t(21q21q)/r[t(21q21q)] mosaic in two unrelated patients with mild stigmata of Down's syndrome

Two cases of t(21q21q)/r[t(21q21q)] mosaic in unrelated infants, 17 and 14 months old respectively are reported. The proportion of cells with the ring chromosome was 45% in the former, 80% in the latter. Both cases had mild manifestations of the Down's syndrome. The origin of this unusual mosaicism as well as the significance of the difference in the proportions of the ring chromosome in the two have been discussed.     

Ploidy reduction and genome segregation in cultured carrot cell lines. I. Prophase chromosome reduction

Cytological analysis of different carrot cell lines in culture has shown various cytogenetic anomalies generating new levels of ploidy and novel chromosome numbers. Polyploidy may be considered a reservoir of variability that can be released in the form of distinct new segregants of different ploidy. Mechanisms alternative to mitosis (reductional grouping, prophase chromosome reduction) operate from a polyploid state (possibly reached by means of endopolyploidy, endomitosis, nuclear fusion, or restitution nuclei) to generate new levels of ploidy and novel chromosome numbers necessary for selection to operate in vitro. The segregational phenomena require chromosome recognition in haploid set complements and abnormal behaviour of mitoses; the resulting chromosome variability suggests that chromosomes are arranged, in the resting nuclei, in an orderly and predictable manner.The knowledge of the molecular events governing these mechanisms, and how to control them, would be of great help for future applications of plant cell culture.     

Estimate of the intrafamilial correlation for serum creatine kinase and pyruvate kinase in females at risk for Duchenne and Becker muscular dystrophies.

In order to verify the possibility of nonrandom X-inactivation in females heterozygous for Duchenne (DMD) and Becker (BMD) muscular dystrophies, intrafamilial correlations and the heritabilities for serum creatine kinase (CK) and pyruvate kinase (PK) were estimated in a large sample of females belonging to families with affected patients. The results of the present investigation suggest that the apparent intrafamilial correlations for serum CK reported in previous studies in DMD families are not related with the presence of the DMD/BMD gene. Our data do not seem to support the hypothesis of a gene leading to a preferential inactivation of the X-chromosome in females at risk for the dystrophin gene.     

Scatter hoarding by kangaroo rats (Dipodomys merriami) and pilferage from their caches

We observed radio-implanted Merriam's kangaroo rats disposingof 10-g bonanzas of rolled oats in 48 trials in the field. Theprincipal determinant of the initial disposition of discoveredfood was apparently its distance from the day burrow: food foundwithin about 10m was mainly larder hoarded, whereas food encounteredfarther afield was usually dispersed immediately in shallowcaches. Cache sites were newly dug for the purpose and not reused;most caches were nearer the current day burrow than was thefood source, but a few were placed far from both the cacher'sday burrow and its habitual nocturnal range. An experiment withartificial caches indicated that security from discovery increaseswith spacing and with proximity to perennial shrubs. Nine kangaroorats cached dyed food, and fecal dye traces revealed extensivepilferage from five of them, by both conspecifics and otherrodent species. Limited evidence indicates that food encounterednearer home and initially larder hoarded was more secure frompilferage than food initially scattered, and yet kangaroo ratswere observed to scatter caches soon after initial larder hoarding.A kangaroo rat whose dyed stores escaped pilferage fed fromthem at intervals for at least 12 days. Even cachers who incurredpilferage made as much, or more, use of their caches as anythief, suggesting that scattering caches may be a defense againstcatastrophic losses.     

The source of ascitic fluid in experimental cirrhosis in the rat.

In order to disclose the source of ascitic fluid in liver cirrhosis, normal and cirrhotic rats were injected with fluorescein into the paracecal vein. The green fluorescence was then evaluated on the surface of the liver, the intestine and the peritoneum. Among healthy rats and in those with anascitic cirrhosis a very slight fluorescence was detected on the liver capsule whereas among rats with ascitic cirrhosis a distinct fluorescence was shown on the liver surface, the small intestine and the peritoneum. Therefore, the peritoneum is a source of ascitic fluid in cirrhosis of the rat.