Biological effects of selenium and relationships with carcinogenesis†

Selenium is an element that is both essential, at low levels of dietary intake, and toxic, at high levels, to man and a wide range of animals. The purpose of the communication is to review the evidence for the involvement of hyper‐ and hypo‐selenosis in the aetiology of cancer. High levels of selenium intake have been blamed for an increase in cancer, dental caries and an array of other conditions. Critical evaluation of the evidence, however, leads to the conclusion that such claims have little substance. On the other hand, low levels of selenium intake may be associated with an increased incidence of certain forms of cancer and there appears to be an inverse relationship between blood selenium levels and cancer death rate in the United States. Keshan Disease, in the People's Republic of China has only been shown to occur in populations severely depleted of selenium. In well nourished populations there is no evidence to indicate that selenium supplements have any prophylactic or therapeutic benefit against human diseases such as cancer, cardiovascular disease or cystic fibrosis.     

Characterisation of cysteine proteinase activities in the digestive tract of juvenile <Emphasis Type="Italic">Paragnathia formica</Emphasis> isopods,ectoparasites of estuarine fish

Juveniles of Paragnathia formica Hesse (Isopoda; Gnathiidae) are haematophagous ectoparasites, feeding on fish blood which supplies the nutrients for their development through growth and moulting, and the subsequent survival and reproduction of the free-living adults. Little is known of the mechanisms of digestion in juvenile gnathiids, and biochemical studies on the digestive tract of these interesting estuarine isopods have not been undertaken previously. Here, functionally active cathepsin-like cysteine proteinases are identified in the digestive system of juvenile praniza (fed) and zuphea (unfed) forms. The physiological pH of the digestive tract and the optimum proteolytic activities detected in praniza 3 homogenates using the cathepsin B/L, cathepsin B, and cathepsin H fluorogenic substrates, N-Carbobenzoxy-Phe-Arg-4-methoxy-2-naphthylamine (Z-phe-arg-MNA), N-Carbobenzoxy-Arg-Arg-4-methoxy-2-naphthylamine (Z-arg-arg-MNA) and Arg-4-methoxy-2-naphthylamine (H-arg-MNA), respectively, are in the acidic range (pH 5.8–6.7). Inhibition profiles against Z-phe-arg-MNA and Z-arg-arg-MNA using the cathepsin B inactivator urea, and cysteine proteinase inhibitors, support the presence of cathepsin L- and B-like enzymes. These proteolytic activities are 10–50 times higher in homogenates of praniza 3 compared with zuphea 3 forms. Histochemistry of praniza 3 sections reveals that the predominant enzyme activity towards Z-phe-arg-MNA is limited to the digestive glands during early and mid stages of digestion; later, this activity appears in the lining of the anterior hindgut. Moreover, activity towards Z-arg-arg-MNA is generally restricted to the digestive glands, and only occasionally present in the anterior hindgut. In conclusion, the digestive glands are the main site of cathepsin-like cysteine proteinase activities in P. formica juveniles; these enzymes appear to be important to the digestion of host fish blood enabling development through to the free-living adult.     

A regional-scale sustainable development index: the case of Baja California Sur,Mexico

Sustainable development, as a multi-dimensional concept, is difficult to measure. Some efforts using indicators and indices have appeared in recent years, but most were developed on a national scale. Use of sustainability indicators has proven valuable for attaining better management of the environment by minimizing information gaps and maximizing community capabilities in terms of economic, social, environmental, and institutional sustainability dimensions. However, at least in the case of developing countries, the potential exists that national sustainability measures, based on national level indicators, may mask problems in sub-national zones with highly unsustainable conditions. This paper proposes a methodology to evaluate sustainable development at a local level, the use of which could be helpful in comparing different regions within a country or even among different countries. National sustainability indicators should result from a combination (whether additive or proportional) of regional sustainability indicators, as developed in this paper.     

Geographic structure in Alaskan Pacific ocean perch (<Emphasis Type="Italic">Sebastes alutus</Emphasis>) indicates limited lifetime dispersal

Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005) sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there was significant, geographically related genetic structure (F _ST = 0.0123, P < 10⁻⁵). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management, which suggests that measures for POP fisheries conservation should be revisited.     

Assessment of patch quality by ladybirds: relative response to conspecific and heterospecific larval tracks a consequence of habitat similarity?

