Potential cellular targets of platinum in the freshwater microalgae Chlamydomonas reinhardtii and Nitzschia palea revealed by transcriptomics.

Platinum group element levels have increased in natural aquatic environments in the last few decades, in particular as a consequence of the use of automobile catalytic converters on a global scale. Concentrations of Pt over tens of µg L-1 have been observed in rivers and effluents. This raises questions regarding its possible impacts on aquatic ecosystems, as Pt natural background concentrations are extremely low to undetectable. Primary producers, such as microalgae, are of great ecological importance, as they are at the base of the food web. The purpose of this work was to better understand the impact of Pt on a cellular level for freshwater unicellular algae. Two species with different characteristics, a green alga C. reinhardtii and a diatom N. palea, were studied. The bioaccumulation of Pt as well as its effect on growth were quantified. Moreover, the induction or repression factors of 16 specific genes were determined and allowed for the determination of possible intracellular effects and pathways of Pt. Both species seemed to be experiencing copper deficiency as suggested by inductions of genes linked to copper transporters. This is an indication that Pt might be internalized through the Cu(I) metabolic pathway. Moreover, Pt could possibly be excreted using an efflux pump. Other highlights include a concentration-dependent negative impact of Pt on mitochondrial metabolism for C. reinhardtii which is not observed for N. palea. These findings allowed for a better understanding of some of the possible impacts of Pt on freshwater primary producers, and also lay the foundations for the investigation of pathways for Pt entry at the base of the aquatic food web.

[The ``tobacco-free hospital and campus'' action: mid-term evaluation of the needs expressed by students and professionals]. / Action « hôpital et campus sans tabac ¼ : évaluation à mi-parcours des connaissances de l'action et des besoins exprimés par les étudiants et les professionnels.

INTRODUCTION: In 2021, smoking was considered to be the leading cause of avoidable death in the world, causing numerous pathologies. The rate of smoking in French department of Finistère is high, and the ARS (regional health authority) has funded a prevention campaign for a tobacco-free hospital and campus in Brest. Some health students' smoke (17.8%) and/or vape (5.6%). The aim of this article was to study the middle-term impact of the Smokefree campus prevention campaign. MATERIAL AND METHOD: A descriptive cross-sectional study by self-administered questionnaire was carried out between 24/01/2022 and 21/02/2022, using Sphinx software. RESULTS: The participation rates were 29.9% (students) and 29.4% (professionals). Among students, 12.6% were smokers, as were 13.3% of professionals. Just over 75% of respondents were aware of Smokefree campus, and 75% knew that it concerned both vaping and smoking. Nearly 60% of respondents thought that the smoke-free campus program could improve coherence between (a) the care training function of the faculty and the IFPS and (b) its exemplarity on the issue of smoking. Among smokers, 44% thought that quitting smoking or vaping during working hours was possible, while and 44% thought that it was possible to quit, whatever the setting. For student smokers, this was contemplated by only 18.2%, and deemed possible by 24%. CONCLUSION: While the smoking rate has remained relatively high, the Smokefree campus campaign is widely known and understood. It is important to pursue this kind of prevention campaign insofar as it could have a positive impact on the health of future caregivers and their patients.

[Smoking, vaping among hospital staff during the Covid-19 pandemic: Appraisal of the "tobacco-free hospital, campus" campaign in Brest]. / Tabagisme et vapotage dans un CHRU en période de pandémie de covid-19 : Point de la campagne Hôpital et Campus Sans Tabac à Brest.

INTRODUCTION: In the framework of a "tobacco-free hospital and campus" campaign, we conducted a study on the prevalence of smoking and vaping among a university hospital (CHRU) staff. The study took place in late 2020 (from 1 September to 15 December), and involved self-assessment of the impact of the covid-19 pandemic on smoking. MATERIAL AND METHOD: A cross-sectional study was carried out using an online questionnaire, which was distributed by email and QR code posting and included socio-professional details as well as data on participants' smoking and vaping. RESULTS: There were 782 responses, representing a participation rate of 13.5%. The sample included 73.3% women and 22.7% men; 28.9% nurses, 24.9% medical staff, 3.6% nursing assistants and 42.6% other professional categories. The overall smoking rate was 13%. Sixty-two (7.9%) participants vaped; 37 (5%) vaped exclusively, 25 (3.2%) combined smoking and vaping. Men smoked more than women: 23.7% vs. 9.4% (P < 0.01). Medical staff smoked and vaped less than other categories; 6.2% vs 14.8% (P < 0.01) and 4.1% vs 9.1% respectively (P=0.02). Doctors were more often non-smokers: OR=2.71 (95% CI: 1.14-6.46). Among smokers, 25% said they had increased their cigarette consumption during the covid-19 pandemic, frequently as a means of combating stress or fatigue. CONCLUSION: This study showed a lower smoking rate than in the literature, possibly due to the high participation of physicians. Ours were the initial estimates of vaping among hospital staff.

