Showing posts with label venom. Show all posts
Showing posts with label venom. Show all posts

Tuesday, January 17, 2012

Biosensor Technology for Snake Venom

The following story by T. Nandakumar is from The Hindu, originally published in November 1, 2011 and was sent by Dr. A. Buji Kumar.
Naja naja, JCM
A team of researchers at the State Inter-University Centre for Excellence in Bioinformatics (SIUCEB) under the University of Kerala is working on the development of a biosensor for identification of snake venom that could help bring down the mortality rate of snake bite victims in the country significantly.

The State-funded project, essentially an amalgamation of biology and electronics, will enable targeted treatment of snake bite victims by precise detection of the type of snake. The sensor under development is a gadget like a glucometer that can read a strip laced with the body fluid of a snake bite victim and provide a read out on a screen. The blood, urine or fluid from the bite site can be used to analyse the specific type of venom. The prototype of the biosensor is expected to be ready in eight months.

According to WHO estimates, India has the highest number of deaths (35,000 to 50,000 a year) due to snake bites. The States with the largest number of snake bite cases include Kerala, Maharashtra, West Bengal, Uttar Pradesh, and Tamil Nadu.

In India, the conventional clinical practice is to administer polyvalent anti-snake venom (ASV) which comprises antibodies of four different species (Big Four), namely the Spectacled (Indian) cobra, the Common krait, Saw-scaled viper and Russell's viper, that account for most of the bite cases.
The polyvalent method accounts for the high incidence of snake bite deaths in India. It often causes severe allergic reaction in the victim, (seen in up to 30 per cent of the recipients worldwide) demanding secondary treatment.

Australia has the highest number of venomous snakes, yet the number of death cases is less because the country follows the targeted monovalent technique based on identification of species using a snake venom detection kit.

“The polyvalent treatment method results in collateral damage, affecting internal organs. To confirm a snake bite, doctors often wait for symptoms like dizziness, nausea or imbalance, typical of neurotoxins, or anti-coagulation of blood that is characteristic of haemotoxins. The delay can lead to complications or death,” says R. Dileepkumar, Post Doctoral Fellow at SIUCEB and principal investigator of the project.

The biosensor, based on ELISA (Enzyme Linked Immuno Sorbent Assay) technology, will obviate the need to wait for symptoms and avoid the complications inherent in administering polyvalent antivenom.

The project team at SIUCEB is currently raising antibodies in mammalian models against the Big Four species that account for the maximum number of snake bites in India.

The sensor is expected to overcome many limitations in the conventional approach like cross reactivity and sensitivity, says Mr. Dileepkumar. “It can also be used to quantify the extent of envenomation (to determine the dose of monovalent ASV required) and to monitor the venom clearance from the body,”

When a snake bite victim is brought to the hospital, the doctor or technician collects body fluids from the person and applies them to the strips coated with species-specific antibodies. The unreacted materials in the fluid are washed off and the strips are administered with enzyme-labelled secondary antibody that can generate electrons measurable as electric current for a reaction. The strips are then inserted into the biosensor to give a reading that can be classified as one of the Big Four venoms.

While the technical design of the biosensor is complete, the biological study is on. Mr. Dileepkumar says efforts are on to tie up with research institutions in the Middle East for sourcing more stable antibodies raised from the camel. This, he says, would avoid the need to store the strips at low temperature.

Sunday, April 10, 2011

Scutulatus from Cochise County, AZ

The Mojave Rattlesnake, Crotalus scutulatus. JCM
Mojave rattlesnakes (Crotalus scutulatus) in Arizona have two quite different kinds of venom. The venom of population A (venom A) contains the toxin known as ‘Mojave toxin’ and it lacks hemorrhagic and specific proteolytic activities- instead it acts on the nervous system. Population B (venom B) does not contain Mojave toxin but instead produces hemorrhagic and proteolytic activities, acting on blood and blood vessels. This situation has been known since at least 1988. Glenn and Straight (1988) examined the venom of 15 Crotalus scutulatus scutulatus from the regions between the venom A and venom B populations in Arizona for the presence of Mojave toxin Seven of the venoms contained both the Mojave toxin of venom A and the proteolytic and hemorrhagic activities of venom B. The i.p. LD50 values of the A+B venoms were 0.4–2.6 mg/kg, compared to 0.2–0.5 mg/kg for venom A individuals and 2.1–5.3 mg/kg for the venom B individuals.Thus, populations with the A+B venom type are almost twice as venomous (at least to mice) as snakes with venom A or B types. Their results suggested an intergrade zone exists between the two venom types which arcs around the western and southern regions of the venom B population. Within these regions, three major venom types (A, B and A+B) can occur in Crotalus s. scutulatus. Thus, the reason for the following article. Crotalus scutulatus is most likely the most dangerous North American rattlesnake.

