Glucocorticoids and aging

In this review we analyze the morphologic changes, hypothalamic-pituitary-adrenal (HPA) axis functions, glucocorticoid (GC) receptors, and steroidogenic enzyme activities in both animals and humans during aging. In rodent studies, older animals tend to show: 1) hypertrophy of adrenal zona fasciculata (ZF) cells; 2) neuronal loss in the hypothalamic area; 3) loss of GC receptors in the hippocampus; 4) raised circulating adrenocorticotropic hormone (ACTH) and GC levels, and increased release of corticotropin-releasing hormone from the hypothalamus; 5) reduced suppression of endogenous GC secretion after administration of dexamethasone; 6) decreased attenuation of response to chronic stress; and 7) increased activity of P450scc and 21-hydroxylase. According to the GC cascade hypothesis, stress and GCs facilitate the aging process in rats. Stress induces downregulation of GC receptors in the hippocampus, then impairs GC feedback on stress-induced HPA axis activation. Finally, an increase in the basal level of corticosterone and extended GC secretion following stress occurs. Because activation of the hippocampus decreases HPA axis function, the unrestrained elevation of GC concentration and the reduction in the level of GC receptors in the hippocampus may gradually weaken the feedback mechanisms and halt the response to stress. In humans, there are conflicting reports of HPA axis function during aging, so it is difficult to make a final conclusion regarding the relationship between aging and HPA axis function.     

KINETICS OF THE SIMULTANEOUS SORPTION OF NONIONIC SURFACTANT AND COPPER(II) BY POLY ACRYLIC ACID - FUNCTIONALIZED ION EXCHANGER

ABSTRACT

Kinetics of the simultaneous sorption of nonionic surfactant oxyethylated alcohols (OS-20) and copper(II) by hydrogen containing form of Purolite C 106 polyacrylic acid-functionalized cation exchanger was investigated: kinetic curves measured, effective coefficients of intraparticle diffusion (D), effective kinetic coefficients of the external mass transfer ((β) were calculated. The sorption of copper (II) and OS-20 is controlled by the intraparticle diffusion. The diffusion rate depends on the solution acidity: on increasing the acidity both the rate of copper (II) intraparticle diffusion and the equilibrium sorption decrease while the rate of intraparticle diffusion and the equilibrium sorption of OS-20 increase. The presence of copper (II) results in an increase in OS-20 diffusion rate but leads to a decrease in the equilibrium sorption of OS-20. The action of OS-20 results in the decrease in the equilibrium sorption of copper (II).The simultaneous sorption of oxyethylated alcohols and copper (II) by Purolite C 106 can be applicable for the purification of sewage including copper plating rinsewater A column filled with Purolite C 106 would not limit the productivity if integrated into the system of sewage purification by ion exchange |The simultaneous sorption of OS-20 and copper (II) by Purolite C 106 ion exchanger can be applicable for the purification of sewage including copper plating rinsewater. With respect to the coefficients of intraparticle diffusion for both copper (II) and OS-20 the column filled with Purolite C 106 would not limit the productivity if integrated into the system of sewage purification using ion exchange,     

Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber‐reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10–12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100–600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced post‐use shelf life as composites, with benefits while in use and at the same time post‐use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43290.     

The Performance of Small‐Pore Microporous Aluminophosphates in Low‐Temperature Solar Energy Storage: The Structure–Property Relationship

The utilization of the reversible chemical and physical sorption of water on solids provides a new thermal energy storage concept with a great potential for lossless long‐term storage. The performance of microporous aluminophosphates in heat storage applications is highlighted by a comparative thermogravimetric and calorimetric study of three known materials (SAPO‐34, AlPO₄‐18, APO‐Tric) and is correlated with their structural features. The maximum water sorption capacity is similar for all three samples and results in a stored energy density of 240 kWh m^?3 in the 40–140 °C range. The elemental composition influences the gradual (silicoaluminophosphate SAPO‐34) or sudden (aluminophosphates AlPO₄‐18, APO‐Tric) water uptake, with the latter being favourable in storage systems. The driving force for the determined sorption process is the formation of highly ordered water clusters in the pores, which is enabled by rapid and reversible changes in the Al coordination and optimal pore diameters. The ease with which changes in the Al coordination can occur in APO‐Tric is related to the use of the fluoride route in the synthesis. The understanding of these fundamental structure/sorption relationships forms an excellent basis for predicting the storage potential of numerous known or new microporous aluminophosphates and other porous materials from their crystal structures.     

A cross‐layer partner‐based fast handoff mechanism for IEEE 802.11 wireless networks

In wireless/mobile networks, users freely and frequently change their access points (APs) while they are communicating with other users. To support the mobility of mobile nodes (MNs), Mobile IPv6 (MIPv6) is used to inform the information of MN's home address and current care‐of‐address (CoA) to its home agent. MIPv6 suffers from a long delay latency and high packet losses (PLs) because MIPv6 does not support micromobility. A Hierarchical Mobile IPv6 (HMIPv6) is proposed which provides micromobility and macromobility to reduce handoff latency (HL) by employing a hierarchical network structure. In this paper, we propose a cross‐layer partner‐based fast handoff mechanism based on HMIPv6, called the PHMIPv6 protocol. Our PHMIPv6 protocol is a cross‐layer, layer‐2 + layer‐3, and cooperative approach. A cooperative node, called a partner node (PN), is adopted in the PHMIPv6 protocol. A new layer‐2 trigger scheme used in the PHMIPv6 protocol accurately predicts the next AP and then invites a cooperative PN in the area of the next AP. With the cooperation of the PN, the CoA can be pre‐acquired and duplicate address detection operation can be pre‐executed by the PN before the MN initializes the handoff request. The PHMIPv6 protocol significantly reduces the handoff delay time and PLs. In the mathematical analysis, we verified that our PHMIPv6 protocol offers a better HL than the MIPv6, HMIPv6, and SHMIPv6 protocols. Finally, the experimental results also illustrate that the PHMIPv6 protocol actually achieves performance improvements in the handoff delay time, PL rate, and handoff delay jitter. Copyright © 2009 John Wiley & Sons, Ltd.     

