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Biomedical subjects

S Moskalewski

Publications and source records attributed to S Moskalewski.

At least 55 records · Page 3Linked to original sources
PubMed1985

Removal of large lipid droplets from cytochalasin B-treated chondrocytes by high speed centrifugation.

Chondrocytes isolated from auricular cartilage of 10-week-old rabbits were exposed to cytochalasin B and centrifuged in Percoll solution at 50.000 g for 1 h. This treatment removed the large fat droplets present in the majority of chondrocytes without impairing their viability. It appears that after destruction of actin filaments by cytochalasin, large fat droplets are extruded from the cells during high speed centrifugation due to the difference in the specific weight of fat and chondrocyte cytoplasm. Conceivably, on the same principle other materials could also be eliminated from the cells.

Animals↗
PubMed1985

Microtubules and the organization of the Golgi complex.

Electron microscopic and cytochemical studies indicate that microtubules play an important role in the organization of the Golgi complex in mammalian cells. During interphase microtubules form a radiating pattern in the cytoplasm, originating from the pericentriolar region (microtubule-organizing centre). The stacks of Golgi cisternae and the associated secretory vesicles and lysosomes are arranged in a circumscribed juxtanuclear area, usually centered around the centrioles, and show a defined orientation in relation to the rough endoplasmic reticulum. Exposure of cells to drugs such as colchicine, vinblastine and nocodazole leads to disassembly of microtubules and disorganization of the Golgi complex, most typically a dispersion of its stacks of cisternae throughout the cytoplasm. These alterations are accompanied by disturbances in the intracellular transport, processing and release of secretory products as well as inhibition of endocytosis. The observations suggest that microtubules are partly responsible for the maintenance and functioning of the Golgi complex, possibly by arranging its stacks of cisternae three-dimensionally within the cell and in relation to other organelles and ensuring a normal flow of material into and away from them. During mitosis, microtubules disassemble (prophase) and a mitotic spindle is built up (metaphase) to take care of the subsequent separation of the chromosomes (anaphase). The breaking up of the microtubular cytoskeleton is followed by vesiculation of the rough endoplasmic reticulum and partial atrophy, as well as dispersion of the stacks of Golgi cisternae. After completion of the nuclear division (telophase), the radiating microtubule pattern is re-established and the rough endoplasmic reticulum and the Golgi complex resume their normal interphase structure. This sequence of events is believed to fulfil the double function to provide tubulin units and space for construction of the mitotic spindle and to guarantee an approximately equal distribution of the rough endoplasmic reticulum and the Golgi complex on the two daughter cells.

Animals↗
PubMed1985

Regenerating rib cartilage tentatively used as a source of chondrocytes for transplantation.

In search for cartilage which could serve as a source of chondrocytes for autogeneic transplantation in mature individuals we studied the morphological appearance and digestibility of normal rib cartilage and regenerated cartilage formed after subperichondrial removal of the former in adult dogs. Cells liberated after collagenase digestion were transplanted intramuscularly to see whether they will reconstruct cartilage similarly as it happens after transplantation of fetal chondrocytes. Chondrocytes in normal rib cartilage were arranged in three zones and lay in large isogenous groups. Collagenase dissolved only the peripheral zone. Isolated cells did not reconstruct cartilage after transplantation. No distinct zones could be seen in regenerated cartilage. Chondrocytes lay singly or in pairs but were not numerous. Regenerated cartilage could be completely dissolved by collagenase, but the yield of cells was low owing to their low content in digested material. After transplantation chondrocytes from regenerated cartilage reconstructed cartilage in one out of ten transplants. The possibility of increasing the cellularity of regenerated cartilage by stimulation of the perichondrium with factors known to promote chondrocyte growth in vitro is discussed.

Animals↗
PubMed1984

Effects of bunaftine on morphology, microfilament integrity, and mitotic activity in cultured human fibroblasts and HeLa cells.