[Cigarette and e-cigarette use among a sample of French health students]. / Consommation de cigarettes et de cigarettes électroniques des étudiants en santé.

INTRODUCTION: Smoking is one of the leading causes of preventable death worldwide. Data from the literature show that caregivers and health students have a high prevalence. The purpose of this article was to study the prevalence among health students (medicine, dentistry, physiotherapy, nursing) at a University and a Teaching Hospital in France. MATERIAL AND METHOD: This was a cross-sectional study using a self-administered questionnaire completed at the start of university meetings. This study was carried out as part of a campaign to combat smoking supported by the Brittany Regional Health Agency. RESULTS: The participation rate was 76.4%: 1349 respondents out of 1766 health students surveyed. The prevalence of smoking 17.8% and that of vaping 5.6%. Nursing students smoked and vaped more than students in other streams: respectively, for smoking, 21.8% (73/335) vs. 16.5% (167/1014) (P<0.001), for vaping, 10.4% (35/335) vs. 4.0% (39/980) (P<0.001). Students in 3rd year nursing smoked and vaped significantly more than those in the first 2 years (P=0.02 and P<0.001). CONCLUSION: The smoking rate was high, but comparable to the data for health students. Nursing students were significantly greater smokers, especially in the last year. Their vaping rate was higher than in other studies.

Competition Among Trivalent Elements (Al, Eu, Fe, Gd, Nd, Tm, and Y) for Uptake in Algae and Applicability of the Biotic Ligand Model.

Rare earth elements (REE) are essential in many new technologies. While anthropogenic dispersion of REE into the environment are expected in the future, their biogeochemical fate and interactions at biological interfaces are still largely unexplored. Due to their chemical nature (generally trivalent and hard metals), REE can potentially compete among themselves or with other ubiquitous trivalent metals for uptake sites at the surface of aquatic organisms. In the current study, the bioavailability and uptake of gadolinium (Gd) was assessed in the green alga, Chlamydomonas reinhardtii, while in the presence of various trivalent elements (Al, Eu, Fe, Nd, Tm, and Y). In the absence of competitors, Gd uptake was well described by a Michaelis-Menten equation with an affinity constant (KGd) of 107.1 and a maximum internalization flux (Jmax) of 1.95 ± 0.09 × 10-2 amol µm-2 min-1. Neither Al(III) nor Fe(III) had notable effects on Gd uptake in the conditions tested; however, Gd uptake was reduced with increasing concentrations of other REE. These had binding constants with uptake sites very similar to that of Gd (KNd, Y, Tm, Eu = 107.0). Our results suggest that the different REE likely share common transport sites and that the biotic ligand model (BLM) can be used to predict their uptake.

Multicenter Evaluation of the Clinical Performance and the Neutralizing Antibody Activity Prediction Properties of 10 High-Throughput Serological Assays Used in Clinical Laboratories.

As the coronavirus disease 2019 (COVID-19) pandemic second wave is emerging, it is of the upmost importance to screen the population immunity in order to keep track of infected individuals. Consequently, immunoassays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with high specificity and positive predictive values are needed to obtain an accurate epidemiological picture. As more data accumulate about the immune responses and the kinetics of neutralizing-antibody (nAb) production in SARS-CoV-2-infected individuals, new applications are forecast for serological assays such as nAb activity prediction in convalescent-phase plasma from recovered patients. This multicenter study, involving six hospital centers, determined the baseline clinical performances, reproducibility, and nAb level correlations of 10 commercially available immunoassays. In addition, three lateral-flow chromatography assays were evaluated, as these devices can be used in logistically challenged areas. All assays were evaluated using the same patient panels in duplicate, thus enabling accurate comparison of the tests. Seven immunoassays examined in this study were shown to have excellent specificity (98 to 100%) and good to excellent positive predictive values (82 to 100%) when used in a low (5%)-seroprevalence setting. We observed sensitivities as low as 74% and as high as 95% at ≥15 days after symptom onset. The determination of optimized cutoff values through receiver operating characteristic (ROC) curve analyses had a significant impact on the diagnostic resolution of several enzyme immunoassays by increasing the sensitivity significantly without a large trade-off in specificity. We found that spike-based immunoassays seem to be better correlates of nAb activity. Finally, the results reported here will add to the general knowledge of the interlaboratory reproducibility of clinical performance parameters of immunoassays and provide new evidence about nAb activity prediction.

