Estimation of instantaneous flow from the indicator-dilution curve after bolus injection of indicator

The indicator-dilution technique is commonly used to determine mean flow estimates. The estimation of instantaneous flow from the shape of an indicator-dilution curve is the objective of this study. Based on a mixing chamber approach to the flow system, a mathematical relationship is derived to reconstruct momentary flow from an indicator-dilution curve. This relationship is verified in a model setup both with only constant flow and with a sinusoidal flow variation superimposed. This method proved to give good flow estimates for limited values of flow parameters. Also, some preliminary experiments were performed in a pulsating flow system simulating heart action. The results were promising although the method proved to be very sensitive to baseline offset.     

宫颈腺癌细胞DNA流式细胞光度分析

应用流式细胞计对３０例宫颈腺癌和混合癌细胞的ＤＮＡ指数和细胞增殖周期各时相细胞分布比例进行分析，结果显示非整倍体肿瘤２９例，占９６．７％．流式细胞计在诊断恶性肿瘤方面是有价值的。细胞增殖周期比ＤＮＡ指数对预后的估价更有意义．乳头型腺癌、分化Ｉ级的肿瘤，Ｓ＋Ｇ２Ｍ比率最低，５年生存率最高．     

Local and central sympathetic reflex control of blood flow in skeletal muscle and subcutaneous tissue in normal man

Summary. The effect of age and sex on relative changes in blood flow and vascular resistance in skeletal muscle and subcutaneous tissue during postural changes and during local increase in transmural pressure was studied in 33 healthy subjects. The intra-individual variation was studied in five subjects. Blood flow was measured by the local ¹³³Xenon wash-out method. No relation to age or sex was seen in the centrally elicited sympathetic vasoconstrictor responses in subcutaneous tissue and skeletal muscle and in the locally elicited vasoconstriction in subcutaneous tissue. A small, but statistically significant, correlation to sex and age was found in the local sympathetic vasoconstrictor response in skeletal muscle. The age correlation was caused only by an attenuated response in the young subjects below 40 years of age and may be fortuitous. The intra-individual variation was acceptably small. Based on the present results, a reduction in blood flow in skeletal muscle and subcutaneous tissue during centrally or locally elicited sympathetic vasoconstriction of 10% or less should be considered abnormal. The local ¹³³Xenon wash-out method is of value in examining patients suspected of dysfunction in the sympathetic part of the autonomic nervous system.     

A study of some current methods for assessment of nasal histamine reactivity

The aim of this study was to investigate the reactivity of the nasal mucosa of patients with pollen allergy compared to healthy controls, when challenged with histamine outside the pollen season. Assessments were made with symptom score, acoustic rhinometry, nasal peak expiratory and inspiratory flow (NPEF and NPIF) and rhinomanometry in order to find the most sensitive method for the purpose. Twenty-one patients with seasonal allergic rhinitis and 20 healthy controls were challenged with histamine dihydrochloride in increasing concentrations (0.01, 0.1, 1.0 mg/ml) locally in the nose. Our results show no difference in mucosal reactivity between the patients and controls regardless of the method used. When comparing the methods we find that NPIF and NPEF are more sensitive to mucosal changes than the other methods we have studied.     

Local variations in the cerebral microcirculatory response to hypercapnia and haemorrhage

Summary This study evaluates local variations of the cerebral vasomotor responses to hypercapnia and haemorrhagic hypotension in a pig model. Four laser Doppler flow probes were used in each pig. There was considerable variation in laser Doppler signals between the four probes in baseline recordings. The increases in flow after CO₂ administration in 7 pigs had a mean coefficient of variation of 0.43 ± 0.31, and the flow changes after blood loss in another 7 pigs had a mean coefficient of variation of 0.45 ± 0.34. The range of flow changes within each animal was large; the probe with the highest CO₂ response showed on the average a 273% ± 157% larger CO₂ response than the probe with the lowest CO₂ response. Correspondingly, the probe with the best preserved blood flow after blood loss had on the average a flow value of 93% ± 12% of the baseline value, while the probe that changed most with haemorrhage had a flow value of 44% ± 24% of the baseline value. Single laser Doppler recordings have been used for the monitoring of cerebral blood flow in neurosurgical critical care, but our results suggest that a single laser Doppler flow probe is not an adequate method to monitor vasoreactivity in neurosurgical patients because flow signals from one probe may be unrepresentative for other sites in the brain.     

