Leishmaniasis and AIDS co-infection: the Spanish example

There are an estimated 300 instances of Leishmania/HIV co-infection, of which 200 have occurred in Spain. Jorge Alvar here asks: is there an epidemiological or immunological basis for this high proportion?     

Reproduction of Pratylenchus penetrans on Potato and Crops Grown in Rotation with Potato

The relative suitability of potato and crops frequently grown in rotation with potato as hosts for Pratylenchus penetrans was evaluated. Suitability of rye, wheat, corn, oat, sorgho-sudangrass, and potato were compared in pot studies based on ratios of final population : initial population density and densities of nematodes in roots at harvest. Population densities increased more on potato, oat, and corn than on rye, wheat, and sorgho-sudangrass. There were no differences among the four rye cultivars or between the two oat cultivars in host suitability. Population increases were not related to root weight or consistently to nematode densities in roots. Although rye and wheat were equally suitable hosts in pot studies, P. penetrans increased more on wheat than on rye in a field study, indicating that reproduction was reduced or mortality was increased on rye under field conditions.     

Clinical and laboratory studies on theileriosis outbreaks in Sicily, Italy

A total of 153 blood samples were collected all over the Sicilian island in 15 farms. 29.4% and 25.5% were PCR positive for Theileria annulata and T. buffeli/orientalis respectively. 15.7% of cattle blood samples showed a mixed infection with both Theileria species. Each farm showed an infection rate ranging from 0% to 100%. Hyalomma marginatum and Boophilus annulatus were the most common ticks collected in April and November 1998 respectively. The aim of the present work was to investigate on haemoparasite species spread in Sicily. Ticks vectors involved in the transmission, distribution, risk areas and seasons, state of healthy carrier, are also discussed in this paper.     

Potato Cultivar, Pathogen Isolate and Antagonist Cultivation Medium Influence the Efficacy and Ranking of Bacterial Antagonists of Fusarium Dry Rot

The process of selecting biological control agents for further development frequently does not involve conducting bioassays of strain effectiveness on a range of pathogen isolates or host cultivars. Additionally, though previous studies have demonstrated that the medium used to produce biomass of an antagonist can alter its efficacy, this factor is also rarely considered when selecting for the most effective antagonist. Host cultivar, pathogen isolate, and the cultivation medium used to produce the antagonists' biomass were examined as factors of potential importance for assessing the relative effectiveness of bacterial biocontrol strains accurately. Five bacterial antagonists that control Fusarium dry rot on stored potato tubers were assayed for effectiveness against 10 isolates of Gibberella pulicaris . All antagonists reduced disease severity (35-81%) regardless of the specific assays conducted. However, when the antagonists' biomass were produced on two media that differed both in nutrient composition and phase, the efficacy ranking of antagonist Enterobacter sp. S11:P:08 varied from first to fourth most effective. For the antagonists studied, the phase of a nutritionally identical medium had little impact on the efficacy ranking of the five antagonists. Four of the five antagonists had efficacy rankings that ranged from first to last depending on the isolate of the pathogen used to conduct the bioassay. The cultivar of the host also caused variations in the efficacy ranking of the antagonists. These results indicate that bioassays should be conducted using a range of liquid culture production media, pathogen isolates, and host cultivars in order to choose an antagonist that has the highest likelihood for commercial development as an effective biological control product.     

Crystallization and characterization of the thallium form of the Oxytricha nova G-quadruplex

The crystal structure of the Tl⁺ form of the G-quadruplex formed from the Oxytricha nova telomere sequence, d(G₄T₄G₄), has been solved to 1.55 Å. This G-quadruplex contains five Tl⁺ ions, three of which are interspersed between adjacent G-quartet planes and one in each of the two thymine loops. The structure displays a high degree of similarity to the K⁺ crystal structure [Haider et al. (2002), J. Mol. Biol., 320, 189–200], including the number and location of the monovalent cation binding sites. The highly isomorphic nature of the two structures, which contain such a large number of monovalent binding sites (relative to nucleic acid content), verifies the ability of Tl⁺ to mimic K⁺ in nucleic acids. Information from this report confirms and extends the assignment of ²⁰⁵Tl resonances from a previous report [Gill et al. (2005), J. Am. Chem. Soc., 127, 16 723–16 732] where ²⁰⁵Tl NMR was used to study monovalent cation binding to this G-quadruplex. The assignment of these resonances provides evidence for the occurrence of conformational dynamics in the thymine loop region that is in slow exchange on the ²⁰⁵Tl timescale.     

