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Human Experiments (human + experiment)
Selected Abstracts2265: Safety evaluation of intravitreal use of a beta2-agonist in rabbit eyesACTA OPHTHALMOLOGICA, Issue 2010J VAN CALSTER Purpose There is no known information on the use and safety of a long-acting beta-agonist, such as Clenbuterol when administered by intravitreal injection. Therefore, it is appropriate to perform this intravitreal injection in an animal model prior to start with a human experiment. The aim is to investigate the safety of an intravitreal injection of the beta2-agonist Clenbuterol in rabbit eyes. This study is in preparation of using of this molecule in human eyes. That trial will be a monocentric, academic (investigator driven) trial to investigate the safety and efficacy of an intravitreal beta2-agonist in patients with persistent subfoveal fluid after retinal detachment surgery. Approval of the ethics committee for the human trial has already been obtained, pending a re-evaluation after the results of the animal study will be known. Methods An intravitreal injection of 0,1 ml solution containing 0.08µg Clenbuterol or 0.1ml NaCl 0.9% was given in 10 eyes of 10 rabbits. The distribution occurred at random and was masked. A masked investigator examined both eyes after 1, 3 and 7 days (biomicroscopy, intraocular pression and ophthalmoscopy). After one week, the rabbits were sacrificed, the eyes enucleated and fixated for histopathological examination and electron microscopy by a masked investigator. Cell death was monitored by a DNase type I/II activity assay. Results There was no clinical or histopathological difference between the clenbuterol and the control group. Conclusion Clenbuterol is not toxic for the retina of rabbit eyes after intravitreal injection. It can be considered for the use in human eyes. Final approval of the ethics committee for the human trial is awaited. [source] Safety evaluation of intravitreal use of a beta2-agonist in rabbit eyesACTA OPHTHALMOLOGICA, Issue 2009J VAN CALSTER Purpose There is no known information on the use and safety of a long-acting beta-agonist, such as Clenbuterol when administered by intravitreal injection. Therefore, it is appropriate to perform this intravitreal injection in an animal model prior to start with a human experiment. The aim is to investigate the safety of an intravitreal injection of the beta2-agonist Clenbuterol in rabbit eyes. This study is in preparation of using of this molecule in human eyes. That trial will be a monocentric, academic (investigator driven) trial to investigate the safety and efficacy of an intravitreal beta2-agonist in patients with persistent subfoveal fluid after retinal detachment surgery. Approval of the ethics committee for the human trial has already been obtained, pending a re-evaluation after the results of the animal study will be known. Methods 5 rabbits will receive an injection of 0.1 ml solution containing 0.08µg Clenbuterol in one eye and an injection of 0.1ml NaCl 0.9% in the other eye. Since the volume of an adult rabbit eye is only one third of an adult human eye, the achieved concentration with be three time the concentration suggested for use in a human eye. [source] R-wave Amplitude in Lead II of an Electrocardiograph Correlates with Central Hypovolemia in Human BeingsACADEMIC EMERGENCY MEDICINE, Issue 10 2006John G. McManus MD Abstract Objectives Previous animal and human experiments have suggested that reduction in central blood volume either increases or decreases the amplitude of R waves in various electrocardiograph (ECG) leads depending on underlying pathophysiology. In this investigation, we used graded central hypovolemia in adult volunteer subjects to test the hypothesis that moderate reductions in central blood volume increases R-wave amplitude in lead II of an ECG. Methods A four-lead ECG tracing, heart rate (HR), estimated stroke volume (SV), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured during baseline supine rest and during progressive reductions of central blood volume to an estimated volume loss of >1,000 mL with application of lower-body negative pressure (LBNP) in 13 healthy human volunteer subjects. Results Lower-body negative pressure resulted in a significant progressive reduction in central blood volume, as indicated by a maximal decrease of 65% in SV and maximal elevation of 56% in HR from baseline to ,60 mm Hg LBNP. R-wave amplitude increased (p < 0.0001) linearly with progressive LBNP. The amalgamated correlation (R2) between average stroke volume and average R-wave amplitude at each LBNP stage was ,0.989. Conclusions These results support our hypothesis that reduction of central blood volume in human beings is associated with increased R-wave amplitude in lead II of an ECG. [source] TSE with average-specific phase encoding ordering for motion detection and artifact suppressionJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2007Ling Zhang ME Abstract Purpose To detect motion-corrupted measurements in multiaverage turbo-spin-echo (TSE) acquisitions and reduce motion artifacts in reconstructed images. Materials and Methods An average-specific phase encoding (PE) ordering scheme was developed for multiaverage TSE sequences in which each echo train is assigned a unique PE pattern for each preaveraged image (PAI). A motion detection algorithm is developed based