bluuebunny/crossref_metadata_2025 huggingface dataset:
Changing clothes easily: connexin41.8 regulates skin pattern variation
Authors: Watanabe Masakatsu , Kondo Shigeru
Published: February 2012

The skin patterns of animals are very important for their survival, yet the mechanisms involved in skin pattern formation remain unresolved. Turing’s reaction–diffusion model presents a well‐known mathematical explanation of how animal skin patterns are formed, and this model can predict various animal patterns that are observed in nature. In this study, we used transgenic zebrafish to generate various artificial skin patterns including a narrow stripe with a wide interstripe, a narrow stripe with a narrow interstripe, a labyrinth, and a ‘leopard’ pattern (or donut‐like ring pattern). In this process, connexin41.8 (or its mutant form) was ectopically expressed using the mitfa promoter. Specifically, the leopard pattern was generated as predicted by Turing’s model. Our results demonstrate that the pigment cells in animal skin have the potential and plasticity to establish various patterns and that the reaction–diffusion principle can predict skin patterns of animals.
Isolation from Friend erythroleukemia cells of an RNase‐sensitive nuclear matrix fibril fraction containing hnRNA and snRNA
Authors: Long B. H. , Schrier W. H.
Published: February 2012

Chromatin‐depleted nuclei (CDN) were prepared from Friend erythroleukemia cell nuclei by partial digestion with DNase I and extraction of the chromatin by 2 mM EDTA as described in the preceding paper (Long and Ochs, 1983. Biol. Cell 48, 99‐108). These structures contained dense networks of matrix fibrils surrounded by distinct laminae but no morphologically distinct residual nucleoli. CDN disrupted by gentle shearing or 1 microgram/ml RNase were fractionated into laminae and matrix fibrils by differential centrifugation. Protein composition of the lamina fraction was dominated by two prominent lamina proteins that were not detectable in the matrix fraction. Mild RNase treatment led to a conversion of the fibrous network to a particulate morphology while mild shearing resulted in an apparently unaltered fibril fraction. The matrix fibril fractions contained hnRNP proteins and the snRNAs. These results suggest that EDTA‐prepared CDN may provide a system for studying snRNP‐hnRNP interactions and hnRNP processing that is less complex than intact nuclei.
Nuclear bodies in mouse splenic lymphocytes: II ‐ Cytochemistry and autoradiography during stimulation by concanavalin A
Authors: Chaly N. , Setterfield G. , Kaplan J. G. , Brown D. L.
Published: February 2012

Nuclear bodies (NB) are poorly understood nucleoplasmic structures frequently observed in many animal cell types. Murine lymphocytes mitogenically stimulated with concanavalin A contain 5 types of NB. In order to examine the origin and function of the NB we have carried out cell fractionation and have performed cytochemistry, immunocytochemistry and autoradiography at the electron microscope level. Regressive staining for RNP showed that simple NB (types I and II) and the shells of complex NB (types III, IVa and V) consist of a non‐chromatinic fibrillar material which is most likely proteinaceous. Projections of this material from the NB surface appear to link the NB to nucleoplasmic fibrogranular elements. The fibrillar, filamentous and granular components of the cores of complex NB were largely RNP and in some instances closely resembled fibrogranular areas in the nucleoplasm. Chromatin masses were seen occasionally in the cores. All NB types remained unstained after nucleolus‐specific silver nitrate staining, and were also not stained by a centromere‐specific antibody. Autoradiography was performed along long‐term labelling with 3H‐uridine, 3H‐thymidine or 3H‐leucine. The NB were not labelled by any of the precursors, indicating that macromolecular synthesis does not play a major role in NB evolution in these cells. By fractionation, we showed that NB co‐isolated with the nuclear matrix, and were linked to the fibrogranular nuclear matrix component by projections from the surface of the NB. A possible role of NB in RNA processing is discussed.
The cytoskeletal lattice of the neurohypophysial cells
Authors: Kondo H. , Pappas G. D. , Wolosewick J. J.
Published: February 2012

The cytoskeleton of rat neurohypophysial cells as seen in resinless sections is an irregular three‐dimensional lattice of short strands of cytoplasmic matrix (the microtrabeculae) that interconnect parallel arrays of neurotubules, neurofilaments, abundant neurosecretory granules, and other membrane‐bound organelles including the plasma membrane. This morphological finding suggests that the cytoplasmic ground substance constitutes a cytoskeletal continuum that may be the ultrastructural expression of a motile apparatus responsible for neurosecretory granule movement and hormone release in the neurohypophysis.
Human and bovine vascular endothelial cells. Comparative effect on cell growth and longevity of an eye‐derived growth factor (EDGF) and of extracellular matrix
Authors: Romquin N. , Plouet J. , Barritault D. , Courtois Y.
Published: February 2012

Human and bovine vascular endothelial cells from the umbilical vein and the aorta, respectively, were cultured in the presence of EDGF (a growth factor prepared from bovine retina) on plastic or on extracellular matrix (ECM). Both EDGF and ECM are required to allow the maximal proliferation of human cells and their organization in a typical monolayer. Conversely, bovine aortic endothelial cells grow perfectly in the absence of both factors in 6% fetal calf serum. However, a requirement for EDGF can also be demonstrated in low serum conditions, or in cells at high passage number. ECM had no growth promoting activity by itself. Thrombin acts similarly to EDGF on bovine serum‐starved cells. EDGF prolongs the in vitro lifespan of both types of cells. Cells at all stages still synthesize factor VIII antigen as revealed by immunofluorescence. Thus EDGF, like other growth factors from brain, FGF or ECGF, may have an important role in angiogenesis, a critical problem in pathological retinas.
Lutropin is processed much more rapidly than human choriogonadotropin by porcine Leydig cells in primary culture
Authors: Salesse R. , Genty N. , Garnier J.
Published: February 2012

