bluuebunny/crossref_metadata_2025_split huggingface dataset:
Understanding ecosystem dynamics for conservation of biota
Authors: SINCLAIR A. R. E. , BYROM ANDREA E. 
Published: February 2006

Summary Ecosystems have higher‐order emerging properties that can affect the conservation of species. We identify some of these properties in order to facilitate a better understanding of them. Nonlinear, indirect effects of food web interactions among species can produce counterintuitive changes in populations. Species differ in their roles and linkages with other species in the system. These roles are a property of the system. Such differences in roles influence how we conserve individual species. Ecosystems operate at a multitude of interacting spatial and temporal scales, which together structure the system and affect the dynamics of individual populations. Disturbance also structures an ecosystem, producing both long‐term slow changes and sudden shifts in ecosystem dynamics. Ecosystems therefore can have multiple states, determined both by disturbance regimes and biotic interactions. Conservation should recognize a possible multiplicity of natural states while avoiding aberrant (human‐induced) states. Ecosystem processes are influenced by the composition of the biota they contain. Disturbances to the biota can distort processes and functions, which in turn can endanger individual species. The goal of ecosystem conservation is the long‐term persistence of the biota in the system. There are two paradigms: community‐based conservation (CBC) and protected area conservation. Both have their advantages but neither is sufficient to protect the biota on its own. CBC is required to conserve the majority of the world's biota not included in protected areas. However, current CBC methods favour a few idiosyncratic species, distort the species complex, and ignore the majority. More comprehensive methods are required for this approach to meet the goal of ecosystem conservation. Protected areas are essential to conserve species unable to coexist with humans. They also function as ecological baselines to monitor the effects of humans on their own ecosystems. However, protected areas suffer from loss of habitat through attrition of critical areas. Thus, renewal (addition) of habitat is required in order to achieve the long‐term persistence of biota in functioning ecosystems. Identification of minimum habitat areas and restoration of ecosystems become two major priorities for future research.
Effects of predation and dispersal on Mastomys natalensis population dynamics in Tanzanian maize fields
Authors: VIBE‐PETERSEN SOLVEIG , LEIRS HERWIG , BRUYN LUC DE 
Published: February 2006

Summary

We investigate the effects of different levels of predation pressure and rodent dispersal on the population dynamics of the African pest rodent Mastomys natalensis in maize fields in Tanzania.
Three levels of predation risk were used in an experimental set‐up: natural level (control), excluding predators by nets and attracting avian predators by nest boxes and perch poles. Because dispersal of the rodents could mask the predation pressure treatment effects, control and predator exclusion treatments were repeated with enclosed rodent populations.
Population growth during the annual population rise period was faster in the absence of predators and peak population size was higher, but otherwise dynamics patterns were similar for populations where predators had access or were attracted, indicating that compensatory mechanisms operate when rodents are exposed to high levels of predation risk. Reducing dispersal of rodents removed the effect of predation on population growth and peak size, suggesting that local predators may play a role in driving rodent dispersal, but have otherwise little direct effect on population dynamics.
Species loss and secondary extinctions in simple and complex model communities
Authors: EKLÖF ANNA , EBENMAN BO 
Published: February 2006

Summary

The loss of a species from an ecological community can trigger a cascade of secondary extinctions. Here we investigate how the complexity (connectance) of model communities affects their response to species loss. Using dynamic analysis based on a global criterion of persistence (permanence) and topological analysis we investigate the extent of secondary extinctions following the loss of different kinds of species.
We show that complex communities are, on average, more resistant to species loss than simple communities: the number of secondary extinctions decreases with increasing connectance. However, complex communities are more vulnerable to loss of top predators than simple communities.
The loss of highly connected species (species with many links to other species) and species at low trophic levels triggers, on average, the largest number of secondary extinctions. The effect of the connectivity of a species is strongest in webs with low connectance.
Most secondary extinctions are due to direct bottom‐up effects: consumers go extinct when their resources are lost. Secondary extinctions due to trophic cascades and disruption of predator‐mediated coexistence also occur. Secondary extinctions due to disruption of predator‐mediated coexistence are more common in complex communities than in simple communities, while bottom‐up and top‐down extinction cascades are more common in simple communities.
Topological analysis of the response of communities to species loss always predicts a lower number of secondary extinctions than dynamic analysis, especially in food webs with high connectance.
Spatial aggregation and association in different resource‐patch distributions: experimental analysis withDrosophila
Authors: TAKAHASHI KAZUO H. 
Published: February 2006

