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Biomedical subjects

M Aihara

Publications and source records attributed to M Aihara.

At least 91 records · Page 5Linked to original sources
PubMed1997

Mechanisms involved in Helicobacter pylori-induced interleukin-8 production by a gastric cancer cell line, MKN45.

Accumulating evidence suggests an important role of interleukin-8 (IL-8) in Helicobacter pylori infection-associated chronic atrophic gastritis and peptic ulcer. We observed in this study that a gastric cancer-derived cell line, MKN45, produced a massive amount of IL-8 upon coculture with live H. pylori but not with killed H. pylori, H. pylori culture supernatants, or live H. pylori separated by a permeable membrane, indicating that IL-8 production requires a direct contact between the cells and live bacteria. Moreover, the tyrosine kinase inhibitor herbimycin but neither a protein kinase C inhibitor (staurosporine) nor a protein kinase A inhibitor (H89) inhibited IL-8 production by MKN45 cells cocultured with live bacteria, suggesting the involvement of a tyrosine kinase(s) in H. pylori-induced IL-8 production. In addition, coculture of H. pylori induced IL-8 mRNA expression in MKN45 cells and an increase in luciferase activity in cells which were transfected with a luciferase expression vector linked with a 5'-flanking region of the IL-8 gene (bp -133 to +44), indicating that the induction of IL-8 production occurred at the transcriptional level. This region contain three cis elements important for induction of IL-8 gene expression: AP-1 (-126 to -120 bp), NF-IL6 (-94 to -81 bp), and NF-kappaB (-80 to -70 bp) binding sites. Mutation of the NF-kappaB binding site abrogated completely the induction of luciferase activity, whereas that of the AP-1 site partially reduced the induction. However, mutation of the NF-IL6 binding site resulted in no decrease in the induction of luciferase activity. Moreover, specific NF-kappaB complexes were detected in the nuclear proteins extracted from MKN45 cells which were infected with H. pylori. Collectively, these results suggest that H. pylori induced the activation of NF-kappaB as well as AP-1, leading to IL-8 gene transcription.

Gene Expression Regulation↗
PubMed1997

How does the contractile vacuole of Paramecium multimicronucleatum expel fluid? Modelling the expulsion mechanism

To examine the forces needed for discharge of the fluid contents from the contractile vacuole of Paramecium multimicronucleatum, the time course of the decrease in vacuole diameter during systole (the fluid-discharging period) was compared with that of various vacuole discharge models. The observed time course did not fit that predicted by a model in which contraction of an actin­myosin network surrounding the vacuole caused discharge nor that predicted by a model in which the surface tension of the lipid bilayer of the vacuole caused discharge. Rather, it fitted that predicted by a model in which the cell's cytosolic pressure was responsible for discharge. Cytochalasin B, an effective inhibitor of actin polymerization, had no effect on the in vivo time course of systole. An injection of a monoclonal antibody raised against the proton pumps of the decorated spongiomes (now known to be the locus of fluid segregation in P. multimicronucleatum) disrupted the decorated spongiomes and reduced the rate of fluid segregation, whereas it did not alter the time course of systole. We conclude that in P. multimicronucleatum the internal pressure of the contractile vacuole is caused predominantly by the cytosolic pressure and that the fluid-segregation mechanism does not directly affect the fluid-discharge mechanism. Elimination of this cytosolic pressure by rupturing the cell revealed the presence of a novel fluid-discharge mechanism, apparently centered in the vacuole membrane. The involvement of tubulation of the vacuole membrane as the force-generating mechanism for fluid discharge in disrupted cells is discussed.

Journal Article↗
PubMed1997

A selective pulmonary thrombosis associated with sepsis-induced disseminated intravascular coagulation.

