Aspects of the biology and heavy metal accumulation of Ciliata mustela

The feeding habits, rates of growth, fecundity and other aspects of the general biology of five-bearded rockling from the Severn Estuary and the Bristol Channel are reviewed for the period 1974/76. Additionally the changes in heavy metal accumulation during this time have been measured and an attempt has been made to relate them to the diet of the fish.     

Preliminary observations on the heavy metal content of four species of freshwater fish in NW England

The concentrations of zinc, lead and cadmium in four species of fish from several lacustrine sites were determined. Cyprinids were found to have significantly higher levels of the three metals studied than perch, Perca fluviatilis . Whilst zinc thresholds may be species specific, levels of lead and cadmium vary both within species and sites. There is some evidence that lead and cadmium levels increase with age in roach, Rutilus rutilus . Additionally both cadmium and lead appear to accumulate in the heart, liver, kidney and brain as well as in the bone. Relatively high levels of lead and cadmium were recorded in the eyes of bream, Abrama bramis .     

Fecal collection, ambient preservation, and DNA extraction for PCR amplification of bacterial and human markers from human feces

Feces contain intestinal bacteria and exfoliated epithelial cells that may provide useful information concerning gastrointestinal tract health. Intestinal bacteria that synthesize or metabolize potential carcinogens and produce anti-tumorigenic products may have relevance to colorectal cancer, the second most common cause of cancer deaths in the USA. To facilitate epidemiological studies relating bacterial and epithelial cell DNA and RNA markers, preservative/extraction methods suitable for self-collection and shipping of fecal samples at room temperature were tested. Purification and PCR amplification of fecal DNA were compared after preservation of stool samples in RNAlater (R) or Paxgene (P), or after drying over silica gel (S) or on Whatman FTA cards (W). Comparisons were made to samples frozen in liquid nitrogen (N2). DNA purification methods included Whatman (accompanying FTA cards), Mo-Bio Fecal (MB), Qiagen Stool (QS), and others. Extraction methods were compared for amount of DNA extracted, DNA amplifiable in a real-time SYBR-Green quantitative PCR format, and the presence of PCR inhibitors. DNA can be extracted after room temperature storage for five days from W, R, S and P, and from N2 frozen samples. High amounts of total DNA and PCR-amplifiable Bacteroides spp. DNA (34%+/-9% of total DNA) with relatively little PCR inhibition were especially obtained with QS extraction applied to R preserved samples (method QS-R). DNA for human reduced folate carrier (SLC19A1) genomic sequence was also detected in 90% of the QS-R extracts. Thus, fecal DNA is well preserved by methods suitable for self-collection that may be useful in future molecular epidemiological studies of intestinal bacteria and human cancer markers.     

Mutants in Drosophila TRPC Channels Reduce Olfactory Sensitivity to Carbon Dioxide

Background

Members of the canonical Transient Receptor Potential (TRPC) class of cationic channels function downstream of Gαq and PLCβ in Drosophila photoreceptors for transducing visual stimuli. Gαq has recently been implicated in olfactory sensing of carbon dioxide (CO₂) and other odorants. Here we investigated the role of PLCβ and TRPC channels for sensing CO₂ in Drosophila.

Methodology/Principal Findings

Through behavioral assays it was demonstrated that Drosophila mutants for plc21c, trp and trpl have a reduced sensitivity for CO₂. Immuno-histochemical staining for TRP, TRPL and TRPγ indicates that all three channels are expressed in Drosophila antennae including the sensory neurons that express CO₂ receptors. Electrophysiological recordings obtained from the antennae of protein null alleles of TRP (trp³⁴³) and TRPL (trpl³⁰²), showed that the sensory response to multiple concentrations of CO₂ was reduced. However, trpl³⁰²; trp³⁴³ double mutants still have a residual response to CO₂. Down-regulation of TRPC channels specifically in CO₂ sensing olfactory neurons reduced the response to CO₂ and this reduction was obtained even upon down-regulation of the TRPCs in adult olfactory sensory neurons. Thus the reduced response to CO₂ obtained from the antennae of TRPC RNAi strains is not due to a developmental defect.

Conclusion

These observations show that reduction in TRPC channel function significantly reduces the sensitivity of the olfactory response to CO₂ concentrations of 5% or less in adult Drosophila. It is possible that the CO₂ receptors Gr63a and Gr21a activate the TRPC channels through Gαq and PLC21C.