Maturation-dependent patterns of knee injuries among symptomatic pediatric soccer players on MRI.

OBJECTIVE: To systematically investigate the prevalence of knee MRI findings among symptomatic pediatric soccer players with respect to skeletal maturity and to identify predictors of surgery. METHODS: This IRB-approved, HIPAA-compliant retrospective study included soccer players (< 18 years of age) who underwent MRI examinations in the past 5 years (2018-2023). Two radiologists retrospectively and independently reviewed all examinations to categorize skeletal maturity and to identify osseous and soft tissue findings. Findings were compared between maturation groups, and logistic regression models were used to identify predictors of surgery. RESULTS: Ninety-seven players (45 boys, 52 girls) included 39 skeletally immature, 21 maturing, and 37 mature knees. Kappa coefficient for interobserver reliability ranged between 0.65 and 1.00. Osgood-Schlatter disease (OSD) was more common among immature than maturing and mature knees (25% vs 14% and 5%, p = 0.04); anterior cruciate ligament (ACL) injury was more common among maturing and mature than immature knees (59% and 48%, vs 15%, p < 0.01); and meniscal tears were more common among mature than immature and maturing knees (medial, 41% vs 18% and 14%, p = 0.03; lateral, 43% vs 21% and 19%, p = 0.04). Players in the mature group were more likely to undergo surgery (p = 0.01). The presence of an effusion (OR = 19.5, 95% CI 2.8-240.9, p = 0.01), ACL injury (OR = 170.0, 95% CI 1.3-6996.9, p < 0.01), and lateral meniscal tears (OR = 10.8, 95% CI 1.8-106.1, p = 0.02) were independent predictors of surgery. CONCLUSION: Differential patterns of injury were found among symptomatic pediatric soccer players; the presence of an effusion, ACL injury, and lateral meniscal tears were independent predictors of surgery, likely contributing to the higher rates of surgery among skeletally mature players.

Early targeted heart rate aerobic exercise versus placebo stretching for sport-related concussion in adolescents: a randomised controlled trial.

BACKGROUND: Sport-related concussion is a public health problem, particularly in adolescents. Quality of life is reduced in adolescents with persistent post-concussive symptoms (symptoms >28 days). We replicated a previous randomised controlled trial to validate the safety, efficacy, and generalisability of, and objective adherence to, prescribed early targeted heart rate subsymptom threshold aerobic exercise compared with placebo-like stretching exercise for adolescent recovery from sport-related concussion and for reducing the risk of persistent post-concussive symptoms. METHODS: This randomised controlled trial was done at three community and hospital-affiliated sports medicine concussion centres in the USA. Male and female adolescent athletes (aged 13-18 years) presenting within 10 days of sport-related concussion were randomly assigned to individualised subsymptom threshold aerobic or stretching exercise at least 20 min daily, for up to 4 weeks after injury. Exercise adherence and intensity were measured by heart rate monitors. The primary outcome was clinical recovery (ie, return to baseline symptoms, normal exercise tolerance, and a normal physical examination) within the 4-week intervention period, and development of persistent post-concussive symptoms beyond 28 days after injury. This study is registered with ClinicalTrials.gov, NCT02959216. FINDINGS: Between Aug 1, 2018, and March 31, 2020, 118 adolescents were recruited (61 were randomly assigned to the aerobic exercise group and 57 to the stretching exercise group) and included in the intention-to-treat analysis. On survival analysis, controlling for sex, site, and mean daily exercise time, patients assigned to aerobic exercise were more likely to recover within 4 weeks after injury compared with those assigned to stretching exercise, with a 48% reduced risk of persistent post-concussive symptoms (hazard ratio for stretching vs aerobic exercise of 0·52 [95% CI 0·28-0·97], p=0·039). No adverse events were reported. INTERPRETATION: This multicentre study found that early treatment with subsymptom threshold aerobic exercise safely speeds recovery from sport-related concussion and reduces the risk for persistent post-concussive symptoms, an important result given the impact of delayed recovery on adolescent quality of life. Adherence was good and there were no adverse events from this non-pharmacological treatment. These results suggest that physicians should not only permit, but consider prescribing, early subsymptom threshold physical activity to adolescents as treatment for sport-related concussion and to reduce the risk of persistent post-concussive symptoms. FUNDING: American Medical Society for Sports Medicine.

Effect of cognitive activity level on duration of post-concussion symptoms.

