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Biomedical subjects

N Takata

Publications and source records attributed to N Takata.

At least 19 recordsLinked to original sources
PubMed2005

Hippocampal synthesis of estrogens and androgens which are paracrine modulators of synaptic plasticity: synaptocrinology.

Hippocampal pyramidal neurons and granule neurons of adult male rats are equipped with a complete machinery for the synthesis of pregnenolone, dehydroepiandrosterone, testosterone, dihydrotestosterone and 17beta-estradiol. Both estrogens and androgens are synthesized in male hippocampus. These brain steroids are synthesized by cytochrome P450s (P450scc, P45017alpha and P450arom), hydroxysteroid dehydrogenases and reductases from endogenous cholesterol. The expression levels of enzymes are as low as 1/300-1/1000 of those in endocrine organs. Synthesis is dependent on the acute Ca(2+) influx upon neuron-neuron communication via NMDA receptors. Estradiol is particularly important because estradiol rapidly modulates neuronal synaptic transmission such as long-term potentiation via synaptic estrogen receptors. Xenoestrogens may also act via estrogen-driven signaling pathways.

Androgens↗
PubMed2005

Loss of ions in cavity ionization chambers.

Ion losses due to initial recombination, volume recombination, and back diffusion were each determined by measurements and calculations for different size cylindrical ionization chambers and spherical ionization chambers. By measuring signal currents from these ionization chambers irradiated with (60)Co gamma rays, two groups of ion losses were obtained. (Group 1) Ion loss due to initial recombination and diffusion, which changes proportionally to the inverse of the voltage applied to the ionization chambers; (and group 2) ion loss due to volume recombination, which changes proportionally to the inverse of the square of the applied voltage. The diffusion loss was obtained separately by computing electric field distributions in the ionization chambers. It was found that diffusion loss is larger than initial recombination loss for the cylindrical ionization chambers and vise versa for the spherical ionization chambers.

Journal Article↗
PubMed2003

Angle dependence of signal currents from cylindrical ionisation chambers.

A signal current from a cylindrical ionisation chamber with an ionisation volume of 62.7 cm3, 40 mm in diameter and 50 mm long, peaked when the chamber was lixed at 0 degrees and at 90 degrees in 137Cs and 60Co gamma ray fields for source-chamber distances of 1 m and 2 m. A smaller ionisation chamber showed a small peak at 0 degrees in both fields but not at 90 degrees. However, calculations indicated that the signal current from the smaller chamber would also show a peak at 90 degrees in a 137Cs point-source gamma ray field. Peaks occur because gamma rays attenuate along the cylindrical side wall or along the end walls when a chamber is tilted slightly from 0 degrees or 90 degrees and the direction of the gamma ray beam agrees with the plane of one of these walls. These facts suggest the need for care in the common practice of measuring and calculating responses for cylindrical ionisation chambers fixed perpendicular to gamma ray beams.

Cesium Radioisotopes↗
PubMed2001

Autoimmune neutropenia in pregnant women causing neonatal neutropenia.

Autoimmune neutropenia (AIN) can occur during pregnancy. However, neonatal neutropenia occurring in an infant born to a mother with AIN has only rarely been documented. Recently, we have experienced two cases of AIN during pregnancy, both of which caused severe yet transient neonatal neutropenia (< 0.3 x 10(9)/l), probably as a result of transplacental maternal anti-neutrophil autoantibodies. The anti-neutrophil antibodies seemed to be against antigens other than NA1/NA2 because the autoantibodies did not bind to neutrophils of specific NA types selectively in the granulocyte indirect immunofluorescence test. Although AIN is a relatively uncommon disease, neonatal neutropenia caused by maternal AIN may not be quite as rare.

Adult↗
PubMed2001

Change in plasma viral load, and viral DNA and mRNA burdens, in peripheral blood mononuclear cells from patients infected with HIV-1.

OBJECTIVES: To clarify the virological state of human immunodeficiency virus (HIV)-1-infected patients, we compared the plasma HIV-1 RNA copy number (plasma viral load (VL)), viral DNA and mRNA burdens in peripheral blood mononuclear cells (PBMCs), and the other clinical predictors. METHODS: One hundred and thirty-one samples of PBMCs and plasma from 26 patients infected with HIV-1 were obtained during 20 consecutive months for the measurement of VL, viral DNA and mRNA burdens, and CD4 positive (CD4+) cells count. The quantitative polymerase chain reaction (PCR) method with detection by solid phase DNA was utilized for the assay of VL, viral DNA and mRNA burdens. RESULTS: Eighty-six VL, 101 viral mRNA and 129 viral DNA out of 131 samples were detected. There was a significant positive correlation between VL and the viral mRNA burden (r = 0.600, P < or = 0.001), and between VL and the viral DNA burden (r = 0.368, P < or = 0.001). Focused on individuals, the viral mRNA burdens varied in a manner relatively dependent on VL when both values were detectable. However, viral DNA burdens varied relatively independently of VL and the viral mRNA burdens. In six patients the viral mRNA burden was detectable and changed even if the VL was undetectable throughout the observation period. CONCLUSIONS: Both viral DNA and viral mRNA burdens still showed detectable changes even when the VLs became undetectable in most patients. The measurement of viral mRNA or DNA burdens may be clinically available to identify viral replication when VL is undetectable.

