Biomedical subjects

T Oka

Publications and source records attributed to T Oka.

At least 19 recordsLinked to original sources

PubMed1995

Steviol and steviol-glycoside: glucosyltransferase activities in Stevia rebaudiana Bertoni--purification and partial characterization.

The leaves of Stevia rebaudiana Bertoni contain sweet compounds which are glycosides of diterpene derivative steviol (ent-13-hydroxykaur-16-en-19-oic acid). Its main constituents are stevioside (triglucosylated steviol; 13-O-beta-sophorosyl-19-O-beta-glucosyl-steviol) and rebaudioside-A (tetraglucosylated steviol; 2'-O-beta-glucosyl-13-O-beta-sophorosyl-19-O-beta-glucosyl-stev iol). From the extracts of S. rebaudiana Bertoni, two glucosyltransferases (GTases I and IIB) acting on steviol and steviol-glycosides were isolated, and another distinct activity (GTase IIA) acting on steviol was detected. Purified GTase I (subunit M(r) 24,600) catalyzed glucose transfer from UDP-glucose to steviol and steviolmonoside (steviol-13-O-glucopyranoside), but not to other steviol-glycosides. Apparent Km values were 71.4 microM for steviol and 360 microM for UDP-glucose. GTase IIB (subunit M(r) 30,700) showed a broad substrate specificity, acting on steviol, steviolmonoside, steviolbioside (13-O-beta-sophorosyl-steviol), and stevioside. Apparent Km values were 182 microM for steviol, 44 microM for steviolbioside, 95 microM for stevioside, and 385 microM for UDP-glucose. The two enzymes had a similar optimum pH at 6.5. They also acted effectively on ubiquitous flavonol aglycones, quercetin, and kaempferol and utilized kaempferol at a higher rate than steviol and steviol-glycosides. The apparent Km values of GTase I and IIB for kaempferol were 12 and 31 microM, respectively.

Chromatography, Gel↗

PubMed1995

Interaction of rat liver lysosomes with basic polypeptides.

In order to gain knowledge on the interaction of lysosomes with proteins, we have assessed the equilibrium densities of the lysosomal membrane and matrix markers after in vitro incubation of rat liver lysosomes with various polypeptides. The addition of basic polypeptides, polylysine or protamine, to the suspension of lysosomes brought about a profound alteration of lysosomal membrane, causing extensive leakage of lysosomal matrix enzymes. Electron microscopic observation revealed a remarkable aggregation of lysosomes by the basic polypeptides. Polyglutamic acid, an acidic polypeptide, did not produce such effect. ATP was found to stabilize lysosomes during incubation, particularly with basic polypeptides.

Animals↗

PubMed1995

Anatomical distribution and postnatal changes in endogenous free D-aspartate and D-serine in rat brain and periphery.

We have investigated the anatomical distribution and postnatal development of D-aspartate and D-serine in the rat brain and periphery using HPLC techniques. D-Serine was confined predominantly to the brain throughout postnatal life. At birth, a substantial quantity of D-serine was observed throughout the brain areas. The cerebral D-serine content increased from birth to postnatal week (PW) 3 and remained constant thereafter, whereas the cerebellar D-serine content peaked at PW1. In contrast, the transient emergence of D-aspartate was found in almost all brain and peripheral organs. A substantial quantity of D-aspartate was also seen in all brain areas at birth, whereas the D-aspartate content in the cerebrum and cerebellum decreased dramatically by PW1 and 7 respectively. Further, the D-aspartate content and the ratio of D-aspartate to total aspartate were highest in the adrenal at PW3 (608 +/- 70 nmol/g, 45.9%) and in the testis at PW14 (221 +/- 7 nmol/g, 57.8%) respectively. Because D-serine potentiates N-methyl-D-aspartate receptor-mediated transmission through the strychnine-insensitive glycine site and because D-serine exhibits an N-methyl-D-aspartate receptor-related distribution and development, D-serine may be a tenable candidate for an intrinsic ligand for the glycine site. In contrast, because the periods of maximal emergence of D-aspartate in the brain and periphery occur during critical periods of morphological and functional maturation of organs, D-aspartate could participate in the regulation of these developmental processes of organs.

Age Factors↗

PubMed1995

Vitamin B6 modulates expression of albumin gene by inactivating tissue-specific DNA-binding protein in rat liver.

