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1.
J Acoust Soc Am ; 155(1): 145-155, 2024 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-38180155

RESUMO

The call characteristics and vocal behaviour of sei whales (Balaenoptera borealis) off eastern Canada, including potential spatiotemporal variation, is poorly understood. Such information can improve the performance of automated detector-classifiers, enhancing the accuracy and efficiency of identifying sei whales in large acoustic datasets. Ultimately, these data can be used to understand the occurrence, distribution, and population structure of sei whales in Atlantic Canada. We measured sei whale downsweep characteristics recorded from six locations off Nova Scotia (NS) and Newfoundland and Labrador (NFLD), Canada over a two-year period (2015-2017), and examined variation between call subtypes (singlets, doublets, triplets+), and seasons (Spring, Summer, Fall, Winter). We found that downsweeps had a mean duration of 1.58 s, sweeping from 75.66 to 34.22 Hz, with a peak frequency of 43.89 Hz and an intra-call interval of 2.22 s. Most call characteristics did not vary between location, subtype, or season; however, significantly longer downsweeps occurred off NS, within doublet calls, and in fall months. We also found that NFLD had a higher proportion of doublets (70%) than NS (52%). This variation may be evidence of acoustically diverging sei whale populations, as well as useful for improving detector-classifiers of sei whales in the region.


Assuntos
Acústica , Balaenoptera , Animais , Canadá , Citoesqueleto , Estações do Ano
2.
Gen Comp Endocrinol ; 311: 113834, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34181934

RESUMO

Anthropogenic noise is increasing in intensity and scope, resulting in changes to acoustic landscapes and largely negative effects on a range of species. In birds, noise can mask acoustic signals used in a variety of communication systems, including parent-offspring communication. As a result, nestling birds raised in noise may have challenges soliciting food from parents and avoiding detection by predators. Given that passerine nestlings are confined to a nest and therefore cannot escape these challenges, noise may also act as a chronic stressor during their development. Here, we raised Tree Swallow (Tachycineta bicolor) nestlings with or without continuous, white noise to test whether noise exposure affected baseline and stress-induced plasma, integrated feather corticosterone levels, and immune function. Stress physiology and immune function may also vary with the competitive environment during development, so we also examined whether noise effects varied with brood size and nestling mass. We found that overall, exposure to noise did not alter nestling stress physiology or immune function. However, light nestlings raised in noise exhibited lower baseline plasma and integrated feather corticosterone than heavy nestlings, suggesting alternative physiological responses to anthropogenic stimuli. Furthermore, light nestlings in larger broods had reduced PHA-induced immune responses compared to heavy nestlings, and PHA-induced immune responses were associated with higher levels of baseline plasma and feather CORT. Overall, our findings suggest that noise can alter the stress physiology of developing birds; however, these effects may depend on developmental conditions and the presence of other environmental stressors, such as competition for resources. Our findings may help to explain why populations are not uniformly affected by noise.


Assuntos
Andorinhas , Animais , Corticosterona , Plumas , Comportamento de Nidação/fisiologia , Ruído/efeitos adversos , Andorinhas/fisiologia
3.
Proc Biol Sci ; 286(1894): 20181916, 2019 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-30963870

RESUMO

Latitudinal differences in timing of breeding are well documented but how such differences carry over to influence timing of events in the annual cycle of migratory birds is not well understood. We examined geographical variation in timing of events throughout the year using light-level geolocator tracking data from 133 migratory tree swallows ( Tachycineta bicolor) originating from 12 North American breeding populations. A swallow's breeding latitude influenced timing of breeding, which then carried over to affect breeding ground departure. This resulted in subsequent effects on the arrival and departure schedules at autumn stopover locations and timing of arrival at non-breeding locations. This 'domino effect' between timing events was no longer apparent by the time individuals departed for spring migration. Our range-wide analysis demonstrates the lasting impact breeding latitude can have on migration schedules but also highlights how such timing relationships can reset when individuals reside at non-breeding sites for extended periods of time.


