Biomedical subjects

N Sakai

Publications and source records attributed to N Sakai.

At least 37 records · Page 2Linked to original sources

PubMed2003

Clinical and pathological features of children with Henoch-Schoenlein purpura nephritis: risk factors associated with poor prognosis.

OBJECTIVE: To clarify the risk factors related to prognosis in patients with Henoch-Schoenlein purpura nephritis (HSPN), we investigated the cases with HSPN on long-term observation. METHODS: We enrolled 114 patients who had been diagnosed with HSPN from 1974-1997. These patients were divided into 2 groups based upon features at last follow-up. One group, designated "favorable", consisted of 69 patients with normal urine and 25 patients with minor urinary abnormalities, and the second group, designated "unfavorable", consisted of 15 patients with active renal disease and 5 patients with renal failure. The clinical features, laboratory data and pathological findings were investigated in 2 groups. RESULTS: Nephrotic syndrome, decreased factor XIII activity, hypertension and renal failure at onset were more frequent in "unfavorable" than in "favorable". The rate of glomeruli with crescents, macrophage infiltrations, tubulointerstitial changes and acute exacerbation in "unfavorable" were higher than those in "favorable". There were 5 cases with renal insufficiency, and renal survival rate was 95.6% for over 15 years. CONCLUSIONS: These results suggest that the above mentioned risk factors play an important role in prognosis of the patients with active renal disease and renal failure.

Biopsy↗

PubMed2002

Failure of stent-assisted endovascular treatment for ruptured dissecting aneurysms of the basilar artery.

We report two instructive cases of ruptured dissecting aneurysm of the basilar artery. Although stent-assisted endovascular treatment was successful, recurrent bleeding occurred 4 h after the procedure in one patient, and the other's basilar artery occluded 6 days after the procedure. These cases suggest that the high porosity of currently available stents may be insufficient to induce intraluminal thrombosis and merely stenting may fail to prevent bleeding, while postoperative anticoagulation alone may be inadequate to prevent occlusion of the stented vessel.

Adult↗

PubMed2002

New type of vortex pinning structure effective at very high magnetic fields.

We report on a new type of correlated nanometer-scale pinning structure observed in a melt-processed (Nd0.33Eu0.38Gd0.28)Ba(2)Cu(3)O(y) (NEG-123). It consists of NEG/Ba-rich clusters in the stoichiometric NEG-123 matrix forming a lamellar array with a period of a few nanometers. These lamellas appear within regular twins, thus representing their fine substructure-sometimes straight, sometimes wavy. This new material structure correlates well with the significant enhancement of pinning at high fields, represented by irreversibility field above 14 T at 77 K (B parallel c). We believe that the new pinning medium enables one to significantly broaden the limits for high-field applications.

Journal Article↗

PubMed2002

A new neuromodulatory pathway with a glial contribution mediated via A(2a) adenosine receptors.

A low concentration (10 nM) of adenosine potentiated hippocampal neuronal activity via A(2a) adenosine receptors without affecting presynaptic glutamate release or postsynaptic glutamatergic conductance. Adenosine inhibited glutamate uptake through the glial glutamate transporter, GLT-1, via A(2a) adenosine receptors. In addition, adenosine stimulated GLT-1-independent glutamate release from astrocytes, possibly in response to a rise in intracellular Ca(2+), via A(2a) adenosine receptors involving PKA activation. Those adenosine actions could lead to an increase in synaptic glutamate concentrations responsible for the potentiation of hippocampal neuronal activity. The results of the present study thus represent a novel neuromodulatory pathway with a glial contribution, bearing both inhibition of GLT-1 function and stimulation of glial glutamate release, as mediated via A(2a) adenosine receptors.

Adenosine↗

PubMed2002

Mutation analysis of the acid ceramidase gene in Japanese patients with Farber disease.

