Requirement of Ras for the activation of mitogen-activated protein kinase by calcium influx, cAMP, and neurotrophin in hippocampal neurons

Mitogen-activated protein (MAP) kinase plays important roles in the establishment of long-term potentiation both in vitro and in living animals. MAP kinase is activated in response to a broad range of stimuli, including calcium influx through NMDA receptor and L-type calcium channel, cAMP, and neurotrophins. To investigate the role of Ras in the activation of MAP kinase and cAMP response element-binding protein (CREB) in hippocampal neurons, we inhibited Ras function by overexpressing a Ras GTPase-activating protein, Gap1(m), or dominant negative Ras by means of adenovirus vectors. Gap1(m) expression almost completely suppressed MAP kinase activation in response to NMDA, calcium ionophore, membrane depolarization, forskolin, and brain-derived neurotrophic factor (BDNF). Dominant negative Ras also showed similar effects. On the other hand, Rap1GAP did not significantly inhibit the forskolin-induced activation of MAP kinase. In contrast to MAP kinase activation, the inactivation of Ras activity did not inhibit significantly NMDA-induced CREB phosphorylation, whereas BDNF-induced CREB phosphorylation was inhibited almost completely. These results demonstrate that Ras transduces signals elicited by a broad range of stimuli to MAP kinase in hippocampal neurons and further suggest that CREB phosphorylation depends on multiple pathways.

Efficacy of ecabet sodium for Helicobacter pylori eradication triple therapy in comparison with a lansoprazole-based regimen

BACKGROUND

The cytoprotective agent, ecabet sodium, inhibits urease activity and growth of Helicobacter pylori.

AIM

To evaluate the efficacy and safety of ecabet sodium-based eradication of H. pylori infection, compared with a lansoprazole-based regimen, in a randomized multicentre study.

SUBJECTS AND METHODS

A total of 120 H. pylori-positive patients were assigned to one of two treatment regimens for 2 weeks: ecabet sodium 1 g b.d., amoxicillin 500 mg t.d.s. and clarithromycin 400 mg b.d. (EAC: 60 patients); or lansoprazole 30 mg (o.m.) with the same antimicrobial agents (LAC: 60 patients). Cure of infection was assessed by a 13C-urea breath test 1 month after completion of treatment.

RESULTS

One patient in the EAC group and two in the LAC group did not complete therapy because of an adverse event, and three did not undergo the 13C-urea breath test. Cure rates for the intention-to-treat, all-patients-treated and per protocol analysis in the EAC group were 85%, 86% and 88%, respectively, whereas those in the LAC group were 85%, 88% and 91%. There were no significant differences in cure rate or adverse events between the two regimens.

CONCLUSIONS

Ecabet sodium in combination with amoxicillin and clarithromycin is as effective as lansoprazole-based eradication therapy for H. pylori.

4-hydroxynonenal prevents NO production in vascular smooth muscle cells by inhibiting nuclear factor-kappaB-dependent transcriptional activation of inducible NO synthase

The role of lipid peroxidation products in atherogenesis was studied. We investigated whether 4-hydroxy-2-nonenal (HNE) modulates activation of the nuclear factor (NF)-kappaB system or alters expression of the NF-kappaB target gene product, inducible NO synthase (iNOS), in vascular smooth muscle cells (VSMCs) stimulated by lipopolysaccharide (LPS) in combination with interferon (IFN)-gamma (LPS/IFN). NO production induced by LPS/IFN was dose-dependently inhibited by HNE. NF-kappaB activation by LPS/IFN was inhibited by HNE in a dose-dependent manner. HNE significantly decreased LPS/IFN-stimulated proteolysis of IkappaB-alpha. iNOS promoter activity stimulated by LPS/IFN was also decreased by HNE dose-dependently. The treatment of VSMCs with LPS/IFN strongly stimulated iNOS mRNA and protein expression. The LPS/IFN-induced increases in iNOS mRNA and protein levels were dose-dependently decreased by HNE. Our data suggest that treatment with HNE blocks signaling events required for IkappaB-alpha degradation, thereby preventing NF-kappaB activation. Inhibition of NF-kappaB-regulated gene expression, especially modulation of NO production, may contribute to atherogenesis.

