Lipid mediators modulate NMDA receptor currents in a Xenopus oocyte expression system

We determined the modulatory effects of various lipid mediators on mouse N-methyl-D-aspartate (NMDA) receptor currents in the Xenopus oocyte expression system. Arachidonic acid, but not oleic acid potentiated NMDA receptor activity. The epsilon1/zeta1 heterodimer of the NMDA receptor was more sensitive to arachidonic acid than was the epsilon2/zeta1 heterodimer. Platelet-activating factor (PAF) and lysophosphatidic acid (LPA) both activated the NMDA currents, and the effects were more evident in the epsilon2/zeta1 heterodimer than in epsilon1/zeta1. These activations were abolished by treatment with protein kinase inhibitors, suggesting a possible phosphorylation of the receptor. Thus, lipid mediators do have modulatory effects on NMDA receptor currents, the potentiating effects of which differ depending on subtype of the NMDA receptor.

[Rapid detection of Shiga-like toxin gene in feces with rapid-cycle polymerase chain reaction]

A rapid detection for Shiga-like toxin in feces was developed with the nucleic acid extraction method by silicondioxide-guanidine thiothianate and rapid-cycle polymerase chain reaction by RapidCycler (model 1002; Idaho Technology, RC-PCR here after). Twenty-two fecal samples that were collected from patients with diarrhoea caused by E. coli O157:H7 and frozen for 6 months were examined directly by RC-PCR, conventional PCR assay using by ThermalCycler 9600-R (Roche, TC-PCR here after) and by the culture method using tellurite-cefixime sorbitol MacConkey (direct method). These examinations were done also after being injected into TCV-TSB and incutated at 35 degrees C overnight (indirect method). The sensitivity of RC-PCR and TC-PCR using a diluted suspension of broth enriched at 35 degrees C overnight were 4.1 pg and 410 fg, respectively. Positive results in the direct method were obtained in 7 for RC-PCR, 10 for TC-PCR and 5 for culture. Positive results on indirect assay were obtained in 9 for RC-PCR, 9 for TC-PCR and 7 for culture. It was demonstrated that the RC-PCR assay was able to detect Shiga-like toxin gene in feces in less than 90 minutes after being received at the laboratory.

[Rapid detection of Escherichia coli 0157:H7 in feces by latex agglutination and immunochromatographic assay]

The rapid detection method of Escherichia coli O157 in feces by using the latex agglutination test kit (Prolex; Pro Lab Diagnostics) and the immunochromatic assay kit (NOW EH. E. coli; Binax) was studied. 176 fecal samples obtained from 154 healthy men and 22 patients who had diarrhea by E. coli O157 were examined. Tellurite cefixim sorbitol MacConkey (TC-SMAC), Prolex and NOW were used for studies and also these were done after the enriched culture by tellurite cefixime vancomycin toriptic soy broth (TCV-TSB). In the direct inoculation, 5 (23%) of 22 samples, 7 (32%) and 9 (41%), and after the enriched culture, 7 (32%), 10 (46%) and 11 (50%) were positive by culture, Prolex and NOW, respectively. On the other hand, 154 samples from healthy men were all negative in the direct inoculation, but in the enriched culture, 7 of 40 (18%) were positive by NOW. These samples were negative by boiled (100 degrees C, 15 minutes). Our results indicated that Prolex and NOW were useful for accurate and rapid diagnosis of E. coli O157 enteritis, and more sensitivity results were obtained with the enrichment broth.

Effects of liposteroid on skin lesions in autoimmune MRLlpr/lpr mice

Dexamethasone palmitate (D-PAL) incorporated into lipid microspheres (D-PAL emulsion) is taken up by the reticuloendothelial system and by some inflammatory cells. Therefore, it has a stronger anti-inflammatory activity than free corticosteroids in vivo. To study the effect of D-PAL emulsion on systemic lupus erythematosus (SLE), we administered D-PAL emulsion to MRLlpr/lpr mice, an animal model for human SLE. The effect of D-PAL emulsion was compared with that of methylprednisolone (m-PSL), a water-soluble steroid. Percent survival was higher in the group treated with 0.25 mg of D-PAL emulsion intravenously once every 4 weeks than in those groups treated similarly with m-PSL or PBS control. Swelling of lymph nodes was frequent in the group treated with m-PSL or with PBS, while rarely observed in the group treated with D-PAL emulsion. Proteinuria was more frequent in the groups treated with m-PSL or PBS than in the group treated with D-PAL emulsion. Although the frequency of skin lesions was not different between these three groups, the control and m-PSL treated mice had severe skin lesions, such as hair loss of erythematous skin with scales and crusts at the nape, while D-PAL emulsion treated animals showed only facial alopecia without inflammatory skin changes. These data demonstrate that D-PAL emulsion was more effective than a corresponding dose of m-PSL on autoimmune prone mice. This suggests that intermittent administration of D-PAL emulsion may be effective in the treatment of human SLE.

