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Biomedical subjects

J L Lévêque

Publications and source records attributed to J L Lévêque.

At least 19 recordsLinked to original sources
PubMed2004

Ptosis of submental skin: objective measurements and effect of age.

BACKGROUND/PURPOSE: Sagging of the face skin is a visible and unattractive characteristic of skin ageing. This phenomenon, due to both gravitational force and age-related alterations in the mechanical properties of skin, has never been quantitatively studied. The aim of this paper was, first, to define a method and a precise procedure allowing the objective measurement of this phenomenon and, second,to study how it is related to age. METHODS: We used an electronically controlled bed that allows the comparison of submental skin profiles in both the reclined and the upright positions. A parameter that characterises the sagging amplitude for an individual was defined and the reproducibility of measurement of this parameter was verified. RESULTS: Results, obtained from 66 female volunteers, demonstrated a statistically significant positive correlation between this new parameter and age, and also between this new parameter and the elastic recovery parameter of skin, as measured by torquemeter. CONCLUSION: Age-related changes of the skin's mechanical properties and of the various underlying skin tissues would explain this phenomenon. This new method and procedure should allow objective evaluation of the efficacy of any treatments (cosmetic, medical or surgical) proposed for rendering the appearance of people younger.

Adult↗
PubMed2001

Quantitative assessment of skin aging.

Noninvasive methods have allowed physicians to give an objective description of aged skin in terms of functional and esthetic properties. The relative influence of environment (mainly sun) on the true aging process can be assessed through the obtained data. It is also possible to measure the efficacy of topical preparations (cosmetics or drugs) designed for treating the various cutaneous aging marks.

Humans↗
PubMed2001

[Chemistry of cosmetics in antiquity].

Several texts, statues and paintings denote the importance of make up and eye medicines since the earliest periods of Egyptian history. We have investigated cosmetic powders that were preserved in original alabaster and reed containers. Quantitative crystallographic and chemical analysis of the mineral and organic components revealed surprising facts. In addition to the well known galena PbS and cerussite PbCO3, two unexpected constituents have been identified: laurionite PbOHCl and phosgenite Pb2 (CO3) Cl2, which are rare halide minerals found in lead slag only in certain places where the sea water has weathered lead debris left over from silver mining operations in Antiquity. Alteration of natural lead minerals is also unlikely, given the excellent state of conservation of the reed vessels. This evidence indicates that laurionite and phosgenite were synthesised artificially. Support for this statement comes from recipes of medicinal products to be "used in ophthalmology" reported by Greco-Roman authors such as Dioscorides and Pline (1st Century B.C.): silver foam PbO is crushed and mixed with rock salt and sometimes with natron (Na2CO3). The reaction seems to be straightforward. However, our experiments in the laboratory have shown a major difficulty, arising from the concomitant production of alkali, which raises the pH and leads to different products. It follows that the Egyptians very early mastered this kind of chemical synthesis and technology, a fact of great importance in the History of Sciences. Fire-based technology had been mastered to manufacture Egyptian Blue pigments since the third millennium B.C. The present results now suggest that wet chemistry was already known 4000 years ago. This key finding provides a new insight into the chemical technology of far greater antiquity than has previously been believed. Yet, an important question remains relative to the ultimate motivation for these technological developments. If the Egyptians initially only aimed at different nuances of grey, they could use cerussite, an easily accessible mineral, crushed and mixed with galena. Thus, one should seek other motivations; we shall propose to consider a religious-ritual context, ultimately linked to a pharmaceutical aspect.

Cosmetics↗
PubMed2000

Changes in tactile spatial discrimination and cutaneous coding properties by skin hydration in the elderly.

Neurosensory tactile functions were investigated in human subjects by two different and complementary experimental approaches. First, a conventional psychophysical method (two-point gap discrimination) was used to determine the tactile discrimination threshold by analyzing the subjects' ability to detect a gap of variable width between two contact points when a series of stimuli was applied to the skin. Using this method we confirmed the marked degradation of tactile spatial acuity with age and showed that skin discriminative function was partially restored after hydration of the skin with a moisturizer. The second approach consisted of a microneurographic recording of tactile afferent fibers in response to two types of mechanical stimuli applied reproducibly to the corresponding receptive fields. With this method, we found that the afferent messages were depressed following hydration of the skin surface. Thus, partial restoration of tactile spatial acuity after hydration appears to be due to both a softening of the stratum corneum permitting better localization of the stimulus and a weaker transfer of the stimulus toward the sensory receptors.

