Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Antibacterial activity of Turkish propolis and its qualitative and quantitative chemical composition

The antibacterial activity of propolis from different regions of Turkey was studied, accompanied by TLC and GC-MS analyses of its chemical composition and spectrophotometric quantification of the most important active principles. All six samples were active against the bacterial test strains used; however, samples 1 (Yozgat), 2 (Izmir) and 3 (Kayseri) were more active than samples 4 (Adana), 5 (Erzurum) and 6 (Artvin). By TLC comparison all samples were found to contain poplar taxonomic markers but in samples 4 (Adana), 5 (Erzurum) and 6 (Artvin), different substances were observed, which were not present in P. nigra L. bud exudate. The typical poplar samples 1 (Yozgat), 2 (Izmir) and 3 (Kayseri) displayed very similar phenolic and flavonoid content. Samples 4 (Adana), 5 (Erzurum) and 6 (Artvin) were characterized by low phenolic and very low flavonoid concentrations. Qualitative analysis by GC-MS revealed that sample 4 (Adana) contained diterpenic acids and high percent of cinnamyl cinnamate, sample 5 (Erzurum)-significant amounts of hydroxy fatty acids and triterpenic alcohoLs, and sample 6 (Artvin)-phenolic glycerides, characteristic for the bud exudate of Populus euphratica Oliv. The results confirm the importance of phenolics for propolis antibacterial activity, and the significance of P. nigra L. as a propolis source, which provides the hive with the best defense against microorganisms.     

Summer stream habitat partitioning by sympatric Arctic charr, Atlantic salmon and brown trout in two sub-arctic rivers

Summer habitat use by sympatric Arctic charr Salvelinus alpinus, young Atlantic salmon Salmo salar and brown trout Salmo trutta was studied by two methods, direct underwater observation and electrofishing, across a range of habitats in two sub-arctic rivers. More Arctic charr and fewer Atlantic salmon parr were observed by electrofishing in comparison to direct underwater observation, perhaps suggesting a more cryptic behaviour by Arctic charr. The three species segregated in habitat use. Arctic charr, as found by direct underwater observation, most frequently used slow (mean ±s .d . water velocity 7·2 ± 16·6 cm s⁻¹) or often stillwater and deep habitats (mean ±s .d . depth 170·1 ± 72·1 cm). The most frequently used mesohabitat type was a pool. Young Atlantic salmon favoured the faster flowing areas (mean ±s .d . water velocity 44·0 ± 16·8 cm s⁻¹ and depth 57·1 ± 19·0 cm), while brown trout occupied intermediate habitats (mean ±s .d . water velocity 33·1 ± 18·6 cm s⁻¹ and depth 50·2 ± 18·0 cm). Niche overlap was considerable. The Arctic charr observed were on average larger (total length) than Atlantic salmon and brown trout (mean ±s .d . 21·9 ± 8·0, 10·2 ± 3·1 and 13·4 ± 4·5 cm). Similar habitat segregation between Atlantic salmon and brown trout was found by electrofishing, but more fishes were observed in shallower habitats. Electrofishing suggested that Arctic charr occupied habitats similar to brown trout. These results, however, are biased because electrofishing was inefficient in the slow-deep habitat favoured by Arctic charr. Habitat use changed between day and night in a similar way for all three species. At night, fishes held positions closer to the bottom than in the day and were more often observed in shallower stream areas mostly with lower water velocities and finer substrata. The observed habitat segregation is probably the result of interference competition, but the influence of innate selective differences needs more study.     

Decreased brown adipose tissue thermogenic activity following a reduction in brain serotonin by intraventricular p-chlorophenylalanine

The effects of reducing brain serotonin (5-HT) levels by means of intracerebral-ventricular injections of the tryptophan antagonist p-chlorophenylalanine (PCPA) were investigated in male rats. Six days after the operation, PCPA-treated rats, either fedad libitum or pair-fed to the food intake of control rats, showed decreased thermogenic activity and capacity in their interscapular brown adipose tissue (BAT) and also increased fat storage in their white adipose tissue (WAT). These results indicate that serotonergic synapses might play a regulatory role in the sympathetic control of BAT thermogenesis and in the rate of WAT deposition (by an as yet unidentified mechanism), in addition to their well established role in controlling food intake.     

Effect of noradrenaline chronic administration on brown fat phospholipids

Chronic cold exposure of rats (9 days at 5°C) induces an alteration of the fatty acid composition of phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree of these lipids. The phenomenon can be reproduced by 10^–7 mole. h^–1 administration of noradrenaline for 9 days in rats kept at 25°C. Thus, phospholipid alteration in brown fat of cold exposed rats is most probably a consequence of the increase of sympathetic tone which occurs in this tissue during exposure to cold.     

Chromium in plants

Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance. For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared to 0.5–1.5 μg/g).     

Amino acid increases in fruit infested by fruit flies of the family Tephritidae

Solanum mauritianum Scop, (wild tobacco) fruit is the major host of the fruit fly Dacus cacuminatus (Hering), and is a major source of food for the brown pigeon Macropygia phasianella (Temminck) in eastern Queensland. Amino acid analyses were undertaken on fruit fly infested and uninfested S. mauritianum fruits. Infested fruits contained approximately twice the level of protein and essential amino acids compared to uninfested fruit. This increase is probably due to the plant adding additional amino acids to infested tissue and the accompanying growth of bacteria established in the fruit during oviposition. The infested fruit would provide a valuable source of protein during the pigeon breeding season.     

采后预处理控制甜橙褐斑病的效应

采后预处理使甜橙果皮含水量减少,改善理化性状,降低果实对低温的敏感性,从而控制了福斑病的发生,使发病率从61.7～66.0％降至4.7～6.7％。低温贮藏的呼吸强度和内源乙烯的生成也受到明显的抑制,但对果实的主要内含物和质量并无影响。控制褐斑病发生的适宜的预处理,是在10～15℃和85～90％相对湿度下处理7～10d,使果实重耗约2.5～4.0％。     

对冷适应大鼠棕色脂肪和肝脏在非寒颤产热机制中作用的评价

本实验主要观察并比较了大鼠冷适应前后直肠温度(RT)、血清游离脂肪酸(SFFA)浓度、肩胛间棕色脂肪组织(IBAT)和肝脏cAMP含量的变化及其对去甲肾上腺素(NE)反应性的改变。结果表明:①冷适应28d大鼠在冷环境中RT稳定,NE刺激后RT上升幅度大于常温对照组(P<0.005);②冷适应1d组SFFA升高,冷适应28d组SFFA接近对照组,且对NE刺激无反应,对照组给NE后SFFA与RT一致性升高;③冷适应28d组IBAT的cAMP升高,而肝脏的cAMP含量三组间无显著性差异。NE刺激后,冷适应28d组IBAT和肝脏cAMP均升高,与RT反应一致,而对照组不变。结果提示,在5±3℃适应28d的大鼠已建立冷适应机制,非寒颤产热(NST)容量增加,在冷适应的不同时期,肝脏和IBAT调节NST的机制不同。