Impact of arthroscopy on post-procedure intra-articular elbow injections: A cadaveric study.

OBJECTIVE: To determine the influence of arthroscopy and injection volume on post-procedure intra-articular (IA) injection extravasation. STUDY DESIGN: Ex vivo prospective study. SAMPLE POPULATION: A total of 40 paired canine cadaver forelimbs. METHODS: After radiographs and computed tomography (CT) scans with three-dimensional (3D) digital bone model reconstructions, elbows were randomly assigned to the arthroscopy or control group and randomly assigned to receive an IA injection of 2 or 4 mL of contrast. Elbow arthroscopy was performed on assigned specimens, followed by IA injections of contrast in all elbows, and imaging was repeated. 3D digital model volumes were compared. Images were interpreted and scored for extravasation by a radiologist unaware of treatment and volume assignments. RESULTS: Based on CT images and regardless of treatment group, IA injections of 4 mL resulted in a mean extravasation score of 2.25 (SD 0.97) versus 1.55 (SD 1.05) (p = .02) for 2 mL IA injections. The change in 3D model volumes after IA injections was a mean of 13.2 cm3 (SD 5.85) after 4 mL injections, compared to 6.97 cm3 (SD 6.28) (p = .003) after 2 mL injections. On radiographic evaluation, but not CT, the mean extravasation scores were 2.45 (SD 1.15) for the arthroscopy group and 1.25 (SD 0.79) for the control group (p < .001). CONCLUSION: A larger volume of IA injection resulted in higher CT extravasation scores and larger 3D volumes regardless of arthroscopic treatment. CLINICAL SIGNIFICANCE: IA injections performed immediately after arthroscopy resulted in 50% or less extravasation, especially with a smaller IA injection volume.

Association of mesenteric volvulus in police working dogs with and without a prior prophylactic laparoscopic gastropexy.

OBJECTIVE: To evaluate the association of mesenteric volvulus (MV) in New York Police Department police working dogs (PWDs) with and without a prior prophylactic laparoscopic gastropexy (PLG). ANIMALS: 370 PWDs (82 with and 288 without PLG). METHODS: Medical records and surgery and radiology reports were reviewed from 2012 to 2022. Signalment, pertinent history (medical and surgical), gastropexy status, temperament, and training type were recorded. Statistical analysis was used to identify the relationship between prophylactic gastropexy and MV within the patient population. RESULTS: 3 cases of mesenteric volvulus were noted in this patient population. Two (2.4%) of the 82 PWDs that had undergone prophylactic laparoscopic gastropexy developed MV, whereas 1 (0.3%) of the 288 PWDs that had not undergone a gastropexy procedure developed MV. Police working dogs with PLG were estimated to be at 7.2 times greater odds of MV (point estimate OR, 7.18; 95% CI, 0.642 to 80.143); however, the low incidence of MV in this population limited statistical power, and thus this effect did not achieve statistical significance. Evaluation of MV incidence in additional populations of working dogs will allow greater precision in the point estimate. CLINICAL RELEVANCE: Prophylactic gastropexy may be associated with an increased risk for MV. However, patients without prophylactic gastropexy are at risk for gastric dilatation and volvulus, which is more common than MV. Therefore, the authors continue to recommend prophylactic gastropexy to decrease the risk for gastric dilatation and volvulus.

Effect of Nail Grips on Weight Bearing and Limb Function in 30 Dogs 2 Weeks Post Tibial Plateau Leveling Osteotomy.

The objective of this study was to assess the functional outcomes of dogs wearing nail grips in the first 2 weeks following tibial plateau leveling osteotomy (TPLO). Thirty dogs were included (n = 13 nail grips and n = 17 sham grips). Visual lameness scores (VLS), total pressure index (TPI), and client-specific outcome measures (CSOMs) were obtained by blinded observers on day 1 and day 14 +/- 3 post TPLO. CSOMs were also obtained on day 7. There were no differences in VLS and TPI between the treatment and sham group on day 14 (p = 0.44 and p = 0.59, respectively) or at any time point. CSOMs assessing walking on slippery flooring, ability to rise, and consistent use of surgical limb on a 5 min walk were also not different between groups (p = 0.78, p = 0.80, and p = 0.63) at any time point. Nail grips were well tolerated in dogs after orthopedic surgery. This study did not demonstrate a benefit for dogs wearing nail grips during the first two weeks after TPLO; however, further studies are warranted.

