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M Vasseur

Publications and source records attributed to M Vasseur.

At least 55 records · Page 3Linked to original sources
PubMed1987

Sequence of a cDNA encoding human keratin No 10 selected according to structural homologies of keratins and their tissue-specific expression.

We present here the nucleotide sequence of a 1700 bp-long cDNA encoding human epidermal keratin No. 10 (56.5 kDa). cDNA clones of the acidic keratin family were first isolated from a pBR322 human epidermal cDNA library by hybridization with a probe coding for keratin No. 14. Differential hybridization using total cDNA probes prepared from poly(A)+ RNA extracted either from epidermis (which contains keratin No. 10) and from squamous carcinoma or hepatoma cell lines (which do not express keratin No. 10) made possible the selection of clones potentially coding for keratin No. 10. The 1.7 kb sequence exhibits the characteristic features of an acidic keratin with a constant central rod domain and C-terminal variable structures. Moreover, the sequence shows extensive homologies with the cDNA of murine keratin No. 10.

Amino Acid Sequence↗
PubMed1987

Sensitivity of pancreatic beta cell to calcium channel blockers. An electrophysiologic study of verapamil and nifedipine.

Microelectrodes were used to study the comparative effects of 2 calcium channel blockers on glucose-induced electrical activity in mouse beta cells. In 2.8 mM glucose, verapamil (10(-5) M), but not nifedipine (10(-7) M), induces a silent depolarization. In 11.1 mM glucose, verapamil (10(-7) to 5.10(-5) M) induces continuous spike activity by a decrease in the maximum repolarization potential. Nifedipine (10(-10) to 10(-6) M) induces the same activity, but subsequent to a hyperpolarization of the cell at the maximal repolarization potential followed by a silent phase to the plateau potential. The 2 drugs induce a dose-dependent decrease in spike frequency without any change in spike amplitude. In 22 mM glucose exposure to nifedipine, but not to verapamil, induces a transient period of slow-wave activity. The 2 drugs induce a dose-dependent decrease in spike frequency. At higher concentrations (nifedipine greater than 10(-7) M; verapamil greater than 10(-6) M) they induce the disappearance of spikes through a decrease in amplitude. These results show that the beta cell is more sensitive to nifedipine (ED50 = 3 X 10(-8) M) than to verapamil, and that glucose stimulation increases the cell's sensitivity to verapamil (11.1 mM glucose: ED50 = 10(-5) M versus 5 X 10(-7) M in 22 mM glucose) but not to nifedipine.

Animals↗
PubMed1986

Mesenchymal-epithelial conversions induced by 5-azacytidine: appearance of cytokeratin Endo-A messenger RNA.

When mouse-teratocarcinoma-derived fibroblasts (1246 cell line) are subjected to treatment with the inhibitor of DNA methylation, 5-Azacytidine (5 AzaC), they transiently express at 55-kilodalton intermediate-filament protein recognized by the epithelial-specific monoclonal antibody, TROMA-1, although they retain a fibroblastic morphology. However, rare clones (e.g., the 1339 cell line) that permanently express the antigen recognized by TROMA-1 can be derived from the 5 AzaC-treated 1246 population, and these clones have an epithelial phenotype. In the present study, we used cloned DNA probes to demonstrate that, in 1246 fibroblasts, 5 AzaC induces the appearance of Endo-A mRNA. High levels of Endo-A mRNA were also detected in the epithelial derivative, cell line 1339. In both cases, the capping site of the Endo-A mRNA was found to be the same as that in epithelial cells which normally express this RNA.

Animals↗
PubMed1985

RNAs containing B2 repeated sequences are transcribed in the early stages of mouse embryogenesis.

An in situ hybridization technique was used to detect RNAs containing B2 sequences in the early mouse embryo. Accumulation of B2 sequences occurs early from the one cell stage. The level of B2 RNA decreases in the late two cell embryo, and then increases at the moment of second cleavage. In the blastocyst, inner cell mass cells contain more B2 transcripts than trophectoderm cells. In 7.5-day embryos the expression of B2 sequences is restricted to ectoderm and mesoderm. At all stages, transcription of the B2+ strand is greater than B2- strand. We detected B2+ RNAs in the nucleus and cytoplasm, whereas B2- RNAs were present only in the nucleus.

Animals↗
PubMed1985

Expression of the cytokeratin endo A gene during early mouse embryogenesis.

Expression of cytokeratin endo A has been analyzed during mouse blastocyst formation and embryonal carcinoma cell differentiation. To study the regulation of endo A expression, nuclease S1 mapping experiments have been performed on RNA extracted from two-cell to 7.5-day embryos. Low levels of endo A mRNA begin to be detectable in eight-cell embryos. The amount of this mRNA increases at the blastocyst stage, suggesting that endo A expression is regulated at the mRNA level during blastocyst formation. At this stage, in situ hybridization studies show that endo A mRNA is present in the trophectoderm but not in the inner cell mass. In 7.5-day embryos, endo A mRNAs are also detectable in the endoderm layer and in the amnion.

