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Long Term Property Prediction of Polyethylene Nanocomposites
The amorphous fraction of semicrystalline polymers has long been thought to be a significant contributor to creep deformation. In polyethylene (PE) nanocomposites, the semicrystalline nature of the maleated PE compatibilizer leads to a limited ability to separate the role of the PE in the nanocomposite properties. This dissertation investigates blown films of linear low-density polyethylene (LLDPE) and its nanocomposites with montmorillonite-layered silicate (MLS). Addition of an amorphous ethylene propylene copolymer grafted maleic anhydride (amEP) was utilized to enhance the interaction between the PE and the MLS. The amorphous nature of the compatibilizer was used to differentiate the effect of the different components of the nanocomposites; namely the matrix, the filler, and the compatibilizer on the overall properties. Tensile test results of the nanocomposites indicate that the addition of amEP and MLS separately and together produces a synergistic effect on the mechanical properties of the neat PE Thermal transitions were analyzed using differential scanning calorimetry (DSC) to determine if the observed improvement in mechanical properties is related to changes in crystallinity. The effect of dispersion of the MLS in the matrix was investigated by using a combination of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Mechanical measurements were correlated to the dispersion of the layered silicate particles in the matrix. The nonlinear time dependent creep of the material was analyzed by examining creep and recovery of the films with a Burger model and the Kohlrausch-Williams-Watts (KWW) relation. The effect of stress on the nonlinear behavior of the nanocomposites was investigated by analyzing creep-recovery at different stress levels. Stress-related creep constants and shift factors were determined for the material by using the Schapery nonlinear viscoelastic equation at room temperature. The effect of temperature on the tensile and creep properties of the nanocomposites was analyzed by examining tensile and creep-recovery behavior of the films at temperatures in the range of 25 to -100 oC. Within the measured temperature range, the materials showed a nonlinear temperature dependent response. The time-temperature superposition principle was successfully used to predict the long term behavior of LLDPE nanocomposites
Experience of two-components anesthesia on laboratory animals during an acute experiment
лабораторные животные, анестезия, двухкомпонентная анестезия, опыт, острый опы
3D hydrogel/ bioactive glass scaffolds in bone tissue engineering: Status and future opportunities
From Elsevier via Jisc Publications RouterHistory: accepted 2023-06-06, issued 2023-07-05Article version: AMPublication status: AcceptedRepairing significant bone defects remains a critical challenge, raising the clinical demand to design novel bone biomaterials that incorporate osteogenic and angiogenic properties to support the regeneration of vascularized bone. Bioactive glass scaffolds can stimulate angiogenesis and osteogenesis. In addition, natural or synthetic polymers exhibit structural similarity with extracellular matrix (ECM) components and have superior biocompatibility and biodegradability. Thus, there is a need to prepare composite scaffolds of hydrogels for vascularized bone, which incorporates bioactive glass to improve the mechanical properties and bioactivity of natural polymers. In addition, those composites' 3-dimensional (3D) form offers regenerative benefits such as direct doping of the scaffold with ions. This review presents a comprehensive discussion of composite scaffolds incorporated with BaG, focusing on their effects on osteo-inductivity and angiogenic properties. Moreover, the adaptation of the ion-doped hydrogel composite scaffold into a 3D scaffold for the generation of vascularized bone tissue is exposed. Finally, we highlight the future challenges of manufacturing such biomaterials
Flavin Oxidase-Induced ROS Generation Modulates PKC Biphasic Effect of Resveratrol on Endothelial Cell Survival.
