Performance of the ENSEAL X1 Curved Jaw Tissue Sealer in thoracic procedures in a Japanese cohort: a case series report.

BACKGROUND: Advanced vessel sealing electrosurgical systems have been widely adopted for grasping, cutting, and sealing vessels. Data remain sparse with regard to its use in thoracic procedures. Thus, a prospective case series, utilizing the ENSEAL X1 Curved Jaw Tissue Sealer (X1CJ) and its companion energy source, the Generator 11 (GEN11), in thoracic procedures was performed in a Japanese cohort. METHODS: Subjects were recruited at two Japanese surgical sites. The primary endpoint of this post-market study was the achievement of hemostasis (≤ Grade 3) for each thoracic vessel transection. Performance endpoints included scores for tasks completed with X1CJ (adhesiolysis, lymphatics or tissue bundles divided, tissue grasping, tissue cutting, or tissue dissection); hemostasis grading vessel transected; additional products required to achieve hemostasis for Grade 4 vessel transections. Safety was evaluated by evaluating device-related adverse events. All endpoint data were summarized. RESULTS: Forty subjects (50.0% female) of Asian ethnicity with a mean age of 67.6 ± 11.3 years underwent a lung resection. Estimated mean blood loss was 39.5 mL. Hemostasis was achieved in 97.5% of vessel transections. Thirty-seven vessel sealings resulted in a hemostatic Grade 1 (92.5%). All surgeons reported satisfaction/neutral in terms of tissue grasping (100.0%) while most reported satisfaction/neutral with tissue cutting (95.7%). One device-related serious adverse event was reported (2.5%), a chylothorax requiring an extension of hospitalization. There was no post-operative bleeding or deaths reported during the study period. CONCLUSION: The X1CJ demonstrated safe and effective performance without any reports of significant intra-operative or post-operative hemorrhage in thoracic vessel sealing.

Safety and usability of an endo staple line reinforcement device for pulmonary resections.

Background: Pulmonary resection can present technical challenges for surgeons due to the dissection and closure of tissues, which vary in thickness and elastic properties, occasionally leading to prolonged air leaks. Staple line reinforcements (SLRs) are widely utilized tools for fortifying the stability and integrity of closures in thoracic surgery, however, materials available and ease of use for both surgeon and scrub nurse have been suboptimal. A novel "click-and-go" device pre-loaded with bioabsorbable buttress material was recently developed, the Echelon Endopath SLR (ESLR, Ethicon, Inc., Cincinnati, OH, USA). This prospective study examines the safety and efficacy of this novel device in lung resections. Methods: Adult surgical candidates undergoing primary pulmonary resection (both open and thoracoscopic) where the ESLR would be used were enrolled. Exclusion included reoperation/revision in same anatomical location, hypersensitivity to polyglactin or related products, and body mass index (BMI) ≥46.0 kg/m2. The primary endpoint assessed the incidence of specific device-related adverse events (AEs): prolonged air leak and empyema. Additional endpoints included number of devices replaced during surgery due to slippage or bunching, and surgeon-reported usability responses. Data was summarized for AEs deemed device-related and usability questionnaire responses. Results: A total of 131 subjects were included in the primary endpoint analysis data set with 120 subjects completing the study (91.6%). The mean age at consent was 62.8±12.0 years and 55.7% were female. The most common primary indication for the procedure was malignancy 61.1%, and primary non-malignant lung disease (non-chronic obstructive pulmonary disease) 12.2%. Common procedures performed were wedge resection (58.0%) and lobectomy (34.4%). There were zero reported device-specific/-related AEs which counted toward the primary endpoint. Responses from a usability questionnaire found all surgeons (100.0%) reported the ease of setup was superior to previous devices utilized. Surgeons expressed greater confidence in the buttress material of the ESLR than that of previous SLR devices (strongly agree 88.9%; slightly agree 11.1%). Most also felt that there was less wastage with the click-and-go ESLR (strongly agree 77.8%, slightly agree 11.1%, neutral 11.1%). Conclusions: The ESLR device demonstrates safe and effective performance in this post-market study of specific thoracic procedures. Furthermore, surgeons found this was easier to use.

