Overview of surface measurements and spatial characterization of submicrometer particulate matter during the DISCOVER-AQ 2013 campaign in Houston, TX.

The sources of submicrometer particulate matter (PM1) remain poorly characterized in the industrialized city of Houston, TX. A mobile sampling approach was used to characterize PM1 composition and concentration across Houston based on high-time-resolution measurements of nonrefractory PM1 and trace gases during the DISCOVER-AQ Texas 2013 campaign. Two pollution zones with marked differences in PM1 levels, character, and dynamics were established based on cluster analysis of organic aerosol mass loadings sampled at 16 sites. The highest PM1 mass concentrations (average 11.6 ± 5.7 µg/m3) were observed to the northwest of Houston (zone 1), dominated by secondary organic aerosol (SOA) mass likely driven by nighttime biogenic organonitrate formation. Zone 2, an industrial/urban area south/east of Houston, exhibited lower concentrations of PM1 (average 4.4 ± 3.3 µg/m3), significant organic aerosol (OA) aging, and evidence of primary sulfate emissions. Diurnal patterns and backward-trajectory analyses enable the classification of airmass clusters characterized by distinct PM sources: biogenic SOA, photochemical aged SOA, and primary sulfate emissions from the Houston Ship Channel. Principal component analysis (PCA) indicates that secondary biogenic organonitrates primarily related with monoterpenes are predominant in zone 1 (accounting for 34% of the variability in the data set). The relevance of photochemical processes and industrial and traffic emission sources in zone 2 also is highlighted by PCA, which identifies three factors related with these processes/sources (~50% of the aerosol/trace gas concentration variability). PCA reveals a relatively minor contribution of isoprene to SOA formation in zone 1 and the absence of isoprene-derived aerosol in zone 2. The relevance of industrial amine emissions and the likely contribution of chloride-displaced sea salt aerosol to the observed variability in pollution levels in zone 2 also are captured by PCA. IMPLICATIONS: This article describes an urban-scale mobile study to characterize spatial variations in submicrometer particulate matter (PM1) in greater Houston. The data set indicates substantial spatial variations in PM1 sources/chemistry and elucidates the importance of photochemistry and nighttime oxidant chemistry in producing secondary PM1. These results emphasize the potential benefits of effective control strategies throughout the region, not only to reduce primary emissions of PM1 from automobiles and industry but also to reduce the emissions of important secondary PM1 precursors, including sulfur oxides, nitrogen oxides, ammonia, and volatile organic compounds. Such efforts also could aid in efforts to reduce mixing ratios of ozone.

Induction in vivo of cartilage grafts for craniofacial reconstruction.

In the craniofacial region, defects of cartilage structures are preferably reconstructed with autologous cartilage. Donor-site morbidity related to the creation of a new defect elsewhere, and a lack of growth potential of the graft--mandatory in children--have stimulated investigators to find other ways to generate new "extra" cartilage. Several biomaterials have been tested as a matrix for the ingrowth of (peri)chondroblasts in experimental animals. In young (growing) rabbits we have developed a process of heterotopic cartilage induction with the use of a demineralized (bovine) bone matrix which is enfolded in a pedicled flap of ear perichondrium for at least three weeks. During this period the demineralized matrix is colonized by macrophages and polymorphonuclear cells which start a process of complete biodegradation of the material. Simultaneously, the collagen matrix is invaded by mesenchymal cells, originating from the perichondrium and differentiating into chondroblasts and later, into chondrocytes forming the intercellular substance. The developing, very young cartilage could be demonstrated as collagen type II, thus, hyaline cartilage. When applied with its adherent perichondrium as a graft, it merges easily with the more matured host cartilage and even appears to be capable of further growth. Therefore, it seems suitable for the reconstruction of a cartilaginous defect in growing cartilaginous structures like the nasal septum or the larynx.

Cartilage transformation in a composite graft of demineralized bovine bone matrix and ear perichondrium used in a child for the reconstruction of the nasal septum.

For the first time it was observed in a boy that a xenogenic implant of demineralized bovine bone matrix, enfolded in a pedicled flap of autogenic ear perichondrium, was transformed into autogenic cartilage. This new cartilage could be adequately used as a graft to bridge the cartilaginous defect of a nasal septum perforation. The defect was successfully closed by a technique employing four bipedicled mucosal advancement flaps of the septum and the nasal floor. The result of this pilot study, which is based on experiments in growing rabbits, appears to open the possibility to create de novo young and growing autogenic cartilage of substantial quantity in children, without the loss of the cartilage present.

Injury- and age-linked differences in wound healing and stenosis formation in the subglottis.

