Expression of vascular endothelial growth factor and its receptors in rats with protein-overload nephrosis

BACKGROUND: Based on the fact that vascular endothelial growth factor (VEGF) increases vascular permeability, it is speculated that VEGF might be involved in the development of proteinuria, although this remains unconfirmed. The production and site of action of VEGF remains unclear in nephrotic renal diseases. METHODS: Non-radioactive in situ hybridization was performed to examine the expression of VEGF mRNA and its receptors, flt-1 and KDR/flk-1, in a rat model of nephrosis induced by intraperitoneal injection of bovine serum albumin (BSA). Saline injected rats were served as control animals. RESULTS: Neither morphological changes nor deposition of immunoglobulin or complement were observed in our model. Proteinuria developed, reaching a maximum level in rats injected with BSA for 3 days, followed by persistent proteinuria until day 14. The expression of mRNA for VEGF and the two receptors was markedly upregulated in glomeruli of BSA-induced nephritis compared with the control group. VEGF mRNA was localized in glomerular cells, including cells in mesangium, visceral and parietal epithelial cells. In contrast, flt-1 mRNA and KDR/flk-1 mRNA were expressed on glomerular endothelial cells and cells in mesangium. The ratio of glomerular cells positive for VEGF mRNA and its receptors mRNA increased proportionately with the severity of proteinuria. Immunohistochemistry for ED-1 and proliferating cell nuclear antigen showed no significant increase in infiltrating macrophage or cellular proliferation. Conclusions: Our results suggest that altered glomerular expression of VEGF and its receptors is not associated with proliferation of endothelial cells, but rather with proteinuria in BSA-induced nephritis in rats. VEGF may play a different role in different renal diseases.     

Renal proliferative arteriopathies and associated glomerular changes: a light and electron microscopic study

This presentation reports the light and electron microscopic findings relating to the vascular and glomerular changes in the kidney in a series of 25 patients having malignant hypertension, the hemolytic-uremic syndrome, scleroderma, or toxemia of pregnancy. The pathologic changes were generally similar in each of the diseases studied, the changes being related more to the severity and duration of injury than to the specific disease. Vascular narrowing was due mainly to intimal thickening, and by light microscopy the lesions were categorized as onionskin, mucinous, or fibrous with or without associated elastosis. Intimal erythrocyte extravasation, fibrinoid necrosis, and luminal thrombosis were also seen. Electron microscopy provided additional morphologic information: Myointimal cells were found to be the cellular component in each type of intimal thickening; it was possible to distinguish collagen from large intimal accumulations of basement membrane material; mucinous intimal material was characterized ultrastructurally; and fibrinoid necrosis was identified as a lesion inconstantly associated with cellular necrosis and consisting mainly of fibrinoid material and small deposits of fibrin. It seems likely that there is a common pathogenesis for intimal thickening in a variety of diseases and that this involves endothelial cell damage and increased permeability, leakage of serum and erythrocytes into the intima, and a healing reaction of the vessel wall was developing from migration of smooth muscle cells into the intima with subsequent myointimal cell proliferation and fibrogenesis. A common glomerular change in all diseases studied was a striking accumulation of electron lucent material between the endothelium and the lamina densa of the basement membrane. This lesion was interpreted as a manifestation of acute ischemia.     

Nuclear distribution in Alternaria tenuis

Renal functional abnormalities constituting the syndrome of postobstructive diuresis imply both altered tubular and glomerular membrane properties. To determine the morphologic and ultrastructural correlates of this disorder a rat model was developed and 32 postobstructed kidneys were studied by light and electron microscopy at the midpoint of diuresis and compared to 22 controls. The abnormal morphology was: dilated distal tubules and collecting ducts, isolated proximal and distal tubule cells that allowed free access of luminal contents to the basement membrane, widened terminal bars and intercellular spaces, thickening of the glomerular basement membrane and, depending upon the portion of nephron, normal or reduced adenosine triphosphatase and acid phosphatase content. In order to confirm the functional nature of the nephrons studied as well as to assess glomerular and tubular permeability, horseradish peroxidase and cytochrome c were infused. These tracers, normally permeable to the glomerular basement membrane, were found in the intercellular spaces and to a lesser extent within cell organelles in the postobstructed diuretic animals whereas controls demonstrated a retarded filtration of horseradish peroxidase, no tracer in the intercellular spaces and large amounts of tracer contained within cell organelles. Absence of enzyme activity in the medulla and reduced dark to light cell ratios in the cortical collecting ducts correlated with prior observations made by others of diminished concentration and acidification processes, respectively. An increase in adenosine triphosphatase activity and renin granules within the juxtaglomerular cells indicated increased renin activity. These observations suggest that the renal functional abnormalities of postobstructive diuresis are attributable to altered glomerular and tubular permeabilities as well as with changes in metabolic activity.     

