bluuebunny/crossref_metadata_2025 huggingface dataset:
Phorbol esters inhibit the synthesis of acetylcholine receptors in cultured muscle cells
Authors: Bursztajn Sherry , Schneider Larry W. , Jong Yuh‐Jin , Berman Stephen A.
Published: February 2012

The acetylcholine receptor (AChR) synthesis, insertion and degradation rates are regulated by numerous intracellular and extracellular agents. Recent studies have shown that Ca2+ and Ca2+ ionophores have a profound regulatory effect on the appearance of AChR clusters and AChR synthesis [3, 15, 23]. These regulatory effects may be mediated through the activation of calcium and phospholipid‐dependent protein kinases by agents such as phorbol esters. In this study, we have utilized 4‐β‐phorbol‐12‐myristate‐13‐acetate (PMA) in order to determine whether the activation of protein kinase C exerts a regulatory effect on the expression of AChRs in cultured chick myotubes. Our results show that 4‐β‐phorbol‐12‐myristate‐13‐acetate decreased intracellular AChRs and suppressed AChR synthesis without affecting the turnover rate. Control and PMA treated cells labeled with [35S] methionine and immunoprecipitated with a monoclonal antibody to the α subunit of AChRs (mAb35) revealed a significant decrease in radioactivity precipitated after exposure to PMA. Polyacrylamide gel electrophoresis revealed no major changes in protein patterns, or in newly synthesized proteins as determined by [35S] methionine incorporation and autoradiography. Other enzymes important in muscle metabolism were not affected by PMA treatment. Our results indicate that activation of protein kinase C results in the suppression of AChRs synthesis and dispersal of AChR clusters.
Skin cultured with or without an NaCl gradient and aldosterone influence epidermal fibronectin localizations
Authors: Denefle Jean‐Pierre , Lechaire Jean‐Pierre , Zhu Qian‐Long
Published: February 2012

Fibronectin (FN) localizations in the epidermal cells of the frog Rana esculenta were detected in isolated ventral skin fragments 4 day‐cultured with or without an NaCl transepithelial gradient and aldosterone. Without the gradient, few mitochondria‐rich cells (MRCs) were FN‐detected. Stratum germinativum and spinosum cells also contained fibronectin. With the gradient, numerous MRCs were detected. Below them, in the stratum germinativum, clear spaces were recognized. Aldosterone with or without the gradient modified the above effects: In both cases, many MRCs contained fibronectin. It was interesting to note that, for each type of culture, stratum germinativum cells were dramatically FN‐detected.
Three‐dimensional ultrastructure and quantitative analysis of the human Sertoli cell nucleolus
Authors: Cataldo Claude , Souchier Catherine , Stahl André
Published: February 2012

The nucleolus of the human Sertoli cell displays a spontaneous segregation of its components and has only one or 2 large fibrillar centers. The 3‐dimensional reconstruction and quantitative analysis of its components was undertaken using a Quantimet 900 image analysis system in order to define the spatial relationships between the dense fibrillar component and the fibrillar center and especially to investigate whether threads of dense fibrillar component exist independently, without being linked to a fibrillar center. Our 3D reconstructions demonstrated that the dense fibrillar threads or sheets were never independent of fibrillar centers. These structures belonged to a continuous network that joined the layer of dense fibrils surrounding the fibrillar center. When the nucleolus contained 2 different‐sized fibrillar centers, quantitative analysis showed that there was a proportional relationship between the volume of the dense fibrillar component and the volume of the fibrillar center. These data, compared with those previously obtained by means of autoradiographic techniques, suggest that the rDNA‐containing chromatin passes through the fibrillar center and unwinds from there into the dense fibrillar component.
Characterization of a ferritin isolated from the midgut epithelial cells of a homopteran insect, Philaenus spumarius L.
Authors: Collin Olivier , Thomas Daniel , Flifla Mohammed , Quintana Carmen , Gouranton Jean
Published: February 2012

Crystalline accumulations of ferritin‐like particles are present within the cytoplasm and the nucleus in midgut epithelial cells of the homopteran Philaenus spumarius.

A structural study at the electron microscope level reveals that these particles have the morphological characteristics of the ferritin molecule: crystals have a face‐centered cubic structure with a lattice parameter of 14 ± 1 nm; negatively stained isolated particles have the appearance of ferritin; on rotary‐shadowed particles 3 axes of symmetry are clearly seen; image processing performed on selected molecules demonstrates a 4‐fold symmetry.

A semiquantitative electron microprobe analysis effected on aggregates of microcrystals in thin sections reveals a high atomic ratio Fe/P.

Analyzed by SDS‐PAGE, the protein subunit has a molecular weight of 18,600. The amino acid composition of the protein bears the general characteristics of the ferritin molecule in terms of polar and nonpolar residues. But in terms of sequences, this protein displays a strong dissimilarity to rat liver ferritin as demonstrated with a common amino acid index test and with immunoelectrophoresis experiments.
Differential response of primary cultures of human and rat hepatocytes to aflatoxin B1‐induced cytotoxicity and protection by the hepatoprotective agent (+)‐cyanidanol‐3
Authors: Bégué Jean‐Marc , Baffet Georges , Campion Jean‐Pierre , Guillouzo André
Published: February 2012

