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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A multilaminar alteration of endoplasmic reticulum (ER) has been observed in tumor cells of eight patients with Hodgkin's disease and a patient with histiocytic lymphoma. These multilaminar structures are more numerous in dividing cells and thus appear to arise primarily during mitosis. The stacked membranes in the multilaminar structures possibly result from abnormal sticking of organelle membranes, as evidenced in this study of adherence of ER to other elements of ER, nuclear envelope, mitochondria, or lipid droplets. Multilaminar ER was identified in all mitotic tumor cells, a rare mitotic plasma cell, and numerous interphase Hodgkin cells. The paucity of multilaminar ER in normal mitotic cells and its virtual absence for normal interphase cells suggest that this structure represents a pathological alteration in tumor cells from patients with Hodgkin's disease and histiocytic lymphoma. The multilaminar defect of ER is associated with other atypical features of ER in Hodgkin tumor cells, including the excessive length and curving of ER profiles, the collapse of the ER cisternae, and the overall sparsity of this organelle. Other abnormalities observed in mitotic Hodgkin tumor cells include the presence of disorganized microtubules, large cytoplasmic vacuoles, and abnormally clumped chromosomal material and the persistence throughout mitosis of bodies suggestive of nucleoli and of the nuclear bodies of interphase cells.
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PMID:Multilaminar endoplasmic reticulum and abnormal mitosis in Hodgkin tumor cells. 17 30

The histology and ultrastructure of the rat gastric mucosa were investigated during 168 hours of starvation. An increased desquamation of individual foveolar cells was found. In the preserved cells of the foveolae, the content of the PAS positive mucosubstances did not change during starvation, and no changes took place in the appearance and in the amount of the mucous granules at the electron microscopic investigation. The number of lipid droplets increased in the mucous foveolar cells within 24 and 48 hours. During starvation the mitochondria (mainly in the parietal cells) were enlarged and contained rare mitochondrial cristae. Some mitochondria were distintegrated and removed by lysosomes. The number of lysosomes (mainly cytosergresomes) was markedly increased n parietal cells. A collapse of the intracellular canaliculi occurred as well as a narrowing in the tubulovesicular profiles. In chief cells the profiles of the granular endoplasmic reticulum and Golgi apparatus were reduced. It was shown that the ultrastructural changes induced by starvation can be interpreted functionally in changed histochemical parameters of the gastric mucosa.
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PMID:Influence of starving on the rat gastric mucosa -- light and electron microscopical findings. 59 Apr 16

Seasonal changes of the testicular interstitial tissue were studied by electron microscopy. During the breeding season in spring, clusters of Leydig cells are surrounded by wide lymphatic sinusoids. In sexually quiescent moles, these sinusoids collapse, and the abundant Leydig cells become closely packed and occupy most of the testis. During sexual activity, the Leydig cells contain abundant smooth endoplasmic reticulum (SER), mitochondria with tubular cristae, and lipid droplets. Some areas of the cytoplasm are occupied exclusively by tubular SER, arranged in parallel. During regression the SER appears tortuous, and large lipid droplets are found in the cytoplasm, although these gradually become smaller. During the long period of sexual quiescence, the size and abundance of Leydig cells and the appearance of SER, lipid droplets and mitochondria were similar to those observed during sexual activity.
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PMID:The organization of testicular interstitial tissue and changes in the fine structure of the Leydig cells of European moles (Talpa europaea) throughout the year. 63 2

To study the interrelationships of endoplasmic reticulum, mitochondria, intermediate filaments, and microtubules, we have developed a quadruple fluorescence labeling procedure to visualize all four structures in the same cell. We applied this approach to study cellular organization in control cells and in cells treated with the microtubule drugs vinblastine or taxol. Endoplasmic reticulum was visualized by staining glutaraldehyde-fixed cells with the dye 3,3'-dihexyloxacarbocyanine iodide. After detergent permeabilization, triple immunofluorescence was carried out to specifically visualize mitochondria, vimentin intermediate filaments, and microtubules. Mitochondria in human fibroblasts were found to be highly elongated tubular structures (lengths up to greater than 50 microns), which in many cases were apparently fused to each other. Mitochondria were always observed to be associated with endoplasmic reticulum, although endoplasmic reticulum also existed independently. Intermediate filament distribution could not completely account for endoplasmic reticulum or mitochondrial distributions. Microtubules, however, always codistributed with these organelles. Microtubule depolymerization in vinblastine treated cells resulted in coaggregation of endoplasmic reticulum and mitochondria, and in the collapse of intermediate filaments. The spatial distributions of organelles compared with intermediate filaments were not identical, indicating that attachment of organelles to intermediate filaments was not responsible for organelle aggregation. Mitochondrial associations with endoplasmic reticulum, on the other hand, were retained, indicating this association was stable regardless of endoplasmic reticulum form or microtubules. In taxol-treated cells, endoplasmic reticulum, mitochondria, and intermediate filaments were all associated with taxol-stabilized microtubule bundles.
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PMID:Interrelationships of endoplasmic reticulum, mitochondria, intermediate filaments, and microtubules--a quadruple fluorescence labeling study. 136 23

