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Although Neisseria gonorrhoeae is a prolific source of eight c-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes [c.sub.2], [c.sub.4], and [c.sub.5], encoded by the genes cccA, cycA, and cycB, respectively, have been investigated. Single mutations in genes for either cytochrome [c.sub.4] or [c.sub.5] resulted in an increased sensitivity to growth inhibition by excess oxygen and small decreases in the respiratory capacity of the parent, which were complemented by the chromosomal integration of an ectopic, isopropyl-[beta]-D-thiogalactopyranoside (IPTG)-inducible copy of the cycA or cycB gene. In contrast, a cccA mutant reduced oxygen slightly more rapidly than the parent, suggesting that cccA is expressed but cytochrome [c.sub.2] is not involved in electron transfer to cytochrome oxidase. The deletion of cccA increased the sensitivity of the cycB mutant to excess oxygen but decreased the sensitivity of the cycA mutant. Despite many attempts, a double mutant defective in both cytochromes [c.sub.4] and [c.sub.5] could not be isolated. However, a strain with the ectopically encoded, IPTG-inducible cycB gene with deletions in both cycA and cycB was constructed: the growth and survival of this strain were dependent upon the addition of IPTG, so gonococcal survival is dependent upon the synthesis of either cytochrome [c.sub.4] or [c.sub.5]. These results define the gonococcal electron transfer chain to oxygen in which cytochromes [c.sub.4] and [c.sub.5], but not cytochrome [c.sub.2], provide alternative pathways for electron transfer from the cytochrome [bc.sub.1] complex to the terminal oxidase cytochrome [cbb.sub.3]. doi: 10.1128/JB.00002-10

Neurological dysfunction caused by traumatic brain injury results in profound changes in net synaptic efficacy, leading to impaired cognition. Because excitability is directly controlled by the balance of excitatory and inhibitory activity, underlying mechanisms causing these changes were investigated using lateral fluid percussion brain injury in mice. Although injury-induced shifts in net synaptic efficacy were not accompanied by changes in hippocampal glutamate and GABA levels, significant reductions were seen in the concentration of branched chain amino acids (BCAAs), which are key precursors to de novo glutamate synthesis. Dietary consumption of BCAAs restored hippocampal BCAA concentrations to normal, reversed injury-induced shifts in net synaptic efficacy, and led to reinstatement of cognitive performance after concussive brain injury. All brain-injured mice that consumed BCAAs demonstrated cognitive improvement with a simultaneous restoration in net synaptic efficacy. Posttraumatic changes in the expression of cytosolic branched chain aminotransferase, branched chain ketoacid dehydrogenase, glutamate dehydrogenase, and glutamic acid decarboxylase support a perturbation of BCAA and neurotransmitter metabolism. Ex vivo application of BCAAs to hippocampal slices from injured animals restored posttraumatic regional shifts in net synaptic efficacy as measured by field excitatory postsynaptic potentials. These results suggest that dietary BCAA intervention could promote cognitive improvement by restoring hippocampal function after a traumatic brain injury. branched chain amino acids | cognitive impairment | hippocampus | tramautic brain injury www.pnas.org/cgi/doi/10.1073/pnas.0910280107

The Escherichia coli K-12 nir operon promoter can be fully activated by binding of the regulator of fumarate and nitrate reduction (FNR) to a site centered at position--41.5 upstream of the transcript start, and this activation is modulated by upstream binding of the integration host factor (IHF) and Fis (factor for inversion stimulation) proteins. Thus, transcription initiation is repressed by the binding of IHF and Fis to sites centered at position--88 (IHF I) and position--142 (Fis I) and activated by IHF binding to a site at position--115 (IHF II). Here, we have exploited mutational analysis and biochemistry to investigate the actions of IHF and Fis at these sites. We show that the effects of IHF and Fis are position dependent and that IHF II functions independently of IHF I and Fis I. Using in vitro assays, we report that IHF and Fis repress transcription initiation by interfering with RNA polymerase binding. Differences in the upstream IHF and Fis binding sites at the nir promoter in related enteric bacteria fix the level of nir operon expression under anaerobic growth conditions.

