Tuesday, August 18, 2009
8/18/2009 04:18:00 AM Publicado por Alquimia
Researchers have identified what they believe is the original source of malignant malaria: a parasite found in chimpanzees in equatorial Africa.
UC Irvine biologist Francisco Ayala and colleagues think the deadly parasite was transmitted to humans from chimpanzees perhaps as recently as 5,000 years ago - and possibly through a single mosquito, genetic analyses indicate. Previously, malaria's origin had been unclear.
This discovery could aid the development of a vaccine for malaria, which sickens about 500 million people and kills about 1.5 million each year. It also furthers understanding of how infectious diseases such as HIV, SARS, and avian and swine flu can be transmitted to humans from animals.
"When malaria transferred to humans, it became very severe very quickly," said Ayala, co-author of the study that reports these findings. "The disease in humans has become resistant to many drugs. It's my hope that our discovery will bring us closer to making a vaccine."
The study appears online in the Proceedings of the National Academy of Sciences.
Human malignant malaria is caused by a parasite called Plasmodium falciparum, which is responsible for 85 percent of all infections and nearly all malaria deaths. Chimpanzees were known to carry a closely related parasite called Plasmodium reichenowi, but most scientists assumed the two had existed separately in humans and chimpanzees for the last 5 million years.
Scientists in the current study examined several new strains of the parasite found in blood taken from wild and wild-born chimpanzees in Cameroon and Ivory Coast sanctuaries during routine health exams.
A gene analysis linked one chimpanzee strain to all worldwide strains of the human malaria parasite. This connection suggests that one mosquito may have transferred malaria to humans. Because there is little genetic variance among strains of the human parasite, scientists believe the transmission occurred in the recent past - maybe 5,000 to 2 million years ago - though an exact time could not be determined.
The results support an earlier hypothesis by Dr. Ajit Varki of UC San Diego and colleagues that genetic mutations made humans first resistant to sickness from the chimpanzee parasite, then extremely susceptible to illness from the human form.
They also corroborate an earlier finding by Ayala and former UCI graduate student Stephen Rich that malignant malaria started spreading throughout the tropics and world about 5,000 years ago, when agriculture began in Africa. Rich, now a professor at the University of Massachusetts Amherst, is the lead author of the current PNAS study.
(Photo: Daniel A. Anderson / University Communications)
8/18/2009 04:17:00 AM Publicado por Alquimia
University of Florida researchers were able to program bone marrow stem cells to repair damaged retinas in mice, suggesting a potential treatment for one of the most common causes of vision loss in older people.
The success in repairing a damaged layer of retinal cells in mice implies that blood stem cells taken from bone marrow can be programmed to restore a variety of cells and tissues, including ones involved in cardiovascular disorders such as atherosclerosis and coronary artery disease.
“To our knowledge, this is the first report using targeted gene manipulation to specifically program an adult stem cell to become a new cell type,” said Dr. Maria B. Grant, a professor of pharmacology and therapeutics at UF’s College of Medicine. “Although we used genes, we also suggest you can do the same thing with drugs — but ultimately you would not give the drugs to the patient, you would give the drugs to their cells. Take the cells out, activate certain chemical pathways, and put the cells back into the patient.”
In a paper slated to appear in the September issue of the journal Molecular Therapy, scientists describe how they used a virus carrying a gene that gently pushed cultured adult stem cells from mice toward a fate as retinal cells. Only after the stem cells were reintroduced into the mice did they completely transform into the desired type of vision cells, apparently taking environmental cues from the damaged retinas.
After studying the cell-transformation process, scientists were able to bypass the gene manipulation step entirely and instead use chemical compounds that mirrored environmental conditions in the body, thus pointing the stem cells toward their ultimate identities as vision cells.
“First we were able to show you can overexpress a protein unique to a retinal cell type and trick the stem cell into thinking it is that kind of cell,” said Grant, who collaborated with Edward Scott, the director of the Program in Stem Cell Biology and Regenerative Medicine at UF’s McKnight Brain Institute. “As we proceeded, we found we could activate the stem cells by mimicking the body’s natural signaling channels with chemicals. This implies a whole new field of stem cell research that uses drug manipulation rather than genetic manipulation to send these immature cells along new pathways.”
Scientists chose to build retinal pigment epithelial cells, which form the outer barrier of the retina. In addition to being very specialized and easy to identify, RPE cells are faulty in many retinal diseases, including age-related macular degeneration, which affects nearly 2 million people in the United States, and some forms of blindness related to diabetes.
“This work applies to 85 percent of patients who have age-related macular degeneration,” Grant said. “There are no therapies for this devastating disease.”
The work was supported by the National Eye Institute. Researchers removed blood stem cells from the bone marrow of mice, modified the cells in cultures, and injected them back into the animals’ circulatory systems. From there, the stem cells were able to home in on the eye injury and become retinal cells.
At 28 days after receiving the modified stem cells, mice that had previously demonstrated no retinal function were no different than normal mice in electrical measures of their response to light.
(Photo: U. Florida)
University of Florida
8/18/2009 04:17:00 AM Publicado por Alquimia
The tree-climbing lifestyle of Suminia getmanovi, a Paleozoic animal that lived 260 million years ago, is particularly important because it gave this small herbivore the first access to new food resources high off the ground and also provided protection from ground-dwelling predators. The evidence for this lifestyle is based on several skulls and more than a dozen complete skeletons from central Russia, as well as from coprolites (fossilized feces) that were found on the same sediments as the skeleton. The findings appear online in the Proceedings of the Royal Society B.
"Independently, this animal appears to have acquired this evolutionary innovation of a grasping hand," said Professor Robert Reisz, chair of biology at U of T Mississauga. "That would have allowed it to climb trees very efficiently and to grasp things. It would have allowed the animal to bring food to its mouth." Reisz, the senior author of the paper, notes that modern animals like chameleons and flying lemurs have similar foreleg structure.
The study also provides the first evidence of "resource partitioning" -- with smaller arboreal animals taking advantage of food and safety from predators in trees while larger herbivores remained on the ground. This was a change from a large numbers of terrestrial plant-eaters supporting a few top predators and even earlier terrestrial vertebrate communities composed of various sized predators and relatively few herbivores.
University of Toronto Mississauga