Synthesis and biological activity of N-methylated analogs of endomorphin-2

In this paper, we describe the synthesis of a series of endomorphin-2 analogs containing N-methylated amino acids, consecutively in each position. The μ-opioid receptor binding affinities of the new analogs were determined in the displacement experiments. Their in vivo antinociceptive activity was assessed in the hot-plate test in mice after central (icv) and peripheral (ip) administration. [Sar²]endomorphin-2, which had the highest μ-receptor affinity, also showed the strongest analgesic effect when administered centrally and was the only analog that retained activity after peripheral injection.     

Chronic airway infection/inflammation induces a Ca2+i-dependent hyperinflammatory response in human cystic fibrosis airway epithelia

Hyperinflammatory responses to infection have been postulated as a component of cystic fibrosis (CF) lung disease. Studies have linked intracellular calcium (Ca(2+)(i)) mobilization with inflammatory responses in several systems. We have reported that the pro-inflammatory mediator bradykinin (BK) promotes larger Ca(2+)(i) signals in CF compared with normal bronchial epithelia, a response that reflects endoplasmic reticulum (ER)/Ca(2+) store expansion induced by chronic luminal airway infection/inflammation. The present study investigated whether CF airway epithelia were hyperinflammatory and, if so, whether the hyperinflammatory CF phenotype was linked to larger Ca(2+) stores in the ER. We found that DeltaF508 CF bronchial epithelia were hyperinflammatory as defined by an increased basal and mucosal BK-induced interleukin (IL)-8 secretion. However, the CF hyperinflammation expressed in short-term (6-11-day-old) primary cultures of DeltaF508 bronchial epithelia was lost in long-term (30-40-day-old) primary cultures of DeltaF508 bronchial epithelia, indicating this response was independent of mutant cystic fibrosis transmembrane conductance regulator. Exposure of 30-40-day-old cultures of normal airway epithelia to supernatant from mucopurulent material (SMM) from CF airways reproduced the increased basal and mucosal BK-stimulated IL-8 secretion of short-term CF cultures. The BK-triggered increased IL-8 secretion in SMM-treated cultures was mediated by an increased Ca(2+)(i) mobilization consequent to an ER expansion associated with increases in protein synthesis (total, cytokines, and antimicrobial factors). The increased ER-dependent, Ca(2+)(i)-mediated hyperinflammatory epithelial response may represent a general beneficial airway epithelial adaptation to transient luminal infection. However, in CF airways, the Ca(2+)(i)-mediated hyperinflammation may be ineffective in promoting the eradication of infection in thickened mucus and, consequently, may have adverse effects in the lung.     

Alpha-conotoxin residues that interact at close range with gamma-tyrosine-111 and mutant delta-tyrosine-113 on the Torpedo nicotinic acetylcholine receptor

The alpha-conotoxins MI and GI display stronger affinities for the alphagamma agonist site on the Torpedo californica electrocyte nicotinic acetylcholine receptor (ACHR) than for the alphadelta agonist site, while alpha-conotoxin SI binds with the same affinity to both sites. Prior studies reported that the arginine at position 9 on GI and the tyrosine at position 111 on the receptor gamma subunit were responsible for the stronger alphagamma affinities of GI and MI, respectively. This study was undertaken to determine if the alpha-conotoxin midchain cationic residues interact with Torpedo gammaY111. The findings show that lysine 10 on MI is responsible for the alphagamma selectivity of MI and confirm the previously reported importance of R9 on GI and on the SI analogue, SIP9R. The results also show that gammaY111 contributes substantially to the selective alphagamma high affinity of all three peptides. Double-mutant cycle analyses reveal that, in the alphagamma site, K10 on MI and R9 on SIP9R interact with the aromatic ring of gammaY111 to stabilize the high-affinity complex, while in contrast, R9 on GI does not. The substitution of Y for R at position 113 on the delta subunit converts the alphadelta site into a high-affinity site for MI, GI, and SIP9R through the interacting of deltaY113 with K10 on MI and with R9 on both GI and SIP9R. The overall data show that the residues in the two sites with which MI interacts, other than at gamma111/delta113, are either the same or similar enough to exert equivalent effects on MI, indicating that MI binds in the same orientation at the alphagamma and alphadelta sites. Similar findings show that SIP9R probably also binds in the same orientation at the wild-type alphagamma and alphadelta sites. The finding that R9 on GI interacts closely with deltaR113Y but not with gammaY111 means that GI binds in different orientations at the alphagamma and alphadelta sites. This report also discusses the molecular basis of the difference in the MI high-affinity sites on Torpedo and embryonic mouse muscle ACHRs.     