Lutropin (LH) and human choriogonadotropin (hCG) share the same receptor and stimulate testosterone production in porcine Leydig cells in primary culture. Cells were pulsed with [125I]LH or [125I]hCG. During the chase, more than 80% of cell‐bound LH consisted in internalized material which was degraded and excreted (half‐time: 25 min) NH4Cl largely inhibited this degradation. On the contrary, hCG remained essentially bound to the cell surface and was not degraded by the cells with or without NH4Cl up to 160 min.
Effects of diazepam on mitosis and basal body duplication of synchronously dividing flagellate cells
Authors: Marano F. , Santa‐Maria A. , Fries W.
Published: February 2012

We report here that diazepam (Valium, Roche) has an inhibitory effect on proliferation of synchronously dividing cultures of Dunaliella, whenever the drug is added during the cell cycle. The drug induced an accumulation of abnormal mitotic figures after 17 to 24 hr of treatment with the chromosomes distributed around the nuclei and a monopolar spindle, although the pole‐to‐chromosome microtubules were well‐formed. Diazepam seemed to affect mitosis by inhibiting the separation of the basal bodies, whose duplication was perturbed in a dose‐related manner. After 48 hr of treatment, the nucleus returned to interphase without having undergone mitosis, but cytokinesis might have taken place. The mechanism of this action of diazepam on mitosis remains to be elucidated. However, it does not appear to act in the same way here as it does on the central nervous system.
The effect of tunicamycin on Leishmania braziliensis cell growth, cell morphology and ultrastructure
Authors: Dagger F. , Ayesta C. , Hernandez A. G.
Published: February 2012

The effect of tunicamycin (TM) on Leishmania braziliensis promastigotes in culture has been studied. TM at different concentrations (2, 4, 6 micrograms/ml) inhibits promastigote growth as the mean generation time of control cells, 36 hr, is changed to 41, 46 and 55 hr, respectively. Cells remain viable after long exposure to 2 micrograms/ml of TM and can be cultured in the presence of the drug for several generations. Under these conditions cells tend to round up and many “ruffle”‐like structures appear at the parasite cell surface. At the ultrastructural level, cell coat disappears and the rough endoplasmic reticulum appears distended. Other structures remain unaltered by the drug treatment. The changes in cell morphology are discussed in relation to changes in cell surface morphology. The possible use of these TM‐transformed cells as experimental systems for host‐parasite studies is also considered.
The relationships between ribosomal genes and fibrillar centers in thyroid cells cultivated in vitro
Authors: Vagner‐Capodano A. M. , Henderson A. S. , Lissitzky S. , Stahl A.
Published: February 2012

Despite the fact that the fibrillar centers of the nucleolus and the chromosomal nucleolar organisers (NORs) are similarly stained with the NOR‐silver technique, there remain some questions about the identification of fibrillar centers as NORs. The distinct delineation of the fibrillar centers in porcine thyroid cells allowed us to determine whether there was a numerical equivalence or correlation between fibrillar centers and NORs. Hybridization in situ and silver staining performed on pig chromosomes showed that pairs 8 and 10 contained rDNA sites. Silver staining of thyroid cells in electron microscopy showed that the fibrillar centers and their surrounding layer of dense fibrils were the sites of silver deposit. Chromatin fibers were demonstrated within the fibrillar centers through the aid of the osmiumammine reaction and with the oxidized diaminobenzidine technique. It was observed that in cultured thyroid cells the fibrillar centers could be identified in the light microscope as argyrophilic spherules, and easily counted. The number of fibrillar centers was variable according to culture conditions. In cells cultured for 5 hr, the mean number of fibrillar centers was 1.7. After 5 days of culture, the number of fibrillar centers increased, reaching a mean value of 5.93. When thyroid cells were stimulated with thyrotropin, the number of fibrillar centers again increased to a mean value of 7.54. These results demonstrate that the relationship between fibrillar centers and NORs is not a simple proportionality: the number of fibrillar centers increases with increased cellular activity. These data imply that in active cells each NOR may pass through several fibrillar centers.
Ultrastructure and enzyme digestion of nucleoli and associated structures in hypothalamic nerve cells viewed in resinless sections
Authors: Chung S. K. , Cohen R. S. , Pfaff D. W.
Published: February 2012