Expression of two genes of unknown function, Staphylococcus aureus scdA and Neisseria gonorrhoeae dnrN, is induced by exposure to oxidative or nitrosative stress. We show that DnrN and ScdA are di-iron proteins that protect their hosts from damage caused by exposure to nitric oxide and to hydrogen peroxide. Loss of FNR-dependent activation of aniA expression and NsrR-dependent repression of norB and dnrN expression on exposure to NO was restored in the gonococcal parent strain but not in a dnrN mutant, suggesting that DnrN is necessary for the repair of NO damage to the gonococcal transcription factors, FNR and NsrR. Restoration of aconitase activity destroyed by exposure of S. aureus to NO or [H.sub.2][O.sub.2] required a functional scdA gene. Electron paramagnetic resonance spectra of recombinant ScdA purified from Escherichia coli confirmed the presence of a di-iron center. The recombinant scdA plasmid, but not recombinant plasmids encoding the complete Escherichia coli sufABCDSE or iscRSUAhscBAfdx operons, complemented repair defects of an E. coli ytfE mutant. Analysis of the protein sequence database revealed the importance of the two proteins based on the widespread distribution of highly conserved homologues in both gram-positive and gram-negative bacteria that are human pathogens. We provide in vivo and in vitro evidence that Fe-S clusters damaged by exposure to NO and [H.sub.2][O.sub.2] can be repaired by this new protein family, for which we propose the name repair of iron centers, or RIC, proteins.

Many remote-sensing applications produce large sets of images, such as hyperspectral images or time-indexed image sequences. We explore methods to display such image sets by linearly projecting them onto basis functions designed for the red, green, and blue (RGB) primaries of a standard tristimulus display, for the human visual system, and for the signal-to-noise ratio of the dataset, creating a single color image. Projecting the data onto three basis functions reduces the information but allows each datapoint to be rendered by a single color. Principal components analysis is perhaps the most commonly used linear projection method, lint it is data adaptive and, thus, yields inconsistent visualizations that may be difficult to interpret. Instead, we focus on designing fixed basis functions based on optimizing criteria in the perceptual colorspace CIELab and the standardized device colorspace sRGB. This approach yields visualizations with rich meaning that users can readily extract. Example visualizations are shown for passive radar video and Airborne Visible/Infrared Imaging Spectrometer hyperspectral imagery. Additionally, we show hove' probabilistic classification information can be layered on top of the visualization to create a customized nonlinear representation of an image set. Index Terms--Airborne Visible/Infrared hnaging Spectrometer (AVIRIS), CIELab, image fusion, passive radar, sRGB, visualization.

The periplasmic nitrate reductase of Escherichia coli is important during anaerobic growth in low-nitrate environments. The nap operon encoding this nitrate reductase comprises seven genes including a gene, napF, that encodes a putative cytoplasmic iron-sulphur protein of uncertain subcellular location and function. In this study, N-terminal sequence analysis, cell fractionation coupled with immunoblotting and construction of LacZ and PhoA fusion proteins were used together to establish that NapF is located in the E. coli cytoplasm. A bacterial two-hybrid protein-protein interaction system was used to demonstrate that NapF interacted in the cytoplasm with the terminal oxidoreductase NapA, but that it did not self-associate or interact with other electron-transport components of the Nap system, NapC, NapG or NapH, or with another cytoplasmic component, NapD. NapF, purified as a Hiss-tagged protein, exhibited spectral properties characteristic of an iron-sulphur protein. This protein was able to pull down NapA from soluble extracts of E. coli A growth-based assay for NapF function in intact cell cultures was developed and applied to assess the effect of mutation of a number of conserved amino acids. It emerged that neither a highly conserved N-terminal double-arginine motif, nor a conserved proline motif, is essential for NapF-dependent growth. The combined data indicate that NapF plays one or more currently unidentified roles in the post-translational modification of NapA prior to the export of folded NapA via the twin-arginine translocation pathway into the periplasm.

The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position -41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position -54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position -74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position -127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position -74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

Escherichia coli K-12 strains expressing either NarU or NarK as the only nitrate transport protein are both able to support nitrate-dependent anaerobic growth. The narK gene is highly expressed during anaerobic growth in the presence of nitrate, consistent with a role for NarK in nitrate transport coupled to nitrate reduction by the most active nitrate reductase encoded by the adjacent narGHJI operon. The physiological role of NarU is unknown. Reverse transcriptase PCR experiments established that, unlike the monocistronic narK gene, narU is co-transcribed with narZ as the first gene of a five-gene narUZYWV operon. The narK and narU genes were fused in-frame to a myc tag: the encoded fusion proteins complemented the nitrate-dependent growth defect of chromosomal narK and narU mutations. A commercial anti-Myc antibody was used to detect NarK and NarU in membrane fractions. During anaerobic growth in the presence of nitrate, the quantity of NarU-Myc accumulated during exponential growth was far less than that of NarK-Myc, but NarU was more abundant than NarK in stationary-phase cultures in the absence of nitrate. Although the concentration of NarU-Myc increased considerably during the post-exponential phase of growth, NarK-Myc was still more abundant than NarU-Myc in stationary-phase bacteria in the presence of nitrate. In chemostat competition experiments, a strain expressing only narU had a selective advantage relative to a strain expressing only narK during nutrient starvation or very slow growth, but Nar[K.sup.+] bacteria had a much greater selective advantage during rapid growth. The data suggest that NarU confers a selective advantage during severe nutrient starvation or slow growth, conditions similar to those encountered in vivo.

