Using vital microscopy (tscm) to evaluate living kidneys

Tandem Scanning Confocal Microscopy (TSCM) is a non-invasive form of vital microscopy which can be used to evaluate superficial uriniferous tubules in living kidneys. Because TSCM has a number of advantages over conventional microscopic examination of renal biopsies, the present study was undertaken to determine whether the histopathological images obtained by TSCM can be correlated with post-transplant renal function. The kidneys of New Zealand male rabbits were harvested, flushed in Euro-Collins solution, and stored at 0-2 degrees C for periods of 24, 48, 67 and 72 hours prior to transplantation. As expected, there was a significant deterioration in post-transplant renal function as the kidneys were stored for longer periods of time. TSCM observations of the kidneys prior to their transplantation revealed characteristic histopathological changes of the proximal convoluted tubules which correlated closely with post-transplant renal function. These observations support the proposed use of TSCM in evaluating human donor kidneys prior to their transplantation.

Cell cycle delay and apoptosis are induced by high salt and urea in renal medullary cells

We investigated the effects of hyperosmolality on survival and proliferation of subconfluent cultures of mIMCD3 mouse renal collecting duct cells. High NaCl and/or urea (but not glycerol) reduces the number of viable cells, as measured with 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). Raising osmolality from a normal level (300 mosmol/kg) to 550-1,000 mosmol/kg by adding NaCl and/or urea greatly increases the proportion of cells in the G(2)M phase of the cell cycle within 8 h, as measured by flow cytometry. Up to 600 mosmol/kg the effect is only transient, and by 12 h at 550 mosmol/kg the effect reverses and most cells are in G(1). Flow cytometry with 5-bromodeoxyuridine (BrdU) pulse-chase demonstrates that movement through the S phase of the cell cycle slows, depending on the concentrations of NaCl and/or urea, and that the duration of G(2)M increases greatly (from 2.5 h at 300 mosmol/kg to more than 16 h at the higher osmolalities). Addition of NaCl and/or urea to total osmolality of 550 mosmol/kg or more also induces apoptosis, as demonstrated by characteristic electron microscopic morphological changes, appearance of a subdiploid peak in flow cytometry, and caspase-3 activation. The number of cells with subdiploid DNA and activated caspase-3 peaks at 8-12 h. Caspase-3 activation occurs in all phases of the cell cycle, but to a disproportionate degree in G(0)/G(1) and S phases. We conclude that elevated NaCl and/or urea reduces the number of proliferating mIMCD3 cells by slowing the transit through the S phase, by cell cycle delay in the G(2)M and G(1), and by inducing apoptotic cell death.

Organic osmolyte distribution and levels in the mammalian urinary bladder in diuresis and antidiuresis

Inositol, sorbitol, glycerophosphocholine (GPC), and betaine are organic osmolytes that are accumulated by renal medullary cells in response to hyperosmotic stress. Previous screening studies, using nuclear magnetic resonance spectroscopy, have shown some of these same compounds to be present in extracts of whole urinary bladder from rabbits and rats. In the present study, we used high-performance liquid chromatography to quantify levels of these compounds in the separated epithelium and muscle of bladders taken from normal rabbits as well as diuretic and thirsted rats. We find that 1) high concentrations of organic osmolytes, namely inositol, GPC, and sorbitol, are present in urinary bladder; 2) levels of these osmolytes in the bladder epithelium are higher than in the muscle; 3) increased urinary osmolality due to antidiuresis is associated with a 2.4-fold increase in total osmolyte levels in rat bladder epithelium and a lesser (1.5-fold) increase in the muscle, compared with corresponding levels in tissues from diuretic animals; and 4) these increases in total osmolyte amounts in the epithelium are due to increased levels of GPC, sorbitol, and perhaps inositol (P = 0.07), whereas only GPC increases in the bladder muscle.

The spatial organization of corneal endothelial cytoskeletal proteins and their relationship to the apical junctional complex

PURPOSE

To determine the spatial organization of the major cytoskeletal proteins and their relationship to the apical junctional complex (AJC) in the normal rabbit corneal endothelium.

METHODS

Normal endothelial cytoskeletal structure in three dimensions was studied in rabbit eyes by laser scanning confocal microscopy after en bloc immunocytochemical staining of whole corneal tissue with various antibodies and fluorescent probes; specificity of antibodies to rabbit corneal endothelial cell proteins was established by Western blot analysis.

RESULTS

Normal actin microfilament network organization was seen predominantly as a complex apical array forming a circumferential bundle. The tight junction-associated protein ZO-1 was positive at the apical junctions, forming a hexagonal pattern that was localized between and just proximal to the circumferential actin microfilament bundles. The distribution of ZO-1 was discontinuous around the cell, with the largest gaps (1 micron in diameter) occurring at the Y-junction between adjacent endothelial cells; transmission electron microscopy of the apical face of the endothelium confirmed the existence of 1-micron diameter gaps in the adherens junctions located at the Y-junction. Antivimentin antibodies showed a ring of intermediate filaments located just below the circumferential actin microfilament band. This ring appeared to be continuous with a basal mat of filaments, which together formed a basketlike structure within endothelial cells. An intricate cytoplasmic, perinuclear network of microtubules was observed by antitubulin antibodies that appeared unrelated either to the apical circumferential actin microfilament bundle or to intermediate vimentin filament ring. Staining of endothelial cells with NBD-ceramide identified a prominent, perinuclear Golgi complex suggesting an association between microtubules and Golgi.

CONCLUSIONS

The organization of cytoskeletal elements and the tight junction-associated protein ZO-1 is similar to the classical AJC of transporting epithelia, comprised of a zonulae occludens (ZO) located apical to a zonulae adherens (ZA) and desmosomes. The organizational pattern seen in corneal endothelial cells, however, is distinct from transporting epithelia in that the ZO and ZA are discontinuous, with large gaps in the ZO-1 distribution at the Y-junction between adjacent endothelial cells. The authors propose that the structural differences in the AJC underlie the functional differences between classical transporting epithelia, which actively pump fluid from the lumen to the mucosa, and the corneal endothelium, which has a "pump-leak" fluid transport mechanism.

Early lead challenge and subsequent hypertension in Sprague-Dawley rats

OBJECTIVE

The consequences of chronic, low grade lead (Pb) burden from earlier exposure on development of hypertension (HT) and cardiovascular disease is, at best, controversial, even though many epidemiological studies suggest the possibility. Accordingly, we examined ability of a short-term Pb challenge to cause later developing HT in rats.

METHODS

We gave 12 newly weaned Sprague-Dawley rats (SD) a 1% Pb acetate solution to drink for 6 weeks, while 12 control rats drank water. The rats were further subdivided into groups consuming high and low amounts of sugar. All rats were followed for 4 months after cessation of the Pb challenge.

