Single- and multiple-dose pharmacokinetics of sotalol hydrochloride in healthy cats

INTRODUCTION/OBJECTIVES

The objective of this study was to describe the single- and multiple-dose pharmacokinetics and urinary elimination of sotalol in healthy cats.

ANIMALS

Six adult purpose-bred cats MATERIALS AND METHODS: Cats were administered 2 mg sotalol/kg body weight as a single intravenous bolus and as a single oral dose in a randomized crossover study with a 2-week washout period. The same cats then received 3 mg sotalol/kg orally every 12 h for 2 weeks. Blood samples were collected at predetermined time points for 48 h postdose for quantification of sotalol using ultra-high-pressure liquid chromatography with mass spectrometry. Non-compartmental analysis was used to obtain pharmacokinetic parameters. Data are presented as median (min-max).

RESULTS

Following intravenous administration, plasma clearance and volume of distribution were 9.22 mL/min/kg (5.69-10.89) and 2175.56 (1961-2341.57) mL/kg, respectively. Bioavailability was 88.41% (62.75-130.29) following a single oral dose. Peak plasma concentration (Cmax) and time to Cmax were 0.94 μg/mL (0.45-1.17) and 1.5 h (0.5-4) after a single oral dose (2 mg/kg), and 2.29 μg/mL (1.91-2.48) and 1.0 h (0.5-1.5) with chronic oral dosing (3 mg/kg), respectively. Elimination half-life was 2.75 h (2.52-4.10) and 4.29 h (3.33-5.53) for single and chronic oral dosing, respectively. Accumulation index was 1.17 (1.09-1.29) after chronic dosing. Urinary sotalol recovery was 81-108% of the intravenous dose.

CONCLUSIONS

Oral sotalol administration resulted in plasma concentrations reportedly efficacious in other species, with good to excellent oral bioavailability. Urinary excretion appears to be a major route of elimination. Following repeated oral dosing, minimal drug accumulation was estimated. Additional studies in cats are recommended due to the possibility of nonlinear kinetics.

COVID-19 advanced respiratory care educational training programme for healthcare workers in Lesotho: an observational study

OBJECTIVE

To develop and implement a 'low-dose, high-frequency' (LDHF) advanced respiratory care training programme for COVID-19 care in Lesotho.

DESIGN

Prospective pretraining-post-training evaluation.

SETTING

Lesotho has limited capacity in advanced respiratory care.

PARTICIPANTS

Physicians and nurses.

INTERVENTIONS

Due to limited participation in May-September 2020, the LDHF approach was modified into a traditional 1-day offsite training in November 2020 that reviewed respiratory anatomy and physiology, clinical principles for conventional oxygen, heated high-flow nasal cannula and non-invasive ventilation management. Basic mechanical ventilation principles were introduced.

OUTCOME MEASURES

Participants completed a 20-question multiple choice examination immediately before and after the 1-day training. Paired t-tests were used to evaluate the difference in average participant pretraining and post-training examination scores.

RESULTS

Pretraining and post-training examinations were completed by 46/53 (86.7%) participants, of whom 93.4% (n=43) were nurses. The overall mean pretraining score was 44.8% (SD 12.4%). Mean scores improved by an average of 23.7 percentage points (95% CI 19.7 to 27.6, p<0.001) on the post-training examination to a mean score of 68.5% (SD 13.6%). Performance on basic and advanced respiratory categories also improved by 17.7 (95% CI 11.6 to 23.8) and 25.6 percentage points (95% CI 20.4 to 30.8) (p<0.001). Likewise, mean examination scores increased on the post-training test, compared with pretraining, for questions related to respiratory management (29.6 percentage points, 95% CI 24.1 to 35.0) and physiology (17.4 percentage points, 95% CI 12.0 to 22.8).

CONCLUSIONS

An LDHF training approach was not feasible during this early emergency period of the COVID-19 pandemic in Lesotho. Despite clear knowledge gains, the modest post-training examination scores coupled with limited physician engagement suggest healthcare workers require alternative educational strategies before higher advanced care like mechanical ventilation is implementable. Conventional and high-flow oxygen is better aligned with post-training healthcare worker knowledge levels and rapid implementation.

National hospital readiness for COVID-19 in Lesotho: evidence for oxygen ecosystem strengthening

SETTING

Sub-Saharan African country, Lesotho, during the SARS-CoV-2 COVID-19 pandemic.

OBJECTIVE

To evaluate COVID-19 hospital capacity in Lesotho.

DESIGN

We conducted a pragmatic assessment of all public hospitals in Lesotho using a WHO COVID-19 hospital assessment tool during July 2020 (baseline), with targeted follow-up in December 2020. We adapted the WHO tool into a questionnaire with a focus on hospital services and included oxygen ecosystem elements (pulse oximeters, oxygen, and advanced respiratory care). We converted qualitative questionnaire answers into quantitative ordinal variables and used standard statistics for analysis.

RESULTS

At baseline, we found all 12 questionnaire domains demonstrate both hospital preparedness and weakness in infection prevention and control. Key baseline gaps were lack of a dedicated team, and insufficient personal protective equipment and space for donning and doffing. Substantial limitations were noted in hypoxemia diagnosis and treatment; information management and care coordination pathways were also suboptimal. Targeted follow-up after 5 months revealed improvement in the availability of pulse oximetry, oxygen capacity, and heated high-flow nasal cannula devices.

CONCLUSION

Our baseline findings may reflect uneven early pandemic care quality; targeted follow-up suggests strengthening of the oxygen ecosystem.

Does temporary socket removal affect residual limb fluid volume of trans-tibial amputees?

BACKGROUND

Lower-limb prosthesis users typically experience residual limb volume losses over the course of the day that can detrimentally affect socket fit.

OBJECTIVES

To determine whether temporarily doffing the prosthesis encouraged residual limb fluid volume recovery and whether the recovered fluid was maintained.

STUDY DESIGN

Experimental design.

METHODS

Residual limb fluid volume was monitored on 16 participants in three test sessions each. Participants conducted six cycles of resting/standing/walking. Between the third and fourth cycles, participants sat for 30 min with the prosthesis and liner: donned (ON), the prosthesis doffed but the liner donned (LINER), or the prosthesis and liner doffed (OFF).

RESULTS

Percentage fluid volume gain and retention were greatest for the OFF condition followed by the LINER condition. Participants experienced fluid volume losses for the ON condition.

CONCLUSION

Doffing the prosthesis or both the prosthesis and liner during rest improved residual limb fluid volume retention compared with leaving the prosthesis and liner donned.

CLINICAL RELEVANCE

Practitioners should advise patients who undergo high daily limb volume losses to consider temporarily doffing their prosthesis. Fluid volume retention during subsequent activity will be highest if both the prosthesis and liner are doffed.

Development of tuberculosis infection control guidelines in a pediatric HIV clinic in sub-Saharan Africa

SETTING

A well-established pediatric human immunodeficiency virus (HIV) clinic in Lesotho with initial infection control (IC) measures prioritizing blood-borne disease. In line with international recommendations, services have been expanded to include the management of patients with tuberculosis (TB). The creation of comprehensive IC guidelines with an emphasis on TB has become a priority.

