Analysis of mitochondrial ND4 gene DNA sequence in Finnish families with Leber hereditary optic neuroretinopathy

A mutation in the mitochondrial DNA at nt 11,778 has recently been found in Leber hereditary optic neuroretinopathy (LHON), a maternally inherited ocular disease. The mutation is located in the ND4 gene encoding subunit 4 of the respiratory chain enzyme NADH dehydrogenase. The mutation was subsequently not found in 9 of the 20 known Finnish families with LHON, implying that there are at least two different mutations associated with the disease. Using direct sequencing of PCR-amplified mtDNA, we have now sequenced the entire ND4 region in the families without the nt 11,778 mutation to find the other mutations. No new mutations in the ND4 region were found, suggesting that the putative mtDNA mutation in these families may be in the coding regions for other subunits of NADH dehydrogenase enzyme. The sequence of ND4 gene as found to be highly homogeneous.     

Human mitochondrial DNA types in Finland

Summary Variation in mitochondrial DNA (mtDNA) in a sample of 110 Finns was analyzed with six restriction enzymes, AvaII, BamHI, HaeII, HinII, HpaI, and MspI, by using total blood cell DNA probed with mouse mtDNA. Two new enzyme morphs were observed, one for HaeII and one for HindII. Double-digestion experiments indicated that the BamHI morphs 2 and 3 result from base changes leading to AvaII morphs 3 and 9, respectively. Of the ten different mtDNA types observed, defined by restriction fragment patterns, seven have been previously described in Caucasoid populations. The three new Finnish mtDNA types can be derived from Caucasoid lineages by single restriction site changes. The results were used to reconstruct a phylogenetic tree for Caucasoid mtDNA types defined by the enzymes used. The frequencies of mtDNA types were used to compute genetic distances between Finns, Italians, and Israeli Jews. The frequencies of both enzyme morphs and mtDNA types show that the Finnish population is highly homogeneous.     

Genetic heterogeneity in Leber hereditary optic neuroretinopathy revealed by mitochondrial DNA polymorphism.

The presence or absence of a recently observed mitochondrial DNA (mtDNA) mutation associated with Leber hereditary optic neuroretinopathy (LHON) was tested in 19 Finnish families with cases of LHON. Leukocyte and muscle DNA from individuals with optic atrophy, microangiopathy, or normal fundi from maternal lineages were studied by Southern blot analysis, using mouse mtDNA as a hybridization probe. The mtDNA mutation, detected as SfaNI site polymorphism, was seen in 10 of the 19 families. In one family, the mutation was seen only in the two affected individuals, indicating recent origin for the mutation. Nine families and 28 maternally unrelated controls did not show the mutation. The results imply that alternative mtDNA mutations are associated with LHON and that this genetic heterogeneity may be the cause of the interfamilial variation in the clinical expression of LHON. In the families showing the SfaNI site mutation, the mutation was homoplasmic in all individuals irrespective of their disease status, suggesting that the intrafamilial variation in the clinical expression is not due to different ratios of mutant versus normal mtDNA.     

The molecular basis for Duchenne versus Becker muscular dystrophy: Correlation of severity with type of deletion

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.     

Classification of European Mtdnas from an Analysis of Three European Populations

Mitochondrial DNA (mtDNA) sequence variation was examined in Finns, Swedes and Tuscans by PCR amplification and restriction analysis. About 99% of the mtDNAs were subsumed within 10 mtDNA haplogroups (H, I, J, K, M, T, U, V, W, and X) suggesting that the identified haplogroups could encompass virtually all European mtDNAs. Because both hypervariable segments of the mtDNA control region were previously sequenced in the Tuscan samples, the mtDNA haplogroups and control region sequences could be compared. Using a combination of haplogroup-specific restriction site changes and control region nucleotide substitutions, the distribution of the haplogroups was surveyed through the published restriction site polymorphism and control region sequence data of Caucasoids. This supported the conclusion that most haplogroups observed in Europe are Caucasoid-specific, and that at least some of them occur at varying frequencies in different Caucasoid populations. The classification of almost all European mtDNA variation in a number of well defined haplogroups could provide additional insights about the origin and relationships of Caucasoid populations and the process of human colonization of Europe, and is valuable for the definition of the role played by mtDNA backgrounds in the expression of pathological mtDNA mutations     

