The ATP-dependent HslVU protease from Escherichia coli is a four-ring structure resembling the proteasome

HslVU is a new two-component protease in Escherichia coli composed of the proteasome-related peptidase HslIV and the ATPase HsIU. We have used electron microscopy and image analysis to examine the structural organization of HslV and HslU homo-oligomers and the active HslVU enzyme. Electron micrographs of HslV reveal ring-shaped particles, and averaging of top views reveal six-fold rotational symmetry, in contrast to other beta-type proteasome subunits, which form rings with seven-fold symmetry. Side views of HslV show two rings stacked together, thus, HslV behaves as dodecamer. The ATPase HslU forms ring-shaped particles in the presence of ATP, AMP-PNP or ADP, suggesting that nucleotide binding, but not hydrolysis, is required for oligomerization. Subunit crosslinking, STEM mass estimation, and analysis of HslU top views indicate that HslU exists both as hexameric and heptameric rings. With AMP-PNP present, maximal proteolytic activity is observed with a molar ratio of HslU to HslV subunits of 1:1, and negative staining electron microscopy shows that HslV and HsIU form cylindrical four-ring structures in which the HsIV dodecamer is flanked at each end by a HslU ring.

Protein tyrosine phosphatase activities are involved in apoptotic cancer cell death induced by GL331, a new homolog of etoposide

GL331 is a semisynthetic topoisomerase II inhibitor derived from a plant toxin podophyllotoxin. In 72-h exposure assays, LD50 values of GL331 range from 0.5 to 2 microM, which are three- to ten-fold lower than those of its homologous compound etoposide (VP-16), depending on different cancer cell lines including nasopharyngeal, hepatocellular, gastric, cervical and colon cancer types. Apoptotic DNA ladders could be detected when cancer cells were treated with GL331 for 24 h even if the Bcl-2 and Bax protein levels were not altered during the period. Besides acting as topoisomerase II inhibitors, both GL331 and VP-16 decrease the cellular protein tyrosine kinase (PTK) activities in cancer cells. The activities of protein tyrosine phosphatase (PTP) are significantly increased after GL331 treatment but are not affected by VP-16. GL331-induced internucleosomal cleavage can be efficiently prevented by two inhibitors of PTP, sodium orthovanadate and zinc chloride, but not by okadaic acid, which inhibits serine/threonine phosphatase activity. These results indicate that GL331 may induce apoptotic cell death, and that activation of protein tyrosine phosphatases may be involved in this process.

Ischemia-induced alteration of myocardial Na(+)-K(+)-ATPase activity and ouabain binding sites in hypercholesterolemic rabbits

The purpose of this study was to explore the effect of ischemia on the Na(+)-K(+)-ATPase activity and ouabain receptor of the myocardial sarcolemma in hypercholesterolemic rabbits. Male New Zealand white rabbits were fed with either standard chow or standard chow supplemented with 0.5% (w/w) cholesterol and 10% (w/w) coconut oil. After an 8 week feeding period, the rabbits underwent a thoracotomy and myocardial ischemia was induced by occlusion of the coronary artery. Myocardial samples from the ischemic and non-ischemic regions of the left ventricle of control and cholesterol-fed rabbits were taken for study. The cholesterol-fed group showed a decrease in both Na(+)-K(+)-ATPase activity and [3H]ouabain binding sites as compared to the control group. Ischemia caused a reduction in both Na(+)-K(+)-ATPase activity [3H]ouabain bindings sites in both control and cholesterol-fed rabbits. The combination of ischemia and hypercholesterolemia produced an additive effect, with a further decrease in both Na(+)-K(+)-ATPase activity and [3H]ouabain binding sites. Neither the activity of Mg+(+)-ATPase nor the binding affinity for [3H]ouabain was affected by either hypercholesterolemia or ischemia. These findings indicate that hypercholesterolemia may exaggerate certain aspects of functional deterioration arising during myocardial ischemia.

Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy

We recently developed a pig model with naturally occurring hypertrophic cardiomyopathy (HCM). To further characterize the biochemical features of high frequency of sudden death affected by this disease, the protein profiles of ventricular tissues were analyzed on normal, HCM, and HCM with sudden-death pigs. By sodium dodecylsulfate-polyacrylamide gel electrophoresis, a protein corresponding to an apparent molecular mass of 90 kDa (p90) was found to be markedly decreased in the HCM-affected tissues of sudden-death pigs, but not in HCM or normal pigs. Further study showed that the primary decrease of p90 in HCM pigs with sudden death was located mainly in the interventricular septum. As determined by the molecular mass and isoelectric point on 2-dimensional gels and Western immunoblot with a specific 90 kDa heat shock protein (HSP90) monoclonal antibody, the unknown protein was identified as HSP90. Our findings indicate for the first time that substantially decreased heart HSP90 is associated with HCM pigs with sudden death. Although the role that HSP90 may play in protecting pigs with HCM from sudden death is still nuclear, the model itself may provide further insight into understanding the role of heat shock proteins in cardiac sudden death.-Lee, W.-C., Lin, K.-Y., Chiu, Y.-T., Lin, J.-H., Cheng, H.-C., Huang, H.-C., Yang, P.-C., Liu, S.-K., Mao, S. J. T. Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy.

Achromatic wave retarder by phase subtraction

We analyze the method of phase subtraction in two identical optical structures to build an achromatic phase retarder. The two structures are made of right-angle prisms and are aligned orthogonal to each other. They are also made of materials of different refractive indices so that dispersion compensation can be taken advantage of. Essentially the phase retardation between the s and p waves in the first structure is subtracted from the phase retardation in the second structure. This can be done by reversing the roles of the s and p waves. By choosing the materials of the prisms properly, the phase retardation can be made to be constant over a broad spectral range. Indeed, calculations made with commercial optical glasses show that phase errors in the visible and near-infrared regions can be rather small. For example, for a 90° phase retarder (quarter-wave plate), a phase error of 0.35° can be obtained from 0.35 to 0.81 μm and from 0.59 to 1.26 μm.

Legionella pneumophila infection in Taiwan: a preliminary report

Legionella pneumophila infection has been recognized as an important cause of pneumonia. However, epidemiologic baseline data about the occurrence of legionella-related pneumonia and the distribution of legionellae in aquatic environments are still not available in Taiwan. A survey conducted by the National Institute of Preventive Medicine found that 8.6% of 487 pneumonia patients studied were positive for the L. pneumophila serologic test (indirect fluorescent test, IFA) and 32.0% of the 25 water samples were positive for isolation of legionellae. In conclusion, this survey supported the existence of Legionnaires' disease in Taiwan, indicated a preliminary prevalence of L. pneumophila antibodies among pneumonia patients and identified the prevalence of legionellae in water environments.