Horizontal transmission of Toxoplasma gondii in squirrel monkeys (Saimiri sciureus)

The possibility of horizontal transmission of T. gondii was examined in squirrel monkeys. After three monkeys were inoculated perorally with 1.1-2.1 x 10(3) cysts of the T. gondii ME49, the animals were divided into two cages and maintained with one normal monkey for each cage as a cagemate. Two out of the three T. gondii-inoculated monkeys died, and the remaining one monkey was sacrificed in a moribund state one week after infection because of acute toxoplasmosis. Many T. gondii tachyzoites were recovered from broncho-alveolar lavages and were also found histopathologically in the lung, liver, spleen, kidney and lymph nodes and impression smears of tissues from the three T. gondii-inoculated monkeys by Giemsa staining. Anti-T. gondii antibody was examined by immunoblot assay in these animals, and the antibody to T. gondii major surface membrane protein (p30) could be detected after the start of experiment. Furthermore, a specific band of T. gondii NTPase gene was observed by PCR in the liver and lung of infected and cagemate monkeys, and the sequence of the second PCR products obtained from the cagemates, which were clinically normal but gave a positive result in immunoblotting assay, was exactly the same as the sequence of the NTPase gene of T. gondii ME49. These findings suggested that transmission of T. gondii from the infected monkeys to cagemates occurred easily, and since many T. gondii tachyzoites were recovered from the bronchoalveolar lavages of the three T. gondii-inoculated monkeys, we suggest that aerosol infection plays an important role for the enzootic toxoplasmosis in colonies of squirrel monkeys.

Characterization, amino acid sequence and evolution of edema-inducing, basic phospholipase A2 from Trimeresurus flavoviridis venom

Two phospholipases A2 (PLA2s) were purified from the venom of Trimeresurus flavoviridis (Crotalinae) inhabiting Tokunoshima island, Japan, and named PLA-A and PLA-B in the order of elution on a cation-exchange column. Lipolytic activities of PLA-A and PLA-B toward mixed micelles and liposomes were substantially lower than that of PLA2 (an [Asp49]PLA2) which had been isolated from the same venom. Both PLA-A and PLA-B consisted of 122 amino acids and contained aspartate at position 49 (the numbering according to the aligned sequences of PLA2s in Fig. 8), thus belonging to an [Asp49]PLA2 subgroup. PLA-A and PLA-B were identical in sequence with an exception at position 79. PLA-B contained Asn-Gly at positions 79 and 80 which are located in the beta-sheet region. On the other hand, PLA-A had beta-Asp-Gly and alpha-Asp-Gly in high and low proportion, respectively, at the corresponding positions which were produced from Asn-Gly through the base-catalyzed formation and hydrolysis of the succinimide type intermediate. Thus, PLA-A is derived from PLA-B. PLA-B is similar in sequence to PL-X, which had been purified from the venom of T. flavoviridis inhabiting Amami-Oshima island, Japan, and to PL-X', whose cDNA had been cloned from Tokunoshima T. flavoviridis venom gland, rather than PLA2. PLA-B showed strong edema-inducing activity, while PLA-A exhibited rather lower activity. The sequence around position 79 which constitutes a beta-turn segment seems to be crucial for edema-inducing activity. Phylogenetic tree of Tokunoshima T. flavoviridis venom PLA2 isozymes indicated that PLA-B and PL-X' diverged from PLA2 after branching of [Asp49]PLA2 forms and [Lys49]PLA2 forms.

