August 19, 2007, 7:55 PM CT
Finding that 1-in-a-billion that could lead to disease
Errors in the genetic code can give rise to cancer and a host of other diseases, but finding these errors can be more difficult than looking for the proverbial needle in the haystack. Now, researchers at Johns Hopkins have uncovered how the tiny protein-machines in cells tasked to search for such potentially life-threatening genetic damage actually recognize DNA errors.
Appearing online next week in Nature, the Hopkins team describes how the UDG enzyme (for uracil DNA glycosylase) scrutinizes the shape of DNA building blocks by holding onto them and testing their fit into a specially sized pocket. The UDG pocket holds onto mistakes only the enzyme loses its grip on the right building blocks, which fall back in line with the rest of the DNA.
Locating damage in DNA is critical for a cells survival: So much can go wrong if damage goes unrepaired; cells cant tolerate any of this going on, says study author James Stivers, Ph.D., professor of pharmacology and molecular sciences at Hopkins. But the question is how these enzymes find the few mistakes among the billions of correct building blocks in DNA.
One typical error that occurs is to the DNA building block cytosine, being chemically converted to a similar-looking building block not normally found in DNA: uracil. Even water can cause DNA damage, says Stivers. Its not a fast reaction, but water does convert the occasional cytosine into an unwanted uracil.........
Posted by: Scott Read more Source
August 16, 2007, 9:40 PM CT
Cannabis May Alleviate Allergic Skin Disease
Administering a substance found in the cannabis plant can help the bodys natural protective system alleviate an allergic skin disease (allergic contact dermatitis), an international group of scientists from Gera number of, Israel, Italy, Switzerland and the U.S. has found.
Allergic contact dermatitis is caused by reaction to something that directly contacts the skin. A number of different substances (allergens) can cause allergic contact dermatitis. Commonly these substances cause no trouble for most people, but if the skin is sensitive or allergic to the substance, any exposure will produce a rash, which may become very severe. Allergic contact dermatitis affects about 5 percent of men and 11percent of women in industrialized countries and is one of the leading causes for occupational diseases.
An article describing the work of the international research group, led by Dr Andreas Zimmer from the University of Bonn, was published recently in the journal Science. The article deals with alleviating allergic skin disease through what is called the endocannabinoid system. Among the members of the group is Prof. Raphael Mechoulam of the Hebrew University of Jerusalem School of Pharmacy.
In earlier work, Prof.Mechoulams research group at the Hebrew University isolated two naturally occurring cannabinoid (cannabis-like) components one from the brain, named anandamide (from the word ananda, meaning supreme joy in Sanskrit), and another from the intestines named 2-AG. These two cannabinoids, plus their receptors and various enzymes that are involved in the cannnabinoids syntheses and degradations, comprise the endocannabinoid system. These materials have similar effects to those of the active components in hashish and marijuana, produced from the cannabis plant.........
Posted by: JoAnn Read more Source
August 16, 2007, 9:32 PM CT
Are too many people 'depressed?'
Are too a number of people now diagnosed as having depression? Two experts give their views in this weeks BMJ.
Professor Gordon Parker, a psychiatry expert from Australia says the current threshold for what is considered to be clinical depression is too low. He fears it could lead to a diagnosis of depression becoming less credible.
It is, he says, normal to be depressed and points to his own cohort study which followed 242 teachers. Fifteen years into the study, 79% of respondents had already met the symptom and duration criteria for major, minor or sub-syndromal depression.
He blames the over-diagnosis of clinical depression on a change in its categorisation, introduced in 1980. This saw the condition split into major and minor disorders. He says the simplicity and gravitas of major depression gave it cachet with clinicians while its descriptive profile set a low threshold.
Criterion A mandatory a person to be in a dysphoric mood for two weeks which included feeling down in the dumps. Criterion B involved some level of appetite change, sleep disturbance, drop in libido and fatigue. This model was then extended to include what he describes as a seeming subliminal condition sub-syndromal depression.
He argues this categorisation means we have been reduced to the absurd. He says we risk medicalising normal human distress and viewing any expression of depression as necessary of therapy. He says:........
Posted by: JoAnn Read more Source
August 16, 2007, 9:24 PM CT
Umbilical cord clamping should be delayed
Clamping and cutting of the umbilical cord should be delayed for three minutes after birth, especially for pre-term infants, suggests a senior doctor in this weeks BMJ.
Early clamping and cutting of the umbilical cord is widely practised as part of the management of labour, but recent studies suggest that it may be harmful to the baby. The rate of early cord clamping varies widely in Europe, from 17% of units in Denmark to 90% in France.
So Dr Andrew Weeks, a senior lecturer in obstetrics at the University of Liverpool, looked at the evidence behind cord clamping.
