Purification and characterization of myotoxin IV, a phospholipase A2 variant, from Bothrops asper snake venom

A basic myotoxic protein was purified from Bothrops asper venom. Like other basic Bothrops myotoxins, myotoxin IV induces acute muscle damage after intramuscular injection in mice and disrupts negatively charged liposomes but not positively charged ones. Furthermore, this protein exerts a weak anticoagulant effect only at concentrations of 40 micrograms/ml or higher, and is devoid of phospholipase A2 activity. Rabbit polyclonal antibodies to B. asper myotoxin II, a related lysine-49 isoform, cross-react strongly with myotoxin IV by enzyme immunoassay, indicating a high degree of antigenic similarity between these two proteins. The fact that both toxins have similar amino acid compositions and amino-terminal sequences, including leucine-5 and glutamine-11, 2 amino acid residues conserved in all lysine-49 phospholipase A2 variants purified, strongly suggests that B. asper myotoxin IV is a lysine-49 phospholipase A2.

Pharmacological study of edema induced by venom of the snake Bothrops asper (terciopelo) in mice

The effect of several drugs on the edema-forming activity of Bothrops asper venom was studied plethysmographically using the mouse foot pad assay. Bothrops asper venom induced a dose-dependent edema which developed rapidly and peaked 1 hr after envenomation. Incubation of venom with EDTA before injection resulted in a significant reduction of edema. In addition, pretreatment with prazosin, indomethacin, dexamethasone, yohimbine and mepacrine resulted in a significant reduction in edema-forming activity. However, no inhibitory effect was observed when mice were pretreated with verapamil, nordihydroguaiaretic acid, pyrilamine, cimetidine and propranolol. When drugs were administered after venom injection, only prazosin and indomethacin were effective in reducing edema. These results suggest that B. asper venom-induced edema in the mouse foot pad model is mediated, at least partially, by metalloproteinases, phospholipase A2, eicosanoid products and activation of alpha 1 and alpha 2 adrenergic receptors.

Effect of various Viperidae and Crotalidae snake venoms on endothelial cells in vitro

The effect of various crotalid and viperid venoms at 10, 50 and 100 micrograms/ml was examined on bovine and murine endothelial cells in vitro. The venoms caused the cells to lose their processes, leading to the appearance of spaces which were gradually enlarged between clusters of cells. The cells became round and finally detached from the substrate. This effect was more pronounced on bovine normal cells than on murine transformed cells. Most of the venoms did not affect the viability of the cells even after 24 hr of incubation, as determined by the trypan blue dye exclusion procedure. Moreover, after the cells were washed from the venoms and transferred into fresh medium, they regained their original morphology after spreading on the substrate and they then proliferated normally. This reversible effect shows that most of the crotalid and viperid venoms examined were not directly cytotoxic to the endothelial cells at the concentrations tested.

Effect of enriched oil diets on some cardiovascular risk factors in rat's recovery from early undernutrition

This study evaluates the role of soybean and olive oil in the recovery and evolution of some cardiovascular risk factors in rats undernourished in uterus and during lactation. Beginning at 20 days of age, for a period of 130 days, control (C) and malnourished (M) animals were fed three different diets: standard diet (C, M), standard diet enriched with soybean oil (CS, MS) and standard diet enriched with olive oil (CO, MO). Body weight, systolic and diastolic blood pressure, total cholesterol, HDL-cholesterol and triglycerides levels of pups were measured at periods of 15, 30, 90 and 150 days of age. Malnutrition produced a decreased body weight and experimental diets were ineffective in body weight recovery. The controls, however, displayed overweight. Blood pressure values, taken at different ages and under different diets were within normal limits. Plasma triglycerides increased up to 30 days of age with early undernutrition returning, thereafter, to normal limits. Plasma cholesterol level decreased in all animals with age, except in the CS and CO groups, which showed a significant increase in this parameter at 5 months.

