Effects of cannabis on visual function and self-perceived visual quality

Cannabis is one of the most used drugs of abuse in the world. The objective of this study was to analyze the effects of smoking cannabis on vision and to relate these to those perceived by the user. Thirty-one cannabis users participated in this study. Visual function assessment was carried out in a baseline session as well as after smoking cannabis. We evaluated static visual acuity, contrast sensitivity, stereoacuity, accommodative response, straylight, night-vision disturbances (halos) and pupil size. The participants were also divided into two groups depending on whether they perceived their vision to have worsened after smoking cannabis. A logistic regression analysis was employed to identify which visual test could best predict self-perceived visual effects. The study found that smoking cannabis has significant adverse effects on all the visual parameters analyzed (p < 0.05). Self-perceived visual quality results revealed that about two thirds of the sample think that smoking cannabis impairs their vision. Contrast sensitivity, specifically for the spatial frequency 18 cpd, was identified as the only visual parameter significantly associated with self-perceived visual quality (Odds Ratio: 1.135; p = 0.040). Smoking cannabis is associated with negative effects on visual function. Self-perceived visual quality after smoking cannabis could be related to impaired contrast sensitivity

Detection and Measurement of the Intracellular Calcium Variation in Follicular Cells

This work presents a new method for measuring the variation of intracellular calcium in follicular cells. The proposal consists in two stages: (i) the detection of the cell’s nuclei and (ii) the analysis of the fluorescence variations. The first stage is performed via watershed modified transformation, where the process of labeling is controlled. The detection process uses the contours of the cells as descriptors, where they are enhanced with a morphological filter that homogenizes the luminance variation of the image. In the second stage, the fluorescence variations are modeled as an exponential decreasing function, where the fluorescence variations are highly correlated with the changes of intracellular free Ca2+. Additionally, it is introduced a new morphological called medium reconstruction process, which helps to enhance the data for the modeling process. This filter exploits the undermodeling and overmodeling properties of reconstruction operators, such that it preserves the structure of the original signal. Finally, an experimental process shows evidence of the capabilities of the proposal

Predicting Academic Performance: A Systematic Literature Review

The ability to predict student performance in a course or program creates opportunities to improve educational outcomes. With effective performance prediction approaches, instructors can allocate resources and instruction more accurately. Research in this area seeks to identify features that can be used to make predictions, to identify algorithms that can improve predictions, and to quantify aspects of student performance. Moreover, research in predicting student performance seeks to determine interrelated features and to identify the underlying reasons why certain features work better than others. This working group report presents a systematic literature review of work in the area of predicting student performance. Our analysis shows a clearly increasing amount of research in this area, as well as an increasing variety of techniques used. At the same time, the review uncovered a number of issues with research quality that drives a need for the community to provide more detailed reporting of methods and results and to increase efforts to validate and replicate work.Peer reviewe

Anabaena flavodoxin as an electron carrier from photosystem I to ferredoxin-NADP+ reductase. Role of flavodoxin residues in protein-protein interaction and electron transfer

10 pages, 4 figures, 6 tables.-- PMID: 15628849 [PubMed].-- Available online on Dec 4, 2004.Biochemical and structural studies indicate that electrostatic and hydrophobic interactions are critical in the formation of optimal complexes for efficient electron transfer (ET) between ferredoxin-NADP+ reductase (FNR) and ferredoxin (Fd). Moreover, it has been shown that several charged and hydrophobic residues on the FNR surface are also critical for the interaction with flavodoxin (Fld), although, so far, no key residue on the Fld surface has been found to be the counterpart of such FNR side chains. In this study, negatively charged side chains on the Fld surface have been individually modified, either by the introduction of positive charges or by their neutralization. Our results indicate that although Glu16, Glu20, Glu61, Asp65, and Asp96 contribute to the orientation and optimization of the Fld interaction, either with FNR or with photosystem I (PSI) (presumably through the formation of salt bridges), for efficient ET, none of these side chains is involved in the formation of crucial salt bridges for optimal interaction with FNR. These data support the idea that the FNR−Fld interaction is less specific than the FNR−Fd interaction. However, analysis of the reactivity of these mutated Flds toward the membrane-anchored PSI complex indicated that all mutants, except Glu16Gln, lack the ability to form a stable complex with PSI. Thr12, Thr56, Asn58, and Asn97 are present in the close environment of the isoalloxazine ring of FMN in Anabaena Fld. Their roles in the interaction with and ET to FNR and PSI have also been studied. Mutants at these Fld positions indicate that residues in the close environment of the isoalloxazine ring modulate the ability of Fld to bind to and to exchange electrons with its physiological counterparts.This work has been supported by Comisión Interministerial de Ciencia y Tecnología (Grant BQU2001-2520 to M.M., Grant BIO2003-00627 to C.G.-M., and Grant BMC2003-00458 to M.A.R.), the European Union (Network HPRN-CT1999-00095 to M.A.R.), and the Andalusian Government (PAI, Grant CVI-0198 to M.A.R.).Peer reviewe

