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PubMed2004

Development of the renal sexual segment in immature snakes: effect of sex steroid hormones.

The renal sexual segment (RSS) of immature Northern and Diamondback Water Snakes and Red-Sided Garter Snakes exhibited varying responses to testosterone or 17beta-estradiol. In both male and female water snakes, kidney mass was not a reliable indicator of hormone treatment, whereas tubule diameter, epithelial height and number of sexual granules responded to hormone treatment. In male water snakes, either hormone initiated granule development by day 16; by day 23, only testosterone increased granule density. Female water snakes receiving either hormone exhibited a small number of granules by day 16; by day 23, granules increased only in Diamondback Water Snakes receiving testosterone. Hormones did not initiate RSS hypertrophy in female Red-Sided Garter Snakes. Tubule diameter and epithelial height of testosterone-treated males exhibited significant hypertrophy, while 17beta-estradiol initiated significant increases in tubule diameter. Garter snakes initiated sexual granule development in response to hormone treatment with males exhibiting a greater response than females and testosterone stimulating a greater response than 17beta-estradiol. Sex steroids appear to mimic sexual maturity in immature snakes initiating RSS development. Whereas the RSS of adult males respond to testosterone, our data suggest specific changes in the RSS of females during maturation effectively negates the effect of 17beta-estradiol evident in immature female RSS.

Animals↗
PubMed1989

Snake acetylcholine receptor: cloning of the domain containing the four extracellular cysteines of the alpha subunit.

The acetylcholine receptor (AcChoR) at the neuromuscular junction of elapid snakes binds cholinergic ligands but unlike other muscle AcChoRs does not bind alpha-bungarotoxin. Numerous studies indicate that the ligand-binding site of the AcChoR includes cysteine residues at positions 192 and 193 of the alpha subunit. We have previously shown that a synthetic dodecapeptide corresponding to residues 185-196 of the Torpedo AcChoR alpha subunit contains the essential elements of the ligand-binding site. In an attempt to elucidate the structural basis for the precise binding properties of snake AcChoR, we sequenced a portion of the snake AcChoR alpha subunit. First, a mouse AcChoR alpha-subunit cDNA probe was used to screen a size-selected snake (Natrix tessellata) genomic library. A genomic clone was isolated and was found to contain sequences homologous to the exon including the first two cysteines (Cys-128 and -142) of AcChoR alpha subunit. The domain of the alpha subunit from Natrix and cobra AcChoR (amino acid residues 119-222), which contains the four extracellular cysteines (128, 142, 192, and 193), was amplified by reverse transcription of mRNA and the polymerase chain reaction and then sequenced. The deduced amino acid sequence showed that the snake alpha subunit contains the two tandem cysteines at positions 192 and 193, resembling all other AcChoR alpha subunits. Sequence comparison revealed that the cloned region of the snake alpha subunit is highly homologous (75-80%) to other muscle AcChoRs and not to neuronal AcChoR, which also does not bind alpha-bungarotoxin. In the presumed ligand-binding site, in the vicinity of Cys-192 and Cys-193, four major substitutions occur in the snake sequence--at positions 184 (Trp----Phe), 185 (Lys----Trp), 187 (Trp----Ser), and 194 (Pro----Leu). In addition, Asn-189 is a putative N-glycosylation site, present only in the snake. These changes, or part of them, may explain the lack of alpha-bungarotoxin-binding to snake AcChoR.

Amino Acid Sequence↗
PubMed2000

Proliferative osteoarthritis and osteoarthrosis in 15 snakes.