Cleavage of the NH2-terminal octapeptide of Bothrops asper myotoxic lysine-49 phospholipase A2 reduces its membrane-destabilizing effect

Bothrops asper myotoxin II was cleaved with cyanogen bromide to determine the role of NH2-terminal amino acid residues in its ability to destabilize negatively charged liposomes and to induce myonecrosis. After treatment, cleaved toxin was separated from its NH2-terminal octapeptide by reversed-phase HPLC. Cleaved myotoxin II lost its capability to disrupt negatively charged liposomes, whereas it maintained approximately one-third of its muscle-damaging effect. No gross antigenic changes were detected after cleavage, as judged by immunoreactivity with polyclonal sera and a set of monoclonal antibodies. However, two of the tested MAbs showed a decreased binding to CB-myotoxin II. We conclude that the NH2-terminal octapeptide has an important role in the membrane-destabilizing activity of this toxin. This domain might directly participate in the binding of toxin to membranes, as well as in its pharmacological activities. Alternatively, conformational changes might occur in cleaved protein, altering its cytotoxic effects by indirectly modifying other important domains.

Pathological changes induced by BaH1, a hemorrhagic proteinase isolated from Bothrops asper (Terciopelo) snake venom, on mouse capillary blood vessels

The pathological changes induced in capillaries by BaH1, a hemorrhagic metalloproteinase isolated from the venom of Bothrops asper, were studied after i.m. injection in mouse gastrocnemius. Hemorrhage was observed macroscopically, and corroborated histologically, within the first 5 min. At the ultrastructural level, the earliest changes in endothelial cells, observed 1 min after toxin administration, consisted of a decrease in the number of pinocytotic vesicles, the presence of blebs and cytoplasmic projections pinching off to the vascular lumen and the detachment of endothelial cells from the surrounding basal lamina. These processes occurred concomitantly with a thinning of endothelial cells. In capillaries undergoing more advanced degenerative stages, there were gaps or breaks in endothelial cells through which erythrocytes were escaping to the extravascular space. In these cells, the basal lamina was usually absent. Throughout this process, intercellular junctions remained apparently intact and no evidence was found of extravasation through widened intercellular junctions. In addition to this morphological pattern of degeneration, some capillaries presented swollen endothelial cells with dilated endoplasmic reticulum and lacking pinocytotic vesicles. Many capillaries contained platelet plugs and fibrin. Thus, hemorrhage induced by BaH1 occurs per rhexis, as has been also described for other venoms and hemorrhagic toxins.

[Anesthesia and perioperative complications of correcting transposition of the great arteries using the Jatene technique]

We present a retrospective morbi-mortality study in 12 patients undergoing Jatene's arterial repair for transposition of the great vessels between 1988 and 1992. Half of the patients were boys ranging in age from 4 days to 35 months. In 34% heart failure was grade III, while in 65.6% it was grade IV (NYHA). Anesthetic induction was with ketamine in 11 patients and with halothane in 1. Maintenance was with pancuronium and fentanyl supplemented with N2O in 2 and with isoflurane in 1. The overall intra- and perioperative death rate was 16.6%. Nine cases have undergone surgical repair since 1988 with no mortality. We conclude that Jatene's technique is the best alternative for repair of transposition of the great vessels when there is no hypoplasia of the right cavity.

Immunochemical characterization of Micrurus nigrocinctus nigrocinctus venom with monoclonal and polyclonal antibodies

