Effects of exercise training on autonomic and myocardial dysfunction in streptozotocin-diabetic rats

Several investigators have demonstrated that diabetes is associated with autonomic and myocardial dysfunction. Exercise training is an efficient non-pharmacological treatment for cardiac and metabolic diseases. The aim of the present study was to investigate the effects of exercise training on hemodynamic and autonomic diabetic dysfunction. After 1 week of diabetes induction (streptozotocin, 50 mg/kg, iv), male Wistar rats (222 ± 5 g, N = 18) were submitted to exercise training for 10 weeks on a treadmill. Arterial pressure signals were obtained and processed with a data acquisition system. Autonomic function and intrinsic heart rate were studied by injecting methylatropine and propranolol. Left ventricular function was assessed in hearts perfused in vitro by the Langendorff technique. Diabetes (D) bradycardia and hypotension (D: 279 ± 9 bpm and 91 ± 4 mmHg vs 315 ± 11 bpm and 111 ± 4 mmHg in controls, C) were attenuated by training (TD: 305 ± 7 bpm and 100 ± 4 mmHg). Vagal tonus was decreased in the diabetic groups and sympathetic tonus was similar in all animals. Intrinsic heart rate was lower in D (284 ± 11 bpm) compared to C and TD (390 ± 8 and 342 ± 14 bpm, respectively). Peak systolic pressure developed at different pressures was similar for all groups, but +dP/dt max was decreased and -dP/dt max was increased in D. In conclusion, exercise training reversed hypotension and bradycardia and improved myocardial function in diabetic rats. These changes represent an adaptive response to the demands of training, supporting a positive role of physical activity in the management of diabetes.

Effects of aerobic exercise training on heart rate variability during wakefulness and sleep and cardiorespiratory responses of young and middle-aged healthy men

The purpose of the present study was to evaluate the effects of aerobic physical training (APT) on heart rate variability (HRV) and cardiorespiratory responses at peak condition and ventilatory anaerobic threshold. Ten young (Y: median = 21 years) and seven middle-aged (MA = 53 years) healthy sedentary men were studied. Dynamic exercise tests were performed on a cycloergometer using a continuous ramp protocol (12 to 20 W/min) until exhaustion. A dynamic 24-h electrocardiogram was analyzed by time (TD) (standard deviation of mean R-R intervals) and frequency domain (FD) methods. The power spectral components were expressed as absolute (a) and normalized units (nu) at low (LF) and high (HF) frequencies and as the LF/HF ratio. Control (C) condition: HRV in TD (Y: 108, MA: 96 ms; P<0.05) and FD - LFa, HFa - was significantly higher in young (1030; 2589 ms²/Hz) than in middle-aged men (357; 342 ms²/Hz) only during sleep (P<0.05); post-training effects: resting bradycardia (P<0.05) in the awake condition in both groups; VO2 increased for both groups at anaerobic threshold (P<0.05), and at peak condition only in young men; HRV in TD and FD (a and nu) was not significantly changed by training in either groups. The vagal predominance during sleep is reduced with aging. The resting bradycardia induced by short-term APT in both age groups suggests that this adaptation is much more related to intrinsic alterations in sinus node than in efferent vagal-sympathetic modulation. Furthermore, the greater alterations in VO2 than in HRV may be related to short-term APT.

ßS-Haplotypes in sickle cell anemia patients from Salvador, Bahia, Northeastern Brazil

