A cluster-randomised trial of staff education to improve the quality of life of people with dementia living in residential care: the DIRECT study

Background

The Dementia In Residential care: EduCation intervention Trial (DIRECT) was conducted to determine if delivery of education designed to meet the perceived need of GPs and care staff improves the quality of life of participants with dementia living in residential care.

Methodology/Principal Findings

This cluster-randomised controlled trial was conducted in 39 residential aged care facilities in the metropolitan area of Perth, Western Australia. 351 care facility residents aged 65 years and older with Mini-Mental State Examination ≤24, their GPs and facility staff participated. Flexible education designed to meet the perceived needs of learners was delivered to GPs and care facility staff in intervention groups. The primary outcome of the study was self-rated quality of life of participants with dementia, measured using the QOL-Alzheimer''s Disease Scale (QOL-AD) at 4 weeks and 6 months after the conclusion of the intervention. Analysis accounted for the effect of clustering by using multi-level regression analysis. Education of GPs or care facility staff did not affect the primary outcome at either 4 weeks or 6 months. In a post hoc analysis excluding facilities in which fewer than 50% of staff attended an education session, self-rated QOL-AD scores were 6.14 points (adjusted 95%CI 1.14, 11.15) higher at four-week follow-up among residents in facilities randomly assigned to the education intervention.

Conclusion

The education intervention directed at care facilities or GPs did not improve the quality of life ratings of participants with dementia as a group. This may be explained by the poor adherence to the intervention programme, as participants with dementia living in facilities where staff participated at least minimally seemed to benefit.

Trial Registration

ANZCTR.org.au ACTRN12607000417482     

Is formation of visible channels in a phospholipid bilayer by botulinum neurotoxin type B sensitive to its disulfide?

Botulinum neurotoxin, produced by Clostridium botulinum as a approximately 150-kDa single-chain protein, is nicked proteolytically either endogenously or exogenously. The approximately 50- and approximately 100-kDa chains of the dichain molecule remain held together by an interchain disulfide bridge and noncovalent interactions. The neurotoxin binds to receptors of the target cell and is internalized by endocytosis. Thereafter, a portion of the neurotoxin, the approximately 50-kDa chain, escapes to the cytosol, where it blocks neurotransmitter release. Botulinum neurotoxin serotype B is released by the bacteria primarily as an unnicked single chain. We reduced this unnicked protein and used its binding to ganglioside in a lipid layer to produce helical tubular crystals of unnicked botulinum neurotoxin type B in its disulfide-reduced state. The helical arrangement of the neurotoxin allowed determination of the structure of the molecule using cryo-electron microscopy and image processing. The resulting model reveals that neurotoxin molecules formed loops extending out from the surface of the bilayer and bending toward a neighboring loop. Although channels have been seen with disulfide-linked neurotoxin (Schmid, Robinson, and DasGupta (1993) Direct visualization of botulinum neurotoxin-induced channels in phospholipid vesicles, Nature 364, 827-830), no channels were seen here, a finding which suggests that the reduced, unnicked neurotoxin is incapable of forming a visible channel.     

Homocysteine, grey matter and cognitive function in adults with cardiovascular disease

Background

Elevated total plasma homocysteine (tHcy) has been associated with cognitive impairment, vascular disease and brain atrophy.

Methods

We investigated 150 volunteers to determine if the association between high tHcy and cerebral grey matter volume and cognitive function is independent of cardiovascular disease.

Results

Participants with high tHcy (≥15 µmol/L) showed a widespread relative loss of grey matter compared with people with normal tHcy, although differences between the groups were minimal once the analyses were adjusted for age, gender, diabetes, hypertension, smoking and prevalent cardiovascular disease. Individuals with high tHcy had worse cognitive scores across a range of domains and less total grey matter volume, although these differences were not significant in the adjusted models.

Conclusions

Our results suggest that the association between high tHcy and loss of cerebral grey matter volume and decline in cognitive function is largely explained by increasing age and cardiovascular diseases and indicate that the relationship is not causal.     

A human monoclonal IgE antibody defines a highly allergenic fragment of the major timothy grass pollen allergen, Phl p 5: molecular, immunological, and structural characterization of the epitope-containing domain

Almost 90% of grass pollen-allergic patients are sensitized against group 5 grass pollen allergens. We isolated a monoclonal human IgE Fab out of a combinatorial library prepared from lymphocytes of a grass pollen-allergic patient and studied its interaction with group 5 allergens. The IgE Fab cross-reacted with group 5A isoallergens from several grass and corn species. By allergen gene fragmentation we mapped the binding site of the IgE Fab to a 11.2-kDa N-terminal fragment of the major timothy grass pollen allergen Phl p 5A. The IgE Fab-defined Phl p 5A fragment was expressed in Escherichia coli and purified to homogeneity. Circular dichroism analysis revealed that the rPhl p 5A domain, as well as complete rPhl p 5A, assumed a folded conformation consisting predominantly of an alpha helical secondary structure, and exhibited a remarkable refolding capacity. It reacted with serum IgE from 76% of grass pollen-allergic patients and revealed an extremely high allergenic activity in basophil histamine release as well as skin test experiments. Thus, the rPhl p 5A domain represents an important allergen domain containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation and, perhaps later, for the development of generally applicable allergen-specific therapy strategies.     

Structural and thermodynamic insights into the assembly of the heteromeric pyridoxal phosphate synthase from Plasmodium falciparum

Pyridoxal 5′-phosphate (PLP) is required as a cofactor by many enzymes. The predominant de novo biosynthetic route is catalyzed by a heteromeric glutamine amidotransferase consisting of the synthase subunit Pdx1 and the glutaminase subunit Pdx2. Previously, Bacillus subtilis PLP synthase was studied by X-ray crystallography and complex assembly had been characterized by isothermal titration calorimetry. The fully assembled PLP synthase complex contains 12 individual Pdx1/Pdx2 glutamine amidotransferase heterodimers. These studies revealed the occurrence of an encounter complex that is tightened in the Michaelis complex when the substrate l-glutamine binds. In this study, we have characterized complex formation of PLP synthase from the malaria-causing human pathogen Plasmodium falciparum using isothermal titration calorimetry. The presence of l-glutamine increases the tightness of the interaction about 30-fold and alters the thermodynamic signature of complex formation. The thermodynamic data are integrated in a 3D homology model of P. falciparum PLP synthase. The negative experimental heat capacity (C_p) describes a protein interface that is dominated by hydrophobic interactions. In the absence of l-glutamine, the experimental C_p is less negative than in its presence, contrasting to the previously characterised bacterial PLP synthase. Thus, while the encounter complexes differ, the Michaelis complexes of plasmodial and bacterial systems have similar characteristics concerning the relative contribution of apolar/polar surface area. In addition, we have verified the role of the N-terminal region of PfPdx1 for complex formation. A “swap mutant” in which the complete αN-helix of plasmodial Pdx1 was exchanged with the corresponding segment from B. subtilis shows cross-binding to B. subtilis Pdx2. The swap mutant also partially elicits glutaminase activity in BsPdx2, demonstrating that formation of the protein complex interface via αN and catalytic activation of the glutaminase are linked processes.