Influence of Particle Size of Deproteinized Bovine Bone Mineral on New Bone Formation and Implant Stability after Simultaneous Sinus Floor Elevation: A Histomorphometric Study in Minipigs

BACKGROUND Deproteinized bovine bone mineral (DBBM) is one of the best-documented bone substitute materials for sinus floor elevation (SFE). PURPOSE DBBM is available in two particle sizes. Large particles are believed to facilitate improved neoangiogenesis compared with small ones. However, their impact on the rate of new bone formation, osteoconduction, and DBBM degradation has never been reported. In addition, the implant stability quotient (ISQ) has never been correlated to bone-to-implant contact (BIC) after SFE with simultaneous implant placement. MATERIALS AND METHODS Bilateral SFE with simultaneous implant placement was performed in 10 Göttingen minipigs. The two sides were randomized to receive large or small particle size DBBM. Two groups of 5 minipigs healed for 6 and 12 weeks, respectively. ISQ was recorded immediately after implant placement and at sacrifice. Qualitative histological differences were described and bone formation, DBBM degradation, BIC and bone-to-DBBM contact (osteoconduction) were quantified histomorphometrically. RESULTS DBBM particle size had no qualitative or quantitative impact on the amount of newly formed bone, DBBM degradation, or BIC for either of the healing periods (p > 0.05). Small-size DBBM showed higher osteoconduction after 6 weeks than large-size DBBM (p < 0.001). After 12 weeks this difference was compensated. There was no significant correlation between BIC and ISQ. CONCLUSION Small and large particle sizes were equally predictable when DBBM was used for SFE with simultaneous implant placement.

Late-Holocene climate variability and ecosystem responses in Alaska inferred from high-resolution multiproxy sediment analyses at Grizzly Lake

The late-Holocene shift from Picea glauca (white spruce) to Picea mariana (black spruce) forests marked the establishment of modern boreal forests in Alaska. To understand the patterns and drivers of this vegetational change and the associated late-Holocene environmental dynamics, we analyzed radiocarbon-dated sediments from Grizzly Lake for chironomids, diatoms, pollen, macrofossils, charcoal, element composition, particle size, and magnetic properties for the period 4100–1800 cal BP. Chironomid assemblages reveal two episodes of decreased July temperature, at ca. 3300–3150 (ca −1 °C) and 2900–2550 cal BP (ca −2 °C). These episodes coincided with climate change elsewhere in the Northern Hemisphere, atmospheric reorganization, and low solar activity. Diatom-inferred lake levels dropped by ca. 5 m at 3200 cal BP, suggesting dry conditions during the period 3200–1800 cal BP. P. glauca declined and P. mariana expanded at ca. 3200 cal BP; this vegetational change was linked to diatom-inferred low lake levels and thus decreased moisture availability. Forest cover declined at 3300–3100, 2800–2500 and 2300–2100 cal BP and soil erosion as inferred from increased values of Al, K, Si, Ti, and Ca intensified, when solar irradiance was low. Plant taxa adapted to disturbance and cold climate (e.g. Alnus viridis, shrub Betula, Epilobium) expanded during these periods of reduced forest cover. This open vegetation type was associated with high fire activity that peaked at 2800 cal BP, when climatic conditions were particularly cold and dry. Forest recovery lagged behind subsequent climate warming (≤+3 °C) by ca. 75–225 years. Our multiproxy data set suggests that P. glauca was dominant under warm-moist climatic conditions, whereas P. mariana prevailed under cold-dry and warm-dry conditions. This pattern implies that climatic warming, as anticipated for this century, may promote P. glauca expansions, if moisture availability will be sufficiently high, while P. mariana may expand under dry conditions, possibly exacerbating climate impacts on the fire regime.

Particles induce apical plasma membrane enlargement in epithelial lung cell line depending on particle surface area dose

Background Airborne particles entering the respiratory tract may interact with the apical plasma membrane (APM) of epithelial cells and enter them. Differences in the entering mechanisms of fine (between 0.1 μm and 2.5 μm) and ultrafine ( ≤ 0.1 μm) particles may be associated with different effects on the APM. Therefore, we studied particle-induced changes in APM surface area in relation to applied and intracellular particle size, surface and number. Methods Human pulmonary epithelial cells (A549 cell line) were incubated with various concentrations of different sized fluorescent polystyrene spheres without surface charge (∅ fine – 1.062 μm, ultrafine – 0.041 μm) by submersed exposure for 24 h. APM surface area of A549 cells was estimated by design-based stereology and transmission electron microscopy. Intracellular particles were visualized and quantified by confocal laser scanning microscopy. Results Particle exposure induced an increase in APM surface area compared to negative control (p < 0.01) at the same surface area concentration of fine and ultrafine particles a finding not observed at low particle concentrations. Ultrafine particle entering was less pronounced than fine particle entering into epithelial cells, however, at the same particle surface area dose, the number of intracellular ultrafine particles was higher than that of fine particles. The number of intracellular particles showed a stronger increase for fine than for ultrafine particles at rising particle concentrations. Conclusion This study demonstrates a particle-induced enlargement of the APM surface area of a pulmonary epithelial cell line, depending on particle surface area dose. Particle uptake by epithelial cells does not seem to be responsible for this effect. We propose that direct interactions between particle surface area and cell membrane cause the enlargement of the APM.

