Modulating effect of cystamine and unsaturated fatty acids on gamma-glutamyl transpeptidase: Relation to cellular oxidative status

Summary Cell surface gamma-glutamyl transpeptidese activity in cultured neoplastic astrocytes was significantly increased upon treatment of the cells with the hepatoprotective disulfide, cystamine. The cystamine effect was sensitive to cycloheximide and could be significantly depressed by exogenous glutathione. Surface gamma-glutamyl transpeptidase activity was also modulated by the presence in the culture medium of the unsaturated fatty acids, linoleic acid and arachidonic acid. Metabolism of the fatty acids via the cyclooxygenase pathway was not a prerequisite for their modulation of the glycoprotein ectoenzyme. Lipoxygenase, however, was found to potentiate the unsaturated fatty acid effect in neoplastic astrocytes. Lipoxygenase is reported to catalyze the conversion of unsaturated fatty acids to their corresponding peroxides. The data indicate an oxidative influence on the control of gamma-glutamyl transpeptidase activity.     

Complementarity of particles and pits in freeze-fractured hepatic and cardiac gap junctions

Summary Particles and pits of freeze-fractured gap junctions are considered as complementary structures despite the frequent observations of more regular and closer spacings of pits, ascribed to plastic deformation of particle arrays. Recently, however, the noncomplementarity of pits and particles in Purkinje fibers has been reported. To ascertain the relationship between both structures, gap junctions from fixed, cryoprotected liver and myocardium were investigated using spacing and density measurements and complementary replicas.In hepatocyte gap junctions, the center-to-center distances (mean±sd) among pits, 9.57±1.49 nm, and particles, 9.70±1.77 nm, are not significantly different. Density determinations yielded a slightly higher value for the pits, (11,510±830)/m², than for the particles, (11,230±950)/m². In the myocardium, the spacing of the regularly arrayed pits, 9.55±1.33 nm barely exceeds the value of 9.44±1.62 nm for the particles, which show some clustering. However, the packing density for the pits, (10,090±740)/m², appears a little higher than that of the particles (9,890±920)/m². As density and spacing measurements provided no decisive answers, the positions of individual pits and particles of complementary junctional faces were recorded on transparent sheets and compared. In this fashion, a one-to-one correspondence between particles and pits could be established, while small discrepancies may be attributed to plastic deformation. Moreover, the collinearity of pits and particles may be suggested by the observation of a platinum grain in the center of many pits.     

Interrelatedness of 5S RNA sequences investigated by correspondence analysis

Summary Correspondence analysis (a form of multivariate statistics) applied to 74 5S ribosomal RNA sequences indicates that the sequences are interrelated in a systematic, nonrandom fashion. Aligned sequences are represented as vectors in a 5N-dimensional space, where N is the number of base positions in the 5S RNA molecule. Mutually orthogonal directions (called factor axes) along which intersequence variance is greatest are defined in this hyperspace. Projection of the sequences onto planes defined by these factorial directions reveals clustering of species that is suggestive of phylogenetic relationships. For each factorial direction, correspondence analysis points to regions of importance, i.e., those base positions at which the systematic changes occur that define that particular direction. In effect, the technique provides a rapid determination of group-specific signatures. In several instances, similarities between sequences are indicated that have only recently been inferred from visual base-to-base comparisons. These results suggest that correspondence analysis may provide a valuable starting point from which to uncover the patterns of change underlying the evolution of a macromolecule, such as 5S RNA.     

Characterization of murine monoclonal antibodies to human interferon-gamma (IFN-gamma) and their application for sandwich enzyme-linked immunosorbent assay (ELISA)

The three murine monoclonal antibodies (MAb), D1G2, D9D10, and D13C8, are specific for human interferon-gamma (IFN-gamma), but not human IFN-alpha and IFN-beta. They react weakly with heat-treated IFN-gamma. The three antibodies recognize different epitopes of the IFN-gamma molecule, as evaluated by antibody-binding inhibition experiments. We have used these three monoclonal antibodies to construct a sandwich enzyme-linked immunosorbent assay (ELISA). The best result was obtained when we used D1G2 or D9D10 MAb as a solid-phase immunosorbent and D1G2 or D9D10 MAb as a tracer. When we measured IFN-gamma in sera by a combination of D1G2 (a solid-phase) and D1G2 (a tracer), a result similar to the one by a combination of D9D10 (a solid-phase) and D1G2 (a tracer), was obtained. This may suggest that human IFN-gamma exists in oligomeric form. Recombinant human IFN-gamma expressed in E. coli is detectable at a concentration of 1 ng/ml in this sandwich ELISA. This assay can be employed for the analysis of the structural characteristics of the human IFN-gamma molecule as well as measurement of IFN-gamma in human sera and tissue culture fluids.     

Experimental evidence on the affinities ofPapaver somniferum (Papaveraceae)

Results obtained from crossing experiments betweenP. somniferum subsp.somniferum (2n = 22) and subsp.setigerum (2n = 44),P. glaucum (2n = 14) andP. gracile (2n = 14) and from the observation of meiotic chromosome pairing in the various hybrids obtained do not provide straightforward evidence for the hypothesis thatP. somniferum originated as a triploid hybrid between taxa similar toP. glaucum andP. gracile (Kadereit 1986a, b).—On the one hand, the pattern of crossability found reflects the closer similarity of subsp.somniferum toP. glaucum and of subsp.setigerum toP. gracile, which was interpreted as segregation of parental characters, and the high frequency of 2n = 28 chromosomes among F₂-progeny from the hybrid subsp.somniferum × subsp.setigerum (2n = 33) might reveal n = 7 as the base number also ofP. somniferum. On the other hand, however, the general difficulty of obtaining hybrids, and the low incidence of bivalent formation in their meiosis, probably indicating a lack of chromosome homology between the different species, do not fit the above hypothesis.—These results are in marked contrast to the morphological similarity between the three species involved.     

