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PubMed1984

Isolation of plasma membrane, golgi apparatus, and endoplasmic reticulum fractions from single homogenates of mouse liver.

Procedures to isolate plasma membrane, Golgi apparatus, and endoplasmic reticulum from a single homogenate of mouse liver are described. Fractions contain low levels of contaminating membranes as determined from morphometry and analyses of marker enzymes. The method requires only 2-3 gm of liver as starting material and yields approximately 0.7, 0.7, and 0.5 mg protein/gm liver, respectively, for endoplasmic reticulum, Golgi apparatus, and plasma membrane. Golgi apparatus fractions show high levels of galactosyltransferase activity and consist of cisternal stacks and associated secretory vesicles and tubules. Endoplasmic reticulum fractions are enriched in both glucose-6-phosphatase and nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-cytochrome c reductase and contain membrane vesicles with attached ribosomes. K+-stimulated p-nitrophenyl phosphatase and (Na+K+) adenosine triphosphatase activity are enriched in the plasma membrane fraction. This fraction consists of membrane sheets, many with junctional complexes, and bile canaliculi that are representative of the total hepatocyte plasma membrane. The fractionation procedure is designed to utilize small amounts of tissue (e.g., with liver slices), to reduce the total time required for fractionation, and to permit comparisons of constituents of plasma membrane, Golgi apparatus, and endoplasmic reticulum prepared from the same starting homogenates.

Animals↗
PubMed1991

Localization of glycosylation sites in the Golgi apparatus using immunolabeling and cytochemistry.

This review summarizes data on the distribution of certain glycosylation steps in the Golgi apparatus as revealed by immunolabeling and lectin techniques. The methodical basis for such investigations was provided by the introduction of the colloidal gold marker system for immunolabeling and the development of new means of tissue processing such as the low-temperature embedding technique using Lowicryl K4M. The application of these techniques together with highly specific antibodies has provided much of the basis for our current understanding of the Golgi apparatus in functional terms. Thus, in many cell types, three Golgi apparatus compartments can be distinguished, whereas in others no such functional subdivision is evident. Investigations on sialyltransferase distribution have also provided direct evidence that GERL is structurally and functionally part of the Golgi apparatus.

Animals↗
PubMed1988

Effects of colchicine- and cytochalasin B-treatment on the intracellular distribution of yolk droplets, lipid bodies, and Golgi apparatus of the chick neuroepithelial cells.

Treatment with colchicine (antimicrotubular agent) and cytochalasin B (antimicrofilamentous agent) has been used to investigate the possible role played by the cytoskeleton in the maintenance of intracellular distribution of yolk droplets, lipid bodies, and Golgi apparatus of the chick neuroepithelial cells. On the one hand, embryos treated with colchicine showed modifications in their distribution patterns of yolk droplets and lipid bodies, which suggests the involvement of the microtubular integrity of neuroepithelial cells in the maintenance of normal distribution patterns. On the other hand, the close relationships between vitelline and lipid inclusions and Golgi apparatus observed in untreated embryos seems to be kept in the embryos treated with colchicine and cytochalasin B. Moreover, from the effects of colchicine on Golgi apparatus position a possible functional role for the microtubular system in the maintenance of Golgi apparatus polarity in the chick neuroepithelial cells can be proposed. The results provided here constitute new information about the cellular mechanisms involved in chick neurulation.

Animals↗
PubMed2000

The Golgi apparatus segregates from the lysosomal/acrosomal vesicle during rhesus spermiogenesis: structural alterations.

The acrosome is an acidic secretory vesicle containing hydrolytic enzymes that are involved in the sperm's passage across the zona pellucida. Imaging of the acrosomal vesicle and the Golgi apparatus in live rhesus monkey spermatids was accomplished by using the vital fluorescent probe LysoTracker DND-26. Concurrently, the dynamics of living spermatid mitochondria was visualized using the specific probe MitoTracker CMTRos and LysoTracker DND-26 detected the acrosomal vesicle from its formation through spermatid differentiation. LysoTracker DND-26 also labeled the Golgi apparatus in spermatogenic cells. In spermatocytes the Golgi is spherical and, in round spermatids, it is localized over the acrosomal vesicle, as confirmed by using polyclonal antibodies against Golgin-95/GM130, Golgin-97, and Golgin-160. Using both live LysoTracker DND-26 imaging and Golgi antibodies, we found that the Golgi apparatus is cast off from the acrosomal vesicle and migrates toward the sperm tail in elongated spermatids. The Golgi is discarded in the cytoplasmic droplet and is undetectable in mature ejaculated spermatozoa. The combined utilization of three vital fluorescent probes (Hoechst 33342, LysoTracker DND-26, and MitoTracker CMTRos) permits the dynamic imaging of four organelles during primate spermiogenesis: the nucleus, the mitochondria, the acrosomal vesicle, and the Golgi apparatus.

