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1.
J R Soc Interface ; 21(219): 20240409, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39474790

RESUMO

In a chase-and-run dynamic, the interaction between two individuals is such that one moves towards the other (the chaser), while the other moves away (the runner). Examples can be found in both interacting cells and animals. Here, we investigate the behaviours that can emerge at a population level, for a heterogeneous group that contains subpopulations of chasers and runners. We show that a wide variety of patterns can form, from stationary patterns to oscillatory and population-level chase-and-run, where the latter describes a synchronized collective movement of the two populations. We investigate the conditions under which different behaviours arise, specifically focusing on the interaction ranges: the distances over which cells or organisms can sense one another's presence. We find that when the interaction range of the chaser is sufficiently larger than that of the runner-or when the interaction range of the chase is sufficiently larger than that of the run-population-level chase-and-run emerges in a robust manner. We discuss the results in the context of phenomena observed in cellular and ecological systems, with particular attention to the dynamics observed experimentally within populations of neural crest and placode cells.


Assuntos
Modelos Biológicos , Animais , Crista Neural , Dinâmica Populacional
2.
Int J Surg ; 2024 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-39041944

RESUMO

BACKGROUND: Biliary obstruction can be due to both malignant and benign pancreaticobiliary disease. Currently, there are no biomarkers that can accurately help make this distinction. MicroRNAs (miRNAs) are stable molecules in tissue and biofluids that are commonly deregulated in cancer. The MIRABILE study aimed to identify miRNAs in bile that can differentiate malignant from benign pancreaticobiliary disease. MATERIALS AND METHODS: There were 111 patients recruited prospectively at endoscopic retrograde cholangiopancreatography (ERCP) or percutaneous transhepatic cholangiography (PTC) for obstructive jaundice, and bile was aspirated for cell-free RNA (cfRNA) extraction and analysis. In a discovery cohort of 78 patients (27 with pancreatic ductal adenocarcinoma (PDAC), 14 cholangiocarcinoma (CCA), 37 benign disease), cfRNA was subjected to small-RNA sequencing. LASSO regression was used to define bile miRNA signatures, and NormFinder to identify endogenous controls. In a second cohort of 87 patients (34 PDAC, 14 CCA, 39 benign disease), RT-qPCR was used for validation. RESULTS: LASSO regression identified 14 differentially-expressed bile miRNAs of which 6 were selected for validation. When comparing malignant and benign pancreaticobiliary disease, bile miR-340 and miR-182 were validated and significantly differentially expressed (P<0.05 and P<0.001, respectively). This generated an AUC of 0.79 (95%CI 0.70-0.88, sensitivity 65%; specificity 82%) in predicting malignant disease. CONCLUSION: Bile collected during biliary drainage contains miRNAs able to differentiate benign from malignant pancreaticobiliary diseases in patients with obstructive jaundice. These bile miRNAs have the potential to increase diagnostic accuracy.

3.
Bull Math Biol ; 86(3): 28, 2024 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-38341397

RESUMO

Aggregations are emergent features common to many biological systems. Mathematical models to understand their emergence are consequently widespread, with the aggregation-diffusion equation being a prime example. Here we study the aggregation-diffusion equation with linear diffusion in one spatial dimension. This equation is known to support solutions that involve both single and multiple aggregations. However, numerical evidence suggests that the latter, which we term 'multi-peaked solutions' may often be long-transient solutions rather than asymptotic steady states. We develop a novel technique for distinguishing between long transients and asymptotic steady states via an energy minimisation approach. The technique involves first approximating our study equation using a limiting process and a moment closure procedure. We then analyse local minimum energy states of this approximate system, hypothesising that these will correspond to asymptotic patterns in the aggregation-diffusion equation. Finally, we verify our hypotheses through numerical investigation, showing that our approximate analytic technique gives good predictions as to whether a state is asymptotic or transient. Overall, we find that almost all twin-peaked, and by extension multi-peaked, solutions are transient, except for some very special cases. We demonstrate numerically that these transients can be arbitrarily long-lived, depending on the parameters of the system.


