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Biomedical subjects

A Hamada

Publications and source records attributed to A Hamada.

At least 37 records · Page 2Linked to original sources
PubMed2000

Roles of hydrophobicity, protein binding and the probenecid-sensitive transport system in the cerebrospinal fluid delivery of nucleoside analogues with anti-viral activity.

Ten nucleoside analogues with anti-herpes or anti-HIV activity were investigated for their transport into the cerebrospinal fluid (CSF) following intravenous administration in rats. The novel anti-herpes agent 1-beta-D-arabinofuranosyl-2-thio-5-fluorocytosine (5F-araSC) showed the highest CSF/plasma concentration ratio (>20%), while that of acyclovir (ACV) was very low (<5%). A linear relationship was observed between the partition coefficient (chloroform/water) and CSF/unbound plasma concentration in 6 of 9 agents. The exceptions were DDI, AZT and ACV, which showed much lower concentrations in the CSF than expected from their hydrophobicity and protein binding activities. The effects of probenecid treatment on the CSF and plasma concentrations were measured with continuous intravenous administration of ACV, AZT, araC and 5F-araSC. Probenecid markedly increased the CSF concentrations of ACV and AZT, although the effect was minimal in araC and 5F-araSC. These results may provide useful information for molecular design of nucleoside analogues with better transport to the brain.

Animals↗
PubMed1999

Basic study on gene therapy of human malignant glioma by use of the cationic multilamellar liposome-entrapped human interferon beta gene.

For gene therapy of human malignant glioma, we adopted positively charged multilamellar liposomes entrapping the human interferon beta (hIFN-beta) gene. One week after the transplantation of human malignant glioma U251-SP cells to produce glioma in nude mouse brain, the liposomes entrapping the gene (500 ng of DNA per 25 nmol of lipids per 2 microl) were injected into the same site of the cell transplantation once every second day for a total of five injections; and by this means the tumor completely disappeared. To confirm the antiproliferative effect of hIFN-beta, we performed an in vitro study using a plasmid containing a secretion signal sequence-deleted hIFN-beta gene and one containing the hIFN-beta gene inserted in reverse. In both cases, there was no hIFN-beta release into the medium and no growth inhibition effect. On addition of anti-hIFN-beta antibody to the medium, the growth inhibition effect was abolished. As this cell line expresses IFN-alpha/beta receptor, the hIFN-beta produced in the transfected cells could be released and acted in a paracrine manner. For 120 days the body weight change of normal mice treated by the same procedure as used in the curing experiment was not significant among the groups injected with empty liposomes, plasmid only, and liposomes entrapping the gene. In all of these three groups, death, abnormal behavior, and significant histological changes were not observed.

Animals↗
PubMed1999

Mechanisms related to reduction of radical in mouse lung using an L-band ESR spectrometer.

Reduction of radicals in mouse lung was characterized in whole animals using an L-band ESR technique and nitroxide radicals as probes. An aqueous solution of nitroxide radical was immediately instilled intratracheally to mouse after euthanasia. Nitroxide radicals without charged groups were reduced significantly in the lung, while radicals with charged groups were only slightly reduced. Permeation rates across lung plasma membrane were not rate limiting of the stage of reduction of the noncharged nitroxides. Michaelis parameters, apparent Km and apparent Vmax, were obtained from the Lineweaver-Burk plots of the reduction. Among noncharged nitroxides with constant apparent Vmax, radicals with a larger n-octanol/water partition coefficient showed a lower apparent Km, thereby suggesting that the concentration of these nitroxides in the membrane contributes to apparent Km. The reduction rate of noncharged nitroxide, hydroxy-TEMPO, was influenced by noncharged SH reagents instilled together with the nitroxide; dithiothreitol stimulated the reduction, while the oxidized reagent inhibited it. The Lineweaver-Burk plots of the nitroxide reduction in the presence of various concentrations of dithiothreitol suggest the possibility that the reduction system for hydroxy-TEMPO is based on a kind of ping pong bi-reactant mechanism, and that the reduction system utilizes SH as an electron donor. Endogenous glutathione contributed partially to the reduction.

