Tissue engineering of cartilage using poly-epsilon-caprolactone nanofiber scaffolds seeded in vivo with periosteal cells.

OBJECTIVE: To determine the potential of periosteal cells to infiltrate poly-epsilon-caprolactone (PCL) nanofiber scaffolds in vivo and subsequently produce cartilage in vitro. DESIGN: PCL nanofiber scaffolds, with or without chitosan-coating were implanted under periosteum in 6-month-old rabbits. Transforming growth factor-beta1 (TGF-beta1) or vehicle was injected into each implant site. After 1, 3, 5 or 7 days, scaffolds were removed, separated from the periosteum, and the scaffolds and periosteum were cultured separately for 6 weeks under chondrogenic conditions. Sulfated glycosaminoglycan (GAG), type II collagen, DNA content, cartilage yield, and calcium deposition were then analyzed. RESULTS: Cell infiltration was observed in all scaffolds. Cartilage formation in the uncoated scaffolds increased with duration of implantation (maximum at 7 days). Cells in the uncoated scaffolds implanted for 7 days produced significantly higher levels of both GAG [560 (95% confidence interval (CI), 107-1013) vs 228 (95% CI, 177-278) microg GAG/microg DNA] and cartilage yield [9% (95% CI, 3-14%) vs 0.02% (95% CI, 0-0.22%)] compared to chitosan-coated scaffolds (P=0.006 or less). There was no significant difference in GAG content or cartilage yield between the TGF-beta1-injected and vehicle-injected scaffolds. However, significantly more mineral deposition was detected in TGF-beta1-injected scaffolds compared to vehicle-injected scaffolds (P<0.0001). Cartilage yield from the periosteum, moreover, was significantly increased by subperiosteal TGF-beta1 injections (P<0.001). However, this response was reduced when chitosan-coated scaffolds were implanted. CONCLUSIONS: This study demonstrates that it is possible to seed PCL nanofiber scaffolds with periosteal cells in vivo and subsequently produce engineered cartilage in vitro.

Poly-epsilon-caprolactone/gel hybrid scaffolds for cartilage tissue engineering.

The aim of this study was to determine the suitability of hybrid scaffolds composed of naturally derived biopolymer gels and macroporous poly-epsilon-caprolactone (PCL) scaffolds for neocartilage formation in vitro. Rabbit articular chondrocytes were seeded into PCL/HA (1 wt % hyaluronan), PCL/CS (0.5 wt % chitosan), PCL/F (1:3 fibrin sealant plus aprotinin), and PCL/COL1 (0.24% type I collagen) hybrids and cultured statically for up to 50 days. Growth characteristics were evaluated by histological analysis, scanning electron microscopy, and confocal laser scanning microscopy. Neocartilage was quantified using a dimethyl-methylene blue assay for sulfated glycosaminoglycans (sGAG) and an enzyme-linked immunosorbent assay for type II collagen (COL2), normalized to dsDNA content by fluorescent PicoGreen assay. Chondrocytes were homogenously distributed throughout the entire scaffold and exhibited a predominantly spheroidal shape 1 h after being seeded into scaffolds. Immunofluorescence depicted expanding proteoglycan deposition with time. The sGAG per dsDNA increased in all hybrids between days 25 and 50. PCL/HA scaffolds consistently promoted highest yields. In contrast, total sGAG and total COL2 decreased in all hybrids except PCL/CS, which favored increasing values and a significantly higher total COL2 at day 50. Overall, dsDNA content decreased significantly with time, and particularly between days 3 and 6. The PCL/HA hybrid displayed two proliferation peaks at days 3 and 25, and PCL/COL1 displayed one proliferation peak at day 12. The developed hybrids provided distinct short-term environments for implanted chondrocytes, with not all of them being explicitly beneficial (PCL/F, PCL/COL1). The PCL/HA and PCL/CS hybrids, however, promoted specific neocartilage formation and initial cell retention and are thus promising for cartilage tissue engineering.

Molecular markers in stored kidneys using perfluorocarbon-based preservation solution: preliminary results.

BACKGROUND: Delayed graft function (DGF) is a problem in kidney transplantation and cold ischemia has been identified as a risk factor. Perfluorocarbons (PFC) have an enhanced ability to dissolve and release oxygen. We evaluated histologically and a number of molecular changes induced by ischemia in stored kidneys with University of Wisconsin (UW) and PFC-based preservation solutions (PFC-UW). MATERIALS AND METHODS: ACI rats were used as kidney donors. UW (control group) or PFC-UW (study group) preservation solutions were used for kidney perfusion. All kidneys were stored at 4 degrees C for 12, 24, and 36 hours. After this time, intragraft histologic evaluation as well as mRNA HO-1 and iNOS levels were also analyzed. RESULTS: In the kidneys stored at 24 hours, mRNA HO-1 levels were elevated in the study group when compared with the control and mRNA iNOS was decreased. CONCLUSION: We observed overexpression of HO-1 and underexpression of iNOS in the kidney tissue stored with PFC-UW solution at 24 hours. These preliminary data suggest that increasing oxygen delivery by PFC added to the perfusion solution triggers cytoprotective mechanism in kidney transplantation.

Hydrologic response and radionuclide transport following fire at semiarid sites.

Infrequent, high-impact events such as wildfires, droughts, biological shifts, floods, and mechanical disturbances can greatly change land surfaces, including vegetative cover and soil characteristics, which in turn can trigger high rates of hydrologic erosion and associated transport of sediments and sediment-sorbed contaminants. Where persistent soil contamination exists, infrequent mobilization of contaminants may dominate in determining long-term risks to human and ecological receptors. Among these infrequent events, fire stands out as having the capacity to cause large increases in sediment transport. This study measured runoff, sediment yield, and mobility of sediment-sorbed contamination (137Cs) on burned and unburned plots at the Waste Isolation Pilot Plant, New Mexico (WIPP), and the Rocky Flats Environmental Technology Site, Colorado (RFETS). Results showed that 137Cs transport from burned plots was up to 22 times greater than that from unburned plots at WIPP and 4 times greater at RFETS. Associated runoff was up to 12 times greater on burned plots at WIPP and sediment yields up to 6 times greater. Further, 137Cs concentrations in transported sediments were enriched compared with parent soils (expressed as enrichment ratio) by a factor of 2.3 at WIPP, and 1.3 at RFETS. However, enrichment ratios were not significantly different in sediments from burned and unburned plots. Our results provide new data on the effects of fire on the transport of sediment-sorbed contaminants, and demonstrate that rare events such as fire can greatly increase contaminant mobility.

Analysis of the shoulder implant.

Total shoulder arthroplasty (TSA) is implemented for the relief of pain and better joint function. It is desirable that the TSA can achieve and maintain a long-term and secure fixation of the implanted components. The previous biomechanical studies of shoulder implants were simplified and limited to the two-dimensional (2-D) computational finite element analysis (FEA). In this research, reliable 3-D FEA models were established and used to examine the contact stress distribution, contact region and deformation of implant. Based on FEA results, the design of current shoulder implants can be modified for optimum performance. The substantiated 3-D FEA models can provide important engineering data and clinically useful information toward the development of better shoulder implants for a long-term fixation.

Computational contact analysis of joint congruency.

Joint contact analysis of the musculoskeletal system is an important biomedical research topic due to its significant clinical relevance. In this research, the finite element method was used to study the effect of joint congruencies (various radii, R1 and R2), contact area (angles theta), and contact stresses of articular joints (the far-field applied pressure, P = 10,000 Pa). In total, 12 joint congruency cases, ranging from R1/R2 = 100% (congruent) to R1/R2 = -100% (highly incongruent) were analyzed. The linear finite element (quasi-static/equilibrium) results show that peak contact stress delta r of a congruent joint (R1 = R2 theta = 90 degrees) is -13,068 Pa. However, with a slight change of joint congruency (R1/R2 = 99.7%), the contact area decreases dramatically (theta = 30 degrees) and leads to a much higher concentrated contact stress, delta r = -27,894 Pa. When R1/R2 = -100%, the finite element result shows that the contact region is only theta = 3 degrees and the associate peak contact stress delta r is -229,943 Pa.

Cement viscosity affects the bone-cement interface in total hip arthroplasty.

Quantitative information regarding the interface strength and degree of cement penetration associated with cement viscosity during total hip arthroplasty is limited. The aim of the present study was to determine the effect of the viscosity of bone cement at the time of implantation on the mechanical integrity of total hip arthroplasty. Cement that was injected at an early less viscous stage produced greater failure strength in a push-out test than its more viscous counterpart.

An apparatus for spine biomechanical testing.

A testing system that applies a pure bending moment will uniformly load a spinal construct and be capable of identifying its weakest point. This study describes an apparatus for use with a material testing machine that is simple, inexpensive, and reliably creates a pure bending moment along the whole spine. We tested the system using two strain gauges attached to an aluminum alloy beam. First we verified the reliability and accuracy of the strain gauges system by comparing experimental measurement strain to theoretical prediction of strain in a cantilever beam model. The second experiment assessed the moment and strain created at two locations on a beam which was fixed at one end. The mean strain recorded from the two gauges demonstrated that moment is not uniformly distributed along the length of beam that is fixed at one end. The third experiment was similar to the second except that the beam was attached to an X-Y table instead of being fixed. Results demonstrated that a pure bending moment status is achieved when the end of the beam is fixed to an X-Y table.

The use of a direct current electromagnetic tracking device in a metallic environment.

The use of a relatively new direct current (DC) electromagnetic tracking device in conjunction with a hostile metal environment of Material Testing Machine was studied. In this research, we first evaluated the reliability and performance of the DC tracking system operating in an ideal metal-free environment for both the translational and rotational error in static and dynamic conditions. When the tracking system with the same factory default configuration was moved into a heavy metal environment, serious translational and rotational distortion were observed. Through a series of evaluation of the physical environment and modification of the settings, the tracking system could perform satisfactorily and both the translational and angular error could be reduced in manufacturer's specifications. The safe working region for the DC tracking systems operating in a material testing machine environment was successfully mapped out. This study provides information for using the DC electromagnetic tracing device in the heavy metal environment exists in the material testing machine.

Acute inhalation toxicology of oxalyl chloride.

The acute inhalation LC50 of oxalyl chloride was determined in rats following a one-hour exposure. Four groups of 10 animals per group were exposed to a concentration range of 462-2233 ppm. One set of six animals was exposed to a concentration of oxalyl chloride of 1232 ppm for one hour to evaluate the histopathological change to the lungs. The LC50 is 1840 ppm with the 95% confidence interval between 1531 ppm and 2210 ppm. Microscopically, the lungs from the treated animals exhibited acute bronchiolitis, exudate within the alveoli, and congestion. Pulmonary edema appears to contribute significantly to mortality produced by oxalyl chloride. A comparison of the acute one-hour LC50 of oxalyl chloride to that of hydrogen chloride, phosgene, phosphorus oxychloride, boron trichloride, and chlorine indicates that it shares a comparable degree of acute toxicity to hydrogen chloride and is significantly less toxic via inhalation than the latter four chemicals.

Fentanyl for epidural intravascular test dose in obstetrics.

BACKGROUND AND OBJECTIVES: Although dizziness and drowsiness may be produced with either intravenous or epidural fentanyl, their occurrence after an intravenous injection is more rapid and relatively more pronounced. The purpose of this study was to determine whether or not the difference between routes of administration would be a reliable method of detecting an accidental intravascular injection. METHODS: In part 1, using a double-blinded protocol, we prospectively assessed in laboring women the incidence of dizziness, drowsiness, or both associated with intravenous fentanyl (100 micrograms). In random order, subjects received two peripheral intravenous injections: 2 ml of fentanyl and 2 ml of saline, separated by a 3-minute observation period. RESULTS: In group 1 (18/18) and group 2 (22/22), all subjects reported a response to intravenous fentanyl within the one-minute assessment. In part 2, we evaluated in laboring patients the frequency of dizziness, drowsiness, or both to epidural fentanyl (100 micrograms). The study design was identical to part 1; however, the subjects received 2 ml of fentanyl and 2 ml of saline via a functional epidural catheter. In group 3 (1/18) and group 4 (1/22), one subject reported a response to epidural fentanyl within the 3-minute observation period. CONCLUSIONS: Overall, the responses to intravenous fentanyl (40/40) occurred in a remarkably more consistent fashion when compared to epidural fentanyl (2/40). Thus, the results suggest that in laboring patients, intravenous fentanyl produces predictable and easily detectable changes that may be useful in identifying an epidural catheter unintentionally placed intravascularly.

