RESUMO
PURPOSE: To compare the diagnostic utility of metagenomic deep sequencing (MDS) to cytology, flow cytometry and gene rearrangement by PCR in ocular samples of patients with suspected vitreoretinal lymphoma (VRL). METHODS: Patients with suspected VRL underwent ocular sampling of one or both eyes at the Emory Eye Center from September 2017 to June 2022. Ocular samples were evaluated with MDS and conventional diagnostics. MDS was performed at the Ralph and Sophie Heintz Laboratory at the F.I. Proctor Foundation. Relevant demographic and clinical data were retrospectively collected from medical records. Patients were diagnosed with VRL based on clinical assessment and conventional diagnostic testing. RESULTS: This study included 13 patients with suspected VRL who underwent diagnostic vitrectomy, including 1 patient who had an additional subretinal biopsy. Six patients (46.2%) were diagnosed with VRL. Among patients diagnosed with VRL, MDS detected pathogenic mutations in 5 out of 6 patients (83.3%) while cytology was positive for VRL in 4 out of 6 patients (66.7%), flow cytometry in 4 out of 4 patients (100.0%) and PCR in 4 out of 4 patients (100.0%). MDS detected mutations in MYD88 in 2 out of 6 patients diagnosed with VRL. In 7 patients (53.8%) not diagnosed with VRL, MDS detected pathogenic lymphoma mutations in 2 patients (28.6%). DISCUSSION: MDS detected pathogenic mutations in five out of six patients diagnosed with VRL, including in two patients with negative cytology, demonstrating its potential to improve diagnostic rates of VRL as an adjunctive test.
RESUMO
OBJECTIVES: To determine the associated pathogen during the 2023 conjunctivitis outbreak in Vietnam METHODS: RNA-sequencing was used to identify pathogens before and during the outbreak. RESULTS: 24 patients with infectious conjunctivitis between March and October 2023 from Hai Yen Vision Institute in Vietnam were swabbed. Coxsackievirus A24v was the most common pathogen identified. Phylogenetic analysis of these strains demonstrates similarities to the Coxsackievirus identified in the 2022 India outbreak. Human adenovirus D was also circulating. Ocular findings of tearing, purulence, and itching were common in this outbreak. CONCLUSIONS: Multiple viruses can co-circulate during conjunctivitis outbreaks. Hemorrhagic conjunctivitis, commonly associated with coxsackievirus conjunctivitis, was not a common clinical sign in this outbreak. Repeat genetic surveillance, with the notable inclusion of RNA virus detection strategies, is important for outbreak detection.
Assuntos
Infecções por Coxsackievirus , Surtos de Doenças , Filogenia , Humanos , Vietnã/epidemiologia , Infecções por Coxsackievirus/epidemiologia , Infecções por Coxsackievirus/virologia , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Adulto Jovem , Criança , Adolescente , Pré-Escolar , Conjuntivite Viral/epidemiologia , Conjuntivite Viral/virologia , Conjuntivite Hemorrágica Aguda/epidemiologia , Conjuntivite Hemorrágica Aguda/virologiaRESUMO
Infectious conjunctivitis outbreaks remain a public health burden. This study focuses on the pathogen and antimicrobial resistance (AMR) profiles identified in Niger. Sixty-two patients with acute infectious conjunctivitis who presented to health posts were enrolled from December 2021 to May 2022. Nasal and conjunctival swabs were obtained from each patient. Unbiased RNA deep sequencing (RNA-seq) was used to identify associated pathogens. A pathogen was identified in 39 patients (63%; 95% CI, 50-74). Of those, an RNA virus was detected in 23 patients (59%; 95% CI, 43-73). RNA viruses were diverse and included human coronaviruses (HCoVs): SARS-CoV-2, HCoV-229E, HCoV-HKU1, and HCoV-OC43. A DNA virus was identified in 11 patients (28%; 95% CI, 17-44). Of those, four patients had a coinfection with an RNA virus and two patients had a coinfection with both an RNA virus and a bacterium. DNA viruses were predominantly human herpesvirus (cytomegalovirus, Epstein-Barr virus, human herpesvirus 8) and human adenovirus species B, C, and F. Eighteen patients (46%; 95% CI, 32-61) had a bacteria-associated infection that included Haemophilus influenza, Haemophilus aegyptius, Staphylococcus aureus, Streptococcus pneumoniae, and Moraxella spp. Antimicrobial resistance determinants were detected in either the conjunctiva or nasal samples of 20 patients (32%; 95% CI, 22-45) and were found to be more diverse in the nose (Shannon alpha diversity, 1.12 [95% CI, 1.05-1.26] versus 1.02 [95% CI, 1.00-1.05], P = 0.01). These results suggest the potential utility of leveraging RNA-seq to surveil pathogens and AMR for ocular infections.