OBJECTIVE: To determine the effect of cognitive activity level on duration of post-concussion symptoms. METHODS: We conducted a prospective cohort study of patients who presented to a Sports Concussion Clinic within 3 weeks of injury between October 2009 and July 2011. At each visit, patients completed a scale that recorded their average level of cognitive activity since the previous visit. The product of cognitive activity level and days between visits (cognitive activity-days) was calculated and divided into quartiles. Kaplan-Meier Product Limit method was used to generate curves of symptom duration based on cognitive activity level. To adjust for other possible predictors of concussion recovery, we constructed a Cox proportional hazard model with cognitive activity-days as the main predictor. RESULTS: Of the 335 patients included in the study, 62% were male, 19% reported a loss of consciousness, and 37% reported experiencing amnesia at the time of injury. The mean age of participants was 15 years (range, 8-23) and the mean number of previous concussions was 0.76; 39% of athletes had sustained a previous concussion. The mean Post-Concussion Symptom Scale score at the initial visit was 30 (SD, 26). The overall mean duration of symptoms was 43 days (SD, 53). Of all variables assessed, only total symptom burden at initial visit and cognitive activity level were independently associated with duration of symptoms. CONCLUSIONS: Increased cognitive activity is associated with longer recovery from concussion. This study supports the use of cognitive rest and adds to the current consensus opinion.

Emergency ultrasound-assisted examination of skin and soft tissue infections in the pediatric emergency department.

OBJECTIVES: The objective was to evaluate the test characteristics of clinical examination (CE) with the addition of bedside emergency ultrasound (CE+EUS) compared to CE alone in determining skin and soft tissue infections (SSTIs) that require drainage in pediatric patients. METHODS: This was a prospective study of CE+EUS as a diagnostic test for the evaluation of patients 2 months to 19 years of age evaluated for SSTIs in a pediatric emergency department (ED). Two physicians clinically and independently evaluated each lesion, and the reliability of the CE for diagnosing lesions requiring drainage was calculated. Trained pediatric emergency physicians performed US following their CEs. The authors determined and compared the test characteristics for evaluating a SSTI requiring drainage for CE alone and for CE+EUS for those lesions in which the two physicians agreed and were certain regarding their CE diagnosis (clinically evident). The performance of CE+EUS was evaluated in those lesions in which the two physicians either disagreed or were uncertain of their diagnosis (not clinically evident). The reference standard for determining if a lesion required drainage was defined as pus expressed at the time of the ED visit or within 2 days by follow-up assessment. RESULTS: A total of 387 lesions underwent CE+EUS and were analyzed. CE agreement between physicians was fair (κ = 0.38). For the 228 lesions for which physicians agreed and were certain of their diagnoses, sensitivity was 94.7% for CE and 93.1% for CE+EUS (difference = -1.7%; 95% confidence interval [CI] = -3.4% to 0%). The specificity of CE was 84.2% compared to 81.4% for CE+EUS (difference = -2.8%; 95% CI = -9.7% to 4.1%). For lesions not clinically evident based on CE, the sensitivity of CE was 43.7%, compared with 77.6% for CE+EUS (difference = 33.9%; 95% CI = 1.2% to 66.6%). The specificity of CE for this group was 42.0%, compared with 61.3% for CE+EUS (difference = 19.3%; 95% CI = -13.8% to 52.4%). CONCLUSIONS: For clinically evident lesions, the addition of ultrasound (US) did not significantly improve the already highly accurate CE for diagnosing lesions requiring drainage in this study population. However, there were many lesions that were not clinically evident, and in these cases, US may improve the accuracy of the CE.

Multiple Arabidopsis genes primed for recruitment into C4 photosynthesis.

C(4) photosynthesis occurs in the most productive crops and vegetation on the planet, and has become widespread because it allows increased rates of photosynthesis compared with the ancestral C(3) pathway. Leaves of C(4) plants typically possess complicated alterations to photosynthesis, such that its reactions are compartmented between mesophyll and bundle sheath cells. Despite its complexity, the C(4) pathway has arisen independently in 62 separate lineages of land plants, and so represents one of the most striking examples of convergent evolution known. We demonstrate that elements in untranslated regions (UTRs) of multiple genes important for C(4) photosynthesis contribute to the metabolic compartmentalization characteristic of a C(4) leaf. Either the 5' or the 3' UTR is sufficient for cell specificity, indicating that functional redundancy underlies this key aspect of C(4) gene expression. Furthermore, we show that orthologous PPDK and CA genes from the C(3) plant Arabidopsis thaliana are primed for recruitment into the C(4) pathway. Elements sufficient for M-cell specificity in C(4) leaves are also present in both the 5' and 3' UTRs of these C(3) A. thaliana genes. These data indicate functional latency within the UTRs of genes from C(3) species that have been recruited into the C(4) pathway. The repeated recruitment of pre-existing cis-elements in C(3) genes may have facilitated the evolution of C(4) photosynthesis. These data also highlight the importance of alterations in trans in producing a functional C(4) leaf, and so provide insight into both the evolution and molecular basis of this important type of photosynthesis.

Independent and parallel recruitment of preexisting mechanisms underlying C4 photosynthesis.