Eleven murine monoclonal antibodies (MAbs) against Micrurus nigrocinctus nigrocinctus venom were produced and partially characterized. When M. n. nigrocinctus venom proteins were separated by SDS-PAGE under non-reducing conditions four sharp and three diffuse bands were observed. The sharp bands had migration rates comparable to reduced standards of 10, 12, 50 and 72 kDa. The diffuse bands migrate in the range of reduced standards from 14.5 to 32 kDa. When venom proteins were separated under reducing conditions the same sharp bands and an additional prominent 14.5 kDa band were observed. Three antibodies (MAbs 4, 21 and 28) recognized the diffuse bands in western blots of non-reducing SDS-PAGE, whereas MAbs 7G, 22 and 26 reacted with only the 72 kDa protein. MAbs 21 and 28 reacted with the 14.5 kDa band whereas MAb 7G recognized the 72 kDa band in blots of reducing SDS-PAGE. Two M. nigrocinctus antivenoms cross-reacted by ELISA against nine neurotoxic snake venoms, as well as with gamma-toxin from Naja nigricollis and notexin. One antibody (MAb 9A) was used to affinity purify a fraction (called nigroxin) from M. n. nigrocinctus venom. Nigroxin showed phospholipase and myotoxic activities and appeared as a single 15 kDa band in SDS-PAGE under reducing conditions. However, three bands with slight differences in charge were resolved by urea-PAGE, representing isoforms named nigroxin a, b, and c. Nigroxin induced a dose-dependent release of peroxidase trapped in negatively charged liposomes. Nigroxin induced myonecrosis and increased the plasma creatine kinase levels in mice, when injected intramuscularly. The plasma membrane of cultured L6 myoblasts was permeabilized by nigroxin, as evidenced by the release of 3H-uridine nucleotides from prelabelled cells. This effect was completely abolished after preincubation with MAb 9A, although this antibody failed to neutralize the enzymatic activity of nigroxin. Nigroxin was also recognized by MAbs 4, 7H, 21, 27 and 28. Additionally, the epitope recognized by MAb 27 is also present in notexin and beta-bungarotoxin.

Activity of hemorrhagic metalloproteinase BaH-1 and myotoxin II from Bothrops asper snake venom on capillary endothelial cells in vitro

In vivo, hemorrhagic toxins isolated from snake venoms cause a disorganization of the basal lamina of capillaries, with a concomitant degenerative process of endothelial cells. In this study we investigated the effects of BaH-1, a hemorrhagic metalloproteinase purified from the venom of Bothrops asper, on a murine endothelial cell line of capillary origin. A quantitative cytotoxicity assay based on the release of lactic dehydrogenase was utilized. BaH-1, despite its potent hemorrhagic activity, did not exert direct cytolytic activity on the endothelial cells, even at concentrations as high as 65 micrograms/ml. The only visible effect of BaH-1 on the cultured cells was a relatively slow, moderate detachment of cells, interpreted as a consequence of proteolytic degradation of extracellular matrix components. In contrast, myotoxin II, a lysine-49 phospholipase A2 from the same venom, was clearly cytotoxic to this cell type, albeit being devoid of hemorrhagic activity. These findings suggest that the ability of venom metalloproteinases to induce hemorrhage is not related to a direct cytotoxic action on endothelial cells, and that the rapid degenerative changes of endothelium observed in vivo are probably the result of an indirect mechanism.

Caprylic acid fractionation of hyperimmune horse plasma: description of a simple procedure for antivenom production

A simple methodology for hyperimmune horse plasma fractionation, based on caprylic acid precipitation, is described. Optimal conditions for fractionation were studied; the method gives best results when concentrated caprylic acid was added to plasma, whose pH had been adjusted to 5.8, until a final caprylic acid concentration of 5% was reached. The mixture was vigorously stirred during caprylic acid addition and then for 60 min; afterwards the mixture was filtered. Non-immunoglobulin proteins precipitated in these conditions, whereas a highly enriched immunoglobulin preparation was obtained in the filtrate, which was then dialysed to remove caprylic acid before the addition of NaCl and phenol. Thus, antivenom was produced after a single precipitation step followed by dialysis. In order to compare this methodology with that based on ammonium sulfate fractionation, a sample of hyperimmune plasma was divided into two aliquots which were fractionated in parallel by both methods. It was found that caprylic acid-fractionated antivenom was superior in terms of yield, production time, albumin/globulin ratio, turbidity, protein aggregates, electrophoretic pattern and neutralizing potency against several activities of Bothrops asper venom. Owing to its efficacy and simplicity, this method could be of great value in antivenom and antitoxin production laboratories.

