bluuebunny/crossref_metadata_2025 huggingface dataset:
Metapopulation moments: coupling, stochasticity and persistence
Authors: Keeling Matt J.
Published: March 2003

1. Spatial heterogeneity has long been viewed as a reliable means of increasing persistence. Here, an analytical model is developed to consider the variation and, hence, the persistence of stochastic metapopulations. This model relies on a novel moment closure technique, which is equivalent to assuming log‐normal distributions for the population sizes.

2. Single‐species models show the greatest persistence when the mixing between subpopulations is large, so spatial heterogeneity is of no benefit. This result is confirmed by stochastic simulation of the full metapopulation.

3. In contrast, natural‐enemy models exhibit the greatest persistence for intermediate levels of coupling. When the coupling is too low, there are insufficient rescue effects between the subpopulations to sustain the dynamics, whereas when the coupling is too high all spatial heterogeneity is lost.

4. The difference in behaviour between the one‐ and two‐species models can be attributed to the oscillatory nature of the natural‐enemy system.
Prey diversity, prey composition, and predator population dynamics in experimental microcosms
Authors: Petchey Owen L.
Published: March 2003

1.Food‐web complexity‐stability relations are central to ecology, and many empirical studies show greater food‐web complexity leads to lower population stability. Here, predator population variability decreased with increasing prey diversity in aquatic microcosm experiments, an example of greater food‐web complexity leading to greater population stability.

2.Prey diversity as well as different sets of prey species within each level of prey diversity produced differences in predator population dynamics, demonstrating the importance of both prey composition and prey diversity in determining predator population stability.

3.Prey diversity can affect predator population dynamics through at least three groups of mechanisms: prey reliability, prey biomass, and prey composition mechanisms. The results suggest that greater prey reliability at higher prey diversities enhances predator stability and provide support for MacArthur (1955).
Plastic daily fattening routines in willow tits
Authors: Koivula Kari , Orell Markku , Lahti Kimmo
Published: March 2003

Each day small birds must build up sufficient energy reserves, largely fat deposits, for the following night and for the periods when foraging is not possible. The earlier the birds acquire the reserves and the more they carry them, the higher is the insurance value of the reserves. Still, small birds do not forage at maximal capacity during the day and, even at dusk, body reserves are usually below the physiological upper limit. A popular explanation for this is that birds’ fatness levels reflect an optimal compromise between starvation risk and risks associated with reserve carrying and acquisition.

Theoretical works suggest that uncertain or variable feeding conditions should promote high reserve levels, and that in the daily perspective, feeding should peak in the morning hours. In more favourable conditions, reserve levels should be smaller and the acquisition peak should be delayed towards the end of the day. These predictions were tested by experimentally manipulating winter feeding conditions and monitoring subsequent daily body mass increase in northern population of the willow tit Parus montanus (Conrad), a small‐sized forest passerine.

The birds using feeders appeared heavier than the control birds throughout the day. This contradicts the prevailing theory, but is understandable since the feeding procedure probably not only affected food amount but may also have decreased acquisition costs in terms of predation.

Daily mass gain and the gain rates were fairly similar in the food‐manipulated and the control birds. However, the mass gain schedules differed between the treatment groups: the food‐supplemented birds gained mass at a roughly constant rate while among the control birds the gain rate was higher in the morning than in the afternoon. Probably to avoid associated costs, birds abandon early build‐up of reserves if foraging conditions become favourable enough.
Management procedures required to increase chironomid availability to waders feeding on artificial lagoons remain unclear
Authors: Green A.J. , Hilton G.M.
Published: March 2003

1.  Rehfisch (1994) made various recommendations for how to increase chironomid biomass and its availability to waders in artificial lagoons. We argue that his studies form an insufficient basis for some of these recommendations.

2.  He suggested protocols for depth manipulation based on a model predicting biomass in terms of depth and depth squared which was not a meaningful representation of his data. This model should therefore not be used as a guide for managing water levels.

3.  He predicted that biomass would peak at a depth of about 117 cm, yet he only studied depths of up to 54 cm. We used data from a large, permanent, brackish lake to illustrate how biomass at shallow depths cannot be used to predict that found at greater depths.

4.  His aim of a simple model allowing managers to predict chironomid biomass on the basis of depth in artificial lagoons was unrealistic, owing to wide variation in the biomass–depth relationship within and between sites.

5.  The value of his ‘inverted sombrero’ design for a wader lagoon needs to be demon strated empirically. He advocated regular drying‐out of lagoons followed by immediate refilling, a flooding cycle that may not maximize chironomid biomass.
Modelling topoclimatic patterns of egg mortality of Epirrita autumnata (Lepidoptera: Geometridae) with a Geographical Information System: predictions for current climate and warmer climate scenarios
Authors: Virtanen Tarmo , Neuvonen Seppo , Nikula Ari
Published: March 2003

1.  Our aim was to quantify the effects of a warmer winter climate on the egg mortality (and, consequently, the risk of an outbreak) of Epirrita autumnata, a serious defoliator of mountain birch.

2.  The egg survival of E. autumnata was studied in northernmost Finland from 1993 to 1996, when minimum temperatures were also recorded. Utilizing a digital elevation map with a GIS (Geographical Information System), models were developed for egg survival and minimum temperature, taking into account altitude, local topography and temperatures at a meteorological station in the study area.

