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71.
Evans Obura Charles A. O. Midega Daniel Masiga John A. Pickett Mohamed Hassan Shinsaku Koji Zeyaur R. Khan 《Die Naturwissenschaften》2009,96(10):1169-1176
Napier grass (Pennisetum purpureum) is the most important fodder crop in smallholder dairy production systems in East Africa, characterized by small zero-grazing units. It is also an important trap crop used in the management of cereal stemborers in maize in the region. However, production of Napier grass in the region is severely constrained by Napier stunt disease. The etiology of the disease is known to be a phytoplasma, 16SrXI strain. However, the putative insect vector was yet unknown. We sampled and identified five leafhopper and three planthopper species associated with Napier grass and used them as candidates in pathogen transmission experiments. Polymerase chain reaction (PCR), based on the highly conserved 16S gene, primed by P1/P6-R16F2n/R16R2 nested primer sets was used to diagnose phytoplasma on test plants and insects, before and after transmission experiments. Healthy plants were exposed for 60 days to insects that had fed on diseased plants and acquired phytoplasma. The plants were then incubated for another 30 days. Nested PCR analyses showed that 58.3% of plants exposed to Recilia banda Kramer (Hemiptera: Cicadellidae) were positive for phytoplasma and developed characteristic stunt disease symptoms while 60% of R. banda insect samples were similarly phytoplasma positive. We compared the nucleotide sequences of the phytoplasma isolated from R. banda, Napier grass on which these insects were fed, and Napier grass infected by R. banda, and found them to be virtually identical. The results confirm that R. banda transmits Napier stunt phytoplasma in western Kenya, and may be the key vector of Napier stunt disease in this region. 相似文献
72.
73.
Epidemiological, psychophysiological and survey data all converge on the conclusion that driving a bus in an urban area is extremely stressful, posing serious health risks. We show that reductions in job hassles while operating buses largely account for the salutary effects of a job environment intervention designed to lessen traffic congestion, diminish passenger demands on drivers, and generally ease bus operation. This study also makes methodological contributions to the stress and health literature. Independent observers' assessments of changes in job hassles caused by a field intervention predict, in a longitudinal design, multimethodological markers of stress including blood pressure, heart rate, and a standardized self‐report index of stress. The value of utilizing job re‐design studies to more rigorously investigate stress and health is discussed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
74.
Thomas Evans 《Conservation biology》2021,35(4):1268-1277
Although invasive non-native species can adversely affect biodiversity in many ways, predation of native species by non-native species on islands can be severely damaging. Results of numerous studies document non-native birds preying on birds on islands, but our understanding of the number and type of species affected has been limited by the lack of a global review of these impacts. I identified the non-native bird species that have been recorded preying on birds, the locations where this predation occurred, and the bird species affected. Because the impacts of non-native birds can be particularly severe on small islands, I then identified the islands <500 km2 around the world that are occupied by predatory non-native birds. By taking into account their life-history traits and predation history, I also identified the near-threatened and threatened bird species on these islands that they may prey on. The results indicated that predation by non-native birds was primarily a concern for threatened bird conservation on small islands; almost all predation impacts (91%) on near-threatened and threatened birds were recorded on islands, and median island size was 106 km2. I also found non-native bird predation was a poorly known and widespread potential threat to avian biodiversity; worldwide, 194 islands of <500 km2 were occupied by predatory non-native birds, but information on their impacts was unavailable for most of these islands. On them, where the impacts of non-native species can be severe, non-native birds may be preying on approximately 6% of the world's near-threatened and threatened bird species. Four non-native bird species I identified have been successfully eradicated from islands. If they were eradicated from the small islands they occupy, 70% of the near-threatened and threatened bird species I identified would no longer be affected by nest predation by non-native birds on small islands. 相似文献
75.
Two preliminary experiments were performed to explore the use of an intratracheal instillation technique as a cost-effective method of determining the biokinetics of lead (Pb) following respiratory exposure to Pb-contaminated soils. A novel intratracheal instillation procedure was refined and used to deliver a defined dose of Pb-contaminated soil or PbAc to the lower respiratory tract of rats. In the first experiment, rats were sacrificed at numerous time intervals post-dosing, and liver, kidney, blood, and bone tissues were collected for Pb analysis. In the second experiment, rats were dosed with Pb-contaminated soil or PbAc via intratracheal instillation or gastric gavage. All rats were sacrificed 96 h after dose administration and tissues were collected for lead analysis. Data from these experiments indicate Pb is well-absorbed following intratracheal instillation of Pb-contaminated soil, and the intratracheal instillation technique could be used as a cost effective method for exploring the biokinetics of Pb in Pb-contaminated soils following respiratory tract exposure. 相似文献
76.
Maud Bonato Matthew R. Evans Dennis Hasselquist Richard B. Sherley Schalk W. P. Cloete Michael I. Cherry 《Behavioral ecology and sociobiology》2013,67(12):1891-1901
One of the most important measures of offspring performance is growth rate, which is often traded off against another important survival trait, immune function. A particular feature of ostrich chicks maintained in farmed environments is that cohorts of chicks vary widely in size. As parents can have a profound effect on the phenotype and fitness of their offspring, we investigated whether chick growth and immune defence were related to variation in levels of immune defence in their genetic parents. As secondary sexual traits of sires could serve as indicators of male quality, and be used in female mating decisions, we also investigated whether chick growth rate and immune defence were related to male plumage and integumentary colouration. We found that offspring growth rates and humoral responses were related to the humoral responses of their parents, suggesting that at least some components of humoral immune capacity are heritable. The white colour of male ostrich feathers was correlated to the humoral response and growth rate of their offspring, suggesting that this visual cue involved in the male courtship display could serve as an important signal to females of male quality, thereby forming the basis of mate choice in this species. 相似文献
77.
