SOME MECHANISMS INVOLVED IN SELECTIVE CHEMOTHERAPY

A general protocol for evaluating the specific effects of DNA replication inhibitors

Inhibitors of DNA replication in mammalian cells are of great interest because of their potential use in chemotherapy and in cell synchronizing protocols in the laboratory. We have used a combination of isotopic labelling protocols and a two-dimensional gel replicon mapping procedure to determine the specific effects of five different replication inhibitors in cultured cells. Utilizing this protocol, we show that hydroxyurea, aphidicolin, and cytosine arabinoside, three known chain elongation inhibitors, are rather ineffective at preventing fork progression even at relatively high concentrations. In contrast, two related compounds that have been suggested to be G1/S inhibitors (mimosine and ciclopyrox olamine [CPX]) actually appear to inhibit initiation at origins. One of these agents (CPX) appears also to inhibit replication in yeast, opening the possibility that the gene encoding the target (initiator?) protein can first be identified in yeast by genetic approaches and can then be used to isolate the mammalian homologue.

The management of ocular herpesvirus infections

The many treatment methods in current use for every known complaint only seem to aggravate the difficulty of treating ocular herpes simplex virus (HSV) infections, which are generally self-limited in the immunocompetent host. The cornea is already a somewhat immune-deficient tissue since its lack of blood vessels separates it partially from the host, and treatment with glucocorticoids, which are immunosuppressive, increases the risk of damaging complications such as scarring, prolonged morbidity, bacterial or fungal superinfection, and the occasional corenal perforation. Accepted methods of treatment of specific lesions, are discussed, as are some methods that are not yet accepted, but which seem promising. Herpes zoster may result in scarring and significant loss of vision even without the use of glucocorticoids, the disease often manifesting itself in the already compromised host. The major complication is postherpetic neuralgia. None of the available treatment methods has been fully satisfactory, and every effort should be made to prevent eye lesions in patients with early infection of the ophthalmic branch of the trigeminal nerve. Stimulation of cellular immunity by various means appears to offer some new promise for control of the disease. Management of varicella, cytomegalovirus, and infectious mononucleosis are also discussed.