Summary Laboratory experiments using homogeneous resources were conducted to examine intra‐ and interspecific spatial egg distribution ofD. simulans,D. aurariaandD. immigransin three different resource‐patch distribution patterns: patchy, even and clustered. Individuals of each species were introduced separately or simultaneously into the cage, into which artificial substrates were placed and allowed to oviposit for 24 h. Spatial analyses were performed with indices of intraspecific aggregation (J), interspecific association (C) andL‐function based on Ripley'sK‐function. Eggs were always spatially aggregated irrespective of species and the resource‐patch distribution patterns. Spatial egg aggregation was influenced significantly by the resource‐patch distribution pattern and tended to be weaker in the clustered resource‐patch distribution than in the patchy or even resource‐patch distribution. Spatial extent of egg aggregation was always beyond the single resource patch scale, indicating aggregation of ovipositing females. Interspecific association of egg distribution was absent or very weak. Thus, these results present experimental evidence of independent egg aggregation among drosophilids.
Animal movement rates as behavioural bouts
Authors: NAMS VILIS O. 
Published: February 2006

SummaryJohnson et al. (Journal of Animal Ecology, 2002, 71, 225–235) have proposed a new technique for identifying scales of movement in animals. Animals are located at certain time intervals, and movement rates between successive animal relocations are calculated. The null model of a nonscalar response predicts a decreasing linear relationship between log(frequency) vs. movement rate, while a scalar response predicts a monotonically decreasing curve with an inflection point at the separation between the processes. I tested this technique using three types of simulated movement paths: correlated random walks, directed walks, and movements in patchy habitat. None of the simulations showed the results expected by the technique. This occurs because the technique assumes that movement rates are exponentially distributed, which is highly unlikely. Thus before this technique can be applied to animal movement data we need to understand how spatial and temporal scale, as well as sampling interval, affect the frequency histogram of animal movement rates.
Vesicular Glutamate Transporter Expression in Supraoptic Neurones Suggests a Glutamatergic Phenotype
Authors: Ponzio T. A. , Ni Y. , Montana V. , Parpura V. , Hatton G. I. 
Published: February 2006

AbstractMagnocellular neuroendocrine cells of the supraoptic nucleus (SON) release the peptides oxytocin (OT) and vasopressin (VP) from their dendrites and terminals. In addition to peptide‐containing large dense‐core vesicles, axon terminals from these cells contain clear microvesicles that have been shown to contain glutamate. Using multilabelling confocal microscopy, we investigated the presence of vesicular glutamate transporters (VGLUTs) in astrocytes as well as VP and OT neurones of the SON. Simultaneous probing of the SON with antibodies against VGLUT isoforms 1–3, OT, VP and glial fibrillary acidic protein (GFAP) revealed the presence of VGLUT‐2 in somata and dendrites of SON neurones. Immunoreactivity (‐ir) for VGLUT‐3 was also detected in both OT and VP neurones as well as in GFAP‐ir astrocytes and other cells of the ventral glial lamina. Colocalisation of VGLUT‐2 and VGLUT‐3 in individual SON neurones was also examined and VGLUT‐ir with both antibodies could be detected in both types of SON neurones. Although VGLUT‐1‐ir was strong lateral to the SON, only sparse labelling was apparent within the nucleus, and no colocalisation with either SON neurones or astrocytes was observed. The SON or the SON plus its surrounding perinuclear zone was probed using the reverse transcriptase‐polymerase chain reaction and the presence of mRNA for all three VGLUT isoforms was detected. These results suggest that similar arrangements of transmitters exist in SON neuronal dendrites and their neurohypophysial terminals and that magnocellular neuroendocrine somata and dendrites may be capable of glutamatergic transmission.
Site of ATP and Phenylephrine Synergistic Stimulation of Vasopressin Release from the Hypothalamo‐Neurohypophyseal System
Authors: Song Z. , Sladek C. D. 
Published: February 2006

