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a hemorrhagic (basement membrane degrading) zinc metalloproteinase from southern copperhead venom. 19921480009
the action of a fibrin-promoting enzyme from the venom of agkistrodon contortrix contortrix on rat fibrinogen and plasma.the action of a fibrin-promoting enzyme isolated from the venom of a.c.contortrix was investigated. the ratio of fibrinopeptides a and b released was similar in isolated human and rat fibrinogen and human plasma, fibrinopeptide b always being released preferentially. however, no clotting occurred in rat plasma, and no fibrinopeptides were released even after prolonged incubation. the results suggest strong, fast-acting irreversible neutralization of the enzyme activity in rat plasma.19902087698
a direct-acting fibrinolytic enzyme from the venom of agkistrodon contortrix contortrix: effects on various components of the human blood coagulation and fibrinolysis systems.a direct acting fibrinolytic enzyme (fibrolase) has been isolated from venom of the southern copperhead snake (agkistrodon contortrix contortrix). time-course experiments established that the venom enzyme cleaves primarily the a alpha-chain of human fibrinogen and fibrin between the lys-413 and leu-414 position. the b beta-chain is cleaved more slowly, while the gamma-chain is minimally affected. the cleavage pattern of fibrinogen and fibrin clearly varies from plasmin cleavage of the same molec ...19883232124
venom from southern copperhead snake (agkistrodon contortrix contortrix). ii. a unique phospholipase a2 that induces platelet aggregation.a platelet aggregation factor was purified from the venom of southern copperhead snake (agkistrodon contortrix contortrix) by deae-cellulose ion-exchange chromatography, precipitation with ammonium sulfate, affinity chromatography using bovine serum albumin as ligand, and gel filtration on cellulofine gcl-2000. it had molecular weights of 11,000 and 14,000, as determined by gel filtration chromatography and sodium dodecyl sulfate--polyacrylamide gel electrophoresis (sds-page), respectively. it c ...19883363567
isolation of a protein c activator from southern copperhead venom.a protease from the venom of the southern copperhead snake (agkistrodon contortrix contortrix) that activates protein c was purified to homogeneity by a combination of sulfopropyl (sp)-sephadex c-50, sephadex g-150 and mono-s column chromatography. the purified enzyme is a glycoprotein, and migrated as a single band in sodium dodecylsulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 37,000 under non-reducing conditions. upon reduction with 2-mercaptoethanol, the enzy ...19873566762
the effect of thrombin, reptilase, and a fibrinopeptide b-releasing enzyme from the venom of the southern copperhead snake on rabbit platelets. 19734768613
antitumor action of crotalase, a defibrinogenating snake venom enzyme.recent reports have shown that malignant cells release a variety of factors that modulate the tumor microenvironment. these factors, after release or shedding, work in concert to produce extravasation of fibrinogen from surrounding blood vessels with subsequent fibrin deposition around the tumor cells. this fibrin deposit could act to mask the tumor from the host's immune surveillance system. fibrin deposits have been observed by investigators in the vicinity of various malignant tumors of man a ...19863538422
clots of beta-fibrin. viscoelastic properties, temperature dependence of elasticity, and interaction with fibrinogen-binding tetrapeptides.clots of human beta-fibrin, in which only (or predominantly) the b fibrinopeptide is released, were formed at 14 degrees c by copperhead venom procoagulant enzyme (cve or venzyme), at ph 8.5, ionic strength 0.45. the shear modulus of elasticity increased slowly and after several days attained a constant value, which was lower than those of alpha-fibrin or alpha beta-fibrin under the same conditions. before studying the temperature dependence of elasticity, the cve was then inhibited by introduci ...19883349127
venom from southern copperhead snake (agkistrodon contortrix contortrix). i. characterization of a protease that preferentially releases fibrinopeptide b.using gel permeation chromatography with high performance liquid chromatograph (hplc), a highly purified preparation of a protease has been obtained from the venom of the southern copperhead snake (agkistrodon contortrix contortrix). both gel permeation chromatography with hplc and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that it had an apparent mr of 60,000-64,000. it consisted of a single polypeptide chain. the activity was inhibited by dithiothreitol. it neither indu ...19873313813
amidolytic kinetic assay of protein c by selective spectrophotometry in a centrifugal analyzer.this rapid, simple amidolytic assay of protein c activity in whole plasma involves activation by protein c activator from the venom of agkistrodon contortrix contortrix (protac) and use of a cobas fara spectrophotometer programmed for kinetic assay. plasma is incubated with activator venom in the presence or absence of antibody to human protein c in the instrument, chromogenic substrate (s-2366) is added, and the absorbance is measured at 405 nm. the difference between the absorbance of the samp ...19883180421
inactivation of single-chain urokinase (pro-urokinase) by thrombin and thrombin-like enzymes: relevance of the findings to the interpretation of fibrin-binding experiments.whereas crude bovine thrombin activated single-chain urokinase-type plasminogen activator (scu-pa), otherwise called pro-urokinase (pro-uk), purified human thrombin converted pro-uk (scu-pa) to a two-chain form that had no amidolytic activity. the two chains (mr approximately 33,000 and 22,000) were disulfide linked and resistant to subsequent activation by plasmin. by contrast, thrombin did not inactivate tissue plasminogen activator or two-chain urokinase. the enzyme from snake venom agkistrod ...19872949785
[isolation and characterization of a protein c activator from the moccasin snake venom].the protein c activator detectable in the venom of the southern copperhead snake (agkistrodon contortrix contortrix) was isolated by a combination of chromatofocusing on pbe-94 in the range ph9-7 and gel-filtration on sephadex g-100 column. the peak protein c activator from sephadex g-100 column appeared as double diffuse bands with apparent molecular weight of 37,700 and 31,400 after electrophoresis in the presence of sodium dodecylsulfate and 2-mercaptoethanol. the isolated enzyme does not clo ...19892804302
platelet-aggregation is stimulated by lactose-inhibitable snake venom lectins.five lactose-specific lectins from snake venoms were tested for the ability to stimulate the aggregation of human platelets. three of the lectins, bushmaster (lachesis muta), cottonmouth (ancistrodon piscivorous leukostoma) and rattlesnake (crotalus atrox) lectins, consistently stimulated secretion and aggregation. thrombolectin (bothrops atrox) occasionally caused aggregation. copperhead (agkistrodon contortrix contortrix) lectin did not by itself cause platelet aggregation. lactose, a specific ...19892530646
