Are Hummingbirds Facultatively Ammonotelic? Nitrogen Excretion and Requirements as a Function of Body Size

Most birds are uricotelic. An exception to this rule may be nectar-feeding birds, which excrete significant amounts of ammonia under certain conditions. Although ammonia is toxic, because it is highly water soluble its excretion may be facilitated in animals that ingest and excrete large amounts of water. Birdpollinated plants secrete carbohydrate- and water-rich floral nectars that contain exceedingly little protein. Thus, nectarfeeding birds are faced with the dual challenge of meeting nitrogen requirements while disposing of large amounts of water. The peculiar diet of nectar-feeding birds suggests two hypotheses: (1) these birds must have low protein requirements, and (2) when they ingest large quantities of water their primary nitrogen excretion product may be ammonia. To test these hypotheses, we measured maintenance nitrogen requirements (MNR) and total endogenous nitrogen losses (TENL) in three hummingbird species (Archilochus alexandri, Eugenes fulgens, and Lampornis clemenciae) fed on diets with varying sugar, protein, and water content. We also quantified the form in which the by-products of nitrogen metabolism were excreted. The MNR and TENL of the hummingbirds examined were exceptionally low. However, no birds excreted more than 50% of nitrogen as ammonia or more nitrogen as ammonia than urates. Furthermore, ammonia excretion was not influenced by either water or protein intake. The smallest species (A. alexandri) excreted a significantly greater proportion (125%) of their nitrogenous wastes as ammonia than the larger hummingbirds (≈4%). Our results support the hypothesis that nectar-feeding birds have low protein requirements but cast doubt on the notion that they are facultatively ammonotelic. Our data also hint at a possible size-dependent dichotomy in hummingbirds, with higher ammonia excretion in smaller species. Differences in proportionate water loads and/or postrenal modification of urine may explain this dichotomy

Sucrose as a Feeding Deterrent for Fruit-Eating Birds

Economic losses due to bird damage to small fruits such as blueberries, grapes, and cherries can be very high and are expected to increase in the future. The primary sugars in these fruits are glucose and fructose. Sucrose is present in very low concentrations only. Our research has unveiled a physiological trait common to many fruit-eating species in the phylogenetically related families Muscicapidae, Mirnidae, and Sturnidae. These birds are unable to digest sucrose because they lack the intestinal enzyme sucrase which hydrolyzes sucrose into glucose and fructose prior to absorption. In cage tests these birds prefer glucose and fructose to sucrose solutions and reject concentrated sucrose solutions and artificial gel fruits made with sucrose. Is it reasonable and feasible to attempt development of high-sucrose cultivars with the goal of deterring birds in fruit crops? Variation in the proportion of sucrose in mature fruits is present among strawberry, cherry, and blueberry cultivars. Consequently, genetic resources are available to develop high-sucrose cultivars through traditional breeding practices or bioengineering. We suggest that major fm i t-depredating species, such as American robins and European starlings, will avoid eating high-sucrose fruits in an agricultural setting provided that (1) sucrose concentration in these fruits is sufficiently high, (2) there is alternate food available, and (3) high-sucrose fruits are planted in relatively large stands. Despite the obvious need for more data, we believe that increasing the sucrose content of small-berried fruits is a promising direction in integrated pest management research that can result in substantial reductions in bird damage

Comparative isotopic natural history of two native passerines (Troglodytes cobbi and Cinclodes antarcticus) and the invasive rats (Rattus norvegicus) that extirpate them

While several studies have shown that invasive rats can have negative effects on island birds through predation (both direct predation and nest predation), other mechanisms for the effects of invasives on island biota have been given less attention. Here we explore another potential mechanism by which invasive rats can affect native island birds: the competitive use of common resources. We used stable isotope analyses to estimate the fraction of marine and terrestrial sources incorporated into the tissues of two species of passerines (Troglodytes cobbi, Troglodytidae; and Cinclodes antarcticus, Furnariidae) and Norway rats (Rattus norvegicus, Muridae) in the Falkland Islands. These two passerines are absent on islands where rats are present. We found significant incorporation of marine resources in the three species, with the highest incorporation in tissues of T. cobbi. This species appears to be one of the passerines most reliant on marine sources and the most marine member of the family Troglodytidae. We also used the results of these isotopic analyses to estimate the isotopic niche breadth of each of these species and the isotopic niche overlap among them. Rattus norvegicus had a large isotopic niche that overlapped broadly with those of the two passerine species. We propose that different ways of both depicting and estimating isotopic niche widths are complementary rather than alternative. Our results are consistent with the notion that invasive rats might have an impact on these two species of Falkland Island passerines by using common resources, but do not rule out the possibility that part of their effect is through direct predation.MT and CMR were partially funded by National Science Foundation Grants # 0841298 and DIOS-0848028, respectively. SP and KP were funded by Antarctic Research Trust, UK Overseas Territories Environment Programme, Royal Society for Protection of Birds, Joint Nature Conservation Committee, and the Falkland Islands Government.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1442-99932017-10-31hb2017Zoology and Entomolog

