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Biomedical subjects

M Guillon

Publications and source records attributed to M Guillon.

At least 19 recordsLinked to original sources
PubMed2005

[Ewing's tumor].

Ewing's tumor (ET) is a malignant bone tumor occurring in children and young adults. ET affects mainly bones of the central axis, and almost always involves soft tissue infiltration. The discovery of a unique genetic alteration, which is a reciprocal translocation most frequently resulting in the fusion of the EWS gene situated on chromosome 22 with the FLI-1 gene on chromosome 11, currently places ET among neuroectodermal tumors. Moreover, this translocation is a tumor-specific genetic marker at the basis of defining ET today and is used as a diagnostic and potentially prognostic tool complementary to imaging and histopathological work-up. Since the 1970 s, important progress has been made in the clinical management of ET patients. Multiagent chemotherapy in association with local treatment (surgery and/or radiation) has clearly improved outcome. The introduction of systemic treatment was justified by the frequent sub-clinical diffusion of apparently localized ET. Intensified therapeutic strategies have for the first time cured some metastatic ET patients, but at the cost of major side effects. Treatment is currently adapted as a result of a better definition of prognostic factors as well as a better assessment of its adverse effects. Improvement in global patient care and increased management of specific acute complications associated with ET (often interwoven with iatrogeneous effects) represent an important step towards improving the quality of life for ET patients as well as preventing long term complications. In the light of present studies, the majority of surviving adults today describe their health and quality of life as good. ET is a fascinating example of the progress made not only in the diagnostic and therapeutic approach to cancer but also in the comprehension of the mechanisms behind carcinogenesis, and consequently reflects the revolution of medicine over the last century.

Adolescent↗
PubMed1998

Influence of contact lens material surface characteristics and replacement frequency on protein and lipid deposition.

The aim of the study was to quantify the influence of both contact lens material and replacement frequency on protein and lipid deposition. The following hypotheses were tested: (1) both protein and lipid interaction with contact lenses are material-dependent, and (2) the key factors are the material ionicity for the protein deposition and the material chemical composition for the lipid deposition. Three high water content contact lens materials were tested: netrafilcon A (FDA group II, Gentle Touch), etafilcon A (FDA group IV, Acuvue), and vifilcon A (FDA group IV, Focus). Contact lens spoilation was analyzed using ultraviolet spectroscopy and fluorescence spectrophotometry. The results showed that (1) significantly more proteins were deposited on the ionic materials than on the nonionic materials, and that among the ionic materials, the higher the ionicity, the higher the level of protein deposition; (2) there were significantly more surface proteins on the ionic materials after 3 months than after 1 month of wear, but no difference over time was demonstrated for the nonionic materials; and (3) significantly more lipids were deposited onto the surface of vifilcon A than etafilcon A or netrafilcon A, and the presence of vinylpyrrolidone in the vifilcon A formulation was thought to be the cause of increased deposition. The protein and lipid interactions with contact lenses were found to be material- and time-dependent. Protein attraction was found to be related to the material ionicity. The presence of vinylpyrrolidone was a key factor in the attraction of lipids.

Contact Lenses, Hydrophilic↗
PubMed1997

Effect of material ionicity on the performance of daily disposable contact lenses.

The surface of hydrophilic contact lenses is intrinsically hydrophobic. Biocompatibility requires the contact lens surface to be coated with a lipoproteinic biofilm produced by the ocular secretion. For daily disposable modality of wear it is essential that biocompatibility, clinically represented by good in vivo wettability and subjective acceptance, is achieved as quickly as possible following insertion, as the process needs to be repeated daily. It has been hypothesised that non-ionic materials will not achieve biocompatibility as rapidly as ionic materials owing to the latter's ability to attract high levels of adsorbed proteins. The current investigation was a double-masked crossover study that evaluated, over 1 week of wear, a new non-ionic material (Nelfilcon A) and a current ionic material (Etafilcon A) under daily disposable modality. The results obtained showed that overall, both contact lens materials achieved good in vivo tear stability over the first 30 min of wear and good subjective acceptance that remained stable over the period of wear. The results obtained demonstrate that a non-ionic material can achieve rapid biocompatibility and subjective acceptance in a similar manner to an ionic material.

