Does intranasal dexmedetomidine provide adequate plasma concentrations for sedation in children: a pharmacokinetic study.

BACKGROUND: Atomised intranasal dexmedetomidine administration is an attractive option when sedation is required for paediatric diagnostic procedures, as vascular access is not required. The risk of haemodynamic instability caused by dexmedetomidine necessitates better understanding of its pharmacokinetics in young children. To date, intranasal dexmedetomidine pharmacokinetics has only been studied in adults. METHODS: Eighteen paediatric patients received dexmedetomidine 1 or 2 µg kg-1 intranasally or 1 µg kg-1 i.v. Plasma concentrations were determined by liquid chromatography/mass spectrometry. Non-compartmental analysis provided estimates of Cmax and Tmax. Volume of distribution, clearance, and bioavailability were estimated by simultaneous population PK analysis of data after intranasal and i.v. administration. Dexmedetomidine plasma concentration-time profiles were evaluated by simulation for intranasal and i.v. administration. RESULTS: An average peak plasma concentration of 199 pg ml-1 was achieved 46 min after 1 µg kg-1 dosing and 355 pg ml-1 was achieved 47 min after 2 µg kg-1 dosing. A two-compartment pharmacokinetic model, with allometrically scaled parameters, adequately described the data. Typical bioavailability was 83.8% (95% confidence interval 69.5-98.1%). CONCLUSION: Mean arterial plasma concentrations of dexmedetomidine in infants and toddlers approached 100 pg ml-1, the low end reported for sedative efficacy, within 20 min of an atomised intranasal administration of 1 µg kg-1. Doubling the dose to 2 µg kg-1 reached this plasma concentration within 10 min and achieved almost twice the peak concentration. Peak plasma concentrations with both doses were reached within 47 min of intranasal administration, with an overall bioavailability of 84%.

Treadmill measures of ambulation rates in ovine models of spinal cord injury and neuropathic pain.

Our laboratories are developing treadmill-based gait analysis employing sheep to investigate potential efficacy of intra-dural spinal cord stimulation in the treatment of spinal cord injury and neuropathic pain. As part of efforts to establish the performance characteristics of the experimental arrangement, this study measured the treadmill speed via a tachometer, video belt-marker timing and ambulation-rate observations of the sheep. The data reveal a 0.1-0.3% residual drift in the baseline (unloaded) treadmill speed which increases with loading, but all three approaches agree on final speed to within 1.7%, at belt speeds of ≈ 4 km/h. Using the tachometer as the standard, the estimated upper limit on uncertainty in the video belt-marker approach is ± 0.18 km h(-1) and the measured uncertainty is ± 0.15 km h(-1). Employment of the latter method in determining timing differences between contralateral hoof strikes by the sheep suggests its utility in assessing severity of SCI and responses to therapeutic interventions.

Membrane-bound and soluble Fas ligands have opposite functions in photoreceptor cell death following separation from the retinal pigment epithelium.

Fas ligand (FasL) triggers apoptosis of Fas-positive cells, and previous reports described FasL-induced cell death of Fas-positive photoreceptors following a retinal detachment. However, as FasL exists in membrane-bound (mFasL) and soluble (sFasL) forms, and is expressed on resident microglia and infiltrating monocyte/macrophages, the current study examined the relative contribution of mFasL and sFasL to photoreceptor cell death after induction of experimental retinal detachment in wild-type, knockout (FasL-/-), and mFasL-only knock-in (ΔCS) mice. Retinal detachment in FasL-/- mice resulted in a significant reduction of photoreceptor cell death. In contrast, ΔCS mice displayed significantly more apoptotic photoreceptor cell death. Photoreceptor loss in ΔCS mice was inhibited by a subretinal injection of recombinant sFasL. Thus, Fas/FasL-triggered cell death accounts for a significant amount of photoreceptor cell loss following the retinal detachment. The function of FasL was dependent upon the form of FasL expressed: mFasL triggered photoreceptor cell death, whereas sFasL protected the retina, indicating that enzyme-mediated cleavage of FasL determines, in part, the extent of vision loss following the retinal detachment. Moreover, it also indicates that treatment with sFasL could significantly reduce photoreceptor cell loss in patients with retinal detachment.