Animals↗
PubMed1999

Study on Chlamydia trachomatis infection among students and pregnant women in Japan: a step toward developing a reliable method for sexual behavior study.

2450 sera from students and 5215 sera from pregnant women were examined for the presence of Chlamydia trachomatis (CT) antibody. CT antibody positive rates were less than 5% with the students and 24.5% with the pregnant women suggesting the latter is significantly higher than former. The results provided a base for discussing possibility of using CT infection as a reliable method for studying sexual behavior.

Antibodies, Bacterial↗
PubMed1998

[Prevalence of intestinal parasites among Japanese residents in developing countries].

We examined fecal specimens of Japanese residents in developing countries in order to know the prevalence of intestinal parasites in the group. One fecal specimen was collected from each 981 (in 1995) and 1275 (in 1996) Japanese living in Asia, the Middle East, Europe, Africa and Latin America. The specimens were fixed with 10% formalin in each area, and were examined in Japan by concentration method (formalin-ether sedimentation) to find protozoan cysts or helminth eggs. The infection rate of intestinal parasites was 3.0% in 1995 and 2.4% in 1996. The rate was high in Africa (1995: 5.7%, 1996: 4.7%) and Asia (1995: 3.8%, 1996: 3.0%). Regarding to the species of the parasites, Giardia lamblia (17 cases), Trichuris trichiura (14) and Ascaris lumbricoides (11) were detected frequently. Additionally, 7 cases of Heterophyes heterophyes infection were found in Asia and the Middle East. The infection rate was higher in adults than that in children, and a positive relationship between the infection rate and duration of stay was observed. Among the Japanese infected with intestinal parasites, abdominal symptoms such as diarrhea or abdominal pain were common (36.8%). It is also noteworthy that 28.1% of the Japanese infected had a history of gastric diseases such as gastric ulcer. Although the infection rate of intestinal parasites among Japanese residents in developing countries was low, compared to that of the natives in the countries, the rate is still higher than that in Japanese living in the home country. It is necessary to continue preventive measures such as health education in order to eradicate intestinal parasitic infections from this group.

Adolescent↗
PubMed1998

Genomic discordance between monozygotic twins discordant for schizophrenia.

OBJECTIVE: Genomic DNA of monozygotic twins discordant for schizophrenia was analyzed to determine whether their genomes were truly identical. METHOD: The subjects were monozygotic male twins, one of whom had DSM-III-R schizophrenia, undifferentiated type. Genomic DNA was extracted from leukocytes and was applied to restriction landmark genome scanning analysis, which was developed for a high-speed survey of restriction sites throughout a genome and measurement of their copy number in each locus. RESULTS: After comparisons of patterns with approximately 2,000 spots, the authors detected at least two spots with autoradiographic intensities that obviously differed in the two twins. CONCLUSIONS: The discrepancies likely were generated either by differences in the methylation status at NotI sites between the twins or by submicroscopic changes occurring at NotI-flanking sites in one twin after (or simultaneous with) twinning. In either case, the difference may influence the transcription level of one or more genes.

Adult↗
PubMed1998

Subjective evaluation of chewing ability and self-rated general health status in elderly residents of Japan.

The purpose of the present study was to statistically analyse the relationship between subjective evaluation of chewing ability and self-rated general health status in elderly Japanese residents. Interviews were conducted with 1,544 respondents over 65 years of age in Yamanashi Prefecture, Japan. The interviews included questions concerning age, sex, health status, capacity to understand conversation, chewing ability, and ADL status. First, the age-adjusted odds ratio between subjective evaluation of chewing ability and self-rated health status was 2.242 (p < or = 0.01). Second, the age-adjusted odds ratio between respondentive evaluation of chewing ability and ADL status was 2.572 (p < or = 0.01). Third, the age-adjusted odds ratio between self-assessment of chewing ability and the degree of understanding conversations was 5.290 (p < or = 0.01). These results suggest that chewing ability is related to self-rated general health, ADL status, and the degree of understanding conversation among the elderly.

