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C Steinberg

Publications and source records attributed to C Steinberg.

At least 19 recordsLinked to original sources
PubMed2006

Review of solutions for 3D hydrodynamic modeling applied to aquaculture in South Pacific atoll lagoons.

A workshop organized in French Polynesia in November 2004 allowed reviewing the current methods to model the three-dimensional hydrodynamic circulation in semi-enclosed atoll lagoons for aquaculture applications. Mollusk (e.g. pearl oyster, clam) aquaculture is a major source of income for South Pacific countries such as French Polynesia or Cook Islands. This aquaculture now requires a better understanding of circulation patterns to improve the spatial use of the lagoons, especially to define the best area to set larvae collectors. The pelagic larval duration of the relevant species (<20 days) and the size of the semi-closed lagoons (few hundreds of km2) drive the specifications of the model in terms of the spatial and temporal scale. It is considered that, in contrast with fish, mollusk larvae movements are limited and that their cycle occurs completely in the lagoon, without an oceanic stage. Atolls where aquaculture is productive are generally well-bounded, or semi-closed, without significant large and deep openings to the ocean. Nevertheless part of the lagoon circulation is driven by oceanic water inputs through the rim, ocean swells, tides and winds. Therefore, boundary conditions of the lagoon system are defined by the spatial structure of a very shallow rim (exposition and number of hoas), the deep ocean swell climate, tides and wind regimes. To obtain a realistic 3D numerical model of lagoon circulation with adequate forcing, it is thus necessary to connect in an interdisciplinary way a variety of methods (models, remote sensing and in situ data collection) to accurately represent the different components of the lagoon system and its specific boundary conditions. We review here the current methods and tools used to address these different components for a hypothetical atoll of the Tuamotu Archipelago (French Polynesia), representative of the semi-closed lagoons of the South Pacific Ocean. We hope this paper will serve as a guide for similar studies elsewhere and we provide guidelines in terms of costs for all the different stages involved.

Animals↗
PubMed2001

Benefits of lifestyle modification in the pharmacologic treatment of obesity: a randomized trial.

BACKGROUND: Weight loss medications are recommended as an adjunct to diet and exercise modification but seem to be prescribed as a monotherapy by many physicians. This practice is likely to be associated with suboptimal weight loss. METHODS: This 1-year, randomized trial compared the effects of sibutramine hydrochloride used alone (ie, the drug-alone group) to sibutramine plus group lifestyle modification, prescribed with either a 5021- to 6276-kJ/d diet (1200-1500-kcal/d diet) (ie, the drug-plus-lifestyle group) or, for the first 4 months, a 4184-kJ/d diet (1000-kcal/d diet (ie, drug-plus-lifestyle with a portion-controlled diet [the combined treatment] group). Participants were 53 women with a mean (+/-SD) age of 47.2 +/- 9.8 years and weight of 101.3 +/- 9.7 kg. At baseline, they reported the number of pounds they expected to lose at the end of treatment. RESULTS: At month 12, patients treated with the drug alone lost (mean +/- SD) 4.1% +/- 6.3% of their initial body weight compared with significantly (P<.05) larger losses in the drug-plus-lifestyle group of 10.8% +/- 10.3% and the combined treatment group of 16.5% +/- 8.0%. Women in the 2 lifestyle groups achieved a significantly (P<.05) greater percentage of their expected weight loss than those in the drug-alone group and were significantly more satisfied with the medication and with changes in weight, health, appearance, and self-esteem (P<.05 for all). Significant reductions were observed at 12 months in triglyceride and low-density lipoprotein cholesterol levels but systolic and diastolic blood pressure both increased significantly (P<.05 for all). CONCLUSION: The addition of group lifestyle modification to the pharmacologic management of obesity significantly improved weight loss and patients' satisfaction with treatment outcome.

Adult↗
PubMed2001

Toxicokinetics of atrazine in embryos of the zebrafish (Danio rerio).

Atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-triazine) is a widely used selective herbicide. Due to its persistence, it is present in many surface waters, contaminating nontarget organisms such as fish. Teratogeny of atrazine was examined during the first 48 h of zebrafish development (embryo test) and correlated to effects on the microsomal and soluble glutathione S-transferases (m-/sGST; EC 2.5.1.18). Atrazine at 4 mg/L disturbed the normal development to long pec stage, at concentrations between 10 and 20 mg/L it caused retardations in organogenesis, a slowdown of movements, and functional disturbances of heart and circulatory system. m- and sGST activities were affected by atrazine in all investigated developmental stages. Atrazine elevated the mGST activity dose dependently up to a concentration of 5 mg/L, and the sGST up to 1 mg/L. Higher atrazine concentrations caused a decrease of GST activity, especially of the sGST of the younger stages, 32 cells and 75% epiboly. This might indicate that the detoxication system itself is affected, which then gives rise to morphological abnormalities during fish development. In vitro tests were performed to purify and characterize GST-formed atrazine metabolites by the use of ESI--HPLC--MS. mGST showed higher conversion rates compared to sGST.

Abnormalities, Drug-Induced↗
PubMed2001

No enhancement in bioconcentration of organic contaminants by low levels of DOM.

The aim of the present work was to systematically study the effect of low concentrations of dissolved organic matter (DOM) on the bioconcentration of organic contaminants, in order to show whether the phenomenon of enhanced bioconcentration factors (BCFs), that has been reported in the literature, is generally found at low levels of DOM or if BCF enhancements are more likely due to a random scatter in the experimental data. The first part of the study tested the hypothesis that low levels of DOM affect the uptake kinetics of organic contaminants, leading to transient enhancements of BCFs, relative to DOM-free controls, which could have been reported as BCF enhancements in short-term studies. We found that the presence of low concentrations of two different types of DOM consistently decreased the bioconcentration of benzo[a]pyrene (BaP) in the water flea Daphnia magna at all exposure times (1-24 h), and that no transient BCF enhancements occurred. The second part of the study systematically investigated if low concentrations of DOM from a wide range of different aquatic systems can cause enhancements in the bioconcentration of organic contaminants. Water fleas were exposed to combinations of four different organic contaminants (BaP, tetrachlorobiphenyl, pentachlorophenol and naphthalene) with low concentrations of 12 different types of DOM that had been collected from various regions throughout Europe. In several of the DOM treatments, we found mean BCFs being higher than mean BCFs in the controls (especially for naphthalene). This shows that the experimental setup used in this study (and similarly in previous studies) can produce seeming BCF enhancements at low concentrations of DOM. However, statistical analyses showed that treatment means were not significantly different from control means. Thus, this systematic study suggests that the BCF enhancements that have been reported in the literature are more likely the result of random, experimental variations than the result of a systematic enhancement of bioconcentration.

Animals↗
PubMed2001

Genetic diversity of Fusarium oxysporum populations isolated from different soils in France.

The genetic diversity of soil-borne populations of Fusarium oxysporum was assessed using 350 isolates collected from six different French soils. All isolates were characterised by restriction fragment analysis of the PCR-amplified ribosomal intergenic spacer (IGS). Twenty-six IGS types were identified among the 350 isolates analysed. Five to nine different IGS types were detected in each soil. None of the IGS types was common to all of the soils. An analysis of the molecular variance based on IGS type relationships and frequency revealed that the genetic structure of the populations of F. oxysporum varied widely among the soils. Some populations were both highly diverse within the soils and differentiated between the soils. A possible relationship between the intrapopulation or interpopulation level of diversity and some external factors such as the soil type or the crop history was evaluated. A subsample representative of the diversity of the six populations was further characterised by analysing the genomic distribution of two transposable elements, impala and Fot1. One to 10 copies of the impala element were present in most of the isolates, irrespective of their soil of origin. The Fot1 element was only detected in 40% of the isolates originating from the three populations less diverse in terms of IGS types, but in 82.6% of the isolates originating from the three more diverse populations.

Journal Article↗
PubMed2000

Uptake, toxicity, and effects on detoxication enzymes of atrazine and trifluoroacetate in embryos of zebrafish.

The uptake, toxicity, and elimination of atrazine and trifluoroacetate (TFA) were studied in early life stages of the zebrafish (Danio rerio). Furthermore, the effects of these xenobiotics on soluble (s) and microsomal (m) glutathione S-transferases (GST) of zebrafish embryos were investigated using 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), and [(14)C]atrazine. [(14)C]Atrazine was taken up by the embryos within seconds, unhindered by the chorions. It accumulated in the embryos by a factor of 19 after 24 h of exposure time. LC(50) (48 h) was determined at 36.8 mg/L. At a level of 5 mg/L atrazine, activities of s and m GSTs were elevated in most stages, especially in prim 6 and long pec stage (24, 48 h after fertilization, respectively). GST activity toward atrazine was detectable only in untreated D. rerio eggs, increasing with developmental time. [(14)C]Atrazine was eliminated from the embryos between 24 and 48 h, indicating a possible metabolism to a more hydrophilic GSH conjugate. [(14)C]TFA was taken up by embryos, reaching at maximum fivefold the concentration of the incubation medium after 10 h. The chorions served no physiological protection. TFA (1 g/L) caused low elevation of the GST activity. No acute toxic effects (48 h) were observed up to 4 g/L TFA.

