Examining the fungal and bacterial niche overlap using selective inhibitors in soil

It is important to know the contributions of bacteria and fungi to decomposition in connection with both the structure of the food web and the functioning of the ecosystem. However, the extent of the competition between these groups of organisms is largely unknown. The bacterial influence on fungal growth in a soil system was studied by applying three different bacterial inhibitors – bronopol, tylosin and oxytetracycline – in a series of increasing concentrations, and comparing the resulting bacterial and fungal growth rates measured using leucine and acetate-in-ergosterol incorporation, respectively. Direct measurements of growth showed that fungi increased after adding inhibitors; the level of increase in fungal growth corresponded to that of the decrease in bacterial growth, irrespective of the bacterial inhibitor used. Similar antagonistic effects of the bacteria on fungal growth were also found after adding the bacterial inhibitors together with additional substrate (alfalfa or straw plant material). The resulting responses in bacterial and fungal growth indirectly indicated that the negative interaction between fungi and bacteria was mostly attributable to exploitation competition. The results of this study also emphasize the increased sensitivity of using growth-related, instead of biomass-based, measurements when studying bacterial and fungal interactions in soil.     

Trace-element determination in individual peripheral blood cells and possible diagnostic applications

Trace elements are indispensable for the effective and proper functioning of biological systems. Recent years have demonstrated the conspicuous lack of knowledge about trace-element physiology. Establishment of reference values is a very difficult task, requiring the consideration of and compensation for a number of possible simultaneous phenomena. Peripheral blood has been used in medical diagnosis for a very long time, because, among other things, it is easily accessible. In the search for signs of lack or excess of minerals and trace elements in disease, the interest has been focused mainly on blood plasma or serum. The utilization of blood cells as a marker model is proposed here. The advent of the nuclear microprobe made possible the determination of elemental profiles of individual cells. The techniques of blood cell separation and preparation for microprobe analysis are presented and discussed. As an example of a possible diagnostic application, a set of reference data from a control group is compared to corresponding data from a group of patients suffering from acute myeloid leukemia.     

Hydrolysis and Esterification with Lipase from Candida Cylindracea. Influence of the Reaction Conditions and Acid Moiety on the Enantiomeric Excess

The enantiomeric ratio for hydrolysis and synthesis of 1-phenyl ethanol esters of straight chain aliphatic carboxylic acids catalyzed by Candida cylindracea lipase was determined. A distinct maximum in enantiomeric ratio was observed for valeric and caproic acid in the hydrolytic direction. No significant maximum could be determined in the esterification reaction. Even though the enzyme provided larger enantiomeric ratios in the synthetic direction the enantiomeric excess of the alcohol was not higher. The enantiomeric excess was depressed by racemization reactions in the esterification as the reaction approached thermodynamic equilibrium at an insufficient conversion. While choosing the optimal chain length of the acyl donor is important in hydrolytic reactions it seems to be of greater value to raise the equilibrium conversion in the esterification reactions.     

Intact salicylic acid signalling is required for potato defence against the necrotrophic fungus Alternaria solani

Plant Molecular Biology - HbMBF1a was isolated and characterized in H. brevisubulatum, and overexpressed HbMBF1a could enhance the salt tolerance and ABA insensitivity in Arabidopsis thaliana. The...     

Functional analysis and localisation of a delta-class glutathione S-transferase from Sarcoptes scabiei

The mite Sarcoptes scabiei causes sarcoptic mange, or scabies, a disease that affects both animals and humans worldwide. Our interest in S. scabiei led us to further characterise a glutathione S-transferase. This multifunctional enzyme is a target for vaccine and drug development in several parasitic diseases. The S. scabiei glutathione S-transferase open reading frame reported here is 684 nucleotides long and yields a protein with a predicted molecular mass of 26 kDa. Through phylogenetic analysis the enzyme was classified as a delta-class glutathione S-transferase, and our paper is the first to report that delta-class glutathione S-transferases occur in organisms other than insects. The recombinant S. scabiei glutathione S-transferase was expressed in Escherichia coli via three different constructs and purified for biochemical analysis. The S. scabiei glutathione S-transferase was active towards the substrate 1-chloro-2,4-dinitrobenzene, though the positioning of fusion partners influenced the kinetic activity of the enzyme. Polyclonal antibodies raised against S. scabiei glutathione S-transferase specifically localised the enzyme to the integument of the epidermis and cavities surrounding internal organs in adult parasites. However, some minor staining of parasite intestines was observed. No staining was seen in host tissues, nor could we detect any antibody response against S. scabiei glutathione S-transferase in sera from naturally S. scabiei infected dogs or pigs. Additionally, the polyclonal sera raised against recombinant S. scabiei glutathione S-transferase readily detected a protein from mites, corresponding to the predicted size of native glutathione S-transferase.     