AbstractATP and norepinephrine are neurotransmitters carrying cardiovascular information to vasopressin (AVP) neurones. As shown previously, exposure of hypothalamo‐neurohypophyseal system explants to ATP and phenylephrine (PE) (α1‐adrenergic agonist) causes a significantly larger increase in AVP release than with either agent alone and converts the response from a transient to a sustained stimulation of AVP release. Potential mechanisms for this synergism include presynaptic stimulation of excitatory afferent input (i.e. glutamate release), postsynaptic activation of receptors on AVP neurones, modulation of stimulus‐secretion coupling in the neural lobe and/or involvement of glial/neuronal interactions. The response to ATP + PE (100 µM each) was not altered in the presence of either a cocktail of ionotropic glutamate receptor antagonists (CNQX + AP5) or a nonselective metabotropic glutamate receptor antagonist [(RS)‐α‐methyl‐4‐carboxyphenylglycine]. Thus, it is not dependent on activation of glutamate receptors. Treatment with tetrodotoxin (3 µM) eliminated the response to ATP + PE. Because this could reflect blockade of action potentials propagated from the AVP perikarya to the nerve terminals in the neural lobe or action potentials generated in the neural lobe directly, synergism in the neural lobe was addressed by perifusing isolated neural lobes with ATP and PE alone or together. Synergistic stimulation of AVP release by ATP + PE was not observed in isolated, perifused neural lobes. Thus, the synergistic effect persists in the absence of glutamate transmission, is not due to synergistic actions of P2 and α1‐adrenergic receptors occurring at the level of the neural lobe and requires action potentials in either the hypothalamus or neural lobe.
Editorial: Global elimination of lymphatic filariasis: fact or fantasy?
Authors: Gyapong John O. , Twum‐Danso Nana A.Y. 
Published: February 2006

SummaryIn 1997, the World Health Assembly resolved to eliminate lymphatic filariasis as a public health problem by the year 2020. By the end of 2004, almost half of the 83 endemic countries had initiated national programmes, providing mass drug administration to an at risk population of approximately 435 million. This remarkable achievement is the result of an enormous amount of technical, financial and political support from public and private sectors at the community, national, regional and global level. As the global programme to eliminate lymphatic filariasis enters its second quarter of operations, there are substantial opportunities to be taken and critical challenges to be addressed. These are the focus of this editorial.
Drug‐resistance of Trypanosoma b. rhodesiense isolates from Tanzania
Authors: Kibona S. N. , Matemba L. , Kaboya J. S , Lubega G. W. 
Published: February 2006

SummaryObjective  To determine the drug resistance of Trypanosoma brucei rhodesiense strains isolated from sleeping sickness patients in Tanzania.Method  We first screened 35 T. b. rhodesiense strains in the mouse model, for sensitivity to melarsoprol (1.8, 3.6 and 7.2 mg/kg), diminazene aceturate (3.5, 7 and 14 mg/kg), suramin (5, 10 and 20 mg/kg) and isometamidium (0.1, 1.0 and 2 mg/kg). A 13 isolates suspected to be resistant were selected for further testing in vitro and in vivo. From the in vitro testing, IC50 values were determined by short‐term viability assay, and MIC values were calculated by long‐term viability assay. For in vivo testing, doses higher than those in the initial screening test were used.Results  Two T. b rhodesiense stocks expressed resistance in vivo to melarsoprol at 5 mg/kg and at 10 mg/kg. These strains had high IC50 and MIC values consistent with those of the melarsoprol‐resistant reference strain. Another isolate relapsed after treatment with 5 mg/kg of melarsoprol although it did not appear resistant in vitro. One isolate was resistant to diminazene at 14 mg/kg and another was resistant at both 14 and 28 mg/kg of diminazene. These two isolates had high IC50 values consistent with the diminazene‐resistant reference strain. Two isolates relapsed at a dose of 5 mg/kg of suramin, although no isolate appeared resistant in the in vitro tests. Two isolates were resistant to isometamidium at 1.0 mg/kg and had higher IC50 values. Two isolates were cross‐resistant to melarsoprol and diminazene and one isolate was cross‐resistant to suramin and isometamidium.Conclusion  The reduced susceptibility of T. b. rhodesiense isolates to these drugs strongly indicates that drug resistance may be emerging in north–western Tanzania.
Financial implications of skilled attendance at delivery in Nepal
Authors: Borghi Josephine , Ensor Tim , Neupane Basu Dev , Tiwari Suresh 
Published: February 2006