inhibition of hemorrhagic activities of various snake venoms by purified antihemorrhagic factor obtained from japanese habu snake.the ability of purified antihemorrhagic factor isolated from the serum of japanese habu (trimeresurus flavoviridis) was tested on 17 snake venoms to inhibit their hemorrhagic activity. the factor strongly inhibited that of the venoms of crotalus horridus horridus and vipera latastei gaditana in addition to that of the homologous (t. flavoviridis) venom. hemorrhagic activity of agkistrodon halys blomhoffi, agkistrodon contortrix contortrix, bothrops atrox asper and crotalus atrox venoms was also ...19948016857
isolation and characterization of a protein c activator from tropical moccasin venom.a protease from the venom of the tropical moccasin (agkistrodon bilineatus) that activates protein c was purified to homogeneity by ion-exchange and gel permeation chromatography. the purified protease is a glycoprotein, and exhibited a molecular weight of 35,000 and 38,000 in sds-page under non-reducing and reducing conditions, respectively. the purified protease readily activated human protein c and steady-state kinetic parameters indicated an apparent km for human protein c of 1.7 microm and ...19902385829
immunological properties of the fibrinolytic enzyme (fibrolase) from southern copperhead (agkistrodon contortrix contortrix) venom and its purification by immunoaffinity chromatography.an antibody to the fibrinolytic enzyme in southern copperhead venom was produced by immunizing rabbits with chromatographically purified enzyme. the antibody was purified from rabbit blood by ammonium sulfate fractionation and protein-a affinity chromatography. the purified antibody reacted only with the fibrinolytic enzyme in southern copperhead venom as demonstrated by immunodiffusion and immunoelectrophoresis. western immunoblotting revealed that several snake venoms, including agkistrodon pi ...19911926169
sporocysts isolated from the southern copperhead (agkistrodon contortrix contortrix) produce sarcocystis montanaensis-like sarcocysts in prairie voles (microtus ochrogaster).sporulated oocysts and free sporocysts of a sarcocystis sp. were isolated from the feces of a southern copperhead (agkistrodon contortrix contortrix) collected in arkansas (usa). twenty sporocysts measured 11.2 by 8.5 microns, lacked a stieda body, and had four sporozoites and a granular sporocyst residuum. sarcocysts similar to those of sarcocystis montanaensis were present in the tongues of prairie voles (microtus ochrogaster) inoculated orally with 800 sporocysts 128 days previously. sarcocys ...19911902524
purification and characterization of a fibrinolytic enzyme from venom of the southern copperhead snake (agkistrodon contortrix contortrix).a fibrinolytic enzyme present in agkistrodon contortrix contortrix (southern copperhead) venom has been purified by combination of cm-cellulose chromatography, molecular sieve chromatography on sephadex g-100, p-aminobenzamidine-agarose affinity chromatography, and deae-cellulose chromatography. the enzyme, fibrolase, has a molecular weight of 23,000-24,000 and an isoelectric point of ph 6.8. it is composed of approximately 200 amino acids, possesses a blocked nh2-terminus and contains little or ...19911898066
a novel functional assay of protein c in human plasma and its comparison with amidolytic and anticoagulant assays.a simple and fast method for the quantitative determination of protein c activity in plasma is here described. the first step consists in the conversion of protein c in the test sample into activated protein c by means of an activator isolated from southern copperhead venom. subsequently, the degradation of factor va, in presence of protein c-deficient plasma, is measured by the prolongation of the prothrombin time which is proportional to the amount of protein c in the sample. the dose-response ...19921615482
haematopoietic malignancies in zoo animals.myelogenous leukaemia was found in a russell's viper, a honduran milk snake, a marine toad, a byrne's marsupial mouse and an african hedgehog. lymphocytic leukaemia was present in a broad banded copperhead and an indian lion. visceral lymphomatosis was observed in a snowy owl.19921556254
isolation and purification of superbins i and ii from austrelaps superbus (copperhead) snake venom and their anticoagulant and antiplatelet effects.two proteins with anticoagulant and antiplatelet activities were purified from austrelaps superbus (copperhead) venom by gel filtration, ion-exchange and reverse-phase chromatographic methods. these purified proteins were designated superbins i and ii. superbin i was homogeneous, as indicated by electrospray ionization-mass spectrometry, with a mol. wt of 13,252.3 +/- 1.6, whereas superbin ii contained two closely related proteins of mol. wts 13,235.5 +/- 1.1 and 13,212.9 +/- 1.2. both superbins ...19979278973
fractionation of northern copperhead venom by ion-exchange chromatography: preliminary characterization of the primary lethal fraction. 1979574671
effects of the venom of the australian copperhead snake (austrelaps superba) on the isolated atrium and ear artery of the rabbit. 1979473239
fibrinopeptide b and aggregation of fibrinogen.removal of fibrinopeptide b from human fibrinogen by reaction with the procoagulant enzyme from copperhead snake venom below 25 degrees c resulted in tight aggregation of the fibrinogen, which, in turn, progressively blocked a concomitant but sluggish release of fibrinopeptide a by the enzyme. when the clots obtained at less than 25 degrees c were warmed, they dissociated into soluble aggregates and monomers. release of fibrinopeptide a then resumed, and a secondary coagulation followed. the agg ...1979155308
distribution and pathology of copperhead (agkistrodon contortrix) venom. 19807222064
effect of calcium and synthetic peptides on fibrin polymerization.human fibrinogen was subjected to limited proteolytic attack by thrombin, batroxobin or agkistrodon contortrix thrombin-like enzyme, yielding desab-, desa- or desb-fibrin monomers, respectively. turbidity curves demonstrated that, with all three enzymes, the polymerization process was strongly accelerated by increasing the calcium concentration from 10(-5) m to 10(-4) m. synthetic peptide gly-his-arg (5 mm), an analogue of the aminoterminal sequence of fibrin beta-chain, inhibited aggregation of ...19827101230
an enzyme-linked immunoassay for detection of north american pit viper venoms.we describe a method for immunodetection of north american pit viper venoms in clinical materials. antibody-enzyme conjugates prepared against venoms of the western diamondback rattlesnake (crotalus atrox), mojave rattlesnake (crotalus scutulatus), and copperhead (agkistrodon contortrix) detect homologous venoms in concentrations of 0.1-.01 mcg/ml using a double antibody sandwich technique. venoms of 10 additional species of u.s. pit vipers were detected in concentrations of 10 mcg/ml or less. v ...19846527395
