Left ventricular assist device implantation in a patient with congenitally corrected transposition of the great arteries

Congenitally corrected transposition of the great arteries (ccTGA) is a rare anomaly characterized by atrioventricular and ventriculo-arterial discordance and several other malformations that eventually lead to heart failure. We describe the case of a 53-year-old woman with ccTGA and aortic insufficiency who was a candidate for heart transplantation due to end-stage congestive heart failure. Her condition deteriorated before a suitable donor heart could be found; therefore, we placed a left ventricular assist device in the right (systemic) ventricle. Concomitantly, we removed the aortic (systemic) valve, closed the aortic annulus with a bovine pericardial patch, and repaired the mitral valve. The patient recovered uneventfully and was discharged from the hospital 2 months postoperatively. She underwent cardiac transplantation approximately 6 months later and continued to do well after 18 months.     

NMAP: UK's nursing Internet gateway

This article describes the development of NMAP, the UK academic gateway to high-quality Internet resources for Nurses, Midwives and Allied health Professionals. The service is described and the rationale for NMAP summarized, focusing on the increasing use of Internet resources in nursing education and practice. International concerns over the quality of health information available on the Internet are considered, and the approach adopted by NMAP to quality filtering described. The usage data and results of evaluation studies show the need for this type of Internet gateway, and some of the lessons may be relevant to others involved in developing national high-quality Internet gateways for nurses.     

Decrease in infections with the introduction of mupirocin cream at the peritoneal dialysis catheter exit site

Staphylococcus aureus associated peritonitis and catheter exit site infections (ESI) are an important cause of hospitalization and catheter loss in the patients undergoing chronic peritoneal dialysis (PD). We aimed to determine the potential effectiveness of the application of mupirocin cream at the catheter exit site in preventing exit site infection and peritonitis. METHODS: This prospective historically controlled study was done in a total of 86 patients who entered our PD program from April 1999 to January 2001. They were instructed to apply Mupirocin cream 2% to the exit site daily or on alternate days. The patients were not screened to determine whether they were staphylococcus aureus carriers. One hundred and thirteen patients on PD prior to April 1999 acted as historical controls. Both groups were followed prospectively for a period of 22 months. RESULTS: In the study group application of mupirocin lead to a significant reduction in the incidence rate of both exit site infections overall (0.43 vs. 0.09; p<0.0001) and ESI due staphylococcus aureus (0.14 vs. 0.02; p=0.004) amounting to a relative reduction of 79% and 85% respectively. Although the overall incidence of peritonitis did not change (0.28 vs. 0.26; p=0.7) there was a significant reduction in peritonitis caused by staphylococcus aureus (0.07 vs. 0; p=0.01) Although only one catheter required removal in the mupirocin group as against 5 in the control group, this was not statistically significant. CONCLUSIONS: Mupirocin application at the exit site significantly lowers the incidence of ESI and peritonitis caused by staphylococcus aureus without any significant side effects.     

Differential agonist sensitivity of glycine receptor alpha2 subunit splice variants

1. The glycine receptor (GlyR) alpha2A and alpha2B splice variants differ by a dual, adjacent amino acid substitution from alpha2A(V58,T59) to alpha2B(I58,A59) in the N-terminal extracellular domain. 2. Comparing the effects of the GlyR agonists, glycine, beta-alanine and taurine, on the GlyR alpha2 isoforms, revealed a significant increase in potency for all three agonists at the alpha2B variant. 3. The sensitivities of the splice variants to the competitive antagonist, strychnine, and to the biphasic modulator Zn(2+), were comparable. In contrast, the allosteric inhibitor picrotoxin was more potent on GlyR alpha2A compared to GlyR alpha2B receptors. 4. Coexpression of alpha2A or alpha2B subunits with the GlyR beta subunit revealed that the higher agonist potencies observed with the alpha2B homomer were retained for the alpha2Bbeta heteromer. 5. The identical sensitivity to strychnine combined with a reduction in the maximum current induced by the partial agonist taurine at the GlyR alpha2A homomer, suggested that the changed sensitivity to agonists is in accordance with a modulation of agonist efficacy rather than agonist affinity. 6. An effect on agonist efficacy was also supported by using a structural model of the GlyR, localising the region of splice variation to the proposed docking region between GlyR loop 2 and the TM2-3 loop, an area associated with channel activation. 7. The existence of a spasmodic mouse phenotype linked to a GlyR alpha1(A52S) mutation, the equivalent position to the source of the alpha2 splice variation, raises the possibility that the GlyR alpha2 splice variants may be responsible for distinct roles in neuronal function.     