Outcome and Prognostic Factors in Cats Undergoing Resection of Intestinal Adenocarcinomas: 58 Cases (2008-2020).

The purpose of this multi-institutional retrospective study was to expand the available data pertaining to pre-operative clinical findings, progression-free and overall survival times, and potential prognostic factors for cats undergoing surgery for intestinal adenocarcinomas. Fifty-eight cats treated over a 12-year period were included in the study. Progression-free and overall survival times were estimated using Kaplan-Meier analyses. Potential prognostic variables were evaluated for associations with progression-free and overall survival using univariate Cox proportional hazards regression analyses. Prior to surgery, the intestinal mass was identified using ultrasonography in 89% of cats in which it was applied; however, imaging findings suggestive of intrathoracic metastases were observed in only 9% of cats. Among 22 cats undergoing ultrasound-guided fine needle aspiration cytology, the results agreed with the results of histopathology in only 10 cats. Discordant results were most commonly related to the presence of marked inflammation in cytology samples, which may have obscured the presence of neoplastic cells. Diffuse intestinal small cell lymphoma was identified as a comorbidity in 5 cats. Resection of the tumor with the objective of obtaining wide surgical margins was performed in each cat. On histopathology, 20 tumors were classified as mucinous adenocarcinoma and 28 were adenocarcinoma not otherwise specified. Intestinal transection site margins were complete in 94% of cats; however, complete mural margins were present in only 15% of cats. Local lymph node metastases were identified in 52% of cats and carcinomatosis was diagnosed in 81% of cats. Disease progression was documented in 32 of the 58 cats (55%). Of these 32 cats, 14 (43%) had local recurrence of the primary intestinal tumor. Median progression-free survival was 203 days (95% CI 130-299 days), and median overall survival time was 284 days (95% CI 200-363 days). Mitotic count was inversely associated with progression-free survival (HR 1.04; 95% CI 1.01-1.07, P = 0.005); however, none of the remaining potential prognostic factors, including administration of adjuvant chemotherapy, were significantly associated with progression-free or overall survival. Feline intestinal adenocarcinoma remains an aggressive and highly fatal disease. Large, randomized controlled clinical trials will be needed to improve the survival prospects for affected cats.

Decortication, thoracic omentalization, and pericardiectomy for treatment of severe fibrosing pleuritis in a cat.

CASE DESCRIPTION: A 5-year-old spayed female domestic shorthair cat was evaluated because of an acute onset of dyspnea and open-mouthed breathing. CLINICAL FINDINGS: Thoracic radiography revealed pleural effusion and signs consistent with restrictive pleuritis, and results of preoperative CT were consistent with diffuse, severe restrictive pleuritis, bilateral pleural effusion, and pulmonary atelectasis. Thoracocentesis yielded a red, turbid fluid that was identified as chylous effusion with chronic inflammation. TREATMENT AND OUTCOME: Exploratory thoracotomy revealed diffuse, severe fibrous adhesions between the mediastinum, heart, lung lobes, and thoracic wall, with a thick fibrous capsule enveloping all lung lobes. Surgical treatment consisted of complete pleural decortication, pericardiectomy, and thoracic omentalization. The cat remained hospitalized for 6 days, receiving oxygen supplementation, multimodal analgesia, and supportive care. Long-term home care consisted of prednisolone administration, rutin supplementation, and provision of a low-fat diet. At recheck examinations 3-, 7-, and 20-weeks postoperatively, the cat remained tachypneic, but was otherwise clinically normal without dyspnea or respiratory distress. Follow-up thoracic radiography revealed improved pulmonary expansion, decreased pleural effusion, and resolved pneumothorax. CLINICAL RELEVANCE: Surgical management of fibrosing pleuritis secondary to idiopathic chylothorax in cats has historically resulted in poor outcomes. This report details the first successful use of complete decortication in the surgical management of severe fibrosing pleuritis in a cat.

