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J J Grantham

Publications and source records attributed to J J Grantham.

At least 55 records · Page 3Linked to original sources
PubMed1995

Evidence for a potent lipid secretagogue in the cyst fluids of patients with autosomal dominant polycystic kidney disease.

Transepithelial fluid secretion appears to be an important factor in the progressive enlargement of cysts in autosomal dominant polycystic kidney disease. Evidence indicates that the fluid within cysts harbors an autocrine, paracrine, or endocrine secretagogue with the capacity to modulate the rate of cyst expansion. Fluids from five patients with autosomal dominant polycystic kidney disease were studied to determine the chemical nature and the physiologic function of the putative secretagogue. The secretory activity of cyst fluid assayed with polarized monolayers of Madin Darby canine kidney cells could be ascribed to a lipophilic substance of molecular weight < 3,500 d that was not destroyed by freezing, boiling, or proteolytic digestion. This lipid stimulated the production of intracellular cAMP and increased the rate of fluid secretion when added to either surface of cultured renal epithelial cells. Anion exchange chromatography revealed biologic secretory activity to a greater extent in the neutral lipid than in the fatty acid and phospholipid fractions separated from cyst fluid. More extensive chromatographic separation showed preferential appearance of the secretagogue in a fraction of neutral lipids enriched in monoglycerides. Among several candidate lipids, 1-mono-arachidonyl glyceride and arachidonic acid were found to mimic the effect of the cyst fluid to stimulate fluid secretion by Madin Darby canine kidney cells; however, their abundance in cyst fluid was insufficient to account for the degree to which secretion was stimulated by cyst fluid. Moreover, the effect of the arachidonic acid species to stimulate fluid secretion was inhibited by treatment with indomethacin, whereas the effect of the cyst fluid was not. On the basis of this study, it was concluded that human autosomal dominant polycystic kidney disease cyst fluid contains an anonymous lipid with the capacity to stimulate fluid secretion in renal epithelia. This potent endogenous modulator of fluid transport may have an important role in determining the rate at which cysts expand in autosomal dominant polycystic disease.

Animals↗
PubMed1994

Pathogenesis of renal cyst expansion: opportunities for therapy.

Renal epithelial cysts are caused by hereditary or acquired etiologies of undetermined molecular mechanisms. The cysts develop within renal tubules by pathogenetic processes that involve cellular proliferation, accumulation of tubule fluid within distended cavities, and remodelling of extracellular matrix. Evidence is accumulating to support the view that renal cysts are composed of moderately dedifferentiated, immature epithelial cells that proliferate abnormally and transport solute and fluid by secretion, in contrast to the usual absorptive movement of liquid in normal renal tubules. The formation and expansion of renal cysts occurs in conjunction with alterations in the extracellular matrix, including thickening of the tubule basement membrane, infiltration of the interstitium with mononuclear inflammatory cells, and interstitial fibrosis. The pathogenetic elements of cyst formation are understood well enough that it is reasonable, and of considerable importance, to examine in animal models treatment strategies that may be hypothesized to allay the progression of cystic disease to end-stage renal failure.

Animals↗
PubMed1994

Coupling of cell volume and membrane potential changes to fluid secretion in a model of renal cysts.

Renal tubular epithelia ordinarily absorb NaCl and water, although recent evidence indicates that renal cysts secrete fluid. We have utilized the experimental advantages offered by cultured cysts, formed in a collagen matrix by propagating Madin-Darby canine kidney cells, to investigate the mechanisms involved in fluid secretion by this renal epithelium. The rate of fluid transport (adduced from changes in cavity volume), cell volume and changes in membrane potential were measured simultaneously in isolated cysts. Under basal conditions, cysts absorbed fluid (-0.83 +/- 0.34 x 10(-6) ml/min/cm2 cavity surface area, N = 23). AVP and IBMX changed the direction of net fluid transport to secretion (4.24 +/- 0.49 x 10(-6) ml/min/cm2). Cell volume initially fell 7.4 +/- 0.5% and remained stable thereafter as secretion continued. Membrane electrical potential (bis-oxonol epifluorescence) hyperpolarized in 13 cysts and depolarized in 6, the mean change was 1.9 +/- 3.1%. Fluid secretion was abolished by 0.1 mM ouabain. Secretion was not affected by 0.1 mM DIDS and cell pH (bis-carboxyethyl-carboxyfluorescein epifluorescence) was not altered by the induction of secretion, suggesting that secretion is not dependent on Cl-HCO3 exchange. Barium, in the presence of AVP and IBMX, depolarized the cell membrane potential (bis-oxonol fluorescence increased 22.3 +/- 0.03%), reversed secretion to absorption (from 3.21 +/- 0.93 to -1.52 +/- 0.61 x 10(-6) ml/min/cm2), and increased cell volume 2.7 +/- 0.5%. Bumetanide (100 microM) reduced fluid secretion from 4.49 +/- 1.23 to -0.75 +/- 0.55 x 10(-6) ml/min/cm2, further reduced cell volume 4.4 +/- 1.2% and hyperpolarized the membranes (bis-oxonol fluorescence fell 24.3 +/- 5.0%). In the absence of AVP and IBMX bumetanide had no effect on fluid transport, cell volume or membrane potentials. We conclude that AVP reversed the direction of fluid transport in these cultured renal epithelial cysts from absorption to secretion by stimulating a coordinated interaction of basolateral and apical K, Cl and Na transport mechanisms.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1993

