Chemical modifications of momordin-a and luffin-a, ribosome-inactivating proteins from the seeds of Momordica charantia and Luffa cylindrica: involvement of His140, Tyr165, and Lys231 in the protein-synthesis inhibitory activity

Effects of chemical modifications on the protein-synthesis inhibitory (PSI) activities of momordin-a and luffin-a were investigated. Treatment with a 50-fold excess of diethylpyrocarbonate at pH 6.5 modified one histidine residue in momordin-a and luffin-a and reduced their PSI activities to 10% and 8.3%, respectively. Modifications with a 20-fold excess of KI3 at pH 7.0 at 0 degree C greatly reduced their PSI activities to 10% by iodination of nearly one tyrosine residue. The PSI activity of momordin-a was rapidly reduced to 6.4% by the modification of one lysine residue with trinitrobenzensulfonic acid as in the case of luffin-a reported previously. By analyses of the tryptic peptides from the modified momordin-a and luffin-a, the modified residues were identified as His140, Tyr165, and Lys231. Furthermore, the amounts of three modified momordin-a binding to rat liver ribosomes were reduced to about half or less than half of that of native momordin-a. From these results, it was suggested that His140, Tyr165, and Lys231 are highly exposed on the surface of momordin-a and luffin-a molecules and are involved in their PSI activities, probably by binding to ribosomes.

Pharmacological importance of stereochemical resolution of enantiomeric drugs

Drug enantiomers have identical properties in an achiral environment, but should be considered as different chemical compounds. This is because they often differ considerably in potency, pharmacological activity and pharmacokinetic profile, since the modules with which they interact in biological systems are also optically active. Within biological systems, the metabolism of one isomer may be via a different pathway or occur at a different rate from that of the other isomer. Preferential binding of one isomer to plasma proteins may cause differences in circulating free drug and hence alter concentrations at active sites. Interactions of both isomers may differ at the active sites through which pharmacological action is mediated. Actions and levels of activity of the stereoisomers in vivo may also differ. All the pharmacological activity may reside in a single enantiomer, whereas several possibilities exist for the other enantiomer-- it may be inactive, have a qualitatively different effect, an antagonistic effect or produce greater toxicity. Two isomers may have nearly identical qualitative pharmacological activity, qualitatively similar pharmacological activity but quantitatively different potency, or qualitatively different pharmacological activity. To avoid adverse effects and optimise the therapeutic value of enantiomeric drugs, it is necessary that methods for the resolution of racemates be evolved and devolved to determine isomeric purity, establish the effectiveness of isomers of the drug, and detect the presence of an enantiomer with lower therapeutic activity and undesirable adverse effects. Even if a drug is given as a pure enantiomer, methods to discriminate between enantiomers are required because racemisation can occur both in vitro and in vivo. Methods developed for resolution of drug enantiomers should facilitate routine testing of single isomers and their metabolites, studies of pharmacological, toxicological and clinical effectiveness, routine analysis of racemates, pure enantiomers or intermediates in manufacturing processes, and investigation of the potential for inversion of an enantiopure drug substance during the early stages of drug development and therapeutic drug monitoring.

Osteotropic factor-stimulated synthesis of thrombospondin in rat dental pulp cells

The amount of thrombospondin (TSP) mRNA in confluent clonal rat dental pulp cells was increased by transforming growth factor-beta (TGF-beta), 1 alpha-25-dihydroxyvitamin D3 (1,25(OH)2D3), and phorbol 12,13-didecanoate (PDD), with maximal levels 6, 36 and 2 h, respectively, after stimulation. These increases were accompanied by enhanced syntheses of TSP proteins which were found in the different forms in cell layer/matrix fraction (198 and 165 kDa TSP) and the culture medium (180 kDa TSP). These three factors also raised the mRNA level of osteopontin, which is thought to play an important role in mineralization in dentin and bone. The order of effectiveness of these factors was PDD > TGF-beta > 1,25(OH)2D3 for all the stimulations described above. These results suggest that the osteotropic factors enhance TSP synthesis at the pretranslational level and that TSP produced by dental pulp cells participates in formation of reparative dentin.

Enhanced translation of rat beta-glucuronidase cDNA is conferred by 155-bp segment of internal coding sequence

