Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Snakes”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed2002

Snake venom disintegrin, saxatilin, inhibits platelet aggregation, human umbilical vein endothelial cell proliferation, and smooth muscle cell migration.

A novel disintegrin, saxatilin, was purified from Korean snake (Gloydius saxatilis) venom by means of chromatographic fractionations. We have also isolated the cDNA encoding the disintegrin using cDNA library of the snake venom gland and analyzed its complete nucleotide sequence. Saxatilin is a single-chain polypeptide composed of 73 amino acids including 12 cysteines as well as the tripeptide sequence Arg-Gly-Asp (RGD), a proposed recognition site of adhesive proteins. Molecular mass of saxatilin was determined to be 7712 Da by matrix-assisted laser desorption ionization mass spectrometry. Saxatilin inhibits glycoprotein (GP) IIb-IIIa binding to immobilized fibrinogen with IC(50) of 2.0 nM and ADP-induced platelet aggregation with IC(50) of 127 nM, respectively. The snake venom disintegrin also significantly suppresses basic fibroblast growth factor-induced human umbilical vein endothelial cell (HUVEC) proliferation, but has little effect on normal growth of the cell. Interaction of human umbilical vein cell to immobilized vitronectin is also inhibited by binding of saxatilin to alpha(v)beta(3) integrin. Adhesion of smooth muscle cells (SMCs) to vitronectin as well as vitronectin-induced migration of the cells was strongly inhibited by saxatilin. Several lines of experimental evidence suggest potential use of saxatilin for development of therapeutic agents.

Animals↗
PubMed2002

Trimucytin, a collagen-like snake venom protein, activates platelets independent of I-domain within alpha2 subunit of alpha2beta1 integrin.

Trimucytin is a powerful platelet aggregation inducer isolated from the venom of Taiwan habu snake (Trimeresurus mucrosquamatus). In this study, we found that the snake venom protein, crovidisin, which prevents collagen-platelet interaction through its high-affinity binding to collagen, inhibited competitively trimucytin-induced aggregation of washed human platelets with a pA(2) value of 6.65. The ability of trimucytin in triggering platelet aggregation was suppressed by a monoclonal antibody (A2-IIE10) raised against the alpha2 subunit of alpha2beta1 integrin (glycoprotein Ia/IIa), indicating that platelet alpha2beta1 integrin plays a central role in trimucytin's platelet reactivity. Many studies have localized the major reactive site of alpha2beta1 integrin to the I-domain of alpha2 subunit. However, Escherichia coli-produced recombinant alpha2 I-domain (GST-alpha2 fusion protein) blocking collagen-induced platelet aggregation failed to inhibit aggregation of platelets in response to trimucytin. Based on these findings, it is concluded that the platelet reactivity of trimucytin is alpha2beta1 integrin-dependent, while the I-domain present in the alpha2 subunit is not involved. This novel snake venom protein would be useful for mapping the functional domain of alpha2beta1 integrin.

Animals↗
PubMed1998

Purification and molecular cloning of a platelet aggregation inhibitor from the snake (Agkistrodon halys brevicaudus) venom.

A platelet glycoprotein IIb-IIIa (GP IIb-IIIa) antagonist, salmosin, was purified to homogeneity from Korean snake (Agkistrodon halys brevicaudus) venom by means of chromatographic fractionations. We have isolated the cDNA encoding salmosin by using the cDNA library of the snake venom gland and analyzed its complete nucleotide sequence. The molecular identity was confirmed by comparison of the deduced amino acid sequence with the directly determined primary structure of salmosin. This protein is a single-chain polypeptide composed of 73 amino acids including 12 cysteines as well as the sequence Arg-Gly-Asp, a proposed recognition site of adhesive proteins. The primary sequence of salmosin shows considerable homology to previously described proteins of snake venom GP IIb-IIIa antagonist family. A molecular mass of 7474 for the protein was determined by matrix-assisted laser desorption ionization mass spectrometry. Salmosin inhibits GP IIb-IIIa binding to immobilized fibrinogen with an IC50 of 2.2 nM and ADP-induced platelet aggregation with an IC50 of 131 nM, respectively. This work demonstrates the purification, characterization, and cDNA cloning of salmosin, a platelet aggregation inhibitor that may have therapeutic potential as an antithrombotic agent.

