Genetic and technical aspects of the HLA system and its possible role in human malignancy.
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First trimester fetal diagnosis was established in 100 pregnancies at risk by transabdominal chorionic villus sampling (TA-CVS). Forty-eight per cent of the women were 35 years or more at the time of sampling. Using the double needle technique, both the aspiration and the diagnostic success rate were 100 per cent. The mean amount of villi aspirated was 28.2 mg (10-50 mg). The mean needle time was 3 min. Vaginal spotting appeared in 2 per cent of the women. Four women had therapeutic abortion due to abnormal findings and one for social reasons. Three fetuses with normal karyotypes were lost. Excluding the therapeutic abortions, the fetal loss rate was 3.2 per cent. The fetal loss rate in the amniocentesis control group (n = 200) was 3.6 per cent. The cytogenetic diagnosis was carried out by the direct preparation technique as well as by chorion villus cultivation. All karyotypes were confirmed by lymphocyte cultures from umbilical cord blood or heel blood from the newborn or from aborted fetal tissue. Transabdominal CVS is deemed a safe and easy tool for achieving chorionic villi in the first trimester.
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Molecular techniques are now clinically useful for genetic diagnosis, and obstetrician-gynecologists should become familiar with their basic principles. Southern blot analysis and PCR are two of the most commonly used techniques to detect gene deletions and RFLPs. Analysis of RFLPs is perhaps the most widely applicable technique, but detailed family studies are required to determine whether an RFLP is informative.
Technical developments of genetic engineering have been revealed especially interesting in the human therapeutic field. Techniques for gene transfer have been improved to introduce synthetic sequences into the cellular genomes. Candidate cells and culture systems have been screened for their capacity to synthesise the proper recombinant molecules. In the nearest future, high biotechnologies should provide a great quantity of recombinant products, covering a high variety of diseases (clotting factors, cytokines, hormones, monoclonal antibodies, vaccines, thrombolytics). This tendency has been largely initiated, and is accompanied by the quick development of basic sciences such as glycobiology and molecular biology, together with the development of a specific regulatory environment. Besides, genetic engineering offers new therapeutic outlets: transgenic animals, genic therapy, antisense technology.
This article discusses the results of a study of the stand and attitudes of physicians from the Picardie, Nord-Pas-de-Calais region in France and the province of Quebec (Canada) regarding abortion following the diagnosis of a fetal anomaly by ultrasound, amniocentesis, or chorionic villus sampling. The study examined the degree of acceptability of abortion for several specific conditions as well as the physicians' perceptions of their role in the women's decision to abort. The study shows a consensus (over 75 per cent of the physicians surveyed) for aborting a fetus with trisomy 21. There is a similar consensus, except among Francophones in Quebec, for muscular dystrophy, cystic fibrosis, and Huntington disease. Conversely, there is no consensus (below 60 per cent) for several anomalies. In these cases, Quebec Anglophone physicians find abortion more acceptable than Quebec Francophone or French physicians. Concerning the role of the practitioners in the decision to abort, physicians in France tend to be much more directive than their overseas colleagues. Several hypotheses are suggested to explain the difference between the three groups surveyed.
Samples of peripheral blood mononuclear cells (PBMC) were collected during 1990-91 from seropositive healthy, male HIV-1 carriers visiting Taipei Venereal Disease Control Center, and a male AIDS patient admitted to a general hospital. The V3 and its flanking nucleotide (nt) sequences in their DNA were amplified by polymerase chain reaction (PCR) and compared with those of known HIV-1 prototypes. The nt sequences obtained from 21 individuals (e.g., TW92) clustered as Group A, which were highly homologous (95.6-99.5%) to that of HXB2 virus while those from 6 individuals (TW90, TW91, TW97, TW99, TW102 and TW104) were classified as Group B showing low similarities (73.2-84.2%) to those of HXB2 and moderate similarities (80.7-90.0%) to those of SC and Bangkok (BK) viruses. By comparison of their deduced amino acid sequences with those of consensus sequences for subtypes A-F as defined by Myers et al. (1993), both Groups A and B viruses (except TW102) together with those of HXB2, SC and BK viruses could be identified as members or variants of subtype B, and the TW102 virus as a member of subtype E viruses. Individuals with the Group A viruses included 4 homosexual and 17 heterosexual Taiwanese males, 2 of the latter having a history of i.v. drug abuse. Among individuals with Group B viruses, those with TW97, TW99, TW104 and TW91, who was an AIDS patient, were heterosexual Taiwanese males, whereas both TW90 and TW102 viruses were from individuals who were overseas heterosexual Chinese from Thailand, the former with a history of i.v. drug abuse and the latter without.