Farber disease is a rare lysosomal storage disease, characterized by the accumulation of ceramide in tissues due to acid ceramidase deficiency. Here we report the identification of three novel mutations in the acid ceramidase gene from two Japanese patients. Patient 1 showed joint problems at around 10 months of age and the patient is now emaciated, with multiple nodules and mild neurological problems at 10 years of age. Patient 2 had consanguineous parents and showed joint contractures at around 8 months of age. He showed neurological symptoms around 2 years of age and died at 6 years owing to respiratory failure. The diagnosis was made clinically and was confirmed by enzymatic assay of acid ceramidase. Molecular analysis of cultured skin fibroblasts showed normal mRNA levels expressed in both patients. By direct sequencing of cDNA, missense mutations of V97E in exon 4 and G235R in exon 9 were detected in patient 1 and 96delV in exon 4 was homozygously identified in patient 2. These mutations were also confirmed in genomic DNA. Expression of mutated acid ceramidase cDNA in COS-1 cells showed acid ceramidase activity decreased to 35%, 2% and 37% of control value, respectively. We also found a new polymorphism V3691 in exon 14 in the allele from the mother of patient 1. To date, 13 mutations, including our newly identified mutations, have been reported. All these mutations were genetically private and genotype-phenotype correlations could not be made.

Animals↗

PubMed2002

Successfully treated case of cervical abscess and mediastinitis due to esophageal perforation after gastrointestinal endoscopy.

Perforations of the esophagus are uncommon complications of flexible gastrointestinal endoscopy. Perforations after endoscopy are likely to occur in the cervical esophagus, where fiber insertion is difficult anatomically. The diagnosis should be made as soon as possible, because mediastinitis and sepsis frequently develop following esophageal perforations. The surgical strategies are dependent on the location of the perforations and the condition of the patients. For a successful outcome, surgery is a preferred treatment for most perforation cases, and non-operative treatment, such as antibiotics, parental nutrition, and no food intake by mouth, should be applied carefully.

Abscess↗

PubMed2002

Ehlers-Danlos syndrome type IV with few extrathoracic findings: a newly recognized point mutation in the COL3A1 gene.

Ehlers-Danlos syndrome type IV (EDS IV) is caused by mutation within the COL3AI gene, resulting in the disorder of type III procollagen. The diagnosis is confirmed by demonstrating the synthesis of abnormal type III procollagen molecules from cultured dermal fibroblasts or by identifying the mutation in the COL3A1 gene. The authors report a case of EDS IV caused by a novel point mutation in the COL3A1 gene in a 16-yr-old female. Recurrent haemoptysis and cavitary formation of the lung were evidence of pulmonary involvement. However, extrathoracic manifestations of EDS IV were mostly absent. To the best of the authors' knowledge, all previously reported Ehlers-Danlos syndrome IV patients with respiratory disease had the characteristic findings or histories of Ehlers-Danlos syndrome IV. In the present case, connective tissue friability was suspected due to tissue laceration observed in the biopsied lung specimen, and the diagnosis was made beginning from this pivotal finding.

Adolescent↗

PubMed2001

p-octiphenyl beta-barrels with ion channel and esterase activity.

Design, synthesis, and esterase and ion channel activity of a novel barrel-stave supramolecule with hydrophobic exterior and histidine-rich interior are reported. Voltage-dependent binding of pyrenyl-8-oxy-1,3,6-trisulfonates by histidines within p-octiphenyl beta-barrels (and not monomers) via ionic (and not hydrophobic) interactions (K(D), K(I), K(M) < 1 microM) is the basis for superb esterolytic proficiency up to (k(cat)/K(M))/k(uncat) = 9.6 x 10(5) in water and bilayer membranes. The conductance of labile ion channels formed in planar bilayer membranes is shown to be reduced by 8-hydroxypyrene-1,3,6-trisulfonate on the single- and multichannel level. [reaction: see text]

Esterases↗

PubMed2001

Cerebellar ataxia associated with heteroallelic ceruloplasmin gene mutation.