The level of albumin mRNA in the liver of vitamin B6-deficient rats was found to be 7-fold higher than that of control rats. Since the transcriptional activity of the albumin gene, as measured by a nuclear run-on assay, was increased 5-fold in vitamin B6 deficiency, the higher concentration of albumin mRNA in the liver of vitamin-deficient rats could be attributed to the enhanced rate of transcription. The promoter proximal sequences of the albumin gene interact with a number of tissue-specific transcription factors including HNF-1 and C/EBP. We determined the binding activities of liver nuclear extracts to the HNF-1- and C/EBP-binding sites by gel mobility-shift assay and found that the activities of the extract prepared from liver of vitamin B6-deficient rats were greater than those of controls. As the concentrations of C/EBP in nuclear extracts from control and vitamin-deficient rats, estimated by Western-blot analysis, were essentially the same, the lower binding activity of the extract from control liver is probably due to inactivation of tissue-specific factors by pyridoxal phosphate and/or its analogues. We therefore examined the effect of pyridoxal phosphate and its analogues on the binding activity of nuclear extract in vitro and found that only pyridoxal phosphate effectively inhibited the binding. These observations indicate that vitamin B6 modulates albumin gene expression through a novel mechanism that involves inactivation of tissue-specific transcription factors by direct interaction with pyridoxal phosphate.

Albumins↗

PubMed1995

Production of functional chick liver HMG 2a protein in Escherichia coli.

An efficient Escherichia coli system for the production of a variant form of high-mobility group-2a protein (HMG 2a), having the additional 5 amino acid residues (Ala-Pro-Thr-Leu-Glu) at the NH2-terminal, has been constructed. cDNA encoding HMG 2a was ligated with the Omp A signal peptide sequence and was inserted into an inducible bacterial expression vector pSH-L. After the plasmid introduced into E. coli was expressed by temperature shift, the recombinant product was purified by trichloacetic acid precipitation followed by Bio-Rex 70 column chromatography. The purified product showed the expected NH2-terminal sequence and the superhelical activity of circular DNA similar to the authentic HMG 2a isolated from chick liver.

Amino Acid Sequence↗

PubMed1995

Identification of the promoter region of the human histamine H2-receptor gene.

The human histamine H2 receptor gene (a 13 kb 5'-upstream sequence, the 1,077 bp coding region and a 245 bp 3'-downstream sequence) was cloned and its 5'-upstream 1.8 kb nucleotide sequence was determined. Northern blot hybridization showed that the message for the receptor was transcribed in human gastric adenocarcinoma MKN45 cells. When the upstream sequence was ligated in front of the luciferase gene and the construct was introduced into this cell line, the reporter gene was effectively transcribed, as demonstrated by the expression of enzyme activity. The minimum promoter was located in the region between -610 and -278. This sequence contained AP2 sites and GATA motifs, but not a TATA-box like sequence. Further upstream regions (-1,202 approximately -611 bp and -1,773 approximately -1,203 bp) stimulated and inhibited luciferase gene expression, respectively. These regions may be important for modulation of the mRNA level in cells expressing the H2 receptor.

Base Sequence↗

PubMed1995

The effect of a bolus injection of TNF-alpha and IL-1 beta on hepatic energy metabolism in rats.

The effects of intravenous bolus injection of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) on hepatic mitochondrial energy metabolism were investigated in rats. The rats were injected with 15 micrograms/kg body wt of human recombinant TNF-alpha and IL-1 beta. The hepatic energy charge decreased to 0.794 +/- 0.005 and 0.789 +/- 0.006 in comparison with the sham control value of 0.838 +/- 0.007 and 0.835 +/- 0.011 at 12 and 24 hr after the treatment. The mitochondrial redox state (NAD+/NADH) increased from 17.4 +/- 1.9, 16.6 +/- 1.4, and 19.2 +/- 2.1 to 33.5 +/- 3.5, 27.8 +/- 2.8, and 30.9 +/- 2.6 concomitant with an increase in arterial blood ketone body ratio (acetoacetate/beta-hydroxybutyrate) from 0.49 +/- 0.04, 0.34 +/- 0.04, and 0.44 +/- 0.09 to 1.00 +/- 0.16, 0.69 +/- 0.13, and 0.86 +/- 0.15 at 3, 12, and 24 hr after the treatment. Total ketone body concentration in liver tissue and arterial blood was significantly lower at 24 hr after the treatment. State 3 respiration rate of isolated mitochondria increased by 29.2, 30.3, and 19.2% concomitant with an increase in oxidative phosphorylation rate by 26, 33.7, and 24.3% at 3, 12, and 24 hr after the treatment. These results showed that the administration of TNF-alpha and IL-1 beta in rats induced a hypermetabolic state in hepatic mitochondrial energy metabolism, which is a pattern similar to sepsis and presumably a compensatory reaction to the increased energy consumption.