Assuntos
Distribuição Animal , Migração Animal , Andorinhas/fisiologia , Animais , Canadá , Geografia , Reprodução , Estações do Ano , Estados Unidos
4.
Nano Lett ; 17(1): 21-27, 2017 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-28073255

RESUMO

Understanding the mechanism and limits of strain transfer between supported 2D systems and their substrate is a most needed step toward the development of strain engineering at the nanoscale. This includes applications in straintronics, nanoelectromechanical devices, or new nanocomposites. Here, we have studied the limits of biaxial compressive strain transfer among SiO2, diamond, and sapphire substrates and graphene. Using high pressure-which allows maximizing the adhesion between graphene and the substrate on which it is deposited-we show that the relevant parameter governing the graphene mechanical response is not the applied pressure but rather the strain that is transmitted from the substrate. Under these experimental conditions, we also show the existence of a critical biaxial stress beyond which strain transfer become partial and introduce a parameter, α, to characterize strain transfer efficiency. The critical stress and α appear to be dependent on the nature of the substrate. Under ideal biaxial strain transfer conditions, the phonon Raman G-band dependence with strain appears to be linear with a slope of -60 ± 3 cm-1/% down to biaxial strains of -0.9%. This evolution appears to be general for both biaxial compression and tension for different experimental setups, at least in the biaxial strain range -0.9% < ε < 1.8%, thus providing a criterion to validate total biaxial strain transfer hypotheses. These results invite us to cast a new look at mechanical strain experiments on deposited graphene as well as to other 2D layered materials.

5.
Ecotoxicology ; 26(1): 97-103, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27888383

RESUMO

Mercury (Hg) is a ubiquitous heavy metal that occurs naturally in the environment, but its levels have been supplemented for decades by a variety of human activities. Mercury can have serious deleterious effects on a variety of organisms, with top predators being particularly susceptible because methylmercury bioaccumulates and biomagnifies in food webs. Among birds, seabirds can have especially high levels of Hg contamination and Leach's storm-petrels (Oceanodroma leucorhoa), in particular, have amongst the highest known levels. Several populations of Leach's storm-petrels have declined recently in the Northwest Atlantic. The causes of these declines remain uncertain, but the toxic effects of Hg could be a potential factor in this decline. Here, we tested for relationships between adult blood total Hg (THg) concentration and several offspring development parameters, and adult return rate of Leach's storm-petrels breeding on Bon Portage Island (43° 28' N, 65° 44' W), Nova Scotia, Canada, between 2011 and 2015 (blood samples n = 20, 36, 6, 15, and 13 for each year, respectively). Overall, THg levels were elevated (0.78 ± 0.43 µg/g wet wt.) compared to other species of seabirds in this region, and varied significantly among years. However, we found no associations between THg levels and reproductive parameters or adult return rate. Our results indicate that levels of mercury observed in Leach's storm-petrel blood, although elevated, appear not to adversely affect their offspring development or adult return rate on Bon Portage Island.


Assuntos
Aves/fisiologia , Monitoramento Ambiental , Poluentes Ambientais/sangue , Mercúrio/sangue , Reprodução/efeitos dos fármacos , Animais , Aves/sangue , Canadá
8.
Breast Cancer Res Treat ; 131(1): 169-76, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21822637

RESUMO

Hispanics are more likely to be diagnosed with breast cancer at a younger age, with more advanced stage at diagnosis, hormone receptor-negative tumors, and worse prognosis than non-Hispanic whites (NHW). Little is known regarding the association between behavioral risk factors and breast tumor characteristics and whether these associations vary by race/ethnicity. We evaluated the association between several behavioral risk factors and tumor phenotype in a population-based study of Hispanics and NHWs. Participants are cases (846 Hispanic and 1,625 NHW women) diagnosed with breast cancer between 1999 and 2004 in Arizona, Colorado, New Mexico, or Utah. The association between breast cancer characteristics and obesity, physical activity, smoking, alcohol intake, and reproductive factors was examined. Logistic regression was used to compute the ethnic-specific odds ratios for the association between these risk factors and estrogen receptor (ER) status, tumor size, and histologic grade. Hispanics had more ER-negative tumors (28 vs. 20%), tumors >2 cm (39 vs. 27%), and poorly differentiated tumors (84 vs. 77%) than NHW. Among premenopausal women, obesity was associated with more ER-negative cancers among NHW [OR = 2.47 (95% CI: 1.08, 5.67)] but less ER-negative cancers among Hispanics [OR = 0.29 (0.13, 0.66)]. Obesity was associated with larger tumors among NHW [OR = 1.58 (1.09, 2.29)], but not among Hispanics. Never using mammography was associated with larger tumors in both ethnic groups. Moderate alcohol drinking and moderate and vigorous physical activity were weakly associated with smaller tumors in both ethnic groups. Our findings suggest that the association of obesity and other behavioral risk factors with breast cancer characteristics differ by ethnicity. We observed a divergent pattern between Hispanic and NHW cases in the association between obesity and ER status and tumor size. These observations suggest that a complex set of metabolic and hormonal factors related to estrogen and insulin pathways influence tumor characteristics.


Assuntos
Neoplasias da Mama/diagnóstico , Neoplasias da Mama/patologia , Hispânico ou Latino , Adulto , Idoso , Idoso de 80 Anos ou mais , Consumo de Bebidas Alcoólicas , Neoplasias da Mama/metabolismo , Feminino , Humanos , Menopausa , Pessoa de Meia-Idade , Atividade Motora , Obesidade , Aceitação pelo Paciente de Cuidados de Saúde , Receptor ErbB-2/metabolismo , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/metabolismo , Fatores de Risco , Sobreviventes , População Branca
9.
Biol Lett ; 8(4): 530-2, 2012 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-22357939

RESUMO

Ambient noise can mask acoustic cues, making their detection and discrimination difficult for receivers. This can result in two types of error: missed detections, when receivers fail to respond to the appropriate cues, and false alarms, when they respond to inappropriate cues. Nestling birds are error-prone, sometimes failing to beg when parents arrive with food (committing missed detections) or begging in response to stimuli other than a parent's arrival (committing false alarms). Here, we ask whether the frequency of these errors by nestling tree swallows (Tachycineta bicolor) increases in the presence of noise. We found that nestlings exposed to noise had more missed detections than their unexposed counterparts. We also found that false alarms remained low overall and did not differ significantly between noise and quiet treatments. Our results suggest that nestlings living in noisy environments may be less responsive to their parents than nestlings in quieter environments.


Assuntos
Comunicação Animal , Comportamento Alimentar/psicologia , Ruído , Andorinhas/fisiologia , Animais , Percepção Auditiva , Sinais (Psicologia) , Discriminação Psicológica/fisiologia , Comportamento de Nidação
10.
Proc Natl Acad Sci U S A ; 106(38): 16517-22, 2009 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-19666501

RESUMO

Millions afflicted with Chagas disease and other disorders of aberrant glycosylation suffer symptoms consistent with altered electrical signaling such as arrhythmias, decreased neuronal conduction velocity, and hyporeflexia. Cardiac, neuronal, and muscle electrical signaling is controlled and modulated by changes in voltage-gated ion channel activity that occur through physiological and pathological processes such as development, epilepsy, and cardiomyopathy. Glycans attached to ion channels alter channel activity through isoform-specific mechanisms. Here we show that regulated and aberrant glycosylation modulate cardiac ion channel activity and electrical signaling through a cell-specific mechanism. Data show that nearly half of 239 glycosylation-associated genes (glycogenes) were significantly differentially expressed among neonatal and adult atrial and ventricular myocytes. The N-glycan structures produced among cardiomyocyte types were markedly variable. Thus, the cardiac glycome, defined as the complete set of glycan structures produced in the heart, is remodeled. One glycogene, ST8sia2, a polysialyltransferase, is expressed only in the neonatal atrium. Cardiomyocyte electrical signaling was compared in control and ST8sia2((-/-)) neonatal atrial and ventricular myocytes. Action potential waveforms and gating of less sialylated voltage-gated Na+ channels were altered consistently in ST8sia2((-/-)) atrial myocytes. ST8sia2 expression had no effect on ventricular myocyte excitability. Thus, the regulated (between atrium and ventricle) and aberrant (knockout in the neonatal atrium) expression of a single glycogene was sufficient to modulate cardiomyocyte excitability. A mechanism is described by which cardiac function is controlled and modulated through physiological and pathological processes that involve regulated and aberrant glycosylation.


Assuntos
Glicoproteínas/genética , Miocárdio/metabolismo , Miócitos Cardíacos/metabolismo , Transdução de Sinais , Potenciais de Ação , Animais , Animais Recém-Nascidos , Análise por Conglomerados , Eletrofisiologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Glicoproteínas/metabolismo , Glicosilação , Coração/crescimento & desenvolvimento , Coração/fisiologia , Camundongos , Camundongos Knockout , Miocárdio/citologia , Miócitos Cardíacos/citologia , Miócitos Cardíacos/fisiologia , Análise de Sequência com Séries de Oligonucleotídeos , Proteômica/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sialiltransferases/genética , Sialiltransferases/metabolismo , Sialiltransferases/fisiologia , Canais de Sódio/genética , Canais de Sódio/metabolismo , Canais de Sódio/fisiologia , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
11.
Encephale ; 38(3): 266-73, 2012 Jun.
Artigo em Francês | MEDLINE | ID: mdl-22726415

RESUMO

An accurate treatment of first episodes in schizophrenia and bipolar disorders has a significant impact on compliance and prognosis. However, existing therapeutic guidelines may be poorly respected and may concern only typical clinical situations. Medical attitudes in clinical practice have been collected and structured on the basis of small interactive meetings (Focus Group [FG]), and a synthesis of practical attitudes has been compared with updated guidelines. The FG method applied to treatment initiation in schizophrenia and bipolar disorder is seen as complementary to evidence-based guidelines. It reveals that, in a reflexive manner, clinical attitudes are often more diverse and frequently consider first treatments after global evaluation, taking more into account external factors such as clinicians' experience, patient's history and willingness, clinical setting, and environment. A symptomatic approach is sometimes preferred, and a better alliance is always considered as a main objective. The FG method could be a supplementary support to continuous medical education.


Assuntos
Antimaníacos/administração & dosagem , Antipsicóticos/administração & dosagem , Transtorno Bipolar/tratamento farmacológico , Grupos Focais , Transtornos Psicóticos/tratamento farmacológico , Esquizofrenia/tratamento farmacológico , Psicologia do Esquizofrênico , Adulto , Sistemas de Notificação de Reações Adversas a Medicamentos , Idoso , Antimaníacos/efeitos adversos , Antipsicóticos/efeitos adversos , Transtorno Bipolar/diagnóstico , Transtorno Bipolar/psicologia , Esquema de Medicação , Interações Medicamentosas , Quimioterapia Combinada , Medicina Baseada em Evidências , Feminino , Humanos , Masculino , Adesão à Medicação , Pessoa de Meia-Idade , Guias de Prática Clínica como Assunto , Transtornos Psicóticos/diagnóstico , Transtornos Psicóticos/psicologia , Esquizofrenia/diagnóstico
12.
Phys Rev Lett ; 107(18): 186804, 2011 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-22107663

RESUMO

Electrical transport measurements of carbon nanotubes filled with magnetic iron nanoparticles are reported. Low-temperature (40 mK) magnetoresistance measurements showed conductance hysteresis with sharp jumps at the switching fields of the nanoparticles. Depending on the gate voltage, positive or negative hysteresis was observed. The results are explained in terms of a magneto-Coulomb effect: The spin flip of the iron island at a nonzero magnetic field causes a shift of the chemical potential induced by the change of Zeeman energy; i.e., an effective charge variation is detected by the nanotube quantum dot.

13.
Innov Pharm ; 12(3)2021.
Artigo em Inglês | MEDLINE | ID: mdl-35601593

RESUMO

Alzheimer's Disease (AD) is the most prevalent type of dementia and has a high prevalence in the aging population. Due to the requirements for care, it is valuable for members of the healthcare system to be knowledgeable about AD and its treatment. Community pharmacists are particularly valuable in assisting in AD care because of their accessibility to the general public and they are a source for dispensing AD medications. The purpose of this study is to assess the level of knowledge of AD among Ohio community pharmacists based on regional practice settings using the Alzheimer's Disease Knowledge Scale (ADKS). A standardized, 30-question assessment tool known as the Alzheimer's Disease Knowledge Scale exists to measure the level of knowledge of AD among a given population. Studies on AD knowledge have been conducted using this tool, and the use of this scale identifies major misconceptions about AD that could be addressed in education initiatives for both the general public and for health care professionals. This study implemented this tool to compare the knowledge of community pharmacists that serve rural areas to those that serve urban areas. The Ohio Board of Pharmacy provided a list of emails of community pharmacists to send an anonymous survey including both demographic questions and the ADKS. Statistical analyses including independent t-tests and descriptive statistics were conducted using SPSS to determine the significance of the data. This study found no statistically significant difference between urban versus rural community pharmacists. However, in the future we hope to identify specific questions that correlate to areas of AD where continuing education may be helpful in improving patient outcomes by enabling caregivers and healthcare providers with a more accurate understanding of AD.

14.
Artigo em Inglês | MEDLINE | ID: mdl-34594456

RESUMO

The demonstrated gap between skills needed and skills learned within a college education places both undergraduates seeking gainful employment and the employers seeking highly skilled workers at a disadvantage. Recent and up-and-coming college graduates should possess 21st century skills (i.e., communication, collaboration, problem solving), skills that employers deem necessary for the workplace. Research shows that the development of this skillset can help narrow the gap in producing highly skilled graduates for the science, technology, engineering, and mathematics (STEM) workforce. We propose the development of 21st century skills by utilizing the project-based learning (PjBL) framework and creating the inclusive biologist exploring active research with students (iBEARS) program, allowing undergraduate students to hone their 21st century skills and prepare for transition and success within the workplace.

16.
BMC Genomics ; 10: 39, 2009 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-19159465

RESUMO

BACKGROUND: Genomic discovery in oat and its application to oat improvement have been hindered by a lack of genetic markers common to different genetic maps, and by the difficulty of conducting whole-genome analysis using high-throughput markers. This study was intended to develop, characterize, and apply a large set of oat genetic markers based on Diversity Array Technology (DArT). RESULTS: Approximately 19,000 genomic clones were isolated from complexity-reduced genomic representations of pooled DNA samples from 60 oat varieties of global origin. These were screened on three discovery arrays, with more than 2000 polymorphic markers being identified for use in this study, and approximately 2700 potentially polymorphic markers being identified for use in future studies. DNA sequence was obtained for 2573 clones and assembled into a non-redundant set of 1770 contigs and singletons. Of these, 705 showed highly significant (Expectation < 10E-10) BLAST similarity to gene sequences in public databases. Based on marker scores in 80 recombinant inbred lines, 1010 new DArT markers were used to saturate and improve the 'Kanota' x 'Ogle' genetic map. DArT markers provided map coverage approximately equivalent to existing markers. After binning markers from similar clones, as well as those with 99% scoring similarity, a set of 1295 non-redundant markers was used to analyze genetic diversity in 182 accessions of cultivated oat of worldwide origin. Results of this analysis confirmed that major clusters of oat diversity are related to spring vs. winter type, and to the presence of major breeding programs within geographical regions. Secondary clusters revealed groups that were often related to known pedigree structure. CONCLUSION: These markers will provide a solid basis for future efforts in genomic discovery, comparative mapping, and the generation of an oat consensus map. They will also provide new opportunities for directed breeding of superior oat varieties, and guidance in the maintenance of oat genetic diversity.


Assuntos
Avena/genética , Mapeamento Cromossômico/métodos , Marcadores Genéticos , Genoma de Planta , Análise por Conglomerados , DNA de Plantas/genética , Biblioteca Genômica , Genótipo , Análise de Sequência com Séries de Oligonucleotídeos , Polimorfismo Genético , Análise de Sequência de DNA
17.
Ecology ; 90(11): 3209-21, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19967876

RESUMO

In many large pelagic animals, observing behavior is limited to observation by radio or satellite telemetry. In many cases, discriminating different behaviors from telemetry data has been a key, but often elusive, goal. Here we use state-space models (SSMs) to fit a correlated random walk (CRW) model that switches between two unobserved behavioral states (nominally foraging and traveling) to 41 male and 43 female adult grey seal (Halichoerus grypus) satellite telemetry tracks. The SSM results reveal markedly different spatial behavior between the sexes, fitting well with sexual size dimorphism and known dietary differences, suggesting that the sexes deal with seasonal prey availability and reproductive costs differently. From these results we were also able to produce behaviorally informed habitat use maps, showing a complex and dynamic network of small, intensely used foraging areas. Our flexible SSM approach clearly demonstrates sex-related behavioral differences, fine scale spatial and temporal foraging patterns, and a clearer picture of grey seal ecology and role in the Scotian Shelf ecosystem.


Assuntos
Comportamento Alimentar/fisiologia , Focas Verdadeiras/fisiologia , Caracteres Sexuais , Animais , Ecossistema , Feminino , Masculino , Modelos Biológicos , Estações do Ano
18.
J Hosp Infect ; 103(2): 115-120, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279758

RESUMO

BACKGROUND: Detection of faecal carriers of carbapenemase-producing Enterobacteriaceae (CPE) and vancomycin-resistant Enterococci (VRE) has become a routine medical practice in many countries. In an outbreak setting, several public health organizations recommend three-weekly rectal screenings to rule-out acquisition in contact patients. This strategy, associated with bed closures and reduction of medical activity for a relatively long time, seems costly. AIM: The objective of this study was to test the positive and negative predictive values of reverse transcription polymerase chain reaction (RT-PCR; GeneXpert®) carried-out at Day 0, compared with conventional three-weekly culture-based rectal screenings, in identifying, among contact patients, those who acquired CPE/VRE. METHODS: A multicentre retrospective study was conducted from January2015 to October2018. All contact patients (CPs) were included identified from index patients (IPs) colonized or infected with CPE/VRE, incidentally discovered. Each CP was investigated at Day 0 by PCR (GeneXpert®), and by the recommended three-weekly screenings. FINDINGS: Twenty-two IPs and 159 CPs were included. An average of 0.77 secondary cases per patient was noted, with a mean duration of contact of 10 days (range 1-64). Among the 159 CPs, 16 (10%) had a CPE/VRE-positive culture during the monitoring period. Rectal screenings were positive at Day 0 (10 patients), Day 7 (two patients), Day 14 (four patients). Thirteen of 16 patients with positive culture had a positive PCR at Day 0. Overall, a concordance of 97.5% (155/159) was observed between the three-weekly screenings and Day 0 PCR results. When performed on CPs at Day 0 of the identification of an IP, PCR (GeneXpert®) allowed the reduction in turnaround time by five to 27 days, compared to three-weekly screenings. Positive predictive value and negative predictive value were 100% and 98%, respectively. CONCLUSIONS: The use of RT-PCR (GeneXpert®) can avoid the three-weekly rectal samplings needed to rule-out acquisition of CPE/VRE.


