The case of thyroid hormones: how to learn physiology by solving a detective case

Lellis-Santos C, Giannocco G, Nunes MT. The case of thyroid hormones: how to learn physiology by solving a detective case. Adv Physiol Educ 35: 219-226, 2011; doi:10.1152/advan.00135.2010.Thyroid diseases are prevalent among endocrine disorders, and careful evaluation of patients' symptoms is a very important part in their diagnosis. Developing new pedagogical strategies, such as problem-based learning (PBL), is extremely important to stimulate and encourage medical and biomedical students to learn thyroid physiology and identify the signs and symptoms of thyroid dysfunction. The present study aimed to create a new pedagogical approach to build deep knowledge about hypo-/hyperthyroidism by proposing a hands-on activity based on a detective case, using alternative materials in place of laboratory animals. After receiving a description of a criminal story involving changes in thyroid hormone economy, students collected data from clues, such as body weight, mesenteric vascularization, visceral fat, heart and thyroid size, heart rate, and thyroid-stimulating hormone serum concentration to solve the case. Nevertheless, there was one missing clue for each panel of data. Four different materials were proposed to perform the same practical lesson. Animals, pictures, small stuffed toy rats, and illustrations were all effective to promote learning, and the detective case context was considered by students as inviting and stimulating. The activity can be easily performed independently of the institution's purchasing power. The practical lesson stimulated the scientific method of data collection and organization, discussion, and review of thyroid hormone actions to solve the case. Hence, this activity provides a new strategy and alternative materials to teach without animal euthanization.

Effects of Infrared-LED Illumination Applied During High-Intensity Treadmill Training in Postmenopausal Women

Background data: Technology and physical exercise can enhance physical performance during aging. Objective: The purpose of this study was to investigate the effects of infrared-light-emitting diode (LED) illumination (850 nm) applied during treadmill training. Materials and methods: Twenty postmenopausal women participated in this study. They were randomly divided into two groups. The LED group performed treadmill training associated with infrared-LED illumination (n = 10) and the control group performed only treadmill training (n = 10). The training was performed during 3 months, twice a week during 30 min at intensities between 85 and 90% of maximal heart rate. The irradiation parameters were 31 mW/cm(2), treatment time 30 min, 14,400 J of total energy and 55.8 J/cm(2) of fluence. Physiological, biomechanical, and body composition parameters were measured at the baseline and after 3 months. Results: Both groups improved the time of tolerance limit (Tlim) (p < 0.05) during submaximal constant-speed testing. The peak torque did not differ between groups. However, the results showed significantly higher values of power [from 56 +/- 10 to 73 +/- 8W (p = 0.002)] and total work [from 1,537 +/- 295 to 1,760 +/- 262 J (p = 0.006)] for the LED group when compared to the control group [power: from 58 +/- 14 to 60 +/- 15W (p >= 0.05) and total work: from 1,504 +/- 404 to 1,622 +/- 418 J (p >= 0.05)]. The fatigue significantly increased for the control group [from 51 +/- 6 to 58 +/- 5 % (p = 0.04)], but not for the LED group [from 60 +/- 10 to 60 +/- 4 % (p >= 0.05)]. No significant differences in body composition were observed for either group. Conclusions: Infrared-LED illumination associated with treadmill training can improve muscle power and delay leg fatigue in postmenopausal women.

Plasma Kallikrein and Angiotensin I-converting enzyme N- and C-terminal domain activities are modulated by the insertion/deletion polymorphism

