The development of resistance to an inhibitor of a cellular protein reveals a critical interaction between the enterovirus protein 2C and a small GTPase Arf1

The cellular protein GBF1, an activator of Arf GTPases (ArfGEF: Arf guanine nucleotide exchange factor), is recruited to the replication organelles of enteroviruses through interaction with the viral protein 3A, and its ArfGEF activity is required for viral replication, however how GBF1-dependent Arf activation supports the infection remains enigmatic. Here, we investigated the development of resistance of poliovirus, a prototype enterovirus, to increasing concentrations of brefeldin A (BFA), an inhibitor of GBF1. High level of resistance required a gradual accumulation of multiple mutations in the viral protein 2C. The 2C mutations conferred BFA resistance even in the context of a 3A mutant previously shown to be defective in the recruitment of GBF1 to replication organelles, and in cells depleted of GBF1, suggesting a GBF1-independent replication mechanism. Still, activated Arfs accumulated on the replication organelles of this mutant even in the presence of BFA, its replication was inhibited by a pan-ArfGEF inhibitor LM11, and the BFA-resistant phenotype was compromised in Arf1-knockout cells. Importantly, the mutations strongly increased the interaction of 2C with the activated form of Arf1. Analysis of other enteroviruses revealed a particularly strong interaction of 2C of human rhinovirus 1A with activated Arf1. Accordingly, the replication of this virus was significantly less sensitive to BFA than that of poliovirus. Thus, our data demonstrate that enterovirus 2Cs may behave like Arf1 effector proteins and that GBF1 but not Arf activation can be dispensable for enterovirus replication. These findings have important implications for the development of host-targeted anti-viral therapeutics.

Can rhythm-mediated reward boost learning, memory, and social connection? Perspectives for future research

Studies of rhythm processing and of reward have progressed separately, with little connection between the two. However, consistent links between rhythm and reward are beginning to surface, with research suggesting that synchronization to rhythm is rewarding, and that this rewarding element may in turn also boost this synchronization. The current mini review shows that the combined study of rhythm and reward can be beneficial to better understand their independent and combined roles across two central aspects of cognition: 1) learning and memory, and 2) social connection and interpersonal synchronization; which have so far been studied largely independently. From this basis, it is discussed how connections between rhythm and reward can be applied to learning and memory and social connection across different populations, taking into account individual differences, clinical populations, human development, and animal research. Future research will need to consider the rewarding nature of rhythm, and that rhythm can in turn boost reward, potentially enhancing other cognitive and social processes.

Violation of rhythmic expectancies can elicit late frontal gamma activity nested in theta oscillations

Rhythm processing involves building expectations according to the hierarchical temporal structure of auditory events. Although rhythm processing has been addressed in the context of predictive coding, the properties of the oscillatory response in different cortical areas are still not clear. We explored the oscillatory properties of the neural response to rhythmic incongruence and the cross-frequency coupling between multiple frequencies to further investigate the mechanisms underlying rhythm perception. We designed an experiment to investigate the neural response to rhythmic deviations in which the tone either arrived earlier than expected or the tone in the same metrical position was omitted. These two manipulations modulate the rhythmic structure differently, with the former creating a larger violation of the general structure of the musical stimulus than the latter. Both deviations resulted in an MMN response, whereas only the rhythmic deviant resulted in a subsequent P3a. Rhythmic deviants due to the early occurrence of a tone, but not omission deviants, seemed to elicit a late high gamma response (60-80 Hz) at the end of the P3a over the left frontal region, which, interestingly, correlated with the P3a amplitude over the same region and was also nested in theta oscillations. The timing of the elicited high-frequency gamma oscillations related to rhythmic deviation suggests that it might be related to the update of the predictive neural model, corresponding to the temporal structure of the events in higher-level cortical areas.

Visual Function after Implantation of Aniridia Intraocular Lens for Traumatic Aniridia in Vitrectomized Eye

Purpose

To evaluate the efficacy and safety of aniridia posterior chamber intraocular lens (PCIOL) in traumatic aniridia and aphakia in vitrectomized eyes.

