An analysis of the determinants of nephron filtration rate.

Studies on glomerular filtration in the Munich-Wistar rat, a strain with surface glomeruli, have permitted for the first time the evaluation of the four factors that determine filtration rate: 1) the rate of nephron plasma flow (RPF), 2) the glomerular hydrostatic pressure gradient (deltaP) from capillary to Bowman's space, 3) systemic oncotic pressure (piA), and 4) the glomerular permeability coefficient (LpA), and their respective roles in producing change in filtration rate. The process of filtration in the Munich-Wistar rat is characterized by filtration pressure equilibrium and, therefore, filtration should be highly plasma flow-dependent. Analysis of data from this strain suggests that multiple factors can change LpA, and, at least in animals which do not achieve filtration pressure equilibrium, these alterations in LpA can influence the final filtration rate. Multivariate statistical analysis in a variety of experimental conditions in the Munich-Wistar rat suggest that changes in RPF remain the major mediator of change in nephron filtration rate, both in rats at filtration pressure equilibrium and in disequilibrated animals. Although the glomerulus is an ultrafilter driven by hydrostatic forces, changes in deltaP assume a lesser role in producing alterations in filtration rate.     

Effect of Berkefeld filtration on the binding activity of human gastric juice

The intrinsic factor content of Berkefeld-filtered human gastric juice has been studied. This appears to vary with the pH at which filtration is carried out and also between individual filters. Significant losses of intrinsic factor may result from filtration and complete loss when filtration is carried out at a low pH. The most suitable pH for filtration appears to be in the range pH 7 to 8.     

过滤和离心对热原实验影响的初步研究

目的了解医疗器械和生物材料的浸提液能否过滤或离心后再进行热原实验。方法采用《中国药典》2010年版(二部)附录检测细菌内毒素的动态浊度法,进行定量测定浓度为0.2 EU/mL的原液中的细菌内毒素含量,并在过滤和离心后分别测定溶液中细菌内毒素的含量。结果溶液中的细菌内毒素含量过滤后大大减少,甚至小于0.040 EU/mL。离心则不会影响溶液中的细菌内毒素含量,与原液中含量相近,为0.260 EU/mL。结论为除去医疗器械和生物材料的浸提液中的悬浮颗粒,可以离心后再进行热原实验。     

Leukocyte Filtration Mechanisms. Factors Influencing the Removal of Infectious Agents From red Cell Concentrates

The purpose of the present overview was to determine the factors influencing the removal of infectious agents from red cell concentrates by filtration. In general, the efficacy of the filtration method depends on the physical as well as the functional properties of blood cells. These properties are highly influenced by the changes exerted on the blood cells during blood collection, processing and storage and the filtration method itself. In particular, the removal of infectious agents of red cell concentrates by filtration will be determined by the type of virus and therewith the binding towards leukocytes, the type of bacteria and holding period before filtration, the deformability of infected cells and the disintegration of cells in the filter     

应用深度学习网络实现肾小球滤过膜超微病理图像的语义分割

肾小球滤过膜包含内皮细胞、肾小球基底膜和足细胞3层超微结构,其形态改变是诊断肾小球疾病的重要指标之一。准确的滤过膜语义分割有助于病理医生识别和判断滤过膜细微的病理改变,为相关的病理诊断提供帮助。由于肾小球滤过膜的超微病理图像不仅结构复杂而且灰度分辨率很低,传统的分割算法均只能对其中形态最简单的基底膜部分进行分割,分割精度也难以保证。本文提出基于深度学习网络DeepLab-v3的肾小球滤过膜自动语义分割算法,应用空洞卷积扩大感受野,控制图像的特征分辨率,再通过空洞空间金字塔池化来获得多尺度的图像信息,最终将肾小球滤过膜的3个组成部分同时分割出来,并均能达到较好的分割效果。本文通过对重要参数进行实验探究,使得平均分割准确度达到0.776,是目前效果相对较好的模型。     

Hypothesis: Adenosine mediates hemodynamic changes in renal failure

The decreased filtration fraction and glomerular filtration rate characteristic of renal failure could be produced, at least in part, by increased concentration of an endogenous substance which constricts afferent and dilates efferent arterioles. Adenosine satisfies several criteria: (a) exogenous adenosine and its precursors decrease filtration fraction and glomerular filtration rate; (b) the kidneys produce and release adenosine, and production and release are augmented during conditions associated with the induction of renal failure—hypoxia, ischemia, and renal vasoconstriction; (c) several substances known to antagonize adenosine-uptake processes in some cells, which could thereby increase extracellular adenosine concentration, not only have “adenosine-like” effects on the kidney but also induce and/or potentiate existing renal failure. A corollary of this hypothesis is that adenosine-receptor antagonists, such as the methylxanthines, should counteract the hemodynamic changes characteristic of renal failure. It has been known for several years that aminophylline (1,3-dimethylxanthine ethylenediamine) increases the filtration fraction and the glomerular filtration rate.     