OBJECTIVE

To provide a model for developing and implementing IC guidelines in ambulatory care facilities in limited-resource settings with high HIV and TB prevalence. Activities: An IC plan that includes guidance covering both general IC measures and TB-specific guidelines was created by integrating local and international recommendations and emphasizing the importance of administrative measures, environmental controls, and disease-specific precautions. An interdisciplinary committee was established to oversee its implementation, monitoring, and evaluation.

DISCUSSION

Development and implementation of IC guidelines in resource-limited settings are feasible and should be a priority in high HIV and TB prevalence areas. Education should be the cornerstone of such endeavors. Many interventions can be implemented with minimal expertise and material resources. Administrative support and institutional investment are essential to the sustainability of an effective IC program.

Amputee socks: thickness of multiple socks

BACKGROUND AND AIM

It is unclear how total sock ply and thickness are related when more than one sock is worn. The objectives were to determine whether the thickness of one multi-ply amputee sock of ply P was the same as the thickness of a stack of reduced-ply socks of total ply P, and whether the thickness of N single socks stacked one on top of the other was equal to the sum (1 to N) of the single sock thicknesses.

TECHNIQUE

Using a custom instrument, compressive stresses were applied while sock thickness was measured.

DISCUSSION

The thickness of one multi-ply sock of ply P was typically less than the thickness of a stack of reduced-ply socks of total ply P. The thickness of N single socks stacked one on top of the other was approximately equal to the sum (1 to N) of the single sock thicknesses.

CLINICAL RELEVANCE

Our findings suggest three 1-ply socks to be 20% greater in thickness than one 3-ply sock, and one 3-ply + two 1-ply socks to be 30% greater in thickness than one 5-ply sock.

Modulation of gene expression using electrospun scaffolds with templated architecture

The fabrication of biomimetic scaffolds is a critical component to fulfill the promise of functional tissue-engineered materials. We describe herein a simple technique, based on printed circuit board manufacturing, to produce novel templates for electrospinning scaffolds for tissue-engineering applications. This technique facilitates fabrication of electrospun scaffolds with templated architecture, which we defined as a scaffold's bulk mechanical properties being driven by its fiber architecture. Electrospun scaffolds with templated architectures were characterized with regard to fiber alignment and mechanical properties. Fast Fourier transform analysis revealed a high degree of fiber alignment along the conducting traces of the templates. Mechanical testing showed that scaffolds demonstrated tunable mechanical properties as a function of templated architecture. Fibroblast-seeded scaffolds were subjected to a peak strain of 3 or 10% at 0.5 Hz for 1 h. Exposing seeded scaffolds to the low strain magnitude (3%) significantly increased collagen I gene expression compared to the high strain magnitude (10%) in a scaffold architecture-dependent manner. These experiments indicate that scaffolds with templated architectures can be produced, and modulation of gene expression is possible with templated architectures. This technology holds promise for the long-term goal of creating tissue-engineered replacements with the biomechanical and biochemical make-up of native tissues.

The effects of enamel matrix derivative and cyclic mechanical strain on human gingival fibroblasts in an in vitro defect healing model

Gingival fibroblasts (GFs) play a considerable role in the maintenance of the gingival apparatus as well as in connective tissue repair. Mobility of a periodontal wound or soft tissue graft can impair connective tissue healing from the GFs. Enamel matrix derivative (EMD) is an enamel matrix protein used clinically for periodontal regeneration of intrabony defects and furcations, as well as treatment of gingival margin recessions. The goal of this project was to compare the effects of varying concentrations of EMD, with and without cyclic mechanical strain, on cellular wound fill of human GFs using an in vitro defect healing model. GFs were seeded and cultured in six-well flexible-bottomed plates. A 3-mm wound was created in the central portion of each confluent well. Three wells were treated with each EMD concentration of 0 Μg/mL (control), 30 Μg/mL, 60 Μg/mL, or 120 Μg/mL. The plates were placed in an incubator containing a strain unit to subject test plates to cyclic strain. An identical set of control plates were not flexed. Cells were examined on days 4, 8, 12, and 16. Microphotographs were taken and wound fill measurements made using image analysis software. The percent wound fill was calculated. All nonflexed plates, regardless of EMD concentration, reached > 90% defect fill at similar rates by day 16. However, in the flexed plates, EMD had a significant negative effect on defect fill. The defect fill was 55.7% for 0 Μg/mL EMD, 48.2% for 30 Μg/mL EMD, 36.7% for 60 Μg/mL EMD, and 34.1% for 120 Μg/mL EMD on day 16 for the flexed GFs. EMD, in concentrations as high as 120 Μg/mL, did not significantly affect the amount of defect fill with nonflexed GFs. However, when the GFs were flexed, the addition of EMD had a significant negative effect on defect fill in a dose-dependent manner.

The quality of life of adult survivors of childhood hematopoietic cell transplant

Survival rates after myeloablative hematopoietic cell transplantation (HCT) in childhood have improved. We conducted a cross-sectional study evaluating the quality of life (QOL) of 214 adult survivors of a childhood HCT compared with controls using standardized self-report measures with strong psychometric properties to evaluate physical function, psychological function and cognitive symptoms. From these results we conducted a multivariate analysis of risk factors. This analysis for physical functioning showed poorer function among myeloid disease survivors compared with patients with all other diagnoses (P=0.02), men functioned better than women (P=0.05) and those >18 years after transplant functioned more poorly than those <18 years after transplant (P=0.05). Psychological functioning showed that those who received more therapy and females were more likely to be depressed (P=0.03) and (P=0.005). Perceived cognitive symptoms showed that female survivors had more symptoms than male survivors (P=0.01), and those receiving more preceding therapy compared with those with less preceding therapy (P=0.001) or cranial irradiation compared with those without cranial irradiation (P=0.002) had more perceived cognitive symptoms. Overall, these data indicate that the majority of adult survivors of a childhood transplant are functioning well, but some have problems that need to be addressed.

Marrow transplantation for malignant plasma cell disorders: summary of the Seattle experience

28 patients with plasma cell malignancies received marrow transplants from identical twins (N = 8), HLA-identical family members (N = 15), HLA partially-matched relatives (N = 3) or cryopreserved autologous marrow (N = 2). Treatment regimens included cyclophosphamide (CY) and total body irradiation (TBI) for 15 patients and busulphan (BU) and CY for 13 patients. 3 of 8 twins are alive, 2 without disease at 24 and 34 months, and 1 is alive and well at 116 months without evidence of disease except for at small residual monoclonal protein spike. 12 of the 18 allografted patients died of transplant-related causes and 2 died of progressive disease. 4 of 18 allograft recipients are alive; 2 are free of disease at 16 and 15 months, 1 is alive at 6 months without disease except for persistent monoclonal Kappa protein. 1 patient is alive with residual marrow involvement and a persistent IGA lambda monoclonal protein at 7 months. 1 of the 2 autograft recipients is alive 2 months after transplant and is not yet evaluable for tumor response and the other patient died early of transplant-related complications. Both CY + TBI and BU + CY resulted in remissions in patients with advanced plasma cell malignancies. However, the optimal treatment regimen and timing of transplantation remain to be determined.

