Urologic Education in the Era of COVID-19: Results From a Webinar-Based Reconstructive Urology Lecture Series

Objective

To determine the response to a virtual educational curriculum in reconstructive urology presented during the COVID-19 pandemic. To assess learner satisfaction with the format and content of the curriculum, including relevance to learners’ education and practice.

Materials and Methods

A webinar curriculum of fundamental reconstructive urology topics was developed through the Society of Genitourinary Reconstructive Surgeons and partnering institutions. Expert-led sessions were broadcasted. Registered participants were asked to complete a survey regarding the curriculum. Responses were used to assess the quality of the curriculum format and content, as well as participants’ practice demographics.

Results

Our survey yielded a response rate of 34%. Survey responses showed >50% of practices offer reconstructive urologic services, with 37% offered by providers without formal fellowship training. A difference in self-reported baseline knowledge was seen amongst junior residents and attendings (P < .05). Regardless of level of training, all participants rated the topics presented as relevant to their education/practice (median response = 5/5). Responders also indicated that the curriculum supplemented their knowledge in reconstructive urology (median response = 5/5). The webinar format and overall satisfaction with the curriculum was highly rated (median response = 5/5). Participants also stated they were likely to recommend the series to others.

Conclusion

We demonstrate success of an online curriculum in reconstructive urology. Given >50% of practices surveyed offer reconstruction, we believe the curriculum's educational benefits (increasing access and collaboration while minimizing the risk of in-person contact) will continue beyond the COVID-19 pandemic and that this will remain a relevant educational platform for urologists moving forward

Changes in patient reported outcome measures after treatment for female urethral stricture

INTRODUCTION

There is a paucity of patient reported outcome measure (PROM) data for women with urethral strictures. To address this gap, we aim to evaluate change in PROM among women who underwent surgery for a stricture.

METHODS

American Urological Association Symptom Index (AUA-SI) and Urogenital Distress Inventory (UDI-6) data from a multi-institutional retrospective cohort study of women treated for urethral stricture was assessed.

RESULTS

Fifty-seven women had either AUA-SS or UDI-6 and 26 had baseline and postoperative data for either. Most women underwent urethroplasty (77%) and the majority (73%) remained stricture free at median follow-up of 21 months (interquartile range [IQR] 7-37). The median baseline AUA-SI was 21 (IQR 12-28) and follow-up was 10 (IQR 5-24). After treatment, there was a median decrease of 12 (IQR -18 to -2) in AUA-SI (p = 0.003). The median AUA Quality of life (QOL) score at baseline and follow-up were 6 (IQR 4-6) and 3 (IQR 2-5), respectively. There was a median AUA-QOL improvement of 2 points (-5,0; p = 0.007) from a baseline 5 (unhappy) to 3 (mixed). Median UDI-6 scores were 50 (IQR 33-75) at baseline and 17 (IQR 0-39), at follow-up. After treatment, there was a median decrease of 19 (-31 to -11; p = 0.01).

CONCLUSION

Women with urethral strictures have severe lower urinary tract symptoms which improved after surgery. This study substantiates the claims that recognizing and treating women with urethral stricture disease greatly improves lower urinary tract symptoms and QOL.

Lingual versus buccal mucosal graft for augmentation urethroplasty: a meta-analysis of surgical outcomes and patient-reported donor site morbidity

PURPOSE

This study aimed at comparing surgical outcomes and patient-reported donor site morbidity between lingual mucosal graft (LMG) and buccal mucosal graft (BMG) through a meta-analysis of comparative studies.

METHODS

A systematic literature search was performed in January 2019 including non-randomized comparative studies and randomized controlled trials (RCT). The assessed data included urethroplasty outcomes, complications, and donor site morbidities such as pain, bleeding, swelling, numbness, difficulty speaking, difficulty eating, mouth opening, and difficulty with tongue protrusion.

RESULTS

A total of 632 patients (LMG 323, BMG 309) from 12 comparative studies (four RCTs and eight non-randomized) were included in the meta-analysis. Overall pooled effect estimates revealed no significant difference on reported surgical outcomes and operative stricture-related complications. The LMG group reported a higher proportion of patients with difficulty speaking (RR 6.96, 95% CI 2.04-23.70) and difficulty with tongue protrusion (RR 12.93, 95% CI 3.07-54.51) within 30 days post-op. In comparison, the BMG group had significantly more incidence of early post-procedural donor site swelling (RR 0.39, 95% CI 0.25-0.61) and numbness within 30 days post-op (RR 0.48, 95% CI 0.23-0.97) and 3-6 months (RR 0.52, 95% CI 0.30-0.90) post-op.

