Development of a compounded propofol nanoemulsion using multiple non-invasive process analytical technologies.

Propofol is the preferred anaesthetic for induction and maintenance of sedation in critically ill mechanically ventilated COVID-19 patients. However, during the outbreak of the COVID-19 pandemic, regular supply chains could not keep up with the sudden increase in global demand, causing drug shortages. Propofol is formulated as an oil-in-water emulsion which is administered intravenously. This study explores the extemporaneous preparation of a propofol emulsion without specialized manufacturing equipment to temporally alleviate such shortages. A commercially available lipid emulsion (IVLE, SMOFlipid 20 %), intended for parenteral nutrition, was used to create a propofol loaded nanoemulsion via addition of liquid propofol drug substance and subsequent mixing. Critical quality attributes such as mean droplet size and the volume-weighted percentage of large-diameter (>5µm) droplets were studied. The evolution of droplet size and propofol distribution was monitored in situ and non-destructively, maintaining sterility, using Spatially Resolved Dynamic Light Scattering and Near Infrared Spectroscopy, respectively. Using response surface methodology, an optimum was found for a 4 % w/v propofol formulation with a ∼15 min mixing time in a flask shaker at a 40° shaking angle. This study shows that extemporaneous compounding is a viable option for emergency supply of propofol drug product during global drug shortages.

New unique PAT method and instrument for real-time inline size characterization of concentrated, flowing nanosuspensions.

With the rise of nanotherapeutics -and nano based products in general-, there has been an increasing need for better understanding and control of nano-particle (NP) synthesis and formulation processes. Size characteristics are often primary, if not critical, quality attributes of nanodispersions. Process Analytical Technology (PAT) tools for inline size characterization during dispersion processing are therefore highly desired. Traditional methods for NP sizing -based on Dynamic Light Scattering (DLS) - are typically ill-suited for direct inline application: (i) typical dispersion turbidities in process conditions often exceed by far the application limits for DLS (ii) agitation/flow typical for process conditions is incompatible with standard DLS and (iii) direct and convenient inline application requires a non-invasive PAT tool giving measurements on process relevant time scales. In this article we describe a new non-invasive PAT instrument - the NanoFlowSizer (patent pending)- which provides continuous, real-time, inline size and PSD characterization of concentrated and/or flowing nanodispersions in process environments. The instrument employs Fourier Domain low coherence interferometry, yielding path length resolved dynamic light scattering data of nanodispersions. Particle size characteristics can be analyzed from these data while effects of flow and/or multiple scattering are simultaneously characterized and accounted for. As first application examples we describe (i) real-time monitoring of NP size characteristics by remote measurement of mono and bi-disperse suspensions at different turbidities in a stirred beaker (ii) real-time monitoring of NP size characteristics using an online sampling loop with a micro-flow cell and (iii) real-time inline monitoring of size characteristics of a pharmaceutical nanoemulsion during industrial pilot scale nano-emulsification and for a pharmaceutical NP suspension during circulation, at flowrates ranging up to ~l/min.

Actions of primary health care professionals to reduce maternal mortality in the Brazilian Northeast.

BACKGROUND: Maternal mortality is a global public health problem. Statistics show that in 2013, 289,000 women died from complications during pregnancy, childbirth or the postpartum period worldwide. Between 2010 and 2015, there were 10,075 maternal deaths in Brazil, 3,522of which occurred in the Northeast region. The aim of this study was to investigate the actions taken by primary health care (PHC) professionals to reduce maternal mortality. METHOD: This was a cross-sectional, descriptive field study with a qualitative approach. The sample comprised 81 graduate-level professionals working in PHC in the state of Ceará, Brazil. Data were collected from January to March 2016 using structured interviews, which were digitally audio recorded and transcribed. The results were organized using collective subject discourse and analyzed according with the relevant literature. RESULTS: The PHC professionals took both individual and joint measures to reduce maternal mortality. These activities included home visits, health education, active searches, prenatal care consultations, referrals to specialized care and outreach. The challenges that must be overcome to prevent maternal mortality include poor care and ineffective public policies that are associated with a lack of managerial support. CONCLUSION: Interaction among professionals in the health care network is critical to the development of cross-sectoral projects that improve the quality of women's health care. Prenatal care is a key factor in reducing maternal death and enables the identification and classification of the risks to which pregnant women may be exposed and the implementation of early actions that can ensure a safe and uncomplicated delivery. However, all of these actions require effective public policies and managerial support.

