Trichinella spiralis: Differential effect of host bile on the in vitro invasion of infective larvae into epithelial cells

The differential effect of fox and pig bile and its corresponding low molecular weight fraction (LMW) was investigated on the in vitro invasion of MDCK-AA7 epithelial cell monolayers by Trichinella spiralis muscle larvae. Seven invasion experiments were performed and a total of 274 cell monolayers were examined. Fox and pig raw bile at 1:10 and 1:20 dilution and their LMW fractions at 1:10 dilution activated T. spiralis larvae to invade the cell monolayers. In addition, fox raw bile caused significantly larger cell damage than pig raw bile at both dilutions. The area of cell damage was larger at 1:10 than at 1:20 dilution for both fox and pig raw bile (p < 0.05). On the other hand, there was no significant difference between the areas of cell damage caused by the LMW fractions of fox and pig bile. It is concluded that differences between host bile actions may account for differences in host susceptibility to T. spiralis.     

不同秧苗素质和移栽密度条件下臭氧胁迫对水稻光合作用、物质生产和产量的影响

近地层臭氧浓度升高使水稻生长受抑进而使产量下降,但这种影响是否因不同栽培条件而异尚不清楚。2011年依托先进的稻田臭氧FACE(Free Air gas Concentration Enrichment)技术平台,以汕优63为供试材料,臭氧设置大气臭氧浓度(Ambient)和高臭氧浓度(比Ambient高50%),秧苗素质设置弱苗(移栽时无分蘖)和壮苗(移栽时带两个分蘖),移栽密度设置低密度(16穴/m2)、中密度(24穴/m2)和高密度(32穴/m2),研究不同秧苗素质和移栽密度条件下臭氧胁迫对水稻生长和产量的影响。结果表明:高浓度臭氧使水稻结实期叶片SPAD值、净光合速率、气孔导度和蒸腾速率明显下降,但胞间CO2浓度和叶温无显著变化。高浓度臭氧对水稻拔节前物质生产量没有影响,但使拔节至抽穗期、抽穗至成熟期物质生产量平均分别降低13%和29%,进而使成熟期生物产量和籽粒产量均显著下降。方差分析表明,臭氧与秧苗素质间没有互作效应,但臭氧与移栽密度的互作对最终产量的影响达显著水平。以上结果表明,臭氧胁迫使水稻生长后期光合受阻,导致物质生产和产量显著下降;适当增加移栽密度可能会减少臭氧胁迫下水稻产量的损失。     

In vitro migration of Dictyocaulus viviparus larvae: migration of the infective stage inagar gel.

The infective stage of the cattle lungworm, Dictyocaulus viviparus, was able to migrate in agar gel when activated by bile. The number of larvae which penetrated the upper surface of a 2 mm thick agar layer was counted and found to be independent from the agar concentration. Larvae which had migrated out of the agar remained on the surface and did not re-enter. The agar migration process was temperature dependent. Influence of time as well as dependency of agar thickness was investigated. The significance of these findings is discussed.     

Attraction to Carbon Dioxide from Feeding Resources and Conspecific Neighbours in Larvae of the Rhinoceros Beetle Trypoxylus dichotomus

Saprophagous (feeding on decaying matter) insects often use carbon dioxide (CO₂) as a cue for finding food. Humus-feeding larvae of the giant rhinoceros beetle Trypoxylus dichotomus exhibit a clumped distribution in natural microhabitats, but the mechanisms driving the distribution were unknown. Herein, I examined whether larvae use CO₂ as a cue for fermented humus and aggregate in the vicinity of the food. I found that (i) larvae of T. dichotomus are strongly attracted to CO₂, (ii) larvae orient toward highly fermented humus when given a choice between highly and poorly fermented humus, (iii) the highly fermented humus emits more CO₂ than the poorly fermented humus, and (iv) larvae grow larger when fed highly fermented humus rather than poorly fermented humus. The clumped distribution of larvae is probably formed along the concentration gradient of CO₂ induced by heterogeneity of fermented organic materials in soil. My laboratory experiments also revealed that larvae are chemically attracted to each other. Moreover, CO₂ concentrations in soil were increased by the larval respiration, and small amounts of CO₂ (much less than emitted during respiration by a single larva) were sufficient for larval attraction. These results suggest that not only response to fermented food resources, but also respiratory CO₂ from conspecifics may lead to aggregation. Enhanced densities resulted in reduced weight gain under experimental conditions. However, exploiting a high-value resource at enhanced densities still led to greater body weight compared to individually exploiting a low-value resource. This demonstrates the adaptive value of the response to CO₂ sources in this species.     

