Protective efficacy of calcium channel blockers in sulphur mustard poisoning

The present study was designed to ascertain the in vivo protective efficacy of Ca(2+)-channel blockers against dermally applied sulphur mustard (SM). Male albino mice were exposed to 1.5 LD50 of SM (232 mg/kg) percutaneously and the control group received an equal volume of vehicle (polyethylene glycol 300). Prior to SM application, the animals were administered nifedipine and dextrose saline containing antibiotic by intraperitoneal route. The protection assessed by the mean survival time (MST) was determined by Dunnett's method. The MST was significantly increased in nifedipine treated group. The characteristic biochemical indices of SM intoxication, i.e. lipid peroxidation and reduced glutathione (GSH) were determined in liver from animals sacrificed at 24, 48 and 72 h after exposure. SM application (1 LD50) caused a reduction in GSH level which was restored in nifedipine treated group. SM-induced lipid peroxidation was also prevented by nifedipine administration. The protective effect of nifedipine may be related to its capacity of attenuating SM-induced lipid peroxidation and glutathione depletion.

Design of peptides with alpha,beta-dehydro residues: synthesis, crystal structure and molecular conformation of N-Boc-L-Ile-deltaPhe-L-Trp-OCH3

The dehydro-peptide Boc-L-Ile-deltaPhe-L-Trp-OCH3 was synthesized by the azlactone method in the solution phase. The peptide was crystallized from methanol in an orthorhombic space group P2(1)2(1)2(1)with a = 10.777(2), b = 11.224(2), c = 26.627(10) A. The structure was determined by direct methods and refined to an R value of 0.069 for 3093 observed reflections [I > or = 2delta(I)]. The peptide failed to adopt a folded conformation with backbone torsion angles: phi1 = 90.8(8)degrees, psi1 = -151.6(6)degrees, phi2 = 89.0(8)degrees, psi2 = 15.9(9)degrees, phi3 = 165.7(7)degrees, psi3T = -166.0(7)degrees . A general rule derived from earlier studies indicates that a three-peptide unit sequence with a deltaPhe at the (i + 2) position adopts a beta-turn II conformation. Because the branched beta-carbon residues such as valine and isoleucine have strong conformational preferences, they combine with the deltaPhe residue differently to generate a unique set of conformations in such peptides. The presence of beta-branched residues simultaneously at both (i + 1) and (i + 3) positions induces unfolded conformations in tetrapeptides, but a beta-branched residue substituted only at (i + 3) position can not prevent the formation of a folded beta-turn II conformation. On the other hand, the present structure shows that a beta-branched residue substituted at the (i + 1) position prevents the formation of a beta-turn II conformation. These observations indicate that a beta-branched residue at the (i + 1) position prevents a folded conformation whereas it cannot generate the same degree of effect from the (i + 3) position. This may be because of the trans disposition of the planar deltaPhe side-chain with respect to the C=O group in the residue. The molecules are packed in an anti-parallel manner to generate N2-H2...O2 (-x, y -1/2, -z + 3/2) and N3epsilon1-H3epsilon1 ...O1(-X, y -1/2, -z + 3/2) hydrogen bonds.

Dose response of sulphur mustard: behavioral and toxic signs in rats

The present study elucidates the behavioral and toxic signs in rats following dermal application of sulphur mustard (SM). Graded doses of SM (0.10, 0.25, 0.50, 0.75 and 1.0 LD50) were topically applied to male Wister rats. The body weight as well as behavioral/toxic signs and symptoms were recorded at 1, 2, 3, and 4th day after application of SM. Sulphur mustard consistently decreased body weights of rats in a dose and time dependent manner with maximum decrease on 3rd day post treatment. Sedation and diarrhea were significant in response to doses of SM intoxication in rats. It is concluded that the body weight, sedation and diarrhea may be used as a reliable parameter in evaluating SM intoxication. It is also suggested that hydration and hypertonic saline must be used as a rescue agent within 1-3 days after exposure to SM.