Human fibroblasts and HeLa cells were treated with bunaftine (N-butyl-N-/2-(diethylamino)ethyl/-1-naphthalenecarboxamide ) in vitro. At concentrations of 0.5-2.0 mM, the drug caused contraction and rounding of the cells with loss of microvilli-like processes. Aggregates of dense, partly granular, partly fibrillar material formed in the cytoplasm and the rough endoplasmic reticulum became vesiculated. Immunofluorescence microscopy with DNase I and anti-DNase I demonstrated that bundles of actin filaments were disrupted, forming rings, coils, and granules. Filaments stained with antibodies to vimentin (fibroblasts) and prekeratin (HeLa cells) showed less characteristic rearrangements, probably related to the rounding up of the cells. 0.4 mM bunaftine increased and 0.8-1.0 mM markedly decreased the percentage of mitotic cells, without accumulation of cells in any particular stage of mitosis. The drug may arrest the cell cycle at some point before mitosis; it may have a critical concentration above which the arrest becomes permanent. These results suggest that bunaftine interferes with the integrity of microfilament bundles in a different manner from that of cytochalasins. It does not cause any depletion of cellular ATP, indicating that its effect is not a result of inhibition of cell metabolism. It is proposed that bunaftine may be used a complement to cytochalasins in studies of the microfilament system of the cell. The possible binding of bunaftine to actin or myosin and further details of its mechanism of action remain to be elucidated.

Actins↗
PubMed1984

Influence of proteolytic enzymes and calcium-binding agents on nuclear and cell surface topography.

Transmission electron microscopy was used to study the effects of proteolytic enzymes (collagenase, trypsin, clostripain), the calcium chelator ethyleneglycol-bis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA), and the calcium ionophore A 23187 on substrate adhesion and fine structure of chondrocytes and fibroblasts. Monolayer-cultured cells responded to treatment with the proteolytic enzymes followed by EGTA or A 23187 by rounding and detaching from the substrate. This was accompanied by the formation of a microvillous surface, deep nuclear folds, and numerous cytoplasmic vacuoles. Labeling experiments with colloidal thorium dioxide indicated that the vacuoles were formed by endocytosis and fusion of endocytic vesicles with preexisting lysosomes. To a variable extent, similar changes were produced by trypsin or EGTA alone. The cells regained their normal fine structure after withdrawal of the reagents and when seeded onto a substrate. In suspension culture, recovery was incomplete; the cells retained a rounded shape and an increased number of cytoplasmic vacuoles. The results suggest that changes in plasma membrane composition and its permeability to calcium represent the primary signal for cell rounding and detachment. The cellular mechanisms responsible for the associated folding of the nuclear envelope and the cell surface remain unidentified. Nevertheless, this is believed to represent a means of handling of excess membrane during sudden transition from a flattened to a rounded shape. Membrane stored in folds and vacuoles is reutilized when the cells reattach and spread out on a substrate.

Animals↗
PubMed1984

The amount of proteoglycans in cartilage matrix and the onset of mineralization.

An electron microscopic investigation of the relationship between proteoglycans and cartilage mineralization has been carried out. On the basis of the number of matrix granules and the affinity of the matrix for colloidal ThO2, we found that in embryonic mouse radii: The amount of proteoglycans does not decline before the onset of mineralization. In the calcified portions of the cartilage matrix the concentration of proteoglycans remains constant during and after mineralization. There is a degradation of proteoglycans in the uncalcified portions of the matrix near the marrow cavity. This last finding explains why chemical analyses of epiphyseal disks so often show a decline in the amount of proteoglycans in the mineralizing zones. It was concluded that degradation of proteoglycans is not a first, necessary step in cartilage mineralization. The loss of proteoglycans in the uncalcified matrix in the lower zones of the epiphyseal disks is probably devoid of any particular significance for calcification but is rather a preparation for the formation of the marrow cavity.

Animals↗
PubMed1983

Influence of beta-aminoproprionitrile (BAPN) on cell growth and elastic fiber formation in cultures of auricular chondrocytes.