on this new PE ordering to identify which echo trains in which PAIs are motion-corrupted. The detected PE views are discarded and replaced by uncorrupted k-space data of the nearest PAI. Both phantom and human studies were performed to investigate the effectiveness of motion artifact reduction using the proposed method. Results Motion-corrupted echo trains were successfully detected in all phantom and human experiments. Significant motion artifact suppression has been achieved for most studies. The residual artifacts in the reconstructed images are mainly caused by residual inconsistencies that remain after the corrupted k-space data is corrected. Conclusion The proposed method combines a novel data acquisition scheme, a robust motion detection algorithm, and a simple motion correction algorithm. It is effective in reducing motion artifacts for images corrupted by either bulk motion or local motion that occasionally happens during data acquisition. J. Magn. Reson. Imaging 2007;25:1271,1282. © 2007 Wiley-Liss, Inc. [source] Evaluation of MR angiography at 7.0 Tesla MRI using birdcage radio frequency coils with end capsMAGNETIC RESONANCE IN MEDICINE, Issue 2 2008Chang-Ki Kang Abstract The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16-rung high-pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine whether the end cap configuration was effective, the signal intensity profiles along the superior,inferior (S,I) direction were analyzed in phantom and in vivo human experiments. The effects were also investigated in two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) MRA experiments. The signal intensity profiles showed that B1 homogeneity at the service end, that is, the end cap side, was improved as the diameter of the end caps increased and the end cap became closer to the coil end ring. The results of 2D and 3D TOF experiments showed the best improvement of vessel visibility at the BC coil with an 80% end cap, when compared with BC coils with other end cap sizes or without an end cap. In conclusion, the BC coil with an end cap was effective for improving S,I directional homogeneity and suitable for MRA applications, especially at ultrahigh field MRI, such as 7.0T. Magn Reson Med 60:330,338, 2008. © 2008 Wiley-Liss, Inc. [source] Mechanism and control of tooth eruption: overview and clinical implicationsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2009WR Proffit Structured Abstract Authors,,, Proffit WR, Frazier-Bowers SA Objectives,,, To review pre- and post-emergent eruption, with particular emphasis on distinguishing isolated molar ankylosis from primary failure of eruption (PFE) and genetic considerations in eruption problems. Material and Methods,,, Radiographic review of eruption failure patients; animal and human experiments; high precision observations of movements of erupting teeth. Results,,, In pre-emergent tooth eruption, the controlling element is the rate of resorption of overlying structures. A path is cleared, and then the erupting tooth moves along it. This has clinical importance in recognizing the cause of eruption problems, particularly PFE, in which all teeth distal to the most mesial involved tooth do not erupt or respond to orthodontics. In our study of by far the largest sample of PFE cases yet reported, familial cases of PFE accounted for approximately ¼ of all cases examined. Candidate genes now are being evaluated. In post-emergent eruption, control seems to be light forces of long duration that oppose eruption, rather than heavy forces of short duration such as those during mastication. Studies of human premolars in their passage from gingival emergence to the occlusal plane show that in this phase eruption occurs only during a few hours in the early evening. The critical hours for eruption parallel the time that growth hormone levels are highest in a growing child. In this stage intermittent force does not affect the rate of eruption, but changes in periodontal blood flow do affect it. [source] The Effects of Feature-Label-Order and Their Implications for Symbolic LearningCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 6 2010Michael Ramscar Abstract Symbols enable people to organize and communicate about the world. However, the ways in which symbolic knowledge is learned and then represented in the mind are poorly understood. We present a formal analysis of symbolic learning,in particular, word learning,in terms of prediction and cue competition, and we consider two possible ways in which symbols might be learned: by learning to predict a label from the features of objects and events in the world, and by learning to predict features from a label. This analysis predicts significant differences in symbolic learning depending on the sequencing of objects and labels. We report a computational simulation and two human experiments that confirm these differences, revealing the existence of Feature-Label-Ordering effects in learning. Discrimination learning is facilitated when objects predict labels, but not when labels predict objects. Our results and analysis suggest that the semantic categories people use to understand and communicate about the world can only be learned if labels are predicted from objects. We discuss the implications of this for our understanding of the nature of language and symbolic thought, and in particular, for theories of reference. [source] | ||||||||||