507 research outputs found
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Processing of color signals in female carriers of color vision deficiency
The aim of this study was to assess the chromatic sensitivity of carriers of color deficiency, specifically in relation to dependence on retinal illuminance, and to reference these findings to the corresponding red-green (RG) thresholds measured in normal trichromatic males. Thirty-six carriers of congenital RG color deficiency and 26 normal trichromatic males participated in the study. The retinal illuminance was estimated by measuring the pupil diameter and the optical density of the lens and the macular pigment. Each subject's color vision was examined using the Color Assessment and Diagnosis (CAD) test, the Ishihara and American Optical pseudoisochromatic plates, and the Nagel anomaloscope. Carriers of deuteranopia (D) and deuteranomaly (DA) had higher RG thresholds than male trichromats (p < 0.05). When referenced to male trichromats, carriers of protanomaly (PA) needed 28% less color signal strength; carriers of D required âŒ60% higher thresholds at mesopic light levels. Variation in the L:M ratio and hence the absolute M-cone density may be the principal factor underlying the poorer chromatic sensitivity of D carriers in the low photopic range. The increased sensitivity of PA carriers at lower light levels is consistent with the pooling of signals from the hybrid M' and the M cones and the subsequent stronger inhibition of the rods. The findings suggest that signals from hybrid photopigments may pool preferentially with the spectrally closest "normal" pigments
Longitudinal membrane function in functionally anuric patients treated with APD: Data from EAPOS on the effects of glucose and icodextrin prescription
Longitudinal membrane function in functionally anuric patients
treated with APD: Data from EAPOS on the effects of glucose
and icodextrin prescription.
Background: Peritoneal dialysis is associated with changes
in membrane function that can lead eventually to ultrafiltration
(UF) failure. Factors driving these changes are thought to
include hypertonic glucose exposure, but previously reported
associations are confounded by the presence of residual renal
function.
Methods: Longitudinal membrane function (solute transport
and UF capacity) were measured annually in a prospective
cohort of 177 functionally anuric patients as part of the
European Automated Peritoneal Dialysis Outcomes Study
(EAPOS). Subgroup analysis was performed according to glucose
exposure and icodextrin use at baseline.
Results: The whole cohort experienced an increase in solute
transport and reduction in UF capacity at 12 and 24 months
that could not be explained by informative censoring. These
changes were accelerated and more severe in patients using
either 2.27% or 3.86% glucose, or those not using icodextrin
at baseline. These differences could not be explained by age,
comorbidity score, previous time spent on renal replacement,
differential dropout from the study, peritonitis rates, or, by definition,
residual renal function. Patients using icodextrin at baseline
had worse membrane function and were more likely to be
diabetic. There was an association between membrane function
changes and achieved 24-hour ultrafiltration over the 2-year
study period.
Conclusion: Anuric automated peritoneal dialysis (APD) patients
experience significant detrimental changes in membrane
function over a relatively short time period. Glucose appears
to enhance these changes independent of residual renal function. Icodextrin use in these circumstances is associated with
less deterioration in membrane functio
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Color vision assessment-3. An efficient, two-step, color assessment protocol
Color vision tests and multiâtest protocols in current use often fail to detect small changes in red/green (RG) and yellow/blue (YB) color vision due to poor sensitivity. The tests also have low specificity. In this study, we examine how improved understanding of withinâ and interâsubject variability in RG and YB color vision and accurate assessment of the differences in color thresholds between the leastâsensitive, ageâmatched normal trichromats, and the leastâaffected deutans and protans can be used to design an efficient color vision screener (CVS) test. To achieve this objective, we examined two extensive data sets from earlier studies and carried out new experiments to provide better estimates of withinâsubject variability in color thresholds and to validate the CVS test. The data sets provide essential information on interâsubject variability, the effects of normal aging on RG and YB thresholds, and the spread in RG color thresholds in deutan and protan subjects. A statistical model was developed to optimize the parameters of the CVS test and to predict the limits of what can be achieved in color assessment. The efficiency and repeatability of the CVS test were then assessed in 84 subjects. The results match model predictions and reveal close to 100% test efficiency. The test takes between 140 and 160âseconds to complete and has close to 100% repeatability. An efficient, âtwoâstepâ protocol based on the initial use of the CVS test followed by full color assessment in only those who fail the CVS test is also described
