Comparative analysis of diffusive and stress induced nutrient transport efficiency in the lacunar-canalicular system of osteons

Marker migration experiments suggest that cyclic mechanical loading of cortical bone in vivo increases marker penetration into bone. Is this a result of stress induced fluid flow or of stress stimulation of active transport processes? Active lacunar-canalicular transport of nutrients was suggested by Ham in 1979 on the basis of the presence of actin filaments in osteocyte processes and their suspected role in cell motility. In addition, Tanaka in 1984 observed active transport of microperoxidase in bone and Tanaka-Kamioka et al. in 1998 observed experimentally that osteocyte processes are able to actively change their form. In this study we performed parametric and comparative analyses of the transport efficiencies of diffusion and stress generated fluid flow of (glucose) nutrients in lacunar-canalicular systems in cortical bone. The result obtained is that neither diffusion nor stress induced fluid flow is capable of sustaining osteocyte viability. It is possible that cyclic stress stimulates an active nutrient transport mechanism to supplement stress flows.     

Individual variability in the karytype of Chironomus plumosus: atypical puffs in larva from a natural population from the Chita region

Atypical puffing of polytene chromosomes of Chironomus plumosus (1 larvae, IV stage) from the Ivan lake in Chita region, southern part of Siberia, has been described. At the sites of ordinary localization of interdisks and puff-patterns typical of Ch. plumosus the puffs in our material displayed different levels of activity: from a light vacuolous spot to puffs of class 5. Most of these puffs were revealed in Ch. plumosus for the first time, namely, puffs IA10a-r, IB12v-y + 13a-d, IIC14p-z + 15a-z + 16a-e, IIC14p-z + 15a-h, IID14a-m + 13s-w, IID11-2a-d, IID1p-x + 2a-d, IIIE3g-a and IIIF13h-p + 14a-e. Some other puffs, such as IB16a-k, IB15m-r + 16a-m, IB21a-o, IIC20, IVG6 and IVG7, were described earlier (Maksimova, 1979, 1983). The majority of observed puffs turned out to be heterozygous. Only one puff-knob, IIIE3g-a of class 5 activity, was found in all cells of the studied salivary glands. Its origin may be due to the appearance of heterozygoous inversion pluE1.2. All other puffs were observed in some part of cells. It is supposed that the appearance of larvae with unusually high functional activity of chromosomes may be presumably induced by stress influence of certain environmental factors.     

Study of surface properties of chloroplasts of some beans using a binary phase polymer system

The surface properties of chloroplasts in leaves of some leguminous plants--Pisum sativum, Trifolium paratense, Melilotus album, and Vicia cracca--were investigated, based on the analysis of phase formation kinetics of the aqueous polymeric two-phase system dextrane-500/polyethyleneglycol-6000. The surface properties of chloroplasts have been shown to display both species- and sort-specificity. A specific influence of chloroplasts of melilot and non-chlorophyllic pea lines on phase formation kinetics has been noticed.     

The effect of medium viscosity on actin polymerization

A comparative study of the influence of two factors--excluded volume effect, and medium viscosity--on actin polymerization was carried out. Dextrane--500 (1%), poly(ethylene)glycol--6000 (2.7%), Ficol (1.8%), methyl cellulose (0.04%), saccharose (10%), and glycerine (10%) were used for creating a viscous medium. The concentrations of these agents in actin solution made approximately the same viscosity commensurable with the cytoplasm viscosity. By this it was possible to bring conditions of actin polymerization in vitro closer to those in vivo. It is shown that the medium viscosity in contrast to the excluded volume effect, prolongs the nucleation phase during actin polymerization. A conclusion is made that in the cell both factors can be involved in the regulation of actin filament formation.     

Protein determinants of RNA binding by DNA polymerase of the T4-related bacteriophage RB69

DNA polymerase (gp43) of phage T4 plays two biological roles, one as an essential DNA binding replication enzyme and the other as an mRNA-specific autogenous translational repressor. Binding of T4 gp43 to its mRNA target (translational operator RNA) interferes with gp43-DNA interactions, but it is unclear how the protein determinants for binding DNA are affected by the dynamics of gp43-mRNA interactions. We have used RB69 gp43, a natural variant of the T4 enzyme whose crystal structure has been determined to identify protein sites that respond to the interaction with specific RNA. We used protein phosphorylation markers, photocross-linking studies, protease sensitivity assays, and mutational analyses to examine the effects of operator RNA on the enzyme's five structural domains (N, exo, palm, fingers, and thumb). Our studies suggest that this RNA affects gp43-DNA interactions through global effects on protein structure that occlude DNA-binding sites but leave the enzyme accessible to interactions with the sliding clamp (RB69 gp45) and possibly other polymerase accessory proteins. We discuss the possible biological significance of putative RNA-binding motifs in the N and palm domains of RB69 gp43.     