Fifteen snakes representing seven species with segmental, proliferative osteoarthritis and osteoarthrosis of the spine were presented for examination. All the snakes were captive, privately owned, and fed domestic rodents. Physical examination, radiography, blood culture, bone culture, necropsy, and histopathology were performed on each snake. All the snakes had similar physical examination, radiologic, and necropsy findings. There were three histologic types of lesions: active bacterial osteoarthritis, predominantly noninflammatory osteoarthrosis with multifocal inflammation suggestive of chronic bacterial osteoarthritis, and noninflammatory lesions consistent with osteoarthrosis without evidence of inflammation or bacteria. These findings suggest that all these snakes represent a single disease process, bacterial infection of the vertebrae. The different histologic lesions observed in these snakes may be a continuum of lesions, from acute to chronic. Gram-negative bacteria were isolated from the blood or bone lesions of 8 of the 15 snakes. In six of these eight snakes, Salmonella species were isolated. Gram-positive bacteria (Streptococcus sp.) were isolated from two other snakes. Blood and bone culture results were well correlated, so blood culture may be effective for detecting active bacterial osteoarthritis.

Animals↗
PubMed1992

Kallikrein-kinin system in the plasma of snakes.

Using pharmacological preparations suitable for assay of mammalian kinins, it was shown that Bothrops jararaca (Bj) venom and other kininogenases were unable to release kinins from snake plasma. The kallikrein-kinin system presents species-specificity in birds. In order to detect such a specificity in snakes, the effects of Bj venom on snake blood pressure and the effect of incubates of snake plasma with trypsin, on snake blood pressure and snake uterus, were studied. The possibility of activating snake plasma kallikrein with ellagic acid, glass beads or kaolin was also investigated. Whereas plasma of the snakes Waglerophis merremii (Wm) and Crotalus durissus (Cd), were shown to contain factor XII, prekallikrein, kininogen, kininases and to present a low but definite activation rate of the kinin system, the plasmas of Bj, Bothrops mojeni (Bm) and Oxyrophus trigeminus (Ot), yielded only kininogen and kininases. Activation of the system was not even detected by the sensitive substrate Ac-Phe-Arg-Nan (acetyl-phenylalanyl-arginyl-4nitro-anilide), indicating that the plasma of these species does not possess either factor XII and/or prekallikrein. Snake plasma may constitute an interesting model for the study of blood clotting, fibrinolytic and complement systems.

Animals↗
PubMed1978

[Poisonous-snake bites. Therapy and preventive measures].

It is estimated that every year about 500 000 people around the world are bitten by poisonous snakes. Between 30 000 to 50 000 persons die due to snake-bites; the highest frequency is reported from Southern Asia. Clinically three types of snake-bites can be distinguished: 1. Bites with local damage (extreme pain, edema, necrosis), 2. Bites followed by generalized hemorrhagic symptoms and 3. bites with neurotoxic effects of the poison (no local pain, paralysis of cerebral nerves, coma). For tropical snake-bites snake-venom is live-saving. As in many cases the biting animal cannot be identified it is advisable to use polyvalent sera. These are heterologous sera which contain antitoxins against several poisonous snakes of a certain area. Often there is some delay until the snake-venom becomes available. Therefore local and symptomatic treatment is valuable: cleaning of the wound, superficial incision to remove poison, venous congestion, oral and intravenous fluid-therapy, antihistaminic drugs, steroids and prophylaxis of shock. Tourists are only rarely endangered by poisonous snakes, they do not need to carry anti-snake venom; this is recommended for scientific excursions in areas with dense vegetation and for persons living in warm countries.

Age Factors↗
PubMed1984

The electric net trap for the venomous snake, Habu, Trimeresurus flavoviridis.

The electric net trap made of 3 rows of polyethylene net fence with the high voltage electric pulse was examined in the field for capturing the venomous snake, Trimeresurus flavoviridis. The bottom of the center row of the net fence was buried in the ground and that of other two outer rows was partially free from the ground so that snakes were allowed to invade one way into the spaces at both sides of the center net. The examination using a 90 m net trap set for 116 days resulted in the capture of 44 snakes, i.e., 7 T. flavoviridis, 7 Dinodon semicarinatus and 33 Opheodrys semicarinatus, of which the latter two were nonvenomous. The result indicated that the net trap was an efficient tool for capturing snakes and in identifying the direction of snake movement. In the other studies conducted in 1982 and 1983, a 178.5 m net trap was set at a part of a 2,000 m electric net barrier, which surrounded a 12.8 ha sugar cane field and thereby prevented snake invasion. The number of venomous snakes captured by the inner net trap was remarkably reduced from 13 in 1982 to 0 in 1983, in contrast to 8 and 9, respectively, observed in the outer trap. The decrease of snake population was also observed in 100 box traps baited with a live rat set inside the enclosed area. The ratio of immature snakes captured by the net trap was significantly higher than that by the box trap.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Venomous snakes of Saudi Arabia and the Middle East: a keynote for travellers.

