Identification and expression analysis of citrate synthase 3 gene family members in apple / 生物工程学报

As one of the key enzymes in cell metabolism, the activity of citrate synthase 3 (CS3) regulates the substance and energy metabolism of organisms. The protein members of CS3 family were identified from the whole genome of apple, and bioinformatics analysis was performed and expression patterns were analyzed to provide a theoretical basis for studying the potential function of CS3 gene in apple. BLASTp was used to identify members of the apple CS3 family based on the GDR database, and the basic information of CS3 protein sequence, subcellular localization, domain composition, phylogenetic relationship and chromosome localization were analyzed by Pfam, SMART, MEGA5.0, clustalx.exe, ExPASy Proteomics Server, MEGAX, SOPMA, MEME, WoLF PSORT and other software. The tissue expression and inducible expression characteristics of 6 CS3 genes in apple were determined by acid content and real-time fluorescence quantitative polymerase chain reaction (qRT-PCR). Apple CS3 gene family contains 6 members, and these CS3 proteins contain 473-608 amino acid residues, with isoelectric point distribution between 7.21 and 8.82. Subcellular localization results showed that CS3 protein was located in mitochondria and chloroplasts, respectively. Phylogenetic analysis divided them into 3 categories, and the number of genes in each subfamily was 2. Chromosome localization analysis showed that CS3 gene was distributed on different chromosomes of apple. The secondary structure of protein is mainly α-helix, followed by random curling, and the proportion of β-angle is the smallest. The 6 members were all expressed in different apple tissues. The overall expression trend from high to low was the highest relative expression content of MdCS3.4, followed by MdCS3.6, and the relative expression level of other members was in the order of MdCS3.3 > MdCS3.2 > MdCS3.1 > MdCS3.5. qRT-PCR results showed that MdCS3.1 and MdCS3.3 genes had the highest relative expression in the pulp of 'Chengji No. 1' with low acid content, and MdCS3.2 and MdCS3.3 genes in the pulp of 'Asda' with higher acid content had the highest relative expression. Therefore, in this study, the relative expression of CS3 gene in apple cultivars with different acid content in different apple varieties was detected, and its role in apple fruit acid synthesis was analyzed. The experimental results showed that the relative expression of CS3 gene in different apple varieties was different, which provided a reference for the subsequent study of the quality formation mechanism of apple.

Molecular Detection of Tick-borne Pathogens in Ticks Collected from Hainan Island, China / 生物医学与环境科学（英文）

Pathogens like bacteria and protozoa, which affect human and animal health worldwide, can be transmitted by vectors like ticks. To investigate the epidemiology and genetic diversity of bacteria and protozoans carried by ticks in Chengmai county of Hainan province, China, 285 adult hard ticks belonging to two species [

Respiratory muscle training improves diaphragm citrate synthase activity and hemodynamic function in rats with heart failure

Abstract INTRODUCTION: Enhanced respiratory muscle strength in patients with heart failure positively alters the clinical trajectory of heart failure. In an experimental model, respiratory muscle training in rats with heart failure has been shown to improve cardiopulmonary function through mechanisms yet to be entirely elucidated. OBJECTIVE: The present report aimed to evaluate the respiratory muscle training effects in diaphragm citrate synthase activity and hemodynamic function in rats with heart failure. METHODS: Wistar rats were divided into four experimental groups: sedentary sham (Sed-Sham, n=8), trained sham (RMT-Sham, n=8), sedentary heart failure (Sed-HF, n=7) and trained heart failure (RMT-HF, n=7). The animals were submitted to a RMT protocol performed 30 minutes a day, 5 days/week, for 6 weeks. RESULTS: In rats with heart failure, respiratory muscle training decreased pulmonary congestion and right ventricular hypertrophy. Deleterious alterations in left ventricular pressures, as well as left ventricular contractility and relaxation, were assuaged by respiratory muscle training in heart failure rats. Citrate synthase activity, which was significantly reduced in heart failure rats, was preserved by respiratory muscle training. Additionally, a negative correlation was found between citrate synthase and left ventricular end diastolic pressure and positive correlation was found between citrate synthase and left ventricular systolic pressure. CONCLUSION: Respiratory muscle training produces beneficial adaptations in the diaphragmatic musculature, which is linked to improvements in left ventricular hemodynamics and blood pressure in heart failure rats. The RMT-induced improvements in cardiac architecture and the oxidative capacity of the diaphragm may improve the clinical trajectory of patients with heart failure.