Transdermal scopolamine decreases nausea and vomiting following cesarean section in patients receiving epidural morphine.

The authors evaluated the antiemetic properties of transdermal scopolamine (TDS) in healthy patients undergoing elective cesarean section and receiving epidural morphine for postoperative analgesia. Prior to administration of anesthesia, 203 patients had either TDS or a placebo study patch applied behind one ear. All patients were hydrated with lactated Ringer's solution iv and given 2.0% lidocaine with 1:200,000 epinephrine epidurally for surgical anesthesia. Following delivery of the infant, 4 mg of morphine sulphate was injected through the epidural catheter. After the operation patients were evaluated by "blinded" observers at 2, 4, 6, 8, 10, 24, and 48 h for nausea, vomiting, retching, pain relief, itching, and adverse effects. In addition, medications received were noted. No differences were found between the groups in terms of severity or incidence of pain, or requests for analgesic or antipruritic medication. Although there was no difference between the groups in the first 2 h, patients with TDS had significantly less nausea, vomiting, and retching than patients in the placebo group in each time interval between 2 and 10 h. Additionally, the TDS group required less antiemetic medication. There was no difference in the frequency of retching or vomiting between groups. Side effects were minimal and equal in both groups. The authors conclude that TDS results in a decreased incidence of nausea and vomiting in patients who have delivered by cesarean section and received epidural morphine. TDS appears safe for continuous antiemetic administration.

Unrecognized thrombocytopenia and regional anesthesia in parturients: a retrospective review.

Charts from 2929 consecutive parturients were reviewed. Twenty-four had platelet counts less than 100,000/microL in the peripartum period. Seventeen of the 24 had predisposing causes for thrombocytopenia, including preeclampsia (nine), immune thrombocytopenia purpura (two), infection (three), placenta accreta (one), abruption (one), and excessive surgical bleeding (one). Seven had asymptomatic thrombocytopenia of unknown origin. Fourteen of the 24 thrombocytopenic patients received regional anesthesia, and none had permanent sequelae. Based upon this retrospective review, peripartal thrombocytopenia (15,000-99,000/microL) did not increase the risk of neurologic complications after a regional anesthetic. There have been no reports in the literature of spinal or epidural hematomas in parturients after regional anesthesia, except for one patient with a spinal ependymoma.

Hemodynamic, metabolic, and morphological effects of cardiopulmonary bypass with a fluorocarbon priming solution.

Systemic perfusion, myocardial contractility, and morphological changes during and after cardiopulmonary bypass (CPB) were investigated in 22 greyhounds; Fluosol-DA 20% (FDA) and normal saline (NaCl) were compared as priming solutions for hypothermic (25 degrees C) CPB. Hemodynamic and oxygenation indices were similar in all groups. Animals with fluorocarbon primes had higher serum lactate concentrations (mean +/- standard error of the mean [SEM]) during CPB (NaCl 1.64 +/- 0.2, FDA 2.39 +/- 0.3, p less than 0.01), representing an increase over the control of 12% and 319% in the NaCl and FDA groups, respectively. After CPB, serum lactate concentration remained elevated in the FDA group, but it returned to the level of the control in the NaCl group (NaCl 1.49 +/- 0.5, FDA 2.29 +/- 1.1, p less than 0.01); increases over the control level were 7% and 302% in the NaCl and FDA groups, respectively. Myocardial contractility after CPB, expressed as dP/dt[40], was similar in the two experimental groups. Three weeks after CPB, a histological examination by light microscopy of multiple organs obtained from a separate group of 12 animals treated similarly was performed, demonstrating no significant morphological differences between animals primed with fluorocarbon or with saline. The results suggest that FDA is a satisfactory priming agent for hypothermic CPB. It adequately preserves myocardial function and causes no adverse morphological changes, but a persistent, as yet unexplained, elevation in serum lactate concentration occurs.