Biomedical subjects

R Christen

Publications and source records attributed to R Christen.

At least 55 records · Page 3Linked to original sources

PubMed1995

Roseobacter algicola sp. nov., a new marine bacterium isolated from the phycosphere of the toxin-producing dinoflagellate Prorocentrum lima.

We describe a new species on the basis of phenotypic characteristics and the results of an analysis of small-subunit rRNA sequences. Three strains of this organism were isolated from a culture of the toxin-producing dinoflagellate Prorocentrum lima. These bacteria are gram-negative, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37 degrees C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase, beta-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growth. They grow only when glucose, trehalose, saccharose, fructose, maltose, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketogluconate, glutamate, or shikimate is present as a sole carbon source. The three strains have identical small-subunit rRNA sequences. A phylogenetic analysis of these sequences revealed that these bacteria belong to the alpha subdivision of the Proteobacteria and that they form a distinct and robust monophyletic group with Roseobacter denitrificans and Roseobacter litoralis. This result and the general phenotypic characteristics of the organisms place them in the genus Roseobacter, although they do not produce bacteriochlorophyll a, in contrast to previously described Roseobacter species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Corynebacterium argentoratense sp. nov., from the human throat.

A new Corynebacterium species, Corynebacterium argentoratense was isolated from the throats of four human patients. It is characterized by the presence of chemotype IV, a cell wall, corynomycolic acids, and a G+C content ranging from 60 to 61 mol%. Strains belonging to this species exhibit high levels of DNA relatedness as determined by DNA-DNA hybridization experiments (S1 nuclease procedure) but no close DNA relatedness with related Corynebacterium species. Phylogenies based on comparative analyses of nearly complete small-subunit rDNA sequences confirmed the inclusion of this new species within the genus Corynebacterium and grouped it in a cluster with C. diphtheriae, C. ulcerans, C. pseudotuberculosis, and C. kutscheri. PCR experiments revealed an absence of the gene coding for diphtheria toxin. This new species can be identified by its mycolic acid pattern, fermentation of sugars, and enzymatic activities. Strain IBS B10697 (CIP 104296) is the type strain of C. argentoratense.

Amidohydrolases↗

PubMed1995

Phylogeny of the genus Corynebacterium deduced from analyses of small-subunit ribosomal DNA sequences.

We determined almost complete small-subunit ribosomal DNA sequences of 50 reference strains belonging to the genera Corynebacterium, Rhodococcus, and Gordona and compared these sequences with previously published sequences. Three phylogenetic methods (the neighbor-joining, maximum-likelihood, and maximum-parsimony methods), as well as a bootstrap analysis, were used to assess the robustness of each topology which we obtained. The results of comparative phylogenetic analyses confirmed that the genera Corynebacterium, Dietzia, Gordona, Mycobacterium, Nocardia, Tsukamurella, and Turicella form a monophyletic taxon within the phylum containing the high-G+C-content gram-positive bacteria. The genus Corynebacterium appeared to be a monophyletic unit whose members could be divided into four major clusters. The validity of the genus Turicella is doubtful since members of this genus clearly belong to the genus Corynebacterium. The variability of chemotaxonomic characteristics within the genus Corynebacterium suggests that small-subunit ribosomal DNA sequence analysis is probably the most straightforward method for confirming that a bacterium belongs to this genus.

Base Sequence↗

PubMed1995

Phylogenetic analysis of the genera Alteromonas, Shewanella, and Moritella using genes coding for small-subunit rRNA sequences and division of the genus Alteromonas into two genera, Alteromonas (emended) and Pseudoalteromonas gen. nov., and proposal of twelve new species combinations.

Small-subunit ribosomal DNA sequences were determined for 17 strains belonging to the genera Alteromonas, Shewanella, Vibrio, and Pseudomonas, and these sequences were analyzed by phylogenetic methods. The resulting data confirmed the existence of the genera Shewanella and Moritella, but suggested that the genus Alteromonas should be split into two genera. We propose that a new genus, the genus Pseudoalteromonas, should be created to accommodate 11 species that were previously Alteromonas species, including Pseudoalteromonas atlantica comb. nov., Pseudoalteromonas aurantia comb. nov., Pseudoalteromonas carrageenovoa comb. nov., Pseudoalteromonas citrea comb. nov., Pseudoalteromonas denitrificans comb. nov., Pseudoalteromonas espejiana comb. nov., Pseudoalteromonas haloplanktis comb. nov. (with two subspecies, Pseudoalteromonas haloplanktis subsp. haloplanktis comb. nov. and Pseudoalteromonas haloplanktis subsp. tetraodonis comb. nov.), Pseudoalteromonas luteoviolacea comb. nov., Pseudoalteromonas nigrifaciens comb. nov., Pseudoalteromonas rubra comb. nov., and Pseudoalteromonas undina comb, nov., and one species that previously was placed in the genus Pseudomonas, Pseudoalteromonas piscicida comb. nov. We propose that P. haloplanktis (type strain, ATCC 14393) should be the type species of the genus Pseudoalteromonas. At this time the emended genus Alteromonas is restricted to a single species, Alteromonas macleodii.