Effect of myeloablative bone marrow transplantation on growth in children with sickle cell anaemia: results of the multicenter study of haematopoietic cell transplantation for sickle cell anaemia

Although haematopoietic cell transplantation (HCT) is curative for sickle cell anaemia (SCA), concerns about its short- and long-term toxicities limit its application. A potential toxicity is an adverse effect on growth. To identify an HCT growth effect, serial height and weight measurements from 53 children and adolescents with SCA after receiving a transplant were compared to historical controls. Hierarchical Linear Models for longitudinal data were used for analysis. In general growth was not impaired by HCT for SCA in young children; however, diminished growth may occur if HCT is carried out near or during the adolescent growth spurt.

Effects of fluid insert volume changes on socket pressures and shear stresses: case studies from two trans-tibial amputee subjects

Fluid inserts potentially help to overcome prosthetic fit problems resulting from stump volume change. The purpose of this investigation was to add fluid to fluid inserts positioned on the inner socket walls of trans-tibial prostheses and to assess their influence on socket stresses. Pressures and shear stresses were measured at 13 sites on the sockets of two trans-tibial amputee subjects while they ambulated at their self-selected walking speeds. Stresses at the transducer sites generally increased with greater fluid addition and, interestingly, both subjects found relatively high fluid insert volumes most comfortable. The magnitudes of stress change were larger than those resulting from alignment, cadence, and componentry changes as reported in the literature. Possible explanations for why subjects found settings that induced higher measured socket stresses more comfortable than those that induced lower measured stresses include: A reduced shear: pressure ratio; the short duration of the study; and reduced stresses at sites not monitored with transducers.

A unique device for controlled electrospinning

The purpose of this research was to develop a system for controlled electrospinning of fibro-porous scaffolds for tissue engineering applications and to use this system to assess mesh architecture sensitivity to manufacturing parameters. The intent was to achieve scaffolds with well-controlled fiber diameters and inter-fiber spacing. To accomplish these objectives, a custom, closed-loop controlled, electrospinning system was built. The system was unique in that it had a collection surface that was independent of the electrodes. The system allowed independent manipulation and analysis of a number of manufacturing parameters: distance between the electrodes, distance from the nozzle to the collection surface, applied voltage, temperature of the melt, collection surface dielectric strength, and collection surface area. Morphological analysis of fabricated meshes showed that all test parameters significantly affected fiber diameter and inter-fiber spacing. Further, contrary to what is generally accepted in the electrospinning literature, voltage and temperature (inversely related to viscosity) were not the most significant parameters. Features of the collection surface, including dielectric strength and surface area, were more significant. This dominance is, in part, a reflection of the unique electrospinning system used. The collection surface, which was not connected to either of the electrodes, substantially altered the electric field between the electrodes. Using the developed controlled electrospinning system, thermoplastic polyurethane meshes with fiber diameters ranging from 5 to 18 microm with variability less than 1.8% were made; inter-fiber spacing ranged from 4 to 90 microm with variability less than 20.2%. The system has potential use in biomedical applications where meshes with controlled fiber diameter and inter-fiber spacing are of interest.

Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences

For trans-tibial amputees maintenance over time of a quality fit of the prosthesis to the residual limb is an important clinical challenge. The purpose of this research was to compare diurnal and long-term (5 weeks to 6 months) interface stress changes as well as variance in the change in cross-sectional area down the length of the residual limb. If long-term changes were simply accentuated diurnal fluctuations then this result would suggest similar treatment methods should be used for both conditions. Interface pressures and shear stresses at 13 sites and residual limb shape were measured on eight trans-tibial amputee subjects using patellar-tendon-bearing prostheses. Data were collected at diurnal intervals (within the same day at least 5 h apart) as well as at long-term intervals (5, 10, 15, 20, and 25 weeks apart). Absolute diurnal interface stress changes were not significantly different from those at 5-weeks intervals but were significantly smaller than those at 15, 20, and 25-weeks intervals. Mean interface stress changes increased significantly (p<0.05) for increased session-to-session intervals. Variance of the change in cross-sectional area down the length of the residual limb was significantly smaller for diurnal intervals than for 6-months intervals, indicating that long-term changes were more localized than diurnal changes. These results indicate that long-term changes are not simply accentuated diurnal fluctuations, suggesting that different treatment methods should be used to treat each condition.

Outcome of allogeneic bone marrow transplantation for children with advanced acute myeloid leukemia

Allogeneic bone marrow transplantation (BMT) may offer the only chance of cure for children with acute myeloid leukemia (AML) in second complete remission (CR2) or with relapsed disease, but the outcome of these patients has not been clearly defined. We conducted a retrospective study of 58 children, median age 7.4 years (range 0.8-17.3), who received matched related or unrelated BMT at our institution for AML in CR2 (n = 12), in untreated first relapse (n = 11) or with refractory disease (n = 35), to identify risk factors associated with disease-free survival (DFS). Life threatening to fatal regimen-related toxicity was observed in 22% of patients. Estimates of DFS at 5 years (95% confidence interval) for patients in CR2, with untreated first relapse and refractory disease were 58% (27-80%), 36% (11-63%) and 9% (2-21%), respectively. Non-relapse mortality estimates were 0%, 27% (0-54%) and 17% (5-30%), and relapse estimates were 42% (14-70%), 36% (8-65%) and 74% (60-89%), respectively. Advanced disease phase and cytogenetic abnormalities at the time of transplantation were each associated with decreased DFS and increased relapse in multivariable regression models. Survival for children transplanted in CR2 or untreated first relapse is higher than that previously reported, but relapse remains the major cause of treatment failure regardless of disease stage.

Small fiber diameter fibro-porous meshes: Tissue response sensitivity to fiber spacing

The purpose of this research was to determine if fiber spacing for small fiber diameter fibro-porous meshes affected tissue response in vivo. Disk-shaped polyurethane meshes, with mean fiber diameters of 7.6 microm and fiber spacing between 6 and 68 microm, were implanted in rat subcutaneous dorsum for 5-week intervals and then prepared for light microscopy and morphological analysis. Results showed that implants with 12- to 68-microm spacing had no histologically apparent fibrous capsule around the perimeter, a result different from that for 6-microm spacing samples that had a capsule around a mean of 34.2% of the perimeter. For the 12- to 68-microm spacing range, a mean of 21.0% of individual fibers within the meshes were encapsulated. Qualitatively, it appeared that larger fibers were encapsulated more frequently than smaller ones. When nodeless or baggy meshes were implanted, cells tended to cluster three or more fibers into groups and then encapsulate each group. Over the 6- to 68-microm spacing range, cell nuclei volume fraction within the meshes increased from the 6- to the 29-microm spacing (p = 0.000) and then decreased from the 29- to the 68-microm spacing (p = 0.015). There was a trend of an increase in local vessel volume fraction with spacing over the 6- to 68-microm range, though the relationship was weak. The results indicate that the reason for the lack of encapsulation of small-fiber fibro-porous meshes is not exclusively a pore boundary explanation, as is proposed for small-pore porous meshes.

