Effect of Anti-Microtubular Agents on Respiration and Ultrastructural Organization of Wheat Leaf Cells

The effect of anti-microtubular agents oryzalin (15 M) and colchicine (1 mM) on respiration and fine cellular organization of leaves was studied in wheat (Triticum aestivum L.) seedlings. Unlike oryzalin, colchicine considerably suppressed total respiration and the activities of cytochrome and cyanide-resistant pathways of electron transport, probably due to its rotenone-like effect since the latter was negated by vicasol that shunts the first complex of respiratory chain. Oryzalin-induced changes in the ultrastructure of mitochondria and polysomes corresponding to a decrease in their functional activity were detected. The changes in the shape of mitochondria were observed in the companion cells, whereas the mesophyll organelles did not respond to oryzalin. Disintegration of polysomes induced by oryzalin was detected in the cells of both tissues. Association of microtubules with mitochondria, polysomes, and plasma membrane was detected in situ. These data suggest that the intact cytoskeleton may participate in the spatial organization of energy transformation and protein synthesis machinery of the cells; the fact that the observed changes were tissue-specific points at the functional role of microtubules and/or to the number of targets for the inhibitor.     

Effect of oryzalin on root ultrastructure and respiration in various wheat cultivars subjected to cold hardening

The effect of anti-microtubular herbicide oryzalin (10 μM, 2–4 days) on the root ultrastructure and respiration in two cultivars of winter wheat (Triticum aestivum L.) contrasting in their frost-tolerance was studied during plant cold hardening (3°C, 3 days). The sensitivity of subcellular structures to oryzalin depended closely on cell metabolic activity and the extent of development of the cortical microtubule (MT) network. Most pronounced oryzalin-induced changes were related to enhanced cell vacuolation and the appearance of some signs of apoptosis (as judged from cytoplasm fragmentation) in some cells. In the root zone examined, cell heterogeneity increased, when, along with normally functioning cells, dramatically damaged and even completely destroyed cells appeared. Simultaneously, the activity of cyanide-resistant nonphosphorylating respiration pathway was activated, especially during cold hardening. In hardened cells, single cortical microtubules appeared in both wheat cultivars; this fact indicates that new cold-resistant subpopulations of MT were resistant to depolymerizing action of oryzalin.     

Regulation of phenylacetic acid degradation genes of Burkholderia cenocepacia K56-2

Background  

Metabolically versatile soil bacteria Burkholderia cepacia complex (Bcc) have emerged as opportunistic pathogens, especially of cystic fibrosis (CF). Previously, we initiated the characterization of the phenylacetic acid (PA) degradation pathway in B. cenocepacia, a member of the Bcc, and demonstrated the necessity of a functional PA catabolic pathway for full virulence in Caenorhabditis elegans. In this study, we aimed to characterize regulatory elements and nutritional requirements that control the PA catabolic genes in B. cenocepacia K56-2.     

Type I interferon is required for T helper (Th) 2 induction by dendritic cells

Type 2 inflammation is a defining feature of infection with parasitic worms (helminths), as well as being responsible for widespread suffering in allergies. However, the precise mechanisms involved in T helper (Th) 2 polarization by dendritic cells (DCs) are currently unclear. We have identified a previously unrecognized role for type I IFN (IFN‐I) in enabling this process. An IFN‐I signature was evident in DCs responding to the helminth Schistosoma mansoni or the allergen house dust mite (HDM). Further, IFN‐I signaling was required for optimal DC phenotypic activation in response to helminth antigen (Ag), and efficient migration to, and localization with, T cells in the draining lymph node (dLN). Importantly, DCs generated from Ifnar1^?/? mice were incapable of initiating Th2 responses in vivo. These data demonstrate for the first time that the influence of IFN‐I is not limited to antiviral or bacterial settings but also has a central role to play in DC initiation of Th2 responses.     

Influence of cytoskeletal agents on the respiratory electron transport pathways in the cells of winter wheat leaves

The effects of actin and tubulin polymerization inhibitors on the respiratory electron transport pathway activities were investigated using abscisic acid (ABA)- and cold-treated winter wheat seedling leaves. In unstressed control plants, cytochalasin B (15 microm) decreased the capacity of the cytochrome pathway, but stimulated the cyanide-resistant pathway, whereas oryzalin (15 microm) produced the opposite effects. Cold hardening (3 degrees C for 7 days) and ABA treatment 30 microm changed the respiratory pattern in a similar manner to cytochalasin B but to lesser effects. This points to cold- and ABA-induced reduction in microfilament sensitivity to these drugs and hence stabilization of actin-dependent processes. In contrast, oryzalin had only weak effects on control samples and its effects were strengthened in the presence of the cytoskeleton-modifying factors. The data suggest that the potential targets for the agent either increase and/or the degree of involvement of microtubules in the respiratory chain regulation, and therefore that the cytoskeleton can modify the functioning of the respiratory electron transport pathways in winter wheat cells.     

