Toenail dust collected from podiatrist's nail drills was examined for size, endotoxin content and ability to stimulate release of interleukin 8 (IL-8) from macrophages and lung epithelial cells in vitro . The size distribution revealed a large number of particles in the size ranges that would deposit in the nose, airways and lung periphery. Endotoxin was readily measurable in aqueous extracts of the nail particles and a soluble component of the nail dust particles was able to stimulate substantial release of IL-8 from epithelial cells. Suspensions of toenail particles were tested for ability to stimulate IL-8 release from monocyte-derived macrophages; treatment with polymyxin B to remove endotoxin had no effect. We conclude that podiatrists who routinely carry out nail drilling could be inhaling particles that can deposit throughout the respiratory tract, where they could contribute to inflammation by stimulating release of IL-8 from cells via the particles themselves and via endotoxin.
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Exposure to crystalline silica (SiO2), in the form of quartz, tridymite or cristobalite, can cause respiratory diseases, such as silicosis. However, the observed toxicity and pathogenicity of crystalline silica is highly variable. This has been attributed to a number of inherent and external factors, including the presence of impurities. In cristobalite-rich dusts, substitutions of aluminium (Al) for silicon (Si) in the cristobalite structure, and impurities occluding the silica surface, have been hypothesised to decrease its toxicity. This hypothesis is tested here through the characterisation and in vitro toxicological study of synthesised cristobalite with incremental amounts of Al and sodium (Na) dopants. Samples of synthetic cristobalite with incremental amounts of Al and Na impurities, and tridymite, were produced through heating of a silica sol-gel. Samples were characterised for mineralogy, cristobalite purity and abundance, particle size, surface area and surface charge. In vitro assays assessed the ability of the samples to induce cytotoxicity and TNF-α production in J774 macrophages, and haemolysis of red blood cells. Al-only doped or Al+Na co-doped cristobalite contained between 1 and 4 oxide wt% Al and Na within its structure. Co-doped samples also contained Al- and Na-rich phases, such as albite. Doping reduced cytotoxicity to J774 macrophages and haemolytic capacity compared to non-doped samples. Al-only doping was more effective at decreasing cristobalite reactivity than Al+Na co-doping. The reduction in the reactivity of cristobalite is attributed to both structural impurities and a lower abundance of crystalline silica in doped samples. Neither non-doped nor doped crystalline silica induced production of the pro-inflammatory cytokine TNF-α in J774 macrophages. Impurities can reduce the toxic potential of cristobalite and may help explain the low reactivity of some cristobalite-rich dusts. Whilst further work is required to determine if these effects translate to altered pathogenesis, the results have potential implications for the regulation of crystalline silica exposures.
Although the pathogenesis of pulmonary oxygen toxicity is not fully understood, the fact that increased numbers of polymorphonuclear leukocytes (PMN) are found in the lung and that these increases coincide with the massive endothelial damage raises the possibility that PMN may contribute to lung injury caused by hyperoxia. In order to begin to elucidate a mechanism for this influx of PMN, we measured the chemoattractant activity for PMN of lung lavages of rats exposed to greater than 95% oxygen for various durations. We found that the chemoattractant activity of the lavages of the lungs of rats exposed to hyperoxia for 66 h was markedly increased (9.66 +/- 1.0 times greater) compared with activities in lavages of normoxic control rats. Furthermore, these increases in chemoattractant activity in lung lavages correlated well with increases in the number of PMN (7 times greater than that in normoxic control animals) in the alveolar lavages that occurred after the rats had been exposed to hyperoxia for 66 h. These increases were followed in a few hours by the death of most of the rats (71%). These findings suggested that a close temporal relationship exists between the generation of high concentrations of chemoattractants in lung lavages, PMN influx into lung lavages, and death of rats exposed to hyperoxia. The results supported the possibility that PMN may be involved in the pathogenesis of pulmonary oxygen toxicity.