RESULTS

Early Pb challenge caused no significant changes in body weight (BW) from controls; however, systolic blood pressures (SBP) of rats initially receiving Pb continued to rise significantly above their respective dietary controls for months after cessation of challenge. While a high sugar diet alone was associated with elevated SBP, high sugar consumers also challenged with Pb had the highest SBP. Protein excretion did not increase, suggesting, along with other evidence, a lack of significant renal damage.

CONCLUSIONS

Previous exposure to Pb can cause subsequent chronic elevations in SBP.

An evaluation of the ability of dextrans to reduce acute tubular necrosis during cold storage preservation

In this study, the ability of low molecular dextrans to prevent morphologically detectable acute tubular necrosis during cold storage was evaluated. Rat kidneys were flushed with a sodium phosphate buffer (pH 7.2) containing different concentrations of dextran 10 (m.w. of 10,000 or less) and stored at 0-2 degrees C for up to 5 days (samples taken at 24-hr intervals). It was found that solutions containing 20% or more of dextran 10 provided significantly improved morphological preservation of kidney nephrons when compared with currently popular kidney cold storage preservation solutions (i.e. University of Wisconsin and Euro-Collins solutions). Adding smaller amounts (i.e., 15%) of dextran 10 to a cold storage solution already containing another effective osmotic agent (i.e., sucrose) also resulted in superior morphological preservation, indicating a beneficial additive effect of using more than one osmotic agent. Dextran 40 (m.w. 40,000) did not provide as good morphological preservation as did a similar concentration of dextran 10. It is concluded that the use of the proper kind and proper amount of low molecular weight dextrans in preservation solutions can significantly reduce the morphologically detectable acute tubular necrosis during cold storage.

In vivo osmotic pertubation of intercellular fluid channels in the rabbit corneal endothelium

An in vivo rabbit corneal model was used to evaluate morphological changes in the corneal endothelium associated with osmotically increasing fluid movement from the anterior chamber into the stroma. When the corneal stroma is rendered more hypertonic than normal by immersing the scraped epithelial side of the cornea in a hypertonic sucrose solution, intercellular channels and apical pores at the Y-junctions between endothelial cells become greatly enlarged. The foregoing changes are reversible and do not appear to result in damage to the corneal endothelium. These observations suggest that specific intercellular channels in the corneal endothelium may provide pathways for the movement of fluid from the aqueous humor into the stroma.

The histopathology of kidney uriniferous tubules as revealed by noninvasive confocal vital microscopy

Tandem scanning confocal microscopy (TSCM) permits the noninvasive microscopic viewing of unstained, living, solid organs in real time. This article provides an overview of recent studies conducted by the author and other scientists, using TSCM and demonstrating its advantages in evaluating the histopathology of uriniferous tubules associated with normothermic renal ischemia, the nephrotic syndrome, and extracorporeal cold-storage preservation of kidneys.

Noninvasive vital microscopy to monitor tubular necrosis of cold-stored kidneys

This study evaluated the ability of a new form of vital microscopy, termed tandem scanning confocal microscopy (TSCM), to determine the histopathological status of kidneys while they are being preserved in cold storage preservation solutions. The TSCM observations were performed on rat kidneys stored at 0-2 degrees C in one of several cold-storage preservation solutions (Euro-Collins, UW solution, phosphate-buffered dextran), and correlated with conventional light microscopic observations of these same kidney samples. The present investigation provides histopathological guidelines for the use of TSCM in determining the extent of necrosis that a kidney suffers during its cold-storage preservation, and demonstrates that TSCM can be used to observe cold-stored living kidneys repeatedly over time and provide immediate and artifact-free informative images regarding their histopathological status. The combined TSCM and conventional light microscopic observations also provided information regarding the ability of the various cold storage solutions being studied to preserve the normal histology status of cold-stored kidneys.

In vivo confocal microscopic studies of endothelial wound healing in rabbit cornea

Corneal endothelial wound healing in living rabbit eyes after mechanical scrape (MS) and transcorneal freeze (TCF) injury was studied using tandem scanning confocal microscopy (TSCM). MS injury was created on the central corneal endothelium with an olive tip cannula; TCF injury was created using a 3-mm-diameter stainless steel probe cooled with liquid nitrogen. In vivo observation of wound healing using TSCM was correlated with scanning electron microscopy (SEM) for fixed tissues. At 6 h after MS, migrating endothelial cells at the leading edge showed lamellipodial processes on in vivo TSCM and SEM. After 24 h, the denuded area was almost fully resurfaced by migrating endothelial cells showing wide spaces between nuclei by TSCM. After 28 days, resurfaced endothelial cells showed normal hexagonal mosaic appearance with enlarged cells by TSCM and SEM. TCF injury produced fibroblastic changes in the endothelial cells with elongation and spreading by 24 h after injury. After 3 days, the wounded area was resurfaced with two cell types: (a) migrating endothelial cells at the peripheral area, which appeared polygonal in shape with wide intracellular spaces and (b) fibroblast-like cells at the center of the wound, which formed a retrocorneal fibrous membrane (RCFM). The RCFM was posteriorly covered with normal endothelium after 28-60 days. TSCM of the stroma demonstrated spindle-shaped, activated keratocytes migrating into the wounded stroma at 3-14 days. In conclusion, TSCM allows viewing of dynamic four-dimensional morphologic changes (x, y, z, and time) during in vivo cellular repair of corneal wound healing after either MS or TCF injury.

Actin filament organization during endothelial wound healing in the rabbit cornea: comparison between transcorneal freeze and mechanical scrape injuries

PURPOSE

To compare and contrast the in vivo mechanism of wound healing after mechanical scrape and transcorneal freeze (TCF) injury in a rabbit eye model by examining changes in the cytoskeletal organization of contractile, filamentous actin (f-actin) microfilaments as relates to differences in cell migration or translocation during endothelial repair.

METHODS

Endothelial wound healing after mechanical scrape and transcorneal freeze injury was studied in rabbit eyes using laser scanning confocal microscopy (LSCM). Central corneal mechanical scrape injury was made using an olive tip cannula, and TCF injury was made using a 3-mm diameter stainless steel probe cooled with liquid nitrogen. Cytoskeletal changes in f-actin stained with phalloidin-FITC were observed during wound healing using LSCM.