Clustering protein sequences with a novel metric transformed from sequence similarity scores and sequence alignments with neural networks

Background  

The sequencing of the human genome has enabled us to access a comprehensive list of genes (both experimental and predicted) for further analysis. While a majority of the approximately 30000 known and predicted human coding genes are characterized and have been assigned at least one function, there remains a fair number of genes (about 12000) for which no annotation has been made. The recent sequencing of other genomes has provided us with a huge amount of auxiliary sequence data which could help in the characterization of the human genes. Clustering these sequences into families is one of the first steps to perform comparative studies across several genomes.     

Involvement of the energy-dissipating systems in modulating the energetic efficiency of respiration in mitochondria from etiolated winter wheat seedlings

Effects of cyanide-resistant alternative oxidase (AOX) and modulators of plant uncoupling mitochondrial proteins (PUMP) on respiration rate and generation of transmembrane electric potential (ΔΨ) were investigated during oxidation of various substrates by isolated mitochondria from etiolated coleoptiles of winter wheat (Triticum aestivum L.). Oxidative phosphorylation in wheat mitochondria during malate and succinate oxidation was quite effective (it was characterized by high respiratory control ratio as defined by Chance, high ADP/O ratio, and rapid ATP synthesis). Nevertheless, the effectiveness of oxidative phosphorylation was substantially modulated by operation of energy-dissipating systems. The application of safranin dye revealed the partial dissipation of ΔΨ during inhibition of cytochrome-mediated malate oxidation by cyanide and antimycin A and demonstrated the operation of AOX-dependent compensatory mechanism for ΔΨ generation. The complex I of mitochondrial electron transport chain was shown to play the dominant role in ΔΨ generation and ATP synthesis during AOX functioning upon inhibition of electron transport through the cytochrome pathway. Effects of linoleic acid (PUMP activator) at physiologically low concentrations (4–10 μM) on respiration and ΔΨ generation in mitochondria were examined. The uncoupling effect of linoleic acid was shown in activation of the State 4 respiration, as well as in ΔΨ dissipation; this effect was eliminated in the presence of BSA but was insensitive to purine nucleotides. The uncoupling effect of linoleic acid was accompanied by reversible inhibition of AOX activity. The results are discussed with regard to possible physiological role of mitochondrial energy-dissipating systems in regulation of energy transduction in plant cells under stress conditions.     

Vaginal microflora in girls of prepuberal age

The bacteriological study of vaginal microflora in 24 clinically healthy girls aged 7-8 years was carried out. Two criteria of normal vaginal biocenosis in girls of prepuberal age were proposed. The proportion of hemolytic bacteria in the vagina of a girl of prepuberal age could reach 100% of all microflora, provided the total bacterial count (TBC) exceed average values. A high proportion of hemolytic bacteria in the vaginal microflora of girls of prepuberal age in combination with a high level of TBC (even with TBC not exceeding the upper limit of its normal value) could probably by regarded as a border state. No fungi of the genus Candida should be isolated from vagina in girls of prepuberal age. Facultative anaerobic microflora was represented mainly by Staphylococcus epidermidis and S. saprophyticus. In 64.3 +/- 12.8% of cases bifidobacteria were detected in the girls vagina.     

Isometric force development, isotonic shortening, and elasticity measurements from Ca(2+)-activated ventricular muscle of the guinea pig

Isometric tension and isotonic shortening were measured at constant levels of calcium activation of varying magnitude in mechanically disrupted EGTA-treated ventricular bundles from guinea pigs. The results were as follows: (a) The effect of creatine phosphate (CP) on peak tension and rate of shortening saturated at a CP concentration more than 10 mM; below that level tension was increased and shortening velocity decreased. We interpreted this to mean that CP above 10 mM was sufficient to buffer MgATP(2-) intracellularly. (b) The activated bundles exhibited an exponential stress-strain relationship and the series elastic properties did not vary appreciably with degree of activation or creatine phosphate level. (c) At a muscle length 20 percent beyond just taut, peak tension increased with Ca(2+) concentration over the range slightly below 10(-6) to slightly above 10(-4)M. (d) By releasing the muscle length-active tension curves were constructed. Force declined to 20 percent peak tension with a decrease in muscle length (after the recoil) of only 11 percent at 10(-4)M Ca(2+) and 6 percent at 4x10(-6)M Ca(2+). (e) The rate of shortening after a release was greater at lower loads. At identical loads (relative to maximum force at a given Ca(2+) level), velocity at a given time after the release was less at lower Ca(2+) concentrations; at 10 M(-5), velocity was 72 percent of that at 10(-4)M, and at 4x10(-6)M, active shortening was usually delayed and was 40 percent of the velocity at 10(-4) M. Thus, under the conditions of these experiments, both velocity and peak tension depend on the level of Ca(2+) activation over a similar range of Ca(2+) concentration.