Biomedical subjects
Publications and source records attributed to B Michel.
We report seven cases of transient acantholytic dermatosis (Grover's disease) to exemplify a causal association with heat and sweating. The excessive heat and sweating was related to the use of a hot tub, a hot water bottle, a steam bath, an electric blanket, the prolonged wearing of a polyester suit, and postoperative bed confinement.
Recombination efficiency between transforming and resident plasmids was 100 times higher in Bacillus subtilis protoplasts than in Escherichia coli competent cells. In both systems it varied with the square of the length of the sequences common to two plasmids within the studied range 0.96-8.8 kb in B. subtilis, 0.72-3.9 kb in E. coli. The observed exponential dependence may be characteristic of recombination occurring within a relatively short interval bordered by relatively long heterologous regions.
Complex formation between cytochrome c oxidase and cytochrome c perturbs the optical absorption spectrum of heme c and heme a in the region of the alpha-, beta, and gamma-bands. The perturbations have been used to titrate cytochrome c oxidase with cytochrome c. A stoichiometry of one molecule of cytochrome c bound per molecule of cytochrome c oxidase is obtained (1 heme c per heme aa3). In contrast, a stoichiometry of 2:1 was found earlier using a gel-filtration method (Rieder, R., and Bosshard, H.R. (1978) J. Biol. Chem. 253, 6045-6053). From the result of the spectrophotometric titration and from the wavelength position of the perturbation signals it is concluded that cytochrome c oxidase contains only a single binding site for cytochrome c which is close enough to heme a to function as an electron transfer site. The second site detected earlier by the gel-filtration method must be remote from this electron transfer site. Scatchard plots of the titration data are curvilinear, possibly indicating interactions between cytochrome c-binding sites on adjacent monomers of dimeric cytochrome c oxidase. The relationship between cytochrome c binding and the reaction of cytochrome c oxidase with ferrocytochrome c is discussed.
Twelve cases of mental nerve neuropathy observed over a 20-month period are reported. Although benign in appearance, the condition frequently is of somber significance being most often, and sometimes initially, associated with malignant diseases. Cancer, and in particular breast cancer, is the most common cause, but malignant blood diseases may also be responsible. Metastatic lesions of the mandible and/or the mental nerve most probably explain why paresthesia and pain in the chin are relieved by local radiotherapy, combined or not with chemotherapy.
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Bacillus subtilis competent cells harboring plasmid pUB110 were transformed by plasmids unable to replicate in this host but carrying segments of pUB110, 260 to 4500 bp long. Recombinants between the incoming and the resident plasmids were found in the transformed cells. Transforming efficiency of the incoming plasmids depended strongly on their molecular form and the length of their region homologous with the resident plasmid. It increased with the fourth to fifth power of that length for monomers having at least 900 bp of homology. Activity of monomers having less than 900 bp homology was too low to be measured in our experiments. Transforming efficiency of dimers was much greater than that of monomers, and varied with the square of the length of the homologous region. These results indicate that dimeric and monomeric plasmid molecules are processed differently during transformation of B. subtilis competent cells.
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We have constructed plasmids carrying direct internal repeats 260-2000 bp long. Monomers of such plasmids transformed Bacillus subtilis competent cells. The efficiency of transformation varied with the square of the length of repeats. The transformed clones harbored either the entire transforming plasmid and the plasmid arising by recombination between the repeats, or only the latter plasmid. Internally-repeated plasmids linearized by in vitro cleavage with restriction endonuclease could transform, yielding clones which exclusively harbored a plasmid resulting from recombination between the repeats. When the transforming plasmid carried repeats which differed slightly, conversion of one repeat into the other could occur. The following model of plasmid transformation accounts for these data: (1) plasmid DNA is cleaved and rendered linear in contact with competent cells; (2) a linear, at least partially double-stranded plasmid molecule is introduced or formed by repair within the cell; (3) a circular viable plasmid is produced by recombination between repeats carried on this molecule; (4) alternatively, a viable plasmid is produced by repairing the cut within one of the repeats by DNA synthesis which uses the other repeat as a template.
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Human skin may be considered as a target organ for androgens, since events characteristic of androgen action have been described in this tissue, as well as in cultured human skin fibroblasts. The culture of human skin fibroblasts gives the opportunity to work on living cells, under controlled conditions, in a renewable material from a single skin biopsy. Using this method, we showed the presence od DHT-receptors in the human fetus and we studied the ontogenesis of androgen receptors in relation to sexual differentiation. In the neonatal period, the physiological T rise was not concurrent with a variation in sex skin androgen receptors. The evolution of DHT binding during puberty is now under investigation. These data suggest that the androgen receptor is not modulated by plasma androgens. Androgen receptor determination is of value in defining the biochemical defects involved in partial and complete androgen insensitivity syndrome (twenty-six cases in our study). In idiopathic hirsutism, DHT binding is used to detect an eventual local hypersensitivity. Fibroblast cultures have also been shown to be an excellent model for the screening of compounds which might block the expression of androgen action by competing for the androgen receptors. Cultured skin fibroblasts are a valuable model for the study of androgen and antiandrogen action in human skin.
cAMP and cGMP production was determined in normal and psoriatic (involved or uninvolved) epidermis. After homogenization, epidermal strips were incubated with saturating concentrations of ATP or GTP, respectively, for cAMP and cGMP production. Cyclic nucleotides were measured by radioimmunoassay before and after 5, 10, 20 min of incubation. The kinetics of cAMP and cGMP production were linear during the 20 min of incubation. Comparison of normal skin, uninvolved and involved psoriatic skin, prior to and after 20 min of incubation showed the following results: cAMP levels were significantly higher in normal skin than in psoriatic skin at zero time (p less than 0.01) and after incubation (p less than 0.05). cGMP levels were not significantly different in the three tissues at zero time. After incubation, psoriatic involved epidermis exhibited a higher production of cGMP than normal skin (p less than 0.05). Thus, the ratio cAMP/cGMP was higher in normal skin than in psoriatic skin at the basic level (p less than 0.05) and after incubation (p less than 0.01). These results indicate an imbalance in cyclic nucleotides metabolism in psoriatic skin without a significant difference between uninvolved and involved epidermis.