Biomedical subjects

K Tamai

Publications and source records attributed to K Tamai.

At least 181 records · Page 10Linked to original sources

PubMed1993

[Experimental study on local cooling of the eyeball in ocular surgery (4). The local cooling effect on uveal blood circulation, intraocular pressure, and intravitreous pressure].

The effects of local cooling on the uveal blood circulation, intraocular pressure, and intravitreous pressure were evaluated. Saline solutions maintained at 10 degrees C and 35 degrees C were dripped on the rabbit ocular surface. After 5-minute dripping of 10 degrees C saline solution, the temperature decreased by 10.6 degrees C at the ciliary body, 7.7 degrees C at the choroid and 2.9 degrees C at the central region of the vitreous. Hydrogen clearance with electrolytically generated hydrogen gas was employed to measure the tissue blood flow, which fell to 82.9% of normo-thermal value at the ciliary body and 86.3% at the choroid. The intravitreous pressure dropped by 2.8 mmHg. After 30-minute dripping of 10 degrees C saline solution, the intraocular pressure dropped by 3.0 mmHg. We consider that the reduction of intraocular and intravitreous pressure during local cooling of the ocular surface is related to decrease in the uveal blood flow.

Animals↗

PubMed1993

Immunopurified Rb protein inhibits SV40 T antigen-dependent stimulation of DNA polymerase alpha.

It has been shown that purified SV40 large T antigen (Tag) forms a complex with both human and calf thymus DNA polymerase alpha and stimulates its activity. Furthermore, Tag has also been found to complex with purified human Rb protein. Here, we show the effect of Rb protein on the stimulation of DNA polymerase alpha by Tag, in an in vitro system using either purified human or calf thymus DNA polymerase alpha and either primed single-stranded M13 DNA or calf thymus-activated DNA. Both human and calf thymus enzymes were dose-dependently stimulated several fold by Tag. The stimulation was also observed in the coupled reaction of primase and polymerase alpha, using unprimed single-stranded M13 DNA. These stimulatory effects were, however, completely abolished by preincubating Tag with an equimolar amount of Rb protein. Primase activity of DNA polymerase alpha-primase complex was also stimulated by Tag, and this stimulation was abolished by the presence of Rb protein. In contrast, free primase was not affected by either Tag or Rb protein. Kinetic analysis revealed that in the presence of Tag the apparent Km for the template of either human or calf DNA polymerase alpha was decreased by approximately 2.5-fold and the Vmax was increased twofold, whereas Tag complexed with Rb protein did not affect the Km or the Vmax. These results suggest a competition between Rb protein and DNA polymerase alpha for binding to Tag, which may be a key step for the initiation of SV40 DNA replication.

Antigens, Polyomavirus Transforming↗

PubMed1993

[Serial MR imaging of possible Pelizaeus-Merzbacher disease].

We performed serial magnetic resonance imaging (MRI) toward 4 male children with possible Pelizaeus-Merzbacher disease (PMD). They were clinically suspected as PMD on the basis of typical neurological, electrophysiological and MRI examinations. MRI revealed that myelinated fibers were localized in brainstem, cerebellum, internal capsule, optic radiation and proximal corona radiata in case 1, while myelinated fibers were almost absent in case 2-4. On repeated MRI investigation, we found no further extension of myelination in case 1 and the absence of myelination in case 2-4. This study demonstrated that myelination in the brain is arrested immediately after birth in case 1, while no myelination developed before birth in case 2-4. It was speculated that MRI in case 1 and case 2-4 might correspond to neuropathologic findings of classical and connatal form as reported in the literature.

Child, Preschool↗

PubMed1992

Efficient purification of a full length and biochemically active p110Rb, the retinoblastoma gene product.

Rb protein was purified from recombinant baculovirus-infected Sf9 cells to apparent homogeneity by a simple solubilization and by immunoaffinity column chromatography. It was mainly obtained as p110Rb, the underphosphorylated form of the Rb protein family. This p110Rb was shown to form a specific complex in vitro with SV40 Tag and to bind to double or single stranded DNA. It could also affect Tag helicase activity in a biphasic-dose dependent manner, due to these two biochemical functions. This purification procedure provides sufficient amounts of native Rb protein to further elucidate its role as an anti-oncogene protein and a negative regulator of the cell cycle.

