Pilot plant scale extraction of alginate from Macrocystis pyrifera. 1. Effect of pre-extraction treatments on yield and quality of alginate

In the extraction of alginate from brown seaweeds, the acid pre-extraction treatment has been considered by many authors as an essential step because it makes the alginate more readily soluble in an alkaline solution. At pilot plant level, extractions were made (i) using formalin treatment prior to the acid pre-extraction treatment (ii) using different acid treatments so the calcium ions exchanged varied from 83% to 4%. The use of formalin treatment gave a product with less color. During the acid pre-extraction treatment, it was possible to reduce the calcium exchanged from 33.4% to almost zero with a maximum reduction in alginate yield of 7%. The degree of acid treatment was positively correlated to calcium exchanged and yield but negatively correlated with alginate viscosity. Using strong acid conditions the viscosity was 168 mPa s, while mild acid conditions produced an alginate with 623 mPa s. The direct extraction from calcium alginate to sodium alginate is possible because strong alkaline conditions were used, pH 10 at 80 °C for two hours and with a low water volume. The best pre-extraction treatment to obtain an alginate with high viscoity is to hydrate the alga with 0.1% formalin overnight, then wash the alga once with hydrochloric acid at pH 4 using a batch system with continuous agitation during 15 min. This revised version was published online in August 2006 with corrections to the Cover Date.     

Responses ofHevea brasiliensis Muell. Arg. plants to low temperatures under controlled conditions

In this study we have examined the responses ofHevea plants to low temperatures in growth chambers simulating winter conditions in the tropics. The low temperatures increased the leaf diffusive resistance even with a rise in the leaf temperatures toward the end of day. The total chlorophyll levels were reduced by chilling, with no changes in the chlorophyll a/b ratio. Neither organic solute nor electrolyte leakage were observed at low temperatures. These results explain the low growth rate of plants and the lack of serious chilling symptoms (necrosis) in mature leaves during winter conditions near latitude 22° S in Brazil.     

Morphological and physiological changes in Leishmania promastigotes induced by yangambin, a lignan obtained from Ocotea duckei

We have previously demonstrated that yangambin, a lignan obtained from Ocotea duckei Vattimo (Lauraceae), shows antileishmanial activity against promastigote forms of Leishmania chagasi and Leishmania amazonensis. The aim of this study was to determine the in vitro effects of yangambin against these parasites using electron and confocal microscopy. L. chagasi and L. amazonensis promastigotes were incubated respectively with 50 μg/mL and 65 μg/mL of pure yangambin and stained with acridine orange. Treated-parasites showed significant alterations in fluorescence emission pattern and cell morphology when compared with control cells, including the appearance of abnormal round-shaped cells, loss of cell motility, nuclear pyknosis, cytoplasm acidification and increased number of acidic vesicular organelles (AVOs), suggesting important physiological changes. Ultrastructural analysis of treated-promatigotes showed characteristics of cell death by apoptosis as well as by autophagy. The presence of parasites exhibiting multiples nuclei suggests that yangambin may also affect the microtubule dynamic in both Leishmania species. Taken together our results show that yangambin is a promissing agent against Leishmania.     

Physical and Emotional Health Problems Experienced by Youth Engaged in Physical Fighting and Weapon Carrying

Then aims of the current study were 1) to provide cross-national estimates of the prevalence of physical fighting and weapon carrying among adolescents aged 11–15 years; (2) To examine the possible effects of physical fighting and weapon carrying on the occurrence of physical (medically treated injuries) and emotional health outcomes (multiple health complaints) among adolescents within the theoretical framework of Problem Behaviour Theory. 20,125 adolescents aged 11–15 in five countries (Belgium, Israel, USA, Canada, FYR Macedonia) were surveyed via the 2006 Health Behaviour in School Aged Children survey. Prevalence was calculated for physical fighting and weapon carrying along with physical and emotional measures that potentially result from violence. Regression analyses were used to quantify associations between violence/weapon carrying and the potential health consequences within each country. Large variations in fighting and weapon carrying were observed across countries. Boys reported more frequent episodes of fighting/weapon carrying and medically attended injuries in every country, while girls reported more emotional symptoms. Although there were some notable variations in findings between different participating countries, increased weapon carrying and physical fighting were both independently and consistently associated with more frequent reports of the potential health outcomes. Adolescents engaging in fighting and weapon carrying are also at risk for physical and emotional health outcomes. Involvement in fighting and weapon carrying can be seen as part of a constellation of risk behaviours with obvious health implications. Our findings also highlight the importance of the cultural context when examining the nature of violent behaviour for adolescents.     

A consumer's guide to nestedness analysis

Nestedness analysis has become increasingly popular in the study of biogeographic patterns of species occurrence. Nested patterns are those in which the species composition of small assemblages is a nested subset of larger assemblages. For species interaction networks such as plant–pollinator webs, nestedness analysis has also proven a valuable tool for revealing ecological and evolutionary constraints. Despite this popularity, there has been substantial controversy in the literature over the best methods to define and quantify nestedness, and how to test for patterns of nestedness against an appropriate statistical null hypothesis. Here we review this rapidly developing literature and provide suggestions and guidelines for proper analyses. We focus on the logic and the performance of different metrics and the proper choice of null models for statistical inference. We observe that traditional 'gap-counting' metrics are biased towards species loss among columns (occupied sites) and that many metrics are not invariant to basic matrix properties. The study of nestedness should be combined with an appropriate gradient analysis to infer possible causes of the observed presence–absence sequence. In our view, statistical inference should be based on a null model in which row and columns sums are fixed. Under this model, only a relatively small number of published empirical matrices are significantly nested. We call for a critical reassessment of previous studies that have used biased metrics and unconstrained null models for statistical inference.