BACKGROUND: Aceruloplasminemia, an autosomal recessive disorder that affects human iron metabolism, is caused by mutation of the ceruloplasmin gene. Heterozygous individuals with a partial ceruloplasmin deficiency may have normal iron metabolism and no clinical symptoms. METHODS: The authors clinically characterized three Japanese patients from two families who had cerebellar ataxia with hypoceruloplasminemia from the fourth decade of life. Genetic analysis, restriction fragment length polymorphism analysis, and a pathologic study were performed. RESULTS: All three patients presented with cerebellar dysfunction that included relatively nondisabling gait ataxia and dysarthria, as well as hyperreflexia. Brain and abdomen MRI showed cerebellar atrophy and no low-signal intensities in the basal ganglia, thalamus, and liver. Direct mutational analysis excluded SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, SCA-12, and DRPLA. The patients partially lacked serum ceruloplasmin, and the protein concentrations and ferroxidase activities ranged from 36% to 41% of the control values; moreover, they were heterozygous for a nonsense mutation of the ceruloplasmin gene (Trp858ter). Serum iron concentration and transferrin saturation were normal. At autopsy, pathologic and biochemical examinations showed marked loss of Purkinje cells, a large iron deposition in the cerebellum, and small depositions in the basal ganglia, thalamus, and liver. CONCLUSION: Cerebellar ataxia reflects the site of iron deposition. Being heterozygous for mutation of the ceruloplasmin gene may result in cerebellar ataxia.

Aged↗

PubMed2001

Induction of SPARC by VEGF in human vascular endothelial cells.

SPARC/osteonectin/BM-40 is a matricellular protein that is thought to be involved in angiogenesis and endothelial barrier function. Previously, we have detected high levels of SPARC expression in endothelial cells (ECs) adjacent to carcinomas of kidney and tongue. Although SPARC-derived peptide showed an angiogenic effect, intact SPARC itself inhibited the mitogenic activity of vascular endothelial growth factor (VEGF) for ECs by the inhibiting phosphorylation of flt-1 (VEGF receptor 1) and subsequent ERK activation. Thus, the role of SPARC in tumor angiogenesis, stimulation or inhibition, is still unclear. To clarify the role of SPARC in tumor growth and progression, we determined the effect of VEGF on the expression of SPARC in human microvascular EC line, HMEC-1, and human umbilical vein ECs. VEGF increased the levels of SPARC protein and steady-state levels of SPARC mRNA in serum-starved HMEC-1 cells. Inhibitors (SB202190 and SB203580) of p38, a mitogen-activated protein (MAP) kinase, attenuated VEGF-stimulated SPARC production in ECs. Since intact SPARC inhibits phosphorylation ERK MAP kinase in VEGF signaling, it was suggested that SPARC plays a dual role in the VEGF functions, tumor angiogenesis, and extravasation of tumors mediated by the increased permeability of endothelial barrier function.

Cells, Cultured↗

PubMed2001

Attenuation by ambroxol of monochloramine-enhanced gastric carcinogenesis: a possible prevention against Helicobacter pylori-associated gastric carcinogenesis.

The effects of combined administration of a reactive oxidant, monochloramine, and a mucoregulatory agent, ambroxol, on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without subcutaneous injection of ambroxol at high or low doses, until the end of the experiment at week 52. Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers at week 52, whereas concomitant administration of ambroxol with ammonium acetate and sodium hypochlorite significantly attenuated this enhanced gastric carcinogenesis. Results also revealed that ambroxol scavenged monochloramine. Because monochloramine is closely related to Helicobacter pylori-associated gastric carcinogenesis, these findings suggest that ambroxol may prevent H. pylori-associated gastric carcinogenesis.

Ambroxol↗

PubMed2001

Study of the e(g) orbitals in the bilayer manganite La(2--2x)Sr(1+2x)Mn(2)O(7) by using magnetic Compton-profile measurement.

From the magnetic Compton-profile (MCP) measurement, we have directly differentiated for the first time the populations in two e(g)-type orbitals ( x(2) - y(2) and 3z(2) - r(2)) in a manganite. The experimental MCP's along the [001] direction for La(2--2x)Sr(1+2x)Mn(2)O(7) at x = 0.35 and 0.42 are fitted by the theoretical profiles obtained from the (MnO(6))(8-) ab initio calculations. The calculation confirms that the MCP clearly detects the oxygen hybridization in the e(g) orbitals. The e(g) state is dominated by the x(2) - y(2)-type orbital with almost constant population, while the population in the 3z(2) - r(2)-type orbital decreases with increasing the hole concentration x.

Journal Article↗

PubMed2001

The MinD protein from the hyperthermophilic archaeon Pyrococcus horikoshii: crystallization and preliminary X-ray analysis.

