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Biomedical subjects

H Kamiya

Publications and source records attributed to H Kamiya.

At least 235 records · Page 13Linked to original sources
PubMed1995

2-Hydroxyadenine (isoguanine) as oxidative DNA damage: its formation and mutation inducibility.

In our experiments we found that hydroxylation occurs at the C-2 position of adenine by oxygen radical treatment (Fe(2+)-EDTA) of dA, dATP, and single- and double-stranded DNA. This oxidatively damaged base, 2-hydroxyadenine (also known as isoguanine), was produced more efficiently in monomers than in polynucleotides. 2-Hydroxydeoxyadenosine triphosphate was incorporated opposite T and C in a DNA template by DNA polymerase alpha and only opposite T by the Klenow fragment. The Klenow fragment, DNA polymerases alpha and beta incorporated dTMP and other nucleotides opposite 2-OH-Ade in DNA templates in vitro in a sequence-dependent manner. These results suggest that the formation of 2-OH-Ade in DNA will induce mutations in cells.

Base Sequence↗
PubMed1994

Evidence for the existence of vasopressin V2 receptor mRNA in rat hippocampus.

Arginine-vasopressin (AVP) in the septum and hippocampus are thought to be involved in memory and learning, and their receptors have been classified into three subtypes, V1a, V1b and V2. In this study, we tested for AVP V1a- and V2-receptor mRNAs in the hippocampus of adult rats by a reverse transcription-polymerase chain reaction (RT-PCR) method. PCR product of the V2 receptor mRNA was detected in the hippocampus, but that of V1a receptor mRNA was not. This is the first demonstration of the existence of the V2 receptor mRNA in the hippocampus.

Animals↗
PubMed1994

Cloning and analysis of the gene encoding lectin from the acorn barnacle Megabalanus rosa.

In the acorn barnacle Megabalanus rosa, two types of galactose-binding C-type lectins (BRA-2 and BRA-3) have been identified. Here, we report the isolation and characterization of BRA-2 cDNA and genomic clones. In contrast to the BRA-3 gene, which consists of four exons, BRA-2 is encoded by a single exon, implying differences in the physiological roles of the two lectins.

Amino Acid Sequence↗
PubMed1994

Residual Ca2+ and short-term synaptic plasticity.

At many synapses, the amount of transmitter released by action potentials increases progressively during a train of spikes. This enhancement of evoked transmitter release grows during tetanic stimulation with several time constants, each bearing a different name (facilitation: tens to hundreds of milliseconds; augmentation: several seconds; potentiation: several minutes), and the enhancement of release to test spikes after a tetanus decays with similar time constants. All these processes depend on presynaptic Ca2+ influx during the conditioning tetanus. It has often been proposed that these forms of synaptic plasticity are due to residual Ca2+ present in nerve terminals following conditioning activity. We tested this idea directly by using photolabile Ca2+ chelators to reduce residual Ca2+ following conditioning stimulation or to generate an artificial elevation in Ca2+ concentration, and observed the effects on synaptic transmission at crayfish neuromuscular junctions. We found that facilitation, augmentation and potentiation are caused by the continuing action of residual Ca2+. Augmentation and potentiation seem to arise from Ca2+ acting at a separate site from facilitation, and these sites are different from the molecular target triggering neurosecretion.

Action Potentials↗
PubMed1994

Vasopressin V1 receptor in rat hippocampus is regulated by adrenocortical functions.

Two subtypes of arginine vasopressin (AVP) receptors (V1 and V2) have been distinguished. In this study, we examined the characteristics of AVP binding in rat hippocampus and the effects of bilateral adrenalectomy and adrenal steroids on its [3H]AVP binding. [3H]AVP binding to rat liver and the hippocampal membranes was strongly inhibited by the V1 antagonist, OPC-21268. ADX resulted in a significant decrease in the Bmax of AVP binding in the hippocampus. Chronic treatment with aldosterone and corticosterone restored the ADX-induced reduction, but treatment with dexamethasone did not. These results suggest that the AVP V1 receptor in the hippocampus is regulated by adrenocortical neuroregulatory functions.

Adrenal Cortex↗
PubMed1994

Infection course of the strobilar stage of Taenia crassiceps in golden hamsters, with reference to host responses.

