Biomass-size spectra in aquatic communities in shallow fluctuating Mediterranean salt marshes (Emporda wetlands, NE Spain)

The distribution of biomass among phytoplankton and free-livinginvertebrates was analysed in a shallow Mediterranean salt marshsubmitted to fluctuating water level. Among phytoplankton, biomassaccumulated in sizes dominated by mixotrophic species, indicatinga competitive advantage for these species, which also prey onother smaller primary producers. Among invertebrates, biomassaccumulated in the larger sizes, corresponding to species whichpartially exploit other nearby systems, such as the aerial environment(insects), or to those able to exploit particulated organicmatter in marsh-bed sediment (amphipods). Biomass distributionmodels developed for pelagic systems are discussed in relationto fluctuating temporary waters. The integrated spectrum approximated(r² = 0.96) a Pareto distribution with a slope of c = 1.38.Intense disturbances caused a decrease in r² and an increasein c. Under stable conditions, two different tendencies wereobserved, depending on the degree of eutrophy of the basins:higher values of c were measured in the more eutrophic basins,and lower values in the less eutrophic ones. We hypothesizethat highly irregular nutrient input could explain these differences.     

Coordination mode and reactivity of copper(II) complexes with kasugamycin.

Protonation and Cu(II) coordination of kasugamycin were studied by potentiometry, UV-vis, CD, EPR, 13C NMR, and 1H NMR. Mononuclear complexes with stoichiometries ranging from CuHL to CuH(-1)L were found. The aminoamidine moiety provides the coordination site in the CuHL species. The additional axial coordination of the amino nitrogen of the aminosugar ring is present in CuL. Finally, the CuH(-1)L complex is formed as a result of a deprotonation and coordination of the hydroxyl group of the inositol ring. The non-planar arrangement of the chelate rings results in the relative stabilization of a Cu(I) species. As a consequence, Cu(I) and superoxide radicals are involved in the redox mechanism of H(2)O(2) activation by the Cu(II) complex of kasugamycin.     

Murine monoclonal antibody against aldosterone: production, characterization and use for enzymoimmunoassay

Hybridomas secreting monoclonal antibodies to aldosterone were obtained by fusion of myeloma cells and spleen cells from Balb/c mice immunized with aldosterone-3-carboxylmethyloxime-bovine serum albumin. A monoclonal antibody was purified from ascites fluid and characterized. An affinity constant of 1.61 x 10(9) M-1 has been measured and no cross-reactivity with tetrahydroaldosterone (THA), cortisol, cortisone, corticosterone, deoxycorticosterone (DOC), dehydroepiandrosterone (DHA), progesterone and estrone, could be detected. A peroxidase conjugated-antibody (1.5 mole of enzyme per mole of antibody) was obtained and used for microwell enzyme immunoassay and Immun-Blot assay. The high affinity and specificity of this antibody should make the direct determination of aldosterone in biological fluids possible at concentrations as low as 5 x 10(-10) M.     

Effects of electrical stimulation upon post-hatching development of fibre types in normally innervated fast and slow latissimus dorsii muscles of the chicken

In chicken, the main characteristic properties of muscle fibre types in slow anterior (ALD) and fast posterior (PLD) latissimus dorsii are acquired during post-hatching development. At day 4 it becomes possible to distinguish between alpha' and beta' fibre types in ALD muscle. At the same time, mATPase staining and NADH-TR activity permit recognition of alpha w and alpha R fibres within PLD muscle. During further development, muscle fibre typology progressively changes towards the adult slow and fast type. Chronic stimulation at a slow rhythm (5 Hz) of PLD prevents the change in relative proportions of alpha R and alpha W fibres within the muscle that occurs in normal post-hatching development and increases the number of beta R fibres. Moreover, oxidative activity is increased in all muscle fibre types following stimulation. In ALD muscle, chronic stimulation at a fast rhythm (40 Hz) results in a decrease in oxidative activity and inhibits the differentiation of alpha' and beta' muscle fibre types. This study demonstrates that in young chicken, the pattern of activity influences the differenciation of fibre types in slow and fast muscles.     

Elevation of glutathione in phenylalanine mustard-resistant murine L1210 leukemia cells

Murine L1210 leukemia cells resistant to the antineoplastic agent L-phenylalanine mustard have a 1.5-2.0-fold elevation in their cellular GSH and GSSG content as compared to drug-sensitive cells. Cellular uptake of L-[U-14C]cystine and its incorporation into GSH of the resistant tumor are correspondingly elevated. Synthesis of gamma-glutamylcysteine, GSH, and GSSG is elevated 1.5-2.0-fold in cell-free preparations of the resistant tumor. This increased synthesis of GSH is attributed to increased cellular content (1.6-fold) of gamma-glutamylcysteine synthetase. GSH synthetase activity is equivalent in both drug-sensitive and -resistant cells. Investigation into the hydrolysis of selected peptides by cell-free preparations of both sensitive and resistant tumors suggest that aminopeptidase M participates in the formation of L-cysteine from L-Cys-Gly. This is supported by the observation that these preparations readily degrade L-Leu-p-nitroanilide and L-Ala-L-Ala-L-Ala, known substrates for aminopeptidase M, but not dipeptidase. The failure of the tumors to degrade Gly-D-Ala, a dipeptidase substrate, and the marked inhibition of L-Ala-Gly, L-Cys-Gly, and L-Ala-L-Ala-L-Ala hydrolysis by Bestatin further support a role for aminopeptidase M in the generation of L-cysteine from L-Cys-Gly. These results suggest that the drug-resistant tumor cell has developed an efficient mechanism for maintenance of elevated GSH which involves both gamma-glutamyl transpeptidase-initiated catabolism of GSH to cysteine and its reutilization by gamma-glutamylcysteine synthetase.     

