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Biomedical subjects

A Kato

Publications and source records attributed to A Kato.

At least 397 records · Page 22Linked to original sources
PubMed1995

Conformational changes in mutant lysozymes detected with monoclonal antibody.

A monoclonal antibody (mAb) against hen egg white lysozyme (HEWL) with the exquisitely sensitive specificity to native conformation was prepared to detect the conformational changes in mutant lysozymes constructed by genetic modification in a yeast expression system. The binding of mAb with lysozyme was decreased both by denaturation with heat and guanidine-HCl, corresponding to the denaturation curves of lysozyme. These results demonstrate that mAb is a powerful probe to monitor the conformational changes in the lysozyme molecule. By using this probe, the conformational change of various mutant lysozymes was detected. A good correlation was observed between the binding with mAb and the delta G (Gibbs free energy change), reflecting the conformational stability of wild-type and seven mutant lysozymes. This result suggests that a monoclonal antibody with the specificity for native conformation can be used as a powerful probe of protein conformation.

Animals↗
PubMed1995

Induction of G1 arrest by down-regulation of cyclin D3 in T cell hybridomas.

The relationship between activation-induced growth inhibition and regulation of the cell cycle progression was investigated in T cell hybridomas by studying the function of the cell cycle-regulating genes such as G1 cyclins and their associated kinases. Activation of T cell hybridomas by anti-T cell receptor antibody induces growth arrest at G1 phase of the cell cycle and subsequently results in activation-driven cell death. Rapid reduction of both messenger RNA and protein level of the cyclin D3 is accompanied by growth arrest upon activation. Although the residual cyclin D3 protein forms a complex with cdk4 protein, cyclin D3-dependent kinase activity is severely impaired. Stable transfectants engineered to express cyclin D3 override the growth arrest upon activation. These results imply that the activation signal through T cell receptor induces the down-regulation of cyclin D3 expression and cyclin D3-dependent kinase activity, leading to growth arrest in G1 phase of the cell cycle in T cells.

Animals↗
PubMed1995

Gene organization of chicken anemia virus.

The genomic DNA of chicken anemia virus (CAV) was cloned and sequenced from a Japanese isolate CAA82-2. The nucleotide sequence of CAA82-2 isolate was 98% identical with that of the European Cuxhaven-1 strain (Noteborn et al., J. Virol. 65, 3131-3139, 1991). Nine open reading frames (ORFs) consisting of more than 100 nucleotides were found, i.e., four ORFs (CA1-CA4) on the plus strand and five ORFs (CA1R-CA5R) on the minus strand. These ORFs with the exception of CA4 are conserved between the two CAV isolates. All of these ORFs were expressed in Escherichia coli as fusion proteins with beta-galactosidase. By Western blot analysis, the CA2 and CA3 fusion proteins were found to react with CAV-infected chicken sera. Rabbit hyperimmune sera against the CA1, CA2, and CA3 fusion proteins were produced and tested their reactivity to CAV-infected cells. Two viral proteins with the apparent size of 54 and 16 kDa reacted with the antibodies against CA1 and CA3 fusion proteins, respectively. The 16-kDa protein, CA3, was suggested to be a major immunogen on CAV infection.

Animals↗
PubMed1995

Calystegins of Physalis alkekengi var. francheti (Solanaceae). Structure determination and their glycosidase inhibitory activities.

Five calystegins were extracted from the roots of Physalis alkekengi var. francheti (Solanaceae) with hot water and purified to homogeneity by the combination of a variety of ion-exchange column chromatographies. Their structures have been determined from the 1H- and 13C-NMR spectral data, and two of the compounds were identified as calystegins A3 and B2, which have been isolated from the roots of Calystegia sepium (Convolvulaceae). Two of the remaining three were found to be 1 alpha, 3 alpha, 4 beta-trihydroxy-nor-tropane and 1 alpha, 2 alpha, 3 alpha, 4 beta-tetrahydroxy-nor-tropane and given the trivial name calystegins A5 and B3, respectively. The last calystegin was assigned as 1 alpha, 2 beta, 3 alpha, 6 alpha-tetrahydroxy-nor-tropane, which was the same as the relative configuration proposed in the literature for calystegin B1 isolated from C. sepium. However, the 13C-NMR spectral data for the compound from C. sepium differed substantially from our results. From a personal communication with the authors of the original paper on calystegins, it was clarified that the 13C-NMR chemical shifts of calystegin B1 in the original paper had been erroneous. Since their corrected 13C-NMR data of calystegin B1 and its 1H-NMR chemical shifts in the original paper are very close to our present data, we concluded that both compounds from C. sepium and P. alkekengi are identical. Calystegin B2 has been known to be a potent competitive inhibitor of almond beta-glucosidase (Ki = 1.2 microM) and coffee bean alpha-galactosidase (Ki = 0.86 microM). In this study calystegin B1 (1 alpha, 2 beta, 3 alpha, 6 alpha-tetrahydroxy-nor-tropane) proved to be a potent competitive inhibitor of almond beta-glucosidase (Ki = 1.9 microM) and bovine liver beta-galactosidase (Ki = 1.6 microM), but not an inhibitor of alpha-galactosidases. Calystegin A3 was found to be a weaker inhibitor compared to calystegin B2 but with the same inhibitory spectrum. Calystegin A5, a 2-deoxy derivative of calystegin B2, showed no activity against any glycosidases tested. Since calystegin B3, a 2-epimer of calystegin B2, also exhibited only a weak inhibitory activity, it was concluded that the equatorially oriented OH group at C2 is the essential feature for recognition and strong binding by the active site of glycosidases.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkaloids↗
PubMed1995