Base Sequence↗

PubMed1995

Comparison of phenotypical and molecular methods for the identification of bacterial strains isolated from a deep subsurface environment.

Vol. 61, no. 9, p. 3406: the Acknowledgments should read as follows. "This work was supported by the CNRS and by grants of the European Community and ANDRA as part of the project Archimede-Argiles and of the Direction de la Recherche et des Etudes Doctorales. V.B. was a recipient of a CIFRE fellowship." [This corrects the article on p. 3400 in vol. 61.].

Journal Article↗

PubMed1995

Comparison of phenotypical and molecular methods for the identification of bacterial strains isolated from a deep subsurface environment.

Seventy-four bacterial strains were freshly isolated from a mine gallery. Using these bacteria, we have investigated how a molecular identification based on the analysis of small subunit rDNA sequences would compare in terms of precision and reliability to a more classical comparison of phenotypical descriptions (100 morphological and physiological traits). Our data clearly showed that a phylogenetic analysis of small subunit rDNA sequences is more efficient than classical phenotypic methods for the identification of bacterial strains freshly isolated from a natural environment, because occurrences of misidentification are very much decreased by this method. The lack of rDNA sequences for many described species is probably the major cause of a few failures in molecular identification, as the completeness of the database of small subunit rDNA sequences holds much importance in the degree of uncertainty in such identifications.

Journal Article↗

PubMed1995

Corynebacterium seminale sp. nov., a new species associated with genital infections in male patients.

We studied 12 coryneform isolates having similar biochemical profiles which did not permit their assignment to any recognized taxa. Human semen was the source for seven of these strains, whereas the other strains were isolated from urethra, urine, and blood specimens of adult male patients. These bacteria were found in significant quantities (10(4) to 10(5) CFU/ml) in semen specimens from infertile male patients with the diagnosis of prostatitis. These strains had characteristics of the genus Corynebacterium, such as 60 mol% G + C in the DNA and corynemycolic acids, meso-diaminopimelic acid, arabinose, and galactose in the cell wall. Quantitative DNA-DNA hybridizations (S1 nuclease procedure) and phylogenies based on comparisons of almost-complete small-subunit ribosomal DNA sequences confirmed that these strains constitute a single new species within the genus Corynebacterium. All 12 strains showed similar phenotypic features, i.e., good growth on sheep blood agar in contrast with poor growth on the same medium supplemented with 1% Tween 80, a positive CAMP test in the presence of Staphylococcus aureus, glucose and sucrose fermentation, and the presence of beta-glucuronidase. Some strains reduced nitrate and hydrolyzed urea or esculin. These features allowed us to distinguish these strains from members of any other coryneform taxon, and the proposed name is Corynebacterium seminale with strain IBS B12915 (CIP 104297) as the type strain. The description and delineation of these strains as a new species should be useful for further studies, including evaluations of their prevalence among the normal flora and their clinical implications.

Adult↗

PubMed1994

A phylogeny of the genus Nocardia deduced from the analysis of small-subunit ribosomal DNA sequences, including transfer of Nocardia amarae to the genus Gordona as Gordona amarae comb. nov.

According to phylogenetic analyses of nearly complete small-subunit ribosomal DNA sequences, the genus Nocardia should not comprise the two species Nocardia petroleophila and Nocardia amarae. N. amarae should be reassigned to the genus Gordona as Gordona amarae. All of the other Nocardia species form a monophyletic unit, closely related to species of the genus Rhodococcus. It is proposed to revive the name 'CMN' to comprise the genera Corynebacterium, Tsukamurella, Mycobacterium, Gordona, Rhodococcus and Nocardia that form a well identified and monophyletic unit. They are all characterized by a cell wall chemotype IV with mycolic acids.

