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1.
Pediatr Blood Cancer ; : e31259, 2024 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-39118249

RESUMO

INTRODUCTION: Precision in surgical documentation is essential to avoid miscommunication and errors in patient care. Synoptic operative reports are more precise than narrative operative reports, however they have not been widely implemented in pediatric surgical oncology. To assess the need for implementation of synoptic operative reports in pediatric surgical oncology, we examined the completeness of narrative operative reports in patients undergoing resection of Wilms tumor. METHODS: We conducted a retrospective review of narrative operative reports for resection of Wilms tumor at a single pediatric oncology center from January 2022 through July 2023. Primary outcomes were the presence or absence of 11 key operative report components. Inclusion rates were calculated as simple percentages. Unilateral and bilateral operations were considered. RESULTS: Thirty-five narrative reports for Wilms tumor resection were included. The most consistently documented operative report components were estimated blood loss, indication for surgery, intraoperative complications, and specimen naming (100% documentation rates). Documentation of lymph node sampling was present in 94.3% of reports. The least consistently documented components were assessment of intraoperative tumor spillage, completeness of resection, metastatic disease, and assessment of vascular involvement (each ≤40% documentation rate). All 11 key components were documented in three reports. CONCLUSIONS: Even at a large tertiary pediatric oncology referral center, narrative operative reports for pediatric Wilms tumor resection were found to be frequently missing important components of surgical documentation. Often, these were omissions of negative findings. Utilization of synoptic operative reports may be able to reduce these gaps.

2.
J Neuroimaging ; 2024 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-39175143

RESUMO

BACKGROUND AND PURPOSE: The 3-dimensional cranial nerve imaging (CRANI) sequence may assist visualization of anatomical details of extraforaminal cranial nerves and aid in clinical diagnosis and preoperative planning. In this study, we investigated the feasibility of using a combined CRANI and magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) imaging protocol to comprehensively identify trigeminal nerve projections. METHOD: We evaluated the detection of distal regions of three branches of the ophthalmic nerve (V1), three branches of the maxillary nerve (V2), and five branches of the mandibular nerve (V3) in seven healthy adult subjects, with and without contrast injection. Nerve branches were rated on a 5-point scale by three observers. Interobserver reliability was studied using weighted kappa statistics and percentage agreement. RESULTS: Among V1 and V2 branches, the frontal nerve and infraorbital nerve were most successfully identified (average rating of 3.9, agreement >80%) in precontrast MPRAGE images. In V3 branches, lingual and inferior alveolar nerves were most successfully identified (average rating of 3.9, agreement >80%) in precontrast CRANI images, with an excellent average rating. In all cases except one, interobserver reliability was rated good to excellent. The buccal nerve was the only branch with a low average interobserver rating. Gadolinium contrast did not improve nerve segment visualization in our study. This may relate to the specific anatomic regions assessed, gadolinium dose, postcontrast image timing, and lack of pathology. CONCLUSION: A combined CRANI and MPRAGE protocol can be combined to visualize distal branches of V1, V2, and V3 and has potential for clinical use.

3.
Pediatr Blood Cancer ; : e31269, 2024 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-39138619

RESUMO

BACKGROUND: Documentation of intraoperative oncologic findings varies greatly across narrative operative reports (NRs). An international panel of childhood cancer experts recently developed a synoptic operative report (SR) for childhood cancer surgeries. The aim of this study was to compare the documentation of critical intraoperative findings in NRs versus SRs. METHODS: A single-center retrospective review of all surgical resections of primary solid tumors at our pediatric oncology center was conducted from June 2023 to March 2024, after an institutional SR was piloted from October 2023 onwards. Data collected included the presence or absence of six components included in standard pediatric oncology NRs. Inclusion rates were calculated as percentages for each component. Due to the small sample, the Fisher's exact test was used for all hypothesis testing. RESULTS: Seventy primary tumor resections were performed during the study period, as documented by 38 NRs and 32 SRs. All operative reports after October 2023 were SRs. Completeness of tumor resection and specimen naming were consistently documented in NRs (86% and 100%, respectively) and SRs (100% and 100%, respectively). The presence/absence of three components-intraoperative tumor spillage (31%), vascular involvement (31%), and lymph node sampling (26%)-were documented in fewer than a third of the NRs. Documentation of the presence/absence of locoregional spread, intraoperative tumor spillage, vascular involvement, and lymph node sampling was significantly better in SRs than in NRs. CONCLUSION: Adoption of SRs significantly improved the documentation of critical intraoperative findings. Thus, we recommend using SRs in pediatric solid tumor surgery.

