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 703 records · Page 39Linked to original sources
PubMed1996

Purification and characterization of bitiscetin, a novel von Willebrand factor modulator protein from Bitis arietans snake venom.

We have screened 20 snake venoms and purified a novel snake venom protein, named bitiscetin, from Bitis arietans venom that specifically binds to human von Willebrand factor (vWF) and induces platelet agglutination. Bitiscetin showed a heterodimeric structure composed of disulfide-linked alpha (16kDa) and beta (13kDa) subunits on SDS-PAGE and showed a basic nature with pI value of 9.1, in contrast to botrocetin (pI 4.6), a vWF modulator isolated from another snake (Bothrops jararaca) venom. Bitiscetin-induced platelet agglutination was dependent on vWF and platelet membrane glycoprotein (GP) Ib, but not on Ca2+ and GPIIb/IIIa. vWF bound to bitiscetin but not to botrocetin electroblotted to a PVDF membrane after SDS-PAGE and this binding was diminished after reduction of disulfide bonds of bitiscetin. Bitiscetin did not cross-react to anti-botrocetin monoclonal antibodies. These results suggest that bitiscetin directly interacts with vWF and requires the protein conformation for its interaction as well as botrocetin, but its interaction manner with vWF appears to be different from that of botrocetin.

Amino Acid Sequence↗
PubMed1998

AMP activation of snake muscle fructose 1,6-bisphosphatase at alkaline pH.

AMP, an allosteric inhibitor at neutral pH, activates snakes muscle fructose 1,6-bisphosphatase at pH 9.2. The activation is virtually unique for the snake muscle enzyme: activation was not observed for the enzymes from either human and rabbit liver or porcine kidney. The activation is Mg(2+)-dependent but was not observed until the concentration of Mg2+ reaches 1 mM. It is known that subtilisin, trypsin, or lysosomal proteases hydrolyse the N-terminal loop of fructose-1,6-bisphosphatase in the vicinity of amino acid residue 60 generating a form of the enzyme with a pH optimum at 9.2. In the presence of AMP, the pH profile of the native snake muscle enzyme resembles that of the alkaline form and modification of the highly reactive sulfhydryl group abolishes AMP activation. The fact that AMP has a dual function at different pH levels suggests that pH might be an important factor in regulating the activity of the enzyme upon binding of AMP at the allosteric site. Indeed, the mode of AMP binding to the allosteric site may differ at neutral and alkaline pH levels. A residue that ionizes with a pKa of 8.9 might be involved in this process.

Adenosine Monophosphate↗
PubMed1999

Comparison of three classes of snake neurotoxins by homology modeling and computer simulation graphics.

We present a systematic structure comparison of three major classes of postsynaptic snake toxins, which include short and long chain alpha-type neurotoxins plus one angusticeps-type toxin of black mamba snake family. Two novel alpha-type neurotoxins isolated from Taiwan cobra (Naja naja atra) possessing distinct primary sequences and different postsynaptic neurotoxicities were taken as exemplars for short and long chain neurotoxins and compared with the major lethal short-chain neurotoxin in the same venom, i.e., cobrotoxin, based on the derived three-dimensional structure of this toxin in solution by NMR spectroscopy. A structure comparison among these two alpha-neurotoxins and angusticeps-type toxin (denoted as FS2) was carried out by the secondary-structure prediction together with computer homology-modeling based on multiple sequence alignment of their primary sequences and established NMR structures of cobrotoxin and FS2. It is of interest to find that upon pairwise superpositions of these modeled three-dimensional polypeptide chains, distinct differences in the overall peptide flexibility and interior microenvironment between these toxins can be detected along the three constituting polypeptide loops, which may reflect some intrinsic differences in the surface hydrophobicity of several hydrophobic peptide segments present on the surface loops of these toxin molecules as revealed by hydropathy profiles. Construction of a phylogenetic tree for these structurally related and functionally distinct toxins corroborates that all long and short toxins present in diverse snake families are evolutionarily related to each other, supposedly derived from an ancestral polypeptide by gene duplication and subsequent mutational substitutions leading to divergence of multiple three-loop toxin peptides.

