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Biomedical subjects

A Kaji

Publications and source records attributed to A Kaji.

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

Production of env-deficient rous sarcoma virus (RSV) early after infection.

Production of defective virus particles during the early stage of Rous sarcoma virus (RSV) infection of chicken embryo fibroblasts (CEF) was examined. RSV harvested 2 days post infection (2pi) had 10 to 30 times lower specific infectivity (focus forming units/unit reverse transcriptase activity) than 5pi harvest. Virus particles produced on day 2 contained less env proteins than particles harvested on day 5. The amount of other viral proteins was equal in particles harvested on day 2 and day 5. Analysis of infected cells revealed that these cells synthesized less env proteins on day 2 than on day 5. RSV RNA in infected cells was spliced normally on day 2. Infection at a low multiplicity of infection (moi) prolonged the production of defective particles. When infection was initiated by a low moi (0.01), particles harvested on day 5 had the same characteristics as 2pi particles after infection with a high moi (1.0). We conclude that the low infectivity of early harvest is due to the reduced amount of env proteins in virus particles, which is a consequence of the reduced env protein synthesis.

Animals↗
PubMed1997

Molecular basis of the altered gag p19 protein (MA) of the transformation-defective mutant of Rous sarcoma virus, tdPH2010.

The transformation-defective mutant of Rous sarcoma virus (RSV), tdPH2010, has a gag p19 (matrix; MA) protein which migrates on SDS-polyacrylamide gels faster than that of the parental (tsNY68) as well as other wild-type strains of RSV. To study the molecular basis of this altered migration pattern and its biological significance, the nucleotide sequence of the p19 region of tdPH2010 was determined. Comparison of the nucleotide sequence of tdPH2010 with that of the Schmidt-Ruppin A strain of RSV revealed a point mutation at nucleotide 755 (G to A), resulting in an amino-acid substitution at residue 126 of p19 (Glu to Lys). Acidic-methanol esterification of free carboxyl groups suppressed the difference in electrophoretic mobility of p19 between tdPH2010 and the wild-type virus. Recombinant virus constructs having the mutated gag region of tdPH2010 produced a p19 with the same electrophoretic mobility as the p19 of tdPH2010. We concluded that the point mutation caused the altered electrophoretic behavior of p19 of tdPH2010. The mutation had no effect on the growth of infected cells.

Amino Acid Sequence↗
PubMed1996

Molecular cloning and characterization of a newly identified member of the cadherin family, PB-cadherin.

We have isolated cDNA clones encoding novel proteins belonging to the cadherin family. These novel proteins are encoded by two distinct mRNA species generated by alternative splicing from a single gene, and based on preferential expression in the pituitary gland and brain, we named it PB-cadherin. One mRNA species encodes long type PB-cadherin composed of 803 amino acid residues with a longer cytoplasmic domain, whereas the other species encodes short-type PB-cadherin composed of 694 amino acid residues with a shorter cytoplasmic domain. Both long and short type PB-cadherin contain five repeats of a cadherin motif in the extracellular domain, the transmembrane domain, and the cytoplasmic domain, and the deduced amino acid sequences have a 30% homology to those of E-, N-, and P-cadherins. Although the primary structure of N-terminal amino acids is identical between long and short type PB-cadherin, the following structures in the cytoplasmic regions are completely different. The long type PB-cadherin but not the short type contains the putative catenin-binding domain. When these two distinct forms of PB-cadherins were stably expressed in L cells, L cells expressing long type PB-cadherin or short type PB-cadherin both acquired a Ca2+-dependent cell adhesion property, thereby indicating that both types of PB-cadherin are responsible for Ca2+-dependent cell adhesion. Persistent expression of PB-cadherin mRNA was found in the brain of rat embryos at least from embryonic day 15 to the postnatal period. In situ localization of PB-cadherin mRNA in the adult rat brain indicated that PB-cadherin mRNA is expressed in the inner granular layer of the olfactory bulb, Purkinje cell layer of the cerebellum, and in the pineal gland. PB-cadherin may play an important role in morphogenesis and tissue formation in neural and non-neural cells for the development and maintenance of the brain and neuroendocrine organs by regulating cell-cell adhesion.

Aging↗
PubMed1996

Instability of Rts1 (drug-resistant factor) replicon: stabilization by DNA fragments derived from Rts1.