Dietary intake of natural antioxidants is thought to impart protection against oxidative-associated cardiovascular diseases. Despite many in vivo studies and clinical trials, this issue has not been conclusively resolved. Resveratrol (RES) is one of the most extensively studied dietary polyphenolic antioxidants. Paradoxically, we have previously demonstrated that high RES concentrations exert a pro-oxidant effect eventually elevating ROS levels leading to cell death. Here, we further elucidate the molecular determinants underpinning RES-induced oxidative cell death. Using human umbilical vein endothelial cells (HUVECs), the effect of increasing concentrations of RES on DNA synthesis and apoptosis was studied. In addition, mRNA and protein levels of cell survival or apoptosis genes, as well as protein kinase C (PKC) activity were determined. While high concentrations of RES reduce PKC activity, inhibit DNA synthesis and induce apoptosis, low RES concentrations elicit an opposite effect. This biphasic concentration-dependent effect (BCDE) of RES on PKC activity is mirrored at the molecular level. Indeed, high RES concentrations upregulate the proapoptotic , while downregulating the antiapoptotic , at both mRNA and protein levels. Similarly, high RES concentrations downregulate the cell cycle progression genes, , ornithine decarboxylase and cyclin D1 protein levels, while low RES concentrations display an increasing trend. The BCDE of RES on PKC activity is abrogated by the ROS scavenger Tempol, indicating that this enzyme acts downstream of the RES-elicited ROS signaling. The RES-induced BCDE on HUVEC cell cycle machinery was also blunted by the flavin inhibitor diphenyleneiodonium (DPI), implicating flavin oxidase-generated ROS as the mechanistic link in the cellular response to different RES concentrations. Finally, PKC inhibition abrogates the BCDE elicited by RES on both cell cycle progression and pro-apoptotic gene expression in HUVECs, mechanistically implicating PKC in the cellular response to different RES concentrations. Our results provide new molecular insight into the impact of RES on endothelial function/dysfunction, further confirming that obtaining an optimal benefit of RES is concentration-dependent. Importantly, the BCDE of RES could explain why other studies failed to establish the cardio-protective effects mediated by natural antioxidants, thus providing a guide for future investigation looking at cardio-protection by natural antioxidants
The Brain And Exercise: In Sickness And In Health
The brain, like any other organ in the body, is made up of various types of cells. Nerve cells called neurons are the major cells in the brain. Their main function is to transfer messages and orders to and from the organs of the body. Neurons communicate with each other and with other cells through connections that resemble electrical wires. Throughout a person’s life, neurons remodel and rewire their connections to become weaker or stronger. This remodeling is known as brain neuroplasticity, which means “the ability to adapt or change.” Neuroplasticity is affected by several factors. For example, physical activity such as exercise can reshape the brain for the better, by enhancing memory and attention. These changes can improve academic performance and protect people from certain brain diseases. These are just a few reasons why we should all exercise more often
Herbal Medicine for Cardiovascular Diseases: Efficacy, Mechanisms, and Safety
Cardiovascular diseases (CVDs) are a significant health burden with an ever-increasing
prevalence. They remain the leading causes of morbidity and mortality worldwide. The use
of medicinal herbs continues to be an alternative treatment approach for several diseases
including CVDs. Currently, there is an unprecedented drive for the use of herbal
preparations in modern medicinal systems. This drive is powered by several aspects,
prime among which are their cost-effective therapeutic promise compared to standard
modern therapies and the general belief that they are safe. Nonetheless, the claimed
safety of herbal preparations yet remains to be properly tested. Consequently, public
awareness should be raised regarding medicinal herbs safety, toxicity, potentially lifethreatening
adverse effects, and possible herb–drug interactions. Over the years,
laboratory data have shown that medicinal herbs may have therapeutic value in CVDs
as they can interfere with several CVD risk factors. Accordingly, there have been many
attempts to move studies on medicinal herbs from the bench to the bedside, in order to
effectively employ herbs in CVD treatments. In this review, we introduce CVDs and their
risk factors. Then we overview the use of herbs for disease treatment in general and CVDs
in particular. Further, data on the ethnopharmacological therapeutic potentials and
medicinal properties against CVDs of four widely used plants, namely Ginseng, Ginkgo
biloba, Ganoderma lucidum, and Gynostemma pentaphyllum, are gathered and reviewed.
In particular, the employment of these four plants in the context of CVDs, such as
myocardial infarction, hypertension, peripheral vascular diseases, coronary heart disease,
cardiomyopathies, and dyslipidemias has been reviewed, analyzed, and critically
discussed. We also endeavor to document the recent studies aimed to dissect the
cellular and molecular cardio-protective mechanisms of the four plants, using recently
reported in vitro and in vivo studies. Finally, we reviewed and reported the results of the recent clinical trials that have been conducted using these four medicinal herbs with
special emphasis on their efficacy, safety, and toxicity.This work has been made possible thanks to grants (Ager S.O.S.) and (fondo di Ateneo per la ricerca 2019) to GP and Qatar University grant (IRCC-2019-007) to GN and GP
Potential Adverse Effects of Resveratrol: A Literature Review.