Mammalian splicing factor SF1 is encoded by variant cDNAs and binds to RNA.

Mammalian splicing factor SF1 consists of a single polypeptide of 75 kDa and is required for the formation of the first ATP-dependent spliceosomal complex. Three cDNAs encoding variant forms of SF1 have been isolated and four highly related cDNAs have been found in current databases. Comparison of the cDNA sequences suggests that different SF1 mRNAs are generated by alternative splicing of a common pre-mRNA. In agreement with this idea, at least three mRNAs that are differentially expressed in different cell types have been detected by northern blot analysis. All SF1 cDNAs identified encode proteins with a common N-terminal half that contains two structural motifs implicated in RNA binding (an hnRNP K homology [KH] domain and a zinc knuckle), but the proteins differ in the length of a proline-rich region and have distinct C-termini. Three SF1 isoforms expressed in insect cells via baculovirus transfer vectors show comparable activities in the assembly of a pre-splicing complex. Consistent with the presence of a KH domain and a zinc knuckle, we show that SF1 binds directly to RNA. This interaction appears to be largely sequence-independent with a preference for guanosine- and uridine-rich sequences. The KH domain of SF1 is embedded in a 160-amino acid sequence that is shared with human Sam68, a target of Src during mitosis, as well as Caenorhabditis elegans GLD-1 and mouse Qkl, both of which play roles during cellular differentiation. The presence of this shared region in SF1 suggests functions in addition to its role in pre-spliceosome assembly.     

Ouabain receptor interactions in (Na+ + K+)-ATPase preparations. II. Effect of cations and nucleotides on rate constants and dissociation constants

The action of ATP and its analogs as well as the effects of alkali ions were studied in their action on the ouabain receptor. One single ouabain receptor with a dissociation constant ($\text{K}{}_{\mathrm{<mtext>D</mtext>}}$) of 13 nM was found in the presence of ($\text{Mg}{}^{\mathrm{2+}}\text{+ P}{}_{\mathrm{i}}$) and ($\text{Na}{}^{\mathrm{+}}\text{+ Mg}{}^{\mathrm{2+}}\text{+ ATP}$). pH changes below pH 7.4 did not affect the ouabain receptor. Ouabain binding required Mg²⁺, where a curved line in the Scatchard plot appeared. The affinity of the receptor for ouabain was decreased by K⁺ and its congeners, by Na⁺ in the presence of ($\text{Mg}{}^{\mathrm{2+}}\text{+ P}{}_{\mathrm{i}}$), and by ATP analogs (ADP-C-P, ATP-OCH₃). Ca²⁺ antagonized the action of K⁺ on ouabain binding. It was concluded that the ouabain receptor exists in a low affinity (R_α) and a high affinity conformational state (R_β). The equilibrium between both states is influenced by ligands of $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$. With 3 mM Mg²⁺ a mixture between both conformational states is assumed to exist (curved line in the Scatchard plot).     

Protective effects of selenium against mercury toxicity as studied in the rat liver and kidney by nuclear analytical techniques

Mercuric chloride and sodium selenite were separately administered to male rats in the drinking water or in a combination (2.5 mmol Hg/L and 0.1 mmol Se/L). The mercuric chloride group showed histopathological lesions, as evidenced by cell necrosis in the liver and tubular necrosis in the kidney. The sodium selenite group showed some depression in growth, but pathological changes were found neither in the liver nor in the kidney. Simultaneous administration of both compounds produced a protective effect on weight loss and histopathology. These effects were associated with some small structures in the kidney proximal tubules and to some structure in the extracellular space in the liver. Thin, unstained cryosections were freeze-dried and examined in the Studsvik Nuclear Microprobe. The structures observed in the liver and the kidney were shown to contain both selenium and mercury.     

Zinc homeostasis in C6 glioma cells

Zinc homeostasis in mammalian cells is precisely regulated by cellular signal transduction mechanisms. The main result of this study is the finding that modulators of phospholipase C (PLC) activity affect cellular zinc export. Two different PLC inhibitors caused an increase of the total cellular zinc level whereas two different PLC activators caused a decrease. Furthermore, both the inhibition of cyclic nucleotide phosphodiesterases as well as the administration of 8-bromo-cAMP evoked a drop in the intracellular zinc level, indicating the involvement of cAMP in the control of cellular zinc export. It is concluded that the activity of PLC controls cellular zinc transport and that the effect of elevated zinc concentrations on PLC activity might be mediated by cAMP. However, modulation of other major signaling enzymes did not affect the cellular zinc homeostasis. These include activation and inhibition of guanylate cyclase, activation of protein kinase G, activation of protein kinase A, and activation or inhibition of protein kinase C. Furthermore there was no evidence for the existence of a zinc-sensing receptor in C6 glioma cells, which would stimulate PLC activity and evoke a mobilization of intracellular free-calcium levels.