Angiotensin I-converting enzyme (ACE) is recognized as one of the main effector molecules involved in blood pressure regulation. In the last few years some polymorphisms of ACE such as the insertion/deletion (I/D) polymorphism have been described, but their physiologic relevance is poorly understood. In addition, few studies investigated if the specific activity of ACE domain is related to the I/D polymorphism and if it can affect other systems. The aim of this study was to establish a biochemical and functional characterization of the I/D polymorphism and correlate this with the corresponding ACE activity. For this purpose, 119 male brazilian army recruits were genotyped and their ACE plasma activities evaluated from the C- and N-terminal catalytic domains using fluorescence resonance energy transfer (FRET) peptides, specific for the C-domain (Abz-LFK(Dnp)OH), N-domain (Abz-SDK(Dnp)P-OH) and both C- and N-domains (Abz-FRK(Dnp)P-OH). Plasma kallikrein activity was measured using Z-Phe-Arg-AMC as substrate and inhibited by selective plasma kallikrein inhibitor (PKSI). Some physiological parameters previously described related to the I/D polymorphism such as handgrip strength, blood pressure, heart rate and BMI were also evaluated. The genotype distribution was II n = 27, ID n = 64 and DD n = 28. Total plasma ACE activity of both domains in II individuals was significantly lower in comparison to ID and DD. This pattern was also observed for C- and N-domain activities. Difference between ID and DD subjects was observed only with the N-domain specific substrate. Blood pressure, heart rate, handgrip strength and BMI were similar among the genotypes. This polymorphism also affected the plasma kallikrein activity and DD group presents high activity level. Thus, our data demonstrate that the I/D ACE polymorphism affects differently both ACE domains without effects on handgrip strength. Moreover, this polymorphism influences the kallikrein-kinin system of normotensive individuals. (C) 2009 Elsevier Ltd. All rights reserved.

Cardiovascular response during trigeminal ganglion compression for trigeminal neuralgia according to the use of local anesthetics

There are controversies about the use of local anesthetics during balloon compression for trigeminal neuralgia (TN) as a protective factor for cardiovascular events. The objective of this study was to investigate cardiovascular parameters (blood pressure and heart rate [HR]) of patients that underwent trigeminal balloon compression with local anesthetics compared to a control group (placebo). This is a randomized controlled study; 55 patients were randomized into two groups: study (deep sedation and trigeminal block with 0.8-mL lidocaine 2%) and control group (deep sedation and trigeminal injection of 0.8-mL saline). Blood pressure and HR were measured in five distinct moments: preoperative, during puncture for local anesthesia/placebo, during puncture with the catheter, during balloon compression, and final evaluation. Statistical analysis was performed with Pearson`s chi (2) and McNemar tests and the analysis of variance for repetitive measures. The means of systolic and diastolic blood pressures (SBP and DBP, respectively) were higher in the control group when compared to the study group at the evaluation during puncture with the catheter (p < 0.001) and balloon compression (p < 0.001 and p = 0.018 for DBP and SBP, respectively). There was an increase in the HR in the control group during the procedure (p = 0.017). The use of local anesthetics during the trigeminal balloon compression for TN can have a preventive role for the risk of cardiovascular events.

Acute physiological responses to different circuit training protocols

Aim. The purpose of present study was to compare the acute physiological responses to a circuit weight training with the responses to a combined circuit training (weight training and treadmill run). Methods. The sample consisted of 25 individuals at an average state of training, 10 men and 15 female, between 18 and 35 year old. There were selected 60 second sets of resistance exercises to the circuit weight training (CWT). Whereas in the combined circuit training (CCT), the subjects spent 30 seconds on the same resistance exercises and 30 seconds running on the treadmill. The rest intervals between the sets lasted 15 seconds. The analysis of variance (ANOVA) with 5% significance level was utilized to the statistical analysis of the results. Results. Comparing circuit training protocols, it was noted that CCT elicits a higher relative and absolute <(V)over dot>O(2) and energy expenditure values than CWT for both genders (P<0.05). Regarding inter-gender comparison, males showed higher absolute and relative <(V)over dot>O(2) and absolute energy expenditure values for both CWT and CCT than females (P<0.05). Females showed a significant greater % <(V)over dot>O(2max) value for both CWT and CCT. Due to the experimental conditions used to state both circuit training bouts (CWT and CCT), the <(V)over dot>O(2) rate found was higher than the values reported by previous studies which used heavier weight lift. Conclusion. CCT seems adequate to produce cardiovascular improvements and greater energy expenditure for both men and women, while CWT group classes are sufficient only for unfit women.

