Comparing outcomes in the treatment of pediatric and adolescent intraarticular radial head fractures.

Intraarticular radial head (IARH) fractures are uncommon pediatric injuries with unpredictable yet poor outcomes. The aim of this study was to evaluate clinical outcomes of IARH fractures in pediatric and adolescent patients, by testing our hypothesis that surgically managed fractures would have less risk for an unplanned second surgery and better elbow range of motion at the final follow-up. A retrospective review of 53 IARH fractures was performed. Demographic and clinical data were recorded. Concomitant and associated injuries were documented. Initial management and any attempted reduction in the emergency room were documented. The primary outcome was the need for an unplanned second procedure. Motion at final follow-up, presence of pain and need for physical therapy were reviewed. Radiographs were carefully reviewed and analyzed for physeal status, displacement, angulation and percent of radial head involved. We rejected our hypothesis, however, because it was displaced fractures that tended to require an unplanned change in treatment at a higher rate than nondisplaced fractures, regardless of index management with or without surgery. Fracture displacement on the lateral radiograph was a significant risk factor compared to the anterior-posterior images, and younger patients, particularly those with open physis, were at higher risk of an unplanned second procedure. Moreover, 80% of displaced fractures had asymmetric elbow motion after healing was achieved. It is important to counsel patients and families regarding the potential for suboptimal outcomes and elbow stiffness regardless of treatment choice, in the setting of an initially displaced IARH fracture. Level of evidence: Level III.

Factors influencing surgical decision-making in pediatric and adolescent scaphoid fractures.

We aimed to assess the risk of conversion to surgical intervention in children initially managed with casting for an isolated scaphoid fracture with a secondary aim of assessing the incidence and management of occult scaphoid fractures without signs of fracture on initial radiographs. A retrospective review was performed. Our primary outcome was conversion to surgery. Subsequent evidence of fracture in those with only initial snuffbox tenderness was recorded for the secondary aim. Three hundred and eighty-four wrists with radiographic evidence of a scaphoid fracture were included. Twenty-one scaphoid fractures failed conservative treatment. Subjects that failed cast treatment were older than those that did not (15.9 years vs. 14.0 years; P < 0.001). Subjects with a delay in treatment of at least 6 weeks from injury were 8× more likely to require surgery than those with prompt treatment ( P < 0.001). Surgical conversion varied based on fracture location: distal pole 0.7%, waist 7.4%, and proximal pole 23.5% of the time ( P < 0.001). A total of 14% of wrists managed in a cast without radiographic evidence of fracture at presentation subsequently demonstrated a fracture on follow-up films. The primary predictor of failed conservative treatment is a delay in presentation. We found that the sequelae of delay in presentation or diagnosis of a scaphoid fracture increased the likelihood of requiring surgery. Therefore, clinical suspicion should dictate early management and these factors should play a role in determining when to initiate casting in the setting of pediatric scaphoid fractures. Level of evidence: III.

A comparison of cone beam computed tomography, standard computed tomography and plain radiographs in the evaluation of medial epicondyle humerus fractures.

The ideal technique to measure medial epicondyle humerus fracture displacement minimizes radiation exposure while maximizing measurement accuracy and reliability. This study compares the radiation exposure and accuracy of displacement measurements of the four-view X-ray examination (XR), computed tomography (CT) and in-clinic cone-beam CT (CBCT). A cadaveric humerus underwent medial epicondyle osteotomy. The fragment was fixed to the humerus at clinically relevant displacements (6 to 18 mm). Dosimeters were placed around the distal humerus and simulating thyroid location. XR, CT and CBCT were performed at each displacement. Four pediatric orthopedists measured the maximum linear displacement on each XR and 3D reconstruction of the CT and CBCT images. Focal (elbow location) and thyroid radiation exposure was compared between modalities. Intra- and interclass correlation coefficients (ICC) for displacement measurements were determined. Mean focal radiation exposures for XR, CT and CBCT were 0.008, 2.061 and 0.478 rad, respectively (P = 0.001). Exposures 10 inches from the elbow for XR, CT and CBCT were 0.001, 0.066 and 0.010 rad, respectively (P = 0.006). At 12 inches, there was no significant difference in exposure between XR and CBCT ( P = 0.114). Intra- and interobserver reliabilities were excellent for all measures, except lateral x-ray. CBCT and CT had significantly less deviation from the actual displacement compared to XR ( P < 0.05). In-office CBCT of the elbow exposes patients to significantly less radiation than conventional CT. All X-ray images (except lateral), CT and CBCT had equal reliability in evaluating medial epicondyle fractures, which contrasts with previous evidence.

