Article : The penalty of having a sister -- why sibling sex matters for male saiga antelopes

Having a twin sister could put male saiga antelopes at a reproductive disadvantage, says new research published today. The study shows that male twins with a sister are born lighter than those with a brother, making them smaller than the optimal size for males. The research also shows that saigas are the supermums of the hoofed animal world with no other similar species investing more in their offspring during pregnancy.

The study's results call into question current understanding of the development of male and female foetuses of this species, and give scientists a new insight into the importance of sibling sex and what implications this may have for the animals as they mature.

This study shows that when a female is pregnant with mixed-sex twins, the male foetus does not undergo the substantial amount of growth that occurs in a male foetus with a brother, resulting in a sub-optimal birth weight. Saiga males mate with many females and face strong male-male competition during short mating seasons. This means that size matters for males - being smaller than average is one of the major limiting factors for reproductive success.

Aline Kühl from Imperial College London's Division of Biology, lead author of the paper, explains that although they do not yet understand the precise mechanism behind this suboptimal development in male twins, its existence is clear. "When siblings in a litter vary in sex, maternal investment should be sex-specific, meaning that the male foetus grows bigger than the female. However, it seems there are limitations in the ability of the mother to provision mixed twin litters in the womb," she said.

The researchers point out that mixed-sex litters have been shown to have an impact on animal health elsewhere in the animal world. In dairy cows for example, it is well known that calves from mixed litters are less fit. Female heifers from mixed litters are generally infertile. But unlike dairy cows, in cases of saiga mixed-sex twins, the male foetus appears to be worse off, not the female.

Aline adds that the effect of size on male saigas later in life cannot be underestimated: "Even a relatively small decrease in birth weight is likely to have an amplified negative effect on male reproductive fitness in species where competition amongst males for mates is very high."

The saiga antelope provides scientists with an ideal opportunity to investigate the effects of mixed-sex twin litters on size and development, because there are a high proportion of twin births in the population, and because the optimal birth weight for males and females of the species are dramatically different.

The researchers' study of female saigas and their young also showed that they invest more in their pregnancy than any other hoofed mammal, with some mothers carrying young up to 38% of their own body weight.

The research was carried out on populations of saiga antelopes living on the Eurasian steppe in the autonomous Republic of Kalmykia, Russia. Data from saiga antelope monitoring during Soviet times from the Betpak-dala saiga population in Kazakhstan were also analysed. Both data sets are from different populations of saiga, from both before and after the recent extreme decline in saiga numbers – yet the results of both datasets are qualitatively the same.

The research team, alongside local rangers, weighed and measured saiga calves during the birth season in May over a period of three years. Saiga have a mass calving behaviour, whereby females come together in a densely packed herd to all give birth within a week. This makes it relatively easy to monitor the reproductive state of the population. Such monitoring has become vital since saiga have seen a dramatic decline in numbers of over 95% in recent years, making them one of the most critically endangered species on earth.

Future research will investigate what role sibling sex plays for lifetime reproductive success. The monitoring protocol of saiga antelopes is currently being improved to include non-invasive methods for monitoring to determine fecundity rates (from faeces analysis).

Source : Imperial College London

Article : Older African-American men with HIV often have sex without condoms

As many as four out of ten HIV positive African-American men could be putting their partners at risk by not using condoms, according to research in the latest UK-based Journal of Advanced Nursing.

A study of 130 middle-aged and older men in the USA found that many of the 40 to 65 year-olds were engaging in high-risk sexual practices.

38 per cent didn’t use condoms during oral sex, with 25 per cent having unprotected vaginal sex and 22 per cent having unsafe anal sex. The research also showed that men who were single and displayed fewer HIV symptoms were least likely to use condoms during sex.

“Despite the worrying number of men not using condoms, 78 per cent of those who took part in the study were able to answer questions about HIV and AIDS correctly and 25 per cent claimed to be knowledgeable about the subject but still engaged in risky sex” says Dr Christopher Lance Coleman from the University of Pennsylvania School of Nursing in Philadelphia.

“These findings are of particular concern as HIV and AIDS rates among black (non-Hispanic men) in the USA and in people over 50 have risen considerably in recent years. In fact, AIDS prevalence statistics for minority men in the USA are staggering.”

For example:

• In 2005, 127.6 per 100,000 cases of HIV/AIDS were African-American men compared to 18.5 for White men, according to data for 33 US states using confidential name-based reporting. The US Center for Disease Control suggests that this ethnic group is eight times as likely to develop AIDS as white males.

• Figures for 2005 also show that 44 per cent of all new cases of HIV were black (non-Hispanic) males, based on the latest data from 50 US states.

• AIDS rates are also rising in people over 50. In 2006, 27 per cent of adults living with AIDS in the USA were over 50.

77 per cent of the 130 African-American men who completed the questionnaire for this study, after responding to advertisements posted in two infectious disease clinics, were single. The average age of the participants was 46.

60 per cent were homosexual and 40 per cent were heterosexual. 32 per cent had received mental health treatment during the last year and the majority earned less than $10,000.

“While we think that our findings are compelling, it would be unwise to conclude that - as with any study - they are representative of all older African-American men who are HIV positive” stresses Dr Coleman.

“However, the findings of this study are worrying, particularly in view of rising HIV and AIDS rates in both ethnic communities and the over 50s. They definitely point to the need for further research into why older African-American men with HIV don’t use condoms.”

In 2006 UNAIDS - the joint United Nations programme on HIV and AIDS – estimated that there are now 39.5 million cases of HIV and AIDS worldwide. And they called for an international response to curb the stigma experienced by homosexual men who are HIV positive.

