Adjunctive Use of WATS-3D in Symptomatic GERD Patients Increases Detection of Barrett's Esophagus and Dysplasia

BACKGROUND

Patients with gastroesophageal reflux (GERD) symptoms undergoing screening upper endoscopy for Barrett's esophagus (BE) frequently demonstrate columnar-lined epithelium (CLE), with forceps biopsies (FB) failing to yield intestinal metaplasia (IM). Repeat endoscopy is often necessary.

AIM

Assess the yield of IM leading to a diagnosis of BE by the addition of Wide-Area Trans-epithelial Sampling (WATS-3D) to FB in the screening of GERD patients.

METHODS

We performed a prospective registry study of GERD patients undergoing screening upper endoscopy. Patients had both WATS-3D and FB. Patients were classified by their Z line appearance: regular, irregular (<1 cm CLE), possible short-segment BE (1-<3cm), and possible long-segment BE (≥3cm). Demographics, IM yield, and dysplasia yield were calculated. Adjunctive yield was defined as cases identified by WATS-3D not detected by FB, divided by cases detected by FB. Clinicians were asked if WATS-3D results impacted patient management.

RESULTS

Of 23,933 patients, 6,829(28.5%) met endoscopic criteria for BE. Of these, 2,878(42.1%) had IM identified by either FB or WATS-3D. Among patients fulfilling endoscopic criteria for BE, the adjunctive yield of WATS-3D was 76.5%, and absolute yield was 18.1%. 1,317 patients (19.3%) who fulfilled endoscopic BE criteria had IM detected solely by WATS-3D. Of 240 patients with dysplasia, 107(44.6%) were found solely by WATS-3D. Among patients with positive WATS-3D but negative FB, the care plan changed in 90.7%.

CONCLUSION

The addition of WATS-3D to FB in GERD patients being screened for BE resulted in confirmation of BE in an additional 1/5 th of patients. Furthermore, dysplasia diagnoses approximately doubled.

Artificial intelligence-enhanced volumetric laser endomicroscopy improves dysplasia detection in Barrett's esophagus in a randomized cross-over study

Volumetric laser endomicroscopy (VLE) is an advanced endoscopic imaging tool that can improve dysplasia detection in Barrett’s esophagus (BE). However, VLE scans generate 1200 cross-sectional images that can make interpretation difficult. The impact of a new VLE artificial intelligence algorithm called Intelligent Real-time Image Segmentation (IRIS) is not well-characterized. This is a randomized prospective cross-over study of BE patients undergoing endoscopy who were randomized to IRIS-enhanced or unenhanced VLE first followed by the other (IRIS-VLE vs. VLE-IRIS, respectively) at expert BE centers. The primary outcome was image interpretation time, which served as a surrogate measure for ease of interpretation. The secondary outcome was diagnostic yield of dysplasia for each imaging modality. 133 patients were enrolled. 67 patients were randomized to VLE-IRIS and 66 to IRIS-VLE. Total interpretation time did not differ significantly between groups (7.8 min VLE-IRIS vs. 7 min IRIS-VLE, P = 0.1), however unenhanced VLE interpretation time was significantly shorter in the IRIS-VLE group (2.4 min vs. 3.8 min, P < 0.01). When IRIS was used first, 100% of dysplastic areas were identified, compared with 76.9% when VLE was the first interpretation modality (P = 0.06). IRIS-enhanced VLE reduced the time of subsequent unenhanced VLE interpretation, suggesting heightened efficiency and improved dysplasia detection. It was also able to identify all endoscopically non-visible dysplastic areas.

Use of a Novel Portable Non-powered Suction Device in Patients With Oropharyngeal Dysphagia During a Choking Emergency

Choking remains a leading cause of accidental death and morbidity worldwide. Currently, there is no device to assist in the resuscitation of a choking victim when standard maneuvers fail. A novel portable non-powered suction device (LifeVac; LifeVac LLC, Nesconset, NY) has been developed and may have potential use in patients with oropharyngeal dysphagia who are at increased risk of choking. The device is FDA registered and distributed worldwide. This case series provides a summary of self-reported data regarding the use of the suction device in adult patients with oropharyngeal dysphagia during real-world choking emergencies recorded between January 2014 and July 2020. Over a 6-year monitoring period the device has been reported to be successful in the resuscitation of 38 out of 39 patients with oropharyngeal dysphagia during choking emergencies. Although the obstruction was removed with the device from the 39^th patient, resuscitation was not successful and he succumbed to his injuries. This portable, non-powered suction device may be useful in resuscitating patients with oropharyngeal dysphagia who are choking. The reported cases describe successful use of the device in real-world settings with minimal risk. Resuscitating patients with oropharyngeal dysphagia using this device may be a viable option when abdominal thrusts or back blows fail to resolve a choking emergency.

Longitudinal and Circumferential Distributions of Dysplasia and Early Neoplasia in Barrett's Esophagus: A Pooled Analysis of Three Prospective Studies

INTRODUCTION

Studies have shown that dysplasia in Barrett's esophagus (BE) has a predilection for the right hemisphere. There is limited information on the longitudinal distribution. The aim was to determine both the longitudinal and circumferential distributions of dysplasia and early neoplasia from 3 prospective studies.

METHODS

This is a pooled analysis from 3 prospective studies of patients with treatment-naive BE. Both circumferential and longitudinal locations (for BE segments greater than 1 cm) of dysplastic and early neoplastic lesions were recorded.

RESULTS

A total of 177 dysplastic and early neoplastic lesions from 91 patients were included in the pooled analysis; of which 59.3% (n = 105) were seen on high-definition white light endoscopy, 29.4% (n = 52) on advanced imaging, and 11.2% (n = 20) with random biopsies. The average Prague score was C3M5. Of 157 lesions within BE segments greater than 1 cm, 49 (34.8%) lesions were in the proximal half, whereas 92 lesions (65.2%) were in the distal half (P < 0.001). The right hemisphere of the esophagus contained 55% (86/157) of the total lesions compared with 45% (71/157) for the left hemisphere (P = 0.02). This was because of the presence of high-grade dysplasia being concentrated in the right hemisphere compared with the left hemisphere (60% vs 40%, P = 0.002).

DISCUSSION

In this pooled analysis of prospective studies, both low-grade dysplasia and high-grade dysplasia are more frequently found in the distal half of the Barrett's segment. This study confirms that the right hemisphere is a hot spot for high-grade dysplasia. Careful attention to these locations is important during surveillance endoscopy.

Palliative endoscopic spray cryotherapy to prevent worsening of dysphagia and improve quality of life in esophageal cancer

