Comparative analysis of bioinformatics tools to characterize SARS-CoV-2 subgenomic RNAs

During the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), positive-sense genomic RNA and subgenomic RNAs (sgRNAs) are synthesized by a discontinuous process of transcription characterized by a template switch, regulated by transcription-regulating sequences (TRS). Although poorly known about makeup and dynamics of sgRNAs population and function of its constituents, next-generation sequencing approaches with the help of bioinformatics tools have made a significant contribution to expand the knowledge of sgRNAs in SARS-CoV-2. For this scope to date, Periscope, LeTRS, sgDI-tector, and CORONATATOR have been developed. However, limited number of studies are available to compare the performance of such tools. To this purpose, we compared Periscope, LeTRS, and sgDI-tector in the identification of canonical (c-) and noncanonical (nc-) sgRNA species in the data obtained with the Illumina ARTIC sequencing protocol applied to SARS-CoV-2-infected Caco-2 cells, sampled at different time points. The three software showed a high concordance rate in the identification and in the quantification of c-sgRNA, whereas more differences were observed in nc-sgRNA. Overall, LeTRS and sgDI-tector result to be adequate alternatives to Periscope to analyze Fastq data from sequencing platforms other than Nanopore.

Skewed X-chromosome inactivation in unsolved neurodevelopmental disease cases can guide re-evaluation For X-linked genes

Despite major advances in genome technology and analysis, >50% of patients with a neurodevelopmental disorder (NDD) remain undiagnosed after extensive evaluation. A point in case is our clinically heterogeneous cohort of NDD patients that remained undiagnosed after FRAXA testing, chromosomal microarray analysis and trio exome sequencing (ES). In this study, we explored the frequency of non-random X chromosome inactivation (XCI) in the mothers of male patients and affected females, the rationale being that skewed XCI might be masking previously discarded genetic variants found on the X chromosome. A multiplex fluorescent PCR-based assay was used to analyse the pattern of XCI after digestion with HhaI methylation-sensitive restriction enzyme. In families with skewed XCI, we re-evaluated trio-based ES and identified pathogenic variants and a deletion on the X chromosome. Linkage analysis and RT-PCR were used to further study the inactive X chromosome allele, and Xdrop long-DNA technology was used to define chromosome deletion boundaries. We found skewed XCI (>90%) in 16/186 (8.6%) mothers of NDD males and in 12/90 (13.3%) NDD females, far beyond the expected rate of XCI in the normal population (3.6%, OR = 4.10; OR = 2.51). By re-analyzing ES and clinical data, we solved 7/28 cases (25%) with skewed XCI, identifying variants in KDM5C, PDZD4, PHF6, TAF1, OTUD5 and ZMYM3, and a deletion in ATRX. We conclude that XCI profiling is a simple assay that targets a subgroup of patients that can benefit from re-evaluation of X-linked variants, thus improving the diagnostic yield in NDD patients and identifying new X-linked disorders.

Same-day surgery may reduce the risk of losing pain perception in dogs with thoracolumbar disc extrusion

OBJECTIVES

To compare the proportions of dogs with thoracolumbar disc extrusion that lose pelvic limb pain perception if surgery is performed on the day of admission or delayed overnight. To describe the outcome of those dogs that deteriorate to lose pain perception.

MATERIALS AND METHODS

Retrospective, single centre study on 273 client-owned dogs with thoracolumbar disc extrusion and intact pain perception, but inability to walk unaided on their pelvic limbs. Dogs were subdivided into two groups: early surgery (spinal decompression between their examination at day of admission and the following morning), and delayed surgery (did not undergo surgery between admission and the following morning). The proportion of dogs that lost pelvic limb pain perception overnight was compared between the early and delayed surgery groups.

RESULTS

Seven of 151 dogs in the early surgery group lost pain perception overnight compared to 15 of 122 in the delayed surgery group (Fisher's exact test, P = 0.025). Number-needed-to-treat analysis suggested that 14 dogs (95% confidence interval: 7-106 dogs) need early surgery to prevent one losing pain perception overnight. Five of the seven dogs that lost pain perception in the early surgery group recovered pain perception by 3 weeks post-operatively, compared to eight of 14 in the delayed group.

CLINICAL SIGNIFICANCE

This study suggests that an overnight delay before spinal decompression increases the risk of clinically meaningful deterioration in dogs unable to walk following thoracolumbar disc extrusion.