4.
Pediatr Blood Cancer ; : e31206, 2024 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-39030929

RESUMO

Central venous access through tunneled central venous catheters (CVCs) are one of the cornerstones of modern oncologic practice in pediatric patients since CVCs provide a reliable access route for the administration of chemotherapy. Establishing best practices for CVC management in children with cancer is essential to optimize care. This article reviews current best practices, including types of devices, their placement, complications, and long-term outcomes. Additionally, nutrition status and nutritional support are also very important determinants of outcomes and care in pediatric surgical oncology patients. We review current nutritional assessment, support, access for enteral and parenteral nutrition delivery, and their complications, mainly from a surgical perspective. Overall, access surgery, whether for CVCs, or for enteral access can be challenging, and best practice guidelines supported by current though limited evidence are necessary to minimize complications and optimize outcomes.

5.
ACS Chem Biol ; 19(1): 69-80, 2024 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-38146215

RESUMO

Bacteria use a diverse range of carbohydrates to generate a profusion of glycans, with amino sugars, such as N-acetylglucosamine (GlcNAc), being prevalent in the cell wall and in many exopolysaccharides. The primary substrate for GlcNAc-containing glycans, UDP-GlcNAc, is the product of the bacterial hexosamine pathway and a key target for bacterial metabolic glycan engineering. Using the strategy of expressing NahK, to circumvent the hexosamine pathway, it is possible to directly feed the analogue of GlcNAc, N-azidoacetylglucosamine (GlcNAz), for metabolic labeling in Escherichia coli. The cytosolic production of UDP-GlcNAz was confirmed by using fluorescence-assisted polyacrylamide gel electrophoresis. The key question of where GlcNAz is incorporated was interrogated by analyzing potential sites including peptidoglycan (PGN), the biofilm-related exopolysaccharide poly-ß-1,6-N-acetylglucosamine (PNAG), lipopolysaccharide (LPS), and the enterobacterial common antigen (ECA). The highest levels of incorporation were observed in PGN with lower levels in PNAG and no observable incorporation in LPS or ECA. The promiscuity of the PNAG synthase (PgaCD) toward UDP-GlcNAz in vitro and the lack of undecaprenyl-pyrophosphoryl-GlcNAz intermediates generated in vivo confirmed the incorporation preferences. The results of this work will guide the future development of carbohydrate-based probes and metabolic engineering strategies.


Assuntos
Escherichia coli , Lipopolissacarídeos , Escherichia coli/metabolismo , Acetilglucosamina/metabolismo , Polissacarídeos Bacterianos , Peptidoglicano , Difosfato de Uridina
7.
Cancers (Basel) ; 15(15)2023 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-37568791

