Biomedical subjects

N Harada

Publications and source records attributed to N Harada.

At least 127 records · Page 7Linked to original sources

PubMed2000

Ketamine decreased striatal [(11)C]raclopride binding with no alterations in static dopamine concentrations in the striatal extracellular fluid in the monkey brain: multiparametric PET studies combined with microdialysis analysis.

The effects of ketamine, a noncompetitive antagonist of NMDA receptors, on the striatal dopaminergic system were evaluated multiparametrically in the monkey brain using high-resolution positron emission tomography (PET) in combination with microdialysis. L-[beta-(11)C]DOPA, [(11)C]raclopride, and [(11)C]beta-CFT were used to evaluate dopamine synthesis rate, D(2) receptor binding, and transporter availability, respectively, in conscious and ketamine-anesthetized animals. Dopamine concentrations in the striatal extracellular fluid (ECF) were simultaneously measured by PET. Thirty minutes prior to PET scan, intravenous administration of ketamine was started by continuous infusion at a rate of 3 or 10 mg/kg/h. Ketamine infusion dose-dependently decreased [(11)C]raclopride binding, but induced no significant changes in dopamine concentration in the striatal ECF as measured by microdialysis at any dose used. In contrast, ketamine increased both dopamine synthesis and DAT availability as measured by L-[beta-(11)C]DOPA and [(11)C]beta-CFT, respectively, in a dose-dependent manner. These results suggest that the inhibition of glutamatergic neuronal activity modulates dopamine turnover in the striatum by simultaneous enhancement of the dynamics of dopamine synthesis and DAT availability to the same extent, resulting in no apparent changes in ECF dopamine concentration as measured by microdialysis. It also suggests that the alteration of [(11)C]raclopride binding in vivo as measured by PET might not simply be modulated by the static synaptic concentration of dopamine.

Animals↗

PubMed2000

Chiral overcrowded alkenes; asymmetric synthesis of (3S,3'S)-(M, M)-(E)-(+)-1,1',2,2',3,3',4,4'-octahydro-3,3',7,7'-tetramethyl-4, 4'-biphenanthrylidenes.

An asymmetric synthesis route towards (3S,3'S)-(M,M)-(E)-(+)-1,1',2, 2',3,3',4,4'-octahydro-3,3',7,7'-tetramethyl-4,4'-biphenanthrylidene was developed using the Evans procedure as a key step. The absolute configurations of the title compound and of its parent ketone were determined by CD spectroscopy and could be correlated with the stereochemical results of the asymmetric alkylation. Furthermore, a comparison was made with the known (3R,3'R)-(P,P)-(E)-(-)-1,1',2,2', 3,3',4,4'-octahydro-3,3',7,7'-dimethyl-4,4'-biphenanthrylidene. Finally, the X-ray crystallographic analysis of (3S,3'S)-(M, M)-(E)-(+)-1,1',2,2',3,3',4,4'-octahydro-3,3',7,7'-tetramethyl-4, 4'-biphenanthrylidene is presented.

Alkenes↗

PubMed2000

Involvement of caspase 3 in apoptotic death of cortical neurons evoked by DNA damage.

Previous reports have shown that DNA-damage-evoked death of embryonic cortical neurons is delayed by general caspase inhibitors and is accompanied by an increase in DEVD-AFC cleavage activity. We show here that this cleavage activity is lacking in camptothecin-treated caspase 3-deficient neurons. Moreover, we report that death of camptothecin-treated caspase 3-deficient neurons cultured from E16 embryos is delayed and that no significant increase in survival is observed with cotreatment with the general caspase inhibitor BAF. These results indicate that caspase-dependent death of camptothecin-treated cortical neurons requires caspase 3 activity. The delay in death is accompanied by impairment of DNA fragmentation. However, Bax-dependent cytochrome c release still occurs in camptothecin-treated caspase 3-deficient cortical neurons. Accordingly, we hypothesize that the delayed death which occurs in the absence of caspase 3 activity may be due to mitochondrial dysfunction. Finally, we show that the delay in death observed with E16 caspase 3-deficient neurons does not occur in neurons cultured from E19 embryos. This suggests that the requirement for caspase 3 in death of neurons evoked by DNA damage may differ depending upon the developmental state of the cell.