Adult↗
PubMed1999

Comparative effects of retinoic acid, glycolic acid and a lipophilic derivative of salicylic acid on photodamaged epidermis.

BACKGROUND: Studies comparing purported antiaging compounds are rare. OBJECTIVE: To compare in a randomized, placebo-controlled double-blind study 10% glycolic acid (GA), 2% 2-hydroxy-5-octanoyl benzoic acid (beta-lipohydroxy acid, LSA) and 0.05% all-trans-retinoic acid (RA). METHODS: Women volunteers treated one forearm twice daily with one of the active products and the other one with the vehicle. Comparative evaluations of efficacy were made using histochemistry and quantitative immunohistochemistry. RESULTS: Improvement in the various epidermal compartments was the most prominent finding at the RA-treated site. The LSA-treated site also exhibited similar positive changes, although to a lesser degree. GA showed no significant effect. CONCLUSION: In the presently tested concentrations and formulations, RA had a beneficial impact upon the aging epidermis. LSA mimicked RA but with somewhat lesser efficacy. By contrast, GA appeared almost inactive.

Double-Blind Method↗
PubMed1999

EEMCO guidance for the assessment of skin topography. The European Expert Group on Efficacy Measurement of Cosmetics and other Topical Products.

Numerous factors can modify the visibility or the actual dimensions of the skin microrelief and wrinkles. To quantify these changes, several methods, including clinical and non-invasive ones, have been proposed. This article reviews the advantages et drawbacks of all of them and lists some experimental recommendations to make the results of studies using these methods, more reliable.

Face↗
PubMed1998

Mexoryl SX: a broad absorption UVA filter protects human skin from the effects of repeated suberythemal doses of UVA.

There is now considerable evidence that chronic UVA exposure induces damage in animal and human skin; however, little is known about UVA protection of human skin. The aim of this study is to evaluate the efficacy of Mexoryl SX, a broad UVA absorber (lamada max = 345 nm) against UVA-induced changes in human skin. The regimen of UVA exposure (13 weeks with increasing suberythemal doses) induces intense pigmentation with no erythema. Skin hydration and elasticity decrease, whereas total skin thickness, assessed by echography, remains unchanged. Irradiated epidermis reveals a significant thickening of the stratum corneum, an absence of hyperplasia and an increase in the expression of the protective iron-storage protein ferritin. No significant alterations are seen using antisera against type IV collagen or laminin, suggesting that the dermal-epidermal junction (DEJ) is mainly preserved. In dermis, enhanced expression of tenascin is seen just below the DEJ but type I procollagen, which is localized at the same site, is unaltered. Although we are unable to visualize any changes in elastic network organization using Luna staining or specific antiserum directed against human elastin, we notice an increased deposition of lysozyme or alpha-1 antitrypsin on elastin fibres. Mexoryl SX (5%) efficiently prevents these alterations. Thus, these results suggest that UVA photoprotection can prevent early putative alterations leading to photoageing.

Adult↗
PubMed1997

Dermo-epidermal stimulation elicited by a beta-lipohydroxyacid: a comparison with salicylic acid and all-trans-retinoic acid.

Although ageing has been thought to be irreversible, studies made during the last decade have shown that a few topical compounds may limit or improve the age-related skin damages. The efficacy of tretinoin (all-trans-retinoic acid) in treating photoageing is well established. Identifying other compounds with similar effect and improved tolerance would be greatly valued. In this double-blind study, a new beta-lipohydroxyacid compound was evaluated. To address a comparison between products, 6 volunteers completed a 4-week study using twice daily 0.025% tretinoin, 5% salicylic acid, 1.5% beta-lipohydroxyacid or vehicle. Immunohistochemistry and computerized image analysis were performed on skin sections from biopsies taken after treatment. We searched for changes in epidermal renewal (Ki-67 labeling), modifications in cytokeratin (56-65 kD) and filaggrin patterns, and in tumor necrosis factor alpha (TNF-alpha), Ulex europaeus and factor XIIIa expressively. The vehicle- and salicylic-acid-treated areas had an aspect similar to untreated control sites. Both beta-lipohydroxyacid and tretinoin induced enhanced epidermal proliferation and thickness with activation of factor XIIIa+dendrocytes. The effects were more pronounced at the tretinoin-treated site. We speculate that TNF-alpha might mediate some of the dermal effects. The beta-lipohydroxyacid mimics some of the stimulatory effects of tretinoin on the epidermis and dermis. This new compound should be listed among topical products boosting the skin tissues affected by ageing.

