Metapopulation dynamics and foraging plasticity in a highly vagile seabird,the southern rockhopper penguin

Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connectivity and foraging niche overlap among southern rockhopper penguin colonies of the coast of southern South America using genomic and stable isotope analyses. We found two distinct genetic clusters and detected low admixture between northern and southern colonies. Stable isotope analysis indicated niche variability between colonies, with Malvinas/Falklands colonies encompassing the species entire isotopic foraging niche, while the remaining colonies had smaller, nonoverlapping niches. A recently founded colony in continental Patagonia differed in isotopic niche width and position with Malvinas/Falklands colonies, its genetically identified founder population, suggesting the exploitation of novel foraging areas and/or prey items. Additionally, dispersing individuals found dead across the Patagonian shore in an unusual mortality event were also assigned to the northern cluster, suggesting northern individuals reach southern localities, but do not breed in these colonies. Facilitated by variability in foraging strategies, and especially during unfavorable conditions, the number of dispersing individuals may increase and enhance the probability of founding new colonies. Metapopulation demographic dynamics in seabirds should account for interannual variability in dispersal behavior and pay special attention to extreme climatic events, classically related to negative effects on population trends.     

Trophic ecology of a top predator colonizing the southern extreme of South America: Feeding habits of invasive American mink (Neovison vison) in Tierra del Fuego

The American mink (Neovison vison) is a semi-aquatic, generalist carnivore released onto Tierra del Fuego (TDF) Island in the 1940s, subsequently spreading to adjacent islands in the archipelago with potential effects on native prey populations. Knowledge of this new predator's trophic ecology is essential to identify threats, plan control strategies and conserve native fauna. We studied seasonal mink diet in TDF in different habitats. We identified undigested remains from 493 scats collected between May 2005 and March 2009 along marine coasts and freshwater shores (rivers and lakes). Small mammals and fish were the main mink prey in TDF (over 65% of diet items). Seasonal variations were not detected, but diet did vary significantly between marine and freshwater habitats, where more terrestrial items were consumed. Among mammals, mink consumed more small native rodents than exotic species. Native fish consumption was also important with greater representation of species from the families Nototheniidae and Galaxiidae in marine and freshwater habitats respectively. Birds were the third item in importance, but did not constitute a particularly large part of the mink's diet on TDF. Overall, differences found in mink diet between habitats reflected their generalist/opportunistic feeding behaviour and did not differ greatly from observations in its native range or in other areas where it has been introduced. Our results establish the interactions between this novel predator and its prey and also illustrate the need to continue research on native prey populations to quantify mink impact on them and understand the ecological context of this biotic assemblage.     

Pharmacological removal of serum amyloid P component from intracerebral plaques and cerebrovascular Aβ amyloid deposits in vivo

Human amyloid deposits always contain the normal plasma protein serum amyloid P component (SAP), owing to its avid but reversible binding to all amyloid fibrils, including the amyloid β (Aβ) fibrils in the cerebral parenchyma plaques and cerebrovascular amyloid deposits of Alzheimer''s disease (AD) and cerebral amyloid angiopathy (CAA). SAP promotes amyloid fibril formation in vitro, contributes to persistence of amyloid in vivo and is also itself directly toxic to cerebral neurons. We therefore developed (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), a drug that removes SAP from the blood, and thereby also from the cerebrospinal fluid (CSF), in patients with AD. Here we report that, after introduction of transgenic human SAP expression in the TASTPM double transgenic mouse model of AD, all the amyloid deposits contained human SAP. Depletion of circulating human SAP by CPHPC administration in these mice removed all detectable human SAP from both the intracerebral and cerebrovascular amyloid. The demonstration that removal of SAP from the blood and CSF also removes it from these amyloid deposits crucially validates the strategy of the forthcoming ‘Depletion of serum amyloid P component in Alzheimer''s disease (DESPIAD)’ clinical trial of CPHPC. The results also strongly support clinical testing of CPHPC in patients with CAA.     

