Molecular Motion of Drugs in Hydrocolloids Measured by Electron Paramagnetic Resonance

The effects of a polymer, the Li-salt copolymer of methyl-methacrylic acid, and its methyl ester on the motion of drug molecules in hydrocolloids were studied. The investigation was carried out by means of electron paramagnetic resonance (EPR) using the model nitroxide tempol, and the spin-labeled drugs lidocaine (si-lid) and dexamethasone (sl-dex). Synthesis of sl-dex was performed. Spin-labeled molecules dissolved in hydrocolloids undergo a fast reorientation motion. The decreasing order of rotational correlation times () —sl-dex > si-lid > tempol—suggests that the size and the shape of the molecules strongly affect their motion. The inhibition of motion of larger molecules depends also on their flexibility. The values indicate proportionality of the microviscosity of hydrocolloids to the polymer concentration. Rotational motion is dependent on the local environment conditioned by the free spaces between polymer molecules.     

Skin oxygenation after topical application of liposome-entrapped benzyl nicotinate as measured by EPR oximetry in vivo: Influence of composition and size

New and improved drug delivery systems are the important subject of much scientific research. The development of formulations that increase skin oxygenation and of methods for measuring oxygen levels in skin are important for dealing with healing processes affected by the level of oxygen. We have use EPR oximetry in vivo to compare the influence of liposomal formulations of different size and composition with that of hydrogel with respect to the action of the entrapped benzyl nicotinate (BN). Following the topical application of BN onto the skin of mice, pO₂ increase was measured by low-frequency EPR as a function of time. The effect of BN was evaluated by 3 different parameters: lag-time, time needed for maximum pO₂ increase, and overall effectiveness expressed by the area under the response-time curve. An increase in skin oxygenation was observed after BN application. The results show that the effect of BN incorporated in liposomes is achieved more rapidly than the effect from hydrophilic gel. The composition of the liposomes significantly affects the time at which BN starts to act and, to a lesser extent, the maximum increase of pO₂ in skin and the effectiveness of BN action. However, the size of the liposomes influences both the effectiveness of BN action and the time at which BN starts to act. After repeated application of liposomes, the pO₂ baseline increased and the response of the skin tissue was faster. Our results demonstrate that EPR oximetry is a useful method for evaluating oxygen changes after drug application and for following the time course of their action.     

A circuit mechanism for independent modulation of excitatory and inhibitory firing rates after sensory deprivation

Diverse interneuron subtypes shape sensory processing in mature cortical circuits. During development, sensory deprivation evokes powerful synaptic plasticity that alters circuitry, but how different inhibitory subtypes modulate circuit dynamics in response to this plasticity remains unclear. We investigate how deprivation-induced synaptic changes affect excitatory and inhibitory firing rates in a microcircuit model of the sensory cortex with multiple interneuron subtypes. We find that with a single interneuron subtype (parvalbumin-expressing [PV]), excitatory and inhibitory firing rates can only be comodulated—increased or decreased together. To explain the experimentally observed independent modulation, whereby one firing rate increases and the other decreases, requires strong feedback from a second interneuron subtype (somatostatin-expressing [SST]). Our model applies to the visual and somatosensory cortex, suggesting a general mechanism across sensory cortices. Therefore, we provide a mechanistic explanation for the differential role of interneuron subtypes in regulating firing rates, contributing to the already diverse roles they serve in the cortex.

