Search results for "nucleolus"
showing 10 items of 53 documents
Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism
1996
A consistent diploid number of 2n = 36 was determined for the sea urchinParacentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid numbern = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of einbryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five m…
Chromosomal nucleolar organizer region (NOR) phenotypes in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae)
1995
Chromosomal nucleolar organizer region (NOR) phenotypes have been characterized in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae), namely O. notoglandulata, O. sp. macrovifera, O. sp. labronica pacifica, O. labronica labronica, O. puerilis puerilis, O. diadema, O. sp. robusta, O. gracills and O. hartmanni. Irrespective of chromosome number and morphology, Ag positive regions were terminally located in all but one species, O. diadema, where the NORs were pericentromerical in a metacentric pair. The presence of a single chromosome pair bearing NOR in invertebrates is considered an ancestral trait. According to this assumption, O. sp. robusta, O. dialema, and perhaps O. p. p…
Cytogenetics in the sacoglossan Oxynoe olivacea (Mollusca: Opisthobranchia): karyotype, chromosome banding and fluorescent in situ hybridization
2000
Developing embryos and sexually mature follicles of the male portion of ovotestis proved to be a suitable material as a source of cleaving cells for advanced cytological investigations on the sacoglossan species Oxynoe olivacea Rafinesque, 1819 (Mollusca: Opisthobranchia). O. olivacea has a diploid chromosomal number of 30 made up of 15 pairs of which six are metacentric/submetacentric (M/SM), four subtelocentric (ST) and five on the borderline between SM and ST. Correspondingly, 15 bivalents occur in spermatocytes at Metaphase I. Constitutive heterochromatin is scarce and restricted to small C-bands seen in five pachytene bivalents. The use of combined silver staining and fluorescent in si…
Ag-NOR and C-banding analysis of spermatocyte chromosomes ofClavelina lepadiformis(Ascidiacea, Aplousobranchiata)
1991
SUMMARYChromosome number n = 9 and 2n = 18 for Clavelina lepadiformis (Ascidiacea, Aplousobranchiata) from the Gulf of Palermo have been determined. Silver staining analysis of testicular cells reveals that within-individual variability in NOR banding patterns is present. Using the C-banding procedure, a very impressive heterochromatin amount seems to characterize the chromosome set of this species.
Brief communication. Karyotype analysis, banding, and fluorescent in situ hybridization in the scarab beetle Gymnopleurus sturmi McLeay (Coleoptera S…
2000
Conventional staining, differential banding, and in situ hybridization with both ribosomal and telomeric probes to mitotic chromosomes of Gymnopleurus sturmi (Scarabaeoidea : Scarabaeidae) are described. The karyotype is distinguished by a pericentric inversion polymorphism in chromosome 3, which is either acrocentric or subtelocentric. Silver staining (Ag-NOR) and chromomycin A3 (CMA3), failed to study the detection of nucleolar organizer regions (NORs), due to the extensive silver and CMA3 stainability of all GC-rich heterochromatin. Fluorescent in situ hybridization (FISH) using a Paracentrotus lividus (Echinodermata) rDNA probe mapped the ribosomal RNA genes (rDNA). FISH with the all-hu…
Karyotype analysis, nucleolar organizer regions(NORs), and C-banding pattern of Dicentrarchus iabrax(L.) and Dicentrarchus punctatus(Block, 1792)(Pis…
1990
Chromosomes of Dicentrarchus labrax and Dicentrarchus punctatus collected from the Gulf of Palermo are examined from kidney cells. The diploid chromosome number in both species is 2n=48. Ag-NOR and C-banding analyses revealed the presence of structural chromosomal polymorphism involving pair 1.A comparative analysis among the Giemsa, NOR- and C-banded karyotypes suggests that a close phylogenetic relationship between D. labrax and D. punctatus occurs. There are evidences for a conservative evolutionary trend in this genus.
Spermatocyte chromosome banding studies inBuccinulum corneum (Prosobranchia: Neogastropoda): Variation in silver-NOR banding pattern
1990
Diploid number (2n=72), and haploid number (n=36) forBuccinulum corneum (L. 1758) collected from the Gulf of Palermo in December 1987 were determined. A simple method to obtain nucleolar organizer regions (NOR), and constitutive heterochromatin regions (C-bands) of chromosomes ofB. corneum is described. Analyses of silver-stained chromosome preparations ofB. corneum suggest that a within-individual variability in NOR-banding pattern is present in each of the five specimens analysed.
Intracellular trafficking of endogenous fibroblast growth factor‐2
2008
We have previously reported how the release of fibroblast growth factor-2 (FGF-2) is mediated by shed vesicles. In the present study, we address the question of how newly synthesized FGF-2 is targeted to the budding vesicles. Considering that in vitro cultured Sk-Hep1 hepatocarcinoma cells release FGF-2 and shed membrane vesicles only when cultured in the presence of serum, we added serum to starved cells and monitored intracellular movements of the growth factor. FGF-2 was targeted both to the cell periphery and to the nucleus and nucleolus. Movements toward the cell periphery were not influenced by drugs affecting microtubules, but were inhibited by cytocalasin B. Involvement of actin in …
Incomplete sequence homogenization in 45S rDNA multigene families: intermixed IGS heterogeneity within the single NOR locus of the polyploid species …
2014
† Background and Aims Ribosomal sequences have become the classical example of the genomic homogenization of nuclear multigene families. Despite theoretical advantages and modelling predictions that support concerted evolution of the 45S rDNA, several reports have found intragenomic polymorphisms. However, the origins and causes of these rDNA polymorphisms are difficult to assess because seed plants show a wide range of 45S rDNA loci number variation, especially in polyploids. Medicago arborea is a tetraploid species that has a single 45S rDNA locus. This feature makes this species a suitable case study to assess the fate of ribosomal IGS homogenization in polyploid species showing nucleolu…
Ultrastructural biologic effects of sonography with pulse inversion and microbubble contrast in rabbit liver
2005
Purpose This prospective study was conducted to evaluate the biologic effects of microbubble destruction with pulse-inversion harmonic imaging on rabbit liver parenchyma. Methods The livers of 6 albino rabbits were examined sonographically by a single investigator. Three rabbits underwent contrast-enhanced sonography, with scanning starting 5 seconds after injection by using pulse-inversion harmonic imaging with a mechanical index of 1.2. Four time-triggered images were recorded at a rate of 1 frame every 2 seconds. For comparison, 3 control rabbits had pulse-inversion harmonic imaging with a mechanical index of 1.2 only, without contrast medium. Immediately after sonography, the animals we…