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81.
The Natterjack toad, Bufo calamita, is a locally endangered anuran endemic to Europe. It has been used as a model organism in several ecological studies. When studying the genetic structure of marginalized populations of the species, there was a need to involve more loci in the study than those previously published. Here we present the development of six polymorphic microsatellite loci in the Natterjack. The loci will be used for studying population genetic structure and gene flow between populations.  相似文献   
82.
The aim of this work was to assess whether or not oxidative stress had developed in a dwarf shrub bilberry ( Vaccinium myrtillus L.) under long-term exposure to enhanced levels of ultraviolet-B (u.v.-B) radiation. The bilberry plants were exposed to increased u.v.-B representing a 15% stratospheric ozone depletion for seven full growing seasons (1991–1997) at Abisko, Swedish Lapland (68°N). The oxidative stress was assessed on leaves and stems by analysing ascorbate and glutathione concentrations, and activities of the closely related enzymes ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2). The affects of autumnal leaf senescence and stem cold hardening on these variables were also considered. The results showed that the treatment caused scarcely any response in the studied variables, indicating that u.v.-B flux representing a 15% ozone depletion under clear sky conditions is not sufficient to cause oxidative stress in the bilberry. It is suggested that no strain was evoked since adaptation was possible under such u.v.-B increases. The studied variables did, however, respond significantly to leaf senescence and especially to stem cold hardening.  相似文献   
83.
ABSTRACT There are many challenges facing natural resources programs in North American higher education today. Pressures exerted by a new generation of students, changing workplace requirements (including undergraduate core-knowledge requirements), and an increasingly specialized professoriate are great but not insurmountable. We discuss each of these issues and pose potential solutions to address each including adopting new pedagogical techniques for content delivery (e.g., adapting courses to be inclusive of new technologies), revising curriculum to meet the needs of a new suite of learners (e.g., developing curricula that allow structured flexibility of choices, designing a core curriculum that is a mix of single-discipline courses and courses that integrate across disciplines), and new strategies for faculty engagement in discipline-specific survey courses. By remaining deliberate and effective in our pursuit of quality higher education we have the opportunity to ensure we are delivering the best possible education to the future professionals of our disciplines.  相似文献   
84.
Four species of Ordovician Chitinozoa from Öland, Sweden, Cyathochitina stentor, Desmochitina minor, Lagenochitina esthonica , and Lagenochitina tumida , have been investigated by transmission electron microscopy. There is very great variation in the vesicle wall ultrastructure of the specimens studied. The texture of the vesicle wall can be homogeneous or granular and can also contain denser zones. Ultrastructures such as pore canals and 'empty spaces' have been revealed. The systematic affinity of the Chitinozoa is discussed, and it is concluded that chitinozoans display typical metazoan structures represented in eggs and egg capsules of marine invertebrates and possibly also in fish.  相似文献   
85.
Abstract: Artificial nesting islands, or rafts, are often deployed in common loon (Gavia immer) breeding territories to decrease negative impacts of mammalian predation and water-level fluctuations on nesting success. The management value of rafts has been demonstrated in other studies; however, no published studies have quantified the use or associated reproductive benefits of rafts on lakes exhibiting water-level fluctuations. These lakes constitute a major portion of loon nesting habitat in New England and the Midwest. We used long-term data sets from loon survey and raft management efforts on lakes with stable (SWL) and fluctuating water levels (FWL) in New Hampshire and Maine, USA, to compare raft-use patterns on both types of lakes. We then modeled the influence of percentage of nesting attempts on rafts, lake fluctuation type, and human development index on nesting success as a function of the number of nesting attempts. Loons used 76% of all rafts for nesting, and initial use patterns were similar between SWL and FWL lakes. Half (51%) of rafts used for nesting were first used during the initial year of deployment and 90% of those used were used by the third year. Based on our model, we would expect to see an 8.6% increase in nesting success associated with each successive categorical increase in raft use (0–33%, 33–60%, 60–100%). Nesting success varied with lake fluctuation type, increasing by 21.4% from FWL to SWL types. Our model estimated a 12.8% decrease in nesting success associated with an increasing human development index. Naturally nesting loons on FWL lakes are likely to display mean nesting success levels lower than those needed to sustain populations. We suggest that natural nesting habitat on lakes with fluctuating water levels during the loon nesting season may constitute an ecological trap warranting consideration of raft management. Findings in this study are germane for managing breeding loon populations, particularly those on reservoirs requiring permits from the Federal Energy Regulatory Commission.  相似文献   
86.
87.
The sulfur of cystine and methionine may be removed from proteins by Raney nickel catalyst. The method has been applied to casein and egg albumin. Rat repletion studies and microbiological assays demonstrate that the desulfurized proteins retain other essential amino acids. The method may be modified to prepare a methionine-containing, cystine-free protein.  相似文献   
88.
Zootherapy is the treatment of human ailments with remedies made from animals and their products. Despite its prevalence in traditional medical practices worldwide, research on this phenomenon has often been neglected in comparison to medicinal plant research. This review discusses some related aspects of the use of animal-based remedies in Latin America, identifies those species used as folk remedies, and discusses the implications of zootherapy for public health and biological conservation. The review of literature revealed that at least 584 animal species, distributed in 13 taxonomic categories, have been used in traditional medicine in region. The number of medicinal species catalogued was quite expansive and demonstrates the importance of zootherapy as an alternative mode of therapy in Latin America. Nevertheless, this number is certainly underestimated since the number of studies on the theme are very limited. Animals provide the raw materials for remedies prescribed clinically and are also used in the form of amulets and charms in magic-religious rituals and ceremonies. Zootherapeutic resources were used to treat different diseases. The medicinal fauna is largely based on wild animals, including some endangered species. Besides being influenced by cultural aspects, the relations between humans and biodiversity in the form of zootherapeutic practices are conditioned by the social and economic relations between humans themselves. Further ethnopharmacological studies are necessary to increase our understanding of the links between traditional uses of faunistic resources and conservation biology, public health policies, sustainable management of natural resources and bio-prospecting.  相似文献   
89.
THE reactivity of anti-angiotensin sera with several angiotensin analogues and fragments has been studied by several investigators1–9. The importance of the C-terminal for immunological specificity has been emphasized and, in accordance with this concept, the cross-reactivity of anti-angiotensin II sera towards angiotensin I and vice versa, has been found to be quite limited. Indeed, some investigators have failed to demonstrate any cross-reactivity10.  相似文献   
90.
Fluctuating asymmetry (FA) is the most commonly used measure of developmental instability. The relation between FA and individual fitness remains controversial, partly due to limited knowledge on the mechanisms behind variation in FA. To address this, we investigated the associations between FA, growth and reproduction as well as the ontogeny of FA in a clonal population of Daphnia magna . FA was not correlated with growth and reproduction, either at the between- or the within-individual level, in a high ( N  = 48 individuals) or in a low ( N  = 52 individuals) food-quantity regime. There were therefore no indications of functional effects of FA or of phenotypic trade-offs between developmental stability, growth and reproduction. Individual asymmetries varied randomly in sign and magnitude between subsequent molts ( N  = 19 individuals, 9–11 instars), but the levels of FA were generally lowest at intermediate ages. No feedback between right and left sides was detected. This suggests that FA only reflects the most recent growth history, that developmental instability may increase in old age, and that FA depends on processes operating on each side of the body independently. The results also suggest that FA differences within and among individual Daphnia are largely random, with limited biological significance.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 179–192.  相似文献   
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