Interaction between elevated atmospheric concentration of CO2 and humidity on plant growth: comparison between cotton and radish

Cotton plants (Gossypium hirsutum L. var Deltapine 90) and radish plants (Raphanus sativus L var Round Red) were grown under full sunlight using a factorial combination of atmospheric CO₂ concentrations (350 µmol mol^-1 and 700 µmol mol^-1) and humidities (35% and 90% RH at 32 °C during the day). Cotton plants showed large responses to increased humidity and to doubled CO₂. In cotton plants, the enhanced dry matter yield due to doubled CO₂ concentration was 1.6-fold greater at low humidity than at high humidity. Apart from the direct effect of elevated CO₂ level on photosynthesis, the greater effect of doubled CO₂ concentration on dry matter yield at low humidity was probably due to: (1) increased leaf water potential caused by reduction of transpiration resulting from the negative CO₂ response of stomata to increased CO₂ concentration the consequence being greater leaf area expansion; (2) reduction of CO₂ assimilation rate at low humidity and normal CO₂ concentration as a result of humidity response of stomata causing reduction of intercellular CO₂ concentration. In contrast, apart from the very early stage of development, radish plants do not respond to increased humidity but had a relatively large response to doubled CO₂ concentration. Furthermore, due to the determinate growth pattern as well as having a prominent storage root, the extra photoassimilate derived at doubled CO₂ level is allocated to the storage root.Abbreviatios DAE day after emergence - LAD leaf areal density (leaf dry weight/leaf area) - LAR leaf area ratio (leaf area/plant dry weight) - NAR net assimilation rate - c_i internal CO₂ concentration - PPFD photosynthetic photon flux density - RGR relative growth rate - RLAGR relative leaf area growth rate - VPD vapour pressure deficit     

Response of Two Wheat Cultivars to CO(2) Enrichment under Subambient Oxygen Conditions

Two cultivars of wheat (Triticum aestivum L. cvs Sonoita and Yecora Rojo) were grown to maturity in a growth chamber within four sub-chambers under two CO₂ levels (350 or 1000 microliters per liter) at either ambient (21%) or low O₂ (5%). Growth analysis was used to characterize changes in plant carbon budgets imposed by the gas regimes. Large increases in leaf areas were seen in the low O₂ treatments, due primarily to a stimulation of tillering. Roots developed normally at 5% O₂. Seed development was inhibited by the subambient O₂ treatment, but this effect was overcome by CO₂ enrichment at 1000 microliters per liter. Dry matter accumulation and seed number responded differently to the gas treatments. The greatest dry matter production occurred in the low O₂, high CO₂ treatment, while the greatest seed production occurred in the ambient O₂, high CO₂ treatment. Growth and assimilation were stimulated more by either CO₂ enrichment or low O₂ in cv Yecora Rojo than in Sonoita. These experiments are the first to explore the effect of whole plant low O₂ treatments on growth and reproduction. The finding that CO₂ enrichment overcomes low O₂-induced sterility may help elucidate the nature of this effect.     

Oesophagostomum radiatum: Glucose metabolism of larvae grown in vitro and adults grown in vivo

Larval stages of Oesophagostomum radiatum grown in vitro and adults grown in vivo were incubated in complex media or in a simple salt solution containing radioactive glucose. Glucose disappearance and end product accumulation of third-stage larvae in a simple salt solution indicated that they excreted CO₂ and acetic, propionic, and lactic acids. Larvae in third molt, fourth stage, and adults all excreted CO₂, acetic, propionic, and lactic acids at twice the rate of third-stage larvae plus an additional product, methylbutyric acid. Carbon dioxide arose primarily from the 3 or 4 carbons of glucose. An anaerobic atmosphere (95% N₂:5% CO₂) had no apparent effect on metabolism. When incubation was done in complex media, isobutyric and 3-methylbutyric acids were seen as major excretion products (10 and 24%, respectively). However, these acids were quantitatively minor when incubations took place in simple salts-glucose medium (1 and 0–3%, respectively).     

