Conformation and charge distribution of bicyclic beta-lactams: structure-activity relationships.

The structures of 7-oxo-1-azabicyclo[3.2.0]heptane and its 4-oxa, 3-ethylene-4-oxa, and 3-ethylene-6-methyl-4-oxa derivatives, and of 8-oxo-1-azabicyclo[4.2.0]octane and its 5-oxa derivative, were studied by ab initio methods. Conformations were refined without constraints using the 4-21G and the 4-21G* basis sets, and energies and charge distributions were improved by single-point 6-31G*/4-21G* calculations. The results are are interpreted in terms of structural trends related to beta-lactamase inhibitor capability.     

Glucosylenamines as glycosyl acceptors: synthesis of gentiobiosylenamines.

The preparation of 2,3,4-tri-O-benzyl- (3), 2,3,4-tri-O-acetyl- (4), and 2,3,4-tri-O-benzoyl-N-(2,2-diethoxycarbonylvinyl)-6-O-trityl-beta- D-glucopyranosylamine (5) is described. The reaction of 3-5 with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide yields 2,3,4-tri-O-benzyl- (9), 2,3,4-tri-O-acetyl- (10), and 2,3,4-tri-O-benzoyl-N-(2,2-diethoxycarbonylvinyl)-6-O-(2,3,4,6-tet ra-O- acetyl-beta-D-glucopyranosyl)-beta-D-glucopyranosylamine (11), respectively. 2,3,4-Tri-O-benzyl- (6), 2,3,4-tri-O-acetyl- (7), and 2,3,4-tri-O- benzoyl-N-(2,2-diethoxycarbonylvinyl)-beta-D-glucopyranosylamine (8) are also described.     

Induction of cytotoxic T lymphocytes in mice against the principal neutralizing domain of HIV-1 by immunization with an engineered T-cytotoxic-T-helper synthetic peptide construct.

Peptide constructs were engineered by colinear synthesis of two short synthetic peptide determinants; a determinant recognized by T helper cells (TDh) and a determinant recognized by T cytotoxic cells (TDc). Three types of constructs were synthesized: TDc-TDh, TDh-TDc, and TDh-KK-TDc, where KK are two lysine residues. In vivo immunization with free construct induced cytolytic lymphocytes (CTL) only in the case of TDc-TDh. However, immunization with spleen cells to which these constructs had been internalized by hypertonic shock, induced CTL activity in all three cases. No CTL could be induced after immunization with free TDc in either protocol. These results indicate that cell internalization of the construct might be essential for CTL induction, and also, that "help" from the TDh seems to be required.     

Exogenous interleukin-2 abrogates differences in the proliferative responses to T cell mitogens among inbred strains of mice.

The proliferative response of spleen cells from BALB/c mice to stimulation with a T cell mitogen, concanavalin A (Con A), was two or more times stronger than that of cells from C57BL/10SnSc (B10) mice. In contrast, the cells from B10 mice responded better to B cell mitogen bacterial lipopolysaccharide (LPS). The differences in the proliferative response to Con A stimulation were not associated with the function of macrophages nor did they depend on IL-1. Spleen cells from BALB/c and B10 mice synthesized comparable amounts of mRNA for IL-1 alpha, and the production of biologically active IL-1 was even higher in the B10 strain. Indomethacin, an inhibitor of prostaglandin synthesis, had no effect on the differences in reactivity between the cells from BALB/c and B10 mice. In addition, no differences in the synthesis of mRNA for the inducible 55-kDa interleukin-2 (IL-2) receptors were found between the spleen cells from BALB/c and B10 mice. However, Con A-stimulated spleen cells from B10 mice produced a significantly lower amount of biologically active IL-2 than similarly stimulated cells from BALB/c mice. In the presence of exogenous IL-2, these low responder spleen cells from the B10 mice responded by proliferation to Con A stimulation to the same extent as cells from the BALB/c mice. These results thus show that a low proliferative response to Con A stimulation in B10 mice was a consequence of a lower production of IL-2 and possibly abrogated the proliferative hyporeactivity produced by exogenous IL-2. We suggest that the differences in the ability to produce IL-2 could be a reason for the discrepancies observed in the immunological responsiveness between BALB/c and B10 mice.     

A repetitive DNA element,associated with telomeric sequences in Drosophila melanogaster,contains open reading frames

He-T sequences are a complex repetitive family of DNA sequences in Drosophila that are associated with telomeric regions, pericentromeric heterochromatin, and the Y chromosome. A component of the He-T family containing open reading frames (ORFs) is described. These ORF-containing elements within the He-T family are designated T-elements, since hybridization in situ with the polytene salivary gland chromosomes results in detectable signal exclusively at the chromosome tips. One T-element that has been sequenced includes ORFs of 1,428 and 1,614 bp. The ORFs are overlapping but one nucleotide out of frame with respect to each other. The longer ORF contains cysteine-histidine motifs strongly resembling nucleic acid binding domains of gag-like proteins, and the overall organization of the T-element ORFs is reminiscent of LINE elements. The T-elements are transcribed and appear to be conserved in Drosophila species related to D. melanogaster. The results suggest that T-elements may play a role in the structure and/or function of telomeres.by W. Hennig     

Regulation of the final phase of mammalian melanogenesis. The role of dopachrome tautomerase and the ratio between 5,6-dihydroxyindole-2-carboxylic acid and 5,6-dihydroxyindole.

