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thank you very much, that was fast and very informative at the same time!

however, this leaves me irritated for another reason: I thought that proteins being destroyed at temperatures above 42°C was a natural chemical reaction, you make it sound as if this destruction can be started and stopped by the brain...and if that is true, why would the brain have the proteins be destroyed at all?

Hi ice, i am not sure of the exact biological reason. But i will take a crack at explaining how i would think it works. All chemical reactions in the body of a mammal are controlled by hormones . Hormones are released by the brain , many by the hypothalamus of the brain. The brain controls the release of hormones by reacting to physical and environmental changes as well as through a process called negative feedback. If the temperature is too high it may result in an unbalance of certain hormones resulting in the destruction of proteins. The brain will not actively destroy proteins unless effected by a disease. The only other reason i can think of is that at high temperatures the peptide bonds between amino acids which form proteins are broken down due to the increased temperature and energy provided by the heat. Hope that makes sense a bit more. We will have to wait for imberbe to get back for a proper answer .

I think what ice means is why do proteins the the gemsboks body (not brain which is cooled by the carotid rete) not physically breakdown when the body temperature starts exceeding 42C. The technical term when proteins break down due to heat is denaturing. When you fry an egg, the clear protein turns white as it dentures due to heat.

As oddesy correctly pointed out "at high temperatures the peptide bonds between amino acids which form proteins are broken down due to the increased temperature and energy provided by the heat."

So why don't gemsbok body proteins denature when temperatures get up to 46C? Well I've read somewhere that most proteins only begin to denature in temperatures above 50C. So my best opinion is that even though gemsbok bodies get quite hot, it is still not hot enough to cause serious damage to the body proteins.

There are also proteins called heat shock proteins that can prevent normal proteins from denaturing, but I don't know if gemsbok have a higher proportion of heat shock proteins.. maybe..

Hope this helps..

sorry but I still don't get it

fact: proteins are destroyed at certain temperatures without being "ordered" to do so by a brain and without the release of hormons (boiling an egg is the perfect example)

question: are all proteins destroyed at more or less the same temperature or does their "destruction" temperature vary (the latter would make sense to me)?

question: can there really be a situation where a brain will "order" proteins to be destroyed and if so, what kind of sense would that make?

question: how does all this relate to the oryx?

thanks!

Makes sense that it would vary but as I stated before MOST proteins denature at temperature exceeding 50C, which is higher than the maximum that a gemsboks body will reach.



Tricky question. There are thousands of proteins and processes occurring in the body, so it is inevitable that somewhere along the line a bodies own protein is intentionally destroyed.

There is a process called apoptosis, or programmed cell death, where some cells are programmed to die after a while. A tumor may occur when apoptosis fails and cells continue to multiply without some dieing. The net being out of control growth = tumor Hard to explain. Anyway, the brain, through hormone,steroid activation etc. is involved in apoptosis. So I guess the brain does order the death of its own cells/protein, but in a controlled manner.




Well, as I said before although the body temperature of an oryx is much higher than "normal", it is still not high enough to cause massive protein denaturation.

Keep in mind the other morphological and behavioral adaptations gemsbok have to survive in their extreme environment. For example the carotid rete (brain cooling system). They also allow their body temp to rise substantially so as to delay evaporative cooling (and save water) and are inactive for mot of the day.

A poster child for evolution! Numerous adaptations to suit the harsh environment it lives in.

Hope this helps..

ok, so far I'mwith you - but why are body temperatures exceeding 42°C dangerous to humans then, why can't they just sweat and / or drink more and survive this just like oryx do? (

Humans do not have adaptations to deal with extreme body temperatures.
For one they do not have an efficient system, such as the carotid rete, to substantially cool the blood flowing to the brain. The human brain is an extremely sensitive organ, and is vulnerable to even modest increases in temperature.

As I pointed out its all about evolution and what adaptations have arisen to deal with the environment an animal lives in. Gemsbok are adapted to living in extreme arid conditions, humans are not. Why can't humans live off eating grass? Our digestive system has not evolved to do so. Same applies to body temperatures.

is it true that the gender of gemsbok may be determined by how close their horns stand next to each other. that if the horns run almost parallel. it's a male, while a rather v-shaped form belongs to females?

thanks

Ice,

To identify bulls in an oryx herd is not always easy – especially not when they are standing around and resting amongst trees or in long grass and bushes. There are a couple of things one can look at.

The bulls are heavier built than the cows, their horns are noticeably thicker, and the V-form is somewhat narrower than it is with the cows, although this is not always so reliable. Another way to determine whether an animal is a bull or a cow is to look at the space between the horns at the bases. With adult bulls this space is usually too narrow to fit a third horn base in, as the bases are generally far thicker than that of cows. In general the bulls’ horns are also slightly shorter than that of the cows, and are ridged heavier. Also the cows' horns are often somewhat crooked. Another method is to look at the horns where they come out of the head. Seen from the front, a mature bull's horns bell very slightly outwards just above the head, whereas those of the cows usually grow straight up from the head. A mature bull's thicker neck is also noticeable.

Not one of these methods of determining the sex is 100% fallible however. Sometimes you’ll get cows with horns that look just like those of the bulls. The only way to make absolutely sure is to see the penis sheath.

thanks bishop!

A little video about the Gemsbok of the Kgalagadi South Africa from last year 2009.

Sometimes you see strange things in Kgalagadi. We saw a Gemsbok eating a Gemsbok [horn]. First we thought that it was a Lion undercuver but it was a Gemsbok. Probably the gemsbok was chewing on the horn for Calcium. He liked it very much as you can see in the video.

Hello, Nico!

That is strange!

The behaviour is called "pica", herbivores sucking on or eating bones for dietary reasons.

Not horns...but maybe this one is getting a head start, so to speak!

through a google search I found this article about oryx

http://www.bio.davidson.edu/people/veca ... ummary.htm

The author explains, among others, that by increasing the oxygen intake oryx are able to minimize water loss through respiratory evaporation. What does that mean? Simply that oryx increase their breathing rate? or (which would be much more astonishing) that oryx are able to "filter" the air to suck in much than the usual 21 % of oxygene?