Evolution des cellules gonadotropes préhypophysaires au cours du cycle oestral chez la ratte

Résumé L'évolution des cellules gonadotropes préhypophysaires ß et a été étudiée au cours de cycles de 4 jours chez la ratte.Ces 2 catégories cellulaires subissent au cours du cycle ovarien des variations morphologiques et numériques qui paraissent témoigner d'une activité folliculostimulante pour les cellules ß et d'une activité ovulatoire pour les cellules .Les cellules ß se dégranulent une l^ère fois pendant la nuit du dioestrus II au prooestrus, puis une 2^e fois, lors de la phase préovulatoire, l'après-midi du prooestrus.Les cellules présentent, au cours de l'après-midi du prooestrus, une dégranulation massive, qui peut etre mise en rapport avec la décharge de L. H. qui se produit à ce stade du cycle.La l^ère dégranulation des cellules ß en dioestrus II correspondrait à la vague de croissance folliculaire qui, selon Long et Evans, a lieu à ce stade du cycle et mènerait certains follicules à la rupture. La seconde traduirait une décharge de FSH synergique de l'excrétion de L. H. par les cellules , pendant la phase préovulatoire du cycle ovarien.

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Summary Morphological and numerical variations of the pituitary gonadotrophs ß and were studied during 4 days cycles at different stages of the oestrous cycle in the Rat.The highest degree of degranulation of the ß cells was observed first during the night of dioestrous II to prooestrous and afterwards on the afternon of prooestrous.The degranulation of the cells began in the morning of prooestrous and reached its higher degree at 4 p. m. in prooestrous.The first peak of degranulation of the ß cells was supposed to be related to the wave of follicular growth which occurs on the day of dioestrous II according to Long and Evans. The second phase of degranulation of these cells was considered as a prooestrous diurnal discharge of FSH synergically with the ovulatory discharge of LH by the cells during the critical period of the cycle.

     

Ultrastructure du lobe postérieur de l'hypophyse du rat et ses modifications au cours de l'excrétion de vasopressine

Résumé Le lobe postérieur de l'hypophyse a été examiné sur coupes ultrafines chez 45 rats (24 normaux, 17 déshydratés respectivement 1, 2 et 4 jours, et 4 anesthésiés à l'éther), après fixation au glutaraldéhyde ou selon la méthode de Karnovsky, post-fixation osmiée et double contraste à l'acétate d'uranyle et au citrate de plomb. Des fibres neurosécrétoires sombres et claires sont reconnaissables, mais les données manquent encore pour interpréter cette différence. Des densifications juxta-membranaires sont observées dans les terminaisons neurosécrétoires là où se trouvent des amas de microvésicules. Des fibres neurosécrétoires traversent parfois des pituicytes; il est aussi souvent observé des fibres, chargées de granules, libres dans un espace péricapillaire. Les espaces péricapillaires, ramifiés en tous sens loin des vaisseaux, développent une large surface de contact avec les extrémités nerveuses et les prolongements de pituicytes.Dans des conditions techniques bien contrôlées, la déshydratation n'entraîne pas de modifications appréciables des granules de neurosécrétat après 24 h. Ensuite les granules sont diminués en nombre, de façon très considérable le 4e jour; mais les granules restants ont un contenu dense normal; jamais il n'a été observé d'aspects de granules vides . Après anesthésie prolongée à l'éther, il n'y a aucune modification visible ni du nombre, ni de la densité des granules. Ces observations sont discutées quant au mécanisme de l'excrétion de vasopressine; elles sont en faveur de l'existence de deux pools hormonaux, l'un libre et rapidement disponible, l'autre plus fortement lié et certainement contenu dans les granules jouant le rôle de réserve. Toutefois un mécanisme d'exocytose granulaire ne peut être formellement exclu.