Feasibility and Efficacy of Magnetic Sphincter Augmentation for the Management of Gastroesophageal Reflux Disease Post-Sleeve Gastrectomy for Obesity.

BACKGROUND: Patients with medically intractable GERD after laparoscopic sleeve gastrectomy (LSG) have limited surgical options. Fundoplication is difficult post-LSG. Roux-en-Y gastric bypass may be used as a conversion procedure but is more invasive with potential for serious complications. Magnetic sphincter augmentation (MSA) is a less invasive GERD treatment alternative. The objective of this study was to assess safety and efficacy outcomes of MSA after LSG. METHODS: The primary outcome of this observational, multicenter, single-arm prospective study was the rate of serious device and/or procedure-related adverse events (AEs). The efficacy of the LINX device was measured comparing baseline to 12-month post-implant reductions in distal acid exposure, GERD-HRQL score, and average daily PPI usage. RESULTS: Thirty subjects who underwent MSA implantation were followed 12 months post-implant. No unanticipated adverse device effects were observed. There were two adverse events deemed serious (dysphagia, pain, 6.7%) which resolved without sequelae. GERD-HRQL scores showed significant improvement (80.8%, P < 0.001), and reduction in daily PPI usage was seen (95.8%, P < 0.001). Forty-four percent of subjects demonstrated normalization or > = 50% reduction of total distal acid exposure time (baseline 16.2%, 12 months 11%; P = 0.038). CONCLUSIONS: Post-LSG, MSA showed an overall improvement of GERD symptoms, and reduction in PPI use with explants within anticipated range along with improvement in distal esophageal acid exposure time.

K-RAS Mutant Gene Found in Pancreatic Juice Activated Chromatin From Peri-ampullary Adenocarcinomas.

External pancreatic duct stents inserted after resection of pancreatic head tumors provide unique access to pancreatic juice analysis of genetic and metabolic components that may be associated with peri-ampullary tumor progression. For this pilot study, portal venous blood and pancreatic juice samples were collected from 17 patients who underwent pancreaticoduodenectomy for peri-ampullary tumors. Portal vein circulating tumor cells (CTC) were isolated by high-speed fluorescence-activated cell sorting (FACS) and analyzed by quantitative reverse transcription polymerase chain reaction (RT-PCR) for K-RAS exon 12 mutant gene expression (K-RASmut). DNA, chromatin, and histone acetylated active chromatin were isolated from pancreatic juice samples by chromatin immunoprecipitation (ChIP) and the presence of K-RASmut and other cancer-related gene sequences detected by quantitative polymerase chain reaction (PCR) and ChIP-Seq. Mutated K-RAS gene was detectable in activated chromatin in pancreatic juice secreted after surgical resection of pancreatic, ampullary and bile duct carcinomas and directly correlated with the number of CTC found in the portal venous blood (P = .0453). ChIP and ChIP-Seq detected acetylated chromatin in peri-ampullary cancer patient juice containing candidate chromatin loci, including RET proto-oncogene, not found in similar analysis of pancreatic juice from non-malignant ampullary adenoma. The presence of active tumor cell chromatin in pancreatic juice after surgical removal of the primary tumor suggests that viable cancer cells either remain or re-emerge from the remnant pancreatic duct, providing a potential source for tumor recurrence and cancer relapse. Therefore, epigenetic analysis for active chromatin in pancreatic juice and portal venous blood CTC may be useful for prognostic risk stratification and potential identification of molecular targets in peri-ampullary cancers.

Mycotic Superior Mesenteric Artery Aneurysm: Case Report and Literature Review.