Methods

Four aphakic patients with traumatic aniridia and previous pars plana vitrectomy (PPV) due to posterior segment trauma enrolled in the study, and had secondary implantation of an aniridia PCIOL. Two patients were men and two women with mean age of 39.25 years. Complete ophthalmic examinations, including preoperative and postoperative visual acuity in dark and light, glare disability, visual function (using VF-9 questions modified from VF-14), stereopsis, and contrast sensitivity in 3, 6, 12, and 18 cycle per degree frequencies, were done for all patients. Postoperative intraocular pressure (IOP), IOL centration, and intraocular inflammation were monitored. Mean follow-up was 12.25 months (range 7 to 15 months).

Results

Visual acuity improved in all four patients, especially in the light. Glare was subjectively reduced in all of them. Stereopsis was measurable in three of them postoperatively. Contrast sensitivity improved in all patients, especially in brightness and lower frequencies. All four eyes had improved VF-9. All eyes achieved the desired anatomic results. Two cases developed elevated IOP early after surgery. In one eye, IOP elevation was transient and controlled with antiglaucoma medication, but the other eye, which had secondary glaucoma from previous trauma, required cyclophotocoagulation for the IOP to be controlled. No patient developed chronic uveitis or redetachment.

Conclusions

The aniridia PCIOL can overcome aphakia, reduce glare, and increase visual function, contrast sensitivity, and stereopsis in vitrectomized eyes with traumatic aniridia. Although this kind of IOL appears safe, some disadvantages are secondary glaucoma and reduced visibility of peripheral fundus, and caution should be used in its implantation until more patients with longer follow-up are studied.

Retinal nerve fibre layer thickness is reduced in metabolic syndrome

AIMS

To investigate retinal nerve fibre layer (RNFL) thickness in people with metabolic syndrome (MetS) and healthy controls.

METHODS

A cross-sectional study was performed from March 2014 to January 2016. All participants underwent anthropometric and serological biochemical measurements, ophthalmological examination, and spectral-domain optical coherence tomography (SD-OCT). Individuals with elevated intraocular pressure, glaucoma, diabetic retinopathy and other ocular disorders were excluded. T-test, Chi square and general linear models were used to analyse the data.

RESULTS

In total, 278 eyes from 139 participants were investigated [median (interquartile range) age: 37 (32-43) years]. RNFL thickness was lower in the nasal superior (107.8 ± 19.5μm) and temporal superior (135.7 ± 18.9μm) sectors in MetS group compared with the control group (114.6 ± 22.4 μm, P = 0.013 and 140.7 ± 18.2 μm, P = 0.027, respectively). After multiple adjustments for age, gender and the side of the examined [right (OD)/left (OS)] eye, MetS was independently associated with a lower RFNL thickness in the nasal superior (β = 0.20, P = 0.009) and temporal superior (β = 0.14, P = 0.048) sectors. RNFL thickness was significantly reduced in participants with higher numbers of metabolic abnormalities, independent of age, gender and the side of the examined eye (P = 0.043).

CONCLUSION

Our findings demonstrate that MetS is independently associated with reduced RNFL thickness, suggesting that neurodegeneration is implicated in pathogenesis of MetS.

Lens parameters as predictors of intraocular pressure changes after phacoemulsification

PURPOSE

To evaluate intraocular pressure (IOP) change after cataract surgery in non-glaucomatous eyes with narrow and open angles (OAs) and its relation to novel lens parameters measured by anterior segment optical coherence tomography (AS-OCT).

SETTING

University affiliated hospital, Farabi Eye Hospital, Tehran, Iran.

DESIGN

Prospective interventional case series.

