Loss of photoreceptors results in upregulation of synaptic proteins in bipolar cells and amacrine cells.

Deafferentation is known to cause significant changes in the postsynaptic neurons in the central nervous system. Loss of photoreceptors, for instance, results in remarkable morphological and physiological changes in bipolar cells and horizontal cells. Retinal ganglion cells (RGCs), which send visual information to the brain, are relatively preserved, but show aberrant firing patterns, including spontaneous bursts of spikes in the absence of photoreceptors. To understand how loss of photoreceptors affects the circuitry presynaptic to the ganglion cells, we measured specific synaptic proteins in two mouse models of retinal degeneration. We found that despite the nearly total loss of photoreceptors, the synaptophysin protein and mRNA levels in retina were largely unaltered. Interestingly, the levels of synaptophysin in the inner plexiform layer (IPL) were higher, implying that photoreceptor loss results in increased synaptophysin in bipolar and/or amacrine cells. The levels of SV2B, a synaptic protein expressed by photoreceptors and bipolar cells, were reduced in whole retina, but increased in the IPL of rd1 mouse. Similarly, the levels of syntaxin-I and synapsin-I, synaptic proteins expressed selectively by amacrine cells, were higher after loss of photoreceptors. The upregulation of syntaxin-I was evident as early as one day after the onset of photoreceptor loss, suggesting that it did not require any massive or structural remodeling, and therefore is possibly reversible. Together, these data show that loss of photoreceptors results in increased synaptic protein levels in bipolar and amacrine cells. Combined with previous reports of increased excitatory and inhibitory synaptic currents in RGCs, these results provide clues to understand the mechanism underlying the aberrant spiking in RGCs

Robust and Degradable Hydrogels from Poly(ethylene glycol) and Semi-Interpenetrating Collagen

Poly­(ethylene glycol) (PEG) and interpenetrating collagen can be used to synthesize hydrogels that are elastomeric-like, can withstand reversible loadings, degrade, and are bioactive. Here we present the synthesis of a hydrogel system made of PEG modified with lactide and acrylate end groups and then photo cross-linked in the presence of type I collagen. The hydrogel precursor solutions are low viscous and the cross-linked hydrogels form elastomeric-like polymer networks. Mechanical properties of the hydrogels were found to depend predominantly on PEG concentration and less on collagen. This is possibly due to a balance of molecular interactions that reinforce and weaken the network structure. Hydrogel degradation times were strongly dependent on temperature. The experimental results from this project show how to generate robust, and degradable hydrogels containing bioactive collagen. The data show promise and show the versatility of making biotechnologically relevant soft materials from a few components

Chest X ray and cough sample based deep learning framework for accurate diagnosis of COVID-19

All witnessed the terrible effects of the COVID-19 pandemic on the health and work lives of the population across the world. It is hard to diagnose all infected people in real time since the conventional medical diagnosis of COVID-19 patients takes a couple of days for accurate diagnosis results. In this paper, a novel learning framework is proposed for the early diagnosis of COVID-19 patients using hybrid deep fusion learning models. The proposed framework performs early classification of patients based on collected samples of chest X-ray images and Coswara cough (sound) samples of possibly infected people. The captured cough samples are pre-processed using speech signal processing techniques and Mel frequency cepstral coefficient features are extracted using deep convolutional neural networks. Finally, the proposed system fuses extracted features to provide 98.70% and 82.7% based on Chest-X ray images and cough (audio) samples for early diagnosis using the weighted sum-rule fusion method

Retinal levels of synaptophysin protein and mRNA were largely unaltered following photoreceptor loss.

<p>A) Representative blots of synaptophysin and β-tubulin in whole retinas of wild-type and rd1 mice at different developmental stages (“A” is for “Adult”). B) Ratio of synaptophysin to β-tubulin for several animals (Mean ± SE). The ratio in rd1 mouse was not statistically different from that in wild-type mouse at any stage (n = 6, 8, 9, 9 and 7 for 7, 14, 21, 28 days old and adult animals respectively). C) Synaptophysin mRNA levels normalized to 18S rRNA (Mean ± SE) were also similar in adult rd1 and wild-type mice (n = 6). D) Representative blots of synaptophysin and β-tubulin in whole retinas of sham-injected control and at various days after MNU injection. E) Ratio of synaptophysin to β-tubulin for several animals (Mean ± SE). Similar to rd1 mouse, the levels of synaptophysin in MNU-injected animals were not significantly different from the control for up to at least 28 days after the injection, except at 7 days (p>0.1, except for PID-7 where p = 0.044; n = 6 for all stages). *p<0.05</p

Synaptophysin in the IPL of rd1 mouse was upregulated.

<p>A, B) Representative images of vertical sections of adult wild-type (A) and rd1 (B) mouse retinas immunostained for synaptophysin. Scale bar: 50 µm. C) Representative profile of staining intensity through retinal depth covering both plexiform layers of the images shown in A and B. After background subtraction, a line moving vertically from top to bottom across the images measured the signal intensity using Plot Profile function in ImageJ, which is shown here from left to right. Synaptophysin staining is nearly absent in OPL of rd1 mouse retina, whereas that in IPL is higher than in wild-type, particularly in the Off sublamina. D) Levels of synaptophysin in IPL (mean ± SE), measured with quantitative immunohistochemistry were significantly higher in adult rd1 mouse retina than in wild-type (p = 0.018; n = 6). Within IPL, the levels were significantly higher in Off sublamina (p = 0.01), but not in On sublamina (p = 0.068). The data shown here are essentially the area under the curve for On (60% of IPL) and Off (40%) sublaminas shown in 2C. *<i>p</i><0.05.</p

Molecular Pathway to Protection From Age-Dependent Photoreceptor Degeneration in Mef2 Deficiency.

PurposePhotoreceptor degeneration in the retina is a major cause of blindness in humans. Elucidating mechanisms of degenerative and neuroprotective pathways in photoreceptors should afford identification and development of therapeutic strategies.MethodsWe used mouse genetic models and improved methods for retinal explant cultures. Retinas were enucleated from Mef2d+/+ and Mef2d-/- mice, stained for MEF2 proteins and outer nuclear layer thickness, and assayed for apoptotic cells. Chromatin immunoprecipitation (ChIP) assays revealed MEF2 binding, and RT-qPCR showed levels of transcription factors. We used AAV2 and electroporation to express genes in retinal explants and electroretinograms to assess photoreceptor functionality.ResultsWe identify a prosurvival MEF2D-PGC1α pathway that plays a neuroprotective role in photoreceptors. We demonstrate that Mef2d-/- mouse retinas manifest decreased expression of PGC1α and increased photoreceptor cell loss, resulting in the absence of light responses. Molecular repletion of PGC1α protects Mef2d-/- photoreceptors and preserves light responsivity.ConclusionsThese results suggest that the MEF2-PGC1α cascade may represent a new therapeutic target for drugs designed to protect photoreceptors from developmental- and age-dependent loss

List of antibodies used.

<p>List of antibodies used.</p