A plastidial retrograde signal potentiates biosynthesis of systemic stress response activators.

Plants employ an array of intricate and hierarchical signaling cascades to perceive and transduce informational cues to synchronize and tailor adaptive responses. Systemic stress response (SSR) is a recognized complex signaling and response network quintessential to plant's local and distal responses to environmental triggers; however, the identity of the initiating signals has remained fragmented. Here, we show that both biotic (aphids and viral pathogens) and abiotic (high light and wounding) stresses induce accumulation of the plastidial-retrograde-signaling metabolite methylerythritol cyclodiphosphate (MEcPP), leading to reduction of the phytohormone auxin and the subsequent decreased expression of the phosphatase PP2C.D1. This enables phosphorylation of mitogen-activated protein kinases 3/6 and the consequential induction of the downstream events ultimately, resulting in biosynthesis of the two SSR priming metabolites pipecolic acid and N-hydroxy-pipecolic acid. This work identifies plastids as a major initiation site, and the plastidial retrograde signal MEcPP as an initiator of a multicomponent signaling cascade potentiating the biosynthesis of SSR activators, in response to biotic and abiotic triggers.

A Case Series of Successful Repair of Articular Cartilage Fragments in the Knee.

BACKGROUND: It is unclear whether chondral fragments without bone have the potential to heal after fixation. Controversy exists and opinions differ regarding the optimal treatment of chondral defects after pure chondral fracture. PURPOSE: To determine clinical and radiographic outcomes after internal fixation of traumatic chondral fragments repaired to bone in the knee. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A retrospective clinical and radiographic evaluation of 10 male patients with a mean age of 14.6 years (range, 10-25 years) at the time of surgery was performed. Eight of 10 patients were skeletally immature. Patients were selected by operating surgeons per the presence of a large displaced pure chondral fragment on magnetic resonance imaging and confirmed on intraoperative inspection. All patients had a diagnosed traumatic displaced pure chondral fracture of the knee (without bone) and underwent internal fixation with minimum 1-year follow-up. Validated patient-reported and surgeon-measured outcomes were collected pre- and postoperatively. All patients were evaluated at a mean 56 months postoperatively. RESULTS: At surgery, the mean defect size that was primarily repaired with the displaced chondral fragment was 1.9 × 2.0 cm. With minimum 1-year follow-up, there were no clinical failures. All 8 patients who had subsequent magnetic resonance imaging follow-up had radiographic evidence of complete healing of the chondral fragment back to bone. At a mean follow-up of 56 months (range, 13-171 months; median, 36 months), patients had a mean International Knee Documentation Committee score of 94.74 (range, 87.4-100), a mean Marx Activity Scale score of 14.4 (range, 8-16), and a mean Tegner Activity Scale score of 7 (range, 5-9). At final follow-up, all patients except 1 returned to sports. CONCLUSION: The treatment of large traumatic chondral fragments is controversial. In this select series of 10 young patients who underwent primary repair with internal fixation, there were no failures clinically. Patients demonstrated excellent short-term clinical and radiographic results after fixation of these relatively large chondral fragments in the knee.

The MAP4 Kinase SIK1 Ensures Robust Extracellular ROS Burst and Antibacterial Immunity in Plants.

Microbial patterns are recognized by cell-surface receptors to initiate pattern-triggered immunity (PTI) in plants. Receptor-like cytoplasmic kinases (RLCKs), such as BIK1, and calcium-dependent protein kinases (CPKs) are engaged during PTI to activate the NADPH oxidase RBOHD for reactive oxygen species (ROS) production. It is unknown whether protein kinases besides CPKs and RLCKs participate in RBOHD regulation. We screened mutants in all ten Arabidopsis MAP4 kinases (MAP4Ks) and identified the conserved MAP4K SIK1 as a positive regulator of PTI. sik1 mutants were compromised in their ability to elicit the ROS burst in response to microbial features and exhibited compromised PTI to bacterial infection. SIK1 directly interacts with, phosphorylates, and stabilizes BIK1 in a kinase activity-dependent manner. Furthermore, SIK1 directly interacts with and phosphorylates RBOHD upon flagellin perception. Thus, SIK1 positively regulates immunity by stabilizing BIK1 and activating RBOHD to promote the extracellular ROS burst.

Editorial Commentary: Science Bearing Fruit: Can the Inverted Pear Be Quantified?

It has been reported and verified that anterior glenoid bone loss can lead to increased instability of the glenohumeral joint. Many authors have tried to quantify glenoid bone loss in recurrent instability of the glenohumeral joint. Techniques have included radiographic, magnetic resonance imaging, computed tomography (CT), 3-dimensional CT, and arthroscopic visualization. A 3-dimensional CT scan using the perfect circle technique, the Pico technique, has become a technique of choice for many authors. However, some have applied this technique using only the uninvolved shoulder. This practice is questionable, and comparison to the uninvolved shoulder is recommended.

Editorial Commentary: In 2016 Divergence Goes Beyond the United States 2-Party System: Interference Screw Divergence in Anterior Cruciate Ligament Reconstruction of the Knee Revisited.

As a result of emerging technology and techniques developed for anterior cruciate ligament (ACL) reconstruction, it is important to evaluate all aspects of the new procedures. One of these hot topics is retrograde drilling, which leads to inside-out ACL interference screw divergence from ACL sockets created from outside-in. In this paper, the authors look at screw divergence in the femoral tunnel for bone-patella-bone reconstructions performed with an outside-in retrograde drill. The screws are inserted through a separate accessory anterior medial portal, and therefore there is concern on whether or not there is significant divergence compromising their fixation. This study supports the use of this technique with clinically acceptable divergence.

The plastidial retrograde signal methyl erythritol cyclopyrophosphate is a regulator of salicylic acid and jasmonic acid crosstalk.

The exquisite harmony between hormones and their corresponding signaling pathways is central to prioritizing plant responses to simultaneous and/or successive environmental trepidations. The crosstalk between jasmonic acid (JA) and salicylic acid (SA) is an established effective mechanism that optimizes and tailors plant adaptive responses. However, the underlying regulatory modules of this crosstalk are largely unknown. Global transcriptomic analyses of mutant plants (ceh1) with elevated levels of the stress-induced plastidial retrograde signaling metabolite 2-C-methyl-D-erythritol cyclopyrophosphate (MEcPP) revealed robustly induced JA marker genes, expected to be suppressed by the presence of constitutively high SA levels in the mutant background. Analyses of a range of genotypes with varying SA and MEcPP levels established the selective role of MEcPP-mediated signal(s) in induction of JA-responsive genes in the presence of elevated SA. Metabolic profiling revealed the presence of high levels of the JA precursor 12-oxo-phytodienoic acid (OPDA), but near wild type levels of JA in the ceh1 mutant plants. Analyses of coronatine-insensitive 1 (coi1)/ceh1 double mutant plants confirmed that the MEcPP-mediated induction is JA receptor COI1 dependent, potentially through elevated OPDA. These findings identify MEcPP as a previously unrecognized central regulatory module that induces JA-responsive genes in the presence of high SA, thereby staging a multifaceted plant response within the environmental context.

Expressed sequence tag (EST) profiling in hyper saline shocked Dunaliella salina reveals high expression of protein synthetic apparatus components.

The unicellular, halotolerant, green alga, Dunaliella salina (Chlorophyceae) has the unique ability to adapt and grow in a wide range of salt conditions from about 0.05 to 5.5M. To better understand the molecular basis of its salinity tolerance, a complementary DNA (cDNA) library was constructed from D. salina cells adapted to 2.5M NaCl, salt-shocked at 3.4M NaCl for 5h, and used to generate an expressed sequence tag (EST) database. ESTs were obtained for 2831 clones representing 1401 unique transcripts. Putative functions were assigned to 1901 (67.2%) ESTs after comparison with protein databases. An additional 154 (5.4%) ESTs had significant similarity to known sequences whose functions are unclear and 776 (27.4%) had no similarity to known sequences. For those D. salina ESTs for which functional assignments could be made, the largest functional categories included protein synthesis (35.7%), energy (photosynthesis) (21.4%), primary metabolism (13.8%) and protein fate (6.8%). Within the protein synthesis category, the vast majority of ESTs (80.3%) encoded ribosomal proteins representing about 95% of the approximately 82 subunits of the cytosolic ribosome indicating that D. salina invests substantial resources in the production and maintenance of protein synthesis. The increased mRNA expression upon salinity shock was verified for a small set of selected genes by real-time, quantitative reverse-transcription-polymerase chain reaction (qRT-PCR). This EST collection also provided important new insights into the genetic underpinnings for the biosynthesis and utilization of glycerol and other osmoprotectants, the carotenoid biosynthetic pathway, reactive oxygen-scavenging enzymes, and molecular chaperones (heat shock proteins) not described previously for D. salina. EST discovery also revealed the existence of RNA interference and signaling pathways associated with osmotic stress adaptation. The unknown ESTs described here provide a rich resource for the identification of novel genes associated with the mechanistic basis of salinity stress tolerance and other stress-adaptive traits.

Ex vivo comparison of mechanical versus thermal chondroplasty: assessment of tissue effect at the surgical endpoint.

