PubMed Health⌕ Search

Biomedical subjects

N Marceau

Publications and source records attributed to N Marceau.

At least 73 records · Page 4Linked to original sources
PubMed1982

Immunocytochemical localization of actin in the pancreatic exocrine cell.

Immunoreactive actin molecules have been localized in pancreatic acinar cells by the protein A-gold technique. The labeling was found at the level of the filamentous cell web, and in close association with the Golgi cisternae, condensing vacuoles, and zymogen granules delimiting membranes as well as with the plasma membrane. A weak labeling was also present over the dense content of the zymogen granules. The association of actin with different membranes implicates that contractile proteins might constitute structural membrane proteins and, thus, might play an important role in protein secretion.

Actins↗
PubMed1982

Synthesis and degradation of heat shock proteins during development and decay of thermotolerance.

Morris hepatoma 7777 cells, heat conditioned at 43 degrees for 0.5 hr, become gradually thermoresistant during an incubation at 37 degrees as judged by their ability to form colonies following a second heat challenge. Pulse incorporation of [35S]methionine into proteins at various times after the conditioning treatment and subsequent fractionation of the proteins by polyacrylamide gel electrophoresis indicate that the gradual putative modifications occurring at the cellular level and leading to the thermotolerance state are accompanied by an elevated synthesis above the normal level of a small set of polypeptides with apparent molecular weights of 27,000, 65,000, 68,000, 70,000, 89,000, and 107,000. Both thermotolerance development and protein induction are completed after a 6- to 8-hr period. At the end of this period, thermotolerance is at its maximum level and heat shock protein synthesis is returned to normal. This acquired thermal resistance eventually disappears between 60 and 80 hr following conditioning treatment. In a parallel manner, the heat shock-induced proteins synthesized during the first 4 hr following the conditioning treatment are maintained in the cells at a high level for several hr but become undetectable by 82 hr. The results provide strong circumstantial evidence that heat shock proteins are involved in the acquisition, maintenance, and decay of thermotolerance.

Animals↗
PubMed1982

Hormonally induced formation of extracellular biomatrix in cultured normal and neoplastic liver cells. Effect of dexamethasone.

We have examined by scanning electron microscopy the cell surface of rat hepatocytes (HEP), propagable liver epithelial (CE) cells, Morris # 7777 and # 7795 hepatoma (MH) cells at different times after seeding onto fibronectin-precoated substratum in presence of a defined medium. Upon seeding, HEP exhibited numerous microvilli and at later times, the cells flattened and lost most of these structures. When HEP were cultured in presence of dexamethasone (DEX), numerous microfibrils were observed extending into the substratum and on the cells and formed elaborate extracellular matrices. By indirect immunofluorescence we have demonstrated that these extracellular matrices are composed of fibronectin and collagens (type I, III). In contrast to HEP, sparse or confluent CE cells showed few microvilli and only very low amount of extracellular matrices were observed at confluency, even in presence of DEX. Growing or confluent MH # 7777 cells exhibited some microvilli while MH # 7795 cells showed a lower number of these surface structures at confluency. These hepatoma cell lines produced little extracellular matrices in absence or presence of DEX. Tyrosine aminotransferase (TAT), a liver specific intracellular protein, was inducible in HEP and MH but not in CE cells. Thus, these data demonstrate that the hormonal induction of a liver specific function is accompanied by the production of extracellular matrix only in the case of normal hepatocytes (HEP), but not in the case of cancerous (MH) or epithelial (CE) cells.

Animals↗
PubMed1981

The relationship between cell volume, ploidy. and functional activity in differentiating hepatocytes.

Liver cells were isolated by collagenase perfusion from rats of 1 day, and 1, 3, 5, and 12 weeks of age, fractionated by velocity sedimentation at 1 g (STAPUT), and the major cell types were identified in terms of specific functions. Alphafetoprotein and albumin were used as markers of differentiating hepatocytes and these functional activities were evaluated in a quantitative manner using a radioimmunoassay. The capacity of this cell type to store 35S-BSP, an indicator of bile formation, was also evaluated. Sinusoidal cells and hematopoietic cells were identified on the basis of their ability to take up 99mTC-colloid sulfur and to incorporate 59Fe, respectively. The fractionation procedure allowed a good separation of sinusoidal cells from hepatocytes at all postnatal ages and also of erythroid cells still present during the first week after birth. With increasing age, alphafetoprotein-producing hepatocytes exhibited changes in sedimentation velocities that parallelled those of albumin-producers. In turn, the latter hepatocyte subpopulation underwent gradual shifts in modal peak velocities similar to those of bile-forming hepatocytes. The fractionated hepatocytes obtained at different ages were further analyzed in terms of cell volume and nuclear ploidy using a Coulter counter system. This quantitative analysis obtained at the cellular level demonstrated that during the age-related differentiation of hepatocytes, which occurs during the postnatal period and results in the gradual appearance of cells of higher ploidy levels, the extent of albumin production and bile formation can be correlated with the hepatocyte volume.

