Lipids,lipid turnover,and phospholipase D in plant suspension culture cells (Daucus carota)

The lipid pattern of Daucus carota L. suspension culture cells and other plant cell strains was analyzed. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and triacylglycerol were the main components. The characteristic plastidal and mitochondrial lipids could also be identified. All strains tested exhibited a phospholipase D activity. Several lipid precursors were found to be well utilized by the cells and to be special markers for certain lipids or parts of the lipid molecules. The half life times of the major lipids ranged at about half a generation time of the cells.     

Cycling of human dendritic cell effector phenotypes in response to TNF-alpha: modification of the current 'maturation' paradigm and implications for in vivo immunoregulation.

Dendritic cells (DCs) are potent antigen presenting cells reported to undergo irreversible functional 'maturation' in response to inflammatory signals such as TNF-alpha. The current paradigm holds that this DC maturation event is required for full functional capacity and represents terminal differentiation of this cell type, culminating in apoptotic cell death. This provides a possible mechanism for avoiding dysregulated immunostimulatory activity, but imposes constraints on the capacity of DCs to influence subsequent immune responses and to participate in immunological memory. We report that the cell surface and functional effects induced by TNF-alpha are reversible and reinducible. These effects are accompanied by a concordant modulation of cytokine mRNA expression that includes the induction of proinflammatory factors (IL-15, IL-12, LT-alpha, LT-beta, TNF-alpha, RANTES) which is coincident with the down-regulation of counter-regulatory cytokines (IL-10, TGF-beta1, TGF-beta2, IL-1 RA, MCP-1). The resultant net effect is a dendritic cell activation state characterized by a transient proinflammatory posture. These results demonstrate that 1) human DCs do not undergo terminal 'maturation' in response to TNF-alpha, 2) DC phenotypes are more pleiotropic than previously thought, and 3) DCs are potential immunoregulatory effector cells with implications for control of immune responses in both in vivo and in vitro systems.     

Fundamental insights in early-stage inclusion body formation

Early-stage inclusion body formation is still mysterious. Literature is ambiguous about the existence of rod-shaped protein aggregates, a potential sponge-like inclusion body scaffold as well as the number of inclusion bodies per Escherichia coli cell. In this study, we verified the existence of rod-shaped inclusion bodies, confirmed their porous morphology, the presence of multiple protein aggregates per cell and modelled inclusion body formation as function of the number of generations.     

Resistant invaders can convey benefits to native species

Introduced species are recognized as a major threat to native species. One factor that facilitates their spread is that they are often resistant to natural enemies of their native competitor. Negative effects of the invaders are often documented, but invaders may also convey benefits to the natives if they interfere with the native host-parasite interactions. If invaders act as resistant targets for the native parasites, they may reduce the density of the infectious transmission stages ('dilution effect') and decrease the risk of infection for the natives. We tested this hypothesis by exposing coexisting native and introduced freshwater snails to infectious stages of a native parasite. The native hosts showed a significantly reduced infection rate when exposed together with the resistant invader. A significant amount of the parasite transmission stages was wasted on the resistant invader leading to lower risk of infection for the natives. Our results show that invaders may convey benefits to the native competitors by perturbing the native host-parasite interaction and support the idea that the 'dilution effect' could be important for invaded communities.     

Species-specific non-expression of ribosomal RNA genes in a mammalian hybrid,the mule

The expression of nucleolus organizer activity in diploid cells was investigated in a model system for mammalian hybrids, the horse-ass cross (mule), by means of sequential Ag-NOR and chromomycin A3/distamycin ADAPI (CDD) staining in lectin-stimulated peripheral blood lymphocytes (PBL). As a rule we found species-specific nonexpression of the horse-derived NOR chromosomes in the mule, whereas the ass-derived NOR chromosomes were active. The results of PBL interphase studies were compatible with the data gained from mitotic metaphase analyses.     

The multicatalytic proteinase (prosome) is ubiquitous from eukaryotes to archaebacteria

From the thermoacidophilic archaebacterium, Thermoplasma acidophilum, a proteolytically active particle has been isolated which is almost identical in size and shape with the multicatalytic proteinase (prosome) from rat. This result indicates that prosomes have been developed early in evolution and that they possibly serve functions common to all living cells.