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Intracoronary administration of acetylcholine (Ach) induced QTc interval prolongation in all 14 patients with congenital long QT syndrome (LQTS) and torsade de pointes arrhythmia developed following premature ventricular beats in 5 of the patients. In the experimental models of LQT 2 and LQT 3, tridimensional repolarization mapping showed that three layers having a different electrophysiological character existed in the left ventricle; endocardial (End), midmyocardial M-cell (Mid) and epicardial layer (Epi). The refractory period estimated by the activation-recovery interval (ARI) in the Mid layer was longer than that at Epi/End layers, so marked transmural ARI dispersion was created especially between the Mid and Epi layers at the longer basic drive of 60 bpm. The marked transmural dispersion of repolarization was diminished when the pacing rate changed to 100 bpm. Different from the clinical LQTS patients, intracoronary Ach administration in the LQT models did not show any QTc interval prolongation at lower concentrations. Further, at higher concentrations (＞5μg) of Ach, the Epi layer showed greater ARI abbreviation rather than the Mid/End layers which resulted in greater transmural dispersion of repolarization, but no ventricular arrhythmia was induced.

Background: Studies in isolated tissues and myocytes show different repolarisation properties in subepicardium, midmyocardium and subendocardium. Whether these differences are present in vivo and are relevant to humans has been the subject of controversy, Our objectives were (1) to ascertain whether transmural repolarisation gradients are present in humans, (2) to determine whether the greater sensitivity of subepicardial cells to ischaemia in vitro is manifest during early ischaemia in humans in vivo, Methods and results: We studied 21 patients during routine coronary artery surgery. Unipolar activation recovery intervals (ARI) were recorded from five transmural locations between subepicardium and subendocardium in the left ventricular wall. A pacing protocol spanned a range of cycle lengths from a cycle length of 300 ms to the maximum permitted by the intrinsic atrial activity. Following the onset of cardiopulmonary bypass recordings were obtained before (control) and during a 3-min period of global ischaemia. During control transmural ARIs were homogeneous between 300 and 1500 ms (ventricular pacing) and 750 and 1500 ms (atrial spontaneous brats), During ischaemia, ARIs shortened similarly at all transmural electrode sites and transmural homogeneity was maintained, Conclusions: Transmural repolarisation differences within the ventricular wall of the human heart were absent at cycle lengths within the physiological range but also during prolonged cycles. During early (global) ischaemia repolarisation changed equally in subepicardial and subendocardial regions and transmural homogeneity of repolarisation was preserved. (C) 2001 Elsevier Science B.V. All rights reserved.

Background: Studies in isolated tissues and myocytes show different repolarisation properties in subepicardium, midmyocardium and subendocardium. Whether these differences are present in vivo and are relevant to humans has been the subject of controversy, Our objectives were (1) to ascertain whether transmural repolarisation gradients are present in humans, (2) to determine whether the greater sensitivity of subepicardial cells to ischaemia in vitro is manifest during early ischaemia in humans in vivo, Methods and results: We studied 21 patients during routine coronary artery surgery. Unipolar activation recovery intervals (ARI) were recorded from five transmural locations between subepicardium and subendocardium in the left ventricular wall. A pacing protocol spanned a range of cycle lengths from a cycle length of 300 ms to the maximum permitted by the intrinsic atrial activity. Following the onset of cardiopulmonary bypass recordings were obtained before (control) and during a 3-min period of global ischaemia. During control transmural ARIs were homogeneous between 300 and 1500 ms (ventricular pacing) and 750 and 1500 ms (atrial spontaneous brats), During ischaemia, ARIs shortened similarly at all transmural electrode sites and transmural homogeneity was maintained, Conclusions: Transmural repolarisation differences within the ventricular wall of the human heart were absent at cycle lengths within the physiological range but also during prolonged cycles. During early (global) ischaemia repolarisation changed equally in subepicardial and subendocardial regions and transmural homogeneity of repolarisation was preserved. (C) 2001 Elsevier Science B.V. All rights reserved.

