Pollen transport networks reveal highly diverse and temporally stable plant-pollinator interactions in an Appalachian floral community.

Floral visitation alone has been typically used to characterize plant-pollinator interaction networks even though it ignores differences in the quality of floral visits (e.g. transport of pollen) and thus may overestimate the number and functional importance of pollinating interactions. However, how network structural properties differ between floral visitation and pollen transport networks is not well understood. Furthermore, the strength and frequency of plant-pollinator interactions may vary across fine temporal scales (within a single season) further limiting our predictive understanding of the drivers and consequences of plant-pollinator network structure. Thus, evaluating the structure of pollen transport networks and how they change within a flowering season may help increase our predictive understanding of the ecological consequences of plant-pollinator network structure. Here we compare plant-pollinator network structure using floral visitation and pollen transport data and evaluate within-season variation in pollen transport network structure in a diverse plant-pollinator community. Our results show that pollen transport networks provide a more accurate representation of the diversity of plant-pollinator interactions in a community but that floral visitation and pollen transport networks do not differ in overall network structure. Pollen transport network structure was relatively stable throughout the flowering season despite changes in plant and pollinator species composition. Overall, our study highlights the need to improve our understanding of the drivers of plant-pollinator network structure in order to more fully understand the process that govern the assembly of these interactions in nature.

Microvascular reconstruction of segmental mandibular defects without tracheostomy.

OBJECTIVE: To report our experience with mandibular resection and reconstruction using vascularized bone-containing free flaps without an elective tracheostomy. STUDY DESIGN: Case series with chart review. SETTING: Tertiary referral hospital center. SUBJECTS AND METHODS: Sixty-six patients undergoing mandibular reconstruction with vascularized bone-containing free flaps without an elective tracheostomy were identified between 1995 and 2013. We describe patient, tumor, and surgical factors and report perioperative outcomes in this population. RESULTS: Most patients underwent fibula free flap reconstruction (n = 61, 92.44%). The 4 most frequent indications for resection were osteoradionecrosis, parotid carcinoma, oral squamous cell carcinoma, and osteomyelitis. Bone defects ranging from 4.0 to 13.0 cm were reconstructed, and associated soft-tissue defects were reconstructed with skin paddle sizes ranging from 24.0 to 450.0 cm(2). There was only 1 patient with a bilateral central mandibular defect, and there were no tongue/pharyngeal soft-tissue defects or bilateral neck dissections. One case required emergent tracheostomy on postoperative day 1, and 2 more patients developed respiratory complications. There were no cases of perioperative death or flap failure. CONCLUSION: Mandibular free flap reconstruction is feasible without an elective tracheostomy in a subset of carefully selected patients without bilateral central mandibular defects, tongue/pharynx defects, or bilateral neck dissection.

Delivery of bioactive lipids from composite microgel-microsphere injectable scaffolds enhances stem cell recruitment and skeletal repair.

In this study, a microgel composed of chitosan and inorganic phosphates was used to deliver poly(lactic-co-glycolic acid) (PLAGA) microspheres loaded with sphingolipid growth factor FTY720 to critical size cranial defects in Sprague Dawley rats. We show that sustained release of FTY720 from injected microspheres used alone or in combination with recombinant human bone morphogenic protein-2 (rhBMP2) improves defect vascularization and bone formation in the presence and absence of rhBMP2 as evaluated by quantitative microCT and histological measurements. Moreover, sustained delivery of FTY720 from PLAGA and local targeting of sphingosine 1-phosphate (S1P) receptors reduces CD45+ inflammatory cell infiltration, promotes endogenous recruitment of CD29+CD90+ bone progenitor cells and enhances the efficacy of rhBMP2 from chitosan microgels. Companion in vitro studies suggest that selective activation of sphingosine receptor subtype-3 (S1P3) via FTY720 treatment induces smad-1 phosphorylation in bone-marrow stromal cells. Additionally, FTY720 enhances stromal cell-derived factor-1 (SDF-1) mediated chemotaxis of CD90+CD11B-CD45- bone progenitor cells in vitro after stimulation with rhBMP2. We believe that use of such small molecule delivery formulations to recruit endogenous bone progenitors may be an attractive alternative to exogenous cell-based therapy.

Delivery of S1P receptor-targeted drugs via biodegradable polymer scaffolds enhances bone regeneration in a critical size cranial defect.

Biodegradable polymer scaffolds can be used to deliver soluble factors to enhance osseous remodeling in bone defects. To this end, we designed a poly(lactic-co-glycolic acid) (PLAGA) microsphere scaffold to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors. The microsphere scaffolds were created from fast degrading 50:50 PLAGA and/or from slow-degrading 85:15 PLAGA. Temporal and spatial regulation of bone remodeling depended on the use of appropriate scaffolds for drug delivery. The release profiles from the scaffolds were used to design an optimal delivery system to treat critical size cranial defects in a rodent model. The ability of local FTY720 delivery to maximize bone regeneration was evaluated with micro-computed tomography (microCT) and histology. Following 4 weeks of defect healing, FTY720 delivery from 85:15 PLAGA scaffolds resulted in a significant increase in bone volumes in the defect region compared to the controls. A 85:15 microsphere scaffolds maintain their structural integrity over a longer period of time, and cause an initial burst release of FTY720 due to surface localization of the drug. This encourages cellular in-growth and an increase in new bone formation.