CONCLUSION

The evidence suggests no overall significant difference between LMG and BMG with regard to urethroplasty outcomes at 1-year follow-up. While patients undergoing LMG urethroplasty have a higher chance of experiencing difficulty with speech and difficulty with tongue protrusion within 1 month of surgery, the BMG group is more likely to experience early donor site swelling and mouth opening difficulty within 30 days post-op, as well as oral numbness for up to 6 months.

Treatment of urethral stricture disease in women: A multi‐institutional collaborative project from the SUFU research network

AIM

Female urethral stricture disease is rare and has several surgical approaches including endoscopic dilations (ENDO), urethroplasty with local vaginal tissue flap (ULT) or urethroplasty with free graft (UFG). This study aims to describe the contemporary management of female urethral stricture disease and to evaluate the outcomes of these three surgical approaches.

METHODS

This is a multi-institutional, retrospective cohort study evaluating operative treatment for female urethral stricture. Surgeries were grouped into three categories: ENDO, ULT, and UFG. Time from surgery to stricture recurrence by surgery type was analyzed using a Kaplan-Meier time to event analysis. To adjust for confounders, a Cox proportional hazard model was fit for time to stricture recurrence.

RESULTS

Two-hundred and ten patients met the inclusion criteria across 23 sites. Overall, 64% (n = 115/180) of women remained recurrence free at median follow-up of 14.6 months (IQR, 3-37). In unadjusted analysis, recurrence-free rates differed between surgery categories with 68% ENDO, 77% UFG and 83% ULT patients being recurrence free at 12 months. In the Cox model, recurrence rates also differed between surgery categories; women undergoing ULT and UFG having had 66% and 49% less risk of recurrence, respectively, compared to those undergoing ENDO. When comparing ULT to UFG directly, there was no significant difference of recurrence.

CONCLUSION

This retrospective multi-institutional study of female urethral stricture demonstrates that patients undergoing endoscopic management have a higher risk of recurrence compared to those undergoing either urethroplasty with local flap or free graft.

Predictors of surgical complications and evaluation of outcomes after surgical correction of adult-acquired buried penis

OBJECTIVE

To determine predictors for surgical complications and assess patient satisfaction after surgical treatment of Adult-Acquired Buried Penis (AABP).

METHODS

A retrospective review was performed on all patients diagnosed with AABP who underwent surgical treatment at a single institution from January 2013-December 2017. Patient demographics and peri-operative data were extracted. Univariate and multivariate regression analyses were performed to identify predictors for surgical complications. Patients' post-operative satisfaction was likewise assessed for factors such as successful outcome, post-operative erection quality, and complications related to the surgery.

RESULT

Twenty-four patients of median age 61.5 years (IQR 54-67) with median follow-up of 12 months (IQR 3.25-29) were included. Overall success was 87.5% (21/24). Complications occurred in 15 (62.5%) patients with 7 (29%) Clavien-Dindo category ≥ 3. Based on regression analyses, body mass index (BMI) ≥ 40 (HR 25; 95% CI 1.45-431.81) and tobacco smoking (HR 14.6; 95% CI 1.15-199.98) were identified as independent predictors of overall complications. Concomitant performance of abdominal panniculectomy was associated with Clavien-Dindo category ≥ 3 (HR 28; 95% CI 2.4-326.74) complications. Patient satisfaction was associated with surgical success (p < 0.0001), post-operative erection (p < 0.027), and absence of surgical morbidity that needed further surgical intervention (p = 0.032).

CONCLUSION

Surgical management of AABP following an individualized algorithm results in a high success rate but also in relatively high procedure-related morbidity. Peri-operative BMI ≥ 40 and tobacco smoking have higher odds for overall complication occurrence, while concomitant abdominal panniculectomy results in more occurrence of Clavien-Dindo category ≥ 3 morbidities. Patient's eventual satisfaction correlates well with surgical success, post-procedural erection condition, and lack of Clavien-Dindo ≥ 3 morbidity.

Long-term Success Durability of Transobturator Male Sling

OBJECTIVE

To determine the long-term outcome of transobturator sling for male stress urinary incontinence (SUI) clustered according to preoperative SUI severity, and to identify predictors of treatment success durability and failure occurrence in long-term follow-up.