3.  Areas of high egg mortality of E. autumnata can be modelled in the GIS with reasonable accuracy by the model describing areal distribution of minimum winter temperatures, taking account of the fact that the critical limit for egg survival of E. autumnata in midwinter is about −35·5°C. The approach can be applied in short‐term forecasting of outbreak areas when previous year population densities and minimum winter temperatures at meteorological stations are known.

4.  In our study area, from 1961 to 1991 more than one‐third of the years were egg‐killing winters in the mixed birch‐pine forests zone, and 15% of years in the birch forest zone. In order for an outbreak to take place, at least three consecutive seasons with a high population growth rate are needed; in the mixed birch‐pine forests the possibilities of an E. autumnata outbreak during the period 1961–91 were very rare, while in the birch forest zone outbreak possibilities were also noticeably restricted by winter minimum temperatures.

5.  If winter warming takes place according to the scenarios presented, by the middle of the next century the birch‐growing areas in our study area protected by low temperatures from outbreaks of E. autumnata will be only one‐third as great as those of today, and by the end of the next century only one‐tenth of those of today.

6.  The models and methods described in this paper can be applied to other ecological processes. The modelling strategies and techniques described here serve as intermediate tools for linking large scale climate models (general circulation models, GCMs) and ecological processes happening at a smaller scale.
Changes in decomposition rates and Collembola densities during the forestry cycle in conifer plantations
Authors: Butterfield J.
Published: March 2003

1.Conifers have a tendency to produce detrimental changes in the soil that suppress decomposition. It is also possible that clear‐felling and the short plantation rotation (40–50 years), usual in Britain, will eventually cause nutrient depletion. Decomposition rates are important in determining the level of nutrients available, to both the crop and the soil invertebrate community, and this study has compared them at three stages during the plantation cycle.

2.Cotton cloth buried in the soil of open areas decomposed at twice the rate of cloth buried in the soil of closed canopy plantations.

3.The rate of decomposition in the soil layer 0–80 mm from the surface was 1·5 times that in the 81–160 mm layer.

4.In young plantations, the decomposition rate of cloth decreased with an increase in the age of the plantation. It is suggested that the decrease in decomposition rate with plantation age is associated with increased shading and a decrease in the amplitude of the diurnal temperature cycle.

5.Springtail (Collembola) densities were high in spring on an open area and decreased in summer. The opposite occurred in the closed canopy plantation. Drying on the exposed open area is suggested as the cause of the decreased summer densities.

6.On the site where Collembola densities were monitored, decomposition rates were higher in the upper soil layer of the closed canopy plantation than in an open area. It is probable that this was due to the upper layers on the exposed area drying, rather than to the high Collembola densities checking fungal decomposition.

7.The nutrient release that accompanies decomposition has potential importance for the rate of growth of the conifer crop. This preliminary study suggests that the decomposition rate is highest in the years immediately after felling, probably favouring the establishment of the next rotation.

8.This study has not detected suppression of decomposition on open or clear‐felled areas in Hamsterley Forest (NZ0530), suggesting that present planting and harvesting methods are appropriate and should continue. However, further investigation of the interactions between fungi, meso‐ and macrofauna is needed to understand both nutrient cycling and the invertebrate community structure in plantation forestry.
A history of change: causes of miombo woodland decline in a protected area in Malawi
Authors: Abbot Joanne I. O. , Homewood Katherine
Published: March 2003

1. Tropical dry woodlands are thought to be declining as a result of human activity. Aerial photograph analysis showed measurable conversion of closed canopy miombo* to sparse woodland in Lake Malawi National Park, Malawi, from 1982 to 1990. This multi‐disciplinary study investigates the possible contributions to these impacts by local use of domestic fuelwood, construction poles and fuelwood for commercial fish smoking.

2. Domestic fuelwood use was measured in 30 households over an 11‐month period. Domestic fuelwood is collected by women and is headloaded to the village. It comprises a large biomass of mainly dead wood and small branches over a wide species range. Mean total annual domestic fuelwood consumption by the total enclave population was less than half the mean annual production of fallen dead wood in the Park, estimated from three quadrats harvested monthly over an 11‐month period.

3. Construction poles are mostly small, have extended durability and come from a broad species range. Fencing poles frequently take root to form live hedges. Eucalyptus trees are commonly grown for poles. Construction pole use appears sustainable and shows signs of substitution.

4. The 305 commercial fish smoking stations in the enclaves used less fuelwood annually than domestic fuelwood users. However, the men who undertake this activity target large branches and logs from a narrow species range, involving destructive felling of canopy species. 95% of men collecting fuel for fish smoking use cutting tools and three‐quarters transport the wood by boat or bicycle.

5. The scale, size classes and species involved in commercial fish smoking suggest that this activity drives the observed degradation of closed canopy to sparse woodland. Traditional local fishing focused on small species sun‐dried for preservation. Commercial fish smoking was introduced relatively recently by immigrants, along with gill netting that harvests larger fish requiring smoking for preservation. Demand for fish by ever‐increasing urban populations underpins the continuing growth of the fish smoking industry.

