Mechanisms underlying mismatch repair deficiencies in normal cells.

Hereditary nonpolyposis colon cancer (HNPCC) is an autosomal dominantly inherited cancer predisposition which is linked to heterozygous mutations in mismatch repair genes. HNPCC tumour cells, in which the remaining wild-type copy of the mismatch repair gene is inactivated, display instability of microsatellite markers reflecting a defect in mismatch repair. Recently, patients carrying either one of two distinct germline mutations in the MLH1 and PMS2 genes were reported to accumulate somatic mutations of microsatellites in untransformed cells. One of the mechanisms that might account for this phenomenon was a dominant negative effect of the mutant allele. To evaluate this possibility, we examined a different family carrying one of the mutations (deletion of codon 618K in the MLH1 gene) which has been suspected to induce genetic instability in untransformed cells. No mutations in dinucleotide repeat markers were observed in a large number of lymphoblast clones derived from a carrier. Evidence for the deletion of the wild-type allele in two different tumours suggested that the inactivation of both gene copies was required for tumour initiation. These results indicate that the MLH1 618K deletion mutation alone does not necessarily cause marked mismatch repair deficiency in the presence of a wild-type allele.

[The diagnostic importance of different study methods in the recognition of renovascular hypertension at the prehospital stage]. / Diagnosticheskaia znachimost' razlichnykh metodov issledovaniia v raspoznavanii renovaskulianoi gipertenzii na dogospital'nom étape.

A comparative study of diagnostic potential of excretory intravenous urography, radionuclide renography and angionephroscintigraphy, renal ultrasonography and ultrasonic dopplerography of renal arteries in prehospital examination for renovascular hypertension made it possible to give preference to the above dopplerography. The latter is able to provide reliable data on renal artery stenosis and genesis of arterial hypertension.

[A case of prenatal diagnosis of beta-thalassemia by polymerase chain reaction]. / Sluchai prenatal'noi diagnostiki po povodu beta-talassemii na osnove tekhniki polimeraznoi tsepnoi reaktsii.

The prenatal diagnosis of beta-thalassemia in the Udin family, where the parents were the carriers of 2 bp deletion in the codon 8 (-AA) was undertaken using PCR. Five polymorphic restriction endonuclease sites in the beta-globin gene region were tested. They are: 2 HindIII sites in the gamma G and gamma A genes, 2 HincII sites located in the pseudogene and in its 3'-flanking region, and the AvaIII site in the second exon of the beta-globin gene. The heteroduplex analysis was also performed. Two HindIII polymorphic sites were informative and the HincII site in the pseudogene and the AvaII site in the beta-globin gene were partially informative. According to the results of the RFLP analysis, the embryo was heterozygous. The similar result was obtained by heteroduplex analysis.

[Molecular nature of beta-thalassemia in Tajikistan: a four base pair deletion in codons 41-42 of the beta-globin gene]. / Molekuliarnaia priroda beta-talassemii v Tadzhikistane: deletsiia chetyrekh par osnovanii v kodonakh 41-42 beta-globinobogo gena.

Thirty tajiks, whose relatives had beta-thalassemia traits (revealed in previous investigations by determination of the HbA-2 and HbF levels) were selected to screen beta-thalassemia mutations. DNA samples from each individual were subjected to the PCR (polymerase chain reaction) to amplify the 635 bp beta-globin gene fragment. One additional band was detected in three samples after the amplified fragment underwent electrophoresis in 2% agarose gel and the EtBr was stained, and two additional ones were revealed by 6% PAAGE and staining of the EtBr. All additional bands migrated more slowly than appropriate 635 bp fragment. It is supposed that additional bands are heteroduplexes formed from the wild type chains and mutated chains carrying a deletion or insertion. The 4 bp deletion of the 41-42 (-tctt) was detected after the direct sequencing of the amplified fragments. This mutation is common among Chinese but it was not revealed in the Middle Asia populations. The mutation can be easily screened using the PCR and electrophoresis in 2% agarose gel or PAAG of the amplified beta-globin gene fragments.

[Prenatal diagnosis as a method of prevention of congenital and hereditary diseases]. / Prenatal'naia diagnostika kak put' profilaktiki vrozhdennykh i nasledstvennykh zabolevanii.

The program of the prevention of congenital and hereditary diseases with the aid of prenatal diagnosis includes a complex of different methods: ultrasonography, invasive procedures made at different times of pregnancy, obstetrical monitoring, immunochemical blood tests, fetal cytogenetic analysis, pathological, anatomical, and syndromological studies in abortuses. Emphasis is laid on the use of the data on ultrasound screening of the pregnant and screening of the mother's blood for some factors that form a group of women at a greater genetic risk, who require prenatal diagnosis. The efficacy of the preventive measures can be enhanced with combined use of instrumental, obstetrical and laboratory research methods. The establishment of the correct and early diagnosis may, on the one hand, remove the tension and concern in the family; on the other hand, it may prevent bearing a sick child and provide the married couple with a based genetic counselling about progeny.

[Prenatal diagnosis of beta-thalassemia]. / Prenatal'naia diagnostika beta-talassemii.

Mass screening of married couples in the town of Baku has revealed a couple at risk of giving birth to a child with homozygotic beta-thalassemia. Prenatal diagnosis was carried out during week 23 of pregnancy by means of cordocentesis and biochemical analysis of globin chains, in vitro synthesized in fetal blood in the presence of labeled leucin. beta-thalassemia was detected in the fetus, similarly as in the child in this family. Abortion was induced on pregnancy week 25. Prenatal diagnosis is recommended in case of another pregnancy during the first trimester, involving analysis of the chorionic villi DNA.