Gene scene: earlier, eventually more specific, prenatal genetic diagnosis in realm of possibility

Article Abstract:

Preimplantation genetics - determining the genetic make-up of eggs or sperm before fertilization, or of a fertilized egg before its implantation into the uterus - is now a reality. A report from the first International Symposium on Preimplantation Genetics is presented. Researchers in London were recently able to selectively implant female embryos produced by in vitro fertilization (joining an egg and sperm under laboratory conditions); three of five women gave birth to unaffected daughters. The couples involved were at high risk for diseases associated with transmission of the X chromosome, and many had undergone repeated pregnancy terminations because of genetic diseases. Preimplantation genetic diagnosis prevents pregnancies with a diseased embryo and avoids the possible complications of prenatal diagnostic testing. It is only possible because of the development of the polymerase chain reaction (PCR), a method of amplifying embryonic DNA into millions of copies, which can then be evaluated using standard methods. The embryos that were implanted were culled when they had developed to the eight-cell stage. The method needs only one or two embryonic cells, which are evaluated to determine the embryo's sex. Since it only takes a few hours, embryos can be implanted the same day, while male embryos are frozen and stored. The manipulated embryos have been shown to develop in the same manner as control embryos; in fact, even if three of four cells are removed from a four-cell embryo, the remaining cell divides again up to four cells, and progresses normally. Screening for sex in this way is an early, admittedly primitive, method of screening for specific genetic diseases. However, suspect genes differ in their complexity and ease of manipulation, affecting the speed with which tests can be developed. The cystic fibrosis gene seems amenable to such approaches, since most affected genes carry the same mutation. Such approaches demonstrate the extent to which the processes of conception and implantation can now be controlled. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Evaluation, Prevention, Genetic screening, Genetic testing, Genetic disorders, Fertilization in vitro, Human, Human fertilization in vitro, Sex determination, Genetic, Sex determination (Genetics), Prenatal diagnosis

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New tools ready for Chlamydia diagnosis, treatment, but teens need education most

Article Abstract:

Two new developments may simplify the diagnosis and treatment of Chlamydia infections. Chlamydia trachomatis infection is the most common sexually transmitted disease in the US. It is estimated that 4 million new cases of Chlamydia will be reported in 1993. The new diagnostic test is a urine test that can detect Chlamydia DNA. This procedure, which is less painful and more accurate than using a urethral swab to collect samples, will make screening males easier. This is important not only for male health but also for the health of their female partners. Up to 75% of infected females have no symptoms, compared with 20% of males. Left undetected, Chlamydia can cause sterility in females. The new treatment is a single dose of the drug azithromycin, which will be easier for patients to take than the standard 1-week regimen of doxycycline. Two thirds of STDs occur in those under 25, and women under 21 have the greatest risk. Screening for Chlamydia may slow the epidemic, but education would go a long toward preventing this disease.

Sexual behavior, Health aspects, Sexually transmitted diseases, Diagnosis, Teenagers, Chlamydia infections, Teenage sexual behavior

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