Leishmania (L.) amazonensis: fusion between parasitophorous vacuoles in infected bone-marrow derived mouse macrophages.

[Leishmania(L.)] amazonensis amastigotes reside in macrophages within spacious parasitophorous vacuoles (PVs) which may contain numerous parasites. After sporadic fusion events were detected by time-lapse cinemicrography, PV fusion was examined in two different models.

Contraction of cultured human uterine smooth muscle cells after stimulation with endothelin-1.

To our knowledge, the problem of how to maintain isolated smooth cells in a "contractile" phenotypic state without deviation after subculturing has yet to be resolved. The present study characterized the in vitro contractile response of human uterine smooth muscle cell to endothelin-1, which induces contractions in isolated uterine strips. Contractile effects were qualitatively investigated using silicone rubber substrata.

Biogenesis of Leishmania-harbouring parasitophorous vacuoles following phagocytosis of the metacyclic promastigote or amastigote stages of the parasites.

Protozoan parasites Leishmania alternate between a flagellated promastigote form and an amastigote form. In their mammalian hosts, Leishmania survive and multiply in macrophages. Both forms can be internalized by these host cells at different stages of the infectious process and eventually establish themselves within parasitophorous vacuoles exhibiting phagolysosomal properties.

Nuclear envelope disorganization in fibroblasts from lipodystrophic patients with heterozygous R482Q/W mutations in the lamin A/C gene.

Dunnigan-type familial partial lipodystrophy (FPLD), characterized by an abnormal body fat redistribution with insulin resistance, is caused by missense heterozygous mutations in A-type lamins (lamins A and C). A- and B-type lamins are ubiquitous intermediate filament proteins that polymerize at the inner face of the nuclear envelope. We have analyzed primary cultures of skin fibroblasts from three patients harboring R482Q or R482W mutations.

Regulation by phagic T-lymphocytes of a (pluripotent?) organ stem cell present in adult human blood. A beneficial exception to self-tolerance.

Stem cells isolated from adult human blood are able to give rise to several different kinds of cell types such as mesenchymal cells, including striated muscle cells, hepatocytes, and endothelial-cells. Because independently studied by authors whose interests focused on particular tissue types, these stem cells have been described as different. However, they might well represent one unique population of pluripotent stem cells in homeostatic equilibrium with the 'reserve' stem cells buried in organs.

Involvement of the [uPAR:uPA:PAI-1:LRP] complex in human myogenic cell motility.

The urokinase-type plasminogen activator system is a proteolytic system involved in tissue remodeling and cell migration. At the cell surface, receptor (uPAR)-bound urokinase (uPA) binds its inhibitor PAI-1, localized in the matrix, and the complex is internalized by endocytic receptors, such as the low-density lipoprotein receptor-related protein (LRP). We previously proposed a nonproteolytic role for the uPA system in human myogenic cell differentiation in vitro, i.

On the track of a human circulating mesenchymal stem cell of neural crest origin.

The neural markers present in the normal circulating monocytoid cells able, in pathological situations, to trans-differentiate into different mesenchymal-type cells, confirm the hypothesis previously raised that these cells derive from the neural crest. In culture, the normal cells display a great plasticity very reminiscent of microglial cells in culture. Almost a quiescent cell in normal individuals, this monocytoid cell shows its division potentialities in pathological situations of fibrosis and cancer (chondrosarcoma) where it is found to spontaneously proliferate.

Interactions of elastin fibers with fibroblasts a time-lapse cinemicrographic study.

Adhesion of cells to the extracellular matrix is mediated by structural glycoproteins such as fibronectin and laminin, and also elastonectin, whose role is to ensure binding of elastin fibers to cells. Interactions between elastin fibers and human skin fibroblasts cultured in a Rose chamber were investigated by using cinemicrography to observe elastin fiber attachment, detachment, and displacement over a five-day period. Elastin fiber displacement over the cell layer resulted in aggregation, which was measured using morphometry.

In vitro culture of human dental pulp cells: some aspects of cells emerging early from the explant.