Acrosin↗
PubMed1998

Expression of RNUDC, a potential nuclear movement protein, in mammalian cells: localization to the Golgi apparatus.

Prolactin and other cytokines regulate lymphocyte proliferation through the activation of a number of genes, one of which was identified as RnudC from a prolactin-dependent rat T cell line, Nb2. RnudC encodes a 45-kDa protein whose carboxy terminal 94 amino acids are similar to the carboxy terminus of the Aspergillus nidulans nuclear movement protein NUDC. In Nb2 T cells, RNUDC protein levels are induced two- to threefold by prolactin stimulation. This prolactin-inducible increase in RNUDC protein levels is due in part to an increase in RNUDC protein synthesis between 8 and 12 h, during the G1/S transition. Newly synthesized RNUDC protein is very stable, exhibiting a half-life of greater than 8 h. RNUDC has also been identified in many different cell types and species, ranging from fibroblasts to neuronal cells and from mouse to human, suggesting a highly conserved function. Immunocytochemical studies, using affinity-purified rabbit anti-rat RNUDC antibodies, have localized a significant fraction of the RNUDC protein to the region of the Golgi apparatus in interphase rat Nb2 T cells, monkey kidney fibroblast COS-1 cells, and human 2AG10 adenocarcinoma cells. Treatment of 2AG10 cells with the microtubule-depolymerizing drug nocodazole, which causes dispersion of the Golgi apparatus, led to a diffuse pattern of RNUDC staining. Removal of nocodazole, which allowed the reformation of the Golgi apparatus, led to the reconcentration of RNUDC staining to the Golgi region. Taken together, these studies suggest that a fraction of RNUDC is tightly associated with the Golgi apparatus in many different mammalian cell types.

Animals↗
PubMed1993

Features of the polarity of the Golgi apparatus of frog photoreceptors: studies with lectins and with Brefeldin A.

The cis-trans polarity of the Golgi apparatus is important in Golgi functioning in glycosylation, sorting and other processes. The present work extends our prior studies on the polarity of the Golgi apparatus of frog (Rana) rod photoreceptors. We demonstrate that Golgi structures with the morphology and distribution of cis elements show the heaviest deposition of osmium. Elements with morphology and cytochemical reactivities resembling trans Golgi structures remain discernible as discrete arrays after exposure of the cells to Brefeldin A. These properties strengthen our identification of cis and trans elements since they are shared with corresponding Golgi structures in other cell types. We have also investigated the binding of lectins to sections prepared by cryoultramicrotomy. We find that Concanavalin A, with probable chief affinity for core mannoses in oligosaccharides, localizes to cis, medial and trans elements of the photoreceptor's Golgi apparatus. Wheat germ agglutinin, with likely affinity at least partly for terminal N-acetylglucosamines, localizes to trans and medial elements. A trans localization is seen with Ricinus communis agglutinin (RCA 120), but this lectin binds extensively only after neuraminidase treatments suggesting that its chief affinity is for galactose residues that are penultimate to sialic acids (neuraminic acids) in the native oligosaccharides. Overall, the pattern of lectin binding to Golgi structures that we observe resembles that seen in a variety of other cell types. The distribution of glycosylated molecules we detect in the photoreceptor's Golgi apparatus may bear upon such matters as the unusual features of the glycosylation of mature opsin.

Animals↗
PubMed1999

Three-dimensional visualization of the Golgi apparatus: observation of Brunner's gland cells by a confocal laser scanning microscope.

The three-dimensional structure of the Golgi apparatus in cells of the Brunner's gland in the mouse was observed by using a confocal laser scanning microscope. Two lectins, FITC-labeled soybean agglutinin and Texas red-labeled Griffonia simplicifolia agglutinin II, were used to visualize the whole Golgi apparatus. Staining with the former lectin, which has been known to label the cis-stacks, showed a lacy dome-like structure situated in the supranuclear region. Staining with the latter lectin, known to label the intermediate-to-trans-stacks and the secretory granules, showed a dome-like structure consisting of network and cobblestone-like patterns in the same region and also granular stainings near the surface of the cobblestone-like patterns and the apical region of a cell. Double-staining demonstrated that the soybean agglutinin-labeled network always surrounded the G. simplicifolia agglutinin II-stained structure. Based on these observations, we propose a new three-dimensional model of the Golgi apparatus: it forms a dome-like structure over a nucleus, a network of cis-stacks forms its outer boundary, and this outer boundary is lined and paved with successive intermediate and trans-stacks. It is thought that secretory granules are released toward the internal space of the Golgi apparatus and transported to the apical cytoplasm through the holes of the network.

