Differential nutritional, endocrine, and cardiovascular effects in obesity-prone and obesity-resistant rats fed standard and hypercaloric diets

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

EFFECTS of CREATINE SUPPLEMENTATION DURING RESISTANCE TRAINING on MYOSIN HEAVY CHAIN (MHC) EXPRESSION IN RAT SKELETAL MUSCLE FIBERS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Diet-induced obesity causes metabolic, endocrine and cardiac alterations in spontaneously hypertensive rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Quantitative expression of myogenic regulatory factors MyoD and myogenin in pacu (Piaractus mesopotamicus) skeletal muscle during growth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cardiac remodeling in a rat model of diet-induced obesity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Growth hormone attenuates skeletal muscle changes in experimental chronic heart failure

Objective: This study evaluated the effects of growth hormone (GH) on morphology and myogenic regulatory factors (MRF) gene expression in skeletal muscle of rats with ascending aortic stenosis (AAS) induced chronic heart failure.Design: Male 90-100 g Wistar rats were subjected to thoracotomy. AAS was created by placing a stainless-steel clip on the ascending aorta. Twenty five weeks after surgery, rats were treated with daily subcutaneous injections of recombinant human GH (2 mg/kg/day; AAS-GH group) or saline (AAS group) for 14 days. Sham-operated animals served as controls. Left ventricular (LV) function was assessed before and after treatment. IGF-1 serum levels were measured by ELISA. After anesthesia, soleus muscle was frozen in liquid nitrogen. Histological sections were stained with HE and picrosirius red to calculate muscle fiber cross-sectional area and collagen fractional area, respectively. MRF myogenin and MyoD expression was analyzed by reverse transcription PCR.Results: Body weight was similar between groups. AAS and AAS-GH groups presented dilated left atrium, left ventricular (LV) hypertrophy (LV mass index: Control 1.90 +/- 0.15; AAS 3.11 +/- 0.44; AAS-GH 2.94 +/- 0.47 g/kg; p < 0.05 AAS and AAS-GH vs. Control), and reduced LV posterior wall shortening velocity. Soleus muscle fiber area was significantly lower in AAS than in Control and AAS-GH groups; there was no difference between AAS-GH and Control groups. Collagen fractional area was significantly higher in MS than Control; AAS-GH did not differ from both Control and AAS groups. Serum IGF-1 levels decreased in AAS compared to Control. MyoD mRNA was significantly higher in AAS-GH than AAS; there was no difference between AAS-GH and Control groups. Myogenin mRNA levels were similar between groups.Conclusion: In rats with aortic stenosis-induced heart failure, growth hormone administration increases MyoD gene expression above non-treated animal levels, preserves muscular trophism and attenuates interstitial fibrosis. These results suggest that growth hormone may have a potential role as an adjuvant therapy for chronic heart failure. (C) 2009 Elsevier Ltd. All rights reserved.

Neutralization of snake venom phospholipase A(2) toxins by aqueous extract of Casearia sylvestris (Flacourtiaceae) in mouse neuromuscular preparation

Aqueous extract of Casearia sylvestris (Flacourtiaceae) has been shown to inhibit enzymatic and biological properties of some Bothrops and Crotalus venoms and their purified phospholipase A(2) (PLA(2)) toxins. In this work we evaluated the influence of C sylvestris aqueous extract upon neuromuscular blocking and muscle damaging activities of some PLA(2)S (crotoxin from C. durissus terrificus, bothropstoxin-I from B.jararacussu, piratoxin-I from B. pirajai and myotoxin-II from B. moojeni) in mouse phrenic-diaphragm preparations. Crotoxin (0.5 mu M) and all other PLA2 toxins (1.0 mu M) induced irreversible and time-dependent blockade of twitches. Except for crotoxin, all PLA2 toxins induced significant muscle damage indices, assessed by microscopic analysis. Preincubation of bothropstoxin-I, piratoxin-I or myotoxin-II with C. sylvestris extract (1:5 (w/w), 30 min, 37 degrees C significantly prevented the neuromuscular blockade of preparations exposed to the mixtures for 90 min; the extent of protection ranged from 93% to 97%. The vegetal extract also neutralized the muscle damage (protection of 80-95%). Higher concentration of the C. sylvestris extract (1: 10, w/w) was necessary to neutralize by 90% the neuromuscular blockade induced by crotoxin. These findings expanded the spectrum of C. sylvestris antivenom activities, evidencing that it may be a good source of potentially useful PLA2 inhibitors. (c) 2007 Elsevier B.V.. All rights reserved.

