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Biomedical subjects

K Nakajima

Publications and source records attributed to K Nakajima.

At least 73 records · Page 4Linked to original sources
PubMed2002

Dominance of the excitation continuum in the longitudinal spectrum of weakly coupled Heisenberg S=1/2 chains.

A low-field spin-flop transition in the quasi-one-dimensional antiferromagnet BaCu2Si2O7 is exploited to study the polarization dependence of low-energy magnetic excitations. The measured longitudinal spectrum is best described as a single broad continuum, with no sharp "longitudinal mode," in apparent contradiction with the commonly used chain-mean-field and random phase approximation (MF/RPA) theories. The observed behavior is also quite different than that previously seen in the related KCuF3 material, presumably due to a large difference in the relative strength of interchain interactions. The results highlight the limitations of the chain-MF/RPA approach.

Journal Article↗
PubMed2002

Genetic relatedness among Japanese, American and European isolates of viral hemorrhagic septicemia virus (VHSV) based on partial G and P genes.

Molecular virological analyses of 8 Japanese VHSV (viral hemorrhagic septicemia virus) isolates from wild and farmed Japanese flounder Paralichthys olivaceus were performed to investigate their genetic relatedness to American and European isolates of VHSV. Phylogenetic analyses based on the partial nucleotide sequences of G and P genes revealed that there are 2 genogroups of VHSV in Japan. The first one represented by the Obama25 isolate is closely related to the American isolates (Genogroup I) while the other, the KRRV9601 isolate, is closely related to the traditional European isolates (Genogroup III). The 2 types of Japanese VHSV showed differences in the relative mobility of the G protein and intensity of the antibody reaction on the P and M proteins. The Obama25 type of VHSV is widely distributed as a native virus in the coastal areas of western Japan and has been responsible for the occurrence of VHSV infection in farmed Japanese flounder while the KRRV9601 isolate is considered to have been introduced from a foreign country.

Animals↗
PubMed2002

Mechanisms responsible for recurrent gastroesophageal reflux in neurologically impaired children who underwent laparoscopic Nissen fundoplication.

BACKGROUND: In this study, we attempted to define the lower esophageal sphincter (LES) motor events associated with the occurrence of gastroesophageal reflux (GER) in neurologically impaired children in whom of GER disease recurred after laparoscopic Nissen fundoplication (LNF). METHODS: Of 45 neurologically impaired children who had previously undergone LNF, six children in whom recurrence of GER disease was documented by 24-h esophageal pH monitoring were studied. Concurrent esophageal manometry and pH monitoring were conducted for 1 h both before and after the administration of apple juice (10 ml/kg). RESULTS: A total of 89 reflux episodes were recorded in the course of the study. Of these, 51 episodes (57%) were associated with transient LES relaxation. In the remainder, reflux occurred across a contracted LES in 21 episodes (24%) and during absent basal LES tone in 15 episodes (17%). In four of six patients, transient LES relaxation was responsible for more than half of the reflux episodes. CONCLUSION: Transient LES relaxation is the predominant mechanism of reflux in neurologically impaired children with recurrent GER after LNF.

Child↗
PubMed2002

Bond-stretching-phonon anomalies in stripe-ordered La1.69Sr0.31NiO4.

We report a neutron scattering study of bond-stretching phonons in La1.69Sr0.31NiO4, a doped antiferromagnet in which the added holes order in diagonal stripes at 45 to the Ni-O bonds. For the highest-energy longitudinal optical mode along the bonds, a softening of 20% is observed between the Brillouin zone center and the zone boundary. At 45 to the bonds, a splitting of the same magnitude is found across much of the zone. Surprisingly, the charge-ordering wave vector plays no apparent role in the anomalous dispersions. The implications for related anomalies in the cuprates are discussed.

Journal Article↗
PubMed2002

Urinary excretion of selegiline N-oxide, a new indicator for selegiline administration in man.

