What's Hot Archive
November 29, 2000
Cataracts prevented by vitamins
An estimated 80% of all individuals aged seventy-five and older and twenty million people worldwide are visually impaired due to cataracts, a clouding of the lens of the eye which reduces the amount of incoming light.
A five year study reported in the journal Archives of Ophthalmology demonstrated a lower incidence of cataracts amongst vitamin consumers. Three thousand eighty-nine residents of Beaver Dam, Wisconsin, aged 43 to 86 were examined for cataracts from 1988 through 1990 and followed up five years later. Cataract incidence and type was determined through the use of slitlamp photography for nuclear cataracts and retroillumination photographs for cortical and posterior subcapsular cataracts. At the five year follow-up, the study participants were interviewed to obtain detailed information concerning their multivitamin and other supplement use, including dosage and duration of use. The five year risk for cataract was 60% lower for those persons reporting multivitamin use, vitamin C or vitamin E use for more than ten years compared to nonusers. Those who used supplements for less than ten years did not have a lessened risk of developing cataracts. Lifestyle differences between supplement users and nonsupplement users and dietary variations were not determined to have influenced this association, although the authors mentioned that it is possible that unmeasured lifestyle differences could have an influence.
This study supports the theory that cataracts are caused by free radical damage that occurs over a period of decades, and that antioxidants can help prevent it. The authors note that it is of yet undetermined which nutrients specifically confer the protective benefit observed.
November 27, 2000
Melatonin needed by post-op patients
The October 7, 2000 issue of the medical journal The Lancet, presented research conducted at Penn State College of Medicine which showed that on the night following their surgery, patients had melatonin levels that were significantly lower than normal. The patients' levels of melatonin rose on the second night, returning to normal by third night post-op. Assistant Professor of Anesthesiology at Penn State and lead study author Arthur J Cronin MD, stated, "These low levels may indicate why a patient has difficulty sleeping after surgery . . . Melatonin is a marker for the circadian rhythms and when these rhythms are disturbed, your sleep is disrupted."
Melatonin is a hormone released by the pineal gland in the brain, involved in sleep, mood and immune function. Melatonin levels in humans usually peak between 2:00 am and 4:00 am. The study, partly funded by the National Institutes of Health, monitored the melatonin of women ages 32 to 49 who were patients at Penn State Milton S Hershey Medical Center by measuring their blood melatonin levels hourly each night after surgery.
Dr Cronin explained that the timing of the body's internal clock is reflected by melatonin levels and hopes that melatonin replacement therapy can be used to prevent the sleep disturbances experienced by postoperative patients, which is currently being studied. As sleep is essential to the healing process, administering melatonin would aid in that process. He stated that although it is not clear why melatonin levels would drop after surgery, stress on the body from anesthesia or from the surgery could be the cause, and suggests "If we can artificially increase melatonin levels for the first night, we might improve patients' sleep after surgery."
November 22, 2000
Blood expander useful in surgery
In response to articles appearing in this month's issue of Anesthesiology which show that surgical fluids high in chloride contribute to acidosis, Biotime Corporation, makers of the blood plasma volume expander Hextend, announced that the product could be of benefit to surgical patients. Approximately 2.5 million patients per year lose enough blood during surgery to require a transfusion. Blood expanders are used to expand blood volume until a transfusion becomes imperative. Hextend is a synthetic starch-based plasma blood volume extender that can be administered while the patient's blood is being typed, or while waiting for compatible blood. It can be used to replace larger volumes of blood than other starch-based plasma volume expanders, thus reducing the number of blood products used by the patient.
Dr T J Gan of Duke University, where some of the initial research was conducted stated, "Hextend contains substantially less chloride than older saline-based surgical solutions, with glucose and electrolytes in concentrations similar to those normally found in plasma, and lactate which can reduce blood acidity. Hextend also maintains plasma volume during major surgery better than solutions such as saline, or those containing electrolytes and lactate which do not have colloid. Synthetic surgical solutions which do not have starch must often be used in very large amounts, causing the patient to accumulate significant amounts of fluid in his or her tissues."