The genome of Mycobacterium tuberculosis H37Rv includes a homologue of the CRP/FNR (cAMP receptor protein/fumarate and nitrate reduction regulator) family of transcription regulators encoded by Rv3676. Sequencing of the orthologous gene from attenuated Mycobacterium bovis Bacille Calmette-Guerin (BOG) strains revealed point mutations that affect the putative DNA-binding and cNMP-binding domains of the encoded protein. These mutations are not present in the published sequences of the Rv3676 orthologues in M. bovis, M. tuberculosis or Mycobacterium leprae. An Escherichia coli lacZ reporter system was used to show that the M. tuberculosis Rv3676 protein binds to DNA sites for CRP, but this DNA binding was decreased or abolished with the Rv3676 protein counterparts from BOG strains. The DNA-binding ability of the M. tuberculosis Rv3676 protein was decreased by the introduction of base changes corresponding to the BCG point mutations. Conversely, the DNA binding of the BCG Rv3676 proteins from BCG strains was restored by removing the mutations. These data show that in this reporter system the point mutations present in the Rv3676 orthologue in BOG strains render its function defective (early strains) or abolished (late strains) and suggest that this protein might be naturally defective in M. bovis BCG strains. This raises the possibility that a contributing factor to the attenuation of BOG strains may be an inability of this global regulator to control the expression of genes required for in vivo survival and persistence.

The Neisseria gonorrhoeae genome encodes a homologue of the Escherichia coli FNR protein (the fumarate and nitrate reductase regulator). Despite its similarity to E. coli FNR, the gonococcal FNR only partially complemented an E. coli fnr mutation. After error-prone PCR mutagenesis of the gonococcal fnr gene, we identified four mutant fnr derivatives carrying the same S18F substitution, and we showed that the mutant FNR could activate transcription from a range of class I and class II FNR-dependent promoters in E. coli. Prompted by the similarities between gonococcal and E. coil FNR, we made changes in gonococcal fnr that created substitutions that are equivalent to previously characterized substitutions in E. coli FNR. First, our experiments showed that cysteine, C116, in the gonococcal FNR, equivalent to C122 in E. coli FNR, is essential, presumably because, as in E. coli FNR, it binds to an iron-sulfur center. Second, the L22H and D148A substitutions in gonococcal FNR were made. These changes are equivalent to the L28H and D154A changes in E. coli FNR, which had been shown to increase FNR activity in the presence of oxygen. We show that the effects of these substitutions in gonococcal FNR are distinct from those of the S18F substitution. Similarly, substitutions in the putative activating regions of gonococcal FNR were made. We show that the activity of gonococcal FNR in E. coli can be increased by transplanting certain activating regions from E. coli FNR. The effects of these substitutions are additive to those due to S18F. From these data, we conclude that the effects of the S18F substitution in gonococcal FNR are distinct from the effects of the other substitutions. S18 is immediately adjacent to one of three N-terminal cysteine residues that coordinate the iron-sulfur center, and thus the S18F substitution is most likely to stabilize this center. Support for this came from complementary experiments in which we created the S24F substitution in E. coli FNR, which is equivalent to the S18F substitution in gonococcal FNR. Our results show that the S24F substitution changes the activity of E. coli FNR and that the changes are distinct from those due to previously characterized substitutions.