Methylation alteration of SHANK1 as a predictive, diagnostic and prognostic biomarker for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease characterized by the clonal expansion of malignant B cells. To predict the clinical course of the disease, the identification of diagnostic biomarkers is urgently needed. Aberrant methylation patterns may predict CLL development and its course, being very early changes during carcinogenesis. Our aim was to identify CLL specific methylation patterns and to evaluate whether methylation aberrations in selected genes are associated with changes in gene expression. Here, by performing a genome-wide methylation analysis, we identified several CLL-specific methylation alterations. We focused on the most altered one, at a CpG island located in the body of SHANK1 gene, in our CLL cases compared to healthy controls. This methylation alteration was successfully validated in a larger cohort including 139 CLL and 20 control in silico samples. We also found a positive correlation between SHANK1 methylation level and absolute lymphocyte count, in particular CD19+ B cells, in CLL patients. Moreover, we were able to detect gains of methylation at SHANK1 in blood samples collected years prior to diagnosis. Overall, our results suggest methylation alteration at this SHANK1 CpG island as a biomarker for risk and diagnosis of CLL, and also in the personalized quantification of tumor aggressiveness.

Clustered protocadherins methylation alterations in cancer

Background

Clustered protocadherins (PCDHs) map in tandem at human chromosome 5q31 and comprise three multi-genes clusters: α-, β- and γ-PCDH. The expression of this cluster consists of a complex mechanism involving DNA hub formation through DNA-CCTC binding factor (CTCF) interaction. Methylation alterations can affect this interaction, leading to transcriptional dysregulation. In cancer, clustered PCDHs undergo a mechanism of long-range epigenetic silencing by hypermethylation.

Results

In this study, we detected frequent methylation alterations at CpG islands associated to these clustered PCDHs in all the solid tumours analysed (colorectal, gastric and biliary tract cancers, pilocytic astrocytoma), but not hematologic neoplasms such as chronic lymphocytic leukemia. Importantly, several altered CpG islands were associated with CTCF binding sites. Interestingly, our analysis revealed a hypomethylation event in pilocytic astrocytoma, suggesting that in neuronal tissue, where PCDHs are highly expressed, these genes become hypomethylated in this type of cancer. On the other hand, in tissues where PCDHs are lowly expressed, these CpG islands are targeted by DNA methylation. In fact, PCDH-associated CpG islands resulted hypermethylated in gastrointestinal tumours.

Conclusions

Our study highlighted a strong alteration of the clustered PCDHs methylation pattern in the analysed solid cancers and suggested these methylation aberrations in the CpG islands associated with PCDH genes as powerful diagnostic biomarkers.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0695-0) contains supplementary material, which is available to authorized users.

Epidemiological survey on the prevalence of Salmonella spp. in the Sardinian pig production chain, using real-time PCR screening method

The aim of this study was to evaluate the prevalence of Salmonella spp. in the Sardinian pig production chain in order to establish the incidence of monophasic serovariant of Salmonella Typhimurium on isolates with molecular methods (real-time PCR and multiplex PCR). Samples were collected in three EC slaughterhouses, four small slaughterhouses annexed to farmhouses, one meat distribution center, four meat cutting laboratories and four sausage processing plants. A total of 166 samples were collected and analyzed: 46 environmental samples, 48 finishing pigs, 16 piglets, 24 samples of non-processed meat, 28 meat preparations and 4 meat products. All samples were processed with an initial screening using the real-time PCR MicroSEQ® Salmonella spp detection Kit (Applied biosystems, life technologies) and with the TaqMan® Real-time PCR to confirm the kit results. Samples that tested positive for Salmonella spp were confirmed with cultural method using the standard ISO 6579. Positive samples were submitted to phenotypic identification. One colony from each positive sample was serotyped with multiplex PCR method. Salmonella spp was isolated in 7 on 166 samples (4.22 %). Among the positive samples, two came from finishing pigs, two belonged to the category meat preparations, two to meat products, one was an environmental sample. Multiplex PCR confirmed that the collected strains belonged to the species Salmonella Typhimurium (1), Salmonella derby (3) and monophasic serovariant of Salmonella Typhimurium (3).

Analysis of a Sardinian Multiplex Family with Autism Spectrum Disorder Points to Post-Synaptic Density Gene Variants and Identifies CAPG as a Functionally Relevant Candidate Gene

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders with high heritability, although their underlying genetic factors are still largely unknown. Here we present a comprehensive genetic characterization of two ASD siblings from Sardinia by genome-wide copy number variation analysis and whole exome sequencing (WES), to identify novel genetic alterations associated with this disorder. Single nucleotide polymorphism (SNP) array data revealed a rare microdeletion involving CAPG, ELMOD3, and SH2D6 genes, in both siblings. CAPG encodes for a postsynaptic density (PSD) protein known to regulate spine morphogenesis and synaptic formation. The reduced CAPG mRNA and protein expression levels in ASD patients, in the presence of hemizygosity or a particular genetic and/or epigenetic background, highlighted the functional relevance of CAPG as a candidate gene for ASD. WES analysis led to the identification in both affected siblings of a rare frameshift mutation in VDAC3, a gene intolerant to loss of function mutation, encoding for a voltage-dependent anion channel localized on PSD. Moreover, four missense damaging variants were identified in genes intolerant to loss of function variation encoding for PSD proteins: PLXNA2, KCTD16, ARHGAP21, and SLC4A1. This study identifies CAPG and VDAC3 as candidate genes and provides additional support for genes encoding PSD proteins in ASD susceptibility.

