Novel inner monolayer fusion assays reveal differential monolayer mixing associated with cation-dependent membrane fusion

AbstractThe ability to specifically monitor the behavior of the inner monolayer lipids of membranous vesicles during the membrane fusion process is useful technically and experimentally. In this study, we have identified N-NBD-phosphatidylserine as a reducible probe particularly suitable for inner monolayer fusion assays because of its low rate of membrane translocation after reduction of the outer monolayer probes by dithionite. Data are presented on translocation as a function of temperature, vesicle size, membrane composition, and serum protein concentration. Translocation as a result of the fusion event itself was also characterized. We further show here that a second membrane-localized probe, a long wavelength carbocyanine dye referred to a diI(5)C18ds, appears to form a membrane-bound resonance energy transfer pair with N-NBD-PS, and its outer monolayer fluorescence can also be eliminated by dithionite treatment. Lipid dilution of these probes upon fusion with unlabeled membranes leads to an increase in NBD donor fluorescence, and hence is a new type of inner monolayer fusion assay.These inner monolayer probe mixing assays were compared to random lipid labeling and aqueous contents mixing assays for cation-dependent fusion of liposomes composed of phosphatidylserine and phosphatidylethanolamine. The results showed that the inner monolayer fusion assay eliminates certain artifacts and reflects fairly closely the rate of non-leaky mixing of aqueous contents due to fusion, while outer monolayer mixing always precedes mixing of aqueous contents. In fact, vesicle aggregation and outer monolayer lipid mixing were found to occur over very long periods of time without inner monolayer mixing at low cation concentrations. Externally added lysophosphatidylcholine inhibited vesicle aggregation, outer monolayer mixing and any subsequent fusion. The state of vesicle aggregation and outer monolayer exchange that occurs below the fusion threshold may represent a metastable intermediate state that may be useful for further studies of the mechanism of membrane fusion

Trauma as counter-revolutionary colonisation: narratives from (post)revolutionary Egypt

We argue that multiple levels of trauma were present in Egypt before, during and after the 2011 revolution. Individual, social and political trauma constitute a triangle of traumatisation which was strategically employed by the Egyptian counter-revolutionary forces – primarily the army and the leadership of the Muslim Brotherhood – to maintain their political and economic power over and above the social, economic and political interests of others. Through the destruction of physical bodies, the fragmentation and polarisation of social relations and the violent closure of the newly emerged political public sphere, these actors actively repressed the potential for creative and revolutionary transformation. To better understand this multi-layered notion of trauma, we turn to Habermas’ ‘colonisation of the lifeworld’ thesis which offers a critical lens through which to examine the wider political and economic structures and context in which trauma occurred as well as its effects on the personal, social and political realms. In doing so, we develop a novel conception of trauma that acknowledges individual, social and political dimensions. We apply this conceptual framing to empirical narratives of trauma in Egypt’s pre- and post-revolutionary phases, thus both developing a non-Western application of Habermas’ framework and revealing ethnographic accounts of the revolution by activists in Cairo

Enhancement of the in vivo circulation lifetime of l-α-distearoylphosphatidylcholine liposomes: importance of liposomal aggregation versus complement opsonization

AbstractIncorporation of N-(ω-carboxy)acylamido-phosphatidylethanolamines (-PEs) into large unilamellar vesicles (LUVs) of l-α-distearoylphosphatidylcholine (DSPC) was found to dramatically increase the in vivo liposomal circulation lifetime in rats, reaching a maximal effect at 10 mol.% of the total phospholipid. Neither pure DSPC liposomes nor those with the longest circulating derivative, N-glutaryl-dipalmitoylphosphatidylethanolamine (-DPPE), were found to significantly bind complement from serum. Therefore, the relatively short circulation time of pure DSPC liposomes did not appear to be related to greater complement opsonization leading to uptake by the reticuloendothelial system. However, N-(ω-carboxy)acylamido-PEs were particularly efficient inhibitors of a limited aggregation detected for pure DSPC liposomes. The aggregation tendency of DSPC liposomes incorporating various structural analogs of N-glutaryl-DPPE correlated inversely with the circulation lifetimes. Therefore, it is concluded that such PE derivatives enhance the circulation time by preventing liposomal aggregation and avoiding a poorly understood mechanism of clearance that is dependent on size but is independent of complement opsonization. At high concentrations of N-glutaryl-DPPE (above 10 mol.%), the liposomes exhibited strong complement opsonization and were cleared from circulation rapidly, as were other highly negatively charged liposomes. These data demonstrate that both the lack of opsonization and the lack of a tendency to aggregate are required for long circulation. Liposomal disaggregation via N-(ω-carboxy)acylamido-PEs yields a new class of large unilamellar DSPC liposomes with circulation lifetimes that are comparable to those of sterically stabilized liposomes

A person-centered perspective on working with people who have experienced psychological trauma and helping them move forward to posttraumatic growth

Over the past decade posttraumatic growth (PTG) has become a major topic for theory, research and practice in mainstream trauma psychology. The aim of this paper is to discuss the implications of PTG for the person-centered approach. It is argued that PTG provides a new non-medical language for understanding psychological trauma that is consistent with the person-centered approach. Person-centered personality theory provides an explanation for how PTG arises and leads to new testable predictions for research into how person-centered therapy may be able to facilitate PTG

