Expression of the beta2-subunit and apical localization of Na+-K+-ATPase in metanephric kidney

During kidney organogenesis, the Na+-K+-ATPase pump is not restricted to the basolateral plasma membrane of the renal epithelial cell but is instead either localized to the apical and lateral membrane sites of the early nephron or expressed in a nonpolarized distribution in the newly formed collecting ducts. The importance of Na+-K+-ATPase beta-subunit expression in the translocation of the Na+-K+-ATPase to the plasma membrane raises the question as to which beta-subunit isoform is expressed during kidney organogenesis. Immunocytochemical, Western analysis and RNase protection studies showed that both beta2-subunit protein and beta2 mRNA are expressed in the early gestation to midgestation human metanephric kidney. In contrast, although beta1 mRNA abundance is equivalent to that of the beta2-subunit in the metanephric kidney, the beta1-subunit protein was not detected in early to midgestation metanephric kidney samples. Immunocytochemical analysis revealed that both alpha1- and beta2-subunits were present in the apical epithelial plasma membranes of distal nephron segments of early stage nephrons, maturing loops of Henle, and collecting ducts during kidney development. We also detected a significant increase in alpha1 and beta1 mRNA after birth with a marked reduction in beta2 mRNA abundance associated with an increase in alpha1- and beta1-subunit proteins and loss of beta2 protein expression. These studies support the conclusion that the expression of the beta2-subunit in the fetal kidney may be an important mechanism controlling polarization of the Na+-K+-ATPase pump in the epithelia of the developing nephron during kidney organogenesis.

Cystic fibrosis transmembrane conductance regulator in the kidney: clues to its role?

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic adenosine monophosphate dependent, low-conductance chloride channel found on the apical plasma membrane of secretory epithelia. Surprisingly, since cystic fibrosis patients have no kidney phenotype, CFTR is highly expressed in the kidney, present from 12 weeks of gestation in the human metanephric kidney. As well as the mature, full-length, 165-kD wild-type protein (WT-CFTR) associated with renal tubule plasma membranes, intracellular, partially glycosylated forms are also seen in normal kidneys. In addition, a kidney-specific splice variant of CFTR translates a cytoplasmic truncated protein (TNR-CFTR), apparently associated with a specific small endosomal population, and is predominantly expressed in the renal medulla. WT-CFTR and TNR-CFTR show different patterns of developmental regulation, WT-CFTR being the major form expressed early in metanephric development when it is localized at the apical plasma membrane of developing collecting tubules. By contrast, TNR-CFTR expression increases with gestational age, reaching adult levels at 23 weeks. Evidence suggests that WT-CFTR plays a role in chloride secretion into the apical lumen of normal distal tubules. In autosomal dominant polycystic kidney disease, normally targeted CFTR at the apical plasma membrane in association with mislocalized Na-K-ATPase may result in abnormal fluid secretion into cysts. Similar colocalization of WT-CFTR and Na-K-ATPase at the apical plasma membranes is found in collecting tubules during development when it is speculated to play a role in the initiation of opening of the tubule lumen.

Identification of phosphorylation sites in the PKD1-encoded protein C-terminal domain

