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At least 613 records · Page 34Linked to original sources
PubMed1998

Phylogenetic relationships of terrestrial Australo-Papuan elapid snakes (subfamily Hydrophiinae) based on cytochrome b and 16S rRNA sequences.

Phylogenetic relationships among the venomous Australo-Papuan elapid snake radiation remain poorly resolved, despite the application of diverse data sets. To examine phylogenetic relationships among this enigmatic group, portions of the cytochrome b and 16S rRNA mitochondrial DNA genes were sequenced from 19 of the 20 terrestrial Australian genera and 6 of the 7 terrestrial Melanesian genera, plus a sea krait (Laticauda) and a true sea snake (Hydrelaps). These data clarify several significant issues in elapid phylogeny. First, Melanesian elapids form sister groups to Australian species, indicating that the ancestors of the Australian radiation came via Asia, rather than representing a relict Gondwanan radiation. Second, the two major groups of sea snakes (sea kraits and true sea snakes) represent independent invasions of the marine environment. Third, the radiation of viviparous Australian elapids is much older than has been suggested from immunological data. Parsimony analyses were unable to resolve relationships among the Australian radiation, a problem previously encountered with analyses of other (morphological, electrophoretic, karyotypic, immunological) data sets on these species. These data suggest that the reason for this continued difficulty lies in the timing of speciation events: the elapids apparently underwent a spectacular adaptive radiation soon after reaching Australia, such that divergences are ancient even within genera. Indeed, intrageneric divergences are almost as large as intergeneric divergences. Although this timing means that our sequence data cannot fully resolve phylogenetic relationships among the Australian elapids, the data suggest a close relationship of the following clades: Pseudonaja with Oxyuranus; Ogmodon with Toxicocalamus; Demansia with Aspidomorphus; Echiopsis with Denisonia; the "Notechis" lineage with Drysdalia coronoides; and Rhinoplocephalus and Suta with Drysdalia coronata. At least two of the Australian genera (Drysdalia and Simoselaps) appear to be paraphyletic. These sequence data support many of the conclusions reached by earlier studies using other types of data, but additional information will be needed before the phylogeny of the Australian elapids can be fully resolved.

Animals↗
PubMed2005

Use of skin and blood as nonlethal indicators of heavy metal contamination in northern water snakes (Nerodia sipedon).

Relatively little is known about contaminants in reptiles, particularly snakes. The concentrations of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium were examined in blood and skin of 46 northern water snakes (Nerodia sipedon) in Tennessee and correlated with concentrations in internal tissues (liver, kidney, muscle) to determine if blood or skin could serve as a nonlethal indicator of internal metal exposure or body burden. Snakes were collected from the East Fork Poplar Creek (EFPC) within the United States Department of Energy's Y-12 National Security Complex (part of the Oak Ridge National Laboratory) and from a reference stretch of the Little River in East Tennessee. For blood, the only consistent positive correlations with internal organs were for mercury, and correlations were low except for muscle. Skin showed significant positive correlations with all three organs for mercury, chromium, selenium, and lead. For manganese and cadmium, skin level was positively correlated with liver level. Blood generally reflects recent exposure, not necessarily body burden, but in water snakes it correlates with body burden for mercury. Skin proved useful for more metals, although patterns were not necessarily consistent across sex and locality subgroups. The most consistent pattern was for mercury, the metal of greatest concern in many aquatic ecosystems, including EFPC.

Animals↗
PubMed2005

Comparison of active venom components between Eastern brown snakes collected from South Australia and Queensland.

