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At least 19 recordsLinked to original sources
PubMed1991

Neutral lipid synthesis and accumulation during in vitro induction of the lipocyte phenotype in hepatic connective tissue cells.

Connective tissue cells of liver parenchyma are known as hepatic myofibroblasts and lipocytes (fat-storing cells, Ito-cells). They are considered to belong to a single cell lineage, that may switch between these two phenotypes. We have studied cellular and molecular parameters and controls of this switch in the murine GRX cell line, established from liver fibro-granulomatous lesions induced by schistosomal infection. Accumulation of neutral lipids (triacylglycerols, monoalkyl-diacylglycerol, cholesterol) was monitored. It was dependent upon induction with indomethacin. Insulin alone did not induce lipid accumulation in GRX cells, but in cells induced by indomethacin it increased the quantity of stored lipids. We propose that hepatic lipocytes are not cells directly involved in energy storage, but that they represent a particular cell population specialized in storage and in controls of the homoeostasis of lipid-soluble substances at the systemic level.

Animals↗
PubMed1975

[Studies on the number of fat cells and connective tissue cells in white adipose tissue in chronic starvation and after refeeding. I. Investigations on aurothioglucose-obese NMRI-albino-mice(author's transl)].

UNLABELLED: Former investigations (Rakow et al., 1970, 1971 b) on epididymal fat pads of lean NMRI-Albino-mice during starvation and refeeding have shown that the number of fat cells (adipocytes) remained unchanged while the number of cells o connective tissue decreased during starvation and increased during the refeeding period. In the present paper the problem has been investigated whether these variations could be demonstrated also in NMRI-albino-mice obesified by administration of aurothioglucose. MATERIAL AND METHODS: The investigations were performed with male NMRI-Albino-mice rendered obese by administration of aurothioglucose (800 mg per kg body weight). These animals were fed 2.5 g Altromin 1115 R daily for six weeks. After this they were fed Altromin 1115 R and additional oat flakes ad libitum for three (exp. groups HW3) and seven (exp. groups HW 7) days respectively. After this time the animals were sacrificed. The epididymal fat pads were removed and weighed. One of both pads of each animal was used for chemical investigations. After PCA-treatment (0.5 n, 90 degrees C. 15 min.) the DNA (Burton, 1956) and RNA (Ceriotti, 1955) was determined in the supernatant. After NaOH-treatment (0.5 n, 37 degrees C, 24 Hrs) the noncollagen protein content (Lowry et al., 1951) of the sediment was estimated. After HCl-treatment (25%, 110 degrees C, 20 hrs.) the collagen content (Stegemenn, 1958; modified by Rauskolb, 1967) was determined. The remaining fat pad was used for calculations of cell numbers in the fat cell and connective tissue cell compartment. For this reason fat cells were isolated according to Rodbell (1964). The fat cell diameters were determined microscopically and the average masses of the fat cells were estimated. From the wet weight of the fat pads and the average fat cell mass the number of fat cells was calculated. The remaining suspension of fat cells and cells of connective tissue was utilized for cell smears. These smears were stained with Schiff's reagent (Feulgen et al., 1924; Graumann, 1952). With an integrating microdensitometer (Deeley, 1955) the average relative DNA-content of single cell nuclei were measured and the ploidy patterns were estimated. From the whole DNA-content of the fat pads and the DNA-content of the fat cell population the number of cells of the connective tissue was calculated...

Adipose Tissue↗
PubMed1975

[Studies on the number of fat cells and connective tissue cells in white adipose tissue in chronic starvation and after refeeding. II. Investigations on obese and lean C 57 BL/6 J-mice (author's transl)].

UNLABELLED: Former investigations (Rakow et al., 1970, 1971a, b 1974) have demonstrated a constancy of the adipocyte number in white adipose tissue (parepididymal fat pads) of lean NMRI-albino-mice and aurothioglucose-obese NMRI-albino-mice during starvation and subsequent refeeding. In contrast the number of cells of connective tissue showed great variations under the experimental conditions mentioned above. The present paper describes which changes of the different cell populations within the adipose tissue could be demonstrated in lean and obese C57BL/6 J-mice. MATERIAL AND METHODS: The investigations were performed with obese and lean male C57BL/6 J-mice. The control animal groups were fed for six weeks 2.5 g (lean mice) and 2 g (obese mice), respectively, Altromin 1115R daily (starvation phase). After this time some of these animalwere killed (exp. groups H). The remaining animals now were fed Altromin 1115R and additional oat falkes ad libitum. Three (exp. groups HW3) and seven (exp. groups HW 7) days, respectively, after the beginning of the refeeding phase the animals were killed. After sacrifice the epididymal fat pads were weighed and treated with either (fat extraction). The dry mass was hydrolized with PCA (0.5 m, 90 degrees C, 40 min). In the supernatant the DNA (Burton, 1956), RNA (Ceriotti, 1955) and polysaccharide content (Seifter et al., 1950) were measured. The sediment was hydrolized with NaOH (0.5 n, 37 degrees C, 24 hrs). In this solution the protein content (Lowry et al., 1951) was determined. In addition fat cells were isolated according to Rodbell (1964). The fat cell diameters were determined microscopically and the average masses of the fat cells were estimated. From the wet weight of the fat pads and the average fat cell mass and number of fat cells were calculated. The remaining suspension of fat cells and cells of connective tissue were utilized for cell smears. These cell smears were stained with Schiff's reagent (Feulgen et al., 1924; Graumann, 1953). With an integrating microdensitometer (Deeley, 1955) the average relative DNA-content of single cell nuclei was measured and the ploidy patterns were estimated. The DNA-content was measured chemically according to Burton (1956). From the whole DNA-content of the fat pads and the DNA-content of the fat cell population the number of cells of the connective tissue was calculated...

