Isolation, characterization and biological activity of a diuretic myokinin neuropeptide from the housefly, Musca domestica

A competitive ELISA employing a polyclonal antiserum raised against leucokinin-I was used to isolate and purify a myokinin (muscakinin) from 1.05 kg of adult houseflies (Musca domestica). Following solid-phase purification, seven HPLC column steps were used to purify 4.8 nmol of leucokinin-immunoreactive material. Sequence analysis and mass spectrometry were consistent with the structure Asn-Thr-Val-Val-Leu-Gly Lys-Lys-Gln-Arg-Phe-His-Ser-Trp-Gly NH2. This peptide was synthesized and co-eluted with the natural peptide on three different HPLC columns. The activities of natural and synthetic muscakinin were identical, with both producing a 4-5 fold increase in fluid secretion by housefly Malpighian tubules at nanomolar concentrations. The presence of a pair of basic residues (Lys-Lys) suggested muscakinin might be processed further, with the peptide pGlu-Arg-Phe-His-Ser-Trp-Gly NH2 being produced by conversion of an N-terminal glutamine to pyroglutamic acid. However, this analog was 1000-fold less active than the intact peptide, comparable to the activity of AK-V which shares the same C-terminal pentapeptide sequence. The diuretic activity of muscakinin is more than double that of a previously identified CRF-related diuretic peptide (Musca-DP) from the housefly, and the two peptides act synergistically in stimulating fluid secretion. Muscakinin also increased the frequency and amplitude of contractions by housefly hindgut which might further contribute to the excretory process.     

Isolation,identification, and synthesis of a disulfated sulfakinin from the central nervous system of an arthropods the white shrimp Litopenaeus vannamei

Two myotropic peptides displaying tyrosyl sulfation have been isolated from an extract of central nervous systems (brain, suboesophageal ganglion, thoracic ganglia, and ventral nerve cord) of the white shrimp Litopenaeus vannamei. Both peptides were identified by mass spectrometry and belong to the sulfakinin family of neuropeptides, which are characterized by the C-terminal hexapeptide Y(SO(3)H)GHMRF-NH(2) preceded by two acidic amino acid residues. Pev-SK 1 (AGGSGGVGGEY(SO(3)H)DDY(SO(3)H)GH(L/I) RF-NH(2)) has two sulfated tyrosyl residues and a unique (L/I) for M substitution in the C-terminal sequence. Pev-SK 2 (pQFDEY(SO(3)H)GHMRF-NH(2)) fully complies with the typical sulfakinin core sequence and is blocked by a pyroglutamyl residue. Synthetic analogs (sulfated and unsulfated) were synthesized and the tyrosyl sulfations were confirmed by myotropic activity studies and co-elution with the native fractions. Pev-SK 1 is the first disulfated neuropeptide elucidated in the phylum of the arthropoda, with the only other reported disulfated neuropeptide, called cionin, found in a protochordate. The similarities in amino acid sequence and posttranslational modifications of the crustacean sulfakinins and protochordate cionin provide further evidence for the hypothesis stating that gastrin/CCK, cionin, and sulfakinins originate from a common ancestral gastrin/CCK-like peptide.     

T-helper 17 cell cytokines and interferon type I: partners in crime in systemic lupus erythematosus?

Introduction

A hallmark of systemic autoimmune diseases like systemic lupus erythematosus (SLE) is the increased expression of interferon (IFN) type I inducible genes, so-called IFN type I signature. Recently, T-helper 17 subset (Th17 cells), which produces IL-17A, IL-17F, IL-21, and IL-22, has been implicated in SLE. As CCR6 enriches for Th17 cells, we used this approach to investigate whether CCR6⁺ memory T-helper cells producing IL-17A, IL-17F, IL-21, and/or IL-22 are increased in SLE patients and whether this increase is related to the presence of IFN type I signature.

Methods

In total, 25 SLE patients and 15 healthy controls (HCs) were included. SLE patients were divided into IFN type I signature-positive (IFN⁺) (n = 16) and negative (IFN^-) (n = 9) patients, as assessed by mRNA expression of IFN-inducible genes (IFIGs) in monocytes. Expression of IL-17A, IL-17F, IL-21, and IL-22 by CD4⁺CD45RO⁺CCR6⁺ T cells (CCR6⁺ cells) was measured with flow cytometry and compared between IFN⁺, IFN^- patients and HCs.

Results

Increased percentages of IL-17A and IL-17A/IL-17F double-producing CCR6⁺ cells were observed in IFN⁺ patients compared with IFN^- patients and HCs. IL-17A and IL-17F expression within CCR6⁺ cells correlated significantly with IFIG expression. In addition, we found significant correlation between B-cell activating factor of the tumor necrosis family (BAFF)–a factor strongly correlating with IFN type I - and IL-21 producing CCR6⁺ cells.

Conclusions

We show for the first time higher percentages of IL-17A and IL-17A/IL-17F double-producing CCR6⁺ memory T-helper cells in IFN⁺ SLE patients, supporting the hypothesis that IFN type I co-acts with Th17 cytokines in SLE pathogenesis.     