[Toxicity and neutralization of venoms from Peruvian snakes of the genera Bothrops and Lachesis (Serpentes: Viperidae)]

The lethal potencies (Median Lethal Dose) of the venoms of Peruvian snakes (Bothrops atrox, Bothrops barnetti, Bothrops pictus and Lachesis muta muta) were determined in mice by using intravenous and intraperitoneal routes of injection. In addition, the neutralizing ability of three antivenoms (bothropic polyvalent, bothropic bivalent and lachetic) was studied by preincubation-type experiments. B. pictus venom had the highest lethality by the intraperitoneal route whereas B. atrox venom had the highest lethality when tested by the intravenous route. The three antivenoms were effective in neutralizing lethality of the homologous venoms. Bivalent antivenom was more effective than polyvalent antivenom in the neutralization of B. pictus venom. On the basis of these findings, the use of bivalent bothropic antivenom is recommended in the Pacific coastal regions of Perú, whereas polyvalent bothropic antivenom is recommended in the oriental jungle regions of the country.

Effects on cultured mammalian cells of myotoxin III, a phospholipase A2 isolated from Bothrops asper (terciopelo) venom

Myotoxin III (MT-III), a myotoxic phospholipase A2 from Bothrops asper, was studied with respect to interactions with cultured mammalian cells and red blood cells. Tests of the cytopathogenic effect of MT-III on different cell lines indicated that rat skeletal muscle L6 myoblasts were more sensitive to the toxin than chinese hamster ovary cells, human lung fibroblasts, mouse adrenal tumour cells and rat intestinal epithelial cells. Specific plasma-membrane permeabilization was assayed as release of a cytosolic [3H]uridine nucleotide marker from toxin-treated L6 cells. A dose- and time-related membrane permeabilization was induced at 37 degrees C, but not at 0 degree C. A half-maximal effect was obtained after 20 min. 30 micrograms/ml MT-III induced 50% marker release in 1 h, and the effect was not reversed by post-incubation for up to 48 h in toxin-free medium. The membrane permeabilization in L6 cells did not seem to require cellular internalisation of the toxin. The catalytic site of the toxin was inactivated by alkylation with p-bromophenacyl bromide (BPB). This treatment abolished the toxin's specific PLA2 activity, as assayed in vitro, and reduced the PLA2 activity on the myoblast membrane by more than 95%, as measured by release of [14C]arachidonic acid from prelabelled cells. However, the membrane-permeabilizing effect (release of cytosolic marker) was reduced only by 70% upon modification with BPB. We also report that MT-III is not directly haemolytic, and one reason for this is the inability of the toxin to associate with the membranes of human or mouse erythrocytes. Taken together, the data suggest that MT-III at 37 degrees C binds to and penetrates the plasma membrane of cultured myoblasts, thereby inducing a rapid, direct and irreversible membrane permeabilization. This effect apparently depends in part on the PLA2 activity of the toxin and in part on a molecular region which is separate from the catalytic site.

p-Bromophenacyl bromide modification of Bothrops asper myotoxin II, a lysine-49 phospholipase A2, affects its pharmacological activities

Modification of Bothrops asper myotoxin II, a lysine-49 phospholipase A2 variant, was carried out with p-bromophenacyl bromide. Modified toxin did not show changes in its charge and immunological properties but two of its pharmacological activities were modified. Myotoxic activity, measured by histology and by increment of creatine kinase levels in plasma of mice, was significantly reduced after toxin modification. In addition, liposome disruption activity was also significantly lower with the modified toxin both at 3 and 24 hr of incubation with the alkylating reagent. Some of the implications of these results on the structure-function relationship of myotoxins are discussed.

Isolation and characterization of synergistic hemorrhagins from the venom of the snake Bothrops asper

Three hemorrhagic factors (BaH1, BH2 and BH3) were isolated from the venom of Bothrops asper by gel filtration on Sephacryl S-200, DEAE-Sepharose chromatography, metal chelate affinity chromatography and hydrophobic interaction chromatography. They contain 55% of the total hemorrhagic activity of the whole venom when they are mixed, but lose almost half of the activity if they are separated, indicating a synergism between the three. The main hemorrhagin is BaH1 (Bothrops asper hemorrhagin 1); the other two are weak hemorrhagins but contribute to the synergism. They are acidic proteins with a pI of 4.5, 5.2 and 5; their mol. wt is 64,000, 26,000 and 55,000 respectively. The minimal hemorrhagic dose (MHD) of BaH1, BH2 and BH3 is 0.18, 2 and 1.6 micrograms, with a specific activity 55, 5 and 6.25 higher than that of the whole venom. The hemorrhagic activity of all three factors was inhibited by EDTA and ortho-phenathroline, indicating that the hemorrhagic activity is metal dependent. Phosphoramidon, soybean trypsin inhibitor, PMSF, pepstatin and aprotinin did not affect the hemorrhagic activity of the isolated factors.