Journal Article↗
PubMed1997

Preocular tear film characteristics of nonwearers and soft contact lens wearers.

The aims of the current investigation were to: (1) characterize (structure, volume, and stability) the preocular tear film of contact lens wearers and nonwearers and (2) test for any difference between contact lens wearers and nonwearers and between symptomatic and asymptomatic subjects. The tear film structure and stability were tested using the Tearscope in conjunction with the biomicroscope observation system. The tear prism height, which is indicative of the tear volume, was measured with the slitlamp. The study was carried out on 239 subjects (478 eyes) who attended our clinic for contact lens fitting. Of these, 184 were habitual daily soft contact lens wearers who had not been wearing contact lenses for at least 24 h; the other 55 were noncontact lens wearers. The results obtained showed that: (1) the stability of the tear film was correlated for two eyes of the same subject; (2) the structure, volume, and stability of the preocular tear film were similar for both groups; (3) no difference in tear film stability was found between asymptomatic and symptomatic contact lens wearers, but a significant difference was found between asymptomatic and symptomatic noncontact tact wearers; and (4) the stability of the tear film was influenced by the nature of the lipid layer present at the surface of the aqueous layer; the greatest stability was achieved when the lipid layer was thick and homogeneous (amorphous pattern).

Adult↗
PubMed1996

Objective measurement of contact lens-induced conjunctival redness.

Ocular redness is the principal clinical sign of any inflammatory response affecting the anterior segment of the eye. The aims of the current investigation were: (1) to develop an objective method to quantify the severity and geographic distribution of redness, (2) to validate that technique by determining its precision and compare its finding to clinical rating, and (3) to apply this technique to evaluating the diurnal variation in ocular redness associated with daily and extended soft contact lens wear. The objective capture and analysis technique involved the following steps: (1) direct image formation on the CCD array of a high resolution, high sensitivity 3/4 inch Cohu camera via a Nikon Macrolens and (2) capture and image analysis with a PC-based dedicated transputer. The key steps were: filtering to accurately locate the limbus and electronic sectioning with differential intensity color analysis at fixed intervals away from the limbus. The technique gave a direct measurement of the number and size of the vessels present. The result obtained lead to the following conclusions: (1) the digitization and analysis of video recordings of the bulbar conjunctiva provide a precise measurement of the level of conjunctival redness, (2) subjective rating of low level of conjunctival redness, using an overall nine increment clinical scale, did not relate closely to the objective measurement of conjunctival redness, (3) for non-contact lens wearers, redness in the evening was similar to redness measured upon waking, and greater than redness 2 h postwaking. In contrast, in daily soft contact lens wearers, redness was maximal in the evening and greater than before insertion or during wear in the morning. In extended soft contact lens wearers, redness was maximal upon waking when it was greater than in the evening, and (4) digitization and analysis video recordings of the redness response of the bulbar conjunctiva are sufficiently sensitive clinical research tools to monitor diurnal variation of the inflammatory response of the anterior segment of the eye.

Circadian Rhythm↗
PubMed1996

[Foreigners and naturalized French citizens: a slow social diversification (1982-1990)].

"Two decades of economic recession have brought about profound transformations in the social structure of France's working population. In this article we focused on an analysis of socioprofessional statistics from the censuses of 1982 and 1990 (the first ones to use the new terminology) as means of understanding the role and status in these developments of populations produced by immigration. The social gap between working people of foreign origin and the birthright French remains quite considerable. Nevertheless, despite the economic situation, the social homogeneity of the minority population seems to be fading. Although the great majority of working people from a foreign background are still employed in low-echelon industrial and service jobs, there is a tendency for this homogeneity to blur slightly." (SUMMARY IN ENG AND SPA)

Demography↗
PubMed1990

Corneal desiccation staining with hydrogel lenses: tear film and contact lens factors.

