ON ANALYSE LES CAUSES POUVANT PROVOQUER LA DISPERSION DES RESULTATS DES ESSAIS DE RELAXATION REALISES DANS DES CIRCONSTANCES IDENTIQUES DU POINT DE VUE DU MATERIAU, DE LA CONTRAINTE INITIALE ET DE LA TEMPERATURE. ON ETUDIE AINSI L'INFLUENCE DES CONDTIONS DE L'ESSAI LUI-MEME ET LES VARIATIONS INEVITABLES DU METERIAU. ON VERIFIE LA SENSIBILITE PLUS GRANDE DE L'ACIER A LA RELAXATION QU'A LA LIMITE ELASTIQUE ET A LA CHARGE DE RUPTURE. LA DUREE PROLONGEE DES ESSAIS DE RELAXATION A AMENE A METTRE AU POINT DIFFERENTS PROCEDES POUR OBTENIR DES DONNEES DE RELAXATION DES ACIERS A COURT TERME. DANS CE TRAVAIL ON PRESENTE UNE METHODE QUI PERMET D'OBTENIR DES COUPLES DE POINTS DE LA COURBE THEORIQUE DE RELAXATION AU BOUT DE MILLE HEURES, A PARTIR DES RESULTATS D'UN NOMBRE SUFFISANT D'ESSAIS A CENT VINGT HEURES. VOIR FICHE GENERALE 109729 ET FICHES DETAILLEES 109730 A 109770.
High fat diets (HFD) are linked to the development of obesity and type 2 diabetes (T2D), characterized by defects in glycogen storage and increased lipid accumulation in skeletal muscle. Replacement of saturated fatty acids in high fat diets, with unsaturated (mono- and poly-unsaturated) fatty acids has been shown to reduce risks for insulin resistance, obesity and T2D. PURPOSE: The purpose of this study was to determine the effects of HFD differing in fatty acid composition, on skeletal muscle glycogen, mitochondrial, GLUT4, and lipid contents. METHODS: Male Sprague Dawley rats were fed a Western-style (21% fat by weight; 41% total energy) HFD for 9 weeks to induce obesity and then were divided into one of three HFD groups for an additional 6 weeks; a control chow group followed a 15-week low fat diet. Animals consumed either a) low fat Chow diet (CD) (4.8 % fat; 0.74% saturated; 2% mono; 1.77% poly; n=6), b) mixed fat Western diet (WD) (21% fat; 9.76% saturated; 7.68% mono; 3.48% poly; n=6), c) HFD rich in monounsaturated fatty acids (MUFA) (21% fat; 2.82% saturated; 16.01% mono; 2.18% poly; n=6), d) HFD rich in polyunsaturated fatty acids (PUFA) (21% fat; 2% fat; 2.97% mono; 16% poly; n=7). After 15 weeks, glycogen (periodic acid-schiff staining) mitochondria, GLUT4, and lipid content were measured in extensor digitorum longus muscle using immunohistochemical staining techniques and quantified with imageJ software. RESULTS: Following the 6-week treatment period, body weight (g) in the WD group was significantly greater compared to MUFA (p=0.0006), PUFA (p=0.02), and CD (p<0.0001). Glycogen content was significantly greater (p=0.04) in animals fed a WD compared to CD. (AU±SEM; CD: 4.41±0.04; WD: 4.74±0.13; MUFA: 4.54±0.08; PUFA: 4.54±0.11; one-way ANOVA p=0.11). A HFD rich in PUFA resulted in impaired GLUT4 content (p=0.02) compared to a CD (AU±SEM; CD: 77.38±2.22; WD: 63.46±3.80; MUFA: 61.49±8.46; PUFA: 52.84±5.13; one-way ANOVA p=0.03). There were no significant effects on mitochondrial or lipid content. CONCLUSION: A high fat diet rich in polyunsaturated fatty acids results in significantly lower GLUT4 content without negatively impacting skeletal muscle glycogen storage in high fat diet induced obese rats. A high fat diet rich in saturated fat resulted in greater muscle glycogen content compared to low fat fed rats.
