Experimental evidence for the interplay of exogenous and endogenous factors on the movement ecology of a migrating songbird

Movement patterns during songbird migration remain poorly understood despite their expected fitness consequences in terms of survival, energetic condition and timing of migration that will carry over to subsequent phases of the annual cycle. We took an experimental approach to test hypotheses regarding the influence of habitat, energetic condition, time of season and sex on the hour-by-hour, local movement decisions of a songbird during spring stopover. To simulate arrival of nocturnal migrants at unfamiliar stopover sites, we translocated and continuously tracked migratory red-eyed vireos (Vireo olivaceus) throughout spring stopover with and without energetic reserves that were released in two replicates of three forested habitat types. Migrants moved the most upon release, during which time they selected habitat characterized by greater food abundance and higher foraging attack rates. Presumably under pressure to replenish fuel stores necessary to continue migration in a timely fashion, migrants released in poorer energetic condition moved faster and further than migrants in better condition and the same pattern was true for migrants released late in spring relative to those released earlier. However, a migrant's energetic condition had less influence on their behavior when they were in poor quality habitat. Movement did not differ between sexes. Our study illustrates the importance of quickly finding suitable habitat at each stopover site, especially for energetically constrained migrants later in the season. If an initial period prior to foraging were necessary at each stop along a migrant's journey, non-foraging periods would cumulatively result in a significant energetic and time cost to migration. However, we suggest behavior during stopover is not solely a function of underlying resource distributions but is a complex response to a combination of endogenous and exogenous factors.     

Systematic study of high molecular weight compounds in Amazonian plants by high temperature gas chromatography-mass spectrometry

The fractions of hexane and dichloromethane extraction from marupá (Simaruba amara) and (Bertholletia excelsa) leaves were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds can be characterized including unusual high molecular weight compounds.     

SHPS-1 induces aggregation of Ba/F3 pro-B cells via an interaction with CD47

SHPS-1 (SH2-domain bearing protein tyrosine phosphatase (SHP) substrate-1), a member of the inhibitory-receptor superfamily that is abundantly expressed in macrophages and neural tissue, appears to regulate intracellular signaling events downstream of receptor protein-tyrosine kinases and integrin-extracellular matrix molecule interactions. To investigate the function of SHPS-1 in a hematopoietic cell line, SHPS-1 was expressed in Ba/F3 cells, an IL-3-dependent pro-B-cell line that lacks endogenous SHPS-1 protein. Interestingly, expression of either SHPS-1, or a mutant lacking the intracellular domain of SHPS-1 (DeltaCT SHPS-1), resulted in the rapid formation of macroscopic Ba/F3 cell aggregates. As the integrin-associated protein/CD47 was shown to be a SHPS-1 ligand in neural cells, we investigated whether CD47 played a role in the aggregation of SHPS-1-expressing Ba/F3 cells. In support of this idea, aggregate formation was inhibited by an anti-CD47 Ab. Furthermore, erythrocytes from control, but not from CD47-deficient mice, were able to form rosettes on SHPS-1-expressing Ba/F3 cells. Because erythrocytes do not express integrins, this result suggested that SHPS-1-CD47 interactions can take place in the absence of a CD47-integrin association. We also present evidence that the amino-terminal Ig domain of SHPS-1 mediates the interaction with CD47. Although SHPS-1-CD47 binding likely triggers bidirectional intracellular signaling processes, these results demonstrate that this interaction can also mediate cell-cell adhesion.     

Evaluation of methods for the determination of mitochondrial respiratory chain enzyme activities in human skeletal muscle samples

The quantification of mitochondrial enzyme activities in skeletal muscle samples of patients suspected of having mitochondrial myopathies is problematic. Therefore, we have evaluated different methods for the determination of activities cytochrome c oxidase and NADH:CoQ oxidoreductase in human skeletal muscle samples. The measurement of cytochrome c oxidase activity in the presence of 200 microM ferrocytochrome c and the detection of NADH:CoQ oxidoreductase as rotenone-sensitive NADH:CoQ(1) reductase resulted in comparable citrate synthase-normalized respiratory chain enzyme activities of both isolated mitochondria and homogenates from control human skeletal muscle samples. These methods allowed the precise detection of deficiencies of respiratory chain enzymes in skeletal muscle of two patients harboring only 20 and 27% of deleted mitochondrial DNA, respectively. Therefore, citrate synthase-normalized respiratory chain activities can serve as stable reference values for the determination of a putative mitochondrial defect in human skeletal muscle.     

