Human natural killer cell activity is reversibly inhibited by antagonists of lipoxygenation

We here demonstrate that NK cell activity by human peripheral blood mononuclear cells (PBMC) against K562 or MOLT-4 target cells is rapidly and reversibly inhibited by two agents that inhibit the lipoxygenation of fatty acids, BW755C and nordihydroguaiaretic acid (NDGA). Natural killing by nonadherent PBMC was similarly inhibited by both agents, indicating that monocytes were not required for the effect. The inhibition of natural killing was not seen with indomethacin at concentrations that inhibit prostaglandin synthesis but not the lipoxygenation of arachidonic acid. Moreover, indomethacin did not alter inhibition by either BW755C or NDGA. Thus, suppression of natural killing by these agents was not mediated by the effects on prostaglandin synthesis; neither agent inhibited target cell binding. These results suggest that products of lipoxygenation are required for target cell lysis by human NK cells.     

DETERMINATION OF GUSTATORY SUCROSE THRESHOLD IN WATER BY USE OF A LINEAR SUCROSE GRADIENT

A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)).     

A new species of Polystoma (Monogenea: Polystomatidae) parasitic in Hyperolius marmoratus (Anura: Hyperoliidae) in South Africa

Polystoma marmorati n. sp. is described as a new polystomatid species parasitic in the urinary bladder of the painted reed frog Hyperolius marmoratus marmoratus collected in southern Natal, South Africa. Parasite prevalence varied from 14.5 to 47.4% and the mean intensity from 1.0 to 1.1. The hamuli of the new species have a characteristic, partly fragmented appearance, a feature also seen in Polystoma batchvarivi, the only other polystome described from a species of the genus Hyperolius. The similarity between the two species, in spite of their geographical separation, is commented upon.     

INTERSPECIFIC TRANSFORMATION IN BACILLUS

Marmur, J. (Brandeis University, Waltham, Mass.), E. Seaman, and J. Levine. Interspecific transformation in Bacillus. J. Bacteriol. 85:461-467. 1963.-Deoxyribonucleic acids (DNA) from various species of the taxonomic group Bacillaceae were examined for base composition, ability to carry out interspecific transformation, and formation of molecular hybrids in vitro. The minimal requirement for genetic compatibility among different species and for DNA interaction (both reflecting base sequence homologies) is the similarity of the guanine plus cytosine contents of the DNA. The close correlation between the ability of DNA to be competent in interspecific transformation and to form hybrid molecules on denaturation and annealing provided a rational approach to the study of genetic relationship among organisms for which no genetic exchange has yet been demonstrated. Any or all of the criteria (base composition of DNA, transformation, molecular hybrid formation) can be used as tools in the taxonomic assessment of closely related microorganisms.     

Natural killing in estrogen-treated mice responds poorly to poly I.C despite normal stimulation of circulating interferon.

Natural killing by mouse spleen cells can be stimulated in vivo by interferon or by agents that stimulate interferon, such as poly I.C. Natural killing can be suppressed in vivo by the sustained administration of 17 beta-estradiol. In BALB/c mice that had been treated with 17 beta-estradiol for 10 weeks, natural killing did not respond to intravenous poly I.C, although stimulation of circulating interferon was equal to controls. Estradiol, then, does not block interferon production but does suppress the response of natural killer cells to interferon. It is suggested that estrogens either block the maturation of natural killer cells or reduce the number of natural killer cell precursors.     

HIV-1 Neutralizing Antibody Signatures and Application to Epitope-Targeted Vaccine Design

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Cytoplasmic filaments and cellular wound healing in amoeba proteus

The flexibility and self-healing properties of animal cell surface membranes are well known. These properties have been best exploited in various micrurgical studies on living cells (2, 3), especially in amoebae (7, 20). During nuclear transplantation in amoebae, the hole in the membrane through which a nucleus passes can have a diameter of 20-30 μm, and yet such holes are quickly sealed, although some cytoplasm usually escapes during the transfer. While enucleating amoebae in previous studies, we found that if a very small portion of a nucleus was pushed through the membrane and exposed to the external medium, the amoeba expelled such a nucleus on its own accord. When this happened, a new membrane appeared to form around the embedded portion of the nucleus and no visible loss of cytoplasm occurred during nuclear extrusion. In the present study, we examined amoebae that were at different stages of expelling partially exposed nuclei, to follow the sequence of events during the apparent new membrane formation. Unexpectedly, we found that a new membrane is not formed around the nucleus from inside but a hole is sealed primarily by a constriction of the existing membrane, and that cytoplasmic filaments are responsible for the prevention of the loss of cytoplasm.