Surgical stabilization of traumatic elbow joint luxation and proximal ulnar fracture in a silvery langur (Trachypithecus cristatus).

CASE DESCRIPTION: A 3-year-old 5-kg sexually intact female silvery langur housed in a single-species group at a zoological institution was presented because of acute trauma to the left forelimb. CLINICAL FINDINGS: Radiography of the left forelimb revealed a type II Monteggia fracture (proximal ulnar fracture with cranial displacement and caudal luxation of the radial head). During surgery, disruption of the annular ligament and rupture of the lateral collateral ligament were noted. TREATMENT AND OUTCOME: The langur underwent open reduction and internal fixation of the ulnar fracture and placement of a radioulnar positional screw, a prosthetic lateral collateral ligament, and a temporary hinged type 1A external skeletal fixator. The langur was returned to group housing, underwent behavioral training, and was periodically anesthetized for physical therapy sessions to improve range of motion of the left elbow joint. The external skeletal fixator was removed 4 weeks after surgery, and the radioulnar positional screw was removed 6 weeks after surgery. Three months after surgery, the range of motion of the langur's left elbow joint was considered normal, and the animal returned to normal activity. CLINICAL RELEVANCE: For the captive silvery langur of the present report, surgical stabilization and postoperative management of a type II Monteggia fracture of the left forelimb were successful with recovery of elbow joint function. These techniques may be applied to other captive nonhuman primates, including those that brachiate or are members of social species that must be housed with conspecifics in the postoperative period to maintain group dynamics.

Acellular fish skin grafts for the management of wounds in dogs and cats: 17 cases (2019-2021).

OBJECTIVE: To report the clinical outcomes of the use of acellular fish skin grafts (FSGs) for the management of complex soft tissue wounds of various etiologies in dogs and cats. ANIMALS: 13 dogs and 4 cats with complex wounds treated with FSGs between February 2019 and March 2021. PROCEDURES: Medical records were reviewed for information regarding cause, location, size of the wound, management techniques, complications, and clinical outcomes. RESULTS: In dogs, the number of FSG applications ranged from 1 to 4 (median, 2 graft applications). The time between each application ranged from 4 to 21 days (median, 9.5 days). Time to application of the first FSG ranged from 9 to 210 days (median, 19 days). Wounds closed by second-intention healing following the first fish skin application between 26 and 145 days (median, 71 days; n = 12). In cats, 1 or 2 FSGs were used, and the wounds of 3 of 4 cats healed completely by secondary intention. The wounds of 1 dog and 1 cat did not heal. There were no adverse events attributed to the use of the FSGs. CLINICAL RELEVANCE: For dogs and cats of the present study, complete healing of most wounds occurred with the use of FSGs, the application of which did not require special training, instruments, or bandage materials.

Timing of and risk factors for deep surgical site infection requiring implant removal following canine tibial plateau leveling osteotomy.

