ß-Phase Crystallinity, Printability, and Piezoelectric Characteristics of Polyvinylidene Fluoride (PVDF)/Poly(methyl methacrylate) (PMMA)/Cyclopentyl-Polyhedral Oligomeric Silsesquioxane (Cp-POSS) Melt-Compounded Blends.

Poly(vinylidene fluoride) (PVDF) is a semicrystalline polymer that exhibits unique piezoelectric characteristics along with good chemical resistance and high thermal stability. Layer-based material extrusion (MEX) 3D printing of PVDF is desired to create complex structures with piezoelectric properties; however, the melt processing of PVDF typically directs the formation of the α crystalline allomorph, which does not contribute to the piezoelectric response. In this work, PVDF was compounded with poly(methyl methacrylate) (PMMA) and cyclopentyl-polyhedral oligomeric silsesquioxane (Cp-POSS) nanostructured additives in binary and ternary blends to improve MEX printability while maintaining piezoelectric performance. Overall crystallinity and ß phase content were evaluated and quantified using a combination of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). Enhancement of MEX printability was measured by quantifying the interlayer adhesion and warpage of printed parts. All blends studied contained a significant percentage of ß allomorph, but it could be detected by ATR-FTIR only after the removal of a thin surface layer. Inclusion of 1% Cp-POSS and up to 10% PMMA in blends with PVDF improved interlayer adhesion (2.3-3.6x) and lowered warpage of MEX printed parts compared to neat PVDF. The blend of 1% Cp-POSS/1% PMMA/PVDF was demonstrated to significantly improve the quality of MEX printed parts while showing similar piezoelectric performance to that of neat PVDF (average piezoelectric coefficient 24 pC/N). MEX printing of PVDF blends directly into usable parts with significant piezoelectric performance while reducing the challenges of printing the semicrystalline polymer opens the potential for application in a number of high value sectors.

Bronchiolitis recovery and the use of High Efficiency Particulate Air (HEPA) Filters (The BREATHE Study): study protocol for a multi-center, parallel, double-blind, randomized controlled clinical trial.

BACKGROUND: Acute viral bronchiolitis is the most common reason for hospitalization of infants in the USA. Infants hospitalized for bronchiolitis are at high risk for recurrent respiratory symptoms and wheeze in the subsequent year, and longer-term adverse respiratory outcomes such as persistent childhood asthma. There are no effective secondary prevention strategies. Multiple factors, including air pollutant exposure, contribute to risk of adverse respiratory outcomes in these infants. Improvement in indoor air quality following hospitalization for bronchiolitis may be a prevention opportunity to reduce symptom burden. Use of stand-alone high efficiency particulate air (HEPA) filtration units is a simple method to reduce particulate matter ≤ 2.5 µm in diameter (PM2.5), a common component of household air pollution that is strongly linked to health effects. METHODS: BREATHE is a multi-center, parallel, double-blind, randomized controlled clinical trial. Two hundred twenty-eight children < 12 months of age hospitalized for the first time with bronchiolitis will participate. Children will be randomized 1:1 to receive a 24-week home intervention with filtration units containing HEPA and carbon filters (in the child's sleep space and a common room) or to a control group with units that do not contain HEPA and carbon filters. The primary objective is to determine if use of HEPA filtration units reduces respiratory symptom burden for 24 weeks compared to use of control units. Secondary objectives are to assess the efficacy of the HEPA intervention relative to control on (1) number of unscheduled healthcare visits for respiratory complaints, (2) child quality of life, and (3) average PM2.5 levels in the home. DISCUSSION: We propose to test the use of HEPA filtration to improve indoor air quality as a strategy to reduce post-bronchiolitis respiratory symptom burden in at-risk infants with severe bronchiolitis. If the intervention proves successful, this trial will support use of HEPA filtration for children with bronchiolitis to reduce respiratory symptom burden following hospitalization. TRIAL REGISTRATION: NCT05615870. Registered on November 14, 2022.

Efficacy of Air Filtration and Education Interventions on Indoor Fine Particulate Matter and Child Lower Respiratory Tract Infections among Rural U.S. Homes Heated with Wood Stoves: Results from the KidsAIR Randomized Trial.