Animals↗

PubMed2000

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat.

A new colourimetric method is described for the quantification of diquat using a yellow-coloured derivative produced by heating diquat in alkaline solution at 80 degrees C. The absorption maximum of the yellow derivative is 420 nm and the molar absorption coefficient is 2.76 x 10(4) (0.15 in 1 microgram diquat/ml with 1 cm light path). The absorption at 420 nm shows a linear concentration dependence in the range 0.1-10 micrograms/ml and fading of the colour is about 5% after 1 h. Under the same conditions, paraquat does not produce any coloured products. The concentration of diquat in the solution containing both diquat and paraquat can be determined by the absorption of diquat derivative at 420 nm without interference from paraquat. By adding sodium dithionite to the solution the concentration of paraquat can be determined by the absorption of paraquat radicals at 600 nm without interference from diquat, because the yellow derivative does not react with dithionite. This yellow diquat derivative can be extracted completely with cyclohexanol by saturating the solution with Na2SO4. The absorption maximum in cyclohexanol shifts to 440 nm with the same molar absorbance and the same half-band width as in water. Fading of the colour is less than 5% after 24 h in cyclohexanol. Perchloric acid (3%) and trichloroacetic acid (4.5%) which are often used for deproteinization of tissue homogenates, do not inhibit production of the coloured derivative at pH 13.5 or extraction of the derivative with cyclohexanol. This method is suitable for a quick determination of small amounts of diquat in tissues, since the extraction with cyclohexanol not only concentrates the derivative rapidly but also quite efficiently eliminates the coloured substances in tissue homogenates. The detection limit of diquat is 0.02 microgram/ml for blood and 0.05 microgram/g for liver when 1 ml or 1 g is used for analysis. In three human cases of fatal intoxication, both paraquat and diquat were quantified using 50 microliters of serum. In non-toxic dosing of diquat to rats for 14 days, the diquat level was highest in the spleen followed by the kidneys.

Animals↗

PubMed2000

Step by step filter based program for calculations of highly informative derivative curves

We have developed a microcomputer program, based on a recently described approach called step by step filter (SBSF), for calculation of derivative curves directly from spectra recorded as a function of wavelength. This program avoids the long wavelength attenuation featured at conventional method for derivative curves calculation, and in this extent could be very helpful for daily spectroscopy practice. The features of the SBSF program include: easy treatment of data through a windowed environment, calculating of both conventional and step by step filter derivatives, possibilities for selection of the mathematical conditions for smoothing and differentiation simultaneous plotting of the original curve and its derivative and a mouse pointer. Several examples from different branches of the molecular spectroscopy (absorption UV-VIS, CD and fluorescence) are provided and discussed in the terms of advantages of SBSF.

Journal Article↗

PubMed2000

Elevated steroid sulfatase expression in breast cancers.

In situ estrogen synthesis makes an important contribution to the high estrogen concentration found in breast cancer tissues. Steroid sulfatase which hydrolyzes several sulfated steroids such as estrone sulfate, dehydroepiandrosterone sulfate, and cholesterol sulfate may be involved. In the present study, we therefore, assessed steroid sulfatase mRNA levels in breast malignancies and background tissues from 38 patients by reverse transcription and polymerase chain reaction. The levels in breast cancer tissues were significantly increased at 1458.4+/-2119.7 attomoles/mg RNA (mean +/- SD) as compared with 535.6+/-663.4 attomoles/mg RNA for non-malignant tissues (P<0.001). Thus, increased steroid sulfatase expression may be partly responsible for local overproduction of estrogen and provide a growth advantage for tumor cells.

Adult↗

PubMed2000

Development of an automated synthesis apparatus for L-[3-11C] labeled aromatic amino acids.

We have developed an automated synthesis apparatus for L-[3-11C]-labeled aromatic amino acids by improved multi-enzymatic reactions. Use of a specially designed reaction vessel and of CH2Cl2 as a solvent has greatly simplified the overall operation, proving to be suitable for automated synthesis, and also has given better yields and higher specific activities than formerly reported values.

5-Hydroxytryptophan↗

PubMed2000

Development and evaluation of muscarinic cholinergic receptor ligands N-[11C]ethyl-4-piperidyl benzilate and N-[11C]propyl-4-piperidyl benzilate: a PET study in comparison with N-[11C]methyl-4-piperidyl benzilate in the conscious monkey brain.