Animals↗

PubMed1995

A method evaluating population risks from chemical exposure: a case study concerning prohibition of chlordane use in Japan.

The proposed method evaluating population risks from chemical exposure is based on estimation of the individual variabilities in the internal concentration of the chemical of concern and estimation of the magnitude of toxic effect caused at a given internal concentration. We assume a log-normal distribution for individual variability and propose loss of life expectancy (LLE) as a measure of the magnitude of toxic effects. We applied it to the evaluation of the governmental action of prohibiting the use of chlordane as a termiticide in Japan. Because the method is applicable to both carcinogenic and noncarcinogenic chemicals, the cancer risk due to chlordane and the noncancer risk due to chlorpyrifos, a major substitute, were evaluated and compared. The estimated values of risk represented in terms of LLE are 0.10 days for residents of untreated houses, 1.9 days for residents of treated houses, and 4.4 days for termite control workers when chlordane is used, and 0, 2.8, and 31 days when chlorpyrifos is used, respectively. From the result of the case study, we can see that the prohibition of chlordane is not necessarily effective in reducing risk.

Adult↗

PubMed1995

Surgical palliation of cardiac malformations associated with right isomerism.

Between 1985 and 1993, palliative surgery was performed on 13 pediatric patients who had complex cardiovascular anomalies associated with right isomerism. The patients included two neonates, ten infants, and one child who were divided into two groups according to whether or not a total anomalous pulmonary venous connection (TAPVC) was present. Group 1 consisted of six patients with TAPVC and group 2 consisted of seven patients without TAPVC. In group 1, the surgical procedures involved TAPVC repair alone in two patients, combined TAPVC repair with a modified Blalock-Taussig shunt in two, combined TAPVC repair with pulmonary artery banding in one, and a modified Blalock-Taussig shunt alone in one. There were five hospital deaths and one late death in this group: pulmonary venous obstruction in two patients, perioperative myocardial failure in the two neonates, and congestive heart failure caused by increased pulmonary blood flow in two patients. In group 2, all the patients underwent systemic-pulmonary artery shunts, and there was one hospital death and three late deaths, the causes of which were unknown in two patients, and shunt failure and pneumonia in one patient each. These results suggest that surgical palliation for right isomerism produces poor results in young infants with obstructed TAPVC. Thus, we conclude that TAPVC repair should be performed without delay if pulmonary venous obstruction has been diagnosed clinically. Resolving pulmonary venous obstruction without cardiopulmonary bypass (CPB) may be preferable for infants, considering their difficult management. The systemic-pulmonary artery shunt should be of the low-calibrated type, especially if common atrioventricular valve regurgitation exists. If infants survive the surgery, they must be carefully followed up for a long period due to the risk of sudden death or infection.

Adolescent↗

PubMed1995

Comparison of hemodynamic data before and after corrective surgery for Down's syndrome and ventricular septal defect.

Left ventricular function and the extent of pulmonary vascular disease were studied in 18 children with Down's syndrome and 20 children without Down's syndrome who underwent corrective surgery for ventricular septal defect (VSD) and severe pulmonary hypertension. This study was conducted between 1985 and 1993. All patients underwent routine cardiac catheterization preoperatively and postoperatively (mean, 11.4 months after surgery). Left ventricular function was estimated using cineangiographic levograms. In both groups, the pulmonary-to-systemic arterial pressure ratio (Pp/Ps) and pulmonary vascular resistance (PVR) were significantly lower after surgery (P < 0.05). Postoperative improvement was more remarkable in the non-Down group (P < 0.05). Left ventricular end-diastolic volume (percent of normal) (LVEDV%N) was significantly lower after surgery in both groups (P < 0.01). The left ventricular stroke work-to-end-diastolic volume ratio (LVSW/EDV) was significantly higher after surgery in the non-Down group only (P < 0.01). Postoperative left ventricular ejection fraction (LVEF) was significantly lower in the Down group than in the non-Down group (P < 0.01). Some degree of irreversible pulmonary vascular disease was present after repair of VSD in patients with Down's syndrome. In the Down group, there were no significant changes in left ventricular function after surgery, despite the relief of volume overload. These results suggest that early diagnosis and surgical repair are key elements in the management of patients with Down's syndrome and VSD.

Cardiac Catheterization↗

PubMed1995

A method to estimate the potency of the mu-component of an opioid having mixed mu-, and kappa- and/or delta-agonist activities.