The abundance and activity of the prothrombin activator (pseutarin C) within the venom of the Eastern brown snake (Pseudonaja textilis textilis) is the primary determinant of its coagulation potency. Textilinin-1, also in this venom, is a plasmin inhibitor which is thought to exert its toxic effects through the slowing of fibrinolysis. The aim of this report is to determine if there are differences in the potency of the venom from Eastern brown snakes collected from South Australia (SA) compared to those from Queensland (QLD). A concentration of 0.4 microg/ml venom protein from six QLD specimens clotted citrated plasma in an average time of 21.4+/-3.3 s compared to 68.7+/-2.4 s for the same amount of SA venom (averaged for six individuals). The more potent procoagulant activity of the QLD venom was measured between 0.4 and 94 microg/ml venom protein in plasma. The anti-plasmin activity of textilinin was also greater in the venom of the snakes collected from QLD, causing full inhibition of plasmin at approximately 1.88 microg/ml of venom protein compared to approximately 7.5 microg/ml for the SA venoms. It is concluded that geographic differentiation of the Eastern brown snakes results in significant differences venom potency.

Animals↗
PubMed1994

Factors governing the appearance of small-mode miniature endplate currents at the snake neuromuscular junction.

At the snake neuromuscular junction, following a short period of high frequency motor nerve stimulation, a population of 'small-mode' miniature endplate currents (MEPCs) is seen. These small-mode MEPCs are believed to be due to the release of acetylcholine from incompletely refilled recycling synaptic vesicles [Searl et al., Neuroscience, 35 (1991) 145-156]. This study determines the role of the trans-vesicular membrane proton gradient in the generation of small-mode MEPCs. Preserving the trans-vesicular membrane proton gradient during synaptic vesicle exocytosis by exposure of snake nerve/muscle preparations to an extracellular pH approximately equal to the intravesicular pH, leads to an augmentation of the amplitude of the stimulation-induced small-mode MEPCs. Conversely, pretreatment of snake neuromuscular preparations with 10 mM ammonium ions, to buffer intravesicular protons and hence dissipate the trans-vesicular membrane proton gradient, leads to an inhibition of the stimulation-induced appearance of small-mode MEPCs. The data are consistent with the theory that the reduced acetylcholine content of recycled synaptic vesicles in the snake is a consequence of an incomplete restoration of the trans-vesicular membrane proton gradient following synaptic vesicle exocytosis. Thus, in recycling synaptic vesicles the limiting step in the refilling process appears to be generation of the trans-membrane proton gradient and not the transport of acetylcholine into the vesicle.

Ammonium Chloride↗
PubMed1994

Snake odor alters behavior, but not pain sensitivity in mice.

It is known that predator cues (both mammalian odor or avian vocalization) elicit marked analgesia in rodents. The present experiment used olfactory cues produced by an opportunistic rodent predator snake species (100 cc of sawdust scented by Elaphe quatuorlineata). Upon exposure to snake odor (for 30 s, 20 min, or 40 min), adult mice of both the CD-1 and DBA2 strains were assessed for tail-flick or hot-plate analgesia at different times after exposure (from 0 to 40 or 45 min, respectively). In both strains, snake odor exposure induced significant alteration in the frequencies of sniffing, self-grooming, and digging, while it inhibited habituation of locomotor activity in DBA/2 mice. No analgesia emerged with both tests as a consequence of exposure to snake odor. Results suggest that although endogenous analgesia has been demonstrated by other authors to be elicited in response to cues emanating from common and widely distributed mouse predators (such as carnivores or owls), predators such as reptiles, which under natural conditions exert a limited predatory pressure on the house mouse gene pool, may only induce fear-associated behavioral responses but cannot provide ethologically relevant stimuli triggering mouse analgesia.

Animals↗
PubMed1985

Chromogenic proteinase substrates as possible tools in the characterization of Crotalidae and Viperidae snake venoms.

Proteinase activities have been determined photometrically in 25 different Crotalidae and Viperidae snake venoms by using five different chromogenic proteinase substrates. The activity profiles obtained by listing the identity numbers of substrates hydrolyzed by the venoms in a decreasing potency order remained quite stable within a given snake population. Submission of a venom to various physical and chemical treatments did not alter its activity profile. It is therefore concluded that this simple method of determining proteinase activities could be of help in snake venom characterization, as well as in studying the influence of metallic ions and inhibitors of snake venom proteinases.

