The effect of beta-estradiol, progesterone and testosterone on the production of human leukocyte derived interferons

Sex hormones including estrogens, progesterone and testosterones are known to have adverse effects on the immune system and particularly on the proliferative response. Since cytokine production is known to be dissociable from the proliferation of lymphocytes and since other steroid hormones profoundly affect cytokine production, we felt it would be important to know the effect of sex steroids on the production of interferons (IFN), particularly since the latter are known to be key substances in the immune response. We have shown estradiol can slightly reduce gamma IFN yields with certain inducers (Con A, SEA) but only in pharmacologic concentrations. Similarly, progesterone had a modest effect in the same concentrations but only when Con A was the inducer. Testosterone did not effect IFN titers at any concentration. None of the sex steroids affected alpha IFN production and none of them influenced the bioactivity of either IFN species. In all cases these hormones diminished proliferative responses as has been previously noted.     

Hepatocellular Carcinoma in Hepatitis B Surface Antigen Carriers in Eight Institutions

We reviewed records of all persons dying between 1979 and 1986 in eight California institutions for the mentally retarded. Autopsies had been done in 71% of the 1,181 deaths. Nine deaths were due to hepatocellular carcinoma, which invariably developed in carriers of hepatitis B surface antigen (HBsAg) and was fatal within four months of diagnosis. The mean age at death was 32.7 years. The incidence of hepatocellular carcinoma in HBsAg carriers was 140 times greater than in the US population. Persistent hepatitis B infection was probably etiologically related to hepatocellular carcinoma in this population, which is relatively free of exposure to other hepatocarcinogens.     

Characterization of an X-ray-hypersensitive mutant of V79 Chinese hamster cells

A V79 Chinese hamster cell line XR-V15B exhibiting hypersensitivity to X-ray has been isolated and characterized. Additionally to increased X-ray-sensitivity (approximately 8-fold, as judged by D10 values), cross-sensitivity to bleomycin (3-fold increase), 4NQO (3-fold), H2O2, EMS, MMS (2-fold) were observed also. No increased sensitivity to UV and MMC was found. Genetic complementation analysis indicates that XR-V15B belongs to the same complementation group as the X-ray-sensitive (xrs) mutants of Chinese hamster ovary (CHO) cells described by Jeggo (1985). Biochemical analysis of XR-V15B confirms this finding: the mutant showed a decreased ability to rejoin double-strand breaks induced by X-ray as measured by neutral elution. After 4 h of repair more than 50% of the double-strand breaks remain in comparison to 3% in V79 cells. No difference was observed between wild-type and XR-V15B cells in the initial number of single-strand breaks induced, in the kinetics of their rejoining and in the final level of unrejoined single-strand breaks. Treatment with 5-azacytidine did not have an effect on the reversion frequency of XR-V15B, contrary to the results obtained with the xrs mutants. XR-V15B has been grown in continuous culture for more than 3 months without evidence of reversion. The mutation induction by X-ray irradiation at the HPRT locus is not significantly increased in the mutant, but at doses giving the same degree of cell killing, XR-V15B cells are hypomutable.     

Attachment of trivaline changes the specificity of binding of netropsin analogs with DNA

In the present communication, synthesis and DNA binding activities of three analogs of the antibiotic netropsin are reported. Each analog contains two N-propylpyrrolecarboxamide units linked covalently to either Dns-Gly-Val-Val-Val-Gly-Gly- (I), Val-Val-Val-Gly-Gly (II) or Gly-Gly (III). It is shown that analogs I and II can self-associate in aqueous solution and methanol as revealed from the fact that UV absorbance and circular dichroism spectra obtained for these analogs are concentration-dependent. By contrast, analogs III exists as a monomer, even at concentration levels of the order of 1.10(-3) M. Determination of the apparent sizes of intramolecular aggregates by gel-filtration shows that analog I in aqueous solution at concentration levels of the order of 1.10(-3) M forms a series of aggregates containing from 2 to 12 monomers. Analog II exhibits a lower tendency to form intermolecular aggregates as compared with that of analog I. Dimerization constants are determined for analogs I and II in aqueous solution and methanol. The binding of N-propylpyrrolecarboxamide units and peptide fragments of analog I to DNA can be independently monitored by circular dichroism and fluorescence methods. If self-associated species of analog I (or II) are present in solution, the ligand exhibits a markedly different order of base pair sequence preferencies as compared with that of analog III. The results obtained are consistent with the inference that analogs I and II in a beta-associated form recognizes base pair sequences containing two runs of 3 AT pairs separated by two GC pairs.     