METHOD

A nonconcurrent study was conducted on all transobturator male sling cases performed from August 2006 to June 2012 by a single surgeon. Preoperative SUI severity was clustered into mild (≤2 ppd), moderate (3-4 ppd) or severe (≥5 ppd). Success was defined as complete dryness with 0 pads used (cured), and a patient with ≥50% improvement, satisfied without further procedures needed. Otherwise it was considered a treatment failure. Clinical variables significantly associated with long-term treatment success were determined. Time-to-event (Kaplan-Meier) and Multiple-Cox regression analysis were performed to determine predictors of long-term treatment outcome.

RESULTS

A total of 215 patients (mild-59, moderate-94, and severe-62) with a mean follow-up of 56.4 ± 41.6 months were included. On long-term follow-up, 150 (69.8%) patients-maintained treatment success and 96 (44.7%) were dry. The long-term outcome success clustered according to SUI severity as mild, moderate, and severe was 84.7%, 72.3%, and 51.6%, respectively. Kaplan-Meier with Log-rank test and Multiple Cox-regression determined that both concomitant urge incontinence and preoperative SUI severity were independent predictors of long-term durability of treatment success and failure occurrence. Preoperative SUI severity was the only predictor of long-term cure sustainability.

CONCLUSION

The time to event analysis with an average of ∼5 years postoperative follow-up has determined that the preoperative severity and presence of concomitant urge incontinence were independent predictors for long-term outcome.

Urethroplasty After Urethral Urolume Stent: An International Multicenter Experience

OBJECTIVE

To evaluate the outcomes and factors affecting success of urethroplasty in patients with stricture recurrence after Urolume urethral stent.

MATERIAL AND METHODS

This is a retrospective international multicenter study on patients treated with urethral reconstruction after Urolume stent. Stricture and stent length, time between urethral stent insertion and urethroplasty, age, mode of stent retrieval, type of urethroplasty, complications and baseline, and posturethroplasty voiding parameters were analyzed. Successful outcome was defined as standard voiding, without need of any postoperative adjunctive procedure.

RESULTS

Sixty-three patients were included. Stent was removed at urethroplasty in 61 patients. Reconstruction technique was excision and primary anastomosis in 14 (22.2%), dorsal onlay buccal mucosa graft (BMG) in 9 (14.3%), ventral onlay BMG in 6 (9.5%), dorsolateral onlay BMG in 9 (14.3%), ventral onlay plus dorsal inlay BMG in 3 (4.8%), augmented anastomosis in 5 (7.9%), pedicled flap urethroplasty in 6 (9.5%), 2-stage procedure in 4 (6.4%), and perineal urethrostomy in 7(11.1%). Success rate was 81% at a mean 59.7 ± 63.4 months. Dilatation or internal urethrotomy was performed in 10 (15.9%) and redo-urethroplasty in 5 (7.9%). Total International Prostate Symptom Score, quality of life, urine maximum flow, and postvoid residual significantly improved (P <.0001). Complications occurred in 8 (12.7%), all Clavien-Dindo ≤2. Disease-free survival rate after reconstruction was 88.1%, 79.5%, and 76.7% at 1, 3, and 5 years, respectively. Explant of individual strands followed by onlay BMG is the most common approach and was significantly advantageous over the other techniques (P = .018).

CONCLUSION

Urethroplasty in patients with Urolume urethral stents is a viable option of reconstruction with a high success rate and very acceptable complication rate. Numerous techniques are viable; however, urethral preservation, tine-by-tine stent extraction, and use of BMG augmentation produced significantly better outcomes.

Patient-reported outcomes combined with objective data to evaluate outcomes after urethral reconstruction

OBJECTIVE

To report patients' perceptions of urethral reconstruction outcomes by comparing the results from preoperative and postoperative symptom questionnaires and to propose a standardized method of follow-up that includes patient satisfaction questionnaires and objective cystoscopic evaluation to facilitate comparison of different urethral reconstructive techniques and outcomes among surgeons and institutions.

MATERIALS AND METHODS

Data were prospectively collected for 110 consecutive patients undergoing urethral reconstruction. Patient demographics, American Urological Association Symptom Score, quality of life score, International Index of Erectile Function score, flow rate, and postvoid residual urine volume were collected pre- and postoperatively. The patients were evaluated at 3 and 6 months postoperatively and then yearly. Flexible cystoscopy (17F) was performed at 6 months postoperatively. The Wilcoxon signed rank test and Mann-Whitney U test were used to compare the pre- and post-test distributions. One-way analysis of variance was used to compare the mean values among groups.

