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New method to delay evolution of drug resistance in malaria parasite

Fri, 05 Sep 2008 04:40:00 -0400

Researchers at the University of Florida have devised a new method that effectively delays the evolution of drug resistance in malaria parasites.

David Smith, associate director of disease ecology at UF''s Emerging Pathogens Institute and study''s co-author, said that the new research would help scientists and policy makers in extending the longevity of current artemisinin-based malaria drugs combined with partner drugs.

Smith and colleagues created mathematical models assessing the strategic effectiveness and clinical outcomes of using one, two and three first-line drug therapies to treat malaria within a population over a 20-year period.

They found that using two or three drugs simultaneously reduced the total clinical cases and number of failed treatments, and slowed the rate at which drug-resistant genes spread within the parasites that cause malaria: Plasmodium falciparum, P. vivax, P. malariae and P. ovale.

"The models indicate that we can slow the evolution of resistance to current artemisinin-based therapies if nations use them in combination with two or more partner drugs," Smith said.

Smith said that artemisinin-combined therapies, or ACTs, are currently not widely implemented due to operational challenges and expense. However, he said that the study offers compelling evidence for global leaders to collaborate and overcome these issues.

"This is not to say that implementing multiple first-line therapies solves all of our malaria problems. Anti-malarial drug development needs to continue so that we have novel and highly effective anti-malarials that can be plugged into the recommended strategy of deploying multiple therapies," Boni said.

Artemesinin drugs, derived from the herb Artemisia annua, are relatively new and the malaria parasite does not yet appear to have a resistance to it. They work by triggering chemical reactions, which damage the Plasmodium parasite.

"We don''t have anything in the pipeline after ACTs, and it''s basically just a matter of time until drug resistance evolves and artemisinin also fails. So the question becomes how do we keep ACTs in our arsenal for as long as effectively possible?" Smith said.

The researchers'' models also show that cycling through single drugs accelerated the rate at which malaria parasites evolved drug resistance.

Smith said this occurred because cycling a single drug degraded the parasite''s average fitness, which made it easier for drug-resistant genes to spread throughout the parasite population.

The cycling models predicted a declining therapeutic value of a single drug within 3.54 years, versus a longer effective therapeutic value of 9.95 years when three drugs were used in equal proportions within a population.

"Using multiple first-line drugs reduces the selection pressure for resistance to a single drug. This is one way to make the ACTs last longer and benefit more people," Smith said.

The study is scheduled to publish online this week in the Proceedings of the National Academy of Sciences and in print on Sept. 16. (ANI)

Low-birth-weight infants should be screened for BP

Fri, 05 Sep 2008 04:39:00 -0400

Infants with low birth weight should be screened for high blood pressure, suggests researchers from UT South-western Medical Centre.

Previous studies have shown that low-birth-weight infants are likely to develop hypertension later in life.

Blood pressure has not been screened routinely in children with very low birth weights because the measurements were viewed as not feasible or unreliable in infants and toddlers.

“Measuring and validating blood pressure in this population really has not been addressed,” said Dr. Charles Rosenfeld, professor of pediatrics at UT Southwestern and one of the study’s authors.

“This is unfortunate because the earlier that hypertension is identified, the sooner appropriate medications and lifestyle changes can be introduced to stop the development of dangerous complications,” he added.

For the study, the researchers recruited two groups of children aged 1 through 3, whose blood pressure were taken.

The first group consisted of 28 children from the at-risk children’s clinic at Children’s Medical Centre Dallas. Some children had been born preterm with low birth weights, while others were born at term.

Each child’s blood pressure was taken twice randomly by two different trained raters who used a manual method similar to the one used to develop reference blood pressures for children.

They found that just as in adults, children’s blood pressure is affected by their state of mind: Infants who were calm for at least one of the measurements had significantly lower blood pressures than those who were fussy or crying for both.

“This is an important factor to consider if you’re going to achieve accurate blood pressure measurements in this population,” said Dr. Rosenfeld. “It’s something professionals who are taking blood pressure should consider when recording results.”

Another preliminary finding in this group was that, when comparing children with similar mental states, premature low-birth-weight infants had higher blood pressures than infants who had been born at term.

In the second group, 120 very-low-birth-weight infants were observed at the low-birth-weight follow-up clinic at Children’s.

Their blood pressure was measured twice, but this time five minutes apart by the same rater. As in the first group, infants who were not calm had significantly higher blood pressure than those who were tranquil.

The findings appear in the September issue of Pediatrics. (ANI)

DNA shows last woolly mammoths had North American roots

Fri, 05 Sep 2008 04:38:00 -0400

A DNA-based study has revealed that the last of the woolly mammoths, which lived between 40,000 and 4,000 years ago, had roots that were exclusively North American.

“Scientists have always thought that because mammoths roamed such a huge territory—from Western Europe to Central North America—that North American woolly mammoths were a sideshow of no particular significance to the evolution of the species,” said Hendrik Poinar, associate professor in the departments of Anthropology, and Pathology & Molecular Medicine at McMaster University.

