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Background and purpose: Long QT syndrome is a heart arrhythmia identified by prolongation of the QT interval which is a cause of sudden cardiac death in young individuals. In most cases, abnormalities in heart repolarization are reasons of prolongation of action potential and arrhythmia. The activity of ion channels is sensitive to ATP level, therefore, mitochondrial disorders are considered to be very important. The purpose of this study was to investigate the areas of mtDNA that are identified as hot spots in most cardiac diseases. Material and Methods: Total DNA was extracted from the peripheral blood of 30 patients with LQT syndrome and 35 normal persons. Mitochondrial tRNATrp-Ala-Apn-Glugenes and cytochrome b gene were amplified by polymerase chain reaction (PCR). Then, PCR fragments were screened for singlestrand conformation polymorphism analysis (SSCP) and all positive samples were sequenced. Results: We observed a homoplasmic and conserved T14687C mutation in the mitochondrial tRNA glutamic acid gene in one patient with pervious syncope. We found a homoplasmic C14766T transition in five patients that changed threonine to isoleucine substitution at amino acid 7. Also, we found a heteroplasmy G14838A mutation in mitochondrial cytochrome b gene which is nonsense and changed tryptophan to a stop codon in position 31. Conclusion: Mitochondria ATP synthesis is important in heart, therefore, it is possible that mutations in mitochondrial genes could constitute a predisposing factor in combination with environmental factors and may also trigger the syncope in patients with L QT.

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Background and purpose: Gastric cancer is the fourth most common cancer and the second leading cause of cancer death worldwide. North of Iran is a high risk area for gastric cancer. Bcl2 family is the most important regulator of apoptosis and -938C>A single nucleotide polymorphism of bcl2 gene promoter has been demonstrated to influence gastric cancer susceptibility. In this research we studied the effect of -938C>A genotype on gastric cancer.

Materials and methods: This analysis was performed in 87 patients with gastric cancer who underwent surgery in Mazandaran and Golestan province along with 104 healthy individuals as controls. DNA extracted from peripheral blood samples was applied in PCR-SSCP (Polymerase chain reaction-single strand conformation polymorphism) analysis to determine -938C>A genotype. The association of the -938C>A genotype and gastric cancer risk as well as demographic and clinicopathological characteristics were analyzed by logistic regression method.

Results: Frequency of AA, CC and AC genotypes in cases were 13.79, 16.09 and 70.12% and 15.38, 23.08, and 61.54% in control group, respectively. Statistical analysis indicated that the AC genotype was significantly (P=0.0009) associated with a decreased risk for gastric cancer by 0.2 fold (OR=0.276) compared with the combined genotype of AA+CC. No significant association was found between -938C>A genotype with demographic and clinicopathological characteristics. 

Conclusion: The study showed that the presence of AC genotype may decrease the risk of gastric cancer. So, investigating the -938 C>A single nucleotide polymorphism of bcl2 gene promoter could be an appropriate molecular marker that could be used to determine individual sensitivity to gastric cancer and also for designing cancer prevention programs.