1. The metabolism of selegiline (SG) has been studied by investigating the time-course of urinary excretion of SG and its metabolites using high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI MS) in combination with solid-phase extraction. 2. The excretion profiles of SG and its four major metabolites, selegiline-N-oxide (SGO), N-desmethylselegiline (DM-SG), methamphetamine (MA) and amphetamine (AP), were investigated in six healthy volunteers after oral administrations of SG hydrochloride in a single dose of 2.5 or 7.5mg, and a repeat twice-daily dose of 5.0 mg day(-1) (for 3 days). 3. The cumulative amount of SGO excreted within approximately the first 8-12h was comparable with MA, and the amount in the first 72 h was 2.0-7.8 times larger (2.8-13.2% of the dose) than that of DM-SG. 4. These results demonstrate that SGO can be used in place of DM-SG, which is known to be a main specific metabolite of SG, as a new indicator for the discrimination of SG use compared with MA abuse.

Adrenergic Uptake Inhibitors↗
PubMed2002

A new method for measuring dynamic change of tracer distribution using dynamic single photon emission tomography with a slip-ring rotational gamma camera.

The clinical applicability of dynamic single photon emission tomograpy (SPET) using a dual-head gamma camera equipped with a slip-ring rotational mechanism, referred to as serial SPET, was examined in the present investigation. Serial SPET enables the production of tomographic images for any arbitrary time frame from an arbitrary range of data to 360 degrees. In a pre-clinical evaluation, a correlation between radioactivity concentration and serial SPET counts was evaluated in a phantom with continuous changes in 99mTc concentration. A differential value was obtained from each pair of SPET images; moreover, moving average approximation processing was investigated with respect to the elimination of noise in the data. In 11 and one patient presenting with cerebrovascular disease and meningioma, respectively, changes in SPET counts were evaluated when 99mTc ethyl cysteinate dimer (99mTc-ECD) was continuously administered at a constant rate in the resting state. Furthermore, in six of 11 subjects with cerebrovascular disease, changes occurring in SPET counts were examined by using acetazolamide loading while continuously administering 99mTc-ECD at a constant rate. Consequently, serial SPET enabled the evaluation of changes in radioactivity concentration over time in both the phantom and preliminary clinical studies. Data analysis by differential processing utilizing moving average approximation processing enabled the detection of minor changes in radioactivity concentration. An increase of 15.1+/-5.4% was observed in SPET counts of the unaffected cerebral hemisphere with acetazolamide loading. The response of the affected hemisphere was less prominent. These findings suggest that serial SPET would be an effective technique for the pharmacokinetic analysis of radiopharmaceuticals.

Acetazolamide↗
PubMed2002

Analysis of the desialidation process of the haemagglutinin protein of influenza B virus: the host-dependent desialidation step.

It was reported previously that haemadsorption by the haemagglutinin (HA) protein of influenza B virus required that the protein must undergo desialidation. When MDCK and COS cells were infected with influenza B/Kanagawa/73 virus in the presence of a neuraminidase (NA) inhibitor, Zanamivir, haemadsorption on MDCK cells was inhibited but that on COS cells was not. The activity of the NA protein of the two types of infected cells was similar and both were inhibited by Zanamivir in a dose-dependent manner. A comparison of the desialidation of the HA protein was made on MDCK and COS cells in the presence of bacterial NA and both cells were found to have similar sensitivity. On the accumulation of the HA and NA proteins in the trans-Golgi network of MDCK cells by means of low-temperature treatment, desialidation of the HA protein in the presence of Zanamivir was detected by two-dimensional gel electrophoresis. Because this agent was reported to be unable to penetrate cells, these data suggest that, in MDCK cells, desialidation of the HA protein occurs on the cell surface but, in COS cells, the HA and NA proteins might accumulate in the trans-Golgi network, thus allowing NA desialidation before their migration to the cell surface.

Animals↗
PubMed2002

Acetazolamide vasoreactivity in vascular dementia and persistent vegetative state evaluated by transcranial harmonic perfusion imaging and Doppler sonography.

