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1.
Anim Biotelemetry ; 10(1): 10, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-37521810

RESUMEN

Background: Recent developments in both hardware and software of animal-borne data loggers now enable large amounts of data to be collected on both animal movement and behaviour. In particular, the combined use of tri-axial accelerometers, tri-axial magnetometers and GPS loggers enables animal tracks to be elucidated using a procedure of 'dead-reckoning'. Although this approach was first suggested 30 years ago by Wilson et al. (1991), surprisingly few measurements have been made in free-ranging terrestrial animals. The current study examines movements, interactions with habitat features, and home-ranges calculated from just GPS data and also from dead-reckoned data in a model terrestrial mammal, the European badger (Meles meles). Methods: Research was undertaken in farmland in Northern Ireland. Two badgers (one male, one female) were live-trapped and fitted with a GPS logger, a tri-axial accelerometer, and a tri-axial magnetometer. Thereafter, the badgers' movement paths over 2 weeks were elucidated using just GPS data and GPS-enabled dead-reckoned data, respectively. Results: Badgers travelled further using data from dead-reckoned calculations than using the data from only GPS data. Whilst once-hourly GPS data could only be represented by straight-line movements between sequential points, the sub-second resolution dead-reckoned tracks were more tortuous. Although there were no differences in Minimum Convex Polygon determinations between GPS- and dead-reckoned data, Kernel Utilisation Distribution determinations of home-range size were larger using the former method. This was because dead-reckoned data more accurately described the particular parts of landscape constituting most-visited core areas, effectively narrowing the calculation of habitat use. Finally, the dead-reckoned data showed badgers spent more time near to field margins and hedges than simple GPS data would suggest. Conclusion: Significant differences emerge when analyses of habitat use and movements are compared between calculations made using just GPS data or GPS-enabled dead-reckoned data. In particular, use of dead-reckoned data showed that animals moved 2.2 times farther, had better-defined use of the habitat (revealing clear core areas), and made more use of certain habitats (field margins, hedges). Use of dead-reckoning to provide detailed accounts of animal movement and highlight the minutiae of interactions with the environment should be considered an important technique in the ecologist's toolkit.

2.
Sci Total Environ ; 762: 143087, 2021 Mar 25.
Artículo en Inglés | MEDLINE | ID: mdl-33131870

RESUMEN

Potentially Toxic Elements (PTEs) in Badgers (Meles meles), otherwise known as heavy metals, are unique amongst environmental pollutants occurring, both naturally and anthropogenically. PTEs have a broad range of negative health and environmental effects, therefore identifying their sources and pathways through the environment is imperative for public health policy. This is difficult in terrestrial systems due to the compositional nature of soil geochemistry. In this study, a compositional statistical approach was used to identify how PTEs accumulate in a terrestrial carnivorous mammal, Eurasian Badgers (Meles meles). Compositional principal component analysis (PCA) was used on geochemical data from the Tellus survey, the soil baseline and badger tissue data to map geo-spatial patterns of PTEs and show accumulative trends measured in time. Mapping PCs identified distinct regions of PTE presence in soil and PTE accumulation in badger tissues in Northern Ireland. PTEs were most elevated in liver, kidney and then muscle tissues. Liver and kidney showed the most distinct geo-spatial patterns of accumulation and muscle was the most depleted. PC1 and 2 for each type were modelled using generalised additive mixed models (GAMM) to identify trends through time. PC1 for the liver and muscle were associated with rainfall and ∂N15 in the liver, showing a link to diet and a bioaccumulation pathway, whilst PC2 for both tissues was associated with mean temperature, showing a link to seasonal activity and a bioaccessibility pathway. However, in kidney tissue these trends are reversed and PC1 was associated with bioaccessibility and PC2 with bioaccumulation. Combined these techniques can elucidate both geo-spatial trends in PTEs and the mechanisms by which they move in environment and in future may be an effective tool for assessing PTE bioavailability in environmental health surveys.


Asunto(s)
Metales Pesados , Mustelidae , Contaminantes del Suelo , Animales , Metales Pesados/análisis , Irlanda del Norte , Suelo , Contaminantes del Suelo/análisis
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 6086-6089, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-33019359

RESUMEN

Premature infants or neonates in need of advanced clinical care must be transported to specialized hospitals. Past studies have examined vibrations experienced by patients during transport; however, multiple confounding factors limit the utility of on-road data. Hence, the development of a standardized test environment is warranted. The overall purpose of this project is to characterize vibrations during neonatal patient transport and develop mitigation strategies to reduce exposure. This paper focusses on the development of a laboratory test environment and procedure that enables studying the equipment vibration in a comprehensive and repeatable manner. For the first time, a complete neonatal patient transport system, including a stretcher, has been mounted on an industrial shaker. Results largely validate the system's ability to simulate on-road vibrations with high repeatability.


Asunto(s)
Hospitales Especializados , Vibración , Humanos , Lactante , Recién Nacido
4.
Early Hum Dev ; 146: 105051, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32464450

RESUMEN

Interfacility transport to tertiary care for high-risk neonates has become an integral part of equitable access to optimal perinatal healthcare. Excellence in clinical care requires expertise in transport medicine and the coordination of safe transport processes. However, concerns remain regarding environmental stressors involved in the transportation of sick high-risk neonates, including noise and vibration. In order to mitigate the potential deleterious effects of these physical stressors during transport, further knowledge of the burden of exposure, injury mechanisms and engineering interventions/modifications as adjuncts during transport would be beneficial. We reviewed the current literature with a focus on the contribution of new and emerging technologies in the transport environment with particular reference to whole-body vibration. This review intends to highlight what is known about vibration as a physical stressor in neonates and areas for further research; with the goal to making recommendations for minimizing these stressors during transport.


Asunto(s)
Incubadoras para Lactantes , Transporte de Pacientes , Vibración/efectos adversos , Ambulancias , Diseño de Equipo , Humanos , Lactante , Recién Nacido , Recien Nacido Prematuro , Transporte de Pacientes/métodos
5.
Early Hum Dev ; 135: 6-10, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31177037

RESUMEN

Neonates exposed to intra-amniotic infection are at increased risk of early-onset sepsis. Administration of antibiotics to the mother may offer some protection, however a comprehensive description of the determinants influencing their transplacental passage and delivery to the fetus has not been performed. While penicillin G, ampicillin, cefazolin and gentamicin reach therapeutic levels in the fetal serum rapidly following maternal administration, the transfer of second-line intrapartum antimicrobials, such as vancomycin and clindamycin, is slower and less predictable. Erythromycin, used in the context of preterm premature rupture of the membranes, has suboptimal influx into the fetal compartment. This evidence is predominantly drawn from term pregnancies and situations of low infectious risk; however, prematurity may negatively influence fetal exposure to intrapartum antibiotics. Optimal fetal antimicrobial concentrations to target are poorly defined and the extent to which our review findings apply to preterm early-onset neonatal sepsis prevention is unclear. Interpretation of blood cultures drawn in neonates with expected circulating levels of maternal antimicrobials above the minimal inhibitory concentration for Group B Streptococcus is challenging despite the use of contemporary optimized blood culture media.


Asunto(s)
Antibacterianos/farmacocinética , Intercambio Materno-Fetal , Placenta/metabolismo , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Femenino , Feto/efectos de los fármacos , Humanos , Embarazo
6.
Conserv Biol ; 31(3): 513-523, 2017 06.
Artículo en Inglés | MEDLINE | ID: mdl-27783450

