Mutations in the chloride channel gene, CLCNKB, cause Bartter's syndrome type III.

Analysis of patients with inherited hypokalaemic alkalosis resulting from salt-wasting has proved fertile ground for identification of essential elements of renal salt homeostasis and blood-pressure regulation. We now demonstrate linkage of this phenotype to a segment of chromosome 1 containing the gene encoding a renal chloride channel, CLCNKB. Examination of this gene reveals loss-of-function mutations that impair renal chloride reabsorption in the thick ascending limb of Henle's loop. Mutations in seventeen kindreds have been identified, and they include large deletions and nonsense and missense mutations. Some of the deletions are shown to have arisen by unequal crossing over between CLCNKB and the nearby related gene, CLCNKA. Patients who harbour CLCNKB mutations are characterized by hypokalaemic alkalosis with salt-wasting, low blood pressure, normal magnesium and hyper- or normocalciuria; they define a distinct subset of patients with Bartter's syndrome in whom nephrocalcinosis is absent. These findings demonstrate the critical role of CLCNKB in renal salt reabsorption and blood-pressure homeostasis, and demonstrate the potential role of specific CLCNKB antagonists as diuretic antihypertensive agents.

Endogenous inhibitors (GALFs) of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2: derivatives of adrenally produced corticosterone and cortisol.

Two isoforms of 11beta-HSD exist; 11beta-HSD1 is bi-directional (the reductase usually being predominant) and 11beta-HSD2 functions as a dehydrogenase, conferring kidney mineralocorticoid specificity. We have previously described endogenous substances in human urine, "glycyrrhetinic acid-like factors (GALFs)", which like licorice, inhibit the bi-directional 11beta-HSD1 enzyme as well as the dehydrogenase reaction of 11beta-HSD2. Many of the more potent GALFs are derived from two major families of adrenal steroids, corticosterone and cortisol. For example, 3alpha5alpha-tetrahydro-corticosterone, its derivative, 3alpha5alpha-tetrahydro-11beta-hydroxy-progesterone (produced by 21-deoxygenation of corticosterone in intestinal flora); 3alpha5alpha-tetrahydro-11beta-hydroxy-testosterone (produced by side chain cleavage of cortisol); are potent inhibitors of 11beta-HSD1 and 11beta-HSD2-dehydrogenase, with IC50's in range 0.26-3.0 microM, whereas their 11-keto-3alpha5alpha-tetrahydro-derivatives inhibit 11beta-HSD1 reductase, with IC50's in range 0.7-0.8 microM (their 3alpha5beta-derivatives being completely inactive). Inhibitors of 11beta-HSD2 increase local cortisol levels, permitting it to act as a mineralocorticoid in kidney. Inhibitors of 11beta-HSD1 dehydrogenase/11beta-HSD1 reductase serve to adjust the set point of local deactivation/reactivation of cortisol in vascular and other glucocorticoid target tissues, including adipose, vascular, adrenal tissue, and the eye. These adrenally derived 11-oxygenated C21- and C19 -steroidal substances may serve as 11beta-HSD1- or 11beta-HSD2-GALFs. We conclude that adrenally derived products are likely regulators of local cortisol bioactivity in humans.

Perceived aluminum-related disease in a dialysis population. A report from the End-Stage Renal Disease Network 28.

A survey to assess the perceived prevalence of aluminum-related disease was conducted by the Medical Review Board of the End-Stage Renal Disease Network 28 from 1986 to 1987. Responses were obtained for 855 of 3000 patients on dialysis representing 17 of 39 participating dialysis units within the network. Almost 40% of the patients surveyed had been receiving dialysis therapy for over 3 years. Patients on hemodialysis (83% of the study group) had the water used to prepare the dialysate pretreated. Serum aluminum determinations were obtained in 240 (28%) of the 855 patients; other methods of assessing body aluminum burden were performed in less than 10% of the survey population. When obtained, elevated serum aluminum measurements were more likely to be found with each year patients were given dialysis and with each year patients were treated with oral aluminum gels. With the exception of patients with bone pain, clinical signs and symptoms did not correlate with elevated serum aluminum. However, the prevalence of muscle weakness, bone pain, fractures, and dementia in the survey group did correlate with years on dialysis and/or years receiving oral aluminum gels. Data gathered from this survey are consistent with the view that signs and symptoms suggestive of an increased body aluminum burden occur in the minority of patients on dialysis. Nevertheless, patients at risk for aluminum intoxication (years on dialysis, years receiving gels, patients with clinical signs) may not be adequately identified.