Structural and Functional Studies of a Bothropic Myotoxin Complexed to Rosmarinic Acid: New Insights into Lys49-PLA(2) Inhibition

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nandrolone Stimulates Myod Expression During Muscle Regeneration in the Condition of Myonecrosis Induced by Bothrops jararacussu Venom Poisoning

Myonecrosis with permanent loss of muscle mass is a relevant local toxic effect following envenomation with Bothrops jararacussu snake venom. Regeneration of adult skeletal muscle involves the activation of satellite cells, a process regulated by myogenic regulatory factors (MRF). MyoD is an MRF involved in both proliferation and differentiation of satellite cells. Androgens are modulators of skeletal muscle, known to increase muscle mass and strength. This study examined the hypothesis that anabolic androgens improve the muscle regeneration process in mice following envenomation by Bothrops jararacussu snake venom. Myonecrosis was induced by venom injection (30 g/50 l in physiological solution) over the extensor digitorum longus (EDL) muscles of mice. Nandrolone (ND) (6 mg/kg, sc) was administered after 12 h, 7 d, and 14 d following venom injection. The histological changes in EDL muscle at 1, 3, 7, and 21 d after muscle injury were analyzed by light microscopy. Cross-sectional areas of fibers were measured. MyoD was evaluated by immunofluorescence technique. Histological examination revealed the presence of a regeneration process in ND-treated animals, characterized by the appearance of some myotubes at 3 d, and numerous myotubes at 7 d from venom injection. Nandrolone treatment reduced the frequency of small fibers at 7 and 21 d after venom administration, and increased the frequency of large fibers at 7 d postinjury. Nandrolone also significantly augmented the expression of MyoD-positive cells at 7 and 21 d after envenomation. These results suggest that ND accelerates muscle regeneration and indicate the involvement of MyoD in this process.

Expression of protease nexin-1 and plasminogen activators during follicular growth and the periovulatory period in cattle

Extracellular matrix remodeling occurs during ovarian follicular development, mediated by plasminogen activators (PAs) and PA inhibitors including protease nexin-1 (PN-1). In the present study we measured expression/activity of the PA system in bovine follicles at different stages of development by timed collection of ovaries during the first follicular wave and during the periovulatory period, and in follicles collected from an abattoir. The abundance of mRNA encoding PN-1, tissue-type PA (tPA), urokinase (uPA) and PA inhibitor-1 (PAI-1) were initially upregulated by human chorionic gonadotropin (hCG) in bovine preovulatory follicular wall homogenates. PN-1, PAI-1 and tPA mRNA expression then decreased near the expected time of ovulation, whereas uPA mRNA levels remained high. PN-1 concentration in follicular fluid (FF) decreased and reached the lowest level at the time of ovulation, whereas plasmin activity in FF increased significantly after hCG. Follicles collected from the abattoir were classified as non-atretic, early-atretic or atretic based on FF estradiol and progesterone content: PN-1 protein levels in FF were significantly higher in non-atretic than in atretic follicles, and plasmin activity was correspondingly higher in the atretic follicles. No changes in PN-1 levels in FF were observed during the growth of pre-deviation follicles early in a follicular wave. These results indicate that PN-1 may be involved in the process of atresia in non-ovulatory dominant follicles and the prevention of precocious proteolysis in periovulatory follicles.

