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Biomedical subjects

T Asai

Publications and source records attributed to T Asai.

At least 217 records · Page 12Linked to original sources
PubMed1998

Slow intrinsic optical signals in the rat spinal dorsal horn in slice.

Tetanic stimulation of high-threshold primary afferent fibers in the dorsal root was found to elicit intrinsic optical signals (IOSs) in transverse slices of 11- to 20-day-old rat spinal cords. The IOS, lasting for 30 s or longer, was most prominent in the lamina II of the dorsal horn. Treatment with a Na+-K+-2Cl- co-transport blocker, furosemide, abolished the IOS, suggesting that the origin of the IOS is the cellular swelling due to an activity-dependent rise in extracellular K+. Substance P antagonist spantide, glutamate antagonists 2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2,3-dione, and the mu-opioid agonist [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin suppressed IOSs. Thus, IOSs represent at least in part the slow excitatory response that is known to be generated in dorsal horn neurons after tetanic activation of unmyelinated afferent fibers.

2-Amino-5-phosphonovalerate↗
PubMed1998

Establishment and characterization of a murine osteosarcoma cell line (LM8) with high metastatic potential to the lung.

We established a murine osteosarcoma cell line (LM8) with high metastatic potential to the lung from murine Dunn osteosarcoma using 8 repeated Fidler's procedures. We performed the biological characterization of the LM8 and the maternal Dunn cell lines in vitro and in vivo. Morphologically, LM8 possesses many fillopodial protrusions, lamellipodial structures surrounding the cell surface and membrane ruffles suggesting enhanced cell motility. The increased matrix metalloproteinase (MMP) 2 activity of this cell line might help cell invasion after penetration of the endothelial (mesothelial) cell layer. This cell line exhibited high in vitro invasive activity when seeded onto the mesothelial cell monolayer. Higher expression of VEGF mRNA in this cell line might facilitate neovascularization at the site of metastasis, resulting in extremely high metastatic potency after i.v. injection. LM8 also showed a high metastatic incidence (7/7) to the lung even after s.c. transplantation into the back space of mice. This cell line can provide an excellent tool for studying inhibitory agents against pulmonary metastasis as well as the various important factors involved in metastasis of osteosarcoma.

Alkaline Phosphatase↗
PubMed1998

Enhanced expression of p53 and apoptosis induced by blockade of the vacuolar proton ATPase in cardiomyocytes.

Activation of the vacuolar proton ATPase (VPATPase) has been implicated in the prevention of apoptosis in neutrophils and adult cardiac myocytes. To determine the role of the VPATPase in apoptosis of cardiac myocytes, we used a potent and specific inhibitor of the VPATPase, bafilomycin A1. Bafilomycin A1 alone caused increased DNA laddering of genomic DNA and increased nuclear staining for fragmented DNA in neonatal cardiomyocyte apoptosis in a dose- and time-dependent manner. Intracellular acidification in cardiac myocytes was also observed after 18 h of bafilomycin A1 treatment. Accordingly, bafilomycin A1-treated myocytes also showed increased accumulation of p53 protein and p53-dependent transactivation of gene expression, including a persistent upregulation of p21/wild-type p53 activated fragment 1/cyclin kinase inhibitor protein-1 mRNA. The bafilomycin A1-induced increase in p53 protein levels was accompanied by a marked increase in p53 mRNA accumulation. In contrast, cardiac fibroblasts treated with bafilomycin A1 showed no change in p53 protein expression or pHi and did not undergo apoptosis even after 24 h of treatment. Our data suggest that blockade of the VPATPase induces apoptotic cell death of cardiac myocytes and that this may occur through a p53-mediated apoptotic pathway.

Animals↗
PubMed1998

Neospora caninum: tachyzoites express a potent type-I nucleoside triphosphate hydrolase.

We have identified type I nucleoside triphosphate hydrolase (NTPase; EC 3.6. 1.3) activity, previously thought to be restricted to the virulent strains of Toxoplasma gondii, in the cell extracts of Neospora caninum tachyzoites. Sequence analysis of a complete cDNA from Nc-1 strain indicated that N. caninum NTPases shared approximately 69% identity to the NTPases of T. gondii and are most similar to the NTPase-I isozyme. Southern blot analysis of genomic DNA and sequence analysis of two independent NTP clones from the Nc-1 strain revealed the presence of multiple genes, at least two of which are transcribed. Substrate specificity and Km values for MgATP2- and MgADP- hydrolysis for recombinant or partially purified native NcNTPase were the same as those for the type I isozyme (NTPase-I). Significantly, no type II enzyme (NTPase-II) activity for NDP hydrolysis was detected in cell extracts of N. caninum, although it is universally present in all T. gondii strains that have been tested. This intriguing difference between these two closely related apicomplexan parasites may provide insight into the function of the NTPases during intracellular parasitism.

