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The layered Dion-Jacobson phase perovskites HLaTa2O7·xH2O, HLaNb2O7·0.5H2O and structural variants of HLaNb2O7·0.5H2O were prepared and their AC and DC conductivities were measured as a function of temperature and atmosphere. The layered structure in HLaNb2O7·0.5H2O was modified by pillaring, exfoliation-restacking, and further annealing. Exfoliation followed by restacking markedly increased the ionic conductivity, either by creation of mesopores for hydration or by enhanced contact between layers, but pillaring had little effect. HLaNb2O7·0.5H2O was prone to reduction under hydrogen, yielding a mixed ionic-electronic conductor. In-plane conductivity measurements of an oriented film of HLaNb2O7·0.5H2O showed enhanced ionic conductivity attributed to the anisotropic conductivity of the sheets, but reduction under a hydrogen atmosphere was apparent. The reduction could be suppressed by adding water vapor to the ambient atmosphere or by replacing the B-site niobium with tantalum, which is less easily reduced.

CDP-840 is a selective and potent phosphodiesterase type IV inhibitor, whose in vitro metabolism profile was first investigated using liver microsomes from different species. At least 10 phase I oxidative metabolites (M1-M10) were detected in the microsomal incubations and characterized by capillary high-performance liquid chromatography continuous-flow liquid secondary ion mass spectrometry (CF-LSIMS). Significant differences in the microsomal metabolism of CDP-840 were found between rat and other species. The major route of metabolism in rat involved para-hydroxylation on the R4 phenyl. This pathway was not observed in human and several other species. The in vitro metabolism profile of CDP-840 was further examined using freshly isolated hepatocytes from rat, rabbit, and human. The hepatocyte incubations indicated more extensive metabolism relative to that in microsomes. In addition to the phase I oxidative metabolites observed in microsomal incubations, several phase II conjugates were identified and characterized by CF-LSIMS. Interspecies differences in phase II metabolism were also found in these hepatocyte incubations. The major metabolite in human hepatocytes was identified as the pyridinium glucuronide, which was not detected in rat hepatocytes. Simple structural modification on R4, such as p-Cl substitution, greatly reduced the species differences in microsomal metabolism. Furthermore, modifications on R3, such as the N-oxide, eliminated the N-glucuronide formation in human. These results not only helped in determining the suitability of animal species used in the preclinical safety studies but also provided valuable directions for the synthetic efforts in finding backup compounds that are more metabolically stable.

A novel thiadiazole compound, SCH-202676 (N-(2,3-diphenyl-1,2, 4-thiadiazol-5-(2H)-ylidene)methanamine), has been identified as an inhibitor of both agonist and antagonist binding to G protein-coupled receptors (GPCRs). SCH-202676 inhibited radioligand binding to a number of structurally distinct, heterologously expressed GPCRs, including the human mu-, delta-, and kappa-opioid, alpha- and beta-adrenergic, muscarinic M1 and M2, and dopaminergic D1 and D2 receptors, but not to the tyrosine kinase epidermal growth factor receptor. SCH-202676 had no direct effect on G protein activity as assessed by [35S]guanosine-5'-O-(gamma-thio)triphosphate binding to purified recombinant G(oalpha)- or G(betagamma)-stimulated ADP-ribosylation of G(oalpha) by pertussis toxin. In addition, SCH-202676 inhibited antagonist binding to the beta2-adrenergic receptor expressed in Escherichia coli, a system devoid of classical heterotrimeric G proteins. SCH-202676 inhibited radiolabeled agonist and antagonist binding to the alpha2a-adrenergic receptor with an IC50 value of 0.5 microM, decreased the Bmax value of the binding sites with a slight increase in the KD value, and inhibited agonist-induced activation of the receptor. The effects of SCH-202676 were reversible. Incubation of plasma membranes with 10 microM SCH-202676 did not alter subsequent radioligand binding to the alpha2a-adrenergic receptor and the dopaminergic D1 receptor. Taken together, our data suggest that SCH-202676 has the unique ability to allosterically regulate agonist and antagonist binding to GPCRs in a manner that is both selective and reversible. The scope of the data presented suggests this occurs by direct interaction with a structural motif common to a large number of GPCRs or by activation/inhibition of an unidentified accessory protein that regulates GPCR function.