C4 photosynthesis allows increased photosynthetic efficiency because carbon dioxide (CO2) is concentrated around the key enzyme RuBisCO. Leaves of C4 plants exhibit modified biochemistry, cell biology, and leaf development, but despite this complexity, C4 photosynthesis has evolved independently in at least 45 lineages of plants. We found that two independent lineages of C4 plant, whose last common ancestor predates the divergence of monocotyledons and dicotyledons about 180 million years ago, show conserved mechanisms controlling the expression of genes important for release of CO(2) around RuBisCO in bundle sheath (BS) cells. Orthologous genes from monocotyledonous and dicotyledonous C3 species also contained conserved regulatory elements that conferred BS specificity when placed into C4 species. We conclude that these conserved functional genetic elements likely facilitated the repeated evolution of C4 photosynthesis.

The role of proteins in C(3) plants prior to their recruitment into the C(4) pathway.

Our most productive crops and native vegetation use a modified version of photosynthesis known as the C(4) pathway. Leaves of C(4) crops have increased nitrogen and water use efficiencies compared with C(3) species. Although the modifications to leaves of C(4) plants are complex, their faster growth led to the proposal that C(4) photosynthesis should be installed in C(3) crops in order to increase yield potential. Typically, a limited set of proteins become restricted to mesophyll or bundle sheath cells, and this allows CO(2) to be concentrated around the primary carboxylase RuBisCO. The role that these proteins play in C(3) species prior to their recruitment into the C(4) pathway is addressed here. Understanding the role of these proteins in C(3) plants is likely to be of use in predicting how the metabolism of a C(3) leaf will alter as components of the C(4) pathway are introduced as part of efforts to install characteristics of C(4) photosynthesis in leaves of C(3) crops.

Agrobacterium tumefaciens-mediated transformation of Cleome gynandra L., a C(4) dicotyledon that is closely related to Arabidopsis thaliana.

In leaves of most C(4) plants, the biochemistry of photosynthesis is partitioned between mesophyll and bundle sheath cells. In addition, their cell biology and development also differs from that in C(3) plants. We have a poor understanding of the mechanisms that generate the cell-specific accumulation of proteins used in the C(4) pathway, and there are few genes that have been shown to be important for the cell biology and development of C(4) leaves. To facilitate functional analysis of C(4) photosynthesis, and to enable knowledge from Arabidopsis thaliana to be translated to C(4) species, an Agrobacterium tumefaciens-mediated transformation protocol was developed for the C(4) species Cleome gynandra. A. tumefaciens, harbouring the binary vector SLJ1006, was used to transfer the uidA gene under the control of the CaMV 35S promoter into C. gynandra. Co-incubation of hypocotyls or cotyledons with SLJ1006 allowed efficient transfer of DNA into C. gynandra, and media that allowed callus production and then shoot regeneration were identified. Stable transformants of C. gynandra with detectable amounts of beta-glucuronidase (GUS) were produced at an efficiency of 14%. When driven by the CaMV 35S promoter, GUS was visible in all leaf cells, whereas uidA translationally fused to a CgRbcS gene generated GUS accumulation specifically in bundle sheath cells. This transformation procedure is the first for an NAD-ME type C(4) plant and should significantly accelerate the analysis of mechanisms underlying C(4) photosynthesis.

C acid decarboxylases required for C photosynthesis are active in the mid-vein of the C species Arabidopsis thaliana, and are important in sugar and amino acid metabolism.

Cells associated with veins of petioles of C(3) tobacco possess high activities of the decarboxylase enzymes required in C(4) photosynthesis. It is not clear whether this is the case in other C(3) species, nor whether these enzymes provide precursors for specific biosynthetic pathways. Here, we investigate the activity of C(4) acid decarboxylases in the mid-vein of Arabidopsis, identify regulatory regions sufficient for this activity, and determine the impact of removing individual isoforms of each protein on mid-vein metabolite profiles. This showed that radiolabelled malate and bicarbonate fed to the xylem stream were incorporated into soluble and insoluble material in the mid-vein of Arabidopsis leaves. Compared with the leaf lamina, mid-veins possessed high activities of NADP-dependent malic enzyme (NADP-ME), NAD-dependent malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PEPCK). Transcripts derived from both NAD-ME, one PCK and two of the four NADP-ME genes were detectable in these veinal cells. The promoters of each decarboxylase gene were sufficient for expression in mid-veins. Analysis of insertional mutants revealed that cytosolic NADP-ME2 is responsible for 80% of NADP-ME activity in mid-veins. Removing individual decarboxylases affected the abundance of amino acids derived from pyruvate and phosphoenolpyruvate. Reducing cytosolic NADP-ME activity preferentially affected the sugar content, whereas abolishing NAD-ME affected both the amino acid and the glucosamine content of mid-veins.

Photosynthesis in cells around veins of the C(3) plant Arabidopsis thaliana is important for both the shikimate pathway and leaf senescence as well as contributing to plant fitness.