RESUMO

While thyroid nodules are less common in children than in adults, they are more frequently malignant. However, pediatric data are scarce regarding the performance characteristics of imaging and cytopathology classification systems validated to predict the risk of malignancy (ROM) in adults and select those patients who require fine-needle aspiration (FNA) and possibly surgical resection. We retrospectively reviewed the electronic medical records of all patients 18 years of age or younger who underwent thyroid FNA at our institution from 1 July 2015 to 31 May 2022. Based on surgical follow-up from 74 of the 208 FNA cases, we determined the ROM for the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) ultrasound risk stratification system and The Bethesda System for Reporting Thyroid Cytopathology and added our results to those of pediatric cohorts from other institutions already published in the literature. We found the following ROMs for 1458 cases using ACR TI-RADS (TR): TR1. Benign: 2.2%, TR2. Not Suspicious: 9.3%, TR3. Mildly Suspicious: 16.6%, TR4. Moderately Suspicious: 27.0%, and TR5. Highly Suspicious 76.5%; and for 5911 cases using the Bethesda system: Bethesda I. Unsatisfactory: 16.8%, Bethesda II. Benign: 7.2%, Bethesda III: Atypia of Undetermined Significance: 29.6%, Bethesda IV. Follicular Neoplasm: 42.3%, Bethesda V. Suspicious for Malignancy: 90.8%, and Bethesda VI. Malignant: 98.8%. We conclude that ACR TI-RADS levels imply higher ROMs for the pediatric population than the corresponding suggested ROMs for adults, and, in order to avoid missing malignancies, we should consider modifying or altogether abandoning size cutoffs for recommending FNA in children and adolescents whose thyroid glands are smaller than those of adults. The Bethesda categories also imply higher ROMs for pediatric patients compared to adults.

8.
bioRxiv ; 2023 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-37645909

RESUMO

Bacteria use a diverse range of carbohydrates to generate a profusion of glycans, with amino sugars such as N-acetylglucosamine (GlcNAc) being prevalent in the cell wall and in many exopolysaccharides. The primary substrate for GlcNAc-containing glycans, UDP-GlcNAc, is the product of the bacterial hexosamine pathway, and a key target for bacterial metabolic glycan engineering. Using the strategy of expressing NahK, to circumvent the hexosamine pathway, it is possible to directly feed the analogue of GlcNAc, N-azidoacetylglucosamine (GlcNAz), for metabolic labelling in E. coli. The cytosolic production of UDP-GlcNAz was confirmed using fluorescence assisted polyacrylamide gel electrophoresis. The key question of where GlcNAz is incorporated, was interrogated by analyzing potential sites including: peptidoglycan (PGN), the biofilm-related exopolysaccharide poly-ß-1,6-N-acetylglucosamine (PNAG), lipopolysaccharide (LPS) and the enterobacterial common antigen (ECA). The highest levels of incorporation were observed in PGN with lower levels in PNAG and no observable incorporation in LPS or ECA. The promiscuity of the PNAG synthase (PgaCD) towards UDP-GlcNAz in vitro and lack of undecaprenyl-pyrophosphoryl-GlcNAz intermediates generated in vivo confirmed the incorporation preferences. The results of this work will guide the future development of carbohydrate-based probes and metabolic engineering strategies.

