Effects of the sodium channel blocker tetrodotoxin (TTX) on cellular ion homeostasis in rat brain subjected to complete ischemia

Anoxic depolarization (AD) and failure of the cellular ion homeostasis are suggested to play a key role in ischemia-induced neuronal death. Recent studies show that the blockade of Na+ influx significantly improved the neuronal outcome. In the present study, we investigated the effects of 10 microM tetrodotoxin (TTX) on ischemia-induced disturbances of ion homeostasis in the isolated perfused rat brain. TTX inhibited the spontaneous EEG activity, delayed the ischemia-induced tissue acidification, and significantly postponed the occurrence of AD by 65%. The [Ca2+]e elevation prior to AD was attenuated from 17.8% to 6% while the increase of the [Na+]e in this period was enhanced (from 2.9% to 7.3%). These findings implied that the ischemia-induced early cellular sodium load and the corresponding shrinkage of the extracellular space was counteracted by TTX. Our results suggest that the Na+ influx via voltage-dependent channels preceding complete breakdown of ion homeostasis is one major factor leading to cell depolarization. The massive Na+ influx coinciding with AD, however, may be mainly via non-selective cation channels or/and receptor-operated channels. Persistent Na+ influx deteriorates neuronal tissue integrity by favouring Ca2+ influx and edema formation. Blockade of ischemia-induced excessive Na+ influx is, therefore, a promising pharmacological approach for stroke treatment.

[Study on red blood cell immune adherence function in coriaria lactone-induced epileptic seizure rats]

The immune adherence function of red blood cells in 17 rats was studied. It was found that the rosette rate of red blood cell C3b receptor (RBC-C3bRR) was 7.45 +/- 1.36% in the epilepsy group (8 rats), and 10.84 +/- 1.77% in the control group (9 rats); and that the rosette rate of red blood cell immune complex (RBC-ICR) was 7.42 +/- 2.62% in the epilepsy, and 10.80 +/- 1.72% in the control. As compared with the control group, the rosette rate of red blood cell C3b receptor was remarkably decreased in the epilepsy group (P < 0.05). There was no significant difference between the two groups in RBC-ICR. The results from this study demonstrated that the CL-induced seizures might result in decrease in red blood cell immune adherence function of the epilepsy rats.

[Correlationship between cellular DNA and AgNOR protein content in the developing course of colorectal adenocarcinoma]

Cellular DNA and AgNOR protein content were evaluated by automatic image analysis in tissue sections stained by combined Feulgen-AgNOR method of 9 normal colonic mucosae, 45 colorectal adenomas and 27 colorectal correlation between AgNOR protein and DNA contents. In adenocarcinomas, the DNA and AgNOR protein contents were higher than those in adenomas, which were in turn higher than those in normal colonic mucosa. However, there was considerable overlapping in the DNA or AgNOR protein content between adenoma and adenocarcinoma groups and between adenoma and normal colonic mucosa groups. By assessing the correlationship between the DNA and AgNOR protein contents, the number of the overlapping cases was reduced significantly. Therefore it is much more reliable to distinguish colorectal adenomas from adenocarcinomas by using the correlationship between the cellular DNA and the AgNOR protein contents in the same specimens.

[Kaschin-Beck's disease in children's wrists: radiographic findings]

Based on the analysis of hand radiographs in 208 children with Kaschin-Beck's disease, the author's chief conclusions are as follow: The more severe Kaschin-Beck's is, the more opportunity the carpals have to be involved. Generally speaking, the capitatum and hamatum are frequently involved if the disease involves the carpals.

Chimeric evolution of the 2-microns genome in Saccharomyces cerevisiae

We compared the nucleotide substitution pattern over the entire genome of two unique variants of the 6,300-bp selfish DNA (2 microns) plasmid in Saccharomyces cerevisiae. The DNA sequence of the left-unique region is identical among 2-microns variants, while the right-unique region shows substantial divergence. This chimeric pattern cannot be explained by neutral or Darwinian selection models. We propose that horizontal transmission of the 2-microns plasmid coupled with a directed, polarized gene conversion maintains the DNA sequence of the left-unique region, whereas the right-unique region is subject to random drift and Darwinian selection.

