Variation in gentamicin-induced death among independent cultures of proximal tubule cells

This study determined the sensitivity of 12 independent isolates of cultured human proximal tubule (HPT) cells to gentamicin. The TD50 (dose [microgram per ml]) for each isolate was determined by linear regression analysis of cells exposed to a wide concentration range of gentamicin over a 16-day period of exposure. The results of this determination clearly showed that within a series of HPT cell cultures there was significant diversity in sensitivity to gentamicin. Three groups of toxic response were delineated. A single isolate, isolate I, was extremely resistant to gentamicin toxicity and was the sole member of group 1. The majority (9 of 12) of the isolates demonstrated intermediate sensitivity to gentamicin and were classified as group 2. Group 3 included two isolates that were very sensitive to gentamicin, with relatively low doses producing cell death. These results provide initial evidence that a portion of the variability seen in nephrotoxicity among patients receiving the aminoglycoside antibiotics might be mediated by factors intrinsic to each individual's proximal tubule cells.

Increased expression of the insulin-like growth factor I receptor gene, IGF1R, in Wilms tumor is correlated with modulation of IGF1R promoter activity by the WT1 Wilms tumor gene product

Wilms tumor is a pediatric neoplasm that arises from the metanephric blastema. The expression of the gene encoding insulin-like growth factor II (IGF-II) is often elevated in these tumors. Since many of the actions of IGF-II are mediated through activation of the IGF-I receptor (IGF-IR), we have measured the levels of IGF-IR mRNA in normal kidney and in Wilms tumor samples using solution hybridization/RNase protection assays. IGF-IR mRNA levels in the tumors were 5.8-fold higher than in adjacent normal kidney tissue. Among the tumors themselves, the levels of IGF-IR mRNA in those containing heterologous stromal elements were 2-fold higher (P < 0.01) than in tumors without these elements. IGF-IR gene (designated IGF1R) expression in the tumors was inversely correlated with the expression of the Wilms tumor suppressor gene WT1, whose inactivation appears to be a key step in the etiology of Wilms tumor. Cotransfection of Chinese hamster ovary cells with rat and human IGF-IR gene promoter constructs driving luciferase reporter genes and with WT1 expression vectors showed that the active WT1 gene product represses IGF-IR promoter activity in a dose-dependent manner. These results suggest that underexpression, deletion, or mutation of WT1 may result in increased expression of the IGF-IR, whose activation by IGF-II may be an important aspect of the biology of Wilms tumor.

Variation in the electrical properties of cultured human proximal tubule cells

Monolayers of human proximal tubule (HPT) cells, when grown on permeable supports and mounted in Ussing chambers, spontaneously display a transepithelial potential difference (PD), short-circuit current (Isc), and transepithelial specific resistance (RT). These electrical parameters were used to determine the degree of heterogeneity among independent isolates of human proximal tubule cell cultures. Seventeen independent isolates of cells were assessed, totaling 260 individual determinations of spontaneous electrical properties. On average, these cell monolayers displayed an apical-negative PD of 1.5 +/- 0.1 mV, an Isc of 2.7 +/- 0.2 microA/cm2, and an RT of 480 +/- 19 ohms x cm2. Each independent cell isolate, however, displayed electrical values within a narrow range, in some cases allowing isolates to be distinguished from one another. The individual isolates were also assessed for Na-coupled glucose transport, Na+,K(+)-ATPase activity, cAMP stimulation by parathyroid hormone (PTH), forskolin stimulation of Isc, and ouabain inhibition. With the exception of a strong correlation between Na+,K(+)-ATPase activity and Isc, these parameters, in contrast to electrical properties, were found to be consistent and did not reveal distinctions among the isolates. HPT cell cultures seem to consistently retain important features of proximal tubule differentiation while maintaining the variability, as demonstrated by electrical properties, that might be expected of cells isolated from a random population.

