Phenanthrene degradation by estuarine surface microlayer and bulk water microbial populations

Paired surface microlayer and bulk water samples from five sites in the Great Bay Estuary, New Hampshire, were examined with regard to numbers of bacteria,¹⁴C-phenanthrene biodegradation potentials, and organic and inorganic chemical characteristics. Microlayer samples were generally enriched in nutrients (N and P), dissolved organic matter, and culturable heterotrophic bacteria compared with their corresponding bulk waters. Microlayer samples from marina environments were also enriched in aromatic hydrocarbons, as determined by UV spectrophotometric and fluorometric analyses, and demonstrated substantial phenanthrene biodegradation activity in the assay employed. Biodegradation activity of marina bulk water samples ranged from nil to levels exceeding those exhibited by microlayer samples. No diminution of biodegradation activity was observed after filtration (1.2 m effective retention) of microlayer water, indicating that the responsible organisms were not particle-associated. Phenanthrene-degrading bacteria, enumerated by counting clearing zones in a crystalline phenanthrene overlay after colony development on a phenanthrene/toluene agar (PTA) medium, were superior to epifluorescence direct counts or standard plate counts on PTA or estuarine nutrient agar in predicting¹⁴C-phenanthrene biodegradative activity.     

A new method for thawing frozen ram semen

The purpose of this work was to facilitate the on-farm use of frozen semen by initially thawing the straws in laboratory treated sperm (TS) rather than on-farm control sperm (CS), as is usually done. After thawing, TS was diluted, centrifuged, and extended in skim milk for storage at +15° C until utilized 3 to 6 hours later. $\text{In}$$\text{vitro}$: immediately after preparation and addition of skim milk for TS and thawing for CS, the percentage of stained cells and abnormal cells was higher (P < 0.01) in TS than in CS. In contrast, following a 3 hour incubation, TS and CS had the same proportion of motile cells. $\text{In}$$\text{vivo}$: fertility and prolificacy of FGA + PMSG-treated ewes were slightly higher following AI (1 AI/female) with TS than with CS: 52.4% $\text{vs}$ 44.2% and 155.0% $\text{vs}$ 148.0%, respectively. Fertility was also higher (P < 0.01) with fresh semen than with TS, but the difference was only 9.2 points (70.3% $\text{vs}$ 61.1% for the respective 798 and 242 ewes inseminated once). Prolificacy rates were similar (164.3% $\text{vs}$ 167.6%).     

Differential bioavailability of soil-sorbed naphthalene to two bacterial species.

Prediction of the fate of hydrophobic organic contaminants in soils is complicated by the competing processes of sorption and biodegradation. To test the hypothesis that sorbed naphthalene is unavailable to degradative microorganisms, we developed a simple kinetic method to examine the rates and extents of naphthalene degradation in soil-free and soil-containing systems in a comparison of two bacterial species. The method is predicated on the first-order dependence of the initial mineralization rate on the naphthalene concentration when the latter is below the Michaelis-Menten half-saturation constant (Km) for naphthalene for the organism under study. Rates and extents of mineralization were estimated by nonlinear regression analysis of data by using both a simple first-order model and a three-parameter, coupled degradation-desorption model described for the first time here. Bioavailability assays with two bacterial species (Pseudomonas putida ATCC 17484 and a gram-negative soil isolate, designated NP-Alk) gave dramatically different results. For NP-Alk, sorption limited both the rate and extent of naphthalene mineralization, in accordance with values predicted on the basis of the equilibrium aqueous-phase naphthalene concentrations. For strain 17484, both the rates and extents of naphthalene mineralization exceeded the predicted values and resulted in enhanced rates of naphthalene desorption from the soils. We conclude that there are important organism-specific properties which make generalizations regarding the bioavailability of sorbed substrates inappropriate.     

茎花葱臭木化学成分的研究

从茎花葱臭木种子中分离得到5个化合物,经理化与波谱分析鉴定为β-谷甾醇(1)、没食子酸乙酯(2)、胡萝卜苷(3)、1-O-β-D-吡喃葡萄糖基-(2S,3S,4R,8Z)-2-N-(2 ′-羟基二十四烷酰氨基)十八二氧鞘氨-8-烯(4)和2,3,2″,3″-四氢穗花杉双黄酮(5).这5个化合物均首次从该植物中分离得到.其中化合物5进行细胞毒活性测试,没有显示抑制活性.     

