COVID-19 in school settings: webinar aimed at both teachers and educators.

Background: In the COVID-19 era, we designed the webinar "COVID-19: instructions for use" with the aim of providing clear and actionable information to school staff about the characteristics of the disease, the preventive measures to adopt and the path for early detection and control of COVID-19 in primary schools of Modena province. Methods: We performed a cross-sectional survey using a 7-item closed-ended satisfaction questionnaire self-administered to webinar participants among school staff of the Modena Municipality and neighbouring. Results: A total of 103 out of 152 (68%) participants delivered the questionnaires. The participating staff came from 29 schools. Most of respondents (83.5%) were primary school teachers following by kindergarten teachers and educators. The overall webinar assessment index was "very good" for 51% of attendees and "good" for the remaining. Nevertheless, 25.2% highlighted the need to have more time dedicated to the discussion. Conclusions: Our project promotes a virtuous circle between school-family and community; so that the benefits can be sustained and enhanced. This may improve the effectiveness of the preventive measures in terms of transmission of SARS-CoV-2 and other virus.

Blood pressure levels and hypertension prevalence in a high selenium environment: results from a cross-sectional study.

BACKGROUND AND AIMS: Recent human and laboratory studies have suggested the possibility that selenium overexposure may increase blood pressure. We sought to ascertain whether adults living in a seleniferous area exhibit an association between selenium exposure and both blood pressure levels as well as prevalence of hypertension. METHODS AND RESULTS: We measured selenium levels in blood (serum), hair and nail samples obtained from 680 adult volunteers (267 men and 413 women), living in seven Punjabi villages in a seleniferous area and related them to health outcomes, including systolic and diastolic blood pressure and presence of hypertension. In a multivariable restricted cubic spline regression model, adjusted for age, sex and history of hypertension, we found a positive association between systolic blood pressure and both serum (P = 0.004) and hair (P = 0.058) selenium levels, but not with nail selenium content. Little association emerged between the three selenium biomarkers and diastolic blood pressure. Hypertension prevalence was positively associated with the three exposure indicators (P < 0.001). The associations we found were generally stronger in women than in men. CONCLUSIONS: Overall, these findings suggest that chronic overexposure to environmental selenium may increase blood pressure, though there were inconsistencies for this association according to the choice of exposure indicator, the study endpoint and the sex.

Effects of clear aligners on sleep bruxism: randomized controlled trial.

The possible effects on sleep bruxism (SB) of clear aligners in orthodontics are unknown. This study was conducted to analyze the effects of clear aligners on SB. Sixty subjects needing orthodontic treatment and affected by SB (33 m, 27 f, 20±;5 years) were enrolled in the study and randomly assigned to one of the following three groups: 20 were given clear aligners (CAT) (12 m, 8 f, 19±5 years), 20 occlusal splint (MOS) (9 m, 11 f, 22±5 years) and 20 a placebo splint (PMS) (12 m, 8 f, 24±3 years). All groups were followed for 6 consecutive months and monitored for SB with a portable electromyographic-electrocardiographic (EMG-ECG) device (Bruxoff®, OT Bioelettronica, Torino, Italy). MOS subjects reduced masseter contractions after 6 months of treatment (t3) (MD=-29.11, std. error 11.74, p=0.017) but increased phasic contractions related to SB after 3 months of treatment (t2) (MD=4.73, std. error 2.36, p=0.048) and tonic contractions related to SB during all the six months of treatment (t1, t2, t3) when compared to PMS. CAT subjects increased phasic contractions related to SB during the first (t1) (MD=3.94, std. error 2.27, p=0.04) and the third month (t2) of treatment (MD=4.62, std. error 2.36, p=0.046) when compared to PMS. No significant differences were found for SB index at any time for all the three groups. Although MOS and CAT affected EMG signals during sleep time differently, they did not influence the overall SB index.

Knowledge, experiences, and attitudes toward Mantoux test among medical and health professional students in Italy: a cross-sectional study.