Animals↗

PubMed1992

Intermediate form of mucopolysaccharidosis type II (Hunter disease): a C1327 to T substitution in the iduronate sulfatase gene.

Hunter disease, an X-linked recessive lysosomal storage disorder, is caused by a deficiency in iduronate sulfatase activity. Sequence analysis of mRNA of fibroblasts of an intermediate phenotype patient showed a single C1327 to T nucleotide transition. This mutation resulted in a substitution of termination codon for normal arginine at position 443 of the peptide sequence. Expression studies with this abnormal cDNA in fibroblasts from the patient revealed a loss of enzymatic activity and instability of the mutated protein. We posturate that this mutation is probably the cause of the intermediate form of Hunter disease.

Base Sequence↗

PubMed1992

Different modifications by vanillin in cytotoxicity and genetic changes induced by EMS and H2O2 in cultured Chinese hamster cells.

The modifying effects of vanillin on the cytotoxicity and 6-thioguanine (6TG)-resistant mutations induced by two different types of chemical mutagens, ethyl methanesulfonate (EMS) and hydrogen peroxide (H2O2), were examined using cultured Chinese hamster V79 cells. The effects of vanillin on H2O2-induced chromosome aberrations were also examined. Vanillin had a dose-dependent enhancing effect on EMS-induced cytotoxicity and 6TG-resistant mutations, when cells were simultaneously treated with vanillin. The post-treatment with vanillin during the mutation expression time of cells after treatment with EMS also showed an enhancement of the frequency of mutations induced by EMS. However, vanillin suppressed the cytotoxicity induced by H2O2 when cells were post-treated with vanillin after H2O2 treatment. Vanillin showed no change in the absence of activity of H2O2 to induce mutations. Post-treatment with vanillin also suppressed the chromosome aberrations induced by H2O2. The differential effects of vanillin were probably due to the quality of mutagen-induced DNA lesions and vanillin might influence at least two different kinds of cellular repair functions. The mechanisms by which vanillin enhances or suppresses chemical-induced cytotoxicity, mutations and chromosome aberrations are discussed.

Animals↗

PubMed1992

Parallel pathways of gene regulation: homologous regulators SWI5 and ACE2 differentially control transcription of HO and chitinase.

Two independent pathways of transcriptional regulation that show functional homology have been identified in yeast. It has been demonstrated previously that SWI5 encodes a zinc finger DNA-binding protein whose transcription and cellular localization both are cell cycle regulated. We show that ACE2, whose zinc finger region is nearly identical to that of SWI5, shows patterns of cell cycle-regulated transcription and nuclear localization similar to those seen previously for SWI5. Despite their similarities, SWI5 and ACE2 function in separate pathways of transcriptional regulation. SWI5 is a transcriptional activator of the HO endonuclease gene, whereas ACE2 is not. In contrast, ACE2 is a transcriptional activator of the CTS1 gene (which encodes chitinase), whereas SWI5 is not. An additional parallel between the SWI5/HO pathway and the ACE2/CTS1 pathway is that HO and CTS1 both are cell cycle regulated in the same way, and HO and CTS1 both require the SWI4 and SWI6 transcriptional activators. Overproduction of either SWI5 or ACE2 permits transcriptional activation of the target gene from the other pathway, suggesting that the DNA-binding proteins are capable of binding in vivo to promoters that they do not usually activate. Chimeric SWI5/ACE2 protein fusion experiments suggest that promoter specificity resides in a domain distinct from the zinc finger domain.

Amino Acid Sequence↗

PubMed1992

Cloning of partial cDNA for mouse 180-kDa bullous pemphigoid antigen (BPAG2), a highly conserved collagenous protein of the cutaneous basement membrane zone.

