Synaptonemal complexes and XY behavior in two species of argentinian armadillos: Chaetophractus villosus and Dasypus hybridus (Xenarthra, Dasypodidae)

Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete se karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombi-nation nodule (RN) is located in the region of the se nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the se length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells , and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC

Frequency of X-chromatin in pregnant women during the second trimester of gestation

The frequency of X-chromatin was determined in pregnant women during the second trimester of gestation in order to establish possible correlations with the changes in steroid hormone levels occurring during this period and compare the curve with that for normal nonpregnant women. The mean frequency of X-chromatin in oral mucosa cells from a salivary suspension was 19.97% for the 24 patients studied, a statistically higher value than that obtained for nonpregnant women