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Biomedical subjects

T Asano

Publications and source records attributed to T Asano.

At least 325 records · Page 18Linked to original sources
PubMed1997

Basic technology of simulation system for laparoscopic surgery in virtual environment with force display.

A basic simulation system for laparoscopic surgery was constructed. The system consists of force display in a virtual environment construction system. Recently, laparoscopic surgery has become popular around the world. However, this operation strategy requires very high dexterity, so that only some medical doctors can use it. Doctors can see the human organs in a three-dimensional environment in the case of ordinary operations. On the other hand, in the case of laparoscopic surgery, doctors can only see a narrow space in a two-dimensional environment on a CRT monitor and tactile information is decreased during operation procedures. We therefore developed a basic technology of surgical simulator for laparoscopic surgery. The focus of our research is the presentation of resistance from virtual organs.

Computer Simulation↗
PubMed1997

[Age-related changes of diffusional anisotropy in the cerebral white matter in normal subjects].

To investigate age-related changes of diffusional anisotropy in the cerebral white matter, we performed diffusion-weighted MRI studies in 21 normal subjects aged 25 to 96 years. The anisotropic rations (ARs), defined as the apparent diffusion coefficients perpendicular to the nerve fibers to those parallel to the nerve fibers, were significantly higher in elderly than in young subjects in the anterior and posterior white matter surrounding the lateral ventricle. Moreover, significant correlation between age and AR was found in the anterior white matter. The ventricular index (VI) measured on MRI, as a quantitative indicator of brain atrophy, was significantly higher in elderly than younger subjects, and significantly correlated with AR in the anterior white matter. Multiple regression analysis demonstrated that the VI showed the highest correlation for AR. On the other hand, there was no significant correlations between ARs in the corpus callosum and age. These results suggest that morphological changes in the myelin and axon in the white matter occur in elderly normal subjects, probably due to neuronal loss with aging.

Adult↗
PubMed1997

[Changes in alpha 2-adrenoceptor binding nature in guinea-pig brain following the development of morphine dependence].

We examined the effect of morphine dependence on alpha 2-adrenoceptors in guinea-pig brain. We also studied the influence of clonidine on the naloxone-induced withdrawal signs. 1. Guinea-pigs were implanted subcutaneously with MS contin (300 mg.kg-1). Two days after implantation, the binding of 3H-UK14304 (alpha 2 selective ligand) to brain membranes prepared from morphine dependent and control animals was determined. Scatchard plot of the saturation binding data revealed an increase in Bmax values and no change in the Kd values from dependent animals. These results indicate that brain alpha 2-adrenoceptors are up-regulated in morphine dependent guinea pigs. 2. Subcutaneous injection of naloxone on the 2 nd day after implantation caused characteristic withdrawal symptoms. Clonidine has been shown to reduce some opiate withdrawal signs in morphine-dependent animals.

Adrenergic alpha-Agonists↗
PubMed1997

[Changes in opioid receptor binding nature in rat brain and spinal cord following formalin or carrageenan-induced nociception].

Previous reports demonstrated the regulation of opioid and their receptor in nociception, but it is not clear how nociceptive activation may alter opioid receptor binding nature. We determined the change of mu, delta and kappa opioid receptor types in brain and spinal cord homogenates obtained from animal models receiving nociceptive treatment. 1) Rats received a subcutaneous injection of formalin and carrageenan into planter aspect of a hindpaw. These agent-injected animals were observed for appearance of pain-related behavior (guarding of the treated paw) within 2-3 hour after treatment. Following these pain behavior, rats were decapitated and brain and spinal cord were removed rapidly. 2) The binding of 3H-DAGO (mu agonist), 3H-DPDPE (delta agonist) and 3H-EKC (kappa agonist) to brain and spinal cord membranes prepared from nociceptive treatment and control rats was determined. Using these tracer 3H-opioid ligands, we failed to see any change in the total number of opioid binding sites (Bmax values) or the affinity constant (Kd values) for binding in whole brain and spinal cord. These results indicate that in these animal models which use experimentally induced inflammation to stimulate a condition of nociception, there appears to be no alteration in the levels of mu, delta or kappa binding sites.

Animals↗
PubMed1996

Inhibition of peritoneal dissemination of colon carcinoma in syngeneic mice immunized with interleukin-2-producing cells.