Patterns of synthesis and secretion of sulfated glycosaminoglycans in primary cortical and cerebellar astrocytes in vitro

We determined the amounts of [35S]-glycosaminoglycans (GAGs) found on the intracellular, pericellular and extracellular compartments of primary cultures of astrocytes derived from newborn rat cortex and cerebellum in vitro. Our results show that the greatest portion of newly synthesized GAGs were found in different cellular compartments, depending on the source of the astrocytes. In the cells derived from the cerebellum, the proportion of [35S]-GAGs secreted to the culture medium preponderates over the amount found in the two other compartments, whereas cells derived from the cortex accumulated higher proportions of [35S]-GAGs in the intracellular compartment than in the two other compartments. Cortical and cerebellar glial cells synthesised and secreted heparan sulfate (HS) and chondroitin 4-sulfate (C-4S). HS was predominantly accumulated on the pericellular surface, while C-4S was mostly secreted to the culture medium. Beside the difference on the distribution of total [35S]-GAGs among the three cellular compartments, no difference was observed on the relative proportions of HS and C-4S within each compartment. By defining the source of GAGs, the present study may help to complement and extend information on biosynthesis of these compounds by mammalian glial cells.     

Bullatacin, a potent antitumor annonaceous acetogenin, inhibits proliferation of human hepatocarcinoma cell line 2.2.15 by apoptosis induction

Bullatacin, isolated from the fruit of Annona atemoya, is one of the most potentially effective antitumor annonaceous acetogenins. Bullatacin was studied here for its ability to inhibit the proliferation of 2.2.15 cells, hepatitis B virus (HBV) DNA transfected human hepatocarcinoma cell line. It was found that bullatacin induced cytotoxicity of 2.2.15 cells in a time- and dose-dependent manner. Fifty percent effective dose (ED50) on day 1 of exposure to bullatacin were 7.8 +/- 2.5 nM for 2.2.15 cells. [3H]-Thymidine incorporation assays showed almost the same results. Bullatacin-treatment also reduced concentrations of hepatitis B surface antigen (HBsAg) in the cultured medium released from 2.2.15 cells, coincident with the decrease in the cell proliferation. Analysis of mophological changes of bullatacin-treated 2.2.15 by inverted phase-contrast microscope and eletron microscopy revealed a possible model of action for bullatacin to inhibit proliferation of 2.2.15 cells by inducing apoptosis. Most of the bullatacin-induced cell death was found to be due to apoptosis, as determined by double staining with fluorescein-isothiocyanate (FITC)-labeled annexin V and propidium iodide (PI).     

Sexual dimorphic expression of ADH in rat liver: importance of the hypothalamic-pituitary-liver axis

Hepatic alcohol dehydrogenase (ADH) activity is higher in female than in male rats. Although sex steroids, thyroid, and growth hormone (GH) have been shown to regulate hepatic ADH, the mechanism(s) for sexual dimorphic expression is unclear. We tested the possibility that the GH secretory pattern determined differential expression of ADH. Gonadectomized and hypophysectomized male and female rats were examined. Hepatic ADH activity was 2.1-fold greater in females. Because protein and mRNA content were also 1.7- and 2.4-fold greater, results indicated that activity differences were due to pretranslational mechanisms. Estradiol increased ADH selectively in males, and testosterone selectively decreased activity and mRNA levels in females. Effect of sex steroids on ADH was lost after hypophysectomy; infusion of GH in males increased ADH to basal female levels, supporting a role of the pituitary-liver axis. However, GH and L-thyroxine (T4) replacements alone in hypophysectomized rats did not restore dimorphic differences for either ADH activity or mRNA levels. On the other hand, T4 in combination with intermittent administration of GH reduced ADH activity and mRNA to basal male values, whereas T4 plus GH infusion replicated female levels. These results indicate that the intermittent male pattern of GH secretion combined with T4 is the principal determinant of low ADH activity in male liver.     

