Metabolic and Toxic Myelopathies.

Metabolic and toxic causes of myelopathy form a heterogeneous group of disorders. In this review, we discuss the causes of metabolic and toxic myelopathies with respect to clinical presentation, pathophysiology, diagnostic testing, treatment, and prognosis. This review is organized by temporal course (hyperacute, acute, subacute, and chronic) and etiology (e.g., nutritional deficiency, toxic exposure). Broadly, the myelopathies associated with dietary toxins (neurolathyrism, konzo) and decompression sickness present suddenly (hyperacute). The myelopathies associated with heroin use and electrical injury present over hours to days (acutely). Most nutritional deficiencies (cobalamin, folate, copper) and toxic substances (nitrous oxide, zinc, organophosphates, clioquinol) cause a myelopathy of subacute onset. Vitamin E deficiency and hepatic myelopathy cause a chronic myelopathy. Radiation- and intrathecal chemotherapy-induced myelopathy can cause a transient and/or a progressive syndrome. For many metabolic and toxic causes of myelopathy, clinical deficits may stabilize or improve with rapid identification and treatment. Familiarity with these disorders is therefore essential.

COVID-19 in patients with myasthenia gravis.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) has rapidly become a global pandemic, but little is known about its potential impact on patients with myasthenia gravis (MG). METHODS: We studied the clinical course of COVID-19 in five hospitalized patients with autoimmune MG (four with acetylcholine receptor antibodies, one with muscle-specific tyrosine kinase antibodies) between April 1, 2020-April 30-2020. RESULTS: Two patients required intubation for hypoxemic respiratory failure, whereas one required significant supplemental oxygen. One patient with previously stable MG had myasthenic exacerbation. One patient treated with tocilizumab for COVID-19 was successfully extubated. Two patients were treated for MG with intravenous immunoglobulin without thromboembolic complications. DISCUSSION: Our findings suggest that the clinical course and outcomes in patients with MG and COVID-19 are highly variable. Further large studies are needed to define best practices and determinants of outcomes in this unique population.

Recommendations for core critical care ultrasound competencies as a part of specialist training in multidisciplinary intensive care: a framework proposed by the European Society of Intensive Care Medicine (ESICM).

Critical care ultrasound (CCUS) is an essential component of intensive care practice. Although existing international guidelines have focused on training principles and determining competency in CCUS, few countries have managed to operationalize this guidance into an accessible, well-structured programme for clinicians training in multidisciplinary intensive care. We seek to update and reaffirm appropriate CCUS scope so that it may be integrated into the international Competency-based Training in Intensive Care Medicine. The resulting recommendations offer the most contemporary and evolved set of core CCUS competencies for an intensive care clinician yet described. Importantly, we discuss the rationale for inclusion but also exclusion of competencies listed. BACKGROUND/AIM: Critical care ultrasound (CCUS) is an essential component of intensive care practice. The purpose of this consensus document is to determine those CCUS competencies that should be a mandatory part of training in multidisciplinary intensive care. METHODS: A three-round Delphi method followed by face-to-face meeting among 32 CCUS experts nominated by the European Society of Intensive Care Medicine. Agreement of at least 90% of experts was needed in order to enlist a competency as mandatory. RESULTS: The final list of competencies includes 15 echocardiographic, 5 thoracic, 4 abdominal, deep vein thrombosis diagnosis and central venous access aid. CONCLUSION: The resulting recommendations offer the most contemporary and evolved set of core CCUS competencies for an intensive care clinician yet described.

A novel natural tracer method to measure complex carbohydrate metabolism.

