A protonmotive force as the source of energy for galactoside transport in energy depletedEscherichia Coli

Summary Uracil transport inSaccharomyces cerevisiae is mediated by a specific permease which does not recognize other pyrimidines such as uridine, cytosine, thymine, 2-hydroxypyrimidine or 5-amino-uracil; hypoxanthine and 6-amino-uracil slightly inhibit the uptake of uracil in a strain lacking cytosine permease activity. Wild type cells concentrate extracellular uracil before its transformation into UMP and subsequent incorporation into nucleic acids. A strain lacking UMP pyrophosphorylase and uridine ribohydrolase (strainfur 1–8 rh, in which the endogenous production as well as the utilization of uracil are lacking) is able to concentrate¹⁴C-2 uracil from the medium. At the same time no other¹⁴C-2 labelled compound could be detected in this strain, thus suggesting that the uptake of uracil in yeast occurs by active transport which is not coupled to the UMP pyrophosphorylase. The optimal pH of uracil uptake in standard growth conditions was 4.3. It was deduced from experiments performed on strainfur 1–8 rh with³H-5 and¹⁴C-2 uracil that the intracellular pool of uracil is recycled once the steady-state has been reached. First order kinetics with similar rate constants were observed for uracil efflux in strainfur 1–8 rh (k min^–1=0.75±0.08) as well as in the strain lacking uracil permease,fur 1–8 rh fur 4–6 (k min^–1=0.60±0.08). The intracellular pool of¹⁴C-2 uracil can be chased in strainfur 1–8 rh by addition of³H uracil without inducing a large initial acceleration of the exit rate (the rate constant remained at 0.60). 2-4-dinitrophenol inhibits the uptake of uracil but also reduces the efflux of uracil in strainfur 1–8 rh fur 4–6. These data and the comparison with cytosine transport in the same organism support the hypothesis that, whereas uracil uptake is a permease mediated active transport, the efflux of uracil does not involve the uracil uptake permease. A coefficient of permeability of 7.4×10^–7 cm sec^–1 was calculated for uracil.     

Androgen metabolism by rat epididymis. Metabolic conversion of 3H 5alpha-androstane-3alpha,17beta-diol, in vitro

The epididymis of adult rats metabolizes 3H 5alpha-androstane-3alpah,17beta-diol (3alpha-diol) by experiments in vitro. After incubation of tissue slices at 37 degrees C for 2 hours, 2% of the radioactivity was found in the water-soluble fraction whereas 98% was found to be ether soluble (free steroids). Further investigation of the free steroids showed the following to be present: 3alpha-diol 39.9%, DHT (17beta-hydroxy-5alpha-androstan-3-one) 33.7%, androsterone (3alpha-hydroxy-5alpha-androstan-17-one) 9.2%, 3beta-diol (5alpha-androstane-3beta,17beta-diol) 2.6%, 5alpha-A-dione (5alpha-androstan-3,17-dione) 1.1%, delta 16-3alpha-ol (5alpha-androst-16-en-3alpha-ol) 1.0%, delta16-3beta-ol (5alpha-androst-16-en-3beta-ol) 2.6%, delta 16-3-one (5alpha-androst-16-en-3-one) 2.9%, and polar compounds 3.3%. When segments of the epididymis (caput and cauda) were incubated in the same way, qualitatively similar metabolites were formed but a greater amount of 3alpha-diol was metabolized by the cauda epididymis. This increase was mainly accounted for by an increased formation of delta 16 compounds (14.3% in cauda, 4.3% in caput). This is most probably due to the presence of larger numbers of mature spermatozoa, which, as we have previously shown, form delta16 steroids from 3alpha-diol and DHT (5).     

Nosocomial transmission of group B streptococci.

The acquisition of group B streptococci by babies in a special-care baby unit and two postnatal wards was investigated over a six-month period using serology and phage typing. Sixty-three culture-positive babies were identified in the postnatal wards, one-third of whom had been born to mothers who were not carrying the organism in the genital tract or anorectal area during labour. A non-maternal source was identified for 14 of these 21 infants: either colonised mothers and babies in the same ward or, on one occasion, a member of the hospital staff. In the special-care baby unit, however, only one instance of nosocomial acquisition of group B streptococci was recorded despite a high prevalence of colonisation in the staff on the unit and the presence of heavily colonised babies. The results of this survey suggest that although sepsis caused by group B streptococci may be the result of nosocomial transmission, this may be prevented by careful attention to hygiene.     

