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Biomedical subjects

R Youlton

Publications and source records attributed to R Youlton.

At least 37 records · Page 2Linked to original sources
PubMed1982

Pure XX gonadal dysgenesis in identical twins.

Pure gonadal dysgenesis has been described in several sibships. We report a pair of monozygous twins and their younger sister with secondary amenorrhea. They had no associated congenital anomalies. Plasma FSH levels were elevated and the ovarian biopsies showed absence of follicular structures. Their karyotypes were 46XX, further supporting the concept that his form of familial gonadal dysgenesis is an autosomal recessive defect.

Adult↗
PubMedDate not supplied

[Genetic study in twins].

During the period june 1987-January 1988, 35 consecutive pairs of twins born at two maternity hospitals in the northern area of Santiago were studied to search evidence of genetic or other factors which could eventually favour twinning. Sixteen of these pairs were considered to be monozygotic (MZ) after studying five blood group systems (ABO, Rh, MNSs, Duffy and Kidd) applying the method of Smith and Penrose. Maternal age was higher in dizygotic twins (DZ) than in the MZ group (average 30.1 yrs. v/s 26.8 yrs. respectively (p < 0.05). Family history of twinning was positive in 73% of the MZ and in 82% of the DZ twins. The Duffy and Kidd systems were not in Hardy-Weinberg equilibrium due to a deficit of heterozygotes in MZ as well as in DZ twins. There was a significant increase in MS and Ms haplotypes in both groups of twins respect to the Chilean general population (p = 0.01). These results suggest the presence of a genetic determinant that favors the production of twinning of DZ as well as MZ type. A larger number of cases will be required to test this hypothesis.

Blood Group Antigens↗
PubMedDate not supplied

[Clinical and cytogenetic analysis of 257 cases of Down's syndrome].

Among 257 patients with clinical diagnosis of Down's syndrome, 56.4% of male gender, in whom cytogenetic studies were performed, 14 (5.4%) had normal karyotypes and 243 (94.6%) had 21 trisomy. Of these last, 225 (92.6%) had free 21 trisomy, 10 (4.1%) showed mosaics, 8 (3.3%) had translocations. Average maternal age of this sample was significantly higher than that of patients attending the same maternity wards (32.14 vs. 24.85 years) and 41% of Down syndrome's patients came from mothers aged 36 years or more, even though only 9.7% of this country's deliveries proceed from women of that age group. As to seasonal occurrence, the proportions of births which happened in summer almost doubled that of winter (33.1% vs. 16.9%). The frequency of characteristic clinical signs of Down's syndrome was somewhat different than that described for patients from some other countries, for instance: epicanthus, short neck and widening of the space between 1st. and 2nd. toe were more frequent, while Brushfield's spots, depressed occiput, dental anomalies, heart malformations and fissured tongue seemed less frequent. The importance of cytogenetic studies for diagnosis and genetic counseling is stressed.

Chile↗