This week in animal research 25/11/16
Edible dormice: The older they get, the more they rejuvenate their cells
The shortening of telomeres in cells was thought to be an important biomarker for lifespan and ageing. The edible dormouse (Glis glis), a small hibernating rodent, now turns everything upside down. In contrast to humans and other animals, telomere length in the edible dormouse significantly increases in the second half of its life.
This could explain how this species can reach a maximum lifespan of 13 years, which is a Methuselah-like age for a small rodent.
“This extreme lifespan is almost certainly related to their ability to rejuvenate telomeres”, says Hoelzl. Telomeres are the endcaps of chromosomes, which prevent, together with proteins, the degradation of coding DNA sequences.
Climbing the social ladder can strengthen your immune system, monkey study suggests
The research was carried out on 45 female rhesus monkeys who were allowed to form natural hierarchies.
To find out how rank affected their health, the researchers took immune cells from the animals and measured the activity of roughly 9,000 genes.
They found that around 1,600 genes behaved differently in lower-ranking females than in higher-ranking females, particularly those linked to the production of immune cells.
In the second part of the study, the researchers rearranged the monkeys into new social groups with some high-ranking females now finding themselves as the bottom of the social ladder, while others climbed to the top.
The scientists found that the immune cells of formerly low-ranking females became more like high-ranking females, suggesting they would be more capable of fighting off infections.
How diet drinks make you fat
Sometimes people who drink diet soft drinks put on more weight and develop chronic disorders like diabetes. This has puzzled nutritionists, but experiments in mice now suggest that in some cases, this could partly be down to the artificial sweetener aspartame.
Artificial sweeteners that contain no calories are synthetic alternatives to sugar that can taste up to 20,000 times sweeter. They are often used in products like low or zero-calorie drinks and sugar-free desserts, and are sometimes recommended for people who have type 2 diabetes.
But mouse experiments now suggest that when aspartame breaks down in the gut, it may disrupt processes that are vital for neutralising harmful toxins from the bacteria that live there. By interfering with a crucial enzyme, these toxins seem to build up, irritating the gut lining and causing the kinds of low-level inflammation that can ultimately cause chronic diseases.
“Our results are providing a mechanism for why aspartame may not always work to keep people thin, or even cause problems like obesity, heart disease, diabetes and metabolic syndrome,” says Richard Hodin at Massachusetts General Hospital in Boston.
Young blood may not cure ageing ills after all
A new blood transfusion method may help resolve confusion over past experiments on the effects of giving young mouse blood to old mice and vice versa. In those experiments, the rodents’ circulatory systems were connected surgically.
A team at the University of California, Berkeley, including bioengineer Irina M. Conboy and her husband, researcher Michael J. Conboy, used computer-controlled microfluidic pumps to exchange blood between young and old mice, so that each received 50% of the other’s blood (Nat. Comm. 2016, DOI: 10.1038/ncomms13363). After the transfusion, the mice were disconnected.
Past studies that surgically connected old-young mice pairs have produced sometimes controversial evidence that seemed to point to young blood’s power to reverse age-related ills such as impaired cognition and cardiac function.
The new work is “very interesting” and “raises significant questions about the original experiments,” says Michael Rudnicki, director of the regenerative medicine program at the University of Ottawa.
The Conboy team points out that those past studies that surgically connect mice involved the sharing of more than blood: The old mice benefited from having access to the young animals’ organs to help carry out processes like blood oxygenation and filtration.
Dogs have episodic memory - like us
Dogs are able to recall their owner’s actions, even when they were not specifically instructed to do so, suggesting that dogs, like humans, have what is known as “episodic memory” – memories linked to specific times and places.
To probe the nature of doggy memory, Fugazza and colleagues employed 17 dogs of various breeds that were used to being trained to copy their owner’s movements.
In the first step of the study, the dogs were exposed to six different objects and watched as their owner carried out a previously unseen action with one of three of the items, such as climbing on a chair or touching an umbrella. The dogs were then commanded to mimic the action with the words “do it!”.
“This bird acts like it has four sexes"
A mutation in Zonotrichia albicollis had flipped a large section of chromosome 2, leaving it unable to pair up with a partner and exchange genetic information. The more than 1,100 genes in the inversion were inherited together as part of a massive 'supergene' and eventually drove the evolution of two different 'morphs' — subtypes of the bird that are coloured differently, behave differently and mate only with the opposite morph.
This process is nearly identical to the early evolution of certain sex chromosomes, including the human X and Y. The researchers realized that they were effectively watching the bird evolve two sex chromosomes, on top of the two it already had.
“This bird acts like it has four sexes,” says Christopher Balakrishnan, an evolutionary biologist at East Carolina University in Greenville, North Carolina, who worked with Tuttle and Gonser. “One individual can only mate with one-quarter of the population. There are very few sexual systems with more than two sexes.”