Monolayer cell expansion conditions affect the chondrogenic potential of adipose-derived stem cells

Adipose-derived stem cells (ASCs) are an abundant, readily available population of multipotent progenitor cells that reside in adipose tissue. Isolated ASCs are typically expanded in monolayer on standard tissue culture plastic with a basal medium containing 10% fetal bovine serum. However, recent data suggest that altering the monolayer expansion conditions by using suspension culture plastic, adding growth factors to the medium, or adjusting the seeding density may affect the self-renewal rate, multipotency, and lineage-specific differentiation potential of the ASCs. We hypothesized that variation in any of these expansion conditions would influence the chondrogenic potential of ASCs. ASCs were isolated from human liposuction waste tissue and expanded through two passages with different tissue culture plastic, feed medium, and cell seeding densities. Once expanded, the cells were cast in an agarose gel and subjected to identical chondrogenic culture conditions for 7 days, at which point cell viability, radiolabel incorporation, and gene expression were measured. High rates of matrix synthesis upon chondrogenic induction were mostly associated with smaller cells, as indicated by cell width and area on tissue culture plastic, and it appears that expansion in a growth factor supplemented medium is important in maintaining this morphology. All end-point measures were highly dependent on the specific monolayer culture conditions. These results support the hypothesis that monolayer culture conditions may "prime" the cells or predispose them towards a specific phenotype and thus underscore the importance of early culture conditions in determining the growth and differentiation potential of ASCs.     

Biodiversity conservation,yield, and alternative products in coffee agroecosystems in Sumatra,Indonesia

Agroecology and conservation must overlap to protect biodiversity and farmer livelihoods. Coffee agroecosystems with complex shade canopies protect biodiversity. Yet, few have examined biodiversity in coffee agroecosystems in Asia relative to the Americas and many question whether coffee agroecosystems can play a similar role for conservation. We examined vegetation, ant and bird diversity, coffee yields and revenues, and harvest of alternative products in coffee farms and forests in SW Sumatra, Indonesia near Bukit Barisan Selatan National Park (BBS). BBS is among the last habitats for large mammals in Sumatra and >15,000 families illegally cultivate coffee inside of BBS. As a basis for informing management recommendations, we compared the conservation potential and economic outputs from farms inside and outside of BBS. Forests had higher canopy cover, canopy depth, tree height, epiphyte loads, and more emergent trees than coffee farms. Coffee farms inside BBS had more epiphytes and trees and fewer coffee plants than farms outside BBS. Tree, ant, and bird richness was significantly greater in forests than in coffee farms, and richness did not differ in coffee farms inside and outside of BBS. Species similarity of forest and coffee trees, ants, and birds was generally low (<50%). Surprisingly, farms inside the park were significantly older, but farm size, coffee yields, and revenues from coffee did not depend on farm location. Farmers outside BBS received higher prices for their coffee and also more often produced other crops in their coffee fields such that incentives could be created to draw illegal farmers out of the park. We also discuss these results with reference to similar work in Chiapas, Mexico to compare the relative contribution of coffee fields to conservation in the two continents, and discuss implications for working with farmers in Sumatra towards conservation plans incorporating sustainable coffee production.     

Lysinyl macrocyclic hexaoxazoles: synthesis and selective G-quadruplex stabilizing properties

Macrocyclic hexaoxazoles having one or two lysinyl side chains in which the terminal nitrogen is either a primary amine, N,N-dimethylamine, or an acetamide have been synthesized. Sodium ion has been found to be beneficial to the macrocyclization step by acting as a template around which the linear polyoxazole can organize. Each of the targeted compounds selectivity stabilizes G-quadruplex versus duplex DNA. Compounds with one valine and one lysine residue display the best combination of G-quadruplex stabilizing ability with no detectable stabilization of duplex DNA.     

