Predator detection and avoidance by starlings under differing scenarios of predation risk

Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation.     

RECENT APPEARANCE OF CYLINDROSPEMOPSIS (CYANOBACTEIUA) IN FIVE HYPEREUTROPHIC FLORIDA LAKES1

Observations of historical and recent phytoplankton samples from five hypereutrophic Florida lakes indicate that nitrogen-fixing cyanobacteria in the genus Cylindrospermopsis Seenayya et Subba Raju have entered these water-bodies sometime in the last 30 years. Cylindrospermopsis forms a year-round bloom in one of the five lakes, dominates seasonally in another, and is at least at times an important component of the phytoplankton community in the remaining three. The increase in abundance of Cylindrospermopsis in Florida lakes could have implications for water management.     

Growth Phase-Dependent Regulation of Vsr Endonuclease May Contribute to 5-Methylcytosine Mutational Hot Spots in Escherichia coli

Using rabbit polyclonal antibodies, we have shown that the Dcm cytosine methylase of Escherichia coli is maintained at a constant level during cell growth, while Vsr endonuclease levels are growth phase dependent. Decreased production of Vsr relative to Dcm during the log phase may contribute substantially to the mutability of 5-methylcytosine.     

Nitrosating activity in Escherichia coli

Nitrosation activity was measured in Escherichia coli isolates and a range of nitrite reductase (nir) mutants. Activity was only detected in intact cells and could be inhibited by a number of treatments such as sonication and osmotic shock. Aerobically-grown cells had highest nitrosation activity compared to oxygen-limited ones. Inclusion of nitrite in growth media induced high activities of nitrite reductase and for some isolates, nitrosation. Analysis of nir mutants identified two which were unable to nitrosate. This result suggested that NADH-dependent nitrite reductase was implicated either directly or indirectly in nitrosation.     

Dynamic and temporal structure of the troglobitic beetle Speonomus hydrophilus (Coleoptera: Bathyscimae)

The population ecology of the beetle Speonomus hydrophilus , occurring both in caves (reduced fluctuations in many abiotic parameters) and under the deepest layer of soil in mountains (MSS, more exposed to climatic variations), was studied in four habitats in the French central Pyrenees We have assessed some of the characteristics of the environment where these populations occur c g physical data (altitude and exposure), geologic data (nature of the parent-rock) and abiotic parameters (temperature with its seasonal fluctuations) and we investigated the relative importance of environmental structure and ecological characteristics on the temporal organization of S hydrophilus and the troglobitic fauna which cohabits The climatic study shows the existence of an annual thermal cycle which is regular and well marked for the MSS habitats but slightly out of phase with the surface cycle These periodic variations however slight may be stressful for troglobitic species In the MSS populations, the phenology of the entire community is reflected in the pattern seen in Speonomus The analysis of faunal profiles shows that samples follow the same seasonal succession during the annual cycle A potential seasonal rhythm of emergence may reflect a seasonal rhythm of vitellogenesis which produces a rhythm of egg-laying     

Simple, reliable and fast spectrofluorometric method for determination of plasma Verteporfin (Visudyne) levels during photodynamic therapy for choroidal neovascularization.

Photodynamic therapy with Verteporfin, a potent photosensitizer dye, is a very effective treatment for age related macular degeneration due to choroidal neovascularization. Photodynamic therapy offers the potential for selective tissue injury in part attributable to preferential localization of Verteporfin, administrated by intravenous infusion, to the choroidal neovascularization complex and irradiation of the complex with non-laser thermal light at 690 nm resulting in at least temporary thrombosis and vessel closure. Verteporfin is a benzoporphyrin derivative monoacid ring A formulated as a unilamellar liposome. In the blood Verteporfin is associated with lipoprotein fractions and is rapidly cleared via a receptor-mediated uptake mechanism due the high expression of LDL receptors in neovascular tissues. Verteporfin was undetectable in plasma 24 hr after infusion of the recommended dose: 6 mg/m2 of body surface area. The main side effect is photosensitivity of skin which is usually short-lived (24-48 hr) with a low incidence (2.3%). As skin photosensitivity depends on circulating rather than tissue drug levels, we investigate the possibility of developing a simple, fast and reliable spectrofluorometric method to measure plasma Verteporfin levels. Fluorescence emission spectrum (550-750 nm) of 1:10 saline diluted plasma with lambda exc=430 nm showed a characteristic emission peak at 692 nm, the height being proportional to the Verteporfin levels. The sensitivity is around 100 ng/ml and the pharmacokinetics of Verteporfin has been studied from 0 to 5 hr after infusion in six patients older than 65 years with age-related macular degeneration.     

