Highlights d K13 artemisinin resistance-conferring mutations lead to reduced K13 abundance d K13 is localized to cytostome-like structures at the parasite periphery d Reduced K13 abundance impairs hemoglobin catabolism and lessens artemisinin activation d Reduced artemisinin activation limits cell damage, permitting parasite survival

A wound stabilizing effect of expanded polytetrafluoroethylene (ePTFE) membranes was evaluated in supra-alveolar periodontal defects in 5 beagle dogs. The defects, 5 to 6 mm in height, were surgically created around the 2nd, 3rd, and 4th mandibular premolar teeth in contralateral jaw quadrants. The root surfaces were conditioned with heparin, which, in this model, has been demonstrated to compromise periodontal healing and result in formation of a long junctional epithelium. Wound closure included application of ePTFE membranes around each premolar tooth in one jaw quadrant in each dog and flap positioning coronal to the cemento-enamel junction in both jaw quadrants. Healing progressed uneventfully except for 3 teeth in 2 dogs, which experienced membrane exposure. The dogs were sacrificed after a 4-week healing period and tissue blocks were prepared for histometric analysis. Connective tissue repair in heparin+membrane-treated teeth averaged 98% of the defect height compared to 84% in control heparin-treated teeth (P < or = 0.05). Junctional epithelium formation was smaller in membrane-treated teeth than in control teeth (P < or = 0.05) and was usually terminated coronal to the membrane. Bone regeneration was enhanced in membrane-treated teeth compared to controls (P < or = 0.01) and was strongly correlated to the area under the membrane in teeth without membrane exposure (r2 = 0.993; P = 0.002). This correlation was reduced when teeth with membrane exposure were included in the analysis (P < or = 0.05). Cementum regeneration was minimal under both treatment conditions. Root resorption was increased in membrane-treated compared to control teeth (P < or = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Myeloperoxidase (MPO) is an important neutrophil lysosomal enzyme, a major autoantigen, and a potential mediator of tissue injury in MPO-ANCA-associated vasculitis (MPO-AAV) and glomerulonephritis. Here we examined MPO deposition in kidney biopsies from 47 patients with MPO-AAV. Leukocyte accumulation and fibrin deposition consistent with cell-mediated immunity was a major feature. Tubulointerstitial macrophage, CD4+ and CD8+ T-cell, and neutrophil numbers correlated with low presenting eGFR. MPO was not detected in kidneys from patients with minimal change or thin basement membrane disease, but was prominent in glomerular, periglomerular, and tubulointerstitial regions in MPO-AAV. Extracellular MPO released from leukocytes was pronounced in all MPO-AAV patients. Similar numbers of neutrophils and macrophages expressed MPO in the kidneys, but colocalization studies identified neutrophils as the major source of extracellular MPO. Extraleukocyte MPO was prominent in neutrophil extracellular traps in the majority of patients; most of which had traps in half or more glomeruli. These traps were associated with more neutrophils and more MPO within glomeruli. Glomerular MPO-containing macrophages generated extracellular trap-like structures. MPO also localized to endothelial cells and podocytes. The presence of the most active glomerular lesions (both segmental necrosis and cellular crescents) correlated with intraglomerular CD4+ cells and MPO+ macrophages. Thus, cellular and extracellular MPO may cause glomerular and interstitial injury.

The apical complex is the definitive cell structure of phylum Apicomplexa, and is the focus of the events of host cell penetration and the establishment of intracellular parasitism. Despite the importance of this structure, its molecular composition is relatively poorly known and few studies have experimentally tested its functions. We have characterized a novel Toxoplasma gondii protein, RNG2, that is located at the apical polar ring—the common structural element of apical complexes. During cell division, RNG2 is first recruited to centrosomes immediately after their duplication, confirming that assembly of the new apical complex commences as one of the earliest events of cell replication. RNG2 subsequently forms a ring, with the carboxy- and amino-termini anchored to the apical polar ring and mobile conoid, respectively, linking these two structures. Super-resolution microscopy resolves these two termini, and reveals that RNG2 orientation flips during invasion when the conoid is extruded. Inducible knockdown of RNG2 strongly inhibits host cell invasion. Consistent with this, secretion of micronemes is prevented in the absence of RNG2. This block, however, can be fully or partially overcome by exogenous stimulation of calcium or cGMP signaling pathways, respectively, implicating the apical complex directly in these signaling events. RNG2 demonstrates for the first time a role for the apical complex in controlling secretion of invasion factors in this important group of parasites.

Brain cells manufacture and secrete angiogenic peptides after focal cerebral ischemia, but the purpose of this angiogenic response is unknown. Because the maximum possible regional cerebral blood flow is determined by the quantity of microvessels in each unit volume, it is possible that angiogenic peptides are secreted to generate new collateral channels; other possibilities include neuroprotection, recovery/regeneration, and removal of necrotic debris. If the brain attempts to create new collaterals, microvessel density should increase significantly after ischemia. Conversely, if angiogenic-signaling molecules serve some other purpose, microvessel densities may increase slightly or not at all. To clarify, the authors measured microvessel densities with quantitative morphometry. Left middle cerebral arteries of adult male Sprague-Dawley rats were occluded with intraluminal nylon suture for 4 hours followed by 7, 14, 19, or 30 days of reperfusion. Controls received no surgery or suture occlusion. Changes in microvessel density and macrophage numbers were measured by light microscopic morphometry using semiautomated stereologic methods. Microvessel density increased only in the ischemic margin adjacent to areas of pannecrosis and was always associated with increased numbers of macrophages. Ischemic brain areas without macrophages displayed no vascularity changes compared with normal animals. These data suggest that ischemia-induced microvessels are formed to facilitate macrophage infiltration and removal of necrotic brain.