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J Thyberg

Publications and source records attributed to J Thyberg.

At least 127 records · Page 7Linked to original sources
PubMed1983

Spread of Balbiani ring derived messenger RNA in Chironomus salivary gland cell cytoplasm.

We have investigated whether Balbian ring derived mRNA (75S RNA) of Chironomus salivary glands spreads to the different parts of the cytoplasm before or after attachment to the rough endoplasmic reticulum. Glands were fixed after in vivo administration of tritiated uridine and cytidine and the appearance of labelled RNA fractions in microdissected cytoplasm was measured. We chose central cytoplasm rich in rough endoplasmic reticulum (endoplasm) and peripheral cytoplasm with a low content of reticulum (basal zone). A peripheral spread of the mRNA on reticulum membranes would have moved the labelled RNA outwards with time. We found, however, a redistribution in the opposite direction, suggesting that the mRNA spreads over the whole cytoplasm before it attaches to the reticulum membranes. A similar redistribution occurs for the ribosomal subunits.

Animals↗
PubMed1982

Fine structure of arterial smooth muscle cells cultured in the presence of whole blood serum or plasma-derived serum.

Normal diploid cells require serum to proliferate in culture. Platelet-derived growth factor has been identified as the main serum component responsible for this effect. Here, smooth muscle cells were isolated enzymatically from the aorta of 5-day-old rats and cultured in the presence of 10% whole blood serum (WBS) or plasma-derived serum (PDS), i.e. with or without platelet factor, and studied by transmission electron microscopy. The cells proliferated actively in WBS-medium but remained quiescent in PDS-medium. Fine structurally, cells from WBS-cultures demonstrated numerous mitochondria, an extensive rough endoplasmic reticulum (RER), a large Golgi complex, a few lysosomes, and microfilaments arranged in parallel bundles. After transfer to PDS-medium, the RER- and Golgi cisternae were markedly dilated and the number of membrane-associated ribosomes decreased. Segregation of fragments of cytoplasm within autophagosomes was frequently observed and the number of lysosomes increased. Lipid droplets were more abundant and often gathered in the Golgi area. Moreover, the cells had become more irregular in shape and showed many bleb-like processes at their surface. Microfilament bundles had also become more prominent and crossed each other in different directions. These observations show that the removal of platelet factor from the medium clearly modifies the fine structure of cultured smooth muscle cells. The findings are in good agreement with the concept that platelet factor not only supports the proliferation of cultured cells but also stimulates their secretory activity.

Adult↗
PubMed1982

Effects of nicotine on endocytosis and intracellular degradation of horseradish peroxidase in cultivated mouse peritoneal macrophages.

Thioglycollate-elicited mouse peritoneal macrophages were cultivated in vitro in control medium or medium containing nicotine (1 nM-1 microM). The drug caused a moderate lysosomal vacuolation and formation of vesicles with a dense core or ring. Furthermore, it partially inhibited uptake and intracellular degradation of horseradish peroxidase without affecting the specific activities of the lysosomal enzymes beta-glucuronidase and beta-N-acetylglucosaminidase in lysates of the cells. A slight inhibitory effect on the phagocytosis of latex beads was also noted. Since nicotine was used in concentrations of the same magnitude that may be obtained in the blood after smoking one cigarette, it seems worthwhile to further explore these findings in relation to the medical risks of smoking.

Animals↗
PubMed1982

Alkaline phosphodiesterase I of cultured mouse peritoneal macrophages. Distribution between cell surface and cytoplasm, turnover rate, and effects of colchicine.

Mouse peritoneal macrophages were cultivated in vitro and analyzed for activity of alkaline phosphodiesterase I. The specific enzyme activity was 2 to 3 times higher in thioglycollate-elicited than in resident cells and raised slowly for at least 3 days of culture in both cell types. Following phagocytosis of polystyrene latex beads the enzyme activity remained unchanged. About 90% of the activity was lost by treatment of the cells with the diazonium salt of sulfanilic acid (DASA) for 30 min at 37 degrees C. At 4 degrees C the corresponding degree of inactivation was only 40 to 50%. This temperature-dependent variation in the accessibility of the enzyme to inactivation by DASA could be related to the high rate of endocytosis in macrophages. During a 30 min incubation with DASA at 37 degrees C, large amounts of surface membrane will be internalized and replaced from the interior of the cell. Surface membrane is thus transferred into intracellular membrane and vice versa. Moreover, these membranes will be exposed to DASA independent of their location at the start of incubation. At 4 degrees C no comparable membrane traffic will take place. Treatment of the cells with cycloheximide at concentrations that inhibited protein synthesis by 90% or more left the enzyme activity essentially unaltered, indicating a slow turnover rate. On the basis of these findings, it is suggested that about half of the alkaline phosphodiesterase I activity of cultured macrophages is located in the plasma membrane. The other half is believed to be present in endocytic vesicles, lysosomes, and other as yet unidentified organelles that participate in the circulation of membrane constituents between the plasma membrane and the interior of the cell.