Colorectal cancer early methylation alterations affect the crosstalk between cell and surrounding environment, tracing a biomarker signature specific for this tumor

Colorectal cancer (CRC) develops through the accumulation of both genetic and epigenetic alterations. However, while the former are already used as prognostic and predictive biomarkers, the latter are less well characterized. Here, performing global methylation analysis on both CRCs and adenomas by Illumina Infinium HumanMethylation450 Bead Chips, we identified a panel of 74 altered CpG islands, demonstrating that the earliest methylation alterations affect genes coding for proteins involved in the crosstalk between cell and surrounding environment. The panel discriminates CRCs and adenomas from peritumoral and normal mucosa with very high specificity (100%) and sensitivity (99.9%). Interestingly, over 70% of the hypermethylated islands resulted in downregulation of gene expression. To establish the possible usefulness of these non-invasive markers for detection of colon cancer, we selected three biomarkers and identified the presence of altered methylation in stool DNA and plasma cell-free circulating DNA from CRC patients.

Integrated DNA methylation analysis identifies topographical and tumoral biomarkers in pilocytic astrocytomas

Pilocytic astrocytoma (PA) is the most common glioma in pediatric patients and occurs in different locations. Chromosomal alterations are mostly located at chromosome 7q34 comprising the BRAF oncogene with consequent activation of the mitogen-activated protein kinase pathway. Although genetic and epigenetic alterations characterizing PA from different localizations have been reported, the role of epigenetic alterations in PA development is still not clear. The aim of this study was to investigate whether distinctive methylation patterns may define biologically relevant groups of PAs. Integrated DNA methylation analysis was performed on 20 PAs and 4 normal brain samples by Illumina Infinium HumanMethylation27 BeadChips.

We identified distinct methylation profiles characterizing PAs from different locations (infratentorial vs supratentorial) and tumors with onset before and after 3 years of age. These results suggest that PA may be related to the specific brain site where the tumor arises from region-specific cells of origin. We identified and validated in silico the methylation alterations of some CpG islands. Furthermore, we evaluated the expression levels of selected differentially methylated genes and identified two biomarkers, one, IRX2, related to the tumor localization and the other, TOX2, as tumoral biomarker.

Differences in Epidural Pathology between Cervical and Thoracolumbar Intervertebral Disk Extrusions in Dogs

Background

Although the basic pathophysiology is the same in both cervical and thoracolumbar intervertebral disk (IVD) extrusions, there are considerable clinical differences that have only been partially explained.

Hypothesis/Objectives

The epidural inflammatory response differs between cervical and thoracolumbar IVD extrusions.

Animals

Fifty‐five dogs with cervical and 80 dogs with thoracolumbar IVD extrusions.

Methods

Clinical data and histopathologic variables were investigated. Associations between severity of epidural inflammation and clinical and pathologic variables, impact of chondrodystrophic phenotype, and localization (cervical versus thoracolumbar) were evaluated statistically.

Results

Dogs with cervical IVD extrusion were significantly older (P < 0.001), had less severe and longer duration of neurologic signs (both P < 0.001), were more painful (P = 0.038), and had a better outcome (P = 0.005) than dogs with a thoracolumbar IVD extrusion. On histopathology, cervical epidural material had less severe calcification (P = 0.002) and inflammation (P < 0.001). No significant differences regarding chondrodystrophic phenotype were found.

Conclusion and Clinical Importance

There was significantly less intensive inflammatory response in the cervical epidural space. This observation correlated positively with less nucleus pulposus calcification in cervical extrusions indicating biochemical, metabolic, and biomechanical differences between the 2 locations, which remain to be characterized in future studies.

Primary Postnatal Dorsal Root Ganglion Culture from Conventionally Slaughtered Calves

Neurological disorders in ruminants have an important impact on veterinary health, but very few host-specific in vitro models have been established to study diseases affecting the nervous system. Here we describe a primary neuronal dorsal root ganglia (DRG) culture derived from calves after being conventionally slaughtered for food consumption. The study focuses on the in vitro characterization of bovine DRG cell populations by immunofluorescence analysis. The effects of various growth factors on neuron viability, neurite outgrowth and arborisation were evaluated by morphological analysis. Bovine DRG neurons are able to survive for more than 4 weeks in culture. GF supplementation is not required for neuronal survival and neurite outgrowth. However, exogenously added growth factors promote neurite outgrowth. DRG cultures from regularly slaughtered calves represent a promising and sustainable host specific model for the investigation of pain and neurological diseases in bovines.