Macrophage- and RIP3-dependent inflammasome activation exacerbates retinal detachment-induced photoreceptor cell death.

Detachment of photoreceptors from the retinal pigment epithelium is seen in various retinal disorders, resulting in photoreceptor death and subsequent vision loss. Cell death results in the release of endogenous molecules that activate molecular platforms containing caspase-1, termed inflammasomes. Inflammasome activation in retinal diseases has been reported in some cases to be protective and in others to be detrimental, causing neuronal cell death. Moreover, the cellular source of inflammasomes in retinal disorders is not clear. Here, we demonstrate that patients with photoreceptor injury by retinal detachment (RD) have increased levels of cleaved IL-1ß, an end product of inflammasome activation. In an animal model of RD, photoreceptor cell death led to activation of endogenous inflammasomes, and this activation was diminished by Rip3 deletion. The major source of Il1b expression was found to be infiltrating macrophages in the subretinal space, rather than dying photoreceptors. Inflammasome inhibition attenuated photoreceptor death after RD. Our data implicate the infiltrating macrophages as a source of damaging inflammasomes after photoreceptor detachment in a RIP3-dependent manner and suggest a novel therapeutic target for treatment of retinal diseases.

Necrotic enlargement of cone photoreceptor cells and the release of high-mobility group box-1 in retinitis pigmentosa.

Retinitis pigmentosa (RP) refers to a group of inherited retinal degenerations resulting form rod and cone photoreceptor cell death. The rod cell death due to deleterious genetic mutations has been shown to occur mainly through apoptosis, whereas the mechanisms and features of the secondary cone cell death have not been fully elucidated. Our previous study showed that the cone cell death in rd10 mice, an animal model of RP, involves necrotic features and is partly mediated by the receptor interacting protein kinase. However, the relevancy of necrotic cone cell death in human RP patients remains unknown. In the present study, we showed that dying cone cells in rd10 mice exhibited cellular enlargement, along with necrotic changes such as cellular swelling and mitochondrial rupture. In human eyes, live imaging of cone cells by adaptive optics scanning laser ophthalmoscopy revealed significantly increased percentages of enlarged cone cells in the RP patients compared with the control subjects. The vitreous of the RP patients contained significantly higher levels of high-mobility group box-1, which is released extracellularly associated with necrotic cell death. These findings suggest that necrotic enlargement of cone cells is involved in the process of cone degeneration, and that necrosis may be a novel target to prevent or delay the loss of cone-mediated central vision in RP.

Ischemic diabetic retinopathy as a possible prognostic factor for chronic kidney disease progression.

PURPOSE: To assess the value of diabetic retinopathy (DR) severity as a possible predictive prognostic factor for the progression of chronic kidney disease (CKD). PATIENTS AND METHODS: Retrospective cohort study. Patients (51) who were initially diagnosed with DR and CKD were enrolled and their medical records were evaluated. The following ophthalmic factors were assessed by fluorescein angiography at the initial visit: area of capillary nonperfusion, presence of neovascularization and vitreous hemorrhage, and DR grade. The effect of these factors on CKD progression over the 2-year period of the study, defined as doubling of serum creatinine or the development of end-stage renal disease requiring dialysis or renal transplant, was evaluated. RESULTS: The study included 51 patients with DR and CKD; of these, 11 patients (21.6%) were found to have proliferative DR (PDR) and seven patients (13.7%) had high-risk PDR at baseline. Patients with ischemic DR, who showed extensive capillary nonperfusion (≥ 10 optic disc areas) in the retina, had a greater risk for CKD progression (hazard ratio = 6.64; P = 0.002). CONCLUSION: We found that extensive capillary nonperfusion in the retina greatly increased the risk of progression of CKD in patients with DR. This suggests that the retina and the kidney may have shared risk factors for microvascular disease secondary to diabetes mellitus, and emphasizes the need for a team approach to diabetes care.