Animals↗
PubMed1981

Reversible changes in nuclear and cell surface topography in cells exposed to collagenase and EDTA.

Rabbit auricular chondrocytes, SIRC cells, human fibroblasts, and HeLa cells were cultivated in vitro and the fine structural effects of various detachment procedures studied. Treatment with collagenase, trypsin, and trypsin-EDTA caused scalloping of the nuclear envelope, accumulation of phagolysosomes, and an increase in the number of cell surface extensions. Collagenase-EDTA evoked a marked deformation of the nuclei with formation of numerous deep indentations and a redistribution of heterochromatin. Similarly, the cell surface became extensively folded and the vacuolation of the cytoplasm was further increased. These changes were reversible and within 24 h the cells had regained a normal structure. In all cases, chondrocytes and SIRC cells were most prominently affected, whereas fibroblasts and HeLa cells were only slightly changed. Treatment of chondrocytes with colchicine or cytochalasin B did not produce any effects of the type mentioned above. Neither did treatment with the drugs before and during detachment with collagenase-EDTA prevent the structural modification of the cells. It therefore seems unlikely that microtubules and microfilaments are essential for this process. The structural changes occurring during detachment of cells could represent an adoptive mechanism for disposal of excessive membrane in connection with transition from a flattened to a rounded shape.

Animals↗
PubMed1981

Elastin formation in heterotopic transplants of isolated arterial smooth muscle cells.

Smooth muscle cells were isolated from the aorta of 5 day old rats by collagenase digestion and injected intramuscularly into animals of the same strain, where the cells reconstituted an elastic tissue with many similarities to that found in the media of the intact aortic wall. The transplants consisted of partly aligned smooth muscle cells surrounded by an extracellular matrix of microfibrils, elastic fibers, bundles of collagen fibrils, and small granules believed to represent proteoglycans. The production of extracellular matrix was much more efficient than in cultures of arterial smooth muscle cells. This cell transplantation system may be valuable in elucidating the mechanisms of normal growth and development of the arterial wall as well as the pathogenesis of various pathological processes.

Animals↗
PubMed1981

Endocytosis of native and cationized horseradish peroxidase by cultured mouse peritoneal macrophages. Variations in cell surface binding and intracellular traffic and effects of colchicine.

Thioglycollate-elicited mouse peritoneal macrophages were cultivated in vitro and endocytosis of native and cationized horseradish peroxidase was studied electron microscopically and biochemically. Native peroxidase (HRP) was ingested by fluid-phase endocytosis and accumulated in lysosomes. Cationized peroxidase (CHRP) bound diffusely to the macrophage surface in a saturable manner. It was then internalized via membrane folds and transferred not only to lysosomes but also to the Golgi complex, mainly those parts referred to as GERL and positive for acid phosphatase activity. Following initial uptake, surface staining for CHRP was lost, although the tracer remained present in the medium. This indicates that anionic binding sites were internalized together with the ligand and not immediately replaced. Accordingly, continued uptake of CHRP occurred at a rate similar to that for HRP. Exposure of the macrophages to cationized ferritin (CF) decreased their ability to bind CHRP. However, after 2 to 4 h in CF-free medium, the CHRP-binding ability returned and raised to 2 to 3 times higher values than in cells not exposed to CF. Treatment with cycloheximide at a concentration that effectively inhibits protein synthesis did not clearly affect this regeneration. These findings support the concept of recirculation of plasma membrane constituents. They further suggest that there exists an intracellular membrane pool which rapidly exchanges with the cell surface. Colchicine removed cytoplasmic microtubules, caused a characteristic disorganization of the Golgi complex, and inhibited uptake of both HRP and CHRP. Additionally, no transport of CHRP to the Golgi complex or GERL was observed in colchicine-treated cells. The regeneration of surface anions after exposure to CF was also delayed. Contrarily, lumicolchicine was without effect on cell morphology and uptake as well as intracellular transport of the tracers. Nevertheless, the effects of colchicine on endocytosis were not necessarily due to a direct role of microtubules. They could be secondary to a disturbed function of the Golgi complex or other organelles after collapse of the microtubular cytoskeleton.

Animals↗
PubMed1980

Cold and metabolic inhibitor effects on cytoplasmic microtubules and the Golgi complex in cultured rat epiphyseal chondrocytes.

Previous work has shown that exposure of cultured chondrocytes to colchicine leads to disappearance of microtubules and dispersion of the dictyosomes of the Golgi complex throughout the cytoplasm. Here, the effects of cold and metabolic inhibitors on cultured chondrocytes have been investigated in order to characterize further the relationship between these organelle systems. After incubation of cells for 24h at 4 degrees C most, but not all microtubules disappeared, indicating the existence of cold-resistant microtubules. Dictyosomes remained united in one area, until transfer of cultures to 37 degrees C, when they dispersed throughout the cytoplasm in about one-third of the cells. In cells exposed simultaneously to cold and colchicine, microtubules disappeared completely, but spreading of dictyosomes occurred only in some cells and became generalized first upon warming. Application of the metabolic inhibitors sodium azide or sodium fluoride (10(-2) M) or 2-deoxyglucose (5 X 10(-2) M) together with sodium cyanide (10(-2) M) inhibited microtubule removal by colchicine. Consequently, spreading of the Golgi complex was prevented. These findings support the concept of an important role of microtubules in the organization of the Golgi complex. Moreover, depolymerization of microtubules by colchicine appears to be an energy dependent process.

