Accessory nuclei (nuclear membrane balloons) in the oocytes of the dipteran Phryne

Chromosoma ◽  
1979 ◽  
Vol 75 (1) ◽  
pp. 89-99 ◽  
Author(s):  
G. F. Meyer ◽  
S. Sokoloff ◽  
B. E. Wolf ◽  
B. Brand
Keyword(s):  
Nuclear Membrane ◽  
Accessory Nuclei

Memoirs: The Rôles of the Nurse-cells, Oocytes and Follicle-cells in Tenthredinid Oogenesis

1928 ◽  
Vol s2-71 (284) ◽  
pp. 541-561
Author(s):  
A. D. PEACOCK ◽  
R.A. R. GRESSON
Keyword(s):  
Nuclear Membrane ◽  
Nurse Cell ◽  
Follicle Cell ◽  
Narrow Channel ◽  
Nuclear Material ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Accessory Nuclei ◽  
Dark Staining ◽  
The Common

1. Ovary formation in Tenthredinidae follows the general hymenopterous plan. 2. Nurse-cell phenomena are as follows: the nuclei of the first nutritive chamber are surrounded by a chromatin cloud and many of them contain irregular darkly-staining masses of nuclear material, which masses may also be present in the riper chambers; the granules given off from the nuclei into the chromatin cloud eventually become surrounded by a vesicle and give rise to the ‘secondary’ or ‘accessory’ nuclei. 3. Oocyte nucleolar phenomena show the following: the nucleoli in Thrinax mixta and Platycampus luridiventris give rise to buds which become free; in one case buds were observed close to the inner surface of the nuclear membrane in Allantus (Emphytus) pallipes are shown what are apparently later stages of this process, viz. the passage of the buds through the nuclear membrane into the egg substance and their formation there into accessory nuclei. 4. The fate of the nurse-cells is shown in the older nutritive chambers and oocytes--the cell boundaries become indistinct and some of the cytoplasm, together with contained accessory nuclei, passes by a narrow channel into the oocyte. The cytoplasmic flow becomes more marked in the last chamber. In the final stages, shown in the last chamber, all the cells lose their boundaries and the common cytoplasm passes into the oocyte, carrying with it the free nuclei to their engulfment and absorption in the ooplasm. 5. Some of the follicle-cells surrounding the last oocyte in Pristiphora padi, and the fifth, sixth, and seventh of Thrinax mixta, contain granular dark-staining material which may completely fill the cell, these granules probably originating from the nucleus. They pass out of the follicle-cell into the egg where they become surrounded by vesicles, and, finally, present an appearance indistinguishable from that of accessory nuclei. 6. Secondary or accessory nuclei, therefore, have a threefold origin, namely, from the nuclei, of nurse-cells and oocytes and from follicle-cells, their source of derivation in the last being the follicular nuclei. 7. The follicle-cells of the distal pole of the last oocyte of one ovariole of Pristiphora padi have processes which insinuate themselves into the ooplasm. 8. The phenomena of oogenesis described in these four species of sawflies, while embracing certain which have not hitherto been recorded, conform, in essentials, with those already discovered for Hymenoptera generally.

The Formation, Structure, Distribution and Frequency of Nuclear Pores

1971 ◽  
Vol 29 ◽  
pp. 518-519
Author(s):  
G. G. Maul
Keyword(s):  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Dynamic Structure ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Filter Function ◽  
Etching Technique ◽  
Selective Filter ◽  
Membranous Part