One-hundred-eighty kilodalton bullous pemphigoid antigen (BPAG2) is recognized by autoantibodies in the sera of patients with blistering skin diseases, bullous pemphigoid (BP), and herpes gestationis (HG). In this study, we have screened a mouse epidermal keratinocyte cDNA library with a 1.0-kb human BPAG2 cDNA, which has been shown to correspond to two collagenous domains (Giudice et al: J Clin Invest 87:734-738, 1991). Screening of the mouse library identified two cDNA clones, the larger one being 1.8 kb in size. Comparison of the mouse amino acid sequences, as deduced from cDNA, with the corresponding human sequences revealed 86% homology. Furthermore, Northern hybridizations of mouse epidermal RNA with these cDNA revealed the presence of an mRNA transcript of approximately 6 kb, the size of the human BPAG2 mRNA. Elucidation of the deduced amino-acid sequences revealed the presence of definitely one and possibly two putative membrane-associated segments, suggesting that the 180-kDa BP antigen is a transmembrane protein. The sequence analysis also identified a 7-amino-acid segment that was predicted by computer analysis to be antigenic. Elucidation of the divergence between the mouse and previously published human and chicken BPAG2 sequences indicated that this protein segment was relatively well conserved. These data suggest, therefore, that the 180-kDa bullous pemphigoid antigen associated with hemidesmosomes is a well-conserved transmembrane protein that may play a critical role in the attachment of epidermis to the underlying basement membrane.

Amino Acid Sequence↗

PubMed1992

Neuroradiological findings in children with congenital myotonic dystrophy.

We studied seven children with congenital myotonic dystrophy, aged 2.1-8.3 years, and the results of computed tomography and magnetic resonance imaging of the brain were analyzed and neurological development was assessed from the neonatal period. We found that ventricular dilatation that had been seen on the first day of life in two of three infants had not progressed in sequential follow-up computed tomography scans taken at intervals of one to six years. Also, in T2-weighted magnetic resonance imagings, areas of periventricular hyperintensity were identified in all children, as well as areas of subcortical hyperintensity in one child. Further, an asphyxial episode had occurred at birth in five patients and the extent of the periventricular hyperintensity was found to correlate significantly with Apgar scores, indicating that the degree of perinatal asphyxia that had occurred was responsible for the abnormalities uncovered by the magnetic resonance imagings. However, there was no correlation between the neurodevelopment outcome and the extent of the periventricular hyperintensity or ventriculomegaly. Therefore, in patients with congenital myotonic dystrophy, a neonatal episode of asphyxia can be responsible for a finding of periventricular hyperintensity, but it is unlikely that an integral part of the mental retardation is attributable to brain damage due to perinatal asphyxia.

Apgar Score↗

PubMed1992

Specific expression of glutathione S-transferase Pi forms in (pre)neoplastic tissues: their properties and functions.

The detection of preneoplastic cells is very important for the analysis of carcinogenic processes and for developing strategies for prevention and treatment of cancer. We have been investigating enzyme alterations occurring during rat chemical hepatocarcinogenesis, especially to find more specific enzyme markers for preneoplastic hepatic lesions. We identified the placental form of glutathione S-transferase (GST-P; GST 7-7) as a new marker enzyme for preneoplastic hepatocytes. We also found human placental form, GST-pi, to be a possible tumor marker for various human tissues except liver. In this article, their properties and possible functions are reviewed on basis of our recent investigations. A peroxisomal enzyme, enoyl CoA hydratase, in also described as a possible negative marker for rat preneoplastic hepatic foci/nodules and hepatomas induced by peroxisome proliferators.

Animals↗

PubMed1992

[Imaging modalities of rheumatoid arthritis].

Modern diagnostic techniques for rheumatoid arthritis include x-ray examination, arthro- or myelography, CT scan, scintigraphy, thermography, ultrasonography, and MRI. X-ray is the simplest and most common method for assessing the degree of joint destruction. Arthrography provides information on intra-articular pathology. CT is particularly of value in visualizing changes in the axial skeleton. Joint scintigraphy, using 99m-technetium pertechnetate, is available in evaluating the degree of synovial inflammation. Thermography has been performed for a similar purpose. Ultrasound allows a real-time, dynamic study of soft tissues in and around the joint, including tendons, synovium and articular cartilage. MRI most clearly shows various pathological conditions such as pannus, degenerated cartilage or spinal cord compression, although the examination time should be shortened.