Glenn, JL and Straight, RC. 1988. Intergradation of two different venom populations of the Mojave rattlesnake (Crotalus scutulatus scutulatus) in Arizona. Toxicon 27, 411-418.

Cochise County's rattlesnakes even deadlier than most
Carly Kennedy
Arizona-Sonora News Service

Like humans, rattlesnakes like the outdoors this time of the year.

And the Mojave rattlesnake that's commonly found in Cochise County might be more deadly than any rattler in any other area of Arizona.

Emergency room doctors in Tucson and Sierra Vista have noticed that patients who suffer from a Cochise County Mojave rattlesnake bite do respond well to the anti-venom, but they often come back to the hospital complaining of the same symptoms.

Herpetologists have gathered from these cases that the Mojave rattlesnakes in Cochise County have venom that is more potent than that from Mojaves in other counties, said Brian Gill, owner of the Tombstone Reptile Exhibit.

One of the supporting theories behind this confusing trend has to do with the type of food the Cochise Mojave eats.

Mojaves typically eat rodents, but in Cochise County there aren't as many rodents available, and so the rattlesnakes in the region have grown accustomed to eating snacks that are more accessible, such as lizards and geckos, Gill said.

"This might be converting the toxins in their body into a more potent toxin," he added.

The Mojave rattlers are one of only four snakes in Arizona that have venom that is a neurotoxin. Upon entering the human body, the toxin starts attacking the nervous system and can ultimately lead to cardiac arrest or respiratory arrest.

Even with its powerful venom, the Mojave is not the most common species in the county, said Tombstone animal control officer James Everetts. He said the most prevalent species of rattler is the Western diamondback.

The diamondback rattlesnake has venom that is a hemotoxin, which affects the surrounding tissue of the bitten area. After the bite has occurred, the hemotoxin starts eating away tissue and causes a "burning" sensation, said Everetts, who has been bitten three times.

"It's like touching an open flame, but you can feel that pain inside your body," he said.

Rattlesnake season spans throughout early spring well into the summer months, seeing its height in May and June, which is the mating season, Gill said.

Experts warn to avoid the snakes altogether, especially during their midday sunning on nearby rocks. "As the snake's energy level increases, so does its aggression," Gill said.

At night, the snakes migrate to roadways because the asphalt acts as a source of warmth. Nighttime serves as their hunting time, so they can be aggressive and should be avoided, Gill said.

During snake season Tombstone Animal Control receives plenty of calls, but those tend to come in spurts as the rattlesnakes migrate in search of food and water. During runs of hotter weather, there will be an average of two calls a week, Everetts said.

"They spread out everywhere to find food and water, so I can go weeks without hearing of any sightings," he added.  Everetts warned victims of a diamondback strike not to place ice or heat on the infected area.

"Ice will keep the hemotoxin centralized, and it will eat away at the surrounding tissue," he said. "And heat will spread the poison too quickly." The best thing a rattlesnake bite victim can do immediately is wash the area with antibacterial soap, circle the marks the snake has made and write down the approximate time of the bite, Everetts said.

"When you get to the hospital, this allows the physicians to judge the severity of the swelling and how fast the poison is moving through the system."

Sunday, March 27, 2011

Russell's Viper Venom & Blood Clots

Daboia russelii. Photo Credit: 
Abhinav Chawla  
Fibrinolytic drugs are given after a heart attack to dissolve the blood clot blocking the coronary artery, and they have been used experimentally in stroke and in massive pulmonary embolisms. Enzymes that are fibrinolytic have been found in the venoms of several snakes, such as the Malaysian Pit Viper, Calloselasma rhodostoma; the lancehead, Bothrops atrox; the Lebentine Viper, Vipera lebetina; the Eastern Diamondback Rattlesnake, Crotalus adamanteus; the Copperhead, Agkistrodon contortrix; and Russell's Viper, Daboia russelii.  The ability of the fibrinolyrtic enzyme from the Lebetine Viper has been studied for the removal of blood clots using rats and fibrinolytic enzymes from the Malaysian Pit Viper, C. rhodostoma,  and from the lancehead, B. atrox were used in  patients with deep vein thrombosis and ischemic stroke under controlled condition. Recently, recombinant fibrinolytic enzymes derived from snake venom were used in clinical trials. Venom from eastern Indian Russell Vipers (Daboia russelii russelii) has two hemorrhagins as well as VRR-73 that shows fibrinolytic and esterolytic activities that are independent of hemorrhagic activity. Gargi Maity and colleagues have now demonstrated that Russel Viper venom can be denatured at a temperature of 100 C so that it looses its hemorrahgic activity, but it does not alter its fibrinolytic ability. Thus, the fibrinolytic activity of VRR-73 has the potential for development as anticoagulant for therapeutic use once the hemorrhagic activity of the venom has been removed. Viper venoms are rich source of active proteins and peptides that affect hemostatic system and a likely source of more molecules that can have a direct, positive impact on human health.