9.
Microbiol Spectr ; 11(3): e0029623, 2023 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-37098898

RESUMO

Biosynthesis of the Pel exopolysaccharide in Pseudomonas aeruginosa requires all seven genes of the pelABCDEFG operon. The periplasmic modification enzyme PelA contains a C-terminal deacetylase domain that is necessary for Pel-dependent biofilm formation. Herein, we show that extracellular Pel is not produced by a P. aeruginosa PelA deacetylase mutant. This positions PelA deacetylase activity as an attractive target to prevent Pel-dependent biofilm formation. Using a high-throughput screen (n = 69,360), we identified 56 compounds that potentially inhibit PelA esterase activity, the first enzymatic step in the deacetylase reaction. A secondary biofilm inhibition assay identified methyl 2-(2-pyridinylmethylene) hydrazinecarbodithioate (SK-017154-O) as a specific Pel-dependent biofilm inhibitor. Structure-activity relationship studies identified the thiocarbazate as a necessary functional group and that the pyridyl ring could be replaced with a phenyl substituent (compound 1). Both SK-017154-O and compound 1 inhibit Pel-dependent biofilm formation in Bacillus cereus ATCC 10987, which has a predicted extracellular PelA deacetylase in its pel operon. Michaelis-Menten kinetics determined SK-017154-O to be a noncompetitive inhibitor of PelA, while compound 1 did not directly inhibit PelA esterase activity. Cytotoxicity assays using human lung fibroblast cells showed that compound 1 is less cytotoxic than SK-017154-O. This work provides proof of concept that biofilm exopolysaccharide modification enzymes are important for biofilm formation and can serve as useful antibiofilm targets. IMPORTANCE Present in more than 500 diverse Gram-negative and 900 Gram-positive organisms, the Pel polysaccharide is one of the most phylogenetically widespread biofilm matrix determinants found to date. Partial de-N-acetylation of this α-1,4 linked N-acetylgalactosamine polymer by the carbohydrate modification enzyme PelA is required for Pel-dependent biofilm formation in Pseudomonas aeruginosa and Bacillus cereus. Given this and our observation that extracellular Pel is not produced by a P. aeruginosa PelA deactylase mutant, we developed an enzyme-based high-throughput screen and identified methyl 2-(2-pyridinylmethylene) hydrazinecarbodithioate (SK-017154-O) and its phenyl derivative as specific Pel-dependent biofilm inhibitors. Michaelis-Menten kinetics revealed SK-017154-O is a noncompetitive inhibitor and that its noncytotoxic, phenyl derivative does not directly inhibit P. aeruginosa PelA esterase activity. We provide proof of concept that exopolysaccharide modification enzymes can be targeted with small molecule inhibitors to block Pel-dependent biofilm development in both Gram-negative and Gram-positive bacteria.


Assuntos
Polissacarídeos Bacterianos , Pseudomonas aeruginosa , Humanos , Pseudomonas aeruginosa/genética , Biofilmes , Periplasma , Esterases , Proteínas de Bactérias/genética
10.
J Pediatr Surg ; 57(7): 1315-1320, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35307193

RESUMO

Bias is an inclination or preconceived outlook that favors toward or against an idea, person, or group. It manifests in implicit and explicit ways throughout all aspects and institutions of society. These cognitive shortcuts are often based on stereotypes and can lead to prejudice and discrimination in medicine as they mediate interactions with patients, between providers, and at the institutional level. It is important to understand the drivers and consequences of bias in order to overcome barriers to representation, equity, and inclusion. This paper provides definitions of bias; discusses its manifestations across academic medicine at the institutional and individual levels; and concludes by examining techniques to reduce bias and measure progress. Equity for patients, families, and members of the broader surgical community cannot be achieved without reducing bias and discrimination. We call for action to increase intentional efforts that reduce the influences of bias in healthcare, research, and education, particularly in the field of pediatric surgery.


Assuntos
Preconceito , Especialidades Cirúrgicas , Criança , Humanos
11.
ACS Chem Biol ; 17(11): 3036-3046, 2022 11 18.
Artigo em Inglês | MEDLINE | ID: mdl-35170962

RESUMO

Bacteria require polysaccharides for structure, survival, and virulence. Despite their central role in microbiology, few tools are available to manipulate their production. In E. coli, the glycosyltransferase complex PgaCD produces poly-N-acetylglucosamine (PNAG), an extracellular matrix polysaccharide required for biofilm formation. We report that C6-substituted (H, F, N3, SH, NH2) UDP-GlcNAc substrate analogues are inhibitors of PgaCD. In vitro, the inhibitors cause PNAG chain termination, consistent with the mechanism of PNAG polymerization from the nonreducing terminus. In vivo, expression of the GlcNAc-1-kinase NahK in E. coli provided a non-native GlcNAc salvage pathway that produced the UDP-GlcNAc analogue inhibitors in situ. The 6-fluoro and 6-deoxy derivatives were potent inhibitors of biofilm formation in the transformed strain, providing a tool to manipulate this key exopolysaccharide. Characterization of the UDP-GlcNAc pool and quantification of PNAG generation support PNAG termination as the primary in vivo mechanism of biofilm inhibition by 6-fluoro UDP-GlcNAc.