[Tecnologías de la información en la formación de evaluadores del Programa Hospital Seguro en México]. / Information technologies in the training of evaluators of the Safe Hospital Program in Mexico.

OBJETIVO: Describir el proceso para la formación de evaluadores del Programa Hospital Seguro centrado en el uso de las tecnologías de la información. MÉTODO: Estudio observacional descriptivo en el que se analiza la participación dentro del nuevo curso de evaluadores del Programa Hospital Seguro. RESULTADOS: Se inscribieron 1323 participantes, de los cuales aprobaron 298 (18%); la calificación media fue de 8.85. CONCLUSIONES: La plataforma educativa tipo Moodle fue de utilidad para la capacitación del Programa Hospital Seguro. Se tendrían que mejorar los criterios de participación de los alumnos a fin de incrementar la eficiencia terminal. OBJECTIVE: To describe the process for the training of evaluators of the safe hospital program in the use of ICT. METHOD: Descriptive observational study in which the participation in the new course of appraisers of the safe hospital program is analyzed. RESULTS: 1323 participants registered of which 298 (18%) passed; the average grade was 8.85. CONCLUSIONS: The Moodle type educational platform was useful for the training of the Safe Hospital Program. The criteria for student participation would have to be improved in order to increase terminal efficiency.

Acute tension pneumopericardium due to perforated gastric ulcer without diagnostic radiographic findings 72 h before perforation.

INTRODUCTION: Acute tension pneumopericardium due to gastric perforation is a rare and often lethal condition. Only a few case reports have been described in the literature. Diagnosis based on clinical evaluation is difficult and it is usually made incidentally upon computed tomography (CT) or plain radiography of the chest. Since cardiac tamponade caused by pneumopericardium is life-threatening, immediate diagnosis and emergent therapy is vital. CASE REPORT: We report a 75-year-old male with peptic ulcer disease associated with perforation of the pericardium and acute shock. It is the first reported case with a series of two computed tomograms performed during the 72 h preceding the acute onset of tension pneumopericardium. No radiographic evidence of ulcer perforation was present in the three days prior to the acute event. DISCUSSIONS: Gastric ulcer perforation into the pericardium is rare and could not be detected by CT scan prior the deletorious event. Pneumopericardium seems to be fateful and could not be foreseen by clinical or radiological findings..

Minimally invasive, multi-port approach to the lateral skull base: a first in vitro evaluation.

PURPOSE: The aim of the study was to validate a minimally invasive, multi-port approach to the internal auditory canal at the lateral skull base on a cadaver specimen. METHODS: Fiducials and a custom baseplate were fixed on a cadaver skull, and a computed tomography image was acquired. Three trajectories from the mastoid surface to the internal auditory canal were computed with a custom planning tool. A self-developed positioning system with a drill guide was attached to the baseplate. After referencing on a high precision coordinate measuring machine, the drill guide was aligned according to the planned trajectories. Drilling of three trajectories was performed with a medical stainless steel drill bit. RESULTS: The process of planning and drilling three trajectories to the internal auditory canal with the presented workflow and tools was successful. The mean drilling error of the system (Euclidian distance between the planned trajectory and centerline of the actual drilled canal) was [Formula: see text] mm at the entry point and [Formula: see text] mm at the target. The inaccuracy of the drill process itself and its physical limitations were identified as the main contributing factors. CONCLUSION: The presented system allows the planning and drilling of multiple minimally invasive canals at the lateral skull base. Further studies are required to reduce the drilling error and evaluate the clinical application of the system.