OBJECTIVE: To identify demographic risk factors for deep surgical site infection (SSI) requiring tibial plateau leveling osteotomy (TPLO) implant removal and time to implant removal. ANIMALS: Four hundred and thirty-three dogs that underwent a TPLO (144 that developed a deep SSI and required implant removal, 289 that did not). STUDY DESIGN: Retrospective case-control study. METHODS: Records of dogs undergoing implant removal due to a deep SSI after TPLO between 2006 and 2018 at two referral centers were reviewed. These records were frequency-matched by date to dogs undergoing TPLO that did not require implant removal. Multivariable analyses tested associations between demographics and implant removal as well as timing of implant removal. RESULTS: Deep SSI and implant removal occurred in 144 of 4813 (3.0%; 95% CI: 2.5, 3.5) dogs treated with TPLO. Implant removal was performed at a median of 279 days (range 49-2394 days) postoperatively. Male dogs (OR 1.8; 95% CI: 1.2, 2.7) and German Shepherd dogs (GSDs) (OR 7.4; 95% CI: 2.6, 20.5) were associated with plate removal. Earlier TPLO plate removal was associated with GSDs only (HR 2.4; 95% CI: 1.4, 4.1). CONCLUSION: Implant removal due to SSI after TPLO was uncommon, although male dogs and GSDs seemed predisposed to this complication. SIGNIFICANCE: These demographic risk factors can be used to educate owners regarding perioperative management.

Outcomes of dogs undergoing immediate or delayed surgical treatment for gastrointestinal foreign body obstruction: A retrospective study by the Society of Veterinary Soft Tissue Surgery.

OBJECTIVE: To evaluate gastrointestinal injury and outcomes between dogs treated with immediate surgical intervention vs those treated with delayed surgical intervention for gastrointestinal foreign body obstruction (GIFBO). STUDY DESIGN: Retrospective cohort study. SAMPLE POPULATION: Client-owned dogs (n = 855) from five referral hospitals. METHODS: Medical records of dogs in which GIFBO had been diagnosed between 2007 and 2017 were reviewed for preoperative management, timing of surgery, intraoperative findings, postoperative management, outcome, and survival. Surgical intervention was classified as immediate when it occurred within 6 hours of presentation and delayed when it occurred >6 hours after presentation. RESULTS: Outcomes did not differ between dogs treated immediately (n = 584) or over 6 hours after presentation (n = 210). Intestinal necrosis and perforations were more common when surgery was delayed (P = .008; P = .019) but became nonsignificant after controlling for preoperative differences. Risk factors for necrosis and perforations included duration of clinical signs, increased lactate, linear foreign material, and timing of surgery. Enterectomies (P = .004) as well as the duration of surgery (P = .004) and anesthesia (P = .001) were increased when surgery was delayed. Immediate surgery was associated with earlier return to feeding (P = .004) and discharge from the hospital (P < .001); (5%) dogs in each group (n = 33 immediate; n = 11 delayed) either had a negative explore or the foreign body was milked aborally into the colon at the time of surgery. CONCLUSION: Although outcomes were not associated with surgical timing, the unadjusted prevalence of gastrointestinal injury and, thus, the requirement for complex surgical procedures was higher in the delayed group. CLINICAL SIGNIFICANCE: Earlier surgical treatment of stabilized dogs with GIFBO may involve fewer complex procedures and accelerate recovery.

Stable knockout of lanthionine synthase C-like protein-1 (LanCL1) from HeLa cells indicates a role for LanCL1 in redox regulation of deubiquitinating enzymes.

Lanthionine synthase C-like protein-1 (LanCL1) is a glutathione (GSH)-binding protein of uncertain function, widely expressed in mammalian cells. Recent data suggests that LanCL1 has glutathione S-transferase (GST)-like activity, while other reports claim that LanCL1 suppresses mitogen-activated kinase (MAPK) phosphorylation. In the present study, recombinant human LanCL1 had less than 10% the specific activity of GST. When CRISPR-Cas9 was used to stably ablate LanCL1 from HeLa cells, the resulting line was sensitized to H2O2 toxicity. [GSH], [GSSG], [GSH]/[GSSG] and GST activity were unaltered by LanCL1 knockout but glutathione reductase and glutathione peroxidase activities were significantly elevated. LanCL1-KO cells did not differ in basal or H2O2-induced p38-MAPK, ERK p42/p44 or JNK phosphorylation; however, MAPK-targeted transcription factor regulators c-Jun and IκBα were significantly decreased. Because c-Jun and IκBα levels are ubiquitin regulated, experiments addressed the hypothesis that LanCL1 affects ubiquitination dynamics. In the presence of the 26S proteasome inhibitor bortezomib, ubiquitinated proteins accumulated faster in LanCL1-KO cells, suggesting that LanCL1 positively regulates deubiquitination. The activity of ubiquitin C-terminal hydrolase (UCH), a major deubiquitinase (DUB) subclass, was significantly decreased in LanCL1-KO cells while protein levels of A20/TNFAIP3, USP9X and USP10 DUBs were significantly reduced. UCH activity in HeLa cell lysates was lost upon treatment with H2O2 and significantly recovered by addition of recombinant LanCL1 plus GSH. Taken together these data suggest that LanCL1 likely does not act as a GST-like enzyme in vivo, but rather modulates ubiquitin-dependent cell signaling pathways through positive regulation of redox-sensitive DUBs.

