基于敏感性定理的EIT重构算法仿真研究

为了研究性能更好的EIT图像重构算法，我们对基于敏感性定理的EIT图像重构算法进行了计算机仿真研究，并与几种常用图像重构算法进行比较，提出对基于敏感性定理的EIT图像重构算法的改进措施。     

胸部体表导纳变化与胸腔中血管导纳变化的关系

目的：探讨胸部体表导纳变化与胸腔中血管导纳变化的关系。方法：根据导纳与阻抗互为倒数的关系，导出胸部体表导纳变化公式，并用模型实验证明。结果：单根血管在胸部体表引起的导纳变化与血管本身的导纳变化和基础导纳的比值成正比，与血管的长度和胸部体表两检测电极之间的基础导纳成正比，与血管到两检测电极连线的距离成反比；多根血管在胸部体表共同引起的导纳变化等于各血管单独在胸部体表产生的导纳变化的代数和，即在电导纳图测量中导纳变化遵从标量迭加原理。结论：本文结果可为心导纳图的波形重建奠定理论基础。     

Loci on murine chromosomes 7 and 13 that modify the phenotype of the NOA mouse, an animal model of atopic dermatitis

The NOA (Naruto Research Institute Otsuka Atrichia) mouse is an animal model of allergic or atopic dermatitis, a condition characterized by ulcerative skin lesions with accumulation of mast cells and increased serum IgE. We reported earlier that a major gene responsible for dermatitis in the NOA mouse lay in the middle of chromosome 14, and that the incidence of disease clearly differed according to parental strain; the mode of inheritance was autosomal recessive with incomplete penetrance. In the study reported here, we searched for genes that might modify the NOA phenotype, and we identified two candidate loci that appeared to contain genes capable of modifying atopic or allergic dermatitis, one in the middle of chromosome 7 (χ² = 14.66; P = 0.00013 for D7Mit62) and the other in the telomeric region of chromosome 13 (χ² = 15.352; P = 0.000089 for D13Mit147). These loci correspond to regions of synteny in human chromosomes where linkages to asthma, atopy, or related phenotypes, such as serum IgE levels, have been documented. Received: December 18, 2000 / Accepted: January 19, 2001     

Relations between chronic stimulation-induced changes in contractile properties and the Ca2+-sequestering system of rat and rabbit fast-twitch muscles

This study compares changes in contractile properties, Parvalbumin content, and Ca²⁺-uptake by the sarcoplasmic reticulum (SR) of low-frequency stimulated rat and rabbit tibialis anterior (TA) muscles. Time to peak tension increased 1.8-fold in 35-day stimulated rabbit TA, while no change occurred in rat TA. Isometric twitch tension increased 2-fold in rabbit TA, but was unaltered in rat TA. Parvalbumin (PA) content was more than 90% reduced in rabbit TA, but only 60% in rat TA after 35 days. At this time, PA content of the stimulated rat TA was still higher than that of normal rabbit TA. Taking into account the suggested role of PA as a cytosolic Ca²⁺ buffer, its decrease could lead to an impaired free Ca²⁺-decay with a prolonged active state and a higher tension output during a single twitch. This would explain why chronic stimulation led to an increase in isometric twitch tension in rabbit TA, but not in rat TA. The 1.6-fold rise in half-relaxation time of 35-day stimulated rat and rabbit TA most likely resulted from a 50% reduced Ca²⁺-uptake by the SR, due to a still unknown modification of the Ca²⁺-transport ATPase.     

The A427 anchorage-independence assay as a screening tool to identify potential chemopreventive agents

An in vitro model for screening potential chemopreventive agents using inhibition of anchorage-independent growth of a human lung tumor cell line, A427, is described. A427 cells were selected for the model development, as they are known to be tumorigenic in animals, can grow in soft agarose, and their growth can be inhibited by a well-known chemopreventive agent, 13-cis-retinoic acid. Cells are plated on agarose, allowed to develop colonies for 28 days, the stained colonies are enumerated, and the inhibition of spontaneous colony formation measured. A cytotoxicity test is used concurrently with anchorage independent assay for measuring the relative survival of cells to ensure that any observed inhibition of anchorage independent growth is due to the biological activity of the chemopreventive agents, as it uses human cells as substrates rendering the efficacy data feasible for direct extrapolation to humans.     

