Biomedical subjects

K Tokunaga

Publications and source records attributed to K Tokunaga.

At least 271 records · Page 15Linked to original sources

PubMed1995

Pathophysiology and pathogenesis of visceral fat obesity.

Based on the analysis of fat distribution by computed tomography (CT) scans, the classification scheme for obesity should include visceral fat obesity in which fat accumulation is predominant in the intra-abdominal cavity. Obese subjects with visceral fat accumulation more frequently demonstrate impairment of glucose and lipid metabolism than those with subcutaneous fat accumulation. We have shown that visceral fat obesity is present in almost 90% of obese patients with ischemic heart disease. Even in non-obese subjects, visceral fat accumulation is correlated with glucose intolerance, hyperlipidemia and hypertension. Forty percent of non-obese subjects with coronary artery disease (CAD) had increased visceral fat. In non-obese subjects, visceral fat area assessed by abdominal CT at the level of the umbilicus correlates with metabolic risk factors, whereas in obese subjects the visceral fat area to subcutaneous fat area ratio provides a more significant correlation. From clinical and basic investigations, aging, sex hormones, excess intake of sucrose and lack of physical exercise have been suggested to be determinants for visceral fat accumulation. Since intra-abdominal fat (mesenteric and omentum fat) has been shown to have high activities of both lipogenesis and lipolysis, its accumulation can induce high levels of free fatty acids, a product of lipolysis, in portal circulation which go into the liver. Excess free fatty acids may cause the enhancement of lipid synthesis and gluconeogenesis as well as insulin resistance, resulting in hyperlipidemia, glucose intolerance and hypertension and finally atherosclerosis. Thus we propose a disease entity, visceral fat syndrome, which may increase susceptibility to atherosclerosis due to multiple risk factors induced by visceral fat accumulation.

Adipose Tissue↗

PubMed1995

Family segregation analysis of inheritance of human minor histocompatibility antigen.

Disparities in minor histocompatibility antigens (mHAs) between HLA-identical donor and recipient pairs often cause graft-versus-host disease (GVHD) or graft rejection. Minor HAs are thought to be peptides that are associated with specific major histocompatibility complex (MHC) molecules and are presented to specific T cells. Despite the importance of mHAs in constructing a strong immunological barrier following tissue transplantation, little information on mHAs in humans is available. We have already reported establishment of the DR9-restricted mHA-specific CD4+ cytotoxic T cell (CTL) clone "A-6." To investigate the chromosomal localization of the gene encoding the mHA peptide recognized by clone A-6 in context with DR9, we performed a family segregation analysis. We concluded that the mHA-encoding gene was transmitted from parent(s) to some offspring.

B-Lymphocytes↗

PubMed1995

Functionality of chimeric Rev proteins of HIV/SIV.

Studies on functional compatibility of various Rev proteins derived from all known human and simian immunodeficiency virus subgroups have shown that this essential gene product is not always exchangeable among the viruses. In an attempt to map the region of Rev proteins responsible for the observed nonreciprocal complementation, hybrid genomic Rev expression vectors were constructed by exchanging the first and second exons of rev genes, and were examined for their abilities to activate reporter clones by transfection. With one exception, the second coding exon of rev gene determined the functional specificity of Rev proteins.

Animals↗

PubMed1995

Functional analysis of human spuma retrovirus genome.

Human spuma retrovirus (HSRV) belongs to retroviruses that possess a complex genome organization. HSRV carries at least three extra genes in the region between env and the 3' long terminal repeat, which are not found in simple retroviruses. Via alternative splicing, these HSRV genes can encode several proteins. To genetically study the requirements of these viral proteins for viral replication in tissue cultures, a number of mutant viruses were constructed from an infectious molecular clone of HSRV. All mutants grew normally in the cell lines tested, except for those lacking transcriptional transactivator activity. By reporter-based transient assay systems, no Rev/Rex equivalent was detected in the HSRV proteins.

Alternative Splicing↗

PubMed1995

Simplified Manouguian's aortic annular enlargement for aortic valve replacement.

A simplified Manouguian's aortic annular enlargement for aortic valve replacement with prosthetic valve was performed in a patient with severe aortic stenosis and mild regurgitation by preserving both the anterior mitral leaflet and the left atrial roof intact. This method minimized the operative risk by avoiding injury to the mitral valve, while inserting a possibly two-size-larger prosthetic valve. The inserted prosthetic valve was positioned parallel to the original aortic valve. Moreover, the incision from the top of the commissure between the noncoronary cusp and left coronary cusp through the interventricular fibrous trigone appears to be easily extended into the exact center of the anterior mitral leaflet if further enlargement is required.

