Progression from biochemical leak to pancreatic fistula after distal pancreatectomy. Don't cry over spilt amylase

BACKGROUND

Postoperative pancreatic fistula (POPF) is a frequent complication after distal pancreatectomy (DP), but its upgrading from biochemical leak (BL) still represents an unexplored phenomenon. This study aims at identifying risk factors of the clinical evolution from BL to grade-B POPF after DP.

METHODS

Patients who underwent DP between 2015 and 2019 and who developed either BL (n = 89,56%) or BL upgraded to late B fistula (LB) after postoperative day 5 (n = 71,44%) were included. Preoperative, surgical, postoperative predictors were compared between the two groups.

RESULTS

Patients with LB were significantly older (61 vs 56 years, P < 0.025) and received neoadjuvant chemotherapy more frequently (22.5% vs 8.5%,P = 0.017). Extended lymphadenectomy (52.8% vs 31.0%,P = 0.006), longer operative times (OT) (307 vs 250 min,P = 0.002), greater estimated blood loss (250 vs 150 ml, P = 0.021), and the appearance of purulent fluid in surgical drains (58.4% vs 21.1%; P < 0.001) were more frequently observed in LB group. Only purulent fluid in surgical drains and longer OT were confirmed as independent predictors of BL clinical progression.

CONCLUSIONS

Purulent fluid from surgical drains should be suspicious of BL upgrading. Frail patients undergoing longer interventions may represent key targets of mitigation strategies to minimize the magnitude of an incipient fistula and its increase in morbidity.

Sporadic non-functioning pancreatic neuroendocrine tumours: multicentre analysis

BACKGROUND

Outcomes after surgery for sporadic pancreatic neuroendocrine neoplasms (Pan-NENs) were evaluated.

METHODS

This multicentre study included patients who underwent radical pancreatic resection for sporadic non-functioning Pan-NENs. In survival analysis, the risk of mortality in this cohort was analysed in relation to that of the matched healthy Italian population. Relative survival (RS) was calculated as the rate between observed and expected survival. Factors related to RS were investigated using multivariable modelling.

RESULTS

Among 964 patients who had pancreatic resection for sporadic non-functioning Pan-NENs, the overall RS rate was 91.8 (95 per cent c.i. 81.5 to 96.5) per cent. 2019 WHO grade (hazard ratio (HR) 5.75 (s.e. 4.63); P = 0.030) and European Neuroendocrine Tumour Society (ENETS) TNM stage (6.73 (3.61); P < 0.001) were independent predictors of RS. The probability of a normal lifespan for patients with G1, G2, G3 Pan-NENS, and pancreatic neuroendocrine carcinomas (Pan-NECs) was 96.7, 54.8, 0, and 0 per cent respectively. The probability of a normal lifespan was 99.8, 99.3, 79.8, and 46.8 per cent for those with stage I, II, III, and IV disease respectively. The overall disease-free RS rate was 73.6 (65.2 to 79.5) per cent. 2019 WHO grade (HR 2.10 (0.19); P < 0.001) and ENETS TNM stage (HR 2.50 (0.24); P < 0.001) significantly influenced disease-free RS. The probability of disease-free survival was 93.2, 84.9, 45.2, and 6.8 per cent for patients with stage I, II, III, and IV disease, and 91.9, 45.2, 9.4, and 0.7 per cent for those with G1, G2, G3 Pan-NENS, and Pan-NECs, respectively.

CONCLUSION

A surgical approach seems without benefit for Pan-NECs, and unnecessary for small G1 sporadic Pan-NENs. Surgery alone may be insufficient for stage III-IV and G3 Pan-NENs.

Portal vein resection during pancreaticoduodenectomy for pancreatic neuroendocrine tumors. An international multicenter comparative study

BACKGROUND

The role of portal vein resection for pancreatic cancer is well established but not for pancreatic neuroendocrine neoplasms. Evidence from studies providing information on long-term outcome after venous resection in pancreatic neuroendocrine neoplasms patients is lacking.

METHODS

This is a multicenter retrospective cohort study comparing pancreaticoduodenectomy with vein resection with standard pancreaticoduodenectomy in patients with pancreatic neuroendocrine neoplasms. The primary endpoint was to evaluate the long-term survival in both groups. Progression-free survival and overall survival were calculated using the method of Kaplan and Meier, but a propensity score-matched cohort analysis was subsequently performed to remove selection bias and improve homogeneity. The secondary outcome was Clavien-Dindo ≥3.