BACKGROUND: Millions of rural U.S. households are heated with wood stoves. Wood stove use can lead to high indoor concentrations of fine particulate matter [airborne particles ≤2.5µm in aerodynamic diameter (PM2.5)] and is associated with lower respiratory tract infection (LRTI) in children. OBJECTIVES: We assessed the impact of low-cost educational and air filtration interventions on childhood LRTI and indoor PM2.5 in rural U.S. homes with wood stoves. METHODS: The Kids Air Quality Interventions for Reducing Respiratory Infections (KidsAIR) study was a parallel three-arm (education, portable air filtration unit, control), post-only randomized trial in households from Alaska, Montana, and Navajo Nation (Arizona and New Mexico) with a wood stove and one or more children <5 years of age. We tracked LRTI cases for two consecutive winter seasons and measured indoor PM2.5 over a 6-d period during the first winter. We assessed results using two analytical frameworks: a) intervention efficacy on LRTI and PM2.5 (intent-to-treat), and b) association between PM2.5 and LRTI (exposure-response). RESULTS: There were 61 LRTI cases from 14,636 child-weeks of follow-up among 461 children. In the intent-to-treat analysis, children in the education arm [odds ratio (OR)=0.98; 95% confidence interval (CI): 0.35, 2.72] and the filtration arm (OR=1.23; 95% CI: 0.46, 3.32) had similar odds of LRTI vs. control. Geometric mean PM2.5 concentrations were similar to control in the education arm (11.77% higher; 95% CI: -16.57, 49.72) and air filtration arm (6.96% lower; 95% CI: -30.50, 24.55). In the exposure-response analysis, odds of LRTI were 1.45 times higher (95% CI: 1.02, 2.05) per interquartile range (25 µg/m3) increase in mean indoor PM2.5. DISCUSSION: We did not observe meaningful differences in LRTI or indoor PM2.5 in the air filtration or education arms compared with the control arm. Results from the exposure-response analysis provide further evidence that biomass air pollution adversely impacts childhood LRTI. Our results highlight the need for novel, effective intervention strategies in households heated with wood stoves. https://doi.org/10.1289/EHP9932.

Best Practices for Conducting Clinical Trials With Indigenous Children in the United States.

We provide guidance for conducting clinical trials with Indigenous children in the United States. We drew on extant literature and our experience to describe 3 best practices for the ethical and effective conduct of clinical trials with Indigenous children. Case examples of pediatric research conducted with American Indian, Alaska Native, and Native Hawaiian communities are provided to illustrate these practices. Ethical and effective clinical trials with Indigenous children require early and sustained community engagement, building capacity for Indigenous research, and supporting community oversight and ownership of research. Effective engagement requires equity, trust, shared interests, and mutual benefit among partners over time. Capacity building should prioritize developing Indigenous researchers. Supporting community oversight and ownership of research means that investigators should plan for data-sharing agreements, return or destruction of data, and multiple regulatory approvals. Indigenous children must be included in clinical trials to reduce health disparities and improve health outcomes in these pediatric populations. Establishment of the Environmental Influences on Child Health Outcomes Institutional Development Award States Pediatric Clinical Trials Network (ECHO ISPCTN) in 2016 creates a unique and timely opportunity to increase Indigenous children's participation in state-of-the-art clinical trials.

Respiratory Impacts of Wildland Fire Smoke: Future Challenges and Policy Opportunities. An Official American Thoracic Society Workshop Report.

Wildland fires are diminishing air quality on a seasonal and regional basis, raising concerns about respiratory health risks to the public and occupational groups. This American Thoracic Society (ATS) workshop was convened in 2019 to meet the growing health threat of wildland fire smoke. The workshop brought together a multidisciplinary group of 19 experts, including wildland fire managers, public health officials, epidemiologists, toxicologists, and pediatric and adult pulmonologists. The workshop examined the following four major topics: 1) the science of wildland fire incidence and fire management, 2) the respiratory and cardiovascular health effects of wildland fire smoke exposure, 3) communication strategies to address these health risks, and 4) actions to address wildland fire health impacts. Through formal presentations followed by group discussion, workshop participants identified top priorities for fire management, research, communication, and public policy to address health risks of wildland fires. The workshop concluded that short-term exposure to wildland smoke causes acute respiratory health effects, especially among those with asthma and chronic obstructive pulmonary disease. Research is needed to understand long-term health effects of repeated smoke exposures across fire seasons for children, adults, and highly exposed occupational groups (especially firefighters). Other research priorities include fire data collection and modeling, toxicology of different fire fuel sources, and the efficacy of health protective measures to prevent respiratory effects of smoke exposure. The workshop committee recommends a unified federal response to the growing problem of wildland fires, including investment in fire behavior and smoke air quality modeling, research on the health impacts of smoke, and development of robust clinical and public health communication tools.

