chain complementarity determining region 2 (HCDR2) of anti-hen egg white lysozyme (HEL) monoclonal antibody HyHEL10 heavy chain variable region (VH) were randomized. (ii) The randomized VH fragments of HyHEL10 were displayed on a filamentous bacteriophage and mixed with the target antigen, before being applied to a light chain variable region (VL) which was immobilized on microtiter plates and subjected to selection by panning. (iii) After four rounds of panning, four clones that showed significant binding to human lysozyme (hL), which HyHEL10 recognized poorly, were selected from the HCDR2 library. (iv) The soluble Fv fragments selected were expressed in Escherichia coli, purified, and subjected to an inhibition assay of lysozyme enzymatic activities and an isothermal titration calorimetry. These Fv fragments had increased affinity toward hL, and thermodynamic analysis suggested that the reduced entropy loss due to binding by the replacement of residues in HCDR2 resulted in the higher hL binding activity.

Amino Acid Sequence↗
PubMed1997

HTLV-I pX transgenic rats: development of cytokine-producing mammary carcinomas and establishment of the pX mammary carcinoma cell lines.

In two lines of transgenic rats (pX rats) from WKAH and F344 strains and carrying the HTLV-I pX gene under control of the mouse H-2Kd promoter, mammary carcinomas developed predominantly in females starting at about 5 months of age. The incidence of the tumor reached about 40% when the rats were 12 months old. Histology of the tumor was undifferentiated carcinoma with massive infiltration of granulocytes into the tumor tissue. Systemic granulocytosis and hepato-splenomegaly due to extramedullary granulocytopoiesis were seen in pX rats and nude mice bearing pX mammary tumor. mRNAs of both pX and host genes, Gro and MIP-2, which are granulocyte chemoattractants of the IL-8 family, were highly expressed in the tumor tissue. Since expression and point mutation of several oncogenes and anti-oncogene, related with mammary carcinomas, were not demonstrated, hitherto unidentified novel oncogenic pathways may be transactivated by the pX transgene in these pX rats. pX mammary carcinoma cell lines, which have similar characteristics to the primary tumor, were established and the cells underwent apoptosis under the serum deprived conditions. The pX rats and the pX mammary carcinomas appear to be suitable models for analyses of HTLV-I pX oncogenesis and immune pathogenesis in vivo and in vitro.

Animals↗
PubMed1997

[Neovascularization after encephalo-duro-arterio-synangiosis in elderly quasi-moyamoya disease: a case report].

A 65-year-old man who had a history of diabetes mellitus visited a hospital for recent memory disturbance. MR angiography showed stenoses of the main trunks of the intracranial arteries. He was admitted to our hospital, and angiography revealed occlusion of the left cervical internal carotid and right middle cerebral arteries, and stenoses of the right internal carotid, right anterior cerebral, left vertebral, and right posterior cerebral arteries. There was collateral circulation formed from the left external carotid and left posterior cerebral arteries. Basal moyamoya vessels were also observed. 123I-IMP SPECT showed low perfusion of the right cerebral hemisphere, and response to acetazolamide was poor. Based on the angiographical findings and the presence of diabetes mellitus, the patient was diagnosed as having quasi-moyamoya disease. Vascular reconstructive surgery was indicated. Since there was no recipient artery adequate for STA-MCA anastomosis, encephalo-duro-arterio-synangiosis was performed on the right side. Postoperatively, the patient's recent memory improved gradually, and angiography performed 7 months after the operation revealed neovascularization from the superficial and deep temporal arteries. Although indirect bypass surgery has been applied mainly to child moyamoya disease, its effectiveness for cerebral ischemia in adult patients has also been reported, particularly in cases with misery perfusion. Neovascularization with indirect bypass surgery can be expected if the patient is under misery perfusion, even in elderly patients.

Aged↗
PubMed1997

Morphological study of pituitary tumorigenesis in transgenic mice induced by hybrid oncogene of the thyrotropin beta-subunit and the simian virus 40 large T-antigen.