RESUMEN

In a world of shrinking habitats and increasing competition for natural resources, potentially dangerous predators bring the challenges of coexisting with wildlife sharply into focus. Through interdisciplinary collaboration among authors trained in the humanities, social sciences, and natural sciences, we reviewed current approaches to mitigating adverse human-predator encounters and devised a vision for future approaches to understanding and mitigating such encounters. Limitations to current approaches to mitigation include too much focus on negative impacts; oversimplified equating of levels of damage with levels of conflict; and unsuccessful technical fixes resulting from failure to engage locals, address hidden costs, or understand cultural (nonscientific) explanations of the causality of attacks. An emerging interdisciplinary literature suggests that to better frame and successfully mitigate negative human-predator relations conservation professionals need to consider dispensing with conflict as the dominant framework for thinking about human-predator encounters; work out what conflicts are really about (they may be human-human conflicts); unravel the historical contexts of particular conflicts; and explore different cultural ways of thinking about animals. The idea of cosmopolitan natures may help conservation professionals think more clearly about human-predator relations in both local and global context. These new perspectives for future research practice include a recommendation for focused interdisciplinary research and the use of new approaches, including human-animal geography, multispecies ethnography, and approaches from the environmental humanities notably environmental history. Managers should think carefully about how they engage with local cultural beliefs about wildlife, work with all parties to agree on what constitutes good evidence, develop processes and methods to mitigate conflicts, and decide how to monitor and evaluate these. Demand for immediate solutions that benefit both conservation and development favors dispute resolution and technical fixes, which obscures important underlying drivers of conflicts. If these drivers are not considered, well-intentioned efforts focused on human-wildlife conflicts will fail.


Asunto(s)
Animales Salvajes , Conservación de los Recursos Naturales , Ecosistema , Animales , Características Culturales , Humanos , Conducta Predatoria
7.
Ecology ; 95(4): 1033-44, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-24933821

RESUMEN

Environmental conditions and individual strategies in early life may have a profound effect on fitness. A critical moment in the life of an organism occurs when an individual reaches independence and stops receiving benefits from its relatives. Understanding the consequences of individual strategies at the time of independence requires quantification of their fitness effects. We explored this period in the Red Grouse (Lagopus lagopus scoticus). In this system, testosterone and parasite (Trichostrongylus tenuis) levels are known to influence survival and reproduction, the two key components of individual fitness. We experimentally and simultaneously manipulated testosterone and parasites at three levels (high, intermediate, and control levels for both factors) in 195 young males in five populations using a factorial experimental design. We explored the effects of our treatments on fitness by monitoring reproduction and survival throughout the life of all males and estimating lambda(ind), a rate-sensitive index of fitness. Parasite challenges increased the number of worms with a time lag, as previously found. However, we did not find significant effects of parasite manipulations on fitness, possibly because parasite abundance did not increase to harmful levels. Our hormone manipulation was successful at increasing testosterone at three different levels. Such increases in hormone levels decreased overall fitness. This was caused by reduced offspring production in the first breeding attempt rather than by any effect of the treatment on bird survival. Our results highlight that investing in high testosterone levels at independence, a strategy that might enhance short-term recruitment probability in territorial species such as Red Grouse, has a fitness cost, and can influence the resolution of the trade-off between reproduction and survival later in life.


Asunto(s)
Andrógenos/farmacología , Galliformes/fisiología , Testosterona/farmacología , Tricostrongiliasis/veterinaria , Andrógenos/administración & dosificación , Animales , Galliformes/genética , Aptitud Genética , Masculino , Testosterona/administración & dosificación , Tricostrongiliasis/patología , Trichostrongylus
8.
Horm Behav ; 65(5): 435-44, 2014 May.
Artículo en Inglés | MEDLINE | ID: mdl-24698833

RESUMEN

In a reliable signalling system, individual quality is expected to mediate the costs associated with ornamental displays, with relatively lower costs being paid by individuals of higher quality. These relative costs should depend not only on individual quality, but also on levels of intra-sexual competition. We explored the current and delayed effects that testosterone implants have on bird ornamentation in populations with contrasted population densities, as a proxy for intra-sexual competition. In a replicated experiment, we manipulated testosterone in 196 yearling male red grouse Lagopus lagopus scoticus in autumn in populations of high and low levels of intra-sexual competition. Males were assigned to one of three exogenous testosterone (T) treatments: empty implants (T0), small T implants (T1) or larger T implants (T2). We monitored subsequent changes in testosterone levels, ornament size and carotenoid-based colouration, carotenoid levels and body condition from autumn to spring. Testosterone implants increased testosterone levels, comb redness and comb size, and decreased body condition but these effects depended on levels of intra-sexual competition. Specifically, T2-implanted birds increased testosterone levels and comb size more, and reduced body condition more, in populations where intra-sexual competition was low. In the following spring, testosterone levels of T2-treated birds kept increasing in populations where intra-sexual competition was high but not in populations where intra-sexual competition was low. Our results highlight that levels of intra-sexual competition alter the relationship between testosterone levels and ornament expression, influencing their condition-dependence; they also indicate that the outcome of standard hormone manipulation conducted in free-living animals vary depending on the population context.