Modafinil for cognitive neuroenhancement in healthy non-sleep-deprived subjects: A systematic review.

Modafinil is an FDA-approved eugeroic that directly increases cortical catecholamine levels, indirectly upregulates cerebral serotonin, glutamate, orexin, and histamine levels, and indirectly decreases cerebral gamma-amino-butrytic acid levels. In addition to its approved use treating excessive somnolence, modafinil is thought to be used widely off-prescription for cognitive enhancement. However, despite this popularity, there has been little consensus on the extent and nature of the cognitive effects of modafinil in healthy, non-sleep-deprived humans. This problem is compounded by methodological discrepancies within the literature, and reliance on psychometric tests designed to detect cognitive effects in ill rather than healthy populations. In order to provide an up-to-date systematic evaluation that addresses these concerns, we searched MEDLINE with the terms "modafinil" and "cognitive", and reviewed all resultant primary studies in English from January 1990 until December 2014 investigating the cognitive actions of modafinil in healthy non-sleep-deprived humans. We found that whilst most studies employing basic testing paradigms show that modafinil intake enhances executive function, only half show improvements in attention and learning and memory, and a few even report impairments in divergent creative thinking. In contrast, when more complex assessments are used, modafinil appears to consistently engender enhancement of attention, executive functions, and learning. Importantly, we did not observe any preponderances for side effects or mood changes. Finally, in light of the methodological discrepancies encountered within this literature, we conclude with a series of recommendations on how to optimally detect valid, robust, and consistent effects in healthy populations that should aid future assessment of neuroenhancement.

Mineralocorticoid activity of 19-hydroxyaldosterone, 19-nor-aldosterone, and 3 beta-hydroxy-delta 5-aldosterone: relative potencies measured in two bioassay systems.

The mineralocorticoid (MC) activities of 19-hydroxyaldosterone (19-OH-Aldo) and 19-nor-aldosterone (19-nor-Aldo) were tested in adrenalectomized male rats. Potency was assessed by three criteria. Overall MC activity is expressed as the ability to decrease the urinary Na+ to K+ ratio; antinatriuretic activity is represented by decreases in the urinary Na+ to creatinine ratio, and kaliuretic activity by increases in the K+ to creatinine ratio. All measurements were made on urine collected 1-3 h postinjection. In this assay, 19-OH-Aldo was 1/100th to 1/140th as active as Aldo, and 19-nor-Aldo possessed MC activity similar to that of Aldo; both steroids possessed antinatriuretic and kaliuretic activities. In contrast, when assayed in vitro in the isolated toad urinary bladder, the natriferic responses of both 19-OH-Aldo and 19-nor-Aldo (10(-8), 10(-7), and 10(-6) M) were not significantly different from those caused by equivalent concentrations of Aldo. 3 beta-Hydroxy-delta 5-Aldo is active as a MC in the adrenalectomized male rat, being 1/20th to 1/35th as active as Aldo, but, in contrast to 19-OH-Aldo, was less active in the isolated toad bladder system. 19-OH-Aldo, 19-nor-Aldo, and 3 beta-hydroxy-delta 5-Aldo could represent important new classes of Aldo analogs.

Antinatriuretic and kaliuretic activities of the reduced derivatives of aldosterone.