RESULTS

Sixty-one (11%) patients underwent pancreaticoduodenectomy with vein resection and 480 patients pancreaticoduodenectomy. Five (1%) perioperative deaths were recorded in the pancreaticoduodenectomy group, and postoperative clinically relevant morbidity rates were similar in the 2 groups (pancreaticoduodenectomy with vein resection 48% vs pancreaticoduodenectomy 33%). In the initial survival analysis, pancreaticoduodenectomy with vein resection was associated with worse 3-year progression-free survival (48% pancreaticoduodenectomy with vein resection vs 83% pancreaticoduodenectomy; P < .01) and 5-year overall survival (67% pancreaticoduodenectomy with vein resection vs 91% pancreaticoduodenectomy). After propensity score matching, no significant difference was found in both 3-year progression-free survival (49% pancreaticoduodenectomy with vein resection vs 59% pancreaticoduodenectomy; P = .14) and 5-year overall survival (71% pancreaticoduodenectomy with vein resection vs 69% pancreaticoduodenectomy; P = .98).

CONCLUSION

This study demonstrates no significant difference in perioperative risk with a similar overall survival between pancreaticoduodenectomy and pancreaticoduodenectomy with vein resection. Tumor involvement of the superior mesenteric/portal vein axis should not preclude surgical resection in patients with locally advanced pancreatic neuroendocrine neoplasms.

Prognostic Role of Examined and Positive Lymph Nodes after Distal Pancreatectomy for Non-Functioning Neuroendocrine Neoplasms

BACKGROUND

The most appropriate nodal staging system for non-functioning pancreatic neuroendocrine tumours (NF-PanNETs) remains unclear. Despite some evidence is available for pancreaticoduodenectomy, the adequate nodal staging is still unknown for distal pancreatectomy (DP). The aim of the present study was to evaluate the prognostic impact of the number of positive lymph nodes (PLNs) after DP for NF-PanNETs and to define the minimal number of lymph nodes to be harvested for an appropriate nodal staging.

METHODS

Data were retrospectively collected from patients who underwent DP with curative intent (R0-R1) for sporadic well-differentiated NF-PanNETs in 4 European high-volume centres. NF-PanNETs with nodal involvement (N+) were subclassified into N1 (1-3 PLNs) and N2 (4 or more PLNs). Univariate and multivariate analyses of disease-free survival (DFS) were performed.

RESULTS

Of 271 patients in the study, 62 (23%) had nodal involvement (N+). A higher probability of N+ was associated with the following factors: grading, resection margin status, perineural and microvascular invasion, and the number of examined lymph nodes. Three-year DFS rate for N0, N1, and N2 patients was 92, 72, and 50%, respectively (p < 0.001). At multivariate analysis, independent predictors of DFS were grading, T stage, presence of necrosis, and nodal status. For patients with ≥12 examined/resected lymph nodes, the N status remained a significant predictor of disease recurrence (p < 0.001), while it failed to predict recurrence in patients with <12 lymph nodes examined/resected (p = 0.116).

CONCLUSIONS

A minimal number of 12 nodes should be harvested in case of DP for NF-PanNET for an appropriate nodal staging. The number of positive lymph nodes is an independent predictor of DFS after DP for NF-PanNET, and the N0/N1/N2 nodal classification seems to be more relevant than the current N0/N+ staging.

Management of Asymptomatic Sporadic Nonfunctioning Pancreatic Neuroendocrine Neoplasms (ASPEN) ≤2 cm: Study Protocol for a Prospective Observational Study

Introduction: The optimal treatment for small, asymptomatic, nonfunctioning pancreatic neuroendocrine neoplasms (NF-PanNEN) is still controversial. European Neuroendocrine Tumor Society (ENETS) guidelines recommend a watchful strategy for asymptomatic NF-PanNEN <2 cm of diameter. Several retrospective series demonstrated that a non-operative management is safe and feasible, but no prospective studies are available. Aim of the ASPEN study is to evaluate the optimal management of asymptomatic NF-PanNEN ≤2 cm comparing active surveillance and surgery.

Methods: ASPEN is a prospective international observational multicentric cohort study supported by ENETS. The study is registered in ClinicalTrials.gov with the identification code NCT03084770. Based on the incidence of NF-PanNEN the number of expected patients to be enrolled in the ASPEN study is 1,000 during the study period (2017–2022). Primary endpoint is disease/progression-free survival, defined as the time from study enrolment to the first evidence of progression (active surveillance group) or recurrence of disease (surgery group) or death from disease. Inclusion criteria are: age >18 years, the presence of asymptomatic sporadic NF-PanNEN ≤2 cm proven by a positive fine-needle aspiration (FNA) or by the presence of a measurable nodule on high-quality imaging techniques that is positive at ⁶⁸Gallium DOTATOC-PET scan.