Dynamics of long-leaved sundew Drosera intermedia populations at two extremes of a hydrological gradient

Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m⁻¹), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality.     

Differentiation between Xanthomonas campestris pv. graminis (ISPP List 1980), pv. phleipratensis (ISPP List 1980) emend., pv. poae Egli and Schmidt 1982 and pv. arrhenatheri Egli and Schmidt 1982, by Numerical Analysis of Phenotypic Features and Protein Gel Electrophoregrams

A numerical analysis of 257 phenotypic features of 45 bacterial isolates from grasses, revealed three phenons corresponding to (i) X. campestris pv. graminis (ISPP List 1980), (ii) X. campestris pv. phleipratensis (ISPP List 1980) and (iii) X. campestris pv. poae Egli and Schmidt 1982 and X. campestris pv. arrhenatheri Egli and Schmidt 1982. In each phenon, the strains clustered together regardless of the geographical origin of the isolates orthe year of isolation. Polyacrylamide gel electrophoresis of soluble proteins and host range studies, revealed four groups corresponding to the pathovars mentioned above. The four pathovars constitute definite biological entities that can be differentiated by phenotypic, gel electrophoretic and host range features.     

Steroid sulfatase activity in a Peptococcus niger strain from the human intestinal microflora.

A strictly anaerobic gram-positive coccus, identified as Peptococcus niger, that developed sulfatase activity towards steroid-3-sulfate esters was isolated from human fecal material. This strain desulfated the arylsulfate esters estrone-3-sulfate (100%) and beta-estradiol-3-sulfate (50%); only trace amounts of desulfated estriol-3-sulfate were found. In addition, alkylsulfatase activity was found towards the 3 alpha-sulfates of 5 alpha-androstane-17-one and 5 beta-androstane-17-one and towards the 3 beta-sulfates of 5 alpha-androstane-17-one, delta 5-androstene-17-one, 5 alpha-pregnane-20-one, and delta 5-pregnene-20-one, all of which were 100% desulfated. No sulfatase activity was found towards the 17-sulfate esters of beta-estradiol or delta 4-androstene-3-one-17 alpha-ol. The nonsteroid arylsulfate esters paranitrophenyl sulfate, paranitrocatechol sulfate, and phenolphthalein disulfate were desulfated 70, 40, and 40%, respectively. In addition to its sulfatase activity, this strain also developed C-17 oxidoreductase activity towards the estrogens and androsta(e)nes and C-3 oxidoreductase activity towards androsta(e)nes and pregna(e)nes.     

Both 2',3'-dideoxythymidine and its 2',3'-unsaturated derivative (2',3'-dideoxythymidinene) are potent and selective inhibitors of human immunodeficiency virus replication in vitro

2',3'-Dideoxythymidine (ddThd) and its 2',3'-unsaturated derivative 2',3'-dideoxythymidinene (ddeThd) are potent and selective inhibitors of human immunodeficiency virus (HIV) in vitro. When evaluated for their inhibitory effects on the cytopathogenicity of HIV in MT-4 cells, ddThd and ddeThd completely protected the cells against destruction by the virus at a concentration of 1 microM and 0.04 microM, respectively. In this aspect, ddeThd was about 5 times more potent than 2',3'-dideoxycytidine (ddCyd), one of the most potent and selective anti-HIV compounds now pursued for its therapeutic potential in the treatment of AIDS. ddThd and ddeThd also suppressed HIV antigen expression at 1 microM and 0.04 microM, respectively. Their selectivity indexes, as based on the ratio of the 50% cytotoxic dose to the 50% antiviral effective dose, were 120 (ddeThd) and greater than 625 (ddThd).     

The 2',3'-dideoxyriboside of 2,6-diaminopurine selectively inhibits human immunodeficiency virus (HIV) replication in vitro

The 2',3'-dideoxyriboside of 2,6-diaminopurine(ddDAPR) is, like 2',3'-dideoxyadenosine (ddAdo), a potent and selective inhibitor of human immunodeficiency virus (HIV) in vitro. The ddDAPR compound inhibits HIV antigen expression and HIV-induced cytopathogenicity in MT4 cells at a 50% effective dose (ED50) of 2.5-3.6 microM, as compared to 3.1-6.4 microM for ddAdo. Both compounds are endowed with a high selectivity index: 112 for ddDAPR and 139 for ddAdo. The 2',3'-unsaturated derivatives of ddDAPR and ddAdo, i.e. ddeDAPR and ddeAdo, are considerably more cytotoxic and less effective against HIV than the parental compounds. Like ddAdo, ddDAPR is only weakly inhibitory to the proliferation and DNA and RNA synthesis of a series of human B-lymphoblast, T-lymphoblast and T-lymphocyte cell lines. In contrast to ddAdo, which is rapidly deaminated by beef intestine adenosine deaminase at an initial velocity (Vi) of 145 mumol/mg protein/min, ddDAPR and ddeDAPR are poor substrates for the enzyme (Vi: 8 and 0.7 mumol/mg protein/min, respectively), which further contributes to the potential of ddDAPR as a chemotherapeutic agent against AIDS.