Prevalence of L. monocytogenes in environmental samples collected in dairy plants of Sassari Province, Italy

Listeria (L.) monocytogenes is frequently isolated from food production environment and often persists in dairy plants despite vigorous sanitation regimes. In recent years several alert notifications were sent to Rapid Alert System for Food Products system as a consequence of Listeria monocytogenes contamination of ricotta cheese. After the alert of 2012, competent authority (Local Health Unit of Sassari Province) organised an environmental monitoring plan with the partnership of the Institute for Experimental Veterinary Medicine of Sardinia to verify analysis of dairy plants own-check according to Regulation (EC) N° 2073/05 and further modifications. In 2014 n. 665 processing areas samples of n. 50 dairy plants of Sassari Province were examined. UNI EN ISO 11290-1:2005 for detection of L. monocytogenes was used. Non-compliance in n. 5 diary plants are observed (n. 8 positive samples). Post-non-compliance environmental sanitisation was efficient and own-check plans included appropriate corrective actions.

PREPARATION OF B-CYCLODEXTRIN-THIABENDAZOLE-PIPERONYL BUTOXIDE SUPRAMOLECULAR COMPLEX AND ITS ACTIVITY AGAINST BLUE AND GREEN MOULD DECAY ON INOCULATED SATSUMA FRUIT

The supramolecular complex of β-cyclodextrin-thiabendazole-piperony butoxide (βCD-TBZ/PBO) was prepared and its structure was characterized by 1H NMR. Additionally, the antifungal activity of βCD-TBZ/PBO was investigated in comparison with the commercially available thiabendazole (TBZ) fungicide by in vitro tests and on artificially inoculated 'Okitsu' satsuma fruit dipped in water at 20 degrees C or at 50 degrees C to control postharvest blue (Penicillium italicum) and green mould (P. digitatum). β-CD-TBZ/PBO is stable for several months when stored as powder in a dark bottle. At pH 7.0 the water solubility of the βCD-TBZ/PBO complex was consistently higher than free TBZ. Water dip at 20 degrees C did not affect decay incidence caused by blue mould but favoured the development of green mould during 4-8 days of storage at 20 degrees C with respect to untreated (control) fruit. Water at 50 degrees C effectively reduced the incidence of blue mould and totally suppressed green mould during the first 4 days but lost its efficacy afterwards. By contrast, both TBZ and βCD-TBZ/PBO had a lasting effect and were equally effective in controlling green and blue mould decay when applied at 20 degrees C and 60 mg L(-1) active ingredient (a.i.). When applied at 50 degrees C and 20 mg L(-1) a.i. the activity of the complex against blue mould was inferior than the corresponding treatment with TBZ. In vitro assays revealed a significant effectiveness of βCD-TBZ/PBO complex at low concentration compared to commercial formulation of TBZ.

Curcumin and curcumin-like molecules: from spice to drugs

Curcumin is the major yellow pigment extracted from turmeric, a commonly used spice in Asian cuisine and extensively employed in ayurvedic herbal remedies. A number of studies have shown that curcumin can be a prevention and a chemotherapeutic agent for colon, skin, oral and intestinal cancers. Curcumin is also well known for its antiinflammatory and antioxidant properties, showing high reactivity towards peroxyl radicals, and thus acting as a free radical scavenger. Recently, experimental studies have demonstrated that curcumin might be used in the prevention and the cure of Alzheimer's disease. Indeed, curcumin injected peripherally in vivo into aged Tg mice crossed the blood-brain barrier and bound to amyloid plaques, reducing amyloid levels and plaque formation decisively. The present review will resume the most recent developments in the medicinal chemistry of curcumin and curcumin-like molecules.

Clinical and pathological analysis of epidural inflammation in intervertebral disk extrusion in dogs

BACKGROUND

Little is known about the pathologic changes in the epidural space after intervertebral disk (IVD) extrusion in the dog.

OBJECTIVES

To analyze the pathology of the epidural inflammatory response, and to search for correlations between this process and clinical findings.

METHODS

Clinical data from 105 chondrodystrophic (CD) and nonchondrodystrophic (NCD) dogs with IVD extrusion were recorded. Epidural material from these dogs was examined histopathologically and immunohistochemically. Using statistical analysis, we searched for correlations between severity of epidural inflammation and various clinical and pathologic variables.