6. Disaggregation of different wood use practices allows informed management policy for the Park. Currently, management targets and penalizes domestic fuelwood collectors. While seeking to reduce demand and provide alternative fuelwood sources, law enforcement and forestry extension should be reorientated to address the extraction of fuelwood for fish smoking.
Determinants of human–elephant conflict in a land‐use mosaic
Authors: Hoare R.E.
Published: March 2003

1. The resolution of direct conflict between humans and elephants in Africa has become a serious local political issue in recent years, and a continental conservation problem. ‘Problem elephants’ damage crops, food stores and water sources, and sometimes threaten human life.

2. Eighty per cent of the African elephant's range lies outside formally protected areas, and inadequate management of human–elephant conflict is frequently a precursor to further decline in the numbers and distribution of elephants. Conflict appears to be increasing in an assortment of African ecosystems as the agricultural interface with elephant range expands.

3. The present study recorded incidents by problem elephants in small subdivisions of a 15 000 km2elephant range. The level of problem elephant activity over 3 years showed huge variation and could not be explained by elephant density, proximity of a protected area, area of human settlement, human density or local rainfall.

4. It is proposed that the irregular and unpredictable nature of human–elephant conflict incidents in the study area mainly depended upon the behavioural ecology of individual elephant bulls.

5. This study proposes a statistic to quantify problem elephant activity in Africa which can be used to compare the intensity of problem incidents between different ecosystems at different times: ‘elephant incidents per square kilometre of human settlement area per year’. Spatial analyses of appropriate data at the human–elephant interface may yield a more predictive understanding of the conflict process.
Patterns of otterLutra lutraroad mortality in Britain
Authors: Philcox C.K. , Grogan A.L. , Macdonald D.W.
Published: March 2003

1. This paper examines patterns of otter road traffic accidents and the possibilities for reducing this mortality.

2. Records of otter road casualties in Britain (673 between 1971 and 1996) were compiled and accident sites were plotted on 1:50000 scale Ordnance Survey maps. Casualty records were categorized by geographical region, road type, distance to watercourses and presence and type of river crossings. The data were analysed for demographic, seasonal, temporal and spatial trends.

3. A rapid increase in numbers of road traffic accident records has occurred since 1983. Fifty‐six per cent of fatalities were males, representing a statistically significant bias.

4. The number, but not the sex ratio, of otter road casualties differed between seasons and in all areas was positively correlated with either seasonal rainfall or river flow.

5. Significant effects of geographical region, road density and year were found on the annual number of casualties recorded in mainland regions, and the regional rates of increase in numbers of road traffic accidents were significantly different. There is also evidence that road traffic accidents are influenced by otter site occupancy of a region.

6. Trunk and A‐roads accounted for 57% of road traffic accident records, even though they comprise only 13% of the road network.

7. A 100‐m wide zone surrounding fresh water and the coast accounted for 67% of all casualty records. Measures to reduce road mortality should target this zone.

8. The seasonal correlations of otter road traffic accidents with rainfall and river flow, and the fact that 91% of accidents occurred where a road crossed a watercourse, suggest that substantial reductions in road mortality could be achieved by improving the design of road crossings of watercourses.

9. We suggest that the optimal approach to road crossing design is to maintain a continuous, and where possible, natural bank above the level of high flows, using either wide‐span bridges, over‐sized culverts or artificial ledges.

10.The use of otter‐proof fencing may be required to reduce mortality where roads pass close to watercourses, but care must be taken that this does not create a barrier to all movements of otters and other wildlife.
Predation onPinus sylvestrisseeds and juvenile seedlings in Swedish boreal forest in relation to stand disturbance by logging
Authors: Nystrand Ove , Granström Anders
Published: March 2003

1. Forest management involving live tree retention and natural regeneration after cutting is currently increasing in boreal areas. This calls for further analysis of the optimal conditions for seedling establishment from seed following stand disturbances due to logging.

2. We studied post‐dispersal predation on seeds and juvenile seedlings ofPinus sylvestrisover 3 years in 32 north Swedish boreal forest stands with different levels of stand disturbance by logging. The aims were to identify the most important predator species and to quantify the damage inflicted upon seeds and seedlings in relation to disturbance.

3. In most stands and years, seed predation resulted in < 20% seed mortality, although occasionally it reached 60%. Predation on juvenile seedlings ranged from 5% to 100%, with > 70% mortality in 10 cases and < 30% in 44 cases (of a total of 79 observations).

4. The most important seed predators were the carabidsPterostichus oblongopunctatusandCalathus micropterus, and seed predation was correlated with the number of seed‐eating carabids caught in pitfall traps. Microtine rodents caused high damage levels only on a single occasion.

5. Logging affected both catches of carabids and seed predation levels, but the relationship between tree stand density and predation was not linear and, generally, seed predation decreased in the order shelterwood > unlogged forest > clear‐cut.

6. The most important predator on juvenile seedlings was the slugArion subfuscus, which attacked seedlings during the first weeks after germination. Pitfall trap catches ofHylobius abietis, which commonly damage planted (1–3‐year‐old) conifer seedlings, were not related to the levels of seedling predation.

7. Seedling predation was negatively related to stand disturbance, with the highest predation levels by slugs in unlogged forests and the lowest in clear‐cuts. Seedling predation was higher in wet than in dry summers, probably because slugs are moisture‐limited.