HslV-HslU: A novel ATP-dependent protease complex in Escherichia coli related to the eukaryotic proteasome

We have isolated a new type of ATP-dependent protease from Escherichia coli. It is the product of the heat-shock locus hslVU that encodes two proteins: HslV, a 19-kDa protein similar to proteasome beta subunits, and HslU, a 50-kDa protein related to the ATPase ClpX. In the presence of ATP, the protease hydrolyzes rapidly the fluorogenic peptide Z-Gly-Gly-Leu-AMC and very slowly certain other chymotrypsin substrates. This activity increased 10-fold in E. coli expressing heat-shock proteins constitutively and 100-fold in cells expressing HslV and HslU from a high copy plasmid. Although HslV and HslU could be coimmunoprecipitated from cell extracts of both strains with an anti-HslV antibody, these two components were readily separated by various types of chromatography. ATP stimulated peptidase activity up to 150-fold, whereas other nucleoside triphosphates, a nonhydrolyzable ATP analog, ADP, or AMP had no effect. Peptidase activity was blocked by the anti-HslV antibody and by several types of inhibitors of the eukaryotic proteasome (a threonine protease) but not by inhibitors of other classes of proteases. Unlike eukaryotic proteasomes, the HslVU protease lacked tryptic-like and peptidyl-glutamyl-peptidase activities. Electron micrographs reveal ring-shaped particles similar to en face images of the 20S proteasome or the ClpAP protease. Thus, HslV and HslU appear to form a complex in which ATP hydrolysis by HslU is essential for peptide hydrolysis by the proteasome-like component HslV.

Food-borne disease outbreaks in Taiwan, 1994

In 1994, 102 outbreaks of food-borne disease involving 4,726 cases were reported to the Taiwan Department of Health. This is the highest number of outbreaks and cases in recent years in Taiwan. Of these outbreaks, 72.5% (74/102) were caused by bacterial pathogens, with Vibrio parahaemolyticus responsible for 56.7% (42/74), Staphylococcus aureus 20.3% (15/74), Bacillus cereus 14.9% (11/74) and Salmonella spp other than S. typhi and S. paratyphi 8.1% (6/74). V. parahaemolyticus has been a leading cause of problems in Taiwan for many years. Contamination of seafood with this organism has been reported frequently, particularly in the warmer months. In 1994, small outbreaks (fewer than 5 cases) and large outbreaks (more than 50 cases) represented 31.4% (32/102) and 12.7% (13/102), respectively, of the total. The median outbreak size was 10 cases. A high proportion (54%, 7/13) of the large outbreaks was associated with commercial lunch-boxes supplied to elementary and junior high schools. Health education to improve food sanitation and supervision of food sanitation practices need to be strengthened.

Characterization of hsr201 and hsr515, two tobacco genes preferentially expressed during the hypersensitive reaction provoked by phytopathogenic bacteria

During an incompatible interaction between tobacco and the bacterial phytopathogen Pseudomonas solanacearum, 2 classes of genes, the so-called hsr (hypersensitivity-related) genes, activated preferentially during the hypersensitive reaction, and the str (sensitivity-related) genes, expressed strongly during compatible and incompatible interactions, have been identified. In this report, two hsr cDNA clones, hsr515 and hsr201, as well as their expression patterns are presented. Hsr515 was found to encode a P450 monooxygenase and is most similar to the ripening-related avocado gene CYP71A1 (40.6% amino acid identity). Hsr201 presents 58.6% amino acid identity with pTom36, a tomato gene expressed during fruit maturation. The putative functions of the hsr gene products appear to be quite diverse and their characteristics of activation were found to be very conserved: accumulation of the corresponding mRNAs primarily in leaf areas in contact with the avirulent P. solanacearum strain or with a Pseudomonas fluorescens strain containing the hrpZ gene encoding a necrotizing polypeptide, harpin and absence of expression during normal plant development. Our results also suggest that, in a tobacco line expressing NahG, a lower level of salicylic acid, a compound associated with systemic acquired resistance, and also possibly involved in the development of necrotic lesions characteristic of the HR, does not affect the hsr gene expression.

Large-scale preparation of a ribonuclease from Rana catesbeiana (bullfrog) oocytes and characterization of its specific cytotoxic activity against tumor cells

Rana catesbeiana ribonuclease (RC-RNase) is a pyrimidine-guanine sequence-specific ribonuclease found only in R. catesbeiana (bullfrog) oocytes, but not in other organs. The protein is localized in the yolk granules of oocytes but not in other organelles, as detected by immunohistochemistry. More than 99% of RC-RNase was found in the yolk granule pellet when a mild separation method was employed under physiological conditions. The ribonuclease was purified by precipitation of yolk granules, extraction of RC-RNase with 0.09 M NaCl, selective removal of impurities by Hepes buffer, and chromatographies on phosphocellulose and carboxymethyl cellulose columns. Three milligrams of RC-RNase was purified from a 1-g pellet of yolk granules prepared from 2 g of ovary tissue. Therefore, 150 milligrams of RC-RNase could be obtained from a mature female bullfrog (600 g in weight) which had 100 g of ovary tissue. The properties of RC-RNase isolated from yolk granules tested so far are identical to those of RC-RNase isolated from the cytosolic fraction and similar to those of a sialic acid-binding lectin from bullfrog oocytes. To investigate the possible role of RC-RNase in the regulation of cell growth and differentiation during embryogenesis, its cytotoxic activity against various cell lines was examined. The degradation of ribosomal RNA was found in RC-RNase-treated HeLa cells. However, both events were not found in RNase A-treated HeLa cells. Therefore, RC-RNase is proposed to have both ribonucleolytic and cytotoxic activity and a specific receptor on the tumor cell surface is suspected to be involved in the recognition and binding, and possibly entry of RC-RNase.

Diarylspiro[2.4]heptenes as orally active, highly selective cyclooxygenase-2 inhibitors: synthesis and structure-activity relationships

A novel series of 5,6-diarylspiro[2.4]hept-5-enes was shown to provide highly potent and selective cyclooxygenase-2 (COX-2) inhibitors. A study of structure-activity relationships in this series suggests that 3,4-disubstituted phenyl analogs are generally more selective than 4-substituted phenyl analogs and that replacement of the methyl sulfone group on the 6-phenyl ring with a sulfonamide moiety results in compounds with superior in vivo pharmacological properties, although with lower COX-2 selectivity. Several compounds have been shown to possess promising pharmacological properties in adjuvant-induced arthritis and edema analgesia models. The absence of gastrointestinal (GI) toxicity at 200 mpk of several selected compounds in rats and mice corresponds well with the weak potency for inhibition of COX-1 observed in the enzyme assay. Methyl sulfone 55 and sulfonamide 24 were shown to have superior in vivo pharmacological profiles, low GI toxicity, and good oral bioavailability and duration of action.

Identification of a potential regulator of early transcriptional responses to mesoderm inducers in the frog embryo

The activin/transforming growth factor-beta (TGF-beta) family of peptide growth factors plays a central role in the induction of mesoderm during early Xenopus embryogenesis. Immediate transcriptional responses to mesoderm-inducing signals have been described, but the signal transduction steps leading to these early responses are unknown. We describe here the first pre-transcriptional response to activin/TGF-beta mesoderm inducers in the early embryo. We have identified a cellular factor which binds to a 50 bp portion of the promoter for an activin/TGF-beta early response gene. This factor is activated within 4 min of treatment of embryonic prospective ectoderm with mesoderm-inducing factors, making it the earliest response to these factors described in early embryos. This factor can be activated throughout early cleavage and blastula stages, is activated by mesoderm inducers of the activin/TGF-beta superfamily but not the fibroblast growth factor (FGF) family, and does not appear to require an endogenous FGF signal for activation. Characterization of this factor provides a powerful tool for studying the early steps in the induction of mesoderm by members of the activin/TGF-beta superfamily.