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Background: Patients with locally advanced esophageal cancer can have progressive dysphagia and associated worsening quality of life (QOL). Maintenance of esophageal patency by reducing intraluminal tumor burden can improve QOL by palliating dysphagia and delay or prevent the need for feeding tubes and esophageal stents. We aimed to assess the effect of endoscopic palliative cryoablation with trūFreeze Spray Cryotherapy (SCT) on dysphagia burden, QOL, and survival in patients with esophageal cancer. Methods: This is a multi-center prospective study of esophageal cancer patients at 10 sites in the United States. Subjects are 18-89 years old with luminal esophageal cancer, non-surgical candidates, not receiving systemic therapy, without esophageal stents, or history of prior SCT for esophageal cancer. SCT is an endoluminal ablation modality using non-contact medical grade liquid nitrogen (LN2) reaching a temperature of -1960 C delivered by a catheter. SCT was performed at 6 week intervals or as clinically indicated at a dose of 2x30 or 3x30 seconds per every 2-3 cm treatment site. Dysphagia and QOL were assessed with the 5-point Dysphagia score and EORTC QLQ 30 and OES18 esophageal module. Results: Of 49 subjects, mean age is 74.2 ± 11.8, 88% are men, 92% have esophageal adenocarcinoma and 19% have prior esophageal surgery or esophagectomy. 75% had a history of chemotherapy and/or radiation, and 58% (n=21) had a tumor stage >2. Subjects had a total of 258 treatment sessions over a mean follow-up of 329.7 ± 219.1 days, and received a median of 4 (IQR:2-7) SCT sessions with an average dose of 90 (3x30 sec) seconds/treatment site. There were 19 procedure related adverse events (20.4% of patients and 7.4% of procedures), all of which were mild (n=13) or moderate (n=6) in severity. Mean baseline dysphagia score was 1.7 ± 0.9 and 89% maintained (72%) or improved (17%) their baseline dysphagia score after initial SCT, p<0.05, and maintained this degree of symptom burden with ongoing SCT for a mean 239 ± 198 days. 28.6% (n=14) needed an esophageal stent after a mean 168 ± 169 days and 8% (n=4) had a feeding tube placed after a mean 145 ± 76 days after initial treatment. There was improvement in global health status (61.9 ± 23.3 vs 67.7 ± 19.7) and social functioning (73.9 ± 24.7 vs 81.2 ± 28.0) with decreased dysphagia (OES18: 21.5 vs. 16.7) and eating problems (26.1 vs. 20.6), p<0.05 for all. During the follow-up period, 49% of this palliative group survived and median survival was 386 days. Factors associated with survival with SCT were earlier cancer stage (69% stage 1 or 2 were survivors vs. 20% non-survivors; p=0.03) and ≤25% of luminal obstruction by tumor (62% vs. 36%; p=0.06). Conclusions: Liquid nitrogen SCT is an effective option to curb dysphagia progression in palliation of esophageal cancer and improves overall quality of life. Degree of luminal obstruction and tumor stage predicted survival. Clinical trial information: NCT03243734.

Hyperdipsia in sheep bearing lesions in the medial septal nucleus

Previous experiments in rodents showed that ablation of the septal brain region caused hyperdipsia. We investigated which part of the septal region needs ablation to produce hyperdipsia in sheep, and whether increased drinking was a primary hyperdipsia. Following ablation of the medial septal region (n = 5), but not parts of the lateral septal region (n = 4), daily water intake increased from ~2.5-5 L/day up to 10 L/day for up to 3 months post-lesion. In hyperdipsic sheep, plasma osmolality increased on the first day post-lesion and body weight fell, suggesting that initial hyperdipsia was secondary to fluid loss. However hyperosmolality was not sustained long-term and plasma hypo-osmolality persisted from 0.5 to 3 months post-lesion. Acute dipsogenic responses to intravenous hypertonic saline, intravenous or intracerebroventricular angiotensin II, water deprivation for 2 days, or feeding over 5 h were not potentiated by medial septal lesions, showing that the rapid pre-systemic inhibitory influences that cause satiation of thirst upon the act of drinking were intact. However, hyperdipsic sheep continued to ingest water when hyponatremic (plasma [Na] was 127-132 mmol/l) and plasma osmolality was 262-268 mosmol/kg due to retention of ingested fluid resulting from intravenous infusion of vasopressin administered to maintain a basal blood level of antidiuretic hormone. The results show that septal lesion-induced hyperdipsia is not due to disruption of acute pre-systemic influences associated with drinking water that initiates rapid satiation of thirst. Rather, inhibitory influences of hyponatremia, hypo-osmolality or hypervolemia on drinking appear to be disrupted by medial septal lesions.

Efficacy of palliative liquid nitrogen spray cryotherapy in curbing progression of dysphagia in esophageal cancer

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Background: Progressive dysphagia in locally advanced esophageal cancer worsens quality of life (QOL). Endoscopic cryoablation may effectively palliate dysphagia. Aim: To study the effect of palliative cryoablation with trūFreeze Spray Cryotherapy (SCT) in patients with esophageal cancer. Methods: This is an interim analysis of a multi-center prospective study of esophageal cancer patients who are non-surgical candidates, not on active systemic therapy, without esophageal stents, or prior SCT. SCT is an endoscopic ablation modality using liquid nitrogen (LN2) delivered by catheter. SCT occurred at 6 week intervals or as indicated at a dose of 2x30 or 3x30 secs/treatment site. Dysphagia and esophageal symptoms were assessed at baseline and after treatment with a 5-point Dysphagia score and the EORTC-QLQ-OES18 (higher score = more symptoms). Results: 39 subjects (mean age 74.4 ±12.2; 87% men, Table) had 182 treatment sessions over a mean follow-up of 206.9 days, and received a median 3 SCT sessions with an average dose of 90 (3x30) secs/site. There was 1 procedure related SAE (2.6% of patients and 0.5% procedures). Mean follow-up dysphagia score was 1.6 ±0.8 and 90% had same or improved dysphagia score after SCT treatment, p<0.01. On average, treated patients maintained the same or improved levels of dysphagia for 117 days. Esophageal QOL was maintained with improvement in “eating problems” (24.4 before treatment to 18.2 after, p=0.01). Only 4 subjects needed an esophageal stent (n=2) or gastrostomy tube (n=2) for nutrition. Conclusions: SCT for palliation of esophageal cancer was effective in limiting progression of dysphagia, while maintaining esophageal QOL. Only 10% required either esophageal stenting or feeding tube at >6 month follow-up. Clinical trial information: NCT03243734.

[Table: see text]

Volumetric laser endomicroscopy features of dysplasia at the gastric cardia in Barrett's oesophagus: results from an observational cohort study

Objective

Volumetric laser endomicroscopy (VLE) is an advanced imaging modality used in Barrett’s oesophagus (BE) to help identify dysplasia in the oesophagus. VLE criteria exist for oesophageal dysplasia but not for dysplasia in the gastric cardia. The aim of this study was to determine if there are in vivo VLE features that can predict gastric cardia dysplasia in BE.

Design

This was a single-centre observational cohort study from August 2016 to August 2018. Patients were included if they had BE, were undergoing a VLE exam as standard of care, and had a suspicious target laser marked at the gastric cardia. The following VLE features were correlated to histology to determine if an association existed between histology subtype and VLE feature: wide crypts, irregular surface, one large isolated gland, multiple glands, and complex glands.

Results

A total of 110 in vivo gastric cardia targets in 77 patients with BE were analysed. The following abnormalities were identified: 61 wide crypts, 34 isolated glands, 16 irregular surfaces, 15 multiple glands, and 11 complex glands. Complex glands were the only VLE feature that correlated to any histology subtype. They were present in 71% of targets with high-grade dysplasia (HGD), T1a cancer or T1b cancer and had a sensitivity, specificity, and accuracy of 71%, 99%, and 85%, respectively. Of the 10 patients with complex glands on VLE and HGD/cancer on histology, 4 had a normal-appearing mucosa (40%) on endoscopy.

Conclusion

Identification of complex glands on VLE may aid in detection of HGD or early cancer in the gastric cardia in BE. This is particularly important, as dysplasia at the gastric cardia can be difficult to see endoscopically.

Mutational load may predict risk of progression in patients with Barrett's oesophagus and indefinite for dysplasia: a pilot study

Background and aims

Mutational load (ML) has been shown to help risk-stratify those that may progress from non-dysplastic Barrett’s oesophagus (BE) to dysplastic disease. Management of patients with BE and indefinite for dysplasia (BE-IND) is challenging and risk stratification tools are lacking. The aim of this pilot study is to evaluate the utility of ML for risk stratification in patients with BE-IND.

Methods

This is a single-centre, retrospective pilot study evaluating ML quantification in patients with BE-IND. Histology at follow-up endoscopy at least 1 year after the baseline endoscopy was used to determine if a patient progressed to low or high dysplasia. The ML levels were then compared among patients who progressed to dysplasia versus those who did not.

Results

Thirty-five patients who met the inclusion criteria were identified, and seven met the exclusion criteria. Twenty-eight patients were analysed, of whom eight progressed to low-grade dysplasia (6) and high-grade dysplasia (2). Seven of these eight patients had some level of genomic instability detected in their IND biopsy (ML ≥0.5). Ten of the 20 (50%) who did not progress had no ML level. At an ML cut-off above 1.5, the risk of progression to high-grade dysplasia was 33% vs 0% (p=0.005), with a sensitivity of 100% and a specificity of 85%.

Conclusion

These results indicate that ML may be able to risk-stratify progression to high-grade dysplasia in BE-IND. Larger studies are needed to confirm these findings.

Safety and efficacy of endoscopic spray cryotherapy for esophageal cancer

Although surgery is traditionally the standard of care for esophageal cancer, esophagectomy carries significant morbidity. Alternative endoscopic therapies are needed for patients who are not candidates for conventional treatment. The objective of this study is to assess the safety, efficacy, and tolerability of spray cryotherapy of esophageal adenocarcinoma. This study includes patients with esophageal adenocarcinoma who had failed or were not candidates for conventional therapy enrolled retrospectively and prospectively in an open-label registry and patients in a retrospective cohort from 11 academic and community practices. Endoscopic spray cryotherapy was performed until biopsy proven local tumor eradication or until treatment was halted due to progression of disease, patient withdrawal or comorbidities. Eighty-eight patients with esophageal adenocarcinoma (median age 76, 80.7% male, mean length 5.1 cm) underwent 359 treatments (mean 4.4 per patient). Tumor stages included 39 with T1a, 25 with T1b, 9 with unspecified T1, and 15 with T2. Eighty-six patients completed treatment with complete response of intraluminal disease in 55.8%, including complete response in 76.3% for T1a, 45.8% for T1b, 66.2% for all T1, and 6.7% for T2. Mean follow-up was 18.4 months. There were no deaths or perforations related to spray cryotherapy. Strictures developed in 12 of 88 patients (13.6%) but were present before spray cryotherapy in 3 of 12. This study suggests that endoscopic spray cryotherapy is a safe, well-tolerated, and effective treatment option for early esophageal adenocarcinoma.

Safety and efficacy of endoscopic spray cryotherapy for Barrett's dysplasia: results of the National Cryospray Registry

Retrospective series have shown the efficacy of endoscopic spray cryotherapy in eradicating high-grade dysplasia (HGD) in Barrett's esophagus (BE); however, prospective data are lacking, and efficacy for low-grade dysplasia (LGD) is unclear. The aim of this study was to assess the efficacy and safety of spray cryotherapy in patients with LGD or HGD. A multicenter, prospective open-label registry enrolled patients with dysplastic BE. Spray cryotherapy was performed every 2-3 months until there was no endoscopic evidence of BE and no histological evidence of dysplasia, followed by surveillance endoscopies up to 2 years. Primary outcome measures were complete eradication of dysplasia (CE-D) and complete eradication of all intestinal metaplasia (CE-IM). Ninety-six subjects with Barrett's dysplasia (67% HGD; 65% long-segment BE; mean length 4.5 cm) underwent 321 treatments (mean 3.3 per subject). Mean age was 67 years, 83% were male. Eighty patients (83%) completed treatment with follow-up endoscopy (mean duration 21 months). In patients with LGD, rate of CE-D was 91% (21/23) and rate of CE-IM was 61% (14/23). In HGD, CE-D rate was 81% (46/57) and CE-IM was 65% (37/57). In patients with short-segment BE (SSBE) with any dysplasia, CE-D was achieved in 97% (30/31) and CE-IM in 77% (24/31). There were no esophageal perforations or related deaths. One subject developed a stricture, which did not require dilation. One patient was hospitalized for bleeding in the setting of non-steroidal anti-inflammatory drug use. In the largest prospective cohort to date, data suggest endoscopic spray cryotherapy is a safe and effective modality for eradication of BE with LGD or HGD, particularly with SSBE.

Volumetric laser endomicroscopy can target neoplasia not detected by conventional endoscopic measures in long segment Barrett's esophagus

Methods and study aims: The incidence of esophageal cancer is rising despite increased surveillance efforts. Volumetric laser endomicroscopy (VLE) is a new endoscopic imaging tool that can allow for targeted biopsy of neoplasia in Barrett's esophagus. We report a series of 6 patients with long-segment Barrett's esophagus ( > 3 cm), who underwent a session of endoscopy with volumetric laser endomicroscopy, after a separate prior session of standard high-definition endoscopy with narrow band imaging (NBI) and random biopsies that did not reveal neoplasia. In all six patients, the first endoscopy was the index endoscopy diagnosing the Barrett's esophagus. All VLE exams were performed within 6 months of the previous endoscopy. In five patients, VLE-targeted biopsy resulted in upstaged disease/diagnosed dysplasia that then qualified the patient for endoscopic ablation therapy. In one patient, VLE localized a focus of intramucosal cancer that allowed for curative endoscopic mucosal resection. This case series shows that endoscopy with VLE can target neoplasia that cannot be localized by high-definition endoscopy with NBI and random biopsies.

Safety and efficacy of endoscopic spray cryotherapy for esophageal cancer

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Background: Although surgery is traditionally the standard of care for esophageal cancer, esophagectomy carries significant morbidity and mortality. Alternative endoscopic therapies are needed for patients who are not candidates for conventional treatment. The objective of this study was to assess the safety, efficacy, and tolerability of spray cryotherapy of esophageal cancer. Methods: This study includes patients enrolled retrospectively and prospectively in an open-label registry and patients in a retrospective cohort from twelve academic and community practices. Endoscopic spray cryotherapy was performed until local tumor eradication was confirmed by biopsy or until treatment was halted due to progression of disease, patient withdrawal or co-morbidities. Results: One-hundred and eight patients (median age 75.5, 79.6% male, 93.5% adenocarcinoma, mean length 5.2 cm) underwent 442 treatments (mean 4.2 per patient). Tumor stages included 40 with T1a, 27 with T1b, 10 with unspecified T1, 15 with T2, and 16 with no T stage reported. One-hundred and six patients completed treatment with complete response of intraluminal disease in 54.7%, including complete response in 74.4% for T1a, 50% for T1b, 65.3% for all T1, 6.7% for T2, and 50% for those with no T stage reported. Mean follow-up was 17.3 months. There were no deaths or perforations related to spray cryotherapy. Strictures developed in 11 of 108 patients (10.2%) but were present before spray cryotherapy in 3 of 11. Conclusions: This study suggests that endoscopic spray cryotherapy is safe, well tolerated and effective for early esophageal cancer in patients who are not candidates for conventional therapy.

Reflex control of inflammation by sympathetic nerves, not the vagus

We investigated a neural reflex that controls the strength of inflammatory responses to immune challenge - the inflammatory reflex. In anaesthetized rats challenged with intravenous lipopolysaccharide (LPS, 60 μg kg(-1)), we found strong increases in plasma levels of the key inflammatory mediator tumour necrosis factor α (TNFα) 90 min later. Those levels were unaffected by previous bilateral cervical vagotomy, but were enhanced approximately 5-fold if the greater splanchnic sympathetic nerves had been cut. Sham surgery had no effect, and plasma corticosterone levels were unaffected by nerve sections, so could not explain this result. Electrophysiological recordings demonstrated that efferent neural activity in the splanchnic nerve and its splenic branch was strongly increased by LPS treatment. Splenic nerve activity was dependent on inputs from the splanchnic nerves: vagotomy had no effect on the activity in either nerve. Together, these data demonstrate that immune challenge with this dose of LPS activates a neural reflex that is powerful enough to cause an 80% suppression of the acute systemic inflammatory response. The efferent arm of this reflex is in the splanchnic sympathetic nerves, not the vagi as previously proposed. As with other physiological responses to immune challenge, the afferent pathway is presumptively humoral: the present data show that vagal afferents play no measurable part. Because inflammation sits at the gateway to immune responses, this reflex could play an important role in immune function as well as inflammatory diseases.

The cholinergic anti-inflammatory pathway: a critical review

From a critical review of the evidence on the cholinergic anti-inflammatory pathway and its mode of action, the following conclusions were reached. (1) Both local and systemic inflammation may be suppressed by electrical stimulation of the peripheral cut end of either vagus. (2) The spleen mediates most of the systemic inflammatory response (measured by TNF-α production) to systemic endotoxin and is also the site where that response is suppressed by vagal stimulation. (3) The anti-inflammatory effect of vagal stimulation depends on the presence of noradrenaline-containing nerve terminals in the spleen. (4) There is no disynaptic connection from the vagus to the spleen via the splenic sympathetic nerve: vagal stimulation does not drive action potentials in the splenic nerve. (5) Acetylcholine-synthesizing T lymphocytes provide an essential non-neural link in the anti-inflammatory pathway from vagus to spleen. (6) Alpha-7 subunit-containing nicotinic receptors are essential for the vagal anti-inflammatory action: their critical location is uncertain, but is suggested here to be on splenic sympathetic nerve terminals. (7) The vagal anti-inflammatory pathway can be activated electrically or pharmacologically, but it is not the efferent arm of the inflammatory reflex response to endotoxemia.

Brain regions influenced by the lateral parabrachial nucleus in angiotensin II-induced water intake

This study examined which brain regions are influenced by an inhibitory lateral parabrachial nucleus (LPBN) mechanism that affects water intake. Controls and rats with bilateral LPBN lesions were administered angiotensin II (AngII) (0.5mg/kg subcutaneous - SC), drinking responses measured, and brains processed for Fos-immunohistochemistry. A separate group of LPBN-lesioned and non-lesioned animals were denied water for 90 min prior to perfusion to remove any confounding factor of water intake. LPBN-lesioned rats drank a cumulative volume of 9 mL compared with <4 mL by controls (p<0.01). Compared with sham-lesioned animals, Fos expression was attenuated in overdrinking LPBN-lesioned rats in the median preoptic nucleus (MnPO), paraventricular nucleus of the hypothalamus (PVN), supraoptic nucleus (SON) (p<0.001), bed nucleus of the stria terminalis and central nucleus of the amygdala (p<0.01). In LPBN-lesioned rats that did not drink, greater numbers of activated neurons were detected in the PVN (p<0.001), SON (p<0.01), MnPO, nucleus of the solitary tract (NTS) and area postrema (p<0.05) in response to SC AngII, compared with non-lesioned rats. These data suggest that the direct effects of LPBN lesions caused an increase in AngII-induced water intake and in rats that did not drink an increase in Fos expression, while indirect secondary effects of LPBN lesions caused a reduction in Fos expression possibly related to excessive ingestion of water. An inhibitory mechanism, likely related to arterial baroreceptor stimulation, relayed by neurons located in the LPBN influences the responses of the MnPO, PVN and SON to increases in peripheral AngII.

Adaptive appetites for salted and unsalted food in rats: differential effects of sodium depletion, DOCA, and dehydration

Most ingested sodium is contained in food. The aim was to investigate whether sodium depletion, dehydration, or DOCA alters intakes of salted and unsalted foods by rats given choices of two foods: salted (0.2-0.5% Na) and unsalted food containing either similar or different other dietary components. Diuretic-induced (furosemide or acetazolamide, two treatments on successive days) sodium depletion always caused pronounced falls in intake of unsalted food within 24 h, continuing at least another 2 days (e.g., 20.9 ± 1.6 pretreatment to 14.8 ± 1.2, 10.6 ± 1.5, and 14.3 ± 1.3 g/day for 3 days of depletion). Intake and preference for salted food increased after 24-72 h (e.g., 6.5 ± 1.2 pretreatment to 7.1 ± 1.1, 16.4 ± 2.3, and 17.0 ± 1.5 g/day at 1, 2, and 3 days of depletion). Valsartan (10 mg/day) blocked the increased intake of salted food but not the reduced intake of unsalted food. DOCA (2 mg/day) caused equivalent increase and decrease in intakes of salted and unsalted food, respectively. Water-deprived rats reduced intake (e.g., 14.2 ± 3.1 to 3.2 ± 2.0 g/day) of and preference for salted food (e.g., 56 ± 13% to 21 ± 11%) after 2 days of dehydration but did not consistently reduce intake of unsalted food. Total food ingested/day fell in both sodium-depleted and dehydrated rats. Rats regulate intakes of different foods to balance sodium needs, osmoregulatory homeostasis, and energy requirements. Reduced appetite for unsalted food may be a homeostatic response to sodium depletion, which together with subsequent generation of appetite for salted food, drives animals to ingest sodium-containing food, thereby restoring sodium balance.

Neural regulation of inflammation: no neural connection from the vagus to splenic sympathetic neurons

The 'inflammatory reflex' acts through efferent neural connections from the central nervous system to lymphoid organs, particularly the spleen, that suppress the production of inflammatory cytokines. Stimulation of the efferent vagus has been shown to suppress inflammation in a manner dependent on the spleen and splenic nerves. The vagus does not innervate the spleen, so a synaptic connection from vagal preganglionic neurons to splenic sympathetic postganglionic neurons was suggested. We tested this idea in rats. In a preparatory operation, the anterograde tracer DiI was injected bilaterally into the dorsal motor nucleus of vagus and the retrograde tracer Fast Blue was injected into the spleen. On histological analysis 7-9 weeks later, 883 neurons were retrogradely labelled from the spleen with Fast Blue as follows: 89% in the suprarenal ganglia (65% left, 24% right); 11% in the left coeliac ganglion; but none in the right coeliac or either of the superior mesenteric ganglia. Vagal terminals anterogradely labelled with DiI were common in the coeliac but sparse in the suprarenal ganglia, and confocal analysis revealed no putative synaptic connection with any Fast Blue-labelled cell in either ganglion. Electrophysiological experiments in anaesthetized rats revealed no effect of vagal efferent stimulation on splenic nerve activity or on that of 15 single splenic-projecting neurons recorded in the suprarenal ganglion. Together, these findings indicate that vagal efferent neurons in the rat neither synapse with splenic sympathetic neurons nor drive their ongoing activity.

Central osmoregulatory influences on thermoregulation

1. Many mammals maintain a constant core body temperature in the face of a heat load by using evaporative cooling responses, such as sweating, panting and spreading of saliva. These cooling mechanisms incur a body fluid deficit if the fluid lost as sweat, saliva or respiratory moisture is not replaced by the ingestion of water; body fluid hypertonicity and hypovolaemia result. 2. Evidence in several mammals shows that, as they become dehydrated, evaporative cooling mechanisms such as sweating and panting are inhibited so that further fluid loss from the body is reduced. As a result, core temperature in the dehydrated animal is maintained at a higher than normal level. 3. Increasing the osmotic pressure of plasma has an inhibitory effect on panting and sweating in mammals. It has been proposed that osmoreceptors mediate these inhibitory influences of plasma hypertonicity on sweating and panting. 4. The suppression of panting in dehydrated sheep is mediated by cerebral osmoreceptors that are probably located in the lamina terminalis. We speculate that osmoreceptors in the lamina terminalis may also influence thermoregulatory sweating. 5. When dehydrated animals drink water, sweating and panting resume rapidly before water has been absorbed from the gut. It is likely that the act of drinking initiates a reflex that can override the osmoreceptor inhibition of panting, resulting in core temperature falling back quickly to a normal level.

Investigation of the mechanisms by which chronic infusion of an acutely subpressor dose of angiotensin II induces hypertension

The mechanisms by which chronic infusion of an initially subpressor low dose of angiotensin II (ANG II) causes a progressive and sustained hypertension remain unclear. In conscious sheep ( n = 6), intravenous infusion of ANG II (2 μg/h) gradually increased mean arterial pressure (MAP) from 82 ± 3 to 96 ± 5 mmHg over 7 days ( P < 0.001). This was accompanied by peripheral vasoconstriction; total peripheral conductance decreased from 44.6 ± 6.4 to 38.2 ± 6.7 ml·min−1·mmHg−1 ( P < 0.001). Cardiac output and heart rate were unchanged. In the regional circulation, mesenteric, renal, and iliac conductances decreased but blood flows were unchanged. There was no coronary vasoconstriction, and coronary blood flow increased. Ganglion blockade (125 mg/h hexamethonium for 4 h) reduced MAP by 13 ± 1 mmHg in the control period and by 7 ± 2 mmHg on day 8 of ANG II treatment. Inhibition of central AT1 receptors by intracerebroventricular infusion of losartan (1 mg/h for 3 h) had no effect on MAP in the control period or after 7 days of ANG II infusion. Pressor responsiveness to incremental doses of intravenous ANG II (5, 10, 20 μg/h, each for 15 min) was unchanged after 7 days of ANG II infusion. ANG II caused no sodium or water retention. In summary, hypertension due to infusion of a low dose of ANG II was accompanied by generalized peripheral vasoconstriction. Indirect evidence suggested that the hypertension was not neurogenic, but measurement of sympathetic nerve activity is required to confirm this conclusion. There was no evidence for a role for central angiotensinergic mechanisms, increased pressor responsiveness to ANG II, or sodium and fluid retention.