The secretion of fluid by renal cysts from patients with autosomal dominant polycystic kidney disease.

BACKGROUND: The mechanism by which fluid accumulates in renal cysts of adults with autosomal dominant polycystic kidney disease is not known. This study was designed to determine whether transepithelial secretion of fluid may account for this accumulation. METHODS: We studied in vitro intact cysts that were excised from kidneys removed from three patients with end-stage autosomal dominant polycystic kidney disease. The cysts were loaded with natural cyst fluid or with a combination of Dulbecco's modified Eagle's medium and Ham's F12 medium (DME-F12) and incubated in DME-F12 for 24 hours. Fluid secretion, determined by the change in the weight of the cysts, was expressed as the rate of fluid secretion per square centimeter of surface area per 24 hours, to correct for the wide variation in the sizes of the cysts. To test for endogenous secretagogues, cyst fluid was added to confluent monolayer cultures of canine- and human-kidney cells. RESULTS: During the first 24 hours of incubation, the mean (+/- SE) rate of fluid secretion in nine cysts containing natural cyst fluid was 20.8 +/- 5.6 microliters per square centimeter of surface area per 24 hours, as compared with 2.3 +/- 3.6 microliters per square centimeter per 24 hours in nine cysts containing incubation medium. Each group of cysts was then incubated with forskolin, a nonspecific stimulator of adenylate cyclase activity, for an additional 24 hours. During this period the fluid-secretion rate of cysts containing natural cyst fluid did not change; however, the secretion rate of those containing incubation medium increased to 9.1 +/- 4.4 microliters per square centimeter per 24 hours (mean change, 6.8 +/- 1.1; P < 0.001). Cyst fluid stimulated fluid secretion by polarized monolayers of canine- and human-kidney cells. CONCLUSIONS: Renal cysts from patients with autosomal dominant polycystic kidney disease can secrete fluid, and net fluid secretion can be increased by unidentified secretagogues in the cyst fluid. These results suggest that the process of cyst enlargement may be susceptible to pharmacologic intervention.

Cells, Cultured↗
PubMed1993

1992 Homer Smith Award. Fluid secretion, cellular proliferation, and the pathogenesis of renal epithelial cysts.

Renal cysts, caused by hereditary or acquired disorders, develop in tubule segments. The central pathogenetic elements of cyst formation include abnormal cellular proliferation, accumulation of intratubular liquid, and remodeling of the extracellular matrix. This review addresses the pathogenetic basis of liquid collection and cellular proliferation. Cavity liquid. At an early stage of growth, most renal cysts become detached from the tubule segment of origin; thus, transepithelial fluid secretion is the source of the liquid in most macroscopic cysts. Evidence from in situ and in vitro studies of intact cysts and epithelium cultured from cyst walls and normal renal tubules indicates that: (1) solutes (NaCl) are secreted into the cysts and water flows secondarily by osmosis; (2) active Na+ transport has a primary or secondary role in the secretion of Na+ and Cl-; and (3) the rate of liquid secretion can be modulated by hormones (arginine vasopressin), autocoids (prostaglandin E1 and E2), growth factors (epidermal growth factor), and unknown factors in cyst fluids. Cellular proliferation. Epithelial cells of renal cysts appear to proliferate more than normal. Each cyst resembles a tumor, except that the mass is composed primarily of liquid rather than cells. The proliferation of cyst epithelial cells is associated with: (1) abnormal expression of proto-oncogenes; (2) abnormal displays of morphologic and biochemical phenotypic markers; and (3) abnormal responsiveness to growth factors. The maturation arrest hypothesis, introduced as a framework to explore the pathogenetic basis of all renal cysts, supposes that the epithelial cells comprising cysts are "locked" in an immature, dedifferentiated state. Therapeutic strategies to control the growth of renal cysts may reasonably target processes that inhibit fluid secretion, maximize fluid absorption, and redifferentiate the immature and abnormally proliferative epithelial cells within cysts.