Estrogen has been shown to affect ventromedial hypothalamic (VMH) nerve cell nucleoli in ovariectomized rats, by causing an increase in the number of electron‐dense aggregates associated with nucleoli. In order to characterize these nucleolus‐associated structures and other nuclear components, we examined the ultrastructure of ventromedial hypothalamic nucleoli and nuclei revealed by enzyme digestions (pepsin, RNase and DNase) in resinless thin sections. Digestion by pepsin did not cause obvious alterations in the morphology of the nucleolus or its related structures. Pepsin treatment followed by RNase, however, reduced the density of the nucleolus, while that of the nucleolus‐associated structure and other related structures remained unchanged. Conversely pepsin treatment followed by DNase, reduced the density of nucleolus‐associated and other chromatin structures, but had no effect on the density of the nucleolus. Pepsin treatment followed by RNase and then DNase treatment, reduced the density of the nucleolus and nucleolus‐associated structures. A residual nucleolus and nucleolus‐associated structure remained after this treatment. Stereo viewing of resinless sections shows that the nucleolus, its associated structures, and other related structures, are associated with fine filaments that may comprise the nuclear matrix. The nucleolus‐associated structure containing DNA may direct RNA synthesis at an increased rate in estrogen‐treated hypothalamic cells.
Role of lysosomes in gallium concentration by mammalian tissues
Authors: Berry J. P. , Poupon M. F. , Galle S. , Escaig F.
Published: February 2012

Two microanalytical methods, electron probe X ray analysis (E P M A) and ion mass analysis (I A M) were used to study gallium incorporation in normal tissues (kidney, liver, mammary gland, bone marrow, bone tissue) and in experimental tumors. The very high sensitivity of I M A makes possible the detection of very low concentration of gallium (1 ppm) with a spatial resolution of 0.5 micron, on the other hand, E P M A of lower sensitivity (100 ppm) makes possible the relation between the gallium concentration and the ultrastructure of the cell. It was shown that gallium is concentrated in the lysosomes of both types of tissues, where it is precipitated in an insoluble form. In addition, gallium is systematically combined with phosphorus in these precipitates. These observations suggest an active intralysosomal concentrating mechanism related to the presence of local phosphatase activity.
Colicins are not transiently accumulated in the periplasmic space before release from colicinogenic cells
Authors: Cavard D. , Bernadac A. , Pages J. M. , Lazdunski C.
Published: February 2012

Colicins are released into the spent medium from colicinogenic cells. The pathway of release has been investigated in this study. The localization in producing cells of colicins A, E3 and of cloacin DF13 has been determined at various times after mitomycin C addition: no transient accumulation in the periplasmic space of colicinogenic E. coli K12 strains was detected by electron microscopy for any of the bacteriocins tested. Furthermore, asynchronous induction in individual cells was detected for each bacteriocin tested. These results strongly suggest that colicins, as well as cloacin DF13, do not transit through the periplasmic space before release from colicinogenic cells.
Role of the thyroid in the involution of the mesonephric Malpighian corpuscles in the chick embryo
Authors: Vergnaud O. , Maraud R.
Published: February 2012

The mesonephros of the chick embryo normally begins to regress during the second half of embryonic life. Experimental methods, such as adenohypophysis grafting, hypophysectomy or use of antithyroid drugs, which stimulate or depress the thyroid function of the embryo, modified accordingly the regressive processes occurring in the mesonephric Malpighian corpuscles, particularly at the level of the glomerular basement laminae. These results as well as the known sensitivity of the mesonephros to thyroxine and the concordance between the steps of embryonic thyroid development and the mesonephric modifications show that the thyroid normally plays a major determining role in this phenomenon.
TSH stimulation of iodine organification in early foetal rat thyroid in vitro
Authors: Pic P. , Michel‐Bechet M. , Bottini J.
Published: February 2012

Thyroid glands from 15 day‐old rat foetuses were incubated in Eagle's medium containing Na 125I and supplemented, or not, with TSH for 4 or 24 hours. Electron microscopic radioautographic study shows silver grains mainly in follicular cavities only in the thyroids submitted to TSH during 24 hr. A functional differentiation must therefore take place in thyroid cells under TSH stimulation.
Colocalization of U1 and U2 small nuclear RNPs by immunocytochemistry
Authors: Spector D. L.
Published: February 2012

The in situ localization of U1 and U2 snRNPs was examined, using autoantibodies directed against each of these snRNPs, by immunofluorescence and immunoelectron microscopy. This study has shown U1 and U2 snRNPs to colocalize in the nuclei of PtK2 cells. Thirty to fifty immunostained clusters were observed per interphase nucleus. This study suggests these nuclear protein clusters to be the sites of RNA processing.
The mannose 6‐phosphate receptor: function, biosynthesis and translocation
Authors: Sahagian G. G.
Published: February 2012

This report summarizes studies concerning the role of the lysosomal protein: Man‐6‐P receptor and describes some recent data on its biosynthesis and cellular translocation. The receptor functions both in the Golgi apparatus (or GERL) and on the cell surface where it binds lysosomal proteins and mediates their transport to lysosomes. Consistent with its dual role, the receptor in several cell types has been localized to the plasma membrane and Golgi cisternae, to clathrin‐coated structures at both locations, and to vesicles characteristic of endosomes or CURL. Biosynthetic studies have shown that the receptor undergoes several post‐translational modifications including the processing of its asparagine‐linked oligosaccharides, phosphorylation of serine residues, and unknown modifications required for acquisition of immunoreactivity and functional activity. Cellular pools of mature receptor readily mix as evidenced by rapid labeling of intracellular receptor by exogenously added receptor antibodies. Degradation of the receptor occurs non‐lysosomally and is perhaps mediated by extracellular Man‐6‐P‐containing hydrolases. A working hypothesis for the mechanism of Man‐6‐P receptor function that is consistent with these observations is presented.
Mannose‐specific oligosaccharide recognition by mononuclear phagocytes
Authors: Stahl P. D. , Wileman T. E. , Diment S. , Shepherd V. L.
Published: February 2012

