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Notes: Atomic force microscopy is used to characterize the evolution of film morphology produced by heavy-ion bombardment. Pt films, 3 and 5 nm thick, are deposited on SiO2 substrates and subsequently bombarded by 800 keV Kr+. Ion doses of 〉2×1014 initiate pattern formation and the dewetting of Pt films from the substrate. The film morphology becomes increasingly disconnected with increasing dose; at the highest doses, (∼2×1016 cm−2), isolated nanoparticles are formed with a uniform spacing. The results are explained by the nucleation of bare substrate patches and subsequent coarsening of the morphology by the molten zones created by individual Kr+ impacts. © 2000 American Institute of Physics.

Notes: During the late nineteenth century, James Walker Hood was bishop of the North Carolina Conference of the African Methodist Episcopal Zion Church and grand master of the North Carolina Grand Lodge of Prince Hall Masons. In his forty-four years as bishop, half of that time as senior bishop of the denomination, Reverend Hood was instrumental in planting and nurturing his denomination's churches throughout the Carolinas and Virginia. Founder of North Carolina's denominational newspaper and college, author of five books including two histories of the AMEZ Church, appointed assistant superintendent of public instruction and magistrate in his adopted state, Hood's career represented the broad mainstream of black denominational leaders who came to the South from the North during and after the Civil War. Concurrently, Grand Master Hood superintended the southern jurisdiction of the Prince Hall Masonic Grand Lodge of New York and acted as a moving force behind the creation of the region's black Masonic lodges—often founding these secret male societies in the same places as his fledgling churches. At his death in 1918, the Masonic Quarterly Review hailed Hood as “one of the strong pillars of our foundation.” If Bishop Hood's life was indeed, according to his recent biographer, “a prism through which to understand black denominational leadership in the South during the period 1860–1920,” then what does his leadership of both the Prince Hall Lodge and the AMEZ Church tell us about the nexus of fraternal lodges and African American Christianity at the turn of the twentieth century?

Notes: Within the past decade or so, historical studies of early Christianity have been affected by what has been called the “linguistic turn.” This development has entailed a new appreciation of the varied forms of Christian “discourse” and their importance in shaping the cultural, political, and social worlds of late antiquity. For example, historians of religion and culture, such as Judith Perkins and Kate Cooper, have drawn attention to the way in which narrative representation in early Christian literature functioned to construct Christian identities and to negotiate power relations both within the church and in society at large. It has become increasingly difficult for historians to ignore the power of rhetoric in shaping the imaginative (and, therefore, real) worlds of late ancient Christians.

Notes: Using the cellular-automaton-based simulation technique, we study the processes of self-organization in the systems of comblike copolymers with strongly attracting groups located at the ends of side chains. It is found that at a certain critical association energy, dependent both on polymer volume fraction and on the chemical composition of the copolymers, a micellar phase is nucleated. For the combs with large linear grafting density, a weak extension of the macromolecules is observed as attraction between end groups is increased. We find that the micelle formation observed in the sufficiently dense systems is mainly a result of intermolecular association. From the analysis of the static structure factors and snapshot pictures, it is concluded that the system is spatially inhomogeneous on the intermediate length scales related to the average intermicellar distances. Strong attraction stabilizes the aggregates (multiplets) that serve as junction points of a temporary network (micellar gel). We observe the formation of a specific space-filling weblike network in which strongly attracting side-chain ends group into multiplets which are wrapped by neutral polymer sections connecting these multiplets. © 2000 American Institute of Physics.

Notes: Abstract V(D)J recombination proceeds through a series of protein:DNA complexes mediated in part by the RAG1 and RAG2 proteins. These proteins are responsible for sequence-specific DNA recognition and DNA cleavage, and they appear to perform multiple postcleavage roles in the reaction as well. Here we review the interaction of the RAG proteins with DNA, the chemistry of the cleavage reaction, and the higher order complexes in which these events take place. We also discuss postcleavage functions of the RAG proteins, including recent evidence indicating that they initiate the process of coding end processing by nicking hairpin DNA termini. Finally, we discuss the evolutionary and functional implications of the finding that RAG1 and RAG2 constitute a transposase, and we consider RAG protein biochemistry in the context of several bacterial transposition systems. This suggests a model of the RAG protein active site in which two divalent metal ions serve alternating and opposite roles as activators of attacking hydroxyl groups and stabilizers of oxyanion leaving groups.