RESULTS

At 6 hours after mechanical scrape, the leading edge of the migrating sheet showed a decrease in the intensity of phalloidin-FITC staining, suggesting a decrease in cortical f-actin. Migrating endothelial cells in vivo did not appear to develop stress fibers after mechanical scrape, which is consistent with an in vitro cell spreading mechanism of endothelial wound healing. By 24 hours, the denuded area was almost fully resurfaced by migrating endothelial cells. On the other hand, TCF injury produced fibroblastic changes in the endothelial cells with extension and elongation of spindle-shaped endothelial cells at the leading edge by 24 hours after injury. Fibroblastic endothelial cells developed prominent actin stress-fibers, which is consistent with an in vitro cell migration mechanism of endothelial wound healing. Three days after TCF, the wounded area was resurfaced with two cell types: rough, fibroblast-like cells forming a retrocorneal fibrous membrane having prominent f-actin bundles or stress fibers with few cell-cell junctions, and smooth, polygonal-shaped endothelial cells having tight cell junctions with a cortical distribution of f-actin. After 28 days the retrocorneal fibrous membrane was posteriorly covered with normal endothelium.

CONCLUSIONS

These data support the hypothesis that endothelial wound healing involves two separate, injury-dependent, mechanisms--cell spreading and cell migration.

Noninvasive microscopic evaluation of the intact living nephrotic kidney

BACKGROUND

Tandem Scanning Confocal Microscopy (TSCM) is a new form of microscopy that allows one to noninvasively "optically section" into intact structures and record microscopic images in real-time. In this study, we have evaluated the ability of this new technology to distinguish histopathologic changes in unstained living kidneys that occur coincident with the onset of puromycin aminonucleoside-induced nephrosis.

EXPERIMENTAL DESIGN

The rats were anesthetized and a laparotomy was performed to expose the kidneys. Using a TSCM equipped with a 24x water-immersion objective, we viewed and recorded real-time images of subcapsular living uriniferous tubules and glomeruli of puromycin aminonucleoside-induced nephrosis rats exhibiting different levels of proteinuria.

RESULTS

TSCM revealed a variety of histopathologic changes in the puromycin aminonucleoside-induced nephrosis uriniferous tubules including dilation of proximal tubular lumens, loss of microvillous brush border, cellular debris in the tubule lumens, and focal regions of extensive tubular necrosis. Using the fluorescent probe carboxyfluorescein, we were able to demonstrate significant heterogeneity in the movement of this fluorescent probe through the uriniferous tubules (e.g., some tubules were completely blocked), and irregular patterns in flow of carboxyfluorescein through nephrotic glomeruli.

CONCLUSIONS

These observations indicate that TSCM is capable of revealing a variety of histopathologic changes in unstained, intact, living kidneys. In addition, many of the histopathologic features of the uriniferous tubules revealed by TSCM are difficult or impossible to distinguish in biopsied samples of renal tissue.

Effects of dietary protein on renal ischemia induced tubular necrosis

Previously we have shown that the amount of protein in a dietary regimen prior to the induction of renal ischemia will significantly affect the degree of postischemic acute renal failure (Andrews PM, Bates SB: Kidney Int 30:299-303, 1986). The present investigation was undertaken to determine what effect dietary protein regimen has on the histopathology of renal ischemia. Rats were pair-fed for 2 weeks on either 0% or 5% (restricted), 20% (normal), or 60% (high) purified protein isocaloric diets. Ischemia was induced by 45 min of renal pedicle clamping. Light and electron microscopic evaluation of kidney morphology immediately following renal ischemia (prior to blood reflow) revealed that the extent of morphological damage to cells lining proximal convoluted tubules and the thick ascending segments of Henle's loop increased with increasing concentration of dietary protein. However, all dietary protein groups also exhibited heterogeneity in the extent of damage to different nephrons within the same kidney.

Digital image acquisition in in vivo confocal microscopy

A flexible system for the real-time acquisition of in vivo images has been developed. Images are generated using a tandem scanning confocal microscope interfaced to a low-light-level camera. The video signal from the camera is digitized and stored using a Gould image processing system with a real-time digital disk (RTDD). The RTDD can store up to 3200 512 x 512 pixel images at video rates (30 images s-1). Images can be input directly from the camera during the study, or off-line from a Super VHS video recorder. Once a segment of experimental interest is digitized onto the RTDD, the user can interactively step through the images, average stable sequences, and identify candidates for further processing and analysis. Examples of how this system can be used to study the physiology of various organ systems in vivo are presented.

Tandem scanning confocal microscopy (TSCM) of normal and ischemic living kidneys

Tandem Scanning Confocal Microscopy (TSCM) allows one to section optically into and record real-time images of living organs and tissues in a noninvasive fashion. In this paper, we will present some initial TSCM observations of subcapsular nephrons in the living, intact kidneys of Munich-Wistar rats and evaluate the nephron's responses to temporary ischemia and to intravenous infusion of mannitol. The rats were anesthetized with Inactin and a laparotomy performed to expose the kidneys. Using a TSCM equipped with a 20 x water-immersion objective, we optically sectioned through the intact kidney capsule and recorded real-time images of living subcapsular glomeruli and uriniferous tubules. The proximal tubule brush border was highly reflective and allowed us to distinguish between the first and second segments of the proximal tubules as well as the distal tubules. Cellular elements of the blood could be seen passing rapidly through peritubular capillaries and individual glomerular capillary loops. With fluorescent filters in place, intravenously injected carboxyfluorescein was seen to pass through the glomerular capillary loops and then progressively through the different segments of the uriniferous tubules. Ligation of the renal artery resulted in rapid swelling of proximal tubule cells into the tubular lumens, loss of reflectiveness of the microvillous brush borders, and closure of the peritubular capillary spaces. Upon release of the ligature, the proximal tubule lumens again became patent, often opening up abruptly and in a zipper-like fashion down the length of the tubules. Increasing the glomerular filtration rate by intravenous infusion of mannitol resulted in increases in tubular luminal and perimeter dimensions. Mannitol also acted as an effective impermeant osmotic agent and prevented most of the cellular swelling which was otherwise seen in response to renal ischemia.

In vivo, real-time confocal imaging

We have adapted a tandem scanning confocal microscope for real-time, non-invasive imaging of cells under in vivo conditions. This form of in vivo confocal imaging relies on the optical sectioning abilities of the confocal microscope to obtain en face, sequential, reflected light images of cells at various depths, up to 1 mm, within opaque organs in living animals. Of major consideration in the design of an in vivo confocal microscope is maximizing the real-time detection of signals reflected from low contrast structures which can be affected by the microscope design, objective, and image detector systems. Using an in vivo confocal microscope design with a 20 x BioOptics surface contact objective we have obtained live cellular images from selected tissues including cornea, kidney, liver, adrenal, thyroid, epididymis, and muscle and connective tissue of rabbits and rats. Images were captured, digitized, and processed using a DAGE Mti low light level SIT camera coupled to a Gould IP9527 image processor. In vivo images were also compared with conventional bright field light and scanning electron microscopic images of "dead," fixed tissues. Overall, in vivo confocal imaging can provide remarkable detail of living cells comparable to that of conventional microscopic images of "dead," fixed, and stained tissue. A more unique feature of in vivo confocal imaging is the ability to study cellular structure and function sequentially over time in the same organ or tissue and represents a fundamentally new paradigm in microscopy. With continued refinements in the microscope, objective and detection system designs and their consequent improvements in lateral and axial resolution, in vivo confocal microscopy will enable us as observers to see what no one has been able to see before.