Aging↗
PubMed1981

Restricted specialization of differentiating hepatocytes in terms of albumin and alpha-fetoprotein production.

Hepatocytes were isolated from 1-day and 1,2,3 and 12-week old rat livers by collagenase perfusion and the relative numbers of albumin (ALB) and alpha-fetoprotein (AFP) producers were evaluated using the reverse hemolytic plaque assay. The percentage of ALB producers remained essentially constant to 35% over the 12-week period. In contrast, the percentage of AFP producers varied from 19% at 1 day up to 28% at 1 week and then down to 0.1% at 3 weeks. Moreover, a double identification of secreting hepatocytes, using an adaptation of the plaque assay, demonstrated that AFP producing hepatocytes were also ALB producers. These results are explained in terms of a restricted specialization of differentiating hepatocytes during normal development.

Albumins↗
PubMed1980

Hepatocytes from newborn and weanling rats in monolayer culture: isolation by perfusion, fibronectin-mediated adhesion, spreading, and functional activities.

The two-step collagenase perfusion method originally developed for the high yield isolation of parenchymal cells from adult rat livers has been adapted to rats of 1 day, 1 week, and 2 weeks of age. The use of this method to isolate hepatocytes from five or six rats of the respective ages demonstrated its reliability in terms of cell yield, percentage of single cells, and cell viability. In all cases, hepatocytes attach with high efficiency to fibronectin precoated dishes using serum-free culture medium. The dynamics of spreading is faster for newborn hepatocytes than adult ones. The functional integrity of these parenchymal liver cells was assessed by their capacity to secrete albumin and alpha-fetoprotein in serum-free medium and to express lactate dehydrogenase activity over a 24-hr period in primary culture.

Albumins↗
PubMed1979

Cell growth recovery after treatments at various supraoptimal temperatures.

The growth recovery kinetics of HeLa cells was investigated after treatments at intermediate (43-45 degrees) or high (49-55 degrees) supraoptimal temperatures for various periods of time (2 to 300 min) or after irradiations with nanosecond infrared CO2-laser pulses at energy densities equivalent to very high temperatures rises. After treatments at intermediate temperatures, single cells developed into colonies smaller than those obtained from nonheated control cells. Daily incorporations of pulsed [3H]thymidine in whole populations and microscopic observations of individual cell proliferation revealed a complex growth recovery for both survivors and dying cells. In contrast, colonies arising from cells treated at temperatures above 49 degrees do not differ in size from those developed from controls, and growth evaluations by [3H]thymidine and microscopy demonstrated that survivors resume normal proliferation immediately after treatments. The results which are supported by other studies on the effects of dose fractionation and metabolism status on cell survival are further discussed in relation to the "multistep" kinetic model for the cell response to hyperthermia.

Cell Division↗
PubMed1977

Surface membrane differentiation of hemopoietic cells as observed by radioactive labeling.

Bone marrow cells from normal rats were separated by velocity sedimentation into three distinct populations corresponding to granulocytes, lymphocytes and reticulocytes. Cells from each population were surface labelled via the lactoperoxidase radioiodination or the tritiated borohydride reduction. Distinct labeling patterns were observed on SDS-PAGE for each cell populations. Separation of bone marrow cells from anemic rats injected with TAB vaccine led to four populations corresponding to successive stages of erythroid cell maturation. Labelled protein patterns were not in this case as different from one population to the other, except for one species which increased in intensity with the degree of maturation. The tritiated glycoprotein profiles show a shift from high to low molecular weight species during the process of maturation.

Anemia↗
PubMed1975

The relative rates of degradation of the plasma membrane glycoproteins from normal rat liver.

Rat liver plasma membranes, as fractionated by sodium dodecylsulfate/polyacrylamide gel electrophoresis, have been examined for the incorporation in their subunits of radioactive leucine, glucosamine and fucose. Specific spectra were obtained. In contrast to leucine, where the activity is distributed in many peaks all over the fractions, the glucosamine and fucose activities are found principally in the high molecular weight region. The relative rates of degradation of the glycoprotein components of the plasma membrane have been measured in normal liver using the double isotope technique. A marked heterogeneity of degradation was observed among the different subunits and a correlation between the rate of degradation and the size of the labelled subunits was found with glucosamine and fucose as well with leucine. This suggests a similar mode for the degradation of these membrane components.

Animals↗