Systematic separation and purification of elastase, gelatinase (matrix metalloproteinase 9), and collagenase (matrix metalloproteinase 8) from polymorphonuclear leukocytes in dialyzers previously used by patients with renal failure

We developed a simple and effective method for the systematic separation and purification of human polymorphonuclear leukocyte (PMN) proteinases, elastase, gelatinase (matrix metalloproteinase 9, type IV collagenase), and collagenase (matrix metalloproteinase 8), derived from the extracts of hollow fiber dialyzers that had been utilized in the treatment of patients with renal failure. The fraction containing elastase was grossly separated from that containing gelatinase and collagenase by heparin-Sepharose chromatography and purified in an aprotinin column. The remaining two enzymes were then separated using the gelatin-Sepharose column after gel chromatography following ammonium sulfate precipitation. Gelatinase and collagenase were further purified by gelatin-Sepharose chromatography as a latent form and by collagen-Sepharose chromatography as an activated form. This novel method offers procedural advantages over existing methods that separate PMNs from the whole blood of volunteers for experimental research purposes.

A study of the relationship between metabolism using 1H-MRS and function using several neuropsychological tests in temporal lobe epilepsy

Several investigators have reported on the relationship between metabolism, using magnetic resonance spectroscopy (MRS), and function, using neuropsychological tests in temporal lobe epilepsy (TLE) patients, but the opinions regarding the results remain in contention. The aim of this study is to examine the relationship between metabolism, using proton MRS ((1)H-MRS), and function using several neuropsychological tests in the temporal lobes of TLE patients. We studied 29 TLE patients at our hospital using(1)H-MRS and neuropsychological tests. We used a clinical 1.5 T MR unit. We conducted five neuropsychological tests to examine the function of the left or right temporal lobe. There were significant correlations between the N-acetylaspartate/creatine + phosphocreatine (NAA/Cr) ratios and the scores of almost all of the neuropsychological tests for the temporal lobe function ipsilateral to the spike focus. However, in two Wechsler Memory Scale-Revised (WMS-R) subtests we found no significant correlation in the ipsilateral side. These findings suggest that the NAA/Cr ratios, which reflect neural metabolism, are closely related to function in the temporal lobes of TLE patients. The disparity between the results in two subtests of WMS-R show that several tests may be necessary in order to assess temporal lobe function.

Signal transduction pathways through TRK-A and TRK-B receptors in human neuroblastoma cells

Little is known about the signal transduction pathways of TRK family receptors in neuroblastoma (NB) cells. In this study, an NB cell line, designated MP-N-TS, was established from an adrenal tumor taken from a 2-year-old boy. This cell line expressed both TRK-A and TRK-B receptors, which is rare in a single NB cell line. Therefore, the MP-N-TS cell line was used to determine whether the signal transduction through these constitutive receptors is functional. Three neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-4 / 5 (NT-4 / 5), induced tyrosine phosphorylation of panTRK, and BDNF and NT-4 / 5 induced tyrosine phosphorylation of TRK-B. Tyrosine phosphorylation of panTRK and / or TRK-B by the neurotrophins was inhibited in the presence of a tyrosine kinase inhibitor K252a. Tyrosine phosphorylation of Src homologous and collagen (Shc), extracellular signal-regulated kinase (ERK)-1 and ERK-2, and phospholipase C-gamma1 (PLC-gamma1) was increased by the three neurotrophins and the increase was inhibited in the presence of K252a. Activation of Ras, detected as the GTP-bound form of Ras, was induced by the three neurotrophins. The neurotrophins did not modulate the expressions of TRK-A or TRK-B mRNA, but they did induce the expression of c-fos mRNA. Exogenous NGF induced weak neurite outgrowth, whereas exogenous BDNF and NT-4 / 5 induced distinct neurite outgrowth. Exogenous BDNF and NT-4 / 5 increased the number of viable cells, while NGF did not. Our results demonstrate that the signal transduction pathways through TRK-A and TRK-B in MP-N-TS cells are functional and similar, and the main downstream signaling pathways from the three neurotrophins are mitogen-activated protein kinase (MAPK) cascades through Shc, activated Ras, ERK-1 and ERK-2, and the transduction pathway through PLC-gamma1. Further, BDNF and NT-4 / 5 increased cell viability. The MP-N-TS cell line should be useful for clarifying the TRK-A and TRK-B signaling pathways responsible for the different prognoses in patients with NB.

