Behavioral analysis of the choice of oviposition site by single females ofDrosophila Melanogaster (Diptera: Drosophilidae)

The oviposition behavior of single females of Drosophila melanogasterwas studied in population cages over 24 h. Each female shows a different behavior, but they can be arbitrarily separated into those which concentrate their egg laying in only one tube and those which spread it over more than two tubes. A comparison is made between females extracted from the Valdivian population and flies from lines selected for high and low aggregation. When one-tube females were grouped and compared with more-than-one-tube females, the aggregation indices between these groups were significantly different.     

Pentapeptide repeat proteins

The pentapeptide repeat protein (PRP) family has more than 500 members in the prokaryotic and eukaryotic kingdoms. These proteins are composed of, or contain domains composed of, tandemly repeated amino acid sequences with a consensus sequence of [S,T,A,V][D,N][L,F][S,T,R][G]. The biochemical function of the vast majority of PRP family members is unknown. The three-dimensional structure of the first member of the PRP family was determined for the fluoroquinolone resistance protein (MfpA) from Mycobacterium tuberculosis. The structure revealed that the pentapeptide repeats encode the folding of a novel right-handed quadrilateral beta-helix. MfpA binds to DNA gyrase and inhibits its activity. The rod-shaped, dimeric protein exhibits remarkable similarity in size, shape, and electrostatics to DNA.     

HIV-1 trafficking to the dendritic cell-T-cell infectious synapse uses a pathway of tetraspanin sorting to the immunological synapse

Dendritic cells (DCs) are essential components of the early events of HIV infection. Here, we characterized the trafficking pathways that HIV-1 follows during its capture by DCs and its subsequent presentation to CD4(+) T cells via an infectious synapse. Immunofluorescence microscopy indicates that the virus-containing compartment in mature DCs (mDCs) co-labels for the tetraspanins CD81, CD82, and CD9 but contains little CD63 or LAMP-1. Using ratio imaging of pH-reporting fluorescent virions in live DCs, we show that HIV-1 is internalized in an intracellular endocytic compartment with a pH of 6.2. Significantly, we demonstrate that the infectivity of cell-free virus is more stable at mildly acidic pH than at neutral pH. Using electron microscopy, we confirm that HIV-1 accumulates in intracellular vacuoles that contain CD81 positive internal membranes but overlaps only partially with CD63. When allowed to contact T cells, HIV-1-loaded DCs redistribute CD81, and CD9, as well as internalized HIV-1, but not the immunological synapse markers MHC-II and T-cell receptor to the infectious synapse. Together, our results indicate that HIV-1 is internalized into a non-conventional, non-lysosomal, endocytic compartment in mDCs and further suggest that HIV-1 is able to selectively subvert components of the intracellular trafficking machinery required for formation of the DC-T-cell immunological synapse to facilitate its own cell-to-cell transfer and propagation.     

Thin-film IrOx pH microelectrode for microfluidic-based microsystems

Microsensors are valuable tools to monitor cell metabolism in cell culture volumes. The present research describes the fabrication and characterization of on-chip thin-film iridium oxide pH microsensors with dimensions of 20 microm x 20 microm and 20 microm x 40 microm suitable to be incorporated into nl volumes. IrOx thin films were formed on platinum microelectrodes by electrochemical deposition in galvanostatic mode. Anodically grown iridium oxide films showed a near super-Nernstian response with a slope of -77.6+/-2 mV/pH at 22 degrees C, and linear responses within the pH range of 4-11. Freshly deposited electrodes showed response times as low as 6s. Long-term studies showed a baseline drift of 2-3 mV/month, which could easily be compensated by calibration. This work demonstrated for the first time the use of planar IrOx pH microelectrodes to measure the acidification rate of CHO and fibroblast cells in an on chip cell culture volume of 25 nl with microfluidic control.     

Peroxynitrite oxidizes erythrocyte membrane band 3 protein and diminishes its anion transport capacity

We describe an altered membrane band 3 protein-mediated anion transport in erythrocytes exposed to peroxynitrite, and relate the loss of anion transport to cell damage and to band 3 oxidative modifications. We found that peroxynitrite down-regulate anion transport in a dose dependent relation (100–300 μmoles/l). Hemoglobin oxidation was found at all peroxynitrite concentrations studied. A dose-dependent band 3 protein crosslinking and tyrosine nitration were also observed. Band 3 protein modifications were concomitant with a decrease in transport activity. ( ? )-Epicatechin avoids band 3 protein nitration but barely affects its transport capacity, suggesting that both processes are unrelated. N-acetyl cysteine partially reverted the loss of band 3 transport capacity. It is concluded that peroxynitrite promotes a decrease in anion transport that is partially due to the reversible oxidation of band 3 cysteine residues. Additionally, band 3 tyrosine nitration seems not to be relevant for the loss of its anion transport capacity.     