Assuntos
Conceitos Matemáticos , Modelos Biológicos , Difusão
4.
J Acquir Immune Defic Syndr ; 95(1): 97-106, 2024 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-37831608

RESUMO

INTRODUCTION: Because of improved life expectancy in people living with HIV (PLWH), liver disease is increasingly being recognized. We assessed nonviral chronic liver disease burden in PLWH. METHODS: The HIV non-virAL liver disease study (2014-2021) prospectively recruited PLWH with elevated serum alanine aminotransferase levels and negative hepatitis serology. Clinically significant hepatic fibrosis (CSHF) was defined as liver stiffness measurement of >7.1 kPa and hazardous alcohol use as Alcohol Use Disorders Identification Test score ≥ 8. Primary outcome was prevalence/predictors of CSHF. RESULTS: Total recruited were n = 274, 92% male, median age 52 (45-59) years, and 96% having undetectable HIV viral load. Overall, n = 97 (35%) had hazardous alcohol use, n = 72 (26%) had metabolic syndrome, and 17%-27% had exposure to hepatotoxic antiretrovirals. Prevalence of CSHF was 20% (n = 54), prevalence of cirrhosis (liver stiffness measurement > 12.5 kPa) being 7% (19/274). Risk factors for CSHF were hazardous alcohol use in 44% (n = 24), metabolic syndrome in 46% (n = 25), and hepatotoxic antiretrovirals in 56% (n = 30), most having more than one risk factor. Independent predictors of CSHF were serum high-density lipoprotein (odds ratio [OR] 0.220; 95% confidence interval [CI]: 0.061 to 0.790, P = 0.020) (inverse relationship); serum aspartate aminotransferase (OR 1.033, 95% CI: 1.001 to 1.067, P = 0.045), and didanosine use (OR 2.878, 95% CI: 1.228 to 6.774, P = 0.015). Moderate-severe hepatic steatosis was identified in 52% (n = 142). FIB-4 and aspartate aminotransferase-to-platelet ratio index performed poorly in predicting CSHF (positive predictive value 27.3% and 30.6%, respectively) and advanced fibrosis (≥F3) (positive predictive value 17.6% and 5.9%, respectively). CONCLUSION: In this study, 20% of PLWH had CSHF associated with high prevalence of hazardous alcohol use/metabolic syndrome/potentially hepatotoxic antiretrovirals. These potentially modifiable risk factors need addressing.


Assuntos
Alcoolismo , Técnicas de Imagem por Elasticidade , Infecções por HIV , Hepatopatias , Síndrome Metabólica , Masculino , Humanos , Pessoa de Meia-Idade , Feminino , Infecções por HIV/complicações , Infecções por HIV/tratamento farmacológico , Infecções por HIV/epidemiologia , Estudos Transversais , Síndrome Metabólica/complicações , Síndrome Metabólica/epidemiologia , Alcoolismo/complicações , Fígado/patologia , Hepatopatias/complicações , Hepatopatias/epidemiologia , Cirrose Hepática/complicações , Cirrose Hepática/epidemiologia , Fibrose , Antirretrovirais/uso terapêutico , Aspartato Aminotransferases , Técnicas de Imagem por Elasticidade/efeitos adversos
5.
J Anim Ecol ; 92(1): 16-29, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36321473

RESUMO

Uncovering the mechanisms behind animal space use patterns is of vital importance for predictive ecology, thus conservation and management of ecosystems. Movement is a core driver of those patterns so understanding how movement mechanisms give rise to space use patterns has become an increasingly active area of research. This study focuses on a particular strand of research in this area, based around step selection analysis (SSA). SSA is a popular way of inferring drivers of movement decisions, but, perhaps less well appreciated, it also parametrises a model of animal movement. Of key interest is that this model can be propagated forwards in time to predict the space use patterns over broader spatial and temporal scales than those that pertain to the proximate movement decisions of animals. Here, we provide a guide for understanding and using the various existing techniques for scaling up step selection models to predict broad-scale space use patterns. We give practical guidance on when to use which technique, as well as specific examples together with code in R and Python. By pulling together various disparate techniques into one place, and providing code and instructions in simple examples, we hope to highlight the importance of these techniques and make them accessible to a wider range of ecologists, ultimately helping expand the usefulness of SSA.