Agkistrodon↗
PubMed2002

Herding and snaking by the harem stallion in domestic herds.

Four herds of pony mares, each consisting of a stallion and six mares, were used to characterize the nature of herding by the stallion and the factors that induced the herding behavior. Herding behaviors were compared among four successive treatments (six mares alone, stallion added, two new mares added, and entire herd moved to a new pasture). A new treatment was initiated every 7 days and behavior was studied for 5 consecutive days (Days 1-5) for each treatment. Observations were made every 10 min during a 2-h period for each day. The extent of herding was quantitated by the mean distances between mares. The extent of snaking (herding with the head and neck extended and ears held back) was scored 0, 1, 2, or 3 (nil, minimal, intermediate, and maximal, respectively). The mean distance among the original mares on Day 1 when the mares were alone was 5.0 mare lengths and was reduced (P < 0.05) to 1.9 mare lengths when the stallion was added. The mean distance among the original mares of an established stallion/mare herd (3.8 mare lengths) was reduced (P < 0.05) on the day the herd was moved to a new pasture (1.9 mare lengths), similar to the effect of the introduction of the stallion. Scores for the extent of snaking, as well as the extent of herding, were highest (P < 0.05) on Day 1 when the stallion was added or the stallion/mare herd was moved to a new pasture. The extent of herding and snaking decreased (P < 0.05) by Day 2 and was seen only occasionally on Days 3-5. The addition of new mares to the herd did not induce herding of the original mares. However, the new mares maintained mean distances of 8-12 mare lengths from the original mares, resulting primarily from chasing by the stallion. By Day 4, the distances between the new and original mares were not different (P > 0.05) from the distances among the original mares.

Animals↗
PubMed2000

Nice snake, shame about the legs.

Snakes are one of the most extraordinary groups of terrestrial vertebrates, with numerous specializations distinguishing them from other squamates (lizards and their allies). Their musculoskeletal system allows creeping, burrowing, swimming and even gliding, and their predatory habits are aided by chemo- and thermoreceptors, an extraordinary degree of cranial kinesis and, sometimes, powerful venoms. Recent discoveries of indisputable early fossil snakes with posterior legs are generating intense debate about the evolutionary origin of these reptiles. New cladistic analyses dispute the precise significance and phylogenetic placement of these fossils. These conflicting hypotheses imply radically different scenarios of snake origins and relationships with wide biological implications.

Journal Article↗
PubMed2002

Response of the infrared receptors of a crotaline snake to ethanol.

The pit organs of crotaline snakes can sense infrared (IR). The pit membrane has a finer, flatter, more convoluted vasculature than other sensory organs. Using extracellular recording from IR-sensitive trigeminal ganglion (TG) neurons (primary neurons) and tectal (OT) neurons of the crotaline snake Trimeresurus flavoviridis, we examined the IR response to ethanol (EtOH) in vivo. The response to EtOH was recorded in the TG and OT 20-80 s after 10% EtOH in Ringer's solution (100 microl/ 500 g body weight) was injected via the heart. The responses to EtOH and those to lower or higher temperature stimulation were additive. At a constant temperature (25 degrees C), EtOH significantly potentiated the IR-triggered discharges of IR-sensory pathways in this snake. These results suggest that the IR response to EtOH is due to either its vasodilatory effect on the abundant vasculature of the pit membrane or its chemical effect on temperature-sensitive receptors.

Action Potentials↗
PubMed2002

Distribution of aromatase immunoreactivity in the forebrain of red-sided garter snakes at the beginning of the winter dormancy.

