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At least 721 records · Page 40Linked to original sources
PubMed1987

Pinealectomy blocks vernal courtship behavior in red-sided garter snakes.

Male red-sided garter snakes (Thamnophis sirtalis parietalis) court only on emergence from winter dormancy. The salient proximate factor responsible for the initiation of courtship behavior appears to be warm ambient temperatures subsequent to sustained exposure to cold temperatures. In the present study, autumn-captured garter snakes were pinealectomized or sham-pinealectomized 1-2 weeks prior to hibernation. After 17 weeks of maintenance in several ambient lighting and temperature conditions, all males were tested for the presence of courtship behavior. No pinealectomized animals exhibited any indications of reproductive behavior, whereas 53% of sham-pinealectomized males actively courted females. Photoperiod did not influence the prevalence of mating behavior. These results suggest that the pineal gland mediates non-photoperiodic seasonal information in the garter snake. This is the first demonstration, in any vertebrate species, that the pineal gland can directly influence reproductive behavior.

Animals↗
PubMed1994

Effects of monoamine oxidase inhibitors and dopamine agonists on the behavior of mammal- and frog-eating snakes.

Skin mucus of the frog, Xenopus laevis, induces climbing and attenuates tongue flicking in Nerodia sipedon; these effects are induced alone and are potentiated by L-deprenyl, a monoamine oxidase type B inhibitor (MAO-Bi), but not by clorgyline, an MAO type A inhibitor (MAO-Ai). Both MAO-A and MAO-B metabolize dopamine, with MAO-B having the higher affinity; MAO-A selectively metabolizes serotonin and norepinephrine and MAO-B is selective for phenylethylamine. It was hypothesized that clorgyline and L-deprenyl would differentially modulate tongue flicking and climbing in frog-eating (Nerodia erythrogaster) and mammaphagous (Elaphe o. obsoleta) snakes, based on physiological differences between the species. L-Deprenyl caused a decrease in tongue flicking and climbing by Elaphe and an increase in climbing by Nerodia, whereas clorgyline did not alter tongue flicking, climbing, or locomotor activity in either species. To further assess the role of dopamine, hybrid black/gray rat snakes, E. o. spiloides, were administered the D1 and D2 dopamine receptor agonists SKF 77434 (SKF 38393, N-allyl) and quinpirole, respectively. SKF 77434 and quinpirole attenuated climbing, but only SKF 77434 attenuated tongue flicking in Experiment 3; neither drug affected locomotor activity. Results suggest that dopaminergic stimulation by MAO-Bi and dopamine agonists modulates tongue flicking and climbing behaviors in snakes, and that the contrasting climbing reactions induced by MAO-Bi between Elaphe and Nerodia may be linked to quantitative differences in endogenous catecholamine levels and/or to the numbers and sensitivity of receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1986

Respiratory mechanics and control of the ventilatory cycle in the garter snake.

We measured respiratory airflow and intrapulmonary pressure in spontaneously breathing garter snakes (Thamnophis sirtalis) before and after bilateral vagotomy. Each breathing cycle consisted of expiration, inspiration, and a breath-holding period with the glottis closed, as previously reported. Respiratory system compliance was very high compared with that of mammals (0.042 ml/cm H2O per g), but was considerably reduced when the animal was coiled. Resistance to airflow averaged 6.35 cm H2O per ml/sec. Lung volume during the breath-hold was usually above the relaxed volume of the system. Analysis of dynamic pressure-volume and flow-volume loops showed that both expiration and inspiration were active, and that little use was made of passive recoil pressure in expiration. Evidence that vagally mediated, volume-related feedback influenced the breathing pattern was found in some snakes, but this influence was weaker than in most mammals and other reptiles. The results suggest that breathing in snakes is mainly a centrally programmed process, not markedly dependent on respiratory system mechanics or neuromechanical feedback. This arrangement is advantageous in view of the high, posturally variable compliance and the frequent regional distortions of the respiratory system that result from the unique structure of these animals.

