Acute changes in histopathology and intravascular imaging after catheter-based renal denervation in a porcine model.

OBJECTIVES: We first aimed to identify the histopathological changes occurring immediately after renal denervation (RDN) with radiofrequency energy, and then to assess the feasibility of determining procedural success using currently available clinical intravascular imaging techniques. BACKGROUND: Catheter-based RDN has been used as an alternative therapy for hypertension. However, no practical endpoint to determine procedural success during treatment has been established. METHODS: A total of 39 ablation lesions were induced in vivo in eight porcine renal arteries and a total of 15 ablation lesions were induced ex vivo in five excised porcine renal arteries with a radiofrequency delivery device. Acute histological changes and appearance on intravascular imaging of the lesions were investigated with light microscopy, transmission electron microscopy, intravascular ultrasound (IVUS), and optical frequency domain imaging (OFDI). RESULTS: Marked changes were noted in media, adventitia, and perirenal-arterial nerves immediately after in vivo ablation. Changes visualized on IVUS were characterized by focal adventitial thickening comprising a relatively echogenic layer around a heterogeneously hypoechoic interior region, and on OFDI as disappearance of the external elastic membrane signals with high scattering of signals in the surface layer. The changes after ex vivo ablation were histopathologically identical to those from in vivo ablation. There were statistically significant positive correlations in measured dimensions (area, depth, width, and diameter) of ablation lesions between histopathology and IVUS/OFDI findings (Pearson correlation coefficients = 0.69-0.77). CONCLUSIONS: These findings suggest that observation of treated renal arteries by IVUS or OFDI immediately after RDN improves the success rate of RDN.

Unusual lamellar calcifications in two rare cases of splenic aneurysms associated with fibromuscular dysplasia.

Fibromuscular dysplasia (FMD) of the splenic artery is a rare underdiagnosed condition. Here, we report two cases of FMD affecting the splenic artery: one alone and one concomitantly with the renal artery. Histology revealed fibromuscular thickening of the media layer alternating with a circumferential calcification of the whole artery thickness. Ultrastructurally, FMD showed matrix vesicles and dense bodies in the extracellular matrix. A diagnosis of FMD with calcification was made. This is the first report to document circumferential lamellar calcifications alternating with the more typical fibrotic medial areas in the rare FMD localized to splenic artery.

Ultrastructural pathological features of unilateral renal artery stenosis in the rats.

Renal artery stenosis (RAS) is one of the main reasons of renovascular hypertension and its pathogenesis remains unclear. In this study, we aimed to investigate histopathological characteristics in a rat model of RAS. Sprague-Dawley (SD) male rats were randomly divided into unilateral RAS group (Model group, n=30) and Sham group (n=30). The left renal artery was clamped with miniature silver clip for the rats in RAS group, while it was exposed but not clamped for the rats in Sham group. After the surgery, the rats were randomly divided into ten subgroups based on the time after surgery (n=3). Blood pressure, urinary albumin/creatinine ratio, and serum albumin and creatinine levels were measured. The kidneys were dissected for histological and electron microscopy analysis. The results showed that systolic blood pressure was significantly higher since 4 weeks after surgery compared to before surgery. There were no significant differences in urinary albumin/creatinine ratio as well as serum albumin and creatinine levels in Model and Sham groups. During the early acute renal ischemia the stenotic kidney exhibited acute tubular injury, podocyte injury and some crescent formation, and the main components of crescent are podocytes. Although renal tubules and vascular lesions gradually recover and crescent disappears, segmental lesions of podocyte appear in the late stage of RAS. These data reveal ultrastructural pathological changes during RAS, and suggest the role of podocyte lesions in chronic renal ischemia.

Organ Specificity and Functional Relevance of the Arterial Structure: A Comparative Study in the Kidney and the Skeletal Muscle with Electron Microscopy.