We have created a transgenic mouse, TTP-1, generating anterior pituitary tumors by using the simian virus 40 (SV40) large T antigen gene and human thyrotropin beta-subunit gene. To examine characteristics of tumors, histological details were investigated using light and electron microscopies. The main tumor tissues, composed of small chromophobe cells, were located inferior to but clearly separated from the hypothalamus; however, neuron fibers probably derived from the hypothalamus were observed to invade some tumor tissues. Some differentiated endocrine cells occupied the caudal region of the tumor. Immunohistochemically, SV40 large T antigen was expressed in the cell nucleus of the undifferentiated cell area, whereas cells expressing several hormones were mainly distributed in the differentiated cell area. Electron microscopically, the undifferentiated cells were divided into 2 types; electron-dense and -lucent cells, the nuclei of which were composed of obscured nucleoli and many notable invaginations of the nuclear membrane. No intracellular microfilamentous structures were observed. Sometimes it was noted that cytoplasmic processes were connected with gap junctions. In the intercellular spaces, there were neuron fibrous and synapse-like structures. In the differentiated cell area, the cell membranes directly contacting other cells were relatively smooth, and many gap junctions were demonstrated. Secretory granules, which were round and less than 100 nm in diameter, were more electron dense in smaller cells than in larger cells. They were aligned just below the cell membrane. Immuno-electron microscopically, positive reactions for SV40 were observed in the nuclei of the undifferentiated cell area. In the differentiated cell area, most of the secretory granules were labeled by GH. TTP-1 transgenic mice should provide a valuable animal model for studying the pathogenesis of anterior pituitary tumors.

Animals↗
PubMed1997

Magnetic resonance imaging of hepatocellular carcinoma in Long-Evans cinnamon rats under a magnetic field of 7.05 T.

Magnetic resonance (MR) images of livers in 3-, 12- and 29-month-old Long-Evans Cinnamon(LEC) rats (male) were taken under a magnetic field of 7.05 T. MR images of sagittal and transversal sections were obtained in 1-mm-thick slices by T1-weighted and two-dimensional Fourier transformation techniques. The data matrix size was 256 phase-encoded steps. Each image was obtained through four acquisitions. Three-month-old rats gave MR images with low signal intensity over the liver probably due to the shorting of its T1 and T2 relaxation times. However, 12-month-old rats gave hyperintense regions around hepatic veins in right hepatic lobe, which was assigned to hepatocellular carcinoma. In 29-month-old rats, MR images with hyperintensity throughout the hepatic lobe were observed. These MR images, therefore, suggested that hepatocellular carcinoma in LEC rats developed from the restricted regions surrounding hepatic veins. In the present study, T1-weighted MR imaging under a magnetic field of 7.05 T was shown to be applicable to the diagnosis of hepatic cancer in LEC rats.

Animals↗
PubMed1996

Orderly disposition of heterogeneous small subunits in D-ribulose-1,5-bisphosphate carboxylase/oxygenase from spinach.

We determined the crystal structure of spinach ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) by x-ray diffraction at 1.8-A resolution and found that the enzyme contained two kinds of S, SI and SII, present in equal number and disposed in an orderly way within the Rubisco holoenzyme. The electron density maps suggested that leucine was at residue 56 in SI, although histidine was at that position in SII. There were other residue differences. Thus, spinach Rubisco has a L8SI4SII4 subunit structure. The orderly disposition of the heterogeneous small subunits in the Rubisco holoenzyme provides accounts of a multigene family of S in plants.

Crystallography, X-Ray↗
PubMed1996

Visualization of yellowish-orange luminescence from cuprous metallothioneins in liver of Long-Evans Cinnamon rat.

We describe the first use of an emission probe, based on the cuprous thiolate chromophore, for direct microscopical observation of cuprous metallothioneins located in liver of 15-week-old (just before spontaneous hepatitis) Long-Evans Cinnamon rats. The rats show remarkable accumulations of copper and cuprous metallothioneins. In the mildly fixed liver, we visualized the same yellowish-orange luminescence as the specific emission from cuprous metallothioneins, following excitation in 330-385 nm region. In liver from Long-Evans Agouti rat, a counter part of Long-Evans Cinnamon rat, no similar luminescence was found. So, it was thought that cuprous metallothioneins accumulated in the Long-Evans Cinnamon rat liver might emit the yellowish-orange light. To verify this presumption, we tentatively defined three histochemical criteria, quenching tests by oxidation, protonation and mercury treatment, based on the coordination chemical characteristics of metallothioneins. The emission completely satisfied these criteria. Furthermore, the reliability of these criteria was supported by immunocytochemical and biochemical results. Consequently, all results sufficiently indicate that the yellowish-orange luminescence in the Long-Evans Cinnamon rat liver is the emission from cuprous metallothioneins.

Animals↗
PubMed1996

The effects of alpha-phenyl-tert-butyl nitrone (PBN) on copper-induced rat fulminant hepatitis with jaundice.

