Biomedical subjects

T Oka

Publications and source records attributed to T Oka.

At least 487 records · Page 27Linked to original sources

PubMed1995

Intracerebroventricular injection of interleukin-6 induces thermal hyperalgesia in rats.

We assessed the effect of interleukin-6 (IL-6) in the brain on nociception by using the hot-plate test in rats. Recombinant human IL-6 (rhIL-6, 30 pg-300 ng) was microinjected into the lateral cerebroventricle (LCV) and the paw-withdrawal latency was then measured for 60 min after injection. RhIL-6 at 300 pg reduced the paw-withdrawal latency at 15 min after injection. Further increase of rhIL-6 doses to 3, 30 and 300 ng resulted in the decreased paw-withdrawal latency at 15 and 30 min. Although the peak responses observed at 3-300 ng did not differ significantly, the time taken for recovery tended to be longer with increasing doses. The rhIL-6 (30 ng)-induced reduction of the paw-withdrawal latency was completely blocked by the co-injection of either Na salicylate (30 ng, LCV) or alpha-melanocyte stimulating hormone (30 ng, LCV), an anti-cytokine substance. However, it was not affected by the co-injection of IL-1 receptor antagonist (30 ng, LCV) which had been previously shown to be able to block IL-1 beta-induced hyperalgesia. These findings indicate that IL-6 in the brain induces hyperalgesia by its prostanoids-dependent action in rats. The hyperalgesic action of central IL-6 thus does not appear to depend on the action of IL-1.

Animals↗

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

Release of arachidonic acid via Ca2+ increase stimulated by pyrophosphonucleotides and bradykinin in mammary tumour cells.

The relationship between the increase of intracellular Ca2+ and the release of arachidonic acid by bradykinin and pyrophosphonucleotides was studied in cultured mammary tumour cells, MMT060562. Bradykinin, ATP, UTP and UDP induced an increase of intracellular Ca2+ and the release of arachidonic acid from phospholipids into the extracellular fluid. Release of arachidonic acid was also induced by the application of the Ca2+ ionophore, A23187. Liberation of arachidonic acid by bradykinin and ATP was reduced by mepacrine, a blocker of phospholipase A2 and W-7, a calmodulin antagonist. It is suggested that the increase in cytosolic Ca(2+)-induced release of arachidonic acid occurs through activation of calmodulin-dependent phospholipase A2.

Adenosine Triphosphate↗

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

Esophageal duplication cyst associated with pulmonary cystic malformations.

Two cases of esophageal duplication cyst associated with pulmonary cystic malformations (cystic bronchiectasis with pneumonia in one, intrapulmonary bronchogenic cysts with bronchial atresia in the other) are reported. The coexistence of these complex anomalies supports the recognition that esophageal duplication cyst also is an entity of a broad spectrum of developmental abnormalities caused by abnormal budding of the primitive foregut. Nine cases of similar complex anomalies in the lung and esophagus have been reported. Although rare, this malformation complex should be borne in mind in the treatment of pediatric mediastinal and pulmonary malformations.

Abnormalities, Multiple↗

PubMed1995

Familial multiple mesothelial cysts of the spleen.

A 5-month-old boy who was diagnosed as having hydrops fetalis at 25 weeks' gestation had severe ascites of unknown origin. At the age 12 months, ultrasonography and computed tomography showed multiple cysts in the spleen that were increasing in size rapidly. Splenectomy resulted in complete disappearance of the ascites. These cysts were diagnosed as mesothelial cysts because the cell lining of the splenic cysts stained positively with alcian blue and cytokeratin. The boy's mother had undergone splenectomy for splenic and retroperitoneal lymphangiomas at 4 years of age. Histological reevaluation showed that the lining of her splenic cysts had the same mesothelial components as her son's. Their chromosomal assay showed normal karyotypes. Mesothelial cyst of the spleen appears similar to splenic lymphangioma morphologically; however, bleomycin and OK-432 were not effective. Familial splenic mesothelial (epidermoid) cysts have been reported in three sets of siblings, but this is the first report of their occurrence in mother and son.

Adult↗

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↗