ßS-Globin haplotypes were studied in 80 (160 ßS chromosomes) sickle cell disease patients from Salvador, Brazil, a city with a large population of African origin resulting from the slave trade from Western Africa, mainly from the Bay of Benin. Hematological and hemoglobin analyses were carried out by standard methods. The ßS-haplotypes were determined by PCR and dot-blot techniques. A total of 77 (48.1%) chromosomes were characterized as Central African Republic (CAR) haplotype, 73 (45.6%) as Benin (BEN), 1 (0.63%) as Senegal (SEN), and 9 (5.63%) as atypical (Atp). Genotype was CAR/CAR in 17 (21.3%) patients, BEN/BEN in 17 (21.3%), CAR/BEN in 37 (46.3%), BEN/SEN in 1 (1.25%), BEN/Atp in 1 (1.25%), CAR/Atp in 6 (7.5%), and Atp/Atp in 1 (1.25%). Hemoglobin concentrations and hematocrit values did not differ among genotype groups but were significantly higher in 25 patients presenting percent fetal hemoglobin (%HbF) > or = 10% (P = 0.002 and 0.003, respectively). The median HbF concentration was 7.54 ± 4.342% for the CAR/CAR genotype, 9.88 ± 3.558% for the BEN/BEN genotype, 8.146 ± 4.631% for the CAR/BEN genotype, and 4.180 ± 2.250% for the CAR/Atp genotype (P = 0.02), although 1 CAR/CAR individual presented an HbF concentration as high as 15%. In view of the ethnic and geographical origin of this population, we did not expect a Hardy-Weinberg equilibrium for CAR/CAR and BEN/BEN homozygous haplotypes and a high proportion of heterozygous CAR/BEN haplotypes since the State of Bahia historically received more slaves from Western Africa than from Central Africa.

A leucine-supplemented diet improved protein content of skeletal muscle in young tumor-bearing rats

Cancer cachexia induces host protein wastage but the mechanisms are poorly understood. Branched-chain amino acids play a regulatory role in the modulation of both protein synthesis and degradation in host tissues. Leucine, an important amino acid in skeletal muscle, is higher oxidized in tumor-bearing animals. A leucine-supplemented diet was used to analyze the effects of Walker 256 tumor growth on body composition in young weanling Wistar rats divided into two main dietary groups: normal diet (N, 18% protein) and leucine-rich diet (L, 15% protein plus 3% leucine), which were further subdivided into control (N or L) or tumor-bearing (W or LW) subgroups. After 12 days, the animals were sacrificed and their carcass analyzed. The tumor-bearing groups showed a decrease in body weight and fat content. Lean carcass mass was lower in the W and LW groups (W = 19.9 ± 0.6, LW = 23.1 ± 1.0 g vs N = 29.4 ± 1.3, L = 28.1 ± 1.9 g, P < 0.05). Tumor weight was similar in both tumor-bearing groups fed either diet. Western blot analysis showed that myosin protein content in gastrocnemius muscle was reduced in tumor-bearing animals (W = 0.234 ± 0.033 vs LW = 0.598 ± 0.036, N = 0.623 ± 0.062, L = 0.697 ± 0.065 arbitrary intensity, P < 0.05). Despite accelerated tumor growth, LW animals exhibited a smaller reduction in lean carcass mass and muscle myosin maintenance, suggesting that excess leucine in the diet could counteract, at least in part, the high host protein wasting in weanling tumor-bearing rats.

An improved HPLC method for the quantitation of 6-mercaptopurine and its metabolites in red blood cells

