The hardiest bear that never was

Just over a month ago I visited the American Museum of Natural History in New York City. There I was fascinated with the phylogenetically accurate layout of fossils over the museum floorspace, showing the evolution of fish to amphibians, and then to reptiles (no Tiktaalik unfortunately) for example. During my visit I was also enraptured by an exhibition entitled; Life at the limits: Stories of Amazing Species, as one particular species stood out to me as the star of the survival show.
What if I told you there is a species of 'bear' that has existed on earth since the Cambrian period, around 500 million years ago? The word delusional would most probably spring to your mind, however I have evidence from the fossil record. Perhaps the word 'bear' was disconcerting, as I did not mean a member of the Ursidae family, but in fact a species known as the Tardigrade (me and my science word plays...). The Tardigrades have nicknames such as Water Bears or Moss Piglets, perhaps due to physical appearance (I don't see it personally, but they are kinda pudgy) and their favoured habitats; films of water that cling to mosses. Tardigrades are a large group of animals, consisting of 1,150 species, that includes some of the toughest creatures in the world. They can be found the world over; from the Himalayas 20,000 ft above sea level, to the deep sea 13,000 ft below sea level, even in the polar regions and on the equator, where the environment is hardly accommodating. Although I wouldn't hold out any hope of seeing one with the naked eye, as most individuals range from 0.3 to 0.5mm long. The Natural History Museum exhibit depicted the survival abilities of these organisms as a cycle, which I thought worked rater effectively. First, when their surroundings become intolerable, certain species of Tardigrade are able to deflate, draw in their legs and coat themselves in a waxy substance. The resulting structure is called a tun, and is barrel-like in shape with the creature's claws protruding from it. In this state tardigrades are capable of reversibly suspending their metabolism in cryptobiosis, and many members of the species can regularly survive in this state for up to 10 years. At extremely low temperatures, the Water Bear's body can go from 85% water to just 3%, ensuring they are not ripped apart by the water in their bodies expanding during freezing. When re-hydrated, it can take as little as 4 minutes for the animal to bounce back from its near-death state. Natural selection has seemingly thought of every extreme environmental condition on earth; the harshest pressure (they can survive in close to vacuums), temperature, radiation (5,000gy of gamma rays compared to the lethal dose of 5-10gy for humans), dehydration and environmental toxins. Certain species can even survive in outer space! (slight sensationalism), and in my view they truly earn their title of extremophiles. Science has so much to learn from such a tiny animal, particularly the proteins they produce to protect their cells from apoptosis during dehydration. (this seems to be a theme of my blog now), and even if humankind never make inter-planetary colonisation a reality, the Tardigrade is an excellent candidate to be our intergalactic envoy.

Pleasure, Psychoactives and a Basement...

This is a post I've been meaning to write for quite a while, but other exciting biological concepts got in the way. Story of this blog. The title is perhaps misleading, as it implies some kind of lugubrious activity, however the topic at hand is rather removed from such criminality, at least I hope. The lecture was titled; Pleasure, Novel Psychoactives  and the Brain's Basement (see, I wasn't lying about the basement) and was lead by Professor Gaetano Di Chiara of the University of Cagliari's Pharmacology department. The main body of the lecture revolved around the brain's response to psychoactive drugs, and the various experimental methods used to investigate the mechanisms behind the response. Professor Di Chiara was clearly passionate about his field of study, and so he went through the slides of the presentation at an astounding rate. This, combined with his somewhat broken English lead to my notes becoming rather scant at times, but despite this I would like to share what I was able to glean. Firstly, the definition of pleasure used by the Professor and his team; incentive to seek and accept biological incentives (food rewards for example). There are 2 distinctions of pleasure; Appetitive, which is preparatory and so comes from learned stimuli, and Consummatory, which is caused by proximal stimuli, and is unconditioned. The neurotransmitter Dopamine is widely believed to be responsible for the pleasure response of the brain, and is therefore connected to rewarding stimuli, which often aid in the survival of a species (feeding, reproduction etc). Addictive drugs also trigger dopamine release, as when a micro-dialysis tube is used to measure neurotransmission in the ventral striatum of the brain, psychoactive drugs produce a lasting spike in dopamine levels.  These ventral areas, around the amygdala of the brain, are phylogenetically the older areas of the mammalian brain, and are therefore referred to as the brain basement (just to clarify the lecture title). One fact that is, according to the lecture, contentious within the scientific community, or was contentious about 10 years ago, when most of this research was conducted, but also the last time Professor Di Chiara kept up with developments in this area of study (burn) (He referred to the archistriatum of the brain, which only exist in birds and are now called the Arcopallium; it's homologus to the amygdala im mammals essentially) is whether the biological function of dopamine is purely pleasure, or whether it has a motivatory function in survival of organisms. Rats are often the subjects of addiction experiments, and the Master/Yolked experimental paradigms are no different. The 'Master' rats were in a set-up which allowed them to actively expose themselves to the drug heroin, whereas the 'Yolked' (not quite sure about that nomenclature there) rats were passively being administered the drug. It was observed that Master rats experienced a greater dopamine output  in the shell of the nucleus accumbens (part of the ventral striatum), which is involved in the cognitive processing of wanting as well as reward and reinforcement effects. On the other hand the Yolked rats' response non-contingent drug exposure (I hope that's a thing) saw a a smaller increase in dopamine output in the core of the nucleus accumbens, dealing with new motor programs which facilitate the acquisition of a given reward in the future. This suggests that the master rats experienced a heightened euphoria on drug exposure, but why is this? I hear you mumble sleepily... I'm so glad you asked. The fact that the master rat group were self administering the drug was the key, as they were able to predict and therefore better cope with the side effects of the drug, something the passively drugged yolked rats were unable to do, thus prolonging the heroin high. The master rats would eventually have the conditioned stimulus of administering the drug completely replace the primary stimulus of the heroin itself. The drug essentially triggers no dopamine release, and so the IV self-administration becomes the main source, as the user has habituated to the drug. By extension of this paradigm researchers were able to link drugs of abuse with increased extracellular dopamine secretion in the accumbens shell particularly, clearly displaying dopamine's ability to promote expression of incentive-based motivation, in a Pavlovian manner. In my mind I have ended the debate; dopamine is a biological motivation tool, which can all too easily lead to dependance on unsavoury activities to achieve a pleasure sensation. So please, put the needle down...

