April 18th, 2006

homuncul

ЭВОЛЮЦИЯ

Irish Elk - вот такое вымершее чудо. Он мог гордиться своими рогами - они же его и погубили.

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Evolutionary Ecology Research, 1999
Antler growth and extinction of Irish elk

Adult male Irish elk grew the largest antlers of any extinct or extant cervid. These antlers have often been implicated in the extinction of the Irish elk, although the effects of antler growth on Irish elk physiology have not been analysed quantitatively. We used a simulation model of energy and mineral metabolism to compare nutritional requirements for antler growth in Irish elk and moose, the largest extant cervid. The model simulates intake, metabolism, deposition, and excretion of energy, nitrogen, ash, calcium and phosphorus with mass balance for each of these nutrients on a daily time step...

The model predicts that, to grow 40 kg antlers in a 150 day period, more than 60 g of calcium and more than 30 g of phosphorus were deposited in antlers daily for 60 consecutive days when antler mineralization rate was highest in mid-summer... Even though Irish elk fit the allometric relationship between antler size and body size in extant cervids, mineral metabolism does not scale allometrically in the same manner. About 6% of the calcium and 10% of the phosphorus in the antler were resorbed from the skeleton because dietary intake of minerals was insufficient to meet requirements for antler mineralization. The minerals resorbed from the skeleton in summer would have to be replenished by dietary intake over the following winter... The reduction in forage density would have made replenishing calcium and phosphorus in the skeleton even more difficult, as well as making it more difficult for male Irish elk to replenish fat reserves depleted during the rut.



Отдельный вопрос: как такое морфообразование вообще стало возможным в условиях естественного отбора? - В подобных случаях теория полового отбора всегда спешит на помощь. Она всем хороша - в нее отлично вписываются подобные факты. Плоха она другим: отсутствие данных фактов вписывается в нее не менее успешно.

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homuncul

БИОЛОГИЯ

Rewind, please: OMRF scientist reverses process of cell division


Gary J. Gorbsky, Ph.D., a scientist with the Oklahoma Medical Research Foundation, has found a way to reverse the process of cell division.
“No one has gotten the cell cycle to go backwards before now,” said Gorbsky. “This shows that certain events in the cell cycle that have long been assumed irreversible may, in fact, be reversible.”
Cell division occurs millions of times each day in the human body and is essential to life itself. In the lab, Gorbsky and his OMRF colleagues were able to control the protein responsible for the division process, interrupt and reverse the event, sending duplicate chromosomes back to the center of the original cell, an event once thought impossible.

“Our studies indicate that the factors pointing cells toward division can be turned and even reversed,” Gorbsky said. “If we wait too long, however, it doesn’t work, so we know that there are multiple regulators in the cell division cycle. Now we will begin to study the triggers that set these events in motion.”
The findings may prove important to controlling the development and metastasis of certain cancers. It also holds promise for the prevention and treatment of birth defects and a wide variety of other conditions.
“Dr. Gorbsky’s results provide elegant proof that the cell cycle must be precisely controlled,” said Dr. Rodger McEver, OMRF vice president of research. “Now he and his lab can work toward developing innovative methods to probe and better understand the complex process of cell division.”

Nature, April 2006
http://www.nature.com/nature/journal/v440/n7086/pdf/nature04652.pdf


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