Brugia malayi and B. pahangi: Cultivation in vitro of infective larvae to the fourth and fifth stages

Cultivation of fourth stage Brugia pahangi and B. malayi larvae from infective larvae (stage 3) were obtained in culture medium RPMI 1640 supplemented with 10% human AB serum and an LCC-MK₂ rhesus monkey kidney continuous cell line feeder layer. This culture system kept larvae alive in excess of 7 weeks, and served as a source for collection of the worms' secretory, excretory, and moulting antigens.     

Effects of ocean acidification on the early life history of a tropical marine fish

Little is known about how fishes and other non-calcifying marine organisms will respond to the increased levels of dissolved CO₂ and reduced sea water pH that are predicted to occur over the coming century. We reared eggs and larvae of the orange clownfish, Amphiprion percula, in sea water simulating a range of ocean acidification scenarios for the next 50–100 years (current day, 550, 750 and 1030 ppm atmospheric CO₂). CO₂ acidification had no detectable effect on embryonic duration, egg survival and size at hatching. In contrast, CO₂ acidification tended to increase the growth rate of larvae. By the time of settlement (11 days post-hatching), larvae from some parental pairs were 15 to 18 per cent longer and 47 to 52 per cent heavier in acidified water compared with controls. Larvae from other parents were unaffected by CO₂ acidification. Elevated CO₂ and reduced pH had no effect on the maximum swimming speed of settlement-stage larvae. There was, however, a weak positive relationship between length and swimming speed. Large size is usually considered to be advantageous for larvae and newly settled juveniles. Consequently, these results suggest that levels of ocean acidification likely to be experienced in the near future might not, in isolation, significantly disadvantage the growth and performance of larvae from benthic-spawning marine fishes.     

Interactive effects of mycorrhization and elevated carbon dioxide on growth of young pedunculate oak (Quercus robur L.) trees

Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO₂ level and 650 ppmv CO₂ in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 6 month under nutrient non-limiting conditions. Mycorrhization and elevated atmospheric CO₂ each supported the growth of the trees. Stem height, stem diameter, and dry matter accumulation of pedunculate oak were increased by mycorrhization. Elevated atmospheric CO₂ enhanced stem height, stem diameter, fresh weight and dry weight, as well as lateral root formation of the trees. In combination, mycorrhization and elevated atmospheric CO₂ had a more than additive, positive effect on tree height and biomass accumulation, and further improved lateral root formation of the trees. From these findings it is suggested that the efficiency of the roots in supporting the growth of the shoot is increased in mycorrhized oak trees at elevated atmospheric CO₂.Abbreviations DW dry weight - FW fresh weight - RWC relative water content     

Relationship between fresh leaf traits and leaf litter decomposition of 20 plant species in Kerqin sandy land, China

20 plant species (10 monocots and 10 dicots) grown in Kerqin sandy grassland were incubated under indoor conditions to monitor the amount and rate of CO₂ release from the leaf litter. 11 traits of mature fresh leaves including caloric value, contents of Mg, P, N, K, C, C/N, N/P, specific leaf area, dry matter content and leaf surface area were measured to determine the relationship between CO₂ release and leaf characteristics. All those traits have great variation among the 20 species with over 3 fold differences between the maximum and minimum values, and a few traits such as leaf Mg content reached as high as 9 folds. After 28 d's incubation, the average CO₂ release amount from all the species was (4121 ± 1713) μg kg^?1 dry soil. The highest level from Chenopodium acuminatum was (8767 ± 177) μg kg^?1 dry soil, which was 5 folds higher than the lowest level ((1669 ± 47)μg kg^?1 dry soil) from Digitaria sanguinalis. However, CO₂ release rate showed the same trend in all the 20 species, i.e., the leaf litter decomposed faster initially (0–4 d), and gradually slowed down during extended cultural periods. Comparison between monocots and dicots showed that these two taxonomic groups had significant differences in terms of the amount and rate of CO₂ released from leaf litter, and N and C contents, leaf C/N, and dry matter content of mature leaves. Contents of N, C and dry matter, and C/N of mature leaves are significantly correlated with CO₂ release from leaf litter decomposition, which has been revealed by the Pearson correlation test. It can be concluded that these three traits of mature leaves can be used indirectly to predict decomposition rate of the leaf litter.     