1,2-Diarylcyclopentenes as selective cyclooxygenase-2 inhibitors and orally active anti-inflammatory agents

A series of 1,2-diarylcyclopentene methyl sulfones and sulfonamides have been shown to be remarkably potent and selective cyclooxygenase-2 (COX-2) inhibitors. The methyl sulfone analogs 7 showed excellent COX-2 activity, with IC50s ranging from 0.003 (7f,n) to 0.87 (7o) microM. In addition, most analogs of 7 showed no activity (IC50 > 100 microM) against the COX-1 enzyme. Replacement of the methyl sulfone moiety with a sulfonamide group gave a slightly more potent (typically 2-5-fold) but less selective COX-2 inhibitor, mainly due to an increase (20- > 100-fold) in COX-1 activity. However, in vitro COX-1/COX-2 selectivity for the sulfonamides 8 could be increased in many cases by simply incorporating a substituent at the 3-position of the phenyl group. Furthermore, in vitro selectivity increased with the size and number of substituents, as demonstrated in the selectivity trend of 8k (8000) > 8j (1900) > 8i (500) > 8h (100). More importantly, the sulfonamide COX-2 inhibitors showed greatly enhanced oral activity in the rat model of established adjuvant-induced arthritis, with inhibition values of 79.0% (8a), 81.5% (8c), and 83.0% (8g) at 1 mg/kg. On the basis of its overall biological profile, sulfonamide 8c was evaluated as a potential clinical candidate, displaying an ED50 of 22 mpk in the rat carrageenan-induced paw edema model and an ED50 of 0.16 mpk in the rat established adjuvant-induced arthritis model with no indication of gastrointestinal toxicity in rats and mice at 200 mpk. In addition, a preparative-scale synthetic route to sulfonamide 8c has been developed.

The complete hrp gene cluster of Pseudomonas syringae pv. syringae 61 includes two blocks of genes required for harpinPss secretion that are arranged colinearly with Yersinia ysc homologs

Pseudomonas syringae pv. syringae 61 contains a 25-kb hrp cluster that is sufficient to elicit the hypersensitive response (HR) in nonhost plants. Previous studies have shown that mutations in complementation groups VIII, IX, and XI in the hrp cluster abolished the ability of the bacterium to cause the HR. The sequence of a 3.7-kb SmaI-SstI fragment covering groups VIII and IX now reveals five open reading frames (ORFs) in the same transcript, designated as hrpU, hrpW, hrpO, hrpX, and hrpY, and predicted to encode proteins of 14,795, 23,211, 9,381, 28,489, and 39,957 Da, respectively. The hrpU, hrpW, hrpO, hrpX, and hrpY genes are homologous and arranged colinearly with the yscQ/spa33/spaO, yscR/spa24/spaP, yscS/spa9/spaQ, yscT/spa29/spaR, and yscU/spa40/spaS genes of Yersinia spp., Shigella flexneri, and Salmonella typhimurium, respectively. These proteins also show similarity to Fli/Flh proteins of Bacillus and enteric bacteria. The Ysc and Spa proteins are involved in the secretion of virulence factors, like the Yop and Ipa proteins. Fli/Flh proteins are involved in flagellar biogenesis. The sequence of a 2.9-kb EcoRV-EcoRI DNA fragment containing mainly group XI revealed five ORFs, designated hrpC, hrpD, hrpE, hrpF, and hrpG, predicted to encode proteins of 29,096, 15,184, 21,525, 7,959, and 13,919 Da, respectively. The first three genes belong to an operon containing hrpZ, which encodes an extracellular protein that elicits the HR. hrpF and hrpG are two potential ORFs upstream of hrpH in the hrpH operon. HrpC is homologous to Yersinia YscJ, Pseudomonas solanacearum HrpI, Xanthomonas compestris pv. vesicatoria HrpB3, and Rhizobium fredii NolT. HrpE is similar to YscL of Yersinia spp. P. s. pv. syringae 61 Hrp proteins are most similar to Ysc proteins among those homologs. TnphoA insertions in hrpC, hrpE, hrpW, hrpX, and hrpY abolished the ability of P. s.pv. syringae 61 to secrete HrpZ (harpinPss), as determined by immunoblot analysis of cell-bound and culture supernatant fractions. Thus, many of the proteins required for flagellar biogenesis and virulence protein secretion in plant and animal pathogens may have a common ancestry.

The HrpZ proteins of Pseudomonas syringae pvs. syringae, glycinea, and tomato are encoded by an operon containing Yersinia ysc homologs and elicit the hypersensitive response in tomato but not soybean

The Pseudomonas syringae pathovars are composed of host-specific plant pathogens that characteristically elicit the defense-associated hypersensitive response (HR) in nonhost plants. P. s. pv. syringae 61 secretes an HR elicitor, harpinPss (HrpZPss), in a hrp-dependent manner. An internal fragment of the P. s. pv. syringae 61 hrpZ gene was used to clone the hrpZ locus from P. s. pv. glycinea race 4 (bacterial blight of soybean) and P. s. pv. tomato DC3000 (bacterial speck of tomato). DNA sequence analysis revealed that hrpZ is the second ORF in a polycistronic operon. The amino acid sequence identities of HrpZPss/HrpZPsg and HrpZPss/HrpZPst were 79 and 63%, respectively. Although none of the HrpZ proteins showed significant overall sequence similarity with other known proteins, HrpZPst contained a 24-amino acid sequence that is homologous with a region of the PopA1 elicitor protein of the tomato pathogen, Pseudomonas solanacearum GMI1000. hrpA, the upstream ORF, was highly divergent: The amino acid sequence identities of HrpAPss/HrpAPsg and HrpAPss/HrpAPst were 91 and 28%, respectively, and no HrpA sequence showed similarity to known proteins. In contrast, the predicted products of the downstream ORFs in P. s. pv. syringae and P. s. pv. tomato, hrpB, hrpC, hrpD, and hrpE showed varying levels of similarity to those of yscI, yscJ, yscK, and yscL. These are colinearly arranged genes in the virC locus of Yersinia spp., which are involved in the secretion of the Yop virulence proteins via the type III pathway. The similarity of the Ysc proteins was generally stronger in comparisons with the P. s. pv. tomato Hrp proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Latex agglutination test for detection of tetanus antitoxins

A rapid and easy method of slide agglutination test for the detection of human tetanus antitoxins was developed in this study. Testing reagents were prepared from carboxylated polystyrene latex particles with tetanus toxin by soluble carbodiimide. The test was performed on a glass slide with a drop of test sample and a drop of testing reagent. The agglutination reaction was usually completed within five minutes. Sensitivity of this test for tetanus antitoxins can be reached at 0.125 IU/ml. Therefore, the latex agglutination test can be used to determine the immune status of a patient in an emergency.