Until recently, it has been difficult to identify the exact location of aromatase containing cells in the brain. The development of new antibodies has provided a sensitive tool to analyze the distribution of aromatase immunoreactive (ARO-ir) material at a cellular level of resolution. In the present study we examined, for the first time, the distribution of ARO-ir cells in the brain of a reptile, the red-sided garter snake, at the beginning of the winter dormancy. ARO-ir cells were found at all rostro-caudal levels in the red-sided garter snake brain. Although weakly stained cells were distributed throughout the brain, more intensely immunoreactive cells were primarily concentrated in the preoptic area, anterior hypothalamus, septum and nucleus sphericus. Although androgens are elevated upon emergence from hibernation in the male red-sided garter snake, initiation of courtship behavior appears to be independent of direct androgen control. To date, the only known stimulus found to initiate courtship is a period of low temperature dormancy followed by exposure to warm temperatures. Circumstantial data, however, suggest an indirect role in the activation of male copulatory behavior for estrogenic metabolites of testosterone produced in the brain by aromatization during the winter dormancy. This study provides the first documentation of the distribution of ARO-ir cells in a reptilian species and demonstrates that while the aromatase enzyme occurs in most regions of the brain, the ARO-ir cells that appear to contain the highest concentration of enzyme are clustered in brain areas classically associated with the control of courtship behavior and mating in vertebrates. These data are consistent with the idea that estrogens locally produced in the brain may participate in some way to the activation of sexual behavior in this species also. This notion should now be experimentally tested by analyzing annual changes in aromatase activity and immunoreactivity and assessing the effects of pharmacological blockade of the enzyme activity at different times of the year.

Animals↗
PubMed2003

Expression, refolding, and in vitro activation of a recombinant snake venom pro-metalloprotease.

Metalloproteases comprise a family of Zn(2+)-endopeptidases that degrade most components of the extracellular matrix. Snake venoms are rich sources of metalloproteases, which also digest fibrinogen as well as fibrin, and in some cases, induce hemorrhage. A few low-molecular weight snake venom metalloproteases (svMPs) have been described as being devoid of hemorrhagic activity, but they have strong direct-acting fibrinolytic activity. This property could be very helpful in thrombosis therapy. ACLF is a fibrinolytic, non-hemorrhagic metalloprotease from the venom of the North American snake Agkistrodon contortrix laticinctus. We have developed an expression system for production of a recombinant pro-ACLF from a clone (ACLPREF) isolated from a venom gland cDNA library. The coding region including both the pro-enzyme domain and the mature protein domain was amplified by PCR and subcloned into the pET28a vector and the new plasmid was used to transform BL21(DE3) Escherichia coli cells. Culture of the transformants at 37 degrees C led to the overexpression of an insoluble 48kDa protein after induction with 1.0mM IPTG. The expressed protein was recovered from inclusion bodies with 6M buffered urea and purified by affinity chromatography under denaturing conditions. After dithiothreitol treatment, protein refolding was performed by gradual removal of the denaturing agent by dialysis. The pro-enzyme underwent auto-activation during refolding and it was active on fibrinogen and on a synthetic substrate. To control the activation step, the denaturing agent was rapidly removed to keep the protein in an unprocessed form, followed by later addition of Ca(2+) and Zn(2+) ions. This allowed controlling the enzyme activation, when it is needed.

Agkistrodon↗
PubMed2003

Cloning and expression of calglandulin, a new EF-hand protein from the venom glands of Bothrops insularis snake in E. coli.

The EF-hand protein family is comprised of many proteins with conserved Ca(2+)-binding motifs with important biological roles in intracellular communication. During the generation of Expressed Sequence Tags (ESTs) from the venom glands of the Viperidae snake Bothrops insularis, we identified a cDNA coding for a putative Ca(2+) binding protein with four EF-hand motifs, named here calglandulin. The deduced amino acid sequence displayed the greatest sequence similarity with calmodulin (59%), followed by troponin-C (52%). The encoded polypeptide was first expressed in Escherichia coli as a 6XHis-tagged fusion protein. The expressed protein was purified by Ni(2+)-charged affinity chromatography and circular dichroism (CD) spectroscopy confirmed the prevalence of alpha-helix as observed in calmodulin/calmodulin-like proteins. A polyclonal antiserum was generated in mice using this recombinant calglandulin. To investigate the tissue-specific biological occurrence of this protein, this antiserum was used in Western blot experiments, which revealed an immunoreactive band in samples of venom gland extracts from different snakes, but not in the crude venom or in brain, heart and other tissues. This exclusive occurrence suggests a specialized function of calglandulin in snake venom glands.