Centralis superior raphe, reticularis pontis nuclei, and sleep-wakefulness cycle in cats

It has been reported that circumferential mesangial interposition (CMI) is an important morphological feature suggesting the progression of glomerulosclerosis in glomerular disease. The relation between CMI and its associated lesions was investigated in various renal diseases by electron microscopy. In 276 patients, of whom the glomeruli were observed by electron microscopy, CMI was observed non-specifically in 48 patients with various glomerular diseases (IgA nephropathy, 11; non-IgA glomerulonephritis, 1; membranoproliferative glomerulonephritis, 8; membranous nephropathy, 5; lupus glomerulonephritis, 12; toxemia of pregnancy, 2; diabetic nephropathy, 7; mitomycin nephropathy, 1; and Seckel's dwarfism patients, 1). The glomeruli with CMI showed a marked increase in mesangial matrix, as well as various grades of mesangial cell proliferation. Mesangiolysis associated with subendothelial widening was observed in a lesion of CMI in most cases. This phenomenon appears to be an initial alteration that conducts proliferated cells to the peripheral portion of a capillary loop. Localized severe thinning of the glomerular basement membrane was frequently combined with CMI, particularly in IgA nephropathy patients. Endothelial cells were occasionally interposed into the widened subendothelial space. Subendothelial deposits were noticed in the CMI lesion, particularly in MPGN patients. In conclusion, in the process of glomerulosclerosis progression in various glomerular diseases, lytic and edematous changes initially occur in the mesangio-subendothelial system (mesangiolysis and subendothelial widening), then proliferating mesangial cells extend into the widened space (between GBM and endothelial cells), and reach the peripheral portion of a capillary loop.     

Detecting panic disorder in emergency department chest pain patients: a validated model to improve recognition

Non-insulin-dependent diabetes mellitus (NIDDM) and the renal disease attributable to it have been characterized extensively in the Pima Indians, a group of American Indians who form the Gila River Indian Community in Arizona. Both of these diseases are common in this community, and their onset and duration are known with greater certainty than in other populations because research examinations, which include oral glucose tolerance tests and measures of urinary protein excretion, have been performed frequently on most members of the population for the past 30 years. Studies of glomerular structure and hemodynamic function in diabetic Pima Indians indicate that glomerular hyperfiltration often develops at the onset of NIDDM and remains elevated until after overt nephropathy appears. Structurally, the glomeruli in subjects with microalbuminuria are not clearly distinguishable from those in subjects with normoalbuminuria, but macroalbuminuria is characterized by extensive glomerular sclerosis, mesangial expansion, and widening of epithelial cell foot processes that together lead to a rapid decline in the glomerular filtration rate. The decline in glomerular function in subjects with macroalbuminuria is due both to a loss of ultrafiltration surface area and to reduction in glomerular hydraulic permeability.     

Glomerulonephritis

Advances in cell and molecular biology have generated fresh insights into the mechanisms of glomerular injury, a field with very few substantial advances in the past 20 years. Currently, the nature of renal antigens involved in the immune reaction is being identified, as in the case of Goodpasture antigen. Many recent studies focus on T-cell and macrophage functions in glomerulonephritis that initiate acute inflammatory events and determine glomerular disease progression. Recent data established that after inflammatory cell migration to the glomerulus, subsequent damage depends on cell adhesion to cytokine-activated endothelial cells, a process mediated by a variety of specialized molecules. It seems easy to predict that within the next few years these studies will have a major impact on the way these diseases are treated. Already, evidence indicates that, in experimental animals, monoclonal antibodies blocking adhesive molecules prevent or reduce glomerular damage. Cytokines and growth factors, by promoting resident cell proliferation and modulating extracellular matrix synthesis and metabolism, modulate acute glomerular injury and subsequent scarring. Recent studies have established that glomerular injury is related to urinary protein excretion, an issue that has been approached in humans by combining studies on barrier size selectivity with morphometry. An emerging concept suggests that leaking of proteins through the glomerular capillary has an intrinsic renal toxicity that is likely due to proximal tubular over-reabsorption of the abnormally filtered macromolecules. Data are also accumulating that may soon link the degree of tubulointerstitial injury with glomerular damage and subsequent development of renal scarring.     

