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Biomedical subjects

C Robert

Publications and source records attributed to C Robert.

At least 19 recordsLinked to original sources
PubMed1992

[Bacillary angiomatosis].

Bacillary angiomatosis (BA) is a recently described infection usually found in patients with human immunodeficiency virus disease. BA is caused by a Gram-negative coccobacillus. This organism is primarily responsible for skin lesions of the pseudo-botryomycoma type or inflammatory nodules, but it also produces fever, degradation of the general condition and visceral lesions involving the lymph nodes, the liver, the spleen and the bones. Histology shows vascular proliferation with turgid endothelial cells and mostly neutrophilic inflammatory infiltrates. BA is susceptible to many antibiotics. The authors describe the history of the disease and its clinical and histological features, discuss its differential diagnosis and principally deal with the relationship between BA and cat-scratch disease and between BA and verruca peruana. They also present the molecular biology technique which enables a genotypic diagnosis of the disease to be made, replacing a deficient phenotype.

AIDS-Related Opportunistic Infections↗
PubMed1991

Formulas for threshold computations.

Given a continuous variable S, which density functions on two subgroups omega + and omega - of a population omega are known (with for instance a higher mean value on omega + than on omega -), we first define two strategies for classification in these groups; the first one (MWC) consists in determining a threshold alpha such that classifying in omega + when S greater than or equal to alpha, in omega - otherwise, leads to the highest percentage of well-classed elements. The second one consists in choosing the most probable group, given the observed value of S. We give mathematical formulas for the thresholds involved in these two strategies when the density functions, determined by the application of the maximum entropy principle, are those of normal distributions. These formulas prove that the two considered strategies are frequently equivalent, and we give simpler formulas when the partial variances of S on omega + and omega - are unknown or approximately equal. All the formulas are adapted to the case where a cost coefficient is introduced to display the unequal seriousness of the two possible errors (misclassification in omega + or omega -). Then we consider an example, where we see that the computed thresholds can be graphically validated from empirical curves and have the same performances on the learning sample and on a test sample.

Analysis of Variance↗
PubMed1991

Strategies for graphical threshold determination.

Determining a threshold for a quantitative variable (arising in biological measurements for instance) is a common problem in medical decision making. We define seven commonly used strategies: each one leads to an optimal determination. To these strategies correspond relevant empirical curves: the ROC curve for strategies involving the sensitivity or the specificity, the predictive ROC curve (P-ROC curve) for strategies involving the positive and negative predicting values, and the well classified frequencies curve (WCF curve) for classification strategies where all misclassifications have the same importance. For one of the considered strategies, there also exists a theoretical formula for the optimal threshold, elicited within a classical probabilistic model, which gives a considerable advantage to this strategy. These strategies are applied to a stimulated example containing 702 cases, where we see that they lead to different optimal threshold values. Finally, we briefly review a practical application in the determination of thresholds for glycemia measurements, leading to the choice of one of them as the optimal one to consider in the gestational diabetes mellitus prediction.

Diagnosis, Computer-Assisted↗
PubMed1991

Analysis of the lacZ sequences from two Streptococcus thermophilus strains: comparison with the Escherichia coli and Lactobacillus bulgaricus beta-galactosidase sequences.

The lacZ gene from Streptococcus thermophilus A054, a commercial yogurt strain, was cloned on a 7.2 kb PstI fragment in Escherichia coli and compared with the previously cloned lacZ gene from S. thermophilus ATCC 19258. Using the dideoxy chain termination method, the DNA sequences of both lacZ structural genes were determined and found to be 3071 bp in length. When the two sequences were more closely analysed, 21 nucleotide differences were detected, of which only nine resulted in amino acid changes in the proteins, the remainder occurring in wobble positions of the respective codons. Only three bases separated the termination codon for the lacS gene from the initiation codon for lacZ, suggesting that the lactose utilization genes are organized as an operon. The amino acid sequence of the beta-galactosidase, derived from the DNA sequence, corresponds to a protein with a molecular mass of 116860 Da. Comparison of the S. thermophilus amino acid sequences with those from Lactobacillus bulgaricus, E. coli and Klebsiella pneumoniae showed 48, 35 and 32.5% identity respectively. Although little sequence homology was observed at the DNA level, many regions conserved in the amino acid sequence were identified when the beta-galactosidase proteins from S. thermophilus, E. coli and L. bulgaricus were compared.

Amino Acid Sequence↗
PubMed1991

[Hairy leukoplakia: current concepts].

Current data about oral hairy leukoplakia are reported. Clinical manifestations, histological and ultrastructural features and pathogenic mechanisms are firstly described. Then diagnosis are exposed. Finally, management is discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Suramin-induced differentiation of the human colic adenocarcinoma cell clone HT29-D4 in serum-free medium.

The clonal cell line HT29-D4 was able to grow in a completely defined medium containing EGF, selenous acid, and transferrin in the presence of the anti-helminthic drug suramin. In the absence of suramin, the kinetics of cell growth and the cell density obtained were dependent on the external EGF concentration. In the presence of suramin, cell density reached a plateau independent of EGF concentration above 50 ng/ml. At the morphological level, suramin allowed hemicyst formation in the cell monolayer. The cells were polarized with a well-ordered brush border facing the culture medium and mature junctional complexes that divided the cell membrane in two distinct domains. The carcinoembryonic antigen was found to be restricted to the apical membrane domain while the major histocompatibility molecules HLA-ABC were segregated within the basolateral domain. The electrical parameters of suramin-treated cells grown on permeable filters were measured and demonstrated that the cell monolayer was electrically active. These properties were never found in the absence of the drug. Moreover, the vasoactive intestinal polypeptide (VIP) was able to induce a dramatic increase in cAMP only when it was added, in agreement with the localization of the VIP receptor, in the lower compartment of the culture chamber. In conclusion we described for the first time conditions allowing the growth of functionally differentiated human colic cell monolayers in chemically defined medium. This model will contribute to a better understanding of suramin action and of the mechanisms involved in cell polarization.

Adenocarcinoma↗
PubMed1990

Age-related changes of the human skin surface microrelief.

In the present study we describe an original semi-automated image analysis method to quantitate the changes of the geometric properties of cutaneous microrelief with age. The skin surface is composed of very fine lines intersecting each other and forming polygons. The number, average size, perimeter and equivalent diameter of these polygons were quantified on replicas of 190 persons, 101 females and 89 males, from 6 months to 95 years of age. A good correlation was found between the age of the subjects and these four parameters. The evolution of these parameters was not linear but could be best described by a polynomial equation of fourth order for the number of polygons per field, and by an exponential equation for the three other parameters: average surface, perimeter and equivalent diameter of the polygons. A few details of the evolution with age of the skin surface patterns were different for males and females.

Adolescent↗
PubMed1989

[Real-time collection of obstetrical and neonatal data. 1 years' experience].

A real-time program for obstetrical and neonatal data was developed in June 1986 at the maternity hospital in Haguenau. Used routinely, this program has raised comments and controversy. With investigative questionnaires, we have attempted to evaluate how the introduction of computer sciences was perceived by the personnel as well as the patients.

Data Collection↗