Research by S. Blair Hedges and associates
has called into question two long-held
evolutionary beliefs. He said he hopes
additional fossil studies by paleontologists
will be consistent with his gene-research findings.
A common ingredient in shampoos and toothpastes may also protect women from both HIV and a sexually transmitted virus that causes deadly cervical cancer.
The discovery by Mary K. Howett, professor of microbiology and immunology in the College of Medicine, of the first chemical that destroyed human papilloma virus, or HPV, in addition to HIV, has researchers intrigued. The National Institutes of Health cautiously hopes that first-stage testing of the ingredient, sodium dodecyl sulfate, could begin in a small number of women later this year.
Before that can happen, the inexpensive chemical, which researchers already know is safe, will have to be developed into a usable vaginal gel or cream. Scientists have spent years hunting such a "topical microbicide" with little luck. Microbicides are gels or films that women would insert into the vagina before sex to protect against various sexually transmitted diseases.
"This is a major step toward our goal of producing a practical, non-toxic, inexpensive, discreet product which women can apply topically to the vagina prior to intercourse -- a product which would protect them from HPV infection even during encounters with infected partners," said Howett.
"In the case of previously infected women, this agent could prevent them from transmitting the virus to their partners. In addition, this agent could be used alone or with other currently available microbicides or spermicides to prevent HSV-2 and HIV transmission."
Dr. Penny Hitchcock, microbicide chief at The National Institutes of Health, said the HPV protection is particularly intriguing because "it's been a lot harder for us to find anything that works with that."
Human papillomavirus is a common sexually transmitted infection. About one in four women is estimated to have a strain of HPV. Most HPV is symptomless, but some strains go on to cause cervical cancer that kills 5,000 American women and 250,000 women worldwide every year. The global toll is so high because developing countries cannot afford Pap smears, tests that let most American women discover cervical abnormalities before they grow into actual cancer.
"If you could eliminate HPV, you could potentially prevent all those cancers," Howett said.
Research by S. Blair Hedges and associates
has called into question two long-held
evolutionary beliefs. He said he hopes
additional fossil studies by paleontologists
will be consistent with his gene-research findings.
By Barbara K. Kennedy
Eberly College of Science
The ancestors of major groups of animal species began populating Earth more than 600 million years earlier than indicated by their fossil remains, according to the largest study on the subject using gene sequences.
The research suggests that animals have been evolving steadily into different species for at least 1,200 million years, which challenges a popular theory known as the Cambrian Explosion that proposes the sudden appearance of most major animal groups, known as phyla, 530 million years ago.
To gauge the pace of evolution, researcher S. Blair Hedges, associate professor of biology, along with undergraduate student Daniel Y.-C. Wang and postdoctoral Fellow Sudhir Kumar, tested hundreds of gene sequences to find those that developed mutations at a constant rate over time.
"Because mutations start occurring at regular intervals in these genes as soon as a new species evolves -- like the ticking of a clock -- we can use them to trace the evolutionary history of a species back to its actual time of origin," Hedges said.
By comparing individual genes in pairs of species, the researchers identified 75 nuclear genes that had accumulated mutations at a fairly constant rate relative to one another during their evolution. The genes were from species representing three major taxonomic groups, or phyla, of animals (arthropods, chordates and nematodes), plus plants and fungi.
"Not only are all these genes telling us that a wealth of animal species in at least three phyla were already on Earth millions of years before their fossils start appearing," Hedges said, "but they also are telling us when three of the major kingdoms of living things -- animals, plants and fungi -- first diverged from a common ancestor and began evolving down separate evolutionary paths."
That date -- about 1.6 billion years ago -- is the earliest yet obtained by gene studies for this evolutionary event, according to Hedges.
Hedges said his research might be useful for finding life on other planets.
"If we can learn when different stages of life evolved on Earth, we can compare those dates to events in the chemical evolution of Earth's atmosphere and ocean, such as when oxygen and other important gases increased," Hedges said.
This research is an important focus in the Astrobiology Research Center.
"Our goal is to see if the early history of life on Earth can give us clues for how to predict life on other planets and in other solar systems," Hedges said. "We hope to be able to predict the kinds of life forms that are likely to exist on other planets, based on those that existed during Earth's history, just by measuring the chemical content of the planet's atmosphere."
By Barbara K. Kennedy
Eberly College of Science
Turtles, not birds, have been found to be the closest relatives of
crocodiles and alligators, according to an analysis of the largest available
collection of reptile genes. The study's conclusions contradict decades
of research based on anatomical and fossil studies, which had firmly positioned
birds as the reptile group most closely related to crocodiles and alligators,
a group known as crocodilians.
The surprising finding was made by researchers S. Blair Hedges, associate professor of biology, and graduate student Laura L. Poling.
Previous studies of gene similarities -- a relatively newer tool for determining relationships between species -- have never agreed with the more traditional anatomical methods on this issue.
"Turtles turned out to be not where they were supposed to be on the family tree whenever their genes were included in a research study," said Hedges, who decided recently to assemble all the genetic data available in order to resolve the question.
Hedges and Poling collected new data for two nuclear genes and added this new information to all gene-sequence data available for these species in the public genetic databases worldwide. The research included 24 genes from the nucleus and nine DNA segments from the mitochondria of reptile cells.
"The results provide strong evidence that the turtle is the crocodile's closest living relative," Hedges said.
Because the ultimate goal of both anatomical studies and gene studies is to find the proper place of all species on the family tree, researchers would like to see agreement between the two types of studies, wherever possible. To encourage their anatomist colleagues, Hedges and Poling point to an extinct species from the Triassic era, the aetosaur, which appears to share some anatomical characteristics of both turtles and crocodilians.
"We hope paleontologists will take a closer look at reptile fossils from this period to see if they can find any patterns of physical characteristics that would logically reposition the turtle on the family tree in a way consistent with the results of our large study of its genes."