Effect of Different Supports on the Reaction Rate of Rhizomucor Miehei Lipase in Organic Media

Five different aluminas, a silica and a zirconia support were used to adsorb lipase (E.C. 3.1.1.3) from Rhizomucor miehei. The activity of the immobilised lipase was measured by esterification of dodecanol and decanoic acid in hexane. The immobilised lipase and the organic phase were pre-equilibrated separately to known water activities before mixing them to commence the reactions. The aluminas, which varied in pore sizes and surface areas, adsorbed similar amounts of enzyme. However, the esterification activities varied about 10-fold, increasing with increasing surface area. The silica and zirconia supports adsorbed about half as much lipase as the aluminas. The esterification reaction rates per unit quantity of enzyme adsorbed were compared with those for aluminas with similar surface areas; this specific rate was about 2 times higher for the zirconia, but the difference with silica was only small. There was no clear correlation between the esterification rates at fixed water activity and the amount of water adsorbed by the support used.     

PfCRT and the trans-vacuolar proton electrochemical gradient: regulating the access of chloroquine to ferriprotoporphyrin IX

It is accepted that resistance of Plasmodium falciparum to chloroquine (CQ) is caused primarily by mutations in the pfcrt gene. However, a consensus has not yet been reached on the mechanism by which resistance is achieved. CQ-resistant (CQR) parasite lines accumulate less CQ than do CQ-sensitive (CQS) parasites. The CQR phenotype is complex with a component of reduced energy-dependent CQ uptake and an additional component that resembles energy-dependent CQ efflux. Here we show that the required energy input is in the form of the proton electrochemical gradient across the digestive vacuole (DV) membrane. Collapsing the DV proton gradient (or starving the parasites of glucose) results in similar levels of CQ accumulation in CQS and CQR lines. Under these conditions the accumulation of CQ is stimulated in CQR parasite lines but is reduced in CQS lines. Energy deprivation has no effect on the rate of CQ efflux from CQR lines implying that mutant PfCRT does not function as an efflux pump or active carrier. Using pfcrt-modified parasite lines we show that the entire CQ susceptibility phenotype is switched by the single K76T amino acid change in PfCRT. The efflux of CQ in CQR lines is not directly coupled to the energy supply, consistent with a model in which mutant PfCRT functions as a gated channel or pore, allowing charged CQ species to leak out of the DV.     

Local Delivery of Nimodipine by Prolonged-Release Microparticles—Feasibility,Effectiveness and Dose-Finding in Experimental Subarachnoid Hemorrhage

Background and Purpose

To investigate the effect of locally applied nimodipine prolonged-release microparticles on angiographic vasospasm and secondary brain injury after experimental subarachnoid hemorrhage (SAH).

Methods

70 male Wistar rats were categorized into three groups: 1) sham operated animals (control), 2) animals with SAH only (control) and the 3) treatment group. SAH was induced using the double hemorrhage model. The treatment group received different concentrations (20%, 30% or 40%) of nimodipine microparticles. Angiographic vasospasm was assessed 5 days later using digital subtraction angiography (DSA). Histological analysis of frozen sections was performed using H&E-staining as well as Iba1 and MAP2 immunohistochemistry.

Results

DSA images were sufficient for assessment in 42 animals. Severe angiographic vasospasm was present in group 2 (SAH only), as compared to the sham operated group (p<0.001). Only animals within group 3 and the highest nimodipine microparticles concentration (40%) as well as group 1 (sham) demonstrated the largest intracranial artery diameters. Variation in vessel calibers, however, did not result in differences in Iba-1 or MAP2 expression, i.e. in histological findings for secondary brain injury.

Conclusions

Local delivery of high-dose nimodipine prolonged-release microparticles at high concentration resulted in significant reduction in angiographic vasospasm after experimental SAH and with no histological signs for matrix toxicity.     

What Do the Various Principles of Justice Mean Within the Concept of Benefit Sharing?

The concept of benefit sharing pertains to the act of giving something in return to the participants, communities, and the country that have participated in global health research or bioprospecting activities. One of the key concerns of benefit sharing is the ethical justifications or reasons to support the practice of the concept in global health research and bioprospecting. This article evaluates one of such ethical justifications and its meaning to benefit sharing, namely justice. We conducted a systematic review to map the various principles of justice that are linked to benefit sharing and analysed their meaning to the concept of benefit sharing. Five principles of justice (commutative, distributive, global, procedural, and compensatory) have been shown to be relevant in the nuances of benefit sharing in both global health research and bioprospecting. The review findings indicate that each of these principles of justice provides a different perspective for a different benefit sharing rationale. For example, commutative justice provides a benefit sharing rationale that is focused on fair exchange of benefits between research sponsors and communities. Distributive justice produces a benefit sharing rationale that is focused on improving the health needs of the vulnerable research communities. We have suggested that a good benefit sharing framework particularly in global health research would be more beneficial if it combines all the principles of justice in its formulation. Nonetheless, there is a need for empirical studies to examine the various principles of justice and their nuances in benefit sharing among stakeholders in global health research.     

Reaction Rates in Organic Media Show Similar Dependence on Water Activity with Lipase Catalyst Immobilized on Different Supports

Lipase (E.C. 3.1.1.3) from Rhizomucor miehei was adsorbed on silica, zirconia and five alumina support materials. The immobilised preparations were used to catalyse esterincation reactions of decanoic acid and dodecanol in hexane. The immobilised lipase and the organic phase were separately preequilibrated to the desired water activities. The various support materials adsorbed widely different amounts of water at a given water activity. The reaction rates with all the support materials show similar dependence on water activity when the rates were normalised with the optimal rate for that support material. Hence water activity predicts the optimal conditions much better than water content.