E2f1 mediates high glucose-induced neuronal death in cultured mouse retinal explants

Diabetic retinopathy (DR) is the most common complication of diabetes and remains one of the major causes of blindness in the world; infants born to diabetic mothers have higher risk of developing retinopathy of prematurity (ROP). While hyperglycemia is a major risk factor, the molecular and cellular mechanisms underlying DR and diabetic ROP are poorly understood. To explore the consequences of retinal cells under high glucose, we cultured wild type or E2f1^?/? mouse retinal explants from postnatal day 8 with normal glucose, high osmotic or high glucose media. Explants were also incubated with cobalt chloride (CoCl₂) to mimic the hypoxic condition. We showed that, at 7 days post exposure to high glucose, retinal explants displayed elevated cell death, ectopic cell division and intact retinal vascular plexus. Cell death mainly occurred in excitatory neurons, such as ganglion and bipolar cells, which were also ectopically dividing. Many Müller glial cells reentered the cell cycle; some had irregular morphology or migrated to other layers. High glucose inhibited the hyperoxia-induced blood vessel regression of retinal explants. Moreover, inactivation of E2f1 rescued high glucose-induced ectopic division and cell death of retinal neurons, but not ectopic cell division of Müller glial cells and vascular phenotypes. This suggests that high glucose has direct but distinct effects on retinal neurons, glial cells and blood vessels, and that E2f1 mediates its effects on retinal neurons. These findings shed new light onto mechanisms of DR and the fetal retinal abnormalities associated with maternal diabetes, and suggest possible new therapeutic strategies.     

两种荒漠生境条件下泡泡刺水分来源及其对降水的响应

泡泡刺通常以灌丛沙堆的形式存在,具有很强的生态适应性,在防风固沙、抗旱耐盐等方面具有独特的功能,但是水分条件仍然是限制其生存和发展的关键因素.为了明确泡泡刺在不同荒漠生境条件下的水分利用策略,研究了河西走廊临泽绿洲边缘沙质和砾质生境下泡泡刺的水分来源季节动态特征以及对不同降雨事件的响应程度.测定了两种生境下泡泡刺茎水和不同水源(降水、土壤水和地下水)的氧稳定同位素(δ¹⁸O)值,结合IsoSource模型计算了不同水源对泡泡刺水分来源的贡献比例.结果表明:两种生境下泡泡刺茎水δ¹⁸O值及其水分来源都存在显著的季节变化特征,沙质生境下泡泡刺在降水较少的春季和秋季主要利用地下水,其贡献率可达50%以上;而砾质生境下的泡泡刺无法利用深达11.5 m地下水,其水分来源受降水控制,具有较大的季节变异性.两种生境下的泡泡刺对降水响应显著,但是降水过后,随着土壤含水量的快速减小,沙质生境下的泡泡刺转而以丰富的地下水为主要水分来源,而砾质生境下的泡泡刺只能利用降水入渗至较深层土壤的较少水分.因此,两种生境下泡泡刺不同的水分利用策略是导致其生长特征差异的主要原因,同时也表明泡泡刺具有较强的自我调节和适应能力.     

北京土石山区典型植物水分来源

在季节性干旱区,水分是限制植物生长的关键因子.为了分析比较北京山区群落植物的水分利用特征,本文利用稳定同位素(D/H、¹⁸O/¹⁶O)技术,探讨典型群落植物侧柏、荆条、构树和胡枝子的水分来源及其对各水源的利用比率.结果表明: 群落内4种植物的水分来源不同,侧柏主要吸收利用40～60、60～80和80～100 cm深度的土壤水,对这3层的利用率在23.3%～25.9%,对表层0～20和20～40 cm的利用率分别为12.3%和13.0%;荆条主要吸收利用60～80和80～100 cm深度的土壤水,利用率分别为51.9%和25.2%,对其他土壤水利用较少;构树主要吸收利用表层0～20 cm和20～40 cm土壤水,利用率分别为47.5%和36.8%;胡枝子对5个水源层水分均有利用,对0～20、20～40和40～60 cm深度土壤水的利用率在21.4%～22.8%,对60～80和80～100 cm深度土壤水的利用率分别为15.2%和18.3%.侧柏和胡枝子的水分利用深度相似,两个树种混交可能会造成较大的水分竞争;荆条和构树的水分利用深度恰好互补,适宜混交.研究结果可为恢复受损生态环境的最佳植物种组合方式提供参考.     

