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J W Slot

Publications and source records attributed to J W Slot.

At least 37 records · Page 2Linked to original sources
PubMed1997

The autophagic and endocytic pathways converge at the nascent autophagic vacuoles.

We used an improved cryosectioning technique in combination with immunogold cytochemistry and morphometric analysis to study the convergence of the autophagic and endocytic pathways in isolated rat hepatocytes. The endocytic pathway was traced by continuous uptake of gold tracer for various time periods, up to 45 min, while the cells were incubated in serum-free medium to induce autophagy. Endocytic structures involved in fusion with autophagic vacuoles (AV) were categorized into multivesicular endosomes (MVE) and vesicular endosomes (VE). Three types of AV--initial (AVi), intermediate (AVi/d), and degradative (AVd)--were defined by morphological criteria and immunogold labeling characteristics of marker enzymes. The entry of tracer into AV, manifested as either tracer-containing AV profiles (AV+) or fusion profiles (FP+) between AV and tracer-positive endosomal vesicles/vacuoles, was detected as early as 10 min after endocytosis. The number of AV+ exhibited an exponential increase with time. FP+ between MVE or VE and all three types of AV were observed. Among the 112 FP+ scored, 36% involved VE. Of the AV types, AVi and AVi/d were found five to six times more likely to be involved in fusions than AVd. These fusion patterns did not significantly change during the period of endocytosis (15-45 min). We conclude that the autophagic and endocytic pathways converge in a multistage fashion starting within 10 min of endocytosis. The nascent AV is the most upstream and preferred fusion partner for endosomes.

Animals↗
PubMed1997

The glucose transporter GLUT4 and the aminopeptidase vp165 colocalise in tubulo-vesicular elements in adipocytes and cardiomyocytes.

The aminopeptidase vp165 is one of the major polypeptides enriched in GLUT4-containing vesicles immuno-isolated from adipocytes. In the present study we have confirmed and quantified the high degree of colocalisation between GLUT4 and vp165 using double label immuno-electron microscopy on vesicles isolated from adipocytes and heart. The percentage of vp165-containing vesicles that also contained GLUT4 was 91%, 76%, and 86% in rat adipocytes, 3T3-L1 adipocytes, and rat heart, respectively. Internalisation of a transferrin/HRP (Tf/HRP) conjugate by 3T3-L1 adipocytes, followed by diaminobenzidine treatment in intact cells, resulted in ablation of only 41% and 45% of GLUT4 and vp165, respectively, whereas endosomal markers are almost quantitatively ablated. Using immuno-electron microscopy on cryosections it was determined that in atrial cardiomyocytes GLUT4 and vp165 colocalised in a population of tubulo-vesicular (T-V) elements that were often found close to the plasma membrane. Double label immunocytochemistry indicated a high degree of overlap in these T-V elements between GLUT4 and vp165. However, in atrial cardiomyocytes a large proportion of GLUT4 was also present in secretory granules containing atrial natriuretic factor (ANF). In contrast, very little vp165 was detected in ANF granules. These data indicate that GLUT4 and vp165 are colocalised in an intracellular, post-endocytic, tubulo-vesicular compartment in adipocytes and cardiomyocytes suggesting that both proteins are sorted in a similar manner in these cells. However, GLUT4 but not vp165 is additionally localised in the regulated secretory pathway in atrial cardiomyocytes.

3T3 Cells↗
PubMed1996

Improving structural integrity of cryosections for immunogold labeling.

Cryosections of aldehyde-fixed material prepared according to Tokuyasu are a good substrate for immunocytochemistry. However, structural defects occur that limit the resolution of this approach. We found that the step during which sections are thawed and transferred from the cryochamber to the supporting film on an EM grid is most critical for structural preservation. Surface tension of the transfer medium, on which sections are spread during thawing, can easily damage their structure by overstretching. By substituting a mixture of methylcellulose and sucrose for the conventional sucrose transfer medium, we were able to alleviate the problem of overstretching, thus improving greatly the structural integrity of thin cryosections. Also, material extraction from the sections after thawing causes structural damage, particularly when cross-linking is deficient. Incorporation of uranyl acetate in the transfer medium can then further help to maintain the structural integrity of the sections during the immunolabeling procedure. Excellent ultrastructure was featured in sections picked up and dried directly in methylcellulose/uranyl acetate mixtures. Such preparations can provide new insight into subcellular details and is an efficient back-up for immunolabeled sections in respect of their morphology. Cryosections from fresh frozen tissue can be preserved for immunolabeling by using transfer media that contain fixatives. This approach may have advantages if chemical fixation of tissue is thought to induce morphological artifacts or antigen redistribution.