Esophageal Crohn's disease--a case report

A case of esophageal Crohn's disease in a 52-year-old man is described. The patient was treated successfully by surgical excision of the esophagus. Because esophageal Crohn's disease is uncommon, we would like to discuss its clinical characteristics and to review the literature.

Detection of opiate-enhanced increases in DNA damage, HPRT mutants, and the mutation frequency in human HUT-78 cells

In previous studies we have shown highly significant increases in chromosome damage and sister chromatid exchanges in heroin addicts, particularly when caffeine and metabolic inhibitors are added to the medium. Using human HUT-78 T-cell cultures, we now find direct in vitro evidence of opiate-induced or opiate-promoted mutagenesis via several assay systems. First, with microgel electrophoresis (MGE), we observed graded, dose-dependent, significant increases (P < .0001) in the frequency of comet tails of fragmented DNA when cells were treated with morphine alone (5 x 10(-9) M up to 10(-7) M) or when co-treated with the more potent mutagen, ethylmethanesulfonate (EMS). There were also dose-dependent increases in the lengths and densities of the comet tails observed. These findings were confirmed by a series of MGE experiments in which several days of morphine exposure preceded a 2-hr pulse of EMS. Second, mutant frequency (MF) assays also indicated significant opiate effects. These studies required separate assessment of cloning efficiencies and the frequencies of TG-resistant, HPRT-deficient mutant clones under four test conditions: no treatment, morphine alone for 4 days, morphine plus EMS, and EMS alone. Prior to the treatment phase, aminopterin was used to eliminate background HPRT mutations. The medium was changed after the treatment phase, the cells were allowed to express mutant phenotypes, and then TG was added and resistant mutant clones counted after 16 days. The background MF level for controls and for cells treated with EMS alone were negligible at 5.12 x 10(-8) and 7.25 x 10(-8), respectively. In the cells treated with morphine alone or morphine plus EMS, MF levels increased very significantly (P < .001) by > 100-fold to 5.1 x 10(-6) and 7.0 x 10(-6), respectively. Cloning efficiency also decreased significantly with both morphine-exposed conditions. Preliminary analysis with the single strand conformational polymorphism (SSCP) procedure following 6-thioguanine (TG) selection, also confirmed the occurrence of Exon 3 mutants of the HPRT gene in cells exposed to morphine plus EMS. It appears that brief EMS exposure can be repaired, whereas, if morphine exposure persists through one or more cell cycles, direct or indirect mutagenesis is initiated.

Na+/H+ exchangers, NHE-1 and NHE-3, of rat intestine. Expression and localization

Na-H exchange (NHE) is one of the major non-nutritive Na absorptive pathways of the intestine and kidney. Of the four NHE isoforms that have been cloned, only one, NHE-3, appears to be epithelial specific. We have examined the regional and cellular expression of NHE-3 in the rat intestine. NHE-3 message in the small intestine was more abundant in the villus fractions of the small intestine than in the crypts. Analysis of NHE-3 mRNA distribution in the gut by in situ hybridization demonstrated epithelial cell specificity, as well as expression preferential to villus cells. NHE-1 message, in contrast, was ubiquitous, with slightly greater expression exhibited in the differentiating crypt and lower villus cells of the small intestine. Isoform-specific NHE-3 fusion protein antibody identified a 97-kD membrane protein in the upper villus cells of the small intestine, which was exclusively localized in the apical membrane. In contrast, antibody previously developed against the COOH-terminal region of human NHE-1 (McSwine, R. L., G. Babnigg, M. W. Musch, E. B. Chang, and M. L. Villereal, manuscript submitted for publication) identified a 110-kD basolateral membrane protein. These data suggest that unlike NHE-1, which probably serves a "housekeeping" function, NHE-3 may be involved in vectorial Na transport by the intestine.

The microfocus assay system (mfas) - a simple quantitative assay to identify inhibitory drugs targeted against specific oncogenes

We have developed an assay, the microfocus assay system (MFAS), that enables the quantitative assessment of anticancer drugs and their ability to specifically target and inhibit cellular oncogenes. Analysis of three chemotherapeutic reagents showed a differential negative effect against the ability of transformed cells containing either the oncogenic rat neu, human H-ras, or v-mos oncogene to form transformed foci on a background of normal fibroblasts. Though these drugs have not been examined previously for targeting against specific oncogenes, our results with the MFAS indicate preferential inhibitory effects against cells transformed with different oncogenes. Therefore, the MFAS should enable the large scale screening of anti-cancer drugs specifically targeted against known oncogenes and provide a quantitative measurement of their effectiveness.

