RESUMO
Despite a recent surge in high-throughput venom research that has enabled many species to be studied, some snake venoms remain understudied. The long-tailed rattlesnakes (Crotalus ericsmithi, C. lannomi, and C. stejnegeri) are one group where such research lags, largely owing to the rarity of these snakes and the hazardous areas, ripe with drug (marijuana and opium) production, they inhabit in Mexico. To fill this knowledge gap, we used multiple functional assays to examine the coagulotoxic (including across different plasma types), neurotoxic, and myotoxic activity of the venom of the long-tailed rattlesnakes. All crude venoms were shown to be potently anticoagulant on human plasma, which we discovered was not due to the destruction of fibrinogen, except for C. stejnegeri displaying minor fibrinogen destruction activity. All venoms exhibited anticoagulant activity on rat, avian, and amphibian plasmas, with C. ericsmithi being the most potent. We determined the mechanism of anticoagulant activity by C. ericsmithi and C. lannomi venoms to be phospholipid destruction and inhibition of multiple coagulation factors, leading to a net disruption of the clotting cascade. In the chick biventer assay, C. ericsmithi and C. lannomi did not exhibit neurotoxic activity but displayed potential weak myotoxic activity. BIRMEX® (Faboterápico Polivalente Antiviperino) antivenom was not effective in neutralising this venom effect. Overall, this study provides an in-depth investigation of venom function of understudied long-tailed rattlesnakes and provides a springboard for future venom and ecology research on the group.
Assuntos
Anticoagulantes , Venenos de Crotalídeos , Crotalus , Animais , Venenos de Crotalídeos/toxicidade , Humanos , Anticoagulantes/farmacologia , Cannabis/química , Ratos , Coagulação Sanguínea/efeitos dos fármacos , MéxicoRESUMO
The evolution of an aquatic lifestyle from land dwelling venomous elapids is a radical ecological modification, bringing about many evolutionary changes from morphology to diet. Diet is an important ecological facet which can play a key role in regulating functional traits such as venom composition and prey-specific targeting of venom. In addition to predating upon novel prey (e.g., fish, fish eggs and invertebrates), the venoms of aquatic elapids also face the challenge of increased prey-escape potential in the aquatic environment. Thus, despite the independent radiation into an aquatic niche on four separate occasions, the venoms of aquatic elapids are evolving under convergent selection pressures. Utilising a biolayer interferometry binding assay, this study set out to elucidate whether crude venoms from representative aquatic elapids were target-specific to the orthosteric site of postsynaptic nicotinic acetylcholine receptor mimotopes of fish compared to other terrestrial prey types. Representatives of the four aquatic lineages were: aquatic coral snakes representative was Micrurus surinamensis;, sea kraits representative was Laticauda colubrina; sea snakes representatives were two Aipysurus spp. and eight Hydrophis spp; and water cobras representative was Naja annulata. No prey-specific differences in crude venom binding were observed from any species tested, except for Aipysurus laevis, which showed slight evidence of prey-potency differences. For Hydrophis caerulescens, H. peronii, H. schistosus and M. surinamensis, there was a lack of binding to the orthosteric site of any target lineage. Subsequent testing on the in vitro chick-biventer cervicis muscle preparation suggested that, while the venoms of these species bound postsynaptically, they bound to allosteric sites rather than orthosteric. Allosteric binding is potentially a weaker but faster-acting form of neurotoxicity and we hypothesise that the switch to allosteric binding is likely due to selection pressures related to prey-escape potential. This research has potentially opened up the possibility of a new functional class of toxins which have never been assessed previously while shedding light on the selection pressures shaping venom evolution.
RESUMO
Motor vehicle collisions (MVCs) are a significant cause of pediatric morbidity, particularly in low- to middle-income countries. We describe car seat use in children on the USA-Mexico border. A retrospective review was conducted for children 0-9 years old, admitted to the region's only Level I trauma center. Simultaneously, data were obtained from the SAFE KIDS database, a program that encourages car seat use through city checkpoints. There were 250 MVC admissions and nine fatalities in children 0-9 years old from 2010 to 2015. Nine percent of MVCs occurred in Mexico and 49% in El Paso, TX. Comparing trauma admissions to SAFE KIDS, there was some correlation between the location of MVCs and screening checkpoints (r = .50). There was a weaker correlation between injured children's neighborhoods and screening locations (r = .32). Only 37% of parents knew the crash history of the car seat and 3% were using a car seat previously involved in an MVC. While 96% of inspected children were placed appropriately in the backseat, 80% of children were found to be inappropriately restrained. Younger children more likely to be restrained (p < .05). Children from New Mexico and Mexico had the lowest rates of proper restraint and the highest injury severity scores. Proper use of car seats is a public health concern on the USA-Mexico border, and children are not properly restrained. Screening may be improved by focusing where at-risk children live and where most accidents occur. Restraint education is needed, particularly in New Mexico and Mexico.
Assuntos
Acidentes de Trânsito/mortalidade , Acidentes de Trânsito/estatística & dados numéricos , Sistemas de Proteção para Crianças/estatística & dados numéricos , Proteção da Criança , Cintos de Segurança/estatística & dados numéricos , Acidentes de Trânsito/prevenção & controle , Fatores Etários , Criança , Pré-Escolar , Características Culturais , Bases de Dados Factuais , Feminino , Humanos , Lactente , Masculino , México , Veículos Automotores , Estudos Retrospectivos , Fatores de Risco , Fatores Socioeconômicos , Taxa de Sobrevida , TexasRESUMO
While some US populations of the Mohave rattlesnake (Crotalus scutulatus scutulatus) are infamous for being potently neurotoxic, the Mexican subspecies C. s. salvini (Huamantlan rattlesnake) has been largely unstudied beyond crude lethality testing upon mice. In this study we show that at least some populations of this snake are as potently neurotoxic as its northern cousin. Testing of the Mexican antivenom Antivipmyn showed a complete lack of neutralisation for the neurotoxic effects of C. s. salvini venom, while the neurotoxic effects of the US subspecies C. s. scutulatus were time-delayed but ultimately not eliminated. These results document unrecognised potent neurological effects of a Mexican snake and highlight the medical importance of this subspecies, a finding augmented by the ineffectiveness of the Antivipmyn antivenom. These results also influence our understanding of the venom evolution of Crotalus scutulatus, suggesting that neurotoxicity is the ancestral feature of this species, with the US populations which lack neurotoxicity being derived states.