Summary. Aphid colonies can reach high levels of abundance but last for short periods of time. The larvae of aphidophagous ladybirds (Coleoptera: Coccinellidae) that feed on these colonies might therefore suffer from starvation, which favours the occurrence of cannibalism and intraguild predation. Thus, the assessment of patch quality becomes crucial and it has been shown that female ladybirds refrain from laying eggs in the presence of an oviposition deterring semiochemical deposited by their larvae. Adalia bipunctata (L.), Adalia decempunctata (L.) and Coccinella septempunctata L. are 3 sympatric species of ladybirds, which can co-occur in aphid colonies. As a consequence, their eggs and larvae are under threat, not only from cannibalism but also intraguild predation. Females should, therefore, also use the tracks deposited by heterospecific larvae to assess the quality of aphid colonies as oviposition sites. The expectation is that: 1- the strength of the reaction to each other’s larval tracks should be correlated with percentage habitat overlap and that 2- the reaction to conspecific larval tracks should be stronger than to heterospecific tracks. In order to test these hypotheses, females’ oviposition behaviour was analysed and a chemical analysis of the tracks of their larvae undertaken. The results show that oviposition behaviour is not related to habitat overlap. Both species of Adalia react to tracks of their own larvae and those of C. septempunctata, but A. decempunctata reacted more strongly than A. bipunctata. C. septempunctata reacted very slightly to its own tracks but not to those of either species of Adalia. The larval tracks are mainly composed of alkanes. Those of the two species of Adalia are qualitatively 100% similar and 60% so when the quantitative results are compared. They are, however, only 24–29% similar to those of Coccinella septempunctata.     

Ecosystem network analysis indicators are generally robust to parameter uncertainty in a phosphorus model of Lake Sidney Lanier, USA

Understanding how data uncertainty influences ecosystem analysis is critical as we move toward ecosystem-based management. Here, we investigate how 18 Ecological Network Analysis (ENA) indicators that characterize ecosystem growth, development, and condition are affected by uncertainty in an ecosystem model of Lake Sidney Lanier (USA). We applied ENA to 122 plausible parameterizations of the ecosystem developed by Borrett and Osidele (2007, Ecological Modelling 200, 371-387), and then used the coefficient of variation (CV) to compare system indicator variability. We considered Total System Throughput (TST) as a measure of the underlying model uncertainty and tested three hypotheses. First, we hypothesized that non-ratio indicators whose calculation includes the TST would be at least as variable as TST if not more variable. Second, we postulated that indicators calculated as ratios, with TST in the numerator and denominator would tend to be less variable than TST because its influence will cancel. Last, we expected the Average Mutual Information (AMI) to be less variable than TST because it is a bounded function. Our work shows that the 18 indicators grouped into four categories. The first group has significantly larger CVs than the CV for TST. In this group, model uncertainty is amplified rendering these three indicators less useful. The second group of four indicators shows no significant difference in variability with respect to TST. Finally, there are two groups whose CV values are significantly lower than that for TST. The least variable group includes the ratio-based indicators and Average Mutual Information. Due to their low variability, we conclude that these indicators are the most robust to the parameter uncertainty and most useful for ecosystem assessment and comparative ecosystem analysis. In summary, this work suggests that we can be as certain, or more certain, in most of the selected ENA indicators as we are in the parameters of the model analyzed.     

用Autospec-Ultima NT气相色谱-高分辨质谱分析二噁英及相关的持久性有机污染物

“二噁英”是指一类化学结构和生物特征均有某些相似之处的化合物.这些有毒化合物有几百种,可分为相关的三大类:氯代二苯并-对-二噁英(CDDs),氯代二苯并呋喃(CDFs)和某些多氯代联苯(PCBs).CDDs和CDFs并非与生具有,而是由于人类活动不注意而生成的.天然过程也会产生CDDs和CDFs.     

Thermal dependency of burrowing in three species within the bivalve genus <Emphasis Type="Italic">Laternula</Emphasis>: a latitudinal comparison

The upper thermal limits for burrowing and survival were compared with micro-habitat temperature for anomalodesmatan clams: Laternula elliptica (Antarctica, 67°S); Laternula recta, (temperate Australia, 38°S) and Laternula truncata (tropical Singapore, 1°N). Lethal limits (LT₅₀) were higher than burrowing limits (BT₅₀) in L. elliptica (7.5–9.0 and 2.2°C) and L. recta (winter, 32.8–36.8 and 31.1–32.8°C) but the same range for L. truncata (33.0–35.0 and 33.4–34.9°C). L. elliptica and L. truncata had a BT₅₀ 0.4 and 2.4–3.9°C, respectively, above their maximum experienced temperature. L. recta, which experience solar heating during midday low tides, had a BT₅₀ 0.7–2.4°C below and a range for LT₅₀ that spanned their predicted environmental maximum (33.5°C). L. recta showed no seasonal difference in LT₅₀ or BT₅₀. Our single genus comparisons contrast with macrophysiological studies showing that temperate species cope better with elevated temperatures. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.