Amino Acid Sequence↗
PubMed1992

Trace element levels in pine snake hatchlings: tissue and temporal differences.

Trace element levels have seldom been examined in reptiles, although some large snakes are high on the trophic level pyramid. Lead, cadmium, mercury, selenium, chromium and manganese levels were examined in skin and whole body tissue of pine snakes (Pituophis melanoleucus) from the New Jersey Pine Barrens between 1985-1990. Depending on the element, variations in levels were primarily explained by year and tissue, and not by sex or location. There were significantly higher levels of lead, mercury, and chromium in the skin compared to the whole body tissue, suggesting that the frequent shedding of skin can act as a method of toxic metal excretion by snakes. Manganese and selenium levels were significantly higher in the body compared to the skin.

Animals↗
PubMed1996

Blood vessel adaptation to gravity in a semi-arboreal snake.

The effects of vasoactive agonists on systemic blood vessels were examined with respect to anatomical location and gravity acclimation in the semi-arboreal snake, Elaphe Obsoleta. Major blood vessels were reactive to putative neurotransmitters, hormones or local factors in vessel specific patterns. Catecholamines, adenosine triphosphate, histamine and high potassium (80 mM) stimulated significantly greater tension per unit vessel mass in posterior than anterior arteries. Anterior vessels were significantly more sensitive to catecholamines than midbody and posterior vessels. Angiotensin II stimulated significantly greater tension in carotid artery than in midbody and posterior dorsal aorta. Arginine vasotocin strongly contracted the left and right aortic arches and anterior dorsal aorta. Veins were strongly contracted by catecholamines, high potassium and angiotensin II, but less so by adenosine triphosphate, arginine vasotocin and histamine. Precontracted vessel were relaxed by acetylcholine and sodium nitroprusside, but not by atrial natriuretic peptide or bradykinin. Chronic exposure of snakes to intermittent hypergravity stress ( + 1.5 Gz at tail) did not affect the majority of vessel responses. These data demonstrate that in vitro tension correlates with that catecholamines, as well as other agonists, are important in mediating vascular responses to gravitational stresses in snakes.

Adaptation, Physiological↗
PubMed1990

Coagulopathy after snake bite by Bothrops neuwiedi: case report and results of in vitro experiments.

Coagulation studies were performed in a patient who had been bitten by a snake of the species Bothrops neuwiedi. The patient presented with hemorrhagic necrosis at the envenomization site and considerable bleeding from venous puncture sites. He developed a severe defibrination syndrome with a clottable fibrinogen level of approximately 0.1 g/l. Fibrinogen was not measurable by clotting time assay. Fibrin degradation products were greatly elevated. Treatment with antivenom caused an anaphylactic reaction within ten minutes and serum sickness after three days. In vitro experiments revealed that B. neuwiedi venom directly activates Factors II and X, but does not activate Factor XIII. In vivo consumption of Factor XIII after B. neuwiedi envenomization is ascribed to the action of Factor IIa. At low venom concentrations clotting is initiated by activation of prothrombin by the venom either directly or via Factor X activation. Treatment with heparin might be beneficial in coagulopathy secondary to snake bite by reducing circulating active thrombin. The venom contains thrombin-like proteases which cause slow clotting of fibrinogen, and plasmin-like components causing further proteolysis of fibrinogen and fibrin. Antivenom has no effect on the proteolytic action of the snake venom. The in vivo effects of antivenom are presumably caused by acceleration of the elimination of venom components from the circulation. Intravenous administration of antivenom caused normalization of blood coagulation parameters within 48 h.

Adult↗
PubMed1979

Haemoglobin Bohr effect and lactic acid content of the blood of 2 water-snakes with different degrees of aquatic adaptation.

H. modestus, a water-snake with morphological respiratory adaptation to its habitat, presents haemoglobins with a lower Bohr effect than those of L. miliaris, an aquatic snake without such respiratory adaptations. The difference in blood lactic acid content of the 2 snakes submitted to mechanical stimuli appears to be compatible with the properties of their haemoglobins.