A prospective clinical study on inhaled nitric oxide therapy for neonates in Japan

BACKGROUND

This is the first report about a prospective clinical investigation to study the efficacy and safety of nitric oxide (NO) inhalation in infants with persistent pulmonary hypertension of the newborn (PPHN) in Japan.

METHODS

Patients in the present study had to meet the following entry criteria: (i) they had to be younger than 7 days of age; (ii) they had to have evidence of PPHN as defined by echocardiograph; (iii) they had to have severe systemic hypoxemia under mechanical ventilation at 100% oxygen supplementation; and (iv) they had to have a failure to respond to conventional therapies. Patients were excluded from this trial if they had any of the following: hypoplastic lung, structural cardiac lesions or severe multiple anomalies.

RESULTS

Nitric oxide inhalation therapy was performed in 68 infants who had severe PPHN at 18 hospitals between May 1995 and May 1997. At birth, 21 of 68 infants (31%) weighed less than 1,500 g and 39 infants weighed more than 2,500 g. The diagnoses associated with PPHN were as follows: 27 infants had meconium aspiration syndrome, 15 infants had dry lung syndrome, nine infants had congenital diaphragmatic hernia, six infants had respiratory distress syndrome, three infants had pneumonia and eight infants had other diagnoses. The mean oxygenation index (OI) before NO inhalation therapy in 68 infants was 43.2; 55 infants (81%) had good responses.

CONCLUSIONS

These results may be valuable for further randomized controlled and double-blind trials in Japan to evaluate whether NO inhalation therapy is more effective than conventional therapy in infants with severe PPHN.

Effect of IL-12 encoding plasmid administration on tight-skin mouse

The tight-skin (Tsk/+) mutant mice, a putative murine model of scleroderma, are characterized by the excessive deposition of collagen and the presence of antinuclear antibodies. Type 2 cytokines, such as IL-4 and IL-6, are capable of regulating the synthesis of various matrix molecules, including type I collagen, by fibroblasts. IL-12 is well known to induce type 1 cytokine production and to reduce type 2 activity. Here, we examined the effect of IL-12 encoding plasmid (pCAGGSIL-12) on the disease progression of Tsk/+ mice. pCAGGSIL-12 plasmid or pCAGGS parental vector was injected intramuscularly 7 times at 3 week intervals into Tsk/+ mice. One week after the last injection, pCAGGSIL-12 administered Tsk/+ mice exhibited a marked decrease in the skin thickness compared with the mice treated with pCAGGS vector. The serum levels of antinuclear antibodies were diminished in pCAGGSIL-12 treated mice. IL-4 production by spleen cells from pCAGGSIL-12 plasmid treated mice was significantly lower than that from vector treated mice. These results indicate that pCAGGSIL-12 administration into Tsk/+ mice had beneficial effects in preventing the collagen accumulation in the skin and suppressing the autoimmunity via improvement of Th1/Th2 balance. The present study suggests that the IL-12 encoding plasmid administration might have a therapeutic effect on systemic sclerosis.

Unwashed shed blood infusion causes deterioration in right ventricular function after coronary artery surgery

We investigated right ventricular function after infusion of unwashed shed blood collected from mediastinal and chest tube drainage. Changes in thromboxane B2 (TXB2) and 6-keto-PGF1 alpha, which are stable metabolites of thromboxane A2 (TXA2) and prostacyclin respectively, were also investigated. The amount of infused shed blood was 484 +/- 76 ml (mean +/- SD). Right ventricular ejection fraction decreased rapidly after the infusion and did not return to its original level until 120 minutes later (P < 0.05). Mean pulmonary artery pressure rose after infusion of the shed blood (P < 0.05). The TXB2 level in the unwashed shed blood was about 20,000 times higher than the preoperative plasma level. The plasma TXB2 level at 30 minutes after the infusion was significantly elevated (P < 0.05), and at 120 minutes it had returned to the original level. Unwashed shed blood may contain vasoactive substances that induce the release of TXA2 and increase right ventricular afterload.

