Non-invasive high-speed blinking kinematics characterization.

PURPOSE: The objective of this study was to analyze the differences in blinking kinematics of spontaneous and voluntary blinks using for the first time a self-developed, non-invasive, and image processing-based method. METHODS: The blinks of 30 subjects were recorded for 1 min with the support of an eye-tracking device based on a high-speed infrared video camera, working at 250 frames per second, under two different experimental conditions. For the first condition, subjects were ordered to look in the straightforward position at a fixation target placed 1 m in front of them, with no further instructions. For the second, subjects were additionally asked to blink only following a sound signal every 6 s. RESULTS: Mean complete blinks increased by a factor of 1.7 from the spontaneous to the voluntary condition while mean incomplete blinks reduced significantly by a factor of 0.4. In both conditions, closing mean and peak velocities were always significantly greater and durations significantly lower than opening ones. When comparing the values for each condition, velocities and amplitudes for the voluntary condition were always greater than the corresponding values for spontaneous. CONCLUSION: Voluntary blinks revealed significant kinematic differences compared to spontaneous, thus supporting a different supranuclear pathway organization. This study presents a new method, based on image analysis, for the non-invasive kinematic characterization of blinking.

Wild-type Escherichia coli producing microcins B17, D93, J25, and L; cloning of genes for microcin L production and immunity.

For the first time, an Escherichia coli strain producing four microcins (Mcc), B17, D93, J25, and L, and showing immunity to Mcc V was isolated and characterized. Each of the gene clusters encoding the production of Mcc B17, D93, and L was cloned separately. The gene cluster for Mcc L was cloned within a 13.5-kb HindIII-SalI fragment, which includes the Mcc V immunity gene, cvi.

Rapid identification of Escherichia coli microcin J25 producing strains using polymerase chain reaction and colony blot hybridization.

To screen, isolate, and characterize bacterial populations producing microcin J25, we report here two rapid, reliable, and sensitive methods, using polymerase chain reaction and colony blot hybridization with a digoxigenin-labelled probe. A sample of 26 Escherichia coli strains isolated from poultry intestinal contents was evaluated to detect the sequence of mcjA, the gene encoding the MccJ25 precursor. The two molecular techniques were compared with the commonly used cross-immunity tests. They generate accurate data with no obvious cross-reactions with other microcins. The results display that the producers of MccJ25 were widely distributed in the poultry intestinal habitat. The applications of these molecular methods will be useful in future studies of microcinogenic populations, and thus contribute to understand the relationships within the complex intestinal microbial ecosystem.

Influence of the luminance level on visual performance with a disposable soft cosmetic tinted contact lens.

The purpose of the present work was to study the effect on visual performance of wearing disposable soft tinted contact lenses for cosmetic purposes. Parameters such as contrast sensitivity (Vistech 6000), colour vision (Farnsworth-Munsell 100-Hue colour test), visual fields (static Goldmann perimetry) and subjective vision (what the wearer feels while wearing the lenses) were studied under different illumination levels in order to check for possible vision losses while wearing these contact lenses at low illumination levels. Sixteen emmetropic subjects were fitted consecutively with seven pairs of different colour lenses (Optima Colors lenses by Bausch & Lomb), and the experimental parameters were measured under four different illumination levels (60, 6, 1, and 0.1 cd/m2; but 15 and 0.3 cd/m2 for the static perimetry) The results obtained showed no statistically significant differences in visual performance between wearing the lenses and not wearing them (p > 0.01), except for the static perimetry, in which statistically significant differences (p < 0.01) occur at eccentricities greater than 30 degrees.

Isolation, purification and partial amino acid sequence of a highly hydrophobic new microcin named microcin L produced by Escherichia coli.

We report here the production, by an Escherichia coli strain, of two microcins, microcin J25 and a new one that we designated microcin L. The active peptides were separated by solid phase extraction on C(18) cartridges. Microcin L was then purified to homogeneity by cationic-exchange high-performance liquid chromatography. Its molecular mass, determined by mass spectrometry, is 8899 Da. The amino acid composition and the sequence of the first 40 N-terminal residues indicate that microcin L is a hydrophobic peptide, which exhibits high homology to gassericin and lactacin F which both belong to the class II bacteriocins.

Inhibition of the development of microorganisms (bacteria and fungi) by extracts of marine algae from Brittany, France.