Species-specific structural differences in the alpha 1 + alpha 2 domains determine the frequency of murine cytotoxic T cell precursors stimulated by human and murine class I molecules

The frequency of murine CTL precursors (CTLp) that recognize the human histocompatibility Ag HLA-A2 and HLA-B7 was measured and found to be approximately two orders of magnitude lower than the frequency of CTLp that recognize murine H-2 alloantigens. The possible contribution of other cell surface molecules to this difference in response was addressed by expression of the H-2Ld molecule on a human cell and the HLA-B7 molecule on a murine cell. It was found that both human and murine H-2Ld expressing cells elicited comparable levels of H-2Ld specific CTL. Although murine HLA-B7 positive cells stimulated a higher frequency of HLA-B7-specific CTLp than did human cells, this appeared to be largely due to stimulation of CTLp that recognized HLA-B7 in the context of H-2 molecules; consequently, it was concluded that the difference in the frequency of murine CTLp elicited by human and murine class I Ag is due to species specific structural differences in these molecules. The regions of the class I molecule that were responsible for this difference were mapped using chimeric class I molecules constructed to replace domains of the human molecule with their murine counterparts. It was found that the frequency of CTLp is controlled by structures within the alpha 1 and alpha 2 domains of the molecule. These results are discussed in the light of models for T cell recognition of class I Ag and the diversification of the T cell receptor repertoire.     

Chromatin reconstitution on small DNA rings. II. DNA supercoiling on the nucleosome

DNA supercoiling on the nucleosome was investigated by relaxing with topoisomerase I mono- and dinucleosomes reconstituted on small DNA rings. Besides 359 base-pair (bp) rings whose linking differences were integers, two additional series of rings with fractional differences, 341 and 354 bp in size, were used. Mononucleosomes reconstituted on 359 bp rings were found to relax into a single mononucleosome form. In contrast, 341 and 354 bp mononucleosomes relaxed into a mixture of two forms, corresponding to two adjacent topoisomers. The observation that the ratio between these two forms was, within each ring series, virtually independent of the initial linking number of the topoisomer used for the reconstitution suggested that each partition reflected an equilibrium. Comparison with the equilibria observed for the same rings in the absence of histones showed that the formation of a single nucleosome is associated with a linking number change of -1.1(+/-0.1) turn. Dinucleosomes, in contrast, were not relaxed to completion and do not reach equilibria. The corresponding linking number change per nucleosome was, however, estimated to be similar to the above figure, in agreement with previous data from the literature obtained with circular chromatins containing larger numbers of nucleosomes. DNA structure in mononucleosomes was subsequently investigated by means of high-resolution electron microscopy and gel electrophoresis. It was found that the above linking number reduction could be ascribed to a particle with a large open extranucleosomal DNA loop and with no more than 1.5 turns of a superhelix around the histone core. A theoretical model of a nucleosome on a small ring was constructed in which one part of the DNA was wrapped around a cylinder and the other part was free to vary both in torsion and flexion. The linking number reduction predicted was found to be most consistent with experimental data when the twist of the DNA in the superhelix was between 10.5 and 10.65 pb per turn, suggesting that wrapping on the nucleosome does not alter the twist of the DNA significantly. A lower estimate of the linking number reduction associated with a two-turn nucleosome was also derived, based on an analysis of recent data obtained upon treatment of reconstituted minichromosomes with gyrase. The value, 1.6 turns, set a lower limit of 10.44 bp per turn for the twist of nucleosomal DNA, in agreement with the above estimate.(ABSTRACT TRUNCATED AT 400 WORDS)     

Stimulation of the chemiluminescence of human polymorphonuclear leukocytes in various stages of the intraerythrocyte development of Plasmodium falciparum

The synchronized cultures of Plasmodium falciparum were used to stimulate in vitro the chemiluminescence of human polymorphonuclear leukocytes in the presence of immune serum. The schizonts were concentrated by Percoll gradient centrifugation method (density 1.085 and osmolarity 285 mOsmol), and placed in culture, treated 6 hours later by sorbitol. Under incubation at constant temperature and pressure, the rate of synchronization reached 85% for schizonts during 5 replicative cycles. Every asexual stages of Plasmodium falciparum were used separately to stimulate polymorphonuclear leukocytes: merozoites were the most effective, followed by schizonts, trophozoites, and lastly supernatants of cultures containing degradation products of parasites.