“We welcome this move as we believe it is essential to break down barriers to condom use among all people with AIDS and HIV” says Dr Coleman. “Some studies have even suggested that homosexual men have sex with women to hide their sexuality and HIV status.”

The authors hope that their findings will add to the ongoing debate about safe sex and condom use and highlight the need for more tailored initiatives to be developed for older African-American men.

“Health promotion messages have traditionally been targeted at young people” says Dr Coleman. “But the increased prevalence of older ethnic males with HIV and AIDS makes it essential for health professionals to promote safe sex and increase condom use to this target audience.”

Source : Blackwell Publishing Ltd.

Article : Of mice and men ... and kidney stones

Kidney stones are very common – and painful – in men. About 3 in 20 men (1 in 20 women) in developed countries develop them at some stage. Mice, however, rarely suffer though the precise reasons are unknown. Jeffrey S. Clark and colleagues, writing in The Journal of Physiology, have come up with some answers.

Kidney stones are crystalline deposits of various chemicals that should normally be excreted in the urine, particularly oxalate. Common in food, it is usually disposed of by the gut into the faeces by exchanging it for chloride. If there is little chloride available, in a low-salt diet for example, oxalate may be retained by the intestine to eventually be excreted by the kidneys, where the stones may form.

Mice, unlike men, do not spontaneously develop kidney stones, making it difficult to set up an animal model of this common disease. Now, some reasons for this difference between mice and men may have emerged.

The researchers showed that the human form of the protein responsible for secreting oxalate into the faeces requires a lot more chloride for efficient oxalate transport than the same structure in mice. Worse still, a variant form of the protein found in some people has even further reduced ability to export oxalate. Mice, it seems, are far more efficient at disposing of oxalate than we are.

Uncovering the molecular mechanisms of oxalate removal should help to develop improved treatments to prevent or even reverse the formation of kidney stones in humans, and paves the way for a mouse model of the disease to aid kidney stone research.

Source : Wiley-Blackwell

Article : Technology uses live cells to detect food-borne pathogens, toxins

Researchers have developed a new technology that can simultaneously screen thousands of samples of food or water for several dangerous food-borne pathogens in one to two hours.

The technique, which has potential biosecurity and food safety applications, also can estimate the amount of microbes present and whether they pose an active health risk. This could help neutralize potential threats and improve food processing techniques, said Arun Bhunia, a professor of food science at Purdue University.

"For food safety and biosecurity purposes, you need a quick test - a first line of defense - to be able to tell if there is something pathogenic in the food or water," Bhunia said.

The technology utilizes live mammalian cells that release a measurable amount of a signaling chemical when harmed. Optical equipment and computer software can then analyze this quantity to estimate the amount of harmful microbes present, Bhunia said.

"This is very important," he said. "With many toxins or pathogens, there is an effective dose or threshold you must pass before you have to worry. By providing information on quantity, this technology gives you a higher degree of confidence in the test and what steps must be taken to alleviate the problem."

The technology can recognize very small amounts of Listeria monocytogenes, a bacterium that kills one in five infected and is the leading cause of food-borne illness. It also recognizes several species of Bacillus, a non-fatal but common cause of food-poisoning, said Pratik Banerjee, a Purdue researcher and first author of a study detailing the technology that is published in the February issue of the journal Laboratory Investigation.

The cells are suspended in collagen gel, a useful substance for capturing particles of a desired size, and put into small wells within multi-well plates. Each well can test one sample, so tests can be expanded to quickly analyze as many samples as desired.

By using live cells, called biosensors, this technology can identify actively harmful pathogens but ignore those that are inactive, or harmless. Some analogous tests lack this capability, making them prone to false alarms and entailing a relatively lengthy incubation period to grow out any living microbes, Banerjee said. The new technology's discerning power also could help optimize processes to kill harmful microbes or deactivate toxins, he said.

Another advantage to the technique is its mobility and versatility, Bhunia said. The multi-well plates and their contents of gel-suspended mammalian cells could be efficiently prepared in a central location. When desired, the plates could then be shipped to the test location, like a food processing plant, so that analysis could take place on-site, he said.

This technology tests for bacteria and toxins that attack cell membranes. For this reason, researchers employed cells with high amounts of alkaline phosphatase, the signaling chemical released upon damage to the cell membrane. Researchers could conceivably employ other types of cells within this framework to detect additional types of pathogens, Bhunia said.

Samples of food and water are added to biosensor wells before being incubated for one to two hours. To each well a chemical is added that reacts with the biosensor's alkaline phosphatase, yielding a yellow product quantified by a special camera and a computer. A precise calculation may be unnecessary sometimes, however.

"When a large amount of pathogen is present, you can literally see the color change taking place before your eyes," Banerjee said.

The suspension of live mammalian cells within a collagen gel is unique, according to the researchers.

"This is the first time that anybody has trapped these kinds of cells alive in a collagen framework," Bhunia said.

Researchers are trying to get these cells to live within the gel beyond four to six days, a current limitation. But Bhunia said this time-span could be expanded to two weeks, the shelf-life he deems necessary for the technique to have commercial value.

The study was funded by the U.S. Department of Agriculture and Purdue's Center for Food Safety Engineering.

"This paper outlines two key accomplishments: one, we found a way to immobilize cells, which is a necessary and difficult prerequisite for further study. Two, we are able to simultaneously perform multiple tests on a large number of samples," Bhunia said.

Source : Purdue University