DNA, Bacterial↗

PubMed1994

[Aortic valve stenosis in the old age: clinical and echocardiographic aspects].

Among 380 consecutive patients > 70 years of age, patients with a systolic heart murmur were investigated both clinically and by doppler echocardiography. The aim of the study was to compare the validity of the clinical diagnosis of valvular aortic stenosis in elderly patients with the results of doppler echocardiography. 138/380 patients (36%) had a systolic heart murmur. 130 were investigated by doppler echocardiography. 23/130 patients with systolic murmur (18%) had moderate or severe aortic stenosis. Clinically, patients with moderate or severe aortic stenosis had a pulsus parvus et tardus of the carotid artery more often than patients with only slight or no evidence of aortic stenosis (61% vs 16%; p < 0.0001). In patients with moderate or severe aortic stenosis, the murmur radiated more often to the carotid vessels (65% vs 19%; p < 0.0001). Systolic blood pressures and pressure amplitudes were lower in patients with moderate or severe aortic stenosis (132 vs 141 mm Hg; p < 0.01; 61 vs 68 mm Hg; p < 0.001). Electrocardiography showed left ventricular hypertrophy or bundle branch block more often in patients with moderate or severe aortic stenosis (57% vs 15%; p < 0.01). We conclude that moderate or severe aortic stenosis is a frequent finding in elderly patients. Diagnosis by clinical examination may be difficult. For this reason, doppler echocardiography should be performed, especially when therapeutic consequences are to be expected from the diagnosis, such as aortic valve replacement or vasodilator treatment in the case of congestive heart failure.

Aged↗

PubMed1994

Phase I trial of cisplatin in combination with glutathione.

We treated 16 patients in a phase I trial of escalating doses of intravenous cisplatin in combination with the chemoprotectant glutathione given every 21 days. Forty-three of 44 cycles (98%) were evaluable, 85% of cycles were given on time, and the median number of cycles per patient was 2. Dose-limiting nephrotoxicity was reached at a dose of 175 mg/M2 of cisplatin. Other toxicities included ototoxicity in 7 patients (44%) and grade 3 to 4 nausea and vomiting in 15 evaluable cycles (34.9%). Myelosuppression was infrequent. An increase to 175% of standard cisplatin dose intensity is attainable with the administration of glutathione; however, toxicity is substantial and the number of tolerated cycles is limited. Alternatives to the single bolus dose schedule studied in the present trial should be explored in order to better define the clinical utility of glutathione in combination with high-dose cisplatin.

Adult↗

PubMed1994

Induction of the growth arrest and DNA damage-inducible gene GADD153 by cisplatin in vitro and in vivo.

The inability to assess the extent of tumour damage immediately following treatment is a major clinical obstacle to improving the management of cancer patients. Normally, the effectiveness of chemotherapy or radiation therapy cannot be determined for at least several weeks after treatment. We studied the increase in mRNA of the growth arrest and DNA damage-inducible gene GADD153 in human 2008 ovarian carcinoma cells in vitro and in vivo to determine whether treatment-induced increases in the level of GADD153 mRNA could be used as a marker of the extent of tumour damage. GADD153 mRNA was increased in a transient, dose-dependent manner by cisplatin (DDP) when the tumour cells were grown both in vitro and as tumour xenografts in nude mice. The magnitude of induction of GADD153 mRNA did not vary significantly between different 2008 xenografts treated with equal doses of DDP, and GADD153 mRNA induction correlated with the degree of in vitro cytotoxicity for two different schedules of drug exposure. DDP increased GADD153 mRNA levels in melanoma and head and neck xenograft models as well. We conclude that the increase in GADD153 mRNA can be used to detect tumour injury at time points as short as 24 h after administration of DDP.

Animals↗

PubMed1994

Phylogenetic analysis and assessment of the genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas deduced from small-subunit rRNA sequences.

We sequenced nearly complete small-subunit rRNAs of 54 reference strains belonging to the genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas. We then performed a phylogenetic analysis by comparing the sequences which we obtained with all other known sequences for bacteria belonging to the gamma subgroup of the Proteobacteria (thus providing a data base consisting of 70 sequences for the genera investigated), using methods such as neighbor joining, maximum likelihood, and maximum parsimony, as well as bootstrap, to assess the robustness of each topology. Our results confirmed that the family Vibrionaceae should include only Photobacterium and Vibrio species (but not Vibrio marinus); that Aeromonas species deserve family rank; and that Plesiomonas shigelloides is linked to the family Enterobacteriaceae. The genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas, together with the family Enterobacteriaceae, the family Pasteurellaceae, and probably the genus Alteromonas, form a robust monophyletic unit within the gamma 3 subgroup of the Proteobacteria.