Animals↗
PubMed2000

A B220(-), CD19(-) population of B cells in the peripheral blood of quasimonoclonal mice.

We describe a new population of non-naive B cells in the peripheral blood of quasimonoclonal (QM) mice. Surface Ig of switched isotypes is expressed, but not B220 nor CD19. These cells are larger and denser than naive B cells but smaller than blasts or plasma cells; they do not stain with syndecan, a marker for plasma cells. Telomerase, which is usually expressed in B cell blasts, was not present in this population. We sorted the switched, idiotype-positive, B220(-) B cells from the peripheral blood of QM mice and sequenced Ig H chain and lambda L chain cDNA. There were many point mutations but no V gene replacements, gene conversions or other type of diversifications. As they express switched isotypes and have mutated their Ig genes, cells in the B220(-), CD19(-) population must have been in an immune response and we suggest that it includes the memory B cell subset.

Amino Acid Sequence↗
PubMed1999

An experimental solution for the Luria-Delbrück fluctuation problem in measuring hypermutation rates.

A cell line harboring all trans-acting elements necessary for hypermutation was transfected with a plasmid harboring the major cis-acting elements plus a green fluorescent protein gene containing a premature chain-termination codon. Transfected cells do not fluoresce unless the stop codon reverts. When a sizable cell population is purged of revertants by sorting, the frequency of mutants increases linearly with time, and there is no Luria-Delbrück fluctuation effect. Moreover, as mutant frequencies seemed to vary less than cell numbers in replicate cultures, it is suggested that hypermutation might not be coupled closely to cell division.

Cell Line, Transformed↗
PubMed1999

Activity of phase I and phase II detoxication enzymes in different cormus parts of Phragmites australis.

Enzymes of phase I and phase II of the xenobiotic detoxication pathway (ethoxyresorufin-O-deethylase, peroxidases, microsomal and soluble glutathione-S-transferases) were measured in roots, stems, and leaves of Phragmites australis, revealing different enzyme activities in these parts. Highest enzyme activities were measured in the root followed by the leaf. Enzyme activities detected in the stem were low compared with those in the root and leaf. The high detoxication capacity of the root and the leaf might be due to very high exposure to xenobiotics and to the high levels of metabolism in these cormus parts. The function of the stem of Phragmites is mainly transportation, so a high detoxication level is not useful, as indicated by the low enzyme activities.

Cytochrome P-450 CYP1A1↗
PubMed1999

Hypermutation in antibody affinity maturation.

By studying the role of mismatch repair in hypermutation at the immunoglobulin loci, the field of antibody hypermutation has been integrated into the larger area of DNA repair. Trans-acting factors - Ku70, Ku80 and possibly SWAP-70 - have been identified for the temporally related but not mechanistically related immunoglobulin heavy-chain class-switch.

Animals↗
PubMed1999

Clinical experience with the Sorin Monolyth Oxygenator at high altitude.

High altitude combined with low barometric pressure can present unique challenges during cardiopulmonary bypass (CPB), not only for the perfusionist, but also for the oxygenator. Manufacturers of cardiopulmonary devices have responded to the requests from the perfusion community with a variety of oxygenators which balance low priming volumes and low pressure drops against high gas transfer. This paper will feature the first author's clinical studies using the Sorin Monolyth Oxygenator in a selected group of patients at an altitude of approximately 5200 feet and an average barometric pressure of 634 mmHg (sea levels is 760 mmHg). A review of the 47 charts on patients requiring CPB and who met the selection criteria was performed retrospectively. To qualify for this study, the patient needed to weigh more than 91 kg. The data reviewed included type of surgery, age, weight, bypass time, crossclamp time, pump flows (l/min/m2), hematocrits pre- and post-CPB, and pressure drop across the membrane. The PaO2, PaCO2, FiO2 and sweep gas flow at hypothermia and normothermia were recorded. Data concerning oxygen transfer were obtained from the manufacturer's report to the Food and Drug Administration. All patients had adequate blood gases while on CPB. We feel that the design of the Sorin Monolyth Oxygenator met our criteria for an oxygenator: low priming volume, low pressure drop, and sufficient gas transfer to provide safe oxygenation of all patients at high altitude.