The time course of intestinal infection of golden hamsters (Mesocricetus auratus) with Taenia crassiceps was monitored every 2 days up to day 26 postinfection (p.i.). The isolate used was originally obtained from Clethrionomys rutilus on St. Lawrence Island, Bering Sea (USA), and shows a high level of enteral establishment without parenteral infection. Following oral administration of various numbers (3, 15, 30, or 60) of metacestodes, proportional numbers of cestodes attached their scolices to the mucosa of the middle (one-third) segment of the small intestine. Except for animals given 3 metacestodes, dislocation of cestodes to the posterior parts of the intestine was noted on days 10-14 p.i. and began faster in animals that had received larger numbers of metacestodes. Concurrent with dislocation or elimination of cestodes, there existed distinct increases in intestinal eosinophil peroxidase and myeloperoxidase activities. The number of mast cells in the lamina propria peaked on day 16 p.i., and specific serum IgG began to increase within 1 week p.i. The level of all these changes was dose-dependent. In prednisolone-treated animals that received 60 metacestodes, dislocation of cestodes was not evident, and mucosal inflammatory changes were suppressed to a considerable extent. The findings of this study are discussed as a model for the study of canine taeniasis.

Animals↗
PubMed1994

Trichinella spiralis: recovery of newborn larvae from cardiac tissues.

Newborn larvae (NL) of Trichinella spiralis in cardiac tissues were recovered by incubating cardiac tissue blocks of mice and gerbils infected with T. spiralis in RPMI- 1640 medium supplemented with antibiotics and 5% FCS for 24 h in a humidified atmosphere of 5% CO2 in air at 37 degrees C. This technique is effective for the recovery of migrating NL in visceral tissues which are en route to skeletal muscles, and may help to clarify the involvement of NL in the pathogenesis of cardiac or cerebral lesions in trichinellosis.

Animals↗
PubMed1994

Impaired cell-mediated immunity to cytomegalovirus (CMV) in leukemic children with prolonged CMV viruria.

To determine the role of cell-mediated immunity (CMI) to cytomegalovirus (CMV) in leukemic children after CMV infection, CMI to CMV antigen was studied using CMV-specific lymphocyte blastogenic responses (LBR) and interferon (IFN) production. Four children, who continuously secreted CMV in urine more than 2 years after symptomatic CMV infection (CMV disease) (group 1), showed impaired LBR to CMV antigen, though they had normal LBR to phytohemagglutinin (PHA) and concanavalin A (Con A). Impairment of LBR either to AD-169 strains or autologous and heterologous wild strains was observed. IFN production was not detected in three of four children. Six leukemic children, who had no viruria after cessation of CMV disease (group 2), showed good responses to CMV antigens. IFN was detected in all six children in group 2. Eight leukemic children, who were seropositive to CMV at the onset of leukemia (group 3), showed good responses to CMV antigens and IFN production. These results suggest that impaired cell-mediated immunity to CMV antigen might contribute to prolonged excretion of CMV in urine in leukemic children.

Adolescent↗
PubMed1994

Generation of hydrogen peroxide by varicella-zoster virus-stimulated polymorphonuclear leukocytes.

BACKGROUND: In varicella-zoster virus (VZV) infections, the initial response in cutaneous lesions is predominantly polymorphonuclear leukocytes (PMN). However, interaction of VZV and PMN has not yet been fully defined. OBJECTIVES: To explore the potential role of PMN in VZV infections, we investigated the ability of PMN to generate hydrogen peroxide (H(2)O(2)) after stimulation with VZV antigen. STUDY DESIGN: H(2)O(2), one of the reactive oxygen species, was measured by cytofluorography after PMN were incubated with varicella-zoster virus (VZV) antigen in the presence of seropositive or seronegative serum. RESULTS: H(2)O(2) was detectable in unseparated PMN obtained from seropositive children and adults, while unseparated PMN of seronegative donors were not capable of generating H(2)O(2). Separated PMN obtained from either seropositive or seronegative donors were capable of generating H(2)O(2) in the presence of seropositive serum. However, H(2)O(2) was not detectable in separated PMN of seropositive donors in the presence of seronegative serum. The of H(2)O(2) generation did not correlate with concentrations of serum antibodies to VZV. CONCLUSIONS: VZV antigen-antibody complexes might induce H(2)O(2) generation by PMN.

Journal Article↗
PubMed1994

A randomized controlled trial of two acellular pertussis-diphtheria-tetanus vaccines in primary immunization in Ghana: antibody responses and adverse reactions.

