Cooperative Conformational Transitions Underpin the Activation Heat Capacity in the Temperature Dependence of Enzyme Catalysis.

Many enzymes display non-Arrhenius behavior with curved Arrhenius plots in the absence of denaturation. There has been significant debate about the origin of this behavior and recently the role of the activation heat capacity (ΔCP⧧) has been widely discussed. If enzyme-catalyzed reactions occur with appreciable negative values of ΔCP⧧ (arising from narrowing of the conformational space along the reaction coordinate), then curved Arrhenius plots are a consequence. To investigate these phenomena in detail, we have collected high precision temperature-rate data over a wide temperature interval for a model glycosidase enzyme MalL, and a series of mutants that change the temperature-dependence of the enzyme-catalyzed rate. We use these data to test a range of models including macromolecular rate theory (MMRT) and an equilibrium model. In addition, we have performed extensive molecular dynamics (MD) simulations to characterize the conformational landscape traversed by MalL in the enzyme-substrate complex and an enzyme-transition state complex. We have crystallized the enzyme in a transition state-like conformation in the absence of a ligand and determined an X-ray crystal structure at very high resolution (1.10 Å). We show (using simulation) that this enzyme-transition state conformation has a more restricted conformational landscape than the wildtype enzyme. We coin the term "transition state-like conformation (TLC)" to apply to this state of the enzyme. Together, these results imply a cooperative conformational transition between an enzyme-substrate conformation (ES) and a transition-state-like conformation (TLC) that precedes the chemical step. We present a two-state model as an extension of MMRT (MMRT-2S) that describes the data along with a convenient approximation with linear temperature dependence of the activation heat capacity (MMRT-1L) that can be used where fewer data points are available. Our model rationalizes disparate behavior seen for MalL and previous results for a thermophilic alcohol dehydrogenase and is consistent with a raft of data for other enzymes. Our model can be used to characterize the conformational changes required for enzyme catalysis and provides insights into the role of cooperative conformational changes in transition state stabilization that are accompanied by changes in heat capacity for the system along the reaction coordinate. TLCs are likely to be of wide importance in understanding the temperature dependence of enzyme activity and other aspects of enzyme catalysis.

An exploration of loneliness experienced by people living with mental illness and the impact on their recovery journey: An integrative review.

WHAT IS KNOWN ON THE SUBJECT?: There is evidence that social isolation and loneliness is more prevalent in people living with mental illness than in the general population. People living with mental illness frequently experience stigma, discrimination, rejection, repeated psychiatric admissions, low self-esteem, low self-efficacy, and increased symptoms of paranoia, depression, and anxiety. There is evidence of common interventions that can be used to improve loneliness and social isolation such as psychosocial skills training and cognitive group therapy. WHAT THE PAPER ADDS TO EXISTING KNOWLEDGE?: This paper offers a comprehensive assessment of the evidence between mental illness, loneliness, and recovery. The results suggest that people living with mental illness experience elevated levels of social isolation and loneliness leading to poor recovery and quality of life. Social deprivation, social integration and romantic loneliness are related to loneliness, poor recovery, and reduced quality of life. A sense of belonging, ability to trust and hope are important aspects of improved loneliness, quality of life and recovery. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: The existing culture in mental health nursing practice needs to be examined to address loneliness in people living with mental illness and its impact on recovery. Existing tools to research loneliness do not consider dimensions in loneliness experience as reflected in the literature. Practice needs to demonstrate an integrated approach to recovery, optimal service delivery and augmentation of evidence-based clinical practice to improve individual's loneliness, social circumstances, and relationships. Practice needs to demonstrate nursing knowledge in caring for people living with mental illness experiencing loneliness. Further longitudinal research is required to clearly understand the relationship between loneliness, mental illness, and recovery. ABSTRACT: INTRODUCTION: To our knowledge, there are no previous reviews on the impact of loneliness experienced by people aged 18-65, who are living with mental illness and their recovery experience. AIM/QUESTION: To explore the experience and impact of loneliness in people living with mental illness during recovery. METHOD: An integrative review. RESULTS: A total of 17 papers met the inclusion criteria. The search was conducted using four electronic databases: MEDLINE, CINAHL, Scopus and PsycINFO. Across these 17 papers, participants were most commonly, diagnosed with schizophrenia or psychotic disorders and recruited from community mental health services. DISCUSSION: The review revealed loneliness to be substantial in people living with mental illness and that loneliness affected their recovery, and their quality of life. The review identified many factors that contribute to loneliness including unemployment, financial strain, social deprivation, group housing, internalized stigma and mental illness symptoms. Individual factors such as social/community integration and social network size as well as an inability to trust, a sense of not belonging, hopelessness and lack of romance were also evident. Interventions targeting social functioning skills and social connectedness were found to improve social isolation and loneliness. IMPLICATIONS FOR PRACTICE: It is vital for mental health nursing practice to employ an approach integrating physical health as well as social recovery needs, optimal service delivery and augmentation of evidence-based clinical practice to improve loneliness, recovery, and quality of life.