Tubelactomicin A, a novel 16-membered lactone antibiotic, from Nocardia sp. I. Taxonomy, production, isolation and biological properties

A novel 16-membered lactone antibiotic named tubelactomicin A was isolated from the culture broth of an actinomycete strain. The producing organism, designated MK703-102F1, was identified as a member of Nocardia. Tubelactomicin A was isolated from the culture broth by Diaion HP20 absorption, ethyl acetate extraction, silica gel and Sephadex LH-20 column chromatographies and centrifugal liquid-liquid partition chromatography (CPC). Tubelactomicin A showed strong activity against acid-fast bacteria including the drug-resistant strains.

Differential regulation of the secretions of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinases-1 from human keratinocytes in culture

To investigate the pathophysiological roles of matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinases (TIMP)-1 in the differentiation of keratinocytes, we used human keratinocytes in culture to examine the gelatinolytic activity of MMP-2 and MMP-9 by zymographic analysis, MMP-9 mRNA by reverse transcriptase-polymerase chain reaction, and TIMP-1 mRNA by Northern blot analysis. Adding of calcium (1 mM) to the culture medium increased the activity of MMP-9 and MMP-9 mRNA without affecting MMP-2 activity or the expression of TIMP-1 mRNA. These results suggest that keratinocytes regulate the expressions of MMP-9 and TIMP-1 differently during the process of differentiation.

Possible involvement of aminotelopeptide in self-assembly and thermal stability of collagen I as revealed by its removal with proteases

The functions of aminotelopeptide and N-terminal cross-linking of collagen I were examined. Acetic acid-soluble collagen I (ASC) was purified from neonatal bovine skin and treated with three kinds of proteases. The amino acid sequencing analysis of the N terminus showed that ASC contained a full-length aminotelopeptide. Pepsin and papain cleaved the aminotelopeptide of the alpha1 chain at the same site and the aminotelopeptide of the alpha2 chain at different sites. Proctase-treated ASC lost the whole aminotelopeptide, and the N-terminal sequence began from the tenth residue inside the triple helical region. The rates of fibril formation of pepsin-treated ASC and proctase-treated ASC were the same and were slower than that of ASC. The denaturation temperatures, monitored by CD ellipticity at 221 nm, of ASC, pepsin-treated, or papain-treated collagens were the same at 41.8 degrees C. Proctase-treated ASC showed a lower denaturation temperature of 39.9 degrees C. We also observed the morphology of the collagen fibrils under an electron microscope. The ASC fibrils were straight and thin, whereas the fibrils of pepsin-treated ASC were slightly twisted, and the fibrils from papain- and proctase-treated ASC were highly twisted and thick. When the collagen gel strength was examined by a modified method of viscosity-measurement, ASC was the strongest, followed by pepsin-treated ASC, and papain- and proctase-treated ASCs were the weakest. These results suggest that the aminotelopeptide plays important roles in fibril formation and thermal stability. In addition, the functions of intermolecular cross-linking in aminotelopeptides may contribute to the formation of fibrils in the correct staggered pattern and to strengthening the collagen gel.

Differential regulation of MMP-2 and MMP-9 gelatinases in cultured human keratinocytes

BACKGROUND

Among matrix metalloproteinases (MMPs), MMP-2 and MMP-9 are considered to play important roles in the tissue metabolism.

OBJECTIVE

To study the production of MMP-2 and MMP-9 in cultured keratinocytes.

METHODS

We examined the effect of cell passage number and cell differentiation on these enzymes by zymography and immunocytochemistry.

RESULTS

Both MMP-2 and MMP-9 gelatinases were detected in keratinocyte-conditioned media using zymography. The level of MMP-2 in the medium decreased after sequential passage, whereas MMP-9 was detected at a constant level. Treatment of keratinocytes with Ca2+, a potent stimulator for cell differentiation. induced secretion of MMP-9, which was confirmed immunocytochemically. Inversely, treatment with retinoic acid, which inhibits cell differentiation, increased the level of MMP-2.