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Ultrastructure of the rat's hypophysial neural lobe and it's changes during vasopressin release

Summary Hypophysial neural lobes of 45 rats (24 controls, 17 dehydrated resp. 1, 2 and 4 days, and 4 ether anesthetized) were fixed either with glutaraldehyde or according to Karnovsky and post-fixed in osmium tetroxyde; ultrathin sections were stained by uranyl acetate and lead citrate. Dark and clear neurosecretory fibres were observed, but sufficient data are still lacking for a valuable interpretation of these aspects. Juxta-membraneous densifications are visible in limited areas of neurosecretory terminals where clusters of microvesicles are present. Neurosecretory fibres happen to be completely encircled by pituioyte cytoplasm; fibres loaded with elementary granules are frequently encountered running free in a pericapillary space. Pericapillary spaces stretch out branching far away from vessels, resulting in a widespread contact with nerve terminals and pituicyte processes.In accurately controlled technical conditions, dehydratation does not result in any noticeable change of neurosecretory granules after 24 h. A decrease of the number of granules follows and is extremely conspicuous after 4 days; though, remaining granules keep a normal dense content, and aspects of empty granules have never been observed. After prolonged ether anesthesia, no visible change either in number or electron density of granules was observed. These findings are discussed in consideration of the mechanism of vasopressin release; they support the hypothesis of two hormonal pools, one of which would be free and rapidly available for release, the other being more tightly bound and certainly located in granules representing a storage site. Though granular exocytosis cannot be absolutely excluded.

Travail effectué avec l'aide, en matériel et en assistance technique, du Centre National de la Recherche Scientifique. — Nous remercions particulièrement Mme J. Bottini pour son aide précieuse dans la préparation du manuscrit et Mr. B. Dutillet pour sa participation aux contrôles en microscopie optique.     

Ultrastructure des cellules germinales au cours du développement embryonnaire du Lézard vivipare (Lacerta vivipara Jacquin)

Résumé Les gonocytes primaires sont relativement pauvres en polysomes et l'ergastoplasme granulaire est très réduit. Le reticulum endoplasmique de type lisse se développe au cours du développement embryonnaire. L'appareil de Golgi est bien représenté et localisé au niveau de la calotte juxtanucléaire mitochondriale. Les liposomes cytoplasmiques sont très nombreux.Cette étude précise la structure du nucléole «annulaire» et de la «masse paranucléolaire» observés en microscopic photonique. Des modifications nucléolaires sont constatées au cours du développement embryonnaire. Certains aspects ultrastructuraux sont vraisemblablement en rapport avec le déplacement autonome des gonocytes. La signification physiologique du nucléole «annulaire» et de la «masse paranucléolaire» est envisagée.

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Ultrastructural study on the primordial germ cells during embryonic development of Lacerta vivipara Jacquin

Summary The primordial germ cells of Lacerta vivipara have relatively few free polysomes and little ergastoplasm. Smooth endoplasmic reticulum increases during embryonic development. The Golgi apparatus is well developed and lies close to the mitochondrial juxtanuclear cap. This study shows the ultrastructure of the ring-shaped nucleoli and the masse paranucléolaire. Modifications in nucleolar structure are observed during embryonic development. Some ultrastructural features are probably related to the ameboid movement of the primordial germ cells. The physiological meaning of the ring-shaped nucleoli and the masse paranucléolaire is considered.

Avec la collaboration technique de Mme. M. Hubert.     

Modifications des cellules gonadotropes de la préhypophyse chez la ratte injectée de testostérone au cours du cycle oestral

