Nile Red fluorescence spectroscopy reports early physicochemical changes in myelin with high sensitivity

The molecular composition of myelin membranes determines their structure and function. Even minute changes to the biochemical balance can have profound consequences for axonal conduction and the synchronicity of neural networks. Hypothesizing that the earliest indication of myelin injury involves changes in the composition and/or polarity of its constituent lipids, we developed a sensitive spectroscopic technique for defining the chemical polarity of myelin lipids in fixed frozen tissue sections from rodent and human. The method uses a simple staining procedure involving the lipophilic dye Nile Red, whose fluorescence spectrum varies according to the chemical polarity of the microenvironment into which the dye embeds. Nile Red spectroscopy identified histologically intact yet biochemically altered myelin in prelesioned tissues, including mouse white matter following subdemyelinating cuprizone intoxication, as well as normal-appearing white matter in multiple sclerosis brain. Nile Red spectroscopy offers a relatively simple yet highly sensitive technique for detecting subtle myelin changes.

Myelin is a highly ordered, lipid-rich extension of glial cell membrane that facilitates rapid and efficient saltatory conduction of action potentials along axons in the central and peripheral nervous systems. The stability of myelin membranes critically depends on its molecular composition (1–3). Although myelin is maintained roughly at a ratio of 70:30% lipid to protein (4), lipid membranes are highly fluid; changes in lipid composition are defining characteristics of myelin development (5), homeostasis in the adult, and aging in rodents (6, 7), as well as primates (8). Shifts in lipid composition also occur in inflammatory demyelinating disorders like multiple sclerosis (MS) (9, 10). Lipids are even theorized to be targets of immune attacks in autoimmune disorders, a role previously ascribed to proteins (11). Key roles for lipids notwithstanding, tools to interrogate biochemical changes to myelin lipids have largely been restricted to in vitro systems.Once thought to be inert, myelin is now known to be a chemically and structurally dynamic element (12). Specific combinations of proteins and lipids induce formation and compaction of multilamellar vesicles that resemble myelin (13), underscoring the importance of correct chemical composition for assembly. Conversely, alterations in these molecular proportions promote decompaction and myelin vesiculation (3, 14). The polarity of lipid species in cell membranes influences their packing properties and therefore stability (15). Governed by competing thermodynamic forces of lipid curling and hydrocarbon packing (16), myelin sheaths lie at the critical edge of bilayer stability and thus are susceptible to factors in the environment. Indeed, the myelin integrity theory of MS rests on the outsized influence of environmental forces on myelin stability and function (17). Therefore, methods for detecting physicochemical changes in myelin lipid composition in situ would greatly enhance our understanding of early events in myelin development, as well as myelin damage in disease states, with important implications for therapies designed to prevent myelin loss in MS and other demyelinating disorders.The study of myelin lipid biochemistry poses unique challenges (18). Traditional analytical methods, such as thin-layer chromatography and high-performance liquid chromatography (19), depend on tissue homogenization that eliminates informative spatial relationships. Imaging lipid mass spectrometry (20) preserves spatial relationships, but submicron resolution has yet to be realized, and reproducibility at the level of sample preparation remains problematic (21). Coherent anti–Stokes Raman scattering microscopy provides high-resolution, label-free imaging of lipids in histological samples (22), but this method lacks sensitivity and requires expertise in nonlinear optics as well as highly specialized hardware. Finally, fluorescent lipophilic dyes, though widely available and easy to use, have traditionally been employed to detect lipid-rich structures in only a qualitative manner. Conventional fluorescence microscopy is therefore unable to detect subtle shifts in lipid biochemistry. By contrast, Nile Red (NR) is a fluorescent dye that is well situated to report changes in the chemical polarity of cell membranes and myelin, being both lipophilic (23, 24) and differentially fluorescent depending on solvent environment (i.e., exhibits solvatochromism) (25). The current study uses NR fluorescence spectroscopy to identify polarity shifts as an early manifestation of myelin disease prior to overt demyelination. We show that this technique reports subtle biochemical changes in myelin, resulting in a method that is a very sensitive marker of incipient myelin injury.     

Protection of humans against malaria by immunization with radiation-attenuated Plasmodium falciparum sporozoites

During 1989-1999, 11 volunteers were immunized by the bites of 1001-2927 irradiated mosquitoes harboring infectious sporozoites of Plasmodium falciparum (Pf) strain NF54 or clone 3D7/NF54. Ten volunteers were first challenged by the bites of Pf-infected mosquitoes 2-9 weeks after the last immunization, and all were protected. A volunteer challenged 10 weeks after the last immunization was not protected. Five previously protected volunteers were rechallenged 23-42 weeks after a secondary immunization, and 4 were protected. Two volunteers were protected when rechallenged with a heterologous Pf strain (7G8). In total, there was protection in 24 of 26 challenges. These results expand published findings demonstrating that immunization by exposure to thousands of mosquitoes carrying radiation-attenuated Pf sporozoites is safe and well tolerated and elicits strain-transcendent protective immunity that persists for at least 42 weeks.     