Comparison of carbon dioxide laser versus bipolar vessel device for staphylectomy for the treatment of brachycephalic obstructive airway syndrome.

Carbon dioxide (CO2) laser and bipolar vessel sealing device (BSD) are industry standards for soft palate resection. No studies exist to directly compare these 2 techniques in a clinical setting. The purpose of this study was to describe and compare clinical outcomes for dogs that underwent CO2 laser versus BSD staphylectomy. Medical records of brachycephalic dogs that underwent CO2 laser (Group-L) or BSD staphylectomies (Group-B) between September 2013 and September 2017 were reviewed retrospectively. Of 60 dogs that met the inclusion criteria, 26 dogs (43%) were designated Group-L and 34 (57%) Group-B. Techniques did not differ in procedure or anesthetic time (P = 0.52 and P = 0.19, respectively) or major complication rates [intraoperative (P = 1.00), post-operative (P = 0.72), short-term (P = 1.00), and long-term (P = 0.68)]. This study suggests that patient outcomes are similar for dogs undergoing staphylectomy performed by CO2 laser and BSD.

Comparaison du laser au gaz carbonique par rapport au dispositif de coagulation bipolaire lors de la staphylectomie pour le traitement du syndrome de brachycéphalie d'obstruction des voies respiratoires. Le laser au gaz carbonique (CO2) et le dispositif de coagulation bipolaire sont des normes de l'industrie pour la résection du palais mou. Aucune étude n'existe afin de comparer ces deux techniques dans un milieu clinique. Le but de cette étude consistait à décrire et à comparer les résultats cliniques pour les chiens qui ont subi une opération au laser CO2 par rapport à une staphylectomie à l'aide d'un dispositif de coagulation bipolaire. Les dossiers médicaux de chiens brachycéphales qui ont subi des staphylectomies au laser CO2 (Groupe-L) ou à l'aide d'un dispositif de coagulation bipolaire (Groupe-B) entre septembre 2013 et septembre 2017 ont été examinés rétrospectivement. Parmi les 60 chiens qui satisfaisaient aux critères d'inclusion, 26 chiens (43 %) ont été désignés dans le Groupe-L et 34 (57 %) dans le Groupe-B. Les techniques n'ont pas différé pour la durée de l'intervention ou de l'anesthésie (P = 0,52 et P = 0,19, respectivement) ou les taux de complications majeures [intra-opératoires (P = 1,00), postopératoires (P = 0,72), à court terme (P = 1,00) et à long terme (P = 0,68)]. Cette étude suggère que les résultats des patients sont semblables pour les chiens subissant une staphylectomie réalisée par laser au CO2 et à l'aide d'un dispositif de coagulation bipolaire.(Traduit par Isabelle Vallières).

Acute masticatory muscle compartmental syndrome in a dog.

