Newborn Bladder Research Articles

Staged Male Bladder Exstrophy Repair

This chapter details the latest surgical advances and outcomes in the modern surgical management of male classic bladder exstrophy to include patient selection for closure, operative considerations, newborn primary bladder and posterior urethral closure, early epispadias repair, bladder neck reconstruction with an antireflux procedure, and postoperative management. It highlights how to achieve the primary objectives of (1) a secure abdominal closure, (2) reconstruction of a functional and cosmetically acceptable penis, and (3) urinary continence with the preservation of renal function. In addition, it addresses the most common pitfalls and challenges encountered when accomplishing each of the major surgical interventions. This review contains 3 figures, 5 tables, and 47 references. Key Words: Congenital defect, Bladder exstrophy, Epispadias, Reconstruction, Urinary Continence, Magnetic Resonance Imaging, Pain management, Pelvic osteotomy

Perioperative Analgesic Management of Newborn Bladder Exstrophy Repair Using a Directly Placed Tunneled Epidural Catheter with 0.1% Ropivacaine

Effective multimodal analgesia and sedation reduce the postoperative morbidity and mortality associated with newborn bladder exstrophy repair. Epidural analgesia is safe and effective for major surgery in neonates and infants, reducing the need for muscle relaxants, opioids, and ventilator support postoperatively. The risk of epidural catheter colonization typically dictates removal after 3 to 5 days. Tunneling the catheter subcutaneously reduces the risk of colonization, providing prolonged analgesia for patients requiring an extended immobilization to prevent compromise of the repair. In this report, we describe the postoperative analgesic management of an infant undergoing bladder exstrophy repair using a directly placed tunneled epidural catheter with ropivacaine 0.1% infusion. Because of the prolonged infusion, we also monitored plasma ropivacaine levels to preclude systemic toxicity from local anesthetic overdose.

Padded Self-Adhesive Strap Immobilization Following Newborn Bladder Exstrophy Closure: The Utah Straps

Several methods have been described for immobilization of the pelvis following bladder exstrophy closure, which can be challenging to manage. We hypothesized that immobilization can be significantly simplified using a modified mermaid wrap with padded Velcro® straps around the thigh and lower leg. We retrospectively reviewed all patients who underwent bladder exstrophy closure in the newborn period at our institution from 1990 through 2010. Patients with cloacal exstrophy and those who underwent delayed closure due to other medical conditions were excluded. We collected data on closure technique, length of stay and complications of the primary closure as outcomes. A total of 20 boys and 7 girls underwent closure of classic bladder exstrophy. Followup ranged from 2 to 22 years. Seven boys underwent complete primary repair and 13 underwent staged repair. All patients had the legs stabilized with a modified wrap technique using 2 lengths of Velcro straps lined with self-adhering open cell foam pads for 3 weeks. Complications of exstrophy closure included bladder dehiscence in 1 patient (4%) and incisional hernia in 2(7%). Following complete primary repair urethrocutaneous fistula developed in 2 patients and urethral stricture in 2. Average length of stay for patients without significant prematurity was 15 days. Padded Velcro strap immobilization simplifies postoperative care, provides secure fixation, decreases length of stay, and enables parents to hold and bond with the child shortly after repair. We advocate this simplified technique, which can be applied with a rate of complications that is comparable to other procedures.

Signal transduction pathways of muscarinic receptor mediated activation in the newborn and adult mouse urinary bladder

To study the role of M(2) and M(3) muscarinic receptor subtypes, sources of activator Ca(2+), and mechanisms involved in increased force oscillations in muscarinic contractions in the bladders of newborn and adult mice, as in the adult bladder muscarinic M(3) receptors are considered to mediate the main part of bladder contraction, and this has not been established in the newborn bladder. Bladder preparations from newborn (0-2 days) and adult (10-12 weeks) mice were mounted for in vitro force registration and activated with carbachol and high-K(+) solution in the presence of M(3) (4-DAMP 30 nM) or M(2) (methoctramine, 100 nM) receptor antagonists. Thapsigargin (1 microm) or ryanodine (10 microm) were used to inhibit sarcoplasmic reticulum Ca(2+) release. L-NAME (300 microm) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 microm) were used to inhibit nitric oxide synthase and guanylyl cyclase, respectively. Gap-junction function was inhibited with by 18-beta-glycyrrhetinic acid (18-beta-GA; 0.1-100 microm). Big-conductance (BK) and small-conductance (SK) K(+) channels were inhibited by apamine and charybdotoxin (0.3 microm), respectively. Concentration-response relations for carbachol in the presence of 4-DAMP and methoctramine showed that M(3) receptors are the main activating pathway also in the newborn bladder. Neither thapsigargin nor ryanodine influenced the muscarinic responses of the newborn and adult bladders. Carbachol-induced contractions were not influenced by L-NAME or ODQ. The 18-beta-GA inhibited carbachol-induced contractions in both newborn and adult tissue in a similar manner. Apamine and charybdotoxin slightly increased the amplitude of the contractile responses. These results suggest that in the newborn mouse bladder, as in adult bladders, the M(3) muscarinic receptor subtype is mainly responsible for carbachol-induced contractile responses. The main mechanism for muscarinic receptor-induced activation is influx of Ca(2+) from the extracellular medium, and there seems to be no major contribution of Ca(2+) release from intracellular stores. The phasic contractile activity induced by carbachol in the newborn bladder is not influenced by gap junction inhibition and does not involve SK and BK channels.

Perioperative anesthetic and analgesic management of newborn bladder exstrophy repair

Objective Reconstruction of bladder exstrophy in newborn infants requires immobilization, sedation and pain management to prevent distracting forces from compromising the repair. We present a 6-year review of our experience. Subjects and methods We reviewed the perioperative management of newborn infants undergoing reconstruction between November 1999 and October 2006. Data are presented as means ± SD. Results Twenty-three newborn infants underwent surgery under a combined epidural and general anesthetic technique. Tunneled caudal epidural catheters were inserted in all patients and intermittently injected with 0.25% bupivacaine with 1:200,000 epinephrine. Postoperatively, a continuous infusion of 0.1% lidocaine, 0.8–1 mg/kg/h was administered for 15 ± 8 (range 4–30) days. Children were sedated with diazepam for 20 ± 13 (range 2–40) days. Central venous catheters were maintained for 20 ± 9 (range 1–34) days for fluids, drug administration and blood sampling. No patient experienced bladder prolapse or wound dehiscence. Conclusion Perioperative management with tunneled epidural and central venous catheters in newborn infants with bladder exstrophy facilitates immobilization, analgesia and sedation, resulting in an excellent cosmetic repair with no case of bladder prolapse or wound dehiscence.

THE MECHANICAL PROPERTIES OF THE NEWBORN EXSTROPHY BLADDER

You have accessJournal of Urology1 Apr 2008THE MECHANICAL PROPERTIES OF THE NEWBORN EXSTROPHY BLADDER Navroop S Johal, Peter M Cuckow, and Christopher H Fry Navroop S JohalNavroop S Johal More articles by this author , Peter M CuckowPeter M Cuckow More articles by this author , and Christopher H FryChristopher H Fry More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(08)60282-7AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "THE MECHANICAL PROPERTIES OF THE NEWBORN EXSTROPHY BLADDER." The Journal of Urology, 179(4S), pp. 96–97 © 2008 by American Urological AssociationFiguresReferencesRelatedDetails Volume 179Issue 4SApril 2008Page: 96-97 Advertisement Copyright & Permissions© 2008 by American Urological AssociationMetricsAuthor Information Navroop S Johal More articles by this author Peter M Cuckow More articles by this author Christopher H Fry More articles by this author Expand All Advertisement PDF downloadLoading ...