Amino Acid Sequence↗
PubMed2003

Subunit dissociation, unfolding, and inactivation of bothrojaracin, a C-type lectin-like protein from snake venom.

Snake venoms contain a large number of hemostatically active proteins that are structurally related to Ca(2+)-dependent animal lectins. These proteins, called C-type lectin-like proteins (CLPs), are generally found as heterodimers composed of two homologous subunits linked by a disulfide bond. Here, bothrojaracin (BJC), a CLP from Bothrops jararaca venom that is also a thrombin inhibitor, has been used as a model to study the subunit dissociation and unfolding of CLPs from snake venom. Dithiothreitol (DTT) up to 10 mM produces minor effects on the tertiary structure and activity of BJC. On the other hand, chromatographic studies and fluorescence polarization measurements indicate that the interchain disulfide bond is disrupted by DTT, although the dimeric association is maintained. Treatment of BJC with urea produces a progressive red shift in the emission spectra of the tryptophan residues, and circular dichroism measurements show that BJC retains significant secondary structure in the presence of 8 M urea, suggesting only partial unfolding. The effects of urea are fully reversible, as there is complete recovery of BJC activity after removal of the denaturing agent. Addition of DTT to a protein sample previously treated with 8 M urea produces a slightly larger spectral shift than that observed with urea alone. Furthermore, in this condition BJC loses its secondary structure, and its subunits are dissociated. After removal of urea and DTT, BJC is inactive toward thrombin, suggesting the irreversibility of their combined action. Altogether, our data show that (i) BJC is highly resistant to urea or DTT effects, requiring the simultaneous action of both agents to fully denature the protein, and (ii) BJC monomers are tightly associated, and the presence of DTT combined with high urea concentrations is necessary to disrupt them. On the basis of these results we propose the first denaturation model for a CLP from snake venom.

Animals↗
PubMed1998

The length of a single turn controls the overall folding rate of "three-fingered" snake toxins.

Snake curaremimetic toxins are short all-beta proteins, containing several disulfide bonds which largely contribute to their stability. The four disulfides present in snake toxins make a "disulfide beta-cross"-fold that was suggested to be a good protein folding template. Previous studies on the refolding of snake toxins (Ménez, A. et al. (1980) Biochemistry 19, 4166-4172) showed that this set of natural homologous proteins displays different rates of refolding. These studies suggested that the observed different rates could be correlated to the length of turn 2, one out of five turns present in the toxins structure and close to the "disulfide beta-cross". To demonstrate this hypothesis, we studied the refolding pathways and kinetics of two natural isotoxins, toxin alpha (Naja nigricollis) and erabutoxin b (Laticauda semifasciata), and two synthetic homologues, the alpha mutants, alpha60 and alpha62. These mutants were designed to probe the peculiar role of the turn 2 on the refolding process by deletion or insertion of one residue in the turn length that reproduced the natural heterogeneity at that locus. The refolding was studied by electrospray mass spectrometry (ESMS) time-course analysis. This analysis permitted both the identification and quantitation of the population of intermediates present during the process. All toxins were shown to share the same sequential scheme for disulfide bond formation despite large differences in their refolding rates. The results presented here demonstrate definitely that no residues except those forming turn 2 accounted for the observed differences in the refolding rate of toxins.

Alkylation↗
PubMed2001

Pheromone trailing behavior of the brown tree snake, Boiga irregularis.

The ability of snakes to follow pheromone trails has significant consequences for survival and reproduction. Of particular importance is the ability of snakes to locate conspecifics during the breeding season via the detection of pheromone trails. In this study, the ability of male brown tree snakes (Boiga irregularis), a tropical, rear-fanged colubrid, to follow pheromone trails produced by reproductively active conspecifics was tested in the laboratory by using a Y maze. Males displayed a trailing response to both female and male pheromone trails over blank controls. As males of this species display ritualized combat behavior, these responses likely represent both direct and indirect mechanisms, respectively, for the location of potential mates in the wild. Males did not, however, discriminate between male and female trails when given a choice on the Y maze.

