Assessment of novel electrophysiology simulator-a survey study

BACKGROUND

Invasive electrophysiology (EP) training requires intellectual skills related to the interpretation of intracardiac electrograms. The classic approach to the education of young electrophysiologists focused solely on theoretical knowledge and overseen procedures in patients as no real-life-like simulation of EP studies was available.

OBJECTIVE

The purpose of this study was to assess a novel tool for EP training based on fully interactive, online simulator providing real clinical experience to the users.

METHODS

EP simulator users access a system with simulated electrocardiogram, mimicking signals recorded by a catheter. Assessment of EP simulator by 40 electrophysiologists from 16 countries was collected via online questionnaire.

RESULTS

The realism of ECG signals was described as excellent or very good by 90% of responders, of intracardial signals by 82.5%. Realism of signal interactions and user experience was judged as excellent or very good by 75% and 70% accordingly. One hundred percent of users agree definitely or mostly that EP Simulator helps to translate theoretical into practical knowledge. Of responders, 97.5% would include it in EP training programs as it is extremely or very useful for training purposes in the opinion of 87.5%. Of responders, 72.5% think that training on EP simulator can potentially reduce the rate of complications. In 87.5%, the overall experience was completely or mostly satisfying and would be recommended by 100% of responders.

CONCLUSION

EP simulator is a feasible tool for training of young electrophysiologist, and it may be potentially included in the cardiologist curriculum. We should particularly emphasize the positive respondents' assessment of EP simulator overall realism.

Simulation-Based Estimation of the Number of Cameras Required for 3D Reconstruction in a Narrow-Baseline Multi-Camera Setup

Graphical visualization systems are a common clinical tool for displaying digital images and three-dimensional volumetric data. These systems provide a broad spectrum of information to support physicians in their clinical routine. For example, the field of radiology enjoys unrestricted options for interaction with the data, since information is pre-recorded and available entirely in digital form. However, some fields, such as microsurgery, do not benefit from this yet. Microscopes, endoscopes, and laparoscopes show the surgical site as it is. To allow free data manipulation and information fusion, 3D digitization of surgical sites is required. We aimed to find the number of cameras needed to add this functionality to surgical microscopes. For this, we performed in silico simulations of the 3D reconstruction of representative models of microsurgical sites with different numbers of cameras in narrow-baseline setups. Our results show that eight independent camera views are preferable, while at least four are necessary for a digital surgical site. In most cases, eight cameras allow the reconstruction of over 99% of the visible part. With four cameras, still over 95% can be achieved. This answers one of the key questions for the development of a prototype microscope. In future, such a system can provide functionality which is unattainable today.

MATLAB Simulation Environment for Estimating the Minimal Number and Positions of Cameras for 3D Surface Reconstruction in a Fully-Digital Surgical Microscope

Contemporary surgical microscope systems have excellent optical properties but some desirable features remain unavailable. The number of co-observers is currently restricted, by spatial and optical limitations, to only two. Moreover, ergonomics poses are a problem: Current microscope systems impede free movement and sometimes demand that surgeons take uncomfortable postures over long periods of time. To rectify these issues, some companies developed surgical microscope systems based on a streaming approach. These systems remove some of the limitations. Multi-observer positions, for example, are not independent from each other, for example. In order to overcome the aforementioned limitations, we are currently developing an approach for the next generation of surgical microscope: Namely the fully digital surgical microscope, where the current observation system is replaced with a camera array, allowing real-time 3D reconstruction of surgical scenes and, consequently, the rendering of almost unlimited views for multiple observers. These digital microscopes could make the perspective through the microscope unnecessary allowing the surgeon to move freely and work in more comfortable postures. The requirements on the camera array in such a system have to be determined. For this purpose, we propose of estimation the minimal number of cameras and their positions needed for the 3D reconstruction of microsurgical scenes. The method of estimation is based on the requirements for the 3D reconstruction. Within the MATLAB simulation environment, we have developed a 3D model of a microsurgical scene, used for the determination of the number of required cameras. In a next step a small, compact and costefficient system with few opto-mechanical components could be manufactured.