Adolescent↗
PubMed2001

Neurosteroid synthesis by cytochrome p450-containing systems localized in the rat brain hippocampal neurons: N-methyl-D-aspartate and calcium-dependent synthesis.

Neurosteroidogenesis has not been well elucidated due to the very low level of steroidogenic proteins in the brain. Here we report the first demonstration of the neuronal localization of neurosteroidogenic systems as well as the regulation of neurosteroidogenic activity in the adult rat hippocampus. Significant localization of cytochrome P450scc was observed in pyramidal neurons and granule neurons by means of immunohistochemical staining of slices. We also observed the colocalization, in hippocampal neurons, of P450scc with redox partners, hydroxysteroid sulfotransferase and steroidogenic acute regulatory protein. The distributions of astroglial cells and oligodendroglial cells showed very different patterns from that of the P450scc-containing cells. The expression of P450scc, redox partners, the sulfotransferase, and steroidogenic acute regulatory protein was also confirmed by Western blot analysis. The process of active neurosteroidogenesis was stimulated by exposing neurons to N-methyl-D-aspartate. Upon stimulation with N-methyl-D-aspartate, Ca(2+) influx through the N-methyl-D-aspartate subtype of glutamate receptors occurred, and significant net production of pregnenolone and pregnenolone sulfate was observed in the hippocampus. This neurosteroid production was considerably suppressed by the addition of antagonists of N-methyl-D-aspartate receptors, by Ca(2+) depletion, or by the addition of an inhibitor of P450scc. Upon stimulation with N-methyl-D-aspartate, the processing of full-length steroidogenic acute regulatory protein (37-kDa) to the truncated 30-kDa steroidogenic acute regulatory protein was observed. Taken together, these observations imply that hippocampal neurons synthesize neurosteroids. This synthesis may be stimulated and regulated by glutamate-mediated synaptic communication.

Animals↗
PubMed2001

Production of anti-Gordonia amarae mycolic acid polyclonal antibody for detection of mycolic acid-containing bacteria in activated sludge foam.

Mycolic acid-containing actinomycetes (mycolata) are considered the causative agents of foaming of activated sludge and scum formation in activated sludge treatment plants. In this study, the production of anti-Gordonia amarae mycolic acid polyclonal antibodies was investigated. Rabbits were immunized with a conjugate of keyhole limpet hemocyanin and mycolic acids of G. amarae, which contained 48 to 56 carbon atoms (average, 52.0). Enzyme-linked immunosorbent assay (ELISA) demonstrated that the polyclonal antibodies could recognize cells of G. amarae ranging from 0.1 to 10 microg. The antibodies also reacted with other tested mycolata strains belonging to the genera Nocardia, Rhodococcus, Dietzia, Mycobacterium and Tsukamurella. However, reactivities against other gram-positive and gram-negative bacteria not containing mycolic acid were negligible or much lower. The results indicate that the anti-G. amarae mycolic acid antibodies show a reactivity selective for a group of mycolata involved in the foaming of activated sludge.

Journal Article↗
PubMed2000

Sulindac and a cyclooxygenase-2 inhibitor, etodolac, increase APC mRNA in the colon of rats treated with azoxymethane.

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to protect against the development of colon cancer. However, the mechanism(s) by which NSAIDs exert their effects is not clear. AIMS: The aim of this study was to examine the effects of NSAIDs on mRNA expression of tumour suppressor adenomatous polyposis coli (APC) gene in rat colon mucosa. METHODS: Starting at six weeks of age, three groups of rats (groups 1, 2, and 3) were treated with azoxymethane (AOM), a colon specific carcinogen, and another three groups (groups 4, 5, and 6) were not given AOM. Groups 2 and 3 were given 10 mg/kg of sulindac or etodolac, respectively, three times weekly during the experiment. Groups 4 and 5 were also given sulindac or etodolac, respectively, in the same manner as in groups 2 and 3. Group 6 (untreated control) was not given any agent (AOM or NSAIDs). At 10 weeks of age, preneoplastic lesions (aberrant crypt foci (ACF)) induced by AOM in the colon were counted, and the level of expression of APC mRNA in the colonic mucosa was estimated by the reverse transcription-competitive polymerase chain reaction method and northern blot analysis. RESULTS: Mean occurrence of ACF in rats in groups 2 and 3 was reduced to approximately 50% of that in group 1. The level of APC mRNA expression in group 1 (AOM alone) was lower than that in group 6 (untreated control) (p<0.05); however, levels of APC mRNA expression in groups 2, 3, 4, and 5, to which NSAIDs had been administered, were significantly increased compared with levels in groups 1 and 6 (p<0.01). CONCLUSIONS: Both sulindac and etodolac reduced the occurrence of ACF and induced an increase in APC mRNA in rat colon mucosa.