Glycoproteins terminating in mannose are recognized by receptors on macrophages. The mannose receptor is expressed by a variety of macrophages but expression is closely regulated. Activated macrophages, for example, express little mannose receptor activity. Kinetic and fractionation experiments suggest that cell surface mannose receptors recycle to and from an acidic, pre‐lysosomal compartment. Preliminary evidence suggests that the mannose receptor is a large polypeptide and that it is structurally related to the mannose binding protein found in serum. The mannose receptor may, among other possibilities, regulate the extracellular levels of lysosomal hydrolases.
Immunolabelling of bacteriophage lambda receptor protein (LamB) on thin sections of E. coli embedded in Lowicryl
Authors: Whitehouse R. L. , Benichou J. C. , Couture‐Tosi E. , Schenkman S. , Ryter A.
Published: February 2012

LamB is one of the major cellular proteins when E. coli is grown in the presence of maltose and is localized in the outer membrane. Previous immunolabellings obtained with monoclonal antibodies showed that this protein is a transmembrane protein and led to the detection of 4 epitopes exposed on the cell surface and 2 located on the inner surface of the outer membrane (Scheckman et al., 1983). In the present study, we have used this biological model in order to see whether these two classes of epitopes could be distinguished by immunocytochemical labelling performed on thin sections of E. coli embedded in Lowicryl K4M (Carleman et al., 1982). The optimal conditions of fixation and embedding were first established for labelling with poly‐ or monoclonal antibodies detected by Protein A‐gold complexes. The analysis of gold particle distribution on each side of the outer membrane after labelling with a polyclonal serum or after its adsorption on intact bacteria allowed us to conclude that the resolution of immunolabelling on thin sections was about 20 nm. The use monoclonal antibodies met with difficulties due mostly to the nonspecific labelling of the cytoplasm. Although this nonospecific labelling was decreased by fixing bacteria with paraformaldehyde alone, only one antibody gave a correct specific labelling after high dilution (1/3000). The gold particle distribution obtained with this antibody confirmed the location on the cell surface of this epitope.
Monoclonal antibodies binding to nuclear structures and axons in adult avian dorsal root ganglia
Authors: Masurovsky E. B. , Fields K. L.
Published: February 2012

Four monoclonal antibodies raised against embryonic chick dorsal root ganglia (5) recognize epitopes in neuronal and supporting cell nuclei, and in axons and contiguous cytoplasmic elements in some neurons of the adult chicken. Binding, analyzed at the ultrastructural level, is to reaction sites on the nuclear matrix, nucleolar complex, nuclear bodies, and filamentous elements in axons and some perikaryal regions.
Anchorage of the nucleolus in the pore complex‐lamina by a DNA‐bearing structure masked in situ in rat liver nuclei
Authors: Hubert J. , Bureau J. , Bouteille M.
Published: February 2012

We have developed a method by which nuclear shells containing nucleoli can be isolated from membrane‐depleted rat liver nuclei. This method involves the removal of the internal chromatin. This chromatin is expelled from the nuclear shell using combinations of low and high ionic strength buffers. The expelled internal part is subsequently digested with DNase I or micrococcal nuclease. Examination by electron microscopy of the nuclear and the nucleolar structures at various steps of the isolation procedure shows that the nucleoli are anchored in the peripheral lamina by a pedicle that is continuous with an intranucleolar network. This network is masked in situ by nucleolar granules. The pedicle and the network which support the nucleolar DNA are composed mainly of non‐histone proteins insoluble in 2M NaCl.
Pituitary adenomas: patterns of hPRL and hGH secretion as revealed by high resolution immunocytochemistry
Authors: Bendayan M. , Maestracci N. D.
Published: February 2012

Seven human pituitary adenomas obtained by transphenoidal surgery were investigated for the intracellular localization of PRL and GH, using the protein A‐gold immunocytochemical technique. Among the seven cases two were prolactinomas, two were GH‐secreting adenomas and three were mixed PRL and GH‐secreting adenomas. When PRL or GH were revealed, immunoreactivity was found in the cellular compartments involved in protein secretion, RER, Golgi apparatus and secretory granules of corresponding secreting cells. An increasing gradient in the intensity of labeling was observed from the RER to the Golgi and to the granules which may correspond to the increasing concentration of the proteins occurring along their secretory pathway. In addition, crinophagy or destruction of secretory granules by the lysosomal system was observed for both secretory cells. Cells displaying simultaneously PRL and GH reactivity were never found, neither in pure nor in mixed adenomas demonstrating that in the different adenomas studied, secreting cells have retained their specificity and differentiation for the secretion of a single hormone.
Relationships between cytoplasmic microtubular complex, DNA synthesis and cell morphology in mouse embryonic fibroblasts (effects of age, serum deprivation, aphidicolin, cytochalasin B and colchicine)
Authors: Van Gansen P. , Siebertz B. , Capone B. , Malherbe L.
Published: February 2012

