Changes in alanine and glutamine transport during rat red blood cell maturation

Alanine and glutamine transport have been studied during red blood cell maturation in the rat. Kinetic parameters of Na⁺-dependent L-alanine transport were:K _m 0.43 and 1.88 mM andV _max 158 and 45 nmoles/ml ICW/min for reticulocytes and erythrocytes, respectively. During red cell maturation in the rat there is a loss of capacity and affinity of the system ASC for L-alanine transport. The values for Na⁺-dependent L-glutamine transport in reticulocytes wereK _m 0.51 mM andV _max 157 nmoles/ml ICW/min. On the other hand, a total loss of L-glutamine transport mediated by both N and ASC systems is demonstrated in mature red cells. This seems to indicate that during rat red cell maturation the system N disappears. Furthermore, the system ASC specificity in mature cells changes, and glutamine enters the red cell by non-mediated diffusion processes.     

Kinetic study of the reduction mechanism for Desulfovibrio gigas cytochrome c3.

The kinetic aspects of the reduction process in cytochrome c3 from Desulfovibrio gigas have been investigated over a wide range of pH values ranging between pH 5.8 and pH 9.8. The data have been analyzed in the framework of an I2H4 interaction network coupled to a proton-linked equilibrium between two tertiary structures (Cornish-Bowden, A. & Koshland, D.E. Jr (1970) J. Biol. Chem. 245, 6241-6250). The kinetic rate constants for the reduction of the four hemes for the two tertiary conformations have been characterized in the framework of the thermodynamic network obtained from the equilibrium analysis (Coletta, M., Catarino, T., LeGall, J.J. & Xavier, A.V. (1991) Eur. J. Biochem. 202, 1101-1106). The intrinsic reduction rate constants determined by reaction with sodium dithionite for two hemes (namely heme 4 and heme 1) are significantly faster than those for the other two heme residues. In view of the equilibrium redox properties, heme 4 (with the fastest reduction rate) may then work as the kinetic electron-capturing site for the electrons from sodium dithionite. The transfer to hemes 2 and 3 then occurs by virtue of their free-energy levels at equilibrium. At our experimental conditions, there is also transfer of electrons to hemes 2 and 3 from heme 1, which is reduced at a slower rate than heme 4, thus contributing to the biphasic kinetics observed for the overall process. The kinetic parameters obtained are discussed in terms of the mechanism proposed for the coupling between the electron and proton transfer, as induced by the heme/heme cooperativity network.     

rDolphin: a GUI R package for proficient automatic profiling of 1D <Superscript>1</Superscript>H-NMR spectra of study datasets

Introduction

Adoption of automatic profiling tools for ¹H-NMR-based metabolomic studies still lags behind other approaches in the absence of the flexibility and interactivity necessary to adapt to the properties of study data sets of complex matrices.

Objectives

To provide an open source tool that fully integrates these needs and enables the reproducibility of the profiling process.

Methods

rDolphin incorporates novel techniques to optimize exploratory analysis, metabolite identification, and validation of profiling output quality.

Results

The information and quality achieved in two public datasets of complex matrices are maximized.

Conclusion

rDolphin is an open-source R package (http://github.com/danielcanueto/rDolphin) able to provide the best balance between accuracy, reproducibility and ease of use.

     

Effect of Fluorination on Skin Sensitization Potential and Fragrant Properties of Cinnamyl Compounds

A series of three α‐ and three β‐fluorinated representatives of the family of cinnamate‐derived odorants (cinnamaldehyde ( 1 ), cinnamyl alcohol ( 2 ), and ethyl cinnamate ( 3 )) as used as fragrance ingredients is described. Olfactive evaluation shows that the fluorinated compounds exhibit a similar odor profile to their parent compounds, but the olfactive detection thresholds are clearly higher. In vitro evaluation of the skin sensitizing properties with three different assays indicates that α‐fluorination of Michael acceptor systems 1 and 3 slightly improves the skin sensitization profile. α‐Fluorocinnamyl alcohol 2b is a weaker skin sensitizer than cinnamyl alcohol 2a by in vitro tests and the fluorinated product drops below the sensitization threshold of the KeratinoSens^® assay. On the other hand, β‐fluorination of compounds 1  –  3 results in highly reactive products which display a worsened in vitro skin sensitization profile.     