Experiences, Perceptions, and Coping Patterns of Emergency Department Nurses with Occupational Stressors in Saudi Arabian Hospitals: Mixed-Method Study.

Extended working hours, a complicated workplace environment, and engagement in numerous physical and psychological stressors have been associated with the stressful nature of the nursing profession. Only a few studies have provided some insight into workplace stress and coping strategies adopted by nurses in Saudi Arabia and neighboring countries. Therefore, this study utilized a mixed-method design to explore the numerous factors that lead to stress among emergency nurses, their experience and perception of stress, and the coping mechanisms they find useful. A survey containing four domains and 86 items was adapted, pilot tested, and validated. The quantitative phase recruited 296 nurses who returned completed questionnaires, and then 21 nurses were interviewed for the qualitative phase. In total, 89.5% (n = 265) of the participants were female, 51% (n = 151) were aged 20-29 years, 83% (n = 246) were non-Saudi nationals, 49% (n = 145) were married, and 82% (n = 245) had a bachelor's degree. The most common causes of occupational stress were work overload, personnel shortages, and inadequate pay. The qualitative phase data revealed five primary themes, including increased workload, rising living costs despite equal compensation, and staff shortages as main stressors. In addition, the study found that praying and spending quality time with friends are the primary coping techniques among nurses. The study results contribute to a better understanding of nurses' working conditions in the emergency department. Additionally, they may contribute to the development of policies and practice reforms to improve Saudi nurses' well-being, health, and overall work experience.

A systems analysis of the COVID-19 pandemic response in the United Kingdom - Part 1 - The overall context.

The most common reaction to suggesting that we could learn valuable lessons from the way the current pandemic has been/ is being handled, is to discourage the attempt; as it is suggested that it can all be done more accurately and authoritatively after the inevitable Public Inquiry (Slater, 2019). On the other hand, a more constructive approach, is to capture and understand the work that was actually done.This would include normal activities, as well as positive adaptations to challenges and failures that may have occurred. Such an approach aimed at improving what worked, rather than blaming people for what went wrong, has the potential to contribute more successfully to controlling the consequences of the current crisis. Such an approach should thus be aimed at detecting and feeding back lessons from emerging and probably unexpected behaviours and helping to design the system to adapt better to counter the effects. The science and discipline of Human Factors (HF) promotes system resilience. This can be defined as an organisation's ability to adjust its functioning before, during or after significant disturbances (such as a pandemic), enabling adaptation and operation under both anticipated and unanticipated circumstances. A "functional" approach methodology enables the identification of where the system and its various interdependent functions (an activity or set of activities that are required to give a certain output), could be improved and strengthened; if not immediately, at least for the future. Along these lines, suggestions for adding key resilience functions are additionally identified and outlined. The application and insights gained from this functional approach to the 2015 MERS-Cov pandemic in South Korea has been seen as contributing substantially to the effective response to the current crisis in that country (Min, submitted for publication). In this paper, we present an overarching framework for a series of projects that are planned to carry out focussed systems-based analysis to generate learning from key aspects of the COVID-19 pandemic response in the United Kingdom.