Aging, aphidicolin, serum deprivation and cytochalasin B induce a decrease in the rate of DNA synthesis, an increase in cell flattening (cell surface increase) and an extension of the cytoplasmic microtubular complex (CMTC). Age and experimental conditions affect the protein content of the cell, but there is no relationship between cell morphology and cell protein content. Serum deprivation, aphidicolin and cytochalasin B are more effective on DNA synthesis and cytoplasmic actin complex (CAC) of late than of early fibroblasts. Despite these facts, the cell morphology of late cells is fairly stable and is not affected by experimental conditions, which exert an “aging effect” upon the cell morphology in earlier cultures. Colchicine acts upon the CMTC, cell morphology and DNA synthesis at all ages of the cultures. It also induces disruption of the CAC, the intensity of the disruption depending on both the length of the treatment and the age of the culture: the sensitivity of the actin‐microfilaments to colchicine increases with the mitotic age of the cells. We suggest that the microtubular integrity is needed, but not sufficient, to preserve the organization of the CAC into microfilaments. We propose a logical model comprising feedback loops between the number of the mitotic cycles, the rate of DNA synthesis, the extention rate of the plasma membranes and CMTC in normal fibroblasts. CMTC is associated, in this model, with the expression of negative or positive controls, depending on the grade of its extension (Fig. 9).
Slanted centriole and transient anchoring apparatus during spermiogenesis of an Oligochaete (Annelida)
Authors: Ferraguti M.
Published: February 2012

An electron microscopic analysis of Tubifex tubifex (Annelida, Oligochaeta) spermiogenesis has revealed the presence of a slanted basal body during the early stages: the centriole has the shape of a cylinder obliquely cut at one extremity. In these stages an anchoring apparatus is also present, similar to the one of primitive spermatozoa, and disappearing in the mature sperm. The slanted centriole in cross section gives images of “incomplete” centrioles similar to the ones reported in the literature and interpreted as images of centriologenesis. The transient anchoring apparatus is interpreted as a rudimentary organelle used during spermiogenesis to maintain the centriole in a correct position. This function in the mature spermatozoon is performed by the mitochondria.
Effect of the cytotoxin of Clostridium difficile on cultured hepatoma cells
Authors: Rihn B. , Beck G. , Monteil H. , Lecerf F. , Girardot R.
Published: February 2012

Clostridium difficile is the major etiologic agent of human pseudomembranous colitis. It produces two toxins: an enterotoxin and a cytotoxin. In cultured hepatoma cells, at very low doses, the cytotoxin inhibits the incorporation of precursors into biological macromolecules. Protein synthesis is more affected than RNA and DNA synthesis. The toxin also induces severe alterations of the cell morphology consisting in damages to the cytoskeleton and to the cell shape.
Immunolocalization of the 100 K nucleolar protein in CHO cells
Authors: Escande M. L. , Gas N. , Stevens B. J.
Published: February 2012

The localization of a major nucleolar protein with a molecular weight of 100,000 has been followed in Chinese hamster ovary cells using specific antibodies to this protein and immunocytochemical techniques. By immunofluorescence and immunocytochemistry at ultrastructural level in situ, the 100 K protein was detected abundantly in the nucleolus of interphase cells. In exponentially growing cells, the dense fibrillar component was shown to contain more 100 K protein than the granular RNP component but both the nucleolar components were positively immunostained. Fibrillar centers consistently showed weaker or no staining. The 100 K association with the preribosomal RNP components of the interphase nucleolus supports evidence for a role of this protein in pre‐rRNA transcription and preribosomal processing.
Cellular compartments in mitotic cells: ultrahistochemical identification of Golgi elements in PtK‐1 cells
Authors: Schroeter D. , Ehemann V. , Paweletz N.
Published: February 2012

This investigation focuses on the identification, distribution, and transport of intracellular membrane systems during mitosis. The membranes of the Golgi apparatus can be identified cytochemically by staining for acid phosphatase (acPase) and thiamine pyrophosphatase (TPPase) activity. Using this approach we are able to study the disintegration of the Golgi apparatus during mitosis and to follow the dislocation as well as the organized reappearance of Golgi elements after the completion of mitosis. We are able to demonstrate that during mitosis the activity of both enzymes is strong enough to react with the substrate applied during the staining procedure. Furthermore, we observe a characteristic pattern of membrane distribution in mitotic cells. During interphase the TPPase reaction is characteristically limited to one or two cisternae of a dictyosomal stack. The acPase reaction stains the membranes of the total stack, of the GERL, of some vesicles and cisternae near the dictyosomes and lysosomes. After the mitotic breakdown of the dictyosomal stacks the forming vesicles still stain positively and are distributed over the entire cytoplasm. At late anaphase and early telophase the enzyme activity occurs not only in the reconstituting dictyosomes but also in the nuclear envelope and in some ER cisternae. The extended spectrum of membrane structures indicating Golgi enzyme activity becomes obvious. This phenomenon favors the idea that at least some functions of the Golgi apparatus persist during mitosis.
Immunolocalization of the 100 kDa nucleolar protein during the mitotic cycle in CHO cells
Authors: Gas N. , Escande M. L. , Stevens B. J.
Published: February 2012

