Biomedical subjects

J de Rigal

Publications and source records attributed to J de Rigal.

8 recordsLinked to original sources

PubMed1992

Influence of age and sun exposure on the biophysical properties of the human skin: an in vivo study.

The physical properties of the skin were measured by using noninvasive methods on 72 people displaying various levels of solar elastosis on the neck. The physical parameters measured were the skin extensibility, the elastic recovery, the skin colour, the skin thickness and the electrical conductance. The correlation between the above parameters, the clinical grades of elastosis and the chronological age of each subject were studied using two different statistical approaches. They both showed that elastotic skin is less elastic, dryer, darker, more erythematous and less yellowish than the nonexposed skin. The similarities and differences between the properties of elastotic skin and purely chronologically aged skin are discussed.

Adult↗

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

In vivo biophysical characterization of skin physiological differences in races.

The role of race in modulating skin responses has been investigated. Several parameters (skin thickness, transepidermal water loss, water content of the stratum corneum and skin biomechanics) have been measured using noninvasive tools in whites, Hispanics and blacks to assess whether the melanin content could induce changes in skin biophysical properties. Marked differences between races appear in stratum corneum water content and in skin extensibility, recovery and elastic modulus. Measurements done in different sun-exposed sites highlight the effects of solar irradiation on the skin and the role of melanin in preventing skin damage. The study shows that racial differences in skin physiology exist and are mainly related to the protective role of melanin present in races with darker skin. Moreover, differences in skin hydration are not fully explained according to the site and presence of hair.

Black People↗

PubMed1989

Assessment of aging of the human skin by in vivo ultrasonic imaging.

The ultrasonic imaging technique that we have developed provides cross-sectional images of human skin in vivo with a resolution of about 80 microns axially (i.e., deep into the skin) and 250 microns lateral (parallel to the surface). In order to study aging skin, we obtained ultrasonic images from the mid-forearm (volar and dorsal sides) of 142 women. Ultrasonically, on the images, the dermis appears composed of two bands: a dark superficial one where the ultrasonic waves are propagated in a relatively homogeneous or non-echogenic medium, and a deeper one, which is lighter in color, suggesting a heterogeneous medium. Our results show that skin is thicker on the dorsal than on the volar forearm. In contrast to previously published results, skin thickness remains constant until the seventh decade of life, diminishing thereafter. The relative thickness of the two bands show marked variations with age: a progressive thickening of the dark band, from zero in infants to approximately 75% of total skin thickness in aged subjects, while the light band shows the inverse trend. Comparing the amplitude of the bands on the volar and dorsal forearm, the relative thickness of the dark band is larger on the dorsal (exposed) side and increases with age. These findings and the analysis of variously stained biopsies taken in some of our patients lead us to assign this dark band to a zone in the upper dermis where the collagen network is delicate, dense, and well organized. This is supported by some data in the literature. The thickness of this subepidermal non-echo-genic band appears to be a far more sensitive marker of skin aging at the dermal level than is the measurement of skin thickness.

Aging↗

PubMed1989

Age-related mechanical properties of human skin: an in vivo study.

We have investigated in vivo how various viscoelastic parameters that describe the mechanical properties of the human skin may vary with age. Accordingly, we have used a mechanical device that records the torsional extensibility of the skin. When submitted to a low torque, the time-response curve of the skin affords the determination of the immediate extensibility (UE), the immediate recovery (UR), the viscoelastic part of the deformation (UV), the elastic recovery (UR/UE), and the creep relaxation time (tau). Because the skin thickness varies with age and primarily governs the mechanical properties, it was measured through an ultrasound technique at the same sites (forearm) where the torque was applied. The results show that the skin maintains its thickness and extensibility up to the seventh decade as opposed to its elasticity or recovery capacities, which decrease from an early age. The viscous part of the deformation is constant through life, whereas the creep relaxation time decreases linearily with age. Except for skin thickness, no differences in these parameters between men and women were detected. The significance of these results are discussed in terms of structure alterations. The determination of the elastic recovery (UR/UE) appears to be a parameter of choice for illustrating skin aging.

Adolescent↗

PubMed1988

In vivo cross-sectional ultrasonic imaging of human skin.

This paper describes a new experimental set-up allowing routine cross-sectional ultrasonic images of human skin to be obtained in vivo and presents the first high-resolution images it gives. This system is characterized by the utilization of damped, high-frequency ultrasonic transducers. This type of transducer is longitudinally driven along the skin by a stepping motor under the control of a computer, which at the same time stores the digitized reflected signals. After the acquisition sequence, the image of the skin is displayed on a video monitor after data processing of the ultrasonic signals. On the images thus obtained, fascia, hypodermis, reticular dermis, pilosebaceous units, and adventitial dermis can be visualized. Due to a lack of resolution (about 80 microns) epidermis can only be viewed on certain zones like the hand.

Forecasting↗

PubMed1988

Are corneocytes elastic?

By using a microhandling system, we have recorded the force necessary to elongate isolated corneocytes. According to certain hypothesis, it appears that the elastic modulus of corneocyte is far higher than that of stratum corneum itself. Aggregates of corneocytes are disassembled by forces with a wide range of intensity. In the light of these experiments, stratum corneum appears as a very supple material where the deformations occur more by a plastification of the intercellular medium and an unfolding of the microrelief lines than an elongation of the corneocytes themselves. Moreover, desmosomes remnants could play a certain role in the corneocytes cohesiveness.

Cell Adhesion↗

PubMed1985

New experimental approach to measure the skin-reflected light. Application to cutaneous erythema and blanching.

By modifying the blood supply in the upper part of the dermis, the colour of the skin is changed by any material in contact with it. This is a great difficulty when we want to measure the colour intensity in erythema or blanching. To avoid this problem, we designed and built a device which measures the skin reflectance value without any contact with the skin. The use of this device on man to study the skin blanching after application of dermocorticoids allows us to determine the more potent drug among a series (clobetasol propionate) and, for a given drug (betamethasone), the more efficient preparation (oil-in-water emulsion). The study of the effect of increasing irradiation doses of ultraviolet light show that the sensitivity of the device is equivalent to that of the clinical assessment and that the relationship between the irradiation dose and the skin reflectance is sigmoidal.

Betamethasone Valerate↗