Identification of the glycosylphosphatidylinositol-specific phospholipase A2 (GPI-PLA2) that mediates GPI fatty acid remodeling in Trypanosoma brucei

The biosynthesis of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) in the parasitic protozoan Trypanosoma brucei involves fatty acid remodeling of the GPI precursor molecules before they are transferred to protein in the endoplasmic reticulum. The genes encoding the requisite phospholipase A2 and A1 activities for this remodeling have thus far been elusive. Here, we identify a gene, Tb927.7.6110, that encodes a protein that is both necessary and sufficient for GPI-phospholipase A2 (GPI-PLA2) activity in the procyclic form of the parasite. The predicted protein product belongs to the alkaline ceramidase, PAQR receptor, Per1, SID-1, and TMEM8 (CREST) superfamily of transmembrane hydrolase proteins and shows sequence similarity to Post-GPI-Attachment to Protein 6 (PGAP6), a GPI-PLA2 that acts after transfer of GPI precursors to protein in mammalian cells. We show the trypanosome Tb927.7.6110 GPI-PLA2 gene resides in a locus with two closely related genes Tb927.7.6150 and Tb927.7.6170, one of which (Tb927.7.6150) most likely encodes a catalytically inactive protein. The absence of GPI-PLA2 in the null mutant procyclic cells not only affected fatty acid remodeling but also reduced GPI anchor sidechain size on mature GPI-anchored procyclin glycoproteins. This reduction in GPI anchor sidechain size was reversed upon the re-addition of Tb927.7.6110 and of Tb927.7.6170, despite the latter not encoding GPI precursor GPI-PLA2 activity. Taken together, we conclude that Tb927.7.6110 encodes the GPI-PLA2 of GPI precursor fatty acid remodeling and that more work is required to assess the roles and essentiality of Tb927.7.6170 and the presumably enzymatically inactive Tb927.7.6150.

A Trypanosoma brucei β3 glycosyltransferase superfamily gene encodes a β1-6 GlcNAc-transferase mediating N-glycan and GPI anchor modification

The parasite Trypanosoma brucei exists in both a bloodstream form (BSF) and a procyclic form (PCF), which exhibit large carbohydrate extensions on the N-linked glycans and glycosylphosphatidylinositol (GPI) anchors, respectively. The parasite's glycoconjugate repertoire suggests at least 38 glycosyltransferase (GT) activities, 16 of which are currently uncharacterized. Here, we probe the function(s) of the uncharacterized GT67 glycosyltransferase family and a β3 glycosyltransferase (β3GT) superfamily gene, TbGT10. A BSF-null mutant, created by applying the diCre/loxP method in T. brucei for the first time, showed a fitness cost but was viable in vitro and in vivo and could differentiate into the PCF, demonstrating nonessentiality of TbGT10. The absence of TbGT10 impaired the elaboration of N-glycans and GPI anchor side chains in BSF and PCF parasites, respectively. Glycosylation defects included reduced BSF glycoprotein binding to the lectin ricin and monoclonal antibodies mAb139 and mAbCB1. The latter bind a carbohydrate epitope present on lysosomal glycoprotein p67 that we show here consists of (-6Galβ1-4GlcNAcβ1-)≥4 poly-N-acetyllactosamine repeats. Methylation linkage analysis of Pronase-digested glycopeptides isolated from BSF wild-type and TbGT10 null parasites showed a reduction in 6-O-substituted- and 3,6-di-O-substituted-Gal residues. These data define TbGT10 as a UDP-GlcNAc:βGal β1-6 GlcNAc-transferase. The dual role of TbGT10 in BSF N-glycan and PCF GPI-glycan elaboration is notable, and the β1-6 specificity of a β3GT superfamily gene product is unprecedented. The similar activities of trypanosome TbGT10 and higher-eukaryote I-branching enzyme (EC 2.4.1.150), which belong to glycosyltransferase families GT67 and GT14, respectively, in elaborating N-linked glycans, are a novel example of convergent evolution.