Lymphogranuloma venereum in Quebec: Re-emergence among men who have sex with men.

BACKGROUND: Lymphogranuloma venereum (LGV) is a sexually transmitted infection (STI) caused by Chlamydia trachomatis genotypes L1, L2 and L3. This LGV is associated with significant morbidity and increased risk of HIV transmission. While fewer than two cases per year were reported in Quebec before 2005, LGV emerged in 2005-2006 with 69 cases, followed by a period of low incidence (2007-2012), and subsequent re-emergence since 2013. OBJECTIVES: To describe the incidence of LGV in Quebec and the characteristics of the affected population, including demographics and risk factors, clinical manifestations, laboratory tests, treatments and reinfection rates. METHODS: Descriptive data were collected from the notifiable diseases records through the Institut national de santé publique du Québec (INSPQ) infocentre portal. Questionnaires were obtained through the enhanced surveillance system and transmitted anonymously to the Quebec Ministry of Health. In-depth analysis was performed on cases from 2013 to 2016. RESULTS: There were 338 cases of LGV over the four-year period in Quebec. All cases were male, excluding one transsexual. Mean age was 41 years. Most lived in Montréal (81%) and were men who have sex with men (MSM; 99%). The majority (83%) reported four sexual partners or more in the last year, met mostly through the Internet (77%) and in saunas (73%). Frequency of sexual intercourse with out-of-province residents decreased in 2013-2016 (27%) compared with 2005-2012 (38%). History of STIs was frequent: 83% were HIV-infected, 81% reported previous syphilis and 78% previous gonorrhea. Recreational drug use was frequent (57%), reaching 71% in 2016. Most cases were symptomatic, a proportion which decreased in 2016 (68%) compared with 2013-2015 (82%; p=0.006). Clinical presentations included proctitis (86%), lymphadenopathy (13%) and ulcer/papule (12%). Reinfections, mostly within two years of first infection, occurred in 35 individuals (10%).Conclusion: The re-emergence of LGV in Quebec involves an urban subpopulation composed almost exclusively of MSM with STIs, who have a high number of partners and often use drugs.

Intracellular signalling pathways: targets to reverse immunosenescence.

Ageing is a very complex process, the result of the dysregulation of multiple systems interacting in many ways. A prominent change occurring with ageing is related to the architecture and functioning of the immune system, viewed commonly as detrimental and termed 'immunosenescence'. However, age-associated changes may also lead to increased function in certain respects, which can be viewed as adaptive. None the less, on balance it is well-recognized that immunosenescence is accompanied by the low-grade inflammation observed commonly in elderly people, which has been dubbed 'inflamm-ageing'. The exact cause and significance of all these changes is not clear, but there is a consensus that they are related to the occurrence of chronic non-infectious age-associated disease, as well as increased susceptibility to infections. Alterations to immune cell signalling may be a prominent cause of malfunctioning immunity. Emerging attempts to reverse immunosenescence have recently targeted the signalling pathways in various different cell types of the immune system. Here, we review and discuss alterations in the signalling pathways of immune cells with ageing and consider current targets and means to modulate altered functions. We discuss the potential dangers as well as the benefits of these interventions, and consider future approaches to this problem.

Early Initiation Rather Than Prolonged Duration of Antiretroviral Therapy in HIV Infection Contributes to the Normalization of CD8 T-Cell Counts.

