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Biomedical subjects

D Saint-Léger

Publications and source records attributed to D Saint-Léger.

11 recordsLinked to original sources
PubMed2003

[Normal and pathologic sebaceous function. Research in a shallow milieu?].

Modern therapeutic approaches allow to control sebaceous secretion but knowledge about the sebaceous gland and its precise function within the pilosebaceous unit is still insufficient. Steroid hormones are the principal albeit not exclusive regulators of the sebaceous glands. Three phases may be distinguished in sebaceous physiology: secretion-production, stocking in the follicular reservoir, and excretion. Human "native" intracellular sebum, before secretion, is composed of squalene, waxes, and triglycerides. Once secreted, the sebum is colonised by various xenobiots whose development is controlled by several defensive humoral mechanisms and by the contact with ambient oxygen. Oxygen and micro-organisms transform "native" sebum, lysis of triglycerides to fatty acids being the most pronounced activity. Certain components of this complex mixture of molecules present in the sebum are clearly cytotoxic or irritant, provoking reactive follicular hyperkeratosis and comedone formation--the first step to acne. Some lipophilic organisms like Malassezia yeast may be highly antigenic and induce chronic inflammatory reactions like in seborrhoeic dermatitis. Demodex is an inrafollicular parasite feeding on sebum that frequently causes blepharitis. Sebum is also a vehicle transporting and transmitting several endogenous and exogenous molecules, including potential regulatory factors of hair follicles. Recent development of in vitro cultures of functional sebocytes should help to better understand several aspects of the sebaceous gland's biology.

Acne Vulgaris↗
PubMed1993

[Physiology of the pilosebaceous follicle].

The human pilosebaceous follicle shows an extreme diversity with regard both its variation according to its localisation along the human body, and the various physiological dependences of the two tissues which comprise the pilosebaceous follicle. These latter, highly differentiated toward specialised synthesis (proteins, lipids) have their own specific physiology which, though, responds to some common mediators. Each pilosebaceous follicle shows specific cycles and regulation, irrespective with those of its "neighbour". Despite such a complex situation, the most common features of these two tissues, as well as their endogenous and exogenous consequences, are described.

Hair↗
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↗
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

Comparison of the kinetics of sebum secretion in young women with and without acne.

We utilized a sebum-sensitive adhesive film, Sebutape, to visualize the pore patterns of women with and without acne with computerized image analysis. In normal young women, we found a positive correlation between the number of active sebaceous follicles and total sebum excretion. When seborrhea was intense, this correlation was however lost. The situation was more complex in acne. The severity of seborrhea was positively correlated with the mean sebum excretion of individual follicles but not with the number of active follicles.

Acne Vulgaris↗
PubMed1990

[The history of dandruff and dandruff in history. A homage to Raymond Sabouraud].

In one of his books, written at the beginning of this century, Raymond Sabouraud devotes some 280 pages to the history of dandruff. Their reading illustrates how, from the Greeks to Sabouraud's era, this desquamative disease has been subjected to endless doctrinal and scientific conflicts, long before the so-called "present" controversies. One of the early conflicts, between Celsus and Galen, lies in the nature of the squames, i. e. dry or exudating, leading to the inclusion (or non inclusion) or pityriasis in the group of desquamative diseases, such as psoriasis or ichytosis. Translated into Latin (furfur, porrigo) and into Arabic, the word pityriasis was replaced in the Middle Age by tinea which then referred to any disease of the human scalp. With Plenk, Lorry, Willan and others, the 18th century brought a new attitude of mind where observation took precedence over doctrine, but owing to the lack of experimental approach there was no adequate description of the squames and their anatomical origin. This was the case with Hebra who, in the 19th century, claimed that dandruff was nothing but a sebaceous disease. This major turn resulted for decades in a confusion between dandruff and seborrhoea. In the late 19th century, bacteriological studies were decisive steps taken by Rivolta, Malassez and Sabouraud. The presence on scalps affected with dandruff of a bottle-shaped "fungus" (Pityrosporum ovale was initially not regarded as a yeast) was taken as being the definite cause of the disease. The Sabouraud dogma was born, but as early as 1877 it was denied by Vidal who observed these "spores" on healthy scalps.(ABSTRACT TRUNCATED AT 250 WORDS)

Dermatology↗
PubMed1989

Stratum corneum lipids in skin xerosis.

Lipids of the stratum corneum are implicated in cohesion and desquamation of the stratum corneum as well as in the maintenance of normal barrier function. Evidence linking the intercellular lipids to such processes has mainly been derived from studies on acquired or inherited diseases of lipid metabolism manifesting abnormalities in the structure and the function of the stratum corneum. We have studied the composition of stratum corneum lipids in clinically normal individuals with typical xerosis or 'winter dry skin' in order to establish if the lipid composition differs from that of normal individuals, showing no signs of xerosis. The amount of total stratum corneum lipids was not related to xerosis (22.0 +/- 1.8 micrograms/cm2 for normal skin, and 26.3 +/- 2.9 micrograms/cm2 for severe xerosis), and no correlation was evident between polar lipids, cholesterol sulfate (2.8 +/- 0.5% for normal skin, and 1.6 +/- 0.2% for severe xerosis), or ceramides types I-VI, and dry skin. It therefore appears that dramatic changes in stratum corneum lipids are not detectable in normal 'winter dry' skin. However, a decreased proportion of neutral lipids (sterol esters, triglycerides), coupled to increased amounts of free fatty acids, were found associated to the severity of dry skin. Apart from a decline in the sebaceous function and in esterases activity, winter dry skin does not appear to be associated to dramatic changes in polar stratum corneum lipids.

Adult↗
PubMed1985

A photoacoustic investigation of the influence of some constituents of the stratum corneum on ultraviolet absorption.

Photoacoustic spectroscopy (PAS) was used to evaluate light absorption by solid samples. Application of this technique to the human stratum corneum (SC) was used to investigate the influence of some constituents of SC (water, lipids, hydrophilic substances) on ultraviolet (UV) absorption by this tissue. The results showed that the water content of SC modified the PAS signal obtained. For example, there was a fall of over 20% in the UV absorption coefficient when the SC water-content rose from 0 to 30%. Epidermal lipids were not shown to have any direct effect on UV absorption by SC. However, indirectly they do seem to have protected some of the hydrophilic substances from water extraction. After removal of these hydrophilic substances, the UV absorption from SC was greatly decreased. Results indicated that these hydrophilic substances were protected in situ by polar lipids enmeshed within the structure of SC.

Amino Acids↗