Comparative monolayer investigations of surface properties of negatively charged glycosphingolipids from vertebrates (gangliosides) and invertebrates (SGL-II, lipid IV).

The surface properties of four negatively charged glycosphingolipids from vertebrates, the sialo-glycosphingolipids (=gangliosides) GM1, GD1a, GT1b and a sulfo-glycosphingolipid (=sulfatide), and of the two negatively charged glycosphingolipids from lower invertebrates, the glucurono-glycosphingolipid Lipid IV and the aminophosphono-glycosphingo-lipid SGL-II were investigated in monolayers at the air/water interface. The molecular peculiarities under investigation were surface pressure (π) and surface potential (ΔV) which are described for Lipid IV and SGL-II for the first time. The surface pressure/area isotherms of all glycosphingolipids were typical of a liquid-expanded monolayer and, with the exception of SGL-II, exhibited a phase transition to a liquid-condensed state at surface pressures above 20 mN/m. The surface potential/molecular area data found for gangliosides in the closely packed state at π=30 mN/m (GM1: ΔV = −17 mV; GD1a: ΔV = −35 mV; GT1b: ΔV = −39 mV) showed only a slight influence of the additional number of negatively charged residues. For Lipid IV, the surface behavior was very similar to GM1 both possessing one negative group per molecule, whereas in SGL-II also the surface potential data (ΔV = −173 mV) were different compared with GD1a both possessing two negative groups per molecule. The addition of Ca2+ condensed the monolayers of all glycolipids and increased the potential in the direction to more positive values, but these findings were less effective in SGL-II films. On the basis of monolayer results presented here, in biological membranes of invertebrates especially Lipid IV might play a similar role as the ganglioside GM1 in vertebrate cells

Surface potentials and electric dipole moments of ganglioside and phospholipid bilayers: Contribution of the polar headgroup at the water/lipid interface.

Monolayers of different gangliosides (GM1, GD1a, GT1b, GMix), ceramide (Cer), sulfatide (Sulf), phospholipids (DOPC, DPPE, DPPS, DOPA), a quaternary ammonium salt (DOMA) and fatty acids (C16, C18, C20) were investigated at the air/water interface on pure water as well as on buffered subphases. Monolayers at the air/water interface consist of two interfaces: the water/lipid and the lipid/air interfaces. The normal components of the effective total dipole moments (Δμ), the effective local dipole moments (Δμα) and effective local surface potentials (ΔVα) of polar headgroups at the water/lipid interface have been calculated from surface potential (ΔV) and mean molecular area (A) measurements of close-packed monolayers. The contribution of the lipid/air interface was previously determined experimentally by partial dipole compensation approach (Vogel, V. and Möbius, D. (1988) Thin Solid Films 159, 73–81). The surface potentials (ΔV) of ganglioside monolayers are quite similar (e.g., GMI = −17 mV, GTib = −39 mV; at surface pressure π = 30 mN/m triethanolamine (TEA)/HCl buffer, pH 7.4, as subphase); this indicates that variations in molecular structure of gangliosides like the influence of the number of negative charges per ganglioside which lead to appreciate changes in the average molecular packing do not cause large changes in surface potential. The local surface potentials (ΔVα) reach to minus several hundred millivolts for nearly all compounds, but clear differences are shown between negatively charged phospholipids (e.g., DPPS = −296 mV at π = 30 mN/m) and glycolipids (e.g., GM1 = −413 mV), and within glycolipids at different surface pressures (e.g., GD1n: − 342 mV at π = 20 mN/m versus −453 mV at π = 30mN/m nly in gangliosides (except for GD1b) the total dipole moments (Δμ) are negative (−0.029 up to − 0.078 D) and directed to the water. Unlike DOPC (+0.069 D) and DOMA (+0.421 D), the local dipole moments (Δμα of all hydrated polar headgroups are negative (e.g., DPPS = −0.331 D; GM1 = −0.729 D) and directed from the monolayer (−) to the water (+). Under well-defined conditions investigated such data are helpful for a better understanding of the large functional role of gangliosides especially in determining the surface potential of biological membranes

Co-constructing desired activities : Small-scale activity decisions in occupational therapy