The blood expander can also be administered before surgery, with some of the patient's blood being removed so that it is available during surgery, a process known as acute normovolemic hemodilution (ANH). Biotime Chairman Paul Segall, PhD commented, "Evidence is mounting that patients receiving their own blood can often make a very favorable recovery without the well known risks of receiving blood from donors. Hextend, which has been shown to be safe and effective even when used to replace large blood volumes lost during surgery, and innovative procedures such as ANH, could improve the safety of operations and patient recovery. This may be especially true in older patients, in whom biochemical alterations, or the risk of infection, may be more compromising. These advances could also help alleviate the national blood shortage."
November 20, 2000
Type 1 diabetics benefit from vitamin E
A randomized double-blind study reported in November's American Journal of Clinical Nutrition demonstrated that type 1 diabetics taking vitamin E had much less peroxidation of low density lipoprotein (LDL) and very low density lipoprotein (VLDL). The findings are meaningful in light of the increased cardiovascular disease experienced by diabetics, caused in part by oxidation of LDL cholesterol. Although diabetics do not have lower blood levels of vitamin E than normal individuals, it is believed that vitamin E will benefit this group through its antioxidant ability.
Forty four patients were divided into two groups, one receiving 250 iu vitamin E three times per day for one year, and the second group receiving a placebo for six months followed by 250 iu vitamin E three times per day for six months. Patients serum vitamin E levels, LDL and VLDL oxidation, and other values such as serum lipids, were monitored at the begininng at the study and every three months for one year. In the group receiving vitamin E, vitamin E levels rose after three months, but did not thereafter, showing that the transport capacity of vitamin E in serum was saturated by three months of supplementation. Similar results were seen in the second group after beginning their vitamin E supplementation. After the conclusion of the study, vitamin E levels returned to their initial values.
In both groups, the oxidation of LDL and VLDL cholesterol was significantly decreased after three months of vitamin E supplementation. In contrast, the second group did not experience this decrease during the period in which they received the placebo. The study's authors emphasize that vitamin E's antiperoxidative effect in this study was not due to correction of a deficiency, as its effect was not related to initial serum concentrations, nor was it related to a change in lipid levels.
The authors recommend that type 1 diabetics consider life-long supplementation with vitamin E.
November 16, 2000
New digital mammograms deliver less radiation
A new digital mammogram system has been developed in Sweden by the Sectra Company which delivers five times less radiation than the film processing methods currently employed in this country and elsewhere. The system captures the same quality of image and will be able to be processed by and studied with computers. There are currently other digital systems on the market, but they deliver ten times the amount of radiation as this system.
The technology was originated by researchers working in the field of particle physics in Geneva, Switzerland. Mamea Imaging, jointly owned by Sectra and researchers at Sweden's Royal Institute of Technology, developed a new type of sensor which reduces interference, so that at lower dose of radiation can be used.
Unlike film which must be processed, necessitating return visits for women for whom the image quality of the mammogram film was poor, the digital system enables images to be viewed immediately. The new system also offers the advantage of the ability to rapidly transfer images to the appropriate experts for interpretation, a plus in remote areas where medical experts are few.
Torbjorn Kronander, President of Sectra Imtec stated, "Women in almost all countries in the western world are afforded opportunities to participate in some form of mammography programs, with x-ray examinations as the world's most common test method. As a result, we see very significant potential in mammography screening."
Mammograms are currently the most commonly used method of clinically screening for breast cancer. Trials of the new digital system are planned in Sweden, in hopes of making the system available there in early 2002.
November 15, 2000
Colon cancer study questioned
In a press release this week, the American Institute for Cancer Research (AICR) stated that a recent study reported in the Journal of the National Cancer Institute which failed to demonstrate a protective effect of fruits and vegetables against colon cancer, may have wrongly interpreted the data. The study examined data from Harvard's Nurses Health Study and Health Professionals Follow up which surveyed 136,902 men and women. Ritva Butrum, Ph.D., Vice President for Research at AICR commented, "The data show that the subjects in these studies were consuming very few fruits and vegetables. Five to nine servings a day are recommended for protection against cancer, but most of the respondees consumed far less. In fact, fewer than 2% of those in the Nurses' cohort reported eating more than four servings of vegetables a day, while only 3% of those in the Health Professionals' cohort said they consumed more than three servings of vegetables a day. This indicates that the studies' variability - in this case, the statistical range between those respondees who consume the most and the least amount of fruits and vegetables - is small. Statistically speaking, when variability is low, the association with high or low consumption gets harder to see."
