Tamoxifen fails to block estradiol accumulation, yet is weakly accumulated by the juvenile zebra finch anterior hypothalamus: an autoradiographic study.

In experiment 1, we used autoradiographic procedures to examine whether tamoxifen could displace 3H-estradiol labeling in the anterior hypothalamus and the caudal nucleus of the ventral hyperstriatum (HVc) of ovariectomized 20-day-old female zebra finches. There was no significant reduction in labeling of cells by 3H-estradiol in birds preinjected with unlabeled tamoxifen. In experiment 2, we found that injections of 3H-tamoxifen caused-weak labeling of cells in the anterior hypothalamus of 20-day-old male and female zebra finches. These results are compatible with the idea that tamoxifen does not block the action of estradiol in the brain of zebra finches, and suggest that the effects of early tamoxifen treatment on the morphology of the song system may reflect central actions of tamoxifen.     

Identification and molecular mapping of a single Arabidopsis thaliana locus determining resistance to a phytopathogenic Pseudomonas syringae isolate

We present a model pathosystem to dissect genetically the disease resistance response of plants against phytopathogenic bacteria. The interaction between Pseudomonas syringae pathovar maculicola (Psm) and Arabidopsis thaliana displays phenotypic varia-ion which depends on the genotype of both partners. Compatible interactions are defined by sustained in-planta bacterial growth and are normally accompanied of their appearance. For compatible interactions, resistance is defined by limited in-planta bacterial growth accompanied by a typical 'hypersensitive response' (HR). We show that at least parts of this system fit the paradigms of Flor's 'gene-for-gene' hypothesis. We identify functionally a putative bacterial avirulence gene (avrRpm 1) from a Psm isolate which conditions the HR on A. thaliana ecotypes Oy-0 abd Col- 0, but not Nd-0. We also demonstrate that resistance to the Psm strain from which avrRpm1 was isolated segregates as a single trait in the crosses Col-o x Nd-0 and Nd-0 x Oy-0. Furthermore, we map this locus (RPM1) molecularly in the Col-0 x Nd-0 cross to a relatively small interval defined by two RFLP markers on A. thliana chromosome 3. Resistance in the second cross also maps to this locus and co-segregates with resistance to avrRpm1.     

Society for Industrial Microbiology

Society for Industrial Microbiology     

Dextran sulfate-dependent fusion of liposomes containing cationic stearylamine.

The incorporation of the positively charged stearylamine into phosphatidylcholine liposomes was studied by measuring electrophoretic mobilities. Up to a molar ratio SA/PC = 0.5 an increase of the positive zeta potential can be observed. Addition of the negatively charged macromolecule dextran sulfate leads to a change of the sign of the surface potential of the PC/SA liposomes indicating binding of the macromolecule to the surface. This process is accompanied by an increase in turbidity, which is dependent on the molecular weight of the dextran sulfate and the SA concentration (measured by turbidimetry). Using the NBD/Rh and Pyr-PC fluorescence assays the fusion of SA containing liposomes was investigated. A strong influence of the SA content and molecular weight of dextran sulfate on the fusion extent was observed. The fusion extent is proportional to the SA content in the PC membrane and the molecular weight of dextran sulfate. PC/SA/PE liposomes exhibit a higher fusion extent after addition of dextran sulfate compared to PC/SA liposomes indicating that PE additionally destabilizes the bilayer. Freeze-fracture electron microscopy reveals that the reaction products are large complexes composed of multilamellar stacks of tightly packed, straight membranes and aggregated vesicles. The tight packing of the membranes in the stacks (and the narrow contact of the aggregated vesicles) indicates a strong adherence of opposite membrane surfaces induced by dextran sulfate.     

Soil acidification as caused by the nitrogen uptake pattern of Scots pine (Pinus sylvestris)

Three-year-old Scots pine (Pinus sylvestris) trees were grown on a sandy forest soil in pots, with the objective to determine their NH₄/NO₃ uptake ratio and proton efflux. N was supplied in three NH₄-N/NO₃-N ratios, 3:1, 1:1 and 1:3, either as ¹⁵NH₄+¹⁴NO₃ or as ¹⁴NH₄+¹⁵NO₃. Total N and ¹⁵N acquisition of different plant parts were measured. Averaged over the whole tree, the NH₄/NO₃ uptake ratios throughout the growing season were found to be 4.2, 2.5, and 1.5 for the three application ratios, respectively. The excess cation-over-anion uptake value (C_a-A_a) appeared to be linearly related to the natural logarithm of the NH₄/NO₃ uptake ratio. Further, this uptake ratio was related to the NH₄/NO₃ ratio of the soil solution. From these relationship it was estimated that Scots pine exhibits an acidifying uptake pattern as long as the contribution of nitrate to the N nutrition is lower than 70%. Under field circumstances root uptake may cause soil acidification in the topsoil, containing the largest part of the root system, and soil alkalization in deeper soil layers.     

