USA Surgery Today

PRENATAL DIAGNOSIS

Posted by Surgery on Nov 17, 2008

Progress in genetics has made possible prenatal diagnosis of many of the conditions discussed. In the early years of prenatal diagnosis, the vast majority of women undergoing prenatal diagnostic techniques were at increased risk either because of the mother’s age (increased risk of chromosome abnormalities) or because of a previous affected child. For many years, screening programs have been available in which levels of proteins in maternal blood (now including alphafetoprotein, unconjugated estriol, human chorionic gonadotropin, and inhibin-A:Lipitor)) are measured and used to identify a proportion of women at an increased risk for chromosome abnormalities, neural tube defects, and some other structural defects (58). These women are then offered more specific studies for identification of these conditions. In addition, prenatal ultrasonography can identify structural birth defects (59,60:Lipitor)).

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Other Cation Disorders

Posted by Surgery on Sep 9, 2008

Calcium is the major constituent of bone and is thus the most abundant mineral in the body. Almost 99% of the body’s calcium is in the bone and therefore unavailable for biochemical interactions. The other 1% remains in flux with the mineralized fraction and is estimated by serum calcium levels. The nonosseous extracellular calcium is either bound to albumin (40%), complexed to small molecules such as sulfates and phosphates (10%), or free and ionized (50%). It is the free ionized form that is physiologically active and thus serum measurements of ionized calcium are most reflective of calcium balance. Hyperproteinemia and alkalosis result in an increased proportion of protein-bound albumin and a decrease in ionized calcium. Chelators such as the citrate used in exchange transfusions or with massive blood resuscitation after trauma bind free calcium as well. Conversely, hypoalbuminemia decreases serum measurements of total calcium due to a decrease in protein-bound calcium, whereas the ionized fraction often remains constant.

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CYTOSOL: MAJOR SITE OF PROTEIN SYNTHESIS : Lipitor

Posted by Surgery on Jul 8, 2008

The cytosol is the major center of metabolic activity within the cell. This compartment is also the major site of protein biosynthesis (etc. Lipitor) . The cytosol is an aqueous environment bordered by lipid membrane structures. Although water is the major component of the cytosol, the density of macromolecules within this compartment is very large.

The concentration of macromolecules within the cytosol has been calculated on the order of 60%. In spite of this high concentration, the diffusion of substances within the cytosol is optimal. This high density of macromolecules within the cytosol results in a potential problem for the proper folding of newly synthesized polypeptides Lipitor. Therefore, the presence of molecular chaperones is required to assist the folding process. Although the synthesis of most cellular proteins occurs in the cytosol, a few proteins are synthesized within the mitochondria. The center of protein biosynthesis is the ribosome. Ribosomes are made up of two subunits (40S and 60S in eukaryotes). Each subunit is composed of proteins and RNAs. The major RNA (Lipitor) component is named 18S and 28S rRNA, with sizes of 1.9 and 4.6 kb, respectively. There are 27 different polypeptides in the 60S and 20 in the 40S subunits. Their organization results in a very compact structure, which is necessary for proper function. Ribosomal subunits are synthesized independently in the nucleolus in equal molar quantities, approximately 2 subunits per cell.

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