detection of specific proenzyme activators in snake venoms by a new immunoabsorbant-chromogenic substrate method.in separate experiments, antibodies to plasminogen, factor x and protein c were applied to microtitre trays as commonly used in enzyme-linked immunoassays. after incubation with dilute normal human plasma as a source of the corresponding proenzyme antigen, the wells were exposed to dilutions of various snake venoms. after thorough washing, the microtitre tray wells were tested overnight with chromogenic tripeptide substrates known to be relatively specific for the activated forms of the above fa ...19853841012
protein c activators in snake venoms.venoms of 32 snake species were tested for protein c (pc) activating potency. as measured with the chromogenic pc substrate d-pro-l-pro-l-arg-pna, eleven venoms were able to generate amidolytic activity from purified bovine pc. in five venom solutions (bothrops moojeni, b. pradoi, cerastes cerastes, vipera lebetina and v. russellii) the pc activating potency was destroyed during 10 min heating at 70 degrees c at ph 3, whereas in six venom solutions (agkistrodon contortrix contortrix, a. c. mokas ...19863755037
characterization of a protein c activator from agkistrodon contortrix contortrix venom.the protease from southern copperhead venom that activates protein c was purified to homogeneity by sulfopropyl (sp)-sephadex c-50 ion-exchange chromatography, sephadex g-150 gel filtration, and mono-s fast protein liquid chromatography. the purified enzyme is a glycoprotein containing 16% carbohydrate, and migrated as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular mass of 40,000 kda. the enzyme is composed of a single polypeptide chain poss ...19873624272
characterization of the protein c activator protac from the venom of the southern copperhead (agkistrodon contortrix) snake.a single chain glycopeptide with a molecular weight of approximately 37,000, an isoelectric point of 3.0 +/- 0.2 and a carbohydrate content of approximately 20% was isolated from the venom of the southern copperhead agkistrodon contortrix contortrix. it was capable of converting zymogen protein c in plasma of man and various vertebrates into its activated form, a serine proteinase which exerts an anticoagulant effect. conversion of the zymogen protein c into the active proteinase was demonstrate ...19873590209
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 acti ...19817335377
purification of a protein c activator from the venom of the southern copperhead snake (agkistrodon contortrix contortrix).a protease has been purified by ion-exchange chromatography from the venom of agkistrodon contortrix contortrix (southern copperhead snake) that can activate the vitamin k dependent protein, protein c. the apparent molecular weight of this protease, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was 20,000 under nonreducing conditions. incubation of this protease with plasma resulted in a prolongation of the clotting time and a time-dependent increase in amidolytic acti ...19863530318
rickettsia honei: a spotted fever group rickettsia on three continents.rickettsia honei (also known as strain tt-118) has been detected on three continents. originally isolated in thailand in 1962 (and confirmed in 2001), it has also been detected on flinders island (australia) in 1993 and in texas (usa) in 1998. on each continent it has been associated with a different species of tick. the original isolate (thai tick typhus strain tt-118) was from a pool of larval ixodes and rhipicephalus ticks. later it was detected in i. granulatus from rattus rattus. its pathog ...200312860601
ultrastructural and genetic evidence of a reptilian tick, aponomma hydrosauri, as a host of rickettsia honei in australia: possible transovarial transmission.in 1993, a novel rickettsia was isolated from the blood of inhabitants of flinders island, australia, with acute febrile illnesses. this rickettsia was found to be a new species of spotted fever group (sfg) rickettsia, eventually named rickettsia honei. the suspected ectoparasite vector of this rickettsia has yet to be identified. the purpose of this study was to evaluate the presence of this rickettsial species in a suspected tick vector, aponomma hydrosauri, by dna sequencing and electron micr ...200312860602
the chemical basis for interfacial activation of monomeric phospholipases a2. autocatalytic derivatization of the enzyme by acyl transfer from substrate.a basic monomeric phospholipase a2 from the venom of the american water moccasin, agkistrodon piscivorus piscivorus, undergoes ca2+-dependent, autocatalytic acylation during the course of hydrolysis of both model and natural phospholipid substrates. acylation occurs at 2 lysine residues, lys-7 and lys-10, in the nh2-terminal alpha-helical segment of the enzyme, and when both positions are fully derivatized, the stable bisacylphospholipase a2 becomes a dimer in solution. the acylated enzyme is fu ...19883403524
contortrostatin, a snake venom disintegrin, inhibits beta 1 integrin-mediated human metastatic melanoma cell adhesion and blocks experimental metastasis.disintegrins are arg-gly-asp-containing proteins that inhibit integrin-mediated cell-cell and cell-matrix interactions. we have purified a disintegrin, contortrostatin, from agkistrodon contortrix contortrix snake venom that is a potent inhibitor of human metastatic melanoma (m24 met) cell adhesion to extracellular matrix proteins. contortrostatin inhibits m24 met cell adhesion to type i collagen, vitronectin, and fibronectin with 50% inhibitory concentration values of 20, 75, and 220 nm, respec ...19947520832
the copperhead snake as a host for the chigger mite trombicula (eutrombicula) alfreddugèsi. 195014795335
thrombolytic agents in development.the quest continues for thrombolytic agents with a higher thrombolytic potency, specific thrombolytic activity and/or a better fibrin selectivity. several lines of research towards improvement of thrombolytic agents are being explored, including the construction of mutants and variants of plasminogen activators (pas), chimaeric pas, conjugates of pas with monoclonal antibodies, and pas from animal or bacterial origin. some of these new thrombolytic agents have shown promise in animal models of v ...19957588087
a novel plasminogen activator from snake venom. purification, characterization, and molecular cloning.a novel plasminogen activator from trimeresurus stejnegeri venom (tsv-pa) has been identified and purified to homogeneity. it is a single chain glycoprotein with an apparent molecular weight of 33,000 and an isoelectric point of ph 5.2. it specifically activates plasminogen through an enzymatic reaction. the activation of human native glu-plasminogen by tsv-pa is due to a single cleavage of the molecule at the peptide bond arg561-val562. purified tsv-pa, which catalyzes the hydrolysis of several ...19957730329
