Nucleotide analogue inhibitors of purine nucleoside phosphorylase

The diphosphate of the antiherpetic agent acyclovir [9-[(2-hydroxyethoxy)methyl]guanine] has been shown to inhibit purine nucleoside phosphorylase with unique potency (Tuttle, J. V., and Krenitsky, T. A. (1984) J. Biol. Chem. 259, 4065-4069). A major factor contributing to the superior inhibition by this diphosphate over the corresponding mono- and triphosphates is revealed here. Homologues of acyclovir mono- and diphosphate that extend the ethoxy moiety by one to four methylene groups were synthesized. These homologues were evaluated for their ability to inhibit human purine nucleoside phosphorylase. Within the diphosphate series, the Ki values increased progressively with increasing chain length. With the monophosphates, the Ki values reached a minimum with the homologue containing a pentoxy moiety. A plot of chain length versus Ki values for both mono- and diphosphates showed that both series had similar optimal distances between the aminal carbon and the terminal oxygen anion. Monophosphates with optimal positioning were somewhat less potent than diphosphates with similar positioning. Nevertheless, it was clear that a major factor in determining potency of inhibition was the distance of the terminal phosphate from the guanine moiety.     

Are vocal characteristics related to leadership patterns in mixed‐species bird flocks?

What structures the organization of mixed‐species bird flocks, so that some ‘nuclear’ species lead the flocks, and others follow? Previous research has shown that species actively listen to each other, and that leaders are gregarious; such gregarious species tend to make contact calls and hence may be vocally conspicuous. Here we investigated whether vocal characteristics are associated with leadership, using a global dataset of mixed‐species flock studies and recordings from sound archives. We first asked whether leaders are different from following or occasional species in flocks in the proportion of the recordings that contain calls (n = 58 flock studies, 145 species), and especially alarm calls (n = 111 species). We found that leaders tended to have a higher proportion of their vocalizations that were classified as calls than occasional species, and both leaders and following species had a significantly higher proportion of their calls rated as alarms compared to occasional species. Next, we investigated the acoustic characteristics of flock participants’ calls, hypothesizing that leaders would make more calls, and have less silence on the recordings. We also hypothesized that leaders’ calls would be simple acoustically, as contact calls tend to be, and thus similar to each other, as well as being detectable, in being low frequency and with high frequence bandwidth. The analysis (n = 45 species, 169 recordings) found that only one of these predictions was supported: leading species were less often silent than following or occasional species. Unexpectedly, leaders’ calls were less similar to each other than occasional species. The greater amount of information available and the greater variety of that information support the hypothesis that leadership in flocks is related to vocal communication. We highlight the use of sound archives to ask questions about behavioral and community ecology, while acknowledging some limitations of such studies.     

Identification of candidate biomarkers of brain damage in a mouse model of closed head injury: a metabolomic pilot study

We aim to identify candidate brain biomarkers for, and to elucidate the pathophysiology of closed traumatic brain injury (TBI). Nuclear magnetic resonance (NMR) based metabolomic analysis was performed on the whole brain of mice undergoing TBI using a validated technique. There were 10 TBI mice compared to 8 sham operated controls. A total of 45 metabolites were evaluated. There was a statistically significant alteration in concentrations of 29 metabolites in TBI brains as compared to controls (FDR <0.05). Profound disturbances of several metabolic pathways (FDR <1E-07), including pathways associated with purine, alanine, aspartate and glutamine and glutathione metabolism were observed. Also, a significant elevation in glutamate (the main excitatory neurotransmitter) and depression of GABA (the main inhibitory neurotransmitter) was observed. Four metabolites, ADP, AMP, NAD+, and IMP were the most important indicators of TBI, relative to normal controls. All were elevated in the TBI mice. A combination of these 4 biomarkers produced a perfect predictor of TBI status, AUC (95 % CI) = 1.0 (1.0, 1.0). We also detected significant disturbances in mitochondrial function, energy metabolism, neurotransmitter metabolism and other important biochemical pathways in TBI mouse brains. Further studies to assess the utility of metabolomics to detect and classify the severity of and assess the prognosis of TBI is warranted.     

Purification and characterization of the gene 1.2 protein of bacteriophage T7

Gene 1.2 of bacteriophage T7, located near the primary origin of DNA replication at position 15.37 on the T7 chromosome, encodes a 10,059-dalton protein that is essential for growth on Escherichia coli optA1 strains (Saito, H., and Richardson, C. C. (1981) J. Virol. 37, 343-351). In the absence of the T7 1.2 and E. coli optA gene products, the degradation of E. coli DNA proceeds normally, and T7 DNA synthesis is initiated at the primary origin. However, T7 DNA synthesis ceases prematurely and the newly synthesized DNA is degraded; no viable phage particles are released. The gene 1.2 protein has been purified to apparent homogeneity from cells in which the cloned 1.2 gene is overexpressed. Purification of the [35S] methionine-labeled protein was followed by monitoring the radioactivity of the protein and by gel electrophoresis. The purified protein has been identified as the product of gene 1.2 on the basis of molecular weight and partial amino acid sequence. We have found that extracts of E. coli optA1 cells infected with T7 gene 1.2 mutants are defective in packaging exogenous T7 DNA when such extracts are prepared late in infection. Purified gene 1.2 protein restores packaging activity to these defective extracts, thus providing a biological assay for gene 1.2 protein. No specific enzymatic activity has been found associated with the purified gene 1.2 protein.     

Chemical communication in Cavia: Responses of wild (C. aperea), domestic (C. porcellus) and F1 males to urine

Urine preferences of wild (Cavia aperea), domestic (C. porcellus), and F₁ adult male guinea pigs were investigated. Males of all three types preferred female urine to male urine regardless of donor type. When given a choice between female urine of each type, males preferred conspecific urine. In choices between male urine of the three types, a conspecific preference was evident for wild and domestic but not f₁ subjects. These data indicate that a loss of distinctive male and female odours has not occurred as a result of domestication. However, the urine odours of wild and domestic types have diverged. The possible effects of previous individual experience on the preferential response is discussed.     

CD8 marks a subpopulation of lung-derived dendritic cells with differential responsiveness to viral infection and toll-like receptor stimulation

An increasing number of studies suggest that individual subsets of dendritic cells (DC) exhibit distinct capabilities with regard to the generation of the adaptive immune response. In this study, we evaluated the properties of a relatively unexplored DC subset present in the lung-draining mediastinal lymph node. This subset expresses the airway dendritic cell marker CD103 together with CD8. These DC were of interest given that our previous studies using a model of respiratory infection with vaccinia virus revealed a distinct difference in the ability of CD103(+) DC to prime T cells that correlated inversely with the expression of CD8, suggesting a differential role of these DC in the context of respiratory virus infection. To expand our understanding of the role of this DC population, we performed analyses to elucidate the phenotype, migratory capacity, responsiveness to innate stimuli, and priming capacity of CD8(+) CD103(+) DC. We found that expression of surface markers on these DC was similar to that of CD8(-) CD103(+) DC, supporting their close relationship. Further, the two DC types were similar with regard to antigen uptake. However, although both CD103(+) subsets originated from the lung, CD8-bearing CD103(+) DC appeared in the lymph node with delayed kinetics following virus infection. While this subset exhibited increased responsiveness to a number of Toll-like receptor (TLR) agonists, their response to infection was virus specific, demonstrating poor responsiveness to vaccinia virus infection but robust maturation following infection with parainfluenza virus 5 or influenza virus. These findings show that CD8 marks a population of lung airway-derived DC with distinct migratory and maturation responses that likely contribute differentially to the immune response depending on the infecting pathogen.