While the triple tracer isotope dilution method has enabled accurate estimation of carbohydrate turnover after a mixed meal, use of the simple carbohydrate glucose as the carbohydrate source limits its translational applicability to everyday meals that typically contain complex carbohydrates. Hence, utilizing the natural enrichment of [13C]polysaccharide in commercially available grains, we devised a novel tracer method to measure postprandial complex carbohydrate turnover and indices of insulin action and ß-cell function and compared the parameters to those obtained after a simple carbohydrate containing mixed meal. We studied healthy volunteers after either rice (n = 8) or sorghum (n = 8) and glucose (n = 16) containing mixed meals and modified the triple tracer technique to calculate carbohydrate turnover. All meals were matched for calories and macronutrient composition. Rates of meal glucose appearance (2,658 ± 736 vs. 4,487 ± 909 µM·kg-1·2 h-1), endogenous glucose production (-835 ± 283 vs. -1,123 ± 323 µM·kg-1·2 h-1) and glucose disappearance (1,829 ± 807 vs. 3,606 ± 839 µM·kg-1·2 h-1) differed (P < 0.01) between complex and simple carbohydrate containing meals, respectively. Interestingly, there were significant increase in indices of insulin sensitivity (32.5 ± 3.5 vs. 25.6 ± 3.2 10-5 (dl·kg-1·min-2)/pM, P = 0.006) and ß-cell responsivity (disposition index: 1,817 ± 234 vs. 1,236 ± 159 10-14 (dl·kg-1·min-2)/pM, P < 0.005) with complex than simple carbohydrate meals. We present a novel triple tracer approach to estimate postprandial turnover of complex carbohydrate containing mixed meals. We also report higher insulin sensitivity and ß-cell responsivity with complex than with simple carbohydrates in mixed meals of identical calorie and macronutrient compositions in healthy adults.

Neural coding of sound envelope in reverberant environments.

Speech reception depends critically on temporal modulations in the amplitude envelope of the speech signal. Reverberation encountered in everyday environments can substantially attenuate these modulations. To assess the effect of reverberation on the neural coding of amplitude envelope, we recorded from single units in the inferior colliculus (IC) of unanesthetized rabbit using sinusoidally amplitude modulated (AM) broadband noise stimuli presented in simulated anechoic and reverberant environments. Although reverberation degraded both rate and temporal coding of AM in IC neurons, in most neurons, the degradation in temporal coding was smaller than the AM attenuation in the stimulus. This compensation could largely be accounted for by the compressive shape of the modulation input-output function (MIOF), which describes the nonlinear transformation of modulation depth from acoustic stimuli into neural responses. Additionally, in a subset of neurons, the temporal coding of AM was better for reverberant stimuli than for anechoic stimuli having the same modulation depth at the ear. Using hybrid anechoic stimuli that selectively possess certain properties of reverberant sounds, we show that this reverberant advantage is not caused by envelope distortion, static interaural decorrelation, or spectral coloration. Overall, our results suggest that the auditory system may possess dual mechanisms that make the coding of amplitude envelope relatively robust in reverberation: one general mechanism operating for all stimuli with small modulation depths, and another mechanism dependent on very specific properties of reverberant stimuli, possibly the periodic fluctuations in interaural correlation at the modulation frequency.

Mononeuropathy Multiplex After Severe SARS-CoV-2 Infection: A Case Series and Literature Review.

INTRODUCTION: Peripheral nerve injuries are being increasingly recognized in patients recovering from severe SARS-CoV-2 infections. Axonal neuropathies can occur, leading to lasting and disabling deficits. CASE REPORTS: We present the cases of 3 patients who developed weakness and sensory symptoms after severe SARS-CoV-2 pneumonia. The clinical deficits revealed various patterns of injury including a mononeuropathy multiplex (MNM) in the first patient, a brachial plexopathy with superimposed MNM in the second patient, and a mononeuropathy superimposed on a polyneuropathy in the third patient. Electrodiagnostic studies revealed axonopathies. The patients with MNM were left with severe disability. The third patient returned to his baseline level of functioning. CONCLUSIONS: Severe SARS-CoV-2 infections can result in disabling axonopathies. Possible explanations include ischemic nerve damage from the profound inflammatory response and traumatic nerve injuries in the ICU setting. Preventing severe disease through vaccination and antivirals may therefore help reduce neurologic morbidity.

Pancreatic islet cryopreservation by vitrification achieves high viability, function, recovery and clinical scalability for transplantation.

