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Biomedical subjects

J C Garson

Publications and source records attributed to J C Garson.

8 recordsLinked to original sources
PubMed2000

Histological structure of human nail as studied by synchrotron X-ray microdiffraction.

Three layers (characterized by different orientations of the keratin molecules) from the outer to the inner side of human nail were observed by synchrotron X-ray microdiffraction. These layers are associated with the histological dorsal, intermediate and ventral plates. The hair-like type alpha-keratin filaments (81 A in diameter), are only present in the intermediate layer (accounting for approximately 2/3 of the nail width) and are perfectly oriented perpendicular to the growth axis, in the nail plane. Keratin filaments of stratum corneum (epidermis) type, found in the dorsal and ventral cells, are oriented in two privileged directions; parallel and perpendicular to the growth axis. This "sandwich" structure in the corneocytes and the strong intercellular junctions, gives the nail high mechanical rigidity and hardness, both in the curvature direction and in the growth direction. Lipid bilayers (49 A thick) parallel to the nail surface fill certain ampullar dilations of the dorsal plate and intercellular spaces in the ventral plate. Using X-ray micro-diffraction, we show that onychomycosis disrupts the keratin structure, probably during the synthesis phase.

Female↗
PubMed2000

Study of the keratinization process in human hair follicle by X-ray microdiffraction.

Synchrotron X-ray micro-diffraction studies along the follicle and the hair fibre allowed us to follow the keratinization process and the progressive organization of the keratin: i) molecular organization appeared progressively in the follicle; the formation of alpha-helices was completed inside the follicle. ii) supramolecular organization appeared only outside the follicle, far from the bulb; filament structure was observed far from the follicle. Comparisons between structures observed for in vitro and in vivo grown hair, whatever in the bulb or in the fibre, indicate there is no evidence of any structural difference. More, no variation in the transition in vivo/in vitro zone has been observed. In vitro and in vivo fibres exhibited the same structure.

Hair↗
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↗
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

Oriented structure in human stratum corneum revealed by X-ray diffraction.

Various types of human stratum corneum (sheets or callus) were exposed, in parallel and perpendicular geometry, to the high flux of X rays produced by a synchrotron radiation source. Under these conditions, very clear and rich diffraction patterns, corresponding to the supramolecular organization of stratum corneum proteins and lipids, were obtained. The comparative study of normal or delipidized stratum corneum sheets and membrane couplets allows one to attribute certain diffraction features to lipids. Our results in the 3-7-nm range show two different distances for lipid bilayers. Concerning the protein nature of normal stratum corneum, the results show that keratin would occur in the beta form, whereas for callus it is in the alpha form. Indeed, normal stratum corneum sheets never display the 0.514-nm characteristic of alpha keratin. This result means that the supramolecular organization of keratin could depend on the keratinization process. Finally, our studies also confirm the presence of a still-unknown protein component existing in the beta form that would be located either inside the corneocytes or in some dilatated zones of the intercellular spaces.

Humans↗
PubMed1979

[Water in keratin: electrical conductivity measurements].

Measurements of electrical conductivity of keratin fibers show that, for weak hydration (0-5%) interaction between water and protein is strong. This decreases the probability of charges-exchange taking place between them. During the first percentages of elongation, an increase of the percentage of "intermediate water" appears.

Electric Conductivity↗