Conclusion: The ASPEN study is designed to investigate if an active surveillance of asymptomatic NF-PanNEN ≤2 cm is safe as compared to surgical approach.

Endoscopic ultrasound-guided fine-needle aspiration for the diagnosis and grading of pancreatic neuroendocrine tumors: a retrospective analysis of 110 cases

BACKGROUND

Data on the reliability of the Ki-67 index and grading calculations from endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) of pancreatic neuroendocrine tumors (PanNETs) are controversial. We aimed to assess the accuracy of these data compared with histology.

METHODS

Cytological analysis from EUS-FNA in patients with suspected PanNETs (n = 110) were compared with resection samples at a single institution. A minimum of 2000 cells were considered to be adequate for grading. Correlation and agreement between cytology and histology in grading and Ki-67 values, respectively, were investigated. Secondary outcomes included the diagnostic performance of EUS-FNA.

RESULTS

EUS-FNA samples were adequate for PanNET diagnosis and PanNET grading in 98/110 (89.1 %) and 77/110 (70.0 %) patients, respectively; thus, 77 samples were adequate for comparing cytology vs. histology. There were 67 (62.0 %), 40 (36.4 %), and 1 (0.9 %) patients with a final diagnosis of G1, G2, and G3 tumors, respectively. EUS-FNA grading was concordant with surgical pathology in 81.8 % of patients; under- and overgrading occurred in 15.6 % and 2.6 %, respectively. The overall level of agreement for grading was moderate (Cohen's κ = 0.59, 95 % confidence interval [CI] 0.34 - 0.78). Spearman's rho for Ki-67 in tumors ≤ 20 mm and > 20 mm was strong and moderate, respectively (rho = 0.68, 95 %CI 0.47 - 0.83; rho = 0.59, 95 %CI 0.35 - 0.75). The Bland - Altman plot showed that the Ki-67 values were comparable and reproducible between the two measurements.

CONCLUSIONS

Although they were not available for a significant number of patients, grading and Ki-67 values from cytology correlated with histology moderately to strongly.

Seasonal variations in pancreatic surgery outcome A retrospective time-trend analysis of 2748 Whipple procedures

Background

Observing cyclic patterns in surgical outcome is a common experience. We aimed to measure this phenomenon and to hypothesize possible causes using the experience of a high-volume pancreatic surgery department.

Methods

Outcomes of 2748 patients who underwent a Whipple procedure at a single high-volume center from January 2000 to December 2018 were retrospectively analyzed. Three different hypotheses were tested: the effect of climate changes, the “July effect” and the effect of vacations.

Results

Clavien-Dindo ≥ 3 morbidity was similar during warm vs. cold months (22.5% vs. 19.8%, p = 0.104) and at the beginning of activity of new trainees vs. the rest of the year (23.5 vs. 22.5%, p = 0.757). Patients operated when a high percentage of staff is on vacation showed an increased Clavien-Dindo ≥ 3 morbidity (22.3 vs. 18.5%, p = 0.022), but similar mortality (2.3 vs. 1.8%, p = 0.553). The surgical waiting list was also significantly longer during these periods (37 vs. 27 days, p = 0.037). Being operated in such a period of the year was an independent predictor of severe morbidity (OR 1.271, CI 95% 1.086–1.638, p = 0.031).

Conclusion

Being operated when more staff is on vacation significantly affects severe morbidity rate. Future healthcare system policies should prevent the relative shortage of resources during these periods.

Pattern of disease recurrence and treatment after surgery for nonfunctioning well-differentiated pancreatic neuroendocrine tumors

BACKGROUND

The risk of recurrence after curative surgery for pancreatic neuroendocrine tumors is reported to be between 10% and 30%. Among the available locoregional and systemic treatments, there are no specific recommendations regarding the best option for treating recurrent disease. The aims of this study were to evaluate the pattern of recurrence after surgery performed with curative intent for nonfunctioning pancreatic neuroendocrine tumors and to analyze the impact of treatment on disease progression.

METHODS

All patients submitted to curative surgery for sporadic, well-differentiated, nonfunctioning pancreatic neuroendocrine tumors at 2 Italian centers between 2001 and 2018, with evidence of disease recurrence during follow-up, were included (n = 46).

