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Evaluation of molecular-Beacon, TaqMan, and fluorescence resonance energy transfer probes for detection of antibiotic resistance-conferring single nucleotide polymorphisms in mixed Mycobacterium tuberculosis DNA extracts.

The ability of fluorescence resonance energy transfer, molecular-beacon, and TaqMan probes to detect single nucleotide polymorphism (SNP) in the presence of a wild-type allele was evaluated using drug resistance-conferring SNPs in mixed Mycobacterium tuberculosis DNA. It was found that both the absolute quantity and the ratio of alleles determine the detection sensitivity of the probe systems.

Antitubercular Agents↗

The origin of nascent single-stranded DNA extracted from mammalian cells.

In vitro cultured bovine liver cells were labelled with radioactive thymidine and dissolved in 0.5% sodium dodecyl sulphate. Centrifugation of the lysate through sucrose gradients in a zonal rotor revealed a slowly sedimenting fraction of preferentially pulse labelled DNA. The DNA of this zone was further analysed by chromatography on hydroxy-apatite, banding in CsCl density gradients, and sedimentation in neutral and alkaline sucrose gradients. It contained besides small amounts of fragmented bulk DNA, single-stranded nascent DNA and single-stranded pre-labelled DNA which could be separated from each other by using BrdU as a density label. The density labelling also revealed small amounts of nascent-nascent DNA duplexes. The slowly sedimenting fraction was practically absent from cell lysates which were prepared in 2 M NaCl - 50 microgram/ml pronase. The results suggest that nascent single-strands and nascent-nascent duplexes are released from the forks of replicating DNA by branch migration. Pre-labelled single strands may be released by the same branch migration. Pre-labelled single strands may be released by the same mechanism, but the in vivo structure from which they originate has yet to be elucidated.

Animals↗

Use of proteinase K in the excystation of Sarcocystis cruzi sporocysts for in vitro culture and DNA extraction.

Proteinase K was used for the cleaning of Sarcocystis cruzi (Apicomplexa) sporocysts prior to excystation. Bovine pulmonary endothelial cell cultures inoculated with the excysted sporozoites remained free of bacterial contamination for the duration of the experiment and had high yields of merozoites. The excysted sporozoites also yielded genomic DNA that could be labelled efficiently with 32P dATP by the random priming method.

Animals↗

Presence of mitochondrial tRNA(Leu(UUR)) A to G 3243 mutation in DNA extracted from serum and plasma of patients with type 2 diabetes mellitus.

AIMS/BACKGROUND: An A to G substitution at base pair 3243 in the mitochondrial tRNA(Leu(UUR)) gene (mt3243) is commonly associated with maternally inherited diabetes and deafness, and other diseases. It is possible that cell free mitochondrial DNA exists in serum and plasma from these patients, and these samples might be a source of material for the detection of such mutations. METHODS: Sixteen patients with type 2 diabetes mellitus and 25 healthy subjects were tested for the 3243 mutation by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. Plasma and serum from the 41 subjects were tested blind, without knowledge of the final diagnosis. RESULTS: PCR amplification of the mtRNA(Leu(UUR)) region in mitochondrial DNA (mtDNA) in serum samples revealed the presence of mtDNA in all samples. After ApaI digestion of the amplified DNA fragments, mt3243 was detected in the serum and plasma samples of the seven patients with diabetes who had previously been found to have this mutation in their leucocyte DNA. None of the serum/plasma samples from the healthy subjects or those patients negative for mt3243 in their leucocytes had this mutation (p < 0.001). In addition, the degree of heteroplasmy of mt3243 appeared to be higher in serum and plasma samples than in leucocytes among mt3243 carriers (p < 0.05). CONCLUSIONS: Therefore, mtDNA and associated mutations are present and detectable in serum and plasma. Plasma and serum might be alternative sources for the molecular diagnosis of mt3243 associated diabetes mellitus, as well as other mitochondrial mediated diseases.

Adult↗

Usefulness of new DNA extraction procedure for PCR technique in species identification of Entamoeba isolates.

In this study we have developed a modified CLARK and DIAMOND (1992, 1993) method using the polymerase chain reaction to amplify amoebic ribosomal RNA genes that allow either specific detection of Entamoeba histolytica s. str. or amoeba species identification. DNA was isolated from cultured protozoa or from stool samples (cysts and/or trophozoites). Cultures of xenic or axenic material (also stool samples) were treated with Easy Genomic DNA Prep or Genomic DNA Prep Plus (A&A Biotechnology, Poland) for DNA isolation. With these new procedures, DNA can be obtained effectively and with high degree of purity. 13 amoeba strains were investigated. Three strains produced an 876 bp fragment with Psp5 and Psp3 primers (specific product for E. histolytica s. str). Three strains gave a specific 876 bp product for E. dispar with NPsp5 and NPsp3 primers. Two strains were E. moshkovskii as identified by KpnI digestion of PCR products obtained with RD5 and RD3 primers. Four strains (one of them was cultured in two laboratories) were E. invadens as identified by Hinfl or HhaI digestion of PCR products obtained with RD5 and RD3 primers. Characteristic RFLP patterns with these enzymes was also obtained for E. terrapinae and Blastocystis hominis. This RFLP analysis show significant promise as a medical diagnostic tool particularly useful for species identification.

Animals↗

Technical note: Whole-genome amplification of DNA extracted from cattle semen samples.

The bovine genome sequence project and the discovery of many thousands of bovine single nucleotide polymorphisms has opened the door for large-scale genotyping studies to identify genes that contribute to economically important traits with relevance to the beef and dairy industries. Large amounts of DNA will be required for these research projects. This study reports the use of the whole-genome amplification (WGA) method to create an unlimited supply of DNA for use in genotyping studies and long-term storage for future gene discovery projects. Two commercial WGA kits (GenomiPhi, Amersham Biosciences, Sydney, Australia, and REPLI-g, Qiagen, Doncaster, Australia) were used to amplify DNA from straws of bull semen, resulting in an average of 7.2 and 67 microg of DNA per reaction, respectively. The comparison of 3.5 kb of sequences from the amplified and unamplified DNA indicated no detectable DNA differences. Similarly, gene marker analysis conducted on genomic DNA and DNA after WGA indicated no difference in marker amplification or clarity and accuracy of scoring for approximately 10,000 single nucleotide polymorphism markers when compared with WGA samples genotyped in duplicate. These results illustrate that WGA is a suitable method for the amplification and recovery of DNA from bull semen samples for routine genomic investigations.

Animals↗