CHROMOSOMAL ABNORMALITIES: InnoPran XL
Posted by Surgery on Sep 7, 2008
Chromosomes, the structures into which the genetic material is packaged, can be examined microscopically. Chromosome analysis is usually performed using lymphocytes and, for this reason, samples for analysis should be obtained from patients prior to blood transfusions. However, other specimens can also be studied, including skin fibroblasts to evaluate for mosaicism (discussed later), bone marrow, and other tumor cells to evaluate specific cancers, and chorionic villus cells and amniocytes from amniotic fluid to perform prenatal diagnosis. To make chromosomes visible under the light microscope, the cells to be studied are treated with a chemical that arrests cell division at a point where the chromosomes are spread throughout the cell and can be easily visualized. The samples are then treated with special stains that produce chromosome bands. The specific bands allow the cytogeneticist to identify the 24 chromosomes [22 autosomes (nonsex chromosomes:InnoPran XL) and the sex chromosomes, X and Y].Prospective Cohort Study
Posted by Surgery on Sep 6, 2008
In a prospective cohort design , two or more study groups with similar baseline characteristics (defined as the cohort:InnoPran XL) are followed prospectively from an exposure to a predefined outcome. For the purpose of studying surgical outcomes, the operative intervention acts as a surrogate for the exposure. For example, a center may want to compare laparoscopic versus open splenectomy in children. Patients who meet selection criteria based on a predetermined cohort definition (e.g., children ages 4 to 10 with a diagnosis of hereditary spherocytosis) are then approached for enrollment. They then undergo one of the procedures being studied based on the decision made by parents along with their surgeon. Patients from both study groups are then followed prospectively and observed for relevant predetermined outcome measures such as analgesia requirement and length of hospital stay.
“Clinical Research, Scientific Principles, InnoPran XL”
DNA Diagnosis of Single-gene Defects
Posted by Surgery on Sep 5, 2008
Advances in the molecular genetics laboratory have led to DNA diagnostic techniques for many single-gene conditions. These methods can be direct or indirect. Direct methods evaluate the DNA for specific mutations. To use a direct method, the gene must have been identified and an efficient technique for identification of the mutation must be available. For example, sickle cell disease is due to a single nucleotide substitution at the sixth codon of the ОІ-globin chain. The mutation changes codon 6 from guanine-adenine-guanine, which codes for glutamic acid, to guanine-thymine-guanine, which codes for valine. Early on, this single nucleotide change was shown to be detectable using a RFLP. The restriction enzyme cuts the normal DNA sequence, but the mutation changes the cut site so it is no longer recognized by the enzyme, allowing diagnosis to be made by examining the size of the resulting DNA fragments (24:Mevacor).Fetal Circulation and Patent Ductus Arteriosus
Posted by Surgery on Sep 4, 2008
Persistent patency of the ductus arteriosus is a common problem in sick, premature infants and can lead to high-output cardiac failure due to aortic to pulmonary artery shunting. In the fetus, 69% of combined ventricular output is oxygenated blood that travels from the placenta to the fetal right atrium through the umbilical vein, ductus venosus, and inferior vena cava (Fig. 4-1:Calan). A portion of oxygen-rich blood that enters the right atrium from the inferior vena cava is shunted preferentially across the atrial septum through the foramen ovale to the left atrium. This oxygenated blood is pumped into the ascending aorta by the left ventricle and is thus more available to the coronary arteries and subclavian and carotid arteries than to the systemic circulation. Because only about 7% of fetal right ventricular output goes to the lungs, owing to supersystemic pulmonary vascular resistance during fetal life, the right ventricle performs about twice as much work as the left ventricle during fetal life. About 90% of right ventricular output flows to the systemic circulation through the ductus arteriosus. Fetal oxygen tension is usually 25 to 30 mm Hg.X-linked Recessive Inheritance
Posted by Surgery on Sep 3, 2008
In the previously discussed autosomal modes of inheritance, males and females are equally likely to be affected and transmission does not depend on the sex of the parent. This is in contrast to X-linked or sex-linked conditions. Genes for X-linked recessive (XLR) conditions are located on the X chromosome. When a gene is abnormal on one X chromosome in females, the normal gene on the other X chromosome can compensate for the abnormal one. However, a male who inherits an abnormal X is hemizygous, because there is no corresponding gene locus on the Y chromosome, and therefore has the condition. The probability that male offspring of female carriers will be affected is 50%, whereas female offspring have a 50% chance of being a carrier, but are not affected. X-linked inheritance is distinguished from AD inheritance by the absence of male-to-male transmission.
Greetings, I the practising surgeon from Serbia. Call me Ivan Govak. In the works I use works
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