Nitrogen-source-induced activation of neutral trehalase in Schizosaccharomyces pombe and Pachysolen tannophilus: role of cAMP as second messenger

Abstract Resting cells of the fission yeast Schizosaccharomyces pombe , suspended in buffer with glucose, responded to the addition of asparagine by increasing trehalase activity. This response was preceded by a peak in cAMP concentration. The addition of the nitrogen source to resting cells, devoid of the catalytic subunit of cAMP-dependent protein kinase, produced the transient increase in cAMP but did not promote any change in trehalase activity. In the budding yeast Pachysolen iannophilus , the activation of trehalase by nitrogen source was also accompanied by a sharp peak in cAMP. These results suggest that in the two yeasts cAMP acts as a second messenger in the transduction of the nitrogen-source-induced signal causing the activation of trehalase.     

De Novo Generation of Infectious Prions In Vitro Produces a New Disease Phenotype

Prions are the proteinaceous infectious agents responsible for Transmissible Spongiform Encephalopathies. Compelling evidence supports the hypothesis that prions are composed exclusively of a misfolded version of the prion protein (PrP^Sc) that replicates in the body in the absence of nucleic acids by inducing the misfolding of the cellular prion protein (PrP^C). The most common form of human prion disease is sporadic, which appears to have its origin in a low frequency event of spontaneous misfolding to generate the first PrP^Sc particle that then propagates as in the infectious form of the disease. The main goal of this study was to mimic an early event in the etiology of sporadic disease by attempting de novo generation of infectious PrP^Sc in vitro. For this purpose we analyzed in detail the possibility of spontaneous generation of PrP^Sc by the protein misfolding cyclic amplification (PMCA) procedure. Under standard PMCA conditions, and taking precautions to avoid cross-contamination, de novo generation of PrP^Sc was never observed, supporting the use of the technology for diagnostic applications. However, we report that PMCA can be modified to generate PrP^Sc in the absence of pre-existing PrP^Sc in different animal species at a low and variable rate. De novo generated PrP^Sc was infectious when inoculated into wild type hamsters, producing a new disease phenotype with unique clinical, neuropathological and biochemical features. Our results represent additional evidence in support of the prion hypothesis and provide a simple model to study the mechanism of sporadic prion disease. The findings also suggest that prion diversity is not restricted to those currently known, and that likely new forms of infectious protein foldings may be produced, resulting in novel disease phenotypes.     

Sensory Neuron-Derived Eph Regulates Glomerular Arbors and Modulatory Function of a Central Serotonergic Neuron

Olfactory sensory neurons connect to the antennal lobe of the fly to create the primary units for processing odor cues, the glomeruli. Unique amongst antennal-lobe neurons is an identified wide-field serotonergic neuron, the contralaterally-projecting, serotonin-immunoreactive deutocerebral neuron (CSDn). The CSDn spreads its termini all over the contralateral antennal lobe, suggesting a diffuse neuromodulatory role. A closer examination, however, reveals a restricted pattern of the CSDn arborization in some glomeruli. We show that sensory neuron-derived Eph interacts with Ephrin in the CSDn, to regulate these arborizations. Behavioural analysis of animals with altered Eph-ephrin signaling and with consequent arborization defects suggests that neuromodulation requires local glomerular-specific patterning of the CSDn termini. Our results show the importance of developmental regulation of terminal arborization of even the diffuse modulatory neurons to allow them to route sensory-inputs according to the behavioural contexts.     

Genetic relationships and structure among open-pollinated maize varieties adapted to eastern and southern Africa using microsatellite markers

Molecular characterization of open-pollinated maize varieties (OPVs) is fundamentally important in maize germplasm improvement. We investigated the extent of genetic differences, patterns of relationships, and population structure among 218 diverse OPVs widely used in southern and eastern Africa using the model-based population structure, analysis of molecular variance, cluster analysis, principal component analysis, and discriminant analysis. The OPVs were genotyped with 51 microsatellite markers and the fluorescent detection system of the Applied Biosystems 3730 Capillary Sequencer. The number of alleles detected in each OPV varied from 72 to 155, with an overall mean of 127.6. Genetic distance among the OPVs varied from 0.051 to 0.434, with a mean of 0.227. The different multivariate methods suggest the presence of 2–4 possible groups, primarily by maturity groups but also with overlapping variation between breeding programs, mega-environments, and specific agronomic traits. Nearly all OPVs in group 1 and group 2 belong to the intermediate-late and early maturity groups, respectively. Group 3 consisted of mainly intermediate maturing OPVs, while group 4 contained OPVs of different maturity groups. The OPVs widely used in eastern Africa either originated from the southern African maize breeding programs, or the majority of inbred lines used as parents by the two breeding programs in developing the OPVs might be genetically related. Some of the OPVs are much older than others, but they still did not show a clear pattern of genetic differentiation as compared with the recently developed ones, which is most likely due to recycling of the best parental lines in forming new OPVs.     

Climatic patterns in the establishment of wintering areas by North American migratory birds

Long‐distance migration in birds is relatively well studied in nature; however, one aspect of this phenomenon that remains poorly understood is the pattern of distribution presented by species during arrival to and establishment of wintering areas. Some studies suggest that the selection of areas in winter is somehow determined by climate, given its influence on both the distribution of bird species and their resources. We analyzed whether different migrant passerine species of North America present climatic preferences during arrival to and departure from their wintering areas. We used ecological niche modeling to generate monthly potential climatic distributions for 13 migratory bird species during the winter season by combining the locations recorded per month with four environmental layers. We calculated monthly coefficients of climate variation and then compared two GLM (generalized linear models), evaluated with the AIC (Akaike information criterion), to describe how these coefficients varied over the course of the season, as a measure of the patterns of establishment in the wintering areas. For 11 species, the sites show nonlinear patterns of variation in climatic preferences, with low coefficients of variation at the beginning and end of the season and higher values found in the intermediate months. The remaining two species analyzed showed a different climatic pattern of selective establishment of wintering areas, probably due to taxonomic discrepancy, which would affect their modeled winter distribution. Patterns of establishment of wintering areas in the species showed a climatic preference at the macroscale, suggesting that individuals of several species actively select wintering areas that meet specific climatic conditions. This probably gives them an advantage over the winter and during the return to breeding areas. As these areas become full of migrants, alternative suboptimal sites are occupied. Nonrandom winter area selection may also have consequences for the conservation of migratory bird species, particularly under a scenario of climate change.     

Pharmacological reactivity in cricetus aureus uterus (author's transl)]

The motility of the isolated Cricetus auratus uterus was studied and compared to that of other species. Oxitocyn, epinephrine, norepinephrine, histamine, 5-hydroxy-tryptamine and acetylcholine were used as spasmogen agents. There was not contractil response with epinephrine or nor-epinephrine. Histamine reduced basal tonus. There was contraction with acetylcholine, oxytocin and 5-hydroxy-tryptamine. Cricetus auratus uterus appeared more sensitive when the contraction was registered by the isometric method. No taquifilaxy was produced by 5-hydroxy-tryptamine, as opposed to such effect in rat uterus. The Cricetus auratus uterus has, therefore, shown similar reactivity to that of rat, but different from rabbit and guinea-pig.