Technical characterization of dialysis fluid flow and mass transfer rate in dialyzers with various filtration coefficients using dimensionless correlation equation

The objective of the present study is to evaluate the effect of filtration coefficient and internal filtration on dialysis fluid flow and mass transfer coefficient in dialyzers using dimensionless mass transfer correlation equations. Aqueous solution of vitamin B₁₂ clearances were obtained for REXEED-15L as a low flux dialyzer, and APS-15EA and APS-15UA as high flux dialyzers. All the other design specifications were identical for these dialyzers except for filtration coefficient. The overall mass transfer coefficient was calculated, moreover, the exponents of Reynolds number (Re) and film mass transfer coefficient of the dialysis-side fluid (k _D) for each flow rate were derived from the Wilson plot and dimensionless correlation equation. The exponents of Re were 0.4 for the low flux dialyzer whereas 0.5 for the high flux dialyzers. Dialysis fluid of the low flux dialyzer was close to laminar flow because of its low filtration coefficient. On the other hand, dialysis fluid of the high flux dialyzers was assumed to be orthogonal flow. Higher filtration coefficient was associated with higher k _D influenced by mass transfer rate through diffusion and internal filtration. Higher filtration coefficient of dialyzers and internal filtration affect orthogonal flow of dialysis fluid.     

维生素E对慢性染镉肾小体滤过屏障超微结构损伤的保护作用

目的探讨维生素E(Vitamin E,VE)对慢性染镉小鼠肾小体滤过屏障超微结构损伤的保护作用。方法健康昆明种小鼠75只,体重28～32g,随机分3组:染镉组(CdCl 22mg/kg,皮下注射,每周2次,共3个月)、VE+镉组(染镉同时给VE 10mg/kg/天,灌胃)、正常对照组(注射等量生理盐水)。用透射电镜观察结合形态计量分析,研究经VE同时处理的慢性染镉小鼠肾小体滤过屏障的超微结构改变。结果染镉组肾小体滤过屏障的三层结构受损,与正常对照组相比,表现为毛细血管内皮增厚,血管系膜增生,血管球基膜增厚,基膜和内皮间有电子致密物沉积,足细胞次级突起间裂孔缩小和裂孔膜变薄等(P<0.001)。而VE+镉组滤过屏障的三层结构的上述变化明显减轻,形态接近正常(P>0.05)。结论VE可防止慢性染镉对肾小体滤过屏障的损害。     

Renal hypertension following aortic constriction is abolished by angiotensin II converting enzyme inhibitor,but not by low-salt diet

This study evaluates the role of different sodium intakes and the role of angiotensin II in the development and the maintenance of renovascular hypertension in rats with constriction of the aorta proximal to the renal arteries. The rats were studied 3 weeks after surgery when the hypertension was well established. Glomerular filtration rate was decreased and filtration fraction was increased in rats with proximal aortic constriction. Low and high salt intakes had no effect on glomerular filtration and filtration fraction. Treatment with angiotensin II converting enzyme inhibitor increased the glomerular filtration rate and reduced the filtration fraction in rats with proximal aortic constriction to the same levels as in control rats. Serum levels of angiotensin II were about the same in rats with proximal aortic constriction as in control rats.     

Nephrin Localizes at the Podocyte Filtration Slit Area and Is Characteristically Spliced in the Human Kidney

Defects in the newly reported gene NPHS1 in chromosome 19 cause the massive proteinuria of Finnish type congenital nephrotic syndrome (CNF). Together with its gene product, nephrin, NPHS1 is providing new understanding of the pathophysiological mechanisms of glomerular filtration. Here we show the characteristic splicing of NPHS1 mRNA in the normal and CNF kidneys and localize nephrin exclusively in the glomerulus and to the filtration slit area by light and immunoelectron microscopy. These results indicate that nephrin is a new protein of the interpodocyte filtration slit area with a profound role in the pathophysiology of the filtration barrier.     

Kinetics of the glomerular ultrafiltration in the rat kidney. A theoretical study.

