Group Q Streptococci I. Ecology, Serology, Physiology, and Relationship to Established Enterococci

The group Q streptococci possess unique serological and physiological characteristics which differentiate them from established enterococci. The group Q antigen was not demonstrable in all strains; however, all possessed the group D antigen. All group Q strains were physiologically similar regardless of whether or not they possessed the group Q antigen. These strains differed from the established enterococcal species, as they neither hydrolyzed arginine nor initiated growth in 1.0% methylene blue-milk. They also differed radically in the fermentation of various carbohydrates, especially the polyhydric sugar alcohols. The results indicate that the group Q streptococci constitute a unique taxonomic entity; the species designation Streptococcus avium sp. n. is suggested, owing to their characteristic occurrence in chicken fecal specimens.     

载脂蛋白J的结构与功能

载脂蛋白J(apo J)是1990年从人血浆HDL中新分离出的一种酸性糖蛋白,分子量70 000,由α及β亚基通过二硫键相连而成.通过apo J cDNA已确定了apo J 427个氨基酸残基的序列.apo J含双性α螺旋及结合肝素的结构域,可与脂质结合成脂蛋白.apo J mRNA广泛分布于全身各组织,以脑、卵巢、睾丸及肝脏含量最多.apo J的功能可能有:结合与转运脂质;抑制补体C8及C9的激活;参与精子的成熟等.     

Biophysical stimuli induced by passive movements compensate for lack of skeletal muscle during embryonic skeletogenesis

In genetically modified mice with abnormal skeletal muscle development, bones and joints are differentially affected by the lack of skeletal muscle. We hypothesise that unequal levels of biophysical stimuli in the developing humerus and femur can explain the differential effects on these rudiments when muscle is absent. We find that the expression patterns of four mechanosensitive genes important for endochondral ossification are differentially affected in muscleless limb mutants, with more extreme changes in the expression in the humerus than in the femur. Using finite element analysis, we show that the biophysical stimuli induced by muscle forces are similar in the humerus and femur, implying that the removal of muscle contractile forces should, in theory, affect the rudiments equally. However, simulations in which a displacement was applied to the end of the limb, such as could be caused in muscleless mice by movements of the mother or normal littermates, predicted higher biophysical stimuli in the femur than in the humerus. Stimuli induced by limb movement were much higher than those induced by the direct application of muscle forces, and we propose that movements of limbs caused by muscle contractions, rather than the direct application of muscle forces, provide the main mechanical stimuli for normal skeletal development. In muscleless mice, passive movement induces unequal biophysical stimuli in the humerus and femur, providing an explanation for the differential effects seen in these mice. The significance of these results is that forces originating external to the embryo may contribute to the initiation and progression of skeletal development when muscle development is abnormal.     

耕作方式和秸秆还田对华北地区农田土壤水稳性团聚体分布及稳定性的影响

本研究基于10年耕作措施的定位试验,利用湿筛法研究了不同耕作措施和秸秆还田条件下农田土壤水稳性团聚体的分布规律,并利用平均重量直径（MWD）和几何平均直径（GMD）评价了不同处理水稳性团聚体的稳定性。研究结果表明,不同耕作措施处理的水稳性团聚体在0~10cm,10~20cm和20~30cm土层表现出不同的分布趋势,随着土层的加深,各处理水稳定团聚体的分布呈粒径逐渐减小、分布范围逐渐扩大趋势,0~10cm土层的水稳性团聚体多集中于2~5mm粒径范围,10~20cm土层水稳性团聚体多集中在0.5~5mm粒径范围,以0.5~1mm最多,而20~30mm,则广泛分布在0.25~5mm粒径范围。通过MWD和GMD值可以看出,免耕、耙耕和旋耕措施更能有效地保护表层（0~10cm）土壤水稳定团聚体的稳定性,常规耕作和深松处理则显著降低了20~30cm水稳性团聚体稳定性。秸秆还田显著增加了土壤有机碳（SOC）含量,且显著影响了土壤表层水稳性团聚体的稳定性。作用力分析结果表明,在0~10cm表层,秸秆作用在土壤表层显著影响了水稳定大团聚体的数量及其稳定性（P<0.001）,多元回归分析说明其与土壤有机碳含量达到了极显著水平（P<0.01）,且同时也受到来自耕作和秸秆交互效应的影响（P<0.01）;但在10~20cm土层,影响其数量分布的主要因素是不同的耕作措施及耕作和秸秆的交互效应（P<0.001）;而在20~30cm,耕作措施、秸秆和两者的交互效应共同对水稳性大团聚体数量产生重要的影响,但主要作用力来自耕作措施（P<0.001）和两者的交互效应（P<0.001）。免耕秸秆还田措施能显著提高土壤的水稳性团聚体的比例和稳定性。     

