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1.
Clin Cancer Res ; 30(13): 2812-2821, 2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38639918

RESUMO

PURPOSE: Given its heterogeneity and diverse clinical outcomes, precise subclassification of Barcelona Clinic Liver Cancer stage C (BCLC-C) hepatocellular carcinoma (HCC) is required for appropriately determining patient prognosis and selecting treatment. EXPERIMENTAL DESIGN: We recruited 2,626 patients with BCLC-C HCC from multiple centers, comprising training/test (n = 1,693) and validation cohorts (n = 933). The XGBoost model was chosen for maximum performance among the machine learning (ML) models. Patients were categorized into low-, intermediate-, high-, and very high-risk subgroups based on the estimated prognosis, and this subclassification was named the CLAssification via Machine learning of BCLC-C (CLAM-C). RESULTS: The areas under the receiver operating characteristic curve of the CLAM-C for predicting the 6-, 12-, and 24-month survival of patients with BCLC-C were 0.800, 0.831, and 0.715, respectively-significantly higher than those of the conventional models, which were consistent in the validation cohort. The four subgroups had significantly different median overall survivals, and this difference was maintained among various patient subgroups and treatment modalities. Immune-checkpoint inhibitors and transarterial therapies were associated with significantly better survival than tyrosine kinase inhibitors (TKI) in the low- and intermediate-risk subgroups. In cases with first-line systemic therapy, the CLAM-C identified atezolizumab-bevacizumab as the best therapy, particularly in the high-risk group. In cases with later-line systemic therapy, nivolumab had better survival than TKIs in the low-to-intermediate-risk subgroup, whereas TKIs had better survival in the high- to very high-risk subgroup. CONCLUSIONS: ML modeling effectively subclassified patients with BCLC-C HCC, potentially aiding treatment allocation. Our study underscores the potential utilization of ML modeling in terms of prognostication and treatment allocation in patients with BCLC-C HCC.


Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Aprendizado de Máquina , Humanos , Neoplasias Hepáticas/patologia , Neoplasias Hepáticas/mortalidade , Neoplasias Hepáticas/terapia , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Hepáticas/diagnóstico , Carcinoma Hepatocelular/patologia , Carcinoma Hepatocelular/mortalidade , Carcinoma Hepatocelular/terapia , Carcinoma Hepatocelular/tratamento farmacológico , Carcinoma Hepatocelular/diagnóstico , Feminino , Masculino , Prognóstico , Pessoa de Meia-Idade , Idoso , Estadiamento de Neoplasias , Algoritmos , Curva ROC , Adulto
2.
Hum Vaccin Immunother ; 20(1): 2335052, 2024 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-38575149

RESUMO

Emerging SARS-CoV-2 sublineages continue to cause serious COVID-19 disease, but most individuals have not received any COVID-19 vaccine for >1 year. Assessment of long-term effectiveness of bivalent COVID-19 vaccines against circulating sublineages is important to inform the potential need for vaccination with updated vaccines. In this test-negative study at Kaiser Permanente Southern California, sequencing-confirmed BA.4/BA.5- or XBB-related SARS-CoV-2-positive cases (September 1, 2022 to June 30, 2023), were matched 1:3 to SARS-CoV-2-negative controls. We assessed mRNA-1273 bivalent relative (rVE) and absolute vaccine effectiveness (VE) compared to ≥2 or 0 doses of original monovalent vaccine, respectively. The rVE analysis included 20,966 cases and 62,898 controls. rVE (95%CI) against BA.4/BA.5 at 14-60 days and 121-180 days was 52.7% (46.9-57.8%) and 35.5% (-2.8-59.5%) for infection, and 59.3% (49.7-67.0%) and 33.2% (-28.2-68.0%) for Emergency Department/Urgent Care (ED/UC) encounters. For BA.4/BA.5-related hospitalizations, rVE was 71.3% (44.9-85.1%) and 52.0% (-1.2-77.3%) at 14-60 days and 61-120 days, respectively. rVE against XBB at 14-60 days and 121-180 days was 48.8% (33.4-60.7%) and -3.9% (-18.1-11.3%) for infection, 70.7% (52.4-82.0%) and 15.7% (-6.0-33.2%) for ED/UC encounters, and 87.9% (43.8-97.4%) and 57.1% (17.0-77.8%) for hospitalization. VE and subgroup analyses (age, immunocompromised status, previous SARS-CoV-2 infection) results were similar to rVE analyses. rVE of mRNA-1273 bivalent vaccine against BA.4/BA.5 and XBB infections, ED/UC encounters, and hospitalizations waned over time. Periodic revaccination with vaccines targeting emerging variants may be important in reducing COVID-19 morbidity and mortality.


Assuntos
COVID-19 , Vacinas de mRNA , Humanos , Vacina de mRNA-1273 contra 2019-nCoV , Vacinas contra COVID-19 , SARS-CoV-2/genética , COVID-19/prevenção & controle , Vacinas Combinadas
3.
Meat Sci ; 213: 109498, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38520828

RESUMO

This study was conducted to evaluate the effects of relative humidity (RH) on moisture loss and flavor in dry-aged beef. Sixteen strip loins were assigned to one of the four aging treatments: vacuum (WET), dry-aging at 50% RH, dry-aging at 70% RH, or dry-aging at 85% RH and aged for 42 days at 2 °C. Loins were evaluated for evaporation loss, trim loss, tenderness, sensory, and microbiological characteristics. Results show that lower RH results in accelerated moisture loss during the first 3 days of the aging process without significantly affecting the total amount of moisture loss. Pseudomonadales dominated the aerobically dry-aged loins while Enterobacteriales was the most abundant in the wet-aged samples. Dry-aged samples had increased content of free amino acids in the cooked meat juice compared to the wet-aged counterpart. Dry aging at 50% RH tended to associate with more desirable flavor notes.


Assuntos
Manipulação de Alimentos , Umidade , Carne Vermelha , Paladar , Animais , Bovinos , Carne Vermelha/análise , Carne Vermelha/microbiologia , Manipulação de Alimentos/métodos , Humanos , Aminoácidos/análise , Vácuo , Água/análise , Microbiologia de Alimentos
5.
Blood ; 138(26): 2853-2873, 2021 12 30.
Artigo em Inglês | MEDLINE | ID: mdl-34411236

RESUMO

Intracranial hemorrhage (ICH) is a severe complication that is relatively common among patients with hemophilia. This systematic review aimed to obtain more precise estimates of ICH incidence and mortality in hemophilia, which may be important for patients, caregivers, researchers, and health policy makers. PubMed and EMBASE were systematically searched using terms related to "hemophilia" and "intracranial hemorrhage" or "mortality." Studies that allowed calculation of ICH incidence or mortality rates in a hemophilia population ≥50 patients were included. We summarized evidence on ICH incidence and calculated pooled ICH incidence and mortality in 3 age groups: persons of all ages with hemophilia, children and young adults younger than age 25 years with hemophilia, and neonates with hemophilia. Incidence and mortality were pooled with a Poisson-Normal model or a Binomial-Normal model. We included 45 studies that represented 54 470 patients, 809 151 person-years, and 5326 live births of patients with hemophilia. In persons of all ages, the pooled ICH incidence and mortality rates were 2.3 (95% confidence interval [CI], 1.2-4.8) and 0.8 (95% CI 0.5-1.2) per 1000 person-years, respectively. In children and young adults, the pooled ICH incidence and mortality rates were 7.4 (95% CI, 4.9-11.1) and 0.5 (95% CI, 0.3-0.9) per 1000 person-years, respectively. In neonates, the pooled cumulative ICH incidence was 2.1% (95% CI, 1.5-2.8) per 100 live births. ICH was classified as spontaneous in 35% to 58% of cases. Our findings suggest that ICH is an important problem in hemophilia that occurs among all ages, requiring adequate preventive strategies.


Assuntos
Hemofilia A/complicações , Hemorragias Intracranianas/etiologia , Fatores Etários , Humanos , Incidência , Hemorragias Intracranianas/mortalidade , Mortalidade
6.
Med J Malaysia ; 76(4): 597-599, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34305129

RESUMO

Giant splenic cyst is rare disorder affecting the spleen. As the occurrence is so in-frequent that the diagnosis preoperatively remains a challenge. We report a 12-year-old boy who presented to Sarawak General Hospital, Malaysia with left upper abdominal pain initially mistaken as a complex left liver cyst. He underwent surgery which turned out to be a giant splenic cyst and underwent laparotomy and total splenectomy. He was discharged well and remains asymptomatic after 6 months postoperative follow up.


Assuntos
Cistos , Laparoscopia , Esplenopatias , Criança , Cistos/diagnóstico por imagem , Cistos/cirurgia , Humanos , Masculino , Esplenectomia , Esplenopatias/diagnóstico por imagem , Esplenopatias/cirurgia
7.
Meat Sci ; 172: 108365, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33223267

RESUMO

This study aimed to evaluate pH effects on moisture loss and meat quality characteristics of dry-aged beef. Strip loins from six normal pH carcasses (pH = 5.47 ± 0.02) and dark cutting (DC) strip loins from six high pH carcasses (pH = 6.69 ± 0.09) were obtained. One strip loin from each carcass was dry aged and one was wet aged, giving four treatments: DRY, DRY-DC, WET, and WET-DC. Loins were aged for 42 d. Ultimate pH did not affect the rate or amount of moisture loss, trim loss, yield, or tenderness in dry-aged beef (P > 0.05). In general, DC steaks had the lowest lightness (L*), redness (a*), and yellowness (b*) values, regardless of aging method (P < 0.05). Discoloration scores and TBARS values for DC steaks remained low throughout retail display. Dry aging significantly reduced bacterial counts mitigating the microbial damages associated with DC. Flavor characteristics of DC were not improved by dry aging when compared to dry-aged loins from carcasses with normal pH.


Assuntos
Concentração de Íons de Hidrogênio , Carne Vermelha/análise , Animais , Carga Bacteriana , Bovinos , Cor , Comportamento do Consumidor , Manipulação de Alimentos/métodos , Qualidade dos Alimentos , Humanos , Músculo Esquelético , Carne Vermelha/microbiologia , Paladar , Substâncias Reativas com Ácido Tiobarbitúrico/análise
8.
Meat Sci ; 171: 108274, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32818818

RESUMO

The objective of this study was to determine color and lipid stability of steaks from dry-aged beef loins over 7 d of retail display (RD). Sixteen boneless strip loins were assigned to one of four treatments: wet-aging, dry aging at 50% relative humidity (RH), dry aging at 70% RH, or dry aging at 85% RH and aged for 42 days at 2 °C. Dry aging of beef resulted in decreased lightness (L*), redness (a*), and yellowness (b*) values and increased lipid oxidation compared to wet-aged counterparts (P < 0.05). Dry-aged steaks had greater discoloration (P < 0.05) than wet-aged steaks from d 4 to d 7 of RD. Results suggest that under prolonged RD, dry aging of beef has the potential to reduce color and lipid stability compared to wet aging and thus reduce display life. Color and lipid stability were not affected by RH during dry aging.


Assuntos
Cor , Manipulação de Alimentos/métodos , Lipídeos/química , Carne Vermelha/análise , Animais , Bovinos , Umidade , Oxirredução
10.
Orphanet J Rare Dis ; 14(1): 133, 2019 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-31186066

RESUMO

Epidermolysis Bullosa (EB) is a group of rare genetic disorders resulting in skin fragility and other symptoms. Commissioned by DEBRA International and funded by DEBRA Norway, this evidence-bases guideline provides recommendations to optimise psychosocial wellbeing in EB.An international multidisciplinary panel of social and health care professionals (HCP) and people living with EB was formed. A systematic international literature review was conducted by the panel following the Scottish Intercollegiate Guidelines Network (SIGN) methodology. The resulting papers underwent systematic selection and critique processes. Included papers were allocated to 6 different outcome groups to allow data synthesis and exploration: quality of life, coping, family, wellbeing, access to HCP and pain. Based on the evidence in those papers, recommendations were made for individuals living with EB, family and caregivers and HCP working in the field.Few studies have investigated interventions and which factors lead to better outcomes, but general recommendations can be made. EB is a complex disease impacting enormously on every aspect of psychosocial life. People and families living with EB need access to multidisciplinary support, including psychological guidance, in order to improve quality of life and psychosocial wellbeing. Interventions should stimulate social participation to prevent isolation. People with EB and their families should be able to access a supportive network. HCP should be well supported and educated about the complexity of EB. They should work collaboratively with those around the individual with EB (e.g. schools, employers etc.) to provide psychosocial opportunity and care.Attention should be paid to the psychosocial impact of EB as well as physical needs. Directions for research are indicated.


Assuntos
Epidermólise Bolhosa/psicologia , Adaptação Psicológica/fisiologia , Epidermólise Bolhosa/fisiopatologia , Humanos , Qualidade de Vida
11.
Adv Exp Med Biol ; 1074: 135-144, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29721937

RESUMO

Adaptive optics retinal imaging of fluorescent calcium indicators is a minimally invasive method used to study retinal physiology over extended periods of time. It has potential for discovering novel retinal circuits, tracking retinal function in animal models of retinal disease, and assessing vision restoration therapy. We previously demonstrated functional adaptive optics imaging of retinal neurons in the living eye using green fluorescent calcium indicators; however, the use of green fluorescent indicators presents challenges that stem from the fact that they are excited by short-wavelength light. Using red fluorescent calcium indicators such as jRGECO1a, which is excited with longer-wavelength light (~560 nm), makes imaging approximately five times safer than using short-wavelength light (~500 nm) used to excite green fluorescent calcium indicators such as GCaMP6s. Red fluorescent indicators also provide alternative wavelength imaging regimes to overcome cross talk with the sensitivities of intrinsic photoreceptors and blue light-activated channelrhodopsins. Here we evaluate jRGECO1a for in vivo functional adaptive optics imaging of retinal neurons using single-photon excitation in mice. We find that jRGECO1a provides similar fidelity as the established green indicator GCaMP6s.


Assuntos
Cálcio/análise , Proteínas de Fluorescência Verde/análise , Microscopia Intravital/métodos , Proteínas Luminescentes/análise , Imagem Molecular/métodos , Imagem Óptica/métodos , Óptica e Fotônica/métodos , Neurônios Retinianos/ultraestrutura , Animais , Dependovirus/genética , Feminino , Corantes Fluorescentes , Genes Reporter , Vetores Genéticos , Proteínas de Fluorescência Verde/genética , Proteínas Luminescentes/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios Retinianos/química , Neurônios Retinianos/fisiologia , Proteína Vermelha Fluorescente
13.
Biomed Opt Express ; 9(12): 6017-6037, 2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31065410

RESUMO

A combined 32° full field of view refractive fundus camera and fixation target with a -20 to +10 diopter sphere correction range is described and demonstrated. The optical setup partially corrects the average longitudinal chromatic aberration and spherical aberration of the human eye, while providing a long eye relief to allow integration with reflective adaptive optics ophthalmoscopes, as a viewfinder. The fundus camera operates with 940 nm light, using a maximum 2.9 mm diameter imaging pupil at the eye. The fixation target uses a light projector capable of delivering red, green and/or blue spatially and temporally modulated stimuli to the retina. The design and performance of each sub-system are discussed, and retinal imaging at various wavelengths is demonstrated.

14.
Am J Gastroenterol ; 111(11): 1582-1590, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27575713

RESUMO

OBJECTIVES: Propranolol has been used as prophylaxis for variceal bleeding in patients with cirrhosis. More recent data suggest that carvedilol may be more effective for reducing the hepatic venous pressure gradient (HVPG) than propranolol. The primary aim of this study was to evaluate the hemodynamic response to carvedilol compared with propranolol. METHODS: A total of 110 patients with a baseline HVPG value >12 mm Hg were allocated randomly to receive either carvedilol or propranolol. The HVPG measurement was repeated after 6 weeks of daily medication. The primary end point was a ≥20% fall in HVPG compared with baseline or <12 mm Hg. RESULTS: The difference in the proportion of responders in the carvedilol (49.1%) vs. propranolol (30.9%) groups did not reach statistical significance in the intention-to-treat analysis (P=0.08). However, among patients with a model for end-stage liver disease (MELD) score ≥15, carvedilol resulted in a significantly greater response than that of propranolol (7/12, 58.3% vs. 0/10, 0%; P=0.005). Similarly, carvedilol was superior to propranolol in patients with Child-Pugh score ≥9 (46.2 vs. 0%; P=0.046). The presence of ascites also had a significant influence on the response rate (51.5 vs. 24.2%; P=0.042). A MELD score ≥15 was the only significant predictor of response among these post hoc groups after adjusting for multiple comparisons (P=0.005). Severe adverse events were higher in the carvedilol group although drug-associated adverse events were not different. CONCLUSIONS: Overall, carvedilol offered no clear advantage over propranolol but it may be more effective in advanced cirrhotic patients with a MELD score≥15 in reducing the portal pressure gradient. However, this potential benefit may come with a cost of increased risk of side-effects and outcome data over a longer term is needed to understand the relative risk benefit.


Assuntos
Anti-Hipertensivos/uso terapêutico , Carbazóis/uso terapêutico , Hipertensão Portal/tratamento farmacológico , Pressão na Veia Porta , Propanolaminas/uso terapêutico , Propranolol/uso terapêutico , Adulto , Ascite/etiologia , Carvedilol , Doença Hepática Terminal , Varizes Esofágicas e Gástricas/complicações , Feminino , Hemorragia Gastrointestinal/etiologia , Hemorragia Gastrointestinal/prevenção & controle , Hemodinâmica , Veias Hepáticas , Humanos , Hipertensão Portal/etiologia , Cirrose Hepática/complicações , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Razão de Chances , Índice de Gravidade de Doença , Resultado do Tratamento
15.
Medicine (Baltimore) ; 94(20): e872, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25997067

RESUMO

In non-cardioembolic stroke patients, the cardiac manifestations of high blood pressure are of particular interest. Emerging data suggest that echocardiographically determined left ventricular hypertrophy is independently associated with risk of ischemic stroke.The primary objective of this study was to evaluate the frequency of different patterns of left ventricular (LV) remodeling and hypertrophy in a group of consecutive patients admitted with non-cardioembolic stroke or transient ischemic attack (TIA). In particular, we were interested in how often the relative wall thickness (RWT) was abnormal in patients with normal LV mass index (LVMI). As both abnormal RWT and LVMI indicate altered LV remodeling, the secondary objective of this research was to study whether a significant number of patients would be missing the diagnosis of LV remodeling if the RWT is not measured.All patients were referred within 48 hours after a stroke or a TIA for a clinically indicated transthoracic echocardiogram. The echocardiographic findings of consecutive patients with non-cardioembolic stroke or TIA were analyzed.All necessary measurements were performed in 368 patients, who were enrolled in the study. Mean age was 63.7 ±â€Š12.5 years, 64.4% men. Concentric remodeling carried the highest frequency, 49.2%, followed by concentric hypertrophy, 30.7%, normal pattern, 15.5%, and eccentric hypertrophy, 4.1%. The frequency of abnormal left ventricular RWT (80.4%) was significantly higher than that of abnormal LVMI (35.3%), (McNemar P < 0.05).In this group of non-cardioembolic stroke patients, abnormal LV remodeling as assessed by relative wall thickness is very frequent. As RWT was often found without increased LV mass, the abnormal left ventricular geometry may be missed if RWT is not measured or reported.


Assuntos
Ventrículos do Coração/patologia , Acidente Vascular Cerebral/patologia , Ecocardiografia , Feminino , Humanos , Hipertrofia Ventricular Esquerda/patologia , Ataque Isquêmico Transitório/patologia , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Remodelação Ventricular
16.
Curr Biol ; 25(24): 3190-3195, 2015 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-26778654

RESUMO

The dorsal lateral geniculate nucleus (dLGN) in carnivores and primates is a laminated structure, where each layer gets visual input from only one eye [1, 2]. By contrast, in rodents such as mice and rats, the dLGN is not overtly laminated, the retinal terminals from the two eyes are only partially segregated [3, 4], and many cells in the binocular segment of dLGN get excitatory inputs from both eyes [5, 6]. Here, we show that the evolutionary ancient koniocellular (K) division of primate dLGN, like rodent dLGN, forms a subcortical site of binocular integration. We recorded single-cell activity in dLGN of anesthetized marmoset monkeys. As expected, cells in the parvocellular (P) and magnocellular (M) layers received monocular excitatory inputs. By contrast, many cells in the K layers received excitatory inputs from both eyes. The specialized properties of distinct K sub-populations (for example, blue-yellow color selectivity) were preserved across the two eye inputs, and where tested, the contrast sensitivity of each eye input was roughly matched. The results argue that evolutionarily widely separated orders such as rodents and primates have a shared strategy of integrating signals from the two eyes in subcortical circuits.

17.
BMC Cancer ; 14: 212, 2014 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-24650245

RESUMO

BACKGROUND: Cancer is the leading cause of deaths in the world. A widening disparity in cancer burden has emerged between high income and low-middle income countries. Closing this cancer divide is an ethical imperative but there is a dearth of data on cancer services from developing countries. METHODS: This was a multi-center, retrospective observational cohort study which enrolled women with breast cancer (BC) attending 8 participating cancer centers in Malaysia in 2011. All patients were followed up for 12 months from diagnosis to determine their access to therapies. We assess care performance using measures developed by Quality Oncology Practice Initiative, American Society of Clinical Oncology/National Comprehensive Cancer Network, American College of Surgeons' National Accreditation Program for Breast Centers as well as our local guideline. RESULTS: Seven hundred and fifty seven patients were included in the study; they represent about 20% of incident BC in Malaysia. Performance results were mixed. Late presentation was 40%. Access to diagnostic and breast surgery services were timely; the interval from presentation to tissue diagnosis was short (median = 9 days), and all who needed surgery could receive it with only a short wait (median = 11 days). Performance of radiation, chemo and hormonal therapy services showed that about 75 to 80% of patients could access these treatments timely, and those who could not were because they sought alternative treatment or they refused treatment. Access to Trastuzumab was limited to only 19% of eligible patients. CONCLUSIONS: These performance results are probably acceptable for a middle income country though far below the 95% or higher adherence rates routinely reported by centres in developed countries. High cost trastuzumab was inaccessible to this population without public funding support.


Assuntos
Neoplasias da Mama/economia , Neoplasias da Mama/epidemiologia , Países em Desenvolvimento/economia , Saúde Global/economia , Acessibilidade aos Serviços de Saúde/economia , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/diagnóstico , Estudos de Coortes , Feminino , Humanos , Malásia/epidemiologia , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto Jovem
18.
Intern Med J ; 42 Suppl 5: 22-9, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23035678

RESUMO

Coronary computed tomography angiography (CTA) is becoming a popular non-invasive imaging modality for coronary arteries. It has high sensitivity and specificity in the evaluation of coronary artery disease (CAD). Due to its high negative predictive value, the main clinical role of coronary CTA is in the exclusion of significant CAD in the low to intermediate pretest probability patients. In the emergency department, coronary CTA helps to fast-track the triage of acute chest pain patients. One of the major coronary CTA's limitations is its false positive findings in the presence of heavily calcified lesions. With the advance of CT technology, the radiation dose of coronary CTA has been reduced significantly. At present, coronary CTA is still not indicated for screening asymptomatic patients.