The PKD1-encoded protein, "polycystin-1", has a large N-terminal extracellular portion, multiple transmembrane domains, and a short intracellular C-terminal tail with four tyrosine residues and two putative sites for serine phosphorylation. Its function in kidney development and autosomal dominant polycystic kidney disease (ADPKD) is still unknown. We have subcloned the cDNA encoding the polycystin-1 C-terminal domain (PKD1-CTD) into a prokaryotic expression vector, and site-directed mutagenesis was performed to target the four tyrosine residues and four serine residues in two putative phosphorylation sites. In vitro phosphorylation assays were conducted on both wild type and mutant PKD1-CTD fusion proteins. It was found that the wild type PKD1-CTD and all mutant fusion proteins, except S4251G/S4252G, could be phosphorylated by lysates from cultured normal human renal collecting tubule (NHCT) cells, as well as by commercially purified cAMP-dependent protein kinase (PKA). The phosphorylation of the PKD1-CTD fusion protein by NHCT lysates was greatly enhanced by cAMP and its analog 8-Br-cAMP, and inhibited by the specific PKA inhibitors PKI(6-22) and H-89. Activators and inhibitors of protein kinase C (PKC) had no effects on the phosphorylation of the PKD1-CTD fusion protein. Using commercially purified pp60(c-src) (c-src) it was also shown that the PKD1-CTD fusion protein could be phosphorylated by c-src in vitro, and that this phosphorylation could be abolished by a mutation Y4237F. By comparing the amino acid sequence at 4249-4253 (RRSSR) with the consensus sequence for PKA phosphorylation (RRXSX), we suggest that the serine residue at 4252 is the target of phosphorylation by a cAMP-dependent protein kinase in NHCT cell lysates. In addition, we suggest that Y4237 might be phosphorylated by c-src in living cells.

The influence of bladder volume on the position and mobility of the urethrovesical junction

The influence of bladder volume on the position, mobility and funneling of the bladder neck and proximal urethra was determined by transperineal ultrasound in a prospective comparative clinical study at Dunedin Hospital, Dunedin, New Zealand. One hundred and nine women underwent urodynamic assessment, either as part of the investigation of urinary incontinence or as follow-up after incontinence-correcting surgery. Bladder neck descent, retrovesical angle, rotation of the proximal urethra, and simple and extensive funneling/opening of the proximal urethra on Valsalva maneuver were assessed using ultrasound imaging at approximately 50 ml bladder volume and maximum bladder capacity (mean 355 ml, range 125-470 ml). The position of the bladder neck at rest was slightly higher at 50 ml than at maximum capacity (50 ml: 2.6 +/- 0.4 cm, max. cap. 2.5 +/- 0.4 cm; P = 0.003) and it descended further with the Valsalva maneuver (50 ml: 1.9 +/- 1.2 cm, max. cap. 1.7 +/- 1 cm; P = 0.004). There was also a higher degree of urethral rotation (50 ml: 41 +/- 30 degrees, max. cap. 39 +/- 20 degrees) with an empty bladder (P = 0.072). As regards funneling of the bladder neck on Valsalva, equivalent results were obtained for 90 patients. In 19 cases there were discrepancies (Cohen's kappa 0.64). For extensive funneling to the midurethra the respective numbers were 83 and 26 (kappa 0.41). Generally simple and extensive funneling was more frequently seen with a full rather than an empty bladder, simple funneling being diagnosed in an additional 14 cases (P = 0.06) and extensive funneling in an additional 19 (P = 0.03). It was concluded that bladder filling influences the position and mobility of the bladder neck and the proximal urethra, which are both more mobile when the bladder is nearly empty. Funneling of the proximal urethra, however, is more easily observed with a full bladder. Imaging of the lower urinary tract should be undertaken at defined bladder volumes.

Cystic diseases of the kidney: role of adhesion molecules in normal and abnormal tubulogenesis

This short review summarizes some information concerning what is known about matrix adhesion molecules, focal adhesion proteins, and cell-cell adhesion molecules in normal renal development and cystic diseases of the kidney. The focus is on human nephrogenesis and disease, but utilizes critical information gained from genetically manipulated mouse models. Interestingly, a significant role for the human PKD-1-encoded gene product, polycystin-1, has been found in cell-matrix interactions via integrins during development, and mutations lead to autosomal dominant polycystic kidney disease (ADPKD). Recent studies on human ADPKD have implicated polycystin-1 in the formation of multiprotein complexes containing focal adhesion proteins at the basal cell surface of the normal ureteric bud. Further evidence of a critical role of cell-matrix interactions via focal adhesion complex formation is provided by the development of renal cystic disease in tensin knockout mice.