Individual differences in boys' and girls' timing and tempo of puberty: Modeling development with nonlinear growth models.

Pubertal development is a nonlinear process progressing from prepubescent beginnings through biological, physical, and psychological changes to full sexual maturity. To tether theoretical concepts of puberty with sophisticated longitudinal, analytical models capable of articulating pubertal development more accurately, we used nonlinear mixed-effects models to describe both the timing and tempo of pubertal development in the sample of 364 White boys and 373 White girls measured across 6 years as part of the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Individual differences in timing and tempo were extracted with models of logistic growth. Differential relations emerged for how boys' and girls' timing and tempo of development were related to physical characteristics (body mass index, height, and weight) and psychological outcomes (internalizing problems, externalizing problems, and risky sexual behavior). Timing and tempo are associated in boys but not girls. Pubertal timing and tempo are particularly important for predicting psychological outcomes in girls but only sparsely related to boys' psychological outcomes. Results highlight the importance of considering the nonlinear nature of puberty and expand the repertoire of possibilities for examining important aspects of how and when pubertal processes contribute to development. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Role of endothelin in the development of glomerulosclerosis

Enhanced filtered load of proteins in glomerular diseases (overload proteinuria) results in significant increase in the rate of proximal tubular uptake that is true for all proteins tested so far, including albumin. The excess concentration of absorbed proteins in lysosomes may itself lead to cellular damage by spillage of lysosomal enzymes to the cytosol. In vitro evidence is also available of functional alteration of these tubular cells, including upregulation of genes encoding for endothelin-1 (ET-1) and other inflammatory mediators, when they are overloaded in culture with proteins or lipoproteins. This could affect renal function and structure given the inflammatory, growth factor, and vasoactive properties of ET-1. Findings in several experimental models of proteinuric progressive nephropathies have indeed documented enhanced renal ET-1 gene expression and excretion of the peptide into the urine which correlated with proteinuria and the degree of glomerular and tubulointerstitial damage.     

Modern antihypertensive treatment and the progression of renal disease

BACKGROUND: In animal models of hypertension, the resistance state of the preglomerular (afferent) and postglomerular (efferent) capillary arterioles may determine whether a particular form of antihypertensive therapy will spare the kidney from hemodynamic-mediated glomerular injury. In experimental models of renal disease with impaired autoregulation, control of systemic blood pressure is a prerequisite for normalizing glomerular capillary hydraulic pressure. CLINICAL STUDIES: In humans, effective blood pressure control reverses renal hemodynamic abnormalities in hypertensive patients, reduces microalbuminuria in essential hypertensive, nondiabetic, and diabetic renal diseases, and attenuates but does not prevent the progression of nondiabetic and diabetic renal disease. Although some researchers have concluded that angiotensin converting enzyme inhibitors are the renal protective drugs of choice, these pronouncements are not based on clinical trials correlating specific drug-mediated changes in albumin or protein excretion with the longitudinal assessment of glomerular filtration rate (GFR), permitting derivation of a slope-defining change in GFR, and/or the longitudinal assessment of renal structure (i.e. renal biopsy). Definitive clinical trials have not been reported. It is important to recognize that an elevated serum creatinine is a powerful predictor of mortality and that, in most patients, death is caused by a cardiovascular or cerebrovascular event, rather than by renal failure. CONCLUSION: Because morbidity and mortality of essential hypertension and nondiabetic or diabetic renal disease is related primarily to cardiovascular or cerebrovascular events, the antihypertensive 'drugs of choice' should be those that reduce these risks, prevent or regress target-organ damage, and optimize treatment of concomitant diseases.     