Mammalian STE20-like kinase 2, not kinase 1, mediates photoreceptor cell death during retinal detachment.

Photoreceptor cell death is the definitive cause of vision loss in retinal detachment (RD). Mammalian STE20-like kinase (MST) is a master regulator of both cell death and proliferation and a critical factor in development and tumorigenesis. However, to date the role of MST in neurodegeneration has not been fully explored. Utilizing MST1(-/-) and MST2(-/-) mice we identified MST2, but not MST1, as a regulator of photoreceptor cell death in a mouse model of RD. MST2(-/-) mice demonstrated significantly decreased photoreceptor cell death and outer nuclear layer (ONL) thinning after RD. Additionally, caspase-3 activation was attenuated in MST2(-/-) mice compared to control mice after RD. The transcription of p53 upregulated modulator of apoptosis (PUMA) and Fas was also reduced in MST2(-/-) mice post-RD. Retinas of MST2(-/-) mice displayed suppressed nuclear relocalization of phosphorylated YAP after RD. Consistent with the reduction of photoreceptor cell death, MST2(-/-) mice showed decreased levels of proinflammatory cytokines such as monocyte chemoattractant protein 1 and interleukin 6 as well as attenuated inflammatory CD11b cell infiltration during the early phase of RD. These results identify MST2, not MST1, as a critical regulator of caspase-mediated photoreceptor cell death in the detached retina and indicate its potential as a future neuroprotection target.

Programmed necrosis, not apoptosis, is a key mediator of cell loss and DAMP-mediated inflammation in dsRNA-induced retinal degeneration.

There is no known treatment for the dry form of an age-related macular degeneration (AMD). Cell death and inflammation are important biological processes thought to have central role in AMD. Here we show that receptor-interacting protein (RIP) kinase mediates necrosis and enhances inflammation in a mouse model of retinal degeneration induced by dsRNA, a component of drusen in AMD. In contrast to photoreceptor-induced apoptosis, subretinal injection of the dsRNA analog poly(I : C) caused necrosis of the retinal pigment epithelium (RPE), as well as macrophage infiltration into the outer retinas. In Rip3(-/-) mice, both necrosis and inflammation were prevented, providing substantial protection against poly(I : C)-induced retinal degeneration. Moreover, after poly(I : C) injection, Rip3(-/-) mice displayed decreased levels of pro-inflammatory cytokines (such as TNF-α and IL-6) in the retina, and attenuated intravitreal release of high-mobility group box-1 (HMGB1), a major damage-associated molecular pattern (DAMP). In vitro, poly(I : C)-induced necrosis were inhibited in Rip3-deficient RPE cells, which in turn suppressed HMGB1 release and dampened TNF-α and IL-6 induction evoked by necrotic supernatants. On the other hand, Rip3 deficiency did not modulate directly TNF-α and IL-6 production after poly(I : C) stimulation in RPE cells or macrophages. Therefore, programmed necrosis is crucial in dsRNA-induced retinal degeneration and may promote inflammation by regulating the release of intracellular DAMPs, suggesting novel therapeutic targets for diseases such as AMD.

Pharmacometric Analyses to Support Early Development Decisions for LY2878735: A Novel Serotonin Norepinephrine Reuptake Inhibitor.

LY2878735 is a novel dual serotonin (5-hydroxytryptamine (5-HT)) and norepinephrine (NE) reuptake inhibitor (SNRI) in development for chronic pain indications. In vitro profile suggests a more balanced profile as compared with other SNRI's, which is expected to confer superior clinical efficacy. LY2878735 is metabolized partly by the genetically polymorphic cytochrome P450 (CYP) 2D6 pathway, raising pharmacokinetic (PK) variability concerns. Phase 1 PK and biomarker data were analyzed by pharmacometric methods to characterize the balance between dual-target engagement and adverse effects on heart rate (HR) and blood pressure (BP). A narrow range of plasma LY2878735 levels was associated with an acceptable balance. As compared with poor metabolizers (PM), CYP2D6 extensive metabolizers (EM) have 21- and threefold higher clearance and distribution volume, respectively. Even with a CYP2D6-based dosing paradigm, a superior therapeutic index comparable to duloxetine, a widely used SNRI, was not achievable and LY2878735 development was thus terminated. Model-based approach effectively synthesizes PK-pharmacodynamic (PD) relationships, enabling efficient early development decisions.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e66; doi:10.1038/psp.2013.43; published online 21 August 2013.