Syphacia muris: response to environmental stimuli when hatching in vitro.

It is known that several oxyurids have hatched in fluids without extra stimuli except digestive enzymes, whereas the eggs of several other nematodes require for hatching optimal temperature, pH, redox potential, and pCO₂ but no enzymes. Consequently, a study was carried out on the effect of external stimuli on hatching of the eggs of the oxyurid Syphacia muris.Eggs of S. muris, attached to pieces of transparent adhesive tape, proved themselves able to hatch in a PO₄-buffer to which only trypsin and bile had been added. Trypsin acted, like NaOH on other nematode eggs, by dissolving proteins from the surface of the eggshell. The addition of reducing agents, and to some extent CO₂, had a stimulating effect. Hatching began to occur at 19 C and at pH 3, although 41 C and pH 7 gave optimal results.The conclusion is that the eggs of S. muris react in the same way to the environment as those of Ascaris lumbricoides and other nematodes which hatch inside the hosts' intestinal tracts. S. muris eggs distinguish themselves, however, by being dependent on the environment to an appreciably lesser extent.This last characteristic makes it possible to use simple media for routine hatchings of these eggs, for instance, in disinfection tests.     

CO2 enhances effects of hypoxia on mortality,development, and gene expression in cowpea bruchid, Callosobruchus maculatus

Modified atmosphere based on lack of O₂ offers a safe, residue-free alternative to chemical fumigants for pest control in stored grains. In this study, we intended to determine whether elevated CO₂ (at a biologically achievable level) has an enhanced suppressive effect over low O₂ atmosphere alone on the cowpea bruchid (Callosobruchus maculatus), a storage pest of cowpea and other legumes. Experiments were performed under two modified atmospheric conditions, (1) 2% O₂ + 18% CO₂ + 80% N₂ and (2) 2% O₂ + 98% N₂. Both hypoxic environments significantly affected the development and survival of all insect developmental stages. Eggs were most vulnerable to hypoxia, particularly at the early stage (4–6 h old), surviving only up to a maximum of 2 days in both treatments. These were followed by adults, pupae and larvae, in order of decreasing susceptibility. The 3rd and 4th instar larvae were most resilient to hypoxia and could survive up to 20 days of low O₂. The presence of 18% CO₂ significantly increased the mortality of adults, the later stage of eggs, as well as 1st and 4th instar larvae caused by hypoxia. However, the surviving insects exhibited faster development, evidenced by their earlier emergence from cowpea seeds compared to those without CO₂. One interesting observation was the frequent, premature opening of the emergence windows in the 4th instar larvae when CO₂ was involved. This phenomenon was not observed at all in insects stressed by low O₂ alone. Differential expression profiling of metabolic genes and proteolytic activity of midgut digestive enzymes suggested that the rate of metabolic activity could contribute in part to the difference in insect development and survival under hypoxia in the presence and absence of CO₂.     

Effects of increased atmospheric CO2 on nutritional contents in poplar (Populus pseudo-simonii [Kitag.]) tissues and larval growth of gypsy moth (Lymantria dispar)

Changes in the concentrations of phytochemical compounds usually occur when plants are grown under elevated atmospheric CO₂. CO₂-induced changes in foliar chemistry tend to reduce leaf quality and may further affect insect herbivores. Increased atmospheric CO₂ also has a potential influence on decomposition because it causes variations in chemical components of plant tissues. To investigate the effects of increased atmospheric CO₂ on the nutritional contents of tree tissues and the activities of leaf-chewing forest insects, samples of Populus pseudo-simonii [Kitag.] grown in open-top chambers under ambient and elevated CO₂ (650 μmol mol^-1) conditions were collected for measuring concentrations of carbon, nitrogen, C : N ratio, soluble sugar and starch in leaves, barks, coarse roots (>2 mm in diameter) and fine roots (<2 mm in diameter). Gypsy moth (Lymantria dispar) larvae were reared on a single branch of experimental trees in a nylon bag with 1 mm 1 mm grid. The response of larval growth was observed in situ. Elevated CO₂ resulted in significant reduction in nitrogen concentration and increase in C : N ratio of all poplar tissues. In all tissues, total carbon contents were not affected by CO₂ treatments. Soluble sugar and nonstructural carbohydrate (TNC) in the poplar leaves significantly increased with CO₂ enrichment, whereas starch concentration increased only on partial sampling dates. Carbohydrate concentration in roots and barks was generally not affected by elevated CO₂, whereas soluble sugar contents in fine roots decreased in response to elevated CO₂. When second instar gypsy moth larvae consuming poplars grew under elevated CO₂ for the first 13 days, their body weight was 30.95% lower than that of larvae grown at ambient CO₂, but no significant difference was found when larvae were fed in the same treatment for the next 11 days. Elevated atmospheric CO₂ had adverse effects on the nutritional quality of Populus pseudo-simonii [Kitag.] tissues and the resultant variations in foliar chemical components had a significant but negative effect on the growth of early instar gypsy moth larvae.     