Cloning and characterization of the endogenous retroviral-tRNA(Glu) multigene family from human genomes of different racial backgrounds

An 8.3-kb human endogenous retroviral-tRNA(Glu) (HERV-E)-encoding cDNA clone and a 1.5-kb genomic clone were isolated from a Chinese-derived cervical cancer cell line, CC7T, and their sequences determined. The former is a full-length endogenous retroviral cDNA containing corresponding u5-gag-pol-env-u3-r regions. The latter is a partial retroviral DNA segment, covering the gag and pol genes. Analysis of normal human DNA by Southern blot hybridization with three specific HERV-E molecular DNA probes revealed complex restriction-fragment length polymorphisms (RFLP), implying that the human genome contains diverse proviral structures and dispersed integration sites. The complex patterns were virtually identical between DNAs from African-Americans, Asians and Caucasians, with only a few minor variations. The data suggest that these proviral sequences were mostly incorporated into the human genome before racial divergence and, hence, may serve as markers for distinct chromosomal sites.

Inhibition of protein kinase C by snake venom toxins: comparison of enzyme inhibition, lethality and hemolysis among different cardiotoxin isoforms

Cardiotoxins, neurotoxins and phospholipase A2 (PLA2) are three major classes of toxic components present in the Taiwan cobra, Naja naja atra of the Elapidae family. Cardiotoxins (or called cytotoxins), a group of major polypeptides of around 60 amino-acid residues present abundantly in the elapid family of snakes, comprise about 45-55% of the crude venom of Taiwan cobra. In contrast to another prominent group of structurally similar neurotoxins with well-established acetylcholine receptors and modes of action, cardiotoxins showed no defined cellular targets and very diverse pharmacological functions. A systematic structure/function comparison of these toxins was made by their relative inhibitory effects on protein kinase C (PKC) isolated from mouse brains. Lethality and hemolysis of various cardiotoxin isoforms were also compared in order to shed some insight on the biological targets and mechanisms of these surface-active amphiphilic polypeptides. A structure comparison of these cardiotoxins based on computer model-building revealed that some defined and subtle differences can be detected upon the superposition of these three-dimensional polypeptide chains, which may reflect the intrinsic differences in the hydrophobic peptide segments present on the surface loops of toxin molecules. The differences seem to correlate with different inhibitory activities exhibited by cardiotoxins in contrast to the lack of activity by cobrotoxin and PLA2 on PKC.

Differential correlation between translocation and down-regulation of conventional and new protein kinase C isozymes in C6 glioma cells

Correlation between translocation and down-regulation of conventional protein kinase C alpha (cPKC alpha) and new PKC delta (nPKC delta) induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) at different time courses (5 min, 30 min, 1 h, 3 h, 6 h, 10 h, 17 h, and 24 h) was studied in C6 glioma cells. From the dose-dependent translocations of these two isoforms by 10-min treatment with TPA (1, 3, 10, 30, 100, 300, and 1,000 nM), we found that cPKC alpha was translocated by 3-1,000 nM and nPKC delta was translocated by 10-1,000 nM TPA. Both isoforms were maximally translocated by 100-1,000 nM TPA, whereas 1 nM did not translocate these two isoforms. When the cells were treated with 1,000 nM TPA for 5 min to 17 h, the translocation of these two isoforms occurred rapidly after 5-min treatment and could be sustained for 1 h, whereas down-regulation occurred after 3-h treatment and almost complete down-regulation was observed after 17-h treatment. However, the extent of down-regulation of nPKC delta was greater than that of cPKC alpha at 3-, 6-, and 10-h treatment. Further studies by using different doses of TPA (100, 10, 3, and 1 nM) and extending the time to 24 h showed that cPKC alpha was more resistant to down-regulation. This conventional isoform was maintained at a translocation state even after long-term treatment with 3-100 nM TPA, and complete down-regulation was only shown after 1,000 nM treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence comparison and computer modelling of cardiotoxins and cobrotoxin isolated from Taiwan cobra

Six cardiotoxins and one neurotoxin isolated and purified from the Taiwan cobra venom (Naja naja atra) possess distinct pharmacological and biochemical properties despite the existence of a grossly similar tertiary structure among these toxins, i. e., a core consisting of a series of short loops and four disulfide bridges. A systematic structure comparison of these major toxin isoforms was made by the secondary-structure predictions together with computer model-building based on the primary sequences and the established X-ray and NMR structures of one published cardiotoxin isoform and cobrotoxin. It is of interest to find that some defined and subtle differences can be detected upon the superposition of these three-dimensional polypeptide chains, which may reflect the intrinsic differences in the surface hydrophobicity of cardiotoxins and cobrotoxin as revealed by hydropathy profiles of these toxins in one of three major loops. The differences seem to correlate with different inhibitory activities exhibited by cardiotoxins in contrast to the lack of activity by cobrotoxin on protein kinase C (PKC).

Morphological evidence for the antiatherogenic effect of scoparone in hyperlipidaemic diabetic rabbits

OBJECTIVE

Scoparone (6,7-dimethoxycoumarin), a coumarin isolated from a hypolipidaemic Chinese herb Artemisia scoparia, has vasodilator and antiproliferative activities and possesses free radical scavenging properties in vitro. The aim of the study was to investigate the morphological effects of scoparone in the antiatherogenic process in vivo by using hyperlipidaemic diabetic rabbits as an animal model.

METHODS

Male New Zealand White rabbits were divided into three groups: control (normal), hyperlipidaemic diabetic, and scoparone treated hyperlipidaemic diabetic. The plasma concentration of total cholesterol and triglycerides were determined. The thickness of the tunica intima was measured on paraffin sections of the aortas stained with Movat's pentachrome. The aortic samples were also processed for scanning and transmission electron microscopy.

RESULTS

Neither the lipid profile in the plasma nor the structures of the aortic wall from the control group showed abnormalities. In contrast, the aortas from the hyperlipidaemic diabetic group showed prominent atherosclerotic plaques. Large numbers of monocytes were found adherent to the luminal surface and a markedly thickened intima filled with many lipid laden foam cells was clearly observed. By comparison, the scoparone treated group showed less advanced atherosclerosis with a lower plasma cholesterol. In the scoparone treated rabbits, the proportion of the aortic surface area covered with macroscopic plaques was 30%, and the thickness of the tunica intima 17%, of that of the non-scoparone treated hyperlipidaemic diabetic rabbits.

CONCLUSIONS

Scoparone has an antiatherogenic action in hyperlipidaemic diabetic rabbits.

A preliminary report on Borrelia burgdorferi infection in the Taiwan area

A total of 273 serum specimens from different areas and sources were tested against Borrelia burgdorferi antigens by enzyme-linked immunosorbent assay method. Positive rates of serological reactions were 3% and 58% for healthy persons and syphilis patients, respectively. Obviously, there was a lot of cross-reaction in the venereal disease group. Meanwhile, positive rates were 3% and 13% in the sera collected from Taiwan and Orchid Island, respectively. This difference may reflect a less developed environment in the latter. Since reported cases of Lyme disease in Taiwan are rare, serologic tests are usually adapted for rapid diagnosis in common laboratories. As for disease confirmation, clinical observations, epidemiological data and exposure in an endemic area must also be considered.

