Biomedical subjects

H Akimoto

Publications and source records attributed to H Akimoto.

At least 19 recordsLinked to original sources

PubMed2001

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

Journal Article↗

PubMed2001

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Journal Article↗

PubMed2001

[Aortic root replacement after operation for the ascending aorta and/or aortic valve].

We reviewed ten cases who underwent aortic root replacement after operation for the ascending aorta and/or aortic valve. As initial operation, aortic valve replacement (AVR) was performed in five patients, replacement of the ascending aorta in two, original Bentall operation in two, and entry closure and suspension of the aortic valve in one. At reoperation, three patients were diagnosed as aneurysm of the ascending aorta, two were annulo-aortic ectasia, and one was acute aortic dissection, chronic dissecting aneusym, pseudoaneurysm of the ascending aorta, prosthetic valve endocarditis, and massive aortic regurgitation. Aortic root replacement was performed using mechanical valved composite graft in all cases. One patient who underwent repeat aortic root replacement for prosthetic valve endocarditis was died of septemia and ventricular fibrillation. Five patients had nine complications (two low output syndrome, respiratory failure and cerebral infarction, one gastrointestinal bleeding, septemia and ventricular fibrillation). In conclusion, aortic root replacement after operation for the ascending aorta and/or aortic valve was performed with acceptable morbidity and mortality.

Adult↗

PubMed2000

Measurement of J/psi and psi(2S) polarization in pp collisions at sqrt[s] = 1.8 TeV.

We have measured the polarization of J/psi and psi(2S) mesons produced in pp collisions at sqrt[s] = 1.8 TeV, using data collected at the Collider Detector at Fermilab during 1992-1995. The polarization of promptly produced J/psi [psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4 [5.5]<P(T)<20 GeV/c and |y|<0.6. For P(T) greater than or approximately equal 12 GeV/c we do not observe significant polarization in the prompt component.

Journal Article↗

PubMed2000

Melting process and interface instability of highly magnetized solid 3He: role of the magnetization gradient

We elucidate the melting process of highly magnetized solid 3He by observing the magnetization profile and the liquid-solid interface simultaneously. Clear enhancements of magnetization and magnetization gradients at the interface of both the solid and the liquid were observed during melting. These measurements provide a mesoscopic confirmation of the melting scenario of Castaing and Nozieres, and explain the long delay before the instability sets in: The magnetization gradient in the liquid leads to an initial suppression of the melting instability, in accordance with our extension of the stability analysis of Puech et al. This resolves the discrepancy between theory and experiment.

Journal Article↗

PubMed2000

4'-Hydroxy aceclofenac suppresses the interleukin-1-induced production of promatrix metalloproteinases and release of sulfated-glycosaminoglycans from rabbit articular chondrocytes.

This study demonstrates the novel actions of a non-steroidal anti-inflammatory drug aceclofenac, which is frequently used for rheumatoid arthritis and osteoarthritis. 4'-Hydroxy aceclofenac, a main metabolite of aceclofenac in humans, down-regulated the production of promatrix metalloproteinase-1/procollagenase 1 and promatrix metalloproteinase-3/prostromelysin 1 along with a decrease in their mRNAs in rabbit articular chondrocytes and synoviocytes, and interfered with the release of sulfated-glycosaminoglycans (proteoglycans) from the chondrocytes. 4'-Hydroxy aceclofenac also suppressed the proliferation of rabbit synoviocytes. In contrast, aceclofenac itself and its other metabolites, diclofenac and 4'-hydroxy declofenac, did not exert obvious actions on cellular functions. Therefore, it is suggested that the therapeutic effects of aceclofenac on rheumatoid arthritis and osteoarthrits are, at least in part, due to the novel chondroprotective effect of 4'-hydroxy aceclofenac via the suppression of promatrix metalloproteinase production and proteoglycan release. There is also evidence that inhibition of synoviocyte proliferation and the known inhibitory action on prostaglandin E(2) production play a role.

Animals↗

PubMed2000

High-precision measurement of the left-right Z Boson cross-section asymmetry.

We present a measurement of the left-right cross-section asymmetry ( A(LR)) for Z boson production by e(+)e(-) collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider during the period 1996-1998. Using a sample of 383 487 Z decays collected during the 1996-1998 runs we measure the pole value of the asymmetry, A(0)(LR), to be 0.150 56+/-0.002 39 which is equivalent to an effective weak mixing angle of sin (2)straight theta(eff)(W) = 0.231 07+/-0.000 30. Our result for the complete 1992-1998 data set comprising approximately 537 000 Z decays is sin (2)straight theta(eff)(W) = 0.230 97+/-0.000 27.