The muscarinic cholinergic receptor ligands N-[(11)C]ethyl-4-piperidyl benzilate (4-EPB) and N-[(11)C]propyl-4-piperidyl benzilate (4-PPB) were developed and evaluated in comparison with N-[(11)C]methyl-4-piperidyl benzilate (4-MPB) in the conscious monkey brain using positron emission tomography (PET). Time-activity curves of [(11)C]4-EPB, unlike [(11)C]4-MPB, showed peaks within 91 min in regions rich in muscarinic receptors. [(11)C]4-PPB showed no specific binding even in the regions rich in these receptors. These observation demonstrated that increases in [(11)C]alkyl chain length could alter the kinetic properties of receptor ligands for PET.

Animals↗

PubMed2000

Enantiomeric excess of a cruciferous phytoalexin, spirobrassinin, and its enantiomeric enrichment in an achiral HPLC system.

Enantiomeric purity of a cruciferous phytoalexin, spirobrassinin (1), was determined by chiral HPLC analysis. The enantiomeric excesses of two natural spirobrassinin fractions separated by nonchiral chromatography were considerably different. A significant enantiomeric enrichment was observed during the nonchiral chromatographic separation of an artificial enantiomeric mixture of 1.

Brassica↗

PubMed2000

Activated neutrophils impair gastric cytoprotection role of neutrophil elastase.

Neutrophil elastase decreases production of PGI2 by cultured endothelial cells. Thus, neutrophil elastase may play an important role in gastric mucosal injury by decreasing the tissue level of PGI2, an important gastric cytoprotective substance. We examined whether activated neutrophils inhibit gastric PGI2 production in rats subjected to water-immersion restraint stress. Gastric 6-keto-PGF1alpha levels were determined by enzyme immunoassay. Gastric mucosal blood flow was determined by laser-Doppler flowmeter. Gastric microvascular permeability was determined by Evans blue leakage. Gastric levels of 6-keto-PGF1alpha were transiently increased 0.5 hr after the stress, followed by a decrease to below baseline at 6 hr, when mucosal blood flow fell to 60% of baseline. Gastric levels of 6-keto-PGF1alpha were significantly higher in animals with nitrogen mustard-induced leukocytopenia than in controls 1 and 6 hr after the stress. In leukocytopenic animals, levels 6 hr after stress were not lower than those preceding stress. Leukocytopenia markedly limited both the decrease in mucosal blood flow and the increase in gastric microvascular permeability. The level of gastric mucosal injury observed 6 hr after the stress was markedly attenuated by leukocytopenia. Pretreatment with neutrophil elastase inhibitors (ONO-5046 and Eglin C) or an anti-P-selectin monoclonal antibody produced effects similar to leukocytopenia. Neutrophil elastase is involved in the stress-induced gastric mucosal injury by decreasing gastric production of PGI2. Thus, pharmacologic inhibition of neutrophil elastase should help to prevent stress-induced gastric mucosal injury.

6-Ketoprostaglandin F1 alpha↗

PubMed2000

Strain differences in SA gene expression in brain and kidney of normotensive and hypertensive rats.

1. In situ hybridization done using a 35S-cRNA probe was carried out to obtain information on the expressions of the SA gene in brains and kidneys of the spontaneously hypertensive rat (SHR) strain obtained from the Izumo colony (/Izm) and from Charles River Laboratories (/Crj). 2. In the brain, SA mRNA expression was most abundantly observed in epithelial cells of the choroid plexus. High to moderate levels was present on neurons of the CA1-CA4 pyramidal cell layer and the dentate gyrus of the hippocampus and the cerebellar Purkinje cell layer. The solitary tract nucleus and the dorsal motor nucleus of the vagus expressed the SA gene at very low levels. An increase in the expression was noted in the choroid plexus of WKY/Crj; there was no difference, however, in expression levels of other brain areas between WKY/Izm, SHR/Izm, and SHRSP/Izm, and between WKY/Crj and SHR/Crj. 3. In the kidney, expression signals of SA mRNA were observed in renal medullary rays and focal cortex of WKY/Izm, SHR/Izm, SHRSP/Izm, and SHR/Crj, whereas mRNA expression in the WKY/Crj kidney was observed in medullary rays and outer strips of the outer medulla. Microscopically, hybridization signals were predominant in the proximal tubules. 4. Expression densities decreased only in the kidney of WKY/Crj in 4-and 8-week-old rats, but not in the WKY/Izm kidney, compared with findings in SHR and SHRSP kidneys. These observations are in good agreement with data from Northern blot analysis. 5. The SA gene expressions in the brain and the kidney seem not to relate to states of elevated blood pressure, but rather to strain differences. Abundant expressions in the brain and the kidney may mean that the SA gene plays a role in the water-electrolyte transport system. It is noteworthy that there are neuronal expressions of the SA gene in hippocampal pyramidal cells and cerebellar Purkinje cells.