Adult worms as a factor in the inhibition of development of Ostertagia ostertagi in the host

The removal, by anthelmintic treatment, of adult worms from calves that had been infected daily for 204 days with larvae of Ostertagia ostertagi, stimulated the resumed development of inhibited early fourth stage larvae. The calves remained susceptible to the establishment of worms and the continued administration of infective larvae after the 204th day reduced the rate at chich the burden of inhibited forms decreased. The relevance of these findings to the regulation of worm burdens is discussed.     

Growth and shoot: root ratio of seedlings in relation to nutrient availability

The influence of mineral nutrient availability, light intensity and CO₂ on growth and shoot:root ratio in young plants is reviewed. Special emphasis in this evaluation is given to data from laboratory experiments with small Betula pendula plants, in which the concept of steady-state nutrition has been applied.Three distinctly different dry matter allocation patterns were observed when growth was limited by the availability of mineral nutrients: 1, Root growth was favoured when N, P or S were the major growth constraints. 2, The opposite pattern obtained when K, Mg and Mn restricted growth. 3, Shortage of Ca, Fe and Zn had almost no effect on the shoot:root ratio. The light regime had no effect on dry matter allocation except at very low photon flux densities (< 6.5 mol m^-2 day^-1), in which a small decrease in the root fraction was observed. Shortage of CO₂, on the other hand, strongly decreased root development, while an increase of the atmospheric CO₂ concentration had no influence on dry matter partitioning. An increased allocation of dry matter to below-ground parts was associated with an increased amount of starch in the tissues. Depletion of the carbohydrate stores occurred under all conditions in which root development was inhibited. It is concluded that the internal balance between labile nitrogen and carbon in the root and the shoot system determines how dry matter is being partitioned in the plant. The consistency of this statement with literature data and existing models for shoot:root regulation is examined.     

Populations of strongyloid nematode infective stages in sheep pastures: Comparison between direct pasture sampling and tracer lambs as estimators of larval abundance

Waller P.J., Dobson R.J., Donald A.D. and Thomas R.J. 1981. Populations of strongyloid nematode infective stages in sheep pastures : comparison between direct pasture sampling and tracer lambs as estimators of larval abundance. International Journal for Parasitology11: 359–367. Over a 2-year period, numbers of infective larvae in samples of pasture herbage, and numbers of worms in previously worm-free “tracer” lambs allowed 4 weeks grazing, were compared as estimators of the abundance of infective larvae on pastures.Transformation of sample estimates of infective larval numbers per 100 g herbage dry matter (DM) and of worm numbers in tracer sheep, according to the expression y = log₁₀ (x+25), was effective in stabilizing variances. Estimates of error variance for each technique did not differ significantly among the genera Haemonchus, Ostertagia or Trichostrongylus and the pooled estimate for the tracer sheep method was 4 times greater than that for pasture sampling. From these results, more tracer sheep than pasture samples would be required to achieve the same level of precision with the two techniques. Using conventional statistical methods, the effects of numbers of pasture samples or tracer sheep on the size of the difference between two means which can be detected as significant and on the width of the confidence interval about a single mean, are illustrated. These can be used as a guide in the choice of sample sizes. Error variances for Nematodirus spp. were significantly less than for the other genera by pasture sampling, and greater by the tracer sheep technique. Possible reasons for this are discussed, but it is concluded that pasture sampling is likely to be much the more precise method for estimating Nematodirus spp. infective larval availability.Changes with time in infective larval abundance, for Haemonchus, Trichostrongylus and Nematodirus spp. which were present in moderate to low numbers, followed similar trends by both techniques. However, for Ostertagia spp. larvae, which were much more abundant, peak levels were defined more sharply and occurred earlier by pasture sampling than by the tracer method. It is suggested that worm counts from tracer sheep, especially those grazing for 4 weeks rather than shorter periods, may systematically underestimate the infective larval population on pasture at high levels of abundance owing to density-dependent worm loss.     