The acute hepatotoxicity induced by aflatoxin B1 (AFB1) and the potential protective effect of (+)‐cyanidanol‐3 (Catergen®) were evaluated in both human and rat hepatocyted in primary culture. AFB1‐induced acute toxicity was visualized by light microscope observation and quantified by measurement oflactic dehydrogenase activity in the medium. Human hepatocytes were susceptible to AFB1‐induced cytotoxicity but no evident relationship between the concentration of mycotoxin and the extent of cellular damage was established. (+)‐Cyanidanol‐3 was not toxic at concentrations up to 2×10−3M, but no obvious protective effect from AFB1‐induced injury was evidenced in human cells. By contrast, rat hepatocytes responded in a dose‐related manner toAFB1. (+)‐Cyanidanol was toxic at 10−3M, but even at this concentration exerted a strong protective effect against AFB1‐induced cytotoxicity. Such species differences suggest the existence of metabolic differences in both AFB1 and (+)‐cyanidanol‐3 activating and deactivating mechanisms.
Comparative determination of the asialoglycoprotein receptor by ligand and antibody binding in hepatocytes from normal and diabetic rats
Authors: Slama Abdelhamid , Zinbi Hassan , Feger Jeanne , Dodeur Michèle
Published: February 2012

The number of cell surface and total asialoglycoprotein receptors was investigated in normal and diabetic rat hepatocytes using 2 methods: ligand and polyclonal antibody binding. An identical number of immunoreactive receptors was found in both types of cells, while the ligand binding activity of cell surface receptors was reduced by 58% in diabetic rats compared with normal ones, or by 33% for total cell receptors.
Analysis by polarizing microscopy of chromosomal structure among dinoflagellates and its phylogenetic involvement
Authors: Cachon Jean , Sato Hidemi , Cachon Monique , Sato Yukiko
Published: February 2012

Dinoflagellate chromosomes are highly interesting because of their condensed state, their lack of histone, and their ultrastructure reminiscent of that of bacterial nucleoid.

With the use of a highly sensitive resolution polarization microscope coupled with electron microscope observations, and by studying and comparing a great variety of species, we confirm the intrinsic nature of birefringence and bring new data about the evolution of interphasic chromosomes among dinoflagellates. Three types are observed: the A‐type, characterized by positive birefringence, condensed state, and lack of basic proteins; the B‐type, with a half positive‐half negative birefringence corresponding to a neck lace chromosome shape and possessing no or very few basic proteins; and the C‐type, which has a negative birefringence because of its loosely gathered filament bundle possessing few basic proteins.
Nucleolar component behaviour in plant cells under different physiological conditions. A morphological, cytochemical and quantitative study
Authors: Moreno Francisco Javier , Rodrigo Rosa M. , Gracia‐Navarro Francisco , Garcia‐Herdugo Gregorio
Published: February 2012

Different nucleolar components of Allium cepa L. root meristem cells under physiological conditions of proliferation and quiescence were quantitatively analyzed after the application of morphometric and cytochemical techniques.

Our data show that quiescent cells have a diminished nucleolar size when compared with proliferating cells. However, the silver stained area in relation to the nucleolar area (fibrillar component) is maintained constant in both physiological conditions. We also detected a smaller number of vacuoles per nucleolar volume unit in the case of low transcriptional activity. Cytochemical results obtained in both physiological conditions allowed us to postulate about the distribution of the acidic nucleolar proteins responsible for the NOR‐silver staining.
Immunoelectron microscopic localization of the nucleolar protein B‐36 (fibrillarin) during the cell cycle of Physarum polycephalum
Authors: Pierron Gérard , Pedron Jacqueline , Schelling Margaret , Christensen Mark
Published: February 2012

Monoclonal antibodies raised against the 34‐kD nucleolar protein, B‐36, from the slime mold Physarum polycephalum have been used to examine the electron microscopic localization of B‐36 during the cell cycle in Physarum. During interphase, B‐36 is found primarily in regions corresponding to the dense fibrillar component. This is similar to what has been observed for the putative mammalian homologue of B‐36, fibrillarin. During mitosis, B‐36 remains associated with perichromosomal nucleolar remnants. With the Gautier DNA‐specific staining procedure, the same nucleolar remnants are shown to contain short DNA segments, presumably rDNA molecules. These findings suggest that in Physarum, where the nucleolus is composed of several hundred extrachromosomal rDNA molecules, the dense fibrillar component and the “NOR” equivalents do not separate during mitosis as in mammalian cells. In addition, the B‐36‐enriched nucleolar remnants appear to be recycled from one cell cycle to the next.
Renewal of goblet cell mucus granules during the cell migration along the crypt‐villus axis in rabbit jejunum: an immunolabeling study
Authors: Chambraud Lydie , Bernadac Alain , Gorvel Jean‐Pierre , Maroux Suzanne
Published: February 2012

A monoclonal antibody against intestinal mucins (5H7) was obtained and used to immunolabel thin frozen sections and Epon‐embedded sections of rabbit jejunum. It recognized a mucin oligosaccharide, the synthesis of which increased during goblet cell migration along the crypt‐villus axis. During the earliest steps in their differentiation, the goblet cells located at the bottom of crypts synthesized mucins devoid of the 5H7 epitope, thus generating unlabeled granules. These unlabeled granules were gradually replaced by more and more labeled granules during the cell maturation. During goblet cell migration along the middle half of the villi, the mucus granules were found to be totally renewed twice. However, some newly formed labeled granules were observed to reach the apical pole of the cells before older unlabeled ones and might have had a faster turnover.

