Medical News from Johns Hopkins

This is a service for doctors worldwide from Johns Hopkins International.  To receive reports directly, please send e-mail to jhis@jhmi.edu.

November 2004

1.  Antipsychotic Drugs Linked to Insulin Resistance in Children
2.  Low Dose Radiation Evades Cancer Cells' Radar
3.  Rapid Heartbeat Mystery: Is Odd Electrical Wave the Key?
4.  Meet the Colleague:  Neurologist John McDonald, M.D., Ph.D.
5.  New on www.jhintl.net: Welcome to Hopkins Video Gallery; Medical News now in more languages.

1.  Antipsychotic Drugs Linked to Insulin Resistance in Children
Researchers at Johns Hopkins say a group of drugs known as “atypical antipsychotics” that are commonly used to treat children with aggression, bipolar disorder, and schizophrenia may trigger insulin resistance, a condition that increases the risk of developing Type 2 diabetes and heart disease later in life. Results of the study were presented October 20 at the annual meeting of the American Academy of Child and Adolescent Psychiatry.  “The insulin resistance seen in these children was greater than what would be expected from weight gain alone, suggesting there is a factor distinct from excess weight that directly induces insulin resistance,” says the study’s lead author, psychiatrist Mark Riddle, M.D.

In general, this group of new-generation antipsychotics creates fewer side effects than older drugs and has successfully treated countless numbers of children since being introduced in the 1990s. “Treatments are always a matter of risk and benefit balance," adds Dr. Riddle. "Clearly these drugs are an important treatment option. But diabetes and heart disease are serious health issues, so it’s important to further investigate this apparent relationship between atypical antipsychotics and insulin production and consumption.”  If the study’s findings are confirmed by larger follow-up studies, Riddle says he would expect monitoring of metabolic side effects to become standard practice among clinicians prescribing atypical antipsychotics to children.

2.   Low Dose Radiation Evades Cancer Cells' Radar
A new study shows that lower doses of radiation can elude a damage detection "radar" in DNA and actually kill more cancer cells than high-dose radiation. With these findings, scientists believe they can design therapy to dismantle this "radar" sensor and destroy even greater numbers of cancer cells.  Hopkins researchers tested the low-dose radiation strategy on cultured prostate and colon cancer cell lines and found that it killed up to twice as many cells as high-dose radiation. The extra lethality of the low-dose regimen resulted from suppression of a protein, called ATM (ataxia telangiectasia mutated), which works like a radar to detect DNA damage and begin repair. Radiation oncologist Ted DeWeese, who led the study, presented his evidence last month at the annual meeting of the American Society for Therapeutic Radiology and Oncology.

DeWeese speculates that cells hit with small amounts of radiation fail to switch on the ATM radar, which prevents the repair process.  "DNA repair is not foolproof--it can lead to mistakes that are passed down to other generations of cells," he explains. "A dead cell is better than a mutant cell, so if the damage is mild, cells die instead of risking repair."  Higher doses of radiation cause extreme DNA damage and widespread cell death, so the ATM damage sensor is activated to preserve as many cells as possible, protecting, ironically, the cancer cells targeted for destruction by the radiation. The Hopkins scientists are now studying ways to use viruses that can deliver ATM-blocking drugs to the cells.

3.  Rapid Heartbeat Mystery: Is Odd Electrical Wave the Key?
For people who suffer from tachycardia, an implanted device can usually nudge the racing blood pump back to normal rhythm by applying electrical pulses to the heart. But, in a twist that has baffled physicians, on rare occasions the anti-tachycardia pulses produce the opposite effect: they trigger an even faster and more dangerous heartbeat.  By electrically jolting cardiac cells in a lab and mapping the change in electrical activity, biomedical engineers at Hopkins may have found an answer to this mystery.

Writing in the Oct. 26 edition of Proceedings of the National Academy of Sciences the researchers proposed that maverick electrical waves called multiarm spirals may be causing the accelerated heartbeats. The findings could lead to improvements in the next generation of implantable defibrillators used by patients with heart rhythm abnormalities. "At present, the devices can be programmed by the physician to deliver one of many different combinations of pulse parameters, and although standard algorithms exist, the optimum algorithm is not known," said biomedical engineer Leslie Tung, Ph.D., co-author and director of the lab in which the research was conducted.

4.  Meet the Colleague:  Neurologist John MacDonald, M.D.
For years, Hopkins has been on the cutting-edge of spinal cord and paralysis research and clinical treatment. Now, with the addition of John McDonald III, M.D., Ph.D., the pace of that research and treatment will increase exponentially.  Arriving recently from the Washington University at St. Louis, McDonald, who was the physician of the late actor Christopher Reeve, is leading an exciting initiative on spinal cord and paralysis recovery headquartered at the Kennedy Krieger Institute, an affiliate of Johns Hopkins specializing in children's developmental disabilities.  He also holds  appointments in Neurology, Neuroscience and Physical Medicine and Rehabilitation at Johns Hopkins School of Medicine. 

McDonald will see children, adolescents and young adults with acute and chronic injuries-from trauma, birth defects or disease, utilizing “activity-based restoration therapies” to treat patients with spinal cord injury. He has discovered that the central nervous system often holds the keys to recovery, and that progress can be made many years after injury. His collaborative research on the underlying pathophysiology of spinal cord recovery and paralysis has intrigued scientists worldwide. You can read an interview with Dr. Macdonald in the next issue of International Physician Update, due out in late November. To receive this free publication, please e-mail jhis@jhmi.edu.

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