We have previously shown that prostanoids inhibit electroneutral sodium absorption in Cryptosporidium parvum-infected porcine ileum, whereas glutamine stimulates electroneutral sodium absorption. We postulated that glutamine would stimulate sodium absorption via a cyclooxygenase (COX)-dependent pathway. We tested this hypothesis in C. parvum-infected calves, which are the natural hosts of cryptosporidiosis. Tissues from healthy and infected calves were studied in Ussing chambers and analyzed via immunohistochemistry and Western blots. Treatment of infected tissue with selective COX inhibitors revealed that COX-1 and -2 must be blocked to restore electroneutral sodium absorption, although the transporter involved did not'appear to be the expected [Na.sup.+]/[H.sup.+] exchanger 3 isoform. Glutamine addition also stimulated sodium absorption in calf tissue, but although this transport was electroneutral in healthy tissue, sodium absorption was electrogenic in infected tissue and was additive to sodium transport uncovered by COX inhibition. Blockade of both COX isoforms is necessary to release the prostaglandin-mediated inhibition of electroneutral sodium uptake in C. parvum-infected calf ileal tissue, whereas glutamine increases sodium uptake by an electrogenic mechanism in this same tissue. Cryptosporidium parvum; Na/H exchanger 3; cyclooxygenase-2; diarrhea

The crystal structure of the periplasmic penta-heme cytochrome c nitrite reductase of Escherichia coli shows that four hemes of the enzyme exhibit bis-histidine axial heme-iron ligation with the catalytic heme-iron showing a distal lysine ligand and a proximal oxygen ligand. The spectroscopic signals and redox potentials of individual hemes are discussed.

Hosts for Strophitus undulatus (Bivalvia: Unionidae) were identified through laboratory infestations. Strophitus undulatus had a low degree of host specificity, transforming on 15 of 22 species examined, including three non-native species and one anadromous species. Suitable hosts included five cyprinid species, two salmonids, two centrarchids, two percids and Acipenser oxyrhynchus (Atlantic sturgeon), Ameiurus natalis (yellow bullhead), Cottus cognatus (slimy sculpin) and Notophthalmus viridescens viridescens (red-spotted newt). Ten hosts were previously unknown. No metamorphosis was observed in a control treatment without a potential host. Recovery of juveniles occurred 12-41 d after infestation at 13-18 C. Duration of glocidial attachment to the hosts declined with increasing water temperature.

The relationship between liquid equivalent snowfall rate and visibility is investigated using data collected at the National Center for Atmospheric Research Marshall Snowfall Test Site during two winter field seasons and using theoretical relationships. The observational data include simultaneous liquid equivalent snowfall rate, crystal types, and both automated and manual visibility measurements. Theoretical relationships between liquid equivalent snowfall rate and visibility are derived for 27 crystal types, and for 'dry' and 'wet' aggregated snowflakes. Both the observations and theory show that the relationship between liquid equivalent snowfall rate and visibility depends on the crystal type, the degree of riming, the degree of aggregation, and the degree of wetness of the crystals, leading to a large variation in the relationship between visibility and snowfall rate. Typical variations in visibility for a given liquid equivalent snowfall rate ranged from a factor of 3 to a factor of 10, depending on the storm. This relationship is shown to have a wide degree of scatter from storm to storm and also during a given storm. The main cause for this scatter is the large variation in cross-sectional area to mass ratio and terminal velocity for natural snow particles. It also is shown that the visibility at night can be over a factor of 2 greater than the visibility during the day for the same atmospheric extinction coefficient. Since snowfall intensity is defined by the U.S. National Weather Service using visibility, this day/night difference in visibility results in a change in snowfall intensity category caused by only whether it is day or night. For instance, a moderate snowfall intensity during the day will change to a light snowfall intensity at night, and a heavy snowfall intensity during the day will change to a moderate snowfall intensity at night, for the same atmospheric extinction coefficient. Thus, the standard relationship between snowfall intensity and visibility used by many national weather services (1/4 mile or less visibility corresponds to heavy snowfall intensity, between 5/16 and 5/8 mile corresponds to moderate intensity, and greater than 5/8 mile corresponds to light intensity) does not always provide the correct indication of actual liquid equivalent snowfall rate because of the variations in snow type and the differences in the nature of visibility targets during day and night. This false indication may have been a factor in previous ground-deicing accidents in which light snow intensity was reported based on visibility, when in fact the actual measured liquid equivalent snowfall rate was moderate to heavy.

MISSION CULTURE ON THE UPPER AMAZON: NATIVE TRADITION, JESUIT ENTERPRISE, AND SECULAR POLICY IN MOXOS, 1660-1880. By David Block. (Lincoln: University of Nebraska Press, 1994. Pp. 240. $30.00 cloth.) HACIENDAS [...]

Twenty years ago, Lewis Hanke and Benjamin Keen exchanged notes in the Hispanic American Historical Review concerning the value of controversy surrounding the "White Legend" versus the "Black Legend" in [...]

Twenty years ago, Lewis Hanke and Benjamin Keen exchanged notes in the Hispanic American Historical Review concerning the value of controversy surrounding the "White Legend" versus the "Black Legend" in [...]