Geographically Saudi Arabia and the Middle East include Asian Turkey, Syria, Lebanon, Jordan, Israel, Palestine, the Arabian Peninsula, Iraq, Iran and the previous Southern Asiatic Soviet Republics. The snake fauna contains species in common with northern Africa, Europe and central Asia and towards the east there is infiltration of species characteristic of tropical Asia. A classification of the venomous snakes of this area together with their distribution in the different countries is presented. The epidemiology of snake bites, pathophysiology of toxicity and the clinical features of envenoming by the different species of snakes are discussed. Management of snake bite victims including first aid, treatment at the hospital, clues from signs and symptoms that can help in the identification of the causative snake and antivenom treatment is stressed. Traditional manipulations like local incision and suction, use of caustics, oxidizing agents and cryotherapy and the injudicious use of tourniquets are evaluated and criticized. Finally the preventive control of snake bites for travellers in areas infested with venomous snakes is presented and discussed.

Animals↗
PubMed1998

Behavioural responses of Mallorcan midwife toad tadpoles to natural and unnatural snake predators

The activity levels of Mallorcan midwife toad tadpoles, Alytes muletensis, were compared in two natural torrent pools which differed in their use by predatory viperine snakes, Natrix maura. Activity levels were lower in a pool regularly used by snakes than they were in a snake-free pool, but were reduced in both pools when snakes were experimentally introduced in nylon bags. In the presence of snakes, however, activity was more suppressed in the pool that was usually snake-free. Corresponding reductions in activity were also observed when tadpoles were treated with chemical cues from Mallorcan N. maura in a gravitational flow-through system. However, tadpoles failed to respond to chemical cues from other species of amphibian-eating snakes, or even to those from N. maura collected from a different population in mainland Spain. As none of the snakes used had previously eaten midwife toads, the responses cannot be related to previous diet, and seem to be specific to those N. maura from the island of Mallorca. As viperine snakes were probably introduced to Mallorca about 2000 years ago, the evolution of anti-predator behaviour in midwife toad tadpoles must have occurred relatively recently. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMedDate not supplied

Thermoregulation by a nocturnal elapid snake (Hoplocephalus bungaroides) in southeastern Australia.

Studies of reptilian thermoregulation have tended to focus on diurnal heliothermic taxa that display overt thermoregulatory behavior, with nocturnal reptiles attracting less attention. We studied thermoregulation by the broad-headed snake (Hoplocephalus bungaroides), a small (mean snout-vent length = 57 cm) nocturnal elapid that spends long periods sequestered in diurnal retreat sites. The snakes selected body temperatures of 28.1 degrees-31.1 degrees C in laboratory thermal gradients. Prey-capture ability (strike speed and accuracy) increased at higher body temperatures over the range 20 degrees-30 degrees C. Using temperature-sensitive radio transmitters, we obtained 7,801 body-temperature measurements of 19 free-ranging snakes. Information on operative environmental temperatures was obtained at the same time. From these data, we quantified the degree to which the snakes exploit the environmental thermal heterogeneity available to them (i.e., the time they spent within their set-point range, relative to the total time that these body temperatures were available to them). Mean body temperatures (both diurnally and nocturnally) differed among seasons but not among different types of retreat sites. Inclement weather prevented snakes from attaining "preferred" body temperatures on 30% of days. However, even when preferred temperatures were available, the snakes exploited this opportunity for only 26% of the time: they remained within retreat sites and rarely emerged to bask. Nonetheless, judicious retreat-site selection resulted in snakes being within their set-point range for 60% of the time at the most crucial time of day (i.e., the 2-h period around dusk, when the opportunity to capture prey is highest). Basking may be rare not only because of its high potential costs (e.g., risk of avian predation) but also because high body temperatures enhance snake fitness for only a short time each day and can be attained over that short period without the "expense" of heliothermy. Our results suggest that precise thermoregulation may not be widespread among snakes, particularly small nocturnal species that spend long periods sequestered in retreat sites.