Could White Coat Ocular Hypertension Affect to the Accuracy of the Diagnosis of Glaucoma? Relationships Between Anxiety and Intraocular Pressure in a Simulated Clinical Setting

Sixty-one healthy subjects participated in a laboratory study carried out in a simulated clinical setting. Anticipatory anxiety-state was assessed at the arrival and immediately after, with no brief phase of adaptation, measurements of intraocular pressure, heart rate, systolic and diastolic blood pressure were collected. At the end of the procedure, anxiety-trait was also assessed. Results suggest that high levels of both anxiety-state and anxiety-trait significantly predicted a clinically relevant increase of intraocular pressure. Anxiety-state mediated the relationship between anxiety-trait and intraocular pressure, which also was found to be related with heart rate but not related to both systolic and diastolic blood pressure. These results suggest a common mechanism of regulation underlying anxiogenic variability found on both intraocular pressure and heart rate. A reduction in parasympathetic activity appears as a possible mechanism underlying to this phenomenon. This anxiety-enhanced intraocular pressure could be considered a phenomenon analogous to white coat hypertension found in the measurement of blood pressure; therefore, it probably should be taken into account in the clinical context to prevent errors in the diagnosis of glaucoma. Further research on cognitive and emotional regulation of intraocular pressure is needed to best characterize this hypothetical phenomenon.     

Modelling the distribution and compositional variation of plant communities at the continental scale

Aim

We investigate whether (1) environmental predictors allow to delineate the distribution of discrete community types at the continental scale and (2) how data completeness influences model generalization in relation to the compositional variation of the modelled entities.

Location

Europe.

Methods

We used comprehensive datasets of two community types of conservation concern in Europe: acidophilous beech forests and base‐rich fens. We computed community distribution models (CDMs) calibrated with environmental predictors to predict the occurrence of both community types, evaluating geographical transferability, interpolation and extrapolation under different scenarios of sampling bias. We used generalized dissimilarity modelling (GDM) to assess the role of geographical and environmental drivers in compositional variation within the predicted distributions.

Results

For the two community types, CDMs computed for the whole study area provided good performance when evaluated by random cross‐validation and external validation. Geographical transferability provided lower but relatively good performance, while model extrapolation performed poorly when compared with interpolation. Generalized dissimilarity modelling showed a predominant effect of geographical distance on compositional variation, complemented with the environmental predictors that also influenced habitat suitability.

Main conclusions

Correlative approaches typically used for modelling the distribution of individual species are also useful for delineating the potential area of occupancy of community types at the continental scale, when using consistent definitions of the modelled entity and high data completeness. The combination of CDMs with GDM further improves the understanding of diversity patterns of plant communities, providing spatially explicit information for mapping vegetation diversity and related habitat types at large scales.

     

Assessment of genetic diversity and structure in cocoa trees (<Emphasis Type="Italic">Theobroma cacao</Emphasis> L.) in Côte d’Ivoire with reference to their susceptibility to Cocoa swollen shoot virus disease (CSSVD)