Animals↗
PubMed1992

Polycystic kidney disease: I. Etiology and pathogenesis.

Geneticists and cell biologists are simultaneously studying the disease's underlying mechanisms. Although a great many questions remain about cyst formation and its role in kidney failure, three fundamental constructs on its etiology and pathogenesis have been generated: renal tubular epithelial proliferation, fluid accumulation, and remodeling of the extracellular matrix.

Humans↗
PubMed1992

C-fos expression is hypersensitive to serum-stimulation in cultured cystic kidney cells from the C57BL/6J-cpk mouse.

Cystic kidneys of the C57BL/6J-cpk murine model of polycystic kidney disease show a marked overexpression of the proto-oncogenes c-fos, c-myc, and c-Ki-ras, consistent with an increased rate of cell proliferation and an altered state of differentiation. To determine if cystic cells have increased responsiveness to stimulation with mitogenic agents, quiescent primary cultures from normal and cystic cpk kidneys were treated with fetal bovine serum (FBS), 8-bromo-cAMP (cAMP), or epidermal growth factor (EGF). The level of c-fos induction following stimulation by FBS was found to be dramatically higher in cystic cells than in normal cells; whereas induction by cAMP or EGF was essentially the same in both cell types and much less than that seen in FBS-stimulated cells. To determine if this serum hypersensitivity reflects an increased proliferative state in vivo, c-fos induction was examined in cultures derived from normal kidneys stimulated to regenerate by folic acid-induced acute renal injury. As with cystic kidneys, the folic acid-injured kidneys showed increased c-fos responsiveness to FBS in cell culture. These experiments suggest that cystic and regenerating kidneys have an altered phenotypic state in vivo that is manifested in cell culture by serum hypersensitivity. However, whereas the folic acid-injured kidneys ultimately reestablish normal kidney function, cystic kidneys further progress to renal failure, suggesting that cystic epithelial cells are locked in this altered state of differentiation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

In vitro formation and expansion of cysts derived from human renal cortex epithelial cells.

Acquired renal cysts derive from terminally differentiated tubular epithelium in adults as a consequence of increased epithelial cell proliferation, fluid accumulation and extracellular matrix remodelling. To understand better how human epithelial cysts may be initiated and progressively expand, cells from primary cultures of normal human adult renal cortex were dispersed in polymerized type I collagen. The transparent matrix permitted repeated observation by light microscopy of cyst formation from individual renal cells. The cyst cells reacted strongly with distal nephron histochemical markers (cytokeratin antibodies AE1/AE3, epithelial membrane antigen, and Arachis hypogaea lectin) but inconsistently or not at all to markers of proximal tubules (Tetragonolobus purpureas lectin and Phaseolus vulgaris erthroagglutinin lectin). The number of spherical, fluid-filled epithelial cysts that developed in a standardized microscope field quantified cyst initiation. Cyst progression was determined from the increase in the diameter (surface area) of cysts and represents a hyperplastic event. EGF or TGF alpha, were required in serum-free defined medium to cause cysts to develop from individual epithelial cells dispersed in the matrix; insulin was required as a co-factor. The EC50 for EGF was approximately 0.1 ng/ml, and for insulin 1 microgram/ml. Early cultures of normal cortex formed cysts more efficiently when dispersed in collagen matrix than cells passaged several times before suspension in the gel. Agonists of adenylate cyclase (PGE1, AVP, VIP, PTH, forskolin, cholera toxin), methylisobutylxanthine, and 8-Br-cAMP, though incapable of causing cyst formation alone in defined medium, enhanced cyst initiation and progression in the presence of EGF and insulin. Angiotensin II, TNF alpha, beta-estradiol, and pertussis toxin had no effect in the absence or presence of EGF and insulin. Pertussis toxin inhibited cyst initiation and expansion caused by EGF and forskolin but potentiated cyst initiation and expansion caused by EGF and PGE1. Cyst formation and expansion were inhibited by TGF beta 1 and 2-chloroadenosine. Polarized monolayers of human renal cortical cells grown on permeable membranes were used to independently quantify the effects of agonists on the net secretion of solute and water from the basolateral to the apical surface of the cells. PGE1, forskolin, and 8-Br-cAMP stimulated net fluid secretion that was sustained for several days; EGF enhanced forskolin-stimulated fluid secretion. We conclude that the formation and expansion of in vitro cysts derived from solitary human cortex cells depends on the coordinated interplay between cellular proliferation and fluid secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Body Fluids↗
PubMed1992

Localization of overexpressed c-myc mRNA in polycystic kidneys of the cpk mouse.