A theory on reports of constructive (real) and illusory posttraumatic growth

It has been suggested that self-reported posttraumatic growth could sometimes be considered as a way for people to protect themselves from the distress of trauma. In this case, reports of posttraumatic growth could be illusory. We suggest a theory on self-reported constructive (real) posttraumatic growth and illusory posttraumatic growth by using Rogers’s (1959) theory and the work by Vaillant (1995). Through this theoretical framework we attempt to explain when reports of posttraumatic growth are likely to be constructive and real and when such reports are likely to represent aspects of illusions. We will also consider the implications for research practice

Inhibition of HIV-1 infectivity and epithelial cell transfer by human monoclonal IgG and IgA antibodies carrying the b12 V region

Both IgG and secretory IgA Abs in mucosal secretions have been implicated in blocking the earliest events in HIV-1 transit across epithelial barriers, although the mechanisms by which this occurs remain largely unknown. In this study, we report the production and characterization of a human rIgA(2) mAb that carries the V regions of IgG1 b12, a potent and broadly neutralizing anti-gp120 Ab which has been shown to protect macaques against vaginal simian/HIV challenge. Monomeric, dimeric, polymeric, and secretory IgA(2) derivatives of b12 reacted with gp120 and neutralized CCR5- and CXCR4-tropic strains of HIV-1 in vitro. With respect to the protective effects of these Abs at mucosal surfaces, we demonstrated that IgG1 b12 and IgA(2) b12 inhibited the transfer of cell-free HIV-1 from ME-180 cells, a human cervical epithelial cell line, as well as Caco-2 cells, a human colonic epithelial cell line, to human PBMCs. Inhibition of viral transfer was due to the ability of b12 to block both viral attachment to and uptake by epithelial cells. These data demonstrate that IgG and IgA MAbs directed against a highly conserved epitope on gp120 can interfere with the earliest steps in HIV-1 transmission across mucosal surfaces, and reveal a possible mechanism by which b12 protects the vaginal mucosal against viral challenge in vivo

Retelling racialized violence, remaking white innocence: the politics of interlocking oppressions in transgender day of remembrance

Transgender Day of Remembrance has become a significant political event among those resisting violence against gender-variant persons. Commemorated in more than 250 locations worldwide, this day honors individuals who were killed due to anti-transgender hatred or prejudice. However, by focusing on transphobia as the definitive cause of violence, this ritual potentially obscures the ways in which hierarchies of race, class, and sexuality constitute such acts. Taking the Transgender Day of Remembrance/Remembering Our Dead project as a case study for considering the politics of memorialization, as well as tracing the narrative history of the Fred F. C. Martinez murder case in Colorado, the author argues that deracialized accounts of violence produce seemingly innocent White witnesses who can consume these spectacles of domination without confronting their own complicity in such acts. The author suggests that remembrance practices require critical rethinking if we are to confront violence in more effective ways. Description from publisher's site: http://caliber.ucpress.net/doi/abs/10.1525/srsp.2008.5.1.2

Nonspecific protease and elastase activities in rat leukocytes

Extracts were prepared from rat peritoneal leukocytes obtained 4 h after glycogen injection and assayed for proteolytic enzyme activities against various substrates. The substrates used included acid-denatured bovine hemoglobin, bovine serum albumin, a partially purified preparation of rat pulmonary basement membrane, bovine neck ligament elastin, and an artificial substrate with elastase specificity. A high level of activity was observed when hemoglobin was used as the substrate. The serum albumin and basement membrane preparation were also readily hydrolyzed by the leukocyte extract. In contrast, the native elastin and synthetic elastase substrate were much more resistant. Although the leukocyte extract demonstrated little intrinsic elastase activity, when it was mixed with a commercial hog pancreatic elastase preparation, it greatly potentiated the elastolytic activity, suggesting the activation of a latent enzyme.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44534/1/10753_2004_Article_BF00916242.pd

Lactation and neonatal nutrition: defining and refining the critical questions.

This paper resulted from a conference entitled "Lactation and Milk: Defining and refining the critical questions" held at the University of Colorado School of Medicine from January 18-20, 2012. The mission of the conference was to identify unresolved questions and set future goals for research into human milk composition, mammary development and lactation. We first outline the unanswered questions regarding the composition of human milk (Section I) and the mechanisms by which milk components affect neonatal development, growth and health and recommend models for future research. Emerging questions about how milk components affect cognitive development and behavioral phenotype of the offspring are presented in Section II. In Section III we outline the important unanswered questions about regulation of mammary gland development, the heritability of defects, the effects of maternal nutrition, disease, metabolic status, and therapeutic drugs upon the subsequent lactation. Questions surrounding breastfeeding practice are also highlighted. In Section IV we describe the specific nutritional challenges faced by three different populations, namely preterm infants, infants born to obese mothers who may or may not have gestational diabetes, and infants born to undernourished mothers. The recognition that multidisciplinary training is critical to advancing the field led us to formulate specific training recommendations in Section V. Our recommendations for research emphasis are summarized in Section VI. In sum, we present a roadmap for multidisciplinary research into all aspects of human lactation, milk and its role in infant nutrition for the next decade and beyond

Doing research in immigration removal centres: ethics, emotions and impact

Immigration Removal Centres (IRCs) are deeply contested institutions that rarely open their doors to independent research. In this article we discuss some of the complications we faced in conducting the first national study of everyday life in them. As we will set out, research relationships were difficult to forge due to low levels of trust, and unfamiliarity with academic research. At the same time, many participants had unrealistic expectations about our capacity to assist while most exhibited high levels of distress. We were not immune from the emotional burden of the field sites. Such matters were compounded by the limited amount of published information about life in IRCs and a lack of ethical guidelines addressing such places. Drawing on related literature from prison sociology, we use our experiences in IRCs to set out a methodological account of understanding, ethics, and impact within these complex sites