Contamined lands: a Canadian perspective

The existence of contaminated sites in Canada has become a problem of nation-wide concern. Actions at civil and common law based on the traditional requirements of showing that property interests have been affected or personal injury has resulted are inadequate to address widespread harms arising from pollution. At the national level programs and policies have been developed to address clean-up of contaminated sites. At the provincial level legislation is being developed, directed at making persons responsible for the pollution they cause. Nonetheless, there are shortcomings under the present system in matters concerning victim redress and clean-up and restoration of contaminated sites. Victims are still struggling to obtain redress and compensation, especially in cases of defendant bankruptcy. It may be necessary as in the U.S. to create a Superfund to ensure compensation when there are orphan sites or when the defendant has become insolvent. There may be merit in establishing at the Federal level and in the other provinces a class action scheme along the lines of the Quebec model with an Assistance Fund to help litigants. In addition, there is a need to develop in legislation comprehensive requirements of clean-up and restoration of contaminated sites, that can be applied consistently nation-wide.La question des sols contaminés au Canada est devenue une question d'intérêt national. Les recours du droit civil et du droit commun, qui requièrent un dommage à la propriété ou un préjudice personnel, ne sont plus adéquats pour faire face aux dommages considérables qui résultent de la pollution. Au niveau national, des politiques et des programmes de décontamination des sols ont été élaborés. Au niveau provincial, des efforts législatifs sont en cours et visent à imputer la responsabilité aux pollueurs. Toutefois, le système en place accuse certaines faiblesses particulièrement en ce qui a trait aux recours des victimes ainsi qu'à la décontamination et restauration des lieux contaminés. Les victimes doivent lutter pour obtenir une indemnisation surtout lorsque le défendeur fait faillite. Il peut s'avérer nécessaire, à l'instar de ce qui s'est fait aux États-Unis, de créer un fonds spécial d'indemnisation dans les cas des sites orphelins ou lorsque le défendeur devient insolvable. Il pourrait être utile au niveau fédéral et dans les autres provinces canadiennes d'instaurer un mécanisme de recours collectif comme celui qui existe au Québec de même qu'un fonds d'aide pour soutenir financièrement ceux qui exercent un tel recours. Au surplus, il importe de légiférer pour établir des standards de décontamination et de restauration des lieux contaminés qui puissent s'appliquer à l'échelle nationale

Myoclonic Epilepsy and Ragged Red Fibers (MERRF) Syndrome: Selective Vulnerability of CNS Neurons Does Not Correlate with the Level of Mitochondrial tRNA^(lys) Mutation in Individual Neuronal Isolates

Selective vulnerability of subpopulations of neurons is a striking feature of neurodegeneration. Mitochondrially transmitted diseases are no exception. In this study CNS tissues from a patient with myoclonus epilepsy and ragged red fibers (MERRF) syndrome, which results from an A to G transition of nucleotide (nt) 8344 in the mitochondrial tRNA^(Lys) gene, were examined for the proportion of mutant mtDNA. Either individual neuronal somas or the adjacent neuropil and glia were microdissected from cryostat tissue sections of histologically severely affected brain regions, including dentate nuclei, Purkinje cells, and inferior olivary nuclei, and from a presumably less affected neuronal subpopulation, the anterior horn cells of the spinal cord. Mutant and normal mtDNA were quantified after PCR amplification with a mismatched primer and restriction enzyme digestion. Neurons and the surrounding neuropil and glia from all CNS regions that were analyzed exhibited high proportions of mutant mtDNA, ranging from 97.6 ± 0.7% in Purkinje cells to 80.6 ± 2.8% in the anterior horn cells. Within each neuronal group that was analyzed, neuronal soma values were similar to those in the surrounding neuropil and glia or in the regional tissue homogenate. Surprisingly, as compared with controls, neuronal loss ranged from 7% of the Purkinje cells to 46% of the neurons of the dentate nucleus in MERRF cerebellum. Thus, factors other than the high proportion of mutant mtDNA, in particular nuclear-controlled neuronal differences among various regions of the CNS, seem to contribute to the mitochondrial dysfunction and ultimate cell death