Assuntos
Ecologia , Ecossistema , Animais , Ecologia/métodos , Movimento
6.
J Math Biol ; 85(5): 56, 2022 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-36264394

RESUMO

Deriving emergent patterns from models of biological processes is a core concern of mathematical biology. In the context of partial differential equations, these emergent patterns sometimes appear as local minimisers of a corresponding energy functional. Here we give methods for determining the qualitative structure of local minimum energy states of a broad class of multi-species nonlocal advection-diffusion models, recently proposed for modelling the spatial structure of ecosystems. We show that when each pair of species respond to one another in a symmetric fashion (i.e. via mutual avoidance or mutual attraction, with equal strength), the system admits an energy functional that decreases in time and is bounded below. This suggests that the system will eventually reach a local minimum energy steady state, rather than fluctuating in perpetuity. We leverage this energy functional to develop tools, including a novel application of computational algebraic geometry, for making conjectures about the number and qualitative structure of local minimum energy solutions. These conjectures give a guide as to where to look for numerical steady state solutions, which we verify through numerical analysis. Our technique shows that even with two species, multi-stability with up to four classes of local minimum energy states can emerge. The associated dynamics include spatial sorting via aggregation and repulsion both within and between species. The emerging spatial patterns include a mixture of territory-like segregation as well as narrow spike-type solutions. Overall, our study reveals a general picture of rich multi-stability in systems of moving and interacting species.


Assuntos
Ecossistema , Difusão
7.
Therap Adv Gastroenterol ; 15: 17562848221122473, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36187366

RESUMO

Background: Fully covered intraductal self-expanding metal stents (IDSEMS) have been well described in the management of post-liver transplant (LT) anastomotic strictures (ASs). Their antimigration waists and intraductal nature make them suited for deployment across the biliary anastomosis. Objectives: We conducted a multicentre study to analyse their use and efficacy in the management of AS. Design: This was a retrospective, multicentre observational study across nine tertiary centres in the United Kingdom. Methods: Consecutive patients who underwent endoscopic retrograde cholangiopancreatography with IDSEMS insertion were analysed retrospectively. Recorded variables included patient demographics, procedural characteristics, response to therapy and follow-up data. Results: In all, 162 patients (100 males, 62%) underwent 176 episodes of IDSEMS insertion for AS. Aetiology of liver disease in this cohort included hepatocellular carcinoma (n = 35, 22%), followed by alcohol-related liver disease (n = 29, 18%), non-alcoholic steatohepatitis (n = 20, 12%), primary biliary cholangitis (n = 15, 9%), acute liver failure (n = 13, 8%), viral hepatitis (n = 13, 8%) and autoimmune hepatitis (n = 12, 7%). Early AS occurred in 25 (15%) cases, delayed in 32 (20%) cases and late in 95 (59%) cases. Age at transplant was 54 years (range, 12-74), and stent duration was 15 weeks (range, 3 days-78 weeks). In total, 131 (81%) had complete resolution of stricture at endoscopic re-evaluation. Stricture recurrence was observed in 13 (10%) cases, with a median of 19 weeks (range, 4-88 weeks) after stent removal. At removal, there were 21 (12%) adverse events, 5 (3%) episodes of cholangitis and 2 (1%) of pancreatitis. In 11 (6%) cases, the removal wires unravelled, and 3 (2%) stents migrated. All were removed endoscopically. Conclusion: IDSEMS appears to be safe and highly efficacious in the management of post-LT AS, with low rates of AS recurrence.