Poinar and Regis Debruyne, a postdoctoral research fellow in Poinar’s lab, spent the last three years collecting and sampling mammoths over much of their former range in Siberia and North America, extracting DNA and meticulously piecing together, comparing and overlapping hundreds of mammoth specimen using the second largest ancient DNA dataset available.

“Migrations over Beringia (the land bridge that once spanned the Bering Strait) were rare; it served as a filter to keep eastern and western groups or populations of woollies apart,” said Poinar.

“However, it now appears that mammoths established themselves in North America much earlier than presumed, then migrated back to Siberia, and eventually replaced all pre-existing haplotypes of mammoths,” he added.

According to Ross MacPhee, curator of mammalogy at the American Museum of Natural History, and one of the researchers on the study, “Small-scale population replacements, as we call them, are not a rare phenomenon within species, but ones occurring on a continental scale certainly are.”

“We never expected that there might have been a complete overturn in woolly mammoths, but this is the sort of discoveries that are being made using ancient DNA. Bones and teeth are not always sensitive guides,” she added.

Like paleontologists, molecular biologists have long been operating under a geographic bias.

“For more than a century, any discussion on the woolly mammoth has primarily focused on the well-studied Eurasian mammoths,” said Debruyne.

“Little attention was dedicated to the North American samples, and it was generally assumed their contribution to the evolutionary history of the species was negligible. This study certainly proves otherwise,” he added.

“The study of evolution is an evolution in itself. This latest research shows we’re drilling down and getting a closer and better understanding of the origins of life on our planet,” said Poinar. (ANI)

Bumblebees escape predators by slowing down their ‘race for food’

Fri, 05 Sep 2008 04:37:00 -0400

A new study by scientists from Queen Mary, University of London, has suggested that bumblebees learn to avoid camouflaged predators like crab spiders by sacrificing their foraging (hunting for food) speed for detecting the animals.

One of the bumblebee’s main predators is the crab spider.

Crab spiders hunt pollinating insects like bees and butterflies by lying in wait on flowers, and are particularly difficult for their prey to spot because they can change their colour to blend in with their surroundings.

According to a report in New Scientist, Dr Tom Ings and Professor Lars Chittka from Queen Mary’s School of Biological and Chemical Sciences wanted to discover whether bumblebees could learn to avoid these crab spiders.

Their study shows how a run in with a spider affected the bees’ foraging patterns.

Dr Ings and his team allowed a colony of bumblebees (Bombus terrestris) to forage in a meadow of artificial flowers in a ‘flight arena’, which contained ‘robotic’ crab spiders.

Some of the spiders were well hidden, others were highly visible.

Whenever a bee landed on a flower which contained a robot spider, the spider ‘caught’ the bee by trapping it briefly between two foam pincers, before then setting it free to continue foraging.

The team used 3D tracking software to follow the bees’ movements, and found that the bees which were caught by a camouflaged spider slowed down their subsequent inspection flights.

Although they lost valuable foraging time by slowing down, they were more likely to accurately detect whether there was a hidden crab spider present.

In addition, the bees which had already been caught a few times the day before by the hidden spiders behaved as if they saw spiders where there were none, i.e. they rejected foraging opportunities on safe flowers, ‘just in case’ and were more wary than bees which had been caught by the more conspicuous spiders.

According to Dr Ings, “Surprisingly, our findings suggest that there is no apparent benefit to the spider in being camouflaged, at least in terms of prey capture rates. Spider camouflage didn’t increase the chances of a bumblebee being captured, or reduce the rate at which the bees learnt to avoid predators.”

“But our results did show that the bees which encountered camouflaged spiders were worse off in terms of reduced foraging efficiency,” he added. (ANI)

Obese asthmatic patients five times more likely to be hospitalized

Fri, 05 Sep 2008 04:36:00 -0400

Obese people suffering from asthma are nearly five times more likely to be hospitalized for the condition than their non-obese peers, according to a new study.

The study has been published in the September issue of the Journal of Allergy and Clinical Immunology.

This is the first research to control for the risk factors – smoking, use of oral or inhaled corticosteroid medications, gastroesophageal reflux disorder, and demographics – that might explain the obesity-asthma association.

Earlier studies have shown that obese people are more likely to suffer asthma than non-obese people, and that obese patients often have more severe asthma than their non-obese counterparts.

In the latest study, researchers at Kaiser Permanente Center for Health Research in Portland, Ore., and the Kaiser Permanente Institute for Health Research in Denver surveyed 1,113 patients in Oregon, Washington, and Colorado, age 35 and older, who have persistent asthma.

The researchers asked the patients about their weight, height, smoking habits, other illnesses, treatment and their asthma-specific quality of life, asthma control and asthma-related hospitalizations.

"The big finding here is that even after adjusting for risk factors, obese adults were nearly five times more likely to be hospitalized for their asthma," said study lead author David M. Mosen, Ph.D., MPH, of the Kaiser Permanente Center for Health Research.

The study found that obese people with asthma had significantly worse asthma control, lower asthma-related quality of life, and had 4.6 times higher risk for asthma-related hospitalizations than non-obese asthmatics

Also, obese people with asthma were younger and less educated than non-obese people with asthma. (ANI)