Communicating With Parents and Preschool Children: A Qualitative Exploration of Dental Professional-Parent-Child Interactions During Paediatric Dental Consultations to Prevent Early Childhood Caries.

The aim of this study was to explore communication interactions and identify phases adopted by dental professionals with parents and their young children and to examine the hypothesis that successful social talking between the actors together with the containment of worries allows the formation of a triadic treatment alliance, which leads to achieving preventive dental treatment goals. Conversation analysis of the transcribed data from video recordings of dental professionals, parents and preschool children when attending for preventive dental care was conducted. The transcriptions were read, examined and analysed independently to ensure the trustworthiness of the analysis. The transcriptions were explored for interactive patterns and sequences of interaction. Forty-four individual consultations between dental professionals, parents, and preschool children were recorded. The number of communication behaviours was 7,299, with appointment length ranging from 2 min 10 s to 29 min 18 s. Two patterns of communication were identified as dyadic (between two people) and triadic (between three people) interactions within a continuous shifting cycle. The three phases of communication were social talking, containing worries and task-focusing. Social talking was characterised by shifts between dyadic and triadic communication interactions and a symmetry of communication turns and containing worries. This typified the cyclical nature of the triadic and dyadic communication interactions, the adoption of talk-turn pairs, and triadic treatment alliance formation. Task-focusing pattern and structure were different for dentists and extended-duty dental nurses. For dentists, task-focusing was characterised by a dyadic interaction and as an asymmetrical communication pattern: for extended-duty dental nurses, task-focusing was typified by symmetrical and asymmetrical communication patterns within dyadic and triadic interactions. Empathy and understanding of the young child's emotional needs during containing worries allowed the formation of the triadic treatment alliance and with this treatment alliance, the acceptance of interventions to prevent early childhood caries during "task-focusing." This qualitative exploration suggests that dyadic and triadic communication interactions are of a dynamic and cyclical quality and were exhibited during paediatric dental consultations. The communication phases of social talking, containing worries and task-focusing were evident. Successful social talking signalled the entry to containing worries and triadic treatment alliance formation which permitted the preventive goals of the consultation to be achieved (task-focusing). Future work should generate additional data to support the hypotheses created here namely that, social talking and containing worries triggers an integral pathway to task-focusing and the achievement of preventive dental goals.

PAK4 suppresses PDZ-RhoGEF activity to drive invadopodia maturation in melanoma cells.

Cancer cells are thought to use actin rich invadopodia to facilitate matrix degradation. Formation and maturation of invadopodia requires the co-ordained activity of Rho-GTPases, however the molecular mechanisms that underlie the invadopodia lifecycle are not fully elucidated. Previous work has suggested a formation and disassembly role for Rho family effector p-21 activated kinase 1 (PAK1) however, related family member PAK4 has not been explored. Systematic analysis of isoform specific depletion using in vitro and in vivo invasion assays revealed there are differential invadopodia-associated functions. We consolidated a role for PAK1 in the invadopodia formation phase and identified PAK4 as a novel invadopodia protein that is required for successful maturation. Furthermore, we find that PAK4 (but not PAK1) mediates invadopodia maturation likely via inhibition of PDZ-RhoGEF. Our work points to an essential role for both PAKs during melanoma invasion but provides a significant advance in our understanding of differential PAK function.

Protein-coated nanoparticles embedded in films as delivery platforms.