RESULTS

The mean patient age was 47 years, and the mean stricture length was 4.9 cm. Of the 110 patients, 32 received anastomotic (29%), 60 onlay (55%), 7 staged (6%), and 11 fasciocutaneous flap (10%) urethroplasty. The median individual change comparing the pre- and postoperative data was an improvement of 11 for the American Urological Association Symptom Score (P <.0001), 4 for the quality of life score (P <.0001), and 0 for International Index of Erectile Function (P = .05). No unifying individual follow-up questionnaire or flow rate correlated with recurrence.

CONCLUSION

Patients undergoing urethral reconstruction reported significant improvement in urinary bother and quality of life scores while maintaining or improving their erectile function. Cystoscopic evaluation can be a valuable component of the postoperative follow-up algorithm, providing a consistent data point for comparison and confirming the patency of repair. Standardization of the measured outcomes is critical to validate the reported urethral reconstructive outcomes.

Abstract 1161: Detection and identification of a miRNA expression profile from cell-free urine: Potential utility in bladder cancer

Introduction/Objective: MicroRNAs are small, non-coding RNAs that have been shown to play an important role in tumorigenesis. There is differential expression of miRNA in cancer progression, and profiling of miRNA is promising for both diagnosis and treatment of malignant tumors. In this study we isolated RNA from cell-free urine in an attempt to characterize miRNA profiles indicating the presence of urothelial carcinoma and its potential use as a non-invasive assay to identify patients with cancer progression.

Methods: Urine was collected from patients diagnosed with bladder cancer and control patients with no history of cancer under an IRB-approved protocol. Urine was centrifuged and total RNA was isolated from the supernatants using the mirVana Paris™ kit. A total of 178 samples were grouped according to grade and stage (healthy controls (35), TaG1 (19), T1G3 (16), ≥T2 (30), carcinoma in situ (CIS; 28) and no evidence of disease following therapy (50). Seven hundred and thirty miRNAs were profiled by qRT-PCR on pooled samples within each group. Validation of selected miRNAs was performed on individual samples using qRT-PCR.

Results: Cell-free RNA was isolated from urine of 35 healthy controls and 143 patients with bladder cancer. Of the 730 miRNAs tested, 236 were detected in at least one of the pooled samples using a Ct cutoff of 35. The number of miRNAs detected in the pooled samples correlated with disease progression where the healthy control group and the ≥T2 group expressed 8 and 228 miRNAs, respectively. qRT-PCR of individual samples revealed a gradual increase of some miRNAs with disease progression. Statistical analysis adjusted for multiple comparisons demonstrated differences between groups based on miRNA expression levels. In addition, a panel of miRNAs was identified which discriminated between cancer and cancer-free patients.

Conclusion: This study demonstrates the successful isolation of miRNAs from cell-free urine. Utilizing non-invasive urine based assays, we identified a miRNA panel that can discriminate between cancer-free patients and patients with urinary carcinoma of the bladder. These findings provide evidence that profiling of miRNAs from cell-free urine holds the promise for the development of valuable clinical tools.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1161. doi:10.1158/1538-7445.AM2011-1161

The effects of the novel benzodiazepine receptor inverse agonist Ru 34000 on ethanol-maintained behaviors

Ru 34000 [5-ethyl-7-methoxy-imidazo (1,2-a) pyrimidin-2-yl cyclopropyl methanone] is a novel imidazopyrimidine benzodiazepine inverse agonist that exhibits low affinity for central benzodiazepine receptors (Ki approximately 0.98 microM). The present study examined the in vivo actions of Ru 34000 (0.5-5 mg/kg) following intraperitoneal (i.p.), subcutaneous (s.c), oral (p.o.), and intraventral tegmental administration in alcohol-preferring (P) rats trained under a concurrent operant schedule (FR4-FR4) for ethanol (10% v/v) and a palatable saccharin (0.025% or 0.75% w/v) reinforcer. Ru 34000 (i.p., s.c., p.o.) markedly reduced ethanol responding by 28-96% of control levels without affecting saccharin responding, except for the highest dose level. Clear dose-dependent suppressant effects were observed with all routes of administration on ethanol responding. Flumazenil [ethyl-8-fluro-5, 6-dihydro-5-methyl-6-4H-imidazo [1,5-a]-[1,4]-benzodiazepine-3-carboxylate] (6 mg/kg; i.p.), a benzodiazepine receptor antagonist reversed the Ru 34000-reduction of ethanol responding, suggesting that the effects were mediated at the benzodiazepine receptor. Bilateral microinjections of Ru 34000 (50, 100, 200 ng) into the ventral tegmental area dose-dependently reduced ethanol responding by as much as 97% of control levels. The results suggest that the in vivo actions of Ru 34000 are determined not only by its binding affinity, but also by its bioavailability at active benzodiazepine sites and route of drug administration. Low affinity imidazopyrimidines may be useful pharmacological probes to further understand the role of the GABA(A)-benzodiazepine receptor complex in ethanol motivated behaviors.

