Hi Jeff:

Good question! I have no idea how long a hook takes to 'dissolve' (it would depend on what it is made of and I think even fine-wire hooks would take months to dissolve in the stomach!) but in my fishing experience for the hook to dislodge it depends on where it was actually embedded. If the hook was barbless then it will usually work free very quickly. Other embedded hooks dislodge as the fish grows!

P.S. nice size rainbow!

(posted in General Biology)

If the exams are essay-type questions (and even if they're not) I often found it helpful to write sample essays or paragraphs as a way of revision, e.g. function of the gastro-intestinal tract. But if you do this pay special attention to David's points 3 & 4.
Best of luck!

The Smithsonian National Museum of Natural History on the Mall in Washington DC is excellent, and if you get tired of dinosaur bones, whales, spiders, evolution, etc you can see the Hope diamond which is one of the world's most famous gemstones. Also when you have finished your visit you can make a short walk across the Mall and look at the Air and Space Museum (from Kitty Hawk to Saturn rockets and lunar modules!!). And free admission!

see - http://www.mnh.si.edu/

G'Day Sam:

It may depend on which one is bigger! Both can be very aggressive. Great whites have been attacked by other (bigger!!) sharks before. See -

http://news.sky.com/skynews/Home/World- … 0415419981

The isolation and characterisation of the brain cannabinoid receptor (CB1) gene is an interesting case of scientific research called by some ‘planned serendipidity’. Scientists cloned a receptor from the brain for which there was no apparent ligand - this is called an orphan receptor. For a long time (> 1 year) they tried to get a whole lot of different neurotransmitters to bind to the receptor without success. They then discovered that the receptor’s gene was expressed in cell lines and brain regions previously reported by other workers as containing cannabinoid receptors. The scientists tested whether THC and synthetic THC derivatives bound to the receptor, and ‘viola’, the receptor was activated by cannabinoids! This work corroborated previous biochemical studies demonstrating the existence of cannabinoid binding sites in the brain. Endocannabinoids such as anandamide were identified soon thereafter as was a second cannabinoid receptor (CB2) expressed mainly in places like the immune system.

As the bacterial ORFan gene's function is known it will usually be registered in the databases under a new gene name. As David says we use the word "orphan" to denote a receptor where the ligand is not known, and it becomes 'de-orphanated' when the scientific community is satisfied that it's ligand has been established (e.g., a number of scientists have repeated the observation) - although we may now know the ligand for the orphan receptor we can still be a long way off establishing its function in the body.

There is a whole lot of beauty in biology to inspire us, and sometimes we get a glimpse of something new about the way life works after a lot of hard work. It is a fantastic feeling!

Fascinating stuff!

I was under the impression that under laboratory conditions rats are generally much less sensitive than mice to synchronisation of cycles with cage-mates so I suppose synchronicity will be quite species (and strain?)-specific as well.  Some reproductive behaviour e.g., the Bruce effect, where pheromones from an unfamiliar male can block implantation of embryos into the uterine walls of a recently bred female, is apparently more pronounced in mice than rats, and is dependent in part on the action of hormones such as vasopressin and oxytocin in the brain. Other behaviours like the Whitten effect (cycle synchronization of females exposed to male pheromones) seem to be more pronounced in rats than mice. I guess cycle synchronicity also depends on whether you are a monogamous or polygomous species as well!

Hi Bas:

Most people who try to quit smoking feel irritable and moody, and maybe
even depressed. There are studies to suggest that antidepressants
might help in smoking cessation. The idea is that some antidepressants
may relieve the 'depressive symptoms' caused by nicotine withdrawal, or
that antidepressants may substitute for nicotine which may act as an
antidepressant itself (e.g., by releasing dopamine in the brain).
Selective serotonin re-uptake inhibitors (SSRIs) such as Prozac
allow more serotonin to act on the serotonin receptors. Not all
antidepressants work this way - some have specific effects on neural
pathways (e.g., inhibiting the enzyme monoamine oxidase that breaks down
neurotransmitters like serotonin, noradrenaline and dopamine) or
neurotransmitter receptors (e.g., blockade of acetylcholine receptors)
underlying nicotine addiction. Antidepressants may have their own
side-effects as well, which can include problems with libido and
erections. For SSRIs this is likely mediated by the effects of serotonin
on serotonin receptors located in the brain (to affect behaviour)
and/or peripherally on penile tissue. For different classes of
antidepressants other neurotransmitter systems may be involved.

Hope
this help!

(posted in Plants & Fungi)

Hi Jaer

This is an interesting question! Perhaps surprisingly plants have a number of receptors resembling neurotransmitter receptors in animals (e.g., acetylcholine receptors - atropine, the acetylcholine receptor blocker, comes from plants; glutamate receptors). Plants also have immune receptors that have some structural similarity to 'equivalent' receptors in animals. As far as I am aware animals do not have receptors for plant hormones such as auxins (a growth hormone that Charles Darwin was interested in), gibberellins (signalling molecules) and jasmonates (more growth hormones). Quite possibly there are other receptors as well! There is also the question of when do you call a receptor in a plant the same as a receptor in an animal - how much DNA or protein identity should there be? It would be difficult to compare 'function'....in most cases!!

Please see the following for more info:
www.biologie.uni-hamburg.de/b-online/e31/31a.htm
Dharmasiri et al. Nature 435: 441-445, 2005.
Marcinkowska E & Wiedlocha A. Acta Biochimica Polonica 49: 735-745, 2002.