Design and validation of a new image analysis method for automatic quantification of interstitial fibrosis and glomerular morphometry

Interstitial fibrosis and morphologic changes in kidney glomeruli, the structural effects of many diseases, lead to significant pathologic alterations. A reliable and objective method to accurately quantify the extent of interstitial fibrosis and the degree of alteration in glomerular morphology is needed for both clinical practice and experimental work. The morphometric methods of quantification described to date are time-consuming and require trained personnel. This article describes the design and validation of an image analysis-based application (Fibrosis HR) for automatically and rapidly quantifying interstitial fibrosis and glomerular morphology in the same tissue section stained with Sirius red. The image processing algorithms described herein automatically segment interstitial fibrosis and mesangial matrix using automatic thresholding and morphologic filtering. The glomerular region is extracted by a simple interactive step and an automatic mathematical morphology algorithm, whereas the glomerular tuft is automatically segmented with automatic thresholding and a sequence of Boolean and mathematical morphology operations. All extracted areas are automatically quantified in absolute (microm2) and relative (%) values. For validation of this method, interstitial fibrosis, mesangial matrix, and glomerular and glomerular tuft areas were manually segmented and their quantifications statistically compared with those obtained automatically. Statistical analyses showed significant intra- and interoperator variability in manual segmentation of interstitial fibrosis, mesangial matrix, and glomerular tuft areas. Automatic quantifications of the same areas did not differ significantly from their mean manual evaluations. There was no significant intra- or interoperator variability in the interactive identification of the glomerular region. In conclusion, Fibrosis HR produces robust, fully reproducible, accurate, objective, and reliable quantifications, which facilitate the evaluation of in vivo experimental models of renal interstitial and glomerular pathologies and improve the accuracy of clinicopathologic analyses of renal diseases in human biopsies.     

Involvement of reactive oxygen species in kidney damage

There is considerable evidence suggesting that reactive oxygen species (ROS) are implicated in the pathogenesis of ischemic, toxic, and immunologically-mediated renal injury. In experimental renal ischemia, ROS sources include the electron transport chain, oxidant enzymes (xanthine oxidase), phagocytes, and auto-oxidation of epinephrine. ROS cause lipid peroxidation of cell and organelle membranes and, hence, disruption of the structural integrity and capacity for cell transport and energy production, especially in the proximal tubule segment. In experimental immune glomerulonephritis, ROS are generated by both infiltrating blood-borne cells (polymorphonuclear leukocytes and monocytes) and resident glomerular cells, mainly mesangial cells. Their formation results in morphologic lesions and in modifications of glomerular permeability to proteins through activation of proteases and reduction of proteoglycan synthesis. Additionally, they promote a reduction in glomerular blood flow and glomerular filtration rate through liberation of vasoconstrictory bioactive lipids (prostaglandins, thromboxane, and platelet activating factor) and, possibly, inactivation of relaxing nitric oxide. Further studies are needed to address the role of ROS in human glomerular diseases.     

Reading skills in hyperlexia: A developmental perspective.

Hyperlexia is characterized by advanced word-recognition skills in individuals who otherwise have pronounced cognitive, social, and linguistic handicaps. Language, word recognition, and reading-comprehension skills are reviewed to clarify the nature and core deficits associated with the disorder. It is concluded that hyperlexia should be viewed as part of the normal variation in reading skills, which are themselves associated with individual differences in phonological, orthographic, and semantic processing, short-term memory, and print exposure. A compulsive preoccupation with reading may also be crucial to the development of a hyperlexic reading profile. A theoretical framework, based on recent connectionist models of reading development, is described. This perspective provides a satisfactory account for how individual differences in a number of different skills can lead to a variety of manifestations of reading behavior, including hyperlexia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pardaxin, a new pharmacological tool to stimulate the arachidonic acid cascade in PC12 cells

BACKGROUND: Calcium channel blockers (CCBs) are known to have differential effects on both changes in proteinuria as well as progression of diabetic nephropathy. No clinical study, however, has evaluated whether the differential antiproteinuric effects of CCBs may be explained by their effect on glomerular membrane permeability. We, therefore, tested the hypothesis that certain subclasses of CCBs reduce proteinuria by changing size selectivity of the glomerular membrane, hence changing its permeability. METHODS: Twenty-one patients with type 2 diabetes and the presence of nephropathy with hypertension were randomized to receive either diltiazem CD or nifedipine GITS after baseline data for mean systolic and diastolic pressure, urinary protein excretion, glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearances were obtained. Glomerular filtration rate, renal plasma flow, neutral dextran and IgG clearance were measured every three months, arterial pressure and heart rate every month. Patients were followed for 21 months. RESULTS: At 21 months, both patient groups had similar levels of blood pressure control, however, only the diltiazem group had a change in proteinuria (4+/-10%delta, nifedipine vs. -57+/-18%delta, diltiazem; P < 0.001) with improvement in glomerular size selectivity and change in IgG clearance. CONCLUSIONS: These data support the hypothesis that CCBs that provide sustained reductions in proteinuria do so, in part, by improving glomerular size permselectivity.     

