Imaging of the host/parasite interplay in cutaneous leishmaniasis

An understanding of host-parasite interplay is essential for the development of therapeutics and vaccines. Immunoparasitologists have learned a great deal from ‘conventional’ in vitro and in vivo approaches, but recent developments in imaging technologies have provided us (immunologists and parasitologists) with the ability to ask new and exciting questions about the dynamic nature of the parasite-immune system interface. These studies are providing us with new insights into the mechanisms involved in the initiation of a Leishmania infection and the consequent induction and regulation of the immune response. Here, we review some of the recent developments and discuss how these observations can be further developed to understand the immunology of cutaneous Leishmania infection in vivo.     

Spatial modelling of succession-disturbance dynamics in forest ecosystems: Concepts and examples

Over the last few decades it has become increasingly obvious that disturbance, whether natural or anthropogenic in origin, is ubiquitous in ecosystems. Disturbance-related processes are now considered to be important determinants of the composition, structure and function of ecological systems. However, because disturbance and succession processes occur across a wide range of spatio-temporal scales their empirical investigation is difficult. To counter these difficulties much use has been made of spatial modelling to explore the response of ecological systems to disturbance(s) occurring at spatial scales from the individual to the landscape and above, and temporal scales from minutes to centuries. Here we consider such models by contrasting two alternative motivations for their development and use: prediction and exploration, with a focus on forested ecosystems. We consider the two approaches to be complementary rather than competing. Predictive modelling aims to combine knowledge (understanding and data) with the goal of predicting system dynamics; conversely, exploratory models focus on developing understanding in systems where uncertainty is high. Examples of exploratory modelling include model-based explorations of generic issues of criticality in ecological systems, whereas predictive models tend to be more heavily data-driven (e.g. species distribution models). By considering predictive and exploratory modelling alongside each other, we aim to illustrate the range of methods used to model succession and disturbance dynamics and the challenges involved in the model-building and evaluation processes in this arena.     

Properties of the periplasmic nitrate reductases from Paracoccus pantotrophus and Escherichia coli after growth in tungsten-supplemented media

Paracoccus pantotrophus grown anaerobically under denitrifying conditions expressed similar levels of the periplasmic nitrate reductase (NAP) when cultured in molybdate- or tungstate-containing media. A native PAGE gel stained for nitrate reductase activity revealed that only NapA from molybdate-grown cells displayed readily detectable nitrate reductase activity. Further kinetic analysis showed that the periplasmic fraction from cells grown on molybdate (3 microM) reduced nitrate at a rate of V(max)=3.41+/-0.16 micromol [NO(3)(-)] min(-1) mg(-1) with an affinity for nitrate of K(m)=0.24+/-0.05 mM and was heat-stable up to 50 degrees C. In contrast, the periplasmic fraction obtained from cells cultured in media supplemented with tungstate (100 microM) reduced nitrate at a much slower rate, with much lower affinity (V(max)=0.05+/-0.002 micromol [NO(3)(-)] min(-1) mg(-1) and K(m)=3.91+/-0.45 mM) and was labile during prolonged incubation at >20 degrees C. Nitrate-dependent growth of Escherichia coli strains expressing only nitrate reductase A was inhibited by sub-mM concentrations of tungstate in the medium. In contrast, a strain expressing only NAP was only partially inhibited by 10 mM tungstate. However, none of the above experimental approaches revealed evidence that tungsten could replace molybdenum at the active site of E. coli NapA. The combined data show that tungsten can function at the active site of some, but not all, molybdoenzymes from mesophilic bacteria.     

