Influence of Fluorescent Labelling of Polystyrene Particles on Phagocytic Uptake,Surface Hydrophobicity,and Plasma Protein Adsorption

Purpose. To investigate the influence of fluorescent labelling of polystyrene particles on phagocytic uptake, surface hydrophobicity and protein adsorption. Methods. Phagocytic uptake was analysed using chemiluminescence. Hydrophobicity was quantified by adsorption measurements of a hydrophobic dye. Protein adsorption was evaluated by two-dimensional electrophoresis. Results. Commercially available fluorescently labelled particles showed marked differences when compared to unlabelled particles: phagocytic uptake and surface hydrophobicity of labelled particles were diminished. Also the plasma protein adsorption pattern was found to be different from the unlabelled particles: for example, the amount of fibrinogen adsorbed was strongly reduced on the labelled particles. On the other hand, some unknown proteins could be detected on the fluorescently marked particles. In contrast, plain polystyrene particles and labelled ones could be successfully synthesised by Paulke which did not show any considerable differences in phagocytic uptake, surface hydrophobicity and protein adsorption. Polysorbate 20 added as stabilizer to particle suspensions led to completely different behaviour of the particles: the particles showed altered protein adsorption patterns, dominated by immunoglobulins and especially by apolipoproteins. Furthermore, these particles were not phagocytized at all. Conclusions. Surface hydrophobicity and phagocytic uptake in vitro as well as the interactions with plasma proteins of commercially available polystyrene particles were strongly affected by fluorescent labelling. Particles synthesised by Paulke remained unchanged after labelling. The results show the importance of thorough surface characterization for using particles in test systems in vitro and in vivo.     

Mucoadhesion of Latexes. I. Analytical Methods and Kinetic Studies

A Fourier transform infrared spectroscopy/attenuated total reflection technique for direct quantification of adsorbed poly(styrene) latexes on rat intestinal mucosa was developed for deposited latex amounts up to 1.5 g/m². The method agreed well with another dosage assay of adsorbed particles by turbidimetry after denaturation of the mucus. Adsorption kinetics were made under static conditions at latex concentrations of 4 g/L in physiological saline. Ninety percent of equilibrium was reached after 10 min for a particle size of 230 nm, 20 min for a size of 320 nm, and 30 min for a size of 670 nm. The plateaus were between 0.6 and 0.9 g/m² (adsorbed mass per apparent surface of mucosa). The first phase of the kinetics was theoretically approached by a diffusion model in the suspension medium. Mucosa from rat jejunum and ileum could be considered as a homogeneous biological model for latex adsorption.     

Furosemide dynamics in conscious rabbits: Modulation by angiotensin II

Summary The aim of this study was to investigate the effects of an infusion of angiotensin II (50 ng/kg/min) on furosemide pharmacodynamics and kinetics in the conscious rabbit. The protocol included a 90-minute phase to estimate the glomerular filtration rate and the renal plasma flow, followed by a 60-minute phase where 5 mg/kg (n=12) or 10 mg/kg (n=9) of furosemide were administered. During the pre-furosemide phase, compared to control rabbits, angiotensin II increased natriuresis and diuresis. In the presence of angiotensin II, the furosemide-induced natriuresis decreased, that is, it was 174±14 versus 95±25 µmol/min (p<0.05) and 187±17 versus 89±21 µmol/min (p<0.05) for the 5 and the 10 mg/kg doses, respectively. The infusion of angiotensin II decreased renal plasma flow without modifying the glomerular filtration rate, thus the filtration fraction was increased. Angiotensin II increased the area under the furosemide plasma concentrations as a function of time since it decreased its systemic clearance. However, furosemide urinary excretion rate was not altered and its renal clearance decreased slightly without reaching statistical significance. It is concluded that angiotensin II decreases the response to furosemide and the mechanism underlying this effect is related to the pharmacodynamics rather than the kinetics of the diuretic.     

紫杉醇和三尖杉磷碱在多孔硅胶上的吸附及扩散研究

吸附和扩散特性是进行色谱过程的基础,本文测定了紫杉醇及其类似物的三尖杉磷碱在多孔的吸附及扩散特性,结果表明：紫杉醇和三尖杉磷酸在硅胶上的吸附不符合Ｌａｎｇｍｕｉｒ单分子层吸附理论,但在低浓度下可用溶剂调整型Ｌａｎｇｍｕｉｒ模型描述。扩散研究表明,用醇和三尖彬磷碱在硅胶上吸附罗弱,表面扩散可以忽略,相同条件下,紫杉醇的吸附量受强溶剂影响罗大,强溶剂组成的增加会造成紫杉醇吸附量很快下降,这和在正相色谱     

Selective strategies in food webs

Food webs are described as control systems where the controlsare chosen according to given myopic strategies. In particular,strategies describing selective feeding and selective escapeare defined. The existence of optimal myopic solutions and theiruniqueness are discussed. Computer simulations modelling ‘switching’are given for a one-predator—two-prey system.     