CASE DESCRIPTION A5.5-year-old sexually intact male Bull Terrier was referred for evaluation because of sudden facial swelling and an inability to close its mouth. CLINICAL FINDINGS Physical examination revealed bilaterally elevated nictitating membranes, an inability to adduct the mandible without assistance, and severe, diffuse, firm masticatory muscle swelling. Computed tomographic examination of the head revealed symmetric bilateral enlargement of the temporalis, masseter, and pterygoid muscles with heterogeneous contrast enhancement. Intracompartmental pressures in the left and right temporalis muscles as measured with an invasive arterial blood pressure transducer were 72 and 96 mm Hg, respectively. TREATMENT AND OUTCOME Emergent fasciotomy of the temporalis and masseter muscles was performed, followed by medical management with corticosteroids and analgesics. The diffuse facial swelling resolved within 1 week after surgery. Results of serologic testing for antibody against masticatory 2M muscle fibers were negative. Results of histologic examination of temporalis muscle specimens were consistent with mild to moderate multifocal neutrophilic and histiocytic myositis with myofiber degeneration and necrosis. CLINICAL RELEVANCE Acute compartmental syndrome should be considered as a differential diagnosis for dogs with a sudden onset of severe skeletal muscle swelling, signs of pain, and dysfunction. Findings for this dog with acute compartmental syndrome isolated to the masticatory muscles suggested that emergent fasciotomy followed by medical management may be an effective technique for treatment of this rare disease in dogs.

Computed tomographic characteristics of intrapelvic masses in dogs.

In people, the computed tomography (CT) characteristics of intrapelvic masses can be used to distinguish a malignant from a benign mass. As prognosis varies greatly between malignant and benign intrapelvic masses, knowledge of their biological behavior can aid treatment planning before surgery. The purpose of this study was to determine if CT characteristics exist to help differentiate benign from malignant intrapelvic masses in dogs. The CT images of 14 dogs with a histopathologically confirmed intrapelvic mass were evaluated. Postcontrast internal heterogeneity of the mass was the only characteristic significantly associated with malignancy (P = 0.005). Preoperative CT examination of intrapelvic masses in dogs can provide prognostic information before invasive surgical treatment.

Ex vivo biomechanical comparison of the 2.4 mm uniLOCK reconstruction plate using 2.4 mm locking versus standard screws for fixation of acetabular osteotomy in dogs.

OBJECTIVE: To compare the accuracy of reduction and the biomechanical characteristics of canine acetabular osteotomies stabilized with locking versus standard screws in a locking plate. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Cadaveric canine hemipelves and corresponding femurs (n=10 paired). METHODS: Transverse acetabular osteotomies stabilized with 5-hole 2.4 mm uniLOCK reconstruction plates using either 2.4 mm locking monocortical or standard bicortical screw fixation (Synthes Maxillofacial). Fracture reduction was assessed directly (craniocaudal acetabular width measurements and gross observation) and indirectly (impression casts). All constructs were fatigue-tested, followed by acute destructive testing. All outcome measures (mean+/-SD) were evaluated for significance (P<.05) using paired t-tests. RESULTS: Craniocaudal acetabular diameters before and after fixation were not significantly different (21.9+/-1.2 and 21.5+/-1.2 mm; P=.45). No significant differences were observed in acetabular width differences between pre- and postoperative fixation between groups (locking -0.4+/-0.4 mm; standard -0.4+/-0.3 mm; P=.76). Grossly, there was no significant difference in the repairs and impression casts did not reveal a significant (P=.75) difference in congruency between the groups. No significant differences were found in fracture gap between groups either dorsally (locking 0.38+/-0.23 mm versus standard 0.22+/-0.05 mm; P=.30) or ventrally (locking 0.80+/-0.79 mm versus standard 0.35+/-0.13 mm; P=.23), and maximum change in amplitude dorsally (locking 0.96+/-2.15 mm versus standard 0.92+/-0.89 mm; P=.96) or ventrally (locking 2.02+/-2.93 mm versus standard 0.15+/-0.81 mm; P=.25). There were no significant differences in stiffness (locking 241+/-46 N/mm versus standard 283+/-209 N/mm; P=.64) or load to failure (locking 1077+/-950 N versus standard 811+/-248 N; P=.49). CONCLUSION: No significant differences were found between pelves stabilized with locking monocortical screw fixation or standard bicortical screw fixation with respect to joint congruity, displacement of fracture gap after cyclic loading, construct stiffness, or ultimate load to failure. CLINICAL RELEVANCE: There is no apparent advantage of locking plate fixation over standard plate fixation of 2-piece ex vivo acetabular fractures using the 2.4 mm uniLOCK reconstruction plate.