Pathophysiology and clinical management of polycystic kidney disease in women

Women of all geographic, racial, and ethnic groups are afflicted by autosomal dominant polycystic kidney disease (ADPKD), which is the most common, lethal genetic disease that is inherited as a dominant trait. General issues concerning epidemiology, diagnostic testing, clinical management of pain, hypertension, and intracranial aneurysms are discussed, as well as a short overview of our current understanding of the pathophysiological features, including some new molecular insights. Specific issues affecting the care of women are also discussed, including the management of liver cysts and fertility and pregnancy in ADPKD.

Modelling in nutrition: an introduction

The purpose of the present paper is to provide an introduction to modelling, particularly mathematical modelling, for nutritional researchers with little or no experience of the modelling process. It aims to outline the function of modelling, and to give some guidance on factors to consider when designing protocols to generate data as part of the modelling process. It is not intended in any way to be a comprehensive guide to mathematical modelling. The paper discusses the uses of modelling, and presents a 'hydrodynamic analogy' to compartmental modelling, to explain the process to the non-mathematically-minded and to examine some of the pitfalls to be avoided when using stable-isotope tracers. Examples of the use of modelling in nutrition are presented, including methods for determining absorption, as well as a discussion of possible future avenues for nutritional modelling.

ATP release mechanisms in primary cultures of epithelia derived from the cysts of polycystic kidneys

Autosomal dominant polycystic kidney disease (ADPKD) cyst enlargement is exacerbated by accumulation of fluid within the lumen of the cyst. Extracellular nucleotides and nucleosides stimulate fluid and chloride (Cl-) secretion across epithelia and are potent autocrine and paracrine agonists within tissues. This study tests the hypothesis that ATP may be released by ADPKD epithelial cells. Once released, extracellular nucleotides and their metabolites may become "trapped" in the cyst lumen. As a consequence, extracellular ATP may augment ADPKD cyst enlargement through stimulation of salt and water secretion across ADPKD epithelia that encapsulate ADPKD cysts. To test this hypothesis, bioluminescence detection assays of ATP released from primary cultures of human ADPKD epithelial cells were compared with non-ADPKD human epithelial primary cultures. ADPKD cultures release comparable or greater amounts of ATP than non-ADPKD cultures derived from proximal tubule or cortex. ATP release in both ADPKD and non-ADPKD primary epithelial monolayers was directed largely into the apical medium; however, basolateral-directed ATP release under basal and stimulated conditions was also observed. Hypotonicity potentiated ATP release into the apical and basolateral medium in a reversible manner. Reconstitution of isotonic conditions with specific osmoles or inhibition with mechanosensitive ion channel blockers dampened hypotonicity-induced ATP release. "Flash-frozen" cyst fluids from ADPKD cysts, harvested from multiple donor kidneys, were screened by luminometry. A subset of cyst fluids contained as much as 0.5 to 10 microM ATP, doses sufficient to stimulate purinergic receptors. Taken together, these results show that ADPKD and non-ADPKD human epithelial primary cultures release ATP under basal and stimulated conditions and that ATP is released in vitro and into the cyst fluid by cystic epithelial cells in concentrations sufficient to stimulate ATP receptors. It is hypothesized that extracellular nucleotide release and signaling may contribute detrimentally to the gradual expansion of cyst fluid volume that is a hallmark of ADPKD.

Anatomical assessment of the bladder outlet and proximal urethra using ultrasound and videocystourethrography

In a prospective blinded comparative clinical study 125 women underwent videocystourethrography and cystometry as well as transperineal ultrasound as part of their diagnostic work-up for urinary incontinence or after incontinence-correcting surgery. Comparisons between ultrasound and X-ray imaging were carried out on 117 women for whom complete data sets were available. Mean bladder neck descent was significantly greater with ultrasound compared to VCU (US: 2.1 +/- 1.2 cm vs. VCU: 1.8 +/- 0.9; P = 0.003). Rotation of the proximal urethra was not always seen on X-ray, but when it was (44 patients) there was good correlation with US (US rotation 55 +/- 27 degrees vs. VCU rotation 55 degrees +/- 29). There was also good agreement between both tests regarding visualization of funneling or opening of the proximal urethra, with both tests showing equivalent results in 95 out of 117 patients (Cohen's kappa 0.58). On comparing extensive funneling to the midurethra on US with frank leakage on VCU the methods were in agreement for 90 out of 117 patients (kappa 0.54). Overall a good correlation between ultrasound and radiological findings was observed. Both methods allow anatomic assessment of the bladder neck and have different strengths and weaknesses. Ultrasound imaging may be preferable as it is cheaper, requires less technological back-up and avoids the risks of radiation exposure and allergic reactions to contrast medium.