BACKGROUND: CD8 T-cell counts remain elevated in human immunodeficiency virus (HIV) infection even after long-term antiretroviral therapy (ART), which is associated with an increased risk of non-AIDS-related events. We assessed the impact of ART initiation in early versus chronic HIV infection on trajectories of CD8 cell counts over time. METHODS: Of 280 individuals enrolled during primary HIV infection (PHI), 251 were followed up for 24 months; 84 started ART before 6 months of infection (eART), 49 started between 6 and 24 months, and 118 remained untreated. Plasma HIV viral load (VL), CD4 and CD8 cell counts were assessed at each study visit. CD8 counts were also examined in 182 age-matched HIV-infected individuals who started ART during chronic infection and maintained undetectable plasma VL for ≥5 years. RESULTS: At PHI baseline, higher CD8 cell counts were associated with more recent infection (P = .02), higher CD4 cell counts (P < .001), and higher VL (P < .001). The CD8 count in the eART group decreased from 797 to 588 cells/µL over 24 months (P < .001), to a level lower than that in untreated PHI (834 cells/µL; P = .004) or in long-term-treated patients with chronic HIV infection (743 cells/µL; P = .047). More prominent CD4 T-cell recovery was observed in the eART group than in the delayed ART group. CONCLUSIONS: ART initiated in early HIV infection is associated with improved resolution of CD8 T-cell elevation compared with long-term ART initiated in chronic infection. Early ART may help reduce the risk of non-AIDS-related events by alleviating this elevation.

Subthreshold traits of the broad autistic spectrum are distributed across different subgroups in parents, but not siblings, of probands with autism.

Autism is a categorical developmental disorder characterized by impairment in socialization, communication, and by restricted and circumscribed interests. Several authors have described the presence of subthreshold autistic traits in the general population, pervasive developmental disorders representing the extreme end of their distribution. In this study, we explored the presence of autistic traits in siblings and parents of a proband with autism, and in siblings and parents of a normally developing child, using the previously validated self-report French Autism Quotient, an adaptation of the AQ developed by S. Baron-Cohen. Scores were distributed between two main factors, F1 corresponding to socialization and communication, F2 to imagination and rigidity. Here, we show that both parents and siblings of a child with autism have more symptomatic scores in the domains of communication and socialization. In addition, we show that in these families the parents, but not the siblings, are distributed across different subcategories, according to their scores for the F1 and F2 domains. We hypothesize that these different subgroups may correspond to different underlying genetic mechanisms.

Development of action representation during adolescence as assessed from anticipatory control in a bimanual load-lifting task.

The aim of this study was to explore, during adolescence, alterations in the use of a sensori-motor representation as unveiled by the measurement of anticipatory postural control in a bimanual load-lifting task. We hypothesised that adolescence constitutes a period of refinement of anticipatory postural control due to on-going updates of the body schema and sensori-motor representations. The anticipatory postural control was assessed using a bimanual load-lifting paradigm in which subjects stabilise their left postural forearm, which is supporting an object, while they use their right hand to lift up the object. Kinematics and electromyographic data were recorded in two groups of adolescents (11-13 and 14-16 years of age) and a group of adults. Age and gender effects were tested. During voluntary unloading, the postural forearm stabilisation in adolescents was still different from the adult one, suggesting that further improvement of the postural forearm stabilisation must take place after the age of 16. No differences occur in the two adolescent groups. Moreover, girls presented a better stabilisation of the postural forearm than boys, indicating an earlier refinement of anticipatory postural control. The decrease of activity over postural flexors, which ensure postural stabilisation, appeared later in adolescents with respect to adults. Delayed timing adjustments and increased variability could reflect intense developmental processes underlain by an intense period of CNS maturation during adolescence. We discuss the role of brain maturation in the refinement of sensori-motor representations and the update of body schema.

[The FAQ self-report is a valid instrument to characterize endophenotypes of the autistic spectrum in parents of children with autism]. / L'autoquestionnaire FAQ : un outil valide pour le repérage des endophénotypes des parents d'enfants autistes.

