Biomedical subjects

J Arai

Publications and source records attributed to J Arai.

At least 19 recordsLinked to original sources

PubMed2000

Crystal structure of a plant ribonuclease, RNase LE.

Ribonuclease LE (RNase LE) from cultured tomato (Lycopersicon esculentum) cells is a member of the RNase T(2) family showing broad base specificity. The crystal structure of RNase LE has been determined at 1.65 A resolution. The structure consists of seven alpha-helices and seven beta-strands, belonging to an alpha+beta type structure. Comparison of the structure of RNase LE with that of RNase Rh, a microbial RNase belonging to the RNase T(2) family, reveals that while the overall folding topologies are similar to each other, major insertions and deletions are found at the N-terminal regions. The structural comparison, an amino acid sequence alignment of the RNase T(2) enzymes, and comparison of the disulfide-bonding pattern of these enzymes show that the structure of RNase LE shown here is the basic framework of the animal/plant subfamily of RNase T(2) enzymes (including a self-incompatibility protein called S-RNase), and the structure of RNase Rh is that of the fungal subfamily of RNase T(2) enzymes (including RNase T(2)). Subsequently, we superposed the active-site of the RNase LE with that of RNase Rh and found that (1) His39, Trp42, His92, Glu93, Lys96, and His97 of RNase LE coincided exactly with His46, Trp49, His104, Glu105, Lys108, and His109, respectively, of RNase Rh, and (2) two conserved water molecules were found at the putative P(1) sites of both enzymes. These facts suggest that plant RNase LE has a very similar hydrolysis mechanism to that of fungal RNase Rh, and almost all the RNase T(2) enzymes widely distributed in various species share a common catalytic mechanism. A cluster of hydrophobic residues was found on the active-site face of the RNase LE molecule and two large hydrophobic pockets exist. These hydrophobic pockets appear to be base binding sites mainly by hydrophobic interactions and are responsible for the base non-specificity of RNase LE.

Amino Acid Sequence↗

PubMed2000

Granule exocytosis, and not the fas/fas ligand system, is the main pathway of cytotoxicity mediated by alloantigen-specific CD4(+) as well as CD8(+) cytotoxic T lymphocytes in humans.

We investigated the cytotoxicity mechanisms of alloantigen-specific human CD4(+) and CD8(+) cytotoxic T lymphocytes (CTLs) using cells from family members with the Fas gene mutation. Alloantigen-specific CD4(+) and CD8(+) CTL bulk lines and clones were generated from 2 individuals by stimulation of their peripheral blood lymphocytes with allogeneic Fas(-/-) or Fas(+/-) cell lines that were established from B-lymphocytes of a patient with Fas deficiency and her mother, respectively. Both CD4(+) and CD8(+) CTL bulk lines and clones directed against allogeneic HLA antigens exerted cytotoxicity against Fas(-/-) and Fas(+/-) cells to almost the same degree. The cytotoxicity of CD4(+) and CD8(+) CTLs appeared to be Ca(2+)-dependent and was completely inhibited by concanamycin A, an inhibitor of perforin-mediated cytotoxicity. Messenger RNAs for the major mediators of CTL cytotoxicity, Fas ligand, perforin, and granzyme B were all detected in these CD4(+) CTLs with the use of the reverse transcriptase polymerase chain reaction. The majority of CD4(+) CTL clones that showed Fas-independent cytotoxicity were T(H)0, as determined by their cytokine production profile. These data, obtained with the use of a novel experimental system, clearly show that the main pathway of cytotoxicity mediated by alloantigen-specific human CD4(+) as well as by CD8(+) CTLs is granule exocytosis, and not the Fas/Fas ligand system.

