Physicians and scientists at New York-Presbyterian Hospital/Weill Cornell Medical Center have successfully established a diagnostic technique that virtually eliminates the risk of passing on certain genetic traits from parent to offspring, a significant medical advancement that could spell the end to a family’s history of dealing with a deadly disease. In this case, doctors successfully used the technique preimplantation genetic diagnosis (PGD) to isolate the gene responsible for causing retinoblastoma, the most common primary cancer of childhood. The result? The world’s first two babies born free of the deadly disease. PGD, or embryo biopsy, is employed with in vitro fertilization to determine the genetic status of embryos before implantation, allowing parents to know with a relatively degree of certainty that their child will be normal, before the mother even begins carrying the child. If a parent has retinoblastoma, the chances are 50 percent likely that their offspring will be affected, often with fatal results. Children born with the gene often develop retinal tumors; they also have more of a proclivity for developing other cancers, such as osteosarcomas of the skull or extremities, soft-tissue sarcomas, and melanomas. Led by Dr. Zev Rosenwaks, director of the Center for Reproductive Medicine and Infertility, the interdisciplinary team used the relatively new technology to biopsy single cells from the DNA of a mother whose first child was born with the defect three-and-a-half years ago and later developed retinoblastoma at a young age. Embryos determined not to carry the gene were implanted within the mother’s uterus. She went on to have two successful pregnancies through PGD — resulting in a daughter, now 18 months old, and a son, now 8 months. “Previous methods for detecting retinoblastoma have had their limits,” says Dr. Rosenwaks. Other procedures, such as amniocentesis or chorionic villus sampling necessitate tissue or fluid to be removed from around the developing fetus. Couples with a positive test result face a tremendously difficult decision — whether to terminate the pregnancy or go forward knowing their child may be prone to develop cancer. New York-Presbyterian/Weill Cornell’s Center for Reproductive Medicine and Infertility is credited with the nation’s first PGD baby, as well as America’s first babies born free of hemophilia and sickle cell. PGD procedures are also offered to couples with genetic disorders and chromosomal abnormalities, including Tay Sach’s, cystic fibrosis, thalassemia and Fanconi’s anemia, among others.
A strong case for vitamin D?
In the first study of the role dietary intake of vitamin D plays in the development of multiple sclerosis in women, researchers from the Harvard School of Public Health have found that women with the highest intake of the vitamin through supplement use had a 40 percent lower risk of developing the disease as compared to women who did not use supplements. “These results are encouraging. We have suspected that vitamin D may play a role in reducing the risk of developing MS,” says the study’s lead author, Kassandra Munger, a researcher at the Harvard School of Public Health’s Department of Nutrition in Boston. The National Institutes of Health-funded study appears in a recent issue of the medical journal Neurology. Of the more than 185,000 women selected to participate in the study who were free of the disease, 173 developed MS during the span of the research, which occurred from 1980-1999. Women who had the highest intake of vitamin D supplements (400 IU per day or more) had a 40 percent reduced risk of developing the chronic central nervous system disease than those who did not use vitamin supplements. No reduction in risk was associated with vitamin D intake through food alone. Manufactured by the body via exposure to sunlight and artificial sources of ultraviolet light, foods like milk, liver and fish are also good sources of vitamin D. Although the precise causes of the debilitating disease remain unknown, the study’s results point to the deficiency of vitamin D as a principal factor in the onset of MS in women. Previous research has also pointed to the role of vitamin D in MS. Studies in 2002 and 2003 linked inadequate exposure to UV-B light to an array of other serious diseases, such as rickets and diabetes. Currently, an estimated 250,000 to 350,000 Americans have MS. Most people experience their first symptoms of MS between the ages of 20 and 40. Whites are more than twice as likely as other races to develop MS and, in general, women are affected at almost twice the rate of men. Another study, conducted recently by scientists at the Unit of Health-Care Epidemiology at Oxford University’s Department of Public Health in London, showed that sunshine may protect against the development of MS, particularly the closer people live to the equator. Published in the March 2004 Journal of Epidemiology and Community Health, the study suggests that a minimum level of exposure to sunlight’s UV-B ultraviolet rays throughout the year may be important in protecting individuals against the deadly disease. The exposure, researchers held, may better protect people against MS by beneficially influencing the immune system response, possibly through changes in production levels of vitamin D and melanin, the substance involved in acquiring a tan. “Because the number of cases of MS increases the farther you get from the equator, one hypothesis has been that sunlight exposure and high levels of vitamin D may reduce the risk of MS,” Munger says. According to the National Institute of Neurological Disorders and Stroke, MS is five times more prevalent in temperate climates such as those found in the northern United States, Canada, and Europe. The prevalence rate in the U.S. is higher for individuals who live above the 37th parallel, accounting for 110-140 cases per 100,000 people, compared to 60-80 cases per 100,000 for people living below the 37th parallel. New York City lies just south of the 41st parallel. — Kirsten Matthew
