Biomedical subjects

C Verge

Publications and source records attributed to C Verge.

4 recordsLinked to original sources

PubMed2007

New sample treatment for determination of linear alkylbenzene sulfonate (LAS) in agricultural soils by liquid chromatography with fluorescence detection.

A new sample-treatment procedure has been developed for determination of total linear alkylbenzene sulfonate (LAS), i.e. homologues and isomers, in agricultural soil. The procedure involves two steps, ultrasound-assisted extraction of LAS from the samples with methanol then clean-up of the methanolic extracts and preconcentration of the LAS by solid-phase extraction on two adsorbent cartridges (SAX and C18). The ultrasound-assisted procedure reduces extraction time (10 min in contrast with 6-12 h for conventional Soxhlet extraction) and requires only small volumes of organic solvent. The effect of different variables interacting in the ultrasound-assisted extraction process was studied. Finally, separation and quantification of the homologues and isomers of LAS was performed by liquid chromatography with fluorescence detection (LC-FD). 2-Octylbenzenesulfonic acid sodium salt (Na-2ØC8-LAS) was used as internal standard. The proposed method was satisfactorily used for determination of LAS in agricultural soil samples from the fertile plain of Granada (Spain).

Agriculture↗

PubMed2001

Influence of water hardness on the bioavailability and toxicity of linear alkylbenzene sulphonate (LAS).

In the present work, the influence of Ca2+ concentration on the toxicity of single cut linear alkylbenzene sulfonate (LAS) homologues was studied. Precipitation boundary diagrams for each homologue were obtained, indicating turbid and clear zones depending on the LAS and Ca2+ concentrations. The separation between transparent and turbid zones is given by the so-called precipitation line. LAS toxicity to Daphnia magna was determined at concentrations close to this precipitation line. It was observed that when Ca(LAS)2 precipitation progresses, LAS bioavailability decreases for test animals, and the toxicity diminishes even at high nominal LAS concentrations. According to the "free ion activity model" (FIAM), the toxicity of a given chemical compound is mainly due to the ionic species (Ca2+-LAS-) and not due to the precipitated molecule, Ca(LAS)2. The significance of the present study is in connection with the assessment of LAS sorption/precipitation studies in soils and sediments, where in situ toxicity is strongly influenced by Ca2+/Mg2+ ions, according to the results presented in this work.

Alkanesulfonic Acids↗

PubMed1996

Conformity of Workers' and Occupational Health Physicians' Descriptions of Working Conditions.

To determine whether workers, describing their own work, and occupational physicians, describing typical workstations, would report the same working conditions, and whether the relationships between health status and working conditions described by these two sources would be similar. An epidemiologic survey was carried out in 1987-88 in 17 poultry slaughterhouses and six canneries in France. The data were collected in two ways: workers described their own working conditions, and occupational physicians described the working conditions at workstations in the same factories. The study included 507 workers who worked at fixed workstations that had been described by the 24 occupational physicians. Health data were obtained from the workers by the physicians during their annual visits. The agreement between workers and physicians in the descriptions of seven working conditions was analyzed. On the whole, the prevalences of exposures to the seven selected working conditions estimated by the two sources were similar. Nevertheless, the observed agreement was not necessarily high. When agreement existed about specific working conditions, the relationships observed between those conditions and workers' health were generally similar for the two sources. This result was stronger for physical health problems than for mental health problems. When both sources agreed that the worker was being exposed to a risk factor, the risk estimation was higher compared with the cases of discordant judgment. This study confirms the usefulness of information provided by experts but also the necessity to interview workers themselves about their working conditions.

Journal Article↗

PubMed1996

Antiislet autoantibodies usually develop sequentially rather than simultaneously.

The goal of this study was to address whether antiislet autoantibodies appear sequentially or simultaneously before the onset of type I diabetes. We analyzed sequential serum samples from 155 siblings and offspring (aged < 7 yr) of patients with type I diabetes from the Denver Diabetes Autoimmunity Study in the Young study and from a separate group of first degree relatives (aged 2-40 yr) for autoantibodies reacting with three defined autoantigens: glutamic acid decarboxylase (GAD65), insulin, and ICA512/IA-2. The youngest age at which 1 of the 3 autoantibodies appeared was 1.1 yr, and the oldest was 60.9 yr. Of the total 26 autoantibody conversion events observed, in only 3 instances did more than 1 autoantibody appear simultaneously. Among individuals (n = 12) with sequential conversion to expression of multiple autoantibodies, anti-GAD65 autoantibodies or antiinsulin autoantibodies appeared first (4 expressed antiinsulin autoantibodies first, and 8 anti-GAD65 autoantibodies first). We conclude that antiislet autoantibodies usually appear sequentially and not simultaneously. This corroborates early suggestions that humoral autoimmunity to islets develops chronically in a process usually measured in months to years. As expression of multiple autoantibodies is associated with a high risk of progression to diabetes, and sequential appearance of autoantibodies can occur late in life, long term follow-up is necessary to fully delineate the relationship of diabetes risk to autoantibody expression.

Adolescent↗