Summary 4-day cyclic adult female Wistar rats were injected subcutaneously with testosterone propionate on diestrus 1 at 16:00 and on diestrus 2 at 10:00 respectively. Non-injected females served as controls. Autopsy was performed on diestrus 2 at 23:00, and on proestrus at 14:00 and 17:00 respectively. The blue Alcian-PAS staining was used to evidence FSH () and LH () pituitary cells.In control animals and in diestrus 2 injected females only a small number of FSH cells could be detected on diestrus 2 at 23:00. This number increased markedly on proestrus at 14:00 and decreased on proestrus at 17:00. A similar evolution was observed in diestrus 1 testosterone injected females, but the number of FSH cells appeared higher at any stage of autopsy in these females than in diestrus 2 injected females and in control rats.In control females, numerous LH cells were observed on diestrus 2 at 23:00. The number of these cells was diminished on proestrus at 14:00 and still more at 17:00. On the contrary few LH cells were detected in testosterone injected females on the evening of diestrus 2. An increase of these cells occurred on proestrus at 14:00, followed at 17:00 by only a weak diminution as established by comparison with control animals.An inhibition of FSH release and a suppression of the proestrus surge of LH were therefore supposed to cause, on one hand, the slowing up of follicular growth observed in diestrus 1 injected females and, on the other hand, the blockage of ovulation noted in both diestrus 1 and diestrus 2 treated animals.

Travail effectué avec l'aide de la D.G.R.S.T. Contrat n^o 72.7.0030.     

Analyse morphométrique semi quantitative de l’histologie testiculaire au cours du vieillissement

Testicular aging is usually studied using sperm and quantitative hormone analysis. Testicular samples are obviously difficult to obtain from a control aging population. Body donations from the Anatomy Department of the Saint-Peres University provided access to testicular samples from deceased men between the ages of 53 to 102 years. We present the first results of a semiquantitative histological morphometric study of testicular aging. We studied a series of 39 subjects. After removal of the sample within the first 24 hours, several investigations were conducted. Macroscopic examination (volume, weight) was followed by histological examination and computer-assisted morphometric analysis: N.I.H images based on the following parameters: (i) transverse sections of the seminiferous tubules (total surface, thickness of the basal membrane, and nuclear density of Sertoli cells, spermatogonia, spermatocytes and spermatozoids; (ii) histological sections were studied for interstitial tissue, number of clusters and the surface occupied by Leydig cells (percentage per parenchyma area), their appearance, size and nuclear density were determined; (iii) this study was completed by visual count of the various cell types in the seminiferous epithelium. The results obtained on a series of 39 subjects aged from 53 to 102 showed various alterations, such as thickening of the tunica albuginea and basal membrane and intertubule hyalinization. The most frequent histological pattern of the aging testis is a mosaic of various seminiferous tubule lesions varying from tubules with complete although reduced spermatogenesis to entirely sclerosed tubules. Individual variations are extremely marked with major alterations of spermatogenesis as early as 60 years old, with atrophied Leydig cells and, on the contrary, preserved spermatogenesis until the age of 95 years.     

Etude cytologique et cytochimique des cellules germinales des reptiles au cours du développement embryonnaire et après la naissance

Résumé Les gonocytes primaires des Reptiles sont très riches en granules vitellins et en liposomes cytoplasmiques; ils contiennent aussi un peu de glycogène. Les mitochondries se groupent dans une zone juxtanucléaire. La répartition de la chromatine est diffuse et chez certains Reptiles le nucléole des gonocytes est annulaire; une plage nucléaire particulière que nous avons dénommée «masse paranucléolaire» est visible à proximité de ce nucléole. L'évolution de ces différents constituants cellulaires est suivie au cours du développement embryonnaire et après la naissance. Les caractères cytologiques mis en évidence permettent de reconnaître sans ambiguïté les gonocytes dès les jeunes stades du développement embryonnaire. La «masse paranucléolaire» permet d'établir une continuité directe de la lignée germinale, sur le plan cytologique, depuis la fin de la gastrulation jusque chez l'adulte.

