Physiological characteristics of chemostatically grownCitrobacter freundii as a function of the specific growth rate and type of nutrient limitation

Citrobacter freundii was grown aerobically in a chemostat on a mineral medium witn galactose or glucose as carbon and energy sources under limitation by carbon or nitrogen source respectively. At various specific growth rates ranging from 7 to 95% μ_max the culture in steady state was analysed and growth yield, specific metabolic rate of substrate utilization, intracellular concentration of pyruvate, ATP, ADP, AMP and energy charge were determined and plotted as functions of dilution rate. In all four types of experiments the physiological state of cells remained practically independent of dilution rate up toD = 0.6 μ_max, and at a given specific growth rate nearly independent on μ_max and type of limitation. At approximatelyD = 0.6 μ_max, which is close to the maximum output dilution rateD _m, the physiological state of the cells changed: growth yields decreased and intr cellular pyruvate and adenylates concentrations increased. Consequently, in a given medium two dilution rates exist at which growth rate dx/dt is the same but the physiology of the population is quite different.     

Regulation of hypoxanthine transport in Neurospora crassa.

Hypoxanthine uptake and hypoxanthine phosphoribosyltransferase activity (EC 2.4.2.8) were determined in germinated conidia from the adenine auxotrophic strains ad-1 and ad-8 and the double mutant strain ad-1 ad-8. The mutant strain ad-1 appears to lack aminoimidazolecarboximide ribonucleotide formyltransferase (EC 2.1.2.3) or inosine 5'monophosphate cyclohydrolase (EC 3.5.1.10) activities, or both, whereas the ad-8 strain lacks adenylosuccinate synthase activity (EC 6.3.4.4). Normal (or wild-type) hypoxanthine transport capacity was found to the ad-1 conidia, whereas the ad-8 strains failed to take up any hypoxanthine. The double mutant strains showed intermediate transport capacities. Similar results were obtained for hypoxanthine phosphoribosyl-transferase activity assayed in germinated conidia. The ad-1 strain showed greatest activity, the ad-8 strain showed the least activity, and the double mutant strain showed intermediate activity levels. Ion-exchange chromatography of the growth media revealed that in the presence of NH+/4, the ad-8 strain excreted hypoxanthine or inosine, the ad-1 strain did not excrete any purines, and the ad-1 ad-8 double mutant strain excreted uric acid. In the absence of NH+/4, none of the strains excreted any detectable purine compounds.     

土壤水分条件对克隆植物互花米草表型可塑性的影响

在互花米草草滩挖掘沙蚕是海岸带常见的行为,会造成土壤结构松散,蓄水能力下降,局部土壤水分含量低.能否利用这些条件,降低互花米草种群的入侵性,并进而对互花米草的控制提供对策是一个重要的生态学命题.为此,实验模拟3种不同土壤蓄水条件,并测定互花米草在该条件下的形态与存活指标、克隆特征参数及生物量积累与分配格局.结果表明:土壤水分条件对互花米草的叶长和根状茎生物量均没有显著影响(p> 0.05);而其株高、分枝强度、克隆存活数、克隆存活率及地上生物量在各土壤水分条件间差异显著(p< 0.05);在低水分条件下,互花米草的芽数、基茎粗、地上生物量比和叶生物量比均显著低于其他两组处理(p< 0.05),地下生物量比则显著高于其他两组处理(p< 0.05);在中等水分条件下,互花米草的根状茎长、根状茎节数、地下生物量和茎生物量比与其他两组处理差异不显著(p> 0.05),而在其他两组处理间差异显著(p< 0.05);在高水分条件下,总生物量、茎生物量和根生物量显著高于其他两组处理(p< 0.05),根状茎生物量比则显著低于其他两组处理(p< 0.05),而这些指标在其他两组处理间均差异不显著(p> 0.05).由此推断,土壤水分条件适中有利于互花米草的生长扩张以占领有利的资源环境,而土壤水分条件低则抑制互花米草的生长繁殖,影响其种群延续.     

Distinct basolateral amygdala excitatory inputs mediate the somatosensory and aversive-affective components of pain

