No sex-specific differences in the influence of high air temperatures during early development on nestling mass and fledgling survival in the Southern Pied Babbler (Turdoides bicolor)

Sex-biased mortality in response to environmental adversity during early development occurs in a number of bird species. The three most prominent theories proposed to explain sex-biased mortality in response to early-life adversity are that (1) the heterogametic sex (e.g. females in birds), (2) the larger sex (could be male or female depending on species) or (3) the sex with the more costly and complex endocrine system (e.g. males producing higher levels of testosterone) will suffer higher mortality compared with the other sex when exposed to challenging conditions (e.g. suboptimal weather during early development). We tested for sex-specific differences in the effects of very hot weather on nestling body mass and tarsus length, and survival of fledglings to nutritional independence in the Southern Pied Babbler Turdoides bicolor. The effect of exposure to high air temperatures did not differ by sex but had a consistently negative impact on nestling body mass, nestling tarsus length and fledgling survival, raising concerns about population replacement and the persistence of this species under rapidly advancing climate change.     

低温下阻遏蛋白MogR对单增李斯特菌鞭毛形成的影响

【目的】单核细胞增生李斯特菌(简称单增李斯特菌) (Listeria monocytogenes, Lm)是食源性病原菌,可以引发李斯特菌病(listeriosis)。Lm能在低温下生长,对冷藏食品的安全构成严重威胁,并对人类健康造成潜在的危害。Lm能低温生长与抑制鞭毛基因表达以减少鞭毛的合成有关。MogR是Lm鞭毛基因转录的阻遏蛋白,在机体里或37 ℃环境下具有阻遏作用,Lm不产生鞭毛;然而,当Lm处于20-0 ℃时MogR无阻遏作用,Lm产生鞭毛。我们研究发现在4 ℃生长条件下Lm鞭毛合成减少,但具体的分子机制尚未明确。本文探究在4 ℃下Lm鞭毛合成少与MogR起阻遏作用的关系。【方法】以Lm ATCC 19115为亲本株,分别构建了MogR和鞭毛丝蛋白FlaA的缺失株ΔmogR和ΔflaA (作为无鞭毛对照株)及其回补株cΔmogR和cΔflaA,测定了菌株在4、28、37 ℃时的运动性、鞭毛产生情况和鞭毛基因表达量,并对所构建的菌株进行了4、28、37 ℃时生长曲线的测定。【结果】在4 ℃时,mogR缺失后,菌株运动性显著强于亲本株(P<0.01),鞭毛合成量显著多于亲本株(P<0.001),鞭毛基因转录水平显著高于亲本株(P<0.001);缺失株ΔmogR的生长能力显著弱于亲本株(P<0.05)。回补株cΔmogR的运动能力、鞭毛合成量和鞭毛基因转录水平与亲本株相比,无显著性差异。【结论】在4 ℃时,Lm鞭毛产量少与MogR对鞭毛基因起转录抑制作用有关,低温条件下Lm能生长繁殖与MogR对鞭毛基因表达的抑制作用有关。本研究结果为揭示Lm低温生长机制提供了新的信息。     

油蒿与中国和以色列沙漠中的两种蒿属植物种子萌发策略的比较

油蒿（Ａｒｔｅｍｉｓｉａ ｏｒｄｏｓｉｃａ Ｋｒａｓｃｈ．）是中国戈壁荒漠的固定沙丘上分布的优势种灌木,属蒙古植被地理分布区成分。油蒿的瘦果在光下萌发,萌发在暗中受到抑制光是调节其在沙土不同深度萌发的限制因素。瘦果在春天或秋天萌发,适宜温度为２０℃。瘦果的粘淮物质能吸收大量水分,具有重要的生态功能。不同浓度的盐溶液能影响瘦果的萌发。土壤湿度也是调节瘦果在沙中萌发的因素。尽管油蒿、白沙蒿（Ａ．ｓｐｈ     

Laboratory studies on aestivation in the cabbage root fly (Delia radicum)

Laboratory experiments at 16°–30°C showed that the cabbage root fly can only be induced into aestivation during the early part of the pupal stage. The relationship between the percentage of pupae entering aestivation (y) and the average daily temperature (T) was the same under both constant and alternating temperatures. The percentage of pupae entering aestivation at a particular temperature was given by y=13T–255. An additional 13% of the pupae entered aestivation for each degree rise between 20° and 27°C. There was no constant period of arrested development following the induction of aestivation. Aestivating pupae started to develop into flies as soon as the temperature fell below 20°C. The reinduction of aestivation occurred more readily than the initial induction. Insect survival was not reduced after a month of aestivation. The effects of aestivation on forecasting the time of the second (summer) generation of flies are discussed.

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Étude au laboratoire de l'estivation de la mouche du Chou (Delia radicum)

Résumé Au laboratoire, à 10°–30°C, l'induction de l'estivation ne peut être obtenue qu'avec des pupes formées depuis peu.Le rapport pourcentage de pupes entrant en estivation (y) température journalière moyenne (T) a été le même, que la température soit constante ou alternée. La relation entre la température et ce pourcentage est donnée par y=13 T–255. Le pourcentage de pupes entrant en estivation a augmenté de 13% pour chaque élévation d'un degré entre 20° et 27°C. L'estivation une fois induite, la période d'arrêt de développement n'est pas constante. Dès que la température est devenue inférieure à 20°C, la formation d'imagos a commencé dans les pupes en estivation. Une nouvelle estivation a été plus facile à provoquer que l'estivation initiale. Le taux de survie des insectes n'avait pas diminué après un mois d'estivation. La discussion examine l'utilisation des conséquences de l'estivation dans la prédiction de la seconde génération d'adultes: génération d'été.

