Term of the Day

Telomere Clock: A theory concerning cellular aging and death. The telomere clock is presumed to determine the maximum number of times a given cell can divide. Telomeres are strings of nucleotides at the very ends of chromosomes, presumably to keep the chromosome from fraying or fusing with other chromosomes. In humans, the telomere base sequence TTAGGG repeats itself over a thousand times. The sequence, itself, does not code for anything, but every time the cell divides, up to 100 bases are lost from the telomere, which gets shorter. The theory is that when telomeres shorten to a critical point, then a signal to cease further mitosis is given. Credence to this theory was given by the 1994 discovery of the telomerase enzyme, which protects telomeres from degrading. Interestingly, telomerase is found in almost all cancer cells (which undergo uncontrollable mitosis), but not in other cell types.

Pathophysiology News: Mobile Phones and Meningioma

Here is some good news for those of you worried about a possible connection between cell phone use and intracranial malignancies. In an international study published in the International Journal of Epidemiology, researchers tracked 1209 meningioma cases and 3299 population-based control subjects. Data were collected regarding regularity of mobile phone use, duration of use, cumulative number of hours of use, cumulative number of calls, and several other indicators of cell phone use patterns.

When the researchers tried to correlate these data with meningioma risk, they found no connection. In fact, the risk of meningioma among regular cell phone users was actually lower than that for never or non-regular users! Furthermore, meningioma risk did not increase with years of mobile phone use, cumulative hours of use, or cumulative number of calls. These findings were similar regardless of age, gender, or telephone network type (analog vs. digital).

So, one more health scare bites the dust! You cell phone junkies can rest a little easier now.

Pathophysiology News -- Vitamin Supplements and Cancer Prevention

Bad news for those of you counting on vitamin supplements (especially antioxidants) to reduce your cancer risk. A new study to be released in the 7 January 2009 issue of the Journal of the National Cancer Institute indicates that vitamin C, vitamin E, and beta carotene do not help prevent cancer or reduce cancer mortality. The study followed 7627 women who were cancer-free at the outset of the experiment. Control subjects were given placebos; one experimental group was given 500 mg of vitamin C daily; another experimental group was given 600 IU of vitamin E every other day; and a third experimental group took 50 mg of beta carotene every other day. The average duration of treatment was 9.4 years.

Six hundred twenty-four women went on to develop invasive cancer, with 176 of them dying. None of the antioxidants performed any better than the placebo in reducing total cancer incidence. Neither was there any statistically significant difference among the 4 groups in cancer mortality. Combined use of all three antioxidants was also found to have no effect.