Efficiency of cross presentation of vaccinia virus-derived antigens by human dendritic cells.

Dendritic cells (DC) utilize at least two pathways to process viral antigens onto MHC class I molecules. The conventional endogenous route is used to acquire antigens from both infectious and non-replicating virions. Exogenous pathways are used by DC to acquire and "cross-present" antigens derived from virus-infected donor cells that by themselves lack the ability to activate T cells directly. We analyzed the role of this pathway for antigens derived from vaccinia, a virus which inhibits DC maturation and causes extensive apoptosis of infected cells, yet is highly immunogenic. Using recombinant vaccinia virus encoding the influenza matrix protein as model vector, DC were shown to cross-present vaccinia-derived antigens from both apoptotic and necrotic infected cells to antigen-specific CD8(+) T cells. Efficient cross presentation required uptake of dead cells by immature DC and exposure to maturation stimuli, especially CD40 ligand. The responding CD8(+) T cells secreted IL-2 and IFN-gamma, proliferated and developed into cytotoxic effectors. Quantification of the cross presentation of vaccinia-derived antigens showed this pathway to be highly efficient, corresponding to a peptide pulse of 10-100 nM. While monocytes also phagocytosed apoptotic and necrotic cells, they were far less efficient at cross-presenting vaccinia-derived antigens to CD8(+) T cells. The ability of DC to cross-present vaccinia-derived antigens from infected apoptotic cells or necrotic cell lysates, bypasses the deleterious effects of direct infection of DC and provides one explanation for this pathogen's immunogenicity.     

Exposure and effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River, Rhode Island, USA

Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River northwest of Providence (RI, USA) in 2000 and 2001 were some of the highest ever reported in avian tissues. Mean concentrations in eggs ranged from 300 to >1,000 pg/g wet weight at the two most contaminated ponds, Allendale and Lyman. Mean egg concentrations at Greystone, the upstream reference pond, were 12 and 29 pg/g. Positive accumulation rates and concentrations in diet samples from 12-day-old nestlings indicated that the contamination was accumulated locally. Concentrations in diet of between 71 and 219 pg/g wet weight were more than 6 and 18 times higher than concentrations considered safe for birds (10-12 pg/g). Hatching success was negatively associated with concentration of TCDD in eggs. Only about half the eggs hatched at Allendale compared with >77% at Greystone. The national average for hatching success in successful nests is 85%. No other contaminants, such as polychlorinated biphenyls and mercury, were present in any sample at concentrations known to affect avian reproduction. Three bioindicators, half-peak coefficient of geometric variation, ethoxyresorufin-O-dealkylase activity, and brain asymmetry were assessed relative to TCDD contamination.     

.VO2 is attenuated above the lactate threshold in endurance-trained runners

PURPOSE: To determine whether a deviation from linearity occurs in the .VO2-speed relationship, above the lactate threshold (LT) in running; and whether the length of the submaximal exercise bouts alters the magnitude of any deviation. METHODS: Ten endurance-trained runners (N = 3 state level, N = 4 club level, and N = 3 recreational) (mean +/- SE; age 24.4 +/- 2.8 yr, mass 76.1 +/- 2.2 kg, .VO2 59.3 +/- 10.6 mL.kg-1.min-1) completed a .VO2, LT test and 10 x 4-min submaximal constant load exercise bouts. Data were evenly spread above and below LT, which was fitted by a dual linear regression model. RESULTS: There was a significant decrease (51.4%) in slope of the .VO2-speed relationship above LT. The use of 3-min, in comparison with 4-min, submaximal data did not alter the slope of the .VO2-speed regression above LT. There was no significant difference in the .VO2max estimated from the .VO2-speed regression above LT (58.1 +/- 3.3 mL.kg-1.min-1) but a significant difference below LT (63.6 +/- 3.9 mL.kg-1.min-1) to that obtained during the .VO2max test. CONCLUSION: Data from the current study suggest that the use of the linear regression of .VO2-speed data below the LT may potentially overestimate the prediction of .VO2 values above LT.     

Mitochondrial DNA analysis of hybridization between sympatric white-tailed deer and mule deer in west Texas.

Sympatric populations of white-tailed deer and mule deer (Odocoileus virginianus and Odocoileus hemionus, respectively) on a west Texas ranch share a common mitochondrial DNA restriction map genotype. Phylogenetic analysis indicates that this genotype is more characteristic of O. virginianus than of O. hemionus. The genotype of west Texas deer differs from that of O. virginianus from South Carolina by five mutational events (1.3% sequence divergence), whereas it differs from that of O. hemionus from California by 17 events (5.5% divergence). We suggest that interspecies hybridization has occurred, primarily between mule deer bucks and white-tailed deer does, with preferential absorption of hybrid offspring into the mule deer gene pool. Introgressive hybridization may be involved in ongoing displacement of mule deer by white-tailed deer in west Texas.     