The differences in circulation among various organs are well known, but the structural differences have only been poorly investigated. In the present study the wall structure of arteries was observed with electron microscopy in rat kidney and skeletal muscle. The wall thickness was almost equal in both organs at about 40 µm in luminal diameter, while it was relatively thin in the larger arteries and thick in the smaller arteries in the kidney compared with that in the skeletal muscle. The smooth muscle cells were regularly arranged in parallel in circular or slightly spiral orientation in the kidney, whereas those in the skeletal muscle were irregularly arranged in heterogeneous orientations. Extracellular matrices were more abundant in the arterial media in the skeletal muscle than in the kidney. The inner elastic lamina was continuous in the kidney, and arranged in longitudinal bundles in the skeletal muscle. The adventitial collagen fibers were abundant and dense in the skeletal muscle, and were scattered in small bundles in the fluid-filled spaces in the kidney. While the arteries in the skeletal muscle are under severe mechanical stress during muscle contraction and dilate dramatically during exercise, those in the kidney regulate glomerular pressure almost constantly.

[Ultrastructural assessment of the role of dysangiogenesis in congenital hydronephrosis].

OBJECTIVE: To confirm the key role of vascular malformation by ultrasound examination and to make a more detailed study of the manifestations of dysnephro- and angiogenesis. SUBJECTS AND METHODS: The study enrolled 34 children aged 3 days to 7 years with congenital hydronephrosis, who were divided into 3 groups in accordance with the degree of renal hemodynamic disorders, the criterion for which was a resistive index (RI). RESULTS: The performed electron microscopic study revealed the signs of malformed vessels of all diameters, as well as hypoplastic changes in the renal parenchyma in children of all ages in all the groups. The most significant ultrastructural signs demonstrating a close correlation between dysangio- and dysnephrogenetic processes are the uniformity of structural failure in the glomerular and arteriolar basement membrane, which shows up in the irregularity of its thickness and obliteration of its layers, as well as the immaturity of endothelial cells of both glomerular and arteriolar capillaries (large sizes and a round shape). The important factor confirming their relationship is a direct correlation between the increased RI in all branches of the renal artery as hypoplastic changes progress in the parenchyma of hydronephrotic kidneys. CONCLUSION: The investigation demonstrated the interdependence of dysangio- and dysnephrotic processes in children with congenital hydronephrosis.

Endothelial dysfunction and subsequent decline in glomerular filtration rate in hypertensive patients.

BACKGROUND: Chronic kidney disease is a risk factor for cardiovascular disease, increasing all-cause mortality. Some evidence suggests that endothelial dysfunction is present in the early stages of renal insufficiency, but no data exist about its possible role in the progression of renal disease. Thus, we prospectively evaluated the effect of endothelial function on estimated glomerular filtration rate (eGFR) in essential hypertension. METHODS AND RESULTS: We enrolled 500 never-treated uncomplicated hypertensive subjects with serum creatinine < or =1.5 mg/dL. Endothelial function was measured by strain-gauge plethysmography during intra-arterial infusion of acetylcholine and sodium nitroprusside. eGFR was calculated by use of the Chronic Kidney Disease Epidemiology Collaboration equation. The annual rate of decline of eGFR (DeltaeGFR/y) was determined as the difference between the follow-up and baseline eGFR values, with this value divided by the time interval in years. During follow-up (92.3+/-36.2 months), mean DeltaeGFR/y was 1.49+/-1.65 mL . min(-1) . 1.73 m(-)(2), with no significant differences between men and women (1.55+/-1.72 versus 1.43+/-1.58 mL . min(-1) . 1.73 m(-)(2), respectively; P=0.455). This was correlated with acetylcholine-stimulated forearm blood flow (r=-0.256, P<0.0001), creatinine (r=0.141, P=0.001), systolic blood pressure (r=-0.103, P=0.01), and eGFR (r=0.092, P=0.020). In multivariable regression analysis, forearm blood flow and systolic blood pressure remained associated with change in eGFR. On average, eGFR changed by 0.37 mL . min(-1) . 1.73 m(-)(2) for each 100% change in forearm blood flow (P<0.001) and by 0.1 mL . min(-1) . 1.73 m(-)(2) for each difference of 10 mm Hg in systolic blood pressure (P=0.032). CONCLUSIONS: We demonstrated that acetylcholine-stimulated vasodilation and systolic blood pressure were associated with eGFR loss after adjustment for other cardiovascular risk factors and antihypertensive treatment.

Avaliação do fluxo na artéria renal fetal entre a 22ª e a 38ª semana em gestações normais / Evaluation of blood flow in the fetal renal artery between the 22nd and 38th week in normal pregnancies

OBJETIVO: descrever os valores encontrados para o índice de resistência (IR), índice de pulsatilidade (IP) e relação sístole/diástole (S/D) das artérias renais fetais em gestações sem complicações entre a 22ª e a 38ª semana de gestação e avaliar se estes valores variam durante esse período. MÉTODOS: estudo observacional, no qual 45 fetos de gestações não-complicadas foram avaliados na 22ª, 26ª, 30ª, 34ª e 38ª semanas gestacional. Os exames ultra-sonográficos com Doppler foram feitos por um único observador que utilizou aparelho com transdutor de 4 a 7 MHz. Para a aquisição do traçado de velocidade das artérias renais, uma amostra, com tamanho entre 1 e 2 mm, foi posicionada no terço médio da artéria renal para avaliação através da ultra-sonografia com Doppler pulsado, sempre por um único observador. A avaliação do IR, do IP e da relação S/D das artérias renais (direita e esquerda) foi realizada a partir de três ondas consecutivas utilizando-se o modo automático. Para demonstrar diferença nos valores dos índices com a variação da idade gestacional, comparamos os valores obtidos nas diferentes idades gestacionais através do teste ANOVA com medidas repetidas no tempo (repeated measures ANOVA) com pós-teste de Tukey. RESULTADOS: Não houve diferença significativa entre a artéria renal direita e a esquerda quando se compararam o IR, o IP e a relação S/D. Entretanto, observou-se modificação dos valores destes parâmetros entre a 22ª semana (IR=0,9 ± 0,02; IP=2,44 ± 0,2; relação S/D=11,6 ± 2,2; média ± desvio padrão do valor médio da artéria renal direita e esquerda) e a 38ª semana (IR=0,8 ± 0,03; IP=2,1 ± 0,2; relação S/D=8,7 ± 2,3) de idade gestacional. CONCLUSÕES: os parâmetros avaliados (IR, IP e relação S/D) apresentam valores decrescentes entre a 22ª e a 38ª semana, sem diferença entre os lados direito e esquerdo do feto.

PURPOSE: to describe values found for the resistance index (RI), pulsatility index (PI) and the systole/diastole (S/D) ratio of fetal renal arteries in non-complicated gestations between the 22nd and the 38th week, and to evaluate whether those values vary along that period. METHODS: observational study, where 45 fetuses from non-complicated gestations have been evaluated in the 22nd, 26th, 30th and 38th weeks of gestational age. Doppler ultrasonography has been performed by the same observer, using a device with 4 to 7 MHz transducer. For the acquisition of the renal arteries velocity record, a 1 mm to 2 mm probe has been placed in the mean third of the renal artery for the evaluation through pulsed Doppler ultrasonography. The measurement of RI, PI and S/D ratio from three consecutive waves was performed with the automatic mode. To detect significant differences in the indexes' values along gestation, we have compared values obtained at the different gestational ages, through repeated measures ANOVA, followed by Tukey's post-hoc test. RESULTS: There were no significant differences between the right and left renal arteries, when the RI, IP and S/D ratio were compared. Nevertheless, a change in the values of these parameters has been observed between the 22nd week (RI=0.9 ± 0.02; PI=2.4 ± 0.02; S/D ratio=11.6 ± 2.2; mean ± standard deviation of the combined mean values of the right and left renal artery) and the 38th week (RI=0.8 ± 0.03; PI=2.1 ± 0.2; S/D ratio=8.7 ± 2.3) of gestation. CONCLUSIONS: the parameters evaluated (RI, PI and S/D ratio) have presented decreasing values between the 22nd and 38th, with no difference between the fetus's right and left sides.