Assuntos
Acetilglucosamina , Escherichia coli , Polimerização , Biofilmes , Difosfato de Uridina
12.
Elife ; 112022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34986091

RESUMO

Cholesterol is a major component of the cell membrane and commonly regulates membrane protein function. Here, we investigate how cholesterol modulates the conformational equilibria and signaling of the adenosine A2A receptor (A2AR) in reconstituted phospholipid nanodiscs. This model system conveniently excludes possible effects arising from cholesterol-induced phase separation or receptor oligomerization and focuses on the question of allostery. GTP hydrolysis assays show that cholesterol weakly enhances the basal signaling of A2AR while decreasing the agonist EC50. Fluorine nuclear magnetic resonance (19F NMR) spectroscopy shows that this enhancement arises from an increase in the receptor's active state population and a G-protein-bound precoupled state. 19F NMR of fluorinated cholesterol analogs reveals transient interactions with A2AR, indicating a lack of high-affinity binding or direct allosteric modulation. The combined results suggest that the observed allosteric effects are largely indirect and originate from cholesterol-mediated changes in membrane properties, as shown by membrane fluidity measurements and high-pressure NMR.


Assuntos
Regulação Alostérica/efeitos dos fármacos , Colesterol/metabolismo , Receptor A2A de Adenosina/química , Animais , Escherichia coli , Espectroscopia de Ressonância Magnética , Saccharomycetales , Células Sf9 , Spodoptera
13.
Surgery ; 170(5): 1474-1480, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34092374

RESUMO

BACKGROUND: Research shows improved safety and treatment outcomes for patients undergoing pancreaticoduodenectomy at high-volume centers. Regionalization of pancreaticoduodenectomy to high-volume urban centers can result in unintended negative consequences for rural patients and communities. This report examines outcomes after pancreaticoduodenectomy performed at a rural hospital and compares them with national standards. METHODS: A prospectively maintained database of pancreatic operations performed at a rural tertiary hospital was queried. Demographic and clinical information for patients undergoing pancreaticoduodenectomy (2007-2019) was analyzed. Primary outcomes were the rates of patient mortality and morbidity. Secondary outcomes were readmission rates, indications, and associations with clinical variables. RESULTS: We included 118 patients in our study. There were 41 postoperative complications (34.7%), including 1 death (0.9%). The 90-day readmission rate was 24.6%. The most common indication for readmission was deep space infection (n = 7, 24.1%). Patients requiring an intraoperative transfusion were more likely to need hospital readmission (41.4% vs 9.0% of patients without transfusion, P = .016). Patients with postoperative complications required readmission more frequently (51.7% vs 29.2%, P = .093). These findings are similar to data from urban hospitals. CONCLUSION: Patient safety and surgical outcomes after pancreaticoduodenectomy performed in appropriately resourced rural hospitals can be comparable with national standards. Safely treating rural patients near their home benefits patients and their communities.


Assuntos
Hospitais com Alto Volume de Atendimentos/estatística & dados numéricos , Hospitais Rurais/estatística & dados numéricos , Neoplasias Pancreáticas/cirurgia , Pancreaticoduodenectomia/métodos , Complicações Pós-Operatórias/epidemiologia , Idoso , Feminino , Mortalidade Hospitalar/tendências , Humanos , Masculino , Pessoa de Meia-Idade , Morbidade/tendências , Neoplasias Pancreáticas/epidemiologia , Readmissão do Paciente/tendências , Segurança do Paciente , Estudos Retrospectivos , Fatores de Risco , Estados Unidos/epidemiologia
15.
Carbohydr Res ; 495: 108071, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32634644

RESUMO

UDP-sugar analogs are useful for the study of glycosyltransferases and the production of unnatural glycans. The preparation of five UDP-GlcNAc derivatives is reported with 6-deoxy, 6-azido, 6-amino, 6-mercapto, or 6-fluoro substitutions. A concise chemoenzymatic synthesis was developed using the kinase NahK (B. longum JCM1217) and the uridyl transferase GlmU (E. coli K12).