Molecular and Biochemical Characterization of Opisthorchis viverrini Calreticulin

Calreticulin (CALR), a multifunctional protein thoroughly researched in mammals, comprises N-, P-, and C-domain and has roles in calcium homeostasis, chaperoning, clearance of apoptotic cells, cell adhesion, and also angiogenesis. In this study, the spatial and temporal expression patterns of the Opisthorchis viverrini CALR gene were analyzed, and calcium-binding and chaperoning properties of recombinant O. viverrini CALR (OvCALR) investigated. OvCALR mRNA was detected from the newly excysted juvenile to the mature parasite by RT-PCR while specific antibodies showed a wide distribution of the protein. OvCALR was localized in tegumental cell bodies, testes, ovary, eggs, Mehlis’ gland, prostate gland, and vitelline cells of the mature parasite. Recombinant OvCALR showed an in vitro suppressive effect on the thermal aggregation of citrate synthase. The recombinant OvCALR C-domain showed a mobility shift in native gel electrophoresis in the presence of calcium. The results imply that OvCALR has comparable function to the mammalian homolog as a calcium-binding molecular chaperone. Inferred from the observed strong immunostaining of the reproductive tissues, OvCALR should be important for reproduction and might be an interesting target to disrupt parasite fecundity. Transacetylase activity of OvCALR as reported for calreticulin of Haemonchus contortus could not be observed.

Effects of dietary leucine supplementation on the hepatic mitochondrial biogenesis and energy metabolism in normal birth weight and intrauterine growth-retarded weanling piglets

BACKGROUND/OBJECTIVES: The study was conducted to evaluate the effects of dietary leucine supplementation on mitochondrial biogenesis and energy metabolism in the liver of normal birth weight (NBW) and intrauterine growth-retarded (IUGR) weanling piglets. MATERIALS/METHODS: A total of sixteen pairs of NBW and IUGR piglets from sixteen sows were selected according to their birth weight. At postnatal day 14, all piglets were weaned and fed either a control diet or a leucine-supplemented diet for 21 d. Thereafter, a 2 × 2 factorial experimental design was used. Each treatment consisted of eight replications with one piglet per replication. RESULTS: Compared with NBW piglets, IUGR piglets had a decreased (P < 0.05) hepatic adenosine triphosphate (ATP) content. Also, IUGR piglets exhibited reductions (P < 0.05) in the activities of hepatic mitochondrial pyruvate dehydrogenase (PDH), citrate synthase (CS), α-ketoglutarate dehydrogenase (α-KGDH), malate dehydrogenase (MDH), and complexes I and V, along with decreases (P < 0.05) in the concentration of mitochondrial DNA (mtDNA) and the protein expression of hepatic peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α). Dietary leucine supplementation increased (P < 0.05) the content of ATP, and the activities of CS, α-KGDH, MDH, and complex V in the liver of piglets. Furthermore, compared to those fed a control diet, piglets given a leucine-supplemented diet exhibited increases (P < 0.05) in the mtDNA content and in the mRNA expressions of sirtuin 1, PGC-1α, nuclear respiratory factor 1, mitochondrial transcription factor A, and ATP synthase, H+ transporting, mitochondrial F1 complex, β polypeptide in liver. CONCLUSIONS: Dietary leucine supplementation may exert beneficial effects on mitochondrial biogenesis and energy metabolism in NBW and IUGR weanling piglets.