Adaptation, Physiological↗
PubMed1994

Mutational analysis of the Drosophila snake protease: an essential role for domains within the proenzyme polypeptide chain.

Two genes involved in the generation of dorsoventral asymmetry in the developing Drosophila melanogaster embryo, snake and easter, encode the zymogen form of serine proteases. Mutant alleles of snake were cloned and sequenced revealing two types of lesions: point mutations which alter the amino acid sequence (snk073 and snkrm4) and point mutations which alter the splicing (snk229 or snk233) of intron 1 of the mRNA from the normal 3' end of the intron to a cryptic site. snake mutant embryos derived from homozygous mothers can be fully rescued by injection of RNA transcripts of the wild-type snake cDNA. RNA phenotypic rescue and site-directed mutagenesis experiments indicate that snake requires the serine, histidine and aspartic acid of the catalytic triad for normal activity. Deletion experiments show that an acidic proenzyme domain is required for snake rescue activity to be uniformly distributed throughout the embryo. A second proenzyme domain, called the disulfide knot, appears to be essential for normal regulation of activity of the snake catalytic chain. Transcripts encoding only the proenzyme polypeptides of either snake or easter can dorsalize wild type embryos. We propose a model in which the proenzyme determinants of both the snake and easter enzymes mediate interaction between the serine proteases and other components of the dorsal-ventral patterning system.

Alleles↗
PubMed1981

A study of the major Australian snake venoms in the monkey (Macaca fascicularis). II. Myolytic and haematological effects of venoms.

Rhesus monkeys were kept in a restraining apparatus and while conscious injected with the venoms of a range of Australian snakes. Although the action of restraining itself caused an elevation of the animals' plasma creatine kinase (C.K.), the rise was up to 5 times greater in envenomed monkeys. The venoms of the Tiger snake, Mulga, Beaked Sea snake, Rough-Scaled, Copperhead and Red-Bellied snakes were all powerfully myolytic, and those of the Taipan and Small-Eyed snake less so. No myolytic activity was found in the venoms of the Common Brown snake and Death Adder, and the results with Dugite, Gwardar and Small-Scaled snake venom were equivocal. Significant coagulation disturbances were produced by all venoms studied except those of the Small-Eyed and Rough-Scaled snakes. When first aid measures were used, the coagulation disturbances which developed after the release of the injected venom were significantly less than when no first aid was used. This finding, which was observed with all snake venoms studied, suggests that the procoagulant factor may be subject to some inactivation whilst immobilized at the injection site.

Animals↗
PubMed2006

Snake fangs from the Lower Miocene of Germany: evolutionary stability of perfect weapons.

There is a general consensus that most of today's nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stab-like application of highly toxic venoms. Our findings therefore indicate that the other components of the venom-delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.

Animals↗
PubMed2005

Practical applications of snake venom toxins in haemostasis.

Snake venom toxins affecting haemostasis have facilitated extensively the routine assays of haemostatic parameters in the coagulation laboratory. Snake venom thrombin-like enzymes (SVTLE) are used for fibrinogen/fibrinogen breakdown product assay and for the detection of fibrinogen dysfunction. SVTLE are not inhibited by heparin and can thus can be used for assaying antithrombin III and other haemostatic variables in heparin-containing samples. Snake venoms are a rich source of prothrombin activators and these are utilised in prothrombin assays, for studying dysprothrombinaemias and for preparing meizothrombin and non-enzymic forms of prothrombin. Russell's viper (Daboia russelli) venom (RVV) contains toxins which have been used to assay blood clotting factors V, VII, X, platelet factor 3 and, importantly, lupus anticoagulants (LA). Other prothrombin activators (from the taipan, Australian brown snake and saw-scaled viper) have now been used to assay LA. Protein C and activated protein C resistance can be measured by means of RVV and Protac, a fast acting inhibitor from Southern copperhead snake venom and von Willebrand factor can be studied with botrocetin from Bothrops jararaca venom. The disintegrins, a large family of Arg-Gly-Asp (RGD)-containing snake venom proteins, show potential for studying platelet glycoprotein receptors, notably, GPIIb/IIIa and Ib. Snake venom toxins affecting haemostasis are also used in the therapeutic setting: Ancrod (from the Malayan pit viper, Calloselasma rhodostoma), in particular, has been used as an anticoagulant to achieve 'therapeutic defibrination'. Other snake venom proteins show promise in the treatment of a range of haemostatic disorders.