The mineralocorticoid activities of the two dihydro- and the four tetrahydroisomers of the ring A-reduced derivatives of aldosterone were tested in adrenalectomized male rats. Potency was assessed by three criteria. Overall mineralocorticoid activity is expressed as the ability to reduce the urinary Na+/K+ ratio; antinatriuretic activity is represented by decreases in urinary Na+/creatinine; kaliuretic activity is shown by increases in K+/creatinine. All measurements were made on urine collected in the period 1-3 h postinjection. Measurements of overall activity indicate that the potency of aldosterone is greater than 5 alpha-dihydroaldosterone (DHA) greater than 3 alpha, 5 alpha-tetrahydroaldosterone (THA) greater than 3 alpha, 5 beta-THA greater than 3 beta, 5 alpha-THA greater than 5 beta-DHA greater than 3 beta, 5 beta-THA. Measurements of individual cation effects indicated that reduced derivatives generally, and the 5 alpha-reduced derivatives in particular, have greater antinatriuretic than kaliuretic activity. For example 5 alpha-DHA possesses between 7% and 17% of the antinatriuretic activity of aldosterone but only 0.7-2.7% of the kaliuretic activity. 5 alpha-DHA and 3 alpha, 5 beta-THA at concentrations of 10(-7)M were also shown to have mineralocorticoid activity in the isolated toad bladder; both caused an increase in the short circuit current across this epithelium although not to the level shown by a similar concentration of aldosterone. 5 beta-DHA appeared to be inactive at this dose.

11BetaOH-progesterone affects vascular glucocorticoid metabolism and contractile response.

Vascular smooth muscle (VSM) contains a bidirectional isoform of 11beta-hydroxysteroid dehydrogenase (11beta-HSD), the enzyme that can metabolize endogenous glucocorticoids to their respective 11-dehydro derivatives. 11BetaOH-progesterone (11betaOH-P), a compound that can be produced in vivo, is as potent or more potent than licorice derivatives in inhibiting renal and hepatic 11beta-HSD. When studied in homogenates prepared from primary cultures of rat VSM, 11betaOH-P and its derivative, 11-keto-progesterone (11-keto-P), proved to be potent, directionally specific inhibitors of vascular 11beta-HSD. 11BetaOH-P selectively inhibited the forward dehydrogenase reaction (corticosterone-->11-dehydrocorticosterone), whereas 11-keto-P selectively blocked the reverse oxidoreductase reaction. To test the physiological effects, vascular rings were prepared from rat aorta. Rings were incubated in culture media containing either a submaximal concentration of corticosterone (10 nmol/L), 11-dehydrocorticosterone (100 nmol/L), 11betaOH-P (1 micromol/L), 11-keto-P (1 micromol/L), or a combination of glucocorticoid and inhibitor for 24 hours. After the 24-hour incubation, rings were briefly stimulated sequentially with phenylephrine (10 nmol/L to 1 micromol/L) and angiotensin II (1 micromol/L). The immediate contractile response in rings incubated with both corticosterone and 11betaOH-P was greater than in rings previously incubated with either the corticosterone or 11betaOH-P alone (eg, response to 100 nmol/L phenylephrine in milligrams of force, mean+/-SE: corticosterone, 728+/-56, n=9; 11betaOH-P, 325+/-105, n=4; both, 1132+/-122, n=8; corticosterone versus both, P<.01). In contrast, the immediate contractile responses to phenylephrine and to angiotensin II were attenuated in rings exposed previously to both 11-dehydrocorticosterone and 11-keto-P. Thus, 11betaOH-P and 11-keto-P (and possibly structurally similar compounds) alter the vascular effects of glucocorticoids and may play a role in glucocorticoid-induced hypertension.

Localization of 2 11beta-OH steroid dehydrogenase isoforms in aortic endothelial cells.

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) is expressed in vascular smooth muscle cells (VSMC) but has not been reported to be present in vascular endothelial cells. This enzyme assists in regulating the cellular concentration of active endogenous glucocorticoids (GCs). We have observed that endothelium intact rat aortic rings express message for both Type 1 and Type 2 11beta-HSD whereas primary cultures of VSMC express only mRNA for the Type I isoform. Since GCs diminish prostacyclin synthesis in endothelial cells, we hypothesized that 11beta-HSD is present in vascular endothelial cells. In primary cultures of rat aortic endothelial (RAE) cells, mRNA from both isoforms of 11beta-HSD could be detected by RT-PCR with higher levels of the Type 1 isoform. The oxo-reductase reaction "activating" 11-dehydro metabolites back to the parent steroid is the preferred enzyme direction (12:1 after a 120 minutes steroid incubation) in intact RAE cells. When RAE cells are grown in the presence of antisense oligonucleotides specific for Type 1 11beta-HSD, oxo-reductase activity is decreased by approximately 50% but the dehydrogenase reaction, which inactivates endogenous GCs and is characteristic of the Type 2 isoform, is unaffected. Thus endothelial cells appear to express both isoforms of 11beta-HSD; the Type 1 isoform dominates functioning in the oxo-reductase mode. Inhibition of the oxo-reductase reaction may lower the local concentrations of GC and indirectly allow for increased production of prostacyclin in endothelial cells.

