Showing papers on "Ring chromosome published in 1986"

Multifocal meningiomas in a patient with a constitutional ring chromosome 22.

Abstract: We report a patient with a constitutional ring chromosome 22, in whom multifocal meningiomas were confirmed at necropsy, and discuss the relationship between the constitutional chromosome change and tumourigenesis of meningiomas in this patient.

Ring chromosome 21 in healthy persons: different consequencies in females and in males

Abstract: A stable ring chromosome 21 was found in an azoospermic man with an otherwise normal phenotype. Meiotic studies in another known azoospermic male with r(21) had indicated that breakdown of spermatogenesis resulted from pairing failure of chromosome 21, followed by degenerative changes in the chromosomes, before the cells had completed the first meiotic division. While primary sterility was a constant feature in the three adult males, eight healthy females with r(21) were fertile. However, they were at risk for Down syndrome and spontaneous abortions.

Regional assignment of human liver-type 6-phosphofructokinase to chromosome 21q22.3 by using somatic cell hybrids and a monoclonal anti-L antibody.

Abstract: The three structural loci encoding human phosphofructokinase, a key regulatory enzyme of glycolysis, are located on separate chromosomes. The gene coding for the liver-type subunit PFKL has previously been assigned to chromosome 21. We have used a subunit- and human-specific monoclonal antibody to liver PFK to detect the expression of human PFKL in hamster x human hybrid cell lines. A cell line carrying an 8;21 translocation which contains all of chromosome 21 except the band 21q22.3 was negative for the expression of PFKL whereas cell lines carrying the reciprocal 8;21 translocation were positive. In addition, a cell line with a ring chromosome 21 containing a breakpoint which excluded the distal part of the q22.3 band was negative for expression of PFKL. These results indicate that human PFKL is located on chromosome 21q22.3.

Aniridia, congenital glaucoma, and hydrocephalus in a male infant with ring chromosome 6

Abstract: A premature infant with unilateral aniridia and congenital ectropion uveae, contralateral Rieger anomaly, bilateral congenital glaucoma, and hydrocephalus was found to have ring chromosome 6. The findings are consistent with multiple manifestations of a neural crest-derived maldevelopment of the anterior segment and central nervous system. Comparison with the 14 previously reported cases of ring chromosome 6 illustrates the phenotypic variability of this syndrome.

Spontaneous and 3-aminobenzamide-induced sister-chromatid exchange frequencies estimated by ring chromosome analysis.

Abstract: Ring chromosomes offer an opportunity to measure sister-chromatid exchange (SCE) frequencies without the use of an agent to differentiate sister chromatids: SCE frequencies can be determined from the number of dicentric rings formed in cells from a cell line carrying a monocentric ring chromosome. Ash is a pseudotetraploid Chinese hamster ovary cell line in which approximately 40% of metaphase cells have a large ring chromosome. We have used this cell line to investigate the spontaneous rate of SCE by determining the rate of dicentric ring formation and have compared this with the rate of loss of the ring chromosomes over time. In the absence of both [3H]thymidine and bromodeoxyuridine, the spontaneous rate of SCE in Ash cells was 0.12 SCEs/ring/cell cycle; this rate was increased by bromodeoxyuridine, by the polyfunctional alkylating agent mitomycin C, and by the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide. This indicates that spontaneous SCE occurs in this line and that not all 3-amino-benzamide-induced SCEs are dependent upon incorporated bromodeoxyuridine. Ring chromosomes were not lost over time as rapidly as predicted by the SCE frequencies observed. Non-disjunction of the dicentric ring, or anaphase bridge breakage followed by reunion to form one or two monocentric rings, are the most likely explanations for this discrepancy.

A case of female hemophilia with a 46,XXr karyotype studied with X-chromosome DNA probes.

Abstract: A case of female hemophilia with a 46,XXr/45,X karyotype and signs of Turner syndrome, has been followed for the past 10 years. One of her brothers also has hemophilia A. A study with polymorphic DNA probes located in the Xq27-qter region has enabled us to demonstrate that the ring chromosome is of paternal origin and that the factor VIII gene region is deleted. The hemizygous state allowed expression of the hemophilia A mutation, present on the morphologically normal X chromosome, inherited from her carrier mother.

