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The presence in the spleens of unsensitized CBA mice of cells that are spontaneously cytotoxic for Sendai virus-infected L cells was confirmed. This innate cytotoxic activity to virus-infected cells was shown to exhibit some H-2 restriction. Partial identity of only the D end of the H-2 gene complex between the target and effector cells was required to produce cytolysis. Attempts to characterize the kind of cell active in this system indicated that neither the theta antigen nor the surface immunoglobulin markers were present. Furthermore, the cells appeared to have no adherent or phagocytic properties. The relationship between the effector cells responsible for innate cytotoxicity to virus-infected cells and the natural killer (NK) cells spontaneously cytotoxic for certain tumor cells is discussed.

The genetic and physical structures of commonly used F-prime factors carrying the galactose region of the Escherichia coli chromosome were analyzed. Deletions in the chromosomal DNA sequences in the F-prime factors were found to be frequent events. A genetic method was developed to reconstruct the original F-prime factors from deletion variants. Heteroduplex analysis of the reconstructed F-prime factors confirmed the derivation of the F-prime factors F100 and F152, from the same Hfr, and finally determined the normal E. coli chromosomal sequence in the region between fep and uvrB, containing about 5 min in genetic units and about 246.5 in kilobase units (kb). This sequence could be connected with the DNA sequences of the lac-purE region, which had been physically determined previously. Together they constituted a total of 528.6 kb. From these combined sequences, the distance from lacPO to galK was calculated to be 412.9 kb, which corresponds to 8.8 min in genetic units.

Hyperpigmentation believed to be due to melanin, is a feature of chronic liver disease, especially primary biliary cirrhosis and hemochromatosis. Normal plasma concentrations of immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) have been found in both these conditions; thus elevation of plasma beta-MSH plays no role in the pathogenesis of hepatic pigmentation. Normal levels are also found in hepatocellular failure, which supports the hypothesis that the kidney and not the liver is the site of metabolism of this hormone.

2'-Deoxy-2'-fluoroadenosine was chemically transformed to its 5'-diphosphate and polymerized with polynucleotide phosphorylase to give poly(2'-deoxy-2'-fluoroadenylic acid) [poly(Af)]. Polymerization proceeded smoothly as in the case of poly(A) and the yield of the polymerization was 55%. The UV absorption spectra of poly(Af) closely resembled those of poly(A) and the hypochromicity was 32% at pH 7.0. The CD profile at 25 degrees and neutrality showed similar pattern to that of other poly(2'-deoxy-2'-halogenoadenylic acids) with somewhat larger [theta] values both in the positive and negative maxima. Acid titration of poly(Af) showed a transition point at pH 5.2 and the Tm of the acid form was 37 degrees which was significantly lower than that of poly(A), but similar to that of poly(2'-azido-2'-deoxyadenylic acid). Poly(Af) formed 1:1 and 1:2 complexes with poly-(U) having Tm of 49 degrees and 62 degrees at 0.04M and 0.15M Na(+) concentration, respectively. Poly(Af) also formed a 1:2 complex with poly(I) and its Tm was 36 degrees at 0.05M Na(+) concentration. These data showed that poly(Af) has rather similar properties to those of poly(A), but not to poly(dA).