Due to its health benefits, resveratrol (RE) is one of the most researched natural polyphenols. Resveratrol's health benefits were first highlighted in the early 1990s in the French paradox study, which opened extensive research activity into this compound. Ever since, several pharmacological activities including antioxidant, anti-aging, anti-inflammatory, anti-cancerous, anti-diabetic, cardioprotective, and neuroprotective properties, were attributed to RE. However, results from the available human clinical trials were controversial concerning the protective effects of RE against diseases and their sequelae. The reason for these conflicting findings is varied but differences in the characteristics of the enrolled patients, RE doses used, and duration of RE supplementation were proposed, at least in part, as possible causes. In particular, the optimal RE dosage capable of maximizing its health benefits without raising toxicity issues remains an area of extensive research. In this context, while there is a consistent body of literature on the protective effects of RE against diseases, there are relatively few reports investigating its possible toxicity. Indeed, toxicity and adverse effects were reported following consumption of RE; therefore, extensive future studies on the long-term effects, as well as the in vivo adverse effects, of RE supplementation in humans are needed. Furthermore, data on the interactions of RE when combined with other therapies are still lacking, as well as results related to its absorption and bioavailability in the human body. In this review, we collect and summarize the available literature about RE toxicity and side effects. In this process, we analyze in vitro and in vivo studies that have addressed this stilbenoid. These studies suggest that RE still has an unexplored side. Finally, we discuss the new delivery methods that are being employed to overcome the low bioavailability of RE
Biochemical and cellular basis of oxidative stress: Implications for disease onset
Cellular oxidation–reduction (redox) systems, which encompass pro- and antioxidant molecules, are integral components of a plethora of essential cellular processes. Any dysregulation of these systems can cause molecular imbalances between the pro- and antioxidant moieties, leading to a state of oxidative stress. Long-lasting oxidative stress can manifest clinically as a variety of chronic illnesses including cancers, neurodegenerative disorders, cardiovascular disease, and metabolic diseases like diabetes. As such, this review investigates the impact of oxidative stress on the human body with emphasis on the underlying oxidants, mechanisms, and pathways. It also discusses the available antioxidant defense mechanisms. The cellular monitoring and regulatory systems that ensure a balanced oxidative cellular environment are detailed. We critically discuss the notion of oxidants as a double-edged sword, being signaling messengers at low physiological concentrations but causative agents of oxidative stress when overproduced. In this regard, the review also presents strategies employed by oxidants including redox signaling and activation of transcriptional programs such as those mediated by the Nrf2/Keap1 and NFk signaling. Likewise, redox molecular switches of peroxiredoxin and DJ-1 and the proteins they regulate are presented. The review concludes that a thorough comprehension of cellular redox systems is essential to develop the evolving field of redox medicine.Open Access funding provided by Qatar National Library. [Correction added on 25 July 2023, after first online publication: Acknowledgement section has been inserted.
Epac as a tractable therapeutic target
In 1957, cyclic adenosine monophosphate (cAMP) was identified as the first secondary messenger, and the first signaling cascade discovered was the cAMP-protein kinase A (PKA) pathway. Since then, cAMP has received increasing attention given its multitude of actions. Not long ago, a new cAMP effector named exchange protein directly activated by cAMP (Epac) emerged as a critical mediator of cAMP's actions. Epac mediates a plethora of pathophysiologic processes and contributes to the pathogenesis of several diseases such as cancer, cardiovascular disease, diabetes, lung fibrosis, neurological disorders, and others. These findings strongly underscore the potential of Epac as a tractable therapeutic target. In this context, Epac modulators seem to possess unique characteristics and advantages and hold the promise of providing more efficacious treatments for a wide array of diseases. This paper provides an in-depth dissection and analysis of Epac structure, distribution, subcellular compartmentalization, and signaling mechanisms. We elaborate on how these characteristics can be utilized to design specific, efficient, and safe Epac agonists and antagonists that can be incorporated into future pharmacotherapeutics. In addition, we provide a detailed portfolio for specific Epac modulators highlighting their discovery, advantages, potential concerns, and utilization in the context of clinical disease entities
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