Adaptation, Physiological↗
PubMed1977

Snake venom action: are enzymes involved in it?

Enzymes were the first clearly recognized components of snake venoms. When several more were discovered, attempts were made to correlate venom action with enzymic functions. The last few years have seen most successful efforts in the identification, isolation and structrual elucidation of highly toxic polypeptides present in snake venoms, in particular of 'neurotoxins' and membrane-active toxins. Following this development the polypeptides were called the true toxic components and the enzymes lost their previous central position in venom pharmacology. The time, therefore, has come re-evaluate the role of enzymes in the complex interaction between snake and prey. While highly active polypeptides indeed dominate the actionof hydrophiid venoms, they appear to play a lesser role in crotalid venom action as compared with enzyme components. Enzymes are involved in many levels of venom action, e.g. by serving as spreading factors, of by producing very active agents, such as bradykinin and lysolecithins in tissues of preys or predators. Some toxins, e.g. the membrane-active polypeptides appear to participate in the interaction between membrane phospholipids and venom phospholipases. The classical neurotoxin, beta-bungarotoxin, has been recognized as a powerful phospholipase. Several instances are known which indicate that some enzymes potentiate the toxic action of others; the analysis of a single enzyme may, therefore, not fully reveal its biofunction. For 3 enzymes,ophidian L-amino acid oxicase, ATPpyrophosphatase, and acetylcholinesterase, some of the problems pertaining to venom toxicity are discussed.

Acetylcholinesterase↗
PubMed1998

What have snakes taught us about integrins?

Snake venoms contain unique components that affect cell-matrix interactions. Disintegrins represent a class of low molecular weight, Arg-Gly-Asp (RGD)-containing, cysteine-rich peptides purified from the venom of various snakes among the Viperidae and Crotalidae. They bind with various degrees of specificity to integrins alpha IIb beta 3, alpha 5 beta 1 and alpha V beta 3 expressed on cells. Snake venom metalloproteases (high molecular mass haemorrhagins) also contain disintegrin-like domains, in addition to zinc-chelating sequences. Membrane-anchored ADAMs (A Disintegrin And Metalloprotease domain), multidomain molecules consisting of metalloprotease, disintegrin-like, cysteine-rich, and epidermal growth factor domains, a transmembrane domain and a cytoplasmic tail, are a new family of proteins. In the light of the large number and wide distribution of ADAMs, they may participate in cell-cell fusion events, including sperm-egg binding and fusion, myoblast fusion and other cell-cell and cell-matrix interactions. The structure-function relationship of these molecules is discussed.

Amino Acid Sequence↗
PubMed2005

Therapeutic effects and possible mechanisms of a snake venom preparation in the fibrotic rat liver.

The effects of a Chinese snake venom preparation from Agkistrodon halys pallas, used for treatment of hepatic fibrosis/cirrhosis in China, was investigated in an in vivo rat model and using in situ hepatic perfusion. Four groups were used in the experiments: (i) healthy, (ii) healthy/venom-treated, (iii) carbon tetrachloride (CCl4)-treated, and (iv) CCl4/venom-treated. Treatment effects were assessed by determining hepatic histopathology, biochemistry and fibrosis index parameters, bile production, biliary taurocholate recovery, hepatic mRNA expression of four bile salt transporters (Ntcp, Bsep, Oatp-1, and Oatp-3), comparison of hepatic microcirculation, fibrinolytic activity, and antithrombotic effects. Liver histopathology, biochemistry, and fibrosis index showed a dramatic improvement in venom-treated animals. There were significant differences in bile production between healthy/venom-treated and all other experimental groups and between CCl4/venom-treated and CCl4-treated animals, but no significant differences were found between CCl4/venom-treated and healthy animals. Biliary taurocholate recovery was significantly increased in healthy/venom-treated and CCl4/venom-treated animals. The expression of mRNA levels of the four bile salt transporters showed an increase after venom treatment. The hepatic microcirculation studies showed normalized sinusoidal beds in CCl4/venom-treated animals compared to healthy animals, whereas CCl4-treated animals showed abnormal profiles to the healthy and the CCl4/AHPV-treated animals. The fibrinogen and plasma thromboxane B2 levels of healthy rats decreased with increasing dose after venom treatment. It was concluded that snake venom treatment may be therapeutic in treatment of hepatic fibrosis/cirrhosis by possibly a combination of increased bile flow and improved hepatic microcirculation, changes in bile salt transporter expression, and fibrinolytic and antithrombotic effects of the snake venom preparation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1989