When cDNAs for human and rodent beta-glucuronidases were expressed in COS-7 cells using several different promoters, rodent beta-glucuronidases were produced three times more than human beta-glucuronidase, although their transcriptional levels were similar. Similar observations were also recorded in LMTK- cells using SV40 early or chicken beta-actin promoters. In hopes of enhancing yields of recombinant human beta-glucuronidase for enzyme replacement therapy, we sought to determine the region within the linear sequences responsible for the higher levels of expression of the rodent cDNAs. To do so, we made various rat-human chimeric cDNAs utilizing conserved restriction enzyme sites. The levels of products expressed from these chimeric cDNAs in COS cells were assessed by activity assay and by metabolic labeling of the proteins followed by immunoprecipitation and SDS-PAGE. From the results of these expression studies, we identified a 155-bp ClaI (643)-AflII (797) fragment in the rat open reading frame responsible for the increased rate of translation of the rat beta-glucuronidase (RBG) cDNA. Replacement of the homologous ClaI (683)-AflII (838) fragment in human beta-glucuronidase (HBG) with this 155-bp fragment from RBG increased the translation level of the resulting chimeric HRaH. Conversely, substitution of the 155-bp human fragment for that of rat in RBG cDNA reduced the total synthesis of the resulting chimeric HHaR. Placement of the 155-bp segment between the initiation ATG and the promoter has only negative effects on the expression of either cDNA. A more stable secondary structure of the human cDNA in this region might explain a reduced rate of translation. However, secondary structure analysis of mRNAs from the 155-bp fragment of rat and human cDNAs predicted that, while both can form stem-loops, the rat fragment (delta Gzero = -42.1 kcal/ mol) is actually more stable than the human fragment (delta Gzero = -32.1 kcal/mol). In fact, the free energy of stability of the first 50 bp within this ClaI-AflII fragment from rat (-10.3 kcal/mol) indicates that the secondary structure is considerably more stable than the corresponding 50 bp from human (-2.1 kcal/mol). This segment of the rat sequence also contains a tar-like sequence in a stem-loop. Although tar-like sequences can enhance rates of translation, altering this sequence by mutagenesis had no effect on the rate of synthesis of rat beta-glucuronidase. Thus, although the region conferring enhanced rate of synthesis from rat cDNA has been identified, the mechanism by which it does so is not yet clear.

beta-Glucuronidase P408S, P415L mutations: evidence that both mutations combine to produce an MPS VII allele in certain Mexican patients

Mucopolysaccharidosis type VII (MPS VII, Sly syndrome) is an autosomal recessively inherited lysosomal storage disease caused by a deficiency in beta-glucuronidase. We identified and studied a novel allele containing two C-to-T transitions resulting in P408S and P415L alterations, which is present in homozygous state in one Mexican patient and in heterozygous state in another. None of the previous reports describing mutations in the MPS VII gene include Mexican patients. Expression of either of the mutations individually showed only modest effects on the properties of the enzyme. However, expression of the doubly mutant allele resulted in markedly reduced activity and rapid degradation in an early biosynthetic compartment.

Molecular analysis of patients with beta-glucuronidase deficiency presenting as hydrops fetalis or as early mucopolysaccharidosis VII

Although not all mucopolysaccharidosis type VII (MPS VII) neonates present with hydrops fetalis or with related symptoms, hydrops fetalis is a common form of presentation of this mucopolysaccharidosis. We used reverse-transcription-PCR-SSCP and direct sequencing to screen for mutations in the human beta-glucuronidase cDNA of 17 MPS VII patients with severe presentation of the disease. Mutations resulting in an unstable mRNA were detected in genomic DNA with direct sequencing of the PCR-amplified beta-glucuronidase exons. We found extensive genetic heterogeneity in MPS VII alleles: in addition to 6 or 12 previously reported mutations (L176F, R216W, R357X, R382C, W507X, and W627C), we detected 14 undescribed mutations in the beta-glucuronidase coding region that produce MPS VII alleles (G136R, E150K, S312X, Y320S, Y320C, H351Y, R382H, R374C, R435P, R477W, G572D, Y508C, K606N and 1900 delta GA). The mutations in hydropic fetuses were widely scattered in the beta-glucuronidase gene. Analysis of three polymorphic sites of the mutant alleles (1766T/C, 1972C/T and a new 1091+27C/G polymorphism) allowed exclusion of identity by descent for some recurrent mutations. Three of four mutations introducing a premature translation stop codon were found to affect mRNA abundance and/or structure. Expression studies provided evidence for the causal relationship between each of the mutations found in MPS VII alleles and the enzyme deficiency, in that all mutations identified exhibited markedly reduced enzyme activity expressed in COS7 cells following transfection with the mutant cDNA.

A pseudodeficiency allele (D152N) of the human beta-glucuronidase gene

We present evidence that a 480G-->A transition in the coding region of the beta-glucuronidase gene, which results in an aspartic-acid-to-asparagine substitution at amino acid position 152 (D152N), produces a pseudodeficiency allele (GUSBp) that leads to greatly reduced levels of beta-glucuronidase activity without apparent deleterious consequences. The 480G-->A mutation was found initially in the pseudodeficient mother of a child with mucopolysaccharidosis VII (MPSVII), but it was not on her disease-causing allele, which carried the L176F mutation. The 480G-->A change was also present in an unrelated individual with another MPSVII allele who had unusually low beta-glucuronidase activity, but whose clinical symptoms were probably unrelated to beta-glucuronidase deficiency. This individual also had an R357X mutation, probably on his second allele. We screened 100 unrelated normal individuals for the 480G-->A mutation with a PCR method and detected one carrier. Reduced beta-glucuronidase activity following transfection of COS cells with the D152N cDNA supported the causal relationship between the D152N allele and pseudodeficiency. The mutation reduced the fraction of expressed enzyme that was secreted. Pulse-chase experiments indicated that the reduced activity in COS cells was due to accelerated intracellular turnover of the D152N enzyme. They also suggested that a potential glycosylation site created by the mutation is utilized in approximately 50% of the enzyme expressed.

