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The incidence of snake bites grows more and more. The effects of the snake poison depend on the snake species. They can be cardio-, neuro-, myo-, tissue-, and/or cytotoxic, as well as hemorrhagically. In most cases a symptomatically therapy together with close controls of the labor parameters and a good monitoring is enough. Antivenom-therapy should be reserved for cases with strong indication.
Adult male red-sided garter snakes (Thamnophis sirtalis parietalis) received radio-frequency lesions prior to 17 weeks of low-temperature hibernation. Animals found to have bilateral lesions of the anterior hypothalamus-preoptic area (AH-POA) failed to exhibit courtship behavior on emergence from hibernation. Those individuals in which the major portion of the destruction was centered in the anterior POA also exhibited deficits in thermoregulatory behavior. Animals that received unilateral lesions of the AH-POA initiated courtship behavior after controls and had an abbreviated period of courtship; these animals exhibited normal responses to thermal stimuli. Male snakes with lesions outside the AH-POA courted normally and demonstrated no differences in thermoregulatory behavior compared with the surgical controls. These results indicate that in male red-sided garter snakes, an intact AH-POA is critical for the integration of thermal stimuli that activate seasonal courtship behavior.
Lesions of the medial preoptic area and/or the ventromedial hypothalamus resulted in an abrupt and immediate decline in courtship behavior in adult male Canadian red-sided garter snakes (Thamnophis sirtalis parietalis). Lesions of the more anterior portions of the preoptic area resulted in a more gradual, delayed decline in courtship behavior. Male snakes sustaining lesions dorsal, ventral, or caudal to the anterior hypothalamus-preoptic area exhibited no change in courtship behavior relative to controls. Measurements of testis size, spermatogenic stage, and circulation levels of androgens revealed no differences between any of the groups. There were marked differences in the change in hematocrit over time between the groups. These results indicate that the anterior hypothalamus-preoptic area is involved in the control of courtship behavior in the adult male red-sided garter snake. Moreover, it is suggested that the stimulus affecting the anterior hypothalamus-preoptic area to activate courtship is temperature related.
The observation that snakes and spiders are found faster among flowers and mushrooms than vice versa and that this search advantage is independent of set size supports the notion that fear-relevant stimuli are processed preferentially in a dedicated fear module. Experiment 1 replicated the faster identification of snakes and spiders but also found a set size effect in a blocked, but not in a mixed-trial, sequence. Experiment 2 failed to find faster identification of snake and spider deviants relative to other animals among flowers and mushrooms and provided evidence for a search advantage for pictures of animals, irrespective of their fear relevance. These findings suggest that results from the present visual search task cannot support the notion of preferential processing of fear relevance.
Using a Y-maze apparatus, nine garter snakes were trained to follow an earthworm-extract trail. Correct trailing improved significantly as training progressed. All snakes were able to attain a trailing criterion of 8 out of 10 correct trials by the termination of training. For each trial, the number of tongue flicks each snake made was recorded and tongue flick rate calculated. Tongue flick rate was found to be highly characteristic and constant for individual subjects. In addition, running speed and tongue flick rate were found to be significantly correlated.
Most vertebrate gliders, such as flying squirrels, use symmetrically paired 'wings' to generate lift during flight, but flying snakes (genus Chrysopelea) have no such appendages or other obvious morphological specializations to assist them in their aerial movements. Here I describe the three-dimensional kinematics of gliding by the paradise tree snake, Chrysopelea paradisi, which indicate that the aerial behaviour of this snake is unlike that of any other glider and that it can exert remarkable control over the direction it takes, despite an apparent lack of control surfaces.
The morphology of organisms is generally well matched to their environment, presumably because expression of their genes is tailored either at the population or the individual level to suit local conditions: for example, snake populations that persistently encounter large prey may accumulate gene mutations that specify a large head size, or head growth may be increased in individual snakes to meet local demands (adaptive developmental plasticity). Here we test the relative contributions of genetics and environment to the jaw sizes of two tiger snake populations: one that consumes small prey on the mainland, and an island population that relies on larger prey and has a larger jaw size. Although the idea of adaptive plasticity in response to environmental pressures is controversial, we find that both factors influence the difference in jaw size between the two populations, and the influence of developmental plasticity is greater in the island population.