High-affinity benzodiazepine antagonists reduce responding maintained by ethanol presentation in ethanol-preferring rats

In the present study, we examined two high-affinity and selective benzodiazepine (BDZ) receptor antagonists (ZK 93426, CGS 8216) in ethanol (EtOH)-preferring rats whose responding (i.e., lever pressing) was maintained by the presentation of EtOH. The in vivo actions of CGS 8216 (1-30 mg/kg) and ZK 93426 (5-75 mg/kg) were examined after intraperitoneal or oral administration. Flumazenil (10-40 mg/kg) was used as a reference BDZ antagonist. EtOH (10% v/v) and saccharin (0.05 g/v) solutions were concurrently available for 30 min each day under a two-lever fixed-ratio schedule in which four responses on one lever produced the EtOH solution and four responses on the other lever produced the saccharin solution. A 40 mg/kg intraperitoneal injection of flumazenil given on the first injection day (day 1) nonsignificantly reduced control levels of responding maintained by EtOH by 36%. No effects were observed 24 hr after drug administration (day 2). Oral administration of flumazenil was without effect. On day 1, intraperitoneal administration of CGS 8216 (1-20 mg/kg) and ZK 93426 (1-50 mg/kg) reduced control levels of responding maintained by EtOH by 44% to 73%; on day 2, EtOH maintained responding continued to be suppressed with the highest doses (> or = 20 mg/kg) suppressing control levels of responding by as much as 62%. Oral administration of higher doses of CGS 8216 (5-30 mg/kg) and ZK 93426 (10-75 mg/kg) reduced responding maintained by EtOH by as much as 54% to 84% of controls; however, no effects were seen on day 2. Only the highest intraperitoneal dose of ZK 93426 (50 mg/kg) suppressed responding maintained by saccharin. These findings demonstrate that some BDZ antagonists decrease responding maintained by EtOH. The findings suggest that certain BDZ antagonists may have potential as pharmacotherapies to prevent or decrease EtOH abuse in humans.

Apical Na+ permeability of frog skin during serosal Cl- replacement

Gluconate substitution for serosal Cl- reduces the transepithelial short-circuit current (Isc) and depolarizes short-circuited frog skins. These effects could result either from inhibition of basolateral K+ conductance, or from two actions to inhibit both apical Na+ permeability (PapNa) and basolateral pump activity. We have addressed this question by studying whole-and split-thickness frog skins. Intracellular Na+ concentration (CcNa) and PapNa have been monitored by measuring the current-voltage relationship for apical Na+ entry. This analysis was conducted by applying trains of voltage pulses, with pulse durations of 16 to 32 msec. Estimates of PapNa and CcNa were not detectably dependent on pulse duration over the range 16 to 80 msec. Serosal Cl- replacement uniformly depolarized short-circuited tissues. The depolarization was associated with inhibition of Isc across each split skin, but only occasionally across the whole-thickness preparations. This difference may reflect the better ionic exchange between the bulk medium and the extracellular fluid in contact with the basolateral membranes, following removal of the underlying dermis in the split-skin preparations. PapNa was either unchanged or increased, and CcNa either unchanged or reduced after the anionic replacement. These data are incompatible with the concept that serosal Cl- replacement inhibits PapNa and Na,K-pump activity. Gluconate substitution likely reduces cell volume, triggering inhibition of the basolateral K+ channels, consistent with the data and conclusions of S.A. Lewis, A.G. Butt, M.J. Bowler, J.P. Leader and A.D.C. Macknight (J. Membrane Biol. 83:119-137, 1985) for toad bladder. The resulting depolarization reduces the electrical force favoring apical Na+ entry. The volume-conductance coupling serves to conserve volume by reducing K+ solute loss. Its molecular basis remains to be identified.

