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H Akimoto

Publications and source records attributed to H Akimoto.

At least 73 records · Page 4Linked to original sources
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

Time course of trace of diffusion tensor [Trace(D)] and histology in brain edema.

We examined the correlation between changes in the trace of diffusion tensor [Trace(D)], regional water content and tissue ultrastructure relating to cellular (cytotoxic) and vasogenic brain edema. Cellular edema was induced by left middle cerebral artery occlusion in cats (Kuroiwa T et al., 1998). Vasogenic edema was induced in the white matter of cats by a cold lesion (Kuroiwa T et al., 1999). In cellular edema, the water content increase correlated linearly with the Trace(D) decrease in both the gray and white matter. However, both the slopes and intercepts of the correlation lines were significantly different. Hydropic astrocytic swelling was seen in both structures, and in the white matter, oligodendrocytic and myelinated axonal swelling were observed. In vasogenic edema, the increase in Trace(D) showed a significant linear correlation with the increase in tissue water content. Histologically, nerve fibers were dissociated and the extracellular space was markedly enlarged with protein-rich fluid. These result showed that the different slopes and intercepts of the water content--Trace(D) correlation lines for different subtype of brain edema, which reflect different ultrastructural localization of water, should be taken into account when evaluating brain edema using Trace(D) mapping.

Animals↗
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↗
PubMed1999

Quantitative analysis of cardiac 3-L-nitrotyrosine during acute allograft rejection in an experimental heart transplantation.

BACKGROUND: Recent studies have shown that nitric oxide interacts with superoxide to form peroxynitrite, a potent oxidant that modifies cellular proteins producing 3-L-nitrotyrosine (N-Tyr). This study was designed to evaluate N-Tyr quantitatively with high-performance liquid chromatography (HPLC) during cardiac allograft rejection. METHODS: Rat transplanted hearts (allogeneic or syngeneic grafts) were examined with HPLC analysis, immunohistochemistry for N-Tyr, and histological studies on 0, 1, 3, and 7 days after transplantation. RESULTS: No histological rejection was found in syngeneic grafts, or day 0 or 1 allografts. HPLC demonstrated that N-Tyr in allografts increased on day 1 and continued to increase through day 7, while N-Tyr was not detected in any syngeneic grafts. Immunostaining of the allografts did not show N-Tyr on day 1. CONCLUSION: These results demonstrate that N-Tyr shows a time-dependent accumulation in cardiac allografts during acute rejection. N-Tyr detection using HPLC may be an useful maker for early diagnosis of acute rejection before pathological rejection occurs.

Acute Disease↗
PubMed1999

Transcriptional analysis of two endoinulinase genes inuA and inuB in Aspergillus niger and nucleotide sequences of their promoter regions.

Aspergillus niger 12 contained two copies of endoinulinase genes (inuA and inuB) in the genome (K. Ohta et al., Biosci. Biotechnol. Biochem., 62, 1731-1738, 1998). The inuA- and inuB-specific DNA probes were constructed according to the respective 3'-noncoding sequences that diverged from each other. Poly(A)+ RNA was prepared from mycelia grown on inulin, fructose, or glucose in submerged culture. Three endoinulinase cDNA sequences that corresponded to the coding regions and their 5'- and 3'-flanking regions were obtained by reverse transcription and subsequent polymerase chain reaction. Southern blot analysis revealed that the amplified cDNA 3'-noncoding sequences hybridized to the inuB probe but not to the inuA probe, regardless of the carbon source. The data suggest that only the inuB gene was transcribed constitutively. Four distinct 5' ends of the transcripts were observed at positions -80(A), -72(G), -69(A), and -65(A) from the start codon. The inuB mRNAs were polyadenylated at various sites between 94 and 297 bp downstream of the stop codon. We have determined the nucleotide sequences of the 1201- and 1017-bp 5'-noncoding regions of the inuA and inuB genes, respectively. The inuB promoter region included a putative TATA box at -116 (TATATA).

Journal Article↗
PubMed1999

Moyamoya disease: evaluation with diffusion-weighted and perfusion echo-planar MR imaging.