8.
iScience ; 25(9): 105008, 2022 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-36105597

RESUMO

Travel represents a major cost for many animals so there should be selection pressure for it to be efficient - at minimum cost. However, animals sometimes exceed minimum travel costs for reasons that must be correspondingly important. We use Dynamic Body Acceleration (DBA), an acceleration-based metric, as a proxy for movement-based power, in tandem with vertical velocity (rate of change in depth) in a shark (Rhincodon typus) to derive the minimum estimated power required to swim at defined vertical velocities. We show how subtraction of measured DBA from the estimated minimum power for any given vertical velocity provides a "proxy for power above minimum" metric (PPAmin), highlighting when these animals travel above minimum power. We suggest that the adoption of this metric across species has value in identifying where and when animals are subject to compelling conditions that lead them to deviate from ostensibly judicious energy expenditure.

9.
Ecol Lett ; 25(5): 1139-1151, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35235709

RESUMO

Life-history strategies differ with respect to investment in current versus 'future' reproduction, but when is this future? Under the novel 'temporality in reproductive investment hypothesis', we postulate variation should exist in the time frame over which reproductive costs are paid. Slow-paced individuals should pay reproductive costs over short (e.g. inter-annual) time scales to prevent reproductive costs accumulating, whereas fast-paced individuals should allow costs to accumulate (i.e. senescence). Using Fourier transforms, we quantify adjustments in clutch size with age, across four populations of blue tits (Cyanistes caeruleus). Fast populations had more prevalent and stronger long-term changes in reproductive investment, whereas slower populations had more prevalent short-term adjustments. Inter-annual environmental variation partly accounted for short-, but not long-term changes in reproductive investment. Our study reveals individuals differ in when they pay the cost of reproduction and that failure to partition this variation across different temporal scales and environments could underestimate reproductive trade-offs.


Assuntos
Características de História de Vida , Passeriformes , Animais , Tamanho da Ninhada , Humanos , Reprodução
10.
J Anim Ecol ; 91(5): 946-957, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35277858

RESUMO

The energetic gains from foraging and costs of movement are expected to be key drivers of animal decision-making, as their balance is a large determinant of body condition and survival. This fundamental perspective is often missing from habitat selection studies, which mainly describe correlations between space use and environmental features, rather than the mechanisms behind these correlations. To address this gap, we present a novel parameterisation of step selection functions (SSFs), that we term the energy selection function (ESF). In this model, the likelihood of an animal selecting a movement step depends directly on the corresponding energetic gains and costs, and we can therefore assess how moving animals choose habitat based on energetic considerations. The ESF retains the mathematical convenience and practicality of other SSFs and can be quickly fitted using standard software. In this article, we outline a workflow, from data gathering to statistical analysis, and use a case study of polar bears Ursus maritimus to demonstrate application of the model. We explain how defining gains and costs at the scale of the movement step allows us to include information about resource distribution, landscape resistance and movement patterns. We further demonstrate this process with a case study of polar bears and show how the parameters can be interpreted in terms of selection for energetic gains and against energetic costs. The ESF is a flexible framework that combines the energetic consequences of both movement and resource selection, thus incorporating a key mechanism into habitat selection analysis. Further, because it is based on familiar habitat selection models, the ESF is widely applicable to any study system where energetic gains and costs can be derived, and has immense potential for methodological extensions.


Assuntos
Ecossistema , Ursidae , Animais , Movimento
11.
Clin Transplant ; 36(10): e14614, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35143096