We have examined the antitumor effect of murine colon carcinoma cells engineered to produce human interleukin-2 (IL-2) in syngeneic mice. Subcutaneous inoculation of retrovirally-transduced cells with IL-2 gene formed small tumors, but they became regressed spontaneously. Consequently, the inoculated mice showed prolonged survival. Histological examination of the tumors derived from IL-2-producers revealed predominant infiltration of macrophages around tumor necrotic masses. Thus, inoculation of IL-2-producing cells could protect the mice from subsequent subcutaneous or intraperitoneal challenges with wild-type cells, suggesting the induction of acquired immunity due to the effect of tumor vaccination.

Animals↗
PubMed1996

Interaction between the two signal transduction systems of the histamine H2 receptor: desensitizing and sensitizing effects of histamine stimulation on histamine-dependent cAMP production in Chinese hamster ovary cells.

The histamine H2 receptor is a member of the family of G-protein-coupled receptors and is linked to the activation of adenylate cyclase phospholipase C (PLC). In this study we examined the effects of protein kinase C (PKC) activation in Chinese hamster ovary (CHO) cells stably expressing canine histamine H2 receptors. Pretreatment with 100 nM phorbol 12-myristate 13-acetate at 37 degrees C for 15 min led to significant potentiation of histamine-dependent and forskolin-dependent cAMP production, whereas the biologically inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate, was without effect. These potentiating effects were abolished by preincubation with 0.5 microM bisindolylmaleimide, a PKC inhibitor. Thus the activation of PKCs seems to be involved in the potentiation of cAMP production by acting on a post-receptor mechanism. Preincubation of a CHO cell line, CHO-H2R, with 10 microM histamine for 30 min had two effects. Maximal histamine-dependent cAMP production and forskolin-dependent cAMP production were potentiated by 36% and 105.2% respectively. The other effect was a desensitization of the histamine-dependent adenylate cyclase response as demonstrated by a three-fold increase in EC50. Administration of 0.5 microM bisindolylmaleimide before preincubation of CHO-H2R with 10 microM histamine did not alter the desensitizing effect on cAMP production, but did abolish the sensitizing effect. Preincubation of CHO-H2R cells with 10 nM histamine resulted in moderate potentiation, which was also abolished by bisindolylmaleimide, but not in desensitization of the histamine-dependent cAMP production. Thus these results suggest that preincubation with histamine had a sensitizing effect on cAMP production mediated by PLC and PKC activation, as well as a desensitizing effect on the H2 receptor. The former effect is dependent on the intensity of PLC and PKC signals delivered by H2 receptors. The latter effect requires a higher concentration of histamine.

Animals↗
PubMed1996

Transfection of human topoisomerase II alpha into etoposide-resistant cells: transient increase in sensitivity followed by down-regulation of the endogenous gene.

We have investigated the possibility of overcoming the resistance of human brain tumour cells (HBT20) to etoposide by transferring the normal human topoisomerase II alpha (H-topo II) gene into these cells. H-topo II in a mammalian expression vector containing a glucocorticoid-inducible mouse mammary tumour virus (MMTV) promoter was transfected into etoposide-resistant HBT20 cells (HBT20-hTOP2MAM). HBT20 cells transfected with pMAMneo vector alone served as control cells (HBT20-MAM). These were stable transfections. Following a 2 h dexamethasone treatment, H-topo II mRNA expression, protein production, etoposide-induced DNA-protein complex formation and sensitivity to etoposide were increased in HBT20-hTOP2MAM cells compared with control HBT20-MAM cells and with HBT20-hTOP2MAM cells not treated with dexamethasone. However, mRNA and protein levels and cell sensitivity returned to baseline when incubation with dexamethasone was continued for 24 h. This decrease from the 2 h values could not be explained by a loss of the MMTV promoter response to dexamethasone. (H-topo II alpha promoter)-(chloramphenicol acetyltransferase) constructs containing regions -559-0 and -2400-0 were significantly down-regulated in HBT20-hTOP2MAM cells treated for 24 h with dexamethasone compared with dexamethasone-treated control cells. H-topo II mRNA stability after 24 h of dexamethasone treatment was not altered compared with that in control cells. Our data indicate that the exogenously produced H-topo II may have a negative-feedback effect on the endogenous topoisomerase II promoter, causing down-regulation of the endogenous gene.

Animals↗
PubMed1996

Cloning of cDNAs encoding two isoforms of 68-kDa type I phosphatidylinositol-4-phosphate 5-kinase.

