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Abstract:Although over 80 cytochrome P450 (CYP) encoding genes have been identified in the genome of the nematode Caenorhabditis elegans very little is known about their involvement in biotransformation. This paper demonstrates a concentration dependent relationship of C. elegans CYP35A1, A2, A5, and C1 gene expression in response to four organic xenobiotics, namely atrazine, PCB52, fluoranthene, and lansoprazole. The toxicity of these xenobiotics was determined using a reproduction assay. CYP-specific messenger RNA expression was analyzed by semi-quantitative RT-PCR resulting in a strongly increasing, concentration-dependent induction well below the EC 50 for reproduction. For PCB52, approximately 0.5 % of the EC 50 induces a two-fold increase of CYP35 gene expression. Using a double mutant and multiple RNAi of CYP35A/C it was possible to diminish the reproduction decline caused by PCB52 and fluoranthene.

Humic materials are complex organic molecules constituting the most abundant source of natural organic matter (NOM) in freshwater and soil ecosystems. Recent advances have identified that they interfere with biological systems, via the induction of biotransformation enzymes, the inhibition of photosynthetic oxygen release (in freshwater plants), the production of internal oxidative stress, or through the feminization of fish and amphibians. The nematode model organism Caenorhabditis elegans was chosen to investigate whether a natural and a synthetic humic material induce (i) a behavioral attraction, (ii) the reproduction, and (iii) a response in whole genome transcriptional expression. The phenomenological attractant experiments provided evidence that both humic material sources attract the worm and exert distinct chemical cues. In the reproduction assay, only the highest concentration (32 mg/L DOC of Fuchskuhle NOM, 38 mg/L DOC of HS 1500) resulted in a decrease in brood size, highlighting an overall intrinsic tolerance toward humic material. Finally, oligonucleotide-based whole genome DNA microarray experiments were performed from control and humic material treated worms. Significant transcriptional changes (exceeding a 2-fold increase or decrease) were identified in chemosensors, olfactory receptors, as well as enzymes of the biotransformation system (cytochromes P450, UDP-glucuronosyltransferases, glutathione S-transferases), thereby confirming that humic material is recognized as an environmental signaling chemical.

Myostatin, a negative regulator of muscle growth, has recently been found to be expressed in tendons. Myostatin-deficient mice have weak and brittle tendons, which suggest that myostatin could be important for tendon maintenance. Follistatin expression in the callus tissue after tendon transection is influenced by loading. We found that follistatin antagonises myostatin, but not GDF-5 or OP-1 in vitro. To study if myostatin might play a physiological role in soft tissue, we transected 64 rat Achilles tendons and studied the gene expression for myostatin and its receptors at four different time-points during healing. Intact tendons were also studied. All samples were studied with or without mechanical loading. Unloading was achieved with botulinum toxin injections in the calf muscles. The expression of the myostatin gene was more than 40 times higher in intact tendons than in the callus tissue during tendon healing. The expression of myostatin was also influenced by loading status in both intact and healing tendons. Thereafter, we measured the mechanical properties of healing tendons after local myostatin administration. This treatment increased the volume and the contraction of the callus after 8 days, but did not improve its strength. Our results indicate that myostatin plays a positive role in tendon maintenance and that exogenous protein administration stimulates proliferation and growth of early repair tissue. However, no effect on further development towards connective tissue formation was found.