Head regeneration inHydra is initiated release of head activator and inhibitor

Summary Hydra regenerating heads release at least two substances into the surrounding medium: one stimulates and one inhibits head formation. The inhibitor is released mainly during the first hour after cutting, the activator is released more slowly with a maximum in the second hour and with substantial release still during the following six hours. The release of both substances seems to be specific for head regeneration: it is not found in animals regenerating feet. The sequential release of these substances leads to the early changes observed at the cellular level during head regeneration inhydra: the inhibitor produces a decrease, the activator an increase in the mitotic activity of interstitial and epithelial cells, if assayed on intact animals. Head regeneration is blocked, if the release of the head activator is prevented. It is therefore suggested that these substances are necessary to initiate head regeneration inhydra.     

How do plant growth substances work?

Abstract. Despite intensive research effort, the role of growth substances in the life of the intact growing plant is far from clear. Two reasons are suggested which may account for the lack of progress. The first is the failure to recognize the unique aspects of plant development. These which are expressed by the regenerative, organizational and developmental plasticity of the meristem probably result from the possession of growth substances. The second is the concept of growth substances as hormones. This represents the main conceptual thrust of research and is considered critically, starting with the historical system, the coleoptile and dealing with other major growth substance systems in turn. It is concluded that a hormonal concept which includes control by changes in growth substance concentration fails to explain the developmental phenomena under examination. A role for growth substances as integrating agents is suggested and the notion of quantitative tissue sensitivity variation is developed to explain the major growth patterns of developing shoots.     

Cytokinin-like substances and accumulation of labelled metabolites at infection sites of Alternaria brassicicola

Green islands were observed on mustard leaves beneath the infection drops containing germinating conidia of Alternaria brassicicola, when the surrounding uninfected tissue had yellowed due to senescence. Green island formation has been correlated with the secretion of cytokinin-like substances by the pathogens. A. brassicicola secreted cytokinin-like substances in a liquid synthetic medium and their application to detached host leaves evoked the formation of green islands in the dark. ¹⁴C studies confirmed that green islands act as metabolic sinks in which photosynthates are retained or accumulated. Cytokinin-like substances appear to be actively involved in infection and pathogenesis of A. brassicicola.     

Rodent stomach sample preparation for nitrogen NIRS analysis

Near infrared reflectance spectroscopy is a highly promising method for estimating food quality in small mammals. The method used to prepare rodent stomach content samples, however, may influence nitrogenous substance results. In this study, we focus on comparing methods of preparation of samples and finding the optimal preparation method, which means saving time and costs as well as maintenance of reliability and precision of estimation. We examined 1497 stomachs of the following species: Apodemus flavicollis, A. sylvaticus, Clethrionomys glareolus and Microtus arvalis. We used two preparation methods (grinding and abrasion). Where possible, cardiac and pyloric stomach sections were also examined separately. We found no significant difference between these data, hence only financial, time and equipment factors need determine the processing method in future studies.     

High risk water pollution hazards affecting Aveiro coastal lagoon (Portugal) – A habitat risk assessment using InVEST

Anthropogenic pressures put at jeopardy ecosystem services (ES) provided by natural habitats. Ecosystem Based Management (EBM) approaches can support policymakers dealing with physical, chemical, and biological stresses caused by high-risk water pollution (HRWP) and sudden-accidental pollution (SAP). The objective of this study is to evaluate how alarming HRWP pressures might become in fragile marine, coastal, estuarine, and freshwater socio-ecological systems (MCEF-SES) surrounded by heavily industrialized and urbanized areas. To this end a spatially explicit analysis, using the InVEST-Habitat Risk Assessment (InVEST-HRA) model in combination with expert judgement from researchers from various fields, is performed. An application is provided for the case of the Ria de Aveiro (RdA) coastal lagoon in Portugal. Results show high spatial variance of HRWP hazards across RdA, with one major multi-layer risk hotspot at the center of the research area and a second patch of multiple risk hotspots towards the North of RdA. Salines emerge as the most threatened habitat followed by Intertidal flats and Saltmarshes. The most significant water pollution risk sources contributing to Salines cumulative risk are Fossil fuel processing, storage and sale units, Industrial units, Aquaculture, and the Marinas. Industries involving dangerous substances in the region threaten primarily Watercourses. This study confirms the InVEST-HRA model in combination with expert judgement is a transparent and easily replicable approach to build ES-based knowledge about habitat risks threatening MCEF-SES in a Natura 2000 site heavily pressured by HRWP hazards. After further valuation analysis, pondering gains and losses from regional development and environmental protection, this knowledge can support the planning and management of coastal areas and the prioritization of pollution abatement interventions. In particular, by estimating the loss that HRWP causes in the value of ecosystem services, defining HRWP abatement policies, assessing the effectiveness, costs and benefits of those abatement policies and, ultimately, evaluating the results for the well-being of local communities through global efficiency analysis, cost-benefit analysis or cost-effectiveness analysis. Hence, it bridges the gap between an informed EBM and the development policies of fragile regions.     