Detection of Rickettsia bellii and Rickettsia amblyommii in Amblyomma longirostre (Acari: Ixodidae) from Bahia state, Northeast Brazil

Studies investigating rickettsial infections in ticks parasitizing wild animals in the Northeast region of Brazil have been confined to the detection of Rickettsia amblyommii in immature stages of Amblyomma longirostre collected from birds in the state of Bahia, and in immatures and females of Amblyomma auriculariumcollected from the striped hog-nosed skunk (Conepatus semistriatus) and armadillos (Euphractus sexcinctus) in the state of Pernambuco. The current study extends the distribution of R. amblyommii (strain Aranha), which was detected in A. longirostre collected from the thin-spined porcupine Chaetomys subspinosus and the hairy dwarf porcupine Coendou insidiosus. In addition, we report the first detection of Rickettsia bellii in adults of A. longirostre collected from C. insidiosus in the state of Bahia.

Screening Molecular Chaperones Similar to Small Heat Shock Proteins in Schizosaccharomyces pombe

To screen molecular chaperones similar to small heat shock proteins (sHsps), but without alpha-crystalline domain, heat-stable proteins from Schizosaccharomyces pombe were analyzed by 2-dimensional electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Sixteen proteins were identified, and four recombinant proteins, including cofilin, NTF2, pyridoxin biosynthesis protein (Snz1) and Wos2 that has an alpha-crystalline domain, were purified. Among these proteins, only Snz1 showed the anti-aggregation activity against thermal denaturation of citrate synthase. However, pre-heating of NTF2 and Wos2 at 70degrees C for 30 min, efficiently prevented thermal aggregation of citrate synthase. These results indicate that Snz1 and NTF2 possess molecular chaperone activity similar to sHsps, even though there is no alpha-crystalline domain in their sequences.

Mitochondrial activities of citrate synthase, carnitine palmitoyltransferase-1 and cytochrome C oxidase are increased during the apoptotic process in hepatocytes of a rat model of acute liver failure / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To determine the roles of mitochondrial apoptosis and energy metabolism in hepatocytes during the pathogenic process of acute renal failure (ALF) by assessing disease-related differential activities of several key mitochondrial enzymes, including citrate synthase (CS), carnitine palmitoyltransferase-1 (CPT-1) and cytochrome c oxidase (COX).</p><p><b>METHODS</b>Thirty-two male Sprague Dawley rats were given D-galactosamine followed by and lipopolysaccharide (LPS) to induce acute liver failure and sacrificed after 4 (4 h group), 8 (8 h group) 12 (12 h group) and 24 hours (24 h group) of treatment. Eight unmodeled rats served as controls. Effects related to apoptosis were evaluated by pathological analysis of hepatic tissues and TUNEL staining. Ultrastructural changes in mitochondria were assessed by electron microscopy. The activity and expression of CS, CPT-1 and COX were measured.</p><p><b>RESULTS</b>Hepatocyte apoptosis was present in the 4 h treatment group and was increased obviously in the 8 h treatment group. Hepatocyte necrosis was first observed in the 12 h treatment group and was significantly higher in the 24 h treatment group, with inflammatory cell invasion. Ultrastructural changes in mitochondria were present in the 4 h treatment group, and the 24 h treatment group showed mitochondria with completely destroyed outer membranes, which resulted in mitochondrial collapse. Activity and protein expression of CS, CPT-1 and COX were increased in the 4 h group (vs. controls), were at their peak in the 8 h group (CS:t =1.481, P less than 0.01; CPT-1:t =2.619, P less than 0.05; COX:t =1.014, P less than 0.01) and showed a decreasing trend in the 12 h group. In addition, the activities of CS, CPT-1 and COX were enhanced at the stage of hepatocyte apoptosis, suggesting that these enzymes were involved in the initiation and development of ALF.</p><p><b>CONCLUSION</b>Energy metabolism plays an important role in hepatocyte apoptosis during ALF.</p>