Evaluation of the biological differences of canine and human factor VIII in gene delivery: implications in human hemophilia treatment

The canine is the most important large animal model for testing novel hemophilia A (HA) treatment. It is often necessary to use canine factor VIII (cFIII) gene or protein for the evaluation of HA treatment in the canine model. However, different biological properties between cFVIII and human FVIII (hFVIII) indicated that the development of novel HA treatment may require careful characterization of non-human FVIII. To investigate whether the data obtained using cFVIII can translate to HA treatment in human, we analyzed the differential biological properties of canine heavy chain (cHC) and light chain (cLC) by comparing with human heavy chain (hHC) and light chain (hLC). The secretion of cHC was 5-30-fold higher than hHC, with or without light chains (LCs). cHC+hLC group exhibited ~18-fold increase in coagulation activity compared with hHC+hLC delivery by recombinant adeno-associated viral vectors. Unlike hHC, the secretion of cHC was independent of LCs. cLC improves the specific activity of FVIII by two- to threefold compared with hLC. Moreover, the cLC, but not cHC, contributes to the higher stability of cFVIII. Our results suggested that the cFVIII expression results in the canine model should be interpreted with caution as the cHC secreted more efficiently than hHC and cLC exhibited a more active and stable phenotype than hLC.

The Effects of List Difficulty and Modality of Presentation on a Computerized Version of the Paced Serial Addition Test (PSAT)

The Paced Serial Addition Test (PSAT) presents a series of digits at different speeds with the requirement that the two most recent numbers be added together. Although the PSAT is a relatively difficult test, its level of difficulty may be decreased by changing the number list to make the answers simpler and by presenting the digits visually rather than aurally. In view of this, the present experiment varied both task difficulty (easy vs. hard) and mode of presentation (visual vs. auditory). Task difficulty was manipulated by using two different lists composed of single digits whose answers ranged between 2 and 10 (easy) or 2 and 18 (hard). All stimuli were presented by computer which permitted measurement of response latencies, as well as correctness of responding. The results showed that mode of presentation, but not task difficulty, produced highly significant effects. Additional evidence showed that the ability to compute answers to simple addition problems must be considered as a modulator variable. However, an individual's basic arithmetic ability is not as critical as the modality in which a stimulus is presented. The lower performance associated with the auditory version (i.e., PASAT) was interpreted as an interference effect caused by both the stimulus and the response occurring in a single auditory information processing channel. This interpretation suggests that the PASAT's well documented sensitivity to traumatic brain injury (TBI) may be due, at least in part, to an increased susceptibility to interference effects rather than attributable solely to a decreased rate of information processing.

Randomized, controlled trial of telcagepant for the acute treatment of migraine

BACKGROUND

The neuropeptide calcitonin gene-related peptide (CGRP) plays a key role in migraine pathophysiology. In this large phase 3 clinical trial, we sought to confirm the efficacy of telcagepant, the first orally bioavailable CGRP receptor antagonist.

METHODS

Adults with migraine with or without aura (International Headache Society criteria) treated a moderate or severe attack with oral telcagepant 50 mg (n = 177), 150 mg (n = 381), 300 mg (n = 371), or placebo (n = 365) in a randomized, double-blind trial. The 5 co-primary endpoints were pain freedom, pain relief, and absence of photophobia, absence of phonophobia, and absence of nausea, all at 2 hours postdose. The key secondary endpoint was 2-24 hour sustained pain freedom. The prespecified primary efficacy analyses evaluated the 150 mg and 300 mg groups; the 50-mg group was included on an exploratory basis to further characterize the dose response but was not prespecified for analysis. Tolerability was assessed by adverse experience reports.

RESULTS

Telcagepant 300 mg was more effective (p <or= 0.001) than placebo on all primary endpoints and the key secondary endpoint, as was telcagepant 150 mg (p <or= 0.05). Telcagepant 300 mg showed a slight numeric advantage over telcagepant 150 mg on most measures. Telcagepant 50 mg values were numerically intermediate between placebo and telcagepant 150 mg and 300 mg. The percentages of patients with adverse experiences were 32.2% for telcagepant 50 mg, 32.0% for telcagepant 150 mg, 36.2% for telcagepant 300 mg, and 32.2% for placebo.

CONCLUSIONS

This study confirmed previous findings that telcagepant 300 mg was effective at relieving pain and other migraine symptoms at 2 hours and providing sustained pain freedom up to 24 hours. In this study, telcagepant 150 mg was also effective. Telcagepant was generally well tolerated.