WT1 expression induces features of renal epithelial differentiation in mesenchymal fibroblasts

The WT1 tumor suppressor gene, implicated in hereditofamilial and sporadic Wilms' tumor, is required for normal renal development and is up-regulated during the mesenchymal-epithelial transition. NIH3T3 fibroblasts overexpressing WT1 were less proliferative, larger in size and more firmly attached to tissue culture plastic, suggesting an alteration of their state of differentiation. These cells were studied in vivo by subcutaneous injection into nude mice. The resulting tumors exhibited epithelioid histopathology and formed desmosome-like structures. Molecular analyses of these WT1 expressing fibroblasts grown in culture and in nude mice revealed significant alterations in the expression of many kidney epithelial markers. These studies indicate that WT1 expression can initiate features of a program of epithelial differentiation consistent with a prominent role for WT1 in the mesenchymal epithelial transition that occurs during renal development. Through this work we identified a number of novel target genes for the WT1 transcription factor, including uvomorulin, integrin alpha8 and perlecan, and suggest that WTI may activate the IGF-II gene, also implicated in the development of Wilms' tumor.

A randomized controlled trial of pelvic floor muscle exercises to treat postnatal urinary incontinence

A randomized controlled trial was carried out to evaluate the extent to which a program of reinforced pelvic floor muscle exercises (PFME) reduces urinary incontinence 1 year after delivery. Two hundred and thirty women who were incontinent 3 months postpartum were randomized to either a control group doing standard postnatal pelvic floor muscle exercises (n = 117) or to an intervention group (n = 113) who saw a physiotherapist for instruction at approximately 3, 4, 6 and 9 months postpartum. Results collected 12 months after delivery included prevalence and frequency of incontinence and PFME, sexual satisfaction, perineometry measurements and pad tests. Twenty-six (22%) of the control group and 59 (52%) of the intervention group withdrew before the final assessment. The prevalence of incontinence was significantly less in the intervention group than in the control group (50% versus 76%, P=0.0003), and this group also did significantly more PFME. There were no significant differences between the groups as regards sexual satisfaction, perineometry measurements or pad test results.

The coefficient of error of optical fractionator population size estimates: a computer simulation comparing three estimators

The optical fractionator is a design-based two-stage systematic sampling method that is used to estimate the number of cells in a specified region of an organ when the population is too large to count exhaustively. The fractionator counts the cells found in optical disectors that have been systematically sampled in serial sections. Heretofore, evaluations of optical fractionator performance have been made by performing tests on actual tissue sections, but it is difficult to evaluate the coefficient of error (CE), i.e. the precision of a population size estimate, by using biological tissue samples because they do not permit a comparison of an estimated CE with the true CE. However, computer simulation does permit making such comparisons while avoiding the observational biases inherent in working with biological tissue. This study is the first instance in which computer simulation has been applied to population size estimation by the optical fractionator. We used computer simulation to evaluate the performance of three CE estimators. The estimated CEs were evaluated in tests of three types of non-random cell population distribution and one random cell population distribution. The non-random population distributions varied by differences in 'intensity', i.e. the expected cell counts per disector, according to both section and disector location within the section. Two distributions were sinusoidal and one was linearly increasing; in all three there was a six-fold difference between the high and low intensities. The sinusoidal distributions produced either a peak or a depression of cell intensity at the centre of the simulated region. The linear cell intensity gradually increased from the beginning to the end of the region that contained the cells. The random population distribution had a constant intensity over the region. A 'test condition' was defined by its population distribution, the period between consecutive sampled sections and the spacing between consecutive sampled disectors. There were 1000 independently simulated cell populations for each test condition, and a 'trial' was conducted for each of these cell populations. In each trial we calculated the (unique) true CE of the population size estimate and the three CE estimates obtained by applying the Scheaffer-Mendenhall-Ott (SMO) and both Gundersen-Jensen (GJ) estimators. We compared the estimated CEs with the true CEs for each population distribution. We found that the CE estimates obtained by the SMO estimator were closer to the true CEs and had less scatter than those of the nugget-modified GJ estimator. Both had small positive bias. The CE estimates obtained by the unmodified GJ estimator exhibited widely varying bias and large scatter. In all the population distributions we tested, the average true CE was very nearly proportional to 1/square root of QT, where QT is the average number of cells counted in the two-stage systematic sample.