Ln order to obtain new data concerning muscle contraction at the molecular level, the interrelation water-contractile proteins has been investigated by means of 1 H NMR Spectroscopy. Rat heart muscle from 6 and 37 months old rats has been used for proton transverse relaxation time measurements in Ri, Co and Re. at different [ATP].The distribution of negative charges in contraction and relaxation has been measured by exposing glycerinated muscle from 6 to 37 months old rats to different [Mn+2].Our data have pointed out the existence of two proton relaxation tinies:T2s and 121 accounted for two water compartments. The modification in water state are related with modifications in contractile activity. The elongation od proton transverse relaxation times is associated with a decrease in the degree of water molecules aggregation.T2s and T2l are correlated with a reduction in muscle hydration, contraction being a function of ions binding to the protein sites. These sites are implicated in determination of protein hydration state.
The aim of the present study was to investigate the effect of acute and long term treatment with D3 vitamin upon 40 Wistar rats aged between 6-24 months old. Significant modification in 45 Ca uptake in striated muscle from young rats with acute and long term treatment with D3 vitamin has been noticed. Acute and long term treatment with D3 vitamin in old rats determined an increase in 45 Ca at the level of heart and aorta. The results have an important clinical significance in administration of D3 vitamin in aging people because of the Ca accumulation danger on cardiac muscle and aorta leading to acceleration of functional disorders of the cardiovascular system affected by atherosclerosis process.
The aim of our study was related with investigation of hormone excess treatment (Thyroxine and Hydrocortisone) upon heart and skeletal muscle metabolism, looking for modifications in nucleic acid and protein synthesis by means of radioisotope methods of 45Ca,3H Tryptohane and 3H Uridine uptake. In young heart rabbits treated with 0.625mg Hydrocortisone, a reduction in 45Ca uptake has been recorded ,while in old rabbits there is a progressive increase in 45Ca uptake as a function of dose of hormone used. As far as skeletal muscle is concerned, both in young and old rabbits treated with Hydrocortisone there is a progressive decline in cellular receptors for 45Ca affinity. An increase in the uptake of 3H Uridine for 0.15 and 1.50 mg thyroxine in rabbit heart has been recorded while at 0.75mg there is a decrease in the uptake. In skeletal muscle, there is a progressive increase in RNA synthesis under hormone impulse as a function of admitted dose in comparison with Controls.
Zinc deficiencies have been reported in numerous pathologies, such as diabetes mellitus, but also in the physiological process of ageing. Similarly, the end products of glycoxidation processes, advanced glycation end products (AGEs), are damaging compounds, a myriad of reports linking them to the development and progression of several age-associated chronic diseases. The aim of the present study was to analyze the relationships between zinc status, glycoxidative stress and insulin resistance (IR) in elderly subjects with type 2 diabetes mellitus (T2DM). A group of 52 non-smoking subjects (9 men and 43 women, aged 65-83 years) were enrolled in this cross-sectional study: 27 patients with T2DM, and 25 apparently healthy control subjects. Serum zinc (Zn) levels were assessed using a commercial kit based on an end-point colorimetric method, and serum AGEs were evaluated with a fluorimetric analytic procedure. The calculated glucose-to-zinc ratio (Gly/Zn), insulin-to-zinc ratio (Ins/Zn) and insulin-zinc resistance index (HOMA-IR/Zn) were further used to study the associations between serum Zn levels, secretory function of β-pancreatic cells and AGEs. T2DM patients presented significantly higher serum insulin and Zn levels, as compared to the controls. We found a significant inverse correlation between Zn and AGEs, and a strong positive correlation between AGEs and the Gly/Zn ratio, suggesting that both Zn and AGEs are biomarkers that could reflect the persistence of hyperglycemia. We identified new surrogate biomarkers useful for the assessment of glycemic control with great potential for the development of preventive and therapeutic strategies for elderly diabetics, based on the evaluation of serum Zn levels.
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