An automatic system for detecting and counting sister chromatid exchanges in human chromosomes has been developed. Metaphase chromosomes from lymphocytes which had incorporated 5-bromodeoxyuridine for two replication cycles were treated with the dye 33258 Hoechst and photodegraded so that the sister chromatids exhibited differential Giemsa staining. A computer-controlled television-microscope system was used to acquire digitized metaphase spread images by direct scanning of microscope slides. Individual objects in the images were identified by a thresholding procedure. The probability that each object was a single, separate chromosome was estimated from size and shape measurements. An analysis of the spatial relationships of the dark-chromatid regions of each object yielded a set of possible exchange locations and estimated probabilities that such locations corresponded to sister chromatid exchanges. A normalized estimate of the sister chromatid exchange frequency was obtained by summing the joint probabilities that a location contained an exchange within a single, separate chromosome over the set of chromosomes from one or more cells and dividing by the expected value of the total chromosome area analyzed. Comparison with manual scoring of exchanges showed satisfactory agreement up to levels of approximately 30 sister chromatid exchanges/cell, or slightly more than twice control levels. The processing time for this automated sister chromatid exchange detection system was comparable to that of manual scoring.

Automatic measurement of sister chromatid exchange frequency.

(1983). Ionizing Radiation: Sources and Biological Effects. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 43, No. 5, pp. 585-586.

Ionizing Radiation: Sources and Biological Effects

Diabetes mellitus and birth defects

Mutation is one of the basic phenomena of life. Without mutation, the gradual development of life from inorganic material would have been impossible, and the evolution of living beings from the first groups of molecules in which a primitive, information-carrying unit cooperated with an energy gaining device59 up to the present diversity of highly refined living organisms could not have occurred. Therefore, one would expect that mutation, and especially “spontaneous” mutation, i.e., that occurring naturally and without any detectable external reasons, would attract the research activity of many biologists, especially geneticists. Surprisingly, however, this is not the case. In most experimental studies—for example, on microorganisms, Drosophila or the mouse—research on spontaneous mutation is being carried out more or less as a sideline of other work, and the results are widely scattered.

Spontaneous mutation in man.

Over 600 cases with a Y aneuploidy (other than non-mosaic 47,XYY) were reviewed for phenotype/karyotype correlations. Except for 93 prenatally diagnosed cases of mosaicism 45,X/46,XY (79 cases), 45,X/47,XYY (8 cases), and 45,X/46,XY/47,XYY (6 cases), all other cases were ascertained postnatally. Special emphasis was placed on structural abnormalities. This review includes 11 cases of 46,XYp-; 90 cases of 46,XYq- (52 cases non-mosaic; 38 cases 45,X mosaic); 34 cases of 46,X,r(Y) (9 cases non-mosaic and 25 cases 45,X mosaic); 8 cases of 46,X,i(Yp) (4 non-mosaic and 4 mosaic with 45,X); 12 cases of 46,X,i(Yq) (7 non-mosaic and 5 mosaic); 44 cases of 46,X,idic(Yq); 80 cases of 46,X, idic(Yp) (74 cases had breakpoints at Yq11 and 6 cases had breakpoints at Yq12); 130 cases of Y/autosome translocations (50 cases with a Y/A reciprocal translocation, 20 cases of Y/A translocation in 45,X males, 60 cases of Y/DP or Y/Gp translocations); 52 cases of Y/X translocations [47 cases with der(X); 4 cases with der(Y), and 1 case with 45,X with a der(X)], 7 cases of Y/Y translocations; 151 postnatally diagnosed cases of 45,X/46,XY; 14 postnatally diagnosed cases of 45,X/47,XYY; 18 cases of 45,X/46,XY/47,XYY; and 93 aforementioned prenatally diagnosed cases with a 45,X cell line. It is clear that in the absence of a 45,X cell line, the presence of an entire Yp or a region of it including SRY would lead to a male phenotype in an individual with a Y aneuploidy, whereas the lack of Yp invariably leads to a female phenotype with typical or atypical Ullrich-Turner syndrome (UTS). Once there is a 45,X cell line, regardless of whether there is Yp, Yq, or both Yp and Yq, or even a free Y chromosome in other cell line, there is an increased chance for that individual to be a phenotypic female with UTS manifestations or to have ambiguous external genitalia. This review once again shows a major difference in reported phenotypes between postnatally and prenatally diagnosed cases of 45,X/46,XY, 45,X/47,XYY, and 45,X/46,XY/47,XYY mosaicism. It appears that ascertainment bias can explain the fact that all known patients with postnatal diagnosis are phenotypically abnormal, while over 90% of prenatally diagnosed cases are reported to have a normal male phenotype. Further elucidation of major Y genes and their clinical significance can be expected in the rapidly expanding gene mapping projects. More, consequently better, phenotype/karyotype correlations can be anticipated at both the cytogenetic and the molecular level.