BACKGROUND: The World Health Organization's Action Framework for tuberculosis elimination in low-tuberculosis incidence countries includes the screening for active and latent tuberculosis in selected high-risk groups, including health care workers. In this context, medical and health profession students, exposed to nosocomial tuberculosis transmission during training and clinical rotations, are target populations for tuberculosis screening. No updated data are available on tuberculosis screening practice and knowledge of medical and health profession students in Italy. METHODS: Within the activities Italian Study Group on Hospital Hygiene of the Italian Society of Hygiene, Preventive Medicine and Public Health, we carried out a multicentre cross-sectional study to assess knowledge, attitude and practices on tuberculosis prevention and control among Medical, Dentistry, Nursing and other health professions' students. Students were enrolled in the study on a voluntary basis and were administered a previously piloted structured questionnaire. Logistic regression models were applied to explore knowledge on tuberculosis prevention by selected socio-demographic variables and University-based tuberculosis prevention practice. RESULTS: Students of seventeen Universities across Italy participated in the study, and 58.2% of them received compulsory tuberculin skin test either at enrollment or while attending clinical practice. A total of 5,209 students filled the questionnaire. 37.7% were medicine and dentistry students (Group 1), 44.9% were nursing students (Group 2) and 17.4% were other health professions' students (Group 3). Age and gender had different distributions by groups, as well as knowledge and practice on tuberculin skin test. 84.4% of the study population (95% CI = 83.3-85.3) was aware of the existence of the tuberculin skin test, 74.4% (95% CI = 73.2-75.6) knew what is the first-level screening test for latent tuberculosis and only 22.5% (95% CI = 21.4-23.6) knew how to proceed after a positive tuberculin skin test result. Overall, knowledge on tuberculosis prevention was higher in Group 2 and lower Group 3, as compared to Group 1. CONCLUSION: In Italy, the knowledge on tuberculosis screening among University students is generally good. To reduce some of the criticalities found among the different study courses, it would be appropriate to harmonize both the regulations on tuberculosis screening practices for admission to University courses, and the educational activities on the topic of tuberculosis, to be extended to all workers involved in health care setting.

Hospital-acquired Legionella infections: an update on the procedures for controlling environmental contamination.

The waterborne healthcare-associated infections are mainly sustained by Legionella and Pseudomonas spp. Various water factors and plumbing characteristics, and the interaction with other water microorganisms are considered to be predictive of Legionella contamination. It is therefore mandatory to organize plans of surveillance, prevention and control in order to avoid disease appearance in immunosuppressed patients, with higher risk of death. Guidelines for the prevention of Legionnaires' disease have been published, benefiting those who face this problem, but definitive standardized solutions do not exist yet. Here we describe fifteen years of activity, during which our study group gathered interesting data on the control of Legionella contamination. Water disinfection is not generally sufficient to control the risk of infection, but a complex water safety plan should be developed, including system maintenance, training of staff and implementation of a clinical surveillance system aimed at early detection of cases. Concerning the control measures, we evaluated the effectiveness of different treatments suggested to reduce Legionella spp contamination, comparing our results with the current literature data. The performance ranking was highest for the filter, followed by boilers at high temperature, monochloramine and, at a lower level, chlorine dioxide; the effectiveness of hyperchlorination was limited, and thermal shock was even more ineffective.

Agreement between clinical and portable EMG/ECG diagnosis of sleep bruxism.

The aim of this study was to compare clinical sleep bruxism (SB) diagnosis with an instrumental diagnosis obtained with a device providing electromyography/electrocardiography (EMG/ECG) recordings. Forty-five (N = 45) subjects (19 males and 26 females, mean age 28 ± 11 years) were selected among patients referring to the Gnathology Unit of the Dental School of the University of Torino. An expert clinician assessed the presence of SB based on the presence of one or more signs/symptoms (i.e., transient jaw muscle pain in the morning, muscle fatigue at awakening, presence of tooth wear, masseter hypertrophy). Furthermore, all participants underwent an instrumental recording at home with a portable device (Bruxoff; OT Bioelettronica, Torino, Italy) allowing a simultaneous recording of EMG signals from both the masseter muscles as well as heart frequency. Statistical procedures were performed with the software Statistical Package for the Social Science v. 20.0 (SPSS 20.0; IBM, Milan, Italy). Based on the EMG/ECG analysis, 26 subjects (11 males, 15 females, mean age 28 ± 10 years) were diagnosed as sleep bruxers, whilst 19 subjects (7 males, 12 females, mean age 30 ± 10 years) were diagnosed as non-bruxers. The correlation between the clinical and EMG/ECG SB diagnoses was low (ϕ value = 0.250), with a 62.2% agreement (28/45 subjects) between the two approaches (kappa = 0.248). Assuming instrumental EMG/ECG diagnosis as the standard of reference for definite SB diagnosis in this investigation, the false-positive and false-negative rates were unacceptable for all clinical signs/symptoms. In conclusion, findings from clinical assessment are not related with SB diagnosis performed with a portable EMG/ECG recorder.