development of an enzyme-linked immunosorbent assay (elisa) for identification of venoms from snakes in the agkistrodon genus.an enzyme-linked immunosorbent assay (elisa) using a purified myotoxin from the venom of agkistrodon contortrix laticintus (broad-banded copperhead) as immunogen was developed for potential use in the identification of envenomation by snakes belonging to the genus agkistrodon native to north america. the specificity of the assay was tested using a total of 43 venom samples from snakes of diverse geographic locations. venom samples used for cross-reactivity determination represent eight snake fam ...19947886691
thrombolytic effects of recombinant fibrolase or apsac in a canine model of carotid artery thrombosis.thrombolytic agents used clinically rely on the activation of plasminogen to plasmin. plasmin possesses multiple actions including increasing thrombin activity and activation of platelets. thus, after successful thrombolytic therapy, arterial hyperactivity and reocclusion may be the result of a predominant plasmin-induced thrombogenic action at the site of the residual thrombus. fibrolase, a direct-acting fibrinolytic enzyme from southern copperhead snake venom, induces rapid clot lysis in vitro ...19947955202
purification and characterization of platelet aggregation inhibitors from snake venoms.proteins that inhibit glycoprotein (gp) iib/iiia mediated platelet aggregation have been purified from the venom of two snake species. a small platelet aggregation inhibitor (p1.ai), multisquamatin (mr = 5,700), was purified from echis multisquamatus venom by hydrophobic interaction hplc and two steps on c18 reverse phase hplc. a larger p1.ai, contortrostatin (mr = 15,000), was purified by a similar hplc procedure from the venom of agkistrodon contortrix contortrix. both p1.ais inhibit adp-induc ...19948178312
purification and characterisation of a snake venom phospholipase a2: a potent inhibitor of platelet aggregation.an inhibitor of human platelet aggregation was identified from the venom of an australian copperhead snake, austrelaps superba, as a novel phospholipase a2. the inhibitor was purified to homogeneity by chromatography on q-sepharose, s-sepharose and c8 reverse phase hplc. the purified phospholipase a2 has a molecular weight of 15 kda as assessed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (sds-page). n-terminal sequence analysis of the platelet inhibitor revealed 70-80% sequence ...19938362372
isolation of a hemorrhagic toxin from the venom of agkistrodon contortrix laticinctus (broad-banded copperhead) and pathogenesis of the hemorrhage induced by the toxin in mice.1. a hemorrhagic toxin was isolated from the venom of agkistrodon contortrix laticinctus (broad-banded copperhead) by sephacryl s-200 hr column chromatography followed by high performance chromatography on waters deae 5pw and protein pak 125 columns. 2. homogeneity was determined by the presence of a single band in acrylamide gel electrophoresis with silver staining. 3. acl hemorrhagic toxin i has a molecular weight of about 29,000, is slightly acidic, and is a metalloprotease with activity towa ...19938444323
different sensitivity of fast- and slow-twitch muscles to some snake venoms and myotoxins.we examined the effect of some crude snake venoms, isolated toxins and non-specific cytotoxic agents on isolated extensor digitorum longus (edl) and soleus (sol) muscles of the mouse. the muscles were continuously perfused with a physiological saline solution. crude venoms from crotalus viridis viridis, agkistrodon contortrix laticinctus and notechis scutatus scutatus were tested at a concentration of 25-50 micrograms ml-1. the increase in the rate of creatine kinase (ck) release (above basal le ...19968817811
a new global test for the evaluation of the protein c-protein s system.we have developed a simple screening assay for evaluating the global activity of the protein c/protein s system. the new test consists of measuring the prothrombin time (pt) with bovine thromboplastin before and after activation of the pc present in the plasma sample by protac, derived from agkistrodon contortrix snake contortrix venom. prolongation of the pt was directly related to the activity of the pc/ps system. one hundred and nineteen thrombophilic patients including 36 with pc deficiency, ...19968839999
chimeric fibrolase: covalent attachment of an rgd-like peptide to create a potentially more effective thrombolytic agent.we have prepared an agent possessing both thrombolytic and antiplatelet properties, by conjugating fibrolase, a direct-acting fibrinolytic enzyme isolated from southern copperhead venom, to a peptide which inhibits platelet aggregation. heterobifunctional coupling reagents, n-succinimidyl 3-(2-pyridyldithio) propionate (spdp) or sulfosuccinimidyl 6-[alpha-methyl-alpha-(2-pyridyldithio)-toluamido]hexanoate (sulfo-lc-smpt), were used in a molar ratio of 10:1 (coupling agent/fibrolase). the n-hydro ...19979263396
un-cross-linked fibrin substrates inhibit keratinocyte spreading and replication: correction with fibronectin and factor xiii cross-linking.wound repair is characterized by the presence of a fibrin-rich matrix, but the effect of fibrin on re-epithelialization remains unclear. in this study, we determined the effects of different fibrin matrices on cultured human neonatal keratinocytes. using purified fibrinogen and fibrin gels generated by the enzymatic action of thrombin, batroxobin (it leads to retention of fibrinopeptide b), or agkistrodon contortrix thrombin-like enzyme (acte; it leads to retention of fibrinopeptide a), we deter ...19989397156
regeneration and change of muscle fiber types after injury induced by a hemorrhagic fraction isolated from agkistrodon contortrix laticinctus venom.tibialis anterior (ta) muscles of rats were evaluated 3h, 3 and 30days after intramuscular injection of acl hemorrhagic toxin i (aclht-i, 5mg/kg), partially purified from the venom of agkistrodon contortrix laticinctus. contralateral muscles were injected with saline. three hours after aclht-1 injection: presence of hemorrhagic areas and myonecrotic muscle fibers. three days: injured muscles showed areas in regeneration, some regions with delay of regeneration and bundles of normal fibers. an in ...200111072042
expression of an active recombinant lysine 49 phospholipase a(2) myotoxin as a fusion protein in bacteria.acl myotoxin (aclmt) is a k49 phospholipase a(2)-like protein isolated from the venom of the snake agkistrodon contortrix laticinctus (broad-banded copperhead) that induces necrosis of skeletal muscle. we have previously cloned and sequenced the cdna coding for aclmt from a venom gland cdna library. in order to perform structure and function studies, we have developed an expression system for production of aclmt as a fusion protein with maltose binding protein (mbp) from the periplasm of bacteri ...200111478968
