Chromosome analysis of four species of marmosets (Callithrix jacchus, Tamarinus mystax, Tamarinus nigricollis, Cebuella pygmaea)

A composite idiogram is presented for four species of marmosets (<i>Callithricidae): Callithrix jacchus, Tamarinus mystax, Tamarinus nigricollis </i>and <i>Cebuella pygmaea</i>. Similarities and differences are indicated where they exist in the idiograms. Analysis of the chromosome complement of <i>C</i>. <i>pygmaea </i>indicates that centric fusion between two chromosomes may have occurred during the evolution of this species.

Investigation with tritiated thymidine of the relationship between the sex chromosomes, sex chromatin, and the drumstick in the cells of the female nine-banded armadillo, Dasypus novemcinctus

The functional analogies between the sex chromosomes, sex chromatin, and the drumstick in the cells of the female nine-banded armadillo (<i>Dasypus no&#965;emcinctus</i>) were investigated utilizing tritium labelled thymidine both <i>in vitro </i>and <i>in vivo</i>. Tissue culture studies demonstrated that one of the female X chromosomes is asynchronous and synthesizes DNA later than the other X and most of the autosomal complement. In interphase nuclei a peripheral focus of heavier labelling was found overlying the Barr body, indicating that the sex chromatin is formed by a great part or all of the late replicating X chromosome. Localized labelling was also observed over several drumsticks in studies performed <i>in vivo </i>supporting the view that a relationship exists between the drumstick and the asynchronous X chromosome.

Chromosomes of testicular teratomas

Eight testicular teratomas arising in proven males were examined for nuclear sex chromatin. Nuclear DNA content was measured in seven of the tumors and attempts were made to study the karyotype in seven and the chromosome late-replication pattern in five. Sex-chromatin-positive stromal, endothelial and epithelial cells possessing near-diploid or near-triploid DNA values were present in five of the eight tumors. Aneuploid DNA values of chromatin-negative regions corresponded with the aneuploid karyotype found in six tumors. The modal chromosome numbers ranged from 53 to 111 Not only was there marked karyotypic instability within each tumor but there was no overall similarity between different tumors. The terminal sequence of chromosome replication, successfully studied in two cases, one of which possessed sex-chromatin-positive cells, failed to reveal a late-replicating X-chromosome. Unfortunately, it was impossible to prove that the chromatin-positive teratoma did not contain a second X-chromosome: the failure to demonstrate an unequivocal XX sex chromosome constitution might be connected with special cultural requirements of the sex-chromatin-positive cells. However, other varieties of embryonic and undifferentiated cell tumors in males have been reported to display nuclear sex chromatin, and even certain normal testicular elements are sex-chromatin-positive. It is concluded that the existence of sex-chromatin-positive teratomas in males does not necessarily imply production from haploid gametes. The present observations do not rule out gametal origin. However, they provide more support for the idea that teratomas arise from diploid cells, possibly misplaced blastomere or primordial germ cells.

Absent Umbilical Artery: A Review of 113 Cases

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