环境因素对安徽虫瘟霉生长发育的影响

安徽虫瘟霉是目前仅发现于我国的重要蚜虫病原真菌,对桃蚜具有明显的自然控制作用。本研究了温度和紫外光对安徽虫瘟等固体培养性状及不同温湿度组合对安徽虫瘟霉分生孢子萌发的影响。     

Light responses,growth factors and phytochrome transformations of Cucumis seedling tissues

Summary The elongation of hypocotyl segments cut from etiolated Cucumis sativus seedlings is not affected by a single red light exposure at the start of the 20-hour growth period, but is inhibited by brief exposures repeated each hour or two even though these give no greater total energy. The inhibition is annulled if each red exposure is followed by far-red. The time course of phytochrome transformations in this tissue after a single red light exposure, followed spectrophotometrically, shows no anomalous characteristics that might correlate with the unusual pattern of responsiveness to red light. In intact seedlings, hypocotyl elongation responds similarly, but the opening of the hypocotyl hook is saturated by a single initial red light treatment. Excised hypocotyl segments on water alone appear insensitive to repeated red light treatment, but the growth increments caused by the addition of potassium ion, 2-propanol or cobaltous ion, or by leaving the cotyledons attached, are all inhibited roughly 40%. However, continuous white light inhibits the entire growth increment, reducing elongation to that of the water controls. Some implications of these results for current hypotheses and future investigations on the mechanisms of growth regulation by light are discussed.Research carried out in part at Brookhaven National Laboratory under the auspices of the U.S. Atomic Energy Commission and supported in part by Cancer Research Funds of the University of Califonia and by National Science Foundation Grant GB-3248 to WKP.     

The influence of skeletal muscle on systemic aging and lifespan

Epidemiological studies in humans suggest that skeletal muscle aging is a risk factor for the development of several age‐related diseases such as metabolic syndrome, cancer, Alzheimer's and Parkinson's disease. Here, we review recent studies in mammals and Drosophila highlighting how nutrient‐ and stress‐sensing in skeletal muscle can influence lifespan and overall aging of the organism. In addition to exercise and indirect effects of muscle metabolism, growing evidence suggests that muscle‐derived growth factors and cytokines, known as myokines, modulate systemic physiology. Myokines may influence the progression of age‐related diseases and contribute to the intertissue communication that underlies systemic aging.     

Proteomic identification of age-dependent protein nitration in rat skeletal muscle

Age-related protein nitration was studied in skeletal muscle of Fisher 344 and Fisher 344/Brown Norway (BN) F1 rats by a proteomic approach. Proteins from young (4 months) and old (24 months) Fisher 344 rats and young (6 months) and old (34 months) Fisher 344/BN F1 animals were separated by 2-D gel electrophoresis. Western blot showed an age-related increase in the nitration of a few specific proteins, which were identified by MALDI-TOF MS and ESI-MS/MS. We identified age-dependent apparent nitration of beta-enolase, alpha-fructose aldolase, and creatine kinase, which perform important functions in muscle energy metabolism, suggesting that the nitration of such key proteins can be, in part, responsible for the decline of muscle motor function of the muscle. Furthermore, we have identified the apparent nitration of succinate dehydrogenase, rab GDP dissociation inhibitor beta (GdI-2), triosephosphate isomerase, troponin I, alpha-crystallin, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH).     

An age-dependent stochastic model of population growth

A stochastic model of population growth is treated using the Bellman-Harris theory of agedependent stochastic branching processes. The probability distribution for the population size at any time and the expectation are obtained when it is assumed that there is probability (1−σ), 0≤σ<1, of the organism dividing into two at the end of its lifetime, and probability σ that division will not take place.     

Soluble age-related factors from skeletal muscle which influence muscle development

Successful regeneration of damaged striated muscle in adult mice is dependent on the regeneration of newly differentiated myofibers from proliferating satellite cells and inhibition of scar tissue formation by fibroblasts. As with most tissues, the ability of skeletal muscle to regenerate decreases in older animals. In this study, we have analysed soluble extracts from intact and regenerating skeletal muscle from mice of different ages for their ability to affect avian myogenesis in tissue culture. We were interested in determining whether an age-dependent difference could be detected with this tissue culture bioassay system. Total cell proliferation in the cultures, measured by [3H]thymidine incorporation was increased equally by muscle extracts from both young and older mice but the resulting cell populations differed in proportion of cell types. The ratio of myoblasts to fibroblasts was significantly greater in cultures exposed to extracts from younger mouse muscle as compared with cultures exposed to extracts from older animals. This age-related activity was found to reside in a low molecular weight (MW) (greater than 12 kD) component of the extract. This fraction had dissimilar effects on myoblasts and fibroblasts. Relative to saline controls, myoblast proliferation was increased and fibroblast proliferation decreased. The low MW fraction from younger mouse muscle extracts stimulated myogenic cell proliferation and myotube formation to a greater extent than the similar fraction prepared from older mouse muscle. Conversely, younger mouse muscle fractions had significantly greater inhibitory activity against fibroblast proliferation than did older mouse muscle fractions.     

The age-dependent induction of apoptosis-inducing factor (AIF) in the human semitendinosus skeletal muscle

To assess the dependence on age of the expression of apoptosis regulatory proteins in the human semitendinosus muscle, we measured the expression levels of several apoptosis-related genes, including apoptosis-inducing factor (AIF), Bax, Bcl-2, caspase-3 and heat shock protein 70 (HSP70), using RT-PCR, immunohistochemistry and TUNEL assays. We found that the DNA fragmentation was proportional to the age of the tissues sample donors. The expression levels of AIF were significantly elevated (by 10 to 25%) in semitendinosus tissue samples from older individuals, but the Bax, Bcl-2, caspase-3 and HSP 70 levels remained almost constant. This data suggests that the morphological and functional changes observed in aged human semitendinosus muscle correlates with the apoptosis of muscle cells through the induction of AIF.     

The influence of ethylenediaminetetraacetate on white skeletal muscle myosin.

Myosin from rabbit white skeletal muscle was treated with 10 mM EDTA in 150 mM phosphate buffer. After precipitation of myosin by dialysis against a 14-fold volume of water, EDTA-treated myosin, myosin before treatment and the supernatant from the treatment of myosin with EDTA were examined on sodium dodecyl sulphate-polyacrylamide gels by electrophoresis. It has been found that the quantity of LC2 light chains diminished after treatment with EDTA, and the supernatant contained the LC2 light chains. Treatment of myosin with EDTA in the presence of Mg2+ does not change the stoichiometry of the LC2 light chain and the supernatant is free from LC2 light chains. The treatment of myosin with p-chloromercuri-benzoate leads to dissociation of the same amount of LC2 light chains. It is suggested that divalent cations and thiol groups are engaged in the attachment of LC2 light chain to the myosin molecule.