Chromatic Correction Applied to Outdoor Images

Abstract. The color of an image may be affected by many factors such as illumination, complex and multispectral reflections, and even the acquisition device. Especially in outdoor scenes, these conditions cannot be controlled. In order to use the information of an image, the latter must present the information as closer as possible to the original scene. Sometimes images are affected by a dominant color (cast) that changes its chromatic information. In order to avoid this effect, a color correction must be done. In this work, a novel method for correcting the color of outdoor images is proposed. This method consists in a complete improvement process of three steps: cast detection, color correction, and color improvement

Flavodoxin-mediated electron transfer from photosystem I to ferredoxin-NADP+ reductase in Anabaena: role of flavodoxin hydrophobic residues in protein-protein interactions

11 pages.-- PMID: 18177021 [PubMed].-- Printed version published Jan 29, 2008.Three surface hydrophobic residues located at the Anabaena flavodoxin (Fld) putative complex interface with its redox partners were replaced by site-directed mutagenesis. The effects of these replacements on Fld interaction with both its physiological electron donor, photosystem I (PSI), and its electron acceptor, ferredoxin-NADP+ reductase (FNR), were analyzed. Trp57, Ile59, and Ile92 contributed to the optimal orientation and tightening of the FNR:Fld and PSI:Fld complexes. However, these side chains did not appear to be involved in crucial specific interactions, but rather contributed to the obtainment of the optimal orientation and distance of the redox centers required for efficient electron transfer. This supports the idea that the interaction of Fld with its partners is less specific than that of ferredoxin and that more than one orientation is efficient for electron transfer in these transient complexes. Additionally, for some of the analyzed processes, WT Fld seems not to be the most optimized molecular species. Therefore, subtle changes at the isoalloxazine environment not only influence the Fld binding abilities, but also modulate the electron exchange processes by producing different orientations and distances between the redox centers. Finally, the weaker apoflavodoxin interaction with FNR suggests that the solvent-accessible region of FMN plays a role either in complex formation with FNR or in providing the adequate conformation of the FNR binding region in Fld.This work has been supported by the Spanish Ministry of Education and Science (Grants BQU2004-00279 to M.M., BIO2003-00627 to C.G.-M., and BMC2003-00458 and BFU2006-01361 to M.A.R.), the Aragonian Government (Grant PIP122/2005 to M.M.), and the Andalusian Government (PAIDI, Grant CVI-0198 to M.A.R.). G.G. was a recipient of a BSCH Fellowship.Peer reviewe

Flavodoxin-mediated electron transfer from photosystem I to ferredoxin-NADP+ reductase in Anabaena: role of flavodoxin hydrophobic residues in protein-protein interactions

11 pages.-- PMID: 18177021 [PubMed].-- Printed version published Jan 29, 2008.Three surface hydrophobic residues located at the Anabaena flavodoxin (Fld) putative complex interface with its redox partners were replaced by site-directed mutagenesis. The effects of these replacements on Fld interaction with both its physiological electron donor, photosystem I (PSI), and its electron acceptor, ferredoxin-NADP+ reductase (FNR), were analyzed. Trp57, Ile59, and Ile92 contributed to the optimal orientation and tightening of the FNR:Fld and PSI:Fld complexes. However, these side chains did not appear to be involved in crucial specific interactions, but rather contributed to the obtainment of the optimal orientation and distance of the redox centers required for efficient electron transfer. This supports the idea that the interaction of Fld with its partners is less specific than that of ferredoxin and that more than one orientation is efficient for electron transfer in these transient complexes. Additionally, for some of the analyzed processes, WT Fld seems not to be the most optimized molecular species. Therefore, subtle changes at the isoalloxazine environment not only influence the Fld binding abilities, but also modulate the electron exchange processes by producing different orientations and distances between the redox centers. Finally, the weaker apoflavodoxin interaction with FNR suggests that the solvent-accessible region of FMN plays a role either in complex formation with FNR or in providing the adequate conformation of the FNR binding region in Fld.This work has been supported by the Spanish Ministry of Education and Science (Grants BQU2004-00279 to M.M., BIO2003-00627 to C.G.-M., and BMC2003-00458 and BFU2006-01361 to M.A.R.), the Aragonian Government (Grant PIP122/2005 to M.M.), and the Andalusian Government (PAIDI, Grant CVI-0198 to M.A.R.). G.G. was a recipient of a BSCH Fellowship.Peer reviewe

Towards a new interaction enzyme:coenzyme

Abstract Ferredoxin-NADP + reductase catalyses NADP + reduction, being specific for NADP + /H. To understand coenzyme specificity determinants and coenzyme specificity reversion, mutations at the NADP + /H pyrophosphate binding and of the C-terminal regions have been simultaneously introduced in Anabaena FNR. The T155G/A160T/L263P/Y303S mutant was produced. The mutated enzyme presents similar k cat values for NADPH and NADH, around 2.5 times slower than that reported for WT FNR with NADPH. Its K m value for NADH decreased 20-fold with regard to WT FNR, whereas the K m for NADPH remains similar. The combined effect is a much higher catalytic efficiency for NAD + /H, with a minor decrease of that for NADP + /H. In the mutated enzyme, the specificity for NADPH versus NADH has been decreased from 67,500 times to only 12 times, being unable to discriminate between both coenzymes. Additionally, giving the role stated for the C-terminal Tyr in FNR, its role in the energetics of the FAD binding has been analysed.