Assuntos
Angiografia Coronária/tendências , Doença da Artéria Coronariana/diagnóstico por imagem , Tomografia Computadorizada Multidetectores/tendências , Animais , Angiografia Coronária/métodos , Doença da Artéria Coronariana/fisiopatologia , Eletrocardiografia/métodos , Eletrocardiografia/tendências , Humanos , Tomografia Computadorizada Multidetectores/métodos , Doses de Radiação , Tomografia Computadorizada por Raios X/métodos , Tomografia Computadorizada por Raios X/tendências
19.
J Neurophysiol ; 106(3): 1310-21, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21653705

RESUMO

Prolonged exposure to an effective stimulus generally reduces the sensitivity of neurons early in the visual pathway. Yet eye and head movements bring about frequent changes in the retinal image, and it is less clear that exposure to brief presentations will produce similar desensitization. To address this, we made extracellular recordings from single neurons in the lateral geniculate nucleus of anesthetized marmosets, a New World primate. We measured the contrast response for drifting gratings before and after 0.5-s exposure to a high-contrast drifting grating, a stationary grating, or a blank screen. Prior exposure to the drifting grating reduced the contrast sensitivity of cells in the magnocellular pathway, on average by 23%; this reduction remained strong when the adapting and test stimuli were separated by 0.4 s. Exposure to a stationary grating of the preferred spatial phase did not change the contrast response; exposure to the opposite spatial phase did. None of the brief adaptors reduced the sensitivity of parvocellular cells. We conclude that brief periods of high contrast, such as those that would be expected to occur during a normal visual fixation, are sufficient to reduce the sensitivity of magnocellular-pathway cells.


Assuntos
Sensibilidades de Contraste/fisiologia , Corpos Geniculados/fisiologia , Neurônios/fisiologia , Estimulação Luminosa/métodos , Animais , Callithrix , Masculino , Fatores de Tempo , Vias Visuais/fisiologia
20.
J Neurophysiol ; 104(4): 1884-98, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20685925

RESUMO

Several parallel pathways convey retinal signals to the visual cortex of primates. The signals of the parvocellular (P) and magnocellular (M) pathways are well characterized; the properties of other rarely encountered cell types are distinctive in many ways, but it is not clear that they can provide signals with the same fidelity. Here we study this by characterizing the temporal receptive field of neurons in the lateral geniculate nucleus of anesthetized marmosets. For each neuron, we measured the response to a flickering uniform field, and, from this, estimated the linear and nonlinear receptive fields using spike-triggered average (STA) and spike-triggered covariance (STC) analyses. As expected the response of most P-cells was dominated by the STA, but the response of most M-cells required additional nonlinear components, and these usually acted to suppress cell responses. The STC analysis showed stronger suppressive axes in suppressed-by-contrast cells, and both suppressive and excitatory axes in on-off cells. Together, the STA and the STC analyses form a model of the temporal response to a large uniform field: under this model, the information that was provided by suppressed-by-contrast cells or on-off cells approached that provided by the P- and M-cells. However, whereas P- and M-cells provided more information about luminance, the nonlinear cells provided more information about the contrast energy. This suggests that the nonlinear cells provide complimentary signals to those of P- and M-cells, with reasonably high fidelity, and may play an important role in normal visual processing.


Assuntos
Potenciais Evocados Visuais/fisiologia , Corpos Geniculados/fisiologia , Neurônios/fisiologia , Dinâmica não Linear , Estimulação Luminosa/métodos , Vias Visuais/fisiologia , Animais , Callithrix , Modelos Lineares , Córtex Visual/fisiologia
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