Influence of usual source of care on differences by race/ethnicity in receipt of preventive services

OBJECTIVE: We examined the relation between race/ethnicity and receipt of preventive services and the effect of having a usual source of care (USOC) on receipt of preventive services in different racial and ethnic groups. DESIGN/PARTICIPANTS: We analyzed data from adults, aged 18 to 64 years in the Household Component of the 1996 Medical Expenditure Panel Survey, a nationally representative survey of health care use for the United States. MEASUREMENTS: The proportion of adults who received age-appropriate preventive services. RESULTS: Compared to white respondents, Hispanics were less likely to receive breast exams and blood pressure and cholesterol screening than were white respondents, and blacks were more likely to report receiving a Pap smear. Despite being less likely to report having a USOC, black and Hispanic women were as likely or more likely to report receiving breast and cervical cancer screening, after controlling for having a USOC and other factors. Hispanics reported receiving blood pressure screening less often, and blacks reported receiving more cholesterol screening. For each race/ethnicity group, having a USOC was associated with receiving preventive services. However, controlling for USOC and other confounders attenuated, but did not eliminate, differences by race/ethnicity. CONCLUSION: The differences by race in receipt of preventive services suggest the need for different starting points for devising strategies to address racial differences in disease outcomes. While having a USOC will be important in narrowing the differences by race in receipt of preventive services, attending to other factors that contribute to disparities in health will also be essential.     

Goal satisfaction improves with individualized powered wheelchair skills training

Purpose: To determine improvements in goal satisfaction following individualized mobility-related powered wheelchair skills training and whether changes in satisfaction are maintained 3 months post-training.

Materials and methods: Seventeen powered wheelchair users, from two centres, who were randomized to the training intervention from a larger multicentre study, were included in this secondary analysis. The intervention consisted of five 30-min individualized Wheelchair Skills Training Program sessions. Participants rated their current satisfaction with each of their goals from 0 to 10 (10 being the highest) prior to training, immediately after the intervention, and approximately 3 months following the intervention. Themes relating to the participants’ goals were also explored.

Results: Goal satisfaction scores improved statistically (p?r?=?0.387, n?=?17, p?=?.125). The majority of goals set fell into the broader “manoeuvring” category.

Conclusion: Goal satisfaction following the Wheelchair Skills Training Program improved years after initially learning how to operate a powered wheelchair. The five training sessions were effective in improving goal satisfaction. The quantification of goal satisfaction appears to be a sensitive outcome for powered wheelchair users undergoing mobility-related training.

• Implications for rehabilitation

• Goal satisfaction improved following the Wheelchair Skills Training Program.

• Even with years of powered wheelchair experience, the majority of goals set fell into the broader “manoeuvring” category.

• An individual’s goal satisfaction may not correlate with whether they have attained their goal as determined by a trainer.

     

Influence of High and Low Autonomy-Supportive Climates on Physical Activity in Children with and without Developmental Disability

The aim of this study was to compare the influence of two different instructional climates on the accumulation of moderate-to-vigorous physical activity (MVPA) during a fully-inclusive adapted recreational physical activity program. A total of 32 children (18 typically-developing (TD), and 14 with developmental disabilities (DD) ranging in ages from 5 to 9 years, participated in six, 60-min adapted recreational sessions. Of those six sessions, three incorporated an autonomy-supportive climate (high autonomy), and three incorporated direct instruction (low autonomy). MVPA was measured using accelerometers. A repeated measures ANOVA was conducted to determine significant differences in MVPA between group (TD/DD), climate (autonomy/direct), and a group x climate interaction. Significant group and climate main effects were observed (p?=?0.002 and 0.014, respectively). However, there was not a significant group x climate interaction (p?=?0.313). These results suggest that although the group of children with disabilities spent less time in MVPA compared to their typically-developing peers, all participants spent more time in MVPA for the autonomy-supportive climate compared to the low-autonomous climate. This study is the first to quantitatively assess the efficacy of a fully-inclusive autonomy-supportive climate on physical activity levels in children with and without developmental disabilities.     

Nurses best practices for the management of thrombotic thrombocytopenic purpura

A group of Canadian apheresis nurses developed best practice for in the management of thrombotic thrombocytopenic purpura (TTP). The recommendations address issues related to infusion protocols, preventing and managing adverse events, comprehensive patient assessments, treatment procedures, as well as pre- and post- treatment care. The Canadian group encourages institutes to include nurses on committees that examine recommendations for TTP management.