The impact of anthropogenically induced degradation on the vegetation and biochemistry of South African palmiet wetlands

There are many different anthropogenic causes of wetland degradation, such as disturbances which affect the physical structure of wetlands, resulting in erosion (altered fire regimes, road and railway building through wetlands, channelization of wetlands), pollution, land-cover change, and climate change. These different types of degradation have various impacts, depending on the type of wetland, soils, biochemistry and other factors. We researched a poorly-studied South African valley-bottom peatland that is dominated by the ecosystem engineer Palmiet: Prionium serratum. We ask the question: what is the impact of degradation by gully erosion, pollution and alien tree invasion on biochemistry and plant community composition of palmiet wetlands? In 39 plots from three palmiet wetlands situated approximately 200 km apart we found that channel erosion, through a loss of alluvium, has probably resulted in leached soils with lower soil organic matter and water content, less able to retain nutrients and cations. Soil leaching is a possible explanation for the groundwater of degraded wetlands having higher electrical conductivity and pH than that of pristine wetlands and a lower soil cation exchange capacity (21.3?±?5.80–7.7?±?4.91 meq/100 g). The loss of alluvium typically resulted in a completely new plant community, composed mostly of pioneer species and several alien species. The increase in base saturation (17.5?±?8.46–30.2?±?17.85%) and soil pH (4.8?±?0.51–5.1?±?0.50) with degradation was hypothesized to be the result of liming practices. Once extremely degraded, i.e. all the alluvium is lost, it is unlikely that these sensitive palmiet wetlands will recover original vegetation communities and lost functions, except on long timescales. We recommend conservation of the few pristine wetlands that remain, and rehabilitation of those that still retain some of their original function.     

Mutational and Structural Analyses of Caldanaerobius polysaccharolyticus Man5B Reveal Novel Active Site Residues for Family 5 Glycoside Hydrolases

CpMan5B is a glycoside hydrolase (GH) family 5 enzyme exhibiting both β-1,4-mannosidic and β-1,4-glucosidic cleavage activities. To provide insight into the amino acid residues that contribute to catalysis and substrate specificity, we solved the structure of CpMan5B at 1.6 Å resolution. The structure revealed several active site residues (Y12, N92 and R196) in CpMan5B that are not present in the active sites of other structurally resolved GH5 enzymes. Residue R196 in GH5 enzymes is thought to be strictly conserved as a histidine that participates in an electron relay network with the catalytic glutamates, but we show that an arginine fulfills a functionally equivalent role and is found at this position in every enzyme in subfamily GH5_36, which includes CpMan5B. Residue N92 is required for full enzymatic activity and forms a novel bridge over the active site that is absent in other family 5 structures. Our data also reveal a role of Y12 in establishing the substrate preference for CpMan5B. Using these molecular determinants as a probe allowed us to identify Man5D from Caldicellulosiruptor bescii as a mannanase with minor endo-glucanase activity.     

Huntingtin-Interacting Protein 1 Phosphorylation by Receptor Tyrosine Kinases

Huntingtin-interacting protein 1 (HIP1) binds inositol lipids, clathrin, actin, and receptor tyrosine kinases (RTKs). HIP1 is elevated in many tumors, and its expression is prognostic in prostate cancer. HIP1 overexpression increases levels of the RTK epidermal growth factor receptor (EGFR) and transforms fibroblasts. Here we report that HIP1 is tyrosine phosphorylated in the presence of EGFR and platelet-derived growth factor β receptor (PDGFβR) as well as the oncogenic derivatives EGFRvIII, HIP1/PDGFβR (H/P), and TEL/PDGFβR (T/P). We identified a four-tyrosine “HIP1 phosphorylation motif” (HPM) in the N-terminal region of HIP1 that is required for phosphorylation mediated by both EGFR and PDGFβR but not by the oncoproteins H/P and T/P. We also identified a tyrosine residue (Y152) within the HPM motif of HIP1 that inhibits HIP1 tyrosine phosphorylation. The HPM tyrosines are conserved in HIP1''s only known mammalian relative, HIP1-related protein (HIP1r), and are also required for HIP1r phosphorylation. Tyrosine-to-phenylalanine point mutations in the HPM of HIP1 result in proapoptotic activity, indicating that an intact HPM may be necessary for HIP1''s role in cellular survival. These data suggest that phosphorylation of HIP1 by RTKs in an N-terminal region contributes to the promotion of cellular survival.     