Myoclonic Epilepsy and Ragged Red Fibers (MERRF) Syndrome: Selective Vulnerability of CNS Neurons Does Not Correlate with the Level of Mitochondrial tRNA^(lys) Mutation in Individual Neuronal Isolates

Selective vulnerability of subpopulations of neurons is a striking feature of neurodegeneration. Mitochondrially transmitted diseases are no exception. In this study CNS tissues from a patient with myoclonus epilepsy and ragged red fibers (MERRF) syndrome, which results from an A to G transition of nucleotide (nt) 8344 in the mitochondrial tRNA^(Lys) gene, were examined for the proportion of mutant mtDNA. Either individual neuronal somas or the adjacent neuropil and glia were microdissected from cryostat tissue sections of histologically severely affected brain regions, including dentate nuclei, Purkinje cells, and inferior olivary nuclei, and from a presumably less affected neuronal subpopulation, the anterior horn cells of the spinal cord. Mutant and normal mtDNA were quantified after PCR amplification with a mismatched primer and restriction enzyme digestion. Neurons and the surrounding neuropil and glia from all CNS regions that were analyzed exhibited high proportions of mutant mtDNA, ranging from 97.6 ± 0.7% in Purkinje cells to 80.6 ± 2.8% in the anterior horn cells. Within each neuronal group that was analyzed, neuronal soma values were similar to those in the surrounding neuropil and glia or in the regional tissue homogenate. Surprisingly, as compared with controls, neuronal loss ranged from 7% of the Purkinje cells to 46% of the neurons of the dentate nucleus in MERRF cerebellum. Thus, factors other than the high proportion of mutant mtDNA, in particular nuclear-controlled neuronal differences among various regions of the CNS, seem to contribute to the mitochondrial dysfunction and ultimate cell death

Mitochondrial Fusion Is Required for mtDNA Stability in Skeletal Muscle and Tolerance of mtDNA Mutations

Mitochondria are highly mobile and dynamic organelles that continually fuse and divide. These processes allow mitochondria to exchange contents, including mitochondrial DNA (mtDNA). Here we examine the functions of mitochondrial fusion in differentiated skeletal muscle through conditional deletion of the mitofusins Mfn1 and Mfn2, mitochondrial GTPases essential for fusion. Loss of the mitofusins causes severe mitochondrial dysfunction, compensatory mitochondrial proliferation, and muscle atrophy. Mutant mice have severe mtDNA depletion in muscle that precedes physiological abnormalities. Moreover, the mitochondrial genomes of the mutant muscle rapidly accumulate point mutations and deletions. In a related experiment, we find that disruption of mitochondrial fusion strongly increases mitochondrial dysfunction and lethality in a mouse model with high levels of mtDNA mutations. With its dual function in safeguarding mtDNA integrity and preserving mtDNA function in the face of mutations, mitochondrial fusion is likely to be a protective factor in human disorders associated with mtDNA mutations

MELAS Mutation in mtDNA Binding Site for Transcription Termination Factor Causes Defects in Protein Synthesis and in Respiration but no Change in Levels of Upstream and Downstream Mature Transcripts