Aorta↗

PubMed1995

Fasting plasma insulin level is an important risk factor for the development of complications in Japanese obese children--results from a cross-sectional and a longitudinal study.

It is not known what types of factors may contribute to the development of complications in obese children. In the current investigation, we have performed a cross-sectional and a longitudinal study in Japanese obese children to clarify the relationship of the extent of obesity, fat distribution, insulin resistance, and aging to the development of obesity-related complications. In the cross-sectional study of 329 obese boys and 142 obese girls aged 7 to 15 years, the fasting plasma immunoreactive insulin (IRI) level was significantly higher than that of 46 non-obese boys and 48 non-obese girls (boys, 13.4 +/- 6.7 v 4.9 +/- 1.9 microU/mL, P < .001; girls, 14.0 +/- 5.9 v 4.8 +/- 1.8, P < .001). Linear regression analysis demonstrated that fasting plasma IRI correlated positively with fasting plasma glucose (FPG), triglycerides (TG), uric acid (UA), and systolic blood pressure (SBP) in obese boys, and with TG, SBP, and diastolic blood pressure (DBP) in obese girls, and negatively with serum high-density lipoprotein cholesterol (HDL-C) in both obese boys and girls. Multiple regression analysis demonstrated that fasting plasma IRI was independently and positively correlated with FPG, TG, and SBP in obese boys. Fasting plasma IRI in obese girls was positively correlated with TG, SBP, and DBP, and negatively with HDL-C. FPG decreased significantly in non-obese children at the onset of puberty, but it remained unchanged in obese children. Fasting plasma IRI and the IRI to glucose ratio increased with age in obese children, whereas they did not show any significant changes in non-obese children.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed1995

A new B18 sequence (B*1802) from Asian individuals.

A new HLA-B18 allele (B*1802) derived from a Thai individual was sequenced. Comparison of this B18 nucleotide sequence with the published B*1801 sequence indicated that this Asian B18 allele has a nucleotide sequence different from that of B*1801. Three nucleotide changes were observed in exon 3, in which two substitutions at codon 97, AGG in B*1801 to AAT in the B*1802, result in an amino acid change from arginine to asparagine. The residue 97Asn has also been described in some B27 subtypes. A silent mutation was also observed at codon 99, TAC in B*1801 to TAT in the B*1802. This sequence has been reported in many class I alleles published so far. Moreover, 18 HLA-B18-positive samples were examined by the PCR-SSO method using specific probes for B*1801 and B*1802. The results demonstrated that three Asian samples possess B*1802 and share HLA-Cw7, DR12, and DQ7.

Alleles↗

PubMed1995

A new HLA-A9 subtype lacking the Bw4 epitope. Ancestral or revertant allele?

The HLA-A9 group has been subdivided into three serologically defined splits, A23, A24, and A2403. We have found a new HLA-A9 split antigen, tentatively called A24AK, in the Japanese population. Sequence analysis of A24AK (officially assigned A*2404) showed that this new allele was different from HLA-A*2402, which codes for the common A24 antigen, by seven nucleotides, and the two alleles could be discriminated by the PCR-SSCP method. These nucleotide substitutions are predicted to result in substitution of six amino acid residues at positions 76, 79, 80, 81, 82, and 83. In all HLA-A9-group alleles described to date, this region is known to code for the Bw4 epitope, which is usually localized on HLA-B molecules. However, the new allele lacks the Bw4 coding sequence. Sequencing results are supported by results showing that the lymphocytes from A24AK-positive individuals did not react with anti-Bw4 antiserum. The nucleotide sequence of A*2404 in this region was identical to that of A*0101, A*2601, A*2602, and several other alleles. These findings suggest several possible paths of evolution of this new allele.

Alleles↗

PubMed1995

High-resolution HLA-DQB1 typing by combination of group-specific amplification and restriction fragment length polymorphism.

A reliable method for high-resolution HLA-DQB1 typing using the combination of group-specific amplification and RFLP analysis is described. Group-specific amplification was carried out for the alleles of two groups using the two primer pairs under the same PCR conditions. One group contains DQ5 and DQ6 specificities and the other DQ2, DQ3, and DQ4 specificities. Computer analysis on cleavage patterns for 19 alleles of the DQB1 gene showed that the 11 alleles of the former group could be distinguished with five restriction enzymes and the eight alleles of the latter group could be distinguished with four enzymes. We could reduce the number of restriction endonucleases required compared with the number used in previous studies because we selected appropriate restriction enzymes which had at least one recognition site in almost all DQB1 alleles as a form of internal control. Moreover, DQB1*0602 and 0603, which were indistinguishable using the previously reported PCR-RFLP methods, could be distinguished by the present method. The results of typing of 100 samples from Japanese individuals by this method showed no discrepancy with the results obtained by serologic methods. The calculated allele frequencies showed good agreement with those reported at the 11th International Histocompatibility Workshop.

