Metabonomic assessment of toxicity of 4-fluoroaniline, 3,5-difluoroaniline and 2-fluoro-4-methylaniline to the earthworm Eisenia veneta (Rosa): identification of new endogenous biomarkers

High-resolution 1H nuclear magnetic resonance (NMR) spectroscopy can be used to produce a biochemical fingerprint of low-molecular-weight metabolites from complex biological mixtures such as tissue extracts and biofluids. Changes in such fingerprint profiles can be used to characterize the effects of toxic insult in in vivo systems. The technique is nonselective and requires little sample preparation or derivatization. In the present study, earthworms (Eisenia veneta) were exposed to three different model xenobiotics by a standard filter paper contact test, and toxicant-induced biochemical changes were then investigated by characterizing the changes in endogenous metabolites visible in 600-MHz 1H NMR spectra of tissue extracts. The NMR spectral intensities were converted to discrete numerical values and tabulated in order to provide data matrices suitable for multivariate analysis. Principal component analysis showed that changes had occurred in the biochemical profiles relative to the undosed controls. The 2-fluoro-4-methylaniline-treated worms showed a decrease in a resonance from a compound identified as 2-hexyl-5-ethyl-3-furansulfonate using a combination of high-performance liquid chromatography (HPLC)-Fourier transform mass spectrometry (IonSpec, Lake Forest, CA, USA) and 1H and 13C NMR spectroscopy. An increase in inosine monophosphate was also observed. The 4-fluoroaniline-treated worms showed a decrease in maltose concentrations, and 3,5-difluoroaniline exerted the same effect as 2-fluoro-4-methylaniline but to a lesser extent. These changes could potentially be used as novel biomarkers of xenobiotic toxicity and could be used to determine the mechanism of action of other toxic chemicals.

Evaluation of tissue and cellular biomarkers to assess 2,4,6-trinitrotoluene (TNT) exposure in earthworms: effects-based assessment in laboratory studies using Eisenia andrei

The lysosomal neutral red retention time (NRRT) assay, a biomarker for lysosomal membrane stability, and the total immune activity (TIA) assay, a measure of non-specific immune system activity, were used in laboratory studies to assess the toxic effects of 2,4,6-trinitrotoluene (TNT) on earthworms (Eisenia andrei) in vivo. The results were compared with the concentration of TNT and its metabolites in earthworm tissue, as well as standard sublethal toxicity endpoints including growth (i.e. weight change) and reproduction effects from previously published studies. Filter paper experiments indicated a significant decrease in NRRT at >or=1.8 micro g TNT cm(-2), whereas sublethal (weight loss) and lethal effects to earthworms were detected at >or=3.5 and 7.1 micro g TNT cm(-2), respectively. Experiments in artificial soil showed that NRRT effects could be detected at lower TNT concentrations (>or=55 mg TNT kg(-1) soil dry weight) compared with other sublethal endpoints (effects on growth and reproduction). The TIA biomarker did not significantly respond to TNT. Copper (as CuSO4, filter paper contact tests) and 2-chloroacetamide (soil tests), which were used as reference toxicants, also decreased the NRRT. The use of the NRRT assay linked with tissue concentrations of TNT metabolites in earthworms was identified as a potentially appropriate biomarker approach for TNT exposure assessment under laboratory conditions and a novel tool for effects-based risk assessment.

Earthworm species of the genus Eisenia can be phenotypically differentiated by metabolic profiling

The universality of low molecular weight metabolites allows rapid and straightforward investigation of the biochemistry of genetically uncharacterised species. Thus ex vivo metabolic profiling in combination with multivariate data analysis (metabonomics) offers great potential in comparative biology. Here we present the first use of high resolution nuclear magnetic resonance (NMR) spectroscopy to distinguish closely related animal species via their metabolic phenotype (metabotype). We have profiled the three Eisenia (Oligochaeta, Lumbricidae) species Eisenia fetida, Eisenia andrei and Eisenia veneta using tissue extracts and coelomic fluid analysis. The low molecular weight biochemical profiles of tissue extracts were highly conserved for all three species, with E. fetida and E. andrei being more similar to each other than to E. veneta. However the metabolic profiles of the coelomic fluid of the different species were highly distinctive - the NMR spectra allowed unequivocal identification of species. Multivariate statistics were also used to quantify these spectral differences and to enable simplified graphical visualisation of species similarity. These results show that two morphologically undistinguishable species (E. fetida and E. andrei) differ markedly in their biochemical profiles despite apparently occupying the same ecological niche, and indicate that metabolic phenotype profiling can be used as a powerful functional genomics tool.

