Categories
Cardiovascular
Diagnostics
Endocrinology
Health Insurance
Medical Devices
Mental Health
Nutrition
Oncology
Public Health
Sexual Health
Popular Articles

Teasing Apart T Helper Cells
The cytokine IL-9 promotes a multiple sclerosis-like disease in mice, according to a new study by Nowak et al. published online in the Journal of Experimental Medicine. In a related Commentary, Richard Locksley discusses the molecular and genetic regulation of cytokine production by CD4+ T helper (Th) cells and the plasticity among different Th subsets. The Commentary was published online in the Journal of Experimental Medicine on Monday, July 27th.

Getting Obese Mice Moving And Curing Their Diabetes
Mice lacking the fat hormone leptin or the ability to respond to it become morbidly obese and severely diabetic - not to mention downright sluggish. Now, a new study in the June Cell Metabolism shows that blood sugar control in those animals can be completely restored by returning leptin sensitivity to a single class of neurons in the brain, which account for only a small fraction of those that normally carry the hormone receptors.
News of the day
Most, But Not All, Canadians With Chronic Conditions Get Clinically Recommended Tests
Most Canadians with chronic conditions have a regular place of care, but there are some reported gaps in the management of their conditions according to a new study released today by the Canadian Institute for Health Information (CIHI). The study, Experiences With Primary Health Care in Canada, measures access to and quality of care from a patient perspective across Canada"s 10 provinces. The study is based on the responses of more than 11,000 people age 18 and older to Statistics Canada"s 2008 Canadian Survey of Experiences With Primary Health Care, which was jointly funded by CIHI and the Health Council of Canada.
Medical Devices

Intestinal Cells Surprisingly Active In Pursuit Of Nutrition And Defense

Every cell lining the small intestine bristles with thousands of tightly packed microvilli that project into the gut lumen, forming a brush border that absorbs nutrients and protects the body from intestinal bacteria. In the June 29, 2009 issue of the Journal of Cell Biology, Matthew McConnell, Matthew Tyska, and colleagues now find that microvilli extend their functional reach even further using a molecular motor to send vesicles packed with gut enzymes out into the lumen to get a head start on breaking down their substrates. Microvilli have traditionally been viewed as passive scaffolds that increase the surface area of the gut wall. The apical plasma membrane tightly wraps around each protrusive bundle of actin, providing more space for nutrient processing and absorption. The motor protein myosin-1a (myo1a) maintains this structure by connecting the plasma membrane to the actin filaments. In 2007, Tyska and colleagues found that myo1a functions in isolated brush borders to actively move membrane along the length of the microvilli, like a "membrane escalator." To their surprise, at the top of these escalators - the tips of the microvilli - the membrane pinched off to form small vesicles that were released into the surrounding medium. According to Tyska, when they showed their data to gastroenterologists, they immediately asked "Why would brush borders do that? They"re wasting perfectly good apical membrane!" Tyska therefore wanted to see if vesicle shedding was a bona fide physiological function for microvilli. Sure enough, scanning electron micrographs of rat intestines showed protrusions at the tips of microvilli that looked similar to budding vesicles. And a look at the gut"s contents revealed vesicles enriched in the brush border enzyme intestinal alkaline phosphatase (IAP). The vesicles were packed with classical brush border membrane proteins such as aminopeptidases and sugar-processing enzymes, suggesting that the vesicles were derived from microvilli. The vesicles also contained several proteins such as annexin A13 that bend cell membranes and could form part of the vesicle budding machinery. One protein definitely involved in vesicle formation is myo1a. Myo1a knockout mice still produce lumenal vesicles but they are irregularly sized and no longer enriched in specific proteins like IAP. Tyska thinks that these knockout vesicles are actually chunks of microvillar membrane that are nonspecifically shed when myo1a isn"t present to keep them attached to the actin core. Returning to the gastroenterologists" question: Why would brush borders do that? McConnell et al. showed that the packaged enzymes were exposed on the vesicles" outer surface and were catalytically active. Releasing the enzymes in vesicles might increase their mixing with substrates in the gut"s contents. Tyska is particularly interested in IAP, which has recently been shown to detoxify the bacterial outer-membrane component lipopolysaccharide. Releasing IAP in lumenal vesicles could be an important defense mechanism against intestinal pathogens. McConnell, R.E., et al. 2009. J. Cell Biol. doi:10.1083/jcb.200902147. Rita Sullivan Rockefeller University Press


Add your comment:
Name:
Site address: http://
Your message:
Enter today\\\\'s date, 2 digits
(spam protection):

© Copyright 2009