Superior mesenteric artery (SMA) aneurysm is the third most common splanchnic artery aneurysm. A 73-year-old woman presented with a minimally symptomatic SMA aneurysm, which was resected by laparoscopic surgical technique. The patient recovered quickly and remained well after 8 months of follow-up. This case report and literature review presents a rare mycotic aneurysm that developed in the SMA. Laparoscopic surgery can be a useful technique for the treatment of mycotic SMA aneurysms.

T1R2 receptor-mediated glucose sensing in the upper intestine potentiates glucose absorption through activation of local regulatory pathways.

OBJECTIVE: Beyond the taste buds, sweet taste receptors (STRs; T1R2/T1R3) are also expressed on enteroendocrine cells, where they regulate gut peptide secretion but their regulatory function within the intestine is largely unknown. METHODS: Using T1R2-knock out (KO) mice we evaluated the role of STRs in the regulation of glucose absorption in vivo and in intact intestinal preparations ex vivo. RESULTS: STR signaling enhances the rate of intestinal glucose absorption specifically in response to the ingestion of a glucose-rich meal. These effects were mediated specifically by the regulation of GLUT2 transporter trafficking to the apical membrane of enterocytes. GLUT2 translocation and glucose transport was dependent and specific to glucagon-like peptide 2 (GLP-2) secretion and subsequent intestinal neuronal activation. Finally, high-sucrose feeding in wild-type mice induced rapid downregulation of STRs in the gut, leading to reduced glucose absorption. CONCLUSIONS: Our studies demonstrate that STRs have evolved to modulate glucose absorption via the regulation of its transport and to prevent the development of exacerbated hyperglycemia due to the ingestion of high levels of sugars.

Pancreatic and bile duct cancer circulating tumor cells (CTC) form immune-resistant multi-cell type clusters in the portal venous circulation.

Circulating tumor cells (CTC) enter the blood from many carcinomas and represent a likely source of metastatic dissemination. In contrast to the peripheral circulation, KRAS mutation- positive CTC thrive in the portal venous blood of patients with pancreatic ductal adenocarcinoma (PDAC). To analyze the essential interactions that contribute to carcinoma CTC growth and immune resistance, portal venous blood was collected during pancreatico-duodenectomy in 41 patients with peri-ampullary pathologies (PDAC = 11; ampullary adenocarcinoma (AA) = 15; distal cholangiocarcinoma (CC) = 6; IPMN = 7; non-malignant pancreatitis = 2). FACS-isolated cell populations from the portal circulation were reconstituted ex vivo using mixed cell reaction cultures (MCR). During the first 48hr, PDAC, AA, and CC patient CTC were all highly proliferative (mean 1.7 hr/cell cycle, 61.5% ± 20% growing cells) and resistant to apoptosis (mean 39% ±  25% apoptotic cells). PDAC CTC proliferation and resistance to T cell cytotoxicity were decreased among patients who received pre-operative chemotherapy (p = 0.0019, p = 0.0191, respectively). After 7 days in culture, CTC from PDAC, CC, and AA patients recruited multiple immune cell types, including CD105 + CD14 + myeloid fibroblasts, to organize into spheroid-like clusters. It was only in PDAC and CC-derived MCR that cluster formation promoted CTC survival, growth, and fibroblast differentiation. FACS depletion of CTC or myeloid fibroblast cells eliminated cluster network formation, and re-introduction of these cell populations reconstituted such ability. Our findings suggest that PDAC and CC CTC survival within the portal venous circulation is supported by their interactions with immune cells within multi-cell type clusters that could represent vectors of local recurrence and metastatic progression.

Age as a prognostic indicator for adjuvant therapy in patients who underwent pancreatic resections for cancer.

