Comparative Assessment of the Cytotoxicity of Various Substrates in Organ Culture and Cell Culture: A Scanning Electron Microscopy Study

A comparative study of the behavior of chick embryo endothelial cells grown on various substrates was performed in order to establish the reliability and the limitation of both cell and organ culture methods. Following substrates were analyzed to compare these two different culture techniques: bovine serum albumin, pigskin gelatin and albumin + gelatin cross-linked by glutaraldehyde or carbodiimide, fibrin glue and negative control (Thermanox*). Parameters of cell growth and adhesion were calculated and compared with electron microscopic observations of cell morphology and of the extracellular matrix. Both culture methods provided complementary results and led to a similar classification of the biomaterials. However, the cell culture method exhibited a higher sensitivity to the surface properties of biomaterials which limited further experimentation. This was well illustrated by glutaraldehyde cross-linked protein membranes which did not support the growth of dispersed cells but enabled the formation of a cellular tissue in organ culture, thus allowing a cytocompatibility assessment. Endothelial cell morphology and extracellular matrix elaborated on biomaterials were compared to chicken blood vessels. Both methods showed that cells grown on fibrin glue and on gelatin or albumin + gelatin cross-linked by carbodiimide had a microscopic morphology similar to that of vessel wall. Organ and dispersed cell cultures provide complementary information relative to the cell behavior towards vascular prosthesis materials

Reliability of Human Fresh and Frozen Gingiva Explant Culture in Assessing Dental Materials Cytocompatibility

An explant culture of human gingival epithelium has been set up in order to provide a valuable test for evaluating the cytocompatibility of dental material s. In an attempt to supply a bank of gingiva ex plants, frozen and freshly excised specimens were cultured in parallel. Optical and scanning electron microscopy showed an early release of cuboidal cells forming a dense layer around the explants. Afterwards, cultures evolved differently . Spread cells grew and migrated more rap idly in fresh than in frozen explant cultures but their adhesion to substratum increased earlier in frozen ones. Epithelial phenotype of cells had been immunologically characterized by using a battery of monoclonal antibouies to cytokeratins (CKs). We found a time increasing expression of CKs 5, 6, 13 , 14115 , 16 and 17, whereas amounts of CKs 1, 2, 10 and 11 , specific for terminal differentiation , remained constant. The freezing procedure decreased the yield of CKs but did not modify the electrophoretic pattern . These results suggested that the differentiation of epithelial cells might proceed as in vivo. As an application, the cytocompatibility of precious (Au, Pd, Ag) and non-precious (Ni-Cr) alloys was assessed, the reference metals being Ti, which was chosen for its cytocompatibility and Cu, which was chosen for its cytotoxicity. Alloys differed by their ability to modulate cell proliferation and migration . Pd and Au exhibited a high migration potential, whereas Au-Pd and Ti allowed efficient cell proliferation but restricted migration . Reduced migration and proliferation attested the low cytocompatibility of Ag. The toxicity of Cu and Ni-Cr prevented cell migration. These result s showed the availability of this method for selecting biomaterials

Behavior of Melanoma Cells in Cell and Organ Cultures: Use of Biomaterials to Activate Cells

It is well known that cell behaviors such as adhesion, proliferation and various synthesis are initiated from transmembrane signals. This study uses biomaterials as primary messengers of the cell activation pathways, and we have analyzed the effects of two biomaterials on highly metastatic tumor cells. B16F10 melanoma cells formed heterogeneous populations whose size varied with cell differentiation. In long-term organ cultures grown comparatively on AN 69 and Cuprophan (a biomembrane known to activate cells), we found that Cuprophan increased both adhesion and proliferation of small melanin-rich cells which represented differentiated melanocyte&. In dissociated cell cultures, the rate of early cell attachment decreased on Cupropban compared to AN 69 and control Thermanox® (Nunc Inc., Naperville, IL). Scanning electron microscopy of melanocytes four hoUl11 after plating out on Cuprophan revealed only cell aggregates, comparable to the 3T3 fibroblasts aggregates previously described. Nevertheless, the production of the second messenger cyclic adenosine monophosphate (cAMP) was the same on both materials, in contrast to previous results showing more cAMP in cells on Cuprophan. Therefore, biomaterials appear to be useful tools for investigating as well attachment, growth, differentiation as signal transduction pathways of cancerous cells