Animals↗
PubMed1996

The biogenesis of the MHC class II compartment in human I-cell disease B lymphoblasts.

The localization and intracellular transport of major histocompatibility complex (MHC) class II molecules nd lysosomal hydrolases were studied in I-Cell Disease (ICD) B lymphoblasts, which possess a mannose 6-phosphate (Man-6-P)-independent targeting pathway for lysosomal enzymes. In the trans-Golgi network (TGN), MHC class II-invariant chain complexes colocalized with the lysosomal hydrolase cathepsin D in buds and vesicles that lacked markers of clathrin-coated vesicle-mediated transport. These vesicles fused with the endocytic pathway leading to the formation of "early" MHC class II-rich compartments (MIICs). Similar structures were observed in the TGN of normal beta lymphoblasts although they were less abundant. Metabolic labeling and subcellular fractionation experiments indicated that newly synthesized cathepsin D and MHC class II-invariant chain complexes enter a non-clathrin-coated vesicular structure after their passage through the TGN and segregation from the secretory pathway. These vesicles were also devoid of the cation-dependent mannose 6-phosphate (Man-6-P) receptor, a marker of early and late endosomes. These findings suggest that in ICD B lymphoblasts the majority of MHC class II molecules are transported directly from the TGN to "early" MIICs and that acid hydrolases cam be incorporated into MIICs simultaneously by a Man-6-P-independant process.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1996

The glucose transporter (GLUT-4) and vesicle-associated membrane protein-2 (VAMP-2) are segregated from recycling endosomes in insulin-sensitive cells.

Insulin stimulates glucose transport in adipocytes by translocation of the glucose transporter (GLUT-4) from an intracellular site to the cell surface. We have characterized different synaptobrevin/vesicle-associated membrane protein (VAMP) homologues in adipocytes and studied their intracellular distribution with respect to GLUT-4. VAMP-1, VAMP-2, and cellubrevin cDNAs were isolated from a 3T3-L1 adipocyte expression library. VAMP-2 and cellubrevin were: (a) the most abundant isoforms in adipocytes, (b) detectable in all insulin responsive tissues, (c) translocated to the cell surface in response to insulin, and (d) found in immunoadsorbed GLUT-4 vesicles. To further define their intracellular distribution, 3T3-L1 adipocytes were incubated with a transferrin/HRP conjugate (Tf/HRP) and endosomes ablated following addition of DAB and H2O2. While this resulted in ablation of > 90% of the transferrin receptor (TfR) and cellubrevin found in intracellular membranes, 60% of GLUT-4 and 90% of VAMP-2 was not ablated. Immuno-EM on intracellular vesicles from adipocytes revealed that VAMP-2 was colocalized with GLUT-4, whereas only partial colocalization was observed between GLUT-4 and cellubrevin. These studies show that two different v-SNAREs, cellubrevin and VAMP-2, are partially segregated in different intracellular compartments in adipocytes, implying that they may define separate classes of secretory vesicles in these cells. We conclude that a proportion of GLUT-4 is found in recycling endosomes in nonstimulated adipocytes together with cellubrevin and the transferrin receptor. In addition, GLUT-4 and VAMP-2 are selectively enriched in a postendocytic compartment. Further study is required to elucidate the function of this latter compartment in insulin-responsive cells.

3T3 Cells↗
PubMed1996

Differential targeting of facilitative glucose transporters in polarized epithelial cells.

We have examined the intracellular localization of five facilitative glucose transporter proteins, one endogenous (GLUT-1) and four exogenous (GLUT-2, -3, -4, and -5), in polarized epithelial cells. GLUT-2, -3, -4, and -5 were stably transfected into Madin-Darby canine kidney (MDCK) cells, and peptide-specific antibodies were used to establish their distribution by immunofluorescence and immunoelectron-microscopic techniques. GLUT-1 and -2 were predominantly targeted to the basolateral domain of the cell, whereas GLUT-3 and -5 were targeted to the apical plasma membrane. The insulin-regulatable glucose transporter GLUT-4 was found in intracellular tubulovesicular structures beneath the surface of the cell. Vectorial 2-deoxy-D-glucose uptake measurements revealed that approximately 95% of glucose entry into wild-type MDCK cells occurs via the basolateral membranes. In GLUT-3-transfected cells, however, apical glucose uptake increased to approximately 55%; this was not observed in cells expressing the other GLUT isoforms. The discrete and differential intracellular localizations of the various GLUTs, in addition to the high level of sequence homology and predicted secondary structure similarity, render the GLUT family ideal for the study of intrinsic targeting motifs involved in the establishment and maintenance of cellular polarity.