Airway Resistance↗
PubMed1989

Intrapulmonary CO2 inhibits inspiration in garter snakes.

This study was undertaken to assess the role of intrapulmonary chemoreceptors in the control of breathing in reptiles. Garter snakes were tracheostomized to remove the influence of upper airway receptors. After recovery from anesthesia, the animals were unidirectionally ventilated or allowed to ventilate normally, but without glottal control of the breath-hold. Breathing movements were recorded by means of a pneumotachograph. When a bidirectionally breathing snake was presented with CO2 at the tracheal tube, inspiratory duration and volume decreased. When CO2 was removed from the inspired air between breaths, inspiratory duration and volume increased. Removing CO2 from the airstream of a unidirectionally ventilated snake during a breath-hold produced apnea, but removing CO2 at the beginning of inspiration caused the duration and volume of the inspiration to increase. This reflex appears to represent a positive feedback mechanism for enhancing inspiration once a breath has been initiated.

Animals↗
PubMed1976

A septicaemic disease of East African snakes associated with enterobacteriaceae.

A bacterial epizootic disease of snakes at a snake farm in Kenya is described. The condition shows characteristic clinical signs and post mortem lesions and is characterized by a bacteraemia and septicaemia. The mortality rate is high and newly captured snakes die within a few weeks. Attempted control of the disease is discussed briefly and attention is drawn to the significance of such a condition in a commercial enterprise.

Aeromonas↗
PubMed1988

Factors contributing to fatal snake bite in the rural tropics: analysis of 46 cases in Thailand.

Records of 46 cases of fatal bites by identified snakes from 15 provincial hospitals throughout Thailand contained sufficient information for detailed analysis. Bungarus candidus and Calloselasma rhodostoma were each responsible for 13 deaths, Naja kaouthia for 12, Vipera russelli for 7 and B. fasciatus for one. Major causes of death among elapid victims were respiratory failure (26) and complications of prolonged mechanical ventilation (10), and among viper victims shock (12), intracranial haemorrhage (9), complications of local wound necrosis (7) including tetanus (2), and renal failure (2). Factors contributing to fatal outcome included inadequate dose of antivenom (15 cases), misidentification of the snake leading to use of the wrong antivenom (12), problems associated with mechanical ventilation (10), and delayed arrival in hospital after traditional (herbal) treatment (10). Similar problems have been identified in other tropical countries. Education of medical staff and the patient population at highest risk could reduce snake bite mortality.

Adolescent↗
PubMedDate not supplied

Snake bite and antivenom complications in Belo Horizonte, Brazil.

Factors associated with clinical complications of snake bite and antivenom therapy were studied in 310 hospital patients admitted with snake bite over 6 years to a tertiary referral hospital in Belo Horizonte, southeast Brazil. Overall, 17.4% had early clinical complications including tissue loss associated with abscess and necrosis, acute renal failure, shock, acute lung oedema and intracranial haemorrhage. 3% had permanent sequelae, caused by muscle contractures and amputations, chronic renal failure, or death. Early complications were associated with the following: age under 9 years (P = 0.04), residence in a rural area (P = 0.04), and a delay of more than 8 h in seeking clinical care (P < 0.01). Antivenom was administered to 98.1% of patients; 13.8% presented with anaphylaxis and 11.8% with pyrexia. Individuals from a rural area had a higher occurrence of anaphylactic reactions (P = 0.03). Neither anaphylaxis nor pyrexia was linked with antivenom type and dosage. This study suggested that antivenom might be associated with a reduced risk of serious injuries related to snake bite, especially when administered within the first 8 h. Complications appeared to be a far greater risk than adverse reactions to the antivenom.

Adolescent↗
PubMedDate not supplied

The epidemiology of snake bite in Central Province and National Capital District, Papua New Guinea.