A procedure is described for the rapid determination of the intra-erythrocyte concentration of 6-mercaptopurine (6-MP) and its metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP). Erythrocytes (8 x 10(8) cells) in 350 µl Hanks solution containing 7.5 mg dithiothreitol were treated with 50 µl 70% perchloric acid. The precipitate was removed by centrifugation (13,000 g) and the supernatant hydrolyzed at 100°C for 45 min. After cooling, 100 µl was analyzed directly by HPLC using a Radialpack Resolve C18 column eluted with methanol-water (7.5:92.5, v/v) containing 100 mM triethylamine. 6-TG, 6-MP and the hydrolysis product of 6-MMP, 4-amino-5-(methylthio)carbonyl imidazole, were monitored at 342, 322 and 303 nm using a Shimadzu SPD-M10A diode array UV detector. The analytes eluted at 5.3, 6.0 and 10.2 min, respectively. The calibration curves were linear (r² > 0.998), and the analytical recoveries were 73.2% for 6-TG, 119.1% for 6-MP and 97.4% for 6-MMP. The intra- and inter-assay variations were highest for 6-MP (9.6 and 14.3%, respectively). The lowest detectable concentrations were 3, 3 and 25 pmol/8 x 10(8) erythrocytes for 6-TG, 6-MP and 6-MMP, respectively. The quantification limits (coefficients of variation <15%) were 8, 10 and 70 pmol/8 x 10(8) erythrocytes for 6-TG, 6-MP and 6-MMP, respectively. The method was applied to the analysis of 183 samples from 36 children under chemotherapy for acute lymphoblastic leukemia. The concentrations of the metabolites in the red cells of the patients ranged from 0 to 1934 pmol/8 x 10(8) erythrocytes for 6-TGN, and from 0 to 105.8 and 0 to 45.9 nmol/8 x 10(8) erythrocytes for 6-MP and 6-MMP, respectively. The procedure gave results that were in agreement with those obtained with other methods designed to detect cases of non-compliance with treatment, including patient interviews and medical evaluation, among others, demonstrating its applicability to monitoring the treatment of leukemic children.

Effect of bullfrog (Rana catesbeiana) oil administered by gavage on the fatty acid composition and oxidative stress of mouse liver

The aim of the present study was to investigate the effects of daily intragastric administration of bullfrog oil (oleic, linoleic and palmitoleic acid-rich oil), corresponding to 0.4% of body weight for four weeks, on fatty acid composition and oxidative stress (lipid peroxidation and catalase activity) in mouse liver. The activities of aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT), biomarkers of tissue injury, were determined in liver homogenates and serum. The proportions of 18:2n-6, 20:4n-6, 20:5n-3, and 22:6n-3 (polyunsaturated fatty acids, from 37 to 60%) in the total fatty acid content were increased in the liver of the bullfrog oil-treated group (P < 0.05) compared to control. At the same time, a significant decrease in the relative abundance of 14:0, 16:0, and 18:0 (saturated fatty acids, from 49 to 25%) was observed. The hepatic content of thiobarbituric acid reactive substances (TBARS) was increased from 2.3 ± 0.2 to 12.3 ± 0.3 nmol TBA-MDA/mg protein and catalase activity was increased from 840 ± 32 to 1110 ± 45 µmol reduced H2O2 min-1 mg protein-1 in the treated group. Bullfrog oil administration increased AST and ALP activities in the liver (from 234.10 ± 0.12 to 342.84 ± 0.13 and 9.38 ± 0.60 to 20.06 ± 0.27 U/g, respectively) and in serum (from 95.41 ± 6.13 to 120.32 ± 3.15 and 234.75 ± 11.5 to 254.41 ± 2.73 U/l, respectively), suggesting that this treatment induced tissue damage. ALT activity was increased from 287.28 ± 0.29 to 315.98 ± 0.34 U/g in the liver but remained unchanged in serum, whereas the GGT activity was not affected by bullfrog oil treatment. Therefore, despite the interesting modulation of fatty acids by bullfrog oil, a possible therapeutic use requires care since some adverse effects were observed in liver.

Loss of resting bradycardia with detraining is associated with intrinsic heart rate changes

The mechanisms underlying the loss of resting bradycardia with detraining were studied in rats. The relative contribution of autonomic and non-autonomic mechanisms was studied in 26 male Wistar rats (180-220 g) randomly assigned to four groups: sedentary (S, N = 6), trained (T, N = 8), detrained for 1 week (D1, N = 6), and detrained for 2 weeks (D2, N = 6). T, D1 and D2 were treadmill trained 5 days/week for 60 min with a gradual increase towards 50% peak VO2. After the last training session, D1 and D2 were detrained for 1 and 2 weeks, respectively. The effect of the autonomic nervous system in causing training-induced resting bradycardia and in restoring heart rate (HR) to pre-exercise training level (PET) with detraining was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. T rats significantly increased peak VO2 by 15 or 23.5% when compared to PET and S rats, respectively. Detraining reduced peak VO2 in both D1 and D2 rats by 22% compared to T rats, indicating loss of aerobic capacity. Resting HR was significantly lower in T and D1 rats than in S rats (313 ± 6.67 and 321 ± 6.01 vs 342 ± 12.2 bpm) and was associated with a significantly decreased intrinsic HR (368 ± 6.1 and 362 ± 7.3 vs 390 ± 8 bpm). Two weeks of detraining reversed the resting HR near PET (335 ± 6.01 bpm) due to an increased intrinsic HR in D2 rats compared with T and D1 rats (376 ± 8.8 bpm). The present study provides the first evidence of intrinsic HR-mediated loss of resting bradycardia with detraining in rats.

