Biomedical subjects

J M Benoit

Publications and source records attributed to J M Benoit.

8 recordsLinked to original sources

PubMed2001

The influence of sulfide on solid-phase mercury bioavailability for methylation by pure cultures of Desulfobulbus propionicus (1pr3).

To help understand the mechanism and control of Hg uptake in Hg-methylating bacteria, we investigated the effect of sulfide on Hg methylation by pure cultures of the sulfate-reducing bacterium Desulfobulbus propionicus (1pr3). Our previous research in natural sediments has suggested that Hg methylation occurs most rapidly when sulfide concentrations favor formation of neutral dissolved Hg-S species. In this study, the chemical speciation of Hg in culture media was manipulated by growing D. propionicus across a range of sulfide concentrations, with inorganic Hg (HgI) added in the form of ground ores. A solid-phase, rather than a dissolved source of Hg, was used to simulate the controls on Hg partitioning between solid and aqueous phases found in natural sediments. Methylmercury (MeHg) production by cultures was not related to the absolute solid-phase concentration of Hg in the ores, and it was only weakly related to the dissolved HgI concentration in the medium. However, MeHg production was linearly related to the calculated concentration of the dominant neutral complex in solution, HgS degrees. Furthermore, the diffusive membrane permeability of HgS degrees, as estimated from its octanol-water partitioning coefficient, was found to be sufficient to support MeHg production by cells. The present paper expands on our previous work by providing experimental support of our hypothesis that sulfide influences methylation by affecting the speciation of dissolved HgI and its uptake via passive diffusion.

Biological Availability↗

PubMed2001

Aspects of bioavailability of mercury for methylation in pure cultures of Desulfobulbus propionicus (1pr3).

We have previously hypothesized that sulfide inhibits Hg methylation by decreasing its bioavailability to sulfate-reducing bacteria (SRB), the important methylators of Hg in natural sediments. With a view to designing a bioassay to test this hypothesis, we investigated a number of aspects of Hg methylation by the SRB Desulfobulbus propionicus, including (i) the relationship between cell density and methylmercury (MeHg) production, (ii) the time course of Hg methylation relative to growth stage, (iii) changes in the bioavailability of an added inorganic Hg (Hg(I)) spike over time, and (iv) the dependence of methylation on the concentration of dissolved Hg(I) present in the culture. We then tested the effect of sulfide on MeHg production by this microorganism. These experiments demonstrated that under conditions of equal bioavailability, per-cell MeHg production was constant through log-phase culture growth. However, the methylation rate of a new Hg spike dramatically decreased after the first 5 h. This result was seen whether methylation rate was expressed as a fraction of the total added Hg or the filtered Hg(I) concentration, which suggests that Hg bioavailability decreased through both changes in Hg complexation and formation of solid phases. At low sulfide concentration, MeHg production was linearly related to the concentration of filtered Hg(I). The methylation of filtered Hg(I) decreased about fourfold as sulfide concentration was increased from 10(-6) to 10(-3) M. This decline is consistent with a decrease in the bioavailability of Hg(I), possibly due to a decline in the dissolved neutral complex, HgS(0).

Biological Availability↗

PubMed2000

[Critical review of quality of life scales].

Methods of construction and required metrologic properties of quality of life scales are reviewed while looking for such tools in the field of urinary tract infections. To capture the subjectivity of patients, to reach a simple measure scale, to build a reliable tool, are conflicting aims. Although they appeared several years ago and are broadly spread in all medical fields, including urology, quality of life scales are still in early ages and are not always widely admitted. Quality of life scales can be criticized, but they capture specific data and are very useful in some fields. Today, there are no quality of life scales in the field of urinary infectiology.

Humans↗

PubMed1998

The biogeochemistry of an ombrotrophic bog: evaluation of use as an archive of atmosphere mercury deposition.

The utility of ombrotrophic bogs as archives of atmospheric mercury deposition was assessed with an investigation in Arlberg Bog, Minnesota, U.S.A. Since the use of ombrotrophic bogs as archives depends on the immobility of deposited trace metals, we examined the postdepositional transport processes revealed by the solid-phase distributions of mercury and ancillary metals (Fe, Al, Mn, and Pb) in this bog. We modeled metal speciation in bog porewaters as a function of pe in order to understand metal behavior in ombrotrophic peat. Specifically, we considered the effect of water movement and resultant shifts in redox potential gradients on metal retention. Our results indicate that Hg and Pb are immobile in ombrotrophic peat, so their distribution can be used to determine temporal changes in deposition. To substantiate the deposition estimates determined in this study, we emphasized the importance of confirming the validity of the dating scheme, assessing the degree of horizontal homogeneity in the accumulation record, and providing evidence for retention of Hg based on geochemical modeling. As recorded in Arlberg Bog, historic atmospheric Hg deposition increased gradually after the mid-1800s, peaked between 1950 and 1960, and may have declined thereafter. Preindustrial deposition was about 4 micrograms/m2 year and recent deposition about 19 micrograms/m2 year. The results of this study indicate that deposition at Arlberg Bog has been influenced by a regional and/or local-scale source.