Snake bite is an important medical problem in some areas of Papua New Guinea and appears to be most common in the Central Province and National Capital District. The overall incidence for Central Province is 215.5 per 100,000 population, but Kairuku subprovince has an incidence of 526 per 100,000, which is amongst the highest in the world. The clinical pattern of envenoming also varies within the Province, suggesting that different species of snake may be responsible for bites in different areas. Most envenomed patients are bitten during daylight on the lower limb and are rarely able to describe the snake. The mortality rate in Central Province is 7.9 per 100,000; most patients die from ventilatory failure due to severe neurotoxicity. Mortality might be reduced by increased use of compression bandaging as a first aid measure, earlier treatment with antivenom and earlier referral to hospital.

Adolescent↗
PubMed1983

The application of immunoassay techniques, including enzyme-linked immunosorbent assay (ELISA), to snake venom research.

The development and application of immunoassay techniques in relation to snake venom research is reviewed. Enzyme linked immunosorbent assay (ELISA) is compared with radioimmunoassay, immunodiffusion, immunofluorescence, haemagglutination and immunoelectrophoresis. It is concluded that ELISA is the most versatile immunoassay technique so far applied to the field of venom research, its main advantages over other methods including relatively high levels of sensitivity and specificity, reproducibility, simplicity and ease of sample collection. It can also be readily modified into kit form and is easily adapted for use in large scale epidemiological studies and for accurate retrospective diagnosis of snake bite. None of the other assay systems considered fulfil these criteria to the same extent. ELISA is helping to advance epidemiological knowledge of snake bite, in exploring the role of active immunisation and in the compilation of accurate clinical patterns of envenoming. Other applications of the test include its use for potency screening of both new and developed commercially available antivenoms and for the detection of monoclonal antibodies which should eventually result in increased specificity of the assay system by eliminating cross reactions between venoms and antibodies of closely related species.

Animals↗
PubMed1988

Snake venom hemorrhagins: neutralization by commercial antivenoms.

One monovalent (habu-antivenom) and five polyvalent antivenoms (Crotalidae; Orient, North, Central and South Africa) were tested for their ability to neutralize the hemorrhagic activity of 12 snake venoms (Agkistrodon, Bothrops, Crotalus, Sistrurus, Trimeresurus, Bitis, Echis spp.) when mixed prior to injection into the hind leg of mice. Considerable cross-neutralization was observed: antivenoms prepared against African snake venoms were equally or more potent in neutralizing the hemorrhagic activity of Crotalidae venoms. The same applies to Crotalidae antivenom which neutralized the activity of African snake venoms. Anti-hemorrhagic antibodies were isolated from a polyvalent antivenom by affinity chromatography using purified hemorrhagins from Bitis arietans and Crotalus adamanteus venom as ligands. These antibodies neutralized the activity of both hemorrhagins indicating common antigenic determinants in these molecules.

Animals↗
PubMed1992

Structural and functional properties of snake venom prothrombin activators.

In this review we have summarized the current knowledge about the prothrombin activating principles present in the venom of a large number of different snake species. It appears that snake venom prothrombin activators can be classified into four different groups based on their structural properties and on their functional properties in prothrombin activation. Group I activators efficiently convert prothrombin into meizothrombin and their activity is not influenced by the non-enzymatic cofactors of the prothrombinase complex (CaCl2, factor Va and phospholipid). Group II and III activators can cleave both peptide bonds in prothrombin necessary to convert prothrombin into thrombin. The prothrombin-converting activity of Group II activators is strongly stimulated by phospholipids and factor Va in the presence of CaCl2, whereas the activity of group III activators is only stimulated by CaCl2 and phospholipid. Group IV consists of snake venom proteases which do not convert prothrombin into enzymatically active products but cleave peptide bonds in prothrombin, resulting in the formation of inactive precursor forms of thrombin.

Animals↗
PubMed1992

Citrate is an endogenous inhibitor of snake venom enzymes by metal-ion chelation.

