By L. Vibald. University of Colorado, Colorado Springs. 2017.
Amniocentesis in some higher-order pregnan- increased to one in 65 purchase 60 mg alli overnight delivery, and discount 60 mg alli amex, at age 45, this risk is one in cies, such as triplets, has also been reported. The dye will temporarily a previous child with, a known genetic condition; abnor- tinge the fluid blue-green. A second needle is inserted mal prenatal screening results, such as ultrasound or a into the next amniotic sac with ultrasound guidance. If blood test; or one parent with a previously identified the fluid withdrawn is pale yellow, a sample from the structural chromosome rearrangement. In the case of may make it more likely for a couple to have a child with monoamniotic (in one amniotic sac) twins or triplets, the a genetic condition. Side effects Women who have had an amniocentesis often Indications for amniocentesis describe it as uncomfortable, involving some mild pres- Amniocentesis has been considered a standard of sure or pain as the needle is inserted. This medicine has no effect on the fetus, that amniocentesis be offered to all expectant mothers but may help the mother feel more comfortable during age 35 and older. An experienced physician can, on average, because advancing maternal age is associated with an perform amniocentesis in approximately one to two increasing risk of having a baby with a numerical chro- minutes. At age 35, this risk is approxi- Common complaints after amniocentesis include mately equivalent to the risk of pregnancy loss associated mild abdominal tenderness at the site of needle insertion with amniocentesis. These usually go away within one to A person normally has a total of 46 chromosomes two days. More serious complications are significantly in each cell of his or her body, with the exception of less common but include leakage of amniotic fluid, vagi- sperm or egg cells, which each have only 23. These complications get older, there is an increased risk of producing an egg are estimated to occur in fewer than 1% of pregnancies. This leads to an egg cell In some women, complications after amniocentesis may with 24 chromosomes rather than the normal 23. Aneuploidy results in a con- out amniocentesis, is approximately 2–3% in her second ceptus (product of conception) with either too much or trimester. This, in turn, leads to abnormal or technician, the risk for an amniocentesis-related preg- 74 GALE ENCYCLOPEDIA OF GENETIC DISORDERS KEY TERMS Amnion—Thin, tough membrane surrounding the Fetus—The term used to describe a developing embryo and containing the amniotic fluid. The term embryo is Anesthetic—Drug used to temporarily cause loss of used prior to the third month.
With form (blue dots) order 60mg alli with amex, whereas the other half cheap alli 60 mg on line, few exceptions, therapeutically used representing the uncharged amine drugs and their metabolites have much (orange dots), can leave the tubular lu- smaller molecular weights and can, men in accordance with the resulting therefore, undergo glomerular filtra- concentration gradient. Lowering or raising urinary pH by barrier for high-molecular-weight sub- half a pH unit would result in analogous stances. The relative density of this bar- changes for an amine having a pKa of rier depends on the electrical charge of 7. The same considerations hold for Apart from glomerular filtration acidic molecules, with the important (B), drugs present in blood may pass difference that alkalinization of the into urine by active secretion. Certain urine (increased pH) will promote the cations and anions are secreted by the deprotonization of -COOH groups and epithelium of the proximal tubules into thus impede reabsorption. Intentional the tubular fluid via special, energy- alteration in urinary pH can be used in consuming transport systems. These intoxications with proton-acceptor sub- transport systems have a limited capac- stances in order to hasten elimination of ity. During passage down the renal tu- bule, urinary volume shrinks more than 100-fold; accordingly, there is a corre- sponding concentration of filtered drug or drug metabolites (A). The resulting concentration gradient between urine and interstitial fluid is preserved in the case of drugs incapable of permeating the tubular epithelium. However, with lipophilic drugs the concentration gra- dient will favor reabsorption of the fil- tered molecules. In this case, reabsorp- tion is not based on an active process but results instead from passive diffu- sion. Accordingly, for protonated sub- stances, the extent of reabsorption is dependent upon urinary pH or the de- Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved. Drug Elimination 41 Blood Plasma- protein Endothelium Basal membrane Drug 180 L Glomerular Epithelium Primary filtration urine of drug Primary urine B. Tubular reabsorption Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved.