A Putative O-Linked ß-N-Acetylglucosamine Transferase Is Essential for Hormogonium Development and Motility in the Filamentous Cyanobacterium Nostoc punctiforme.

Most species of filamentous cyanobacteria are capable of gliding motility, likely via a conserved type IV pilus-like system that may also secrete a motility-associated polysaccharide. In a subset of these organisms, motility is achieved only after the transient differentiation of hormogonia, which are specialized filaments that enter a nongrowth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycles of many filamentous cyanobacteria, the molecular regulation of hormogonium development is largely undefined. To systematically identify genes essential for hormogonium development and motility in the model heterocyst-forming filamentous cyanobacterium Nostoc punctiforme, a forward genetic screen was employed. The first gene identified using this screen, designated ogtA, encodes a putative O-linked ß-N-acetylglucosamine transferase (OGT). The deletion of ogtA abolished motility, while ectopic expression of ogtA induced hormogonium development even under hormogonium-repressing conditions. Transcription of ogtA is rapidly upregulated (1 h) following hormogonium induction, and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of PilA but not HmpD is dependent on ogtA Reverse transcription-quantitative PCR (RT-qPCR) analysis indicated equivalent levels of pilA transcript in the wild-type and ΔogtA mutant strains, while a reporter construct consisting of the intergenic region in the 5' direction of pilA fused to gfp produced lower levels of fluorescence in the ΔogtA mutant strain than in the wild type. The production of hormogonium polysaccharide in the ΔogtA mutant strain is reduced compared to that in the wild type but comparable to that in a pilA deletion strain. Collectively, these results imply that O-GlcNAc protein modification regulates the accumulation of PilA via a posttranscriptional mechanism in developing hormogonia.IMPORTANCE Filamentous cyanobacteria are among the most developmentally complex prokaryotes. Species such as Nostoc punctiforme develop an array of cell types, including nitrogen-fixing heterocysts, spore-like akinetes, and motile hormogonia, that function in dispersal as well as the establishment of nitrogen-fixing symbioses with plants and fungi. These symbioses are major contributors to global nitrogen fixation. Despite the fundamental importance of hormogonia to the life cycle of filamentous cyanobacteria and the establishment of symbioses, the molecular regulation of hormogonium development is largely undefined. We employed a genetic screen to identify genes essential for hormogonium development and motility in Nostoc punctiforme The first gene identified using this screen encodes a eukaryotic-like O-linked ß-N-acetylglucosamine transferase that is required for accumulation of PilA in hormogonia.

Wear Resistance Comparison of Prefabricated Primary Crowns Using a Novel 3D Computed Tomography Method.

PURPOSE: The purpose of this study was to compare the wear resistance of stainless steel crowns, (SSCs), zirconia crowns (ZRCs), and nanohybrid crowns (NHCs) using a 3D tomography method. METHODS: Prefabricated SSCs, ZRCs, and NHCs (n equals 80) were worn for 400,000 cycles, equivalent to three years of simulated clinical wear, at 50 N and 1.2 Hz using the Leinfelder-Suzuki wear tester. Wear volume, maximum wear depth, and wear surface area were computed using a 3D superimposition method and 2D imaging software. Data were statistically analyzed using one-way analysis of variance with the least significant difference post hoc test (P<0.05). RESULTS: After a wear simulation of three years, NHCs had a 45 percent failure rate; NHCs also had the greatest wear volume loss (0.71 mm³), maximum wear depth (0.22 mm), and wear surface area (4.45 mm²). SSCs (0.23 mm³ , 0.12 mm, 2.63 mm²) and ZRCs (0.03 mm³ , 0.08 mm, 0.20 mm ²) had less wear volume, area, and depth (P<0.001). ZRCs were the most abrasive to their antagonists (P<0.001). The NHC (against SSC wearing group) had the greatest total wear facet surface area (4.43 mm²). CONCLUSIONS: Stainless steel crowns and zirconia crowns were the most wear-resistant materials. Based on these laboratory findings, in the primary dentition, nanohybrid crowns are not recommended as long-term restorations beyond 12 months (P=0.001).

Effectiveness of patient education training on health professional student performance: A systematic review.

BACKGROUND: Despite the fundamental role of patient education, concerns have been raised by health professionals, students, and professional bodies regarding student preparation for this area of practice. OBJECTIVE: To evaluate the effectiveness of patient education training on health professional student performance. METHOD: A systematic search was performed across PubMed, Cinahl, Embase, and Cochrane Library. Reference and forward citation searches of included articles were conducted. Inclusion criteria were published journal articles from 2010 to 2020 regarding patient education training for health professional students with measures relating to patient education performance. Quality appraisal of individual studies was conducted using Cochrane risk-of-bias v2 or ROBINS-I; overall appraisal was also determined. Sixteen articles met eligibility criteria. Independent data extraction was undertaken. RESULTS: Fourteen studies reported improvements in student performance following patient education training; two studies reported no significant improvements. Of different modalities examined, simulation-based learning appeared to be most effective. CONCLUSION: Patient education training enhances health professional students' performance of patient education. Future research is needed to evaluate effectiveness of pedagogically informed interventions across health professions using objective approaches to assess student performance in clinically relevant settings. PRACTICAL VALUE: This review supports the use of specific training approaches to improve student performance of patient education.

Hypoxia and trophoblast differentiation: a key role for PPARγ.

Tissue oxygen tension regulates differentiation of multiple types of stem cells. In the placenta, hypoxia has been associated with abnormal trophoblast differentiation and placental insufficiency syndromes of preeclampsia (PE) and intrauterine growth restriction (IUGR). Peroxisome proliferator-activated receptor-γ (PPARγ) is a ligand-activated transcription factor involved in many cellular processes, including differentiation. We have previously shown that PPARγ-null trophoblast stem (TS) cells show a defect in differentiation to labyrinthine trophoblast, instead differentiating preferentially to trophoblast giant cells (TGC). Since PPARγ is known to be regulated by hypoxia in adipose tissue, we hypothesized that there may be a link between oxygen tension, PPARγ expression, and trophoblast differentiation. We found that hypoxia reduced PPARγ expression by a mechanism independent of both hypoxia-inducible factor (HIF) and histone deacetylases (HDACs). In addition, PPARγ partially rescued hypoxia-induced inhibition of labyrinthine differentiation in wild-type TS cells but was not required for hypoxia-induced inhibition of TGC differentiation. Finally, we show that induction of labyrinthine trophoblast differentiation by HDAC inhibitor treatment is independent of both PPARγ and Gcm1. We propose a model with two pathways for labyrinthine trophoblast differentiation of TS cells, one of which is dependent on PPARγ and inhibited by hypoxia. Since hypoxia is associated with PE and IUGR, we propose that PPARγ may at least partially mediate hypoxia-induced placental insufficiency and as such may be a promising therapeutic target for these disorders.