Treatment of Hip Instability in Children With Down Syndrome: Keys to Managing a Challenging Problem.

INTRODUCTION: Management of hip instability in children with Down syndrome is a challenging task to undertake for even the most experienced surgeons. As life expectancy of these patients increases, the importance of preserving functional mobility and hip joint stability in order to minimize late hip degeneration and pain has become a priority. The aim of this study is to evaluate the clinical and radiographic outcomes of children with Down syndrome and hip instability who underwent surgical reconstruction with femoral and/or acetabular procedures. METHODS: We performed a retrospective review of all children with Down syndrome age 18 years and younger, who underwent surgical intervention to address hip instability between 2003 and 2017. Data was recorded detailing the patient's demographics, preoperative and postoperative functional status and surgical details. Preoperative and postoperative radiographic analysis was performed as well as 3-dimensional computed tomography scan evaluation, when available. All major and minor complications were recorded and classified using the Severin radiographic classification and the Clavien-Dindo-Sink clinical classification. RESULTS: We studied 28 hips in 19 children that were followed for an average of 4.4 years postsurgical intervention for hip instability. The majority of patients improved in all radiographic parameters. A total of 14 hips (50%) had complications and 9 hips (32%) required a secondary surgery. Of those complications, 2 hips (7%) developed avascular necrosis and 4 hips (14%) developed recurrent instability after the index procedure. Two of these hips had a subsequent anteverting periacetabular osteotomy that produced a stable hip at final follow up. DISCUSSION: Surgical management of hip instability in children with Down syndrome remains challenging. The treating surgeon must have a thorough understanding of the pathoanatomy and design the surgical treatment to meet all of the underlying sources of instability. Combined femoral and acetabular osteotomies plus capsulorrhaphy are often required along with postoperative hip spica immobilization. Although complication and revision surgery rates are high, hip stability and good functional outcomes can be achieved.

Distal tibial osteotomy to address internal tibial torsion: Should the fibula be cut?

Background Rotational tibial osteotomy seeks to address pathologic tibial torsion. Inclusion of fibular osteotomy during this procedure remains controversial. This study aimed to determine how external rotation through a tibial osteotomy, with or without a fibular osteotomy, would influence tibiofibular joint congruity. Methods Eight cadaveric legs underwent distal tibial osteotomies. Pins were placed to designate neutral, 10°, 20°, 30° of external rotation. Computed tomography (CT) imaging was performed at each rotation without, then with a fibular osteotomy. Magnetic Resonance Imaging was performed prior to fibular osteotomy to confirm that ligaments remained intact. Custom software calculated tibial torsion using CT scan 3D reconstructions. Proximal tibiofibular joint rotation, distal tibiofibular gapping and ankle mortise were measured on each CT exam. Groups without and with fibular osteotomy were compared. Findings There was no difference between tibial osteotomy rotation magnitude with or without the fibular osteotomy (P = 0.2). The group without the fibular osteotomy had greater proximal fibular rotation at the tibiofibular joint at 20°, 30° (P < 0.05), greater posterior distal tibiofibular gap at 10°, 20°, 30° (P < 0.05) and less anterior distal tibiofibular gap at 20°, 30° (P < 0.05). The medial tibiotalar space was narrowed without the fibular osteotomy at 20°, 30° (P < 0.05) compared to pre-rotation. Interpretation Deformity at the proximal tibiofibular and ankle joints become most pronounced at >20° of tibial rotation without a fibular osteotomy. The first joint to be affected is the distal tibiofibular joint. To limit ankle and proximal tibiofibular articular deformation during tibia rotational osteotomy, a fibular osteotomy is recommended when correcting over 20° of rotation.