Evidence for flexibility in the function of ribonuclease A

The dynamic properties of the enzyme ribonuclease A (RNase A) were investigated through the use of solution NMR spin relaxation experiments. As determined by "model-free" analysis, RNase A is conformationally rigid on time scales faster than overall rotational tumbling (picoseconds to nanoseconds). The average order parameter, S(2), for RNase A is 0.910 +/- 0.051. However, 28 of the amino acid residues in RNase A were identified as undergoing chemical exchange on the microsecond to millisecond time scale. For 16 of these residues the microscopic chemical exchange rates, k(ex), were quantitated through the use of the relaxation-compensated CPMG (rcCPMG) experiment. The value of k(ex) was identical for all residues with an average of 1640 s(-1) and is similar to the RNase A k(cat) value of 1900 s(-1). Many of these mobile residues localize to the active site in RNase A and include the catalytically crucial amino acids His119 and Asp121. Additional motion is found in the B1, B2, and P0 subsites, suggesting a coupling of motion between the binding and catalytic sites. The activation energy of the observed millisecond motion was measured by applying the rcCPMG experiment at temperatures of 283, 293, and 298 K and was determined to vary between 3.6 and 7.4 kcal/mol. The measured barrier to conformational motion is similar to the activation barrier for the RNase A catalyzed reaction and thus would not be thermodynamically limiting to catalysis. These studies suggest a correlation of conformational exchange kinetics and thermodynamics derived from NMR measurements with those determined by biochemical means and are suggestive of an important role for flexibility in enzyme function.     

Immune up-regulation and tumor apoptosis by androstene steroids

beta Androstenes steroid up-regulates immunity to increase resistance against lethal infection and lethal radiation, and mediates a rapid recovery of hematopoietic precursor cells after radiation injury. beta Androstenetriol increases the levels of the TH(1) cytokines, IL-2, IL-3, IFN gamma and counteracts hydrocortisone mediated immune suppression. In contrast, 17 alpha androstenediol inhibits proliferation and mediates apoptosis in tumor cells of murine and human origin. Its epimer 17beta androstenediol does not. The antiproliferative functions of 17 alpha androstenediol are not dependent on either the estrogen or androgen receptors.Our findings show that beta androstenes and analogs protect the host from lethal infection by DNA or RNA viruses such as, herpesvirus type 2, coxsackievirus B4, influenza, and arthropod borne viruses. These androstenes also protected the host from lethal bacterial infections by Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumonia and from parasites infections, i.e. Cryptosporidium parvum, and malaria. In vivo, the level of potency follows the order: dehydroepiandrosterone相似文献   

Horizontal transfer of the plant virulence gene, nec1, and flanking sequences among genetically distinct Streptomyces strains in the Diastatochromogenes cluster

Evidence for the horizontal transfer of a pathogenicity island (PAI) carrying the virulence gene nec1 and flanking sequences among Streptomyces strains in the Diastatochromogenes cluster is presented. Plant-pathogenic, thaxtomin-producing Streptomyces strains, previously classified as S. scabiei based on the conventionally used phenotypic characteristics, were found to be genetically distinct from the type strain of S. scabiei based on DNA relatedness and 16S rDNA sequence analysis. Pairwise DNA-DNA hybridizations between some of these strains and the S. scabiei type strain were as low as 36%, a value much below what is conventionally accepted for species identity (70%). The sequence of the nec1 gene, however, was identical in all the S. scabiei and S. scabiei-like strains tested, irrespective of their DNA relatedness to the type strain of S. scabiei, their geographic origin, or the isolation host. Furthermore, a 26-kb DNA fragment including and flanking nec1 was also conserved among these strains based on restriction and Southern analyses. These data indicate that the etiology of potato scab is more complex than previously recognized; this result has important implications for potato scab management strategies. Previous research has suggested that horizontal transfer of a PAI was the mechanism for evolution of pathogenicity in S. acidiscabies and S. turgidiscabies, species that lie outside of the Diastatochromogenes cluster. Data presented here support this model and indicate that PAI transfer also has occurred frequently in species closely related to S. scabiei.     

The effects of competition and the presence of an audience on weight lifting performance

The purpose of this investigation was to examine the effects of the presence of an audience and competition on maximal weight lifting performance. Thirty-two recreationally trained participants (15 men, 17 women; 21 +/- 2.5 years) performed a 1 repetition maximum (1 RM) bench press during 3 different situations (coaction, competitive coaction, and audience condition). Subjects also completed the Activation-Deactivation Adjective Checklist Short Form following the 3 trials to measure arousal state during each of the 3 trials. Significant differences (p < 0.05) were found between competitive coaction and coaction trials as well as between audience and coaction trials. Both men and women demonstrated the highest performance in front of an audience (105 +/- 48 kg) followed by competition (103 +/- 46 kg) and then the coaction trial (93 +/- 43 kg). No significant difference in arousal was measured between trials. The data suggest that performing a maximal lift in the presence of an audience or in competition facilitates performance and support the self-presentation and self-awareness theories. Social facilitation effects should be controlled in research settings and may aid the performance of weight lifting activities during events or competition.