Disseminated intravascular coagulation (DIC) is a pathologic condition associated with critical illnesses, including sepsis. Recent studies have suggested that endogenous cytokines and leukocytes are involved in major roles of its pathophysiology. We report a case of sepsis-induced DIC due to pneumonia that was associated with diffuse and selective thrombosis in pulmonary arteries, yielding to sudden death from pulmonary massive embolism. This report suggests that the selective and lethal pulmonary thromboembolism progresses under the standard therapies in sepsis-induced DIC.

Adult↗
PubMed1997

[Efficacy and side effects of lidocaine by intravenous drip infusion in children with intractable seizures].

Intravenous drip infusions of lidocaine (IDIL; 1-5 mg/kg/h) were performed in ten patients with intractable seizures. The medication was very effective in five patients, whose seizures disappeared immediately after the treatment of IDIL. In four patients, the medication proved to be effective judging from decreased incidence of seizures. In one patient with intractable seizures, the therapy was not effective. In nine patients with the effective medication, five had generalized seizures and four had partial seizures. Side effects were observed in four patients. Two patients had muscle hypotonia, one had visual and auditory hallucination and another had bradycardia. These symptoms completely disappeared after the ceasing of IDIL. Serum concentrations of lidocaine at the appearance of the side effects ranged from 1.8 to 4.7 micrograms/ml, although the toxicity level is more than 5.0 micrograms/ml for arrhythmic adult patients. These findings suggest that the serum toxic level of lidocaine in children is different from that in adults, and that careful observation and appropriate management for the children with lidocaine therapy should be necessary, even though the serum level of lidocaine ranges within the therapeutic level.

Adolescent↗
PubMed1997

[Cerebral cortical dysplasia associated with epilepsy: MRI and clinical aspects].

Clinical and electroencephalographic (EEG) studies were performed in nine patients with cerebral cortical dysplasia (CD). Interictal single photon emission computed tomography (SPECT) using 99mTc-hexamethyl propylene amine oxime were studied in four patients. A patient with hemimegalencephaly and agyria had poor outcome in both developmental and epileptic aspects. The prognoses of clinical seizures were generally related to the severity, location and size of CD. The size of the lesion was not always correlated with the clinical seizure outcome. Four patients had focal pachygyria. Clinical pictures were diverse in these patients. One patient underwent callosotomy for the control of intractable seizures. The others had no clinical seizures despite of the appearance of paradoxical discharges in the area of pachygyria. The distribution of CD detected by MRI did not always correlate with that of paradoxical discharges in EEG and/or hypoperfusional areas seen in SPECT. These findings suggest that a detailed neuroimaging study is useful to elucidate the epileptogenesis in patients with CD, and that all the cortical abnormalities in patients with intractable epilepsy are not detected by MRI.

Adolescent↗
PubMed1997

[Infectious disease in Kenya--epidemiological study of diarrhoeal disease in children].

I participated in a project concerning diarrhea in children caused by bacteria (Japan International Cooperation Association) in the Republic of Kenya between April 1993 and March 1994. According to the Health Information Report by the Ministry of Health in 1993, diarrhea was at the 5th most frequent disease among outpatients and these patients numbered about eight hundred thousand. On microbiological examination, diarrhoegenic agents were detected from 767 of 1,362 (56.3%) fecal specimens collected from children under five years of age with diarrhea. Major causative agents were diarrhogenic Escherichia coli (DgEC), Rota virus, Shigella spp., Entamoeba histolytica, Salmonella spp., and Giardia lamblia, which were detected from 17.2%, 11.4%, 6.3%, 5.8%, 5.4% and 3.6%, respectively. The results suggested that diarrhea was caused by drinking water with fecal contamination. We bacteriologically examined drinking water in the patients' houses, and many Enterobacteriaceae were detected in most of the specimens.

Age Factors↗
PubMed1997

Localization of platelet-activating factor receptor messenger RNA in the rat eye.

