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C Forest

Publications and source records attributed to C Forest.

At least 55 records · Page 3Linked to original sources
PubMed1987

A preadipocyte clonal line from mouse brown adipose tissue. Short- and long-term responses to insulin and beta-adrenergics.

A clonal cell line has been established from the interscapular brown adipose tissue (BAT) of the C57 BL/6J +/+ mouse. The line, designated BFC-1, is aneuploid and exhibits both morphological and biochemical properties characteristics of mature adipocytes. Adipose conversion begins after confluence and is accompanied by an early emergence of lipoprotein lipase; a later emergence of glycerol-3-phosphate dehydrogenase and acid: CoA ligase; an increase in the average triglyceride content. Adipose conversion, estimated by activities of enzyme markers, is enhanced at any given time by the continuous presence in the culture medium of insulin and triiodothyronine, both within their physiological range of concentrations. In addition to both hormones, chronic exposure of confluent cells to beta-adrenergics brings similar long-term effects on adipose conversion. The uptake of labelled 2-deoxyglucose by differentiated BFC-1 cells is stimulated by insulin; the half-maximum effect is observed at 1 nM insulin. Differentiated BFC-1 cells, in which endogenous triglycerides have been prelabelled on the fatty acid moiety, do respond to beta-adrenergics by releasing radioactive fatty acids. The agonist potency order and the EC50 value for each agonist are BRL 37344 (0.5 nM) greater than isoproterenol (1.5 nM) greater than norepinephrine (3 nM) greater than epinephrine (7 nM) greater than salbutamol (15 nM). The half-maximally and maximally effective concentrations of corticotropin to stimulate lipolysis are found to be 4 and 100 nM, respectively. The lipolytic response to isoproterenol is counteracted by prior addition of insulin or simultaneous addition of propranolol. Parallel studies performed on Ob17 cells, a clonal line established from mouse white adipose tissue (Négrel et al., Proc natl acad sci US 75 (1978) 6054), show that the agonist potency order and the EC50 value for each agonist are BRL 37344 (3 nM) greater than isoproterenol (10 nM) greater than norepinephrine (20 nM) greater than epinephrine (40 nM). Thus both BFC-1 cells and Ob17 cells show an atypical beta-adrenoreceptor similar to that described in rat adipocytes (Arch et al., Nature 309 (1984) 163), but the sensitivity of BFC-1 cells toward beta-agonists is found to be 6-fold higher than that of Ob17 cells. Thus the BFC-1 line represents a useful model for the study of short- and long-term responses to beta-adrenergics.

Adenosine↗
PubMed1987

Expression of the mitochondrial uncoupling protein in brown adipocytes. Absence in brown preadipocytes and BFC-1 cells. Modulation by isoproterenol in adipocytes.

The expression of the uncoupling protein has been compared in cells of BFC-1 clonal line established from mouse brown adipose tissue (BAT) and in preadipocytes, as well as in adipocytes from mouse BAT, both in primary culture. The results of immunoblots show that, after one week in culture, adipocytes have a reduced level of the 32 kD protein. This level can be raised 2-3.5-fold by a 24-h exposure to isoproterenol. Thus a direct modulation by a beta-agonist drug in the expression of the uncoupling protein is observed. Under the same conditions as well as under various other conditions, preadipocytes in primary culture and BFC-1 cells do not express the uncoupling protein. At the same time these cells are able both to differentiate into adipose cells, as demonstrated by the emergence of enzyme markers and triglyceride accumulation, and to respond to isoproterenol. Thus isoproterenol is not sufficient to trigger the expression of the uncoupling protein and behaves as a mere modulator once the cells have acquired the capacity to express it. Injection of undifferentiated BFC-1 cells into athymic mice bearing catecholamine-containing mini-osmotic pumps, or co-cultures of BFC-1 cells and pheochromocytoma PC-12 cells do not allow BFC-1 cells to express the uncoupling protein. Taken together, the results suggest that the formation of brown preadipocytes is critically linked during development to the release by sympathetic nerves of specific trophic factors acting locally.