Resistance to Cocoa Swollen Shoot Virus disease (CSSVD) is becoming an increasingly important criterion for selection of new cocoa cultivars in Côte-d’Ivoire, where the disease resurfaced since 2003. This virus can seriously affect the yield of trees with a loss of 25%, 1 year after infection, to around 100% 3 years after. In order to find tolerant plant material, 337 farm accessions have been collected on fields affected by CSSVD, according to the status of accessions potentially tolerant (APT) or susceptible (APS). Both phenotypic groups were genotyped using 30 microsatellite markers (SSR) in the presence of representative clones of the ten genetic groups of cocoa. This study revealed 214 alleles with the set of primer pairs used. The number of alleles per locus was between 3 and 16 with an average of 7.13 alleles per locus. The results showed a high contribution of genetic diversity within population (H_s?=?0.51) to the total genetic diversity (H_t?=?0.53) for the two studied groups. There was no significant difference between tolerant and susceptible groups (Fst?=?0.05). These results suggest that APT could be a potential genetic reservoir for other traits of interest associated with virus resistance. The phylogenetic tree, as the STRUCTURE analysis of Ivorian cocoa population, showed a distribution of individuals following four groups marked by a high contribution of group 4 (Nanay, Maranon, Guiana) followed by group 2 (Criollo), and group 1 (Amelonado), and a lower contribution of group 3 (Iquitos, Purus, Nacional, Curaray, Contamana).     

Elusive data underlying debate at the prokaryote-eukaryote divide

Background

The origin of eukaryotic cells was an important transition in evolution. The factors underlying the origin and evolutionary success of the eukaryote lineage are still discussed. One camp argues that mitochondria were essential for eukaryote origin because of the unique configuration of internalized bioenergetic membranes that they conferred to the common ancestor of all known eukaryotic lineages. A recent paper by Lynch and Marinov concluded that mitochondria were energetically irrelevant to eukaryote origin, a conclusion based on analyses of previously published numbers of various molecules and ribosomes per cell and cell volumes as a presumed proxy for the role of mitochondria in evolution. Their numbers were purportedly extracted from the literature.

Results

We have examined the numbers upon which the recent study was based. We report that for a sample of 80 numbers that were purportedly extracted from the literature and that underlie key inferences of the recent study, more than 50% of the values do not exist in the cited papers to which the numbers are attributed. The published result cannot be independently reproduced. Other numbers that the recent study reports differ inexplicably from those in the literature to which they are ascribed. We list the discrepancies between the recently published numbers and the purported literature sources of those numbers in a head to head manner so that the discrepancies are readily evident, although the source of error underlying the discrepancies remains obscure.

Conclusion

The data purportedly supporting the view that mitochondria had no impact upon eukaryotic evolution data exhibits notable irregularities. The paper in question evokes the impression that the published numbers are of up to seven significant digit accuracy, when in fact more than half the numbers are nowhere to be found in the literature to which they are attributed. Though the reasons for the discrepancies are unknown, it is important to air these issues, lest the prominent paper in question become a point source of a snowballing error through the literature or become interpreted as a form of evidence that mitochondria were irrelevant to eukaryote evolution.

Reviewers

This article was reviewed by Eric Bapteste, Jianzhi Zhang and Martin Lercher.

     

Distribution patterns of the fish assemblage in the Mamanguape River Estuary,North-eastern Brazil

The Mamanguape River Estuary was studied along a continuum ranging from shallow sandstone reefs adjacent to the river mouth up to the limit of influence of seawater, the upper portions of the estuary. Fish samples were gathered using three types of nets along 17 sample sites, grouped in four regions according to salinity range (reefs and low, middle and upper estuaries), to seasonality (dry and rainy seasons) and to habitat usage (marine visitor, marine estuarine-opportunist, marine estuarine-dependent, estuarine resident and estuarine &; marine). Differences were found in the fish assemblages along the estuarine-reef gradient, with most species (n?=?30) being considered marine, estuarine-opportunists or estuarine-dependent, according to its abundance and distribution. A low number of species (n?=?11) were considered estuarine residents. Some species exhibited significant differences in spatial distribution pattern, in which juveniles and adults predominated in different portions of the estuary, suggesting an ontogenetic migration both in relation to the adjacent reef area and across estuarine regions. Several species were newly recorded in the Mamanguape Estuary: Anchoa spinifer, Halichoeres poeyi, Hyporhamphus roberti, Scomberomorus cavalla, Sphyraena barracuda and Ocgocephalus vesperilio.     

Crayfish invasion facilitates dispersal of plants and invertebrates by gulls

相似文献