Simultaneous time-varying systemic appearance of oral and hepatic glucose in adults monitored with stable isotopes

The rates (and extent) of appearance of glucose in arterialized plasma from an oral glucose load and from liver (RaO, RaH) can be estimated in humans using radioisotopes, but estimates vary among laboratories. We investigated the use of stable isotopes and undertook 22 primed intravenous infusions of D-[6,6-2H2]glucose with an oral load including D-[13C6]glucose in healthy humans. The effective glucose pool volume (VS) had a lower limit of 230 ml/kg body weight (cf. 130 ml/kg commonly assumed). This VS in Steele's one-compartment model of glucose kinetics gave a systemic appearance from a 50-g oral glucose load per 70 kg body weight of 96 +/- 3% of that ingested, which compared with a theoretical value of approximately 95%. Mari's two-compartment model gave 100 +/- 3%. The two models gave practically identical RaO and RaH at each point in time and a plateau in the cumulative RaO when absorption was complete. Less than 3% of 13C was recycled to [13C3]glucose, suggesting that recycling errors were practically negligible in this study. Causes of variation among laboratories are identified. We conclude that stable isotopes provide a reliable and safe alternative to radioactive isotopes in these studies.

Splanchnic retention of intraduodenal and intrajejunal glucose in healthy adults

Estimates of the spanchnic retention and appearance in the systemic circulation of orally administered glucose vary among laboratories even after recently identified sources of error have been accounted for [Livesey, G., P. D. G. Wilson, J. R. Dainty, J. C. Brown, R. M. Faulks, M. A. Roe, T. A. Newman, J. Eagles, F. A. Mellon, and R. Greenwood. Am. J. Physiol. 275 (Endocrinol. Metab. 38): E717-E728, 1998]. We questioned whether, in healthy humans, D-glucose delivered intraluminally to the midjejunum appeared systemically as extensively as that delivered intraduodenally. Subjects were infused over a period of 90 min with 50 g of glucose in 1 liter of isotonic saline (incorporating 0.5 g D-[13C6]glucose) per 70 kg of body weight. Infusions were via enteral tubes terminating approximately 15 and 100 cm postpylorus. The systemic appearance of glucose was monitored by means of a primed-continuous intravenous infusion of D-[6,6-2H2]glucose. Whereas 98 +/- 2% (n = 7) of the duodenally infused glucose appeared in the systemic circulation, only 35 +/- 9% (n = 7) of midjejunally infused glucose did so, implying that 65 +/- 9% was retained in the splanchnic bed. Either glucose was less efficiently absorbed at the midintestinal site or hepatic glucose sequestration was increased 10-fold, or both. The proximal intestine plays a key role in the delivery of glucose to the systemic circulation, and the distal intestine potentially delivers more glucose to the liver.