Air Pollutants↗

PubMed1995

Enhancement of endotoxin-induced interleukin-10 production by SR 31747A, a sigma ligand.

SR 31747A is a new sigma ligand eliciting immunosuppressive and anti-inflammatory properties. Here, we show that SR 31747A greatly enhances lipopolysaccharide (LPS)-induced systemic release of interleukin (IL)-10, while it inhibits the secretion of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. In line with this finding, we also show by using quantitative reverse transcription-polymerase chain reaction analysis that SR 31747A increased LPS-induced IL-10 mRNA accumulation in spleen cells, whereas the level of both TNF-alpha and IFN-gamma mRNA was dramatically decreased. The enhancement of IL-10 production by SR 31747A treatment was also apparent in nude and severe-combined immunodeficient mice treated with LPS, clearly indicating that T and B cells were not involved. Finally, SR 31747A conferred protection against the lethal effect of LPS. The finding that SR 31747A strongly stimulates the synthesis of the natural anti-inflammatory cytokine IL-10, a property not observed with dexamethasone, provides new insights for the clinical use of this original compound, particularly in chronic inflammatory diseases where IL-10 is believed to be a pivotal regulatory component.

Animals↗

PubMed1984

[Recurrent cystitis and crenotherapy. 302 cases].

This article analyzes a series of 302 female patients prone to cystitis. The fact that these women were seen in a urological crenotherapy center highlights the very evolutive nature of the disease. The high rate of E coli present in the urine should be noted. Most of the women had a normal intravenous urogram and a normal endoscopy. The "classic" causes are rarely responsible for attacks of cystitis, but sexual intercourse and pregnancy seem to play a part. Several of the women took estroprogestative pills, or wore an intra-uterine device. The rate of bowel symptomatology-colopathy or constipation--should be noted. The article assesses the evolution of cystitis before and after crenotherapy at La Preste.

Adolescent↗

PubMedDate not supplied

Chronobiologic study in the domestic duck. I. Quantitative and temporal study of the action of the white light, factor releasing the gonad-stimulation.

I. White light is an essential and specific external factor in the development and growth of the duck gonads. The effects of light vary according to: a. Its intensity, up to a certain maximum, beyond which the effect on the gonads becomes reduced. b. Its daily duration. c. Its duration throughout the year. Too prolonged daily exposure to light throughout the year, as in temperate climates, produces a refractory phase due to a sort of temporary fatigue of the gonad-stimulating mechanism and not to weakness or fall in the testicular reaction. d. Its distribution in time. Dividing of the exposure to light for a given time, favors growth of the testis. II. Light is not essential for testicular development in ghe duck. This development occurs in total darkness but is slower, smaller and presents fluctuations which are less marked and shorter than in natural light. When several ducks are placed in darkness in the same surroundings, the fluctuations of various individuals present certain synchronization which can only be explained by the intervention of social factors which are probably tactile. III. Submitted to constant, continuous and prolonged light for years, male ducks present, with a few differences, a behavior similar to that of subjects submitted to total darkness. Finally, light is not essential for testicular growth, but it is necessary in nature to trigger off and stimulate testicular development and ensure its annual cyclic character. Social fractors, and other external factors, also play and important role to ensure synchronization of the development of the gonads of subjects in the same group.

Animals↗

PubMedDate not supplied

Chronobiologic study in the domestic duck. II. Physiological mechanism of the chronobiologic action of visible light on the gonads of the male duck.

1. The physiological mechanism of the gonad-stimulant effect of light rays on the pre-pubertal duck testis, is the basis of any chronobiolgical study of this effect. 2. The light stimulates the chain formed by the retina, the optic nerve, the hypothalamus and the anterior part of the pituitary. This chain includes 2 photo-receptors, a superficial one, the retina and a deep one, the hypothalamus. The retina is here only sensitive to orange and red rays. Consequently an autonomic retina intervenes instead of the visual retina. The hypothalamus, on the other hand, is sensitive to all visible rays when they are brought directly in contact with it through a quartz rod placed in the orbit which has been previously emptied. 3. The hypothalamus, which is thus enlightened directly is more than a hundred times more sensitive than the retina. This great sensitivity allows normal stimulation by the most penetrating rays in the orbital region. 4. Ultra-violet and infra-red rays are inactive on the autonomic retina and on the hypothalamus. 5. The neuro-secretory cells of the latter, stimulated directly or indirectly, secrete hormones which via the axones reach a capillary network covering the median eminence, then, by series of portal veins, the anterior part of the pituitary, the corresponding cells of which secrete various hormones, which through the systemic circulation reach the corresponding target organs and in particular the gonads. It is thus a neuro-hormonal mechanism which the external factor light, brings into play to stimulate various functions of the autonomic life of the organism.

Animals↗