Metformin increases liver accumulation of vitamin B12 - an experimental study in rats.

AIMS/HYPOTHESIS: Patients treated with metformin exhibit low levels of plasma vitamin B12 (B12), and are considered at risk for developing B12 deficiency. In this study, we investigated the effect of metformin treatment on B12 uptake and distribution in rats. METHODS: Sprague Dawley rats (n = 18) were divided into two groups and given daily subcutaneous injections with metformin or saline (control) for three weeks. Following this, the animals received an oral dose of radio-labeled B12 ((57)[Co]-B12), and urine and feces were collected for 24 h. Plasma, bowel content, liver, and kidneys were collected and analyzed for B12, unsaturated B12-binding capacity, and (57)[Co]-B12. RESULTS: Three weeks of metformin treatment reduced plasma B12 by 22% or 289 [47-383] pmol/L (median and [range]) (p = 0.001), while no effect was observed on unsaturated B12-binding capacity. Compared with controls, the amount of B12 in the liver was 36% (p = 0.007) higher in metformin-treated rats, while the B12 content in the kidney was 34% (p = 0.013) lower. No difference in the total amount of absorbed (57)[Co]-B12 present in the tissues and organs studied was found, suggesting that metformin has no decreasing effect on the B12 absorption. CONCLUSIONS/INTERPRETATION: These results show that metformin treatment increases liver accumulation of B12, thereby resulting in decreases in circulating B12 and kidney accumulation of the vitamin. Our data questions whether the low plasma B12 observed in patients treated with metformin reflects impaired B12 status, and rather suggests altered tissue distribution and metabolism of the vitamin.

Vitamin D in African Americans with multiple sclerosis.

OBJECTIVE: To evaluate whether vitamin D is associated with multiple sclerosis (MS) status and disease severity in African Americans. METHODS: Serum 25-hydroxyvitamin D was compared in a cross-sectional sample of 339 African Americans with MS and 342 African American controls. Correlations between disease severity (Multiple Sclerosis Severity Score [MSSS]) and 25-hydroxyvitamin D levels were sought. RESULTS: A total of 71% of controls and 77% of patients with MS were vitamin D deficient (<50 nmol/L; <20 ng/mL), and 93% of controls and 94% of patients with MS were vitamin D insufficient (<75 nmol/L; <30 ng/mL). Median unadjusted (29.7 vs 36.6 nmol/L, p = 0.0001) and deseasonalized (p = 0.0013) 25-hydroxyvitamin D levels were lower in the MS group. Multivariable analysis revealed that differences in latitude and ultraviolet index accounted for much of this association. The median (interquartile range) MSSS was 6.1 (4.8-8.1). There was no apparent association between the MSSS and vitamin D status. A greater proportion of European genetic ancestry, a measure of genetic admixture, was positively correlated with 25-hydroxyvitamin D (p = 0.007). CONCLUSIONS: Levels of 25-hydroxyvitamin D were lower in African Americans with MS than controls, an observation primarily explained by differences in climate and geography. There was no apparent association between vitamin D status and disease severity. These results are consistent with observations in other populations that lower 25-hydroxyvitamin D is associated with having MS, but also highlight the importance of climate and ancestry in determining vitamin D status.

Transcobalamin C776G genotype modifies the association between vitamin B12 and homocysteine in older Hispanics.