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.

Roles of C-terminal Src kinase in the initiation and the termination of the high affinity IgE receptor-mediated signaling

As an attempt to analyze the roles of C-terminal Src kinase (Csk) in the high affinity IgE receptor (FcepsilonRI)-mediated signaling, we overexpressed Csk, a membrane-targeted form of Csk (mCsk), and a kinase-defective, membrane-targeted form of Csk (mCsk(-)) in rat basophil leukemia (RBL) 2H3 cells. Specific activity of Lyn at the basal state was decreased in Csk-expressing cells, and further decreased in mCsk-expressing cells. In mCsk(-)-expressing cells, basal specific activity of Lyn was increased, thereby indicating that mCsk(-) functioned as a dominant negative molecule. The onset of FcepsilonRI-mediated Lyn activation was delayed in Csk-expressing cells, and further delayed in mCsk-expressing cells. In mCsk(-)-expressing cells, Lyn activation was rapid and quite long lasting. These findings indicate (i) Csk negatively regulates rapid FcepsilonRI/Lyn coupling, and (ii) Csk activity is potentially required for its termination. The onsets of the series of events including tyrosyl phosphorylation of Syk, mitogen-activated protein (MAP) kinase activation, elevation of intracellular calcium concentration ([Ca2+]i), and histamine release were all stepwisely delayed in Csk-expressing cells and in mCsk-expressing cells. The durations of Syk phosphorylation and MAP kinase activation also closely correlated with those of Lyn activation, but [Ca2+]i elevation and histamine release followed different temporal patterns: the delayed responses in Csk-expressing cells and in mCsk-expressing cells led to sustained [Ca2+]i oscillation and histamine release, while the prompt responses in parent cells and mCsk(-)-expressing cells rapidly subsided. These findings provide further evidence that the initiations of the FcepsilonRI-mediated signals are upstreamly regulated by Src family protein tyrosine kinases and revealed that their terminations are regulated by Lyn-dependent (Syk and MAP kinase) and -independent ([Ca2+]i elevation and histamine release) mechanisms.

Effect of azelastine on PGE2 production in fibroblasts in normal skin. The possibility of inhibition of inducible cyclooxygenase by azelastine

The effects of azelastine on prostaglandin E2 (PGE2) production were investigated by using cultured normal dermal fibroblasts obtained from the same traumatic region of 3 patients and the CRL-1475 cell line. Interleukin-1beta (IL-1) enhanced PGE2 production in cultured normal fibroblasts and CRL-1475 cells. 10(-6) M azelastine inhibited PGE2 production in these IL-1-stimulated fibroblasts. However, the drug did not influence spontaneous PGE2 production in cultured CRL-1475 fibroblasts not stimulated with IL-1 but slightly it increased in cultured normal dermal fibroblasts under the same conditions. These results suggest that azelastine either regulates synthesis of an inducible cyclooxygenose protein or inhibits PGE2 production as an inducible cyclooxygenase inhibitor.

Role of the C terminus in histamine H2 receptor signaling, desensitization, and agonist-induced internalization

To evaluate the role of the histamine H2 receptor C terminus in signaling, desensitization, and agonist-induced internalization, canine H2 receptors with truncated C termini were generated. Wild-type (WT) and truncated receptors were tagged at their N termini with a hemagglutinin (HA) epitope and expressed in COS7 cells. Most of the C-terminal intracellular tail could be truncated (51 of 70 residues, termed T308 mutant) without loss of functions: cAMP production, tiotidine binding, and plasma membrane targeting. In fact, the T308 mutant produced more cAMP than the WT when cell-surface expression per cell was equivalent. Pretreatment of cells with 10(-5) M histamine desensitized cAMP productions via WT and T308 receptors to similar extents. Incubation of cells expressing WT receptors with 10(-5) M histamine reduced cell-surface anti-HA antibody binding by approximately 30% (by 30 min, t1/2 approximately 15 min), but did not affect the Bmax of tiotidine in membrane fractions, which represents total receptor amounts, suggesting that WT receptors were internalized from the cell surface. In contrast, no internalization was observed with T308 receptors following histamine treatment. A mutant with a deletion of the 30 C-terminal amino acids, termed T329, was functional but was as potent as the WT in terms of cAMP production. Apart from being desensitized by histamine, the internalization of the receptor was indistinguishable from that of the WT. Internalization was observed in the T320 but not in T313 mutant, narrowing the region involved in internalization to that between Glu314 and Asn320 (ETSLRSN). Of these seven residues, either Thr315, Ser316, or both, were replaced with Ala. Thr315 and Ser316 are conserved among species. The mutation at Thr315 (but not that at Ser316) abolished internalization. Taken together, these results demonstrate that Thr315 is involved in agonist-induced internalization. Furthermore, the finding that T308 receptors were desensitized in the absence of internalization suggests that internalization and desensitization are meditated by independent mechanisms.