For the mother, trials show that early cord clamping has no ill effects, he writes. But what about the baby".
At birth, he says, the umbilical cord sends oxygen-rich blood to the lungs until breathing establishes. So as long as the cord is unclamped, the average transfusion to the newborn is equivalent to 21% of the neonates final blood volume and three quarters of the transfusion occurs in the first minute after birth.
For babies born at term, the main effect of this large autotransfusion is to increase their iron status. This may be lifesaving in areas where anaemia is endemic.
In the developed world, however, there have been concerns that it could increase the risk of polycythaemia and hyperbilirubinaemia (abnormally high levels of red blood cells and bile pigments in the bloodstream, often leading to jaundice). But trials show this is not the case.........
Posted by: Emily Read more Source
August 16, 2007, 8:59 PM CT
Whiplash may produce delayed jaw pain
One in three people exposed to whiplash trauma is at risk of developing delayed TMJ symptoms that may require therapy, as per research reported in the recent issue of The Journal of the American Dental Association.
Scientists at Ume University, Sweden, studied short- and long-term temporomandibular joint (TMJ) pain and dysfunction in 60 patients in hospital emergency rooms directly after they were involved in a rear-end car collision and reviewed them again one year later.
As per the study, the occurence rate of new symptoms of TMJ pain, dysfunction or both between the initial examination and follow-up was five times higher in subjects than in uninjured control subjects. In the year between the two examinations, 7 percent of control subjects developed symptoms in the TMJ versus 34 percent of study subjects.
As per the American Dental Association, the TM joint is one of the most complex joints in the body. Located on each side of the head, these joints work together and can make a number of different movements, including a combination of rotating and translocational (gliding) action, used when chewing and speaking. Any problem that prevents this system of muscles, ligaments, discs and bones from working together properly may result in a painful TMJ disorder.........
Posted by: Janet Read more Source
August 16, 2007, 8:56 PM CT
More Successful Bone Implants
High-magnification scanning electron microscopy shows (center of micrograph) the leg of an osteoblast (bone precursor), called a cytoplasmic extension, attaching to nano-sized hydroxyapatite crystals, similar to those in natural bone, that make up a CPC implant.
Scientists from the American Dental Association Foundation (ADAF) and the National Institute of Standards and Technology (NIST) have developed a new method for layering two kinds of biomaterials into one strong, yet porous unit that may lead to improved reconstruction or repair of bones.
Currently, calcium phosphate cements (CPCs)-water-based pastes of powdered calcium and a phosphate compound that form hydroxyapatite, a material found in natural bone-are used for reconstructing or repairing skeletal defects, but only in bones that are not load-bearing (such as those in the face and skull). Macropores built into the CPCs make it easier for new bone cells to infuse and, eventually, solidify the implant. Until this happens, however, the macropores leave the implant brittle and susceptible to failure.
In the September 2007 issue of Biomaterials,* Hockin Xu and his colleagues describe a unique approach for providing the strength needed to help an implant better survive its early stages. First, a macroporous CPC paste is placed into the area needing reconstruction or repair. Then, a strong, fiber-reinforced CPC paste is layered onto the first CPC to support the new implant. Once new bone has grown into the macroporous layer and increased its strength, the absorbable fibers in the strong layer dissolve and create additional macroporous channels that promote even more bone tissue ingrowth. This method mimics the natural bone structure in which a strong layer, called cortical bone, covers and strengthens a weaker, macroporous layer (spongy bone).........
Posted by: Mark Read more Source
August 15, 2007, 9:34 PM CT
Fat still on the children's menu
Parents should think twice before offering a low-fat menu to youngsters, despite concerns over obesity. Children burn more body fat than adults for each calorie spent, as per research in the online open access publication, Nutrition Journal, evidence that fat can be included as part of a childs healthy and balanced diet.
A US team led by John Kostyak from The Pennsylvania State University used calorimetry to measure whole body fat oxidation in 10 children (aged 6-10) and 10 adults. All had a body mass index (BMI) within the healthy, middle range. Kostyak's team checked subjects cardiovascular fitness and body fat, and all were given the same typical American diet for three days previous to testing (eventhough adults had larger portions). Test subjects spent nine hours on three separate days at a low physical activity level, watching movies or reading, in either a room calorimeter or under a hood system, which quantify oxygen and carbon dioxide gas levels. The authors also measured the total amount of nitrogen in the subjects urine, and used these measurements to calculate how much fat they oxidised.
Eventhough the absolute amount of fat burned in a day did not differ greatly between children and adults, children burned considerably more fat relative to the amount of energy they used. In an attempt to determine the contribution of fat oxidation to daily calorie expenditure, the scientists calculated the grams of fat oxidized per kcal of energy expenditure. This value was higher in children (0.047 0.01 g/kcal) in comparison to adults (0.032 0.01, p<0.02). Women and girls used fat at a higher rate than men and boys of a comparable age.........