New techniques and findings in the study of a candidate allelochemical implicated in invasion success

Allelopathy has been hypothesized to promote the success of invasive plants. Support for the role of allelopathy in invasions has emerged from research on the candidate allelochemical (?)‐catechin, which is secreted by spotted knapweed. Here we describe new methods to quantify catechin in liquid and soil. With a new technique, we assayed catechin production by individual plants in liquid media and found levels up to two orders of magnitude less than previously reported. An acetone/water solution provided consistent recovery of catechin from soil, with percent recovery depending upon soil type. We evaluated soils from two spotted knapweed sites in Montana, USA, but found no measurable catechin. Idaho fescue, a native species reportedly sensitive to catechin, only exhibited slightly reduced growth at concentrations 10 times higher than previously reported to cause 100% mortality. Our results emphasize that more research is required to clarify the role of catechin in the invasion of spotted knapweed.     

Longitudinal Study of Fecal Shedding of Escherichia coli O157:H7 in Feedlot Cattle: Predominance and Persistence of Specific Clonal Types despite Massive Cattle Population Turnover

Identification of the sources and methods of transmission of Escherichia coli O157:H7 in feedlot cattle may facilitate the development of on-farm control measures for this important food-borne pathogen. The prevalence of E. coli O157:H7 in fecal samples of commercial feedlot cattle in 20 feedlot pens between April and September 2000 was determined throughout the finishing feeding period prior to slaughter. Using immunomagnetic separation, E. coli O157:H7 was isolated from 636 of 4,790 (13%) fecal samples in this study, with highest prevalence earliest in the feeding period. No differences were observed in the fecal or water trough sediment prevalence values of E. coli O157:H7 in 10 pens supplied with chlorinated drinking water supplies compared with nonchlorinated water pens. Pulsed-field gel electrophoresis of XbaI-digested bacterial DNA of the 230 isolates obtained from eight of the pens revealed 56 unique restriction endonuclease digestion patterns (REDPs), although nearly 60% of the isolates belonged to a group of four closely related genetic subtypes that were present in each of the pens and throughout the sampling period. The other REDPs were typically transiently detected, often in single pens and on single sample dates, and in many cases were also closely related to the four predominant REDPs. The persistence and predominance of a few REDPs observed over the entire feeding period on this livestock operation highlight the importance of the farm environment, and not necessarily the incoming cattle, as a potential source or reservoir of E. coli O157:H7 on farms.     

An age-related shift in the force-frequency relationship affects quadriceps fatigability in old adults.

We examined the effect of an age-related leftward shift in the force-frequency relationship on the comparative quadriceps fatigability of nine young (27 +/- 1 yr old) and nine old men (78 +/- 1 yr old) during low-frequency electrical stimulation. Two different protocols of intermittent trains (6 pulses on, 650 ms off) of electrical stimulation at 25% maximum voluntary contraction were performed by both groups: 1) 180 trains at 14.3 Hz [constant frequency (CF) protocol], and 2) 180 trains at the frequency corresponding to 60% of each subject's force-frequency curve [normalized frequency (NF) protocol; young 14.9 +/- 0.4 vs. old 12.7 +/- 0.5 Hz; P < 0.05]. The quadriceps of the old men were weaker (approximately 31%) and relaxation was slower compared with the young men, as assessed by the maximal relaxation rate constant of the 50-Hz tetanus (young 12.1 +/- 0.2 vs. old 9.2 +/- 0.5 s(-1); P < 0.05) and a leftward shift in the force-frequency relationship. The NF protocol revealed a decreased fatigability in the quadriceps with old age (percentage of 1st contraction force remaining at 180th: old 63.4 +/- 1.5 vs. young 58.2 +/- 1.7%; P < 0.05) that was masked during the CF protocol (old 60.7 +/- 1.6 vs. young 58.6 +/- 2.3%; P > 0.05). Irrespective of the protocol, the maximal relaxation rate was reduced to approximately 73 and approximately 57% of the prefatigue value in the young and old men, respectively. The age-related leftward shift in the force-frequency relationship of the quadriceps contributed to an underestimation of the fatigue resistance with old age during the CF protocol. However, when the stimulation frequency used in the NF protocol was adjusted to account for the age-related shift in the force-frequency relationship, the quadriceps muscles of the old men were less fatigable than those of the young men. Thus we suggest that whole muscle fatigability is better examined by electrical stimulation protocols that are adjusted for inter- and intragroup differences in the force-frequency relationship.     

