Comparison Of Nuclei Research Articles

Comparison of Nucleus and Cytoplasm Diameter of Buccal Mucosa Cells in Cigarette Smokers and Nonsmokers: A Cytomorphometric Study using Feulgen and Papanicolaou Stains

Comparison of Nucleus and Cytoplasm Diameter of Buccal Mucosa Cells in Cigarette Smokers and Nonsmokers: A Cytomorphometric Study using Feulgen and Papanicolaou Stains

The Second Nucleus of NGC 7727: Direct Evidence for the Formation and Evolution of an Ultracompact Dwarf Galaxy*

Abstract We present new observations of the late-stage merger galaxy NGC 7727, including Hubble Space Telescope/WFPC2 images and long-slit spectra obtained with the Clay telescope. NGC 7727 is relatively luminous ( = −21.7) and features two unequal tidal tails, various bluish arcs and star clusters, and two bright nuclei 480 pc apart in projection. These two nuclei have nearly identical redshifts, yet are strikingly different. The primary nucleus, hereafter Nucleus 1, fits smoothly into the central luminosity profile of the galaxy and appears—at various wavelengths—“red and dead.” In contrast, Nucleus 2 is very compact, has a tidal radius of 103 pc, and exhibits three signs of recent activity: a post-starburst spectrum, an [O iii] emission line, and a central X-ray point source. Its emission-line ratios place it among Seyfert nuclei. A comparison of Nucleus 2 ( = −15.5) with ultracompact dwarf galaxies (UCDs) suggests that it may be the best case yet for a massive UCD having formed through tidal stripping of a gas-rich disk galaxy. Evidence for this comes from its extended star formation history, long blue tidal stream, and elevated dynamical-to-stellar-mass ratio. While the majority of its stars formed ago, ∼1/3 formed during starbursts in the past 2 Gyr. Its weak active galactic nucleus activity is likely driven by a black hole of mass . We estimate that the former companion’s initial mass was less than half that of then NGC 7727, implying a minor merger. By now this former companion has been largely shredded, leaving behind Nucleus 2 as a freshly minted UCD that probably moves on a highly eccentric orbit.

Gazing into a Nuclear Mirror

A comparison of nuclei with opposite numbers of protons and neutrons shows that the two nuclear particles are similar as can be.

Ultrastructure of pancreatic B-cells of Atlantic salmon ( Salmo salar) during smoltification and seawater adaptation

Pancreatic B-cells of Atlantic salmon ( Salmo salar) were identified by immunostaining and the ultrastructure and morphology of these cells were investigated during smoltification and acclimation to seawater. Fish were classified as smolts based on length, condition factor, silvering, branchial Na + K + - ATPase activity and salinity tolerance. Individuals measuring less than 15 cm long were used as age-matched, non-smolting controls. Tissue samples were collected from juvenile salmon in February, April and May and, also, in June from post-smolts retained in fresh water or transferred to seawater for 1 month. Pancreas islet size was measured and B-cells were identified by immunohistochemistry and immunocytochemistry. The surface areas of B-cells, nuclei and granules within the cells were quantified, allowing comparison of nucleus: cell (N:C) and total granule: cytoplasm (G:Cyt) ratios. Additionally, the ratio of the number of homogeneous granules: total granules (Hom:G) was determined. No significant changes in size of islets were detected in parr and smolts. In fish undergoing smoltification a slight increase in G:Cyt and a significant decrease in Hom:G ratios ( P<0.05) were observed, whereas in non-smolting parr the G:Cyt ratio increased significantly ( P<0.05) and the Hom:G ratio remained significantly higher than in smolts. A decrease in B-cell area ( P<0.05) was observed in post-smolts retained in fresh water or transferred to seawater. Results are consistent with decreased insulin synthesis or secretion during parr-smolt transformation. In parr during this same period, enhanced B-cell activity was indicated by increases in G:Cyt and elevated Hom:G ratios compared to smolts.

Induction of apoptosis in cultured hepatocytes and in the regressing liver by transforming growth factor-β1 occurs without activation of an endonuclease

In previous studies in vivo apoptotic liver cells were found to be positive for transforming growth factor-β1 (TGF-β1). In hepatocyte cultures TGF-β1 induced rounding up and fragmentation of the cells into multiple vesicles. As revealed by the DNA specific stain H33258 the chromatin of these cells condensed and segregated into masses at the nuclear membrane, followed by nuclear fragmentation. Ultrastructurally the cytoplasm was well preserved as demonstrated by the presence of intact cell organelles. These features strongly suggest the occurrence of apoptosis. Furthermore we administered TGF-β1 in vivo using an experimental model in which regression of the liver was initiated by a short preceding treatment with the hepatomitogen cyproterone acetate (CPA). Two doses of 1 nM TGF- β1/ kg each augmented the incidence of apoptotic hepatocytes 5-fold. These studies strongly suggest that TGF-β1 is involved in the initiation of apoptosis in the liver In TGF-β1 treated hepatocytes both from the liver and monolayer culture no DNA fragmentation into oligosomes could be detected. Comparison of nuclei in which endonuclease was activated by Ca 2+ with apoptotic nuclei revealed no obvious similarities, as demonstrated by FACS analysis, H33258 staining and electron microscopy. Thus, apoptosis induced by a growth inhibitor obviously occurs without activation of an endonuclease.

Preservation of specific RNA distribution within the chromatin-depleted nuclear substructure demonstrated by in situ hybridization coupled with biochemical fractionation.

Biochemical fractionation procedures previously shown to remove 95% of cellular protein, DNA, and phospholipid, were combined with fluorescence in situ hybridization to provide a critical evaluation of the retention and spatial preservation of specific primary transcripts within the chromatin-depleted nuclear substructure, operationally defined as the nuclear "matrix." This unique approach made it possible to directly address whether nuclear extraction procedures preserve, create, or destroy ribonucleoprotein filament structures. Comparison of nuclei before and after fractionation demonstrated that localized foci or "tracks" of specific nRNA are unambiguously retained in the nuclear matrix preparation. Two well-characterized nuclear fractionation procedures were used and three Epstein-Barr virus-infected cell types investigated, including latently and permissively infected cells carrying integrated or episomal genomes. The EBV primary transcripts as well as nucleolar RNA were preserved within the remaining nuclear substructure with unambiguous spatial and quantitative fidelity. Image processing and quantitative microfluorimetry, together with [3H]thymidine labeling of DNA, show that essentially 100% of the RNA signal intensity remained after removal of 85% of the DNA. That the native RNA distribution was unchanged was shown in other experiments in which the same individual nRNA tracks were examined before and after fractionation. Results conclusively demonstrate that the tight restriction of RNA to highly localized sites is independent of bulk DNA removal and of extensive extraction of proteins and phospholipids. Hence, this work provides direct visual evidence that the primary transcripts studied are localized via their binding to, or comprising part of, non-chromatin nuclear substructure.