Computational models of hair cell bundle mechanics: II. Simplified bundle models

Simplified versions of hair cell bundles are mechanically modeled. The influence of various geometric and material combinations on bundle stiffness, link tensions and deformation shape are examined. Three models are analyzed within this paper: two stereocilia connected by one link, two stereocilia connected by a biologically realistic set of links, and a column of stereocilia connected by realistic links. Stereocilia are modeled using a distributed parameter model [J. Biomech. Eng. 122, 44]. Some fundamental rules for linking bundles emerge from these tests: (1) Links must have a threshold stiffness value for the bundle to deform as a whole. Beyond this value, the stereocilia are perfectly linked and variations in link stiffness do not significantly effect the bundle stiffness or link tension. (2) Decreasing the relative heights of successive stereocilia may increase link tension while decreasing bundle stiffness. (3) When lateral links exist, the top most lateral links carry the majority of tension. Lower links in single column model appear mechanically insignificant. (4) Extending the length of the bundle in a column does not increase the stiffness once the column reaches a certain length.     

An evaluation of functional outcomes (speech,swallowing) in patients attending speech pathology after head and neck cancer treatment(s): results and analysis at 12 months post-intervention

We have earlier reported establishing a computerized database to audit functional outcomes in patients who underwent head and neck cancer treatment in Victoria, Australia and attended speech pathology services from April 1997-April 1999. This paper presents the statistical analyses and results from this study. Speech pathologists collected, prospectively, functional outcome data on 293 patients who underwent head and neck cancer treatment, and sent these for analysis to La Trobe University. Clinician and patient assessments of outcomes: speech, swallowing, activity, pain, employment, health, QOL status were made. Initial data on 293 patients were collected and data on mortality and morbidity were compiled at three, six and 12 months post-treatment. Within twelve months, 74 patients had died. Three, six and/or 12-month follow-up data was available on 219 patients, with both clinician and patient assessments of status completed. The status forms are presented as appendices to this paper. Complete status forms on 179 patients at 12 months were obtained. This clinical audit of functional outcomes represents the first study of this kind, collecting data from speech pathologists and patients in a multi-centre study of patients with head and neck cancer. We present data to demonstrate optimal recovery of function at six months, such that this may represent a good reference point for reporting and comparison of functional outcomes.     

Rise of circulating thrombopoietin following cardiothoracic surgery is potentiated in patients with coronary atherosclerosis: correlation with a preceding increase in levels of interleukin-6

Thrombopoietin (TPO) is the major regulator of platelet production. Plasma levels of TPO are thought to be regulated by its binding to platelets and megakaryocytes. Here we have used a model of cardiac surgery with cardiopulmonary bypass (CBP) to test the possibility that changes in TPO levels are influenced by the presence of coronary artery disease (CAD) and by changes in interleukin-6 (IL-6). After surgery patients with CAD (n = 22) or with normal coronary arteries (n = 11) showed a significant thrombocytopaenia followed by a reactive thrombocytosis. The platelet recovery was preceded by a significant rise in TPO (from 62.6 +/- 9.4 pg/ml at baseline to 129.2 +/- 19 pg/ml at 60 h, P <0.001), which in turn was preceded by, and was positively correlated with, a marked increase in circulating IL-6 (from 1.5 +/- 0.3 pg/ml at baseline to 269.3 +/- 30.6 pg/ml at 3-12 h, P <0.001). The rise of both IL-6 and TPO was significantly larger in patients with CAD. No correlation was found between the post-operative drop in platelet mass and changes in either the TPO or IL-6 levels. These findings suggest that in man circulating TPO levels, besides being controlled by changes in platelet mass, are influenced by inflammatory processes, including the presence of coronary atherosclerosis.     

Capillary gel electrophoresis: separation of major erythrocyte membrane proteins

A new separation method of human erythrocyte membrane proteins by sodium dodecyl sulfate capillary gel electrophoresis (SDS-CGE) is described. In this method, a replaceable gel matrix was used. Seven major erythrocyte membrane proteins, alpha-and beta-spectrin, ankyrin 2.1, band 3 (anion-exchanger), 4.1a and b, and 4.2 (pallidin), were separated and identified by SDS-CGE method. High reproducible migration times of these proteins (inter-assay coefficients of variation less than 2%), as well as quantification (inter-assay coefficients of variation less than 11%) were obtained. This new SDS-CGE method may provide important diagnostic evidence for hereditary spherocytosis. It can be a powerful diagnostic tool in place of SDS polyacrylamide gel electrophoresis for erythrocyte membrane protein analysis.     

Spiral CT versus MRI in neonatal airway evaluation

Magnetic resonance imaging has become the standard means of imaging pediatric airway obstruction due to vascular anomalies. However, magnetic resonance imaging requires a long acquisition time and is prone to motion artifacts. The development of spiral or helical computed tomography provides an alternative imaging modality for evaluating pediatric airway obstruction. We present the case of a neonate with a double aortic arch which initially was not identified on magnetic resonance imaging but was visualized with spiral computed tomography. If suspicion of an intra-thoracic abnormality is high, spiral computed tomography may be a useful adjunct or replacement to magnetic resonance imaging.     

Fatal cardiac tamponade complicating anticoagulant therapy in rheumatoid arthritis

Haemopericardium with tamponade is a rare complication of anticoagulant therapy. A case of fatal haemopericardium is described in a patient with rheumatoid pericarditis in whom the precipitating factor appeared to be intravenous anticoagulant therapy.