Tuesday, December 10, 2013
Tuesday, November 19, 2013
Wednesday, November 13, 2013
Friday, November 1, 2013
Tuesday, October 8, 2013
Friday, September 27, 2013
Tuesday, September 17, 2013
Thursday, August 29, 2013
One of the pivotal roles of the cell membrane in living cells is providing the medium through which individual cells communicate with their external environment. For complex organisms such as mammals this is especially critical in order for cells to successfully respond to all the chemical signals that are generated in order to maintain and sustain a state of homeostasis – the regulation of an organism’s internal environment to maintain constancy and stability – so vital for survival.
To fulfill this purpose there is a particular class of membrane-bound proteins referred to as G protein-coupled receptors (GPCRs) that modulate cellular responses to a whole host of stimuli. A sub-category of this class of proteins is represented by the melanocortin receptors (MCRs). Within this group there exists a subset of receptors tied to specific functions as the following table demonstrates –
Receptor Type Associated Function
MC1R Skin Pigmentation
MC2R Hypothalamic-Adrenal-Pituitary Axis – responsive to stress in the external environment MC3R, MC4R Energy Homeostasis
MC5R Exocrine Function
Previous studies have implicated MCR4 in connection with mammalian obesity. Furthermore, it has been shown that there are so-called accessory proteins that play an important role in the function of the MCRs that have been described above. One of these accessory proteins, MRAP2, is associated with MCR4. Given these data, MRAP2, produced in the mammalian brain, would make an excellent candidate for further study. Dr. Asai together with his colleagues genetically modified mice to produce an organism with a dysfunctional MRAP2 protein. These animals developed severe obesity at a young age.
Finally, a study of humans with severe early-onset obesity revealed four rare and possibly pathogenic genetically-derived modifications in MRAP2 further suggesting that this protein may be the causative link to this disease. These represent very important findings in regards to this kind of severe obesity in humans. This may prove to have therapeutic value in the future.
Monday, August 19, 2013
- The stomach is divided producing a small gastric pouch (GP) that can only accommodate a small amount of food.
- A portion of the small intestine is transected – made into two branches – and one arm of the transection is connected to the GP and is referred to as the Roux limb (RL)
- Both of these branches meet at the so-called “common limb” (CL) and all contents of the GP then proceed through the rest of the digestive tract.
As a result of these modifications, food entering the esophagus travels to the GP and then to the RL bypassing the remaining part of the stomach – the so-called “distal stomach” (DS) -, the duodenum and part of the jejunum – these areas represent the upper portion of the small intestine. The RL is thereby exposed to undigested nutrients. This change may be implicated in the positive effect that this procedure exerts on diabetes.
Thursday, August 8, 2013
Friday, July 26, 2013
Friday, July 19, 2013
- What are the mosquito’s natural defenses against this parasite?
- How does the P. falciparum successfully elude these defenses?
Thursday, July 4, 2013
Thursday, June 27, 2013
- Discovery of 27 de-novo genetic mutation events in 16 genes
- 59% of these mutations predicted to either shorten the protein gene products or disrupt the splicing that is required to yield functional protein products
- Recurrent disruptive mutations in six genes – CHD8, DYRK1A, GRIN2B, TBR1, PTEN AND TBL1XR1. Five of these genes are contained within the catenin-chromatin-remodeling network.
Monday, June 17, 2013
Wednesday, June 5, 2013
Tuesday, May 21, 2013
Friday, May 3, 2013
Tuesday, April 23, 2013
Friday, April 5, 2013
Tuesday, March 26, 2013
Friday, March 15, 2013
Thursday, February 28, 2013
Wednesday, February 13, 2013
According to this paradigm, a low-velocity impact of a planetary body (impactor) roughly the size of Mars could produce an iron-poor debris disk with sufficient total mass and energy in the form of angular momentum – a measure of the rotation of a body that is the product of its inertia and angular velocity - to produce an iron-poor Moon. In addition, this model also predicts that the debris disk would contain material primarily from the impactor's mantle. This data is where the inconsistency lies; for, the Earth and Moon, in fact, share many similarities in regards to composition, including the isotopes of oxygen, chromium and titanium. It is unlikely that any postulated impactor would share these similarities.
Dr. Robin M Canup from the Planetary Science Directorate at the Southwest Research Institute in Boulder, Colorado has proposed a solution to this apparent dilemma. Canup has postulated through the use of sophisticated and computer-assisted simulations that if a larger-sized impactor than the one proposed in the giant impact theory was involved, then the resulting collision with Earth would produce a disk with the same composition as the Earth's mantle. The actual size of the impactor used in these simulations was comparable in mass to the Earth.
This proposed scenario demonstrates just how chaotic and disruptive the environment of our solar system was during the early stages of its evolution. The cosmos is, in fact, ever-changing in its past, its present and for the foreseeable future.