RESULTS

Most dogs exhibited an epidural inflammatory response, ranging from acute invasion of neutrophils to formation of chronic granulation tissue. The mononuclear inflammatory infiltrates consisted mostly of monocytes and macrophages and only few T and B cells. Surprisingly, chronic inflammatory patterns also were found in animals with an acute clinical history. Severity of the epidural inflammation correlated with degree of the epidural hemorrhage and nucleus pulposus calcification (P = .003 and .040), but not with age, chondrodystrophic phenotype, neurologic grade, back pain, pretreatment, or duration. The degree of inflammation was statistically (P = .021) inversely correlated with the ability to regain ambulation.

CONCLUSION AND CLINICAL IMPORTANCE

Epidural inflammation occurs in the majority of dogs with IVD extrusion and may develop long before the onset of clinical signs. Presence of calcified IVD material and hemorrhage in the epidural space may be the triggers of this lesion rather than an adaptive immune response to the nucleus pulposus as suggested in previous studies. Because epidural inflammation may affect outcome, further research is warranted.

Effect of heat treatments on biomolecular profile of Sardinian apple cultivars

Postharvest heat treatments (hot water or hot air treatment) may be applied to horticultural crops to control fungal diseases, insect infestation and to reduce chilling injury in cultivars susceptible to low storage temperatures. The present study investigated the influence of hot water (53 degrees C for 60s) and hot air treatment (38 degrees C for 24h) applied to two typical Sardinian apple varieties, cvs. Miali and Caddina, on the composition of the lipophilic extracts of the peel as well as on the antioxidant activity of ethanolic extracts of both peel and pulp. The lipophilic extracts of the peel of the two varieties were almost similar and resulted to be dominated by the presence of triterpenes being ursolic and oleanoic acids the main metabolites in both analysed fruits. The chemical analysis of the extracts obtained from the different heat-treated samples for each variety revealed no significant difference in the relative distribution of triterpene components with respect to untreated control samples. This strongly suggested that heat treatment does not affect the composition of terpene metabolite profile of the fruit peel. On the other hand, the antioxidant activity of the ethanolic extracts of the peel and the pulp of heat treated was significantly different from that of control In particular, on Caddina variety the antioxidant activity levels of the peel were consistently higher than in the pulp and were affected by storage conditions. Differently, on Miali variety the antioxidant activity of heat-treated samples was higher than control sample in both peel and pulp.

Effect of different film packaging on microbial growth in minimally processed cactus pear (Opuntia ficus-indica)

Microorganisms are natural contaminants of fresh produce and minimally processed products, and contamination arises from a number of sources, including the environment, postharvest handling and processing. Fresh-cut products are particularly susceptible to microbial contaminations because of the changes occurring in the tissues during processing. In package gas composition of modified atmosphere packaging (MAP) in combination with low storage temperatures besides reducing physiological activity of packaged produce, can also delay pathogen growth. Present study investigated on the effect of MAPs, achieved with different plastic films, on microbial growth of minimally processed cactus pear (Opuntio ficus-indica) fruit. Five different plastic materials were used for packaging the manually peeled fruit. That is: a) polypropylene film (Termoplast MY 40 micron thickness, O2 transmission rate 300 cc/m2/24h); b) polyethylene film (Bolphane BHE, 11 micron thickness, O2 transmission rate 19000 cc/m2/24h); c) polypropylene laser-perforated films (Mach Packaging) with 8, 16 or 32 100-micron holes. Total aerobic psychrophilic, mesophilic microorganisms, Enterobacteriaceae, yeast, mould populations and in-package CO2, O2 and C2H4 were determined at each storage time. Different final gas compositions, ranging from 7.8 KPa to 17.1 KPa O2, and 12.7 KPa to 2.6 KPa CO2, were achieved with MY and micro perforated films, respectively. Differences were detected in the mesophilic, Enterobacteriaceae and yeast loads, while no difference was detected in psychrophilic microorganisms. At the end of storage, microbial load in fruits sealed with MY film was significantly lower than in those sealed with BHE and micro perforated films. Furthermore, fruits packed with micro-perforated films showed the highest microbial load. This occurrence may in part be related to in-package gas composition and in part to a continuous contamination of microorganisms through micro-holes.

Evidence for antiseptic behaviour towards sick adult bees in honey bee colonies

Social life is generally associated with an increased risk of disease transmission, but at the same time it allows behavioural defence at both the individual and collective level. Bees infected with deformed-wing virus were introduced into observation hives; through behavioural observations and chemical analysis of cuticular hydrocarbons from healthy and infected bees, we offer the first evidence that honeybee colonies can detect and remove infected adult bees, probably by recognising the cuticular hydrocarbon profiles of sick individuals. We also found that health-compromised colonies were less efficient at defending themselves against infected bees, thus facing an ever increasing risk of epidemics. This work reveals a new antiseptic behaviour that can only be interpreted as an adaptation at colony level and one which should be considered an element of the social immunity system of the beehive, re-enforcing the view of a colony as an integrated organism.