Lifestyle and food habits changes after migration: a focus on immigrant women in Modena (Italy).

BACKGROUND: This study aimed to explore post-migration lifestyle and weight changes in a sample of migrant women recruited in Modena, Italy. Taking into account the importance of the perceived personal susceptibility in improving prevention and treatment seeking behaviors, we further investigated women's self-recognition of overweight/obesity. We also examined the changes in self-perceived quality of life after the arrival in Modena. METHODS: A cross-sectional study was conducted among 97 female migrants visiting a family counseling in Modena. Socio-demographic information, post-migration changes in lifestyle, dietary habits and self-perceived quality of life were obtained by administering an anonymous questionnaire, created ad hoc with expert consultation and previously tested in a pilot study. Thereafter blood pressure, height and weight were measured. RESULTS: More than half of the sample met criteria for overweight/obesity and 58% reported a weight increase after the arrival in Italy. The increased risk of weight gain after migration was significantly associated with women age, lower education level, African ethnicity and post-migration increased consumption of cheese and snacks/sweets. After applying a conditional multiple logistic regression, ethnicity, age and increased post-migration cheese consumption remained the main predictors of weight gain. More than half of subjects with BMI ≥ 25 Kg/m² were not aware of their own overweight or obesity. Such weight underestimation was more common in African migrants than in other ethnicities. Findings about the perceived quality of life showed an overall improved economic situation, although more than half of women revealed deterioration in their social relationships after migration. CONCLUSIONS: Our results are important to identify the gaps in the current migrant populations' health promotion in Modena and suggest that strategies to support female migrants to reinforce good dietary patterns may be the key in preventing unhealthy weight gain. Indeed, understanding immigrant women's culture, beliefs and traditions of their country of origin, as well as food acculturation, is essential to improve the efficiency of these interventions.

Detection of sleep bruxism: comparison between an electromyographic and electrocardiographic portable holter and polysomnography.

Recent polysomnographic (PSG) studies showed that the sleep bruxism (SB) event is preceded by a sudden shift in autonomic cardiac activity. Therefore, heart rate could be the simplest-to-record parameter for use in addition to portable home EMG monitoring to improve the accuracy in automatic detection of SB events. The aim of the study was to compare the detection of SB episodes by combined surface electromyography and heart rate (HR) recorded by a compact portable device (Bruxoff(®) ), with the scoring of SB episodes by a PSG recording. Twenty-five subjects (14 'probable' bruxers and 11 non-bruxers) were selected for the study. Each subject underwent the Bruxoff and the PSG recordings during the same night. Rhythmic masseter muscle activities (RMMAs) were scored according to published criteria. Correlation coefficients and the Bland-Altman plots were calculated to measure the correlation and agreement between the two methods. Results showed a high correlation (Pearson's r = 0·95, P < 0·0001) and a high agreement (bias = 0·05) between Bruxoff and the PSG. Furthermore, the receiver operating characteristic curve analysis showed a high sensitivity and specificity of the portable device (92·3% and 91·6%, respectively) when the cut-off was set at 4 SB episodes per hour according to published criteria. The Bruxoff device showed a good diagnostic accuracy to differentiate RMMA from other oromotor activities. These findings are important in the light of the need for simple and reliable portable devices for the diagnosis of SB both in the clinical and research settings.

Ecological behaviour of three serogroups of Legionella pneumophila within a model plumbing system.

Three Legionella pneumophila strains isolated from water samples and belonging to serogroups (sgs) 1, 6 and 9 were analysed for their capacity to colonise an experimental model simulating a domestic hot water distribution system. Ecological factors that could influence the persistence of the sgs such as intracellular life within protozoan hosts and bacterial interference by the production of antagonistic compounds were also studied. Viable counts of L. pneumophila increased both in the planktonic and in the sessile phases. Sg 6 showed a marked prevalence during the whole experiment and exhibited the highest host infection efficiency. Sg 1 was significantly less represented, but showed the highest capacity to reproduce in the protozoan hosts. Sg 9 was poorly represented and less adapted to intracellular life. Among the 14 bacteria constantly isolated in the system, five (35.7%) produced antagonistic substances against Legionella, with differences according to the bacterial strain and L. pneumophila sgs.