Rts1 is a large naturally occurring plasmid which has a kanamycin resistance gene and exhibits various temperature-sensitive phenotypes. A smaller derivative of plasmid, pOK, contains the Rts1 replicon and the kanamycin resistance gene of Rts1. This plasmid, pOK, is much more unstable than Rts1 at 42.5 degrees C. A DNA fragment, G3, 1590 nucleotides long from Rts1 DNA, stabilized pOK completely at 42.5 degrees C but only in the cis configuration. G3 did not change the copy number of pOK. The pOK derivative containing G3 was destabilized by the presence of a compatible plasmid containing G3. G3 has four inverted repeats, two 14-base direct repeats, and three ORFs. Smaller fragment of G3 also had a stabilization effect and these studies showed that the ORF does not play any role in stabilization.

Base Sequence↗
PubMed1996

Presence of a hypervariable region within the hr2 domain of the host range determining sequences of the envelope protein gp85 (SU) of subgroup-A avian sarcoma-leukosis viruses.

The nucleotide sequence of the gene for the envelope protein gp85 (SU) of the Schmidt-Ruppin subgroup A (NY) strain of Rous sarcoma virus [SRA(NY)] was determined, and the deduced amino acid sequence was compared with those of other avian sarcoma-leukosis viruses. Among the five host-range determinant sequences (vr1, vr2, hr1, hr2, and vr3), the host-range determinant sequence hr2 of SRA(NY) showed a significant deviation from the hr2 sequences of other subgroup A viruses namely, RAV-1 and SRA(SF). A phylogenetic analysis of the amino acid sequence of this region indicated that this intra-subgroup diversity was as great as or even greater than the inter-subgroup diversity found among other subgroups of ASLV. Within the hr2 region, we found a short hypervariable segment that differs in length and sequence from hr2 of other subgroup-A viruses. The difference in the hr2 amino acid sequence between SRA(NY) and SRA(SF) is reflected in the predicted protein secondary structure of this region.

Amino Acid Sequence↗
PubMed1996

A case of bronchial cast.

We report a case of bronchial cast in a boy 1 year and 5 months old. Bronchial casts often obstruct the main bronchi, causing dyspnea and hypoxia. The bronchial cast was studied pathologically, with findings of eosinophilia and neutrophilic infiltration; the cast seemed to involve an allergic reaction. Such casts can be removed during bronchoscopy, but we used aspiration.

Airway Obstruction↗
PubMed1996

Anti-vaccinia virus effect of M13 bacteriophage DNA.

Single-stranded DNA derived from M13 phage was evaluated for antiviral activity in mice infected with vaccinia virus. M13 DNA at a dose as low as 16.7 mg/kg was effective in reducing the number of tail lesions caused by vaccinia virus by more than 90%. A single administration of M13 DNA 1 day before infection was sufficient to reduce significantly the number of tail lesions caused by vaccinia virus. Denatured eukaryotic nucleic acids such as calf thymus DNA and human placenta DNA were not effective. A mixture of nucleotides prepared according to the nucleotides composition of M13 DNA was also ineffective. Within 4 h after the administration of M13 DNA, the serum interferon (IFN, predominantly type beta) titer rose from undetectable levels to as much as approximately 700 IU/ml. IFN was detectable for up to 12 h after the administration of M13 DNA. IFN titers as high as 1050 IU/ml were detected in vitro when M13 DNA was added to spleen cultures. We conclude that at least part of the antiviral activity of M13 DNA can be explained on the basis of IFN induction.

Animals↗
PubMed1996

Alterations in ICAM-1 and ELAM-1 expression in psoriatic lesions following various treatments.

The expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1) in psoriatic lesions was immunohistochemically examined before and after various single and combination therapies. The increased staining intensity of both adhesion molecules on the proliferated papillary venules in pretreated lesion was markedly reduced after cyclosporin-A monotherapy and etretinate therapy combined with oral eicosapentaenoic acid (EPA), psoralen plus ultraviolet-A radiation (PUVA) or ultraviolet-B radiation (UVB). Less pronounced alterations were observed with etretinate, EPA, PUVA, UVB, and topical corticosteroid alone. The epidermal expression of ICAM-1, on the other hand, faded out completely following any of the treatment measures. The findings suggest that cyclosporin-A monotherapy and the etretinate combination therapies have greater inhibitory effects on the endothelial expression of the adhesion molecules than the other monotherapies. Loss of the epidermal expression of ICAM-1 may be nonspecific to the treatment.

Adrenal Cortex Hormones↗
PubMed1996

Dual functions of ribosome recycling factor in protein biosynthesis: disassembling the termination complex and preventing translational errors.

