Neurophysiological and behavioral development in birds: Song learning as a model system

The avian song system is a particularly good model for studying the behavioral and physiological aspects of animal development. One seemingly trivial but very important reason for this is that the sound spectrograph enables sounds to be described, measured and analyzed objectively and in detail. Secondly, birdsong is one of the few behaviors which is performed by a separate chain of brain regions and is therefore relatively easy to investigate neurophysiologically. Work on song also provides a clear illustration of the subtle way in which birds are influenced by their internal and external environments during development.     

Sources and toxicities of phenolic polychlorinated biphenyls (OH-PCBs)

Polychlorinated biphenyls (PCBs), a group of 209 congeners that differ in the number and position of chlorines on the biphenyl ring, are anthropogenic chemicals that belong to the persistent organic pollutants (POPs). For many years, PCBs have been a topic of interest because of their biomagnification in the food chain and their environmental persistence. PCBs with fewer chlorine atoms, however, are less persistent and more susceptible to metabolic attack, giving rise to chemicals characterized by the addition of one or more hydroxyl groups to the chlorinated biphenyl skeleton, collectively known as hydroxylated PCBs (OH-PCBs). In animals and plants, this biotransformation of PCBs to OH-PCBs is primarily carried out by cytochrome P-450-dependent monooxygenases. One of the reasons for infrequent detection of lower chlorinated PCBs in serum and other biological matrices is their shorter half-lives, and their metabolic transformation, resulting in OH-PCBs or their conjugates, such as sulfates and glucuronides, or macromolecule adducts. Recent biomonitoring studies have reported the presence of OH-PCBs in human serum. The occurrence of OH-PCBs, the size of this group (there are 837 mono-hydroxyl PCBs alone), and their wide spectra of physical characteristics (pKa’s and log P’s ranging over 5 to 6 orders of magnitude) give rise to a multiplicity of biological effects. Among those are bioactivation to electrophilic metabolites that can form covalent adducts with DNA and other macromolecules, interference with hormonal signaling, inhibition of enzymes that regulate cellular concentrations of active hormones, and interference with the transport of hormones. This new information creates an urgent need for a new perspective on these often overlooked metabolites.     

Authentication of synthetic environmental contaminants and their (bio)transformation products in toxicology: polychlorinated biphenyls as an example

Environmental Science and Pollution Research - Toxicological studies use “specialty chemicals” and, thus, should assess and report both identity and degree of purity (homogeneity) of...     

On the cytotoxicity of some microbial volatile organic compounds as studied in the human lung cell line A549

The cytotoxicity of 13 microbial volatile organic compounds (MVOC) was studied using a human lung carcinoma epithelial cell line A549 in a colony formation assay and two colorimetric assays: the microculture tetrazolium assay (MTT assay) and the cellular protein assay (methylene blue-MB assay). For comparison, two known cytotoxic substances: the non-volatile mycotoxin gliotoxin and the mono-functional alkylating agent methyl methanesulfonate (MMS) were studied. Concentration-response curves for each agent were established and the IC50 value (concentration resulting in 50% inhibition of colony growth or absorbance) was estimated. There are differences in toxicity levels between the MVOC tested and gliotoxin and MMS. The most toxic MVOC was 1-decanol which was as effective as MMS in all test systems. 1-decanol was about 10-fold more toxic than the other MVOC. All MVOC tested were more than 1000-fold less toxic than gliotoxin.