Altitude↗
PubMed1998

Mismatch repair co-opted by hypermutation.

Mice homozygous for a disrupted allele of the mismatch repair gene Pms2 have a mutator phenotype. When this allele is crossed into quasi-monoclonal (QM) mice, which have a very limited B cell repertoire, homozygotes have fewer somatic mutations at the immunoglobulin heavy chain and lambda chain loci than do heterozygotes or wild-type QM mice. That is, mismatch repair seems to contribute to somatic hypermutation rather than stifling it. It is suggested that at immunoglobulin loci in hypermutable B cells, mismatched base pairs are "corrected" according to the newly synthesized DNA strand, thereby fixing incipient mutations instead of eliminating them.

Adenosine Triphosphatases↗
PubMed1998

Meiotic synapsis in the absence of recombination.

Although in Saccharomyces cerevisiae the initiation of meiotic recombination, as indicated by double-strand break formation, appears to be functionally linked to the initiation of synapsis, meiotic chromosome synapsis in Drosophila females occurs in the absence of meiotic exchange. Electron microscopy of oocytes from females homozygous for either of two meiotic mutants (mei-W68 and mei-P22), which eliminate both meiotic crossing over and gene conversion, revealed normal synaptonemal complex formation. Thus, synapsis in Drosophila is independent of meiotic recombination, consistent with a model in which synapsis is required for the initiation of meiotic recombination. Furthermore, the basic processes of early meiosis may have different functional or temporal relations, or both, in yeast and Drosophila.

Animals↗
PubMed1998

Effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic organisms--a review.

Current knowledge on the effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic animals (water fleas, mussels, amphipods and fish) is summarized. A graphical representation of the available data gives an overview of the magnitude of the observed effects. Most of the studies have shown decreases in bioconcentration in the presence of DOM (2 to 98% relative to DOM-free controls). However, at low DOM levels, up to 10 mg/L, also enhancements of bioconcentration due to DOM, ranging from 2 to 303% have been reported. Generally, the change in BCFW (Bioconcentration factor on a wet weight basis) per mg/L DOC was most pronounced at low levels of DOC. The data also show that DOM from different sources with different characteristics and quality can lead to substantial variations in the bioconcentration of organic compounds at comparable levels of DOC. While decreases in bioconcentration have generally been attributed to a lack of bioavailability of DOM-bound chemical, no mechanisms have been proposed to explain increased uptake of xenobiotics caused by DOM.

Animals↗
PubMed1998

Molecular mechanisms involved in receptor editing at the Ig heavy chain locus.

In receptor editing, a phenomenon that has recently come to light and into favor, a rearranged VDJ or VJ gene segment encoding a variable region of an Ig chain is replaced by another. In this commentary, the molecular mechanisms involved in the editing process are examined in some detail. Editing is most likely mediated by the same V(D)J recombinase activity responsible for the formation of the original VDJ or VJ segment. An embedded heptamer, which is present near the 3' end of many VH elements, is used as the recombination signal sequence at the Ig heavy chain locus. It has been postulated that the mediation of receptor editing is the evolutionary force maintaining the embedded heptamer. Some of the evidence for and against this hypothesis is discussed.

Animals↗
PubMed1997

Critical test of hot spot motifs for immunoglobulin hypermutation.

In hypermutation at the immunoglobulin loci, some bases are much more mutable than others. The increased mutability of the hot spots has been attributed to their being embedded in short sequence motifs. Among the suggested motifs are palindromes, TAA and RGYW (i.e. A/G G C/T A/T). We have tested these proposed motifs in a transfection system in vitro, which ordinarily uses the hypermutable stop codon TAG. The stop codon TAA is not hypermutable in our system, even when embedded in the pentamer and hexamer palindromes TAATA and ATTAAT; in fact, the revertants isolated were due to deletions. Single or double base changes in an RGYW motif containing a hypermutable stop codon result in a reduction of one order of magnitude or more in point mutation frequency. When the nonamer GACTAGTAT, which includes the same RGYW motif, was moved over hundred base pairs upstream, hypermutability was reduced by an order of magnitude. Thus, while RGYW apparently is a hypermutability motif, it cannot be the sole determinant of mutability.

Animals↗