BACKGROUND: We have previously developed the FAQ self-report, an adaptation of the Baron-Cohen's Autism Quotient self-report, in order to detect traits of the autistic spectrum in the parents and siblings of children with autism. We have previously shown that parents of children with autism show significant differences in their global scores and in their social functioning scores according to their answers to the FAQ self-report. OBJECTIVE: Our aim was to validate the FAQ self-report in a population of control parents, and to confirm our previous results concerning parents of children with autism. METHODOLOGY: Hundred and twenty-seven adults (67 female, 60 male), parents of children with normal development were recruited in the general population. They were asked to fulfill the 40 questions of the FAQ self-report at two different times. Sixty-six parents of children with autism were asked to fulfill the FAQ self-report, for group comparisons. Statistical factor analysis and test-retest reliability analysis was performed with the Matlab toolbox(©) software. RESULTS: Statistical factor analysis and test-retest reliability show that the FAQ is structured in two main factors, socialization and communication on one hand, rigidity and imagination on the other, with good test-retest reliability. Further comparison between parents of children with autism and control parents shows a significant difference between the two groups for the socialization and communication domain, and for the global score. We show for the first time that scores of the parents of children with autism remain unchanged from infancy to adulthood. CONCLUSION: The FAQ is the first French validated self-report focused on the detection of traits of the autistic spectrum in parents and siblings of children with autism. It is structured in two main factors, corresponding to imagination/rigidity, which are negatively correlated, and communication and socialization, which are positively correlated. The FAQ is therefore a reliable instrument to measure endophenotypes associated with the autistic spectrum in parents of children with autism, and may be useful in genetic studies.

Disseminated Histoplasma capsulatum infection presenting with panniculitis and focal myositis in rheumatoid arthritis treated with etanercept.

We report the case of a patient with rheumatoid arthritis (RA) on etanercept who presented with panniculitis and focal myositis as manifestations of disseminated histoplasmosis. Systematic search of the literature showed 11 additional case reports of disseminated histoplasmosis with tumour necrosis factor-alpha (TNFalpha) blockade therapy (infliximab, n = 8; etanercept, n = 3). Although disseminated histoplasmosis may manifest with classical symptoms of fever and respiratory complaints, it may also present atypically, such as with panniculitis and focal myositis. This review illustrates and emphasizes the importance of being highly suspicious for infection, including by opportunistic organisms, and to exclude such process in patients treated with a TNFalpha inhibitor when faced with unusual complications, even when an alternative aetiology appears plausible.

[Investigation of the behavioural phenotype of parents of autistic children through the new FAQ self-report]. / Intérêt de l'autoquestionnaire FAQ dans le repérage d'un endophénotype chez les parents d'enfants autistes.

INTRODUCTION: Autism is characterized by impairments in communication and socialization and by the presence of circumscribed and stereotyped interest. Previous studies have shown that genetic mechanisms may enhance the vulnerability to autism. These mechanisms are complex and may involve the combination of several genes, in interaction with the environment. The genetic mechanism involved in the vulnerability to autism may also concern other disorders and some features, with enhanced prevalence in relatives of autistic patients. It has been shown, for example, that the frequency of language disorders or serial difficulties is increased in the siblings of autistic patients. Characterization and taking into account the presence of such phenotypic traits in the relations may help in understanding the results of genetic studies, in particular association studies in sibling pairs or trios. OBJECTIVE: In this study, we used a new self-report in order to identify endophenotype traits in socialization, communication, rigidity and imagination in parents of autistic children. This self-report is the French adaptation of the previous self-report created by Baron-Cohen et al., aimed at the identification of Asperger profiles in a population of students studying science. METHODOLOGY: Ten autistic children and their parents from a clinical setting were asked to participate in the study. Autistic children were characterized using the ADI-R and various psychometric tests, according to the possibilities of the child (PEP-R, WPPSI-R, WISC3). Twenty parents of normal children were recruited from three different professional settings. There were no differences between the two groups of parents in terms of age or social status. Parents of both groups were asked to fill in the FAQ self-report. RESULTS: We performed a post-hoc analysis comparing the scores of the parents in the two groups. We found a main group, but no sex effect [F (1,37)=5.46; p<0.05]. Scores of autistic parents were higher in all domains compared to the control parents (p<0.05). However, the score on the socialization subscale was the only one that significantly differed from the scores on the imagination, language and rigidity subscales [F (3,111)=20.75, p<0.001]. CONCLUSION: Our results show significant differences between the two groups of parents in the socialization domain. This is of interest both for the interpretation of the presence of allelic variants in the genetic association studies, and for the understanding of the interplay between genotype and phenotype in the development of the autistic disorder.

Cadmium uptake in rat hepatocytes in relation to speciation and to complexation with metallothionein and albumin.