Study on the chaperone properties of conserved GTPases

As a large family of hydrolases, GTPases are widespread in cells and play the very important biological function of hydrolyzing GTP into GDP and inorganic phosphate through binding with it. GTPases are involved in cell cycle regulation, protein synthesis, and protein transportation. Chaperones can facilitate the folding or refolding of nascent peptides and denatured proteins to their native states. However, chaperones do not occur in the native structures in which they can perform their normal biological functions. In the current study, the chaperone activity of the conserved GTPases of Escherichia coli is tested by the chemical denaturation and chaperone-assisted renaturation of citrate synthase and α-glucosidase. The effects of ribosomes and nucleotides on the chaperone activity are also examined. Our data indicate that these conserved GTPases have chaperone properties, and may be ancestral protein folding factors that have appeared before dedicated chaperones.

Exercise training and selenium or a combined treatment ameliorates aberrant expression of glucose and lactate metabolic proteins in skeletal muscle in a rodent model of diabetes

Exercise training (ET) and selenium (SEL) were evaluated either individually or in combination (COMBI) for their effects on expression of glucose (AMPK, PGC-1alpha, GLUT-4) and lactate metabolic proteins (LDH, MCT-1, MCT-4, COX-IV) in heart and skeletal muscles in a rodent model (Goto-Kakisaki, GK) of diabetes. Forty GK rats either remained sedentary (SED), performed ET, received SEL, (5 micromol/kg body wt(-1)/day(-1)) or underwent both ET and SEL treatment for 6 wk. ET alone, SEL alone, or COMBI resulted in a significant lowering of lactate, glucose, and insulin levels as well as a reduction in HOMA-IR and AUC for glucose relative to SED. Additionally, ET alone, SEL alone, or COMBI increased glycogen content and citrate synthase (CS) activities in liver and muscles. However, their effects on glycogen content and CS activity were tissue-specific. In particular, ET alone, SEL alone, or COMBI induced upregulation of glucose (AMPK, PGC-1alpha, GLUT-4) and lactate (LDH, MCT-1, MCT-4, COX-IV) metabolic proteins relative to SED. However, their effects on glucose and lactate metabolic proteins also appeared to be tissue-specific. It seemed that glucose and lactate metabolic protein expression was not further enhanced with COMBI compared to that of ET alone or SEL alone. These data suggest that ET alone or SEL alone or COMBI represent a practical strategy for ameliorating aberrant expression of glucose and lactate metabolic proteins in diabetic GK rats.

Effect of hydrogen peroxide on rabbit urinary bladder citrate synthase activity in the presence and absence of a grape suspension

PURPOSE: The etiology of obstructive bladder dysfunction includes free radical damage to mitochondria. Feeding rabbits a standardized grape suspension protects the ability of the bladder to contract and empty in part by preventing mitochondrial damage, thus maintaining smooth muscle and mucosal metabolism. The objective of the current study is to determine the direct effect of this grape suspension on the response of mitochondria to the oxidative effects of hydrogen peroxide. MATERIALS AND METHODS: Six male rabbits were anesthetized with sodium pentobarbital and the bladders excised. Four full thickness strips were obtained for contractile studies and the balance separated into smooth muscle and mucosa compartments by blunt dissection. The effect of hydrogen peroxide on the contractile response to field stimulation was quantitated. Each tissue was homogenized and the effects of increasing concentrations of hydrogen peroxide in the presence and absence of grape suspension on citrate synthase activity was determined. RESULTS: Citrate synthase activity was significantly higher in the mucosa than in the muscle. The grape suspension had no effect on control citrate synthase activity. However, the grape suspension provided significant protection of both smooth muscle and mucosal citrate synthase activity. CONCLUSIONS: These studies support the conclusion that the grape suspension provides direct protection of mitochondrial function.