Assuntos
Uridina Difosfato N-Acetilglicosamina/síntese química , Configuração de Carboidratos , Uridina Difosfato N-Acetilglicosamina/química
16.
J Surg Educ ; 77(6): 1528-1533, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32457000

RESUMO

OBJECTIVE: In academic settings, surgical residents often serve as co-surgeon in complex operations such as pancreatic resections. These operations are typically performed by fellowship-trained primary surgeons with extensive experience in the field. Our study aimed to evaluate how the participation of general surgery residents in these complex operations affected patient outcomes. Our hypothesis was that resident involvement as co-surgeon would not adversely impact key patient outcomes including complications, readmission, and mortality. DESIGN: A REDCap database of perioperative variables for patients undergoing pancreatic resection was established at a single independent academic medical center. The database was populated via retrospective chart review. Patient demographics, surgical indications, operative time, estimated blood loss, postoperative hospital length of stay, intensive care unit length of stay, postoperative complications, and 30- and 90-day survival for patients with and without cancer were reviewed. We further categorized the data based on the designation of a general surgery resident or a second staff surgeon as co-surgeon in each operation. SETTING: The study was performed at the Marshfield Clinic Health System-Marshfield Medical Center, an independent academic medical center located in central Wisconsin. PARTICIPANTS: Data were abstracted from the medical records of all adult patients (18 years of age and older) who underwent pancreatic resection from 2007 to 2018 (n = 173). RESULTS: 173 pancreatic resections were performed by 8 different primary staff surgeons over 10.5 years. All co-surgeons were either another staff surgeon or a senior-level (postgraduate year 4 or 5) general surgery resident. Perioperative and postoperative patient outcomes were statistically similar in both groups. CONCLUSIONS: Resident involvement as co-surgeon in complex pancreatic resections constituted no increased risk for patients at our institution. Senior residents should continue to operate on these important learning cases under appropriate staff supervision.


Assuntos
Procedimentos Cirúrgicos do Sistema Digestório , Internato e Residência , Cirurgiões , Adolescente , Adulto , Competência Clínica , Humanos , Estudos Retrospectivos , Wisconsin
17.
Orthopedics ; 43(3): 187-190, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32077966

RESUMO

Understanding trends in reimbursement for orthopedic surgery is important, especially considering the changing landscape of health care delivery and payment models. Although other studies have examined these trends using a sampling of common orthopedic procedures compared with non-orthopedic specialties, robust examination across all orthopedic specialties is not available in the current literature. This study aimed to critically analyze the trends in reimbursement in the field of orthopedic surgery. Inflation-adjusted Medicare reimbursement and work relative value units (RVUs) between 2000 and 2016 for more than 200 individual Current Procedural Terminology codes across all major orthopedic subspecialties were analyzed, and inherent value of work RVUs was assessed by dividing reimbursement dollar values by work RVUs annually and tracking the changes. Between 2000 and 2016, reimbursement decreased across all orthopedic subspecialties by an average of 29%, except oncology, which showed a 6% increase. Work RVUs increased by an average of 10%, but the inherent value of work RVUs decreased across all orthopedic subspecialties by an average of 39%. Increased active involvement of orthopedic attending physicians and residents in coding documentation and fee-schedule representation is needed. [Orthopedics. 2020;43(3):187-190.].