Dependence of low-frequency sonophoresis on ultrasound parameters; distance of the horn and intensity

Sonophoresis at a frequency of 20 kHz has been shown to enhance transdermal drug delivery, a phenomenon referred to as low-frequency sonophoresis. This study provides an investigation of the dependence of low-frequency sonophoresis on various ultrasound parameters, including the distance of the horn from the skin, intensity, and frequency. We performed in vitro experiments with full thickness pig skin to measure enhancements of skin conductivity and drug permeability. Ultrasound was applied to pretreat the skin using a sonicator operating at a frequency of either 20 or 40 kHz. We also measured pitting of aluminum foil to measure cavitation, which is the principal mechanism of low-frequency sonophoresis. The skin conductivity enhancement was found to be inversely proportional to the distance of the horn from the skin. As the intensity increased, skin conductivity enhancement also increased up to a certain threshold, and then dropped off. The intensities (I(max)) at which maximum enhancement occur are about 14 W/cm2 for 20 kHz and 17 W/cm2 for 40 kHz. These findings may be useful in optimizing low-frequency sonophoresis. Overall, the dependence of transport on ultrasound parameters is similar to that of aluminum foil pitting. These results support the role of cavitation in low-frequency sonophoresis.

Transdermal delivery of heparin and low-molecular weight heparin using low-frequency ultrasound

PURPOSE. Heparin and low-molecular weight heparin (LMWH) are the most commonly used anticoagulants and are administered by intravenous or subcutaneous injections. However, injections of heparin have the potential risk of bleeding complications and the requirement of close monitoring in some cases. We hypothesized that transdermal delivery of heparin may provide an attractive alternative to injections. However, the dose of transdermally delivered heparin is limited by low skin permeability.

METHODS

We increased skin permeability to heparin and LMWH using low-frequency (20 kHz) ultrasound. Biologic activity of transdermally delivered heparin was measured by using activated clotting time assays and by using anti-Xa (aXa) activity. Structural integrity of heparin was also assessed by using gel electrophoresis.

RESULTS

Low-frequency ultrasound increased permeability of pigskin in vitro and rat skin in vivo and allowed delivery of biologically active doses of heparin and low-molecular weight heparin transdermally. A prolonged contact of transdermally delivered heparin with pigskin was found to reduce the biologic activity of heparin, although no such deactivation was observed during short exposures. Transdermally delivered LMWH resulted in sustained aXa levels in the blood. This result was in strong contrast to subcutaneous or intravenous injections of LMWH, which resulted in only temporary elevations of aXa level.

CONCLUSIONS

Transdermal delivery of low-molecular weight heparin is a potential alternative to injections.

Assessment of murine bladder permeability with fluorescein: validation with cyclophosphamide and protamine

OBJECTIVES

Bladder hyperpermeability should result in elevated blood levels of intravesically administered agents. Reabsorption from a hyperpermeable bladder should result in prolonged urinary excretion of an agent after parenteral administration. To test these hypotheses, urinary clearance and plasma levels of sodium fluorescein (NaF) were measured in mice before and during cyclophosphamide (CYP) and protamine-induced hemorrhagic cystitis.

METHODS

To measure the plasma uptake of NaF from the bladder, 10 mg/mL NaF was instilled, either by catheter or retrograde urethral infusion, 15 minutes before retro-orbital or ventricular sampling. The plasma levels were measured 24 hours and 14 days after exposure to CYP 300 mg/kg or 15 minutes after instillation of protamine 10 mg/mL. Hourly urine concentrations were measured immediately after intraperitoneal administration of 10 mg/kg NaF. Pretreatment samples were compared with those obtained 24 hours after intraperitoneal administration of 300 mg/kg CYP.

RESULTS

Urinary NaF excretion was delayed in CYP-exposed mice. A bi-exponential model provided an appropriate fit of the data, both before and after CYP administration. The plasma levels of NaF were significantly elevated at 24 hours and 14 days after CYP exposure when sampled by ventricular nick or retro-orbitally. The median concentration of fluorescein in the protamine-treated mice was significantly higher than in the control mice.

CONCLUSIONS

Fluorescein can be used to measure alterations in bladder permeability after bladder mucosal injury in mice. Urinary excretion of NaF is a bi-exponential process that is delayed after bladder mucosal injury, presumably because of increased mucosal permeability and resorption from the urine into the bloodstream.

Responsive polymeric delivery systems

This paper discusses the state of the art in a relatively new approach in the field of controlled drug delivery-responsive polymeric drug delivery systems. Such systems are capable of adjusting drug release rates in response to a physiological need. The fundamental principles of externally and self-regulated delivery systems are examined. Special attention is paid to specific clinical settings such as diabetes, presenting the advantages and disadvantages of different approaches.

Analysis of ultrasonically extracted interstitial fluid as a predictor of blood glucose levels

Transdermal extraction of clinically relevant analytes offers a potentially noninvasive method of diagnostics. However, development of such a method is limited by the low permeability of skin. In this paper, we present a potential method for noninvasive diagnostics based on ultrasonic skin permeabilization and subsequent extraction of interstitial fluid (ISF) across the skin using vacuum. ISF extracted by this method was collected and analyzed for glucose and other analytes. Glucose concentration in the extracted fluid correlates well with blood glucose concentration over a range of 50-250 mg/dl. A mathematical model describing vacuum-induced transport of ISF through ultrasonically permeabilized skin is presented as well. The model accounts for convective, as well as diffusive, transport processes across blood capillaries, epidermis, and the stratum corneum. The overall predictions of the model compare favorably with the experimental observations.

Characterization of glucose-sensitive insulin release systems in simulated in vivo conditions

We studied the glucose-responsive insulin controlled release system based on the hydrogel poly(2-hydroxyethyl methacrylate-co-N,N-dimethylaminoethyl methacrylate), also called poly(HEMA-co-DMAEMA), with entrapped glucose oxidase, catalase and insulin. When exposed to physiological fluids, glucose diffuses into the hydrogel, glucose oxidase catalyzes the glucose conversion to gluconic acid, causing swelling of the pH-sensitive hydrogel and subsequently increased insulin release. The higher the glucose concentration in the medium, the higher and faster the swelling and release rates. The effects of polymer morphology and oxygen availability on hydrogel swelling and on insulin release kinetics were tested. Polymer morphology was modified by changing the crosslinking agent (tetraethylene glycol dimethacrylate) concentration (0-0.95 vol%). Oxygen availability was modified by changing the immobilized catalase concentration (0-15 units catalase per unit glucose oxidase) and by bubbling oxygen through the medium. The results indicated that: (i) Hydrogels without crosslinking agent were found to be stable in water, and their sensitivity to pH and glucose was higher than the chemically crosslinked hydrogels. (ii) Immobilization of catalase in addition to glucose oxidase in hydrogels prepared without crosslinking agent, resulted in enhanced swelling kinetic. In addition, we carried out primary in vivo experiments on rats, which demonstrated that at least some of the entrapped insulin retains its active form and is effective in reducing blood glucose levels. Moreover, no tissue encapsulation was observed around matrices implanted in the peritoneum. In conclusion, the pH-sensitive hydrogel poly(HEMA-co-DMAEMA) can be manipulated to produce glucose-responsive insulin release system that is effective in reducing blood glucose levels.

Synergistic effect of low-frequency ultrasound and sodium lauryl sulfate on transdermal transport

Application of low-frequency ultrasound has been shown to enhance transdermal transport of drugs (low-frequency sonophoresis). In this paper, we show that the efficacy of low-frequency ultrasound in enhancing transdermal transport can be further increased by its combination with sodium lauryl sulfate (SLS), a well-known surfactant. The dependence of the ultrasound-SLS-mediated transport on ultrasound parameters, including intensity, net exposure time, and duty cycle, is discussed. The transdermal transport enhancement is proportional to ultrasound intensity as well as to exposure time, and is independent of duty cycle as long as the net exposure time is the same. The synergistic effect of SLS and ultrasound on transdermal transport increases linearly with SLS concentration. The enhancement is also proportional to the ultrasound energy density beyond a threshold value, which suggests that a certain minimum amount of energy density is required before noticeable changes in skin permeability occur. A similar dependence of the transdermal transport enhancement on energy density is observed in the case of the enhancement induced by ultrasound alone. Although the threshold energy density value in the presence of SLS is about 10 times lower than that in the case of ultrasound alone, the relationship between enhancement and energy density in the presence and in the absence of SLS is otherwise similar. Possible mechanisms for the synergistic effect of ultrasound and SLS are also discussed.

