Genetically altered mice: phenotypes,no phenotypes,and Faux phenotypes

Phenotype means different things, but whatever the measure, phenotype can be profoundly influenced by genetic, environmental and infectious variables. The laboratory mouse is a complex multisystemic organism which, despite its genetically inbred nature, as highly variable pathophysiologic characteristics. Mouse strains have background characteristics that can influence genomics research. In addition to the mouse itself, different approaches toward creating mutant mice each create variables that influence phenotype. Different background strains of mice are utilized for these different approaches, and various strains are preferred among different laboratories. Background genotype significantly influences phenotype of gene mutations, as can insufficient genetic stabilization of a mutation. Research programs engaged in functional mouse genomics not only must use genetically well-defined mice, but also must incorporate environmental and infectious disease quality assurance/prevention programs. Laboratory mice are subject to over 60 different infectious disease agents, including a wide variety of viruses, bacteria, protozoa, and metazoa. Although these agents can be readily diagnosed and prevented, a number of forces are resulting in their rise in prevalence in mouse colonies. Infectious disease, including clinically silent infections, can and do influence phenotype, and can jeopardize research considerably through lost time, wasted effort, cost, and even loss of valuable strains.     

Microplate quantification of plant leaf superoxide dismutases

Superoxide dismutases (SODs) catalyze the dismutation of superoxide radicals in a broad range of organisms, including plants. Quantification of SOD activity in crude plant extracts has been problematic due to the presence of compounds that interfere with the dose-response of the assay. Although strategies exist to partially purify SODs from plant extracts, the requirement for purification limits the rapidity and practical number of assays that can be conducted. In this article, we describe modification of a procedure using o-dianisidine as substrate that permits relatively rapid quantification of SOD activity in crude leaf extracts in a microplate format. The method employs the use of a commercial apparatus that permits lysis of 12 tissue samples at once and the use of Pipes buffer to reduce interference from compounds present in crude leaf extracts. The assay provided a linear response from 1 to 50 units of SOD. The utility of the assay was demonstrated using tissue extracts prepared from a group of taxonomically diverse plants. Reaction rates with tissue extracts from two grasses were linear for at least 60 min. Tissues of certain species contained interfering compounds, most of which could be removed by ultrafiltration. The presence of plant catalases, peroxidases, and ascorbate in physiological quantities did not interfere with the assay. This approach provides a means to quantify SOD activity in relatively large numbers of plant samples provided that the possibility for the presence of interfering compounds is considered. The presence of interfering compounds in certain plant tissues necessitates caution in interpreting the effects of plant stresses on SOD.     

Different Patterns of Changes in the Dry Season Diameter at Breast Height of Dominant and Evergreen Tree Species in a Mature Subtropical Forest in South China

Information on changes in diameter at breast height （DBH） is important for net primary production （NPP） estimates, timing of forest inventory, and forest management. In the present study, patterns of DBH change were measured under field conditions during the dry season for three dominant and native tree species in a monsoon evergreen broad-leaved forest in the Dinghushan Biosphere Reserve. For each tree species, different patterns of DBH change were observed. In the case of the fast-growing tree species Castanopsis chinensis Hance, large diurnal fluctuations occur, with a peak DBH in the early morning （around 05：00 h） that decreases to a minimum by about 14：00 h. Both Schima superba Gardn. et Chemp and Cryptocarya chinensis （Hance） Hemsh exhibited less diurnal swelling and shrinkage. Diurnal fluctuations for these species were observed on a few occasions over the period of observation. Graphical comparisons and statistical analysis of changes in DBH with meteorological variables indicate that for different trees, the different changes in DBH observed responded to different meteorological variables. Large stem changes were found to occur for Ca. chinensis trees that were associated with variations in solar radiation. However, both S. superba and Cr. chinensis were found to be less sensitive to solar radiation. Changes in the DBH of these two species were found to be controlled mainly by soil temperature and soil moisture. During the later dry season, with a lower soil temperature and soil moisture, all three tree species stopped growing and only negligible shrinkage, expansion, or fluctuation occurred, suggesting that the optimum time to measure tree growth in the Dinghushan Biosphere Reserve is the later dry season.     

Novel calcium-binding GTPase (AtCBG) involved in ABA-mediated salt stress signaling in Arabidopsis

We have identified a novel Ca²⁺-signal sensing GTPase (643 amino acid residues with an estimated molecular mass of 79 kDa) from the Arabidopsis genome database. This protein contains a RHO-like GTPase domain at the N-terminus (15–184 amino acids) and two calcium-binding EF-hand motifs (199–227 and 319–347 amino acids, respectively). It has the capability to bind calcium and hydrolyze GTP; in addition, its GTPase activity is regulated by changes in Ca²⁺ concentration. The expression of this gene was induced by ABA and salt stresses, and specific knock-out mutants were highly sensitive to ABA and salt treatments. These findings suggest that this protein is a novel ABA- and salt stress-related Ca²⁺ signal transducer.     