The glomerular filtration process was evaluated theoretically from micropuncture data obtained from Sprague-Dawley rats. The hydrostatic pressures in the glomerular capillaries and Bowman's space minus the oncotic pressure in systemic plasma gave the net driving force at the proximal end of the glomerular capillary. From the single nephron filtration fraction the mean net driving force over the glomerular membrane was calculated to be 20 mm Hg during normotension, decreasing to 12 mm Hg during a perfusion pressure of 80 mm Hg. The hydraulic permeability for one glomerulus was 0.7-0.8 nl/min-100 g b.wt. mmHg. The pressures at the distal end of the glomerular capillaries were 13 and 6 mm Hg under the above two conditions, indicating non-equilibrium of the filtration process at the end of the glomerular capillary. It was shown that the glomerular filtration rate is mainly influenced by the driving pressures. During hypotension an increased plasma flow dependency was evident. Brenner et al. found a filtration equilibrium and a plasma flow dependent glomerular filtration rate in a mutant Wistar rat strain. The discrepancy between their results and ours is due to the low glomerular plasma flow and hydrostatic pressures in the Wistar rats. It is concluded from our results that both pre- and postglomerular resistances may influence the glomerular filtration rate and glomerular plasma flow independently.     

Correlation between single nephron glomerular filtration rate and filtration area in superficial glomeruli of developing rats

Single nephron glomerular filtration rate (SNGFR) was correlated to the area of the glomerular basement membrane (GBM) determined by stereological techniques in rats between 20 and 40 days of age. Single nephron glomerular filtration rate increased 8.4 times in parallel with a twofold increase in GBM area. The much greater postnatal increase in SNGFR than in GBM area demonstrates that the increase in GBM area cannot account for the entire increase in SNGFR. Instead a combination of other factors influencing SNGFR most likely determines the largest part of the increase in SNGFR during this period. Thus, the drop in vascular resistance known to occur during maturation will increase the renal blood flow and may cause the filtration process to turn from a state of filtration equilibrium to or close to disequilibrium, thereby increasing GFR. Additional increase in GFR may be due to an increased net driving force for filtration and/or changed hydraulic permeability.     

Comparison of polyvinylidene fluoride and polyether sulfone membranes in filtering viral suspensions

Low-protein-binding membranes with a pore size of 0.22 microm are used to filter aqueous solutions containing viruses. Virus adsorption to the membranes is avoided if they are made of polyvinylidene fluoride (PVDF) or if they are made of cellulose esters saturated with beef extract. Recently, a new kind of membrane filter made of polyether sulfone (PES) has become available commercially. The manufacturers claim that such membranes allow the filtration of greater volumes of sample than those made of PVDF. We compared the filtration rate and volume that could be filtered before clogging for these two membranes. The bacteriophage and enterovirus counts were then compared in sewage after filtration through the two membranes. There were no differences in virus recovery after filtration, but PES membranes allowed a higher filtration rate and clogged more slowly. The use of PES membranes is recommended.     

Size and filterability of human and hamster pulmonary macrophages exposed to cigarette smoke

Pulmonary alveolar macrophages (PAM) obtained from healthy human cigarette smokers generated greater pressure in filtration through small cylindrical pores than PAM from nonsmoking controls. A well standardized hamster smoking model was employed to study the structural basis for the impaired PAM filtration accompanying cigarette smoke exposure. Hamsters also demonstrated increased PAM filtration pressure through cylindrical pores less than half a cell diameter in size after inhalation of cigarette smoke, but not after exposure to vapor phase smoke that had been strained through a particle filter. Cigarette smoker PAM were equally filterable as control through larger diameter channels, and showed comparable improvements in filterability with cytochalasin B treatment. Altered PAM filtration was associated with the formation of characteristic cytoplasmic smoker inclusions, an increase in cell size, and loss of redundant, ruffled surface membrane. The study of smoker and control PAM separated into different sizes on the basis of variations in cell density suggested that discrepancies in cell size were insufficient to explain the filtration disparity. A loss of availability of surface membrane for deformation appeared to be the most important factor responsible for the impaired filtration.     