RESULTS

The most frequent type of recurrence was distant metastases (n = 38, 83%), located in the liver in 100% of cases, whereas 8 patients (17%) had an isolated local recurrence. Therapy for first disease recurrence included both locoregional (n = 14) and systemic treatments (n = 32). A second disease recurrence/progression occurred in 28 patients (61%). Patients who underwent systemic treatment after the first disease recurrence had better progression-free survival (1-year progression-free survival 78%) compared with those submitted to a locoregional procedure (1-year progression-free survival 50%; P = .007). Independent predictors of shortened progression-free survival after the first disease recurrence were the type of treatment (locoregional, hazard ratio 4.452, P = .001), the presence of necrosis (hazard ratio 2.732, P = .022) and age (>60 year, hazard ratio 2.494, P = .040).

CONCLUSION

Upfront locoregional treatment of the first recurrence of nonfunctioning pancreatic neuroendocrine tumors after curative surgery should be avoided in favor of systemic therapy.

Outcomes of Primary Chemotherapy for Borderline Resectable and Locally Advanced Pancreatic Ductal Adenocarcinoma

Importance

Chemotherapy is the recommended induction strategy in borderline resectable and locally advanced pancreatic ductal adenocarcinoma. However, the associated results on an intention-to-treat basis are poorly understood.

Objective

To investigate pragmatically the treatment compliance, conversion to surgery, and survival outcomes of patients with borderline resectable and locally advanced pancreatic ductal adenocarcinoma undergoing primary chemotherapy.

Design, Setting, and Participants

This prospective study took place in a national referral center for pancreatic diseases in Italy. Consecutive patients with borderline resectable and locally advanced pancreatic ductal adenocarcinoma were enrolled at the time of diagnosis (January 2013 through December 2015) and followed up to June 2018.

Exposures

The chemotherapy regimen, assigned based on multidisciplinary evaluation, was delivered either at a hub center or at spoke centers. By convention, primary chemotherapy was considered completed after 6 months. After restaging, surgical candidates were selected based on radiologic and biochemical response. All surgeries were carried out at the hub center.

Main Outcomes and Measures

Rates of receipt and completion of chemotherapy, rates of conversion to surgery, and disease-specific survival.

Results

Of 680 patients, 267 (39.3%) had borderline resectable and 413 (60.7%) had locally advanced pancreatic ductal adenocarcinoma. Overall, 66 patients (9.7%) were lost to follow-up. The rate of chemotherapy receipt was 92.9% (n = 570). The chemotherapeutic regimens most commonly used included FOLFIRINOX (fluorouracil, leucovorin, oxaliplatin, and irinotecan) (260 [45.6%]) and gemcitabine plus nanoparticle albumin-bound-paclitaxel (123 [21.6%]). Nineteen patients (3.3%) receiving chemotherapy died within 6 months, mainly for disease progression. The treatment completion rate was 71.6% (408 of 570). The overall rate of resection was 15.1% (93 of 614) (borderline resectable, 60 of 249 [24.1%]; locally advanced, 33 of 365 [9%]; resection:exploration ratio, 63.3%). Independent predictors of resection were age, borderline resectable disease, chemotherapy completion, radiologic response, and biochemical response. The median survival for the whole cohort was 12.8 (95% CI, 11.7-13.9) months. Factors independently associated with survival were completion of chemotherapy, receipt of complementary radiation therapy, and resection. In patients who underwent resection, the median survival was 35.4 (95% CI, 27.0-43.7) months for initially borderline resectable and 41.8 (95% CI, 27.5-56.1) months for initially locally advanced disease. No pretreatment and posttreatment factors were associated with survival after pancreatectomy.

Conclusions and Relevance

This pragmatic observational cohort study with an intention-to-treat design provides real-world evidence of outcomes associated with the most current primary chemotherapy regimens used for borderline resectable and locally advanced pancreatic ductal adenocarcinoma.

Long term outcome after minimally invasive and open Warshaw and Kimura techniques for spleen-preserving distal pancreatectomy: International multicenter retrospective study

BACKGROUND

The Warshaw (WT) and the Kimura (KT) techniques are both used for open or minimally invasive (MI) spleen preserving distal pancreatectomy (SPDP). Multicenter studies on long-term outcome of WT and KT are lacking.

METHODS

Multicenter retrospective study with transversal follow-up moment, including patients who underwent SPDP from 2000 to 2017 at three high-volume centers in Italy and the Netherlands. Primary endpoint was the incidence of short and long term complications. Patients without regular follow-up were interviewed about symptoms and complications.