CONCLUSION

These results suggest that keratinocytes regulate their secretion of MMP-2 and MMP-9 gelatinase in distinct and independent patterns during differentiation.

Association of polymorphic alleles of the calcium-sensing receptor gene with parathyroid hormone secretion in hemodialysis patients

The present study was performed to investigate the association of calcium-sensing receptor (CaSR) genotypes with parathyroid hormone (PTH) secretion in hemodialysis patients. Subjects were 122 Japanese hemodialysis patients, including 39 patients with diabetes mellitus (DM). The CaSR polymorphisms tested were codon 990 in intracellular domain (A/A, A/G, and G/G groups) as well as T to C base change of intron 4 (T/T, T/C, and C/C groups). Statistical analysis of these polymorphisms revealed that the serum PTH level was significantly higher in the A/A group than in the G/G group in the former. In addition, the serum PTH level was also significantly higher in patients displaying C allele, as compared with the T/T group in the latter. This association of two polymorphisms with the serum PTH level was observed only in non-DM patients. Although two polymorphisms affected the PTH level independently, patients who possessed both genotypes (AAC+) had a markedly high level of PTH not only in the non-DM group but also in the DM group. The present findings indicate the possibility of the prediction for the extensive progression of secondary hyperparathyroidism through analyzing the CaSR polymorphisms in chronic hemodialysis patients.

A study of the relationship between the seizure focus and 1H-MRS in temporal lobe epilepsy and frontal lobe epilepsy

Several studies of temporal lobe epilepsy (TLE) patients have investigated the relationship between the seizure focus and 1H magnetic resonance spectroscopy (1H-MRS). There have also been a few reports in other types of partial epilepsy. We examined the relationship between the seizure focus and the reduction in N-acetylaspartate: creatine (NAA : Cr) ratio using 1H-MRS in both TLE and frontal lobe epilepsy (FLE) patients. We studied 21 patients with unilateral TLE and seven patients with unilateral FLE. We used a 1.5 Tesla magnetic resonance unit (Signa Horizon; General Electric). Approximately 15 x 15 x 20 mm3 voxel of interest (VOI) was placed over the anterior portion of the bilateral hippocampus in the TLE patients, and the anterodorsal position of bilateral frontal lobe in the FLE patients. The seizure focus was identified by interictal scalp electro-encephalogram (EEG). In the TLE patients the NAA : Cr ratios were reduced in the seizure focus, while in the FLE patients they were not always reduced in the seizure focus. In the TLE patients the coincidence rate between the seizure focus and the reduction in the NAA:Cr ratio was 90% (19 of 21 patients), while in the FLE patients the coincidence rate was only 57% (four of seven patients).

Thermacetogenium phaeum gen. nov., sp. nov., a strictly anaerobic, thermophilic, syntrophic acetate-oxidizing bacterium

A novel anaerobic, thermophilic, syntrophic acetate-oxidizing bacterium, strain PB(T), was isolated from a thermophilic (55 degrees C) anaerobic methanogenic reactor which had been treating kraft-pulp waste water. The bacterium oxidized acetate in co-culture with a thermophilic hydrogenotrophic methanogen. Strain PB(T), a gram-positive, spore-forming, rod-shaped bacterium grew optimally at 58 degrees C and pH 6.8. The bacterium grew acetogenically on several alcohols, methoxylated aromatics, pyruvate, glycine, cysteine, formate and hydrogen/CO2. Strain PB(T) also oxidized acetate with reduction of sulfate or thiosulfate as the electron acceptor. The bacterium contained MK-7 as the major quinone. The G+C content of the DNA was 53.5 mol%. Comparative 16S rDNA analysis indicated that strain PB(T) belongs to the Bacillus-Clostridium subphylum. However, it was distant from any known genera or micro-organism. The closest known relative was Thermoterrabacterium ferrireducens with 87.4% similarity. The name Thermacetogenium phaeum gen. nov., sp. nov. is proposed. The type strain is strain PBT (= DSM 12270T).