Corticosterone Assimilation by a Voluntary Oral Administration in Palatable Food to Rats

Drug delivery in research on nonhuman animals in the laboratory is still challenging because it is usually invasive and stressful. Stress-free voluntary oral drug administration in water lacks precise control of dose and timing of substance ingestion. Voluntary oral consumption of corticosterone has been previously successfully applied in mice using oat flakes, but protocols for oral corticosterone administration in rats remain unavailable. This study assessed the effectiveness of voluntary oral administration to rats of a palatable piece of bread soaked with corticosterone that can be rapidly prepared and is reliably dose- and timing-controllable. After three familiarization days, all rats ate the bread within 120 seconds of presentation, irrespective of the presence or absence of corticosterone or vehicle. Corticosterone plasma levels remained at basal levels with consumption of vehicle-containing bread, and they were significantly increased with corticosterone-containing bread. Hence, the method enabled corticosterone bodily assimilation while avoiding stress, making it a possible alternative for invasive and stressful procedures. This article includes a methodological refinement that lessens unnecessary discomfort to laboratory animals and is potentially suitable for acute and chronic protocol studies.     

Nutritional Requirements of <Emphasis Type="Italic">Lactobacillus delbrueckii</Emphasis> subsp. <Emphasis Type="Italic">lactis</Emphasis> in a Chemically Defined Medium

This study was undertaken to determine the nutritional requirements of Lactobacillus delbrueckii subsp. lactis and to develop a minimal chemically defined medium that supports sustained growth of these microorganisms. The single-omission technique was applied to each component of complete chemically defined medium in order to determine the nutritional requirements. L. delbrueckii subsp. lactis was prototrophic for alanine, glycine, aspartic acid, asparagine, glutamine, threonine, and proline. The lysine requirement was strain-dependent. Magnesium was the only essential oligoelement. These microorganisms also required uracil and guanine and adenine as pyrimidine and purine sources, respectively. In view of the nutritional requirements we designed a new minimal defined medium which supports sustained growth of L. delbrueckii subsp. lactis. This medium is simple and well defined, and should be preferable to complex media for conducting future biochemical, physiological, and genetic studies on L. delbrueckii subsp. lactis.     

Isolation and characterization of a slowly milk-coagulating variant of Lactobacillus helveticus deficient in purine biosynthesis

A slowly milk-coagulating variant (Fmc(-)) of Lactobacillus helveticus CRL 1062, designated S1, was isolated and characterized. Strain S1 possessed all the known essential components required to utilize casein as a nitrogen source, which include functional proteinase and peptidase activities as well as functional amino acid, di- and tripeptide, and oligopeptide transport systems. The amino acid requirements of strain S1 were similar to those of the parental strain. However, on a purine-free, chemically defined medium, the growth rate of the Fmc(-) strain was threefold lower than that of the wild-type strain. L. helveticus S1 was found to be defective in IMP dehydrogenase activity and therefore was deficient in the ability to synthesize XMP and GMP. This conclusion was further supported by the observation that the addition of guanine or xanthine to milk, a substrate poor in purine compounds, restored the Fmc(+) phenotype of L. helveticus S1.     

Sequence analysis of pLBB1, a cryptic plasmid from Lactobacillus delbrueckii subsp. bulgaricus

The first report of the complete nucleotide sequence of a cryptic plasmid from Lactobacillus delbrueckii subsp. bulgaricus (Lactobacillus bulgaricus) is presented. The plasmid pLBB1 consists of 6127 bp with a GC content of 44.8%. No ssDNA was detected by hybridization experiments, which is consistent with the notion that pLBB1 does not replicate by a rolling circle mechanism. A putative replication region of pLBB1 was cloned and found to be functional in Lactobacillus johnsonii and Lactococcus lactis. Plasmid pLBB1 showed significant DNA sequence identity with plasmid pLL1212 from Lactobacillus delbrueckii subsp. lactis (Lactobacillus lactis) CRL1212 (GenBank accession No. AF109691). Four open reading frames (ORFs) larger than 100 amino acids were identified. ORFA shared similarity with a putative primase-helicase system, and ORFB and ORFC exhibited limited identity with a mobilization protein and a transposase, respectively. Curing experiments did not allowed us to assign a function to the ORFs.     

A probabilistic model for the establishment of neuron polarity

The main aim of this paper is to present a simple probabilistic model for the early stage of neuron growth: the specification on an axon out of several initially similar neurites. The model is a Markov process with competition between the growing neurites, wherein longer objects have more chances to grow, and parameter alpha determines the intensity of the competition. For alpha > 1 the model provides results which are qualitatively similar to the experimental ones, i.e. selection of one rapidly elongating axon out of several neurites while other less successful neurites stop growing at some random time. Rigorous mathematical proofs are given.