Molecular characterization of a glyoxysomal citrate synthase that is synthesized as a precursor of higher molecular mass in pumpkin.

A cDNA clone for glyoxysomal citrate synthase (gCS) was isolated from a lambda gt11 cDNA library prepared from etiolated pumpkin cotyledons. The cDNA of 1989 bp consisted of a 1548 bp open reading frame that encoded 516 amino acid residues. The deduced amino acid sequence of gCS did not have a typical peroxisomal targeting signal at its carboxyl terminal. A study of expression in vitro of the cDNA and an analysis of the amino-terminal sequence of the citrate synthase indicated that gCS is synthesized as a larger precursor that has a cleavable amino-terminal presequence of 43 amino acids. The predicted amino-terminal sequence of pumpkin gCS was highly homologous to those of other microbody enzymes, such as 3-ketoacyl-CoA thiolase of rat and malate dehydrogenase of watermelon that are also synthesized as precursors of higher molecular mass. Immunoblot analysis showed that the level of gCS protein increased markedly during germination and decreased rapidly during the light-induced transition of microbodies from glyoxysomes to leaf peroxisomes. By contrast, the level of mRNA for gCS reached a maximum earlier than that of the protein and declined even in darkness. The level of the mRNA was low during the microbody transition. These results indicate that the accumulation of the gCS protein does not correspond to that of the mRNA and that degradation of gCS is induced during the microbody transition, suggesting that post-transcriptional regulation plays an important role in the microbody transition.

Animals↗
PubMed1995

Role of thromboxane A2 and prostacyclin in uninephrectomy-induced attenuation of ischemic renal injury.

Contralateral uninephrectomy attenuates unilateral renal ischemic injury. The present work was performed to elucidate whether the beneficial effect of uninephrectomy was mediated through the modification of the actions of thromboxane A2 (TxA2) or prostacyclin. Unilateral ischemic injury was provoked by a 60-minute left renal artery occlusion in right nephrectomized (Nx) and in sham-nephrectomized (Sham-Nx) rats. Inulin clearance (CIn) of left kidney 48 hours after ischemia was significantly higher in the Nx group than in the Sham-Nx group (0.11 +/- 0.07 vs. 0.00 +/- 0.00 ml/min/kidney, P < 0.05). Ischemia-induced tubular necrosis was also less in Nx animals. Proliferating cell nuclear antigen (PCNA) staining, a marker for cell proliferation, was found more markedly in Nx rats than in Sham-Nx animals. Forty-eight hours after ischemia, renal cortical TxB2 content was greater in Sham-Nx rats than in Nx rats (29.5 +/- 4.4 vs. 18.3 +/- 1.7 pg/mg protein, P < 0.05). No significant difference was found in the intrarenal content of 6-keto prostaglandin F1 alpha between two ischemia groups. A thromboxane synthetase inhibitor, OKY-046 (100 mg/kg/day, i.p.), significantly increased CIn 48 hours after ischemia (0.00 +/- 0.00 vs. 0.17 +/- 0.09 ml/min/kidney, P < 0.05) and attenuated ischemic tubular damage in Sham-Nx rats but not in Nx animals. Under OKY-046 treatment, no significant difference was found in postischemic CIn and ischemic tubular damage between the Nx and Sham-Nx groups. OKY-046 also increased PCNA expression in the cortex and outer stripe in Sham-Nx animals. These data suggest that less production of intrarenal TxB2 plays an important role for the uninephrectomy-induced attenuation of ischemic renal damage and for the facilitation of tubular recovery.