Role of inflammatory markers in the preoperative evaluation of patients undergoing salvage total hip arthroplasty.

Surgeons may use laboratory tests, including erythrocyte sedimentation rate, C-reactive protein (CRP), and white blood cell count, as well as joint aspirations to diagnose prosthetic joint infections. There is a paucity of literature correlating preoperative inflammatory markers with risk of infection in the setting of salvage total hip arthroplasty (THA). This retrospective case analysis included patients who underwent a THA salvage procedure a minimum of 3 months after a failed fixation of a proximal femur or acetabulum, with a goal of assessing the utility of inflammatory markers as a screening tool in preoperative evaluation of salvage THA. Eighty-five patients met inclusion criteria. Thirteen patients were diagnosed with an infection preoperatively or intraoperatively during salvage THA. An elevated preoperative CRP level was a significant marker for infection. A CRP of 7.1 produced 80% sensitivity, 88% specificity, and a receiver operating characteristic curve of 0.840. There was a high rate of perioperative complications (17.6%) in salvage THA regardless of the presence of infection. In conclusion, CRP levels are useful in the preoperative evaluation for periprosthetic joint infection before salvage THA.

The Clavicle Continues to Grow During Adolescence and Early Adulthood.

BACKGROUND: As more adults undergo surgical fixation of clavicle fractures with improved outcomes, interest is renewed in managing clavicle fractures in adolescents. The medial clavicular physis does not fuse until 23 to 25 years of age, but studies report minimal clavicular growth during adolescence-studies that employed cross-sectional methodologies, which cannot not capture growth in patients over time. The assumption that clavicle length at each stage is uniform, as is the final overall length, may not be accurate if the age groups studied comprise various ethnicities, socioeconomic status, or height. QUESTIONS/PURPOSES: We sought to quantify longitudinal clavicular growth on serial radiographs in adolescents and young adults. Our hypothesis was that substantial clavicular growth would be seen beyond the age of 12 years. METHODS: We conducted a longitudinal case series of non-syndromic patients in a single orthopedic clinic and analyzed serial radiographic images of the clavicles. For ethical reasons, only patients with non-neuromuscular scoliosis and kyphosis (in whom the existing standard of care includes serial thoracic radiographs) were considered for inclusion. Patients ages 10 to 25 years old were included in the study if three or more serial thoracic radiographs over a minimum 5 years were available that captured the entire length of at least one non-rotated clavicle. Three types of radiographs were included for analysis: digital low-dose-radiation stereoradiographic (EOS Imaging, Paris, France), non-EOS digital, and non-EOS printed. The overall longitudinal growth, yearly growth, and the yearly growth percentage were calculated for each clavicle. RESULTS: Fifty-seven patients (22 male and 35 female) met the inclusion criteria. In male patients, at ages 12 to 15 years, the clavicular growth was 4.9 mm/year, or 4%/year; at ages 16 to 19 years, growth was 3.2 mm/year, or 2.4%/year; and at ages 20 to 25 years, growth was 1.7 mm/year, or 1.1%/year. In female patients, at ages 12 to 15 years, growth was 4.7 mm/year, or 4%/year; at 16 to 19 years, growth was 2.2 mm/year, or 1.7%/year; and at ages 20 to 25 years, growth was 0.2 mm/year or 0.1%/year. We could not detect the age of terminal growth in either sex because growth was ongoing in most patients in the oldest group. CONCLUSION: We found substantial clavicular growth potential after age 18 years, when growth is thought to be nearly finished, as well as remodeling potential even up to age 25 years. Further research is needed, but our findings suggest that strategies for managing clavicle fracture in adults may not be applied universally to adolescents and young adults.

