Endogenous expression and developmental changes of HSP72 in rat skeletal muscles

The purpose of the present study was to determine whether endogenous factor(s) contributes to the expression of heat shock proteins (HSPs) during the early developmental stages of rat skeletal muscles. HSP72 was expressed in both the soleus and plantaris muscles at embryonic day 22 (E22). On the basis of myosin heavy chain (MHC) immunohistochemistry, HSP72 was specifically expressed in slow type I fibers in both muscles. These slow fibers were observed throughout the entire cross section of the soleus muscle and only in the deep region (close to the bone) of the plantaris muscle. These results indicate that the expression of HSP72 is related to endogenous factors associated with type I fibers, because E22 rats have minimal exogenous influences and the soleus and plantaris muscles of E22 rats have similar metabolic and contractile profiles at this stage of development. We then examined the changes in HSP72 and heat shock cognate (HSC) 73 in the same two muscles from E22 to postnatal day 56 via Western blotting. The level of HSP72 in the soleus muscle gradually increased in parallel with the increment in the type I MHC isoform. Compared with the soleus, only a small amount of HSP72 could be detected in the plantaris muscle throughout the developmental period. For both muscles, HSC73 reached levels observed in adult muscles at postnatal day 3, and these levels were unchanged thereafter. These results indicate that the expression of HSP72, but not HSC73, is influenced by both endogenous and exogenous factors during the embryonic and early developmental periods.     

Exercise-induced changes of MCT1 in cardiac and skeletal muscles of diabetic rats induced by high-fat diet and STZ

We hypothesized that a part of therapeutic effects of endurance training on insulin resistance is mediated by increase in cardiac and skeletal muscle mitochondrial lactate transporter, monocarboxylate transporter 1 (MCT1). Therefore, we examined the effect of 7 weeks endurance training on the mRNA and protein expression of MCT1 and MCT4 and their chaperon, CD147, on both sarcolemmal and mitochondrial membrane, separately, in healthy and type 2 diabetic rats. Diabetes was induced by injection of low dose of streptozotocin and feeding with high-fat diet. Insulin resistance was confirmed by homeostasis model assessment-estimated insulin resistance index and accuracy of two membranes separation was confirmed by negative control markers (glucose transporter 1 and cytochrome c oxidase. Real-time PCR and western blotting were used for mRNA and protein expression, respectively. Diabetes dramatically reduced MCT1 and MCT4 mRNA and their expression on sarcolemmal membrane whereas the reduction in MCT1 expression was less in mitochondrial membrane. Training increased the MCT1 mRNA and protein expression in both membranes and decreased insulin resistance as an adaptive consequence. In both tissues increase in CD147 mRNA was only parallel to MCT1 expression. The response of MCT1 on sarcolemmal and mitochondrial membranes was different between cardiac and skeletal muscles which indicate that intracellular lactate kinetic is tissue specific that allows a tissue to coordinate whole organism metabolism.     

Vanadyl sulfate protects against streptozotocin-induced morphological and biochemical changes in rat aorta

The aim of this study was to investigate the protective effects of vanadyl sulfate on aorta tissue of normal and streptozotocin (STZ)-induced diabetic rats, morphologically and biochemically. The animals were made diabetic by an intraperitoneal injection of streptozotocin (65 mg/kg) and vanadyl sulfate (100 mg/kg) that was given every day for 60 days by gavage technique to rats. Under the light and transmission electron microscopes, hypertrophy of the vessel wall, focal disruption in the elastic lamellae, an increase in thickness of total aortic wall, tunica intima, subendothelial space and adventitial layer, and a disorganization in smooth muscular cells of the tunica media were observed in diabetic animals. The aorta lipid peroxidation (LPO) levels were significantly increased and the aorta glutathione (GSH) levels were significantly reduced in STZ diabetic rats. In diabetic rats administered vanadyl sulfate for 60 days, aorta LPO levels significantly decreased and the aorta GSH level significantly increased. In conclusion, in vivo treatment with vanadyl sulfate of diabetic rats prevented the morphological and biochemical changes observed in thoracic aorta of diabetic animals.     

Morphological and biochemical changes in old rat muscles: effect of increased use

Male Wistar rats were strength and swim trained during a substantial period of old age to determine the influence of aging and activity on the histochemical and metabolic characteristics of a predominantly slow (soleus) and a predominantly fast (plantaris) skeletal muscle. Strength training counteracted the age-related atrophy of the fibers and the age-induced changes in fiber-type distribution of both muscles. Swim training, on the other hand, was without any effect on these parameters. The activity of both mitochondrial and cytoplasmic enzymes became lower with aging in the soleus muscle, whereas only the activity of the cytoplasmic enzymes became lower in the plantaris. Strength training reduced the aerobic capacity of both muscles, whereas swim training had the opposite effect. Aging induced a lower glycogen concentration of the lateral gastrocnemius muscle. This was avoided by swim training. The phosphocreatine and adenosine 5'-triphosphate concentrations were unchanged with aging but became higher with strength training. The activity pattern, therefore, seems to have a considerable influence on the age-related modification of the histochemical and metabolic characteristics of skeletal muscles of the rat. The effect, however, is related to the recruitment pattern of the fiber populations and the form of activity.     

Physiological, histological and biochemical properties of rat skeletal muscles in response to hindlimb suspension.

In previous study, we found that the reduced exercise-induced production of reactive oxygen species (ROS) reported in slow-oxidative muscle of hypoxemic rats and also in chronic hypoxemic patients did not simply result from deconditioning. In control rats and after a 3-week period of hindlimb suspension (HS), the slow-oxidative (Soleus, SOL) and fast-glycolytic skeletal muscles (Extensor digitorum longus, EDL) were sampled. We determined the response to direct muscle stimulation (twitch stimulation (TS), Maximal force (Fmax)), twitch amplitude and maximal relaxation rate, tetanic frequency, endurance to fatigue after muscle stimulation (MS), the different fibre types based on their myofibrillar adenosinetriphosphatase (ATPase) activity, and the intra-muscular redox status (Thiobarbituric Acid Reactive Sustances: TBARS, reduced glutathione: GSH, reduced ascorbic acid: RAA). After the 3-w HS period: (1) the contractile properties were modified in SOL only (reduced Fmax and twitch amplitude, increased tetanic frequency); (2) the fibre typology was modified in both muscles (in SOL: increased proportion of IIa and IIc fibres, in EDL: increased proportion of IId/x fibres but decreased proportion of IIb fibres); and (3) only in SOL, the TBARS level increased and the GSH and RAA concentrations decreased at rest and after fatiguing MS. Thus, HS accentuates the exercise-induced ROS production in slow-oxidative muscle in a direction opposite to that measured in chronic hypoxemic rats. This strongly suggests that hypoxemia reduces the ROS production independently from any muscle disuse.     

Ultrastructural and gene-expression changes in the calcium regulation system of rat skeletal muscles under exhausting exercise

The expression of genes responsible for the synthesis of essential proteins regulating the calcium-ion balance and ultrastructural characteristics of fast-twitch (m. extensor digitorum longus, EDL) and slow-twitch (m. soleus, SOL) skeletal muscles under prolonged exercise were studied in an experimental model of forced-swimming rats. A day after the end of the exercise, no significant changes in any of the five investigated genes were revealed in the SOL. A few triad elements (T-tubules and cisternae of sarcoplasmic reticulum) were revealed. A small number of excitation-contraction coupling (ECC) structures in the control and a slight increase in their amount after exercises were noticed. Polymorphism and mitochondrial defects within SOL muscles indicate the importance of these structures in the regulation of calcium balance. In EDL muscles, adaptation mechanisms are aimed mainly at pumping Ca²⁺ ions to the sarcoplasmic reticulum, where the main calcium buffer is calsequestrin. Expression of SERCA1 gene increased by an order of magnitude, and that of CASQ1 increased by three times. Electron microscopy showed a major role of triads in the maintenance of calcium homeostasis in the EDL muscles, as well as a greater destruction of these muscles compared to SOL after exhausting exercise. The high level of triads and a possible activation of the CICR (calcium-induced calcium release) mechanism in fast-twitch muscles can cause damage to them during exhausting exercise. Adaptation of SOL muscles is associated with structural rearrangements of the mitochondrial apparatus, while adaptation of the EDL muscles is caused by calcium removal from the sarcoplasm with Ca-ATPase and its retention in the sarcoplasmic reticulum by calsequestrin.     

Time course of changes in markers of myogenesis in overloaded rat skeletal muscles.

During the process of compensatory muscle hypertrophy, satellite cells are thought to proliferate, differentiate, and then fuse with existing myofibers. We hypothesized that early in this process changes occur in the expression of cellular markers indicative of the onset of myogenic processes. The plantaris muscles of rats were overloaded via the unilateral ablation of synergists. Groups of rats were killed at time points from 6 h to 12 days. Changes in muscle gene expression (mRNA) of cyclin D1, p21, myogenin, MyoD, and insulin-like growth factor I (IGF-I, mRNA and peptide) were measured. Cyclin D1 (a cell cycle marker) was increased after 24 h of overloading and corresponded with changes in muscle DNA content. In contrast, p21 and myogenin, markers of cellular differentiation, were increased after just 12 h. Muscle IGF-I peptide levels were also increased at early time points. The results of this study indicate that myogenic processes are activated in response to increased loading at very early time points (e.g., 12 h) and that IGF-I may be modulating this response. Furthermore, these findings suggest that some cells may have been differentiating very early in the adaptation process before events leading to cellular proliferation have been initiated.     

Effect of cycloheximide on the morphological and biochemical changes in chromatin in non-irradiated and irradiated rat thymocytes

The level of chromatin degradation was studied and the method of electron-microscopy was used to estimate the changes in the ultrastructure of irradiated and nonirradiated thymocytes of rats treated with cycloheximide. The latter was found to decrease the degree of derangement of nuclear ultrastructure and the level of chromatin degradation in exposed animals and to increase the yield of these damages in thymocytes of nonirradiated animals. The electronmicroscopic determinations showed that the percentage of thymocytes with the impaired nucleus structure is twice as high as that of degraded chromatin. The causes of the quantitative disagreement between the morphological and biochemical indices of the interphase thymocyte death are discussed.     

Relationship of biochemical and morphological changes in rat thyroid and proton spin-relaxation of the tissue water.

The effect was studied of biochemical and morphological changes induced by antithyroid substances (PTU, C10(-4)) on proton spin-relaxation properties of rat thyroid gland. It was found that thyroid stimulated by PTU (0.05%) or C10(-4) (1.0%) exhibit marked morphological changes (hyperplasia and epithelial hypertrophy) with alteration of the soluble iodoprotein pattern (content and composition.). Both relaxation times spin-lattice (T1) and spin-spin (T2) were increasing with the lenght of treatment with antithyroid drugs. Reversibility of the process was noted in accordance with biochemical and morphological data. The relaxation rate (formula: see text) for thyroid tissue water was in positive correlation with the suluble protein concentration and particularly with the TG content in the gland. There was no difference in relaxation times between normal thyroid and gland of rats treated chronically with excess iodide. The observed difference in T1 between normal glands and glands of PTU,-C10(-4)--treated rats was comparable with that found in cases of human thyroid cancer. This finding is of importance when the diagnostic potential of NMR in the detection of malignancy is considered. In conclusion, a strong correlation was found between microstructural and biochemical changes of the thyroid gland and proton magnetic relaxation of tissue water. The striking difference between the proton spin-relaxation times in normal and in goiter thyroid glands of rats suggests that pulsed NMR spectroscopy could be a method for evaluation of some disturbances in thyroid gland.     

Time course of changes in lipoprotein lipase activity in rat skeletal muscles during denervation-reinnervation.

The effects of denervation-reinnervation after sciatic nerve crush on the activity of extracellular and intracellular lipoprotein lipase (LPL) were examined in the soleus and red portion of gastrocnemius muscles. The activity of both LPL fractions was decreased in the two muscles within 24 h after the nerve crush and remained reduced for up to 2 wk. During the reinnervation period, LPL activity was still reduced in the soleus and started to increase only on the 40th day. In the red gastrocnemius, LPL activity increased progressively with reinnervation, exceeding control values on the 30th day post-crush. The LPL activity in the soleus from the contralateral to denervated hindlimb was also affected, being increased on the postoperation day and then gradually decreased during the following days. In conclusion, the time course of changes in muscle LPL activity after nerve crush confirmed the predominant role of nerve conduction in controlling muscle potential to take up free fatty acids derived from the plasma triacylglycerols. However, other factors, such as muscle fiber composition and the fiber transformation, should also be considered in this aspect of the denervation-reinnervation process. Moreover, it was found that denervation of muscles from one hindlimb may influence LPL activity in muscles from the contralateral leg.