6-Ketoprostaglandin F1 alpha↗
PubMed1995

Endoscopic-image display system mounted on the surgical microscope.

This report describes a newly developed endoscopic-image display system which is mounted on the optical unit of the surgical microscope. This system permits the neurosurgeon to watch the endoscopic image through one of the eye lenses of a surgical microscope during application of neurosurgical endoscopy under open microsurgical procedures. It frees the neurosurgeon from the major conventional inconvenience that he has to discontinue watching the microscopic view in order to look at the endoscopic images through the ocular of the endoscope or on the video monitor.

Brain Diseases↗
PubMed1995

Three protein fractions that bind to a narrow region of the promoter of the ribosomal RNA gene in Vicia faba.

We previously described the preparation of a protein fraction that bound to the promoter region of the rRNA gene of Vicia faba. We now describe two additional protein fractions that interact with this DNA element. The three protein fractions have similar binding properties with the exception of their binding stabilities. DNase I footprinting experiments revealed that these protein fractions bind to a region that is located about 60 bp upstream from the site of initiation of transcription. From methylation interference experiments and gel-retardation assays with mutated oligonucleotides, it was evident that the protein fractions required the same residues for the formation of stable DNA-protein(s) complexes. However, the three protein fractions were chromatographically distinguishable and the stability of their binding to DNA was different. Although the functions of these fractions are still unknown, the fact that several protein fractions can bind to a narrow region near the site of initiation of transcription is of considerable interest in terms of the mechanism of transcription of the rRNA gene.

Base Sequence↗
PubMed1995

Characterization of a novel human tumor necrosis factor-alpha mutant with increased cytotoxic activity.

Various novel recombinant human tumor necrosis factor-alpha (TNF) mutants were prepared using protein engineering techniques, and their cytotoxic activity was compared with that of the intact form of TNF (intact TNF). Mutant 471 (a TNF mutant molecule with the deletion of 7 amino acids at the amino-terminal and the substitution of Pro8Ser9Asp10 by ArgLysArg) had a 6-fold higher cytotoxic activity against murine L929 cells. The mutant TNF had an increased ability to bind to TNF receptor on murine L929 fibroblasts cells. A cross-linking study revealed that mutant 471 had an increased ability to form an active trimer. Mutant 471 also showed higher cytotoxic activity against human KYM myosarcoma cells and human MIA PaCa-2 pancreatic carcinoma cells. The possible cachectin activity of the mutant was almost the same as that of intact TNF. These results suggest that mutant 471 might be a more promising candidate as an anticancer agent than intact TNF.

Amino Acid Sequence↗
PubMed1995

A point mutation (Arg271-->Cys) of a homozygote for dysfunctional prothrombin, prothrombin Obihiro, which has a region of high sequence variability.

The molecular defect of a congenitally dysfunctional form of prothrombin, prothrombin Obihiro, was identified in a patient with a severe bleeding tendency. He showed reduced fibrinogen clotting activity, despite a normal prothrombin antigen level. Nucleotide sequencing of amplified DNA revealed a C-->T change at nucleotide 7311 of exon VIII of the prothrombin gene. This resulted in the substitution of Arg271 by Cys at the factor Xa cleavage site which precludes normal activation of prothrombin Obihiro by factor Xa and the generation of thrombin. The proband was homozygous for this mutation. In addition, seven new nucleotide changes were identified in the prothrombin gene of this patient by comparison with the published gene sequence. Three polymorphisms at nucleotides 4291, 4298 and 7223 were exclusively identified in the prothrombin gene from Japanese. Particularly in the region containing exon VI and introns E and F (nucleotides 4048-4303), the prothrombin gene proved to be of high-sequence variability.

Base Sequence↗
PubMed1995

Assessment of MRI criteria for MS in Japanese MS and HAM/TSP.

We evaluated the usefulness of the MRI criteria for multiple sclerosis (MS) proposed by Paty et al and Fazekas et al in 36 Japanese MS patients, using HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP) as the control. Although 30 of 36 HAM/TSP patients had multiple white matter lesions on T2-weighted cranial MRI, only two fulfilled the MRI criteria for MS. At the same time, 31 of the 36 MS patients fulfilled the primary MRI criterion, yielding 93% specificity and 86% sensitivity for the criterion. MS has disease-specific MRI abnormalities.

Brain↗
PubMed1995

Effect of senegin-II on blood glucose in normal and NIDDM mice.