Morphology and growth characteristics of epithelial cells from classic Wilms' tumors

The ability to establish cell cultures representing the epithelial component of Wilms' tumor was determined for 18 cases of classic Wilms' tumors. From these 18 cases only two resulted in the culture of epithelial cells. Although the tumors from both cases were composed of a prominent epithelial component, other classic tumors not producing epithelial cell cultures also possessed appreciable epithelial components. Likewise, heterotransplants of these two primary tumors failed to give rise to epithelial cell cultures, although cultures of the blastemal element were produced. This suggests that Wilms' tumors may be prone to differentiate in different directions at varying times during tumor growth, possibly dependent on local tumor environment. Epithelial cells from these two classic cases were grown in culture in basal medium composed of a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12 medium, supplemented with selenium, insulin, transferrin, hydrocortisone, tri-iodothyronine, and epidermal growth factor, on a collagen type I matrix with absorbed fetal calf serum proteins. One of the two cases also required the addition of bovine pituitary extract, ethanolamine, prostaglandin E1, and putrescine for optimum growth. Morphological analysis disclosed that the cultured cells were very similar to normal renal tubular cells in culture, except that the cells displayed little evidence for differentiated active ion transport and tended to grow in a multilayered arrangement. The culture of the epithelial cells from classic Wilms' tumors provides a model system for the study of tumor differentiation and progression.

Automatic quantitation of cell growth and determination of mitotic index using DAPI nuclear staining

The growth rate of primary tumors and derived cell lines is an important identifying trademark to researchers studying the growth and differentiation of pediatric neoplasms. For the in vivo tumor specimen, the mitotic index is utilized to assess growth potential while, in vitro, the determination of the growth curve and doubling time of the cells is employed. Because of the importance of these parameters this laboratory has developed a technique for the simultaneous determination of cell number and mitotic index for adherent cultured cells, as well as solid tumors, using the polycationic dye DAPI (4',6-diamino-2-phenylindole). DAPI, when bound to nuclear DNA, fluoresces, and this property has been utilized to develop an image analysis based technique to determine cell number automatically based on gray scale discrimination. In addition, DAPI staining clearly delineates mitotic figures and this has allowed the simultaneous manual determination of mitotic index for each automatic cell count. This technique was first tested using four different human cell lines and was shown to determine cell growth and mitotic index simultaneously. Lastly, employing an atypical mesoblastic nephroma, it was shown that the mitotic index of the primary tumor could easily be obtained and compared to both the mitotic index of tumor heterotransplant in nude mice and the mitotic index of the tumor-derived cell culture. This technique should be useful in studies assessing the effects of various factors on the growth of adherent cultured cells as well as the accurate determination of the mitotic index in solid tumors.

The G401 cell line, utilized for studies of chromosomal changes in Wilms' tumor, is derived from a rhabdoid tumor of the kidney

The histology, ultrastructure, and messenger RNA expression of heterotransplants derived from the G401 cell line (American Type Culture Collection) have been characterized by comparison with Wilms' and rhabdoid tumors of the kidney. This analysis illustrates that the properties of G401 heterotransplant were consistent with a rhabdoid phenotype rather than that of a Wilms' tumor. The G401 cell line has been utilized in recent experiments to demonstrate the central role of chromosome 11 in Wilms' tumor. However, the present results suggest that these experiments may be more relevant to define the involvement of chromosome 11 in rhabdoid tumor of the kidney, a malignancy distinct from Wilms' tumor. This is clinically relevant since the rhabdoid tumor of the kidney is very aggressive and associated with an extremely poor prognosis.

Developmental pattern of Thy-1 immunoreactivity in the human kidney and the application to pediatric renal neoplasms