A molecular model of the human melanin-concentrating hormone (MCH) peptide was constructed and docked into a helical, bacteriorhodopsin-based model of the recently identified human MCH receptor. From this hormone-receptor complex, potential sites of agonist-receptor interaction were identified, and site-directed mutagenesis was used to substitute residues predicted to reside within the receptor binding pocket. Substitution of Asp(123)(3.32) in the third transmembrane domain of the receptor resulted in a loss of detectable (125)I-MCH binding and of MCH-stimulated Ca(2+) flux; cell surface expression of the mutant receptor was not affected. Arg(11) and Arg(14) of the MCH ligand were identified as potential sites of interaction with Asp(123)(3.32). [Ala(14)]-MCH was equipotent to native MCH in its ability to bind to and activate the wild-type MCH receptor, whereas [Ala(11)]-MCH displayed a 3000-fold reduction in binding affinity and a complete loss of measurable functional activity. Furthermore, [Lys(11)]-MCH and [D-Arg(11)]-MCH displayed reduced affinity for the receptor. [Lys(11)]-MCH was observed to be a partial agonist, eliciting approximately 67% of the native peptide's activity in a Ca(2+) flux assay, and [D-Arg(11)]-MCH was determined to be a functional antagonist with a K(b) valve of 15.8 microM. These data provide evidence that a basic moiety with specific stereochemical requirements at this site is needed for receptor activation. We conclude that both Asp(123)(3.32) in the MCH receptor and Arg(11) in the MCH peptide are required for the formation of the MCH peptide/receptor complex and propose that they form a direct interaction that is critical for receptor function.

Prolactin and Cortisol responses to dl-fenfluramine challenge were examined in 11 patients with chronic fatigue syndrome and in 11 healthy controls who were age and gender matched. After obtaining two baseline samples, each subject was given 60 mg of dl-fenfluramine orally and further blood samples were drawn hourly during the following five hours in order to measure prolactin and Cortisol levels. There was no difference in either baseline or fenfluramine-induced hormonal responses between patients with chronic fatigue syndrome and controls. There was also no correlation between depression scores on HAM-D and hormonal responses in patients with chronic fatigue syndrome. The findings of this study do not support a role for 5-HT in chronic fatigue syndrome.

The stability of SP82G bacteriophage deoxyribonucleic acid (DNA) after its uptake by competent Bacillus subtiliswas examined by determining the ability of superinfecting phage particles to rescue genetic markers carried by the infective DNA. These experiments show that a DNA inactivation process within the cell is inhibited after infection of the cell by intact phage particles. The inhibition is maximally expressed 6 min after phage infection and is completely prevented by the addition of chloramphenicol at the time of infection. The protective effect of this function extends even to infective DNA which was present in the cell before the addition of intact phage. Continued protein synthesis does not appear to be a requirement for the maintenance of the inhibition. In an analogous situation, if infectious centers resulting from singly infecting phage particles are exposed to chloramphenicol shortly after the time of infection, an exponential decrease in the survival of infectious centers with time held in chloramphenicol is observed. If the addition of chloramphenicol is delayed until 6 min after infection, the infectious centers are resistant to chloramphenicol. The sensitivity of infectious centers treated with chloramphenicol at early times after infection is strongly dependent upon the multiplicity of infection and is consistent with a model of multiplicity reactivation. These results indicate that injected DNA is also susceptible to the intracellular inactivation process and suggest that the inhibition of this system is necessary for the successful establishment of an infectious center.

A generalized assessment of the functions of 26 genes of SP82G, a bacteriophage of Bacillus subtilis, has been made. The production of phage-specific deoxyribonucleic acid (DNA), DNA-filled phage heads, completed phage particles, phage-specific antigen, and developmental aberrations has been examined in lysates of temperature-sensitive mutants grown under selective conditions. The genes show a tendency to occur on the genome in three groups of related function: genes involved with DNA synthesis, with tail synthesis, and with head synthesis.

The last genetic markers to be transferred during bacteriophage SP82G infection have a higher sensitivity to the decay of incorporated radioactive phosphorous (32P) than those which are located on the proximal end of the genome. If 32P decay is permitted to take place after DNA transfer is complete (in frozen infective centers) and in the absence of DNA replication, no dependence of marker sensitivity on map position is observed. These results indicate that the decay of incorporated 32P leads to damages that prevent the efficient transfer of portions of the genome distal to the lesion. At 4 C, failure to transfer some portion of the genome occurs in 49% of all lethal events. Even though damages that prevent transfer of the genome are in themselves lethal, they do not prevent rescue of genetic markers on portions of the genome that are transferred. The portion of the genome that is transferred, is transferred at the same rate as an undamaged genome. We interpret these results to mean that double-strand breaks in the DNA are the lesions that prevent distal transfer and that single-strand breaks have little or no effect on the transfer of the bacteriophage SP82G genome.

Analysis, by the recovery of specific genetic “markers,” of the effects of DNase I, physical shear, and temperature shock on DNA-cell complexes demonstrates that sequential attachment of both ends of bacteriophage SP82G DNA to Bacillus subtilisprecedes entry of the DNA molecule into the cell, and that each attachment is end-and time-specific. The first attachment involves an initial reversible phase, followed by irreversible binding. After a latent period, the second end then attaches to the cell. Entry of the molecule begins immediately after binding of the second end has occurred, and entry is complete within 3 min. The polarity of entry, as judged by attainment of resistance to DNase I, is the reverse of that observed in normal phage injection.