New ultrastructural features on the cream hamster thyroid with special reference to the second kind of follicle

The thyroid cells of the cream hamster, characterized by abundance of microtubules and stratification of the organelles, undergo a particular evolution when the animals grow older. These changes are characterized by an increase of the number of lysosomes which in extreme cases become so prominent that they occupy the whole cytoplasm of the cell which thus loses its organelle stratification. As in other species, cream hamster thyroid contains so-called ultimobranchial follicles made up of at least six cell types: fibrillar dark and light cells, parafollicular cells, ciliated cells, vesicular cells, and cells with myelinic inclusions. The ultrastructure of these follicles in the cream hamster represents a mixture of the ultrastructural characteristics of the same follicles encountered in the rat and the mouse thyroid. Here also mixed follicles are seen. Nevertheless vesicular cells present such abundant "secretion granules" that the question arises as to whether these follicles produce a special secretion and perhaps a new hormone. Incubation of cream hamster thyroids in the prescence of vincristine induces vanishing of microtubules, formation of paracrystalline structures, and loss of stratification of the organelles. Although these last effects might be due to some specific toxic effect of the drug, it is suggested that the disappearing of the organelle stratification might result from a specific vincristine-induced disaggregation of the microtubules acting as a cytoskeleton.     

Primordial follicle activation is affected by the absence of Sohlh1 in mice

Previous studies have reported that only primordial follicles and empty follicles can be found in 7.5 days postparturition (dpp) Sohlh1^?/? mouse ovaries and females are infertility. There appears to be a defect in follicle development during the primordial‐to‐primary follicle transition in Sohlh1^?/? mouse ovaries. However, detailed analyses of these phenomena have not been performed. In this study, we used Sohlh1^?/? transgenic mice to explore the role of Sohlh1 in folliculogenesis. The results showed that only primordial follicles and empty follicles can be observed in Sohlh1^?/? ovaries from 0.5 to 23.5 dpp. The expression of Foxo3 and FOXO3 was downregulated; nucleocytoplasmic shuttling of FOXO3 was normal in 7.5‐dpp Sohlh1^+/+ but not Sohlh1^?/? ovaries; and primordial follicle activation (PFA) was not observed in 7.5‐dpp Sohlh1^?/? mice. The expression levels of KIT, AKT, and P308‐AKT were downregulated (p < 0.05), whereas that of P473‐AKT was not significantly changed (p > 0.05). The KIT/PI3K/AKT pathway was inhibited. Furthermore, we conducted a dual luciferase assay and chromatin immunoprecipitation. The results showed that SOHLH1 can upregulate the Kit gene by binding to the ?3698 bp E‐box motif. The absence of Sohlh1 may affect PFA in mouse ovaries via downregulation of Kit and inhibition of the KIT/PI3K/AKT pathway.     

Influence of collagen gel on the orientation of epithelial cell polarity: follicle formation from isolated thyroid cells and from preformed monolayers

The influence of collagen gels on the orientation of the polarity of epithelial thyroid cells in culture was studied under four different conditions. (a) Isolated cells cultured on the surface of a collagen gel formed a monolayer. The apical pole was in contact with the culture medium and the basal membrane was attached to the substratum. (b) Isolated cells embedded inside the gel organized within 8 into follicles. The basal pole was in contact with collagen and the apical pole was oriented towards the interior of the follicular lumen. (c) Cells were first organized into floating vesicles, structures in which the apical surface is in contact with the culture medium, and the vesicles were embedded inside the collagen gel. After 3 d, cell polarity was inverted, the apical pole being oriented towards the cavity encompassed by cells. Vesicles had been transformed into follicles. (d) Monolayers formed on collagen gels as in a were overlaid with a second layer of collagen, which was polymerized in contact with the apical cell surface. A disorganization of the continuous pavement occurred within 24 h; cells attached to the upper layer of collagen and reorganized into follicles in the collagen sandwich within 4-8 d. A similar process occurred when the monolayer was grown on plastic and overlaid with collagen, or grown on collagen and covered with small pieces of glass cover slips. No reorganization was observed between two glass surfaces. In conclusion, first, a basal pole was always formed in the area of contact between the cell membrane and an adhesive surface and, second, the interaction of a preformed apical pole with an adhesive surface was not compatible with the stability of this domain of the plasma membrane. The interaction of the cell membrane with extracellular components having adhesive properties appears to be a determinant factor in the orientation and stabilization of epithelial cell polarity.     