Administration, Topical↗
PubMed1994

Organization of stratum corneum lipids in relation to permeability: influence of sodium lauryl sulfate and preheating.

The role of the structural organization of intercorneocyte lipids in the barrier function of human stratum corneum was evaluated by treatment with heat and sodium lauryl sulfate. Measurement of transepidermal water loss in treated samples was used to quantify variations in stratum corneum permeability. Thermodynamic transition of lamellar lipids and their degree of organization were evaluated by differential scanning calorimetry and small-angle X-ray diffraction, respectively. Progressively preheating stratum corneum samples from 75 degrees C to 90 degrees C increased stratum corneum permeability to water vapor, while the fusion temperature of lamellar lipids and the intensity of the X-ray diffraction peaks of the polar lipids decreased. Sodium lauryl sulfate induced similar variations of these three parameters. These results support the hypothesis that, in addition to the chemical nature of intercorneocyte lipids, their structural arrangement and thermodynamic properties play an important role in the barrier function of the stratum corneum to water vapor.

Calorimetry, Differential Scanning↗
PubMed1994

In vivo hydration profile in skin layers by high-resolution magnetic resonance imaging.

In recent years magnetic resonance imaging has become a very efficient tool for in vivo quantification of water content and water behavior in living tissues. We have applied this technique to the study of the in vivo hydration profile in heel skin layers by quantification of the mobile water proton density versus depth. Effects of a bath, a moisturizer and repeated soaping are present. Hydration profiles by magnetic resonance imaging delineate two different structures in stratum corneum: an outer layer where hydration can be modified by external mechanisms and an inner layer where hydration is not altered. The main interest of this method lies in the fact that the physical signal is exactly located, as spatial encoding is the basis of in vivo imaging. This method differs from other noninvasive methods which acquire an averaged signal from a nondelimited volume of interest.

Administration, Topical↗
PubMed1994

[Microscopic diagnosis of onychomycoses].

INTRODUCTION: The microbiological identification of onychomycosis may be uncertain as some fungi growing in culture from this material are not necessarily pathogen and invasive. Conversely, the negativity of a culture is not rare even when fungi are seen by microscopy. MATERIALS AND METHODS: We compared the information brought by standard histological examination, immunohistochemistry and in vivo confocal microscopy. RESULTS: The histological examination of nails is of importance in this pathology. We present a laboratory technique that proves to be easy and rapid. We report diagnostic criteria allowing the distinction between dermatophytes, yeasts and non-dermatophyte molds. The standard microscopic examination may further be improved by immunohistochemistry using some antibodies to fungi. In vivo confocal microscopy is a technique for the future. The dermatologist will be able to see fungi in the nail at the clinical examination, without any sampling or peculiar preparation. CONCLUSION: The histological examination is a routine technique useful for defining the nature and localization of fungi in the nail plate. Immunohistochemistry applied to onychomycosis is an experimental approach bringing prominent informations about the identification of fungi. In vivo confocal microscopy is a door opened to the future.

Arthrodermataceae↗
PubMed1993

How does sodium lauryl sulfate alter the skin barrier function in man? A multiparametric approach.

The effects of topically applied sodium lauryl sulfate were studied in vivo, in man, through noninvasive methods and compared with those obtained in vitro, using human stratum corneum as a model. The results show that the very marked increase of transepidermal water loss obtained in vivo cannot be related to any removal of epidermal lipids. The most likely explanation of our findings lies in the hyperhydration of stratum corneum consecutive to the inflammation process and a possible disorganization of the lipid bilayers.

Adult↗
PubMed1993

In vivo vision of the human skin with the tandem scanning microscope.