Accumulating evidence suggests that phosphatidylinositol metabolism is essential for membrane traffic in the cell. Of particular importance, phosphatidylinositol transfer protein and the type I phosphatidylinositol- 4-phosphate 5-kinase (PI4P5K) have been identified as cytosolic components required for ATP-dependent, Ca2+-activated secretion. In order to identify PI4P5K isoforms that may play important roles in regulated insulin secretion from pancreatic beta-cells, we employed the polymerase chain reaction with degenerate primers and screening of a cDNA library of the murine pancreatic beta-cell line MIN6. Two novel cDNAs, designated PI4P5K-Ialpha and PI4P5K-Ibeta, were identified, which contained complete coding sequences encoding 539- or 546-amino acid proteins, respectively. These cDNAs were expressed in mammalian cells with an adenoviral expression vector. Proteins of both isoforms migrated at 68 kDa on SDS-polyacrylamide gel electrophoresis and exhibited phosphatidylinositol-4-phosphate 5-kinase activity, which was activated by phosphatidic acid, indicating that these proteins were type I isoforms. While these isoforms share a marked amino acid sequence homology in their central portion, the amino- and carboxyl-terminal regions differ significantly. Northern blot analysis depicted that tissue distributions differed between the two isoforms. Molecular identification of type I PI4P5K isoforms in insulin-secreting cells should provide insights into the role of phosphatidylinositol metabolism in regulated exocytosis of insulin-containing large dense core vesicles.

Amino Acid Sequence↗
PubMed1996

Overexpression of catalytic subunit p110alpha of phosphatidylinositol 3-kinase increases glucose transport activity with translocation of glucose transporters in 3T3-L1 adipocytes.

To elucidate the mechanisms of phosphatidylinositol (PI) 3-kinase involvement in insulin-stimulated glucose transport activity, the epitope-tagged p110alpha subunit of PI 3-kinase was overexpressed in 3T3-L1 adipocytes using an adenovirus-mediated gene transduction system. Overexpression of p110alpha was confirmed by immunoblot using anti-tagged epitope antibody. p110alpha overexpression induced a 2.5-fold increase in PI 3-kinase activity associated with its regulatory subunits in the basal state, an increase exceeding that of the maximally insulin-stimulated control cells, while PI 3-kinase activity associated with phosphotyrosyl protein was only modestly elevated. Overexpression of p110alpha induced an approximately 14-fold increase in the basal glucose transport rate, which was also greater than that observed in the stimulated control. No apparent difference was observed in the cellular expression level of either GLUT1 or GLUT4 proteins between control and p110alpha-overexpressing 3T3-L1 adipocytes. Subcellular fractionation revealed translocation of glucose transporters from intracellular to plasma membranes in basal p110alpha-overexpressing cells. The translocation of GLUT4 protein to the plasma membrane was further confirmed using a membrane sheet assay. These findings indicate that an increment in PI 3-kinase activity induced by overexpression of p110alpha of PI 3-kinase stimulates glucose transport activity with translocation of glucose transporters, i.e., mimics the effect of insulin.

3T3 Cells↗
PubMed1996

The Fyn tyrosine kinase binds Irs-1 and forms a distinct signaling complex during insulin stimulation.

Irs-proteins link the receptors for insulin/IGF-1, growth hormones, and several interleukins and interferons to signaling proteins that contain Src homology-2 (SH2). To identify new Irs-1-binding proteins, we screened a mouse embryo expression library with recombinant [32P]Irs-1, which revealed a specific association between p59fyn and Irs-1. The SH2 domain in p59fyn bound to phosphorylated Tyr895 and Tyr1172, which are located in YXX(L/I) motifs. Mutation of p59fyn at the COOH-terminal tyrosine phosphorylation site (Tyr531) enhanced its binding to Irs-1 during insulin stimulation. Binding experiments with various SH2 protein revealed that Grb-2 was largely excluded from Irs-1 complexes containing p59fyn, whereas Grb-2 and p85 occurred in the same Irs-1 complex. By comparison with the insulin receptor, p59fyn kinase phosphorylated a unique cohort of tyrosine residues in Irs-1. These results outline a role for p59fyn or other related Src-kinases during insulin and cytokine signaling.

Amino Acid Sequence↗
PubMed1996

High-performance liquid chromatographic measurements of urinary hydroxycarboxylic acids as an index of the metabolic control in non-insulin-dependent diabetic patients.

