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Physiology & Medicine / Re: What determines the colour of reflections when an animals' eyes are illuminated?

« on: 01/12/2015 19:38:36 »

The red-eye effect in humans comes from the blood supply in the back of the eye.

In the vernacular, it is exacerbated by excessive alcohol and/or insufficient sleep, although this affects a different part of the eye...

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Physiology & Medicine / Re: What determines the colour of reflections when an animals' eyes are illuminated?

« on: 30/11/2015 23:56:13 »

Some animals have a layer at the back of the eye called the "tapetum lucidum" which improves night-vision, that's responsible for the colour of eye-shine other than red.

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Physiology & Medicine / Re: How do bowels transport gas separately from solids?

« on: 07/11/2015 14:05:28 »

As I understand it, the issue is gas moving from high pressure to low pressure, and the fact that it is going down and out is not really going "against gravity." Just as air escapes from the open end of an inflated balloon no matter what direction it is pointed in.

I am not really sure of the mechanism of the separation, but as long as the intestine isn't completely blocked off (air-tight), the gases probably have higher mobility than the solids. Then it is a simple matter of the intestines being able to effectively close off at the top, and open enough at the bottom periodically to allow pressure to release.

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Cells, Microbes & Viruses / Re: How do probiotics survive stomach acid exposure?

« on: 28/07/2015 11:52:07 »

There are hints that newborns have a very different environment in their guts, which allows them to pick up antibodies from mothers milk, without actually chopping them up into their constituent amino acids, as an adult digestive system would.

Presumably, this milder environment would also allow them to pick up bacteria from people with whom they have close contact (especially the mother, during birth).

Some live bacteria are tolerant of the acid conditions in the stomach, although it would be a rare bacterium that could survive while passing through the acid conditions of the stomach, and then thrive in the more basic conditions further down the gut. However, some bacteria can enter a hardy spore stage, which would allow them to pass through these adverse environments, returning to active growth when they find conditions that better suit their lifestyle.

The unfortunate fact is that probiotics are limited to a small number of bacteria species that can be easily grown in a factory environment. In contrast, a healthy human micro biome contains many bacterial species which we can recognise from their genetic fingerprints, but currently have no way of growing in the lab, or of delivering to an appropriate ecological niche in the gut (short of a "poo transplant").