PURPOSE: To determine the distribution of platelet-activating factor (PAF) receptor in the rat eye. METHODS: Platelet-activating factor receptor messenger RNA (mRNA) expression was evaluated with reverse transcription-polymerase chain reaction (RT-PCR) in RNAs from several rat ocular tissues. Distribution of the expression was determined with in situ hybridization in adult rat eye sections and a 35S-labeled complementary RNA probe synthesized from the rat PAF receptor complementary DNA. In situ hybridization was also done with sections immunostained with OX-42, a microglia marker. RESULTS: RT-PCR revealed that levels of PAF receptor expression were similar among the ocular tissues studied. The in situ hybridization signals were found in the corneal epithelium, iris and ciliary body, and ganglion and microglial cells in the retina. CONCLUSIONS: Platelet-activating factor receptor mRNA was ubiquitously expressed in the rat eye with relative concentration in the corneal epithelium, iris and ciliary body, and retinal ganglion and microglial cells.

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

Predominant expression of platelet-activating factor receptor in the rat brain microglia.

Cellular localization of platelet-activating factor (PAF) receptor in the rat brain was determined by (1) in situ hybridization, (2) Northern blot analysis in primary cell cultures of neurons, microglia, astrocytes, and fibroblasts, and (3) Ca2+ imaging in hippocampal culture. In situ hybridization revealed that the PAF receptor mRNA is expressed intensely in microglia and moderately in neurons. Northern blot analysis revealed that PAF receptor mRNA is the most abundant in microglia. In primary hippocampal cultures, PAF elevated intracellular Ca2+ concentration in microglia and also in neurons, but to a lesser extent. These results suggest predominant presence of PAF receptor in microglia. Cultured microglia also expressed cPLA2 mRNA the most intensely. PAF-activated microglia released arachidonic acid in a Ca(2+)-dependent manner and without conversion to its derivatives. We propose that microglia as well as neurons contribute to PAF-related events in the CNS by releasing arachidonic acid.

Animals↗
PubMed1996

On-line column preconcentration for the determination of cobalt in sea water by flow-injection chemiluminescence detection.

A flow-injection method for the determination of dissolved cobalt(II) in sea water has been studied based on a combination of column preconcentration using 8-quinolinol immobilized on silica gel, fluoride containing metal alkoxide glass (8HQ-MAF) and chemiluminescence detection with a gallic acid-hydrogen peroxide system. Co(II) is selectively recovered from an acidified sample with 8-quinolinol immobilized on silica gel. After elution with dilute hydrochloric acid the resultant eluent is mixed with the reagent solutions, heated to 60 ( degrees )C and then introduced into the CL cell. The analysis time including the 2-min sample load was 8 min per sea water sample with a corresponding detection limit of 0.62 ng l(-1) (3sigma). The average standard deviation calculated for 10 replicate measurements of artificial sea water samples with a concentration of 10 ng l(-1) cobalt was +/-2.1%. The method has been tested with the standard reference sea waters NASS and CASS.

Journal Article↗
PubMed1996

Platelet-activating factor and somatostatin activate mitogen-activated protein kinase (MAP kinase) and arachidonate release.

Platelet-activating factor (PAF) receptor and somatostatin receptor (SSTR4) were cloned, and their primary structures were identified. They are both highly expressed in the rat hippocampus. When expressed in Chinese hamster ovary cells, these receptors activated mitogen-activated protein (MAP) kinase cascade and phospholipase A2. Arachidonic acid or its derivatives, thus produced by the activation of these receptors may play some roles in synaptic transmission and synaptic plasticity.

Animals↗
PubMed1996

Deoxyribonucleic acid ploidy status as no basis for pathologic stage prediction in clinically resectable prostate cancer.