Effect of antimicrobial (nalidixic acid) therapy in shigellosis and predictive values of outcome variables in patients susceptible or resistant to it

We observed the clinical features and results of simple laboratory tests on stools of 33 children with bacteriologically proven shigellosis to identify features that could be used to assess the effectiveness of antimicrobial therapy. Persistence of fever (rectal temperature > 37.8 degrees C), abdominal pain/tenderness and anorexia on days 3 and 5 were significantly more common (P < 0.001) among children who received an antimicrobial to which the infecting Shigella was resistant. Similarly, a significantly higher number of children treated with an ineffective antimicrobial had faecal leucocytes of > 50/high power microscopic field (HPF), erythrocytes of > 50/HPF and macrophages of > 5/HPF on study day 5. The best predictors of ineffective antimicrobial therapy on days 3 and 5 of treatment were fever, presence of blood by naked eye examination of stool, and minimum change in stool frequencies. These observations suggest that by careful follow-up of clinical features and simple laboratory tests, such as stool microscopic examinations, it is possible to identify patients unlikely to respond to initial therapy by 72 hours permitting the start of alternative antimicrobial treatment. This may be of great help where stool culture and sensitivity facilities for Shigella spp. are not available.

Comparative trial of five antimicrobial compounds in the treatment of cholera in adults

To compare the efficacy of ciprofloxacin, erythromycin, nalidixic acid and pivmecillinam in the treatment of tetracycline-resistant strains of Vibrio cholerae O1 in adults, a randomized, open, clinical trial was conducted. A tetracycline group was used for comparison. Seventy-five adult men infected with V. cholerae O1 were randomly assigned to receive either 400 mg pivmecillinam or 500 mg of one of each of the other drugs. Ciprofloxacin was given every 12 h and the others every 6 h for 3 d. The mean total stool volume per kg was 155 mL for the ciprofloxacin group, 212 mL for the erythromycin and pivmecillinam groups, 246 mL for nalidixic acid, and 293 mL for tetracycline. The difference between ciprofloxacin and tetracycline was significant (P = 0.045). After 72 h, diarrhoea had stopped in 14 patients (93%) in the ciprofloxacin group and 12 (80%) in the erythromycin group, compared to 5 (42%) of those receiving tetracycline (P = 0.006 and 0.049, respectively). Bacteriological clearance was 100% at 24 h in patients treated with ciprofloxacin compared to 20% and 8.3% (P < 0.001 for both comparisons) in the erythromycin and tetracycline groups. Ciprofloxacin in conjunction with appropriate fluid therapy was the most effective treatment for cholera in adults; erythromycin was the next best.

Double-blind comparison of oral gentamicin and nalidixic acid in the treatment of acute shigellosis in children

To compare the efficacy of oral gentamicin with nalidixic acid in the treatment of acute shigellosis, we studied, in a double blind-trial, 79 comparable children with bloody diarrhoea of less than 72 h duration. Of them Shigella spp. were isolated in 71 patients. Patients were randomly assigned to receive either gentamicin 30 mg/kg/day or nalidixic acid 60 mg/kg/day, both given orally in four equal doses for 5 days. Stool frequency differed significantly between the groups from day two until completion of the study. Treatment failure was observed in 14 (42 per cent) patients receiving oral gentamicin compared to none of those with nalidixic acid-sensitive strains of Shigella spp. (P = 0.0002). Although all the shigella isolates were sensitive to gentamicin in vitro, 19 (58 per cent) patients on gentamicin therapy failed to eliminate shigella organisms from stool, compared to none in the nalidixic acid treated group infected with nalidixic acid-sensitive Shigella spp. (P < 0.001). One patient in each group had a bacteriological relapse. We conclude that gentamicin given orally was therapeutically ineffective in the treatment of acute shigellosis.

Early pathogenesis in chicks of infection with a trypsin-sensitive avian reovirus

Experiments are described which show how the sensitivity to trypsin of avian reovirus strain TR1 restricts its replication in the intestine of the chicken in comparison with a trypsin-resistant strain R2. Following oral infection with a high dose (5.3 log10 TCID50), the trypsin-sensitive virus generally showed lower titres than the resistant one in all tissues examined. Infection of chicks with strain TR1 via the respiratory route enabled the virus to spread throughout the body and localize in the hock joint, an important target site for reoviruses. Trypsin-sensitive reoviruses might be transmitted via the respiratory route, even though TR1 caused little damage to the respiratory epithelium. Dose-response studies showed that TR1 injected via the footpad can localize in the hock joint after very low doses, but high oral doses (4-5 log10) are necessary for such localization. Intranasal infection was intermediate in effect.

Plant resistance to rusts and mildews: genetic control and possible mechanisms

Genes in plants that confer race-specific resistance to rusts and mildews are widely exploited in agriculture and can prevent huge losses at little cost. However, nothing is known of the molecular basis of their action. Genetic studies, together with observations of responses at the ultrastructural level, can provide broad insights into how resistance is achieved, which may help in cloning resistance genes.

Comparison of pivmecillinam and nalidixic acid in the treatment of acute shigellosis in children

The efficacy of oral pivmecillinam was compared with nalidixic acid in the treatment of acute shigellosis in children 1-8 years of age. In a double-blind trial we studied 80 comparable children with bloody diarrhoea of less than 3 days' duration. Shigella spp. was isolated in 71 children. Patients were randomly assigned to receive either pivmecillinam, 50 mg/kg.day, or nalidixic acid, 60 mg/kg.day, both given orally for 5 days. The stool frequency decreased progressively in both treatment groups. Nalidixic acid failed to eradicate Shigella species in 10 patients, compared with three in the pivmecillinam group (p = 0.04). Similarly, clinical failure was observed in 11 of 37 patients receiving nalidixic acid and in 2 of 26 patients infected with nalidixic acid-susceptible strains as against none in the group receiving pivmecillinam. The results suggest that pivmecillinam given orally was, in fact, more effective than nalidixic acid in the treatment of acute shigellosis in children, particularly when the resistant strains are taken into account.