RESULTS

In total, 164 patients were enrolled, 55 WT (33.5%) and 109 kT (66.5%), of which 95 (57.9%) MI. There was no 30-day mortality (0%).The only significant difference in short-term outcome was more delayed gastric emptying (DGE) after WT (9.1% vs 1.8%, p = 0.043). MI-SPDP was associated with less blood loss (median 150 vs 250 ml, respectively, p < 0.001), less DGE (0% vs 10%, p = 0.002), less abdominal abscesses (8.4% vs 18.4%, p = 0.03) and less splenic infarctions (3.2% vs. 13%, p = 0.042), than open SPDP. Long-term follow-up (median 41 months) was available for 111 patients (67.7%) of whom 18 (16.2%) had an SPDP-related long-term sequela, mostly perigastric varices (n = 11, 9%) but without differences between WT and KT. Less long-term sequelae were reported after MI as compared to open SPDP (12.5% vs 21.2%, p = 0.032).

CONCLUSIONS

In this international retrospective study, the WT and KT had comparable short- and long-term outcomes. If a KT does not seem feasible during SPDP, a WT is recommended, rather than performing a splenectomy. MI-SPDP was associated with less short- and long term complications as compared to an open SPDP.

Patterns of Recurrence after Resection for Pancreatic Neuroendocrine Tumors: Who, When, and Where?

BACKGROUND/AIMS

Pancreatic neuroendocrine tumors (pan-NENs) represent an increasingly common indication for pancreatic resection, but there are few data regarding possible recurrence after surgery. The aim of the study was to describe the frequency, timing, and patterns of recurrence after resection for pan-NENs with consequent implications for postoperative follow-up.

METHODS

We performed a retrospective analysis of pan-NENs resected between 1990 and 2015 at The Pancreas Institute, University of Verona Hospital Trust. Predictors of recurrence were assessed. Survival analysis was conducted using the Kaplan-Meier and conditional survival (CS) methods.

RESULTS

The cohort consisted of 487 patients with a median follow-up of 71 months. Recurrence developed in 12.3%: 54 (11.1%) liver metastases, 11 (2.3%) local recurrence, 10 (2.1%) nodal recurrence, and 8 (1.6%) metastases in other organs. Thirty-one (6.4%) died due to disease recurrence. Size > 21 mm, G3 grade, nodal metastasis, and vascular infiltration were independent predictors of overall recurrence. Recurrence occurred either during the first year of follow-up (n = 9), or after 10 years (n = 4). CS analysis revealed that nonfunctioning G1 pan-NEN ≤20 mm without nodal metastasis or vascular invasion had a negligible risk of developing recurrence. In the present series, after 5 years of follow-up without developing recurrence, tumor recurrence occurred only in the form of liver metastases.

CONCLUSIONS

Recurrence of pan-NENs is rare and is predicted by tumor size, nodal metastasis, grading, and vascular invasion. Patients with G1 pan-NEN without nodal metastasis and vascular invasion may be considered cured by surgery. After 5 years without recurrence, follow-up should focus on excluding the development of liver metastases.

Are Cystic Pancreatic Neuroendocrine Tumors an Indolent Entity Results from a Single-Center Surgical Series

INTRODUCTION

Cystic pancreatic neuroendocrine tumors (CPanNETs) represent an uncommon variant of pancreatic neuroendocrine tumors (PanNETs). Due to their rarity, there is a lack of knowledge with regard to clinical features and postoperative outcome.

METHODS

The prospectively maintained surgical database of a high-volume institution was queried, and 46 resected CPanNETs were detected from 1988 to 2015. Clinical, demographic, and pathological features and survival outcomes of CPanNETs were described and matched with a population of 92 solid PanNETs (SPanNETs) for comparison.

RESULTS

CPanNETs accounted for 7.8% of the overall number of resected PanNETs (46/587). CPanNETs were mostly sporadic (n = 42, 91%) and nonfunctioning (39%). Two functioning CPanNETs were detected (4.3%), and they were 2 gastrinomas. The median tumor diameter was 30 mm (range 10-120). All tumors were well differentiated, with 38 (82.6%) G1 and 8 (17.4%) G2 tumors. Overall, no CPanNET showed a Ki-67 >5%. A correct preoperative diagnosis of a CPanNET was made in half of the cases. After a median follow-up of >70 months, the 5- and 10-year overall survival of resected CPanNETs was 93.8 and 62.5%, respectively, compared to 92.7 and 84.6% for SPanNETs (p > 0.05). The 5- and 10-year disease-free survival rates were 94.5 and 88.2% for CPanNETs and 81.8 and 78.9% for SPanNETs, respectively (p > 0.05).