Gene and genon concept: coding versus regulation: A conceptual and information-theoretic analysis of genetic storage and expression in the light of modern molecular biology

We analyse here the definition of the gene in order to distinguish, on the basis of modern insight in molecular biology, what the gene is coding for, namely a specific polypeptide, and how its expression is realized and controlled. Before the coding role of the DNA was discovered, a gene was identified with a specific phenotypic trait, from Mendel through Morgan up to Benzer. Subsequently, however, molecular biologists ventured to define a gene at the level of the DNA sequence in terms of coding. As is becoming ever more evident, the relations between information stored at DNA level and functional products are very intricate, and the regulatory aspects are as important and essential as the information coding for products. This approach led, thus, to a conceptual hybrid that confused coding, regulation and functional aspects. In this essay, we develop a definition of the gene that once again starts from the functional aspect. A cellular function can be represented by a polypeptide or an RNA. In the case of the polypeptide, its biochemical identity is determined by the mRNA prior to translation, and that is where we locate the gene. The steps from specific, but possibly separated sequence fragments at DNA level to that final mRNA then can be analysed in terms of regulation. For that purpose, we coin the new term “genon”. In that manner, we can clearly separate product and regulative information while keeping the fundamental relation between coding and function without the need to introduce a conceptual hybrid. In mRNA, the program regulating the expression of a gene is superimposed onto and added to the coding sequence in cis - we call it the genon. The complementary external control of a given mRNA by trans-acting factors is incorporated in its transgenon. A consequence of this definition is that, in eukaryotes, the gene is, in most cases, not yet present at DNA level. Rather, it is assembled by RNA processing, including differential splicing, from various pieces, as steered by the genon. It emerges finally as an uninterrupted nucleic acid sequence at mRNA level just prior to translation, in faithful correspondence with the amino acid sequence to be produced as a polypeptide. After translation, the genon has fulfilled its role and expires. The distinction between the protein coding information as materialised in the final polypeptide and the processing information represented by the genon allows us to set up a new information theoretic scheme. The standard sequence information determined by the genetic code expresses the relation between coding sequence and product. Backward analysis asks from which coding region in the DNA a given polypeptide originates. The (more interesting) forward analysis asks in how many polypeptides of how many different types a given DNA segment is expressed. This concerns the control of the expression process for which we have introduced the genon concept. Thus, the information theoretic analysis can capture the complementary aspects of coding and regulation, of gene and genon

Adsorption de protéines sur une électrode de dioxyde d’étain polarisée anodiquement en présence d’ions chlorure

L’oxydation électrochimique des ions chlorure produit l’acide hypochloreux qui est un oxydant puissant. Cette réaction est utilisée pour protéger, vis-à-vis des biosalissures, des dispositifs optiques immergés en milieu marin, la réaction se déroulant sur une électrode transparente en dioxyde d’étain. Après une séquence sous polarisation, la fenêtre optique reste exempte de salissures pendant une à deux semaines. Nous avions précédemment recherché, sans succès, la formation éventuelle de composés inorganiques chlorés. Nous étudions actuellement la possibilité d’une contribution de la matière organique ayant interagi avec l’acide hypochloreux produit sous polarisation. Celui-ci peut en effet réagir avec des molécules biologiques comme les protéines et les modifier. Nous avons choisi ici comme protéine modèle l’albumine du sérum bovin (BSA). Son adsorption sur SnO2 a été étudiée in situ à l’aide d’une microbalance à quartz en fonction de sa concentration volumique, de la concentration en ions Cl- et du potentiel appliqué. Les milieux d’étude sont soit des solutions de BSA, soit du sérum de veau fœtal SVF, additionnés de NaCl 0,5 M pour se rapprocher des conditions de l’eau de mer. Sous polarisation à +1,5 V/ECS, la BSA s’adsorbe notablement, avec un bon accord entre les mesures in situ par microbalance et ex situ, par des tests biologiques et des analyses XPS. Ces dernières révèlent la présence de chlore dans le film organique, suggérant la formation de groupements chloramine qui pourraient constituer l’agent antisalissure