Conditional genome engineering reveals canonical and divergent roles for the Hus1 component of the 9-1-1 complex in the maintenance of the plastic genome of Leishmania

Leishmania species are protozoan parasites whose remarkably plastic genome limits the establishment of effective genetic manipulation and leishmaniasis treatment. The strategies used by Leishmania to maintain its genome while allowing variability are not fully understood. Here, we used DiCre-mediated conditional gene deletion to show that HUS1, a component of the 9-1-1 (RAD9-RAD1-HUS1) complex, is essential and is required for a G2/M checkpoint. By analyzing genome-wide instability in HUS1 ablated cells, HUS1 is shown to have a conserved role, by which it preserves genome stability and also a divergent role, by which it promotes genome variability. These roles of HUS1 are related to distinct patterns of formation and resolution of single-stranded DNA and γH2A, throughout the cell cycle. Our findings suggest that Leishmania 9-1-1 subunits have evolved to co-opt canonical genomic maintenance and genomic variation functions. Hence, this study reveals a pivotal function of HUS1 in balancing genome stability and transmission in Leishmania. These findings may be relevant to understanding the evolution of genome maintenance and plasticity in other pathogens and eukaryotes.

A DiCre recombinase-based system for inducible expression in Leishmania major

Here we present the establishment of an inducible system based on the dimerizable Cre recombinase (DiCre) for controlled gene expression in the protozoan parasite Leishmania. Rapamycin-induced DiCre activation promoted efficient flipping and expression of gene products in a time and dose-dependent manner. The DiCre flipping activity induced the expression of target genes from both integrated and episomal contexts broadening the applicability of the system. We validated the system by inducing the expression of both full length and truncated forms of the checkpoint protein Rad9, which revealed that the highly divergent C-terminal domain of Rad9 is necessary for proper subcellular localization. Thus, by establishing the DiCre-based inducible system we have created and validated a robust new tool for assessing gene function in Leishmania.

Conditional gene deletion with DiCre demonstrates an essential role for CRK3 in Leishmania mexicana cell cycle regulation

Leishmania mexicana has a large family of cyclin‐dependent kinases (CDKs) that reflect the complex interplay between cell cycle and life cycle progression. Evidence from previous studies indicated that Cdc2‐related kinase 3 (CRK3) in complex with the cyclin CYC6 is a functional homologue of the major cell cycle regulator CDK1, yet definitive genetic evidence for an essential role in parasite proliferation is lacking. To address this, we have implemented an inducible gene deletion system based on a dimerised Cre recombinase (diCre) to target CRK3 and elucidate its role in the cell cycle of L. mexicana. Induction of diCre activity in promastigotes with rapamycin resulted in efficient deletion of floxed CRK3, resulting in G2/M growth arrest. Co‐expression of a CRK3 transgene during rapamycin‐induced deletion of CRK3 resulted in complementation of growth, whereas expression of an active site CRK3^T178E mutant did not, showing that protein kinase activity is crucial for CRK3 function. Inducible deletion of CRK3 in stationary phase promastigotes resulted in attenuated growth in mice, thereby confirming CRK3 as a useful therapeutic target and diCre as a valuable new tool for analyzing essential genes in Leishmania.

The clinical pharmacology of viloxazine hydrochloride-a new anti-depressant of novel chemical structure

1 The clinical pharmacological properties of viloxazine hydrochloride (ICI 58,834, Vivalan), a new antidepressant of novel chemical structure, have been investigated in a series of double-blind randomized studies comparing it with placebo and imipramine. Throughout the studies, viloxazine hydrochloride was given in single doses of 100 mg (expressed as base), and imipramine hydrochloride was given in single doses of 50 mg (expressed as salt). 2 The effect of viloxazine upon the following parameters was measured: pulse rate, blood pressure, forced expiratory volume, reaction time, critical flicker frequency, salivary flow, pupil size and palpebral fissure size. In addition, the possible interaction between viloxazine and alcohol was investigated using measurements of reaction time. 3 Both viloxazine and imipramine produced a transient tachycardia, but no consistent effect on blood pressure was seen. Neither drug had any effect upon forced expiratory volume. 4 The differences that emerged between viloxazine and imipramine were that viloxazine depressed critical flicker frequency whereas imipramine did not, and imipramine prolonged reaction time whilst viloxazine did not. Imipramine reduced salivary flow and increased the size of the pupil and palpebral fissure. Viloxazine did neither. 5 Imipramine was shown to potentiate alcohol whereas, at the doses used, viloxazine did not. 6 It is concluded that viloxazine appears to have less anticholinergic and possibly less sympathomimetic properties than imipramine. It is also concluded that viloxazine, unlike imipramine, does not potentiate alcohol.