Comparison between a moving bed membrane bioreactor and a conventional membrane bioreactor on membrane fouling

A membrane bioreactor filled with carriers instead of activated sludge named a moving bed membrane bioreactor (MBMBR) was investigated to minimize the effect of suspended solids on membrane fouling. The MBMBR and a conventional membrane bioreactor (CMBR) were operated in parallel for about two months. Unexpectedly, the rate of membrane fouling in MBMBR was about three times of that in CMBR. MBMBR showed a higher cake layer resistance than CMBR due to plenty of filamentous bacteria inhabited in suspended solids in MBMBR. Protein and polysaccharide contents of soluble EPS in MBMBR were obviously larger than those in CMBR. It could be speculated that the overgrowth of filamentous bacteria in MBMBR resulted in severe cake layer and induced a large quantity of EPS, which deteriorated the membrane fouling.     

Bacopa monnieri modulates endogenous cytoplasmic and mitochondrial oxidative markers in prepubertal mice brain

Bacopa monnieri (BM) an herb, found throughout the Indian subcontinent in wet, damp and marshy areas is used in Ayurvedic system of medicine for improving intellect/memory, treatment of anxiety and neuropharmacological disorders. Although extensively given to children as a memory enhancer, no data exists on its ability to modulate neuronal oxidative stress in prepubertal animal models. Hence in this study, we examined if dietary intake of BM leaf powder has the propensity to modulate endogenous markers of oxidative stress, redox status (reduced GSH, thiol status), response of antioxidant defenses (enzymic), protein oxidation and cholinergic function in various brain regions of prepubertal (PP) mice. PP mice maintained on a BM-enriched diet (0.5 and 1%) for 4 weeks showed a significant diminution of basal oxidative markers (malondialdehyde levels, reactive species generation, hydroperoxide levels and protein carbonyls) in both cytoplasm and mitochondria of all brain regions. This was accompanied with enhanced reduced glutathione, thiol levels and elevated activities of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase). Significant reduction in the activity of acetyl cholinesterase enzyme in all brain regions suggested the potential of BM leaf powder to modulate cholinergic function. Further evidence that dietary intake of BM leaf powder confers the prepubertal brain with additional capacity to cope up with neurotoxic prooxidants was obtained by exposing cortical/cerebellar synaptosomes of normal and BM fed mice to 3-nitropropionic acid (3-NPA). While synaptosomes from control mice exhibited a concentration related lipid peroxidation and ROS generation, synaptosomes obtained from BM fed mice showed only a marginal induction at the highest concentration clearly suggesting their increased resistance to 3-NPA-induced oxidative stress. Collectively these data clearly indicate the potential of Bacopa monnieri to modulate endogenous markers of oxidative stress in brain tissue of PP mice. Based on these results, it is hypothesized that dietary intake of BM leaf powder confers neuroprotective advantage and is likely to be effective as a prophylactic/therapeutic agent for neurodegenerative disorders involving oxidative stress.     

Structure and Dynamics of Exopolymers in an Intertidal Diatom Biofilm

Diatom biofilms growing at the surface of the intertidal mudflat of Marennes Oléron, France, were incubated for 48 h in the laboratory under simulated conditions of high- and low tide (immersed and emersed in seawater) and day and night (illuminated or dark conditions). The biofilms were subsequently sampled using the cryolander technique, without disturbing the structure. The samples were kept in liquid nitrogen until they were transferred to the cooled stage of a field-emission cryo-scanning electron microscope, which was used to study the structural relationships between the sediment particles, the diatoms and the different types of extracellular polymeric substances (EPS) produced by these organisms. The diatoms were most abundant at the sediment surface when incubated in the light under emersed conditions. In the dark or when immersed, the diatoms migrated into the sediment. In the light, the diatoms were coated with EPS, while this was not the case when incubated in the dark. When immersed, the sediment surface appeared smooth as the result of the deposition of mud. Under emersed conditions, the coarser silt grains were prominently present. These grains were wrapped with organic matter and bound together through threads of EPS. This was the case both in light and in dark incubated sediment. It is proposed that this latter type of EPS contributes to the increased erosion threshold of intertidal mudflats colonized by biofilms of diatoms.     

The photoprotective role of humus-DOC for Selenastrum and Daphnia

Cell numbers and fluorescence of the green algae Selenastrum capricornutuum and survival of Daphnia magna exposed to simulated sun-light was assessed along a gradient of DOC (0, 1, 5 10 and 50 mg C l^–1). When exposed to UV-doses and spectral distribution (295–750 nm) closely resembling surface solar radiation during mid summer, Selenastrum showed major losses of cell fluorescence. In the absence of DOC, fluorescence was severely depressed, with successively decreasing effects with increased DOC. Surviving cells also required an extensive recovery period (10–12 d) for regrowth after exposure, while an almost immediate recovery was observed at concentrations above 1 mg DOC l^–1. For Daphnia, survival was reduced to less than 10% after 4 h exposure, and almost zero after 8 h exposure in the absence of humus DOC, while no effects were observed in treatments with 10 and 50 mg C l^–1. Selenastrum and Daphnia that were not directly irradiated, but exposed to UV-irradiated water with the same concentrations of DOC did not reveal negative effects. This indicates negligible indirect effects mediated by long-lived free radicals or other toxic compounds. Irradiation of Daphnia under increased oxygen concentration (200% saturation) did not indicate acute effects, suggesting that effects of ambient radicals and oxidants would be of minor importance relative to intracellular photoproducts.