[Architectonic characteristics of the renal intraorgan arterial blood vessels in norm and in some cariovascular diseases].

The investigation included the study of 68 kidneys obtained from the persons of different age which died from mechanical asphyxia (control group) and 110 kidneys from the patients which died from cardiovascular failure that developed against a background of an ischemic heart disease, atherosclerosis, hypertension and their combinations. The studies were conducted using the complex of methods, which included macromicroscopic, histological, scanning electron microscopy and morphometry. In the patient group, vessel tortuosity, microvaricosities, contour irregularities and vessel deformations were found. Diameter of the vascular glomeruli and their number were reduced. Most pronounced changes in renal microvascular architectonics were detected in essential and renal hypertension, least expressed--in atherosclerosis with prevalent lesions in abdominal aorta. The disturbances of microcirculatory bed included juxtamedullary shunting, and excessive plethora or significant deterioration of blood supply to both cortex and medulla.

Renoprotective effect of early inhibition of the renin-angiotensin system in renal transplant recipients.

The aim of this work was to study the effect of early administration of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II type-I receptors blockers (ARB) on renal function and proteinuria in renal transplant recipients with good, stable renal function and mild proteinuria. Twenty four patients started ACEI/ARB therapy within 14 months after surgery (RAS-). Before (T0) and every month for 2 years after the initiation of ACEI/ARB we evaluated creatinine clearance (CrCl), proteinuria/day (UP), UP/CrCl (FUP), arterial blood pressure, and serum lipid levels. Twenty-eight patients who never received ACEI/ARB (RAS+) were studied in the same fashion. In the RAS+ CrCl was reduced after 2 years compared with T0 (64.5 +/- 2.6 vs 75.0 +/- 3.2 mL/min, P < .003); UP and FUP were both significantly increased (666 +/- 65 vs 132 +/- 20 mg/day 8.8 +/- 1.2 vs 2.6 +/- 0.6 mg/mL x 10(3); P < .001 and .002) compared with T0. Moreover, UP (P < .04), FUP (P < .03), and the percentage reduction of CrCl (11.4% +/- 5% vs 4.6% +/- 1.8%; P < .05) were greater in RAS+ than RAS- subjects at 2 years of the study. The values of other parameters did not show significant differences between the two groups. In conclusion, this study suggested that ACEI/ARB have renoprotective effects, when used in patients with good stable renal function and mild proteinuria. These drugs may play a role to prevent chronic allograft nephropathy.

The microscopic transitional zone between elastic and muscular arteries.

The microscopic transitional zone (TZ) is a segment of the arterial tree, where elastic-type wall architecture is relayed by one of muscular type. Since arterial TZ's are often sites of atherosclerotic and non-atherosclerotic lesions, this histologic anatomic substrate should be considered in the etiology and pathogenesis of vascular diseases. Herein, the topography and fine structure of TZ in renal arteries and carotid bifurcation (tripod) is described, based on randomly collected human autopsy specimens. The average length of the TZ was found to be 10 mm in the renal arteries. The TZ In the carotid tripod was localised only in the postbifurcational segments, where the length varied between 5 and more than 20 mm. In accordance with previous data from the literature, our results confirm a different ratio of scleroprotein components (elastin, collagen) and vascular smooth muscle cells (VSMC) in the microscopic TZ of arteries. Immunohistochemistry for lymphomonocytic antigens revealed no underlying inflammatory condition, especially no evidence of active cellular scavenging and an increased apoptotic rate of VSMC. We perceive the TZ as an arterial segment of reduced architectural compliance and, therefore, as a potential site of mechanotransductional failure leading to vascular diseases.