人肺腺癌细胞分化相关基因cDNAs的克隆

在用10^-5 mol/L全反式维甲酸(RA)诱导人肺腺癌细胞系GLC-82分化的基础上,以M13噬菌粒pSPORT1为载体,应用定向克隆技术,分别构建了未经RA诱导和RA诱导1d及4d细胞的3个cDNA文库.以含重组子的诱导文库单链DNA为靶标(Target)同未诱导文库的cDNA驱除子(Driver)进行消减杂交,富集RA特异性单链DNA,将富集的单链DNA回复为双链后转化感受态菌,建立细胞诱导分化过程中活化表达基因的cDNA消减文库,得到124个cDNA消减克隆.经同源性分析和与文库总cDNA作Southern印迹杂交,进而与RA诱导前后细胞的RNA作Northern印迹杂交,筛选出2个(RA5,RA28)诱导后呈早期瞬时表达和1个(RA42)呈早期并持续表达的cDNA克隆,cDNA全长分别为1.8,1.5和0.7kb.序列测定及初步功能分析结果表明,RA5,RA28和RA42这3个首次报道的序列,可能是人肺腺癌细胞分化相关基因的cDNA克隆.     

Monotonic Change of the Mean Phenotype in Two-Locus Models

It is shown that the mean phenotype monotonically approaches the optimum in a class of symmetric, two-locus, two-allele models with stabilizing selection. In this model, mean fitness does not change monotonically. Thus, Fisher's fundamental theorem does not hold, even though another quantity of evolutionary interest, the mean phenotype, can be shown to change monotonically. Using this quantity, it is proven that global stability results for this model.     

Validated predictive modelling of the environmental resistome

Multi-drug-resistant bacteria pose a significant threat to public health. The role of the environment in the overall rise in antibiotic-resistant infections and risk to humans is largely unknown. This study aimed to evaluate drivers of antibiotic-resistance levels across the River Thames catchment, model key biotic, spatial and chemical variables and produce predictive models for future risk assessment. Sediment samples from 13 sites across the River Thames basin were taken at four time points across 2011 and 2012. Samples were analysed for class 1 integron prevalence and enumeration of third-generation cephalosporin-resistant bacteria. Class 1 integron prevalence was validated as a molecular marker of antibiotic resistance; levels of resistance showed significant geospatial and temporal variation. The main explanatory variables of resistance levels at each sample site were the number, proximity, size and type of surrounding wastewater-treatment plants. Model 1 revealed treatment plants accounted for 49.5% of the variance in resistance levels. Other contributing factors were extent of different surrounding land cover types (for example, Neutral Grassland), temporal patterns and prior rainfall; when modelling all variables the resulting model (Model 2) could explain 82.9% of variations in resistance levels in the whole catchment. Chemical analyses correlated with key indicators of treatment plant effluent and a model (Model 3) was generated based on water quality parameters (contaminant and macro- and micro-nutrient levels). Model 2 was beta tested on independent sites and explained over 78% of the variation in integron prevalence showing a significant predictive ability. We believe all models in this study are highly useful tools for informing and prioritising mitigation strategies to reduce the environmental resistome.     

Action Spectrum for Resetting the Circadian Phototaxis Rhythm in the CW15 Strain of Chlamydomonas: II. Illuminated Cells

The action spectrum for resetting the phase of the circadian clock in Chlamydomonas reinhardtii is different depending upon whether the light stimuli are presented to cells that were in darkness versus dim illumination before stimulation. In this report, we show that phase resetting of illuminated cells appears to be mediated by components of the photosynthetic apparatus. This conclusion is based upon the action spectrum for phase-shifting illuminated cells (which looks like that for photosynthesis) and upon the fact that inhibitors of photosynthetic electron transport also inhibit the light-induced phase shift of illuminated cells. Both of these characteristics differ from that of cells taken from darkness. We, therefore, believe that at least two resetting pathways for this circadian clock exist and that both of these pathways are ecologically significant.     

Relationship of aerobic and anaerobic parameters with 400 m front crawl swimming performance

The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake (V.O2PEAK) and total anaerobic contribution (C_ANA). The C_ANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique (V.O2PEAK and alactic contributions of C_ANA) and blood lactate concentration analysis (lactic anaerobic contributions of C_ANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s^-1) and LMS (1.3±0.1 m·s^-1; r = 0.80), V.O2PEAK (4.5±3.9 L·min^-1; r = 0.72) and C_ANA (4.7±1.5 L·O₂; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and V.O2PEAK explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, C_ANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance.