Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 36
Filtrar
1.
J Dairy Sci ; 106(4): 2498-2509, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36797180

RESUMO

Precision livestock farming (PLF) technologies have been widely promoted as important tools to improve the sustainability of dairy systems due to perceived economic, social, and environmental benefits. However, there is still limited information about the level of adoption of PLF technologies (percentage of farms with a PLF technology) and the factors (farm and farmer characteristics) associated with PLF technology adoption in pasture-based dairy systems. The current research aimed to address this knowledge gap by using a representative survey of Irish pasture-based dairy farms from 2018. First, we established the levels of adoption of 9 PLF technologies (individual cow activity sensors, rising plate meters, automatic washers, automatic cluster removers, automatic calf feeders, automatic parlor feeders, automatic drafting gates, milk meters, and a grassland management decision-support tool) and grouped them into 4 PLF technology clusters according to the level of association with each other and the area of dairy farm management in which they are used. The PLF technology clusters were reproductive management technologies, grass management technologies, milking management technologies, and calf management technologies. Additionally, we classified farms into 3 categories of intensity of technology adoption based on the number of PLF technologies they have adopted (nonadoption, low intensity of adoption, and high intensity of adoption). Second, we determined the factors associated with the intensity of technology adoption and with the adoption of the PLF technology clusters. A multinomial logistic regression model and 4 logistic regressions were used to determine the factors associated with intensity of adoption (low and high intensity of adoption compared with nonadoption) and with the adoption of the 4 PLF technology clusters, respectively. Adoption levels varied depending on PLF technology, with the most adopted PLF technologies being those related to the milking process (e.g., automatic parlor feeders and milk meters). The results of the multinomial logistic regression suggest that herd size, proportion of hired labor, agricultural education, and discussion group membership were positively associated with a high intensity of adoption, whereas age of farmer and number of household members were negatively associated with high intensity of adoption. However, when analyzing PLF technology clusters, the magnitude and direction of the influence of the factors in technology adoption varied depending on the PLF technology cluster being investigated. By identifying the PLF technologies in which pasture-based dairy farmers are investing more and by detecting potential drivers and barriers for the adoption of PLF technologies, the current study could allow PLF technology companies, practitioners, and researchers to develop and target strategies that improve future adoption of PLF technologies in pasture-based dairy settings.


Assuntos
Indústria de Laticínios , Gado , Feminino , Bovinos , Animais , Fazendas , Indústria de Laticínios/métodos , Agricultura , Tecnologia , Leite
2.
Ir J Psychol Med ; : 1-7, 2022 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-35357295

RESUMO

OBJECTIVES: Infant mental health (IMH), an area which focuses on the social and emotional development of infants in the context of the parent-infant relationship, has become an increasingly prominent field of both research and clinical practice worldwide. IMH network groups are initiatives which aim to facilitate continuous learning in the IMH approach, provide an opportunity for case discussion and encourage reflective practice. This study aimed to explore the experiences of staff working within an adult mental health (AMH) service and their participation in a perinatal IMH network group (PIMH-NG). METHODS: This study had a qualitative research design and the data were collected using a focus group methodology. Participants were recruited from a PIMH-NG which aimed to provide staff working within an AMH setting with the opportunity for continuous development of IMH knowledge. The data were analysed using thematic analysis. RESULTS: The data gathered from the focus group indicated that staff participating in a PIMH-NG enhanced their clinical skill, reflective practice and supported the dissemination of IMH knowledge throughout their respective teams. The PIMH-NG facilitated this work by providing the opportunity for continuous learning, reflective group discussion and ongoing peer support. CONCLUSIONS: The findings of this study indicate that incorporating elements of an IMH model into AMH services can be beneficial for staff, service users and overall service delivery and development. These findings may be used to develop the structure and content of future network groups of this nature.

3.
J Dairy Sci ; 103(5): 3895-3911, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32113761

RESUMO

Locomotion scoring is time consuming and is not commonly completed on farms. Farmers also underestimate their herds' lameness prevalence, a knowledge gap that impedes lameness management. Automation of lameness detection could address this knowledge gap and facilitate improved lameness management. The literature pertinent to adding lameness detection to accelerometers is reviewed in this paper. Options for lameness detection systems are examined including the choice of sensor, raw data collected, variables extracted, and statistical classification methods used. Two categories of variables derived from accelerometer-based systems are examined. These categories are behavior measures such as lying and measures of gait. For example, one measure of gait is the time a leg is swinging during a gait cycle. Some behavior-focused studies have reported accuracy levels of greater than 80%. Cow gait measures have been investigated to a lesser extent than behavior. However, classification accuracies as high as 91% using gait measures have been reported with hardware likely to be practical for commercial farms. The need for even higher accuracy and potential barriers to adoption are discussed. Significant progress is still required to realize a system with sufficient specificity and sensitivity. Lameness detection systems using 1 accelerometer per cow and a resolution lower than 100 Hz with gait measurement functions are suggested to balance cost and data requirements. However, gait measurement using accelerometers is rather underdeveloped. Therefore, a high priority should be given to the development of novel gait measures and testing their ability to differentiate lame from nonlame cows.


Assuntos
Acelerometria/veterinária , Doenças dos Bovinos/diagnóstico , Indústria de Laticínios , Coxeadura Animal/diagnóstico , Animais , Comportamento Animal , Bovinos , Indústria de Laticínios/métodos
4.
Animal ; 12(s2): s262-s271, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30345940

RESUMO

Precision technologies and data have had relatively modest impacts in grass-based livestock ruminant production systems compared with other agricultural sectors such as arable. Precision technologies promise increased efficiency, reduced environmental impact, improved animal health, welfare and product quality. The benefits of precision technologies have, however, been relatively slow to be realised on pasture based farms. Though there is significant overlap with indoor systems, implementing technology in grass-based dairying brings unique opportunities and challenges. The large areas animals roam and graze in pasture based systems and the associated connectivity challenges may, in part at least, explain the comparatively lower adoption of such technologies in pasture based systems. With the exception of sensor and Bluetooth-enabled plate metres, there are thus few technologies designed specifically to increase pasture utilisation. Terrestrial and satellite-based spectral analysis of pasture biomass and quality is still in the development phase. One of the key drivers of efficiency in pasture based systems has thus only been marginally impacted by precision technologies. In contrast, technological development in the area of fertility and heat detection has been significant and offers significant potential value to dairy farmers, including those in pasture based systems. A past review of sensors in health management for dairy farms concluded that although the collection of accurate data was generally achieved, the processing, integration and presentation of the resulting information and decision-support applications were inadequate. These technologies' value to farming systems is thus unclear. As a result, it is not certain that farm management is being sufficiently improved to justify widespread adoption of precision technologies currently. We argue for a user need-driven development of technologies and for a focus on how outputs arising from precision technologies and associated decision support applications are delivered to users to maximise their value. Further cost/benefit analysis is required to determine the efficacy of investing in specific precision technologies, potentially taking account of several yet to ascertained farm specific variables.


Assuntos
Bem-Estar do Animal , Indústria de Laticínios/economia , Meio Ambiente , Poaceae , Ruminantes/fisiologia , Agricultura , Animais , Análise Custo-Benefício , Coleta de Dados , Fazendas , Feminino , Gado
5.
J Dairy Sci ; 101(12): 11275-11284, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30268625

RESUMO

The way in which farm managers' attitudes, personality, behavior, values, and sociodemographic characteristics influence farm business performance is, at best, only partially understood. The study reported here expands on this understanding by analyzing the attitudes and personal attributes of 80 dairy farmers in Great Britain in relation to the profitability over 3 yr of their farm businesses. Business goals, temperament, purchasing behavior, and having a growth mindset toward the business were found to be associated with profitability. A linear regression model consisting of 5 variables related to the above was presented that predicts 34% of the observed variation in profitability. Each of these variables were questions related to the participants' personal attitudes or beliefs. Other assessed variables, such as specific husbandry behaviors or practices, or management practices and sociodemographic characteristics, did not warrant inclusion in the final model. These results uniquely contribute to understanding how the attitudes, personality, behaviors, and attributes of dairy farmers are associated with, and thus likely to influence, the profitability of their farm businesses.