Attributable fraction for cardiac malformations

To the authors' knowledge, attributable fractions for cardiac malformations have not been reported before. The Baltimore-Washington Infant Study published factors associated with several major cardiac malformations in Maryland, the District of Columbia, and adjacent counties of northern Virginia in 1981-1989. For eight of these malformations, the authors provide attributable fractions of those factors that are potentially causal. Summary attributable fractions range from 13.6% (four factors) for hypoplastic left heart to 30.2% (seven factors) for transposition of great arteries with intact ventricular septum. Extra attributable fraction for factor x, defined as summary attributable fraction for all factors minus that for all but x, is largest for: 1) paternal marijuana use in transposition of great arteries with intact ventricular septum, 7.8%; 2) paternal anesthesia in tetralogy of Fallot, 3.6%; 3) painting in atrioventricular septal defect with Down syndrome, 5.1 %; 4) solvent/degreasing agent exposure in hypoplastic left heart, 4.6%; 5) sympathomimetics in coarctation of aorta, 5.8%; 6) pesticide exposure in isolated membranous ventricular septal defect, 5.5%; 7) hair dye in multiple/multiplex membranous ventricular septal defect, 3.3%; and 8) urinary tract infection in atrial septal defect, 6.4%. Percent-of-cases-exposed dominates relative risk in attributable fraction. If these factors are causal, the larger extra attributable fractions suggest the potential for prevention by specific interventions before/during pregnancy.

Modification of a phospholipid stabilized emulsion interface by bile salt: effect on pancreatic lipase activity

Lipase is activated by binding to an insoluble emulsified or aggregated substrate. The extent of binding is related to the physicochemical as well as the compositional structure of the interface, the quality of the interface. 'Quality' is as yet undefined but thought to contain contributions from electrostatic interactions, orientation of substrate, and hydration forces. To investigate the electrostatic and compositional factors we have used olive oil-in-water emulsions prepared with phosphatidylcholine and four bile salts of varying hydrophobicities. By measurement of the droplet zeta potential we have monitored semi-quantitatively the incorporation of bile salts within the interface. No correlation was found between droplet surface charge as monitored by the zeta potential and lag phase. The duration of the observed lag phase was found to be inversely related to the degree of incorporation of the bile salts. Simultaneously there was evidence of lipase binding to monomeric bile salts, reducing its availability for adsorption. Calcium ions reduced the surface charge but there was no correlation with lag phase duration. The evidence presented here agrees with a more specific role for calcium ions, i.e., the formation of a new catalytically active enzyme complex, (enzyme)-(mixed micelle)-(calcium ion).

Preconceptional folate intake and malformations of the cardiac outflow tract. Baltimore-Washington Infant Study Group

We compared cases with outflow tract defects (N = 126) with controls representative of the same birth cohort (N = 679). Infants with clinically recognized syndromes were excluded. Daily total maternal folate intake of > or =245 microg was inversely related to risk of cardiac outflow tract defects among those with transposition (odds ratio estimates: 0.65, 0.78, and 0.76 with increasing quartile of daily folate intake), but positively related among those with normally related vessels (corresponding odds ratio estimates: 1.18, 1.59, and 1.68). This difference disappeared when maternal intake of supplemental folic acid of > or =400 microg compared with <400 microg was considered, excluding dietary intake [odds ratio (OR) = 1.04; 95% confidence interval (CI) = 0.5-2.2 for infants with transposition, and OR = 0.91; 95% CI = 0.5-1.8 for those without transposition of the great arteries].