OBJECTIVES: This work aimed to evaluate the performance of nanoparticle-loaded films based on matrices of polymethacrylates and hydroxypropylmethylcellulose (HPMC) intended for delivery of macromolecules. METHODS: Lysozyme (Lys)-loaded nanoparticles were manufactured by antisolvent co-precipitation. After size, loading efficiency and stability characterization, the selected batch of particles was further formulated into films. Films were characterized for mechanical properties, mucoadhesion, Lys release and activity after manufacture. KEY FINDINGS: We found that protein-coated nanoparticles could be obtained in USP phosphate buffer pH 6.8. Particles obtained at pH 6.8 had a z-average of 347.2 nm, a zeta-potential of 21.9 mV and 99.2% remaining activity after manufacture. This formulation was further studied for its application in films for buccal delivery. Films loaded with nanoparticles that contained Eudragit RLPO (ERL) exhibited excellent mechanical and mucoadhesive properties. Due to its higher water-swelling and solubility compared with ERL, the use of HPMC allowed us to tailor the release of Lys from films. The formulation composed of equal amounts of ERL and HPMC revealed a sustained release over 4 h, with Lys remaining fully active at the end of the study. CONCLUSIONS: Mucoadhesive films containing protein-coated nanoparticles are promising carriers for the buccal delivery of proteins and peptides in a stable form.

Monitoring the depth of anesthesia using entropy features and an artificial neural network.

Monitoring the depth of anesthesia using an electroencephalogram (EEG) is a major ongoing challenge for anesthetists. The EEG is a recording of brain electrical activity, and it contains valuable information related to the different physiological states of the brain. This study proposes a novel automated method consisting of two steps for assessing anesthesia depth. Initially, the sample entropy and permutation entropy features were extracted from the EEG signal. Because EEG-derived parameters represent different aspects of the EEG features, it would be reasonable to use multiple parameters to assess the effect of the anesthetic. The sample entropy and permutation entropy features quantified the amount of complexity or irregularity in the EEG data and were conceptually simple, computationally efficient and artifact-resistant. Next, the extracted features were used as input for an artificial neural network, which was a data processing system based on the structure of a biological nervous system. The experimental results indicated that an overall accuracy of 88% could be obtained during sevoflurane anesthesia in 17 patients to classify the EEG data into awake, light, general and deep anesthetized states. In addition, this method yielded a classification accuracy of 92.4% to distinguish between awake and general anesthesia in an independent database of propofol and desflurane anesthesia in 129 patients. Considering the high accuracy of this method, a new EEG monitoring system could be developed to assist the anesthesiologist in estimating the depth of anesthesia in a rapid and accurate manner.

A design of experiments to optimize a new manufacturing process for high activity protein-containing submicron particles.

A novel method for the manufacture of protein/peptide-containing submicron particles was developed in an attempt to provide particles with increased activity while using high energy input technologies. The method consists of antisolvent co-precipitation from an aqueous solution containing both an amino acid core material (e.g. D,L-valine), and either bovine serum albumin (BSA) or lysozyme (Lys) as model proteins. The aqueous solution was added to the organic phase by means of a nebulizer to increase the total surface area of interaction for the precipitation process. Sonication proved to be an effective method to produce small particle sizes while maintaining high activity of Lys. The use of a polysorbate or sorbitan ester derivatives as stabilizers proved to be necessary to yield submicron particles. Particles with very high yields (approximately 100%) and very high activity after manufacture (approximately 100%) could be obtained. A particle size of 439.0 nm, with a yield of 48.8% and with final remaining activity of 98.7% was obtained. By studying various factors using a design of experiments strategy (DoE) we were able to establish the critical controlling factors for this new method of manufacture.

Investigating paradoxical hysteresis effects in the mouse neocortical slice model.

