Body surface potential mapping was performed in 60 clinical cases and an ideal 0 potential was calculated in each case at 2msec intervals, which corresponds to the potential at infinity. Maximal ...deviation of the Wilson terminal voltage the ideal potential was 0.14mv on the average. Time course of potential variations of the central terminal was in proportion to the measured surface potentials. The lead vector of Wilson terminal was determined for each case, with a method to make a minimal difference between calculate and observed Wilson terminal voltage. The lead vector was directed superiorly and posteriorly with the magnitude of 24% of that of lead I on the average.
Three sponge species (Xestospongia, Acervochalina, Plakortis spp.) from Mactan I., Philippines, were shown to release allelochemicals directly into the water. These allelochemicals were demonstrated ...to be toxic to one or more scleractinian coral species (Acropora, Pocillopora, Porites spp.) and, for one of the sponges tested, to one hydrozoan coral (Millepora sp.). The five coral species tested (including Montipora) were both numerically and spatially dominant organisms at the study site. Toxicity tests involved exposing corals brought into the laboratory to water that had been conditioned by the sponges. Responses of each coral species to each sponge allelochemical varied. The allelochemical from Acervochalina was found to be highly toxic (51-75% tissue death) to both Pocillopora and Acropora, and had only a moderate effect (26-50% tissue death) on Porites. Allelochemicals of Xestospongia and Plakortis were moderately and weakly toxic (11-25% tissue death) to Millepora, respectively. Neither sponge was toxic towards the other coral species. Montipora was not affected by allelochemicals from any of the sponges. Dead coral was noted in many positions around the sponges in the field, but mainly in the direction of the current. This might support, although not confirm, an allelopathic effect. The influence of allelochemicals on the small scale and large scale spatial structuring of coral reefs is discussed.
A three-dimensional computer model was developed to stimulate the ventricular depolarization and repolarization in a clinical setting. The ventricle is composed of approximately 50,000 units arranged ...in a cubic close-packed structure and the specialized conduction system is distributed so as to obtain the excitation sequence resembling normal ventricular depolarization. The normal distribution of action potential waveforms with the longest duration on the endocardium and the shortest on the epicardium is used in the model. The heart model is mounted in a homogeneous torso model, and the body surface potential distribution generated by the electric dipoles is calculated using the boundary element method. The QRST waveforms corresponding to the normal and some abnormal heart conditions, such as bundle branch block, myocardial infarction, apical hypertrophic cardiomyopathy, and Wolff-Parkinson-White syndrome, is obtained by assuming the abnormal area with altered electrical properties. Thus the three-dimensional computer model may provide further insight into the genesis of the clinical electrocardiogram.
The absolute potential value of Wilson's central terminal was calculated at 2 msec intervals during a cardiac cycle in 60 clinical cases. Starting from the body surface potential data at 128 thoracic ...locations, the effect of immersion of the body into an infinite conductor on the surface potential was calculated to obtain values with reference to zero potential at infinity. The conductivity of the outside medium was then made to approach zero. Comparison of the result with the original map showed nearly a constant shift of the potential, corresponding to the voltage of Wilson's terminal. In addition, the cardiac vector was calculated as the first approximation of the cardiac electromotive force and the lead vector of Wilson's terminal was obtained in order that the scalar product of the cardiac vector and the lead vector approximated the observed voltage of Wilson's terminal. The results indicate that the voltage of the Wilson electrode depended on the surface voltage with a peak value near the maximal QRS force in most of the cases. The peak voltage of Wilson's terminal was either positive or negative, and was 0.15mV in absolute value on average. Voltage variations of Wilson's terminal during a cardiac cycle were 0.20mV as an average of all cases. The voltage of Wilson's terminal also depended on the direction of the equivalent cardiac vector. The lead vector of Wilson's terminal was found to be directed superiorly in most of the cases. The average magnitude of the lead vector of Wilson's terminal was 0.097Ω/cm, which corresponded to about 1/4 of that of lead I.
