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Showing papers on "Cellular compartment published in 1976"


Journal ArticleDOI
TL;DR: Although the acetyl moiety of acetyl-CoA generated in brain mitochondria is largely translocated as citrate from these organelles to the cytosol, a cytosolic pathway exists by which acetoacetate is converted directly intoacetyl-COA in this cellular compartment.
Abstract: The metabolism of acetoacetate via a proposed cytosolic pathway in brain of 1-week-old rats was investigated. (-)-Hydroxycitrate, an inhibitor of ATP citrate lyase, markedly inhibited the incorporation of carbon from labelled glucose and 3-hydroxybutyrate into cerebral lipids, but had no effect on the incorporation of labelled acetate and acetoacetate into brain lipids. Similarly, n-butylmalonate and benzene-1,2,3-tricarboxylate inhibited the incorporation of labelled 3-hydroxybutyrate but not of acetoacetate into cerebral lipids. These inhibitors had no effect on the oxidation to 14CO2 of the labelled substrates used. (-)-Hydroxycitrate decreased the incorporation of 3H from 3H2O into cerebral lipids by slices metabolizing either glucose or 3-hydroxybutyrate, but not in the presence of acetoacetate. (-)-Hydroxycitrate also differentially inhibited the incorporation of [2-14C]-leucine and [U-14C]leucine into cerebral lipids. The data show that, although the acetyl moiety of acetyl-CoA generated in brain mitochondria is largely translocated as citrate from these organelles to the cytosol, a cytosolic pathway exists by which acetoacetate is converted directly into acetyl-COA in this cellular compartment.

70 citations


Journal ArticleDOI
01 Jan 1976-Planta
TL;DR: The accumulation and localisation of flavonoids in the different cellular compartments (plasts, vacuoles, cytoplasm, cell walls) have been determined for each period of the secretory cycle.
Abstract: Lipophilic material produced by buds and young leaves of Populus nigra L. contains flavonoid aglycones. Under precise experimental conditions a green-yellow fluorescent light can be detected from these phenolic compounds. A cytophotometric technique using this property has been established: localisation and quantitative estimation of intracellular flavonoid material are realized by fluorometry. The accumulation and localisation of flavonoids in the different cellular compartments (plasts, vacuoles, cytoplasm, cell walls) have been determined for each period of the secretory cycle. These results were obtained from, in situ, investigations or from experiments with ethanolic extracts of cellular compartments.

51 citations


Journal ArticleDOI
TL;DR: The data suggest that in dog thyroid tissue Ca2+ is distributed at least in two compartments, and the translocations of stored intracellular calcium may be a crucial step in the activation of the thyroid cell.

27 citations


Journal ArticleDOI
TL;DR: Gel electrophoresis of the membrane proteins of the Golgi apparatus-rich and plasma membrane-rich fractions showed a close similarity, and it is possible that membrane similarity may be mediated by the transfer of membrane-bound vesicles from the Gol Gi apparatus to the cell membrane.
Abstract: A Golgi apparatus-rich fraction and a plasma membrane-rich fraction were isolated from a common homogenate of rat liver. Their respective buovant densities, appearances in the electron microscope and 5'-nucleotidase and UDP-galactose ovalbumin galactosyltransferase activities were in accord with published data on separately isolated Golgi apparatus-rich and plasma membrane-rich fractions. Contamination by endoplasmic reticulum and mitochondria was low. Gel electrophoresis of the membrane proteins of the Golgi apparatus-rich and plasma membrane-rich fractions (separately and mixed) showed a close similarity. After Neville's demonstration that electrophoretic patterns of membrane protein subunits from different subcellular fractions are easily distinguishable, the present work demonstrates an unusually close relationship between the Golgi apparatus membrane and the cell membrane. It is possible that membrane similarity may be mediated by the transfer of membrane-bound vesicles from the Golgi apparatus to the cell membrane.