The regulation of the final steps of the melanogenesis pathway, after L-2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome) formation, is studied. It is shown that both tyrosinase and dopachrome tautomerase are involved in the process. In vivo, it seems that tyrosinase is involved in the regulation of the amount of melanin formed, whereas dopachrome tautomerase is mainly involved in the size, structure and composition of melanin, by regulating to the incorporation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) into the polymer. Moreover, using L-3,4-dihydroxyphenylalanine (dopa) and related compounds, it was shown that the presence of dopachrome tautomerase mediates an initial acceleration of melanogenesis since L-dopachrome is rapidly transformed to DHICA, but that melanin formation is inhibited because of the stability of this carboxylated indole compared to 5,6-dihydroxyindole (DHI), its decarboxylated counterpart obtained by spontaneous decarboxylation of L-dopachrome. Using L-dopa methyl ester as a precursor of melanogenesis, it is shown that this carboxylated indole does not polymerize in the absence of DHI, even in the presence of tyrosinase. However, it is incorporated into the polymer in the presence of both tyrosinase and DHI. Thus, this study suggests that DHI is essential for melanin formation, and the rate of polymerization depends on the ratio between DHICA and DHI in the medium. In the melanosome, this ratio should be regulated by the ratio between the activities of dopachrome tautomerase and tyrosinase.     

A monoclonal antibody that detects a specific human neutrophil antigen involved in phorbol myristate acetate- and formyl-methionyl-leucyl-phenylalanine-triggered respiratory burst.

A mouse IgM mAb termed P1E3 was raised against resting human peripheral blood neutrophils and has been shown to recognize a cell-surface Ag with an apparent molecular mass of 155 kDa, as assessed by immunoprecipitation analysis. In addition to the main 155-kDa protein, an additional band of about 210 kDa was also recognized by P1E3 in Western blot analysis. Sequential immunoprecipitation assays showed that the Ag recognized by P1E3 differed from the CD29 and CD45 Ag. However, sequential immunoprecipitation assays carried out with two distinct anti-CD15 mAb and P1E3 showed that P1E3 reacted with CD15 or with a CD15-like Ag. P1E3 stained strongly resting human peripheral blood neutrophils, hardly reacted with peripheral blood monocytes and did not react with PBL and platelets, as assessed by immunofluorescence flow cytometry. P1E3 inhibited the respiratory burst induced by PMA or FMLP, but not the oxidative response induced by Con A or the calcium ionophores A23187 or ionomycin. Furthermore, P1E3 inhibited the activation of the Na+/H+ antiporter in response to PMA or FMLP and the phosphorylation of a protein of about 50 kDa in response to PMA. However, preincubation of neutrophils with P1E3 did not affect the increase in cytosolic free calcium concentration induced by FMLP. These data suggest that the Ag recognized by P1E3 may play a role in modulating the activation of the respiratory burst induced by PMA or FMLP, and that P1E3 seems to affect protein kinase C-mediated signal transduction mechanisms coupled to the induction of the respiratory burst.     

Genetic and functional analysis of the basic replicon of pPS10, a plasmid specific for Pseudomonas isolated from Pseudomonas syringae patovar savastanoi.

The sequence of a 1823 base-pair region containing the replication functions of pPS10, a narrow host-range plasmid isolated from a strain of Pseudomonas savastanoi, is reported. The origin of replication, oriV, or pPS10 is contained in a 535 base-pair fragment of this sequence that can replicate in the presence of trans-acting function(s) of the plasmid. oriV contains four iterons of 22 base-pairs that are preceded by G+C-rich and A+T-rich regions. A dnaA box located adjacent to the repeats of the origin is dispensable but required for efficient replication of pPS10; A and T are equivalent bases at the 5' end of the box. repA, the gene of a trans-acting replication protein of 26,700 Mr has been identified by genetic and functional analysis. repA is adjacent to the origin of replication and is preceded by the consensus sequences of a typical sigma 70 promoter of Escherichia coli. The RepA protein has been identified, using the minicell system of E. coli, as a polypeptide with an apparent molecular mass of 26,000. A minimal pPS10 replicon has been defined to a continuous 1267 base-pair region of pPS10 that includes the oriV and repA sequences.     

Further characterization of alpha N-acetyl beta-endorphin-(1-31) regulatory activity, I: Effect on opioid- and alpha 2-mediated supraspinal antinociception in mice.

Picomol doses of the acetylated derivative of beta-endorphin-(1-31), injected intracerebroventricularly (icv) in mice, reduced the analgesic activity of morphine, etorphine and beta-endorphin-(1-31), while the efficiency of DAGO and DADLE in producing analgesia was enhanced. The effects of the delta agonists DPDPE and [D-Ala2]-Deltorphin II were not altered by this treatment. After alpha N-acetyl beta-endorphin-(1-31) injection, morphine antagonized the analgesia of DAGO. The regulatory effect of alpha N-acetyl beta-endorphin-(1-31) was exhibited when giving the peptide both before (up to 24 h) and after the opioids. Naloxone did not prevent or reverse that modulatory activity; moreover, pretreatment with the acetylated peptide did not change the pA2 value displayed by the antagonist at the mu receptor. The antinociceptive activity of the alpha 2-adrenoceptor agonist clonidine was also increased in mice treated with alpha N-acetyl beta-endorphin-(1-31). The reducing activity of alpha N-acetyl beta-endorphin-(1-31) upon morphine- and beta-endorphin-induced analgesia was not exhibited in mice undergoing treatment with pertussis toxin or N-ethylmaleimide, agents known to impair the function of Gi/Go transducer proteins. However, the enhancing activity displayed by this peptide upon DAGO- DADLE and clonidine-evoked antinociception was still manifested. These results confirm and strengthen the idea of alpha N-acetyl beta-endorphin-(1-31) acting as a non-competitive regulator of mu opioid- and alpha 2-adrenoceptor-mediated supraspinal antinociception. A neural substrate acted on by both receptors (likely Gi/Go transducer proteins) appears to be involved in the effects of that neuropeptide.