Localization of metabotropic glutamate receptor type 2 in the human brain

Metabotropic glutamate receptors are a heterogeneous family of G-protein-coupled receptors that are linked to multiple second messenger systems to regulate neuronal excitability and synaptic transmission. To elucidate the physiological role of these receptors in human central nervous system function and dysfunction at the receptor protein level requires the use of selective antibodies to determine the phenotype of cells expressing particular receptor subtypes. To this end the present study has examined the regional and cellular localization of the metabotropic glutamate type 2 receptor protein in selected human brain regions. After epitope prediction, antibodies have been generated against a short synthetic peptide corresponding to amino acid residues located in the putative intracellular carboxy-terminus and subsequently applied to an immunohistochemical investigation. Antibodies specifically detected the type 2 receptor in transfected mammalian cells and also recognized a major band of 98,000 mol. wt in western blots of human brain tissue membranes. At the light microscope level immunohistochemical studies have demonstrated that type 2-like immunoreactivity was widely distributed in the human brain, being characterized by the presence of a strong immunoreaction in multiple cortical regions, and in structures comprising the basal ganglia, to include the caudate nucleus, putamen, globus pallidus, substantia nigra and subthalamic nucleus. In the hippocampal formation, immunoreactivity was predominant in selective cell layers of both the dentate gyrus and cornu ammonis, the subicular complex and entorhinal cortex. In the thalamus, multiple subnuclei showed reaction product. In the cerebellar cortex, immunoreactivity was expressed in a number of cell layers and cell types. Furthermore, using double immunofluorescence we confirmed that the type 2 receptor is a product of normal resting astrocytes in the cerebral cortex in particular. This antibody provides a new immunological tool with the potential to evaluate the distribution of human metabotropic glutamate receptor 2 protein in other brain regions and in human central nervous system diseases.

The intrinsic specification of gamma-aminobutyric acid type A receptor alpha6 subunit gene expression in cerebellar granule cells

The patterns of gamma-aminobutyric acid type A (GABAA) receptor subunit gene expression in the brain are complex. For example, mouse hippocampal dentate granule cells express many subunit genes, whereas adult cerebellar granule cells, which may share differentiation mechanisms, have a smaller compliment and uniquely express the alpha6 subunit gene. To see how the alpha6 expression component arises, i.e. if intrinsically or environmentally specified, we used a mouse line (Deltaalpha6lacZ) with a beta-galactosidase reporter inserted into the alpha6 gene. Precursor cells from postnatal day 1 Deltaalpha6lacZ cerebellum were transplanted to the adult hippocampus and cerebellum of wild-type mice; 4 weeks after transplantation, Deltaalpha6lacZ cells expressed alpha6-lacZ in the hippocampus, amygdala and cerebellum. Thus, different adult environments support both the development and maintenance of alpha6 gene expression from cerebellar granule cell precursors. Establishing alpha6 gene expression is not likely to require specific patterns of neurotransmitter innervation or other factors present only in the developing brain; instead, alpha6 expression can be timed and maintained autonomously.

Regional potential for oligodendrocyte generation in the rodent embryonic spinal cord following exposure to EGF and FGF-2

The origin of oligodendrocytes in the developing rodent spinal cord has not been fully established, with some evidence that oligodendrocyte progenitors arise exclusively from the ventral neuroepithelium, other studies suggesting that both halves of the spinal cord have oligodendrogenic potential. One way of exploring this issue is to study more primitive oligodendrocyte precursors. Although specific markers are not available, their presence may be inferred using mitogens such as EGF and FGF-2, which stimulate the proliferation of immature neuroepithelial cells, and subsequently studying their differentiation into lineage restricted cells. We used this approach to assess whether the dorsal embryonic rodent spinal cord has the intrinsic potential for oligodendrocyte formation at E14. We confirm that significant numbers of oligodendrocytes and their immediate (A2B5+) precursors are present only in the ventral spinal cord of the E14 rodent, but following exposure to EGF and FGF-2, significant numbers of oligodendrocytes and A2B5+ precursor cells also develop from isolated E14 dorsal derived cells without interaction from the ventral spinal cord. In addition, bromodeoxyuridine studies demonstrate that isolated dorsal derived cells proliferate and express A2B5 following exposure to EGF and FGF-2. The observation that from E14, the dorsal cord already has latent oligodendrogenic potential provides an alternative mechanism for oligodendrocyte formation to ventro-dorsal migration of oligodendrocyte precursors.

Relevance and applicability of a simple earthworm biomarker of copper exposure. II. Validation and applicability under field conditions in a mesocosm experiment with Lumbricus rubellus

Earthworms Lumbricus rubellus were exposed to a range of increasing soil copper concentrations in a mesocosm experiment for 17, 40, 70, and 110 days, respectively. Neutral-red retention times were measured along with earthworm tissue copper residues and earthworm growth and survival. The neutral-red retention assay demonstrated a clear dose-response threshold preceding a copper exposure value where increased regulatory activity had resulted in the copper bioconcentration factor (BCF) decreasing from 1 to 0.5. Effects on earthworm growth and survival occurred only at soil copper concentrations where the earthworm BCFs were lowered to ca. 0.5. Thus, the position of the neutral-red threshold could potentially make it possible to differentiate between copper exposure and actual toxicity. In terms of field applicability it was demonstrated that natural and seasonal variations in climatic parameters had little or no effect on the neutral-red response. Neutral-red retention assay has a potential role in environmental risk assessment and routine monitoring, as it is likely to provide a sufficiently accurate warning of impending ecological damage at a level below that found to cause actual physiological damage to the earthworms.

