春潮

春天来了,万物复苏,三家平时不动声色的超级豪华轿车制造商不约而同地有了行动。一时间,宾利出了四门车大陆 Flying Spur(Continental Flying Spur),劳斯莱斯加长了幻影(Phantom),迈巴赫(Maybach)为3月开幕的日内瓦车展带来了新开发的迈巴赫57特别版     

Structure of a bacterial 30S ribosomal subunit at 5.5 A resolution.

The 30S ribosomal subunit binds messenger RNA and the anticodon stem-loop of transfer RNA during protein synthesis. A crystallographic analysis of the structure of the subunit from the bacterium Thermus thermophilus is presented. At a resolution of 5.5 A, the phosphate backbone of the ribosomal RNA is visible, as are the alpha-helices of the ribosomal proteins, enabling double-helical regions of RNA to be identified throughout the subunit, all seven of the small-subunit proteins of known crystal structure to be positioned in the electron density map, and the fold of the entire central domain of the small-subunit ribosomal RNA to be determined.     

The spread of HIV-1 in Africa: sexual contact patterns and the predicted demographic impact of AIDS

The spread of HIV-1 in Africa is examined here in the light of recent information on the main epidemiological and behavioural determinants of transmission. Mathematical models incorporating demographic, epidemiological and behavioural processes are used to assess the potential demographic impact of the disease AIDS. These analyses highlight the significance of patterns of sexual behaviour, and in particular networks of sexual contact, on the predicted spread of infection. Current data reveal substantial variations in the degree of spread between and in countries, but new analyses support earlier predictions that in the worst-afflicted areas AIDS is likely to change population growth rates from positive to negative values in a few decades.     

风险与无常

在科学的边界上我们并不是始终能知道将会发生些什么?     

Transmission dynamics of HIV infection

Simple mathematical models of the transmission dynamics of human immunodeficiency virus help to clarify some of the essential relations between epidemiological factors, such as distributed incubation periods and heterogeneity in sexual activity, and the overall pattern of the AIDS epidemic. They also help to identify what kinds of epidemiological data are needed to make predictions of future trends.     

Chemical excitability of axons: excitatory and inhibititory effects of putative neurotransmitters and modulators on frog sciatic nerves.

The microiontophoretic administration of putative neuromodulators (acetylcholine, norepinephrine, dopamine, 2-phenylethylamine, tryptamine, histamine) triggered firing or inhibited on-going activity in isolated frog sciatic nerves.     

Exercise-induced BCL2-regulated autophagy is required for muscle glucose homeostasis

Exercise has beneficial effects on human health, including protection against metabolic disorders such as diabetes. However, the cellular mechanisms underlying these effects are incompletely understood. The lysosomal degradation pathway, autophagy, is an intracellular recycling system that functions during basal conditions in organelle and protein quality control. During stress, increased levels of autophagy permit cells to adapt to changing nutritional and energy demands through protein catabolism. Moreover, in animal models, autophagy protects against diseases such as cancer, neurodegenerative disorders, infections, inflammatory diseases, ageing and insulin resistance. Here we show that acute exercise induces autophagy in skeletal and cardiac muscle of fed mice. To investigate the role of exercise-mediated autophagy in vivo, we generated mutant mice that show normal levels of basal autophagy but are deficient in stimulus (exercise- or starvation)-induced autophagy. These mice (termed BCL2 AAA mice) contain knock-in mutations in BCL2 phosphorylation sites (Thr69Ala, Ser70Ala and Ser84Ala) that prevent stimulus-induced disruption of the BCL2-beclin-1 complex and autophagy activation. BCL2 AAA mice show decreased endurance and altered glucose metabolism during acute exercise, as well as impaired chronic exercise-mediated protection against high-fat-diet-induced glucose intolerance. Thus, exercise induces autophagy, BCL2 is a crucial regulator of exercise- (and starvation)-induced autophagy in vivo, and autophagy induction may contribute to the beneficial metabolic effects of exercise.     

The biosynthesis of diterpenoid alkaloids

Zusammenfassung Die diterpenoiden Alkaloide Browniin und Lycoctonin wurdenin vivo aus Mevalonsäure-2-¹⁴C hergestellt. Sie zeigten, aus Acetat-1-¹⁴C und -2-¹⁴C gewonnen, eine geringere Wirksamkeit. Die Biosynthese dieser Alkaloide scheint somit der der anderen Terpene analog.