Animals↗
PubMed1994

A potent antihemorrhagin in the serum of the non-poisonous water snake Natrix tessellata: isolation, characterization and mechanism of neutralization.

The main natural antihemorrhagic factor (NtAH), which inhibits the hemorrhagic activity of Bothrops asper snake venom, was isolated from the serum of the non-poisonous water snake Natrix tessellata by ammonium sulfate precipitation at 35-55%, Sephadex G-75 gel filtration, ion exchange chromatography on DEAE-Sepharose and CM-Sepharose and hydrophobic Phenyl-Sepharose chromatography. The purified protein showed one band with an isoelectric point of 4.5 and a molecular mass of about 880 kDa. The antihemorrhagic activity was stable between pH 5.5-11.7 and up to 50 degrees C, but lost activity after 20 min at 60 degrees C. It did not form a precipitin line with the main hemorrhagin of Bothrops asper snake venom (BaH1), nor with the whole venom, which suggests that the antihemorrhagic factor is not an immunoglobulin. The mechanism of neutralization by the isolated antihemorrhagic factor NtAH did not include digestion of the hemorrhagic toxin BaH1. Chromatography of NtAH with active 125I-labeled BaH1 toxin as well as ELISA experiments demonstrated that the mechanism of neutralization involves formation of an inactive soluble complex between the natural NtAH of the non-poisonous water snake and the main hemorrhagin of Bothrops asper venom.

Animals↗
PubMed2004

Infrared imaging in vipers: differential responses of crotaline and viperine snakes to paired thermal targets.

Pit vipers use infrared-sensitive pit organs to accurately target homeothermic prey even in the absence of visual cues. It has been suggested that other vipers, including large ambush predators of the genus Bitis, also may use radiant infrared information for predatory targeting. We compared behavioral responses of pit vipers and snakes of the viperine genus Bitis to paired targets of different temperatures (i.e. cool and warm balloons), some scented with rodent odors. The rates of tongue flicking, head turning and approaches by pit vipers (Agkistrodon contortrix and Crotalus atrox) were significantly higher toward warm targets than toward cool ones. Moreover, they all were significantly higher in pit vipers than in the vipers Bitis arietans, Bitis gabonica, and Bitis nasicornis. Bitis sp. exhibited no significant differences in their behaviors toward warm versus cool targets. Pit vipers often struck at targets (always the warm target even when paired with a prey-scented cool target), but Bitis sp. never struck at either warm or cool targets. These results show that the behavioral correlates of infrared-based predatory and/or defensive targeting differ significantly between these two groups of viperid snakes, and suggest that the neural substrates of infrared imaging in crotaline snakes are either absent or functionally distinct in viperine snakes of the genus Bitis.

Animals↗
PubMed2004

Sources and timing of calcium mobilization during embryonic development of the corn snake, Pantherophis guttatus.

Embryos of oviparous Reptilia (=turtles, lepidosaurs, crocodilians and birds) extract calcium for growth and development from reserves in the yolk and eggshell. Yolk provides most of the calcium to embryos of lizards and snakes. In contrast, the eggshell supplies most of the calcium for embryonic development of turtles, crocodilians and birds. The yolk sac and chorioallantoic membrane of birds recover and transport calcium from the yolk and eggshell and homologous membranes of squamates (lizards and snakes) probably transport calcium from these two sources as well. We studied calcium mobilization by embryos of the snake Pantherophis guttatus during the interval of greatest embryonic growth and found that the pattern of calcium transfer was similar to other snakes. Calcium recovery from the yolk is relatively low until the penultimate embryonic stage. Calcium removal from the eggshell begins during the same embryonic stage and total eggshell calcium drops in each of the final 2 weeks prior to hatching. The eggshell supplies 28% of the calcium of hatchlings. The timing of calcium transport from the yolk and eggshell is coincident with the timing of growth of the yolk sac and chorioallantoic membrane and expression of the calcium binding protein, calbindin-D28K, in these tissues as reported in previous studies. In the context of earlier work, our findings suggest that the timing and mechanism of calcium transport from the yolk sac of P. guttatus is similar to birds, but that both the timing and mechanism of calcium transport by the chorioallantoic membrane differs. Based on the coincident timing of eggshell calcium loss and embryonic calcium accumulation, we also conclude that recovery of eggshell calcium in P. guttatus is regulated by the embryo.

