BackgroundBrazil is the world's largest producer of sugarcane. Harvest is predominantly manual, exposing workers to health risks: intense physical exertion, heat, pollutants from sugarcane burning.DesignPanel study to evaluate the effects of burnt sugarcane harvesting on blood markers and on cardiovascular system.MethodsTwenty-eight healthy male workers, living in the countryside of Brazil were submitted to blood markers, blood pressure, heart rate variability, cardiopulmonary exercise testing, sympathetic nerve activity evaluation and forearm blood flow measures (venous occlusion plethysmography) during burnt sugarcane harvesting and four months later while they performed other activities in sugar cane culture.ResultsMean participant age was 31±6.3 years, and had worked for 9.8±8.4 years on sugarcane work. Work during the harvest period was associated with higher serum levels of Creatine Kinase – 136.5 U/L (IQR: 108.5–216.0) vs. 104.5 U/L (IQR: 77.5–170.5), (p = 0.001); plasma Malondialdehyde–7.5±1.4 µM/dl vs. 6.9±1.0 µM/dl, (p = 0.058); Glutathione Peroxidase – 55.1±11.8 Ug/Hb vs. 39.5±9.5 Ug/Hb, (p<0.001); Glutathione Transferase– 3.4±1.3 Ug/Hb vs. 3.0±1.3 Ug/Hb, (p = 0.001); and 24-hour systolic blood pressure – 120.1±10.3 mmHg vs. 117.0±10.0 mmHg, (p = 0.034). In cardiopulmonary exercise testing, rest-to-peak diastolic blood pressure increased by 11.12 mmHg and 5.13 mmHg in the harvest and non-harvest period, respectively. A 10 miliseconds reduction in rMSSD and a 10 burst/min increase in sympathetic nerve activity were associated to 2.2 and 1.8 mmHg rises in systolic arterial pressure, respectively.ConclusionWork in burnt sugarcane harvesting was associated with changes in blood markers and higher blood pressure, which may be related to autonomic imbalance.

Abstract-Autonomic dysfunction, including baroreceptor attenuation and sympathetic activation, has been reported in patients with myocardial infarction (MI) and has been associated with increased mortality. We tested the hypotheses that exercise training (ET) in post-MI patients would normalize arterial baroreflex sensitivity (BRS) and muscle sympathetic nerve activity (MSNA), and long-term ET would maintain the benefits in BRS and MSNA. Twenty-eight patients after 1 month of uncomplicated MI were randomly assigned to 2 groups, ET (MI-ET) and untrained. A normal control group was also studied. ET consisted of three 60-minute exercise sessions per week for 6 months. We evaluated MSNA (microneurography), blood pressure (automatic oscillometric method), heart rate (ECG), and spectral analysis of RR interval, systolic arterial pressure (SAP), and MSNA. Baroreflex gain of SAP-RR interval and SAP-MSNA were calculated using the ␣-index. At 3 to 5 days and 1 month after MI, MSNA and low-frequency SAP were significantly higher and BRS significantly lower in MI patients when compared with the normal control group. ET significantly decreased MSNA (bursts per 100 heartbeats) and the low-frequency component of SAP and significantly increased the low-frequency component of MSNA and BRS of the RR interval and MSNA. These changes were so marked that the differences between patients with MI and the normal control group were no longer observed after ET. MSNA and BRS in the MI-untrained group did not change from baseline over the same time period. ET normalizes BRS, low-frequency SAP, and MSNA in patients with MI. These improvements in autonomic control are maintained by long-term ET. Key Words: myocardial infarction Ⅲ sympathetic nerve activity Ⅲ exercise training Ⅲ autonomic control Ⅲ baroreflex control P revious studies show that myocardial infarction (MI) is linked to increased sympathetic nervous activity 1,2 and impaired arterial baroreflex sensitivity (BRS). 3 These findings of autonomic dysfunction have been associated with increased mortality in patients after MI. 4 -10 La Rovere et al 7 demonstrated that decreased BRS is associated with cardiac mortality risk. A follow-up of 61 months in uncomplicated post-MI patients with preserved left ventricular function showed that depressed BRS discriminated a subgroup at long-term high risk for cardiovascular mortality. 10 Increased muscle sympathetic nerve activity (MSNA) is an independent predictor of poor prognosis in patients with chronic heart failure, including patients with chronic heart failure after MI. 11 Thus, a therapeutic strategy targeted to the improvement in autonomic control in patients with MI represents an important clinical goal.In patients with cardiovascular disease, studies have shown that physical exercise is an important strategy to improve autonomic function. Exercise training has been shown to decrease MSNA 12 and improve BRS 12-14 in patients with MI. It remains unknown whether the magnitude of change in autonomic control actually normalizes BRS and sy...

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Summary: Purpose:To analyze the effect of prolonged (daily) electrical vagus nerve stimulation (VNS) on daily amygdaloid kindling (AK) in freely moving cats.Methods: Fifteen adult male cats were implanted in both temporal lobe amygdalae, both lateral geniculate bodies, and prefrontal cortices. A bipolar hook (5-mrn separation) stainless steel electrode also was implanted in the unsectioned left vagus nerve. AK only was performed on five of the cats as a control. The remaining 10 cats were recorded under the following experimental conditions: VNS (1.2-2.0 mA, 0.5-ms pulses, 30 Hz) for 1 min along with AK (I-s train, 1 -ms pulses, 60 Hz, 300-600 PA), followed by VNS alone for 1 min, four times between I1:OO a.m. and 2 p.m. At different times, VNS was arrested, and AK was continued until stage VI kindling was reached.Results: The behavioral changes evoked by VNS were as follows: left miosis, blinking, licking, abdominal contractions, swallowing, and eventually yawning, meowing, upward gaze, and short head movements. Compulsive eating also was present with a variable latency. Outstanding polygraphic changes consisted of augmentation of eye movements and visual evoked potentials while the animal was awake and quiet, with immobility and upward gaze. An increase of the pontogeniculooccipital (PGO) wave density in rapid eye movement (REM) sleep also was noticeable. AK was completed (to stage VI) in the control animals without a vagus nerve implantation in 23.4 & 3.7 trials. In animals with VNS, the AK was significantly delayed, remaining for a long time in the behavioral stages and showing a reduction of afterdischarge duration and frequency. Stage VI was never reached despite 50 AK trials, except when the vagus nerve electrodes were accidentally broken or vagal stimulation was intentioilally arrested. Under these circumstances, 24.4 8.16 AK trials alone were necessary to reach stage VI of kindling.Conclusions: Our results indicate that left, electrical VNS interferes with AK epileptogenesis. This anticonvulsant effect could be related to the increase of REM sleep.

The attenuation of heart rate recovery after maximal exercise is impaired to a greater degree where metabolic syndrome (MetS) is associated with moderate to severe obstructive sleep apnea (OSA) than by MetS with no or mild or no OSA. This is at least partly explained by sympathetic hyperactivity.