physiology
clock | September 12, 2006Scientists discover molecule behind birds' magnetic sense:
"Some birds, notably migratory species, are able to detect the Earth's magnetic field and use it to navigate. New results from a team of Franco-German researchers suggest that light-sensitive molecules called cryptochromes could be the key to the birds' magnetic sense.
They did not suggest it - they tested a 10-year old hypothesis.
Cryptochromes are photoreceptors which are sensitive to blue light, and they are involved in a number of processes linked to the circadian cycle, such as growth and development.
Caution: cryptochromes have…
clock | September 1, 2006What?....
There is a slang phrase in Serbo-Croatian that means "doing nothing; being idle; wasting time", and it is "hladiti jaja", which means "cooling (one's) balls". So, if you see a guy just sitting there, clutching a beer bottle and gazing into the distance, you may ask him "Hey, man, whatcha doin'?" and he may reply " 'ladim jaja", i.e., "I'm coolin' me balls".
Well, this slang phrase, indicating a thermoregulatory behavior, has its origin in the real theromoregulatory physiology. Yes, mammals have to cool their balls. That is why mammalian testes are located outside the body inside…
clock | August 21, 2006Why Piglets Shudder To Keep Warm:
Brown fat helps newborn mammals maintain their body temperature by burning fat, which converts into heat. The protein UCP1 (Uncoupling Protein 1) has a key role in this energy conversion, which takes place in the cell mitochondria.
No brown fat or UCP1 protein has been found in domesticated pigs, however. In their study, Berg and colleagues show that the UCP1 gene was shut down about 20 million years ago in an ancestor of the wild boar. They identified four different mutations, each of which would be sufficient to knock out the function of the protein.
This…
clock | August 19, 2006Correct me if I am wrong, but I think this is really ground-breaking:
Study Finds Brain Cell Regulator Is Volume Control, Not On/off Switch:
He and his colleagues studied an ion channel that controls neuronal activity called Kv2.1, a type of voltage-gated potassium channel that is found in every neuron of the nervous system.
"Our work showed that this channel can exist in millions of different functional states, giving the cell the ability to dial its activity up or down depending on the what's going on in the external environment," said Trimmer. This regulatory phenomenon is called '…
clock | August 19, 2006Have You Ever Seen An Elephant ... Run?:
Dr John Hutchinson, a research leader at the UK's Royal Veterinary College (RVC), has already shown that, contrary to previous studies and most popular opinion, elephants moving at speed appear to be running. Now with funding from the Biotechnology and Biological Sciences Research Council (BBSRC) his team is using Hollywood-style motion capture cameras combined with MRI and CT scans of elephants to build 3D computer models of elephant locomotion to show the forces and stresses at work on muscles, tendons and bones.
The research team has been working…
clock | August 18, 2006One of the several hypotheses floating around over the past several years to explain the phenomenon of repeated wake-up events in hibernating animals although such events are very energy-draining, is the notion that the immune system needs to be rewarmed in order to fend off any potential bacterial invasions that may have occured while the animal was hibernating:
Now, a group of researchers provided a mathematical model that supports this hypothesis:
"A habit in some animals to periodically wake up while hibernating may be an evolutionary mechanism to fight bacterial infection, according to…
clock | August 2, 2006When I saw this article in SEED Maagazine, I had only one thought - Mokie-Koke!
Readers of science fiction know what I am talking about. I was reminded of "The Merchant's War", the 1984 sequel to the 1952 brilliant dystopia "The Space Merchants", the book that beat "1984" and "Brave New World" in its accuracy of prediction. The initial novel - one of the all-time-greats of the genre, was written by Frederick Pohl and Cyril Kornbluth. The sequel, 32 years later, was written by Pohl alone.
It's been at least 15 years since I last read The Merchants' War, but if I remember correctly, each…
clock | July 22, 2006This is by far the most popular of the four installments in this series because it contains the nifty puzzle exercise. Click on the spider-web-clock icon to see the comments on the original post.
Just like last week, I have scheduled this post to appear at the time when I am actually teaching this very lab again. If there are any notable difference, I'll let you know in the afternoon.
When teaching the lecture portion of the course, I naturally have to prepare the lectures in advance, and each lecture has to cover a particular topic. This makes biology somewhat fragmentary and I try to use…
clock | July 21, 2006
Some plants do not want to get eaten. They may grow in places difficult to approach, they may look unappetizing, or they may evolve vile smells. Some have a fuzzy, hairy or sticky surface, others evolve thorns. Animals need to eat those plants to survive and plants need not be eaten by animals to survive, so a co-evolutionary arms-race leads to ever more bizzare adaptations by plants to deter the animals and ever more ingenious adaptations by animals to get around the deterrents.
One of the most efficient ways for a plant to deter a herbivore is to divert one of its existing biochemical…
clock | July 18, 2006Scientists Discover Why Cornea Is Transparent And Free Of Blood Vessels, Allowing Vision:
The key, say the researchers, is the unexpected presence of large amounts of the protein VEGFR-3 (vascular endothelial growth factor receptor-3) on the top epithelial layer of normal healthy corneas.