     

Differential response of fourTrichogramma species to low temperatures for short term storage

Differential response was noticed when 4 species ofTrichogramma egg parasitoids were stored at 2°, 5° and 10°C for 7 to 49 days. Pupal stage was found to be most appropriate for storage. Emergence ofTrichogramma achaeae Nagaraja and Nagarkatti andTrichogrammatoidea eldanae Viggiani was greater in comparison toTrichogramma chilonis Ishii andTrichogramma japonicum Ashmead at all 3 temperature regimes. Fecundity and longevity declined drastically after storage of 14 days at 2° and 5°C and 21 days at 10°C, when removed to room temperature. 10°C was found to be the best temperature for storage up to 49 days. Contribution No. 51004 of Biological Control Centre (NCIPM), Bangalore.     

Effect of reduced temperatures and brefeldin A on prolactin secretion and on subcellular distribution of the secretory product and membrane antigens in GH3 pituitary cells.

The effects of reduced temperatures (20, 15 or 10 degrees C) and brefeldin A (BFA) on prolactin (PRL) secretion in the GH3 rat pituitary cell line have been compared. Both treatments inhibit PRL release to different extents. Ultrastructural immunocytochemistry reveals that, depending on the treatment, PRL is blocked at different steps during its intracellular transit. The temperatures of 20 and 15 degrees C block the PRL transport at one face of the Golgi stacks whereas both the temperature of 10 degrees C and BFA treatment induce an arrest of PRL at the level of the rough endoplasmic reticulum (RER) cisternae. Moreover, exposure to 10 degrees C or BFA induces an accumulation of a specific Golgi membrane antigen in the dilated RER structures. However, although disorganized and no longer definable under BFA treatment, the Golgi apparatus remains visible at 10 degrees C. These two last treatments cause also an increase in the number of partly rough, partly smooth tubular structures tentatively called 'paired cisternae'.     

Effects of constant and fluctuating temperature on time to budburst in Betula pubescens and its relation to bud respiration

 Effects of fluctuating and constant temperatures on budburst time, and respiration in winter buds were studied in Betula pubescens Ehrh. Dormant seedlings were chilled at 0°C for 4 months and then allowed to sprout in long days (LD, 24 h) at constant temperatures of 6, 9, 12, 15, 18 and 21°C, and at diurnally fluctuating temperatures (12/12 h, LD 24 h) with means of 9, 12, 15 and 18°C. No difference in thermal time requirements for budburst was found between plants receiving constant and fluctuating temperatures. The base temperature for thermal time accumulation was estimated to 1°C. Respiration in post-dormant (dormancy fully released) excised winter buds from an adult tree increased exponentially with temperature and was 20 times as high at 30°C than at 0°C. However, respiration in buds without scales was 30% higher at 0°C, and it was 2.7 times higher at 24°C than in intact buds. Thus, the tight bud scales probably constrain respiration and growth and are likely to delay budburst in spring. Arrhenius plots of the respiration data were biphasic with breaks at 13–15°C. However, this phase transition is unlikely to be associated with chilling sensitivity since the present species is hardy and adapted to a boreal climate. Received: 10 January 1997 / Accepted: 23 June 1997     

Lateral phase separations in Escherichia coli membranes

Membranes from unsaturated fatty acid auxotrophs of Escherichia coli were studied by spin labeling and freeze-fracturing. From measurements of the partition of the spin label TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) between the aqueous phase and fluid lipids in isolated membranes, temperatures, corresponding to the onset and completion of a lateral phase separation of the membrane phospholipids were determined. By freeze-fracture electron microscopy a change in the distribution of particle in the membrane was observed around the temperature of the onset of the lateral phase separation. When cells were frozen from above that temperature a netlike distribution of particles in the plasma membrane was observed for unfixed preparations. When frozen after fixing with glutaraldehyde the particle distribution was random. In membranes of cells frozen with or without fixing from a temperature below the onset of the phase separation, the particles were aggregated and large areas void of particles were present. This behavior can be understood in terms of the freezing rate with the aid of phase diagrams.     

Skin temperatures at the nape in infants at high altitude.

Skin temperatures were measured on three Quechua Indian infants resident at 4,000 meters above sea level in Peru. Nape temperatures were warmer than other skin sites, suggesting that the brown adipose tissue associated with non-shivering thermogenesis is metabolically active despite the reduced oxygen availability at high altitude. The question of the role of non-shivering thermogenesis in infant thermoregulation under the covariant stresses of hypoxia and cold is still open.     

Temperature Effects on Reproduction and Pathogenicity of Pratylenchus coffeae and P. brachyurus and Survival of P. coffeae in Roots of Citrus jambhiri

Optimum temperature for reproduction of Pratylenchus coffeae on Rough lemon, Citrus jambhiri Lush. was 29.5 C. Pratylenchus coffeae populations reached 7653 per g of root 2 months after initial inoculation with 140 nematodes. Maximum plant weight reduction was 38%; root weights were reduced by as much as 47%. Pratylenchus brachyurus significantly reduced plant and root weights but population sizes never approached those of P. coffeae. Pratylenchus coffeae survived in stored excised roots and were still infective after 4 months at temperatures ranging from 4.5 to 32 C.