METHODS

In this prospective study, 85 non-glaucomatous eyes underwent phacoemulsification and lens implantation. Thirty-nine eyes had OAs and 46 eyes had narrow angles (NAs). IOP and biometric parameters were measured by AS-OCT preoperatively and 3 months after surgery. Change in IOP and its relation to biometric parameters, including lens vault (LV), anterior vault (AV), defined as the sum of the LV and the ACD, and relative LV (rLV), defined as the ratio of the LV to the AV, were evaluated. The main outcome measure was degree of IOP change after phacoemulsification.

RESULTS

Of the 85 patients included in the analysis, 35 were male and 50 were female with an overall mean age of 62.2 ± 8.9 years. The average IOP reduction was -4.95 ± 2.26 mm Hg, from a preoperative mean of 17.12 ± 2.47 mm Hg, at 3 months after cataract surgery. The amount of IOP reduction was significantly greater in the NA compared with the OA group. In multivariate linear regression analysis, preoperative IOP and AV were significantly associated with IOP decrease (all ≤ 0.03).

CONCLUSION

Cataract surgery results in IOP reduction in both OA and NA eyes. The amount of IOP reduction is related to AV.

Relationship between GDx VCC and Stratus OCT in juvenile glaucoma

PURPOSE

To compare the ability of scanning laser polarimetry (GDx VCC) and optical coherence tomography (OCT) to discriminate eyes with juvenile glaucoma from normal eyes and to assess the relationship between their parameters.

METHODS

A total of 24 glaucomatous eyes of 24 patients and 24 normal eyes were enrolled. The age range of the patient was 11-40 years with a mean age of 25.1+/-8.2 years. Control groups consisted 24 eyes of 24 individuals without glaucoma with a mean age of 33.2+/-8.2 years. All subjects underwent a full ophthalmic examination, automated perimetry, GDx VCC, and OCT. Correlation coefficients between the parameters of OCT and GDx VCC were calculated. We calculated the area under the receiver operating characteristic curve (AROC) for the main parameters of GDx VCC and OCT.

RESULTS

Statistically significant correlations were observed between GDx VCC and OCT parameters. Pearson coefficients ranged from 0.75 for inferior average to 0.86 for nerve fibre indicator (NFI)/average thickness OCT. The greatest AROC parameter in OCT (inferior average: 0.92) had a lower area than that in GDx VCC (NFI: 0.99). There was a significant statistical significance in all visual field, GDx VCC, and OCT variables between two groups (P<0.05).

CONCLUSIONS

Many GDx VCC parameters were significantly correlated with those of the OCT in patients with juvenile glaucoma. Inferior average and NFI had the greatest AROC parameter in OCT and GDx VCC, respectively. NFI had high sensitivity and specificity for the diagnosis of JOAG.

Biometric indices evaluation in central retinal vein occlusion using partial coherence laser interferometry

PURPOSE

To evaluate the association of axial length and posterior segment length with central retinal vein occlusion (CRVO) using optical coherence interferometry.

METHODS

The study group consisted of 29 patients (13 female and 16 male) with unilateral CRVO who were referred to Farabi Eye Hospital. Patients with macular edema were excluded. The mean keratometry (mean K), axial lengths (AL), anterior chamber depths (ACD), and posterior segment lengths (PSL, defined by AL - ACD) of affected and fellow eyes were measured using optical coherence interferometry.

RESULTS

Age range was 45 to 74 years (mean 59.2 +/- 7.5 years). The mean K of affected eyes was not statistically significantly lower than that of unaffected eyes in the CRVO group. This was also true for ACD. Although affected eyes had shorter axial length (23.26 mm vs 23.33 mm), the difference was not significant. There was a statistically significant difference in PSL affected and unaffected eyes (20.15 mm vs 20.26 mm) (p=0.008).

CONCLUSIONS

Posterior segment length of eyes with CRVO may be shorter than unaffected eyes. This may predispose them to more crowding of central retinal vein and artery in lamina cribrosa, and developing CRVO.

Transplantation of conjunctival limbal autograft and amniotic membrane vs mitomycin C and amniotic membrane in treatment of recurrent pterygium

AIM

To compare the efficacy and complications of conjunctival limbal autograft (CLAU) and amniotic membrane transplantation (AMT) vsintraoperative mitomycin C (MMC) and AMT for treatment of recurrent pterygium.