Nurses' experience of violence in Alberta and British Columbia hospitals

This study examined responses to a survey on violence in the workplace from a sample of 8,780 registered nurses practising in 210 hospitals in the Canadian provinces of Alberta and British Columbia. Findings relate to the frequency of violence against nurses, reported as the number of times they experienced a violent incident in the workplace. Nearly half (46%) of those surveyed had experienced 1 or more types of violence in the last 5 shifts worked. Frequency varied by type: emotional abuse 38%, threat of assault 19%, physical assault 18%, verbal sexual harassment 7.6%, sexual assault 0.6%. Further, 70% of those who had experienced violence indicated they had not reported it. Patients constituted the main source of all types of violence. The most prevalent type, emotional abuse, was further explored for its possible determinants. This was also the type of violence most evenly distributed among sources (patients, families, co-workers, physicians). Multiple regression modelling using the individual nurse as the unit of analysis showed the significant predictors of emotional abuse to be age, casual job status, quality of care, degree of hospital restructuring, type of unit, relationships among hospital staff, nurse-to-patient ratios, and violence-prevention measures; using the hospital as the unit of analysis the predictors were found to be quality of care, age, relationships with hospital staff, presence of violence-prevention measures, and province. These findings illustrate important differences in models that use the individual and the institution as the unit of analysis. Implications include targeting prevention strategies not only at the nurse but, perhaps more importantly, at the hospital. Overall, the findings suggest that health-care institutions are not always healthy workplaces and may increasingly be stressful and hazardous ones.

A synthesis of C(16),C(18)-bis-epi-cytochalasin D via Reformatsky cyclization

Triene 5 has been prepared by the E-selective olefination of aldehyde 12 with the ylide 11. Several alternative syntheses of 12 were evaluated, and the successful route involved conversion of 22 into the vinyl ether 23 by Petasis olefination, followed by Claisen rearrangement. Diels-Alder cycloaddition of 5 with 4 gave the adduct 6 in 77% yield, and Reformatsky cyclization under dilution conditions afforded 10 (67%). After conversion to enol silane 32, oxidation with dimethyldioxirane produced 34. Conversion to a key intermediate 38 using electrophilic selenenylation and selenoxide rearrangement, followed by enolate alkylation and deprotection, gave 43. The X-ray crystal structure of 43 was determined to prove the stereochemistry.

"Nurses as health evangelists"?: The evolution of public health nursing in Canada, 1918-1939

Public health nurses provided leadership for the advancement of public health in Canada in the early decades of this century, although leadership by nurses is not celebrated in public health history. The historical period (1918-1939) selected for this inquiry is one in which public health nurses created a legacy of achievements in public health nursing education, practice, and the organization of community health services within the most challenging of social, economic, and political contexts. The practice of public health nursing in Canada during the interwar years included strategies that were then and still are integral to the discipline--those of forming connections with the community, providing leadership in the public health movement, and facilitating community organization. It is vital to understand the significance of these origins of public health nursing as forces in the present context of practice threaten to alter fundamentally the nature of public health nursing's connection with the community. The purpose of this article is to highlight aspects of this historical legacy so that its influence can be more fully understood and strengthened in current health system transitions.

Empowerment strategies in nursing education: a foundation for population-focused clinical studies

Building on the already substantial body of literature on education for population-focused practice, this article incorporates the teaching of empowerment strategies into this literature. These strategies provide a framework for teaching nursing students to promote the health of populations by shifting their focus of care to one that is compatible with principles of primary health care and health promotion within a context of health care reform. Since 1989, education for these shifts in practice has taken place within a clinical studies course on population-focused practice and has continued to evolve within an innovative nursing curriculum developed by The University of Victoria and its collaborative partners in nursing education in British Columbia, Canada. Faculty have worked to develop innovative teaching strategies and practica that provide students with opportunities to practice empowerment strategies with populations. Examples of how students have learned and practiced these strategies in a baccalaureate nursing program at the University College of the Cariboo in Kamloops, British Columbia, Canada provide useful illustration of the shifts in nursing education that are needed to shape the next era of health care.