Inhibition of red cell Ca2+-dependent K+ channels by snake venoms.

We have investigated the effects of several snake venoms on the Ca2+-dependent K+ channels of human red cells. A heat-resistant component of the venom of the snake Notechis scutatus irreversibly inhibited Ca2+-dependent K+ transport with a Ki value of 0.1-0.2 micrograms/ml. Metabolic changes of the cells modified the maximal effect of the venom. Binding of the venom required extracellular Ca2+ and was quick, but development of full inhibition required additional time. The effects of the venoms from Notechis scutatus and Leiurus quinquestriatus were additive, suggesting that both venoms act through different mechanisms. Venoms of the snakes Vipera russelli russelli and Oxyuranus scutellatus also inhibited Ca2+-dependent K+ transport with the same characteristics as the Notechis scutatus venom.

Biological Transport↗
PubMed1987

The primary optic system in a microphthalmic snake (Calabaria reinhardti).

The retinal projections in the microphthalmic snake Calabaria reinhardti were investigated by means of the radioautographic method following intraocular injections of [3H]proline. The results demonstrated the existence of a general pattern of organization of the primary visual system comparable to that observed in macrophthalmic snakes. However, most of the primary optic centers appeared reduced and showed varying signs of atrophy, whereas others were completely absent. Elsewhere, the ipsilateral visual component appeared as well developed as that found in macrophthalmic snakes. The evolutionary significance of the differential microphthalmic pattern of organization of the primary visual system is discussed.

Animals↗
PubMed1986

Blood pressure homeostasis in the snake, Ptyas korros.

Three putative pressor systems, the alpha-adrenergic system (AS), the renin angiotensin system (RAS), and the arginine vasotocin system (AVT-S), were studied for their roles in blood pressure regulation and their possible interactions in the rat snake. Ptyas korros. Norepinephrine (NE), angiotensin I (ANG I), and arginine vasotocin (AVT) increased the mean arterial pressure (MAP) of the snake while administration of phentolamine, an alpha-adrenergic antagonist, and captopril, an ANG-converting enzyme inhibitor, but not KBIV24, an AVT antagonist, decreased the MAP. Treatment with any combination of two of these antagonists/inhibitor invariably decreased the MAP. Treatment with the agonist of the remaining third system invariably returned the MAP to normal or above. Phentolamine and KBIV24 attenuated the vasopressor effect of ANG I. Phentolamine and captopril enhanced the vasopressor effect of AVT. The pressor effect of NE was not altered by KBIV24 and captopril. It was concluded that there were at least two pressor systems (AS and RAS) regulating the basal MAP in the snake. There was also interaction among the three systems which could affect the MAP.

Angiotensin I↗
PubMed1990

Neurohypophysial hormones and cardiac activity in the frog, Rana tigrina, and in the snake, Ptyas mucosa.

The cardiac effects of neurohypophysial hormones (NH) in the frog, Rana tigrina, and in the snake, Ptyas mucosa, were studied in isolated atrial preparations. Arginine vasopressin (AVP), vasotocin (AVT), isotocin (ISN), mesotocin (MSN), and oxytocin (OXY) produced dose-related positive chronotropic and inotropic responses in the frog atria. AVT was the most potent. In the snake, AVP, AVT, MSN, and OXY produced dose-related positive inotropic but not chronotropic changes. OXY was the most potent. Data indicate that there is a direct action of NH on the heart in both animals, the atrial rate and tension responses to NH are not coupled, and judging by the efficacy, AVT and OXY might be the natural NH in the frog and snake, respectively, which may account for the high concentrations required of other NH to be cardiac stimulating.