Animals↗

PubMed2000

Protective effect of melatonin against alpha-naphthylisothiocyanate-induced liver injury in rats.

The protective effect of melatonin against alpha-naphthylisothiocyanate (ANIT)-induced liver injury with cholestasis was examined in rats injected once with the toxicant (75 mg/kg body weight (BW)). In rats injected with ANIT alone, liver injury with cholestasis did not occur 12 hr after the injection but appeared at 24 hr, judging from the serum levels of marker enzymes and components. When melatonin (10 or 100 mg/kg BW) was orally administered to the ANIT-injected rats at 12 hr after the injection, the administered indoleamine dose-dependently prevented the formation of liver injury with cholestasis. In rats injected with ANIT alone, serum lipid peroxide (LPO) concentration increased 24 hr after the injection, while liver LPO concentration increased 12 hr after the injection and further increased at 24 hr. Myeloperoxidase (MPO) activity, an index of tissue neutrophil infiltration, in the liver of the ANIT-injected rats increased 12 hr after the injection and further increased at 24 hr. The oral administration of melatonin (10 or 100 mg/kg BW) to the ANIT-injected rats attenuated the increases in serum and liver LPO concentrations and liver MPO activity found at 24 hr after the injection in a dose-dependent manner. These results indicate that orally administered melatonin at pharmacological doses protects against ANIT-induced liver injury with cholestasis in rats, and suggest that this protective effect of melatonin could be due to its antioxidant action and its inhibitory action against neutrophil infiltration in the liver of ANIT-injected rats.

1-Naphthylisothiocyanate↗

PubMed2000

Hepatosplenic gammadelta T-cell lymphoma: relation to Epstein-Barr virus and activated cytotoxic molecules.

AIMS: Hepatosplenic gammadelta T-cell lymphoma (TCL) is a rare, aggressive subset of peripheral TCL that presents with hepatosplenomegaly and cytopenia. Epstein-Barr virus (EBV) infection and activated cytotoxic molecules (granzyme and perforin) are uncommon in hepatosplenic gammadelta CTL. EBV infection and activated cytotoxic molecules are occasionally detected in non-hepatosplenic gammadelta TCL. We describe the clinicopathological features of three Japanese cases who were not immunodeficient. METHODS AND RESULTS: All cases showed gammadelta T-cell type (CD2+, CD3+, T-cell receptor (TCR)delta-1+, betaF1-). Two cases expressed natural killer (NK) cell-associated antigens (CD8-, CD16+, CD56+; CD8-, CD16-, CD56+), and one expressed CD8 (CD8+, CD16-, CD56-). All cases expressed cytotoxicity-associated molecules (perforin, granzyme B, TIA-1 and Fas ligand). However, perforin and Fas ligand were not detected in one case. In-situ hybridization analysis with EBER probes revealed strong nuclear positivity in all neoplastic cells. In addition, two cases showed clonal bands of the EBV terminal repeat (TR) gene. Cytologically, instead of the presence of monomorphic medium-sized cells, our three cases showed pleomorphic medium-sized and large cells. CONCLUSIONS: Our gammadelta TCL cases were clinicopathologically considered to be compatible with hepatosplenic gammadelta T-cell lymphoma. However, with regard to EBV association, activated cytotoxic profile and cytological features they resembled non-hepatosplenic gammadelta TCL. EBV may play a role in this disease by inducing cellular activation.

