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Biomedical subjects

M Nakai

Publications and source records attributed to M Nakai.

At least 217 records · Page 12Linked to original sources
PubMed1993

Cloning of the YAP19 gene encoding a putative yeast homolog of AP19, the mammalian small chain of the clathrin-assembly proteins.

Mouse brain AP19 is the smallest polypeptide chain component of AP-1, the clathrin-assembly protein complex located at the Golgi complex. We isolated a gene, termed YAP19, potentially encoding a homolog of AP19 from the genomic DNA of the yeast Saccharomyces cerevisiae. The deduced amino acid sequence, 156 amino acids long, shows 53% identity with the mouse brain AP19 protein, but 37% with Yap17p, a yeast homolog of the mammalian AP17 in AP-2, another clathrin-assembly protein complex located at the plasma membrane. The identification of YAP19 supports the proposal that yeast cells also contain the Golgi-associated clathrin-assembly protein complex.

Adaptor Protein Complex 1↗
PubMed1993

Inner architecture of human and simian immunodeficiency viruses.

The cores of human and simian immunodeficiency viruses (HIV and SIV) were observed by negative staining after isolation of the core with Nonidet P40 and glutaraldehyde. Four kinds of cores were found: asymmetric and symmetric sectoral shapes, a bar shape, and a triangular shape. These results were confirmed by the examination of ultrathin sections of whole virions. In some virions, the connection between the core and the envelope was observed after freeze fracturing. Its structure was considered to be characteristic of an intermediate stage of viral maturation. The HIV-1 core was reacted with anti-HIV-1 p24 mouse monoclonal antibody.

Animals↗
PubMed1993

Sec-Y protein is localized in both the cytoplasmic and thylakoid membranes in the cyanobacterium Synechococcus PCC7942.

Members of the SecY protein family mediate protein export in bacterial cells. Southern analyses showed that secY is likely a single copy gene in the cyanobacterium Synechococcus PCC7942. Then the subcellular location of the cyanobacterial SecY protein was determined; i) antiserum raised against a fusion protein between the SecY fragment and maltose binding protein were used for immunoblotting of the membrane fractions, and ii) a modified SecY protein carrying the c-Myc peptide tag was expressed in the cyanobacterial cells, and the subcellular distribution of the SecY-c-Myc fusion protein was analyzed with the anti-c-Myc antibodies. The obtained results suggest that the SecY protein is localized in the thylakoid membrane as well as the cytoplasmic membrane; the SecY protein probably mediates protein translocation across both the cytoplasmic and thylakoid membranes in Synechococcus PCC7942.

Amino Acid Sequence↗
PubMed1993

Neutralizing antibodies to human interleukin 6 reverse hypercalcemia associated with a human squamous carcinoma.

Bone resorbing cytokines may be associated with abnormalities in bone cell function and calcium homeostasis in a number of pathological conditions. One of these cytokines is interleukin 6 (IL-6), which is a multifunctional cytokine which has been shown to be associated with increased formation of bone resorbing osteoclasts in vitro. In this report, we demonstrate that neutralizing antibodies to human IL-6 lower the blood calcium in nude mice carrying a human tumor associated with increased IL-6 production. There was no effect on blood calcium in hypercalcemic nude mice carrying tumors not associated with increased IL-6 production and normocalcemic tumor-bearing nude mice. These results suggest that increased production of IL-6 may contribute to disturbances in calcium homeostasis in some malignancies, and suggest that neutralization of IL-6 effects can lower the serum calcium in these tumors.

Animals↗
PubMed1993

Epithelial reorganization and irregular growth following carbendazim-induced injury of the efferent ductules of the rat testis.

Occlusions of the rat efferent ductules were induced by an oral gavage of carbendazim and the capacity for regeneration or recanalization of the ductules was histologically evaluated between 2 and 70 days post-treatment. At 2 days post-treatment, the efferent ductules were occluded by sloughed materials and showed various degrees of inflammation. Severely damaged epithelium showed few regenerative features at later intervals. On the other hand, epithelia with medium inflammation often exhibited irregular epithelial growth along the luminal contents or the formation of multiple abnormal ductules. These abnormal ductules were formed by migrated and original epithelia at the periphery of the occluded lumen at 16 days post-treatment, indicating attempted recanalization. At later time periods, 32 and 70 days post-treatment, the occluded original lumen was filled in by fibrotic connective tissue and surrounded by a series of abnormal ductules. These abnormal ductules were characterized by cuboidal epithelia, a small luminal diameter, fewer cilitated cells than normal, less developed organelles in the epithelial cells, and basal laminae of irregular thickness. However, there was no evidence that occluded ductules formed patent re-connections via abnormal ductules. The results suggest that occluded efferent ductules have the ability to initiate epithelial regrowth and to form new ductules, but the newly formed ductules are abnormal and are not adequate to recover from azoospermia at least at 70 days post-treatment.