RESUMO

BACKGROUND: The optimal immunosuppression protocol to prevent early acute cellular rejection (ACR) after liver transplantation (LT) avoiding prolonged hospitalization and early hospital readmission is undefined. OBJECTIVES: To identify the most suitable immunosuppression regimen for inclusion in ERAS programs in order to minimize early ACR after LT and to provide expert panel recommendations DATA SOURCES: Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central. METHODS: Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel. Studies from January 2000 onward focusing on early ACR were included. Rates of early renal dysfunction and infection were evaluated. CRD42021245586 RESULTS: Thirty-seven studies met inclusion criteria; 23 randomized controlled trials, 14 retrospective or prospective observational comparative or noncomparative studies. Several sources of biases which potentially confound conclusions were identified: heterogeneity in immunosuppression protocols, higher serum tacrolimus levels than currently used in clinical practice, differences in the definition of ACR. CONCLUSIONS: Tacrolimus is the standard immunosuppression after LT and can be used in combination with other drugs such as corticosteroids and MMF, and in association with anti-IL2 receptor antibody (IL2Ra) induction. (Quality of Evidence; Low | Grade of Recommendation; Strong). Low dose or delayed introduction of tacrolimus in association with corticosteroids and MMF and/or anti-IL2Ra induction can be used to reduce acute kidney injury. (Quality of Evidence; Low | Grade of Recommendation; Strong). Use of tacrolimus in association with corticosteroids and MMF and/or anti-IL2Ra induction does not lead to increased infection rates. (Quality of Evidence; Low | Grade of Recommendation; Weak).


Assuntos
Transplante de Rim , Transplante de Fígado , Humanos , Ácido Micofenólico , Imunossupressores/uso terapêutico , Transplante de Rim/métodos , Transplante de Fígado/efeitos adversos , Estudos Retrospectivos , Tacrolimo/uso terapêutico , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controle , Corticosteroides , Estudos Observacionais como Assunto
12.
Frontline Gastroenterol ; 13(1): 57-63, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34970429

RESUMO

Liver transplant is a life-saving treatment with 1-year and 5-year survival rates of 90% and 70%, respectively. However, organ demand continues to exceed supply, such that many patients will die waiting for an available organ. This article reviews for the general gastroenterologist the latest developments in the field to reduce waiting list mortality and maximise utilisation of available organs. The main areas covered include legislative changes in organ donation and the new 'opt-out' systems being rolled out in the UK, normothermic machine perfusion to optimise marginal grafts, a new national allocation system to maximise benefit from each organ and developments in patient 'prehabilitation' before listing. Current areas of research interest, such as immunosuppression withdrawal, are also summarised.

13.
Ann Gastroenterol ; 34(6): 829-835, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34815649

RESUMO

BACKGROUND: COVID-19 pandemic is an unprecedented global medical emergency. National and international gastrointestinal societies recommended that any endoscopic activity during the lockdown phase of the pandemic should be limited to emergency or non-deferrable procedures only. We assessed the financial implications and impact on endoscopy activity of the lockdown phase in a tertiary referral endoscopy unit. METHODS: The number of endoscopy procedures canceled and performed in our endoscopy unit during our "delay phase" (16-22/03/2020) and "lockdown phase" (23/03-29/05/2020) was reviewed and compared with endoscopy activity conducted during the same period in 2019. The financial impact was subsequently analyzed. RESULTS: Between 16/03/2020 and 29/05/2020, 683 procedures were canceled and 365 non-deferrable procedures were performed. In contrast, in 2019, 3437 procedures were performed over the same timeframe, resulting in a revenue contraction of approximately €2,062,857. We estimated that the number of lists required to recuperate the canceled endoscopic activity, ranges from 103-155, depending on the level of personal protective equipment required and mitigating policy relating to COVID-19. CONCLUSION: Our results highlight that COVID-19 pandemic had a substantial negative impact on our endoscopy activity and on the revenue generated by our endoscopy unit.