Cells emerging from a dental pulp explant were studied in order to elucidate the origin of precursor cells implicated in the formation of reparative dentin in vivo. Such cells observed at the very early stage of culture (days 5-10) were different from fibroblast-like cells obtained after one subculture. These early cells were round or elongated, with thin spinous processes, highly mobile, and contained numerous lipid vesicles.

TGF beta 1 promotes actin cytoskeleton reorganization and migratory phenotype in epithelial tracheal cells in primary culture.

In the present study we have investigated the effects of transforming growth factor beta (TGF beta 1) on rabbit tracheal epithelial cells in primary culture, with respect to cell proliferation and differentiation. Epithelial tracheal cells derived from an explant plated on an extracellular matrix, formed an outgrowth resulting from cell division and cell migration. TGF beta 1 treatment produced a negative effect on cell proliferation, but in contrast, promoted a marked enhancement of cell migration and increase in outgrowth surface.

Human granulosa cells in culture exhibit functional cyclic AMP-regulated gap junctions.

Numerous gap junctions exist between granulosa cells, between cumulus cells and between cumulus cells and the oocyte. They may play a role in the regulation of both follicular development and oocyte status. We used primary cultures of human granulosa cells to study the molecular nature and functionality of these gap junctions.

Fusion of Leishmania amazonensis parasitophorous vacuoles with phagosomes containing zymosan particles: cinemicrographic and ultrastructural observations.

Studies on fixed preparations have shown that vacuoles containing zymosan (Z) particles internalized by infected macrophages can selectively fuse with the large parasitophorous vacuoles (PVs) that shelter Leishmania amazonensis. To examine the kinetics of vacuolar fusion in individual cells, particles were followed by time-lapse cinemicrography from their uptake to their entry in a PV. Newly formed Z-containing vacuoles moved centripetally and, if they contacted a PV, the two vacuoles remained closely apposed for variable, often extended, periods of time before they eventually fused.

Cell shape change reveals the cyclic AMP-mediated action of follicle stimulating hormone, human chorionic gonadotrophin and vasoactive intestinal peptide in primary cultured human granulosa-lutein cells.

Granulosa cells are known to be the site of action of various hormones and agents that regulate ovarian function. This study was conducted to evaluate the effects of gonadotrophins, vasoactive intestinal peptide (VIP), prostaglandin (PG) F2 alpha and angiotensin II on the cyclic AMP (c-AMP) signalling transduction pathway in human granulosa-lutein cells. Exposure to agents that elevate c-AMP or mimic c-AMP action caused the cells to become rounded in a process that was rapid and reversible.

Blockage of urokinase receptor reduces in vitro the motility and the deformability of endothelial cells.

The binding of urokinase (u-PA) to its cell surface receptor (u-PAR) is critical for tumor cell invasion. Here, we report that the distribution of this binding by a u-PAR antagonist ATF-HSA inhibits in vitro the motility of endothelial cells in a dose-dependent manner. This inhibition was also observed when the cells were first stimulated with potent angiogenic factors, including bFGF or VEGF.

Protein kinase A phosphorylation of RhoA mediates the morphological and functional effects of cyclic AMP in cytotoxic lymphocytes.

We have observed that stimulation of human natural killer cells with dibutyryl cAMP (Bt2cAMP) reproduced the effects of ADP ribosylation of the GTP binding protein RhoA by Clostridium botulinum C3 transferase: both agents induced similar morphological changes, inhibited cell motility and blocked the cytolytic function. We demonstrate here that cAMP-dependent protein kinase A (PKA) phosphorylates RhoA in its C-terminal region, on serine residue 188. This phosphorylation does not affect the ability of recombinant RhoA to bind guanine nucleotides, nor does it modify its intrinsic GTPase activity.

Urokinase receptor mediates mechanical force transfer across the cell surface.

The tripartite complex formed by the urokinase receptor, urokinase, and its inhibitor is an enzymatic system that controls plasmin formation involved in degradation of extracellular matrix proteins. With the use of magnetic twisting cytometry with urokinase-coated ferromagnetic beads, we applied mechanical stress directly to the urokinase receptor on the surface of human myogenic cells in culture. The stiffness and the stiffening response measured through the urokinase receptor resembled those of integrins, which are linked mechanically to the cytoskeleton.