Allogeneic bone marrow transplantation in children with myelodysplastic syndrome or juvenile myelomonocytic leukemia: the Seattle experience

The purpose of this study was to evaluate the role of allogeneic bone marrow transplantation (BMT) in children with myelodysplastic syndrome (MDS). In total, 94 consecutive pediatric patients with MDS received an allogeneic BMT from 1976 to 2001 for refractory anemia (RA) (n=25), RA with ringed sideroblasts (RARS) (n=2), RA with excess blasts (RAEB) (n=20), RAEB in transformation (RAEB-T) (n=14), juvenile myelomonocytic leukemia (JMML) (n=32) or chronic myelomonocytic leukemia (CMML) (n=1). The estimated 3-year probabilities of survival, event-free survival (EFS), nonrelapse mortality and relapse were 50, 41, 28 and 29%, respectively. Patients with RA/RARS had an estimated 3-year survival of 74% compared to 68% in those with RAEB and 33% in patients with JMML/CMML. In multivariable analysis, patients with RAEB-T or JMML were 3.9 and 3.7 times more likely to die compared to those with RA/RARS and RAEB (P=0.005 and 0.004, respectively). Patients with RAEB-T were 5.5 times more likely to relapse (P=0.01). The median follow-up among the 43 surviving patients is 10 years (range 1-25). We conclude that allogeneic BMT for children with MDS is well tolerated and can be curative.

Fibrous encapsulation of single polymer microfibers depends on their vertical dimension in subcutaneous tissue

The purpose of this research was to investigate possible explanations for why small-diameter microfiber implants do not experience encapsulation in subcutaneous tissue as do large-diameter fiber implants. Single polypropylene microfibers of approximately rectangular cross-section with rounded edges were twisted about their longitudinal axes and affixed at their ends to polycarbonate frames. The frames were implanted in rat subcutaneous dorsum for a 5-week period, then removed and processed for light microscopy analysis. Fibrous capsule presence/absence and thickness around the implants were assessed, and their relationships to geometric features of the fibers investigated. A logistic regression analysis between presence/absence of a fibrous capsule and geometric features of interest demonstrated strong predictive ability (92.4% correct predictions) for implant height and a well-defined threshold separating the presence and absence of a fibrous capsule at 5.9 microm (p < 0.001). Implant height was defined as the vertical distance between the most superficial and deepest level of the implant. This 5.9-microm threshold value of implant height is comparable to the 6.0-microm diameter threshold for capsule presence/absence in fibers of circular cross-section [Sanders et al. J Biomed Mater Res 2000; 52(1):231-237]. Fiber major axis length, minor axis length, aspect ratio, surface area per unit length, implant width, and implant angle did not show similar predictive ability or a well-defined threshold separating the presence and absence of a fibrous capsule. It is reasoned that for fibers greater than the threshold height of 5.9 microm, separation of collagen fibers in the extracellular matrix creates dead space regions adjacent to the fibers that attract inflammatory cells and stimulate fibrous capsule formation.

Biomaterial Mesh Seeded with Vascular Remnants from a Quail Embryo Has a Significant and Fast Vascular Templating Effect on Host Implant Tissue

Seeding biomaterial implants with vascular remnants has the potential to facilitate host vessel ingrowth via a vascular templating effect. Vessels from quail embryo were grown into a polyurethane fibroporous mesh and the samples were frozen-thawed and then implanted in rat subcutaneous dorsum. Results show that the process of revascularization, using the quail vessel remnants, occurred over the first 3 days after implantation and resulted in functional vessels. Rat endothelial cells were found in the quail templates on day 1. On day 2 the endothelial cells formed a confluent layer and started producing laminin. By this time approximately 70% of the rat vessel tissue in the implant had grown into quail vascular remnants, indicating that the quail vessels were extensively used as templates for host vessel ingrowth. Laminin production was increased and collagen production started by day 3, at which time the vessels were functional in that rat blood flowed through them. At 2 weeks host vessel density was approximately twice that of control samples; thus the implant substantially enhanced the size of the vascular network. For meshes that additionally received vascular endothelial growth factor (VEGF) seeding before implantation, vessel density at 2 weeks was enhanced over samples with quail embryo alone. However, the quail was found to have the greatest angiogenic effect above any of the implant components-quail, VEGF, and collagen. Tissue engineering of vessel templates may thus be a realistic solution to effective fast vascularization of biomaterials.

Polymer microfiber mechanical properties: A system for assessment and investigation of the link with fibrous capsule formation

A novel microtensile testing instrument was developed to assess the mechanical properties of small-diameter polyethylene, polyurethane, and polyester microfibers. The instrument had a root-mean-square error of 2.96 microN for force measurement and 1.91 microm for displacement measurement. Microfibers ranging in diameter from 1.0 to 10.9 microm were strained at 2 mm/s in the device, and the slopes of their stress-strain curves (material moduli) were determined. Correlations between material modulus and previously published data on fibrous capsule presence and thickness for implanted polyethylene, polyurethane, and polyester microfibers were investigated. Results for the 1.0-5.9-microm microfiber diameter range showed that neither the percentage of unencapsulated fibers nor the capsule thickness correlated well with modulus. Correlation coefficients were 0.04 and 0.09, respectively. However, for the 6.0-10.9 microm diameter range the correlations were strong, 1.00 for both percentage of unencapsulated fibers and capsule thickness. It is suggested that the results reflect the greater attachment and mechanical interaction of cells with microfibers for the 6.0-10.9 microm-diameter range than for the 1.0-5.9 microm-diameter range.

Incidence, risk factors, and mortality from pneumonia developing late after hematopoietic stem cell transplantation

The incidence, etiology, outcome, and risk factors for developing pneumonia late after hematopoietic stem cell transplantation (SCT) were investigated in 1359 patients transplanted in Seattle. A total of 341 patients (25% of the cohort) developed at least one pneumonic episode. No microbial or tissue diagnosis (ie clinical pneumonia) was established in 197 patients (58% of first pneumonia cases). Among the remaining 144 patients, established etiologies included 33 viral (10%), 31 bacterial (9%), 25 idiopathic pneumonia syndrome (IPS, 7%), 20 multiple organisms (6%), 19 fungal (6%), and 16 Pneumocystis carinii pneumonia (PCP) (5%). The overall cumulative incidence of first pneumonia at 4 years after discharge home was 31%. The cumulative incidences of pneumonia according to donor type at 1 and 4 years after discharge home were 13 and 18% (autologous/syngeneic), 22 and 34% (HLA-matched related), and 26 and 39% (mismatched related/unrelated), respectively. Multivariate analysis of factors associated with development of late pneumonia after allografting were increasing patient age (RR 0.5 for <20 years, 1.2 for >40 years, P=0.009), donor HLA-mismatch (RR 1.6 for unrelated/mismatched related, P=0.01), and chronic graft-versus-host disease (GVHD; RR 1.5, P=0.007). Our data suggest that extension of PCP prophylaxis may be beneficial in high-risk autograft recipients. Further study of long-term anti-infective prophylaxis based on patient risk factors after SCT appear warranted.

