A previously unreported nanoscale lamella structure in a direct spun high strength carbon nanotube (CNT) yarn was identified and characterized. The thickness of the lamellae is in the order of 100 ...nm. The lamella structure is present in the entire cross-section. It is hypothesized that the lamella structure originates from a single thin sheet (felt) during the manufacturing process, between steps of CNT aerogel and CNT roving. The existence of this lamella structure has direct implications on the yarn-resin interface behavior of derived composites and, subsequently, the mechanical performance of CNT yarn composites. Peridynamic simulations of four distinct yarn pullout experiments captured the observed failure behavior influenced by microstructure.
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•The CNT yarns examined show a prominent lamella structure with thicknesses on the order of 100 nm.•Flaws and cracking within the CNT yarns follow lamella boundaries, indicating weaker mechanical properties than the surrounding material.•The failure modes predicted by the peridynamic simulations are consistent with the pullout experiments.•The presence of lamella structure helps explain the observed sword-in-sheath failure behavior.
Heparan Sulfate Analysis from Diabetic Rat Glomeruli Lauer, Mark E.; Hascall, Vincent C.; Wang, Aimin
Journal of biological chemistry/The Journal of biological chemistry,
01/2007, Volume:
282, Issue:
2
Journal Article
Peer reviewed
Open access
One of the major complicating factors in insulin-dependent diabetes mellitus is nephropathy. Several investigators have linked heparan sulfate (HS) alterations in the glomerular basement membrane ...(GBM) with albuminuria as a marker of abnormal blood filtration and the subsequent progression to renal failure. In this study, we examined the fine structure of HS in the glomerulus and the GBM isolated from the kidneys of rats injected with streptozotocin. Using fluorophore-assisted carbohydrate electrophoresis, we obtained disaccharide composition analyses for HS. In a time course study, we observed that normal rat HS isolated from the GBM becomes more N-sulfated as the glomeruli mature over a period of 8 weeks. Diabetic rats injected with streptozotocin at the beginning of this period showed a reversal of this trend. Using a graded sieve technique, we found that two different sizes of glomeruli could be isolated from the rat kidneys and that there was a significant difference in the HS disaccharide content between these two pools of glomeruli. Only the larger sized glomeruli had less N-sulfation of HS as a result of insulin-dependent diabetes mellitus. This change in the fine structure of HS was localized to the GBM and was not associated with cell surface HS. We also generated oligosaccharides of HS that portray fine structural alterations in the diabetic rats indicative of a loss of the sulfation of N-acetylglucosamine.
The importance of the pathological changes in proteoglycans has driven the need to study and design novel chemical tools to control proteoglycan synthesis. Accordingly, we tested the fluorinated ...analogue of glucosamine (4-fluoro-N-acetyl-glucosamine (4-F-GlcNAc)) on the synthesis of heparan sulfate (HS) and chondroitin sulfate (CS) by murine airway smooth muscle (ASM) cells in the presence of radiolabeled metabolic precursors. Secreted and cell-associated CS and HS were assessed for changes in size by Superose 6 chromatography. Treatment of ASM cells with 4-F-GlcNAc (100 μm) reduced the quantity (by 64.1–76.6%) and decreased the size of HS/CS glycosaminoglycans associated with the cell layer (Kav shifted from 0.30 to 0.45). The quantity of CS secreted into the medium decreased by 65.7–73.0%, and the size showed a Kav shift from 0.30 to 0.50. Treatment of ASM cells with 45 μm and 179 μm 4-F-GlcNAc in the presence of a stimulator of CS synthesis, 4-methylumbelliferyl-β-d-xyloside, reduced the amount of the xyloside-CS chains by 65.4 and 87.0%, respectively. The size of xyloside-CS chains synthesized in the presence of 4-F-GlcNAc were only slightly larger than those with xyloside treatment alone (Kav of 0.55 compared with that of 0.6). The effects of 4-F-GlcNAc to inhibit CS synthesis were not observed with equimolar concentrations of glucosamine. We propose that 4-F-GlcNAc inhibits CS synthesis by inhibiting 4-epimerization of UDP-GlcNAc to UDP-GalNAc, thereby depleting one of the substrates required, whereas HS elongation is inhibited by truncation when the nonreducing terminus of the growing chain is capped with 4-F-GlcNAc.
Hyaluronan Rafts on Airway Epithelial Cells Abbadi, Amina; Lauer, Mark; Swaidani, Shadi ...
The Journal of biological chemistry,
01/2016, Volume:
291, Issue:
3
Journal Article
Peer reviewed
Open access
Many cells, including murine airway epithelial cells, respond to a variety of inflammatory stimuli by synthesizing leukocyte-adhesive hyaluronan (HA) cables that remain attached to their cell ...surfaces. This study shows that air-liquid interface cultures of murine airway epithelial cells (AECs) also actively synthesize and release a majority of their HA onto their ciliated apical surfaces to form a heavy chain hyaluronan (HC-HA) matrix in the absence of inflammatory stimuli. These matrices do not resemble the rope-like HA cables but occur in distinct sheets or rafts that can capture and embed leukocytes from cell suspensions. The HC-HA modification involves the transfer of heavy chains from the inter-α-inhibitor (IαI) proteoglycan, which has two heavy chains (HC1 and HC2) on its chondroitin sulfate chain. The transesterification transfer of HCs from chondroitin sulfate to HA is mediated by tumor necrosis factor-induced gene 6 (TSG-6), which is up-regulated in inflammatory reactions. Because the AEC cultures do not have TSG-6 nor serum, the source of IαI, assays for HCs and TSG-6 were done. The results show that AECs synthesize TSG-6 and their own heavy chain donor (pre-IαI) with a single heavy chain 3 (HC3), which are also constitutively expressed by human renal proximal tubular epithelial cells. These leukocyte adhesive HC3-HA structures were also found in the bronchoalveolar lavage of naïve mice and were observed on their apical ciliated surfaces. Thus, these leukocyte-adhesive HA rafts are now identified as HC3-HA complexes that could be part of a host defense mechanism filling some important gaps in our current understanding of murine airway epithelial biology and secretions.
Authors' reply Vries, Bradley S.; Lauer, Mark; McDonald, Sarah ...
BJOG : an international journal of obstetrics and gynaecology,
October 2022, Volume:
129, Issue:
11
Journal Article
Authors' reply de Vries, Bradley S.; Lauer, Mark; McDonald, Sarah ...
BJOG : an international journal of obstetrics and gynaecology,
10/2022, Volume:
129, Issue:
11
Journal Article
Authors' reply de Vries, Bradley S; Lauer, Mark; McDonald, Sarah ...
BJOG : an international journal of obstetrics and gynaecology,
10/2022, Volume:
129, Issue:
11
Journal Article
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