Animals↗
PubMed1993

Promotion of cell adhesion on fibronectin during adenovirus infection of KB cells.

Cytopathic effects of adenovirus-infected human cells consist of rounding and detachment from the substrate at late times postinfection. It is not known, however, whether any changes in cell adhesion are induced by adenoviruses before cytopathic effects become evident. We show here that attachment and spreading of human adenovirus type 2 (Ad2)-infected KB cells on fibronectin (FN) are, unexpectedly, promoted at intermediate times postinfection. The promotion of spreading by Ad2 is not only on fibronectin but also on laminin and vitronectin. In contrast, Ad2 or Ad5 mutants defective in the E1b 19-kDa function did not lead to a promotion in cell attachment but they led to a promotion in cell spreading. Inhibition of spreading of Ad2-infected KB cells on FN by the peptide Gly-Arg-Gly-Asp-Ser-Pro is partial, although it is complete in uninfected KB cells. We found, however, that Ad2 infection does not significantly change the levels of expression of beta 1 integrin mRNA and FN receptor polypeptides. Our results thus suggest that adenovirus infection leads to a promotion in adhesion through influencing integrin molecules without altering the quantity and/or through activation in the cytoskeleton or some other pathway.

Adenoviridae Infections↗
PubMed1993

Cytotoxic activity of rev protein of human immunodeficiency virus type 1 by nucleolar dysfunction.

The rev protein (Rev) of the human immunodeficiency virus type 1 (HIV-1) is known as a post-transcriptional regulator of viral gene expression. It is located in the cell nucleolus. Transiently expressed Rev caused nucleolar ballooning and deformity with aberrant accumulation of rRNAs, and de novo synthesis of rRNAs decreased dramatically in these cells. However, similarly expressed rex protein (Rex) of the human T-cell leukemia virus type I, which is a functional homologue to Rev, did not affect nucleolar structure and function. Rev expression resulted in cell death with nucleolar destruction in an inducible cell line. Analysis of Rev mutants revealed that both the nucleolar targeting signal of Rev and the multimerization domain are prerequisites to the nucleolar disintegration by Rev. Human T-cells acutely infected with HIV-1 contained nucleoli which were deformed and filled with Rev, but chronically infected cells had intact nucleoli. Involvement of Rev in cytopathic effects in HIV-1 infection is discussed.

Base Sequence↗
PubMed1993

Isolation and characterization of simian immunodeficiency virus from African white-crowned mangabey monkeys (Cercocebus torquatus lunulatus).

Forty-eight of 236 sera from seven species of African non-human primates in Kenya, including those of white-crowned mangabey monkeys (Cercocebus torquatus lunulatus) had antibodies to simian immunodeficiency viruses (SIVs). Isolates of simian lentivirus were obtained from seropositive white-crowned mangabey monkeys which are indigenous in West Africa. This virus, designated as SIVWCM, appeared morphologically similar to HIV by electron microscopy, showed Mg(2+)-dependent reverse transcriptase activity, and induced cytopathic effects in human CD4-positive cells. Western blotting analysis revealed that env products of SIVWCM cross-reacted with those of SIVAGM more strongly than with those of HIV-1 and SIVMAC, and clear hybridization bands were detected with an SIVAGM probe. For comparison of the virus sequence with those of other primate lentiviruses, part of the pol gene and the long terminal repeats (LTRs) were amplified and cloned. Sequencing showed that SIVWCM isolates were closely related to SIVAGM isolates. This study suggested that SIVAGM from the Cercopithecus genus and SIVWCM from the Cercocebus genus may be members of an SIV group that is genetically distinct from the SIV from a sooty mangabey monkey (SIVSMM) of the genus Cercocebus, to which the white-crowned mangabey monkey also belongs.

Animals↗
PubMed1993

Acidic regions of cytochrome c1 are essential for ubiquinol-cytochrome c reductase activity in yeast cells lacking the acidic QCR6 protein.

It has been suggested that the two acidic regions around residue 70 and residue 170 in yeast cytochrome c1, a subunit of ubiquinol-cytochrome c reductase (complex III), interact with cytochrome c in the electron transfer reaction and that the QCR6 protein, the acidic subunit of yeast complex III, enhances this interaction. In order to determine the roles of the acidic regions of cytochrome c1 more precisely, we introduced several mutations in the two acidic regions and examined their effects on the ability of modified cytochrome c1 to complement the respiration deficiency of yeast cells lacking only cytochrome c1 or both cytochrome c1 and the QCR6 protein. The mutant cytochrome c1 with the deletion of the first acidic region (delta 68-80) was still functional in the cytochrome c1-deficient strain. Mutant cytochrome c1 with the deletion of the second acidic region (delta 168-179) caused a decrease in the complementing ability, but this is probably due to failure in its proteolytic maturation and/or correct assembly into complex III. Mutant cytochrome c1 with altered charge distribution in the acidic regions (Asp170Asp171-->Asn170Asn171 or Asp170Asp171-->Asn170Lys171) made the cytochrome c1-deficient cells respiration-competent. On the other hand, mutant cytochrome c1 with the deletion of the first acidic region (delta 68-80) or altered charge distribution in the second region (Asp170Asp171-->Asn170Lys171) did not restore the respiration deficiency of the cells lacking not only cytochrome c1 but also the QCR6 protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