a novel snake venom disintegrin that inhibits human ovarian cancer dissemination and angiogenesis in an orthotopic nude mouse model.ovcar-5 is a human epithelial carcinoma cell line of the ovary, established from the ascitic fluid of a patient with progressive ovarian adenocarcinoma without prior cytotoxic treatment. the unique growth pattern of ovarian carcinoma makes it an ideal model for examining the anticancer activity of contortrostatin (cn), a homodimeric disintegrin from southern copperhead venom. facs analysis revealed that ovcar-5 is integrin alphavbeta3 negative, but alphavbeta5 positive. cn effectively blocks the ...200111910184
role of d and e domains in the migration of vascular smooth muscle cells into fibrin gels.the structure of fibrin plays an important role in the organization of thrombi, the development of atherosclerosis, and restenosis after ptca. in this study, we examined the mechanisms of the migration of vascular smooth muscle cells (smcs) into fibrin gels, using an in vitro assay system. cultured smcs from bovine fetal aortic media migrated into fibrin gels prepared with thrombin, which cleaves both fibrinopeptides a and b from fibrinogen, without other chemotactic stimuli. both desa fibrin ge ...200212095535
comparison of the in vitro neuromuscular activity of venom from three australian snakes (hoplocephalus stephensi, austrelaps superbus and notechis scutatus): efficacy of tiger snake antivenom.1. tiger snake antivenom, raised against notechis scutatus venom, is indicated not only for the treatment of envenomation by this snake, but also that of the copperhead (austrelaps superbus) and stephen's banded snake (hoplocephalus stephensi). the present study compared the neuromuscular pharmacology of venom from these snakes and the in vitro efficacy of tiger snake antivenom. 2. in chick biventer cervicis muscle and mouse phrenic nerve diaphragm preparations, all venoms (3-10 microg/ml) produ ...200312603339
copperhead envenomations in the carolinas.although the copperhead (akistrodon contortrix) is responsible for most crotaline envenomations in the carolinas, manifestations and treatment are poorly characterized.200312645965
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. acl ...200312651104
preclinical assessment of the ability of polyvalent (crotalinae) and anticoral (elapidae) antivenoms produced in costa rica to neutralize the venoms of north american snakes.polyvalent (crotalinae) and anticoral (elapidae) antivenoms produced by instituto clodomiro picado, costa rica, were assessed for their ability to neutralize various toxic activities of the venoms of north american snakes of the genera crotalus, agkistrodon and micrurus, in assays involving preincubation of venom and antivenom. when the intraperitoneal route of injection was utilized, polyvalent (crotalinae) antivenom was effective in the neutralization of the venoms of crotalus atrox, crotalus ...200312782085
discovery of highly divergent repeat landscapes in snake genomes using high throughput sequencing.we conducted a comprehensive assessment of genomic repeat content in two snake genomes, the venomous copperhead (agkistrodon contortrix) and the burmese python (python molurus bivittatus). these two genomes are both relatively small (∼1.4 gb), but have surprisingly extensive differences in the abundance and expansion histories of their repeat elements. in the python, the readily identifiable repeat element content is low (21%), similar to bird genomes, whereas that of the copperhead is higher (4 ...201121572095
contortrostatin, a dimeric disintegrin from agkistrodon contortrix contortrix, inhibits angiogenesis.contortrostatin, a 13.5 kda disulfide-linked homodimeric polypeptide possessing an arg-gly-asp sequence, was isolated from venom of the southern copperhead snake. daily injection of contortrostatin into the primary tumor of human breast cancer mda-mb-435 carried in nude mice significantly inhibited tumor growth and neovascularization of the tumor tissue. on the chick embryo chorioallantoic membrane, contortrostatin inhibited angiogenesis induced by mda-mb-435 cells, basic fibroblast growth facto ...199914517425
initial experience with crotalidae polyvalent immune fab (ovine) antivenom in the treatment of copperhead snakebite.crotalidae polyvalent immune fab (ovine) (crofab; fabav) effectively treats patients bitten by rattlesnakes. the copperhead snake (agkistrodon contortrix) caused 37% of venomous snakebites reported to us poison centers in 2001 and is the major envenomating reptile in the southeastern united states. fabav has not been tested in human beings envenomated by copperhead snakes.200414747809
diagnostic and therapeutic measure for copperhead snake bite. 1994284666
inhibitory effects on phospholipase a2 and antivenin activity of melanin extracted from thea sinensis linn.antivenin activity of melanin extracted from black tea (mebt) was reported for the first time. the antagonistic effect of mebt was evaluated for agkistrodon contortrix laticinctus (broadbanded copperhead), agkistrodon halys blomhoffii (japanese mamushi), and crotalus atrox (western diamondback rattlesnake) snake venoms administered i.p. to icr mice. mebt was injected i.p. immediately after the venom administration in dose of 3 mg per mouse in the same place of venom injection. mebt demonstrated ...200414967198
anti-angiogenic activity of contortrostatin, a disintegrin from agkistrodon contortrix contortrix snake venom.previous work in our laboratory has shown that contortrostatin (cn), a disintegrin from southern copperhead snake venom, possess anti-angiogenic activity. in the present study we further examined the anti-angiogenic activity of cn, focusing on the mechanisms of cn inhibition of angiogenesis. cn inhibited migration and invasion, and significantly altered matrigel-induced tube formation of human umbilical vein endothelial cells (huvec), but did not affect cell viability, or mmp-2 and mmp-9 activit ...200315041797
intravenous liposomal delivery of the snake venom disintegrin contortrostatin limits breast cancer progression.despite significant research in this area, metastatic breast cancer remains a disease with a poor prognosis. until an effective therapy is developed, it is imperative that new treatment modalities be investigated. in this report, we describe an effective method for delivery of a novel snake venom disintegrin, contortrostatin (cn), in an orthotopic, xenograft model of human mammary cancer in immunodeficient mice. cn (mr 13,500) is a homodimeric disintegrin isolated from venom of the southern copp ...200415078994
effects of a myotoxic asp49 phospholipase a2 (acl-i pla2) isolated from agkistrodon contortrix laticinctus snake venom on water transport in the isolated toad urinary bladder.an asp49 pla2 (acl-i pla2) was purified from the venom of agkistrodon contortrix laticinctus by gel filtration and cation-exchange chromatography. it has a relative molecular mass of 14,000, and its n-terminal sequence has more than 65% of identity with other snake venom pla2s. acl-i pla2 injected into the tibialis anterior muscle of rats and mice at doses of 0.3 and 1.6 mg/kg, respectively, induced muscle fiber necrosis, cellular infiltration and edema 3 and 48 h after injection. the effect of ...200415284020