Assuntos
Medicare/tendências , Procedimentos Ortopédicos/economia , Mecanismo de Reembolso/tendências , Current Procedural Terminology , Tabela de Remuneração de Serviços/economia , Humanos , Mecanismo de Reembolso/economia , Estados Unidos
18.
Org Lett ; 22(4): 1453-1457, 2020 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-31990566

RESUMO

3,6-Anhydro sugars are common structures in algal polysaccharides and occur in the furanodictine and sauropunol natural products. We have found that treatment of 6-O-tosylpyranosides with tetrabutylammonium fluoride provides a mild, high-yielding synthesis of 3,6-anhydro sugars. Using O-glycoside substrates, 3,6-anhydropyranosides are isolated and the use of N,O-dimethyl hydroxylamine glycosides yields 3,6-anhydrofuranosides. Applying this approach, concise synthetic routes to several 3,6-anhydro sugar natural products are reported, including furanodictine A and sauropunols A-D.

19.
J Pediatr Hematol Oncol ; 42(6): e541-e543, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-31688624

RESUMO

A 2-month-old girl with conjugated hyperbilirubinemia was found at the surgery and by computed tomography to have a large mass originating in the pancreas. Histopathology, molecular testing, and staging evaluations showed this to be a stage 3, MYCN unamplified, intermediate-risk neuroblastoma. The patient had a partial response to risk-stratified chemotherapy. The mass remained unresectable, but the response was sustained after 18 months. Although fewer than a dozen cases of primary pancreatic neuroblastoma have been reported, our experience and a literature review suggest that these tumors can be managed in the same way as similar-risk neuroblastoma of other sites.


Assuntos
Proteína Proto-Oncogênica N-Myc/genética , Neuroblastoma/patologia , Neoplasias Pancreáticas/patologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Feminino , Amplificação de Genes , Humanos , Lactente , Neuroblastoma/tratamento farmacológico , Neuroblastoma/genética , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/genética , Prognóstico
20.
Arch Biochem Biophys ; 666: 116-126, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-30935886

RESUMO

Mandelate racemase (MR) catalyzes the interconversion of the enantiomers of mandelate using a two-base mechanism with Lys 166 acting as the Brønsted base to abstract the α-proton from (S)-mandelate. The resulting intermediate is subsequently re-protonated by the conjugate acid of His 297 to yield (R)-mandelate. The roles of these amino acids are reversed when (R)-mandelate is the substrate. The side chains of Tyr 137, Lys 164, and Lys 166 form a H-bonding network and the proximity of the two ε-NH3+ groups is believed to lower the pKa of Lys 166. We used site-directed mutagenesis, kinetics, and pH-rate studies to explore the roles of Lys 164 (K164 C/M) and Tyr 137 (Y137  L/F/S/T) in catalysis. The efficiency (kcat/Km) was reduced ∼3.5 × 105-fold for K164C MR, relative to wild-type MR, indicating a major role for this residue in catalysis. The efficiency of Y137F MR, however, was reduced only 25-30-fold. pH-Rate profiles (log kcat vs. pH) revealed that substitution of Tyr 137 by Phe increased the kinetic pKa of Lys 166 from 5.88 ±â€¯0.02 to 7.3 ±â€¯0.2. Hence, Tyr 137 plays an important role in facilitating the reduction of the pKa of the Brønsted base Lys 166 by ∼1.4 units. Interestingly, the Phe substitution also increased the kinetic pKa of His 297 from 5.97 ±â€¯0.04 to 7.1 ±â€¯0.1. Thus, the Tyr 137-Lys 164-Lys 166 H-bonding network plays a broader role in modulating the pKa of catalytic residues by influencing the electrostatic character of the entire active site, not only by decreasing the observed pKa value of Lys 166, but also by decreasing the pKa of His 297 by 1.1 units.


Assuntos
Racemases e Epimerases/metabolismo , Sítios de Ligação , Catálise , Concentração de Íons de Hidrogênio , Cinética , Lisina/química , Mutagênese Sítio-Dirigida , Racemases e Epimerases/química , Racemases e Epimerases/genética
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