Journal Article↗

PubMed2000

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Journal Article↗

PubMed2000

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions.

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

Journal Article↗

PubMed2000

A strong source of methyl chloride to the atmosphere from tropical coastal land.

Methyl chloride (CH3Cl), the most abundant halocarbon in the atmosphere, has received much attention as a natural source of chlorine atoms in the stratosphere. The annual global flux of CH3Cl has been estimated to be around 3.5 Tg on the grounds that this must balance the loss through reaction with OH radicals (which gives a lifetime for atmospheric CH3Cl of 1.5 yr). The most likely main source of methyl chloride has been thought to be oceanic emission, with biomass burning the second largest source. But recent seawater measurements indicate that oceanic fluxes cannot account for more than 12% of the estimated global flux of CH3Cl, raising the question of where the remainder comes from. Here we report evidence of significant CH3Cl emission from warm coastal land, particularly from tropical islands. This conclusion is based on a global monitoring study and spot measurements, which show enhancement of atmospheric CH3Cl in the tropics, a close correlation between CH3Cl concentrations and those of biogenic compounds emitted by terrestrial plants, and OH-linked seasonality of CH3Cl concentrations in middle and high latitudes. A strong, equatorially located source of this nature would explain why the distribution of CH3Cl is uniform between the Northern and Southern hemispheres, despite their differences in ocean and land area.

Arctic Regions↗

PubMed2000

Cerebral ischemic hypoxia: discrepancy between apparent diffusion coefficients and histologic changes in rats.

PURPOSE: To compare the apparent diffusion coefficients (ADCs) and histologic changes in young rats subjected to cerebral ischemic hypoxia (IH). MATERIALS AND METHODS: Fifteen 3-week-old rats were subjected to a 30-minute IH insult (unilateral common carotid arterial ligation and exposure to 8% oxygen) and were examined at diffusion-weighted magnetic resonance imaging and light and electron microscopy on cessation of the insult (n = 5), 60 minutes after resuscitation (n = 5), or 48 hours after resuscitation (n = 5). Twelve control rats either underwent unilateral common carotid arterial ligation or were subjected to hypoxia. RESULTS: The experimental rats showed primary ADC reduction during the insult, transient ADC recovery after resuscitation, and secondary ADC reduction 48 hours after the insult. Histologic examination revealed dendritic swelling and mild swelling of the perivascular astrocytic end-feet during the primary ADC reduction phase, dark neurons and pronounced swelling of the perivascular astrocytic end-feet during the transient ADC recovery phase, and severely retracted dark neurons and extensive swelling of the astrocytic end-feet during the secondary ADC reduction phase. CONCLUSION: Transient ADC normalization after cerebral IH does not necessarily mean that histologic normalization has occurred. The transient ADC recovery phase appeared to have limited potential for neuronal salvage.

Animals↗

PubMed2000

Non-glutamate type pyrrolo[2,3-d]pyrimidine antifolates. III. Synthesis and biological properties of N(omega)-masked ornithine analogs.

The glutamic acid moiety of N-[4-[3-(2,4-diamino-7H-pyrrolo[2,3-d]pyrimidin-5-yl)propyl]benzoyl]-L-g lutamic acid (1b, TNP-351) and the related compound (1a), was replaced with various N(omega)-acyl-, sulfonyl-, carbamoyl- and aryl-2,omega-diaminoalkanoic acids, and the inhibitory effects of the resulting products (9, 11, 14, 18, 21, 23, 25, 30, 36) on dihydrofolate reductase (DHFR), the growth of murine fibrosarcoma Meth A cells, and methotrexate-resistant human CCRF-CEM cells, were examined. Compounds (9a-f) acylated with a hemiphthaloyl group were efficiently synthesized by coupling pyrrolo[2,3-d]pyrimidine carboxylic acids (7a,b) and N(omega)-phthaloyl 2,omega-diaminoalkanoic acid methyl esters (6a-c) and subsequent hydrolysis. The other N(omega)-acyl- and sulfonyl-ornithine analogs (21, 23, 25) were synthesized by acylation of free amino intermediates (19a,b) derived from tert-butoxycarbonyl-ornithine analogs (17a,b). A free ornithine analog (18) did not strongly inhibit Meth A cell growth, whereas all N(omega)-acyl-, sulfonyl-, carbamoyl- and aryl-ornithine analogs (9, 11, 21, 23, 25, 30, 36) exhibited much more potent inhibitory activities against both DHFR and Meth A cell growth. In particular, compounds 9c, 21k and 36a also showed remarkable growth-inhibitory activities against methotrexate-resistant CCRF-CEM cells. These results demonstrate that the potent inhibitory activities of N(omega)-masked ornithine analogs against the growth of Meth A cells and methotrexate-resistant CCRF-CEM cells, results from effective uptake via reduced folate carrier and their potent DHFR inhibition.