Social inclusion and exclusion are buzzwords in today’s political discourse. While there are many causes of social exclusion, one of the factors repeatedly shown to lead to social exclusion is mental illness, which may hinder people in developing themselves in accordance with their wishes and abilities. Participation is a key dimension of social inclusion—and one that we particularly seek to increase understanding of in this volume. We focus on participation taking place in face-to-face social encounters, seeking to get to the root of the preconditions and consequences of participation by unraveling the interactional processes that underlie what makes it possible. We presuppose that participation in any social or societal sphere presupposes social interaction, which in turn requires the capacity to coordinate with and make sense of others’ actions. Thus, drawing on joint decision-making as a specific arena of social interaction, where the participants’ collaborative management of the turn-by-turn sequential unfolding of interaction can have tangible consequences for the participants’ social and economic circumstances, we seek to increase understanding of the specific vulnerabilities that individuals with mental illness have in this context.In occupational therapy, a therapist and client engage in shared activities that they perform collaboratively during therapeutic sessions. An important part of this joint performance involves providing the client with the opportunity to make short-term decisions on the activities they wish to perform. Analyzing 15 occupational therapy encounters at psychiatric outpatient clinics, in the chapter I explore the functions of these small-scale decisions. The analysis demonstrates that therapists (1) make room for the client’s proposals by shaping the activity context and (2) make proposals themselves on the ways the performance should be accomplished. To summarize, clients are given decision-making power over the content of the activity, whereas therapists use their decision-making power to assist the client’s performance. The analysis shows how small-scale decisions can be employed to construct the occupational performance as shared endeavors and to position the clients as active subjects rather than objects of the professionals’ performance.Peer reviewe

Promoting Client Participation and Constructing Decisions in Mental Health Rehabilitation Meetings

The chapter analyzes practices by which support workers promote client participation in mental health rehabilitation meetings at the Clubhouse. While promoting client participation, the support workers also need to ascertain that at least some decisions get constructed during the meetings. This combination of goals—promoting participation and constructing decisions—leads to a series of dilemmatic practices, the dynamics of which the chapter focuses on analyzing. The support workers may treat clients’ turns retrospectively as proposals, even if the status of these turns as such is ambiguous. In the face of a lack of recipient uptake, the support workers may remind the clients about their epistemic access to the content of the proposal or pursue their agreement or commitment to the idea. These practices involve the support workers carrying primary responsibility over the unfolding of interaction, which is argued to compromise the jointness of the decision-making outcome.The chapter analyzes practices by which support workers promote client participation in mental health rehabilitation meetings at the Clubhouse. While promoting client participation, the support workers also need to ascertain that at least some decisions get constructed during the meetings. This combination of goals—promoting participation and constructing decisions—leads to a series of dilemmatic practices, the dynamics of which the chapter focuses on analyzing. The support workers may treat clients’ turns retrospectively as proposals, even if the status of these turns as such is ambiguous. In the face of a lack of recipient uptake, the support workers may remind the clients about their epistemic access to the content of the proposal or pursue their agreement or commitment to the idea. These practices involve the support workers carrying primary responsibility over the unfolding of interaction, which is argued to compromise the jointness of the decision-making outcome.Peer reviewe

Estimation of Fish Biomass Using Environmental DNA

Environmental DNA (eDNA) from aquatic vertebrates has recently been used to estimate the presence of a species. We hypothesized that fish release DNA into the water at a rate commensurate with their biomass. Thus, the concentration of eDNA of a target species may be used to estimate the species biomass. We developed an eDNA method to estimate the biomass of common carp (Cyprinus carpio L.) using laboratory and field experiments. In the aquarium, the concentration of eDNA changed initially, but reached an equilibrium after 6 days. Temperature had no effect on eDNA concentrations in aquaria. The concentration of eDNA was positively correlated with carp biomass in both aquaria and experimental ponds. We used this method to estimate the biomass and distribution of carp in a natural freshwater lagoon. We demonstrated that the distribution of carp eDNA concentration was explained by water temperature. Our results suggest that biomass data estimated from eDNA concentration reflects the potential distribution of common carp in the natural environment. Measuring eDNA concentration offers a non-invasive, simple, and rapid method for estimating biomass. This method could inform management plans for the conservation of ecosystems