Clinically, anesthetic drugs show hysteresis in the plasma drug concentrations at induction versus emergence from anesthesia induced unconsciousness. This is assumed to be the result of pharmacokinetic lag between the plasma and brain effect-site and vice versa. However, recent mathematical and experimental studies demonstrate that anesthetic hysteresis might be due in part to lag in the brain physiology, independent of drug transport delay - so-called "neural inertia". The aim of this study was to investigate neural inertia in the reduced neocortical mouse slice model. Seizure-like event (SLE) activity was generated by exposing cortical slices to no-magnesium artificial cerebrospinal fluid (aCSF). Concentration-effect loops were generated by manipulating SLE frequency, using the general anesthetic drug etomidate and by altering the aCSF magnesium concentration. The etomidate (24 µM) concentration-effect relationship showed a clear hysteresis, consistent with the slow diffusion of etomidate into slice tissue. Manipulation of tissue excitability, using either carbachol (50 µM) or elevated potassium (5mM vs 2.5mM) did not significantly alter the size of etomidate hysteresis loops. Hysteresis in the magnesium concentration-effect relationship was evident, but only when the starting condition was magnesium-containing "normal" aCSF. The in vitro cortical slice manifests pathway-dependent "neural inertia" and may be a valuable model for future investigations into the mechanisms of neural inertia in the cerebral cortex.

Changes in frequency of seizure-like events in stimulated cortical slices.

Epilepsy affects nearly 3 million people in the United States alone. Given the fact that many people suffer from seizures that are intractable to pharmacological intervention, research groups are investigating the use of electrical stimulation to interact with and ameliorate symptoms of epileptic seizures. In mouse cortical slices made seizuregenic through chemical means, we applied precision controlled current pulses and measured local field potentials through a four point probe system to investigate the response of seizing tissue to electrical stimulation. We have determined that the frequency of the spontaneous seizure-like events may be modified by low amplitude, current controlled stimulation (0.5 microA). Differently from previously thought, this change in frequency is however not accompanied by any alteration of the tissue permittivity or conductivity during the inter-seizure interval.

The electrocortical effects of enflurane: experiment and theory.

BACKGROUND: High concentrations of enflurane will induce a characteristic electroencephalogram pattern consisting of periods of suppression alternating with large short paroxysmal epileptiform discharges (PEDs). In this study, we compared a theoretical computer model of this activity with real local field potential (LFP) data obtained from anesthetized rats. METHODS: After implantation of a high-density 8 x 8 electrode array in the visual cortex, the patterns of LFP and multiunit spike activity were recorded in rats during 0.5, 1.0, 1.5, and 2.0 minimum alveolar anesthetic concentration (MAC) enflurane anesthesia. These recordings were compared with computer simulations from a mean field model of neocortical dynamics. The neuronal effect of increasing enflurane concentration was simulated by prolonging the decay time constant of the inhibitory postsynaptic potential (IPSP). The amplitude of the excitatory postsynaptic potential (EPSP) was modulated, inverse to the neocortical firing rate. RESULTS: In the anesthetized rats, increasing enflurane concentrations consistently caused the appearance of suppression pattern (>1.5 MAC) in the LFP recordings. The mean rate of multiunit spike activity decreased from 2.54/s (0.5 MAC) to 0.19/s (2.0 MAC). At high MAC, the majority of the multiunit action potential events became synchronous with the PED. In the theoretical model, prolongation of the IPSP decay time and activity-dependent EPSP modulation resulted in output that was similar in morphology to that obtained from the experimental data. The propensity for rhythmic seizure-like activity in the model could be determined by analysis of the eigenvalues of the equations. CONCLUSION: It is possible to use a mean field theory of neocortical dynamics to replicate the PED pattern observed in LFPs in rats under enflurane anesthesia. This pattern requires a combination of a moderately increased total area under the IPSP, prolonged IPSP decay time, and also activity-dependent modulation of EPSP amplitude.

Excitatory effects of gap junction blockers on cerebral cortex seizure-like activity in rats and mice.