Animals↗
PubMed2005

Estimates of disease burden due to land-snake bite in Sri Lankan hospitals.

Snake bite is a common cause of hospital admission in Sri Lanka. Despite this, there have been no countrywide studies or national estimates of disease burden due to snake bites in Sri Lankan hospitals. We assessed the disease burden due to snake bite in our hospitals and estimated the frequency of admissions due to bites by different snake species. Sri Lanka was divided into four zones based on climate and topography. Hospital morbidity and mortality data, which are available on an administrative district basis, were collated for the four zones. A survey of opinion among specialist physicians (the Delphi technique) was used to estimate the proportion of bites by different species, and requirements for anti-venom (AV) and intensive care facilities for management of snake bites in hospitals in each of the four zones. A study of hospital admissions due to snake bites in seven selected hospitals was also performed to validate the opinion survey. There was a clear difference in the incidence of hospital admissions due to snake bites in the different zones. Estimates of hospital admissions due to bites by different species also varied considerably between zones. These trends corresponded to estimates of requirements of AV and other supportive health care. Health care planning using data based on environmental information, rather than merely on political boundaries, could lead to targeted distribution of AV and intensive care requirements to manage snake bites.

Animals↗
PubMed1990

BALB/cAn B cells and T cells have distinct susceptibilities to cytotoxic effects of snake venom.

Previous studies have analyzed abilities of snake venoms to preferentially kill certain animal cells. Some studies have examined selective cytotoxic effects of snake venoms on B and T lymphocytes, but few studies have determined abilities of snake venoms to interact with B and T cells at distinct stages of cellular development. Thus, this study has analyzed susceptibilities of immature and mature BALB/cAn splenic B cells and T cells to cytotoxic effects of crude venoms of snakes belonging to the families of Crotalidae, Elapidae, and Viperidae. Both mitogen-stimulated and unstimulated BALB/cAn Ig- splenic T cells are sensitive to cytotoxic effects of snake venoms whereas mitogen-stimulated but not unstimulated Ig+ splenic B lymphocytes are sensitive to snake venoms. We also find that BALB/cAn myelomas but not B cell lymphomas are sensitive to cytotoxic effects of snake venoms. In addition, plaque forming cells making IgG1 subclass in BALB/cAn mitogen-stimulated spleens and in myelomas are preferentially killed by venom of pit viper Bothrops asper. Thus, the cytotoxic effects of crude snake venoms can distinguish BALB/cAn PFC making IgG1 subclass from other B and T cells.

Animals↗
PubMed2001

Development of a polymerase chain reaction to distinguish monocellate cobra (Naja khouthia) bites from other common Thai snake species, using both venom extracts and bite-site swabs.

A PCR technique was used in this study to identify and distinguish monocellate cobra snake bites using snake venoms and swab specimens from snake bite-sites in mice from bites by other common Thai snakes. The sequences of nucleotide primers were selected for the cobrotoxin-encoding gene from the Chinese cobra (Naja atra) since the sequences of monocellate cobra (Naja kaouthia) venom are still unknown. However, the 113-bp fragment of cDNA of the cobrotoxin-encoding gene was detected in the monocellate cobra venom using RT-PCR. This gene was not found in the venoms of Ophiophagus hannah (king cobra), Bungarus fasciatus (banded krait), Daboia russelii siamensis (Siamese Russell's Viper, and Calloselasma rhodostoma (Malayan pit viper). Moreover, direct PCR could detect a 665-bp fragment of the cobrotoxin-encoding gene in the monocellate cobra venom but not the other snake venoms. Likewise, this gene was only observed in swab specimens from cobra snake bite-sites in mice. This is the first report demonstrating the ability of PCR to detect the cobrotoxin-encoding gene from snake venoms and swab specimens. Further studies are required for identification of this and other snakes from the bite-sites on human skin.