Adipose Tissue↗
PubMed1987

Characterization of mitochondrial-uncoupling protein in bovine fetus and newborn calf.

Development changes in the content of the mitochondrial-uncoupling protein (UCP) have been studied in adipose depots of bovine fetuses and a newborn calf as well as in adipose depots of newborn and aging lambs. The occurrence of UCP unique to brown adipose tissue (BAT) was investigated by GDP binding, photoaffinity labeling with 8-azidoadenosine 5'-triphosphate, and immunoblots using specific antibodies directed against rat UCP. A protein of 32,000 relative molecular weight was characterized in both species with properties similar to those of rodent UCP. In bovine, UCP became detectable in the perirenal adipose tissue at day -80 and its content increased until birth. Both in bovine (perirenal, subscapular, and retroperitoneal sites) and in ovine (perirenal, subscapular, retroperitoneal, and pericardiac sites), all adipose tissues except the subcutaneous adipose tissue contained at birth UCP and thus can be considered as BAT. The data indicate that the perirenal adipose depot should play in bovine and ovine a major thermogenic role at birth, whereas perirenal and pericardiac adipose tissues of lambs held under cold conditions for 45 days after birth did not show any immunoreactive UCP.

Adipose Tissue↗
PubMed1985

[Lipoprotein lipase and adipocyte differentiation].

Some hormonal factors, possibly involved in the proliferation and differentiation of adipose precursor cells in vivo, have been characterized in vitro using different preadipocyte cell lines established from rodent adipose tissue. The process of adipose conversion has also been studied using these cell lines; in this process, stem cells (adipoblasts) were committed at any cell division during the growth phase. At confluence, committed cells (preadipocytes) underwent a limited number of mitoses and differentiated into adipose cells, whereas the uncommitted cells remained as stem cells in the cell population. This stochastic model could be extended to the development of rat adipose tissue in vivo. The study of adipose conversion showed the early emergence of lipoprotein lipase (LPL) and monoglyceride lipase (MGL). LPL activity appeared in the cells before any triglyceride accumulation. In contrast, this accumulation seemed dependent upon the emergence of glycerol-3-phosphate dehydrogenase. In vitro experiments clearly established that LPL-containing (differentiating) cells underwent postconfluent mitoses. This limited proliferation was in agreement with previous data obtained in vivo and indicates that only triglyceride-containing (mature) cells could not divide.

Adipose Tissue↗
PubMed1985

Adipose conversion of ob17 cells and hormone-related events.

The ob17 preadipocyte clonal line has been established from the adipocyte fraction of the epididymal fat pads of adult C57 BL/6J ob/ob mice. In vivo, injection of ouabain-resistant mutant cells (ob 17OR11 cell line) into athymic mice is followed by the formation of fat pads containing ouabain-resistant mature fat cells. In vitro, ob17 cells develop after confluence biochemical and morphological characteristics of adipocytes. The adipose conversion process is best represented by a stochastic model in which a pool of stem cells (adipoblasts) give rise to clusters of adipose cells and to additional stem cells that remain in the population. The role of the different factors involved in such conversion is discussed; (1) factors that enhance the number of susceptible cells (ACF or ACF-like compounds), (2) factors without which no adipose conversion takes place (triiodothyronine, growth hormone and other factors still to be characterized), (3) factors that enhance the expression of the differentiation program (insulin). The early emergence of lipoprotein lipase occurs normally in insulin-depleted medium. The separation of ob17 cells by isopycnic centrifugation shows that lipoprotein lipase is present at high levels in early differentiating cells which are still devoid of late markers, ie glycerol-3-phosphate dehydrogenase and triglycerides. These results are discussed with respect to the determination of cellularity during development of adipose tissue in vivo.

