Métabolisme du chloro-2 (p-chlorophényl)-3 propionate de méthyle et problème de sélectivité

The product of hydrolysis of the active principle of the herbicide Bidisine® is degraded in at least two different ways. One way gives p-chlorobenzoic acid. The other, more important one, gives a conjugate with l-cysteine, which is further oxidized. The ability to oxidize the conjugate provided a means of distinguishing between susceptible and resistant plant species.     

Studies of copper(II) binding to glycylglycyl-L-tyrosine-N-methyl amide, a peptide mimicking the NH2-terminal copper(II)-binding site of dog serum albumin by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy

Unlike human serum albumin (HSA), dog serum albumin (DSA) does not possess the characteristics of the specific first binding site for Cu(II). In DSA, the important histidine residue in the third position, responsible for the Cu(II)-binding specificity in HSA, is replaced by a tyrosine residue. In order to study the influence of the tyrosine residue in the third position of DSA, a simple model of the NH2-terminal native sequence tripeptide of DSA, glycylglycyl-L-tyrosine-N-methylamide (GGTNMA) was synthesized and its Cu(II)-binding properties studied by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy. The species analysis indicated the existence of five mono-complexes at different protonation states: MHA, MA, MH-1A, MH-2A, MH-3A, and only one bis-complex MH-2A-2. The complexing ability of GGTNMA to Cu(II) was found to be weaker than that of the Cu(II) binding peptide models of HSA. The visible absorption spectra of Cu(II)-GGTNMA complexes are similar to those observed in the case of DSA-Cu(II) complexes. The weaker binding and the spectral properties of Cu(II)-GGTNMA complexes are consistent with less specific Cu(II)-binding properties of the peptide of this sequence similar to what was noted with DSA. CD results are in excellent agreement with species analysis and visible spectra where it is clearly evident that Cu(II) binds to GGTNMA starting from the alpha-NH2 group and step by step to deprotonated amide nitrogens as the pH is raised. The absence of any charge transfer band around 400 nm strongly indicates that Cu(II) does not bind to the phenolate group. Furthermore, NMR results are consistent with the noninvolvement of the tyrosine residue of GGTNMA in Cu(II) complexation. Thus, it is clear that the low Cu(II)-binding affinity of DSA is due to the genetic substitution of tyrosine for histidine at the NH2-terminal region of the protein.     

Photoreactivity of buckminsterfullerene-bis(triphenylphosphite)platinum(0) induced by metal-to-ligand charge transfer excitation

The complex C₆₀Pt[P(OPh)₃]₂ displays C₆₀ ππ^* intraligand bands in the UV-Vis region and a long-wavelength absorption at λ_max = 770 nm which is assigned to a metal-to-ligand charge transfer (MLCT) transition from platinum to fullerene. The irradiation of the complex leads to the population of the reactive MLCT state and subsequently to the dissociation (C₆₀Pt[P(OPh)₃]₂ → C₆₀ + Pt[P(OPh)₃]₂) in the primary photochemical step. Product formation takes place by the interception of Pt[P(OPh)₃]₂ with suitable scavengers such as CHCl₃ or O₂.     

A radioimmunoassay of plasma estradiol-17beta with the use of polyethylene glycol to separate free and antibody-bound hormone

A radioimmunoassay for plasma estradiol-17β was developed using polyethylene glycol to separate free from antibody-bound hormone. Specificity for estradiol-17β was achieved by a modified celite microcolunm procedure in which estradiol was.separated from interfering estrogens, including estrone. Using trace ³H-estradiol to monitor procedural losses, the method was shown to be sensitive and accurate. Intra- and inter-assay coefficient of variation of the method was 8.7 and 10.6%, respectively. Polyethylene glycol used for antibody precipitation appears to be a generally applicable method for steroid hormone radioimmunoassays. The simplicity, precision and rapid analysis, coupled with its lack of time dependence and ease in automation, makes this a convenient and practical method.     