8. There was a large between‐site variation in both seed and seedling predation, but predation was not strongly related to forest site types. The fact that predation was strongly affected by logging operations indicates that there may be opportunities to reduce damage through modification of the silvicultural practices.
Large−scale disturbances, biological control and the dynamics of gorse populations
Authors: Rees M. , Hill R.L.
Published: March 2003

Simulation and analytical models were developed for gorse Ulex europaeus. The simulation model incorporated spatially local density−dependent competition, disturbance, asymmetric competition between seedlings and established plants, a seed bank, local seed dispersal, an age structured established plant population, and temporal variation in the probability of disturbance. The analytical models were simple approximations of the simulation.

The models extended our previously published model for Scotch broom Cytisus scoparius to include large−scale disturbances and possible management options, such as the use of fire, herbicides and oversowing with perennial grasses. Fire was assumed to influence established plant mortality, seed survival in the seed bank, and the probability of germination.

We reviewed published data on the demography of gorse in New Zealand, the current management techniques, and the ongoing biological control programme.

Over a wide range of biologically reasonable parameter values, the analytical models accurately predicted the outcome of the simulations. The analytical models worked well, providing gorse occupied a high proportion of the available sites and large−scale disturbances did not occur too frequently.

The potential impact of seed−feeding biological control agents on gorse abundance was assessed, using the models, for several environmental and management scenarios. In particular, we explored how large−scale disturbance, such as fire and herbicide application, influences the outcome of biological control.

The success of a biological control programme was found to depend critically on the frequency and intensity of disturbance, whether disturbed sites became suitable for recruitment, and the effects of disturbance on germination and seed mortality.

The models highlight the need to manage recruitment opportunities carefully in order to maximize the effect of biological control agents. The models also indicate that details of plant population biology can have a profound effect on the success of any management strategy.
Linking agricultural practice to insect and bird populations: a historical study over three decades
Authors: Benton Tim G. , Bryant David M. , Cole Lorna , Crick Humphrey Q. P.
Published: March 2003

There is continuing debate about the impact of agricultural practices on farmland wildlife. In particular, it has been postulated that a general decline in insect abundance linked with intensification of agriculture may have contributed to farmland bird decline. While some autecological studies have supported this hypothesis, larger‐scale and long‐term studies are needed.

Suction traps mounted on 12·2‐m towers (Rothamsted‐type) have been sampling aerial insects for nearly 40 years throughout the UK. Their catches are correlated over large spatial scales. We analysed insect catch data from a single suction trap run for 27 years in a rural location in Scotland, and showed that insect numbers have changed significantly over time, although non‐linearly. The multivariate data set (numbers from the 12 common arthropod groups) was summarized using principal components analysis (PCA) to extract three components explaining 62% of the variation.

We also used PCA to describe agricultural change, using published agricultural data for eight measures of farming in Scotland. Arthropod abundance and principal component (PC) scores were significantly related to the agricultural PC scores as well to summary climatic measures.

Using Scottish data from the British Trust for Ornithology Common Birds Census, we extracted three PC to describe the time‐dependent average densities of 15 common farmland birds in Scotland. Measures of bird density were significantly related to insect abundance and PC scores and, independently, to measures of agriculture and climate.

These data from a broad suite of species provide support for linked temporal change between farmland birds, invertebrate numbers and agricultural practice in Scotland. Although entirely correlative, the results are consistent with the view that agricultural change has influenced birds through changes in food quality or quantity. The work also shows how large‐scale invertebrate sampling, in this case using suction traps, is useful for monitoring farmland biodiversity.
Waterbird responses to experimental drawdown: implications for the multispecies management of wetland mosaics
Authors: Taft Oriane W. , Colwell Mark A. , Isola Craig R. , Safran Rebecca J.
Published: March 2003

The loss and human modification of wetlands world‐wide underscores the importance of efficient management. For wetlands that provide habitats for non‐breeding waterbirds, such management often aims to support a rich and abundant waterbird community.

Among the world's many seasonal, moist‐soil managed wetlands, annual winter flooding is followed by spring drawdown to encourage germination of waterfowl food plants. Recommendations on how best to maintain flooded wetlands for multiple species are mostly theoretical, and drawdown management typically focuses on spring for migrating shorebirds. The benefits and drawbacks of shallow‐water management in winter have not been examined, especially where sizeable populations of wintering shorebirds and waterfowl occur together.

We considered The Grasslands Ecological Area in California's Central Valley, USA, as a model wetland complex in which to assess optimal winter flood‐depth for multispecies use. We also examined the relative benefits for each waterbird group (e.g. shorebirds and waterfowl) of drawdowns conducted in winter and spring. We experimentally dewatered wetlands of measured topography in the winter and spring of 1994–95, documenting changes in waterbird species richness and abundance associated with daily changes in habitat diversity and availability.

Results indicated limited regional availability of shallow‐water habitat across the landscape in winter but not spring, as use by shorebirds and teal increased on drawndown wetlands in winter only. Use by deeper‐water dabbling ducks and diving waterbirds declined during the later stages of drawdown in both seasons, but not until use by shorebirds and teal had peaked. The maximum diversity and abundance of waterbirds occurred at average depths of 10–20 cm on wetlands with topographic gradients of 30–40 cm.