C-terminal processing of human beta-glucuronidase. The propeptide is required for full expression of catalytic activity, intracellular retention, and proper phosphorylation

beta-Glucuronidase undergoes proteolytic C-terminal processing during or after its transport to lysosomes or endosomes. We determined the C-terminal processing site for human placental beta-glucuronidase to be the peptide bond between Thr633-Arg634. To evaluate the role of the 18-amino acid peptide removed in C-terminal processing, we changed the codon for Arg634 to a stop codon by site-directed mutagenesis and studied expression of the truncated mutant enzyme in COS-7 cells. An increased fraction of newly synthesized enzyme from R634Stop cDNA was secreted. Pulse-chase experiments provided no evidence for increased degradation of the intracellular R634Stop enzyme. The total amount of catalytic activity expressed from the R634Stop mutant cDNA was only half that seen with the wild type cDNA, and the Kcat of the mutant enzyme was 52% that of wild type enzyme. These results indicate that the C-terminal propeptide in the precursor is important for beta-glucuronidase to achieve maximal activity. The truncated enzyme formed hybrid tetramers in cotransfection experiments with the cDNA for rat beta-glucuronidase. There appeared to be no decrease in stability of the R634Stop enzyme, since chaotropic agents, heat treatment, and pH had similar effects on the mutant and the wild type enzymes. The uptake rate of the truncated mutant (R634Stop) enzyme by beta-glucuronidase-deficient human fibroblast cells was only 55-60% that of the wild type enzyme. Binding to the immobilized cation-independent mannose-6-phosphate receptor and measurement of the 32P-labeled phosphorylated oligosaccharides revealed that the truncated mutant enzyme was 32-34% less phosphorylated and appeared to contain proportionately more covered phosphate groups than the wild type enzyme. These results suggest that the propeptide influences the accessibility to both processing enzymes that produce the mannose-6-phosphate recognition marker on beta-glucuronidase.

Models of crossed categorization and intergroup relations

Two studies explored 6 models of crossed categorization. In Experiment 1, Muslims (majority) and Hindus (minority) in Bangladesh evaluated 1 of 4 target groups created by crossing religion (Hindu or Muslim) and nationality (Bangladeshi or Indian) and then rated the target group's perceived variability. Experiment 2 was an extension of the research, including new measures. Both studies showed additive effects of religion and nationality, as predicted by 3 models, a strong effect of category dominance for religion, and out-group homogeneity only when the religious in-group was the dominant and majority group in its country. Experiment 2 also showed a significant relationship between discrimination based on religion and self-esteem and marginal support for the hierarchical ordering model. When and how specific models of crossed categorization might operate in different intergroup contexts are discussed.

Models of crossed categorization and intergroup relations

Two studies explored 6 models of crossed categorization. In Experiment 1, Muslims (majority) and Hindus (minority) in Bangladesh evaluated 1 of 4 target groups created by crossing religion (Hindu or Muslim) and nationality (Bangladeshi or Indian) and then rated the target group's perceived variability. Experiment 2 was an extension of the research, including new measures. Both studies showed additive effects of religion and nationality, as predicted by 3 models, a strong effect of category dominance for religion, and out-group homogeneity only when the religious in-group was the dominant and majority group in its country. Experiment 2 also showed a significant relationship between discrimination based on religion and self-esteem and marginal support for the hierarchical ordering model. When and how specific models of crossed categorization might operate in different intergroup contexts are discussed.

Effect of FK506 on the development of diabetes in BB rats in comparison with that of cyclosporin

FK506, a agent extracted from a streptomyces, has more potent immunosuppressive properties compared with cyclosporin in vitro. We compared the preventive effect of FK506 on the development of diabetes mellitus with that of cyclosporin in BB rats, which are regarded as a useful model of insulin-dependent diabetes mellitus. BB rats aged 30 days were treated intramuscularly with FK506 (0.1 mg/kg/day and 0.32 mg/kg/day) or with cyclosporin (10 mg/kg, alternate days) until 150 days of age. Diabetes developed in 2 (10.5%) of 19 rats treated with the lower dose of FK506 and none of 20 rats with the higher dose of FK506; on the other hand, 1 (5.3%) of 19 rats treated with cyclosporin developed diabetes. In contrast, 9 (36.0%) of 25 control rats became diabetic. The cumulative incidence of diabetes mellitus in the group treated with FK506 (0.32 mg/kg) showed a decrease similar to or more than that of the cyclosporin-treated group. Histological examination showed that FK506 and cyclosporin prevented the reduction in the average size of islets and in the area of beta cells. The analysis of lymphocyte subsets proved the decrease of W3/25: OX8 ratio in both FK506- and cyclosporin-treated groups. These data suggest that the administration of FK506 might be a more useful tool for preventing the development of insulin-dependent diabetes mellitus.

