Showing papers on "Cellular compartment published in 1977"

Alterations in the endoplasmic reticulum and golgi complex of intestinal epithelial cells during fat absorption and after termination of this process: A morphological and morphometric study

Abstract: Earlier investigations of intestinal fat-absorption have stressed the importance of continued protein synthesis to provide membranes which are utilized for the intracellular transport of resynthesized lipid. The resulting membranes, when incorporated into the endoplasmic reticulum (ER) and Golgi complex, serve as vehicles for the movement of fat within the cell and for its release to the extracellular space. In the current study, attention was focused on the morphological changes in the ER and Golgi complex both during fat absorption and at successive time intervals after fat-absorption termination. Morphological interpretations were confirmed by morphometric analysis. This investigation supports the interpretation that during fat absorption, membrane synthesis by the rough endoplasmic reticulum (RER) is insufficient to accomodate membrane utilization and intraconversion, resulting in a decrease of both ER and Golgi complex components. However, following fat-absorption termination, and cell is able to replace previously depleted components of the ER and Golgi complex and regain the full membrane complement of the fasted state. Replenishment of cellular membranes is postulated as resulting from a continued synthesis of new membranes by the RER which eventually exceeds membrane utilized during lipid transport.

Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining.

Abstract: The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in some vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.

The reversibility of the ethidium bromide-induced alterations of mitochondrial structure and function in the cellular slime mold, Dictyostelium discoideum.

Abstract: Addition of ethidium bromide to ameboid cultures of the slime mold,Dictyostelium discoideum, caused a cessation of cell division after 1 or 2 generations. The replication of mitochondrial DNA was immediately blocked as indicated by the 50% decrease in the DNA content of purified mitochondria from ethidium-bromide-treated cultures. The activity of the respiratory chain was also inhibited, resulting in a 75% decrease in cyanide-sensitive whole cell respiration. Spectral analysis at low temperature indicated that the amount of cytochromec1 was decreased 80% and that of cytochromec increased 100% in mitochondria from treated cells. Two cytochromesb absorbing at 556 and 561 nm were observed in mitochondria from both control and ethidium-bromide-treated cultures. The content of cytochromeb561 appeared to decline more than didb556, but it is hard to quantitate the decrease. The effects of ethidium bromide were fully reversible. When the drug was removed, the cells resumed a normal growth rate without any discernible lag. The activity of oligomycin-sensitive ATPase, cytochrome oxidase, and succinate-cytochrome-c reductase as well as the cytochrome content began to increase after 1 day returning to control levels within 5 days. Electron micrographs of whole cells treated with ethidium bromide revealed that mitochondrial profiles were elongated and had greatly reduced cristae. Numerous membrane whorls were apparent, as was a profound loss of rough endoplasmic reticulum. Three days after removal of ethidium bromide, mitochondria were again ovoid in shape and contained well-developed cristae. In all of the cells during recovery, there was a single large vacuole that appeared to enclose a large portion of the cell volume, forming a new cellular compartment that may simplify the breakdown of previously damaged organelles.

Subcellular reactions to injury. I. Ultrastructural and biochemical investigations on the hepatic cellular damage produced by haemorrhagic shock in dogs

Abstract: The ultrastructural changes produced by haemorrhagic shock in hepatocytes have been studied in dogs. The associated biochemical and biophysical system alterations allow us to propose a unitary pathogenetic mechanism of the cellular injury based on oxygen deprivation and its effect on the function and structure of the cellular compartments.