When do parasites fail to speciate in response to host speciation?

Cospeciation generally increases the similarity between host and parasite phylogenies. Incongruence between host and parasite phylogenies has previously been explained in terms of host switching, sorting, and duplication events. Here, we describe an additional process, failure of the parasite to speciate in response to host speciation, that may be important in some host-parasite systems. Failure to speciate is likely to occur when gene flow among parasite populations is much higher than that of their hosts. We reconstructed trees from mitochondrial and nuclear DNA sequences for pigeons and doves (Aves: Columbiformes) and their feather lice in the genus Columbicola (Insecta: Phthiraptera). Although comparisons of the trees from each group revealed a significant amount of cospeciation, there was also a significant degree of incongruence. Cophylogenetic analyses generally indicated that host switching may be an important process in the history of this host-parasite association. Using terminal sister taxon comparisons, we also identified three apparent cases where the host has speciated but the associated parasite has not. In two of these cases of failure to speciate, these comparisons involve allopatric sister taxa of hosts whose lice also occur on hosts sympatric with both of the allopatric sisters. These additional hosts for generalist lice may promote gene flow with lice on the allopatric sister species. Relative rate comparisons for the mitochondrial cytochrome oxidase I gene indicate that molecular substitution occurs about 11 times faster in lice than in their avian hosts.     

The cholinergic anti-inflammatory pathway: a missing link in neuroimmunomodulation

This review outlines the mechanisms underlying the interaction between the nervous and immune systems of the host in response to an immune challenge. The main focus is the cholinergic anti-inflammatory pathway, which we recently described as a novel function of the efferent vagus nerve. This pathway plays a critical role in controlling the inflammatory response through interaction with peripheral a7 subunit-containing nicotinic acetylcholine receptors expressed on macrophages. We describe the modulation of systemic and local inflammation by the cholinergic anti-inflammatory pathway and its function as an interface between the brain and the immune system. The clinical implications of this novel mechanism also are discussed.     

Biophysical characterization of a large conductance anion channel in hypodermal membranes of the gastrointestinal nematode,Ascaris suum

Patch-clamp recordings from muscle- and cuticle-facing hypodermal membranes of the gastrointestinal nematode Ascaris suum reveal a high-conductance, voltage- sensitive Ca(2+) -dependent Cl(-) channel. The hypodermal channel has a conductance of 195 pS in symmetrical 160 mM NaCl. The open probability of the channel is highly voltage-sensitive, and channel activity is not observed when Ca(2+) is reduced to <100 microM. The channel is permeable to organic anions that are major end-products of carbohydrate metabolism in A. suum, including acetate, butyrate and 2-methylvalerate. The conductances and relative permeabilities of these organic anions are inversely related to size, with 2-methylvalerate being only approximately 3% as permeable as Cl(-). The diameter of the channel pore was 12.3+/-0.2 A, calculated from the relative permeability coefficients of Cl(-) and the organic anions. Results of this study are consistent with the hypothesis that the large conductance anion channel in A. suum hypodermal membranes provides a low energy pathway for organic anion excretion from the hypodermal compartment, followed by diffusion across the aqueous channels of the cuticle matrix.     

Domain fusion analysis by applying relational algebra to protein sequence and domain databases

Background  

Domain fusion analysis is a useful method to predict functionally linked proteins that may be involved in direct protein-protein interactions or in the same metabolic or signaling pathway. As separate domain databases like BLOCKS, PROSITE, Pfam, SMART, PRINTS-S, ProDom, TIGRFAMs, and amalgamated domain databases like InterPro continue to grow in size and quality, a computational method to perform domain fusion analysis that leverages on these efforts will become increasingly powerful.     

Molecular monitoring of the Leu-164 mutation of dihydrofolate reductase in a highly sulfadoxine/pyrimethamine-resistant area in Africa

Background

Procalcitonin (PCT) is closely correlated with parasite burden and clinical outcome in falciparum malaria. The role of PCT in tertian malaria has not previously been investigated.

Patients and methods

PCT serum levels in 37 patients with tertian malaria were analysed. Clinical and laboratory parameters were assessed and statistically correlated both to the initial PCT levels and during the course of the disease.

Results

PCT levels rose for one day after commencing treatment and declined thereafter. However, there was no significant correlation with parasite burden, clinical parameters, laboratory values, or the presence of semi-immunity. Before treatment, the majority of patients showed normal or slightly elevated PCT levels (< 2.5 ng/ml), but PCT was markedly elevated (4.8 – 47 ng/ml) in one third of the population. The two groups did not differ by any other of the assessed parameters. Thus, while the post-treatment course of PCT resembles falciparum malaria, the lack of correlation between disease severity and even high PCT levels in a large proportion of patients is intriguing.

Conclusions

There is a fundamental difference in the relationship of PCT with tertian malaria not seen in other infectious diseases in which elevated PCT levels have been observed. This suggests distinct pathophysiological pathways in malaria.     