Characterization of a polymeric PLGA-injectable implant delivery system for the controlled release of proteins

Physico-chemical properties of injectable polymeric implant systems, based on the principle that a water-insoluble polymer dissolved in a biocompatible solvent will precipitate upon contact with water, were studied and utilized to predict the release of proteins from these systems. Polylactide-co-glycolide copolymer (PLGA) and glycofurol were chosen since they both have pharmaceutical precedence. Changes in polymer composition, its weight percent in solution, molecular weight, and protein loading level were assessed to provide formulations with the desired release rates and duration of release.

Low-frequency sonophoresis: a noninvasive method of drug delivery and diagnostics

Transdermal drug delivery offers an attractive alternative to injections and oral medications. However, applications of transdermal drug delivery are limited to only a few drugs as a result of low skin permeability. Application of low-frequency ultrasound enhances skin permeability, a phenomenon referred to as low-frequency sonophoresis. In this method, a short application of ultrasound is used to permeabilize skin for a prolonged period of time. During this period, ultrasonically permeabilized skin may be utilized for drug delivery. In addition, a sample of interstitial fluid or its components may be extracted through permeabilized skin for diagnostic applications. In this paper, we report our in vivo studies that demonstrate the principles of both of these concepts. Detailed studies on drug delivery are performed using inulin and mannitol as model drugs. Studies on diagnostics are performed using glucose as a model analyte. Applications of this technology to drug delivery and diagnostics are discussed.

Transdermal extraction of analytes using low-frequency ultrasound

PURPOSE

Transdermal extraction of clinically relevant analytes offers a potentially non-invasive method of diagnostics. However, development of such a method is limited by the low skin permeability. In this paper, we report a potential method for non-invasive diagnostics based on ultrasonic skin permeabilization and subsequent extraction of interstitial fluid (ISF) across the skin.

METHODS

In vivo experiments were performed using Sprague Dawley rats to assess ultrasound-induced skin permeabilization and subsequent extraction of various analytes. Serum and ISF concentrations of various analytes were measured.

RESULTS

Application of low-frequency ultrasound rapidly increased skin permeability. Skin remained in a state of high permeability for at least three hours. During this period, application of vacuum extracted ISF across rat skin in vivo at a rate of 25.7 microl/cm2/hr. We measured concentrations of various analytes including glucose, albumin, calcium, urea, triglycerides, lactate, and dextran in transdermally extracted fluid. The composition of the fluid extracted transdermally is similar to that of ISF.

CONCLUSIONS

Application of low-frequency ultrasound allows skin permeabilization and extraction of ISF across the skin.

Determination of threshold energy dose for ultrasound-induced transdermal drug transport

Low-frequency (20 kHz) ultrasound has been shown to enhance transdermal transport of drugs, a phenomenon referred to as sonophoresis. In this paper, we report the threshold energy dose for ultrasound-induced transdermal drug transport. The threshold was determined by in vitro measurements of the dependence of sonophoretic enhancement on ultrasound parameters, including intensity, duty cycle, and exposure time. While the enhancement varies linearly with ultrasound intensity and exposure times, it is independent of the duty cycle in the range of parameters studied. The enhancement is also directly proportional to the ultrasound energy density once the threshold value is crossed. For full thickness pig skin, the threshold value is about 222 J/cm(2). The overall dependence of transport enhancement on ultrasound parameters is similar to that of cavitation measured in a model system, pitting of aluminum foil. Specifically, the extent of pitting is proportional to ultrasound intensity and exposure time and is independent of duty cycle. Furthermore, the extent of pitting is also proportional to the ultrasound energy density. The similarity between the parametric dependence of transport enhancement and cavitation is consistent with previous findings that cavitation plays the dominant role in sonophoresis.

Electrical properties of glucose-sensitive hydrogels: swelling and conductivity relationships

The electrical characteristics of a glucose-sensitive polymeric hydrogel have been studied. The hydrogel matrices were prepared by radical polymerization of solutions containing 2-hydroxyethyl methacrylate, N,N-dimethyl aminoethyl methacrylate, tetraethylene glycol dimethacrylate, ethylene glycol, water, and glucose oxidase. The hydrogels displayed faster and higher swelling rates for lower levels of a crosslinking agent. Electrical conductivity was found to be a sensitive measurement of the state of the swelling. A simple model that relates hydrogel swelling and conductivity has been proposed.