The localization of Thy-1, a surface membrane lipoglycoprotein, was investigated using a monoclonal antibody specific for human Thy-1 (HB-2S-1). The localization of Thy-1 during development was established in a series of five fetal, three childhood, and two adult normal kidneys. In this series, Thy-1 immunolocalization progressed from mesangial and endothelial cell staining in the 16- to 17-week fetuses to similar staining along with staining of the parietal epithelium of the capsule and proximal tubule staining in the 20- to 24-week fetuses. Glomerular mesangial cell and endothelial cell staining was absent by 9 months postnatally when the adult pattern of staining was apparent. The localization of Thy-1 during development was also compared with a series of pediatric renal tumors including 14 Wilms' tumors, 3 congenital mesoblastic nephromas, 1 clear cell sarcoma, and 1 pediatric renal cell carcinoma. Thy-1 staining was demonstrated in epithelial tubules of Wilms' tumors and in the spindle-shaped cells of congenital mesoblastic nephroma correlating with Thy-1 immunoreactivity in the kidney proximal tubule and fetal medullary stroma, respectively. Thy-1 staining was absent in the anaplastic epithelial Wilms' tumor, the renal cell carcinoma, and the clear cell sarcoma. This staining pattern fails to provide evidence that these tumors may arise from the medullary mesenchyme or the differentiated proximal convoluted tubule. These results show that Thy-1 is a renal differentiation marker and is useful in the characterization of tumors of renal development.

5-methyltetrahydrofolate urinary excretion: modeling by cultured human kidney cells

Initial attempts to model urinary folate reabsorption using cultures of HPT cells on porous filter inserts produced disappointing results in that large amounts of 5M were transported across the epithelial monolayer in a nonspecific manner. Since the impermeable molecule inulin was also transported, there apparently existed a significant leakage pathway in the way that the cultured cells were used for transport studies. 5M was bound to the AP membrane and taken up into the HPT cell by specific processes, while inulin was excluded, suggesting that the HPT cells were nevertheless operating functionally. TER values from cultured HPT cells plateaued at a high level when cells became confluent, suggesting an epithelial layer with functional tight junctions. However, when growth media were removed and replaced with transport buffers, there was an immediate loss of TER that fully recovered if the transport buffers were preincubated for 60 min. Under these conditions, transport studies showed the expected results--no movement of inulin through the cell layer and much reduced transfer of folate through the paracellular pathway. These results suggest that a transient opening of tight junctions occurs when growth media are replaced with biological buffers (or with fresh growth media), but that recovery of tight junction function occurs with time.

Folate transport and binding by cultured human proximal tubule cells

Because mechanisms for the renal regulation of folate excretion are poorly understood, a cell culture system representative of the human proximal tubule (HPT) was used for studies of renal folate transport. After confluent cultures of HPT cells were incubated with 3H-labeled folic acid (PteGlu), binding to the apical membrane was determined by an acid removal procedure, and transport was subsequently measured in solubilized cells. Although PteGlu binding was almost all specific (suppressed by excess unlabeled PteGlu), HPT cells transported PteGlu by specific and nonspecific processes. Specific PteGlu binding and transport were both saturable processes, reaching maxima of 0.5 and 0.1 pmol/mg protein, respectively, with half-maximal constants of 12 and 50 nM, respectively. The PteGlu analogues methotrexate and 5-methyltetrahydrofolic acid (5-CH3-H4PteGlu) inhibited both the binding and transport of PteGlu, with 5-CH3-H4PteGlu being more potent (lower half-maximal inhibitory concentration). In contrast, 5-formyltetrahydrofolic acid significantly reduced PteGlu transport at concentrations (100-250 nM) that had no effect on binding. These data suggest that the HPT cells will serve as a good model for studies of renal folate reabsorption. Initial characterization of the transport of folate by HPT cells suggests two distinct processes, binding to a high-affinity membrane folate-binding protein followed by a structurally specific transfer into the cell.

Aminoglycoside antibiotics alter the electrogenic transport properties of cultured human proximal tubule cells

Monolayers of human proximal tubule (HPT) cells, when grown on permeable supports and mounted in Ussing chambers, spontaneously display a transepithelial potential difference (PD) and short-circuit current (Isc). These electrical parameters were used in the present study to determine if aminoglycoside exposure altered electrogenic sodium transport by HPT cells. The results of this determination demonstrated that exposure to gentamicin, at levels below that producing cell necrosis, caused a marked reduction in Isc and that this reduction followed the known in vivo nephrotoxicities of the aminoglycosides streptomycin, gentamicin, and neomycin. It was concluded through a similar analysis on a total of 14 isolates of HPT cells that the aminoglycosides repeatably reduced the electrogenic sodium transport of HPT cells. It was further determined that this alteration in electrogenic transport by gentamicin was mediated through exposure of the drug to the basolateral cell surface and that apical exposure had little effect. Evidence was obtained against the involvement of Na+, K(+)-ATPase, adenosine 3',5'-cyclic monophosphate, and sodium-coupled substrate transport in this alteration in electrogenic transport by the aminoglycosides. The basolaterally located Na+: CO3(-2):HCO3(-1) symporter is a possible site for aminoglycoside-induced nephrotoxicity.