PURPOSE: In pancreatic cancer, the greatest increase in survival is attained by surgical resection followed by adjuvant chemotherapy. Although surgical complications and functional status are recognized as independent factors for halting adjuvant therapy in patients that undergo pancreatic resections, other elements may play a role in deciding which patients get treated postoperatively. Here we determined demographic and clinical characteristics of patients receiving adjuvant chemotherapy, with the primary intent to investigate if age alone affects rates of adjuvant therapy. METHODS/MATERIALS: National Cancer Database (NCDB) was queried for patients that underwent surgery for pancreatic cancer. Groups were divided into: adjuvant chemotherapy (n=17,924) and no adjuvant chemotherapy (n=12,947). Basic demographics and treatment characteristics were analyzed. Age was compared with an independent means test; other comparisons used Chi-square test of independence. RESULTS: There was a statistical difference in age (adjuvant therapy 64.86±9.89 vs. no therapy 67.78±11.22, p<0.001), insurance type, facility type, and cancer stage for patients that received adjuvant therapy and those that did not. Average age of patients not receiving chemotherapy was significantly older at each pathologic stage. Subset analysis of patients treated with chemotherapy showed that the majority of patients received single agent regimens (62%), at an average of 59days following surgery, and at academic cancer programs (52%). CONCLUSIONS: Regardless of postoperative complications and functional status, age alone appears to affect rates of adjuvant therapy in patients with resected pancreatic cancer. Older patients should be offered tailored regimens that would allow them to complete the intended extent of treatment.

Routine versus selective upper gastrointestinal contrast series after omental patch repair for gastric or duodenal perforation.

BACKGROUND: There are no guidelines on the routine or selective use of contrast upper gastrointestinal series (UGI) after omental patch repair (OPR) of a gastric (GP) or duodenal perforation (DP). This study aims to elucidate whether the use of selective versus routine contrast study will lead to worse clinical outcomes. METHODS: A retrospective analysis of 115 (n = 115) patients with OPR of GP or DP was performed. Data were obtained from seven Florida Hospital campuses. Patients aged 18 and older from 2006 to 2016 were identified by ICD9 billing information. Patients were divided into two groups: UGI and no UGI. The UGI group was subdivided into selective versus routine. A selective UGI was defined as one or more of the following after post-operative day 3: WBC >12,000, peritonitis, fever >100.4 F, tachycardia >110 bpm on three or more assessments, and any UGI performed after POD 7. Perioperative symptoms, perforation location, size, abdominal contamination, laparoscopic or open, leak detection, length of stay, mortality, and reoperation within 2 weeks were also examined. RESULTS: No differences between the UGI group and non-UGI group relating to preoperative symptoms, leak detection, death, and reoperation rate were revealed. Differences in length of stay were found to be statistically significant with the UGI group and non-UGI at a median of 15.5 and 8 days, respectively. In the UGI subgroup, 20 of the 29 patients received selective studies. There were no statistical differences identified in leak detection, death, and reoperation. CONCLUSIONS: Rates of leak detection, reoperation, and death in patients with GP or DP repaired with omental patch utilizing an UGI study were not statistically significant. An increased length of stay was observed within the UGI group. There was no advantage demonstrated between a selective versus routine UGI; therefore, the use of selective UGI should be based upon clinical indications.

Portal Venous Blood Circulation Supports Immunosuppressive Environment and Pancreatic Cancer Circulating Tumor Cell Activation.

OBJECTIVES: Aggressive spread and liver metastases are predominant features of pancreatic ductal adenocarcinoma (PDAC). This study investigates activation of PDAC circulating tumor cells (CTC) and immunosuppression in the portal venous system. METHODS: Portal venous and peripheral blood were collected during pancreaticoduodenectomy from patients with PDAC (n = 21) or other non-PDAC pancreatic conditions (n = 20). Circulating tumor cells were isolated by fluorescence-activated cell sorting and characterized for messenger RNA (mRNA) expression and acetylated chromatin encoding K-RAS exon 12 mutation (K-RASmut). Myeloid-derived suppressor cells (MDSC) were identified using flow cytometry. RESULTS: Pancreatic ductal adenocarcinoma K-RASmut mRNA expression in portal venous blood CTC was significantly elevated compared with preoperative and postoperative peripheral blood (P = 0.0123 and P = 0.0246, respectively). There was no significant variation in total CTC numbers between portal and peripheral blood.Portal venous M-MDSC were elevated compared with peripheral blood in PDAC patients (P = 0.0065). M-MDSC increases correlated with K-RASmut mRNA-expressing CTC present in PDAC portal blood (P < 0.0001). CONCLUSIONS: Association of MDSC with active CTC in portal venous blood may support immunosuppression within the portal venous circulation to promote PDAC CTC survival.