Kidney 11 beta-HSD2 is inhibited by glycyrrhetinic acid-like factors in human urine.

We have previously shown that human urine contains substances that, like glycyrrhetinic acid, inhibit 11 beta-HSD1. We have named these substances "glycyrrhetinic acid-like factors" or GALFs. We now have found that human urine contains measurable quantities of both 11 beta(HSD1)- and 11 beta(HSD2)-GALF inhibitory substances. Both are markedly elevated in pregnancy. Their chemical and high-performance liquid chromatography (HPLC) characteristics suggest that several of the GALFs are steroidal. Large quantities of neutral 11 beta(HSD1)- and 11 beta(HSD2)-GALFs can be extracted directly from urine into ethyl acetate, yielding fraction EA1. Hydrolysis of the GALFs remaining in the aqueous phase by beta-glucuronidase markedly increases the total amounts of GALFs, with the majority now being ethyl acetate extractable (fraction EA2). These EA2 post-hydrolysis GALFs can be separated by HPLC resulting in at least six components with inhibitory activity against each isoenzyme. Only two GALF peaks are active against both 11 beta-HSD1 and 11 beta-HSD2. The others are peaks with specific 11 beta(HSD1)- and 11 beta(HSD2)-GALF inhibitory activity. The GALFs in the same posthydrolysis EA2 extract are also inhibitory toward the 11 beta-HSD1 that is present in vascular smooth muscle where they may play a role in the mechanisms controlling blood pressure. We have also found that 11 beta-HSD2 is selectively inhibited by 5 alpha- (but not by 5 beta-) reduced steroids. GC-MS analysis of the 11 beta(HSD2)-GALFs in EA2 is now being performed to determine whether this group includes 3 alpha,5 alpha-ring A-tetrahydro-reduced derivatives of steroids.

Continuous-cycling peritoneal dialysis for children: an alternative to hemodialysis treatment.

Treatment of end-stage renal failure in children is invasive and prolonged. Although kidney transplantation is often the desired therapy, children usually require some form of life-sustaining dialysis until a suitable donor is found. Home continuous-cycling peritoneal dialysis (CCPD) is a useful alternative to in-center hemodialysis for these children. Adequate biochemical control of the uremic state can be achieved with continuous-cycling peritoneal dialysis. Peritonitis remains the major complication of this form of dialysis, averaging approximately one episode per 12 patient-months. Growth rates of children maintained on continuous-cycling peritoneal dialysis appear to be equivalent to growth rates of children treated with hemodialysis. The advantage of continuous-cycling peritoneal dialysis lies in the fact that exchanges occur during the evening hours and parental intervention is minimized.

A prospective comparison of urinary tract infections in patients treated with either clean intermittent catheterization or urinary diversion.

Clean intermittent catheterization (CIC) has replaced urinary diversion as the treatment of choice for patients with neurogenic bladder. Yet, no well controlled studies are available assessing the efficacy of CIC over ileal loop diversion (ILD). Consequently, a one-year pospective study was carried out comparing short-term patient morbidity, infection rates, and bacterial organisms in 33 children with meningomyelocele. Twenty-four of the children were treated with CIC whereas nine children had an ILD. A minimum of four cultures per year were obtained on each patient. Patients maintained on CIC had 36.8% of their cultures positive for bacteriuria whereas children with ILD had 61.8% of their cultures positive (P less than .001). The incidence of bacteriuria associated with clinical signs and symptoms was similar in both groups. Four of 24 children treated with CIC had sterile urine whereas none of the children with ILD were persistently free from bacteriuria. Only five of 24 children receiving CIC had 50% or more of their cultures positive as contrasted with seven of nine children with an ILD (P less than .01). Escherichia coli accounted for approximately one third of organisms recovered from infected urine in both groups. Although the short-term morbidity associated with both treatment modalities is similar, the incidence of asymptomatic bacteriuria in children maintained on CIC is significantly less than in children with ILD. Whether this factor plays a role in determining long-term morbidity is a subject for further study.