Mass transport enhancement by ultrasound in non-degradable polymeric controlled release systems

In this work, an attempt was made to characterize mass transport enhancement in non-erodible polymeric matrices, caused by ultrasound. It was found that drug release rates from polymeric matrices exposed to ultrasound, can be controlled by modifying parameters like: ultrasound frequency, molecular weight of the incorporated drug and structure of the polymeric matrix (size of pores in the network). It is suggested that the enhancing effect of ultrasound on drug release from non-erodible polymers is due to the contribution of a convective term, generated by cavitation, without any destructive effect on morphology of the polymer. This phenomenon was found to be more pronounced in systems which are mass-transport limited.

In vitro analysis of bromine chemical burns with use of full-thickness human skin

Parameters of bromine injury were studied in vitro with the use of full-thickness human skin (HS) specimens--discards from various surgical procedures. The morphology of in vitro-treated HS resembled that of in vivo-injured skin. The damage was pronounced in the epidermis (destruction of the stratum corneum, and extensive vacuolation of keratinocytes) and the dermis (collagen coagulation), depending on the bromine concentration, exposure time, and application method. A decreased viability of epidermal cells, assayed by dye exclusion, was observed as well. Permeation parameters of bromine via abdominal HS were determined by quantitating bromine concentration in the donor and receiving compartments. The amount of bromine that permeated HS was inversely related to the concentration gradient applied. This in vitro study suggests that prompt treatment and early medical intervention may be required for successful healing of both severe and mild cases of bromine injuries.

Long-term protection against the effects of tumour necrosis factor by controlled delivery of the soluble p55 TNF receptor

Chronic inflammatory diseases are associated with increased soluble tumour necrosis factor (TNF) receptor concentrations in serum. To obtain such an increase, we implanted mice with ethylene vinyl-acetate or poly (lactic-co-glycolic) acid copolymers containing human soluble p55 TNF receptor. Copolymers containing rather small amounts of the receptor (about 20 micrograms) maintained prolonged increases in serum receptor concentrations. Mice implanted with these copolymers were effectively protected against lethal wasting and from arthritis resulting from chronic exposure to TNF. These findings suggest that the increased production of soluble TNF receptors in chronic inflammatory diseases counteracts deleterious effects of TNF, and suggest a therapeutic application for the natural forms of the receptors in such diseases.

A role of transforming growth factor-beta 1 in the control of corneal neovascularization

Transforming growth factor beta 1 (TGF-beta 1) has been implicated in both the stimulation of angiogenesis in vivo and in the inhibition of endothelial cell proliferation in vitro systems. In this study we present evidence showing that under certain experimental conditions TGF-beta 1 may inhibit neovascularization in vivo. TGF-beta 1 was incorporated into ethylene vinyl acetate copolymer (Elvax 40) matrixes which provide a valuable vehicle for the controlled and sustained delivery of bioactive peptides. The biological effectiveness of TGF-beta 1 sequestered in polymer matrices was assessed by measuring the inhibition of [3H]-thymidine incorporation into the DNA of cultured mink lung epithelial cells. Neovascularization was induced in both corneas of albino rabbits by one deep-seated limbal silk suture. Elvax 40 matrixes loaded with TGF-beta 1 (release rate, 1.66 ng/24 h) were implanted in rabbit corneal stroma. "Empty" polymers in the contralateral eye served as controls. Aliquots of aqueous fluid were withdrawn, and the presence activity of phagocytic cells was assessed by the production of superoxide anion (O2) which was measured by the superoxide dismutase-inhibitable reduction of ferricytochrome C. Polymer-enclosed TGF-beta 1 implanted in rabbit corneas significantly suppressed angiogenesis (2.65 +/- 0.4 mm compared to 3.05 +/- 0.3 mm in contralateral controls p < 0.05). Superoxide production in 100 microliters aliquots of aqueous fluid was 0.95 +/- 0.18 and 0.6 +/- 0.18 nmol O2/10 min in control eyes and in the eyes bearing sequestered TGF-beta 1, respectively (p < 0.02). These results indicate that under the experimental conditions selected in this study, TGF-beta 1 significantly suppressed in vivo angiogenesis.

Ultrasonically enhanced transdermal drug delivery. Experimental approaches to elucidate the mechanism

The effect of therapeutic range ultrasound on skin permeability was studied in vitro. Permeating molecule ionization state, pH, ultrasound duration, reversibility of the enhancement phenomenon, and skin structural alterations were evaluated. It was found that ultrasound affects the permeability of both ionized and unionized molecules. No irreversible structural alterations due to the ultrasound exposure were detected in the stratum corneum. Ultrasound enhancing mechanism was discussed.