Response of nodulated alfalfa to water supply,temperature and elevated CO2: productivity and water relations

Exposing plants to long-term CO₂ enrichment generally leads to increases in plant biomass, total leaf area and alterations on leaf net photosynthetic rates, stomatal conductance and water use efficiency. However, the magnitude of such effects is dependent on the availability of other potentially limiting resources. The aim of our study was to elucidate the effects of elevated CO₂, applied at different temperature and water availability regimes, on nodulated alfalfa plants. Regardless of water supply, elevated CO₂ enhanced plant growth, especially when combined with increased temperature although no differences were detected until 30 days of treatment. Absence of differences in leaf relative growth rate, and gas exchange measurements, suggested that plants grown in a low water regime adjusted their growth to the amount of available water. Elevated CO₂ enhanced water use efficiency because of reduced water consumption and a greater dry mass production. Increased dry matter production of plants grown under elevated CO₂ and temperature was the result of stimulated photosynthetic rates, greater leaf area and water use efficiency. Lack of CO₂ effect on photosynthesis of plants grown at ambient temperature might be consequence of down-regulation phenomena. Plants grown at 700 μmol mol⁻¹ CO₂ maintained control nitrogen levels, discarding enhanced nitrogen availability as the main factor explaining enhanced dry matter.     

Elevated CO2 alleviates the effects of low P on the growth of N2-fixing Acacia auriculiformis and Acacia mangium

Nodulated seedlings of Acacia auriculiformis Cunn. ex Benth and Acacia mangium Willd were grown with different phosphorus (P) regimes for 90 days, and half of them were exposed to elevated CO₂ (800 μl l⁻¹) during the last 30 days. Under ambient CO₂, plant growth and the amount of N fixed symbiotically in N₂-fixing seedlings decreased with the decrease of supplied P; this relationship did not occur under elevated CO₂. The increase in plant biomass by elevated CO₂ at low P was accompanied by the increase in internal P use efficiency, the amount of N fixed symbiotically and N use efficiency. Elevated CO₂ recovered the low P-induced reduction in leaf dry matter per unit area or unit fresh weight, but it had no effect on the low P-induced increase in partitioning dry matter to roots. These results suggest that elevated CO₂ alleviates the low P effect mainly by increasing the use efficiency of internal P for plant growth and symbiotic N₂ fixation, and the source-sink relationship is possibly an important driving force for this effect of elevated CO₂ in A. auriculiformis and A. mangium.     

Comparative growth analyses of panicum species with differing rates of photorespiration

Panicum milioides, a naturally occurring species with reduced photorespiration, P. bisulcatum, a C₃ species, and P. miliaceum, a C₄ species, were grown for 4 weeks at altered pO₂ and pCO₂ and several vegetative growth parameters were determined at weekly intervals. Compared to a pO₂ of 10%, a greater O₂ inhibition of the relative growth rate and dry matter production was observed for P. bisulcatum than for P. milioides at both 21% and 40% O₂, whereas little effect of O₂ was noted for P. miliaceum. Similarly, exposures to elevated pCO₂ of 500 and 1000 μ1 CO₂/liter resulted in a greater stimulation of vegetative growth for P. bisulcatum than for P. milioides, with little effect on P. miliaceum. The CO₂ compensation concentration of P. milioides was less than that of P. bisulcatum over a pO₂ range of 5 to 40%. At 5% O₂, the compensation concentration was relatively O₂-insensitive, whereas above 5% it increased with increasing pO₂. It is concluded that P. milioides represents the first well documented example of a C₃ plant with reduced photorespiration, based on both leaf CO₂ exchange parameters and growth analyses of dry matter production.