Gravitational collapse of depletion-induced colloidal gels.

We study the ageing and ultimate gravitational collapse of colloidal gels in which the interparticle attraction is induced by non-adsorbing polymers via the depletion effect. The gels are formed through arrested spinodal decomposition, whereby the dense phase arrests into an attractive glass. We map the experimental state diagram onto a theoretical one obtained from computer simulations and theoretical calculations. Discrepancies between the experimental and simulated gel regions in the state diagram can be explained by the particle size and density dependence of the boundary below which the gel is not strong enough to resist gravitational stress. Visual observations show that gravitational collapse of the gels falls into two distinct regimes as the colloid and polymer concentrations are varied, with gels at low colloid concentrations showing the onset of rapid collapse after a delay time. Magnetic resonance imaging (MRI) was used to provide quantitative, spatio-temporally resolved measurements of the solid volume fraction in these rapidly collapsing gels. We find that during the delay time, a dense region builds up at the top of the sample. The rapid collapse is initiated when the gel structure is no longer able to support this dense layer.

Erratum: Towards a Unified Description of the Rheology of Hard-Particle Suspensions [Phys. Rev. Lett. 115, 088304 (2015)].

This corrects the article DOI: 10.1103/PhysRevLett.115.088304.

Towards a Unified Description of the Rheology of Hard-Particle Suspensions.

The rheology of suspensions of Brownian, or colloidal, particles (diameter d≲1 µm) differs markedly from that of larger grains (d≳50 µm). Each of these two regimes has been separately studied, but the flow of suspensions with intermediate particle sizes (1 µm≲d≲50 µm), which occur ubiquitously in applications, remains poorly understood. By measuring the rheology of suspensions of hard spheres with a wide range of sizes, we show experimentally that shear thickening drives the transition from colloidal to granular flow across the intermediate size regime. This insight makes possible a unified description of the (noninertial) rheology of hard spheres over the full size spectrum. Moreover, we are able to test a new theory of friction-induced shear thickening, showing that our data can be well fitted using expressions derived from it.

Creep and flow of glasses: strain response linked to the spatial distribution of dynamical heterogeneities.

Mechanical properties are of central importance to materials sciences, in particular if they depend on external stimuli. Here we investigate the rheological response of amorphous solids, namely colloidal glasses, to external forces. Using confocal microscopy and computer simulations, we establish a quantitative link between the macroscopic creep response and the microscopic single-particle dynamics. We observe dynamical heterogeneities, namely regions of enhanced mobility, which remain localized in the creep regime, but grow for applied stresses leading to steady flow. These different behaviors are also reflected in the average particle dynamics, quantified by the mean squared displacement of the individual particles, and the fraction of active regions. Both microscopic quantities are found to be proportional to the macroscopic strain, despite the non-equilibrium and non-linear conditions during creep and the transient regime prior to steady flow.

Determination of the positions and orientations of concentrated rod-like colloids from 3D microscopy data.

Confocal microscopy in combination with real-space particle tracking has proven to be a powerful tool in scientific fields such as soft matter physics, materials science and cell biology. However, 3D tracking of anisotropic particles in concentrated phases remains not as optimized compared to algorithms for spherical particles. To address this problem, we developed a new particle-fitting algorithm that can extract the positions and orientations of fluorescent rod-like particles from three dimensional confocal microscopy data stacks. The algorithm is tailored to work even when the fluorescent signals of the particles overlap considerably and a threshold method and subsequent clusters analysis alone do not suffice. We demonstrate that our algorithm correctly identifies all five coordinates of uniaxial particles in both a concentrated disordered phase and a liquid-crystalline smectic-B phase. Apart from confocal microscopy images, we also demonstrate that the algorithm can be used to identify nanorods in 3D electron tomography reconstructions. Lastly, we determined the accuracy of the algorithm using both simulated and experimental confocal microscopy data-stacks of diffusing silica rods in a dilute suspension. This novel particle-fitting algorithm allows for the study of structure and dynamics in both dilute and dense liquid-crystalline phases (such as nematic, smectic and crystalline phases) as well as the study of the glass transition of rod-like particles in three dimensions on the single particle level.

