Studies of nucleolar organizer regions and mucin histochemistry in ulcerative colitis

Human pituitary corticotropins have unique morphologic markers: bundles of type-1 filaments, measuring approximately 70 A in width and representing cytokeratin. The extreme ring-like accumulation of type-1 filaments, known as Crooke's hyalinization, signals functional suppression of the corticotropins and occurs in endogenous and exogenous glucocorticoid excess, caused by ACTH-secreting pituitary adenoma, glucocorticoid secreting adrenocortical tumor, ectopic ACTH-syndrome and administration of pharmacologic doses of glucocorticoids. Cells of autonomous corticotroph adenomas usually do not show Crooke's hyalin change. A minority of these tumors, however, retains sensitivity to the negative feed-back effect of elevated blood glucocorticoid levels and display typical Crooke’s change.In the present study pituitary corticotropins in various phases of Crooke's hyalinization were investigated in patients with glucocorticoid excess of various origin, applying histology, immunocytochemistry, count of argyrophilic nucleolar organizer regions (AgNOR), and transmission electron microscopy.

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A role for upstream binding factor in organizing ribosomal gene chromatin

Biochemical Society Symposium ◽

10.1042/bss0730077 ◽

2006 ◽

Vol 73 ◽

pp. 77-84 ◽

Cited By ~ 14

Author(s):

Jane E. Wright ◽

Christine Mais ◽

José-Luis Prieto ◽

Brian McStay

Keyword(s):

Nucleolar Organizer ◽

Ribosomal Gene ◽

Rna Polymerase I ◽

Nucleolar Organizer Regions ◽

Binding Factor ◽

Upstream Binding Factor ◽

Acrocentric Chromosomes ◽

Polymerase I ◽

Secondary Constrictions ◽

Active Nors

Human ribosomal genes are located in NORs (nucleolar organizer regions) on the short arms of acrocentric chromosomes. During metaphase, previously active NORs appear as prominent chromosomal features termed secondary constrictions, which are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I transcription factor UBF (upstream binding factor) binds extensively across the ribosomal gene repeat throughout the cell cycle. Evidence that UBF underpins NOR structure is provided by an examination of cell lines in which large arrays of a heterologous UBF binding sequences are integrated at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus, and during metaphase form novel silver-stainable secondary constrictions, termed pseudo-NORs, that are morphologically similar to NORs.

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Structure and variability of nucleolar organizer regions in Parodontidae fish

Canadian Journal of Genetics and Cytology ◽

10.1139/g84-089 ◽

1984 ◽

Vol 26 (5) ◽

pp. 564-568 ◽

Cited By ~ 51

Author(s):

Orlando Moreira-Filho ◽

Luiz Antonio Carlos Bertollo ◽

Pedro Manoel Galetti Jr.

Keyword(s):

Chromosome Pair ◽

Constitutive Heterochromatin ◽

Nucleolar Organizer ◽

Nucleolar Organizer Regions ◽

Mitotic Chromosomes ◽

Homozygous Condition ◽

Nucleolar Organizing Regions ◽

Nucleolar Chromosome

Nucleolar organizer regions (NORs) were studied in mitotic chromosomes of four species of fish of family Parodontidae: Parodon tortuosus, Apareiodon affinis, Apareiodon ibitiensis, and Apareiodon piracicabae. All four species exhibited only a single nucleolar chromosome pair in their karyotypes. Intraspecific differences were observed in the size of these chromosomes; however, these were not very clear for A. affinis and A. piracicabae, Apareiodon piracicabae exhibited two clearly visible NORs in each of the nucleolar chromosomes, which was the only configuration practically found in this species. This trait therefore predominates in a homozygous condition in the population investigated. Regions of constitutive heterochromatin adjacent to the two NORs were detected. Possible mechanisms that may have originated the two NORs are discussed.Key words: nucleolar organizing regions, fish.

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