Expectations of Task Demands Dissociate Working Memory and Long-Term Memory Systems.

Many aspects of the complex relationship between working memory (WM) and long-term memory (LTM) remain unclear. Here, we manipulated task demands on a brief delayed-recognition paradigm to reveal behavioral and neural dissociations between these systems. Variations from a Baseline task included 3 challenges: increased delay duration, distraction during maintenance, and more closely matched memory probes, which were presented in behavioral experiments and during functional magnetic resonance imaging. Each of the challenges resulted in a significant decline in WM accuracy, and interestingly, a concurrent improvement in incidental LTM. Neural data revealed that, in task blocks, when participants anticipated, and then experienced, increased demands, they engaged medial temporal lobe (MTL) regions more during both the encoding and delay periods. Overall, these results indicate that distinct memory systems are recruited based on anticipated demands of a memory task, and MTL involvement underlies the observed dissociation between WM and LTM performance.

A new form of myeloma "kidney": shortened hemofilter survival and implications for membrane filtration plasmapheresis.

BACKGROUND: Despite rigorous focus on extracorporeal CRRT parameters such as access, blood flow, hemoconcentration, and anticoagulation, some patients have unexpected repetitive hemofilter clotting. We instead explored patient or disease-related factors that could be responsible, and present a case of plasma cell dyscrasia in which paraproteins caused hollow fiber failure. METHODS: A patient with IgG kappa chain multiple myeloma complicated by sepsis and acute renal failure was started on CVVH with a regional citrate anticoagulation protocol that typically yields filter life of >50 h. Polysulfone hemofilters repetitively clotted every 2-4 h, even after excluding circuit-related problems. Failed filters were examined by light, electron (EM), and immunofluorescence (IF) microscopy. RESULTS: Imaging of the hemofilters revealed several ultrastructural features typical for myeloma-associated alterations in native human tissue. Red cell rouleaux formation occurred within the hollow fibers. There was extensive protein layering on the luminal surface of the fibers with some extension into their walls: these deposits were IF+ for IgG kappa, and had a fibrillary substructure on EM. CONCLUSION: Extracorporeal hollow fiber phenomena recapitulate many intra-corporeal paraprotein effects such as those described in the kidney with plasma cell dyscrasias. Rapid protein layering suggests fouling of the membrane, decreased solute clearance before total device failure, and raises the theoretical concern that this might also occur during filtration plasmapheresis: we thus suggest serial serum free light chain levels to confirm their removal when using that technique. These findings emphasize the importance of disease rather than circuit-related factors that are under-appreciated causes of premature hemofilter failure.

Neurofibromatosis type 1 gene haploinsufficiency reduces AP-1 gene expression without abrogating the anabolic effect of parathyroid hormone.

Approximately 50% of neurofibromatosis type 1 (NF1) patients exhibit skeletal pathology, such as premature osteoporosis or pseudoarthroses. Loss of neurofibromin deregulates Ras signal transduction to affect generation of mitogen-activated protein kinase and Akt, both of which have been implicated in parathyroid hormone (PTH) anabolic mechanisms. Our aim was to determine if loss of neurofibromin impaired the anabolic effect of PTH on bone mass. Nf1 heterozygote (Nf1(+/-)) and wild type (Nf1(+/+)) mice were treated with recombinant human PTH(1-34) or vehicle once daily for 3-28 days. PTH enhanced mRNA expression of c-fos, junB, and fra2 in the distal femur metaphyses of both genotypes; expression of these transcripts was consistently lower in PTH-treated Nf1(+/-) mice. Despite lowered c-fos expression in Nf1(+/-) mice, PTH increased bone mass equivalently in both genotypes by 28 days. Ex vivo, Nf1 heterozygosity was associated with increased inducible osteoclasts in PTH-treated bone marrow cells and impairment of the actin stress fiber and cyclic adenosine monophosphate response to PTH in osteoprogenitors. Lower c-fos expression was previously thought to abrogate PTH responsiveness. Our results suggest crosstalk might occur between Ras signal transduction and the protein kinase A pathway in Nf1(+/-) mice. Ras signal transduction does not appear to be essential for the anabolic actions of PTH on bone. Because PTH was effective in the absence of Nf1, it may offer a useful approach to treat osteoporosis in NF1 patients.

Induction of LTP in the human auditory cortex by sensory stimulation.

