Neurotrophin regulation of energy homeostasis in the central nervous system

Our hypothesis is that one cause of neuronal cell death and shrinkage in the aged central nervous system is an inability of neurons to maintain oxidant homeostasis in the face of increased levels of reactive oxygen species, decreased endogenous antioxidants, and impaired energy metabolism associated with physiological senescence, Alzheimer's, and Parkinson's diseases. Since treatment with nerve growth factor (NGF) reverses behavioral impairments in aged rats and stimulates cholinergic activity in the basal forebrain, while brain-derived neurotrophic factor appears to play a similar role in the striatum, we propose that neurotrophin-mediated cell-sparing reflects effects on oxidant homeostasis. Neurotrophins may play a similar cell-sparing role in hypoxic/ischemic injury to the nervous system, which also is mediated in part by reactive oxygen species. The degradation of one such species, H2O2, is catalyzed by catalase and glutathione peroxidase (GSH Px). The activity of the latter enzyme is dependent on glutathione reductase and the availability of NADPH for regeneration of reduced GSH. The GSH redox cycle is also regulated by enzymes of the hexose monophosphate shunt. NGF protects PC12 cells from H2O2 injury by stimulating the synthesis of antioxidant enzymes including catalase, GSH Px, glucose-6-phosphate dehydrogenase, and gamma-glutamylcysteine synthetase, the rate-limiting enzyme for glutathione synthesis. NGF also enhances recovery from the NAD+ losses occurring as a consequence of H2O2 treatment.     

Innovative Final-Year Undergraduate Design Project Course Using an International Project

This paper describes the organization and conduct of a 4th year capstone project for civil engineering students at the University of Calgary that embodied a very significant international component and the difficulties inherent to that component. The project design education process results in numerous contributions to university, industry, and society by permitting students to develop innovative design solutions that reflect multicultural influences, while also recognizing that Civil Engineering design is universal. This paper explains the novel approach adopted for the final-year civil engineering design course in 2002–2003 using the largest urban renewal project currently underway in Europe, for which the students had the opportunity to develop designs. The concept, structure, challenges, and contributions as well as the successful outcome of the civil engineering design course are also explained in the paper. Overall, this design project provided the students with valuable experience in communication, design, professional practice, and organizational skills that will be useful in their future careers, in addition to the challenges of dealing with a real and international client of a complex project.     

Strain matrix method of analysis for reinforced concrete members under combined bending and direct load

This paper presents a method of analysis for R.C. members of any cross section subjected to loads with large eccentricities causing bending and direct stress. Compressive strain and curvature at a fibre are taken as unknowns and the forces in concrete and steel are expressed in terms of these strains. Two matrix equations are developed with the strains using the equations of equilibrium. The position of neutral axis is calculated from the strains, by iteration of the above procedure assuming the total section to be in compression as a first approximation. Stresses in concrete and steel are determined from the final iteration. This method is also well suited for computer calculation.

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Résumé La méthode d'étude conventionnelle des poteaux de béton armé soumis à des charges de compression avec de grandes excentricités implique des solutions avec des équations compliquées du 3^e degré lorsque les sections transversales ne sont pas rectangulaires. La méthode de la matrice de déformation offre une autre solution. C'est une méthode d'étude fortement itérative et convergente qu'on développe en traitant la déformation et la courbure de la fibre la plus proche comme étant inconnue. Dans la méthode itérative, on prend l'épaisseur de la section comme la valeur initiale de l'épaisseur de l'axe neutre. On calcule les forces internes du béton et de l'acier au moyen des relations contrainte/déformation et de la géométrie de la section transversale, ainsi que des principes des sections planes pour la flexion. Les équations d'équilibre sont appliquées par rapport à ces forces internes et externes; la déformation de la courbure et la courbure inconnue sont évaluées. Le rapport de la déformation à la courbure donne une meilleure valeur approchée de l'épaisseur de l'axe neutre qui entre dans l'itération subséquente. Lorsqu'on connait les valeurs finales de la courbure et la déformation, les contraintes maximales dans le béton peuvent être déterminées. Cette méthode de la matrice des déformations peut entrer dans un programme d'informatique, et on peut aussi la traiter au moyen d'une calculatrice de bureau, car elle n'implique l'étude que de deux équations linéaires simultanées. On peut se servir de la méthode de la matrice de déformation comme d'une simple méthode de remplacement de la méthode d'étude conventionnelle des éléments en béton armé soumis à des charges à grande excentricité.

     

Opposite effects of osteogenic protein and transforming growth factor beta on chondrogenesis in cultured long bone rudiments

Osteogenic protein-1 (OP-1, also called BMP-7) is a bone morphogenetic member of the TGF-beta superfamily. In the present study, we examined the effect of recombinant human OP-1 on cartilage and bone formation in organ cultures of metatarsal long bones of mouse embryos and compared the OP-1 effects with those of human TGF-beta 1 and porcine TGF-beta 1 and beta 2. Cartilage formation was determined by measurement of longitudinal growth of whole bone rudiments during culture and by the incorporation of 35SO4 into glycosaminoglycans. Mineralization was monitored by 45Ca incorporation in the acid-soluble fraction and by measuring the length of the calcifying center of the rudiment. Toluidine blue-stained histologic sections were used for quantitative histomorphometric analysis. We found that OP-1 stimulated cartilage growth as determined by sulfate incorporation and that it increased remarkably the width of the long bones ends compared with controls. This effect was partly caused by differentiation of perichondrial cells into chondrocytes, resulting in increased appositional growth. In contrast to OP-1, TGF-beta 1 and beta 2 inhibited cartilage growth and reduced the length of whole bone rudiments compared with controls. In the ossifying center of the bone rudiments, both OP-1 and TGF-beta inhibited cartilage hypertrophy, growth of the bone collar, and matrix mineralization. These data demonstrate that OP-1 and TGF-beta exhibit opposite effects on cartilage growth but similar effects on osteogenesis in embryonic mouse long bone cultures. Since both OP-1 and TGF-beta have been demonstrated in embryonic cartilage and bone, these results suggest that they act as autocrine or paracrine regulators of embryonic bone development.     