Agglutinins↗
PubMed1990

The presence of a juxtaglomerular apparatus in elasmobranch fish.

UNLABELLED: Previous studies have concluded that a juxtaglomerular apparatus evolved in phylogenetic groups "higher" than elasmobranch fishes. The present study shows for the first time a distinct juxtaglomerular apparatus in four marine elasmobranchs, the spiny dogfish Squalus acanthias), the smooth dogfish (Mustelus canis), the little skate (Raja erinacea), and the cownose ray (Rhinoptera bonasus). Serial semithin sections of these fishes' kidneys reveal the four morphological components of a juxtaglomerular apparatus at the vascular pole of the renal corpuscle: (1) an afferent arteriole surrounded by smooth muscle cells which have granules containing a material exhibiting a periodic substructure comparable to that of renin granules in higher vertebrates; (2) an efferent arteriole usually devoid of smooth muscle cells but having pericyte-like cells; (3) a macula densa portion of the distal tubule juxtaposed between the afferent and efferent arterioles; and (4) elongated, fusiform cells (Goormaghtigh cells), which are in continuity with similar cells of the abundant intra-glomerular mesangium, and fill the space bordered by the distal tubule and by the afferent and efferent vessels. The distal tubule, from the site where it lies close to the afferent arteriole, moves directly toward the urinary pole, frequently indenting the renal corpuscle. Within this indentation, the tubule may be flanked by the efferent vessel, by the extraglomerular mesangium, or by Bowman's capsule only. Facing these structures the tubular epithelial cells possess basally dilated intercellular spaces. Endothelial cells of the efferent vessel(s) are fenestrated, possessing pores which are closed by a diaphragm. CONCLUSION: marine elasmobranch fish possess the morphological components of a juxtaglomerular apparatus which suggests that these fishes, like most other vertebrates, possess a renin-angiotensin system and a glomerular-tubular feedback mechanism.

Animals↗
PubMed1981

A quantitative study of the position of the Golgi apparatus in the early developing chick eye.

A quantitative evaluation of the positional changes of the Golgi apparatus during the invagination of the lens placode and the presumptive neural retina of the chick embryo was carried out by silver impregnation. The Golgi apparatus is predominantly polarized in the apical process of the elongated interphasic cells; however, basal and lateral positions are also present. When the nuclei are located close to the luminal surface, basal and lateral positions increase significantly showing that a loss of Golgi apparatus polarization takes place, associated with the mitotic cycle. At the beginning of the invagination of lens and neural retina rudiments, a marked shift in orientation occurs between lateral and apical positions of the Golgi apparatus; this is associated with the nuclei located close to the luminal surface. The possible significance of these results is related to some processes concerning the invagination of these rudiments, such as interkinetic nuclear migration and secretion of extracellular materials.

Animals↗
PubMed1975

The structure of the human juxtaglomerular apparatus. A morphometric, lightmicroscopic study on serial sections.

49 juxtaglomerular apparatuses were examined using 1.9mu thick Giemsa-stained serial sections from human renal tissue embedded in plexiglass. In 43 juxtaglomerular apparatus the direct contact areas between the different juxtaglomerular structures and the basal area of the macula densa were calculated. A positive, significant correlation was found between the size of the macula densa and the direct contact area between macula densa and Goormaghtigh's cell field on the one hand, and between the macula densa and the direct contact area between Goormaghtigh's cell field and the afferent arteriole on the other. There was also a significant, positive correlation between the direct contact area of Goormaghtigh's cell field with the macula densa and that of Goormaghtigh's cell field with the afferent arteriole. On the efferent side none of these correlations were significant. Thus a "flow of information" from the macula densa via the Goormaghtigh cells to the afferent arteriole is morphologically possible. The direct contact areas between macula densa and the afferent or the efferent arterioles were not correlated with any of the other parameters. Epithelioid cells were present in the interlobular arteries, prior to and within the juxtaglomerular apparatus in the afferent arterioles, as well as within and beyond the juxtaglomerular apparatus in the efferent arterioles.

Adult↗
PubMed2003

Juxtaglomerular apparatus T-cell infiltration affects glomerular structure in Type 1 diabetic patients.