Physiological demands of match-play in elite tennis: A case study

The physiological and perceptual demands together with match notation of a four-set tennis match were studied in two elite professional players during the preparation for the 2008 Davis Cup. The design of this case report is unique in that it is the first to describe the demands of prolonged match-play (197 min) over four sets in ecologically valid conditions. The variables measured before and after each set included blood lactate and glucose concentrations, body mass, and perception of effort. Stroke count for each rally and heart rate were recorded during each set while salivary cortisol concentration was determined before and after the match. The rally length decreased as the match progressed. The results showed significant physiological stress, with each player losing greater than 2.5% of body mass (as fluid) and having elevated salivary cortisol concentrations after the match. Heart rate and perception of effort were also increased following each set indicating increasing stress. However, blood lactate decreased following the fourth set while blood glucose was maintained. The results also suggest that elite players may adjust work rates or tactics to cope with the increased perception of effort. This report shows that four sets of tennis are associated with increasing stress and fatigue.

Cardiac and peripheral adjustments induced by early exercise training intervention were associated with autonomic improvement in infarcted rats: role in functional capacity and mortality

Aims To test the effects of early exercise training (ET) on left ventricular (LV) and autonomic functions, haemodynamics, tissues blood flows (BFs), maximal oxygen consumption (VO(2) max), and mortality after myocardial infarction (MI) in rats. Methods and results Male Wistar rats were divided into: control (C), sedentary-infarcted (SI), and trained-infarcted (TI). One week after MI, TI group underwent an ET protocol (90 days, 50-70% VO2 max). Left ventricular function was evaluated noninvasively and invasively. Baroreflex sensitivity, heart rate variability, and pulse interval were measured. Cardiac output (CO) and regional BFs were determined using coloured microspheres. Infarcted area was reduced in TI (19 +/- 6%) compared with SI (34 +/- 5%) after ET. Exercise training improved the LV and autonomic functions, the CO and regional BF changes induced by MI, as well as increased SERCA2 expression and mRNA vascular endothelial growth factor levels. These changes brought about by ET resulted in mortality rate reduction in the TI (13%) group compared with the SI (54%) group. Conclusion Early aerobic ET reduced cardiac and peripheral dysfunctions and preserved cardiovascular autonomic control after MI in trained rats. Consequently, these ET-induced changes resulted in improved functional capacity and survival after MI.

Exercise intensity optimization for men with high cardiorespiratory fitness

Exercise intensity is a key parameter for exercise prescription but the optimal range for individuals with high cardiorespiratory fitness is unknown. The aims of this study were (1) to determine optimal heart rate ranges for men with high cardiorespiratory fitness based on percentages of maximal oxygen consumption (%VO(2max)) and reserve oxygen consumption (%VO(2reserve)) corresponding to the ventilatory threshold and respiratory compensation point, and ( 2) to verify the effect of advancing age on the exercise intensities. Maximal cardiorespiratory testing was performed on 210 trained men. Linear regression equations were calculated using paired data points between percentage of maximal heart rate (%HR(max)) and %VO(2max) and between percentage of heart rate reserve (%HRR) and %VO(2reserve) attained at each minute during the test. Values of %VO(2max) and %VO(2reserve) at the ventilatory threshold and respiratory compensation point were used to calculate the corresponding values of %HRmax and %HRR, respectively. The ranges of exercise intensity in relation to the ventilatory threshold and respiratory compensation point were achieved at 78-93% of HR(max) and 70-93% of HRR, respectively. Although absolute heart rate decreased with advancing age, there were no age-related differences in %HR(max) and %HRR at the ventilatory thresholds. Thus, in men with high cardiorespiratory fitness, the ranges of exercise intensity based on %HR(max) and %HRR regarding ventilatory threshold were 78-93% and 70-93% respectively, and were not influenced by advancing age.

Heat and exercise acclimation increases intracellular levels of Hsp72 and inhibits exercise-induced increase in intracellular and plasma Hsp72 in humans