Assuntos
Enterobacteriáceas Resistentes a Carbapenêmicos/isolamento & purificação , Infecções por Enterobacteriaceae/diagnóstico , Monitoramento Epidemiológico , Infecções por Bactérias Gram-Positivas/diagnóstico , Fechamento de Instituições de Saúde/estatística & dados numéricos , Reação em Cadeia da Polimerase em Tempo Real/métodos , Enterococos Resistentes à Vancomicina/isolamento & purificação , Adulto , Idoso , Idoso de 80 Anos ou mais , Infecções por Enterobacteriaceae/microbiologia , Feminino , Infecções por Bactérias Gram-Positivas/microbiologia , Hospitais , Humanos , Achados Incidentais , Masculino , Pessoa de Meia-Idade , Técnicas de Diagnóstico Molecular/métodos , Valor Preditivo dos Testes , Estudos Retrospectivos , Adulto Jovem
19.
Proc Biol Sci ; 275(1638): 1061-5, 2008 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-18252675

RESUMO

Nestlings of many avian brood parasites are virtuosos at mimicking host nestling vocalizations, which, like egg mimicry, presumably ensures acceptance by host parents. Having been accepted, parasitic nestlings then often exaggerate the aspects of the host's display to increase parental care. Host nestlings may, in turn, exaggerate their vocalizations to keep up with the parasite, though this possibility has not been evaluated. We experimentally parasitized song sparrow (Melospiza melodia) nests with a brown-headed cowbird (Molothrus ater) chick to evaluate how host nestlings respond. Vocalizations emitted from experimentally parasitized nests were higher in frequency, and louder, than those from unparasitized nests, consistent with the cowbird exaggerating its signalling. In response, host nestlings exaggerated the frequency and amplitude of their vocalizations, such that they resembled the cowbird's while they 'scaled back' on calls per parental provisioning bout. Sparrows in parasitized nests were fed equally often as sparrows in unparasitized nests, suggesting that exaggerating some aspects of vocalization while scaling back on others can help host nestlings confronted with a cowbird. Our results support the recently proposed hypothesis that signalling in parasitized nests involves a dynamic interaction between parasitic and host nestlings, rather than a one-way process of mimicry by the parasite.


Assuntos
Comportamento de Nidação , Pardais/fisiologia , Vocalização Animal , Animais , Comportamento Alimentar , Feminino , Masculino , Comportamento Materno , Comportamento Paterno , Estações do Ano , Vitória
20.
J Microsc ; 231(2): 299-316, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18778428

RESUMO

Reduction-oxidation-sensitive green fluorescent protein (roGFP1 and roGFP2) were expressed in different sub-cellular compartments of Arabidopsis and tobacco leaves to empirically determine their performance as ratiometric redox sensors for confocal imaging in planta. A lower redox-dependent change in fluorescence in combination with reduced excitation efficiency at 488 nm resulted in a significantly lower dynamic range of roGFP1 than for roGFP2. Nevertheless, when targeted to the cytosol and mitochondria of Arabidopsis leaves both roGFPs consistently indicated redox potentials of about -320 mV in the cytosol and -360 mV in the mitochondria after pH correction for the more alkaline matrix pH. Ratio measurements were consistent throughout the epidermal cell layer, but results might be attenuated deeper within the leaf tissue. Specific interaction of both roGFPs with glutaredoxin in vitro strongly suggests that in situ both variants preferentially act as sensors for the glutathione redox potential. roGFP2 targeted to plastids and peroxisomes in epidermal cells of tobacco leaves was slightly less reduced than in other plasmatic compartments, but still indicated a highly reduced glutathione pool. The only oxidizing compartment was the lumen of the endoplasmic reticulum, in which roGFP2 was almost completely oxidized. In all compartments tested, roGFP2 reversibly responded to perfusion with H(2)O(2) and DTT, further emphasizing that roGFP2 is a reliable probe for dynamic redox imaging in planta. Reliability of roGFP1 measurements might be obscured though in extended time courses as it was observed that intense irradiation of roGFP1 at 405 nm can lead to progressive photoisomerization and thus a redox-independent change of fluorescence excitation ratios.


Assuntos
Arabidopsis/metabolismo , Citoplasma/química , Glutationa/metabolismo , Proteínas de Fluorescência Verde/análise , Microscopia Confocal/métodos , Nicotiana/metabolismo , Organelas/química , Oxirredução , Folhas de Planta/metabolismo
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