Arthritis, Rheumatoid↗

PubMed1992

cdc2-like kinase is associated with the retinoblastoma protein.

The growth-suppressive activity of the retinoblastoma (RB) protein is suggested to be regulated by phosphorylation. In studies on the kinase that phosphorylates the RB proteins, we have previously found that RB proteins can be phosphorylated by purified cdc2 kinase. In this study, we noted that RB proteins immunoprecipitated from human cell lysates are weakly phosphorylated in the absence of purified cdc2 kinase. Immunoblot analysis showed the presence of p34cdc2 in the immunoprecipitates with anti-RB monoclonal antibody. In addition, the coprecipitated kinase was found to have the same substrate specificity as cdc2 kinase. The associated kinase activity was particularly high in cells arrested in G1/S and S phase by aphidicolin. Furthermore, RB proteins were shown to be phosphorylated in nuclear extracts by some endogenous cdc2-like kinase(s). These results suggest that cdc2-like kinase is the main kinase for phosphorylation of RB proteins in vivo.

Amino Acid Sequence↗

PubMed1991

Defect of a fiber cell-specific 94-kDa protein in the lens of inherited microphthalmic mutant mouse Elo.

Deficiency in a 94,000-dalton protein in the non-crystallin fraction from the Elo mouse lens was shown. To perform further investigations, we raised an antibody against the 94,000-dalton protein isolated from normal mouse lens. Western blot analysis with the antibody indicated that the protein was only present in the lens and not in the brain, lung, heart, liver, and kidney. In the lens, it was unique to the cortex and nucleus fractions, not being present in the epithelial cells. Furthermore, it was observed in the water-soluble fraction as well as in the urea-soluble fraction. The antibody weakly but clearly reacted with the chick CP97 lens peptide, a fiber cell-specific protein, and anti-CP97 antibody also reacted with the 94,000-dalton protein. From these results, we concluded that the protein corresponds to CP97 cytoskeletal protein in the mouse lens. The protein was deficient in the lenses from Elo mice, but microphthalmic lenses from CTA mice contained a normal level.

Animals↗

PubMed1991

Role of cysteine residues in the activity of rat glutathione transferase P (7-7): elucidation by oligonucleotide site-directed mutagenesis.

To clarify the role(s) of thiol (sulfhydryl) groups of cysteine (Cys) residues in the activity of the rat glutathione transferase P (7-7) form (GST-P), a cDNA clone, pGP5, containing the entire coding sequence of GST-P (Y. Sugioka et al., (1985) Nucleic Acids Res. 13, 6044-6057) was inserted into the expression vector pKK233-2 and the recombinant GST-P (rGST-P) expressed in E. coli JM109. All four Cys residues in rGST-P were independently substituted with alanine (Ala) by site-directed mutagenesis, the resultant mutants as well as the rGST-P being identical to GST-P purified from liver preneoplastic nodules with regard to molecular weight and immunochemical staining. Since all mutants proved as enzymatically active towards 1-chloro-2,4-dinitrobenzene as liver GST-P, it was indicated that none of the four Cys residues is essential for GST-P activity. However, the mutant with Ala at the 47th position from the N-terminus (Ala47) became resistant to irreversible inactivation by 0.1 mM N-ethylmaleimide (NEM), whereas the other three mutants remained as sensitive as the nonmutant type (rGST-P). Ala47 was also resistant to inactivation by the physiological disulfides, cystamine or cystine, which cause mixed disulfide and/or intra- or inter-subunit disulfide bond formation. These results suggest that the 47-Cys residue of GST-P may be located near the glutathione binding site, and modulation of this residue by thiol/disulfide exchange may play an important role in regulation of activity.

Animals↗

PubMed1991

Modulation of class Pi glutathione transferase activity by sulfhydryl group modification.