Factors associated with bacteremia due to multidrug-resistant Gram-negative bacilli in hematopoietic stem cell transplant recipients

The epidemiology of bacteremia developing during neutropenia has changed in the past decade, with the re-emergence of Gram-negative (GN) bacteria and the development of multidrug resistance (MDR) among GN bacteria. We conducted a case-control study in order to identify factors associated with bacteremia due to multidrug-resistant Gram-negative (MDRGN) isolates in hematopoietic stem cell transplant recipients. Ten patients with MDRGN bacteremia were compared with 44 patients with GN bacteremia without MDR. Bacteremia due to Burkholderia or Stenotrophomonas sp was excluded from analysis (3 cases), because the possibility of intrinsical resistance. Infection due to MDRGN bacteria occurred in 2.9% of 342 hematopoietic stem cell transplant recipients. Klebsiella pneumoniae was the most frequent MDRGN (4 isolates), followed by Pseudomonas aeruginosa (3 isolates). Among non-MDRGN, P. aeruginosa was the most frequent agent (34%), followed by Escherichia coli (30%). The development of GN bacteremia during the empirical treatment of febrile neutropenia (breakthrough bacteremia) was associated with MDR (P < 0.001, odds ratio = 32, 95% confidence interval = 5_190) by multivariate analysis. Bacteremia due to MDRGN bacteria was associated with a higher death rate by univariate analysis (40 vs 9%; P = 0.03). We were unable to identify risk factors on admission or at the time of the first fever, but the occurrence of breakthrough bacteremia was strongly associated with MDRGN bacteria. An immediate change in the antibiotic regimen in such circumstances may improve the prognosis of these patients.

Evaluation of beetroot (Beta vulgaris L.) leaves during its developmental stages: a chemical composition study

Beetroot leaves (Beta vulgaris L.) are commonly cut off and discarded before using its bulb due to lack of knowledge of how to use them. Aiming at using these leaves, in the present study, in natura and dehydrated beetroot leaves were chemically characterized in terms of fatty acid composition, proximate composition, minerals, total phenolic compounds (TPC), and antioxidant activity by DPPH• in different stages (60, 80, and 100 days) of development. The beetroot leaves showed significant levels of protein and lipids in all developmental stages, and all proximate composition nutrients decreased during these maturation stages; the highest content was observed at 60 days. The Fe content decreased during the developmental stages (from 342.75 to 246.30 mg.kg-1), while the content of K increased (from 13,367.64 to 20,784.90 mg.kg-1). With regard to to fatty acid composition, linolenic acid was present in the greatest quantity, and it increase up to 2.58 mg.g-1 (in natura) and 40.11 mg.g-1 (dehydrated) at 100 days of development. The n-6/n-3 ratios were low in all stages. The TPC and antioxidant activity by DPPH• changed during the developmental stages. The TPC was highest in the 100-day dehydrated leaves (15.27±0.12 mg GAE.g-1 FW), and the 50% inhibition of DPPH• (IC50 89.52 µg.mL-1) were better in the 60-day in natura leaves. This study shows that all developmental stages produced satisfactory results, and therefore, these leaves can be reused as food. The antioxidant activity and the chemical constituents, mainly the ω-3fatty acid, increased during the stages of development.