Assuntos
Coinfecção , Conjuntivite , Infecções por Vírus Epstein-Barr , Infecções Respiratórias , Humanos , Antibacterianos , Infecções Respiratórias/epidemiologia , Níger/epidemiologia , Farmacorresistência Bacteriana , Herpesvirus Humano 4RESUMO
Importance: Acute infectious conjunctivitis is a common ocular condition with major public health consequences. Objective: To assess regional variations and microbial etiologies of acute infectious conjunctivitis to guide treatment. Design, Setting, and Participants: In this cross-sectional study, patients with presumed acute infectious conjunctivitis were enrolled in the study at 5 sites (Honolulu, Hawaii; Los Angeles, San Francisco, and San Diego, California; and Petah-Tikva, Israel) from March 2021 to March 2023. Patients with allergic or toxic conjunctivitis were excluded. Main Outcomes and Measures: Pathogens were identified by unbiased RNA deep sequencing. Results: In all, 52 patients (mean [range] age, 48 [7-80] years; 31 females [60%]) were enrolled at 5 sites (6 patients from Honolulu, 9 from San Diego, 11 from Los Angeles, 13 from San Francisco, and 13 from Petah-Tikva). RNA deep sequencing detected human adenovirus species D in one-quarter of patients (13 of 52). A wide range of pathogens, including human coronavirus 229E, SARS-CoV-2, and herpes simplex virus type 1, was also identified, as well as several bacteria and fungi. Moreover, 62% (32 of 52) of patients presented with purulent discharge, while only 8% (4 of 52) of patients had confirmed bacterial pathogens. Conclusion and Relevance: In this cross-sectional study, pathogens associated with acute infectious conjunctivitis varied between all 5 sites in the US and Israel. Purulent discharge was a common presenting sign in this study, with a low specificity for bacteria-associated conjunctivitis, suggesting that further diagnostic workup may be necessary to inform antibiotic stewardship. Additional research on cost-effectiveness of using RNA deep sequencing is needed to ascertain whether it is better to monitor patients clinically until resolution of disease.
Assuntos
Conjuntivite , Feminino , Humanos , Pessoa de Meia-Idade , Bactérias , Conjuntivite/microbiologia , Estudos Transversais , Doença Aguda , Vigilância em Saúde PúblicaRESUMO
Purpose: To identify pathogens associated with the 2022 conjunctivitis outbreak in Tamil Nadu, India. Methods: This prospective study was conducted in November of 2022. Patients with presumed acute infectious conjunctivitis presenting to the Aravind Eye Clinic in Madurai, India were eligible. Anterior nares and conjunctival samples from participants were obtained and processed for metagenomic RNA deep sequencing (RNA-seq). Results: Samples from 29 patients were sequenced. A pathogen was identified in 28/29 (97%) patients. Coxsackievirus A24v, a highly infectious RNA virus, was the predominant pathogen and detected in 23/29 patients. Human adenovirus D (HAdV-D), a DNA virus commonly associated with conjunctivitis outbreaks, was detected in the remaining patients (5/29). Hemorrhagic conjunctiva was documented in both HAdV-D and coxsackievirus A24v affected patients but was not the predominant clinical presentation. Phylogenetic analysis of coxsackievirus A24v revealed a recent divergence from the 2015 outbreak. Conclusions: Coxsackievirus A24v and HAdV-D were co-circulating during the 2022 conjunctivitis outbreak in Tamil Nadu, India. Clinical findings were similar between patients with HAD-V and coxsackievirus A24v associated conjunctivitis. As high-throughput technologies become more readily accessible and cost-effective, unbiased pathogen surveillance may prove useful for outbreak surveillance and control.
RESUMO
SIGNIFICANCE: Acute infectious conjunctivitis poses significant challenges to eye care providers. It can be highly transmissible, and because etiology is often presumed, correct treatment and management can be difficult. This study uses unbiased deep sequencing to identify causative pathogens of infectious conjunctivitis, potentially allowing for improved approaches to diagnosis and management. PURPOSES: This study aimed to identify associated pathogens of acute infectious conjunctivitis in a single ambulatory eye care center. CASE REPORTS: This study included patients who presented to the University of California Berkeley eye center with signs and symptoms suggestive of infectious conjunctivitis. From December 2021 to July 2021, samples were collected from seven subjects (ages ranging from 18 to 38). Deep sequencing identified associated pathogens in five of seven samples, including human adenovirus D, Haemophilus influenzae , Chlamydia trachomatis , and human coronavirus 229E. CONCLUSIONS: Unbiased deep sequencing identified some unexpected pathogens in subjects with acute infectious conjunctivitis. Human adenovirus D was recovered from only one patient in this series. Although all samples were obtained during the COVID-19 pandemic, only one case of human coronavirus 229E and no SARS-CoV-2 were identified.
Assuntos
COVID-19 , Conjuntivite , Humanos , Doença Aguda , California/epidemiologia , COVID-19/diagnóstico , COVID-19/epidemiologia , Sequenciamento de Nucleotídeos em Larga Escala , PandemiasRESUMO
The first manifestation of a viral infection may be conjunctivitis. There are limited data on the etiology of viral conjunctivitis in Vanuatu, a country in the South Pacific Ocean. Patients presenting to one of two Vanuatu health centers with presumed infectious conjunctivitis were eligible if symptom onset was within 14 days of screening. Conjunctival and anterior nasal swabs were obtained and subjected to unbiased RNA deep sequencing (RNA-seq) to identify DNA and RNA viruses. For samples collected from May to November 2021, RNA-seq identified a viral etiology in 12/48 patients. Human adenovirus species were the most common viruses (58%) detected, followed by human herpes viruses (cytomegalovirus, varicella zoster virus, and human herpes 7 virus). Rhinovirus C, Epstein-Barr virus, and bocavirus were also detected. In summary, the etiology for viral conjunctivitis in Vanuatu appears broad. Unbiased testing may be useful for disease surveillance.
Assuntos
Conjuntivite Viral , Conjuntivite , Infecções por Vírus Epstein-Barr , Humanos , Vanuatu , Herpesvirus Humano 4 , Herpesvirus Humano 3/genéticaRESUMO
BACKGROUND: Seasonal and epidemic conjunctivitis (pink eye) infections are highly contagious and impose a significant economic burden worldwide. Long-term visual impairment can occur. METHODS: This study used metagenomic deep sequencing to evaluate pathogens causing acute infectious conjunctivitis in Burkina Faso. RESULTS: We found that pathogens causing conjunctivitis in Burkina Faso are diverse, with human adenoviruses responsible for a small fraction of the samples tested. CONCLUSIONS: These results are unexpected and suggest the importance of regional surveillance.
Assuntos
Conjuntivite , Epidemias , Humanos , Burkina Faso/epidemiologia , Conjuntivite/epidemiologia , Doença Aguda , Sequenciamento de Nucleotídeos em Larga EscalaRESUMO
Purpose: Conjunctivitis epidemics and pandemics remain a global burden. This study aims to comprehensively identify pathogens associated with conjunctivitis in Vietnam. Methods: Patients with acute conjunctivitis presented to an outpatient clinic in Ho Chi Minh City, Vietnam, were enrolled from September 2022 to March 2023. Swabs were obtained from conjunctiva and anterior nares of all patients. Unbiased RNA deep sequencing (RNA-seq) was used to identify any replicating pathogens in the samples. Results: Samples from 35 patients were analyzed. A pathogen was identified in 80% of the patients. 72% (95% confidence interval: 54% to 85%) were infected with either HAdV-D or HAdV-B. RNA viruses detected were rhinoviruses and human coronavirus 229E. Bacteria etiologies included Streptococcus pneumoniae, Hemophilus influenza, and Pseudomonas spp. One patient had co-infection of rhinovirus A and HAdV-B. Vittaforma corneae, a fungus, was identified in one patient. Corneal sub-epithelial infiltrates, pseudomembranes, or pre-auricular lymphadenopathy were not reported in any patient. Conclusions: Human adenoviruses are the common circulating pathogens associated with infectious conjunctivitis in Vietnam. HAdV species, however, appear to vary between geographic locations within Vietnam. Other under-recognized pathogens identified in this study, such as RNA viruses, suggest broader pathogen surveillance may be beneficial.
RESUMO
BACKGROUND: Viral conjunctivitis (pink eye) can be highly contagious and is of public health importance. There remains significant debate whether SARS-CoV-2 can present as a primary conjunctivitis. The aim of this study was to identify pathogens associated with outpatient infectious conjunctivitis during the COVID-19 Delta surge. METHODS: This prospective study was conducted in the spring and summer months of 2021. 106 patients with acute conjunctivitis who presented to the Aravind Eye Center in Madurai, India were included. One anterior nasal swab and one conjunctival swab of each eye were obtained for each enrolled patient. Samples were subsequently processed for unbiased metagenomic RNA deep sequencing (RNA-seq). Outcomes included clinical findings and codetection of other pathogens with SARS-CoV-2 in patients with conjunctivitis. RESULTS: Among the 13 patients identified with human coronavirus RNA fragments in their swabs, 6 patients had SARS-CoV-2 infection, 5 patients had coinfections of SARS-CoV-2 and human adenovirus (HAdV), 1 patient had a coinfection with human coronavirus OC43 and HAdV, and 1 patient had a coinfection of Vittaforma corneae and SARS-CoV-2. 30% had bilateral disease and symptoms on presentation. Petechial hemorrhage was noted in 33% of patients with SARS-CoV-2 infection. No patients with SARS-CoV-2 or SARS-CoV-2 and HAdV infections had subepithelial infiltrates on presentation. All patients denied systemic symptoms. CONCLUSIONS: Among the patients presented with conjunctivitis associated with human coronavirus infection, over 50% of the patients had co-infections with other circulating pathogens, suggesting the public-health importance of broad pathogen testing and surveillance in the outpatient conjunctivitis population.
Assuntos
COVID-19 , Coinfecção , Conjuntivite , Humanos , SARS-CoV-2 , Coinfecção/epidemiologia , Pacientes Ambulatoriais , Estudos Prospectivos , Índia/epidemiologia , RNARESUMO
BACKGROUND: Seasonal outbreaks of infectious conjunctivitis remain a public health issue. Determination of outbreak etiologies in the context of a worldwide pandemic may provide useful information to guide public health strategies. The aim of this study was to identify pathogens associated with outpatient infectious conjunctivitis during the COVID-19 Delta surge. METHODS: This prospective study was conducted from April 2021 to September 2021. All outpatients presenting to the Aravind Eye Center (Madurai, India) with signs and symptoms consistent with acute infectious conjunctivitis were eligible. Three swabs were obtained from each participant: one from each conjunctiva and one from the anterior nares. Samples were processed for metagenomic RNA deep sequencing (RNA-seq). RESULTS: Samples from 106 study participants were sequenced. The most common presenting symptoms were tearing (86%) and itching (71%). Preauricular lymphadenopathy was present in 38% of participants. 20% of participants had close contacts with similar symptoms. Systemic symptoms such as coughing, runny nose, vomiting or diarrhea were uncommonly reported. 60% of all participants used some medicated eye drops upon enrollment. 75% of study participants demonstrated infection with human adenovirus D (HAdV-D). 11% of conjunctivitis was associated with SARS-CoV-2. 15% had no definitive pathogen detected. 8% of all participants had codetection of more than one pathogen on RNA-seq. CONCLUSIONS: During the COVID-19 Delta surge in India, HAdV-D was the most common pathogen associated with infectious conjunctivitis. SARS-CoV-2 was the second most common associated pathogen. Seasonal surveillance may be necessary for the determination of emerging and reemerging pathogens responsible for infectious conjunctivitis.
Assuntos
Adenovírus Humanos , COVID-19 , Conjuntivite , Humanos , SARS-CoV-2 , Estudos Prospectivos , Índia/epidemiologia , Conjuntivite/epidemiologia , Adenovírus Humanos/genética , Doença Aguda , Sequenciamento de Nucleotídeos em Larga EscalaRESUMO
Infections with DNA viruses are frequent causes of morbidity and mortality in transplant recipients. This study describes the analytical and clinical performance characteristics of the Arc Bio Galileo Pathogen Solution, an all-inclusive metagenomic next-generation sequencing (mNGS) reagent and bioinformatics pipeline that allows the simultaneous quantitation of 10 transplant-related double-stranded DNA (dsDNA) viruses (adenovirus [ADV], BK virus [BKV], cytomegalovirus [CMV], Epstein-Barr virus [EBV], human herpesvirus 6A [HHV-6A], HHV-6B, herpes simplex virus 1 [HSV-1], HSV-2, JC virus [JCV], and varicella-zoster virus [VZV]). The mNGS 95% limit of detection ranged from 14 copies/ml (HHV-6) to 191 copies/ml (BKV), and the lower limit of quantitation ranged from 442 international units (IU)/ml (EBV) to 661 copies/ml (VZV). An evaluation of 50 residual plasma samples with at least one DNA virus detected in prior clinical testing showed a total percent agreement of mNGS and quantitative PCR (qPCR) of 89.2% (306/343), with a κ statistic of 0.725. The positive percent agreement was 84.9% (73/86), and the negative percent agreement was 90.7% (233/257). Furthermore, mNGS detected seven subsequently confirmed coinfections that were not initially requested by qPCR. Passing-Bablok regression revealed a regression line of y = 0.953x + 0.075 (95% confidence interval [CI] of the slope, 0.883 to 1.011; intercept, -0.100 to 0.299), and Bland-Altman analysis (mNGS - qPCR) showed a slight positive bias (0.28 log10 concentration; 95% limits of agreement, -0.62 to 1.18). In conclusion, the mNGS-based Galileo pipeline demonstrates analytical and clinical performance comparable to that of qPCR for transplant-related DNA viruses.
Assuntos
Infecções por Vírus de DNA/diagnóstico , Vírus de DNA/isolamento & purificação , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Metagenômica/métodos , Técnicas de Diagnóstico Molecular/métodos , Transplante/efeitos adversos , Biologia Computacional/métodos , Vírus de DNA/classificação , Vírus de DNA/genética , Humanos , Sensibilidade e EspecificidadeRESUMO
PURPOSE: The etiology of conjunctivitis is often misdiagnosed. An ideal diagnostic test would identify all possible infectious causes. In this study, we apply unbiased metagenomic RNA deep sequencing (MDS) to identify pathogens causing conjunctivitis. DESIGN: Molecular study of prospectively collected conjunctival swabs from patients with presumed infectious conjunctivitis. PARTICIPANTS: Patients with presumed acute infectious conjunctivitis. METHODS: Conjunctival swabs were collected from patients presenting with acute conjunctivitis. Swabs were processed for MDS. Pathogens were identified using a rapid computational pipeline to analyze the nonhost sequences obtained from MDS. Differential gene expression analysis was performed to evaluate for host transcriptome signatures for infectious types. Clinical samples were deidentified, and laboratory personnel handling the samples and interpreting the data were masked. MAIN OUTCOME MEASURES: Pathogens and differential transcripts identified by MDS. RESULTS: Metagenomic RNA deep sequencing detected pathogens in 86% (12/14) of the patients tested. Swabs from 10 of 14 patients were positive for human adenovirus (HAdV) while swabs from 2 of 14 patients were positive for Vittaforma corneae (a parasitic fungal species of the microsporidia group). Samples positive for HAdV by RNA-seq were independently verified in a CLIA-certified laboratory. Pathogen-directed polymerase chain reaction confirmed the presence of V. corneae genome in the samples positive by RNA-seq. Local host transcriptome analysis identified 12 differentially expressed genes that provided distinct expression signatures for patients infected with HAdV compared with V. corneae. CONCLUSIONS: Metagenomic RNA deep sequencing can reliably detect and quantify common and rare pathogens causing conjunctivitis, and identify strains. The unbiased nature of metagenomic RNA deep sequencing allowed an expanded scope of pathogen detection, including fungal species not commonly associated with acute conjunctivitis. In addition, the identification of infection type-specific local host transcriptome signatures may allow for pathogen detection even when the pathogen load is too low for direct identification.
Assuntos
Conjuntivite/diagnóstico , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Metagenômica/métodos , Adulto , Idoso , Conjuntivite/microbiologia , DNA Bacteriano/análise , DNA Fúngico/análise , DNA Viral/análise , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Pollinators use their sense of smell to locate flowers from long distances, but little is known about how they are able to discriminate their target odor from a mélange of other natural and anthropogenic odors. Here, we measured the plume from Datura wrightii flowers, a nectar resource for Manduca sexta moths, and show that the scent was dynamic and rapidly embedded among background odors. The moth's ability to track the odor was dependent on the background and odor frequency. By influencing the balance of excitation and inhibition in the antennal lobe, background odors altered the neuronal representation of the target odor and the ability of the moth to track the plume. These results show that the mix of odors present in the environment influences the pollinator's olfactory ability.
Assuntos
Datura/fisiologia , Flores/fisiologia , Manduca/fisiologia , Neurônios/fisiologia , Odorantes , Neurônios Receptores Olfatórios/fisiologia , Animais , Antenas de Artrópodes/inervação , Antenas de Artrópodes/fisiologia , Comportamento Animal , Encéfalo/fisiologia , Fenômenos Eletrofisiológicos , Comportamento Alimentar , Voo Animal , Interneurônios/fisiologia , Masculino , Inibição Neural , Condutos Olfatórios/fisiologia , Percepção Olfatória , Néctar de Plantas , Polinização , Olfato , Compostos Orgânicos VoláteisRESUMO
Insect antennae are sensory organs involved in a variety of behaviors, sensing many different stimulus modalities. As mechanosensors, they are crucial for flight control in the hawkmoth Manduca sexta. One of their roles is to mediate compensatory reflexes of the abdomen in response to rotations of the body in the pitch axis. Abdominal motions, in turn, are a component of the steering mechanism for flying insects. Using a radio controlled, programmable, miniature stimulator, we show that ultra-low-current electrical stimulation of antennal muscles in freely-flying hawkmoths leads to repeatable, transient changes in the animals' pitch angle, as well as less predictable changes in flight speed and flight altitude. We postulate that by deflecting the antennae we indirectly stimulate mechanoreceptors at the base, which drive compensatory reflexes leading to changes in pitch attitude.