Protein-tyrosine kinase Pyk2 is involved in interleukin-2 production by Jurkat T cells via its tyrosine 402

We established Jurkat transfectants that overexpress Pyk2 or its mutants, K457A (lysine 457 was mutated to alanine), Pyk2-Y402F (tyrosine 402 to phenylalanine), and Pyk2-Y881F to investigate the role of Pyk2 in T cell activation. Pyk2 as well as kinase-inactive Pyk2-K457A, was phosphorylated at tyrosine residues 402, 580, and 881 upon T cell antigen receptor cross-linking, indicating that these residues are phosphorylated by other tyrosine kinase(s). However, no tyrosine phosphorylation of Pyk2-Y402F was detected while more than 60% of the tyrosine phosphorylation was observed in Pyk2-Y881F. Pyk2-Y402F inhibited the activation of endogenous Pyk2. The degree of activation of both c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-regulated protein kinase after concurrent ligation of T cell antigen receptor and CD28 was reduced by more than 50% in the clones expressing Pyk2-Y402F. Consistent with this inhibition, IL-2 production was significantly diminished in the Pyk2-Y402F-expressing clones. Furthermore, we found that Pyk2, when overexpressed, associates with Zap70 and Vav. Taken together, these findings suggest that Pyk2 is involved in the activation of T cells through its tyrosine 402.

Regulatory proteins of R-Ras, TC21/R-Ras2, and M-Ras/R-Ras3

We studied the regulation of three closely related members of Ras family G proteins, R-Ras, TC21 (also known as R-Ras2), and M-Ras (R-Ras3). Guanine nucleotide exchange of R-Ras and TC21 was promoted by RasGRF, C3G, CalDAG-GEFI, CalDAG-GEFII (RasGRP), and CalDAG-GEFIII both in 293T cells and in vitro. By contrast, guanine nucleotide exchange of M-Ras was promoted by the guanine nucleotide exchange factors (GEFs) for the classical Ras (Ha-, K-, and N-), including mSos, RasGRF, CalDAG-GEFII, and CalDAG-GEFIII. GTPase-activating proteins (GAPs) for Ras, Gap1(m), p120 GAP, and NF-1 stimulated all of the R-Ras, TC21, and M-Ras proteins, whereas R-Ras GAP stimulated R-Ras and TC21 but not M-Ras. We did not find any remarkable difference in the subcellular localization of R-Ras, TC21, or M-Ras when these were expressed with a green fluorescent protein tag in 293T cells and MDCK cells. In conclusion, TC21 and R-Ras were regulated by the same GEFs and GAPs, whereas M-Ras was regulated as the classical Ras.

Role of the von Hippel-Lindau tumor suppressor protein during neuronal differentiation

The von Hippel-Lindau (VHL) tumor suppressor protein down-regulates transcription by transcriptional elongation enhanced by antagonizing elongin B and C. Transcriptional regulation is an important control mechanism for embryogenesis and tumorigenesis. The VHL gene and protein are expressed in neuronal cells of the fetal and adult brain. However, the role of the VHL gene in the central nervous system (CNS) has not been elucidated. The VHL gene might modify the expression of various genes during embryogenesis and tumorigenesis in CNS. We investigated the role of the VHL gene in CNS development using rodent CNS progenitor cells. Here we show that expression of the VHL protein is correlated with neuronal differentiation but not with glial differentiation in CNS progenitor cells, and we also show that VHL gene transduction induces neuronal differentiation. In addition, a VHL mRNA antisense oligonucleotide inhibits differentiation of CNS progenitor cells and up-regulates their cell cycle. In conclusion, the VHL gene plays an essential role in neuronal differentiation as well as transcription.