SummaryObjective  To measure costs and willingness‐to‐pay for delivery care services in 8 districts of Nepal.Method  Household costs were used to estimate total resource requirements to finance: (1) the current pattern of service use; (2) all women to deliver in a health facility; (3) skilled attendance at home deliveries with timely referral of complicated cases to a facility offering comprehensive obstetric services.Results  The average cost to a household of a home delivery ranged from 410 RS ($5.43) (with a friend or relative attending) to 879 RS ($11.63) (with a health worker). At a facility the average fee for a normal delivery was 678 RS ($8.97). When additional charges, opportunity and transport costs were added, the total amount paid exceeded 5300 RS ($70). For a caesarean section the total household cost was more than 11 400 RS ($150). Based on these figures, the cost of financing current practice is 45 RS ($0.60) per capita. A policy of universal institutional delivery would cost 238 RS ($3.15) per capita while a policy of skilled attendance at home with early referral of cases from remote areas would cost around 117 RS ($1.55) per capita. These are significant sums in the context of a health budget of about 400 RS ($5) per capita.Conclusions  The financial cost of developing a skilled attendance strategy in Nepal is substantial. The mechanisms to direct funding to women in need must to be improved, pricing needs to be more transparent, and payment exemptions in public facilities must be better financed if we are to overcome both supply and demand‐side barriers to care seeking.
Determinants of skilled birth attendance in rural Cambodia
Authors: Yanagisawa Satoko , Oum Sophal , Wakai Susumu 
Published: February 2006

SummaryObjective  To identify the determinants of skilled and unskilled birth attendance.Method  Population‐based survey in a rural area in Cambodia, of women aged 15–49 years who had delivered during the previous 3‐month period. An analytical framework based on Andersen's behavioural model served to identify determinants according to delivery place (facility vs. non‐facility), birth attendant at home births (skilled vs. unskilled), and change of birth attendant during delivery (changed vs. unchanged). We used logistic regression to analyse the data.Results  Of 980 women included in the analyses, 19.8% had skilled attendants present during delivery. The determinants of facility delivery were different from those for having skilled attendants assisting in home births. In case of facility deliveries, previous contact with a skilled attendant through antenatal care was a significant determinant. In case of home births, the type of birth attendant (i.e. skilled or unskilled) at the preceding delivery was a significant determinant.Conclusion  Community‐based programmes need to reach primiparas, because once a woman has delivered with the aid of an unskilled attendant, she is five to seven times less likely to seek skilled help than a primipara.
Condom use after voluntary counselling and testing in Central Mozambique
Authors: Mola O. D. , Mercer M. A. , Asghar R. J. , Gimbel‐Sherr K. H. , Gimbel‐Sherr S. , Micek M. A. , Gloyd S. S. 
Published: February 2006