Aggression↗
PubMed2003

Pheromonally mediated sexual isolation among denning populations of red-sided garter snakes, Thamnophis sirtalis parietalis.

Utilizing behavioral experiments and chemical analyses, we examined whether pheromonally mediated sexual isolation exists between denning populations of red-sided garter snakes (Thamtnophis sirtalis parietalis) in Manitoba, Canada. Simultaneous choice tests conducted during the breeding season revealed that adult males from a hibernaculum in central Manitoba displayed a strong courtship preference for females from their own population over females from a hibernaculum in western Manitoba, whereas males from the western Manitoba hibernaculum showed no such preference. In addition. trailing experiments testing the response of males from the two hibernacula to familiar and unfamiliar female trails showed similar results, demonstrating that the observed male preference is mediated through chemical cues. Subsequent chemical analysis of the female sexual attractiveness pheromone. a homologous series of long-chain saturated and (omega-9 cis-unsaturated methyl ketones responsible for eliciting male courtship behavior and trailing behavior in garter snakes, showed significant variation in the composition of the pheromone between the two populations. Specifically, the two populations varied in the relative concentrations of individual unsaturated methyl ketones expressed by females. These results suggest that sexual isolation exists to a degree among denning populations of red-sided garter snakes due to variation in the expression of the female sexual attractiveness pheromone.

Animals↗
PubMedDate not supplied

The nerve-muscle synapse of the garter snake.

Snake nerve-muscle preparations are well-suited for study of both motor innervation patterns at the systems level and NMJ function at the cellular level. Their small size ( approximately 100 myofibers) and thinness (one fiber) allows access to all NMJs in one muscle. Snake NMJs are of three types, two twitch subtypes and a single tonic type. Properties of the NMJs supplied by a particular motor neuron, and of the motor unit fibers they innervate, are precisely regulated by the motor neuron in a manner consistent with the Henneman Size Principle. Unlike its amphibian or mammalian cousins, the snake NMJ comprises approximately 50 (twitch) or approximately 20 (tonic) individual one-bouton synapses, similar to synapses found in the central nervous system. Each bouton releases a few quanta per stimulus. Larger fibers, which require more synaptic current to initiate contraction, receive nerve terminals that contain more boutons and express receptor patches with higher sensitivity to transmitter. Quantal analysis suggests that transmitter release sites in one bouton do not behave independently; rather, they may cooperate to reduce fluctuations and enhance reliability. After release, two mechanisms coexist for retrieval and reprocessing of spent vesicles-one involving clathrin-mediated endocytosis, the other macropinocytosis. Unanswered questions include how each mechanism is regulated in a use-dependent manner.

Animals↗
PubMed2002

Snake circumvents constraints on prey size.

For animals who are unable to take bites out of their food, the size of the food item that can be consumed is constrained by the maximal size of the mouth opening (gape)--snakes are an example of gape-limited predators and they usually swallow their prey whole. Here we describe unique feeding behaviours in two closely related species of snake, which circumvent their gape limitation by removing and consuming pieces from newly moulted crabs that are too large to be swallowed intact. This evolutionary innovation is surprising, as the needle-like teeth and highly mobile bones that facilitate the capture and engulfment of large, whole prey by snakes are ill-suited both to cutting and to generating large bite forces.

Animals↗
PubMed2005

Postmortem study of the spinal cord showing snake-eyes appearance due to damage by ossification of the posterior longitudinal ligament and kyphotic deformity.

