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Murine Rauscher leukemia virus (MuRLV) from BALB/c plasma consisting of a mixture of an ecotropic and a xenotropic virus could be separated out by a selection process when propagated in human and simian cell cultures. This hypothesis is supported by obtaining consistently lower infectivity titers of human cell propagated RLV in human and simian cells as compared to MuRLV propagated in mouse cell cultures. Furthermore, RLV passaged in a simian cell culture failed to replicate in mouse cells, had a wide host range, was able to rescue Moloney sarcoma genome, possessed murine type C group-specific antigen, and was neutralized by anti-HRLV. Its reverse transcriptase was strongly inhibited by antiserum to MuRLV enzyme; however, antiserum to woolly monkey enzyme also inhibited (30%) its reverse transcriptase, suggesting some difference in antigenic properties. Inoculation of this virus in rhesus monkeys was inconclusive.

In strain K-12 of Escherichia coli, beta-glucuronidase synthesis was induced only by beta-glucuronides: all intermediates of the hexuronate pathway able to enter the cells failed to induce the enzyme significantly. The induction pattern of beta-glucuronidase clearly differentiates the mode of regulation of its synthesis from those of the subsequent enzymes of the pathway, which are induced by fructuronate and/or tagaturonate. In mutant strains blocked in glucuronate metabolism after the isomerase step, beta-glucuronidase synthesis was still induced by a beta-glucuronide. Glucuronate and fructuronate, which are accumulated and mutually interconverted within the cells, become good inducers of beta-glucuronidase: they induce up to a level one-half that obtained in the wild-type strain in the presence of beta-glucuronide alone. In an isomerase-negative strain where fructuronate is not produced, beta-glucuronidase was no longer induced by beta-glucuronide unless supplemented with fructuronate. In this strain, glucuronate alone or fructuronate alone exhibited greater inducing ability than in the wild-type strain. Moreover, fructuronate could also enhance glucuronate-induced synthesis of beta-glucuronidase. Glucuronate was not able to activate beta-glucuronideinduced synthesis of beta-glucuronidase. Therefore, the induction of beta-glucuronidase synthesis depends upon two factors which, when acting separately, are both poor inducers but can act cooperatively; one factor is beta-glucuronide or glucuronate and the second is fructuronate. The specific inducing capacity of each of these three compounds as well as the hypothetical mechanism(s) of the action of fructuronate are discussed.

The enzymatic activities of three lymphoblastoid cell lines were subjected to a comparative analysis of 22 enzymatic activities with a new microtechnique "Apizym". This method is easy, requires only a small number of cells and allows simultaneous testing of many enzymatic activities from the same sample. The three cell lines can be easily distinguished despite their close origin: NAB, derived from a malignant retroperitoneal mass in an American patient, is the cell line with the greatest total activity and HRlK (a clone of P3J, derived from an African lymphoma) with the lowest and RAJI (a non-virus producing line derived from an African lymphoma) being the intermediate. The more striking differences concern the activity of phosphatases (NAB greater than RAJI greater than or equal to HRlK), esterases-lipases (NAB greater than or equal to RAJI greater than HRlK), beta glucosaminidase, beta glucuronidase beta glucosidase (NAB greater than or equal to RAJI greater than HRlK). On the other hand, alpha mannosidase and alpha fucosidase are more active in RAJI (RAJI greater than NAB greater than or equal to HRlK).