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Epidemiological data have demonstrated rapid growth of HIV-1 infections among injecting drug users (IDUs) in the Ukraine and Russia, during 1996. Here we describe the results of genetic analysis of isolates derived from 12 HIV-1-infected IDUs in different sites of Russia and the Ukraine. The blood samples were taken within a 1- to 2-month period after the first HIV-1-positive test. The results of the heteroduplex mobility assay as well as gag/env phylogenetic analysis reveal that all sequences belong to gag/env genetic subtype A. Moreover, interpatient genetic distances between the nucleotide sequences encompassing the C2-V3, the V4-V5, and p17-encoding regions within this group were low (the average means were 0.9, 1.3, and 0.4%, respectively). These data show a marked homogeneity of HIV-1, probably spreading during primary infection. It is possible that the current epidemic of subtype A HIV-1 among IDUs in the former Soviet Union is caused by a point source exposure.
Contraception and elective abortion are two of the controversial ethical issues with which social workers must deal. Since policies regarding these issues have recently been established by the courts, the author presents a review of the relevant decisions. The policy questions stemming from a related family planning issue, namely, selective abortion because of genetic defects, are also discussed.
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Mutational analysis of large genes with complex genomic structures plays an important role in medical genetics. Technical limitations associated with current mutation screening protocols have placed increased emphasis on the development of new technologies to simplify these procedures. High-density arrays of >90,000-oligonucleotide probes, 25 nucleotides in length, were designed to screen for all possible heterozygous germ-line mutations in the 9.17-kb coding region of the ATM gene. A strategy for rapidly developing multiexon PCR amplification protocols in DNA chip-based hybridization analysis was devised and implemented in preparing target for the 62 ATM coding exons. Improved algorithms for interpreting data from two-color experiments, where reference and test samples are cohybridized to the arrays, were developed. In a blinded study, 17 of 18 distinct heterozygous and 8 of 8 distinct homozygous sequence variants in the assayed region were detected accurately along with five false-positive calls while scanning >200 kb in 22 genomic DNA samples. Of eight heterozygous sequence changes found in more than one sample, six were detected in all cases. Five previously unreported sequence changes, not found by other mutational scanning methodologies on these same samples, were detected that led to either amino acid changes or premature truncation of the ATM protein. DNA chip-based assays should play a valuable role in high throughput sequence analysis of complex genes.
In a 1-year follow-up study, the effects of amniocentesis for genetic diagnosis upon 22 infants and their mothers were assessed. The infants were tested at 1 year of age on the Bayley Infant Scale of Mental and Motor Development. No deviations from normal mental or motor development were found. The mothers were interviewed at the same time, in order to better understand the emotional aspects of the experience. Women between ages 35-39 with no previously affected child tended to accept amniocentesis easily, as an appropriate part of parnatal care. Mothers with a previous defective child tended to have more painful emotional reactions, including higher anxiety over the test and more conflict about a possible abortion. They needed more intensive and extended counseling. We suggest that the issue of abortion is important, even if manageable by most women, and that a chance to discuss it may be significant.
The polymerase chain reaction is a powerful technique for amplifying a few copies of double-stranded genetic material to millions of copies in a few hours. The sensitivity and specificity of the polymerase chain reaction technique depend to some extent on the nucleotide sequences of the oligonucleotide primer pair used in the amplification. We report new oligonucleotide primers and probes which can be used for the amplification and detection of human immunodeficiency virus type 1 provirus sequences of not only structural but also regulatory genes. These primers are very sensitive and specific and can be used for the detection of African and North American strains of human immunodeficiency virus type 1.