Material and Methods: The present study was conducted on 40 specimens of breast carcinoma out of which 12 cases were of Grade II and 28 cases were of Grade III. Percentage positivity and scoring of Ki-67 and mean AgNOR count was done with relation to grades. Observations: Ki-67 positivity was seen in 12 cases with the percentage positivity of 2.33±5.516 in grade II and 9.67±7.671 in grade III t...

The use of Toombak has been reported to play a major role in the etiology of oral cancer in Sudan. The cellular proliferative activity on the oral epithelium of 210 Toombak dippers was assessed by applying the micronuclei frequency, mean argyrophilic nucleolar organizer region (AgNOR) counts, Papanicolaou method, and 1% crystal violet stain. Participants were divided into 3 groups: 200 were app...

The simultaneous ultrastructural localization of the Ag-NOR proteins and ribonucleoproteins (RNP) was carried out during mitosis in human breast cancerous tissues using a one-step silver staining method followed by acetylation. Owing to the good preservation of the cells and to the high precision of the Ag staining we were able to follow the behaviour of the argyrophilic nucleolar components fr...

The level of redundancy of ribosomal genes, and the relationship of this level to nucleolar formation at different stages of embryonic development, have been examined in the Mexican axolotl, Ambystoma mexicanum. Individuals from 4 inbred stocks were examined, as well as descendants from 2 nucleolar variants which, in the heterozygous condition, are distinguished by exceptionally small nucleoli....

Interspecific hybrids of D. melanogaster and D. simulans normally exhibit a secondary constriction only at the D. melanogaster nucleolus organizer (NO). This phenomenon, termed nucleolar dominance, occurs only when the NO-bearing sex chromosomes of both species are present in conjunction. Experiments were initiated to localize regions on the sex chromosomes of D. melanogaster involved in mediat...

Nucleolar RNA synthesis in salivary glands from XX, XY, and XO larvae having different numbers of nucleolus organizers was examined autoradiographically following incubation of the tissues in [H]uridine. In addition, the presence or absence of secondary constrictions was monitored in neuroblast preparations using acridine orange staining. It was observed that: (1) The rate of nucleolar [H]uridi...

Histone acetylation and deacetylation are connected with transcriptional activation and silencing in many eukaryotic organisms. Gene families for enzymes that accomplish these modifications show a surprising multiplicity in sequence and expression levels, suggesting a high specificity for different targets. We show that mutations in Arabidopsis (Arabidopsis thaliana) HDA6, a putative class I hi...

We transposed Dissociation (Ds) elements from three start loci on chromosome 5 in Arabidopsis (Nossen ecotype) by using a local transposition system. We determined partial genomic sequences flanking the Ds elements and mapped the elements' insertion sites in 1,173 transposed lines by comparison with the published genomic sequence. Most of the lines contained a single copy of the Ds element. One...

The silencing of one parental set of rRNA genes in a genetic hybrid is an epigenetic phenomenon known as nucleolar dominance. We showed previously that silencing is restricted to the nucleolus organizer regions (NORs), the loci where rRNA genes are tandemly arrayed, and does not spread to or from neighboring protein-coding genes. One hypothesis is that nucleolar dominance is the net result of h...

Studies of karyotypes have been revealing important information on the taxonomic relationships and evolutionary patterns in various groups of birds. However, the order Caprimulgiformes is one of the least known in terms of its cytotaxonomy. So far, there are no cytogenetic data in the literature on birds belonging to 3 of 5 families of this order -Nyctibiidae, Steatornithidae and Aegothelidae. ...