Variation in sorbitol accumulation and polyol-pathway activity in cultured human proximal tubule cells

The polyol pathway is present in tissues of several organs where its activation may participate in the development of diabetic complications. We measured the accumulation of polyol-pathway intermediates in HPT cells isolated from 21 different human kidneys from nondiabetic individuals. When exposed to 27.5 mM glucose in the growth media, cells isolated from approximately 75% of individuals (accumulators) accumulated sorbitol within 1-4 days, whereas 25% (nonaccumulators) accumulated only negligible amounts, even when the period of exposure was extended to 2 wk. Surprisingly, measurement of the activities of the polyol-pathway enzymes showed no difference in the levels of either AR or SDH between accumulators and nonaccumulators, even when the conversion of galactose to galactitol was used to measure AR activity in intact cells independently of SDH. Measurement of sorbitol in the growth media indicated that nonaccumulators were not releasing sorbitol into the growth media. Fructose levels in the conditioned growth media were 4 times higher in the sorbitol-accumulating cells. Together, these results indicate that the tendency of cells from an individual to accumulate significant amounts of sorbitol may reflect the cells' ability to metabolize sorbitol in steps subsequent to the polyol pathway.

In situ freeze-fracture of monolayer cell cultures grown on a permeable support

The growth of cultured epithelial cells on permeable supports allows increased cell differentiation and the assessment of a variety of transcellular and paracellular transport processes. The need to assess the corresponding ultrastructural characteristics of these cells under identical conditions prompted this laboratory to develop a reliable method for producing freeze-fracture replicas of these cultures. Sections of filter inserts with the cell-side facing up are placed between layers of polyvinyl alcohol with a strip of mylar positioned on the layer of polyvinyl alcohol. Following freezing, the monolayer is fractured by lifting the mylar strip from the assembly. The result is a consistent fracture of the apical membrane sufficient for analysis of tight junction sealing strands, microvilli distribution, and intramembranous particle (IMP) distribution between apical and lateral membrane domains. This method utilizes standard equipment and readily available materials and, most importantly, allows the freeze-fracture and replication of an undisturbed cell monolayer.

Expression of the 11p13 Wilms' tumor gene, WT1, correlates with histologic category of Wilms' tumor

Homozygous inactivation of WT1, a Wilms' tumor gene located on chromosome 11 at p13, is believed to predispose to Wilms' tumor and therefore may be a common occurrence in this cancer. The expression of this gene in primary Wilms' tumors was examined by northern and quantitative RNA slot blot analysis and compared with clinical, histologic, and molecular features of each case. The characteristic 3.2 kb RNA was readily detected in most primary tumors although there was marked variation in the level of WT1-specific transcripts. No abnormal-sized RNA products were detected and expression of WT1 was not coordinated with that of several other oncofetal genes: N-myc, insulinlike growth factor 2 (IGF-2), and c-myc. The relative abundance of WT1-specific RNA did correlate with the histologic category of Wilms' tumor such that those tumors with heterologous differentiation have, in general, lower relative levels of WT1 transcripts than those tumors without heterologous differentiation. These results further establish the heterogeneity of Wilms' tumor with respect to the expression of tumor-associated oncofetal genes and suggest a relationship between WT1 expression and cellular differentiation.