The hypoglycemic effect of senegin-II, the main component of Polygala senega (Polygalaceae), was examined in normal and KK-Ay mice, one of the model animals of non-insulin-dependent diabetes mellitus (NIDDM). Senegin-II (2.5 mg/kg) reduced the level of blood glucose in normal mice from 220 +/- 8 to 131 +/- 5 mg/dl 4 hours after intraperitoneal administration (P < 0.001), and also significantly lowered the blood glucose of KK-Ay mice from 434 +/- 9 to 142 +/- 6 mg/dl under similar conditions (P < 0.001).

Animals↗
PubMed1995

The difference in hypoglycemic action between polygonati rhizoma and polygonati officinalis rhizoma.

The hypoglycemic effect of the rhizomes of Polygonatum sibricum and Polygonatum officinale (Liliaceae) was investigated in KK-Ay mice, one of the animal models of non-insulin dependent diabetes mellitus (NIDDM). The methanol extract of the rhizomes of both Polygonatum sibricum (OM) and Polygonatum officinale (IM) (800 mg/kg) reduced the blood glucose levels in KK-Ay mice 4h after intraperitoneal administration. In terms of hypoglycemic effect, the blood glucose of 1M was lower than that of OM. IM-treated mice significantly decreased the blood glucose level in an insulin tolerance test, but OM-treated mice did not change. We estimated that the hypoglycemic effect of IM raised insulin sensitivity.

Animals↗
PubMed1995

Effects of steroidal glycosides on blood glucose in normal and diabetic mice.

Two steroidal glycosides, PO-1 and PO-2, were tested as a new hypoglycemic drug. PO-2 showed remarkable hypoglycemic activity on i.p. injection into normal mice. PO-1 slightly lowered the blood glucose in normal mice. Furthermore, PO-1 and PO-2 exhibited significant hypoglycemic effects in streptozotocin-induced diabetic mice. However, a steroid, diosgenin, did not affect the blood glucose level in either normal or streptozocin-induced diabetic mice, indicating that the branching glucose units are essential for the biological activity.

Animals↗
PubMed1995

Effect of polygonati rhizoma on blood glucose and facilitative glucose transporter isoform 2 (GLUT2) mRNA expression in Wistar fatty rats.

The intraperitoneal administration of the methanol extract of Polygonati Rhizoma (OM) to Wistar fatty rats caused a significant decrease in the blood glucose level 4h after its administration at 800 mg/kg (p < 0.01). The hepatic content of facilitative glucose transporter isoform 2, liver type glucose transporter (GLUT2) mRNA content from rat liver significantly decreased in the intraperitoneally OM-treated rats compared to that in the controls (p < 0.01). These results suggest that the hypoglycemic effect of OM is presumably due, at least in part, to the reduction of GLUT2 mRNA expression. Because of this unique therapeutic mechanism, OM could be a new category of therapeutic agent for non-insulin-dependent diabetes mellitus.

Animals↗
PubMed1995

Hypoglycemic effect of the rhizomes of ophiopogonis tuber in normal and diabetic mice.

The hypoglycemic effect of the rhizomes of Ophiopogonis Tuber (Liliaceae) was investigated in normal and streptozotocin-induced diabetic mice. The n-butanol extract of rhizomes of Ophiopogonis Tuber (BM) (100 mg/kg) reduced the blood glucose of normal mice from 201 +/- 13 to 151 +/- 7 mg/100 ml 4h after intraperitoneal administration (p < 0.054), and also significantly lowered the blood glucose of streptozotocin-induced diabetic mice from 590 +/- 28 to 470 +/- 37 mg/100 ml under similar conditions (p < 0.05). BM also tended to suppress epinephrine-induced hyperglycemia in mice. We concluded that the hypoglycemic effect of BM does not alter the insulin concentration.

Animals↗
PubMed1995

Aromatase inhibitors: synthesis, biological activity, and structure of 1,2-imidazolylmethylcyclopentanol derivatives.

Two series of 1,2-disubstituted imidazolylmethylcyclopentanol derivatives (5a-d, 10a-d) were prepared by using easily available methyl 2-oxocyclopentanecarboxylate as the starting material. Evaluation of the aromatase inhibitory activities in vitro was performed. Their activities were compared with those of a steroidal aromatase inhibitor, Formestane, and a non-steroidal inhibitor, Fadrozole. Among these compounds, the aromatase inhibitory activities of 5d, 10a, 10b, 10c, 11a, 15a, and 15b were more potent than Formestane. One compound, 1-(4-chlorobenzyl)-cis-2-(1H-imidazol-1-ylmethyl)cyclopentanol+ ++ (10a) was in particular identified as a potent aromatase inhibitor in vitro, exhibiting an IC50 value of 4 x 10(-8)M. The enantiomers of 10a were separated, and their absolute configuration were determined by X-ray crystallography.

Androstenedione↗