One exon of the human LSF gene includes conserved regions involved in novel DNA-binding and dimerization motifs

The transcription factor LSF, identified as a HeLa protein that binds the simian virus 40 late promoter, recognizes direct repeats with a center-to-center spacing of 10 bp. The characterization of two human cDNAs, representing alternatively spliced mRNAs, provides insight into the unusual DNA-binding and oligomerization properties of LSF. The sequence of the full-length LSF is identical to that of the transcription factors alpha CP2 and LBP-1c and has similarity to the Drosophila transcription factor Elf-1/NTF-1. Using an epitope-counting method, we show that LSF binds DNA as a homodimer. LSF-ID, which is identical to LBP-1d, contains an in-frame internal deletion of 51 amino acids resulting from alternative mRNA splicing. Unlike LSF, LSF-ID did not bind LSF DNA-binding sites. Furthermore, LSF-ID did not affect the binding of LSF to DNA, suggesting that the two proteins do not interact. Of three short regions with a high degree of homology between LSF and Elf-1/NTF-1, LSF-ID lacks two, which are predicted to form beta-strands. Double amino acid substitutions in each of these regions eliminated specific DNA-binding activity, similarly to the LSF-ID deletion. The dimerization potential of these mutants was measured both by the ability to inhibit the binding of LSF to DNA and by direct protein-protein interaction studies. Mutations in one homology region, but not the other, functionally eliminated dimerization.

Effects of baicalein and esculetin on transduction signals and growth factors expression in T-lymphoid leukemia cells

The possible mechanisms of antiproliferative effect of baicalein were studied in human T-lymphoid leukemia cells (CEM cells) and compared with those of esculetin. Baicalein, esculetin and related compounds, baicalein, wogonin, esculin and scoparone, inhibited CEM cell proliferation. Baicalein exhibited the greatest antiproliferative activity with an IC50 of 4.7 +/- 0.5 microM and the maximal suppression of 91.5 +/- 1.4% in CEM cells. The protein tyrosine kinase activity in the CEM cells was significantly reduced by baicalein (10(-6)-10(-4) M) and esculetin (10(-4) M). Baicalein exhibited a greater inhibitory activity on the protein tyrosine kinase than did esculetin (74.1 +/- 3.3% vs. 64.6 +/- 2.8% inhibition at 10(-4) M). On the other hand, the protein kinase C activity stimulated by phorbol-12-myristate 13-acetate was reduced by directly incubating with baicalein (10(-6)-10(-4) M) and esculetin (10(-4) M). However, the inhibitory activities on protein kinase C did not show a dose-dependency. The reverse transcription-polymerase chain reaction analysis of platelet-derived growth factor-A (PDGF-A) and transforming growth factor-beta 1 (TGF-beta 1) messenger RNA levels demonstrates that baicalein and esculetin reduced the PDGF-A mRNA level, but less affected the TGF-beta 1 mRNA. Baicalein exhibited the greater reduction on the expression of PDGF-A mRNA than did esculetin. It is suggested that baicalein and esculetin may affect cell proliferation by direct inhibition of growth-related signal, protein tyrosine kinase, as well as reduction of mRNA expression of growth factor, platelet-derived growth factor.

Intussusception of mucocele of the appendix: a case report

A 63-year-old man had had repeated episodes of ileo-caecal intussusception, and a pre-operative barium enema revealed appendiceal mucocele as a leading cause. Resection of appendix and part of the caecum were undertaken through exploration. The post-operative course was smooth. This unusual etiology is reported and discussed.

Antiproliferative effect of baicalein, a flavonoid from a Chinese herb, on vascular smooth muscle cell

The effects of baicalein, baicalin and wogonin, the flavonoids from Scutellaria baicalensis, on the proliferative responses of cultured rabbit vascular smooth muscle cells were studied. The proliferative response was determined from the uptake of tritiated thymidine. In rabbit vascular smooth muscle cells, all three flavonoids dose dependently inhibited the proliferative response induced by 5% fetal calf serum at the dose range of 10(-6) to 10(-4) M. Baicalin and wogonin were less effective than baicalein as inhibitors of the serum-induced smooth muscle cell proliferation, indicating that the three hydroxyl groups on positions 5, 6 and 7 seem to be necessary and sufficient for full inhibitory activity against the proliferative response of smooth muscle cells. Baicalein had a greater inhibitory effect on the proliferative reponse stimulated by platelet-derived growth factor than on serum-stimulated proliferation. Baicalein, a flavonoid with antiproliferative and lipoxygenase-inhibitory activities, may be useful as another template for the development of better drugs to prevent the pathological changes of atherosclerosis and restenosis.

Protection by scoparone against the alterations of plasma lipoproteins, vascular morphology and vascular reactivity in hyperlipidaemic diabetic rabbit

1. The in vivo pharmacological effects of scoparone (6,7-dimethoxycoumarin) in a hyperlipidaemic diabetic rabbit model were investigated. 2. Three groups of rabbits were studied: (1) normal, (2) hyperlipidaemic and diabetic-untreated and (3) hyperlipidaemic and diabetic-scoparone treated. The hyperlipidaemic diabetic rabbits were fed with 1% cholesterol and treated with alloxan, a diabetogenic agent. The plasma levels of total cholesterol, total triglyceride, very low-density lipoprotein (VLDL) cholesterol, low density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol were markedly increased as soon as the rabbit became diabetic at the second week. Scoparone-treatment (5 mg kg-1 day-1, s.c.) significantly reduced the plasma lipid and lipoprotein cholesterol levels of the hyperlipidaemic diabetic rabbit to 73.3% of total cholesterol, 48.3% of total triglyceride, 66.0% of VLDL cholesterol, 55.7% of LDL cholesterol and 79.5% of HDL cholesterol. 3. Six weeks after cholesterol-feeding, the aortic arch and thoracic aorta were dissected for morphological and functional studies. In vascular rings from the untreated hyperlipidaemic diabetic rabbit, there was intimal thickening with accumulation of fatty streaks, foam cells and migration of smooth muscle cells to the intima. In the rabbits treated with scoparone, there were fewer pathological morphology changes found in vascular segments than in the untreated hyperlipidaemic diabetic rabbits. 4. In the vascular reactivity experiments, the phenylephrine-induced contraction and nitroprusside induced dilatation did not differ significantly among the three rabbit groups, except that the contraction was enhanced in the thoracic aorta of hyperlipidaemic diabetic rabbits either untreated or treated withscoparone, as compared to the normal group, and the sensitivity to nitroprusside was increased in the thoracic aorta of the scoparone-treated group as compared to the untreated group.5. The endothelium-dependent dilatation induced by acetylcholine was significantly attenuated in both the aortic arch and thoracic aorta from the hyperlipidaemic diabetic rabbits as compared to the normal rabbits. This attenuation was partially prevented, when scoparone (5 mg kg-1) was administered daily.6. These results suggest that scoparone protects against some alterations of plasma lipoproteins,vascular morphology and vascular reactivity in the hyperlipidaemic diabetic rabbit. These protective effects of scoparone may be partly related to its free radical scavenging property.