Kinetics of the Glomerular Ultrafiltration in the Rat Kidney. A Theoretical Study

The glomerular filtration process was evaluated theoretically from micropuncture data obtained from Sprague-Dawley rats. The hydrostatic pressures in the glomerular capillaries and Bowman's space minus the oncotic pressure in systemic plasma gave the net driving force at the proximal end of the glomerular capillary. From the single nephron filtration fraction the mean net driving force over the glomerular membrane was calculated to be 20 mm Hg during normotension, decreasing to 12 mm Hg during a perfusion pressure of 80 mm Hg. The hydraulic permeability for one glomerulus was 0.7-0.8 nl/min. 100g b. wt. mmHg. The pressures at the distal end of the glomerular capillaries were 13 and 6 mm Hg under the above two conditions, indicating non-equilibrium of the filtration process at the end of the glomerular capillary. It was shown that the glomerular filtration rate is mainly influenced by the driving pressures. During hypotension an increased plasma flow dependency was evident. Brenner et al. found a filtration equilibrium and a plasma flow dependent glomerular filtration rate in a mutant Wistar rat strain. The discrepancy between their results and ours is due to the low glomerular plasma flow and hydrostatic pressures in the Wistar rats. It is concluded from our results that both pre- and postglomerular resistances may influence the glomerular filtration rate and glomerular plasma flow independently.     

Evaluation of lysis filtration as an adjunct to conventional blood culture.

A lysis filtration system was used in conjunction with conventional broth culture for 1112 blood cultures. The system, which entailed collection of 5 ml of blood into bottles containing 50 ml isotonic phosphate buffer, Tween 20, and Rhozyme with subsequent filtration using a 0.45 micron Millipore field monitor, was simple and economical to use. Positive results were obtained earlier than those obtained with conventional broth cultures, and almost twice as many fungi and yeasts were isolated. Some fastidious organisms such as Haemophilus influenzae and Streptococcus pneumoniae however, were not recovered from the lysis system, and contaminants in lysis cultures were three times as common as in conventional culture. The number of positive cultures was also adversely influenced by incubation of the blood lysis mixture overnight before filtration. We conclude that this lysis filtration system is useful as an adjunct to conventional broth culture in selected patients in cases in which filtration can be carried out soon after collection.     

Limitations in the determination of total filtration of x-ray tube assemblies

A brief introduction is given to various inferential methods for the determination of total filtration of x-ray tube assemblies. The HVL method, which is most commonly used, was investigated in detail. The influence of a number of parameters on the relationship between filtration and HVL was systematically studied. The results clearly show that the HVL method only provides a rough estimate for filtration with errors of typically +/- 30%. As a consequence, quality assurance checks on the acceptance and status test level must consider the limited accuracy of this method. Changing requirements from minimum filtration to minimum HVL permitted at particular kVp does not considerably improve the situation.     

Influence of uranyl nitrate upon tubular reabsorption and glomerular filtration in blood perfused isolated dog kidneys

The early changes in tubular reabsorption, glomerular filtration, blood flow and sodium excretion brought about by uranyl nitrate were investigated in isolated, bloodperfused dog kidneys during water diuresis. No significant changes in urine volume were observed; the decrease in fluid reabsorption was counterbalanced quantitatively by a reduction in glomerular filtration rate; only a small diminution of renal blood flow was found. The balance between reabsorption and filtration was observed as well when angiotensin action or prostaglandin synthesis were inhibited. The intrarenal venous pressure rose, suggesting that an increase in proximal intratubular hydrostatic pressure caused the decrease in filtration. Tubular back-leak of fluid, or backdiffusion, induced by the toxin, were excluded. The presence of natriuretic compounds in the urine was confirmed.     

Concentration and identification of Cryptosporidium sp. by use of a parasite concentrator

A new disposable plastic tube device and technique for ovum and parasite concentration, with upper and lower chambers separated by a fine screen, was compared with the standard gauze and open-funnel filtration technique as well as with the technique of direct smearing with an acid-fast stain. The new concentrator was distinctly superior to gauze filtration in concentrating Cryptosporidium sp. oocysts. Processing time was reduced. The new technique was less messy and as a closed system was considered to be much safer than gauze filtration.     

微孔过滤实验中红细胞变形性的表达

在用微孔过滤法测定红细胞变形性的实验中,为了便于定量地评定和比较红细胞变形性,我们对目前常用的表达变形性的各种物理参数和人为定义的指标的确切含义和适用性进行了较为全面的分析和讨论。认为红细胞平均过孔时间(或相对过孔阻力）和堵孔红细胞比例分别用于表达红细胞平均变形性和堵孔特性比较合适。早期研究力求避免过滤过程中红细胞堵塞膜孔现象对实验的干扰,但通过对近年来不同实验方法下实验结果的分析,发现红细胞堵孔特性蕴涵着重要信息,反映了红细胞变形性的不同方面。表达这一特性的参数对一些物理、化学,尤其是病理因素引起的变形性改变,比平均变形性参数更敏感。