Animals↗
PubMed1984

Hormonal independence of courtship behavior in the male garter snake.

Garter snakes exhibit a dissociated reproductive tactic in which gonadal activity is minimal at the time of mating, increasing only after the breeding season has ended. Experiments are presented demonstrating that neither short-term nor longterm castration affects courtship behavior in adult male red-sided garter snakes (Thamnophis sirtalis parietalis). So long as males have passed through a low-temperature dormancy period (hibernation), castration either shortly after emergence in the spring, or before entering winter dormancy in the fall, does not prevent the display of intense courtship behavior on emergence. Similarly, males castrated during mating activity the previous spring prior to the annual testicular growth phase actively courted females on emergence from hibernation. Males adrenalectomized and castrated during low-temperature dormancy also courted females on emergence. Hypophysectomy during or before low-temperature dormancy did not prevent males from displaying high-intensity courtship behavior on emergence from hibernation. Treatment with sex steroid hormones, as well as hypothalamic and pituitary hormones, and a variety of neural and metabolic affectors also fails to elicit courtship behavior in noncourting males during the summer. It was concluded that causal mechanisms controlling courtship behavior in the red-sided garter snake are fundamentally different, at least at the physiological level, from those mechanisms described for many laboratory and domesticated species.

Adrenal Glands↗
PubMed1985

Role of the anterior hypothalamus-preoptic area in the regulation of courtship behavior in the male Canadian red-sided garter snake (Thamnophis sirtalis parietalis): intracranial implantation experiments.

Testosterone (T) was administered intracranially to intact adult male Canadian red-sided garter snakes (Thamnophis sirtalis parietalis) in the fall and in the summer. Implants in the anterior hypothalamus-preoptic area (AH-POA) as well as other regions of the brain, including the medial and basal hypothalamus, thalamus, medial cortex, and third ventricle, failed to elicit courtship behavior. The spermatogenic stage was more advanced, and the circulating level of androgens was significantly higher, in animals that received implants of T in the AH-POA. These findings suggest the sex steroid-concentrating sites in the AH-POA of the garter snake are involved in feedback regulation of pituitary gonadotropin secretion and not in the control of courtship behavior. Hematocrit was found to be higher in animals that received implants of T, regardless of location, a response that may be related to changes in blood chemistry prior to hibernation. These findings support previous research indicating that in the adult male red-sided garter snake, a species exhibiting a dissociated reproductive tactic, courtship behavior is independent of testicular androgens.

Androgens↗
PubMed1983

Infectious necrotic hepatitis caused by an unclassified anaerobic bacillus in the water snake.

Necrotic hepatitis resembling black disease of ruminants is described in a group of five water snakes (Natrix sipedon pictiventirs). Lesions varied from multifocal granulomas to massive coagulation necrosis. A bacterium recovered from the livers could not be classified, but closely resembled Eubacterium tarantellus. The bacterium was isolated from all snake livers and from snake mites (Ophionyssus natricis) which were probably implicated in the transmission of the disease and it is possible that trematodes were concerned in producing the initial damage to the liver.

Animals↗
PubMed1975

Role of the tongue and senses in feeding of naive and experienced garter snakes.

Prey attack behavior was studied in two species of garter snakes (Thamnophis sirtalis and T. radix). Newborn, ingestively naive, and experienced snakes had their tongues severed surgically, while control groups retained their tongues. Attack latency, tongue flick frequency and an orientation-interest measure were recorded for each subject on responses to extracts prepared from species-characteristic prey. Feeding, as well as responses to prey extracts, were found to be suppressed almost totally in the tongueless naive snakes. A detongued adult, however, readily ate although its behavior was abnormal. Temporary blind and anosmic conditions did not have a significant effect on response rates of the tongueless or control groups. While importance of the tongue-Jacobson's organ system is demonstrated, the length of tongue removed and presurgery experience are important factors.

Animals↗