Background: Studies in isolated tissues and myocytes show different repolarisation properties in subepicardium, midmyocardium and subendocardium. Whether these differences are present in vivo and are relevant to humans has been the subject of controversy, Our objectives were (1) to ascertain whether transmural repolarisation gradients are present in humans, (2) to determine whether the greater sensitivity of subepicardial cells to ischaemia in vitro is manifest during early ischaemia in humans in vivo, Methods and results: We studied 21 patients during routine coronary artery surgery. Unipolar activation recovery intervals (ARI) were recorded from five transmural locations between subepicardium and subendocardium in the left ventricular wall. A pacing protocol spanned a range of cycle lengths from a cycle length of 300 ms to the maximum permitted by the intrinsic atrial activity. Following the onset of cardiopulmonary bypass recordings were obtained before (control) and during a 3-min period of global ischaemia. During control transmural ARIs were homogeneous between 300 and 1500 ms (ventricular pacing) and 750 and 1500 ms (atrial spontaneous brats), During ischaemia, ARIs shortened similarly at all transmural electrode sites and transmural homogeneity was maintained, Conclusions: Transmural repolarisation differences within the ventricular wall of the human heart were absent at cycle lengths within the physiological range but also during prolonged cycles. During early (global) ischaemia repolarisation changed equally in subepicardial and subendocardial regions and transmural homogeneity of repolarisation was preserved. (C) 2001 Elsevier Science B.V. All rights reserved.

The active transcytosis of many different polypeptides (either presented free or adsorbed on latex nanoparticles), found in the respiratory mucosa of the upper nasal concha, has previously been shown to be proportional to the total volume of the lymphoid aggregates present in the tissue. By combining the use of fluorescent nanoparticles, flux measurements, confocal and scanning electron microscopy and conventional histology, it is shown in this paper that: (i) the areas of epithelium overlying lymphoid aggregates are the only transporting polypeptides; (ii) the respiratory epithelium in these areas consists mainly of non-ciliated microvillar cells, with numerous ciliated cells and rare mucous goblet cells at the periphery of the area only; (iii) non-ciliated microvillar cells are distinguishable in cells with well developed finger-like microvilli and cells with an irregularly pleated apical membrane, similar to that of intestinal and bronchial antigen-sampling M-cells; (iv) groups of polypeptide-coated nanospheres are found bound to this latter type of cells, demonstrating that these are the transporting cells, detected at the first stage of the transcytotic cycle.

In 1895 Willem Einthoven first described the electrocardiogram. The electrical activation of the heart and its translation into the body surface ECG was revealed by Durrer in 1970. Yet, 100 years after the first ECG, we still don't understand the repolarization of the heart, and most 'knowledge' on the T-wave and ECG interpretation therefore is empirical. Most experiments have been performed in animal models, in isolated cells, or wedge preparations. In such wedge preparations a group of midmural cells have been described in the dog, that have intrinsically longer action potentials. However, such a midmural zenith in action potential duration has not been observed in in vivo studies, not in the dog and not in the human (this thesis). Strong coupling between cells and cell layers probably abolishes intrinsic differences between the cells, if even they exist. The long QT syndrome is a hereditary disease in which repolarization is prolonged. It is characterized by a long QT interval on the ECG and the occurrence of life-threatening cardiac arrhythmias. The two most common forms of this syndrome are type 1 and 2, which are based on mutations in potassium channels. Clinical differences exist between these 2 subtypes, e.g. with regards to triggering stimuli for arrhythmic events. However, in this thesis it is shown that typical triggers for patients with the long QT syndrome type 2, startling or a loud acoustic stimulus, are only typical for a subgroup of mutation types and locations and not for the whole long QT 2 population. We show that similar differences exist within subtypes of long QT 2 for ECG parameters, response to ß-blockers, and the occurrence of arrhythmias. The long QT syndrome bore the promise, because of its monogenetic nature, to be simple disease model to increase our understanding of repolarization and related disorders. Yet the uncovering of large variations in clinical presentation not only between, but also within subtypes, complicates the picture.

