Rapid patterning of Dictyostelium discoideum cells under confined geometry and its relation to differentiation

The following was recently reported by Bonner et al. (1995): (1) Rapid differentiation occurred into two zones in Dictyostelium discoideum cells confined in a fine glass capillary. The cells in the anterior zone exposed to the air appear similar to prestalk cells, while the posterior zone isolated from the air mimics prespore cells. (2) The volumes of the two zones are proportional to each other for different sized cell masses, and the proportion is the same as that in normal migrating slugs. We investigated the nature of this newly discovered rapid differentiation in a slightly modified geometry. Exponentially growing cells were harvested, washed to remove external nutrients, and pelleted by centrifugation. Subsequently, a small drop of the pelleted (starved) cells was placed on a slide glass and then confined in a two-dimensional space between the slide glass and a coverslip, with help of spacers whose thickness varied from 25 to 100 μm. As a result, a dark zone, which looked optically different, emerged within several minutes in the periphery of the disc of the confined cells, corresponding to the zonation in a capillary as previously reported. When the width of the peripheral zone was measured for more than 30 samples of different diameters for each thickness of the spacers, the width was found to be always about 100 μm, irrespective of the size difference of the cell mass placed. This seems to be contradictory to the previous observation made by Bonner et al. (1995). We also examined oxygen concentration dependence on the zone width. The zone width was found to be independent of the oxygen concentration at low concentrations, but increased rapidly at high concentrations. A reaction-diffusion mechanism for formation of the zone and possible involvement of atmospheric oxygen (O₂) in the initial steps of cell differentiation and pattern formation is discussed.     

Rapid data collection and assessment of the biology of Acanthurus nigrofuscus at Woleai Atoll, Micronesia

Traditional community fishing methods commonly employed in the tropical Pacific were used to generate information on the fishery biology of Acanthurus nigrofuscus at Woleai Atoll, Micronesia, over a short time period. A simple depletion model was used to estimate the biomass of A. nigrofuscus at four back reef lagoon sites at Woleai, using two different fishing methods; spear fishing and drive-in-net fishing. The mean biomass and density of A. nigrofuscus on the lagoon reefs was 8000 g ha ⁻¹ and 183 fish ha ⁻¹ respectively, with a total estimated standing stock for the lagoon of 91 500 fish or a biomass of 4·0 t. The size frequencies of fish caught by spear fishing were biased towards larger sized individuals, while those from drive-in-net fishing were thought to be more representative of the true population size frequencies. Variation in the density and biomass of A. nigrofuscus at the four reef sites was thought to be due to the length of time between episodes of community fishing at each reef site. The sex ratio (male: female) of A. nigrofuscus was significantly different from unity (1: 0·47) and males grew larger than females. Sexually mature fish were present in all size classes above the minimum capture length and spawning activity was greatest during the period of the full moon.     

A Laboratory Study of Sleep and Dreaming in a Case of Asperger's Syndrome

Asperger's Syndrome (AS) is a pervasive developmental disorder whose continuity with High-Functioning Autism is still a matter of debate. Clinical observations suggest that patients with AS may present the same sleep disorders as autistic patients, including difficulties in initiating and maintaining sleep as well as poor dream recall. We recorded the sleep of a 25-year-old male patient with AS for two nights using a full EEG montage and compared the second night to that of a group of normal participants. We found low levels of slow wave sleep (SWS: stages 3 + 4), high levels of stage 1, and a large number of awakenings. The organization of REM sleep was unremarkable, including normal REM density. Analyses of phasic EEG events revealed a very low incidence of sleep spindles and a normal number of K-complexes over bilateral frontal and central EEG leads. In order to collect dream reports, the patient was awakened three times over two nights following at least 15 minutes of REM sleep in each case. On each occasion the patient was not aware of any mental activity happening just prior to awakening. These observations are discussed with regards to the connections that may exist between EEG sleep spindle activity, selective attention, and the capacity to generate a dream report.     

Hardening trumps acclimation in improving cold tolerance of Drosophila melanogaster larvae

Abstract Chill‐susceptible insects are able to improve their survival of acute cold exposure over both the short term (i.e. hardening at a relatively severe temperature) and longer term (i.e. acclimation responses at milder temperatures over a longer time frame). However, the mechanistic overlap of these responses is not clear. Four larval stages of four different strains of Drosophila melanogaster are used to test whether low temperature acclimation (10 °C for 48 h) improves the acute cold tolerance (LT₉₀, ～2 h) of larvae, and whether acclimated larvae still show hardening responses after brief exposures to nonlethal cold or heat, or a combination of the two. Acclimation results in increased cold tolerance in three of four strains, with variation among instars. However, if acclimation is followed by hardening pre‐treatments, there is no improvement in acute cold survival. It is concluded that short‐term thermal responses (e.g. hardening) may be of more ecological relevance to short‐lived life stages such as larvae, and that the mechanisms of low temperature hardening and acclimation in D. melanogaster may be antagonistic, rather than complementary.     