Adipose Tissue↗
PubMed1985

Liver connective tissue cells isolated from human schistosomal fibrosis or alcoholic cirrhosis represent a modified phenotype of smooth muscle cells.

Hepatic connective tissue cells associated with schistosomal fibrosis and alcoholic cirrhosis were studied in vitro. Primary cell lines were isolated from all biopsies: they were identified as specific homogeneous cell populations, named liver connective tissue cells (LCTC). They were recognized as analogous to smooth muscle cells, different from true fibroblasts by morphological and physiological criteria. The proliferative capacity of LCTC is directly proportional to the degree of fibrosis in hepatic tissues. LCTC are able to secrete type I, III and IV collagen, fibronectin, laminin and amyloid P component. Their relationship with specific pathology of intrahepatic vascular tree in schistosomiasis is hypothesized.

Amyloid↗
PubMed1990

In vitro induction of the fat-storing phenotype in a liver connective tissue cell line-GRX.

Liver connective tissue cells have been characterized as perisinusoidal myofibroblasts and hepatic lipocytes (Ito cells, fat-storing cells). A concept of a single mesenchymal cell population that may be modulated between these two phenotypes has been postulated. We have previously established a continuous murine cell line, GRX, obtained from fibrotic granulomatous lesions induced by schistosomal infection in mouse liver. This cell line is considered to represent liver myofibroblasts. In the present study we have induced the conversion of these cells into lipocyte (fat storing) phenotype by treatment with insulin and indomethacin. We have quantified the lipid synthesis and the increase of activity of involved enzymes during the induction of the fat-storing phenotype and described modifications of cell organization along this modulation of cell functions.

Animals↗
PubMed1975

A complex junctional system in endothelial and connective tissue cells of the choroid plexus.

Endothelial and connective tissue cells of the choroid plexus have been studied by the freeze-etching technique. The endothelial cells of pre- and postcapillary segments are coupled by a complex junctional system consisting of a combination of tight and gap junctions. Connective tissue cells revealed the same intercellular contacts. Furthermore two different types of gap junctions occurring in membranes of the connective tissue cells are described.

Animals↗
PubMedDate not supplied

Interaction of human liver connective tissue cells, skin fibroblasts and smooth muscle cells with collagen gels.

Interactions of liver connective tissue cells, skin fibroblasts and smooth muscle cells with collagen gels in vitro were studied and compared. Liver connective tissue cells showed the lowest rate of migration into the gel and the highest speed of gel contraction, reflecting their high adhesiveness to the substrate as compared to the other cell lines studied. The analysis of their ultrastructural morphology showed that liver connective tissue cells and smooth muscle cells developed cytoskeletal and cytoplasmic organelle polarities, in response to the contact with gel surface. This polarity was lost when cells were embedded in the gel. Skin fibroblasts did not show this characteristic, neither on top nor in the gel. Although liver connective tissue cells have been recognized as analogous to smooth muscle cells, they represent a defined cell population, present in fibrotic livers, with specific behavior and with particular relationship to the extracellular matrix.

Cell Line↗
PubMed1984

Histochemistry of connective tissue cells in subcutaneous adipose tissue of normal and decapitated pig fetuses.