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Color vision assessment-1: Visual signals that affect the results of the Farnsworth D-15 test
The Farnsworth Dâ15 test (Dâ15) is commonly used to screen for moderate to severe congenital color vision deficiency. The aim of this study was to establish reliable Dâ15 statistics for normal, deutan and protan subjects, and to investigate the different visual signals one can use to carry out the test, even in dichromats and rod monochromats. Six hundred and seventyâfour subjects were examined using the Dâ15, the Colour Assessment and Diagnosis test and the Nagel anomaloscope. A rod monochromat and five dichromats were tested using the standard Dâ15 protocol before the caps were separated into two groups and subjects were asked to repeat the task. Dâ15 spectral radiance data, measured under D65 illumination, were used to estimate differences in photoreceptor excitations for each of the caps. When no crossings and up to two adjacent transpositions on the Dâ15 results diagram are accepted as a pass, 100% of normal trichromats, 54% of deutans and 43% of protans pass the Dâ15. A rod monochromat and two protanopes and deuteranopes were able to complete the Dâ15 when the caps were separated into two groups, despite severe loss or even complete absence of color vision. When up to two adjacent transpositions are accepted 50% of color deficient subjects, some with severe red/green loss, pass the Dâ15. While the Dâ15 is normally used to screen for moderate to severe color deficiency, subjects with severe loss can still use combined, residual red/green, yellow/blue and luminance signals to pass
Synergistic Effect of 3 ',4 '-Dihidroxifenilglicol and Hydroxytyrosol on Oxidative and Nitrosative Stress and Some Cardiovascular Biomarkers in an Experimental Model of Type 1 Diabetes Mellitus
The objective of this study was to assess a possible synergistic effect of two extra-virgin olive oil polyphenols, 3,4,-dyhydroxyphenylglycol (DHPG) and hydroxytyrosol (HT), in an experimental model of type 1 diabetes. Seven groups of animals were studied: (1) Nondiabetic rats (NDR), (2) 2-month-old diabetic rats (DR), (3) DR treated with 5 mg/kg/day p.o. HT, (4) DR treated with 0.5 mg/kg/day p.o. DHPG, (5) DR treated with 1 mg/kg/day p.o. DHPG, (6) DR treated with HT + DHPG (0.5), (7) DR treated with HT + DHPG (1). Oxidative stress variables (lipid peroxidation, glutathione, total antioxidant activity, 8-isoprostanes, 8-hydroxy-2-deoxyguanosine, and oxidized LDL), nitrosative stress (3-nitrotyrosine), and some cardiovascular biomarkers (platelet aggregation, thromboxane B2, prostacyclin, myeloperoxidase, and vascular cell adhesion protein 1 (VCAM-1)) were analyzed. The diabetic animals showed an imbalance in all of the analyzed variables. HT exerted an antioxidant and downregulatory effect on prothrombotic biomarkers while reducing the fall of prostacyclin. DHPG presented a similar, but quantitatively lower, profile. HT plus DHPG showed a synergistic effect in the reduction of oxidative and nitrosative stress, platelet aggregation, production of prostacyclin, myeloperoxidase, and VCAM-1. This synergism could be important for the development of functional oils enriched in these two polyphenols in the proportion used in this study
Brain aging and Parkinson's disease: new therapeutic approaches using drugs delivery systems
ABSTRACT
The etiology and pathogenesis of Parkinsonâs disease (PD) is unknown, aging being the
strongest risk factor for brain degeneration. Understanding PD pathogenesis and how
aging increases the risk of disease would aid the development of therapies able to slow
or prevent the progression of this neurodegenerative disorder. In this review we provide
an overview of the most promising therapeutic targets and strategies to delay the loss of
dopaminergic neurons observed both in PD and aging. Among them, handling alphasynuclein
toxicity, enhancing proteasome and lysosome clearance, ameliorating
mitochondrial disruptions and modifying the glial environment are so far the most
promising candidates. These new and conventional drugs may present problems related
to their labile nature and to the difficulties in reaching the brain. Thus, we highlight the
latest types of drug delivery system (DDS)-based strategies for PD treatment, including
DDS for local and systemic drug delivery. Finally, the ongoing challenges for the
discovery of new targets and the opportunities for DDS-based therapies to improve and
efficacious PD therapy will be discussed
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