Thiotepa, a reliable marker for sperm precedence measurement in a polyandrous moth

The determination of paternity of offspring produced by polyandrous females is essential for the understanding of sperm competition mechanisms. The sterile male technique using radiation is one of the most commonly employed methods for this purpose. However, sterilization using radiation is likely to be restricted by the equipment availability and cost. Chemosterilization may thus be a cheaper and easier alternative for sterilizing male insects in sperm competition studies. Here we report a reliable chemomarker, thiotepa (N,N′,N″-triethylenethiophosphoramide), for the study of sperm competition and precedence in a polyandrous moth, Ephestia kuehniella (Lepidoptera: Pyralidae). Dipping heads of male moths in 1% thiotepa aqueous solution for 10 s resulted in complete sterilization, i.e. their sperm still fertilized eggs but those eggs did not hatch. The sterilization treatment did not significantly affect male copulation ability, female fecundity, and sperm transfer, motility and fertilization. Our results indicate that 86% offspring of the twice-copulated females were fathered by the second males and 14% by the first males. Males treated with 5% thiotepa aqueous solution died within 24 h while those treated with 0.5% thiotepa were not fully sterilized.     

Drainage Size, Stream Intermittency, and Ecosystem Function in a Sonoran Desert Landscape

Understanding the interactions between terrestrial and aquatic ecosystems remains an important research focus in ecology. In arid landscapes, catchments are drained by a channel continuum that represents a potentially important driver of ecological pattern and process in the surrounding terrestrial environment. To better understand the role of drainage networks in arid landscapes, we determined how stream size influences the structure and productivity of riparian vegetation, and the accumulation of organic matter (OM) in soils beneath plants in an upper Sonoran Desert basin. Canopy volume of velvet mesquite (Prosopis velutina), as well as overall plant cover, increased along lateral upland–riparian gradients, and among riparian zones adjacent to increasingly larger streams. Foliar δ¹³C signatures for P. velutina suggested that landscape patterns in vegetation structure reflect increases in water availability along this arid stream continuum. Leaf litter and annual grass biomass production both increased with canopy volume, and total aboveground litter production ranged from 137 g m⁻² y⁻¹ in upland habitat to 446 g m⁻² y⁻¹ in the riparian zone of the perennial stream. OM accumulation in soils beneath P. velutina increased with canopy volume across a broad range of drainage sizes; however, in the riparian zone of larger streams, flooding further modified patterns of OM storage. Drainage networks represent important determinants of vegetation structure and function in upper Sonoran Desert basins, and the extent to which streams act as sources of plant-available water and/or agents of fluvial disturbance has implications for material storage in arid soils.     

间歇升温和热处理对‘紫李’果实采后生理的影响

以美国‘紫李’为试材,测定经间歇升温和热处理后果实的褐变度、抗氧化酶活性、抗氧化剂含量、膜质过氧化水平、总酚和可滴定酸含量的变化。结果表明:间歇升温和热处理可适当恢复因冷害而降低的细胞抗氧化活性,清除活性氧自由基,减少膜脂过氧化产物丙二醛的积累,抑制多酚氧化酶和过氧化物酶活性升高,强化抗低温防御系统,阻止多酚逆境代谢发生,使冷害和褐变症状得以延缓和减轻;同时,还可抑制可滴定酸含量的减少和固酸比的上升,延缓后熟衰老。间歇升温处理,李贮藏两个月果实品质良好。初步认为,-0.5～0℃贮藏,每15 d加温至18～20℃并保持l d,是贮藏美国‘紫李’适宜的变温模式。     

Evaluation of bactericidal effects of low-temperature nitrogen gas plasma towards application to short-time sterilization

To develop a novel low-temperature plasma sterilizer using pure N(2) gas as a plasma source, we evaluated bactericidal ability of a prototype apparatus provided by NGK Insulators. After determination of the sterilizing conditions without the cold spots, the D value of the BI of Geobacillus stearothermophilus endospores on the filter paper was determined as 1.9 min. However, the inactivation efficiency of BI carrying the same endospores on SUS varied to some extent, suggesting that the bactericidal effect might vary by materials of sterilized instruments. Staphylococcus aureus and Escherichia coli were also exposed to the N(2) gas plasma and confirmed to be inactivated within 30 min. Through the evaluation of bactericidal efficiency in a sterilization bag, we concluded that the UV photons in the plasma and the high-voltage pulse to generate the gas plasma were not concerned with the bactericidal effect of the N(2) gas plasma. Bactericidal effect might be exhibited by activated nitrogen atoms or molecular radicals.     

Heat Generation and its Impact on Lamp Fouling During Cheese Whey Sterilization using Ultraviolet Radiation

Summary In previous studies we found that lamp fouling was a major limitation when tubular ultraviolet reactors were used for sterilization of cheese whey over an extended period of time. Heat generation by ultraviolet lamps causes the temperature of the flowing fluid to rise and thus enhances fouling. In this study, the heat generated by a low pressure mercury ultraviolet lamp during continuous sterilization of cheese whey in three tubular reactors having different gap sizes (18, 13 and 6 mm) was calculated using a heat balance formula. The technique quantified the heat produced in and lost from each reactor. The heat balance calculations showed that lamp heat generation decreased with decreasing gap size (50.48, 47.71 and 31.91 kJ/h for 18, 13 and 6 mm gap sizes, respectively). However, the heat gain per unit volume and consequently the steady state temperature of the cheese whey effluent increased with decreasing gap size (91.79, 159.03 and 319.12 kJ/l and 44.5, 53.4 and 62.8 °C for 18, 13 and 6 mm gap sizes, respectively). A strong correlation between the amount of heat gain per unit volume and the amount of fouling material accumulated on the quartz surface was realized. The amount of accumulated fouling material increased with decreasing gap size (14.42, 15.31 and 25.26 g on wet basis for 18, 13 and 6 mm gap sizes, respectively). A new design in which the direct contact between the lamp and the flowing cheese whey is avoided and lamp cooling is introduced should be investigated.     

Modeling incomplete sterility in a sterile release program: interactions with other factors

Models were constructed for control of a pest species by the release of sterile insects and these models explored the consequences of incomplete sterility. This feature was then coupled with the lack of competitive ability of released insects, the immigration of insects from outside the control area, and the mode of population regulation (density independent vs. density dependent). Using the density-independent models, it was seen that the limits on residual fertility of treated insects become much more stringent when incomplete sterilization is combined with a lack of competitive ability and immigration of insects into the control area. Strong density dependence in the system has a marked moderating effect on the requirements for sterility, competitive ability, and immigration. However, if the density-independent limits on these factors are exceeded, then suppression is possible, but collapse of the pest population is impossible using sterile releases alone. Even suppression might not be satisfactory if these three detrimental factors are prominent. It is suggested that one remedy is the use of the sterile release method in combination with other control methods. Received: January 18, 2001 / Accepted: August 7, 2001     

压力蒸汽灭菌指示剂的筛选和效果验证

利用结晶物质在一定温度下熔融的特性,通过对几种灭菌指示剂内容物进行熔点测定,选出苯甲酸化学试剂和升华硫化学试剂作为高压灭菌指示剂和灭菌参考指示剂。试验表明,这两种指示剂终点明确,简便快速,价格便宜,能满足121℃高压灭菌的温度要求,可以对高压灭菌的日常监测提供依据。