Multilayer cell-seeded polymer nanofiber constructs for soft-tissue reconstruction.

IMPORTANCE: Cell seeding throughout the thickness of a nanofiber construct allows for patient-specific implant alternatives with long-lasting effects, earlier integration, and reduced inflammation when compared with traditional implants. Cell seeding may improve implant integration with host tissue; however, the effect of cell seeding on thick nanofiber constructs has not been studied. OBJECTIVE: To use a novel cell-preseeded nanofiber tissue engineering technique to create a 3-dimensional biocompatible implant alternative to decellularized extracellular matrix. DESIGN: Animal study with mammalian cell culture to study tissue engineered scaffolds. SETTING: Academic research laboratory. PARTICIPANTS: Thirty-six Sprague-Dawley rats. INTERVENTIONS: The rats each received 4 implant types. The grafts included rat primary (enhanced green fluorescent protein-positive [eGFP+]) fibroblast-seeded polycaprolactone (PCL)/collagen nanofiber scaffold, PCL/collagen cell-free nanofiber scaffold, acellular human cadaveric dermis (AlloDerm), and acellular porcine dermis (ENDURAGen). Rats were monitored postoperatively and received enrofloxacin in the drinking water for 4 days prophylactically and buprenorphine (0.2-0.5 mg/kg administered subcutaneously twice a day postoperatively for pain for 48 hours). MAIN OUTCOMES AND MEASURES: The viability of NIH/3T3 fibroblasts cultured on PCL electrospun nanofibers was evaluated using fluorescence microscopy. Soft-tissue remodeling was examined histologically and with novel ex vivo volume determinations of implants using micro-computed tomography of cell-seeded implants relative to nanofibers without cells and commonly used dermal grafts of porcine and human origin (ENDURAGen and AlloDerm, respectively). The fate and distribution of eGFP+ seeded donor fibroblasts were assessed using immunohistochemistry. RESULTS: Fibroblasts migrated across nanofiber layers within 12 hours and remained viable on a single layer for up to 14 days. Scanning electron microscopy confirmed a nanoscale structure with a mean (SD) diameter of 158 (72) nm. Low extrusion rates demonstrated the excellent biocompatibility in vivo. Histological examination of the scaffolds demonstrated minimal inflammation. Cell seeding encouraged rapid vascularization of the nanofiber implants. Cells of donor origin (eGFP+) declined with the duration of implantation. Implant volume was not significantly affected for up to 8 weeks by the preseeding of cells (P > .05). CONCLUSIONS AND RELEVANCE: Polymer nanofiber-based scaffolds mimic natural extracellular matrix. Preseeding the nanofiber construct with cells improved vascularization without notable effects on volume. An effect of cell preseeding on scaffold vascularization was evident beyond the presence of preseeded cells. This 3-dimensional, multilayer method of cell seeding throughout a 1-mm-thick construct is simple and feasible for clinical application. Further development of this technique may affect the clinical practice of facial plastic and reconstructive surgeons.

Timing for repair of mandible fractures.

OBJECTIVES/HYPOTHESIS: Timing for repair of mandible fractures is a significant factor with regard to the rate of complication. STUDY DESIGN: Retrospective chart review of the previous 5 years (January 2005-January 2010). METHODS: All patients undergoing mandible fracture fixation performed in the study period and having complete records were analyzed (n = 83). Patients were stratified by time to fixation following initial injury. Subjects were then separated by the presence or absence of any of the following complications: infection, malunion, and nonunion. Logistical regression was then performed. RESULTS: Out of 83 patients there were 4 patients with six complications including malunion (n = 4) and infection (n = 2). There were no cases of nonunion. Delay in surgical intervention did not influence the complication rate. CONCLUSIONS: Complications from repair of mandible fractures are rare; it is difficult to detect significant variables that may impact outcomes. We found no relationship between complications and timing to repair.

Four years of accreditation council of graduate medical education duty hour regulations: have they made a difference?

OBJECTIVES/HYPOTHESIS: Measure compliance with the Accreditation Council of Graduate Medical Education (ACGME) residents' work hour regulations and evaluate their impact on patient care and residents' performance on the Otolaryngology Training Examination (OTE). STUDY DESIGN: Retrospective review of an otolaryngology residency program's resident duty hours violations and OTE scores, and review of the associated hospital's benchmark patient data. METHODS: Residents' duty hour violations were compiled and analyzed for individual violation, postgraduate year (PGY), and service in the program. Annual OTE scores and the department's hospital benchmark measures (inpatient mortality, inpatient length of stay, 30-day readmission rate) were compared before and after the institution of the ACGME duty hours mandate. RESULTS: The 10-hour rule was most frequently violated; residents on the oncology service and PGY-2 year were most commonly in violation. There was no difference before and after institution of the ACGME duty hours mandate in 30-day hospital readmission rates (P = .42), hospital mortality index (P = .55), length of stay (P = .55), OTE scores (P = .11, Student's t test), and graduating resident's operative volume. CONCLUSIONS: Institution of the ACGME duty hour regulations did not improve patient care as measured by the 30-day readmission rate, inhospital mortality, and patient's length of stay. Residents' performance on the OTE did not change after implementation of the ACGME rules. Further studies are warranted to assess the impact of the ACGME work hour regulations on patient care and resident-physicians' training.