Immediate mandibular reconstruction of a 5 cm defect using rhBMP-2 after partial mandibulectomy in a dog.

OBJECTIVE: To report treatment of a complex odontoma of the mandible by partial mandibulectomy and immediate surgical reconstruction using bridging plate fixation with a synthetic graft. STUDY DESIGN: Clinical case report. ANIMALS: A 4-year-old male castrated cocker spaniel. METHODS: Immediate reconstruction of the left mandible (5 cm gap) was performed after complete excision of a complex odontoma. Locking plate fixation was applied immediately before complete excision of the mass. Fixation was removed, then after partial mandibulectomy, including all abnormal tissue, restored to achieve occlusion. The resulting mandibular defect was filled with recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in an absorbable collagen sponge containing hydroxyapatite/tricalcium phosphate granules (compression resistant matrix [CRM]). RESULTS: New bone growth was evident radiographically and on palpation at 3 months. Bony remodeling was evident during follow-up examinations up to 26 months. Bone collected by biopsy at the graft site at 7 months had robust new bone formation and evidence of continued remodeling. Only minor complications (repeated intraoral plate exposure) were encountered postoperatively and were easily resolved. CONCLUSIONS: An osteoinductive factor (rhBMP-2/CRM) was successfully used as a graft substitute in immediate reconstruction of a large mandibular defect. CLINICAL RELEVANCE: Immediate reconstruction of large mandibular defects with osteoinductive materials as a graft substitute may be a viable alternative to partial mandibular resection or radiation therapy for benign odontogenic tumors in dogs.

New membrane-associated and soluble peptide methionine sulfoxide reductases in Escherichia coli.

It is known that reactive oxygen species can oxidize methionine residues in proteins in a non-stereospecific manner, and cells have mechanisms to reverse this damage. MsrA and MsrB are members of the methionine sulfoxide family of enzymes that specifically reduce the S and R forms, respectively, of methionine sulfoxide in proteins. However, in Escherichia coli the level of MsrB activity is very low which suggested that there may be other enzymes capable of reducing the R epimer of methionine sulfoxide in proteins. Employing a msrA/B double mutant, a new peptide methionine sulfoxide reductase activity has been found associated with membrane vesicles from E. coli. Both the R and S forms of N-acetylmethionine sulfoxide, D-ala-met(o)-enkephalin and methionine sulfoxide, are reduced by this membrane associated activity. The reaction requires NADPH and may explain, in part, how the R form of methionine sulfoxide in proteins is reduced in E. coli. In addition, a new soluble Msr activity was also detected in the soluble extracts of the double mutant that specifically reduces the S epimer of met(o) in proteins.

A methionine sulfoxide reductase in Escherichia coli that reduces the R enantiomer of methionine sulfoxide.

It is known that Escherichia coli methionine mutants can grow on both enantiomers of methionine sulfoxide (met(o)), i.e., met-R-(o) or met-S-(o), indicating the presence of enzymes in E. coli that can reduce each of these enantiomers to methionine (met). Previous studies have identified two members of the methionine sulfoxide reductase (Msr) family of enzymes, MsrA and fSMsr, that could reduce free met-S-(o), but the reduction of free met-R-(o) to met has not been elucidated. One possible candidate is MsrB which is known to reduce met-R-(o) in proteins to met. However, free met-R-(o) is a very poor substrate for MsrB and the level of MsrB activity in E. coli extracts is very low. A new member of the Msr family (fRMsr) has been identified in E. coli extracts that reduces free met-R-(o) to met. Partial purification of FRMsr has been obtained using extracts from an MsrA/MsrB double mutant of E. coli.