CHECKUP : PREPARATION, SIZE OF FRIES CULPABLE - NOT POTATO ITSELF NEWS, TIPS AND TRENDS.

Wider french fries, sometimes called ``steak fries,'' may contain less fat than an equal portion of thin fries because they have less surface area available to absorb frying oil. However, several other factors also may result in great differences between the fat content of french fries.

While you can bake frozen french fries, containing only 3 to 5 grams of fat in a 3-ounce serving (about 15 to 18 medium fries or just over a half-cup), without adding extra fat, a similar portion of deep-fried potatoes may contain 15 grams of fat. Check the package labels to compare the fat content of the different brands of grocery store french fries.

Limit portion size, too, since fat content can increase dramatically with larger amounts.

Although french fries have a bad reputation as a high-fat food, remember that it's the amount of fat added to a potato, and not the potato itself, that can cause weight problems. Home-baked and fast-food baked potatoes smothered in sour cream, cheese or margarine provide as much or more fat than those ``bad-guy'' fries.

Mutant gene slows AIDS: Scientists have uncovered more evidence that a mutated gene protects a small percentage of people from infection with HIV, the virus that causes AIDS, according to a new report.

The scientists, led by Dr. Stephen J. O'Brien, of the National Cancer Institute research center in Frederick, Md., also documented that some people with the mutation progress more slowly to AIDS following infection with HIV than people without the mutation.

O'Brien and colleagues based their findings on a study of 1,955 men either infected with HIV or at high risk for HIV infection.

Most people have two normal copies of a gene that directs production of a protein called CKR-5 on the surface of white blood cells. Researchers call this protein an HIV receptor. It allows the virus to bind to and enter the cells.

Findings by O'Brien and colleagues, as well as other groups, may enable development of new anti-HIV treatments, said Dr. Mary Carrington, a member of the O'Brien team.

``Inhibition of HIV binding to the CKR-5 receptor is likely to be an effective therapy against HIV infection,'' Carrington said. ``It may not be perfect, but it is likely that it will be extremely effective.''

The O'Brien team confirmed findings of previous studies showing that people must have two mutant copies of the gene to resist HIV infection. Among 612 people at high risk for HIV infection, 17, or 3 percent, had two mutant copies of the CKR-5 gene, the researchers reported. In contrast, none of 1,343 HIV-infected people had a mutant copy.

Researchers have estimated that about one in 100 white people have two mutant copies. In addition, they found that the mutation occurs much less frequently in black people than in whites.

O'Brien and colleagues reported that single mutant copies of the CKR-5 gene occurred in 15 percent of HIV-infected subjects and in 14 percent of subjects not infected with HIV. This similar frequency suggests that a single mutant copy does not protect people from HIV infection, according to the researchers.

Single mutant copies, however, may delay AIDS onset in people already infected with the virus, the scientists reported.

The average time to AIDS for all HIV-infected men in the study was 10 years, Carrington said. When the investigators looked at HIV-infected men who had the mutation, they found that the men progressed to AIDS in an average of 13 years.

Unaffected fish: Some human-caused disasters can be as devastating as the suppression of natural disasters.

Many scientists predicted that an accident such as the 1986 Soviet nuclear disaster at Chernobyl might produce fish with fantastic deformities.

But crucian carp in radioactive ponds near the meltdown site didn't have three eyes or extra tails sprouting from their heads. A team of scientists from Georgia, South Carolina and the Ukraine couldn't find any physical evidence of fish illness. That was pretty surprising, scientists said, considering that the carp did have extensive genetic damage.

The researchers, who describe their results in the October issue of Ecotoxicology, measured the amount of a radioactive form of the element cesium in carp tissue. The scientists were surprised that the extent of genetic damage in the fish wasn't related to the amount of radioactive cesium in the tissue. That may be because there were other radioactive chemicals in the carp tissues that the biologists didn't measure.

Radioactivity released during the Chernobyl accident probably has caused the high rates of thyroid cancer and leukemia found in people who lived nearby. But it's actually a bit of a mystery why more people didn't get sick, scientists say.

Normal-looking carp add to the mystery.

Don't eat ointment: Three toddlers died after consuming small amounts of over-the-counter ointments containing the anesthetic dibucaine, according to a new report.

Dibucaine often is found in topical ointments used to treat sunburn, cuts and hemorrhoids.

The children, who ranged in age from 18 months to 2 years, became listless after eating the medicine, and then had seizures, reported Dr. Peter Dayan, the lead author and an emergency physician in New York.

The children were treated in an emergency room, but all died following cardiac arrest, according to Dayan.

Parents should keep all medications containing dibucaine, as well as lidocaine, another anesthetic, out of the reach of children, he advised.

Work off the pain: Contrary to popular belief, most people with lower-back pain would be better off engaging in regular physical activity, not taking it easy, speakers said last week at the annual meeting of the American Academy of Family Physicians.

Exercise can help speed recovery from most cases of lower-back pain, said Dr. Louis Kuritzky, a clinical professor of health and family medicine at the University of Florida in Gainesville.

In fact, people who are sedentary have more lower-back problems than those who maintain an active lifestyle, he said.

In December 1994, the federal Agency for Health Care Policy and Research issued back-pain treatment guidelines, which urged back-pain sufferers to swim, walk or ride a bicycle within the first two weeks of back-pain symptoms.

About 90 percent of people who see a doctor for lower-back pain will get better without any treatment at all, Kuritzky noted.