Regression Techniques for Examining Land Use/Cover Change: A Case Study of a Mediterranean Landscape

In many areas of the northern Mediterranean Basin the abundance of forest and scrubland vegetation is increasing, commensurate with decreases in agricultural land use(s). Much of the land use/cover change (LUCC) in this region is associated with the marginalization of traditional agricultural practices due to ongoing socioeconomic shifts and subsequent ecological change. Regression-based models of LUCC have two purposes: (i) to aid explanation of the processes driving change and/or (ii) spatial projection of the changes themselves. The independent variables contained in the single ‘best’ regression model (that is, that which minimizes variation in the dependent variable) cannot be inferred as providing the strongest causal relationship with the dependent variable. Here, we examine the utility of hierarchical partitioning and multinomial regression models for, respectively, explanation and prediction of LUCC in EU Special Protection Area 56, ‘Encinares del río Alberche y Cofio’ (SPA 56) near Madrid, Spain. Hierarchical partitioning estimates the contribution of regression model variables, both independently and in conjunction with other variables in a model, to the total variance explained by that model and is a tool to isolate important causal variables. By using hierarchical partitioning we find that the combined effects of factors driving land cover transitions varies with land cover classification, with a coarser classification reducing explained variance in LUCC. We use multinomial logistic regression models solely for projecting change, finding that accuracies of maps produced vary by land cover classification and are influenced by differing spatial resolutions of socioeconomic and biophysical data. When examining LUCC in human-dominated landscapes such as those of the Mediterranean Basin, the availability and analysis of spatial data at scales that match causal processes is vital to the performance of the statistical modelling techniques used here.     

SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification

The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWC^OFF and AWC^ON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWC^ON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWC^ON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWC^ON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.     

The biogeochemistry of basic cations in two forest catchments with contrasting lithology in the Czech Republic

The biogeochemistry of Ca, Mg, K, and Nawere investigated in two forested catchments in theCzech Republic, one underlain by leucogranite, theother by serpentinite. High weathering rates at theserpentinite site at Pluhv Bor resultedin Mg²⁺ as the dominant cation on the soilexchange complex and in drainage water. Other basiccations (Ca²⁺, K⁺, Na⁺) showedrelatively low concentrations and outflow instreamwater. The catchment exhibited high basesaturation in mineral soils (>70%), and nearneutral soil and stream pH, despite elevated inputsof acidic deposition. Slow growth of Norway spruceat Pluhv Bor may be caused by K deficiency, Mgoversupply and/or Ni toxicity. In contrast, thegranitic site at Lysina showed low concentrations ofbasic cations on the soil exchange complex and instreamwater. Soil and drainage water at Lysina werehighly impacted by acidic deposition. Soil pH wasextremely acidic (<4.5) throughout the soilprofile, and the base saturation of the mineral soilwas very low (<5%). Supplies of basic cationsfrom atmospheric deposition and soil processes wereless than inputs of SO^2- ₄ on anequivalence basis, resulting in low pH and highconcentrations of total Al in drainage water. Needle yellowing in Norway spruce was possibly theresult of Mg deficiency at Lysina. Because of theirextremely different lithologies, these catchmentsserve as valuable end-members of ecosystemsensitivity to elevated levels of acidicdeposition.     

Hepatic monoacylglycerol acyltransferase: ontogeny and characterization of an activity associated with the chick embryo

Hepatic monoacylglycerol acyltransferase is expressed during the perinatal period in rats and guinea pigs and appears to be related temporally to the availability of fatty acids and to the development of hepatic steatosis. In order to determine when monoacylglycerol acyltransferase activity is expressed in an avian species, its ontogeny was investigated in chick liver total particulate preparations. In livers from 11- to 21-day-old chick embryos, monoacylglycerol acyltransferase specific activity was 34.5 +/- 8.1 nmol/min per mg of total particulate protein. The specific activity decreased 93% to 2.6 +/- 1.3 nmol/min per mg by the 6th day after hatching. The specific activities of fatty acid CoA ligase, diacylglycerol acyltransferase, and microsomal and mitochondrial glycerol-P acyltransferases changed comparatively little during this time period. In the embryos, the monoacylglycerol acyltransferase activity per liver rose 28-fold between the 11th and 21st day, corresponding exactly to the increase in liver total particulate protein during this time. Monoacylglycerol acyltransferase activity in other tissues was 25- to 115-fold lower than observed in liver. Optimal activity was measured using 25 microM palmitoyl-CoA and 50 microM sn-2-monooleoylglycerol. The activity with the 1- and 2-monooleoylglycerol ethers and 1-monooleoylglycerol was very low. In contrast to microsomes from rat liver, about 70% of the product with the 1- and 2-monooleoylglycerol ethers was triradylglycerol, suggesting that the diacylglycerol acyltransferase from chick liver can acylate acyl, alkylglycerols. The activity with sn-2-monooleoylglycerol amide was 12.5% of that observed with the corresponding 2-monooleoylglycerol suggesting that the ester bond is important; the 1-monooleoylglycerol amide was not a substrate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of β-endorphin- and α-MSH-related peptides in rat heart

