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Cytogenetic and molecular genetic findings in 91 patients with Turner syndrome are reported. In 87 patients, chromosome studies were carried out both in lymphocyte and fibroblast cultures. Mosaicism was demonstrated in 58 of these patients (66.7%), whereas only 18 (20.7%) were apparent non-mosaic 45,X, and 11 patients (12.6%) showed non-mosaic structural aberrations of the X chromosome. Among the mosaic cases 16 (18.4% of all patients) displayed a second cell line containing small marker chromosomes. The association of Y-specific chromosomal material with the presence of marker chromosomes was demonstrated in 6 out of 7 mixoploid fibroblast cell lines by polymerase chain reaction amplification and by Southern-blot analysis. The observation of ring formation and morphological variability in vivo and in vitro, and the continuous reduction in the percentage of cells containing marker chromosomes in longterm cultivation experiments indicated an increased instability of marker chromosomes. The findings suggest that in vivo selection of structurally altered sex chromosomes exists. Thus, the observation of apparent non-mosaic 45,X chromosomal complements in liveborn individuals with Turner syndrome does not contradict the hypothesis that some degree of mosaicism is necessary for survival in early pregnancy.

As various isoenzymes of gastric alcohol dehydrogenase exist and as the effect of sex and age on these enzymes is unknown, this study measured the activity of gastric alcohol dehydrogenase at high and low ethanol concentrations in endoscopic biopsy specimens from a total of 290 patients of various ages and from 10 patients with chronic alcoholism. Gastric alcohol dehydrogenase was also detected by immunohistological tests in biopsy specimens from 40 patients by the use of a polyclonal rabbit antibody against class I alcohol dehydrogenase. A significant correlation was found between the immunohistological reaction assessed by the intensity of the colour reaction in the biopsy specimen and the activity of alcohol dehydrogenase measured at 580 mM ethanol. While alcohol dehydrogenase activity measured at 16 mM ethanol was not significandy affected by age and sex, both factors influenced alcohol dehydrogenase activity measured at 580 mM ethanol. Young women below 50 years of age had significantly lower alcohol dehydrogenase activities in the gastric corpus and antrum when compared with age matched controls (SEM) (6.4 (0.7) v 8-8 (0.6) nmol/min/mg protein; p<0-001 and 6-0 (1-3) v 9.5 (1.3) nmol/min/mg protein; p<0001). Over 50 years ofage this sex difference was no longer detectable, as high Km gastric alcohol dehydrogenase activity decreases with age only in men and not in women. In addition, extremely low alcohol dehydrogenase activities have been found in gastric biopsy specimens from young male alcoholics (2-2 (0.5) nmol/min/mg protein), which returned to normal after two to three weeks of abstinence.The activity of alcohol dehydrogenase in the human stomach measured at 580 mM ethanol is decreased in young women, in elderly men, and in the subject with alcoholism. This decrease in alcohol dehydrogenase activity may contribute to the reduced first pass metabolism ofethanol associated with raised ethanol blood concentrations seen in these people. (Gut 1993; 34: 1433-1437 Recent studies in men '-3and

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