WARD: a pneumatic system for body weight relief in gait rehabilitation

The paper presents Walking Assistance and Rehabilitation Device (WARD), a system for walking rehabilitation devised to relieve the patient of his/her body weight of a constant and prescribed amount by externally supporting the subject at the upper trunk and pelvis level by means of a harness. The system is based on a pneumatic actuator that has proved to be effective at maintaining a constant relief force. The constancy of this force that should be maintained even under high body weight support (BWS) conditions (70-80% of body weight) seems to be important for a correct motor pattern. A law has been identified that may be useful to adjust walking speed as a function of the prescribed BWS. WARD is simple to construct, practical to use, and has been characterized on healthy subjects.

Retinal sensitivity to flicker modulation: reduced by early age-related maculopathy

PURPOSE

To evaluate retinal, cone-mediated flicker sensitivity (CFS) in age-related maculopathy (ARM) by quantifying response gain and threshold of the focal electroretinogram (FERG) to flicker modulation.

METHODS

Nineteen patients with ARM (visual acuity > or =20/30) and 11 age-matched control subjects were examined. Twelve patients had less than 20 soft drusen in the macular region and no hyper-/hypopigmentation (early lesion), whereas seven had more than 20 soft drusen and/or focal hyper-/hypopigmentation (advanced lesion). Macular (18 degree ) FERGs were elicited by a sinusoidally flickering (41 Hz) uniform field (on a light-adapting background) whose modulation depth was varied between 16.5% and 94%. Amplitude and phase of the response's fundamental harmonic were measured.

RESULTS

In both control subjects and patients with ARM, log FERG amplitude increased with log stimulus modulation depth with a straight line (power law) relation. However, the slope (or gain) of the function was, on average, steeper in control subjects than in patients with either early or advanced lesions. Mean FERG threshold, estimated from the value of the log modulation depth that yielded a criterion response, did not differ between control subjects and patients with early lesions but was increased (0.35 log units) compared with control subjects in those with advanced lesions. In both patient groups, but not in control subjects, mean FERG phase tended to delay with decreasing stimulus modulation depth.

CONCLUSIONS

Retinal CFS losses can be detected in ARM by evaluating the FERG as a function of flicker modulation depth. Reduced response gain and phase delays, with normal thresholds, are associated with early lesions. Increased response thresholds, in addition to gain and phase abnormalities, may reflect more advanced lesions. Evaluating CFS by FERG may directly document different stages of macular dysfunction in ARM.

The fundamental and second harmonic of the photopic flicker electroretinogram: temporal frequency-dependent abnormalities in retinitis pigmentosa

OBJECTIVES

The flicker electroretinogram (FERG) consists mainly of a linear (fundamental, 1F) and a non linear (second harmonic, 2F) component. Previous results indicate that 2F originates more proximally in the retina than 1F, and that retinitis pigmentosa (RP) may affect 2F to a greater extent than 1F. The aim of this study was to evaluate FERG 1F and 2F abnormalities in RP as a function of the stimulus temporal frequency (TF).

METHODS

Twelve patients with typical RP and 10 age-matched controls were examined. FERGs were recorded in response to uniform fields (18 degrees) presented in the macula on a light-adapting background. Stimuli were flickered sinusoidally at different, closely spaced TFs between 3.7 and 52 Hz. Amplitudes and phases of the Fourier analysed 1F and 2F components were measured. Components' apparent latencies were estimated from the rate at which phase lagged with TF.

RESULTS

When compared to controls, mean 1F amplitudes of patients were reduced at both low (3.7-12.6 Hz) and high (14-52 Hz) TFs, with greatest losses (0.5 log units) around the peaks (3.7 and 41 Hz) of the normal TF function. Mean 2F amplitudes were reduced mainly at low TFs, with greatest losses (0.5 log units) at 5-8 Hz. On average, the shape of the 2F, but not 1F amplitude versus TF function, differed between patients and controls, showing a selective attenuation at low TFs. Mean 1F apparent latencies were delayed at both low and high TFs, with greater delays at low (85 ms) than at high (33 ms) TFs. Mean 2F apparent latencies were delayed only at low TFs (58 ms).

CONCLUSIONS

In RP, 1F and 2F phase delays as well as 2F amplitude losses are dependent on TF, suggesting that FERG generators' subpopulations in both distal and proximal retina are differentially affected. Analysis of the FERG TF response is potentially useful to characterize cone system dysfunction in different genetic subtypes of RP.