Notes on Diplonaevia (Discomycetes inoperculati), with special regard to the species on Juncaceae

The only monocotyledonous families that take members of Diplonaevia Sacc. (= Merostictis Clem.) are found to be Juncaceae, Cyperaceae (Caricoideae–Caricieae and Trichophorum ) and Poaceae (especially Nardus ). The presence or absence of stromatic, clypeus–like tissues is studied in several species and found to be very variable not only from species to species but also within individual species. The patterns of variation exhibited by the excipulum, the asci and the spores are also discussed. No less than ten species are known to grow on Juncaceae, eight on Juncus and two on Luzula. D. helicospora (on J. trifidus), D. hyperborea (on Juncus subgen. Alpini ) and D. savilei (on L. arctica ) are new species. New combinations are D. antaretica (Dennis) Nannf., D. junciseda (Schroet.) Nannf. and D. microsticla (Dennis) Nannf. Host ranges and distributions are also studied and discussed.     

Light microscopic studies on the pineal organ in teleost fishes with special regard to its function

The antennal flagellum of the male sorghum midge is about a millimeter long and may bear over 500 sense organs. These consist of (1) tactile hairs, (2) thin-walled pegs, (3) circumfila and (4) very small pegs of unknown function. Each of the 12 subsegments of the flagellum is divided into two globular nodes and each of these is encircled by a circumfilum of from 6 to 14 loops. The circumfila are attached to the antennal surface by short stalks. The loops of the circumfila have the basic structure of thin-walled chemoreceptors: (1) very small pores in their delicate wall and (2) a lumen filled with branches of dendrites from sensory neurons. The outer surface of the circumfilum is covered with a labyrinth of fine ridges between which the pores are located. Some evidence was obtained that the circumfila are produced in the pupa by bifurcate trichogen cells. The flagellum of the female is shorter than that of the male and composed of 12 cylindrical subsegments. The circumfila of the female lie close to the surface to which they are attached by short stalks. Each is composed of two parts that encircle the subsegment and of two others that run lengthwise between the circles. The surface is nearly smooth, perforated by fine openings and lacks the complex pattern of ridges seen in the male. It also has more dendrite branches but, otherwise, has the same basic structure.     

Esterase activity in the guinea pig thyroid under normal and pathological conditions (vitamin A deficiency) with special regard to cyst-like structures.

By use of different activators and inhibitors, TOCP(tri-o-cresyl phosphate), PCMB (parachloromercury benzoate), NiCl2, Pb(NO3)2, HgCl2, Hg(NO3)2, eserine and sodium taurocholate, it is shown that the esterase in the cyst cells and in group I cells of the guinea pig thyroid probably are A-esterase isoenzymes. The activity in the majority of cyst cells is considerably stronger than in the other thyroid epithelial cells, and it is resistant to Hg inactivation. Neither esterase type nor intensity of the reaction product is altered in group I-II or cyst cells during vitamin A-deficiency. When a normal diet is given, the esterase in all thyroid epithelial cells is very sensitive to sodium taurocholate, while in cyst cells it is rather resistant to this inhibitor at vitamin-A-deficiency.     

Age-dependent alterations in the assembly of signal transduction complexes at the site of T cell/APC interaction

TCR interaction with peptide-MHC complexes triggers migration of protein kinases, actin-binding proteins, and other accessory molecules to the T cell/APC synapse. We used confocal immunofluorescence methods to show that the adapter protein LAT (linker for activation of T cells) and the guanine nucleotide exchange factor Vav also move to the APC interface in mouse CD4 T cells conjugated to anti-CD3 hybridoma cells, and in TCR-transgenic CD4 cells conjugated to APC bearing agonist (but not closely related nonagonist) peptides. The proportion of CD4+ T cells able to relocalize LAT or Vav, or to relocate cytoplasmic NT-AT (NF-ATc) from cytoplasm to nucleus, declines about 2-fold in aged mice. The decline in LAT relocalization is accompanied by a similar decline in tyrosine phosphorylation of LAT in CD4 cells stimulated by CD3/CD4 cross-linking. Two-color experiments show that LAT redistribution is strongly associated with relocalization of both NF-ATc and protein kinase C-theta among individual cells. LAT migration to the immunological synapse depends on actin polymerization as well as on activity of Src family kinases, but aging leads to only a small change in the percentage of CD4 cells that redistribute F-actin to the site of APC contact. These results suggest that defects in the ability of T cells from aged donors to move kinase substrates and coupling factors, including LAT and Vav, into the T cell/APC contact region may contribute to the decline with age in NF-ATc-dependent gene expression, and thus to defects in T cell clonal expansion.