High dietary protein regimens provide significant protection from mercury nephrotoxicity in rats

The effects of high protein dietary regimens prior to the administration of inorganic mercury were investigated. Male Sprague-Dawley rats were pair-fed on purified test diets containing either normal (20%) or high (60%) concentrations of protein. Mercury was administered as a single intravenous injection of mercuric chloride (1 mg/kg). All rats maintained on normal dietary protein prior to and following mercury injection exhibited severe kidney dysfunction, extensive necrosis of both second (S2) and third (S3) segments of the kidney proximal tubules, and 100% mortality. In contrast, rats maintained on high dietary protein for 48 hr or longer just prior to mercury injection and returned to normal dietary protein immediately following mercury administration all survived and exhibited normal serum creatinine and BUN values within 4 days following mercury administration. The kidneys of this latter group took up significantly less radiolabeled mercury during the first 12 hr following mercury injection, and exhibited relatively little damage to the second segments (S2) of the proximal tubules. The third segments (S3) of the proximal tubules, however, exhibited the same degree of necrosis as that observed in the control group. Maintaining rats on high dietary protein regimens for shorter periods of time prior to mercury infusion (i.e., 12 or 24 hr) also dramatically reduced subsequent acute renal failure and improved survival, although not to the extent noted following 48 hr or longer on these diets. These observations suggested that high dietary protein regimens may protect from mercury nephrotoxicity by reducing mercury uptake to the second segments (S2) of the proximal tubules during the initial period of exposure to intravenously administered mercury.

Dietary protein regimen prior to renal ischemia significantly affects the postischemic uremic response

Recently we reported that maintaining rats on restricted dietary protein regimens prior to renal ischemia will significantly improve postischemic survival rates. This effect required a week or more of maintenance on a restricted protein diet prior to the renal insult and appeared to be independent of the postischemic dietary protein regimen. The present study was designed to evaluate the role of systemic toxicity in this protection. Adult male Sprague-Dawley rats were pair-fed by weight on restricted or high isocaloric protein diets for 8-10 days prior to 45 min of renal ischemia induced by renal pedicle clamping. When placed on a normal dietary protein regimen immediately following ischemia, the rats preconditioned to restricted dietary protein exhibited significantly less acidosis, less hyperkalemia, lower blood urea nitrogen values, and improved survival rates compared with rats preconditioned on a high dietary protein regimen. In order to separate the possible effects of prior dietary protein regimen on acute tubular necrosis suffered during renal ischemia from its effects on the uremic response, bilateral nephrectomies were performed on rats preconditioned for 14 days to low, normal, and high dietary protein regimens. Although all of the rats were placed on the same dietary protein regimen immediately following bilateral nephrectomy, those that had previously been on a lower dietary protein regimen exhibited a significantly reduced uremic response and lived longer. These findings indicate that dietary protein regimen prior to renal ischemia is a risk factor which can have a significant lingering effect on the severity of postischemic systemic toxicity.

Regional chemotherapy in an experimental model of Wilms' tumor in rats

A s.c. experimental model of Wilms' tumor in rats was used to compare the effects of intratumoral treatment with vincristine plus actinomycin D to i.v. treatment with these chemotherapeutic drugs. The Wilms' tumor model is a fast-growing solid tumor that has been shown to be resistant to traditional clinical treatment procedures used for Wilms' tumor in man. Injection of the chemotherapeutic drugs directly into the tumor mass was found to be more effective than i.v. therapy in causing long-term remission of the tumor. Intratumoral therapy was also less toxic to the animals than i.v. therapy when measured by post-treatment survival rates and weight loss during the 1st week following treatment. However, intratumoral treatment caused an initial fibrosis of the tumor tissue, which resulted in a slower rate of absorption of the resultant fibrotic tumor mass than was seen in tumors treated i.v. Also, intratumoral injection resulted in necrosis of the overlying skin, which healed as the fibrotic tumor tissue was absorbed. Intratumoral treatment of a cervical tumor was found to cause the remission of a second major tumor mass located at some distance from the initial injection (i.e., in the lumbar region). No significant benefits were noted when dimethylsulfoxide (DMSO) was used in place of aqueous mannitol as a vehicle to deliver the chemotherapeutic agents. There was a significant correlation between the drug dose-to-tumor-size ratio (D/T ratio) and the effectiveness of the chemotherapy. When this ratio was high enough, a single treatment with a combination of vincristine and actinomycin D usually resulted in total remission of the experimental Wilms' tumor in response to either intratumoral or i.v. therapy.

Dietary protein as a risk factor in gentamicin nephrotoxicity

The effects of dietary protein on renal function and structure, both prior to and after initiation of daily gentamicin treatment, were investigated. Male Sprague-Dawley rats were pair-fed on low-protein (LP, 5%), normal-protein (NP, 20%), or high-protein (HP, 60%) diets for 10 days prior to gentamicin treatment. Gentamicin was administered as daily subcutaneous injections (150 mg/kg) for 6 days. Immediately after beginning daily gentamicin injections some of the rats on NP diets were switched to LP or HP diets, and some of the rats on HP diets were switched to LP diets. Renal function was monitored by evaluating serum creatinine levels and 24-h urine volumes; renal histology was evaluated by light and electron microscopy; and gentamicin uptake was determined using radioimmunoassay. Our findings indicate that conditioning to higher dietary protein prior to gentamicin administration results in less uptake of gentamicin by the kidneys. If rats on HP diets are placed on LP coincident with gentamicin administration, there is a significant improvement in survival. Switching rats from NP to LP protein coincident with gentamicin administration does not improve renal function, histology, or survival. However, switching rats from NP to HP coincident with gentamicin administration significantly increases mortality. Maintaining rats on LP both prior to and after gentamicin administration results in a significant improvement in survival but does not improve renal function. These results indicate that dietary protein both prior to and following the administration of gentamicin can significantly affect the nephrotoxicity of gentamicin.