Transcriptomic Characterization of Temperature Stress Responses in Larval Zebrafish

Temperature influences nearly all biochemical, physiological and life history activities of fish, but the molecular mechanisms underlying the temperature acclimation remains largely unknown. Previous studies have identified many temperature-regulated genes in adult tissues; however, the transcriptional responses of fish larvae to temperature stress are not well understood. In this study, we characterized the transcriptional responses in larval zebrafish exposed to cold or heat stress using microarray analysis. In comparison with genes expressed in the control at 28°C, a total of 2680 genes were found to be affected in 96 hpf larvae exposed to cold (16°C) or heat (34°C) for 2 and 48h and most of these genes were expressed in a temperature-specific and temporally regulated manner. Bioinformatic analysis identified multiple temperature-regulated biological processes and pathways. Biological processes overrepresented among the earliest genes induced by temperature stress include regulation of transcription, nucleosome assembly, chromatin organization and protein folding. However, processes such as RNA processing, cellular metal ion homeostasis and protein transport and were enriched in genes up-regulated under cold exposure for 48 h. Pathways such as mTOR signalling, p53 signalling and circadian rhythm were enriched among cold-induced genes, while adipocytokine signalling, protein export and arginine and praline metabolism were enriched among heat-induced genes. Although most of these biological processes and pathways were specifically regulated by cold or heat, common responses to both cold and heat stresses were also found. Thus, these findings provide new interesting clues for elucidation of mechanisms underlying the temperature acclimation in fish

Effect of cholesterol on the dipole potential of lipid membranes

The membrane dipole potential, ψd, is an electrical potential difference with a value typically in the range 150 – 350 mV (positive in the membrane interior) which is located in the lipid headgroup region of the membrane, between the linkage of the hydrocarbon chains to the phospholipid glycerol backbone and the adjacent aqueous solution. At its physiological level in animal plasma membranes (up to 50 mol%), cholesterol makes a significant contribution to ψd of approximately 65 mV; the rest arising from other lipid components of the membrane, in particular phospholipids. Via its effect on ψd, cholesterol may modulate the activity of membrane proteins. This could occur through preferential stabilization of protein conformational states. Based on its effect on ψd, cholesterol would be expected to favour protein conformations associated with a small local hydrophobic membrane thickness. Via its membrane condensing effect, which also produces an increase in ψd, cholesterol could further modulate interactions of polybasic cytoplasmic extensions of membrane proteins, in particular P-type ATPases, with anionic lipid headgroups on the membrane surface, thus leading to enhanced conformational stabilization effects and changes to ion pumping activity.Australian Research Counci

Effects of temperature in juvenile seabass (Dicentrarchus labrax L.) biomarker responses and behaviour: implications for environmental monitoring

The effects of temperature on European seabass (Dicentrarchus labrax L.) juveniles were investigated using a 30-day bioassay carried out at 18 and 25 °C in laboratory conditions. A multiparameter approach was applied including fish swimming velocity and several biochemical parameters involved in important physiological functions. Fish exposed for four weeks to 25 °C showed a decreased swimming capacity, concomitant with increased oxidative stress (increased catalase and glutathione peroxidase activities) and damage (increased lipid peroxidation levels), increased activity of an enzyme involved in energy production through the aerobic pathway (isocitrate dehydrogenase) and increased activities of brain and muscle cholinesterases (neurotransmission) compared to fish kept at 18 °C. Globally, these findings indicate that basic functions, essential for juvenile seabass surviving and well performing in the wild, such as predation, predator avoidance, neurofunction and ability to face chemical stress may be compromised with increasing water temperature. This may be of particular concern if D. labrax recruitment phase in northwest European estuaries and coastal areas happens gradually inmore warm environments as a consequence of global warming. Considering that the selected endpoints are generally applied in monitoring studies with different species, these findings also highlight the need of more research, including interdisciplinary and multiparameter approaches, on the impacts of temperature on marine species, and stress the importance of considering scenarios of temperature increase in environmental monitoring and in marine ecological risk assessment