Transient dynamics during stress overshoots in binary colloidal glasses.

We investigate, using simultaneous rheology and confocal microscopy, the time-dependent stress response and transient single-particle dynamics following a step change in shear rate in binary colloidal glasses with large dynamical asymmetry and different mixing ratios. The transition from solid-like response to flow is characterised by a stress overshoot, whose magnitude is linked to transient superdiffusive dynamics as well as cage compression effects. These and the yield strain at which the overshoot occurs vary with the mixing ratio, and hence the prevailing caging mechanism. The yielding and stress storage are dominated by dynamics on different time and length scales, the short-time in-cage dynamics and the long-time structural relaxation respectively. These time scales and their relation to the characteristic time associated with the applied shear, namely the inverse shear rate, result in two different and distinct regimes of the shear rate dependencies of the yield strain and the magnitude of the stress overshoot.

Gastrin-releasing peptide acts via postsynaptic BB2 receptors to modulate inward rectifier K+ and TRPV1-like conductances in rat paraventricular thalamic neurons.

Gastrin-releasing peptide (GRP) is a bombesin-like peptide with a widespread distribution in mammalian CNS, where it has a role in food intake, circadian rhythm generation, fear memory, itch sensation and sexual behaviour. While it has been established that GRP predominantly excites neurons, details of the membrane mechanism involved in this action remain largely undefined. We used perforated patch clamp recording in acute brain slice preparations to investigate GRP-affected receptors and ionic conductances in neurons of the rat paraventricular thalamic nucleus (PVT). PVT is a component of the midline and intralaminar thalamus that participates in arousal, motivational drives and stress responses, and exhibits a prominence of GRP-like immunoreactive fibres. Exposure of PVT neurons to low nanomolar concentrations of GRP induced sustained TTX-resistant membrane depolarizations that could trigger rhythmic burst discharges or tonic firing. Membrane current analyses in voltage clamp revealed an underlying postsynaptic bombesin type 2 receptor-mediated inward current that resulted from the simultaneous suppression of a Ba(2+)-sensitive inward rectifier K(+) conductance and activation of a non-selective cation conductance with biophysical and pharmacological properties reminiscent of transient receptor potential vanilloid (TRPV) 1. A role for a TRPV1-like conductance was further implied by a significant suppressant influence of a TRPV1 antagonist on GRP-induced membrane depolarization and rhythmic burst or tonic firing. The results provide a detailed picture of the receptor and ionic conductances that are involved in GRP's excitatory action in midline thalamus.

Self-assembly of a colloidal interstitial solid with tunable sublattice doping.

We determine the phase diagram of a binary mixture of small and large hard spheres with a size ratio of 0.3 using free-energy calculations in Monte Carlo simulations. We find a stable binary fluid phase, a pure face-centered-cubic (fcc) crystal phase of the small spheres, and binary crystal structures with LS and LS(6) stoichiometries. Surprisingly, we demonstrate theoretically and experimentally the stability of a novel interstitial solid solution in binary hard-sphere mixtures, which is constructed by filling the octahedral holes of an fcc crystal of large spheres with small spheres. We find that the fraction of octahedral holes filled with a small sphere can be completely tuned from 0 to 1. Additionally, we study the hopping of the small spheres between neighboring octahedral holes, and interestingly, we find that the diffusion increases upon increasing the density of small spheres.

Postsynaptic and presynaptic group II metabotropic glutamate receptor activation reduces neuronal excitability in rat midline paraventricular thalamic nucleus.