Effect of sulphur mustard inhalation exposure on some urinary variables in mice

The effect of sulphur mustard (2,2'-dichlorodiethyl sulphide) exposure through inhalation at 0.5. 1.0 and 2.0 LC50 (21.2, 42.3 and 84.6 mg m(-3) for 1 h) on some urinary variables was studied in female mice at 6, 24 and 48 h and 7 days post-exposure. The urinary excretion and circulatory blood accumulation of uric acid increased significantly. The level of creatine was also elevated significantly as compared to the control at 2 LC50. It is concluded that sulphur mustard alkylates DNA and triggers catabolism of apurinated purine bases in a very short time. The increase in uric acid excretion in urine can be detected only when the exposure concentration is high.

Changes in certain hematological and physiological variables following single gallium arsenide exposure in rats

Gallium arsenide (GaAs), a group III-VA intermetallic semiconductor, possesses superior electronic and optical properties and has a wide application in electronic industry. Exposure to GaAs in the semiconductor industries could be a possible occupational risk. The aim of the present study was to determine the dose-dependent effect of single oral exposure to GaAs (500, 1000, or 2000 mg/kg) on some biochemical variables in heme synthesis pathway and few selected physiological variables at d 1, 7, and 15 following administration. The results indicate that GaAs produced a significant effect on the activity of delta-aminolevulinic acid dehydratase (ALAD) in blood and heart (particularly at d 7) following exposure to 2000 mg/kg, whereas urinary delta-aminolevulinic acid (ALA) excretion was elevated only at d 7. No marked influence of GaAs on blood hemoglobin, zinc protoporphyrin, and packed cell volume was noticed. Blood glutathione (GSH) was significantly reduced at d 7, but remained unchanged at two other time intervals. On the other hand, heart GSH contents remained uninfluenced on GaAs exposure. Most of the physiological variables, viz. blood pressure, heart and respiration rate, and twitch response, remained unchanged, except for some minor alterations observed at d 7 and 15 following exposure to GaAs at a dose of 2000 mg/kg. Blood gallium concentration was not detectable in normal animals and rats exposed to 500 mg/kg GaAs. Blood arsenic concentration was, however, detectable even at the a lower dose level and increased in a dose-dependent manner. All these changes showed a recovery pattern at d 21, indicating that the alterations are reversible.

Modifications of breathing pattern induced by inhaled sulphur mustard in mice

A head-only exposure assembly was used for exposing mice to vapours of sulphur mustard (SM). The respiration was monitored using an on-line computer program, capable of recognizing the breathing pattern as sensory irritation, airflow limitation and pulmonary irritation. SM was dissolved in acetone and vapourized using a compressed air nebulizer. Mice were exposed to the vapours (8.5, 16.9, 21.3, 26.8, 42.3 and 84.7 mg/m3) for 1 h in a body plethysmograph fitted with a 20-gauge needle and a microphone for sensing the respiratory flow signals. The signals were amplified, digitized and integrated to give tidal volume, and stored in a computer for further analysis. The respiration of the mice was followed for modifications in the breathing pattern until 7 days post-exposure. SM induced sensory irritation during exposure, and there was a concentration dependent decrease in the respiratory frequency and an increase in tidal volume. Lower concentrations showed recovery after stopping the exposure. RD50, the concentration that depresses 50% of the respiration was estimated to be 27.4 mg/m3. Following exposure to higher concentrations the animals started dying after 6 days. The LC50 was estimated to be 42.5 mg/m3 (14 days observation period). The respiratory frequency decreased on subsequent days of exposure depending upon the exposure concentration, and the breathing pattern was characteristic of airflow limitation. The ratio of flow/tidal volume was decreased following exposure to concentrations of 26.8 and 42.3 mg/m3. The ratio of flow/tidal volume may be a better measurement than the measurements based on flow alone for the assessment of airflow limitation. Pulmonary irritation was not observed showing that the lungs were not affected. The body weight of the animals decreased progressively. The present methodology will be useful for identifying the effects of SM on the respiratory system, one of the endpoints considered when establishing occupational exposure limits.