Aeromonas↗

PubMed1994

Use of computer graphic filters for the nuclear grading of hematoxylin and eosin-stained specimens from prostatic lesions.

An inexpensive workstation is being developed to assist pathologists in diagnosing routine hematoxylin and eosin-stained slides. A linear discriminant model was applied to karyometric features of prostate lesions, and a grade according to Mostofi was determined from the discriminant values. Twenty cases, five of hyperplasia and five each of carcinoma Mostofi grades I, II and III, for a total of 600 nuclei, were selected to train the model. Computer graphic filters were constructed from the discriminant values. Each segmented nucleus has a colored frame (the graphic filter) displayed around it. The color, determined from discriminant values and correlated with the grades, ranges from green for hyperplasia, yellow for low grade, orange for medium grade and red for high grade. An additional 20 cases, 5 of hyperplasia and 5 each of the Mostofi grades, for a total of 538 nuclei, were selected to test the graphic filter. Ninety-six percent of the hyperplasia nuclei were framed in green, 84% of low grade nuclei were framed in yellow, 90% of medium grade nuclei were framed in orange, and 89% of high grade nuclei were framed in red. These results indicate the potential of the color graphic filter to show the pathologist immediate and accurate visual information about the grade of a nucleus. This method may help with the difficult diagnosis of borderline lesions and may help in making the diagnosis from scanty biopsy material.

Cell Nucleus↗

PubMed1994

Importance of different nuclear morphologic patterns in grading prostatic adenocarcinoma. An expanded model for computer graphic filters.

The aim of this work was to continue the development of an interactive workstation for the nuclear grading of prostatic lesions by including a large range of nuclear patterns. A previous model was based on four groups: hyperplasia, Mostofi grade 1, Mostofi grade 2 and Mostofi grade 3. Each group included the most common nuclear patterns of the lesions. One set used to test the model included cases showing patterns different from the typical ones of the model. Poor results were obtained for low and medium grades. A review of all the cases in our database led to the conclusion that different nuclear patterns can belong to the same "nuclear grade." Thus, in this work the model was expanded to include six groups: hyperplasia, two subgroups for Mostofi grade 1, two subgroups for Mostofi grade 2 and Mostofi grade 3. A set of 900 nuclei, 150 in each group, was selected to test the model. An additional 300 nuclei, 50 in each group, were used for a test set. The overall success rate for classifying the nuclei in the test set using the new model was 93% as compared to a rate of 71% obtained for the similar test set, described above, using the previous model. Moreover, correlating karyometric features with nuclear morphology indicated a role for nucleoli in nuclear grading. The good results obtained with large and heterogeneous sets of cases indicate that the procedures used to develop this model may be adapted for the development of models for the nuclear grading of other tumors.

Adenocarcinoma↗

PubMed1994

An algorithm for automatic tracking of nuclear boundaries.

An image segmentation algorithm, based on boundary tracking, was introduced to achieve automatic segmentation of nuclei. This will improve reliability and reproducibility for the computer-assisted grading of routinely stained material, especially from biopsies, which often offer only scanty clinical material. Nuclear grading systems using karyometric features were developed earlier. However, hematoxylin and eosin-stained tissues have proven difficult for automatic segmentation, which is a crucial part of an objective grading system. In this paper we describe an automatic tracking method that traces nuclear boundaries on the basis of edge information and local boundary features. There were two phases to the procedure. First, approximate boundaries were extracted by automatic thresholding; then, boundaries were refined through interactive tracking. The results are encouraging.

Algorithms↗

PubMed1993

Phylogenetic relationships of Cryptococcus neoformans and some related basidiomycetous yeasts determined from partial large subunit rRNA sequences.