The tandem scanning reflected light microscope invented by Petran and Hadravsky provides real-time vision in the confocal mode. It performs nondestructive optical sectioning of biological material to a depth that depends on the transparency of the tissue. This real-time facility adds a fourth dimension (time) to the study of living specimens. In the present work, human skin was explored in vivo, at the cellular level to a depth of 150 microns. Two different anatomical sites were investigated: the back of the hand and the volar aspect of the forearm. The stratification of the horny layers, the nuclei of the living keratinocytes through the whole epidermis and the capillary loops within the superficial dermis constituted clear reference points. These permitted thickness measurements of the stratum corneum and epidermis to an accuracy of 1 microns. This method of exploration provides a new challenge for dermatologists and cosmetologists.

Epidermal Cells↗
PubMed1992

[Biophysical characterization of the stratum corneum. Relationship between structure and properties].

Studies carried out over the last ten years have determined the structure and chemical composition of the stratum corneum and their significance for biologic function; the stratum corneum (SC) is composed of flat layers linked to each other by desmosome plates. Intercellular spaces are composed mainly of double lipid layers which are responsible for the main part of the barrier function of the SC. This barrier between the body and the environment must be effective despite the deformations and various insults (chemical, physicochemical) to which the SC is subjected. The SC fulfills its barrier function through remarkable physical properties of which most originate in an ability to bind water molecules to protein sites whose presence depends on the humidity of the environment in which the SC was produced. Lastly, the SC exhibits some enzyme activities and consequently can no longer be considered as an inert membrane.

Body Water↗
PubMed1991

Effect of topical corticosteroids on human sebum production assessed by two different methods.

Topical corticosteroids are widely used in cutaneous diseases. Although their mode of action on different skin compartments has been documented, little is known about their effects on the human sebaceous gland. We investigated the effects of two corticosteroids of differing potency on the excretion of sebum by means of two validated techniques: the Sebutape and the Lipometre. This study was conducted on the forehead skin of normal healthy subjects. The results obtained with both techniques correlated well. The application of both corticosteroids during a 4-week period led to a significant decrease in sebum excretion. This decrease was more pronounced with the more potent corticosteroid (Dermovate). In the light of these findings, it is likely that topical corticosteroids exert an anti-proliferative action upon the sebaceous cells in a similar manner to their effect in other skin compartments.

Administration, Cutaneous↗
PubMed1991

Extension-induced changes in the microrelief of the human volar forearm: variations with age.

The skin microrelief can be assessed in vivo using a noninvasive method based on the image analysis of negative replicas, shadowed by oblique illumination. This technique was used to study changes in the surface furrows of the human volar forearm, related to the degree of extension, in volunteers of three age groups. Results confirmed that the skin in elderly subjects can be characterized by the lack of one of the two perpendicular furrow orientations observed in the young. During extension of the arm, the response of the microrelief in young subjects was clearly different from that in the elderly. Young skin buffered strain through a progressive shift in line density and furrow depth from one orientation to the other, whereas in the elderly, a progressive rotation of the single furrow orientation occurred. These differences would appear to be related to changes in the architecture and physical properties of the dermis. Microrelief, in the elderly subjects, showed a mean line density of 24/cm, regardless of the degree of extension. This constancy may reflect the ultimate stage in the chronological aging of the skin and may be characteristic of a loosened and relaxed dermis.

Adult↗
PubMed1991

In vivo proton relaxation times analysis of the skin layers by magnetic resonance imaging.

If in vivo magnetic resonance imaging is nowadays a powerful non-invasive method in medical diagnosis, its application in order to study the skin in vivo is not yet in common use because skin imaging requires a high resolution, at least in the direction perpendicular to the skin surface. We have therefore designed a specific imaging module, which, connected to a standard whole-body imager at 1.5 Tesla, allows us to obtain in vivo magnetic resonance images of skin on most parts of the body. With a depth resolution of about 70 microns, we are able to differentiate the skin layers: epidermis, dermis, subcutaneous fat, and even a thickened stratum corneum on palm as well as on heel. This paper reports the T1 and T2 water proton relaxation times of the different skin layers, in vivo, which are magnetic resonance parameters extracted from the images. Results show that skin layers are characterized by shorter T2 relaxation times than other biologic soft tissues. On the contrary, the measured T1 values are in the same range as in other tissues. These short T2 values may be assigned to the fibrous protein content of the skin and particularly of the dermis. This study on normal skin is the precursor of further works such as the influence of aging. As regards skin pathologies, it will be a powerful tool to follow the evolution of skin diseases under treatment.

Adult↗