At least one glycoconjugate of the goblet cell microvillar membrane also bore the 5H7 epitope. It was rapidly carried from the Golgi apparatus to the apical plasma membrane domain by a transport process that was independent of baseline mucin secretion.
Synthesis of frog virus 3 proteins occurs on intermediate filament‐bound polyribosomes
Authors: Murti Kuruganti , Goorha Rakesh
Published: February 2012

Immunogold labeling and biochemical methods were used to localize the site of viral protein synthesis in frog virus 3 (FV3)‐infected baby hamster kidney (BHK) cells. Immunogold labeling studies of Triton‐extracted (cytoskeletons), FV3‐infected BHK cells with antivimentin antibodies showed that the major components of the detergent‐resistant residue are the intermediate filaments (IF) and polyribosomes. Double immunogold labeling studies with anti‐FV3 and antivimentin antibodies revealed that FV3 proteins are associated with polyribosomes that are bound to the If network. Biochemical studies of the cytoskeletons prepared from FV3‐infected cells showed that a substantial fraction of all newly synthesized FV3 proteins associate with the cytoskeleton and that the association is not disrupted by colchicine (microtubule‐disrupting drug) or cytochalasin B (microfilament‐disrupting drug). Together the above studies suggest that IF may provide the scaffold for the attachment of polyribosomes that are active in viral protein synthesis.
In vitro growth properties and PCR ras gene analysis of a murine embryonal carcinoma cell line harboring an amplified C‐Ki‐ras gene
Authors: Vilette Didier , d'Auriol Luc , Galibert Francis , Peries Jorge , Emanoil‐Ravier Rodica
Published: February 2012

Ras proto‐oncogenes are thought to be involved in both proliferation and malignant processes. We examined some growth properties of a murine embryonal carcinoma cell line (ECC), PCC4, that have been shown previously to be amplified for the c‐KI‐ras gene. Our results show that doubling time and plating efficiency are not significantly affected by such amplification. To examine the possible link between malignant behavior and c‐Ki‐ras alteration, we investigated activating mutations in this PCC4 cell line as well as in other ECC. Analysis of the in vitro amplified Ki‐ras gene by PCR technology has not revealed point mutations in any of the ECC examined.
Effects of iron overload on transferrin secretion by cultured fetal rat hepatocytes
Authors: Lescoat Gérard , Jouanolle Hervé , Desvergne Béatrice , Pasdeloup Nicole , Kneip Bernard , Deugnier Yves , Guillouzo Andre , Brissot Pierre
Published: February 2012

Primary cultures of fetal rat hepatocytes were maintained in an arginine‐free medium deprived of serum but supplemented with 0.03 mM L‐ornithine and 10−8 M dexamethasone. Ferric nitrilriacetate was added to the culture medium in order to obtain iron concentrations ranging from 10 to 100 μM. After 24 h of treatment, iron was visualized inside the hepatocytes by the staining method of Perls and electron microscope study. The present data demonstrate that iron overload decreases transferrin secretion; this effect appears not to be specific, since albumin production is affected in a similar manner. This depressed transferrin secretion is not the consequence of hepatocyte death, as the phenomenon is confirmed when expressed per cell. Since the corresponding mRNA is unaffected, it may be postulated that iron overload decreases transferrin secretion at some post‐transcriptional level.
Epithelial cell migration on small intestinal villi in the neonatal rat. Comparison between [3H] thymidine and cytoplasmic labelling after Pu‐citrate ingestion
Authors: Moutairou Kabirou , Fritsch Paul , Meslin Jean‐Claude , Poncy Jean‐Luc , Metivier Henri , Masse Roland
Published: February 2012

This study compares, in 2‐d‐old rats, the migration rates of epithelial cells on villi of the small intestine, using two labelling methods: a single [3H] thymidine injection; and cytoplasmic labelling by a single ingestion of Pu‐citrate. Histoautoradiography shoed negligible diffusion of Pu after the initial retention, which was mostly confined to the epithelial cells of the villi. However, after sloughing of labelled cells in the intestinal lumen, Pu was reabsorbed by the distal epithelial cells. In segments in which Pu reabsorption was negligible, the migration rates of Pu‐ and 3H‐labelled cells were very close. These rates, expressed in micrometers, were almost constant along the length of the villus, and the Pu and 3H labelling edges reached the top of the villi in about 5 and 7 d, respectively.

Once Pu retention had reached its maximum in 9 equal segments cut along the small intestine, tissue counting showed an exponential Pu release of 30–40%d from each segments until the end of the experiment at d16. This constant release might reflect a constant cell migration rate during the period from Pu ingestion until d16.
Size‐related differences in the branching pattern of the motor nerve terminals in triangularis sterni muscle of the mouse
Authors: Tomasi Josep , Fenol Rosa , Santafe Manel , Mayayo Emili
Published: February 2012

A light microscopy morphometric study was performed in singly innervated synaptic areas of the triangularis sternal muscle of the normal adult Swiss mouse. Investigating mechanisms of the motor nerve growth control, we tested the hypothesis that significant differences in the nerve terminal branching pattern can be detected between different populations of nerve endings classified according to their arborization complexity or size.

