Dehydroepiandrosterone and neurotrophins favor axonal growth in a sensory neuron-keratinocyte coculture model.

We have previously shown that axonal growth from a subset of sensory neurons was promoted by keratinocytes when the two cell types were co-cultured in a low calcium medium. This phenomenon involves the production of one or several diffusible factors. Here we show that the neuritogenic effect of keratinocytes was significantly reduced in the case of rat primary sensory dorsal root ganglion (DRG) neurons, or completely suppressed in the case of the sensory neuron cell line ND7-23, when the activity of neurotrophin receptors (Trk receptors) was blocked with K252a. This trophic effect apparently involved the activation of tyrosine kinase receptors A and B (TrkA and TrkB) expressed by subpopulations of small- to medium-sized DRG neurons, or only of TrkA receptors in the case of ND7-23 neurons. A residual neurite growth promoting effect of keratinocytes persisted in a fraction of DRG neurons after Trk receptor blockade. This effect was mimicked by the steroid dehydroepiandrosterone (DHEA) but not by other steroids such as pregnenolone, progesterone or 17beta-estradiol. The use of pharmacological agents which inhibit different steps of steroidogenesis indicated that DHEA was probably synthesized from cholesterol in keratinocytes. Our results strongly suggest that DHEA might act as a neurotrophic signal derived from keratinocytes to promote axonal outgrowth from a subpopulation of sensory neurons.

A histological study of human wrinkle structures: comparison between sun-exposed areas of the face, with or without wrinkles, and sun-protected areas.

Wrinkles are a major topic in dermocosmetology; the purpose of this work has been to go deeper into the knowledge of cutaneous damage underlying these modifications of skin surface. Up to now, the number of published works about the histological structure of wrinkles is not very large. Therefore to complete the findings, we studied 46 subjects of both sexes, between 57 and 98-year-old, enabling us to obtain 157 skin biopsies of wrinkles (face) and sun-protected areas (abdomen). We used different histological techniques involving histochemistry, immunohistochemistry, electron microscopy and quantification by image analysis in addition to classic standard techniques. This study has allowed us to confirm published structural modifications of wrinkles, but also to display many other original alterations. The increased thinning of the epidermis atrophied with age is confirmed by the study of desmoplakins outlining the cellular contours of keratinocytes. Such a thinning is accompanied by a decrease in several markers of epidermal differentiation at the bottom of the wrinkles: filaggrin, keratohyalin granules and transglutaminase I, disturbing desquamation and the capacity of the horny layer to retain water. The dermoepidermal junction is modified by a decrease of collagen IV and VII, which, combined with fewer and fewer oxytalan fibres under wrinkles, weakens this interface. The deposition of abnormal elastotic tissue in the dermis, with an interruption of these deposits under wrinkles and an atrophy of dermal collagen more pronounced under wrinkles, boosts the magnitude and depth of wrinkles. The composition of the other dermal constituents is also altered with, more particularly, a marked decrease of chondroitin sulphates in the papillary dermis under wrinkles, combined with an asymmetrical variation of glycosaminoglycans on both edges of wrinkles. The atrophy of the hypodermis, also more marked under wrinkles, with a thickening of fibrous lines, also makes the depth of wrinkles more pronounced. Wrinkle formation appears at the same time as numerous modifications in different cutaneous structures, which may be mutually amplified. Such a study by pointing out altered elements in skin physiology, makes the development of specific treatments possible in order to mitigate this unwelcome cutaneous deterioration.

The liver and primary type IV hyperlipoproteinaemia: a pathological study.

We studied the histological structure of the livers of 36 patients presenting type IV primary hyperlipoproteinaemia. Electron microscopy revealed dilation of the smooth endoplasmic reticulum and rough endoplasmic reticulum as well as the presence of giant mitochondria containing para-crystalline inclusions. Steatosis was present in all type IV hyperlipoproteinaemic patients regardless of their weight or nutritional sensitivity (to alcohol or carbohydrate). The ultrastructural modifications observed by electron microscopy indicate an increased synthesis of very-low-density lipoproteins by the hepatocytes. An alteration in excretion cannot be ruled out with certainty even though the microfilamentary microtubular system was intact, since the qualitative and functional modifications in this system may be undetectable by electron microscopy.