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Cytological and cytochemical studies of germ cells throughout the embryonic development and after birth in reptiles

Summary The primary gonocytes contain numerous yolk granules and lipid droplets; there is also some glycogen in their cytoplasm. Mitochondria are located in a juxtanuclear area. The chromatin is diffuse and in some reptiles a ring-shaped nucleolus is noted. Near the nucleolus there is a peculiar area which we have called masse paranucléolaire. The fate of all these cellular components was studied throughout embryonic development and during postnatal life. These cytologic characteristics permit the identification of the gonocytes from the gastrula stage. The masse paranucléolaire permits the clear demonstration of a continuity of the germinal line from gastrulation to the adult stage.

     

Détection par immunofluorescence des cellules corticotropes et mélanotropes dans l'hypophyse de la grenouille,Rana temporaria L., au cours du développément

Summary During the embryonic and larval developmental stages of the frog, Rana temporaria L, anti- 1–24, 17–39 corticotropine, and MSH antibodies were used to define, with immunofluorescence technique, the appearence of corticotropic and melanotropic cells.A very small number of fluorescent corticotropic cells appears for the first time during the embryonic stage (10 mm), just before the differentiation of the pars intermedia. The cells are small, their large nucleus is surrounded by a fine rim of fluorescent cytoplasm.During premetamorphic stage, the anti-ACTH antibodies (anti- 1–24 and anti- 17–39 corticotropine) reveal more fluorescent cells in the whole pars distalis. The pars intermedia cells can also be visualized by both antisera.At the end of prometamorphosis and during climax the corticotropic cells show a more precise localization. As in adult frog pars distalis, they are concentrated in the rostral half of the lobe. With the same technique anti- and MSH antibodies reveal only the cells of the pars intermedia. No other cell type of the pars distalis reacts with these antibodies. This technique has the advantage to show that the ACTH and the MSH cells appear very early during the embryonic life.

     

Répartition de l'activité phosphatasique acide dans les cellules gonadotropes de la Grenouille au cours de leur cycle sécrétoire

Résumé Dans les cellules de l'hypophyse de la Grenouille, Rana temporaria, produisant l'hormone gonadotrope, nous avons analysé la localisation et l'évolution de l'activité phosphatasique acide au cours du cycle sécrétoire.Durant l'élaboration des sécrétions, l'activité enzymatique est essentiellement localisée au niveau de l'ergastoplasme, des saccules et des vésicules golgiennes, avec quelques accumulations plus importantes dans les grains juxta-golgiens et dans certains grains de diamètre plus important. A ce stade, quelques vésicules du réticulum endoplasmique lisse et un petit nombre de formations globuleuses présentent également une réaction positive. Ces images pourraient être en relation d'une part avec un processus de formation des lysosomes, d'autre part avec le fonctionnement normal de l'appareil de Golgi.Dans les cellules en phase de stockage et en cours d'excrétion, aucune activité n'est décelable dans la région golgienne. On note, par contre, la présence d'un grand nombre de corpuscules lytiques dispersés parmi les grains de sécrétion. Dans la matrice de ces corpuscules on distingue parfois des formations granulaires qui pourraient être en voie de résorption.Ces formations qui interviennent dans le processus de résorption intracellulaire des produits de sécrétion non excrétés pourraient également à certains moments du cycle cellulaire jouer un rôle, dans le processus de libération de l'hormone.

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Localization of phosphatasic acid activity in gonadotrophs of the frog during their secretory cycle

Summary The localization and evolution of acid phosphatase activity during the secretory cycle of the gonadotropic cells of Rana temporaria are described.During the secretory phase of the cells the enzymatic activity is demonstrable in the rough endoplasmic reticulum, the Golgi saccules or vesicles and in granules of different diameters. Some vesicles of the smooth endoplasmic reticulum and a few number of globular formations contain also acid phosphatase. This picture corresponds to the normal function of Golgi zone or to the first step of the formation of lysosomes.During the phases of accumulation and excretion of secretory granules acid phosphatase activity is concentrated in lytic bodies which sometimes contain secretory granules. This picture may be interpreted as an intracellular digestion of secretory products. At this time the Golgi zone lacks acid phosphatase activity.From these findings it may be concluded that in gonadotropic cells lysosomes act in the regulation of secretory process, specially the resorption of accumulated secretory granules, but a role in the hormone releasing process cannot be excluded.