Increased survival in sepsis by in vivo adenovirus-induced expression of IL-10 in dendritic cells

The dendritic cell (DC) is the most potent APC of the immune system, capable of stimulating naive T cells to proliferate and differentiate into effector T cells. Recombinant adenovirus (Adv) readily transduces DCs in vitro allowing directed delivery of transgenes that modify DC function and immune responses. In this study we demonstrate that footpad injection of a recombinant Adv readily targets transduction of myeloid and lymphoid DCs in the draining popliteal lymph node, but not in other lymphoid organs. Popliteal DCs transduced with an empty recombinant Adv undergo maturation, as determined by high MHC class II and CD86 expression. However, transduction with vectors expressing human IL-10 limit DC maturation and associated T cell activation in the draining lymph node. The extent of IL-10 expression is dose dependent; transduction with low particle numbers (10(5)) yields only local expression, while transduction with higher particle numbers (10(7) and 10(10)) leads additionally to IL-10 appearance in the circulation. Furthermore, local DC expression of human IL-10 following in vivo transduction with low particle numbers (10(5)) significantly improves survival following cecal ligation and puncture, suggesting that compartmental modulation of DC function profoundly alters the sepsis-induced immune response.     

Structure,function and floristic relationships of plant communities in stressful habitats marginal to the Brazilian Atlantic rainforest

The Brazilian Atlantic rainforest consists of a typical tropical rainforest on mountain slopes, and stands out as a biodiversity hotspot for its high species richness and high level of species endemism. This forest is bordered by plant communities with lower species diversity, due mostly to more extreme environmental conditions than those found in the mesic rainforest. Between the mountain slopes and the sea, the coastal plains have swamp forests, dry semi-deciduous forests and open thicket vegetation on marine sand deposits. At the other extreme, on top of the mountains (>2000 m a.s.l.), the rainforest is substituted by high altitude fields and open thicket vegetation on rocky outcrops. Thus, the plant communities that are marginal to the rainforest are subjected either to flooding, drought, oceanicity or cold winter temperatures. It was found that positive interactions among plants play an important role in the structuring and functioning of a swamp forest, a coastal sandy vegetation and a cold, high altitude vegetation in the state of Rio de Janeiro. Moreover, only a few species seem to adopt this positive role and, therefore, the functioning of these entire systems may rely on them. Curiously, these nurse plants are often epiphytes in the rainforest, and at the study sites are typically terrestrial. Many exhibit crassulacean acid metabolism. Conservation initiatives must treat the Atlantic coastal vegetation as a complex rather than a rainforest alone.     

Effects of water stress on antioxidant enzymes of leaves and nodules of transgenic alfalfa overexpressing superoxide dismutases

The antioxidant composition and relative water stress tolerance of nodulated alfalfa plants ( Medicago sativa L. ×  Sinorhizobium meliloti 102F78) of the elite genotype N4 and three derived transgenic lines have been studied in detail. These transgenic lines overproduced, respectively, Mn-containing superoxide dismutase (SOD) in the mitochondria of leaves and nodules, MnSOD in the chloroplasts, and FeSOD in the chloroplasts. In general for all lines, water stress caused moderate decreases in MnSOD and FeSOD activities in both leaves and nodules, but had distinct tissue-dependent effects on the activities of the peroxide-scavenging enzymes. During water stress, with a few exceptions, ascorbate peroxidase and catalase activities increased moderately in leaves but decreased in nodules. At mild water stress, transgenic lines showed, on average, 20% higher photosynthetic activity than the parental line, which suggests a superior tolerance of transgenic plants under these conditions. However, the untransformed and the transgenic plants performed similarly during moderate and severe water stress and recovery with respect to important markers of metabolic activity and of oxidative stress in leaves and nodules. We conclude that the base genotype used for transformation and the background SOD isozymic composition may have a profound effect on the relative tolerance of the transgenic lines to abiotic stress.