1株耐高温生物表面活性剂产生菌的特性研究

研究了耐高温生物表面活性剂产生菌ZY-3的生理生化特性,并通过测定发酵液的菌体密度、表面张力和乳化活性等指标,研究不同碳源和初始pH对菌株ZY-3生长和产生物表面活性剂的影响,同时对其所产生物表面活性剂进行了初步分离和性质分析。菌株ZY-3被初步鉴定为芽胞杆菌属(Bacillus),具有产酸、不产H_2S、还原硝酸盐等特性。在以淀粉为碳源、初始pH 6.0的培养基中发酵,产生物表面活性剂多且稳定;在种子培养基和发酵培养基中都有淀粉的条件下,菌体生长较多,降低表面张力和乳化的作用均较强,所产生物表面活性剂可以使发酵液的表面张力从72.1 mN/m降到53.1 mN/m,乳化活性从0升高到24%。初步判断产物为糖脂类阴离子表面活性剂。     

Effect of a carbon source on polyphosphate accumulation in Saccharomyces cerevisiae

The cells of Saccharomyces cerevisiae accumulate inorganic polyphosphate (polyP) when reinoculated on a phosphate-containing medium after phosphorus starvation. Total polyP accumulation was similar at cultivation on both glucose and ethanol. Five separate fractions of polyP: acid-soluble fraction polyP1, salt-soluble fraction polyP2, weakly alkali-soluble fraction polyP3, alkali-soluble fraction polyP4, and polyP5, have been obtained from the cells grown on glucose and ethanol under phosphate overplus. The dynamics of polyP fractions depend on a carbon source. The accumulation rates for fractions polyP2 and polyP4 were independent of the carbon source. The accumulation rates of polyP1 and polyP3 were higher on glucose, while fraction polyP5 accumulated faster on ethanol. As to the maximal polyP levels, they were independent of the carbon source for fractions polyP2, polyP3, and polyP4. The maximal level of fraction polyP1 was higher on glucose than on ethanol, but the level of fraction polyP5 was higher on ethanol. It was assumed that accumulation of separate polyP fractions has a metabolic interrelation with different energy-providing pathways. The polyphosphate nature of fraction polyP5 was demonstrated for the first time by ³¹P nuclear magnetic resonance spectroscopy, enzymatic assay, and electrophoresis.     

Ecological role of mountain ridges in and around gwangneung royal tomb forest in central Korea

We assessed the ecological structure and function of mountain ridges connected to a reserve area, Gwangneung Royal Tomb Forest (GRTF), in central Korea. This site has been strictly preserved since the 15th century. Our objectives were to 1 ) investigate the interactions between and the influence of a protected old-growth forest on its surrounding forests, and 2) suggest management strategies for forests outside that reserve area. Three ridges were surveyed and divided into two categories — A and B ridges covered with secondary forests connected to GRTF, and the C ridge, covered with primary forests and plantations within GRTF (from core zone to managed zone). The ridge forests had a characteristic lobe shape. We found no significant decline in species richness (peninsular effect) with distance from GRTF for any tree-layer or herbaceous-layer species on Ridges A or B. However, when only the species that appeared in primary forests on the C ridge were considered, the richness of tree- and herbaceous-layer species was significantly decreased there. This meant that the neighboring forests of GRTF could serve as a buffer zone. Differences were obvious between the two categorized forests in their species composition, species richness, basal area, and regeneration patterns. DCA ordination of quadrats on Ridges A and B showed that Axis 1 was significantly correlated with distance from GRTF, indicating that this protected area affects regeneration within neighboring forests. Thus, reserves are important not only to the conservation of biodiversity, but also to the ecological management of surrounding forests.     