Novel WWP2 ubiquitin ligase isoforms as potential prognostic markers and molecular targets in cancer.

The WWP2 E3 ubiquitin ligase has previously been shown to regulate TGFß/Smad signalling activity linked to epithelial-mesenchymal transition (EMT). Whilst inhibitory I-Smad7 was found to be the preferred substrate for full-length WWP2-FL and a WWP2-C isoform, WWP2-FL also formed a stable complex with an N-terminal WWP2 isoform (WWP2-N) in the absence of TGFß, and rapidly stimulated activating Smad2/3 turnover. Here, using stable knockdown experiments we show that specific depletion of individual WWP2 isoforms impacts differentially on Smad protein levels, and in WWP2-N knockdown cells we unexpectedly find spontaneous expression of the EMT marker vimentin. Re-introduction of WWP2-N into WWP2-N knockout cells also repressed TGFß-induced vimentin expression. In support of the unique role for WWP2-N in regulating TGFß/Smad functional activity, we then show that a novel V717M-WWP2 mutant in the MZ7-mel melanoma cell line forms a stable complex with the WWP2-N isoform and promotes EMT by stabilizing Smad3 protein levels. Finally, we report the first analysis of WWP2 expression in cancer cDNA panel arrays using WWP2 isoform-specific probes and identify unique patterns of WWP2 isoform abundance associated with early/advanced disease stages. WWP2-N is significantly downregulated in stage IIIC melanoma and up-regulated in stage II/III prostate cancer, and we also find isolated examples of WWP2-FL and WWP2-C overexpression in early-stage breast cancer. Together, these data suggest that individual WWP2 isoforms, and particularly WWP2-N, could play central roles in tumourigenesis linked to aberrant TGFß-dependent signalling function, and also have potential as both prognostic markers and molecular therapeutic targets.

A novel co-operative mechanism linking TGFß and Lyn kinase activation to imatinib resistance in chronic myeloid leukaemia cells.

The advent of a mechanism specific inhibitor imatinib, targeting Bcr-Abl kinase, has paved the way for new treatment strategies in chronic myeloid leukaemia (CML). However, resistance to imatinib is common in patients and has recently been linked to both transforming growth factor-ß (TGFß) and elevated Lyn kinase activity, although molecular mechanisms remain largely unknown. Here, using leukaemic MYL cell lines derived from CML patients, we show that TGFß plays a key role in imatinib-resistance via direct effects on Lyn ubiquitination and turnover that results in bursts of Lyn kinase activity, and identify c-cbl is a candidate E3 ubiquitin ligase. Furthermore, blockade of TGFß signalling activity with the TGFß receptor kinase inhibitor SB431542 significantly reduces Lyn turnover and activation, and subsequently enhances imatinib-mediated CML cell death in a proteasomal-dependent manner. Collectively, our data reveals novel co-operative mechanisms in CML involving TGFß and Lyn kinase linked to proteasome function and ubiquitination, and thus supports therapeutic approaches that target TGFß pathway activity as a strategy for overcoming imatinib-resistance in CML.

Chronic oscillatory strain induces MLCK associated rapid recovery from acute stretch in airway smooth muscle cells.

A deep inspiration (DI) temporarily relaxes agonist-constricted airways in normal subjects, but in asthma airways are refractory and may rapidly renarrow, possibly due to changes in the structure and function of airway smooth muscle (ASM). Chronic largely uniaxial cyclic strain of ASM cells in culture causes several structural and functional changes in ASM similar to that in asthma, including increases in contractility, MLCK content, shortening velocity, and shortening capacity. However, changes in recovery from acute stretch similar to a DI have not been measured. We have therefore measured the response and recovery to large stretches of cells modified by chronic stretching and investigated the role of MLCK. Chronic, 10% uniaxial cyclic stretch, with or without a strain gradient, was administered for up to 11 days to cultured cells grown on Silastic membranes. Single cells were then removed from the membrane and subjected to 1 Hz oscillatory stretches up to 10% of the in situ cell length. These oscillations reduced stiffness by 66% in all groups (P < 0.05). Chronically strained cells recovered stiffness three times more rapidly than unstrained cells, while the strain gradient had no effect. The stiffness recovery in unstrained cells was completely inhibited by the MLCK inhibitor ML-7, but recovery in strained cells exhibiting increased MLCK was slightly inhibited. These data suggest that chronic strain leads to enhanced recovery from acute stretch, which may be attributable to the strain-induced increases in MLCK. This may also explain in part the more rapid renarrowing of activated airways following DI in asthma.