Contractility and detrusor cell function of the newborn exstrophy bladder

Purpose There is no information concerning the contractile and detrusor cell properties of detrusor smooth muscle from neonatal exstrophy bladders (NE). The aim of this study was to examine these properties of NE and compare them to those with normal bladder (N) function. Material and methods Following ethical approval and patient consent full thickness bladder samples were obtained from patients with NE and N. Detrusor strips were superfused at 37°C with HCO3/CO2 buffered physiological solution. Nerve-mediated responses were elicited by electrical field stimulation. Muscle-mediated responses were generated by carbachol and a,bmethylene-ATP (ABMA). Tension was normalised to unit cross-sectional area (mN.mm-2). Data is presented as mean±s.d. Detrusor cells were isolated using collagenase and loaded with a Ca2+ indicator (fura-2). The 340/380 ratio, a direct measure of intracellular calcium [Ca2+]i changes was measured following addition of carbachol, ABMA, and KCl. Significance of differences (p Results Nerve-mediated were significantly less (0.8±0.3 vs 2.9±4.7 mN.mm-2), as were the muscle-mediated responses (5.4±3.6 vs 30.8±22.2) in samples from NE compared to N (n=5, 20 respectively). The NE strips however were more sensitive after addition of carbachol (EC50s; 1.8±0.5 vs 3.2±1.2). Following addition of carbachol, ABMA, and KCl to isolated cells, [Ca2+]i transients were observed. The 340/380 ratios were not statistically significantly different between NE and N bladders (carbachol; 0.4 vs 0.4, ABMA; 0.7 vs 0.8, KCl; 0.4 vs 0.4, n=9,15 respectively). Conclusions The data show that contractile function is reduced in patients with NE compared to N. The detrusor cell function appears normal. Altered muscle-matrix interaction content and/or dysfunctional excitation-contraction coupling could play a role in this hypocontractility.

Developmental regulation of nerve and receptor mediated contractions of mammalian urinary bladder smooth muscle

The development of nerve-induced activation, receptor properties and cellular signalling was examined by comparing the urinary bladder of new-born (0–2 days) and adult mice. Tissue strips were isolated and the effects of different neuromuscular agents on force were investigated during electrical field stimulation. The nerve-induced contractions of the urinary bladders from new-born mice were less influenced by desensitisation with α, β-methylene ATP and more sensitive to scopolamine compared with those of the adult bladder. There were no differences in α, β-methylene ATP or ATP responsiveness between adult and new-born tissue, showing that the lower purinergic component of the nerve-induced responses in the new-born mice was due to properties of the transmitter release rather than to a change in receptor function. Dose–response curves for carbachol revealed a lower peak response in new-born bladders compared with adults. The phasic component of the cholinergic contractions was pronounced and initiated at low carbachol concentrations in the new-born tissue. The carbachol contractions of both new-born and adult urinary bladder tissue were inhibited by the Rho kinase inhibitor Y27632 and by the protein kinase G activator 8-Br-cGMP. However, the sustained phase of carbachol contraction was significantly less sensitive to Y27632 and 8-Br-cGMP in new-born tissue. These results suggest that the receptor mediated calcium sensitisation mechanism is less prominent in new-born compared with adult mice and that the contractions of new-born bladders are less influenced by the nitric oxide (NO)-cGMP inhibitory pathway.

Decreased Phosphatase Activity, Increased Ca2+ Sensitivity, and Myosin Light Chain Phosphorylation in Urinary Bladder Smooth Muscle of Newborn Mice

Developmental changes in the regulation of smooth muscle contraction were examined in urinary bladder smooth muscle from mice. Maximal active stress was lower in newborn tissue compared with adult, and it was correlated with a lower content of actin and myosin. Sensitivity to extracellular Ca2+ during high-K+ contraction, was higher in newborn compared with 3-wk-old and adult bladder strips. Concentrations at half maximal tension (EC50) were 0.57 ± 0.01, 1.14 ± 0.12, and 1.31 ± 0.08 mM. Force of the newborn tissue was inhibited by ∼45% by the nonmuscle myosin inhibitor Blebbistatin, whereas adult tissue was not affected. The calcium sensitivity in newborn tissue was not affected by Blebbistatin, suggesting that nonmuscle myosin is not a primary cause for increased calcium sensitivity. The relation between intracellular [Ca2+] and force was shifted toward lower [Ca2+] in the newborn bladders. This increased Ca2+ sensitivity was also found in permeabilized muscles (EC50: 6.10 ± 0.07, 5.77 ± 0.08, and 5.55 ± 0.02 pCa units, in newborn, 3-wk-old, and adult tissues). It was associated with an increased myosin light chain phosphorylation and a decreased rate of dephosphorylation. No difference was observed in the myosin light chain phosphorylation rate, whereas the rate of myosin light chain phosphatase–induced relaxation was about twofold slower in the newborn tissue. The decreased rate was associated with a lower expression of the phosphatase regulatory subunit MYPT-1 in newborn tissue. The results show that myosin light chain phosphatase activity can be developmentally regulated in mammalian urinary bladders. The resultant alterations in Ca2+ sensitivity may be of importance for the nervous and myogenic control of the newborn bladders.

Modern staged reconstruction of bladder exstrophy—still the gold standard

Early efforts at the management of bladder exstrophy were dogged by high morbidity and complications leading to poor long-term outcomes for continence and renal function. 1 Martinez-Pineiro J.A. Long-term results of surgical treatment of bladder exstrophy. Eur Urol. 1976; 2: 168-174 PubMed Google Scholar The staged reconstruction of bladder exstrophy was proposed by Jeffs 2 Jeffs R.D. Functional closure of bladder exstrophy. Birth Defects Orig Artic Ser. 1977; 13: 171-173 PubMed Google Scholar and led to significant improvements in continence and renal function with excellent cosmetic results. 3 Jeffs R.D. Exstrophy and cloacal exstrophy. Urol Clin North Am. 1978; 5: 127-140 PubMed Google Scholar Once universal survival was ensured, the paradigm for management shifted to additional reduction in complications and improvement in voiding continence. The initial staged management consisted of newborn bladder and posterior urethral closure followed by bladder neck reconstruction at 2 to 3 years of age and later epispadias repair. 3 Jeffs R.D. Exstrophy and cloacal exstrophy. Urol Clin North Am. 1978; 5: 127-140 PubMed Google Scholar The understanding that appropriately timed epispadias repair may lead to enhancement in bladder capacity led to performance of epispadias repair at 2 to 3 years of age followed by later bladder neck reconstruction. The current modification of the staged repair consists of secure bladder and posterior urethral closure in infancy followed by epispadias repair at 6 to 12 months of age and bladder neck reconstruction when the patient is able to cooperate in a good voiding program. 4 Chan D.Y. Jeffs R.D. Gearhart J.P. Determinants of continence in the bladder exstrophy population predictors of success?. Urology. 2001; 57: 774-777 Abstract Full Text Full Text PDF PubMed Google Scholar

Decrease in Maximal Force Generation in the Neonatal Mouse Bladder Corresponds to Shift in Myosin Heavy Chain Isoform Composition

A change in calcium handling has been proposed as the cause of decreased maximal force generation by neonatal bladders with growth. Recent studies suggest that increased myosin heavy chain isoform SM1 increases force generation. We studied force generation in neonatal mouse bladders to determine if decreases in SM1 corresponded with decreased force. C57Bl/6 mice were studied from birth to 12 weeks of life (adulthood). The bladder strip contractile response to KCl and bethanechol was followed by the inhibition of rho-kinase activity by Y-27632. The mRNA levels for SM1/SM2 were determined using reverse transcriptase-polymerase chain reaction and protein levels were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Muscle fraction per cross-sectional area was determined by trichrome staining. Newborn bladders generated significantly more tension in response to KCl (43.3 vs 17.4 mN/mm2, p = 0.02) and bethanechol (40.6 vs 11.9 mN/mm2, p = 0.05) than adult bladders. Inhibition of rho-kinase resulted in similar decreases in tension in all bladders. SM1 mRNA decreased slightly from 60% at birth to 50% at 12 weeks. SM1 protein decreased from 72.5% at birth to 50% by 3 weeks and it remained stable at 12 weeks. Total myosin per gm protein remained stable. Muscle fraction decreased from 63.8% at birth to 58.6% at 12 weeks (p = 0.4). We noted a decrease in SM1 that corresponded to a decrease in bladder force generation. The concept that SM1 contributes to the optimal assembly of myosin filaments suggests that changes in myosin isoforms may have a role in the decrease in voiding pressures seen in normal children.

Age-related smooth muscle reactivity changes in the rat bladder: an in vitro study

An experimental study was conducted to investigate developmental changes of the rat detrusor smooth muscle (DSM) reactivity from newborn to adult period. Urinary bladders were obtained from adult (4 months old), 1-month-old and newborn (4–7 days old) male Sprague-Dawley rats. DSM reactivity of the three groups was evaluated in organ chambers. The newborn DSM strips revealed markedly increased purinoceptor- and cholinoceptor-mediated contractions (ATP, carbachol) with increased maximum response (2.98- and 8.96-fold increase for ATP, 2.90- and 4.22-fold increase for carbachol, when the newborn bladder compared with 1-month-old and adult groups, respectively) and sensitivity (1.65- and 1.29-fold increase for ATP when the newborn bladder compared with the 1-month-old and adult groups, respectively). Additionally the maximum contractile response to KCl in the bladder from the newborn was 1.65- and 8.96-fold increased compared to bladders of the 1-month-old and adult groups, respectively. However, no significant changes in the adrenoceptor-mediated relaxation (isoproterenol) of the rat DSM were observed among the groups. These results indicate that development alters the in vitro responsiveness of rat DSM. The newborn rat bladder gains some of the adult bladder properties within 1 month. These changes are likely to reflect the changing role of parasympathetic regulation in the DSM reactivity during development of the rat bladder.

Heterogeneity of bladder myocytes in vitro: modulation of myosin isoform expression

We studied the expression of myosin heavy chain isoforms differing at the N-terminal (SM-A, SM-B) and the C-terminal (SM1, SM2) regions and non-muscle myosin heavy chain II-A and II-B (NMMHC II-A and B) in newborn and adult rabbit bladder smooth muscle cells (SMCs) and in cultures of enzymatically dissociated neonatal detrusor. RT-PCR analyses revealed that 94.5 ± 3.27% of MHC transcripts of the adult bladder SMCs contained the 21-nucleotide insert (SM-B) compared with 83.8 ± 3.2% in the newborn bladder, with the remainder of the mRNA being non-inserted (SM-A). In 3, 7, and 10 days of primary culture (proliferating, confluent, and post-confluent, respectively) and up to 4 subculture passages, bladder myocytes expressed predominantly SM-A. Immunofluorescence microscopy revealed heterogeneity in cultured myocytes, i.e. SM-B positive cells coexisting with negatively stained cells. In adult bladder, the C-terminal isoforms SM1 and SM2 represented, 43.1 ± 4.3% and 56.89 ± 4.3% of the mRNA, respectively, while newborn bladders expressed 72.5 ± 7% SM1 and 27.5 ± 7% SM2. Upon culturing, cells predominantly expressed SM1 at both the mRNA and protein levels. NMMHC II-A was expressed by both adult and newborn bladders and in culture, whereas NMMHC II-B was expressed at low levels only in newborn bladders, but upregulated in culture. These data indicate that bladder myocytes in vitro undergo modulation with relative overexpression of SM-A and SM1 and upregulation of NMMHC II-B. Information on the mechanisms responsible for this modulation in vitro might provide an understanding of the nature of altered myosin isoform expression associated with smooth muscle dysfunction in certain bladder diseases.

THE NEWBORN EXSTROPHY BLADDER INADEQUATE FOR PRIMARY CLOSURE: EVALUATION, MANAGEMENT AND OUTCOME

The surgical approach to the small newborn exstrophy bladder inadequate for primary closure remains undetermined. Various methods for long-term management have been implemented. We evaluated our experience with late primary closure of the small exstrophied bladder template. Our institutional database of patients treated and followed for the exstrophy-epispadias complex was reviewed. Of these patients 19 had a bladder template that was too small to close in the newborn period. The treatment and outcome of these 19 patients were reviewed. Of the 19 children who had delayed closure due to a small bladder template 14 were males and 5 were females. Followup from birth ranged from 2 to 36 years (mean 18 years). Primary closure was performed at a mean patient age of 13 months (range 6 months to 2 years). Pelvic osteotomy was performed in 16 patients. Of the 19 patients 9 achieved continence after gaining a bladder capacity sufficient for bladder neck reconstruction, 4 required enterocystoplasty to augment bladder volume and perform clean intermittent catheterization (2 per stoma and 2 per urethra), 1 required a colon conduit for an extremely small bladder, and 1 underwent cystectomy and ureterosigmoidostomy for rhabdomyosarcoma. Four patients are currently incontinent, including 3 who are awaiting bladder neck reconstruction and 1 who has frequent nighttime incontinence that is medically managed. Delayed primary closure of the small bladder exstrophy template can allow the native bladder tissue adequate time to grow to a size feasible for successful closure. Epispadias repair can usually be performed at the same time and is facilitated by prior testosterone administration. Bladder neck reconstructive techniques have achieved continence without the need for augmentation or bladder replacement in 47% of the patients in our series. For patients who do not achieve adequate capacity for bladder neck reconstruction, preservation of the native bladder template facilitates future augmentation and ureteral reimplantation, thus requiring use of less bowel in the growing child.

Mesenchymal-epithelial interactions in bladder smooth muscle development: epithelial specificity.

We previously showed that mesenchymal-epithelial interactions are necessary for the development of bladder smooth muscle. Specifically without bladder epithelium embryonic bladder mesenchyme does not differentiate into smooth muscle. We determine whether this process is specific to bladder epithelium or whether epithelial cells from other organ systems induce bladder mesenchyme to differentiate into smooth muscle, as well as whether epithelial age is an important variable. We recombined 14-day bladder mesenchyme before smooth muscle differentiation with rat epithelium from 14-day, 19-day, newborn and adult bladder, ureter, colon, ileum, stomach, cornea and epidermis. In addition, bladder epithelium was recombined with 14-day embryonic small intestinal, 14-day embryonic gastric and newborn seminal vesicle mesenchyme. All tissue recombinants were grafted under the renal capsule of an adult rat syngeneic host for 3 weeks. Immunohistochemical analysis with antibodies directed against smooth muscle alpha-actin revealed that all epithelial types studied induced bladder mesenchyme to differentiate into smooth muscle, although to different degrees. Induction of smooth muscle was independent of urothelial age. In addition, bladder epithelium induced intestinal, gastric and seminal vesicle mesenchyme to differentiate into smooth muscle and express an overall morphological pattern indicative of the bladder fibromuscular wall. The mechanism whereby urothelium induces bladder mesenchyme to differentiate into smooth muscle is not specific to embryonic urothelium. Older urothelium and heterotypic epithelium also induce smooth muscle differentiation. With the common use of bowel, stomach and ureteral segments for bladder augmentation it is important to understand the interaction of different types of epithelium with the native bladder.

Ontogeny of the rat bladder: smooth muscle and epithelial differentiation.

The sequential expression of smooth muscle and epithelial markers in the rat bladder has been defined. Smooth muscle differentiation, based on cell morphology and immunohistochemical localization of smooth muscle alpha-actin, myosin, vinculin, desmin, vimentin and laminin, begins at 16 days of gestation (birth = 22 days) in the rat bladder. Smooth muscle cell differentiation begins in the periphery of the bladder mesenchyme immediately subadjacent to the serosa and continues toward the urothelium. The cytokeratins 5, 7, 8, 14, 18, and 19 are expressed in the bladder epithelium as a function of developmental age with cytokeratin 7, 8, 18, and 19 being coexpressed at 15 days' gestation followed by cytokeratin 5 at 17 days' gestation and cytokeratin 14 in the newborn bladder. An understanding of the ontogeny of both smooth muscle and epithelial differentiation markers in the normal bladder will allow us to study events that occur in the diseased bladder.