Phenotype/Karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

Skeletal anomalies of the lower extremities and lower spine have been observed in infants of diabetic mothers. Forty-three such cases have been collected from the literature. Maternal diabetes may play a role in the etiology of these malformations.

Syndrome of caudal regression in infants of diabetic mothers: observations of further cases.

A WIDE variety of chemical mutagen/carcinogens induce sister chromatid exchanges (SCE) in cultured Chinese hamster cells and can thus be studied at the chromosomal level1,2. Certain polycyclic hydrocarbons, such as benzo(a)-pyrene, 3-methylcholanthrene, dimethylbenzanthracene and others are important in the aetiology of human bronchial carcinoma3. The substances are not themselves carcinogenic, but are converted to carcinogenic epoxides by the enzyme arylhydrocarbonhydroxylase.4 Epoxides bind non-enzy-matically to DNA, unless they are converted enzymatically to inert water-soluble metabolites by epoxide hydratase5 and glutathione-S-transferase6. The carcinogenic effect of poly-cyclic hydrocarbons is closely connected with the regulation of the enzyme activities and genetic variability can thus be expected. It has been observed at the population level by family studies7 and at the cellular level by biochemical differences in the hydrocarbon-degrading enzyme system8. We have investigated the possible induction of sister chromatid exchanges by benzo(a)pyrene and show that the rate of SCE does not correlate with different rates of benzpyrene metabolism. We therefore suggest that genetic differences in benzpyrene metabolism are unrelated to genetic variation in the predisposition to bronchial carcinomas.

Benzpyrene induces sister chromatid exchanges in cultured human lymphocytes.

Rapid diagnosis of maple syrup urine disease (branched chain ketoaciduria) by micro-enzyme assay in leukocytes and fibroblasts.

Cocultivation of fibroblast cells from a male patient with Bloom syndrome (BS) and a female control reduced the rate of sister chromatid exchanges in the BS cells from a mean of 54 SCE per metaphase (range 42–65) to 41 (range 24–59). Medium used to culture control cells for 48 h also reduced the rate of SCE (from 40–65 to 33–54), whereas medium used for only 24h altered the SCE rate only slightly (to 39–61). Dialyzed medium concentrate with molecular cutoff at 15,000 did not alter the SCE rate. These initial studies suggest that normal cells produce an agent, presumably lacking in BS cells, that is capable of mitigating the chromosomal manifestation of the BS mutation (bl) in bl/bl cells.

Frequency of sister chromatid exchanges in Bloom syndrome fibroblasts reduced by cocultivation with normal cells.

Summary. This report describes the results from cultured lymphocytes studied at metaphase, anaphase, and interphase from an individual with a ring chromosome 4. A ring was present in 90.1°/o of metaphases. Special attention was directed towards the occurrence of derivative chromosomal structures, such as partially duplicated and triplicated rings, tricentric rings, chains of 3 interlocked rings, rod-shaped chromosomes, "pulverized" rings, and others. The clinical features of the individual (small stature and impaired mental development, hypoplastic thmnbs, ptosis palpebrae hypoplastic external male genitalia, abnormal dermatoglyphic pattern) did not conform to a specific phenotype. Zusammen/assung. ]Die Lymphocyten eines Patienten mit Ringchromosom 4 wurden in der Meta-, Ana- und Interphase beobachtet. 90,1~o der Metaphasen wiesen einen Ring auf. Besondere Aufmerksarnkeit wurde abnormen, aus dem Ring entstandenen Chromosomen zugewandt. Es fanden sich u. a. : partielle Doppel- und Dreifachringe, Ringe mit 3 Zentromeren, Ringe aus 3 miteinander verketteten Ringen, stabfSrmige Chromosomen und ,,pulverisierte" Ringe. Die Symptome des t?atienten (Minderwuehs, Schwachsinn, Hypoplasie der Daumen, Ptosis palpebrae, Hypoplasie des gugeren Genitale, abnorme Dermatoglyphen) waren zum gr6Bten Tell unspezifisch.

Derivative chromosomal structures from a ring chromosome 4

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