Enhancement of Exercise Capacity by Black Ginseng Extract in Rats / 한국실험동물학회지

This study was carried out to investigate an enhancing effect of black ginseng extract (BGE) on exercise capacity in an endurance exercising animal model. Fifty Sprague-Dawley rats were assigned to 5 experimental groups including non-training control, training control, and 3 treated groups (BGE at doses of 75, 150 and 300 mg/kg). The animals were treated with BGE for 6 weeks and their exercise ability in the maximal running distance test was determined using a treadmill every week. The blood lactic acid (LA) level and the activity of citrate synthase (CS) in the muscle were also measured after the exercise. The levels of glucose and glucose-6-phosphate (G-6-P) in the liver and muscle were determined using commercial assay kits. BGE treatments at the doses of 150 and 300 mg/kg significantly increased the exercise capacity compared with the non-training control or training control groups (P<0.05). The level of blood LA was decreased but the activity of CS was increased by the treatment of BGE at the dose of 300 mg/kg compared with the training control group. The level of G-6-P in the liver was elevated by the treatment of BGE at the dose of 300 mg/kg, compared to the training group. As compared with non-training control group, the treatments of BGE increased the levels of glucose and G-6-P in the liver and soleus muscle of rats. These results indicate that BGE have a potential for promoting exercise capacity by increasing CS activity in the muscle and decreasing LA in the serum of rats. These results also suggested that BGE can be used as a candidate supplement of health food products for promoting endurance exercise capacity in human athletes.

Enhancement of Exercise Capacity by Black Ginseng Extract in Rats / 한국실험동물학회지

This study was carried out to investigate an enhancing effect of black ginseng extract (BGE) on exercise capacity in an endurance exercising animal model. Fifty Sprague-Dawley rats were assigned to 5 experimental groups including non-training control, training control, and 3 treated groups (BGE at doses of 75, 150 and 300 mg/kg). The animals were treated with BGE for 6 weeks and their exercise ability in the maximal running distance test was determined using a treadmill every week. The blood lactic acid (LA) level and the activity of citrate synthase (CS) in the muscle were also measured after the exercise. The levels of glucose and glucose-6-phosphate (G-6-P) in the liver and muscle were determined using commercial assay kits. BGE treatments at the doses of 150 and 300 mg/kg significantly increased the exercise capacity compared with the non-training control or training control groups (P<0.05). The level of blood LA was decreased but the activity of CS was increased by the treatment of BGE at the dose of 300 mg/kg compared with the training control group. The level of G-6-P in the liver was elevated by the treatment of BGE at the dose of 300 mg/kg, compared to the training group. As compared with non-training control group, the treatments of BGE increased the levels of glucose and G-6-P in the liver and soleus muscle of rats. These results indicate that BGE have a potential for promoting exercise capacity by increasing CS activity in the muscle and decreasing LA in the serum of rats. These results also suggested that BGE can be used as a candidate supplement of health food products for promoting endurance exercise capacity in human athletes.

Detection and Identification of the Spotted Fever Group Rickettsial Agents from Haemaphysalis Ticks in Jeju Island, Korea

This study investigated the presence of nucleic acids of various Rickettsial agents in ticks collected in Jeju Island, Korea from June 2007 to August 2008, through the nested polymerase chain reaction (PCR) and sequencing analysis of partial citrate synthase (gltA), Rickettsial outer membrane protein B (ompB), and 17-kDa genes. Examination of the 1,584 ticks showed that the subspecies distribution of Haemaphysalis longicornis was 99.81% (n=1,581) and H. flava was 0.19% (n=3). A total 224 out of 250 pools from one to 15 ticks were found to be positive in ompB-PCR assay (minimal infection rate 141 ticks/1,000 tested). From the positive samples, 26 were analyzed by gltA- and 17-kDa-PCR assays. The nucleotide sequences of the ompB- and gltA-PCR products showed a high degree of similarity with those of the Rickettsia japonica (98.7~99.2% and 98.7~99.3%, n=25) and R. monacensis (99% and 99.7%, n=1). However, analysis of the nucleotide sequences of the 17-kDa-PCR amplicons showed that the sequences of the 25 PCR amplicons were more close to R. marmionii (99.4~100%) than R. japonica (98.6~99.1%). These findings suggest that various rickettsial diseases could be transmitted via the bite of tick vectors in Jeju Island, Korea.

What is the Key Step in Muscle Fatty Acid Oxidation after Change of Plasma Free Fatty Acids Level in Rats?

The purpose of this study was to discern the critical point in skeletal muscle fatty acid oxidation by changing plasma free fatty acids (FFA) level in rat. In the study, 3 key steps in lipid oxidation were examined after changing plasma FFA level by acipimox. The rates of both palmitate and palmitoyl- carnitine oxidation were decreased by decrease of plasma FFA level, however, carnitine palmitoyl transferase (CPT) 1 activity was not changed, suggesting CPT1 activity may not be involved in the fatty acid oxidation at the early phase of plasma FFA change. In the fasted rats, beta-hydroxy acyl-CoA dehydrogenase (beta-HAD) activity was depressed to a similar extent as palmitate oxidation by a decrease of plasma FFA level. This suggested that beta-oxidation might be an important process to regulate fatty acid oxidation at the early period of plasma FFA change. Citrate synthase activity was not altered by the change of plasma FFA level. In conclusion, the critical step in fatty acids oxidation of skeletal muscles by the change of plasma FFA level by acipimox in fasting rats might be the beta-oxidation step rather than CPT1 and TCA cycle pathways.

Swimming training increases cardiac vagal activity and induces cardiac hypertrophy in rats

The effect of swimming training (ST) on vagal and sympathetic cardiac effects was investigated in sedentary (S, N = 12) and trained (T, N = 12) male Wistar rats (200-220 g). ST consisted of 60-min swimming sessions 5 days/week for 8 weeks, with a 5 percent body weight load attached to the tail. The effect of the autonomic nervous system in generating training-induced resting bradycardia (RB) was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. Cardiac hypertrophy was evaluated by cardiac weight and myocyte morphometry. Plasma catecholamine concentrations and citrate synthase activity in soleus muscle were also determined in both groups. Resting heart rate was significantly reduced in T rats (355 ± 16 vs 330 ± 20 bpm). RB was associated with a significantly increased cardiac vagal effect in T rats (103 ± 25 vs 158 ± 40 bpm), since the sympathetic cardiac effect and intrinsic heart rate were similar for the two groups. Likewise, no significant difference was observed for plasma catecholamine concentrations between S and T rats. In T rats, left ventricle weight (13 percent) and myocyte dimension (21 percent) were significantly increased, suggesting cardiac hypertrophy. Skeletal muscle citrate synthase activity was significantly increased by 52 percent in T rats, indicating endurance conditioning. These data suggest that RB induced by ST is mainly mediated parasympathetically and differs from other training modes, like running, that seems to mainly decrease intrinsic heart rate in rats. The increased cardiac vagal activity associated with ST is of clinical relevance, since both are related to increased life expectancy and prevention of cardiac events.

Ginseng administration protects skeletal muscle from oxidative stress induced by acute exercise in rats

Enzymatic activity was analyzed in the soleus, gastrocnemius (red and white) and plantaris muscles of acutely exercised rats after long-term administration of Panax ginseng extract in order to evaluate the protective role of ginseng against skeletal muscle oxidation. Ginseng extract (3, 10, 100, or 500 mg/kg) was administered orally for three months to male Wistar rats weighing 200 ± 50 g before exercise and to non-exercised rats (N = 8/group). The results showed a membrane stabilizing capacity of the extract since mitochondrial function measured on the basis of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities was reduced, on average, by 20 percent (P < 0.05) after exercise but the activities remained unchanged in animals treated with a ginseng dose of 100 mg/kg. Glutathione status did not show significant changes after exercise or treatment. Lipid peroxidation, measured on the basis of malondialdehyde levels, was significantly higher in all muscles after exercise, and again was reduced by about 74 percent (P < 0.05) by the use of ginseng extract. The administration of ginseng extract was able to protect muscle from exercise-induced oxidative stress irrespective of fiber type.