Focal electroretinograms and fundus appearance in nonexudative age-related macular degeneration. Quantitative relationship between retinal morphology and function

BACKGROUND

The aim of this study was to evaluate the focal electroretinogram (FERG), an objective indicator of outer retinal function, in nonexudative age-related macular degeneration (NE-AMD), and to compare FERG results with morphological lesions assessed by stereoscopic fundus photographs and fluorescein angiograms.

METHODS

Twenty-five patients (25 eyes) with bilateral NE-AMD (visual acuity of the study eyes > or = 0.4) as well as 10 age- and sex-matched control subjects (10 eyes) were evaluated. FERGs were recorded from the macular region (9 degrees) in response to sinusoidal stimuli flickered at 32 Hz. Amplitude and phase angle of the Fourier-analyzed FERG fundamental component were measured. Fundus lesions were graded from color slides according to the Wisconsin age-related maculopathy grading system . Fluorescein angiograms were evaluated by an image analysis technique to compute the area with pathological hyperfluorescence (associated with drusen and/or retinal pigment epithelial atrophy) within the macular (approximately 9 degrees x 9 degrees) region.

RESULTS

Compared to control eyes, NE-AMD eyes had a reduction in the mean FERG amplitude (57% loss, P<0.001) with no phase changes. Amplitudes of individual affected eyes were negatively correlated with either the Wisconsin grading score (r = -0.63, P < 0.001) or the percentage area of pathological hyperfluorescence (r = -0.70, P<0.01). Eyes with minimal NE-AMD lesions (Wisconsin score < or = 6) and normal acuity had a lower mean amplitude (47% loss, P < 0.05) than that of control eyes.

CONCLUSIONS

The results indicate that, in NE-AMD, the FERG is altered in parallel with the extent and severity of fundus lesions. However, a functional impairment of outer macular layers, which is detected by FERG losses, could precede morphological changes typical of more advanced disease.

The spatial tuning of steady state pattern electroretinogram in multiple sclerosis

In normal subjects, the steady-state electroretinogram in response to contrast reversing gratings (PERG), is spatially band-pass tuned in amplitude, with a maximum at intermediate spatial frequencies and an attenuation at lower and higher ones. The amplitude attenuation at low spatial frequencies is believed to reflect centre-surround antagonistic interactions in the receptive fields of inner retinal neurons. The aim of this study was to evaluate the PERG spatial tuning in multiple sclerosis (MS) patients without a previous optic neuritis history. Steady- state PERGs in response to counterphase-modulated (8 Hz) sinusoidal gratings of variable spatial frequency (0.6, 1.0, 1.4, 2.2 and 4.8 c/deg), were recorded from 18 patients with definite or probable MS and no history of optic neuritis (ON-). Nine of them had no signs of subclinical optic nerve demyelination (asymptomatic) in either eye, while nine had symptoms or signs of optic pathways involvement (symptomatic) in one or both eyes. Results were compared with those obtained from 10 MS patients with a previous history of optic neuritis (ON+) in one or both eyes, as well as from 21 age-matched controls. The amplitudes and phases of the responses' 2nd harmonics were measured. Compared with the controls, asymptomatic ON- patients showed selective losses in mean PERG amplitudes at medium and high (1.0-4.8 c/deg) spatial frequencies. Symptomatic ON- patients and ON+ patients had reductions in mean PERG amplitudes, with respect to controls, involving the whole spatial frequency range, but with greater losses at medium-high (1.0-4.8 c/deg) than at lower spatial frequencies. In all patients' groups, the average PERG spatial tuning function differed significantly from that of the controls, assuming a low-pass instead of the normal band-pass shape. The PERG phase was delayed in ON+ but not in ON- patients, as compared to controls. However, the phase delay was independent of spatial frequency. In both ON- and ON+ patients, losses in PERG amplitude and spatial tuning tended to be associated with corresponding abnormalities in perimetric sensitivity, visual acuity, colour vision and transient visual evoked potential (VEP) latency. The results indicate that abnormalities of the spatial tuning of steady-state PERG can be found in MS patients without either optic neuritis or signs of subclinical optic nerve demyelination. These changes may reflect a retinal dysfunction, developing early in the course of MS, due to a loss of specific subpopulations of inner neurons, changes in lateral interactions of their receptive fields, or both.

Precision LED-based stimulator for focal electroretinography

The authors discuss the technical problems commonly encountered in the design of devices used in the functional analysis of the central retina (macula) and its neuronal elements. They present a simple effective solution for introducing some of the most recent and interesting results of neurophysiological and psychophysical research into the eye clinic.