Observation of therapeutic effect in 50 cases of chronic renal failure treated with rhubarb and adjuvant drugs

Treatment of chronic renal failure with rhubarb and adjuvant drugs combined with other appropriate measures alleviates the suffering of the patients and improves the quality of their survival. Most patients can take care of themselves after treatment, and some can engage in half-day work. The treatment prolongs the life of the patient, and reduces medical expenses. It is of definite social and economic benefit, and conforms with China's conditions. Except for very severe cases whose blood creatinine exceeds 884 mumol/L, it can be given to all patients. It can also be used as a transitional measure before more radical therapies may be instituted.

Differential transcription and translation of immediate early genes in the gerbil hippocampus after transient global ischemia

Excitotoxic activation of glutamate receptors is thought to be a key event for the molecular pathogenesis of postischemic delayed neuronal death of CA-1 neurons in the gerbil hippocampus. Glutamate receptor stimulation also causes induction of transcription factors that belong to the class of immediate early genes. We examined the expression of six different immediate early genes in the gerbil hippocampus after transient global ischemia. Comparative analysis of c-fos and Krox-24 expression was carried out in the same animals at the transcriptional and translational level by in situ hybridization and immunocytochemistry. Postischemic synthesis of four additional immediate early gene (IEG)-encoded proteins (FOS-B, c-JUN, JUN-B, and JUN-D) was investigated by immunocytochemistry at recirculation intervals between 1 and 48 h. After 5 min of ischemia, transcription of c-fos and Krox-24 mRNA was induced in all hippocampal subpopulations with peak expression at 1 h after recirculation. In vulnerable CA-1 neurons, increased transcription of c-fos and Krox-24 was not followed by translation into protein. Induction of immediate early gene-encoded proteins was restricted to neuronal populations less vulnerable to brief ischemia and identified neurons that are targets of glutamate receptor-mediated neurotoxicity but that are destined to survive. Our data indicate an asynchronous synthesis and persistence of individual IEG-encoded proteins in these neurons. The staggered induction implies that combinatorial changes of transcription factors allow a differential postischemic regulation of target gene expression both spatially and over time.

Identification and characterization of a factor which is essential for assembly of transcarboxylase

Transcarboxylase (TC) from Propionibacterium shermanii is a biotin-containing enzyme which catalyzes the reversible transfer of a carboxyl group from methylmalonyl-CoA to pyruvate. It is composed of a central, hexameric 12S subunit with six outer, dimeric 5S subunits held in a stable 26S complex by twelve 1.3S biotinyl subunits. Each of these subunits has been cloned from the P. shermanii genome and expressed in Escherichia coli. The purified, expressed recombinant proteins are all indistinguishable from their authentic counterparts except for the recombinant 5S subunit (termed 5S WT), which does not form TC complexes or catalyze the overall transcarboxylase reaction. Circular dichroism and isoelectric focusing suggested differences existed between the authentic and E. coli-expressed 5S proteins. HPLC gel filtration was used to separate the authentic 5S dimer from additional components in the preparation. 5S dimer thus purified was unable to form TC complexes or catalyze the overall reaction, behaving identically to the recombinant 5S WT subunit. Fractions from the HPLC gel-filtration purification of authentic 5S were then added to 5S WT or 5S dimer, and one fraction was identified which catalyzed the assembly of TC complexes with either 5S preparation. This assembly activity was shown to be dependent on the concentration of this HPLC fraction. Assembly-promoting factor (APF) is heat-stable and probably a protein, on the basis of its protease susceptibility. Studies with APF and the other TC subunits demonstrate its ability to promote complex formation with 12S and 1.3S subunits. Since the APF was purified from crystals of 26S TC, we believe it to be a novel, previously unidentified subunit of transcarboxylase.