Efficacy of a single dose of furazolidone for treatment of cholera in children

To test the efficacy and safety of furazolidone given as a single dose for childhood cholera, a randomized double-blind placebo-controlled trial was carried out among 118 culture-positive dehydrated children with diarrhea. Patients were randomly assigned to one of four groups to receive medication orally in liquid suspension: furazolidone at 7 mg/kg/day once, furazolidone at 7 mg/kg/day divided into four doses for 3 days, placebo once, or placebo for 3 days. After 12 patients with furazolidone-resistant infections were excluded from the analysis of efficacy, it was determined that both groups treated with furazolidone showed significantly higher rates of bacteriologic success (stool cultures negative for Vibrio cholerae on days 2 to 4 after start of therapy) and clinical success (cessation of diarrhea within 72 h after start of therapy) than corresponding placebo groups (P less than 0.001). There were no significant differences between responses to the 3-day and single-dose regimens of furazolidone, but there was a trend toward better clinical responses in patients who received furazolidone for 3 days. No patient treated with furazolidone dropped out because of side effects. These results indicate that furazolidone, given as either a single dose or divided doses for 3 days, is effective treatment for childhood cholera.

Conserved amino acid residues in ribosome-inactivating proteins from plants

The amino acid sequences of eleven RIPs sequenced to date have been compared in the expectation that this would be useful in the location of functionally and/or structurally important sites of these molecules. In addition to several highly conserved hydrophobic amino acids, thirteen absolutely conserved residues have been found in ricin A-chain: Tyr21, Phe24, Arg29, Tyr80, Tyr123, Gly140, Ala165, Glu177, Ala178, Arg180, Glu208, Asn209 and Trp211. The role of these residues as well as of the C-terminal region have been discussed based on the results of chemical and enzymatic modifications, site-directed mutagenesis, and deletion studies.

N-acetyl-D-glucosamine-asparagine structure in ribosome-inactivating proteins from the seeds of Luffa cylindrica and Phytolacca americana

Glycosylation-site-containing peptides were isolated from the proteolytic digests of luffin-a, luffin-b, PAP-S and CNBr-fragments of PAP-S by reverse-phase HPLC, and their amino acid compositions and sequences were analyzed. Six peptides were obtained from luffin-a, and three each from luffin-b and PAP-S. All of these peptides were negative toward the phenol-H2SO4 reaction and gave only N-acetyl-D-glucosamine in gas chromatography after methanolysis and reacetylation. Amounts of N-acetyl-D-glucosamine in these peptides were determined as D-glucosamine to be approximately one mol per peptide by an amino acid analyzer after HCl hydrolysis. Based on these results we concluded that Asn residues at positions of 28, 33, 77, 84, 206, and 227 in luffin-a, of 2, 78, and 85 in luffin-b, and of 10, 44, and 255 in PAP-S were glycosylated with only GlcNAc, and contained one residue per site.

Direct enantiomeric high performance liquid chromatographic separation of aminoglutethimide and its major metabolite on a series of Chiralcel OD and Chiralcel OJ columns and its application to biological fluids

A direct, isocratic, sensitive and precise liquid chromatographic method is presented for the enantiomeric separation of aminoglutethimide (AG) and its acetylated metabolite (AcAG) using cellulose tris-3,5-dimethyl phenyl carbamate (Chiralcel OD) and cellulose tris(4-methylphenyl benzoate) ester (Chiralcel OJ) columns in series. The enantiomeric elution order is determined by separate chromatography of the racemate AG and racemate AcAG and of their separate enantiomers under similar conditions. This method has been used to determine and identify the enantiomers of AG and AcAG in the urine sample collected from a metastatic breast cancer patient after administration of AG for 24 h. Large amounts of (+)-R-AG are excreted unchanged in the urine together with smaller quantities of (+)-R-AcAG, while most of the (-)-S-AG is metabolically converted into (-)-S-AcAG.

Complete amino acid sequence of luffin-b, a ribosome-inactivating protein from sponge gourd (Luffa cylindrica) seeds

The complete amino acid sequence of luffin-b has been determined. All the twenty-seven tryptic peptides were isolated by reverse-phase HPLC from the tryptic digests of intact luffin-b and one of its CNBr fragments (CB4), and sequenced using the DABITC/PITC double coupling method. The overlap of these peptides was achieved by analyzing the CNBr fragments and their chymotryptic peptides. Luffin-b consists of 250 amino acid residues with a relative molecular mass of 27,275 Da. Investigation for glycosylation sites indicated that Asn at positions 2, 78, and 85 might carry sugars. Sequence comparison with luffin-a showed that amino acid substitution occurred in 55 positions. Luffin-b contains three glycosylation sites instead of the six sites in luffin-a, of which two were found to be conserved.

Complete amino acid sequence of luffin-a, a ribosome-inactivating protein from the seeds of sponge gourd (Luffa cylindrica)

The complete amino acid sequence of luffin-a has been determined. Twenty-two peptides were isolated from the tryptic digest of luffin-a and sequenced employing the DABITC/PITC double coupling method. Overlaping of these peptides was achieved by analyzing the chymotryptic peptides or CNBr-fragments of luffin-a and their S. aureus V8 protease peptides. Luffin-a consists of 248 amino acid residues and its relative molecular mass is calculated to be 27,021 Da, excluding the attached sugar chains reasoned to be present at each Asn residue of positions 28, 33, 77, 84, 206, and 227. A comparison with the sequence of ricin A-chain showed 33% sequence identity indicating that these proteins are homologous.