OBJECTIVES: Assessment of deoxyribonucleic acid (DNA) ploidy status of a tumor as a means for predicting pathologic stages in prostate cancer. METHODS: DNA ploidy of each focus of a cancer in 70 radical prostatectomy specimens was determined by nuclear image analysis. DNA ploidy was compared with the pathologic features of tumors. RESULTS: One hundred three individual cancers in 70 patients were used for DNA ploidy analysis. Of these, 39 (38%) were diploid and 64 (62%), nondiploid. DNA ploidy was weakly correlated with increase in tumor volume (P = 0.049) but not tumor grade. The relationship between DNA content and extraprostatic spread was not statistically significant. Increase in tumor volume and grade promoted extraprostatic spread more than nondiploidy, as shown by multivariate analysis. CONCLUSIONS: The incidence of a nondiploid cell population in a tumor focus in prostate cancer is essentially the same, at least for Americans and Japanese. DNA ploidy of a tumor cannot serve as a means of pathologic stage prediction in clinically resectable prostate cancers, contrary to many previous studies. Thus, DNA content analysis would be of no use for deciding on the treatment strategy of prostate cancer.

DNA, Neoplasm↗
PubMed1996

Impalpable prostate cancer: clinicopathological features.

OBJECTIVE: To determine the clinicopathological features of impalpable prostate cancer. PATIENTS, MATERIALS AND METHODS: The numbers of T1a and T1b cancers detected in transurethral resections of the prostate (TURP) performed before and after the advent of the test for serum prostate-specific antigen (PSA) were compared and the incidence of T1 disease in specimens from 400 consecutive radical prostatectomies examined. RESULTS: The incidence of T1b disease detected at TURP decreased significantly between the periods examined, but that of T1a was unaffected. Similarly, in radical prostatectomy specimens, T1b cancers were largely replaced by T1c and impalpable T2 cancers detected by ultrasonography. CONCLUSIONS: Cancers detected incidentally at TURP tend to be small T1a tumours, possibly suitable for conservative management. T1b cancers are likely to be detected by PSA level and treated radically. T1c and impalpable T2 cancers are morphologically unlike T1b disease and justifiably belong in separate stages in the current UICC staging system.

Aged↗
PubMed1996

The use of artificial dermis on the donor defect of the free forearm flap.

Microsurgical grafting of a free flap is an established technique of surgical reconstruction. The forearm free flap is frequently used following removal of oral and/or pharyngeal tumors. However, simple split-thickness skin grafting on full-thickness defects of the skin on the flexor side of the forearm results in deformations, pigmentation, and the adhesion of the graft to the tendons. The authors attempted to minimize such problems by repairing the flap donor site with a collagen sponge used as an artificial dermis. This artificial dermis was used to reconstruct postoperative defects in the skin of 5 patients. Split-thickness skin measuring 0.25 to 0.30 mm was grafted onto the defect. The donor site skin was successfully repaired in 2 to 3 weeks without adverse effects, without the development of depressed deformations, and with only slight pigmentation. The artificial dermis formed a matrix on the donor wound bed, with good cosmetic results.

Adolescent↗
PubMed1996

Endothelin-1 kinetics in plasma, urine, and blister fluid in burn patients.

Endothelin-1, a peptide isolated from vascular endothelial cells, facilitates the constriction of vascular smooth muscle and various pharmacological actions including vasodilation, the proliferation of smooth muscle cells and fibroblasts, and the stimulation of arachidonic acid metabolism. In this study, plasma, urine, and blister fluid endothelin-1 concentrations were determined in burn patients and changes in vasoactive substances derived from endothelial cells secondary to burns were investigated. Plasma endothelin-1 concentrations in burn patients were significantly lower than those in healthy individuals at rest. However, extremely high blister fluid endothelin-1 concentrations were observed within 30 hours of a burn. The amounts of endothelin-1 excreted in urine by burn patients over 24 hours also were higher than those in healthy individuals. The finding of high concentrations of endothelin-1 in blister fluids suggests that endothelin-1 is produced at wound regions in burn victims. Clinically, it appears that endothelin-1 is involved in circulation at the wound surface or in the healing of burns.

Adult↗