Characterization of the unusual basic proteins of cricket spermatid nuclei on the basis of their molecular weights and amino acid compositions

Typical somatic cell type histones are lost from the nucleus during late spermiogenesis in the house cricket; they are replaced by unusual basic proteins specific to the spermatid. We wish to characterize these proteins because they appear to determine the unusual chromatin structures of the spermatid. Molecular weights of the unusual basic proteins were estimated by chromatographing them on Bio-Gel A 0.5 M agarose columns eluted with 6 M guanidine hydrochloride. Two proteins named TH1 and TH2 have molecular weights in the range spanned by the somatic histones. The molecular weight of TH1 is 17 500 and that of TH2 is 15 500. Three additional spermatid proteins were also analyzed by molecular weight determination. They are called here protamines A, B and C, and they have molecular weights in the range typical of protamines. That of A is 6200, of B is 5500 and of C is 3800. They span the range from the large protamines typical of mammalian sperm to the small protamines of salmonid fish. The molecular weights of the TH proteins were also examined by electrophoresis on SDS-polyacrylamide gels. Amino acid compositions determined for TH1 and TH2 show that both are basic proteins rich in arginine relative to lysine. Their compositions are histone-like, but they appear to be distinct histone types rather than variant forms of the somatic histones.     

Detection of Aldehydes and Their Conjugated Hydroperox Ydiene Precursors in Thermally-Stressed Culinary Oils and Fats: Investigations Using High Resolution Proton Nmr Spectroscopy

High field (400 and 600 MHz) proton NMR spectroscopy has been employed to investigate the thermally-induced autoxidation of glycerol-bound polyunsaturated fatty acids present in intact culinary frying oils and fats. Heating of these materials at 180°C for periods of 30, 60 and 90 min. generated a variety of peroxidation products, notably aldehydes (alkanals, trans-2-alkenals and alka-2, 4-dienals) and their conjugated hydroperoxydiene precursors. Since such aldehydes appear to be absorbed into the systemic circulation from the gut in vivo, the toxicological significance of their production during standard frying practices is discussed.     

Generation of lymphokine-activated killer cell activity from human thymocytes

We have generated lymphokine-activated killer (LAK) cells from human thymocytes in order to assess the relationship between LAK cells and T cells. Fresh thymocytes lack natural cytotoxic activity, and cytotoxicity cannot be stimulated by short term (1 hr) incubation with interferon or recombinant interleukin 2 (rIL-2). In addition, thymocytes are phenotypically devoid of cells bearing the natural killer (NK)-associated markers cluster designation (CD) 16 and NKH-1. After culture for 5 to 8 days with rIL-2, thymocytes display high levels of cytotoxic activity against both NK-sensitive and NK-resistant targets. Thymocytes require slightly more IL-2 than do peripheral blood lymphocytes to generate LAK activity. We have examined the phenotype of the thymocyte LAK precursor and effector cells. Thymocyte LAK precursors are of low to medium density, CD1-negative, and predominantly CD3-negative. Although CD3-positive cells proliferate in response to rIL-2, they are low in cytolytic capabilities. The effector cells, like the LAK precursors, are low to medium density lymphocytes. The cytotoxic cells are predominantly CD3-negative, and cytotoxic activity cannot be blocked with the use of anti-CD3 monoclonal antibodies. The effector cells also lack most NK-associated markers (HNK-1, and the CD16 markers Leu-11b and B73.1) but possess the NK-associated marker NKH-1 (N901). The responsive cell appears to be at a very early stage of thymic development, and it does not appear to either require or express the CD3-T cell receptor complex.     

Modulation of natural killer-mediated lysis by red blood cells

Natural killer (NK)-mediated cytotoxicity is significantly enhanced in the presence of red blood cells (RBC). The enhancement is dose dependent on the number of RBC present and can be induced by autochthonous, allogeneic, or xenogeneic RBC. The enhancement was demonstrated in cytotoxicity against two different NK-sensitive tumor target cell lines, K562 and U937, and by three different assay systems, chromium release, lactate dehydrogenase release, and inhibition of thymidine incorporation. RBC directly enhance the cytotoxic activity of NKH-1/Leu19+ large granular lymphocyte NK cells. Intact RBC have to be present during the cytotoxicity assay to induce the enhancement, which probably occurs at a postbinding, preprogramming phase. The anti-CD2 antibody Leu5 cannot block the enhancement at a concentration inhibitory to lymphocyte rosetting with sheep RBC, suggesting that the enhancement is not induced by interaction through the CD2 antigen. These results indicate that RBC are a potent modulator of NK cytotoxicity and suggest that in vitro NK studies using purified lymphocytes may not always truly reflect NK activity in the blood stream.     

Effect of the structure of the prosthetic group on the catalytic properties of prostaglandin H synthetase

The effect of vinyl groups of protohemin IX on its cofactor properties with respect to prostaglandin H synthetase has been studied. It was shown that substitution of ethyl groups or a hydrogen for vinyl groups affects neither binding of the prosthetic group to the apoenzyme nor catalytic properties of holo-prostaglandin H synthetase. Replacement of vinyl groups with bulkier substituents (hydroxyethyl or acetyl groups) decreases holoenzyme stability and catalytic activity. By comparison of the cofactor properties of protoporphyrin and hematoporphyrin macrocycles with different central ions (Fe3+, Mn2+, 2H+ in the case of protoporphyrin, and Fe3+, Mg2+, Cd2+ and Cu2+ in the case of hematoporphyrin), the presence of Fe3+ ions was shown to be mandatory for prostaglandin H synthetase activity. It was demonstrated that the cofactor structure modifications do not affect the holo-prostaglandin H synthetase inactivation rate constant in a reaction.