Assuntos
Atitude , Comportamento , Indústria de Laticínios/economia , Fazendeiros/psicologia , Animais , Comércio , Indústria de Laticínios/métodos , Fazendas , Feminino , Renda/estatística & dados numéricos , Modelos Lineares , Registros , Temperamento , Reino Unido
6.
Diabetes Res Clin Pract ; 110(3): 241-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26520567

RESUMO

AIMS: The prevalence of type 2 diabetes and pre-diabetes has increased rapidly in recent decades and this trend will continue as the global population ages. This study investigates the prevalence of, and factors associated with, diagnosed and undiagnosed type 2 diabetes mellitus and pre-diabetes in older adults in Ireland. METHODS: Cross-sectional data from 5377 men and women aged 50 and over from Wave 1 of the Irish Longitudinal Study on Ageing (TILDA) was analysed. Diagnosed diabetes was defined using self-reported doctors' diagnosis and medications data. Glycated haemoglobin (HbA1c) analysis was used to identify undiagnosed and pre-diabetes. Age and sex-specific prevalence estimates were generated. Logistic regression was used to investigate the association between diabetes classification and the demographic, health and lifestyle characteristics of the population. RESULTS: The prevalence of diagnosed and undiagnosed type 2 diabetes was 8.6% (95% confidence interval (CI): 7.6-9.5%) and 0.9% (95% CI: 0.6-1.1%) respectively. Diabetes was more prevalent in men than women and increased with age. The prevalence of pre-diabetes was 5.5% (95% CI: 4.8-6.3%) and increased with age. Diabetes and pre-diabetes were independently associated with male sex, central obesity and a history of hypertension, while undiagnosed diabetes was associated with geographic location and medical costs cover. CONCLUSION: Despite high rates of obesity and other undiagnosed health conditions, the prevalence of undiagnosed and pre-diabetes is relatively low in community-dwelling older adults in Ireland. Addressing lifestyle factors in this population may help to further reduce the prevalence of pre-diabetes and improve outcomes for those with a previous diagnosis.


Assuntos
Diabetes Mellitus Tipo 2/epidemiologia , Hemoglobinas Glicadas/análise , Estado Pré-Diabético/epidemiologia , Idoso , Envelhecimento , Estudos Transversais , Diabetes Mellitus Tipo 2/diagnóstico , Feminino , Humanos , Hipertensão/complicações , Irlanda/epidemiologia , Estilo de Vida , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Obesidade/complicações , Estado Pré-Diabético/diagnóstico , Prevalência
7.
Ir J Med Sci ; 182(1): 107-12, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22843427

RESUMO

BACKGROUND: Co-morbid conditions (CMCs) are present in over half of patients with cancer over 50 years of age. As life-limiting illnesses progress, the benefits and burdens of treatments for CMCs become unclear. Relevant issues include physiological changes in advanced illness, time-to-benefit of medications, burden of medications, and psychological impact of discontinuing medications. Optimal prescribing is unclear due to lack of evidence. OBJECTIVES: The objectives are to determine prescribing practice, for CMCs, in a single SPC service. METHODS: Patients referred to a single specialist palliative care (SPC) service, who died between 1/8/2010 and 30/9/2012, were identified. Medical notes were reviewed, and data collected on prescribing at 3 months, 1 month, and 1 week prior to death. RESULTS: Fifty-two patients with a median age of 74.5 years were identified; 41 patients (79%) had a malignant condition. 50% died in hospital. Patients had a mean of three CMCs. A mean of 4.6 medications for CMCs were prescribed to patients over 65. A mean of 10 medications in total were prescribed at 1 week before death. One week before death, one-third of patients continued to be prescribed aspirin, and over one-quarter a statin. CONCLUSIONS: Total medication burden increases as time to death shortens, due to continuation of medications for CMCs, and addition of medications for symptom control. There is a need for research to demonstrate the impact of polypharmacy at the end of life, in order to formulate a framework to guide practice.


Assuntos
Neoplasias/tratamento farmacológico , Polimedicação , Doença Pulmonar Obstrutiva Crônica/tratamento farmacológico , Acidente Vascular Cerebral/tratamento farmacológico , Assistência Terminal , Idoso , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/epidemiologia , Comorbidade , Feminino , Humanos , Prescrição Inadequada , Falência Renal Crônica/tratamento farmacológico , Falência Renal Crônica/epidemiologia , Masculino , Pessoa de Meia-Idade , Neoplasias/epidemiologia , Doenças Vasculares Periféricas/tratamento farmacológico , Doenças Vasculares Periféricas/epidemiologia , Doença Pulmonar Obstrutiva Crônica/epidemiologia , Acidente Vascular Cerebral/epidemiologia
8.
Eye (Lond) ; 26(12): 1554-62, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23079756

RESUMO

PURPOSE: To examine the rates of retinal nerve fibre layer thickness (RNFLT) change in glaucoma patients and healthy, age-similar control subjects with three techniques: scanning laser polarimetry with variable corneal compensation (VCC) and enhanced corneal compensation (ECC), and time-domain optical coherence tomography (OCT). METHODS: Sixty-one patients and thirty-three controls were examined with each technique and with standard automated perimetry (SAP) every 6 months. Rates of global RNFLT change and SAP mean deviation (MD) change were estimated with linear mixed-effects models. RESULTS: The median (interquartile range) baseline age was 64.4 (58.2, 71.0) years for patients and 62.4 (56.3, 70.1) years for controls (P=0.56). There was a median of seven examinations over 3.1 years for patients and six examinations in 3.0 years for controls. Baseline visual field MD and RNFLT for all imaging modalities were significantly lower (P<0.01) in patients compared with controls. Rates of RNFLT change were not significantly different between patients and controls (P≥0.19). Mean rates of VCC-measured RNFLT change were -0.18 and -0.37 µm per year in patients and controls, whereas the respective figures for ECC and OCT were -0.13 and -0.31 µm per year, and 0.04 and 0.61 µm per year. Mean rates of MD change were -0.20 and 0.03 dB per year in patients and controls, respectively (P=0.01). CONCLUSION: Rates of RNFLT change in glaucoma patients were not statistically different from control subjects for any modality. A significantly negative rate of MD change in patients suggests a genuine, continued deterioration in these patients not reflected by RNFLT changes.


Assuntos
Glaucoma de Ângulo Aberto/patologia , Pressão Intraocular , Fibras Nervosas/patologia , Células Ganglionares da Retina/patologia , Campos Visuais , Idoso , Feminino , Seguimentos , Glaucoma de Ângulo Aberto/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Disco Óptico/patologia , Estudos Prospectivos , Reprodutibilidade dos Testes , Polarimetria de Varredura a Laser , Índice de Gravidade de Doença , Tomografia de Coerência Óptica/métodos , Testes de Campo Visual
9.
J Appl Microbiol ; 111(4): 787-99, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21777355

RESUMO

Marine ecosystems are home to bacteria which are exposed to a wide variety of environmental conditions, such as extremes in temperature, salinity, nutrient availability and pressure. Survival under these conditions must have necessitated the adaptation and the development of unique cellular biochemistry and metabolism by these microbes. Thus, enzymes isolated from these microbes have the potential to possess quite unique physiological and biochemical properties. This review outlines a number of function-based metagenomic approaches which are available to screen metagenomic libraries constructed from marine ecosystems to facilitate the exploitation of some of these potentially novel biocatalysts. Functional screens to isolate novel cellulases, lipases and esterases, proteases, laccases, oxidoreductases and biosurfactants are described, together with approaches which can be employed to help overcome some of the typical problems encountered with functional metagenomic-based screens.


Assuntos
Bactérias/enzimologia , Biotecnologia , Enzimas/isolamento & purificação , Metagenômica/métodos , Água do Mar/química , Tensoativos/isolamento & purificação , Bactérias/genética , Biblioteca Genômica , Microbiologia Industrial , Água do Mar/microbiologia
10.
J Biomed Mater Res B Appl Biomater ; 95(1): 141-9, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20737556

RESUMO

A series of doped apatites have been deposited onto titanium (V) substrates using a novel ambient temperature blasting process. The potential of these deposited doped apatites as non-colonizing osteoconductive coatings has been evaluated in vitro. XPS, EDX, and gravimetric analysis demonstrated that a high degree of coating incorporation was observed for each material. The modified surfaces were found to produce osteoblast proliferation comparable to, or better than, a hydroxyapatite finish. Promising levels of initial microbial inhibition were observed from the Sr- and Ag-doped surfaces, with the strontium showing prolonged ability to reduce bacteria numbers over a 30-day period. Ion elution profiles have been characterized and linked to the microbial response and based on the results obtained, mechanisms of kill have been suggested. In this study, the direct contact of coated substrate surfaces with microbes was observed to be a significant contributing factor to the antimicrobial performance and the anticolonizing activity. The silver substituted apatite was observed to out-perform both the SrA and ZnA in terms of biofilm inhibition.