METHODS

Forty eyes of 40 patients with recurrent pterygium underwent CLAU and AMT (20 eyes) or intraoperative MMC (0.02%, 3 min) and AMT (20 eyes). Three eyes (15%) had symblepharon before surgery in each group. Recurrence was compared in each group by using chi(2) test.

RESULTS

No major postoperative complications occurred during 6-19 months of follow-up. In CLAU/AMT group, no pterygium recurrence was observed. Recurrence occurred in four eyes (20%) in MMC/AMT group after 3 and 4 months (P-value=0.035, chi(2) test). No recurrence of pterygium or symblepharon was seen in six eyes with recurrent pterygium and symblepharon (three eyes in each group).

CONCLUSION

CLAU with AMT seems to be more effective than intraoperative MMC with AMT for treatment of recurrent pterygium.

Intracameral tissue plasminogen activator to prevent severe fibrinous effusion after congenital cataract surgery

BACKGROUND/AIMS

To evaluate the efficacy of intracameral recombinant tissue plasminogen activator (r-TPA) in prevention of fibrinous effusion after lensectomy, anterior vitrectomy, and posterior chamber intraocular lens (PCIOL) implantation in patients with congenital cataract.

METHODS

The study was done as a double masked randomised clinical trial between April 2002 and November 2003 in Farabi Eye Hospital. 34 eyes of 26 patients with congenital cataract were included in the study and randomised into two groups (18 cases and 16 controls). Mean age was 8.1 years (3--14 years). Each eye underwent lensectomy and anterior vitrectomy with PCIOL implantation. At the end of surgery 20 microg r-TPA was injected intra-camerally in the case group. The control group received only balanced salt solution. All patients received periocular, systemic, and topical steroids after surgery. Patients underwent follow up examinations for 3 months.

RESULTS

The incidence of intraocular fibrin membrane formation was significantly lower in the case group on days 1, 3, 7, 14 (p=0.02, p=0.01, p=0.01, and p=0.01, respectively, chi(2) test), but there was no significant difference on days 30 and 90. The frequency of pigmented intraocular lens precipitates was significantly lower in the case group at the end of the third month (p<0.001, chi(2) test). No gross ocular side effects were noted after r-TPA injection.

CONCLUSION

It seems that prophylactic intracameral r-TPA is effective in prevention of fibrinous effusion at least in the first 2 weeks after cataract extraction in the paediatric age group and decreases the incidence of pigmented IOL precipitates.

Posterior polar cataract: minimizing risk of posterior capsule rupture

PURPOSE

To study a preferred technique of phacoemulsification in eyes with posterior polar cataract and report its outcome.

METHODS

Under topical anesthesia, phacoemulsification was carried out after hydrodelination in 23 cases (38 eyes) with ages ranging from 19 to 65 years (mean=33.5 years). Hydrodissection was not performed.

RESULTS

Mean duration of follow-up was 9.5 months. None of the eyes developed posterior capsule rupture, but seven eyes (18.4%) revealed posterior capsule plaque postoperatively, which needed neodymium : YAG laser capsulotomy. Mean visual acuity improved significantly after surgery (P=0.0001, paired t-test); In all, 34 eyes achieved a best-corrected visual acuity of 20/40 or more (89.4%). However, the postoperative visual acuity was less than 20/25 in 11 eyes (28.9%). The causes of the low acuity were amblyopia in eight eyes (21.0%) and macular degeneration due to retinitis pigmentosa in two others (5.2%).

CONCLUSION

Phacoemulsification is an effective and safe method to treat posterior polar cataract with gentle hydrodelination 'hydrodissection free phacoemulsification technique'. This is especially true when great attention is paid to the 'floppy' posterior capsule. Although previous amblyopia might interfere with excellent surgical outcome in patients with a unilateral or highly asymmetric bilateral cataract, visual acuity improved significantly in most cases.