Activities of Daily Living↗
PubMed1997

Complete nucleotide sequence of the chloroplast genome from the green alga Chlorella vulgaris: the existence of genes possibly involved in chloroplast division.

The complete nucleotide sequence of the chloroplast genome (150,613 bp) from the unicellular green alga Chlorella vulgaris C-27 has been determined. The genome contains no large inverted repeat and has one copy of rRNA gene cluster consisting of 16S, 23S, and 5S rRNA genes. It contains 31 tRNA genes, of which the tRNALeu(GAG) gene has not been found in land plant chloroplast DNAs analyzed so far. Sixty-nine protein genes and eight ORFs conserved with those found in land plant chloroplasts have also been found. The most striking is the existence of two adjacent genes homologous to bacterial genes involved in cell division, minD and minE, which are arranged in the same order in Escherichia coli. This finding suggests that the mechanism of chloroplast division is similar to bacterial division. Other than minD and minE homologues, genes encoding ribosomal proteins L5, L12, L19, and S9 (rpl5, rpl12, rpl19, and rps9); a chlorophyll biosynthesis Mg chelating subunit (chlI); and elongation factor EF-Tu (tufA), which have not been reported from land plant chloroplast DNAs, are present in this genome. However, many of the new chloroplast genes recently found in red and brown algae have not been found in C. vulgaris. Furthermore, this algal species possesses two long ORFs related to ycf1 and ycf2 that are exclusively found in land plants. These observations suggest that C. vulgaris is closer to land plants than to red and brown algae.

Base Sequence↗
PubMed1997

Combined chemoreduction and adjuvant treatment for intraocular retinoblastoma.

OBJECTIVE: The purpose of the study is to investigate chemoreduction and adjuvant treatment (AT) for retinoblastoma and its effect on complete retinal tumor control, vitreous seed control, and subretinal seed control. DESIGN: The study design was a prospective, nonrandomized clinical trial. PARTICIPANTS: There were 130 intraocular retinoblastomas in 52 eyes of 32 consecutive patients observed for at least 1 year after initiation of treatment. INTERVENTION: Treatment with chemoreduction using vincristine, etoposide, and carboplatin (VEC) and adjuvant treatment (+ AT) (cryotherapy, laser photocoagulation, thermotherapy, chemothermotherapy, plaque radiation therapy, or external beam radiation therapy) were assessed. MAIN OUTCOME MEASURES: The effect of chemoreduction for 6 cycles (VEC x 6) versus fewer than 6 cycles (VEC x <6) on retinoblastoma control was analyzed. Furthermore, the impact of adjuvant treatment (+ AT) versus no adjuvant treatment (no AT) on retinoblastoma control was analyzed. RESULTS: Retinal tumors showed favorable initial regression with chemoreduction. Adjuvant treatment was applied to 93% of the retinal tumors after chemoreduction and only 2% recurred over the mean follow-up of 17 months (range 13-27 months). Vitreous seeds and subretinal seeds showed initial regression and often complete disappearance with chemoreduction. In those eyes with seeds before treatment, the addition of AT to VEC for 6 cycles decreased the vitreous seed recurrence from 75% to 0% (P = 0.04) and also decreased the subretinal seed recurrence from 67% to 0% (P = 0.003). More important, when considering that enucleation or external beam radiation therapy was the only other treatment option for these 52 eyes, the authors were successful in avoiding these methods in 42% of cases. Of the 36 eyes classified as Reese-Ellsworth group 5, there was 78% ocular salvage, and external beam radiation therapy was avoided in 25% of these eyes. There was a 100% ocular salvage in the group 5 eyes that received VEC for 6 cycles + AT to retinal tumors and seeds. CONCLUSIONS: Chemoreduction and AT to intraocular retinoblastoma and its seeds provides good retinal tumor control, even in eyes with advanced disease. Chemoreduction alone generally is not adequate to achieve complete tumor seed control. Cautious follow-up of affected patients is recommended because the risk for recurrent vitreous and subretinal seeds is substantial and proper treatment is critical for salvaging the eye.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Inhibition of 5'-deoxy-5-fluorouridine phosphorolysis by acyclothymidine in tumor cell homogenates.