Interpretation and optimization of the dissolution specifications for a modified release product with an in vivo-in vitro correlation (IVIVC)

This article considers the in vivo significance attached to in vitro dissolution testing. Almost invariably, the in vitro dissolution test is interpreted in terms of bioequivalence. The literature that describes methods for setting in vitro dissolution specifications is reviewed. The most common interpretation of these specifications is a deterministic one, that is, those batches passing the dissolution specifications would be bioequivalent with the reference if tested in vivo and those failing the dissolution specifications would not be bioequivalent if tested in vivo. Due to random variation, the deterministic interpretation is not appropriate. Instead, we need to consider the conditional probability that a batch that has passed the in vitro dissolution test would demonstrate bioequivalence if tested in vivo, and that a batch known to have failed the in vitro dissolution test would demonstrate bioinequivalence if tested in vivo. One way to estimate these probabilities is by means of a simulated experiment in which the production and testing (in vivo and in vitro) of a large number of batches is computer simulated. Such a simulation can only be performed if the relationship between the in vitro dissolution characteristics and the in vivo performance of the product has been modeled. These models are generally referred to as in vivo-in vitro correlations (IVIVC). The results of one such experiment are described. The above-mentioned conditional probabilities are shown to depend on the choice of dissolution specifications. This result leads to the notion of optimal dissolution specifications. However, both of the conditional probabilities cannot be maximized simultaneously. The probability of making a correct decision on the basis of the in vitro dissolution test is introduced as a possible optimality criterion. This probability is a linear combination of the two conditional probabilities of interest. Using this criterion, the optimal dissolution specifications can be found by searching over the multidimensional space defined by the half width of each interval used in the specifications to find the combination that maximizes this probability. This process is demonstrated using the Nelder-Mead search routine. The choice of dissolution specifications has profound implications for the routine production of the product because if the specifications were very narrow the probability of a batch passing would be low, resulting in a low hit rate. The same computer program used to perform the simulation experiment can be used to estimate the hit rate. Furthermore, it can be used to explore the magnitude of changes required in the parameters describing the test product (particularly variability) to increase a low hit rate to an acceptable level.     

TRPV1 and CB(1) receptor-mediated effects of the endovanilloid/endocannabinoid N-arachidonoyl-dopamine on primary afferent fibre and spinal cord neuronal responses in the rat

N-arachidonoyl-dopamine (NADA) is an endogenous ligand at TRPV1 and CB(1) receptors, which are expressed on primary afferent nociceptors. The aim of this study was to determine contributions of proposed pronociceptive TRPV1 and antinociceptive CB(1) receptors to effects of peripheral NADA on primary afferent fibre function. Effects of NADA on primary afferent nociceptor function, determined by whole cell patch clamp and calcium imaging studies of adult dorsal root ganglion (DRG) neurons, were determined. Application of NADA (1 microm) to DRG neurons depolarized the resting membrane potential (Vm) from -58 +/- 1 to -44 +/- 3 mV (P < 0.00001) and evoked a significant increase (P < 0.0001) in intracellular calcium (74 +/- 11% of response to 60 mm KCl), compared to basal. The TRPV1 receptor antagonist capsazepine abolished NADA-evoked depolarization of Vm (P < 0.0001) and NADA-evoked calcium responses (P < 0.001), which were also blocked by the CB(1) receptor antagonist SR141716A (P < 0.001). Effects of NADA (1.5 microg and 5 microg/50 microL) on mechanically evoked responses of dorsal horn neurons in anaesthetized Sprague-Dawley rats were studied. Intraplantar injection of the higher dose of NADA (5 microg/50 microL) studied significantly inhibited innocuous (8, 10 g) mechanically evoked responses of dorsal horn neurons compared to vehicle, effects blocked by intraplantar injection of SR141716A. Higher weight (26-100 g) noxious-evoked responses of dorsal horn neurons were also significantly inhibited by NADA (5 microg/50 microL), effects blocked by intraplantar injection of the TRPV1 antagonist, iodo-resiniferatoxin. NADA has a complex pattern of effects on DRG neurons and primary afferent fibres, which is likely to reflect its dual site of action at TRPV1 and CB(1) receptors and the differential expression of these receptors by primary afferent fibres.     

