The cloning and expression of human deoxyribonuclease II. A possible role in apoptosis

We have previously implicated deoxyribonuclease II (DNase II) as an endonuclease responsible for DNA digestion during apoptosis. The full-length human cDNA has now been cloned. The cDNA contains an open reading frame of 1078 bases coding for a 40-kDa protein. This protein is 10 kDa larger than commercially supplied enzyme, which has been proteolytically cleaved at an internal aspartate residue. The gene is located at chromosome 19p13.2, and has no significant homology to other human proteins, but has >30% identity to three predicted genes in Caenorhabditis elegans. To determine whether overexpression of DNase II induces apoptosis in Chinese hamster ovary cells, the cDNA was cotransfected with a plasmid encoding green fluorescent protein. Within 24 h, a significant proportion of green fluorescent protein-positive cells contained condensed chromatin, whereas vector-only controls remained viable. Considering that DNase II is normally active only at low pH, it was surprising that transfection induced chromatin condensation. To confirm that transfection was not activating another endonuclease, cells were incubated with the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(O-methyl)-fluoromethylketone; this failed to inhibit chromatin condensation induced by DNase II. These results demonstrate that DNase II acts downstream of caspase activation and that it may be activated by an as yet unknown mechanism to induce DNA digestion during apoptosis.     

A different approach to the analysis of pure ventricular parasystole

Until recently, it had not been recognized that predictions regarding the number of sinus beats interposed between two consecutive parasystolic beats could be made. In a case of perfect, pure parasystole resulting from unintentional fixed rate ventricular pacing, the following was observed: there were consistently three different values (0,2,3) for the number of interposed sinus beats; only one of these values was odd, and the sum of the two smaller values was one less than the larger value. Our findings, which are in keeping with those obtained in an mathematical model, may be of additional help in the diagnosis of this elusive arrhythmia.     

Potential bioreductively activated hypoxia probes and post-irradiation radiosensitizers related to NITP

NITP (1) is an effective marker of hypoxia in tumours for both microscopy and cell sorting studies and, additionally, the compound shows post-irradiation sensitization, probably by inhibition of repair of radiation damage to DNA. However, NITP does not have the substitution pattern which the immunochemical reagents are raised to recognize and the compound has very low solubility in water. We report the synthesis of an isomer (13) of NITP which has the desirable substitution pattern and is also soluble in very weak aqueous base. The successful synthesis of 13 uses a nitrosation and cyclization of a substituted uracil (16), but earlier approaches from 5 and 12 yielded the pyridoxanthine derivative 6. The preparative use of nitro group displacement reactions from 8-nitrocaffeine is shown to be a useful entry to a range of 8-substituted caffeines and is utilized to obtain two derivatives of NITP which carry aliphatic amine chains, i.e. 34 and 35.     

Cure of Helicobacter pylori infection: role of duration of treatment with omeprazole and amoxicillin

A case of ankylosing spondylitis with pronounced osteolysis of the 12th thoracic vertebral body as part of posttraumatic pseudoarthrosis is described. The appearance of posttraumatic osteolysis simulates a malignant lesion, and it is important to consider the diagnosis in cases of osteolytic lesions of unknown origin.     

The synthesis of symmetrical and unsymmetrical P1/P1' cyclic ureas as HIV protease inhibitors

Cyclic urea SD146, a potent HIV protease inhibitor bearing a flat resistance profile, possessed poor solubility and bioavailability, which precluded further development of the compound. In an effort to improve upon the pharmacokinetic profile of the compound, several analogs modified at the P1/P1' residues were prepared and evaluated. Several of those compounds displayed significant improvement of physical properties.