The inhibitory effects of aqueous, ethanolic and dichloromethane fractions from 16 marine algae from the Atlantic shores of North-East Brittany, France, have been investigated against microorganisms frequently associated with immersed surfaces. The extracts were tested in vitro against isolates of marine fungi, bacteria and yeasts potentially involved at different stages in the formation of biofilms in the sea. The high levels of inhibitory activity of nine extracts against marine fungi and Gram-positive bacteria and their apparent absence of toxicity against larvae of oysters and sea urchins suggests a potential for novel active ingredients.

Antibacterial activity evaluation of microcin J25 against diarrheagenic Escherichia coli.

The inhibitory activities of known microcins were evaluated against some diarrheagenic Escherichia coli strains. Some antibacterial properties of microcin J25, the most active one, were studied. A rapid two-step purification was performed. The MIC and the minimum bactericidal concentration of J25 against E. coli O157:H7 were 1 and 100 microg ml(-1), respectively. A 10(4)-CFU ml(-1) contamination by this strain was destroyed in milk and meat extract by 6.25 microg of J25 ml(-1) and in half-diluted egg yolk by 50 microg of J25 ml(-1).

A Fusobacterium mortiferum strain produces a bacteriocin-like substance(s) inhibiting Salmonella enteritidis.

Seven strictly anaerobic strains showing anti-Salmonella enteritidis activity were isolated from poultry caecal contents. Among them, the most inhibitory one, a strain of Fusobacterium mortiferum, called FM1025, was selected. Biochemical tests, showing the proteinaceous structure of the antagonist(s) produced, indicated that the strain Fus. mortiferum FM1025 synthesized (a) bacteriocin-like compound(s) active against Salm. enteritidis. Among the other strains tested, both Gram-negative and Gram-positive bacteria were inhibited. These preliminary results suggested the important role of the Fusobacterium strains against pathogenic bacteria among the intestinal flora.

Eye-hand and eye-foot visual reaction times of young soccer players.

PURPOSE: The aim of this study was to investigate the eye-hand and eye-foot visual reaction time among young soccer players and to compare those with non-soccer players in order to evaluate possible differences. METHODS: A vision screening of 53 young male soccer players belonging to the Valencia Soccer Club was done. Soccer players were divided in three categories, with mean ages of 8.2 +/- 0.5 years (range, 8- to 9-year olds), 10.6 +/- 0.2 years (range, 10- to 11-year-olds), and 12.7 +/- 0.3 years (range, 12- to 13-year-olds). An age-matched sample of 60 young male non-soccer players served as a control population. Mean ages in this population were 8.3 +/- 0.6 years, 10.5 +/- 0.4 years, and 12.6 +/- 0.2 years for each category, respectively. Eye-hand and eye-foot visual reaction times were determined in players and non-players by means of a computer-controlled stimuli device. RESULTS: We obtained a mean and standard deviation value (in seconds) of eye-hand reaction time in soccer players of 0.301 +/- 0.037, 0.256 +/- 0.040, and 0.207 +/- 0.031, respectively, for each category, and for non-soccer players of 0.382 +/- 0.061, 0.320 +/- 0.063, and 0.282 +/- 0.043, respectively. The values for eye-foot reaction time in players were: 0.412 +/- 0.062, 0.406 +/- 0.046, and 0.387 +/- 0.034, respectively, for each category, and for nonplayers of 0.496 +/- 0.081, 0.460 +/- 0.026, and 0.446 +/- 0.054, respectively. There are statistically significant differences between eye-hand and eye-foot reaction times between players and nonplayers (p < 0.05). There was no correlation between visual reaction times and age (p > 0.05). CONCLUSIONS: Eye-hand and eye-foot visual reaction times were found to be different between the two populations evaluated. The results show differences between soccer and non-soccer players, with the soccer players demonstrating faster reaction times.

Inhibition of pathogenic Salmonella enteritidis growth mediated by Escherichia coli microcin J25 producing strains.

For the first time, microcin-producing strains showing inhibitory activities against enteropathogen Salmonella enteritidis were isolated from poultry intestinal contents. Among the numerous strains isolated, two strains of Escherichia coli, named J02 and J03, showing the greatest activities against S. enteritidis, were studied. Biochemical tests and purification identified the main antagonist compound produced as microcin J25. In order to evaluate the protective potential of E. coli J02 and J03 against S. enteritidis infection, the ability of these strains to inhibit growth of S. enteritidis was investigated in mixed culture. A strong antagonist activity was obtained with a preculture phase of the active strain in minimal medium before incubation with S. enteritidis. In a bioreactor experiment simulating the chicken gastric and intestinal tract environment, a mixture of the two strains E. coli J02 and J03, provided an enhanced inhibitory effect. Microcinogenic strain activities were not affected by bile, pancreatic enzymes addition, or acidic conditions. These results suggest the relevant role of microcin-producing microorganisms in microbial intestinal ecology. To conclude, this study shows that microcin J25 strains could exert a beneficial protective effect against S. enteritidis growth in situ.

