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Tansley Review No. 112 总被引:4,自引:0,他引:4
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Changes in the heat resistance of Salmonella typhimurium during heating at rising temperatures 总被引:12,自引:8,他引:4
The heat resistance of Salmonella typhimurium , measured as survival following a standard heat challenge at 55°C for 25 min, increased progressively as cells were heated up at linearly rising temperatures. The amount by which heat resistance increased depended on the rate of temperature rise; the slower the temperature rise, the greater the increase in resistance. 相似文献
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Body size but not colony size increases with altitude in the holarctic ant,Leptothorax acervorum 下载免费PDF全文
ABEL BERNADOU CHRISTINE RÖMERMANN NANA GRATIASHVILI JÜRGEN HEINZE 《Ecological Entomology》2016,41(6):733-736
1. Bergmann's rule states that organisms inhabiting colder environments show an increase in body size or mass in comparison to their conspecifics living in warmer climates. Although originally proposed for homoeothermic vertebrates, this rule was later extended to ectotherms. In social insects, only a few studies have tested this rule and the results were ambiguous. Here, ‘body size’ can be considered at two different levels (the size of the individual workers or the size of the colony). 2. In this study, data from 53 nests collected along altitudinal gradients in the Alps were used to test the hypotheses that the worker body size and colony size of the ant Leptothorax acervorum increase with increasing altitude and therefore follow Bergmann's rule. 3. The results show that the body size of workers but not the colony size increases with altitude. Whether this pattern is driven by starvation resistance or other mechanisms remains to be investigated. 相似文献
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Potatoes (Solanum tuberosum L.) were grown in containers undera rain shelter for measurement of leaf water relations. Leafwater potentials ( 相似文献
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Water Relations of Potato Leaves. II. Pressure--Volume Analysis and Inferences About the Constancy of the Apoplastic Fraction 总被引:1,自引:0,他引:1
Water relations characteristics of potato (Solanum tuberosumL. cv. Bintje) leaves were determined from pressurevolumeanalysis using a pressure chamber. Turgor was 077 MPa and thebulk volumetric modulus of elasticity 81 MPa at full turgidity;turgor loss occurred when water potential () had declined to087 MPa at a relative water content (RWC) of 0912;the apoplastic water fraction (A) was 0235. As is usually found,there was a linear relation between 1/ and RWC beyond turgorloss. This finding supports the assumptions of the constancyof A during leaf dehydration. Beyond turgor loss the difference between and [measured afterfreezing and thawing (d)] was about 01 MPa. This differencedid not increase as the leaf water content decreased. This resultcontradicts the constancy of A. It was concluded from calculations with a simple model of leafdehydration that analysis of the relation between and d providesmore insight in the changes in the apoplastic fraction thanthe relation between 1/ and RWC. Research on the size of theapoplastic fraction and its changes with water potential wouldcomplement current understanding of leaf water relations. Solanum tuberosum, L., water potential, pressure chamber, osmotic potential, pressure potential, relative water content, apoplast, symplast 相似文献
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CHRISTINE A. SUNDERMANN DAVID S. LINDSAY ROBERT E. TIBBS MARK A. BAILEY 《The Journal of eukaryotic microbiology》1988,35(4):465-469
The development of Caryospora bigenetica in vitro is described by light microscopy. Sporozoites from snake-derived oocysts were purified and inoculated onto cultures of primary testicle cells of the cotton rat, cotton rat kidney cells, and human fetal lung cells. Intracellular sporozoites were observed one and two days postinoculation (DPI). Motile, extracellular first-generation merozoites were present 3 DPI, and second-generation merozoites were present 5 DPI. Mature gamonts were observed 9 DPI and developed into unsporulated oocysts by 10 DPI. Oocysts sporulated in vitro, and excystation was observed. Cells that were penetrated by in vitro-produced sporozoites formed caryocysts by 16 DPI. To test infectivity of in vitro-derived stages, merozoites were removed from cultured cells 5 DPI and inoculated intraperitoneally into a mouse; infection resulted. Sporulated oocysts removed from cell cultures 12 DPI produced facial swelling in an orally inoculated cotton rat. 相似文献
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The surfaces of the main cell body, tentacle shaft, and knob of Discophrya collini, a freshwater suctorian ciliate, were characterized using various cytochemical techniques. Cells prepared for conventional transmission electron microscopy exhibited a 50–60 nm thick fuzzy layer over the cell body surface; this layer was absent from the tentacle knob. A thick (240 nm), two-layered surface coat surrounding the main cell body was stained with ruthenium red. This heavy coat was absent from the surface of the knob where a thin, dense, ruthenium red-positive layer and projecting filaments were present. Freeze-etched material revealed a “particle region” (150–250 nm in thickness) closely associated with the outer cell surface of the suctorian. Fixed specimens were treated with four different lectins and analyzed with electron microscopy in order to obtain information about the carbohydrate composition of the outer surface of D. collini. Concanavalin A bound to the surface of the cell body and tentacle shaft as a dense, particulate layer (80 nm thick) but thinned to 13–16 nm over the surface of the knob. Wheat germ agglutinin-treated cells also displayed a heavy, electron-dense layer (128 nm thick) that surrounded the main cell body and tentacle shaft, but only scattered patches of bound wheat germ agglutinin were observed on the surface of the knob. Discophrya treated with Helix agglutinin or peanut agglutinin appeared similar to control cells. Suctorians were treated with lectins in vivo in an attempt to inhibit capture and ingestion of their prey, Tetrahymena pyriformis, by masking prey receptor sites on the knob. Concanavalin A and, to a lesser degree, wheat germ agglutinin, successfully inhibited attachment of the prey organism. Helix agglutinin and peanut agglutinin had little effect on prey capture. 相似文献