Purification and characterization of the recombinant 5 S subunit of transcarboxylase from Escherichia coli

Transcarboxylase from Propionibacterium shermanii is a biotin-containing enzyme which catalyzes the reversible transfer of a carboxyl group from methylmalonyl-CoA to pyruvate. It is composed of a central, hexameric 12 S subunit, 6 outer dimeric 5 S subunits which are held in a complex by 12 1.3 S biotinyl subunits. The transcarboxylase reaction requires two partial reactions, one of which is specific to 5 S. The cloning and expression of each of these subunits in Escherichia coli have been reported. We have designed a method for the purification of the 5 S subunit from an E. coli expression system. Protein purified to homogeneity by this method was shown to be active in the 5 S partial reaction, but unable to catalyze the overall transcarboxylase reaction. This protein was characterized as to its ability to form stable dimers, associate with the 1.3 S subunit in stable complexes referred to as 6 S, and assemble whole TC. The latter activity was shown to be lacking. The purified protein has a native molecular weight of 120 kDa and a subunit molecular weight of 60 kDa, consistent with the 5 S dimer. Plasma emission analysis of the metal content of the recombinant protein demonstrated the presence of both Co and Zn, comparable to the authentic protein. Fluorescence analysis verified the ability of the purified protein to bind substrates and 1.3 S subunits appropriately. Sequencing of the amino terminus and determination of the amino acid composition of the recombinant protein relative to that of the authentic subunit further verified the identity of the purified protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium nitroprusside stimulates anion secretion and inhibits sodium chloride absorption in rat colon

The effects of sodium nitroprusside (SNP) on intestinal electrolyte transport were studied in rat colon mounted in Ussing chambers. Serosal addition of SNP increases short-circuit current (Isc) in a concentration-dependent manner. The maximal change in Isc was 35.6 +/- 2.3 microA/cm2 at 1 mM SNP (ED50 approximately 81 microM). S-nitroso-N-acetylpenicillamine, a nitrosothiol which can release nitric oxide, also stimulated an increase in Isc of 13.9 +/- 3.1 microA/cm2 at a concentration of 100 microM. The response to SNP was rapid, peaking at about 4 min with partial return to baseline at 20 to 30 min. Isc responses to SNP were significantly less in the cecum and ileum as well as after mucosal addition in the distal colon. Pretreatment with serosal atropine, cimetidine, pyrilamine, ketanserin, and N omega-nitro-L-arginine and mucosal amiloride did not inhibit the SNP-stimulated Isc; iodine, methylene blue, bumetanide, piroxicam, and tetrodotoxin each significantly decreased the response and piroxicam plus tetrodotoxin abolished it. Transmural 22Na+ and 36Cl- flux studies demonstrated that the change in Isc produced by SNP was attributable to anion secretion. SNP also inhibited neutral Na+ and Cl- absorption, with the inhibition of Na+, but not Cl- absorption eliminated by tetrodotoxin and piroxicam pretreatment. In summary, SNP has several effects on intestinal electrolyte transport, suggesting that nitric oxide or other components of nitrovasodilators may be important physiological mediators of salt and water transport and may play a role in stimulated colonic epithelial electrolyte transport in inflamed tissues.

Light-regulated and cell-specific expression of tomato rbcS-gusA and rice rbcS-gusA fusion genes in transgenic rice

A previously isolated rice (Oryza sativa) rbcS gene was further characterized. This analysis revealed specific sequences in the 5' regulatory region of the rice rbcS gene that are conserved in rbcS genes of other monocotyledonous species. In transgenic rice plants, we examined the expression of the beta-glucuronidase (gusA) reporter gene directed by the 2.8-kb promoter region of the rice rbcS gene. To examine differences in the regulation of monocotyledonous and dicotyledonous rbcS promoters, the activity of a tomato rbcS promoter was also investigated in transgenic rice plants. Our results indicated that both rice and tomato rbcS promoters confer mesophyll-specific expression of the gusA reporter gene in transgenic rice plants and that this expression is induced by light. However, the expression level of the rice rbcS-gusA gene was higher than that of the tomato rbcS-gusA gene, suggesting the presence of quantitative differences in the activity of these particular monocotyledonous and dicotyledonous rbcS promoters in transgenic rice. Histochemical analysis of rbcS-gusA gene expression showed that the observed light induction was only found in mesophyll cells. Furthermore, it was demonstrated that the light regulation of rice rbcS-gusA gene expression was primarily at the level of mRNA accumulation. We show that the rice rbcS gene promoter should be useful for expression of agronomically important genes for genetic engineering of monocotyledonous species.

