Biomedical subjects

J Vassy

Publications and source records attributed to J Vassy.

46 records · Page 3Linked to original sources

PubMed1985

The effect of dexamethasone on albumin production by fetal rat hepatocytes in culture.

Hepatocytes derived from 15 and 19-day gestation rats synthesize and secrete albumin during culture. Albumin secretion is maintained when the culture medium is supplemented with dexamethasone but declines in its absence. The fall in secretion rate correlates with the level of albumin messenger RNA in the respective cultures. Even when dexamethasone is present, the level of albumin production in 19-day gestation hepatocytes is 6 to 7 times greater than that observed in hepatocytes derived from 15-day gestation rats. Immunocytochemical studies were undertaken to establish whether the difference in secretion rate was due to a difference in the amount of albumin produced by all the hepatocytes of the respective cultures or whether there were fewer hepatocytes which were capable of synthesizing albumin in the less mature liver. The results indicate that albumin production is reduced in all hepatocytes when cultured in the absence of dexamethasone.

Albumins↗

PubMed1984

Ultrastructural indirect immunolocalization of transferrin in cultured rat hepatocytes permeabilized with saponin.

Transferrin was localized in 48-hr cultured adult rat hepatocytes by indirect immunoperoxidase following paraformaldehyde--glutaraldehyde fixation and the use of saponin as a membrane permeabilizing agent. The protein, present in all the parenchymal cells in variable amounts, was found to be specifically located in the endoplasmic reticulum and Golgi apparatus. These results are consistent with recent reports claiming that all adult hepatocytes may synthesize a given liver plasma protein at a given time. The procedure used in this study should be particularly useful for the detection of intracellular antigens in various intact cell types.

Animals↗

PubMed1984

The influence of mode of fixation, type of fixative and vehicles on the same rat liver: a morphometric/stereologic study by light and electron microscopy.

The influence on cellular and subcellular structure was studied by comparing perfusion versus immersion fixation with cacodylate buffered glutaraldehyde, osmium or glutaraldehyde immersion fixation with two vehicles, phosphate and cacodylate buffer. The study was performed in the same animal using the left liver lobe for the four immersion fixation experiments and the remaining lobes for perfusion. The preparative steps were done under identical conditions in one operation. The mode of fixation was the most influential factor with clear (15%) increases for the volume of hepatocytes (mainly their cytoplasm), and the mitochondria (30%), when comparing immersion to perfusion fixation. This mitochondrial enlargement was particularly displayed in the organelles' average profile area, being more than doubled (211%) in immersion fixation. Similarly high profile enlargements (150%) were also found after osmium immersion fixation. Changes in nuclei were minor compared to the cytoplasm. There was a good correlation between the volume changes of the hepatocyte cytoplasm and the mitochondria (r = 0.85, p less than 0.01). Qualitative results revealed that there exists a zone of good electron microscopic preservation 2-3 cell layers beneath the block edge in immersion fixed material, whereas perfusion fixed tissue displays a homogeneous fine structure.

Animals↗

PubMed1984

[Effect of fixation on immunolocalization of transferrin and albumin in the liver of the adult rat].

The influence of the fixation procedure on the localization of albumin and transferrin in adult rat liver has been carried out using an indirect immunoperoxidase technique at the light and electron microscopic levels. Perfusion and immersion fixations with different concentrations of paraformaldehyde (with or without addition of glutaraldehyde) have been investigated. According to the mode of fixation (perfusion versus immersion) and the concentration of the fixative, the number of albumin and transferrin containing hepatocytes could vary from 10% to 100%, and different labeling patterns could be observed at the electron microscopic level. For the same concentration of fixative, a perfusion fixation induces a less intense labeling than an immersion fixation. Thus similar results are obtained after immersion fixation in 6% paraformaldehyde + 0.25% glutaraldehyde or after perfusion fixation in 4% paraformaldehyde + 0.025% glutaraldehyde. Similar data are noticed after immersion fixation in 4% paraformaldehyde or after perfusion fixation in 1% paraformaldehyde + 0.025% glutaraldehyde. Moreover, perfusion fixation induced a more fine cell structure preservation than immersion fixations and avoided the appearance of zones of fixation.

Albumins↗

PubMed1983

[Effect of paraformaldehyde fixation on the qualitative preservation and stereological parameters of the adult rat liver].

Studies were made to compare the impact of immersion fixations with different concentrations of paraformaldehyde (10%, 6% + 0,25% glutaraldehyde, 4% and 1%) on the cellular and subcellular structure preservation. The study was performed on 3 animals. Similar conditions existed for all the preparative steps, since they were done in one operation. Cellular parameters as the volume densities of hepatocytes (VVH), nuclei (VVNH), cytoplasm (VVCYT) and extra-hepatocytic space (VVEX) were assessed by light microscopy on toluidine blue stained semi-thin sections at X 1 000. The volume (VVM), the surface density of mitochondria (SVMO) and their mean profile size (am) were measured at the electron microscopic level (X 15 000). The most striking differences were observed in the volume density (VVM), surface to volume ratio (SV) and mean profile area of the mitochondria (am). Qualitative results revealed that the zone of good electron microscopic observation varied according to the concentrations of the fixative. In conclusion, the best qualitative and quantitative preservation is assumed with 4% paraformaldehyde and at a less degree with 6% paraformaldehyde + 0,25% glutaraldehyde.

