Selective heart rate reduction with ivabradine slows ischaemia-induced electrophysiological changes and reduces ischaemia-reperfusion-induced ventricular arrhythmias.

Heart rates during ischaemia and reperfusion are possible determinants of reperfusion arrhythmias. We used ivabradine, a selective If current inhibitor, to assess the effects of heart rate reduction (HRR) during ischaemia-reperfusion on reperfusion ventricular arrhythmias and assessed potential anti-arrhythmic mechanisms by optical mapping. Five groups of rat hearts were subjected to regional ischaemia by left anterior descending artery occlusion for 8min followed by 10min of reperfusion: (1) Control n=10; (2) 1µM of ivabradine perfusion n=10; (3) 1µM of ivabradine+5Hz atrial pacing throughout ischaemia-reperfusion n=5; (4) 1µM of ivabradine+5Hz pacing only at reperfusion; (5) 100µM of ivabradine was used as a 1ml bolus upon reperfusion. For optical mapping, 10 hearts (ivabradine n=5; 5Hz pacing n=5) were subjected to global ischaemia whilst transmembrane voltage transients were recorded. Epicardial activation was mapped, and the rate of development of ischaemia-induced electrophysiological changes was assessed. HRR observed in the ivabradine group during both ischaemia (195±11bpm vs. control 272±14bpm, p<0.05) and at reperfusion (168±13bpm vs. 276±14bpm, p<0.05) was associated with reduced reperfusion ventricular fibrillation (VF) incidence (20% vs. 90%, p<0.05). Pacing throughout ischaemia-reperfusion abolished the protective effects of ivabradine (100% VF), whereas pacing at reperfusion only partially attenuated this effect (40% VF). Ivabradine, given as a bolus at reperfusion, did not significantly affect VF incidence (80% VF). Optical mapping experiments showed a delay to ischaemia-induced conduction slowing (time to 50% conduction slowing: 10.2±1.3min vs. 5.1±0.7min, p<0.05) and to loss of electrical excitability in ivabradine-perfused hearts (27.7±4.3min vs. 14.5±0.6min, p<0.05). Ivabradine administered throughout ischaemia and reperfusion reduced reperfusion VF incidence through HRR. Heart rate during ischaemia is a major determinant of reperfusion arrhythmias. Heart rate at reperfusion alone was not a determinant of reperfusion VF, as neither a bolus of ivabradine nor pacing immediately prior to reperfusion significantly altered reperfusion VF incidence. This anti-arrhythmic effect of heart rate reduction during ischaemia may reflect slower development of ischaemia-induced electrophysiological changes.

Phenotypic profiling of keloid scars using FT-IR microspectroscopy reveals a unique spectral signature.

Keloid disease (KD) is a quasineoplastic fibroproliferative tumour of unknown origin causing a progressive, recurrent dermal lesion. KD is not homogeneous in nature and shows phenotypic structural differences between its distinct peripheral margins compared to its centre. The keloid margin is often symptomatically more active with increased dermal cellularity, compared to a symptomatically dormant and hypocellular centre of lesion. The aim of this study was to delineate the morphological components of a keloid scar tissue by measuring the differences between various anatomical locations within the keloid tissue, such as the margin and the centre of the lesion compared to its surrounding normal skin using Fourier transform infrared (FT-IR) microspectroscopy. FT-IR microspectroscopy is a technique that produces spectra with detailed molecular biochemical information inherent of the chemical structure. Chemical maps were constructed on extralesional cross sections taken from six keloid scars. H&E stained sections were used to confirm diagnosis of keloid and orientate the experimental cross sections prior to FT-IR. Spectral band assignment and principal components analysis were conducted. Distinct vibrational bands (100 spectra) were observed using FT-IR spectroscopy. Partial least squares discriminant analysis, with bootstrapping (10,000 analyses), identified whether a spectrum was from the keloid or normal tissue showing an average accuracy of 84.8%, precision of 80.4%, specificity of 76.2%, and sensitivity of 92.9%. FT-IR microspectroscopy showed significant differences in spectral profiles in keloid tissue in different anatomical locations within the cross section. We believe that this proof-of-concept study may help substantiate the use of FTIR spectroscopy in keloid diagnosis and prognosis.

Quantitative analysis of methyl green using surface-enhanced resonance Raman scattering.

Surface-enhanced resonance Raman scattering (SERRS) spectra of aqueous solutions of the triphenylmethane dye methyl green have been obtained for the first time by use of citrate-reduced silver colloids and a laser excitation wavelength of 632.8 nm. Given the highly fluorescent nature of the analyte, which precluded collection of normal Raman spectra of the dye in solution and powdered state, it was highly encouraging that SERRS spectra showed no fluorescence due to quenching by the silver sol. The pH conditions for SERRS were optimised over the pH range 0.5-10 and the biggest enhancement for SERRS of this charged dye was found to be at pH 2.02, thus this condition was used for quantitative analysis. SERRS was found to be highly sensitive and enabled quantitative determination of methyl green over the range 10(-9) to 10(-7) mol dm(-3). Good fits to correlation coefficients were obtained over this range using the areas under the vibrational bands at 1615 and 737 cm(-1). Finally, a limit of detection of 83 ppb was calculated, demonstrating the sensitivity of the technique.

Surface-enhanced Raman scattering from intracellular and extracellular bacterial locations.

While surface-enhanced Raman scattering (SERS) can increase the Raman cross-section by 4-6 orders of magnitude, for SERS to be effective it is necessary for the analyte to be either chemically bonded or within close proximity to the metal surface used. Therefore most studies investigating the biochemical constituents of microorganisms have introduced an external supply of gold or silver nanoparticles. As a consequence, the study of bacteria by SERS has to date been focused almost exclusively on the extracellular analysis of the Gram-negative outer cell membrane. Bacterial cells typically measure as little as 0.5 by 1 mum, and it is difficult to introduce a nanometer sized colloidal metal particle into this tiny environment. However, dissimilatory metal-reducing bacteria, including Shewanella and Geobacter species, can reduce a wide range of high valence metal ions, often within the cell, and for Ag(I) and Au(III) this can result in the formation of colloidal zero-valent particles. Here we report, for the first time, SERS of the bacterium Geobacter sulfurreducens facilitated by colloidal gold particles precipitated within the cell. In addition, we show SERS from the same organism following reduction of ionic silver, which results in colloidal silver depositions on the cell surface.

Analysis of the conversion of indigo into indigo carmine dye using SERRS.

In a novel application SERRS has been used, by employing a silver sol, to monitor and analyse the conversion of indigo into the indigo carmine dye.