PURPOSE: To determine the clinical efficacy of diffusion-weighted and perfusion echo-planar magnetic resonance (MR) imaging in the evaluation of moyamoya disease. MATERIALS AND METHODS: Seventeen patients with moyamoya disease were examined prospectively with diffusion-weighted and perfusion echo-planar MR imaging and conventional angiography. The change in the effective transverse relaxation rate (delta R2*) peak value, delta R2* peak time, and delta R2* integral were calculated to assess regional cerebral perfusion. The MR images were compared with angiographic images. RESULTS: Of the 34 posterior cerebral arteries (PCAs) of the 17 patients, 14 PCAs (41%) in 11 patients showed stenosis or occlusion. The delta R2* peak value ratio in the cerebral hemispheres decreased significantly, and the delta R2* peak time ratio increased significantly, with PCA stenosis and occlusion. However, no correlation was apparent between perfusion and extent of the stenotic or occlusive lesions of the internal carotid artery bifurcation. The frequency of cerebral infarctions was significantly increased in patients with stenotic or occlusive PCA lesions. For three acute infarctions, a decrease in the apparent diffusion coefficient was significantly correlated with a decrease in the delta R2* peak value, an increase in the delta R2* peak time, and a decrease in the delta R2* integral. CONCLUSION: Regional cerebral perfusion in moyamoya disease is decreased and delayed with PCA stenosis, with greater decrease and delay with PCA occlusion. Diffusion-weighted and perfusion imaging are useful for evaluating cerebral ischemia in moyamoya disease.

Adult↗
PubMed1999

Correlations between the apparent diffusion coefficient, water content, and ultrastructure after induction of vasogenic brain edema in cats.

OBJECT: The authors examined the correlation between changes in the apparent diffusion coefficient, regional water content, and tissue ultrastructure after vasogenic brain edema. METHODS: Vasogenic edema was induced in the white matter of six cats by cortical cold lesioning. The trace of diffusion tensor (Trace[D]) obtained from magnetic resonance imaging to measure the orientationally averaged water diffusibility was compared with the corresponding tissue water content determined by gravimetric studies and with ultrastructural water localization. Edema fluid had spread to the subcortical and deep white matter by 4.5 hours postlesioning. The increase in Trace(D) showed a significant linear correlation with the increase in tissue water content, both in the subcortical and deep white matter as follows: y = 45.5x - 2367 (r = 0.94) and y = 37.0x - 1769 (r = 0.93), respectively, where x is the water content (gram water/gram tissue) and y the Trace(D) (x 10(-6) mm2/second). On histological examination, nerve fibers were found to be dissociated in the white matter and the extracellular space was markedly enlarged with protein-rich fluid. No noticeable hydropic swelling of the cellular components was observed. CONCLUSIONS: A linear correlation was observed between increases in Trace(D) and increases in extracellular water volume in in vivo vasogenic brain edema. A similar correlation between the subcortical and deep white matter showing different arrangements of nerve fibers (parallel compared with intermingled, respectively) indicated that measurement of Trace(D) is a suitable parameter for the evaluation of vasogenic brain edema.

Animals↗
PubMed1999

Circulating levels of beta-chemokines in systemic lupus erythematosus.

OBJECTIVE: Recent evidence suggests the role of beta-chemokines and their receptors in human immunodeficiency virus infection. We examined the serum levels of beta-chemokines in patients with systemic lupus erythematosus (SLE). METHODS: The serum levels of beta-chemokines, macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, RANTES, and monocyte chemoattractant protein-1 (MCP-1) in patients with SLE were determined by ELISA. RESULTS: There were significant differences between the patients with SLE and healthy controls in the serum concentrations of RANTES (p < 0.001) and MCP-1 (p < 0.01), but not MIP-1alpha (p = 0.07) and MIP-1beta (p = 0.68). A decrease of RANTES and an increase of MCP-1 was observed with the progression of disease activity in the patients with SLE. CONCLUSION: Changes in the serum levels of RANTES and MCP-1 may indicate an interaction between SLE disease activity and the production of beta-chemokines.

Adolescent↗