Imaging the distribution and secondary structure of immobilized enzymes using infrared microspectroscopy

Synchrotron infrared microspectroscopy (SIRMS) was used for the first time to image the distribution and secondary structure of an enzyme (lipase B from Candida antarctica, CALB) immobilized within a macroporous polymer matrix (poly(methyl methacrylate)) at 10 microm resolution. The beads of this catalyst (Novozyme435) were cut into thin sections (12 microm). SIRMS imaging of these thin sections revealed that the enzyme is localized in an external shell of the bead with a thickness of 80-100 microm. Also, the enzyme was unevenly distributed throughout this shell. Furthermore, by SIRMS-generated spectra, it was found that CALB secondary structure was not altered by immobilization. Unlike CALB, polystyrene molecules of similar molecular weight diffuse easily throughout Novozyme435 beads. Scanning electron micrograph (SEM) images of the Novozyme435 beads showed that the average pore size is 10 times larger than CALB or polystyrene molecules, implying that there is no physical barrier to enzyme or substrate diffusion throughout the bead. Thus, the difference between polystyrene and enzyme diffusivity suggests that protein-matrix and protein-protein interactions govern the distribution of the enzyme within the macroporous resin.     

Heterogeneity of CD4 and CD8+ memory T cells in localized and generalized Wegener's granulomatosis

Memory T cells display phenotypic heterogeneity. Surface antigens previously regarded as exclusive markers of naive T cells, such as L-selectin (CD62L), can also be detected on some memory T cells. Moreover, a fraction of CD45RO+ (positive for the short human isoform of CD45) memory T cells reverts to the CD45RA+ (positive for the long human isoform of CD45) phenotype. We analyzed patients with biopsy-proven localized Wegener's granulomatosis (WG) (n = 5), generalized WG (n = 16) and age- and sex-matched healthy controls (n = 13) to further characterize memory T cells in WG. The cell-surface expression of CD45RO, CD45RA, CD62L, CCR3, CCR5 and CXCR3 was determined on blood-derived T cells by four-color flow cytometric analysis. The fractions of CCR5+ and CCR3+ cells within the CD4+CD45RO+ and CD8+CD45RO+ memory T cell populations were significantly expanded in localized and generalized WG. The mean percentage of Th1-type CCR5 expression was higher in localized WG. Upregulated CCR5 and CCR3 expression could also be detected on a fraction of CD45RA+ T cells. CD62L expression was seen on approximately half of the memory T cell populations expressing chemokine receptors. This study demonstrates for the first time that expression of the inducible inflammatory chemokine receptors CCR5 and CCR3 on CD45RO+ memory T cells, as well as on CD45RA+ T cells ('revertants'), contributes to phenotypic heterogeneity in an autoimmune disease, namely WG. Upregulated CCR5 and CCR3 expression suggests that the cells belong to the effector memory T cell population. CCR5 and CCR3 expression on CD4+ and CD8+ memory T cells indicates a potential to respond to chemotactic gradients and might be important in T cell migration contributing to granuloma formation and vasculitis in WG.     

The medical therapy of prostatic symptoms study: what will we learn?

Until recently, benign prostatic hyperplasia (BPH) was thought of as a relatively uncomplicated disease process resulting from age-related enlargement of the prostate gland, which was thought to cause all of the symptoms associated with the disease. Prostatectomy was considered the state-of-the art treatment of BPH. Advances in our understanding of the pathogenesis of BPH and the relationship among clinical signs and symptoms has allowed for the development of pharmacologic therapies for this disorder, namely, selective alpha-blockers and 5-alpha-reductase inhibitors. These 2 classes of drugs have been demonstrated to be safe and effective for the treatment of BPH. Evidence supports different mechanisms of action, suggesting that, when used in combination, these therapies may act synergistically. The Medical Therapy of Prostatic Symptoms study was designed, in part, to test this hypothesis. Initial results of the trial are presented in this article.     

Metabolic phenotype of phosphoglucose isomerase mutants of Corynebacterium glutamicum

A series of experiments reported in the literature using fluxomics as an efficient functional genomics tool revealed that the L-lysine production of the Corynebacterium glutamicum strain MH20-22B correlates with the extent of intracellular NADPH supply. Some alternative metabolic engineering strategies to increase intracellular NADPH supply in the C. glutamicum strain DSM5715 were considered and finally the redirection of carbon flux through the pentose phosphate pathway with two NADPH generating enzymatic reactions was favored. Elsewhere, the construction of a phosphoglucose isomerase (Pgi) null mutant of the C. glutamicum strain DSM5715 has been described by utilizing genetic engineering as well as some aspects of its metabolic phenotype. Most interestingly, it was shown that not only could the L-lysine formation be increased by 1.7-fold but the by-product concentration for the null mutant strain was also able to be drastically reduced. In this publication we discuss this metabolic phenotype in detail and present additional data on by-product formation as well as yield considerations. Results from isotope based metabolic flux analysis in combination with considerations on NADPH metabolism clearly exclude the existence of Pgi isoenzymes in C. glutamicum strain DSM5715. The genome region containing the pgi gene was analyzed. It cannot be excluded that polar effects might have been caused by the disruption of the pgi gene and might have contributed to the observed metabolic phenotype of C. glutamicum Pgi mutants. We illustrate growth characteristics of a Pgi mutant of an industrial L-lysine production strain. A reduced growth rate and a biphasic growth behavior was observed. The importance of NADPH reoxidation for well balanced growth in Pgi mutants is discussed. Another phosphoglucose isomerase mutant of C. glutamicum has been described in literature with which an increase in L-lysine yield from 42 to 52% was observed. This finding highlights the general potential of metabolic flux redirection towards the pentose phosphate pathway, which could be used for metabolic engineering of the biotechnological synthesis of (1) aromatic amino acids and (2) chemicals whose synthesis depends on intracellular NADPH supply.