The use of low concentrations of digitonin allowed the quantitative determination of the mitochondrial membrane potential of Leishmania donovani promastigotes in situ using safranine O. L. donovani mitochondria were able to build up and retain a membrane potential of a value comparable with that of mammalian mitochondria. The response of promastigotes mitochondrial membrane potential to phosphate, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), valinomycin and Ca2+ indicates that these mitochondria behave similarly to vertebrate mitochondria with regard to the properties of their electrochemical proton gradient. When L. donovani promastigotes were permeabilized with digitonin in a reaction medium containing MgATP, succinate and 3.5 microM free Ca2+, they lowered the medium Ca2+ concentration to the submicromolar level (0.05-0.1 microM). The presence of 1 microM-FCCP decreased by about 75% the initial rate of Ca2+ sequestration by these permeabilized cells. This FCCP-insensitive Ca2+ uptake, probably by the endoplasmic reticulum, was completely inhibited by 500 microM-vanadate. On the other hand, when vanadate instead of FCCP was present, the initial rate of Ca2+ accumulation was decreased by about 25% and the Ca2+ set point was increased to 0.7 microM. The succinate-dependence and FCCP-and Ruthenium Red-sensitivity of the Ca2+ uptake detected in the presence of vanadate indicate that this uptake is probably by the mitochondria. This interpretation was further supported by the Ruthenium Red-sensitive decrease in the mitochondrial membrane potential caused by Ca2+ addition. The anti-leishmanial cationic drugs pentamidine and WR-6026 also induced a rapid collapse of the mitochondrial inner membrane potential of L. donovani promastigotes.
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PMID:Ca2+ transport by digitonin-permeabilized Leishmania donovani. Effects of Ca2+, pentamidine and WR-6026 on mitochondrial membrane potential in situ. 137 13

Pulmonary surfactant, a complex consisting of 90% lipids and 10% specific proteins, lines the alveoli of the lung and prevents alveolar collapse and transudation by lowering the surface tension at the air-liquid interface. Dipalmitoylphosphatidylcholine constitutes approximately 50% of the surfactant lipids and is primarily responsible for the surface tension-lowering property of the surfactant mixture. This phospholipid, together with the other surfactant phospholipids, is produced at the endoplasmic reticulum of the alveolar type II epithelial cells. The characteristic lamellar bodies in these cells serve as storage depot for the surfactant before this is secreted onto the alveolar surface. This article reviews the pathways via which the surfactant lipids are synthesized, our current knowledge of the regulation of these pathways, and what is known about intracellular traffic of phospholipids from their site of synthesis to the lamellar bodies.
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PMID:Surfactant phospholipids: synthesis and storage. 156 54

The proliferating cells in fibromatoses are myofibroblasts that produce abundant stromal collagen and contain intracellular native and widely spaced collagen fibers. To assess the clinical and cellular effects of colchicine in such tumors, this drug was administered to three patients, one with musculoaponeurotic desmoid fibromatosis, one with Dupuytren's palmar fibromatosis, and one with Peyronie's disease. All three patients had an excellent clinical response, with reduction of tumor size and improvement of contracture. Two cases were studied ultrastructurally; the main cellular changes detected were collapse of the rough endoplasmic reticulum cisternae, reduction of myofilaments, and disappearance of intracellular widely spaced collagen. The findings from this study indicate another probable application for colchicine and support the concept that collagen fibers can be formed intracellularly.
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PMID:Clinical and cellular effects of colchicine in fibromatosis. 156 69