The pathogenetic mechanism of the mitochondrial tRNA^(Leu)_(UUR) gene mutation responsible for the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome was investigated in transformants obtained by transfer of mitochondria from three genetically unrelated MELAS patients into human mitochondrial DNA (mtDNA)-less (ρ°) cells. Marked defects in mitochondrial protein synthesis and respiratory activity were observed in transformants containing virtually pure mutant mtDNA, as compared to the parent of the ρ° cells (the 143B cell line) or to transformants containing exclusively wild-type mtDNA, derived from one of the patients or a maternally related asymptomatic individual. A striking protective effect against the mutation was exerted in the transformants by levels of residual wild-type mtDNA above 6%. The MELAS mutation occurs within the mtDNA binding site for a protein factor (mTERF) that promotes termination of transcription at the 16S rRNA/tRNA^(Leu)_(UUR) gene boundary. A marked decrease in affinity of purified mTERF for the mutant target sequence was observed in in vitro assays. By contrast, RNA transfer hybridization experiments failed to show any significant change in the steady-state amounts of the two rRNA species, encoded upstream of the termination site, and of the mRNAs encoded downstream, in the transformants carrying the MELAS mutation

Assessment of a joint farmer-veterinarian discussion about biosecurity using novel social interaction analyses

Veterinarians are trusted by farmers and play an important role in assisting them to implement biosecurity. More research is needed that particularly focuses on the impact of joint farmer-veterinarian discussions to further understand the role of communication in altering biosecurity behaviours. The aim of this study was to analyse joint dairy cattle farmer-veterinarian discussions about the adoption of on-farm biosecurity using novel social interaction methodologies. Farmer and veterinarian stakeholders were invited to take part in a face-to-face meeting. Introductory presentations were given, followed by separate facilitated veterinarian and farmer discussions. All stakeholders were brought together for a final facilitated group discussion which was audio recorded. Corresponding transcripts from the recordings were analysed via thematic and conversation analyses. Conversation analysis assessments such as turn taking, repair, sequence organisation, overlap and asymmetry were employed to investigate the nature of the conversation. Thematic analysis identified the negative repercussions of conflicting information or ineffective communication surrounding biosecurity implementation. The type of, and importance of, the relationship farmers had with veterinarians and other stakeholders was highlighted. The need to provide personalised biosecurity protocols on farms was identified. Four key factors were identified via conversation analyses. These included: 1) how the conversation facilitated agreement, 2) how the conversation allowed the farmer and veterinarian participants to learn from one another in real time, 3) how the discussion enabled participants to expand upon points they were making, and 4) how participants were able to obtain a greater understanding of the other participants’ opinions, even without total resolution. Debate around the effective implementation of biosecurity measures on farms, explored using novel techniques, demonstrated the potential for utilising a discussive approach between veterinarians and farmers to lead to solutions not previously considered. Because of the nature of the discussion, conversation analysis resulted in an informative approach to encapsulating the nuanced dialogue between stakeholders, highlighting the potential of this analysis framework

Detection of the A189G mtDNA heteroplasmic mutation in relation to age in modern and ancient bones.

International audienceThe aim of this study was to demonstrate the presence of the A189G age-related point mutation on DNA extracted from bone. For this, a peptide nucleic acid (PNA)/DNA sequencing method which can determine an age threshold for the appearance of the mutation was used. Initially, work was done in muscle tissue in order to evaluate the sensitivity of the technique and afterwards in bone samples from the same individuals. This method was also applied to ancient bones from six well-preserved skeletal remains. The mutation was invariably found in muscle, and at a rate of up to 20% in individuals over 60 years old. In modern bones, the mutation was detected in individuals aged 38 years old or more, at a rate of up to 1%, but its occurrence was not systematic (only four out of ten of the individuals over 50 years old carried the heteroplasmy). For ancient bones, the mutation was also found in the oldest individuals according to osteologic markers. The study of this type of age-related mutation and a more complete understanding of its manifestation has potentially useful applications. Combined with traditional age markers, it could improve identification accuracy in forensic cases or in anthropological studies of ancient populations

Correction of the consequences of mitochondrial 3243A>G mutation in the MT-TL1 gene causing the MELAS syndrome by tRNA import into mitochondria