A soluble interleukin 2 receptor produced by a normal alloreactive human T cell clone binds interleukin 2 with low affinity

Several alloreactive human T cell clones derived from a rejected kidney graft were found to produce in their culture supernatants soluble interleukin 2 receptors (IL-2R) upon specific antigenic challenge (irradiated B cell line from the graft's donor). Among them, the 2B11, a high producer clone, was used to purify a soluble IL-2R preparation which was analyzed, in comparison with the high and low affinity cell-surface IL-2R expressed by 2B11 cells, for its parameters of interaction with a set of anti-IL-2R monoclonal antibodies (mAb) and IL-2. This soluble receptor purified by affinity chromatography (anti-IL-2R mAb column) and sodium dodecyl sulfate gel electrophoresis is composed of a single chain of 35,000 to 45,000 Da. Immunoradiometric assays (IRMA) at equilibrium were set up, using pairs of mAb directed against two separate epitopes on the Tac antigen of the human IL-2R, to measure the respective dissociation constant of these mAb for the soluble IL-2R. They were found to be identical to those found on the cell-surface IL-2R. A 1:1 stoichiometry between the two epitopes were found both on the membrane and soluble species. Competition experiments between membrane and soluble IL-2R for binding the mAb allowed the quantitative analysis of the concentration of soluble IL-2R without the need of amino acid analysis on purified material and set up a quantitative IRMA for the human soluble IL-2R (detection limit 5 pM). The affinity of the soluble IL-2R for IL-2 was determined by various techniques including an IRMA using an anti-IL-2R mAb and radiolabeled IL-2. The results obtained led us to conclude that the soluble IL-2R binds IL-2 with a dissociation constant (KD = 30 nM) identical to that found for the binding of IL-2 to low affinity cell-surface IL-2R (Tac antigen). Whereas 2.5% of cell-surface IL-2R expressed 2 days after antigenic stimulation of 2B11 cells were of high affinity for IL-2 (KD = 25 pM), no (less than 0.07%) high affinity binding sites could be detected on the purified soluble IL-2R. This soluble IL-2R therefore likely corresponds to a truncated, extracellular part of the membrane Tac antigen. The amounts of soluble Tac antigen produced by the 2B11 alloreactive human T cell clone did not exceed 1 nM and, as expected from the binding studies, did not affect IL-2-induced T cell proliferation. The physiologic and pathologic implications of our results are discussed.     

Diastereomers of thymidine 3'-O-(methanephosphonothioate): synthesis, absolute configuration and reaction with 3'-methoxyacetylthymidine under conditions of triester approach to oligonucleotide synthesis

Diastereomers of the title compound were obtained and absolute configuration was assigned by means of stereochemical correlation. Their reaction with 3'-O-methoxyacetylthymidine in the presence of triisopropylbenzenesulphonyl (4-nitro) triazole is neither chemo- nor stereo-selective and leads to diastereomeric pairs of dithymidyl (3',5')methanephosphonate and -methanephosphonothioate. Obtained results are discussed in terms of mechanism of activation of phosphodiesters under conditions known as "phosphotriester approach to oligonucleotide synthesis".     

Amino acid sequence of rat mast cell protease I (chymase)

The amino acid sequence has been determined for rat mast cell protease I (RMCP I), a product of peritoneal mast cells. The active enzyme contains 227 residues, including three corresponding to the catalytic triad characteristic of serine protease (His-57, Asp-102, and Ser-195 in chymotrypsin). A computer search for homology indicates 73% and 33% sequence identity of RMCP I with rat mast cell protease II from mucosal mast cells and bovine chymotrypsin A, respectively. When the structure of RMCP I is compared to those of cathepsin G from human neutrophils and two proteases expressed in activated lymphocytes, 48-49% of the sequences are identical in each case. RMCP I has six half-cystine residues at the same positions as in RMCP II, cathepsin G, and the two lymphocyte proteases, suggesting disulfide pairs identical with those reported for RMCP II. A disulfide bond near the active site seryl residue and substrate binding site, present in pancreatic and plasma serine proteases, is not found in RMCP I or in the other cellular proteases. These results indicate that RMCP I and other chymotrypsin-like proteases of granulocyte and lymphocyte origin are more closely related to each other than to the pancreatic or plasma serine proteases.     

Circumferential analysis of digitalized gamma angiocardiography by assessment of regional left ventricular contraction

After acquisition of a digital equilibrium gamma-angiocardiographie, circumferential analysis of end-diastolic and end-systolic frames gives 120 points diastolic and systolic curves. Their difference represents systolic volume and leads to regional left ventricular ejection fraction assessment at the considered radius level. The circumferential analysis evolute gives the regional left ventricular ejection fraction representative curves which allows especially differential diagnosis between left ventricular akinesia and dyskinesia.     

Population Heterogeneity of Agrobacterium tumefaciens in Galls of Populus L. from a Single Nursery

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the pathogenic subpopulations.