Animal movement drives variation in seed dispersal distance in a plant-animal network

Frugivores play differing roles in shaping dispersal patterns yet seed dispersal distance is rarely quantified across entire communities. We model seed dispersal distance using gut passage times and bird movement for the majority (39 interactions) of known bird-tree interactions on the island of Saipan to highlight differences in seed dispersal distances provided by the five avian frugivores. One bird species was found to be a seed predator rather than a disperser. The remaining four avian species dispersed seeds but differences in seed dispersal distance were largely driven by interspecific variation in bird movement rather than intraspecific variation in gut passage times. The median dispersal distance was at least 56 m for all species-specific combinations, indicating all species play a role in reducing high seed mortality under the parent tree. However, one species-the Micronesian Starling-performed 94% of dispersal events greater than 500 m, suggesting this species could be a key driver of long-distance dispersal services (e.g. linking populations, colonizing new areas). Assessing variation in dispersal patterns across this network highlights key sources of variation in seed dispersal distances and suggests which empirical approaches are sufficient for modelling how seed dispersal mutualisms affect populations and communities.

Pharmacological differences between the human and rat vanilloid receptor 1 (VR1)

Vanilloid receptors (VR1) were cloned from human and rat dorsal root ganglion libraries and expressed in Xenopus oocytes or Chinese Hamster Ovary (CHO) cells. Both rat and human VR1 formed ligand gated channels that were activated by capsaicin with similar EC(50) values. Capsaicin had a lower potency on both channels, when measured electrophysiologically in oocytes compared to CHO cells (oocytes: rat=1.90+/-0.20 microM; human=1.90+/-0.30 microM: CHO cells: rat=0.20+/-0.06 microM; human=0.19+/-0.08 microM). In CHO cell lines co-expressing either rat or human VR1 and the calcium sensitive, luminescent protein, aequorin, the EC(50) values for capsaicin-induced responses were similar in both cell lines (rat=0.35+/-0.06 microM, human=0.53+/-0.03 microM). The threshold for activation by acidic solutions was lower for human VR1 channels than that for rat VR1 (EC(50) pH 5.49+/-0.04 and pH 5.78+/-0.09, respectively). The threshold for heat activation was identical (42 degrees C) for rat and human VR1. PPAHV was an agonist at rat VR1 (EC(50) between 3 and 10 microM) but was virtually inactive at the human VR1 (EC(50)>10 microM). Capsazepine and ruthenium red were both more potent at blocking the capsaicin response of human VR1 than rat VR1. Capsazepine blocked the human but not the rat VR1 response to low pH. Capsazepine was also more effective at inhibiting the noxious heat response of human than of rat VR1.

Evidence for the emergence of a type-1-like immune response in intestinal mucosa of calves recovering from cryptosporidiosis

This study was undertaken to characterize the mucosal response to Cryptosporidium parvum in infected calves that had recovered from diarrhea. Flow cytometric surface phenotypes of lamina propria lymphocyte (LPL) suspensions from infected calves and age-matched controls revealed the presence of a significantly larger proportion of CD25+ LPL in infected calves than in controls. Freshly isolated LPL from infected calves expressed more iNOS and interferon (IFN)-gamma than did controls. Infected calves excreted IgG1 and IgG2 isotype antibodies to C. parvum p23 by the end of the experiment. Moreover, immunohistochemistry of ileal sections revealed the presence of IgG1+ and IgG2+ B lymphocytes in the villi and IgG1+ but not IgG2+ B lymphocytes in continuous Peyer's patch nodules. These data are consistent with the emergence of a type-1-like mucosal immune response in terminal ileal mucosa as calves recover from cryptosporidiosis.

Excretion patterns of mucosally delivered antibodies to p23 in Cryptosporidium parvum infected calves

Fecal samples obtained at intervals from six calves with acute cryptosporidiosis contained antibodies of multiple isotypes to p23. IgM-, IgA-, and IgG(1)-isotype anti-p23 appeared before IgG(2)-isotype antibodies. All anti-p23 antibodies had declined by 2 months after infection. One calf that failed to shed oocysts following initial exposure developed IgG(1)-isotype anti-p23 antibodies. One calf that died following exposure to Cryptosporidium parvum oocysts lacked detectable anti-p23 antibodies. Re-inoculation with C. parvum resulted in a brief, marked recall response to p23.