Anti-vascular endothelial growth factor (VEGF) agents may provide a prophylactic effect in high-risk eyes with intermediate dry age-related macular degeneration (AMD) against conversion to exudative AMD (eAMD), lowering the risk of vision loss.To evaluate intravitreal aflibercept injection (IAI) as prophylaxis against the conversion to eAMD in high-risk eyes at 24 months.This single-masked, sham-controlled, randomized clinical trial performed at 4 US clinical sites enrolled patients with intermediate AMD in 1 eye (study eye), defined as presence of more than 10 medium drusen (≥63 to <125 μm), at least 1 large druse (≥125 μm), and/or retinal pigmentary changes, and eAMD in the fellow eye. Patients were treated from June 23, 2015, to March 13, 2019.Intravitreal aflibercept injection (2 mg) or sham quarterly injection for 24 months (1:1 randomization).The primary end point was the proportion of patients with conversion to eAMD at month 24 characterized by development of choroidal neovascularization, as assessed by leakage on fluorescein angiography and fluid on spectral-domain optical coherence tomography by an independent masked reading center.Of 128 patients enrolled, 127 (63 in the IAI group and 64 in the sham group) were included in the primary analysis (68 men [53.5%]; mean [SD] age, 76.5 [8.1] years). Baseline demographic and clinical characteristics were balanced between the groups. By month 24, 6 patients (9.5%) in the IAI group and 7 (10.9%) in the sham group developed eAMD (P = .98). Patients with a history of eAMD for longer than 2 years in their fellow eye at baseline showed a lower rate of conversion to eAMD in the study eye compared with those with a history of eAMD for 2 years or less in the fellow eye. Safety was consistent with previous studies involving intravitreal anti-VEGF injections.In this evaluation of quarterly anti-VEGF exposure as prophylaxis to reduce conversion of eyes with high-risk dry AMD to eAMD, the rates of conversion were not lower in the IAI group compared with the sham treatment group at month 24. Understanding the mechanism of conversion to eAMD and therapies that could prevent this event remains an important unmet need.ClinicalTrials.gov Identifier: NCT02462889.
Skin grafts can be used effectively to inhibit wound contraction. A critical element of this inhibition is the adherence of the graft to the wound bed. Fibrin glue has been shown to increase the adherence of skin grafts to wound beds. We therefore devised an experiment to determine the effect of fibrin glue on skin graft inhibition of wound contraction. Two 2.5 x 2.5-cm full-thickness defects were created on the dorsa of 15 Sprague-Dawley rats. Thirty partial-thickness grafts were harvested from isogeneric donor animals using a brown dermatome. Prior to grafting, one full-thickness defect, each animal received 0.2 mL of fibrin glue (Immuno AG, Vienna, Austria). The adjacent wound served as the control and received 0.2 mL of normal saline. Grafts were applied, sutured, and protected with an occlusive dressing. The size of graft sites treated with fibrin glue or normal saline was determined at the time of graft application and thereafter at 3-day intervals for 21 days using standardized photographic techniques. The percentage of change from initial wound size at each point was recorded for each group. Graft sites treated with fibrin glue contracted less than the controls from the ninth postgraft day to the completion of the study. The mechanism by which fibrin glue inhibits wound contraction may be related to increased adherence of grafts to the underlying wound bed. As an adjunct in skin grafting, fibrin glue may offer certain advantages that are not achieved by suturing alone.
Animal models of diabetes mellitus allow for the manipulation of the metabolic state and the performance of experiments that may shed light on the pathogenesis of diabetic nephropathy. Rats with long-standing chemically induced diabetes develop glomerular mesangial thickening and immunoglobulin and complement deposition. These glomerular changes are reversible on the transplantation of a kidney from a diabetic rat into a normal host and on cure of the diabetic state by pancreatic islet transplantation. Conversely, diabetic renal changes develop in normal kidneys transplanted into diabetic rats (within tow to four months) and humans (within two years). These studies suggest that nephropathy results from the diabetic state. The mesangium is thickened in diabetic rats, mice, and humans. In rats, mesangial function is the processing of macromolecules localized therein is disturbed in areas of mesangial pathology. The finding that glomerulopathy is accelerated in uninephrectomized diabetic rats and is retarded in rat kidneys "protected" by narrowing of the renal artery suggests that alterations in glomerular blood flow are related to the pathogenesis of diabetic glomerular damage. Marked hyperglycemia in animals and man leads to "glycogen nephrosis," which affects the distal tubule at the level of the macula densa of the juxtaglomerular apparatus (JGA). This could lead to disturbance of JGA blood pressure regulation. Disturned mesangial function may result from failure of macula densa cells to process macromolecules that have reached that site from the mesangium.
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