High-frequency, repetitive, auditory stimulation was used to determine whether induction of a long-lasting increase of the human auditory evoked potential (AEP) was possible. Recording non-invasively with electroencephalogram scalp electrodes, stable increases in amplitude were observed in the N1 component of the AEP, which is thought to reflect activity within auditory cortex (N1). The increase was maintained over an hour and was shown to be independent of alterations in the state of arousal. This is the first demonstration of the induction of long-lasting plastic changes in AEPs, and suggest that this represents the first direct demonstration of long-term potentiation in the auditory cortex of normal, intact humans.

Neurofibromin and its inactivation of Ras are prerequisites for osteoblast functioning.

Skeletal problems and osteoporosis occur in up to 50% affected neurofibromatosis type 1 (NF1) humans. Inactivation of neurofibromin results in deregulation of Ras signal transduction. Little is known of bone biology in humans with NF1. The goal of our work was to determine if loss-of-function of Nf1 gene was associated with altered bone homeostasis and Ras signal transduction. Because homozygous Nf1 mice are embryonically lethal, heterozygote Nf1 (Nf1+/-) male mice were used to investigate skeletal phenotypes and osteoprogenitor functions, using standard in vivo and in vitro assays. We found that bone mass and geometry of Nf1+/- mice did not differ from wild type controls, despite a trend to less bone formation. Nf1+/- committed osteoprogenitors from femur metaphysis exhibited premature apoptosis and higher proliferation. Ras signaling was activated in primary Nf1+/- bone marrow-inducible osteoprogenitors. Inducible osteoprogenitors exhibited lower induction of osteoblast differentiation, assessed as alkaline phosphatase positive CFU-f. A screen of osteoblast marker genes showed a selective increase in osteopontin (OPN) mRNA and protein expression in these cells. OPN protein was increased in Nf1+/- bone, especially in cortical bone matrix. Because bone cell abnormalities in Nf1 haploinsufficiency were detected in vitro, redundant pathways must compensate for the deregulation of Ras signaling in vivo to maintain normal bone mass and function in vivo. Our in vitro data revealed that neurofibromin and its control of Ras signaling are required for osteoprogenitor homeostasis.

Turn that frown upside down: ERP effects of thatcherization of misorientated faces.

When inverted, thatcherized faces appear normal. This may be due to a decrease in configural and an increase in featural processing. It is not known whether this processing is continuous or reflects two distinct processing systems. Using event-related potentials (ERPs), we investigated the Thatcher effect on thatcherized and normal faces at varying orientations. The ERPs paralleled the perceptual illusion. The effect of thatcherization on upright faces was visible in P1 and N170 ERP components, possibly reflecting attentional engagement due to unpleasantness of thatcherized faces. Effects were also found over two later components, the P250 component, which has been related to configural recognition, and a late parietal component possibly reflecting featural processing. The effect of thatcherization on the two later components decreased gradually (for the P250 component) and abruptly (for the late parietal component) as the faces were rotated away from the upright.

Outcome of kidney transplants in patients known to be flow cytometry crossmatch positive.

BACKGROUND: The clinical significance of the flow cytometry crossmatch has been addressed in several retrospective studies, but the results have been controversial. There are no prospective studies in which patients known to be antibody positive underwent transplantation. METHODS: The flow cytometry crossmatch was performed prospectively in 1130 renal transplant recipients. A decision to perform transplantation was based on whether the positive results were on T or B cells, in the current or peak specimen, and taking into account the presence or absence of other immunological risk factors. One hundred antibody-positive patients received a transplant. Graft survival and rejection episodes were analyzed in this group and compared with 100 crossmatch-negative patients matched for age, sex, race, and time of transplantation. RESULTS: The incidence of rejection at 1 month was higher in antibody-positive patients (26%) than in antibody-negative patients (12%, P<0.01). Early rejection seemed to be more frequent in antibody-positive patients regardless of whether the antibodies were current or historic, or against T or B cells. There were more steroid-resistant rejections in antibody-positive than in antibody-negative patients. However, biopsy specimens showed that vascular lesions that can be associated with humoral rejection were not more frequent in the antibody-positive patients than in the controls. There were no differences in graft survival between the two groups. CONCLUSIONS: Low-level preformed alloantibodies detected by flow cytometry represent a risk of rejection even for patients purposely selected for having no additional immunological risk factors. The risk seems to be due to donor-specific memory rather than to a direct effect of the antibodies. The results indicate that flow cytometry provides useful information to assess donor-recipient compatibility.

Proteinuria: potential causes and approach to evaluation.