The inhibitory effect of acyclothymidine[AcyT, 5-methyl-1-(2'-hydroxyethoxymethyl) uracil], a potent pyrimidine nucleoside phosphorylase (PyNPase) inhibitor, on 5'-deoxy-5-fluorouridine (5'-DFUR) phosphorolysis in human and mouse tumor cell homogenates was measured. Competitive inhibition was observed in MKN-74 and Lewis lung carcinoma (LLC), whereas non-competitive inhibition was observed in HeLa. The strength of the inhibitory effect by AcyT showed the following pattern: HeLa < human normal intestine < mouse normal intestine < Colon 26 < LLC < MKN-74 < DLD-1. From the kinetic parameter obtained, we simulated the inhibitory effect of AcyT on 5'-DFUR phosphorolysis in tumor cells and the intestine. These data indicated that AcyT was more sensitive in normal mouse intestine than in Colon 26 and LLC, and that orally administered AcyT can reduce the intestinal toxicity of 5'-DFUR without reducing the antitumor effect in the mouse. The present finding may have an important implication for attempts to introduce AcyT, a potent PyNPase inhibitor, into the clinic.

Animals↗
PubMed1996

Eosinophil chemotactic activity in Leishmania amazonensis promastigotes.

Tissue eosinophilia was observed in the subcutaneous tissue of mice shortly after their inoculation not only with living but also with lysed promastigotes of Leishmania amazonensis. Intraperitoneal inoculation of lysed promastigotes from five different Leishmania species (L. donovani, L. chagasi, L. tropica, L. amazonensis, and L. braziliensis) induced eosinophil accumulation in the mouse peritoneum. This eosinophil infiltration was also detected in C5-deficient AKR mice, indicating complement independent eosinophil chemotaxis by the parasite. The induced eosinophils were hypodense, suggesting activation of the cells. Finally, we demonstrated in vitro eosinophil chemotactic activity in the promastigote lysates using purified eosinophils and blind well chambers. These results suggest the presence of an eosinophil chemotactic factor in Leishmania, a protozoan parasite.

Animals↗
PubMed1996

In vivo ESR studies on pharmacokinetics and metabolism of parenteral lipid emulsion in living mice.

PURPOSE: We applied non-invasive and real-time method with in vivo ESR spectroscopy to determining pharmacokinetics and metabolism of lipid emulsion as a drug carrier in living mice. METHODS: A spin-labeled triglyceride (SL-TG) was newly synthesized and lipid emulsion containing SL-TG was prepared. In vivo ESR spectra in mice were observed after intravenous administration of the lipid emulsion. RESULTS: In vivo ESR spectra consisted of three components, coinciding with the in vitro spectra of SL-TG particles, free and immobilized fatty acids. The amount of the components depended on both the observing domain and the period after administration. In the chest, all three components were observed, while SL-TG particle was lacking in the abdomen. The half-life of the lipid particles in the chest was 2 hr. CONCLUSIONS: Non-invasive and real-time analysis of drug carriers in living animal is successfully accomplished using an in vivo ESR method.

Animals↗
PubMed1996

Nerve growth factor enhances survival and cytotoxic activity of human eosinophils.

Phenotypic change of blood-type eosinophils to tissue-type eosinophils is induced by various cytokines. We examined the effect of nerve growth factor (NGF) as a candidate for a constitutive cytokine which is able to induce the phenotypic change of eosinophils. The viability of human peripheral blood eosinophils cultured for 4 d was increased from a mean of 26% to a mean of 50% (P<0.001) by the addition of NGF (50 ng/ml). Cytotoxic activity of eosinophils determined by larvicidal activity was increased 2-3-fold by the addition of NGF (50 ng/ml) (P<0.05). Furthermore, eosinophil chemotactic activity of NGF was demonstrated by the blind well chamber method. Since NGF is produced constitutively from various kinds of cells in local tissues, it is suggested that NGF might be a cytokine responsible for phenotypic change to tissue type eosinophils in conditions without immune stimuli.