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.

Suppressive effects of tranilast on the expression of inducible cyclooxygenase (COX2) in interleukin-1beta-stimulated fibroblasts

We investigated the effects of tranilast on inducible cyclooxygenase (COX2)-mediated prostaglandin E2 (PGE2) production and enzyme induction in interleukin-lbeta (IL-1beta)-stimulated cultured dermal fibroblasts. IL-1beta enhanced PGE2 production in cultured fibroblasts. Tranilast did not affect constitutive cyclooxygenase (COX1) or COX2 activity in non-stimulated or IL-lbeta-stimulated fibroblasts. However, the COX2 expression induced by IL-1beta was inhibited by tranilast. This result, that IL-1beta-induced COX2 expression was suppressed by tranilast, was confirmed by immunohistochemical analysis. Thus, it is possible for tranilast to regulate PGE2 production by inhibiting COX2 induction.

[Significance of Aspergillus fumigatus rDNA detected by polymerase chain reaction in diagnosis of pulmonary aspergillosis]

We have studied the clinical significance of Aspergillus fumigatus rDNA detected by polymerase chain reaction (PCR) for diagnosing aspergillosis. For this purpose, a specific and sensitive PCR assay was developed to amplify the 26S rDNA/intergenic spacer region of A. fumigatus. Control experiments showed that the set of primers used was capable of amplifying A. fumigatus DNA specifically and that the DNA amount of detection limit was 1 pg. Eighteen samples from 13 patients with aspergillosis and 36 samples from 24 patients without aspergillosis were tested by means of PCR, culture, latex agglutination test for galactomannan antigen and double gel diffusion assay for precipitation of antibodies to A. fumigatus. PCR showed positive test in 8 among 13 patients with pulmonary aspergillosis. On the other hand, culture of samples detected A. fumigatus in 6 patients. Galactomannan antigen and antibodies specific to A. fumigatus were positive in 2 and 6 patients respectively. These results indicated that PCR is the most sensitive among these 4 methods. Five patients showed negative PCR test despite of having pulmonary aspergillosis. Two of these patients were proved to have aspergillosis caused by A. flavus and A. niger. On the other hand, galactomannan antigen and A. fumigatus antibody were positive in one and 2 patients, respectively. PCR was positive in 2 out of 24 patients diagnosed as not having aspergillosis: one patient had diagnosis of acute bronchitis, but she showed positive culture of A. fumigatus. The other patient had diagnosis of lobar pneumonia, because any pathogens were not detected before PCR assay. The PCR assay we developed is a useful method for diagnosing aspergillosis caused by A. fumigatus as compared with other conventional methods.

Ictal EEG and single photon emission computed tomography in a patient with cortical dysplasia presenting with atonic seizures

PURPOSE

Ictal studies of atonic seizures in children with epilepsy are rare. To clarify the neurophysiologic mechanism of such seizures, we describe a cluster of atonic seizures in a 6-year-old girl with cortical dysplasia.

METHODS

Ictal activity was recorded as slow-wave bursts beginning over the right frontocentral regions, where the cortical dysplasia was detected by magnetic resonance imaging (MRI), and propagating to the left hemisphere.

RESULTS

The polygraphic recording demonstrated that the atonia indicated by the sudden interruption of electromyogram (EMG) discharges corresponded to the bilaterally synchronous spike-and-wave complexes. An ictal single photon emission computed tomography (SPECT) study with 99mTc hexamethyl propylene amine oxime ([99mTc]HMPAO) simultaneously performed during EEG recording showed marked bilateral mesial frontal and right frontoparietal hyperperfusion.

CONCLUSIONS

Our findings suggest that the neurophysiological mechanism of the atonic seizures may be produced by a strong inhibition in the bilateral motor cortexes. Ictal SPECT is valuable in demonstrating the pathophysiology of both atonic seizures and secondary bilaterally synchronous spike-and-wave complexes in the EEG.

[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.

Differential expression of somatostatin receptors in the rat eye: SSTR4 is intensely expressed in the iris/ciliary body

Distribution of somatostatin receptors (SSTR1-5) was determined in the rat eye. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses revealed that SSTR4 and SSTR2 are major subtypes expressed predominantly in the iris/ciliary body and retina, respectively, and that SSTR1, SSTR3 and SSTR5 are minor subtypes expressed preferentially in the posterior eye segments including the retina. In situ hybridization showed predominant SSTR4 expression in the posterior iris epithelium and ciliary body, suggesting functional roles of somatostatin in the autonomic nervous system in the anterior segments of the eye. The differential expression of SSTR1-5 may be related to distinct roles of somatostatin in the physiology of different ocular tissues.

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.

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.

[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.

[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.

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.