Inter-laboratory validation of a rapid assay for the detection and quantification of Legionella spp. in water samples.

AIMS: To compare the standard culture method with a new, rapid test (ScanVIT-Legionella™) using fluorescently labelled gene probes for the detection and enumeration of Legionella spp. The new technique was validated through experiments conducted on both artificially and naturally contaminated water and through an inter-laboratory comparison. METHODS AND RESULTS: All samples were processed by the ScanVIT test according to the manufacturer's instructions and by a culture method (ISO 11731). ScanVIT detected significantly more positive samples, although concentrations were similar and a strong positive correlation between the two methods was observed (r = 0.888, P < 0.001). The new test was more accurate in identifying the co-presence of Legionella pneumophila and Leg. non-pneumophila. ScanVIT showed a slightly higher Legionella recovery from water samples artificially contaminated with Leg. pneumophila alone or together with Pseudomonas aeruginosa. Lastly, the inter-laboratory comparison revealed that the ScanVIT test exhibits a lower variability than the traditional culture test (mean coefficient of variation 8.7 vs 16.1%). CONCLUSIONS: The results confirmed that the ScanVIT largely overlaps the reference method and offers advantages in terms of sensitivity, quantitative reliability and reduced assay time. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed method may represent a useful validated alternative to traditional culture for the rapid detection and quantification of Legionella spp. in water.

Natural killer cell activity decreases in workers occupationally exposed to extremely low frequency magnetic fields exceeding 1 microT.

In a preliminary study a reduction in natural killer (NK) cell activity in peripheral blood lymphocytes (PBL) was observed in a group of workers exposed to levels of extremely low frequency-magnetic fields (ELF-MF) exceeding 1 microT. This study was performed to confirm the results. In 121 workers engaged in various occupational activities, individual ELF-MF exposure was monitored for 2 work shifts. Exposure levels were calculated as time-weighted average (TWA). Subjects were classified as Low exposure (TWA < or = 0.2 microT), Medium exposure (TWA 0.21-0.99 microT), or Higher exposure (TWA > or = 1 microT). In higher exposure workers NK activity proved significantly reduced compared to low exposure,(p<0.01). In medium exposure a reduction was also observed, but the difference was not significant. Multivariate analysis also confirmed the relation between exposure and NK activity. It has been suggested that ELF might affect tumour progression by inducing changes in the immune system: due to the role played by NK activity in host defence against cancer, the interference with the NK cell activity observed in this study is in agreement with this hypothesis. Furthermore, an increased risk for some neurodegenerative disorders has been reported in some epidemiological studies in ELF-MF-exposed workers: changes in NK function were also described in these diseases. Our results, showing the effect on NK activity of exposure exceeding 1 microT, suggest a possible mechanism for ELF-MF effects. This could open new horizons regarding the adverse long-term effects of these fields.

Prevalence of anti-legionella antibodies among Italian hospital workers.

This study evaluated the prevalence of anti-legionella antibodies in workers at hospitals with a long-term history of legionella contamination. The hospitals are located in Milan and Turin, northern Italy, and in Naples and Bari, southern Italy. Antibody prevalence and titres of healthcare workers, medical and dental students and blood donors were assessed. In total 28.5% of subjects were antibody positive, most frequently to L. pneumophila serogroups 7-14. Major differences were observed in seroprevalence and type of legionella antibody in persons from different geographic areas. Healthcare workers had a significantly higher frequency of antibodies compared with blood donors in Milan (35.4 vs 15.9%, P<0.001), whereas in Naples both groups exhibited high antibody frequency (48.8 vs 44.0%) and had a higher proportion of antibodies to legionella serogroups 1-6. Dental workers had a higher seroprevalence than office staff in Bari, but not in Turin, where daily disinfecting procedures had been adopted to avoid contamination of dental unit water. No association was found between the presence of antibodies and the presence of risk factors for legionellosis, nor with the occurrence of pneumonia and/or flu-like symptoms. In conclusion, the presence of legionella antibodies may be associated with occupational exposure in the hospital environment, but there was no evidence of any association with disease.

Risk factors for particulate and microbial contamination of air in operating theatres.