The main observations of this morphometric study are first, that the mean segment length of the terminal arborization between branch points behaves as an independent variable from the remaining parameters; the mean value of this parameter did not change in nerve endings of differing size and complexity. Secondly, the increase in size of the nerve endings is accompanied by a significant reduction in the mean length of the distal free‐end segments. Results are discussed in the context of the possible regulatory mechanisms governing nerve terminal growth and remodelling.
The endoplasmic reticulum network in the ascidian egg: localization and calcium content
Authors: Gualtieri Roberto , Sardet Christian
Published: February 2012

In contrast with most other eggs, where the endoplasmic reticulum is mixed with many other organelles, in ascidians, continuous sheets and tubes of endoplasmic reticulum constitute the only prominent organelle in the immediate layer (0.5‐1μm) beneath the plasma membrane, and occupies 16–20% of the cortical volume. We took advantage of this unusual stratification of the organelles in the ascidian egg, to carry X‐ray microanalysis. Our measurements provide the first estimate of the calcium content of the endoplasmic reticulum network in an egg, and show it is the main calcium store.
Cytokeratin analysis of breast and leukemia tumor cell lines by flow cytometry
Authors: Ferrero Magali , Spyratos Frédérique , Desplaces Andrée , Andrieu Catherine , Phillips Edelmira , Rouëssé Jacques
Published: February 2012

Using four human tumor cell lines, MCF‐7 and T47‐D from breast tumors, MOLT‐4 and K‐562 from leukemia, flow cytometric DNA analysis of pure and mixed cell population was performed using monoclonal antibodies to cytokeratin to distinguish cytokeratin‐containing carcinoma cells from leukemia cells which do not contain cytokeratins. Surprisingly, on pure or mixed K‐562 cells, we found positive labeling with KL1, CK8, and CK18 antibodies (results confirmed by immunocytology). This preliminary study has allowed a DNA analysis on epithelial cells of human breast tumors.
Localization of barriers to water flow in toad urinary bladder
Authors: Levine Sherman D. , Jacoby Monica
Published: February 2012

Although it is well accepted that vasopressin (ADH) increases the permeability to water of the toad bladder granular cell's luminal membrane, recent studies have suggested that regulation also takes place at an additional “postluminal” site within the epithelial granular cell. These studies are based upon the observation that a number of experimental maneuvers can alter tissue permeability to water, but do not change the number of particle aggregates observed on the protoplasmic face of the granular cell's luminal membrane with freeze‐fracture electron microscopy. These aggregates are believed by many investigators to mediate the transport of water across the luminal membrane.

The dissociation between permeability and aggregate frequency described above has been variously interpreted as the consequence of changes in the permeability of the aggregates themselves, or of changes in the permeability of a “postluminal” barrier that is functionally in series with the luminal membrane.

We attempted to distinguish between these 2 possibilities by studying paired toad bladders during 3 protocols that alter vasopressin‐stimulated water flow across the intact tissue without altering aggregate frequency. Estimates of the permeability of postluminal barriers were obtained by exposing the luminal surface to amphotericin B, an antibiotic that forms water‐permeant channels in the luminal membrane.

Of the 3 protocols, only diminishing bladder filling volume decreased the water flow elicited by luminal amphotericin B, suggesting that only that protocol indeed decreased the permeability of some postluminal barrier. The other 2 protocols, increasing PCO2 and repeatedly stimulating the bladder with vasopressin, did not alter amphotericin B‐elicited flow, suggesting that postluminal barriers were not altered by these 2 protocols. We thus conclude that a decrease in luminal membrane aggregate permeability or a decreased frequency of fusion of aggregate‐rich tubules to the luminal membrane mediates the decreased flow‐response in the latter 2 protocols, and not modulation of a postluminal membrane barrier.
Isolation of frog urinary bladder plasma membranes with polycation coated beads
Authors: Valenti G. , Casavola V. , Svelto M.
Published: February 2012

It is now generally accepted that the increase in water permeability induced by antidiuretic hormone (ADH) in responsive epithelia is accompanied by the insertion of specific structures in the apical membrane of epithelial cells. There are strong indications that these particles, probably proteic in nature, represent water channels.

In order to evaluate the nature and role of such proteins, plasma membranes were isolated by the affinity chromatography technique. The method is based on the firm attachment of the external face of the membrane to polycations covalently bound to the surface of polyacrylamide beads, followed by shearing of the rest of the cells. Maximal binding of epithelial cells to beads was achieved in a medium of low ionic strength and pH 5.2 (i.e. sucrose‐MES buffer). By this procedure plasma membranes were obtained from both cAMP‐stimulated cells and control cells.

Membranes isolated on beads were enriched in the activity of typical membrane marker enzymes (LAP; H+ ATPase; Na+, K+ ATPase) with respect to a whole cell homogenate, whereas contamination of plasma membrane fraction by endoplasmic reticulum, lysosomes, and mitochondria was relatively low.

Analysis by SDS polyacrylamide gel electrophoresis showed an interesting difference between cAMP‐treated and control samples.
Cellular permeation pathways in a leaky epithelium: the human amniochorion
Authors: Hardy Marcos A. , Leonardi Ronald T. , Scheide John I.
Published: February 2012

The presence of cellular permeation pathways in human fetal membranes at term was evaluated. Electrical parameters (transepithelial potential [TEP], and conductance [Gt], and intracellular potentials [cell PD]), and water and urea diffusional coefficients (Pdw, Pdu), were determined in Ussing‐like chambers.

In amniochorion, the TEP was practically 0 (0.1±0.03 mV), and the Gt very high (144±14 mS/cm2). The Cell PD of amnion cells was −37±3 mV. Increasing the [K+] of the amniotic perfusate between 5.8 and 125.8 mM depolarized the cells with a slope of 23 mV. The deletion of Na+ hyperpolarized the cells, whereas amiloride and ouabain depolarized them.

The Pdw and Pdu were determined in intact amnion and chorion and in their epithelial cell layers. The Pdw/Pdu ratio in amnion was 4.0, and 7.0 in its cell layer; the ratio in chorion was 2.5, and 3.3 in its cell layer.