Drugs that interact with group II metabotropic glutamate receptors (mGluRs) are presently being evaluated for a role in the treatment of anxiety disorders and symptoms of schizophrenia. Their mechanism of action is believed to involve a reduction in excitatory neurotransmission in limbic and forebrain regions commonly associated with these mental disorders. In rodents, the glutamatergic neurons in the midline paraventricular thalamic nucleus (PVT) provide excitatory inputs to the limbic system and forebrain. PVT also displays a high density of group II mGluRs, predominantly the metabotropic glutamate 2 receptor (mGluR2). Because the role of group II mGluRs in regulating cellular and synaptic excitability in this location has yet to be determined, we used whole-cell patch-clamp recording and acute rat brain slice preparations to evaluate PVT neuron responses to a selective group II mGluR agonist, (1R,4R,5S,6R)-4-amino-2-oxabicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY 379268). LY 379268 consistently induced membrane hyperpolarization and suppressed firing by postsynaptic receptor-mediated activation of a barium-sensitive background K(+) conductance. This effect could be blocked by (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl)propanoic acid (LY 341495), a selective group II mGluR antagonist. In addition, LY 379268 acted at presynaptic receptors to reduce ionotropic glutamate receptor-mediated excitatory synaptic transmission. An mGluR2-positive allosteric modulator, 2,2,2-trifluoro-N-[4-(2-methoxyphenoxy)phenyl]-N-(3-pyridinylmethyl)ethanesulfonamide hydrochloride (LY 487379), resulted in leftward shifts of the LY 379268 dose-response curve for both postsynaptic and presynaptic actions. The data demonstrate that activation of postsynaptic and presynaptic group II (presumably mGluR2) mGluRs reduces neuronal excitability in midline thalamus, an action that may contribute to the effectiveness of mGluR2-activating drugs in rodent models of anxiety and psychosis.

Mechanisms of burn-induced impairment in gastric slow waves and emptying in rats.

Delayed gastric emptying is common following severe large cutaneous burns; however, the mechanisms of burn-induced delayed gastric emptying remain unknown. The aim of this study was to explore the possible involvement of hyperglycemia and cyclooxygenase-2 receptors in the burn-induced gastric dysrhythmias. Gastric slow waves and gastric emptying were assessed in rats 6 h following sham or burn injury. Animals were randomized to one sham-burn and seven burn groups: untreated; two groups of saline treated (control); insulin treated (5 IU/kg); cyclooxygenase-2 inhibitor treated (10 mg/kg); ghrelin treated (2 nmol/rat); and gastric electrical stimulation treated. It was found that 1) severe burn injury impaired gastric slow waves postprandially and delayed gastric emptying; 2) the impairment in gastric slow waves included a decrease in the slow-wave frequency and in the percentage of normal slow waves, and an increase in the percentage of bradygastria (P = 0.001, 0.01, and 0.01, respectively vs. preburn values). None of the gastric slow-wave parameters was significantly correlated with gastric emptying; 3) cyclooxygenase-2 inhibitor normalized burn-induced delayed gastric emptying (P = 0.3 vs. sham-burn), but not gastric dysrhythmias (P < 0.002 vs. sham), whereas insulin normalized both gastric emptying (P = 0.4 vs. sham-burn) and gastric dysrhythmias (P = 0.3 vs. sham-burn); 4) both gastric electrical stimulation and ghrelin accelerated burn-induced delayed gastric emptying (P = 0.002 and 0.04, respectively, vs. untreated burn). In conclusion, hyperglycemia alters gastric slow-wave activity and delayed gastric emptying, while cyclooxygenase-2 inhibition delays gastric emptying without altering gastric slow-wave activity.

Crystal nucleation of hard spheres using molecular dynamics, umbrella sampling, and forward flux sampling: a comparison of simulation techniques.