[Non-radioisotopic reverse transcriptase assay using biotin-11-deoxyuridine-triphosphate and a primer-immobilized microtiter plate: application for detection and identification of isolated retroviruses from HIV-1-seropositive hemophiliac patients].

Non-radioisotopic reverse transcriptase assay (Non-RTA) was successfully applied for detection and identification of the retroviruses isolated from peripheral mononuclear cells from eight HIV-1-seropositive hemophiliac patients. Of 40 samples, 36 (90%) were consistent in detection between Non-RI and RI RTA. Four samples which showed RT activities slightly above the cutoff level of RI RTA were not detected by Non-RI RTA. Non-specific RT-inhibitors in the culture supernatant decreased the sensitivity of Non-RI RTA more significantly than that of RI RTA. It was demonstrated that higher concentrations (> 20%) of fetal calf serum in RPMI-1640 culture medium inhibited the hybridization of poly rA template with immobilized primer, resulting in reducing the sensitivity of Non-RI RTA. Then we identified the isolated retroviruses using specific RT-inhibiting (RTI) antibodies against HIV-1 and HIV-2. HIV-1 RTI antibody specifically inhibited RTs of isolated retroviruses and HIV-1 strain, LAV-1, but not HIV-2 and Rous-associated virus 2 (RVA-2) RT. Conversely, HIV-2 RTI antibody specifically inhibited HIV-2 RT, but not HIV-1 and RAV-2 RT. These findings agreed with previously reported results showing the type-specificity of HIV-1 and -2 RTI antibodies, and suggest the possibility that isolated retroviruses could be identified by these antibodies.

Biotin↗
PubMed1993

Saliva-binding region of Streptococcus mutans surface protein antigen.

A 190-kDa surface protein antigen (PAc) of Streptococcus mutans binds to human salivary components. For detection of specific binding of the PAc protein to human salivary components, a simple sandwich assay was used. Microtiter plates precoated with recombinant PAc (rPAc), PAc fragments, or S. mutans whole cells were allowed to react with human whole saliva and then were incubated with biotinylated rPAc. The biotinylated rPAc bound to salivary components was detected by use of alkaline phosphatase-conjugated streptavidin and p-nitrophenylphosphate. In this assay, the binding of whole cells of S. mutans and purified rPAc to salivary components was confirmed. For determination of a saliva-binding region of the PAc molecule, 14 truncated PAc fragments were constructed by use of the polymerase chain reaction and an expression vector, pAX4a+. The binding of these truncated PAc fragments to human salivary components was determined by the sandwich assay. Among the truncated PAc fragments, fragments corresponding to residues 39 to 864 and residues 39 to 1000 of PAc showed a high ability to bind to salivary components. Shorter recombinant fragments corresponding to residues 39 to 217, residues 200 to 481, residues 470 to 749, and residues 688 to 864 did not exhibit any binding ability. The fragment that corresponds to a proline-rich repeating region (residues 828 to 1000) bound directly to the PAc protein. These results suggest that residues 39 864 of the PAc molecule are important in the binding of the surface protein to human salivary components, and the proline-rich repeating region of the PAc protein may contribute to spontaneous self-aggregation of the PAc protein.

Antigens, Bacterial↗
PubMed1993

Identification of antigenic epitopes in an alanine-rich repeating region of a surface protein antigen of Streptococcus mutants.

A surface protein antigen (PAc) of Streptococcus mutans with a molecular mass of 190 kDa is considered to play an important role in the initial attachment of this streptococcus to the tooth surface. Two internal repeating amino acid sequences are present in the PAc molecule. One repeating region located in the N-terminal region is rich in alanine (A-region), and the other, located in the central region, is rich in proline (P-region). To identify antigenic epitopes on the A-region of the PAc protein, 82 sequential overlapping synthetic decapeptides covering one of the repetitive units of the A-region were synthesized. In the epitope scanning analyses using murine antisera raised against recombinant PAc (rPAc), multiple antigenic epitopes were found in the repetitive unit of the A-region, and some of them reacted with antisera to rPAc from BALB/c, B10, B10.D2, and B10.BR mice. In particular, a peptide YEAALKQY (residues 366 to 373) was recognized by anti-rPAc sera from all four strains of mice. The reactivities of anti-rPAc sera in the epitope scanning were confirmed by using a purified synthetic peptide, NAKATYEAALKQYEADLAA (corresponding to residues 361 to 379). Furthermore, antisera against a surface protein antigen PAg (SpaA) of Streptococcus sobrinus from BALB/c mice reacted strongly to residues 330 to 337, 362 to 369, and 366 to 373 of the PAc protein by the epitope scanning analysis. An AKATYEAALKQY (residues 362 to 373 of the PAc protein)-like sequence, AKANYEAKLAQY, was found within the A-region of S. sobrinus PAg, suggesting that the amino acid sequences AKA-YEA and YEA-L-QY may be major cross-reactive epitopes of the S. mutans PAc protein and the S. sobrinus PAg protein.