To clarify the pathophysiological differences of the cerebrovascular reserve capacity in relation to cerebral cognitive impairments between vascular dementia (VaD) and persistent vegetative state (PVS), we evaluated acetazolamide (ACZ) vasoreactivity testing by transcranial harmonic perfusion imaging (HPI) and Doppler sonography (TCD). Sixteen patients (age: 29-85 years; mean: 62) were divided into three groups: 7 VaD, 4 PVS, and 5 nondementia patients. Mean velocity (Vm) in the middle and posterior cerebral artery (MCA, PCA) was measured, and time-intensity curves of the HPI were evaluated at three regions of interest-the bilateral temporal lobe (TL), basal ganglia (BG), and thalamus (Th). TCD and HPI were evaluated before (resting state) and after ACZ administration, and vasoreactivity was compared among the three groups in terms of resting values and relative changes (%Delta) of Vm, peak intensity (PI), area under curve (AUC), and mean transit time (MTT). Results of the resting state: Decreased Vm, PI, and AUC of the VaD and PVS groups were more obvious in the right side. Results of vasoreactivity: In the PVS group, %DeltaVm decreased in the left PCA and MCA; %DeltaPI and %DeltaAUC decreased in the left TL and bilateral BG. In the VaD group, %DeltaPI and %DeltaAUC decreased in the right TL; %DeltaMTT tended to increase in the left side. ACZ vasoreactivity tests by transcranial HPI and TCD allowed bedside, noninvasive quantitative evaluation of the pathophysiology of cognitive function impairment in relation to cerebrovascular reserve capacity in VaD and PVS.

Acetazolamide↗
PubMed2002

Acute renal failure and hearing loss due to sodium bromate poisoning: a case report and review of the literature.

Acute renal failure with hearing loss due to sodium bromate intoxication is described. A 48-year-old woman who ingested permanent wave neutralizer in a suicide attempt and developed anuria was admitted to our hospital for hemodialysis. Bromate intoxication was suspected and hemodialysis was carried out; she required maintenance dialysis 3 times a week. Irreversible severe sensorineural hearing loss continued and peripheral polyneuropathy developed in the lower limbs. We measured the concentration of bromine in the serum before and after the first hemodialysis and found its removal rate to be 61.3%. This is the first report that proved the utility of hemodialysis for bromate intoxication in a clinical setting.

Acute Kidney Injury↗
PubMed2001

Cloning and sequencing of the beta-glucosidase gene from Acetobacter xylinum ATCC 23769.

The beta-glucosidase gene (bglxA) was cloned from the genomic DNA of Acetobacter xylinum ATCC 23769 and its nucleotide sequence (2200 bp) was determined. This bglxA gene was present downstream of the cellulose synthase operon and coded for a polypeptide of molecular mass 79 kDa. The overexpression of the beta-glucosidase in A. xylinum caused a tenfold increase in activity compared to the wild-type strain. In addition, the action pattern of the enzyme was identified as G3ase activity. The deduced amino acid sequence of the bglxA gene showed 72.3%, 49.6%, and 45.1% identity with the beta-glucosidases from A. xylinum subsp. sucrofermentans, Cellvibrio gilvus, and Mycobacterium tuberculosis, respectively. Based on amino acid sequence similarities, the beta-glucosidase (BglxA) was assigned to family 3 of the glycosyl hydrolases.

Amino Acid Sequence↗
PubMed2001

Observation of plasma focusing of a 28.5 GeV positron beam.

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0+/-0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

Journal Article↗
PubMed2001

Risk factors for massive hemoptysis after endobronchial brachytherapy in patients with tracheobronchial malignancies.