An AFLP marker approach to lower-level systematics in Eucalyptus (Myrtaceae)

Genus Eucalyptus, with over 700 species, presents a number of systematic difficulties including taxa that hybridize or intergrade across environmental gradients. To date, no DNA marker has been found capable of resolving phylogeny below the sectional level in the major subgenera. Molecular markers are needed to support taxonomic revision, assess the extent of genetic divergence at lower taxonomic levels, and inform conservation efforts. We examined the utility of 930 amplified fragment length polymorphisms (AFLPs) for analyzing relationships among Tasmanian taxa of subgenus Symphyomyrtus section Maidenaria. Phenetic and cladistic analyses resolved species into clusters demonstrating significant genetic partitioning, largely concordant with series defined in the most recent taxonomic revision of Eucalyptus. Some departures from current taxonomy were noted, indicating possible cases of morphological convergence and character reversion. Although the resolution obtained using AFLP was greatly superior to that of single sequence markers, the data demonstrated high homoplasy and incomplete resolution of closely related species. The results of this study and others are consistent with recent speciation and reticulate evolution in Maidenaria. We conclude that a combination of phylogenetic and population genetic approaches using multiple molecular markers offers the best prospects for understanding taxonomic relationships below the sectional level in Eucalyptus.     

Loss of housekeeping selenoprotein expression in mouse liver modulates lipoprotein metabolism

Selenium is incorporated into proteins as selenocysteine (Sec), which is dependent on its specific tRNA, designated tRNA^[Ser]Sec. Targeted removal of the tRNA^[Ser]Sec gene (Trsp) in mouse hepatocytes previously demonstrated the importance of selenoproteins in liver function. Herein, analysis of plasma proteins in this Trsp knockout mouse revealed increases in apolipoprotein E (ApoE) that was accompanied by elevated plasma cholesterol levels. The expression of genes involved in cholesterol biosynthesis, metabolism and transport were also altered in knockout mice. Additionally, in two transgenic Trsp mutant mouse lines (wherein only housekeeping selenoprotein synthesis was restored), the expression of ApoE, as well as genes involved in cholesterol biosynthesis, metabolism and transport were similar to those observed in wild type mice. These data correlate with reports that selenium deficiency results in increased levels of ApoE, indicating for the first time that housekeeping selenoproteins have a role in regulating lipoprotein biosynthesis and metabolism.     

三个褐飞虱寄主种群对氨基酸需求的分化(英文)

取分别在水稻品种TN1 (常用感虫对照 )、Mudgo(含Bph1 )或ASD7(含bph2 )上连续饲养 3 0代以上的3个褐飞虱Nilaparvatalugens寄主种群 ,分别饲养于 2 0种氨基酸总量与配比不同的全纯人工饲料上 ,以羽化率、短翅率、若虫历期以及初羽化成虫体重为指标对不同种群的氨基酸需求进行了比较。发现不同褐飞虱种群随氨基酸营养条件的改变有明显不同的表现 ,其中Mudgo种群最容易受到氨基酸营养条件的影响 ,而TN1种群所受影响最小。抗虫品种ASD7和Mudgo上的两褐飞虱种群所需的最佳氨基酸总浓度 (分别为 4 0 %～ 4 8%、4 0 % )高于TN1种群 (2 4%～ 3 2 % ) ,同时 ,前两种群对必需氨基酸浓度的变化较TN1种群敏感。这些结果表明 ,不同褐飞虱寄主种群对饲料氨基酸的需求存在明显的分化 ,推测氨基酸可能是抗虫水稻品种胁迫褐飞虱致害性变异的一种重要机制。