Lipid and protein oxidation in hepatic homogenates and cell membranes exposed to bile acids

Cholestasis occurs in a variety of hepatic diseases and causes damage due to accumulation of bile acids in the liver. The aim was to investigate the effect of several bile acids, i.e. chenodeoxycholic, taurochenodeoxycholic, deoxycholic, taurodeoxycholic, ursodeoxycholic, lithocholic and taurolithocholic (TLC), in inducing oxidative damage. Hepatic tissue of male Sprague-Dawley rats was incubated with or without 1 mM of each bile acid, with or without 0.1 mM FeCl₃ and 0.1 mM ascorbic acid for the purpose of generating free radicals. Several bile acids increased lipid and protein oxidation, with TLC being the most pro-oxidative (657% and 175% in homogenates and 350% and 311% in membranes, respectively). TLC also enhanced iron-induced oxidative stress to lipids (21% in homogenates and 29% in membranes) and to proteins (74% in membranes). This enhancement was dose- and time-dependent and was reduced by melatonin. These results suggest that bile acids differentially mediate hepatic oxidative stress and may be involved in the physiopathology of cholestasis.     

Tracking reveals behavioural coordination driven by environmental constraints in the Black-vented Shearwater Puffinus opisthomelas

During the breeding season, seabird foraging trips are constrained by nest attendance schedule and are necessarily colony centred. Oceanographic cues play a major role in the choice of foraging areas to minimize the time spent away from the nest. Here, we analysed the foraging tracks of Black-vented Shearwaters Puffinus opisthomelas during the incubation and chick-rearing periods of 2016 and 2017 at Isla Natividad (Mexico). We applied expectation-maximization binary clustering to track data to clusterize different behaviour patterns during foraging flights. We then applied binary generalized linear mixed models to characterize of foraging areas based on of environmental variables. We finally used kernel estimation techniques to describe main foraging areas. In 2016, breeding shearwaters used two core areas for foraging and resting on the water; the core area delineated by males was located northward from the colony in the Vizcaino Bay and the core area for females was located southward from the colony at the entrance of San Ignacio Lagoon. In 2017, males and females used the same areas with no evident segregation. Our study provided the first information on Black-vented Shearwater foraging areas during the breeding season and indicated that sexual segregation within coastal waters off the central Baja California Peninsula might be a foraging strategy during years of warmer ocean, likely less productive regimes. Factors including ocean-climate-mediated sexual segregation at sea, leading to interannual variation in foraging areas, should be considered when evaluating management actions intended to protect critical foraging habitats for Black-vented Shearwaters.     

Fluorescence index as an indicator of dissolved organic carbon quality in hydrologic flowpaths of forested tropical watersheds

Over two hundred samples were collected in tropical headwater forested catchments in the lowland Amazon basin near Juruena, Mato Grosso Brazil. These were analyzed for fluorescence characteristics and DOC concentrations, and represented a range of terrestrial hydrologic flowpaths and first-order streams during baseflow and stormflow conditions. The fluorescence index (FI) of McKnight et al. (2001) was found to have a significant relationship with DOC concentrations for stream water at baseflow conditions, but FI values within individual terrestrial flowpaths and stormflow varied little for the range of DOC concentrations observed. FI values were seen to increase for increasing residence time of water within the terrestrial ecosystem, while DOC concentration decreased for increasing hydrologic residence time. The FI of terrestrial flow paths indicated that DOC became increasingly characterized by microbially derived carbon for flow paths with longer residence times, on the order through fall and overland flow < percolating soil water < groundwater. Base flow samples of stream water had a mean FI value of 1.78, compared with 1.51 and 1.44 for through fall and overland flow, respectively, and 1.65 for percolating soil water. The FI values for stream water at base flow were also seen to vary seasonally, and were inversely proportional to DOC concentrations over time.     

Effect of temperature on the floral scent emission and endogenous volatile profile of Petunia axillaris

The floral scent emission and endogenous level of its components in Petunia axillaris under different conditions (20, 25, 30, and 35 degrees C) were investigated under the hypothesis that floral scent emission would be regulated by both metabolic and vaporization processes. The total endogenous amount of scent components decreased as the temperature increased, the total emission showing a peak at 30 degrees C. This decrease in endogenous amount was compensated for by increased vaporization, resulting in an increase of floral scent emission from 20 degrees C to 30 degrees C. The ambient temperature differently and independently influenced the metabolism and vaporization of the scent compounds, and differences in vapor pressure among the scent compounds were reduced as the temperature increased. These characteristics suggest the operation of an unknown regulator to change the vaporization of floral scent.