Parental anxiety and medical comprehension within 24 hrs of a child's admission to the pediatric intensive care unit*.

OBJECTIVE: Admission of a child to the pediatric intensive care unit (PICU) can create high-parental anxiety. The authors examined the factors that contribute to parental anxiety and the effect of parental anxiety on comprehension of medical information within 24 hrs of a child's admission to the PICU. The physician's recognition of parental anxiety related to their child's hospitalization was also evaluated. DESIGN: Prospective cohort study with a convenience sample of primary caregivers of critically ill children. SETTING: Twenty-bed PICU at an urban tertiary children's hospital. SUBJECTS: The primary caregivers of 35 children with Pediatric Risk of Mortality III scores >or=7 admitted to the PICU as well as PICU fellows. INTERVENTIONS: Parental anxiety was assessed with the State-Trait Anxiety Inventory, a validated tool used to measure both the temporary (State) and long-standing (Trait) anxiety in adults. Comprehension of medical information was assessed by an open-ended questionnaire. Physician assessment of parental anxiety was measured by multiple-choice questionnaire. MEASUREMENTS AND MAIN RESULTS: Of the 34 parents completing the State-Trait Anxiety Inventory, 21 (62%) had State Anxiety that was significantly higher than a validated sample of patients with generalized anxiety disorder. The child's need for mechanical ventilation was the only significant predictor of high-parental State Anxiety (p = .03). Among the 28 parents completing the questionnaire of comprehension of medical information, 26 (93%) demonstrated excellent or fair comprehension. Physicians had generally low recognition of parental anxiety but were significantly more likely to rate a parent's anxiety as high if the child was on mechanical ventilation. CONCLUSION: Parental anxiety is high following a child's admission to the PICU. Physicians failed to recognize high-parental anxiety in nearly one third of the parents. Despite the high anxiety associated with a child's admission to the PICU, parents seem to understand their children's medical issues within the first 24 hrs.

Cyclic strain-induced HSP27 phosphorylation modulates actin filaments in airway smooth muscle cells.

Mechanical stress (cyclic deformational strain) increases proteins of cytoskeletal and contractile domains in airway smooth muscle (ASM) cells in a manner that increases cell contractility. Here we studied the role of HSP27 in strain-induced microfilament formation and stability. Cultured ASM cells showed rapid phosphorylation of HSP27 upon cyclic strain within a few minutes that continued for 30 to 40 minutes. Such increases in HSP27 phosphorylation were abolished with SB 202190, a specific inhibitor of p38 mitogen-activated protein kinase (MAPK), but not by PD 98059 (an inhibitor of extracellular regulated kinase), GF109203X (an inhibitor of protein kinase C), or Y27632 (an inhibitor of Rho kinase). Direct activation of RhoA by GTPgammaS did not alter the level of HSP27 phosphorylation. Confocal microscopy revealed that cells pre-incubated with SB 202190, and/or Y27632 resulted in disorganization of stress fibers upon strain, unlike PD 98059 and GF 1092030X, suggesting that both p38 MAPK and Rho kinase were necessary for strain-induced microfilament formation. To determine the relationship between HSP27 and RhoA in strain-induced microfilament formation, cells were transfected with various isoforms of HSP27 and RhoA before strain. Co-expression of inactive HSP27 (3A-HSP27) with constitutively active EGF-RhoA (RhoV14) caused diminution of microfilaments compared with constitutive active EGFP-RhoA (RhoV14) alone, suggesting that HSP27 is necessary for microfilament stability. Similarly, expression of phosphomimicking HSP27 (3D-HSP27) was sufficient for retaining microfilament formation even when co-expressed with the dominant-negative RhoA (EGFP-RhoN17). Thus, HSP27 activation is necessary for microfilament stability independently of RhoA activation.

Characteristics of urban natural areas influencing winter bird use in southern Ontario, Canada.

