Microbial Community Structure and Dynamics in the Largest Natural French Lake (Lake Bourget)

We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0–50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of “small” cocci, but filaments (>2 μm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization–detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the “clear water phase” was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).     

Target therapy in HER2-overexpressing breast cancer patients

The development of new therapeutic strategies, such as monoclonal antibodies directed against human epidermal growth factor receptor-2 (HER2), has offered new hopes for women with early breast cancer whose tumors overexpress HER2. We retrospectively analyzed the population-based data of Breast Cancer Registry of Palermo in 2004-2006, and selected 1401 invasive breast cancer cases, nonmetastatic at diagnosis, having HER2/neu oncogene expression determined. We have correlated this information to age, tumor stage at diagnosis (TNM), nodal involvement, and receptor status (ER and PgR). Survival analysis was conducted dividing the patients in two different groups according to date of diagnosis: one group diagnosed in 2004 and a second group in 2005-2006. In the 460 cases of 2004, nodal involvement, receptor status, age at diagnosis and TNM maintained a strong predictive value (p?相似文献   

Calcium and pH-induced structural changes in skinned muscle fibers: prevention by N-ethylmaleimide.

Optical diffractometry was used to investigate structural changes in contractile proteins from chemically skinned muscle fibers. The intensity of the first order diffraction line decreased in response to calcium and alkaline pH. Fibers pre-treated with sulfhydryl blocking agents did not exhibit the calcium- or pH- induced intensity decreases. We suggest that the decreases in intensity result from structural changes in the thick filament. Optical diffractometry may be a useful technique for the investigation of conformational changes in myosin.     

Effects of protein kinase C (PK-C) activators and inhibitors on human large granular lymphocytes (LGL): role of PK-C on natural killer (NK) activity

The role of protein kinase C (PK-C) in the early metabolic events involved in human natural killer (NK) cell activation has been studied through the action of PK-C-specific activators and inhibitors. Highly purified human large granular lymphocytes (LGL) were treated for 1 hr with the diacylglycerol analog 1-oleoyl-2-acetyl glycerol (OAG) (10(-4)-10(-5) g/ml) or with 12-O-tetradecanoylphorbol-13-acetate (TPA) (10(-8)-10(-10) g/ml), both specific activators of PK-C. Both these agents consistently increased NK activity against K562 target cells. Suboptimal doses of either OAG or TPA also synergized with Ca2+ ionophores to augment spontaneous cytotoxic activity. Pretreatment of LGL with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrocloride (H7) (5-40 microM), a potent PK-C inhibitor, greatly reduced NK activity in a time- and dose-dependent fashion. By contrast, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide hydrochloride (HA 1004), a potent cAMP- and cGMP-dependent PK inhibitor with almost no effect on PK-C, marginally reduced NK activity. Moreover, almost complete NK activity inhibition was observed when H7 (10 microM), but not HA 1004 (50 microM), was present in the NK assay. Finally, 48 hr stimulation of LGL with TPA (10(-6) g/ml), a treatment able to inactivate most of the PK-C cellular pool, almost completely abrogated NK activity. This functional evidence was supported by phosphorylation of several endogenous substrates which occurs within 5 min in TPA-treated LGL. Two proteins of 70 and 56 kDa have been identified as major PK-C substrates, together with other phosphorylated proteins with MW ranging from 177 to 43 kDa. H7, but not HA 1004, almost completely inhibited the TPA-induced phosphorylation of all of these proteins in the NK cells. These data strongly suggest that selective activation of PK-C plays an essential role in the mechanisms of NK cell activation.     

