Comparison of Bayesian and empirical ranking approaches to visual perception

Much current vision research is predicated on the idea--and a rapidly growing body of evidence--that visual percepts are generated according to the empirical significance of light stimuli rather than their physical characteristics. As a result, an increasing number of investigators have asked how visual perception can be rationalized in these terms. Here, we compare two different theoretical frameworks for predicting what observers actually see in response to visual stimuli: Bayesian decision theory and empirical ranking theory. Deciding which of these approaches has greater merit is likely to determine how the statistical operations that apparently underlie visual perception are eventually understood.     

White spot syndrome virus open reading frame 222 encodes a viral E3 ligase and mediates degradation of a host tumor suppressor via ubiquitination

We have characterized a white spot syndrome virus (WSSV) RING-H2-type protein, WSSV222, which is involved in ubiquitination. WSSV222 exhibits RING-H2-dependent E3 ligase activity in vitro in the presence of the specific conjugating enzyme UbcH6. Mutations in the RING-H2 domain abolished WSSV222-dependent ubiquitination, revealing the importance of this domain in WSSV222 function. Yeast two-hybrid and pull-down analyses revealed that WSSV222 interacts with a shrimp tumor suppressor-like protein (TSL) sharing 60% identity with human OVCA1. To better characterize the interaction of WSSV222 and TSL in vivo, we established a stable TSL-expressing cell line derived from the human ovarian cancer cell line A2780, where we observed a TSL-dependent prolonged G1 phase. Furthermore, we detected WSSV222-mediated ubiquitination and MG132-sensitive degradation of TSL both in shrimp primary cell culture and in the TSL-expressing cell line. Transient expression of TSL in BHK cells leads to apoptosis, which was rescued by WSSV222. Taken together, our data suggest that WSSV222 acts as an antiapoptosis protein by ubiquitin-mediated proteolysis of TSL to ensure successful WSSV replication in shrimp.     

Exploring Eye Movements in Patients with Glaucoma When Viewing a Driving Scene

Background

Glaucoma is a progressive eye disease and a leading cause of visual disability. Automated assessment of the visual field determines the different stages in the disease process: it would be desirable to link these measurements taken in the clinic with patient''s actual function, or establish if patients compensate for their restricted field of view when performing everyday tasks. Hence, this study investigated eye movements in glaucomatous patients when viewing driving scenes in a hazard perception test (HPT).

Methodology/Principal Findings

The HPT is a component of the UK driving licence test consisting of a series of short film clips of various traffic scenes viewed from the driver''s perspective each containing hazardous situations that require the camera car to change direction or slow down. Data from nine glaucomatous patients with binocular visual field defects and ten age-matched control subjects were considered (all experienced drivers). Each subject viewed 26 different films with eye movements simultaneously monitored by an eye tracker. Computer software was purpose written to pre-process the data, co-register it to the film clips and to quantify eye movements and point-of-regard (using a dynamic bivariate contour ellipse analysis). On average, and across all HPT films, patients exhibited different eye movement characteristics to controls making, for example, significantly more saccades (P<0.001; 95% confidence interval for mean increase: 9.2 to 22.4%). Whilst the average region of ‘point-of-regard’ of the patients did not differ significantly from the controls, there were revealing cases where patients failed to see a hazard in relation to their binocular visual field defect.

Conclusions/Significance

Characteristics of eye movement patterns in patients with bilateral glaucoma can differ significantly from age-matched controls when viewing a traffic scene. Further studies of eye movements made by glaucomatous patients could provide useful information about the definition of the visual field component required for fitness to drive.     

Visualizing ocular lens fluid dynamics using MRI: manipulation of steady state water content and water fluxes

Studies using various MRI techniques have shown that a water-protein concentration gradient exists in the ocular lens. Because this concentration is higher in the core relative to the lens periphery, a gradient in refractive index is established in the lens. To investigate how the water-protein concentration profile is maintained, bovine lenses were incubated in different solutions, and changes in water-protein concentration ratio monitored using proton density weighted (PD-weighted) imaging in the absence and presence of heavy water (D(2)O). Lenses incubated in artificial aqueous humor (AAH) maintained the steady state water-protein concentration gradient, but incubating lenses in high extracellular potassium (KCl-AAH) or low temperature (Low T-AAH) caused a collapse of the gradient due to a rise in water content in the core of the lens. To visualize water fluxes, lenses were incubated in D(2)O, which acts as a contrast agent. Incubation in KCl-AAH and low T-AAH dramatically slowed the movement of D(2)O into the core but did not affect the movement of D(2)O into the outer cortex. D(2)O seemed to preferentially enter the lens cortex at the anterior and posterior poles before moving circumferentially toward the equatorial regions. This directionality of D(2)O influx into the lens cortex was abolished by incubating lenses in high KCl-AAH or low T-AAH, and resulted in homogenous influx of D(2)O into the outer cortex. Taken together, our results show that the water-protein concentration ratio is actively maintained in the core of the lens and that water fluxes preferentially enter the lens at the poles.     