genetic variation of a disintegrin gene found in the american copperhead snake (agkistrodon contortrix).disintegrins are small, non-enzymatic proteins produced in snake venom. pcr and dna sequencing analysis of genomic dna for all subspecies of the copperhead snake (agkistrodon contortrix) were analyzed for the presence of a disintegrin gene. four samples each of the subspecies: a. c. contortrix, a. c. laticinctus, a. c. mokasen, a. c. phaeogaster, and a. c. pictigaster were collected from different locations across their geographic range and analyzed. a single pcr fragment from each sample was ob ...200616546330
contortrostatin, a snake venom disintegrin with anti-angiogenic and anti-tumor activity.disintegrins are soluble peptides found in snake venom. they bind to arg-gly-asp (rgd)-responsive integrins with high affinity (nm range) and block integrin function. contortrostatin (cn), the disintegrin from southern copperhead venom, is a homodimer with a molecular weight of 13,500. each chain contains 65 amino acids with an arg-gly-asp motif. cn has anti-invasive and anti-adhesive activity on tumor cells and endothelial cells in vitro, and binds to integrins alphavbeta3, alphavbeta5, and/or ...200516707922
development of a novel recombinant disintegrin, contortrostatin, as an effective anti-tumor and anti-angiogenic agent.contortrostatin (cn) (mr 13,500 da) is a novel homodimeric disintegrin isolated from the venom of agkistrodon contortrix contortrix (southern copperhead) snake and displays two rgd motifs (one on each chain), which modulate its interaction with integrins on tumor cells and angiogenic vascular endothelial cells. in previous studies, we have shown that native cn administered in a liposomal formulation exhibits potent anti-angiogenic and tumor growth inhibitory activities. current isolation of the ...200516707923
copperhead snakebite treated with crotalidae polyvalent immune fab (ovine) antivenom in third trimester pregnancy. 200616749561
expression, refolding, and activity of a recombinant nonhemorrhagic snake venom metalloprotease.snake venoms are rich sources of proteases that strongly affect the vascular system, by promoting blood coagulation, hemorrhage, and fibrinolysis. hemorrhagic activity is mostly due to the enzymatic action of metalloproteases on capillary basement membrane components, such as collagen iv, laminin, and fibronectin. a few low-molecular-weight snake venom metalloproteases (svmp) have been described as being devoid of hemorrhagic activity, but they have strong direct-acting fibrinolytic activity tha ...200010833388
a novel venombin b from agkistrodon contortrix contortrix: evidence for recognition properties in the surface around the primary specificity pocket different from thrombin.a novel thrombin-like enzyme (named contortrixobin) has been purified to homogeneity from the venom of agkistrodon contortrix contortrix by affinity chromatography on arginine-sepharose, anionic exchange chromatography, and hplc. the complete amino acid sequence has been determined by edman degradation and by mass spectral analysis of peptides generated by enzymatic cleavage. a microheterogeneity at the level of residue 234 has been detected, as demonstrated by peptides differing for the occurre ...200010956019
contortrostatin, a dimeric disintegrin from agkistrodon contortrix contortrix, inhibits breast cancer progression.we report the results of a multidisciplinary study on the inhibitory effect of a snake venom disintegrin, contortrostatin, a 13.5 kda homodimeric protein isolated from agkistrodon contortrix contortrix (southern copperhead) venom, on breast cancer progression. we demonstrate that contortrostatin binds to integrins and blocks the adhesion of human breast cancer cells (mda-mb-435) to extracellular matrix (ecm) proteins including fibronectin and vitronectin, but it has no effect on adhesion of the ...200010966001
increase of the cytotoxic effect of bothrops jararacussu venom on mouse extensor digitorum longus and soleus by potassium channel blockers and by na(+)/k(+)-atpase inhibition.we investigated the myotoxicity of bothrops jararacussu crude venom and other cytolytic agents on mouse isolated extensor digitorum longus (edl) and soleus (sol) muscles, which present distinct properties: edl is a fast-twitch, white muscle with predominantly glycolytic fibers, while sol is slow-twitch, red muscle with predominantly oxidative fibers. muscles were exposed to b. jararacussu crude venom (25 microg/ml) and other crotaline venoms (agkistrodon contortrix laticinctus; crotalus viridis ...200818675839
cdna cloning, expression and fibrin(ogen)olytic activity of two low-molecular weight snake venom metalloproteinases.two cdna clones, aplvmp1 and aplvmp2, were isolated from a snake (agkistrodon piscivorus leucostoma) venom gland cdna library. the full-length cdna sequence of aplvmp1 with a calculated molecular mass of 46.61 kda is 1233 bp in length. aplvmp1 encodes pi class metalloproteinase with an open reading frame of 411 amino acid residues that includes signal peptide, pro-domain and metalloproteinase domains. the full-length cdna of the aplvmp2 (1371 bp) has a calculated molecular mass of 51.16 kda and ...200919375443
aapcc database characterization of native u.s. venomous snake exposures, 2001-2005.differences in victim demographics, clinical effects, managements, and outcomes among native viperid (rattlesnake, copperhead, and cottonmouth) and elapid (coral snake) species have not been systematically characterized.200919514880
human cytokine response to texas crotaline envenomation before and after antivenom administration.the aim of this study was to characterize the human cytokine response to texas crotaline envenomation before and after antivenom administration.201020887908
molecular mechanism analysis of gloydius shedaoensis venom gloshedobin interaction with inhibitors by homology modeling.snake venom thrombin-like enzymes (svtles) are widely applied in the treatment of thrombotic diseases, however, the molecular mechanism of its inhibition by synthetic and natural proteinaceous inhibitors is not yet understood. here we investigated effects of protease inhibitors including phenylmethylsulfonil fluoride (pmsf), benzamidine (bmd) and its derivates on the activity of recombinant gloshedobin, a svtle from the snake gloydius shedaoensis. the molecular inhibition mechanism was postulate ...201020969888
in vitro evaluation of total venom-antivenin immune complex formation and binding parameters relevant to antivenin protection against venom toxicity and lethality based on size-exclusion high-performance liquid chromatography.total venom-antivenin immune complex formation and binding parameters relevant to antivenin protection against venom toxicity and lethality can be evaluated using size-exclusion high-performance liquid chromatography (se-hplc). simple integration of regions within se-hplc elution profiles was used to compare binding characteristics of crotalidae polyvalent immune fab (ovine) antivenin (fabav) and crotalus atrox (western diamondback rattlesnake; c. atrox), c. varidis varidis (prairie rattlesnake; ...201121392522