14.
Gastrointest Endosc ; 94(6): 1059-1068, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34216597

RESUMO

BACKGROUND AND AIMS: Digital single-operator cholangioscopy (d-SOC) with cholangioscopic biopsy sampling has shown promise in the evaluation of indeterminate biliary strictures. Some studies have suggested higher sensitivity for visual impression compared with biopsy sampling, although assessors were not blinded to previous investigations. We aimed to investigate the diagnostic accuracy and interobserver agreement (IOA) of d-SOC in the visual appraisal of biliary strictures when blinded to additional information. METHODS: A multicenter, international cohort study was performed. Cholangioscopic videos in patients with a known final diagnosis were systematically scored. Pseudonymized videos were reviewed by 19 experts in 2 steps: blinded for patient history and investigations and unblinded. RESULTS: Forty-four high-quality videos were reviewed of 19 benign and 25 malignant strictures. The sensitivity and specificity for the diagnosis of malignancy was 74.2% and 46.9% (blinded) and 72.7% and 62.5% (unblinded). Cholangioscopic certainty of a malignant diagnosis led to overdiagnosis (sensitivity, 90.6%; specificity, 33%), especially if no additional information was provided. The IOA for the presence of malignancy was fair for both assessments (Fleiss' κ = .245 [blinded] and κ = .321 [unblended]). For individual visual features, the IOA ranged from slight to moderate for both assessments (κ = .059-.400 vs κ = .031-.452). CONCLUSIONS: This study showed low sensitivity and specificity for blinded and unblinded d-SOC video appraisal of indeterminate biliary strictures, with considerable interobserver variation. Although reaching a consensus on the optical features of biliary strictures remains important, optimizing visually directed biopsy sampling may be the most important role of cholangioscopy in biliary stricture assessment.


Assuntos
Endoscopia do Sistema Digestório , Sobrediagnóstico , Estudos de Coortes , Constrição Patológica/etiologia , Humanos , Variações Dependentes do Observador
15.
J Radiol Case Rep ; 15(2): 25-34, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33717408

RESUMO

Hemorrhagic cholecystitis is a potentially deadly and difficult to recognize entity. It is associated with cystic artery pseudoaneurysm and is usually seen in the setting of acute calculous cholecystitis. We report two cases of hemorrhagic cholecystitis with arteriographic findings of cystic artery pseudoaneurysms that were successfully embolized using microcoils, facilitating subsequent cholecystectomy. Both cases had unusual presentations of gallbladder rupture with hemoperitoneum, the latter of which was atypical occurring in the absence of gallstones. We believe when hemorrhagic cholecystitis is suspected, a two-step therapeutic approach should be employed with embolization of the bleeding cystic artery followed by cholecystectomy. A comprehensive literature review and discussion of hemorrhagic cholecystitis will be provided.


Assuntos
Colecistite Aguda/diagnóstico por imagem , Hemoperitônio/diagnóstico por imagem , Idoso , Angiografia , Colecistectomia , Colecistite Aguda/terapia , Embolização Terapêutica , Hemoperitônio/terapia , Humanos , Masculino
16.
Frontline Gastroenterol ; 12(1): 74-76, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33489071

RESUMO

A 60-year-old male liver transplant recipient presented to his local hospital with left-sided partial seizures following a few days of generalised headache. He had undergone transplantation for primary sclerosing cholangitis 4 years earlier and maintained on tacrolimus monotherapy immunosuppression. He had no other comorbidities of note and worked as an arable farmer. At last follow-up, he had been well with preserved graft function and afternoon trough tacrolimus levels of 2-4 ng/mL. Over the preceding 4 weeks, he had been investigated locally for weight loss and a productive cough, where CT of the chest showed calcified mediastinal and hilar lymphadenopathy. Bronchoscopy samples were negative for acid-fast bacilli and he had been empirically treated for assumed community acquired pneumonia. Initial seizure management was with intravenous diazepam and phenytoin. On transfer to our centre, he was noted to be dysarthric with persisting 4/5 left upper limb weakness and nystagmus to all extremes of gaze. Blood tests were significant for mild anaemia (haemoglobin 90 g/L) and elevated C reactive protein (134 mg/L). The peripheral white cell count was 6.6×109/L. Biochemical liver graft function was normal and the 8am trough tacrolimus level was low at 2 ng/mL. CT head revealed bilateral ring enhancing cerebral lesions with surrounding vasogenic oedema but no mass effect. On MRI these exhibited restricted diffusion and marked perilesional oedema, suggestive of infection. Cerebrospinal fluid (CSF) analysis was as follows: white cell count <1/mm3, protein 0.57 g/L (normal range <45 g/L) and glucose 3 mmol/L (paired plasma glucose 4.8 mmol/L). Testing for virological causes via PCR, toxoplasma serology and blood and CSF cultures, including for tuberculosis, were all negative. Whole body positron emission tomography-CT demonstrated uptake in numerous peritoneal and intramuscular lesions as well as right-sided cervical lymphadenopathy, which was sampled with fine needle aspiration. Microscopy revealed a filamentous, beading and branching Gram-positive bacillus that was partially acid-fast, subsequently speciated as Nocardia farcinica.