Type III Collagen Decreases in Normal Fetal Bovine Bladder Development

In normal fetal bovine bladder development we have shown that compliance increases at approximately the same time that urine production first occurs. The late first trimester fetal bladders are relatively stiff with a progressive increase in bladder compliance peaking in the newborn period. From the newborn period through adulthood, we documented a relatively modest decrease in bladder compliance, which may result from the normal aging process. To account for these changes, we have used the bovine model to perform biochemical analyses of the major structural collagens that are found in the bladder (types I and III). These results show that the per cent of type III collagen decreases in the developing bladder from the end of the first trimester until the newborn period. Comparing the newborn bladder to that of a mature adult, we documented a relatively modest increase in the amount of type III collagen. We demonstrated that the ratio of type III-to-type I collagen parallels the normal compliance changes in the developing fetal and mature bovine bladder.

Developmental Aspects of Bladder Contractile Function: Sensitivity to Extracellular Calcium

The urinary bladders of 1-day and 1-week-old rabbits generate higher intravesical pressures in response to bethanechol and field stimulation than bladders isolated from mature 8-week-old rabbits. Yet the density of cholinergic receptors in the rabbit bladder does not change with maturation (1 day to 8 weeks). In an effort to better understand the molecular mechanisms by which newborn rabbit bladders generate greater pressures than the bladders of adult rabbits, we studied the effect of maturation on the relationship between extracellular calcium and contraction. Our results showed quite clearly that (1) at physiologic concentrations of calcium (2.5 mumol/l), isolated bladder strips of 1-day- and 1-week-old rabbits contracted in response to bethanechol to 98% of their maximal tension as opposed to 68% for their 8-week-old counterparts, (2) the ED50 (for calcium) for the 1-day and 1-week bladders was 0.4 mmol/l whereas the ED50 for the adult bladder strips was 2.2 mmol/l, and (3) the neonatal bladders demonstrated a much greater sensitivity to diltiazem than the adult bladders. The contractile response to calcium of the neonatal bladders was significantly inhibited by 1 mumol/l diltiazem whereas the 8-week-old bladders showed no inhibition at this concentration. In a second series of experiments, the effect of extracellular calcium on concentration was correlated with the intracellular concentration of free calcium using the calcium fluoride FURA-2 and surface spectrofluorometry. These studies confirmed that the increased contractile response of the neonatal bladder strips to calcium or cholinergic agonists was associated with an increase in the maximal intracellular free calcium concentration.

Developmental Factors in the Contractile Response of the Rabbit Bladder to Both Autonomic and Non-Autonomic Agents

Previous work in this laboratory has demonstrated that the bladders of 1-day-old and 1-week-old rabbits generate higher pressures in whole-bladder preparations than bladders from mature 8-week-old rabbits. In addition, the density of cholinergic receptors does not change during this maturation period. The present study was designed to determine if the increased responsiveness of the neonatal bladder was specific for cholinergic stimulation. Using bladder strips, we have demonstrated that the newborn bladders generated much greater tension in response to ATP, serotonin, histamine, and substance P. The response of the 1-day-old bladder smooth muscle to these contractile agents was at least double the response of the 8-week-old bladders. However, the response of all age groups to bethanechol was approximately the same, and the response to KCl was only 40% greater in the 1-day-old bladders as compared to the adult. These current studies indicate that the newborn bladder responds to a variety of nonadrenergic, noncholinergic agonists to a significantly higher degree than the adult bladder, and that maturation is accompanied by substantial changes in the pharmacology of the bladder.

3 - Changing Approaches to the Staged Reconstruction of Newborn Bladder Exstrophy

3 - Changing Approaches to the Staged Reconstruction of Newborn Bladder Exstrophy