Muscarinic inhibition of prolactin production in cultures of rat pituitary cells

Acetylcholine inhibits prolactin production from cell cultures of rat pituitary glands with a half-maximal effect at about 0.2 μM, and from GH-cells, clonal strains of rat pituitary cells, with a half-maximal effect at about 1 μM. The inhibition ranges between 80 and 40 % of control values. Inhibition is detectable at 2 hours, and continues for days in the presence of the anticholinesterase, eserine. Muscarinic agonists mimic the cholinergic inhibition and nicotinic agonists do not. The inhibition is blocked by atropine, a muscarinic antagonist, and not by hexamethonium, a nicotinic antagonist.     

Proteomic characterization of postmortem amyloid plaques isolated by laser capture microdissection

The presence of amyloid plaques in the brain is one of the pathological hallmarks of Alzheimer's disease (AD). We report here a comprehensive proteomic analysis of senile plaques from postmortem AD brain tissues. Senile plaques labeled with thioflavin-S were procured by laser capture microdissection, and their protein components were analyzed by liquid chromatography coupled with tandem mass spectrometry. We identified a total of 488 proteins co-isolated with the plaques, and we found multiple phosphorylation sites on the neurofilament intermediate chain, implicating the complexity and diversity of cellular processes involved in the plaque formation. More significantly, we identified 26 proteins enriched in the plaques of two AD cases by quantitative comparison with surrounding non-plaque tissues. The localization of several proteins in the plaques was further confirmed by the approach of immunohistochemistry. In addition to previously identified plaque constituents, we discovered novel association of dynein heavy chain with the plaques in human postmortem brain and in a double transgenic AD mouse model, suggesting that neuronal transport may play a role in neuritic degeneration. Overall, our results revealed for the first time the sub-proteome of amyloid plaques that is important for further studies on disease biomarker identification and molecular mechanisms of AD pathogenesis.     

Natural selection in the laboratory for a change in resistance byDrosophila melanogaster to the parasitoid waspAsobara tabida

The selection response of the polymorphic hostD. melanogaster (Meigen) to the braconid waspA. tabida (Nees) is addressed. Cages of flies with and without wasps were initiated with a population ofD. melanogaster that exhibited variation both in larval foraging behavior and in encapsulation ability. Encapsulation ability was measured as the proportion of parasitized larvae that produce a hardened capsule which encapsulates the wasp egg and ultimately kills the wasp larva. We determined whether the host population changed its encapsulation ability and/or its foraging behavior in response to the wasp. Both species were collected from a local orchard whereA. tabida is the only wasp known to parasitizeD. melanogaster larvae. The naturally occurring genetic polymorphism for rover and sitter larval foraging behavior inD. melanogaster is also found in this field population.A. tabida's vibrotactic search behavior enables it to detect rover more frequently than sitter larvae. Rover larvae move significantly more while feeding than do sitter larvae. In this field population, rover larvae also show higher encapsulation abilities than do sitter larvae. Six cage populations, three without wasps and three with wasps, each containing an equal mixture of rover and sitter flies, were established in the laboratory and maintained for 19 fly generations. Selection pressure in the laboratory was similar to that found in the field population from which the flies and wasps were derived. We found that larvae from cages with wasps developed a significantly higher frequency of encapsulation than those reared without wasps. We were, however, unable to detect a change in larval movement (rover or sitter behavior) in larvae from cages subject to selection from wasps compared to larvae from cages containing no wasps. This may have resulted from a balance between two selective forces, selection against rovers by the wasps' use of vibrotaxis, and selection for rovers resulting from their increased encapsulation abilities     

In vitro regeneration in chile pepper (Capsicum annuum L.) from ‘half-seed explants’