Connective tissue cells that are histochemically and morphologically distinct from 'fibroblasts' are localized around developing hair follicles in the pig and rat. Immature adipose tissue is limited to small areas immediately around fully descended hair follicles in the rat hypodermis. In the present study, connective tissue around large nerves and blood vessels in fetal pig subcutaneous tissue was examined for the presence of enzymes typical of adipocytes. Samples from decapitated pig fetuses were studied so that the effects of an altered hormonal profile could be examined. Samples of dorsal subcutaneous adipose tissue were obtained from fetuses at 65, 70, 85, 90, 110, and 112 days of gestation. Fetuses were decapitated in utero at 45 days of gestation, and adipose tissue samples were obtained from these fetuses at 110 days of gestation. A close spatial relationship was observed between the growth of large blood vessels and nerves and fat cell cluster development in the older (greater than 70 days) fetuses. Connective tissue cells that were contiguous with fat cell clusters were histochemically identical to adipocytes. The lipid histochemistry of the reactive connective tissue cells (histochemically identical to adipocytes) was variable in young fetuses. In all 110-and 112-day-old fetuses, the reactive cells contained lipid, whereas the reactive cells in decapitated fetuses were devoid of lipid. The reactive connective tissue cells were not associated with capillaries and did not contain basement membranes. The histochemistry of these cells suggests that they respond to a particular hormonal or metabolic profile as do adipocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1978

Isolation and characterization of epithelial and connective tissue cells from rat palate.

Epithelial and connective tissue cells were isolated from rat palate by sequential enzymatic digestion. Differences between the two populations were noted with respect to proline uptake and incorporation, % collagen synthesized, effects of parathyroid hormone and metabolism of D-valine. From these studies it can be concluded that the cell populations are viable and distinct with respect to the biochemical parameters examined.

Animals↗
PubMed1990

Evaluation of connective tissue cell responses to orthopaedic implant materials.

We have developed an in vitro cell culture model to examine the interaction between connective tissue cells and orthopaedic implant biomaterials. Human connective tissue cells grown on different materials exhibit distinct responses in terms of attachment, morphology, proliferative capacity and matrix biosynthesis. Our results closely complement in vivo observations concerning biocompatibility and demonstrate the usefulness of this in vitro system for evaluating biomaterials. More importantly, this model can be used to define the specific cellular and biochemical processes that are responsible for the local tissue responses to orthopaedic implant materials.

Alloys↗
PubMed1984

Cultured endothelial cells produce multiple growth factors for connective tissue cells.

Cultured bovine aortic endothelial cells (BAEC) secrete into their medium a growth-promoting factor that stimulates many connective tissue cells in culture. We now report that this growth-promoting activity is due to at least two different proteins which are biochemically separable and immunologically distinct. Cation exchange chromatography (Carboxymethyl-Sephadex) of concentrated BAEC-conditioned medium yields two major peaks of growth-promoting activity which adsorb at pH 8 and elute with a salt gradient. One of these peaks contains as well a protein that inhibits the binding of radioiodinated platelet-derived growth factor (PDGF) to its receptor on target cells. The PDGF-like mitogen is purified approx. 25-fold by this chromatographic step. A second peak of mitogenic activity exhibits no binding to the PDGF receptor. Both the PDGF-like mitogenic activity and the PDGF-distinct mitogenic activity are highly cationic, stable to boiling, sensitive to beta-mercaptoethanol, and between 30 and 50 kD in molecular weight. Complementary studies with human umbilical vein endothelial cells in culture were performed. These human cells also produce both growth-promoting activity and a protein that binds to the PDGF receptor. The latter activity is greatly inhibited by a specific antiserum to human PDGF, whereas the growth-promoting activity of the conditioned medium is minimally affected. The degree of inhibition of the two activities is, however, quantitatively consistent: 3.5 ng of PDGF-like activity in the radioreceptor assay is inhibited, while 5 ng of PDGF-like activity in the DNA synthesis assay is inhibited. The data from the two species are consistent with the proposal that cultured endothelial cells produce at least two distinct mitogens, one of which is biochemically and immunologically related to PDGF.

Animals↗
PubMed1989

Retinoid-mediated induction of the fat-storing phenotype in a liver connective tissue cell line (GRX).

The GRX cell line is derived from murine liver connective tissue cells. It has myofibroblastic characteristics and can be induced to display a phenotype analogous to fat-storing (Ito) cells. Retinol-mediated induction of the fat-storing phenotype was studied in vitro. Based on the incorporation of radiolabelled acetate into cell lipids, cholesterol synthesis increased and phospholipid synthesis was modified shortly after the beginning of the induction, indicating an activation of pre-existing metabolic pathways. Triacylglycerol synthesis was increased only after a delay of 4 d, indicating the de novo induction of enzymes necessary for triacylglycerol metabolism. Retinol incorporation and conversion into retinyl esters were also considerably increased by previous incubation with retinoids. Retinoid-induced changes in GRX cells provide a model for studying in vitro the interconversion of liver connective tissue cells between the myofibroblastic and fat-storing phenotypes. This interconversion is considered to be one of the major control points of normal homeostasis and of pathological modifications of liver connective tissue.

Acetates↗