Direct separation and optimization of timolol enantiomers on a cellulose tris-3,5-dimethylphenylcarbamate high-performance liquid chromatographic chiral stationary phase

A high-performance liquid chromatographic method was developed for the direct resolution and optimization of the separation of timolol enantiomers. The method involves the use of a cellulose tris-3,5-dimethylphenylcarbamate chiral stationary phase (OD-Chiralcel) column. The effects of concentration of 2-propanol, various aliphatic alcohols and diethylamine in the mobile phase and column temperature on the retention and enantioselectivity of timolol enantiomers were studied. The maximum resolution factor obtained was 4.00 when using the solvent system hexane-2-propanol (95:5) containing 0.4% (v/v) diethylamine at 5 degrees C.

Isocratic high-performance liquid chromatographic resolution of glutethimide enantiomers and their 4-hydroxyglutethimide metabolites using cellulose tribenzoate chiral stationary phase

Glutethimide (2-ethyl-2-phenylglutarimide) enantiomers and their corresponding 4-hydroxyglutethimide metabolites (RS and RR) are separated using newly developed commercially available cellulose tris(4-methylphenyl benzoate) ester (Chiralcel OJ) chiral stationary phase and hexane-ethanol or hexane-2-propanol as the mobile phase. The effects of ethanol or 2-propanol concentration in the mobile phase and of column temperature on retention and enantioselectivity of glutethimide enantiomers are also demonstrated. Maximum resolutions of 14.23 and 7.09 are obtained for glutethimide and their 4-hydroxyglutethimide metabolites, respectively, with hexane-ethanol (60:40) at 23 degrees C and a flow rate of 1 mL/min.

Single-dose treatment of cholera with furazolidone or tetracycline in a double-blind randomized trial

To evaluate single doses of 400 mg of furazolidone and 1 g of tetracycline given orally to patients with diarrhea due to Vibrio cholerae, we studied 87 adults in a randomized, double-blind, placebo-controlled trial. All patients received intravenous fluids for rehydration and no other drugs. The total volumes of stool (mean +/- standard deviation) during a 6-day period after treatment were significantly smaller in the tetracycline group (10.5 +/- 8.6 liters) than in the furazolidone group (20.9 +/- 15.9 liters) and the placebo group (19.1 +/- 10.5 liters) (P less than 0.01). The duration of diarrhea and volumes of intravenous fluids were also significantly reduced in the tetracycline group (P less than 0.05). However, there were no differences between the furazolidone and the placebo groups with regard to stool volume, intravenous fluid, and duration of diarrhea. Within 48 h of treatment, tetracycline significantly reduced the number of patients with positive stool cultures for V. cholerae (37%) compared with furazolidone treatment (96%) and the placebo (97%) (P less than 0.001). Although the tetracycline group had a significantly higher incidence (61%) of bacteriologic relapse (negative stool cultures on days 2 and 3, followed by positive cultures afterward) compared with that in the furazolidone group (40%) and the placebo group (33%), this was not associated with clinical relapse. There were no differences between the furazolidone and placebo groups with regard to any of the bacteriologic responses examined. These data indicate that a single dose of 1 g of tetracycline is effective in the treatment of cholera, but it is asymptomatic bacteriologic relapse. A single dose of 400 mg of furazolidone is not therapeutically effective in cholera.

Recombination among genes at the L group in flax conferring resistance to rust

Fourteen of the known genes conferring resistance to rust in flax occur in the L group, and recombinational analysis has been used to study their fine structure. Three important features were observed. (a) Similar to the findings of Shepherd and Mayo, only susceptible recombinants were detected among the testcross progeny of 11 of the 15 heterozygotes involving pairs of L genes. Some of these recombinants showed variation in the degree of their susceptibility and appeared to be unstable in nature. (b) A new class of recombinants exhibiting a modified type of resistance was recovered. They occurred rarely but consistently, with frequencies similar to that of susceptible recombinants. (c) Rare resistant plants occurred among the progeny of susceptible recombinants. In each case, the specificity of the resistant plant corresponded to only one of the parental types. The relative roles of seed contamination, mutation, recombination and the transposition of genetic elements are discussed to account for these features.

Direct liquid chromatographic resolution of racemic aminoglutethimide and its acetylated metabolite using a chiral alpha 1-acid glycoprotein column

A 10-cm long alpha 1-acid glycoprotein column is used for the enantiomeric resolution of the clinically used racemic aminoglutethimide (+/- AG) and its acetylated metabolite (+/- AAG). A direct liquid chromatographic resolution of racemic aminoglutethimide and its acetylated metabolite is accomplished without any derivatizations. Maximum resolutions of 1.37 and 0.73 are obtained for the enantiomers of aminoglutethimide and its acetylated metabolite, respectively. The effect of the 2-propanol content in mobile phase on retention and enantioselectivity of aminoglutethimide and its acetylated metabolite is demonstrated. The variation of the separation factors (alpha) with pH in enantiomeric separation of aminoglutethimide is also shown.

Prevalence and pathology of helminth parasites in domestic ducks of Bangladesh

Parasitism in waterfowl is a very common phenomenon. Two detailed check lists of helminth parasites of waterfowl are available (Lapage, 1961; McDonald, 1969) and many of these parasites are reported to occur in domestic ducks. However, the pathological significance of most of them is unclear. In a preliminary study, Qadir (1979) recorded 13 species of helminths from domestic ducks of Bangladesh. The present paper reports on the prevalence and pathological effects of helminth infections in domestic ducks (Anas platyrhynchos domesticus) of Bangladesh under natural conditions and on their incidence in two age and sex groups of ducks.