BACKGROUND: Massive and mostly fatal hemoptysis is a frequently reported morbidity after endobronchial brachytherapy (EBB) for tracheobronchial malignancies. However, to the authors' knowledge, it remains controversial whether this morbidity is related directly to EBB. To investigate whether massive hemoptysis is related to EBB, the authors retrospectively analyzed risk factors for massive hemoptysis after EBB. METHODS: Thirty-six patients (30 men and 6 women) with a mean age of 70 years underwent high-dose rate EBB for tracheobronchial malignancy using a cobolt-60 (Co-60) afterloading machine. EBB was performed as primary therapy in 6 patients and as salvage treatment for recurrent disease in 30 patients. EBB was delivered to the tracheal lesions in 15 patients and to the main bronchial lesions in 21 patients. EBB was combined with external beam radiation therapy (EBRT) in 24 patients, with laser photocoagulation in 3 patients, and with EBRT plus laser photocoagulation in 5 patients. The dose of EBRT delivered with the EBB ranged from 16-69 grays (Gy), with a mean dose of 37 Gy. RESULTS: At a mean follow-up of 18 months, 33 of the 36 patients had died. Eight of the 33 patients had no evidence of local disease at the time of death. Seven patients died of massive hemoptysis. The cumulative rate of massive hemoptysis was 29.4% at 2 years. According to univariate analysis, no statistically significant correlation with massive hemoptysis was observed for EBRT dose delivered in combination with EBB, EBB fractional and total doses, EBB length, and the sum of all the EBRT doses including that used for the initial treatment. Local failure or persistent malignancy (P = 0.033) and delivery of laser photocoagulation (P = 0.032) were found to be statistically significantly associated with massive hemoptysis. Direct contact between the EBB applicator and the tracheobronchial walls at the vicinity of the great vessels was observed in 16 patients and was found to be statistically significantly associated with massive hemoptysis (P = 0.003). In six patients, the applicator was in direct contact with two or more tracheobronchial walls at the vicinity of the great vessels; all these patients died of massive hemoptysis. CONCLUSIONS: Direct contact between the EBB applicator and the tracheobronchial walls at the vicinity of the great vessels was one of the significant risk factors for massive hemoptysis. To prevent massive hemoptysis, a specific spacer should be employed to maintain a safe distance between the applicator and the bronchial wall.

Aged↗
PubMed2001

Successful laparoscopic fundoplication in children with ventriculoperitoneal shunts.

We reported successful laparoscopic fundoplication in 2 pediatric cases with VPS and discuss the safety and feasibility of the procedure. Case 1: A 13-year-old girl with VPS underwent laparoscopic fundoplication. Case 2: a 9-year-old boy with VPS underwent laparoscopic fundoplication. In both cases, laparoscopic Nissen fundoplication was performed with a standard five-port technique with a low pressure of a pneumoperitoneum. The VPS system had no effect on port layout and intraabdominal manipulation and no adverse complications were observed in either case. The effect of a pneumoperitoneum in the VPS system remains controversial, however, the author emphasized that advanced laparoscopic surgery can be performed safely with creating a low pressure of a pneumoperitoneum.

Adolescent↗
PubMed2001

GDNF is a major component of trophic activity in DA-depleted striatum for survival and neurite extension of DAergic neurons.

Extracts from dopamine (DA)-depleted striatal tissue (lesion extract) and from intact striatal tissue (intact extract) were prepared, and trophic activities in these extracts were evaluated using survival and neurite extension of DAergic neurons as indices. Levels of brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (bFGF), glial cell-line derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) in extracts were measured using enzyme-linked immunosorbent assay (ELISA). The lesion extract exhibited a stronger trophic activity on survival and neurite extension of DAergic neurons than intact extract. In lesion extract, bFGF was slightly and GDNF was significantly increased, while BDNF and NT-3 were the same level in each extract. The peak increase of bFGF and GDNF was during 2 to 3 weeks after DA depletion. Trophic activity of extract was strongly attenuated after immunoprecipitation of GDNF and partly attenuated after immunoprecipitation of bFGF. In parallel immunohistological study, no significant variations were found for striatal microtubule-associated protein-2 (MAP-2)- nor OX-41-immunoreactive cells, while the number of strongly labeled glial fibrillary acidic protein (GFAP)-immunoreactive cells were increased in DA-depleted striatum, suggesting reactive gliosis. Data suggest that bFGF is a minor, while GDNF is a major component of trophic activity for DAergic neurons in DA-depleted striatum, and increased bFGF and GDNF levels may be mediated partly by reactive gliosis.