Characteristics of urban natural areas and surrounding landscapes were identified that best explain winter bird use for 28 urban natural areas in southern Ontario, Canada. The research confirms for winter birds the importance of area (size) and natural vegetation, rather than managed, horticultural parkland, within urban natural areas as well as percent urban land use and natural habitat in surrounding landscapes. Alien bird density and percent ground feeding species increased with percent surrounding urban land use. Higher percent forest cover was associated with higher percentages of forest, bark feeding, small (<20 g) and insectivorous species. Natural area size (ha) was related to higher species richness, lower evenness and higher percentages of insectivorous, forest interior, area-sensitive, upper canopy, bark feeding, and non-resident species. Higher number of habitat types within natural areas and percent natural habitat in surrounding landscapes were also associated with higher species richness. Common, resident bird species dominated small areas (<6.5 ha), while less common non-residents increased with area, indicative of a nested distribution. Areas at least 6.5 ha and more generally >20 ha start to support some area-sensitive species. Areas similar to rural forests had >25% insectivores, >25% forest interior species, >25% small species, and <5% alien species. Indicator species separated urban natural areas from rural habitats and ordination placed urban natural areas along a gradient between urban development and undisturbed, rural forests. More attention is needed on issues of winter bird conservation in urban landscapes.

Hyperoxic conditions inhibit airway smooth muscle myosin phosphatase in rat pups.

Exposure of rat pups to 100% oxygen is a model for studying neonatal lung injury. Airway reactivity is increased in this model, in part due to impaired airway smooth muscle (ASM) relaxation. We compared biochemical determinants of ASM contractility in rat pups exposed to 100% oxygen for 7 days vs. littermates raised in room air. The baseline quantities of ASM contractile proteins, extent of phosphorylation of the 20-kDa myosin regulatory light chain (LC(20)), and amount of the myosin-binding subunit of smooth muscle myosin phosphatase (MYPT) were all comparable between the two groups. Bethanechol-induced contraction increased the extent of phosphorylation of both LC(20) and MYPT in the hyperoxic group (45% and 70% over control, respectively). Relaxation after electrical field stimulation demonstrated greater phosphorylation of both LC(20) and MYPT in the hyperoxic group compared with controls (67% and 84%, respectively). To determine if hyperoxia induced changes in the isoforms of MYPT, isoform expression was also compared but differences were not found. To determine potential mechanisms whereby MYPT phosphorylation was increased by hyperoxia, separate tracheas were treated with the Rho kinase inhibitor Y-27632. This treatment completely eliminated differences in MYPT phosphorylation between the groups. Because phosphorylation of MYPT impairs the phosphatase activity of myosin phosphatase, these data suggest that hyperoxic conditioning during early postnatal life impairs relaxation through prolonging LC(20) phosphorylation. This mechanism might contribute to increased ASM reactivity seen in bronchopulmonary dysplasia.

Cytoskeletal tension regulates both expression and degradation of h2-calponin in lung alveolar cells.

Calponin is an actin filament-associated regulatory protein, and its h2 isoform is expressed in lung alveolar epithelial cells under postnatal upregulation during lung development corresponding to the commencement of respiratory expansion. Consistent with this correlation to mechanical tension, the expression of h2-calponin in alveolar cells is dependent on substrate stiffness and cytoskeleton tension. The function of h2-calponin in the stability of actin cytoskeleton implicates a role in balancing the strength and compliance of alveoli. An interesting finding is a rapid degradation of h2-calponin in lung after prolonged deflation, which is prevented by inflation of the lung to the in situ expanded volume. Decreasing mechanical tension in cultured alveolar cells by reducing the dimension of culture matrix reproduced the degradation of h2-calponin. Inhibition of myosin II ATPase also resulted in the degradation of h2-calponin in alveolar cells, showing a determining role of the tension in the actin cytoskeleton. Alveolar cells statically cultured on silicon rubber membrane build high tension in the cytoskeleton corresponding to a high expression of h2-calponin. Chronic cyclic stretching of cells on the membrane did not increase but decreased the expression of h2-calponin. This finding suggests that when cellular structure adapts to the stretched dimension, cyclic relaxations periodically release cytoskeleton tension and lower the total amount of tension that the cell senses over time. Therefore, the isometric tension, other than tension dynamics, determines the expression of h2-calponin. The tension regulation of h2-calponin synthesis and degradation demonstrates a novel mechanical regulation of cellular biochemistry.

On the terminology for describing the length-force relationship and its changes in airway smooth muscle.