Desarrollo de una herramienta para la evaluación de los examen tipo test y sus aplicaciones en la mejora de la calidad y en los criterios de evaluación de estos exámenes

Depto. de Radiología, Rehabilitación y FisioterapiaFac. de MedicinaFALSEsubmitte

Variable frequency of LRRK2 variants in the Latin American research consortium on the genetics of Parkinson's disease (LARGE-PD), a case of ancestry

ABSTARCT: Mutations in Leucine-Rich Repeat Kinase 2 (LRRK2), primarily located in codons G2019 and R1441, represent the most common genetic cause of Parkinson's disease in European-derived populations. However, little is known about the frequency of these mutations in Latin American populations. In addition, a prior study suggested that a LRRK2 polymorphism (p.Q1111H) specific to Latino and Amerindian populations might be a risk factor for Parkinson's disease, but this finding requires replication. We screened 1734 Parkinson's disease patients and 1097 controls enrolled in the Latin American Research Consortium on the Genetics of Parkinson's disease (LARGE-PD), which includes sites in Argentina, Brazil, Colombia, Ecuador, Peru, and Uruguay. Genotypes were determined by TaqMan assay (p.G2019S and p.Q1111H) or by sequencing of exon 31 (p.R1441C/G/H/S). Admixture proportion was determined using a panel of 29 ancestry informative markers. We identified a total of 29 Parkinson's disease patients (1.7%) who carried p.G2019S and the frequency ranged from 0.2% in Peru to 4.2% in Uruguay. Only two Parkinson's disease patients carried p.R1441G and one patient carried p.R1441C. There was no significant difference in the frequency of p.Q1111H in patients (3.8%) compared to controls (3.1%; OR 1.02, p = 0.873). The frequency of LRRK2-p.G2019S varied greatly between different Latin American countries and was directly correlated with the amount of European ancestry observed. p.R1441G is rare in Latin America despite the large genetic contribution made by settlers from Spain, where the mutation is relatively common

Varenicline in smokers with severe or very severe COPD after 24 weeks of treatment. A descriptive analysis: VALUE study

A large number of COPD patients are smokers. The particular characteristics of this group as well as their need to quit usually require psychological counselling and pharmacological treatment to achieve abstinence and, often, intensively. Little information is available about this issue.  The main objective of the study was to evaluate the effectiveness of varenicline after 24 weeks of treatment, with continuous abstinence between weeks 9 and 24.  This study was a post-authorization, open label, observational study of prospective follow-up. Patients included were smokers with severe or very severe COPD criteria who were treated with varenicline for 24 weeks, i.e. with a 12-week extension over the usual treatment.  The outcomes in the population of subjects completing 24 weeks of follow-up were at week 24: continuous abstinence 36.8%, 7 days point prevalence abstinence 65.7%, and continuous smoking 31.5%.The outcomes in the intention-to-treat population included at baseline were: continuous abstinence 17.7% of patients, 7 days point prevalence abstinence 31.6%, continuous smoking 15.1% and not valid/unknown 51.8%.  The mean CAT score at week 24 was 15 and reduction from the baseline was 3.77 (paired T test, p<0.01). The most common adverse events reported were nausea, vivid dreams, stomach ache, insomnia, headache and vomiting.  Patients included in VALUE were active smokers despite all of them had a severe COPD which suggests a very high degree of dependence. Although the study do not allow to infer the results to the global population of smokers with severe COPD, the outcomes have shown that, at 24 weeks follow up 36.8% of the patients were successful in quitting but from 79 patients enrolled initially only 17.7% quit.