Cytosolic lipid inclusions formed during infection by viral and bacterial pathogens

Lipid inclusions play an important role in several pathological processes. Intracellular bacterial pathogens, such as members of the Mycobacterium and Chlamydia species are able to trigger the formation of lipid-laden foamy macrophages. Lipid droplet accumulation in the host constitutes a reservoir used by the bacilli for long-term persistence. Viruses need lipid droplets as assembly platform. We present the current knowledge about structural, functional and regulatory aspects of lipid inclusions.     

Viral inclusions in raccoon liver cells.

Three young raccoons (Procyon lotor), two from Michigan and one from Arizona, died suddenly from acute infections. Intranuclear inclusion bodies and viral particles typical of herpesvirus were seen in liver cells from all three. Inclusions also were seen in the nuclei of endothelial cells in the lung, liver, glomeruli and reticuloendothelial cells of the spleen. The source of the infection was not determined, but possible transmission from other species could not be ruled out.     

Radiation-dependent limit for the viability of bacterial spores in halite fluid inclusions and on Mars

When claims for the long-term survival of viable organisms are made, either within terrestrial minerals or on Mars, considerations should be made of the limitations imposed by the naturally occurring radiation dose to which they have been exposed. We investigated the effect of ionizing radiation on different bacterial spores by measuring the inactivation constants for B. subtilis and S. marismortui spores in solution as well as for dry spores of B. subtilis and B. thuringiensis. S. marismortui is a halophilic spore that is genetically similar to the recently discovered 2-9-3 bacterium from a halite fluid inclusion, claimed to be 250 million years old (Vreeland et al., Nature 407, 897-900, 2000). B. thuringiensis is a soil bacterium that is genetically similar to the human pathogens B. anthracis and B. cereus (Helgason et al., Appl. Environ. Microbiol. 66, 2627-2630, 2000). To relate the inactivation constant to some realistic environments, we calculated the radiation regimen in a halite fluid inclusion and in the Martian subsurface over time. Our conclusion is that the ionizing dose of radiation in those environments limits the survival of viable bacterial spores over long periods. In the absence of an active repair mechanism in the dormant state, the long-term survival of spores is limited to less than 109 million years in halite fluid inclusions, to 100 to 160 million years in the Martian subsurface below 3 m, and to less than 600,000 years in the uppermost meter of Mars.     

Isolated cilia and crystalloid inclusions in murine bone marrow stromal cells

Bone marrow stromal cells, especially reticular cells and macrophages, are thought to have important functions in the hematopoietic inductive microenvironment (HIM). In order to define the details of their fine structure, the femoral bone marrow of 50 C 57 BL mice was examined by electron microscopy after fixation by vascular perfusion. Almost all the structures of the murine bone marrow stromal cells were similar to those previously reported. Murine bone marrow reticular cells had some isolated cilia (with a frequency of 6.0%) of 9 + 0 pattern in their axoneme. The murine bone marrow macrophages had crystalloid inclusions (CI) that revealed characteristic periodic substructure. These periodic structures could be classified into four types (types A-D). Type A inclusions had a rather amorphous structure and were the most common (with a frequency of 61.9%). Type B inclusions had a periodic lamellar structure oblique to the long axis of the CI itself at intervals of about 3.5 nm. Type C inclusions had a periodic lattice structure at intervals of about 3.7 nm, and were the least frequent (with a frequency of 6.0%). Type D inclusions had periodic laminated structure parallel to the long axis of CI at intervals of about 3.5 nm. Although the true significance of isolated cilia of murine bone marrow reticular cells and the periodic internal structures of CI in murine bone marrow macrophages remains unknown, they must not be ignored as only incidental findings: they may be useful to the understanding of the relationship between function and structure in future research on HIM.     

Cobalt-60 gamma radiation increased the nitric oxide generation in cultured rat vascular smooth muscle cells

Radiation is a promising and new treatment for restenosis following angioplasty. Nitric oxide has been proposed as a potential "anti-restenotic" molecule. We radiated the cultured rat vascular smooth muscle cells with Cobalt-60 gamma radiation at doses of 14 and 25Gy and observed nitrite production, cGMP content, L-arginine uptake, inducible nitric oxide synthase (iNOS) activity, and the gene expression of iNOS. Results showed that radiation at doses of 14 and 25Gy increased cGMP content by 92.4% and 86.4%, respectively. Radiation at the dose of 25Gy increased the iNOS activity and nitrite content, but radiation at the dose of 14Gy had no significant effect on iNOS activity and NO production. Both doses of radiation significantly decreased the L-arginine transport. Radiation at the doses of 14 and 25Gy increased iNOS gene expression significantly, which was consistent with the effect of radiation on iNOS activity. In conclusion, radiation induces the NO generation by up-regulating the iNOS activity.     