This study has important implications for the winter management of seasonal wetland complexes, especially moist‐soil systems where managers provide habitat for different waterbird groups (from shorebirds to diving waterbirds) simultaneously. In general, where topography is variable (e.g. a difference of 30–40 cm between the deepest and shallowest zones), wetlands flooded to average depths of 15–20 cm should accommodate the greatest richness and abundance of waterbirds.
The effect of transgenic nematode resistance on non‐target organisms in the potato rhizosphere
Authors: Cowgill Sue E. , Bardgett Richard D. , Kiezebrink Daan T. , Atkinson Howard J.
Published: March 2003

Plant‐parasitic nematodes are important pests of agriculture and transgenic plants with potential for nematode control are currently being developed. The expression of cysteine proteinase inhibitors (cystatins) in potato confers partial resistance to potato‐cyst nematode (PCN). Here, we used field studies to test for effects of cystatin‐expressing potato on non‐target soil organisms.

Microbial community structure, soil microarthropods and litter decomposition were studied during two growing seasons. In the second year, nematode control options of cystatin‐expressing plants and an oxime carbamate nematicide application were compared for their non‐target effects.

In the first year, the transgenic lines had no effect on the abundance, evenness or metabolic activity of the soil microbial community as determined by ester‐linked phospholipid fatty acid analysis (PLFA). However, one transgenic line (D6/7) influenced the structure of the soil microbial community. PLFA suggested it favoured fungal growth relative to bacterial growth during the latter parts of the growing season. A second transgenic line (D5/13) was more effective against PCN. It reduced the abundance of the fungal fatty acid 18 : 2ω6 in late season, suggesting a suppression of fungal growth.

In the second year PLFA analysis suggested microbial abundance was reduced by 15% and 23% in the nematicide and transgenic treatments, respectively, relative to the control. Nematicidal treatment reduced the bacterial fraction of the microbial community, whereas the transgenic plants suppressed both the bacterial and fungal community components.

The observed changes in soil microbial community structure did not result in changes in the rate of leaf litter decomposition.

The transgenic lines had no significant effect on the abundance of soil microarthropods or free‐living nematodes.

The study is the first stage of a risk assessment of the impact of transgenic nematode resistance on non‐target soil organisms. It has highlighted the importance of including currently used management options when studying the effect of transgenic plants on non‐target organisms. Both nematicide use and the transgenic plants affected components of the soil microbial community. However, the changes brought about by the two treatments were not sufficient to affect soil functioning, as measured by rates of litter decomposition.
Evaluation of an agonist index: affinity ratio for compounds active on muscarinic cholinergic M2 receptors
Authors: Tayebati S. K. , Piergentili A. , Natale D. , Amenta F.
Published: March 2003

1 A protocol for predicting full agonist, partial agonist, and antagonist profiles of compounds with M2 muscarinic cholinergic receptor activity was developed using radioligand binding assay techniques with [3H]‐N‐methyl scopolamine (NMS) and [3H]‐Oxotremorine‐M (Oxo‐M) as radioligands.

2 Full muscarinic cholinergic receptor agonists such as muscarine and oxotremorine‐M expressed a high agonist index (> 3000 for M1 muscarinic cholinergic receptors and > 900 for M2 muscarinic cholinergic receptor), whereas muscarinic receptor antagonists (selective or non‐selective) for different receptor subtypes gave a low (0.5–10) agonist index.

3 Functional studies performed on preparations of guinea‐pig ileum and heart were consistent with radioligand binding assay experiments.

4 The above results suggest that similarly as already established for the M1 muscarinic cholinergic receptor subtype, evaluation of the [3H]‐NMS/[3H]‐Oxo‐M ratio may provide useful information on the profile of compounds acting at the M2 muscarinic cholinergic receptor subtype.

5 The availability of simple and predictive techniques for the characterization of muscarinic M2 cholinergic receptor agonists, may help the identification of new compounds in therapeutic areas in which stimulation or inhibition of this receptor is desirable.
Characterisation of the atypical β‐adrenoceptor in rabbit isolated jejunum using BRL 37344, cyanopindolol and SR 59230A
Authors: MacDonald A. , Watt K.
Published: March 2003

1 The present study was carried out to further investigate the nature of the β‐adrenoceptor in rabbit jejunum using BRL 37344, a selective β3‐adrenoceptor agonist, cyanopindolol, a β‐adrenoceptor antagonist with blocking activity at β3‐adrenoceptors and SR 59230A, a new selective β3‐adrenoceptor antagonist.

2 Isoprenaline produced a concentration‐dependent inhibition of the spontaneous contractions of rabbit jejunum with a pD2 of 7.14. Propranolol (1 μm) shifted the isoprenaline concentration‐response curve (CRC) to the right with a concentration‐ratio of 5.85, considerably less than would be expected for an action at classical β‐adrenoceptors (estimated pA2 6.66).

3 BRL 37344 also produced a concentration‐dependent inhibition of spontaneous contractions with a pD2 of 7.41. The BRL 37344 CRC was unaffected by propranolol (1 μm).

4 In the presence of propranolol (1 μm), cyanopindolol (1 μm) shifted the isoprenaline CRC to the right (concentration‐ratio of 21). Cyanopindolol also shifted the BRL 37344 CRC to the right (concentration‐ratio of 38). These shifts are consistent with the affinity of cyanopindolol for β3‐adrenoceptors (estimated pA2 values of 7.27 and 7.38 against isoprenaline and BRL 37344, respectively).

5 In the presence of propranolol (1 μm), SR 59230A produced a concentration‐dependent rightward shift of the isoprenaline CRC. The Schild plot gave a pA2 value of 7.16, although the slope of the regression line was significantly different from unity (0.65). SR 59230A also produced a concentration‐dependent shift of the BRL 37344 CRC. The Schild plot gave a pA2 of 7.58 with the slope of the regression line not significantly different from unity (0.81).