Studies on sphingomyelin metabolism in rat hepatocytes were facilitated by the use of choline-deficient cells which allowed for the rapid labeling of phosphatidylcholine and as a result sphingomyelin. Pulse and pulse-chase studies with [methyl-3H]choline and [methyl-3H]methionine demonstrated that both compounds were effectively used for sphingomyelin biosynthesis and that newly made and pre-existing phosphatidylcholine could be used for sphingomyelin biosynthesis. When hepatocytes were incubated with brefeldin A, there was a 2.4-fold stimulation of the conversion of phosphatidylcholine into sphingomyelin. Since brefeldin A causes collapse of the cis/medial Golgi into the endoplasmic reticulum the stimulation of sphingomyelin biosynthesis could be due to more rapid access of the labeled phosphatidylcholine in the endoplasmic reticulum to sphingomyelin synthase in the collapsed Golgi. Forskolin inhibited the brefeldin A-induced stimulation of sphingomyelin biosynthesis. To investigate whether or not phosphorylation reactions regulate sphingomyelin metabolism, hepatocytes were incubated with okadaic acid, a potent inhibitor of protein phosphatases 1 and 2A. Rather than stimulating sphingomyelin biosynthesis, okadaic acid enhanced the catabolism of sphingomyelin. In contrast, a cyclic AMP analogue and forskolin had no effect on sphingomyelin biosynthesis or catabolism. Surprisingly, other pulse-chase studies demonstrated that okadaic acid stimulated the catabolism of only newly made sphingomyelin. The brefeldin A and okadaic acid effects were independent of lysosomal involvement. Subcellular fractionation studies revealed that brefeldin A and okadaic acid effects were generalized in all sphingomyelin containing membranes. The brefeldin A studies suggest that the rate of transfer of phosphatidylcholine from the endoplasmic reticulum to the Golgi might be limiting for sphingomyelin biosynthesis. The okadaic acid studies indicate that the catabolism of sphingomyelin by a sphingomyelinase is regulated by an unidentified protein kinase and by either protein phosphatase 1 and/or 2A activity in hepatocytes.
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PMID:Stimulation of sphingomyelin biosynthesis by brefeldin A and sphingomyelin breakdown by okadaic acid treatment of rat hepatocytes. 161 52

The centrifugal elongation of membranes to form extended tubular structures is a widespread form of intracellular organelle movement. Tubular lysosomes and the endoplasmic reticulum, for example, undergo such extension in association with microtubules, and this process has been mimicked in vitro by combining purified microtubules with isolated membranes and the mechanochemical ATPase kinesin. This, along with evidence that kinesin is associated with the endoplasmic reticulum, has led to the suggestion that kinesin provides the motive force for the formation and maintenance of elongated tubulovesicular structures in cells. We have addressed this hypothesis in murine macrophages, which have prominent tubular lysosomes whose form depends on the integrity of microtubules. Here we report that two antikinesin antibodies which disrupt in vitro motility will each cause centripetal collapse of the array of tubular lysosomes when scrape-loaded into macrophages. To our knowledge this provides the first in vivo evidence that kinesin is responsible for extension of tubulovesicular structures along microtubules.
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PMID:Radial extension of macrophage tubular lysosomes supported by kinesin. 169 3

In the tree shrew Tupaia glis, 5 or 6 small ramifying arterioles arose directly from the testicular artery and then gave off numerous small capillaries. The capillaries made a series of anastomoses with neighbouring counterpart capillaries to become a complicated network. Some of the capillaries drained into a small venule, which was connected directly with the testicular vein (pampiniform plexus), to form an arteriovenous connection (A-V shunt) between the testicular artery and the pampiniform plexus. This A-V shunt appears to make the transfer of substances from the pampiniform plexus to the testicular artery more efficient. In addition, the shunt may control the volume of the blood draining into the testis. The capillaries were covered by vesiculated cells which were located adjacent to the pericytes. The vesiculated cells contained abundant mitochondria, rough endoplasmic reticulum, a well developed Golgi complex and cytoplasmic vesicles. Their cellular processes were long and surrounded more than one capillary. The morphological features of the vesiculated cells suggest that they may synthesise substances that are released into the network and which affect the activity of the capillaries. Since the cellular processes contacted each other, the cells could provide support for the capillaries and prevent their collapse when the shunts are closed.
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PMID:Evidence for a direct arteriovenous connection (A-V shunt) between the testicular artery and pampiniform plexus in the spermatic cord of the tree shrew (Tupaia glis). 181 Sep 17


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