Anti-Bacterial Agents↗

PubMed2000

Slow spin relaxation of Rb atoms confined in glass cells filled with dense 4He gas at 1.85 K

At temperatures below 2.1 K, long-lived gaseous Rb atoms in glass cells have been generated with a simple method: irradiating the cells, containing 4He gas and Rb metal, with a cw laser. The obtained atomic Rb density ( approximately 10(8) cm(-3)) decreases with a 1/e time constant of about 10 s at 1.85 K. We have performed optical pumping of the Rb atoms and measured the longitudinal electronic spin relaxation time at 1.85 K as well. For processes (such as Rb-He collisions) which do not remove the atomic Rb from the vapor, this relaxation time is found to be about 60+/-15 s.

Journal Article↗

PubMed2000

Tubby-like protein 1 as an autoantigen in cancer-associated retinopathy.

Cancer-associated retinopathy (CAR) is a rare paraneoplastic syndrome that is characterized by retinal degeneration. Two cDNA clones, recoverin and tubby-like protein 1 (TULP1), were isolated from a human retinal cDNA library by using serum from a CAR patient as the probe. Both recoverin and TULP1 are retina-specific protein, and TULP1 is a member of tubby gene family. A determination of the recognized amino acid sequence of TULP1 by the patient serum and immunohistochemical studies on the distribution of TULP1 in the retina were done in this study.

Amino Acid Sequence↗

PubMed2000

Stromal cells in lymph nodes attract B-lymphoma cells via production of stromal cell-derived factor-1.

Stromal cell-derived factor-1 (SDF-1) is a chemokine produced by bone marrow stromal cells which plays an important role in B-lymphopoiesis and the homing of hematopoietic stem cells to the bone marrow. In the present study, we investigated the role of SDF-1 and its receptor, CXCR4, in the chemotactic interaction between non-Hodgkin B-lymphoma cells and lymph node stromal cells. SDF-1 mRNA was abundantly expressed in stromal cells isolated from the lymph nodes of patients with malignant lymphoma. All B-lymphoma cells freshly isolated from these patients and most laboratory B-lymphoma cell lines, including follicular, diffuse large, and Burkitt's lymphoma cells, expressed surface CXCR4 and migrated in the presence of recombinant human SDF-1alpha. Chemotaxis assays revealed that CXCR4-positive (but not CXCR4-negative) B-lymphoma cells migrated towards lymph node stromal cells, and this migration was almost completely inhibited by the addition of anti-CXCR4 monoclonal antibody to the lymphoma cells or of anti-SDF-1 neutralizing antibody to the culture supernatant of the stromal cells. Down-regulation of surface CXCR4 was detected in B-lymphoma cells which migrated towards the stromal cells but not in those which showed no migratory response. In addition, contact between the lymphoma cells and the stromal cells resulted in down-regulation of surface CXCR4 on the lymphoma cells. These data strongly suggest that SDF-1/CXCR4 is the main chemokine system involved in the chemotactic interaction between B-lymphoma cells and lymph node stromal cells.

Antibodies, Monoclonal↗

PubMed2000

A variant of myelokathexis with hypogammaglobulinemia: lymphocytes as well as neutrophils may reverse in response to infections.

A 7-year-old boy with prolonged and marked leukopenia diagnosed at 6 months of age is described. The polymorphonuclear cells presented no hypersegmented nuclei or concentrated nuclear chromatin, although vacuolated myeloid cells appeared in bone marrow smears. Neutrophils reversed in response to administration of G-CSF. His leukocyte counts were 400-1000/microL during afebrile periods and increased to 2000-3000/microL in response to infections. The increased leukocyte was usually neutrophils, but lymphocytes also increased at EB-virus infection. The serum IgG decreased gradually and was 364 mg/dL at 7 years of age. Antibody responses were normal and recurrent otitis media has been the patient's only problem. Granulocytopenia with hypogammaglobulinemia of this patient mimics myelokathexis with hypogammaglobulinemia, and lymphocytes also increased at viral infections.

Agammaglobulinemia↗

PubMed2000

[Natriuresis and blood pressure in patients with chronic renal failure following L-arginine infusion].