Investigating the s-2 subsite selectivity of alkaline proteases in hydrolysis of diastereo-peptide esters and molecular-modeling interpretation

Diastereomeric peptide-esters (Ala-Ala-AA2-Phe-OMe, AA2 = Gly, D- or L-Ala, Pro, Phe, Lys, and Glu) have been used as substrates, and the kinetic constants (Kcat and Km) of the three alkaline proteases, subtilisin Carlsberg, alcalase, and Nagarse (subtilisin BPN') catalyzed ester-hydrolysis, were measured to investigate the selectivity of the enzyme-catalyzed peptide esterhydrolysis. All three proteases preferred the substrate which had a small side-chain at the s-2 site. Thus, the substrates with a bulky side-chain at the p-2 site such as Phe, Pro, Glu, and Lys, hydrolyzed with a rate of about one-tenth that of Ala at the p-2 site, and the Kcat decreased as the size of the p-2 amino acid residue increased. The diastereoselectivity of the alkaline protease-catalyzed hydrolysis of each diastereomeric pair depended on the size of the amino acid residue at the p-2 position of the substrate. The substrates with a bulky side-chain at the p-2 site hydrolyzed with higher diastereoselectivity than did the substrates with a small side-chain at the p-2 site. Molecular modeling of the enzyme-substrate complex show that: for the enzyme complexed with a substrate which has L-L-L-L configuration, each residue of the L-L-L-L tetrapeptide filled in and was completely enclosed by the cleft of the four subsites of the enzyme. The side-chains of the residues were identically positioned within the pocket of the binding-site. For the complex of enzyme with substrate of L-L-D-L, the side-chain of the D-amino acid residue was far away from the s-2 subsite of the enzyme, and had close contact with the side-chains of Leu-126 and Ile-107 of the enzyme.

Integration of simian virus 40 into cellular DNA occurs at or near topoisomerase II cleavage hot spots induced by VM-26 (teniposide)

Inhibition of DNA topoisomerase II in simian virus 40 (SV40)-infected BSC-1 cells with a topoisomerase II poison, VM-26 (teniposide), resulted in rapid conversion of a population of the SV40 DNA into a high-molecular-weight form. Characterization of this high-molecular-weight form of SV40 DNA suggests that it is linear, double stranded, and a recombinant with SV40 DNA sequences covalently joined to cellular DNA. The majority of the integrants contain fewer than two tandem copies of SV40 DNA. Neither DNA-damaging agents, such as mitomycin and UV, nor the topoisomerase I inhibitor camptothecin induced detectable integration in this system. In addition, the recombination junctions within the SV40 portion of the integrants correlate with VM-26-induced, topoisomerase II cleavage hot spots on SV40 DNA. These results suggest a direct and specific role for topoisomerase II and possibly the enzyme-inhibitor-DNA ternary cleavable complex in integration. The propensity of poisoned topoisomerase II to induce viral integration also suggests a role for topoisomerase II in a pathway of chromosomal DNA rearrangements.

Synthesis and structure-activity relationships of nonpeptide, potent triazolone-based angiotensin II receptor antagonists

2,5-Dibutyl-2,4-dihydro-4-[[2-(1H-tetrazol-5-yl)[1,1'-biphenyl]-4' - yl]methyl]-3H-1,2,4-triazol-3-one, SC-51316, was synthesized as a potent and orally active angiotensin II (AII) receptor antagonist with a long duration of action. To explore the lipophilic pocket in the AII receptor interacting with the substituent at the 2-position of triazolone-based antagonists, a series of compounds were prepared and evaluated for receptor binding affinity and antagonism of AII-contracted rabbit aortic rings. It has been found that the pocket is very spacious and can accommodate different sizes of lipophilic groups and various functionalities. Acidic groups generally result in a slight decrease in binding affinity. Branched chains are unfavorable. The freedom of rotation around C2-C3 in the flexible side chain is crucial for good binding. The 2-phenylethyl-substituted triazolone analogue exhibits the highest in vitro potency among all compounds that have been synthesized.

Pseudomonas syringae pv. syringae harpinPss: a protein that is secreted via the Hrp pathway and elicits the hypersensitive response in plants

The ability of P. syringae to elicit the hypersensitive response in nonhost plants or pathogenesis in hosts is controlled by hrp genes. The P. syringae pv. syringae 61 hrpZ gene encodes harpinPss, a 34.7 kd extracellular protein that elicits hypersensitive necrosis in tobacco and other plants. HarpinPss is heat stable, glycine rich, dissimilar in amino acid sequence to any known protein, produced only in apoplastic fluid-mimicking minimal media, and secreted in a HrpH-dependent manner. The carboxy-terminal 148 amino acid portion of harpinPss contains two directly repeated sequences of GGGLGTP and QTGT and is sufficient and necessary for elicitor activity. The necrosis elicited by harpinPss is an active response of the plant, which can be inhibited by alpha-amanitin, cycloheximide, lanthanum chloride, or sodium vanadate.

Characterization of the Pseudomonas syringae pv. syringae 61 hrpJ and hrpI genes: homology of HrpI to a superfamily of proteins associated with protein translocation

The Pseudomonas syringae pv. syringae 61 hrpJ and hrpI genes were sequenced and found to encode predicted proteins of 37,710 Da and 76,490 Da, respectively. The products of these genes were confirmed by T7 polymerase-dependent expression and sodium dodecyl sulfate-polyacrylamide gel analysis. HrpI belongs to a superfamily of proteins represented by Yersinia pestis LcrD.

In vivo pharmacology of SC-51316, a nonpeptidic angiotensin II receptor antagonist

The depressor activity of a novel nonpeptidic angiotensin II (AII) receptor antagonist, SC-51316 (2,5-dibutyl-2,4-dihydro-4-[[2-(1H-tetrazol-5-yl)[1,1'-biphenyl]-4 '- yl]-methyl]-3H-1,2,4-triazol-3-one), is described. In anesthetized, ganglion-blocked rats, intravenous administration of SC-51316 inhibited the pressor response to an infusion of AII. To determine antihypertensive efficacy, conscious, spontaneously hypertensive rats were administered SC-51316 (30 mg/kg intragastrically) daily for 5 days. Blood pressure was reduced in a similar manner to that observed with the angiotensin converting enzyme inhibitor enalapril (10 mg/kg intragastrically). SC-51316 had no effect on heart rate. In conscious, sodium-deficient dogs, administration of SC-51316 (30 mg/kg orally) or enalapril (10 mg/kg orally) lowered blood pressure similarly over a 24 h observation period. Thus, SC-51316 antagonizes the activity of AII in vivo and is an orally active, antihypertensive agent.

