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Biomedical subjects

M Mikkelsen

Publications and source records attributed to M Mikkelsen.

At least 73 records · Page 4Linked to original sources
PubMed1987

Spontaneous abortion following mid-trimester amniocentesis. Clinical significance of placental perforation and blood-stained amniotic fluid.

The clinical significance of placental perforation and blood-stained amniotic fluid was studied in a group of 7238 Danish women undergoing mid-trimester amniocentesis for prenatal diagnosis under ultrasound guidance. The risk of spontaneous abortion was significantly increased both in pregnancies where the placenta was perforated and in those with blood-stained amniotic fluid. The risk estimate nearly doubled after placental perforation and more than doubled with a bloody tap. It is concluded that for women at relatively low risk of a fetal genetic abnormality, the indication of the amniocentesis should be reconsidered if a placental perforation is unavoidable.

Abortion, Spontaneous↗
PubMed1986

Segregation analysis of balanced pericentric inversions in pedigree data.

The results of the recent European collaborative prenatal study suggested a segregation distortion of balanced pericentric inversions from carrier fathers but not carrier mothers (Boué & Gallano 1984). In an attempt to confirm these unexpected results, we examined 216 pedigrees with balanced pericentric inversions collected from three centers and from the literature. We were unable to detect any significant deviation from the expected 1:1 segregation of balanced pericentric inversions to normal karyotypes among the offspring of either carrier parent. To clarify the discrepancy between the studies, we reanalyzed the data from the prenatal study using all karyotyped individuals and, assuming conventional ascertainment rules, found a normal segregation pattern. We conclude that balanced pericentric inversions segregate normally in both males and females and that some retrospectively selected pedigrees were included as prospective in the prenatal study and this misclassification caused the apparent segregation distortion from carrier fathers.

Chromosome Inversion↗
PubMed1985

Linkage studies of X-linked mental retardation: high frequency of recombination in the telomeric region of the human X chromosome (fragile site/linkage/recombination/X chromosome).

One of the commonest forms of X-linked mental retardation is associated with a fragile site at Xq27 on the human X chromosome which can be visualised structurally after culturing cells in folate-deficient media. Unusually, the mutation can be transmitted through a phenotypically normal male. There is already some evidence that the gene loci for G6PD and factor IX are linked to this mental retardation locus. We have followed the inheritance of a DNA sequence 52A, in fragile site families that are also informative for factor IX. We demonstrate that these probes are localised at Xq27/Xq28-Xqter, close physically to the fragile site. We did not find close linkage between 52A, factor IX, and the fragile site in the families studied despite 52A and factor IX showing linkage in normal families. We discuss the importance of these data for the genetic mapping of this region of the human X chromosome and the implication for the use of these DNA probes for clinical diagnosis.

Animals↗
PubMed1985

Prenatal diagnosis of trisomy 20 mosaicism indicating esophageal and rectal origin.

Trisomy 20 mosaicism in cultured amniotic fluid cells has in only a few cases been confirmed in fetal tissue. This may lead to the assumption that the trisomic cells are of extra-fetal origin and interruption of the pregnancy is not advisable. Chromosome analysis of numerous fetal tissues indicated in two cases the presence of one or more trisomy 20 cell clones in rectum and esophagus, respectively. The clinical significance of trisomy 20 mosaicism in single organs remains to be elucidated. Besides the karyotype, genetic counselling should take into account all accessible information of the pregnancy, e.g. ultra-sound, serum alpha-fetoprotein values and obstetrical history.

Adult↗
PubMed1985

A folate sensitive heritable fragile site at 19p13.

A fragile site at 19p13 was found in the mother of a newborn girl with Downs syndrome. The fragile site was expressed in medium containing low folate and by addition of FdU, whereas high folate, thymidine and thymidine-analogues inhibited the expression. This fragile site may prove valuable for linkage studies on chromosome 19.

Adult↗
PubMed1984

Risk for chromosome abnormality at amniocentesis following a child with a non-inherited chromosome aberration. A European Collaborative Study on Prenatal Diagnoses 1981.

Based on 2890 prenatal diagnoses from 12 European countries the risk for a chromosomally abnormal fetus at amniocentesis after the birth of a child with a chromosome abnormality has been estimated to be 1.3 per cent when the mother's age is 34 years or less at amniocentesis and 1.8 per cent if the mother is older. This risk does not depend on paternal age, and it is independent of the type of the chromosome abnormality of the index child. Some geographical heterogeneities were detected. Therefore, the overall risk has to be considered as a rough estimate. The chromosome constitution of the abnormal fetus differed from that of the index patient in 21 of 41 cases. Several explanations for the higher risk have been discussed. If the index child had trisomy 18, 13 or a sex chromosome abnormality, the fetus tended to be a female. If the index child was a trisomy 21, the fetal sex ratio was normal.

Adult↗
PubMed1984

Advanced grandmaternal age on the mother's side--a risk of giving rise to trisomy 21.

The age distribution of maternal grandmothers of children with Down syndrome was compared with paternal grandparents of the same group and with grandparents of healthy children (controls). The significant advanced maternal grandmaternal age was found in cases of Down syndrome caused by first meiotic error in the maternal oogenesis. The advanced maternal grandmaternal age was found independent of maternal age. No differences were found between the ages of grandfathers of Down syndrome and of controls.

Adult↗