Global study of variability in olfactory sensitivity.

Variability in human olfactory sensitivity has been attributed to individual-level factors such as genetics, age, sex, medical history of infections and trauma, neurogenerative diseases, and emotional disorders. Scarce evidence exists on the cross-cultural variation in olfactory sensitivity. Hence, we performed 2 studies to estimate the variability in olfactory threshold as a function of location and environment. Study 1 involved 11 laboratories from 4 continents (N = 802). In each location, in a designated laboratory, approximately 80 subjects underwent olfactory sensitivity testing with custom-made tests with eucalyptol and phenylethanol (PEA) odors. Tests were based on the Threshold subtest of the Sniffin' Sticks battery. In Study 2, we compared olfactory sensitivity and suprathreshold perception of PEA and eucalyptol in 2 Chinese (N = 160) and 2 Indian (N = 92) populations-one based in their native country and the other in Germany. Both studies present large-scale evidence that olfactory sensitivity varies as a function of geographical location and suggest that environmental factors play an important role in shaping olfactory sensitivity and suprathreshold olfactory perception. We delineate further steps necessary to identify specific factors underlying uncovered variability and the relationship between olfactory sensitivity and suprathreshold odor perception. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Medial Epicondyle Fractures: Biomechanical Evaluation and Clinical Comparison of 3 Fixation Methods Used in Pediatric Patients.

BACKGROUND: Screw fixation is the most commonly employed fixation strategy for displaced medial epicondyle fractures, but in younger patients with minimal ossification, the fracture fragment may not accommodate a screw. In these situations, Kirschner-wires (K-wire) or suture anchors may be utilized as alternatives. The purposes of this study were to examine the biomechanical properties of medial epicondyle fractures fixed with a screw, K-wires, or suture anchors, to evaluate clinical outcomes and complications of patients 10 years of age or younger treated with these approaches, and to perform a cost-analysis. METHODS: Biomechanical assessment: Immature pig forelimbs underwent an osteotomy through the medial epicondyle apophysis, simulating a fracture. These were then fixed with a screw, K-wires or suture anchors. Cyclic elongation (mm), displacement (mm), load to failure (N), and stiffness (N/mm) were assessed. Clinical assessment: a retrospective review was performed of patients 10 years of age or younger with a medial epicondyle fracture fixed with these strategies. Radiographic outcomes, postoperative data and complications were compared. These data were used to perform a cost-analysis of each treatment approach. RESULTS: Biomechanically, screws were stronger (P=0.047) and stiffer (P=0.01) than the other constructs. Clinically, 51 patients met inclusion criteria (screw=27, wires=11, anchor=13). Patients treated with K-wires were younger (P<0.05) and patients treated with screw fixation had a shorter casting duration (P=0.008). Irrespective of treatment strategy, all fractures healed (100%) and only 1 patient in the screw group lost reduction. Clinical outcomes and complications were similar between groups, but the suture anchor group was less likely to require a second surgery for implant removal (P<0.05). This lower reoperation rate led to a cost-saving of 10%. CONCLUSIONS: Biomechanically, all 3 approaches provided initial fixation exceeding the forces observed across the elbow joint with routine motion. The screw construct was the strongest and stiffest. Clinically, all 3 strategies were acceptable, with screw fixation offering a shorter casting duration, but greater implant removal need with higher associated costs.

Early-stage 11C-Flumazenil PET predicts day-14 selective neuronal loss in a rodent model of transient focal cerebral ischemia.