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Avec la collaboration technique de Mme R.-O. Clauss.     

Ultrastructure du mucus (cellules caliciformes du côlon) et des granulations des mastocytes du côlon

Résumé Les auteurs ont étudié la biréfringence du mucus du côlon chez le rat, le cobaye et le lapin, au moyen des colorations métachromatiques au bleu de toluidine et aux acridines. Ils démontrent une biréfringence positive du mucus extracellulaire. Les granulations des mastocytes, dans le même matériel, sont anisotropes. L'anisotropie du mucus et des granulations des mastocytes est présente après fixation-coloration simultanée au bleu Alcian et au vert Alcian. La biréfringence du mucus extracellulaire reste également positive avec les phtalocyanines. En microscopie électronique, les auteurs démontrent, à l'aide du bleu Alcian, une structure filamenteuse parallèle du mucus s'échappant de la cellule. Un aspect hétérogène des granulations des mastocytes est aussi mis en évidence par cette méthode. Ils discutent l'aspect de la réaction métachromatique en fonction de l'anisotropie d'une structure.

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Ultrastructure of mucus in goblet cells and of granules of mastocytes in colonAnisotropy, metachromasia and electron microscopy

Summary The authors have investigated the birefringence of the colic mucus in the guinea pig, the rat and the rabbit before and after of metachromatical staining with toluidine blue and with acridines. They demonstrate a positive birefringence of the extracellular mucus. The granulations of the mast cells in the same animals are anisotropic. The anisotropy can be seen in the mucus and in the granulations of the mast cells after a combined fixation and staining with a mixture of glutaraldehyde and Alcian blue or Alcian green. The birefringence of the extracellular mucus also remains positive with these phtalocyanin dyes. Using the electron microscope, the authors demonstrate, by means of Alcian blue, a filamentous structure with a parallel orientation in the mucus while it flows out of the cells. The same method allows the vizualisation of a heterogenous aspect in the granulations of the mast cells. They discuss the theoretical aspects of the metachromatical reaction in relation with the anisotropy of a structure.

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Nous remercions vivement le Prof. G. Romhányi de l'Université de Pecs (Hongrie) d'avoir bien voulu examiner nos préparations et de nous avoir conseillé dans l'élaboration de ce travail.Nous remercions sincèrement le Dr. J. E. Scott du Canadian Red Cross Memorial Hospital, Taplow, Maidenhead, Berks (Angleterre) d'avoir examiné nos courbes spectrophotométriques du bleu Alcian-héparine et de nous avoir donné son avis.Ce travail a été partiellement réalisé grâce au crédit no 3. 141. 69 du Fonds National Suisse pour le Développement de la Recherche Scientifique.     

Variabilités verticale et temporelle des acides gras d'un phytoplancton lacustre au cours d'un cycle nycthéméral

Vertical and temporal variability in the content and composition of fatty acids in the lake phytoplankton were studied during a diel cycle (48 h). There is temporal variability in total fatty acid (FA) content per biomass unit but it is not strictly diurnal. In contrast, polyunsaturated FA with 20–22 C chains and unsaturated FA/ saturated FA ratio are higher during the day than during the night.The temporal variability was not as great as the variability is between sampling depths characterized by different phytoplankton assemblages. Phytoplankton composition and physiological state were the principal factors affecting FA composition. Thus, a C16:1w7/C18:1w9 ratio distinguishes between diatoms, with a high level of C16 unsaturated FA, and dinoflagellates with C18 unsaturated FA. This ratio was different at the surface and at 20 m depth, where the phytoplankton had the same taxonomic composition but a different physiological activity.

