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N Hauser

Publications and source records attributed to N Hauser.

27 records · Page 2Linked to original sources
PubMed1994

Native cartilage matrix protein (CMP). A compact trimer of subunits assembled via a coiled-coil alpha-helix.

Cartilage matrix protein (CMP), a major component of many types of cartilage, is a noncollagenous glycoprotein with a molecular mass of 148 kDa consisting of three identical subunits. With the aim of performing a more comprehensive characterization, we purified CMP in a native conformation from fetal bovine rib cartilage avoiding the denaturing solvents previously used. CMP could be selectively extracted with EDTA-containing buffer which indicates a divalent cation-dependent anchorage in the cartilage matrix. Determination of the amino-terminal sequence of the bovine protein confirmed its identity when compared with published cDNA sequences of chicken and human CMP. Electron microscopy revealed the presence of three ellipsoid subunits which are connected at one end. Sequence analysis indicated the presence of a coiled-coil alpha-helical assembly domain formed by the COOH-terminal end of the subunits. The trimeric structure was retained after complete reduction under native conditions which shows that the coiled-coil domain is stable also in the absence of interchain disulfide bonds.

Amino Acid Sequence↗
PubMed1992

Interferon-gamma and interleukin-1 beta inhibit adipoconversion in cultured rodent preadipocytes.

Cytokines like tumor necrosis factor (TNF), interferon-gamma (IFN-gamma), and interleukin-1 (IL-1) are known to interfere with the differentiation of cultured cell lines of adipocyte precursors. In the present study, the effect of mouse and rat IFN-gamma, as well as human IL-1 beta, was investigated on rodent preadipocytes in primary cultures, either in the presence of fetal bovine serum (FBS, 10%) or in serum-free defined medium. IFN-gamma exerted an antiproliferative action that was more pronounced when cells reached confluency than during the growth phase of the culture. Morphological observation and quantifications of undifferentiated and differentiating cells revealed that IFN-gamma caused a decrease in the proportion of cells devoid of lipid droplets which would correspond to fibroblast-like cells, whereas preadipocytes remained unaffected. IFN-gamma induced a marked retardation of adipoconversion, resulting in a partial inhibition of lipoprotein lipase (LPL) activity and a severe decrease in glycerol-3-phosphate dehydrogenase (GPDH) activity. The antiproliferative and anti-LPL effects of IFN-gamma were neutralized by adding anti-IFN-gamma antibodies, while these antibodies prevented only partially the depressing effect of IFN-gamma on GPDH activity. Contrary to IFN-gamma, IL-1 beta slightly enhanced the proliferation in preadipocyte cultures. IL-1 beta also depressed adipoconversion, inhibited markedly LPL activity, and partially reduced GPDH activity. These results show that the influence of cytokines on adipoconversion observed in preadipocyte cell lines can be found in normal preadipocytes in culture.

Adipose Tissue↗
PubMed1991

Glucocorticoids induce a drastic inhibition of proliferation and stimulate differentiation of adult rat fat cell precursors.

The effects of physiological glucocorticoids such as cortisol and corticosterone, as well as dexamethasone, on proliferation and differentiation of rat fat cell precursors kept in primary culture were analyzed. In serum-containing medium (10%), glucocorticoids markedly decreased cell proliferation, either on subconfluent or on confluent cultures. This effect was independent of the presence of insulin. In contrast, acute amplification of adipose conversion was observed mainly when glucocorticoids and insulin were added simultaneously. Morphological quantification of lipid-containing cells confirmed acceleration of the maturation process, and an early and specific reorganization of the cytoskeleton was detected at the ultrastructural level. In the presence of insulin, glucocorticoids also enhanced the main marker enzymes, lipoprotein lipase, and glycerol phosphate dehydrogenase. Glucocorticoid effects on precursor proliferation and differentiation were clearly dose-dependent, dexamethasone being 10 times more potent than cortisol and corticosterone. Similar results were obtained in serum-free medium, as well as in preadipocyte cultures derived from different fat deposits. This study demonstrates that in addition to an acute inhibition of precursor growth, glucocorticoids exert a clear stimulation of adipose conversion, which depends mainly on the presence of insulin and the glucocorticoid concentration.

Adipose Tissue↗
PubMed1990

Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria.

Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved the migration of the osteoblasts on glass fragments before trypsinization. Since the plating efficiency, the proportion of alkaline phosphatase-positive cells, the population doubling time, and the calcium deposition were more adequate, the second method was used to further characterize the behavior of the cultures. During the first week of culture, the cells featured shapes similar to those observed in vivo on the surface of periosteum-free calvaria. They formed multilayers and, in the presence of ascorbic acid, synthetized an organic matrix containing exclusively type I collagen. Later, small amounts of type III collagen appeared. The cells were embedded in the matrix and progressively acquired the morphologic phenotype of osteocyte-like cells. The matrix mineralized in the presence of beta-glycerophosphate. The technique of drop-inoculation (high concentration of cells in a small volume of medium) promoted the multilayer formation and the achievement of large mineralized plates (about 1 cm2) in 3 weeks of culture.

Alkaline Phosphatase↗
PubMed1990

The stroma-vascular fraction of rat inguinal and epididymal adipose tissue and the adipoconversion of fat cell precursors in primary culture.

The stroma-vascular fraction (SVF) of inguinal and epididymal fat pads of 4 week-old rats was studied by electron microscopy. Among the various cell types, endothelial cells and preadipocytes were found in both SVF, while mesothelial cells were only detected in the epididymal SVF. The resulting heterogeneity of primary culture and the adipoconversion of the fat cell precursors were studied in a serum-supplemented medium enriched with insulin (14.5 nM) and exogenous triglycerides. Despite the heterogeneity of the inoculum, the primary cultures were rather homogeneous, fat cell precursors being the main cell type. Distinctive contaminant fibroblast-like cells were observed in both cultures, whereas epithelial-like cells, which correspond most probably to mesothelial cells, were only found in epididymal cultures. Differentiation of fat cell precursors was assessed by the appearance of lipoprotein lipase (LPL) and glycerol-3-phosphate dehydrogenase (GPDH). LPL activity was found in the same level in cells of both deposits while GPDH activity was elevated in inguinal vs epididymal derived stroma-vascular cells. The different adipose conversion pattern of both cultures was confirmed by morphological quantification: the maturation of epididymal fat cell precursors was faster but less extensive. These differences could be related mainly to regional localization rather than to different maturation of the two fat deposits.

Adipose Tissue↗
PubMed1987

Effect of aging on the morphology of epididymal adipose tissue in the rat.

Quantitative morphometrical parameters were compared in epididymal adipose tissue of adult (6 months old) and old (24 months old) Wistar rats, using light and electron microscopy of embedded material and freeze-etch replicas, and taking into account the functional unit of adipose tissue: the capillary-adipocyte. Despite an insignificant reduction of the adipocyte number and size in old rats when the whole population was sampled, the confounding factor of size of adipocytes could be excluded from morphometric computations in adult and old rats. Morphometric measures were performed on the whole transit from capillaries to adipocytes. They revealed that the plasma membranes, as seen in freeze etching, and the thicknesses of endothelial and adipocyte cytoplasms, as seen in ultra-thin sections, remained unaltered with aging. By contrast, the basement membranes were changed but differently around capillaries and adipocytes. The capillary-adipocyte distances were shorter and the vascularization density was higher in old rats.

Adipose Tissue↗
PubMedDate not supplied

The cellularity of developing adipose tissues in Pietrain and Meishan pigs.

The development of external, internal, inter- and intramuscular adipose tissues was compared in Pietrain (lean) and Meishan (obese) pigs during their growth, at 0, 7, 30 and 90 days of age. Up to 1 month of age, the total lipid content of external and internal adipose tissues as well as mean adipocyte diameter increased similarly in both breeds of pigs. The percentage of plurilocular adipocytes decreased in both breeds; it remained higher in Meishan up to 30 days of age, which would indicate a delayed maturity of adipose tissue in this pig. Adipocyte hypertrophy characterizing the Meishan pig starts between 1 and 3 months of age. At 90 days, adipocyte diameters were about 50% higher in Meishan than in Pietrain. Muscle lipid content was higher in Pietrain than in Meishan until 1 month of age, whereafter it became lower than that of Meishan. Intramuscular adipocytes appeared later than those of other tissues in both breeds and were larger in Meishan than in Pietrain.

Adipocytes↗