Characterization of the visual performance with soft daily wear disposable contact lenses.

We investigate the visual performance associated with adaptation to a daily wear soft contact lens on the human eye. For this purpose, we used four parameters, one of which was an objective parameter, while the rest were subjective parameters. The objective parameter was a single quality parameter, a Merit function (Mf) derived from the modulation transfer function (MTF) of the overall [eye + contact lens] system The subjective parameters were the visual acuity (VA), the contrast sensitivity function (CSF) and the standard adaptation criterion of Terry et al. (1993). The normality criterion for the MTF was determined by evaluating the fluctuations of the Mf over a day in five emmetropic observers. Fluctuations with no statistically significant differences in the merit function (p > 0.05) and their standard deviation (8%) defined our standard criterion. The CSF and the VA were similarly measured (for emmetropic observers). The results obtained with emmetropic observers allowed us to establish a standard criterion for the evaluation parameters we propose. When this criterion is applied to daily soft wear disposable contact lenses, their performance proves to be good, since both the objective (MTF) and the subjective parameters (CSF, VA, adaptation criterion) always lie within the range defined by our criterion.

A simple technique for measurement of corneal thickness.

Measurement of corneal thickness has potential benefit both in the fitting of contact lenses and in monitoring any pathology that could affect corneal thickness. Corneal thickness measurement is undertaken using an accessory to the biomicroscope, the optical pachometer, or by means of expensive apparatus such as the ultrasonic pachometer. There are other complex methods, such as laser Doppler interferometry, or ultrasonic rasters of the cornea. In this study, an easier and low cost method, based on the measurement of the optical section formed of the cornea by the biomicroscope illumination system, is proposed. The advantages of this new method are the simplicity of its experimental set-up which consists of a calibrated graticule in an eyepiece of the biomicroscope, the speed of the measurement which increases with practice and the low cost, due to the fact that the biomicroscope is standard equipment in the ophthalmic consulting room.

Human contrast sensitivity in coherent Maxwellian view: effect of coherent noise and comparison with speckle.

Lasers have been used in vision for measuring the neural contrast sensitivity function (CSF) by forming interference fringes on the retina. We distinguish among three kinds of illumination with lasers: incoherent (without noise), Maxwellian or coherent (with coherent noise), and diffuse coherent (with speckle). The three have different characteristics and different CSF's. A coherent imaging system is designed to measure the CSF with fully coherent illumination. This is the CSF of the whole visual system, although it is measured with gratings imaged on the retina. It therefore differs from the neural CSF's measured by other authors with partially coherent illumination. However, the neural CSF's are also obtained in this study with and without noise. The effects of coherent noise and speckle on both the visual system and neural sensitivities are studied and compared. Coherent noise differs from speckle in the following ways: (1) It behaves as a high-pass filter, reducing sensitivity in the low-spatial-frequency range, whereas speckle is a low-pass filter; (2) quantitatively, coherent noise reduces neural sensitivity by a factor k(m) with a maximum value between 4 and 6, whereas speckle reduces neural sensitivity by a factor ks with a maximum value of approximately 25 (1.4 log units) for a 3-mm pupil and up to 35 (1.55 log units) for a 1-mm pupil; (3) the masking effect of the coherent noise is affected by changes in luminance but not by changes in pupil diameter; however, the pupil size is the main parameter affecting the masking effect of the speckle.

Standard criterion for fluctuations of modulation transfer function in the human eye: application to disposable contact lenses.

It is well known that the modulation transfer function (MTF) characterizes the optical quality of the eye. Recently, some objective techniques have been introduced in order to measure this function in vivo. These techniques could be employed to display the temporal fluctuations of the eye + compensation system and to isolate the effect of the compensation element provided that the standard fluctuations for a normal observer were known. In this work we carry out a study of the MTF of the human eye over a long period of time to quantify the standard fluctuations of the retinal image quality and to establish a standard criterion of normality. We have defined a single quality parameter from each measured MTF to simplify the analysis of the results. We have evaluated this merit function on normal observers three times a day for one month. As expected, random deviations from the mean value of the merit function have been obtained, although fluctuations with no statistical differences of the merit function (P value from ANOVA test P > 0.01) and the standard deviation of these fluctuations (5%) can be chosen as a standard criterion. We have used this result to study the behaviour of a time-varying compensation element: a disposable contact lens. The study of the eye + contact lens system has been carried out with four types of disposable contact lenses for one month. In spite of their generally good behaviour, statistically significant differences from the standard pattern can be observed. This superimposed continuous fluctuation can be due to lens-dependent processes.