Cobalt- and nickel-binding property of cullin-2.

Treatment with divalent metal ions such as cobalt (Co(2+)) or nickel (Ni(2+)) result in the stabilization of hypoxia-inducible factor-1alpha (HIF1alpha). Recently, HIF1alpha was shown to be ubiquitinated by an E3-ligase complex and be subsequently targeted for proteasomal degradation. In this study, we demonstrated that Co(2+) and Ni(2+) specifically bind to cullin-2. Mutant analysis revealed that cullin-2 possesses at least three sites for the binding. Furthermore, fluorescence spectroscopy revealed that only Co(2+) and Ni(2+) have the binding activity to cullin-2, but other metal ions, including Cu(2+), Ca(2+), Mg(2+), Mn(2+), and Zn(2+), did not. Finally, we found that Co(2+) and Ni(2+) do not bind to any components of the E3-ligase other than cullin-2, suggesting that cullin-2 is a key target of Co(2+) and Ni(2+). Interestingly, Co(2+) did not affect the complex formation of the ligase, suggesting that the metal binding to cullin-2 affects the function, but not the assembly of the E3-ligase.     

Ribosomes in growing and non-growing bacterial cells

1. 1.
   It was found that growing cells always contained more different groups of ribosomes and their total amount was greater than in non-growing cells or spores, in which only two ribosome groups with different sedimentation constants, according to the species of microorganism, were consistently found.     
   
   

Crystalloid lysozyme inclusions in Paneth cells of vitamin A-deficient rats

Summary The effect of vitamin A-deficiency on jejunal Paneth cells in rats was investigated. Crystalloid particles were observed in secretion granules of Paneth cells from 6 out of 8 rats with vitamin A-deficiency. The particles were similar to those found in Paneth cells under other experimental conditions. Using an immuno-electron-microscopic technique we demonstrated a clear lysozyme immunoreactivity of these particles. In 2 vitamin A-deficient rats tubular structures have been detected in addition to the crystalloid particles. Crystalloid particles or tubular structures were not detectable in a control group of 8 vitamin A-supplemented rats. The morphological alterations of Paneth cells may be correlated to an impaired local immunity of the intestine during vitamin A-deficiency.This work represents a portion of a doctoral thesis presented by M.J. Koch in partial fullfillment for the degree of medical doctor     

Intracytoplasmatic inclusions in cells of lettuce leaves with mosaic-like symptoms

Ultrathin sections were prepared from the tissues of lettuce leaves with mosaic-like symptoms and thickened nervature which were studied by means of electron microscopy. Intracellular inclusions surrounded by a membrane were found in the cytoplasm of parenchym cells of the investigated lettuce leaves(Lactuca saliva L. provar.capitata L. nid.jaggeri Helm., cv. Pra?an). Crystals with a distinctly apparent hexagonal lattice could be observed in the inclusions. No crystal containing inclusions were found in the tissues from the leaves without mosaic-like symptoms and in those from thickened nervature.     

Cell division genes and proteins in bacterial cells

In this review, genes and proteins involved in cytokinesis and cell proliferation of cell-wall bacteria and mycoplasms are considered. We hope that this comparative analysis of genes and proteins of phylogenetically distant bacteria, including the minimal cells of mycoplasmas, can be useful for understanding the basic principles of prokaryotic cell division. The ftsZ gene was found among representatives of all bacterial groups. The recent data indicate that FtsZ protein plays the central role in the process of bacterial cell division. FtsZ protein was revealed in all Eubacterial groups (including mycoplasmas), in Archaebacteria and chloroplasts, All FtsZ proteins are able to form protofilaments as a result of polymerization in vitro and demonstrate GTF-ase activity. On the base of these properties and some similarities in amino acid sequences with tubulins, it has been suggested that FtsZ protein is an evolutionary ancestor of Eukaryotic tubulins. On the earliest stage of bacterial cytokinesis FtsZ protein assembles into a submembranous Z-ring which encircles bacterial cell in the predivisional site. Some other bacterial proteins take part in stabilization and contraction of the Z-ring, which is considered as a cytoskeleton-like bacterial structure.