Posted by: JoAnn Read more Source
August 15, 2007, 9:23 PM CT
Dominant cholesterol-metabolism challenged
Aminophospholipid translocase concentrates the phospholipid PS on the inside of the cell.
team of scientists investigating cholesterol and lipid transport haccording toformed experiments that cast serious doubt on the dominant hypothesis of how the body rids its cells of "bad" cholesterol (LDL) and increases "good" cholesterol (HDL). Cholesterol metabolism is an area of intense inquiry because high levels of LDL cholesterol or total cholesterol put about half of all Americans at significant risk of heart disease.
The team was led by Robert A. Schlegel, Professor of Biochemistry and Molecular Biology at Penn State University, and Patrick Williamson, the Edward S. Harkness Professor of Biology at Amherst College. The paper by Schlegel, Williamson, and their colleagues will be published on Wednesday, 15 August 2007, in the on-line journal PLoS One.
A protein called ABCA1 is critical for producing "good" cholesterol: patients who lack the gene for this protein produce no HDL, and as a result, suffer from heart attacks at an early age. An important question is what ABCA1 does that is so important for producing HDL.
The most popular hypothesis was put forth in 2000 by Giovanna Chimini, Group Leader of a laboratory in the Centre d'Immunologie Marseille-Luminy in France, and his colleagues. They suggested that the ABCA1 enzyme plays a major role in the transfer of a phospholipid called phosphatidylserine (PS) from the inside of the cell -- where it is normally concentrated -- across the cell membrane to the outer surface of the cell. This is a crucial first step in the mechanism by which excess lipids and cholesterol are eliminated from the body. Under normal conditions, there is a second important step. After the PS is expressed on the cell surface, the phospholipids and excess cholesterol can be loaded onto a circulating protein, apoA1, to generate an HDL cholesterol particle. HDL cholesterol carries the lipids through the blood stream to the liver, where they are dumped into the intestine for excretion or destruction.........
Posted by: Daniel Read more Source
August 15, 2007, 8:54 PM CT
Toddlers are capable of introspection
Preschoolers are more introspective than we give them credit for, as per new research by Simona Ghetti, assistant professor of psychology at UC Davis.
Ghetti and her co-investigator, Kristen Lyons, a graduate student in psychology at UC Davis, will present their findings Friday morning, Aug. 17, at the annual meeting of the American Psychological Association in San Francisco.
Researchers have demonstrated that dolphins, monkeys and even rats can engage in some form of "metacognition," or an awareness of their own thought processes. But developmental psychology experts have assumed that human children do not develop this capability before about age 5.
Lyons and Ghetti have toppled that assumption by teaching 3- and 4-year-olds to communicate their awareness of their thought processes using pictures rather than words.
"We've shown that even very young children can think about their thinking," Ghetti said. "The reason we haven't appreciated it before now is that the studies that have been used to test for it have been too verbally demanding".
The UC Davis scientists devised a novel method to investigate metacognition in early childhood. They taught their preschool subjects to point to a photo of a confident-looking face when they felt confident they had the right answer to a question, and to a photo of a doubtful-looking child when they were not confident they had the right answer.........
Posted by: JoAnn Read more Source
August 15, 2007, 8:36 PM CT
Obesity, lack of exercise and pancreatic cancer
Obesity and aversion to exercise have become hallmarks of modern society and a new study suggests that a blood protein associated with these lifestyle factors may be an indicator for an increased risk of developing pancreas cancer. Scientists from the Dana Farber Cancer Institute report their findings in the August 15 issue of Cancer Research, a journal of the American Association for Cancer Research.
In a study of 144 patients with pancreas cancer and 429 people without the disease, a subset of patients with low blood levels of a protein called IGFBP-1 were at approximately twice the risk of developing pancreas cancer. Low blood levels of this protein have previously been associated with excess weight and lack of physical activity. Their data originated from tens of thousands of men and women enrolled in four large-scale cohort studies the Health Professionals Follow-Up Study, the Nurses Health Study, the Physicians Health Study and the Womens Health Initiative Observational Study all of which followed the health of participants over numerous years.
The prognosis for a number of patients with pancreas cancer remains poor, so it is vitally important that we indentify and better understand risk factors for the disease, especially risk factors that are modifiable said lead study author, Brian M. Wolpin, M.D., attending doctor at Dana Farber Cancer Institute. In addition to cigarette smoking, exercise and weight control appear to be important modifiable risk factors for this difficult disease.........
Posted by: Sue Read more Source