Citrate levels in selected snake venoms were determined by an enzymatic assay coupled to NADP+ reduction. Citrate concentrations in different viper venoms (n = 5) varied from 95 to 150 mM, in crotalids (n = 3) from 63 to 142 mM, and in elapids (n = 4) from 17 to 163 mM. In Bothrops asper venom Ca(2+)-ion concentrations varied from 2.5 to 3.6 mM, suggesting that the high relative citrate levels may serve to chelate endogenous divalent metal cations, thereby inactivating divalent cation requiring enzymes. Control experiments with B. asper phospholipase A2 MIII in the presence of 2.5 mM Ca2+, showed that the enzyme is completely inhibited by 20 mM citrate. Crotalus adamanteus 5'-nucleotidase and phosphodiesterase are also inhibited 100 and 75%, respectively, by 100 mM citrate. By forming complexes with divalent metal ions, citrate markedly reduces the activities of selected enzymes in snake venoms. Secretion of high concentrations of citrate may represent an important mechanism by which snakes protect themselves against the toxic effects of their own venoms.

5'-Nucleotidase↗
PubMed1994

Presence of heat-stable hemorrhagic toxins in snake venoms.

Twenty-eight snake venoms (seven Agkistrodon venoms, six Bothrops venoms, 13 Crotalus venoms, one Sistrurus venom, and one Bitis venom) were examined for the presence of heat-stable (100 degrees C, 5 min) hemorrhagic toxins. Both heated and unheated venoms were analyzed for their protein composition by SDS-PAGE, and tested for their hemorrhagic activity in vivo in mice and for their proteolytic activity on two different substrates. Heating all venoms led to the denaturation and loss of some proteins; however, most of the venoms retained a significant number of proteins. Seventeen venoms contained more than seven proteins after heating, whereas five venoms contained only one to three proteins. All but nine of the heated venoms had substantial hemorrhagic activity, and Agkistrodon piscivorus piscivorus venom had very high activity, almost four times that of the second most hemorrhagic venom from Crotalus viridis lutosus. Most venoms, heated or unheated, had activity on the two protease substrates. Using succinylated casein as the substrate, there was a wide range of activity, and heating drastically reduced the activity of all venoms except that of Crotalus ruber and Crotalus molossus molossus. With azocoll as substrate, all but two of the unheated venoms (Crotalus adamanteus and Crotalus viridis concolor) had very high activity, whereas upon heating, all except five venoms lost essentially all of their activity. Heated venoms from snakes in the Agkistrodon genus (except for Agkistrodon blomhoffi blomhoffi, an Asian snake) retained activity on azocoll, and this activity tended to correlate better with hemorrhagic activity of the venom than did proteolytic activity on casein.

Animals↗
PubMed1996

Nerve growth factors from snake venoms: chemical properties, mode of action and biological significance.

An overview of nerve growth factors (NGF) and their receptor system is presented. This general introduction deals with mouse and human NGF, since most of the fundamental knowledge is based on these mammalian proteins. Great emphasis is laid on the nonneuronal NGF effects which are well discussed for their possible toxinological function. The snake venom NGFs were reviewed with respect to their purification, classification and properties. From the date of their discovery about 40 years ago, researchers have been interested in the possible function of mouse salivary and snake venom NGFs. The physiological relevance of snake venom NGF is therefore widely discussed on the base of experimental facts and hypothetical considerations.

Animals↗
PubMed1989

Australian snake venoms and their in vitro effect on human platelets.

Thrombocytopenia is generally not associated with cases of envenomation by Australian snakes, however the clinical evidence is conflicting. The in vitro effect of these venoms upon platelets had hitherto not been studied. This study systematically examines the effect on human fresh and fixed platelets of twenty Australian snake venoms, nineteen elapid and an hydrophiid; for comparision four crotalid venoms from the Americas and S.E. Asia were also included. Electron micrographs were taken of platelets after exposure to some of the venoms. Results demonstrated that all venoms except the hydrophiid venom caused fresh platelets to irreversibly aggregate directly, and this was associated with degranulation as evidenced by electron microscopy (EM). Response to all venoms by fixed platelets was less marked and also suggests, that metabolically, active platelets are necessary for the venoms to exert their maximal effect. The hydrophiid venom's action on fresh platelets was unique, as a plasma co-factor was required before aggregation could be induced. Crotalid and hydrophiid venoms were more active against platelets than the elapid venoms. Nevertheless, platelet aggregation and degranulation in the presence of elapid venoms suggests that a platelet response in vitro may be a significant factor in the "defibrination syndrome" induced in humans by Australian snakes.