Enhanced protein blotting from PhastGel media to membranes by irradiation of low-intensity ultrasound

A novel approach to protein blotting based on application of ultrasound is proposed. Three minutes of ultrasound exposure (1 MHz, 2.5 W/cm2) was sufficient for a very clear transfer of proteins from a polyacrylamide gel (PhastGel) to nitrocellulose or nylon 66 Biotrans membranes. The proteins evaluated were prestained sodium dodecyl sulfate-polyacrylamide gel electrophoresis standards (18,500-106,000 Da) and 14C-labeled Rainbow protein molecular weight markers (14,300-200,000 Da). In control experiments, which were performed following similar procedures without turning the ultrasonic generator on, no protein blotting could be seen. For comparable blotting results, 30 min for electroelution or 240 min for elution by convection blotting was required.

Interleukin 7-induced expression of specific T cell receptor gamma variable region genes in murine fetal liver cultures

We previously reported that culture of murine fetal liver (FL) cells with interleukin 7 (IL-7) results in expression of high levels of T cell receptor (TCR) gamma transcripts by a population of cells expressing Thy-1 and Pgp-1, suggesting that IL-7 promotes the growth and/or differentiation of pre-T cells. We demonstrate herein that culture of FL cells for 7 d with IL-7 caused the rearrangement and expression of TCR gamma variable (V) region genes V gamma 4 and V gamma 6, but not V gamma 5 or V gamma 7. Since this effect was not blocked by hydroxyurea, it appeared to represent induction of expression of these genes by IL-7 rather than expansion of a preexisting positive population. We also show that IL-7 induced RAG-1 and RAG-2 mRNA expression by FL cells. These data provide evidence that specific TCR gamma/delta V region genes can be rearranged and expressed by T lineage cells before their migration to the thymus, in response to IL-7.

Glucose-sensitive polymeric matrices for controlled drug delivery

Hydrogel matrices were prepared by chemical polymerization of solutions containing 2-hydroxyethyl methacrylate, N,N-dimethyl-aminoethyl methacrylate, tetraethylene glycol dimethacrylate, ethylene glycol and water solutions containing glucose oxidase, bacitracin or insulin. The hydrogels displayed faster and higher swelling and release rates at lower pH or at higher glucose concentrations. Swelling and release kinetics were also responsive to step changes in glucose concentration in the physiological range. The kinetics of the soluble and immobilized enzyme followed Michaelis Menten's kinetics. In the soluble state the enzyme was more active than the immobilized one due to mass transfer limitations, which may be overcome by preparation of microbead configuration.

Ultrasound for controlled delivery of therapeutics

Release of substances from polymeric drug delivery systems can be repeatedly modulated at will through ultrasound. Nondegradable-diffusion controlled and degradable-erosion controlled polymeric delivery systems have both been shown to have enhanced kinetics of release when exposed to ultrasonic energy. The effect of ultrasound was also evaluated on skin and synthetic membranes permeability. The main factors contributing to this effect included mixing, temperature, cavitation, acoustic streaming and polymer morphological changes. These phenomena have appealing therapeutic and commercial possibilities, as many drugs may benefit from subtle delivery pattern under temporal control to obtain optimal therapeutic effects.

Responsive polymer systems for controlled delivery of therapeutics

The ideal drug-delivery system should provide therapeutics in response to physiological requirements, having the capacity to 'sense' changes and alter the drug-release process accordingly. Such responsive controlled delivery systems are still at an experimental stage. This review focuses on two basic approaches: (1) externally regulated systems (utilizing triggers such as magnetism, ultrasound, temperature and electricity), and (2) self-regulated systems (utilizing pH-sensitive polymers, enzyme-substrate reactions, competitive binding, and antibody interactions).

Chemically-modified polysaccharides for enzymatically-controlled oral drug delivery

Starch polysaccharides were investigated as bioerodible matrices for enzymatically-controlled oral drug delivery. Corn starch was ionically cross-linked with calcium chloride. It was found that the cross-linked starch could be used for entrapment and controlled release of bioactive molecules. The release rate of large molecules was degradation-dependent due to amylase activity, which might target the release to the intestine, when the particles were taken orally. The release of small molecules such as salicylic acid, was mainly by diffusion.