The observation that the length-force relationship in airway smooth muscle can be shifted along the length axis by accommodating the muscle at different lengths has stimulated great interest. In light of the recent understanding of the dynamic nature of length-force relationship, many of our concepts regarding smooth muscle mechanical properties, including the notion that the muscle possesses a unique optimal length that correlates to maximal force generation, are likely to be incorrect. To facilitate accurate and efficient communication among scientists interested in the function of airway smooth muscle, a revised and collectively accepted nomenclature describing the adaptive and dynamic nature of the length-force relationship will be invaluable. Setting aside the issue of underlying mechanism, the purpose of this article is to define terminology that will aid investigators in describing observed phenomena. In particular, we recommend that the term "optimal length" (or any other term implying a unique length that correlates with maximal force generation) for airway smooth muscle be avoided. Instead, the in situ length or an arbitrary but clearly defined reference length should be used. We propose the usage of "length adaptation" to describe the phenomenon whereby the length-force curve of a muscle shifts along the length axis due to accommodation of the muscle at different lengths. We also discuss frequently used terms that do not have commonly accepted definitions that should be used cautiously.

Localized mechanical stress induces time-dependent actin cytoskeletal remodeling and stiffening in cultured airway smooth muscle cells.

Mechanical stress (MS) causes cytoskeletal (CSK) and phenotypic changes in cells. Such changes in airway smooth muscle (ASM) cells might contribute to the pathophysiology of asthma. We have shown that periodic mechanical strain applied to cultured ASM cells alters the structure and expression of CSK proteins and increases cell stiffness and contractility (Smith PG, Moreno R, and Ikebe M. Am J Physiol Lung Cell Mol Physiol 272: L20-L27, 1997; and Smith PG, Deng L, Fredberg JJ, and Maksym GN. Am J Physiol Lung Cell Mol Physiol 285: L456-L463, 2003). However, the mechanically induced CSK changes, altered cell function, and their time courses are not well understood. Here we applied MS to the CSK by magnetically oscillating ferrimagnetic beads bound to the CSK. We quantified CSK remodeling by measuring actin accumulation at the sites of applied MS using fluorescence microscopy. We also measured CSK stiffness using optical magnetic twisting cytometry. We found that, during MS of up to 120 min, the percentage of beads associated with actin structures increased with time. At 60 min, 68.1 +/- 1.6% of the beads were associated with actin structures compared with only 6.7 +/- 2.8% before MS and 38.4 +/- 5.5% in time-matched controls (P < 0.05). Similarly, CSK stiffness increased more than twofold in response to the MS compared with time-matched controls. These changes were more pronounced than observed with contractile stimulation by 80 mM KCl or 10(-4) M acetylcholine. Together, these findings imply that MS is a potent stimulus to enhance stiffness and contractility of ASM cells through CSK remodeling, which may have important implications in airway narrowing and dilation in asthma.

Pharmacokinetic properties and tolerability of single-dose terbutaline in patients with severe asthma treated in the pediatric intensive care unit.

BACKGROUND: Asthmatic children requiring treatment in the pediatric intensive care unit (PICU) receive aggressive drug therapy that may include IV administration of ß 2-receptor agonists to prevent progression to life-threatening respiratory failure. The only pharmacologic agent in this class currently available for parenteral use in the United States is terbutaline. Study of IV dosing of terbutaline in the pediatric population has been limited. OBJECTIVE: The aim of this study was to determine the pharmacokinetic (PK) properties and tolerability of single-dose terbutaline in pediatric patients across a broad age range who were admitted to the PICU and were receiving maximal conventional asthma drug therapy. METHODS: This study was conducted at the PICU at Rainbow Babies and Children's Hospital (Cleveland, Ohio). Patients aged 6 months to 16 years with severe exacerbation of reactive airways disease and who were undergoing maximal conventional therapy and had an arterial catheter were enrolled. Patients were arbitrarily assigned to receive a single IV infusion of 1 of 3 doses of terbutaline (10, 20, or 30 µg/kg), infused over 5 minutes. Blood samples were obtained for the determination of plasma terbutaline concentrations just before terbutaline was administered (baseline), immediately on completion of the IV infusion, and at 10, 20, and 40 minutes and 1, 2, 4, 8, 16, 32, 48, and 72 hours after the 5-minute infusion. PK properties (elimination half-life [tl2], mean residence time [MRT], apparent steady-state volume of distribution [Vdss], and total body clearance [CI]) were determined and adverse effects were recorded. RESULTS: The determination of terbutaline PK properties was possible in 50 of 56 enrolled patients (31 boys, 19 girls; mean [SD] age, 6.5 [4.5] years). The PK properties of terbutaline were linear over the dose range studied and, with the exception of the expected dose-dependent increases in peak terbutaline plasma concentration and area under the terbutaline plasma concentration-time curve, no statistically significant differences were observed in PK relative to dose. Therefore, we pooled the data for all subsequent analyses. Statistically significant correlations with patient age were observed with tl2 (r = 0.4, P < 0.006), MRT (r = 0.4, P < 0.002), and Vdss (r = 0.33, P < 0.02), but not C1 (r = -0.03, P = NS). Single-dose terbutaline administration was generally well tolerated. CONCLUSIONS: Single-dose IV terbutaline was well tolerated in this study. In maximally treated asthmatic patients in the PICU, terbutaline elimination may be more rapid than in nonacutely ill children. These PK data suggest that if the drug is to be administered intravenously, the continuous IV infusion method, including loading doses for any subsequent dose escalations, may be the most appropriate. The influence of age and safety of long-term, continuous terbutaline IV infusion requires further study.