Animals↗
PubMed2005

Cystyl aminopeptidase activity in the plasma, viscera and brain of the snake Bothrops jararaca.

The relationship between plasma osmolality and cystyl aminopeptidase was characterized in the snake Bothrops jararaca and comparisons were made with the emerging picture of this relationship in rats. The profile of cystyl aminopeptidase activity under basal conditions was determined in the soluble and membrane-bound forms in visceral organs and in the central nervous system in comparison with that of alanyl aminopeptidase. The regional localization of cystyl and alanyl aminopeptidase activities was studied in the central nervous system. The basal level of plasma cystyl aminopeptidase, four- to six-fold higher than in rats, suggests its importance to help regulate circulating levels of neurohypophysial peptides in B. jararaca snake. The osmotic sensitivity of this plasma enzyme, undetectable in male, but about three-fold higher in female snakes than in rats, reveals a sexual dimorphism. In marked contrast to those observed in rats, low levels of soluble and particulate forms in the kidney indicate that cystyl aminopeptidase plays a minor metabolizing role at this anatomical location in B. jararaca. Despite of the regional-specific divergence between the levels of rat and snake enzymes, the bilaterally symmetric pattern of the diencephalic distribution of alanyl aminopeptidase reflects functional homologies between these two distantly related species.

Animals↗
PubMed2005

Snake egg immunoglobulins: biochemical characteristics and adjusted isolation procedure.

Transmission of specific immunoglobulins from mothers to their offspring via the egg is a common phenomenon in egg-laying vertebrates but the occurrence of this phenomenon in reptiles, especially in colubrid snakes, has not been proven until recently. Thus, the essential biochemical characteristics of antibodies deposited in eggs of Elaphe guttata (Colubridae, Serpentes) were studied after isolation of the antibody by precipitation and purification by affinity chromatography and gel filtration, with verification by isoelectric focusing and immunoprecipitation. The immunoglobulin deposited in the eggs of colubrid snakes is a singular, non-truncated IgY antibody in a concentration roughly equal to that in the snake's serum. An efficient method to isolate antibody from snake eggs was developed, based on the PEG precipitation technique of avian yolk immunoglobulins; an unsophisticated protocol for the isolation procedure appropriate for reptile eggs is provided.

Animals↗
PubMed2006

Characterization of novel DNA-binding proteins expressed in snake oocyte cDNA library.

DNA-binding proteins play pivotal roles in transcription, DNA-replication, recombination/repair and determine cell-fate in all physiological conditions of differentiation, development and disease. As they are present in extremely small amounts in cells, their isolation/identification, particularly from scarce tissues is impracticable. We cloned the cDNA pool of snake (Ptyas mucosus) oocytes (a scarce tissue) in bacteria, overexpressed total library, purified and identified DNA-binding proteins expressed in the library. Although snake databases do not exist, we identified 23 DNA-binding proteins, obtained 10-15 amino acids internal sequence tags of six of them and succeeded in PCR amplification of the cDNAs of five proteins. We employed electro spray ionization mass spectrometry, matrix assisted laser desorption/ionization time of flight and analyzed the results by peptide mass fingerprint (PMF) and various sequence BLAST analyses. Proteins identified were largely unanimous between the PMF and BLAST analyses. We expect these proteins to play important roles in snake embryonic development and differentiation. We arrived at homologous mouse proteins to some of the identified snake proteins and are working towards characterizing their structure and physiological function. Similar approaches shall prove valuable in isolation and identification of important factors from scarce carcinoma tissues, mammalian oocytes and early embryos, which might be involved in important functions like nuclear reprogramming, embryonic development and differentiation.

