Damage and repair of DNA in cultured mammalian cells with N-diazoacetylglycine amide.

N-Diazoacetylglycine amide, a diazochetoalkane, has been studied in vitro for DNA damage and repair in cells of a cloned subline from a BALB/c mouse. To our present knowledge, none of these compounds have been investigated for such activities. At nontoxic levels, a prolonged dose-dependent unscheduled DNA synthesis was observed by autoradiography. DNA damage was studied by sedimentation through alkaline sucrose gradients after the cells were lysed on the gradients. Treatment of the cells for 1 hr with nontoxic doses of N-diazoacetylglycine amide resulted in slower sedimentation of DNA. The number of single-strand breaks appeared rather linearly dose dependent for a large range of concentrations. Breaks were at their maximum after 1 hr of treatment, and no further increase in the number of breaks was seen. Some repair of the breaks probably occurs, but repair was sluggish even 68 hr after treatment. A significant part of the breaks was observed after incubation at 4 degrees in an ethylenediaminetetraacetate hypotonic solution. This seems to indicate that the compound does not require metabolic activation. Nontoxic doses of N-diazoacetylglycine amide and other similar derivatives exert mutagenic and carcinogenic activities. The presence of DNA damage and the difficulty in its repair at such doses could be related to both of these biological properties.     

Specific killing of tumor cells in vitro in the presence of normal lymphoid cells and sera from hosts immune to the tumor antigens

Evidence is presented for specific in vitro killing of neoplastic target cells in the presence of non-sensitized lymphoid cells and heat decomplemented sera from mice bearing the respective neoplasms or whose tumors had been removed. Such an effect was observed with sera from mice bearing Moloney sarcoma virus (MSV)-induced and 3-methylcholanthrene (MCA)-induced sarcomas, and from mice whose mammary tumor virus (MTV)-induced adenocarcinomas had been removed. Neoplastic target cell death was not characteristically mediated by such sera alone or by normal lymphoid cells in the presence of serum from animals bearing some other tumor, but appeared to be a specific, synergistically produced cytotoxicity.     

Wound healing: a review. II. Environmental factors affecting wound healing.

A variety of factors, both intrinsic and extrinsic, may influence the healing of wounds. Some of these influences are environmental in nature and subject to advantageous manipulation by the practitioner. In this article, the role of humidity, temperature, infection and oxygen tension on the process of wound healing will be discussed.     

Echocardiography in infective endocarditis. Lack of specificity in patients with valvular pathology.

59 patients with suspected infective endocarditis on a natural valve were studied by M-Mode echocardiography to determine the specificity of the ultrasonic technique in detecting valvular vegetations. All echocardiograms were read independently by two observers who were unaware of the final diagnosis. Among 40 patients who later proved not to have infective endocarditis, two (5%) were diagnosed by echocardiography as having either possible or probably vegetation by at least one observer. Both patients with a false positive diagnosis of vegetation had pre-existing valvular pathology, the presence of which greatly complicated the interpretation of the echocardiogram. Inter-observer disagreement occurred in 5 of the 59 studies (8.5%). The results of this study suggest that caution should be exerted in the echocardiographic diagnosis of vegetation in patients with pre-existing valvular pathology.