A randomized comparison of once-monthly or twice-monthly high-dose aerosolized pentamidine prophylaxis

RESULTS

Ten of the 146 (7 percent) evaluable subjects developed PCP during the year study period, and there was no difference in the efficacy of the two regimens. Among patients receiving secondary prophylaxis, the attack rate of PCP at 1 year was 11 percent. This compares favorably with a 1-year attack rate of 19 percent in similar patients receiving standard dose (300 mg) prophylaxis and suggests, but does not prove, a dose-response effect. Concentrations of pentamidine in BAL fluid were not significantly different among the three lobes of the lung. Intrapulmonary pentamidine did not accumulate during the year of study. Aerosolized pentamidine was associated with a marginal but statistically significant increase in the residual volume, decreased flow rates, and increased airway reactivity.

OBJECTIVE

The optimal regimen of aerosolized pentamidine in unknown. Published data suggest that there is a dose-response effect and that the occurrence of Pneumocystis carinii pneumonia (PCP) has been associated with prolongation of the interval between doses. The purpose of this study was to compare the efficacy, pharmacokinetics, and physiologic effects of two high-dose regimens of aerosolized pentamidine prophylaxis.

DESIGN

Prospective, randomized study of 300 mg twice monthly vs 600 mg once monthly during a 1-year observation period. Pentamidine concentrations in plasma and bronchoalveolar lavage (BAL) fluid were measured and serial pulmonary function was measured.

SETTING

A large teaching hospital in San Francisco.

PATIENTS

One hundred fifty-one adult (age > 18 years) men with human immunodeficiency virus infection. Of 146 evaluable patients, prophylaxis was primary (no prior PCP) in 108 (75 percent) and secondary (one prior episode of PCP) in 38 (25 percent).

MEASUREMENTS

Date and diagnosis of PCP, occurrence of drug toxicity, pulmonary function testing, and concentrations of pentamidine in BAL and plasma.

CONCLUSIONS

The data suggest, but do not prove, that a dose-response effect has been demonstrated, and that high-dose aerosolized pentamidine may further reduce the attack rate of PCP. These preliminary observations should be confirmed in a double-blind trial comparing 300 mg with 600 mg administered once monthly. The clinical relevance of the adverse pulmonary effects is unclear and requires further investigation.

Ethical challenge in community health nursing

Community health nurses frequently face situations involving ethical conflicts, but little research has been carried out in this area. This paper, based on a study of dilemmas defined by 30 practising community health nurses in urban and rural British Columbia, Canada, presents an analysis of the situations that contain the most serious ethical conflicts for nurses working in the community. Although issues related to client's rights, nurses' interactions with colleagues and the system, and nurses' rights were explored, nurses in the study reported that situations involving high-risk parenting provided the most serious ethical challenges. Strategies to help nurses caring for such vulnerable clients are described. As well, this paper offers some discussion on implications for community health nursing practice and education in light of current changes and challenges.

The effects of atenolol (tenormin) and methyldopa on simple tests of central nervous function

Two identical studies, one comparing the effect of single doses of a new beta-adrenoceptor blocker, atenolol (Tenormin) (50 mg and 100 mg) and placebo, and the other comparing the effect of single doses of methyldopa (250 mg and 500 mg) and placebo, in healthy volunteers, were carried out. 2 In both studies the effect of the drugs upon reaction time, critical flicker frequency, subjective drowsiness, pulse rate and blood pressure was measured. 3 Atenolol produced no effect upon reaction time, critical flicker frequency or subjective feelings, while methyldopa produced a statistically significant prolongation of reaction time and a statistically significant increase in the subjective sensation of drowsiness. 4 Atenolol produced statistically significant reductions in systolic and diastolic blood pressure and in pulse rate while methyldopa was without effect. 5 It is concluded that atenolol is unlikely to produce the side effects of sedation or drowsiness.