Model of creation and evolution of stable electropores for DNA delivery

Electroporation, in which electric pulses create transient pores in the cell membrane, is becoming an important technique for gene therapy. To enable entry of supercoiled DNA into cells, the pores should have sufficiently large radii (>10 nm), remain open long enough for the DNA chain to enter the cell (milliseconds), and should not cause membrane rupture. This study presents a model that can predict such macropores. The distinctive features of this model are the coupling of individual pores through membrane tension and the electrical force on the pores, which is applicable to pores of any size. The model is used to explore the process of pore creation and evolution and to determine the number and size of pores as a function of the pulse magnitude and duration. Next, our electroporation model is combined with a heuristic model of DNA uptake and used to predict the dependence of DNA uptake on pulsing parameters. Finally, the model is used to examine the mechanism of a two-pulse protocol, which was proposed specifically for gene delivery. The comparison between experimental results and the model suggests that this model is well-suited for the investigation of electroporation-mediated DNA delivery.     

Comparison of checkerboard and time-kill methods for the analysis of two antibiotics combined

Activity interaction analysis of two antibiotics by two methods: checkerboard and "time-kill" was compared during this study. Combinations of procaine penicillin, polymyxin B and bacitracin with neomycin and procaine penicillin with dihydrostreptomycin were examined. Checkerboard method is the most widely used technique for antimicrobials interactions analyses. The "time-kill" method, performed by the broth macrodilution technique, provides a dynamic picture of antimicrobial action and interaction over time (based on serial colony counts). Differences of "time-kill" method and the checkerboard technique, allow single visual examination (after 16 to 24 hours of incubation). Additive and inhibition effects were observed in combinations of neomycin with beta-lactam antibiotic (procaine penicillin) and peptide antibiotics (bacitracin and polymyxin B) on clinical strain S. Enteritidis IL 35 "Time-kill" method also confirmed observations mentioned above. In combinations of procaine penicillin with dihydrostreptomycin on strains E. coli IL 531 and E. coli IL 256 synergy effects on checkerboard technique were noticed. Such observation was not confirmed by the "time-kill" method. The methodologies and definitions of synergism are variable and not standardized. This situation should be improved, because comparison of the results obtained by different methods becomes a very difficult task.     

Application of the AFLP method to differentiate Genista tinctoria microsymbionts

The high-resolution amplified fragment length polymorphism technique (AFLP), with single PstI restriction endonuclease and two selective primers (PstI-G and PstI-GC), was used for genomotyping and study of the genomic relationships between Genista tinctoria microsymbionts sampled in England, Poland, and Ukraine. Out of 906 amplification products obtained with both selective primers, 537 markers were polymorphic and could be used to differentiate studied nodule isolates. Cluster analysis, based on AFLP patterns from PCR reaction with PstI-G and PstI-GC primers, separated Genista tinctoria rhizobia into three subgroups according to their geographic origin. The results presented in this paper emphasize the role of AFLP analysis in taxonomic and ecological studies of rhizobia.     

Growth of an invasive legume is symbiont limited in newly occupied habitats

Mutualisms may play an important role in the establishment and invasion success of introduced species, but their influence is little studied. To test whether a lack of root nodule symbionts may limit the performance of invasive legumes, seedlings of Cytisus scoparius were introduced to an old-field habitat and then either inoculated with Bradyrhizobium strains from existing C. scoparius populations, or left uninoculated. In two separate years, inoculation more than doubled average plant biomass. For uninoculated transplants, nodule formation was positively correlated with proximity to plants of the native legume Desmodium canadense , but not related to distance from a second legume species, Apios americana. Polymerase chain reaction assays and DNA sequencing confirmed that bacteria isolated from uninoculated C. scoparius plants were indistinguishable from Bradyrhizobium strains in root nodules of D. canadense . By contrast, bacterial strains associated with A. americana were never found in C. scoparius nodules. Transplants in seven other habitats across a 160 km region also showed a highly significant, fivefold biomass increase in response to inoculation. Thus, colonizing legumes can suffer from a scarcity of nodule symbionts. However, certain indigenous legumes may create favourable microhabitats for invasion, by increasing symbiont availability in their vicinity.