Streptococcus pneumoniae type 3 encodes a protein highly similar to the human glutamate decarboxylase (GAD65)

Abstract A 2.5-kb Sca I fragment of the type 3 pneumococcal strain 406 DNA containing a 1425-nucleotide open reading frame ( gadA ) and encoding a 475-amino acid protein ( M _rmr 54427) was characterised. The gene gadA was expressed in Salmonella typhimurium . Pulsed-field gel electrophoresis and Southern blotting analysis of DNAs prepared from several pneumococcal serotypes showed that only those clinical isolates belonging to serotype 3 harbour the gadA gene. Sequence comparison of GadA with proteins included in the data banks revealed the highest similarity with human glutamate decarboxylase (GAD₆₅) (59% similarity, 28% identity). Auto-antibodies to GAD₆₅ have been associated with the onset of insulin-dependent diabetes mellitus. Interestingly, several epitopes of GAD₆₅ that have been identified as immunodominant are particularly well conserved in the pneumococcal GadA.     

Dexamethasone effects on liver pyruvate kinase

Dexamethasone in the medium perfusin isolated rabbit livers caused a fast-acting and reversible effect on liver pyruvate kinase. The effect was to lower th assayable V activity (units/g tissue) without changing the concentration (nmol/g enzyme protein). In effect, glucocorticoid lowered the specific activity (units/nmol of enzyme) by direct action on liver. The effect on liver pyruvate kinase is mediated by a relatively stable alteration; 30 min after perfusate (with steroid) was replaced by perfusate (without steroid), the effect remained strongly evident.     

Gene order and recombination rates in the linkage group S-Phi-Hal-H-(Po2)-Pgd in pigs

Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S-Phi = 4.8 % (2.5 % -10.7 %);S-H = 6.8 % (4.3 %-11.7 %); Phi-H = 2.6 % (0.9 %-5.3 9%); H-Pgd = 4.4 % (1.6 %-8.0 %). CCCC-overs were observed also between S- Hal, Hal-H andHal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) -H- (P02) - Pgd.
A striking difference was found between the number of halothane-sensitive pigs (87) and HalⁿHal ⁿ genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete CCC or low expression of halothane sensitivity.     

Endothelin contraction in pig coronary: Receptor types and Ca2+-mobilization

Endothelin is one of the most potent vasoconstrictors known. It plays an important role in the regulation of vascular tone and in the development of many cardiovascular diseases. This study focuses on the receptor types and the Ca²⁺ mobilization responsible for endothelin-1 (ET-1) contraction in de-endothelialized pig coronary artery rings. ET-1 contracted the artery rings with an EC₅₀ = 6.5 ± 1 nM and a maximum contraction which was 98.6 ± 9% of the contraction produced by 60 mM KCl. BQ123 (5 µM), an ET_A antagonist, reversed 78 ± 3% of the ET-1 contraction (50 nM). IRL1620, a selective ET_B agonist, produced 23 ± 3% of the total ET-1 contraction with an EC₅₀ = 12.7 ± 2 nM. More than 85% of the contraction due to 100 nM IRL 1620 was inhibited by 200 nMBQ788, an ET_B antagonist. Therefore, approximately 80% of the ET-1 contraction in this artery occurred via ET_A receptors, and the other 20% was mediated by ET_B receptors. To assess the Ca²⁺ pools utilized during the ET-1 response, ET-1 contraction was also examined in medium containing an L-type Ca²⁺ channel blocker nitrendipine, and in Ca²⁺ free medium containing 0.2 mM EGTA. In Ca²⁺ containing medium the contraction elicited by ET-1 was 98.6 ± 9% of the KCl contraction, however, in the presence 10 µM nitrendipine the ET-1 induced contraction was 54 ± 7% of the KCl contraction, and in Ca²⁺-free medium it was 13 ± 2%. Similarly, the IRL 1620 contractions in Ca²⁺ containing medium, in the presence of nitrendipine and in Ca²⁺-free medium were 22.4 ± 3%, 12 ± 3% and 11 ± 2% of the KCl response respectively. Thus, both ET_A and ET_B contractions utilize extracellular Ca²⁺ pools via L-type Ca²⁺ channels and other undefined route(s), as well as intracellular Ca²⁺ pools. In the pig coronary artery smooth muscle, ET-1 contractions occur predominantly via ET_A receptors, with ET_B receptors using similar Ca²⁺ mobilization pathways, but the ET_B receptors appear to use the intracellular Ca²⁺ stores to a greater extent.