Proteinuria may be associated with a renal or systemic disease, or it may be isolated. The latter occurs in asymptomatic patients without evidence of any disease or abnormality of the urine sediment. Isolated proteinuria may be subdivided into two broad groups: (1) benign forms, with a favorable-to-excellent prognosis and (2) persistent forms, some of which have a worrisome prognosis. Functional proteinuria may occur in disorders with altered renal hemodynamics, usually resolves, and is not associated with progressive renal disease. Idiopathic transient proteinuria is typically discovered on routine screening and usually disappears on subsequent testing. In idiopathic intermittent proteinuria, a significant number (50%) of urine samples exhibit abnormal rates of protein excretion. Although structural abnormalities may be observed on renal biopsy, progressive renal insufficiency is unusual. In orthostatic proteinuria, the rate of protein excretion completely normalizes in the recumbent position. Long-term studies show this to be a benign condition. In persistent isolated proteinuria, at least 80% of random urine samples exhibit abnormal protein excretion. This represents a heterogeneous group, but a significant proportion of these patients have prominent renal pathologic findings and progress to serious renal disease. Proteinuria with significant renal disease may be non-nephrotic or nephrotic range. The former does not exclude glomerular disease, but tubulointerstitial or vascular disorders are also likely when proteinuria is less than 2 g/24 hours. Patients with nephrotic-range proteinuria generally have a glomerular disorder. Distinction between benign and more ominous forms of proteinuria requires careful evaluation.

Compartmentalization of the inflammatory response to inhaled grain dust.

Interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor (TNF)-alpha, and the secreted form of the IL-1 receptor antagonist (sIL-1RA) are involved in the inflammatory response to inhaled grain dust. Previously, we found considerable production of these cytokines in the lower respiratory tract of workers exposed by inhalation to aqueous extracts of corn dust extract. Alveolar macrophages (AM) have long been considered the cell type responsible for producing these cytokines, and only recently has it been realized that airway epithelial cells may also be involved in cytokine production. In order to determine whether airway epithelia are involved in the inflammatory response to inhaled corn dust extract and to compare the magnitude of response of bronchial epithelial cells (BE) and bronchoalveolar lavage (BAL) cells, we used the reverse transcriptase/polymerase chain reaction (RT/PCR) technique in a semiquantitative manner to evaluate the concentration of IL-1beta, IL-6, IL-8, TNF-alpha, and sIL-1RA. Alveolar cells were obtained by BAL, and BE were obtained by endobronchial brush biopsy from 15 grain handlers 6 h after experimental inhalation of saline or an aqueous corn dust extract. After inhalation of saline, BE expressed low but detectable levels of IL-6, IL-8, and IL-1beta (> 1 complementary DNA [cDNA] molecule/cell). After inhalation of corn dust extract, the expression of messenger RNA (mRNA) for IL-1beta and IL-8 in the BE were significantly increased, whereas no change was seen in IL-6, sIL-1RA, and TNF-alpha mRNA expression. Comparing cytokine mRNA levels in BE and BAL cells from the same subjects after inhalation of corn dust extract, BE and BAL cells expressed equivalent amounts of IL-8 mRNA; IL-1beta was 11-fold higher in BAL cells; and TNF-alpha and sIL-1RA were expressed exclusively by BAL cells. Immunostaining for the cytokines in BAL cells showed cytokine protein expression in AMs but not in polymorphonuclear cells (PMNs). On the other hand, sIL-1RA was strongly expressed in both AMs and PMNs. Analysis of cytokine protein levels in endobronchial lavage (EBL) fluid demonstrated that only IL-8 was released in detectable amounts into the airway lumen, whereas all the other cytokines of interest were exclusively found in the BAL fluid. Thus, within 6 h after inhalation exposure to corn dust extract, BE appear to contribute to airway inflammation by producing IL-8. AMs are responsible for most of the IL-1beta and IL-6 production in the alveolar region, whereas AMs and PMNs both produce sIL-1RA. Our findings suggest that the inflammatory response to inhaled grain dust is compartmentalized, involving specific mediators of inflammation released by macrophages, neutrophils, and airway epithelial cells.

Reduction in Ames Salmonella mutagenicity of mainstream cigarette smoke condensate by tobacco protein removal.