Effect of ephedrine on auditory-evoked potentials during light general anaesthesia

Ephedrine, a sympathomimetic drug, may stimulate the central nervous system via its amphetamine-like effect under light general anaesthesia. We compared the effect of ephedrine on auditory-evoked potentials with that of etilefrine, a sympathomimetic drug that lacks an amphetamine-like effect, in patients undergoing abdominal surgery under general anaesthesia with 67% nitrous oxide in oxygen and epidural blockade. Ephedrine (0.08 mg x kg-1 intravenously) significantly decreased the latencies of Nb and P1 from 49.5 (4.2) [mean (SD)] and 63.9 (9.1) ms to 45.9 (4.2) and 59.0 (9.9) ms, respectively; whereas etilefrine (0.02 mg x kg-1 intravenously) caused no significant changes in these potentials. In addition, the latencies of Nb and P1 before drug administration were positively correlated with patient age. These findings suggest that ephedrine can cause excitation of the central nervous system during light general anaesthesia, and that auditory-evoked potentials may be a sensitive indicator of the depth of anaesthesia.

Isolation and characterization of pepsinogen from Trimeresurus flavoviridis (Habu snake)

Pepsinogen was isolated from the gastric mucosa of Trimeresurus flavoviridis (Habu snake) by DEAE-cellulose and DEAE-Sepharose ion-exchange chromatographies, and Sephacryl S-200 gel-chromatography. The yield calculated from the crude extract was 29% with 6.2-fold purification. The purified pepsinogen gave a single band on both native- and SDS-PAGE. As no other active enzyme was detected on the chromatographies, it was concluded that the Habu snake has one major pepsinogen. The molecular mass of the pepsinogen was estimated to be 38 kDa by SDS-PAGE. The sequence of the N-terminal 26 amino acid residues was determined and compared with those of other pepsinogens. The N-terminal structure of Habu snake pepsinogen was more homologous with those of mammalian pepsinogens C than those of mammalian pepsinogens A. The pepsinogen was rapidly converted to pepsin by way of an intermediate form induced by acidification. The optimum pH of Habu snake pepsin for bovine hemoglobin was 1.5-2.0, and it retained full activity at pH 6.2 and 30 degrees C on incubation for 30 min. The optimum temperature for the snake pepsin was 50 degrees C and it was stable at 40 degrees C on incubation for 10 min. The proteolytic activity of the pepsin toward bovine hemoglobin was about two times higher than that of porcine pepsin A, however, the activity toward oxidized bovine insulin B-chain was lower than that of porcine pepsin A, and it did not hydrolyze oligopeptides. The specificity for oxidized bovine insulin B-chain of the pepsin was different from that of porcine pepsin A. Habu snake pepsin was inhibited by pepstatin A but not by serine, cysteine, or metallo protease inhibitors.

Seven-color fluorescence imaging of tissue samples based on Fourier spectroscopy and singular value decomposition

Seven-color analyses of immunofluorescence-stained tissue samples were accomplished using Fourier spectroscopy-based hyperspectral imaging and singular value decomposition. This system consists of a combination of seven fluorescent dyes, three filtersets, an epifluorescence microscope, a spectral imaging system, a computer for data acquisition, and data analysis software. The spectra of all pixels in a multicolor image were taken simultaneously using a Sagnac type interferometer. The spectra were deconvolved to estimate the contribution of each component dye, and individual dye images were constructed based on the intensities of assigned signals. To obtain mixed spectra, three filter sets, i.e., Bl, Gr, and Rd for Alexa488 and Alexa532, for Alexa546, Alexa568, and Alexa594, and for Cy5 and Cy5.5, respectively, were used for simultaneous excitation of two or three dyes. These fluorophores have considerable spectral overlap which precludes their separation by conventional analysis. We resolved their relative contributions to the fluorescent signal by a method involving linear unmixing based on singular value decomposition of the matrices consisting of dye spectra. Analyses of mouse thymic tissues stained with seven different fluorescent dyes provided clear independent images, and any combination of two or three individual dye images could be used for constructing multicolor images.