A centre-manifold analysis of variable speed machining

The mathematical models representing chatter dynamics have been cast as differential equations with delay. The suppression of regenerative chatter by spindle speed variation is attracting increasing attention. In this paper, we study nonlinear delay differential equations with periodic delays which model the machine tool chatter with continuously modulated spindle speed. The explicit time-dependent delay terms, due to spindle speed modulation, are replaced by state-dependent delay terms by augmenting the original equations. The augmented system of equations is autonomous and has two pairs of pure imaginary eigenvalues without resonance. We make used to the centre-manifold reduction and the method of normal forms to determine the periodic solutions and analyse the tool motion. Analytical results show both modest increase of stability and existence of periodic solutions close to the new stability boundary.     

Effects of nerve growth factor on glutathione peroxidase and catalase in PC12 cells

Nerve growth factor (NGF) is a member of the neurotrophin family and is required for the survival and maintenance of peripheral sympathetic and sensory ganglia. In the CNS, NGF regulates cholinergic expression by basal forebrain cholinergic neurons. NGF also stimulates cellular resistance to oxidative stress in the PC12 cell line and protects PC12 cells from the toxic effects of reactive oxygen species. The hypothesis that NGF protection involves changes in antioxidant enzyme expression was tested by measuring its effects on catalase and glutathione peroxidase (GSH Px) mRNA expression in PC12 cells. NGF increased catalase and GSH Px mRNA levels in PC12 cells in a time- and dose-dependent manner. There was also a corresponding increase in the enzyme activities of catalase and GSH Px. Thus, NGF can provide cytoprotection to PC12 cells by inducing the free radical scavenging enzymes catalase and GSH Px.     

The fate and intermediary metabolism of stearic acid

Coming from the Greek for “hard fat”, stearic acid represents one of the most abundant FA in the Western diet. Otherwise known as n-octadecanoic acid (18∶0), stearate is either obtained in the diet or synthesized by the elongation of palmitate, the principal product of the FA synthase system in animal cells. Stearic acid has been shown to be a very poor substrate for TG synthesis, even as compared with other saturated fats such as myristate and palmitate, and in human studies stearic acid has been shown to generate a lower lipemic response than medium-chain saturated FA. Although it has been proposed that this may be due to less efficient absorption of stearic acid in the gut, such findings have not been consistent. Along with palmitate, stearate is the major substrate for the enzyme stearoyl-CoA desaturase, which catalyzes the conversion of stearate to oleate, the preferred substrate for the synthesis of TG and other complex lipids. In mice, targeted disruption of the stearoyl-CoA desaturase-1 (SCD1) gene results in the generation of a lean mouse that is resistant to diet-induced obesity and insulin resistance. SCD1 also has been shown to be a key target of the anorexigenic hormone leptin, thus underscoring the importance of this enzyme, and consequently the cellular stearate-to-oleate ratio, in lipid metabolism and potentially in the treatment of obesity and related disorders.     

Biopreservative technologies of food: an alternative to chemical preservation and recent developments

Food Science and Biotechnology - Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological...     

开发灵活的高性价比宽带接入设备线路卡

电信设备生产商(TEM)在多业务(语音、视频和数据)融合和分布式设备生产上面临很大的挑战,这些设备包括数字用户线接入复用器(DSLAM)、光线路终端(OLT)和多服务接入节点(MSAN)等.尽管可以选择多种介质来实现不同的服务,但是每一种介质都需要不同类型的网络设备来处理所需要的接入协议、流量工程和吞吐量.     

Hypoglycaemic and Hypolipidaemic Effects of Withania somnifera Root and Leaf Extracts on Alloxan-Induced Diabetic Rats

Withania somnifera is an important medicinal plant, which is used in traditional medicine to cure many diseases. Flavonoids were determined in the extracts of W. somnifera root (WSREt) and leaf (WSLEt). The amounts of total flavonoids found in WSREt and WSLEt were 530 and 520 mg/100 g dry weight (DW), respectively. Hypoglycaemic and hypolipidaemic effects of WSREt and WSLEt were also investigated in alloxan-induced diabetic rats. WSREt and WSLEt and the standard drug glibenclamide were orally administered daily to diabetic rats for eight weeks. After the treatment period, urine sugar, blood glucose, haemoglobin (Hb), glycosylated haemoglobin (HbA1C), liver glycogen, serum and tissues lipids, serum and tissues proteins, liver glucose-6-phosphatase (G6P) and serum enzymes like aspartate transaminase (AST), alanine transaminase (ALT), acid phosphatase (ACP) and alkaline phosphatase (ALP) levels were determined. The levels of urine sugar, blood glucose, HbA1C, G6P, AST, ALT, ACP, ALP, serum lipids except high density lipoprotein-bound cholesterol (HDL-c) and tissues like liver, kidney and heart lipids were significantly (p < 0.05) increased, however Hb, total protein, albumin, albumin:globulin (A:G) ratio, tissues protein and glycogen were significantly (p < 0.05) decreased in alloxan-induced diabetic rats. Treatment of the diabetic rats with WSREt, WSLEt and glibenclamide restored the changes of the above parameters to their normal level after eight weeks of treatment, indicating that WSREt and WSLEt possess hypoglycaemic and hypolipidaemic activities in alloxan-induced diabetes mellitus (DM) rats.