Response of <Emphasis Type="Italic">Phragmites</Emphasis> to environmental parameters associated with treatments

This multi-year study evaluated the response of invasive Phragmites australis to changes in pore water geochemistry associated with tidal enhancement, alone or in combination with other prescribed management regimes used by the US Fish and Wildlife Service. A pilot study was conducted prior to the treatment experiment that showed a negative correlation between the growth of Phragmites and cation concentrations in a transitional vegetation zone. In the targeted 535-acre brackish-water impoundment (East Pool) where Phragmites dominated, the soil water chemistry was changed by introducing tidal salt water through water control structures in June of 1999. Soil profiles, pH, salinity and cation concentration data in addition to Phragmites height and density data were collected both before and after the treatments were imposed, where possible. It was generally observed that a soil water salinity above ∼28 would be needed to maintain the reduction of Phragmites and to support its replacement by salt marsh species. In the tidal water manipulated experimental macroplots, the soil water salinity changed from 7.1 to 32 on average between 1999 and 2001. The reduction of the average height of Phragmites ranged from 25% to 84% for different treatment combinations, while untreated sites exhibited a slight increases in height. The reduction in average live density ranged from 51% to 87% for different treatment combinations. The greatest reduction of Phragmites density and height resulted when tidal enhancement was followed by a prescribed burn in the winter. Also, significant negative correlations were observed between Phragmites height and the main cations associated with tidal salt water including Mg²⁺, Na⁺ and K⁺ and to a lesser extent Ca²⁺. pH did not change drastically with the introduction of tidal water over the period of 1999–2001 and did not appear to play a significant role in changing the growth of Phragmites. A reduction of soil adhesiveness associated with the decay of Phragmites roots was observed after a two month period in 2001 when plants were submerged in standing water. This points to the need to maintain tidal exchange to promote a gradual transition from a Phragmites-dominated system to a Spartina-dominated system. Towards the end of the growing season in 2001, Spartina patens and Distichlis spicata had begun to ramify into the center of the island patches.     

Oriented cell division: new roles in guiding skin wound repair and regeneration

Tissue morphogenesis depends on precise regulation and timely co-ordination of cell division and also on the control of the direction of cell division. Establishment of polarity division axis, correct alignment of the mitotic spindle, segregation of fate determinants equally or unequally between daughter cells, are essential for the realization of oriented cell division. Furthermore, oriented cell division is regulated by intrinsic cues, extrinsic cues and other cues, such as cell geometry and polarity. However, dysregulation of cell division orientation could lead to abnormal tissue development and function. In the present study, we review recent studies on the molecular mechanism of cell division orientation and explain their new roles in skin repair and regeneration.     

ESCRTs are everywhere

The ESCRT proteins are an ancient system that buds membranes and severs membrane necks from their inner face. Three “classical” functions of the ESCRTs have dominated research into these proteins since their discovery in 2001: the biogenesis of multivesicular bodies in endolysosomal sorting; the budding of HIV-1 and other viruses from the plasma membrane of infected cells; and the membrane abscission step in cytokinesis. The past few years have seen an explosion of novel functions: the biogenesis of microvesicles and exosomes; plasma membrane wound repair; neuron pruning; extraction of defective nuclear pore complexes; nuclear envelope reformation; plus-stranded RNA virus replication compartment formation; and micro- and macroautophagy. Most, and perhaps all, of the functions involve the conserved membrane-neck-directed activities of the ESCRTs, revealing a remarkably widespread role for this machinery through a broad swath of cell biology.     

Syndecan-4 Is a Major Syndecan in Primary Human Endothelial Cells In Vitro,Modulated by Inflammatory Stimuli and Involved in Wound Healing

Syndecans are important cell surface proteoglycans with many functions; yet, they have not been studied to a very large extent in primary human endothelial cells. The purpose of this study was to investigate syndecan-4 expression in cultured human umbilical vein endothelial cells (HUVECs) and assess its role in inflammatory reactions and experimental wound healing. qRT-PCR analysis revealed that syndecan-3 and syndecan-4 were highly expressed in HUVECs, whereas the expression of syndecan-1 and -2 was low. HUVECs were cultured with the inflammatory mediators lipopolysaccharide (LPS) and interleukin 1β (IL-1β). As a result, syndecan-4 expression showed a rapid and strong increase. Syndecan-1 and -2 expressions decreased, whereas syndecan-3 was unaffected. Knockdown of syndecan-4 using siRNA resulted in changes in cellular morphology and focal adhesion sites, delayed wound healing and tube formation, and increased secretion of the pro-inflammatory and angiogenic chemokine, CXCL8. These data suggest functions for syndecan-4 in inflammatory reactions, wound healing and angiogenesis in primary human endothelial cells.     