Bronchobiliary fistula successfully treated with n-butyl cyanoacrylate via a bronchial approach

A bronchobiliary fistula is an abnormal communication between the biliary tree and the airway that can result in debilitating amounts of bilioptysis, or bile-stained sputum. The authors present an approach for the conservative management of a bronchobiliary fistula in a patient who failed traditional conservative therapy and refused surgical intervention.

Amylin induces natriuresis by a central angiotensin-dependent mechanism

This study provides evidence that amylin acts centrally to increase sodium excretion in the sheep. Amylin was infused at 8 mg/h into a carotid artery (IC), via a lateral ventricle (ICV), intravenously (IV) or intra-renally (IR) into conscious sheep (n=5 per group). Renal sodium excretion increased by at least 3-fold after 1 h of amylin infusion by ICV (66+/-14 to 367+/-35 mmol/min) and IC (78+/-14 to 244+/-22 mmol/min) routes of administration. Amylin infusion IV caused a 1.5-fold increase in sodium excretion while IR infusion did not have a significant effect. The natriuretic effect of ICV infused amylin was blocked by pre-treatment with the angiotensin AT1 receptor antagonist, losartan (1 mg/h). No changes in blood pressure or heart rate were recorded at this dose of amylin by any route of administration. Plasma renin concentration increased (1.32+/-0.22 to 2.55+/-0.73 pmol/Ang I/h; P<0.05) following IR infusion of amylin, and remained unchanged when amylin was infused by the other routes of administration. We conclude that amylin causes changes in sodium excretion in sheep through a central, angiotensin-dependent pathway and that amylin may increase renin secretion by a direct effect on the kidney.

Serotonergic mechanism of the lateral parabrachial nucleus and relaxin-induced sodium intake

It has been shown that central or peripheral injections of the peptide relaxin induces water intake, not sodium intake in rats. Important inhibitory mechanisms involving serotonin and other neurotransmitters in the control of water and NaCl intake have been demonstrated in the lateral parabrachial nucleus (LPBN). In the present study, we investigated the effects of bilateral injections of methysergide (serotonergic receptor antagonist) into the LPBN on intracerebroventricular (i.c.v.) relaxin-induced water and NaCl intake in rats. Additionally, the effect of the blockade of central angiotensin AT(1) receptors with i.c.v. losartan on relaxin-induced water and NaCl intake in rats treated with methysergide into the LPBN was also investigated. Male Holtzman rats with cannulas implanted into the lateral ventricle (LV) and bilaterally in the LPBN were used. Intracerebroventricular injections of relaxin (500 ng/1 microl) induced water intake (5.1+/-0.7 ml/120 min), but not significant 1.8% NaCl intake (0.5+/-0.4 ml/120 min). Bilateral injections of methysergide (4 microg/0.2 microl) into the LPBN strongly stimulated relaxin-induced 1.8% NaCl intake (34.5+/-10.9 ml/120 min) and slightly increased water intake (10.5+/-4.9 ml/120 min). The pretreatment with i.c.v. losartan (100 microg/1 microl) abolished the effects of i.c.v. relaxin combined with LPBN methysergide on 1.8% NaCl intake (0.5+/-0.4 ml/120 min). Losartan (100 microg/1 microl) also abolished relaxin-induced water intake in rats injected with methysergide into the LPBN (1.6+/-0.8 ml/120 min) or not (0.5+/-0.3 ml/120 min). Losartan (50 microg/1 microl) partially reduced the effects of relaxin. The results show that central relaxin interacting with central angiotensinergic mechanisms induces NaCl intake after the blockade of LPBN serotonergic mechanisms.

Physiological and pathophysiological influences on thirst

Thirst motivates animals to seek fluid and drink it. It is regulated by the central nervous system and arises from neural and chemical signals from the periphery interacting in the brain to stimulate a drive to drink. Our research has focussed on the lamina terminalis and the manner in which osmotic and hormonal stimuli from the circulation are detected by neurons in this region and how that information is integrated with other neural signals to generate thirst. Our studies of osmoregulatory drinking in the sheep and rat have produced evidence that osmoreceptors for thirst exist in the dorsal cap of the organum vasculosum of the lamina terminalis (OVLT) and in the periphery of the subfornical organ, and possibly also in the median preoptic nucleus. In the rat, the hormones angiotensin II and relaxin act on neurons in the periphery of the subfornical organ to stimulate drinking. Studies of human thirst using functional magnetic resonance imaging (fMRI) techniques show that systemic hypertonicity activates the lamina terminalis and the anterior cingulate cortex, but the neural circuitry that connects sensors in the lamina terminalis to cortical regions subserving thirst remains to be determined. Regarding pathophysiological influences on thirst mechanisms, both excessive (polydipsia) and inadequate (hypodisia) water intake may have dire consequences. One of the most common primary polydipsias is that observed in some cases of schizophrenia. The neural mechanisms causing the excessive water intake in this disorder are unknown, so too are the factors that result in impaired thirst and inadequate fluid intake in some elderly humans.

Inlet patch: prevalence, histologic type, and association with esophagitis, Barrett esophagus, and antritis

CONTEXT

Inlet patch is a congenital anomaly of the cervical esophagus consisting of gastric mucosa. Case reports have documented the histologic type and its associated complications.

OBJECTIVE

To report the prevalence and histologic types of inlet patch as well as its association with Barrett esophagus and Helicobacter pylori-associated gastritis.

DESIGN

We reviewed 1821 consecutive pathology reports from endoscopies of the upper gastrointestinal tract between 1995 and 2002 and identified 20 patients with inlet patch. The patients' ages ranged from 16 to 75 years (mean, 55 years). We examined biopsies from these patients of the cervical esophagus, distal esophagus, and antrum that had been stained with hematoxylin-eosin and the Steiner stain. Biopsies from the cervical esophagus composed of nonoxyntic gastric mucosa were also stained for gastrin-producing cells.

RESULTS

In our patient population, inlet patch occurred in 1.1% of all patients in whom an inlet patch had been searched for endoscopically and a biopsy performed. In the inlet patch, oxyntic mucosa was the most common histologic type (11/20), followed by cardiac mucosa (5/20). Four specimens of the inlet patch contained only foveolar epithelium and were therefore considered too superficial to be classified. Twelve of 20 biopsies of the inlet patch were inflamed, and 1 of them was associated with H pylori. Pancreatic acinar tissue was noted in 2 patients; no intestinal metaplasia was found. In the distal esophagus, 4 patients with inlet patch had distal esophagitis, 4 had Barrett esophagus, 5 had oxyntic mucosa, 3 had pancreatic acinar tissue (1 coexisting with oxyntic mucosa), and 5 presented with only unremarkable esophageal squamous mucosa. Antral gastritis was seen in 2 patients, 1 of them with H pylori. The same patient also had H pylori in the inlet patch.

CONCLUSION

Inlet patch occurred in about 1% of our study population. Oxyntic mucosa constituted the most common histologic type; inflammation was common. The H pylori infection of the inlet patch correlated with that of the antrum. None of the inlet patch biopsies showed intestinal metaplasia. Pancreatic acinar tissue occurred with similar frequency in the inlet patch and distal esophagus. Esophagitis was noted in 25% of the patients with inlet patch, and Barrett esophagus was noted in 20%.

Inlet patch: prevalence, histologic type, and association with esophagitis, Barrett esophagus, and antritis

CONTEXT

Inlet patch is a congenital anomaly of the cervical esophagus consisting of gastric mucosa. Case reports have documented the histologic type and its associated complications.

OBJECTIVE

To report the prevalence and histologic types of inlet patch as well as its association with Barrett esophagus and Helicobacter pylori-associated gastritis.

DESIGN

We reviewed 1821 consecutive pathology reports from endoscopies of the upper gastrointestinal tract between 1995 and 2002 and identified 20 patients with inlet patch. The patients' ages ranged from 16 to 75 years (mean, 55 years). We examined biopsies from these patients of the cervical esophagus, distal esophagus, and antrum that had been stained with hematoxylin-eosin and the Steiner stain. Biopsies from the cervical esophagus composed of nonoxyntic gastric mucosa were also stained for gastrin-producing cells.

RESULTS

In our patient population, inlet patch occurred in 1.1% of all patients in whom an inlet patch had been searched for endoscopically and a biopsy performed. In the inlet patch, oxyntic mucosa was the most common histologic type (11/20), followed by cardiac mucosa (5/20). Four specimens of the inlet patch contained only foveolar epithelium and were therefore considered too superficial to be classified. Twelve of 20 biopsies of the inlet patch were inflamed, and 1 of them was associated with H pylori. Pancreatic acinar tissue was noted in 2 patients; no intestinal metaplasia was found. In the distal esophagus, 4 patients with inlet patch had distal esophagitis, 4 had Barrett esophagus, 5 had oxyntic mucosa, 3 had pancreatic acinar tissue (1 coexisting with oxyntic mucosa), and 5 presented with only unremarkable esophageal squamous mucosa. Antral gastritis was seen in 2 patients, 1 of them with H pylori. The same patient also had H pylori in the inlet patch.

CONCLUSION

Inlet patch occurred in about 1% of our study population. Oxyntic mucosa constituted the most common histologic type; inflammation was common. The H pylori infection of the inlet patch correlated with that of the antrum. None of the inlet patch biopsies showed intestinal metaplasia. Pancreatic acinar tissue occurred with similar frequency in the inlet patch and distal esophagus. Esophagitis was noted in 25% of the patients with inlet patch, and Barrett esophagus was noted in 20%.

Vasopressin secretion: osmotic and hormonal regulation by the lamina terminalis

The lamina terminalis, located in the anterior wall of the third ventricle, is comprised of the subfornical organ, median preoptic nucleus (MnPO) and organum vasculosum of the lamina terminalis (OVLT). The subfornical organ and OVLT are two of the brain's circumventricular organs that lack the blood-brain barrier, and are therefore exposed to the ionic and hormonal environment of the systemic circulation. Previous investigations in sheep and rats show that this region of the brain has a crucial role in osmoregulatory vasopressin secretion and thirst. The effects of lesions of the lamina terminalis, studies of immediate-early gene expression and electrophysiological data show that all three regions of the lamina terminalis are involved in osmoregulation. There is considerable evidence that physiological osmoreceptors subserving vasopressin release are located in the dorsal cap region of the OVLT and possibly also around the periphery of the subfornical organ and in the MnPO. The circulating peptide hormones angiotensin II and relaxin also have access to peptide specific receptors (AT(1) and LGR7 receptors, respectively) in the subfornical organ and OVLT, and both angiotensin II and relaxin act on the subfornical organ to stimulate water drinking in the rat. Studies that combined neuroanatomical tracing and detection of c-fos expression in response to angiotensin II or relaxin suggest that both of these circulating peptides act on neurones within the dorsal cap of the OVLT and the periphery of the subfornical organ to stimulate vasopressin release.

The sensory circumventricular organs of the mammalian brain

The brain's three sensory circumventricular organs, the subfornical organ, organum vasculosum of the lamina terminalis and the area postrema lack a blood brain barrier and are the only regions in the brain in which neurons are exposed to the chemical environment of the systemic circulation. Therefore they are ideally placed to monitor the changes in osmotic, ionic and hormonal composition of the blood. This book describes their. General structure and relationship to the cerebral ventricles Regional subdivisions Vasculature and barrier properties Neurons, glia and ependymal cells Receptors, neurotransmitters, neuropeptides and enzymes Neuroanatomical connections Functions.

Circulating angiotensin II activates neurones in circumventricular organs of the lamina terminalis that project to the bed nucleus of the stria terminalis

The aim of this study was to determine, in conscious rats, whether elevated concentrations of circulating angiotensin II activate neurones in both the subfornical organ and organum vasculosum of the lamina terminalis (OVLT) that project to the bed nucleus of the stria terminalis (BNST). The strategy employed was to colocalize retrogradely transported cholera toxin B subunit (CTB) from the BNST, with elevated levels of Fos protein in response to angiotensin II. Circulating angiotensin II concentrations were increased by either intravenous infusion of angiotensin II or subcutaneous injection of isoproterenol. Neurones exhibiting Fos in response to angiotensin II were present in the subfornical organ, predominantly in its central core but with some also seen in its peripheral aspect, the dorsal and lateral margins of the OVLT, the supraoptic nucleus and the parvo- and magnocellular divisions of the paraventricular nucleus. Fos-labelling was not apparent in control rats infused with isotonic saline intravenously or injected with either CTB or CTB conjugated to gold particles (CTB-gold) only. Of the neurones in the subfornical organ that were shown by retrograde labelling to project to BNST, approximately 50% expressed Fos in response to isoproterenol. This stimulus also increased Fos in 33% of neurones in the OVLT that project to BNST. Double-labelled neurones were concentrated in the central core of the subfornical organ and lateral margins of the OVLT in response to increased circulating angiotensin II resulting from isoproterenol treatment. These data support a role for circulating angiotensin II acting either directly or indirectly on neurones in subfornical organ and OVLT that project to the BNST and provide further evidence of functional regionalization within the subfornical organ and the OVLT. The function of these pathways is yet to be determined; however, a role in body fluid homeostasis is possible.

The effect of urocortin on ingestive behaviours and brain Fos immunoreactivity in mice

The influence of urocortin (UCN) on ingestive behaviours and brain neural activity, as measured immunohistochemically by the presence of Fos protein, was determined in mice. Rat UCN was administered by continuous intracerebroventricular (ICV) or subcutaneous (SC) infusion. ICV infusion of UCN (100 ng/h, 14 days) transiently reduced daily food and water intakes (days 1-4) but body weight was reduced from day 2 into the post-infusion period. Sodium intake was reduced from day 3 to the end of infusion. SC infusion of UCN caused similar but smaller reductions in food and water intakes and body weight, without change in sodium intake. In separate experiments, Fos immunoreactivity was increased in several brain nuclei known to be involved in the control of body fluid and energy homeostasis, e.g. central nucleus of the amygdala, median preoptic nucleus, bed nucleus of the stria terminalis and arcuate nucleus. Increased Fos expression was similar for ICV and SC infusions when measured on days 2-3 or 6-7 of infusion. In conclusion, increases of brain activity by UCN may be associated with stimulation of adrenocorticotrophic hormone release and sympathetic nervous activity, but increases may also indicate suppression of ingestive behaviours by stimulating central inhibitory mechanisms located in areas known to control body fluid and energy homeostasis.

The brain renin-angiotensin system: location and physiological roles

Angiotensinogen, the precursor molecule for angiotensins I, II and III, and the enzymes renin, angiotensin-converting enzyme (ACE), and aminopeptidases A and N may all be synthesised within the brain. Angiotensin (Ang) AT(1), AT(2) and AT(4) receptors are also plentiful in the brain. AT(1) receptors are found in several brain regions, such as the hypothalamic paraventricular and supraoptic nuclei, the lamina terminalis, lateral parabrachial nucleus, ventrolateral medulla and nucleus of the solitary tract (NTS), which are known to have roles in the regulation of the cardiovascular system and/or body fluid and electrolyte balance. Immunohistochemical and neuropharmacological studies suggest that angiotensinergic neural pathways utilise Ang II and/or Ang III as a neurotransmitter or neuromodulator in the aforementioned brain regions. Angiotensinogen is synthesised predominantly in astrocytes, but the processes by which Ang II is generated or incorporated in neurons for utilisation as a neurotransmitter is unknown. Centrally administered AT(1) receptor antagonists or angiotensinogen antisense oligonucleotides inhibit sympathetic activity and reduce arterial blood pressure in certain physiological or pathophysiological conditions, as well as disrupting water drinking and sodium appetite, vasopressin secretion, sodium excretion, renin release and thermoregulation. The AT(4) receptor is identical to insulin-regulated aminopeptidase (IRAP) and plays a role in memory mechanisms. In conclusion, angiotensinergic neural pathways and angiotensin peptides are important in neural function and may have important homeostatic roles, particularly related to cardiovascular function, osmoregulation and thermoregulation.

The neurochemical characterisation of hypothalamic pathways projecting polysynaptically to brown adipose tissue in the rat

The identification of leptin and a range of novel anorectic and orexigenic peptides has focussed attention on the neural circuitry involved in the genesis of food intake and the reflex control of thermogenesis. Here, the neurotropic virus pseudorabies has been utilised in conjunction with the immunocytochemical localisation of a variety of neuroactive peptides and receptors to better define the pathways in the rat hypothalamus directed polysynaptically to the major thermogenic endpoint, brown adipose tissue. Infected neurones were detected initially in the stellate ganglion, then in the spinal cord followed by the appearance of third-order premotor neurones in the brainstem and hypothalamus. Within the hypothalamus these were present in the paraventricular nucleus, lateral hypothalamus, perifornical region, and retrochiasmatic nucleus. At slightly longer survival times virus-infected neurones appeared in the arcuate nucleus and dorsomedial hypothalamus. Neurones in the retrochiasmatic nucleus and in the adjacent lateral arcuate nucleus which project to the brown adipose tissue express cocaine- and amphetamine-regulated transcript, pro-opiomelanocortin and leptin receptors. Neurones in the lateral hypothalamus, a site traditionally associated with the promotion of feeding, project to brown adipose tissue and large numbers of these contained melanin-concentrating hormone and orexin A and B. These data provide part of an anatomical framework which subserves the regulation of energy expenditure.

"Tannenbaum" Teflon stents versus traditional polyethylene stents for treatment of malignant biliary stricture

BACKGROUND

Premature stent clogging is the major limitation with plastic stents used in the treatment of malignant biliary structures. A pilot study suggested improved duration of patency of the Tannenbaum stent compared with polyethylene stents. The aim of this prospective, multicenter randomized trial was to compare the Tannenbaum Teflon stent with a conventional polyethylene endoprosthesis (Cotton-Leung biliary stent set) for the treatment of malignant biliary strictures.

METHODS

Patients over age 18 years with symptoms caused by nonhilar malignant biliary strictures were enrolled. Patients were randomized to receive a 10F Tannenbaum or polyethylene stent after a guidewire was passed beyond the stricture. One hundred six patients (mean age 72 years and 71 years, respectively) were enrolled (54 Tannenbaum, mean age 72 years; 52 polyethylene, mean age 71 years).

RESULTS

Tannenbaum and polyethylene stent placement was successful in, respectively, 100% and 96% of procedures without complications. The mean (SD) 90-day stent patency of the Tannenbaum stent was 67% (7%) compared with 73% (7%) for the polyethylene stents.

CONCLUSIONS

The present study demonstrated no difference in ease of implantation or stent patency between Tannenbaum and polyethylene stents.

Circulating relaxin acts on subfornical organ neurons to stimulate water drinking in the rat

Relaxin, a peptide hormone secreted by the corpus luteum during pregnancy, exerts actions on reproductive tissues such as the pubic symphysis, uterus, and cervix. It may also influence body fluid balance by actions on the brain to stimulate thirst and vasopressin secretion. We mapped the sites in the brain that are activated by i.v. infusion of a dipsogenic dose of relaxin (25 microg/h) by immunohistochemically detecting Fos expression. Relaxin administration resulted in increased Fos expression in the subfornical organ (SFO), organum vasculosum of the lamina terminalis (OVLT), median preoptic nucleus, and magnocellular neurons in the supraoptic and paraventricular nuclei. Ablation of the SFO abolished relaxin-induced water drinking, but did not prevent increased Fos expression in the OVLT, supraoptic or paraventricular nuclei. Although ablation of the OVLT did not inhibit relaxin-induced drinking, it did cause a large reduction in Fos expression in the supraoptic nucleus and posterior magnocellular subdivision of the paraventricular nucleus. In vitro single-unit recording of electrical activity of neurons in isolated slices of the SFO showed that relaxin (10(-7) M) added to the perfusion medium caused marked and prolonged increase in neuronal activity. Most of these neurons also responded to 10(-7) M angiotensin II. The data indicate that blood-borne relaxin can directly stimulate neurons in the SFO to initiate water drinking. It is likely that circulating relaxin also stimulates neurons in the OVLT that influence vasopressin secretion. These two circumventricular organs that lack a blood-brain barrier may have regulatory influences on fluid balance during pregnancy in rats.

A method for the identification of pseudorabies virus protein and angiotensin AT(1A) receptor mRNA expression in the same CNS neurons

Neurotropic viruses have been used over the last 10 years to map the distribution of chains of synaptically connected neurons in the CNS. The peptide content of infected neurons has been determined in a number of cases immunohistochemically. However, it has been unclear whether specific mRNA can be assessed in virus-infected neurons. We have established a technique which enables the identification of viral protein and mRNA in the same neuron. In the present study pseudorabies virus retrogradely transported from the kidney was localised using immunohistochemistry and mRNA for the angiotensin II AT(1A) receptor was detected by hybridisation histochemistry. Virus protein was visualised using an immunohistochemical procedure with diaminobenzidine as the chromogen and the same sections were exposed to radioactively labelled ((35)S) riboprobes, hybridising the angiotensin II AT(1A) receptor. The combination of these two approaches resulted in the identification of neurons shown to project polysynaptically to the kidney and express AT(1A) mRNA. These data provide neuroanatomical support for previous physiological observations that ablation of the lamina terminalis and administration of losartan, the AT(1) receptor antagonist, blocks the inhibition of renal sympathetic nerve activity following centrally injected Ang II in rats and sheep [5].

Neural pathways from the lamina terminalis influencing cardiovascular and body fluid homeostasis

1. The lamina terminalis, a region of the brain with a high concentration of angiotensin AT1 receptors, consists of three distinct nuclei, the median preoptic nucleus, the subfornical organ and organum vasculosum of the lamina terminalis (OVLT). These latter two regions lack a blood-brain and detect changes in plasma angiotensin (Ang) II concentration and osmolality. 2. Efferent neural pathways from the lamina terminalis to the hypothalamic paraventricular and supraoptic nuclei mediate vasopressin secretion in response to plasma hypertonicity and increased circulating levels of AngII. 3. Studies using the neurotropic virus pseudorabies, which undergoes retrograde transynaptic neuronal transport following injection into peripheral sites, show that neurons in the lamina terminalis have efferent polysynaptic neural connections to the peripheral sympathetic nervous system. Some of these neurons have been shown to have polysynaptic connections to the kidney and to express AT1 receptor mRNA. We propose that circulating AngII acts at AT1 receptors in the subfornical organ and OVLT to influence the sympathetic nervous system. It is likely that the neural pathway subserving this influence involves a synapse in the hypothalamic paraventricular nucleus. 4. The lamina terminalis may exert an inhibitory osmoregulatory influence on renin secretion by the kidney. This osmoregulatory influence may be mediated by inhibition of renal sympathetic nerve activity and appears to involve a central angiotensinergic synapse. 5. The lamina terminalis exerts an osmoregulatory influence on renal sodium excretion that is independent of the renal nerves and is probably hormonally mediated.