In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0 +/- 0.7 years; 80.5 +/- 2.0 kg; 180 +/- 2 cm, mean +/- SE) exercised for 60 min in a hot, dry environment (40 +/- 0A degrees C and 45 A +/- 0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1A degrees C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored. Subjects showed expected adaptations to HA: reduced exercise rectal and mean skin temperatures and heart rate, and augmented sweat rate and exercise tolerance. In HST1, plasma Hsp72 increased from REST to POST and then returned to resting values 1 h POST (REST: 1.11 A +/- 0.07, POST: 1.48 A +/- 0.10, 1 h POST: 1.22 A +/- 0.11 ng mL(-1); p < 0.05). In HST2, there was no change in plasma Hsp72 (REST: 0.94 A +/- 0.08, POST: 1.20 A +/- 0.15, 1 h POST: 1.17 A +/- 0.16 ng mL(-1); p > 0.05). HA increased resting levels of intracellular Hsp72 (HST1: 1 A +/- 0.02 and HST2: 4.2 A +/- 1.2 density units, p < 0.05). Exercise-induced increased intracellular Hsp72 expression was observed on HST1 (HST1: REST, 1 A +/- 0.02 vs. POST, 2.9 A +/- 0.9 density units, mean +/- SE, p < 0.05) but was inhibited on HST2 (HST2: REST, 4.2 +/- 1.2 vs. POST, 4.4 +/- 1.1 density units, p > 0.05). Regression analysis showed that the lower the pre-exercise expression of intracellular Hsp72, the higher the exercise-induced increase (R = -0.85, p < 0.05). In conclusion, HA increased resting leukocyte Hsp72 levels and inhibited exercise-induced expression. This intracellular adaptation probably induces thermotolerance. In addition, the non-increase in plasma Hsp72 after HA may be related to lower stress at the cellular level in the acclimated individuals.

Post-concurrent exercise hemodynamics and cardiac autonomic modulation

Concurrent training is recommended for health improvement, but its acute effects on cardiovascular function are not well established. This study analyzed hemodynamics and autonomic modulation after a single session of aerobic (A), resistance (R), and concurrent (A + R) exercises. Twenty healthy subjects randomly underwent four sessions: control (C:30 min of rest), aerobic (A:30 min, cycle ergometer, 75% of VO(2) peak), resistance (R:6 exercises, 3 sets, 20 repetitions, 50% of 1 RM), and concurrent (AR: A + R). Before and after the interventions, blood pressure (BP), heart rate (HR), cardiac output (CO), and HR variability were measured. Systolic BP decreased after all the exercises, and the greatest decreases were observed after the A and AR sessions (-13 +/- 1 and -11 +/- 1 mmHg, respectively, P < 0.05). Diastolic BP decreased similarly after all the exercises, and this decrease lasted longer after the A session. CO also decreased similarly after the exercises, while systemic vascular resistance increased after the R and AR sessions in the recovery period (+4.0 +/- 1.7 and +6.3 +/- 1.9 U, respectively, P < 0.05). Stroke volume decreased, while HR increased after the exercises, and the greatest responses were observed after the AR session (SV, A = -14.6 +/- 3.6, R = -22.4 +/- 3.5 and AR = -23.4 +/- 2.4 ml; HR, A = +13 +/- 2, R = +15 +/- 2 vs. AR = +20 +/- 2 bpm, P < 0.05). Cardiac sympathovagal balance increased after the exercises, and the greatest increase was observed after the AR session (A = +0.7 +/- 0.8, R = +1.0 +/- 0.8 vs. AR = +1.2 +/- 0.8, P < 0.05). In conclusion, the association of aerobic and resistance exercises in the same training session did not potentiate postexercise hypotension, and increased cardiac sympathetic activation during the recovery period.

Post-resistance exercise hypotension in spontaneously hypertensive rats is mediated by nitric oxide

1. Postexercise hypotension (PEH) plays an important role in the non-pharmacological treatment of hypertension. It is characterized by a decrease in blood pressure (BP) after a single bout of exercise in relation to pre-exercise levels. 2. The present study investigated the effect of a single session of resistance exercise, as well as the effect of nitric oxide (NO) and the autonomic nervous system (ANS), in PEH in spontaneously hypertensive rats (SHR). 3. Catheters were inserted into the left carotid artery and left jugular vein of male SHR (n = 37) for the purpose of measuring BP or heart rate (HR) and drug or vehicle administration, respectively. Haemodynamic measurements were made before and after acute resistance exercise. The roles of NO and the ANS were investigated by using N(G)-nitro-L-arginine methyl ester (L-NAME; 15 mg/kg, i.v.) and hexamethonium (20 mg/kg, i.v.) after a session of acute resistance exercise. 4. Acute resistance exercise promoted a pronounced reduction in systolic and diastolic BP (-37 +/- 1 and -8 +/- 1 mmHg, respectively; P < 0.05), which was suppressed after treatment with L-NAME. The reduction in systolic BP caused by exercise (-37 +/- 1 mmHg) was not altered by the administration of hexamethonium (-38 +/- 2 mmHg; P > 0.05). After exercise, the decrease in diastolic BP was greater with hexamethonium (-26 +/- 1 mmHg; P < 0.05) compared with the decrease caused by exercise alone. 5. The results suggest that acute resistance exercise has an important hypotensive effect on SHR and that NO plays a crucial role in this response.

