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Biomedical subjects

D Barritault

Publications and source records attributed to D Barritault.

At least 145 records · Page 8Linked to original sources
PubMed1982

gamma Heavy chain disease in man: cDNA sequence supports partial gene deletion model.

Human gamma heavy chain disease (HCD) is characterized by the presence in serum of a short monoclonal Ig gamma chain unattached to light chains. Although most HCD proteins have internal deletions, in some the defect is NH2-terminal. The OMM gamma 3 HCD serum protein is of the latter type, having undergone an extensive NH2-terminal deletion with a sequence starting within the hinge. A cell line synthesizing the OMM protein has enabled us to study the biogenesis of the abnormal molecule. In vitro translation of isolated mRNA yields a protein containing a hydrophobic NH2-terminal leader sequence. In the intact cell, the precursor molecule is processed normally to yield a protein with an NH2-terminal sequence homologous to the beginning of the variable (V) region. The nucleotide sequence of cDNA prepared from the OMM mRNA encodes a 19-amino acid leader followed by the first 15 residues of the V region. An extensive internal deletion encompasses the remainder of the V and the entire CH1 domain. Immediately following the short V region, there is information in the cDNA for the entire normal hinge. The primary synthetic product is thus an internally deleted molecule that undergoes postsynthetic degradation to yield the NH2-terminally deleted serum protein. The structure of the OMM mRNA suggests that the protein abnormality results from a partial gene deletion rather than defective splicing.

Amino Acid Sequence↗
PubMed1981

Photocrosslinking of thiolated aminoacyl-tRNA to ribosomal RNA and proteins.

tRNA has been converted to a form that can be photoactivated by chemical modification of some of the exposed cytidine residues to thio-4-uridine A certain percentage of the modified molecules can be charged and bound to the ribosome; thiolated fMet-tRNAfMet is bound to the P-site as shown by puromycin reactivity. Near the UV irradiation produces covalent crosslinks between total thiolated AA-tRNA or fMet-tRNAfMet and the ribosome. AA-tRNA becomes crosslinked to both 30S and 50S subunits but fMet-tRNAfMet to 50S subunits alone. In each case, crosslinking of tRNA was found to be not only to ribosomal proteins, but also to rRNA. The covalent complexes appear sufficiently stable to allow identification of the proteins or rRNA sequences involved.

Escherichia coli↗
PubMed1981

Modulation of the shape of epithelial lens cells in vitro directed by a retinal extract factor. A model of interconversions and the role of actin filaments and fibronectin.

We have shown previously [1] that bovine epithelial lens cells can be stimulated to divide and elongate by a retinal extract (RE). In this report we show that the morphological response to the stimulatory factor is directly related to the target-cell shape, and we describe how the cell shape can be modulated into morphologically different types. If the cells are grown continuously from the explant in the presence of the RE factor, they keep a typical regular pavement-like epithelial shape (type I), even after serial passages. If the same cells are cultured in the absence of the factor, they become extremely irregular in shape and enlarge enormously (type II), and during serial passage elongate spontaneously to a fibroblast-like pattern. However, when type II cells are stimulated by RE, they elongate dramatically into type III cells as described in [1], provided they are stimulated at the optimal cell density. We show that the transformation of one type to another is directly under the control of RE, and we demonstrate that the changes in cell morphology are accompanied by alterations in cytoplasmic actin filaments. Type I cells contain few microfilaments, while type II cells display actin-tropomyosin polygonal fibre networks that reform during conversion to type III cells and then to elongated stress fibres. The change from type I to type II cells is also accompanied by massive accumulation of surface-associated fibronectin. We conclude that factors obtained directly from the eye have a direct ability to control morphology and proliferation of ocular cells like lens cells perhaps by modulation of cellular adhesiveness mediated by surface fibronectin and reorganization of cytoplasmic actin-based filaments.

Actins↗
PubMed1981

Is there a ubiquitous growth factor in the eye? Proliferation induced in different cell types by eye-derived growth factors.

In a previous work [1] we showed that a neutral extract of bovine adult retina RE can stimulate the growth and modify the morphology of bovine epithelial lens (BEL) cells in vitro. We were also able to demonstrate that the differences in cell shape are closely related to the cell growth properties induced by RE and are mediated by cytoskeletal protein organization as well as external proteins. In this study, we report the results of further investigations on this retinal extract. We show that it possesses all the characteristics of other growth factors such as promoting proliferation in low serum concentration or of enhancing the colony-forming efficiency of BEL cells considerably. By comparing the morphological response of BEL cells treated with RE with the response of other cells to other growth factors, we propose that the phenotypic modifications are cell specific, but not growth factor specific. We report also that RE has a broad spectrum of activity since it is able to stimulate cells from different origins and species (vascular and corneal endothelial cells, myoblasts, chondrocytes, neuroblastoma cells, and keratinocytes), but not all of them, since it can be toxic for fibroblasts. In this respect, it has an activity similar in many aspects to FGF and EGF, while it differs from them for some target cells. Its action has also been compared with the effects of retinoic acid derivatives and shown to be strikingly different. RE-like activity can be found in other ocular tissues from bovine and other species. The highest growth-promoting capacities were found in extracts of iris, pigmented epithelium with choroid, and vitreous body. The nature of all these extracts has not yet been determined. Since they are prepared in a similar way and since they have similar growth-promoting activity, we postulate that there is an ubiquitous growth factor in the eye called eye-derived growth factor (EDGF) which may play an important role in physiology and pathology of the eye.

Animals↗
PubMed1980

[Growth factors and cell cultures: a new approach for research in ophthalmology].

Tissue culture technology applied to ophtalmology has produced an extensive knowledge of ocular cell physiology. In this work, we review the various factors known to control proliferation and differentiation in lens epithelial cells and corneal endothelial cells. We discuss the role of a new ocular growth factor that we discovered in the retina and whose ubiquitous distribution suggests that it could be involved in tissue-tissue interactions.

Animals↗
PubMed1979

Reconstitution of active 30-S ribosomal subunits in vitro using heat-denatured 16-S rRNA.

30-S ribosomal subunits which have been reconstituted using heat-denatured 16-S rRNA can participate in the synthesis of lysosyme in vitro. Therefore all the information contributed by 16-S rRNA to the reconstitution process is carried in the primary sequence of this RNA. The specific protein-synthesizing activity of 30-S subunits reconstituted from 30-S subunit proteins and heat-denatured 16-S rRNA is about one third of that observed if unheated 16-S rRNA is used and is comparable to the activity of 30-S particles isolated after dissociation of 70-S ribosomes in the presence of 0.1 mM Mg2+.

Base Sequence↗
PubMed1978

Gamma heavy chain disease in man: translation and partial purification of mRNA coding for the deleted protein.

Lymphoid cells obtained from the peripheral blood of a patient with heavy chain disease have been established in long-term culture. They continue to produce a protein antigenically identical to the deleted gamma3 heavy chain disease protein found in the patient's serum. The availability of the cell line has made it possible to analyze the mRNA coding for this protein. The primary in vitro translation product is 1500-2000 daltons larger than the polypeptide portion of the cytoplasmic or secreted protein and has methionine at the amino terminus. The mRNA sediments at 15.5 S on sucrose gradients and therefore appears to be smaller than the 17S message coding for normal-sized mouse gamma chains. It contains a base sequence that codes for a hydrophobic amino-terminal peptide not found in the cytoplasmic protein. There was no evidence for the synthesis of translatable light chain message by these cells. The present data suggest that this protein results from a primary somatic genetic event that gave rise to a cell product bearing a normal aminoterminus sensitive to limited proteolytic digestion. The serum protein thus appears to begin in the hinge region but, in fact, contains a normal heavy chain initiation site.

Cells, Cultured↗
PubMed1977

Localisation of part of the binding sites of 30S ribosomal proteins S4 and S20 in a small uninterrupted fragment of 16S RNA.

Analyses of the T1 ribonuclease-alkaline phosphatase fingerprint of a continuous fragment of the 16S rRNA, 170-230 nucleotides long, isolated from the products of autodigestion of 30S ribosome subunits show that it contains a sequence near the 5'-phosphate terminus of intact 16S rRNA and corresponds to segment H'-M of this molecule as defined by Ehresmann et al [29]. Incubation of this fragment with total 30S ribosomal proteins under reconstitution conditions leads to the formation of a complex containing proteins S4, S20, and one or both of proteins S16 and S17. The stoichiometry of these proteins in the complex is discussed.

Alkaline Phosphatase↗
PubMed1975

[Nearest-neighbor relationships among 50S ribosomal proteins of E. coli].

Dimethyl suberimidate has been used to study the proximity relations between E. coli 50 S ribosomal proteins. The composition of two cross-linked protein complexes has been determined; one is a quaternary complex containg proteins L2, L20, L27 and L32-33, and the other is a ternary complex containing proteins L2, L13 and L20. The vicinity of these proteins in the ribosome is discussed.

Dimethyl Suberimidate↗