Pancreatic islet transplantation can cure diabetes but requires accessible, high-quality islets in sufficient quantities. Cryopreservation could solve islet supply chain challenges by enabling quality-controlled banking and pooling of donor islets. Unfortunately, cryopreservation has not succeeded in this objective, as it must simultaneously provide high recovery, viability, function and scalability. Here, we achieve this goal in mouse, porcine, human and human stem cell (SC)-derived beta cell (SC-beta) islets by comprehensive optimization of cryoprotectant agent (CPA) composition, CPA loading and unloading conditions and methods for vitrification and rewarming (VR). Post-VR islet viability, relative to control, was 90.5% for mouse, 92.1% for SC-beta, 87.2% for porcine and 87.4% for human islets, and it remained unchanged for at least 9 months of cryogenic storage. VR islets had normal macroscopic, microscopic, and ultrastructural morphology. Mitochondrial membrane potential and adenosine triphosphate (ATP) levels were slightly reduced, but all other measures of cellular respiration, including oxygen consumption rate (OCR) to produce ATP, were unchanged. VR islets had normal glucose-stimulated insulin secretion (GSIS) function in vitro and in vivo. Porcine and SC-beta islets made insulin in xenotransplant models, and mouse islets tested in a marginal mass syngeneic transplant model cured diabetes in 92% of recipients within 24-48 h after transplant. Excellent glycemic control was seen for 150 days. Finally, our approach processed 2,500 islets with >95% islets recovery at >89% post-thaw viability and can readily be scaled up for higher throughput. These results suggest that cryopreservation can now be used to supply needed islets for improved transplantation outcomes that cure diabetes.

Bioactive hydrogel microcapsules for guiding stem cell fate decisions by release and reloading of growth factors.

Human pluripotent stem cells (hPSC) hold considerable promise as a source of adult cells for treatment of diseases ranging from diabetes to liver failure. Some of the challenges that limit the clinical/translational impact of hPSCs are high cost and difficulty in scaling-up of existing differentiation protocols. In this paper, we sought to address these challenges through the development of bioactive microcapsules. A co-axial flow focusing microfluidic device was used to encapsulate hPSCs in microcapsules comprised of an aqueous core and a hydrogel shell. Importantly, the shell contained heparin moieties for growth factor (GF) binding and release. The aqueous core enabled rapid aggregation of hPSCs into 3D spheroids while the bioactive hydrogel shell was used to load inductive cues driving pluripotency maintenance and endodermal differentiation. Specifically, we demonstrated that one-time, 1 h long loading of pluripotency signals, fibroblast growth factor (FGF)-2 and transforming growth factor (TGF)-ß1, into bioactive microcapsules was sufficient to induce and maintain pluripotency of hPSCs over the course of 5 days at levels similar to or better than a standard protocol with soluble GFs. Furthermore, stem cell-carrying microcapsules that previously contained pluripotency signals could be reloaded with an endodermal cue, Nodal, resulting in higher levels of endodermal markers compared to stem cells differentiated in a standard protocol. Overall, bioactive heparin-containing core-shell microcapsules decreased GF usage five-fold while improving stem cell phenotype and are well suited for 3D cultivation of hPSCs.

A Rare Presentation of a Rare Disease: Oropharyngeal Dysphagia as The Main Manifestation of Myasthenia Gravis.

Oropharyngeal dysphagia is defined as the inability or difficulty to initiate swallowing. It has a wide array of etiologies including structural and neurologic diseases. Myasthenia gravis (MG) is a rare autoimmune condition caused by antibodies against the post-synaptic membranes of the neuromuscular junction, leading to fatigable weakness of skeletal muscles. Bulbar symptoms are less prevalent than ocular symptoms or limb weakness but can be particularly morbid. Non-neurologists are more likely to be the first providers to evaluate patients with dysphagia and should be familiar with MG. We report a unique case of newly diagnosed MG with the initial presentation of solid food and liquid dysphagia.

Core-shell hydrogel microcapsules enable formation of human pluripotent stem cell spheroids and their cultivation in a stirred bioreactor.