Cell Survival↗
PubMed1996

Acyclothymidine alleviates intestinal toxicity of 5'-deoxy-5-fluorouridine without loss of antitumor activity in mice.

To reduce the intestinal toxicity of orally administered 5'-deoxy-5-fluorouridine (5'-DFUR) in mice, we co-administered 5'-DFUR with acyclothymidine [AcyT, 5-methyl-(2'-hydroxyethoxymethyl) uracil], a potent inhibitor of pyrimidine nucleoside phosphorylase (PyNPase). Orally administered 5'-DFUR alone caused intestinal toxicity and severe damage to the intestinal villi, while 5'-DFUR with AcyT reduced the intestinal toxicity, and prevented damage to the intestinal villi. This toxicity arising from orally administered 5'-DFUR could not be reduced by intravenous administration of AcyT, but was alleviated by oral administration. Orally co-administered AcyT showed little effect on antitumor activity of 5'-DFUR toward subcutaneously implanted Lewis lung carcinoma, though the intestinal toxicity was reduced in the tumor-bearing mice. This finding suggests that orally co-administered AcyT may prevent the undesirable conversion of 5'-DFUR to 5-FU by PyNPase during the process of absorption in the intestinal tract.

Administration, Oral↗
PubMed1996

Modulation of the pharmacokinetics of 5'-deoxy-5-fluorouridine and 5-fluorouracil in rats by oral co-administration of acyclothymidine.

The effect of an inhibitor of pyrimidine nucleoside phosphorylase (PyNPase), acyclothymidine (AcyT), on the pharmacokinetics of 5'-deoxy-5-fluorouridine (5'-DFUR) and 5-fluorouracil (5-FU) was investigated in an oral co-administration of 5'-DFUR and AcyT in rats. AcyT increased the maximal plasma concentration (Cmax) and apparent absorption rate constant (ka) of 5'-DFUR, as expected, but the increase in AUC (area under the curve) was not significant. It was expected that AcyT would only inhibit the phosphorolytic degradation of 5'-DFUR to 5-FU, but the effect was more evident on the pharmacokinetic parameters of 5-FU than on those of 5'-DFUR. AcyT also increased AUC and Cmax of 5-FU when orally co-administered with 5-FU. An inhibitory effect of AcyT on the enzymatic degradation of 5-FU in rat liver and intestinal extract was investigated. AcyT inhibited the degradation in intestinal extract but not in the liver. The result suggests that orally administered AcyT affects the pharmacokinetics of 5-FU partly by inhibiting 5-FU degradation in the process of intestinal absorption as well as by acting as an inhibitor of PyNPase.

Administration, Oral↗
PubMed1996

Free radicals from 1-palmitoyl-2-arachidonoylphosphatidylcholine liposomes in Fe2+/ascorbic acid solution.

The generation of free radicals during the lipid peroxidation of liposomes composed of 1-palmitoyl-2-arachidonoylphosphatidylcholine (PAPC-liposome) in Fe2+/ascorbic acid (AsA) solution was studied by the ESR spin trapping technique. A carbon-centered radical adduct was observed using alpha-(4-pyridyl-1-oxide)-N-tert-butyl-nitorone (4-POBN) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), but no oxygen-centered radicals such as .OH, LO., and LOO. were observed. The lipid peroxidation evaluated as 2-thiobarbituric acid reactive substances was inhibited by the addition of 4-POBN. The intensity of this inhibitory effect was dependent on the time when 4-POBN was added to the mixture of PAPC-liposomes and Fe2+/AsA solution, and no inhibitory effect could be observed after 4 min. The signal intensity of the carbon-centered radical adduct was dependent on the lipid concentration of PAPC-liposomes. These results suggest that the alkyl radicals generated from PAPC-liposome peroxidation induced by Fe2+/AsA were trapped by DMPO or 4-POBN at an earlier stage of lipid peroxidation.

Ascorbic Acid↗