Australia↗
PubMed1989

Mating increases plasma levels of prostaglandin F2 alpha in female garter snakes.

Plasma levels of prostaglandin F2 alpha (PGF2 alpha) in female red-sided garter snakes (Thamnophis sirtalis parietalis) were measured at intervals after mating or exposure to males. PGF2 alpha levels increased significantly within 15 minutes of mating and peaked 6-24 hr after mating. Females that did not mate, but received similar amounts of male courtship, had levels of PGF2 alpha significantly lower than those of females that mated. These results extend previous findings that unmated female garter snakes injected with PGF2 alpha exhibit sexual behavior characteristic of females that have mated. Together these data indicate that female garter snakes elaborate PGF2 alpha in response to stimuli associated with mating and that PGF2 alpha has a functional role in inducing post-mating declines in sexual behavior of this species.

Animals↗
PubMed1993

MAO-A and -B inhibitors selectively alter Xenopus mucus-induced behaviors of snakes.

Skin mucus of the frog Xenopus laevis, contacted orally by snakes, induces dyskinetic oral movements and climbing behavior that promote escape. The mucus contains peptides and indoleamines known to produce drug-induced movement disorders in other species. We hypothesized that inhibition of monoamine oxidase-A (MAO-A) by N-methyl-N-propargyl-3-(2,4-dichlorophenoxy)-propylamine [clorgyline (CLG)] and MAO-B by R(-)-N, alpha-Dimethyl-N-2-propynyl-benzene-ethanamine [L-deprenyl (LDL)] would selectively modify mucus-induced behaviors by elevating norepinephrine and serotonin (with CLG), phenylethylamine (with LDL), or dopamine (with both drugs). In Experiment 1 (EXP1), adult snakes received mucus and/or 20 micrograms/g (IP) of both drugs. In EXP2, juveniles received mucus and/or 5, 10, and 20 micrograms CLG or LDL. CLG given alone had no effect on tongue flicking, activity, and climbing (EXP1,2). LDL alone decreased tongue flicking in EXP2 and increased climbing (EXP1,2). Given with mucus, both drugs further lowered the tongue flicking rates attenuated by mucus (EXP1,2); only LDL potentiated mucus-induced climbing. Yawning was the only mucus-induced dyskinesia attenuated (20 micrograms CLG, adults; 20 micrograms LDL, juveniles). We suggest that dopamine and/or phenylethylamine, the substrates for MAO-B, may promote mucus-induced climbing and tongue flicking but may have some protective role against mucus-induced yawning in water snakes.

Analysis of Variance↗
PubMed1993

Studies on the subunit structure of textilotoxin, a potent presynaptic neurotoxin from the venom of the Australian common brown snake (Pseudonaja textilis). 3. The complete amino-acid sequences of all the subunits.

The complete amino-acid sequences of subunits A, B, C and D of textilotoxin, the presynaptic neurotoxin from the venom of the Australian common brown snake, Pseudonaja textilis, were determined. These confirmed that it is structurally the most complex of any of the known snake venom neurotoxins. Textilotoxin consists of 623 amino-acid residues in five subunits (subunit A, 118 residues; subunit B, 121 residues; subunit C, 118 residues; subunit D, two chains of 133 residues each). All subunits A, B, C and D contain the putative phospholipase A2 active site. Only subunit A showed any lethality on its own (4 mg/kg i.v. in mice). Subunit D contained two identical covalently-linked subunits and was weakly glycosylated. All subunits were necessary for maximum lethality at 1 micrograms/kg mice intraperitoneally. Details of the sequences of the subunits A, B and C are reported and interesting homology with other snake venom phospholipase A2 neurotoxins indicated.

Amino Acid Sequence↗