Animals↗
PubMed1985

One gene and one pseudogene for the cytokeratin endo A.

The recombinant cDNA RecXVI, which hybridizes to the endo A mRNA, detects two specific bands on a Southern blot of EcoRI-digested genomic mouse DNA. We have screened a mouse genomic library with this cDNA and isolated these two sequences. Endo A is encoded by a 7.5-kilobase gene and by a 1.6-kilobase pseudogene devoid of introns. A repetitive sequence belonging to the B2 family is located in the third intron of the gene. We have observed that transcription of B2 sequences and of the endo A gene are mutually exclusive.

Animals↗
PubMed1982

Polyoma virus mutants as probes of variety among mouse embryonal carcinoma cell lines.

Embryonal carcinoma (EC) cells are resistant to infection with polyoma virus and become permissive when allowed to differentiate. Polyoma host-range (PyEC) mutants have been selected on two embryonal carcinoma cell lines, PCC4 and F9, which differ in their differentiation potential, both in vitro and in vivo. Since PyEC mutants selected on one line failed to develop, or developed only poorly on the other, we used these two classes of mutants as probes towards several EC lines which differed in their origin and differentiation properties. From their susceptibility to either mutant, and from the effect of temperature upon the efficiency of infection, we inferred a classification of these teratocarcinoma cell lines, which is an agreement with a previous one based upon metabolic coupling. We also discussed results indicating that different EC cell lines might present steps in the process of cell determination at the embryonic level.

Animals↗
PubMed1982

Physical and biological features of polyoma virus mutants able to infect embryonal carcinoma cell lines.

Three new polyoma mutants were selected for their ability to grow on the embryonal carcinoma cell line F9. These mutants share in common an insertion of two nucleotides, a thymine and an adenine, in the noncoding region located on the late side of the origin of replication. We have found that these insertions exist in all of the other polyoma virus mutants able to grow on F9 cells (Fujimura et al., Cell 23:809-814, 1981; Katinka et al., Nature (London) 290:720-722, 1981; K. Sekikawa and A. J. Levine, Proc. Natl. Acad. Sci. U.S.A. 78:1100-1104, 1981). The region containing these insertions could be folded into a stable secondary structure which included a guanine plus cytosine (G + C)-rich stem. The adenine and thymine were inserted in such a way that they maintained the palindrome in the G + C-rich stem and were complementary in the putative secondary structure that we present here. Another class of polyoma virus mutants selected on a multipotential carcinoma cell line (PCC4-Aza) were characterized by a more complex rearrangement (deletion and duplication) which occurred in the same region. This arrangement preserved the G + C-rich palindrome and also yielded a sequence which still allowed the folding of another type of stable secondary structure. The significance of these findings is discussed.

Animals↗
PubMed1981

Polyoma DNA sequences involved in control of viral gene expression in murine embryonal carcinoma cells.

Polyoma virus can develop lytically in differentiated mouse cells, but is unable to express either early or late functions in undifferentiated early embryonic cells or in embryonal carcinoma (EC) cells of the mouse. However, the EC cells become susceptible during differentiation and then behave as do mouse somatic cells. We have recently described the isolation of a new class of polyoma virus mutant (Py EC) able to develop normally in an EC cell line (PCC4-Aza) that is capable of trigerminal differentiation in vivo but exhibits a very limited differentiation in vitro. The mutants do not grow in another EC cell line (F9) that is 'blocked'--'nullipotent' in vivo, but able to differentiate in vitro when grown in the presence of chemical inducers. Compared with their parental strain, all Py EC genomes analysed so far have an extra 20-50 bases in their HpaII-3 restriction fragment. We now describe polyoma mutants that will grow in EC F9 cells, and the sequence changes in two of them. The region involved in the mutations can be folded into a putative tRNA-like secondary structure which may be involved in the regulation of viral early transcription with respect to the state of differentiation of the host cell.

Animals↗
PubMed1981

Imbalance in brush border enzyme activities as a possible cause of hepatic dysfunction after jejunoileal bypass in the rat.

Previous work in our laboratory and in others suggest that protein malnutrition plays an important role in the pathogenesis of hepatic dysfunction after jejunoileal bypass for morbid obesity. This experimental study was undertaken to attempt to correlate hepatic dysfunction (the criterion used was the bromsulphalein clearance) to morphological and enzymatic adaptation of the functioning intestine in the rat. It was observed that the period of impaired bromsulphalein clearance is concomitant with a slight ileal morphological adaptation and especially with a period of selective adaptation of maltase and sucrase activities, whereas there is no increase in aminopeptidase activity. These data support the hypothesis that after jejunoileal bypass a preferential absorption of carbohydrates along with a protein deficiency state could occur and as in kwashiorkor it results in an impaired nutritional status, a major contributing factor to bypass-induced liver injury.

Aminopeptidases↗
PubMed1980

Temperature dependent expression of polyoma virus in murine embryonal carcinoma cells.