Two acellular pertussis vaccines combined with diphtheria and tetanus toxoids (APDT vaccines) were compared with a whole cell PDT (WCPDT) vaccine in primary immunization in Ghana. One is a liquid vaccine which is used for general immunization in Japan and the other is a freeze-dried vaccine newly developed as a heat-stable vaccine. Eighty-nine infants were recruited in the study. Sixty-eight who completed three doses of the immunization were assessed for immunological responses. Twenty-one dropped out because of sickness or moving from the study area. A total of 242 vaccinations in 89 infants were followed up for adverse reactions. Geometric mean titres (GMTs) to filamentous haemagglutinin in the two APDT vaccinees were significantly higher than in the WCPDT recipients. GMTs to pertussis toxin, diphtheria and tetanus toxoids were not significantly different among the three groups. Seropositive rates to pertussis antigens, tetanus and diphtheria toxoids were 94.4 to 100% in the two APDT vaccines. Systemic reactions within 7 days of inoculation were similarly low in the three groups, but significantly fewer infants had local reactions after either of the two APDT vaccines than after the WCPDT vaccine.

Antibodies, Bacterial↗
PubMed1994

Cytotoxicity against varicella zoster virus infected targets in children with acute leukemia.

To eliminate the role of natural killer (NK), antibody-dependent cell-mediated cytotoxicity (ADCC), and polymorphonuclear leukocyte (PMN)-mediated cytotoxicity in Varicella zoster virus (VZV) infections, peripheral blood mononuclear cell (PBMC)-mediated NK and ADCC, and phorbol myristate acetate-stimulated PMN-mediated cytotoxicity against VZV-infected targets were studied in children with leukemia. Natural killer and PMN-mediated cytotoxic activity was depressed for 6 months after complete remission and ADCC activity was depressed for 1 year after complete remission. The magnitude of three cytotoxic mechanisms in leukemic children gradually increased while they continued in complete remission. These results suggested that decreased cytotoxic activities of PBMC and PMN might contribute to serious VZV infections and susceptibility to herpes zoster in leukemic children.

Adolescent↗
PubMed1994

A flow cytometric method for measurement of hydrogen peroxide generation by pediatric polymorphonuclear leukocytes stimulated by Staphylococcus aureus and Escherichia coli.

The generation of hydrogen peroxide (H2O2), one of the reactive oxygen species, by polymorphonuclear leukocytes (PMN) stimulated by Staphylococcus aureus and Escherichia coli was studied in infants by cytofluorography. After heparinized whole blood was incubated with bacteria for 60 min, generated H2O2 was measured. The positive rate of H2O2 generation of PMN and mean fluorescent intensity of positive PMN stimulated by S. aureus and E. coli were significantly reduced in infants aged < 1 year and H2O2 generation increased with advancing age. In 10-15 year old children, the level of generated H2O2 reached adult levels. When sera from 1 year old children were added to separated PMN from healthy adults, H2O2 generation was reduced. In contrast, H2O2 generation by PMN from 1 year old children was increased by the addition of adult sera. These results suggest that the ability to generate H2O2 in response to S. aureus and E. coli is lower in infants and that such reduced activity may be related to the susceptibility of such infants to S. aureus and E. coli infections.

Adolescent↗
PubMed1994

Effect of varicella zoster virus antigen-antibody complexes on hydrogen peroxide generation by human polymorphonuclear leukocytes.

Hydrogen peroxide (H2O2) generation by human polymorphonuclear leukocytes (PMN) incubated with varicella zoster virus (VZV) antigen was studied by cytofluorography. Hydrogen peroxide generation was detected in the presence of VZV-seropositive sera. When seropositive sera were heat-inactivated, H2O2 generation was reduced. When PMN were pre-incubated with Leu-11b, a monoclonal antibody to the Fc receptor on PMN, H2O2 generation was also reduced. These results suggest that VZV antigen-antibody-complement complexes induce H2O2 generation by PMN after these complexes attach to Fc receptors on PMN.

Antibodies, Viral↗
PubMed1994

[Clinical evaluation of aciclovir granules in the treatment of chickenpox in otherwise healthy children].

The efficacy and safety of aciclovir granules (containing 40% w/w aciclovir) were evaluated in the treatment of chickenpox in otherwise healthy children. Patients presenting with chickenpox received aciclovir granules at a dose of 20 mg/kg four times daily for five to seven days. Overall 51 children received treatment with aciclovir. A further 53 patients receiving conventional symptomatic therapy acted as a control. In the aciclovir group the overall efficacy rate was 92.2%. There were reductions in the numbers of lesions, fever, itching and the duration of symptoms. No adverse experiences were reported. Overall this formulation of aciclovir appears to be a safe and effective treatment for chickenpox in this patient population. However the need for anti-viral therapy in otherwise healthy children is still the subject of debate and it might be appropriate to identify sub-groups for whom such therapy is justified.

Acyclovir↗
PubMed1994

Interferon-gamma induces interleukin-3 release from peripheral blood eosinophils.

