Signal transduction cascades regulating mating, filamentation, and virulence in Cryptococcus neoformans.

Cryptococcus neoformans is a basidiomycetous fungal pathogen that infects the central nervous system. The organism has a defined sexual cycle involving mating between haploid MATalpha and MATa cells. Recent studies have revealed signaling cascades that coordinately regulate differentiation and virulence of C. neoformans. One signaling cascade involves a conserved G-protein alpha subunit and cAMP, and senses nutrients during mating and virulence. The second is a conserved mitogen activated protein (MAP) kinase cascade that senses pheromone during mating, and also regulates haploid fruiting and virulence. Interestingly, some of the MAP kinase components are encoded by the MAT locus itself, which may explain the unique association of the MATalpha locus with physiology and virulence.     

Signalling pathways in the pathogenesis of Cryptococcus

Efficient communication with the environment is critical for all living organisms. Fungi utilize complex signalling systems to sense their environments and control proliferation, development and in some cases virulence. Well-studied signalling pathways include the protein kinase A/cyclic AMP (cAMP), protein kinase C (PKC)/mitogen-activated protein kinase (MAPK), lipid signalling cascades, and the calcium–calcineurin signalling pathway. The human pathogenic basidiomycetous fungus Cryptococcus neoformans deploys sensitive signalling systems to survive in the human host, leading to life-threatening meningoencephalitis. Known virulence traits of this fungus, including the antioxidant melanin production, the antiphagocytic polysaccharide capsule and the ability to grow at 37°C, are orchestrated by complex signalling networks, whose understanding is crucial to better treat, diagnose and prevent cryptococcosis.     

Ambient temperature and protein level in the ration of growing pigs

Feed intake and body weight of 48 pigs in four trials were measured for 28- or 35-day periods under conditions including either constant optimal temperature or a temperature 10°C higher and at three levels of crude protein (CP) in the feed (12%, 14%, or 16%). The effect of CP level was significantly related (P<0.01) to average daily weight gain and feed utilization. The interaction between CP level and temperature for gain approached significance at the 5% level. Comparison of CP levels at each temperature revealed that increasing little or no effect. Temperature stress lowered weight gain and feed consumption in this study, which confirms many previous studies.