Management of patients susceptible to malignant hyperthermia: A surgeon's perspective.

OBJECTIVES: Malignant hyperthermia (MH) susceptibility caries broad implications for the care of pediatric surgical patients. While precautions must often be taken for only a vague family history, two options exist to assess MH-susceptibility. We evaluate the use of MH precautions and susceptibility testing at a freestanding children's hospital. METHODS: This single institution retrospective cohort study identified patients of any age who received general anesthetics utilizing MH precautions over a five-year period. The electronic medical record was further queried for patients diagnosed with MH. The indication for MH precautions and uses of susceptibility testing are assessed. Secondary outcomes included a diagnosis of bona fide MH. RESULTS: A total of 125 patients received 174 anesthetics with MH precautions at a mean age of 114 months (0-363 months). Otolaryngology was the procedural service most frequently involved in the care of the cohort (n = 45; 26%). A reported personal or family history of MH (n = 102; 59%) was the most common indication for precautions, followed by muscular dystrophy (n = 29; 17%). No MH events occurred in the cohort and further review of ICD-9 and -10 diagnosis codes found no MH diagnoses. No study subjects received muscle biopsy and contracture testing and only 5 (4%) underwent genetic testing for genomic variants known to cause MH susceptibility. A case example is given to highlight the implications of a reported MH history. CONCLUSION: Otolaryngologists should maintain a familiarity with the precautions necessary to manage patients at risk for MH and MH-like reactions. Without an accessible test to rule out susceptibility, surgeons must rely on a careful history to appropriately utilize precautions. An inappropriate label of "MH-susceptible" may result in decreased access to care and treatment delays.

Sleep disturbance and symptom burden in sarcoidosis.

INTRODUCTION: Sarcoidosis is a systemic inflammatory disease associated with myriad symptoms, including fatigue. It can affect physiological processes like sleep, leading to poor sleep quality and excessive daytime sleepiness. We hypothesized that sarcoidosis patients would report more severe sleep disturbance than healthy controls and that relationships would be found with sleep disturbance and the severity of other symptoms. METHODS: We enrolled 84 sarcoidosis patients and 30 healthy controls and recorded demographic and clinical characteristics. Self-report measures were used to assess sleep disturbance, psychosocial symptoms, and quality of life at enrollment and longitudinally. Relationships between different self-report outcomes were analyzed using correlation statistics. RESULTS: Using the General Sleep Disturbance Scale, 54% of sarcoidosis patients reported frequent and occasional sleep disturbance compared to only 17% of healthy controls (p < 0.0001). This significant increase in sleep disturbance found in sarcoidosis patients strongly correlated with multiple psychosocial symptoms, including fatigue, depression, and cognitive dysfunction, and negatively impacted quality of life (p < 0.01). Traditional measures of sarcoidosis disease severity or activity were not associated with sleep disturbance. Sleep disturbance scores remained stable at follow-up (mean time between first and last administration of questionnaire was 17.3 months) in 56 of the sarcoidosis patients. CONCLUSIONS: Sarcoidosis patients experienced significant sleep disturbance that correlated with higher levels of fatigue, depression, and cognitive dysfunction, and poorer quality of life. These associations were present regardless of disease severity or activity and result in decrements in quality of life and mental health.

Bipolar filaments of human nonmuscle myosin 2-A and 2-B have distinct motile and mechanical properties.

Nonmusclemyosin 2 (NM-2) powers cell motility and tissue morphogenesis by assembling into bipolar filaments that interact with actin. Although the enzymatic properties of purified NM-2 motor fragments have been determined, the emergent properties of filament ensembles are unknown. Using single myosin filament in vitro motility assays, we report fundamental differences in filaments formed of different NM-2 motors. Filaments consisting of NM2-B moved processively along actin, while under identical conditions, NM2-A filaments did not. By more closely mimicking the physiological milieu, either by increasing solution viscosity or by co-polymerization with NM2-B, NM2-A containing filaments moved processively. Our data demonstrate that both the kinetic and mechanical properties of these two myosins, in addition to the stochiometry of NM-2 subunits, can tune filament mechanical output. We propose altering NM-2 filament composition is a general cellular strategy for tailoring force production of filaments to specific functions, such as maintaining tension or remodeling actin.

Clinical and Biological Insights from the University of California San Francisco Prospective and Longitudinal Cohort.

INTRODUCTION: Sarcoidosis is a systemic inflammatory disease characterized by non-necrotizing granulomas in involved organs, most commonly the lung. Description of patient characteristics in the Western United States is limited. Furthermore, blood-based measures that relate to clinical sarcoidosis phenotypes are lacking. We present an analysis of a prospective, longitudinal sarcoidosis cohort at a Northern Californian academic medical center. METHODS: We enrolled 126 sarcoidosis subjects and 64 healthy controls and recorded baseline demographic and clinical characteristics. We used regression models to identify factors independently associated with pulmonary physiology. We tested whether blood transcript levels at study entry could relate to longitudinal changes in pulmonary physiology. RESULTS: White, non-Hispanics composed ~70% of subjects. Hispanics and Blacks had a diagnostic biopsy at an age ~7 years younger than whites. Obstructive, but not restrictive, physiology characterized Scadding Stage IV patients. Subjects reporting use of immunosuppression had worse FEV1%p, FVC%p, and DLCO%p compared to subjects never treated, regardless of Scadding stage. We defined sarcoidosis disease activity by a drop in pulmonary function over 36 months and found that subjects meeting this definition had significant repression of blood gene transcripts related to T cell receptor signaling pathways, referred to as the "TCR factor." CONCLUSION: Obstructive pulmonary physiology defined Stage IV patients which were mostly white, non-Hispanics. Genes comprising the composite gene expression score, TCR factor, may represent a blood-derived measure of T-cell activity and an indirect measure of active sarcoidosis inflammation. Validation of this measure could translate into individualized treatment for sarcoidosis patients.