modular design, expression and characterization of novel bifunctional mutants of fibrolase with combined platelet aggregation-inhibition and fibrinolytic activity.fibrolase is a non-hemorrhagic zinc metalloproteinase found in southern copperhead snake (agkistrodon contortrix contortrix) venom that acts directly on fibrin clots and does not require plasminogen or any other blood-borne intermediate for activity. chimeras of fibrolase with rgd peptides conferring antiplatelet activity have been synthesized covalently, but we describe a simpler, cheaper and less toxic method, using site-directed mutagensis. fibrolase variants that constitute the arginine-glyc ...201121479991
fibrolase: trials and tribulations.fibrolase is the fibrinolytic enzyme isolated from agkistrodon contortrix contortrix (southern copperhead snake) venom. the enzyme was purified by a three-step hplc procedure and was shown to be homogeneous by standard criteria including reverse phase hplc, molecular sieve chromatography and sds-page. the purified enzyme is a zinc metalloproteinase containing one mole of zinc. it is composed of 203 amino acids with a blocked amino-terminus due to cyclization of the terminal gln residue. fibrolas ...201022069611
identification of presynaptic neurotoxin complexes in the venoms of three australian copperheads (austrelaps spp.) and the efficacy of tiger snake antivenom to prevent or reverse neurotoxicity.the venom of the australian lowlands copperhead, austrelaps superbus, produces significant and potentially lethal neurotoxic paralysis in cases of clinical envenomation. however, little is known about the neurotoxic components within this venom or venoms from the related alpine copperhead (austrelaps ramsayi) or pygmy copperhead (austrelaps labialis). using the isolated chick biventer cervicis nerve-muscle preparation, all austrelaps venoms were found to exhibit potent and rapid inhibition of ne ...201121854797
primary structure of a protein c activator from agkistrodon contortrix contortrix venom.the amino acid sequence of a protease, protein c activator, from agkistrodon contortrix contortrix venom was determined. peptide fragments obtained by chemical or enzymatic cleavage of the s-carboxymethylated protein were purified by gel filtration and reverse-phase high-performance liquid chromatography. the present study demonstrates that protein c activator from a. contortrix contortrix venom is a trypsin-type serine protease that is composed of 231 residues with a molecular weight of 25,095 ...19982653426
amino acid sequence of fibrolase, a direct-acting fibrinolytic enzyme from agkistrodon contortrix contortrix venom.the complete amino acid sequence of fibrolase, a fibrinolytic enzyme from southern copperhead (agkistrodon contortrix contortrix) venom, has been determined. this is the first report of the sequence of a direct-acting, nonhemorrhagic fibrinolytic enzyme found in snake venom. the majority of the sequence was established by automated edman degradation of overlapping peptides generated by a variety of selective cleavage procedures. the amino-terminus is blocked by a cyclized glutamine (pyroglutamic ...20041304358
a simple, automated functional assay for protein c.protein c is an important anticoagulant in circulating blood. the balance between the procoagulant and anticoagulant pathways determines whether a patient is at risk for thrombosis or hemorrhage, and low levels of protein c may result in thrombotic disease. it is important for clinical coagulation laboratories to measure protein c. for this purpose, a simple functional assay is needed. this article describes an automated assay for functional protein c with activation by copperhead venom. the aut ...20092756936
detection of eastern equine encephalomyelitis virus rna in north american snakes.the role of non-avian vertebrates in the ecology of eastern equine encephalomyelitis virus (eeev) is unresolved, but mounting evidence supports a potential role for snakes in the eeev transmission cycle, especially as over-wintering hosts. to determine rates of exposure and infection, we examined serum samples from wild snakes at a focus of eeev in alabama for viral rna using quantitative reverse transcription polymerase chain reaction. two species of vipers, the copperhead (agkistrodon contortr ...201223033405
[properties of extracellular proteinase--an activator of protein c in blood plasma formed by aspergillus ochraceus].the properties of an extracellular proteinase activating plasma protein c isolated from the culture supernatant of a. ochraceus vkm f-4104d have been studied. this enzyme demonstrated a substrate specificity absent of hydrolyzing activity toward chromogenic proteinase substrates. on the basis of inhibitory analysis, the protein c-activating proteinase from a. ochraceus vkm f-4104d appeared to be a serine proteinase, together with that isolated from the venom of agkistrodon contortrix contortrix. ...201525842908
the effect of post-translational modifications on the hemorrhagic activity of snake venom metalloproteinases.metalloproteinases (mps) are zn(+)-dependent endoproteolytic enzymes, abundant in crotalid and viperid snake venoms. most snake venom metalloproteinases (svmps) are active on extracellular matrix components and this effect is thought to result in bleeding as a consequence of the basement membrane disruption in capillaries. jararhagin and aclh are hemorrhagic svmps from bothrops jararaca and agkistrodon contortrix laticinctus venom, respectively. both enzymes demonstrate proteolytic activity on f ...200415313443
clinically significant envenomation from postmortem copperhead (agkistrodon contortrix).over 14,000 copperhead (agkistrodon contortrix) bites were reported to united states poison centers between 1983 and 2008, and 1809 cases were reported to poison centers in 2014. the copperhead is primarily found in the southeastern united states and belongs to the pit viper subfamily crotalinae, which also includes the water moccasin (agkistrodon piscivorus) and rattlesnakes (crotalus and sistrurus genera). postmortem rattlesnakes have been reported to cause clinically significant envenomation; ...201727876196
expression of soluble and functional snake venom fibrinolytic enzyme fibrolase via the co-expression of dsbc in escherichia coli.fibrolase is a non-hemorrhagic zinc metalloproteinase found in southern copperhead snake venom (agkistrodon contortrix contortrix). it is capable of degrading fibrin clots that result from purified fibrinogen or blood plasma. the dna of fibrolase was amplified by recursive pcr, and cloned into the pet25b(+) expression vector. the effect of co-expression of signalless versions of catalysts or molecular chaperones fkpa, skp and dsbc in cytoplasm was examined. when co-expressed with dsbc, compared ...200616842109