The resistance of macrophage-like tumour cell lines to growth inhibition by lipopolysaccharide and pertussis toxin

The process of tumorigenesis is frequently associated with resistance to growth inhibition by physiological regulators of normal cells. Murine macrophage-like cell lines BAC1.2F5, RAW264, J774.1A and PU5/1.8 were resistant to growth inhibition by bacterial lipopolysaccharide (LPS) and pertussis toxin, agents that blocked growth of primary bone marrow-derived macrophages (BMDM) in the presence of macrophage colony-stimulating factor (CSF-1). The resistance of the CSF-1-dependent cell line BAC1.2F5 to growth inhibition by pertussis toxin argues against the possibility that pertussis toxin-sensitive G proteins are essential for the pathway of growth stimulation by CSF-1. Conversely, these data add further weight to the argument that LPS mediates some of its biological activities by mimicking the action of pertussis toxin and inhibiting G protein function. The resistance of cell lines to LPS and pertussis toxin was not correlated with any alteration in the expression of mRNA encoding any of three pertussis-toxin sensitive G protein alpha subunits. The pattern of G protein expression was consistent between primary cells and tumour cells, suggesting that this is a differentiation marker. In particular, Gi alpha 2 mRNA was expressed at remarkably high levels in all of the cells. The specificity of LPS resistance was investigated by studying down-regulation of CSF-1 binding and induction of protooncogene c-fos and tumour necrosis factor (TNF) mRNA. BAC1.2F5 cells were LPS-resistant in each of these assays. In CSF-1 binding, RAW264 and J774.1A responded in the same way as bone marrow-derived macrophages but required higher doses of LPS, whereas c-fos and TNF mRNA were induced in these cells at concentrations that did not inhibit growth. In PU5/1.8 cells, CSF-1 binding was already very low and was not further down-regulated, but c-fos and TNF mRNA was inducible by LPS. By contrast to primary macrophages, the cell lines did not respond to LPS with down-regulation of c-fms mRNA, which encodes the CSF-1 receptor. Hence, the resistance of macrophage-like tumour cells to LPS and pertussis toxin was specific to the pathways controlling growth, and was correlated with altered regulation of the CSF-1 receptor.

Isoglobotetraosylceramide is a marker for highly metastatic cells in rat mammary adenocarcinomas

We have previously identified a neutral glycolipid antigen which appears to be a surface antigenic marker for the metastatic subpopulation in the R3230AC rat mammary adenocarcinoma (S.A. Carlsen, M. Barry, and K. Newton, Clin. Exp. Metastasis, 8: 141-151, 1990). In this article we describe the structural characterization of this glycolipid antigen. The sequence of the sugars in the saccharide portion of the molecule was determined by specific glycosidase cleavage and further confirmed by mass spectroscopic analysis. The nature of the linkages between the monosaccharide units was determined by methylation analysis. The final structure was confirmed by NMR analysis and found to be isoglobotetraosylceramide (GalNAc beta 1-3Gal alpha 1-3Gal beta 1-4Gle beta 1-O-ceramide). We also present evidence that the cells marked by this antigen have a higher metastatic potential than the cells lacking this glycolipid as measured by the formation of lung colonies after i.v. injection of the cells into the tail vein of the rat. Furthermore, isoglobotetraosylceramide seems to play a direct role in the metastatic process since the blocking of exposed antigen with monoclonal antibodies, or their Fab fragments, results in a highly significant decrease in lung colony formation.

Molecular cloning and adhesive properties of murine platelet/endothelial cell adhesion molecule 1

We describe the isolation and characterization of a functional murine platelet/endothelial cell adhesion molecule (PECAM) 1 cDNA clone from a mouse lung library. At the nucleotide level, the coding sequence of murine PECAM-1 is 73% identical to human PECAM-1, and at the amino acid level, the sequence is 79% homologous to its human counterpart. Southern hybridization reveals that one copy of the gene exists in the mouse genome; Northern hybridization reveals a single mRNA species in mouse lung tissue. COS-7 and mouse L cells transfected with murine PECAM-1 expressed a 130-kDa glycoprotein on their surfaces that reacted with anti-murine PECAM-1 monoclonal antibody and comigrated on SDS/PAGE with human PECAM-1. Stable L-cell transfectants aggregate with each other in a PECAM-dependent, homophilic manner.