Elicitation of sorbitol accumulation in cultured human proximal tubule cells by elevated glucose concentrations

The human proximal tubule (HPT) is the characteristic site within the kidney that mediates absorption of glucose. This study was designed to determine whether cultured HPT cells would respond to a hyperglycemic environment through activation of the polyol pathway. The results of this study clearly indicate that exposure of the HPT cells to an extracellular glucose concentration greater than or equal to 11 mM results in substantial intracellular accumulation of sorbitol. This accumulation is inhibited by approximately 70% by treatment with 100 microM sorbinil. When cells growing 24 h on 27.5 mM glucose were changed to medium containing 5.5 mM glucose, sorbitol concentration returned to the control level within 12 h. The activity of aldose reductase was increased by a factor of 1.6 by exposure to elevated glucose concentrations, and the relative reactivity of the enzyme with glucose as substrate was approximately 0.1 compared with that of glyceraldehyde as substrate. Together, these results indicate that cultured cells derived from the HPT undergo activation of the polyol pathway when exposed to a hyperglycemic environment.

Growth factor binding and bioactivity in human kidney epithelial cell cultures

Insulinlike growth factors (IGF) and epidermal growth factor (EGF) are produced in renal tissue, as are specific receptors for these hormones. To evaluate the significance of these observations to regulation of renal tubular cell proliferation, we have examined the interaction of IGF and EGF with cultured human proximal tubular epithelial cells (HPT). HPT cells showed specific binding of IGF-1, insulin, and EGF. IGF-1 binding was inhibited by antibody to the type 1 IGF receptor (alpha-IR3). Insulin receptors and type 1 IGF receptors were identified by bifunctional cross-linking. IGF-1, insulin, and EGF stimulated [3H]thymidine incorporation by 77, 73, and 87%, respectively. Half maximal stimulation by IGF-1, insulin, and EGF were produced with 4 X 10(-9) M, 2.5 X 10(-8) M, and 8 X 10(-10) M concentrations of these hormones. Alpha-IR3 inhibited stimulation of thymidine incorporation by IGF-1 and insulin but had no effect in EGF-stimulated thymidine incorporation. EGF and high concentrations of insulin both stimulated cell proliferation by 83 and 79%, respectively. These data are consistent with regulation of tubular epithelial proliferation by IGF-1, insulin, and EGF and suggest that the mitogenic activity of both insulin and IGF-1 is mediated by the type 1 IGF receptor.

Antibody to type I insulinlike growth factor receptor inhibits growth of Wilms' tumor in culture and in athymic mice

The role of the type I insulinlike growth factor (IGF) receptor in regulating growth of Wilms' tumor (WT) was evaluated by examining the effect of antibody-mediated inhibition of this receptor on tumor growth in cell cultures and as heterotransplants in athymic mice. An antibody to the human type I IGF receptor (alpha IR-3) inhibited 125I-IGF-1 binding and prevented stimulation of thymidine incorporation by IGF-1 in vitro. Intraperitoneal administration of alpha IR-3 to nude mice bearing WT heterotransplants prevented tumor growth for 4 weeks and resulted in partial regression of established tumors. These data indicate the importance of IGF action in control of WT growth in vivo, and suggest potential therapeutic application using antigrowth factor receptor antibodies to block growth factor action.

Protein kinase A, cytosolic calcium, and phosphate uptake in human proximal renal cells

Phosphate uptake by proximal renal cells derived from the human kidney occurs by a saturable process that is approximately 85% dependent on the presence of sodium. Kinetic analysis is consistent with two distinct transport events with Km of 0.08 and 0.63 mM and Vmax of 3.4 and 11.0 nmol.mg-1.3 min-1, respectively. Parathyroid hormone (PTH), isoproterenol, and prostaglandin E2 (PGE2) increased cellular adenosine 3',5'-cyclic monophosphate (cAMP). PTH-stimulated cAMP prevented binding of the photolabel 8-azido[32P]cAMP with a half-maximal effective concentration (EC50) of 1 nM PTH, 30-fold lower than the EC50 for intracellular cAMP accumulation. These data are qualitatively similar to those observed in OK cells. PTH did not inhibit phosphate uptake in human cells, although it activated cAMP-dependent protein kinase and increased cytosolic calcium. Thus phosphate uptake in human proximal renal cells maintained in short-term culture is unresponsive to PTH in spite of increased cytosolic calcium and activation of the cAMP pathway.

