Environmental and morphological factors influencing predatory behaviour by invasive non-indigenous gammaridean species

Predatory behaviour seems to be more frequent in invasive gammaridean species than in native ones. This results in the exclusion of other, mostly native gammaridean species and a change in benthic communities. The present study analysed the influence of environmental factors (water temperature) and morphological factors (sex, body parts involved in catching and holding prey) on the predatory behaviour of Dikerogammarus villosus. A diet study of invasive relatives of D. villosus showed that predation intensity is especially high in spring and summer, that is, at increasing and high temperatures. Experiments with D. villosus in climate rooms at various temperatures, using the native Gammarus fossarum as prey, showed that the average predation rate by both sexes gradually increased over the temperature range from 5 to 30°C. Natural mortality during the experiments was negligible compared to losses due to predation. At each temperature, the predation rate by females was lower than that by males. Males showed a steep allometric growth of body parts involved in the process of catching and holding prey, compared to females at increasing body size in a number of measurements. This may explain the difference in predatory behaviour between males and females, which plays a role in intraguild predation a supposed mechanism for species displacement.     

Development of a sensitive and selective assay for the determination of procarboxypeptidase U (thrombin-activatable fibrinolysis inhibitor) in plasma

To date, several assays for procarboxypeptidase U (proCPU) determination exist, all having their own inherent disadvantages and advantages. A drawback of activity-based assays is the interference of the constitutively active carboxypeptidase N (CPN) in plasma. Recent screening of Bz-Xaa-Arg peptides with modified aromatic amino acids at the P1 position revealed a selective CPU substrate, N-benzoyl-ortho-cyano-phenylalanyl-arginine (Bz-o-cyano-Phe-Arg), which will allow straightforward determination of proCPU in plasma. Our assay shows an excellent linearity in the concentration range of 20-2600 U/L, with within- and between-run precision values of 2.7% and 4.6%, respectively. A good correlation with our high-performance liquid chromatography (HPLC)-assisted proCPU activity assay using hippuryl-l-arginine (HipArg) as substrate was found. Besides the major improvement regarding the selectivity, the assay is much easier to perform and far less time-consuming compared with the proCPU activity assay using HipArg as substrate.     

Improving guideline adherence in the treatment of atrial fibrillation by implementing an integrated chronic care program

Background / Objectives. Atrial fibrillation (AF) is a very frequent and complex disease often associated with other medical conditions. The Euro Heart Survey (EHS) on AF showed that adherence to guidelines may reduce morbidity and mortality in AF patients. Therefore a nurse-driven, guideline-based, ICT-supported integrated chronic care program (ICCP) was developed and implemented in daily practice. The objective of this study is to evaluate the clinical feasibility of the ICCP, with guideline adherence as the endpoint. Methods. 111 ambulant patients referred for treatment of their AF were enrolled in the ICCP. In this group, patients underwent standardised clinical testing and were subsequently managed by a nurse, supported by a dedicated ICT program and supervised by cardiologists. For comparison, we used a recent historical control group of 102 patients who participated in the Maastricht part of the Euro Heart Survey (EHS) on AF. Results. Guideline adherence was excellent within the ICCP and compared favourably with the EHS-AF data concerning both clinical testing (trigger factors recorded in 100 vs. 44%; echocardiogram performed in 99 vs. 88%; thyroid-stimulating hormone level recorded in 96% vs. 63%) as well as treatment (antithrombotic therapy in 90 vs. 78%; rhythm control avoided in completely asymptomatic patients in 100 vs. 54%; class I drugs avoided in patients with structural heart disease in 90 vs. 95%; rhythm control avoided in permanent AF patients in 100 vs. 92%). Conclusion. The high level of guideline adherence suggests that a nurse-driven, guideline-based, ICT-supported ICCP for AF patients is feasible. (Neth Heart J 2010;18:471-7.)     

Fasting ghrelin does not predict food intake after short-term energy restriction

Objective: To study the role of ghrelin as a hunger signal during energy restriction and to test the hypothesis that changes in fasting leptin concentrations during energy restriction are associated with changes in fasting ghrelin concentrations. Research Methods and Procedures: Thirty‐five healthy, lean men (23 ± 3 years of age; BMI: 22.3 ± 1.6 kg/m²) participated in a controlled intervention study. Fasting ghrelin and leptin concentrations were measured before and after 2 days of 62% energy restriction and after a 2‐day period of ad libitum food intake. Energy intake during the latter period was assessed. Results: On average, ghrelin concentrations did not change (0.05 μg/liter; 95% confidence interval, ?0.03; 0.12) during energy restriction. Changes in ghrelin concentration during energy restriction were not associated with energy intake during the ad libitum period (r = 0.07; not significant). Ad libitum energy intake was, however, associated with the change in ghrelin concentrations during the same period (r = ?0.34; p = 0.05). Ghrelin and leptin concentrations were not associated. In addition, the ratio of percentage changes in ghrelin and leptin during energy restriction was not correlated with ad libitum food intake after energy restriction (r = ?0.26; p = 0.14). Discussion: Fasting ghrelin concentrations did not rise after a 2‐day energy restriction regimen. Moreover, changes in ghrelin concentrations during energy restriction were not associated with subsequent ad libitum food intake, suggesting that fasting ghrelin does not act as a hunger signal to the brain. The data did not support our hypothesis that leptin suppresses ghrelin levels.     