Amino Acid Sequence↗
PubMed1995

Ultrastructural and immunocytochemical characterization of autophagic vacuoles in isolated hepatocytes: effects of vinblastine and asparagine on vacuole distributions.

The interactions between the autophagic and the endocytic degradation pathways were investigated by means of immunogold labeling of autophagic vacuoles (AVs) in ultrathin frozen sections from isolated rat hepatocytes. AVs were identified by their autophagocytosed contents of the degradation-resistant cytosolic enzyme CuZn-superoxide dismutase (SOD). Another cytosolic enzyme, carbonic anhydrase (CAIII), was rapidly degraded in the lysosomes, making the vacuolar CAIII/SOD ratio useful as a rough indicator of the progress of autophagic-lysosomal degradation. Lysosomes could be recognized by the presence of the lysosomal membrane glycoprotein lgp120, which was absent from hepatocytic endosomes. Endocytic inputs into the AVs were detected by the presence of gold-conjugated bovine serum albumin (BSA-gold), taken up by fluid-phase endocytosis. All vacuoles recognized morphologically as AVs were SOD-positive, as were essentially all of the lysosomes (96%). The majority (72%) of the lysosomes also labeled positively for BSA within 2 h of endocytosis. The data are thus compatible with the notion that all lysosomes can engage in both autophagic and endocytic degradation. Lgp120 appeared to distinguish well between lysosomes and nonlysosomal AVs: the lgp120-negative AVs (nonlysosomes) had a CAIII/SOD ratio identical to that of the cytosol, indicating that no degradation had occurred. In the lgp120-positive AVs (lysosomes), the ratio was only 43% of the cytosolic value, consistent with substantial CAIII degradation. Among the nonlysosomal AVs (about one-third of all AVs), one-half were BSA-positive, suggesting that early AVs (autophagosomes) and suggesting that early AVs (autophagosomes) and intermediary AVs (amphisomes) that had fused with endosomes were equally abundant. These morphological data thus support previous biochemical evidence for a prelysosomal meeting of the autophagic and endocytic pathways. The microtubule inhibitor vinblastine inhibited the autophagic influx to the lysosomes, causing an accumulation of autophagosomes and a reduction in average lysosomal size. Vinblastine also inhibited the endocytic flux, thereby precluding the formation of amphisomes and of BSA-positive lysosomes. High concentrations (20 mM) of asparagine induced swelling of amphisomes and of BSA-positive lysosomes, probably reflecting an acidotropic effect of ammonia generated by asparagine deamination. Asparagine also caused an accumulation of autophagosomes, amphisomes, and BSA-negative lysosomes, presumably as a result of impaired fusion with the swollen BSA-positive lysosomes. The two agents thus appear to perturb the autophagic-endocytic-lysosomal vacuole dynamics by different mechanisms, making them useful in the further study of these complex organelle interactions.

Animals↗
PubMed1995

Reassessment of the subcellular localization of p63.

p63 is a type II integral membrane protein that has previously been suggested to be a resident protein of a membrane network interposed between the ER and the Golgi apparatus. In the present study, we have produced a polyclonal antibody against the purified human p63 protein to reassess the subcellular distribution of p63 by confocal immunofluorescence, immunoelectron microscopy, and cell fractionation. Double immunofluorescence of COS cells showed significant colocalization of p63 and a KDEL-containing lumenal ER marker protein, except for differences in the staining of the outer nuclear membrane. Immunoelectron microscopy of native HepG2 cells and of COS cells transfected with p63 revealed that both endogenous and overexpressed p63 are predominantly localized in the rough ER. While p63 was colocalized with protein disulfide isomerase, an ER marker protein, very little overlap of p63 was found with ERGIC-53, an established marker for the ER-Golgi intermediate compartment. When rough and smooth membranes were prepared from rat liver, p63 was found to copurify with ribophorin II, a rough ER protein. Both p63 and ribophorin II were predominantly recovered in rough microsomes and were largely separated from the intermediate compartment marker protein p58. From these results it is concluded that p63 is localized in the rough ER.

