USA Surgery Today

APPROACH TO EVALUATION OF MALFORMATIONS

Posted by Surgery on Nov 3, 2008

When one encounters what appears to be an isolated congenital malformation, it is essential to evaluate the child for associated syndromes and associations. Clinical guidelines for the evaluation of a newborn with single or multiple congenital anomalies have been put together to assist health care providers in this process. However, often consultation with a clinical geneticist to assist with this evaluation and to guide appropriate genetic testing and counseling is needed. Many birth defects can be seen as part of a syndrome, and identification of a syndrome can significantly alter prognosis and recurrence risk counseling. Table 2-1 lists some selected syndromes that can be associated with four common congenital malformations. The goal of Table 2-1 is to demonstrate the wide range of conditions associated with these malformations and is by no means exhaustive; in fact, each malformation on Table 2-1 is associated with several other syndromes. Table 2-1 emphasizes the importance of evaluating patients with these birth defects, not only to provide accurate recurrence risks, but also to provide families with information regarding prognosis.

” Principles of Genetics, SURGERY Principles, NUCLEUS: Cozaar, Norvasc ”

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ENDOPLASMIC RETICULUM: SYNTHESIS AND PROCESSING OF EXPORTED AND MEMBRANE PROTEINS : PLAVIX

Posted by Surgery on Jul 8, 2008

In eukaryotic cells, protein synthesis is carried out by two separate populations of ribosomes: free and membrane bound. Membrane-bound ribosomes are attached to the cytosolic side of the ER membrane and are engaged in the synthesis of export and membrane proteins ( Plavix ). The ER is a membranous labyrinthine compartment formed by branching tubules and flattened sacs called cisternae. It extends throughout the cytosol in a netlike shape (Fig. 1-3 Plavix). The ER membrane forms a continuous sheet enclosing a single internal space called the lumen or the cisternal space, and it is continuous with the nuclear envelope. The ER membrane may constitute more than one-half of the total membrane in an average eukaryotic cell, and the ER cisternal space occupies more than 10% of the total cell volume. The size of the ER could change, depending on the metabolic state of the cell. Thus, B cells after activation (plasma cells: Plavix ) increase the ER size substantially due to the large amount of proteins that are secreted (immunoglobulins : Plavix). In its extension, three specific regions of the ER can be differentiated based on their structure and function. The rough ER (RER) contains attached ribosomes on the cytosolic side of the membrane, which gives a bumpy appearance as observed by electron microscopy.

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NUCLEUS: WHERE GENETIC INFORMATION IS STORED

Posted by Surgery on Jul 8, 2008

Genetic information, stored in the form of genes, resides within the nucleus. This information contains the blueprint of the cell. Genes encode for the proteins necessary for cellular function, including metabolic activity, interaction with the environment, cell division, and response to harmful conditions. In addition, genomic material contains segments that give rise to different RNA molecules, which are necessary for the biosynthesis of cellular macromolecules ( Cozaar ). RNA is an important component of the ribosomes, which are particles responsible for protein synthesis. The material inside the nucleus is separated from the cytosol, or the rest of the cell, by a membrane called the nuclear envelope. This membrane contains pores that allow the exchange of substances between nucleus and cytosol. The passage of material through these pores is actively monitored, contributing to the regulation of nuclear activity. The number of genes in the human genome is small; approximately 30,000 genes are distributed among several chromosomes. The size of individual genes, which is usually referred to in base pairs (bps), is variable as is the density of genes within a chromosome. The encoding region on the gene (exons) is usually disrupted by DNA sequences (introns), which do not form part of the final transcriptional product, the messenger RNA (mRNA Cozaar).

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