Comparison of the immunogenicity and antigenic composition of ten Central American snake venoms

The immunological reactivity of five crotaline antivenoms for the venoms of ten Costa Rican snakes was determined. Venoms from Bothrops asper, B. godmani, B. lateralis, B. nasutus, B. ophryomegas, B. schlegelii, B. nummifer, B. picadoi, Crotalus durissus durissus and Lachesis muta stenophrys were separated by SDS-PAGE, transferred to cellulose nitrate membrane and reacted against five different antivenoms. Antisera used in the immunoblotting were prepared in rabbits to the crotaline venoms from Crotalus viridis viridis (prairie rattlesnake), Crotalus durissus terrificus (South American rattlesnake), Crotalus atrox (western diamondback rattlesnake), and Bothrops atrox (fer de lance). SDS-PAGE analysis of the ten venoms indicated that all venoms had components in the high-medium mol. wt (> 15,000) and low mol. wt (< 15,000) range, but they all had at least twice as many components in the high-medium mol. wt range. The venoms of B. nummifer and B. nasutus have the greatest number of bands (24) whereas B. asper has the lowest (17). There appeared to be no difference in immunogenicity between high-medium mol. wt components and low mol. wt components; however, with the venoms of B. nasutus, B. ophryomegas, and B. schlegelii, there were few reactions between antivenoms and low mol. wt components. Half of the ten venoms tested had the highest reactivity with antivenom against B. atrox venom. Two venoms reacted most with antivenom against C. adamanteus venom; one with antivenom to C. atrox venom; one with antivenom to C. v. viridis venom and one with antivenom to C. d. terrificus venom.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystallization and preliminary diffraction data of two myotoxins isolated from the venoms of Bothrops asper (Terciopelo) and Bothrops nummifer (jumping viper)

Two myotoxins isolated from B. asper (myotoxin II) and B. nummifer (myotoxin I) snake venoms have been crystallized and their diffraction properties are described. These myotoxins are phospholipase A2 variants which lack enzymatic activity; B. asper myotoxin II is a lysine-49 phospholipase. Crystals were obtained at room temperature by standard hanging-drop vapour diffusion methods. Crystals diffracted to a resolution of 2.8 and 2.3 A, respectively.

Biological and biochemical activities of Vipera berus (European viper) venom

Vipera berus is widely distributed throughout the northern part of Europe and Asia. Characterization of several toxic effects of its venom in the mouse, as well as of in vitro enzymatic activities was performed. Vipera berus venom displayed in vitro proteolytic, fibrinolytic, anticoagulant, and phospholipase A2 activities. The i.p. LD50 of the venom for Swiss mice was 0.86 micrograms/g (95% confidence limits 0.71-1.01 microgram/g). Significant local tissue-damaging effects, including edema, hemorrhage and myonecrosis, were observed. The local edema was characterized by rapid onset, reaching a maximum after 0.5-1 hr, and with dose-dependent persistence. The hemorrhagic potency was measured by a skin test, giving a minimum hemorrhagic dose value of 3.2 micrograms. The venom also induced a moderate local myonecrosis, evidenced by histological evaluation of injected tissue (gastrocnemius), and by biochemical parameters (increase of plasma creatine kinase activity, and decrease of muscle residual MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide)-reducing activity). Characterization of the venom by SDS-polyacrylamide gel electrophoresis revealed 10 (reduced) or 11 (unreduced) main protein bands, which were further analyzed in relation to mol. wt and relative concentration by densitometry. A rabbit antiserum to V. berus venom recognized all main venom bands by immunoblotting. This antiserum cross-reacted to a variable extent with several crotaline venoms, as assessed by enzyme immunoassay.