The first and second harmonics of the macular flicker electroretinogram: differential effects of retinal diseases

We evaluated the effects of retinal diseases on the macular electroretinogram first and second harmonic components, which are dominated by outer and inner retinal activity, respectively. Macular electroretinograms in response to a uniform field (9 degrees x 9 degrees) flickering sinusoidally at either 32 or 8 Hz (peak frequencies of the first and second harmonics, respectively) were recorded in 14 patients with maculopathies involving photoreceptors (e.g., age-related macular degeneration), in 16 patients with postreceptoral macular diseases (e.g., branch occlusion of central retinal artery), and in 38 normal controls. Amplitude and phase of the first and second harmonic response components were evaluated by Fourier analysis. When compared to controls, patients with photoreceptor diseases had reduction in both first and second harmonic mean amplitudes and second harmonic phase delay; patients with postreceptoral diseases had normal first harmonic components but reduced and delayed second harmonic components. A discriminant analysis, by using first and second harmonic values, correctly classified 13 of 14 patients with photoreceptor diseases and 14 of 16 patients with postreceptoral disorders. These results indicate that combined evaluation of the macular electroretinogram first and second harmonic components is a useful test for identifying the site(s) of retinal dysfunction in patients with macular diseases.

Postreceptoral contribution to macular dysfunction in retinitis pigmentosa

PURPOSE

To understand the sites of macular dysfunction in retinitis pigmentosa by evaluating focal electroretinogram (FERG) fundamental and second harmonic components, which are dominated by the activity of the outer and inner retina, respectively.

METHODS

FERGs were recorded in response to a uniform field (9 degrees x 9 degrees) flickered sinusoidally at either 8 Hz or 32 Hz. The fundamental components of the responses to both the 8-Hz and 32-Hz stimuli and the second harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. Normal subjects (n = 17), as well as patients with typical retinitis pigmentosa (n = 22), cone dystrophy (CD, n = 7) and X-linked congenital retinoschisis (XLR, n = 5) served as subjects. The fundamental (32-Hz)-second harmonic (8 Hz) amplitude ratio was taken as an index of the relative function of outer-inner layers of the macula.

RESULTS

Compared to controls, patients with retinitis pigmentosa showed losses of both FERG fundamental and second harmonic and an increase of the fundamental-second harmonic ratio. Patients with CD also showed losses of both fundamental and second harmonic, but the fundamental-second harmonic ratio was normal. Patients with XLR had a selective loss of the second harmonic, resulting in an increased fundamental-second harmonic ratio. On average, the fundamental-second harmonic ratio of patients with retinitis pigmentosa tended to increase with age.

CONCLUSIONS

The results suggest that in retinitis pigmentosa, both receptoral and postreceptoral sites contribute to macular dysfunction. This differs from CD and XLR, where losses appear more selective for the outer and the inner retina. Postreceptoral losses in retinitis pigmentosa may become larger with increasing age.

Simultaneous foveal and parafoveal electroretinograms in hereditary degeneration of the central retina

Simultaneous foveal and parafoveal electroretinograms (ERG) in response to two identical checks (6 degrees per side) alternating at constant mean luminance were recorded in 26 patients (52 eyes) affected by central hereditary chorioretinal diseases and in 14 age-matched normal subjects (14 eyes). Patients were divided into four groups according to clinical diagnoses: 1. Stargardt's disease; 2. cone dystrophy; 3. vitelliform degeneration; 4. pattern dystrophy. The amplitude and latency of the foveal ERG and the amplitude ratio between foveal and parafoveal ERG (F:PF ratio) were measured. The mean foveal ERG amplitude was significantly lower than the control mean in all patient groups. The foveal ERG latency showed a trend to a increase in all pathological groups. However, this difference was not statistically significant. The mean value of F:PF ratio was significantly reduced as compared with the control mean in Stargardt's disease and cone dystrophy only. In 46 of 52 affected eyes (88.5%) at least one of the electrophysiological parameters was abnormal. Our results suggest that the simultaneous foveal and parafoveal ERG recording may be a sensitive technique in hereditary degenerations of the central retina. This method may also contribute to a better understanding of cone degeneration pathophysiology.

The pattern electroretinogram by skin electrodes: effect of spatial frequency and age

Steady-state (8 Hz) pattern electroretinograms in response to sinusoidal gratings were recorded from 18 elder subjects (mean age 62.7 years) and 22 young subjects (mean age 27 years) by means of skin electrodes. All subjects were free from ocular pathology and their corrected visual acuity was 1.0 or better. In young subjects the second harmonic amplitude as a function of spatial frequency is spatially tuned, with a maximum at around 1.7 c/deg. The response of elder subjects is significantly (P less than 0.05) reduced over the whole range of spatial frequency as compared with that of younger ones. This decrease is more marked (P less than 0.01) at intermediate spatial frequencies, resulting in a shallower tuning. The response phase is not significantly different between young and elder subjects.