Evolution of mechanoregulation of bone growth will lead to non-optimal bone phenotypes

Mechanical forces acting on the bones during growth affect their final shape and strength. Mechanoregulation of bone growth may be recognized in embryogenesis, and also in the adaptation of the adult skeleton to changes in mechanical loading. Mechanoregulatory responses for tissues have arisen during evolution, but does evolution give rise to responses that produce optimal skeletal phenotypes? In this paper, we investigate the emergence of an optimal mechanoregulation response in a population. By combining equations describing long bone growth with a genetic algorithm to describe evolutionary change, we created a computational model to simulate the evolution of mechanoregulation in bone growth. A population of individuals is created where each individual is assigned a diploid gene set which controls the growth and remodelling of the bone. At maturity, each bone is assessed and its 'fitness' calculated; fitness is quantified as bone strength relative to bone mass. The simulation continues for many generations, and includes mutations and a varying environment. The genes present in the population are tracked and the evolution of parameters governing mechanoregulation is calculated. The results indicate that a population may converge to one bone growth algorithm but, more usually, a range of mechanoregulation algorithms for different individuals will persist after many generations. Even if the population converges to one mechanoregulation law, convergence to the 'optimum' bone was never found. Although many researchers propose that natural selection has pushed skeletal structure towards an optimum, our computational model suggests that this is unlikely to be the case.     

TNF-alpha regulates myogenesis and muscle regeneration by activating p38 MAPK

Although p38 MAPK activation is essential for myogenesis, the upstream signaling mechanism that activates p38 during myogenesis remains undefined. We recently reported that p38 activation, myogenesis, and regeneration in cardiotoxin-injured soleus muscle are impaired in TNF- receptor double-knockout (p55^–/–p75^–/–) mice. To fully evaluate the role of TNF- in myogenic activation of p38, we tried to determine whether p38 activation in differentiating myoblasts requires autocrine TNF-, and whether forced activation of p38 rescues impaired myogenesis and regeneration in the p55^–/–p75^–/– soleus. We observed an increase of TNF- release from C2C12 or mouse primary myoblasts placed in low-serum differentiation medium. A TNF--neutralizing antibody added to differentiation medium blocked p38 activation and suppressed differentiation markers myocyte enhancer factor (MEF)-2C, myogenin, p21, and myosin heavy chain in C2C12 myoblasts. Conversely, recombinant TNF- added to differentiation medium stimulated myogenesis at 0.05 ng/ml while inhibited it at 0.5 and 5 ng/ml. In addition, differentiation medium-induced p38 activation and myogenesis were compromised in primary myoblasts prepared from p55^–/–p75^–/– mice. Increased TNF- release was also seen in cardiotoxin-injured soleus over the course of regeneration. Forced activation of p38 via the constitutive activator of p38, MKK6bE, rescued impaired myogenesis and regeneration in the cardiotoxin-injured p55^–/–p75^–/– soleus. These results indicate that TNF- regulates myogenesis and muscle regeneration as a key activator of p38. myocyte enhancer factor-2C; myogenin; p21; myosin heavy chain; Akt; tumor necrosis factor-; mitogen-activated protein kinase     

胰岛素对大鼠载脂蛋白AⅠ,CⅡ和CⅢ基因表达的影响

以sprague-Dawley大鼠为实验对象,研究胰岛素对大鼠肝脏及小肠apoAⅠ、CⅡ和CⅢ mRNA相对含量的影响。RNA斑点杂交技术分析表明,注射胰岛素后12h,大鼠肝脏和小肠apoAⅠ和CⅡ以及肝脏apoCⅢ mRNA相对含量均显著下降,小肠apoCⅢ mRNA相对含量无变化。