植物丝氨酸/精氨酸丰富(SR)蛋白的结构和功能及其在植物发育中的作用

丝氨酸／精氨酸丰富（SR）蛋白家族是真核生物中的一类剪接因子,在前体mRNA的组成性和选择性剪接中起作用。本文就近十几年来SR蛋白结构和功能及其在植物发育中的作用的研究进展作以介绍。     

川芎嗪对Aβ25-35诱导体外大鼠海马神经元细胞凋亡的影响

本文通过Aβ25-35诱导体外原代培养的SD乳大鼠海马神经元,建立Aβ毒性损伤细胞模型,结合AnnexinV-FITC/PI荧光双染法流式细胞术、MTT比色法、实时荧光定量PCR及Western blot方法检测川芎嗪(tetrameth-ylpyrazine,TMP)对原代培养的海马神经元细胞活性、早期凋亡率和Bax、Bcl-2基因表达的影响。结果显示川芎嗪高、中剂量可明显增强细胞活性,增加神经元细胞的存活率(P<0.01),可显著抑制海马神经元细胞早期凋亡(P<0.01),抑制凋亡蛋白Bax的表达(P<0.01),增强抗凋亡蛋白bcl-2的表达(P<0.01)。川芎嗪可通过调节Bax/Bcl-2平衡抵抗Aβ25-35诱导的海马神经元凋亡,降低Aβ的神经元毒性,对海马神经元损伤有明显的保护作用。     

New mutants resistant to glucose repression affected in the regulation of the NADH reoxidation

Spontaneous mutants resistant to vanadate, arsenate or thiophosphate were isolated from a haploid strain of Saccharomyces cerevisiae. These three anions have an inhibitory effect on some mitochondrial functions and at the level of glyceraldehyde 3-phosphate dehydrogenase, a glycolysis enzyme. All the selected mutants had the same phenotype: they were deficient in alcohol dehydrogenase I, the terminal enzyme of the glycolysis, and possessed a high content of cytochrome c oxidase, the terminal enzyme of the respiratory chain. Moreover, cytochrome c oxidase biosynthesis had become insensitive to the catabolite repression, while the biosynthesis of the other enzymes sensitive to this phenomenon were always inhibited by glucose. Metabolic effects of this pleiotropic mutation manifested themselves in the following ways. 1. Growth rate and final cell mass were enhanced, compared to the wild type, when cells were grown on glucose or on glycerol, but not on lactate or ethanol. 2. Growth under anaerobiosis was nil and mutants did not ferment. 3. Mitochondrial respiration of the mutant strains was identical to the wild type with succinate or 2-oxo-glutarate as substrate, and weak with ethanol. But with added NADH, respiration rate of the mutants was higher than that of the wild type and partially insensitive to antimycin, even when cells were grown in repression conditions. It is postulated that in mutants strains, NADH produced at the level of glyceraldehyde 3-phosphate dehydrogenase, failing to be reoxidized via alcohol dehydrogenase, could be reoxidized with a high turnover owing to the enhancement of the amount of cytochrome c oxidase. Since NADH reoxidation is partially insensitive to antimycin, a secondary pathway going from external NADH dehydrogenase to cytochrome c oxidase is suggested.     

Neurophysiological and behavioural evidence for an olfactory function for the dorsal organ and a gustatory one for the terminal organ in Drosophila melanogaster larvae

Multicellular electrophysiological responses from the dorsal organ on the cephalic lobes of third instar Drosophila melanogaster larvae (wild-type Canton S) stimulated with a cold-trapped banana volatile extract showed that this structure has an olfactory function in the fruit fly. Responses of the dorsal organ were also recorded to constituents of the banana volatile extract as they eluted from a gas chromatographic column (GC-coupled dorsal organ electrophysiology). The active chemostimulants were identified as 2-heptanone, isoamyl alcohol, hexyl acetate, hexanol and hexyl butyrate by gas chromatography-coupled mass spectrometry. Applying the same recording system to the terminal organ sensilla, no responses were obtained to either the banana volatile bouquet or its constituents. By contrast, high frequency multicellular responses were recorded in response to touching the terminal organ with the gustatory stimuli KCl and grapefruit juice; responses were absent on similar stimulation of the dorsal organ with either NaCl or KCl. This suggests a role for olfaction by the dorsal organ and for gustation by the terminal organ in Drosophila larvae.In a 7-mm high wind tunnel with a thin 1.2% agar floor, the Drosophila larvae showed odour-conditioned upwind responses in an air stream of 0.1 m/s bearing banana volatiles. Drosophila larvae responded best to the odour of cut bananas. A 1:1 mixture of the banana odour constituents 2-heptanone and hexanol (at either 50 or 100 &mgr;g source dose each) proved as attractive as the known larval attractants propionic acid and isoamyl acetate on their own at 100 &mgr;g, whereas hexanol and 2-heptanone on their own at a 100 &mgr;g source dose were less attractive. The stronger behavioural response to the banana volatile bouquet and to the binary mixture serves to underline the multireceptor nature of the dorsal organ response to food odour in Drosophila.