Acupuncture for ovulation induction in polycystic ovary syndrome: a randomized controlled trial.

Acupuncture has been demonstrated to improve menstrual frequency and to decrease circulating testosterone in women with polycystic ovary syndrome (PCOS). Our aim was to investigate whether acupuncture affects ovulation frequency and to understand the underlying mechanisms of any such effect by analyzing LH and sex steroid secretion in women with PCOS. This prospective, randomized, controlled clinical trial was conducted between June 2009 and September 2010. Thirty-two women with PCOS were randomized to receive either acupuncture with manual and low-frequency electrical stimulation or to meetings with a physical therapist twice a week for 10-13 wk. Main outcome measures were changes in LH secretion patterns from baseline to after 10-13 wk of treatment and ovulation frequency during the treatment period. Secondary outcomes were changes in the secretion of sex steroids, anti-Müllerian hormone, inhibin B, and serum cortisol. Ovulation frequency during treatment was higher in the acupuncture group than in the control group. After 10-13 wk of intervention, circulating levels of estrone, estrone sulfate, estradiol, dehydroepiandrosterone, dehydroepiandrosterone sulfate, androstenedione, testosterone, free testosterone, dihydrotestosterone, androsterone glucuronide, androstane-3α,17ß-diol-3-glucuronide, and androstane-3α,17ß-diol-17-glucuronide decreased within the acupuncture group and were significantly lower than in the control group for all of these except androstenedione. We conclude that repeated acupuncture treatments resulted in higher ovulation frequency in lean/overweight women with PCOS and were more effective than just meeting with the therapist. Ovarian and adrenal sex steroid serum levels were reduced with no effect on LH secretion.

Assessment of endogenous growth hormone pulsatility in gelded yearling horses using deconvolution analysis.

HYPOTHESIS/OBJECTIVES: Defining normal Growth Hormone (GH) secretory dynamics in the horse is necessary to understand altered GH dynamics related to issues like welfare and disease. ANIMALS AND METHODS: Twelve healthy yearlings and two mature Standardbreds were used to quantify GH secretion. Endogenous GH half-life was determined after administration of 1.0 µg/kg BW GH releasing hormone (GHRH). Exogenous GH half-life was determined after administration of 20 µg/kg BW recombinant equine GH (reGH) with and without suppression of endogenous GH secretion by somatostatin infusion (50 µg/m(2)/h). Pulse detection algorithm (Cluster) as well as deconvolution analysis was used to quantify GH secretory dynamics based on GH concentration-time series sampled every 5 min from 22:00 till 06:00 h. In addition, reproducibility, impact of sampling frequency and influence of altering initial GH half-life on parameter estimates were studied. RESULTS: Mean endogenous GH half-life of 17.7 ± 4.4 (SD) min and mean exogenous half-life of 26.0 ± 2.9 min were found. The mean number of GH secretion peaks in 8 h was 12 ± 3.2. Ninety-nine percent of the total amount of GH secreted occurred in pulses, basal secretion was 0.012 ± 0.014 µg/L/min and half-life was 8.9 ± 2.6 min. Compared with a 5-min sampling frequency, 20- and 30-min sampling underestimated the number of secretory events by 45% and 100%, respectively. CONCLUSIONS: The deconvolution model used was valid to GH time series in Standardbreds. As in man, the equine pituitary gland secretes GH in volleys consisting of multiple secretory bursts, without measurable intervening tonic secretion. The required GH sampling frequency for the horse should be around 3 min. CLINICAL RELEVANCE: Defining normal GH secretory dynamics in the horse will make it possible to detect alterations in the GH axis due to pathophysiologic mechanisms as well as abuse of reGH.

Validation of a deconvolution procedure (AutoDecon) for identification and characterization of fasting insulin secretory bursts.

BACKGROUND: Insulin secretion is pulsatile, and has been shown to be altered in both physiologic and pathophysiologic conditions. The identification and characterization of such pulses have been challenging, partially because of the low concentrations of insulin during fasting and its short half-life. Existing pulse detection algorithms used to identify insulin pulses either cannot separate hormone pulses into their secretory burst and clearance components, or have been limited by both the subjective nature of initial peak selection and a lack of statistical verification of bursts. METHODS: To address these concerns, we have developed AutoDecon, a novel deconvolution computer program. RESULTS: AutoDecon was applied to synthetic insulin concentration-time series modeled on data derived from normal fasting subjects and simulated to reflect several sampling frequencies, sampling durations, and assay replicates. The operating characteristics of AutoDecon were compared to those obtained with Cluster, a standard pulse detection algorithm. AutoDecon performed considerably better than Cluster with regard to sensitivity and secretory burst detection rates for true positives, false positives, and false negatives. As expected, given the short half-life of insulin, sampling at 30-second intervals is required for optimal analytical results. The choice of sampling duration is more flexible and relates to the number of replicates assayed. CONCLUSION: AutoDecon represents a viable alternative to standard pulse detection algorithms for the appraisal of fasting insulin pulsatility.

AutoDecon: a robust numerical method for the quantification of pulsatile events.

This work presents a new approach to the analysis of aperiodic pulsatile heteroscedastic time-series data, specifically hormone pulsatility. We have utilized growth hormone (GH) concentration time-series data as an example for the utilization of this new algorithm. While many previously published approaches used for the analysis of GH pulsatility are both subjective and cumbersome to use, AutoDecon is a nonsubjective, standardized, and completely automated algorithm. We have employed computer simulations to evaluate the true-positive, the false-positive, the false-negative, and the sensitivity percentages of several of the routinely employed algorithms when applied to GH concentration time-series data. Based on these simulations, it was concluded that this new algorithm provides a substantial improvement over the previous methods. This novel method has many direct applications in addition to hormone pulsatility, for example, to time-domain fluorescence lifetime measurements, as the mathematical forms that describe these experimental systems are both convolution integrals.

Signal-response modeling of partial hormone feedback networks.

BACKGROUND: Endocrine feedback control networks are typically complex and contain multiple hormones, pools, and compartments. The hormones themselves commonly interact via multiple pathways and targets within the networks, and a complete description of such relationships may involve hundreds of parameters. In addition, it is often difficult, if not impossible, to collect experimental data pertaining to every component within the network. Therefore, the complete simultaneous analysis of such networks is challenging. Nevertheless, an understanding of these networks is critical for furthering our knowledge of hormonal regulation in both physiologic and pathophysiologic conditions. METHODS: We propose a novel approach for the analysis of dose-response relationships of subsets of hormonal feedback networks. The algorithm and signal-response quantification (SRQuant) software is based on convolution integrals, and tests whether several discretely measured input signals can be individually delayed, spread in time, transformed, combined, and discretely convolved with an elimination function to predict the time course of the concentration of an output hormone. Signal-response quantification is applied to examples from the endocrine literature to demonstrate its applicability to the analysis of the different endocrine networks. RESULTS: In one example, SRQuant determines the dose-response relationship by which one hormone regulates another, highlighting its advantages over other traditional methods. In a second example, for the first time (to the best of our knowledge), we show that the secretion of glucagon may be jointly controlled by the ß and the δ cells. CONCLUSION: We have developed a novel convolution integral-based approach, algorithm, and software (SRQuant) for the analysis of dose-response relationships within subsets of complex endocrine feedback control networks.