The genus Cryptococcus was found to be heterogeneous on the basis of partial rRNA sequences. The human-pathogenic species C. neoformans, comprising 4 serotypes and having Filobasidiella neoformans and F. bacillispora as teleomorphs, was found at a relatively large distance from Filobasidium. Serotypes B and C had identical sequences, while in A and D they were different, with D closer to B and C than to A. Filobasidiella depauperata, which lacks a yeast-like anamorph, clustered with F. neoformans. The genus Filobasidium was clearly separated from Filobasidiella and clustered with C. albidus, C. kuetzingii, C. gastricus, C. lupi, C. vishniaciae, C. bhutanensis, C. aerius, C. terreus and C. ater. The latter may represent the anamorph of Filobasidium elegans. The orange to red species of Cryptococcus, as well as C. aquaticus and C. yarrowii, were found completely unrelated with these taxa, C. macerans being affiliated to Cystofilobasidium capitatum. The genus Trichosporon was found relatively homogeneous; it includes C. humicola, C. curvatus and the filamentous species Hyalodendron lignicola. Cryptococcus flavus and C. dimennae probably belong to the Tremellales, though distances between these species are large. The positions of C. laurentii and C. luteolus remains to be determined.

Base Sequence↗

PubMed1993

Chromatin texture features in hematoxylin and eosin-stained prostate tissue.

A pilot study was undertaken to determine the expression of certain nuclear features in prostatic lesions. Twenty cases, 5 of hyperplasia and 5 each of carcinoma, Mostofi grades I-III, were selected as a training set, and an additional 20 cases were used as a test set, including 5 cases of hyperplasia and 5 cases each in Mostofi grades I-III. Images of hematoxylin and eosin-stained, 4-microns paraffin sections were obtained with a JVC BY-110 three-color camera and digitized by an IBM personal computer with a Matrox MVP-AT/NP imaging board. Thirty nuclei for each case from the training set, for a total of 600 nuclei, and 10 nuclei for each case from the test set, for a total of 200 nuclei, were analyzed by quantitative cytometric software on a SUN 3/60 workstation. A linear discriminant model was used for statistical analysis. One hundred percent of the hyperplasia group, 98% of the low grade group, 92% of the medium grade group and 82% of the high grade group were classified correctly in the test set with an overall success rate of 93%. Statistically significant chromatin texture features included heterogeneity, condensation, margination, run length nonuniformity, long run emphasis, gray level nonuniformity and inertia. Area, roundness and staining intensity (total extinction) were also significant. The results with standard hematoxylin and eosin-stained tissue sections were similar to those previously obtained with Feulgen-stained material. These results indicate that routine hematoxylin and eosin-stained material offers consistent diagnostic clues.

Chromatin↗

PubMed1992

Comparative variation of morphological and molecular evolution through geologic time: 28S ribosomal RNA versus morphology in echinoids.

The comparatively good fossil record of post-Palaeozoic echinoids allows rates of morphological change to be estimated over the past 260 million years and compared with rates of molecular evolution. Parsimony analysis of morphological data, based predominantly on skeletal characteristics, and parsimony, distance and maximum likelihood analyses of molecular data, from the first 380 bases from the 5' end of the 28S rRNA molecule, for 10 species of echinoid produce congruent phylogenies. The molecular sequence chosen is demonstrably far from saturation and sister groups have divergence times ranging from about 15 to 260 Ma. Parsimony analysis allows the great majority of molecular and morphological apomorphies to be placed in one of 18 independent geological time intervals, providing a direct measure of rates of evolution for periods in the geological past. Because most molecular fixed point mutations in our sequences cannot be polarized unambiguously by outgroup comparison (making the outgroup states effectively random), distance and parsimony analyses both tend spuriously to root the echinoid tree on the longest internal branch. A topology identical to that derived from morphological data is, however, obtained using Maximum Likelihood and also parsimony analysis where outgroup rooting is restricted to more conserved regions. This is taken as the correct topology for assessing rates of evolution. Overall, both morphological and molecular changes show a moderately strong correlation with time elapsed, but a weaker correlation with one another. Statistically significant differences in evolutionary rate are found between some, but not all, pair-wise comparisons of sister lineages for both molecular and morphological data. The molecular clock rate for echinaceans is three times faster than that for cidaroids and irregular echinoids. Spearman's rank correlation test, which requires only relative magnitude of changes to be known, suggests that morphological change has a slightly better correlation with time than does molecular change, averaged over all ten species. However, when just echinaceans are considered an extremely good correlation is found between the number of molecular changes and time elapsed, whereas morphological change remains poorly correlated. Thus, molecular rates approximate to a clocklike model within restricted echinoid clades, but vary significantly between clades. Averaging results over all echinoids produces a correlation that is no better than the correlation between morphological change and time elapsed.

Animals↗