treatment of snakebite in australia: the current evidence base and questions requiring collaborative multicentre prospective studies.despite the wealth of anecdotes and case reports there are fundamental questions of management of snakebite in australia that remain unresolved or for which the current evidence is limited. the efficacy in the field, potential limitations and possibility of improvements in pressure immobilisation first aid need objective studies in humans. optimal bandage sizes, stretch and pressure for different sized limbs need further evaluation, as does the use of pressure pads. better definitions of specifi ...200616930660
effect of raclf, a recombinant snake venom metallopeptidase on cell viability, chemokine expression and degradation of extracellular matrix proteins.snake venom metallopeptidases (svmps) comprise a family of zinc-dependent enzymes, which display many different biological activities. aclf is a 23kda fibrinolytic non-hemorrhagic metallopeptidase from the venom of the snake agkistrodon contortrix laticinctus. we have previously developed an expression system for production of recombinant aclf (raclf) in bacteria. to achieve a better understanding of the role of such enzyme in envenoming cases, we have studied the biological properties of raclf, ...200616949115
molecular isoforms of cobra venom factor-like proteins in the venom of austrelaps superbus.cobra venom factor (cvf) is characteristic of the elapid cobras and has not been reported from venoms of any other families of snakes. during our search for novel proteins, we isolated a polypeptide from the venom of the snake austrelaps superbus (lowland copperhead) that showed structural similarity to c-terminal segment of the alpha-chain of cvf and hence named as avfalphac (avf-a. superbus venom factor). cdna sequence of avfalphac and its precursor indicated the presence of two isoforms of cv ...200717412383
laterality in coiling behaviour of snakes: another interpretation.the direction of coiling was periodically recorded for two species of viperid snakes--copperheads (agkistrodon contortrix) and cottonmouths (agkistrodon piscivorus). overall, neither species showed a significant preference for coiling in a particular direction. only 1 of 22 snakes exhibited an individual preference, a result within expectation for random direction of coiling when using a 5% rejection level for statistical testing. a previously published claim for laterality in coiling direction ...200717852698
citrate is a major component of snake venoms.citrate has been identified as a major component of snake venoms by gas liquid chromatography and mass spectrometry. the venoms of bothrops asper, crotalus atrox, crotalus viridis viridis, crotalus adamanteus, sistrurus miliarius barbouri, crotalus horridus horridus, agkistrodon contortrix mokasen, agkistrodon contortrix contortrix and agkistrodon piscivorus piscivorus contain citrate at concentration levels which can serve as effective buffers. calcium, magnesium, zinc, iron, sodium and potassi ...19921626327
hplc-based two-step purification of fibrinolytic enzymes from the venom of agkistrodon contortrix contortrix and agkistrodon piscivorus conanti.in investigations aimed at characterizing snake venom blood clot-dissolving enzymes, we have developed a rapid two-step high-performance chromatography method for the isolation of these fibrinolytic enzymes from the venoms of agkistrodon contortrix contortrix and agkistrodon piscivorus conanti. the first step consisted of hydrophobic interaction chromatography on a propyl-aspartamide column. fractions containing the fibrinolytic activity were then concentrated and applied to a hydroxylapatite co ...19902152182
analysis of a cdna sequence encoding a novel member of the snake venom metalloproteinase, disintegrin-like, cysteine-rich (mdc) protein family from agkistrodon contortrix laticinctus.in this paper, we present a cdna sequence encoding a full-length precursor form of a new member (acld) of the metalloproteinase-disintegrin-like protein family from the venom glands of agkistrodon contortrix laticinctus (broad-banded copperhead) snake. comparison of the deduced amino acid sequence of acld with those of other members of the metalloproteinase-disintegrin protein family from both mammalian and snake venom origin suggests that some conserved residues may be involved in processing of ...19979392519
infrared imaging in vipers: differential responses of crotaline and viperine snakes to paired thermal targets.pit vipers use infrared-sensitive pit organs to accurately target homeothermic prey even in the absence of visual cues. it has been suggested that other vipers, including large ambush predators of the genus bitis, also may use radiant infrared information for predatory targeting. we compared behavioral responses of pit vipers and snakes of the viperine genus bitis to paired targets of different temperatures (i.e. cool and warm balloons), some scented with rodent odors. the rates of tongue flicki ...200415302110
thrombin-like and fibrinolytic enzymes in the venoms from the gaboon viper (bitis gabonica), eastern cottonmouth moccasin (agkistrodon p. piscivorus) and southern copperhead (agkistrodon c. contortrix) snakes.crude venom from b. gabonica contained weak fibrinogen clotting activity but no visible fibrinolytic activity, whereas venoms from a. p. piscivorus and a. c. contortrix exhibited fibrinolytic activity (by fibrin plate assay) but no thrombin-like activity. these snake venoms were fractionated on sephadex g-100 with the following results. thrombin-like activity in b. gabonica venom was eluted in a single protein peak with a molecular weight of 40,000. agkistrodon p. piscivorus venom contained a si ...19827043785
stable isotope tracer reveals that viviparous snakes transport amino acids to offspring during gestation.viviparity and placentation have evolved from oviparity over 100 times in squamate reptiles (lizards and snakes). the independent origins of placentation have resulted in a variety of placental morphologies in different taxa, ranging from simple apposition of fetal and maternal tissues to endotheliochorial implantation that is homoplasious with mammalian placentation. because the eggs of oviparous squamates transport gases and water from the environment and calcium from the eggshell, the placent ...201222323198
bioenergetic components of reproductive effort in viviparous snakes: costs of vitellogenesis exceed costs of pregnancy.reproductive effort has been defined as the proportion of an organism's energy budget that is allocated to reproduction over a biologically meaningful time period. historically, studies of reproductive bioenergetics considered energy content of gametes, but not costs of gamete production. although metabolic costs of vitellogenesis (mcv) fundamentally reflect the primary bioenergetic cost of reproductive allocation in female reptiles, the few investigations that have considered costs of reproduct ...201121884815
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