Brivanlou and Melton, 1992; Kessler and Melton, 1994; Schulte-Merker et al., 1994). At a later stage, signals Clare Hudson, Debbie Clements, Rosalind V. Friday, David Stott, and Hugh R. Woodland* originating in the dorsal organizer region (e.g., noggin, Department of Biological Sciences chordin, and nodal-related molecules) and local signalUniversity of Warwick ing molecules in the ventral and ...

We present the karyotypic characterization of 26 specimens of the side-necked turtle Hydromedusa tectifera collected in the upper Iguaçu River, Paraná state, Brazil. The turtles were cytogenetically analyzed using Giemsa staining and other banding techniques (C, G, Ag-NOR and CMA3) as well as fluorescence in situ hybridization (FISH) with a rDNA 18S probe. All the specimens showed a diploid num...

The aim of this study was to define the relation between silver stained nucleolar organizer regions (AgNORs) count and histological grade, and clinical stage in needle biopsy specimens of 65 prostatic adenocarcinomas. Histological grade was determined according to the modified Gleason system. AgNORs were evaluated by the counting method on routine histological sections stained with silver. Ther...

Banded chromosomes of a male marbled polecat, Vormela peregusna, from the Konya province in Turkey were studied. Conventional chromosome staining, Ag-NOR staining and C-banding were used to reveal the detailed morphology of the karyotype. The karyotype included eight metacentric, four submetacentric , five subtelocentric and one acrocentric autosomal pair (NFa = 70). The X chromosome was a medi...

The ovaries of newly metamorphosed Xenopus females contain oocytes in all stages of early meiotic prophase. In pachytene nuclei extrachromosomal nucleolar DNA appears in the form of a thin cap covering one side of the nucleus. During pachytene this cap of DNA enlarges to occupy half the nucleus. After pachytene the nucleus grows rapidly and the cap of DNA disperses into numerous tiny granules w...

We investigated the karyotype of 18 didelphid species captured at 13 localities in the Brazilian Amazon, after conventional staining, C-banding, Ag-NOR and fluorescent in situ hybridization (FISH) using the 18S rDNA probe. Variations were found in the X chromosome, heterochromatin distribution and the 18S rDNA sequence. The main variation observed was in the position of the centromere in the X ...

The term ‘organizer’ was coined by Hans Spemann and Hilde Mangold in 1924, based on the seminal observation that a small region of the amphibian gastrula, the dorsal lip, when transplanted to an ectopic location, had the ability to induce, or organize, the formation of a twinned embryo, recruiting neighboring cells from the host into a variety of cell differentiation pathways. The gastrula orga...

The Hairy and Enhancer-of-Split (HES) family of transcriptional repressors plays important roles in pattern formation during development throughout the animal kingdom. Generally, HES proteins repress the expression of genes specific for neighboring tissues to maintain the nature of cells expressing HES proteins, resulting in pattern formation. Xhairy2b, a Xenopus HES, establishes the prospectiv...

BACKGROUND Serous effusion smears reported as (suspicious for malignancy) pose problems in clinical management. Silver staining for argyrophilic nucleolar organizer regions (AgNOR) has proved useful in making a cytopathologic differential diagnosis between benign and malignant cells. Nucleolar organizer regions(NORs) are loops of DNA located in acrocentric chromosomes. These NORs are visualized...

The diagnosis of uterine smooth muscle neoplasms by light microscopy is difficult. Multiple classification schemes have been proposed based on mitotic rate, nuclear atypia, and the presence or absence of necrosis. None of these classification systems has been entirely successful. This study was undertaken to evaluate the use of selected immunohistochemical and histochemical markers in different...