Base Sequence↗

PubMed1995

Sequence-based typing of HLA-A2 alleles using a primer with an extra base mismatch.

A PCR-SBT method using genomic DNA for HLA-A2 alleles was established. To achieve specific amplification for detecting a single base difference between A2 alleles and other HLA-A alleles, a primer having one extra mismatch at the second position from its 3'-end was designed. The primer exhibited a high specificity with annealing temperatures from 64 degrees C to 68 degrees C. Thirty-eight Japanese samples were screened using this method. The majority of Japanese A2 antigens were coded by A*0201. A*0206 and A*0207 were observed at relatively high frequencies. Serologically defined split antigens, A2S and A2AK, which we have recently identified, corresponded to A*0203 and A*0210, respectively. Moreover, A*0207 was strongly associated with B46 and DR8.1.

Alleles↗

PubMed1995

Both HLA-B1301 and B1302 exist in Asian populations and are associated with different haplotypes.

A B13 split antigen was newly identified with three alloantisera in Japanese, and two B13 split antigens were found in a Thai family. To confirm the variation of B13 and understand the correspondence between the serologic splits and the published B13 alleles, B*1301 and B*1302, we determined the sequences of genes coding for these B13 splits. The common Japanese B13 allele was found to be B*1301, whereas another split antigen was shown to be coded by B*1302. Two B13 variants identified in a Thai individual corresponded to B*1301 and B*1302. Moreover, 57 B13-positive samples from several ethnic groups were examined using the PCR-SSO method. Differing from previous reports, both B*1301 and B*1302 were found in samples from Asian populations. These two alleles were separately associated with different antigens: HLA-B*1301 exhibited a strong association with A2, Cw10, DR12, and DQ7 antigens, whereas HLA-B*1302 was strongly associated with A30, Cw6, DR7, and DQ2 antigens. In addition, applying the PCR-SSCP method, B*1301 and B*1302 could also be simply distinguished from each other.

Alleles↗

PubMed1995

A new HLA-C allele, Cw*1403, associated with HLA-B44 in Japanese.

An allele encoding an HLA-C antigen, tentatively called CX44, associated with HLA-B44 was identified as a new member of the Cw14 group, Cw*1403. The nucleotide sequence of Cw*1403 was closest to that of Cw*1401: five bases were different between the two alleles, in which three bases in Cw*1403 (two in exon 3 and one in exon 4) were the same as those of most HLA-C alleles. Two substitutions from guanine to adenine were found in the new allele, both of which are in exon 2, one at position 134 (61 of exon 2) and the other at position 201 (128 of exon 2). The former nucleotide substitution leads to the substitution of amino acid residue 21 from Arg to His, and the other substitution was synonymous. The former substitution was shared with Cw2, 3, 5, 13, and 15 alleles, and the latter was shared with Cw2, 4, 5, 8, 12, 13, 15 and 16 alleles. The other seven unrelated Japanese samples with CX44 were analyzed by a PCR-SSO method. It was confirmed that all the seven samples have the same substitutions as the sequenced allele, and the allele demonstrates a strong association with A33, B44, DR13, and DQ1, which are known to form a common haplotype in Japanese and Koreans.

Alleles↗

PubMed1995

Maintenance of high virus load even after seroconversion in newborn cats acutely infected with feline immunodeficiency virus.

The viral loads in adult and newborn cats have been compared following injection with feline CD4+ FeL-039 line cells acutely infected with feline immunodeficiency virus (FIV). The level of virus genome in peripheral blood mononuclear cells (PBMC) increased progressively despite seroconversion in the newborn cats, whereas the virus genome was apparently cleared after seroconversion in the adult cats. Immunohistochemical staining of thymus of the FIV-infected newborn cats showed clusters of viral antigen-positive cells. These results indicate that FIV infection of the newborn cat results in higher virus loads than infection of the adult cat. We discuss these findings in relation to FIV as a model system for studies of the infection of neonates with an immunosuppressive retrovirus.

Acute Disease↗

PubMed1995

Lack of primary association between transporter associated with antigen processing genes and atopic dermatitis.