This study was designed to standardize dust collection in recently built operating theatres equipped with a continuous monitoring system. The objectives were to establish the relationship between microbiological and dust contamination, and then to compare those parameters with the main indicators of surgical activity in order to better define risk factors affecting air quality. The air quality during 23 surgical operations was studied in three conventionally ventilated operating theatres. Microbiological air counts were taken using both passive and active sampling methods. Air dust particles, > or =0.5 and > or =5 microm in size, were measured using a light-scattering particle analyser. The overall dust load was mainly (98%) composed of fine particulate matter, most probably due to its longer suspension time before settlement. These particles positively correlated with operation length, but not with surgical technique, suggesting that fine particles may be a good tracer of operation complexity. In contrast, the surgical technique was the main predictor for the concentration of particles > or =5 microm, with a higher risk from general conventional surgery compared with scope surgery. The frequency of door-opening, taken as an index of staff and visitor movement, was the main negative predictor of over-threshold values of both fine and larger dust particles but, conversely, was a positive predictor of raised bacterial counts.

[Active clinical surveillance for detection of Legionnaires' disease: implications for health care structures]. / Sorveglianza clinica attiva per la ricerca di polmoniti da Legionella: risultati e considerazioni per le strutture sanitarie.

In an university hospital of about 900 beds, a clinical surveillance was activated to detect cases of Legionnaires' disease in patients affected by community and/or nosocomial-acquired pneumonia. In the hospital Legionella spp was detected in the hot water distribution system and various disinfecting and control procedures were adopted to reduce contamination. Contemporary, the clinical surveillance began with the systematic detection of Legionella urinary antigen among recovered pneumonia, seroconversion as confirmation test and the collection of respiratory secretions or other biological materials to isolate the microorganism in patients positive to the urinary antigen. From September 2003 to May 2005, 486 pneumonia were followed, 98 of which considered of nosocomial origin. In total, 15 cases of community-acquired Legionnaires' disease were detected by the urinary test, whereas no cases of nosocomial origin were found. The characteristics of the detected cases are described in comparison with the other pneumonia and the surveillance cost was evaluated. The systematic clinical surveillance for Legionella infections is feasible with limit costs, allows to detect community-acquired cases otherwise unknown and to ascertain the absence/presence of nosocomial-acquired pneumonia, irrespective of the environment contamination.

The use of non-radioactive chromium as an alternative to 51Cr in NK assay.

A novel method to measure target cell cytolysis based on the use of 'cold', non-radioactive chromium and on the determination of metal release by graphite furnace atomic absorption spectroscopy (FAAS) is proposed. Natural killer (NK) assays were performed by labelling target cells with chromium as Na2CrO4, and results were compared with those obtained by conventional overnight labelling with 51Cr of targets killed by the same effectors. The cytotoxic capacity of peripheral blood lymphocytes from healthy subjects was evaluated, and NK activity measured with both methods showed a good agreement at each of the tested effector to target cell ratios (between 100:1 and 1:1), with a high and significant coefficient of correlation (r = 0.931, p < 0.0001). The selection of the appropriate Cr concentrations for labelling target cells took into account both the sensitivity of our instrumentation and the possible toxic effects of the metal. A study of the effects of Cr on the cell line (K562) which is usually employed as a target in NK tests showed that Cr could have a detrimental effect on cellular function, with significant numbers of cells with depolarised mitochondria and reduced DNA synthesis after 24 h incubation using Cr levels higher than 15 mumol/l (780 micrograms/l). The method proposed here has a number of advantages, including the use of a non-radioactive tracer, limited costs, high sensitivity and reproducibility, and the possibility of storing samples. In addition, the technique uses a fixed Cr concentration which is known to be non toxic.

Emotional stability, anxiety, and natural killer activity under examination stress.

This study was performed to evaluate the relation between a stable personality trait, a mood state and immune response to an examination stress. A self-reported measure of emotional stability (BFQ-ES scale) was obtained in a sample (n = 39) randomly selected from 277 cadets; this personality trait was also investigated by completing a neuroticism scale (Eysenck personality inventory) and a trait-anxiety scale (STAI). Natural killer (NK) cell activity was measured at baseline, long before the examination time and the examination day. The state-anxiety scale evaluated the response to the stressful stimulus. Taking subjects all together, the academic task did not result in significant modification over baseline in NK cell activity. Subjects were then divided into three groups based on emotional stability and state-anxiety scores: high emotional stability/low anxiety, medium, and low emotional stability/high anxiety. Examination stress induced significant increases in NK cell activity in the high emotional stability/low anxiety group, no effect in the medium group, and significant decreases in the low emotional stability/high anxiety group. The repeated-measure ANOVA revealed a significant interaction of group x period (baseline vs. examination) for both lytic units and percent cytolysis. The results did not change after introducing coffee and smoking habits as covariates. Our findings suggest that the state-anxiety acts in concert with a stable personality trait to modulate NK response in healthy subjects exposed to a psychological naturalistic stress. The relation between anxiety and poor immune control has been already described, whereas the ability of emotional stability to associate with an immunoenhancement has not yet reported. The peculiarity of our population, a very homogeneous and healthy group for life style and habits, can have highlighted the role of emotional stability, and may account for the difference with other studies.