Asunto(s)
Conducta Competitiva/fisiología , Plumas/fisiología , Galliformes/fisiología , Conducta Sexual Animal/fisiología , Testosterona/farmacología , Animales , Carotenoides/metabolismo , Color , Cresta y Barbas/efectos de los fármacos , Cresta y Barbas/crecimiento & desarrollo , Cresta y Barbas/fisiología , Femenino , Galliformes/parasitología , Masculino , Nematodos , Parásitos , Estaciones del Año , Testosterona/administración & dosificación , Testosterona/sangre
9.
Parasite Immunol ; 36(6): 233-52, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24666543

RESUMEN

The host response to infection requires an immune response to be strong enough to control the pathogen but also restrained, to minimize immune-mediated pathology. The conflicting pressures of immune activation and immune suppression are particularly apparent in parasite infections, where co-evolution of host and pathogen has selected many different compromises between protection and pathology. Cytokine signals are critical determinants of both protective immunity and immunopathology, and, in this review, we focus on the regulatory cytokine IL-10 and its role in protozoan and helminth infections. We discuss the sources and targets of IL-10 during parasite infection, the signals that initiate and reinforce its action, and its impact on the invading parasite, on the host tissue, and on coincident immune responses.


Asunto(s)
Helmintiasis/inmunología , Interleucina-10/inmunología , Infecciones por Protozoos/inmunología , Animales , Citocinas/inmunología , Helmintiasis/parasitología , Interacciones Huésped-Parásitos , Humanos , Parásitos/clasificación , Parásitos/fisiología , Infecciones por Protozoos/parasitología
10.
Conserv Biol ; 27(5): 936-44, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23869557

RESUMEN

Conservation conflicts are increasing on a global scale and instruments for reconciling competing interests are urgently needed. Multicriteria decision analysis (MCDA) is a structured, decision-support process that can facilitate dialogue between groups with differing interests and incorporate human and environmental dimensions of conflict. MCDA is a structured and transparent method of breaking down complex problems and incorporating multiple objectives. The value of this process for addressing major challenges in conservation conflict management is that MCDA helps in setting realistic goals; entails a transparent decision-making process; and addresses mistrust, differing world views, cross-scale issues, patchy or contested information, and inflexible legislative tools. Overall we believe MCDA provides a valuable decision-support tool, particularly for increasing awareness of the effects of particular values and choices for working toward negotiated compromise, although an awareness of the effect of methodological choices and the limitations of the method is vital before applying it in conflict situations.


Asunto(s)
Conservación de los Recursos Naturales/métodos , Técnicas de Apoyo para la Decisión , Conflicto Psicológico , Humanos , Negociación/métodos , Confianza
11.
J Evol Biol ; 25(1): 20-8, 2012 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-22022806

RESUMEN

Numerous studies have shown positive associations between ornaments and condition, as predicted by indicator models of sexual selection. However, this idea is continuously challenged by opposite results, which reveal our lack of full understanding of how sexual selection works. Environmental heterogeneity may explain such inconsistencies, but valid field tests of this idea are currently lacking. We first analysed the relationship between condition and ornament expression from nine populations over 7 years in a wild bird, the red grouse Lagopus lagopus scoticus. We then manipulated male aggressiveness at the population level by means of testosterone implants in a replicated field experiment. We found that the relationship between condition and ornamentation varied greatly between environments and became stronger when environmental conditions (ECs) were worse or when aggressiveness in the population was experimentally increased. Some ornaments may therefore reliably advertise a better condition only in adverse ECs. Considering environmental heterogeneity can help reconcile conflicting findings regarding the reliability of ornaments as indicators of condition and will help our understanding of sexual selection processes.