Effects of dietary protein on uranyl-nitrate-induced acute renal failure

The effects of dietary protein both before and after uranyl-nitrate-induced acute renal failure were investigated. Male Sprague-Dawley rats were maintained on high-protein (60%), normal-protein (20%), low-protein (5%) and no-protein diets for 8 days prior to intravenous administration of uranyl nitrate (10 mg/kg). Immediately following uranyl nitrate injection, some rats on normal-protein diets were switched to no-protein, low-protein or high-protein diets, while some of the rats on high-protein diets were switched to low-protein diets. Serum and urine creatinine levels and urine volumes were monitored for 2 weeks following uranyl nitrate treatment. Rats conditioned to no-protein and low-protein diets exhibited significantly lower mortalities than rats maintained on normal-protein diets. Rats maintained on high protein diets exhibited better renal function than rats maintained on lower dietary protein regimes, but these rats had mortality rates similar to rats maintained on normal-protein diets. Shifting the rats on normal-protein diets to low- or no-protein diets immediately after uranyl nitrate administration did not improve their renal function or survival rates. However, shifting the rats on normal-protein diets to high-protein diets immediately following uranyl nitrate injection resulted in significantly higher mortalities (93%) than in rats maintained on either normal or high dietary protein throughout the experimental period. Finally, shifting rats on high dietary protein to low-protein diets immediately following uranyl nitrate administration resulted in both improved renal function and survival compared with rats shifted from normal to restricted dietary protein (5%) immediately following uranyl nitrate injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary protein prior to renal ischemia dramatically affects postischemic kidney function

Male Sprague-Dawley rats were maintained on high protein (60%), normal protein (20%), low protein (5%), or no protein (0%) diets for two or four weeks prior to 45 minutes of renal ischemia induced by renal pedicle clamping. Most (93%) of the rats on the high protein diet died within three days following renal ischemia. In addition, 69% of the rats on normal protein diets also died, most before the fourth day following ischemic insult. In contrast, 88% of the rats on the low protein diet lived, although some exhibited elevated serum creatinine levels for up to one to two weeks following ischemia. Finally, all of the rats on no protein diets lived, and most (75%) exhibited normal serum creatinine levels by the fourth day following ischemia. Shifting the diets of high protein and normal protein adapted rats to no protein diets immediately following ischemia did not improve postischemic survival. Also, changing the diets of no protein adapted rats to high protein diets immediately following ischemia did not significantly affect postischemic recovery. When rats were maintained on no protein diets for shorter periods of time prior to ischemia, it was found that approximately a week on this diet is necessary to provide maximum protection from postischemic acute renal failure. These findings demonstrate a dramatic effect of dietary protein prior to ischemic induced acute renal failure, and suggests that preoperative dietary protein intake should be an important consideration in those situations which are predisposed to postoperative acute renal failure.

Dose-dependent movement of cationic molecules across the glomerular wall

Different concentrations of the polycation polyethyleneimine (PEI) were administered by single intravenous injections or by constant vascular perfusion to the kidneys of Sprague-Dawley rats. At a fixed time interval after administration of PEI, the kidneys were fixed and the distribution of PEI in the glomerular wall was evaluated by electron microscopy. At the lower concentrations (e.g., 0.005%), PEI bound only to the glomerular endothelial glycocalyx and preferentially to microvillous projections on this endothelium. At higher concentrations (e.g., 0.05%), PEI also bound to discrete anionic sites in the lamina rara interna (LRI) but was rarely seen in the lamina rara externa (LRE). As the concentration of PEI was further increased (e.g., 0.5%), PEI moved deeper into the glomerular basement membrane (GBM) and bound extensively to discrete anionic sites in the lamina rara externa. Although anionic sites in the LRI and LRE appeared nearly saturated following infusion of 0.5% PEI, this cationic molecule was rarely seen to cross filtration slits and pass into the urinary space. At still higher concentrations (e.g., 2%), however, PEI moved freely across the filtration slits, bound extensively to the glomerular epithelial glycocalyx, and induced a narrowing of the filtration slits. When PEI was mechanically perfused through the kidney vasculature for 3 minutes, PEI binding to the epithelial glycocalyx caused very extensive adherence of adjacent podocyte processes and the narrowing and loss of filtration slits. Also in these latter samples, discrete anionic sites in the LRE were no longer apparent and a dense band of PEI was seen under the foot processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a flushing solution designed to protect kidneys from in situ ischemia

An in situ flushing solution was evaluated with regard to the following: (1) its ability to protect the kidney during 60, 90, and 120 minutes of normothermic ischemia; (2) the effects of using an intracellular versus extracellular electrolyte composition in the flushing solution; and (3) the ability of the flushing solution to complement in situ hypothermia as a protective measure during long-term ischemia. Rat kidneys were briefly flushed in situ with an isotonic phosphate buffered solution (pH 7.2) containing 50 milliosmole of sucrose. The left renal pedicle was then immediately clamped to render the kidney ischemic and to hold the flushing solution in the kidney. Following removal of the pedicle clamp, a contralateral nephrectomy of the right kidney was performed and daily serum creatinine levels determined to evaluate postischemic renal function. The results indicate the following: (1) the flushing procedure is very effective in preventing postischemic acute renal failure following 60 minutes of normothermic ischemia, but is considerably less effective for ischemic times of 90 minutes or more; (2) an intracellular electrolyte composition in the flushing solution does not improve the protective effects of this solution; and (3) the flushing procedure can significantly improve on the protection otherwise provided by in situ hypothermia.

Filamentous actin bundles in the kidney

The distribution of filamentous actin bundles in the rat kidney was studied using a fluorescent phallotoxin label and transmission electron microscopy. The microvillous brush border lining proximal tubules, smooth muscle in renal vessels, and renal corpuscles were the structures most intensely labeled with rhodamine phalloidin. Closer evaluation of renal corpuscles revealed intense labeling of filamentous actin within podocyte foot processes enveloping the glomerular capillary loops. Rhodamine phalloidin also labeled basal bands of filamentous actin in the parietal epithelium and basal bands of actin in proximal and distal tubules. Finally, a band of filamentous actin was evident along the innermost aspect of the kidney capsule, within cells which often joined to form sinus-like compartments.