We examined polymorphisms of transporter associated with antigen processing (TAP) genes in 37 Japanese patients with atopic dermatitis and 52 control subjects. We have evaluated, again, the specificity polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method since our previous report and have also developed a mismatch PCR-RFLP method for discriminating two dimorphic sites of TAP1 gene and four dimorphic sites of TAP2 gene. Amplified products from genomic DNA were digested with restriction endonucleases: Sau3A1 for TAP1 codon 333 (Ile-Val), AccI for TAP1 codon 637 (Asp-Gly), and BfaI for TAP2 codon 687 (Stop-Gln). The other sites of TAP2 gene were analyzed by mismatch PCR-RFLP: AccII for TAP2 codon 379 (Val-Ile), RsaI for codon 565 (Ala-Thr), and MspI for codon 665 (Thr-Ala). We observed three TAP1 alleles and six TAP2 alleles. Infrequent allele TAP1 C was observed in one patient and one control subject. We did not identify any differences in TAP allele frequencies between those patients with atopic dermatitis and Japanese control subjects. Analysis of TAP gene polymorphisms will provide better understanding of susceptibility loci in HLA class II-associated disease because TAP genes are located between HLA-DQB1 and HLA-DPB1 loci.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Analysis of disease-associated amino acid epitopes on HLA class II molecules in atopic dermatitis.

We investigated the association between HLA class II alleles and severe atopic dermatitis with high serum IgE levels (greater than 8000 U/ml). The frequencies of HLA-DRB1*1302 and DQB1*0604 were increased, whereas the frequency of HLA-DQB1*0302 was decreased. A strong haplotype, HLA-DRB1*1302-DQB1*0604, has been reported in the Japanese population, and this haplotype is conserved in patients with AD. Further analysis of the amino acid epitopes on the HLA-DR beta 1 and DQ beta 1 domains revealed that DR beta 1 71Glu (RR = 5.71, p < 0.05) and DQ beta 1 30His (RR = 3.25 p < 0.01), and 57Val (RR = 3.13, p < 0.05) were increased in frequency. DR beta 1 71Glu was exclusively unique to DRB1*1302. DQ beta 1 30His was shared by the following alleles: DQ beta 1*0501, *0502, *0503, and *0604, which were all increased in patients with AD. DQ beta 1 57Val was shared by DQB1*0501 and *0604. A well-known haplotype, HLA-DRB1*1302-DQB1*0604, contains DR beta 1 71Glu and DQ beta 1 30His and 57Val. Therefore HLA-DR beta 1 71Glu and/or DQ beta 1 30His/57Val are considered to play the most important role in the development of atopic dermatitis.

Adolescent↗

PubMed1995

Superinfection of a defective human immunodeficiency virus type 1 provirus-carrying T cell clone with vif or vpu mutants gives cytopathic virus particles by homologous recombination.

The partially CD4-expressing T cell clone, Vpr-1, which carries a latent vpr-defective HIV-1 genome and expresses HIV-1 Nef protein only, was permissive to superinfection by HIV-1. Superinfection of Vpr-1 with vif- or vpu-defective mutants, which were noncytopathic, reactivated the vpr-defective virus and led to homologous recombination and cytopathogenesis. The data provide an experimental model for homologous recombination being an important mechanism whereby HIV-1 acquires genetic heterogeneity, and when occurring among defective virus in vivo bestows novel biological activities and virulence.

CD4-Positive T-Lymphocytes↗

PubMed1995

Function of human immunodeficiency virus type 1 Vpu protein in various cell types.

We evaluated the function of human immunodeficiency virus type 1 vpu gene in various cell lines. We established a highly sensitive system consisting of chloramphenicol acetyltransferase and reverse transcriptase assays and used it to monitor the effects of mutation of the vpu gene. In some cell lines, Vpu protein was not required at the early phase of viral replication but was important for efficient virion production. In these cells, the Vpu protein functioned effectively irrespective of the presence of intact env gene products. Likewise, CD4 gene expression had no effects on Vpu function. In the other cell lines tested, Vpu protein was not important for virion release, and the vpu mutant clone generated a normal level of progeny virions upon transfection.

3T3 Cells↗

PubMed1995

Early replication block of human immunodeficiency virus type 1 in monkey cells.

The genetic and functional basis of the replication-defective nature of human immunodeficiency virus type 1 (HIV-1) in monkey cells was studied. By the generation and characterization of chimeras between HIV-1 and simian immunodeficiency virus, the sequence encompassing the 3' half of the long terminal repeat, gag and pol genes of HIV-1 was found to be responsible for the growth restriction. Early and late phases of HIV-1 replication in monkey cells were analysed in detail using several assay systems: transfection/coculture, transcomplementation between various proviral clones carrying the CAT gene and effector clones and evaluation of transcription and reverse transcription. All the data were consistent with the notion that HIV-1 replication is blocked at a very early stage(s) such as uncoating and/or reverse transcription in monkey cells.

Animals↗