Asunto(s)
Agresión/efectos de los fármacos , Galliformes , Interacción Gen-Ambiente , Aptitud Genética , Preferencia en el Apareamiento Animal , Caracteres Sexuales , Animales , Peso Corporal , Ambiente , Femenino , Galliformes/anatomía & histología , Galliformes/genética , Galliformes/fisiología , Modelos Lineales , Masculino , Modelos Biológicos , Tamaño de los Órganos , Distribución Aleatoria , Selección Genética , Testosterona/farmacología
12.
Biol Lett ; 7(3): 364-7, 2011 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-21247939

RESUMEN

In many species, females display brightly coloured and elaborate traits similar to those that males use in intra- and inter-sexual selection processes. These female characters are sometimes related to fitness, and might function as secondary sexual characteristics that have evolved through sexual selection. Here, we used descriptive data from 674 females in 10 populations and an experimental removal of Trichostrongylus tenuis parasites in four populations, to examine the effects of season, age, condition, and parasites on the size of supra-orbital combs displayed by female red grouse Lagopus lagopus scoticus. We found that comb size (i) was greater during the breeding than the non-breeding season, (ii) was greater in adult than in young females, (iii) was positively correlated with body condition, and (iv) negatively correlated with parasite abundance. Experimentally, we showed that comb size increased proportionally to the number of worms removed after parasite dosing. Our findings provide a better understanding of proximate mechanisms behind the expression of a male-like trait in females, and we discuss its possible function as a female ornament.


Asunto(s)
Cresta y Barbas/fisiología , Galliformes/fisiología , Interacciones Huésped-Parásitos , Estaciones del Año , Trichostrongylus/fisiología , Envejecimiento , Animales , Femenino , Galliformes/parasitología , Masculino
13.
Brain Inj ; 24(6): 802-11, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20455671

RESUMEN

PRIMARY OBJECTIVE: To investigate the attitudes of healthcare professionals towards individuals with traumatic brain injury (TBI) and their relationship to intended healthcare behaviour. RESEARCH DESIGN: An independent groups design utilized four independent variables; aetiology, group, blame and gender to explore attitudes towards survivors of brain injury. The dependent variables were measured using the Prejudicial Evaluation and Social Interaction Scale (PESIS) and Helping Behaviour Scale (HBS). METHODS AND PROCEDURES: A hypothetical vignette based methodology was used. Four hundred and sixty participants (131 trainee nurses, 94 qualified nurses, 174 trainee doctors, 61 qualified doctors) were randomly allocated to one of six possible conditions. MAIN OUTCOMES AND RESULTS: Regardless of aetiology, if an individual is to blame for their injury, qualified healthcare professionals have more prejudicial attitudes than those entering the profession. There is a significant negative relationship between prejudice and helping behaviour for qualified healthcare professionals. CONCLUSIONS: Increased prejudicial attitudes of qualified staff are related to a decrease in intended helping behaviour, which has the potential to impact negatively on an individual's recovery post-injury.


Asunto(s)
Actitud del Personal de Salud , Lesiones Encefálicas/psicología , Conducta de Ayuda , Prejuicio , Sobrevivientes/psicología , Adulto , Lesiones Encefálicas/etiología , Femenino , Humanos , Masculino , Relaciones Profesional-Paciente , Factores Sexuales , Encuestas y Cuestionarios
14.
Arch Clin Neuropsychol ; 22(5): 665-73, 2007 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-17540538

RESUMEN

The purpose of the present work was to investigate if a hierarchy of aetiology exists which would influence attitudes towards survivors of brain injury. An independent groups design utilised four independent variables; aetiology (measured at five levels: 'Road Traffic Accident' (RTA), 'Alcohol', 'Drug Use', 'Aneurysm' and 'Recreation'), blame (blame and no-blame), group (psychology students and members of the public) and gender to explore attitudes towards survivors of brain injury. The dependent variables were measured using the Prejudicial Evaluation Scale (PES) and Social Interaction Scale (SIS). Three hundred and twenty-five participants (173 students and 152 members of the public) were randomly allocated to 1 of 10 possible conditions. Among individuals who contributed to receiving their injury greater prejudice was displayed towards those in the 'Drugs' condition followed by 'Recreation', 'RTA', 'Alcohol' and 'Aneurysm'. Findings suggest that a hierarchy of aetiology exists, which results in prejudicial attitudes, and is influenced by issues of blame.