The estimation of the plasma free fraction of cyclosporine in rabbits and heart transplant patients: The application of a physiological model of renal clearance

We estimated the free fraction (f_u) of cyclosporine (CyA) in the plasma from concentrations of CyA in urine (C_u) and plasma (C_p), urine flow rate (UF), and glomerular filtration rate in rabbits and in heart transplant patients. Following intravenous administration of CyA (5–30 mg kg^?1) in ten NZW rabbits and oral administration of CyA (4.8–12.1 mg kg^?1) in nine heart transplant patients, CyA concentrations in urine and plasma were measured by HPLC. The ratios of C_u to C_p and UF data were fitted to a physiological model of renal clearance using NONMEM. The free fraction of cyclosporine in the rabbits and the heart transplant patients was 0.0122 and 0.14, respectively. Because of the relatively low permeability of CyA across the tubular epithelium, no apparent equilibrium between C_u and C_p at any urine flow rate was reached and, therefore, the C_u to C_p ratio will not be equal to f_u.     

应用流式细胞仪对肺癌细胞增殖活力的分析

本文应用流式细胞仪对35例肺癌、10例良性病变肺组织及10例正常肺组织的细胞增殖活力(S％)进行了分析,结果显示肺癌组织细胞增殖活力非常显著高于良性病变组,良性病变组细胞增殖活力亦非常显著高于正常组,提示检测细胞增殖活力对肺癌的诊断、筛选有一定意义。     

Development of an isolated, pulsatile blood-perfused rat lung model for evaluating the preserved lung functions

The purpose of this study was to develop an isolated, pulsatile blood-perfused rat lung model that allows us to evaluate the preserved lung functions. Lungs isolated from Sprague-Dawley rats, were perfused with venous whole blood by either a pulsatile or constant flow. The effuent was continuously deoxygenated with a 95% N₂/5% CO₂ gas mixture. Airway resistance, lung compliance, elastic work, flow resistive work, pulmonary vascular resistance, and blood gas analysis were assessed. Pressor responses toN ^G -monomethyl-l-arginine (l-NMMA) were compared between pulsatile and constant blood flow. At a flow of 0.1 ml/g body weight/min, pulsatile perfusion allowed for stable perfusion at least for 2h (mean 162.5±15.1 min) with stable aerodynamic and hemodynamic variables including blood gas tensions, whereas constant perfusion resulted in immediate lung failure. Whenl-NMMA was added to the perfusate, the mean pulmonary artery pressure did not show any change in the constant flow (6.0±2.6% increase), but did show a significant increase in the pulsatile flow (45±11% increase). Pulsatile blood flow reduced the pulmonary vascular resistance relative to the constant flow and allowed for a 2-h perfusion period to evaluate the lung function. The vasorelaxant mechanism in the pulsatile perfusion is related in part to the endothelial-dependent relaxation observed in the nitric oxide pathway. Presented in part at the 79th, Annual Clinical Congress of the American College of Surgeons (ACS) held in San Francisco, CA USA, 1993.     

The anterior inferior cerebellar arterial network supplying the rat cochlea and its role in autoregulation of cochlear blood flow

Summary The sensitivity of the cochlea is dependent upon maintenance of a delicate homeostatic environment. One mechanism which participates in providing this environment is the autoregulation of cochlear blood flow. This autoregulation is ensured through the interaction of sympathetic, peptidergic and hemodynamic mechanisms. The current study demonstrates an adaptation that also participates in cochlear blood flow autoregulation. Specifically, an anterior inferior cerebellar arterial network is described and the relative contributions of each of its vessels to total cochlear blood flow is measured using laser Doppler flowmetry. The results show that each collateral vessel contributes to the blood supply of the cochlea and that reperfusion is accompanied by hyperemia. These findings suggest an adaptation that provides stable blood flow through redundancy and compensatory potential. Additionally, these observations have implications for experimental models of ischemia.