Cadmium (Cd) uptake has been studied in primary cultures of rat hepatocytes focusing on the impact of inorganic and organic speciation. Uptake time-course studies over a 60-min exposure to 0.3 microM (109)Cd revealed a zero-time uptake and a slower process of accumulation which proceeds within minutes. (109)Cd uptake showed saturation kinetics (K(m) = 3.5 +/- 0.8 microM), and was highly sensitive to inhibition by Zn and Hg. There was no evidence for sensitivity to the external pH nor for any preferential transport of the free cation Cd(2+) over CdCl(n) (2-n) chloro-complexes. According to the assumption that only inorganic metal species are available, metal uptake decreased upon albumin (BSA) addition to the exposure media. In contrast, higher levels of (109)Cd accumulation were obtained under optimal conditions for Cd complexation by MT. Comparison among uptake data obtained under inorganic and organic conditions revealed that Cd-MT would be taken up 0.4 times as rapidly as Cd(inorg). We conclude that uptake of Cd in rat hepatocytes involves specific transport mechanism(s) subjected to Zn or Hg interactions. Uptake of inorganic Cd is not proportional to the levels of free Cd(2+) and does not involve the divalent cation transporter DCT1 nor the co-transporter Fe(2+)-H(+) NRAMP2. We found Cd-MT but not Cd-BSA to be available for the liver cells, and have estimated a binding affinity four orders of magnitude higher for Cd complexation with MT compared to BSA; MT may have a significant role in Cd delivery to the liver.

Assessment and comparison of intraoperative and postoperative pain associated with NovaSure and ThermaChoice endometrial ablation systems.

STUDY OBJECTIVE: To assess and compare intraoperative and postoperative pain associated with NovaSure impedance-controlled endometrial ablation system and ThermaChoice system. DESIGN: Prospective, international, multicenter, double-arm study (Canadian Task Force classification II-1). Setting. Academic medical centers and private offices. PATIENTS: Sixty-seven premenopausal women with menorrhagia. INTERVENTION: Endometrial ablation with either the NovaSure (37 women) or ThermaChoice (30) system. NovaSure-treated patients received no endometrial pretreatment; those treated with ThermaChoice received the recommended 3-minute suction dilatation and curettage. MEASUREMENTS AND MAIN RESULTS: Standard pain measurement instruments (visual analog scale, numeric rating scale) were used to assess intraoperative and postoperative pain. Serum levels of prostaglandin-F(2alpha) were measured before and 5, 30, and 60 minutes after the procedure. Patients treated with the NovaSure system reported statistically significantly lower intraoperative and postoperative pain than those treated with the ThermaChoice system (p <0.0001). Procedure time was statistically significantly shorter with the NovaSure system (p <0.0001). Prostaglandin-F(2alpha) values did not differ statistically between groups. CONCLUSION: The NovaSure system is associated with statistically significantly lower intraoperative and postoperative pain than ThermaChoice system, and endometrial ablation with NovaSure could become an office-based procedure.

Feasibility study of patient-specific surgical templates for the fixation of pedicle screws.

Surgery for scoliosis, as well as other posterior spinal surgeries, frequently uses pedicle screws to fix an instrumentation on the spine. Misplacement of a screw can lead to intra- and post-operative complications. The objective of this study is to design patient-specific surgical templates to guide the drilling operation. From the CT-scan of a vertebra, the optimal drilling direction and limit angles are computed from an inverse projection of the pedicle limits. The first template design uses a surface-to-surface registration method and was constructed in a CAD system by subtracting the vertebra from a rectangular prism and a cylinder with the optimal orientation. This template and the vertebra were built using rapid prototyping. The second design uses a point-to-surface registration method and has 6 adjustable screws to adjust the orientation and length of the drilling support device. A mechanism was designed to hold it in place on the spinal process. A virtual prototype was build with CATIA software. During the operation, the surgeon places either template on patient's vertebra until a perfect match is obtained before drilling. The second design seems better than the first one because it can be reused on different vertebra and is less sensible to registration errors. The next step is to build the second design and make experimental and simulations tests to evaluate the benefits of this template during a scoliosis operation.

Thiosulfate enhances silver uptake by a green alga: role of anion transporters in metal uptake.