We summarize in this communication the data supporting the two functions of ribosome recycling factor (RRF, originally called ribosome releasing factor). The first described role involves the disassembly of the termination complex which consists of mRNA, tRNA and the ribosome bound to the mRNA at the termination codon. This process is catalyzed by two factors, elongation factor G (EF-G) and RRF. RRF stimulated protein synthesis as much as eight-fold in the in vitro lysozyme synthesis system, when ribosomes were limiting. In the absence of RRF, ribosomes remain mRNA-bound at the termination codon and translate downstream codons. In the in vitro system, the site of reinitiation is the triplet codon 3' to the termination codon. RRF is an essential protein for bacterial life. Temperature sensitive (ts) RRF mutants were isolated and in vivo translational reinitiation due to inactivation of ts RRF was demonstrated using the beta-galactosidase reporter gene placed downstream from the termination codon. A second function of RRF involves preventing errors in translation. In polyphenylalanine synthesis programmed by polyuridylic acid, misincorporation of isoleucine, leucine or a mixture of amino acids was stimulated upto 17-fold when RRF was omitted from the in vitro system. RRF did not influence the large error (10-fold increase) induced by streptomycin. This means that RRF participates not only in the disassembly of the termination complex but also in peptide elongation. Extending this concept and its conventional role for releasing ribosomes from mRNA, involvement of RRF in the reinitiation in the 3A' system (a construct using S aureus protein A, a collaborative work with Dr Isaksson), in programmed frame shifting, in trans-translation with 10Sa RNA (collaborative work with Dr Muto), and in the reinitiation downstream from the ORF A of the IS 3 (insertion sequence of a transposon, collaborative work with Dr Sekine) are discussed on the basis of preliminary data to be published elsewhere. Finally, we review the known RRF sequences from various organisms including eukaryotes and discuss the possible mechanism for disassembly of the eukaryotic termination complex.

Bacteria↗
PubMed1995

An unusual mutation in RepA increases the copy number of a stringently controlled plasmid (Rts1 derivative) by over one hundred fold.

A copy number mutant of the Rts1 replicon (copy number 1-2 copies/cell) was obtained. A one-base substitution in the repA region results in a single amino acid change from histidine to asparagine at position 159. This mutation increased the plasmid copy number by up to 120-fold depending upon the growth conditions. At 42.5 degrees C the plasmid with the wild type replicon was unstable while the mutated replicon was relatively stable.

Bacterial Proteins↗
PubMed1995

Antiviral action of oligodeoxyguanylic acids against human immunodeficiency virus type 1.

Deoxyguanylic acids, but not other deoxynucleotides, as short as 3- to 4-mer, were effective in preventing HIV-1-induced cytopathicity. In addition, they prevented giant cell formation of infected Sup-T1 cells, and p24 production in HIV-1 infected H9 cells. Phosphorylation at either the 5'- or 3'-end enhanced these activities. Furthermore, 5'-phosphorylated phosphorothioate tetradeoxyguanylic acid was effective in reducing HIV production in chronically infected cells (H9/IIIB). The search for the target steps of this compound revealed that it inhibits at least 3 steps in the life cycle of HIV: interaction with CD4 (measured by inhibitory effect on the syncytia formation between Sup-T1 and H9/IIIB cells), reverse transcriptase, and step(s) after integration. These results suggest that phosphorylated phosphorothioate tetradeoxyguanylic acid may be a novel candidate for a therapeutic agent of AIDS.

Antiviral Agents↗
PubMed1995

Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase.

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.

Antiviral Agents↗
PubMed1995

Production of defective virus by terminally differentiated myotubes infected with Rous sarcoma virus.

The generally accepted concept that the replication of Rous sarcoma virus (RSV) is dependent on host cell DNA synthesis was reexamined. As the host we used terminally differentiated myotubes (MT), in which no cellular DNA synthesis is observed. As an extension of our previous study which indicated that RSV-infected MT produce various virus components, we examined viral particles produced by infected MT. Electron microscopy showed presence of viral particles released from infected MT. Immunoprecipitation analysis revealed that these particles contained an equal amount of the gag but a decreased amount of the env proteins as compared with the particles from infected chicken embryo fibroblasts (CEF). Consequently, viral particles from infected MT had an infectivity only 6% of that of particles from infected CEF cells. In a parallel experiment, we microinjected molecularly cloned RSV DNA into MT. In contrast to the infection mediated by viral particles, both MT and CEF cells produced the same amount of infectious particles when microinjected with viral DNA. We conclude that RSV replicates in the complete absence of host DNA synthesis, though infectivity of the progeny virus depends on the initial condition of the infection.