Nitric oxide (NO) is known to be generated from L-arginine and may regulate glomerular filtration, tubular sodium reabsorption, and renin secretion. Impairment of renal function might influence NO production secondary to endothelial dysfunction, decreased NO synthesis and increased activity of arginine analogues inhibiting NO synthase. In this study, we evaluated the effect of L-arginine on the blood pressure and urinary sodium excretion in patients with chronic renal failure. A 300-ml dose of 10% L-arginine solution was administered intravenously over 30 min and blood pressure was monitored every 10 min under basal conditions and for 120 min after infusion. The patients were divided into two groups based on the reduction in mean blood pressure (dMBP) following infusion, namely non-responders (dMBP < 10 mmHg) and responders (dMBP > 10 mmHg). Urine and blood samples were collected to determine electrolytes, urinary NO2 + NO3 by the Griess method, urinary cGMP, plasma renin activity (PRA), and the plasma aldosterone concentration (PAC). L-arginine significantly decreased MBP in 8 patients and caused no significant change in 10 patients. Urinary sodium excretion and the NO2 + NO3 level were significantly increased following L-arginine infusion and the increment of fractional excretion of sodium was higher in responders. However, there were no significant changes in PRA, PAC, and cGMP. Our findings suggest that a vasodilator effect of NO induced by L-arginine loading may, at least in part, be associated with increased renal sodium excretion in patients with chronic renal failure.

Adult↗

PubMed2000

[Subcutaneous panniculitic T-cell lymphoma with chromosomal abnormalities and large granular lymphocytes morphology].

A 72-year-old woman was admitted because of a subcutaneous hip tumor. A biopsy specimen of the tumor showed a mixture of medium-sized and large lymphocytes infiltrating the subcutaneous fat tissue with a lobular panniculitis-like pattern--a histologic feature of subcutaneous panniculitic T-cell lymphoma (SPTCL). May-Grünwald-Giemsa-stained cytospin slides of freshly isolated neoplastic cell explants showed that the cells had the characteristics of large granular lymphocytes. Immunophenotypic analysis showed that the cells expressed CD56--a natural killer-associated antigen--as well as the cytotoxic T-cell phenotype CD3+ CD4- CD8+. Southern blot analysis revealed rearrangement bands of the TCR-beta chain gene. Chromosome analysis showed complex abnormalities including t(1;6) (q11; p21). The present case may shed some light on the origin and pathogenesis of SPTCL.

Aged↗

PubMed1999

Fas-independent cytotoxicity mediated by human CD4+ CTL directed against herpes simplex virus-infected cells.

The present study was undertaken to clarify the mechanisms of cytotoxicity mediated by virus-specific human CD4+ CTLs using the lymphocytes of family members with a Fas gene mutation. CD4+ CTL bulk lines and clones directed against HSV-infected cells were established from lymphocytes of a patient with a homozygous Fas gene mutation and of the patient's mother. HSV-specific CD4+ CTLs generated from lymphocytes of the patient and her mother exerted cytotoxicity against HSV-infected cells from the patient (Fas-/-) and from her mother (Fas+/-) to almost the same degree in an HLA class II-restricted manner. mRNAs for the major mediators of CTL cytotoxicity, Fas ligand, perforin, and granzyme B, were detected in these CD4+ CTLs using the RT-PCR and flow cytometry. The cytotoxicity of the HSV-specific CD4+ CTLs appeared to be Ca2+-dependent and was almost completely inhibited by concanamycin A, a potent inhibitor of the perforin-based cytotoxic pathway. Although the Fas/Fas ligand system has been reported to be the most important mechanism for CD4+ CTL-mediated cytotoxicity in the murine system, the present findings strongly suggest that granule exocytosis, not the Fas/Fas ligand system, is the main pathway for the cytotoxicity mediated by HSV-specific human CD4+ CTLs.

Anti-Bacterial Agents↗

PubMed1999

Down-regulation of CXCR4 by human herpesvirus 6 (HHV-6) and HHV-7.