PURPOSE: The purpose of this study was to evaluate tissue effect (tissue removal plus underlying cell death) of two chondroplasty techniques: mechanical debridement (MD) using a rotary shaver blade and thermal chondroplasty using radiofrequency energy (RFE). METHODS: Forty-eight human chondromalacic cartilage samples were treated with either MD or RFE. Pre- and post-treatment arthroscopic images of the cartilage surface were recorded. Samples were incubated with cell viability stain and visualized with confocal laser microscopy to determine tissue effect. Smoothing was quantitated by three surgeons using a visual analog scale (VAS) as well as a subjective rating regarding whether smoothing was "arthroscopically acceptable." RESULTS: Tissue effect at the surgical endpoint of arthroscopically acceptable smoothing was 385 microm for MD versus 236 microm for RFE, a significant difference (P < .0001). Mean post-treatment VAS for MD was 2.8 points less smooth than for RFE (P < .0001). Overall, arthroscopically acceptable smoothing was achieved in 90% of RFE samples compared to 49% of MD samples. CONCLUSIONS: Our results shown that chondroplasty using a RFE probe results in greater smoothing of chondromalacic cartilage in fewer treatment passes and with decreased total tissue effect than MD using a rotary shaver blade. CLINICAL RELEVANCE: If safety and efficacy can be shown in vivo, thermal chondroplasty may represent an alternative for treatment of symptomatic chondromalacia.

Incidence of os acromiale in patients with shoulder pain.

A prospective case series was undertaken to determine the incidence of os acromiale in patients presenting to an orthopedic clinic with shoulder pain during a 6-month period. Ninety-three shoulders in 88 consecutive patients were evaluated by history, physical examination, and radiographs. Radiographs included anteroposterior, scapular Y, and axillary views in all patients. Based on history and physical examination, no patient was given a primary diagnosis of os acromiale. However, when the plain films were specifically reviewed for this entity, it was present in 6 (6.82%) of the 88 patients. It was seen on the axillary view in each case. Five (83.3%) of the 6 patients had been given a diagnosis of either impingement or rotator cuff tear based on physical examination. Os acromiale is an infrequent but not rare entity that must be kept in mind when evaluating patients with shoulder pain, as failure to recognize an os acromiale may negatively influence treatment results. An axillary view should be obtained when evaluating patients with shoulder pain.

Complications of the treatment of the acromioclavicular and sternoclavicular joint injuries, including instability.

Treatment of AC joint injuries and SC joint injuries continues to evolve. The risk of complications of both the operative and nonoperative management of these injuries can be minimized by the treating physician if the physician thoroughly evaluates and understands the problem. Making an accurate diagnosis of the underlying pathology and then selecting the appropriate treatment for this will minimize the risk of an associated complication. Paying attention to detail and using the appropriate technique before any operative intervention is chosen will decrease the risk of failure and complication. Close follow-up and early detection of complications will lead to less severe sequelae. AC joint injuries are more common and operative management is accepted for specific indications. Most Orthopaedic Surgeons are comfortable treating these. SC joint injuries are less common and nonoperative treatment is the mainstay. As our approach to these complex problems evolves, we must keep a wary eye towards avoiding and minimizing the complications of the new techniques.

Two-year follow-up of meniscal repair using a bioabsorbable arrow.

PURPOSE: The value of meniscal repair is well established. Several all-inside arthroscopic techniques have become available to achieve this goal. One such technique involves the use of a biodegradable polylactic acid tack, which has made repair technically easier to perform. This study evaluates the 2-year results of arthroscopic meniscal repair using this device. TYPE OF STUDY: Retrospective case series. METHODS: We reviewed charts of 38 patients who had undergone 39 meniscal repairs with the bioabsorbable arrow. All procedures were performed by one of 4 fellowship-trained sports medicine orthopaedic surgeons in 1 of 2 affiliated hospitals, with a minimum follow-up of 2 years. Review consisted of evaluation of patient records, interview, and clinical examination by an independent examiner. Lysholm and Tegner knee scores were recorded. Complications and clinical failure, defined as reoperation, were noted. RESULTS: The average age of the patients was 29.9 years. The ratio of medial to lateral meniscal repair was 5:1. Twenty-one patients underwent concurrent anterior cruciate ligament reconstruction, and in this subgroup, there were no clinical failures. In the remaining group, isolated meniscal repairs in stable knees, the clinical failure rate was 7% (2 reoperations). Local soft-tissue complications occurred in 31.6% of patients, including 2 with arrow migration through the skin. These symptoms typically resolve over several months. CONCLUSIONS: The availability of sutureless all-inside absorbable techniques for meniscal repair has made the procedure technically easier to perform arthroscopically. In our patients, local complications related to device migration, device prominence, and soft-tissue inflammation associated with absorption of the device were common (31.6%). These complications were usually transient. We emphasize the importance of selecting the correct length of device so as to minimize these effects. As with other meniscal repair techniques, a higher success rate was found in knees undergoing concurrent anterior cruciate ligament reconstruction. Our results show a clinical success rate using an absorbable all-inside technique with an absorbable device comparable to reported results using established inside-out techniques.