An MTT-based method for the in vivo quantification of myotoxic activity of snake venoms and its neutralization by antibodies

The reduction of the tetrazolium compound MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) was used as the basis for the development of a simple method for the quantitative estimation of metabolically active skeletal muscle tissue remaining after in vivo venom-induced myonecrosis. Using the venom of the snake Micrurus nigrocinctus as a potent myotoxic agent, this MTT-based technique was evaluated in comparison with available methods based on the measurement of creatine kinase (CK) activity, and a quantitative histological technique considered as a reference. Homogenates of the gastrocnemius muscle prepared in the presence of 1% Triton X-100 reduced MTT and this activity correlated closely with the number of viable cells in the tissue, as determined by histological evaluation. After venom injection, residual MTT-reducing activity of muscle homogenates showed higher correlation to the myonecrosis index obtained by histological analysis, than residual muscle CK activity. Using the new MTT-based assay, the ability of an anti-M. nigrocinctus equine antivenom to neutralize venom myotoxins was studied. The myotoxic activity of the venom was completely neutralized using 4 ml antivenom/mg venom, with a 50% effective dose (ED50) value of about 2.5 ml/mg. The MTT-based method described should be useful in the estimation and standardization of anti-myotoxic potency of antivenoms, and in the screening of other neutralizing agents, as a convenient and reliable alternative to the time-consuming quantitative histological methods.

[Hyperkalemia and its electrocardiographic consequences in professional cyclists at the end of a bicycle race]

The plasma potassium levels were measured in 15 cyclists during the "Vuelta Ciclista al País Valenciano" (700 km, 6 days), both at the start and at the end of the last stage. Plasma potassium levels increased from 4.3 +/- 1.9 mmol/l (resting) to 7.3 +/- 3.2 mmol/l at the end of the stage. The increase in plasma potassium levels was related to changes in other plasma electrolyte levels and it led to electrocardiographic T wave and QRS abnormalities.

Effects of Bothrops asper (terciopelo) myotoxin III, a basic phospholipase A2, on liposomes and mouse gastrocnemius muscle

The action of Bothrops asper myotoxin III, a basic phospholipase A2 which induces acute muscle damage, was studied in mouse gastrocnemius muscle in vivo and in vitro and in multilamellar liposomes. Myonecrosis occurred rapidly after myotoxin injection, as indicated by histological alterations and by a drastic increment in plasma creatine kinase levels. A dose-dependent release of creatine kinase from mouse gastrocnemius muscle incubated in vitro with the toxin was observed. Myotoxin III affected negatively charged multilamellar liposomes, as evidenced by the release of peroxidase trapped in the vesicles. In contrast, very little effect was observed on positively charged vesicles. When gastrocnemius muscle or liposomes were incubated at 4 degrees C there was no membrane-disruptive effect. Inhibition of phospholipase A2 activity, by elimination of calcium and addition of EDTA, resulted in a significant, but not total, reduction in both muscle-damaging and liposomal disrupting effects. It is proposed that B. asper myotoxin III affects cellular and artificial membranes inducing prominent alterations in membrane permeability to ions and macromolecules. Membrane-disrupting activity is probably related to a molecular region different from the catalytic site, although enzymatic activity greatly enhances myotoxin action.

Turbidity of hyperimmune equine antivenom: the role of phenol and serum lipoproteins

Twenty batches of polyvalent antivenom produced at the Instituto Clodomiro Picado were analyzed for turbidity, both before and after freezing-thawing and lyophilization. Eight batches became turbid upon freezing-thawing, and this change correlated with high levels of cholesterol, triglycerides and lipoproteins, especially beta-lipoprotein. Since normal horse serum does not become turbid after freezing-thawing, despite the fact that it has high lipoprotein levels, the possibility was raised that phenol, used as a preservative during serum fractionation, might affect lipoproteins, inducing the appearance of turbidity after freezing-thawing. This hypothesis was tested by fractionating a sample of hyperimmune serum either without phenol or using two different phenol concentrations (0.1 g/dl and 0.25 g/dl). Results showed that, although the three samples had the same cholesterol and triglyceride levels before fractionation, only the one having 0.25 g/dl phenol became turbid upon freezing-thawing, containing a diffuse lipoprotein band on electrophoresis. This finding suggests that turbidity in equine antivenoms depends on the interaction of at least three factors: (a) freezing, (b) high initial cholesterol and lipoprotein concentration in the serum, and (c) addition of phenol during fractionation of serum.