Linear growth of children with nephrotic syndrome: effect of alkylating agents.

Growth velocity measurements were assessed in 12 children with steroid responsive but frequent relapsing or dependent nephrotic syndrome prior to and following treatment with either cyclophosphamide or chlorambucil and alternate day prednisone. Patients averaged 6 +/- 3 years (mean +/- SD) of age at the time of treatment. All of the patients underwent renal biopsy prior to treatment; 5 of the 12 showed mesangial proliferation; and in 10 of the 12, IgM deposits were seen within the mesangium of the glomerulus. Growth rates before treatment with the alkylating agent were 4.3 +/- 1.3 cm/y increasing to 8.7 +/- 2.5 cm/y (P less than .001) after therapy despite the relapses that occurred in 5 of the patients in the year following treatment. Short-term side effects of the treatment were minimal. The significant increase in growth associated with diminished use of steroids makes the use of alkylating agents reasonable for children with nephrosis who show signs of decreased growth velocity.

Insights Into Glucocorticoid-Associated Hypertension.

The association between excess glucocorticoids and hypertension has been much discussed but poorly understood. From both clinical observations and laboratory studies, it is clear that glucocorticoids exert their effects at many different sites responsible for blood pressure regulation. Isoforms of the enzyme 11ss-hydroxysteroid dehydrogenase (11ss-HSD), located in steroid-responsive tissues, metabolize endogenously produced glucocorticoids. These enzymes limit steroid access to mineralocorticoid and/or glucocorticoid receptors. In the kidney, synthetic and endogenous glucocorticoids are capable of enhancing transepithelial sodium transport in the presence of 11ss-HSD inhibition. Proximal tubule reabsorption of sodium can be indirectly augmented after chronic exposure to glucocorticoids. In this segment, steroids have a permissive effect, increasing the expression of both Na(+), K(+) adenosine triphosphatase along the basolateral membrane and Na(+)-H(+) exchanger along the apical membrane of epithelial cells. Although glucocorticoids themselves produce no increase in sodium reabsorption in this segment, angiotensin II-stimulated sodium transport is significantly greater in proximal tubular cells pretreated with glucocorticoids. The increased transport in distal renal segments is more direct and stems in part from glucocorticoid cross-over binding to mineralocorticoid receptors. In vascular tissue, synthetic and endogenous glucocorticoids, after inhibition of the dehydrogenase reaction, magnify the response to circulating vasoconstrictors. The effects of glucocorticoids in vascular tissue is indirect, upregulating the expression of receptors to many vasoconstrictors and downregulating the effects of potential vasodilators. Thus, glucocorticoids have the potential to alter both circulating volume and vascular resistance.

Outcome data on pediatric dialysis patients from the end-stage renal disease clinical indicators project.

Network 1 (New England) initiated the Clinical Indicator Project to survey dialysis adequacy (Kt/V), nutrition (serum albumin level), and anemia management in patients maintained on chronic dialysis. Because little information is available in children, data were specifically recorded covering these variables in patients (age, 1 to 18 years) maintained on either hemodialysis (HD) or peritoneal dialysis (PD). During the 18 months of data collection, 29 observations were recorded on 23 HD patients (age, 14.3 +/- 3.6 years), and 43 observations were made on 30 PD patients (age,10.6 +/- 4.7 years). Kt/V correlated inversely with the age of the patient (HD, P < 0.004; PD, P < 0.0007). Although serum albumin level was not associated with dialysis adequacy in HD patients, there was a strong inverse relationship between albumin level and Kt/V in PD patients (P < 0.002). Hematocrit values were not significantly different in the two groups (HD, 31.0% +/- 5.5% versus PD, 32.9% +/- 4.8%) and could not be correlated with weekly erythropoietin dose. Weekly erythropoietin dose was directly related to patient age in both groups (HD, P < 0.05; PD, P < 0.02). The weekly erythropoietin dosage needed to maintain the hematocrit was greater in HD patients (HD, 11,211 +/- 7,484 U versus PD, 3,790 +/- 1,968 U; P < 0.0001). We conclude that (1) smaller children in both groups tend to have a greater Kt/V, (2) Kt/V greater than 2.75 in PD patients may not improve nutrition per se and could result in increased albumin losses, and (3) erythropoietin dosing appears to correlate best with patient size (age) rather than degree of anemia.