Relevance and applicability of a simple earthworm biomarker of copper exposure. I. Links to ecological effects in a laboratory study with Eisenia andrei

A simple earthworm biomarker, neutral-red retention by coelomocyte lysosomes, was measured concurrently with ecological parameters in order to link effects at different levels of biological organization in a laboratory study. Exposure of the earthworm Eisenia andrei to an increasing range of soil copper concentrations in the laboratory indicated a threshold range for the neutral-red assay at soil copper concentrations between 40 and 80 mg Cu kg-1. This threshold coincided with the soil to worm copper bioconcentration factor decreasing from 1 to 0.3 and thus an apparent onset of a copper regulatory mechanism. Effects at the individual and population levels only occurred at soil copper concentrations beyond that of the biomarker threshold. Thus, it was possible to differentiate between exposure and toxicity. It was therefore possible to conclude that the neutral-red assay has great potential and relevance in earthworm ecotoxicity studies. The assay provides an early warning that can be linked directly to important physiological changes that were observed to precede adverse effects on individuals or populations in this laboratory study.

Prevalence of HPV in premalignant and malignant cervical lesions in Greenland and Denmark: PCR and in situ hybridization analysis on archival material

Archival formalin-fixed paraffin-embedded cervical specimens from 125 women in Greenland and 139 women in Denmark who had CIN I-III or cervical cancer diagnosed between 1983 and 1987 were analysed for human papillomavirus type 16 (HPV-16) by in situ hybridization and for HPV-16, 18, 31, 33, 35 and 45 by PCR. In situ hybridization analysis showed an HPV-16 prevalence of 17% (16/95) and 23% (24/105) in the premalignant lesions from Greenland and Denmark, respectively. The HPV-16 prevalence rate in the cancer specimens was 10% (3/30) in the samples from Greenland and 29% (10/34) in the Danish specimens. A total of 82 Greenlandic and 107 Danish specimens were beta-globin-positive by PCR reaction. HPV-16-specific PCR on these samples showed 63% (34/54) of the Greenlandic and 68% (50/74) of the Danish preinvasive lesions to be positive. The corresponding HPV-16-positive rates for the invasive cancers were 82% (23/28) for Greenland and 70% (23/33) for Denmark. This study of patient samples supports our previous population-based studies in which similar HPV-detection rates were found among random samples of women from Greenland and Denmark, although Greenland has a 4-5-fold higher cervical cancer incidence.

Simultaneous measurement of monoamines, metabolites and amino acids in brain tissue and microdialysis perfusates

A high-performance liquid chromatographic method with coulometric array electrochemical detection is described for the simultaneous analysis of monoamines, their metabolites and o-phthalaldehyde (OPA)-derivatized amino acids. This method has been used to examine metabolite levels in both striatal tissue homogenates and striatal microdialysis perfusates. An aliquot of sample was initially analyzed for monoamines and metabolites by isocratic elution and electrochemical detection on a serial electrode array of eight coulometric flow-through graphite electrodes (0 to 490 mV; 70-mV increment). The remaining sample was derivatized pre-column with OPA-beta-mercaptoethanol and after column switching was analyzed for amino acids on a second isocratic system with electrochemical detection on four electrodes. Metabolites were then identified based on their retention time as well as electrochemical behavior across the arrays. The analysis, derivatization procedure, column switching, data reduction and peak identification were fully automated. The limit of detection for striatal tissue homogenates was approximately 1.38 ng/g wet weight for the monoamines and 8.25 ng/g wet weight for amino acids. The limit of detection for striatal perfusates was approximately 2.5 pg per 20-microliters sample for the monoamines and 15 pg per 20-microliters sample for the amino acids with analysis completed within 25 min making it ideal for microdialysis samples.

The substantia innominata in Alzheimer's disease: an histochemical and biochemical study of cholinergic marker enzymes

Acetylcholinesterase staining was examined in the substantia innominata of 3 normal human brains. Large intensely stained neurones were seen within the region of the basal nucleus of Meynert which is believed to be the origin of the cholinergic projection to the neocortex in animals. On the basis of the acetylcholinesterase staining pattern, the substantia innominata was dissected from post-mortem brain tissue of 19 cases of Alzheimer's disease (AD) and 16 controls so as to include the basal nucleus. Choline acetyltransferase (ChAT) activity was found to be reduced in the substantia innominata and amygdala in AD but not in the adjacent lentiform nucleus and hypothalamus.