MinD is one of the proteins regulating cell division. MinD from Escherichia coli has been designated as a type of motor protein which has an ATPase activity. This paper deals with the first crystallization and preliminary crystallographic analysis of recombinant MinD from Pyrococcus horikoshii (molecular weight 26.3 kDa) expressed in E. coli. Crystals of MinD were obtained by the hanging-drop vapour-diffusion method. MinD crystals belong to space group P2(1)3, with unit-cell parameters a = b = c = 98.5 A, and diffract to 3.0 A resolution. The asymmetric units each contain one molecule of MinD, giving a crystal volume per protein mass (V(M)) of 3.0 A(3) Da(-1) and a solvent content of 59.0%.

Adenosine Triphosphatases↗

PubMed2001

Tumor suppressor protein VHL is induced at high cell density and mediates contact inhibition of cell growth.

In spite of the general recognition of von Hippel-Lindau (VHL) as a tumor suppressor gene, the physiological and pathological importance of VHL protein in cell growth regulation and tumorigenesis remains unclear. Here we show that in normal human renal proximal tubule epithelial cells (RPTEC), the steady-state amount of VHL protein is strictly regulated by cell density. The cellular VHL content is more than 100-fold higher in dense cultures than in sparse cultures. The increase in VHL protein at high cell density was also observed for NIH3T3 fibroblasts, suggesting the generality of the phenomenon. The growth rates of renal cell carcinoma cells lacking an intact VHL gene and their derivatives with wild-type or mutant VHL expression vector do not differ significantly when they are growing in log-phase. Importantly, however, there is a difference when they reach confluency: cells lacking wild-type VHL grew continuously, while cells expressing exogenous VHL protein showed relatively limited cell growth. Using an ecdysone-inducible VHL expressing cell line, we also show that the growth inhibition at high cell density can be released by attenuating the VHL expression. Taken together, we propose that VHL protein functions as a growth suppressor at high cell density, and this might be the basis of the tumor suppressor function of VHL.

3T3 Cells↗

PubMed2001

Reduced adhesion of monocyte-derived macrophages from CD36-deficient patients to type I collagen.

CD36 is an 88-kDa glycoprotein expressed on platelets and monocyte/macrophages (Mphi). CD36 is a multifunctional receptor for collagen, thrombospondin, oxidized low density lipoproteins (LDL), and long-chain fatty acids. The present study was performed to investigate whether CD36 can function as an adhesion molecule which is involved in mediating human macrophages (Mphi) adhesion to type I collagen in vitro. The Mphi of human CD36-deficient as well as normal control subjects were isolated and cultured on the multi-well plates coated with type I collagen, a natural ligand for CD36. Up to 2 h of incubation, the Mphi from CD36-deficient patients showed almost a approximately 55% decrease in adhesion to type I collagen in comparison to those from controls (P < 0.01). However, there was no significant difference in the adhesion thereafter. Furthermore, the addition of antibody against CD36 into the media of control Mphi significantly inhibited the adhesion by approximately 50% (P < 0.05). The addition of oxidized LDL (OxLDL) did not alter adhesion of Mphi from both CD36-deficient and controls. These data suggest that CD36 is involved in the adhesion of Mphi to type I collagen, especially in the early stage of adhesion.

Antibodies, Monoclonal↗

PubMed2001

Electrostatics of cell membrane recognition: structure and activity of neutral and cationic rigid push-pull rods in isoelectric, anionic, and polarized lipid bilayer membranes.

Design, synthesis, and structural and functional studies of rigid-rod ionophores of different axial electrostatic asymmetry are reported. The employed design strategy emphasized presence of (a) a rigid scaffold to minimize the conformational complexity, (b) a unimolecular ion-conducting pathway to minimize the suprastructural complexity and monitor the function, (c) an extended fluorophore to monitor structure, (d) variable axial rod dipole, and (e) variable terminal charges to create axial asymmetry. Studies in isoelectric, anionic, and polarized bilayer membranes confirmed a general increase in activity of uncharged rigid push-pull rods in polarized bilayers. The similarly increased activity of cationic rigid push-pull rods with an electrostatic asymmetry comparable to that of alpha-helical bee toxin melittin (positive charge near negative axial dipole terminus) is shown by fluorescence-depth quenching experiments to originate from the stabilization of transmembrane rod orientation by the membrane potential. The reduced activity of rigid push-pull rods having an electrostatic asymmetry comparable to that in alpha-helical natural antibiotics (a positive charge near the positive axial dipole terminus) is shown by structural studies to originate from rod "ejection" by membrane potentials comparable to that found in mammalian plasma membranes. This structural evidence for cell membrane recognition by asymmetric rods is unprecedented and of possible practical importance with regard to antibiotic resistance.