Ultrasound-enhanced polymer degradation and release of incorporated substances

The effect of ultrasound on the degradation of polymers and the release rate of incorporated molecules within those polymers was examined. Up to 5-fold reversible increases in degradation rate and up to 20-fold reversible increases in release rate of incorporated molecules were observed with biodegradable polyanhydrides, polyglycolides, and polylactides. Up to 10-fold reversible increases in release rate of incorporated molecules within nonerodible ethylene/vinyl acetate copolymer were also observed. The release rate increased in proportion to the intensity of ultrasound. Temperature and mixing were relatively unimportant in effecting enhanced polymer degradation, whereas cavitation appeared to play a significant role. Increased release rates were also observed when ultrasound was applied to biodegradable polymers implanted in rats. Histological examination revealed no differences between normal rat skin and rat skin that had been exposed to ultrasonic radiation for 1 hr. With further study, ultrasound may prove useful as a way of externally regulating release rates from polymers in a variety of situations where on-demand release is required.

Effect of ultrasound on transdermal drug delivery to rats and guinea pigs

The effect of therapeutic range ultrasound (1 MHz) on skin permeation of D-mannitol, a highly polar sugar alcohol, inulin, a high molecular weight polysaccharide and physostigmine, a lipophilic anticholinesterase drug was studied in rats and guinea pigs. D-Mannitol and inulin are totally and rapidly excreted, once they have penetrated through the skin into the blood stream, permitting direct in vivo monitoring. For evaluating skin penetration of physostigmine the decrease of whole blood cholinesterase was measured. Ultrasound nearly completely eliminated the lag time usually associated with transdermal delivery of drugs. 3-5 min of ultrasound irradiation (1.5 W/cm2 continuous wave or 3 W/cm2 pulsed wave) increased the transdermal permeation of inulin and mannitol in rats by 5-20-fold within 1-2 h following ultrasound application. Ultrasound treatment also significantly increased (P less than 0.05) the inhibition of cholinesterase during the first hour after application in both physostigmine treated rats and guinea pigs: while in control guinea pigs no significant inhibition of cholinesterase could be detected during the first 2 h after application of physostigmine, the ultrasound treated group showed a 15 +/- 5% (mean +/- SEM) decrease in blood cholinesterase 1 h after ultrasound application. For physostigmine-treated rats the level of cholinesterase inhibition 1 h after ultrasound application was 53 +/- 5% in the ultrasound-treated group and 35 +/- 5% in the controls.

Treatment of an influenza A outbreak in a teaching nursing home. Effectiveness of a protocol for prevention and control

The safety and efficacy of current ACIP guidelines for the prevention and control of influenza in nursing home populations are uncertain. An outbreak of influenza A/Sichuan (H3N2) in a teaching nursing home during 1988 gave us the opportunity to evaluate the effectiveness of an influenza vaccination and amantadine prophylaxis protocol. Over 13 days, 12 of 60 residents developed influenza. Prior influenza vaccination had been given to 94% of the residents. Protection from infection occurred in those tested who had antibody levels greater than or equal to 1:16 to the A/Leningrad (H3N2) antigen contained in the standard 1987-88 trivalent vaccine. However, five of 17 vaccinated residents who were tested had antibody levels less than or equal to 1:16 at the start of the outbreak. Amantadine (less than or equal to 100 mg/day) was given to all but one resident starting on the third day of the outbreak, and to employees starting on the sixth day of the outbreaks. Seven residents developed illness after the start of amantadine, although amantadine appeared to ameliorate their symptoms. Although amantadine was generally well tolerated by residents, employees receiving amantadine identified a high incidence of side effects and only 44% of employees took at least 70% of the prescribed amantadine. In our opinion, early detection and protocol-directed intervention probably abated a more severe influenza outbreak. Therefore we support existing recommendations that formal nursing home policies be established to ensure that residents and employees receive annual influenza vaccine and that chemoprophylaxis be used when outbreaks of influenza A are suspected.

Magnetically enhanced insulin release in diabetic rats

Polymer matrices containing insulin and embedded magnets were implanted subcutaneously in diabetic rats for 51 days. Passive release of insulin from the polymer resulted in a decrease in the blood glucose level. When the diabetic rats were exposed to an oscillating magnetic field, the blood glucose levels were additionally lowered by nearly 30%. No statistically significant effect in blood glucose decrease was observed in four different sets of control animals subjected to the magnetic field. Because of the very small size of the implants, they may, with additional study, provide an alternative to current modes of therapy using programmable implantable infusion pumps.