PDZ domains – glue and guide

PDZ domains are small globular building blocks that are amongst the most abundant protein interaction domains in organisms. Over the past several years an avalanche of data has implicated these modules in the clustering, targeting and routing of associating proteins. An overview is given of the types of interactions displayed by PDZ domains and how this relates to the current knowledge on their spatial structure. Furthermore, the different levels on which PDZ – ligand binding can be regulated and the consequences of PDZ domain-mediated clustering for activity, routing and targeting of interacting proteins will be addressed. Finally, some cell and animal models that illustrate the impact of PDZ domain-containing proteins on (multi-) cellular processes will be discussed.     

Impaired precursor B cell differentiation in Bruton's tyrosine kinase-deficient mice

Bruton's tyrosine kinase (Btk) is a cytoplasmic signaling molecule that is crucial for precursor (pre-B) cell differentiation in humans. In this study, we show that during the transition of large cycling to small resting pre-B cells in the mouse, Btk-deficient cells failed to efficiently modulate the expression of CD43, surrogate L chain, CD2, and CD25. In an analysis of the kinetics of pre-B cell differentiation in vivo, Btk-deficient cells manifested a specific developmental delay within the small pre-B cell compartment of about 3 h, when compared with wild-type cells. Likewise, in in vitro bone marrow cultures, Btk-deficient large cycling pre-B cells showed increased IL-7 mediated expansion and reduced developmental progression into noncycling CD2(+)CD25(+) surrogate L chain-negative small pre-B cells and subsequently into Ig-positive B cells. Furthermore, the absence of Btk resulted in increased proliferative responses to IL-7 in recombination-activating gene-1-deficient pro-B cells. These findings identify a novel role for Btk in the regulation of the differentiation stage-specific modulation of IL-7 responsiveness in pro-B and pre-B cells. Moreover, our results show that Btk is critical for an efficient transit through the small pre-B cell compartment, thereby regulating cell surface phenotype changes during the developmental progression of cytoplasmic mu H chain expressing pre-B cells into immature IgM(+) B cells.     

PDZ Motifs in PTP-BL and RIL Bind to Internal Protein Segments in the LIM Domain Protein RIL

The specificity of protein–protein interactions in cellular signaling cascades is dependent on the sequence and intramolecular location of distinct amino acid motifs. We used the two-hybrid interaction trap to identify proteins that can associate with the PDZ motif-rich segment in the protein tyrosine phosphatase PTP-BL. A specific interaction was found with the Lin-11, Isl-1, Mec-3 (LIM) domain containing protein RIL. More detailed analysis demonstrated that the binding specificity resides in the second and fourth PDZ motif of PTP-BL and the LIM domain in RIL. Immunohistochemistry on various mouse tissues revealed a submembranous colocalization of PTP-BL and RIL in epithelial cells. Remarkably, there is also an N-terminal PDZ motif in RIL itself that can bind to the RIL-LIM domain. We demonstrate here that the RIL-LIM domain can be phosphorylated on tyrosine in vitro and in vivo and can be dephosphorylated in vitro by the PTPase domain of PTP-BL. Our data point to the presence of a double PDZ-binding interface on the RIL-LIM domain and suggest tyrosine phosphorylation as a regulatory mechanism for LIM-PDZ associations in the assembly of multiprotein complexes. These findings are in line with an important role of PDZ-mediated interactions in the shaping and organization of submembranous microenvironments of polarized cells.     

Rhizobium Lipooligosaccharides Rescue a Carrot Somatic Embryo Mutant

At a nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot cell mutant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type embryos. The causative component in the conditioned medium has previously been identified as a 32-kD acidic endochitinase. In search of a function for this enzyme in plant embryogenesis, several compounds that contain oligomers of N-acetylglucosamine were tested for their ability to promote ts11 embryo formation. Of these compounds, only the Rhizobium lipooligosaccharides or nodulation (Nod) factors were found to be effective in rescuing the formation of ts11 embryos. These results suggest that N-acetylglucosamine-containing lipooligosaccharides from bacterial origin can mimic the effect of the carrot endochitinase. This endochitinase may therefore be involved in the generation of plant analogs of the Rhizobium Nod factors.     

Alkanes of the essential oil of Cannabis sativa

A waxy fraction obtained by column chromatography of the essential oil of Cannabis sativa consists of n-alkanes ranging from C₉ to C₃₉, 2-methyl and 3-methyl alkanes and some dimethyl alkanes. The qualitative and quantitative composition of this fraction has been compared with the alkane fraction obtained by extraction of the herb.