Observations on the use of plasma, hair and tissue to evaluate trace element status in cancer.

Selenium, zinc and copper were measured in plasma, hair and tissue of patients affected by either breast or lung cancer and their controls. A decrease in plasma Se and Zn in women affected by breast cancer was observed, whereas plasma Cu was increased in lung cancer. No significant modification was found in hair trace element levels adjusted for the main confounders, in particular for hair treatment which altered Se content. The examined elements were highly concentrated in cancerous vs normal tissue, but results changed according to the unit used to express results. The usefulness and significance of these biomarkers of trace element status are discussed in the light of the most recent literature data.

Effects of chronic exposure to anaesthetic gases on some immune parameters.

A cross-sectional survey was carried out to evaluate the relation between occupational exposure to low levels of anaesthetic gases (nitrous oxide and isoflurane) and immune parameters. Fifty-one anaesthetists were recruited among different Services of Anaesthesiology and Reanimation. The control group consisted of non-exposed physicians, similar for gender, age, and job grade. Total number of lymphocytes, lymphocyte subpopulations and the natural killer (NK) cytotoxic activity were measured. Information on personal and professional characteristics and on short- and long-term exposure was collected. Percentages of T cells (CD3) decreased significantly in anaesthetists compared to controls, whereas numbers of NK cells (CD16+ CD3-) increased. After correction for confounders, short-term (last 2 weeks) exposure was associated with a decrease in percentages of total T and T helper (CD4) cells. Furthermore, T helper percentages were significantly reduced with increasing individual exposure score evaluated on the basis of working days and levels of anaesthetic gases in operating rooms. A significant X-ray-associated increase of numbers and percentages of NK cells was lastly observed. Despite limited present exposure to anaesthetic gases, a specific derangement in lymphocyte subpopulations, with T lymphocytes more affected than B, has been observed.

The role of magnetic resonance imaging in the evaluation of neoplastic lesions of the breast.

Thirty-seven patients were evaluated for suspected breast cancer by magnetic resonance imaging (MRI) using 0.5- and 1.5-Tesla. We examined the patterns in breast images and the use of MRI in evaluating neoplasms. At the moment the cost/benefit ratio is unfavorable, mainly because of the availability of alternative methods of high accuracy and low cost, like mammography and ultrasonography. Furthermore fine needle aspiration biopsy is not possible with MRI. The widespread use of MRI for breast pathology seems not to be justified by the results obtained.

Chemical form of selenium greatly affects metal uptake and responses by cultured human lymphocytes.

In this work, possible interference with functional activities of human lymphocytes after in vitro treatment with selenium was examined. Sodium selenite and selenomethionine compounds were tested in parallel, and their capability to inhibit or to increase the antibody production by lymphocytes was investigated. Furthermore, after incubation for 7 d, total cell-associated Se was measured by a fluorimetric method. The in vitro doses of Se employed in this study mainly reflect those measured in blood of individuals with different Se intake. Low doses of Se (0.5-2.0 microM) added either as sodium selenite or selenomethionine did not alter the secretion of antibodies. When Se was added at higher levels, instead, an inhibitory effect was found using selenite, whereas a progressive increase in immunoglobulin production was observed after exposure to selenomethionine. In both cases, modifications were detected at 5 microM (395 micrograms Se/L), and were significant at 10 microM (789 micrograms Se/L). A different trend between the two chemical forms was also observed with regard to Se uptake by cells. Interestingly, both Se uptake and cell sensitivity were influenced by the density of the cells in culture. Our data suggest that the biological effects of Se in mammalian systems are strongly influenced by its chemical form, and caution should be exerted to avoid toxic effects of selenium.