Acute and chronic cobalt toxicity in Dugesia dorotocephala

2011 Fall.Includes bibliographical references.Limited data are available regarding cobalt toxicity for water quality criteria and risk assessment evaluation for freshwater organisms. These experiments were performed to establish median lethal concentrations from short term studies and to identify the most sensitive sublethal effect in a long term study in a flatworm species, Dugesia dorotocephala. Another study was conducted to elucidate the relationship between calcium, magnesium and cobalt toxicity in D. dorotocephala. During 4 and 7 day studies, median lethal concentrations of cobalt increased with total hardness indicating a protective effect. Calcium was shown to be more protective than magnesium in the presence of cobalt. A 60 day study showed fissioning rate, a process essential for maintenance of the D. dorotocephala population, to be the most sensitive endpoint. A lowest observable adverse effect concentration (LOAEC) of 1 mg Co/L (nominal) was incorporated into the calculation of an acute to chronic ratio (ACR), an important metric for risk analysis accounting for sublethal effects that may occur by mechanisms different from lethal ones. A NOAEC (no observable adverse effect concentration) was not determined because significant effects were observed at the lowest cobalt concentrations tested (<1 mg Co/L). Without an exact NOAEC, the ACR values established in this study represent the upper and lower bounds of the acute to chronic ratio for cobalt in D. dorotocephala

16p13.3 duplication associated with non-syndromic pierre robin sequence with incomplete penetrance.

BACKGROUND: Pierre Robin sequence (PRS) is a condition present at birth. It is characterized by micrognathia, cleft palate, upper airway obstruction, and feeding problems. Multiple etiologies including genetic defects have been documented in patients with syndromic, non-syndromic, and isolated PRS. CASE PRESENTATION: We report a 4-year-old boy with a complex small supernumerary marker chromosome (sSMC) who had non-syndromic Pierre Robin sequence (PRS). The complex marker chromosome, der(14)t(14;16)(q11.2;p13.13), was initially identified by routine chromosomal analysis and subsequently characterized by array-comparative genomic hybridization (array CGH) and confirmed by fluorescence in situ hybridization (FISH). Clinical manifestations included micrognathia, U-type cleft palate, bilateral congenital ptosis, upslanted and small eyes, bilateral inguinal hernias, umbilical hernia, bilateral clubfoot, and short fingers and toes. To our best knowledge, this was the first case diagnosed with non-syndromic PRS associated with a complex sSMC, which involved a 3.8 Mb gain in the 14q11.2 region and an 11.8 Mb gain in the 16p13.13-pter region. CONCLUSIONS: We suggest that the duplicated chromosome segment 16p13.3 possibly may be responsible for the phenotypes of our case and also may be a candidate locus of non-syndromic PRS. The duplicated CREBBP gene within chromosome 16p13.3 is associated with incomplete penetrance regarding the mandible development anomalies. Further studies of similar cases are needed to support our findings