Objective: To mechanically test the intact cardiac structure to determine the sequence of contraction within the myocardial mass to try to explain ejection and suction. Methods: In 24 pigs (30–85 kg), segment shortening at the site of sonomicrometer crystals was continuously recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. Results: Study of segment shortening defined a sequence of contraction within the myocardial mass, starting at the free wall of the right ventricle and on the endocardial side of the antero-septal wall of the left. Crystal location defined underlying contractile trajectory; transverse in right ventricle followed by basal posterior left ventricle, and from the endocardial anterior wall to the posterior apical segment and finally to the epicardial side of the anterior wall. Mean shortening fraction averaged 18±3%, with endocardial exceeding epicardial shortening by 5±1%. Epicardial segment crystal displacement followed endocardial shortening by 82±23 ms in the anterior wall, and finished 92±33 ms after endocardial shortening stopped, time frame that matches the interval of fast drop of ventricular pressure and the start of suction. Conclusions: Crystal shortening fraction sequence followed the rope-like myocardial band model to contradict traditional thinking, with two starting points of excitation–contraction, the right anterior free wall of the right ventricle, and the endocardial side of the anterior wall. Active suction may be due to active shortening of the epicardial fibers of the anterior wall, because relaxation was not detected when both mitral and aortic valves were closed during the interval previously termed ‘isovolumetric relaxation’. 相似文献
This audit has been conducted in order to provide an evidence base that clarifies the strengths and weaknesses of acute pain management at a UK hospital. Consequently, it sets the strategic direction for service improvement. Awarding up to three stars has identified the quality of each component that constitutes the acute pain service. Six different components were audited and star ratings have been awarded as shown below:
• Pain tool (including patient and staff understanding): no stars.
• Pain team (including education and clinical support): two stars.
• Intermittent opioid analgesia (sub-cut and oral morphine): two stars.
• Epidural patient controlled analgesia (EPCA): two stars.
• Intravenous patient controlled analgesia (IVPCA): two stars.
• Single-dose intrathecal opioid analgesia: three stars.
These star ratings were pulled together in order to award the acute pain service an overall rating. Consequently, the acute pain service was awarded two stars. The findings of this audit identify that this acute pain service provides a safe way to deliver hi-tech pain relief at ward level and can be relied upon to provide good quality pain management. However, too many patients are likely to miss out on the full benefits of the service due to the weaknesses as identified. The quality of the pain relief is impeded across the hospital due to low patient expectation and poor patient education, and also due to a lack of relevant knowledge amongst nursing staff. Developments in the role of the acute pain nurse, staff training and education programs, and a reduction in the variety of pain management pumps are combining to facilitate the opportunities required to address the weaknesses and to build on the strengths of the acute pain service. 相似文献
All cells that constitute mature tissues in an eukaryotic organism undergo a multistep process of cell differentiation. At
the terminal stage of this process, cells either cease to proliferate forever or rest for a very long period of time. During
terminal differentiation, most of the genes that are required for cell ‘housekeeping’ functions, such as proto-oncogenes and
other cell-cycle and cell proliferation genes, become stably repressed. At the same time, nuclear chromatin undergoes dramatic
morphological and structural changes at the higher-order levels of chromatin organization. These changes involve both constitutively
inactive chromosomal regions (constitutive heterochromatin) and the formerly active genes that become silenced and structurally
modified to form facultative heterochromatin. Here we approach terminal cell differentiation as a unique system that allows
us to combine biochemical, ultrastructural and molecular genetic techniques to study the relationship between the hierarchy
of chromatin higher-order structures in the nucleus and its function(s) in dynamic packing of genetic material in a form that
remains amenable to regulation of gene activity and other DNA-dependent cellular processes. 相似文献
A questionnaire was used to compare undergraduate student satisfaction with orthodontic teaching in two units; one in Leeds, UK, the other in Marburg, Germany. Whilst the methods of teaching differed between the units, the aim was to highlight aspects of both courses which students might wish to see improved. Statistical analysis suggested that students appreciate clarity of course structure and means of assessment and that use of a course manual is helpful in achieving this. Recommended texts to back-up course work are also appreciated whilst students from both locations, want to see more patients. Alternatives, such as patient case folders, computer-assisted learning packages and use of videos showing treatment progression, seem to be acceptable alternatives should there be difficulty in supplying “real” patients. The relevance of laboratory courses needs to be reviewed. Overall, the use of student questionnaires is seen as a useful tool in monitoring standards of teaching. 相似文献