The amniochorion is a leaky structure, but its cellular layers possess definite transcellular permeation pathways. The ionic conductances in amnion cells are complex, with the Cell PD being determined by at least K+ and Na+ conductances, and ouabain‐ and amiloride‐sensitive pathways. The amnion is a more effective diffusional barrier to water and urea than chorion is; its diffusional characteristics are comparable to those of nystatin‐treated lecithin: cholesterol bilayers and the membranes of human erythrocytes.
Freeze‐fracture study of the pavement cell in the lamprey gill epithelium. Analogy of membrane structure with the granular cell in the amphibian urinary bladder
Authors: Bartels Helmut
Published: February 2012

Freeze‐fracture studies of the lamprey gill epithelium reveal structural differences of the luminal and basolateral plasma membrane of the pavement cells. The luminal membrane is characterized by only a few intramembrane particles on the P face and numerous large (10–13 nm) particles on the E face, whereas the basolateral membrane shows the majority of intramembrane particles (6–8 nm) on the P face. The structural specialization of the luminal membrane and the differences between the luminal and basolateral membranes of the pavement cell are similar to those previously demonstrated for the unstimulated granular cell of the amphibian urinary bladder. Because of this similarity, it is suggested that the 2 cell types are analogous and that the luminal membrane of the pavement cell in the lamprey gill epithelium is functionally characterized by a low water permeability. A possible role of sodium uptake by the pavement cells from freshwater and putative differences of osmoregulatory mechanisms in the gills of lampreys and teleosts in freshwater environments are discussed.
Coupling of volume and Na+ transport in frog skin epithelium
Authors: Tang Cherng‐Shing R. , Peterson‐Yantorno Kim , Civan Mortimer M.
Published: February 2012

Whole skins and isolated epithelia were bathed with isotonic media (‐ 244 mOsm) containing sucrose or glucose. The serosal osmolality was intermittently reduced (to ‐ 137 mOsm) by removing the nonelectrolyte. Transepithelial and intracellular electrophysiological parameters were monitored while serosal osmolality was changed. Serosal hypotonicity increased the short‐circuit current (Isc) and the basolateral conductance, hyperpolarized the apical membrane (Φmc), and increased the intracellular Na+ concentration. The increases in apical conductance and apical Na+ permeability (measured from Goldman fits of the relationship between amiloride‐sensitive current and Φmc) were not statistically significant.

To verify that the osmotically induced changes in Isc were mediated primarily at the basolateral membrane, the basolateral membrane potential of the experimental area was clamped close to 0 mV by replacing the serosal Na+ with K+ in Cl−‐free media. The adjoining control area was exposed to serosal Na+. Serosal hypotonicity produced a sustained stimulation of Isc across the control, but not across the adjoining depolarized tissue area.

The current results support the concept that hypotonic cell swelling increases Na+ transport across frog skin epithelium by increasing the basolateral K+ permeability, hyperpolarizing the apical membrane, and increasing the electrical driving force for apical Na+ entry.
Localization of functional centers on the prokaryotic ribosome: immuno‐electron microscopy approach
Authors: Spirin Alexander S. , Vasiliev Victor D.
Published: February 2012

Immuno‐electron microscopy studies on the morphology of the Escherichia coli ribosome and the topography of its functional centers are summarized. A three‐dimensional model of the ribosome with indications of the mRNA‐binding site, the peptidyl‐transferase center, the EF‐Tu and EF‐G‐binding sites and the tRNA‐binding sites in given. Thus, the mutual arrangement of the centers corresponding to the main functional activities of the ribosome during the process of translation is presented.
Direct visualization of an IgM directed against a membrane antigen involved in both cell‐matrix interactions and microfilament organization
Authors: Lesot Hervé , Meyer Jean Marie , Staubli Aline , Schmitt Didier A. , Ruch Jean Victor
Published: February 2012

Dental mesenchymal cells were cultured in the presence of a monoclonal antibody. MC16A16, consisting of IgM and directed against a hydrophobic 165 kDa protein. Since the epitope recognized by MC16A16 was found to be at the outer cell surface, a direct visualization of IgM antibodies was used to localize the 165 kDa antigen by transmission electron microscopy. The present results demonstrate that the 165 kDa antigen is a membrane protein.
Wheat germ agglutinin (WGA) reduces ADH‐induced water flow and induces cell surface changes in epithelial cells of frog urinary bladder
Authors: Favard Pierre , Favard Nina , Zhu Qian Long , Bourguet Jacques , Lechaire Jean‐Pierre , Maillard Maryvonne
Published: February 2012

The functional and structural changes induced by apical wheat germ agglutinin (WGA) 100 μg/ml exposure on frog urinary bladder have been investigated and the possible correlation between these effects discussed. Bladders, apically exposed to WGA for 30 min to 3 hr exhibit a marked reduction of their response to antidiuretic hormone (ADH) challenge and of their hydrosmotic reactivity. Structural changes triggered by WGA trreatmentare: 1. apical invaginations of the plasma membrane, interpreted as endocytotic in nature, taking into account the results of carbohydrate cytochemical detection and horseradish peroxidase (HRP) exposure: 2. cytoskeleton disorganization and microvilli collapse. These phenomena do not interfere with cortical granule traffic and are independent of ADH challenge: they occur in ADH‐stimulated bladders as well as in bladders at rest. These findings could be interpreted as follows: binding of the divalent lectin WGA to its coat specific receptors would induce changes in the apical membrane structure which in turn could provoke disorganization and disruption of apical cytoskeletal elements associated with plasma membrane. Reduction of bladder response to ADH challenge could result from a reduced recyling of aggrephores, as they are associated with cytoskeletal elements in the subapical cytoplasm. Collapse of microvilli and endocytotic events also could result from apical cytoskeleton disruption, as microvilli are sustained by bundles of actin filaments interconnected with apical cytoskeleton filaments and as plasma membrane is associated with apical cytoskeleton. However, these two last events evidently occur in ADH‐challenged or non‐challenged bladders.
The helicoidal plant cell wall as a performing cellulose‐based composite
Authors: Roland Jean‐Claude , Reis Danièle , Vian Brigitte , Roy Stéphane
Published: February 2012