Adult↗

PubMed2000

Ontogeny of aromatase and tyrosine hydroxylase activity and of aromatase-immunoreactive cells in the preoptic area of male and female Japanese quail.

The aromatization of testosterone into oestrogens plays a key role in the control of many behavioural and physiological aspects of reproduction. In the quail preoptic area (POA), aromatase activity and the number of aromatase-immunoreactive (ARO-ir) cells are sexually differentiated (males > females). This sex difference is implicated in the control of the sexually dimorphic behavioural response of quail to testosterone. We analysed the ontogenetic development of this sex difference by measuring aromatase activity and counting ARO-ir cells in the POA of males and females from day 1 post hatch to sexual maturity. We investigated in parallel another enzyme: tyrosine hydroxylase, the rate limiting step in catecholamine synthesis. Between hatching and 4 weeks of age, aromatase activity levels were low and equal in males and females. Aromatase activity then markedly increased in both sexes when subjects initiated their sexual maturation but this increase was more pronounced in males so that a marked difference in aromatase activity was present in 6 and 8 week-old subjects. Tyrosine hydroxylase activity progressively increased with age starting immediately after hatching and there was no abrupt modification in the slope of this increase when birds became sexually mature. No sex difference was detected in the activity of this enzyme. The number of ARO-ir cells in the POA progressively increased with age starting at hatching. No sex difference in ARO-ir cell numbers could be detected before subjects reached full sexual maturity. The analysis of the three-dimensional organization of ARO-ir cells in the POA revealed that, with increasing ages, ARO-ir cells acquire a progressively more lateral position: they are largely periventricular in young birds but they are found at higher density in the lateral part of the medial preoptic nucleus in adults. These data indicate that aromatase activity differentiates sexually when birds reach sexual maturity presumably under the activating effects of the increased testosterone levels in males. The number of ARO-ir cells, however, begins to increase in a non sexually differentiated manner before the rise in plasma testosterone in parallel with the increased tyrosine hydroxylase activity. Whether this temporal coincidence results from a general ontogenetic pattern or from more direct causal links remains to be established.

Aging↗

PubMed2000

Preoperative staging of rectal cancer using a 7.5 MHz front-loading US probe.

BACKGROUND: Conventional echoendoscopes have disadvantages when used for staging colorectal cancer including the inability to pass the instrument through tight stenosis and limited maneuverability. This study evaluated the preoperative use of a newly developed 7.5 MHz front-loading ultrasound probe (FLUP) for local staging of rectal cancer. METHODS: A 7.5 MHz FLUP, diameter 7.3 mm, was used in this study. The mechanical shaft portion of the probe can be passed in retrograde fashion through the accessory channel of a standard colonoscope. Thirty-nine patients with rectal cancer underwent ultrasonography with this probe. The tumors were staged using the TNM system, and the results were compared with the histologic findings of the resected specimens. RESULTS: The FLUP proved to be satisfactory, with respect to maneuverability, for traversing stenosis and accurate recognition of small tumors under direct endoscopic control. The accuracy of the FLUP for T staging was 82% (32 of 39) for all tumors, 90% in pT1, and 79% in pT2 to pT4 tumors. The accuracy of the FLUP for N staging was 72% (23 of 32) overall. The sensitivity was 83%, the specificity was 65%, the positive predictive value was 59%, and the negative predictive value was 87%. CONCLUSIONS: The 7.5 MHz FLUP appears to be useful for preoperative local staging of rectal cancer. This system makes it technically easier to image small cancers as well as advanced rectal cancers.

Adult↗

PubMed2000

Extracellular adenosine 5'-ATP-induced calcium signaling in isolated vestibular ganglion cells of the guinea pig.