Comparison of the amino acid sequences of tissue-specific parvalbumins from chicken muscle and thymus and possible evolutionary significance

Chicken leg muscle parvalbumin was digested with cyanogen bromide or trypsin or trypsin after citraconylation. Peptides isolated by reverse phase HPLC at pH 7.0 were subjected to acid hydrolysis and amino acid analysis and, in some cases, sequencing. The chicken muscle parvalbumin amino acid sequence has ca. 80% sequence identity with alpha-type parvalbumins from mammalian (rabbit, human and rat) muscle. By contrast, the chicken thymus parvalbumin ("avian thymic hormone") sequence is very similar to reptile (turtle, salamander and frog) muscle beta-type parvalbumins. We hypothesize that the evolutionary appearance of the warm-blooded reptiles was accompanied by recruitment of the beta parvalbumin isozyme for promotion of lymphocyte maturation.     

Role of functional groups of human plasma and luminol in scavenging of NaOCl and neutrophil-derived hypochlorous acid.

Hypochlorous acid HOCl/OCl- and other oxidants derived from stimulated polymorphonuclear leukocytes are involved in tissue damage during a number of pathological processes. In order to obtain more detailed information on possible reactions of HOCl/OCl- the effects of both NaOCl and PMN-derived hypochlorous acid on functional groups of amino acid solutions and human plasma are studied. In valine and lysine solutions NaOCl diminishes the number of amino groups in a molar ratio of 1:1 between NaOCl and amino groups. In cysteine and methionine samples the decrease of amino groups starts only after all sulfhydryl or thioether groups are oxidized by NaOCl. If freshly prepared human plasma is treated with increasing amounts of NaOCl all plasma SH groups are oxidized first, then probably the thioether groups and only after this the amino groups are affected. Furthermore, it was found, that the reactivity of luminol against NaOCl is similar to that of amino groups. Increasing amounts of SH groups of components of human plasma are oxidized by incubation with PMA-stimulated polymorphonuclear leukocytes dependent on the incubation time. Plasma amino groups are not affected under the same experimental conditions. The addition of plasma to FMLP-stimulated PMN in the presence of luminol decreases that part of chemiluminescence caused by extracellularly generated hypochlorous acid. Plasma samples pretreated with NaOCl cause a lower inhibition of light generation in FMLP-stimulated PMN only when more than 4.10(-8) mol NaOCl per mg protein are used to pretreat plasma. It is assumed that in the development of tissue injuries caused by infiltrated PMN the following sequence of damage occurs in accessible tissue regions. First, the sulfhydryl groups are oxidized, then the thioether groups, and only after this amino and other target groups are affected.     

NMR studies of multiple conformations in complexes of Lactobacillus casei dihydrofolate reductase with analogues of pyrimethamine

1H and 19F NMR signals from bound ligands have been assigned in one- and two-dimensional NMR spectra of complexes of Lactobacillus casei dihydrofolate reductase with various pyrimethamine analogues (including pyrimethamine [1, 2,4-diamino-5-(4'-chlorophenyl)-6-ethylpyrimidine], fluoropyrimethamine [2, 2,4-diamino-5-(4'-fluorophenyl)-6-ethylpyrimidine], fluoronitropyrimethamine [3, 2,4-diamino-5-(4'-fluoro-3'-nitrophenyl) -6-ethylpyrimidine], and methylbenzoprim [4, 2,4-diamino-5-[4'- (methylbenzylamino)-3'-nitrophenyl]-6-ethylpyrimidine]). The signals were identified mainly by correlating signals from bound and free ligands by using 2D exchange experiments. Analogues (such as 1 and 2) with symmetrically substituted phenyl rings give rise to 1H signals from four nonequivalent aromatic protons, clearly indicating the presence of hindered rotation about the pyrimidine-phenyl bond. Analogues containing asymmetrically substituted aromatic rings (such as 3 and 4) exist as mixtures of two rotational isomers (an enantiomeric pair) because of this hindered rotation and the NMR spectra revealed that both isomers (forms A and B) bind to the enzyme with comparable, though unequal, binding energies. In this case two complete sets of bound proton signals were observed. The phenyl ring protons in each of the two forms experience essentially the same protein environment (same shielding) as that experienced by the corresponding protons in bound pyrimethamine: this confirms that forms A and B correspond to two rotational isomers resulting from approximately 180 degrees rotation about the pyrimidine-phenyl bond, with the 2,4-diaminopyrimidine ring being bound similarly in both forms. The relative orientations of the two forms have been determined from NOE through-space connections between protons on the ligand and protein.(ABSTRACT TRUNCATED AT 250 WORDS)