Recent studies have demonstrated that human herpesvirus 6 (HHV-6) and HHV-7 interact with HIV-1 and alter the expression of various surface molecules and functions of T lymphocytes. The present study was undertaken to clarify whether coreceptors for HIV-1, CXCR4 and CCR5, are necessary for HHV-6 and HHV-7 infection. Although CXCR4 and CCR5 appeared not to be the coreceptors for these viruses, marked down-regulation of CXCR4, but not CCR5, was detected in HHV-6 variant A (HHV-6A)-, HHV-6 variant B (HHV-6B)-, and HHV-7-infected cells. Down-regulation of CXCR4 resulted in impairment of chemotaxis and a decreased level of elevation of the intracellular Ca2+ concentration in response to stromal cell-derived factor-1. Northern blot analysis of mRNAs extracted from HHV-6A-, HHV-6B-, and HHV-7-infected CD4+ T lymphocytes demonstrated a markedly decreased level of CXCR4 gene transcription, but the posttranscriptional stability of CXCR4 mRNA was not significantly altered. These data demonstrate that unlike HIV-1, HHV-6 and HHV-7 infections do not require expression of CXCR4 or CCR5, whereas marked down-regulation of CXCR4 is induced by these viruses, suggesting that HHV-6 and HHV-7 infections may render CD4+ T lymphocytes resistant to T lymphocyte-tropic HIV-1 infection.

Antibodies, Monoclonal↗

PubMed1999

Stimulation by low concentrations of fluoride of the proliferation and alkaline phosphatase activity of human dental pulp cells in vitro.

Fluoride has been used for decades, either systemically or topically, to prevent dental caries. The purpose of this study was to clarify the effects of low concentrations of fluoride on proliferation, differentiation and extracellular-matrix synthesis in normal human dental pulp cells (DP-1 and DP-2) in vitro. The effects were compared with those on a human osteoblastic osteosarcoma cell line, TE-85. Fluoride at micromolar concentrations significantly and dose-dependently stimulated [3H]thymidine incorporation into DNA in DP-1, DP-2 and TE-85 cells, with optimal effects around 50 microM, by 127 +/- 7%, 124 +/- 0.6% and 152 +/- 13.4%, respectively. To assess the potential influence of fluoride on cell differentiation, the effects of mitogenic concentrations on alkaline phosphatase activity were measured. Fluoride significantly increased the enzyme's activity in DP-1 and TE-85 by 177 +/- 12% and 144 +/- 12.3%. To evaluate the effect on extracellular-matrix synthesis, the synthesis of type I collagen was indirectly determined by an assay of procollagen type I c-peptide production. Fluoride significantly increased that production by 150 +/- 8.7% in TE-85, but not in either DP-1 or DP-2. These observations suggest that fluoride, if used at low concentrations, could be a useful therapeutic agent where increased regeneration of dentine is desired, such as after pulp amputation, by stimulating the proliferation and differentiation of the dental pulp cells.

Alkaline Phosphatase↗

PubMed1999

Influence of spironolactone on neonatal screening for congenital adrenal hyperplasia.

AIM: To determine if the diuretic spironolactone cross reacts with 17alpha-hydroxyprogesterone (17OHP) in an enzyme linked immunosorbent assay (ELISA) kit used for the mass screening of congenital adrenal hyperplasia. METHODS: Concentrations of 17OHP on a blood filter paper disc were measured using an ELISA kit (kit C-7: ENZAPLATE N-17alpha -OHP-7; Chiron, Tokyo, Japan). The cross reactivity of spironolactone and its metabolites with 17OHP was determined. The concentrations of spironolactone and its metabolites in blood were measured using HPLC (high performance liquid chromatography). RESULTS: Spironolactone cross reacted with 17OHP using kit C-7 (0.01%), by increasing 17OHP concentration in a dose dependent manner. The blood concentration of spironolactone and its metabolites was nearly 900 ng/ml, high enough to show an additive effect on the 17OHP concentration. About 12% of the false positive cases screened using the kit were due to the administration of spironolactone. CONCLUSIONS: Spironolactone interferes with 17OHP concentrations, leading to false positive test results for CAH.