The C57BL/6J-cpk mouse has a form of autosomal-recessive polycystic kidney disease characterized by the rapid growth of large collecting duct cysts and the development of severe renal failure usually by three to four weeks of age. Previous studies had shown higher steady-state levels of proto-oncogene mRNA in these cystic kidneys. It is now shown using nuclear run-on transcription that the c-fos and c-myc proto-oncogenes are transcribed at higher rates in cystic kidneys, and thus that increased transcription, in part, may account for the increased mRNA levels. c-myc mRNA was detected by in situ hybridization in nephron anlagen and elongating tubules of normal and cystic kidneys during late fetal and early neonatal kidney development. Localization of c-myc expression in the normal kidney decreased with age over the three-week postnatal period. By contrast, c-myc mRNA was found in cysts as early as three days of age, with increased levels at two and three weeks. c-myc expression was also elevated in apparently normal, non-dividing proximal tubules in three-week-old cystic animals. On the basis of these findings, we suggest that c-myc expression is linked to the proliferation of cells engaged in the primary cystogenic process, and that expression of this gene in proximal tubule cells of severely azotemic animals reflects the compensatory response of residual tubular epithelial cells to progressive renal dysfunction.

Animals↗
PubMed1992

Specificity of basolateral organic anion exchanger in proximal tubule for cellular and extracellular solutes.

We used an epifluorimetric technique to study the mechanism of organic anion transport across the basolateral surface of isolated S2 segments of rabbit proximal tubules. Fluorescein influx and efflux rates across the basolateral surface of lumen-collapsed tubules were determined from serial measurements of cellular fluorescein content after its addition to or removal from the bathing medium. We examined the effect on fluorescein transport of monocarboxylic and dicarboxylic metabolic intermediates added to the bathing medium or preloaded into the cells. The presence of the monocarboxylates (octanoate, valerate, butyrate, propionate, and acetate) in the bathing medium inhibited fluorescein influx. The eight-carbon-chain fatty acid, octanoate, was nearly as potent an inhibitor as probenecid and was more potent than p-aminohippurate (PAH) (IC50 = 10, 6, and 141 microM, respectively); the shorter chain fatty acids were much less effective (IC50 greater than or equal to 1,000 microM). The dicarboxylates (succinate, adipate, and alpha-ketoglutarate) moderately inhibited fluorescein influx (IC50 = 505, 245, and 257 microM, respectively). To determine the effect of intracellular organic anions on fluorescein influx, tubules were preincubated with organic anions to load the cells; the compounds were then removed from the bath, and fluorescein influx was measured. Preincubation with monocarboxylates, octanoate, butyrate, acetate, and PAH had no effect. In contrast, the dicarboxylates alpha-ketoglutarate, glutarate, and adipate stimulated fluorescein influx by 58, 53, and 43%, respectively, but succinate had no effect. Fluorescein efflux was accelerated by medium octanoate, PAH, alpha-ketoglutarate, and succinate but not by acetate. Probenecid alone had no effect on fluorescein efflux, but it blocked the stimulation caused by medium PAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Cyst fluid from human autosomal dominant polycystic kidneys promotes cyst formation and expansion by renal epithelial cells in vitro.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive renal enlargement, culminating in renal insufficiency in over one half of affected individuals. The highly variable onset and clinical course of ADPKD may be due to factors extrinsic to the genetically defined renal cysts. In this study, cyst fluid samples from 12 nonazotemic and 18 azotemic ADPKD subjects were examined for in vitro biologic activity that promotes cellular proliferation and the secretion of fluid by renal epithelial monolayers, two pathogenetic mechanisms that have critical roles in the formation and the rate of expansion of renal cysts. Cyst fluid added to culture medium (final concentrations, 1 to 20%) caused Madin-Darby canine kidney cells and human kidney cortex (HKC) cells derived from primary cultures to form cysts in Type I collagen matrix. Cyst fluid stimulated the net transepithelial secretion of fluid by polarized monolayers composed of these same cells. Absolute levels of fluid secretory activity determined by MDCK bioassay were correlated directly with the rate of fluid secretion by HKC cell monolayers and with the extent of cyst formation by MDCK and HKC cells embedded in collagen matrix. The secretory activity of urine was negligible; secretory activity was detectable in the serum of normal and ADPKD subjects, but the levels were much lower than in cyst fluid. cAMP agonists prostaglandins E1 and E2, arginine vasopressin, and 8-Br-cAMP stimulated fluid secretion by MDCK and HKC monolayers, but these substances did not cause HKC cells to form cysts in collagen matrix, whereas cyst fluid did. Among other naturally occurring growth factors and autacoids, only epidermal growth factor and transforming growth factor alpha stimulated cyst formation by HKC cells; however, the capacity of cyst fluid to stimulate fluid secretion was not affected by treatment with antiserum to epidermal growth factor. It was concluded that potent, and possibly unique, substances in the cyst fluids of individuals with ADPKD support and augment biologic processes in renal epithelial cells that may be important in the promotion of progressive cyst expansion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Calcified renal stones and cyst calcifications in autosomal dominant polycystic kidney disease: clinical and CT study in 84 patients.