How does skin adapt to repetitive mechanical stress to become load tolerant?

Skin breakdown from mechanical stress application is a difficult health care problem for lower-limb amputees using prosthetic limbs. Post-operative treatments to encourage skin adaptation do exist, but are largely unsuccessful. Potentially, by understanding skin adaptation on a molecular level, appropriate biomolecules can be identified and then delivered to skin to encourage adaptation in at-risk patients. Based from a critical review of the literature, it is expected that adaptation occurs by forming new collagen fibrils with larger diameters as opposed to increasing diameters of existing fibrils. Small collagen fibril breakdown by stress activated metalloproteinases is expected to be followed by increased expressions of decorin, biglycan, fibromodulin, lumican, thrombospondin-2, and collagens I and III, facilitating formation of new fibrils with larger diameters. After remodeling, total collagen fibril cross-sectional area is expected to return to baseline values since increased collagen content would increase mass and be redundant towards the purpose of adaptation.

Relative influence of polymer fiber diameter and surface charge on fibrous capsule thickness and vessel density for single-fiber implants

Single polypropylene microfibers plasma-coated with polymers of different surface charge [N,N-dimethylaminoethyl methacrylate (NN) (positive charge), methacrylic acid (MA) (negative charge), and hexafluoropropylene (HF) (neutral)] were implanted in the subcutaneous dorsum of Sprague-Dawley rats for 5-week intervals. Thee groups of fiber diameters were used: (I) 1.0 to 5.9 microm; (II) 6.0 to 10.9 microm; and (III) 11.0 to 15.9 microm. Fibrous capsule thickness and blood-vessel density (number of vessels within 100 microm of the fiber) were assessed in tissue sections in the planes of microfiber cross-sections. Results from a multifactorial analysis of variance demonstrated statistically significant main effects (p < 0.05) for microfiber diameter but not for surface-charge coating. The mean differences in capsule thickness among the microfiber diameter groups were: between groups II and I: 5.4 microm; between groups III and I: 10.2 microm; and between groups III and II: 4.7 microm. The mean differences in capsule thickness among surface-charge coatings were: between MA and NN: 0.7 microm; between MA and HF: 1.4 microm; and between NN and HF: 0.7 microm. Many of the 1.0 to 5.9 microm-in-diameter fibers had no capsule and no sign of a foreign-body reaction. For the vessel density analysis, neither microfiber diameter nor surface-charge coating had a statistically significant effect. Thus the geometric feature of microfiber diameter was more important than was surface charge relative to fibrous capsule formation but not relative to local vessel density. This ranking of the relative influence of design features in relation to tissue response provides useful information for prioritization in biomaterial design.

Interface pressure and shear stress changes with amputee weight loss: case studies from two trans-tibial amputee subjects

Interface pressures and shear stresses were measured at monthly intervals on two trans-tibial amputee subjects who lost more than 12% of their body weight over the course of the study. For one subject interface pressures and shear stresses during the weight-acceptance phase of gait decreased over the study interval at all 13 sites monitored, while the other subject experienced increased pressures distally but decreased pressures proximally. Subjects' stumps appeared to atrophy over the study interval, increasing distal end and patellar tendon loading, but not increasing interface shear stresses at other locations. Adding socks at the end of the study did not return interface pressures to first session values at all sites. It is expected that local stump shape changes occurred, causing a non-uniform change in interface stress patterns.

Use of vascular explants for ex vivo neovascularization of biomaterials

Biomaterial polymers have been proposed as scaffolds for cell assembly in vascular bioengineering. We describe here a new method for the neovascularization of polyurethane meshes from explants of rat aorta. Aortic rings embedded in collagen-permeated polyurethane meshes and cultured in medium supplemented with fetal bovine serum and vascular endothelial growth factor generated florid microvascular outgrowths that efficiently vascularized the available spaces between polyurethane fibers. The neovessels could be identified in the live cultures by phase-contrast microscopy, and in formalin-fixed preparations by the ABC peroxidase procedure, using the endothelial-specific Griffonia isolectin B4. The aortic outgrowths were successfully labeled with the intravital fluorescent dyes Calcein AM or SPDiOC(18), which are nontoxic and can be used for tracking studies. This study shows that artificial biomaterial meshes can be colonized ex vivo with histotypic microvascular networks, and provides the proof of concept for the future development of stably vascularized devices for in vivo implantation.

Tissue response to microfibers of different polymers: polyester, polyethylene, polylactic acid, and polyurethane

Tissue response to single polymer microfibers of polyester (PET), polyethylene (PE), poly(L-lactic acid) (PLA), and polyurethane (PU) was assessed using a rat subcutaneous model. Fibers of diameters ranging from 1 to 15 microm were aligned parallel to each other on polycarbonate frames and implanted in the subcutaneous dorsum in the subscapular region. After 5 weeks of implantation, fibrous capsule thickness was significantly less for fibers of diameters 1-5 than for those of 11-15 microm for all polymers tested. For PET and PU, 75.0 and 71.4% respectively of the 1-5 microm fibers had no capsule, while for PE and PLA only 45.5 and 56.3% respectively had no capsule. For 1-5 microm fibers, PE had significantly thicker capsules than PET and PU. Reducing fiber diameters from 6-10 to 1-5 microm induced a greater reduction in capsule thickness than changing polymers among PET, PE, and PLA. PU showed the least encapsulation of all polymers, demonstrating significantly thinner capsules than PET, PE, and PLA for 6-10 and 11-15 microm fibers.

Busulfan concentration and graft rejection in pediatric patients undergoing hematopoietic stem cell transplantation

We retrospectively analyzed the relationship between busulfan average steady-state plasma concentration (C(SS)) and graft rejection in 53 children receiving busulfan/cyclophosphamide (BU/CY) preparative regimens prior to hematopoietic stem cell transplantation (HSCT). Patients received a total oral busulfan dose of 11 to 28 mg/kg followed by a total cyclophosphamide dose of 120 to 335 mg/kg in preparation for allogeneic grafts (HLA-matched or HLA partially matched sibling, parent or unrelated donor). Graft rejection occurred in eight (15%) patients. Busulfan C(SS) (P = 0.0024) was the only statistically significant predictor of rejection on univariate logistic regression analysis, with the risk of rejection decreasing with an increase in busulfan C(SS). Severe (grade 3 or 4) regimen-related toxicity (RRT) occurred in four patients. Ten patients (19%) had a busulfan C(SS) higher than 900 ng/ml, one of whom had severe RRT. Higher and variable doses of cyclophosphamide may explain the lack of a relationship between busulfan C(SS) and RRT in children. It may be possible to improve the outcome of HSCT in pediatric patients receiving the BU/CY regimen through optimization of busulfan C(SS) and better definition of the contribution of activated cyclophosphamide metabolites to toxicity.