AutoDecon, a deconvolution algorithm for identification and characterization of luteinizing hormone secretory bursts: description and validation using synthetic data.

Hormone signaling is often pulsatile, and multiparameter deconvolution procedures have long been used to identify and characterize secretory events. However, the existing programs have serious limitations, including the subjective nature of initial peak selection, lack of statistical verification of presumed bursts, and user-unfriendliness of the application. Here we describe a novel deconvolution program, AutoDecon, which addresses these concerns. We validate AutoDecon for application to serum luteinizing hormone (LH) concentration time series using synthetic data mimicking real data from normal women and then comparing the performance of AutoDecon with the performance of the widely employed hormone pulsatility analysis program Cluster. The sensitivity of AutoDecon is higher than that of Cluster ( approximately 96% vs. 80%, P=0.001). However, Cluster had a lower false-positive detection rate than did AutoDecon (6% vs. 1%, P=0.001). Further analysis demonstrated that the pulsatility parameters recovered by AutoDecon were indistinguishable from those characterizing the synthetic data and that sampling at 5- or 10-min intervals was optimal for maximizing the sensitivity rates for LH. Accordingly, AutoDecon presents a viable nonsubjective alternative to previous pulse detection algorithms for the analysis of LH data. It is applicable to other pulsatile hormone concentration time series and many other pulsatile phenomena. The software is free and downloadable at http://mljohnson.pharm.virginia.edu/home.html.

Amplification of pulsatile glucagon counterregulation by switch-off of alpha-cell-suppressing signals in streptozotocin-treated rats.

Glucagon counterregulation (GCR) is a key protection against hypoglycemia that is compromised in diabetes via an unknown mechanism. To test the hypothesis that alpha-cell-inhibiting signals that are switched off during hypoglycemia amplify GCR, we studied streptozotocin (STZ)-treated male Wistar rats and estimated the effect on GCR of intrapancreatic infusion and termination during hypoglycemia of saline, insulin, and somatostatin. Times 10 min before and 45 min after the switch-off were analyzed. Insulin and somatostatin, but not saline, switch-off significantly increased the glucagon levels (P = 0.03), and the fold increases relative to baseline were significantly higher (P < 0.05) in the insulin and somatostatin groups vs. the saline group. The peak concentrations were also higher in the insulin (368 pg/ml) and somatostatin (228 pg/ml) groups vs. the saline (114 pg/ml) group (P < 0.05). GCR was pulsatile in most animals, indicating a feedback regulation. After the switch-off, the number of secretory events and the total pulsatile production were lower in the saline group vs. the insulin and somatostatin groups (P < 0.05), indicating enhancement of glucagon pulsatile activity by insulin and somatostatin compared with saline. Network modeling analysis demonstrates that reciprocal interactions between alpha- and delta-cells can explain the amplification by interpreting the GCR as a rebound response to the switch-off. The model justifies experimental designs to further study the intrapancreatic network in relation to the switch-off phenomenon. The results of this proof-of-concept interdisciplinary study support the hypothesis that GCR develops as a rebound pulsatile response of the intrapancreatic endocrine feedback network to switch-off of alpha-cell-inhibiting islet signals.

Novel ghrelin assays provide evidence for independent regulation of ghrelin acylation and secretion in healthy young men.