Predicting tissue outcome early after stroke is an important goal. MRI >3 h accurately predicts infarction but is insensitive to selective neuronal loss (SNL). Previous studies suggest that chronic-stage 11C-flumazenil PET (FMZ-PET) is a validated marker of SNL in rats, while early-stage FMZ-PET may predict infarction. Whether early FMZ-PET also predicts SNL is unknown. Following 45-min distal MCA occlusion, adult rats underwent FMZ-PET at 1 h and 48 h post-reperfusion to map distribution volume (VT), which reflects GABA-A receptor binding. NeuN immunohistochemistry was performed at Day 14. In each rat, VT and %NeuN loss were determined in 44 ROIs spanning the hemisphere. NeuN revealed isolated SNL and cortical infarction in five and one rats, respectively. In the SNL subgroup, VT-1 h was mildly reduced and only weakly predicted SNL, while VT-48 h was significantly increased and predicted SNL both individually (p < 0.01, Kendall) and across the group (p < 0.001), i.e. the higher the VT, the stronger the SNL. Similar correlations were found in the rat with infarction. Our findings suggest GABA-A receptors are still present on injured neurons at the 48 h timepoint, and the increased 48 h VT observed here is consistent with earlier rat studies showing early GABA-A receptor upregulation. That FMZ binding at 48 h was predictive of SNL may have clinical implications.

Stabilizing effect of the rib cage on adjacent segment motion following thoracolumbar posterior fixation of the human thoracic cadaveric spine: A biomechanical study.

BACKGROUND: Although the rib cage provides substantial stability to the thoracic spine, few biomechanical studies have incorporated it into their testing model, and no studies have determined the influence of the rib cage on adjacent segment motion of long fusion constructs. The present biomechanical study aimed to determine the mechanical contribution of the intact rib cage during the testing of instrumented specimens. METHODS: A cyclic loading (CL) protocol with instrumentation (T4-L2 pedicle screw-rod fixation) was conducted on five thoracic spines (C7-L2) with intact rib cages. Range of motion (±5 Nm pure moment) in flexion-extension, lateral bending, and axial rotation was captured for intact ribs, partial ribs, and no ribs conditions. Comparisons at the supra-adjacent (T2-T3), adjacent (T3-T4), first instrumented (T4-T5), and second instrumented (T5-T6) levels were made between conditions (P ≤ 0.05). FINDINGS: A trend of increased motion at the adjacent level was seen for partial ribs and no ribs in all 3 bending modes. This trend was also observed at the supra-adjacent level for both conditions. No significant changes in motion compared to the intact ribs condition were seen at the first and second instrumented levels (P > 0.05). INTERPRETATION: The segment adjacent to long fusion constructs, which may appear more grossly unstable when tested in the disarticulated spine, is reinforced by the rib cage. In order to avoid overestimating adjacent level motion, when testing the effectiveness of surgical techniques of the thoracic spine, inclusion of the rib cage may be warranted to better reflect clinical circumstances.

Scurvy Findings in a Child with Jacobsen Syndrome: A Case Report.

CASE: We describe the first reported case of scurvy developing secondary to behavioral traits of Jacobsen syndrome. The diagnosis of scurvy was significantly delayed because bleeding symptoms were initially attributed to baseline thrombocytopenia and platelet dysfunction associated with Jacobsen syndrome and patient's medication. Following vitamin C supplementation, signs and symptoms of the patient's disease quickly resolved. CONCLUSIONS: We aim to reinforce the need to consider nutritional deficiencies in patients with complex medical histories and behavioral issues, especially when presenting with new complaints.

Magnetic resonance imaging predictors of shoulder instability in adolescents.