BACKGROUND/OBJECTIVES: A common polymorphism, C776G, in the plasma B12 transport protein transcobalamin (TC), encodes for either proline or arginine at codon 259. This polymorphism may affect the affinity of TC for B12 and subsequent delivery of B12 to tissues. SUBJECTS/METHODS: TC genotype and its associations with indicators of B12 status, including total B12, holotranscobalamin (holoTC), methylmalonic acid and homocysteine, were evaluated in a cohort of elderly Latinos (N=554, age 60-93 years) from the Sacramento Area Latino Study on Aging (SALSA). RESULTS: The distribution of TC genotypes was 41.3% homozygous reference (776CC) and 11.6% homozygous variant (776GG). No differences between the homozygous genotypes were observed in total B12, holoTC, methylmalonic acid or homocysteine. The holoTC/total B12 ratio was lower in the 776GG group compared with the 776CC group (P=0.04). Significant interactions of TC genotype with total B12 (P=0.04) and with holoTC (P< or =0.03) were observed such that mean homocysteine concentrations and the odds ratios for hyperhomocysteinemia (>13 micromol/l) were higher in the 776CC subjects compared with all carriers of the G allele (776CG and 776GG combined) when total B12 (<156 pmol/l) or holoTC (<35 pmol/l) were low. CONCLUSIONS: This population of older Latinos has a lower prevalence of the TC 776GG variant than reported for Caucasian populations. The association between vitamin B12 and homocysteine concentrations is modified by TC 776 genotype. It remains to be determined whether the TC C776G polymorphism has a significant effect on the hematological and neurological manifestations of B12 deficiency or on vascular and other morbidities associated with hyperhomocysteinemia.

Comprehensive simultaneous shipboard and airborne characterization of exhaust from a modern container ship at sea.

We report the first joint shipboard and airborne study focused on the chemical composition and water-uptake behavior of particulate ship emissions. The study focuses on emissions from the main propulsion engine of a Post-Panamax class container ship cruising off the central coast of California and burning heavy fuel oil. Shipboard sampling included micro-orifice uniform deposit impactors (MOUDI) with subsequent off-line analysis, whereas airborne measurements involved a number of real-time analyzers to characterize the plume aerosol, aged from a few seconds to over an hour. The mass ratio of particulate organic carbon to sulfate at the base of the ship stack was 0.23 +/- 0.03, and increased to 0.30 +/- 0.01 in the airborne exhaust plume, with the additional organic mass in the airborne plume being concentrated largely in particles below 100 nm in diameter. The organic to sulfate mass ratio in the exhaust aerosol remained constant during the first hour of plume dilution into the marine boundary layer. The mass spectrum of the organic fraction of the exhaust aerosol strongly resembles that of emissions from other diesel sources and appears to be predominantly hydrocarbon-like organic (HOA) material. Background aerosol which, based on air mass back trajectories, probably consisted of aged ship emissions and marine aerosol, contained a lower organic mass fraction than the fresh plume and had a much more oxidized organic component. A volume-weighted mixing rule is able to accurately predict hygroscopic growth factors in the background aerosol but measured and calculated growth factors do not agree for aerosols in the ship exhaust plume. Calculated CCN concentrations, at supersaturations ranging from 0.1 to 0.33%, agree well with measurements in the ship-exhaust plume. Using size-resolved chemical composition instead of bulk submicrometer composition has little effect on the predicted CCN concentrations because the cutoff diameter for CCN activation is larger than the diameter where the mass fraction of organic aerosol begins to increase significantly. The particle number emission factor estimated from this study is 1.3 x 10(16) (kg fuel)(-1), with less than 1/10 of the particles having diameters above 100 nm; 24% of particles (>10 nm in diameter) activate into cloud droplets at 0.3% supersaturation.

Do atmospheric pressure changes influence seizure occurrence in the epilepsy monitoring unit?

In a prior study of epilepsy and atmospheric pressure, we were able to show a small association between changes in atmospheric pressure and increased seizure frequency in consecutive patients with epilepsy undergoing video telemetry. In this study, we used a larger data set of similar patients undergoing telemetry at another Seattle institution, and examined the possible impact of atmospheric pressure (AP) changes on seizure onset in subtypes of seizures (focal, generalized, and nonepileptic). Comparisons were made between AP score at time of seizure onset and AP score at selected time ranges prior to the event (hour of seizure and 3, 6, and 24 hours prior) and a random sample of AP scores collected over similar time frames using nonparametric testing with correction for multiple comparisons. We could find no evidence to suggest atmospheric pressure changes made seizure occurrence more likely in any of the seizure groups across any of the time periods.