Renal inflammation and elevated blood pressure in a mouse model of reduced {beta}-ENaC

Previous studies suggest β-epithelial Na(+) channel protein (β-ENaC) may mediate myogenic constriction, a mechanism of blood flow autoregulation. A recent study demonstrated that mice with reduced levels of β-ENaC (β-ENaC m/m) have delayed correction of whole kidney blood flow responses, suggesting defective myogenic autoregulatory capacity. Reduced renal autoregulatory capacity is linked to renal inflammation, injury, and hypertension. However, it is unknown whether β-ENaC m/m mice have any complications associated with reductions in autoregulatory capacity such as renal inflammation, injury, or hypertension. To determine whether the previously observed altered autoregulatory control was associated with indicators of renal injury, we evaluated β-ENaC m/m mice for signs of renal inflammation and tissue remodeling using marker expression. We found that inflammatory and remodeling markers, such as IL-1β, IL-6, TNF-α, collagen III and transforming growth factor-β, were significantly upregulated in β-ENaC m/m mice. To determine whether renal changes were associated with changes in long-term control of blood pressure, we used radiotelemetry and found that 5-day mean arterial blood pressure (MAP) was significantly elevated in β-ENaC m/m (120 ± 3 vs. 105 ± 2 mmHg, P = 0.016). Our findings suggest loss of β-ENaC is associated with early signs of renal injury and increased MAP.     

Single Administration of p2TA (AB103), a CD28 Antagonist Peptide,Prevents Inflammatory and Thrombotic Reactions and Protects against Gastrointestinal Injury in Total-Body Irradiated Mice

The goal of this study was to elucidate the action of the CD28 mimetic peptide p2TA (AB103) that attenuates an excessive inflammatory response in mitigating radiation-induced inflammatory injuries. BALB/c and A/J mice were divided into four groups: Control (C), Peptide (P; 5 mg/kg of p2TA peptide), Radiation (R; total body irradiation with 8 Gy γ-rays), and Radiation + Peptide (RP; irradiation followed by p2TA peptide 24 h later). Gastrointestinal tissue damage was evaluated by analysis of jejunum histopathology and immunohistochemistry for cell proliferation (Cyclin D1) and inflammation (COX-2) markers, as well as the presence of macrophages (F4/80). Pro-inflammatory cytokines IL-6 and KC as well as fibrinogen were quantified in plasma samples obtained from the same mice. Our results demonstrated that administration of p2TA peptide significantly reduced the irradiation-induced increase of IL-6 and fibrinogen in plasma 7 days after exposure. Seven days after total body irradiation with 8 Gy of gamma rays numbers of intestinal crypt cells were reduced and villi were shorter in irradiated animals compared to the controls. The p2TA peptide delivery 24 h after irradiation led to improved morphology of villi and crypts, increased Cyclin D1 expression, decreased COX-2 staining and decreased numbers of macrophages in small intestine of irradiated mice. Our study suggests that attenuation of CD28 signaling is a promising therapeutic approach for mitigation of radiation-induced tissue injury.     

Genetic Admixture in the Culturally Unique Peranakan Chinese Population in Southeast Asia

The Peranakan Chinese are culturally unique descendants of immigrants from China who settled in the Malay Archipelago ∼300–500 years ago. Today, among large communities in Southeast Asia, the Peranakans have preserved Chinese traditions with strong influence from the local indigenous Malays. Yet, whether or to what extent genetic admixture co-occurred with the cultural mixture has been a topic of ongoing debate. We performed whole-genome sequencing (WGS) on 177 Singapore (SG) Peranakans and analyzed the data jointly with WGS data of Asian and European populations. We estimated that Peranakan Chinese inherited ∼5.62% (95% confidence interval [CI]: 4.76–6.49%) Malay ancestry, much higher than that in SG Chinese (1.08%, 0.65–1.51%), southern Chinese (0.86%, 0.50–1.23%), and northern Chinese (0.25%, 0.18–0.32%). A sex-biased admixture history, in which the Malay ancestry was contributed primarily by females, was supported by X chromosomal variants, and mitochondrial (MT) and Y haplogroups. Finally, we identified an ancient admixture event shared by Peranakan Chinese and SG Chinese ∼1,612 (95% CI: 1,345–1,923) years ago, coinciding with the settlement history of Han Chinese in southern China, apart from the recent admixture event with Malays unique to Peranakan Chinese ∼190 (159–213) years ago. These findings greatly advance our understanding of the dispersal history of Chinese and their interaction with indigenous populations in Southeast Asia.     

Genetically determined differences in liver alcohol dehydrogenase activity in male rats

Alcohol dehydrogenase (EC 1.1.1.1) activity was measured in liver extracts from one outbred and three inbred strains of rats. Strain-specific differences in enzyme activity were observed in the adult male rats. The differences appeared as the animals reached puberty. Studies on the enzyme purified from Sprague-Dawley and ACI rats indicate that the enzymes in these strains are identical and that the difference in activity found in liver extracts is due to differences in the amount of enzyme present. Genetic crosses between Sprague-Dawley and ACI rats suggest that the liver content of alcohol dehydrogenase is controlled by an autosomal regulatory locus with the characteristics of a temporal gene.