Combined therapeutic potential of meso-2,3-dimercaptosuccinic acid and calcium disodium edetate on the mobilization and distribution of lead in experimental lead intoxication in rats

Asymptomatic lead poisoning remains a serious public health problem in developed and developing countries. Chelation therapy particularly with calcium disodium ethelenediamine tetracetic acid (CaNa2EDTA) is often used therapeutically to reduce the body burden of lead. This chelating drug has serious side effects and drawbacks primarily related to redistribution of lead, nephrotoxicity, and essential metal depletion. The present study was planned to determine the effectiveness of CaNa2EDTA and meso-2,3-dimercaptosuccinic acid (DMSA) used in combination. Both drugs, when administered individually, resulted in significant urinary excretion of lead and lowered the tissue lead burden. Combined treatment with CaNa2EDTA and DMSA elicits an additive response in promoting urinary lead elimination, depleting body lead burden, and restoring altered lead-sensitive biochemical variables. Further, no redistribution of lead to brain or any other soft organ following combined DMSA-CaNa2EDTA treatment was observed indicating a definite advantage of combined therapy over the conventional treatment with CaNa2EDTA or DMSA alone. However, an elevation of serum transaminase activity, creatinine level, and depletion of blood zinc level may limit the usefulness of this combined treatment.

Effect of inhaled aerosol of 1-chloroacetophenone (CN) and Dibenz (b,f)-1,4 oxazepine (CR) on lung mechanics and pulmonary surfactants in rats

Inhalation toxicity following exposure to 1-Chloroacetophenone (CN) and Dibenz(b,f)-1,4 oxazepine (CR) aerosols for 60 min at sublethal concentrations were studied in rats. The dynamic surface tension (gamma max and stability ratio) of lung homogenate increased significantly on CN exposure. The lung mechanics studies revealed a significant increase in compliance in CN exposed rats. CR, on the other hand did not influence any of the above variables except for a decrease in compliance. Total lung phospholipids and sphingomyelin contents decreased significantly following exposure to CN, while CR exposure produced an increase in sphingomyelin, reduction in phosphatidylcholine and ethanolamine, with no change in total phospholipid contents. Histomorphological observations indicated cellular degeneration in the epithelium of the bronchiole and alveolar septal-wall thickening due to the presence of an increased number of mononuclear cells in CN exposed rats. However, CR induced inflammatory reaction and enlargement of respiratory air spaces. It is concluded that of the two sensory irritants (tear gases) examined, CN is potentially more toxic compared to CR in rats.

Computer assisted recognition and quantitation of the effects of airborne chemicals acting at different areas of the respiratory tract in mice

The pattern and timing of a normal breath in unanesthetized mice was analyzed from measurement of inspiratory and expiratory airflows (VI and VE). Airflow was measured via a differential pressure transducer, attached to a pneumotachograph, which itself was attached to a body plethysmograph into which a mouse was placed. The analog voltage from the differential pressure transducer was digitized and stored for analysis on a microcomputer. Criteria were developed to classify each breath as normal (N) or belonging into one of seven abnormal categories. The abnormal categories were arrived at by computer analysis, recognizing specific modifications of the normal pattern into patterns of: sensory irritation of the upper respiratory tract (S), airflow limitation within the conducting airways of the lungs (A) or pulmonary irritation at the alveolar level (P). Combinations of these effects, i.e., S+A, P+A, P+S and P+S+A were also recognized. Computer analysis of each breath also permitted quantitative evaluation of the degree of S, A or P abnormalities. To induce each type of effect we used inhalation exposures to 2-chlorobenzylchloride, carbamylcholine or propranolol. We propose that this approach will permit rapid evaluation of the possible effects of airborne chemicals at three levels of the respiratory tract, with the classification of the type of effect easily obtained in an objective way using well defined criteria, followed by quantitation of the degree of each effect.