Acute toxicity of cadmium,zinc, and cadmium-zinc mixtures toDaphnia magna

Experiments were performed in flow-through apparatus to determine the acute toxicity of zinc, cadmium, and their mixtures toDaphnia magna in order to compare sensitivity ofDaphnia relative to that of other organisms and to determine if the metal mixture behaves differently than expected on the basis of single metal experiments. Dosage-mortality curves are derived forDaphnia populations exposed to zinc and cadmium for 36, 48, 60, 72, and 96 hr periods. Similar curves are derived forDaphnia exposed to equally potent mixtures of zinc and cadmium as calculated from initial experiments and forDaphnia exposed to equal concentration mixtures of the metals. Cadmium is more toxic than zinc, but zinc-cadmium mixtures are less toxic than expected.Daphnia magna is considerably more sensitive to these metals than are other invertebrates and vertebrates previously studied. This study demonstrates errors which can arise in attempts to set water quality criteria based upon short term studies of organisms with long life spans.This work was supported by a Quebec Minister of Education grant to P. D. Anderson, by a Quebec scholarship to E. N. Attar, and by a National Science and Engineering Council grant to E. J. Maly. We thank G. Leduc and P. D. Anderson for helpful criticism and discussion     

Serological and DNA-based evaluation of Chlamydia pneumoniae infection in inflammatory bowel disease

OBJECTIVES: Chlamydia has been associated with autoimmune diseases, but a link between chlamydial infection and the aetiopathogenesis of inflammatory bowel disease (IBD) remains controversial. In this study we assessed the relationship between chlamydial infection and IBD, as evidenced by serological measurement and DNA analysis of mucosal biopsy specimens. PATIENTS AND METHODS: The sera of 78 patients with Crohn's disease (CD), 24 patients with ulcerative colitis (UC), 73 healthy family members, and 20 healthy controls were tested for anti-C. pneumoniae IgG titres. A subgroup consisting of 13 UC and 39 CD patients was screened for the presence of chlamydial DNA on 42 inflamed versus 30 non-inflamed biopsy specimens and for mutations of their NOD2/CARD15 gene. RESULTS: Anti-C. pneumoniae IgG antibodies were found in the sera of 32 (41%) patients with CD, 11 (46%) patients with UC, 35 (48%) of unaffected family members, and nine (45%) unrelated healthy controls. Thirty-five percent of the control, 18% CD and 24% UC biopsy specimens contained C. pneumoniae DNA. In CD, however, C. pneumoniae DNA was significantly more frequently found in inflamed (27%) versus non-inflamed (8%) biopsy specimens (P < 0.05, Fisher's exact test). The frequencies of NOD2/CARD15 mutations were 33% for CD patients with C. pneumoniae DNA compared to 47% for CD patients without C. pneumoniae DNA. CONCLUSION: We found no marked differences in respect to anti-C. pneumoniae serum IgG or C. pneumoniae DNA between healthy controls and patients with IBD. However, in CD patients, inflamed tissue specimens contained significantly more likely C. pneumoniae DNA compared with biopsies from unaffected areas. Thus C. pneumoniae is unlikely to be of pathogenic importance in IBD while it may still influence local clinical manifestations.     

Respiratory viral infection in lower airways of asymptomatic children

Aim: The aim of this study was to determine if asthmatic children have viruses more commonly detected in lower airways during asymptomatic periods than normal children. Methods: Fifty‐five asymptomatic children attending elective surgical procedures (14 with stable asthma, 41 normal controls) underwent non‐bronchoscopic bronchoalveolar lavage. Differential cell count and PCR for 13 common viruses were performed. Results: Nineteen (35%) children were positive for at least one virus, with adenovirus being most common. No differences in the proportion of viruses detected were seen between asthmatic and normal ‘control’ children. Viruses other than adenovirus were associated with higher neutrophil counts, suggesting that they caused an inflammatory response in both asthmatics and controls (median BAL neutrophil count, 6.9% for virus detected vs. 1.5% for virus not detected, p = 0.03). Conclusions: Over one‐third of asymptomatic children have a detectable virus (most commonly adenovirus) in the lower airway; however, this was not more common in asthmatics. Viruses other than adenovirus were associated with elevated neutrophils suggesting that viral infection can be present during relatively asymptomatic periods in asthmatic children.