AIMS/HYPOTHESIS: Type 1 diabetes is an autoimmune disorder associated with T-cell mediated injury to multiple endocrine tissues. T-cell infiltration of the juxtaglomerular apparatus could be associated with changes in local renin angiotensin system activity and, thus, with changes in the renal microenvironment. We examined the frequency of juxtaglomerular apparatus T-cell infiltration early in Type 1 diabetes and tested whether this is associated with renal structure and function. METHODS: We classified 89 Type 1 diabetic patients by immunohistochemical analysis as either juxtaglomerular apparatus T-cell positive ( n=37) or T-cell negative ( n=38). Borderline cases ( n=14) were not considered further. RESULTS: T-cell positive patients had a shorter duration of diabetes (6.7+/-2.5 years) than T-cell negative patients (9.2+/-5.0 years, p=0.011) and lower albumin excretion rate, but they had a similar glomerular filtration rate and blood pressure. Renal biopsy morphometric analysis showed similar glomerular basement membrane width and mesangial fractional volume in these two groups. However, glomerular capillary surface density ( p=0.0012) and filtration surface per glomerulus ( p=0.0155) were greater in the T-cell positive patients. CONCLUSION/INTERPRETATION: Increased filtration surface per glomerulus could be associated with glomerular filtration rate preservation in diabetes. Thus, juxtaglomerular apparatus immunologic injury in Type 1 diabetes patients could delay the clinical consequences of diabetic nephropathy.

Adolescent↗
PubMed2001

The Golgi apparatus of goblet cells in the mouse descending colon: three-dimensional visualization using a confocal laser scanning microscope.

The three-dimensional structure of the Golgi apparatus was studied in goblet cells in lectin-stained sections of the mouse descending colon by using a confocal laser scanning microscope. In the lower part of the crypt, the Golgi apparatus formed a dome- or globe-like structure in the supranuclear region. The wall of the dome had some holes, one of which usually faced toward the nucleus and others toward the apical cytoplasm. Mucous granules seemed to be initially released into the interior of the dome and transported toward the apical cytoplasm through the holes. In the upper part of the crypt, on the other hand, the Golgi apparatus formed a cup- or funnel-like structure with a larger opening toward the cell apex and a smaller opening toward the nucleus. A large mass of mucous granules occupied the inside of the cup to the apical cytoplasm. It is thought that the accumulation of mucous granules enlarges holes at the ceiling of the dome to form a large opening, which makes the configuration of the Golgi apparatus cup-shaped.

Animals↗
PubMed2002

The assembly of hepatic very low density lipoproteins: evidence of a role for the Golgi apparatus.

Previous studies from our laboratory have suggested that the assembly of lipoproteins by the liver is not completed in the rough endoplasmic reticulum but continues while the particles are en route to or within the Golgi apparatus. To investigate further the role of the Golgi apparatus in lipoprotein assembly, mice were injected with [3H]glycerol and killed 7.5 to 45 min after injection. Microsomes and Golgi apparatus-rich fractions were isolated from the livers and separated into membrane and content fractions. TG within microsomal and Golgi membranes were labeled, rapidly reaching peak specific activity within 7.5 min of isotope injection. The specific activity of TG in microsomal membranes decreased to approximately 40% of peak values by 45 min, whereas the specific activity of TG in the Golgi membranes decreased to approximately 30% of peak values by 45 min. To determine whether the turnover of the Golgi membrane TG pool was dependent on microsomal TG transfer protein (MTP), mice were gavaged with an MTP inhibitor, and the labeling experiments were repeated. Inhibition of MTP attenuated the turnover of newly synthesized Golgi membrane TG by approximately 50% and the turnover of microsomal membrane TG by approximately 40%. Based on the rapid turnover of the Golgi membrane TG pool and the attenuation of the turnover of this pool by MTP inhibitor, we propose that lipid is transferred from the Golgi membrane to luminal lipoproteins in an MTP-dependent manner. The results support our hypothesis that assembly of VLDL continues within the Golgi apparatus.

Animals↗
PubMed1992

Distribution of ADPase activity in the lactating rat mammary gland and its possible role in an ATP cycle in the Golgi apparatus.

A Ca2+/Mg(2+)-stimulated ADPase has been found to occur in the lactating rat mammary gland. The enzyme is membrane associated and occurs in mitochondrial, microsomal, and Golgi apparatus fractions. The pH activity curves for the Golgi apparatus and microsomal fractions display two distinct maxima, one at pH 6.3 and one at pH 7.4. Studies with inhibitors and activators indicate that the enzyme is similar to ADPases found in other tissues and is distinct from the uridine nucleoside diphosphatase previously reported in the mammary Golgi apparatus. The occurrence of ADPase in the Golgi apparatus indicates a possible role for this enzyme in the milk secretory process, while the microsomal enzyme could be involved in extracellular activities.