Using immunological techniques, cases of human snake-bite can be proven and individual snake species identified. A series of experiments is described, to test the antigenic stability and physical properties of an Elapid venom, venom properties which will have implications in field use, transport, or the laboratory procedures relating to the immunological characterization of Australian snake venoms. Using venom from the Elapid, Tropidechis carinatus, we have demonstrated significant immunological stability at a temperature of 37 degrees for 48 h at least, and for 24 h at least when incubated continuously with skin, muscle, and fat homogenates; the venom is stable at 56 degrees for 2 h at least. No loss of venom occurs over the pH range 7-10; at pH ranges less than 4 and at ranges greater than 10 only 30% of venom is detected after 30 min incubation. Sonication (10 min at 100 watts) does not destroy immunological properties of the venom; 10 freeze-thaw cycles result in some 9% loss of immunologically detectable activity. Venom is adsorbed significantly on to dacron swabs, only 13% of the applied does being detected after 48 h incubation at 28 degrees. Sixty-seven percent of applied venom can be recovered from the skin of human volunteers 6 h after a simulated bite. The venom of this Elapid is antigenically robust. With the currently available sensitive assays, venom from human skin should still be detected in material kept without special preparation under field conditions for up to 2 days at least.
Acute renal failure complicates the course in 5% to 30% of victims of severe viper poisoning. No consensus exists on the single mechanism causing acute renal failure after viper bite. It is known, however, that viper venom induces several clinical abnormalities that favor the development of acute renal failure. These alterations include a varying degree of bleeding, hypotension, circulatory collapse, intravascular hemolysis, and disseminated intravascular coagulation with or without microangiopathy. A direct cytotoxic action of snake venom on the kidney is suspected, but convincing evidence is still lacking. Severe hypocomplementemia is consistently present, but I doubt its role in the causation of renal lesions. Hypersensitivity to venomous or antivenomous protein occasionally causes acute renal failure. In sea snake poisoning, myonecrosis and myoglobinuria appear to play the predominant pathogenetic role. The renal lesions of clinical significance in envenomed patients are acute tubular and patchy or diffuse cortical necrosis. Glomerulonephritis, interstitial nephritis, and papillary necrosis have been reported in rare patients. I trust that this overview of the clinical and basic-science aspects of snake-bite-induced acute renal failure will prompt investigators to further define the pathogenetic mechanisms involved. Lessons learned may aid patients with acute renal failure of diverse causes, both here in India and around the world.
Over the last several decades, research on snake venom toxins has provided not only new tools to decipher molecular details of various physiological processes, but also inspiration to design and develop a number of therapeutic agents. Blood circulation, particularly thrombosis and haemostasis, is one of the major targets of several snake venom proteins. Among them, anticoagulant proteins have contributed to our understanding of molecular mechanisms of blood coagulation and have provided potential new leads for the development of drugs to treat or to prevent unwanted clot formation. Some of these anticoagulants exhibit various enzymatic activities whereas others do not. They interfere in normal blood coagulation by different mechanisms. Although significant progress has been made in understanding the structure-function relationships and the mechanisms of some of these anticoagulants, there are still a number of questions to be answered as more new anticoagulants are being discovered. Such studies contribute to our fight against unwanted clot formation, which leads to death and debilitation in cardiac arrest and stroke in patients with cardiovascular and cerebrovascular diseases, arteriosclerosis and hypertension. This review describes the details of the structure, mechanism and structure-function relationships of anticoagulant proteins from snake venoms.