The SC administration of either typical mu-agonists such as morphine, pethidine, fentanyl and levorphanol or a mixed mu- and delta-agonist like [D-Ala2, D-Leu5]-enkephalin to 10-day-old rats produced loss of righting reflex. Additionally, the loss of righting reflex induced by these opioid agonists was antagonized by naloxone, an opioid antagonist having a preference for mu-receptors, but by neither nor-binaltorphimine nor naltrindole, a specific kappa- or delta-antagonist, respectively, indicating that the loss of righting reflex was produced by the interaction of an opioid with mu-receptors. Moreover, the potency of each opioid agonist relative to that of morphine estimated by the present in vivo method was similar to that determined by the traditional in vitro isolated preparation. In contrast to mu-agonists, neither typical kappa-agonists such as U-50, 488H, ketocyclazocine, pentazocine and butorphanol, nor a selective delta-agonist like [D-Pen2, D-Pen5]-enkephalin affected the righting reflex of 10-day-old rats, indicating that mu-agonists, but neither kappa- nor delta-agonists, produced the naloxone-reversible loss of righting reflex in infant rats. By employing the present in vivo method to estimate the mu-agonist activity of an opioid with mixed agonist activities, it was indicated that the mu-agonist activity of ethylketocyclazocine, which had been employed as a representative kappa-agonist, was essentially the same as that of morphine, a representative mu-agonist.

Animals↗

PubMed1995

Histologic modification by cryopreservation in rat aortic allografts.

Histologic changes after the cryopreserved rat aortic transplantation were studied, and the influences of the cryopreservation and of the allografting on the histology were examined. Four groups of Brown Norway (RT1n) and Lewis rats (RT1(1)) were used (n = 4 at each examined period in each group): the cryopreservation-allograft group (from Brown Norway to Lewis with cryopreservation), the cryopreservation-isograft group (from Lewis to Lewis with cryopreservation), the fresh allograft group (from Brown Norway to Lewis without cryopreservation), and the fresh isograft group (from Lewis to Lewis without cryopreservation). The graft was harvested from a descending thoracic aorta of a donor rat, implanted to an infrarenal abdominal aorta of a recipient rat, and extracted at 10 days, 1, 3, 6, and 12 months after the operation. The intimal thickening, cellular loss in the media, and cellular infiltration in the adventitia were observed, which were the same phenomena seen in chronic rejection of human organ allografts. Although the degree of intimal thickening and cellular loss in the media were higher in the cryopreserved groups than in the fresh groups, the cryopreservation procedure suppressed cellular infiltration in the adventitia after allotransplantation. The immunologic attack against the graft might be diminished by cryopreservation.

Animals↗

PubMed1995

Effects of muramyl dipeptide derivatives as adjuvants on the induction of antibody response to recombinant hepatitis B surface antigen.

The ability of two muramyl dipeptide (MDP) derivatives, B30-MDP and MDP-Lys(L18), to enhance the immunogenicity of recombinant hepatitis B surface antigen (rHBsAg) was examined. When mice were immunized intraperitoneally with rHBsAg together with each MDP derivative, the antibody titres were higher than those in mice immunized with alum-adsorbed rHBsAg, which is a commercially available hepatitis B vaccine. When mice were given a subcutaneous or intramuscular injection of rHBsAg and either MDP derivative, the antibody titres were the same as those in mice given alum-adsorbed rHBsAg. These results indicate the usefulness of MDP derivatives as immunoadjuvants for a new-generation vaccine.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1995

Extracellular concentration of endogenous free D-serine in the rat brain as revealed by in vivo microdialysis.

Using an in vivo microdialysis technique, we have measured the extracellular concentration of endogenous free D-serine in comparison with that of L-serine, glycine and L-glutamate in the discrete brain areas of the freely moving rat. A high concentration of D-serine was observed in the dialysate obtained from the medial prefrontal cortex and striatum, whereas the cerebellar dialysate contained only a trace amount of the D-amino acid. The regional variation in the basal overflow of D-serine was proportional to that of its tissue levels which has been shown to closely correlate with the distribution of the N-methyl-D-aspartate type excitatory amino acid receptor. In contrast, the extracellular release of glycine and L-glutamate was higher in the cerebellum and very low in the striatum. The extracellular concentrations of L-serine were more than three times those of striatal D-serine in the three regions. Neither addition of a sodium channel blocker, tetrodotoxin (2 microM), nor deprivation of Ca2+ from the perfusate reduced the basal extracellular levels of the four amino acids tested in the medial prefrontal cortex. Furthermore, intra-frontal cortex perfusion of a sodium channel activator, veratrine (200 micrograms/ml), caused an increase in the extracellular release of glycine and L-glutamate but a slight decrease in that of D-serine in a tetrodotoxin-sensitive manner in the cortical region.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1995

Cell viability of aortic allografts after long-term cryopreservation and clinical application to aortic root replacement in a patient with aortitis.