Cellular therapies based on human pluripotent stem cells (hPSCs) offer considerable promise for treating numerous diseases including diabetes and end stage liver failure. Stem cell spheroids may be cultured in stirred bioreactors to scale up cell production to cell numbers relevant for use in humans. Despite significant progress in bioreactor culture of stem cells, areas for improvement remain. In this study, we demonstrate that microfluidic encapsulation of hPSCs and formation of spheroids. A co-axial droplet microfluidic device was used to fabricate 400 µm diameter capsules with a poly(ethylene glycol) hydrogel shell and an aqueous core. Spheroid formation was demonstrated for three hPSC lines to highlight broad utility of this encapsulation technology. In-capsule differentiation of stem cell spheroids into pancreatic ß-cells in suspension culture was also demonstrated.

Holoprosencephaly and ectrodactyly: Report of three new patients and review of the literature.

Holoprosencephaly (HPE) and ectrodactyly represent congenital malformations of the developing forebrain and developing digits, respectively. The combination of these conditions is rare, with only 15 cases known to date (12 previously reported, and 3 new cases described here). While the findings in these patients overlap with previously described genetic conditions, the similarity in phenotypes among these patients has led to the establishment of a at least one distinct syndrome: HPE, ectrodactyly, and bilateral cleft lip-palate syndrome (OMIM 300571). There has been great interest in identifying a genetic cause for the findings in patients with HPE and ectrodactyly; however the cause(s) of this rare association still remain unknown.

Middle ear function and cochlear input impedance in chinchilla.

Simultaneous measurements of middle ear-conducted sound pressure in the cochlear vestibule P(V) and stapes velocity V(S) have been performed in only a few individuals from a few mammalian species. In this paper, simultaneous measurements of P(V) and V(S) in six chinchillas are reported, enabling computation of the middle ear pressure gain G(ME) (ratio of P(V) to the sound pressure in the ear canal P(TM)), the stapes velocity transfer function SVTF (ratio of the product of V(S) and area of the stapes footplate A(FP) to P(TM)), and, for the first time, the cochlear input impedance Z(C) (ratio of P(V) to the product of V(S) and A(FP)) in individuals. mid R:G(ME)mid R: ranged from 25 to 35 dB over 125 Hz-8 kHz; the average group delay between 200 Hz and 10 kHz was about 52 mus. SVTF was comparable to that of previous studies. Z(C) was resistive from the lowest frequencies up to at least 10 kHz, with a magnitude on the order of 10(11) acoustic ohms. P(V), V(S), and the acoustic power entering the cochlea were good predictors of the shape of the audiogram at frequencies between 125 Hz and 2 kHz.

TBK1 regulates regeneration of pancreatic ß-cells.

Small-molecule inhibitors of non-canonical IκB kinases TANK-binding kinase 1 (TBK1) and IκB kinase ε (IKKε) have shown to stimulate ß-cell regeneration in multiple species. Here we demonstrate that TBK1 is predominantly expressed in ß-cells in mammalian islets. Proteomic and transcriptome analyses revealed that genetic silencing of TBK1 increased expression of proteins and genes essential for cell proliferation in INS-1 832/13 rat ß-cells. Conversely, TBK1 overexpression decreased sensitivity of ß-cells to the elevation of cyclic AMP (cAMP) levels and reduced proliferation of ß-cells in a manner dependent on the activity of cAMP-hydrolyzing phosphodiesterase 3 (PDE3). While the mitogenic effect of (E)3-(3-phenylbenzo[c]isoxazol-5-yl)acrylic acid (PIAA) is derived from inhibition of TBK1, PIAA augmented glucose-stimulated insulin secretion (GSIS) and expression of ß-cell differentiation and proliferation markers in human embryonic stem cell (hESC)-derived ß-cells and human islets. TBK1 expression was increased in ß-cells upon diabetogenic insults, including in human type 2 diabetic islets. PIAA enhanced expression of cell cycle control molecules and ß-cell differentiation markers upon diabetogenic challenges, and accelerated restoration of functional ß-cells in streptozotocin (STZ)-induced diabetic mice. Altogether, these data suggest the critical function of TBK1 as a ß-cell autonomous replication barrier and present PIAA as a valid therapeutic strategy augmenting functional ß-cells.