Short-term (< 1 h) silver uptake by the green alga Chlamydomonas reinhardtii was measured in the laboratory in defined inorganic media in the presence or absence of ligands (chloride and thiosulfate). In contradiction to the free-ion model of metal uptake, silver accumulation by the alga proved to be sensitive to the choice of ligand used to buffer the free silver concentration. For a low fixed free Ag+ concentration of 10 nM, silver uptake in the presence of thiosulfate (0.11 microM) was 2x greater than in the presence of chloride (4 mM). When sulfate was removed from the exposure medium (i.e., 81 microM-->0 microM), silver uptake in the presence of thiosulfate was even more markedly enhanced (more than 4x greater than in the presence of chloride). Varying the sulfate concentration in the exposure medium only affected silver uptake if thiosulfate was present. We conclude that silver-thiosulfate complexes are transported across the plasma membrane via sulfate/thiosulfate transport systems and that sulfate acts as a competitive inhibitor of this uptake mechanism.

Cadmium uptake by Caco-2 cells: effects of Cd complexation by chloride, glutathione, and phytochelatins.

Short-term cadmium uptake by the highly differentiated TC7 clone of enterocytic-like Caco-2 cells was studied as a function of Cd speciation. For low metal concentrations and with a constant free [Cd(2+)] = 43 nM, initial uptake rates of (109)Cd increased linearly as a function of increasing concentration of chlorocomplexes (Sigma[(109)CdCl(2-n)(n)]) over the range from 0 to 250 nM. When normalized as a function of the metal concentration, the absorption rate for the chlorocomplexes was less than that estimated for uptake of the free Cd(2+) cation. Metal absorption decreased upon organic ligand addition in the exposure media, but much less than predicted from the assumption that only inorganic metal species would be transported. Under exposure conditions where the concentration of each of the inorganic species was kept constant, (109)Cd uptake increased with increasing concentrations of cadmium glutathione ((109)Cd-GSH) or phytochelatin ((109)Cd-hmPC(3)) complexes. A specific system of very high affinity but low capacity has been characterized for (109)Cd-GSH transport, whereas accumulation data increased linearly with (109)Cd-hmPC(3) up to 6 microM. Comparison among uptake data for 0.3 microM inorganic (109)Cd, (109)Cd-GSH, or (109)Cd-hmPC(3) yields the following accumulation ratios: Cd-GSH/Cd(inorg) = 0.2; Cd-hmPC(3)/Cd(inorg) = 0.5. These results clearly show that Cd(2+) is not the exclusive metal species participating in Cd absorption, though, for comparable Cd concentrations, its contribution to transport would be more important than that of other species. Cadmium bound to thiol-containing peptides may be absorbed via transport systems that differ from those involved in absorption of the inorganic metal species.

Spatial variation in mercury concentrations in wild mink and river Otter carcasses from the James bay territory, Québec, Canada.

Mercury concentrations were analyzed in different organs/tissues of wild minks (Mustela vison) and river otters (Lutra canadensis) trapped during two seasons in the James Bay territory (49 degrees N to 55 degrees N, Québec, Canada). In 1993-94, mean total Hg concentration (microg/g, wet weight) in 39 wild mink and 12 river otter carcasses was greatest in fur/hair samples (30.1 and 20.7 microg/g, respectively) and least in brain samples (0.96 and 0.8 microg/g, respectively) with liver, kidney, and muscle samples showing intermediate values. Pooling data from the 1993-94 and 1994-95 trapping seasons revealed mean (SD) liver total Hg concentrations of 3.71 microg/g (3.91) in 316 wild mink carcasses and 4.05 microg/g (3.41) in 153 river otter carcasses. Log liver total Hg concentration increased with age in wild mink but not in river otter. Log liver total Hg concentration in each species was greatest in areas with moraine deposits and least in areas with rich clay deposits, but the effect of soil deposits could be confounded by uneven deposition of anthropogenic Hg. Controlling for type of soil deposits, log liver total Hg concentration decreased with increasing distance from local industrial centers in each species but varied little with changes in distance from hydroelectric reservoirs. In a subsample of carcasses from the moraine sector, log liver total Hg concentration was higher in wild mink than in river otter. Spatial variation in log liver total Hg concentration in relation to soil deposit type and proximity to industrial centers suggests that the two wild furbearer species could be useful indicators of environmental contamination.