The mutagenic activity of cigarette smoke condensates (CSC) made from tobacco before and after removal of protein was assessed by the Ames Salmonella assay in bacterial strains TA98 and TA100. Removal of protein and peptides from flue-cured tobacco via water extraction followed by protease digestion reduced the mutagenicity of the resultant CSC by 80% in the TA98 strain and 50% in the TA100 strain. Similarly, reductions of 81% in TA98 and 54% in TA100 were seen following water extraction and protease digestion of burley tobacco. The significant reductions in Ames mutagenicity following protein removal suggest that protein pyrolysis products are a principal contributor to the genotoxicity of CSC as measured in this assay.

Macrophages and chronic renal allograft nephropathy.

In a previous study we demonstrated that macrophage infiltrates stained for thromboxane A synthase (TxAS) correlated inversely with renal function six months after biopsy. We propose that macrophage based inflammation is a cofactor leading to chronic allograft nephropathy. For this study we compared four indices of renal allograft nephropathy with renal survival. The Banff Score of Inflammatory Changes (BSI) is an index of acute inflammation. The Banff Chronic Index (BCI) and Chronic Allograft Damage Index (CADI) are indexes of chronic disease. The Macrophage Index (MI) is the same as the BSI applied only to macrophages. These indices were determined on renal allograft biopsies obtained because of delayed graft function within the first week of transplantation, and for increasing plasma creatinine levels after stable function. All four indices predicted renal survival in the post-biopsy interval. MI predicted renal survival for the entire transplant period. In addition, the presence of TxAS transcripts in the renal allografts was determined using a reverse transcription-polymerase chain reaction-based assay. This confirms previous observations of TxAS in the grafts. This study supports the hypothesis that macrophage derived inflammation is a cofactor for chronic allograft nephropathy.

The role of atopy in grain dust-induced airway disease.

To determine whether atopy influences the physiologic or inflammatory response to grain dust, we compared spirometric measures of airflow and bronchoalveolar lavage (BAL) measures of lower respiratory tract inflammation between demographically similar nonatopic (n = 10) and atopic (n = 10) study subjects after each of two inhalation exposures: Hanks' balanced salt solution (HBSS) and corn dust extract (CDE; 0.4 microgram of endotoxin/kg body weight). Subjects were healthy nonsmokers with similar baseline pulmonary function, without bronchial hyperreactivity, and had not participated in agriculture. Atopic subjects had two or more positive skin responses to 10 common environmental allergens. Both groups developed significant airflow obstruction and lower airway inflammation after CDE inhalation. Importantly, the magnitude of the post-CDE exposure airflow decrements, BAL cellularity, and BAL concentration of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, and IL-8 did not significantly differ between atopics and nonatopics. The concentrations of histamine and eosinophils in the BAL fluid were unaffected by CDE inhalation and did not significantly differ between atopics and nonatopics. Atopic status does not appear to be a significant determinant of airflow obstruction or lower airway inflammation following CDE inhalation. Our findings suggest that atopy may play, at most, a minor role in the development of grain dust-induced airway disease.

Thromboxane synthase expression in renal transplant patients with rejection.

Thromboxane synthase (TS) catalyzes the formation of thromboxane (TxA2) in monocytes/macrophages, platelets, and various tissues. TxA2 is likely to play a role in graft dysfunction due to its vasoconstrictive and platelet aggregatory properties. We studied the expression of TS in 7 normal native kidneys, 29 consecutive renal allograft biopsies (performed for rising serum creatinine, n = 23, and delayed graft function, n = 6), and one transplant nephrectomy specimen with severe acute rejection. TS expression was determined by immunocytochemistry using a monoclonal antibody against human TS, Kon-7. Histologic grading of the transplant biopsy specimens was based on the Banff classification. The degree of TS staining was graded in the glomeruli, interstitium, tubules and vessels from 0 to 3+. Of 29 biopsies, 13 had chronic nephropathy (CN), 6 had acute rejection (AR) with chronic nephropathy (AR/CN), 4 had acute rejection (AR), and 6 had acute tubular necrosis (ATN). TS staining of native kidneys showed sporadic interstitial cells. The biopsy and transplant nephrectomy specimens showed significant staining, predominantly in the glomeruli and interstitium. Positively staining cells appeared to be of macrophage/monocyte lineage by morphology. The mean glomerular staining grade was significantly increased in specimens with AR (2.3 +/- 0.9) and the mean interstitial staining was increased in specimens with AR/CN (2.2 +/- 0.9). Follow-up renal function 6 months post-biopsy showed that patients with higher TS staining grades had a faster decline in graft function. In conclusion, TS expression is increased in patients with acute rejection with or without chronic nephropathy and is associated with more rapid deterioration in function.