Report of the symposium

Summary The past decades have seen considerable shifts of emphasis in surgical care. The recognition that pus was not laudable, was followed by a realisation that not all complications were inevitable and that prophylaxis could effectively reduce the incidence of most common problems in the post-operative period. As anaesthesia has become safer, it has been possible to embark on more intricate and prolonged procedures and for sufficient time to be available to ensure adequate intraoperative care.These two phenomena have firstly increased the complexity of management in the post-operative period, and have brought this aspect of surgical care more obviously to the limelight. However, many separate disciplines are involved in the care of the patient post-operatively, and the Symposium was organised¹ to bring the different groups together to identify the areas of recent development in the different specialities and to integrate the overall care of the individual patient.Abbreviations ARDS adult respiratory distress syndrome - DIC disseminated intravascular clotting     

Accuracy of pulse oximetry at various haematocrits and during haemolysis in anin vitro model

In situations in which it may be impossible and/or unethical to evaluate pulse oximetry in humans, an in vitro model with circulating blood may be a necessity. The main objective was to develop such an in vitro model and, in this model, validate the pulse oximetry technique at various haematocrit levels. The pulsating character of arterial blood flow in a tubing system was simulated by using a specially constructed pressure-regulated roller pump. The tubing system was designed to minimise damage to red blood cells. The pulse oximeter readings (SpO₂) were compared with oxygen saturation analyses by a haemoximeter (SaO₂). The pulse oximetry readings were recorded at various haematocrit levels and during haemolysis in the SaO₂ range 60–100 per cent. At a haematocrit level of 41–44 per cent, there was no correlation between SaO₂ and SpO₂ readings. After diluting the blood with normal saline to a haematocrit of 10–11 per cent, a good correlation between SaO₂ and SpO₂ was found. Following haemolysis, the agreement between SaO₂ and SpO₂ was further improved. Using the developed in vitro model, the results indicate that the accuracy of a pulse oximeter may be dependent on the haematocrit level.     

Primary respiratory syncytial virus infection in mice

A mouse model of respiratory syncytial virus (RSV) infection is described. A high-titered, large-volume inoculum results in replication of RSV to a high titer in lungs of BALB/c mice. Mice older than 15 weeks of age are more susceptible to RSV infection. Titers up to 10(6.9) plaque-forming units (pfu)/gram lung can be attained in 32-week-old mice. Older mice experience a clinical illness manifested by ruffled fur, reduced activity, and weight loss. Lung histology of older mice infected with RSV shows bronchiolitis and increased number of lymphocytes and macrophages in alveolar spaces compared with that of mice less than 8 weeks old. This model will serve as the basis for investigating immunodeterminants of recovery and protection from RSV infection.     

Immunodeficiency in RFM/(T6xRFM)F1 mouse chimaeras with lethal host-versus-graft syndrome.

Rather than central tolerance, the perinatal inoculation of related F1 hybrid spleen cells into inbred mice may result in host-versus-graft (HVG) reactions manifested as transient autoimmunity, or as a lethal immunodeficiency syndrome. RFM/(T6xRFM)F1 chimaeras with lethal disease die in 30 days with lymphosplenomegaly, immune complexes and impaired immune responses. The present studies used in vitro proliferation assays to show that the HVG reaction caused hyperplasia sufficient to account for the lymphosplenomegaly, while also causing severe impairment of splenic and nodal cell responses to concanavalin A (Con A) and to bacterial lipopolysaccharide (LPS). By 25 days, HVG mice could not distinguish between self and non-self as judged by mixed lymphocyte reactions (MLR) to RFM, (T6xRFM)F1 and third party A/J cells. There were no indications that host cells reactive to F1 donor cells had undergone clonal deletion, anergy or expansion. Flow cytometry revealed that donor T lymphocytes achieved stable engraftment, mostly in the nodes, despite the HVG reaction. Taken together with previous observations, these studies showed that HVG reactions in young parent F1/chimaeras can result in an immunodeficiency state which is characterized by an early appearing, profound and persistent impairment of both host and donor T and B cell functions. The results suggest that HVG reactions can contribute directly to immune deficits seen after clinical allogeneic bone marrow transplantation.     

Psychopathology and Public Policy

An effective definition of psychopathology would be helpful in distinguishing between normal and abnormal behavior and would provide guidance for important public policy decisions. Overinclusive definitions, such as the capacity/disability formulation, do not provide meaningful direction for defining need or assessing eligibility for insurance or other entitlements. Coping failures due to lack of skill, inadequate preparation, or other factors should be distinguished from those due to dysfunction or disturbance of psychological mechanisms. The capacity/disability formulation encourages confusion between different performance decrements and gives no guidance for appropriate boundaries for psychotherapy.