Antiproliferative effect of esculetin on vascular smooth muscle cells: possible roles of signal transduction pathways

The effect of esculetin, a coumarin derivative with lipoxygenase inhibitor activity, on the proliferation response of cultured rabbit vascular smooth muscle cells was studied. Proliferation response was determined by the uptake of tritiated thymidine. Esculetin (10(-5)-10(-4) M) dose dependently inhibited the enhanced proliferation stimulated by 5% fetal calf serum. The structure-activity relationship of esculetin and eight other coumarin derivatives indicates that two adjacent phenolic hydroxyl groups at the C-6 and C-7 positions in the coumarin skeleton are necessary for the potent antiproliferative effect. The antiproliferative effects of other lipoxygenase inhibitors, 5,8,11,14-eicosatetraynoic acid (ETYA) and ketoconazole, were comparable to the effect of esculetin. However, esculetin exhibited the greatest maximal suppression. The enhanced releases of 12-hydroxyeicosatetraenoic acid (12-HETE), prostaglandin E2 and 6-keto-prostaglandin F1 alpha in the culture medium of smooth muscle cells stimulated by 5% fetal calf serum were significantly reduced by esculetin. Furthermore, the fetal calf serum-stimulated protein tyrosine kinase activity was reduced by esculetin (10(-5)-10(-4) M) in a dose-dependent manner. In contrast, the protein kinase C activity stimulated by phorbol-12-myristate-13-acetate was not affected by esculetin (10(-6)-10(-4) M). These results suggest that the antiproliferative effect of esculetin on vascular smooth muscle cells may be partly mediated through inhibition of protein tyrosine kinase and modulated by inhibition of lipoxygenase.

Analysing a mental health survey by chi-squared automatic interaction detection

Based on a mental health survey conducted in 1987 by the Singapore Association for Mental Health, an exploratory statistical technique CHAID (Chi-Squared Automatic Interaction Detection), which is an offshoot of AID (Automatic Interaction Detection) designed for a categorical dependent variable, was employed to establish the characteristics of people who were vulnerable to mental problems in Singapore. Of the sixteen predictors considered, five were found to play significant roles in identifying the various vulnerable groups. They were the respondent's perception of his or her own health, the number of problems encountered during the four weeks before the survey, whether experiencing a depression or not during the four weeks prior to the survey, the respondent's perception of family support and the number of life events in the past six months before the survey, summarised into a weighted score. The dendrogram obtained from CHAID was very useful in displaying the structure of the relationship of the predictors with mental health. Examining the dendrogram, one can easily classify the various vulnerable groups by tracing each of the terminal groups to the root of the tree.

The Pseudomonas syringae pv. syringae 61 hrpH product, an envelope protein required for elicitation of the hypersensitive response in plants

Pseudomonas syringae pv. syringae 61 contains a 25-kb cluster of hrp genes that are required for elicitation of the hypersensitive response (HR) in tobacco. TnphoA mutagenesis of cosmid pHIR11, which contains the hrp cluster, revealed two genes encoding exported or inner-membrane-spanning proteins (H.-C. Huang, S. W. Hutcheson, and A. Collmer, Mol. Plant-Microbe Interact. 4:469-476, 1991). The gene in complementation group X, designated hrpH, was subcloned on a 3.1-kb SalI fragment into pCPP30, a broad-host-range, mobilizable vector. The subclone restored the ability of hrpH mutant P. syringae pv. syringae 61-2089 to elicit the HR in tobacco. DNA sequence analysis of the 3.1-kb SalI fragment revealed a single open reading frame encoding an 81,956-Da preprotein with a typical amino-terminal signal peptide and no likely inner-membrane-spanning hydrophobic regions. hrpH was expressed in the presence of [35S]methionine by using the T7 RNA polymerase-promoter system and vector pT7-3 in Escherichia coli and was shown to encode a protein with an apparent molecular weight of 83,000 on sodium dodecyl sulfate-polyacrylamide gels. The HrpH protein in E. coli was located in the membrane fraction and was absent from the periplasm and cytoplasm. The HrpH protein possessed similarity with several outer membrane proteins that are known to be involved in protein or phage secretion, including the Klebsiella oxytoca PulD protein, the Yersinia enterocolitica YscC protein, and the pIV protein of filamentous coliphages. All of these proteins possess a possible secretion motif, GG(X)12VP(L/F)LXXIPXIGXL(F/L), near the carboxyl terminus, and they lack a carboxyl-terminal phenylalanine, in contrast to other outer membrane proteins with no known secretion function. These results suggest that the P. syringae pv. syringae HrpH protein is involved in the secretion of a proteinaceous HR elicitor.

Inhibitory effect of curcumin, an anti-inflammatory agent, on vascular smooth muscle cell proliferation

The effects of curcumin, an anti-inflammatory agent from Curcuma longa, on the proliferation of blood mononuclear cells and vascular smooth muscle cells were studied. Proliferative responses were determined from the uptake of tritiated thymidine. In human peripheral blood mononuclear cells, curcumin dose dependently inhibited the responses to phytohemagglutinin and mixed lymphocyte reaction at the dose ranges of 10(-6) to 3 x 10(-5) and 3 x 10(-6) to 3 x 10(-5) M, respectively. Curcumin (10(-6) to 10(-4) M) dose dependently inhibited the proliferation of rabbit vascular smooth muscle cells stimulated by fetal calf serum. Curcumin had a greater inhibitory effect on platelet-derived growth factor-stimulated proliferation than on serum-stimulated proliferation. Cinnamic acid, coumaric acid and ferulic acid were much less effective than curcumin as inhibitors of serum-induced smooth muscle cell proliferation, suggesting that the cinnamic acid and ferulic acid moieties alone are not sufficient for activity, and that the characteristics of the diferuloylmethane molecule itself are necessary for activity. Curcumin may be useful as a new template for the development of better remedies for the prevention of the pathological changes of atherosclerosis and restenosis.

Vasodilator effect of scoparone (6,7-dimethoxycoumarin) from a Chinese herb

A possible mechanism of the vasodilator effect of scoparone was investigated. Scoparone (10(-6)-3 x 10(-5) M) dilated rat aortic rings precontracted with phenylephrine in a dose-dependent manner. The presence of endothelium facilitated the vasodilator effect. Scoparone depressed the contractile responses to phenylephrine and serotonin, but not that to potassium chloride. Both the vasoconstriction and O2- production induced by alloxan, a diabetogenic compound, were depressed by scoparone. It appears that scoparone exhibited a free radical scavenger-like effect. The dilatation elicited by acetylcholine was potentiated by scoparone. The dilator activity of scoparone was markedly inhibited by methylene blue and hemoglobin, guanylate cyclase inhibitors. Furthermore, the basal guanosine 3',5'-cyclic monophosphate (cGMP) level was elevated in the presence of scoparone. The dilator activity of scoparone was also inhibited by quinacrine (inhibitor of phospholipase A2) and indomethacin (inhibitor of cyclooxygenase). Our results showed further that the output of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, was enhanced by scoparone. It is suggested that the vasodilator effect of scoparone in rat aorta may be mediated through the enhancement of prostacyclin release, protecting against EDRF inactivation, and activating guanylate cyclase.