Phenotypic variations of enterococci in surface waters: analysis of biochemical fingerprinting data from multi-catchments

Aims:  The aim of this study was to identify the prevalence of environmentally adapted enterococci strains by analysing biochemical fingerprinting (BF) data of 3952 enterococci isolates collected over 5 years from the six catchments in Southeast Queensland, Australia.
Methods and Results:  A BF method was used to type 3952 enterococci isolates from six catchments. The environmental isolates were compared with a large existing BF library comprised of 5803 enterococci isolates from 10 host groups. Environmental isolates belonged to 801 biochemical phenotypes (BPTs), of which, an average of 29.2% was specific to each catchment. When compared with the BF library, an average of 79·5% BPTs from each catchment was identical to those in the library (i.e. host-origin BPTs). The remaining 20·5% was regarded as non-host origin BPTs, as they were not in the library and constituted only 5·3% of the total isolates tested for each catchment.
Conclusions:  Our data suggest that less than 5% of studied environmental strains was not identical to those in the library and seemed to be of environmental origin. From a microbial source tracking context, such low level of environmentally adapted strains can have a minimal impact on the performance of the library-based methods if a large number of isolates were tested from both the host groups and environmental waters.
Significance and Impact of the Study:  These data shed light on the importance of the size and representativeness of library–based source-tracking methods and their implications for the identification of faecal pollution in environmental waters.     

A novel finding that Streptomyces clavuligerus can produce the antibiotic clavulanic acid using olive oil as a sole carbon source

Aims: This study aims to establish whether commercially available food oils can be used by Streptomyces clavuligerus as sole carbon sources for growth and clavulanic acid production. Methods and results: Batch cultures in bioreactors showed that Strep. clavuligerus growth and clavulanic acid yields in a P‐limited medium containing 0.6% (v/v) olive oil were respectively 2.5‐ and 2.6‐fold higher than in a glycerol‐containing medium used as control. Glycerol‐ and olive oil‐grown cells present different macromolecular composition, particularly lipid and protein content. Conclusions: Streptomyces clavuligerus uses olive oil as the sole carbon and energy source for growth and clavulanic acid production. Yields and production rates in olive oil are comparable to those reported for oil‐containing complex media. Differences in yields and in the macromolecular composition indicate that different metabolic pathways convert substrate into product. Significance and impact of the study: This is the first report of oils being used as the sole carbon source by Strep. clavuligerus. Apart from economic benefits, interesting questions are raised about Strep. clavuligerus physiology. Defined culture media allow physiological studies to be performed in the absence of interference by other compounds. Understanding how Strep. clavuligerus catabolises oils may have an economic impact in clavulanic acid production.     

The contribution of parasitism to selection on floral traits in Heuchera grossulariifolia

Parasites are ubiquitous and have well-documented ecological consequences. In contrast, the extent to which parasites drive phenotypic evolution in hosts remains obscure. We use a recently developed statistical technique--selective source analysis--to analyse the strength of phenotypic selection acting on floral traits in the plant Heuchera grossulariifolia attributable to attack by the seed-parasitic moth, Greya politella. This analysis spanned 3 years and included two sympatric populations of the host plant H. grossulariifolia that differ in ploidy. Our analyses revealed that attack by G. politella contributed to phenotypic selection for flowering time and floral display size, favouring earlier flowering in the polyploid population, later flowering in the diploid population and increased floral display size in the polyploid population. Although selection imposed by parasite attack was generally quite weak, in one of the 3 years parasites generated a modestly strong selection gradient (beta = -0.059) that explained 38.6% of total observed phenotypic selection for earlier flowering in the polyploid population. Together, our results demonstrate parasites can generate significant phenotypic selection, but that such selection may be sporadic across populations and time.