The localization of a major nucleolar protein with a molecular weight of 100,000 has been followed during mitosis in Chinese hamster ovary CHO cells using specific antibodies to this protein and immunocytochemical techniques. The 100 kDa protein was visualized at discrete sites on metaphase chromosomes, corresponding to nucleolus organizer regions, and in large, immunostained nucleolar remnants that are discarded in the cytoplasm after nucleolar disintegration. After mitosis, the 100 kDa protein was shown to play an early role in nucleolar reformation. It was first detected in small deposits around the anaphase chromosomes. In telophase, the protein accumulated simultaneously in prenucleolar bodies and in the reforming nucleoli. The early presence of the 100 kDa protein in the telophase nucleus suggests that it is essential for the reestablishment of nucleolar function after mitosis. Thus this protein is present throughout the CHO cell cycle, an observation which supports the hypothesis that it plays a fundamental role in cell organization.
Aberrant distribution of the peri‐axonemal structures in the human spermatozoon: possible role of the axoneme in the spatial organization of the flagellar components
Authors: Escalier D. , Serres C.
Published: February 2012

A quantitative ultrastructural study combined with stereology was performed on semen samples from four men selected for apparently isolated anomalies of the peri‐axonemal structures. Comparison of the results with those of a control group revealed a decrease: in the mean length of the principal piece; in the mean length of the 9 dense fibres and in the difference in length between the 9 dense fibres, all the fibres being approximately as long as the medium length fibres of the normal spermatozoon. In addition, longitudinal columns were single and/or in abnormal position. However, the extent of the dense fibres (along 60% of the principal piece) and their proportion within the flagellum (35.1% of the principal piece per fibre on average) were normal. Analysis of the results suggests that: A‐tubules of the axonemal doublets are involved in the spatial arrangement of the peri‐axonemal structures; axonemal microtubule‐associated proteins (MAPs) may be responsible for this structural function; and three different types of longitudinal doublet differentiations may exist along the flagellar axoneme.
Two mucous cell types revisited after quick‐freezing and cryosubstitution
Authors: Sandoz D. , Nicolas G. , Laine M. C.
Published: February 2012

The ultrastructures of mucous cell from mouse colon and quail oviduct were revisited after quick‐freezing followed by cryosubstitution and compared with results from standard fixation. After quick‐freezing, the mucous cells of both models do not show the classical aspect of the goblet cell. The secretory granules which contain a dense product do not swell and coalesce as observed after standard fixation. The large condensing vacuoles which are formed in the Golgi region can be discriminated from mature granules only after quick‐freezing. Cytoplasmic organelles and cytoskeletal elements are observed between the secretory granules. The nucleus is ovoid and contains dispersed chromatin, whereas it has a reduced volume and contains condensed chromatin after standard fixation. It is assumed that during standard fixation, the membrane of mucous granules becomes permeable to water inducing hydration of mucous and swelling of granules. The term “goblet cell” could be descriptive of a fixation artefact.
Dome formation in the human colon carcinoma cell line Caco‐2 in culture. Influence of ouabain and permeable supports
Authors: Ramond M. J. , Martinot‐Peignoux M. , Erlinger S.
Published: February 2012

We studied formation of domes in cell monolayers of the human colon carcinoma cell line Caco‐2 which has been shown to exhibit signs of enterocytic differentiation and transport properties. After a 24 hr incubation with 4 × 10(‐8) M ouabain, the number of domes seen on Caco‐2 cell monolayers grown on plastic dishes was not significantly altered. After a 90 min preincubation with ouabain, 86rubidium uptake by Caco‐2 cells was inhibited by ouabain, indicating that the cells have an ouabain‐sensitive Na+, K+‐ATPase, while dome formation was unaffected by ouabain. Domes were observed in Caco‐2 cell monolayers grown on Nuclepore filters when the pore size was 0.015 micron but not when it was 0.030 micron. Our results suggest that dome formation in the Caco‐2 cell line could be independent of Na+, K+‐ATPase activity and might be due to accumulation of molecules having an effective hydrodynamic radius comprised between 0.015 and 0.030 micron.
Nuclear protein, matrix and structural changes in rooster liver after estrogenic induction of vitellogenesis
Authors: Brasch K. , Peters K. E.
Published: February 2012

The estrogenic induction of vitellogenesis in avian and amphibian liver has been well characterized at the target gene level. Comparatively little however, is known about cognate nuclear events associated with the response, particularly those involving large‐scale structural changes and the non‐histone proteins (NHP). We have examined these aspects further in primary stimulated roosters. In the first 24 hr post induction with estradiol, hepatocyte nuclei enlarged by 50% and exhibited sharp rises in total protein and RNA content. In particular, the mass of residual NHP rose about 40%. Extensive internal reorganization was evident, including partial disaggregation of chromatin, proliferation of interchromatin components and de novo appearance of prominent “nuclear bodies”. These changes were accompanied by quantitative fluctuations in nucleoplasmic and several matrix fraction proteins. A marked relative decrease was evident in all three lamins, as well as approximately 75 and approximately 175 kD proteins. Hn‐RNP‐associated polypeptides however, and various unidentified components became much more prominent. By 24 hr, cells were fully differentiated for bulk export of vitellogenin and low density lipoproteins. All changes persisted for several days before gradually regressing to normal over a 2‐4 week period. Many key nuclear modifications, however, did not regress fully, including persistent enlargement, elevated NHP content and modified matrix fraction proteins. Collectively, these may reflect part of the “memory” effect, commonly observed in steroid target tissues, whereby a second, more pronounced response can be triggered long after primary induction has subsided.
The release of acetylcholine: from a cellular towards a molecular mechanism
Authors: Israël M. , Manaranche R.
Published: February 2012