Human leukemic cells loaded with α-galactosylceramide (α-GalCer) activate murine NKT cells in situ

Invariant NKT cells (NKT) cells become activated after stimulation with antigen-presenting cells (APCs) loaded with the NKT cell ligand, α-galactosylceramide (α-GalCer). In this study, we investigated whether human APCs loaded with α-GalCer have the ability to activate NKT cells in mice. We found that human dendritic cells (DCs) loaded with α-GalCer (hDC/Gal) and injected into C57BL/6 mice stimulated the secretion of IFN-γ by activated murine NKT cells. Furthermore, the number of transferred hDC/Gal correlated with the number of recovered IFN-γ-producing spleen cells, indicating that the capacity of APCs to load α-GalCer can be measured by IFN-γ release in an ELISPOT assay. Finally, α-GalCer-loaded human leukemic cell lines and primary leukemic cells injected into C57BL/6 mice also had the capacity to stimulate murine NKT cells in vivo. These results indicate that in vivo murine NKT cell responses can be used to quantitate the α-GalCer-loading capacity of human APCs. This method could be utilized to develop future immunotherapies in which NKT cells are targeted for activation.     

Potential effects of environmental contaminants on P450 aromatase activity and DNA damage in swallows from the Rio Grande and Somerville, Texas

Cliff swallows (Petrochelidon pyrrhonota) and cave swallows (P. fulva) were sampled during the breeding season at several locations in the Rio Grande, Texas, to evaluate the potential effects of environmental contaminants on P450 aromatase activity in brain and gonads and DNA damage in blood cells. The tritiated water-release aromatase assay was used to measure aromatase activity and flow cytometry was used to measure DNA damage in nucleated blood cells. There were no significant differences in brain and gonadal aromatase activities or in estimates of DNA damage (HPCV values) among cave swallow colonies from the Lower Rio Grande Valley (LRGV) and Somerville. However, both brain and gonadal aromatase activities were significantly higher (P < 0.05) in male cliff swallows from Laredo than in those from Somerville. Also, DNA damage estimates were significantly higher (P < 0.05) in cliff swallows (males and females combined) from Laredo than in those from Somerville. Contaminants of current high use in the LRGV, such as atrazine, and some of the highly persistent organochlorines, such as toxaphene and DDE, could be potentially associated with modulation of aromatase activity in avian tissues. Previous studies have indicated possible DNA damage in cliff swallows. We did not observe any differences in aromatase activity or DNA damage in cave swallows that could be associated with contaminant exposure. Also, the differences in aromatase activity and DNA damage between male cliff swallows from Laredo and Somerville could not be explained by contaminants measured at each site in previous studies. Our study provides baseline information on brain and gonadal aromatase activity in swallows that could be useful in future studies.     

Re-assessing accumulated oxygen deficit in middle-distance runners

The purpose of this study was to re-assess the accumulated oxygen deficit (AOD), incorporating recent methodological improvements i.e., 4 min submaximal tests spread above and below the lactate threshold (LT). We Investigated the Influence of the VO2 -speed regression, on the precision of the estimated total energy demand and AOD. utilising different numbers of regression points and including measurement errors. Seven trained middle-distance runners (mean +/- SD age: 25.3 +/- 5.4y, mass: 73.7 +/- 4.3kg. VO2max 64.4 +/- 6.1 mL x kg(-1) x min(-1)) completed a VO2max, LT, 10 x 4 min exercise tests (above and below LT) and high-intensity exhaustive tests. The VO2 -speed regression was developed using 10 submaximal points and a forced y-intercept value. The average precision (measured as the width of 95% confidence Interval) for the estimated total energy demand using this regression was 7.8mL O2 Eq x kg(-1) x min(-1). There was a two-fold decrease in precision of estimated total energy demand with the Inclusion of measurement errors from the metabolic system. The mean AOD value was 43.3 mL O2 Eq x kg(-1) (upper and lower 95% CI 32.1 and 54.5mL o2 Eq x kg(-1) respectively). Converting the 95% CI for estimated total energy demand to AOD or including maximum possible measurement errors amplified the error associated with the estimated total energy demand. No significant difference in AOD variables were found, using 10,4 or 2 regression points with a forced y-intercept. For practical purposes we recommend the use of 4 submaximal values with a y-intercept. Using 95% CIs and calculating error highlighted possible error in estimating AOD. Without accurate data collection, increased variability could decrease the accuracy of the AOD as shown by a 95% CI of the AOD.