Chromosome numbers, morphology, and nucleolus organizer region (NOR) locations are useful cytological characters for taxonomic and evolutionary studies. In this study, we provide the first cytogenetic analysis of Phyllomedusa bahiana and Phasmahyla spectabilis, and report new cytogenetic data on variation in NOR numbers and positions in Phyllomedusa rohdei and Phyllomedusa nordestina using conv...

STUDY OBJECTIVES To evaluate the usefulness of argyrophilic nucleolar organizer region (AgNOR) counting and flow cytometric DNA analysis in the differential diagnosis of thymoma and thymic carcinoma, as well as in the differences among various stages and histologic subtypes of these tumors. DESIGN AND INTERVENTIONS Paraffin-embedded blocks of 64 thymic epithelial tumors (20 noninvasive thymom...

Within the Orthopteran species, those of the suborder Ensifera have been rarely studied from the cytogenetic point of view, mainly due to the difficulties for taxonomic identification of its species. The Gryllidae is the second largest family of this suborder and possesses some genera, such as Anurogryllus, that occur only on the American continents. The aim of this work was to determine the ka...

We have developed a procedure for sequential silver staining and in situ hybridization to analyze the relationship between the amount of rDNA present in nucleolar organizer regions, as estimated by in situ hybridization, and their level of expression, as estimated by the silver signal. For simplicity we used cells from the insectivorous mole Talpa occidentalis, which have a single pair of nucle...

BACKGROUND The relationship between the population doubling time and the quantity of silver-stained nucleolar organizer region (AgNOR) interphase proteins was studied in cell culture at three different temperatures used to modulate the cell cycle duration. METHODS After MIB 1 and AgNOR combined staining, the quantity of AgNOR proteins was measured in cycling cells by image cytometry. RESULT...

Spemann's Organizer, located in the dorsal marginal zone of the amphibian gastrula, induces and differentiates dorsal axial structures characteristic of this and other vertebrates. To trace the cellular origins of the Xenopus Organizer, we labelled dorsal blastomeres of three of the four tiers (A, B and C) of the 32-cell embryo with green, red and blue fluorescent lineage tracers. A strong vege...

The paradoxical frog Pseudis tocantins is the only species in the Hylidae family with known heteromorphic Z and W sex chromosomes. The Z chromosome is metacentric and presents an interstitial nucleolar organizer region (NOR) on the long arm that is adjacent to a pericentromeric heterochromatic band. In contrast, the submetacentric W chromosome carries a pericentromeric NOR on the long arm, whic...

The Spemann organizer can be subdivided into head- and trunk-inducing tissues along the anteroposterior axis (Mangold, 1933. Naturwiisenschaften 43, 761-766; Spemann, 1931. Wilhelm Roux Arch. Entwicklungsmech. Org. 123, 389-517). Recent studies have suggested that head formation is brought about by repression of both Wnt and BMP signalling (Glinka et al., 1998. Nature 391, 357-362; Glinka et al...

Nucleolar organizer regions identified by means of an argyrophilic technique (AgNOR) were quantified by digital image analysis in 81 patients with squamous cell carcinoma of the lung. Survival rate was modeled as function of AgNOR expression by Cox regression models controlled for staging, histologic grade, age, and sex. Our results indicate that AgNOR expression has a significant prognostic ro...