Formations lamellaires concentriques dans des cellules antéhypophysaires chez le hamster doré

Résumé Des formations lamellaires concentriques, issues du reticulum endoplasmique, sont décrites dans des cellules antéhypophysaires chez le Hamster doré. Ces formations sont en continuité avec le reticulum endoplasmique de la cellule. Elles sont plus fréquentes pendant l'hiver et semblent se modifier à la fin de l'hiver. Après une comparaison avec les données de la littérature, le rôle et l'origine des formations lamellaires concentriques sont discutés.

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Concentric lamellar formations in anterior pituitary cells of the golden hamster

Summary Concentric lamellar formations arising from and remaining in continuity with the endoplasmic reticulum have been observed in anterior pituitary cells of the golden hamster. They have more frequently been observed during the winter and appear to change at the end of winter. Their role and origin have been discussed.

Avec la collaboration technique de Monsieur M. Lheritier.     

Existence of "endorphin cells" in the adenohypophysis of the cat; comparison with "corticotropin cells." Immunocytochemical study]

Indirect immunofluorescence technique with anti-17-39ACTH and anti beta-endorphin sera has allowed us to detect "corticotropic cells" in the anterior and intermediate lobes of the adenohypophysis of the male cat. The corticotropic cells of the anterior lobe are localized in the median zone; they are PAS-positive and appeared intensively coloured in dark blue with the Herlant's tetrachrome. All the cells of the intermediate lobe react with the anti-17-39ACTH serum. Using an anti-beta-endorphin serum, we have observed that all the corticotropic cells of the anterior lobe react; but in the intermediate lobe, only a part of "corticotropic cells" react with the anti-beta-endorphin serum.     

Immunohistochemical localization of FSH and LH in the pars distalis of vervet (Cercopithecus aethiops) and babbon (Papio hamadryas) pituitaries

Summary Antisera against oLH¹, oLH and hFSH were used to localize gonadotropic cells in the pars distalis of Cercopithecus aethiops and Papio hamadryas. Three separate cell types were observed for FSH and LH: 85% of immunohistochemically identified gonadotropic cells reacted to all the various antisera; 10% reacted with the anti-LH antibody only; and 5% with the anti-hFSH antibody only. Comparisons between adjacent serial sections treated with various antisera, other than anti-gonadotropic hormones, demonstrated that the gonadotropic cells of these monkeys did not respond to these antisera.

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Résumé Des anticorps anti-LH ovine, anti-LH ovine et anti-FSH humaine ont été utilisés pour localiser les cellules gonadotropes dans la pars distalis de l'hypophyse des Singes Cercopithecus aethiops et Papio hamadryas. Trois catégories cellulaires distinctes, réagissant avec des anticorps anti-hormones gonadotropes, ont été observées. 85% des cellules immunoréactives identifiées en tant que cellules gonadotropes réagissent simultanément avec les différents anticorps mentionnés; 10% des cellules gonadotropes réagissent seulement avec l'anticorps anti-oLH et 5% de ces cellules seulement avec l'anticorps anti-hFSH. La comparaison avec des coupes adjacentes traitées par divers anticorps autres que les anticorps anti-gonadotropines prouve que les cellules gonadotropes de ces Singes ne réagissent jamais simultanément avec l'un ou l'autre de ces anticorps.

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Abbreviations used in this Article oLH ovine luteinizing hormone - hFSH human follicle stimulating hormone - ACTH corticotropin - GH growth hormone - LPH lipotropin - TSH thyrotropin     

Immunocytochemical evidence for the presence of somatostatin-like immunoreactivity in scattered cells of the duct system of the submandibular glands in the monkey, Macaca irus

Using the indirect immunofluorescent technique with anti-somatostatin serum, the distribution of scattered cells in the duct system of submandibular glands in the Monkey, Macaca irus has been assessed. In both males and females, these cells are located only in some portions of the duct system, e.g. striated ducts and excretory ducts. No immunoreactive cells were observed in the intercalated ducts or in secretory endpieces. The lymphatic node constantly adjacent to the submandibular gland did not contain immunoreactive cells. In the parotid glands, no immunoreactive cells to antisomatostatin immuneserum were ever observed.     

Immunohistochemical study of the pars tuberalis of the adenohypophysis in the monkey,Macaca irus

Summary The pars tuberalis of the hypophysis in the monkey Macaca irus encompasses the hypophysial stem up to the median eminence. Histologically, it consists of several layers of chromophobic cells. A few PAS¹-positive cells also stainable with Alcian blue (pH 3.0) can be observed among the unstained elements. Using the indirect immunofluorescence antibody technique, scattered immunoreactive cells were revealed with the anti-oLH antibody; these cells did not react with the anti-hFSH antibody. In contrast, the immunoreactions to anti-hGH, anti-hPRL, anti-ACTH, anti-MSH, anti-LPH and anti-endorphin sera were completely negative. Single cells reacting with the anti-hTSH serum were observed at the inferior end of the hypophysial stalk (zona tuberalis), i.e., beyond the pars tuberalis proper. These results are compared with data reported in the literature.

