1,721,032 research outputs found
Reassociation of eukaryotic ribosomal subunits and polyamine concentration in Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during growth
No full textThe activity on ribosome monomers of dissociation factor preparations obtained by high salt wash from ribosomes and from the post-ribosomal supernatant (cytosol) of Yoshida rat ascites hepatoma and Ehrlich mouse ascites carcinoma cells and from the liver of control and tumor-bearing animals has been determined at different periods of intraperitoneal tumor growth. The concentration of the polyamines spermine, spermidine and putrescine has also been measured under the same conditions. Results here reported show the presence of an association factor activity on subunit ribosomes at low Mg2+ concentrations in the post-ribosomal supernatant fractions of Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during tumor growth. An association factor activity also takes place in the ribosomal high salt wash extracts of Yoshida ascites cells at the terminal stages of tumor growth. Since an increase of spermidine to putrescine ratios occurs during tumor growth the changes in the rate of ribosome monomer dissociation into units here observed might be attributable, at least in part, to changes in polyamine concentrations under the conditions studied
Reassociation of eukaryotic ribosomal subunits by a factor from rat ascites hepatoma cytosol
No full textPost-ribosomal supernatant extracts from Yoshida AH 130 ascites hepatoma cells promote the in vitro association of ribosomal subunits at low Mg2+ concentration. Comparable extracts from rat liver show, on the contrary, dissociation factor activity on ribosome monomers
Background levels of polybrominated diphenyl ethers (PBDEs) in soils from Mount Meru area, Arusha district (Tanzania)
No full textThis study investigates the contamination by 13 polybrominated diphenyl ether (PBDE) congeners in an altitudinal soil transect on Mt. Meru area, Northern Tanzania. A ∑13PBDEs mean concentration of 386±200pg/g d.w. (4900±3500pg ∑13PBDEs/g soil organic matter - SOM) was measured, pointing out that, in a prevalently agricultural area from the southern hemisphere, PBDE contamination can be even higher than in similar semi-remote environment of industrialized country of the northern one. The Mt. Meru PBDE pattern of contamination was characterized by the prevalence of intermediate brominated congeners (tetra- and penta-BDEs). Among the detected compounds, BDE-47 was the main congener, followed by BDE-99, BDE-190 and BDE-100. The distribution of PBDEs confirmed that organic carbon had a substantial impact on their accumulation in Tanzanian soils. The altitudinal profile of PBDEs (log TOC-normalized concentrations) fitted a second order polynomial model with altitude, with an initial concentration decrease, interpreted as a dilution effect from local/regional sources, and a following consistent increase with altitude according to the cold condensation theory. Evidences of distillation effect among PBDE congeners were also observed
Environmental variables affecting the distribution of POPs on Mt. Meru, Tanzania
No full textTanzania is an equatorial country characterized by warm temperatures, which should increase the volatilization of persistent organic pollutants (POPs), but this scenario could be different in mountainous areas like Mount Meru, a volcano situated in the East African Rift (Tz). We collected soil samples along an altitudinal transect upto 4577 m a.s.l., reporting the first data about POP contamination in this area (DDX, HCHs, HCB and PCBs). The DDX contamination pattern in Mt. Meru shows levels slightly higher than those of other remote places with a strong increase in the metabolites/DDT historical trend, which is different from DDX, PCBs, HCHs and particularly HCB as this shows very low contamination levels. Back trajectory analysis allowed a discussion about putative contamination sources, while analysis of the environmental features (climatic and pedological) allowed us to discriminate their relative importance. The distribution of POPs shows a strong correlation with soil organic matter and vegetation. SOM-normalization evidenced altitudinal dependence according to cold condensation for PCBs and HCHs, while DDX are present in larger amounts in the agricultural area at the volcano foot. OM-normalized concentrations suggested also a possible role of the OM composition on the POPs' distribution
Highly spatially- and seasonally-resolved predictive contamination maps for persistent organic pollutants : development and validation
