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Ann Hulsmans Bram Vanschoenwinkel Chris Pyke Bruce J. Riddoch Luc Brendonck 《Ecosystems》2008,11(1):89-100
Ecological and evolutionary processes in temporary rock pools operate within constraints imposed by their hydrologic regimes.
These shallow pools flood when seasonal rains accumulate on impermeable substrates. Despite the ecological importance of hydrologic
conditions for these ecosystems, we typically lack tools and empirical data required to understand the implications of hydrologic
variability and climate change for biotic populations and communities in these habitats. In this study, we developed a hydrologic
model to simulate rock pool hydrologic regimes based on rainfall, evapotranspiration, and basin geometry. The model was used
to investigate long-term patterns of seasonal and inter-annual variation in hydroregime. In addition, hydrologic conditions
associated with potential climate change scenarios were simulated and evaluated with respect to the biological requirements
of the anostracan Branchipodopsis wolfi. The model’s output for daily inundation matched with field observations with an overall accuracy of 85% and correctly estimated
complete hydroperiods with an overall accuracy of 70%. Simulations indicate large variation in individual hydroperiods (76–115%)
as well as in the number of hydroperiods per year (19–23%). Furthermore, this study suggests that climate change may significantly
alter the rock pool hydroregime. These findings confirm the hydrologic sensitivity of these ephemeral habitats to precipitation
patterns, and their potential sensitivity to future climate change. Modelling indicates that the suitability of average inundation
conditions for B. wolfi deteriorates significantly under future climate predictions. High levels of spatial and temporal variation in hydrologic
conditions are dominant features of these habitats and an essential consideration for understanding population and community-level
ecological processes. 相似文献
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Stimulation of Melatonin Synthesis in Ovine Pineals In Vitro 总被引:2,自引:1,他引:1
Static and superfused pineal slices (750 micron) have been used to study the control of melatonin synthesis by ovine pineals. Static incubates show a time-dependent accumulation of melatonin in the medium; this is significantly increased by stimulation with norepinephrine (NE) (10(-5) M), reaching 300% above control levels after 4 h. Perifused pineal slices show a rapid rise in melatonin release within 12-18 min in response to NE stimulation. This reaches a 3.5-4.5-fold increase in melatonin released within 30 min. Withdrawal of NE is associated with a rapid return to prestimulated levels within 12-18 min. These time-course characteristics compare favorably to those changes seen in vivo. The formation of [14C]melatonin from [14C]-tryptophan shows a linear increase with time. In the presence of NE (10(-5) M), the rate of synthesis is increased, albeit after an initial time lag of at least 30 min. The latter may reflect an N-acetyltransferase-independent mechanism of synthesis and release. In static incubations, propranolol (10(-5) M) inhibited NE-induced melatonin production by about 60%, but prazosin (10(-5) M) had no effect. As dibutyryl cyclic AMP (10(-3) M) stimulated melatonin production, it is concluded that beta-receptors are of primary importance to the control of melatonin production, as in the rat. The role of alpha 1-receptors is less clear, but the stimulatory action of phorbol 12-myristate 13-acetate on melatonin release implicates a receptor linked to phosphatidylinositol turnover. 相似文献
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Lancelot Barrington-Ward Hubert Bond Edwin Bramwell Duncan C. L. Fitzwilliams Francis Fraser R. S. Frew William Goschen F. J. McCann Macmillan Arthur MacNalty Frederick Kay Menzies George Newman George Riddoch Humphry Rolleston Bertram Shires Frederick Still G. A. Sutherland James Taylor James Walton David Wilkie 《BMJ (Clinical research ed.)》1938,2(4046):195-196
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Ann Hulsmans Sofie Bracke Kelle Moreau Bruce J. Riddoch Luc De Meester Luc Brendonck 《Hydrobiologia》2006,571(1):123-132
The anostracan Phallocryptus spinosa has an almost exclusively palearctic distribution. The Makgadikgadi Pans area in Botswana represents the only distribution
record south of the Sahara. In this ephemeral wetland, it is an important food item in the diet of migrating birds. By studying
egg bank characteristics (such as depth and density) and hatching requirements, we investigated the persistence of this sub-Saharan
population. At localities in the middle and north basin of Sua Pan, sediment cores were taken along a transect, and dormant
eggs were isolated. Densities of the active dormant egg bank ranged from 833 to 31449 dormant eggs m−2, indicating that this species is well established. Most of the dormant eggs were found in the top 4 cm of the sediments,
and densities decreased to zero at a depth of 13 cm. Considering the expected low sedimentation rate, the presence of dormant
eggs down to 13 cm indicates long-time occurrence of P. spinosa in the Makgadikgadi Pans area. We observed high hatching fractions (up to 85%) at a temperature of 22 °C and a salinity of
5 ppt. A second anostracan species, Branchinella ornata, co-occurred with P. spinosa in our study site. This population also had a large active dormant egg bank (ranging from 6634 to 50557 dormant eggs m−2) with dormant eggs present until a depth of about 11 cm. This pattern indicates a long-time co-occurrence of P. spinosa and B. ornata. 相似文献
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A new solid-phase labeling strategy for the preparation of (99m)Tc and Re chelate complexes and associated peptide derivatives, was developed. Resin-bound monoamide monoamine (MAMA) chelates were prepared in such a manner that upon the addition of a suitable Re(V) and Tc(V) precursor the target metal complexes were selectively released from the resin. The desired products were isolated from unreacted ligand by a simple filtration/solid-phase extraction procedure. In addition to the preparation of a series of functionalized ligands, a peptide conjugate was constructed from one of the resin-bound chelates using a conventional automated peptide synthesizer. The yields of the Re chelate complexes were typically greater than 70%, while the maximum yield for reactions run at the tracer level using (99m)Tc was 50%. The reported approach has a number of attractive features, including the opportunity to prepare libraries of novel agents, the ability to isolate macroscopic amounts of Re complexes for use in in vitro screening studies and as well-characterized standards for tracer level work, and the ability to produce (99m)Tc complexes that are free of any unreacted starting material without having to employ preparative HPLC. 相似文献
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Patients with left neglect were tested with "chimeric" figures composed of the right and left halves of two different objects. The connectivity relation was modulated between the two half figures. For some displays, the two chimeric halves were separated by a small gap, while in others, the separate halves were connected by a line segment. In line with previous reports, performance on reporting the left half improved when the chimera were separated; but when a line connected the two separated halves the advantage was lost. If the connecting line was broken, the performance was again enhanced. The results suggest an important role for connectedness in the representation of perceptual objects and in the distribution of attention in neglect. 相似文献
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