Cell biology international reports最新文献

The effect of mechanical stress on Golgi apparatus was examined in thin slices of rat liver. The findings should be of relevance both to electron microscopists who routinely mince tissue, and to biochemists who homogenize tissues to isolate membranous components. The swelling response of Golgi apparatus to monensin was used as an assay because the swelling response is distinct and is thought to result from a well-characterized metabolic process, namely the acidification of vesicles. The results showed that the swelling response was compromised by monensin as far away as 6–7 cells from a cut surface even though other aspects of cell ultrastructure were not altered from normal. The monensin-induced swelling response was also evaluated in isolated Golgi apparatus and found to be similar to that with tissue. Thus, mechanical stress such as commonly used to mince tissue or isolate tissue components, appears to markedly alter Golgi apparatus function compared to the situation in vivo. In this example, the altered response of Golgi apparatus to monensin indicated that some aspects associated with the ATP-dependant proton-pumping machinery of the transmost cisternae and trans Golgi network were compromised.

Vascular smooth muscle cells exhibit a unique pattern of growth in culture. They have the capacity for multilayer growth and form large macroscopic nodules. We find that nodulation is inhibited in the presence of phorbol esters and that there is a concomitant decrease in the production of a 38 kd secreted protein associated with nodulation in porcine smooth muscle. Examination of the organization of actin filaments within the cells using a rhodamine phalloidin stain indicates that there is a rearrangement of actin filaments in response to phorbol esters. This rearrangement increases the number of attachment sites to the culture surface and may contribute to the inhibition of nodulation in smooth muscle cells by phorbol esters.

The correlation between the extracellular deposition of fibronectin and the development of the actin-containing cytoskeleton was studied during the attachment and spreading of the rat mammary epithelial cell line Rama 25. During the initial phase of cell spreading, actin is localised in peripheral microfilament bundles. As cell spreading increases, the peripheral ring is displaced towards the perinuclear region. Fibronectin, deposited beneath the basal surface, co-localises with the actin-containing peripheral ring. The peripheral ring subsequently disappears and is replaced by a system of radial microfilaments that extend from the perinuclear region to the cell periphery. At this stage, there is no correlation between the distribution of fibronectin and actin. As cells form colonies, radial microfilament bundles are replaced by peripheral microfilament bundles which do not co-localise with fibronectin. Cells at the edges of colonies extend lamellae that contain microfilament stress fibres. In these structures there is co-localisation of actin, fibronectin and the a5ß1-integrin fibronectin receptor.

More epithelial-like cells are found in primary cultures of transcathetel arterial embolization (TAE)-untreated human liver cancer tissues than in those of TAE-treated tissues. A new cell strain, HUH-33, established from the former, grows slowly and is untransplantable into nude mice and secretes alpha-fetoprotein, albumin and some other tumor markers. Chromosome numbers are widely distributed. HUH-33 expresses hepatocyte type keratin and contains desmosome-or intermediate filament bundle-like structures.

When cell lines derived from tumor tissues were plated simultaneously with the lignin derivative or dextran sulfate in plastic culture dishes, the cells did not completely adhere to dishes and/or the shape of even the adhering cells changed significantly. On the other hand, using cell lines derived from normal tissues, no significant effect of the polyanions was observed. The present study revealed that the lignin derivatives demonstrated differential responses between cells derived from tumor tissues and from normal tissues, and that the lignin derivatives strongly inhibited the growth of mouse sarccoma cells (FRUKTO) and rat foetal cells (Ad12-3Y1-Z19) transformed with adeno virus type 12.

We show here that purified platelet derived growth factor (PDGF) stimulates DNA synthesis in normal endosteal mouse and human osteoblastic cells isolated by selective migration from the trabecular bone surface. Maximum DNA synthesis as measured by (³H)-thymidine incorporation into DNA was increased at 50 ng/ml PDGF (48–72 hours). In both species, the effect of PDGF (25ng/ml) was lower than the mitogenic effect of 10%FCS. We found that the mitogenic effect of PDGF on human trabecular cells decreased with the number of cell passages. DNA synthesis was increased about 4-fold by PDGF (25 ng/ml) in early passaged cells that expressed low basal growth rate and high osteocalcin production in basal conditions and in response to 1,25(OH)₂ vitamin D, whereas DNA synthesis was increased 1.2 fold by PDGF in late passaged cells that showed high basal growth rate and low osteocalcin release in absence or presence of 1,25(OH)₂ D. PDGF alone had no effect on osteocalcin production. These results indicate that PDGF has mitogenic effect on normal mouse and human osteoblastic cells lining the trabecular bone surface and that the responsiveness to PDGF of human trabecular cells varies with the stage of differentiation.