Contact lenses: do they really change the optical performance?

In this investigation the quality of two types of optical correction, hydrogel contact lenses and ophthalmic lenses, was compared by measuring the modulation transfer function (MTF) of the correcting lens plus visual optics system using an objective method. A merit function was defined in order to allow the direct comparison between the optical performance with the two corrections. A study on 10 subjects was undertaken, measuring the MTF of both corrections by using the double pass method. The results show that the optical quality of contact lenses was higher than that with ophthalmic lenses. The contrast sensitivity function (CSF) and visual acuity (VA) were determined as subjective parameters of visual performance.

Influence of the tear film on optical quality of the eye.

The optical quality of the tear film of the eye was tested by measuring the retinal image before and after the break-up time (BUT). An objective method was used based on the evaluation of the retinal image of a point test projected onto the fovea. The loss of an entire tear film would result in a decrease in the optical quality because of corneal irregularities and the formation of an irregular tear lens after the BUT. Our results confirm the expected loss both of non-contact lens wearers and contact lens wearers. Also, the fact that the optical deterioration found after the BUT is greater for contact lens wearers confirms that soft contact lens wear produces a disruption of the tears.

Influence of contrast on the recognition of defocused letters: a geometrical model.

We show how contrast (C) affects the recognition of defocused letters. To do this, the maximum distance (threshold distance) at which a subject, with an induced refraction of -5.5 D, can recognize a letter was determined. Our results show that when C = 1, the recognition threshold distance is such that the ratio eta/xi, between the pseudoimage of the letter (eta) and the blur circle (xi), corresponding to any point of the letter at this distance is about eta/xi = 2; the exact value depends on the difficulty of recognition, in agreement with previous experiments. This ratio represents the sharpness of the image in a geometrical treatment of image formation, providing a geometrical criterion for recognition. Reduction in contrast can be compensated by improving the geometrical sharpness; i.e. bringing the object closer to the subject's are point. Our results show that the increment of eta/xi as a function of the contrast is between C = 0.1 and 1.0. We suggest that a similar geometrical criterion for recognition could be used for any contrast (at least down to C = 0.1 and defocus > 1 D), provided that the proper value of eta/xi is used in each case. On this basis we propose a purely geometrical model, which agrees well with the data and predicts the relationships between tolerance to defocus, contrast and visual acuity; including the well-known relation between visual acuity and defocus when contrast is unity.

[Influence of glyoxylic acid on properties of isolated mitochondria]. / Influence de l'acide glyoxylique sur les propriétés des mitochondries isolées

Glyoxalate is an effector of oxidative phosphorylation in isolated mitochondria : it slows down State 3 but does not affect State 4 respiration. This report presents the findings of our study on the mechanism of action of glyoxalate ; these findings are listed below. The inhibition of Stage 3 respiration by glyoxalate does not set in immediately, can be reversed in part by the addition of an uncoupling agent or a dithiol, is non-competitive against succinate and can be demonstrated with substrates requiring the involvement of other membrane transport systems. Glyoxalate prevents the increased oxygen uptake stimulated by 2,4-DNP or Sr++. Glyoxalate also inhibits phosphate transport and this inhibition can account for most of the effect observed. The inhibition of State 3 respiration is paralleled by a decrease in the mitochondrial accumulation of succinate : this decrease could arise from a direct effect of glyoxalate on dicarboxylic acid transport or could be the result of an inhibiton of the phosphate transport system, which is connected with the former. The decrease in the respiratory rate of uncoupled mitochondria placed in a phosphate free medium demonstrates that the effector acts directly at the substrate transport or/and electron transfer level. Phosphate, by delaying the respiratory inhibiton due to glyoxalate, has a protecting effect on mitochondrial functions. Glyoxalate is thus acting at several mitochondrial sites. It acts presumably by forming hemimercaptals, blocking sulfhydryl groups. Its effects can be accounted for by the unfolding of such (hemicercaptal) groups under the influence of ADP, Pi, uncoupling or others agents which bring about conformational changes in the internal mitochondrial membrane.