Pain is a multidimensional perception that includes unpleasant somatosensory and affective experiences; however, the underlying neural circuits that mediate different components of pain remain elusive. Although hyperactivity of basolateral amygdala glutamatergic (BLA^Glu) neurons is required for the somatosensory and emotional processing of pain, the precise excitatory inputs to BLA^Glu neurons and their roles in mediating different aspects of pain are unclear. Here, we identified two discrete glutamatergic neuronal circuits in male mice: a projection from the insular cortex glutamatergic (IC^Glu) to BLA^Glu neurons, which modulates both the somatosensory and affective components of pain, and a projection from the mediodorsal thalamic nucleus (MD^Glu) to BLA^Glu neurons, which modulates only the aversive-affective component of pain. Using whole-cell recording and fiber photometry, we found that neurons within the IC→BLA and MD→BLA pathways were activated in mice upon inflammatory pain induced by injection of complete Freund’s adjuvant (CFA) into their paws. Optical inhibition of the IC^Glu→BLA pathway increased the nociceptive threshold and induced behavioral place preference in CFA mice. In contrast, optical inhibition of the MD^Glu→BLA pathway did not affect the nociceptive threshold but still induced place preference in CFA mice. In normal mice, optical activation of the IC^Glu→BLA pathway decreased the nociceptive threshold and induced place aversion, while optical activation of the MD^Glu→BLA pathway only evoked aversion. Taken together, our results demonstrate that discrete IC^Glu→BLA and MD^Glu→BLA pathways are involved in modulating different components of pain, provide insights into its circuit basis, and better our understanding of pain perception.     

Spatiotemporal spread of Plasmodium falciparum mutations for resistance to sulfadoxine-pyrimethamine across Africa, 1990–2020

BackgroundSulfadoxine-pyrimethamine (SP) is recommended in Africa in several antimalarial preventive regimens including Intermittent Preventive Treatment in pregnant women (IPTp), Intermittent Preventive Treatment in infants (IPTi) and Seasonal Malaria Chemoprevention (SMC). The effectiveness of SP-based preventive treatments are threatened in areas where Plasmodium falciparum resistance to SP is high. The prevalence of mutations in the dihydropteroate synthase gene (pfdhps) can be used to monitor SP effectiveness. IPTi-SP is recommended only in areas where the prevalence of the pfdhps540E mutation is below 50%. It has also been suggested that IPTp-SP does not have a protective effect in areas where the pfdhps581G mutation, exceeds 10%. However, pfdhps mutation prevalence data in Africa are extremely heterogenous and scattered, with data completely missing from many areas.Methods and findingsThe WWARN SP Molecular Surveyor database was designed to summarize dihydrofolate reductase (pfdhfr) and pfdhps gene mutation prevalence data. In this paper, pfdhps mutation prevalence data was used to generate continuous spatiotemporal surface maps of the estimated prevalence of the SP resistance markers pfdhps437G, pfdhps540E, and pfdhps581G in Africa from 1990 to 2020 using a geostatistical model, with a Bayesian inference framework to estimate uncertainty. The maps of estimated prevalence show an expansion of the pfdhps437G mutations across the entire continent over the last three decades. The pfdhps540E mutation emerged from limited foci in East Africa to currently exceeding 50% estimated prevalence in most of East and South East Africa. pfdhps540E distribution is expanding at low or moderate prevalence in central Africa and a predicted focus in West Africa. Although the pfdhps581G mutation spread from one focus in East Africa in 2000, to exceeding 10% estimated prevalence in several foci in 2010, the predicted distribution of the marker did not expand in 2020, however our analysis indicated high uncertainty in areas where pfdhps581G is present. Uncertainty was higher in spatial regions where the prevalence of a marker is intermediate or where prevalence is changing over time.ConclusionsThe WWARN SP Molecular Surveyor database and a set of continuous spatiotemporal surface maps were built to provide users with standardized, current information on resistance marker distribution and prevalence estimates. According to the maps, the high prevalence of pfdhps540E mutation was to date restricted to East and South East Africa, which is reassuring for continued use of IPTi and SMC in West Africa, but continuous monitoring is needed as the pfdhps540E distribution is expanding. Several foci where pfdhps581G prevalence exceeded 10% were identified. More data on the pfdhps581G distribution in these areas needs to be collected to guide IPTp-SP recommendations. Prevalence and uncertainty maps can be utilized together to strategically identify sites where increased surveillance can be most informative. This study combines a molecular marker database and predictive modelling to highlight areas of concern, which can be used to support decisions in public health, highlight knowledge gaps in certain regions, and guide future research.     

Local Recurrence of Soft Tissue Sarcoma Revisited: Is there a Role for “Selective” Radiation?

BackgroundRadiation therapy (RT) is often utilized in cases of high-grade soft tissue sarcoma (STS), but there remain situations where treatment is with surgical excision alone. Our goals were to determine (1) the local recurrence (LR) rate with and without perioperative RT and (2) associations between local recurrence, patient, tumor, and treatment variables.MethodsWe performed a retrospective review of 165 consecutive STS patients. A Cox proportional hazards model was used to investigate variables associated with local recurrence.ResultsLR occurred in 15/78 (19%) without RT, 4/29 (14%) with postoperative RT, and 0/58 with preoperative RT (p=0.002). We found increased rates of local recurrence at 24 months for myxofibrosarcoma (p=0.001) and no-RT (p=0.003). Myxofibrosarcoma accounted for 33 (20%) of the study patients and 12 (63%) of the local recurrences.ConclusionThe LR rate in patients treated with surgery alone was disproportionately attributable to myxofibrosarcoma (11/23 cases, 48%). Other subtypes demonstrated a lower rate of LR in the absence of RT (4/55 cases, 7%), and no LR occurred when final margins were >2 mm. In certain circumstances treatment with a negative margin surgical resection followed by close observation is justifiable. RT is effective and should continue to be considered routinely in myxofibrosarcoma or when surgical margins are inadequate. Level of Evidence: III     

Developing outcome measures for pediatric mitochondrial disorders: Which complaints and limitations are most burdensome to patients and their parents?