The chromatin of eukaryotic cells is separated from the cytoplasm by a double membrane. One obvious structural specialization of the nuclear membrane is the presence of pores which have been implicated to facilitate the selective nucleocytoplasmic exchange of a variety of large molecules. Thus, the function of nuclear pores has mainly been regarded to be a passive one. Non-membranous diaphragms, radiating fibers, central rings, and other pore-associated structures were thought to play a role in the selective filter function of the nuclear pore complex. Evidence will be presented that suggests that the nuclear pore is a dynamic structure which is non-randomly distributed and can be formed during interphase, and that a close relationship exists between chromatin and the membranous part of the nuclear pore complex.Octagonality of the nuclear pore complex has been confirmed by a variety of techniques. Using the freeze-etching technique, it was possible to show that the membranous part of the pore complex has an eight-sided outline in human melanoma cells in vitro. Fibers which traverse the pore proper at its corners are continuous and indistinguishable from chromatin at the nucleoplasmic side, as seen in conventionally fixed and sectioned material. Chromatin can be seen in octagonal outline if serial sections are analyzed which are parallel but do not include nuclear membranes (Fig. 1). It is concluded that the shape of the pore rim is due to fibrous material traversing the pore, and may not have any functional significance. In many pores one can recognize a central ring with eight fibers radiating to the corners of the pore rim. Such a structural arrangement is also found to connect eight ribosomes at the nuclear membrane.

A High Resolution Cytochemical Study of Nuclear ATPase in Human Spermatozoa

1975 ◽  
Vol 33 ◽  
pp. 594-595
Author(s):  
A. Sosa ◽  
L. Calzada
Keyword(s):  
High Resolution ◽  
Atpase Activity ◽  
Nuclear Membrane ◽  
Human Sperm ◽  
Sperm Nucleus ◽  
Human Spermatozoa ◽  
Cytochemical Study ◽  
Membrane Bound ◽  
Sperm Nuclei ◽  
Interchromatin Space

The dependence of nuclear metabolism on the function of the nuclear membrane is not well understood. Whether or not the function of the nuclear membrane is partial or totally responsible of the repressed template activity of human sperm nucleus has not at present been elucidated. One of the membrane-bound enzymatic activities which is concerned with the mechanisms whereby substances are thought to cross cell membranes is adenosintriphosphatase (ATPase). This prompted its characterization and distribution by high resolution photogrammetry on isolated human sperm nuclei. Isolated human spermatozoa nuclei were obtained as previously described. ATPase activity was demonstrated by the method of Wachstein and Meisel modified by Marchesi and Palade. ATPase activity was identified as dense and irregularly distributed granules confined to the internal leaflet of the nuclear membrane. Within the nucleus the appearance of the reaction product occurs as homogenous and dense precipitates in the interchromatin space.

Lamin B receptor: role on chromatin structure, cellular senescence and possibly aging

2020 ◽  
Vol 477 (14) ◽  
pp. 2715-2720
Author(s):  
Susana Castro-Obregón
Keyword(s):  
Cellular Senescence ◽  
Nuclear Membrane ◽  
Chromatin Structure ◽  
Cholesterol Synthesis ◽  
Reductase Activity ◽  
Chimeric Protein ◽  
Nuclear Lamina ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Lamin B Receptor

The nuclear envelope is composed by an outer nuclear membrane and an inner nuclear membrane, which is underlain by the nuclear lamina that provides the nucleus with mechanical strength for maintaining structure and regulates chromatin organization for modulating gene expression and silencing. A layer of heterochromatin is beneath the nuclear lamina, attached by inner nuclear membrane integral proteins such as Lamin B receptor (LBR). LBR is a chimeric protein, having also a sterol reductase activity with which it contributes to cholesterol synthesis. Lukasova et al. showed that when DNA is damaged by ɣ-radiation in cancer cells, LBR is lost causing chromatin structure changes and promoting cellular senescence. Cellular senescence is characterized by terminal cell cycle arrest and the expression and secretion of various growth factors, cytokines, metalloproteinases, etc., collectively known as senescence-associated secretory phenotype (SASP) that cause chronic inflammation and tumor progression when they persist in the tissue. Therefore, it is fundamental to understand the molecular basis for senescence establishment, maintenance and the regulation of SASP. The work of Lukasova et al. contributed to our understanding of cellular senescence establishment and provided the basis that lead to the further discovery that chromatin changes caused by LBR reduction induce an up-regulated expression of SASP factors. LBR dysfunction has relevance in several diseases and possibly in physiological aging. The potential bifunctional role of LBR on cellular senescence establishment, namely its role in chromatin structure together with its enzymatic activity contributing to cholesterol synthesis, provide a new target to develop potential anti-aging therapies.

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