Glutathione transferases (GSTs) in Class Pi (rat GST-P (7-7) and human GST-pi) were inactivated by treatment with 0.05-1 mM hydrogen peroxide (H2O2), while GSTs in Class Alpha (1-2) and Class Mu (3-3, 3-4) were not, even with 5 mM H2O2. In the presence of 1 mM reduced glutathione (GSH), the inactivated GST-P (-pi) was effectively reactivated by the action of thioltransferase, which had been partially purified from rat liver by GSH-Sepharose affinity chromatography and gel filtration using Sephadex G-75. Thus, inactivation of GST-P by H2O2 was indicated to involve concomitant formation of disulfide bonds between cysteinyl residues. Single GST-P or GST-pi subunits are known to have four cysteinyl residues at the same positions, which can react with sulfhydryl group modifiers. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, GST-P treated with 1 mM H2O2 showed several extra bands, at least three, with apparent molecular weights of 21.5, 18, 37 kDa in addition to the native GST-P subunit band with a molecular weight of 23.5 kDa. These extra bands were identified as inactive forms since they returned to the native band with accompanying restoration of the activity when treated with dithiothreitol, mercaptoethanol, or thioltransferase. Disulfide bonds were formed mainly within subunits, causing an apparent reduction in molecular weight, only small amounts of binding between subunits being observed.

Animals↗

PubMed1991

Stimulation by carrageenan of arachidonate 12-lipoxygenase activity in dog gingival tissue.

At 4 h after injection of carrageenan into the gingiva, the 12-lipoxygenase activity of the gingival homogenate was markedly increased. Activity in the cytosol and microsomal fractions was markedly increased when assessed as the specific activity based on nmol/min/mg of protein, and in the cytosol fraction as the percentage distribution of total activity. The 12-lipoxygenase activity in the homogenate from carrageenan-treated gingiva was not affected by either EDTA or calcium ion, or a combination of the two. 12-lipoxygenase activity in both carrageenan-treated and untreated gingiva was inhibited dose-dependently by AA861, a striking difference from its effect on platelet 12-lipoxygenase. There was a marked increase of 12-lipoxygenase activity in experimentally inflamed gingiva compared to the non-inflamed gingiva.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1991

Expression of glutathione S-transferase-pi in malignant skin tumors.

GST-pi has been known to be markedly increased in human (pre) neoplasms of several organs. In this paper, the significance of immunohistochemical detection of GST-pi in human malignant tumors of the skin was studied. In specimens from 40 patients with various skin cancers, malignant melanoma, Paget's disease and undifferentiated squamous cell carcinoma showed strong reactivity in GST-pi staining. The reactions were negative or weak in Bowen's disease, basal cell epithelioma and solar keratosis. In normal melanocytes, eccrine, apocrine, and breast gland cells stained positively but not in keratinocytes, sebaceus gland and fibroblasts. While immunohistochemical detection of GST-pi in the skin was not specific for malignancies, it contributed to aid the distinction of squamous cell carcinoma from other keratinocytic tumors. GST-pi might provide potentially useful information on chemosensitivity of skin cancer, and might serve as a biomarker of disease activity.

Biomarkers, Tumor↗

PubMed1991

[Bacteriological examination of infections in the field of oral surgery].

Etiology of bacterial infections in the field of oral surgery was studied. A total of 270 samples collected from patients with encapsulated abscess in their oral cavities was examined and bacteria were isolated from the 244 samples (90.4%). The following results were found; 1) Organisms more than one from one sample were frequently isolated from cases with parodontitis, pericoronitis and gnathitis. Isolation of anaerobic bacteria was common (54.2%). 2) Streptococcus milleri and Streptococcus sanguis and Capnocytophaga species were the most common isolates among aerobic gram-positive and gram-negative bacteria, respectively. 3) Peptostreptococcus micros and Eubacterium lentum were most frequent isolates among gram-negative anaerobic bacteria. Among gram-negative bacteria, Oral Group Bacteroides, especially Bacteroides gingivalis, Bacteroides intermedius, Bacteroides buccae and Bacteroides oralis were most prominent. 4) Isolation frequency of bacteria (both species and strains) was high from samples obtained from patients before antibiotic chemotherapy. 5) Most strains were sensitive to Midecamycin acetate and Josamycin. Minimum inhibitory concentration of 80% isolates (MIC80) against these antibiotics was 0.39 microgram/ml.

Bacteria↗