Short‐term larval food stress and associated compensatory growth reduce adult immune function in a damselfly

Abstract 1. In animals with a complex life cycle, larval stressors may carry over to the adult stage. Carry‐over effects not mediated through age and size at metamorphosis have rarely been studied. The present study focuses on the poorly documented immune costs of short‐term food stress both in the larval stage and after metamorphosis in the adult stage. 2. The present study quantified immune function [number of haemocytes, activity of prophenoloxidase (proPO) and phenoloxidase (PO)] in an experiment where larvae of the damselfly Lestes viridis were exposed to a transient starvation period. 3. Directly after starvation, immune variables were reduced in starved larvae. Levels of proPO and PO remained low after starvation, even after metamorphosis. In contrast, haemocyte numbers were fully compensated by the end of the larval stage, yet were lower in previously starved animals after metamorphosis. This can be explained as a cost of the observed compensatory growth after starvation. Focusing only on potential costs of larval stressors within the larval stage may therefore be misleading. 4. The here‐identified immunological cost in the adult stage of larval short‐term food stress and associated compensatory growth strongly indicates that physiological costs may explain hidden carry‐over effects bridging metamorphosis. This adds to the increasing awareness that the larval and adult stages in animals with a complex life cycle should be jointly studied, as trade‐offs may span metamorphosis.     

扶桑绵粉蚧与长角立毛蚁的互惠关系及其对寄主棉花叶片叶绿素荧光特性的影响

【背景】草食动物对寄主植物的取食或损伤会诱导改变植物的光合作用,从而直接影响植株的健康生长。产蜜昆虫与蚂蚁的互惠关系是物种相互促进的一种重要的生态学现象,能够促进产蜜昆虫的种群数量,然而这种互惠关系及其对寄主植物光合生理的影响还知之甚少。【方法】在室内条件下,运用叶绿素荧光动力学技术研究了外来入侵害虫扶桑绵粉蚧与长角立毛蚁的互惠对寄主棉花叶片叶绿素荧光特性的影响。【结果】随着扶桑绵粉蚧危害时间的延续,寄主植物上蚂蚁和扶桑绵粉蚧的数量均呈现显著上升的趋势,而在危害后期,蚂蚁存在情况下扶桑绵粉蚧的数量要明显低于无蚂蚁处理;在扶桑绵粉蚧取食寄主棉花20 d后,有、无蚂蚁存在的棉花叶片的光合利用率α值较无虫处理分别下降了53.5%和37.0%;存在蚂蚁或扶桑绵粉蚧危害后期对棉花叶片最大相对电子传递效率r ETRmax有显著影响,然而扶桑绵粉蚧单独取食或与蚂蚁互作的情况下未显著影响棉花叶片对强光的耐受能力(Ek)。【结论与意义】研究明确了扶桑绵粉蚧与长角立毛蚁的互惠关系对寄主棉花叶片的光合生理产生了一定的负面效应,为进一步解释扶桑绵粉蚧入侵、扩散及暴发的生态学过程提供了科学依据。     

Detection of Botrytis cinerea by loop-mediated isothermal amplification

Aims: To develop a sensitive, rapid and simple method for detection of Botrytis cinerea based on loop‐mediated isothermal amplification (LAMP) that would be suitable for use outside a conventional laboratory setting. Methods and Results: A LAMP assay was designed based on the intergenic spacer of the B. cinerea nuclear ribosomal DNA (rDNA). The resulting assay was characterized in terms of sensitivity and specificity using DNA extracted from cultures. The assay consistently amplified 65 pg B. cinerea DNA. No cross‐reactivity was observed with a range of other fungal pathogens, with the exception of the closely related species Botrytis pelargonii. Use of a novel real‐time LAMP platform (the OptiGene Genie I) allowed detection of B. cinerea in infected rose petals, with amplification occurring in <15 min. Conclusions: The LAMP assay that was developed is suitable for rapid detection of B. cinerea in infected plant material. Significance and Impact of the Study: The LAMP method combines the sensitivity and specificity of nucleic acid‐based methods with simplified equipment and a reduced reaction time. These features make the method potentially suitable for on‐site use, where the results of testing could help to inform decisions regarding the storage and processing of commodities affected by B. cinerea, such as cut flowers, fruit and vegetables.     

Intracellular ethanol accumulation in yeast cells during aerobic fermentation: a Raman spectroscopic exploration

Aims: To investigate the intracellular ethanol accumulation in yeast cells by using laser tweezers Raman spectroscopy (LTRS). Methods and Results: Ethanol accumulation in individual yeast cells during aerobic fermentation triggered by excess glucose was studied using LTRS. Its amount was obtained by comparing intracellular and extracellular ethanol concentrations during initial process of ethanol production. We found that (i) yeasts start to produce ethanol within 3 min after triggering aerobic fermentation, (ii) average ratio of intracellular to extracellular ethanol is 1·54 ± 0·17 during the initial 3 h after addition of 10% (w/v) excess glucose and (iii) the accumulated intracellular ethanol is released when aerobic fermentation is stimulated with decreasing glucose concentration. Conclusions: Intracellular ethanol accumulation occurs in initial stage of a rapid aerobic fermentation and high glucose concentration may attribute to this accumulation process. Significance and Impact of the Study: This work demonstrates LTRS is a real‐time, reagent‐free, in situ technique and a powerful tool to study kinetic process of ethanol fermentation. This work also provides further information on the intracellular ethanol accumulation in yeast cells.