Interferon-gamma (IFN-gamma) upregulates eosinophil effector functions and prolongs the in vitro survival of eosinophils. We examined the possible capacity of IFN-gamma to stimulate eosinophils to produce eosinophil-activating cytokines. Eosinophils purified from mild atopic volunteers were cultured with 100 U/ml IFN-gamma. Viability of eosinophils was counted and supernatants were tested for the presence of cytokines by neutralization of eosinophil viability-enhancing activity with specific antibodies to IFN-gamma, interleukin-5 (IL-5), IL-3, or granulocyte-macrophage colony-stimulating factor (GM-CSF). IFN-gamma-enhanced eosinophil viability was up to 95% on the 4th day of culture. Pretreatment with anti-IL-3 antibody partially blocked the IFN-gamma-enhanced eosinophil survival. IFN-gamma-stimulated eosinophil supernatants had eosinophil survival. IFN-gamma-stimulated eosinophil supernatants had eosinophil viability-enhancing activity that was blocked by pretreatment not only with anti-IFN-gamma but also with anti-IL-3. Antibodies to IL-5 or GM-CSF did not have the blocking effect. To further confirm the production of IL-3 by eosinophils, we performed reverse transcription polymerase chain reaction (RT-PCR) for IL-3 messenger RNA (mRNA) in IFN-gamma-stimulated eosinophils. Significant IL-3 mRNA expression in eosinophils was observed at 6 h of incubation with IFN-gamma. These results suggest that IFN-gamma stimulates the autocrine function of eosinophils and may play an important role in allergic inflammation.

Cell Survival↗
PubMed1994

Guinea pig asthma induced by red soft coral (Dendronephthya nipponica) inhalation.

Spiny lobster fishermen on the Pacific coast of Miyazaki Prefecture in Japan develop bronchial asthma due to occupational sensitization to red soft coral (Dendronephthya nipponica). To assess the role of sensitization in the development of bronchial hyperresponsiveness and the relationship between bronchial responsiveness and bronchial inflammation, we established a guinea pig model of red soft coral induced asthma. Twenty-four guinea pigs were intramuscularly immunized with a priming dose of red soft coral, 5 OD280 (15 mg protein) per 0.5 ml, and 0.5 ml complete Freund's adjuvant on day 1. Booster doses were repeated on day 15. By day 43 all sensitized animals showed high hemagglutination titers against red soft coral conjugated sheep erythrocytes and high IgG1 titers by passive cutaneous anaphylaxis. On day 43, the animals were challenged by inhalation of red soft coral extracts, 20 OD280 for 30 min. The respiratory resistance was monitored by the oscillation method. The respiratory resistance increased immediately upon inhalation in all sensitized animals and returned to baseline within 4 h. The bronchial reactivity to acetylcholine, measured 6 h after red soft coral inhalation in the sensitized animals when the respiratory resistance was returned to baseline, increased significantly (p < 0.05) as compared with the values measured 24 h before inhalation. The acetylcholine response measured 30 h later did not differ from preinhalation levels. There was a significant difference in the number of eosinophils (p < 0.001) in lamina propria and epithelium and of lymphocytes (p < 0.05) in the lamina propria 6 h after inhalation in the sensitized animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1994

The mechanism of muscarinic agonist-stimulated inositol phosphate formation in permeabilized ileal smooth muscle.

Muscarinic agonists and guanylyl-5'-imidodiphosphate (Gpp(NH)p) stimulated formation of inositol phosphates in permeabilized longitudinal smooth muscle of guinea pig ileum. Gpp(NH)p markedly potentiated the formation of inositol bisphosphate (IP2) and inositol trisphosphate (IP3) stimulated by carbachol, but increased inositol monophosphate formation (IP1) only slightly. Gpp(NH)p enhanced the formation of IP2 + IP3 induced by either acetylcholine or carbachol about fourfold in a synergistic manner, but enhanced the effects of oxotremorine and pilocarpine less than twofold in an additive manner. Elevation of Ca2+ concentration resulted in increases of the inositol phosphate levels stimulated by both carbachol and Gpp(NH)p. The optimal concentration of Ca2+ for carbachol-stimulated formations of IP2 + IP3 was shifted to a lower Ca2+ concentration in the presence of Gpp(NH)p. These findings suggest that muscarinic receptor-stimulated polyphosphoinositide hydrolysis in ileal smooth muscle results in inositol polyphosphate formation via GTP binding protein (G-protein). The muscarinic receptor-activated G-protein decreases the Ca2+ requirement of polyphosphoinositide hydrolysis. Muscarinic agonists stimulate inositol polyphosphate formation by interaction of the G-protein activation of a phosphoinositide specific phospholipase C with Ca2+ influx.

Acetylcholine↗