An in vitro regeneration protocol has been developed from half-seed explants of a mild (cv. New Mexico-6) and a pungent (cv. Rajpur Hirapur) chile pepper (Capsicum annuum L). Imbibed seeds were cut into two parts such that one portion contained the cotyledons and a part of the hypocotyl (part A) while the other part had the proximal part of the hypocotyl and the radicle (part B). These explants were cultured on MS medium with or without cytokinins (KIN, BA, ZEA, 2iP). Cytokinins dramatically increased both the percentage of explants forming buds as well as the number of buds per explant, and also hastened the rate of bud production. The relative efficacy of cytokinins in inducing the formation of leafy buds varied in the two cultivars. However, the best response was observed with ZEA in both cultivars. The highest percentage of bud formation was recorded after presoaking part B explants for 72 hours. The elongation growth of leafy buds was severely inhibited in the continuous presence of high concentrations of cytokinins, and frequently the buds became quite thick, ill-defined and vitreous. Within 3–5 weeks of transfer to Magenta boxes containing vermiculite and soil (1:3), 70–85% of the rooted hypocotyls developed 1–2 elongated shoots. Following transfer to pots, these plantlets grew into normal plants.Abbreviations BA benzylamino purine - IAA indole-3-acetic acid - 2iP 6--dimethyl (allyl) amino purine - KIN kinetin - MS Murashige and Skoog medium - NAA napthaleneacetic acid - ZEA zeatin     

Effects of Nile perch, Lates niloticus, on functional and specific fish diversity in Uganda's Lake Kyoga system

The introduction of Nile perch, Lates niloticus, to Lake Victoria, East Africa, interacted with eutrophication to cause a reorganization of the lake's food web and the extirpation of many endemic fishes. The Lake Kyoga satellite system lies downstream from Lake Victoria. It encompasses species‐rich lakes where Nile perch are absent or very rare, and low diversity lakes where L. niloticus is abundant. In 1999 we surveyed seven lakes in the Kyoga system using experimental monofilament gill nets (1/4–1 inches variable mesh). At Boston University we assessed δ¹⁵N signatures of epaxial muscle from subsamples of the catch (n = 361). These signatures are often highly correlated with the near‐term mean realized trophic position of an individual organism. A neural network analysis of fish length, species name, trophic level, and lake of origin fish explained 94% of the sample variance in δ¹⁵N. We analysed statistical patterns in these signatures at a number of spatial scales. The relationship between trophic level and δ¹⁵N varied greatly among lakes. Higher diversity perch‐free lakes had greater variance in δ¹⁵N values and fish lengths than lower diversity Nile perch lakes, suggesting an important relationship between species diversity and functional diversity. Against expectations, lake size was negatively correlated with δ¹⁵N. Patterns in stable isotope signatures indicated that Nile perch lakes have shorter food chains than perch‐free lakes. The results throw up two management problems for the Kyoga system. Impacted lakes need to be studied to understand and ameliorate the community‐level effects of Nile perch introduction, whereas the species‐rich nonperch lakes, which harbour a large proportion of the remaining diversity of regionally endemic taxa, are in need of conservation planning.     

The striking polyphyly of Suiriri: Convergent evolution and social mimicry in two cryptic Neotropical birds

Two species of Suiriri (Aves: Tyrannidae) inhabit semi‐open habitats in South America: the polytypic Suiriri Flycatcher (S. suiriri) and the monotypic Chapada Flycatcher (S. affinis). The phylogenetic relationship between these congeneric species has never been investigated in detail. Here we used molecular tools—three nuclear introns and two mitochondrial genes—to investigate the systematic position of the Chapada Flycatcher, comparing the results found with morphological and behavioral data. We found that the polytypic Suiriri Flycatcher to be monophyletic and that it is included in a clade of Elaeniini flycatchers including Phyllomyias, Phaeomyias, and Capsiempis among other genera. The Chapada Flycatcher, on the other hand, is a member of the Fluvicolini, sister to Sublegatus, and should be allocated on its own monospecific genus, which we herein describe. We suggest that social mimicry is responsible for the remarkable convergence in size, shape, plumage coloration, and behavior in the adults of the Suiriri Flycatcher and the Chapada Flycatcher.