CONCLUSION

In the setting of a surgical cohort, CPanNETs are rare, nonfunctional, and well-differentiated neoplasms. After surgical resection, they share the excellent outcome of their well-differentiated solid counterparts for both survival and recurrence.

Neoadjuvant Therapy Versus Upfront Resection for Pancreatic Cancer: The Actual Spectrum and Clinical Burden of Postoperative Complications

BACKGROUND

Neoadjuvant therapy (NAT) is used for borderline-resectable or locally advanced pancreatic cancer (PDAC) and exhibits promising results in terms of pathological outcomes. However, little is known about its effect on surgical complications.

METHODS

We analyzed 445 pancreatic resections for PDAC from 2014 to 2016 at The Pancreas Institute, Verona University Hospital. The Modified Accordion Severity Grading System and average complication burden (ACB) were used to compare patients treated with NAT with patients who underwent upfront surgery (UFS).

RESULTS

Of 305 pancreaticoduodenectomies (PD), patients treated with NAT (n = 99) had less pancreatic fistula (POPF, 9.1% vs. 15.6%, p = 0.05) without grade C cases, but grade B ACB was increased (0.28 for NAT vs. 0.24 for UFS, p = 0.05). The postpancreatectomy hemorrhage (PPH) rate was lower in the NAT group (9.1% vs. 14.6%, p = 0.02), but ACB grades B (0.37 for NAT vs. 0.26 for UFS, p = 0.03) and C (0.43 for NAT vs. 0.29 for UFS, p = 0.05) were increased. Delayed gastric emptying (DGE) was increased in NAT cases (15.2% vs. 8.3%, p = 0.04), with higher grade C ACB (0.43 for NAT vs. 0.29 for UFS, p = 0.03). Of 94 distal pancreatectomies (DP), NAT patients (n = 26) developed more grade C POPF (11.5% vs. 1.5%, p = 0.04) and DGE (11.5% vs. 2.9%, p = 0.01) without differences in ACB.

CONCLUSIONS

Patients undergoing PD for PDAC after NAT exhibited reduced incidence of POPF and PPH but increased incidence of DGE compared with patients treated with UFS. Among patients developing postoperative complications after PD, those receiving NAT were associated with increased clinical burden.

Radioguided Parathyroidectomy with Portable Mini Gamma-Camera for the Treatment of Primary Hyperparathyroidism

Background. A proper localisation of pathological parathyroid glands is essential for a minimally invasive approach in the surgical treatment of primary hyperparathyroidism (PHP). The recent introduction of portable mini gamma-cameras (pMGCs) enabled intraoperative scintigraphic scanning. The aim of our study is to evaluate the efficacy of this new method and compare it with the preoperative localisation surveys. Methods. 20 patients were studied; they were evaluated preoperatively by neck ultrasound and (99mm)Tc-sestaMIBI-scintigraphy and intraoperatively with the pMGC IP Guardian 2. The results obtained from the three evaluations were compared. Results. The pMGC presented a sensitivity of 95%, a specificity of 98.89%, and a diagnostic accuracy of 98.18%, which were higher than those of preoperative ultrasound (sensitivity 55%; specificity 95%; diagnostic accuracy 87%) and scintigraphy with (99mm)Tc-sestaMIBI (sensitivity 73.68%; specificity 96.05%; diagnostic accuracy 91.58%). Conclusions. The pMGC can be used effectively as an intraoperative method to find the correct location of the pathological parathyroid glands. The pMGC is more reliable than the currently used preoperative and intraoperative localisation techniques.

Crystal structure of a novel germination protease from spores of Bacillus megaterium: structural arrangement and zymogen activation

The DNA in the core of spores of Bacillus species is saturated with a group of small, acid-soluble proteins (SASP) that protect DNA from a variety of harsh treatments and play a major role in spore resistance and long-term spore survival. During spore germination, SASPs are rapidly degraded to amino acids and this degradation is initiated by a sequence-specific protease called germination protease (GPR), which exhibits no obvious mechanistic or amino acid sequence similarity to any known class of proteases. GPR is synthesized during sporulation as an inactive tetrameric zymogen termed P(46), which later autoprocesses to a smaller form termed P(41), which is active only during spore germination. Here, we report the crystal structure of P(46) from Bacillus megaterium at 3.0 A resolution and the fact that P(46) monomer adopts a novel fold. The asymmetric unit contains two P(46) monomers and the functional tetramer is a dimer of dimers, with an approximately 9 A channel in the center of the tetramer. Analysis of the P(46) structure and site-directed mutagenesis studies have provided some insight into the mechanism of zymogen activation as well as the zymogen's lack of activity and the inactivity of P(41) in the mature spore.