Animals↗

PubMed1981

Ultrastructural localization of transferrin synthesis in rat hepatocytes during prenatal and postnatal development.

The synthesis of transferrin has been investigated in rat hepatocytes during pre- and postnatal development of the liver by ultrastructural immunoperoxidase cytochemistry. Transferrin was detected in fetal and postnatal hepatocytes on the rough endoplasmic reticulum and in the Golgi apparatus, but the amount and distribution of the protein varied according to the stage of the hepatocyte maturation. Between days 13 and 19 of gestation, nearly all hepatocytes exhibited transferrin. After day 20 of pregnancy more and more unstained hepatocytes were detected. Two periods (19th day of gestation and one day after birth) were characterized by an intense labeling of the Golgi apparatus; in contrast, only a small amount of transferrin was located in this organelle at other stages of the rat liver development. The accumulation of transferrin in the Golgi apparatus is interpreted as a transitory storage of the protein. Transferrin could be produced by immature as well as mature hepatocytes.

Animals↗

PubMed1979

[Ultrastructural demonstration of transferrin synthesis in the adult rat liver].

An ultrastructural immunoenzymatic study allowed us to demonstrate in Rat adult hepatocytes the presence of transferrin on the rough endoplasmic reticulum and in the Golgi apparatus. Such localizations suggest that the different steps of transferrin synthesis could possibly be related topographically to them. These results further an approach to the problems of maturation and secretion of transferrin.

Animals↗

PubMed1979

Demonstration of the simultaneous presence of transferrin, hemopexin and albumin in the same adult rat hepatocyte.

The location of three plasma proteins (transferrin, hemopexin, and albumin) in hepatocytes was investigated in adult rats. The synthesis of transferrin anf hemopexin has been established by ultrastructural studies showing a labeling of the rough endoplasmic reticulum (RER). By using an indirect immunoenzymatic method with monospecific antibody solutions, the three proteins were detected in the same hepatocyte. The simultaneous presence of different plasma proteins in hepatocytes seems to point to the fact that the synthesis in these cells could be a non-specialized type.

Animals↗

PubMedDate not supplied

Protective effect of superoxide dismutase against hair graying in a mouse model.

Oxygen free radicals play a role in the aging process, and the protective effect of various antioxidants has been intensively studied, in particular for cutaneous aging. Besides hereditary factors, free radical-mediated damage to melanocytes of the hair follicle has been considered as a mechanism for aging of the hair. It was the aim of this study to evaluate the role of photosensitization reactions for hair graying and to demonstrate potential protective effects of superoxide dismutase (SOD). Mice with black hair were depilated with the fingertips on a surface of 6 x 2.5 cm on both sides of the dorsum. The right side received five applications of a SOD-containing gel before exposure to psoralen (concentration 0.5 mg/mL) plus UV-A (365 nm, 4 J/cm2). The left side was pretreated in the same way with a gel free of SOD. When the hair started growing again, the SOD-protected side was covered with black hair, whereas the hair on the vehicle-treated side was gray or white in 27 of the 30 animals studied. The 0.01% SOD concentration was as protective as the 0.1% concentration. Heat-inactivated SOD, applied in another five animals, was not protective. Using fluorescent labeling of the SOD with fluorescein isothiocyanate, epifluorescence microscopy and digital imaging processing, we show that SOD applied to the skin surface penetrates through the follicular appendages, as well as through the unbroken stratum corneum. Our findings suggest that superoxide radicals, generated by interaction of UV-A light with the sensitizer, initiated the formation of secondary products with well-known DNA-damaging effects, such as lipid peroxidation products and tumor necrosis factor alpha. SOD prevented the damage to melanocyte DNA by dismutating superoxide. Photosensitization may be another mechanism for hair graying, which can be influenced by antioxidants. Given the large number of exogenous and endogenous sensitizers, this mechanism deserves further study for human hair graying.

Animals↗

PubMedDate not supplied

Remodeling of vimentin cytoskeleton correlates with enhanced motility of promyelocytic leukemia cells during differentiation induced by retinoic acid.

The intermediate filament (IFs) cytoskeleton is one of the major determinants for the mechanical properties of cytoplasm. Vimentin is the major IFs protein in peripheral blood neutrophils. We investigated its expression and function during neutrophil differentiation using the promyelocytic leukemia cell line NB4. The differentiation of NB4 cells along the neutrophil lineage and the monocytic pathway was induced by all-trans retinoic acid (ATRA) and phorbol esters (PMA), respectively. We demonstrated a down-regulation of vimentin after ATRA treatment of NB4 cells by immunoblotting and immunofluorescence. The architecture of the vimentin cytoskeleton in differentiated NB4 cells resembled that observed in mature neutrophils. In contrast, we showed a slight increase of vimentin content in phorbol ester (PMA)-treated NB4 cells. The structural features of the vimentin cytoskeleton obtained by image analysis showed significant differences in network density and directionality between ATRA-treated NB4 cells and controls. The functional consequence of the cytoskeletal remodeling for the mechanical properties of NB4 cells was assessed in migration assays. After ATRA treatment, we found a 4-fold increased migration of NB4 cells across transwell membranes with a 8 microm pore size without any cell size modification. No significant differences between PMA-treated NB4 cells and control cells could be observed using similar tests. These results indicate that both vimentin expression and network architecture are tightly controlled during neutrophil differentiation to regulate the mechanical properties of these cells.

Antineoplastic Agents↗