27 citations


Journal ArticleDOI
TL;DR: The results presented suggest that pseudo-cleavage induced by cytochalasin B arises as a consequence of a limited interaction of the drug with the oocyte surface and/or cortex and that it may represent a topographical dissociation of transporting and non-transporting regions of the membrane.
Abstract: Mouse oocytes are induced by cytochalasin B to undergo 'pseudo-cleavage' in vitro into 2 equally sized and separable compartments. This response to the drug is dependent upon the meiotic state of the oocytes, as well as upon the presence of an intact zona pellucida. The resulting 2 cellular compartments can be completely separated from another and cultured in vitro. Each of the compartments possesses characteristic structural features. The most pronounced structural differences include: (i) the presence of a nucleus (germinal vesicle) and nucleolus in one compartment; (ii) the presence of microvilli on the surface of the anucleate, but not the nucleate, compartment; and (iii) the localization (segregation) of mitochondria at the periphery of the anucleate, but not the nucleate, compartment. The results presented suggest that pseudo-cleavage induced by cytochalasin B arises as a consequence of a limited interaction of the drug with the oocyte surface and/or cortex and that it may represent a topographical dissociation of transporting and non-transporting regions of the membrane. These and other features of mouse oocytes treated with cytochalasin B are of interest in view of the involvement of the oocyte zona pellucida and plasma membrane during meiotic maturation, fertilization, and early embryogenesis.

13 citations


Journal ArticleDOI
TL;DR: Root cortical explants from seedlings of Pisum sativum L., cv.
Abstract: Root cortical explants from seedlings ofPisum sativum L., cv. Little Marvel were cultured on a sterile nutrient medium in the presence of auxins or auxins and cytokinin. Explants were fixed (and subsequently processed for electron microscopic observation) at the outset and after 30, 60, and 72 hours of culture under the two hormonal conditions. In the presence of auxin alone, the cell walls of the cortical parenchyma showed distinctive structural changes involving the deposition of a new, diffusely fibrillar primary wall. A considerable increase of rough ER in the adjacent cytoplasm was associated with the new wall synthesis. These wall changes are interpreted as auxin-induced and prelude to cell enlargement and later cell separation. No dramatic changes occurred in other cytoplasmic organelles or in the nucleus. In the presence of cytokinin and auxin, the striking cytological events observed included marked nuclear changes and greater cytoplasmic density due to increased organelles associated with the onset of DNA synthesis, mitosis and cytokinesis. New cell walls formed from the developed phragmoplasts, cleaving the original parenchyma cells into smaller cellular compartments with no accompanying cell enlargement. No marked changes in the original primary cell walls were observed in cytokinin-auxin-treated explants. By 72 hours some cells already had completed two successive cell divisions. No ultrastructural evidence was obtained suggesting that these cells were committed to their known fate of differentiating into mature tracheary elements in the subsequent 2–4 days. At 72 hours each explant represented a population of actively dividing, still considerably vacuolated meristematic cells.

7 citations


Book ChapterDOI
01 Jan 1976
TL;DR: This chapter provides an overview on the current interpretation of the anatomy of the mammalian cell and discusses various membranous components.
Abstract: Publisher Summary This chapter provides an overview on the current interpretation of the anatomy of the mammalian cell. It discusses various membranous components. The plasmalemma of a living cell cannot be the complete barrier that superficially it appears to be. With the electron microscope, these surface cell membranes are viewed in cross section as trilaminar structures of relatively uniform width. Mitochondria is divided into two compartments: (1) the lesser compartment, which lies between the two parts of the double membrane and includes the area between the two leaves of the cristae projecting into the mitochondrion, and (2) the greater compartment, which is the area internal to both double membranes and between the cristae. The endoplasmic reticulum is a cytoplasmic system of closed unit membranes surrounding flattened or dilated cisternae. Similar to the endoplasmic reticulum, the Golgi complex is part of the cytoplasmic vacuolar system. Lysosomes are round or oval small bodies that are enclosed by a single unit membrane. Annulate lamellae are the stacks of membrane. Filaments, microtubules, centrioles, ribosomes, lipids, glycogen, and chromatin are general non-membranous components, whereas, keratohyalin granule is a special non-membranous components.

1 citations