Crystallization and preliminary diffraction studies of a truncated form of a novel protease from spores of Bacillus megaterium

During germination of spores of Bacillus species, a novel protease termed GPR initiates the degradation of a group of small acid-soluble spore proteins which protect the dormant spore's DNA from damage. Trypsin digestion of the zymogen of B. megaterium GPR removes approximately 15 kDa from the C-terminal end of the 46 kDa zymogen subunit, leaving a 30 kDa subunit. Single crystals of this truncated form of GPR have been obtained by the vapor-diffusion method using PEG 4000 as a precipitating agent. The crystals belong to the monoclinic space group P2(1), with unit-cell parameters a = 67.99, b = 105.34, c = 108.63 A, beta = 95.68 degrees. The cryofrozen crystals diffract X-rays to about 3.3 A using synchrotron radiation.

Structural studies of a novel germination protease from spores of Bacillus megaterium

The amino acid sequence-specific protease (termed GPR) in the bacterium Bacillus megaterium initiates the rapid degradation of small, acid-soluble spore proteins during the germination of spores of this organism. GPR is synthesized during spore formation as an inactive zymogen termed P46, which later autoprocesses to a smaller active form termed P41, which acts during spore germination. However, GPR exhibits no obvious mechanistic or amino acid sequence similarity to any of the known classes of proteases. To initiate the determination of the mechanisms of P46 to P41 conversion, P46 inactivity, and P41 catalysis, B. megaterium GPR has been overexpressed in Escherichia coli and purified to homogeneity by anion-exchange and size exclusion chromatography, and crystals of both P46 and P41 have been obtained by the vapor diffusion method. P46 crystals diffracted x rays to 3.5 A but the crystals of P41 diffracted x rays to only 6.5 A. A native x-ray diffraction data set of P46 has been collected; the unit cell parameters are a = b = 76.8, c = 313.1 A, alpha = beta = gamma = 90 degrees; the space group is tetragonal P41212 or P43212. The asymmetric unit contains two monomeric molecules with a crystal volume per unit protein mass of 2. 85 A3/Da and a solvent content of about 57%. An isomorphous heavy atom derivative data set has also been obtained for P46 crystals with potassium dicyanoaurate (I).

Structure and mechanism of action of the protease that degrades small, acid-soluble spore proteins during germination of spores of Bacillus species

The germination protease (GPR) of Bacillus megaterium initiates the degradation of small, acid-soluble proteins during spore germination. Trypsin treatment of the 46-kDa GPR zymogen (termed P46) removes an approximately 15-kDa C-terminal domain generating a 30-kDa species (P30) which is stable against further digestion. While P30 is not active, it does autoprocess to a smaller form by cleavage of the same bond cleaved in conversion of P46 to the active 41-kDa form of GPR (P41). Trypsin treatment of P41 cleaves the same bond in the C-terminal part of the protein as is cleaved in the P46-->P30 conversion. While the approximately 29-kDa species generated by trypsin treatment of P41 is active, it is rapidly degraded further by trypsin to small inactive fragments. These results, as well as a thermal melting temperature for P41 which is 13 degreesC lower than that for P46 and the unfolding of P41 at significantly lower concentrations of guanidine hydrochloride than for P46, are further evidence for a difference in tertiary structure between P46 and P41, with P46 presumably having a more compact stable structure. However, circular dichroism spectroscopy revealed no significant difference in the secondary structure content of P46 and P41. The removal of approximately 30% of P46 or P41 without significant loss in enzyme activity localized GPR's catalytic residues to the N-terminal two-thirds of the molecule. This finding, as well as comparison of the amino acid sequences of GPR from three different species, analysis of several site-directed GPR mutants, determination of the metal ion content of purified GPR, and lack of inhibition of P41 by a number of protease inhibitors, suggests that GPR is not a member of a previously described class of protease.

Most of the propeptide is dispensable for stability and autoprocessing of the zymogen of the germination protease of spores of Bacillus species

Loss of 3, 7, or 10 of the amino-terminal 15 residues removed upon autoactivation of the zymogen of the germination protease (GPR), which initiates protein degradation during germination of spores of Bacillus species, did not result in significant changes in (i) the lack of enzymatic activity of the zymogen, (ii) the rate of zymogen autoactivation, or (iii) the unreactivity of the zymogen's single SH group. Removal of 13 amino-terminal residues resulted in a partially active enzyme whose SH group was as reactive as the fully active enzyme. These findings suggest that at least a part of the propeptide blocks access to the enzyme's active site. However, the free propeptide did not inhibit the enzyme.