Cell Division↗

PubMed2000

Molecular cloning and sequence analysis of an endoinulinase gene from Penicillium sp. strain TN-88.

A genomic DNA segment and cDNAs encoding an extracellular endoinulinase of Penicillium sp. strain TN-88 were cloned and sequenced. Southern blot analysis indicated that the endoinulinase gene (inuC) was present as a single copy in the genome. An open reading frame, consisting of 1,545 bp, was not interrupted by introns, and it encoded a 25 amino acid signal peptide and a 490 amino acid mature protein. The mature protein contained three Cys residues and ten potential N-linked glycosylation sites. Three distinct transcriptional start points were observed at positions -242 (A), -215 (A), and -75 (C) from the start codon. The 5'-noncoding region had a putative TATA box at position -120 (TATATATA) and two contiguous CAAT sequences at -159 to -151. The deduced amino acid sequence showed 72 and 85% identities with those of Aspergillus niger and Penicillium purpurogenum endoinulinase genes, respectively. A neighbor-joining tree showed that fungal endoinulinases form a distinct cluster from other members of the beta-fructofuranosidase superfamily and that they are more closely related to bacterial levanases than to a fungal fructosyltransferase, yeast invertases, or a yeast exoinulinase.

3' Untranslated Regions↗

PubMed2000

Histopathologic correlates of temporal diffusion changes in a rat model of cerebral hypoxia/ischemia.

BACKGROUND AND PURPOSE: Although diffusion-weighted MR imaging is a powerful tool for evaluating brain ischemia, histopathologic correlates of temporal diffusion changes in cerebral hypoxia/ischemia have not been extensively examined. Diffusion-weighted MR imaging was used to evaluate the relationship between the time course of apparent diffusion coefficient (ADC) changes and the histopathologic findings in cerebral hypoxia/ischemia. METHODS: Thirty 3-week-old rats were subjected to either a 15-, 30-, or 60-minute hypoxic/ischemic insult (unilateral common carotid artery ligation and exposure to 8% oxygen), during and after which diffusion- and T2-weighted MR imaging was performed. Each animal was killed 48 hours or 6 hours after the insult, and fixed sections of the parietal cortex were examined by light microscopy. Ten other (control) rats were subjected to only unilateral common carotid artery ligation or hypoxia. RESULTS: The experimental rats showed three patterns of ADC change, depending on the duration of the hypoxic/ischemic insult: transient (15-minute), biphasic (15-, 30-, or 60-minute), and persistent (60-minute) ADC reduction patterns. The transient ADC reduction pattern (reduction during the insult and recovery after resuscitation) was associated with selective neuronal death. The biphasic and persistent ADC reduction patterns (transient recovery and no recovery after resuscitation, respectively) were associated with cerebral infarction. CONCLUSION: Different temporal patterns of ADC change are associated with different histopathologic findings. Although the clinical manifestations of these different histopathologic presentations are not yet defined, this study indicates that sequential diffusion studies are a potentially powerful tool in the evaluation of hypoxic/ischemic brain injury.

Animals↗

PubMed2000

[The possible role of adhesion molecule, alpha 3 integrin, in the synthesis of intracrescentic extracellular matrix in accelerated anti-GBM nephritis].

Studies were performed on the behavior of crescent-composing cells of crescent glomerulonephritis induced by the injection of anti-GBM antibody to WKY rats. alpha 3 integrin, podocalyxin and ED1 were stained immunohistochemically as markers of parietal, visceral epithelial cells, and macrophages, respectively. Cellular fibronectin (cFn) and type I collagen were also stained in the same manner. Fluoresceine- and Rhodamine-conjugated IgGs were used as second antibodies for double staining to show the geographic relation of the two target molecules. Morphological examinations were performed at day 7, 14 and 28 after disease induction. Periodic acid-methenamine-silver (PAM) and Azan staining showed time-dependent increase in extension and cellularity. PAM-positive intracrescentic fibers were likewise increased, which was related to an increased frequency of ruptured capsules. Intracrescentic cFn increasing in parallel with PAM-positive fibers and type I collagen, was remarkably stained at day 28. Intracrescentic ED1-positive cells showed also a significant increase at day 28. Podocalyxin was not stained in the crescent, while ED1 and alpha 3 integrin were remarkably stained. Double staining showed apposition of cFn and alpha 3 integrin, indicating close contact of these molecules, but such apposition was not observed between ED1 and cFn. These findings indicate that ED1 and alpha 3 integrin--(possibly visceral cell derived) positive cells occupy significant cellular components of the crescent and that the latter plays a part in synthesis of the intracrescentic extracellular matrix.