Since some drug intervention effects are only experienced by the patient, organizations such as the Food and Drug Administration prefer clinically meaningful outcome measures. Here, we evaluated which symptoms and limitations in daily life are most burdensome to pediatric patients with mitochondrial disorders and their parents, using two questionnaires. In a study of 78 patients, the most burdensome complaints included fatigue, behavior and speech disturbances, epilepsy and muscle weakness and a high degree of limitations in daily activities was found. Importantly, there was a discrepancy between what symptoms metabolic pediatricians estimated would be most burdensome compared to the patients'/caretakers' opinion. To include feasible and relevant outcome measures in intervention studies, the experience and opinions of patients and caretakers should therefore be heard.     

Chemical composition of the Tatra Mountain lakes: Recovery from acidification

Ninety-one lakes distributed along the Tatra Mountains (most of lakes > 1 ha and 65% of lakes > 0.01 ha) were sampled and analysed for ionic and nutrient composition in September 2004 (15 years after reduction in acid deposition). Eighty-one lakes were in alpine zone and ten lakes in Norway spruce forest. The results were compared to similar lake surveys from 1994 (the beginning of water recovery from acidification) and 1984 (maximum acidification). Atmospheric deposition of SO ₄ ^2? and inorganic N decreased 57% and 35%, respectively, in this region from the late 1980s to 2000. Lake water concentrations of SO ₄ ^2? and NO ₃ ^? have decreased both by ～50% on average (to 23 and 19 μmol L^?1, respectively, in 2004) since 1984. While the decrease in SO ₄ ^2? concentrations was stable throughout 1984–2004, most of the NO ₃ ^? decrease occurred from 1994 to 2004. The declines in SO ₄ ^2? and NO ₃ ^? concentrations depended on catchment coverage with vegetation, being most rapid for SO ₄ ^2? in forest lakes and for NO ₃ ^? in rocky lakes. Concentrations of the sum of base cations (dominated by Ca²⁺) significantly decreased between 1984 and 2004, with the highest change in rocky lakes. Most of this decline occurred between 1994 and 2004. Acid neutralising capacity (ANC) did not change in the 1984–1994 period, but increased on average by 29 μmol L^?1 between 1994 and 2004, with the highest change in rocky lakes. Over the last decade, the proportion of lakes with ANC > 150 μmol L^?1 increased from 15% to 21% and that of ANC < 20 μmol L^?1 decreased from 37% to 20%. The highest decline in H⁺ and Al concentrations occurred in the most acid lakes. On a regional basis, no significant change was observed for total phosphorus, total organic nitrogen, and dissolved organic carbon (DOC) in the 1994–2004 period. However, these parameters increased in forest lakes, which exhibited an increasing trend in DOC concentrations, inversely related (P < 0.001) to their decreasing ionic strength (30% on average in 1994–2004).     

人胃癌BGC-823细胞中去甲斑蝥素抑癌作用机理的蛋白质组学研究

去甲斑蝥素是我国自行研制的抗肿瘤药物,在临床上主要用于消化道肿瘤的治疗．实验表明,去甲斑蝥素可引起人胃癌BGC-823细胞发生 M期阻滞及细胞凋亡．进一步利用双向电泳和质谱技术,筛选出了去甲斑蝥素抑癌作用相关蛋白．研究显示,线粒体热休克蛋白CH60、线粒体ATP合酶d亚单位、内质网葡萄糖调节蛋白GRP78、线粒体Hsp70的辅助因子GRPE1、SH3L3以及染色质组装因子1小亚基RBBP4参与了去甲斑蝥素的抑癌作用．研究提示,去甲斑蝥素可能通过促进线粒体热休克蛋白及p53的表达进而激活caspase-3依赖的凋亡通路,并且去甲斑蝥素在引发内质网协迫之后,可通过抑制胞外信号调节激酶(extracellular signal regulated kinase, ERK)的活性促进肿瘤细胞的凋亡．进一步分析了去甲斑蝥素与线粒体ATP合酶抑制剂寡霉素A的联合用药对人胃癌细胞生长的影响,结果表明,联合用药的抑瘤效果比单独用药的抑瘤效果显著,提示去甲斑蝥素可能通过抑制线粒体ATP合酶功能抑制BGC-823生长．上述结果为优化去甲斑蝥素的联合用药方案提供了新线索．