Double transgenic mice with type 1 diabetes mellitus develop somatic, metabolic and vascular disorders.

The double transgenic mice (dTg) were obtained by mating: (i) transgenic mice expressing the hemagglutinin of influenza virus under the insulin promoter with (ii) transgenic mice expressing specific T lymphocytes with receptor for the immunodominant epitope of the same virus. In this study we show that dTg mice developed type 1 diabetes mellitus associated with hyperglycemia, low level of plasma insulin, glucosuria, weight loss and approximately 90% mortality (at 3 months biological age). The membrane of red blood cells was more sensitive to osmotic shock in diabetic mice, compared to non-diabetic mice, assessing systemic oxidative stress. Both vasoconstriction and vasorelaxation of the renal arteries decreased significantly in diabetic mice (compared to the control group of non-diabetic mice) related to the phenotypic change of endothelium and smooth muscle cells within the artery wall. This animal model, may be used in developing various strategies to study pancreatic beta-cell function, as well as for a better metabolic control conducting to a reduced risk of vascular complications.

Structure and ultrastructure of microvessels in the kidney seen by the corrosion casting method.

Scanning electron microscopic observation of corrosion casts is the finest technique to describe spatial patterns of microvessels in many organs, giving a readily interpreted representation of their vascular architecture without interference from surrounding tissues. We focused on the renal cortex of guinea pigs to make an in-depth morphological analysis of structural and ultrastructural details left by the cells on the resin cast. In addition, we made a qualitative description of normal variants usually observed in glomerular disposition, arteriolar morphology or capillary arrangement in the space to shed more light on the relationship between vascular tissue and surrounding cells. The study also disclosed some examples of vascular adaption to physiological and pathological conditions occurring in renal microvessels such as many systems essential to flow regulation, filtration and excretory processes. At lower magnification, all major vessels can be readily distinguished: interlobar, arciform and interlobular arteries and veins, along with a web of peritubular and capsular capillaries. At higher magnification, the glomeruli become visible and the afferent and efferent arteries and the tortuosity the inner vessels can be distinguished. In some of them, the resin, due to the narrowing sizes, suddenly stopped leaving a half-casted glomerulus. This helped to reveal its internal circulation characterized by thin capillaries with a high degree of bi or trifurcation. In addition, we confirmed the close correspondence between cellular ultrastructural detail (pores, corrugations of cellular membrane, perivascular cell branches) and the impressions left on the resin visible only at high magnifications.

Development of gold stents for the treatment of intracranial aneurysms: an experimental study in a canine model.

BACKGROUND AND PURPOSE: Gold has often been used in medicine because of its radiopacity and flexibility. To perform stent-supported coil embolization of intracranial aneurysms, we prepared a gold stent and examined its flexibility, radiopacity, and thrombogenic properties in comparison with a stainless steel device implanted in vitro and in vivo. METHODS: Gold stents were prepared by plating gold on stainless steel stents as a template. Their mechanical properties and trackability in vitro were determined and compared with those of stainless steel stents of the same design. Twenty gold stents and two stainless steel stents were implanted in canine external carotid, vertebral, and renal arteries, as a muscle branch of the maxillary arteries, to examine their performance in vivo. RESULTS: The gold stent exhibited much less radial force and greater flexibility than the stainless steel stent. It also demonstrated superior trackability and radiopacity in the experimental endovascular procedures in canines. Histologic examination showed good patency of the stented artery with slight endothelial hypertrophy. CONCLUSION: Although there is still room for more radial strength, less influence on intimal hypertrophy, a more suitable flexibility, and a smoother surface, the superior trackability and radiopacity of gold stents seem to support use of this device for the endovascular treatment of intracranial aneurysms.

