The origin of circadian and amphetamine-induced changes in the extracellular concentration of brain ascorbate

Circadian and amphetamine-induced changes in the extracellular concentration of ascorbate in the striatum and hippocampus of unrestrained rats were measured voltammetrically; the amphetamine-induced changes in striatal ascorbate were confirmed using a push-pull perfusion technique. Circadian changes in the level of blood plasma ascorbate, and the distribution of [¹⁴C]ascorbate after the intraperitoneal administration of amphetamine were also measured. Circadian changes in brain and plasma ascorbate levels were 6 h out of phase. Amphetamine caused little change in the distribution of blood-borne ascorbate in the striatum or hippocampus.

These results suggest that changes in extracellular ascorbate levels in the brain are not secondary to changes in the supply of ascorbate from the blood; they arise from the modulation in ascorbate release from, and/or the uptake into, neuropil.     

Ecological cues, gestation length, and birth timing in African buffalo (Syncerus caffer)

We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year.     

Absence of the symbiont Candidatus Midichloria mitochondrii in the mitochondria of the tick Ixodes holocyclus

OprG of Pseudomonas aeruginosa is a member of the very large and widely distributed but poorly characterized OmpW (PF0392) family of outer membrane proteins. It was established here that OprG was highly transcribed in anaerobic environments rich in iron via the ANR regulator. In the absence of OprG, P. aeruginosa was significantly less cytotoxic toward human bronchial epithelial cells. Planar bilayer studies indicated that purified OprG formed cationic-selective channels with a conductance of 500 pS in 1 M KCl; however, contrary to previous reports, OprG did not appear to be involved in either iron or antibiotic uptake.