Possible mechanism of immunosuppressive effect of scoparone (6,7-dimethoxycoumarin)

The possible mechanism of the immunosuppressive effect of scoparone (6,7-dimethoxycoumarin) was investigated. Human peripheral blood mononuclear cells (10(6) cells/ml) were stimulated with 0.25% phytohemagglutinin (PHA) and the proliferative response was determined from the uptake of tritiated thymidine. Scoparone (10(-6) to 3 x 10(-4) M) reduced the proliferative response in a dose-dependent manner. The proliferative response of mononuclear cells to mixed lymphocyte reaction was also reduced by scoparone (10(-5) to 10(-4) M). Interleukin-1, interleukin-2 production and interleukin-2 receptor expression were all reduced in the presence of scoparone. Scoparone (10 and 30 microM) significantly reduced the suppression elicited by the diabetogenic drug, alloxan (10 mM). The suppressive activity of scoparone was significantly reduced by quinacrine (a phospholipase A2 inhibitor), indomethacin (a cyclooxygenase inhibitor) and nordihydroguaiaretic acid (a lipoxygenase inhibitor). The levels of prostaglandin E2, prostaglandin F2 alpha, leukotriene B4 and 2,3-dinor-thromboxane B2 in culture medium of PHA-stimulated mononuclear cells, measured with an enzyme immunoassay, were elevated by scoparone treatment. We compared the effect of scoparone on the mononuclear cell response to genistein, a specific inhibitor of protein tyrosine kinase and demonstrated the non-additivity and cross-desensitization of the two compounds. Our results suggest that the immunosuppressive effect of scoparone may be exerted in part through inhibition of protein tyrosine kinase and release of arachidonic acid metabolites.

In vitro pharmacology of a nonpeptidic angiotensin II receptor antagonist, SC-51316

The properties of a novel nonpeptidic angiotensin II (AII) receptor antagonist, 2,5-dibutyl-2,4-dihydro-4-([2-(1H-tetrazol-5-yl)(1,1'-biphenyl) -4'-yl]methyl)-3H-1,2,4-triazol-3-one (SC-51316), are described. SC-51316 inhibited [125I]AII binding selectively to the AT1 receptor with IC50 values of 3.6 and 5.1 nM in rat adrenal cortical and rat uterine membrane preparations, respectively. The compound was a competitive and reversible antagonist of AII-mediated contraction of rabbit aortic rings with a pA2 of 8.86. In addition, SC-51316 inhibited AII-induced aldosterone release from rat adrenal zona glomerulosa cells and blocked inhibition of renin release by AII from rat kidney slices with pA2 values of 8.62 and 8.9, respectively. The agent (0.1 mM) did not inhibit angiotensin-converting enzyme or plasma renin activity. These data demonstrate that SC-51316 is a potent AII receptor antagonist which may prove to be useful as a pharmacologic tool for studying the role of the renin-angiotensin system in cardiovascular diseases.

Immunosuppressive effect of emodin, a free radical generator

The possible mechanism of immunosuppressive effect of emodin (1,3,8-trihydroxy-6-methylanthraquinone) was investigated in this study. Human mononuclear cells (10(6) cells/ml) were stimulated with 0.25% phytohemagglutinin for 24, 48 and 72 h, and the proliferative response was determined by the uptake of tritiated thymidine. In the presence of emodin (10(-6) to 3 x 10(-5) M), the proliferative response was reduced in a dose-dependent manner. Emodin (3 x 10(-7) to 3 x 10(-5) M) also dose dependently reduced the proliferative response to mixed lymphocyte reaction. After 72 h exposure to emodin (10 microM), interleukin-1 (IL-1), interleukin-2 (IL-2) production and IL-2 receptor expression were all reduced. The structure-activity relationship of emodin and 10 other anthraquione derivatives indicates that the free hydroxyl group at the beta-position of the anthraquinone nucleus plays an important role in the immunosuppressive effect. The suppressive activity of emodin was significantly inhibited by catalase (a scavenger of hydrogen peroxide), but little affected by superoxide dismutase (a scavenger of superoxide radical) and mannitol (a scavenger of hydroxyl radical). Methylene blue and hemoglobin, guanylate cyclase inhibitors, did not significantly affect the suppressive activity of emodin. Nordihydroguaiaretic acid (a lipoxygenase inhibitor) significantly potentiated the suppressive activity whereas quinacrine (a phospholipase A2 inhibitor) and indomethacin (a cyclooxygenase inhibitor) did not significantly affect it. The results suggest that the immunosuppressive effect of emodin may be partly mediated through hydrogen peroxide generated from semiquinone and regulated by arachidonic acid metabolites or byproducts.

Vasorelaxant effect of emodin, an anthraquinone from a Chinese herb

The possible mechanism underlying the vasorelaxant effect of emodin isolated from a Chinese herb, was investigated in this study. Emodin dose dependently relaxed isolated vascular rings of human internal mammary artery and saphenous vein, rabbit thoracic aorta, abdominal aorta and mesenteric artery, and rat thoracic aorta. There were no differences in the sensitivity (IC50) and maximal relaxation between intact and endothelium-denuded preparations of rat aorta. In the presence of emodin (10 microM), the contractile responses of rat aorta to phenylephrine, serotonin and potassium chloride were depressed. The relaxation response to acetylcholine was attenuated by emodin, whereas that to isoproterenol was unaffected. The relaxation response to emodin was inhibited by free radical scavengers, superoxide dismutase, catalase and mannitol, and guanylate cyclase inhibitors, methylene blue and hemoglobin. Catalase was the most effective scavenger. Quinacrine (phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor) and nordihydroguaiaretic acid (NDGA, lipoxygenase inhibitor) potentiated the relaxation induced by emodin. NDGA was the most effective potentiator. Exposure of aortic rings to emodin (10 microM) increased the basal level of guanosine 3',5'-cyclic monophosphate (cGMP). It is suggested that the vasorelaxant effect of emodin may be mainly due to cGMP accumulation as a result of guanylate cyclase activation by free radicals and/or hydrogen peroxide generated from semiquinone.

Perfluorochemical emulsion effect on human albumin binding of valproic acid

At 37 degrees C, valproic acid was weakly bound by a PFCE through an interaction with the emulsifiers that was independent of both buffer and PFCE concentration. The binding by PFCE was dependent on valproic acid concentration in 0.1 M buffer, but not in 0.2 M buffer. The addition of PFCE to 4% HSA increased the percent free valproic acid due to both HSA dilution and displacement of HSA bound drug. This displacement was apparently due to an interaction with the PFC liquids and/or intact PFCE droplets, and with the oleic acid component of the PFCE.

Insulinoma: a case report

Insulinoma is a rare disease, which frequently causes hypoglycemic symptoms and signs or even shock. However, other diseases that produce similar symptoms and signs should firstly be ruled out. We describe a 63 years old male veteran who suffered from repeated episodes of seizure and conscious disturbance upon fasting, on and off for 8 years. Serial examinations led to the suspicion that this might be a case of insulinoma; the suspicion was later confirmed by pathologic examination after the tumor had been excised, and his problems disappeared. After six years, a follow-up examination showed that his condition was still stable.

Vasorelaxants from Chinese herbs, emodin and scoparone, possess immunosuppressive properties

Emodin and scoparone, the active principles isolated from Polygonum multiflorum and Artemisia scoparia, respectively, both exhibit vasorelaxant and immunosuppressive effects. Emodin (10(-6)-3 x 10(-5) M) and scoparone (10(-6)-3 x 10(-5) M) dose dependently relaxed rat thoracic aortic rings precontracted with phenylephrine. Emodin (3 x 10(-7)-10(-4) M) and scoparone (10(-6)-3 x 10(-4) M) also dose dependently suppressed the responses of human mononuclear cells to phytohemagglutinin and mixed lymphocyte reaction. These compounds may be useful as new templates for the development of better immunosuppressive agents with vasorelaxant actions for use against transplantation rejection and autoimmune disease.