Diverse interneurons serve multiple cell-type-specific functions in the cortex (1, 2). The connectivity among excitatory pyramidal neurons and different subtypes of interneurons plays a key role in establishing these functions. In mature cortical circuits, interneurons are involved in disinhibition during locomotion and learning (3, 4), response reversal during top-down modulation (3, 5–7), surround suppression (8, 9), and affect excitatory tuning (10, 11). Inhibitory synapses are plastic (12, 13) and drive plasticity in excitatory circuits (14); however, we still do not understand how the plasticity of connections among the different interneuron subtypes and excitatory neurons shapes circuit dynamics and computations.Cortical circuits are particularly sensitive to perturbations in development and young adulthood during so-called critical periods, when manipulating sensory experience can induce long-lasting changes in circuit connectivity (15–17). Depriving rodents of vision in one eye (known as monocular deprivation, or MD) causes a biphasic response in the monocular region of the primary visual cortex (V1m), driven exclusively by the contralateral eye, that first reduces and then restores excitability (18–20). The plasticity of inhibitory synapses contributes to these processes (21–25). However, it primarily pertains to fast-spiking interneurons, which most likely correspond to parvalbumin-expressing (PV) interneurons, the most abundant and best-studied interneuron subtype in the cortex (2).Previous work has found that the plasticity of recurrent connectivity, and especially the potentiation of intracortical inhibition, dominates over the depression of feedforward connectivity to explain the initial decrease of excitatory and inhibitory activity after MD (24). However, recent experiments show that the network behavior might be more complex with fast-spiking, putative PV inhibitory neurons decreasing their firing rates 1 d after MD (MD1), while excitatory neurons are delayed by an additional day (19, 26). What mechanism lies behind this independent modulation of excitatory and inhibitory firing rates remains unclear.We used a spiking recurrent network with balanced excitation and inhibition to study this process in a microcircuit model of the sensory cortex. Theoretical work has shown that the dynamics of these networks depend on the operating regime, which is determined by the strength of recurrent coupling (27–31). Strong excitatory recurrent coupling needs to be stabilized by sufficiently strong inhibition, giving rise to “inhibition-stabilized networks” (ISNs) (8, 32). A signature of inhibition stabilization is the “paradoxical effect,” which refers to the decrease of inhibitory firing rate following direct excitatory drive to inhibitory interneurons (32). Recent experiments have confirmed the paradoxical effect in cortical circuits, suggesting that they operate in the ISN regime (33, 34). This raises the important question of whether ISNs can explain the independent modulation of excitatory and inhibitory firing rates after brief MD.We found that ISNs cannot capture the independent modulation of excitatory and inhibitory firing rates after brief MD. Even in the presence of heterogeneous connectivity, recurrently driven inhibitory neurons cannot independently modulate their firing rates relative to excitatory neurons. Considering the diversity of interneuron subtypes in the sensory cortex and their role in modulating cortical dynamics, we also modeled somatostatin-expressing (SST) interneurons, the second-most-abundant subtype of interneurons in the cortex (2). Our results demonstrate that the addition of SST interneurons inverts the firing-rate response of PV interneurons relative to excitatory neurons in response to MD-induced plasticity by reversing the paradoxical effect. In contrast to previous work that focused on the paradoxical effect in response to externally injected currents (6, 35, 36), we find that recurrent interactions are the main drivers, specifically, the strength of the feedback from SST interneurons to PV interneurons and excitatory neurons. Importantly, we implement synaptic changes observed experimentally both along the feedforward [from the thalamus (24, 37)] and recurrent [within the cortex (21, 23, 38)] pathways that significantly expand the possibilities for modulating cortical firing rates beyond external drive to the inhibitory population. Hence, our results explain the independent modulation of excitatory and inhibitory firing rates, consistent with their sequential suppression during early MD with inhibitory preceding excitatory firing rates (19, 20). We also applied our model to whisker deprivation (WD) in the somatosensory cortex, which affects interneuron intrinsic excitability rather than synaptic strength onto interneurons (39). Our model predicts similar modulations of the firing rates when changing the intrinsic excitability, suggesting that similar principles might be at work in different sensory cortices. Therefore, our work provides a mechanistic explanation for the experimentally observed temporally offset modulation of excitatory and inhibitory activity after sensory deprivation. It also establishes a more general framework to study how the interaction of three factors—cortical operating regime, interneuron diversity, and plasticity in feedforward and recurrent pathways—shapes circuit dynamics and computations.     

Ammonium accumulation and chemokine decrease in culture media of Gcdh−/− 3D reaggregated brain cell cultures

Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain.We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh^?/? mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys).Significant amounts of GA and 3-OHGA were detected in Gcdh^?/? aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh^?/? aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh^?/? aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh^?/? aggregates at DIV 14 and after exposure to Lys at DIV 8.This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh^?/? brain cells. We described for the first time a decrease of chemokines in Gcdh^?/? culture media which might contribute to brain cell injury in GA-I.     

Effect of calcium ions on the gelling and drug release characteristics of xanthan matrix tablets

Xanthan is a well-known biopolymer. It is an anionic polysaccharide, whose primary structure depends on the bacterial strain and fermentation conditions. Xanthan was extensively studied in combination with galactomannans, and over 90 patents cover the technology of this preparation. Our aim was to investigate the relation between the physical properties of a xanthan matrix in the absence or presence of calcium ions and its influence on the release of pentoxifylline. The release of pentoxifylline from xanthan tablets in purified water was shown to be very slow and governed by the process of polymer relaxation. The presence of calcium ions significantly increased the drug release, changing the release mechanism into a more diffusion controlled one. Xanthan matrices showed substantially faster and more extensive swelling in water than in the presence of Ca2+ ions. Surprisingly, negative correlation between drug release and degree of swelling was obtained for xanthan: the higher the swelling, the slower the drug release. Higher ionic strength led to lower erosion of xanthan tablets, and the gel layers formed were more rigid and of firmer texture, as shown by rheological experiments and textural profiling. The results indicate that the presence of Ca2+ ions in the solution or in matrices does not cause crosslinking of xanthan polymers, but causes charge screening of ionized groups on the trisaccharide side chains of xanthan, leading to lower inter-molecular repulsion and changing water arrangement. The understanding of the parameters influencing drug release leads to the conclusion that xanthan is suitable for controlled release formulations, especially with the incorporation of certain small counterions.     

