ACCESSORY CHROMOSOMES IN ANIMALS, ESPECIALLY IN POLYCELIS TENUIS

The Origin and Continuous Replacement of Epidermal Cells in the Planarian Polycelis Tenuis (iijima).

R A Y L A N K E S T E R (1873) coined the term 'Triploblastic' and supposed that the gut, parenchyma and epidermis of Turbellaria corresponded to the germ layers of contemporary dogma. This idea is still current, though neither the origin, nor the maintenance of the epidermis of planarians has been investigated in detail. Most embryological studies have been restricted to early development, but...

B chromosomes and sex in animals.

Supernumerary (B) chromosomes are dispensable elements found in many eukaryote genomes in addition to standard (A) chromosomes. In many respects, B chromosomes resemble sex chromosomes, so that a common ancestry for them has frequently been suggested. For instance, B chromosomes in grasshoppers, and other insects, show a pycnotic cycle of condensation-decondensation during meiosis remarkably si...

Localization of 45S rDNA and telomeric sites on holocentric chromosomes of Rhynchospora tenuis Link (Cyperaceae)

Rhynchospora tenuis Link (Cyperaceae) is a weed widely distributed in Brazil that presents a small number of holocentric chromosomes (2n = 4) with some autopolyploid populations (2n = 8). The haploid number n = 2 is considered as a derivative of the base number x = 5. 45S rDNA probes and telomeric DNA were hybridized in both chromosome races of R. tenuis, looking for indications of chromosome f...

Scorpion Venom Pisoning in Experimental Animals

Morphine and Angiogenesis in Hypertensive Animals