Cyclosporine protects glomeruli from FSGS factor via an increase in glomerular cAMP

Cyclosporine (CsA) administration to patients with recurrent focal segmental glomerulosclerosis (FSGS) after transplantation results in remission of proteinuria. We have shown that sera from patients with recurrent FSGS can increase the glomerular albumin permeability (Palbumin) and that increase in glomerular cAMP levels can alter the permeability characteristics of glomeruli in vitro. The purpose of this study was to determine if the increased glomerular levels of cAMP were related to the protective effects of CsA on an increase in Palbumin by FSGS sera. Glomeruli from Sprague-Dawley rats following intraperitoneal administration of CsA (25 mg/kg/day), cremophore (25 mg/kg/day), or saline for 5 days were incubated with 1:50 dilution of serum from three FSGS patients or with pooled normal human serum prior to calculation of Palbumin. Glomerular cAMP was measured by radioimmunoassay. Glomerular ultrastructural changes were assessed by transmission electron microscopy (TEM). Serum from three FSGS patients markedly increased Palbumin of glomeruli from saline or cremophore treated rats (saline, 0.68+/-0.08; 0.72+/-0.07; 0.70+/-0.07; and cremophore, 0.79+/-0.05; 0.81+/-0.02; 0.79+/-0.01; n=25 glomeruli in each group). In contrast Palbumin of glomeruli from CsA treated rats was not increased by any of the three FSGS sera tested (0.03+/-0.02; 0.04+/-0.05; 0.02+/-0.07, n=25 glomeruli in each group). Glomerular cAMP (pmol/mg of protein) increased 5 fold in CsA treated rats (328+/-26; 5 rats) compared with cremophore or saline treated rats (87+/-24 and 65+/-23, P<0.01; 5 rats in each group). The glomerular basement membrane appeared to be thickened and the lamina densa had an irregular appearance after treatment with CsA. No ultrastructural changes of glomerular epithelial or endothelial cells were evident. We conclude that CsA may have a direct protective effect on the glomerular filtration barrier in FSGS. We postulate that increased levels of glomerular cAMP by CsA may play an important role in protecting the glomerular Palbumin effect of the FSGS factor and may contribute to remission of proteinuria in FSGS patients.     

Impairment of endothelial and subendothelial sites by a circulating plasma factor associated with minimal change disease

BACKGROUND: The pathogenesis of albuminuria in minimal change disease (MCD) is unknown. A human plasma factor (denoted as 100KF) is able to induce minimal change-like glomerular alterations, i.e. loss of glomerular sialoglycoproteins and decreased expression of glomerular ecto-ATPase, following in vitro incubation with kidney tissue. In addition, increased (selective) permeability for plasma proteins occurs after perfusion of 100KF into the rat kidney ex vivo. As in kidney tissue from subjects with minimal change disease, subendothelial injury has also been observed, i.e. reduced anionic sites in the lamina rara interna, the question was raised whether injury induced by the plasma factor 100KF involves vascular endothelium or subendothelial matrix of the glomerular capillary wall. METHODS: Permeability studies were carried out by using confluent endothelial monolayers (HUVEC) cultured on a standard two-compartment system. The permeability for a macromolecular marker (horse radish peroxidase) was tested following incubation of the monolayers with either the native plasma factor 100KF or the control factor (heat-inactivated 100KF), in combination with histochemical evaluation of the cells for ecto-ATPase expression. Also quantification of glomerular anionic sites at the ultrastructural level was carried out, after ex vivo perfusion of 100KF or control factor into rat kidneys. RESULTS: The plasma factor 100KF is able to increase the permeability of human endothelial monolayers for macromolecules in a dose-dependent manner (relative increase 122.4 +/- 24, 178.4 +/- 34 and 236.1 +/- 58% after preincubation with 0.05; 0.5 and 1.5 mg/ml 100KF respectively), concomitant with induction of minimal change-like histochemical alterations such as reduced expression of ecto-ATPase. The number of anionic sites in the lamina rara interna of the glomerular capillary wall is significantly diminished following perfusion with the plasma factor 100KF versus control factor (7.58 +/- 1.60 versus 12.57 +/- 2.05 per 1000 nm; P < or = 0.02); in contrast to the lamina rara externa (22.71 +/- 3.15 versus 22.27 +/- 2.92 per 1000 nm; statistically not significant). CONCLUSIONS: Endothelial cells and subendothelial matrix along the glomerular filtration barrier may be considered as target structures for the plasma factor 100KF, leading to initial minimal change-like alterations associated with glomerular albumin leakage.     