Making a zebrafish kidney: a tale of two tubes.

The kidney can be thought of as the pairing of two tubes: an epithelial tube (the nephron), carrying filtered blood and engaged in ion and water transport; and endothelial tubes (the blood vessels), delivering blood and carrying away recovered solute. The development of the nephron presents several interesting questions. How does an epithelial tube form and how is it patterned into functionally distinct components and segments? What guides the interaction between the vasculature and kidney epithelia? How are epithelial cell shape and lumen diameter maintained, and what goes wrong when kidney tubules balloon into cysts? Here, I outline the progress that has been made in answering these questions using the zebrafish pronephros as a simple, accessible model of nephron development.

Renal corpuscle of the sturgeon kidney: an ultrastructural, chemical dissection, and lectin-binding study.

The sturgeon is an ancient species of fish that thrives in a wide range of ecological environments, from freshwater to seawater. Basic in this process of adaptation is the ability of the kidney to control fluid filtration and urine formation. However, the morphological basis of this process is mostly unknown. The aim of the present study was to use microdissection techniques (scanning electron microscopy (SEM), transmission electron microscopy (TEM), and lectin-binding histochemistry) to examine the structure of the renal corpuscle of the sturgeon Acipenser nacarii in order to reveal morphologic features that could be related to function, phylogeny, and habitat. The renal corpuscles are aligned along the intrarrenal arteries. The urinary pole shows a siphon-like neck segment (NS) in 92% of the nephrons, whose structural characteristics are different from those of other fish. The podocytes have cuboidal cellular bodies, intercellular contacts, and poorly developed cell processes. The podocyte glycocalyx contains N-acetylglucosamine and lacks sialic acid. The structural and lectin-binding patterns are similar to those found in the immature mammalian kidney. The glomerular basement membrane (GBM) is very thick and consists of three layers: a lamina rara externa, a lamina densa, and a thick subendothelial lamina. The latter contains tubular microfibrils, collagen fibers, and long mesangial cell processes. Frequently, the podocyte bodies attach directly to the GBM, and the area occupied by the filtration slits is very small. Furthermore, the GBM shows a glycosylation pattern different from that observed in most vertebrates. Contrary to what would be expected in sturgeons living in freshwater, the A. nacarii renal corpuscle morphology suggests a low glomerular filtration rate.

Disruption of the elastin gene in adult Williams syndrome is accompanied by a paradoxical reduction in arterial stiffness.

Although the aetiology of Williams syndrome (WS) is related to elastin gene disruption, its pathogenesis remains unknown, particularly that of vascular lesions. The aim of the present study was to compare the elastic properties of three WS patients with age- and gender-matched normotensive and hypertensive controls. Common carotid arteries of WS patients had a higher distensibility, a thicker intima-media and a lower elastic modulus. Electron microscopy studies of one WS renal artery showed major abnormalities of the elastic fibres, which displayed a reticular structure and a thickening of the internal elastic lamina, whereas the ultrastructure of elastic fibres was normal in a control subadventitial muscular fibrodysplasia. In this WS arterial stenosis, we studied the expression patterns of several major smooth muscle (SM) phenotypic markers using immunofluorescence and used a normal renal artery as a control. In WS, SM-alpha-actin- and myosin-heavy-chain-positive cells contained low amounts of heavy caldesmon, and laminin-beta1 chain was expressed into the basement membranes, indicating a less differentiated phenotype. In conclusion, in WS patients, the carotid artery wall was abnormally distensible and thick, and major ultrastructural abnormalities of elastic fibres were observed in association with smooth muscle cell de-differentiation. These results indicate that the haplo-insufficiency of the elastin gene in WS patients leads to abnormal elastic fibre assembly within the media. Arterial wall hypertrophy found with a primary defect in elastin may represent a major factor responsible for increased distensibility. We suggest that, in WS, the increased proliferative response and the associated de-differentiation process represent two important mechanisms underlying the matrix accumulation and the development of arterial stenosis.