Over the last number of years several simulation methods have been introduced to study rare events such as nucleation. In this paper we examine the crystal nucleation rate of hard spheres using three such numerical techniques: molecular dynamics, forward flux sampling, and a Bennett-Chandler-type theory where the nucleation barrier is determined using umbrella sampling simulations. The resulting nucleation rates are compared with the experimental rates of Harland and van Megen [Phys. Rev. E 55, 3054 (1997)], Sinn et al. [Prog. Colloid Polym. Sci. 118, 266 (2001)], Schätzel and Ackerson [Phys. Rev. E 48, 3766 (1993)], and the predicted rates for monodisperse and 5% polydisperse hard spheres of Auer and Frenkel [Nature 409, 1020 (2001)]. When the rates are examined in units of the long-time diffusion coefficient, we find agreement between all the theoretically predicted nucleation rates, however, the experimental results display a markedly different behavior for low supersaturation. Additionally, we examined the precritical nuclei arising in the molecular dynamics, forward flux sampling, and umbrella sampling simulations. The structure of the nuclei appears independent of the simulation method, and in all cases, the nuclei contains on average significantly more face-centered-cubic ordered particles than hexagonal-close-packed ordered particles.

Fabrication of large binary colloidal crystals with a NaCl structure.

Binary colloidal crystals offer great potential for tuning material properties for applications in, for example, photonics, semiconductors and spintronics, because they allow the positioning of particles with quite different characteristics on one lattice. For micrometer-sized colloids, it is believed that gravity and slow crystallization rates hinder the formation of high-quality binary crystals. Here, we present methods for growing binary colloidal crystals with a NaCl structure from relatively heavy, hard-sphere-like, micrometer-sized silica particles by exploring the following external fields: electric, gravitational, and dielectrophoretic fields and a structured surface (colloidal epitaxy). Our simulations show that the free-energy difference between the NaCl and NiAs structures, which differ in their stacking of the hexagonal planes of the larger spheres, is very small (approximately 0.002 k(B)T). However, we demonstrate that the fcc stacking of the large spheres, which is crucial for obtaining the pure NaCl structure, can be favored by using a combination of the above-mentioned external fields. In this way, we have successfully fabricated large, 3D, oriented single crystals having a NaCl structure without stacking disorder.

Effects of VPAC2 receptor activation on membrane excitability and GABAergic transmission in subparaventricular zone neurons targeted by suprachiasmatic nucleus.

The hypothalamic suprachiasmatic nucleus (SCN) harbors the master circadian pacemaker. SCN neurons produce the amino acid gamma-aminobutyric acid (GABA) and several peptide molecules for coordination and communication of their circadian rhythms. A subpopulation of SCN cells synthesizes vasoactive intestinal polypeptide (VIP) and provides a dense innervation of the subparaventricular zone (SPZ), an important CNS target of the circadian pacemaker. In this study, using patch-clamp recording techniques and rat brain slice preparations, the contribution of VIP to SCN efferent signaling to SPZ was evaluated by examining membrane responses of SPZ neurons to exogenous VIP receptor ligands. In approximately 50% of the SPZ neurons receiving monosynaptic GABAA receptor-mediated inputs from SCN, bath-applied VIP (0.5-1 microM) resulted in a membrane depolarization caused by tetrodotoxin-resistant inward currents reversing at approximately -23 mV. These data suggest the existence of postsynaptic receptors that activate a nonselective cationic conductance. In addition, a subset of SPZ neurons showed an increase in the amplitude of SCN-evoked GABAergic inhibitory postsynaptic currents (IPSCs) and a decrease in their paired-pulse ratios. This, together with an increase in frequency of spontaneous and miniature IPSCs, implies the presence of presynaptic receptors that facilitate GABA release from SCN and possibly other synaptic terminals. The effects occurred in separate neurons and could be mimicked by the selective VPAC2 receptor agonist BAY 55-9837 (0.2-0.5 microM) and partially blocked by the VIP receptor antagonist VIP(6-28) (5 microM). The results indicate that VIP acts via both post- and presynaptic VPAC2 receptors to differentially modulate SCN GABAergic signaling to distinct subpopulations of SPZ neurons.

Ciencia Brasil

Blog de autoria de Marcelo Hermes, biólogo e professor da Universidade de Brasília. Trata de ciencia em geral e política científica.