Asunto(s)
Lesiones Encefálicas/psicología , Conductas Relacionadas con la Salud , Prejuicio , Opinión Pública , Sobrevivientes/psicología , Accidentes de Tránsito/psicología , Adolescente , Adulto , Anciano , Intoxicación Alcohólica/psicología , Lesiones Encefálicas/etiología , Femenino , Humanos , Aneurisma Intracraneal/psicología , Masculino , Persona de Mediana Edad , Recreación , Trastornos Relacionados con Sustancias/psicología , Encuestas y Cuestionarios
15.
Brain Inj ; 18(9): 861-9, 2004 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-15223739

RESUMEN

PRIMARY OBJECTIVE: To investigate the public's attitudes towards survivors of brain injury in Northern Ireland. RESEARCH DESIGN: Four hypothetical vignettes were constructed to test how the acquisition of a brain injury impacted on people's attitudes. The stories of protagonists that they either acquired their injury through organic (e.g. haemorrhage) means or in some self-initiated (e.g. brawl) behaviour. The gender of the protagonists was varied to examine differences in attitudes to males and females. METHODS AND PROCEDURES: Adapted versions of the Prejudicial Evaluation Scale (PES) and Social Interaction Scale (SIS) were administered to 96 university students. MAIN OUTCOMES AND RESULTS: The data was analysed using three 2 x 2 between subjects ANOVAs and showed that there was no significant main effect of gender, a highly significant effect of injury on negative attitudes (F(1, 92) = 68.30, p < 0.001], amount of desired social interaction [F(1, 92) = 46.27, p < 0.001] and willingness to help [F(1, 92) = 44.66, p < 0.001]. CONCLUSION: The perception that an individual's behaviour contributed to their injury may lead to stigmatization and its negative consequences.


Asunto(s)
Actitud Frente a la Salud , Lesiones Encefálicas/psicología , Opinión Pública , Adolescente , Adulto , Lesiones Encefálicas/etiología , Hemorragia Cerebral/complicaciones , Femenino , Humanos , Relaciones Interpersonales , Masculino , Estudios Prospectivos , Apoyo Social , Estereotipo
16.
J Helminthol ; 78(1): 69-76, 2004 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-14972040

RESUMEN

The reliability of different egg counting methods for estimating the intensity of Trichostrongylus tenuis infections in red grouse, Lagopus lagopus scoticus, was investigated in the autumn, when grouse may harbour high parasite intensities. Possible limitations to the use of these methods were also examined. Faecal egg counts were found to accurately estimate T. tenuis worm intensities, at least up to an observed maximum of c. 8000 worms. Two egg counting methods (smear and McMaster) gave consistent results, although the exact relationship with worm intensity differed according to the method used. Faecal egg counts significantly decreased with increasing length of sample storage time, but egg counts were reliable for estimating worm intensity for three weeks. The concentration of eggs in the caecum was also found to reliably estimate worm intensity. However, egg counts from frozen gut samples cannot be used to estimate worm intensities. These results conclude that, despite some limitations, faecal and caecum egg counts provide useful and reliable ways of measuring T. tenuis intensities in red grouse.


Asunto(s)
Enfermedades de las Aves/parasitología , Heces/parasitología , Parasitosis Intestinales/veterinaria , Tricostrongiliasis/veterinaria , Trichostrongylus , Animales , Ciego/parasitología , Congelación , Estilo de Vida , Recuento de Huevos de Parásitos , Factores de Tiempo , Conservación de Tejido
17.
Nature ; 421(6924): 737-9, 2003 Feb 13.
Artículo en Inglés | MEDLINE | ID: mdl-12610624

RESUMEN

A central issue in ecology lies in identifying the importance of resources, natural enemies and behaviour in the regulation of animal populations. Much of the debate on this subject has focused on animals that show cyclic fluctuations in abundance. However, there is still disagreement about the role of extrinsic (food, parasites or predators) and intrinsic (behaviour) factors in causing cycles. Recent studies have examined the impact of natural enemies, although spatial patterns resulting from restricted dispersal or recruitment are increasingly recognized as having the potential to influence unstable population dynamics. We tested the hypothesis that population cycles in a territorial bird, red grouse Lagopus lagopus scoticus, are caused by delayed density-dependent changes in the aggressiveness and spacing behaviour of males. Here we show that increasing aggressiveness experimentally for a short period in autumn reduced recruitment and subsequent breeding density by 50%, and changed population trajectories from increasing to declining. Intrinsic processes can therefore have fundamental effects on population dynamics.