Production and characterization of monoclonal immunoglobulin A antibodies directed against Salmonella H:g,m flagellar antigen

Hybridomas were generated after intragastral immunization of BALB/c mice with live Salmonella suberu and subsequent fusion between isolated spleen lymphoblasts and myeloma cells. Three monoclonal antibodies (MAbs) of immunoglobulin A (IgA) isotype were selected and characterized. All of them were found to recognize the H:g epitope in enzyme-linked immunosorbent assay and immunoblotting but did not react with all H:g-expressing strains in slide agglutination test. All MAbs strongly agglutinated Salmonella enteritidis type strain and a large number of S. enteritidis clinical isolates. They were not bactericidal in the presence of complement. All hybridoma clones produced secretory IgA forms, which were found in the gastrointestinal tract of mice bearing hybridoma as a subcutaneous 'backpack' tumor or after intravenous application of purified MAbs. The IgA MAbs stability demonstrated in different tests together with their antigen specificity and strong agglutination ability make them a useful diagnostic tool for serotyping of Salmonella strains.     

Cell division and cell enlargement in isolated Cucurbita cotyledons grown in darkness and in light

The spatial and temporal patterns of post-embryonal cell growth and cell division were characterised in excised cotyledons of vegetable marrow (Cucurbita pepo L. var. giromontia Alef.) incubated in water. The concurrent roles of these two processes in cotyledon growth were determined using paradermal sections of the first palisade layer of developing cotyledons. Tissue specificity was observed in the pattern of cell division. The daughter cells derived from an initial cell, which had already differentiated before imbibition of the seeds, were tightly packed in a cluster, which enabled us to monitor cell division during early cotyledon development. Heterogeneity of cell size was recognised during the process of cell proliferation in the cluster, suggesting that cell division is uncoupled from control of cell size. There was significantly more cell division in the marginal part of the cotyledons than in other parts, suggesting high activity of the marginal meristem. Light enhanced cell and cotyledon enlargement, but had no effect on the number of divisions. This study elucidated the cellular basis of post-germinative Cucurbita cotyledon morphogenesis and development. Electronic Publication     

Monoclonal antibody of IgG isotype against a cross-reactive lipopolysaccharide epitope of Chlamydia and Salmonella Re chemotype enhances infectivity in L-929 fibroblast cells

A murine monoclonal antibody (MAb) 202D7 of IgG3 isotype recognizes a lipopolysaccharide (LPS) epitope of Chlamydia spp. and cross-reacts with the Re chemotype LPS of Salmonella and Escherichia coli. The antibody exhibits strong complement activating properties and stimulates phagocytosis of Salmonella enterica serovar Minnesota Re mutant by murine macrophages. Salmonella Re mutants are non-invasive for cell monolayers but still can enter and replicate in L-929 murine fibroblast cells. The entry of bacteria within the cells increases five-fold in the presence of MAb 202D7. The antibody mediates attachment and enhances five-fold the infectivity of Chlamydia pneumoniae into L-929 cells, which suggests a possible IgG-mediated mechanism of entry and survival of the pathogen in fibroblast cells.     

Removal of heavy metals from aqueous solution using Rhizopus delemar mycelia in free and polyurethane-bound form

This study assesses the ability of mycelia of Rhizopus delemar (both free and immobilized on polyurethane foam) to remove heavy metals from single-ion solutions as well as from a mixture of them. All experiments were conducted using 0.5-5 mm solutions of CuSO4 x 5H2O, CoCl2-6H2O and FeSO4 7H2O. Mycelia immobilized on polyurethane foam cells showed some times increase in uptake compared with that of free cells. Metal ions accumulation from a mixed solution was decreased slightly for cobalt and iron and considerable for copper ions. Heavy metal uptake was examined in the immobilized column experiments and more than 92% heavy metal removal (mg heavy metals removed/mg heavy metals added) from a mixed solution was achieved during the 5 cycles. During these experiments, the dry weight of the immobilized cells was decreased by only 2%. These results showed that immobilized mycelia of Rhizopus delemar can be used repeatedly for removal of heavy metals from aqueous solutions.