In the present study we demonstrated the protective effects of the spin-trapping agent alpha-phenyl-tert-butyl nitrone (PBN) against fulminant hepatitis with jaundice in LEC rats. In LEC rats an excess amount of copper is accumulated in the liver and causes hepatitis with severe jaundice. PBN was subcutaneously administered every 2 d at the concentration of 128 mg/kg, beginning with 13-week-old rats and continuing for 17 weeks. PBN prevented the loss of body weight, reduced death rate, and suppressed the increase in GTP and GOT values reflecting hepatic cell destruction. Ocular inspection also confirmed the suppressive effects of PBN on jaundice. In parallel with these phenomena, the amounts of thiobarbituric acid-reactive substances (TBARS) in livers of PBN-administered rats were found to be lower than those of non-PBN-administered rats. Little histological changes were observed in PBN-administered rats in comparison with non-PBN-administered rats. The protective effect of PBN on the formation of oxidative damage in liver DNA was observed but not so remarkable as that on lipid peroxidation. From these results, it was concluded that PBN had the liver-protective effects against fulminant hepatitis with jaundice. This suggested that free radicals play an important role in abnormally accumulated copper-induced liver injury and that PBN potentially has therapeutic value for the treatment of hepatitis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Distribution of Corynebacterium renale among apparently healthy rats.

We examined the distribution of Corynebacterium renale, a causative agent of urinary calculus, in clinically normal rats at 6 animal facilities in Japan. Swabs of the vulva and vaginal vestibule or prepuce of the rats were cultured for isolation of the organisms. C. renale has been isolated at only one animal facility, where cases of urinary calculus were reported several years ago. In this facility, 32% of female (43/135) and 22% of male (18/82) rats, 4-28 weeks old, were positive for C. renale. In contrast, 92 female and 169 male rats at other facilities without a history of the disease were negative for the organisms.

Animals↗
PubMed1996

Case report: primary splenic non-Hodgkin's B cell lymphoma in a patient with chronic hepatitis C.

A case of primary splenic lymphoma in a patient with chronic hepatitis C is reported. A 69-year-old man with chronic hepatitis C was admitted to Fukuoka City Hospital for evaluation of an enlarging splenic tumour. In the spleen, ultrasonographic examination revealed a hypoechoic tumour and computed tomography demonstrated a non-enhancing low density area measuring 7 cm in diameter; coeliac angiography revealed a hypovascular tumour. Gallium scintigraphy showed uptake of the radioisotope in the splenic tumour. A splenectomy was performed and the morphological and immunohistochemical findings of this tumour were compatible with those of non-Hodgin's B cell lymphoma. Recently, cases of malignant B cell lymphoma associated with hepatitis C virus infection have been reported. Lymphotropism of hepatitis C virus may play a pathological role in the development of non-Hodgkin's lymphoma. We emphasize the importance of considering lymphoma in the differential diagnosis of extrahepatic disorders during the course of chronic hepatitis C virus infections.

Aged↗
PubMed1996

Direct visualization of copper-metallothionein in LEC rat kidneys: application of autofluorescence signal of copper-thiolate cluster.

We report on the histochemistry of copper-metallothionein (Cu-MT) in the kidneys of Long Evans Cinnamon (LEC) rats. We used the visualization principle of histochemistry based on the autofluorescence emission from the fluorophore of Cu(+)-thiolate clusters in proteins. Intense autofluorescence signals were observed with a ring at the outer stripe of the outer medulla. Orange fluorescence signals were observed in the nuclei and cytoplasm of proximal straight tubular (PST) cells of segment 3 (S3) at the outer stripe of the outer medulla, and yellow-orange signals were detected in lysosome-like organelles in the proximal convoluted tubule (PCT) cells of segments 1 and 2 (S1 and S2) adjacent to the glomeruli in the cortex. These fluorescent materials were identified as Cu-MT because both signals were quenched by withdrawing Cu+ or by blocking cysteine residues, the distributions of cysteine residues and immunoreactive MT showed identical patterns to the localization of the fluorescence signals, and the fluorescent proteins containing Cu were eluted at the same Kd value of purified Cu-MT by gel filtration chromatography. However, a high level of MT mRNA was detected only in the outer stripe of the outer medulla where the orange fluorescence signals were detected, but not in the cortex. This difference in localization between the protein and the mRNA suggested that synthesis of renal MT occurs do novo in the outer stripe of the outer medulla. The yellow-orange fluorescent Cu-MT located in the lysosomal organelles at S1 and S2 of the PCT cells in the cortex could be Cu-MT of nonrenal origin, i.e., Cu-MT transported from other organs.

Animals↗
PubMed1995

Complete amino acid sequence of a zinc metalloendoprotease from Streptomyces caespitosus.