Amino Acid Sequence↗
PubMed1995

Immunocytochemical localization of the sites of superoxide dismutase induction by hyperoxia in rat lungs.

BACKGROUND: Rats exposed to 85% O2 can survive subsequent exposures to 100% O2. The development of this tolerance to oxygen toxicity is associated with an increase in total pulmonary content of both CuZn and Mn superoxide dismutases (SOD). It is not known, however, in which cells increases in these antioxidant enzymes occur. We carried out an electron microscopic immunocytochemical study to define the distribution of CuZnSOD and MnSOD and their sites of induction in rat lungs. EXPERIMENTAL DESIGN: The lungs of rats exposed to either air or 85% O2 were fixed by instillation of fixative 7 and 14 days after the exposures were started. Cryoultrathin sections were prepared from randomly selected, frozen tissue blocks and were immunolabeled for either CuZnSOD or MnSOD. The labeling densities of the two enzymes in the major alveolar parenchymal cells (type I and type II epithelial cells, interstitial fibroblasts, and endothelial cells), were evaluated. RESULTS: All of the alveolar septal cells studied displayed similar concentrations of CuZnSOD. After 7 or 14 days of exposure to 85% O2, the total lung content of CuZnSOD was increased because of cell hyperplasia and hypertrophy, but the intracellular concentrations of CuZnSOD did not increase. MnSOD was present in the mitochondria of all lung cells in control rat lungs but was highest in alveolar type II epithelial cells. Exposure to 85% O2 increased the concentration of MnSOD in the mitochondria of interstitial fibroblasts by 197 and 139% after O2 exposure of 7 days and 14 days, respectively. A significant induction of MnSOD also occurred in the mitochondria of alveolar type II cells after 7 days of hyperoxia exposure. Biochemical analyses showed that a significant fraction of the hyperoxia-induced MnSOD was in the form of an enzymatically inactive protein. CONCLUSIONS: Hyperoxia induced total lung CuZnSOD in proportion to lung cell hypertrophy and hyperplasia. Total lung MnSOD was increased in association with specific inductions of MnSOD protein expression in the mitochondria of type II alveolar epithelial cells and interstitial fibroblasts. Hyperoxia appeared to result in inactivation and accumulation of the inactive MnSOD as well as induction of enzymatically active MnSOD. The ability of fibroblasts and alveolar type II cells to replace inactive MnSOD or to augment active MnSOD in the mitochondria appears to play important roles in the development of tolerance to hyperoxia by rats.

Animals↗
PubMed1994

Ultrastructural localization of CTP:phosphoethanolamine cytidylyltransferase in rat liver.

CTP:phosphoethanolamine cytidylyltransferase (EC 2.7.7.14) (ethanolamine-phosphate cytidylyltransferase, ET) was recently purified to homogeneity from a post-microsomal supernatant of rat liver and subsequently used to raise a polyclonal antibody against the enzyme in rabbits (Vermeulen, P. S., Tijburg, L. B. M., Geelen, M. J. H., and van Golde, L. M. G. (1993) J. Biol. Chem 268, 7458-7464). In the present study, we used the affinity-purified antibody against ET for ultrastructural immunogold labeling studies on rat liver cryosections. Single-label experiments clearly demonstrated that ET label was not randomly distributed in hepatocytes. The ET label was concentrated in areas that contained cisternae of the rough endoplasmic reticulum, whereas other cellular organelles (nuclei, mitochondria, and peroxisomes) were only marginally labeled for ET. Double-label experiments for ET and established markers for either soluble or integral endoplasmic reticulum proteins suggested a bimodal distribution of ET between the RER cisternae and the cytosolic space. Complementary single-label studies for ET and the soluble marker protein showed that the fraction of ET label that was present on RER cisternae was significantly greater than that of the soluble marker, supporting the idea of an uneven distribution. These immunoelectron microscopy studies strongly suggest that the cellular organization of ET differs considerably from that reported recently for the corresponding enzyme in the CDP-choline pathway, CTP:phosphocholine cytidylyltransferase (Wang, Y., Sweiter, T. D., Weinhold, P. A., and Kent, C. (1993) J. Biol. Chem. 268, 5899-5904).