Absorption of all-trans and 9-cis beta-carotene in human ileostomy volunteers

1. Mass balance studies were carried out in fasted ileostomy subjects (n = 5) given an oral physiological dose (10 mg) of beta-carotene [all-trans: 9-cis, 84:16 (w/w)] dispersed in vegetable oil. Blood and ileal effluent samples were collected and analysed for beta-carotene. 2. Results showed that 90% (range 97.0-74.3%) of the total beta-carotene was absorbed without measurable perturbation of plasma total beta-carotene concentration, or change in the all-trans: 9-cis beta-carotene ratio. Peak loss of beta-carotene in ileal effluent occurred at 4.9 h (range 2.9-8.4 h) postingestion, and no further loss was detected after 5.4-12.4 h, depending upon the individual. Comparison of the ratio of all trans-beta-carotene to 9 cis-beta-carotene in the test meal and effluent indicated that isomerization did not occur during passage through the gastrointestinal tract and that both isomers were similarly absorbed. However, the all-trans: 9-cis beta-carotene ratio of the plasma did not change. Reasoned assumptions allowed the construction of a mathematical model of plasma beta-carotene disposal. 3. It is concluded that physiological doses of isolated all-trans and 9-cis beta-carotene are well absorbed without necessarily causing detectable excursions in plasma beta-carotene concentrations, or altering the ratio of all-trans to 9-cis beta-carotene. Isomerization of beta-carotene does not occur during passage through the gastrointestinal tract. Absorbed beta-carotene is rapidly cleared from the plasma to an unobservable pool at a rate similar to that of chylomicron triacylglycerol.

Vaginal electrostimulation for the treatment of genuine stress incontinence

The value of vaginal electrostimulation for genuine stress incontinence was evaluated in 30 women with this condition. Subjective and objective measurements were made before and after 3 and 15 months of treatment using urinary diaries, perineometry and pad tests. After 3 months use, 21 women (70%) reported a subjective improvement, but this had fallen to 9 (30%) by 15 months. There were significant reductions in the numbers of daily incontinent episodes and pad/pant changes and significant increases in the perineometry readings at both 3 and 15 months. There were no side-effects observed with electrostimulator use, but 1 patient withdrew due to a dislike of the method of treatment. Vaginal electrostimulation would seem to be a simple and well tolerated means of managing genuine stress incontinence in a selected group of women.

Time course of 5-HT2A receptor occupancy in the human brain after a single oral dose of the putative antipsychotic drug MDL 100,907 measured by positron emission tomography

MDL 100,907 is a potent and selective antagonist of 5-HT2A serotonin receptors. Animals studies suggest that MDL 100,907 may behave as an atypical antipsychotic drug. Positron emission tomograph (PET) using [11C]NMSP as the radiotracer was used to define the time course of 5-HT2 receptor occupancy in the human frontal cerebral cortex after a single oral dose of MDL 100,907 (10 or 20 mg) in nine healthy subjects. After the baseline scan each subject was studied three times post dosing at various time points. 5-HT2 occupancies were in the range of 70 and 90% after each dose. While the occupancy remains in this range over 24 hours after 20 mg MDL 100,907, it decreases by about 20% at 24 hours compared to the timepoint at 8 hours, when only 10 mg are administered (p < 0.05). Our results should allow determination of the appropriate dosing regimen for future trials in schizophrenic patients.

Acidic FGF regulation of hyperproliferation of fibroblasts in human autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cystic tubule enlargement and expansion of the interstitium associated with fibrosis. Our previous studies have analyzed the increased proliferation of cystic epithelial cells and this study examines the basis of increased proliferation of interstitial fibroblasts associated with ADPKD disease progression. ADPKD fibroblasts show phenotypic alterations in vitro, have acquired the capacity to grow in soft agar, and show an increased mitogenic response to a variety of growth factors particularly acidic FGF (aFGF). ELISA, Western immunoblot analysis, and immunocytochemistry showed increased aFGF content in ADPKD tissues and fibroblasts in culture, and aFGF was secreted into the extracellular matrix and conditioned medium, respectively. No alterations in aFGF receptor number were found, but Scatchard analysis of 125I-aFGF binding suggested an increased affinity of binding to the low affinity receptor, and covalent cross-linking analysis suggested the presence of novel putative receptors (120 kDa) in ADPKD fibroblasts. Signaling abnormalities were found, since aFGF incubation resulted in the tyrosine phosphorylation of additional substrates, more rapidly and for a more sustained duration in ADPKD fibroblasts than in normal fibroblasts. These findings suggest an important role for acidic FGF in the hyperproliferation of interstitial fibroblasts associated with disease progression in human ADPKD.