Asunto(s)
Agresión , Aves/fisiología , Territorialidad , Envejecimiento , Animales , Perros , Masculino , Densidad de Población , Dinámica Poblacional , Reproducción , Estaciones del Año , Testosterona/análisis
18.
Annu Rev Microbiol ; 55: 531-60, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11544366

RESUMEN

The dynamics of the relationship between the immune system and latent viruses are highly complex. Latent viruses not only avoid elimination by the host's primary immune response, they also remain with the host for life in the presence of strong acquired immunity, often exhibiting periodic reactivation and recurrence from the latent state. The continual battle between reemergent infectious virus and immunological memory cells provides an essential virus-host regulatory loop in latency. In this review, we speculate on the critical importance of immune interference mechanisms by viruses contributing to the regulatory loop in viral homeostasis of latency. Central to the notion of viral homeostasis, we further invoke the concept of threshold limits in naive and memory states of immunity to account for the failure of the host to completely eradicate these intracellular parasites.


Asunto(s)
Latencia del Virus/inmunología , Fenómenos Fisiológicos de los Virus , VIH/fisiología , Inmunidad Celular , Inmunidad Innata , Memoria Inmunológica
19.
Trends Microbiol ; 9(2): 86-92, 2001 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-11173248

RESUMEN

Macrophages play a central role in infections, as a target for pathogens and in activation of the immune system. Interleukin-10 (IL-10), a cytokine produced by macrophages, is a potent immunosuppressive factor. Some intracellular pathogens specifically target macrophages for infection and use IL-10 to dampen the host immune response and stall their elimination from the host. Certain viruses induce production of cellular IL-10 by macrophages, whereas other viruses encode their own viral IL-10 homologs. Additionally, specific bacteria, including several Mycobacteria spp. and Listeria monocytogenes, can survive and replicate in macrophages while inducing cellular IL-10, highlighting a potential role for IL-10 of macrophage origin in the immunosuppressive etiology of these pathogens. Thus, the exploitation of IL-10 appears to be a common mechanism of immunosuppression by a diverse group of intracellular pathogens that can infect macrophages.


Asunto(s)
Citomegalovirus/inmunología , VIH-1/inmunología , Tolerancia Inmunológica , Interleucina-10/biosíntesis , Macrófagos/microbiología , Macrófagos/virología , Mycobacterium tuberculosis/inmunología , Infecciones por Citomegalovirus/inmunología , Infecciones por Citomegalovirus/virología , Infecciones por VIH/inmunología , Humanos , Interleucina-10/inmunología , Macrófagos/inmunología , Tuberculosis/inmunología , Tuberculosis/microbiología
20.
Immunol Res ; 21(2-3): 225-31, 2000.
Artículo en Inglés | MEDLINE | ID: mdl-10852121

RESUMEN

The kinetics of the interaction between T cell receptor (TCR) and major histocompatibility complex (MHC) has an important role in determining thymocyte-positive and -negative selection in the thymus, as well as in T cell activation. The alpha chain of the TCR is the major player in determining how the TCR fits onto the MHC ligand, and thus has a major role in determining whether a T cell develops as class I or class II restricted. In this article, we summarize recent data from our laboratory and others on the role of polymorphism in the Valpha combining site in determining MHC class restriction, and on kinetic parameters in thymocyte selection.


Asunto(s)
Complejo Mayor de Histocompatibilidad/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/inmunología , Linfocitos T/inmunología , Animales , Humanos , Cinética , Activación de Linfocitos , Complejo Mayor de Histocompatibilidad/genética , Polimorfismo Genético , Receptores de Antígenos de Linfocitos T alfa-beta/genética
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