The epsilon hinge-ear region regulates membrane localization of the AP-4 complex

Adaptor protein (AP) complexes are key factors for the spatial and temporal regulation of intracellular trafficking events. Four complexes (AP-1, -2, -3, -4) are known, among which AP-4 is only poorly characterized. Recent work suggests a role for AP-4 in the intracellular trafficking of the β-amyloid precursor protein and molecular genetics showed that the loss of functional AP-4 is associated with congenital neuronal disorders of severe cognitive dysfunction. To unravel the molecular mechanisms controlling AP-4 functions, we established the intracellular expression of recombinant AP-4 complex. This approach combined with the analysis of mutant complexes allowed us to discover that the epsilon adaptin hinge-ear region has a function in membrane recruitment of AP-4. We further show that this process is phosphorylation dependent and involves PP2A-like protein phosphatases and a staurosporine-sensitive kinase. Deletion of the residues 839-871 in the carboxy-terminal region of the hinge of epsilon adaptin abrogated the membrane/cytosol recycling of AP-4. As targets of phosphorylation, we identified three serine residues: S847, S868 and S871. We conclude that the terminal hinge region and the appendage of the AP-4 epsilon subunit are involved in membrane association in a process that is controlled by phosphorylation and dephosphorylation events.     

Power output estimation in vertical jump performed by young male soccer players

The purpose of the study was (a) to assess the accuracy of the regression equations available in the literature to estimate the actual peak power (PPac) of the countermovement jump (CMJ) executed by young male soccer players, (b) to develop new regression equations from this population, and (c) to verify whether regression equations obtained from age-based subgroups could increase the accuracy of the estimation (PPes) of PPac. In all, 117 young players (age: 13.6 ± 2.4 years) were enrolled in the study. Each subject performed 5 CMJs on a force platform. The new regression equations were obtained from the entire experimental sample (G1) and 3 age-based subsamples (G2 = prepubertal, G3 = peripubertal, G4 = postpubertal) using 2 different approaches: the best jump and the mean values achieved by each subject. All the equations in the literature underestimated the peak power (p < 0.00005) in all the groups. The approach based on the mean values was more accurate (adjusted R = 0.925, SEE = 302.9 W) than the one based on the best jump (adjusted R = 0.892; SEE = 360.8 W). Moreover, calculating the regression equations from the 3 age-based subsamples, SEE resulted improved (15.5% in G2, 5.6% in G3 and 0.9% in G4). Regression equations must be derived from homogeneous populations, in terms of gender, sports practice, and age. The approach based on the mean values for each subject was more accurate than the approach used in the literature up to now. In practical applications, regression equation estimates cannot be used to assess the performance of a single subject, because errors may exceed 50%, whereas they may be useful for group comparisons.     

Tree-growth responses across environmental gradients in subtropical Argentinean forests

Subtropical forests in montane ecosystems grow under a wide range of environmental conditions. However, little is known about the growth responses of subtropical trees to climate along ecological gradients. To assess how, and to what extent climate controls tree growth, we analyzed tree responses to climate for 15 chronologies from 4 different species (Schinopsis lorentzii, Juglans australis, Cedrela lilloi, Alnus acuminata) across a variety of environments in subtropical forests from northwestern Argentina (22–28°S, 64–66°W). Using correlation and principal component analysis, site and species differences in tree-growth responses to precipitation and temperature were determined along the elevation gradient from the dry-warm Chaco lowlands to the wet-cool montane Yungas. Our results show that species responses differ according to the severity in climate conditions along the elevation gradient. At sites with unfavorable conditions, mainly located at the extremes of the environmental gradient, responses of different species to climate variations are similar; in contrast, at sites with relatively mild conditions, tree growth displays a large variety of responses reflecting differences in both local environmental conditions and species physiology. Our research suggests that individualistic responses to environmental variability would determine differences in the type and timing of the responses of dominant trees to climate, which ultimately may shift species’ assemblages in montane subtropical regions of South America under future climate changes.     

Cardiac substances that influence blood-pressure. I. Identification of the agent that lowers blood-pressure in anaesthetized rats

Extracts of the atrium of the mammalian heart contain a natriuretic factor which may be associated with the atrium-specific granules. It has often been observed that the intravenous injection of a crude atrial extract into anaesthetized rats, causes a transient decrease in blood-pressure. In rabbits, this activity is present in stored aqueous extracts prepared from both atrial and ventricular tissue. The hypotensive activity, which can be readily separated from the natriuretic factor, is mainly due to the presence of adenosine and its derivatives, of which 5'-adenosine monophosphate is the major contributor. However, an extract from rabbit atrial muscle, carefully prepared under stringent conditions, caused a rapid and striking increase in blood-pressure, an activity that could not be detected in ventricular tissue.