Interactions in a tritrophic acarine predator-prey metapopulation system III: effects of Tetranychus urticae (Acari: Tetranychidae) on host plant condition

Spider mites are serious pests on many economically important plant species, because they may reduce plant productivity and, at high mite densities, overexploit and even kill the host plants. We have conducted a series of greenhouse experiments to quantify the effects of two-spotted spider mites (Tetranychus urticae) on host plants (Phaseolusvulgaris). The average amount of chlorophyll per cm² leaf area was used as a measure of plant condition. It was shown that chlorophyll concentration decreases with plant age and intensity of spider mite feeding. Damage caused by spider mites was assessed visually, using the Leaf Damage Index (LDI) defined by, and a mathematical relationship between the visual measurements and the amount of chlorophyll/cm² was fitted to data. The relationship may serve as a short-cut to estimate overall plant injury, expressed as the relative loss of chlorophyll/cm² leaf area caused by spider mites (D). D takes values between 0 (no injury) and 1 (all leaves dead). A highly significant positive relationship between the instantaneous spider mite density and D was found, even though D is expected to reflect the cumulated density of mites (mite-days). A model of plant growth incorporating information about plant age and D predicts that plant area has a maximum when plant age is about 60 days, and that plant area decreases exponentially with an increase in D. This revised version was published online in July 2006 with corrections to the Cover Date.     

Local adaptation in the rock pocket mouse (Chaetodipus intermedius): natural selection and phylogenetic history of populations

Elucidating the causes of population divergence is a central goal of evolutionary biology. Rock pocket mice, Chaeotdipus intermedius, are an ideal system in which to study intraspecific phenotypic divergence because of the extensive color variation observed within this species. Here, we investigate whether phenotypic variation in color is correlated with local environmental conditions or with phylogenetic history. First, we quantified variation in pelage color (n=107 mice) and habitat color (n=51 rocks) using a spectrophotometer, and showed that there was a correlation between pelage color and habitat color across 14 sampled populations (R2=0.43). Analyses of mtDNA sequences from these same individuals revealed strong population structure in this species across its range, where most variation (63%) was partitioned between five geographic regions. Using Mantel tests, we show that there is no correlation between color variation and mtDNA phylogeny, suggesting that pelage coloration has evolved rapidly. At a finer geographical scale, high levels of gene flow between neighboring melanic and light populations suggest the selection acting on color must be quite strong to maintain habitat-specific phenotypic distributions. Finally, we raise the possibility that, in some cases, migration between populations of pocket mice inhabiting different lava flows may be responsible for similar melanic phenotypes in different populations. Together, the results suggest that color variation can evolve very rapidly over small geographic scales and that gene flow can both hinder and promote local adaptation.     

Stem cell transplantation in pediatric leukemia and myelodysplasia: state of the art and current challenges

The role of stem cell transplantation in the treatment of leukemia and myelodysplasia (MDS) in children has changed over the past decade. In pediatric acute lymphoblastic leukemia (ALL), the overall cure-rate is high with conventional chemotherapy. However, selected patients with a high-risk of relapse are often treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first remission (CR1). Patients with a bone-marrow relapse who attain a second remission frequently receive HSCT. High minimal residual disease (MRD) levels directly prior to HSCT determines the relapse risk. Therefore, MRD positive patients are eligible for more experimental approaches such as intensified or experimental chemotherapy pre-HSCT, as well as immune modulation post-HSCT. In pediatric acute myeloid leukemia (AML) the role of allo-HSCT in CR1 is declining, due to better outcome with modern multi-agent chemotherapy. In relapsed AML patients, allo-HSCT still seems indispensable. Targeted therapy may change the role of HSCT, in particular in chronic myeloid leukemia, where the role of allografting is changing in the imatinib era. In MDS, patients are usually transplanted immediately without prior cytoreduction. New developments in HSCT, such as the role of alternative conditioning regimens, and innovative stem cell sources such as peripheral blood and cord blood, will also be addressed.     

Recombination and Speciation: Loci Near Centromeres Are More Differentiated Than Loci Near Telomeres Between Subspecies of the European Rabbit (Oryctolagus cuniculus)

Recent empirical and theoretical studies suggest that regions of restricted recombination play an important role in the formation of new species. To test this idea, we studied nucleotide variation in two parapatric subspecies of the European rabbit (Oryctolagus cuniculus). We surveyed five loci near centromeres, where recombination is expected to be suppressed, and five loci near telomeres, where recombination is expected to be higher. We analyzed this multilocus data set using a divergence-with-gene flow framework and we report three main findings. First, we estimated that these subspecies diverged ~1.8 MYA and maintained large effective population sizes (O. c. algirus N_e ≈ 1,600,000 and O. c. cuniculus N_e ≈ 780,000). Second, we rejected a strict allopatric model of divergence without gene flow; instead, high rates of gene flow were inferred in both directions. Third, we found different patterns between loci near centromeres and loci near telomeres. Loci near centromeres exhibited higher levels of linkage disequilibrium than loci near telomeres. In addition, while all loci near telomeres showed little differentiation between subspecies, three of five loci near centromeres showed strong differentiation. These results support a view of speciation in which regions of low recombination can facilitate species divergence in the presence of gene flow.