The influence of age on acute renal toxicity of uranyl nitrate in the dog

The influence of age upon uranyl nitrate (UN) induced acute renal failure (ARF) was evaluated in 30 canine puppies 1-2 wk and 3-5 wk old. Renal function and morphologic studies were performed 2 h (initiation phase) and 24 h (maintenance phase) after UN administration. Age-matched controls received vehicle alone. Administration of UN to 1-2-wk-old puppies produced no changes in whole kidney glomerular filtration rate (GFR), despite a significant reduction in renal plasma flow (RPF) (P less than 0.01). In contrast, during the maintenance phase, GFR was 60% lower than in the control group (P less than 0.02) whereas values for RPF were nearly identical to control values. In 3-5-wk-old puppies the magnitude of response to the heavy metal was much greater and GFR was nearly completely suppressed during the maintenance phase. This major alteration of GFR was independent of changes in RPF, because RPF remained similar to control values. Morphologic alterations consistent with the nephrotoxic effects of UN were observed in the proximal tubules of the most differentiated nephrons. These age-related morphologic alterations correlated well with the functional response (GFR) observed after UN administration, i.e., a proportionately greater degree of both morphologic and functional alterations followed the administration of the heavy metal in the oldest group of puppies.

Cytoplasmic contractile elements in glomerular cells

The presence and possible roles of cytoplasmic contractile elements in glomerular epithelial podocytes and the glomerular mesangium are briefly discussed. Glomerular podocytes contain actinlike filaments distributed throughout their cytoplasm and more concentrated filamentous material within their foot processes. Antibody labeling and nitrobenzoxadiazole-phallacidin labeling have confirmed the presence of especially high concentrations of actin within podocyte foot processes. Studies with cytochalasins have suggested that contraction of actin within podocytes leads to a flattening of foot processes and a loss of the intervening filtration slits. Conversely, relaxation of these contractile elements leads to a narrowing of the bases of foot processes and an increase in the number of fully open intervening filtration slits. These observations have led to the proposal that glomerular podocytes have the potential to regulate the glomerular filtration rate by changing the shapes of their foot processes and thereby decreasing or increasing the number of filtration slits available for solute efflux across the glomerular wall. There is also evidence to indicate the presence of contractile elements within the glomerular mesangium. These contractile elements may be represented in part by bundles of fine filaments associated with electron-dense bodies that are present within many processes that radiate from these cells. In vitro studies in particular have suggested that these cells may possess contractile properties. It has been proposed that contraction of the mesangial cells may lead to a shunting of blood within the glomerulus or to a decrease in glomerular size.

Protection of kidneys from acute renal failure resulting from normothermic ischemia

Rat kidneys were flushed in situ with selected preservation solutions prior to clamping the renal vessels for 1 hour. Collins and Euro-Collins flushing solutions did not appear to protect the physiologic or morphologic status of rat kidneys when examined 2 days after the ischemic insult. These experimental groups exhibited serum creatinine levels similar to those seen in ischemic controls, correspondingly low urine creatinine levels, anuria, and significant deterioration of the uriniferous tubules as revealed by light and electron microscopy. In situ flushing with hypertonic Sacks or isotonic phosphate-buffered sucrose solutions, however, resulted in significant improvements in serum and urine creatinine levels, prevented anuria, and dramatically improved the morphologic integrity of the uriniferous tubules. Flushing with a phosphate-buffered sucrose solution that contained ATP-MgCl2 further improved the physiologic and morphologic status of ischemic kidneys to the point that they were indistinguishable from the nonischemic controls. The degree of protection obtained by flushing kidneys with the isotonic phosphate-buffered sucrose solution plus ATP-MgCl2 is greater than that provided by any other single pretreatment or posttreatment for ischemia that is currently available. We, therefore, believe that the use of this procedure can provide a valuable approach to surgical situations in which postischemic acute renal failure is a potential problem.

Ultrastructure of kidney preservation: varying the amount of an effective osmotic agent in isotonic and hypertonic preservation solutions

Currently the level of effective (i.e., impermeant) osmotic agent necessary to prevent cell swelling during the cold storage of kidneys is not known. In the present investigation, we used light microscopy and transmission electron microscopy to evaluate the amount of the osmotic agent sucrose which is needed to protect the rat kidney parenchyma from damage over 24 and 48 hr of cold storage. Our observations indicate that when sucrose contributes 140 mOsmol or more to the total osmolality of phosphate-buffered solutions, most cell swelling and associated ultrastructural damage can be prevented over 48 hr of cold storage. We also found little difference between the quality of kidney ultrastructural preservation which results when kidneys are stored in isotonic (300 mOsmol) versus hypertonic (400 mOsmol) solutions that contain the same amount of sucrose. The overall quality of preservation seen with solutions which contain 140 or 200 mOsmol of sucrose is dramatically better than that which we previously observed with such clinically popular kidney preservation solutions as Collins, Euro-Collins, and Sacks.

Factors that improve the preservation of nephron morphology during cold storage

Light and electron microscopy were used to evaluate the nephron morphology of rat kidneys that were perfused and stored at 0 to 2 degrees C. for up to 48 hours in preservation solutions which (1) contained different osmotic agents, (2) were adjusted to different levels of osmolality, and (3) which had different ionic compositions (e.g., intracellular-like, extracellular-like). Storage in an enriched phosphate-buffered isotonic culture medium that contained very little effective osmotic agent (i.e., medium 199) results in significant necrosis of glomeruli and uriniferous tubules with 12 to 24 hours. Storage in Collins solution that has an intracellular-like ionic composition and that contains dextrose as an osmotic agent results in significantly better preservation of kidney nephrons. When the dextrose in Collins solution is replaced with mannitol or sucrose, there is dramatic improvement in the preservation of glomeruli and uriniferous tubules. Overall, sucrose appears to be the most effective osmotic agent in preventing degeneration of the nephron during cold storage. Further improvement in nephron preservation is seen when the osmolality of Collins solution is raised (i.e., 400 to 600 mOsmoles) by adding more of the osmotic agents. Finally, storage in simple sodium phosphate-buffered solutions containing either dextrose, mannitol, or sucrose results in the same quality of morphologic preservation as seen with Collins intracellular-like solutions containing similar amounts of these osmotic agents. It appears, therefore, that the selection of an effective osmotic agent (e.g., sucrose) and making the preservation solution hypertonic with this osmotic agent are of primary importance in preserving nephron morphologic integrity during cold storage. The presence of an intracellular-like ionic composition in the preservation solution, however, does not appear to influence morphologic preservation. The effects of the above variables on the ultrastructural morphology of different segments of the uriniferous tubules and the renal corpuscles are described and illustrated.