Adenosine Triphosphate↗
PubMed1994

Cell-free transfer of phospholipids between the endoplasmic reticulum and the Golgi apparatus of leek seedlings.

The transfer of lipids between the endoplasmic reticulum and the Golgi apparatus was investigated in vitro using a cell-free system from leek seedlings. Lipids of the donor membranes (endoplasmic reticulum) were radiolabeled either by incubating leek seedlings with [1-14C]acetate or [3H]acetate. Acceptor membranes (Golgi apparatus) were unlabeled and immobilized on nitrocellulose strips. The assay measured the lipid transfer resulting from both an ATP-independent process and an ATP- and cytosol-dependent process. A significant ATP- and cytosol-dependent lipid transfer was observed only in the case of the endoplasmic reticulum as donor and the Golgi apparatus as acceptor. Lipids transferred in an ATP-dependent manner were chiefly phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. The stimulation of lipid transfer by ATP as compared to the ATP-independent process was +79% (PC), +123% (PS) and +69% (PE). On the other hand, PI was not transferred in an ATP-dependent manner (the stimulation by ATP was only 20%). This supports the theory that a sorting of phospholipids takes place in the donor membrane. Moreover, a formation of lysoPC was observed only in the presence of ATP (+330%). The ATP-dependent lipid transfer was inhibited by N-ethylmaleimide, indicating the involvement of cytosolic (but no phospholipid transfer proteins) or membrane proteins in the transfer process. The ATP-dependent transfer of lipids was also diminished at 12 degrees C showing the sensitivity to low temperatures of the transfer of lipids between the endoplasmic reticulum and the Golgi apparatus.

Adenosine Triphosphate↗
PubMed1994

Acyl transfer reactions associated with cis Golgi apparatus of rat liver.

Isolated Golgi apparatus, highly purified from rat liver, were found to contain an acyl transfer activity capable of restoring the acyl chains of the lysophospholipid products of the action of phospholipase A2 on phosphatidylcholine. The activity was located primarily in cis and medial Golgi apparatus fractions, had a pH optimum of 6.0 to 7.5 and was stimulated by various acyl-CoA derivatives but not by fatty acids plus ATP. The activity, determined from the conversion of [14C]lysophosphatidylcholine to [14C]phosphatidylcholine, was unaffected by EGTA, inhibited by manoalide at high concentrations (0.2 mM), and temperature-dependent. Temperature dependency, however, showed no definite transition temperature over the range 15 to 37 degrees C. The results demonstrated that cis Golgi apparatus membranes have the enzymatic capacity to restore fatty acids lost from phospholipids through the action of phospholipase A. The latter has been previously suggested to occur at the cis Golgi apparatus membranes based on analyses of cell-free transfer of radiolabeled phosphatidylcholine.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1989

Swelling of the Golgi apparatus and decrease of galactosyltransferase in polyamine-deficient bovine lymphocytes and epithelium of mouse small intestine.

When bovine small lymphocytes stimulated by concanavalin A were treated with inhibitors (alpha-difluoromethylornithine (5 mM) and ethylglyoxal bis(guanylhydrazone) (100 microM)] of polyamine biosynthesis, swelling of the Golgi apparatus was observed. This was accompanied by decreases in the amount of the Golgi apparatus and of the specific activity of galactosyltransferase. Both spermidine and spermine, at physiological concentrations, stimulated galactosyltransferase activity 2-3-fold. When mice were treated with these inhibitors, the following changes were observed in the epithelial cells of small intestine: swelling of the Golgi apparatus; decrease in the amount of the Golgi apparatus; and decrease of galactosyltransferase activity.

Animals↗
PubMed1986

Is the Golgi apparatus the obligatory final step for lipoprotein secretion by intestinal cells?

It is currently admitted that the synthesis and excretion of triglyceride-rich lipoproteins (chylomicrons and 'small chylomicrons') by intestinal epithelial cells involves the Golgi apparatus as an obligatory final step before exocytosis. The cells of the proximal intestine of the trout are an excellent model for investigating functional compartmentalization in the course of lipid absorption. Using this model, our data invalidate morphological data which were the basis for considering the Golgi apparatus as the mandatory final stage for their secretion. In particular, we show that triglyceride-rich particles can be transported directly from the endoplasmic reticulum to the intercellular space. Two pathways of intestinal lipoprotein excretion appear to coexist. One follows the classical export route, the second functions in a manner that bypasses the Golgi apparatus. The arguments used to affirm the requirement for the Golgi apparatus as a final step (glycosylation of apoprotein B, membrane vehicle for exocytosis) are discussed.

Animals↗