Auricular chondrocytes isolated from 4-day-old rabbits and grown in vitro for 14 days, proliferated rapidly and produced a conspicuous network of elastic fibers. Beta-aminoproprionitrile (BAPN), which in vivo inhibits cross-linking of elastin, decreased the formation of elastic fibers at a concentration of 10-20 micrograms/ml and prevented formation at 40 micrograms/ml. At a concentration of 5 micrograms/ml only the so-called patches of elastin appeared to be absent. The inhibitory effect of BAPN on cell growth did not exceed 10%, which indicates that BAPN is only slightly harmful to auricular chondrocytes and can safely be used in studies on elastin deposition by these cells in vitro.

Aminopropionitrile↗
PubMed1983

Bone formation by isolated calvarial osteoblasts in syngeneic and allogeneic transplants: light microscopic observations.

Taking advantage of recently developed methods for osteoblast isolation, we used these cells to study bone morphogenesis in syngeneic and allogeneic intramuscular transplants. Syngeneic osteoblasts from fetal rat calvaria produced small islands of bone by the third day after transplantation. These islands increased in size and began to fuse after about 14 days. At the surface of the woven bone laid down first, lamellar bone developed. The amount of this bone increased, and in 56-day-old transplants solid blocks of bone were present. Osteoclasts were scarce, and the woven bone remained unresorbed. Bone marrow was absent. The structure of bone in transplants differed from that of mature calvarial bones in which only remnants of woven bone remained and bone marrow was well developed. The scarcity of osteoclasts in transplants could be caused by their relative paucity among the injected cells, since these cells responded strongly to added parathyroid hormone by increased production of cyclic adenosine monophosphate (cAMP) but only weakly to calcitonin. Osteoblasts isolated from the surface of calvarial lamellar bone of 28-day-old rats formed woven bone similar to the bone formed by fetal cells. This suggests that the type of bone produced does not depend on the intrinsic properties of the osteoblasts. Bone formed in an allogeneic system was surrounded by infiltrations containing lymphocytes, macrophages, and osteoclastlike cells in 14-day-old transplants. Osteoblasts at the bone periphery were destroyed and bone matrix was resorbed by infiltrating cells. Numerous bone lacunae were enlarged, suggesting the occurrence of osteocytic osteolysis. Isolated osteoblasts cultured for three population doublings or longer did not form bone after transplantation, although they retained some reactivity toward parathyroid hormone.

Alcian Blue↗
PubMed1983

Synthesis of proteoglycans, collagen, and elastin by cultures of rabbit auricular chondrocytes--relation to age of the donor.

Chondrocytes were isolated from the auricular cartilage of rabbits, aged 1 week to 30 months, and grown in short-term cell culture. The cells from the 1-week animals were small, polygonal, and mononucleated, while the chondrocytes from the older animals were larger, rounded, and frequently binucleated. The synthesis of proteoglycans, collagen, and elastin was determined by isotope incubation. Chemical characterization of the proteoglycans was also performed. The production of the matrix macromolecules showed a clear age dependence with peak synthesis occurring at different ages. Proteoglycans were actively synthesized by chondrocytes from all age groups with a broad maximum between 2 weeks and 5 months followed by a sharp decline to about 50% of the 1-week level at 12-30 months. Collagen synthesis peaked at 2 weeks, declining progressively thereafter to about 60% of the 1-week level at 30 months. Elastin synthesis was highest in the 1-week cultures and thereafter fell quickly to very low levels. In all age groups the chondrocytes synthesized predominantly cartilage-typic proteoglycans, i.e., large aggregate forming molecules containing chondroitin sulfate. Monomers and aggregates showed a size maximum at 2-8 weeks. The degree of sulfation of the chondroitin sulfate and the proportion of 6-sulfate increased with age. These findings support the concept of "age programs" for the biosynthesis and turnover of different matrix macromolecules.

Aging↗
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

The elastogenetic process in transplants and cultures of isolated auricular chondrocytes.

Chondrocytes isolated from auricular cartilage of rabbits in the early postnatal period were transplanted intramuscularly into closely related animals and the reconstruction of cartilage and formation of elastic fibers monitored. Elastogenesis was most produced in transplants from younger donors. Auricular chondrocytes from 7 day old rabbits also produced elastic fibers in tissue culture, undergoing morphological changes similar to those occurring in vivo. The ability to form elastic fibers declined after prolonged cultivation.

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↗