Category Archives: Science

受保護的文章:Diary of a Naïve Postdoc




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This is about as exciting as it gets in the realm of molecular biology research: GTCA, a promotional video made by Bio-Rad (a biotech company) and a spoof on YMCA, made me cringe and laugh at the same time. It’s amazing how much length the company is willing to go to promote one product. They have my approval: it’s 100% nerd-tastic. And does anyone think that the voiceover at the end sound like Dr Spaceman from 30 Rock?


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Science: It’s About Time!


Browsing through the BBC News website a while ago, a particular headline caught my eye: “Viagara could aid jetlag recovery". I was immediately intrigued, for this subject remains close to my heart. Before you say or even think it, no, I’m not talking about the little blue pill; rather, I meant the study of the body clock, specifically the circadian clock, to which I dedicated four years of PhD research.

My doctoral thesis begins thus:

The solar system is such that geophysical rhythms dominate life on the planet Earth: at regular intervals, the sun rises and sets, the tides flow and ebb, the moon waxes and wanes, the seasons come and go. It is a testament to the power of evolution that a wide range of organisms have developed systems to attune themselves with these cycles in order to improve their chances of survival in this rhythmic environment."

One of these systems confers approximately daily rhythms – also known as “circadian rhythms", where “circadian" derives from the Latin for approximate (circa) and day (diem). Circadian rhythms are found at many levels of the evolutionary tree, from certain bacteria all the way up to humans, which underlines the importance of synchrony with the solar cycle. A central feature of such rhythms is that they are innate – in other words, they are hard-wired into our biology, our DNA, so that in the absence of time cues, we will carry on exhibiting circadian rhythms. Experiments involving human volunteers have been performed, where they were confined in spaces without any knowledge of the time in the outside world – the results showed that the subjects continued to sleep and wake in roughly 24-hour cycles, lasting for months. Thus, it is no exaggeration to say that there is a (circadian) clock ticking inside each of us, instructing our bodies to do things at certain times. The most obvious example, as far as humans are concerned, is the regulation of rest-activity cycles, although many other aspects of our physiology – blood pressure, heart rate, hormone levels – also fall under circadian control. (One thing to note, however, is that sleep is not entirely orchestrated by the circadian clock, but also receives input from the “sleep homeostat", which determines how much sleep we need.)

So if the circadian clock controls so many different things, it would be a good idea to have a “headquarters" to co-ordinate the various subsidiaries. The “headquarters", it so happens, is indeed in the head, specifically in a part of the brain called the hypothalamus, . A small group of approximately 20,000 nerve cells – collectively known as the suprachiasmatic nuclei (SCN) – is (we believe) all it takes! Consequently, mice (and humans) whose SCN are damaged fail to sleep and rest with a regular, daily pattern. These highly specialised cells also receive direct input from the eyes, via the optic nerves, thereby allowing the circadian clock to adjust itself according to the light/dark cycle of the environment. This property of the clock allows us to synchronise with the solar cycle, and is especially important when we experience significant shifts in time, exemplified by air travel across time zones. Jet-lag occurs as a result of our circadian clocks trying to accustom themselves to the new environmental time, and the sympotms are alleviated once the internal and external times are in sync.


More recently, a number of mouse genes have been uncovered that are responsible for orchestrating our circadian clock, and with the human genome having been sequenced, it was found that these genes are evolutionarily conserved in us too. Presently, the challenge remains to find out how the circadian clock ticks inside a cell – for almost every cell in your body possesses its own clockwork, which is brought into synchrony with other cells by your SCN. Understanding the precise molecular mechanism is the Holy Grail of circadian research – targets will then become available for treating jet-lag and other circadian-related sleep disorders.

Regarding the effects of Viagara on jet-lag, a group of Argentinian scientists have shown that an injection of the drug into hamsters made them adapt faster to a 6-hour phase advance, equivalent to an eastward flight across six time-zones: from New York to Paris, for example. The cynics amongst you might want to know that this dose was not enough to cause an erection in the little cuddly rodents, so any effect observed should not be groin-related. Having read the primary research paper in the Proceedings of the National Academy of Sciences of the USA, I would say that the effect is convincing enough, though how it extrapolates to humans is yet to be seen. If all goes well, perhaps a change in marketing strategy is necessary. How about Viagara: guaranteed to make you get up sooner?

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