Inhibition of N-linked oligosaccharide processing does not prevent the secretion of thyroglobulin. A study with swainsonine and deoxynojirimycin

The effects of two drugs, swainsonine (SW) and deoxynojirimycin (dNM), on synthesis and export of thyroglobulin were studied in folliculized porcine thyroid cells cultured in a serum-free medium. These drugs were expected to alter N-linked glycans in thyroglobulin. Newly synthesized thyroglobulin labeled with [2-3H]mannose or [4,5-3H]leucine was obtained by immunoprecipitation from the follicular contents, culture media and cell extracts; the first two compartments, containing secreted thyroglobulin, were sometimes analyzed together. Leucine incorporation was not inhibited by SW and only slightly by dNM. In contrast dNM strongly decreased mannose incorporation (by up to 50-75% at 1-3 mM). However after 16-h mannose labelings, SW and/or dNM at 2.5 microM and 3 mM respectively did not significantly modify the relative proportions of radioactive thyroglobulin in the above-mentioned compartments. Pronase glycopeptides prepared from these thyroglobulins were examined with respect to behaviour on concanavalin-A-Sepharose and position on Bio-Gel P-4. Oligosaccharides released by endoglucosaminidase H and with high affinity for the lectin, i.e. high-mannose and certain hybrids, were further characterized by various exoglycosidase treatments. Thyroglobulin from control cells displayed complex and high-mannose glycans comparable in size and proportion to those attributed to tissue-extracted porcine thyroglobulin. After treatment with SW (an inhibitor of alpha-mannosidase II), complex glycans were almost totally replaced by sialylated hybrid glycans. In contrast to this nearly total suppression, dNM (an inhibitor of the trimming glucosidases) caused only a 30% decrease in labeling of complex units and an about 50% increase in high-mannose glycans, covered to some degree by glucose. Finally a [3H]leucine pulse-chase study was performed on thyroglobulin secretion in the absence or presence of both SW and dNM. Though a slowdown was detectable in the first few hours, this study revealed no change in the long-term export of thyroglobulin.     

Immunochemical evidence for a role of complex carbohydrate chains in thyroglobulin antigenicity

Thyroglobulin secreted by porcine thyroid cells in serum-free culture was previously found (Ronin, C., Fenouillet, E., Hovsepian, S., Fayet, G., and Fournet, B. (1986) J. Biol. Chem. 261, 7287-7293) to contain more highly branched complex carbohydrate chains than the thyroid-derived molecules. When assayed for their ability to react with polyclonal antibodies directed against the natural prohormone in competitive radioimmunoassays, using the porcine antigen as iodinated tracer and standard competitor, in vitro thyroglobulin appeared to be 4-fold less immunoreactive than the in vivo molecule. However, both types of thyroglobulin exhibited superimposable incomplete displacement curves after peripheral deglycosylation using a mixture of neuraminidase, alpha-, and beta-galactosidases while they behave as good competitors as the native antigen after removal of the majority of the carbohydrate chains by Endo-beta-N-acetylglucosaminidase F. Solid-phase binding assays revealed that in vitro thyroglobulin was able to bind less antibodies than its thyroid-derived counterpart before as well as after treatment with exo- or endoglycosidases. Furthermore, only 20% of thyroglobulin biosynthetically labeled with glucosamine could be precipitated with specific antibodies followed by addition of staphylococcal-protein A, whereas up to 61% of the labeling was specifically bound when the antibodies were preincubated with protein A. After pronase digestion, both thyroglobulin-like material displayed different carbohydrate structures as judged by concanavalin A-Sepharose analysis. Thus, substituting multiantennary complex carbohydrate chains to the usual biantennary and high mannose structures present on thyroid-derived thyroglobulin had a profound effect on the prohormone immunoreactivity.     

Multidrug resistance evaluation by confocal microscopy in primary urothelial cancer explant colonies

Assessing functional multidrug resistance (MDR) status in clinical biopsy material using drug autofluorescence has potential applications to clinical management. The small size of many cystoscopy specimens has led us to develop, as an alternative to flow cytometry, a protocol for studying epirubicin accumulation in adherent colonies of primary bladder cancer cells viewed live andin situ by confocal microscopy. The limitations to quantitation inherent in this technique are compensated for by preservation of cellular organisation and the elimination of non-malignant cells. Biopsy material is disaggregated and explanted into culture-grade petri dishes. After incubation for three to seven days plaques of epithelial cells have developed. Classical patterns of sensitive and resistant drug distribution are observed. Cells of the rolled edges of the colony accumulate more drug than those of the inner epithelial monolayer. Some central areas of larger colonies give the appearance of drug arrested at the intercellular junctions to give a fenestrated pattern. These observations contribute to the understanding of mechanisms in MDR as well as forming the basis for a clinical urological MDR evaluation protocol.