Quantifying apoprotein synthesis in rodents: coupling LC-MS/MS analyses with the administration of labeled water

Stable isotope tracer studies of apoprotein flux in rodent models present difficulties as they require working with small volumes of plasma. We demonstrate the ability to measure apoprotein flux by administering either (2)H- or (18)O-labeled water to mice and then subjecting samples to LC-MS/MS analyses; we were able to simultaneously determine the labeling of several proteolytic peptides representing multiple apoproteins. Consistent with relative differences reported in the literature regarding apoprotein flux in humans, we found that the fractional synthetic rate of apoB is greater than apoA1 in mice. In addition, the method is suitable for quantifying acute changes in protein flux: we observed a stimulation of apoB production in mice following an intravenous injection of Intralipid and a decrease in apoB production in mice treated with an inhibitor of microsomal triglyceride transfer protein. In summary, we demonstrate a high-throughput method for studying apoprotein kinetics in rodent models. Although notable differences exist between lipoprotein profiles that are observed in rodents and humans, we expect that the method reported here has merit in studies of dyslipidemia as i) rodent models can be used to probe target engagement in cases where one aims to modulate apoprotein production and ii) the approach should be adaptable to studies in humans.     

In vivo antitumour activity of amphiphilic silicon(IV) phthalocyanine with axially ligated rhodamine B

We explore the possible cellular cytotoxic activity of an amphiphilic silicon(IV) phthalocyanine with axially ligated rhodamine B under ambient light experimental environment as well as its in vivo antitumour potential using Hep3B hepatoma cell model. After loading into the Hep3B hepatoma cells, induction of cellular cytotoxicity and cell cycle arrest were detected. Strong growth inhibition of tumour xenograft together with significant tumour necrosis and limited toxicological effects exerted on the nude mice could be identified.     

New and noteworthy plants from Great Barrier Reef sand cays,Australia

Observations are presented on new and critical plants from the northern sand cays on the Great Barrier Reef, Queensland, Australia, based mainly on recent collections made by David R. Stoddart and Ralf Buckley. New species and varieties are described:Lepturus stoddartii (Poaceae),Boerhavia fistulosa var.fistulosa and var.puberuliflora (Nyctaginaceae),Boerhavia albiflora var.heronensis, Spermacoce everistiana (Rubiaceae), andSpermacoce buckleyi; a new combination is made:Diospyros ferrea var.compacta (R. Br.) (Ebenaceae); and additional taxonomic notes are given onBoerhavia, Euphorbia (Euphorbiaceae), andAbutilon (Malvaceae).     

Net Glutamate Release from Astrocytes Is Not Induced by Extracellular Potassium Concentrations Attainable in Brain

Abstract: Elevated extracellular potassium concentration ([K⁺]_e) has been shown to induce reversal of glial Na⁺-dependent glutamate uptake in whole-cell patch clamp preparations. It is uncertain, however, whether elevated [K⁺]_e similarly induces a net glutamate efflux from intact cells with a physiological intracellular milieu. To answer this question, astrocyte cultures prepared from rat and mouse cortices were incubated in medium with elevated [K⁺]_e (by equimolar substitution of K⁺ for Na⁺), and glutamate accumulation was measured by HPLC. With [K⁺]_e elevations to 60 m M , medium glutamate concentrations did not increase during incubation periods of 5–120 min. By contrast, 45 min of combined inhibition of glycolytic and oxidative ATP production increased medium glutamate concentrations 50–100-fold. Similar results were obtained in both rat and mouse cultures. Studies were also performed using astrocytes loaded with the nonmetabolized glutamate tracer d -aspartate, and parallel results were obtained; no increase in medium d -aspartate content resulted from [K⁺]_e elevation up to 90 m M , whereas a large increase occurred during inhibition of energy metabolism. These results suggest that a net efflux of glutamate from intact astrocytes is not induced by any [K⁺]_e attainable in brain.