17-alpha-Hydroxyprogesterone↗

PubMed1999

Caspaselike proteases activated in apoptotic photoreceptors of Royal College of Surgeons rats.

PURPOSE: To study the role of caspase-like proteases, especially roles of more extensively characterized caspase-1 and caspase-2, in apoptotic photoreceptor cell degeneration in Royal College of Surgeons (RCS) rats. METHODS: Both RCS and Sprague-Dawley rats were used. Cryosections of the retinas at various postnatal times were immunostained with antibodies against caspase-1 (interleukin-1beta-converting enzyme, ICE) and caspase-2 (Nedd2/Ich-1). Double staining with TdT-dUTP terminal nick-end labeling (TUNEL), propidium iodide, and the antibodies was also performed. To evaluate the time course of protein expression, western blot analysis was carried out. The temporal profile of caspase-like protease activity was studied using a fluorogenic tetrapeptide substrate, acetyl-tyrosyl-valyl-alanyl-aspartic acid alpha (4-methyl-coumaryl-7-amide) (Ac-YVAD-MCA). Intravitreal injection of a caspase-1 inhibitor, acetyl-tyrosyl-valyl-alanyl-aspartic-aldehyde (Ac-YVAD-CHO), at postnatal days 21 (P21) and P26 was performed to see if this caused a decrease in apoptotic cell number at P28. RESULTS: TUNEL-positive photoreceptors of RCS rats stained strongly with antibodies against caspase-1 and caspase-2. Double staining studies revealed that caspase-1 and caspase-2 were coexpressed in apoptotic cells. Western blot analysis showed that active forms of caspase-1-like and caspase-2-like proteases were upregulated at P28, concurrent with the peak in TUNEL-positive cells. The enzymatic activity of caspase-1-like protease was elevated in RCS rat retinas at P28, and the inhibitor of caspase-1 transiently reduced the number of the apoptotic photoreceptors. CONCLUSIONS: Activation of caspase-like proteases plays an important role in photoreceptor apoptosis of RCS rats.

Animals↗

PubMed1999

Measuring respiration of cultured cell with oxygen electrode as a metabolic indicator for drug screening.

New trend in methods for assessing pharmacological action to bacteria and cell is to measure their metabolic activities induced, while the conventional methods used population growth. We focused on respiration volume as an indicator of cell metabolism, and developed inexpensive disposable oxygen electrode sensor and multi-channel dissolved oxygen meters (DOX-10 and DOX-96KB). Using these instruments, cytotoxicity was measured for 48 hrs and the method showed superior features to conventional methods in its handiness of one step assay, and excellent adaptability to automated systems. Total usability of this oxygen electrode method is being evaluated in bacterial drug susceptibility test, anticancer drug susceptibility test, and alternatives to animal experiment.

Antineoplastic Agents↗

PubMed1998

Ataxia-telangiectasia in the Japanese population: identification of R1917X, W2491R, R2909G, IVS33+2T-->A, and 7883del5, the latter two being relatively common mutations.

We analyzed the data regarding six Japanese ataxia-telangiectasia (A-T) patients from four unrelated families, at the DNA level, to search for possible common mutations in the Japanese population. Among eight mutant alleles in the four families, c. 4612del165 (exon 33 skipping) was identified in two alleles, and c. 5749A to T (R1917X), c. 7471T to C (W2491R), c.7883de15, and c. 8725A to G (R2909G) were identified in one allele each. We found no mutations in the other two alleles. The IVS33 + 2T-->A mutation was identified at the genomic level as the cause of exon 33 skipping. We also identified the IVS33 + 2T-->A mutation in a Japanese patient ATL105 who was previously found to be a homozygote of c. 4612del165. W2491R and R2909G mutations were not detected in more than 100 control Japanese alleles. The latter is located in a highly conserved PI-3 kinase domain and is a completely conserved residue among ATM-related proteins. Taken together with previously documented mutations in five other Japanese A-T patients, IVS33 + 2T-->A and 7883del5 were identified in four and five alleles, respectively, in a total of 18 mutant alleles of Japanese A-T patients. These results suggest that these two mutations are relatively common mutations in the Japanese population.