Acid Anhydride Hydrolases↗
PubMed1998

Inhibition of angiogenesis on glycated collagen lattices.

Advanced glycation endproduct (AGE) accumulation in extracellular matrix proteins has been demonstrated in diabetic patients with a significant correlation with the severity of diabetic complications. AGE accumulation induces matrix protein cross-link formation, resulting in an increased stiffness of matrix fibres and the reduction of the susceptibility of matrix proteins to proteolytic degradation. We examined whether glycation-induced collagen cross-linking may affect vascular endothelial cell behaviours such as invasion, proliferation and differentiation, using the in vitro angiogenesis model of capillary-like structure formation in three-dimensional matrices of collagen type I. Endothelial cells cultured on collagen gel with angiogenic factors (the combination of fibroblast growth factor-2 and vascular endothelial growth factor) invaded the underlying collagen matrix, and organized capillary-like cord structures in the gel. We found that endothelial cell invasion into glycated collagen gel was significantly attenuated without any effect on proteinase activity including cell-associated plasminogen activator and matrix metalloproteinase in the conditioned medium. In addition, subsequent capillary-like cord formation was also inhibited in glycated collagen gel. In contrast, endothelial cell proliferation was enhanced on glycated collagen gel with or without angiogenic factors compared with control collagen gel. These results suggest that the structural alterations of extracellular matrix proteins through the glycation-induced cross-link formation affect the interaction between endothelial cell and extracellular matrix, resulting in the impairment of an adequate neovascularization in diabetic patients.

Angiogenesis Inducing Agents↗
PubMed1998

Aggressive non-Hodgkin's lymphoma after successful eradication of Helicobacter pylori and regression of gastric lymphoma of mucosa-associated lymphoid tissue.

A 57-year-old woman presented to our clinic with low-grade gastric lymphoma of mucosa-associated lymphoid tissue (stage IE) and Helicobacter pylori infection. She received a 2-week course of omeprazole and clarithromycin, resulting in eradication of H. pylori and histological disappearance of the lymphoma. However, 9 months later (May 1996), multiple mass lesions were found around the pancreas and hepato-duodenal ligament on abdominal computed tomography. Inguinal lymph node biopsy revealed aggressive nodal type B-cell non-Hodgkin's lymphoma, diffuse large cell type. She received chemotherapy with cyclophosphamide, adriamycin, vincristine, and prednisolone, but failed to achieve remission and died in December 1996. There was no evidence of recurrent gastric lymphoma. This case emphasizes the importance of performing follow-up examinations to detect other neoplasms in patients with gastric lymphoma of mucosa-associated lymphoid tissue.

Diagnosis, Differential↗
PubMed1998

Continued circulation of reassortant H1N2 influenza viruses in pigs in Japan.

In 1991 and 1992, H1N2 influenza A viruses were isolated from the lungs of pigs with overt signs of respiratory disease at farms in the Chiba and Kanagawa prefectures of Japan. To determine the genetic origin of these isolates, we phylogenetically analyzed partial nucleotide sequences of their genes. The results indicate that influenza viruses possessing the N2 of human influenza virus and seven other gene segments of classical H1N1 swine influenza virus, which were first isolated in 1980, have become established in Japanese pigs.

Animals↗
PubMed1998

Up-regulation of vascular endothelial growth factor in response to glucose deprivation.