Animals↗
PubMed2000

Potential interaction between ritonavir and carbamazepine.

Ritonavir (RTV), a protease inhibitor, and carbamazepine (CBZ), an anticonvulsant, were administered concurrently to a patient who had human immunodeficiency virus infection and epilepsy. The combination resulted in elevated serum concentrations of CBZ, with accompanying vomiting, vertigo, and transient liver dysfunction. After discontinuing RTV and reducing the dosage of CBZ, the serum concentration of CBZ returned to the optimal range, symptoms subsided, and liver function returned to baseline. Carbamazepine is metabolized in the liver to a large extent by the cytochrome P450 (CYP) system, especially CYP3A4, 2C8, and 1A2, whereas RTV is metabolized primarily by CYP3A and is a potent inhibitor of this enzyme. Careful clinical monitoring may help prevent adverse drug interactions when these drugs are administered concurrently.

Adult↗
PubMed2000

[Multimodality therapy for synchronous liver metastases of gastric cancer--significance of aggressive hepatic resection of liver lesions].

We analyzed 15 gastric cancer patients with synchronous liver metastases, and studied the significance of hepatic resection with multimodality therapy. 1. Both gastric and hepatic resections followed by intra-arterial or systemic chemotherapy were performed for six patients, two of whom had intra-operative MCT or EIT. The survival time of four patients without recurrence was 5 Y 4 M, 4 Y 5 M, 2 Y 4 M and 11 M. Two patients died of recurrence in the retroperitoneum or residual liver 3 Y 10 M and 8 M after therapy, respectively. The three-year survival rate was 83%. 2. The longest survival among the five patients treated with gastric resection without hepatic resection followed by intra-arterial or systemic chemotherapy was 1 Y 1 M. 3. Four patients with non-curative factors (P, N, M) were treated with systemic chemotherapy only, and the longest survival was 1 Y 1 M. In conclusion, when local control is obtained during surgery in patients with gastric cancer with synchronous liver metastasis, aggressive hepatic resection supported with MCT or EIT should be performed on liver lesions to improve the prognosis.

Aged↗
PubMed1999

[A long-survival case of gastric cancer with multiple liver metastasis: usefulness of intraoperative multimodality therapy and post-operative intra-arterial chemotherapy for liver lesions].

A 62-year-old man was found to have advanced cancer of the gastric cardia with multiple liver metastasis. Total gastrectomy was performed, and 11 hepatic lesions were simultaneously treated by intraoperative multimodality therapy. The therapy included hepatic resections for seven easily-resectable lesions, microwave coagulation therapy for two lesions, and ethanol injection therapy for two. Post-operative intra-arterial infusion of 1,000 mg of 5-FU was performed weekly or every two weeks through the hepatic artery using a reservoir. No recurrence was found during the follow-up period of 35 months. When local control is obtained during surgery in patients with gastric cancer with multiple liver metastasis, intraoperative multimodality therapy and post-operative intra-arterial chemotherapy should be performed for liver lesions.

Adenocarcinoma↗
PubMed1998

Interleukin-9 receptor alpha chain mRNA formation in CD8+ T cells producing anti-human immunodeficiency virus type 1 substance(s).

A search for gene(s) associated with anti-human immunodeficiency virus type 1 (HIV-1) activity of CD8+ T cells was attempted using molecular cloning and the relation between the anti-HIV activity of CD8+ T cells and the interleukin-9 receptor alpha chain (IL-9R-alpha) mRNA expression from the cDNA clones obtained was examined. The anti-HIV-1 activity of CD8+ T cell culture supernatants was assessed by measuring the level of HIV-1 replication of a CD4+ T cell line transfected with an infectious HIV-1 DNA clone. IL-9R-alpha mRNA was assayed by reverse transcriptase-polymerase chain reaction (RT-PCR). Of 5 cases showing high level of anti-HIV-1 activity (more than 80% suppression of HIV-1 replication), the mRNA was detected in 4 cases. Of 10 cases showing low level of anti-HIV-1 activity (less than 80% suppression of HIV-1 replication), the mRNA was detected in one case. Soluble recombinant human IL-9 receptor (rhIL-9sR) did not suppress HIV-1 replication at a concentration of 1 microgram/ml. These data suggest that the IL-9R-alpha mRNA formation in CD8+ T cells may correlate with and play some role in the anti-HIV-1 activity of CD8+ T cells from HIV-1-infected individuals.

CD4-Positive T-Lymphocytes↗