Adolescent↗

PubMed1998

[Acute respiratory distress syndrome complicating imported Plasmodium falciparum malaria].

A 25-year-old male, who had returned from the Republic of Mali in Africa, was admitted to our hospital because of a 3-day history of high fever, on the first of October 1996. He was diagnosed as Plasmodium falciparum malaria by peripheral blood smear. From the admission day he was treated with quinine HCL, 1,500 mg per day, and sulfamethoxazole 2,400 mg trimethoprim 480 mg per day, but on October 2nd blood examination showed 35% parasite density and he was given mefloquine. However he was complicated with DIC on October 3rd, ARDS on October 5th. By anti-coagulant therapy and methylprednisolone pulse therapy he became afebrile and respiratory function improved rapidly. ARDS should be emphasized as a severe complication of imported severe malaria.

Adult↗

PubMed1998

[Anticancer susceptibility test method using general-purpose dissolved oxygen meter].

Drug susceptibility of cell can be rapidly measured by continuously monitoring its metabolic changes. We focused on respiration volume as a signal of metabolic change, and developed a new dissolved oxygen measuring system which can detect respiration volume of cells. The main feature of the system is the use of a new type bare oxygen electrode which can easily detect the changing rate of dissolved oxygen concentration. In this study, single type electrode was used to evaluate this rapid anticancer drug susceptibility test. The result obtained was almost equivalent to that with MTT method, which is a conventional method for susceptibility test of HL-60 to various kinds of anticancer drugs. We have also developed multi-type electrode plate with oxygen electrodes embedded in the bottom of 96-well plate, with which clinical evaluation of this method can be easily made.

Antineoplastic Agents↗

PubMed1997

A new method for studying the binding of human IgE to CD23 and the inhibition of this binding.

CD23, a low-affinity receptor for IgE (Fc epsilonRII), is a type II membrane-bound glycoprotein expressed on many hematopoietic cells, particularly activated B-cells. CD23 binds to IgE at a domain homologous to Ca2+-dependent (C-type) animal lectin. This paper describes a binding assay by which only the specific binding of IgE to CD23 expressed on Epstein-Barr virus (EBV)-transformed B-cell line, L-KT9 cells, can be detected. This assay is useful in the search for CD23 ligands among many chemical compounds, because it is easily carried out and does not require the use of any radiolabeled reagents. Using the assay, we investigated the inhibition of IgE binding to CD23 by fucose-1-phosphate which has been reported to inhibit the binding of sCD23 to IgE [Delespesse, G., Sarfati, M., Wu, C.Y., Fournier, S., Letellier, M., 1992. The low affinity receptor for IgE. Immunol. Rev. 125, 77.] and the binding of CD23 to CD21 [Pochon, S., Graber, P., Yeager, M., Jansen, K., Bernard, A.R., Aubry, T.-P., Bonnefoy, J.-Y., 1992. Demonstration of second ligand for the low affinity receptor for immunoglobulin E (CD23) using recombinant CD23 reconstituted into flourescent liposomes. J. Exp. Med. 176, 389.]. Although both alpha- and beta-L-fucose-l-phosphate/di(cyclohexylammonium) salt decreased the extent of IgE binding to CD23, the inhibitory effects were not due to alpha- or beta-L-fucose-1-phosphate but to cyclohexylamine. The inhibitory effect of cyclohexylamine was dose dependent and the effect was decreased when inhibition tests were carried out in the presence of a 10-fold excess of IgE. These results suggest that cyclohexylamine specifically interacts with the binding of CD23 and IgE.

B-Lymphocytes↗