Assuntos
Antenas de Artrópodes/fisiologia , Voo Animal , Manduca/fisiologia , Mecanotransdução Celular , Animais , Antenas de Artrópodes/citologia , Antenas de Artrópodes/inervação , Estimulação Elétrica , Manduca/citologia , Mecanorreceptores/fisiologia , Músculos/fisiologia , Tecnologia sem FioRESUMO
Flying insects rely on the integration of feedback signals from multiple sensory modalities. Thus, in addition to the visual input, mechanosensory information from antennae is crucial for stable flight in the hawkmoth Manduca sexta. However, the nature of compensatory reflexes mediated by mechanoreceptors on the antennae is unknown. In this study we describe an abdominal flexion response mediated by the antennal mechanosensory input during mechanical body rotations. Such reflexive abdominal motions lead to shifts in the animal's center of mass, and therefore changes in flight trajectory. Moths respond with abdominal flexion both to visual and mechanical rotations, but the mechanical response depends on the presence of the mass of the flagellum. In addition, the mechanically mediated flexion response is about 200° out of phase with the visual response and adds linearly to it. Phase-shifting feedback signals in such a manner can lead to a more stable behavioral output response when the animal is faced with turbulent perturbations to the flight path.
Assuntos
Antenas de Artrópodes/fisiologia , Mecanorreceptores/fisiologia , Movimento/fisiologia , Tato/fisiologia , Abdome/fisiologia , Animais , Comportamento Animal/fisiologia , Voo Animal/fisiologia , Masculino , Manduca , Estimulação Física/métodosRESUMO
A morphologically identifiable type of olfactory sensillum on the antenna of the American cockroach contains a pair of ON and OFF cells that responds oppositely to changes in the concentration of fruit odours. The odour of lemon oil was used to study the accuracy with which these cells can discriminate between rapid step-like, ramp-like and oscillating changes in odour concentration. The discharge rates of both cells are not only affected by the actual concentration at particular instants in time (instantaneous concentration) but also by the rate at which concentration changes. The impulse frequency of the fruit odour ON cell is high when odour concentration is high, but higher still when odour concentration is also rising. Conversely, the impulse frequency of the fruit odour OFF cell is high when odour concentration is low and higher still when odour concentration is also falling. Thus, the effect of odour concentration on the responses of both cells is reinforced by the rate of change. Sensitivity to the rate of concentration change becomes greater when the rate is low. Because of the high sensitivity to low rates of change, these cells are optimized to detect fluctuations in fruit odour concentration. Whereas the ON cell signals the arrival and presence of fruit odour, the OFF cell detects its termination and absence. These cells provide excitatory responses for both increase and decrease in fruit odour concentration and may therefore reinforce contrast information.
Assuntos
Potenciais de Ação/fisiologia , Baratas/fisiologia , Odorantes , Neurônios Receptores Olfatórios/fisiologia , Receptores Odorantes/fisiologia , Órgãos dos Sentidos/citologia , Potenciais de Ação/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Modelos Lineares , Microscopia Eletrônica de Varredura/métodos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/ultraestrutura , Óleos de Plantas/farmacologia , Receptores Odorantes/efeitos dos fármacos , Fatores de TempoRESUMO
In insects, information about food odour is encoded by olfactory receptor cells with characteristic response spectra, located in several types of cuticular sensilla. Within short, hair-like sensilla on the cockroach's antenna, antagonistic pairs of olfactory receptor cells shape information inflow to the CNS by providing excitatory responses for both increases and decreases in food odour concentration. The segregation of food odour information into parallel ON and OFF responses suggests that temporal concentration changes become enhanced in the sensory output. When food odour concentration changes slowly and continuously up and down with smooth transition from one direction to another, the ON and OFF olfactory cells not only signal a succession of odour concentrations but also the rate with which odour concentration happens to be changing. Access to the values of such cues is of great use to an insect orientating to an odour source. With them they may extract concentration gradients from odour plumes.