Establishment and characterization of a mouse Schwann cell line which produces myelin in vivo.

A Schwann cell line (MSC 80) was established from purified mouse Schwann cell cultures using large doses of serum. MSC 80 cell line is an aneuploid cell line which has a doubling time of 17 hr and has been maintained through more than 110 passages. Most of MSC 80 cells are of bipolar or stellate (3-5 processes) shape.

Microcinematographic and autoradiographic kinetic studies of bone cell differentiation in vitro: matrix formation and mineralization.

Matrix formation and mineralization have been reported in vitro with cells isolated from rat calvaria bones by collagenase digestion (Nefussi et al., 1985). In the current study, kinetics of bone nodule formation and osteoblastic cell differentiation were studied in this in vitro system using an improved microcinematographic device and flash and follow-up labeling autoradiographic techniques.

Leishmania mexicana: destruction of isolated amastigotes by amino acid esters.

Amino acid esters can destroy intracellular as well as isolated amastigotes of Leishmania mexicana amazonensis. In the present study we examined, using a tetrazolium reduction assay, the toxicity of the esters for amastigotes isolated from mouse lesions. Parasite killing by the "prototype" compound L-leucine methyl ester at 1 mM concentration and at pH 7.

Correspondence of two nuclear networks observed in situ with the nuclear matrix.

In resting lymphocytes, three well defined networks are observed and attempts were made to superimpose them upon the networks described in isolated nuclear matrices. These three nuclear structures are seen after DNase and RNase treatment. They are digested by pepsin but their sensitivity to this enzyme is different.

The spatial organization of nucleolar DNA in phytohemagglutinin-stimulated lymphocytes of the guinea pig.

The ultrastructural changes in the spatial organization of nucleolar DNA in lymphocytes during phytohemagglutinin (PHA) stimulation was studied in guinea pigs by means of oxidized diaminobenzidine (DAB) at low pH as a differentially contrasting stain for nucleic acids and by the use of reconstruction of serial sections. The extended DNA filaments situated inside the fibrillar area originate from a large aggregation of heterochromatin, which is closely associated with the nucleolus, and from the perinucleolar shell of condensed chromatin. It is suggested that these two distinct regions of chromatin might be associated with different functions.

Nucleolus and large nucleolar aggregates of condensed chromatin in interphase nuclei of L 929 cells.

Three-dimensional reconstructions show that the nucleoli from L 929 cells are associated with one or several large aggregates of chromatin displaying a honeycomb-like structure. The form and the number of both nucleoli and honeycomb structures vary as the cells emerge from the resting state and enter exponential growth. Quantitative data show that the number of honeycomb structures decreases as the number of nucleoli diminishes; both numerical regressions are significant.

Localization of the 70 000 dalton heat-induced protein in the nuclear matrix of BHK cells.

The exposure of exponentially growing BHK cells to supranormal temperatures (41-44 degrees C, for 15 min to 1 h) induces the synthesis of a new set of proteins, the heat shock proteins, while the synthesis of proteins made before heat shock is repressed at 43 degrees C. Among the two major heat shock proteins induced, of molecular weight 70 K and 68 K, only the 70 kD protein is found bound to the nuclear matrix. This protein is resolved differently from the normal matrix proteins by isoelectric focusing and, when blotted, does not react with antibodies directed against nuclear matrices.

[Nucleolar lesions induced by ribonuclease in living cultured cells].

The nucleolar lesions provoked by the action of ribonuclease (RNase) on living chick embryo fibroblasts were studied by means of microcinematographic analysis and at the ultrastructural level using oxidized diaminobenzidine as a differentially contrasting stain for nucleic acids. This study has shown that the induction of nucleolar dispersion by RNase was only the beginning of a series of discrete steps. The following sequences are described: dispersion of the nucleolus into fragments, their reassembly, and the emission of spherules which appear of chromatin origin.