The control of biofilm formation by hydrodynamics of purified water in industrial distribution system

Systems for storage and distribution of purified water at ambient temperature are highly susceptible to microbial contamination. The water flow, microbial content and chemical quality of the purified water in an industrial water system have been simulated in a biofilm annular reactor (BAR) to study the impact of different hydrodynamic conditions on biofilm development. Our results reveal the potential of stagnant purified water at total organic compounds (TOC) below 50ppb to develop biofilm that allows detachment of planktonic bacteria and colonization of new surfaces within 24h. However, under constant water flow over 7 days, the growth of initial biofilm was 40 times less, fewer bacteria were detached, and new surfaces were colonized to a lesser extent. Heterotrophic plate counts (HPCs) in biofilm were highly positively correlated with numbers of detached planktonic bacteria in effluent water. The study shows that the hydrodynamic conditions and level of planktonic HPC in water are critical for the development of biofilm at very low TOC. The results in the BAR agreed well with those from regular industrial microbial monitoring of purified water. To conclude, the BAR successfully simulates biofilm growth and can be used to establish an effective biofilm control strategy. However, the microbial quality of purified water in industrial system is a constant challenge; any increase of HPC in effluent water is a sign to take steps against excessive microbial growth.     

Inactivation of harmful tumour-associated proteolysis by nanoparticulate system

The primary aim in cancer therapy is to deliver anti-cancer drugs to their specific molecular targets in the tumour. Here we present a system composed of poly(d,l-lactide-co-glycolide) nanoparticles, cytokeratin specific monoclonal antibody and cystatin, a potent protease inhibitor, that can neutralize the excessive proteolytic activity associated with the invasive and metastatic potential of breast tumour cells. The antibody provides specific targeting of the delivery system to invasive breast epithelial cells and, additionally, prevents the generation of plasmin, a central extracellular protease involved in malignant progression. Polymeric nanoparticles rapidly enter the targeted cells and release the inhibitor cargo within the endosomes/lysosomes. The inhibitor is capable to inactivate lysosomal cysteine proteases, in particular cathepsin B, which is involved in the degradation of extracellular matrix inside the tumour cells. Our approach, which combines nanoparticulate delivery system with the inhibitory potential against extracellular and intracellular proteases, may improve the efficacy of therapy in patients with breast tumours compared to the application of individual protease inhibitors.     

Left Ventricular Longitudinal Strain in Characterization and Outcome Assessment of Mixed Aortic Valve Disease Phenotypes

ObjectivesThe aims of this study were to characterize the interplay between mixed aortic valve disease (MAVD) phenotypes (defined by concomitant severities of aortic stenosis and aortic regurgitation) and left ventricular global longitudinal strain (LV-GLS), and to assess the prognostic utility of LV-GLS in MAVD.BackgroundLittle is known about the way LV-GLS separates MAVD phenotypes and if it is associated with their outcomes.MethodsThis observational cohort study evaluated 783 consecutive adult patients with left ventricular ejection fraction ≥50% and MAVD, which was defined as coexisting with at least moderate aortic stenosis and at least moderate aortic regurgitation. We measured the conventional echocardiographic variables and average LV-GLS from apical long, 2- and 4-chamber views. The primary endpoint was all-cause mortality.ResultsMean age of patients was 69 ± 15 years, and 58% were male. Mean LV-GLS was –14.7 ± 2.9%. In total, 458 patients (59%) underwent aortic valve replacement at a median period of 50 days (25th to 75th percentile range: 6 to 560 days). During a median follow-up period of 5.6 years (25th to 75th percentile range: 1.8 to 9.4 years), 391 patients (50%) died. When stratified patients into tertiles according to LV-GLS values, patients with worse LV-GLS had worse outcomes (p < 0.001). LV-GLS was independently associated with mortality (hazard ratio: 1.09; 95% confidential intervals: 1.04 to 1.14; p < 0.001), with the relationship between LV-GLS and mortality being linear.ConclusionsLV-GLS is associated with all-cause mortality. LV-GLS may be useful for risk stratification in patients with MAVD.     

Implementation of a palliative care team in an Austrian university hospital

Implementation of hospital-based palliative care team is a new subject in German-speaking areas, especially in university hospitals. Our Section of Palliative Care was subsequently built up to a 12-bed palliative care unit, a home-based, and a hospital-based palliative care team. Analysis of the implementation strategies, development of the working profile, and documentation of the hospital-based palliative care team were done. During the first 2 years, quality and number of inquiries for palliative care increased significantly. In our opinion, a high degree of expertise, involvement of the nursing staff, and personal contact play a key role for a successful implementation of a palliative care team in a large university hospital.