Duration-controlled swimming exercise training induces cardiac hypertrophy in mice

Exercise training associated with robust conditioning can be useful for the study of molecular mechanisms underlying exercise-induced cardiac hypertrophy. A swimming apparatus is described to control training regimens in terms of duration, load, and frequency of exercise. Mice were submitted to 60- vs 90-min session/day, once vs twice a day, with 2 or 4 percent of the weight of the mouse or no workload attached to the tail, for 4 vs 6 weeks of exercise training. Blood pressure was unchanged in all groups while resting heart rate decreased in the trained groups (8-18 percent). Skeletal muscle citrate synthase activity, measured spectrophotometrically, increased (45-58 percent) only as a result of duration and frequency-controlled exercise training, indicating that endurance conditioning was obtained. In groups which received duration and endurance conditioning, cardiac weight (14-25 percent) and myocyte dimension (13-20 percent) increased. The best conditioning protocol to promote physiological hypertrophy, our primary goal in the present study, was 90 min, twice a day, 5 days a week for 4 weeks with no overload attached to the body. Thus, duration- and frequency-controlled exercise training in mice induces a significant conditioning response qualitatively similar to that observed in humans.

Caracterizaçäo de miopatias mitocondriais através da avaliaçäo das atividades enzimáticas envolvidas no metabolismo energético / Characterization of mitochondrial myopathies through the evaluation of the enzymatic activities involved in the energetic metabolism

Foi determinada a atividade das enzimas NADH desidrogenase, NADH citocromo e redutase, succinato desidrogenase, succinato citocromo e redutase, citocromo e oxidase e citrato sintase em mitocôndrias de músculo esquelético humano normal e doente (suspeito de miopatia mitocondrial). O grupo controle foi constituído de 13 indivíduos normais e que nao faziam uso contínuo de fármacos. O grupo doente era constituído de 10 pacientes cujo diagnóstico anatomopatológico indicava suspeita de miopatia mitocondrial. Observou-se reduçao na atividade das enzimas em todos os pacientes: 7 com anormalidades em todas as enzimas ensaiadas; 2 com deficiências em todas as enzimas exceto na citocromo e oxidase; e 1 paciente com disfunçao apenas na atividade da succinato desidrogenase e succinato citocromo e redutase. Este perfil possibilitou caracterizar múltiplas deficiências ou deficiência combinada da cadeia respiratória, além da disfunçao na citrato sintase em 9 pacientes. Um dos casos constituiu exceçao, sendo a deficiência enzimática restrita ao complexo II. Foi possível concluir que a metodologia usada é adequada e facilmente aplicável aos objetivos clínicos. Os resultados obtidos possibilitam a caracterizaçao dos complexos enzimáticos mitocondriais deficientes, mostrando que tais enfermidades sao originadas de disfunçao no metabolismo energético.

Physiological constraints in the aerobic performance of hummingbirds

Hovering flight has been described as the most energetically expensive form of locomotion. Among the vertebrates, hummingbirds weighing only 1.5-20 g are the elite practitioners of this aerial art. Their flight muscles are, therefore, the most oxygen demanding locomotor muscles per unit tissue mass of all vertebrates. Tissue level functional and structural adaptations for oxygen transport are compared between hummingbirds and mammals in this paper. Hummingbirds present extreme structural adaptations in their flight muscles. Mitochondrial densities greater than 30 per cent are observed in their pectoral muscles, and the surface area of the inner membrane of their mitochondria is tvace that of mammals. This doubling of their mitochondrial oxidative capacity is accompanied by a proportional increase in the specific activity (per g tissue) of the mitochondrial manganese superoxide dismutase (SOD-Mn) in their flight muscles, thus indicating that oxygen toxicity is not a constraint in the aerobic performance of hummingbirds during hovering flight. Finally, the liver appears to play a major role in providing the necessary substrates for their high aerobic performance, and also in eliminating the oxygen free radicals formed during oxidative phosphorylation.