A spatially specified systems pharmacology therapy for axonal recovery after injury.

There are no known drugs or drug combinations that promote substantial central nervous system axonal regeneration after injury. We used systems pharmacology approaches to model pathways underlying axonal growth and identify a four-drug combination that regulates multiple subcellular processes in the cell body and axons using the optic nerve crush model in rats. We intravitreally injected agonists HU-210 (cannabinoid receptor-1) and IL-6 (interleukin 6 receptor) to stimulate retinal ganglion cells for axonal growth. We applied, in gel foam at the site of nerve injury, Taxol to stabilize growing microtubules, and activated protein C to clear the debris field since computational models predicted that this drug combination regulating two subcellular processes at the growth cone produces synergistic growth. Physiologically, drug treatment restored or preserved pattern electroretinograms and some of the animals had detectable visual evoked potentials in the brain and behavioral optokinetic responses. Morphology experiments show that the four-drug combination protects axons or promotes axonal regrowth to the optic chiasm and beyond. We conclude that spatially targeted drug treatment is therapeutically relevant and can restore limited functional recovery.

Spinal cord injury regulates circular RNA expression in axons.

Introduction: Neurons transport mRNA and translational machinery to axons for local translation. After spinal cord injury (SCI), de novo translation is assumed to enable neurorepair. Knowledge of the identity of axonal mRNAs that participate in neurorepair after SCI is limited. We sought to identify and understand how axonal RNAs play a role in axonal regeneration. Methods: We obtained preparations enriched in axonal mRNAs from control and SCI rats by digesting spinal cord tissue with cold-active protease (CAP). The digested samples were then centrifuged to obtain a supernatant that was used to identify mRNA expression. We identified differentially expressed genes (DEGS) after SCI and mapped them to various biological processes. We validated the DEGs by RT-qPCR and RNA-scope. Results: The supernatant fraction was highly enriched for mRNA from axons. Using Gene Ontology, the second most significant pathway for all DEGs was axonogenesis. Among the DEGs was Rims2, which is predominately a circular RNA (circRNA) in the CNS. We show that Rims2 RNA within spinal cord axons is circular. We found an additional 200 putative circRNAs in the axonal-enriched fraction. Knockdown in primary rat cortical neurons of the RNA editing enzyme ADAR1, which inhibits formation of circRNAs, significantly increased axonal outgrowth and increased the expression of circRims2. Using Rims2 as a prototype we used Circular RNA Interactome to predict miRNAs that bind to circRims2 also bind to the 3'UTR of GAP-43, PTEN or CREB1, all known regulators of axonal outgrowth. Axonally-translated GAP-43 supports axonal elongation and we detect GAP-43 mRNA in the rat axons by RNAscope. Discussion: By enriching for axonal RNA, we detect SCI induced DEGs, including circRNA such as Rims2. Ablation of ADAR1, the enzyme that regulates circRNA formation, promotes axonal outgrowth of cortical neurons. We developed a pathway model using Circular RNA Interactome that indicates that Rims2 through miRNAs can regulate the axonal translation GAP-43 to regulate axonal regeneration. We conclude that axonal regulatory pathways will play a role in neurorepair.

Spatiotemporal Contrast Sensitivity of Brown-Norway Rats under Scotopic and Photopic Illumination.

Rats are a popular animal model for vision research and for investigating disorders of the visual system. The study aimed to quantify the spatiotemporal contrast sensitivity function (CSF) of healthy adult Brown-Norway rats under scotopic and photopic illumination. Animals were trained to jump onto the one of two adjacent platforms behind which was displayed a sinewave grating pattern. Contrast thresholds of light- and dark-adapted rats were determined using a staircase method of adjustment for gratings that varied in spatial frequency (sf) and temporal frequency (tf) and ranged several log-units in mean luminance. Photopic CSFs showed strong bandpass spatial tuning, consistent with prior measurements, and weak bandpass temporal tuning. CSFs were parameterized by a truncated log-parabola model, yielding a peak contrast sensitivity of 52 ±â€¯9, peak sf of 0.17 ±â€¯0.05 cycles/degree, sf limit of 1.6 ±â€¯0.3 cycles/degree, low sf attenuation of 85 ±â€¯9%, peak tf of 1.7 ±â€¯1.1 Hz, extrapolated tf limit of 166 ±â€¯44 Hz, and low tf attenuation of 55 ±â€¯12%. CSFs became more lowpass and decreased systematically in contrast sensitivity and spatiotemporal acuity as mean luminance was reduced. CSFs were also measured via the visual head-tracking reflex. Photopic contrast sensitivity, spatial acuity, and temporal acuity were all markedly below that of the grating detection task and optomotor findings for other rat strains. The CSF data provide a comprehensive and quantitative description of rat spatial and temporal vision and a benchmark for evaluating effects of ocular diseases on their ability to see.

A teenager with fever, chest pain, and respiratory distress during the coronavirus disease 2019 pandemic: a lesson on anchoring bias.

Symptoms of coronavirus disease 2019 overlap with other important illnesses affecting young adults. We report a case of a 17-year old male presenting to the emergency department in the midst of a pandemic with symptoms of coronavirus disease 2019. He had fever, dyspnea, chest pain, and myalgias, with bilateral infiltrates on chest radiograph, and developed septic shock secondary to infectious thromboembolic events. However, his blood cultures grew group G streptococcus secondary to his oropharyngeal infection, and he experienced an infectious thrombus in the internal jugular vein, consistent with the rare but well-described Lemierre's syndrome. This case report calls attention to the importance of maintaining differential diagnoses and thereby minimizing the biases and assumptions that come with clinical care during a pandemic.

Bilateral efferents from nucleus isthmi to the optic tectum in goldfish (Carassius auratus) are spatially restricted.

The projection from nucleus isthmi (NI) to the optic tectum (OT) was investigated in the goldfish, Carassius auratus, by retrograde transport of biocytin applied at various sites in a tectal lobe. In previous studies, this projection is described as predominantly from the ipsilateral NI and maps topographically along the approximate rostrocaudal axis of both brain areas. However, the rostromedial tectal lobe, the tectal region representing the binocular visual field, receives afferents from both the ipsilateral and the contralateral NI. The contralateral isthmic neurons are found at the most caudal position in NI and are not topographic with the tectum. The bilateral projection from NI to the tectum may play a role in functions requiring the coordination of both eyes.