     

Étude expérimentale de certains aspects des capacités discriminatives des larves deLocusta migratoria migratorioides (R et F) au cours de leur cycle quotidien d'activité au laboratoire

Sans résumé     

Cinétique et caractérisation du phénomène “apoptosis-like” induit au cours de la congélation des spermatozoïdes bovins

Cryopreservation of ejaculated bovine spermatozoa induces severe cell death. In a preliminary study, we observed that cryopreservation and/or thawing was also associated with early apoptotic features in living spermatozoa: i) decrease of the mitochondrial membrane potential^αψm), ii) caspase activation, iii) increase of membrane permeability, without the appearance of late characteristics: iv) no DNA fragmentation. This process has been called “apoptosis-like”. In this study, we evaluated the consequences of each step of cryopreservation of bovine spermatozoa: dilution in cryopreservation medium, equilibration and cryopreservation in liquid nitrogen/thawing. Apoptosis and acrosomal reaction were analysed by flow cytometry and the presence of AIF (Apoptosis Inducing Factor) was analysed by western blot. We observed that dilution in cryopreservation medium induced a marked and immediate increase of the proportion of living spermatozoa with a low^Δψm. After equilibration, the proportion of living spermatozoa with active caspases then began to increase. After the complete cryopreservation/thawing process, this population reached a maximum, and a significant increase of membrane permeability was observed. These results, showing that some features of the “apoptosis-like” phenomenon are initiated in the early steps of cryopreservation, suggest that ice formation may not be the only factor affecting spermatozoa. The consequence of this^Δψm decrease could be the release and/or activation of various pro-apoptotic factors in the cytoplasm. Presence of the pro-apoptotic AIF factor in bovine spermatozoa suggests a possible role of this protein during the cryopreservation process. We also confirmed that cryopreservation of bovine spermatozoa induced an acrosomal reaction. It would be of interest to investigate the relationship between this acrosomal reaction and membrane permeability. A better understanding of the cellular mechanisms involved in sperm cryopreservation would help to improve the preservation of bovine sperm.     

Variations du taux des ecdystéroïdes au cours des cycles de mue et de vitellogenèse chez le Crustacé Amphiphode,Orchestia gammarellus

Ecdysteroid titer in whole extracts of female O. gammarellus varies during the course of the moult cycle: it is minimal at the beginning of the intermoult cycle (stages A, B and C_a) and in D₀, and maximal in D₂. In hemolymph, the hormone content presents a single peak level in D₂; this peak is constituted by ecdysterone, as revealed by HPLC. Ovaries, at the end of vitellogenesis, contain ecdysterone and low polarity substances. Ecdysteroids are also present in eggs after laying.

Variations in ecdysteroid levels seem to influence oocyte growth; vitellogenin synthesis, however, is independent of hormonal fluctuations.     

Evolution de la structure plastidiale et des reserves polysaccharidiques au cours de la déshydratation des gamétophytes feuillés du Polytrichum formosum Hedw. (Polytrichales)

Abstract

The effects of a 24 h dehydration period on plastid ultrastructure and their starch content have been studied on the leafy gametophyte of a poikilohydrous moss Polytrichum formosum Hedw. It has been shown that desiccation induces a swift resorption of the starch grains in the plastids of the meristematic cells of the shoot apex without any major disorganisation of the thylakoids. However starch grains are preserved in the dehydrated tissues of the adult leaves. The starch hydrolysis is continued with a marked increase of the sucrose concentration to this may be attributed an osmoregulatory role in the first stages of the water loss. Upon rehydration the plastid ultrastructure is entirely restored with new starch inclusions appearing in less than 4 h.     

Dérivés glucosés des acides hydroxycinnamiques de la tomate: Évolution au cours de la vie du fruit et formation in vitro

Glucose derivatives of hydroxycinnamic acids have been identified in tomato fruits either as esters or glucosides, the latter always being the most abundant and increasing during growth and at the time of ripening. These compounds can be synthesized in vitro by a fruit glucosyltransferase from free hydroxycinnamic acids and UDPG; glucosides are always formed in higher amounts than esters.