This investigation monitored the response of established contact lens wearers using contact lenses made from Filcon 4a 77% water-content material in three different thicknesses (0.08, 0.10 and 0.12 mm) over a 6-hour period of wear under adverse environmental conditions. The results obtained showed the following. (1) In accordance with previous studies carried out with lenses of similar water content, the present lenses produced corneal desiccation staining under the challenging conditions of use. However, the staining produced was similar for all three lens thicknesses tested. (2) Corneal desiccation staining was present despite the good and stable fitting characteristics observed during the study, confirming that mechanical trauma is not a necessary cause for soft-lens-induced desiccation staining. (3) Corneal desiccation staining was associated with a rapidly destabilizing pre-lens tear film (PLTF) and a thinning lipid layer. The initial break-up of the PLTF and corneal staining were recorded with a higher incidence in the vertical quadrants than in the horizontal quadrants. The PLTF is thinnest and most unstable at the tear prism margin border, hence least efficacious at preventing evaporation. Corneal desiccation staining may be due, at least partly, to excessive evaporation at the contact lens front surface.

Adult↗
PubMed1990

Hypoxic effects on corneal morphology and function.

Normal corneal metabolism depends on a critical level of oxygen, below which a series of acute corneal responses occur, including an increase in stromal lactate, a reduction in intercellular pH, and an increase in corneal hydration. These acute responses are reversible when normal oxygen is restored; however, it has been shown that chronic exposure to low oxygen levels can result in permanent morphologic changes in the corneal endothelium. Clinicians have expressed concern that these observed structural changes may also be accompanied by alterations in corneal physiology. Whether such effects occur is not known, since it has been difficult to assess human corneal function accurately. Recently, we have developed an in vivo test, able to measure overall corneal hydration control, that can be used to study the effects of hypoxia on corneal function. This test provides information on several characteristics of hydration control, one of which is the percent corneal thickness recovery per hour (PRPH) after inducing corneal swelling. In this study, we assumed that corneal hypoxia accompanies both extended and polymethylmethacrylate (PMMA) contact lens wear and that the dose received is related to the years of past lens wear. Using this paradigm, we explored the relationship of hypoxic dose to an endothelial polymegethism index (EPI), endothelial cell density (ECD), and PRPH in 36 subjects with varying contact lens wearing histories. Based on multiple regression analysis, the relative change (expressed as percent per year) associated with hypoxic dose (adjusted for age and gender) was found to be dose-dependent and corresponded to estimated changes of 1.70%/yr, -0.25%/yr, and -1.26%/yr, with 95% confidence limits of (-0.3, 3.7), (-1.4, 0.9), and (-2.6, 0.06) for EPI, ECD, and PRPH, respectively. These preliminary data suggest that hypoxic exposure alters endothelial morphology and reduces corneal function; however, it is important to indicate that this was a exploratory investigation with several limitations, and that therefore these results should be viewed as preliminary until more definitive studies are completed.

Adolescent↗
PubMed1989

Hydrogel lens wettability during overnight wear.

The in vivo wettability of soft contact lenses worn by a group of 10 subjects was monitored over a 24-hour period including 8 hours closed eye. Two types of lenses were tested: Igel 67 (Prima) and Bausch & Lomb 70. They were each worn once in both eyes by all the subjects. The in vivo wettability of the lenses tested was evaluated by measuring the pre-lens non-invasive break-up-time (NIBUT) and assessing the nature of the pre-lens tear film structure. The results obtained showed good wettability throughout the study and no difference between the two materials tested, but a significant difference between open and closed eye wear. The tear film was far more stable (p less than 0.01) immediately upon waking (mean NIBUT 21.2 s) than during open eye wear (mean NIBUT 11.2 s). Also at waking the pre-lens lipid layer was thicker than during open eye wear and the lens surface had a greater mucous coating. The presence of a more stable pre-lens tear film at waking was associated with a different tear film structure. We believe these differences in pre-lens tear film structure are responsible for the greater stability recorded.

Adult↗
PubMed1988

Effect of target contrast and luminance on soft contact lens and spectacle visual performance.

The visual performance of four soft contact lenses was investigated using visual acuity charts at six contrast levels (from 90 to 8%) under normal (250cd/m2) and reduced 92.5cd/m2) luminances. This investigation reveals significant differences not detected by conventional visual acuity measurements; in general, reducing luminance or contrast increases the magnitude of any recorded difference. Furthermore, the study pointed to a significantly poorer visual performance with spectacles compared to standard thickness soft contact lenses under low luminance and contrast conditions. Finally, a recommended examination routine is described.

Adult↗