Auxin-induced leaf blade expansion in Arabidopsis requires both wounding and detachment

Elevation of leaf auxin (indole-3-acetic acid; IAA) levels in intact plants has been consistently found to inhibit leaf expansion whereas excised leaf strips grow faster when treated with IAA. Here we test two hypothetical explanations for this difference in growth sensitivity to IAA by expanding leaf tissues in vivo versus in vitro. We asked if, in Arabidopsis, IAA-induced growth of excised leaf strips results from the wounding required to excise tissue and/or results from detachment from the plant and thus loss of some shoot or root derived growth controlling factors. We tested the effect of a range of exogenous IAA concentrations on the growth of intact attached, wounded attached, detached intact, detached wounded as well as excised leaf strips. After 24 h, the growth of intact attached, wounded attached, and detached intact leaves was inhibited by IAA concentrations as little as 1 µM in some experiments. Growth of detached wounded leaves and leaf strips was induced by IAA concentrations as low as 10 µM. Stress, in the form of high light, increased the growth response to IAA by leaf strips and reduced growth inhibition response by intact detached leaves. Endogenous free IAA content of intact attached leaves and excised leaf strips was found not to change over the course of 24 h. Together these results indicate growth induction of Arabidopsis leaf blade tissue by IAA requires both substantial wounding as well as detachment from the plant and suggests in vivo that IAA induces parallel pathways leading to growth inhibition.     

Energy metabolism in the granulation tissue of diabetic rats during cutaneous wound healing

The skin cells chiefly depend on carbohydrate metabolism for their energy requirement during cutaneous wound healing. Since the glucose metabolism is greatly hampered in diabetes and this might affect wound repair process. This prompted us to investigate the intermediate steps of energy metabolism by measuring enzyme activities in the wound tissues of normal and streptozotocin-induced diabetic rats following excision-type of cutaneous injury. The activities of key regulatory enzymes namely hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and glucose-6 phosphate dehydrogenase (G6PD) have been monitored in the granulation tissues of normal and diabetic rats at different time points (2, 7, 14 and 21 days) of postwounding. Interestingly, a significant alteration in all these enzyme activities was observed in diabetic rats. The activity of PFK was increased but HK, LDH and CS showed a decreased activity in the wound tissue of diabetics as compared to normal rats. However G6PD exhibited an elevated activity only at early stage of healing in diabetic rats. Thus, the results suggest that significant alterations in the activities of energy metabolizing enzymes in the wound tissue of diabetic rats may affect the energy availability for cellular activity needed for repair process and this may perhaps be one of the factor responsible for impaired healing in these subjects. (Mol Cell Biochem 270: 71–77, 2005)     

Close association of invading Plasmodium berghei and beta integrin in the Anopheles gambiae midgut

We have used confocal microscopy and an antibody against Anopheles gambiae beta integrin to study this protein's distribution in the mosquito midgut and its relationship to invading Plasmodium berghei parasites. An extensive reorganization of integrin is seen to take place in the midgut epithelial cells following the uptake of either non-infected or parasite-infected blood meal, probably reflecting the reshaping of the gut due to the presence of the food bolus and the peritrophic membrane that surrounds it. Furthermore, malaria parasites are coated with beta integrin immediately upon entry into the epithelium, independent of whether they develop intra- or extracellularly. Although this coat is shed a few days after the invasion, beta integrin remains concentrated in the cells surrounding the maturing oocyst for several days. Finally, the antibody detects a structural change in the midgut epithelial cells in the immediate vicinity of the invading ookinete, which is consistent with Plasmodium-induced apoptosis followed by wound healing. This intimate association suggests a specific role of beta integrin in the invasion process.     

Wound healing ability of Xenopus laevis embryos. II. Morphological analysis of wound marginal epidermis

We previously showed that bisectional wounds made in Xenopus laevis embryos at the primary eye vesicle stage were rapidly closed. In this study, microscopic analyses, including scanning electron microscopy, on the morphology of the epidermis were conducted during wound closure in the half embryos. Bright fluorescence of Texas red-phalloidin showing actin filaments started to be visualized at the cut edge 10 min after wounding. It increased with time, forming a distinguished, though discontinuous, bundle along the wound margin. The wound closure was completely inhibited by 20 microm cytochalasin B, and almost completely by 50 mm 2,3-butanedione 2-monoxime, an inhibitor to myosin ATPase activity. Scanning electron microscopy revealed that the outer epidermal cells became extensively elongated in the radial direction, and the contour of the closing wound edge did not become smoother but remained ragged. Thus, a representative embryonic type of wound closure may be driven in Xenopus embryos by a complex mechanism, involving not only the actin 'purse-string' but also an inward movement of individual cells. Anyhow, the wound closure is a movement of the epidermal sheet maintaining cell-cell contact, and not involving locomotion of single cells separated from the wound edge.