Amino Acid Sequence↗

PubMed2001

p53 regulates ceramide formation by neutral sphingomyelinase through reactive oxygen species in human glioma cells.

The present study was designed to elucidate the relationship between p53 and ceramide, both of which are involved in apoptotic signaling. Treatment of human glioma cells with etoposide caused apoptosis only in cells expressing functional p53. p53 activation was followed by the formation of reactive oxygen species (ROS), superoxide anion (O2-*) measured by hydroethidium oxidation into ethidium and hydrogen peroxide (H2O2) measured by oxidation of 2',7'-dichlorofluorescin (DCFH) into 2',7'-dichlorofluorescein (DCF), which was accompanied with ceramide generation through the activation of neutral, but not acid, sphingomyelinase. Superoxide dismutase (SOD), a selective antioxidant for O2-*, had no effects on p53 expression but inhibited ceramide generation and apoptotic cell death caused by etoposide. However, catalase, a specific antioxidant for H2O2, only weakly inhibited and sodium formate, a hydroxyl radical (* OH) scavenger, unaffected etoposide-induced apoptosis. Like etoposide-induced cell death, treatment of glioma cells with the O2-*-releasing agent, pyrogallol, induced typical apoptosis and ceramide generation even in the presence of catalase. In contrast, human glioma cells lacking functional p53, either due to mutation or the expression of E6 protein of human papillomavirus, were highly resistant to etoposide and exhibited no significant change in the ceramide level. Moreover, expression of functional p53 protein in glioma cells expressing mutant p53 using a temperature-sensitive human p53(Val138) induced ceramide accumulation by the activation of neutral sphingomyelinase which was dependent on the generation of O2-*. Taken together, these results suggest that p53 may modulate ceramide generation by activation of neutral sphingomyelinase through the formation of O2-*, but not its downstream compounds H2O2 or * OH.

Apoptosis↗

PubMed2001

Roles of plasma lipid transfer proteins in reverse cholesterol transport.

Plasma lipid transfer proteins include plasma cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP). Plasma CETP facilitates the transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to apolipoprotein (apo) B-containing lipoproteins, and is a key protein in reverse cholesterol transport which protects vessel walls from atherosclerosis. The importance of plasma CETP in lipoprotein metabolism was highlighted by the discovery of CETP-deficient subjects with a marked hyperalphalipoproteinemia (HALP). The deficiency of CETP causes various abnormalities in the concentration, composition, and functions of both HDL and low-density lipoprotein (LDL). Although the significance of CETP in terms of atherosclerosis has been controversial, the in vitro evidence showed that large CE-rich HDL particles in CETP deficiency are defective in cholesterol efflux. Recent epidemiological studies in Japanese-Americans and in Omagari area where HALP subjects with the intron 14 splicing defect of CETP gene are markedly frequent, have demonstrated an increased incidence of coronary atherosclerosis in CETP-deficient patients. Similarly, scavenger receptor BI (SR-BI) knockout mice show a marked increase in HDL-cholesterol but accelerated atherosclerosis in atherosclerosis-susceptible mice. Thus, CETP deficiency is a state of impaired reverse cholesterol transport which may possibly lead to the development of atherosclerosis. PLTP transfers phospholipids from triglyceride (TG)-rich lipoproteins to HDL during lipolysis. Human plasma PLTP has a 20% sequence homology to human CETP and human PLTP gene has a marked similarity in the exon-intron organization. Both CETP and PLTP belong to the lipid transfer/lipopolysaccharide binding protein (LBP) gene family, which also includes LBP and bactericidal/permeability-increasing protein (BPI). Although these 4 proteins possess different physiological functions, they share marked biochemical similarities. The current review will also focus on the molecular genetics and function of plasma lipid transfer proteins, including CETP and PLTP.

Biological Transport↗