Animals↗
PubMed2006

A comparative analysis of the clotting and fibrinolytic activities of the snake venom (Bothrops atrox) from different geographical areas in Venezuela.

Venom constitution within the same snake species can present considerable geographical variations. Bothrops atrox venoms were obtained from adult snakes captured at different geographical locations: Parguasa (Bolívar state); Puerto Ayacucho 1, Serranía del Cuao and Puerto Ayacucho 2 (Amazon state). The coagulant and fibrinolytic activities of these venoms were compared. Amidolytic activity of crude snake venom was measured by a micromethod designed in our laboratory. Coagulant activity on plasma and fibrinogen due to thrombin-like activity in venoms was also determined. Crude snake venom fibrinolytic activity by the fibrin plate method was assayed. Chromatographic studies were developed on Protein-Pack 300 column. Polyacrylamide gel electrophoresis was carried out under reduced conditions. After SDS-PAGE of samples, the fibrin-zymography was tested on agarose-fibrin plates. The results demonstrated several differences among B. atrox venoms from different geographical areas. Chromatograms and SDS-PAGE profiles indicated that venoms from the same species presented differences in the molecular mass of their components. The procoagulant activity depended on the utilized method (amidolytic versus clotting). Parguasa and Puerto Ayacucho 2 venoms presented procoagulant activity for both methods. Furthermore, Parguasa venom had also the highest hemorrhagic activity and the lowest LD50. In relation to the fibrinolytic activity, Puerto Ayacucho 1 venom was the most active, equally for fibrin plates as for the amidolytic method (t-PA like). This venom had the lowest coagulant activity, which induced us to think that probably its procoagulant activity was interfered by its fibrinolytic activity.

Animals↗
PubMed2004

Relict snakes of North America and their relationships within Caenophidia, using likelihood-based Bayesian methods on mitochondrial sequences.

This paper focuses on the phylogenetic relationships of eight North American caenophidian snake species (Carphophis amoena, Contia tenuis, Diadophis punctatus, Farancia abacura, Farancia erytrogramma, Heterodon nasicus, Heterodon platyrhinos, and Heterodon simus) whose phylogenetic relationships remain controversial. Past studies have referred to these "relict" North American snakes either as colubrid, or as Neotropical dipsadids and/or xenodontids. Based on mitochondrial DNA ribosomal gene sequences and a likelihood-based Bayesian analysis, our study suggests that these North American snakes are not monophyletic and are nested within a group (Dipsadoidea) that contains the Dipsadidae, Xenodontidae, and Natricidae. In addition, we use the relationships proposed here to highlight putative examples of parallel evolution of hemipenial morphology among snake clades.

Animals↗
PubMed2005

Sea snakes (Lapemis curtus) are sensitive to low-amplitude water motions.

The sea snake Lapemis curtus is a piscivorous predator that hunts at dusk. Like land snakes, sea snakes have scale sensillae that may be mechanoreceptive, i.e. that may be useful for the detection of water motions produced by prey fish. In addition, inner ear hair cells of sea snakes may also be involved in the detection of hydrodynamic stimuli. We generated water motions and pressure fluctuations with a vibrating sphere. In the test range 50-200 Hz evoked potentials were recorded from the midbrain of L. curtus in response to vibrating sphere stimuli. In terms of water displacement the lowest threshold amplitudes were in the frequency range 100-150 Hz. In this range peak-to-peak water displacement amplitudes of 1.8 microm (at 100 Hz) and 2.0 microm (150 Hz) generated a neural response in the most sensitive animal. Although this low sensitivity may be sufficient for the detection of fish-generated water motions, it makes it unlikely that L. curtus has a special hydrodynamic sense.