The isolation of synaptic vesicles rich in acetylcholine (ACh) from the electric organ of Torpedo has indeed strengthened the hypothesis of transmitter exocytosis, but soon after it was found that non‐vesicular free ACh was released and renewed upon stimulation. In contrast, vesicular ACh and the number of vesicles remained stable during physiological stimulations. In addition free ACh variations (representing the cytoplasmic pool) were correlated to the release kinetics as measured by the electroplaque discharge. Consequently, the mechanism releasing ACh from the cytoplasm in a packet form was searched at the presynaptic membrane itself. With synaptosomes isolated from the electric organ of Torpedo, it became possible to freeze them rapidly at the peak of ACh release and study their membrane and contents after cryofracture. A statistical analysis showed that the main structural change was the occurrence of large intramembrane particles at the peak of ACh release and under all release conditions. This impressive change contrasted with the stability in the number of vesicles. Another role for the vesicle was envisaged during intense stimulations when the cytoplasmic ACh and ATP pools become exhausted. The decrease in ATP leads to an increase in calcium and protons in the cytoplasm; this signals the depletion of vesicular ACh and ATP stores in the cytoplasm. Release can go on, while ATP promotes the uptake of calcium by vesicles. At the end of its cycle the vesicle will be full of calcium and will perhaps release it. As far as the mechanism of ACh release is concerned it probably depends on a membrane component (perhaps the large particles) activated by calcium and able to translocate ACh in a quantal or subquantal form. In most recent work we showed that if a lyophilized presynaptic membrane was used to make proteoliposomes filled with ACh, they released ACh upon calcium action.
Ammonium chloride, methylamine and chloroquine reversibly inhibit antibody secretion by plasma cells
Authors: Antoine J. C. , Goud B. , Jouanne C. , Maurice M. , Feldmann G.
Published: February 2012

The effects of the lysosomotropic weak bases, NH4Cl, methylamine and chloroquine, on the secretory process of antibody‐synthesizing cells were studied. Popliteal lymph node cells taken from rats immunized against horseradish peroxidase (HRP) were incubated with the lysosomotropic agents. The rate of secretion of anti‐HRP antibodies was measured using an indirect enzyme‐linked immunosorbent assay. These agents induced an inhibition of antibody release within 5 min, and for all four concentrations tested, maximal inhibition was reached after 15 min. A 50% inhibition was obtained with 20 mM NH4Cl, 21.7 mM methylamine and 8.8 × 10(‐4) M chloroquine. This effect was rapidly and entirely reversible, regardless of the weak base used, and it increased as the pH of the extracellular media was raised. Under these conditions, intracellular ATP contents remained normal, and protein synthesis did not undergo marked changes except with chloroquine. Inhibition of secretion was accompanied by an intracellular accumulation of antibodies which was equal to the degree of inhibition of antibody release. Immunocytochemical studies of the weak base‐treated cells performed by light and electron microscopy showed that this accumulation probably occurred within certain dilated Golgi saccules. In addition, reduced incorporation of fucose into immunoglobulins as well as partial inhibition of the secretion of fucosylated immunoglobulins were observed in the presence of weak bases. These results are consistent with the hypothesis that weak bases inhibit antibody secretion by acting within saccules of the Golgi apparatus. These saccules could maintain an acidic pH important for the migration and/or sorting of immunoglobulins.
Identification of an ATPase activity associated with the high molecular weight proteins of the human spermatozoon axonemes
Authors: Cibert C.
Published: February 2012

The high salt extract obtained from demembranated human spermatozoa contains high molecular weight proteins. These proteins are associated with an ATPase activity inhibited by sodium orthovanadate. In association with lower molecular weight proteins, they constitute a 20 S particle and are probably localized in the dynein arms (and in the radial spokes) of the human spermatozoon axonemes. Evidence is shown for a biochemical analogy between the dynein ATPases extracted from the invertebrate axonemes and the human dynein‐like ATPase described in this study.
The orientation of ciliary basal bodies in quail oviduct is related to the ciliary beating cycle commencement
Authors: Boisvieux‐Ulrich E. , Laine M. C. , Sandoz D.
Published: February 2012

In mature ciliated cells, the basal feet associated to the basal bodies point out in the direction of the effective stroke of the ciliary beating. In contrast, during ciliogenesis, the basal feet of the newly anchored basal bodies are randomly oriented. The reorientation of basal bodies occurs during the beginning of the coordinated beating cycle of the cilia.
Apical material extracted from amphibian urinary bladder epithelium by enzymes and detergent treatment
Authors: Bidet S. , Berthonaud V. , Gobin R. , Chevalier J. , Bourguet J. , Ripoche P.
Published: February 2012

The apical plasma membrane of epithelial cells of frog and toad urinary bladder is subject to large modifications during the induction of water permeability by the antidiuretic hormone. A better characterization of the apical membrane is necessary for a clear understanding of the mechanisms of hormone action. Towards this end, apical material was extracted by enzymatic treatment and by incubation with detergent. Proteolytic enzyme alone had little effect under our conditions. A pretreatment with several glycosidases (alpha‐mannosidase or endo‐beta‐N‐acetylglucosaminidase H) increased the hydrolytic action of papain, elastase, proteinase K or Staphylococcus aureus V8 protease and allowed the detection of a major 76 kD in SDS gel electrophoresis. The n‐octyl‐beta‐D‐glucopyranoside (0.2%) led to the extraction after 150 mn of 1 to 5 micrograms proteins per cm2 of amphibian urinary bladder apical surface. The extracted proteins migrated as several bands on SDS gels. One of them probably corresponds to the 76 kD fragment obtained after proteolysis. The absence of alteration of the water permeability after extraction and the good preservation of the ultrastructure are evidence for the localisation of the 76 kD at the apical membrane surface. This protein may be the best candidate as antigen to raise antibodies against the apical surface of amphibian urinary bladder epithelial cells.
Ultrastructural organization of freeze‐fractured interphase nuclei
Authors: Maraldi N. M. , Marinelli F. , Galanzi A. , Zini N. , Ognibene A. , Del Coco R. , Matteucci A. , Papa S.
Published: February 2012