6 The presence of β3‐adrenoceptors mediating relaxation of spontaneous contractions in rabbit jejunum is supported by the relatively poor antagonism of isoprenaline by propranolol, the relaxant effect of BRL 37344 and the antagonism of isoprenaline and BRL 37344 by cyanopindolol and SR 59230A. The lack of simple competitive antagonism of isoprenaline, but not BRL 37344, by SR 59230A may suggest more than one population of atypical β‐adrenoceptor.
β1‐ and β3‐adrenoceptors mediate relaxation in ovine trachealis smooth muscle
Authors: Mustafa S. M. D. , Yousif M. , Cherian A. , Oriowo M. A.
Published: March 2003

1 Isoprenaline (non‐selective) and noradrenaline (β1‐selective) concentration‐dependently relaxed ovine tracheal strips precontracted with carbachol. The pD2 values were 7.07 ± 0.08 and 6.13 ± 0.10 for isoprenaline and noradrenaline, respectively. In the same preparation, salbutamol either produced weak relaxation or in some cases, contractile responses indicating the presence of very little or no β2‐adrenoceptors in this preparation.

2 Isoprenaline‐and noradrenaline‐induced relaxations were antagonized by propranolol and atenolol with pA2 values in the range reported in the literature for an action on β1‐adrenoceptors. ICI 118551 also antagonized isoprenaline‐ and noradrenaline‐induced relaxation but at concentrations much higher than are required to block β2‐adrenoceptors, confirming that β2‐adrenoceptors do not contribute significantly to these responses.

3 The selective β3‐adrenoceptor agonist, BRL 37344A produced concentration‐dependent relaxation of tracheal strips. BRL 37344A was a full agonist producing 100% relaxation of carbachol‐induced tone. BRL 37344A‐induced relaxation was weakly antagonized by propranolol confirming an action, mainly, on β3‐adrenoceptors. Cyanopindolol antagonized isoprenaline‐induced relaxation (in the presence of propranolol, 10−−7 m) with a pA2 value of 8.06 ± 0.24.

4 It was therefore concluded that β1‐ and β3‐adrenoceptors mediated agonist‐induced relaxation in sheep tracheal strips.
Comparison of the effects of nitric oxide synthase, guanylate cyclase and potassium channel inhibition on vascular contractions in vitro in the rat
Authors: Abdullah K. , Docherty J. R.
Published: March 2003

1 We have investigated the differences between the nitric oxide synthase inhibitor L‐NMMA, the guanylate cyclase inhibitor methylene blue and the potassium channel blockers apamin and charybdotoxin or apamin and iberiotoxin, in their abilities to increase vasoconstrictor responses in rat small mesenteric arterial rings.

2 When administered during the maintained contraction to PGF2α (10 μm), L‐NMMA (100 μm) or the combination of apamin (0.7 μm) and charybdotoxin (0.1 μm) significantly increased the contractile response. Methylene blue (10 μm) increased the contraction, but this did not reach significance. However, apamin (0.7 μm) and iberiotoxin (0.1 μm) also significantly increased the contractile response.

3 The combination of L‐NMMA or methylene blue with apamin/charybdotoxin produced significantly greater increases in the contractile response to PGF2α than achieved individually.

4 Relaxations to acetylcholine (10 μm) were significantly reduced by L‐NMMA or methylene blue but not by apamin in combination with charybdotoxin or iberiotoxin.

5 Since apamin/iberiotoxin had similar effects to apamin/charybdotoxin, it is likely that the actions of these agents involve direct actions on smooth muscle potassium channels rather than inhibition of endothelium‐derived hyperpolarising factor (EDHF). These results suggest that endothelium‐derived nitric oxide but not EDHF has a major role in modulating vascular tone under these conditions.
The effects of histamine on the isolated mouse uterus
Authors: Rubio E. , Navarro‐Badenes J. , Palop V. , Morales‐Olivas F. J. , Martínez‐Mir I.
Published: March 2003

1 A study is made of the contractile and relaxant effects, and mechanism of action, of histamine on isolated uterus from mice treated with diethylstilboestrol, employing acetylcholine and adrenaline as contractile and relaxant standard agents.

2 Concentration‐response curves for histamine agonists were obtained in the absence and presence of selective histaminergic blocking drugs (clemizole, ranitidine and thioperamide) and indomethacin. A number of experiments were carried out in uterus from reserpinised mice. Concentration‐response curves for acetylcholine and adrenaline were also obtained in the absence and presence of their selective antagonist (atropine and propranolol).

3 In isolated oestrogenised mouse uterus, histamine and acetylcholine produced a concentration‐related contractile response. When the uterus was precontracted with KCl, histamine at lower doses produced a slight contraction, though in the presence of clemizole it induced concentration‐related relaxation, reminiscent of that produced by adrenaline. Atropine and propranolol antagonised the contractile and relaxant effects of acetylcholine and adrenaline, respectively.