Investigations of cytoplasmic contractile and cytoskeletal elements in the kidney glomerulus

Electron microscopy and in vitro techniques were used to evaluate the morphologic responses of glomerular podocytes and glomerular endothelial cells to compounds that affect either cytoplasmic contractile elements or cytoplasmic microtubules. In response to in vitro incubation in the presence of cytochalasin D or B (compounds that inhibit contraction of actin-like microfilaments), podocyte foot processes change in shape from short processes with broad bases to taller processes with narrow bases. Coincident with these shape changes, there is an increase in the number of fully patent filtration slit spaces between adjacent foot processes. In view of these observations, it is proposed that glomerular podocytes have the potential for monitoring the filtration slit area available for solute efflux across the glomerular wall by modifying the shapes of their foot processes (that is, expanding and contracting the bases of these structures). As in vitro incubation continues for 1 to 2 days, the cytochalasins inhibit the shape changes of glomerular podocytes that normally occur during 2 days of in vitro incubation--the loss of foot processes, filtration slits, endothelial pores, and thickening of the endothelium. The cytochalasins also inhibit the loss of foot processes and filtration slits that otherwise occur in response to enzymatic removal of glomerular-free surface sialic acid. The in vitro depolymerization of glomerular microtubules by any of a variety of drugs (for example, vinblastine sulfate, colchicine) results in the rounding up of podocyte cell bodies, the thinning of podocyte major processes, and a partial collapsing of the glomerular endothelial walls. These latter observations suggest that microtubules play an important cytoskeletal role in maintaining the structural integrity of these cells.

Cationized ferritin binding to anionic surfaces in normal and aminonucleoside nephrotic kidneys

The distribution and effects of polycationized ferritin (PCF) bound ot anionic sites on living plasmalemmas and basal laminae of normal and puromycin aminonucleoside nephrotic (PAN) kidneys were studied using an in vitro model system. Immersion of normal glomeruli in physiological saline solutions containing low concentrations of PCF (0.01 to 0.1 mg/ml) for 10 seconds results in preferential binding of PCF to microvillous projections on the glomerular epithelium (i.e., podocytes). Exposure to higher concentrations of PCF (1.0 mg/ml) for 10 seconds results in several layers of PCF distributed evenly over the urinary aspect of epithelial podocytes. In these short treatment times, the thin slit diaphragms which span the filtration slits appear to be impermeable to PCF. Within several minutes after PCF treatment, ferritin is found within caveolae on the surface of epithelial podocytes and within numerous pinosomes and larger endocytic vesicles within these cells. Longer treatment with PCF results in the narrowing of filtration slit spaces and the formation of junctions between adjacent podocyte foot processes. Occurringg coincident with these structural changes is a gradual accumulation of PCF in regular patches along the lamina rara externa (LRE) of the glomerular basement membrane. Loss of foot processes and accumulation of PCF in the LRE are prevented by treatment with either cytochalasin B (25 micro g/ml), D (2 micro g/ml) or incubation at low temperatures (0-4 degrees C). When PCF-coated glomeruli are incubated in PCF-free media, the ferritin coat is shed form the free surfaces within 1/2 to 1 hour except at the tips and sides of microvillous projections. Pretreatment of normal glomeruli with neuraminidase or protamine sulfate results in a dramatic reduction in the binding of PCF to the glomerular epithelial free surface. Treatment of PAN glomeruli with PCF often results in patchlike distributions of PCF over the glomerular epithelial free surface. High concentrations of PCF (1.0 mg/ml) bind preferentially to microvillous projections on the parietal epithelial luminal surface and in distinct patchlike patterns along the basal laminae of parietal and tubular epithelial cells.

The presence of proximal tubulelike cells in the kidney parietal epithelium in response to unilateral nephrectomy

Five months following unilateral nephrectomy, the parietal epithelia in the remaining kidneys of Sprague-Dawley rats were examined by light and electron microscopy. Compared with controls, the kidneys from uninephrectomized rats exhibited a dramatic increase in mass characteristic of compensatory hypertrophy. Approximately 20% of the renal corpuscles in the hypertrophied kidneys had parietal epithelia lined by tall cells which possessed a brush border and other morphological characteristics of proximal tubule cells. In some instances proximal tubulelike cells made up over half of the cells lining the parietal epithelium. The possible significance of this finding is discussed.

Scanning electron microscopy of the kidney glomerular epithelium after treatment with polycations in situ and in vitro

Changes in fine structure of glomerular epithelial cells (podocytes) were examined after treatment in situ and in vitro with polycations (i.e., protamine sulfate and poly-1-lysine). Scanning and transmission electron microscopic observations indicate that polycation-induced alterations of the glomerular epithelium are similar in many respects to those resulting from puromycin aminonucleoside nephrosis. These alterations include the formation of junctional complexes between adjacent podocyte processes, flattening and retraction of podocyte processes, extensive folding of the slit diaphragms, formation of interpedicular microbridges, and development of irregular knobby surface-microprojections. Prolonged treatment in vitro with high concentrations of polycations results in nearly complete loss of podocyte processes and the transformation of these once elaborate cells into simple polyhedral cells. The foregoing observations support the view that pedicel loss in puromycin aminonucleoside nephrosis may be due to a reduction in the glomerular epithelial polyanionic sialic acid surface coat.

Personality profile of pediatric nurse practitioners associated with role change

In a study of personality needs conducive to desired role change for nurse practitioners, 125 nursing students in a four-month pediatric nurse practitioner training program at Northeastern University, Boston, Massachusetts, were given the Edwards Personal Preference Schedule before and after the course. Students in the program were found to have needs associated with the assertiveness and flexibility required by the new role. Before and after training they were low in need for order, endurance, abasement, and deference and high in need for autonomy and aggression. During training, the need for order, endurance, and abasement decreased further. Inconsistent with this interpretation was the finding that students were actually lower in dominance and higher in succorance after training. The decrease in dominance may be related to the program's special emphasis on counseling; the high succorance at the end of the program may have resulted from the transitional state associated with leaving the program.

The effect of vinblastine-induced microtubule loss on kidney podocyte morphology

The effect of intravenous injections of vinblastine sulfate on the renal glomerular epithelium was studied by scanning and transmission electron microscopy. Two hours after treatment with vinblastine, microtubules were almost completely lost from the podocyte cell bodies and major processes, and crystalline inclusions of a tubular nature had appeared within the cytoplasm. Coincident with this loss of microtubules, podocyte major processes at first collapsed and then became significantly thinner as they appeared to lose much of their cytoplasm to the nucleated cell body. These observations suggest that microtubules serve to maintain the shape and integrity of podocyte major processes. At no time after vinblastine treatment did we note any alteration in podocyte pedicel morphology.