Are great Cascadia earthquakes recorded in the sedimentary records from small forearc lakes?

Here we investigate sedimentary records from four small inland lakes located in the southern Cascadia forearc region for evidence of earthquakes. Three of these lakes are in the Klamath Mountains near the Oregon–California border, and one is in the central Oregon Coast range. The sedimentary sequences recovered from these lakes are composed of normal lake sediment interbedded with disturbance event layers. The thickest of these layers are graded, and appear to be turbidites or linked debrites (turbidites with a basal debris-flow deposit), suggesting rapid deposition. Variations in particle size and organic content of these layers are reflected in the density and magnetic susceptibility data. The frequency and timing of these events, based on radiocarbon ages from detrital organics, is similar to the offshore seismogenic turbidite record from trench and slope basin cores along the Cascadia margin. Stratigraphic correlation of these anomalous deposits based on radiocarbon ages, down-core density, and magnetic susceptibility data between lake and offshore records suggest synchronous triggering. The areal extent and multiple depositional environments over which these events appear to correlate suggest that these deposits were most likely caused by shaking during great Cascadia earthquakes.

Size-Dependent Uptake of Particles by Pulmonary Antigen-Presenting Cell Populations and Trafficking to Regional Lymph Nodes

The respiratory tract is an attractive target organ for novel diagnostic and therapeutic applications with nano-sized carriers, but their immune effects and interactions with key resident antigen-presenting cells (APCs) such as dendritic cells (DCs) and alveolar macrophages (AMs) in different anatomical compartments remain poorly understood. Polystyrene particles ranging from 20 nm to 1,000 nm were instilled intranasally in BALB/c mice, and their interactions with APC populations in airways, lung parenchyma, and lung-draining lymph nodes (LDLNs) were examined after 2 and 24 hours by flow cytometry and confocal microscopy. In the main conducting airways and lung parenchyma, DC subpopulations preferentially captured 20-nm particles, compared with 1,000-nm particles that were transported to the LDLNs by migratory CD11blow DCs and that were observed in close proximity to CD3+ T cells. Generally, the uptake of particles increased the expression of CD40 and CD86 in all DC populations, independent of particle size, whereas 20-nm particles induced enhanced antigen presentation to CD4+ T cells in LDLNs in vivo. Despite measurable uptake by DCs, the majority of particles were taken up by AMs, irrespective of size. Confocal microscopy and FACS analysis showed few particles in the main conducting airways, but a homogeneous distribution of all particle sizes was evident in the lung parenchyma, mostly confined to AMs. Particulate size as a key parameter determining uptake and trafficking therefore determines the fate of inhaled particulates, and this may have important consequences in the development of novel carriers for pulmonary diagnostic or therapeutic applications.

Circulating oxidized low-density lipoprotein (LDL) is associated with risk factors of the metabolic syndrome and LDL size in clinically healthy 58-year-old men (AIR study).

OBJECTIVES Hypothetically the atherogenic effect of the metabolic syndrome may be mediated through the increased occurrence of small LDL-particles which are easily modified to atherogenic oxidized LDL (ox-LDL). The aim of this study was to test this concept by examining the association between circulating ox-LDL, LDL-particle size, and the metabolic syndrome. DESIGN AND RESULTS A population-based sample of clinically healthy 58-year-old men (n = 391) was recruited. Ox-LDL was measured by ELISA (specific monoclonal antibody, mAb-4E6) and LDL-particle size by gradient gel electrophoresis. The results showed that ox-LDL significantly correlated to factors constituting the metabolic syndrome; triglycerides (r = 0.43), plasma insulin (r = 0.20), body mass index (r = 0.20), waist-to-hip ratio (r = 0.21) and HDL (r = -0.24); (P < 0.001). Ox-LDL correlated also to LDL-particle size (r = -0.42), Apo-B (r = 0.70), LDL (r = 0.65); (P < 0.001) and, furthermore, with Apo A-1 (r = -0.13) and heart rate (r = 0.13); (P < 0.01). CONCLUSION The metabolic syndrome was accompanied by high plasma ox-LDL concentrations compared with those without the syndrome. Ox-LDL levels were associated with most of the risk factors constituting the metabolic syndrome and was, in addition related to small LDL-particle size. To our knowledge the present study is the first one to demonstrate that circulating ox-LDL levels are associated with small LDL-particle size in a population representative sample of clinically healthy middle-aged men. The high degree of intercorrelation amongst several factors makes it difficult to clarify the independent role of any specific factor.