17.
J Anim Ecol ; 89(12): 2763-2776, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32779181

RESUMO

Home ranging is a near-ubiquitous phenomenon in the animal kingdom. Understanding the behavioural mechanisms that give rise to observed home range patterns is thus an important general question, and mechanistic home range analysis (MHRA) provides the tools to address it. However, such analysis has hitherto been principally restricted to scent-marking territorial animals, so its potential breadth of application has not been tested. Here, we apply MHRA to a population of long-tailed tits Aegithalos caudatus, a non-territorial passerine, in the non-breeding season where there is no clear 'central place' near which birds need to remain. The aim is to uncover the principal movement mechanisms underlying observed home range formation. Our foundational models consist of memory-mediated conspecific avoidance between flocks, combined with attraction to woodland. These are then modified to incorporate the effects of flock size and relatedness (i.e. kinship), to uncover the effect of these on the mechanisms of home range formation. We found that a simple model of spatial avoidance, together with attraction to the central parts of woodland areas, accurately captures long-tailed tit home range patterns. Refining these models further, we show that the magnitude of spatial avoidance by a flock is negatively correlated to both the relative size of the flock (compared to its neighbour) and the relatedness of the flock with its neighbour. Our study applies MHRA beyond the confines of scent-marking, territorial animals, so paves the way for much broader taxonomic application. These could potentially help uncover general properties underlying the emergence of animal space use patterns. This is also the first study to apply MHRA to questions of relatedness and flock size, thus broadening the potential possible applications of this suite of analytic techniques.


Assuntos
Comportamento de Retorno ao Território Vital , Passeriformes , Animais , Movimento , Feromônios , Territorialidade
18.
Ecol Evol ; 10(10): 4291-4302, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32489597

RESUMO

Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head-mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head "movement" is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing ("environmental framing").We propose a new approach to visualize the data of such head-mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by "longitude" position and head pitch by "latitude" on this "orientation sphere" (O-sphere).We construct the O-sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading-independent head rotation, and propose the derivation of O-sphere-metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.Visualizations of the O-sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free-ranging animals.

20.
J Anim Ecol ; 89(1): 186-206, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31424571

RESUMO

The paradigm-changing opportunities of biologging sensors for ecological research, especially movement ecology, are vast, but the crucial questions of how best to match the most appropriate sensors and sensor combinations to specific biological questions and how to analyse complex biologging data, are mostly ignored. Here, we fill this gap by reviewing how to optimize the use of biologging techniques to answer questions in movement ecology and synthesize this into an Integrated Biologging Framework (IBF). We highlight that multisensor approaches are a new frontier in biologging, while identifying current limitations and avenues for future development in sensor technology. We focus on the importance of efficient data exploration, and more advanced multidimensional visualization methods, combined with appropriate archiving and sharing approaches, to tackle the big data issues presented by biologging. We also discuss the challenges and opportunities in matching the peculiarities of specific sensor data to the statistical models used, highlighting at the same time the large advances which will be required in the latter to properly analyse biologging data. Taking advantage of the biologging revolution will require a large improvement in the theoretical and mathematical foundations of movement ecology, to include the rich set of high-frequency multivariate data, which greatly expand the fundamentally limited and coarse data that could be collected using location-only technology such as GPS. Equally important will be the establishment of multidisciplinary collaborations to catalyse the opportunities offered by current and future biologging technology. If this is achieved, clear potential exists for developing a vastly improved mechanistic understanding of animal movements and their roles in ecological processes and for building realistic predictive models.


Assuntos
Ecologia , Movimento , Animais
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