Mercury and chlorinated hydrocarbons in the food chain of Lake Päijänne, Finland

The sediments and various organisms in Lake Päijänne were examined for contaminants. The average mercury content of water plants was 9, of plankton 14, of sediment 114, of zoobenthic predators 83, of fish 332–1510 and of birds 240–13685 μg kg⁻¹ (wet weight). The average PCB content of plants was 3, of plankton 21, of the zoobenthos 44, of fish 36-117 and of birds 219–13490 μg kg⁻¹. The average ΔDDT content of plants was 0.5, of plankton 6, of the zoobenthos 14, of fish 7–42 and of birds 144-8262 μg kg⁻¹. Regional differences in mercury content were most pronounced in sediment and fish. PCB concentration was highest near a town. ΔDDT was quite evenly distributed. Water plant species did not differ from each other, nor did the plankton fractions. The zoobenthic predators contained more chlorinated hydrocarbons than did the herbivores. There were clear differences between most species of fish and the chlorinated hydrocarbon content was highest in vendace. In adult birds levels of all residues were significantly higher than in juveniles.
In most cases PCB content was positively correlated with ΔDDT and in birds PCB, ΔDDT and mercury levels were correlated. DDT residues occurred mostly as DDE, but in vendace the proportion of DDT was high. At most trophic levels, ΔDDT/PCB was 0.15-0.40 but in birds it reached 1–2.     

Survival of Campylobacter Jejuni/Coli in Ground Refrigerated and in Ground Frozen Beef Liver and in Frozen Broiler Carcasses

Survival of 5 strains of Campylobacter jejuni/coli in ground beef liver stored at 4° C and at –20° C was studied. After 6 days of storage at 4° C the beef liver was spoiled, which was indicated by APG log 7.25 and lactobacilli count log 7.0. During this storage Campylobacter counts decreased only slightly. After 12 weeks of storage at –20° C Campylobacter counts decreased by 2–3 logs in frozen ground beef liver. Survival of 4 strains of C. jejuni/coli on frozen broiler carcasses was also studied. Two inoculation levels, 103–104/g and 104–105/g were used. On frozen broiler carcasses Campylobacter counts decreased by 0.5–2.0 logs during 12 weeks at –20° C.     

The distribution of C-arachidonic acid in hamster lungs is sensitive to quinacrine

Isolated hamster lungs were labelled with ¹⁴C-arachidonic acid. When the lungs were ventillated with a respirator only a small amount of radioactivity was released to the perfusion effluent. This release was not changed significantly by pulmonary infusion of quicacrine (0.5 mM), a known inhibitor of phospholipase A₂. After the perfusion about 75% of the radioactivity in the lungs was in phospholipids, mainly in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinostil and to a lesser degree in phosphatidylserine and phosphatidic acid. About one fourth of the radioactivity was in neutral lipids (tri- and diacylglycerols) and as free unmetabolized ¹⁴C-arachiodonic acid. Pulmonary infusion of quinacrine increased the amount of radioactivity in diacylglycerols and phosphatidylinositol but had no effect on that in phosphatidylcholine, phosphatidylserine, phosphatidic acid and triacylglycerols. The amount of radioactivity in phosphatidylethanolamine was decreased by quinacrine and increased in the vicinity of an unidentified phospholipid-quinacrine complex. The present study indicates that the distribution of ¹⁴C-arachidonic acid in hamster lung lipids is sensitive to quinacrine. The detected changes can, however, not be explained by an overall inhibition of phospholipase A₂ activities.     

A new mtDNA mutation associated with Leber hereditary optic neuroretinopathy.

A single base mutation at nucleotide position 3460 (nt 3460) in the ND1 gene in human mtDNA was found to be associated with Leber hereditary optic neuroretinopathy (LHON). The G-to-A mutation converts an alanine to a threonine at the 52d codon of the gene. The mutation also abolishes an AhaII restriction site and thus can be detected easily by RFLP analysis. The mutation was found in three independent Finnish LHON families but in none of the 60 controls. None of the families with the nt 3460 mutation in ND1 had the previously reported nt 11778 mutation in the ND4 gene. The G-to-A change at nt 3460 is the second mutation so far detected in LHON.     

Comparison of Four Enrichment Media in the Recovery of Campyloracter Jejuni

The effectiveness of 4 enrichment media for the recovery of low levels of inoculated cells of Campylobacter jejuni was evaluated. The media contained antibiotics or antibiotics and bile acids as selective compounds. Three of the media recovered most of the inoculated low numbers of 6 C. jejuni strains. In the 3 media the growth rate of 3 strains, indicated by the increase in the log number of cells during 24 h or 48 h incubation at 42 ° C, was about the same as in the control medium without selective compounds. The same 3 media also recovered a low number of Campylobacter cells from artificially contaminated raw milk or ground meat samples. The enrichment medium B containing 40 I.U. Colistin, 5 μg novobiocin, 2 mg Na-cholic acid and 50 mg cycloheximide per ml was inhibitory for most Campylobacter strains studied.