A scanning and transmission electron microscopic comparison of puromycin aminonucleoside-induced nephrosis to hyperalbuminemia-induced proteinuria with emphasis on kidney podocyte pedicel loss

Ultrastructural changes in the visceral epithelium and proximal tubules of rats were studied by scanning and transmission electron microscopy during the onset and progression of puromycin aminonucleoside nephrosis (PAN)-induced proteinuria. These changes were compared with those that occur during a similar degree of proteinuria induced by intraperitoneal injections of albumin. With the onset of proteinuria and oliguria, PAN rats exhibit loss of podocyte pedicels and podocyte major processes, an increase in pinocytotic activity, and an accumulation of cytoplasmic vacuoles and granules of variable size, shape, and electron density. Loss of podocyte pedicels involves a gradual decrease in pedicel height beginning at the pedicel tip and progressing down the pedicel arm, formation of nublike protrusions and interpedicel microbridges (35 to 45 nm. in width and 40 to 60 nm. in length) along the pedicel's base, the merging of microbridges to form more extensive regions of interpedicel contact, and a gradual broadening and retraction of pedicels. In response to hyperalbuminemia-induced proteinuria, kidney podocytes exhibit reactions during PAN, however, the podocyte pedicels, slit pores, and major processes of rats with hyperalbuminemia-induced proteinuria remain discrete. The loss of pedicels and major processes during PAN, therefore, apparently results from the effects of puromycin aminonucleoside per se rather than from the proteinuria associated with this disease. The proximal tubules of rats with hyperalbuminemia-induced proteinurea exhibit the same characteristic changes as PAN rat proximal tubules (i.e., loss of brush border, dilated lumina, abnormally thin walls, and accumulation of periodic acid-Schiff positive electron-dense luminal casts and cytoplasmic protein absorption droplets). The significance of these ultrastructural findings during PAN and hyperalbuminemia-induced proteinurea are discussed in terms of the etiology of PAN.

Scanning electron microscopy of dissociated pancreatic acinar cell surfaces

The pancreatic acinar cell surfaces have been studied by SEM with a dissection of technique and correlated with results obtained by TEM. The SEM results demonstrate characteristic arrangement of microplicae which in some areas are densely packed. In many areas, the microplicae are distributed in such a manner that they create zones with typical geometrical shapes and show a relatively smooth surface. These smooth areas may coincide, as indicated by correlated TEM results, with the limits of intimate contact between adjacent acinar cells which, in turn, represent part of the junctional complex. Another aspect revealed by these SEM preparations concerns the presence of groups of densely packed microplicae, arranged in regular rows and distributed along some grooves and/or infoldings of the cellular surface. On the basis of SEM and TEM information, it is likely that these structures correspond to intercellular (and possibly, in some cases, intracellular) canaliculi which topographically form a kind of extensive microlabyrinthine arrangement running along all the cell sides. One final point revealed by fractured samples concerns the finding of spherical zymogen droplets within the vesicles of the Golgi complex. Because in many scanning images these vesicles appear connected by small openings, it is suggested that they may represent a system of intercommunicating chambers (vacuoles) through which the zymogen droplets can be continuously accumulated and discharged into the acinar lumen.

Scanning electron microscopy of the endometrium during the secretory phase

Scanning electron microscopy was used to study the surface morphology of the rabbit endometrium during the secretory phase of the oestrous cycle. The free surfaces of ciliated and of inactive active secretory cells are described. Changes in secretory cell surface morphology resulting from accumulation and secretion of material involve the apparent retraction of microvilli and the formation of one or more bulbous protrusions of the cell's apical surface. These protrusions may be relatively smooth surfaced or exhibit long slender micro-extensions. The protrusions grow in size and are eventually pinched off. Loss of the bulbous protrusions often leaves behind crater-like invaginations of the cell's surface. Secretory cells adjacent to the endometrial glands are the first to exhibit signs of mucin accumulation and secretion. The single cilium of a secretory cell is not apparently affected by the secretory process. Signs of ciliated and secretory cell degeneration, and possible sloughing, are also described.

Microplicae: characteristic ridge-like folds of the plasmalemma

Scanning electron microscopy reveals that the free surfaces of stratified squamous epithelial cells lining the alimentary tract, cornea, and conjunctiva exhibit characteristic ridge-like folds of plasmalemma. These microplicae are approximately 0.1-0.2 micronm in width, of variable height (0.2-0.8 micronm) and length, may followstraight or winding paths, often branch, and exhibit a wide variety of patterns over the surfaces of cells. Transmission electron microscopy reveals that microplicae often have a fine (100-150 A) electron-dense zone subjacent to their plasmalemma and an intracellular matrix characterized by a disorderly arrary of fine filaments (40-60 A in diameter). Microplicae appear to arise from plasmalemmal fold which once provided for intercellular interdigitation and desmosome abhesion between adjacent cells. Ruthenium red staining demonstrates that microplicae and interplical grooves are covered with a polyanionic glycocalyx. Although free surface microplicae may merely represent the renmants of intercellular interdigitations or a modified expression of microvillous-like extensions, it is also possible that they serve another specific function. In this regard it is speculated that microplical and interplical grooves may function to hold a layer of lubricating and cushioning mucin designed to protect the underlying plasmalemma from abrasive abuse.

Scanning electron microscopy of the nephrotic kidney

Scanning electron microscopy (SEMy), supplemented with light microscopy and transmission electron microscopy, was used to study aminonucleoside nephrosis in rats. The visceral epithelium undergoes dramatic restructing in response to aminonucleoside nephrosis. Due in part to an accumulation of intracellular vacuoles, kidney podocytes swell in size. Podocyte major processes lose their many pedicles and slit pores and form close junctions (80 A) with adjacent podocytes. Although no prominant pores opening into the urinary space are found in the visceral epithelium, there is evidence that podocyte vacuoles may rupture and thereby release protein into the urinary space. Many parietal cells also increase in size, accumulate intracellular vacuoles and come into very cose proximity to the visceral epithelium. Casts of PAS-positive, electron-dense material fill the lumina of many uriniferous tubules. Although most proximal tubules exhibit an extensive loss of brush border, no significant changes in other kidney microprojections or cilia were noted. Transmission electron and light microscopy of nephrotic kidneys reveal considerable changes in proximal and distal tubules including a reduction in mitochondria, in cell height, in electron density of the cytoplasmic matrix, in lateral and basal plasmalemma infolds, enlarged euchromatic nuclei, dilated lumens, and accumulation of PAS-positive cytoplasmic granules. SEMy of kidney needle biopsies from patients with proteinuria reveal that SEMy is useful for evaluating glomerular changes in man.

Scanning electron microscopy of human and rhesus monkey kidneys

Human kidney biopsies fixed by immersion fixation and a rhesus monkey kidney fixed by vascular perfusion were critical point-dried and studied by scanning electron microscopy. The surface morphologies of the parietal and visceral epithelial cells and cells lining the uriniferous tubules are described. Many instructive views of these cells as well as some new nephronal features are presented. This study demonstrated that both scanning and transmission electron microscopy may be undertaken on the same biopsy sample. In view of these results, the possibility of using scanning electron microscopy for routine diagnosis of human biopsies is discussed.