Control of in vivo microvessel ingrowth by modulation of biomaterial local architecture and chemistry

We developed a method for controlling local architecture and chemistry simultaneously in biomaterial implants to control microvessel ingrowth in vivo. Porous polypropylene disks (5 mm in diameter and 40 microm thick) were plasma-coated with a fluoropolymer and then laser-drilled with 50-microm-diameter holes through their thickness. We then oxidized the disks to create hydroxyl functionality on the exposed polypropylene (inside the holes). Acrylamide was grafted to the hydroxyl groups through polymerization in the presence of activating ceric ions. Staining with toluidine blue O demonstrated that grafting occurred only inside the holes. We used the Hoffman degradation reaction to convert the amide groups of acrylamide to amine groups, and then we used ethylene glycol diglycidyl ether to attach biomolecules of interest inside the holes: secreted protein acidic and rich in cysteine (SPARC) peptide Lys-Gly-His-Lys (KGHK; angiogenic), thrombospondin-2 (TSP; antiangiogenic), or albumin (rat; neutral). In vivo testing in a rat subcutaneous dorsum model for a 3-week interval demonstrated a greater vessel surface area (p = 0.032) and a greater number of vessels (p = 0.043) in tissue local to the holes with KGHK-immobilized disks than with TSP-immobilized disks. However, differences between KGHK-immobilized and albumin-immobilized disks were less significant (p = 0.120 and p = 0.289 for the vessel surface area and number of vessels, respectively). The developed methods have potential applications in biomaterial design applications for which selective neovascularization is desired.

Administration of cyclosporine for 24 months compared with 6 months for prevention of chronic graft-versus-host disease: a prospective randomized clinical trial

This study compared the incidence of clinical extensive chronic graft-versus-host disease (GVHD), transplantation-related mortality, survival, and relapse-free survival among recipients randomly assigned to receive a 24-month or a 6-month course of cyclosporine prophylaxis after transplantation of allogeneic marrow from an HLA-identical sibling or alternative donor. Patients who did not have clinical manifestations of chronic GVHD on day 80 after transplantation were eligible for the study if they previously had acute GVHD or if a skin biopsy showed histologic evidence of chronic GVHD. Clinical extensive chronic GVHD developed in 35 of the 89 patients (39%) in the 24-month group and 37 of the 73 patients (51%) in the 6-month group. The hazard of developing chronic GVHD was not significantly different in the 2 groups (hazard ratio = 0.76; 95% confidence interval, 0.48-1.21; P =.25). In addition, there were no significant differences between the 2 groups in transplantation-related mortality, survival, or disease-free survival.

Collagen fibril diameters increase and fibril densities decrease in skin subjected to repetitive compressive and shear stresses

Understanding microstructural changes that occur in skin subjected to repetitive mechanical stress is crucial towards the development of therapies to enhance skin adaptation and load tolerance in patients at risk of skin breakdown (e.g. prosthesis users, wheelchair users). To determine if collagen fibril diameter, collagen fibril density, dermal thickness, epidermal thickness, basement membrane length, and dermal cell density changed in response to repetitive stress application, skin subjected to moderate cyclic compressive and shear stresses for 1h/d, 5d/week, for 4 weeks was compared with skin from an unstressed contralateral control. The lateral aspects of the hind limbs of 12 Landrace/Yorkshire pigs were used. Skin from under the stressed site and a contralateral control site was processed for electron microscopy and light microscopy analysis. Electron microscopy results demonstrated significant (p<0.01) increases in collagen fibril diameter of 15.9%, 22.4%, and 22.9% for the upper, mid, and lower layers of the dermis, respectively, for the stressed skin compared with the control skin. Collagen fibril density (fibrils/unit cross-sectional area) decreased significantly for stressed vs. control by 19.8%, 29.2%, and 31.8% for the upper, mid, and lower layers, respectively. Light microscopy results demonstrated trends of a decrease in dermal thickness and an increase in cell density for stressed vs. control samples, but the differences were not significant. Differences in epidermal thickness and basement membrane length were not significant. These results demonstrate that quantifiable changes occur in collagen fibril architecture but not in the gross tissue morphology following in vivo cyclic loading of pig skin.

Mechanical performance of inflatable inserts used in limb prosthetics

Inflatable insert products used to overcome residual limb shrinkage were evaluated in a bench test environment under compressive loading conditions. Pressure-loss tests under static loading demonstrated that after inserts were inflated to 43.4 to 45.6 kPa, insert pressures reduced from 0.09%/min to 1.36%/min in the first 5 min and from 0.00%/min to 0.27%/min in the subsequent 55 min. As inserts were inflated, they demonstrated at least two phases in their pressure versus thickness curves: A relatively low-slope portion (Phase I) was followed by a high-slope portion (Phase II). The transition from Phase I to Phase II occurred at more than a 12-mm thickness, a thickness greater than that considered acceptable for practical clinical use (10 mm). This result suggests that in a socket, stress to resist insert expansion is taken by the residual limb and socket more than by the insert itself. Cyclic-loading tests under constrained thickness conditions demonstrated that local stiffness was more sensitive to insert pressure than to constraint spacing (insert thickness). The static and dynamic test results help to explain why some users claim that inserts do not provide equal and consistent support unless inflated to a very high insert pressure. An insert that allowed adjustment of the location of the Phase I to Phase II transition point in the pressure versus thickness curve might help to overcome these limitations.

The role of NF-kappa B in TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis of melanoma cells

Previous studies have shown that activation of NF-kappaB can inhibit apoptosis induced by a number of stimuli. It is also known that TNF-related apoptosis-inducing ligand (TRAIL) can activate NF-kappaB through the death receptors TRAIL-R1 and TRAIL-R2, and decoy receptor TRAIL-R4. In view of these findings, we have investigated the extent to which activation of NF-kappaB may account for the variable responses of melanoma lines to apoptosis induced by TRAIL and other TNF family members. Pretreatment of the melanoma lines with the proteasome inhibitor N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal (LLnL), which is known to inhibit activation of NF-kappaB, was shown to markedly increase apoptosis in 10 of 12 melanoma lines with death receptors for TRAIL. The specificity of results for inhibition of NF-kappaB activation was supported by an increase of TRAIL-induced apoptosis in melanoma cells transfected with a degradation-resistant IkappaBalpha. Furthermore, studies with NF-kappaB reporter constructs revealed that the resistance of melanoma lines to TRAIL-induced apoptosis was correlated to activation of NF-kappaB in response to TRAIL. TRAIL-resistant sublines that were generated by intermittent exposure to TRAIL were shown to have high levels of activated NF-kappaB, and resistance to TRAIL could be reversed by LLnL and by the superrepressor form of IkappaBalpha. Therefore, these results suggest that activation of NF-kappaB by TRAIL plays an important role in resistance of melanoma cells to TRAIL-induced apoptosis and further suggest that inhibitors of NF-kappaB may be useful adjuncts in clinical use of TRAIL against melanoma.