POMC-derived peptides and mRNA have been identified in heart tissue, although POMC processing has not been fully characterized. In the present study, we found that β-lipotropin and ACTH were localized in rat heart, although they were almost entirely converted to β-endorphin- and α-MSH-related peptides. Ion exchange HPLC analysis revealed that β-endorphin(1–31) was further processed to α-N-acetyl-β-endorphin(1–31), which comprised 35.9 ± 0.1% of total immunoreactivity, and smaller amounts of β-endorphin(1–27), β-endorphin(1–26), and their α-N-acetylated derivatives. The predominant α-MSH immunoreactive peptides coeluted with α-MSH and N,O-diacetyl-α-MSH by reverse-phase HPLC, although small amounts of ACTH(1–13)-NH₂ were also present. Thus, multiple forms of β-endorphin and α-MSH are localized in rat heart. β-Endorphin(1–31) is a minor constituent, however, indicating that nonopioid β-endorphin peptides predominate.     

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency: diagnosis by acylcarnitine analysis in blood.

Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is a disorder of fatty acid catabolism, with autosomal recessive inheritance. The disease is characterized by episodic illness associated with potentially fatal hypoglycemia and has a relatively high frequency. A rapid and reliable method for the diagnosis of MCAD deficiency is highly desirable. Analysis of specific acylcarnitines was performed by isotope-dilution tandem mass spectrometry on plasma or whole blood samples from 62 patients with MCAD deficiency. Acylcarnitines were also analyzed in 42 unaffected relatives of patients with MCAD deficiency and in other groups of patients having elevated plasma C8 acylcarnitine, consisting of 32 receiving valproic acid, 9 receiving medium-chain triglyceride supplement, 4 having multiple acyl-coenzyme A dehydrogenase deficiency, and 8 others with various etiologies. Criteria for the unequivocal diagnosis of MCAD deficiency by acylcarnitine analysis are an elevated C8-acylcarnitine concentration (> 0.3 microM), a ratio of C8/C10 acylcarnitines of > 5, and lack of elevated species of chain length > C10. These criteria were not influenced by clinical state, carnitine treatment, or underlying genetic mutation, and no false-positive or false-negative results were obtained. The same criteria were also successfully applied to profiles from neonatal blood spots retrieved from the original Guthrie cards of eight patients. Diagnosis of MCAD deficiency can therefore be made reliably through the analysis of acylcarnitines in blood, including presymptomatic neonatal recognition. Tandem mass spectrometry is a convenient method for fast and accurate determination of all relevant acylcarnitine species.     

Cell shape in the algaPediastrum (Hydrodictyaceae; Chlorophyta)

Summary Species ofPediastrum, a genus in which the colonies assemble from aggregating zoospores, differ in the number and form of prongs on peripheral cells and the amount of space between cells of the colony; cell shape appears to be genetically based. Peripheral cells of theP. boryanum colony, for example, have two prongs per cell;P. simplex has one prong per cell. Prong extension is suppressed in the interior cells ofP. boryanum, but prong sites have been reported in scanning electron micrographs of the cell walls. A mutant unicellular strain in which cells of the colony separate after attaining typical form reveals several prong sites (6 or more) in each cell. Multiple suppressed prong sites are evident inP. simplex cells as well. Polyeders, 4- and 5-pronged unicells, occur in the life cycle ofP. simplex. Based on these observations and a recent report byMarchant (1979) of a microtubule organizing center associated with the prongs, it is suggested that several microtubule organizing centers are to be found in zoospores ofPediastrum species and may be related to species differences in cell shape.Research supported in part by Argonne Center for Educational Affairs, U.S. Department of Energy, under contract No. W-31-109-ENG-38.