Animals↗

PubMed2000

Cerebral blood flow, vascular response and metabolism in patients with MELAS syndrome--xenon CT and PET study.

UNLABELLED: Two patients with MELAS syndrome underwent serial measurement of cerebral blood flow (CBF) with xenon CT while they were presenting stroke like episodes accompanying cerebral lesion detectable with CT. One of them underwent PET measurement of regional cerebral metabolic rate of oxygen (CMRO2) and glucose (CMRGlu) after his symptoms and lesion disappeared. METHODS: The xenon CT CBF study was performed by 4 min wash-in and 3 min wash-out protocol with serial measurement of endexpiratory concentration of xenon gas. The CBF after acetazolamide loading was also quantified in one of them. The PET study was performed to quantify CBF, CMRO2, oxygen extraction fraction (OEF) and cerebral blood volume (CBV) by continuous inhalation of O-15 labeled gases and arterial blood sampling. The PET measurement of CMRGlu was performed by i.v. injection of F-18 FDG and arterial blood sampling. RESULTS: 1) During the symptomatic period, Xe-CBF was normal or slightly increased both in and outside the low density lesion. 2) The CBF response to acetazolamide loading was well preserved both in and outside the low density lesions. 3) After the neurological symptoms and low density lesions disappeared, Xe-CBF pattern and vascular response was the same as during the symptomatic period. 4) In the PET study, normal or slightly increased PET-CBF, increased CMRGlu and markedly decreased CMRO2 in comparison to normal control was noted resulting in a marked decrease in OEF and CMRO2/CMRGlu ratio, a characteristic metabolic pattern for MELAS. CONCLUSION: In the present cases, resting CBF and vasomotor reactivity was well preserved both in symptomatic and remission period. On the contrary, abnormal metabolic pattern was noted. The stroke like episode of the present patients is more likely attributed to metabolic failure than vascular accident.

Adult↗

PubMed2000

[Recent surgical treatment for patients with true aortic arch aneurysm].

From december 1996 to april 1999, 25 patients with true aortic arch aneurysm underwent aortic arch aneurysm repair using selective cerebral perfusion. There were 17 males and 8 females ranging in age from 62 to 79 years (mean 71 years). Orikaesi method was used in the procedure of distal anastomosis for complete aortic arch replacement with a prosthetic graft. This technique allowed us a simple approach to the lesion and the easy additional stitch. The average duration of extracorporeal circulation, aortic crossclamping, selective cerebral perfusion were 269 minutes, 140 minutes, and 122 minutes, respectively, under 19.3 degrees C of lowest esophageal temperature. There were no cases complicated with postoperative low output syndrome and cerebrovascular accident, and no hospital mortality. Replacement of the aortic arch using selective cerebral perfusion is a safe procedure with acceptable hospital mortality.

Aged↗

PubMed2000

[The effect of exogenous nitric oxide on endothelial dysfunction in two-kidney, one-clip renovascular hypertensive rats].

Previous studies have shown that hypertension causes endothelial dysfunction. To study the influence of exogenous nitric oxide(NO) on endothelial dysfunction produced by hypertension, we administered a non-depressor dose of nipradilol to two-kidney, one-clip renovascular hypertensive rats(2K1C). Sprague-Dawley rats underwent either sham surgery(G-1) or clipping of the left renal artery. From day seven, 2K1C were randomized into 3 groups, placebo treatment(G-2), nipradilol treatment(G-3,) and propranolol treatment(G-4). Urinary NO2- + NO3-(NOx) excretion (UNOx V) was measured 4 weeks after clipping, and then, acetylcholine(Ach), A23187, or sodium nitroprusside(SNP)-induced relaxation were measured in the aorta. Blood pressure was increased in G-2, G-3, and G-4 compared to G-1. UNOx V was lower in G-2, G-3, and G-4 compared to G-1, but UNOx V was higher in G-3 compared to G-2 and G-4. Although Ach or A23187-induced relaxation was significantly decreased in isolated artery from G-2, G-3, and G-4 compared with those from G-1. Ach- or A23187-induced relaxation was improved in G-3. SNP-induced relaxation did not differ among the 4 groups. These results suggest that exogenous NO from nipradilol reduces the endothelial dysfunction caused by hypertension without changing the blood pressure.

Acetylcholine↗