Vascular endothelial growth factor (VEGF), also known as a vascular permeability factor (VPF), is an endothelial specific mitogen and is a potent inducer of angiogenesis. Recently it has been reported that hypoxia induces VEGF mRNA expression in various cells. Since both oxygen and glucose are required for efficient production of energy, we examined the effect of glucose deprivation on VEGF mRNA expression and VEGF protein production in U-937 (a human monocytic cell line) cells. Both the mRNA expression and secretion of VEGF increased after exposure to low glucose. Addition of L-glucose, the L-stereoisomer of D-glucose, did not prevent the up-regulation of VEGF expression. The conditioned medium from glucose-deprived cells, followed by supplementation with glucose, did not up-regulate VEGF mRNA expression in U-937 cells. The low glucose-induced VEGF mRNA expression returned to the control level after supplementation with D-glucose. Furthermore, oligomycin, a mitochondrial ATP synthase inhibitor, increased VEGF protein production. The results suggest that the up-regulation of VEGF mRNA in U-937 cells in response to glucose deprivation is not mediated by autocrine factors from the cells nor is the osmotic change of the medium mediated by the deficiency of glucose metabolism in the cells. Our results also suggest that the intracellular ATP depletion due to glucose deprivation may be one of the causes for increased VEGF mRNA expression. We speculate that local hypoglycemia may act as an essential trigger for angiogenesis through the VEGF gene expression.

Adenosine Triphosphate↗
PubMed1998

Increased soluble Fas-ligand in sera of bone marrow transplant recipients with acute graft-versus-host disease.

Acute graft-versus-host disease (aGVHD) is a major complication following allogeneic bone marrow transplantation (BMT). Recently, accumulating evidence indicates that the Fas/Fas ligand (FasL) system is implicated in the pathogenesis of aGVHD in murine models. We determined the serum levels of soluble FasL (sFasL) in BMT recipients using an enzyme-linked immunosorbent assay. The serum sFasL was suppressed during the period of myelosuppression following the preparative regimen and subsequently increased with hematopoietic reconstitution after BMT. In patients with aGVHD, the serum sFasL level was significantly higher than in those without aGVHD. In the mixed lymphocyte reaction assay, sFasL in the supernatants was increased with a significant correlation to the level of 3H-thymidine uptake. Our findings suggest that the Fas/FasL system is activated by allogeneic stimulation and may have close correlation to the development of aGVHD in human BMT.

Adolescent↗
PubMed1998

Timing of removal of the laryngeal mask airway.

Previous studies reported that complications associated with removal of the laryngeal mask were more frequent in awake patients than in anaesthetised patients; however, these studies did not comply with the method described in the manufacturer's instruction manual. The reported incidences of regurgitation during the use of the laryngeal mask also differ considerably between studies. We studied these factors in 66 patients in whom the method described in the manual was used. After induction of anaesthesia, the laryngeal mask and a pH probe were inserted and the cuff of the mask was inflated with a minimum volume of air. Anaesthesia was maintained with nitrous oxide and isoflurane in oxygen. At the end of the operation, we randomly allocated patients to one of two groups and the laryngeal mask was removed either while they were still deeply anaesthetised or after they had regained consciousness. No apparent regurgitation occurred in any patient during operation, but one patient in the anaesthetised group regurgitated immediately after removal of the mask. The incidence of complications during or after removal of the laryngeal mask was significantly greater in the anaesthetised group than that in the awake group (p << 0.001; difference [95% CI]: 48.5 [30.5-66.5]%). Therefore, the laryngeal mask can be safely left in place until the patient has regained consciousness after emergence from anaesthesia.

Adolescent↗
PubMed1998

Respiratory complications associated with tracheal extubation. Timing of tracheal extubation and use of the laryngeal mask during emergence from anaesthesia.

Sixty patients were randomly allocated to one of three groups and the incidences of respiratory complications which occurred during emergence from anaesthesia were compared under the following three circumstances: tracheal extubation after the patient had regained consciousness (awake group); tracheal extubation while the patient was still anaesthetised (anaesthetised group); and the use of the laryngeal mask during emergence from anaesthesia (mask group). In the mask group, the laryngeal mask was inserted under deep anaesthesia before tracheal extubation and the lungs were ventilated through the laryngeal mask after tracheal extubation. In the awake group, straining (bucking) occurred in 18 patients and desaturation (arterial oxygen haemoglobin saturation < 95%) in two patients. In the anaesthetised group, airway obstruction occurred in 17 patients and desaturation in one of these patients. In the mask group, ventilation through the laryngeal mask was temporarily difficult immediately after tracheal extubation in one patient and coughing occurred before removal of the mask in three patients. No respiratory complications occurred in two patients in the awake group, three patients in the anaesthetised group and 16 patients in the mask group. The incidence of respiratory complications during recovery from anaesthesia was significantly lower in the mask group than in the other two groups (pooled) (p << 0.001). Therefore, the use of the laryngeal mask after tracheal extubation decreases the incidence of respiratory complications during recovery from anaesthesia.