Animals↗
PubMed1994

Expression of functional growth hormone receptor in a mouse L cell line infected with recombinant vaccinia virus.

The growth hormone receptor is a member of a large family of receptors including the receptors for prolactin and interleukins. Upon binding to one molecule of growth hormone two growth hormone receptor polypeptides dimerize. We have expressed the rabbit growth hormone receptor DNA in transfected mouse L cells infected with polymerase T7-producing vaccinia virus. The growth hormone receptor was synthesized as a 85-kDa protein and transported to the cell surface. Western blotting and metabolic labeling combined with immunoprecipitation using a rabbit antibody probably directed against the cytosolic domain of the receptor showed that its expression was dependent on both transfection of the growth hormone receptor DNA and vaccinia infection. Binding studies with 125I-labeled growth hormone demonstrated specific binding sites at the cell surface 20 h after transfection. Permeabilization with saponin showed that the growth hormone receptor binding sites were almost exclusively present at the cell surface with little intracellularly. Chemical crosslinking of the 125I-growth hormone complex resulted in a 180-kDa complex which could specifically be immunoprecipitated with the antiserum. Electron microscopic immunocytochemistry confirmed the presence of growth hormone receptor at the cell surface. Furthermore, specific growth hormone receptor antigen was also associated with intracellular membranes. These results thus show that this transient transfection system will be useful for cell biological studies of growth hormone receptor regulation.

Animals↗
PubMed1994

Insulin stimulation of GLUT-4 translocation: a model for regulated recycling.

Insulin stimulates glucose transport in muscle and fat cells by causing the redistribution of a facilitative glucose transporter, GLUT-4, from an intracellular compartment to the cell surface. But what is this intracellular GLUT-4 compartment? It may be a specialized compartment, perhaps analogous to synaptic vesicles, or may simply be part of the endosomal system. Other constituents of this compartment might be regulators of GLUT-4 movement to the cell surface, and their identification should make it possible to find the link between the insulin signal transduction pathway and GLUT-4 translocation.

Journal Article↗
PubMed1994

Quantitative immunocytochemical analysis of Mn SOD in alveolar type II cells of the hyperoxic rat.

We have analyzed the magnitude and uniformity of the expression of manganese superoxide dismutase (Mn SOD) protein in alveolar type II cells of rats exposed to hyperoxia using quantitative colloidal gold immunocytochemistry and morphometric techniques. Sprague-Dawley rats were exposed continuously to normal air or to 85% oxygen for 7 and 14 days. The lungs were fixed by intratracheal instillation of a paraformaldehyde-glutaraldehyde fixative. Lung samples were dehydrated in ethanol and embedded in LR-White. Thin sections for electron microscopy were labeled with anti-rat Mn SOD rabbit antiserum followed by protein-A gold. The labeling density (gold particles/micron 2) over subcellular compartments was determined, and relative organelle volumes were measured using a random point overlay. The results confirm that alveolar type II cells are a locus of Mn SOD response in the lungs of hyperoxic rats and contribute to this response through a combination of changes: an increase of Mn SOD concentration in the mitochondrial matrix, an increase of mitochondrial volume per cell, and type II cell hyperplasia.

Animals↗
PubMed1994

Cryosubstitution dehydration of aldehyde-fixed tissue: a favorable approach to quantitative immunocytochemistry.

Several tissue-processing procedures were studied for their applicability in quantitative immunoelectron microscopy (IEM). Three aspects were mainly considered: maintenance of the natural dimensions of cellular structures (no shrinkage), equal efficiency of immunolabeling throughout a specimen, and the possibility of non-interfering double labeling. These aspects were studied in a gelatin model system and in rat pancreatic tissue, which we subjected to different processing procedures. Some aldehyde-fixed specimens were kept hydrated and prepared for cryosectioning directly or after embedding in polyacrylamide (PAA). Other samples were dehydrated and embedded in different resins, i.e., Lowicryl HM20, LR Gold, or LR White. Dehydration was performed under conditions of cryosubstitution (CS) at -90 degrees C or progressive lowering of the temperature (PLT). We found that only CS dehydration followed by embedding at temperatures below -45 degrees C, which is compatible with Lowicryl HM20, gave satisfactory results in all three aspects investigated. We have previously introduced this procedure for IEM of glycolipids. Unlike in other non-aqueous embedding procedures, aldehyde-fixed material can be embedded via this CS-HM20 procedure without detectable shrinkage. The method also provides homogeneous labeling efficiency by equalizing the accessibility of antigens, irrespective of the original matrix in which they are packed. In this respect the CS-HM20 method equals the previously introduced but more bothersome PAA method. In addition, two-sided labeling of CS-HM20 sections allows double labeling without mutual hindrance of both immunoreactions, and these sections present a well-defined ultrastructure.