Animals↗
PubMed1994

Short, terminally phosphorylated oligoriboguanylic acids effectively inhibit cytopathicity caused by human immunodeficiency virus.

Various synthetic ribonucleic acids were evaluated for inhibition of HIV-induced cytopathicity of cultured cells; only poly and oligoguanylic acids, but not other homopolymers, showed potent inhibitory activity. Phosphorylation of either the 5'- or 3'-end of oligoribonucleotides converted short inactive oligomers, such as dimers to effective anti-HIV agents. The efficacy of the 3'-phosphorylated phosphorothioate trimer of guanylic acid was comparable to that of other longer oligonucleotides so far reported. Phosphorothioate oligoriboguanylic acids were superior to the corresponding oligodeoxyguanylic acids in their capacity to prevent HIV cytopathicity.

Antiviral Agents↗
PubMed1994

Molecular cloning and expression of a novel hydroxymethylcytosine-specific restriction enzyme (PvuRts1I) modulated by glucosylation of DNA.

The kanamycin resistance plasmid Rts1 restricts the growth of bacteriophage T2, T4 and T6. The DNA of these phage contains hydroxymethylcytosine (HMC) in place of regular cytosine and is modified by glucosylation. When HMC is not glucosylated, as in the DNA of glucosyl transferase-deficient T4 phage, this restriction becomes less apparent, a phenomenon not observed with any other known restriction systems. On the other hand, glucosylation of HMC in T6 phage leads to a less efficient restriction, while restriction of bacteriophage T2 remains unchanged. The modulating effect of glucose cannot be seen when cells contain a large amount of this enzyme, as in the case when multiple copies of its determinant are present in the cells. T-odd phage and bacteriophage lambda are not restricted by Rts1 suggesting that the restriction is specific to DNA containing HMC. The restriction phenotype is due to a single gene coding for a polypeptide of 293 amino acids. This enzyme has been named PvuRts1I. A gene with the sequence motifs similar to modification enzymes was found upstream of the gene coding for PvuRts1I. This gene, however, neither modifies the restriction phenotype of PvuRts1I, nor codes for detectable modification enzyme. T4 mutants with increased resistance to PvuRts1I appear to have deficiency in their beta-glucosyl transferase enzyme.

5-Methylcytosine↗
PubMed1994

Ribosome recycling factor (ribosome releasing factor) is essential for bacterial growth.

Ribosome releasing factor, product of the frr gene in Escherichia coli, is responsible for dissociation of ribosomes from mRNA after the termination of translation. It functions to "recycle" ribosomes and is renamed ribosome recycling factor in this paper. An E. coli strain was constructed (MC1061-2), which carried frame-shifted frr in the chromosome and wild-type frr on a temperature-sensitive plasmid. MC1061-2 is temperature-sensitive in its growth and does not segregate its frr-carrying plasmid under the plasmid incompatibility pressure. In contrast, isogenic E. coli carrying wild-type frr in the chromosome and mutated frr on the temperature-sensitive plasmid is not temperature-sensitive in its growth and segregates its plasmid from incompatible plasmids. All spontaneously formed thermoresistant colonies derived from MC1061-2 carried wild-type frr that resided either in the bacterial chromosome by re-exchange or in the plasmid, which became temperature-resistant. These observations establish that frr is an essential gene for cell growth.

Bacterial Proteins↗
PubMed1994

Four new metabolites of Aspergillus terreus.

Four new metabolites (1-4) were isolated from mycelium of Aspergillus terreus IFO 6123 producing asterriquinone (ARQ). The structures of 1 and 2 were shown to be 3,6-bis[1-(1,1-dimethyl-2-propenyl)-1H-indol-3-yl]-furo[3,2-b]furan- 2,5-dione (asterridinone) and 2,5-bis[1-(1,1-dimethyl-2-propenyl)-1H-indol-3- yl]-3-acetoxy-6-hydroxy-2,5-cyclohexadiene-1,4-dione (ARQ monoacetate), respectively, by the chemical and spectral data. Compounds 3 and 4 were identified with known asterriquinone isomers, 2-[1-(1,1-dimethyl-2-propenyl)-1H-indol-3-yl]-5-[2-(3-methyl-2-butenyl)- 1H-indol-3-yl]-3,6-dihydroxy-2,5-cyclohexadiene-1,4-dione (isoARQ) and 2,5-bis[2-(3-methyl-2-butenyl)-1H-indol-3-yl]-3,6-dihydroxy- 2,5-cyclohexadiene-1,4-dione (neoARQ), respectively.

Animals↗