Ring chromosome 18 in a mother and son.

Abstract: Inheritance of ring chromosomes is reported infrequently. We report on a mother and her son both with a ring 18 chromosome, and describe the associated manifestations. The son had microcephaly, ptosis, short stature, and mental retardation; the mother was mentally retarded and had a similar facial appearance.

Ring chromosome 11. A case report and review of the literature.

Abstract: A female infant with severe growth-weight retardation and with a ring chromosome 11, associated with trisomy X in 15% of metaphases, has been reported. A literature review of cases of r(11) shows that the clinical features of these patients, although showing different frequencies, are similar to those of the del(11q) syndrome. It has been suggested that the variability of the mental retardation in r(11) patients is attributable to the unstability of the ring and to the different break points in these two chromosomal rearrangements. The origin of the r(11) was also addressed by studying fragile sites of the parents at 11p15 and 11q25.

[Prenatal diagnosis of 3 cases of ring G chromosomes: one 21 and two 22, one of which was de novo].

Abstract: Three cases of ring G chromosome diagnosed by amniocentesis are reported. In two instances there was paternal transmission of a ring (one r21 and one r22) without clinical manifestation in the fathers, and the two babies resulting from these pregnancies were normal at birth. In the third case, in which a de novo ring 22 was observed in association with IUGR and oligoamnios, the fetus was aborted. The variable phenotypic effects of ring G chromosomes, as well as several aspects of genetic counseling are discussed.

Congenital ocular and other systemic abnormalities associated with ring-11 chromosome.

Abstract: The ocular and systemic abnormalities in a boy with ring chromosome 11 [46, XY/46, XY, r(11) (p 15.5 → q25] are described. The ocular anomalies consisted of bilateral hypermetropia, microcornea, anterior chamber cleavage syndrome with prominent Wolfflin nodes, and cartwheel configuration of the anterior iris leaf. The systemic changes consisted of skeletal, muscular and articular defects, obesity, cryptorchidism, and mild mental retardation.

Severe growth failure associated with atrophic intestinal mucosa and ring chromosome 15.

Abstract: . Ring chromosome 15 was detected in a boy with severe growth failure and no dysmorphic features who had previously been found to have an atrophic intestinal mucosa, a finding not observed in about 300 patients with ring autosome reported so far. Of the 137 metaphases examined, 8.1 % had secondary aneuploidy produced by the structural and behavioural instability of the ring. Ring derivatives could also be seen in lymphocytes after only one cycle in the culture, indicating that such cells are also generated in vivo. We observed an increased cell death rate in fibroblast culture by Trypan Blue exclusion. These results suggest that there is a continuous in vivo generation of cells with increased mortality resulting in both growth failure and atrophic intestinal mucosa in the patient. The atrophic intestinal mucosa might be a manifestation of ring instability.

Transmission of an 18 ring chromosome in two generations in subjects of normal phenotype

Abstract: We report the clinical and cytogenetic findings on three cases with ring chromosome 18. These patients are phenotypically apparently normal. The 18 ring chromosome was segregating in two generations. In the available literature, we found only one report of a r (18) transmission through generations, and none report of case without giving any phenotypic effect or mental retardation.

Ring chromosome 21 and SOD activity of blood cells.

Abstract: . A female infant was found to have an abnormal karyotype with mosaicism: 45,XX,-21/ 46,XX,r(21) (pll.2 q22.3). She showed a slightly decreased level of superoxide dismutase (SOD) activity in erythrocytes, polymorphonuclear and mononuclear leukocytes. The cupro-zinc SOD (SOD-1) activity of leukocytes was 70-80% of normal level, while their manganese SOD (SOD-2) activity was within the normal range. The relationship between the chromosomal aberration and the SOD activity is discussed in relation to the gene dosage effect.