SummaryObjective To evaluate the efficacy of voluntary counselling and testing (VCT) for HIV/AIDS in changing risky sexual behaviour in central Mozambique.Method  Longitudinal cohort study of men and women aged at least 18 years from October 2002 to June 2003. We interviewed 622 participants in VCT groups and 598 in non‐VCT groups. The interviews occurred before counselling and 4 and 6 months afterwards.Results  Reported use of condoms while having sex with a friends/prostitute increased over each time period in the VCT group and between baseline and first visit in the non‐VCT group. Both men and women in the VCT group increased their condom use over time, but the women in the non‐VCT group did not. Reported always/sometimes use of condoms for both literate and illiterate subjects was higher and rose over time in the VCT group.Conclusion  People who undergo voluntary counselling and testing fro HIV/AIDS change their behaviour, presumably as a result of their counselling.
L'impact de la guerre sur l'evolution de la THA dans le centre‐ouest de la cote d'ivoire
Authors: Kaba D. , Dje N. N. , Courtin F. , Oke E. , Koffi M. , Garcia A. , Jamonneau V. , Solano P. 
Published: February 2006

Résumé Objectif  Evaluer la situation de la maladie du sommeil dans le centre‐ouest de la Côte d'Ivoire de 2000 à 2003, en tenant compte des évènements survenus depuis en septembre 2002.Méthodes  Enquête active réalisée par des équipes médicales et détection passive des cas.Résultats  Entre 2000 et 2003, 250 patients ont été diagnostiqués pour la maladie du sommeil. De prime abord la prévalence de la maladie du sommeil semblait avoir baissé depuis le début de la guerre. Mais cette baisse apparente était due à une faible couverture de la population. La participation dans l'enquête médicale était différente selon le groupe ethnique, reflétant les conflits entre les différentes communautés pour les terres. De tels conflits sont courants dans la zone mais ont été exacerbés par la guerre.Conclusion  L’évaluation de l'importance de la maladie du sommeil durant la guerre par enquête médicale seule est très difficile. Mais la détection de la maladie du sommeil par surveillance passive a augmenté.
Accessibility of diagnostic and treatment centres for visceral leishmaniasis in Gedaref State, northern Sudan
Authors: Gerstl S. , Amsalu R. , Ritmeijer K. 
Published: February 2006

SummaryObjective  To evaluate the accessibility of visceral leishmaniasis (VL) treatment.Method  Community‐based study using in‐depth qualitative interviews and focus group discussions with key informants, as well as quantitative questionnaires with 448 randomly selected heads of households in nine representative villages in three geographical sub‐regions.Results  Despite the high incidence of the disease, most people in Gedaref State know little about VL, and help at a treatment centre is usually sought only after traditional remedies and basic allopathic drugs have failed. Factors barring access to treatment are: lack of money for treatment and transport, impassability of roads, work priorities, severe cultural restrictions of women's decision‐making power and distance to the next health center.Conclusions  To provide more VL patients with access to treatment in this highly endemic area, diagnostic and treatment services should be decentralized. Health education would be a useful tool to rationalise people's health‐seeking behaviour.
Urban malaria in the Sahel: prevalence and seasonality of presumptive malaria and parasitaemia at primary care level in Chad
Authors: Othnigué Nadjitolnan , Wyss Kaspar , Tanner Marcel , Genton Blaise 
Published: February 2006

SummaryObjective To assess malaria prevalence rates and seasonal patterns among clinically diagnosed malaria cases at the level of primary care facilities in an urban Sahelian setting.Method Screening all patients consulting two private and two governmental providers on a randomly selected weekday over a period of 9 months. Patients with presumptive malaria underwent a blood test.Results Of 1658 patients included in the survey, 47% were clinically diagnosed and treated as malaria cases. Malaria was more often diagnosed by private providers. There were no clear seasonal patterns in presumptive malaria. A 30% of clinically diagnosed cases were positive for Plasmodium (all falciparum) by thick film examination. Thus, false positive cases constituted more than 70% of the clinically diagnosed malaria cases. The highest positive prevalence rates were found at the end and shortly after the rainy season (44%–47%) and the lowest during the dry season (2%).Conclusions Clinical diagnosis of malaria has a very low positive predicted value in this low endemicity urban setting, and its low specificity leads to inappropriate care for a large proportion of patients. This has a major impact on economic costs for health services and households. In the Sahel, systematic use of microscopy‐based diagnosis and/or rapid diagnostic tests should be considered to appropriately manage malaria and non‐malaria cases.