Calcium ion independent membrane leakage induced by phospholipase-like myotoxins

The two snake venom myotoxins ammodytin L and myotoxin II, purified respectively from Vipera ammodytes ammodytes and Bothrops asper, have phospholipase-like structures but lack an Asp-49 in the active site and are without normal phospholipase activity. The interaction of these proteins with different types of liposomes indicated that the myotoxins were able to provoke rapid and extensive release of the aqueous content of liposomes. Leakage was measured by two different methods: fluorescence dequenching of liposome-entrapped carboxyfluorescein and ESR measurement of intravesicular TEM-POcholine reduction by external ascorbate. The process was independent of Ca2+ and took place without any detectable phospholipid hydrolysis. Nonmyotoxic phospholipases tested under the same conditions were unable to induce liposome leakage, which could be detected only when Ca2+ was added to the medium and with the concomitant hydrolysis of phospholipids. The kinetics of Ca(2+)-dependent and Ca(2+)-independent leakage were completely different, indicating two different mechanisms of interaction with the lipid bilayer. Studies using diphenylhexatriene as a probe of lipid membrane organization indicated that the myotoxins gave rise to a profound perturbation of the arrangement of the lipid chains in the membrane interior, whereas interaction of Naja naja phospholipase A2 with the membrane surface did not affect lipid organization. On the basis of these results we suggest that a new type of cytolytic reaction mechanism is responsible for the effects of phospholipase-like myotoxins in vivo.

Effect of maternal food restriction on the evolution of pregnancy in the rat

The present work analyzes the role of food and water intake, nitrogen balance, and in vivo D-glucose intestinal absorption in body weight gain during the second half of pregnancy in malnourished mother rats. Our results indicate that nitrogen balance and intestinal absorption of D-glucose were not changed as a result of food restriction, but important negative correlations between water intake and micturition and weight gain and micturition were found in experimental mothers. The retention of water seems to be one of the most important factor influencing body weight gain in malnourished mother rats in the second half of pregnancy.

Experimental myonecrosis induced by the venoms of South American Micrurus (coral snakes)

Venoms from 11 taxa of Micrurus (coral snakes) from Brazil and Colombia were tested for myotoxic activity in mice. All venoms, except that of M. surinamensis, induced myotoxicity as judged by the increase in plasma creatine kinase levels and by histological analysis. Qualitatively, these venoms induced a similar necrotic pattern, although there were conspicuous quantitative differences between them.

Ultrastructural alterations in mouse capillary blood vessels after experimental injection of venom from the snake Bothrops asper (Terciopelo)

Histological and ultrastructural alterations in capillary blood vessels were studied at various time intervals after im injection of 50 micrograms of Bothrops asper snake venom in mouse gastrocnemius muscle. Hemorrhage was observed as early as 5 min after envenomation, as abundant erythrocytes appeared in the interstitial space. Ultrastructural observations revealed two different patterns of pathological changes: in the majority of damaged capillaries, endothelial cells had blebs and cytoplasmic projections pinching off to the lumen. This phenomenon was observed together with a decrease in the number of pinocytotic vesicles, with endothelial cells becoming very thin. As an apparent consequence of this process, some endothelial cells had evident gaps in their continuity. In addition, basal laminae surrounding these capillaries were altered and discontinuous. Other endothelial cells underwent a morphologically different process of degeneration, characterized by swelling of the endoplasmic reticulum and of the cytosol. These cells had a diffuse appearance and their basal laminae were discontinuous or absent. No major changes in the intercellular junctions were noticed in damaged endothelial cells. Samples obtained 30 and 60 min after venom injection were devoid of normal capillaries in many areas, and only diffuse remnants of their structure were found. Many altered capillaries had platelet aggregates and fibrin, the latter also being observed in the interstitial space. It is concluded that B. asper venom induces rapid and drastic pathological effects on capillaries leading to hemorrhage per rhexis i.e., erythrocytes probably escape through gaps in damaged endothelial cells and not through widened intercellular junctions.