No full textA reliable spatial assessment of the POPs contamination in soils is essential for burden studies and flux evaluations. Soil characteristics and properties vary enormously even within small spatial scale and over time; therefore soil capacity of accumulating POPs varies greatly. In order to include this very high spatial and temporal variability, models can be used for assessing soil accumulation capacity in a specific time and space and, from it, the spatial distribution and temporal trends of POPs concentrations. In this work, predictive contamination maps of the accumulation capacity of soils were developed at a space resolution of 1 × 1 m with a time frame of one day, in a study area located in the central Alps. Physical algorithms for temperature and organic carbon estimation along the soil profile and across the year were fitted to estimate the horizontal, vertical and seasonal distribution of the contamination potential for PCBs in soil (Ksa maps). The resulting maps were cross-validated with an independent set of PCB contamination data, showing very good agreement (e.g. for CB-153, R2 = 0.80, p-value ≤ 2.2 . 10−06). Slopes of the regression between predicted Ksa and experimental concentrations were used to map the soil contamination for the whole area, taking into account soil characteristics and temperature conditions. These maps offer the opportunity to evaluate burden (concentration maps) and fluxes (emission maps) with highly resolved temporal and spatial detail. In addition, in order to explain the observed low autumn PCB concentrations in soil related to the high Ksa values of this period, a dynamic model of seasonal variation of soil concentrations was developed basing on rate parameters fitted on measured concentrations. The model was able to describe, at least partially, the observed different behavior between the quite rapid discharge phase in summer and the slow recharge phase in autumn
The effect of the organic matter composition on POPaccumulation in soil
No full textThe effect of different humic fractions on polychlorinated biphenyl (PCB) contamination in soils was tested in the field by means of 53 soil samples from a high altitude grassland plateau in the Italian Alps. The three humic fractions (humin, humic acids and fulvic acids) were characterised in parallel by quantifying 12 PCB congeners to establish a direct relationship between PCB levels and humic fraction concentrations. Humin (the most hydrophobic fraction) appears to be the most closely correlated with the amount of PCBs in soil (R2 = 0.83), while fulvic acid shows the lowest correlation (R2 = 0.49). The idea of preferential sorption of hydrophobic compounds in the humin fraction is discussed, and the humin carbon content (fhuminC) is proposed as an improved parameter for evaluating the potential for POP accumulation in soils, replacing total organic carbon (foc). Congener studies revealed that penta- and hexa-substituted-CBs show the optimal combination of physicochemical properties for equilibrating with the humin content in soil. Moreover, fhuminC/foc is conceptually equivalent to the empirical coefficients used in predictive Ksa equations. In our samples, the fhuminC/foc was 0.55, a value in between the empirical coefficients proposed in the literature. In predictive equations, the use of fhuminC instead foc avoids the necessity of using an empirical parameter for a ‘generic’ condition by introducing an experimental parameter (fhuminC) that takes into account a local conditions (organic matter composition)
Increased activity of the ribosomal dissociation factor in the pre-replicative phase of liver regeneration after partial hepatectomy
No full textThe activity of the ribosomal dissociation factor and the formation in vitro of free 60S and 40S subunits increased in the first 12--48 h after partial hepatectomy. This suggests an accelerated reconversion into active subunits of ribosomes that complete a translation cycle in the early phases of liver regeneration
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Activity of a purified nonsteroidal gametic factor on the inducibility of hepatic delta-aminolevulinic acid synthetase, NADPH-oxidase and tyrosine aminotransferase in senescent rats
No full textThe effect of a water soluble nonsteroidal factor extracted from the male gamete on the activity of certain liver inducible enzymes during aging has been examined. Three enzymes have been studied: delta-aminolevulinic acid synthetase, NADPH-oxidase and tyrosine aminotransferase whose inducibility by ethanol, phenobarbital and ACTH, respectively, show age dependent alterations. The results here reported show that this factor is able to restore the enzyme inducibility in the liver of aging (600-day-old) rats without affecting the response of young (40-day-old) rats. Since the enzyme inducibility is altered during aging, and in the majority of rat hepatomas this factor might enter, possibly, in the regulation of enzyme activity also of neoplastic cells
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