BACKGROUND: Managing recurrent shoulder instability in an athlete of any age is challenging. The pediatric literature regarding recurrence of instability is difficult to interpret because of the variable treatment protocols and varying ages. The adult literature suggests that bone loss on the humerus, glenoid or both, as detected by CT, has high rates of recurrence following surgical intervention. OBJECTIVE: The purpose of this study was to evaluate risk factors for recurrence following arthroscopic capsulorrhaphy in adolescent athletes using preoperative MR arthrograms. MATERIALS AND METHODS: We reviewed a retrospective shoulder instability database for adolescents (age ≤18 years), who underwent an isolated arthroscopic capsulorrhaphy from 2006 to 2011. We recorded preoperative MRI measurements regarding the dimensions of the glenohumeral joint, as well as glenoid, humeral and labral pathologies. We performed statistical analysis to determine MRI findings that might have predicted recurrence of shoulder instability following capsulorrhaphy. RESULTS: We reviewed a total of 50 patients (13-18 years) and found 22 patients (44%) to have recurrent instability following capsulorrhaphy. Presence of glenoid bone loss or a bipolar bone lesion (defined as bone loss on both the glenoid and humerus) significantly predicted recurrence of shoulder instability (both P=0.03). There was not a threshold size of glenoid bone loss or bipolar lesion that predicted recurrence. All remaining glenohumeral dimensions or presence or size of an isolated Hill-Sachs did not significantly predict recurrence of instability. CONCLUSION: Athletes ≤18 years old have a high rate of failure following arthroscopic capsulorrhaphy in the presence of glenoid bone loss or a bipolar lesion on MRI. Surgeons should consider addressing these lesions in adolescent athletes with shoulder instability. Additionally, MRI is a valid imaging tool to diagnose and measure osseous lesions of the shoulder.

Arthroscopic Bankart Repairs With and Without Remplissage in Recurrent Adolescent Anterior Shoulder Instability With Hill-Sachs Deformity.

BACKGROUND: Recurrent shoulder dislocation after surgical intervention in adolescents with anterior instability is now understood to occur with a relatively high frequency. The remplissage procedure is successfully used in the adult population to mitigate the ability of a Hill-Sachs lesion to engage the anterior glenoid and can be used during an arthroscopic Bankart repair for anterior shoulder instability. PURPOSE: To compare the clinical outcomes in adolescent patients who underwent a Bankart repair with or without remplissage for treatment of recurrent anterior shoulder instability and associated Hill-Sachs defects. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A retrospective review was conducted on adolescents who underwent a remplissage procedure for recurrent anterior shoulder instability from 2009 to 2017 at a single institution. Controls were identified in a cohort of patients who underwent a Bankart repair only and were matched based on age, sex, and size of Hill-Sachs lesion. All patients were then contacted to determine instability recurrence as well as to complete the shortened version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) and the Pediatric Adolescent Shoulder Score (PASS) outcome surveys. RESULTS: Twenty-one adolescents underwent a remplissage procedure, and 20 matched controls underwent only a Bankart procedure. A significantly higher rate of recurrence was noted in the Bankart-only patients (8/17) compared with remplissage patients (2/15) (P = .04). No statistical difference was found in patient-reported outcome scores between treatment groups or in range of motion measurements (P > .05). In a subset of patients in the remplissage group with pre- and postoperative surveys available, mean ± SD scores for PASS (77 ± 11) and QuickDASH (19 ± 12) improved when compared with preoperative scores (PASS, 54 ± 16; QuickDASH, 35 ± 28), but only the PASS score was statistically improved (PASS, P = .003; QuickDASH, P = .23). CONCLUSION: The addition of the remplissage procedure to a Bankart repair is a reasonable surgical option to treat a Hill-Sachs deformity in adolescents with anterior shoulder instability. The success of this additional procedure may be due to filling the Hill-Sachs defect, or perhaps it augments stability through a mechanism of posterior capsulorrhaphy. Either way, this young athletic population appears to have a lower rate of recurrence and improved patient-reported outcomes with a remplissage procedure to address the Hill-Sachs deformity.

Infection Rates in Arthroscopic Versus Open Rotator Cuff Repair.