Acrylic Resins↗
PubMed1993

GLUT4 phosphorylation and inhibition of glucose transport by dibutyryl cAMP.

To investigate the mechanism responsible for the inhibition of glucose transport by dibutyryl cAMP (Bt2cAMP), two different transporter isoforms (GLUT1 and GLUT4) and several GLUT1/4 chimeric transporters were expressed in Chinese hamster ovary (CHO) cells by using a Sindbis virus expression system. Bt2cAMP inhibited GLUT4-mediated 2-deoxy[3H]glucose (2DOG) uptake by 50% but was without effect on GLUT1-mediated uptake. When the subcellular distribution of GLUT4 was assessed by quantitative immunocytochemistry, neither the overall concentration of GLUT4 nor the regional distribution of GLUT-4 within the plasma membrane was found to be altered by Bt2cAMP. Thus, inhibition of 2DOG uptake by Bt2cAMP appears to be due to a decrease in transporter activity rather than a decrease in the number of transporters exposed at the plasma membrane. By using chimeric transporters, a region of GLUT4 necessary for the inhibitory effect of Bt2cAMP was localized to the last 29 amino acids in the COOH terminus. This intracellular region contains the site (Ser488) phosphorylated in vitro by cAMP-dependent protein kinase (cAdPK). Changing Ser488 to an Ala abolished phosphorylation of GLUT4; however, the inhibitory effect of Bt2cAMP on glucose transport was not diminished by this mutation. Therefore, phosphorylation of GLUT4 was not required for the inhibition. The effects of other nucleotides on GLUT4 transport activity were assessed to investigate the role of cAdPK. Uptake of 2DOG by GLUT4 was inhibited by 8-bromo-AMP, but not by 8-bromo-cAMP, suggesting that the inhibitory effect did not involve activation of cAdPK. Results consistent with this interpretation were obtained with CHO cells (line 10248), which express a cAdPK that is resistant to activation by cAMP. No difference in the concentrations of Bt2cAMP required to inhibit GLUT4-mediated transport was observed in normal CHO cells and 10248 cells. The results presented suggest that the inhibitory effects of Bt2cAMP could be mediated by direct binding of a nucleotide to GLUT4 at a site involving the intracellular COOH terminus of the transporter.

Animals↗
PubMed1993

Distribution of CuZn superoxide dismutase in rat liver.

Morphological and cell fractionation approaches were used to establish unambiguously the distribution of CuZn superoxide dismutase (CuZn SOD) in rat hepatocytes. Immunocytochemical observations revealed a primarily cytoplasmic localization of the enzyme. While only trace amounts were found in cell organelles like mitochondria and peroxisomes, lysosomes were labelled stronger than the cytoplasm. The presence of CuZn SOD in lysosomes was also identified in cell fractions of normal and Triton WR-1339-treated rats. Microscopic studies showed that the distribution of CuZn SOD was not affected by Triton, but the Triton treatment induced an apparent increase in the number and size of lysosomes with electron lucent contents which corresponded with a shift of lysosomes to low buoyant density fractions. The majority of CuZn SOD originally present in the mixed mitochondrial-peroxisomal-lysosomal fractions of the normal liver comigrated with the main peak of the lysosomal marker, beta-hexosaminidase, after Triton treatment. The peroxisomal marker, catalase, did not migrate with the CuZn SOD/beta-hexosaminidase-rich fractions in livers from Triton-treated animals. These results confirm earlier observations in rat liver cells, showing that CuZn SOD, a primarily cytosolic enzyme, accumulates in lysosomes. It is not present in significant amounts in rat hepatocyte peroxisomes.

Animals↗
PubMed1993

The immunofluorescent era of membrane traffic.

In recent years immunofluorescence microscopy has been increasingly used to study membrane traffic. In this article seven electron microscopists, all with considerable experience in using light microscopy, take a critical look at the immunofluorescence approach and argue that results obtained with this method are often overinterpreted.

Journal Article↗