Reduced high shear platelet adhesion to the vascular media: defective von Willebrand factor binding to the interstitial collagen.

Fibrillar collagen serves as a thrombogenic surface for platelet adhesion mediated by von Willebrand factor (vWf) at high shear. Although abundant throughout the arterial wall, vWf-dependent platelet deposition to artery cross-sections from perfused citrated blood is localized to the adventitia of the vessel wall. Here we describe a similarly skewed distribution of vWf-binding sites in artery cross-sections. Binding of vWf-coated fluorescent beads, as well as detection of plasma vWf bound to artery cross-section at 3350 s(-1) shear rate with indirect particle-immunofluorescence or immunoelectron microscopy demonstrate vWf binding sites in the adventitia, but not in the media. A monoclonal anti-vWf antibody that interferes with vWf-binding to collagen in a microplate ELISA inhibits vWf-binding to both the adventitia and sections of collagen fibrils. Our data suggest that the media, despite its fibrillar collagen content, evidenced by electron microscopy, is defective for vWf-binding, which may explain its thromboresistant nature at high shear rates.

Morphostructural changes of the kidney microvasculature during the prenatal period in Bubalus bubalis.

The microcirculation of the foetal kidney was studied in the buffalo using light (LM) and scanning electron microscopy (SEM). The primordial glomerules originated from the peripheral zone of the metanephros at the stage of 8 cm CRT. The glomerular capillaries started to differentiate at the stage of 10-15 cm CRT. They were sparse and showed a few primordial pores. In addition, they began to make contacts with primordial podocytes. At the stage of 40-60 cm CRT, the renal microcirculation showed a complex and almost completely organized morphology.

The three-dimensional structure of the neonatal mouse kidney as revealed by scanning electron microscopy after KOH treatment.

The shape and arrangement of the developing nephrons were studied three-dimensionally by scanning electron microscopy (SEM) of the neonatal mouse kidney. The specimens were treated with the KOH digestion method in order to remove extracellular connective tissue components, thus enabling the direct observation of the developing nephrons at various stages. At the subcapsular region of the renal cortex, the ureteric ducts were observed as branched tubules with terminal swellings or ampullae. Newly formed blood vessels were often associated with terminals of these ureteric ducts. The cup-shaped renal corpuscles had aggregations of mesangial cells with blood vessels in the groove. At the vascular pole of mature nephrons, extraglomerular mesangial cells were observed as a cellular sheet, which was continuous with the smooth muscle layer of afferent and efferent blood vessels. The present study also demonstrated the shape of the immature podocytes in relation to the endothelial morphology of glomerular capillaries.

Interstitial capillary in normal and in transplanted kidneys: an ultrastructural study.

Knowledge about the normal structure and pathology of interstitial capillary is limited. Splitting and multilayering of the basal membrane (BM), as a marker of chronic rejection, has been published in association with transplant glomerulopathy. The authors investigated the ultrastructural features of the interstitial capillary basal membrane in normal (15 biopsies) and in transplanted kidneys (27 biopsies from 21 patients), expressing transplant glomerulopathy (8 biopsies from 6 patients), acute tubulo-interstitial rejection (9 biopsies from 6 patients), and recurrent or de novo glomerulonephritis (10 biopsies from 8 patients). All biopsies were fixed in 1% OsO4, embedded in Epon, and examined by electron microscope. Measurements of the interstitial capillary BM were made. The BM of interstitial capillary of intact kidney was a homogenous continuous structure, 88 nm in width on average. Thickening with diffuse multilayering of BM was most intensive in patients with transplant glomerulopathy, and much less intensive in patients with acute tubulointerstitial rejection and in patients with recurrent or de novo glomerulonephritis. These findings may provide the first information about the morphology of the normal basal lamina of interstitial capillary and support the diagnostic value of interstitial capillary changes in chronic rejection.