BACKGROUND: The prevalence of rotator cuff repair continues to rise, with a noted transition from open to arthroscopic techniques in recent years. One reported advantage of arthroscopic repair is a lower infection rate. However, to date, the infection rates of these 2 techniques have not been directly compared with large samples at a single institution with fully integrated medical records. PURPOSE: To retrospectively compare postoperative infection rates between arthroscopic and open rotator cuff repair. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: From January 2003 until May 2011, a total of 1556 patients underwent rotator cuff repair at a single institution. These patients were divided into an arthroscopic repair group and an open group. A Pearson chi-square test and Fisher exact test were used, with a subgroup analysis to segment the open repair group into mini-open and open procedures. The odds ratio and 95% CI of developing a postoperative infection was calculated for the 2 groups. A multiple-regressions model was then utilized to identify predictors of the presence of infection. Infection was defined as only those treated with surgical intervention, thus excluding superficial infections treated with antibiotics alone. RESULTS: A total of 903 patients had an arthroscopic repair, while 653 had open repairs (600 mini-open, 53 open). There were 4 confirmed infections in the arthroscopic group and 16 in the open group (15 mini-open, 1 open), resulting in postoperative infection rates of 0.44% and 2.45%, respectively. Subgroup analysis of the mini-open and open groups demonstrated a postoperative infection rate of 2.50% and 1.89%, respectively. The open group had an odds ratio of 5.645 (95% CI, 1.9-17.0) to develop a postoperative infection compared with the arthroscopic group. CONCLUSION: Patients undergoing open rotator cuff repair had a significantly higher rate of postoperative infection compared with those undergoing arthroscopic rotator cuff repair.

Borrelia burgdorferi surface-localized proteins expressed during persistent murine infection are conserved among diverse Borrelia spp.

Borrelia burgdorferi, the causative agent of Lyme disease in the United States, regulates numerous genes encoding lipoproteins on linear plasmid 54 in response to environmental cues. We analyzed a subset of these genes/proteins that were historically categorized as paralogous gene family 54 (BBA64, BBA65, BBA66, BBA68, BBA69, BBA70, BBA71, and BBA73) and found that the expression of several genes was influenced by the sigma(N)-sigma(S) regulatory cascade at the level of transcription and protein synthesis. Moreover, we established in this and a previous study that BBA65, BBA66, BBA69, BBA71, and BBA73 are temporally expressed during persistent infection of immunocompetent mice, as determined by quantitative real time-PCR of ear tissue, by enzyme-linked immunosorbent assay, and by immunoblotting. Correspondingly, BBA65, BBA66, BBA71, and BBA73 proteins were detectable in infectious B. burgdorferi B31 isolates but undetectable in noninfectious isolates. BBA65, BBA66, BBA71, and BBA73 proteins were also found to partition into the Triton X-114 detergent phase and were sensitive to protease treatment of intact cells, indicating that they are membrane associated and surface localized. Lastly, Southern blotting and PCR with specific gene primer/probes for BBA64, BBA65, BBA66, BBA71, and BBA73 suggest that many of these genes are conserved among the B. burgdorferi sensu lato isolates and the relapsing-fever Borrelia species. Together, the data presented suggest that these genes may play a part in Borrelia infection and/or pathogenicity that could extend beyond the sensu lato group.

Regulated synthesis of the Borrelia burgdorferi inner-membrane lipoprotein IpLA7 (P22, P22-A) during the Lyme disease spirochaete's mammal-tick infectious cycle.

Results of previous immunological studies suggested that Borrelia burgdorferi regulates synthesis of the IpLA7 lipoprotein during mammalian infection. Through combined use of quantitative reverse transcription PCR, immunofluorescence analyses, ELISA and immunoblotting, it is now demonstrated that IpLA7 is actually expressed throughout mammalian infection, as well as during transmission both from feeding ticks to naïve mice and from infected mice to naïve, feeding ticks. However, proportions of IpLA7-expressing B. burgdorferi within tick midguts declined significantly with time following completion of blood feeding. Cultured bacteria differentially expressed IpLA7 in response to changes in temperature, pH and concentration of 4,5-dihydroxy-2,3-pentanedione, the precursor of autoinducer 2, indicative of mechanisms governing IpLA7 expression. Previous studies also reported mixed results as to the cellular localization of IpLA7. It is now demonstrated that IpLA7 localizes primarily to the borrelial inner membrane and is not surface-exposed, consistent with the ability of these bacteria to produce IpLA7 throughout mammalian infection despite being the target of a robust immune response.