At 37 degrees C, undifferentiated murine teratocarcinoma cells (PCC4) are resistant to infection with SV40 and Polyoma virus. When infection is carried out at 31 degrees C, these cells become fully susceptible to a variety of polyoma virus strains, including wt, ts-a, and hr-t; they also display an increased susceptibility to polyoma virus mutants (PyE.C.) which have been selected for their ability to develop in PCC4 cells at 37 degrees C (Vasseur et al., '80). However, expression of SV40 is still restricted at 31 degrees C and no T antigen can be detected. PCC4 cells grown at 31 degrees C express the characteristic embryonal surface antigen(s), but no H2 antigen, and do not produce plasminogen activator. PyE.C. mutants and other polyoma virus strains cannot develop at 37 degrees C in nullipotent F9 embryonal carcinoma cells and restriction is not abolished at 31 degrees C. The results indicate that: i) Resistance of PCC4 cells to polyoma virus and to SV40 are not mediated by the same process; ii) loss of restriction of polyoma in PCC4 cells does not require cell differentiation; iii) F9 and PCC4 cells control polyoma virus expression through different mechanisms.

Animals↗
PubMed1980

Quantitative analysis of the mixed activating effects of the alkali metal ions on intestinal brush-border sucrase at pH 5.2.

The activation of rabbit brush-border sucrase by the alkali metal ions, Li+, Na+ and K+, was analyzed using the equations of the random-order allosteric model previously proposed for sucrase (Mahmood, A. and Alvarado, F. (1975) Arch. Biochem. Biophys. 168, 585). The alkali metals have mixed activating effects in tert-butylamine buffers at pH 5.2, including: 1. Affinity-type activation, where the apparent Km decreases as a hyperbolic function of the metal concentration. 2. Capacity-type activation, where the apparent V increases with the metal concentration. These two effects were analyzed quantitatively: firstly, by using linear transformations that allowed us to solve each partial equation separately and secondly, by iteration of the general equation, which permits treating the mixed effects as a whole. Results are consistent with the interpretation that a single metal-binding (activator) site suffices to explain the simultaneous occurrence of the two types of kinetic effect. Nevertheless, complicating factors exist that may require the postulation of additional sites for monovalent cations. In particular, the tert-butylammonium ion appears to interface with the effects of the alkali metals, especially Li+.

Allosteric Site↗
PubMed1980

Expression of polyoma early functions in mouse embryonal carcinoma cells depends on sequence rearrangements in the beginning of the late region.

Established mouse cell lines, primary cultures of mouse cells, and differentiated cell lines derived from mouse teratocarcinoma are permissive to polyoma virus. No viral early or late functions are expressed upon infection and penetration of multipotential embryonal cell lines. Polyoma mutants capable of growth on these cells were isolated and their DNA was cloned. Both the linear cloned viral DNA and a hybrid composed of mutant Bam HI (0.58) to Bgl I (0.72) 750 bp fragment (containing the origin of replication) ligated to the complementary wild-type 4.5 kb fragment are able to multiply on PCC4 embryonal carcinoma cells. The nucleotide sequence of two mutants indicated a genomic rearrangement on the late side of the origin, in which a deletion starting at nucleotides 46 (Py 204) and 77 (Py97) and terminating for both in nucleotide 107 was replaced by the duplication of a downstream late sequence starting at nucleotide 138 (Py 204) and 157 Py97) and terminating in nucleotide 220. The fact that the sequence rearrangements permit the expression of early and late functions upon infection suggests that this region participates in the control of early transcription. This control is different in embryonal and differentiated mouse cells.

Animals↗
PubMed1980

The relationship between surface tension and release of rat jejunal brush border membrane hydrolases induced by sodium deoxycholate.

Rat jejunum was perfused in vivo with sodium deoxycholate concentrations ranging from 0.125 to 4 mM. The release of total protein and some brush border hydrolases (sucrase, maltase, leucine aminopeptidase and alkaline phosphatase) was followed as a function of both the time and the deoxycholate concentration. 1. Protein and enzyme release increased during deoxycholate perfusion only at concentrations greater than 0.5 mM. For each case, a plateau was reached at 2 mM deoxycholate. 2. After removal of deoxycholate from the perfusion fluid, the rate of protein and enzyme release dropped to the control levels. Following perfusion with 0.125 mM deoxycholate, however, there was a stabilizing effect so that the release rate of sucrase, maltase and alkaline phosphatase (but not of protein and leucine aminopeptidase) was smaller than that of the controls. 3. Protein and enzyme release was correlated with the deoxycholate-induced changes in surface tension. Significant increases in the release rates began between 0.5 and 1 mM deoxycholate when the surface tension fell below 50 dynes/cm. The plateau observed at or above 2 mM deoxycholate coincided with the stabilization of surface tension at 46 dynes/cm. 4. The maximum releasing effect also coincided with the critical micellar concentration of deoxycholate (1.5-2.5 mM).

Alkaline Phosphatase↗