Adipose Tissue↗
PubMed1983

Modulation of lipid-synthesizing enzymes by insulin in differentiated ob17 adipose-like cells.

ob17 cells convert into adipose-like cells when maintained in the presence of physiological concentrations of insulin and tri-iodothyronine. After this conversion, insulin removal from differentiated ob17 cells gives within 24-48 h a large decrease in fatty acid synthetase, glycerol 3-phosphate dehydrogenase and acid:CoA ligase activities, as well as in the rate of fatty acid synthesis determined by [14C]acetate incorporation into lipids. All parameters are restored by insulin addition to initial values within 24-48 h. Dose-response curves of insulin on the restoration of glycerol 3-phosphate dehydrogenase activity and of fatty acid synthesis give half-maximally effective concentrations close to 1 nM, in agreement with the affinity for insulin of the insulin receptors previously characterized in these cells. Immunotitration experiments indicate that the changes in the specific activity of fatty acid synthetase are due to parallel changes in the cellular enzyme content. Therefore the ob17 cell line should be a useful model to study the long-term effects of insulin on the modulation of lipid synthesis in adipose cells.

Acetates↗
PubMed1983

Establishment of a preadipocyte cell line from the epididymal fat pad of the lean C57 BL/6J mouse--long term effects of insulin and triiodothyronine on adipose conversion.

A clonal cell line has been established from the epididymal fat pad of the C57 BL/6J +/? mouse. This line, designated HGFu, is aneuploid and exhibits both morphological and biochemical properties characteristic of mature adipocytes. Adipose conversion begins after confluence and is accompanied by (a) an early emergence of lipoprotein lipase, (b) an increase in the incorporation of [14C]acetate into lipids and in the activities of acid:CoA ligase and glycerol-3-phosphate dehydrogenase, (c) a 27- to 35-fold increase in the average triglyceride content per cell. In the presence of a beta-agonist (isoproterenol) a full lipolytic response (measured by fatty acid release) is observed with differentiated cells, whereas the responsiveness examined by cyclic AMP (cAMP) production is present both in undifferentiated and differentiated cells. Adipose conversion, estimated by activities of enzyme markers, is accelerated by the continuous presence in the culture medium of insulin and triiodothyronine both within their physiological range of concentrations, whereas insulin at supraphysiological concentrations shows a growth promoting activity. The concentrations of insulin and triiodothyronine required for half-maximal lipogenic effects are in agreement with the Kd values of their respective high affinity binding sites present in HGFu cells. The HGFu cell line seems to be a useful model for the study on a long term basis of the mechanisms of action both of insulin and triiodothyronine. Moreover it will make it possible to realize comparative studies between clonal lines established from the lean adult mouse (HGFu line) and from the genetically obese adult mouse (Ob17 line).

Adipose Tissue↗
PubMed1983

Lipogenic and mitogenic effects of insulin during conversion of Ob17 cells to adipose-like cells.

Chronic exposure to insulin of confluent cells of a preadipocyte clonal line (Ob17) leads to an acceleration of their development into adipose cells. The short-term effects of insulin have been examined by the stimulation of [14C] alpha-aminoisobutyrate uptake and the long-term effects by the increase in the activity levels of several lipogenic enzymes and in the intracellular triacylglycerol content. These metabolic effects of insulin occur within a physiological range of concentrations (EC50 congruent to 1 nM). As compared to insulin, dose-response curves obtained with proinsulin on these parameters show at least a 10-fold decrease in sensitivity of the cells. In contrast, the growth-promoting effects of both insulin and proinsulin occur at supraphysiological concentrations (EC50 greater than 300 nM). This mitogenic response is likely mediated through binding to receptors of insulin-like growth factors. Our data demonstrate that long-term effects of insulin on lipid synthesis can be dissociated from its effect on cell growth. Therefore the Ob17 cell line should be a useful model to study the role of insulin in the regulation of lipid synthesis in adipose cells.

Adipose Tissue↗
PubMed1983

Establishment of a human cell line after transformation by a plasmid containing the early region of the SV40 genome.

A human clonal cell line, designated TAH9, has been established from cells of adipose tissue by fusion with E. coli protoplasts containing a recombinant plasmid carrying the early genes of Simian virus 40. The establishment of the cell line is preceeded by a delayed growth crisis. The results indicate that, after cell transformation, another event(s) of low frequency is required for cell immortalization. Some biological properties of TAH9 cells are also described.

Adipose Tissue↗