4 In isolated uterus from reserpinised mice, histamine and 2‐pyridylethylamine, but not 4‐methylhistamine, produced a concentration‐related contractile response. Ranitidine potentiated the contractile effect of histamine, though clemizole – in the presence of ranitidine – competitively antagonised the contractile effect of histamine (pA2 = 10.50 ± 0.81). The concentration‐relaxant curve of histamine in the presence of clemizole was not modified by ranitidine or indomethacin, but shifted to the right with thioperamide. The same displacement was also observed in the presence of clemizole plus ranitidine.

5 In mouse isolated uterus, histamine mainly produced contraction mediated by histamine H1‐receptors, though the existence of histamine H2‐or H3‐receptors mediating relaxation could not be excluded.
Influence of alpha‐adrenoceptor blockade on antigen‐ and propranolol‐induced bronchoconstriction in guinea‐pigs in vivo
Authors: Ishiura Y. , Fujimura M. , Myou S. , Amemiya T. , Nobata K. , Liu Q. , Yamamori C.
Published: March 2003

1 Beta‐adrenoceptor antagonists, such as propranolol, can provoke severe bronchoconstriction only in asthmatic subjects. Recently, we developed a guinea‐pig model of propranolol‐induced bronchoconstriction (PIB) and the purpose of this study was to investigate the role of alpha‐adrenergic nerve pathways in this reaction.  2 Phentolamine administered after an antigen challenge did not inhibit PIB; however, its administration before the antigen challenge significantly inhibited the antigen‐induced bronchoconstriction and also bronchoconstriction induced by methacholine inhalation.  3 We conclude that the alpha‐adrenergic nerve system is not involved in the development of PIB following allergic reaction in our guinea‐pig model.
Inhibitory mechanism of pinacidil on catecholamine secretion from the rat perfused adrenal gland evoked by cholinergic stimulation and membrane depolarization
Authors: Lim Dong‐Yoon , Park Geun‐Hong , Park Sang‐Hak
Published: March 2003

1 The present study attempted to investigate the effect of potassium channel openers on secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from rat isolated perfused adrenal gland.  2 The perfusion of pinacidil (30–300 μm) into an adrenal vein for 20 min produced dose‐dependent inhibition of CA secretion evoked by acetylcholine (ACh; 5.32 m
m), high K+ (56 m
m), 1,1‐dimethyl‐4‐phenylpiperazinium iodide (DMPP; 100 μm for 2 min), 3‐(m‐chloro‐phenyl‐carbamoyl‐oxy)‐2‐butynyl trimethyl ammonium chloride (McN‐A‐343; 100 μm for 2 min), cyclopiazonic acid (CPA; 10 μm for 4 min) and methyl‐1,4‐dihydro‐2,6‐dimethyl‐3‐nitro‐4‐(2‐trifluoromethylphenyl)‐pyridine‐5‐carboxylate (Bay‐K‐8644; 10 μm for 4 min).  3 In the presence of minoxidil (100 μm), which is also known to be a potassium channel activator, CA secretory responses evoked by ACh, high potassium, DMPP, McN‐A‐343, Bay‐K‐8644 and CPA were also significantly depressed.  4 In adrenal glands preloaded with pinacidil (100 μm) in the presence of glibenclamide (GB; 1 μm), a specific blocker of ATP‐regulated potassium channels, CA secretory responses evoked by ACh, high potassium, DMPP, McN‐A‐343, Bay‐K‐8644 and CPA were restored to a considerable extent of the control release as compared with that of pinacidil only.  5 These results suggest that pinacidil causes marked inhibition of CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors, as well as by membrane depolarization, indicating that this effect may be mediated by inhibiting influx of extracellular calcium and release of intracellular calcium in the rat adrenomedullary chromaffin cells. Furthermore, these findings suggest that these potassium channel opener‐sensitive membrane potassium channels also play a modulatory role in regulating CA secretion.
The α‐adrenoceptor antagonist, zolertine, inhibits α1D‐ and α1A‐adrenoceptor‐mediated vasoconstriction in vitro
Authors: Ibarra M. , Hong E. , Villalobos‐Molina R.
Published: March 2003

1 The antagonist effect of zolertine (4‐phenyl‐1‐[2‐(5‐tetrazolyl)ethyl]piperazine trihydrochloride), on vascular contraction elicited by noradrenaline in aorta, carotid (α1D‐adrenoceptors), mesenteric (α1A/D‐adrenoceptors) and caudal arteries (α1A‐adrenoceptors) from Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats and rabbit aorta (α1B‐adrenoceptors), was investigated in endothelium‐denuded arterial rings.  2 The selective α1D‐adrenoceptor agonist, noradrenaline, elicited concentration‐dependent contractions in all arterial rings from both species. Noradrenaline selectivity was: carotid=aorta>>.Gt;mesenteric=rabbit aorta>caudal arteries.  3 The contractile responses induced by noradrenaline were competitively antagonized by zolertine in rat carotid and aorta arteries, yielding pA2 values of WKY, 7.48±0.18; SHR, 7.43±0.13 and WKY, 7.57±0.24; SHR, 7.40±0.08, respectively. Zolertine was a non‐competitive antagonist in some blood vessels as Schild plot slopes were lower than unity. The pKb estimates for zolertine were WKY, 6.98±0.16; SHR, 6.81±0.18 in the mesenteric artery, WKY, 5.73±0.11; SHR, 5.87±0.25 in the caudal artery and 6.65±0.09 in rabbit aorta.  4 Competition binding experiments using the α1‐adrenoceptor antagonist [3H]prazosin showed a zolertine pKi of 6.81±0.02 in rat liver (α1B‐adrenoceptors) and 6.35±0.04 in rabbit liver (α1A‐adrenoceptors) membranes.  5 Zolertine showed higher affinity for α1D‐adrenoceptors compared to α1A‐adrenoceptors, while it had an intermediate affinity for α1B‐adrenoceptors. The ability of the α1‐adrenoceptor antagonist zolertine to block α1D‐adrenoceptor‐mediated constriction in different vessels of WKY and SHR rats may explain its antihypertensive efficacy despite its low order of potency.
Different sensitivity of isoprenaline‐induced responses in ventricular muscle to sodium nitroprusside in normotensive and spontaneously hypertensive rats 1
Authors: Manso A. M. , Encabo A. , Redondo J. , Salaices M. , Marín J.
Published: March 2003