UNLABELLED: CLINICAL DESIGN: A case report. OBJECTIVES: To elucidate the clinical role of snake-eyes appearance in this case, correlation between radiological, clinical and postmortem study was performed. SETTING: Aichi, Japan. CASE REPORT: A 73-year-old man developed weakness and pain in the upper limbs due to kyphotic deformity secondary to laminectomy for cervical ossification of the posterior longitudinal ligament. Axial magnetic resonance imaging revealed snake-eyes appearance from C4 to C6. He died of acute myocardial infarction 3 months after anterior decompressive surgery. RESULTS: A postmortem examination of the cervical spinal cord showed small cystic six necrotic areas at the junction of the central gray matter and the ventrolateral posterior column, one in the right and one in the left, in association with neuronal loss in the anterior horn. CONCLUSIONS: Bilateral small intramedullary high-signal areas known as 'snake-eyes appearance' located around the central gray matter and the ventrolateral posterior column, are associated with neuronal loss in the compressed anterior horn that played an important role in worsening weakness of the upper limbs.

Aged↗
PubMed1978

Three neurotoxins from the venom of a sea snake Astrotia stokesii, including two long-chain neurotoxic proteins with amidated C-termini.

From the venom of a sea snake Astrotia stokesii three neurotoxic components, toxins Astrotia stokesii a, b and c were isolated in 40, 15 and 5% yield by weight respectively of the whole venom. Their LD50 values for 20g mice were 0.13, 0.096 and 0.098 microgram/g body wt. respectively and accounted for almost all the lethal activity of the venom. Their amino acid sequences were determined. Astrotia stokesii a was composed of 60 amino acid residues with nine half-cystine residues and was quite homologous to other sea-snake short-chain neurotoxins in its amino acid sequence. Toxins Astrotia stokesii b and c were composed of 70 and 72 amino acid residues respectively with 10 half-cystine residues. They are the first long-chain neurotoxins with high activity isolated from sea-snake venoms. The C-terminal carboxy groups of toxins b and c were found to be amidated; the amidation is known for some polypeptides, but is novel for a protein. The amide group may make a hydrogen-bond with glutamic acid-39, which replaces a lysine that has so far been found invariably in long-chain neutrotoxins. Astrotia stokesii b and c are also novel in having phenylalanine-25 and isoleucine- or valine-42. The ordinary Tyr-Glu pair, which is observed in X-ray structure [Low, Preston, Sato, Rosen, Searl, Rudko & Richardson (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2991-2994] and n.m.r.study [Inagaki, Tatsumi, Miyazawa, Hori & Tamiya (1977) Abstr. Int. Congr. Pure Appl. Chem. 26th, p. 336] on erabutoxins may be replaced by a hydrophobic pair. Detailed evidence for the amino acid sequences of the proteins has been deposited as Supplementary Publication SUP 5009o (30 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7B1, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.

Amides↗
PubMed2004

Proteomic characterization of two snake venoms: Naja naja atra and Agkistrodon halys.

Snake venom is a complex mixture of proteins and peptides, and a number of studies have described the biological properties of several venomous proteins. Nevertheless, a complete proteomic profile of venom from any of the many species of snake is not available. Proteomics now makes it possible to globally identify proteins from a complex mixture. To assess the venom proteomic profiles from Naja naja atra and Agkistrodon halys, snakes common to southern China, we used a combination strategy, which included the following four different approaches: (i) shotgun digestion plus HPLC with ion-trap tandem MS, (ii) one-dimensional SDS/PAGE plus HPLC with tandem MS, (iii) gel filtration plus HPLC with tandem MS and (iv) gel filtration and 2DE (two-dimensional gel electrophoresis) plus MALDI-TOF (matrix-assisted laser desorption ionization-time-of-flight) MS. In the present paper, we report the novel identification of 124 and 74 proteins and peptides in cobra and viper venom respectively. Functional analysis based upon toxin categories reveals that, as expected, cobra venom has a high abundance of cardio- and neurotoxins, whereas viper venom contains a significant amount of haemotoxins and metalloproteinases. Although approx. 80% of gel spots from 2DE displayed high-quality MALDI-TOF-MS spectra, only 50% of these spots were confirmed to be venom proteins, which is more than likely to be a result of incomplete protein databases. Interestingly, these data suggest that post-translational modification may be a significant characteristic of venomous proteins.

Agkistrodon↗