Comparisons of faecal collection methods for digestibility determinations in gilthead sea bream

The absorption of carbon, nitrogen, phosphorus and dry matter along the intestine of Sparus aurata has been measured and the reliability of different methods to estimate apparent digestibility coefficients has been evaluated.     

A nonheme iron(II) complex that models the redox cycle of lipoxygenase

The air-stable complex [Fe(6-Me3-TPA) (O2CAr)]+ [1; 6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine] has been synthesized as a model for the iron(II) site of lipoxygenase. This iron(II) complex reacts with 0.5 equiv ROOH to form a yellow species, which has been formulated as [FeIII(OH)(6-Me3-TPA) (O2CAr)]+ (2) by electrospray mass spectrometry. Addition of more ROOH converts 2 into a purple species, which is characterized by electrospray ionization mass spectrometry and resonance Raman spectroscopy as [FeIII(OOR)(6-Me3-TPA)(O2CAr)]+. The purple species is metastable and decomposes via Fe-O bond homolysis to regenerate the starting iron(II) complex. These metal-centered transformations parallel the changes observed for lipoxygenase in its reaction with its product hydroperoxide.     

Modes of inhibition of protein kinase C by triphenylacrylonitrile antiestrogens

Protein kinase C (PKC) I (gamma), II (beta) and III (alpha) subspecies' activities are inhibited by three triphenylacrylonitrile (TPE) antiestrogens at micromolar concentrations. TPE 1 (having a p-hydroxy and a p-diethylaminoethoxy group on the 3-, and 3'- phenyl rings respectively) and TPE 2 (having a p-diethylaminoethoxy group on both the 3-, and 3'- phenyl rings) are competitive with the mechanism of activation by phosphatidylserine (PS). TPE 3 (having p-hydroxy groups on each of the three phenyl rings) is non-competitive with PS and inhibits the Ca2+- and PS-independent phosphorylation of protamine sulfate by PKC subspecies. This evidence suggests that PKC activity can be inhibited by different routes depending on the TPE structure: diethylaminoethoxy side chain-substituted TPEs (TPE 1 and 2) interact with PS as well as with the regulatory domain, whereas the trihydroxylated derivative (TPE 3) inhibits the enzyme by interacting with the catalytically active site.     

Determination of mitogenic properties and lymphocyte target sites of Dolichos lablab lectin (DLA): comparative study with concanavalin A and galactose oxidase cell surface receptors

A mannoside-directed lectin has been isolated and purified from the seeds of Dolichos lablab L. by affinity chromatography. We have established that this glycoprotein, which displays high erythroagglutinating activity without blood group specificity, highly activates murine T lymphocytes, and we have described for the first time its mitogenic properties. Although its main properties are close to those of concanavalin A (Con A), the well-known mannoside-directed mitogen devoid of sugar moiety, several differences were found in some of the early events triggered by the two lectins during lymphocyte mitogenic stimulation: higher level of interleukin-2 (IL-2) synthesis, optimal dose for IL-2 synthesis at suboptimal mitogenic concentration, lack of ecto-5' nucleotidase inhibition, and lack of mitogenic inhibition at high lectin concentration. Because the two lectins did not act on the cell surface in exactly the same way, we have compared their receptors involved in mitogenesis on the plasma membrane of murine lymphocytes. We had previously established that the polyclonal activation of these cells probably occurred through high-molecular-weight receptors (200-230 kDa). Since the mitogenic stimulation of lymphocyte by galactose oxidase (GO), like that of Con A, was inhibited by DLA, we analyzed the cell surface receptors that were common to these three polyclonal mitogens. After labeling the neuraminidase/GO-treated cell surface glycoproteins with NaB3H4, we immunoprecipitated the Con A and DLA receptors which are the target of GO mitogenic action. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the precipitates demonstrated that there exist on the lymphocyte cell surface receptors common to the polyclonal mitogens DLA, Con A, and GO. Because Con A and DLA sterically inhibit GO mitogenic stimulation, the common glycoproteins which represent the necessary sites of oxidative mitogenic action are probably those which are involved in DLA and Con A-triggered mitogenesis, despite the different properties of the two lectins. These differences could be explained by the lower molecular weight receptors of the two lectins which are not identical.     

A global risk assessment for the success of bird introductions

1.  Concern over the impact of invasive species has led to the development of risk assessment methodologies to identify potential invaders and prevent future ecological and economic problems. However, developing a risk assessment tool is challenging because of the difficulties of accurately predicting the outcome of species introductions.
2.  In this study, we develop a global risk assessment for birds. We integrate two approaches, generalized linear mixed models (GLMM) and hierarchical tree models, to help identify those introductions with the highest risk of establishment success.
3.  Past work has shown that the number of individuals released is the main factor influencing establishment success in animals, a conclusion that was supported in our analyses. Establishment success was also higher for species with broader ecological niches and larger brains relative to body size. These features should increase the likelihood of finding an appropriate niche in the region of introduction.
4.  The GLMM and tree model predicted the probability of establishment success of birds in Europe and Australia with high accuracy (over 80% of introductions correctly classified). This highlights that establishment risk can be reasonably assessed with information on general habitat use, brain size and the size of the founder population. When compared with an alternative risk assessment tool based on a qualitative ranking, our quantitative approaches achieved higher accuracy with less information.
5.   Synthesis and applications. Quantitative risk assessments based on traits related to establishment success are difficult but feasible, providing a useful tool for guiding preventive polices aimed at mitigating the impact of invasive species.     

Is the future blue-green or brown? The effects of extreme events on phytoplankton dynamics in a semi-arid man-made lake

Aquatic Ecology - In arid and semi-arid regions, a hydrological regime characterized by an annual cycle of drought and rainy seasons changes the volume and retention time of reservoirs. Such...     

Hepatic endothelial lipase activity in neonatal rat liver

Hepatic endothelial lipase (HEL) activity is as high in the neonatal (1-day old) rat liver as in adults. Most of the HEL activity is located at the capillaries since 75% of the total activity is released by heparin or collagenase perfusion. The residual activity (non-releasable) is located in hepatocytes and not in hemopoietic cells, which are the major cell type in neonatal liver. Per mg of protein, the HEL activity is 50% higher in neonatal than in adult hepatocytes. We suggest that neonatal hepatocytes have an increased capacity to synthesize and secrete HEL activity, so maintaining a high activity in the whole organ. it might contribute to the hepatic uptake of cholesterol from circulating lipoproteins, in a period in which endogenous cholesterol synthesis is known to be inhibited in the liver.