Pharmacological effects of propylthiouracil on corticosterone secretion in male rats

BACKGROUND: We investigated the direct effects of propylthiouracil (PTU) on corticosterone secretion both in vivo and in vitro. METHODS: Male rats were divided into 4 groups and then injected subcutaneously with saline, PTU, PTU plus thyroxine (T4), or T4 once daily for 2 weeks. After 2 weeks, rats were decapitated or received adrenocorticotropic hormone (ACTH), intravenously. Zona fasciculata-reticularis (ZFR) cells from normal, saline-, PTU-, PTU plus T4-, or T4-treated rats were incubated with ACTH, forskolin, 8-Br-cAMP, deoxycorticosterone (DOC) +/- PTU (1, 2, or 5 mg/mL) at 37 degrees C for 2 hours. Corticosterone concentrations in plasma and cell media, and 3':5'-cyclic adenosine monophosphate (cAMP) production in ZFR cells were determined by radioimmunoassay. The effects of PTU on the activities of steroidogenic enzymes in ZFR cells were measured by the amounts of intermediate steroidal products separated by thin-layer chromatography. RESULTS: The basal and ACTH-stimulated levels of plasma corticosterone in PTU-treated rats were lower as compared to saline-treated animals. Both basal and ACTH-stimulated corticosterone secretion were inhibited by PTU > 2 mg/mL in rat ZFR cells. The cAMP production induced by forskolin was lower in PTU, PTU plus T4, or T4-treated rats than in saline-treated animals. Chronic administration of PTU or PTU plus T4 inhibited the 3 beta-hydroxysteroid dehydrogenase, 21 beta-hydroxylase, and 11 beta-hydroxylase activities. Administration of PTU (1, 2, and 5 mg/mL) suppressed the basal, ACTH, 8-Br-cAMP, forskolin, and DOC-stimulated corticosterone secretion in rat ZFR cells. Likewise, PTU > 2 mg/mL inhibited the ACTH and 8-Br-cAMP-stimulated levels of intracellular cAMP in rat ZFR cells. CONCLUSIONS: These results suggest that PTU counteracts both basal and ACTH-induced adrenal steroidogenesis through their attenuation of the activity of 11 beta-hydroxylase and cAMP production in rat ZFR cells.     

Comparison of measured and self-reported anthropometric information among firefighters: implications and applications

This study evaluated the accuracy of self-reported body weight and height compared to measured values among firefighters and identified factors associated with reporting error. A total of 863 male and 88 female firefighters in four US regions participated in the study. The results showed that both men and women underestimated their body weight ( ? 0.4 ± 4.1, ? 1.1 ± 3.6 kg) and overestimated their height (29 ± 18 , 17 ± 16 mm). Women underestimated more than men on weight (p = 0.022) and men overestimated more than women on height (p < 0.001). Reporting errors on weight were increased with overweight status (p < 0.001) and were disproportionate among subgroups. About 27% men and 24% women had reporting errors on weight greater than ± 2.2 kg, and 59% men and 28% women had reporting errors on height greater than 25 mm.

Practitioner Summary: This study along with literature revealed that the self-reported approach is not a sustainable option for anthropometric surveys, even for gathering data from physically active professional groups, such as firefighters, who presumably are knowledgeable of their body dimensions. Self-reported anthropometric information is undependable in important population subgroups.     

Human responses to augmented virtual scaffolding models

This study investigated the effect of adding real planks, in virtual scaffolding models of elevation, on human performance in a surround-screen virtual reality (SSVR) system. Twenty-four construction workers and 24 inexperienced controls performed walking tasks on real and virtual planks at three virtual heights (0, 6 m, 12 m) and two scaffolding-platform-width conditions (30, 60 cm). Gait patterns, walking instability measurements and cardiovascular reactivity were assessed. The results showed differences in human responses to real vs. virtual planks in walking patterns, instability score and heart-rate inter-beat intervals; it appeared that adding real planks in the SSVR virtual scaffolding model enhanced the quality of SSVR as a human - environment interface research tool. In addition, there were significant differences in performance between construction workers and the control group. The inexperienced participants were more unstable as compared to construction workers. Both groups increased their stride length with repetitions of the task, indicating a possibly confidence- or habit-related learning effect. The practical implications of this study are in the adoption of augmented virtual models of elevated construction environments for injury prevention research, and the development of programme for balance-control training to reduce the risk of falls at elevation before workers enter a construction job.     

Evaluation of fall arrest harness sizing schemes

OBJECTIVE: This paper evaluated harness sizing schemes and anthropometric criteria for harness design applications. BACKGROUND: Updated harness sizing systems are needed to accommodate diverse populations in the current workforce. METHOD: Three-dimensional torso scan data and human-harness interfaces from 108 women and 108 men were digitally captured. Abounding box approach was employed to quantify the effect of torso shape and size on fall harness fit. RESULTS: A logistic regression model with eight equations was developed and tested to classify more than 96% of participants to the best-fitting size. CONCLUSION: Study outcomes suggested an alternative system of two sizes for women and three sizes for men over the current four-size unisex system. In addition, thigh strap angle and back D ring location could be utilized along with current harness static fit test criteria to further enhance postfall harness fit predictions. APPLICATION: This research could help reduce the risk of worker injury resulting from poor fit, improper size selection, or failure to don the harness properly.