IFN-γ-Producing T-Helper 17.1 Cells Are Increased in Sarcoidosis and Are More Prevalent than T-Helper Type 1 Cells.

RATIONALE: Pulmonary sarcoidosis is classically defined by T-helper (Th) cell type 1 inflammation (e.g., IFN-γ production by CD4(+) effector T cells). Recently, IL-17A-secreting cells have been found in lung lavage, invoking Th17 immunity in sarcoidosis. Studies also identified IL-17A-secreting cells that expressed IFN-γ, but their abundance as a percentage of total CD4(+) cells was either low or undetermined. OBJECTIVES: Based on evidence that Th17 cells can be polarized to Th17.1 cells to produce only IFN-γ, our goal was to determine whether Th17.1 cells are a prominent source of IFN-γ in sarcoidosis. METHODS: We developed a single-cell approach to define and isolate major Th-cell subsets using combinations of chemokine receptors and fluorescence-activated cell sorting. We subsequently confirmed the accuracy of subset enrichment by measuring cytokine production. MEASUREMENTS AND MAIN RESULTS: Discrimination between Th17 and Th17.1 cells revealed very high percentages of Th17.1 cells in lung lavage in sarcoidosis compared with controls in two separate cohorts. No differences in Th17 or Th1 lavage cells were found compared with controls. Lung lavage Th17.1-cell percentages were also higher than Th1-cell percentages, and approximately 60% of Th17.1-enriched cells produced only IFN-γ. CONCLUSIONS: Combined use of surface markers and functional assays to study CD4(+) T cells in sarcoidosis revealed a marked expansion of Th17.1 cells that only produce IFN-γ. These results suggest that Th17.1 cells could be misclassified as Th1 cells and may be the predominant producer of IFN-γ in pulmonary sarcoidosis, challenging the Th1 paradigm of pathogenesis.

Repurposing cAMP-modulating medications to promote ß-cell replication.

Loss of ß-cell mass is a cardinal feature of diabetes. Consequently, developing medications to promote ß-cell regeneration is a priority. cAMP is an intracellular second messenger that modulates ß-cell replication. We investigated whether medications that increase cAMP stability or synthesis selectively stimulate ß-cell growth. To identify cAMP-stabilizing medications that promote ß-cell replication, we performed high-content screening of a phosphodiesterase (PDE) inhibitor library. PDE3, -4, and -10 inhibitors, including dipyridamole, were found to promote ß-cell replication in an adenosine receptor-dependent manner. Dipyridamole's action is specific for ß-cells and not α-cells. Next we demonstrated that norepinephrine (NE), a physiologic suppressor of cAMP synthesis in ß-cells, impairs ß-cell replication via activation of α(2)-adrenergic receptors. Accordingly, mirtazapine, an α(2)-adrenergic receptor antagonist and antidepressant, prevents NE-dependent suppression of ß-cell replication. Interestingly, NE's growth-suppressive effect is modulated by endogenously expressed catecholamine-inactivating enzymes (catechol-O-methyltransferase and l-monoamine oxidase) and is dominant over the growth-promoting effects of PDE inhibitors. Treatment with dipyridamole and/or mirtazapine promote ß-cell replication in mice, and treatment with dipyridamole is associated with reduced glucose levels in humans. This work provides new mechanistic insights into cAMP-dependent growth regulation of ß-cells and highlights the potential of commonly prescribed medications to influence ß-cell growth.

Kinetic characterization of nonmuscle myosin IIb at the single molecule level.

Nonmuscle myosin IIB (NMIIB) is a cytoplasmic myosin, which plays an important role in cell motility by maintaining cortical tension. It forms bipolar thick filaments with ~14 myosin molecule dimers on each side of the bare zone. Our previous studies showed that the NMIIB is a moderately high duty ratio (~20-25%) motor. The ADP release step (~0.35 s(-1)) of NMIIB is only ~3 times faster than the rate-limiting phosphate release (0.13 ± 0.01 s(-1)). The aim of this study was to relate the known in vitro kinetic parameters to the results of single molecule experiments and to compare the kinetic and mechanical properties of single- and double-headed myosin fragments and nonmuscle IIB thick filaments. Examination of the kinetics of NMIIB interaction with actin at the single molecule level was accomplished using total internal reflection fluorescence (TIRF) with fluorescence imaging with 1-nm accuracy (FIONA) and dual-beam optical trapping. At a physiological ATP concentration (1 mm), the rate of detachment of the single-headed and double-headed molecules was similar (~0.4 s(-1)). Using optical tweezers we found that the power stroke sizes of single- and double-headed heavy meromyosin (HMM) were each ~6 nm. No signs of processive stepping at the single molecule level were observed in the case of NMIIB-HMM in optical tweezers or TIRF/in vitro motility experiments. In contrast, robust motility of individual fluorescently labeled thick filaments of full-length NMIIB was observed on actin filaments. Our results are in good agreement with the previous steady-state and transient kinetic studies and show that the individual nonprocessive nonmuscle myosin IIB molecules form a highly processive unit when polymerized into filaments.