Search PubMed⌕ Search

Biomedical subjects

U Friberg

Publications and source records attributed to U Friberg.

At least 73 records · Page 4Linked to original sources
PubMed1978

Effects of antimicrotubular agents on the fine structure of the Golgi complex in embryonic chick osteoblasts.

Embryonic chick frontal bones were cultured in the presence of colchicine or vinblastine and subsequently examined by tranmission electron microscopy. In control cultures the osteoblasts showed a large Golgi complex consisting of dictyosomes arranged in a well-defined juxtanuclear area. Microtubules were particularly numerous within this Golgi area although they could be observed throughout the cytoplasm. Colchicine and vinblastine caused the disappearance of cytoplasmic microtubules, while bundles of 10 nm diameter filaments appeared more frequently. In addition, cell polarity was lost and the Golgi complex became disorganized, with the dictyosomes randomly dispersed in the cytoplasm and showing a decreased number of cisternae and an increased number of vacuoles, the latter generally lacking stainable material. Increased number of autophagosomes were also noted. These findings indicate that microtubules function in the organization of the Golgi complex in osteoblasts. In view of the well documented role of this organelle system in collagen secretion it is suggested that previously observed secretory disturbances produced by antimicrotubular drugs may be due to a defective transfer of material to the dictyosomes and/or a defect in the packaging and transport of such material away from them.

Animals↗
PubMed1977

Electron microscopic studies on embryonic chick spinal ganglion cells: relationship between microtubules and the Golgi complex.

Spinal ganglia from 11 day chick embryos were fixed immediately after removal, or after a short incubation in media with or without nerve growth factor (NGF), and were subsequently examined by transmission electron microscopy. Qualitatively, incubation did not effect the fine structure of the neuroblasts. Morphometrically, however, NGF was found to cause a marked increase in the amounts of microtubules and microfilaments in the perikarya of the cells with a threefold increase in the volume density of these organelles after 4 h. The cells displayed a prominent Golgi complex, mostly with dictyosomes organized in one continuous band or area. Individual dictyosomes consisted of a stack of 3-6 parallel cisternae associated with small vesicles and occasional larger vacuoles. Microtubules were observed in all parts of the cyotplasm but were particularly numerous within the Golgi area. They occurred both on the forming and maturing sides of the dictyosomes and in the latter site were closely associated with small vesicles and peripheral dilatations of the cisternae. These observations indicate a possible role of microtubules in the organization and function of the Golgi complex.

Animals↗
PubMed1977

Fine structure of the golgi complex during mitosis of cartilaginous cells in vitro.

Chondrocytes were isolated enzymatically from guinea-pig epiphyses and grown in vitro. The fate of the Golgi complex during mitosis in relation to changes in the cytoplasmic microtubules was then studied by transmission electron microscopy. Interphase cells were observed to be polarized, with the Golgi complex occupying a well-defined juxtanuclear area of the cell's cytoplasmic pole. During prophase the cytoplasmic microtublues were largely lost, the nucleus moved to the center of the cell and the Golgi complex dissolved into single dictyosomes spread diffusely throughout the cytoplasm. The distribution of other organelles also changed to a more random pattern. In telophase, i.e. after the completion of nuclear division, the mitotic spindle decomposed and cytoplasmic microtubules reappeared. Furthermore, the organization of the Golgi complex and other organelles returned to that characteristic of interphase cells. Previous studies on cells treated with colchicine have indicated that the polarized distribution of cell organelles is dependent on the presence of intact cytoplasmic microtubules. It is suggested that the disappearance of such tubules observed here to be coupled with the disorganization of cell interphase structure fulfills the double function of providing free tubulin units from which to build the mitotic spindle and ensuring an approximately equal distribution of dictyosomes and other organelles to the daughter cells during cytokinesis.

Anaphase↗
PubMed1977

Effects of colchicine and vinblastine on the phytohaemagglutinin-induced transformation of lymphocytes.

The effects of 2 microtubular-disruptive drugs, colchicine and vinblastine, on the phytohaemagglutinin (PHA)-induced blast transformation and mitogenic stimulation of human lymphocytes were studied. Both drugs markedly inhibited cell growth and DNA synthesis and lowered the mitotic index. No microtubules were seen with the electron microscope in cells treated with PHA plus colchicine or vinblastine. Moreover, the PHA-induced development of all organelles was partially inhibited by these drugs, especially that of the Golgi complex. As compared to cells treated with PHA alone, the dictyosomes were fewer, not so clearly localized in one area of the cytoplasm, and contained a decreased number of cisternae and an increased number of vacuoles. These results indicate that cytoplasmic microtubules play an important role in the PHA-induced blast transformation and mitogenic stimulation of lymphocytes. It is suggested that the microtubules function in the structural organization of the cell and particularly the Golgi complex. In the drug-induced absence of microtubules this and other organelle systems do not respond as usual to PHA stimulation, which could largely explain the decreased cell growth. This in turn suggests that lowered mitotic activity is a result of inhibition of cell growth, as a critical amount of G1-associated cell growth is believed to be required for the initiation of DNA synthesis and thus mitosis.

Colchicine↗
PubMed1976

Heterotopic allotransplantation of isolated aortic cells. An electron microscopic study.

Smooth muscle cells were enzymatically isolated from the tunica media of the aorta of 5-day-old rats. Following in vitro exposure to colloidal thorium dioxide particles the cells displayed numerous lysosomes filled with these particles. Intramuscular injection of isolated cells into the tongues of young rats of the same strain, resulted in the formation by both freshly isolated and thorium dioxide-labeled cells of a characteristic tissue similar to that found in the intact aortic wall. Thus, the transplants consisted of typical smooth muscle cells surrounded by an extracellular matrix consisting of a microfibrillar network, patches and fibers of elastin, collagen fibrils and small polygonal granules believed to represent proteoglycans. This system can be used for experimental studies on the production of extracellular matrix components and on other functions of arterial smooth muscle cells growing outside the vascular wall.

Animals↗
PubMed1975

Electron microscopie and enzyme cytochemical studies on the guinia pig metaphysis with special reference to the lysosomal system of different cell types.

A transmission electron microscopic study of demineralized, methaphyseal bone of the young guinea pig is presented. Special attention is paid to the lysosomal system of the different cell types. Visualization of acid phosphatase and aryl sulfatase activity was used to identify tissue components as belonging thereto. The distribution of alkaline phosphatase activity, a plasma membrane marker, was also examined. Osteoblasts were distinguished by a marked development of the granular endoplasmic reticulum and the Golgi complex. Perivascular cells type A, morphologically resembled the osteoblasts, and are believed to represent an early stage in the specialization of the latter. A few lysosomes were normally found in the osteoblasts; they were less common in the type A cells. In contrasts to their regular occurrence in guinea pig epiphyseal cartilage, dense bodies of lysosomal nature ("type I vesicles") were only rarely seen in the bone matrix. Structures analogous to the type II vesicles in cartilage were, however, normally present. Their membrane showed activity of alkaline phosphatase. Possible functions of lysosomes and matrix vesicles in osteogenesis are discussed. Perivascular cells type B and chondroclasts both contained a prominent Golgi complex and large numbers of free ribosomes, mitochondria and lysosomes. In the type B cells, inclusion material of varying appearance often occurred in the lysosomes and in endocytic vesicles. The chondroclasts sometimes presented a ruffled border, with associated vacuoles and lysosomes in the subjacent cytoplasm. It is suggested that both cell types participate in the resorption of the epiphyseal cartilage. Chondroclasts presumably arise by fusion of type B cells and/or monocytic precursors from the peripheral blood.

Acid Phosphatase↗