1 The aim of the present work was to study the possible modulatory role of nitric oxide (NO) on the positive inotropic effect induced by the β‐adrenoceptor agonist isoprenaline in myocardial contractility, and whether this modulation is altered by hypertension.  2 The study was performed using right ventricular strips from the hearts of 6‐month‐old male Wistar–Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The contractile force of electrically‐stimulated ventricular strips was measured by a force‐displacement transducer.  3 Isoprenaline (from 10 nmol l−1 to 10 μmol l−1) induced a concentration‐dependent increase in cardiac contractility in strips from both rat strains. This positive inotropic effect to isoprenaline was reduced by the NO donor sodium nitroprusside (SNP, 0.1 mmol l−1) in muscles from WKY rats and slightly increased in those from SHR. The SNP‐induced increase in strips from SHR was abolished by superoxide dismutase (100 U ml−1).  4 NG‐nitro‐arginine‐methyl ester (L‐NAME, 0.1 mmol l−1) and 1H‐[1,2,4]oxadiazolo[4,3]quinoxalin‐1‐one (ODQ, 10 μmol l−1), respective inhibitors of NO synthase and guanylate cyclase, increased the response to isoprenaline in muscles from WKY rats, whereas it was unaltered in strips from SHR.  5 In strips from WKY rats, the combination of ODQ and SNP produced an increase in the response elicited by isoprenaline, which was similar to that observed with ODQ or L‐NAME. 8‐Br‐cyclicGMP (8‐Br‐cGMP, 0.1 mmol l−1), a permeable and structural cGMP analogue, decreased the effect induced by isoprenaline only in muscles from WKY rats.  6 These results suggest that the positive inotropic response to isoprenaline in ventricular strips from WKY rats is negatively modulated by NO, and positively by superoxide anions in those from SHR. The lack of a modulatory response to NO in ventricular strips from SHR is probably a result of an alteration of mechanisms in NO‐signalling pathway downstream of cGMP formation in SHR hearts.
Functional antagonism between nitric oxide and ATP in the motor responses of guinea‐pig ileum
Authors: Ivancheva Chr. , Itzev D. , Radomirov R.
Published: March 2003

1 The interaction of nitric oxide and ATP in the non‐adrenergic, non‐cholinergic (NANC) motor responses and the presence of NADPH‐diaphorase and quinacrine‐positive myenteric neurones were studied on guinea‐pig ileum using mechanographic, histochemical and quinacrine‐fluorescence techniques. In the presence of phentolamine, propranolol and atropine, the non‐precontracted longitudinally oriented organ bath preparations responded to sodium nitroprusside (1–100 μm) or ATP (5–50 μm) with tetrodotoxin (0.1 μm)‐resistant relaxation or contraction, respectively. The effects of ATP were suramin (50 μm)‐ and apamin (5 μm)‐sensitive.  2 The NANC motor responses elicited by electrical stimulation (0.8 ms, 1–20 Hz, 20 s) consisted of tetrodotoxin‐sensitive relaxation phase followed by a phase of twitch‐like and tonic contractions.  3 NG‐nitro‐L‐arginine (L‐NNA, 0.1–0.5 mm) inhibited or abolished the relaxation phase. L‐arginine (0.5 mm), but not D‐arginine (0.5 mm), restored the relaxation phase in L‐NNA‐pretreated preparations. The relaxation phase increased after ATP‐induced desensitization of purinoceptors and in the presence of suramin (50 μm) but was abolished by apamin (5 μm).  4 The phase of contractions was enhanced by L‐NNA (0.1–0.5 mm) and restored by L‐arginine (0.5 mm). The twitch‐like and tonic contractions were decreased during ATP‐induced purinoceptor desensitization and in the presence of suramin (50 μm). Apamin (5 μm) inhibited the tonic contractions.  5 The desensitization of purinoceptors by ATP did not change the L‐NNA‐induced inhibition of the relaxation phase but decreased the L‐NNA‐increased phase of contractions. L‐NNA reduced the relaxation phase and increased the phase of contractions during purinoceptor desensitization.  6 We conclude that in the longitudinal muscle layer of the guinea‐pig ileum, nitric oxide mediates the relaxation phase while ATP contributes via smooth muscle P2 purinoceptors to the phase of contractions suggesting a postjunctional functional antagonism between nitric oxide and ATP. The presence of NADPH‐diaphorase‐ and quinacrine‐positive neuronal cells and processes running to the muscle cells confirms a physiological role of nitric oxide and ATP in the ileal neurotransmission.