Crystallization of NAD+ synthetase from Bacillus subtilis

NAD(+)-synthetase is a ubiquitous enzyme catalyzing the last step in the biosynthesis of NAD+. Mutants of NAD+ synthetase with impaired cellular functions have been isolated, indicating a key role for this enzyme in cellular metabolism. Crystals of the enzyme from Bacillus subtilis suitable for x-ray crystallographic investigation have been grown from polyethylene glycol solutions. Investigation on the structural organization of NAD+ synthetase, an enzyme fundamental for NAD+ biosynthesis, and belonging to the recently characterized amidotransferase enzymatic family, will provide more insight into the catalytic mechanism of deamido-NAD+-->NAD+ conversion, a biosynthetic process that is a potential target for the development of antibiotic compounds against Bacillus sp. and related bacteria.

Crystal structure of NH3-dependent NAD+ synthetase from Bacillus subtilis

NAD+ synthetase catalyzes the last step in the biosynthesis of nicotinamide adenine dinucleotide. The three-dimensional structure of NH3-dependent NAD+ synthetase from Bacillus subtilis, in its free form and in complex with ATP, has been solved by X-ray crystallography (at 2.6 and 2.0 angstroms resolution, respectively) using a combination of multiple isomorphous replacement and density modification techniques. The enzyme consists of a tight homodimer with alpha/beta subunit topology. The catalytic site is located at the parallel beta-sheet topological switch point, where one AMP molecule, one pyrophosphate and one Mg2+ ion are observed. Residue Ser46, part of the neighboring 'P-loop', is hydrogen bonded to the pyrophosphate group, and may play a role in promoting the adenylation of deamido-NAD+ during the first step of the catalyzed reaction. The deamido-NAD+ binding site, located at the subunit interface, is occupied by one ATP molecule, pointing towards the catalytic center. A conserved structural fingerprint of the catalytic site, comprising Ser46, is very reminiscent of a related protein region observed in glutamine-dependent GMP synthetase, supporting the hypothesis that NAD+ synthetase belongs to the newly discovered family of 'N-type' ATP pyrophosphatases.

Role of FlgM in sigma D-dependent gene expression in Bacillus subtilis

The alternative sigma factor sigma D directs transcription of a number of genes involved in chemotaxis, motility, and autolysis in Bacillus subtilis (sigmaD regulon). The activity of SigD is probably in contrast to that of FlgM, which acts as an antisigma factor and is responsible for the coupling of late flagellar gene expression to the assembly of the hook-basal body complex. We have characterized the effects of an in-frame deletion mutation of flgM. By transcriptional fusions to lacZ, we have shown that in FlgM-depleted strains there is a 10-fold increase in transcription from three different sigmaD-dependent promoters, i.e., Phag, PmotAB, and PfliDST. The number of flagellar filaments was only slightly increased by the flgM mutation. Overexpression of FlgM from a multicopy plasmid under control of the isopropyl-beta-D-thiogalactopyranoside-inducible spac promoter drastically reduced the level of transcription from the hag promoter. On the basis of these results, we conclude that, as in Salmonella typhimurium, FlgM inhibits the activity of SigD, but an additional element is involved in determining the number of flagellar filaments.

The outB gene of Bacillus subtilis codes for NAD synthetase

The outB gene of Bacillus subtilis is involved in spore germination and outgrowth and is essential for growth. The OutB protein was obtained by expression in Escherichia coli and purified to apparent homogeneity. Here we report experiments showing that OutB is a NH3-dependent NAD synthetase, the enzyme that catalyzes the final reaction in the biosynthesis of NAD. The enzyme is composed of two identical subunits of 30,240 Da and is NH3-dependent, whereas glutamine is inefficient as an amide donor. The NAD synthetase is highly resistant to heat, with a half-time of inactivation at 100 degrees C of 13 min. A mutant NAD synthetase was purified from a B. subtilis strain temperature-sensitive during spore germination and outgrowth. The mutant enzyme was 200 times less active than the wild-type one, with a lower temperature optimum and a non-hyperbolic kinetic versus NH4+. The time course of synthesis of OutB showed that synthesis of the enzyme started during germination and outgrowth, and reached the highest level at the end of exponential growth. The enzyme could be recovered from dormant spores.