The review is mainly devoted to snake venom alpha-neurotoxins which target different muscle-type and neuronal nicotinic acetylcholine receptors. The primary and spatial structures of other snake venom proteins as well as mammalian proteins of the Ly-6 family, which structurally resemble the 'three-finger' snake proteins, are also briefly discussed. The main emphasis is placed on recent data characterizing the alpha-neurotoxin interactions with nicotinic acetylcholine receptors.
Fractionation of the serum of the venomous snake Bothrops jararaca with (NH4)2SO4, followed by phenyl-Sepharose and C4-reversed phase chromatographies, resulted in the isolation of the anti-hemorrhagic factor BJ46a. BJ46a is a potent inhibitor of the SVMPs atrolysin C (class P-I) and jararhagin (P-III) proteolytic activities and B. jararaca venom hemorrhagic activity. The single-chain, acidic (pI 4.55) glycoprotein has a molecular mass of 46 101 atomic mass units determined by MALDI-TOF MS and 79 kDa by gel filtration and dynamic laser light scattering, suggesting a homodimeric structure. mRNA was isolated from the liver of one specimen and transcribed into cDNA. The cDNA pool was amplified by PCR, cloned into a specific vector and used to transform competent cells. Clones containing the complete coding sequence for BJ46a were isolated. The deduced protein sequence was in complete agreement with peptide sequences obtained by Edman degradation. BJ46a is a 322-amino-acid protein containing four putative N-glycosylation sites. It is homologous to the proteinase inhibitor HSF (member of the fetuin family, cystatin superfamily) isolated from the serum of the snake Trimeresurus flavoviridis, having 85% sequence identity. This is the first report of a complete cDNA sequence for an endogenous inhibitor of snake venom metalloproteinases (SVMPs). The sequence reveals that the only proteolytic processing required to obtain the mature protein is the cleavage of the signal peptide. Gel filtration analyses of the inhibitory complexes indicate that inhibition occurs by formation of a noncovalent complex between BJ46a and the proteinases at their metalloproteinase domains. Furthermore, the data shows that the stoichiometry involved in this interaction is of one inhibitor monomer to two enzyme molecules, suggesting an interesting mechanism of metalloproteinase inhibition.
Of 291 juvenile and adult snakes examined post mortem over a 20-year period (1978-1997) at the National Zoological Park (NZP) in Washington, DC, 36 (24 females and 12 males) had neoplasms. Two snakes had tumours of two or three different types, but the other 34 snakes had only one type. All affected animals were adults and their average time on exhibit at the NZP was 108-9 months. Malignant neoplasms (79.5%) outnumbered benign neoplasms (20.5%). Of the malignant tumours, 19 (61.3%) were considered to have arisen in mesenchymal tissues, 11 (35.5%) were of epithelial origin, and one (3.2%) was derived from neuroectodermal tissues. All the benign neoplasms were of epithelial origin. Neoplasms of the lymphoid and haematopoietic tissues were the most common (12 cases), followed by tumours of the liver and biliary tract (seven cases) and the gastrointestinal tract (four cases).
A 2.5-kilobase fragment of a sex-specific satellite DNA from the Colubrid snake species Elaphe radiata has been cloned, and its sequence has been determined. It contains 26 and 12 copies, respectively, of two base quadruplets, G-A-T-A and G-A-C-A, as its sole highly repetitious elements. Southern hybridization experiments with genomic DNA of the chicken, the mouse, and man indicated male sex-specific conservation of at least parts of this cloned DNA. In situ hybridization experiments with metaphase chromosomes of the mouse showed that elements that can cross-hybridize with parts of the cloned snake DNA are concentrated in the pericentric region of the Y chromosome. In blot hybridization experiments with liver poly(A)+ polysomal RNAs of male and female mice, a probe consisting of the first 1,224 bases of the cloned snake DNA singled out a male-specific RNA of 1,250-1,400 bases. Inasmuch as the proximal end of this probe contained an open reading frame (44 consecutive amino acid-specifying codons), the male-specific putative mRNA so detected may specify H-Y antigen. By contrast, a probe consisting of bases 1,480-1,906, containing the simple repeats of the quadruplets, singled out a shorter (approximately 1,000-base) RNA from males and females alike. Although this RNA is poly(A)+, we have yet to establish its attachment to ribosomes.