Apical sodium entry in split frog skin: current-voltage relationship

Apical Na+ entry into frog skin epithelium is widely presumed to be electrodiffusive in nature, as for other tight epithelia. However, in contrast to rabbit descending colon and Necturus urinary bladder, the constant field equation has been reported to fit the apical sodium current (INa)-membrane potential (psi mc) relationship over only a narrow range of apical membrane potentials or to be inapplicable altogether. We have re-examined this issue by impaling split frog skins across the basolateral membrane and examining the current-voltage relationships at extremely early endpoints in time after initiating pulses of constant transepithelial voltage. In this study, the rapid transient responses in psi mc were completed within 0.5 to 3.5 msec. Using endpoints to 1 to 25 msec, the Goldman equation provided excellent fits of the data over large ranges in apical potential of 300 to 420 mV, from approximately -200 to about +145 mV (cell relative to mucosa). Split skins were also studied when superfused with high serosal K+ in order to determine whether the INapsi mc relationship could be generated purely by transepithelial measurements. Under these conditions, the basolateral membrane potential was found to be -10 +/- 3 mV (cell relative to serosa, mean +/- SE), the basolateral fractional resistance was greater than zero, and the transepithelial current was markedly and reversibly reduced. For these reasons, use of high serosal K+ is considered inadvisable for determining the INa-psi mc relationship, at least in those tissues (such as frog skin) where more direct measurements are technically feasible. Analysis of the INa-psi mc relationships under baseline conditions provided estimates of intracellular Na+ concentration and of apical Na+ permeability of 9 to 14 mM and of approximately 3 X 10(-7) cm X sec-1, respectively, in reasonable agreement with estimates obtained by different techniques.

Microelectrode study of K+ accumulation by tight epithelia: I. Baseline values of split frog skin and toad urinary bladder

Toad bladder and split frog skin were impaled with fine-tipped single- and double-barrelled K+-selective microelectrodes. In order to circumvent membrane damage induced by impaling toad bladder, a null point method was developed, involving elevations of mucosal potassium concentration. The results suggest that intracellular potassium activity of short-circuited toad bladder is approximately 82 mM, twice as large as earlier estimates. Far more stable and rigorously defined intracellular measurements were recorded from short-circuited split frog skins. The intracellular positions of the micropipette and microelectrode tips were verified by transient hyperpolarizations of the membrane potential with mucosal amiloride or by transient depolarizations with serosal barium or strophanthidin. Simultaneous impalement of distant cells with separate micropipettes demonstrated that both the baseline membrane potentials and the responses to depolarizing agents were similar, further documenting that frog skin is a functional syncytium. Measurements with double-barrelled microelectrodes and simultaneous single-barrelled microelectrodes and reference micropipettes suggest that the intracellular potassium activity is about 104 mM, lower than previously reported. Taken together with measurements of intracellular potassium concentration, this datum suggests that potassium is uniformly distributed within the epithelial cells.

Microelectrode study of K+ accumulation by tight epithelia: II. Effect of inhibiting transepithelial Na+ transport on reaccumulation following depletion

The effects of restoring serosal potassium to potassium-depleted toad urinary bladders have been re-examined using double-barrelled microelectrodes. The data confirm the existence of a time-lag phenomenon, a dissociation between potassium reaccumulation and restoration of short-circuit current. Returning serosal potassium stimulates an increase in intracellular potassium activity 21-26 min before any increase can be detected in short-circuit current. The reaccumulation of potassium has been further studied using split frog skin, a far more suitable preparation for electrophysiologic study than toad bladder. Under baseline short-circuited conditions, potassium is accumulated against an electrochemical gradient of 22 +/- 4 mV. Reaccumulation of potassium by potassium-depleted tissues can be blocked by inhibiting the Na,K-exchange pump with high concentrations of ouabain. On the other hand, blocking apical sodium entry by the addition of 10(-4) M amiloride to the outer bathing medium does not interfere with reaccumulation of potassium. The data support the concept that the time-lag phenomenon of toad bladder reflects stimulation of potassium reaccumulation by the sodium pump in exchange for the extrusion of excess cell sodium collected during the period of potassium depletion. This reaccumulation of potassium can proceed before the entry of significant added amounts of sodium across the apical plasma membrane.

A pressure- and flow-insensitive reference electrode liquid junction

The design and construction of a pressure- and flow-insensitive reference liquid junction for use in ion concentration electrode measuring systems is described. The junction is inexpensive, is very easily and rapidly constructed, is rugged, and is adaptable to various applications. When used in a pH-measuring system, drift, pressure artifacts, and flow artifacts are negligible. The response time of the system appears to be less than 10 ms. Using the pH electrode device as described, the dissociation reaction rate constant of H2CO3 at 24 degrees C was determined to be 22 s-1.