Standing interface stresses as a predictor of walking interface stresses in the trans-tibial prosthesis

Interface pressures and shear stresses within the socket, in standing and walking, were measured for two unilateral, male, trans-tibial amputee subjects, during two sessions each. The ratios of equal weight-bearing standing stresses to peak walking stresses showed regional variation, ranging from 0.24:1 for pressure over the anterior region to 1.01:1 for resultant interface shear stress over the lateral region. Interface stresses in standing were only moderate predictors of peak walking stresses. The best correlation coefficient between standing in full weight-bearing and peak walking stress was 0.88 for pressure over the lateral region. As the amputees progressed from minimal to full weight-bearing in standing, and then to walking, the interface stresses increased in a nonlinear fashion, consistent with the assumption that the anterior tibia provides much resistance to the bending moment in the sagittal plane during walking.

Granulocyte colony-stimulating factor given to donors before apheresis does not prevent aplasia in patients treated with donor leukocyte infusion for recurrent chronic myeloid leukemia after bone marrow transplantation

We conducted 2 sequential studies of donor leukocyte infusion (DLI) in 26 patients with chronic myeloid leukemia in hematologic relapse after unmodified allogeneic bone marrow transplantation. In the first study, cells for DLI were collected from 13 donors who were not treated with granulocyte colony-stimulating factor (G-CSF) (group 1). In the second study, cells were collected from 13 donors who received G-CSF before apheresis (group 2) in an attempt to avoid aplasia after DLI. Patients in group 2 received 550-fold more CD34+ cells than those in group 1. We found no significant difference in the incidence (31% versus 22%), onset time (41 vs. 48 days), or duration (15 vs. 14 days) of cytopenia after DLI in the 2 groups. G-CSF given to donors before collection of cells did not prevent aplasia. These findings support the hypothesis that the pathogenesis of aplasia after DLI is not restricted to the destruction of recipient hematopoietic cells but also involves failure of donor hematopoiesis by undefined mechanisms.

A device to apply user-specified strains to biomaterials in culture

An apparatus was developed to apply user-specified displacements to biomaterial samples in culture. The device allowed cyclic waveforms of bandwidth 0 Hz to 20 Hz to be applied under physiologic thermal (37.5 degrees C) and [CO2] (5%) conditions. For a 0 Hz to 20 Hz bandwidth signal similar in shape to a ventricular pressure waveform, the mean displacement error was 0.26% of the full-scale output. The maximum overshoot was 0.700%. Environmental system evaluation tests demonstrated a specimen cartridge temperature of 37.20 +/- 0.15 degrees C during cyclic loading and 37.23 +/- 0.21 degrees C during static conditions. [CO2] was 5.29 +/- 0.54% during cyclic loading and 5.25 +/- 0.61% during static conditions. Laminar flow applied at the loading rod entrances to the specimen cartridge ensured the sample remained sterile during testing. As a preliminary evaluation, polyurethane samples were seeded with fetal foreskin fibroblasts and subject to intermittent cyclic displacements. Results demonstrated enhanced cell proliferation and increased [PGE2] for samples subjected to 10% strain compared with unstrained controls. A next step will be to evaluate cell response sensitivity to strain magnitude, duration, direction, and frequency. The long-term intent is to establish mechanical loading configurations that induce acceptable or adaptation-inducing responses for use in implant design and tissue engineering applications.

Thalidomide for treatment of patients with chronic graft-versus-host disease

In a randomized, placebo-controlled, double-blind trial, thalidomide or placebo together with glucocorticoids and either cyclosporine or tacrolimus was administered as initial therapy for clinical extensive chronic graft-versus-host disease (cGVHD). All patients had thrombocytopenia or cGVHD that evolved directly from acute GVHD as an indicator of a poor prognosis. The study drug (thalidomide or placebo) was administered initially at a dose of 200 mg orally per day, followed by a gradual increase to 800 mg/d if side effects were tolerable. Treatment with the study drug was discontinued before resolution of cGVHD in 23 (92%) of the 25 patients who received thalidomide and in 17 (65%) of the 26 patients who received placebo (P =.02). Neutropenia and neurologic symptoms were the most frequent reasons for early discontinuation of treatment with thalidomide. The duration of treatment with thalidomide was too short to assess its efficacy in controlling cGVHD. (Blood. 2000;96:3995-3996)

Phase I topotecan preparative regimen for high-risk neuroblastoma, high-grade glioma, and refractory/recurrent pediatric solid tumors

We evaluated the toxicity and maximum tolerated dose of topotecan in a novel myeloablative regimen as treatment for high-risk pediatric tumors. Patients received an assigned topotecan dosage in combination with fixed doses of carboplatin and thiotepa, followed by autologous hematopoietic stem cells infusion. Topotecan dose was escalated in cohorts of four patients until the maximum tolerated dose of topotecan was defined or until accrual of 30 patients. Pharmacokinetics of topotecan were examined, and event-free survival was estimated. We describe preliminary results following treatment of 25 pediatric patients with high-risk solid tumors.

Effects of changes in cadence, prosthetic componentry, and time on interface pressures and shear stresses of three trans-tibial amputees

OBJECTIVE

To evaluate the effects of changes in cadence, prosthetic componentry, and time on interface pressures and resultant shear stresses in trans-tibial amputee case studies.

DESIGN

Interface stresses were monitored using custom-designed instrumentation at 13 sites on three subjects with unilateral trans-tibial amputation walking with patellar-tendon-bearing prosthetic limbs.

BACKGROUND

Previous studies suggested that week-to-week residual limb changes altered interface stresses more than did alterations in prosthetic alignment. No studies investigating effects of changes in cadence or componentry on interface stress distributions nor comparing their influence with week-to-week changes have been conducted previously.

METHODS

Five different prosthetic componentry configurations were tested at each of three cadences in four sessions. Data were analysed for the magnitudes and timings of peak pressures and resultant shear stresses as well as corresponding resultant shear angles.

RESULTS

None of the three cadences or five componentry configurations consistently induced significantly (P<0.05) higher or lower interface stress magnitudes for all subjects. However, an Aluminium Pylon/SACH Foot combination compared with an AirStance (pneumatic shank)/Seattle LightFoot unit induced later peak interface stress timings as a percentage of stance phase. Higher and more frequent interface stress changes were seen between the weekly sessions than between different cadences or between different componentry configurations.

CONCLUSION

The amputees' capabilities to compensate for week-to-week residual limb changes were less than those for intra-session cadence or componentry alterations.

RELEVANCE

Results suggest that effective techniques to accommodate week-to-week residual limb fluctuations could have a greater impact on maintaining consistent interface stress distributions than do adjustments in cadence or componentry.