Cells associated with veins of C(3) species often contain significant amounts of chlorophyll, and radiotracer analysis shows that carbon present in the transpiration stream may be used for photosynthesis in these cells. It is not clear whether CO2 is also supplied to these cells close to veins via stomata, nor whether this veinal photosynthesis supplies carbon skeletons to particular metabolic pathways. In addition, it has not been possible to determine whether photosynthesis in cells close to veins of C(3) plants is quantitatively important for growth or fitness. To investigate the role of photosynthesis in cells in and around the veins of C(3) plants, we have trans-activated a hairpin construct to the chlorophyll synthase gene (CS) using an Arabidopsis thaliana enhancer trap line specific to veins. CS is responsible for addition of the phytol chain to the tetrapyrolle head group of chlorophyll, and, as a result of cell-specific trans-activation of the hairpin to CS, chlorophyll accumulation is reduced around veins. We use these plants to show that, under steady-state conditions, the extent to which CO2 is supplied to cells close to veins via stomata is limited. Fixation by minor veins of CO2 supplied to the xylem stream and the amount of specific metabolites associated with carbohydrate metabolism and the shikimate pathway were all reduced. In addition, an abundance of transcripts encoding components of pathways that generate phosphoenolpyruvate were altered. Leaf senescence, growth rate and seed size were all reduced in the lines with lower photosynthetic ability in veins and in cells close to veins.

Cleome, a genus closely related to Arabidopsis, contains species spanning a developmental progression from C(3) to C(4) photosynthesis.

C(4) photosynthesis involves alterations to leaf development, cell biology and biochemistry. Different lineages of C(4) plants use varying mechanisms to generate the C(4) pathway. Although the biochemistry of C(4) photosynthesis was described around 20 years ago, the phylogenetic distance between Arabidopsis and the traditional C(4) models has not facilitated the transfer of knowledge from Arabidopsis research to understanding C(4) systems. We show that Cleome, a genus closely related to Arabidopsis, contains species spanning a developmental progression from C(3) to C(4) photosynthesis. The majority of species we assessed are C(3) plants but have increased venation in leaves. Three C(3) species have both increased venation and enlarged bundle sheath cells, and there is also a tendency to accumulate proteins and transcripts needed for C(4) photosynthesis. Cleome gynandra shows all the characteristics needed for efficient C(4) photosynthesis, including alterations to leaf biochemistry, cell biology and development, and belongs to the NAD-dependent malic enzyme subtype. Combined with its phylogenetic proximity to Arabidopsis, the developmental progression from C(3) to C(4) photosynthesis within the genus provides a potentially excellent new model to increase our understanding of C(4) photosynthesis, and provide insights into its evolution.

Light and plastid signals regulate the expression of the pea plastocyanin gene through a common region at the 5' end of the coding region.

Expression of the pea plastocyanin gene (PetE) is regulated by light and plastid signals. Previous work indicated that light and plastid regulation of pea PetE operates post-transcriptionally in transgenic tobacco, and requires the correct 5' terminus of the PetE transcript and the PetE-coding region. The post-transcriptional light and plastid regulation of pea PetE has now been demonstrated to operate in transgenic Arabidopsis, where in contrast the endogenous PETE gene is regulated transcriptionally. Transgenic tobacco seedlings containing constructs with progressive 3' deletions of the PetE-coding region fused to the luciferase (Luc) reporter gene demonstrate that the first 60 nucleotides of the coding region are sufficient for regulated accumulation of Luc transcripts by light and plastid signalling pathways affected by treatment with norflurazon and lincomycin. PetE constructs containing premature stop codons were generated to investigate whether translation has a role in light or plastid regulation. Insertion of a stop codon in place of the second codon of the PetE-coding region diminished both light and plastid regulation of PetE transcripts, whereas stop codons inserted later in the transcript had no effect on light or plastid regulation. These experiments indicate that the 5' end of the plastocyanin-coding region contains sequences important for regulation by light and plastid signals.

The future of C4 research--maize, Flaveria or Cleome?

C4 photosynthesis has evolved multiple times among the angiosperms: the spatial rearrangement of the photosynthetic apparatus, combined with alterations to the leaf structure, allows CO2 to be concentrated around Rubisco. Higher CO2 concentrations at Rubisco decrease the rate of oxygenation and therefore reduce the amount of energy lost through photorespiration. C4 plants are particularly prevalent in tropical and subtropical regions because they can sustain higher rates of net photosynthesis; they also represent some of our most productive crops. To date, most progress in identifying genes crucial for C4 photosynthesis has been made using maize and Flaveria. We propose that Cleome, the most closely related genus containing C4 species to the C3 model Arabidopsis, be used together with Arabidopsis resources to accelerate our progress in elucidating the genetic basis of C4 photosynthesis.