John Potter, MD, PhD, who is the head of the Cancer Prevention Research Program at Seattle's Fred Hutchinson Cancer Research Center added, "A greater issue is whether the analysis should actually control for total energy intake. Table 1 of the report makes it clear that those who consumed more fruits and vegetables consumed more food in general. A greater calorie consumption may have blunted the association one would expect to see with fruits and vegetables alone." Dr Potter concluded that for these and other reasons related to their methodology, these studies cannot make a definitive determination.
The AICR warned against discontinuing diets containing high amounts of fruits and vegetables because of this study, and note that many other studies have confirmed the protective benefit of this type of diet.
November 13, 2000
Blocking TGF-beta halts programmed neuron death
In an commentary published in the November issue of the journal Nature Neuroscience, authors Richard J Miller and Clifton W Ragsdale of the University of Chicago discuss the function of transforming growth factor-beta, or TGF-beta in the programmed death, or apoptosis, of nerve cells. TGF-beta is part of a superfamily of growth factors by the same name that are involved in many biological functions in all of the body's tissues, such as embryonic development, reproduction and wound healing.
In a study reported in the same in the same issue, chick embryos were immunized to neutralize the three forms of TGF-beta during the restricted period of embryonic development in which 50% of the neurons that have formed experience apoptosis. Neuron death was halted in all of the cells that were destined to die, which included central nervous system motorneurons and peripheral nervous system autonomic neurons. It is possible that TGF-beta works only on those neurons that will die, acting in a way that permits rather than instructs the cells to die. In other circumstances TGF-betas may enhance neuron survival. The researchers, led by Kerstin Krieglstein of the University of Saarland at Homburg, Germany conclude that TGF-beta could function as a molecular switch, which determines the life and death of neurons.
The authors of the commentary state that the findings may have important implication for diseases such as amyotrophic lateral sclerosis (ALS) which is characterized by the death of motorneurons and may involved programmed cell death. Spinal cord trauma may involve neuron death by apoptosis as well. The removal of TGF-betas may be able to reduce the death of neurons and prevent some of the disability associated with this and other conditions.
November 10, 2000
Femara more effective than Tamoxifen
The Chemotherapy Foundation Symposium in New York on November 9 was the site of the announcement of the findings from two new clinical studies that the drug Femara (letrozole) was more effective than tamoxifen in treating advanced breast cancer in postmenopausal women. Femara is an oral aromatase inhibitor currently approved by the FDA for the treatment of breast cancer in women for whom antiestrogen therapy such as Tamoxifen is ineffective. Aromatase is an enzyme that converts androgenic hormones to estrogen. One study which included over 900 postmenopausal women, the largest to evaluate hormone therapy for advanced breast cancer thus far, demonstrated that Femara was more effective than Tamoxifen as a first-line treatment, with 50% more patients experiencing a lack of progression of the disease after one year. Not only did the drug delay the progression of the disease, but it showed an increase in tumor response and time to treatment failure over Tamoxifen.
In another study, 324 breast cancer patients were given Tamoxifen or Femara before surgery to reduce the size of the tumor. Following four months of therapy, 55% of the women given Femara responded versus 36% of those on Tamoxifen. This meant that more women on Femara were able to undergo breast conserving surgery rather than mastectomy. After adjustment for other factors, the odds of being able to elect breast conserving surgery were increased by over 70% for the Femara group.
Matthew Ellis, MD, Ph.D, FRCP, Clinical Director, Duke Breast Cancer Program, Duke University Medical Center commented, "Femara is the first breast cancer treatment to demonstrate consistent superiority over tamoxifen in multiple efficacy endpoints. These study results will lead us to consider changing practice guidelines for advanced breast cancer and could pave the way for Femara as first-line therapy."