The acute response of left ventricular filling dynamics to intravenous verapamil predicts the changes in exercise tolerance after oral verapamil therapy in patients with hypertrophic cardiomyopathy

We studied the correlation between changes in left ventricularfilling dynamics induced by acute intravenous administrationof verapamil and the changes in exercise tolerance induced byoral administration of the agent in 30 patients with hypertrophiccardiomyopathy. Diastolic cardiac function was measured by meansof a nuclear stethoscope before and 10 min after intravenousadministration of verapamil, 0.15mg. kg^–1 over 2 min.Treadmill exercise tests using a modified Bruce protocol wereperformed before the initiation of oral verapamil treatmentand after 4 weeks of oral therapy at a dose of 320–360mg. day^–1 (mean±SD 332±17mg. day^–1). Peak filling rate (PFR) increased in 21 patients, 18 of whom(86%) also had an increase in exercise duration. PFR showedno increase in nine patients, eight of whom (89%) had no changein exercise duration (sensitivity 95%, specificity 73%, predictivevalue of the positive result 86%, predictive value of the negativeresult 89%). Acute changes in time from the beginning of rapidfilling to PFR (t-PFR) and in left ventricular end-diastolicvolume (EDV) were less useful in predicting improvement in exercisetolerance. In 19 patients the changes in PFR and EDV parallelled.Twelve of the 13 patients (92%) will an increase in both parametersalso had an increase in exercise duration, whereas all six inwhom these parameters were reduced showed no increase in exerciseduration (sensitivity 100%, specificity 86%, predictive valueof positive results 92%, and predictive value of negative results100%). In conclusion, the response of PFR, and even more so the combinedresponse of PFR and EDV to intravenous verapamil, accuratelyidentify patients with hypertrophic cardiomyopathy who are likelyto show improvement in exercise tolerance after oral verapamiltherapy.     

Salbutamol disposition and dynamics in conscious rabbits: Influence of the route of administration and of the dose

This study assessed the influence of dose and route of administration on salbutamol kinetics and hypokaliemic effect. Salbutamol plasma kinetics were studied in a first group of 6 rabbits who received 60, 800, and 60 g/kg by the intravenous (iv), oral (po), and intratracheal (it) routes, respectively, at 1-week intervals. A second group of 6 rabbits received 120, 2400, and 120 g/kg of salbutamol by the same three routes. Multiple blood samples were withdrawn to assay salbutamol and potassium. Following iv salbutamol (60 g/kg), total plasma clearance was 82±5 ml/min per kg, apparent volume of distribution was 5.0±0.5 l/kg, and terminal half- life was 41±2 min. Similar values were estimated when 120 g/kg of salbutamol was administered iv or was given po or it. The bioavailability of po and it salbutamol was approximately 1 and 20%, respectively. For the first group, the maximal decrease in plasma potassium elicited by salbutamol was 0.80±0.19, 0.48±0.22, and 0.78±0.46 mmol/l, and for the second group, maximal decrement was 1.31±0.37, 0.70±0.24, and 0.84±0.17 mmol/l for the iv, po, and it routes, respectively. Compared to salbutamol peak plasma concentrations, maximal decrease in plasma potassium appeared between 60 and 108 min later for the iv route, 90 and 25 min later for po and it routes, and for this reason, the hypokaliemic effect was not associated to salbutamol plasma concentrations. The hypokaliemic effect was dependent upon the route, e.g., po>it>iv. It is concluded that (i) salbutamol plasma kinetics are first-order independently of the route of administration, and (ii) salbutamol hypokaliemic effect is modulated by the dose and the route of administration.List of abbreviations AUC Area under salbutamol plasma concentration-time curve - cl_INT Salbutamol intrinsic clearance - cl_T Salbutamol total plasma clearance - c_MAX Salbutamol maximal plasma concentration - F Fraction of the dose of salbutamol reaching the systemic circulation - iv Intravenous route of administration - it Intratracheal route of administration - po Oral route of administration - V_area Salbutamol apparent volume of distribution - T ₂ ¹ Salbutamol half-life of the terminal phase - t_MAX Time to observe the maximal decrease in plasma potassium - e_MAX Predicted maximal effect of salbutamol - EC₅₀ Concentration of salbutamol eliciting 50% of e_MAX Supported by the Medical Research Council of Canada (MT-10874). Sylvie Perreault is recipient of a Bourse Formation de troisième cycle des Fonds de la Recherche en Santé du Québec.     

The rotational component in the dynamics of the C2–3 spinal segment

Summary The technique of the PA axial projection of the arches of the upper cervical vertebrae into the occipital foramen and the normal findings, are described. The influence of maximum forced anteflexion at the craniocervical junction and rotation of the head on the relations of atlas and axis is demonstrated. It seems that in this position rotation at atlasaxis level is restricted and partly transmitted to the C_2–3 segment. Thus, selective clinical examination of the rotational component of the dynamics at C_2–3 can be achieved and the pathological restrictions of movement can be assessed.     

Monoamine acid metabolites in ventricular CSF of patients with brain tumours

Summary Homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA) in ventricular CSF were determined in 19 patients (12 female 7 male) with brain tumours. No relationship was found between ventricular fluid pressure (VFP) and levels of HVA and 5-HIAA. A relationship was observed between ventricular CSF, HVA concentrations and tumour induced alterations in CSF dynamics. HVA concentrations were very high in patients whose tumours involved the third ventricle, the aqueduct, or the fourth ventricle, producing marked alterations in CSF flow. HVA concentrations significantly lower than in controls were observed in cases where tumours involved the lateral ventricles. Concentrations of acid metabolites in patients with little or no alteration in CSF dynamics corresponded with those in patients with other neurosurgical disorders.     

纳洛酮治疗脑梗死的疗效观察

目的　观察纳洛酮治疗脑梗死的疗效。方法　将 2 6 0例脑梗死患者随机分组 ,治疗组 12 8例 ,予纳洛酮治疗 ;对照组 132例 ,予一般治疗 ,观察神经功能缺损变化及血液流变学变化。结果　治疗组较对照组神经功能改善和血液流变学改变有显著性差异。结论　纳洛酮具有抗凝作用 ,对脑梗死患者神经功能恢复有较好疗效。