PURPOSE: The role of gap junctions in seizures is an area of intense research. Many groups have reported anticonvulsant effects of gap junction blockade, strengthening the case for a role for gap junctions in ictogenesis. The cerebral cortex is underrepresented in this body of research. We have investigated the effect of gap junction blockade on seizure-like activity in rat and mouse cerebral cortex slices. METHODS: Seizure-like activity was induced by perfusing with low-magnesium artificial cerebrospinal fluid. The effect of three gap junction blockers was investigated in rat cortical slices; quinine (200 and 400 microm), quinidine (100 and 200 microm), and carbenoxolone (100 and 200 microm). In addition, the effect of mefloquine was investigated in wild-type mice and connexin36 knockout mice. The data were analyzed for the effect on frequency and amplitude of seizure-like events. RESULTS: Paradoxical excitatory effects on seizure-like activity were observed for all three agents in rat cortical slices. Quinine (200 microm) and carbenoxolone (100 microm) increased both the frequency and amplitude of seizure-like events. Quinidine (100 microm) increased the frequency of events. Higher doses of quinine (400 microm) and carbenoxolone (200 microm) had biphasic excitatory-inhibitory effects. Similar excitatory effects were observed in adult wild-type mouse cortical slices perfused with mefloquine (5 microm or 10 microm), but were absent in slices from connexin36-deficient mice. DISCUSSION: In conclusion, we have shown a paradoxical proseizure effect of pharmacologic gap junction blockade in a cortical model of seizure-like activity. We suggest that this effect is probably due to a disruption of inhibitory interneuron coupling secondary to connexin36 blockade.

A pharmacoscintigraphic study of three time-delayed capsule formulations in healthy male volunteers.

Three time-delayed capsule (TDC) formulations were investigated in a pharmacoscintigraphic study, using a three-way crossover design in eight healthy male volunteers. Additionally, the pulsed release of a TDC was investigated with time-lapse photography, using a nondisintegrating riboflavin tablet. The photographic study indicated how the release characteristics of the TDC relied on the erosion of a tablet containing hypromellose (HPMC). Each TDC was duel radio labelled with indium-111 and technetium-99 m DTPA complexes, to observe drug release scintigraphically (theophylline was a marker compound). Three formulations, having in vitro dissolution release times of 1.8, 2.9 or 4.0 h were shown to compare favourably with mean in vivo scintigraphic release times of 2.7, 3.0 and 4.0 h for each formulation containing 20, 24 or 35% (w/w) HPMC concentrations respectively. An increase in HPMC concentration was associated with a delayed technetium release time, and followed the same rank order as the in vitro dissolution study. Observed radiolabel dispersion always occurred in the small intestine. In conclusion, the study established that the TDC performs and demonstrates an in vitro-in vivo correlation. Additionally, time and site of release were accurately visualized by gamma scintigraphy, and confirmed with determination of theophylline absorption.

Immobilisation of vaccines onto micro-crystals for enhanced thermal stability.

The thermal instability of many vaccines leads to the wastage of half of all supplied vaccines. In this note, we report the application of a novel technology: protein-coated micro-crystals (PCMC) to improve the thermostability of a model vaccine (diphtheria toxoid, DT). The latter was immobilised onto the surface of a crystalline material (L-glutamine) via a rapid dehydration method, resulting in the production of a fine free-flowing powder. The PCMC consisted of thin, flat crystals with an antigen loading of 3.95% (w/w). The DT-coated glutamine crystals and free DT (the controls) were incubated at different temperatures for a defined time period (4 degrees C, RT and 37 degrees C for 2 weeks and 45 degrees C for 2 days), after which the crystals were suspended in buffer and intramuscularly administered to mice. Incubation of DT (free and crystal-coated) at room temperature and at 37 degrees C for 2 weeks did not result in any change in the antibody response compared to DT that had always been stored properly (i.e. in the refrigerator). In contrast, incubation of free DT at 45 degrees C resulted in a reduced IgG response, indicating thermal instability of free DT at that temperature. The antibody response was not reduced, however, with the crystal-coated DT. These preliminary studies show that PCMC is a promising technology for the thermal stabilisation of vaccines.