We studied the effects of superficial and deep endolaryngeal trauma of the subglottic airway in young and adult rabbits. In both age groups a soft stenosis was formed as long as the cartilaginous cricoid ring is not involved. This stenosis comprised a thickened subepithelial zone of scar tissue, separated from the cricoid cartilage by a layer of fatty tissue. Injury of the internal side of the cricoid cartilage induced a compact mass of scar tissue with local differentiation into fibrocartilage. In young animals only, injury of the cartilage led to remodelling of the cricoid ring (indentation or collapse of the traumatized sectors). On the basis of the differentiating effects of age and depth of the lesion, three histopathological types of subglottic stenosis were distinguished. The experimental results provide an explanation for the variability in the histopathological features of the wall of the stenotic subglottic airway, as observed in biopsies and postmortem specimens.

Management of infant laryngeal disorders in relation to wound healing processes of the rabbit larynx.

Laryngotracheal injury caused by prolonged intubation is mostly treated by reintubation or surgical intervention. To understand the histopathological processes involved in wound healing of laryngeal trauma and to assess the value of reintubation as treatment for post-intubation injury, the findings of a study in preterm infants were placed next to the results of experimental studies on laryngeal disorders in young, growing rabbits. Observations at laryngobronchoscopy in the child are compared to histopathological investigations in the animal. In both series various, evidently similar categories of injury could be distinguished viz. edema, ulcerations and granulations. The results of treatment like reintubation would vary with the diagnosed category of the injury; the more granulation tissue, the less successful conservative treatment will be. It is concluded that histopathologic classification is essential for good management of intubation injuries and that therapeutic re-intubation in case of superficial lesions should precede the decision for surgery.

Reconstruction of the anterior laryngeal wall with a composite graft of demineralized bovine bone matrix and autogenous perichondrium. An experimental study in adult rabbits.

In this study the feasibility to reconstruct the anterior laryngeal wall in adult rabbits with a composite graft of demineralized bovine bone matrix and autogenous perichondrium was investigated. It is demonstrated that demineralized bovine bone, which is a porous biomaterial, is completely transformed into autologous cartilage, once it is implanted in a vascularized perichondrial pocket. It appeared to be possible to reconstruct the anterior laryngeal wall in adult rabbits with this newly formed cartilage. As the biomaterial has been transformed into autologous tissue it is entirely incorporated at the recipient site giving rise to solid connections (cartilaginous and/or fibrous) with the surrounding tissues.

Intrinsic and extrinsic factors relevant to the morphology of the growing cricoid ring after a combined anterior and posterior cricoid split: an experimental study in rabbits.

The effects of a Rethi procedure upon the cricoid is investigated in young rabbits. An anterior and posterior cricoid split carried out upon the larynx of a young rabbit was demonstrated to result in an enlarged cricoid lumen in the adult stage due to an enhancement of both the anterior and posterior transversal diameter of the ring. These changes are ascribed to a release of interlocked stresses in the cricoid cartilage and the action of the cricopharyngeal and cricothyroid muscle.

Reconstruction of the growing cricoid with a composite graft of demineralized bovine bone and autogenous perichondrium; a comparative study in rabbits.

In growing rabbits, the feasibility of a new type of composite graft for the reconstruction of defects in the cricoid ring is studied. This graft consists of Demineralized Bovine Bone matrix (DBBM) enfolded in a perichondrial flap. The cartilage formed in the DBBM by cells, derived from the perichondrium, is demonstrated to provide a valuable substitute for resected parts of the cricoid. A specific feature of this reconstruction is that it allows further growth and does not result in a secondary stenosis during later development.

The influence of ageing on wound healing of the cricoid.

In young and adult rabbits the effects of one anterior or two bilateral splits of the cricoid were studied. Interruption of the cricoid ring elicits wound healing of the cut edges and induces changes in form and size of the separated parts of the cricoid (indirect effect). It was demonstrated that with increasing age i) the wound healing capacities of the hyaline cartilage is highly diminished or lost and ii) the induced remodelling, involving the total ring in young animals, is in the adult stage confined to the posterior part. Moreover, the observations suggest that dividing the cricoid ring in an anterior and posterior part at a young age can result in a stimulation of growth of the anterior part, in comparison with unoperated control animals.

Trauma of the cricoid and interlocked stress.

In young rabbits the effects were studied of an anterior midline and a bilateral split with and without traumatisation of the perichondrium and subperichondrial cartilage on the inner side of the ring. Various interventions produced specific patterns of distortions. It is concluded that release of interlocked stress in the cartilage is of paramount importance for the development of deformities. A specific feature of the circular cartilaginous structure seems to be that the tensile forces on the outer side of the ring exceed those on the inner side.