Active cholesterol 20 years on

This review considers the following hypotheses, some well-supported and some speculative. Almost all of the sterol molecules in plasma membranes are associated with bilayer phospholipids in complexes of varied strength and stoichiometry. These complexes underlie many of the material properties of the bilayer. The small fraction of cholesterol molecules exceeding the binding capacity of the phospholipids is thermodynamically active and serves diverse functions. It circulates briskly among the cell membranes, particularly through contact sites linking the organelles. Active cholesterol provides the upstream feedback signal to multiple mechanisms governing plasma membrane homeostasis, pegging the sterol level to a threshold set by its phospholipids. Active cholesterol could also be the cargo for various inter-organelle transporters and the form excreted from cells by reverse transport. Furthermore, it is integral to the function of caveolae; a mediator of Hedgehog regulation; and a ligand for the binding of cytolytic toxins to membranes. Active cholesterol modulates a variety of plasma membrane proteins-receptors, channels and transporters-at least in vitro.

Access to primary care for persons with spinal cord injuries in the greater Gaborone area, Botswana

Background

People with spinal cord injury (SCI) often have great need for healthcare services, but they report access challenges. Primary care access to people with SCI has not been explored in Botswana.

Objective

This study aimed to identify barriers and facilitators that users with spinal cord injuries experience in accessing primary care services in the greater Gaborone area, Botswana.

Methods

A quantitative, cross-sectional, observational study was conducted. Data were collected with a structured questionnaire from 57 participants with traumatic and non-traumatic SCI. Descriptive and inferential analysis was performed.

Results

The male to female ratio was 2.8:1. The mean age of participants was 40 years (standard deviation 9.59). Road traffic crashes caused 85% of the injuries. Most participants visited primary care facilities between 2 and 10 times in the 6 months before the study. Participants were satisfied with the services (63%) and felt that facilities were clean (95%) and well maintained (73.5%). Preferential treatment, respect, short waiting times and convenient hours facilitated satisfaction with services. Availability was hampered by insufficient provider knowledge on SCI as indicated by 71.9% of participants, and shortage of consumables (80.7%). Structural challenges (42.1% could not enter the facility by themselves and 56.5% could not use the bathroom) and lack of height-adjustable examining couches (66.7%) impeded accessibility. Cost was incurred when participants (64.9%) utilised private health services where public services failed to address their needs.

Conclusion

Primary care services were mostly affordable and adequate. Availability, acceptability and accessibility aspects created barriers.

Effects of hydration on steric and electric charge-induced interstitial volume exclusion--a model

The presence of collagen and charged macromolecules like glycosaminoglycans (GAGs) in the interstitial space limits the space available for plasma proteins and other macromolecules. This phenomenon, known as interstitial exclusion, is of importance for interstitial fluid volume regulation. Physical/mathematical models are presented for calculating the exclusion of electrically charged and neutral macromolecules that equilibrate in the interstitium under various degrees of hydration. Here, a central hypothesis is that the swelling of highly electrically charged GAGs with increased hydration shields parts of the neutral collagen of the interstitial matrix from interacting with electrically charged macromolecules, such that exclusion of charged macromolecules exhibits change due to steric and charge effects. GAGs are also thought to allow relatively small neutral, but also charged macromolecules neutralized by a very high ionic strength, diffuse into the interior of GAGs, whereas larger macromolecules may not. Thus, in the model, relatively small electrically charged macromolecules, such as human serum albumin, and larger neutral macromolecules such as IgG, will have quite similar total volume exclusion properties in the interstitium. Our results are in agreement with ex vivo and in vivo experiments, and suggest that the charge of GAGs or macromolecular drugs may be targeted to increase the tissue uptake of macromolecular therapeutic agents.