Pathogenesis of experimental reovirus tenosynovitis in chickens: influence of the route of infection

Four groups of specific pathogen-free, day-old chicks were infected experimentally with an avian arthrotropic reovirus strain R2 by four different routes:--oral, subcutaneous, foot-pad and intra-articular. These groups were followed sequentially to study: pathological changes in the hock joints and liver; cloacal virus shedding and the presence of virus in hock joints; serological responses as determined by enzyme linked immunosorbent assay (ELISA), agar gel precipitation (AGP) and virus neutralization tests. All 4 infected groups developed arthritis or tenosynovitis with synovial hyperplasia and lymphocytic infiltration. Foot-pad and intra-articular routes of infection were found to advance the disease process by 2 to 3 weeks after infection by these routes were associated with superficial degenerative changes in articular cartilage. Antibodies were detected at 2 to 3 weeks p.i. by all 3 methods, but there were no significant differences between the patterns of serological response in the infected groups. Injection into the foot-pad appears to be the most convenient and effective parenteral route of experimental infection.

Bioelectric current image reconstruction from magneto-acoustic measurements

An investigation is conducted of the possibility of reconstructing images of current dipoles in a volume conductor from data obtained by the magnetoacoustic technique. A modified form of the algebraic reconstruction technique (ART) is used. Reconstruction results of simulated data show that it is possible to find the location, relative magnitude, and orientation of the dipoles with reasonable accuracy for simple dipole configurations.

Single dose tetracycline in cholera

A randomised clinical trial was carried out to explore the efficacy of single dose tetracycline therapy in cholera. One hundred and eighteen adult patients were assigned to receive either tetracycline in a single 1 g, or a single 2 g dose, or tetracycline 500 mg every six hours four times, or no antibiotics as controls. The means of total liquid stool volumes after treatment were lower in the single 1 g dose group (168.0 +/- 20.9 ml/kg), in single 2 g dose group (229.5 +/- 45.6 ml/kg), and multiple dose group (214 +/- 28.5 ml/kg), than in the control group (499.1 +/- 56.5 ml/kg) (p less than 0.05). Similarly, the means of durations of diarrhoea and intravenous fluid requirements were significantly lower in the single dose and multiple dose tetracycline groups, than in the controls (p less than 0.05). The mean durations of excretion of Vibrio cholerae were significantly shortened from 3.9 +/- 0.2 days in the control group to 1.9 +/- 0.2 days in single 1 g dose, to 2.2 +/- 0.4 days in single 2 g dose and 1.3 +/- 0.1 days in multiple dose groups, respectively (p less than 0.05). Three patients in the single 1 g dose group and two patients in single 2 g dose group had clinical relapses with excretion of V cholerae during the relapses, but this was not significantly more frequent than that in the multiple dose group (p greater than 0.05). These findings suggest that although multiple dose tetracycline therapy remains the best choice, a single dose of either 1 g or 2 g tetracycline appears to be a reasonable alternative for the treatment of cholera as an adjunct to rehydration therapy.

Causes of death in diarrhoeal diseases after rehydration therapy: an autopsy study of 140 patients in Bangladesh

The cause of death (besides dehydration) for 140 diarrhoeal patients who died in hospital following rehydration was determined by autopsy examination. Children under 5 years comprised 74% of the patients. Diarrhoeal pathogens were identified as Shigella spp. in 27%, enterotoxigenic Escherichia coli in 17%, Entamoeba histolytica in 16%, Campylobacter jejuni in 12%, Salmonella spp. in 4%, Vibrio cholerae in 4%, and Giardia lambliain 4% of cases. The most frequent underlying causes of death were colitis in 44% and pneumonia in 38%. The most frequent immediate causes of death were septicaemia in 27%, hypoglycaemia in 9%, and hypokalaemia in 9%; multiple causes of death were present in 89% of cases. Kwashiorkor or marasmus was present in 59% and fatty degeneration of the liver was detected in 61% of cases. It is concluded that, in susceptible children, diarrhoeal pathogens produce destructive inflammation in the intestine and cause death or contribute to it by provoking disease in other tissues, especially septicaemia and fatty liver, or by combining these effects with antecedent or concomitant conditions, especially pneumonia and malnutrition.

A randomized double blind trial of aspirin versus placebo in cholera and non-cholera diarrhoea

A randomized double blind controlled clinical trial was conducted on 30 patients with cholera and 18 patients with severe non-cholera diarrhoea, to study the antisecretory effect of acetylsalicylic acid (aspirin). The criteria for selection of patients was a stool output of 4 ml/kg per hour over 6 hours of baseline observation. On inclusion into the study, the groups were comparable in sex, age, body weight, duration of diarrhoea and severity of dehydration. Aspirin and placebo (starch) were given by mouth in doses of 25 mg/kg/day for 24 hours in four equally divided doses. Fourteen patients with cholera and 10 with non-cholera diarrhoea received aspirin and the others received placebo. The aspirin and the placebo groups did not differ in their rate of stool output. The results suggest that aspirin in the above mentioned dose has no antisecretory activity.