Second allogeneic transplantation after failure of first autologous transplantation

We evaluated the outcome of second allogeneic bone marrow transplantations (BMTs) in 59 patients aged 1-57 years who relapsed after initial autologous transplantation. Patients received a second transplantation for recurrent acute myeloid leukemia (AML) (n = 24), acute lymphoblastic leukemia (ALL) (n = 13), lymphoma (n = 18), multiple myeloma (n = 3), or chronic myelogenous leukemia (n = 1) from an HLA-matched related (n = 14), mismatched related (n = 25), or matched unrelated (n = 20) donor. The probabilities of nonrelapse mortality, relapse, and disease-free survival (DFS) 2 years after the second BMT were 51%, 26%, and 23%, respectively. The 2-year DFS estimates for AML, ALL, and lymphoma were 46%, 23%, and 0%. Univariate analysis demonstrated that superior DFS was associated with age < or =17 years at the time of the second transplantation, remission before the second transplantation, total-body irradiation-based preparative regimen for the second transplantation, and the diagnosis of AML. These data demonstrate that an allogeneic transplantation after a failed autologous transplantation can result in disease-free survivors, especially in the young. The outcomes after a second transplantation for patients aged >17 years and for those with lymphoma were especially grim. These data suggest that pediatric patients may be appropriate candidates for a second transplantation. In adults, however, the use of an allogeneic transplantation as salvage therapy after failure of the initial autologous transplantation is generally unsuccessful. Alternative experimental strategies, such as low-dose nonmyeloablative allogeneic minitransplantations, should be considered.

Mechanisms of resistance of normal cells to TRAIL induced apoptosis vary between different cell types

Resistance of normal cells to tumour necrosis factor related apoptosis inducing ligand (TRAIL) induced apoptosis is believed to be mediated by expression of two decoy receptors. Here we show that the expression and localisation of TRAIL receptors (TRAIL-Rs) vary between different cells and that resistance to TRAIL is mediated by different mechanisms. The decoy receptor, TRAIL-R3, appeared important in protection of endothelial cells, whereas lack of surface death receptor expression and as yet unknown intracellular inhibitor(s) of apoptosis downstream of caspase-3 may play a major role in protection of melanocytes and fibroblasts from TRAIL induced apoptosis, respectively. Differential subcellular location of decoy receptors may be an important determinant of their effectiveness in different types of normal cells.

Tissue response to single-polymer fibers of varying diameters: evaluation of fibrous encapsulation and macrophage density

An in vivo study was conducted to assess the sensitivity of fibrous capsule thickness and macrophage density to polymer fiber diameter. Single polypropylene fibers of diameters ranging from 2.1 to 26.7 microm were implanted in the subcutaneous dorsum of Sprague-Dawley rats. Results at 5 weeks demonstrated reduced fibrous capsule thickness for small fibers. Capsule thickness was 0.6 (+/-1.8) microm, 11.7 (+/-12.0) microm, 20.3 (+/-11.6) microm, and 25.5 (+/-10.0) microm for fibers in the ranges of 2.1 to 5.9, 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, respectively. Fibers very near to blood vessels had smaller capsules than did those with local vasculature further away. The macrophage density in tissue with fiber diameters 2.1 to 5.9 microm (23.03 +/- 8.67%) was comparable to that of unoperated contralateral control skin (18.72+/-10.06%). For fibers with diameters in the ranges of 6.5 to 10.6, 11.1 to 15.8, and 16.7 to 26.7 microm, macrophage densities were 33.90+/-13.08%, 34.40+/-15.77%, and 41.68+/-13.98%, respectively, all of which were significantly larger (p<0.002) than that for the control. The reduced fibrous capsule thickness and macrophage density for small fibers (<6 microm) compared with large fibers could be due to the reduced cell-material contact surface area or to a curvature threshold effect that triggers cell signaling. A next step will be to extend the analysis to meshes to evaluate fiber-spacing effects on small-fiber biomaterials.

Thermal response of skin to cyclic pressure and pressure with shear: a technical note

The thermal response of skin to pressure alone and to pressure with shear was compared under cyclic loading conditions. Stresses were applied to the anterior aspect of the leg of three healthy subjects for time intervals up to 10 min, and the difference in temperature between the stressed site and a contralateral control site was assessed after load release. The thermal recovery time (TRT), the time interval between load release and either a maximum or a stabilization in the temperature difference vs. time record was determined. Results demonstrated that for a resultant stress of 142.9 kPa, TRTs were longer for combined pressure and shear than for pressure alone. For Subjects A, B, and C, TRT increases were 1.5 min, 5.5 min, and 2.0 min respectively. For a resultant stress magnitude of 71.4 kPa, increases were 1.5 min, 3.5 min, and -0.5 min respectively. Comparing responses for different resultant stress magnitudes for pressure-only application, TRTs were 1.5 min, 1.5 min, and 5.5 min longer for the 142.9-kPa condition than for the 71.4-kPa condition for Subjects A, B, and C. For combined pressure and shear, increases were 1.5 min, 3.5 min, and 8.0 min respectively. A next step will be to determine if the TRT differences measured here are physiologically relevant and have clinical meaning. The thermal response assessment method could then potentially be used to quantitatively evaluate the effects of different interface design features in lower-limb prosthetics on tissue response.

Unrelated donor marrow transplantation for acute myeloid leukemia: an update of the Seattle experience

Between 1985 and 1998, 161 patients with primary acute myeloid leukemia (AML) received T-replete bone marrow transplantation (BMT) from unrelated donors in Seattle. Median age was 30 (range 1-55) years. Conditioning for BMT consisted of cyclophosphamide and total body irradiation in 154 (96%) cases and graft-versus-host disease prophylaxis was the standard methotrexate and cyclosporine combination in 134 (83%) cases. Median post-transplant follow-up was 2.9 years. Leukemia-free survival (LFS) at 5 years was 50+/-12% for transplants during first complete remission (n = 16), 28+/-8% during second CR (n = 40), 27+/-17% during subsequent CR (n = 8), 7+/-3% during relapse (n = 81) and 19+/-10% during primary induction failure (n = 16). The cumulative incidences of relapse were 19%, 23%, 25%, 44% and 63%, for the five groups, respectively. Transplantation during remission, a marrow cell dose above 3.5 x 10(8)/kg, and cytomegalovirus seronegative status before BMT in both patient and donor were favorable prognostic factors. Adults in any CR who received a marrow cell dose above 3.5 x 10(8)/mg had a LFS of 54+/-9% at 5 years. These data extend our previous findings on the association between a high marrow cell dose and improved survival and support the use of unrelated donor BMT for treatment of patients with high risk AML when a family match is not available.

Changes in interface pressure and stump shape over time: preliminary results from a trans-tibial amputee subject

Interface stresses and stump shape were measured during sessions over a two-month interval on a trans-tibial amputee subject. Results from thirteen transducer sites monitored during four sessions showed greater interface pressure changes over time at anterior sites than at lateral or posterior locations. There was a trend of decreased pressure with stump swelling and increased pressure for stump atrophy. During one session in which stump shape was monitored over a 23.1 min interval after ambulation, stump swelling was localised. Swelling tended to increase in the regions of initial enlargement, as opposed to redistributing through different areas over time. Regions of swelling were anterior lateral and posterior proximal, areas of thick underlying soft tissue. Identification of localised areas of swelling and atrophy and understanding of their effects on interface pressures could be used to improve individual socket design.