Assuntos
Antibacterianos/química , Apatitas/química , Apatitas/farmacologia , Materiais Revestidos Biocompatíveis/química , Osteoblastos/citologia , Osteogênese/efeitos dos fármacos , Titânio/química , Bactérias/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Linhagem Celular , Proliferação de Células , Materiais Revestidos Biocompatíveis/farmacologia , Humanos , Prata/farmacologia , Estrôncio/farmacologia , Propriedades de Superfície , Zinco/farmacologia
11.
Ir Med J ; 101(8): 245-7, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18990955

RESUMO

To evaluate the relationship between serum CA125 tumour marker level before and after surgery of epithelial ovarian carcinoma and assess its potential role as a prognostic factor. A retrospective review of 87 patients with epithelial ovarian carcinoma at a single centre between January 2001 and December 2005 was performed. Serum CA125 levels were assessed for their relationship to pathological stage, tumour grade, tumour volume and age as well as overall survival. A total of 75 patients, mean age 58.94 years and median follow-up of 24 months were included in the analysis. While the preoperative CA125 level did not correlate significantly with stage, tumour grade or survival, the postoperative CA125 correlated to FIGO stage (p<0.0001), tumour grade (p<0.0001) and overall survival (p=0.01). Reduced survival was noted with increasing age at the time of surgery (p=0.009) and bulk of the residual disease postoperatively (p=0.011).


Assuntos
Biomarcadores Tumorais/sangue , Antígeno Ca-125/sangue , Neoplasias Epiteliais e Glandulares/epidemiologia , Neoplasias Ovarianas/epidemiologia , Feminino , Humanos , Irlanda/epidemiologia , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Neoplasias Epiteliais e Glandulares/imunologia , Neoplasias Epiteliais e Glandulares/mortalidade , Neoplasias Epiteliais e Glandulares/patologia , Neoplasias Ovarianas/imunologia , Neoplasias Ovarianas/mortalidade , Neoplasias Ovarianas/patologia , Estudos Retrospectivos , Análise de Sobrevida , Resultado do Tratamento
13.
Acta Crystallogr A ; 61(Pt 3): 321-4, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-15846035

RESUMO

In a conventional transmission electron microscope, stigmators are used to correct for the effects of axial astigmatism in the diffraction lens. It seems feasible that these same stigmators could also be used to form a series of 'astigmatic' diffraction patterns. It is shown how this series of diffraction patterns could then be used to perform exit-surface wavefunction reconstruction. This has the advantage that the diffraction patterns are not resolution limited by the objective aperture as are images when performing exit-surface wavefunction reconstruction from a focal series. A scheme for carrying out phase reconstruction from a series of astigmatic diffraction patterns in an electron microscope is presented.

14.
Acta Crystallogr A ; 61(Pt 2): 252-9, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15724076

RESUMO

The ability to determine the structure of a sample at atomic resolution is crucial for the development of nanotechnology and materials science. Consequently, structure retrieval must become a quantitative rather than a qualitative exercise. A method to retrieve the projected potential of a crystalline sample by inversion from an exit-surface wavefunction in high-resolution electron microscopy is proposed. This method accounts for both multiple scattering and absorption.

15.
Phys Rev Lett ; 93(23): 233902, 2004 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-15601161

RESUMO

It is commonly understood that the retrieval of a complex-valued object from its diffraction pattern using a support constraint is a difficult problem, the more so if the support is symmetric. In this Letter we show that, for just such a symmetric support, use of an iterative algorithm in which the basic iteration is specified by a difference map converges routinely. All that is required is sufficient oversampling in the diffraction pattern coupled with judicious choices of the parameters defining the difference map.

16.
FEMS Microbiol Lett ; 239(2): 285-93, 2004 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-15476978

RESUMO

A novel indole dioxygenase (idoA) gene has been cloned from Pseudomonas alcaligenes PA-10, based on its ability to convert indole to indigo. The chromosomally encoded idoA gene exhibits no similarity to previously cloned naphthalene dioxygenases or to aromatic oxygenases from other species at the nucleotide level. Phylogenetic analysis indicates that the idoA gene product is most similar to an acyl-CoA dehydrogenase from Novosphingobium aromaticivorans. The enzyme encoded by the idoA gene is essential for the metabolism of fluoranthene, since a mutant in which the idoA gene has been disrupted looses the ability to degrade this compound. The idoA gene appears to be constitutively expressed in PA-10, but its expression is also subject to regulation following prior exposure to salicylate and to fluoranthene degradative intermediates.


