University of North Texas

About: University of North Texas is a education organization based out in Denton, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 11866 authors who have published 26984 publications receiving 705376 citations. The organization is also known as: Fight, North Texas & UNT.

Quinol-based cyclic antioxidant mechanism in estrogen neuroprotection

Abstract: Substantial evidence now exists that intrinsic free-radical scavenging contributes to the receptor-independent neuroprotective effects of estrogens. This activity is inherently associated with the presence of a phenolic A-ring in the steroid. We report a previously unrecognized antioxidant cycle that maintains the “chemical shield” raised by estrogens against the most harmful reactive oxygen species, the hydroxyl radical (•OH) produced by the Fenton reaction. In this cycle, the capture of •OH was shown to produce a nonphenolic quinol with no affinity to the estrogen receptors. This quinol is then rapidly converted back to the parent estrogen via an enzyme-catalyzed reduction by using NAD(P)H as a coenzyme (reductant) and, unlike redox cycling of catechol estrogens, without the production of reactive oxygen species. Due to this process, protection of neuronal cells against oxidative stress is also possible by quinols that essentially act as prodrugs for the active hormone. We have shown that the quinol obtained from a 17β-estradiol derivative was, indeed, able to attenuate glutamate-induced oxidative stress in cultured hippocampus-derived HT-22 cells. Estrone quinol was also equipotent with its parent estrogen in reducing lesion volume in ovariectomized rats after transient middle carotid artery occlusion followed by a 24-h reperfusion. These findings may establish the foundation for a rational design of neuroprotective antioxidants focusing on steroidal quinols as unique molecular leads.

Dynamical-mechanical and thermal analysis of polymeric composites reinforced with keratin biofibers from chicken feathers

Abstract: Keratin fibers from chicken feathers were used as short-fiber reinforcement for a poly(methyl methacrylate) matrix. The composites were evaluated via thermal and dynamical–mechanical analysis. The thermal stability and transition temperature were found to be higher than standard PMMA. The storage modulus at room temperature increased with 1% and 2% weight of keratin biofibers and, at high temperature, the reinforcement provides higher stability, as reflected in the modulus behavior. Keratin fibers within the rigid polymer reduces tan δ peak, indication of a strong interface, as optical images confirm.

Fractional diffusion and Lévy stable processes

Abstract: Anomalous diffusion in which the mean square distance between diffusing quantities increases faster than linearly in ``time'' has been observed in all manner of physical and biological systems from macroscopic surface growth to DNA sequences. Herein we relate the cause of this nondiffusive behavior to the statistical properties of an underlying process using an exact statistical model. This model is a simple two-state process with long-time correlations and is shown to produce a random walk described by an exact fractional diffusion equation. Fractional diffusion equations describe anomalous transport and are shown to have exact solutions in terms of Fox functions, including L\'evy \ensuremath{\alpha}-stable processes in the superdiffusive domain (1/21).

Transforming Growth Factor–β Induces Extracellular Matrix Protein Cross-Linking Lysyl Oxidase (LOX) Genes in Human Trabecular Meshwork Cells

Abstract: Glaucoma is a leading cause of irreversible visual impairment and blindness in the world, with primary open-angle glaucoma (POAG) being the major form.1,2 Elevated intraocular pressure (IOP) is a major risk factor for the development and progression of glaucoma,3,4 and this ocular hypertension is due to increased aqueous humor outflow resistance in the trabecular meshwork (TM) and is associated with increased deposition of extracellular matrix (ECM) material within the TM. The profibrotic cytokine TGFβ2 has been implicated in the pathogenesis of POAG.5 Levels of TGFβ2 are elevated in the aqueous humor6–8 and TM (Tovar-Vidalez T et al., manuscript submitted) of POAG patients. TM cells express TGFβ receptors, and TGFβ2 has direct effects on the TM.9 TGFβ2 has been shown to increase aqueous outflow resistance and to elevate IOP in perfusion cultured human and porcine eyes10–12 and in rodent eyes.13 TGFβ1 is elevated in the aqueous humor of patients with exfoliation glaucoma,14 suggesting that this TGFβ isoform is associated with the accumulation of exfoliation material, including ECM proteins, in the anterior segments of patients with this syndrome. TGFβ2 regulates ECM metabolism in TM cells and tissues. This cytokine increases expression of a variety of ECM proteins, including fibronectin, collagen, elastin, and proteoglycans, as well as PAI-1 and TIMP-1, inhibitors that suppress proteolytic degradation of the ECM.15 In addition, TGFβ2 increases expression of the ECM cross-linking enzyme transglutaminase (TGM)-2 in TM cells.16 The combination of increased ECM synthesis, increased cross-linking, and decreased degradation causes increased ECM deposition in the TM, which may be responsible for the TGFβ2-mediated increased resistance to aqueous humor outflow. Similar changes occur in the TM of POAG patients, with increased levels of fibronectin,17 collagen,18 PAI-1,19 and TGM2.20 In addition to TGM2, there is a second important class of ECM cross-linking enzymes. The lysyl oxidase (LOX) family contains five genes (LOX and LOXL1 to -4) encoding enzymes that covalently cross-link elastin and collagens via generation of aldehydes on lysine residues.21,22 This cross-linking reaction provides additional mechanical strength to the ECM and makes it more resistant to degradation. LOX enzymes play a role in a variety of fibrotic diseases.21–25 Single-nucleotide polymorphisms (SNPs) in LOXL1 are associated with a significantly increased risk of exfoliation glaucoma,26,27 further suggesting potential roles for LOXs in glaucoma pathogenesis. The purpose of the present study was to determine (1) whether the LOX and LOXL genes and proteins are expressed in human TM cells, (2) whether TGFβ induces LOX gene expression and activity in the TM, and (3) which TGFβ signaling pathway(s) regulate LOX expression in the TM.

Metal-Organic Frameworks for Enzyme Immobilization: Beyond Host Matrix Materials

Abstract: Enzyme immobilization in metal-organic frameworks (MOFs) as a promising strategy is attracting the interest of scientists from different disciplines with the expansion of MOFs' development. Different from other traditional host materials, their unique strengths of high surface areas, large yet adjustable pore sizes, functionalizable pore walls, and diverse architectures make MOFs an ideal platform to investigate hosted enzymes, which is critical to the industrial and commercial process. In addition to the protective function of MOFs, the extensive roles of MOFs in the enzyme immobilization are being well-explored by making full use of their remarkable properties like well-defined structure, high porosity, and tunable functionality. Such development shifts the focus from the exploration of immobilization strategies toward functionalization. Meanwhile, this would undoubtedly contribute to a better understanding of enzymes in regards to the structural transformation after being hosted in a confinement environment, particularly to the orientation and conformation change as well as the interplay between enzyme and matrix MOFs. In this Outlook, we target a comprehensive review of the role diversities of the host matrix MOF based on the current enzyme immobilization research, along with proposing an outlook toward the future development of this field, including the representatives of potential techniques and methodologies being capable of studying the hosted enzymes.