We determined the complete amino acid sequence of a zinc metalloendoprotease from Streptomyces caespitosus (ScNP). Peptide fragments obtained by digestion of Rcm-ScNP with trypsin, ScNP and endoproteinase Asp-N were purified by reverse-phase HPLC and their amino acids were analyzed using an automatic sequencer. ScNP consisted of a single polypeptide chain of 132 amino acid residues with one disulfide bond between residues 99 and 112 (M(r) 14376). Thus, the number of amino acid residues determined for this enzyme is much lower than the number of residues previously reported for metalloendoproteases. The amino acid sequence indicated that although ScNP has the zinc-binding motif. His-Glu-Xaa-Xaa-His, which is found at the active site of most zinc metalloendoproteases, it does not share overall significant similarity to the sequences of other zinc metalloendoproteases. Moreover, an analysis of the X-ray structure of ScNP at 0.2-nm resolution (Kirisu et al., unpublished results) revealed that Asp93, together with two histidine residues in the zinc-binding motif (His83 and His87) and a water molecule, is a zinc ligand. We propose that ScNP, which bears the HEXXHXXGXXD motif, represents a novel subfamily of zinc-containing metalloendoproteases.

Amino Acid Sequence↗
PubMed1995

The suppression of age-related accumulation of lipid peroxides in rat brain by administration of Rooibos tea (Aspalathus linearis).

The protective effects of Rooibos tea (RT), Aspalathus linearis, against damage to the central nervous system (CNS) accompanying aging were examined by both the thiobarbituric acid reaction (TBA) and magnetic resonance imaging (MRI) methods in brains of chronically RT-treated rats. Ad libitum administration of RT was begun with 3-month-old Wistar female rats and continued for 21 months. The contents of TBA reactive substances (TBARS) in the frontal cortex, occipital cortex, hippocampus and cerebellum in 24-month-old rats after administration with water were significantly higher than those in young rats (5 weeks old). However, no significant increase of TBARS was observed in RT-administered aged rats. When MR images of the brains of 24-month-old rats with and without RT as well as 5-week-old rats were taken, a decrease of the signal intensity was observed in the cerebral cortex, hippocampus and cerebellum in MR images of aged rats without RT, whereas little change of the signal intensity was observed in MR images of the same regions of 24-month-old rats treated with RT, whose images were similar to those of young rats. These observations suggested that (1) the age-related accumulation of lipid peroxides in the brain was closely related to the morphological changes observed by MRI, and (2) chronic RT-administration prevented age-related accumulation of lipid peroxides in several regions of rat brain.

Administration, Oral↗
PubMed1995

Cytokine-producing mammary carcinomas in transgenic rats carrying the pX gene of human T-lymphotropic virus type I.

In two lines of transgenic rats (pX rats) from WKAH and F344 strains and carrying the human T-lymphotropic virus type I pX gene, undifferentiated mammary carcinomas developed predominantly in females starting at about 5 months of age, and there was massive infiltration of granulocytes in the tumor tissue. The incidence of the tumor reached about 40% when the rats were 12 months old. mRNAs of both pX and host genes Gro and MIP-2, which are granulocyte chemoattractants of the interleukin 8 family, were highly expressed in the tumor tissue. Since expression and point mutation of several oncogenes and the antioncogene were not demonstrated, hitherto unidentified novel oncogenic pathways may be transactivated by the pX transgene in these pX rats.

Animals↗
PubMed1995

Accumulation of isogloboside and ganglio-N-tetraosyl ceramide having blood group B determinant in the hepatomas of female LEC rats.

We have studied the neutral glycolipid composition of spontaneous hepatomas in LEC female rats. Neutral lipid fractions were isolated and purified by column chromatographies on DEAE-Toyopearl 650(M) and Iatrobeads. The neutral glycolipid fraction contained 3.2 to 4.4 micrograms lipid-bound glucose (Glc) per mg protein, and consisted of isogloboside (iso-Gb4, 50.8% of total neutral glycolipids) and IV3Gal, IV2Fuc, GgOse4Cer (asialo-BGM1, 13.5%) as the major neutral glycolipids and Gb3 and iso-Gb3 (9.2%), GlcCer (7.2%), LacCer (6.1%) as the other species. The structure of iso-Gb4 was elucidated by gas-liquid chromatography (GLC), permethylation study, liquid secondary ion (LSI) mass spectrometry, and nuclear Overhauser enhancement spectroscopy (NOESY) and that for asialo-BGM1 by GLC, LSI mass spectrometry, and high-performance thin-layer chromatography (HPTLC)-overlay method using anti-asialo-BGM1 antibody. Isogloboside and asialo-BGM1 which are found in negligible amounts in normal liver tissues may represent excellent markers for studying tumor metastasis and cellular adhesion.

ABO Blood-Group System↗