The helicoidal plant cell wall can be considered as a composite in which cellulose is the constant reinforcing fiber. In order to strengthen the analogy with cholesteric liquid crystals, and taking into account a range of data, we describe a progressive series showing that cellulosic helicoidal systems are versatile and multifunctional. The following examples were considered: a) the cellulose microfibrils, with their rigid backbone possibly coated with a plastifying matrix; b) actual cholesteric cellulosic derivatives, such as in vitro liquid crystals and in vitro cellulosic mucilages; c) viscoplastic. growing cell walls; d) consolidated “stony” cell walls with their adaptation to intercellular communications. The series shows a dramatic progression from a liquid construction to what is the hardest in the plant cells, i.e. the sclerified walls.
Freeze fracture study of the plasma membrane of the marine loricate ciliate Eufolliculina uhligi: morphology and distribution of intramembrane particle aggregates in the swarmer and in the lorica secreting cell
Authors: Mulisch Maria , Nielsen Jürgen , Hausmann Klaus
Published: February 2012

Our freeze‐fracture study has revealed the presence of two types of intramembrane particle (IMP) aggregates in the somatic plasma membrane of Eufolliculina uhligi: rectangular particle arrays and rosettes. Their morphology and distribution differ in the motile and in the lorica secreting stage. Rectangular particle arrays occur to the left of the kineties. They are not very obvious in the swarmer, but increase in size and number during lorica formation. We discuss whether they are involved in the contractility of this ciliate. Rosettes occur to the right of the kinetics where they mark attachment sites of extrusive vesicles at the plasma membrane of the swarmer. No annulus‐like structure as e.g. in Tetrahymena mucocysts and Paramecium trichocysts has been found in the membrane of these vesicles. The rosettes consist of 10‐nm particles and lack an outer ring. Vesicle membrane and plasma membrane appear to remain separated during exocytosis. In the course of lorica secretion, the number of rosettes continuously decreases, following an anterior‐posterior gradient. This indicates that new insertion of extrusive vesicles from intracellular stores occurs preferably at the anterior of the cell.
Endocytosis in spermatids during spermiogenesis of the mouse
Authors: Segretain Dominique
Published: February 2012

In the course of spermiogenesis in the mouse, spermatid cytoplasm contains numerous membrane pits, vesicles and membranous tubules which are frequently anastomosed. Pale and dense multivesicular bodies (MVB) and secondary lysosome‐like structures are also present in the cytoplasm. In order to study the pathway of non‐specific adsorptive endocytosis in spermatids, cationic ferritin (CF) was directly microinjected into the lumen of seminiferous tubules, and added to germinal cell culture. Tissue and cultures were fixed at various time intervals after injection.

Two‐5 hr after microinjection of tracer, CF was found simultaneously in vesicles, tubules, MVB and in lysosome‐like bodies present in spermatids at all steps of spermiogenesis. Various membranous components of the Golgi medulla, and the innermost transsaccule of the Golgi cortex were labelled simultaneously. In primary cultures of spermatids, the vesicles contained the marker 5 min after its deposition; 10 min after deposition, CF was evident in tubules; at 30 min, CF was present in pale MVB; at 1 hr, the dense MVB and lysosome‐like bodies were labelled. Finally, at 2 hr 30 min, vesicles and tubules of the Golgi medulla contained CF grains.

Apparently spermatids are very active cells in the process of adsorptive endocytosis throughout spermiogenesis. Endocytosis in spermatids is probably one of the mechanisms involved in the uptake of material used to build up spermatozoa components. The strong labelling of the Golgi region probably point to its role in recycling endocytosed membranes.
Proliferative response of foetal liver peroxisomes to clofibrate treatment of pregnant rats. A quantitative evaluation
Authors: Stefanini Stefania , Mauriello Alessandro , Farrace Maria Grazia , Cibelli Anna , Ceru Maria Paola
Published: February 2012

Liver peroxisomes during prenatal development were studied by means of morphological and morphometric analysis in foetuses growing both in untreated and in clofibrate‐treated rats. Pregnant rats were fed a standard diet (25 g/d) containing or not 0.8% clofibrate during the week preceding sacrifice and livers were excised from 13, 15, 17, 19 and 21‐day old foetuses and newborn rats. The morphometric analysis of hepatocyte peroxisomes, performed by a semiautomatic method in specimens incubated with 3,3′ diaminobenzidine, shows that the peroxisome volume density and average diameter in test animals were significantly increased over the control values. While the increase in the average diameter was roughly the same (×1.4) at all examined stages, the volume density increased over the control values particularly in foetuses over 19d‐old and in newborn rats; over the same period the peroxisome numerical density also significantly increased over the control values. Finally, the average diameters of peroxisome profiles in test rats showed a more dispersed distribution (SD 40%) than in control animals (SD 30%). These results demonstrate that clofibrate, given to rats during pregnancy, induces peroxisomal proliferation in the livers of their foetuses. Data are discussed in view of the models proposed for peroxisomal biogenesis.
Immunoelectron microscopical identification of the uncoupling protein in brown adipose tissue mitochondria
Authors: Cinti Saverio , Zancanaro Carlo , Sbarbati Andrea , Cicolini Massimo , Vogel Peter , Ricquier Daniel , Fakan Stanislav
Published: February 2012

The distribution of the uncoupling protein (UCP) in brown adipocyte mitochondria of the hibernant Muscardinus avellanarius was obtained by ultrastructural immunocytochemistry. In both cryosections and sections of Lowicryl‐embedded material UCP was localized in the mitochondrial cristae of brown adipocytes, but not in liver mitochondria. It should now be possible to easily identify the morphology of cells committed to BAT differentiation in the tissue as well as in cell culture.
In vitro effects of colchicine and nocodazole on ciliogenesis in quail oviduct
Authors: Boisvieux‐Ulrich Emmanuelle , Lainé Marie‐Christine , Sandoz Daniel
Published: February 2012

Summary— Oviduct implants from quails which were primarily stimulated in vivo by estrogen so as to induce ciliogenesis in some epithelial cells were cultured in vitro in the presence or absence of colchicine or nocodazolc. After 24 or 48 hr of culture, implants were examined by transmission and scanning electron microscopy to determine drug‐induced alterations in ciliogenesis.

After 24 hr of 10−5 M colchicine treatment, the formation of basal bodies was totally inhibited, though the precursor material of generative complexes was unchanged. The inhibitory effect was not reversed when colchicine was removed in a 24 hr recovery culture. Treatment with 10−6 M nocodazole for 24 hr, partially inhibited the assembly of basal bodies, which exhibited altered morphology. The assembly of basal bodies was restored during the 24 hr recovery period, after removal of nocodazole.

Colchicine and nocodazole did not prevent polarized migration towards the apical surface of basal bodies formed prior to drug treatment. They anchored to the plasma membrane, but the formation of cilia was strongly disturbed in the presence of the drug. Numerous cells possessed anchored basal bodies which failed to induce the formation of cilia.

The elongation of cilia was inhibited, as seen by their abnormal capping structure. In the enlarged tip, microtubules diverged. In contrast, these very short cilia possessed a mature ciliary necklace which was constructed during drug treatment. Differentiation of this membrane ciliary structure appeared to be unrelated to axoneme growth.
Organization of actin microfilaments in the apical border of oviduct ciliated cells
Authors: Chailley Bernadette , Nicolas Gisèle , Lainé Marie‐Christine
Published: February 2012

Summary— Actin microfilaments were localized in quail oviduct ciliated cells using decoration with myosin subfragment S1 and immunogold labeling. These polarized epithelial cells show a well developed cytoskeleton due to the prosence of numerous cilia and microvilli at their apical pole. Most S1‐decorated microfilaments extend from the microvilli downward towards the upper part of the ciliary striated rootlets with which they are connected. From the microvillous roots, a few microfilaments connect the proximal part of the basal body or the basal foot associated with the basal body. Microfilament polarity is shown by S1 arrowheads pointing away from the microvillous tip to the cell body. Furthermore, short microfilaments are attached to the plasma membrane at the anchoring sites of basal bodies and run along the basal body. The polarity of these short microfilaments is directed from the basal body anchoring fibers downward to the cytoplasm. At the cell periphery, microfilaments from microvillous roots and ciliary apparatus are connected with those of the circumferential actin belt which is associated with the apical zonula adhaerens.

Together with the other cytoskeletal elements, the microfilaments increase ciliary anchorage and could be involved in the coordination of ciliary beating. Moreover, microvilli surrounding the cilia probably modify ciliary beating by offering resistance to cilium bending. The presence of microvilli could explain the fact that mainly the upper part of the cilia appanars to be involved in the axonemal bending in metazoan ciliated cells.
Effect of streptozotocin‐diabetes on rat liver asialoglycoprotein receptor turnover: in vivo degradation and in vitro biosynthesis
Authors: Couderc Elisabeth , Appel Martine , Slama Abdelhamid , Feger Jeanne
Published: February 2012

Summary— — The metabolic turnover of the Hepatic Binding Protein (HBP) was investigated in streptozotocin‐diabetic rats. We have already shown that diabetes induced a decreased ligand binding capacity while the immunoreactive HBP was normal. To explore the eventual modifications due to diabetic state upon the turnover of HBP, we followed the in vivo degradation of HBP and its biosynthesis in vitro. After in vivo labelling with l‐[3H] leucine and purification of HBP from rat livers, we found a 20% decrease in diabetic HBP half‐life. By in vitro incubations of freshly isolated hepatocytes and a 2 h‐pulse in the presence of l‐[35S] methionine, we showed that diabetes provokes an increased uptake of l‐[35S] methionine in hepatocytes allowing an augmented synthesis of HBP although the l‐[35S] methionine incorporation into total proteins was less efficient.
Methionine‐independence, tumorigenicity and oncogene expression of rat hepatocarcinoma cells
Authors: Cassingena Roland , Lafarge‐Frayssinet Christiane , Painchault Véronique , Estrade Simone , Nardeux Pierre , Frayssinet Charles
Published: February 2012