The morphology of intact or membrane‐deprived interphase nuclei has been analysed by freeze‐fracture electron microscopy. This method appears particularly useful for providing information on the distribution and organisation of chromatin and ribonucleoproteins in the absence of dehydration and embedding artifacts of conventional electron microscope techniques which, among other effects, appear to affect heterochromatin distribution, inducing its aggregation along the nuclear envelope. The main levels of chromatin superstructure, from nucleosome to solenoid fibres, are detectable in the replicas of freeze‐fractured nuclei on the basis of the size of their shadow, a parameter particularly suitable for automated image analyses.
Evaluation of androgen action on fibroblast growth by flow cytometry
Authors: Loire C. , Favier F. , Sultan C.
Published: February 2012

The action of androgen (dihydrotestosterone‐DHT‐) on fibroblast growth was evaluated by 3H thymidine incorporation in DNA, by DNA assay using 3‐5 diaminobenzoic acid fixation, and by a more sophisticated technique: flow cytometry. Cell DNA and proteins were stained with propidium iodide and fluorescein isothyocyanate, respectively. We did not observe any detectable DNA variation when fibroblats were incubated in the presence of DHT. Moreover, DHT did not modify DNA and protein distribution, either in the total cell cycle or in each phase of the cell cycle. These results suggest that androgens do not induce total protein synthesis nor increase DNA in target cells. It is likely that they induce specific protein synthesis.
Characterization and expression of collagen‐like genes in Drosophila melanogaster
Authors: Le Parco Y. , Cecchini J. P. , Knibiehler B. , Mirre C.
Published: February 2012

We have used a cloned chicken collagen cDNA sequence to help identify hypothetic members of the collagen gene family from Drosophila melanogaster. Several experimental evidences have been obtained which indicate that the Drosophila genome contains numerous collagen‐like sequences. We have characterized in more detail ten distinct DNA sequences that hybridized strongly to the heterologous collagen probe. By in situ hybridization we have shown that these sequences are dispersed throughout the Drosophila genome. Two of them are shown to originate from the previously described DCg 1 and DCg 2 collagen genes. In other respects, we show that in addition to DCg 1 and DCg 2, at least five putative collagen genes are expressed during the Drosophila lifetime. These genes are unique, and some of them are seen to be transcribed into different size classes of mRNAs. Additionally, the data presented so far demonstrate that the expression of these genes is regulated temporally and/or quantitatively during the Drosophila life cycle.
Post‐fusion reaction of mouse oocyte cortex to incorporated thymocyte cells
Authors: Sołtynska M. S. , Szöllösi D. , Czołowska R.
Published: February 2012

Ovulated alcohol‐activated or inactivated mouse oocytes were fused with mouse thymocytes. Activated oocytes react to the presence of foreign nuclei by forming in the peripheral cytoplasm incorporation cones. In this region the cell membrane is smooth and a cortical layer of thin filaments underlies it. It resembles the fertilization cone. In non‐activated oocytes a layer of thin cortical filaments of the same thickness is formed over the foreign chromatin but the surface protuberance (cone) is absent. These results suggest that the cortical alteration in the oocyte architecture may be a general reaction of the oocyte surface to various chromatins introduced, not only to sperm chromatin. The role of oocyte activation in the evolution of these cortical changes is discussed.
An electron microscopic study of nucleolus‐organizing regions at some stages of the cell cycle (G0 period, G2 period, mitosis)
Authors: Hozák P. , Zatsepina O. , Vasilyeva I. , Chentsov Y.
Published: February 2012

Nucleolus‐organizing regions (NORs) at some stages of the cell cycle (G0 period, G2 period and mitosis), differing in the level of NOR transcription activity, were studied on ultra‐thin serial sections of pig embryo kidney cells. Particular attention was given to the spatial organization of fibrillar centers (FCs) in the nucleoli and to comparing the number of FCs with that of NORs. It was shown that within nucleoli, FCs may be located singly or form groups surrounded by a dense fibrillar component. The overall number of FCs exceeds that of NORs 1.7‐fold in the G0 period, and 4.6‐fold in the G2 period. At prophase, with progressive condensation of chromosomes and NOR inactivation, the number of FCs decreases and at metaphase corresponds to the number of silver‐stained NORs. The data thus obtained make it possible to conclude that in active nucleoli, the number of FCs is higher than that of NORs. Proceeding from these numerical and ultrastructural data, it is suggested that a single NOR of pig embryo kidney cells corresponds to one “fibrillar complex”, i.e., to an association of a different number of FCs with the dense fibrillar component. These “fibrillar complexes” contain 1 to 3 FCs in the G0 period and 1 to 12 FCs in the G2 period.