A key point in the establishment of a tissue cryopreservation system is to maintain cell viability for an extended period. The viability of the tissue cells in the authors' cryopreservation system was examined, and the first clinical application reported. The tissue culture method demonstrated 95% of rat aortas (21 of 22 specimens) and 88% of human cardiac valves (seven of eight) to be viable after 6.4 months and 5.8 months of cryopreservation, respectively. The first clinical case, a 54-year-old man with aortic valve replacement and complications of aortitis, underwent successful aortic root replacement. Whereas the use of allografts in aortitis cases is controversial, such an approach was assumed reasonable because the mechanical stress between the native aortic annulus and the inserted valve could be reduced by aortic root replacement with the allograft.

Adult↗

PubMed1995

Peptides with carboxyl-terminal sequence of alanine-proline: detection by a human monoclonal antibody.

A human B lymphoblastoid cell line JWCI-L94 secretes an IgM human monoclonal antibody (HuMAb) that reacts with human melanoma cell lines, M14 and M12. To identify the antigenic epitope of this antibody, we screened lambda gt11 expression libraries constructed from M14 and M12. A total of 12 immunoreactive clones were isolated, and their DNA sequences were determined. The only sequence shared by all these clones was alanine-proline (A-P) at the carboxyl (C) terminal. HuMAb L94 reacted not only with C-terminal A-P-containing fusion proteins, but also with the synthetic dipeptide A-P. None of the peptides containing A-P internally or amino terminally reacted to HuMAb L94. Proline or alanine alone had no ability to bind to HuMAb L94. When alanine was replaced by glycine (G-P) or proline (P-P), the binding activity of these peptides was similar to that of A-P. On the other hand, when alanine was replaced by serine, valine, leucine, glutamine, lysine, methionine, phenylalanine, or hydroxyl proline, the resulting peptide completely lost the antigenic activity of HuMAb L94. These results demonstrate that HuMAb L94 recognizes C-terminal A-P, G-P, or P-P, and that a human antibody can recognize peptides as small as a two-amino acid residue.

Amino Acid Sequence↗

PubMed1995

The rat intrinsic factor gene: its 5'-upstream region and chief cell-specific transcription.

A DNA segment containing the 5'-upstream region and amino terminal reading frame of the gastric intrinsic factor gene was cloned from rat and its nucleotide sequence was determined. S1 mapping demonstrated that the transcription initiation site is located downstream of the second TATA-box sequence. Similar sequence motifs to those in the pepsinogen genes transcribed in gastric chief cells were found in the deduced sequence, suggesting that the rat intrinsic factor gene is transcribed in these cells. The genes for the intrinsic factor and its homologous protein transcobalamin I were apparently derived from a common ancestoral gene, since the positions of their intron insertions as well as the amino acid residues are conserved. Northern blot hybridization showed that the gene for the intrinsic factor is transcribed in the stomach but not detectably in the intestine, kidney, testis, brain, heart, liver, lung, or spleen. In situ hybridization using radioactive complementary RNA clearly indicated that the major transcription site in gastric glands is chief cells. Different locations of expression of intrinsic factor proteins in various mammals were observed previously using antibodies: in rat parietal cells and chief cells, in mouse chief cells, and in human parietal cells. The present results clearly demonstrated the intrinsic factor mRNA mainly in chief cells of adult rats, as in mice, suggesting that transcriptional regulation of the intrinsic factor gene is essentially the same in rodents.

Animals↗

PubMed1995

Clonal and non-clonal karyotypically abnormal cells in haemophagocytic lymphohistiocytosis.

We studied chromosomes in bone marrow (BM) or peripheral blood cells of nine patients with haemophagocytic lymphohistiocytosis (HLH); three of them had a family history of HLH and four others underwent concurrent Epstein-Barr virus (EBV) infection. In addition to a large population of normal mitotic cells, karyotypically abnormal clonal cells were found in two patients, abnormal clonal cells and a nonclonal (single) abnormal cell in one, and nonclonal abnormal cells in three. All the six patients with chromosome abnormalities died of progressive disease; one of them also had EBV infection and EBV-associated clonal proliferation. Two of three patients with EBV infection and only normal mitotic cells in BM completely recovered from the disease. Although HLH did not show histological and/or haematological evidence of a neoplastic disease, clonal chromosome abnormalities and the fatal clinical outcome found in some of the patients suggest that the disease may be heterogenous and include malignancy. HLH patients with karyotypically abnormal clonal cells in BM should warrant more intensive chemotherapy than that presently being applied to them and should be considered as candidates for BM transplantation.

Adolescent↗