Impaired sodium-evoked paraventricular nucleus neuronal activation and blood pressure regulation in conscious Sprague-Dawley rats lacking central Gαi2 proteins

Aim

We determined the role of brain Gαi₂ proteins in mediating the neural and humoral responses of conscious male Sprague–Dawley rats to acute peripheral sodium challenge.

Methods

Rats pre‐treated (24‐h) intracerebroventricularly with a targeted oligodeoxynucleotide (ODN) (25 μg per 5 μL) to downregulate brain Gαi₂ protein expression or a scrambled (SCR) control ODN were challenged with an acute sodium load (intravenous bolus 3 m NaCl; 0.14 mL per 100 g), and cardiovascular parameters were monitored for 120 min. In additional groups, hypothalamic paraventricular nucleus (PVN) Fos immunoreactivity was examined at baseline, 40, and 100 min post‐sodium challenge.

Results

In response to intravenous hypertonic saline (HS), no difference was observed in peak change in mean arterial pressure between groups. In SCR ODN pre‐treated rats, arterial pressure returned to baseline by 100 min, while it remained elevated in Gαi₂ODN pre‐treated rats (P < 0.05). No difference between groups was observed in sodium‐evoked increases in Fos‐positive magnocellular neurons or vasopressin release. V_1a receptor antagonism failed to block the prolonged elevation of arterial pressure in Gαi₂ODN pre‐treated rats. A significantly greater number of Fos‐positive ventrolateral parvocellular, lateral parvocellular, and medial parvocellular neurons were observed in SCR vs. Gαi₂ODN pre‐treated rats at 40 and 100 min post‐HS challenge (P < 0.05). In SCR, but not Gαi₂ODN pre‐treated rats, HS evoked suppression of plasma norepinephrine (P < 0.05).

Conclusion

This highlights Gαi₂ protein signal transduction as a novel central mechanism acting to differentially influence PVN parvocellular neuronal activation, sympathetic outflow, and arterial pressure in response to acute HS, independently of actions on magnocellular neurons and vasopressin release.

Selective up-regulation of JunD transcript and protein expression in vasopressinergic supraoptic nucleus neurones in water-deprived rats

The magnocellular neurones (MCN) of the supraoptic nucleus (SON) undergo reversible changes during dehydration. We hypothesise that alterations in steady-state transcript levels might be partially responsible for this plasticity. In turn, regulation of transcript abundance might be mediated by transcription factors. We have previously used microarrays to identify changes in the expression of mRNAs encoding transcription factors in response to water deprivation. We observed down-regulation of 11 and up-regulation of 31 transcription factor transcripts, including members of the activator protein-1 gene family, namely c-fos, c-jun, fosl1 and junD. Because JunD expression and regulation within the SON has not been previously described, we have used in situ hybridisation and the quantitative reverse transcriptase-polymerase chain reaction to confirm the array results, demonstrating a significant increase in JunD mRNA levels following 24 and 72 h of water deprivation. Western blot and immunohistochemistry revealed a significant increase in JunD protein expression following dehydration. Double-staining fluorescence immunohistochemistry with a neurone-specific marker (NeuN) demonstrated that JunD staining is predominantly neuronal. Additionally, JunD immunoreactivity is observed primarily in vasopressin-containing neurones with markedly less staining seen in oxytocin-containing MCNs. Furthermore, JunD is highly co-expressed with c-Fos in MCNs of the SON following dehydration. These results suggest that JunD plays a role in the regulation of gene expression within MCNs of the SON in association with other Fos and Jun family members.

Chronic intermittent hypoxia sensitizes acute hypothalamic-pituitary-adrenal stress reactivity and Fos induction in the rat locus coeruleus in response to subsequent immobilization stress

Obstructive sleep apnea (OSA) is associated with several pathophysiological conditions, including hypertension, obesity, insulin resistance, hypothalamic-pituitary-adrenal (HPA) dysregulation, and other endocrine and metabolic disturbances comprising the "metabolic syndrome." Repeated episodes of hypoxia in OSA may represent a chronic intermittent stress, leading to HPA dysregulation. Alterations in HPA reactivity could then contribute to or exacerbate other pathophysiological processes. We showed previously that another metabolic stressor, chronic intermittent cold stress, enhanced noradrenergic facilitation of acute HPA stress reactivity. In this study, we investigated whether chronic intermittent hypoxia (CIH), a rat model for the arterial hypoxemia that accompanies OSA, similarly sensitizes the HPA response to novel acute stress. Rats were exposed to CIH (alternating cycles of normoxia [3 min at 21% O(2)] and hypoxia [3 min at 10% O(2)], repeated continuously for 8 h/day during the light portion of the cycle for 7 days). On the day after the final CIH exposure, there were no differences in baseline plasma adrenocorticotropic hormone (ACTH), but the peak ACTH response to 30 min acute immobilization stress was greater in CIH-stressed rats than in controls. Induction of Fos expression by acute immobilization stress was comparable following CIH in several HPA-modulatory brain regions, including the paraventricular nucleus, bed nucleus of the stria terminalis, and amygdala. Fos induction was attenuated in lateral hypothalamus, an HPA-inhibitory region. By contrast, acute Fos induction was enhanced in noradrenergic neurons in the locus coeruleus following CIH exposure. Thus, similar to chronic cold stress, CIH sensitized acute HPA and noradrenergic stress reactivity. Plasticity in the acute stress response is important for long-term adaptation, but may also contribute to pathophysiological conditions associated with states of chronic or repeated stress, such as OSA. Determining the neural mechanisms underlying these adaptations may help us better understand the etiology of such disorders, and inform the development of more effective treatments.

Identification of central nervous system sites involved in the water diuresis response elicited by central microinjection of nociceptin/ Orphanin FQ in conscious rats via c-Fos and inducible cAMP early repressor immunocytochemistry

Intracerebroventricular (i.c.v.) administration of the opioid-like peptide, nociceptin/Orphanin (nociceptin), in conscious rats produces diuretic and antinatriuretic effects. The present study utilised changes in Fos and inducible cAMP early repressor (ICER) immunocytochemistry expression to examine the central nervous (CNS) sites activated or inhibited, respectively, by central administration of nociceptin. Urine samples were collected during control (15 min) and after i.c.v. vehicle (5 microl, n = 12) or nociceptin (10 microg/5 microl; n = 12). Four additional urine samples (15-min) were collected after the i.c.v. injection. The brain was processed for Fos using a commercially available antibody (Oncogene AB-5) and for ICER using a polyclonal anti-ICER antibody raised in rabbits. In vehicle-injected conscious rats, renal excretion of water or sodium was not altered. However, nociceptin produced a rapid and marked increase in urine flow (V) and a decrease in urinary sodium excretion rate. In addition, i.c.v. nociceptin produced a significant increase in Fos staining in the dorsomedial nucleus of the hypothalamus, the perinuclear zone of the supraoptic nucleus, the organum vasculosum of the lamina terminalis (OVLT), the lateral preoptic area and the lateral hypothalamic area compared to control. By contrast, Fos expression decreased in the area postrema and locus coeruleus compared to controls. Furthermore, ICER staining was significantly increased in the perinuclear zone of the supraoptic nucleus, supraoptic nucleus, median preoptic nucleus, OVLT, medial preoptic area, central nucleus of the amygdala, and medial nucleus of the solitary tract. Together, central opioid receptor-like type 1 activation in these CNS regions may participate in the neural pathways involved in the diuretic and antinatriuretic effects of nociceptin.

Lesions of the diagonal band of broca enhance drinking in the rat

This study examined the role of the diagonal band of Broca (DBB) in drinking behaviour and vasopressin release. Adult male rats were anaesthetized (pentobarbital 50 mg/kg) and received DBB injections of either ibotenic acid (0.5 microl of 5 micro g/ microl) or vehicle (0.5 microl of phosphate-buffered saline). Although baseline drinking and urine output were not affected, drinking to 30% polyethylene glycol (MW 8000; 1 ml/100 g s.c.) and angiotensin II (0, 1.5 and 3.0 mg/kg s.c.) were significantly increased in ibotenic acid in phosphate-buffered saline (DBBX) rats. Drinking to hypertonic saline (0.9, 4 and 6%; 1 ml/100 g), and water deprivation were not significantly affected. DBBX rats had significantly lower basal heart rates than controls but the cardiovascular responses to infusions of angiotensin II (100 ng/kg/min i.v. for 45 min) were not affected. DBBX rats had significantly higher basal vasopressin, but angiotensin-stimulated vasopressin release was not significantly different. Although the DBB is not involved in basal water intake, it is involved in dipsogenic responses to hypovolemic stimuli and possibly basal autonomic function and basal vasopressin release.

Proposed role of the paraventricular nucleus in cardiovascular deconditioning

AIM

Cardiovascular deconditioning occurs in individuals exposed to prolonged spaceflight or bedrest and is associated with the development of orthostatic intolerance. Although the precise mechanisms remain to be fully elucidated, astronauts returning from space or bedrest patients returning to normal upright posture present with decreases in plasma volume and alterations in autonomic function. The hindlimb unloaded (HU) rat has been a useful model to study the effects of cardiovascular deconditioning as it mimics many of the changes that occur after spaceflight and bedrest.

RESULTS

Experiments performed in HU rats suggest that cardiovascular deconditioning attenuates baroreflex mediated sympathoexcitation and enhances cardiopulmonary receptor mediated sympathoinhibition. These alterations appear to be due to changes in the central nervous system and may contribute to the pre disposition towards orthostatic intolerance associated with cardiovascular deconditioning. The paraventricular nucleus (PVN) of the hypothalamus is important in basal and reflex control of sympathetic outflow. Recent evidence suggests that nitric oxide (NO) is an important inhibitory neurotransmitter in the PVN and that alterations in nitroxidergic transmission in the PVN may be involved in elevated sympathetic tone in certain disease states.

CONCLUSION

Based on evidence from other laboratories and published and preliminary data from our own laboratories, this review proposes a role for the PVN in cardiovascular deconditioning. In particular, we discuss the hypothesis that increased NO in the PVN contributes to the altered cardiovascular reflexes observed following deconditioning and how these reflexes may be related to the orthostatic intolerance observed after prolonged spaceflight or bedrest.

Evaluation of unexplained acute and acute recurrent pancreatitis using endoscopic retrograde cholangiopancreatography, sphincter of Oddi manometry and endoscopic ultrasound

BACKGROUND AND STUDY AIMS

Unexplained pancreatitis represents a diagnostic challenge. The aim of this study was to determine the diagnostic utility of endoscopic retrograde cholangiopancreatography (ERCP) with sphincter of Oddi manometry (SOM), bile analysis, and endoscopic ultrasound (EUS) in evaluating such patients.

PATIENTS AND METHODS

Of 162 patients referred for evaluation of pancreatitis, 72 with a known cause were excluded. The remainder ( n=90) was classified as having prior acute ( n=24) or recurrent acute pancreatitis ( n=66). Bile sampling and SOM were performed at the time of ERCP. EUS was used to assess for tumors and for chronic pancreatitis. Clinical outcomes were evaluated by questionnaire.

RESULTS

ERCP was successful in 88/89 patients (99 %). Manometry was successful in 63/67 patients (94 %), and 56 patients underwent EUS. Findings were categorized into five distinct etiologies: sphincter of Oddi dysfunction (SOD) ( n=28; 31 %), pancreas divisum ( n=18; 20 %), biliary ( n=18; 20 %), idiopathic ( n=18; 20 %) and tumor-related ( n=8; 9 %). Features of moderate or severe chronic pancreatitis by EUS and ERCP criteria were found in 18 patients (21 %); an additional nine patients had chronic pancreatitis by EUS criteria alone. EUS identified all the tumors. The condition was improved in 96 % of all patients undergoing endoscopic therapy.

CONCLUSION

An etiology was identified in the majority of patients with unexplained pancreatitis. SOD represented the most common finding. Moderate to severe chronic pancreatitis was found in over one-fifth of these patients. Bile analysis, SOM, and EUS are useful tools in the evaluation of unexplained acute pancreatitis.

Fos immunoreactivity in the diagonal band and the perinuclear zone of the supraoptic nucleus after hypertension and hypervolaemia in unanaesthetized rats

We used Fos immunocytochemistry to study the effects of hypertension and hypervolaemia on neurones in the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus, two nuclei that are both involved in the baroreceptor regulation of vasopressin neurones in the supraoptic nucleus. In addition, we used sino-aortic denervation to examine the role of arterial baroreceptors in the response to these haemodynamic changes. Sham-operated and sino-aortic denervated rats were infused with phenylephrine sufficient to increase blood pressure for 2 h. Control rats were infused with the same volume of isontonic saline. Only Sham sino-aortic denervated rats showed reflex bradycardia in response to the increased blood pressure. Volume expansion was produced by infusing the rats with isotonic saline equal to 10% of their body weight for 10 min, which significantly increased central venous pressure. In the diagonal band of Broca and the perinuclear zone, the number of Fos-positive neurones was significantly increased after phenylephrine infusion. Sino-aortic denervation blocked the significant increase in both regions. After volume expansion, a significant increase in Fos staining was observed only in the perinuclear zone of the supraoptic nucleus. This increase was not blocked by sino-aortic denervation. Our results indicate that both the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus are activated by stimulating arterial baroreceptors; however, the perinuclear zone of the supraoptic nucleus is stimulated during volume expansion. Furthermore, the activation of perinuclear zone of the supraoptic nucleus after volume expansion is not dependent on intact arterial baroreceptors.

Integration of neuroscience and endocrinology in hybrid PBL curriculum

At the University of Missouri-Columbia, the medical school employs a problem-based learning curriculum that began in 1993. Since the curriculum was changed, student performance on step 1 of the United States Medical Licensing Examination has significantly increased from slightly below the national average to almost one-half a standard deviation above the national mean. In the first and second years, classes for students are organized in classes or blocks that are 8 wk long, followed by 1 wk for evaluation. Initially, basic science endocrinology was taught in the fourth block of the first year with immunology and molecular biology. Student and faculty evaluations of the curriculum indicated that endocrinology did not integrate well with the rest of the material taught in that block. To address these issues, basic science endocrinology was moved into another block with neurosciences. We integrate endocrinology with neurosciences by using the hypothalamus and its role in neuroendocrinology as a springboard for endocrinology. This is accomplished by using clinical cases with clear neuroscience and endocrinology aspects such as Cushing's disease and multiple endocrine neoplastic syndrome type 1.

Endoscopic treatment of post-liver transplantation biliary leaks with stent placement across the leak site

BACKGROUND

Biliary tract leaks occur in over 10% of patients undergoing liver transplantation and are the most common cause of biliary tract-related death in these patients. A number of treatment options are available, but a standard approach has not been established.

METHODS

Twenty-six patients were retrospectively studied who had post-transplantation leaks develop with special reference to those who underwent endoscopic placement of a "leak-bridging" stent.

RESULTS

Endoscopic retrograde cholangiography was performed in all cases with no procedure-related complications. Twenty-four patients had a leak-bridging stent, 1 a transpapillary stent, and 1 a nasobiliary drain. Leak resolution occurred in 23 cases (88%) after initial stent placement. The median time to stent removal was 8 weeks. Three patients did not respond to initial treatment; 2 were successfully treated with another stent and a single patient required surgical repair. Four deaths occurred during follow-up, all unrelated to the biliary leak.

CONCLUSIONS

Placement of a leak-bridging stent is a safe and effective initial treatment for post-liver transplantation biliary leaks.

Cardiovascular regulation of vasopressin neurons in the supraoptic nucleus

This paper reviews the regulation of hypothalamic vasopressin and oxytocin neurosecretory cells in the neural response to plasma volume expansion. Many questions remain unanswered regarding how an increase in volume affects neurohypophysial hormone secretion, what receptors are important in mediating this response, and which neural pathways are responsible for conveying the signal from those receptors to the hypothalamus. Plasma volume expansion activates regions of the central nervous system associated with inhibition of vasopressin release, oxytocin secretion, and inhibition of sympathetic nerve activity. Cardiac receptors, not arterial baroreceptors, are primarily responsible for activation of the regions associated with regulation of vasopressin secretion and sympathetic outflow. Other stimuli that as yet are undefined account for activation of oxytocin-secreting neurons. Electrophysiology experiments have measured the inhibition of vasopressin-secreting magnocellular neurons in the supraoptic nucleus by select stimulation of cardiac receptors in the caval-atrial junction. Further experiments suggest that the perinuclear zone, a population of neurons surrounding the supraoptic nucleus, is a necessary part of the pathway by which caval-atrial stretch decreases the excitability of vasopressin neurons. The perinuclear zone is also a necessary synapse for arterial baroreceptor-mediated inhibition of vasopressin neurons. This suggests that the neural pathways that inhibit vasopressin release in response to an increase in blood pressure and an increase in blood volume may overlap at the perinuclear zone of the supraoptic nucleus. Finally, the integration of various neural pathways activated by multiple receptors to ultimately determine the activity of magnocellular neurons and vasopressin secretion is discussed.

The decision-making value of magnetic resonance cholangiopancreatography in patients seen in a referral center for suspected biliary and pancreatic disease

OBJECTIVE

To assess the ability of MRCP to alter the differential diagnosis and to prevent diagnostic and/or therapeutic ERCP. The diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) for biliary and pancreatic disease is well documented. Some believe MRCP may prevent diagnostic ERCP or add useful information, however there are no reports of its impact on clinical management.

METHODS

Consecutive patients referred for ERCP underwent clinic evaluation, then MRCP, and then ERCP. In Phase 1, the number of differential diagnoses and the perceived need for diagnostic ERCP were evaluated after each step by the endoscopist who performed the ERCP. In Phase 2, the process was repeated after presenting clinical information and MRCP results to different individual physicians: another endoscopist, a hepatologist, a radiologist, and a surgeon (all were blinded to ERCP results).

RESULTS

Forty patients were enrolled. Clinical contexts were jaundice (19.7%), abnormal liver enzymes (42.6%), abdominal pain (11.5%), recurrent acute pancreatitis (11.5%), and suspected complications of chronic pancreatitis (14.7%). In Phase 1, adding MRCP information to diagnostic ERCP information did not change the mean number of differential diagnoses significantly and prevented no therapeutic ERCP. In Phase 2, adding MRCP to clinical information only (without ERCP) reduced the differential diagnosis significantly for the radiologist and the surgeon only and would have prevented < or =3% of diagnostic and therapeutic ERCP for all physicians.

CONCLUSION

The value of MRCP information may be limited if patient selection is inappropriate and may differ in physicians depending on their speciality.

Lesion of the perinuclear zone attenuates cardiac sensitivity of vasopressinergic supraoptic neurons

Discrete stretch of the caval-atrial junction decreases the activity of vasopressin-secreting neurons in the supraoptic nucleus (SON). The perinuclear zone (PNZ) of the SON is necessary for inhibition of vasopressin neurons following an increase in blood pressure. To determine whether the PNZ is necessary for cardiopulmonary regulation of vasopressin neurons, male rats received three unilateral injections of the excitotoxin ibotenic acid (n = 9) or phosphate-buffered saline vehicle (n = 10) into the PNZ. Extracellular activity of antidromically identified phasic vasopressin neurons in the ipsilateral SON was recorded. Of the 26 neurons recorded from vehicle-injected rats 26 were inhibited by an increase in blood pressure and 22 of those neurons were sensitive to caval-atrial distension. Of the neurons recorded from PNZ-lesion rats, only 12 of 29 were inhibited by an increase in blood pressure (P < 0.05), and only 11 neurons were sensitive to caval-atrial stretch (P < 0.05). Functional lesion of the PNZ significantly attenuates both arterial and cardiopulmonary baroreceptor-mediated inhibition of supraoptic vasopressin neurons, suggesting that the PNZ is a necessary component of both pathways.

Baroreceptor sensitivity of rat supraoptic vasopressin neurons involves noncholinergic neurons in the DBB

Previous studies suggest that cholinergic neurons in the diagonal band of Broca (DBB) participate in the baroreceptor-mediated inhibition of phasic vasopressin neurons in the supraoptic nucleus (SON). To test this hypothesis, extracellular recordings were obtained from putative vasopressin SON neurons of anesthetized rats injected with the cholinergic immunotoxin 192 IgG-saporin (0.8 microg/microl) in the DBB. Baroreceptor sensitivity of neurons was tested with brief phenylephrine-induced (10 microg/10 microl iv) increases in blood pressure of at least 40 mmHg. In rats injected with vehicle or unconjugated saporin, 19 of 21 and 18 of 20 phasic neurons, respectively, were inhibited by increased blood pressure. In rats injected with 192 IgG-saporin, which significantly reduced the number of choline acetyltransferase (ChAT)-positive DBB neurons, 33 of 36 phasic neurons were inhibited. Normal rats and rats with DBB saporin injections received rhodamine bead injections into the perinuclear zone (PNZ) to retrogradely label DBB neurons, and their brains were stained for ChAT. ChAT-positive DBB neurons were not retrogradely labeled from the PNZ. Together, these results indicate that the pathway relaying baroreceptor information to the SON involves noncholinergic DBB neurons.

Role of the locus ceruleus in baroreceptor regulation of supraoptic vasopressin neurons in the rat

The goal of this study was to identify the source of baroreceptor-related noradrenergic innervation of the diagonal band of Broca (DBB). Male Sprague-Dawley rats underwent sinoaortic denervation (SAD, n = 13) or sham SAD surgery (n = 13). We examined Fos expression produced by baroreceptor activation and dopamine-beta-hydroxylase immunofluorescence in hindbrain regions that contain noradrenergic neurons. Baroreceptors were stimulated by increasing blood pressure >40 mmHg with phenylephrine (10 microgram. kg(-1). min(-1) iv) in sham SAD and SAD rats. Controls were infused with 0.9% saline. Only the locus ceruleus (LC) demonstrated a baroreceptor-dependent increase in Fos immunoreactivity in dopamine-beta-hydroxylase-positive neurons. In a second experiment, normal rats received rhodamine-labeled microsphere injections in the DBB (n = 12) before phenylephrine or vehicle infusion. In these experiments, only the LC consistently contained Fos-positive cells after phenylephrine infusion that were retrogradely labeled from the DBB. Finally, we lesioned the LC with ibotenic acid and obtained extracellular recordings from identified vasopressin neurons in the supraoptic nucleus. LC lesions significantly reduced the number of vasopressin neurons that were inhibited by acute baroreceptor stimulation. Together, these results suggest that noradrenergic neurons in the LC participate in the baroreflex activation of the DBB and may thus be important in the baroreflex inhibition of vasopressin-releasing neurons in the supraoptic nucleus.

Effects of right atrial distension on the activity of magnocellular neurons in the supraoptic nucleus

A small balloon placed at the junction of the superior vena cava and right atrium was used to stimulate cardiac volume receptors in pentobarbital sodium-anesthetized male rats. Extracellular recordings were obtained from antidromically identified vasopressinergic and oxytocinergic neurosecretory cells of the supraoptic nucleus. Cells were considered sensitive to the stimulus if balloon inflation resulted in a 30% change in firing frequency. Balloon inflation that did not stretch the caval-atrial junction had no significant effect on vasopressin neurons (n = 51, P > 0.05). Stretch of the caval-atrial junction decreased the firing activity in 64 of 83 putative vasopressin neurons (P < 0.01 compared with control). Stretch of the caval-atrial junction influenced the firing activity of only 3 of 26 antidromically activated oxytocinergic neurons, an effect not statistically different from control (P > 0. 05). When bilateral vagotomy was performed while recording from vasopressin neurons (n = 5), sensitivity to stretch of the caval-atrial junction was eliminated. Cardiac receptors located at the junction of the superior vena cava and right atrium may be important in regulating the activity of vasopressinergic but not oxytocinergic neurons of the supraoptic nucleus.

Area postrema and sympathetic nervous system effects of vasopressin and angiotensin II

1. Precise control over the cardiovascular system requires the integration of both neural and humoral signals related to blood volume and blood pressure. Humoral signals interact with neural systems, modulating their control over the efferent mechanisms that ultimately determine the level of pressure and volume. 2. Peptide hormones such as angiotensin (Ang)II and arginine vasopressin (AVP) act through circumventricular organs (CVO) to influence cardiovascular regulation. 3. The area postrema (AP), a CVO in the brainstem, mediates at least some of the central actions of these peptides. Vasopressin appears to act in the AP to cause sympathoinhibition and a shift in baroreflex control of the sympathetic nervous system (SNS) to lower pressures. These effects of AVP and the AP appear to be mediated by alpha2-adrenoceptor and glutamatergic mechanisms in the nucleus tractus solitarius. 4. In contrast to AVP AngII has effects in the AP to blunt baroreflex control of heart rate and cause sympathoexcitation. The effects of chronic AngII to increase activity of the SNS may be due to AP-dependent activation of neurons in the rostral ventrolateral medulla.

Therapeutic ERCP in the management of pancreatitis in children

BACKGROUND

The use of diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP) is increasing in the management of pancreatobiliary diseases in children.

METHODS

Over a 32-month period, we performed 34 ERCP procedures for the treatment of pancreatitis in 22 children at two university hospitals. Demographics and clinical data and ERCP findings were documented. Clinical status was assessed 6 months before the first ERCP and 6 months after the last ERCP, according to general condition, severity and frequency of pain, and health care encounters (emergency department visits, clinic visits, and hospital admissions related to the pancreatitis).

RESULTS

Mean age of the patients was 10.7 years (range 1.5 to 17 years). Abdominal pain was the main presenting symptoms with hyperamylasemia and hyperlipasemia. Clinical diagnoses included acute pancreatitis (6), recurrent pancreatitis (5), and chronic pancreatitis (11). The mean follow-up was 16.4 months. Nine patients had sphincter manometry, with abnormal results leading to biliary sphincterotomy in 4. Fifteen patients underwent a total of 23 therapeutic ERCP procedures unrelated to sphincter dysfunction. There were 2 complications of 34 procedures (6%), both being mild pancreatitis after sphincter manometry. There were no deaths. There was a significant reduction in frequency (p < 0.01) and severity of pain (p < 0.01) after intervention. Patients without pancreatographic changes of chronic pancreatitis had the most marked clinical improvement (p < 0.05). In those with ductal changes of chronic pancreatitis, clinical improvement was not predicted by the extent of ductal changes. There was a significant decrease in health care encounters (p < 0.05) and improvement in general condition (p < 0.01) after endoscopic therapy, especially in those with a normal pancreatogram.

CONCLUSIONS

Therapeutic ERCP is safe in pediatric patients with pancreatitis. Significant clinical improvement is achieved in patients with biliary or pancreatic stone disease. Prospective studies with long-term follow-up are needed to determine the impact of endoscopic therapy in patients with chronic pancreatitis and sphincter of Oddi dysfunction.

Fos expression in brain stem nuclei of pregnant rats after hydralazine-induced hypotension

Fos and dopamine beta-hydroxylase immunoreactivity were evaluated in the brain stems of 21-day pregnant and virgin female rats injected with either hydralazine (HDZ; 10 mg/kg iv) or vehicle. HDZ produced significant hypotension in both groups, although baseline blood pressure was lower in pregnant rats (96 +/- 2.5 mmHg) than in virgin female rats (121 +/- 2.8 mmHg). There were no differences in Fos immunoreactivity in the brain stems of pregnant and virgin female rats after vehicle treatment. HDZ-induced hypotension significantly increased Fos expression in both groups; however, the magnitude of the increases differed in the caudal ventrolateral medulla (CVL), the area postrema (AP), and the rostral ventrolateral medulla (RVL). Fos expression after HDZ in pregnant rats was augmented in noncatecholaminergic neurons of the CVL but was attenuated in the AP and in noncatecholaminergic neurons in the RVL. These results are consistent with differences in the sympathetic response to hypotension between pregnant and virgin female rats and indicate that the central response to hypotension may be different in pregnant rats.

Same-day discharge after endoscopic biliary sphincterotomy: observations from a prospective multicenter complication study. The Multicenter Endoscopic Sphincterotomy (MESH) Study Group

BACKGROUND

Same-day discharge after endoscopic biliary sphincterotomy (ES) is a common clinical practice, but there have been few data to guide appropriate selection of patients. Using a prospective, multicenter database of complications, we examined outcomes after same-day discharge as it was practiced by a variety of endoscopists and evaluated the ability of a multivariate risk factor analysis to predict which patients would require readmission for complications.

METHODS

A 150-variable database was prospectively collected at time of ES, before discharge and again at 30 days in consecutive patients undergoing ES at 17 centers. Complications were defined by consensus criteria and included all specific adverse events directly or indirectly related to ES requiring more than 1 night of hospitalization.

RESULTS

Six hundred fourteen (26%) of 2347 patients undergoing ES were discharged on the same day as the procedure, ranging from none at 6 centers to about 50% at 2 centers. After initial observation and release, readmission to the hospital for complications occurred in 35 (5.7%) of 614 same-day discharge patients (20 pancreatitis and 15 other complications, 3 severe). Of the same-day discharge patients, readmission was required for 14 (12.2%) of 115 who had at least one independently significant multivariate risk factor for overall complications (suspected sphincter of Oddi dysfunction, cirrhosis, difficult bile duct cannulation, precut sphincterotomy, or combined percutaneous-endoscopic procedure) versus 21 (4.2%) of 499 without a risk factor (odds ratio 3.1: 95% confidence interval [1.6, 6.3], p < 0.001). Of complications presenting within 24 hours after ES, only 44% presented within the first 2 hours, but 79% presented within 6 hours.

CONCLUSIONS

Same-day discharge is widely utilized and relatively safe but results in a significant number of readmissions for complications. For patients at higher risk of complications, as indicated by the presence of at least one of five independent predictors, observation for 6 hours or overnight may reduce the need for readmission.

Comparative costs of metal versus plastic biliary stent strategies for malignant obstructive jaundice by decision analysis

BACKGROUND

For palliation of patients with malignant obstructive jaundice, expansile metal stents provide longer patency than plastic stents but are more expensive. The optimal cost-effective strategy has not been established. Our aim was to compare the relative costs of 3 strategies: (1) plastic stent, with exchange on occlusion; (2) metal stent initially, with coaxial plastic stent insertion in the event of occlusion; or (3) plastic stent initially, with metal stent exchange in the event of occlusion.

METHODS

A decision analysis model was created using DATA 2.6 software to assess the relative costs of the three strategies. Values for variables including the probabilities of reintervention and patient survival were obtained from published data. Costs were based on Medicare reimbursements of hospital charges, and the model was evaluated from the perspective of a third-party payer. One-way and two-way sensitivity analysis of the variables was performed over a wide range.

RESULTS

The outcome is highly sensitive to the ratio of metal stent cost relative to endoscopic retrograde cholangiopancreatography cost (cost ratio M:ERCP) and to the length of survival of the patient. The most economical strategies were (2), (3) and (1) for M:ERCP cost ratios of <0.5, 0.5 to 0.7, and >0.7, respectively.

CONCLUSIONS

The choice of stent should be guided by the relative local costs of ERCP and metal stents and by the prognosis of the patient. At current metal stent costs and Medicare reimbursement rates, initial placement of a plastic stent, followed by metal stent placement at first occlusion in longer survivors, is an economical option. If metal stent cost is less than half of ERCP cost, then initial insertion of a metal stent would be most economical. Use of plastic stents is preferable for patients surviving less than 4 months, whereas metal stents are more economical for patients with longer survival.

Pancreatic stenting prevents pancreatitis after biliary sphincterotomy in patients with sphincter of Oddi dysfunction

BACKGROUND & AIMS

Patients with sphincter of Oddi dysfunction are at high risk of developing pancreatitis after endoscopic biliary sphincterotomy. Impaired pancreatic drainage caused by pancreatic sphincter hypertension is the likely explanation for this increased risk. A prospective, randomized controlled trial was conducted to determine if ductal drainage with pancreatic stenting protects against pancreatitis after biliary sphincterotomy in patients with pancreatic sphincter hypertension.

METHODS

Eligible patients with pancreatic sphincter hypertension were randomized to groups with pancreatic duct stents (n = 41) or no stents (n = 39) after biliary sphincterotomy. The primary measured outcome was pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP).

RESULTS

Pancreatic stenting significantly decreased the risk of pancreatitis from 26% to 7% (10 of 39 in the no stent group and 3 of 41 in the stent group; P = 0.03). Only 1 patient in the stent group developed pancreatitis after sphincterotomy, and 2 others developed pancreatitis at the time of stent extraction. Patients in the no stent group were 10 times more likely to develop pancreatitis immediately after sphincterotomy than those in the stent group (relative risk, 10.5; 95% confidence interval, 1.4-78.3).

CONCLUSIONS

Pancreatic duct stenting protects significantly against post-ERCP pancreatitis in patients with pancreatic sphincter hypertension undergoing biliary sphincterotomy. Stenting of the pancreatic duct should be strongly considered after biliary sphincterotomy for sphincter of Oddi dysfunction; pancreatic sphincter of Oddi manometry identifies which high-risk patients may benefit from pancreatic stenting.

Angiotensin hypertension

1. One of the most important issues in the field of hypertension research centres on the therapeutic use of inhibitors of the renin-angiotensin system (RAS). Inhibitors of the RAS have potent anti-hypertensive effects, even in experimental models of hypertension and in human essential hypertension, where the activity of the peripheral RAS is low or normal. 2. It is suggested here that determining the mechanisms by which activation of the peripheral RAS produces hypertension will help us determine the anti-hypertensive effects of these inhibitors in low/normal renin-angiotensin hypertension. 3. Three hypotheses describing the hypertensive effects of angiotensin are discussed. The first hypothesis involves the direct vasoconstrictor effects of angiotensin. The second hypothesis suggests that chronic angiotensin produces hypertension by increasing Na+ reabsorption leading to volume expansion and hypertension. The final hypothesis suggests that, in angiotensin-induced hypertension, the increased Na+ reabsorption is not associated with volume expansion but, rather, is associated with an increase in vascular tone resulting from an interaction between angiotensin and the nervous system. 4. It is also hypothesized that the interaction between angiotensin and the nervous system produces a differential activation of sympathetic outflow that spares the kidney.

Mechanosensitive ion channels in putative aortic baroreceptor neurons

Cell-attached patch-clamp experiments were performed on dissociated neurons from nodose ganglia of adult rats. Putative aortic baroreceptor neurons were identified by labeling nerve endings in the adventitia of the aortic arch with the carbocyanine dye DiI. Whereas previous experiments demonstrated the presence of mechanosensitive (MS) whole cell currents, these experiments studied single MS ion channels and examined the influence of culture conditions on their expression. Single MS channels were activated by applying negative pressure through the recording pipette. Channel openings became more frequent as the negative pressure was increased, with open probability increasing significantly above 30 mmHg. MS channels had a slope conductance of 114 pS and a reversal potential of approximately 0 mV, consistent with a nonspecific cation conductance. Channels were not affected by antagonists of voltage-gated conductances but were blocked by 20 microM gadolinium, a known blocker of MS ion channels. When nodose neurons were cocultured with aortic endothelial cells, but not aortic smooth muscle cells, the percentage of patches exhibiting MS ion channels increased significantly, suggesting that aortic endothelial cells secrete a diffusible factor that increases channel expression.

Prospective assessment of the ability of endoscopic ultrasound to diagnose, exclude, or establish the severity of chronic pancreatitis found by endoscopic retrograde cholangiopancreatography

BACKGROUND

Our aim was to verify endoscopic ultrasound (EUS) accuracy to diagnose, rule out, and establish the severity of chronic pancreatitis found by endoscopic retrograde cholangiopancreatography (ERCP).

METHODS

Patients undergoing ERCP for unexplained abdominal pain and/or suspected chronic pancreatitis underwent EUS. EUS was performed by experienced operators who were aware of the history but blinded to ERCP results. Chronic pancreatitis was defined using the Cambridge classification: 0 to 1 = "normal," 2 to 4 = "all chronic pancreatitis," 3 to 4 = "moderate to severe chronic pancreatitis." The number of EUS criteria required to obtain sensitivity, specificity, positive and negative predictive values > or = 85% was determined. EUS criteria for chronic pancreatitis are hyperechoic foci, hyperechoic strands, lobularity, hyperechoic duct, irregular duct, visible side-branches, ductal dilation, calcification, and cysts.

RESULTS

One hundred twenty-six patients underwent EUS and ERCP. EUS was highly sensitive and specific (> 85%) depending on the number of criteria present. Chronic pancreatitis is likely (PPV > 85%) when more than two criteria (for "all chronic pancreatitis") and more than six criteria (for "moderate to severe chronic pancreatitis") are present. "Moderate to severe chronic pancreatitis" is unlikely (NPV > 85%) when fewer than three criteria are present. Independent predictors of chronic pancreatitis were "calcification" (p = 0.000001), history of alcohol abuse (p = 0.002), and the total number of EUS criteria (p = 0.008).

CONCLUSIONS

EUS can accurately diagnose, rule out, and establish the severity of chronic pancreatitis found by ERCP.

Endoscopic electrohydraulic lithotripsy in the management of pancreatobiliary lithiasis

BACKGROUND

Clinical evaluation of intraoperative endoscopy with electrohydraulic lithotripsy (EHL) in the management of 13 patients with pancreatobiliary lithiasis was undertaken.

METHODS

Ten patients with chronic pancreatitis with intraductal lithiasis in the head and three with biliary lithiasis (one choledochal, one cystic, one right intrahepatic) underwent intraoperative endoscopy with EHL. Shock waves were applied by visual contact with a 3-Fr gauge EHL probe until all stones were fragmented and irrigated free. All pancreatitis patients had failed ERCP attempts to stent their pancreatic ducts secondary to ductal lithiasis. Patients with pancreatic stones underwent lateral pancreatojejunostomy. Biliary stone patients underwent laparoscopic cholecystectomy with common duct exploration (two cases) and open cholecystectomy with choledochoduodenostomy (one case).

RESULTS

Intraductal stone eradication was successful in all patients. Transampullary visualization of the duodenum was achieved in eight cases. Average EHL time was 65 min. There was no evidence of postoperative pancreatitis, cholangitis, or retained common duct stones.

CONCLUSION

Intraoperative pancreatobiliary endoscopy with EHL is safe and effective in the eradication of pancreatic and bile duct stones. This novel technique represents a valuable adjunct in the management of chronic fibrocalcific pancreatitis with ductal lithiasis in the head region and in the open and laparoscopic management of intra- and extrahepatic bile duct stones.

Fos expression following isotonic volume expansion of the unanesthetized male rat

Cardiopulmonary afferents, baroreceptor afferents, or atrial natriuretic peptide binding to circumventricular organs may mediate the central response to volume expansion, a condition common to pregnancy, exercise training, and congestive heart failure. This study used Fos immunocytochemistry to examine brain regions activated by volume expansion. Male Sprague-Dawley rats were infused with isotonic saline equal to 10% of their body weight in 10 min followed by a maintenance infusion of 0.5 ml/min for 110 min. Control animals received 2-h infusions at 0.01 ml/min. Five minutes after the start of volume expansion, central venous pressure of expanded animals was significantly greater than control animals. The volume-expanded group exhibited significantly greater Fos activation (P < 0.05) in the area postrema, nucleus of the solitary tract, caudal ventrolateral medulla, paraventricular nucleus, supraoptic nucleus, and perinuclear zone of the supraoptic nucleus. Double labeling indicates that oxytocinergic neurons in the supraoptic nucleus are activated. Neurons in brain regions known to inhibit both sympathetic activity and vasopressin release show increased Fos expression following isotonic volume expansion.

Outcome of lateral pancreaticojejunostomy in the management of chronic pancreatitis with nondilated pancreatic ducts

Lateral pancreaticojejunostomy has demonstrated variable success in the management of chronic pancreatitis associated with ductal dilation, but its role in patients with nondilated ducts is poorly defined. The aim of this study was to assess the outcome of lateral pancreaticojejunostomy in chronic pancreatitis with nondilated pancreatic ducts. The records of all patients who underwent lateral pancreaticojejunostomy with a pancreatic duct measuring less than 7 mm in diameter were reviewed. Seventeen patients underwent lateral pancreaticojejunostomy for chronic pancreatitis and intractable pain between 1995 and 1996. Endoscopic retrograde cholangiopancreatography demonstrated features of chronic pancreatitis that were mild in seven patients, moderate in five, and severe in four. Postoperative complications occurred in two patients (11.7%). There were no deaths. Mean length of follow-up was 10.3 months (range 3 to 16 months). Rehospitalization for recurrent pancreatitis or pain was necessary in 59% of patients. Emergency room visits were reported by 76%. Narcotic use continued in 88%, with 76% of the patients reporting their pain as the same or worse than before the operation, and 65% continuing to view their health status as poor. In chronic pancreatitis patients with a nondilated pancreatic duct, lateral pancreaticojejunostomy appears to be of little benefit with respect to pain relief, subsequent hospitalization, continued narcotic use, or overall health status.

Fos-like immunoreactivity in the medulla after acute and chronic angiotensin II infusion

Acute and chronic angiotensin (Ang) II hypertension are reported to have different mechanisms that involve differential contributions of the peripheral vasculature and the nervous system. Acute Ang II hypertension is mediated primarily by Ang acting at vascular smooth muscle, whereas chronic Ang II hypertension appears to have a neural component. In our experiments, the transition from a peripheral to a neural effect occurs over 10 hr of Ang II infusion in rats. To identify the role of the central nervous system in this transition, we measured Fos immunoreactivity, an indicator of neural activity, in the nucleus of the solitary tract (NTS), caudal ventrolateral medulla (CVL) and rostral ventrolateral medulla (RVL) in normal, sinoaortic denervated (SAD) and sham SAD rats after 2- or 18-hr Ang II infusion (50 ng/kg/min intravenously). Vehicle (5% dextrose) was infused in normal rats as control. Comparable increases in arterial pressure were produced by 2- and 18-hr Ang II infusion in all groups. Fos was increased in the NTS in sham SAD rats by 2- and 18-hr Ang II infusion (P < .05 vs. vehicle control). In the CVL, only 2-hr Ang II infusion was associated with increased Fos in normal and sham SAD rats (P < .05 vs. vehicle control) but not in SAD rats. In the RVL, 18-hr Ang II infusion elevated Fos in all groups (P < .05 vs. vehicle control). Activation of NTS during Ang II infusion is baroreceptor mediated and independent of infusion duration. Acute Ang II infusion produced a baroreceptor-mediated activation of the CVL, a region associated with baroreflex sympathoinhibition. Chronic Ang II infusion produced a baroreceptor-independent activation of the RVL, a brain area associated with sympathoexcitation, suggesting a centrally mediated increase in sympathetic outflow that may be associated with chronically infused Ang II.

Endoscopic sphincterotomy for stones by experts is safe, even in younger patients with normal ducts

OBJECTIVE

To provide current information on the risks of endoscopic sphincterotomy for stone.

SUMMARY BACKGROUND DATA

In recent years (since the popularity of laparoscopic cholecystectomy), endoscopic sphincterotomy has been used increasingly for the management of bile duct stones in relatively young and healthy patients. The validity of this trend has been questioned using data on short-term complications derived from earlier decades that involved more elderly and high-risk patients.

METHODS

Seven academic centers collected data prospectively using a common database. Complications within 30 days of the procedures were documented by standard criteria.

RESULTS

Of 1921 patients, 112 (5.8%) developed complications; two thirds of these events were graded as mild (<3 days in hospital). There was no evidence of increased risk in younger patients or in those with smaller bile ducts. There was only one severe complication and there were no fatalities in 238 patients age <60, with bile duct diameters of <9 mm.

CONCLUSION

Sphincterotomy for stones can be performed very safely by experienced endoscopists.

Outcome after laparoscopic cholecystectomy for chronic acalculous cholecystitis

Patients with typical symptoms of biliary tract disease but no gallstones on ultrasonography may benefit from cholecystectomy for presumed chronic acalculous cholecystitis. We retrospectively analyzed the outcome of 50 patients with a preoperative diagnosis of chronic acalculous cholecystitis based upon history (chronic or recurrent, postprandial right upper quadrant abdominal pain), the absence of acid-peptic disease, and normal biliary sonography treated with laparoscopic cholecystectomy (LC) and transcholecystic cholangiography from 1991 to 1996. All patients had preoperative cholecystokinin-stimulated hepatobiliary scintigraphy (CCK-HBS). There were 42 women and 8 men with a mean age of 43 years. CCK-HBS was abnormal in 45 patients (< or = 35 per cent gallbladder ejection fraction or nonfilling of the gallbladder). There was no postoperative mortality and one morbidity (urinary retention). All patients had microscopic evidence of chronic cholecystitis. At mean follow-up of 30 months, (range, 7-62 months) 39 patients (78%) were free of abdominal pain. Thirty-five of 45 patients with abnormal CCK-HBS were pain free (positive predictive value, 0.78). Four of five patients with normal CCK-HBS were pain free (negative predictive value, 0.20). The positive and negative likelihood ratios for CCK-HBS were 0.99 and 1.13, respectively, confirming that this test was not useful for predicting benefit from LC. Seven patients with persistent right upper quadrant pain had abnormal postoperative sphincter of Oddi manometry; they improved after endoscopic sphincterotomy. Patients with symptoms typical of biliary colic with normal gallbladder sonography and absence of acid-peptic disease benefit from LC in the majority of cases. Those who remain symptomatic after LC may benefit from endoscopic retrograde cholangiopancreatography with sphincter of Oddi manometry and endoscopic sphincterotomy when manometry is abnormal.

Magnetic resonance cholangiopancreatography: a novel approach to the evaluation of suspected pancreaticobiliary neoplasms

BACKGROUND

Magnetic resonance cholangiopancreatography (MRCP) is a new noninvasive diagnostic method for pancreaticobiliary (PB) imaging without endoscopy, sedation, or iodinated contrast. The purpose of this study was to evaluate the ability of MRCP to depict pancreatic and biliary ductal anatomy compared to that of endoscopic retrograde cholangiopancreatography (ERCP) and to evaluate the ability of MRCP to accurately diagnose PB neoplasms.

METHODS

Twenty patients had MRCP, and 17 also had ERCP. All studies were read prospectively by experienced reviewers blinded to other imaging data. Pathologic diagnosis was made in all patients.

RESULTS

Bile duct dilatation seen by ERCP in 14 of 17 patients was correctly identified by MRCP in all 14 patients, and normal ducts were correctly identified by MRCP in the other 3 patients. The pancreatic duct was visible on MRCP in the pancreatic head in 17 of 20 patients, the body in 17 of 20 patients, and the tail in 15 of 20 patients. At ERCP, pancreatic duct dilatation was present in 11 cases and was identified by MRCP in 10 of them. Eighteen of 20 patients had malignant PB neoplasms. MRCP indicated PB neoplasm in 19 patients. Seventeen of these 19 patients had histologically confirmed malignant neoplasms pathologically, whereas 2 had benign pathology (both chronic pancreatitis). Among the 17 patients who also had ERCP, MRCP and ERCP correctly agreed on a final diagnosis of malignant neoplasm in 14 cases. In the three cases in which MRCP and ERCP disagreed on a final diagnosis, MRCP was correct in one and incorrect in two.

CONCLUSIONS

MRCP can accurately and noninvasively delineate PB ductal anatomy and diagnose PB neoplasms comparably to ERCP. MRCP is an interesting new noninvasive method for evaluating patients with suspected PB neoplasms.

Differentiation of benign from malignant pancreatic masses by endoscopic ultrasound

BACKGROUND

It is often difficult to determine whether a mass in the pancreas is benign or malignant. The goal was to evaluate whether endoscopic ultrasound (EUS) can reliably establish whether a mass is benign or malignant.

METHODS

One hundred five patients with possible pancreatic tumors were referred for EUS. Those who were found to have a lesion suspicious for carcinoma and did not have a known malignancy also underwent EUS-guided FNA.

RESULTS

A mass suspicious for cancer was identified in 73 patients, whereas inflammatory changes or a normal pancreas was noted in 32 patients. Four of the latter 32 patients were subsequently found to have cancer. EUS-guided FNA was performed on 47 of the 73 patients with a suspicious mass and was read as cancer in 27 patients, atypia in 10 patients, and benign in 10 patients. All 10 patients with atypia were subsequently confirmed to have cancer, and 6 of the 10 patients with a benign FNA were proved to have a tumor at surgery. EUS could differentiate the lesion as malignant with a sensitivity of 95%, specificity 88%, positive predictive value 95%, and negative predictive value 88%.

CONCLUSIONS

Radial array EUS is helpful in supporting or refuting a diagnosis of cancer in a patient with a pancreatic mass. Although EUS-guided FNA can confirm the diagnosis, a negative FNA should not preclude exploration when clinically indicated.