In 1895 Willem Einthoven first described the electrocardiogram. The electrical activation of the heart and its translation into the body surface ECG was revealed by Durrer in 1970. Yet, 100 years after the first ECG, we still don't understand the repolarization of the heart, and most 'knowledge' on the T-wave and ECG interpretation therefore is empirical. Most experiments have been performed in animal models, in isolated cells, or wedge preparations. In such wedge preparations a group of midmural cells have been described in the dog, that have intrinsically longer action potentials. However, such a midmural zenith in action potential duration has not been observed in in vivo studies, not in the dog and not in the human (this thesis). Strong coupling between cells and cell layers probably abolishes intrinsic differences between the cells, if even they exist. The long QT syndrome is a hereditary disease in which repolarization is prolonged. It is characterized by a long QT interval on the ECG and the occurrence of life-threatening cardiac arrhythmias. The two most common forms of this syndrome are type 1 and 2, which are based on mutations in potassium channels. Clinical differences exist between these 2 subtypes, e.g. with regards to triggering stimuli for arrhythmic events. However, in this thesis it is shown that typical triggers for patients with the long QT syndrome type 2, startling or a loud acoustic stimulus, are only typical for a subgroup of mutation types and locations and not for the whole long QT 2 population. We show that similar differences exist within subtypes of long QT 2 for ECG parameters, response to ß-blockers, and the occurrence of arrhythmias. The long QT syndrome bore the promise, because of its monogenetic nature, to be simple disease model to increase our understanding of repolarization and related disorders. Yet the uncovering of large variations in clinical presentation not only between, but also within subtypes, complicates the picture.

The use of nano- and micro-particulate carriers as delivery systems for oral vaccines has been under investigation for several decades. Surprisingly little is known of their uptake in the human intestine, despite the fact that substantial improvement is required to achieve adequate immune responses in man after oral administration. In this thesis, various aspects of particle transcytosis across the human intestinal epithelium were studied, in order to identify strategies for improved uptake of nano- and micro-particulate drug delivery systems. The follicle associated epithelium (FAE) overlying Peyer´s patches contains M-cells, which have an increased capacity for uptake of particulate antigens. Therefore, a model of human FAE was developed to study mechanisms of particle uptake and transport. Receptors that could be used for targeting to the FAE had previously not been identified in humans. By use of the model FAE, two new targets were identified on human intestinal FAE; CD9 and β1-integrin. Furthermore, studies of isolated human intestinal tissue showed that an integrin-adherent peptide motif, RGD, could be utilized to achieve selective and improved transport of nanoparticles into human Peyer´s patches. Studies of factors influencing intestinal particle uptake and transcytosis revealed that two cytokines, TNF-α and LTα1/β2, but also one growth factor, TGF-β1, induced uptake of particles in Caco-2 cells and transcytosis of particles in the model FAE. Furthermore, it was shown that an enteric bacterium, Yersinia Pseudotuberculosis, could trigger uptake and transcytosis of particles across model absorptive epithelial cells. In conclusion, this thesis provides a platform for further investigations of particle transcytosis across the human intestinal epithelium. The identification of two new proteins with increased expression in human FAE and a targeting sequence that improves particle uptake into Peyer’s patches, gives new hope for the development of subunit oral vaccines.

In rabbit nasal mucosa, polypeptides and polypeptide-coated nanospheres are actively transported from lumen to blood by M-cells present in specialized transport areas of the epithelium. The largest transport is shown here to occur when some molecules of the polypeptides coating the nanospheres, after adsorption, are bound to the specific anti-polypeptide IgG, e.g. when insulin is bound to the anti-insulin IgG. The transport kinetics of nanospheres coated by insulin bound to its antibody, as a function of bead concentration or of the antibody/insulin coating ratio, have been analyzed. On this basis it was possible to assess the maximal transport capacity of the epithelium and to calculate the percentage of M-cells involved.