Summary— Methionine‐dependent (Met−Hcy+) revertant sublines were isolated from a methionine‐independent (Met+Hcy−) rat hepatocarcinoma cell line (LF). Characterization of these sublines has shown that long‐term culture in methionine‐deprived medium significantly decreases their ability to grow in vitro, their tumorigenicity in new‐born syngeneic animals and their level of transcription of 3 oncogenes (c‐Ki‐ras, c‐Ha‐ras, c‐myc) involved in hepatic growth. These data strongly support a relationship between methioninedependence and ability to grow in vivo as tumors. A shift in methionine‐supplemented medium for several cell generations of the various sublines grown in methionine deprived medium, has revealed that under these conditions, the cells maintain a diminished in vitro growth and tumorigenic capacity, despite an increased transcription of c‐Ki‐ras, c‐Ha‐ras and c‐myc. This points out the complexity of the relationship between the level of activity of some oncogenes and the expression of the malignant phenotypes.
Distribution of sugar‐binding sites within interphase nuclei and mitotic chromosomes of a human cell line
Authors: Bourgeois Claire A , Monsigny Michel
Published: February 2012

Summary— Using gold labelled neoglycoproteins containing either α‐d‐glucose, N‐acetyl‐β‐d‐glucosamine, α‐d‐mannose, 6‐phospho‐α‐d‐mannose, and α‐l‐fucose (BSA), we investigated their intranuclear binding sites in the TG human cell line. Although gold‐labelled BSA did not give any noticeable labelling, the presence of 1% free BSA in the medium containing the gold labelled neoglycoproteins was revealed to be a key factor of the labelling. During interphase in the presence of free BSA most of the labelling was detected in the nucleoplasm. The border of the condensed chromatin, known to be the site of hnRNA synthesis as well as the interchromatin areas enriched in RNPs were labelled. Condensed chromatin also contained binding‐sites. The nucleolus was seen to present low labelling in comparison with the labelling observed over the nucleoplasm. These nucleolar binding sites were located both in the dense fibrillar and granular components. No labelling could be detected over the fibrillar centers which are very conspicuous in this cell line. During mitosis sugar‐binding sites were observed over the chromosomes. Data reported here show for the first time that lectin‐like proteins and chromatin components are colocalized both during interphase and mitosis. In addition, within the nucleolus the presence of sugar‐binding proteins was seen to be restricted to the dense fibrillar and granular components.
The nucleolonema of plant and animal cells: a comparison
Authors: Deltour Roger , Motte Patrick
Published: February 2012

Summary— Depending on the author and the animal or plant origin of the material under study, the term “nucleolonema” is used in different contexts and thus indicates nucleolar ultrastructures that are different. In this paper, we attempt to clarify this state of affairs and to propose a definition for the plant cell nucleolonema
In situ response to vinka alkaloids by microtubules in cultured post‐implanted mouse embryos
Authors: Meininger Vincent , Binet Stéphane , Chaineau Eric , Fellous Arlette
Published: February 2012

Summary— The response of microtubules to treatment with vinca alkaloids was investigated in vivo and in situ in the embryonic nervous system of mice. For this purpose we used rotatory cultures of post‐implanted embryos in a serum medium containing the alkaloid combined with immunofluorescence using a tubulin‐specific polyclonal antibody on high molecular weight polyethylene glycol embedded semithin sections.

In mitotic cells, kinetochore microtubules were seen to be more resistant to the action of vinca alkaloids than interpolar microtubules. Increasing drug concentrations induced an increasing rate of mitosis together with an increasing rate of disassembly of the cytoplasmic microtubule complex, suggesting a probable relation between these events.

In bipolar neuroepithelial cells at interphase, a small pool of microtubules was resistant to the vinca alkaloids. These microtubules were located near the centriolar apparatus associated with the primary cilium; they were short, curly and bent. Disruption of the cytoplasmic microtubule complex did not alter the shape of the bipolar neuroepithelial cells.

In the axonal profiles, a drug‐stable pool of microtubules were not disrupted by the alkaloids and were also short. They seem to act as microtubule organizing centres.

These observations suggest vinca alkaloids seem to act in vivo much more by inducing, at a given concentration, the disruption of a particular group of microtubules without altering the others. The fact that these drugs affect the number, but not the length, of the microtubules raises the hypothesis that these drugs act on microtubules by a mechanism similar to that described as “dynamic instability”.
The culture of human skin fibroblasts on microcarriers in the presence of serum substitute: Ultroser G
Authors: Miech Gilles , Myara Isaac , Mangeot Monique , Gautier Marthe , Lemonnier Alain
Published: February 2012

Summary— The effects of the substitution of serum by Ultroser G on human skin fibroblasts cultured on microcarriers were analysed. Cultures could not be established on microcarriers in the presence of Ultroser G. However, microcarrier cultures started in the presence of 10% foetal calf serum, and transferred to 2% Ultroser G after 7 days resulted in high cell densities.
Location of ribosomal genes in CHO cells; in situ hybridization with a non‐isotopic DNA probe on G‐banded chromosomes*
Authors: Azum‐Gelade Marie‐Claire , Noaillac‐Depeyre Jacqueline , Gas Nicole
Published: February 2012

Summary— A novel in situ hybridization using sulfonated probes is described. This non‐radioactive approach, which employs chemically modified DNA and immunocytochemical procedures, is compatible with pre‐G‐banding and allows a rapid localization of the hybridized sequences on chromosomal spreads with a high spatial resolution. Using this technique was have localised the Chinese hamster ribosomal genes in the telomeric region of ten chromosomes, and among them in the subtelomeric q region of the Z5 chromosome. These results are discussed, the genetic markers confirming and locating the origin of Z group chromosomes by rearrangements of Chinese hamster chromosomes.