Heart failure increases atrogin-1 and MuRF1 gene expression in skeletal muscle with fiber type-specific atrophy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphological and physiological specialization for digging in amphisbaenians, an ancient lineage of fossorial vertebrates

Amphisbaenians are legless reptiles that differ significantly from other vertebrate lineages. Most species dig underground galleries of similar diameter to that of the animal. We studied the muscle physiology and morphological attributes of digging effort in the Brazilian amphisbaenid Leposternon microcephalum (Squamata; Amphisbaenia), which burrows by compressing soil against the upper wall of the tunnel by means of upward strokes of the head. The individuals tested (<72 g) exerted forces on the soil of up to 24 N. These forces were possible because the fibres of the longissimus dorsi, the main muscle associated with burrowing, are highly pennated, thus increasing effective muscle cross-sectional area. The muscle is characterized by a metabolic transition along its length: proximal, medial and distal fibres are fast contracting and moderately oxidative, but fibres closer to the head are richer in citrate synthase and more aerobic in nature. Distal fibres, then, might be active mainly at the final step of the compression stroke, which requires more power. For animals greater than a given diameter, the work required to compress soil increases exponentially with body diameter. Leposternon microcephalum, and probably some other highly specialized amphisbaenids, are most likely constrained to small diameters and can increase muscle mass and effective muscle cross-sectional area by increasing body length, not body diameter.

Co-60 gamma irradiation prevents Bothrops jararacussu venom neurotoxicity and myotoxicity in isolated mouse neuromuscular junction

The ability of gamma radiation from Co-60 (2000 Gy) to attenuate the toxic effects of Bothrops jararacussu venom was investigated on mouse neuromuscular preparations in vitro. A comparative study between the effects of native and irradiated venoms was performed on both phrenic-diaphragm (PD) and extensor digitorum longus (EDL) preparations by means of myographic, biochemical and morphological techniques. Native venom (10 and 20 mug/ml) induced a concentration-dependent paralysis of both directly and indirectly evoked contractions on PD preparations. At 20 mug/ml, it also caused a pronounced myotoxic effect on the EDL muscle preparation that was characterized by an increase of creatine kinase release and by several morphological changes of this preparation. By contrast, irradiated venom, even at concentrations as high as 40 mug/ml, induced neither paralyzing nor myotoxic effects. It was concluded that Co-60 gamma radiation is able to abolish both the paralyzing and the myotoxic effects of B. jararacussu venom on the mouse neuromuscular junction. These findings support the hypothesis that gamma radiation could be an important toot to improve antisera production by reducing toxicity while preserving immunogenicity. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Ischaemia and reperfusion effects on skeletal muscle tissue: morphological and histochemical studies

This was a study on the oxidative stress due to ischaemia (I) and reperfusion (R) in skeletal muscle tissue. Using a tourniquet, groups of rats were submitted to ischaemia for 4 h, followed by different reperfusion periods. The animals were divided in four groups: control; 4 h of ischaemia (IR); 4 h of ischaemia plus 1 h reperfusion (IR-1 h); 4 h of ischaemia plus 24 h reperfusion (IR-24 h); and 4 h of ischaemia plus 72 h reperfusion (IR-72 h). At the end of the procedures, samples of soleus muscle were collected and frozen in n-hexane at -70 degrees C. Cryostat sections were submitted to haematoxylin-eosin, succinate dehydrogenase (SDH) and nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) stains. An additional muscle sample was processed for electron microscopy. No alterations were found in control animals. IR group showed fibres had normal aspect besides some round, acidophilic and hypertrophic fibres. There were several fibres with angular outlines and smaller diameters in this group compared with control group. NADH-TR/SDH reaction was moderately intense in most fibres. In some fibres, cytoplasm showed areas without activity and other fibres had very intense reactivity. IR-1 h group showed oedema hypercontracted fibres with disorganized myofibrils, mitochondria with focal lesions and dilated sarcoplasmic reticulum. NADH-TR/SDH reaction was moderate to weak. IR-24 h showed intense inflammatory infiltrate in the endomysium and perimysium. NADH-TR/SDH reaction was similar to IR-1 h. IR-72 h showed necrotic fibres, areas with inflammatory infiltrate, reduced muscle fibres at different stages of necrosis and phagocytosis, and many small round and basophilic fibres characterizing a regeneration process. NADH-TR/SDH reaction was weak to negative. Our results suggest that ischaemia and the subsequent 1-, 24- and 72-h reperfusions induced progressive histological damage. Although progressive, it may be reversible because there were ultrastructural signs of recovery after 72-h reperfusion. This recovery could in part be due to the low oxidative stress identified by the morphological and histochemical analysis.