Animals↗
PubMed1980

Effects of colchicine on the Golgi complex and GERL of cultured rat peritoneal macrophages and epiphyseal chondrocytes.

Thioglycollate-elicited rat peritoneal macrophages and epiphyseal chondrocytes were cultured in vitro, treated with colchicine, and then studied by electron-microscopic and cytochemical techniques. Colchicine, but not lumicolchicine, caused disappearance of cytoplasmic microtubules and breakup of the Golgi complex with spreading of its dictyosomes from a well defined juxtanuclear area throughout the cytoplasm. There was also an altered distribution of lysosomes, which oriented themselves close to the dictyosomes both in control and colchicine-treated cells. Further, the structure of the individual dictyosomes was changed, especially in the chondrocytes. GERL equivalents were observed in control cells but were difficult to detect after exposure to colchicine. Reaction product for thiamine pyrophosphatase was found in narrow cisternae on the inner side of the dictyosomes in control cells but in vacuole-like structures in colchicine-treated cells. Reaction product for acid phosphatase was present in GERL equivalents and lysosomes in control cells but mainly in lysosomes in colchicine-treated cells. Nevertheless, the total specific activities of these enzymes as well as of 5'-nucleotidase, a plasma membrane marker, remained unaffected by the drug treatment. These observations show that cytoplasmic microtubules play an important and, in many respects similar, cytoskeletal role in two so functionally diverse cell types as macrophages and chondrocytes. They are particularly important for the structural integrity of the Golgi complex, which in both cells is normally organized in the area around the centrioles, from which numerous microtubules radiate into the cytoplasm. The observations further suggest that GERL is an integrated part of the Golgi complex in these cells.

Animals↗
PubMed1980

Effects of colchicine on endocytosis of horseradish peroxidase by rat peritoneal macrophages.

Horseradish peroxidase (HRP) was used as an exogenous marker to study the effects of microtubule-disruptive drugs on endocytosis in cultures of thioglycollate-elicited rat peritoneal macrophages. Colchicine and vinblastine, but not lumicolchicine or cytochalasin B, reduced HRP uptake by about 30-40%. However, as determined by stereological measurements, the size of the HRP-containing compartment within the cells remained unaltered. In both control cells and cells treated with colchicine or vinblastine the HRP-reactive vesicles were preferentially located close to the dictyosomes (stacks of cisternae) despite the fact that the Golgi complex was disorganized in the treated cells. These results suggest that intact cytoplasmic complex was disorganized in the treated cells. These results suggest that intact cytoplasmic microtubules are required to maintain a normal rate of fluid phase endocytosis in macrophages. On the other hand, it seems as if microtubules are not necessary for the translocation of newly formed endocytic vesicles/lysosomes to the dictyosomes, from which they probably are supplied with digestive enzymes.

Animals↗
PubMed1980

Internalization of cationized ferritin into the Golgi complex of cultured mouse peritoneal macrophages. Effects of colchicine and cytochalasin B.

Mouse peritoneal macrophages were cultured in vitro, exposed to exogenous tracers, and examined by transmission electron microscopy. Native, anionic ferritin and horseradish peroxidase did not bind to the cell surface and were exclusively found in endocytic vesicles and lysosomes after uptake into the cells. Cationized ferritin (CF) bound to the plasma membrane and was then rapidly internalized. Intracellularly, CF first reached the lysosomes, but was later also transferred to and passed through the Golgi complex. These findings tentatively suggest that content and membrane of endocytic vesicles partly may follow different routes within macrophages. The content is emptied into lysosomes, from which part of the incoming membrane subsequently can be detached and moved over to the Golgi complex for reutilization. Additional, indirect evidence in support of this idea was obtained in double-labeling experiments with latex beads and CF. Thus, as expected with regard to the persistent nature of the latex-containing phagolysosomes, the transfer of CF to the Golgi complex was of a much smaller magnitude in cells exposed to both tracers than in cells exposed to CF alone. Pretreatment of the macrophages with colchicine removed all cytoplasmic microtubules and led to a characteristic disorganization of the Golgi complex. The treatment did not interfere with the binding of CF to the plasma membrane, however, but distinctly inhibited its uptake and transport to the Golgi complex. Contrarily, lumicolchicine and cytochalasin B did not affect the uptake and intracellular destination of CF. These results confirm previous notions concerning a role of cytoplasmic microtubules in endocytosis. They further indicate that absence of microtubules affects the intracellular handling of molecules binding to the cell surface.

Animals↗