Extracellular adenosine 5'-triphosphate (ATP)-induced intracellular calcium concentration ([Ca2+]i) changes in acutely isolated vestibular ganglion cells (VGCs) of the guinea pig were investigated using the Ca2+ -sensitive dye Fura-2. Extracellular ATP induced an increase in [Ca2+]i in VGCs in a dose-dependent manner. ATP induced an increase in [Ca2+]i even in the absence of extracellular Ca2+ (1 mM Ethylene Glycol-bis (beta-aminoethyl Ether) N,N,N',N'-Tetraacetic Acid (EGTA)), thus suggesting that ATP induces Ca2+ release from the intracellular stores. The P2-receptor antagonists suramin and reactive blue 2 inhibited the ATP-induced [Ca2+]i increase in a dose-dependent manner. The P1-receptor agonist adenosine did not induce any changes in [Ca2+]i. These results suggest that VGCs may possess a P2-purinergic receptor but not a P1-purinergic receptor. La3+, a receptor-mediated calcium channel blocker, inhibited the ATP-induced [Ca2+]i increase but, in contrast, nifedipine, a L-type calcium channel blocker, did not. These results suggest that ATP induces both a Ca2+ -release from the intracellular stores and a Ca2+ influx from the extracellular space through La3+ -sensitive and nifedipine-insensitive Ca2+ channels in VGCs. Our results also suggest that extracellular ATP may act as a neurotransmitter or neuromodulator of the vestibular peripheral system in the guinea pig.

Adenosine Triphosphate↗

PubMed2000

Increase in production of ascorbate radical in tissues of rat treated with paraquat.

The production of ascorbate radical (A*-) was investigated in tissues of rats intoxicated with paraquat (PQ) to know the protective role of antioxidant ascorbate (AH-) in tissues. The electron spin resonance (ESR) method is applied to observe A*-. To eliminate increased biosynthesis of ascorbic acid (AH2) by PQ intoxication, ODS rats were chosen and fed with or without 250 ppm PQ in the diet. The radical A*- was detected only in the lung and spleen homogenates of both intoxicated and control rats at the beginning of ESR measurement. The radical levels of intoxicated rat lung and spleen were increased rapidly to twice the initial level after 3 h and decreased to 0.2-0.6 times the initial level after 24 h, whereas those of control rats were increased slowly to 1.1 times the initial level after 4 h and decreased slowly to 0.7 times the initial level after 24 h at 4 degrees C. In other organs such as liver, kidney, heart and testis, A*- was not detected initially but detected afterwards. Higher A*- level was observed in the intoxicated rat liver than the control but no appreciable differences of A*- levels were observed between the intoxicated kidney, heart and testis and the respective controls. In the intoxicated rat lung the concentration of AH2 is only half but that of A*- is twice as high as that of the control. Larger amounts of A*- produced in the intoxicated rats decayed more quickly than those in the control rats. The simple addition of PQ to the control organ enhanced neither A*- production nor A*- quenching. These facts suggest that the tissues damaged by PQ require larger amounts of AH- to detoxicate harmful oxidants, resulting in concomitant production of A*-.

Animals↗

PubMed2000

Taurine improves insulin sensitivity in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous type 2 diabetes.

BACKGROUND: Taurine, a potent antioxidant, has been reported to improve streptozotocin-induced diabetes mellitus, in which the development of diabetes results from an attack by oxygen free radicals on pancreatic beta cells. However, taurine also increases the excretion of cholesterol via conversion to bile acid and would be expected to improve insulin resistance. OBJECTIVE: The effects of taurine on insulin sensitivity were examined in a model rat of insulin resistance and type 2 diabetes-the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. DESIGN: Male OLETF rats were divided into 2 groups at the age of 16 wk: a taurine-supplemented group and an unsupplemented group. As a nondiabetic control, Long-Evans-Tokushima-Otsuka rats were used. An oral-glucose-tolerance test and hyperinsulinemic euglycemic clamp were performed at the ages of 23 and 25 wk. RESULTS: The OLETF rats had hyperglycemia and insulin resistance and they had a greater accumulation of abdominal fat than did control rats. Abdominal fat accumulation, hyperglycemia, and insulin resistance were significantly lower in the taurine-supplemented group than in the unsupplemented group. Serum and liver concentrations of triacylglycerol and cholesterol were significantly higher in the OLETF rats than in the control rats and were significantly lower in the taurine-supplemented group than in the unsupplemented group, presumably because of the increased secretion of cholesterol into bile acid. Taurine-supplemented rats also showed higher nitric oxide secretion, evidenced by increased urinary excretion of nitrite. CONCLUSION: Taurine effectively improves metabolism in OLETF rats by decreasing serum cholesterol and triacylglycerol, presumably via increased secretion of cholesterol into bile acid and decreased production of cholesterol because of increased nitric oxide production.

Adipose Tissue↗