Effective treatment of diarrhoeal dehydration with an oral rehydration solution containing citrate

To compare the clinical efficacy of oral rehydration salts (ORS) from effervescent tablets containing citrate with the WHO recommended ORS for the treatment of dehydration due to acute diarrhoea, a randomized clinical trial was carried out in 57 adults and 58 children. These patients had mild or moderate degrees of dehydration and acidosis due to acute watery diarrhoea that was caused by enterotoxigenic Escherichia coli in 43-47% of the cases. Efficacies were compared by measuring oral fluid intake, stool output, gain in body weight, decrease in serum specific gravity and correction of acidosis during treatment. Successful rehydration and maintenance of hydration was achieved in 25 adults and 24 children treated with citrate containing ORS and 25 adults and 24 children treated with WHO ORS. The mean intake of ORS/kg body weight in children receiving WHO ORS was greater (p less than 0.05) and correction of acidosis was faster than the citrate group during the initial 24 h of therapy (p less than 0.05). By 48 h, however, both groups showed satisfactory and comparable intake of ORS and correction of acidosis. Thus ORS from effervescent tablets containing sodium citrate base is effective for management of diarrhoea in both adults and children and is a convenient stable form of ORS for use in the home and for travelers.

Can potassium citrate replace sodium bicarbonate and potassium chloride of oral rehydration solution?

Ninety four children aged less than 5 years with diarrhoeal dehydration and acidosis were treated randomly with either World Health Organisation (WHO) oral rehydration solution containing sodium chloride, potassium chloride, sodium bicarbonate and glucose or an oral solution with tripotassium citrate monohydrate replacing the sodium bicarbonate and potassium chloride in the WHO solution. Fifty five children (58%) were hypokalaemic (potassium less than 3.5 mmol/l) on admission. All but two in the citrate group were successfully treated. There were no significant differences in rehydration solution intake, stool output, gain in body weight, and fall in plasma specific gravity and haematocrit between the two treatment groups after 48 hours' treatment. Significant improvement in the serum potassium concentration was observed in the hypokalaemic children receiving potassium citrate solution compared with children receiving WHO solution after 24 and 48 hours' treatment. None developed hyperkalaemia. Although children receiving potassium citrate solution corrected their acidosis at a slower rate than the WHO solution group during the first 24 hours, by 48 hours satisfactory correction was observed in all. Tripotassium citrate can safely replace sodium bicarbonate and potassium chloride and may be the most useful and beneficial treatment for diarrhoea and associated hypokalaemia.

Oral rehydration solution without bicarbonate

The efficacy of oral rehydration solution without bicarbonate was compared with World Health Organisation oral rehydration solution in 98 young children in a double blind and randomised clinical trial. These children had varying degrees of dehydration and acidosis caused by acute watery diarrhoea. The mean serum bicarbonate concentration on admission was 13.3 mmol(mEq)/1 in the former and 13.1 mmol(mEq)/1 in the latter group of children. All but three children who received the rehydration solution without bicarbonate were successfully treated; three treatment failures were attributed to persistent vomiting and severe diarrhoea (greater than 10 ml/kg/hour). Correction of acidosis was slower in the non-bicarbonate treated than the control group during the first 24 hours' treatment (P less than 0.001). By 48 hours, however, acidosis was corrected and mean serum bicarbonate had risen to 17.1 mmol(mEq)/1 compared with 18.9 mmol(mEq)/1 in the control group (P greater than 0.05). Some failures due to sustained acidosis and persistent vomiting and diarrhoea should be expected. Oral rehydration solution without bicarbonate may be used where complete formula solution is not available.

Oral rehydration therapy: efficacy of sodium citrate equals to sodium bicarbonate for correction of acidosis in diarrhoea

Forty patients with moderate degrees of dehydration and acidosis because of acute watery diarrhoea were successfully treated randomly with either WHO recommended oral rehydration solution containing 2.5 g sodium bicarbonate or an oral solution containing 2.94 g sodium citrate in place of sodium bicarbonate per litre of oral rehydration rehydration solution. Efficacies were compared by measuring oral fluid intake, stool and vomitus output, change in body weight, hydration status, and rate of correction of acidosis during a period of 48 hours. Seventy five per cent (21 cases) in the citrate group and 83% (19 cases) in the bicarbonate group were successfully rehydrated (p greater than 0.05). There were no significant differences in intake, output, gain in body weight, fall in haematocrit and plasma specific gravity, and correction of acidosis between the two groups of patients within 48 hours after initiation of therapy. The solution with sodium citrate base was as effective as WHO-oral rehydration solution for management of diarrhoea. This study shows the efficacy, safety, and acceptability of citrate containing oral rehydration solution for rehydration and correction of acidosis in diarrhoea.

The leukemoid reaction in shigellosis

Leukemoid reactions occurred in 136 patients (3.8%) hospitalized with shigellosis in Bangladesh. Sixty-eight percent of the patients with leukemoid reactions were children less than 4 years old. When compared with patients without leukemoid reactions, the leukemoid reactions were significantly associated with children aged less than 10 years. The most common serotype of Shigella in the patients with leukemoid reactions was Shigella dysenteriae 1, isolated from 96 patients (71%), whereas the most common species in patients without leukemoid reactions was Shigella flexneri, isolated from 2,119 patients (62%). The case fatality rate in patients with leukemoid reactions was 21% compared with 7.4% in patients without leukemoid reactions. These findings indicated that in patients with shigellosis, the leukemoid reaction was significantly associated with young children, isolation of S dysenteriae 1, and increased case fatality rate.