Carbovir: the (-) enantiomer is a potent and selective antiviral agent against human immunodeficiency virus in vitro

In this paper we describe the in vitro antiviral activity of the (-) enantiomer of carbocyclic 2',3'-deoxydidehydroguanosine, (-) carbovir, a nucleoside analogue that has selective and potent anti-HIV activity in a series of lymphocyte culture systems. The cellular cytotoxicity of this compound has also been evaluated in a number of systems and compared to the saturated dideoxynucleoside analogues AZT and ddC.

The effect of storage media upon the surface microhardness and abrasion resistance of three composites

The effects of various storage media [distilled water, lactate (pH 4.0), and citrate (pH 6.0) buffers] upon the hardness and wear factor values of three composites [Occlusin (O), P-30 (P), and Fulfil (F)] were studied. Over the one-year storage period, the hardness of all three materials stored in citrate buffer was unchanged. In the case of P in water and all materials stored in lactate buffer, a reduction was observed. There was no significant difference (P greater than 0.05) between the wear factors of specimens after one year or one week of water storage. Specimens of F stored in citrate buffer had a wear factor (P less than 0.01) higher than that of those stored in water. The other materials were not affected by storage in the lactate or citrate buffers. A reduction in surface hardness for some materials did not result in an increase in wear rate. This indicates that the softening effect was limited to a thin surface layer. Although not significant in vitro, this effect would probably increase the rate of in vivo wear, since the softened material would be lost, exposing a fresh surface to further attack. This would adversely prejudice the material's long-term clinical durability by impairing its resistance to abrasion.

The effect of placement technique upon the compressive strength and porosity of a composite resin

This paper examines the effect of two placement techniques upon the compressive strength and level of porosity of specimens of a composite resin. Those specimens prepared by a condensation technique had a significantly lower mean compressive strength (P less than 0.05) and value of Weibull modulus (P less than 0.05) than specimens prepared using a smearing technique. No significant differences in the overall mean percentage area occupied by porosity and mean number of pores were demonstrated (P greater than 0.05) between the two placement techniques. Specimens prepared using the smearing technique, however, had significantly smaller mean maximum pore diameters (P less than 0.05) than those prepared using the condensation technique. It is therefore desirable when placing composite resins to reduce to a minimum handling procedures that are likely to influence the levels of porosity within the material.