According to their findings, VEGFR-3 halts angiogenesis (blood vessel growth) by acting as a "sink" to bind or neutralize the growth factors sent by the body to stimulate the growth of blood vessels.
Nice, except that "Why" is an evolutionary question: they should have used "How" throughout the press…
clock | July 7, 2006You really think I am going to put this above the fold? No way - you have to click:
Today's lesson is on the reproductive anatomy of the domestic pig (Sus scrofa domestica), which probably applies to the wild species in the pig family as well. Although we may reflexively think about invertebrates when pondering diversity of copulatory organs, mammals are not too bad in that department either. After all, the sperm is delivered in some species into the vagina (e.g., dog), in others into the cervix (e.g., pig) and in yet others into the uterus (e.g., horse), so different strategies are needed…
clock | June 29, 2006Here is a wonderful new study that demonstrates that the antifreeze substances in notothenioid fish are not produced by the liver as was believed for decades and taught in Comparative Physiology courses. Instead, it is produced in two places: most of it in the exocrine pancreas, and somewhat less in a portion of the stomach at the entry of the esophagus:
.....AFGPs are secreted into the intestinal lumen where they protect the intestinal fluid from being frozen by ice crystals that come in with seawater and food. Internal fluids in notothenioids are about one-half as salty as seawater. While…
clock | June 27, 2006
The origin and early evolution of circadian clocks are far from clear. It is now widely believed that the clocks in cyanobacteria and the clocks in Eukarya evolved independently from each other. It is also possible that some Archaea possess clock - at least they have clock genes, thought to have arived there by lateral transfer from cyanobacteria.[continued under the fold]
It is not well known, though, if the clocks in major groups of Eukarya - Protista, Plants, Fungi and Animals - originated independently or out of a common ancestral clock. On one hand, the internal logic of the clock…
clock | June 23, 2006From L.A.Times (you'll have to click - I am purposefully citing out of context for humorous purposes):
Military researchers are considering a study to see whether Viagra could help soldiers function better at high altitudes.
High altitudes? How high? Who/what needs to get that high?
None of the cyclists reported an erection during the trials, she said.
Self-reporting, self-schmeporting! What do you think they were thinking about while "cycling"?
"If we send a group of guys into the mountains of Afghanistan, they need to be able to deal with the altitude," Fulco said.
Eh, as if our boys…
clock | June 21, 2006My post about sleep has been translated by Davide 'Folletto' Casali into Italian, and posted on his blog. You can see the translated post here. If you can read Italian (and even you do not - just for fun, and to reward his hard work), go and look around his blog.
clock | June 21, 2006
This was my December 29, 2004 post written in reaction to media reports on the "sixth sense" in animals, avoiding the tsunami by climbing to high ground:
What's Really Important? This
What's Really Not That Important, But I Can't Help It? Did Animals Sense Tsunami?
I hate it when they say "sixth sense"! Days of Aristotle and his Five Senses are long gone. Even we have more than five sensory modalities. Various animals (and even plants) have many more. The original five are vision, audition, olfaction, gustation and touch.
Photoreception is not just vision and is not a unitary modality. There…
clock | June 19, 2006 This is the first in a series of posts from Circadiana designed as ClockTutorials, covering the basics of the field of Chronobiology. It was first written on January 12, 2005:
There are traditionally three approaches to research and teaching of physiology: biochemical, energetic, and homeostatic. The three are by no means exclusive and all good physiologists will include all three in their work and teaching, but each with a different emphasis.
Biochemical approach is typical of human/medical physiology. Physiological mechanisms are described at lower and lower levels, until the molecules…
clock | June 19, 2006
Melatonin is secreted in human mother's milk with a daily rhythm - high at night, undetectable during the day (see the figure under the fold):
It has been known for a long time that mother's melatonin entrains the circadian rhythms in the SCN (suprachiasmatic nucleus) of the embryos - thus they are born with a correct phase (time of day). However, a study in rats suggests that melatonin in mother's milk is unlikely to be able to entrain the pups circadian rhythms after they are born.
So, the appearance of melatonin in the milk of breastfeeding humans may either be:
a) just a by-product…
clock | June 16, 2006Last week we looked at the organ systems involved in regulation and control of body functions: the nervous, sensory, endocrine and circadian systems. This week, we will cover the organ systems that are regulated and controlled. Again, we will use the zebra-and-lion example to emphasize the way all organ systems work in concert to maintain the optimal internal conditions of the body:
So, if you are a zebra and you hear and see a lion approaching (sensory systems), the brain (nervous system) triggers a stress-response (endocrine system). This is likely to happen during the day, as the…
clock | June 16, 2006It is impossible to cover all organ systems in detail over the course of just two lectures. Thus, we will stick only to the basics. Still, I want to emphasize how much organ systems work together, in concert, to maintain the homeostasis (and rheostasis) of the body. I'd also like to emphasize how fuzzy are the boundaries between organ systems - many organs are, both anatomically and functionally, simultaneously parts of two or more organ systems. So, I will use an example you are familiar with from our study of animal behavior - stress response - to illustrate the unity of the well-…