质子交换膜电解制氢氢气渗透研究进展

由于膜的吸水特性,高压质子交换膜(PEM)制氢（尤其是差压式,氢侧高压/氧侧常压）存在氢气渗透问题,影响电解堆的运行安全与效率。基于菲克定律描述的渗透通量与渗透率、分压差的关系,综述了温度/压力、膜水合程度、氢气分压差对氢气渗透的影响规律。在常规运行压力范围（3.5 MPa）内,扩散系数与溶解度主要受温度影响,温度升高则渗透率增大;氢气渗透率随膜水合程度的增加而增大;氢气分压差对渗透的影响表现出线性（渗透池环境）与非线性（电解制氢环境）两种关系,非线性可能源于膜透水性提升与水通道结构改变引起的对流渗透。考虑到电解制氢实际工况存在电流,综述了电流密度对氢渗透的影响,氢气渗透率随运行电流密度的升高而增大,氢过饱和是可能的影响机理,高电流密度下氢过饱和度升高,导致氢气通过膜的渗透增加。      

Stability and leakiness: opposing challenges to the glomerulus

The complex architecture of the glomerular tuft is stabilized by several mechanisms. The basic system consists of the GBM and the mesangium maintaining the branching pattern of the capillary network. Superimposed are the podocytes, which appear to take effect by two mechanisms. First, podocytes contribute to the stabilization of the capillary folding pattern by supporting the angles between neighboring capillaries. Second, podocyte foot processes fixed to the outer aspect of the GBM probably function as contractile patches counteracting the elastic distension of the GBM. Simultaneously, the pattern of foot process interdigitation underlies the elaboration of a filtration slit and is thus pivotal for the high hydraulic permeability and the specificity of the glomerular filter. The loss of this pattern-commonly termed "foot process effacement" or "foot process fusion"-is frequently found in pathological situations and results in a decrease in permeability and impairment in specificity. On the other hand, foot process effacement is associated with prominent hypertrophy of the contractile apparatus of podocytes, suggesting an increased ability to generate forces counteracting capillary expansion. Thus, foot process effacement appears as an adaptive change in podocyte phenotype giving priority to the support function of podocytes for the prize of reducing the specific permeability.     

Development of a novel microperfusion chamber for determination of cell membrane transport properties

A novel microperfusion chamber was developed to measure kinetic cell volume changes under various extracellular conditions and to quantitatively determine cell membrane transport properties. This device eliminates modeling ambiguities and limitations inherent in the use of the microdiffusion chamber and the micropipette perfusion technique, both of which have been previously validated and are closely related optical technologies using light microscopy and image analysis. The resultant simplicity should prove to be especially valuable for study of the coupled transport of water and permeating solutes through cell membranes. Using the microperfusion chamber, water and dimethylsulfoxide (DMSO) permeability coefficients of mouse oocytes as well as the water permeability coefficient of golden hamster pancreatic islet cells were determined. In these experiments, the individual cells were held in the chamber and perfused at 22 degrees C with hyperosmotic media, with or without DMSO (1.5 M). The cell volume change was videotaped and quantified by image analysis. Based on the experimental data and irreversible thermodynamics theory for the coupled mass transfer across the cell membrane, the water permeability coefficient of the oocytes was determined to be 0.47 micron. min-1. atm-1 in the absence of DMSO and 0.65 microns. min-1. atm-1 in the presence of DMSO. The DMSO permeability coefficient of the oocyte membrane and associated membrane reflection coefficient to DMSO were determined to be 0.23 and 0.85 micron/s, respectively. These values are consistent with those determined using the micropipette perfusion and microdiffusion chamber techniques. The water permeability coefficient of the golden hamster pancreatic islet cells was determined to be 0.27 microns. min-1. atm-1, which agrees well with a value previously determined using an electronic sizing (Coulter counter) technique. The use of the microperfusion chamber has the following major advantages: 1) This method allows the extracellular condition(s) to be readily changed by perfusing a single cell or group of cells with a prepared medium (cells can be reperfused with a different medium to study the response of the same cell to different osmotic conditions). 2) The short mixing time of cells and perfusion medium allows for accurate control of the extracellular osmolality and ensures accuracy of the corresponding mathematical formulation (modeling). 3) This technique has wide applicability in studying the cell osmotic response and in determining cell membrane transport properties.