Interactions between glucocorticoids and mineralocorticoids in the regulation of renal electrolyte transport.

The enzyme 11 beta-hydroxy steroid dehydrogenase (11 beta-OHSD) was described and its location in various organs noted more than 30 years ago (Mahesh and Ulrich, 1960; Jenkins, 1966). 11 beta-OHSD inactivates circulating glucocorticoids by transforming the hydroxyl group at the 11-carbon to a keto group. This chemical reaction has taken on a greater degree of physiologic and clinical significance in recent years. It has been suggested that 11 beta-OHSD, present in mineralocorticoid target tissues, can act as a 'guardian' over the mineralocorticoid receptor by transforming circulating endogenous glucocorticoids to their respective 'biologically inert' 11-dehydro derivatives (Edwards et al., 1988; Funder et al., 1988). These derivatives do not bind to mineralocorticoid receptors (MR) while both their parent compounds and mineralocorticoids bind to cloned MR with equal affinity (Arriza et al., 1987). 11 beta-OHSD has generated a growing sense of scientific excitement since this enzyme may represent one of a family of metabolic pathways or mechanisms which can regulate steroid induced renal reabsorption of sodium. Such 'protective' enzymatic pathways, present in the kidney and elsewhere, may not only control the access of glucocorticoids to MR, but control the access of glucocorticoids to glucocorticoid receptors (GR) (Teelucksingh et al., 1990; Monder, 1990) as well as access of mineralocorticoids to their own receptors. This review will focus on this concept of a family of protective enzymatic pathways and the possible physiological implications.

Protein-losing enteropathy in systemic lupus erythematosus.

A 12-year-old girl, who was later found to have systemic lupus erythematosus (SLE), had a protein-losing enteropathy. Histologic documentation of intestinal lymphangiectasia in the absence of congestive heart failure, retroperitoneal masses, or constrictive pericarditis marks this case as demonstrating a unique association of SLE with intestinal lymphangiectasia.

Effect of carbenoxolone sodium on steroid-induced sodium transport in the toad bladder: further studies.

The licorice derivative, carbenoxolone sodium, is a potent inhibitor of the enzyme 11 beta-hydroxysteroid dehydrogenase. When this enzyme is suppressed or is absent, endogenous glucocorticoids induce mineralocorticoid-like sodium retention by the kidney. Carbenoxolone sodium administered in vivo to an adrenalectomized rat has also recently been shown to enhance the mineralocorticoid response to submaximal concentrations of aldosterone, deoxycorticosterone (DOC) and 11-dehydrocorticosterone (compound A). In the present studies conducted on the urinary bladder isolated from the Dominican toad, Bufo marinus, a concentration of carbenoxolone sodium shown previously to increase glucocorticoid-induced sodium transport (2.5 x 10(-5) M) did not appear to alter the response to submaximal concentrations of aldosterone 10(-8) M, DOC 10(-7) M, or compound A 10(-5) M. These findings are consistent with the view that in the whole animal carbenoxolone sodium may modify additional steroid metabolic pathways and/or physiological processes in several organs to produce the enhanced renal response to mineralocorticoids and compound A.

Urinary tract infection in pediatric renal transplantation.

Urinary tract infection is a frequent complication following renal transplantation and represents a potential focus for systemic infection in the immunosuppressed transplant recipient. The incidence, etiologic factors, temporal pattern, bacteriology, and prognostic significance of urinary tract infection were determined by analysis of 85 renal allografts in 69 patients. Significant bacteriuria occurred after 49 of 85 transplants (58 per cent). The incidence of infection was not related to success or source of the allograft, but was related to patient gender. Urinary tract infections developed in 68 per cent of females, while only 43 per cent of males became infected (p less than 0.05). Escherichia coli caused most first infections (30 per cent), while Pseudomonas aeruginosa and E. coli were equally responsible for recurrent infections (25 per cent each). Children with previous reconstructive urologic surgery had similar allograft success (63 per cent) and infection rates (53 per cent) as our other children (61 per cent and 58 per cent, respectively). No apparent correlation was noted between episodes of infection and graft rejection. Thorough preoperative assessment and preparation and prompt, specific treatment minimize the adverse influences of urinary tract infection.