Effect of pedal rate on diurnal variations in cardiorespiratory variables

Recently, it was observed that the freely chosen pedal rate of elite cyclists was significantly lower at 06:00 than at 18:00 h, and that ankle kinematics during cycling exhibits diurnal variation. The modification of the pedaling technique and pedal rate observed throughout the day could be brought about to limit the effect of diurnal variation on physiological variables. Imposing a pedal rate should limit the subject's possibility of adaptation and clarify the influence of time of day on physiological variables. The purpose of this study was to determine whether diurnal variation in cardiorespiratory variables depends on pedal rate. Ten male cyclists performed a submaximal 15 min exercise on a cycle ergometer (50% W_max). Five test sessions were performed at 06:00, 10:00, 14:00, 18:00, and 22:00 h. The exercise bout was divided into three equivalent 5 min periods during which different pedal rates were imposed (70 rev · min^-1, 90 rev · min^-1 and 120 rev · min^-1). No significant diurnal variation was observed in heart rate and oxygen consumption, whatever the pedal rate. A significant diurnal variation was observed in minute ventilation (p=0.01). In addition, the amplitude of the diurnal variation in minute ventilation depended on pedal rate: the higher the pedal rate, the greater the amplitude of its diurnal variation (p=0.03). The increase of minute ventilation throughout the day is mainly due to variation in breath frequency (p=0.01)—the diurnal variation of tidal volume (all pedal rate conditions taken together) being non-significant—but the effect of pedal rate×time of day interaction on minute ventilation specific to the higher pedal rate conditions (p=0.03) can only be explained by the increase of tidal volume throughout the day. Even though an influence of pedal rate on diurnal rhythms in overall physiological variables was not also evidenced, high pedal rate should have been imposed when diurnal variations of physiological variables in cycling were studied.     

Seasonal and diurnal monitoring of leaf polyamine content in Quercus ilex L. resprouts after fire in relation to changes in irradiation and photosynthetic parameters

Seasonal variations in free putrescine, spermidine and spermine content, gas-exchange and chlorophyll fluorescence parameters were followed during winter and summer on leaves of a similar age from undisturbed holm oak trees (control, C) and resprouts (R) originated after fire. We observed a general trend of putrescine content decrease with increasing irradiance. Putrescine content decreased markedly from winter to summer, especially in R, which were located on a site with much higher irradiation. Daily summer variations in putrescine showed a decline at midday from morning values, and they were also more accentuated in R. Measurement of gas-exchange and chlorophyll fluorescence parameters showed marked differences between C and R under their respective light conditions. R showed higher values of PSII quantum yield (Φ_PSII), photochemical quenching (qP) and intrinsic efficiency of open PSII centres () The Φ_PSII/PPFD response curve showed that under the same irradiance, Φ_PSII was enhanced in R and mainly under high light conditions. In spite of increasing irradiance from winter to summer, and especially in burned areas, the mentioned chlorophyll fluorescence parameters were maintained indicating the adaptation of the photosynthetic apparatus. Results derived from A/C _i and A/PPFD response curves showed enhanced photosynthetic capacity and lower non-stomatal limitation of photosynthesis in R during summer stress. The contribution of putrescine decline in the photoadaptation of the photosynthetic apparatus of species growing in natural forest habitats is considered.     

Spatial and bathymetric trends in Harpacticoida (Copepoda) community structure in the Northern Gulf of Mexico deep-sea

Harpacticoid copepod community structure was analyzed at 43 stations in the northern Gulf of Mexico deep-sea to test regional and bathymetric patterns of diversity in relation to environmental variables and topographic complexity of the continental slope. Depth, longitude, and proximity to the Florida Escarpment significantly affect average phylogenetic diversity, but basins and canyons do not. Multivariate analysis reveals a significant inverse relationship between diversity and POM flux, which is confirmed by significant region-scale depth and longitude differences. Although species richness declines linearly with increasing depth, the expected number of species (rarefraction) is maximized at approximately 1200 m, and average taxonomic and phylogenetic diversity continue to increase with depth, suggesting greater morphological or functional harpacticoid diversity with increasing depth. Most stations have unique species compositions, suggesting high regional (2200 species) and global (10⁵-10⁶ species) diversity by extrapolation. Therefore, processes maintaining harpacticoid diversity in the northern Gulf of Mexico deep-sea seem to rely on both small-scale dispersal and large-scale food supply mechanisms.     

Comparative expression profiles of maize genes from a water stress-specific cDNA macroarray in response to high-salinity, cold or abscisic acid

cDNA macroarray has become a useful tool to analyze expression profiles and compare the similarities and differences of various expression patterns. We have prepared a cDNA macroarray containing 190 maize expressed sequence tags (ESTs) specifically induced by water stress to analyze the expression profiles of maize seedlings under abscisic acid (ABA) treatment, high-salinity and cold stress conditions. The results indicated that 48 ESTs in leaves and 111 ESTs in roots were significantly up-regulated by ABA treatment, 36 ESTs in leaves and 41 ESTs in roots by high-salinity stress, 14 ESTs in leaves and 18 ESTs in roots by cold induction, whereas 22 ESTs were induced under all 3 stresses. Results from the hierarchical cluster analysis suggest that the leaves and roots of maize seedlings had different expression profiles after these stresses. The overlap analysis of different stress-induced ESTs indicated that there is more crosstalk between water stress and ABA and high-salinity stress than between water stress and cold stress. It will be helpful to study the precise function of the corresponding overlapping-induced genes for understanding the relationship and crosstalk between different stress signal pathways.