HeLaTG cells have mitochondrial DNA inserted into the c-myc oncogene

To determine whether mitochondrial DNA (mtDNA) fragments found within the nucleus are transcribed, we have differentially screened a HeLaTG cDNA library. A clone that hybridized to mtDNA as well as to c-myc was identified. Analysis of the cDNA disclosed that it contained a mtDNA sequence, encoding cytochrome-c oxidase subunit III (coxIII) that was contiguous with and 5' of a c-myc sequence corresponding to part of exon 2 and exon 3. Hybridization of ScaI-digested DNA with a 1.05 kb c-myc probe revealed a unique band in HeLaTG cells, as well as a band common to HeLaTG and 13 other cell types examined. Solution hybridization of HeLaTG RNA with a radiolabeled, single-stranded cDNA probe containing the coxIII-c-myc junction demonstrated a nuclease-resistant band that matched the full length of the junctional cDNA probe. A smaller band that equaled the size of the c-myc portion alone was also detected. Only the smaller band coinciding with the c-myc sequences was protected from nuclease digestion by RNA from other cells. When a radiolabeled probe synthesized in the opposite orientation was used, nuclease-resistant bands equal in length to the coxIII portion of the probe were detected after hybridization with RNA from all cells. These results indicate that insertion of mtDNA fragments into nuclear genes occurs and that subsequent transcription of a 'chimaeric' or 'fusion' mRNA containing both mitochondrial and nuclear sequences can ensue.

[Clinical features and imaging findings of posterior cerebral artery infarction]

The clinical features and imaging findings of posterior cerebral artery infarction (PCAI) in 18 cases verified by CT scan and/or MRI, DSA, SPECT were reported, and their interrelation were analyzed. It was found that the main clinical feature of PCAI was visual defect with amnesia syndrome, the lesion was predominant in the right hemisphere. In examining the structure and function of brain and vessels, each of CT, MRI, ECT and DSA had its own advantage and might complement the others, CT and MRI were better in displaying the structure of cerebral parenchyma than ECT and DSA, whereas, MRI was superior in distinguishing the lesions in deep white matter and subtentorial region. DSA was better than MRI and CT in displaying vascular structure, but was inferior in disclosing the occlusion of deep perforating branches or cortical arterioles. ECT, besides its ability to show the morphological changes of brain, was mainly used to disclose the functional changes of cerebral parenchyma, being a method to make early diagnosis for CVD. However, ECT was inferior than MRI and CT, in displaying lacunar infarction and lesions of brain-stem.

The use of Chinese herb medicine in experimental radiotherapy

Extracts from a group of destagnative herbs, 764-1, and the effective chemical, 764-3, were tested by an in vitro experiment using a HeLa-S3 cell line. Under aerobic conditions, the shoulder of the cell survival curve diminished or disappeared according to the different doses of 764-1 used, but no change in slope was observed. In nitrogen, when the dose of 764-1 increased to 20 mg/ml (ID20), besides the disappearance of the shoulder, the slope of the curve also showed changes at lower doses (4-8 Gy); up to 10-25 Gy the curve became more flattened. 764-3 showed almost a similar effect by mainly affecting the shoulder of the survival curve. At low drug doses a SER as high as 1.87 might be obtained under hypoxic condition. At the same time 764-1 was used in testing the effect on radiation lung damage. It was found that 764-1 could markedly inhibit the change of alveolar surfactant at 1 and 3 weeks after radiation. A wide field of investigation is thus spread out in front of us on radiosensitization and protection. Further studies on 764-3 are carried out.