Category Archives: Biology

New addition to the snakebite first aid kit

Covering a snakebite wound with an ointment that slows the spread of the snake venom through the body’s lymphatic system could delay the toxin from entering the bloodstream and give snakebite victims more precious time to seek medical help.

In some snake venoms, the toxins are too large to immediately enter the bloodstream and instead first travel through the lymphatic system before entering the heart. As nitric oxide inhibits the pumping action of the body’s lymph system, Megan Saul and colleagues reasoned that applying topical agents that release nitric oxide to the snakebite wound could impede the venom’s progress in the body. Thus, the researchers tested an ointment that contained nitric-oxide-releasing glyceryl trinitrate in their study published in Nature Medicine.

By simulating a snakebite in human volunteers (6 men and 9 women, who were told to remain still throughout the experiment, an important component of snake bite first aid) and injecting participants with a molecular dye, the researchers could track the progress of ‘snake venom’ through the lymph (from the initial ‘bite’ site in the foot to the lymph nodes in the groin). Applying a thick layer of the ointment within 1 minute of the injection markedly increased the foot-to-groin lymph transit time of the dye by nearly fourfold, from 13 min without treatment to 54 min with the ointment. Similarly, using the same principle in rats, the ointment also increased lymph transit time by threefold (from 3.2 min to 9.4 min). The researchers then went on to test whether the ointment could improve survival in rats injected with snake venom (from the Eastern Brown snake, one ofAustralia’s most deadly) and measured how time it took before the animals stopped breathing. Crucially, rats treated with the ointment lived about 50% longer (time to respiratory rest was 65 min in controls and 96 min in treated rats).

Pressure bandages and pads can be used to mechanically block the flow of snake venom in the body, but this approach can’t be used on bites to the face or torso and can be difficult to perform properly. Arguably, carrying a cream with you when out hiking in the wild is a simple new addition to your first aid kit and a bonus is that the ointment used in the study (Rectogesic, Care Pharmaceuticals) is already commercially available, albeit as a treatment for anal fistulas. Even though we don’t know exactly how much additional time this ointment will buy in bitten humans, that extra time could prove vital when seeking suitable antivenom treatment, especially in those in which pressure immobilisation is not possible.

ResearchBlogging.org

Megan E Saul, Paul A Thomas, Peter J Dosen, Geoffrey K Isbister, Margaret A O’Leary, Ian M Whyte, Sally A McFadden &, & Dirk F van Helden (2011). A pharmacological approach to first aid treatment for snakebite Nature Medicine : doi:10.1038/nm.2382

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Be noble, cheats don’t always prosper

Social amoebae have evolved resistance to cheaters, which makes sure that the amoebae work together for the good of the group, say scientists published in Nature last week.

Social amoebae, such as Dictyostelium, co-operate together to form multicellular, fruiting bodies when they reproduce. However, as always some try to cheat the system and reap the benefits without any of the costs, in this case getting more of their fair share of spores into the fruiting bodies than the other Dictyostelium. Cheats must pay though, with lower fitness and can be discriminated against by the other amoebae.

The scientists randomly mutated a group of Dictyostelium and then mixed them with a strain of cheating amoebae (called cheater C). Most of the mutant amoebae got cheated on by the cheater C’s, and died out. However, during this process cheater-resistant strains evolved (called resistant to cheater C), and started to grow. The resistant strains turned out to be noble amoebae, they didn’t take advantage of the weaker mutant strains that had already been bullied by the cheater C’s. The evolution of cheater-resistant strains helps preserve co-operative behaviour in the social amoebae and reduces the number of cheaters in a population. So the moral of this story is…..cheats don’t always prosper and sometimes it is better to work together for the good of society.

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There’s gold in them there bacteria

Scientists have found that the bacterium, Cupriavidus metallidurans, can transform toxic gold compounds to metallic gold, according to research by Reith and colleagues published online on the 7th October in the journal PNAS.

Bacteria are naturally found on gold particles from the earth’s surface; but it is unclear, and controversial, as to whether bacteria have an active role in the formation of these gold particles (biomineralisation). An international team of scientists (from Australia, USA, Canada, Germany, Belgium and France) investigated a metallophilic (metal resistant and able to grow on heavy metals) bacterium called Cupriavidus metallidurans, which forms biofilms (a slimy layer of bacteria stuck together) on grains of gold. They found that C. metallidurans accumulates toxic gold complexes (containing Au III ions) from solution inside the bacterial cell, this accumulation is increased in metabolically active (i.e. living) bacteria. The toxic gold complexes activate bacterial genes involved in the combat against oxidative stress (damage in cells caused by reactive oxygen species, which includes unpaired electrons aka free radicals), and for metal resistance. Also, an uncharacterised cluster of genes which are specifically linked with resistance to gold were activated. Bacteria were then able to detoxify these gold complexes, ultimately turning them into harmless nanoparticles of gold. Similar gold nanoparticles were also seen in bacterial biofilms on grains of gold.

C. metallidurans containing a gold nanoparticle. Reith et al (PNAS 2009).

C. metallidurans containing a gold nanoparticle. Reith et al (PNAS 2009).

The scientists used some very fancy and expensive equipment for their work; including synchotrons at the European Synchotron Radiation Facility (ESRF) and the Advanced Photon Source (APS). Synchotrons are a type of particle accelerator that produces very intense beams of X-rays (1000 billion times brighter than X-rays in hospitals). They were used by the scientists as a super-microscope to see gold particles inside C. metallidurans in great detail.

These findings provide evidence that bacteria in the environment may contribute to the formation of grains of gold, which in turn could form gold nuggets. Gold is a rare and precious metal and these bacteria could be used as a tool to help mineral explorers find new gold deposits.

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