Temporal expression analysis of the Borrelia burgdorferi paralogous gene family 54 genes BBA64, BBA65, and BBA66 during persistent infection in mice.

Members of the Borrelia burgdorferi paralogous gene family 54 (pgf 54) are regulated by conditions simulating mammalian infection and are thought to be instrumental in borrelial host survival and pathogenesis. To explore the activities of these genes in vivo, a comprehensive analysis of pgf 54 genes BBA64, BBA65, and BBA66 was performed to assess the genetic stability, host antibody responses, and kinetics of gene expression in the murine model of persistent infection. DNA sequencing of pgf 54 genes obtained from re-isolates at 1 year postinfection demonstrated that all genes of this family are stable and do not undergo recombination to generate variant antigens during persistent infection. Antibodies against BBA64 and BBA66 appeared soon after infection and were detectable throughout the infection, suggesting that there was gene expression during infection. However, quantitative reverse transcription-PCR revealed that BBA64 gene expression was considerably decreased in Borrelia residing in the mouse ear tissue compared to the expression in cultured spirochetes by 20 days postinfection and that the levels of expression remained low throughout the infection. Conversely, transcription of the BBA65 and BBA66 genes was increased, and both of these genes were continuously expressed until 100 days postinfection; this was followed by periods of differential expression late in infection. The expression profile of the BBA64 gene suggests that this gene has an important role during tick-to-host transmission and early infection, whereas the expression profile of the BBA65 and BBA66 genes suggests that these genes have a role in persistent infection. The differential regulation of pgf 54 genes observed during infection may help confer a survival advantage during persistent infection, influencing mechanisms for B. burgdorferi dissemination, tissue tropism, or evasion of the adaptive immune response.

Imaging of brain hypoxia in permanent and temporary middle cerebral artery occlusion in the rat using 18F-fluoromisonidazole and positron emission tomography: a pilot study.

In acute stroke, the target of therapy is the severely hypoxic but salvageable tissue. Previous human studies using 18F-fluoromisonidazole and positron emission tomography (18F-FMISO PET) have shown high tracer retention indicative of tissue hypoxia, which had normalized at repeat scan >48 h later. In the only validation study of 18F-FMISO, using ex vivo autoradiography in thread middle cerebral artery occluded (MCAo) rats, there was unexpected high uptake as late as 22 h after reperfusion, raising questions about the use of 18F-FMISO as a hypoxia tracer. Here we report a pilot study of 18F-FMISO PET in experimental stroke. Spontaneous hypertensive rats were subjected to distal clip MCAo. Three-hour dynamic PET was performed in 7 rats: 3 normals, 1 with permanent MCAo (two sessions: 30 mins and 48 h after clip), and 3 with temporary MCAo (45 mins, n=1; 120 mins, n=2; scanning started 30 mins after clip removal). Experiments were terminated by perfusion-fixation for standard histopathology. Late tracer retention was assessed by both compartmental modelling and simple side-to-side ratios. In the initial PET session of the permanent MCAo rat, striking trapping of 18F-FMISO was observed in the affected cortex, which had normalized 48 h later; histopathology revealed pannecrosis. In contrast, there was no demonstrable tracer retention in either temporary MCAo models, and histopathology showed ischemic changes only. These results document elevated 18F-FMISO uptake in the stroke area only in the early phase of MCAo, but not after early reperfusion nor when tissue necrosis has developed. These findings strongly support the validity of 18F-FMISO as a marker of viable hypoxic tissue/penumbra after stroke.