Communication of Pulmonary Function Test Results: A Survey of Patient’s Preferences

IntroductionPhysician-patient communication in patients suffering from common chronic respiratory disease should encompass discussion about pulmonary function test (PFT) results, diagnosis, disease education, smoking cessation and optimising inhaler technique. Previous studies have identified that patients with chronic respiratory disease/s often express dissatisfaction about physician communication. Currently there is a paucity of data regarding patient awareness of their PFT results (among those who have undergone PFTs previously) or patient preferences about PFT result communication.MethodsWe undertook a three-month prospective study on outpatients referred to two Pulmonary Function Laboratories. If subjects had undergone PFTs previously, the awareness of their previous test results was evaluated. All subjects were asked about their preferences for PFT result communication. Subjects were determined to have chronic respiratory disease based on their past medical history.Results300 subjects (50% male) with a median age (±SD) of 65 (±14) years participated in the study. 99% of the study participants stated that they were at least moderately interested in knowing their PFT results. 72% (217/300) of the subjects had undergone at least one PFT in the past, 48% of whom stated they had not been made aware of their results. Fewer subjects with chronic respiratory disease preferred that only a doctor discuss their PFT results with them (28% vs. 41%, p = 0.021).ConclusionOur study demonstrates that while almost all subjects want to be informed of their PFT results, this does not occur in a large number of patients. Many subjects are agreeable for their PFT results to be communicated to them by clinicians other than doctors. Further research is required to develop an efficient method of conveying PFT results that will improve patient satisfaction and health outcomes.     

The metamorphosis of the developing cerebellar microcircuit

The cerebellar cortical circuit with its organized and repetitive structure provides an excellent model system for studying how brain circuits are formed during development. The emergence of the mature brain requires that appropriate synaptic connections are formed and refined, which in the rodent cerebellum occurs primarily during the first three postnatal weeks. Developing circuits typically differ substantially from their mature counterparts, which suggests that development may not simply involve synaptic refinement, but rather involves restructuring of key synaptic components and network connections, in a manner reminiscent of metamorphosis. Here, we discuss recent evidence that, taken together, suggests that transient features of developing cerebellar synapses may act to coordinate network activity, and thereby shape the development of the cerebellar microcircuit.     

Synthesis of keyhole limpet hemocyanin by the rhogocytes of Megathura crenulata

Rhogocytes are morphologically distinct cells distributed throughout connective tissues of crustaceans and molluscs. Using light microscopy, rhogocytes of the vetigastropod Megathura crenulata were identified by their ovoid shape, and their cytoplasm filled with spherical inclusions which contained lysosomal enzymes, based on uptake of neutral red and staining with LysoTracker dye. Rhogocytes were most abundant in the digestive gland (2,824 rhogocytes/mm²), followed by the connective tissue layer surrounding the middle and posterior esophagus and intestine (1,431 rhogocytes/mm², 872 rhogocytes/mm², and 1,190 rhogocytes/mm², respectively), and were lowest in abundance in the foot (154 rhogocytes/mm²). At the transmission electron microscopy level, characteristic features of rhogocytes were inclusions showing a variety of electron densities, abundant vesicles, and rough endoplasmic reticulum in the cytoplasm, and regions of plasma membrane folded to produce slits connected by thin diaphragms. Although several functions have been proposed for gastropod rhogocytes, much attention has been focused on their possible role in the synthesis of the respiratory pigment hemocyanin. In M. crenulata, this molecule exists in several isoforms called keyhole limpet hemocyanin (KLH). One isoform, KLH1, is a large didecamer and has been used extensively in studies on vertebrate immunology and cancer therapy. We present four lines of evidence indicating rhogocytes in M. crenulata synthesize KLH1. First, at the transmission electron microscopy (TEM) level, dilated cisternae of RER containing material similar in size and shape to KLH were observed in rhogocytes examined throughout the year. Second, KLH1 mRNA was identified exclusively in tissue samples that contained rhogocytes; no mRNA for KLH1 was identified in samples containing only hemocytes. Third, immunoperoxidase staining with antibodies specific to KLH was localized only to rhogocytes. Fourth, in situ hybridization with a probe specific for M. crenulata KLH1 demonstrated KLH1‐specific mRNA was present only in rhogocytes. Identification of the cells responsible for the synthesis of KLH is important because of the clinical significance of this molecule.     

Visualizing protein partnerships in living cells and organisms

In recent years, scientists have expanded their focus from cataloging genes to characterizing the multiple states of their translated products. One anticipated result is a dynamic map of the protein association networks and activities that occur within the cellular environment. While in vitro-derived network maps can illustrate which of a multitude of possible protein-protein associations could exist, they supply a falsely static picture lacking the subtleties of subcellular location (where) or cellular state (when). Generating protein association network maps that are informed by both subcellular location and cell state requires novel approaches that accurately characterize the state of protein associations in living cells and provide precise spatiotemporal resolution. In this review, we highlight recent advances in visualizing protein associations and networks under increasingly native conditions. These advances include second generation protein complementation assays (PCAs), chemical and photo-crosslinking techniques, and proximity-induced ligation approaches. The advances described focus on background reduction, signal optimization, rapid and reversible reporter assembly, decreased cytotoxicity, and minimal functional perturbation. Key breakthroughs have addressed many challenges and should expand the repertoire of tools useful for generating maps of protein interactions resolved in both time and space.