Grain dust-induced airflow obstruction and inflammation of the lower respiratory tract.

To investigate the relationship between the physiologic and biologic effects of grain dust inhalation, we exposed 15 nonsmoking, nonasthmatic, nonatopic male grain handlers to buffered saline and aqueous corn dust extract by inhalation challenge in a crossover study. The inhalation challenges to buffered saline and corn dust extract were separated by at least 14 d. Compared with buffered saline, inhalation of corn dust extract resulted in significant airflow obstruction, which was observed within 30 min of exposure and persisted for 5 h. Inhalation of corn dust extract resulted in an acute inflammatory response characterized by higher concentrations of neutrophils (p = 0.001), IL-1 beta (p = 0.001), IL-1RA (p = 0.001), IL-6 (p = 0.001), IL-8 (p = 0.001), and TNF-alpha (p = 0.04) in bronchoalveolar lavage (BAL) fluid. mRNA levels specific for IL-1 beta, IL-1RA, IL-6, and IL-8 from cells present in the BAL fluid were significantly greater after challenge with corn dust extract than after challenge with buffered saline. Importantly, no significant differences were observed in the concentration of lymphocytes or eosinophils in the BAL fluid following inhalation of corn dust extract, and the concentrations of histamine and 15-HETE were similar in BAL fluid after the two challenges. The maximal percentage decrease in FEV1 was significantly associated with the absolute neutrophil concentration in the BAL fluid (p = 0.001), as well as the concentration of TNF-alpha (p = 0.03), IL-1 beta (p = 0.005), IL-1RA (p = 0.001), IL-6 (p = 0.001), and IL-8 (p = 0.001) in the BAL fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Segmental localization of mRNAs encoding Na(+)-K(+)-ATPase alpha- and beta-subunit isoforms in rat kidney using RT-PCR.

To characterize the expression of genes encoding the alpha- and beta-subunit isoforms of the Na(+)-K(+)-ATPase in rat kidney, we used reverse transcription (RT)-PCR of microdissected renal structures combined with quantitation of subunit isoform mRNAs in the major renal parenchymal zones. Transcripts for alpha 1, alpha 2, alpha 3, beta 1, and beta 2 subunit isoforms were detected by RT-PCR in microdissected glomeruli, proximal convoluted tubules, medullary thick ascending limbs of Henle, cortical and inner medullary collecting ducts. The truncated alpha 1 (alpha 1-T) isoform was also amplified from cortex, outer and inner medulla and isolated glomeruli, but it was not detected in these nephron segments. The DNA sequence of the renal alpha 1-T PCR product was identical to that of the cDNA previously cloned from aortic smooth muscle cells. RNA dot-blot analysis indicated that the alpha 1, alpha 2, and alpha 3 isoforms contributed approximately 70%, approximately 20%, and approximately 10%, respectively, of the total alpha isoform mRNA in each parenchymal zone. RNase protection assays determined that the beta 1 and beta 2 isoforms accounted for approximately 95% and approximately 5%, respectively, of the beta isoform mRNA in each zone. These data provide definitive evidence for the differential expression of mRNAs encoding all the alpha and beta isoforms in the renal parenchyma, and for the coexpression of these isoforms in the nephron segments examined. The results suggest the potential expression of up to eight different Na(+)-K(+)-ATPase isoenzymes in the kidney, and for multiple molecular levels of regulation of renal Na(+)-K(+)-ATPase expression.

Differential expression and induction of mRNAs encoding two inducible nitric oxide synthases in rat kidney.

We used quantitative PCR methods and renal microdissection to characterize the expression of inducible nitric oxide synthase (iNOS) mRNAs in rat kidney and cultured glomerular mesangial cells. A partial cDNA homologous to murine macrophage iNOS (macNOS), but distinct from rat vascular smooth muscle iNOS (vsmNOS), was cloned from normal rat kidney. macNOS was the principal iNOS isoform tonically expressed in microdissected glomeruli, proximal tubules, medullary thick ascending limbs (mTAL), cortical and inner medullary collecting ducts (IMCD), and cultured mesangial cells, whereas vsmNOS was the major isoform expressed in arcuate and interlobular arteries. Basal macNOS expression was greatest in mTALs and IMCDs. Restriction mapping of RT-PCR products indicated that basal expression of macNOS mRNA was comparable to that of vsmNOS in cortex, but greater than vsmNOS in outer and inner medulla. However, compared to controls, lipopolysaccharide (LPS)-treated rats exhibited a much greater proportion of vsmNOS mRNA and higher levels of total iNOS mRNA in each zone. Similarly, TNF alpha and IF-gamma preferentially induced expression of vsmNOS mRNA in cultured mesangial cells. We conclude that two iNOS isoforms are constitutively and heterogeneously expressed in the normal rat kidney, and that endotoxemia and cytokines differentially induce their expression.