Amino Acid Sequence↗
PubMed1993

Parasympathetic cerebrovasodilator center of the facial nerve.

Functional studies have yet to be undertaken to establish which brain region subserves the parasympathetic regulation of the cerebral circulation. Using 31 anesthetized rats with precluded cervical sympathetic trunks, we therefore attempted to perform chemical stimulation of the greater petrosal nerve (GPN) cell group, which is a subgroup of the superior salivatory nucleus and sends off axons largely to the parasympathetic pterygopalatine ganglion via the GPN component of the facial nerve. The cerebrocortical blood flow was monitored with a laser-Doppler flowmeter. Unilateral stimulation of the GPN cell group by microinjection of L-glutamate reduced the ipsilateral cerebrocortical vascular resistance, maximally by 16.4 +/- 4.1% (mean +/- SD, n = 61). The response was not mediated by the classic muscarinic receptors of the cerebral vessel wall. However, pharmacological blockade of the peripheral parasympathetic ganglia and acute and chronic bilateral removal of the parasympathetic postganglionic fibers originating in the pterygopalatine ganglion abolished the response. The present data thus provide functional evidence that the GPN cell group may constitute a parasympathetic cerebrovasodilator center.

Animals↗
PubMed1993

The characteristics of another small DNA virus isolated from a pig with diarrhea.

A small DNA virus was newly isolated from the small intestines of a pig with diarrhea in 1987, in Japan. Concerning the physicochemical properties, hemagglutination and susceptibility of cell culture to the virus, the virus was identical to a formerly isolated small DNA virus, the H-45 strain and also physicochemically similar to the parvovirus group. In a serological test however, the virus was distinctly, antigenically different from the H-45 strain as well as each of porcine, bovine and canine parvoviruses.

Animals↗
PubMed1993

Isolation of reovirus type 3 from dogs with diarrhea.

Three virus strains were isolated in DK cell cultures inoculated with fecal specimens of dogs manifesting diarrhea. The isolates were identified as reoviruses on the basis of their biological and physico- chemical properties. They possessed reovirus type 3 antigenic specificity revealed by hemagglutination-inhibition and neutrarization tests with the reovirus prototype strains. It was suspected that the isolates were participated in this diarrheic cases.

Animals↗
PubMed1993

Five cases of cranial duplication in calf.

Five cases of cranial duplications in calves were morphologically reported. Each calf had a single body with duplicated heads that showed various degrees of fusion. The medial sides of individual heads were asymmetrically supplied by the branches of hemilateral common carotid or lingual artery. No marked differences in the development of the duplicated head in any of the calves were observed. Cleft palates were observed in all heads. The development and general structures of the organs in the head and neck regions appeared to depend on the degree of duplication of the cranial nerves.

Animals↗
PubMed1993

Cardiovascular responses to gastric hypo-osmolar stimulation in anesthetized dogs.

We compared the cardiovascular response to the gastric infusion of distilled water (DI) with that to the gastric infusion of 0.9% saline (SI) and gastric ballooning with 37 degrees C water (BA) through a gastric fistula in splenectomized mongrel dogs (n = 7). DI, and SI amounting to 5% of body wt and the same volume of water were infused in approximately 20 s through the tube and responses in mean arterial pressure (MAP), CVP, heart rate (HR), and intra-esophageal pressure (EP) were monitored continuously. After DI, SI, and BA, the measured variables showed significant increases and attained maximal increases at about 2 min after the treatments. After DI, the maximum elevation in MAP was 21.3 +/- 1.9 mmHg and 2 times higher than in SI and BA. The corresponding value in CVP was 5.0 +/- 0.3 mmHg and 2-3 times higher than with SI and BA, and HR increased by 26.1 +/- 3.0 beats/min showing 3 to 6 times larger increases compared with SI and BA. These gastro-cardiovascular reflexes were abolished after subdiaphragmatic truncal vagotomy. These findings suggest that both the mechanical and osmotic stimuli to the stomach induce cardiovascular reflexes and that the vagus is involved in the reflex.

Animals↗