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Researchers Locate Gene for Deadly Kidney Disorder

February 11, 2002|THOMAS H. MAUGH II | TIMES STAFF WRITER

Mayo Clinic researchers have identified the gene for a lethal kidney disorder that kills several hundred infants in the United States each year.

The disease is called autosomal recessive polycystic kidney disease--which means that a child must inherit a copy of the gene from each parent to develop the disorder. Sometimes also called infant polycystic kidney disease, the condition is characterized by multiple fluid-filled cysts in the kidney and fibrosis in the liver, and affected infants usually die before birth or shortly afterward.

Although only an estimated one in every 10,000 to 20,000 children is born with the disorder, the odds of developing it are one in four when both parents carry the gene.

Identification of the gene will lead to a better understanding of how the disease progresses and may lead to the first effective treatment. It will also allow effective prenatal testing.

More than seven years ago, German scientists narrowed the search for the gene by concluding that it is located on chromosome 6, one of the 23 pairs of chromosomes that make up the human genetic blueprint. Dr. Peter C. Harris and his colleagues at Mayo reported last week in Nature Genetics online that they first identified the gene that causes the disease in rats, then identified the corresponding gene in humans.

The gene, called PKHD1, is the blueprint for a very large protein called fibrocystin. Researchers do not yet know what the protein does, however. The discovery of the gene in rats provides researchers with an animal model for the disease that will help test new treatments.

Increased Heart Rate Can Relieve Sleep Apnea

Increasing the rate at which the heart beats at night can relieve the symptoms of sleep apnea, French researchers have found.

Sleep apnea is a cessation of breathing, lasting from a few seconds to a minute or more, that can occur hundreds of times during the night. As many as 18 million Americans suffer from sleep apnea, a disproportionate number of them obese males over the age of 40.

The condition leaves victims sleepy by day, increasing the chances of such problems as dozing off while driving. It can also contribute to high blood pressure and heart disease.

Dr. Stephane Garrigue of the Cardiology Hospital of Haut-Leveque in Pessac became intrigued by the subject when some of his patients reported they slept better after receiving pacemakers. He and his colleagues then studied 15 patients in whom they increased the nighttime heart rate from 57 beats per minute to 72.

The researchers reported in the Feb. 14 New England Journal of Medicine that the average hourly number of apnea episodes dropped by 61%, from 28 to 11. The incidence of apnea was reduced in every patient, Garrigue said. But experts cautioned that more studies need to be performed before pacemakers are widely used for treating the disorder.

Researchers are not sure how increasing the heart rate reduces apnea, but they speculate that the faster heart rate may be stimulating various nerves, which then prompt the brain to normalize breathing.

Tanning Beds, Lamps Raise Skin Cancer Risk

Occasional use of tanning beds and lamps can double the risk of skin cancer. Dr. Steven Spencer and his colleagues at the Dartmouth Medical School studied 896 New Hampshire residents with either basal cell carcinoma or squamous cell carcinoma, comparing them with 540 people who did not have skin cancer.

When they controlled for all other factors, the researchers reported in the Feb. 6 Journal of the National Cancer Institute, they concluded that the tanning devices doubled the risk of skin cancer.

"No other factors, including summer outdoor exposure, sunbathing or sunburns, affected our results," they said.

The greatest increase in risk occurred in fair-skinned young women who sunburned easily but who used tanning devices anyway.

Early Magnesium Sulfate May Help Stroke Victims

A preliminary UCLA study indicates that paramedics can safely give magnesium sulfate to stroke victims before they are transported to the hospital, potentially avoiding some of the debilitating effects of the strokes.

Magnesium sulfate dilates blood vessels in the brain and may prevent the buildup of damaging calcium in injured nerve cells when given soon after a stroke occurs.

Dr. Jeffrey Saver and his colleagues organized a program in which Los Angeles paramedics administered the drug to 20 patients. Saver reported last Thursday at a stroke meeting in San Antonio that the drug was given an average of 2 hours and 40 minutes earlier than conventional procedures and that no adverse effects were observed.

Although Saver perceived that the patients fared better than would have been expected, the researchers will have to perform a regular clinical trial to determine if that is the case.

Do Over-the-Counter Cough Syrups Work?

Over-the-counter cough medicines may be a waste of money because they have never been proved to work, according to British researchers.

Dr. Knut Schroeder and Dr. Tom Fahey of the University of Bristol analyzed 15 separate trials of the cough medicines that included more than 2,000 people total. Nine of the studies showed the cough syrups were no better than placebos, the pair reported in the Feb. 9 issue of the British Medical Journal. The other six reported only slightly positive results.

The researchers concluded, therefore, that there is little evidence that the medicines do work or that they don't.

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Thomas H. Maugh II can be reached at thomas.maugh@latim es.com.

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