The effects of inhalation of grain dust extract and endotoxin on upper and lower airways.

To characterize the short-term effects of grain dusts on pulmonary function, mucosal inflammation, and systemic responses, four women and three men inhaled nebulized corn and soybean dust extracts, endotoxin diluted with Hanks' balanced salt solution (HBSS), and HBSS. Subjects were volunteers recruited via newspaper advertisement and were required to be healthy, nonasthmatic, nonatopic never-smokers. The mean age was 26.9 years (range, 19 to 36 years). Using a randomized, double-blind, crossover design, each subject was challenged with each of the 4 substances with at least 10 days between challenges. Serial spirometry, peripheral blood leukocyte and differential cell counts, and 24-h postchallenge nasal lavages were performed. Extracts were produced by mixing 3 g of the corn or soybean dust with 30 ml HBSS followed by shaking for 60 min, centrifugation, then filter sterilization. The endotoxin solution was produced by mixing lyophilized Escherichia coli endotoxin (serotype 0111:B4) with HBSS to attain a final concentration of 7 mg/L, which was the same as the concentration of endotoxin in both grain dust solutions. The pH of all solutions and unmixed HBSS was adjusted to 5.8, which was the native pH of the soybean dust extract. Subjects were challenged with 0.08 ml/kg of each substance, resulting in a range of endotoxin doses of 30 to 60 micrograms, similar to that which a worker might inhale over the course of one workshift. The lowest mean percentage baseline FEV1 (+/- SD) after inhalation challenge was 99.2 +/- 2.1 for HBSS, and it was significantly lower for endotoxin (90.1 +/- 8.5, p = 0.03), corn dust extract (93.1 +/- 4.3, p = 0.02), and soybean dust extract (96.2 +/- 3.7, p = 0.03). In addition, a peripheral blood leukocytosis developed after exposure to all three endotoxin-containing solutions (p < 0.05), yet a lower peripheral blood lymphocyte count was found only after inhalation of corn dust extract (p = 0.02). Interestingly, this was associated with a higher nasal lavage lymphocyte count after inhalation of corn dust extract (p = 0.03). Neither the decrease in peripheral blood lymphocytes nor the increase in nasal lymphocytes were found after inhalation of soybean dust extract or endotoxin. Our results indicate that extracts of grain dusts have physiologic effects similar to endotoxin. However, in spite of the same endotoxin levels, the effects of corn dust extract appear to have different biologic activity than either soybean dust extract or endotoxin.

Regulation of kidney organogenesis: homeobox genes, growth factors, and Wilms tumor.

Factors regulating the temporal and spatial expression of kidney developmental programs are beginning to be identified. Evidence accumulated in the past few years indicates that the Hox and Pax genes, in particular, are important for early kidney development. A number of soluble growth factors were also shown to be essential for nephrogenesis to proceed in vitro. Errors in kidney development include Wilms tumor, a common childhood malignancy, which in many cases seems to be caused by faulty transcriptional regulation.

Potassium conductances in tracheal epithelium activated by secretion and cell swelling.

Increased basolateral membrane K conductance accompanies stimulation of Cl secretion across canine trachea. To assess the K conductance properties, we permeabilized the apical membranes with amphotericin B and monitored the current and conductance caused by K flow across the basolateral membranes. Under basal unstimulated conditions, two K conductances could be distinguished by blockers. One was inhibited only by barium; the other was sensitive also to quinidine and lidocaine. The permeabilities of the basal conductance pathways to K and Rb were similar (PK/PRb approximately equal to 1.5). The secretory agonist, epinephrine, selectively increased the quinidine-insensitive conductance, implicating it in the Cl secretory response. Cell swelling induced a third conductance with a low permeability to Rb (PK/PRb approximately equal to 10) that was quinidine sensitive. In tissues not treated with amphotericin, neither quinidine nor Rb-for-K replacement inhibited transepithelial Cl secretion. Thus neither of the quinidine-sensitive K conductances (basal or swelling induced) contribute to the increase in basolateral K conductance during Cl secretion. Cell shrinkage inhibited all three conductances and secretion, suggesting that the initial priority of the cell is volume regulation.