November 8, 2000
Stem cells from cadavers
At the annual meeting of the Society for Neuroscience held recently, it was revealed that brain stem cells can be taken from cadavers and still be viable up to more than twenty hours after death. Stem cells are immature cells that can grow into many different kinds of adult cells. Fred H Gage and colleagues at the Salk Institute in LaJolla, California, used brain tissue taken from the cadavers of children and young adults and was able to coax some of the cells to divide and differentiate into various nerve cells. He was also able to do the same with cells taken from the brain of a seventy-two year old man.
In an abstract presented at the conference, the Salk Institute team reported that under ideal conditions, tissue from cadavers could be cultured, frozen and later recultured for up to forty population doublings, and that cultures could be made from cryogenically preserved cells with minimal losses in cell recovery. Because the stem cells were still viable at such as great length of time after the death of the donors, the researchers believe that these cells may be uniquely resistant to postmortem ischemic and oxidative stress.
The research offers the possibility of solving the moral issue of using human fetal tissue to supply stem cells. Current research is also showing that stem cells can be derived from skin and bone marrow stem cells. The current challenge is being able to identify stem cells. Dr Gage stated, "We can't look in a dish at a mixed population (of cells) and say 'That is a stem cell'. Different people have different ideas."
November 6, 2000
High serum vitamin C levels mean lower stroke risk
In a study reported in the October, 2000 issue of the journal, Stroke, researchers in Japan followed a group of 880 men and 1241 women forty years of age and older for twenty years in what is called the Shibata study. The study participants had no history of stroke at the beginning of the study, and all incidences of stroke (categorized as cerebral infarction, hemorrhagic stroke, subarachnoid hemorrhage and undetermined) during the study period were documented. At the beginning of the study, the subjects' serum vitamin C levels were measured, and their intake of the vitamin C was determined through the use of food frequency questionnaires. Factors such as blood pressure and serum cholesterol were also measured.
The participants' serum vitamin C concentrations were inversely related to their incidence of stroke during the follow up period. This was true for both cerebral infarction (ischemic) and hemorrhagic stroke. Men and women experienced similar reductions in risk. Higher serum vitamin C levels were also, albeit more weakly, associated with lower blood pressure. The authors' question if vitamin C's protective benefit occurs because of its antioxidant function or its ability to lower blood pressure, an ability which has been reported in other studies and which is known to help prevent stroke. They point out that higher vitamin C levels lowered the risk of hemorrhagic stroke as well as ischemic stroke, and that hemorrhagic stroke would not be prevented by antioxidants in the manner that ischemic stroke would be by preventing oxidation of low density lipoprotein. However, only a portion of the associations between elevated serum vitamin C and low stroke risk could be explained by lowered blood pressure.
The study is significant in that it is the first study of its magnitude to measure the relationship between serum vitamin C and stroke risk. The authors state that mass screening for vitamin C concentration may be effective in decreasing the incidence of stroke.
November 1, 2000
New noninvasive test for colorectal cancers
The November issue of the journal Gastroenterology published a study which announced a new test for cancer of the colon or rectum that could lessen the need for colonoscopy, currently the most accurate screening method for this type of cancer. The new test, developed by researchers at EXACT Laboratories in Maynard, Massachusetts, detects selected genetic alterations of abnormal cells that are shed in the stool. It is scheduled to undergo an NCI-funded three year clinical trial beginning in January.
Researchers at the Mayo Clinic analyzed the stools of sixty-one individuals, twenty-two of which had been diagnosed with colon cancer and eleven of whom had rectal or colon polyps, which can be precancerous. Ninety-one percent of the colon and rectal cancers and 73% of the polyps were detected by the test. Among the twenty-eight people with normal colons in the study, the test did not report any false positives.
The test provides greater accuracy than the screening method of testing for blood in the stool, because of the advantage of being able to detect tumors and polyps that do not bleed.
Lead study author David A Ahlquist MD, commented, "Because of the high rate of accuracy, the DNA colorectal test could require fewer unnecessary colonoscopies to be performed. That will mean a savings in health care expenses because having a colonoscopy in this country currently costs anywhere from $1,000 to $2,500."
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