Cadmium nephrotoxicity in human proximal tubule cell cultures

Human proximal tubule kidney cells grown in a serum-free tissue culture medium were exposed to concentrations of CdCl2 in a range of 0.5 to 10 micrograms/ml. Cells were observed from 1 to 20 d upon initiation of cadmium in the culture fluid. Both confluent and subconfluent populations of cells were treated and evaluated for cytotoxicity. Both populations exhibited a concentration-dependent toxicity to ionic cadmium. For cells treated with 2.0 to 10 micrograms/ml Cd, the decreases in cell numbers were largely irreversible. However, cells treated with Cd in a range of 0.5 to 1.0 micrograms/ml exhibited a partial recovery of cell number and control morphology. In this range, recovery was more efficient in the subconfluent cultures. Fine structural alterations in Cd-treated tubule cells included condensation of nuclear chromatin, loss of microvilli structure, disorganization of lateral membrane interdigitation, as well as decreased uptake of aminoglycoside antibiotics as evidenced by decreased numbers of myeloid bodies in these cells. The results of this study imply that use of a human proximal tubule culture system has potential in discerning structural and functional effects of cadmium as well as other nephrotoxic metals and compounds on the human kidney.

An electrophysiological freeze fracture assessment of cadmium nephrotoxicity in vitro

Human proximal tubule cell cultures exposed to doses of cadmium chloride (CdCl2) between 0.05 microgram/ml and 0.5 microgram/ml exhibited alterations in cell membrane structure and transport function. At these Cd concentrations, cell numbers were not significantly altered from control values in either nonreplicating confluent, or actively replicating subconfluent cultures. Transmission electron microscopy revealed few alterations in cultures treated with 0.05 microgram/ml Cd. Tight junctions were intact; organelles and myeloid body formation appeared normal. Freeze fracture analysis confirmed the integrity of the tight junctions as well as increased numbers of vesicles or pits along the lateral cell membrane, indicating increased endocytotic activity. Cells exposed to 0.1 microgram/ml Cd were characterized by decreased numbers of microvilli and inhibited myeloid body formation. Cd doses of 0.5 micrograms/ml elicited nuclear chromatin condensation, fragmented sealing strands in 5 to 10% of the tight junction profiles, sparse microvilli, and inhibited myeloid body formation. Electrophysiologic assessments of transport function by Ussing chamber analysis revealed decreases in transepithelial potentials for all three concentrations, with significant differences at Cd concentrations of 0.5 to 0.1 micrograms/ml. Cells treated with 0.5 micrograms/ml Cd also exhibited slight decreases in electrical resistance, consistent with the minimal fragmentation of sealing strands observed in freeze fracture replicas. Resistance in cultures treated with 0.1 or 0.05 micrograms/ml Cd remained within control values and indicated that drops in potential difference and short circuit current in these cells reflected true alterations in ion transport.

Growth characteristics of cultured human proximal tubule cells exposed to aminoglycoside antibiotics

It is well known that the nephrotoxic lesions that occur during aminoglycoside-induced nephrotoxicity are both dose- and time-dependent. It was the purpose of this study to determine if a cell culture model based on the human proximal tubule would exhibit similar dose- and time-dependent relationships when exposed to aminoglycosides of various nephrotoxic potential. For this determination, the human proximal tubule (HPT) cells were exposed to increasing concentrations of streptomycin, kanamycin, gentamicin, and neomycin and monitored for cell growth and toxicity over an 18-day period of exposure. Both actively-dividing and resting cells were assessed with regard to aminoglycoside exposure. At high levels of aminoglycoside exposure, linear regression analysis disclosed that the rank order of toxicity of the aminoglycosides to be: neomycin greater than kanamycin greater than gentamicin greater than streptomycin. Both actively-dividing and resting cultures of HPT cells displayed both dose- and time-dependency with regard to toxicity and the ability of the cells to regenerate in the continued presence of aminoglycoside exposure. This pattern of dose- and time-dependency was unique for each aminoglycoside and varied depending on the replicative state of the cells. With the exception of neomycin, clear evidence was obtained that toxicity and cell regeneration were occurring simultaneously throughout the time course of aminoglycoside exposure; the equilibrium between the two processes determining overall cell toxicity or regeneration. In addition, the HPT cells exposed to gentamicin displayed a unique pattern of toxicity and cell regeneration when compared to the other aminoglycosides tested, with gentamicin having an increased ability to stimulate cell proliferation. While the results obtained are in excellent agreement with that known from the clinical experience with the aminoglycosides, the dose- and time-dependency of the responses will require careful attention to growth state during employment in experimental protocols.