Animals↗
PubMed2003

Structural and functional analysis of BmjMIP, a phospholipase A2 myotoxin inhibitor protein from Bothrops moojeni snake plasma.

A protein, which neutralizes the enzymatic, toxic, and pharmacological activities of various basic and acidic phospholipases A(2) from the venoms of Bothrops moojeni, Bothrops pirajai, and Bothrops jararacussu, was isolated from B. moojeni snake plasma by affinity chromatography using immobilized myotoxins on Sepharose gel. Biochemical characterization of this myotoxin inhibitor protein (BmjMIP) showed it to be an oligomeric glycoprotein with a M(r) of 23,000-25,000 for the monomeric subunit. BmjMIP was stable in the pH range from 4.0 to 12.0, between 4 and 80 degrees C, even after deglycosylation. The role of the carbohydrate moiety was investigated and found not to affect the in vitro function of the inhibitor. The corresponding 500bp cDNA obtained by RT-PCR from the liver of the snake encodes a mature protein of 166 amino acid residues including a 19 amino acid signal peptide. The primary structure of BmjMIP showed a high similarity with other snake phospholipase A(2) inhibitors (PLIs) in which the carbohydrate recognition domain (CRD) and the glycosylation site (Asn103) are conserved. Circular dichroism spectroscopy indicated that no significant alterations in the secondary structure of either the BmjMIP or the target protein occur upon their interaction. BmjMIP has a wide range of inhibitory properties against basic and acidic PLA(2)s from Bothrops venoms (anti-enzymatic, anti-myotoxic, anti-edema inducing, anti-cytotoxic, anti-bactericidal, and anti-lethal). However, the inhibitor showed a reduced ability to neutralize the biological activities of crotoxin B (CB), the PLA(2) homologue associated with crotapotin in Crotalus durissus terrificus snake venom. Finally, the purified PLA(2) inhibitor was shown to protect in vivo against the toxic and pharmacological effects of a homologous PLA(2) enzyme, suggesting that PLIs or a corresponding derived peptide may prove useful in the treatment of snakebite victims or, more importantly, in the treatment of the many human diseases in which these enzymes have been implicated.

Amino Acid Sequence↗
PubMed2003

Adaptive evolution in the snake venom Kunitz/BPTI protein family.

Snake venoms are rich sources of serine proteinase inhibitors that are members of the Kunitz/BPTI (bovine pancreatic trypsin inhibitor) family. However, only a few of their gene sequences have been determined from snakes. We therefore cloned the cDNAs for the trypsin and chymotrypsin inhibitors from a Vipera ammodytes venom gland cDNA library. Phylogenetic analysis of these and other snake Kunitz/BPTI homologs shows the presence of three clusters, where sequences cluster by functional role. Analysis of the nucleotide sequences from the snake Kunitz/BPTI family shows that positive Darwinian selection was operating on the highly conserved BPTI fold, indicating that this family evolved by gene duplication and rapid diversification.

Amino Acid Sequence↗
PubMed1996

Accelerated evolution of crotalinae snake venom gland serine proteases.

Eight cDNAs encoding serine proteases isolated from Trimeresurus flavoviridis (habu snake) and T. gramineus (green habu snake) venom gland cDNA libraries showed that nonsynonymous nucleotide substitutions have accumulated in the mature protein-coding regions to cause amino acid changes. Southern blot analysis of T. flavoviridis genomic DNAs using two proper probes indicated that venom gland serine protease genes form a multigene family in the genome. These observations suggest that venom gland serine proteases have diversified their amino acid sequences in an accelerating manner. Since a similar feature has been previously discovered in crotalinae snake venom gland phospholipase A2 (PLA2) isozyme genes, accelerated evolution appears to be universal in plural isozyme families of crotalinae snake venom gland.

Amino Acid Sequence↗