Viperine and crotaline snake venoms contain one or more hemorrhagic principles called hemorrhagins. These are zinc-containing metalloproteases characterized by the presence of a protease domain, with additional domains in some of them. They act essentially by degrading the component proteins of basement membrane underlying capillary endothelial cells. The toxins also act on these cells causing lysis or drifting apart, resulting in hemorrhage per rhexis or per diapedesis. Some of these toxins have been found to exert additional effects such as fibrinogenolysis and platelet aggregation that facilitate hemorrhage. The structural and functional features of this class of toxins have been discussed in this review in an attempt to get a better understanding of their toxicity. This can be of immense therapeutic value in the management of snake venom poisoning, as hemorrhagins are among the major lethal factors in snake venom.
Extract from the snake (Ptyas mucosa) pituitaries was capable of inhibiting the binding of 125I-labelled bovine growth hormone to female rat liver membranes. The growth hormone-like substance was not adsorbed on Concanavalin A-Sepharose nor DEAE-cellulose, but could be purified by gel filtration on Sephadex G-50. It possessed a molecular weight of about 19,000 as judged by SDS-polyacrylamide gel electrophoresis. The iodinated snake growth hormone-like substance bound to membranes prepared from female rat and pregnant rabbit livers. The binding could be inhibited by unlabelled snake growth hormone-like substance as well as by bovine growth hormone.
Do animal species that normally consume large meals at long intervals evolve to down-regulate their metabolic physiology while fasting and to up-regulate it steeply on feeding? To test this hypothesis, we compared postfeeding regulatory responses in eight snake species: four frequent feeders on small meals and four infrequent feeders on large meals. For each species, we measured factorial changes in metabolic rate, in activities and capacities of five small intestinal brush border nutrient transporters, and in masses of eight organs that function in nutrient processing after consumption of a rodent meal equivalent to 25% of the snake's body mass. It turned out that, compared with frequent feeders, infrequent feeders digest that meal more slowly; have lower metabolic rates, organ masses, and nutrient uptake rates and capacities while fasting; have higher energy expenditure during digestion; and have higher postfeeding factorial increases in metabolic rate, organ masses, and nutrient uptake rates and capacities. These conclusions, which conform to the hypothesis mentioned above, remain after phylogeny has been taken into account. The small organ masses and low nutrient transporter activities during fasting contribute to the low fasting metabolism of infrequent feeders. Quantitative calculations of partial energy budgets suggest that energy savings drive the evolution of low mass and activities of organs during fasting and of large postfeeding regulatory responses in infrequent feeders. We propose further tests of this hypothesis among other snake species and among other ectotherms.
Thermoregulatory behavior is an important component of daily activities for many reptiles, especially for small heliothermic (sun-basking) species that inhabit cold climates. However, the relative costs and benefits of thermoregulation depend on numerous factors, such that reptiles may sometimes accord a low priority to precise control of body temperatures. We observed and radio tracked garter snakes (Thamnophis sirtalis parietalis) in central Manitoba during the mating season (spring). Previous studies on this species have documented precise behavioral regulation of body temperatures during summer. In contrast, the courting snakes that we studied in springtime spent little time in overt thermoregulatory behavior. Body temperatures were extremely variable (both in outdoor enclosures and in the field) despite abundant opportunities for more precise thermal control. These small elongate reptiles cool so quickly (relative to the time periods needed for effective courtship) that any benefit to higher body temperatures would be transitory at best. Experiments show that hotter males are no better at obtaining matings or at detecting predators. Thus, male garter snakes concentrate on courtship rather than on basking. In the face of conflicting priorities, reptiles may often forgo precise thermoregulation because its benefits are too low, and its costs too high, compared with alternative behaviors.