A method for the generation of human stem cell-derived alpha cells.

The generation of pancreatic cell types from renewable cell sources holds promise for cell replacement therapies for diabetes. Although most effort has focused on generating pancreatic beta cells, considerable evidence indicates that glucagon secreting alpha cells are critically involved in disease progression and proper glucose control. Here we report on the generation of stem cell-derived human pancreatic alpha (SC-alpha) cells from pluripotent stem cells via a transient pre-alpha cell intermediate. These pre-alpha cells exhibit a transcriptional profile similar to mature alpha cells and although they produce proinsulin protein, they do not secrete significant amounts of processed insulin. Compound screening identified a protein kinase c activator that promotes maturation of pre-alpha cells into SC-alpha cells. The resulting SC-alpha cells do not express insulin, share an ultrastructure similar to cadaveric alpha cells, express and secrete glucagon in response to glucose and some glucagon secretagogues, and elevate blood glucose upon transplantation in mice.

Continuous Glucose Monitor Interference With Commonly Prescribed Medications: A Pilot Study.

BACKGROUND: Reliability of continuous glucose monitors (CGM) is a prerequisite for therapeutic dosing of insulin without the need for confirmatory blood glucose meter measurements. Interference of CGMs with commonly prescribed substances has not been extensively evaluated. METHODS: We sought to undertake a novel pilot study to determine the susceptibility of FDA-approved CGM systems (Medtronic Guardian Sof-Sensor, Dexcom G4 Platinum) to erroneous readings in the presence of common medications. CGMs were placed on the abdomen of healthy subjects 48 hours prior to study. Subjects were admitted to the Clinical Research Trials Unit (CRTU) on the evening before study and fed a standard supper. The following morning, an oral medication was administered in the fasted state and blood was sampled for 9 hours. CGM values were compared to ambient glucose (measured with YSI) to observe variations in CGM readings. Microdialysis catheters were also placed in the abdomen to sample interstitial fluid (ISF) for drug concentrations. RESULTS: Nineteen healthy drug-naïve subjects without diabetes participated in the study. A drug/substance was tested up to a maximum of nine times on separate occasions. Comparison of CGM glucose patterns to actual plasma glucose concentrations show several drugs, including lisinopril, albuterol, and acetaminophen, appear to interfere with commonly used CGM devices. Wine also interfered with CGM readings. CONCLUSIONS: We conclude there is some evidence of CGM interference with lisinopril, albuterol, acetaminophen, atenolol, and red wine. Future studies are required to address interference with newer sensors being approved or in the process of approval.

Randomized Controlled Trial of a MUFA or Fiber-Rich Diet on Hepatic Fat in Prediabetes.

Context: Increased prevalence of type 2 diabetes mellitus and prediabetes worldwide is attributed in part to an unhealthy diet. Objective: To evaluate whether 12 weeks of high monounsaturated fatty acid (MUFA) or fiber-rich weight-maintenance diet lowers hepatic fat and improves glucose tolerance in people with prediabetes. Design: Subjects underwent a [6, 6-2H2]-labeled 75-g oral glucose tolerance test to estimate hepatic insulin sensitivity and liver fat fraction (LFF) using magnetic resonance spectroscopy before and after intervention. Setting: Mayo Clinic Clinical Research Trials Unit. Participants: 43 subjects with prediabetes. Intervention: Subjects were randomized into three isocaloric weight-maintaining diets containing MUFA (olive oil), extra fiber, and standard US food (control-habitual diet). Outcome Measures: LFF, glucose tolerance, and indices of insulin action and secretion. Results: Body weight was maintained constant in all groups during the intervention. Glucose and hormonal concentrations were similar in all groups before, and unchanged after, 12 weeks of intervention. LFF was significantly lower after intervention in the MUFA group (P < 0.0003) but remained unchanged in the fiber (P = 0.25) and control groups (P = 0.45). After 12 weeks, LFF was significantly lower in the MUFA than in the control group (P = 0.01), but fiber and control groups did not differ (P = 0.41). Indices of insulin action and secretion were not significantly different between the MUFA and control groups after intervention (P ≥ 0.11), but within-group comparison showed higher hepatic (P = 0.01) and total insulin sensitivity (P < 0.04) with MUFA. Conclusions: Twelve weeks of a MUFA diet decreases hepatic fat and improves both hepatic and total insulin sensitivity.