Spectral domain optical coherence tomography for quantitative evaluation of drusen and associated structural changes in non-neovascular age-related macular degeneration.

BACKGROUND/AIMS: To demonstrate how spectral domain optical coherence tomography (SDOCT) can better evaluate drusen and associated anatomical changes in eyes with non-neovascular age-related macular degeneration (AMD) compared with time domain optical coherence tomography (TDOCT). METHODS: Images were obtained from three eyes of three patients with AMD using an experimental SDOCT system. Both a titanium-sapphire (Ti:sapphire) laser and a superluminescent diode (SLD) were used as a broadband light source to achieve cross-sectional images of the retina. A qualitative and quantitative analysis was performed for structural changes associated with non-neovascular AMD. An automated algorithm was developed to analyse drusen area and volume from SDOCT images. TDOCT was performed using the fast macular scan (StratusOCT, Carl Zeiss Meditec, Dublin, California). RESULTS: SDOCT images can demonstrate structural changes associated with non-neovascular AMD. A new SDOCT algorithm can determine drusen area, drusen volume and proportion of drusen. CONCLUSIONS: With new algorithms to determine drusen area and volume and its unprecedented simultaneous ultra-high speed ultra-high resolution imaging, SDOCT can improve the evaluation of structural abnormalities in non-neovascular AMD.

VLA-4 blockade suppresses endotoxin-induced uveitis: in vivo evidence for functional integrin up-regulation.

Leukocyte adhesion to the vascular wall is a critical early step in the pathogenesis of inflammatory diseases and is mediated in part by the leukocyte integrin, VLA-4, which binds to endothelial vascular cell adhesion molecule (VCAM) -1. Here, we investigate VLA-4's role in endotoxin-induced uveitis (EIU). At various time points (6-48 h) after EIU induction, the severity of the inflammation was evaluated by quantifying cell and protein content in the aqueous fluid, firm leukocyte adhesion in the retinal vessels, and the number of extravasated leukocytes into the vitreous. Functional activation of VLA-4 in vivo was investigated in our previously introduced autoperfused micro flow chamber assay. Firm adhesion of EIU leukocytes to immobilized VCAM-1 under physiological blood flow conditions was significantly increased compared with normal controls (P<0.05), suggesting an important role for VLA-4 in EIU. VLA-4 blockade in vivo significantly suppressed all uveitis-related inflammatory parameters studied, decreasing the clinical score by 45% (P<0.01), protein content in the aqueous fluid by 21% (P<0.01), retinal leukostasis by 68% (P<0.01), and leukocyte accumulation in the vitreous by 75% (P<0.01). Our data provide novel evidence for functional up-regulation of VLA-4 during EIU and suggest VLA-4 blockade as a promising therapeutic strategy for treatment of acute inflammatory eye diseases.

Rufinamide: Pharmacology, clinical trials, and role in clinical practice.

Rufinamide is a structurally novel compound with anticonvulsant activity that is undergoing evaluation through the European Medicines Agency and the American Food and Drug Administration. Its mechanism of action is thought to be inhibition of sodium-dependent action potentials in neurons, with possible membrane-stabilising effects. Absorption of the drug is significantly enhanced in the fed state. The drug is extensively metabolised by non-CYP450 systems with a half-life of 8-12 h. Most common adverse effects noted are somnolence, fatigue and tremor. Efficacy against partial seizures in adults and adolescents has been demonstrated in three randomised, placebo-controlled trials. Efficacy against seizures of Lennox-Gastaut syndrome, a severe, disabling childhood onset epilepsy syndrome, was shown in a single randomised, placebo-controlled trial. Efficacy against partial onset seizures in children has been suggested in an open-label trial. Should rufinamide become commercially available, reserving the drug as a second- or third-line agent should be considered.