Twenty years ago, Lewis Hanke and Benjamin Keen exchanged notes in the Hispanic American Historical Review concerning the value of controversy surrounding the "White Legend" versus the "Black Legend" in [...]

Cystic fibrosis (CF) is the most common fatal genetic disorder among white populations. The advent of molecular biology has permitted the identification of the gene that is abnormal in patients with CF; the CF gene is called the cystic fibrosis transmembrane regulator or CFTR. Prior to the identification of this gene, the diagnosis of CF could only be based on effects of the genetic mutation, rather than on the mutant gene itself. The traditional diagnostic indicator of CF in patients with suspicious symptoms was the presence of excess chloride in the sweat after stimulation with pilocarpine; the sweat test has been in use since 1959. However, it had become clear that not all patients with CF had abnormal ions in the sweat. Indeed, the symptoms of CF, including viscous mucus, which contributes to respiratory problems, and inadequate secretion of digestive enzymes by the pancreas, have proved to be markedly varied among CF patients. Now that gene cloning techniques have become available, it is possible to determine if at least some of these differences in the observed trait, called the phenotype, may be a direct result of different mutations in the CF gene, the genotype. A genetic study was performed on two sisters with mild cystic fibrosis and normal results on the sweat test. One subject was 50 years old; her sister died at 48 years. Genetic analysis revealed a mutation in the CF gene that is different from previously described mutations. Curiously, this mutation occurred in a spot that would change a particular amino acid in a fold of the resulting protein; this same protein fold has been found to be affected by different mutations in other CF patients. The present patients were found to be homozygous, which means that the CFTR genes on both chromosomes were the same. This occurrence considerably aided the genetic analysis, and reflected the way these cases came to light. The symptoms of cystic fibrosis in the sisters were so mild that cystic fibrosis would not likely have been considered as a possible diagnosis. However, the fact that the parents of these women were second cousins hinted that a genetic disorder might be present. (Consumer Summary produced by Reliance Medical Information, Inc.)

Jacqueline Andall (ed.), Gender and Ethnicity in Contemporary Europe London and New York: Berg, 2003, 288 pp. 50.00 [pounds sterling] h.b. (ISBN 1-85973-647-5) 16.99 [pounds sterling] p.b. (ISBN 1-85973-652-1) A [...]

The glutamine at position 263 in Escherichia coli NrfA was mutated to understand the roles of the active site calcium ion and coordinating glutamine residue in nitrite reduction to ammonia by cytochrome c nitrite reductase. The findings provided insight into important function of unusual Q263-calcium ion pair to increase substrate affinity through its role in stabilization of a network of hydrogen bonded water molecules in the active site heme distal ligand.

Nancy Woloch. Muller v. Oregon: A Brief History with Documents. Boston & New York: Bedford Books of St. Martin's Press, 1996. Pp. xiii, 206. Paper, $13.50; ISBN 0-312-08586-9. Nancy Woloch's [...]

David Ludvigsson, ed. Enhancing Student Learning in History: Perspectives on University History Teaching. Uppsala, Sweden: Swedish Science Press, 2012. Pp. 139. ISBN 978-91-506-2294-2. This slim volume of essays is derived [...]

Helmut Walser Smith, ed. The Holocaust and Other Genocides: History, Representation, Ethics. Nashville: Vanderbilt University Press, 2002. Pp. xxii; 262. Paper, $27.95; ISBN 0-8265-1403-0. There is no shortage of Holocaust-related [...]

T.G. Fraser and Donette Murray. America and the World since 1945. Studies in Contemporary History Series. New York: Palgrave Macmillan, 2002. Pp. xxvi, 323. Paper, $12.95; ISBN 0-333-75432-8. Historians Fraser [...]

Grace Chang, Disposable Domestics: Immigrant Women Workers in the Global Economy Cambridge, MA: South End Press, 2000, $18.00 p.b. (ISBN 0-89608-617-8) From Los Angeles to New York, American professionals have [...]

London and New York: Zed Books, 2000, 213 pp., $65.00/45.00 [pounds sterling] h.b. (ISBN 1-85649-760-7); $25.00/14.95 [pounds sterling] p.b. (ISBN 1-85649-761-5) In cities across Europe today, foreign women push prams, [...]

Identification of the Cystic Fibrosis Gene: Chromosome Walking and Jumping An understanding of the basic defect in the inherited disoder cystic fibrosis requires cloning of the cystic fibrosis gene and [...]