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Résumé La pars tuberalis de l'hypophyse du Singe Macacus irus entoure la tige infundibulaire jusqu'à l'éminence médiane. En techniques histologiques, elle apparaît constituée de plusieurs assises cellulaires d'aspect chromophobe. On y observe quelques cellules PAS-positives réagissant simultanément avec le bleu Alcian (pH3.0). En technique d'immunofluorescence indirecte, des cellules dispersées sont mises en évidence uniquement avec un anticorps anti-oLH; ces cellules ne réagissent pas avec un anticorps anti-hFSH. L'utilisation d'anticorps anti-hGH, anti-hPRL, anti-ACTH, anti-MSH, anti-LPH et antiendorphines ne permet pas de révéler des cellules immunoréactives. Quelques cellules réagissant avec un anticorps anti-hTSH s'observent à la base de la tige hypophysaire (zona tuberalis), c'est-à-dire au-delà de la pars tuberalis proprement dite. Ces résultats sont confrontés à ceux rapportés dans la littérature.

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Abbreviations used in this Article PAS periodic acid Schiff - oLH ovine luteinizing hormone - hFSH human follicle stimulating hormone - hGH human growth hormone - hPRL human prolactin - ACTH corticotropin - MSH melanotropin - LPH lipotropin - hTSH human thyrotropin - BSA and HSA bovine and human serum albumin     

Rab6 coordinates a novel Golgi to ER retrograde transport pathway in live cells

We visualized a fluorescent-protein (FP) fusion to Rab6, a Golgi-associated GTPase, in conjunction with fluorescent secretory pathway markers. FP-Rab6 defined highly dynamic transport carriers (TCs) translocating from the Golgi to the cell periphery. FP-Rab6 TCs specifically accumulated a retrograde cargo, the wild-type Shiga toxin B-fragment (STB), during STB transport from the Golgi to the endoplasmic reticulum (ER). FP-Rab6 TCs associated intimately with the ER, and STB entered the ER via specialized peripheral regions that accumulated FP-Rab6. Microinjection of antibodies that block coatomer protein I (COPI) function inhibited trafficking of a KDEL-receptor FP-fusion, but not FP-Rab6. Additionally, markers of COPI-dependent recycling were excluded from FP-Rab6/STB TCs. Overexpression of Rab6:GDP (T27N mutant) using T7 vaccinia inhibited toxicity of Shiga holotoxin, but did not alter STB transport to the Golgi or Golgi morphology. Taken together, our results indicate Rab6 regulates a novel Golgi to ER transport pathway.     

Structure and functional analyses of the 26S proteasome subunits from plants – Plant 26S proteasome

As initial steps to define how the 26S proteasome degrades ubiquitinated proteins in plants, we have characterized many of the subunits that comprise the proteolytic complex from Arabidopsis thaliana. A set of 23 Arabidopsis genes encoding the full complement of core particle (CP) subunits and a collection encoding 12 out of 18 known eukaryotic regulatory particle (RP) subunits, including six AAA-ATPase subunits, were identified. Several of these 26S proteasome genes could complement yeast strains missing the corresponding orthologs. Using this ability of plant subunits to functionally replace yeast counterparts, a parallel structure/function analysis was performed with the RP subunit RPN10/MCB1, a putative receptor for ubiquitin conjugates. RPN10 is not essential for yeast viability but is required for amino acid analog tolerance and degradation of proteins via the ubiquitin-fusion degradation pathway, a subpathway within the ubiquitin system. Surprisingly, we found that the C-terminal motif required for conjugate recognition by RPN10 is not essential for in vivo functions. Instead, a domain near the N-terminus is required. We have begun to exploit the moss Physcomitrella patens as a model to characterize the plant 26S proteasome using reverse genetics. By homologous recombination, we have successfully disrupted the RPN10 gene. Unlike yeast rpn10 strains which grow normally, Physcomitrella rpn10 strains are developmentally arrested, being unable to initiate gametophorogenesis. Further analysis of these mutants revealed that RPN10 is likely required for a developmental program triggered by plant hormones.     

Semi-automatic quantitation of dense markers in cytochemistry

Summary The quantitation of electron dense labelling is very tedious when it is done by hand. Accordingly we developed software allowing, at electron microscopic level, a semi-automatic counting of dense markers in biological specimens. It includes the digitization of images and extraction of dense particles from the grey level of the background. The definition of the areas of interest was carried out by the observer but all quantitative calculations were done automatically. This method was applied to different biological materials (phospholipid and lysozyme labelling in secretory granules of human submucosal bronchial gland cells). The results obtained by this semi-automatic procedure were in good agreement with those obtained by manual counting of colloïdal gold labelling (r=0.97).     

Spectral imaging and linear un-mixing enables improved FRET efficiency with a novel GFP2-YFP FRET pair

Spectral variants of the green fluorescent protein (GFP) have been extensively used as reporters to image molecular interactions in living cells by fluorescence resonance energy transfer (FRET). However, those GFP variants which are the most efficient donor acceptor pairs for FRET measurements show a high degree of spectral overlap which has hampered in the past their use in FRET applications. Here we use spectral imaging and subsequent un-mixing to quantitatively separate highly overlapping donor and acceptor emissions in FRET measurements. We demonstrate the method in fixed and living cells using a novel GFP based FRET pair (GFP2-YFP (yellow)), which has an increased FRET efficiency compared to the most commonly used FRET pair consisting of cyan fluorescent protein and YFP. Moreover, GFP2 has its excitation maximum at 396 nm at which the YFP acceptor is excited only below the detection level and thus this FRET pair is ideal for applications involving sensitized emission.