Mutations in human mitochondrial DNA are often associated with incurable human neuromuscular diseases. Among these mutations, an important number have been identified in tRNA genes, including 29 in the gene MT-TL1 coding for the tRNALeu(UUR). The m.3243A>G mutation was described as the major cause of the MELAS syndrome (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes). This mutation was reported to reduce tRNALeu(UUR) aminoacylation and modification of its anti-codon wobble position, which results in a defective mitochondrial protein synthesis and reduced activities of respiratory chain complexes. In the present study, we have tested whether the mitochondrial targeting of recombinant tRNAs bearing the identity elements for human mitochondrial leucyl-tRNA synthetase can rescue the phenotype caused by MELAS mutation in human transmitochondrial cybrid cells. We demonstrate that nuclear expression and mitochondrial targeting of specifically designed transgenic tRNAs results in an improvement of mitochondrial translation, increased levels of mitochondrial DNA-encoded respiratory complexes subunits, and significant rescue of respiration. These findings prove the possibility to direct tRNAs with changed aminoacylation specificities into mitochondria, thus extending the potential therapeutic strategy of allotopic expression to address mitochondrial disorders

Gene Expression Pattern in Transmitochondrial Cytoplasmic Hybrid Cells Harboring Type 2 Diabetes-Associated Mitochondrial DNA Haplogroups

Decreased mitochondrial function plays a pivotal role in the pathogenesis of type 2 diabetes mellitus (T2DM). Recently, it was reported that mitochondrial DNA (mtDNA) haplogroups confer genetic susceptibility to T2DM in Koreans and Japanese. Particularly, mtDNA haplogroup N9a is associated with a decreased risk of T2DM, whereas haplogroups D5 and F are associated with an increased risk. To examine functional consequences of these haplogroups without being confounded by the heterogeneous nuclear genomic backgrounds of different subjects, we constructed transmitochondrial cytoplasmic hybrid (cybrid) cells harboring each of the three haplogroups (N9a, D5, and F) in a background of a shared nuclear genome. We compared the functional consequences of the three haplogroups using cell-based assays and gene expression microarrays. Cell-based assays did not detect differences in mitochondrial functions among the haplogroups in terms of ATP generation, reactive oxygen species production, mitochondrial membrane potential, and cellular dehydrogenase activity. However, differential expression and clustering analyses of microarray data revealed that the three haplogroups exhibit a distinctive nuclear gene expression pattern that correlates with their susceptibility to T2DM. Pathway analysis of microarray data identified several differentially regulated metabolic pathways. Notably, compared to the T2DM-resistant haplogroup N9a, the T2DM-susceptible haplogroup F showed down-regulation of oxidative phosphorylation and up-regulation of glycolysis. These results suggest that variations in mtDNA can affect the expression of nuclear genes regulating mitochondrial functions or cellular energetics. Given that impaired mitochondrial function caused by T2DM-associated mtDNA haplogroups is compensated by the nuclear genome, we speculate that defective nuclear compensation, under certain circumstances, might lead to the development of T2DM

A functional peptidyl-tRNA hydrolase, ICT1, has been recruited into the human mitochondrial ribosome

Bioinformatic analysis classifies the human protein encoded by immature colon carcinoma transcript-1 (ICT1) as one of a family of four putative mitochondrial translation release factors. However, this has not been supported by any experimental evidence. As only a single member of this family, mtRF1a, is required to terminate the synthesis of all 13 mitochondrially encoded polypeptides, the true physiological function of ICT1 was unclear. Here, we report that ICT1 is an essential mitochondrial protein, but unlike the other family members that are matrix-soluble, ICT1 has become an integral component of the human mitoribosome. Release-factor assays show that although ICT1 has retained its ribosome-dependent PTH activity, this is codon-independent; consistent with its loss of both domains that promote codon recognition in class-I release factors. Mutation of the GGQ domain common to ribosome-dependent PTHs causes a loss of activity in vitro and, crucially, a loss of cell viability, in vivo. We suggest that ICT1 may be essential for hydrolysis of prematurely terminated peptidyl-tRNA moieties in stalled mitoribosomes