Hydroxycarboxylic acids in urine of patients with non-insulin-dependent diabetes mellitus and of healthy subjects are analyzed as 2-nitrophenylhydrazides by an improved high-performance liquid chromatographic method which has advantages with respect to resolution and analysis time. Variations in levels of hydroxycarboxylic acids, originated from the metabolism of valine, leucine and isoleucine, have been described in the diabetic patients who have good and poor metabolic controls. The sum of the hydroxycarboxylic acids in both groups of diabetic patients was significantly increased compared with the values of the healthy subjects. Statistically significant difference was present between the two groups. In the whole group of diabetic patients, the sum of the hydroxycarboxylic acids correlated with fasting plasma glucose or hemoglobin A1c (r = 0.548, P < 0.01 and r = 0.629, P < 0.01, respectively). These results suggest that the relevance of these abnormalities may be used as an index of metabolic control in diabetic patients.

Adult↗
PubMed1996

Antitumor effect induced by the expression of granulocyte macrophage-colony stimulating factor gene in murine colon carcinoma cells.

Murine colon carcinoma cells which secrete several kinds of cytokine after retroviral transduction with corresponding genes, were examined for their antitumor effects in syngeneic mice. The mice inoculated with granulocyte macrophage-colony stimulating factor (GM-CSF) producer cells showed not only prolonged survival but also reduced tumorigenicity. The antitumor effect caused by the expression of interleukin-4 was less than that of GM-CSF, and interleukin-6 producer cells did not show any effects on the survival of the host animals. Histological examination of the GM-CSF-producing tumor revealed predominant infiltration of neutrophils and necrotic change of the tumor. The present study indicates the feasibility of cancer gene therapy with the expression of GM-CSF gene in tumor cells.

Animals↗
PubMed1996

Murine colon carcinoma cells engineered to produce human interleukin-2 induce tumor-specific anti-tumor response.

Murine colon carcinoma cells (colon 26) transduced by a retrovirus vector with the human interleukin-2 (IL-2) cDNA were studied for their tumorigenicity. Although cell growth in vitro was not affected by integration of the IL-2 gene, s.c. tumors of IL-2-producing colon 26 cells (H2) in syngeneic mice regressed spontaneously after producing small masses. Histological examination of the sites of tumor rejection revealed predominant infiltration of macrophages around the tumor necrotic mass. Subsequent challenge with parent colon 26 cells, but not with Meth A cells (fibrosarcoma of the same genetic background), did not result in tumor formation in mice which had been protected against H2 cells. Inoculation of H2 cells into syngeneic nude mice resulted in tumors with a retarded growth rate. Taken together, T cell-dependent, tumor-specific immunity is obtained by local IL-2 secretion around colon tumors, and this experimental animal model gives us a clue(s) for investigating host anti-tumor responses by cytokine production.

Animals↗
PubMed1996

A novel 55-kDa regulatory subunit for phosphatidylinositol 3-kinase structurally similar to p55PIK Is generated by alternative splicing of the p85alpha gene.

Phosphatidylinositol 3-kinase, which is composed of a 110-kDa catalytic subunit and a regulatory subunit, plays important roles in various cellular signaling mechanisms. We screened a rat brain cDNA expression library with 32P-labeled human IRS-1 protein and cloned cDNAs that were very likely to be generated by alternative splicing of p85alpha gene products. These cDNAs were demonstrated to encode a 55-kDa protein (p55alpha) containing two SH2 domains and an inter-SH2 domain of p85alpha but neither a bcr domain nor a SH3 homology domain. Interestingly, p55 alpha contains a unique 34-amino acid sequence at its NH2 terminus, which is not included in the p85alpha amino acid sequence. This 34-amino acid portion was revealed to be comparable with p55PIK (p55gamma) in length, with a high homology between the two, suggesting that these NH2-terminal domains of p55alpha and p5 gamma may have a specific role that p85 does not. The expression of p55alpha mRNA is most abundant in the brain, but expression is ubiquitous in most rat tissues. Furthermore, it should be noted that the expression of p85alpha mRNA in muscle is almost undetectably low by Northern blotting with a cDNA probe coding for the p85alpha SH3 domain, while the expression of p55alpha can be readily detected. These results suggest that p55 alpha may play an unique regulatory role for phosphatidylinositol 3-kinase in brain and muscle.

Alternative Splicing↗