Assuntos
Fluorenos/metabolismo , Genes Bacterianos/fisiologia , Indóis/metabolismo , Pseudomonas alcaligenes/genética , Clonagem Molecular , Dioxigenases/metabolismo , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Índigo Carmim , Filogenia , Pseudomonas alcaligenes/metabolismo
17.
J Microsc ; 216(Pt 1): 70-5, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15369486

RESUMO

In a recent work we presented an iterative wave function reconstruction (IWFR) method that reconstructs a wave function from measurements of its amplitude taken as it propagates in free space (a focal series of images). Although the ideal environment for application of the IWFR method is in a coherent imaging system, it has been developed so that it can be applied in a partially coherent imaging system, in particular for a high-resolution transmission electron microscope using a field-emission gun. In this paper we investigate the effects of partial coherence on the accuracy of results obtained using the IWFR method. We then show how results obtained under such conditions can be improved by estimating and subtracting components from the amplitude measurements of the wave function that derive from incoherence in the electron beam.

18.
Ultramicroscopy ; 100(1-2): 91-104, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15219694

RESUMO

An iterative method for exit wave function reconstruction based on wave function propagation in free space is presented. The method, which has the potential for application to many forms of microscopy, has been tailored to work with a through focal series of images measured in a high-resolution transmission electron microscope. Practical difficulties for exit wave reconstruction which are pertinent in this experimental environment are the slight incoherence of the electron beam, sample drift and its effect upon the defocus step size that can be utilised, and the number of image measurements that need to be made. To gauge the effectiveness of the method it is applied to experimental data that has been analysed previously using a maximum likelihood formalism (the MAL method).


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Microscopia Eletrônica , Modelos Teóricos , Cristalografia , Microscopia de Contraste de Fase/métodos , Nanotecnologia
20.
Dev Comp Immunol ; 23(4-5): 401-20, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10426431

RESUMO

In recent years, a 'new' pathway for complement activation mediated by the mannose-binding lectin (MBL) has been described as a key mechanism for the mammalian acute phase response to infection. This complement activation pathway is initiated by a non-self recognition step: the binding of a humoral C-type lectin [mannose-binding lectin (MBL)] to microbial surfaces bearing 'foreign' carbohydrate determinants. The recognition factor, MBL, is associated with a serine protease [MBL-associated serine protease (MASP)] which, upon MBL binding to the microbial ligand, activates the complement component C3, leading to either (a) phagocytosis of the opsonized target via the complement receptor, or (b) humoral cell killing via assembly of the membrane attack complex. Galectins (formerly known as S-type lectins) modulate activity of the complement receptor 3 (CR3), the macrophage membrane receptor for complement components C3b and iC3b, downstream products of the MBL pathway which are covalently bound to 'target cells. Galectins also mediate macrophage- and dendrocyte-adhesion to lymphocytes activated by signaling through another C-type lectin, the L-selectin, leading to immunoglobulin-mediated responses. Thus, the functional interplay of MBL, galectins and L-selectin in the acute phase response neutralizes the microbial challenge, and lead to further adaptive immunity. Although the observation of various components of the lectin pathway in different invertebrate species demonstrates the high conservation and ancient roots of the components of innate immunity, there has previously been no evidence supporting the possibility that the integral lectin-mediated complement activation pathway is present in invertebrates. We now have evidence for the coexistence of homologs of all the pathway's key components (MBL, MASP, C3, and galectin) in the protochordate Clavelina picta, suggesting the lectin-mediated pathway of complement activation preceded the immunoglobulin pathway in evolution. Therefore, despite being 'new' to the textbooks, experimental evidence indicates that this pathway is ancient, and has been conserved intact throughout its evolution.


Assuntos
Proteínas de Transporte/imunologia , Ativação do Complemento/imunologia , Hemaglutininas/imunologia , Lectinas Tipo C , Lectinas de Plantas , Sequência de Aminoácidos , Animais , Proteínas de Transporte/química , Colectinas , Ativação do Complemento/efeitos dos fármacos , Complemento C3b/metabolismo , Complemento C3c/química , Galectinas , Hemaglutininas/química , Humanos , Selectina L/imunologia , Lectinas/imunologia , Dados de Sequência Molecular , Receptores de Complemento 3d/metabolismo , Alinhamento de Sequência , Serina Endopeptidases/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA