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Updated 10:00 AM November 7, 2005
 

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Scholarship & Creativity

Scientists create two-sided nanoparticles
As with many things in nature, including nanoparticles, two are better than one.
U-M scientists have used electricity to create nanoparticles with two sides, similar to how a fish bobber is made of two colored half shells. The technique could fuel a new research direction in the field because the limits of size and shape are expanded, says Joerg Lahann, assistant professor of chemical engineering.

An artist’s rendering of the process of making biphasic nanoparticles. The new particles could be used in many applications, including targeted drug delivery or to create new self-assembling particles, U-M scientists have found. (Courtesy Hyunjung Kim)

The new particles are exciting for several reasons, Lahann says, and could be used in many applications including targeted drug delivery or to create new self-assembling particles. The big advantage is that the two sides, or phases, may be modified separately.

A good way to understand this is to picture two full water balloons pushed into a transparent jar. The membranes are pressed together but the contents of each balloon differs because the membrane separates the two balloons. Scientists could load two different drugs into the particles, one on each side, for use in targeted drug delivery.

“You could potentially fill each balloon with a different drug,” Lahann says.

Using the fish bobber analogy, scientists chemically can alter the surfaces of the two halves to create patches—chemically altered spots on the particle with different instructions. The ability to engineer or chemically modify the particles to create different surface patches is crucial to self-assembly of nanoparticles and also in drug delivery, Lahann says. For example, one of the two sides could be modified to ‘dock’ at certain prescribed points on a cell membrane or a cell tissue.

The findings are published on-line in Nature Materials, in a paper entitled, “Biphasic Janus Particles with Nanoscale Anisotrophy,” co-written by Lahann, Kyung-Ho Roh, a doctoral student in materials science and engineering, and David Martin, professor of materials science and engineering, and director of the Macromolecular Science and Engineering Center.


Post-stroke tests not used enough, especially in women
Women who survive a stroke are less likely than men to get crucial tests of their heart and neck arteries that can help improve treatment and reduce the risk of a second stroke, a U-M study finds.

While the tests appear to be under-used in all stroke patients regardless of gender, the difference may help explain why women tend to have a worse long-term outcome from stroke, including a higher death rate.

One in every seven people who has a stroke will have another one within a year, according to the study that looked at the use of tests that cut the risk by assessing the potential for blood clots to form in the heart, and the health of the carotid arteries. The results of such tests can guide doctors to prescribe preventive treatment and help patients understand what they must do to avoid a second stroke.

“Diagnostic evaluations that should be done on every ischemic stroke patient still aren’t being performed on a third to a half of patients, and they’re less likely to be performed on women,” says senior author Dr. Lewis Morgenstern, director of the Stroke Program in the Cardiovascular Center. “Intervention is needed to increase access to quality stroke care for all patients, but especially women.”

Morgenstern, a stroke neurologist who leads the Brain Attack Surveillance in Corpus Christi study from which the new data were gathered, is a professor in the departments of Neurology, Neurosurgery and Emergency Medicine at the Medical School and a professor of epidemiology at the School of Public Health.

The new paper found that women were 36 percent less likely than men to receive an echo-cardiogram of their heart, a test similar to pregnancy ultrasound, that creates a movie of the heart and can look for clot-producing conditions and other problems. Women also were 43 percent less likely to have exams of their carotid arteries, which can become narrowed by cholesterol plaque that blocks blood flow and spawns clots.

“Previous studies have shown that the rate of stroke is lower in women than in men, but that women have worse outcomes than men. Our results may give us a reason for that disparity,” says lead author and neurology research associate Melinda Smith Cox.

The study was published in the Sept. 27 issue of the journal Neurology.


To move chromosomes, tiny motors give nudge, not shove
Understanding how tiny motors nudge chromosomes into proper position during cell division could help scientists find new ways to cure cancer and other diseases caused when cells go awry.

When cells divide, chromosomes split to separate duplicate genetic material to be segregated between the cells. This ensures that each new cell gets a full set of identical chromosomes. Understanding this process is critical because when chromosomes aren’t segregated properly the outcome includes cell death, cancer or genetic disorders such as Down’s syndrome, says Alan Hunt, associate professor of biomedical engineering.

Learning how biological motors position chromosomes during cell division could help scientists understand why such diseases occur, and assist them in the development of cancer treatments that inhibit cell division in cancer cells.

Motors called chromokinesins are positioned along the chromosome arms and they gently propel the chromosomes along microtubules, which serve as a rail system for chromosomes. The force that one of these motors exerts, Hunt says, is comparable to the strength of a flashlight beam hitting a surface, and is intrinsically intermittent. That’s important because chromosomes are mechanically delicate and would tear easily, like elasticized cotton candy, Hunt says.

Scientists used a tool called optical tweezers in which a focused laser beam acts like a tiny vacuum, pulling objects toward it to be manipulated on the nanoscale. Scientists isolated the chromosomes and then used the optical tweezers to flip-flop the chromosome and the microtubule. In that way, they could observe the motors moving the microtubules along the chromosome arms.

The findings appeared Sept. 20 in the Proceedings of the National Academy of Sciences in a paper entitled, “Microtubule movements on the arms of mitotic chromosomes: Polar ejection forces quantified in vitro,” written by Hunt and co-author Gary Brouhard, a postdoctoral student at the Max Planck Institute for Molecular Cell Biology and Genetics.


Schoolwork suffers when ill mothers go easy on discipline
When mothers diagnosed with a mental illness lack parental confidence with regard to discipline, their children are more likely to receive poor grades and behave badly in school, a U-M study shows.

The mother’s mental illness increases the risk of her child’s academic problems by interfering with the ability to provide appropriate childrearing, says senior author Daphna Oyserman, a professor in the School of Social Work (SSW) and research professor at the Institute for Social Research.

“Prior research has shown an association between mental health problems and academic outcomes, but this research shows that the pathway is through parenting. This provides hope to parents, since parenting is more amenable to change,” Oyserman says.

When parents are consistent and clear in rule-setting and set demanding but reasonable standards that let children know what is expected of them, children’s outcomes are likely to be more positive, she says.

Co-authors are Deborah Bybee of Michigan State University and Tamera Hart-Johnson and the late Carol Mowbray, both from SSW. The paper, which appears in the Journal of Adolescence, is based on data from two National Institute of Mental Health-funded research projects examining parenting in women with serious mental illnesses and outcomes for their teenaged children. The women had diagnoses of schizophrenia, depression, bipolar disorder or other dysfunctions for more than one year.

Mothers with young children were significantly more likely to rate themselves as confident and were more likely to follow through on discipline than mothers with teens.

“This suggests that parenting a teenager taxes the mothers’ ability to feel competent and confident of their skills,” Oyserman says.


Doing housework hurts wages of young and middle-aged women
While prior research has shown that housework has an adverse effect on wages, a University study finds that only young and middle-aged women are affected.

“Despite a slight reallocation of housework activities from wives to husbands in recent years, most of the housework as well as the care of children within the home are still primarily the responsibility of the woman,” Paula Malone, a lecturer in economics. “Wives are still primarily doing ‘women’s work,’ such as meals, dishes, cleaning, shopping and laundry, whereas men are engaged in the traditional male tasks, such as yard work, home maintenance and auto repair.”

Only the income of young women (ages 20-34) and middle-aged women (35-49) is negatively affected by the amount of housework they do.

In a study published earlier this year in the journal Contemporary Economic Policy, Malone and Kristin Keith of the University of Toledo found that each additional hour of housework time reduces the wages of young and middle-aged women by 0.1 percent to 0.4 percent. While these wage losses may seem small, the researchers say they are statistically significant.

According to Keith and Malone, the true cause of the wage effect among young and middle-aged women is child care, in conjunction with regular household duties.

“These results suggest that time spent on housework today may have a feedback effect that adversely affects women’s labor market experience, which may in turn amplify the adverse effect on their future wages,” Malone says. “However, attitudes toward the traditional distribution of housework within the family are changing, if numerous recent articles in the popular press are any indication.”

Mammoth moms heavily invested in offspring
Details about the life of a young woolly mammoth that died thousands of years ago are emerging from a study of the animal’s fossil tusk. One intriguing finding: the calf nursed from its mother six or more years, apparently depending on the calorie-rich milk to survive in harsh, arctic conditions.

A tusk of a juvenile woolly mammoth, Mammathus primigenius. By studying the tusk, U-M researchers have discovered many details about the mammoth, and concluded the animal nursed from its mother for six or more years. (Courtesy Adam Rountrey)

“Like the tusks of modern elephants, mammoth tusks were ever-growing, adding a thin layer of dentin (ivory) each day of the animal’s life,” says graduate student Adam Rountrey, a member of the research team. Over years, changes in the rate and conditions of growth also produced visible layering. By analyzing these layers, Rountrey and colleagues were able to reconstruct the mammoth’s growth history and estimate how many years it lived.

The tusk’s chemistry helped fill in other details. The researchers analyzed protein extracted from tusk layers and measured the ratios of different forms (isotopes) of carbon and nitrogen in the tusk. These chemical clues can reveal what type of plants a mammoth ate, whether or not it was nutritionally stressed and, as the new study shows, if it was nursing from its mother.

The research team’s results suggest that weaning took place gradually over at least four and a half years and possibly six or more years.

“That compares with an average of about five years for African elephants at weaning,” says co-author Daniel Fisher, the Claude W. Hibbard Collegiate Professor of
Paleontology and a professor of geological sciences and of ecology and evolutionary biology. “In African elephants weaning age often corresponds to calving interval, so that suggests we might be on the right track.”

The research team from U-M, Wrangel Island State Preserve and the University of Minnesota presented the results of their tusk analysis Oct. 22 at a meeting of the Society of Vertebrate Paleontology in Mesa, Ariz.


Black women with chronic pain have more distress
Black women with chronic pain experience more psychological distress, physical impairments and instances of post-traumatic stress disorder than white women with chronic pain—a finding that researchers say should help lead to a narrowing of the gap in the treatment of chronic pain between Black and white women.

Research from the U-M Health System, published in the Journal of the National Medical Association, suggests Black women with chronic pain have particular needs that should be addressed through access to and quality of pain care.

“Although more than one in five Americans live with chronic pain, women are more likely to suffer from chronic pain conditions than men. What we have found in this research is that there are further differences in the chronic pain experience between Black and white women,” says Dr. Carmen R. Green, associate professor in the Department of Anesthesiology and pain specialist at the Center for Interventional Pain Medicine. “This study has significant public health implications as well as significant socio-economic and familial implications when studying and managing chronic pain in Black women.”

Black women in the study were more likely to report disability due to pain (44 percent versus 37 percent), and to say that pain interfered with recreational (8 percent versus 7 percent), sexual (7.4 percent versus 6.1 percent), social (7 percent versus 6 percent) and other activities.

Black women in the study also were more likely to report psychological distress due to pain, with significantly higher scores of post-traumatic stress disorder and depression. But the picture of the depression scores changed when disability, pain severity and affective distress were accounted for; with those measures factored in, Black women were significantly less likely to show signs of depression than white women.

In addition to Green, the other author on the paper was S. Khady Ndao-Brumblay, senior research associate in the Department of Anesthesiology Research Division.

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