[Histoenzymologic study of the adrenal gland of the dormouse during the annual cycle]. / Etude histoenzymologique de la surrénale du loir au cours du cycle annuel.

The histoenzymologic study of the adrenals in Glis glis was realized for 4 enzymatic activities (acid phosphatase, glucose 1 phosphate dehydrogenase, delta5 3beta-hydroxysteroid dehydrogenase and cholinesterase) completed by the simultaneous dosage of glucose-6-phosphate dehydrogenase. The histophotometric measures made it possible to differentiate the enzymatic activities of the different zones of the adrenal cortex and to show the persistance of an important activity of the zona fasciculata and sometimes of the zona reticulata during hibernation, independantly of the zona glomerulosa. This study confirms the activation of the adrenal cortex during hibernation with a brutal depletion at awakening and reduced activity during estivation.

[Study of correlations linking the volumes of the hypophyseal lobes and the epiphysis to body and brain weights in Chiroptera]. / Etude des corrélations liant les volumes des lobes hypophysaires et de l'epiphyse au poids somatique et au poids de l'encéphale chez les chiroptères

Study of the correlations binding the different lobes of the hypophysis and the pineal gland to body weight and brain weight in Chiroptera shows that the hypophysis is better correlated to body and brain weight than the pineal gland, fact that we already observed in Rodents and Primates. The allometry coefficient (M.R.A.) related to body weight varies from 0,80 to 0,98 for the hypophyseal lobes. The value of this coefficient for the pineal gland (1,60) is greater than that found (1,009) in another group of Mammals (Insectivora, Lemurians and Primates). It is less sure as the important variations in volume of this gland determine a lower correlation coefficient.

[Variations of the glucose 6 phosphodehydrogenase activity at the level of the diencephalon and of the gonads of the dormouse (Glis glis L.) during the annual cycle]. / Variations de l'activité glucose-6-phospho-déhydrogénastique au niveau du diencéphale et des gonades du Loir (Glis glis L.) pendant le cycle annuel

Activity levels of G6-PDH in the diencephalon and testes of Glis glis during the annual cycle show comparable variations. In the autumn, this activity is low and the gonads are inactive. At the anset of hibernation, this activity increases and becomes maximal during the period preceeding awakening. At mid-hibernation, the seminiferous tubules display in important enzymatic activity. Awakening is marked by a fall in enzymatic activity level that is a little more precosius of the diencephalon. The variations of enzymatic activity levels of G6-PDH in the diencephalon are similar in the female with an autumnal minimum and a maximal activity at the end of hibernation.

[Study of the correlations between the volumes of the hypophysis, the epiphysis and the subfornical organ to the somatic weight and the volume of the hypothalamus in rodents]. / Etude des correlations liant les volumes de l'hypophyse, de l'épiphyse et de l'osf au poids somatique et au volume de l'hypothalamus chez les rongeurs

The correlations between volume of the hypophysis, of the epiphysis and of the subfornical organ to body weight and volume of the hypothalamus were studied on 193 rodents belonging to 41 species. Concerning the volume of the hypophyseal lobes the regression slopes of Rodentia occupy an intermediate position between those of Isectivora and Prosimians studied by BAUCHOT. The volume of the epiphysis increases more rapidly with the weight of the body than that of the hypophyseal lobes, the volume of the subfornical organ increases on the contrary more slowly.

[Morphometric data on pineal gland of loir (Glis glis) and lerot (Elioyms quercinus) during the annual cycle]. / Données morphométriques sur la glande pinéale du loir (Clis glis) et du lérot (Eliomys quercinus) au cours du cycle anuel

The important involution of the pineal gland of Glis glis and Eliomys quercinus during the months of july and august belongs to a polyglandular involution (anterior lobe of the hypophysis, male and female genital glands) characteristic of estivation.