More powerful than Aquaman? Impossible.

Fancy seeing me here, on my own blog... Anyway, of late I have been enraptured by the Reckoners series of novels by a hero of mine, Brandon Sanderson. The series thus far tells of ordinary humans being transformed into super-humans, with an immense spectrum of powers, by a deity/celestial body known as Calamity. In the Reckoners universe such super-humans are known as Epics, and their powers corrupt them to such a degree that they have fractured society and created a nightmarish dystopia. This got me thinking, if Epics had dominion over ultra-specific biological processes, would they be stronger than the fictional  superheroes we have bombarded at our retinas every time we go to the cinema? Thor may have Mjolnir, and Bruce Banner may be able to turn into a green thug when his heart rate spikes, but those powers have nothing over the total control of AXOPLASMIC STREAMING (long context is very long). Axoplasmic streaming is the process responsible for the movement of proteins, lipids, mitochondria and other organelles to and from the cell body of a neurone. An example of when this mechanism is relevant is in the synthesis of neurotransmitters and synaptic vesicles in the cell body of motor or sensory neurones, which must then be transported to the synaptic knob (eloquent I know) for the propagation of action potentials across the synaptic cleft. Microtubules, much akin to those that construct the cytoskeleton in your average Joe body cell (all cells are amazing I merely jest), made of the globular subunit tubulin, create the pathways for movement along the axon to the synapse, and 2 vital motor proteins; dynein and kinesin, are used as haulage vehicles for everything synthesised by the Nissl's granules in neuronal cell bodies. The speed of axoplasmic streaming is variable, something I found particularly interesting with regard to my super-human powers investigation. The speed is dependant on the cargo of the motor proteins, with vesicular cargo moving far faster at up to 400mm/day, than other proteins; for example cytoskeleton proteins move as slow as 8mm/day. To clarify, the Epic with this power over Axoplasmic streaming would not manipulate his/her own process.  That would have no biological benefits as the mechanism has been optimised by millions of years of evolution. The Epic would manipulate the streaming in other people, making it a weapon of sorts. By slowing down the streaming of synaptic vesicles and the neurotransmitters within them along the axon to the synaptic knob, less neurotransmitter (acetylcholine for example) would be available for release into the synaptic cleft when an impulse reaches the pre-synaptic membrane, essentially halting the progress of the action potential, due to the reduced permeability of the post synaptic membrane to sodium and potassium ions (acetylcholine binding there increases permeability to ions). This would  create a kind of rapidly induced accommodation effect in the neurone, causing paralysis of muscles comparable to that induced by the botulinum toxin, which inhibits the binding of acetylcholine. So my hypothetical Epic power would allow the wielder to kill a person with spectacular efficacy, just by having dominion over one relatively esoteric, yet vital biological process. In fact, if the wielder could create a wave of axoplasmic manipulation, they could kill in vast volumes over a minuscule time period. Who needs a high-tech suit or the powers of a Norse God, when you can disrupt the highly complex interplay of biological molecules in the nervous system? This Biologist certainly doesn't (therein lies my bias...).