Cell culture and characterization of human minor salivary gland duct cells

In order to facilitate studies on human salivary glands, a method was developed for the culture of minor salivary gland duct cells from tissues obtained from oral surgery protocols. Minor salivary glands were isolated from such tissues, and a serum-free growth medium was developed which supported the growth of the ductal component of these glands. The ductal origin of these cells was confirmed through immunohistochemical localization of replicating nuclei through incorporation of BrdU. The presence of epidermal keratin in replicating cells and the absence of smooth muscle myosin further substantiated the ductal origin of cells. Using normal growth medium calcium concentrations (1.05 mM), these cells produced a keratinized multilayer of cells unable to undergo routine subculture procedures. A reduction in calcium ion concentration to 0.1 mM resulted in a cell monolayer, without evidence of terminal keratinization, which could undergo at least eight serial passages (1:3 ratio) under cell culture conditions. It is advanced that these minor salivary gland duct cell cultures will be of use to those studying diseases and disorders of the salivary glands.

Elevated glucose alters paracellular transport of cultured human proximal tubule cells

Cultures of human proximal tubule cells were exposed to elevated concentrations of glucose and dome formation was assessed over a 22 day period of growth. Cultures grown on 5.5 mM glucose formed five domes per microscopic field while those exposed to elevated glucose concentrations (11.0 mM to 27.5 mM) formed only two to three domes per field. The areas of the domes formed by the cells grown on elevated glucose concentrations were reduced as compared to those formed on 5.5 mM glucose. An analysis of the electrical properties of cells grown on elevated glucose concentrations by Ussing chamber technique disclosed a marked reduction in potential difference, short circuit current, and resistance compared to cells grown on 5.5 mM glucose. Routine ultrastructural analysis disclosed that cells grown on elevated glucose concentrations appeared to have fewer tight junction complexes. Further examination utilizing freeze fracture methodology demonstrated that cells grown on elevated glucose concentrations averaged two to three sealing strands per junction as compared to an average of five sealing strands for cells grown on 5.5 mM glucose. The cells grown on elevated glucose concentrations were also noted to possess a greater number of gap junctions. These results demonstrate that elevated glucose concentrations can alter the paracellular route, and possibly the transcellular route, of transport regulation in cultured human proximal tubule cells.

Distribution of fucosubstance in kidney and related neoplasms. Absence of lectin-reactive alpha-fucose from the vasculature of bilateral Wilm's tumors

Two alpha-fucose-binding lectins, Ulex europaeus agglutinin I (UEA I) and Lotus tetragonolobus agglutinin, were employed to compare and contrast the distribution of fucosubstance in normal human kidneys and a variety of renal tumors. The study employed a total of 31 kidneys surgically removed for the presence of a variety of tumors, including 11 unilateral Wilms' tumors, two cases of bilateral Wilms' tumors, 13 renal cell carcinomas, two congenital mesoblastic nephromas, one renal oncocytoma, one neuroblastoma metastatic to the kidney, and one clear cell sarcoma of the kidney. The results show that UEA I-reactive fucosubstance is detected in vascular endothelium of all kidneys and tumors, except bilateral Wilms' tumors. The presence of UEA I-reactive alpha-fucose in the vasculature of unilateral but not bilateral Wilms' tumors defines a unique histochemical distinction between the two groups of tumors. Conceivably, this property might be exploited as a screening procedure for the more aggressive bilateral neoplasms. Other findings detail histochemical differences between UEA I and L tetragonolobus agglutinin, as evidenced by the ability of one lectin to stain a particular cell type that is not reactive with the other lectin.