CONTEXT: Ghrelin, an acylated peptide hormone secreted from the gut, regulates appetite and metabolism. Elucidating its pattern of secretion in the fed and fasted states is important in the face of the obesity epidemic. OBJECTIVE: Our objective was to examine changes in circulating ghrelin and des-acyl ghrelin in response to meals and fasting using newly developed two-site sandwich assays and sample preservation protocols to allow specific detection of full-length forms. DESIGN: Ten-minute sampling was done for 26.5 h during a fed admission with standardized meals and on a separate admission during the final 24 h of a 61.5-h fast and continuing for 2.5 h after terminating the fast. SETTING: The study was conducted at the University Hospital General Clinical Research Center. PARTICIPANTS: Eight male volunteers participated, mean +/- sd age 24.5 +/- 3.7 yr and body mass index 24 +/- 2.1 kg/m(2). MAIN OUTCOME MEASURES: Ten-minute sampling profiles were assessed for ghrelin and des-acyl ghrelin, fed and fasting. RESULTS: In the fed state, ghrelin and des-acyl ghrelin showed similar dynamics; both were sharply inhibited by meals and increased at night. During fasting, ghrelin decreased to nadir levels seen postprandially, and des-acyl ghrelin remained near peak levels seen preprandially. Total full-length ghrelin (acyl plus des-acyl) levels remained unchanged. CONCLUSIONS: Meals inhibited secretion of both ghrelin and des-acyl ghrelin, yet long-term fasting inhibited acylation but not total secretion. Acylation may be regulated independently of secretion by nutrient availability in the gut or by esterases that cleave the acyl group. These studies highlight the importance of stringent conditions for sample collection and evaluation of full-length ghrelin and des-acyl ghrelin using specific two-site assays.

Evidence for acyl-ghrelin modulation of growth hormone release in the fed state.

CONTEXT: The timing and frequency of GH secretory episodes is regulated by GHRH and somatostatin. This study provides evidence for amplification of these GH pulses by endogenous acyl-ghrelin. DESIGN: Blood was sampled every 10 min for 26.5 h during a fed admission with standardized meals and also during the final 24 h of a 61.5-h fast. GH secretion profiles were derived from deconvolution of 10-min sampling data, and full-length acyl-ghrelin levels were measured using a newly developed two-site sandwich assay. SETTING: The study was conducted at a university hospital general clinical research center. PARTICIPANTS: Participants included eight men with mean (+/- sd) age 24.5 +/- 3.7 yr (body mass index 24 +/- 2.1 kg/m(2)). RESULTS: Correlations were computed between amplitudes of individual GH secretory events and the average acyl-ghrelin concentration in the 60-min interval preceding each GH burst. In the fed state, the peak correlations were positive for all subjects and significantly higher than in the fasting state when acyl-ghrelin levels declined [mean (+/- sem): 0.7 (0.04) vs. 0.29 (0.08), P = 0.017]. In addition, long-term fasting was associated with an increase in the GH secretory pulse mass and amplitude but not frequency [fed vs. fasting pulse mass: 0.22 (0.05) vs. 0.44 (0.06) microg/liter, P = 0.002; amplitude: 5.2 (1.3) vs. 11.8 (1.9) microg/liter/min, P = 0.034; pulses per 24 h: 19.4 (0.5) vs. 22.0 (1.4), P = 0.1]. CONCLUSION: Our data support the hypothesis that under normal conditions in subjects given regular meals endogenous acyl-ghrelin acts to increase the amplitude of GH pulses.

Identifying small pulsatile signals within noisy data: a fluorescence application.

One of the most challenging scientific data analysis quandaries is the identification of small intermittent irregularly spaced pulsatile signals in the presence of large amounts of heteroscedastic experimental measurement uncertainties. We present an application of the use of AutoDecon to a typical fluorescence and/or spectroscopic data sampling paradigm, which is to detect a single fluorophore in the presence of high background emission. Our calculations demonstrate that single events can be reliably detected by AutoDecon with a signal-to-noise ratio of 3/20. AutoDecon was originally developed for the analysis of pulsatile hormone-concentration time-series data measured in human serum. However, AutoDecon has applications within many other scientific fields, such as fluorescence measurements where the goal is to count single analyte molecules in clinical samples.