Animals↗
PubMed2001

Polyvalent cation-sensing mechanism increased Na(+)-independent Mg(2+) transport in renal epithelial cells.

Extracellular Ca(2+)/polyvalent cation-sensing receptor (CaSR) is capable of monitoring changes in extracellular polyvalent cation concentrations. In the present study, we investigated whether CaSR agonists reinforce the decrease of intracellular free Mg(2+) concentration ([Mg(2+)](i)) induced by extracellular Mg(2+) plus Na(+) removal. Interestingly, exposure of NRK-52E renal epithelial cells to increasing extracellular Mg(2+) concentrations from 0.8 to 15 mM for 1-2 days resulted in a twofold increase in the levels of CaSR mRNA and protein. By fluorophotometer (with mag-fura 2 fluorescent dye) and atomic absorption spectrophotometer, we confirmed that activation of CaSR by neomycin (0.5 mM) or gadolinium (1 mM) reinforced the decrease of [Mg(2+)](i) induced by Mg(2+) removal in the cells cultured in 10 mM Mg(2+)-containing medium. The neomycin-induced [Mg(2+)](i) decrease was inhibited by nicardipine (50 microM), but not by verapamil (50 microM) or amiloride (0.1 mM). These results indicate that CaSR monitors extracellular Mg(2+) concentration, and probably cause activation of Na(+)-independent Mg(2+)-transport system.

Amiloride↗
PubMed2001

Intercellular movement of the putative transcription factor SHR in root patterning.

Positional information is pivotal for establishing developmental patterning in plants, but little is known about the underlying signalling mechanisms. The Arabidopsis root radial pattern is generated through stereotyped division of initial cells and the subsequent acquisition of cell fate. short-root (shr) mutants do not undergo the longitudinal cell division of the cortex/endodermis initial daughter cell, resulting in a single cell layer with only cortex attributes. Thus, SHR is necessary for both cell division and endodermis specification. SHR messenger RNA is found exclusively in the stele cells internal to the endodermis and cortex, indicating that it has a non-cell-autonomous mode of action. Here we show that the SHR protein, a putative transcription factor, moves from the stele to a single layer of adjacent cells, where it enters the nucleus. Ectopic expression of SHR driven by the promoter of the downstream gene SCARECROW (SCR) results in autocatalytic reinforcement of SHR signalling, producing altered cell fates and multiplication of cell layers. These results support a model in which SHR protein acts both as a signal from the stele and as an activator of endodermal cell fate and SCR-mediated cell division.

Arabidopsis↗
PubMed2001

Site-dependent effect of O-glycosylation on the conformation and biological activity of calcitonin.

We synthesized seven O-glycosylated calcitonin derivatives, each with a single GalNAc residue attached to either Ser or Thr, and studied their three-dimensional structure and biological activity to examine site-dependent effects of O-glycosylation. The CD spectra in an aqueous trifluoroethanol solution showed that the GalNAc attachment at Thr6 or Thr21 reduced the helical content of calcitonin, indicating that the O-glycosylated residue functions as a stronger helix breaker than the original amino acid residue. Only the GalNAc attachment at Ser2 or Thr21 retained the hypocalcemic activity of calcitonin. This result corresponded well to that of the calcitonin-receptor binding assay. The GalNAc attachment other than Ser2 or Thr21 perturbed the interaction with the receptor, resulting in the loss of the hypocalcemic activity. The biodistribution did not change much among the seven derivatives, but some site dependency could also be observed. Thus, we can conclude that the O-glycosylation affects both the conformation and biological activity in a site-dependent manner.

Acetylgalactosamine↗