The ventricular gradient vector was determined in normal persons and in cases with left and right bundle branch block (BBB) by means of the best fit method from body surface potential mapping data. ...Similar measurements were also made in cases with artificial ventricular pacing and the G vector during sinus rhythm was compared with that of the paced beats. Results indicated that the magnitude of the G vector in cases with BBB was smaller than in normal persons. The directional change in the G vector was found to be along the direction of the QRS change in the majority of cases with left BBB. In right BBB, the direction of the G change was variable but the angle between the QRS change was less than 90 degrees on average. Following right ventricular pacing a small increase of the G magnitude was observed acutely, which was opposite in direction to the QRS change. Possible mechanisms are discussed. The G changes in left and right BBB are considered to be based on certain chronic processes, different from those involved in the acute immediate effect of altered activation.
The initial portion of the QRS complex in WPW syndrome might be represented by a single dipole, since the delta wave corresponds to the localized ventricular activation propagated over the accessory ...atrioventricular pathway. In order to examine whether the site of the accessory pathway in WPW syndrome could be localized by an equivalent dipole method, the dipole positions during the delta wave were determined in 30 patients using a three dimensional model of the torso and were then compared with the sites of accessory pathways localized by body surface maps. The single dipole approximation during the delta wave appeared to be appropriate since the index of the nondipolarity of the potentials was as low as 28% on average. The dipole positions determined on the atrioventricular ring during the delta wave were compatible with the sites of accessory pathways localized by body surface maps in 22 of the 30 patients. The dipole positions were adjacent to the sites of accessory pathways in 7 of the remaining 8 patients. Thus the equivalent dipole method might be an additional noninvasive tool to determine the site of the accessory pathway in WPW syndrome.
The role of mechanical ventilation and catheters in favouring Acinetobacter baumannii infections needs to be better understood. This study evaluated the adherence of 19 isolates of different hospital ...clusters of A. baumannii to abiotic surfaces and epithelial cells (HEp‐2). Of the hydrophobic isolates, 80% adhered to polystyrene, indicating a close relationship between hydrophobicity and adherence. All isolates adhered to epithelial cells to different degrees, and 73·7% showed an aggregated pattern. Analysis of the serum resistance of catheter‐tip isolates showed that all were resistant. These worrisome results showed that the high capacity of A. baumannii to adhere to surfaces and survive in human serum could hinder treatment and control of this pathogen.
Significance and Impact of the Study: Acinetobacter baumannii can colonize inpatients and health workers. The ability to survive in hostile environments allows this bacterium to persist in intensive care units, causing serious infections with high mortality. This study describes, for the first time, the aggregated adherence pattern of a majority of A. baumannii isolates to human epithelial cells, which can favour human colonization. The bacterium was also able to adhere to polystyrene in medical devices and escape the host's defence responses. We believe that this information can help to understand certain factors in the virulence of A. baumannii, enabling its control.
Summary
In monocytes and macrophages, the interaction of Porphyromonas gingivalis with Toll‐like receptor 2 (TLR2) leads to the activation of a MyD88‐dependent antimicrobial pathway and a ...phosphatidylinositol‐3 kinase (PI3K) ‐dependent pro‐adhesive pathway, which activates the β2‐integrin complement receptor 3 (CR3). By means of its fimbriae, P. gingivalis binds CXC‐chemokine receptor 4 (CXCR4) and induces crosstalk with TLR2 that inhibits the MyD88‐dependent antimicrobial pathway. In this paper, we investigated the impact of the P. gingivalis‐CXCR4 interaction on the pro‐adhesive pathway. Using human monocytes, mouse macrophages, or receptor‐transfected cell lines, we showed that the binding of P. gingivalis fimbriae to CXCR4 induces CR3 activation via PI3K, albeit in a TLR2‐independent manner. An isogenic strain of P. gingivalis expressing mutant fimbriae that do not interact with CXCR4 failed to efficiently activate CR3, leading to enhanced susceptibility to killing in vivo compared with the wild‐type organism. This in vivo observation is consistent with previous findings that activated CR3 mediates safe entry of P. gingivalis into macrophages. Taken together with our previous work, these results indicate that the interaction of P. gingivalis with CXCR4 leads to inhibition of antimicrobial responses and enhancement of pro‐adhesive responses, thereby maximizing its adaptive fitness in the mammalian host.
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