Although renal calculi and cyst calcifications occur commonly in patients with autosomal dominant polycystic kidney disease (ADPKD), their true frequency is unknown because it is difficult to distinguish between the two with excretory urography and sonography. A detailed analysis of renal calcifications in ADPKD based on CT findings has not been performed. Accordingly, we retrospectively evaluated clinical and CT findings in 84 patients with ADPKD to determine the frequency of calculi and cyst calcifications, the relationship of these abnormalities to symptoms, and possible factors in their pathogenesis. Of the 84 patients, 53 had both IV contrast-enhanced and unenhanced CT scans and 31 had unenhanced scans only. We examined unenhanced CT scans of all 84 patients for renal calcifications. However, we classified renal calcifications into stones and cyst calcifications in only the 53 patients, because it is often difficult to distinguish between the two when only unenhanced scans are available. Of 84 patients, 18 (21%) had passed renal calculi or had stones treated surgically and 42 (50%) had renal calcifications on CT. Of the 53 patients who had both enhanced and unenhanced CT scans, 19 (36%) had renal calculi on CT. Patients with stones had significantly higher frequencies of previous flank pain (68% vs 35%) and of urinary tract infections (63% vs 18%) than did those without calculi. Cyst calcifications occurred in 13 (25%) of 53 patients and were probably a consequence of cyst hemorrhage. Cyst calcifications were found significantly more often in older patients with larger kidneys and worse renal function. We conclude that renal stones have a high rate of occurrence among patients with ADPKD and are a significant cause of morbidity in this disorder. Cyst calcification is also common in patients with ADPKD, particularly those with more advanced cystic disease.

Adolescent↗
PubMed1991

A hereditary model of slowly progressive polycystic kidney disease in the mouse.

There are two known forms of hereditary polycystic kidney disease (PKD) in humans. Although both forms initiate early in life, autosomal recessive PKD is rapidly progressive to kidney failure shortly after birth whereas autosomal dominant PKD is slowly progressive, taking many years to end stage. Research in this field has been limited by the availability of suitable animal models of PKD. Recently the C57BL/6J-cpk mouse has been used to study the pathogenesis of rapidly progressive hereditary PKD. The study presented here describes a slowly progressive PKD in the DBA/2-pcy mouse. The disease trait is transmitted in an autosomal recessive pattern and was localized to chromosome 9 through linkage to the dilute coat color and transferrin genes. Whereas some cystic changes were seen in fetal and newborn affected mice, renal enlargement did not develop until after 8 weeks of age and azotemia did not develop until after 18 weeks of age. Renal cysts were identified in all segments of the nephron and collecting duct and progressively enlarged with age. Individual cysts were found to be lined by a single layer of epithelial cells in most areas, with focal polyps and mounds of cells principally in collecting duct cysts. Early stages of cyst formation were associated with some abnormalities of tubular and glomerular basement membranes and accelerated eruption of incisors. Late stages of the disease were characterized by azotemia and chronic renal interstitial inflammatory infiltrates in all affected animals and cerebral vascular aneurysms in a few. We conclude that the DBA/2-pcy mouse has a form of renal cystic disease that appears similar in many respects to that seen in the dominant form of human PKD.

Animals↗