Adolescent↗
PubMed1998

The cuffed oropharyngeal airway. Its clinical use in 100 patients.

We studied the efficacy of the cuffed oropharyngeal airway in 100 patients. Insertion of the airway after induction of anaesthesia with propofol was easy in 95 of 100 patients, moderately difficult in four patients and failed in one patient. Complications, such as coughing, gagging or body movement, occurred during induction and insertion in 15 patients. Insertion of the airway was not associated with tachycardia or hypertension. Manual ventilation through the airway was easy in less than 30% of patients immediately after insertion. Manual ventilation became easier after adjusting the position of the patient's head, neck or jaw. During spontaneous breathing, adjustment of the head, neck or jaw was required in 30% of patients. Complete airway obstruction occurred in one patient after insertion of the device and in two patients during maintenance of anaesthesia. The airway was left in place during emergence from anaesthesia in the remaining 97 patients. No complications occurred in 91 patients and coughing occurred in the remaining six patients before or during removal of the airway. No regurgitation, vomiting or laryngospasm occurred in any patient at any time. Therefore, the cuffed oropharyngeal airway has a potential use in anaesthetised patients who are breathing spontaneously.

Adolescent↗
PubMed1998

Use of the McCoy laryngoscope or fingers to facilitate fibrescope-aided tracheal intubation.

In fibrescope-aided tracheal intubation, it can be difficult to advance a tube over a fibrescope, because its passage may be impeded by the epiglottis, arytenoids or pyriform fossa. In two patients with difficult intubation, after successful insertion of a fibrescope into the trachea, it was impossible to advance the tube over the fibrescope. Fibrescope-aided tracheal intubation was accomplished by shifting the epiglottis anteriorly and 'opening up' the glottis either by fingers or the McCoy laryngoscope.

Aged↗
PubMed1998

Modulation by proinflammatory cytokines of Fas/Fas ligand-mediated apoptotic cell death of synovial cells in patients with rheumatoid arthritis (RA).

Synovial cell hyperplasia is a characteristic of patients with RA. Excessive proliferation of RA synovial cells is, in part, responsible for the synovial cell hyperplasia. In addition, synovial cell death that would reduce synovial cell number may be defective, leading to the hyperplasia. Thus, the defective control of cell death as well as cell proliferation may be of central importance in the pathogenesis of RA. In this study we analysed effects of proinflammatory cytokines on Fas/Fas ligand (FasL)-induced synovial cell apoptosis, and evaluated apoptosis-associated protein expression in the synovial cells in patients with RA. RA synovial cells expressed Fas antigen and lymphocytes infiltrating into RA synovium expressed FasL. Apoptotic synovial cells were detected within the sublining layer of RA synovium. Anti-Fas MoAb induced apoptosis of RA synovial cells in vitro, and proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and IL-1beta, but not IL-6 or IL-8, inhibited the anti-Fas-induced apoptosis accompanying up-regulation of Bcl-2 protein expression and reduced expression of CPP32 and ICH-1L. Immunohistochemical study revealed that CPP32 and ICH-1L were expressed weakly in the RA synovial lining cells compared with osteoarthritis (OA) synovial lining cells. Thus, we found that although RA synovial cells could die via apoptosis through Fas/FasL pathway, apoptosis of synovial cells was inhibited by proinflammatory cytokines present within the synovium. Inhibition of apoptosis by the proinflammatory cytokines may contribute outgrowth of synovial cells that leads to pannus formation and the destruction of joints in patients with RA.

Antibodies, Monoclonal↗
PubMed1998

Are minichromosomes valid model systems for DNA replication control? Lessons learned from Escherichia coli.

Initiation of chromosome replication is a key event in the life cycle of any organism. Little is known, however, about the regulatory mechanisms of this vital process. Conventionally, the initiation mechanism of chromosome replication in microorganisms has been studied using plasmids in which an origin of chromosome replication has been cloned, rather than using the chromosome itself. The reason for this is that even bacterial chromosomes are so large that biochemical and genetic manipulations become difficult and cumbersome. Recently, the combination of flow cytometry and genetic methods, in which modifications of the replication origin are systematically introduced onto the chromosome, has made possible detailed studies of the molecular events involved in the control of replication initiation in Escherichia coli. The results indicate that requirements for initiation at the chromosomal origin, oriC, are drastically different from those for initiation at cloned oriC.

Chromosomes, Bacterial↗