Notes: Previous studies demonstrated that the clock gene Per1 and the transcription factor ICER are expressed rhythmically in the suprachiasmatic nucleus (SCN) and in the pars tuberalis (PT). In the Syrian hamster the duration of photoperiod affects the amplitude of gene expression in the PT, and melatonin administered before lights-on suppressed the peak of Per1/ICER expression; these effects were not seen in the SCN. It was speculated that the inefficacy of melatonin was due to the low density of melatonin receptors in the SCN of this species. The aim of the present study was to determine whether this phenomenon also occurs in the Siberian hamster, which expresses a higher density of melatonin receptors in the SCN. Male Siberian hamsters were housed in long days (16 h light : 8 h dark) or short days (8 h light : 16 h dark) and expression of Per1 and ICER mRNA was studied by in situ hybridization. The expression of Per1 and ICER mRNA in the PT peaked 3 h following lights-on (ZT3) under both photoperiods. The amplitudes of these peaks were greatly attenuated under short photoperiod. In the SCN, the duration of Per1 gene expression was proportional to the length of the light phase, but only a modest amplitude effect was observed. Injections of melatonin (25 μg) 1 h before lights-on significantly reduced the expression of both genes in the PT at ZT3, but had no effect in the SCN. These data demonstrate that photoperiod-dependent amplitude modulation of Per1 and ICER gene expression in the PT is conserved across species, and reinforce the argument that this phenomenon is driven by melatonin.

Notes: NRAMPs (natural resistance-associated macrophage proteins) have been characterized in mammals as divalent transition metal transporters involved in iron metabolism and host resistance to certain pathogens. The mechanism of pathogen resistance is proposed to involve sequestration of Fe2+ and Mn2+, cofactors of both prokaryotic and eukaryotic catalases and superoxide dismutases, not only to protect the macrophage against its own generation of reactive oxygen species, but to deny the cations to the pathogen for synthesis of its protective enzymes. NRAMP homologues are also present in bacteria. We report the cloning and characterization of the single NRAMP genes in Escherichia coli and Salmonella enterica ssp. typhimurium, and the cloning of two distinct NRAMP genes from Pseudomonas aeruginosa and an internal fragment of an NRAMP gene in Burkholderia cepacia. The genes are designated mntH because the two enterobacterial NRAMPs encode H+-stimulated, highly selective manganese(II) transport systems, accounting for all Mn2+ uptake in each species under the conditions tested. For S. typhimurium MntH, the Km for 54Mn2+ (≈ 0.1 µM) was pH independent, but maximal uptake increased as pH decreased. Monovalent cations, osmotic strength, Mg2+ and Ca2+ did not inhibit 54Mn2+ uptake. Ni2+, Cu2+ and Zn2+ inhibited uptake with Kis greater than 100 µM, Co2+ with a Ki of 20 µM and Fe2+ with a Ki that decreased from 100 µM at pH 7.6 to 10 µM at pH 5.5. Fe3+ and Pb2+ inhibited weakly, exhibiting Kis of 50 µM, while Cd2+ was a potent inhibitor with a Ki of about 1 µM. E. coli MntH had a similar inhibition profile, except that Kis were three- to 10-fold higher. Both S. typhimurium and E. coli MntH also transport 55Fe2+ however, the Kms are equivalent to the Kis for Fe2+ inhibition of Mn2+ uptake, and are thus too high to be physiologically relevant. In both S. typhimurium and E. coli, mntH::lacZ constructs were strongly induced by hydrogen peroxide, weakly induced by EDTA and unresponsive to paraquat, consistent with the presence of Fur and OxyR binding sites in the promoters. Strains overexpressing mntH were more susceptible to growth inhibition by Mn2+ and Cd2+ than wild type, and strains lacking a functional mntH gene were more susceptible to killing by hydrogen peroxide. In S. typhimurium strain SL1344, mntH mutants showed no defect in invasion of or survival in cultured HeLa or RAW264.7 macrophage cells; however, expression of mntH::lacZ was induced severalfold by 3 h after invasion of the macrophages. S. typhimurium mntH mutants showed only a slight attenuation of virulence in BALB/c mice. Thus, the NRAMP Mn2+ transporter MntH and Mn2+ play a role in bacterial response to reactive oxygen species and possibly have a role in pathogenesis.