Maity, G., et al., 2011. Thermal detoxification of the venom from Daboia russelli russelli of Eastern India with restoration of fibrinolytic activity, Toxicon (2011), doi:10.1016/j.toxicon.2011.02.008.

Monday, March 14, 2011

Diabetes, Venom & the Conservation of Biodiversity

In the next 15 years it is estimated that 380 million people world wide will be diagnosed with diabetes. Obesity and the accompanying resistance to insulin result in the progressive failure of b-cells to produce type 2 diabetes. The chronic complications of diabetes comprise an increased risk of death and disability from coronary heart disease, stroke and peripheral vascular disease, and microvascular disease, resulting in retinopathy, nephropathy and neuropathy. Diabetes is the major medical cause of blindness in developed countries, as well as a major cause of end-stage renal failure. Thus there is a major research effort to find new and effective therapies for diabetes. Byetta, a synthetic exenatide, was approved in 2005 as the first in class of a new molecules for treating Type 2 Diabetes. US sales peaked at $678 million in 2008. The development of Byetta resulted from two lines of investigation, these being the development of the ‘incretin concept’ and a parallel, at first unrelated, study of the venom of the American, the Gila Monster, Heloderma suspectum.The venom contained a molecule identified as exendin-4, a peptide mimicking the incretin hormone glucagon-like peptide 1 (GLP-1). The  ‘incretin concept’ hypothesis proposed that hormones from the gut contributed to the insulin secretion in response to meals, led to the identification of glucagon-like peptide 1 (GLP-1) as an important ‘incretin’ hormone. GLP-1 not only increases insulin secretion but increases b-cell proliferation and survival, while suppressing glucagon secretion, it also delays gastric emptying and suppresses appetite, all of these actions contributing to a potential anti-diabetic effect. However, GLP-1 has a very short half, it is rapidly broken down by dipeptidyl peptidase IV and ectopeptidases. A systematic investigation of the composition and activity of venom from the Gila monster,  led to the isolation of a 39-amino acid peptide, designated exendin-4, showing 53% structural homology with GLP-1. Exendin-4 mimicked GLP-1 through stimulating the GLP-1 receptor. Exendin-4 is not broken down as easily ad GLP-1 and this led to its experimental and clinical evaluation as an anti-diabetic. There is no better argument for the conservation of biodiversity when it comes to arguing with greedy corporations, than stories like this.

Furman, B.L. 2011. The development of Byetta (exenatide) from the venom of the Gila monster as an anti-diabetic agent. Toxicon, In Press, doi:10.1016/j.toxicon.2010.12.016

Sunday, March 13, 2011

Venom Composition in a Litter of Death Adders

Photo Credit: 

Mohammad Al-Saleh
Knowledge of venoms is incomplete and sometimes experiments produce conflicting results. At least one study suggested that juvenile venom was more toxic than adult venom, giving rise to the commonly held, but misleading, belief that neonates snakes were more poisonous than the adults. The primary functions of venom are immobilization of prey, initiation of digestion, and to deter potential predators. Thus, venom has evolved numerous  proteins with different roles to produce substantial variation in venom composition between genera and species as well as within species. Remarkably venom can vary within a single litter and even within an individual over its life time.Genetics determine venom composition but variation during the life of an individuals suggest plasticity in the expression of the venom genes. The metabolism of a snake increases after venom has been spent. In a new study Anna Pintor and colleagues examine the dependence of increases in metabolic rate following venom expenditure on the stage of venom replenishment that the venom producing tissue is in at the time of venom extraction in the Common Death Adder, Acanthophis antarcticus. They found that venom expenditure is followed by a sudden increase in metabolic rate when snakes have previously not expended venom for at least two days, suggesting that repetitive venom expenditure does not further increase the activity of venom gland tissue during this initial time period but that a second upregulation occurs when the tissue is past the initial activation stage. In addition, venom composition appears to remain constant during replenishment within an individual, but they observed  substantial variations between siblings. Thus, venom composition does not appear to change during replenishment in individuals of the Death Adder, A. antarcticus, but variation between individuals is surprisingly high. The authors suggest that venom components are most likely replenished at a similar rate with metabolic costs being related to slow and extended rates of synthesis. They report an apparent absence of additional increases in metabolism after venom expenditure during the early stages of replenishment and suggest the physiological response to venom expenditure is not additive, but is initiated only while the venom glands are past a certain stage of replenishment. The mechanism that activates venom gland tissue is not known and further research in this direction would be of interest. Also see this related post.

Pintor A. F., K. L.Winter, A. K. Krockenberger, and J. E. Seymour. 2011. Venom physiology and composition in a litter of Death Adders (Acanthophis antarcticus) and their parents. Toxicon 57:68-75.