Ratios of the fission products (135)Cs and (137)Cs were determined in soil and sediment samples contaminated from three different sources, to assess the use of (135)Cs/(137)Cs as an indicator of source of radioactive contamination. Soil samples from the Chernobyl exclusion zone were found to have to be heavily depleted in (135)Cs ((135)Cs/(137)Cs approximately 0.45), indicative of a high thermal neutron flux at the source. Sludge samples from a nuclear waste treatment pond were found to have a (135)Cs/(137)Cs ratio of approximately 1, whereas sediment collected downstream from a nuclear reactor was highly variable in both (137)Cs activity and (135)Cs/(137)Cs ratio. Comparison of these preliminary results of variability in radiocaesium isotope ratios with reports of Pu isotope ratios suggests (135)Cs/(137)Cs similarly varies with fuel and reactor conditions, and may be used to corroborate other methods of characterizing radioactive contamination. 相似文献
78.
Assessing the impact of fisheries co-management interventions in developing countries: a meta-analysis 总被引:2,自引:0,他引:2
Co-management is now established as a mainstream approach to small-scale fisheries management across the developing world. A comprehensive review of 204 potential cases reveals a lack of impact assessments of fisheries co-management. This study reports on a meta-analysis of the impact of fisheries co-management in developing countries in 90 sites across 29 case-studies. The top five most frequently measured process indicators are participation, influence, rule compliance, control over resources, and conflict. The top five most frequently measured outcome indicators are access to resources, resource well-being, fishery yield, household well-being, and household income. To deal with the diversity of the 52 indicators measured and the different ways these data are collected and analysed, we apply a coding system to capture change over time. The results of the meta-analysis suggest that, overall fisheries co-management delivers benefits to end-users through improvements in key process and outcome indicators. However, the dataset as a whole is constituted primarily of data from the Philippines. When we exclude this body of work, few generalisations can be made about the impact of fisheries co-management. The lack of comparative data suitable for impact assessment and the difficulties in comparing data and generalising across countries and regions reiterates calls in other fields for more systematic approaches to understanding and evaluating governance frameworks. 相似文献
79.
The Maltese top-shell, Gibbula nivosa Adams 1851, is a critically endangered marine trochid gastropod endemic to the Maltese Islands (central Mediterranean). Previously unrecorded
live since 1981, rediscovery of this species in 2006 has enabled the collection of basic biological data for the first time,
based on a population in Sliema Creek. The field distribution and habitat preferences of G. nivosa were investigated via stratified random sampling, while aspects of its behaviour were studied through laboratory experiments.
Gibbula nivosa occurred primarily in near-homogeneous or homogeneous infralittoral cobble/pebble beds, at an overall density of 17.6 ± 25.0 SD individuals m−2; however, large spatial and temporal variations in abundance were recorded. The snails did not exhibit gregarious behaviour
and the slightly clumped dispersion pattern noted in the field appeared to result from patchiness of the habitat. Recruitment
was observed in post-summer months, which, together with data on shell-size distributions, suggests that G. nivosa spawns in early summer and attains adult size (maximum shell width ~9 mm) in less than 1 year. Gibbula nivosa showed a circadian activity pattern with nocturnal foraging involving indiscriminate ingestion of particles browsed off the
substratum; observations on responses to four potential predators suggest that nocturnal activity may have evolved in response
to diurnal predation. Historical records of snail occurrence and the present study suggest that population declines of G. nivosa in the past were probably related to habitat alteration as a result of anthropogenic pressure. 相似文献
80.
Ahmed A. Nassr Kamran Hessami Elena D’Alberti Antonella Giancotti Nazlisadat Meshinchiasl Mark I. Evans Daniele Di Mascio Alireza A. Shamshirsaz 《黑龙江环境通报》2023,43(11):1425-1432
To evaluate obstetrical outcomes for women having late amniocentesis (on or after 24 weeks). Electronic databases were searched from inception to January 1st, 2023. The obstetrical outcomes evaluated were gestational age at delivery, preterm birth (PTB) < 37 weeks, PTB within 1 week from amniocentesis, premature prelabor rupture of membranes (pPROM), chorionamnionitis, placental abruption, intrauterine fetal demise (IUFD) and termination of pregnancy (TOP). The incidence of PTB <37 weeks was 4.85% (95% CI 3.48–6.56), while the incidence of PTB within 1 week was 1.42% (95% CI 0.66–2.45). The rate of pPROM was 2.85% (95% CI 1.21–3.32). The incidence of placental abruption was 0.91% (95% CI 0.16–2.25), while the rate of IUFD was 3.66% (95% CI 0.00–14.04). The rate of women who underwent TOP was 6.37% (95%CI 1.05–15.72). When comparing amniocentesis performed before or after 32 weeks, the incidence of PTB within 1 week was 1.48% (95% CI 0.42–3.19) and 2.38% (95% CI 0.40–5.95). Amniocentesis performed late after 24 weeks of gestation is an acceptable option for patients needing prenatal diagnosis in later gestation. 相似文献