Mechanical strain increases cell stiffness through cytoskeletal filament reorganization.

We tested the hypothesis that cytoskeletal reorganization induced by cyclic strain increases cytoskeletal stiffness (G'). G' was measured by optical magnetic twisting cytometry in control cells and cells that had received mechanical strain for 10-12 days. G' was measured before and after both contractile and relaxant agonists, and in the strained cells both parallel (Para) and perpendicular (Perp) to the aligned cytoskeleton. Before activation, G' Para was 24 +/- 5% (+/- SE) greater compared with Perp (P < 0.05), and 35% +/- 6 greater compared with control (Cont, P < 0.01). The difference between strained and control cells was enhanced by KCl, increasing G' 171 +/- 7% Para compared with 125 +/- 6% Perp and 129 +/- 8% Cont (P < 10-5 both cases). The decrease in G' from baseline due to relaxant agonists isoproterenol and dibutyryl cAMP was similar in all groups. Long-term oscillatory loading of airway smooth muscle (ASM) cells caused stiffness to increase and become anisotropic. These findings are consistent with the hypothesis that cytoskeletal reorganization can enhance ASM stiffness and contractility. They imply, furthermore, that oscillatory loading of ASM may contribute to airway narrowing and failure of airway dilation in asthma.

Mechanical stress increases RhoA activation in airway smooth muscle cells.

Cultured airway smooth muscle cells subjected to cyclic strain respond with increased cytoskeletal organization and contractility resembling effects described with RhoA activation. To test the hypothesis that strain increases cell cytoskeletal organization through RhoA, cells were subjected to strain in the presence of known activators or inhibitors of RhoA. Ten percent cyclic deformational strain (serum-free conditions) increased F-actin staining (152% over control), and this effect was enhanced by serum or lysophosphatidic acid (180%), but decreased (68%) with Clostridium botulinum toxin inhibition of RhoA or with the Rho kinase inhibitor Y27632 (67%). When cells expressing the dominant negative N17-RhoA isoform were subjected to strain, F-actin staining was disorganized and cells failed to elongate or migrate relative to strain direction. When cells expressing a green fluorescent protein (GFP)-RhoA fusion protein were subjected to strain, GFP showed up to 25% greater cell membrane staining than control cells. Finally, strain caused a 4-fold increase in RhoA activation (Rhotekin binding assay), and a 3-fold increase myosin phosphatase phosphorylation that was inhibited by Y27632. We conclude that mechanical stress activates RhoA, an event that may increase airway smooth muscle contractility.

Clinical profile of 30 infants with acute pulmonary hemorrhage in Cleveland.

Between 1993 and 2000, 30 infants were hospitalized with acute pulmonary hemorrhage at Rainbow Babies and Children's Hospital in Cleveland. Most infants presented with severe pulmonary symptoms requiring intensive support, but a few infants had less severe hemorrhage. Three quarters of the patients required ventilator support and blood transfusions. Eleven patients had transitory hemoglobinuria. Five patients died, but infants who survived did well. There are currently no specific treatment modalities, although we have advised moving to a different home and avoiding environmental tobacco smoke. Subsequently, rebleeding from the lower respiratory tract has decreased from 5 of 7 infants to 1 in 21. On the basis of decreased subsequent fatal hemorrhage, high dose glucocorticoids seem to be of some value. Several patients revealed continued low-grade alveolar hemorrhage for months after their initial bleed, even after removal from their original home environments.