Beneficial pleiotropic vascular effects of rosuvastatin in two hypertensive models.

OBJECTIVES: The goal of this research was to study the effects of rosuvastatin on systemic and regional hemodynamics in two hypertensive rat models, one genetic, the other induced with inhibition of nitric oxide synthesis. BACKGROUND: Rats naturally have low cholesterol levels that are generally unaffected by statin therapy, thus providing a good model for studying cardiovascular effects unrelated to lipid metabolism. METHODS: Male 20-week-old spontaneously hypertensive rats (SHR) were divided into five groups and given either vehicle or 1, 5, 10, and 20 mg/kg of rosuvastatin daily, by gavage, for 12 weeks. Wistar-Kyoto rats (WKY) were divided into four groups; the first received vehicle and the second rosuvastatin (20 mg/kg). The third and fourth groups were given N(omega)-nitro-L-arginine (L-NAME) (15 mg/kg/day) in drinking water, and the fourth group received rosuvastatin daily, 20 mg/kg for six weeks. At the end of the respective treatments, systemic and organ hemodynamics (radionuclide-labeled microspheres) and cardiovascular mass were determined in all rats. RESULTS: Rosuvastatin reduced arterial pressure in SHR rats, but not in WKY/L-NAME rats. Total peripheral resistance decreased with rosuvastatin in both hypertensive models, whereas cardiac output increased with rosuvastatin in WKY/L-NAME rats. Neither cardiac nor aortic mass was changed. Regional hemodynamics improved with rosuvastatin in both hypertensive models, as evidenced by increased blood flows and decreased vascular resistances. No effect on plasma lipids was observed. CONCLUSIONS: These results showed that rosuvastatin reduced arterial pressure in genetic hypertension and improved systemic and regional hemodynamics in both hypertensive models independently of cholesterol levels. Thus rosuvastatin improved systemic and regional hemodynamics by reducing vascular resistance.

Glucocorticoid Excess Increases Hepatic 11ß-HSD-1 Activity in Humans: Implications in Steroid-Induced Diabetes.

CONTEXT: Animal studies indicate that glucocorticoids increase hepatic 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD-1) expression and activity. OBJECTIVE: Our goal was to determine whether glucocorticoid excess increases cortisol production in the liver via 11ß-HSD-1 enzyme pathway in humans. DESIGN: A total of 1 mg each [4-(13)C] cortisone and [9,12,12-(2)H3] cortisol were ingested, and [1,2,6,7-(3)H] cortisol was infused to measure C13 cortisol (derived from ingested [4-(13)C] cortisone) turnover using the triple tracer technique, whereas glucose turnover was measured using isotope dilution technique following [6-6(2)H2] glucose infusion during a saline clamp. SETTING: This study took place at the Mayo Clinic Clinical Research Unit. PARTICIPANTS: Thirty nondiabetic healthy subjects participated. INTERVENTION: Subjects were randomized to hydrocortisone (n = 15) or placebo 50 mg twice daily (n = 15) for 1 week. OUTCOME MEASURES: Hepatic cortisol production and endogenous glucose production were measured. RESULTS: Plasma cortisol concentrations were higher throughout the study period in hydrocortisone group. Rates of appearance of C13 cortisol and hepatic C13 cortisol production were higher in hydrocortisone vs placebo group, indicating increased hepatic 11ß-HSD-1 activity. Higher plasma cortisol and presumably higher intrahepatic cortisol was associated with impaired suppression of endogenous glucose production in hydrocortisone vs placebo group. CONCLUSION: Chronic glucocorticoid excess increases intrahepatic cortisone to cortisol conversion via the 11ß-HSD-1 pathway. The extent to which this causes or exacerbates steroid induced hepatic insulin resistance remains to be determined.