Activation of kidney-directed neurons in the lamina terminalis by alterations in body fluid balance

This study was undertaken to determine if neurons in the lamina terminalis, previously identified as projecting to the kidney (35), were responsive to alterations in stimuli associated with fluid balance homeostasis. Neurons in the lamina terminalis projecting to the kidney were identified by the retrograde transynaptic transport of Bartha's strain of pseudorabies virus in anesthetized rats. Rats were also exposed to 24-h water deprivation, intravenous hypertonic saline, or intracerebroventricular ANG II. To determine if "kidney-directed" neurons were activated following each stimulus, brain sections that included the lamina terminalis were examined immunohistochemically for viral antigen and Fos protein. With the exception of ANG II in the subfornical organ, all regions of the lamina terminalis contained neurons that were significantly activated by water deprivation, hypertonic saline, and ANG II. These results provide evidence for a neural substrate, which may underpin some of the effects of hypertonic saline and ANG II on renal function thought to be mediated through the lamina terminalis.

Influence of ruminal water-loading on renal sodium excretion and water intake following feeding in sheep

We investigated the effect of ruminal water loading before feeding on the natriuretic and drinking responses that follow feeding. Six sheep fed 800 g of chaff drank 1360 +/- 150 mL during the 5 h immediately following feeding and increased renal Na excretion. Plasma Na concentration increased by 4 mmol L (-1) and plasma osmolality by 9 mosmol kg (-1) within 1.5 h and remained elevated. A rumen load of water administered before feeding prevented the increases in plasma Na and osmolality without affecting feeding. The natriuresis, water drinking and vasopressin secretion in response to feeding were abolished. Total sodium excreted during the experiment was halved in water-loaded animals compared with untreated animals (30.4 +/- 2.1 mmol (-1) cf. 63.8 +/- 2.9 mmol-1; P < 0.01). Ruminal loading with isotonic saline caused a 33% reduction in postprandial drinking, however, reducing cerebrospinal fluid NaCl concentration abolished postprandial drinking and natriuresis. Intravenous infusion of isotonic dextran appeared to delay the onset of water intake without changing the total volume of water drunk, suggesting a role of plasma volume in initiating drinking. We conclude from the data that central osmoregulatory mechanisms that include increased sodium excretion as well as thirst and vasopressin release are activated following food intake by sheep.

Brain angiotensin and body fluid homeostasis

Angiotensinogen, the precursor molecule of the peptides angiotensin I, II, and III, is synthesized in the brain and the liver. Evidence is reviewed that angiotensin II, and possibly angiotensin III, that are generated within the brain act within neural circuits of the central nervous system to regulate body fluid balance. Immunohistochemical studies in the rat brain have provided evidence of angiotensin-containing neurons, especially in the hypothalamic paraventricular nucleus, subfornical organ, periventricular region, and nucleus of the solitary tract, as well as in extensive angiotensin-containing fiber pathways. Angiotensin immunoreactivity is observed by electron microscope in synaptic vesicles in several brain regions, the most prominent of these being the central nucleus of the amygdala. Neurons in many parts of the brain (lamina terminalis, paraventricular and parabrachial nuclei, ventrolateral medulla, and nucleus of the solitary tract) known to be involved in the regulation of body fluid homeostasis exhibit angiotensin receptors of the AT(1) subtype. Pharmacological studies in several species show that intracerebroventricular administration of AT(1) receptor antagonist drugs inhibit homeostatic responses to the central administration of hypertonic saline, intravenous infusion of the hormone relaxin, or thermal dehydration. Responses affected by centrally administered AT(1) antagonists are water drinking, vasopressin secretion, natriuresis, increased arterial pressure, reduced renal renin release, salt hunger, and thermoregulatory adjustments. We conclude that angiotensinergic neural pathways in the brain probably have an important homeostatic function, especially in regard to osmoregulation and thermoregulation, and the maintenance of arterial pressure.

Neural mechanisms subserving central angiotensinergic influences on plasma renin in sheep

The mechanisms and brain regions subserving the suppression of plasma renin concentration caused by intracerebroventricular (ICV) infusion of angiotensin II were studied in sodium-depleted sheep. Infusion of angiotensin II (3 microg/h for 1 hour) into the lateral ventricle reduced plasma renin from 4.3+/-0.4 to 1.6+/-0.2 pmol angiotensin I/mL per hour at 1 hour after the commencement of infusion. This change persisted for at least another 90 minutes and was blocked by concomitant ICV infusion of the AT(1) antagonist losartan (1 mg/h). Arterial pressure did not change, but plasma vasopressin secretion was increased. ICV infusion of losartan (1 mg/h) significantly increased plasma renin in sodium-depleted sheep. The reduction of plasma renin concentration in response to either ICV angiotensin II or hypertonic NaCl (0.75 mol/L at 1 mL/h) and the increase in response to ICV losartan was prevented in sheep in which the lamina terminalis of the brain had been ablated. Lesions in the median eminence (MEL), which blocked the increased plasma vasopressin levels, did not prevent suppression of plasma renin in response to ICV angiotensin II. However, bilateral renal denervation largely blocked this inhibition of plasma renin concentration but not the increased plasma renin resulting from ICV infusion of losartan in sodium-depleted sheep. The results show that AT(1) receptors, probably located in the lamina terminalis, mediate a central inhibitory influence of angiotensin II on renin secretion. This inhibition of renin release is probably due to a reduction in activity of renal sympathetic nerves innervating the juxtaglomerular apparatus of the kidney.

Identification of efferent neural pathways from the lamina terminalis activated by blood-borne relaxin

The ovarian hormone relaxin, in addition to its role in pregnancy, exerts an action on the brain to influence oxytocin and vasopressin secretion, water drinking, and cardiovascular function. Intravenous (i.v.) infusion of relaxin causes an acute water drinking response, confirming its role as a dipsogenic hormone. The aim of this study was to determine whether neurones in the lamina terminalis, which project to the hypothalamic paraventricular and supraoptic nuclei, are activated by elevated levels of circulating relaxin in conscious rats. Immunocytochemistry combined with retrograde neuronal tracing with cholera toxin B subunit conjugated to cholera toxin B (CTB-gold) was used to identify populations of neurones responding with elevated cells of Fos protein to i.v. relaxin administration and which project to these specific hypothalamic sites. Neurones exhibiting Fos were present in the outer parts of the subfornical organ (SFO), the dorsal part of the organum vasculosum (OVLT), the supraoptic nucleus and the paraventricular nucleus. These did not occur in control rats with i.v. infusions of isotonic saline. Approximately 90% of neurones concentrated in the outer parts of the SFO and in the dorsal OVLT showed both retrogradely transported CTB-gold and Fos in response to i.v. infusion of relaxin. These data support a role for relaxin acting on the brain to regulate body fluid and electrolyte homeostasis by activating neural pathways subserving water drinking, vasopressin and oxytocin secretion.

Neurons in the lamina terminalis which project polysynaptically to the kidney express angiotensin AT1A receptor

The retrograde transynaptic transport of pseudorabies virus was used in conjunction with hybridisation histochemistry for the angiotensin II AT1A receptor, to characterise neurons in the lamina terminalis projecting to the kidney. These data demonstrate that some neurons in the lamina terminalis, that project polysynaptically to the kidney, may be responsive to angiotensin II.

Efferent neural projections of angiotensin receptor (AT1) expressing neurones in the hypothalamic paraventricular nucleus of the rat

Angiotensin II acts within the hypothalamic paraventricular nucleus (PVN) to help mediate a number of autonomic and endocrine responses. Evidence is sparse in regard to the particular neuronal cell groups that exhibit angiotensin II type 1 receptors within the PVN, and does not exist in relation to specified efferent neuronal populations in the nucleus. In the present experiments, retrogradely transported neuronal tracers were utilized in conjunction with immunohistochemistry using a well characterized polyclonal antibody raised against a decapeptide sequence at the carboxy terminus of the AT1 receptor, to determine whether it is preferentially distributed amongst different efferent populations within the PVN. The AT1 receptor is not associated with neurones in the PVN that project axons to the spinal cord, dorsomedial or ventrolateral medulla but coexists strongly with neurones in the anterior parvocellular division of the nucleus which direct axons to the median eminence. Such neurones often contain corticotropin releasing factor. These findings highlight the role that angiotensin II and AT1 receptors in the PVN may play in the mediation of responses to stress.