Erosion characteristics of an erodible tablet incorporated in a time-delayed capsule device.

A time-delayed oral drug delivery device was investigated in which an erodible tablet (ET), sealing the mouth of an insoluble capsule, controlled the lag-time prior to drug release. The time-delayed capsule (TDC) lag-time may be altered by manipulation of the excipients used in the preparation of the ET. Erosion rates and drug release profiles from TDCs were investigated with four different excipient admixtures with lactose: calcium sulphate dihydrate (CSD), dicalcium phosphate (DCP), hydroxypropylmethyl cellulose (HPMC; Methocel K100LV grade) and silicified microcrystalline cellulose (SMCC; Prosolv 90 grade). Additionally, the compressibility of different insoluble coated capsules was tested at different moisture levels to determine their overall integrity and suitability for oral delivery. Erosion rates of CSD, DCP, and SMCC displayed a nonlinear relationship to their concentration, while HPMC indicated rapid first-order erosion followed by zero-order erosion, the onset of which was dependent on the HPMC concentration. Capsule integrity was confirmed to be most suitable for oral delivery when the insoluble ethyl cellulose coat was applied to a hard gelatin capsule using an organic spray coating process. T50% drug release times varied between 245 (+/-33.4) and 393 (+/-40.8) minutes for 8% and 20% DCP, respectively, T50% release times of 91 (+/-22.1) and 167 (+/-34.6) were observed for 8% and 20% CSD; both formulations showed incidence of premature drug release. The SMCC formulations showed high variability due to lamination effects. The HPMC formulations had T50% release times of 69 (+/-13.9), 213 (+/-25.4), and 325 (+/-30.3) minutes for 15%, 24%, and 30% HPMC concentrations respectively, with no premature drug release. In conclusion, HPMC showed the highest reproducibility for a range of time-delayed drug release from the assembled capsule formulation. The method of capsule coating was confirmed to be important by investigation of the overall capsule integrity at elevated humidity levels. The erosion characteristics of ETs containing HPMC may be described by gravimetric loss. The novel time-delayed capsule device presented in this study may be assembled to include an erodible tablet with a known concentration of HPMC. A variety of suitable drugs for targeted chronopharmaceutical therapy can be incorporated into such a device, ultimately improving drug efficacy and patient compliance, and reducing harmful side effects.

The effect of wet granulation on the erosion behaviour of an HPMC-lactose tablet, used as a rate-controlling component in a pulsatile drug delivery capsule formulation.

The purpose of this study was to investigate the variability in the performance of a pulsatile capsule delivery system induced by wet granulation of an erodible HPMC tablet, used to seal the contents within an insoluble capsule body. Erodible tablets containing HPMC and lactose were prepared by direct compression (DC) and wet granulation (WG) techniques and used to seal the model drug propranolol inside an insoluble capsule body. Dissolution testing of capsules was performed. Physical characterisation of the tablets and powder blends used to form the tablets was undertaken using a range of experimental techniques. The wet granulations were also examined using the novel technique of microwave dielectric analysis (MDA). WG tablets eroded slower and produced longer lag-times than those prepared by DC, the greatest difference was observed with low concentrations of HPMC. No anomalous physical characteristics were detected with either the tablets or powder blends. MDA indicated water-dipole relaxation times of 2.9, 5.4 and 7.7x10(-8)ms for 15, 24 and 30% HPMC concentrations, respectively, confirming that less free water was available for chain disentanglement at high concentrations. In conclusion, at low HPMC concentrations water mobility is at its greatest during the granulation process, such formulations are therefore more sensitive to processing techniques. Microwave dielectric analysis can be used to predict the degree of polymer spreading in an aqueous system, by determination of the water-dipole relaxation time.