Development of low-affinity, membrane-targeted Ca2+ sensors suitable for measuring presynaptic Ca2+

1. Our aim is to measure near-membrane Ca(2+) flux within the presynaptic terminals of central neurons by modifying new genetically encoded Ca(2+) sensors to develop tools capable of measuring localized Ca(2+) signals. 2. We used standard recombinant DNA technologies to generate the DNA coding for a fusion construct of a modified fluorescent 'pericam' Ca(2+) biosensor with a presynaptic P2X7 receptor (P2X7R). The Ca(2+) sensitivity of the biosensor was modified by rational site-directed mutagenesis of the calmodulin portion of the pericam. 3. Biosensor-receptor fusions were transfected into expression systems for evaluation. Expression studies in HEK-293 cells showed that biosensor-receptor fusion construct-delivered protein was localized exclusively to the plasma membrane, confirming that fusion did not affect the ability of the receptor to undergo normal protein synthesis and trafficking. 4. The Ca(2+)-dependent fluorescence of the pericam portion of the fusion protein was also retained. Site-direct mutagenesis within the calmodulin moiety of the pericam significantly reduced the Ca(2+) affinity of the complex. The dynamic range of the sensor following this modification is better matched to the higher Ca(2+) levels expected within presynaptic Ca(2+) microdomains.     

In situ evaluation of drug-loaded microspheres on a mucosal surface under dynamic test conditions

The ability of polymeric microspheres fabricated from Carbopol, polycarbophil, chitosan or Gantrez to retain a model hydrophilic drug (sodium fluorescein) was evaluated in situ, using a dynamic test system and image analysis. This technique used oesophageal tissues and simulated the physiological conditions within the oral cavity in terms of temperature, humidity and saliva flow. The point of sample application was observed over a 2h period by means of a digital camera. No significant differences in fluorescein colour intensity was obtained for the Gantrez and chitosan particles over 100min, indicate that these two polymers provide the possibility of prolonged action. Carbopol and polycarbophil particles became rapidly swollen and released the sodium fluorescein completely within 20min. It was concluded that the test system allowed the evaluation of the in situ behaviour of test particles, in terms of their ability to retain a water-soluble, coloured marker in 'dynamic' test conditions, and that chitosan and Gantrez were promising candidates for the production of mucoadhesive, sustained-release microspheres for water-soluble materials.     

Identification and characterisation of SB-366791, a potent and selective vanilloid receptor (VR1/TRPV1) antagonist

Vanilloid receptor-1 (TRPV1) is a non-selective cation channel, predominantly expressed by peripheral sensory neurones, which is known to play a key role in the detection of noxious painful stimuli, such as capsaicin, acid and heat. To date, a number of antagonists have been used to study the physiological role of TRPV1; however, antagonists such as capsazepine are somewhat compromised by non-selective actions at other receptors and apparent modality-specific properties. SB-366791 is a novel, potent, and selective, cinnamide TRPV1 antagonist isolated via high-throughput screening of a large chemical library. In a FLIPR-based Ca(2+)-assay, SB-366791 produced a concentration-dependent inhibition of the response to capsaicin with an apparent pK(b) of 7.74 +/- 0.08. Schild analysis indicated a competitive mechanism of action with a pA2 of 7.71. In electrophysiological experiments, SB-366791 was demonstrated to be an effective antagonist of hTRPV1 when activated by different modalities, such as capsaicin, acid or noxious heat (50 degrees C). Unlike capsazepine, SB-366791 was also an effective antagonist vs. the acid-mediated activation of rTRPV1. With the aim of defining a useful tool compound, we also profiled SB-366791 in a wide range of selectivity assays. SB-366791 had a good selectivity profile exhibiting little or no effect in a panel of 47 binding assays (containing a wide range of G-protein-coupled receptors and ion channels) and a number of electrophysiological assays including hippocampal synaptic transmission and action potential firing of locus coeruleus or dorsal raphe neurones. Furthermore, unlike capsazepine, SB-366791 had no effect on either the hyperpolarisation-activated current (I(h)) or Voltage-gated Ca(2+)-channels (VGCC) in cultured rodent sensory neurones. In summary, SB-366791 is a new TRPV1 antagonist with high potency and an improved selectivity profile with respect to other commonly used TRPV1 antagonists. SB-366791 may therefore prove to be a useful tool to further study the biology of TRPV1.