Relationships between spatial patterns of bird and mammal species richness in north-eastern Mexic... more Relationships between spatial patterns of bird and mammal species richness in north-eastern Mexico were analysed in relation to the location of three biosphere reserves (El Abra-Tanchipa, El Cielo, and Sierra Gorda) and 13 priority areas recently identified for conservation. Ecological niches were modelled and potential distributions delimited for 285 bird and 114 mammal species using a genetic algorithm based on locality information from museum specimens and 15 selected environmental attributes. Potential distributions were transformed into hypothesized current distributions based on species–habitat associations as reflected in a recent land-use map. Although species richness was lower when distributions were reduced from potential to current, spatial patterns of potential and current richness were similar. Heuristic, complementarity-based prioritization procedures were used to identify combinations of areas and sites with maximal species representation: the biosphere reserves included 79% of birds and 74% of mammal species; eight priority areas provided an additional 11% of birds and 13% of mammals; the remaining 10% of birds and 13% of mammals were concentrated in new sites across the study area.
The effects of adrenaline and isoprenaline on K+ contractures of curarized tonic skeletal fibers ... more The effects of adrenaline and isoprenaline on K+ contractures of curarized tonic skeletal fibers were investigated. The K+ contractures of tonic fibers have a peak tension followed by a sustained tension. The peak tension and total tension (the tension-time integral--area--of K+ contractures) were increased by adrenaline and isoprenaline. The resting potential of tonic skeletal fibers were unaffected by adrenaline. The calcium channel blocker (cadmium and nifedipine) greatly blocked the effects of adrenaline on the peak and total tension of K+ contractures. On the other hand, the peak and sustained tensions of K+ contractures were greatly reduced in Ca(2+)-free solution, but, the peak tension recovered when the fibers were pre-incubated in adrenaline. It is proposed that adrenergic modulation of tension in tonic skeletal muscle fibers could be related with the modulation of Ca2+ channels and/or Ca2+ release from the sarcoplasmic reticulum.
Relationships between spatial patterns of bird and mammal species richness in north-eastern Mexic... more Relationships between spatial patterns of bird and mammal species richness in north-eastern Mexico were analysed in relation to the location of three biosphere reserves (El Abra-Tanchipa, El Cielo, and Sierra Gorda) and 13 priority areas recently identified for conservation. Ecological niches were modelled and potential distributions delimited for 285 bird and 114 mammal species using a genetic algorithm based on locality information from museum specimens and 15 selected environmental attributes. Potential distributions were transformed into hypothesized current distributions based on species–habitat associations as reflected in a recent land-use map. Although species richness was lower when distributions were reduced from potential to current, spatial patterns of potential and current richness were similar. Heuristic, complementarity-based prioritization procedures were used to identify combinations of areas and sites with maximal species representation: the biosphere reserves included 79% of birds and 74% of mammal species; eight priority areas provided an additional 11% of birds and 13% of mammals; the remaining 10% of birds and 13% of mammals were concentrated in new sites across the study area.
The effects of adrenaline and isoprenaline on K+ contractures of curarized tonic skeletal fibers ... more The effects of adrenaline and isoprenaline on K+ contractures of curarized tonic skeletal fibers were investigated. The K+ contractures of tonic fibers have a peak tension followed by a sustained tension. The peak tension and total tension (the tension-time integral--area--of K+ contractures) were increased by adrenaline and isoprenaline. The resting potential of tonic skeletal fibers were unaffected by adrenaline. The calcium channel blocker (cadmium and nifedipine) greatly blocked the effects of adrenaline on the peak and total tension of K+ contractures. On the other hand, the peak and sustained tensions of K+ contractures were greatly reduced in Ca(2+)-free solution, but, the peak tension recovered when the fibers were pre-incubated in adrenaline. It is proposed that adrenergic modulation of tension in tonic skeletal muscle fibers could be related with the modulation of Ca2+ channels and/or Ca2+ release from the sarcoplasmic reticulum.
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