Animals↗
PubMed1998

Hugh Alistair Reid OBE MD: investigation and treatment of snake bite.

Alistair Reid was an outstanding clinician, epidemiologist and scientist. At the Penang General Hospital, Malaya, his careful observation of sea snake poisoning revealed that sea snake venoms were myotoxic in man leading to generalized rhabdomyolysis, and were not neurotoxic as observed in animals. In 1961, Reid founded and became the first Honorary Director of the Penang Institute of Snake and Venom Research. Effective treatment of sea snake poisoning required specific antivenom which was produced at the Commonwealth Serum Laboratories in Melbourne from Enhydrina schistosa venom supplied by the Institute. From the low frequency of envenoming following bites, Reid concluded that snakes on the defensive when biting man seldom injected much venom. He provided clinical guidelines to assess the degree of envenoming, and the correct dose of specific antivenom to be used in the treatment of snake bite in Malaya. Reid demonstrated that the non-clotting blood of patients bitten by the pit viper, Calloselasma rhodostoma [Ancistrodon rhodostoma] was due to venom-induced defibrination. From his clinical experience of these patients, Reid suggested that a defibrinating derivative of C. rhodostoma venom might have a useful role in the treatment of deep vein thrombosis. This led to Arvin (ancrod) being used clinically from 1968. After leaving Malaya in 1964, Alistair Reid joined the staff of the Liverpool School of Tropical Medicine, as Senior Lecturer. Enzyme-linked immunosorbent assay (ELISA) for detecting and quantifying snake venom and venom-antibody was developed at the Liverpool Venom Research Unit: this proved useful in the diagnosis of snake bite, in epidemiological studies of envenoming patterns, and in screening of antivenom potency. In 1977, Dr H. Alistair Reid became Head of the WHO Collaborative Centre for the Control of Antivenoms based at Liverpool.

Animals↗
PubMed1999

Natural protease inhibitors to hemorrhagins in snake venoms and their potential use in medicine.

Snake venoms are complex mixtures of many toxins and enzymes which effectively immobilize prey without a struggle and assist in digestion. Certain animals have a remarkable resistance to envenomation of snakes. Naturally occurring factors that neutralize snake venoms have been found in the sera of most snakes and a few warm-blooded animals. These antihemorrhagic and antineurotoxic factors have been purified from snake and mammalian sera. The antihemorrhagins are not immunoglobulins since they have different physical and chemical characteristics. The natural immunity to hemorrhagins is the result of tissue inhibitors of metalloproteinases (TIMP) found in animal sera of resistant animals. Most animals have matrix metalloproteinases (MMP) and TIMP that are implicated in a wide variety of normal physiological processes and pathological conditions. MMP in animals have many biological functions in embryogenesis, morphogenesis and tissue remodeling. MMP activities are precisely regulated by endogenous TIMP. Disruption of the balance between MMP and TIMP causes various diseases such as arthritis, periodontal diseases, diabetes, ophthalmologic conditions, neoplasia, metabolic bone disease, atherosclerosis and orthopedic conditions. Resistant animals that have a high titer of TIMP would have a survival advantage when bitten by poisonous snakes. Snake venoms are abundant and stable sources of MMP which are medically important. The venom MMP which cause unregulated destruction of tissue have sequences which have some degree of homology with mammalian MMP which control normal biological processes. Resistant animals are important sources of TIMP which can be used to study metalloproteinase related diseases. For these reasons the MMP in snakes and TIMP in resistant animal are excellent candidates for developing new drug therapies.

Animals↗