Cardiovascular adaptive responses in rats submitted to moderate resistance training

The present study investigated the effects of 8 week of resistance training (RT) on hemodynamic and ventricular function on cardiac myosin ATPase activity, and on contractility of papillary muscles of rats. Groups: control (CO), electrically stimulated (ES), trained at 60% (TR 60%) and 75% of one repetition maximum (1RM) (TR 75%). Exercise protocol: 5 sets of 12 repetitions at 60 and 75% of 1RM, 5 times per week. The CO and ES groups had similar values for parameters analyzed (P > 0.05). Blood pressure (BP), heart rate (13%), left ventricle systolic pressure (LVSP 13%) decreased and cardiac myosin ATPase activity increased in the TR 75% group (90%, P < 0.05). The contractile performance of papillary muscles increased in trained rats (P < 0.05). Eight weeks of RT was associated with lowering of resting BP, heart rate and LVSP, improvements in contractility of the papillary muscle and an increase of cardiac myosin ATPase activity in rats.

Baroreflex Sensitivity Impairment Is Associated With Cardiac Diastolic Dysfunction in Rats

Background: Studies have shown that the autonomic dysfunction accompanied by impaired baroreflex sensitivity was associated with higher mortality. However, the influence of decreased baroreflex sensitivity on cardiac function, especially in diastolic function, is not well understood. This study evaluated the morpho-functional changes associated with baroreflex impairment induced by chronic sinoaortic denervation (SAD). Methods and Results: Animals were divided into sinoaortic denervation (SAD) and control (C) groups. Baroreflex sensitivity was evaluated by tachycardic and bradycardic responses, induced by vasoactive drugs. Cardiac function was studied by echocardiography and by left ventricle (LV) catheterization. LV collagen content and the expression of regulatory proteins involved in intracellular Ca(2+) homeostasis were quantified. Results showed higher LV mass in SAD versus C animals. Furthermore, an increase in deceleration time of E-wave in the SAD versus the C group (2.14 +/- 0.07 ms vs 1.78 +/- 0.03 ms) was observed. LV end-diastolic pressure was increased and the minimum dP/dt was decreased in the SAD versus the C group (12 +/- 1.5 mm Hg vs 5.3 +/- 0.2 mm Hg and 7,422 +/- 201 vs 4,999 +/- 345 mm Hg/s, respectively). SERCA/NCX ratio was lower in SAD than in control rats. The same was verified in SERCA/PLB ratio. Conclusions: The results suggest that baroreflex dysfunction is associated with cardiac diastolic dysfunction independently of the presence of other risk factors. (J Cardiac Fail 2011;17:519-525)

The rating of perceived exertion predicts intermittent vertical jump demand and performance

The aims of this study were (a) to assess the ability of the rating of perceived exertion (RPE) to predict performance (i.e. number of vertical jumps performed to a fixed jump height) of an intermittent vertical jump exercise, and (b) to determine the ability of RPE to describe the physiological demand of such exercise. Eight healthy men performed intermittent vertical jumps with rest periods of 4, 5, and 6s until fatigue. Heart rate and RPE were recorded every five jumps throughout the sessions. The number of vertical jumps performed was also recorded. Random coefficient growth curve analysis identified relationships between the number of vertical jumps and both RPE and heart rate for which there were similar slopes. In addition, there were no differences between individual slopes and the mean slope for either RPE or heart rate. Moreover, RPE and number of jumps were highly correlated throughout all sessions (r=0.97-0.99; P0.001), as were RPE and heart rate (r=0.93-0.97; P0.001). The findings suggest that RPE can both predict the performance of intermittent vertical jump exercise and describe the physiological demands of such exercise.

A low carbohydrate diet affects autonomic modulation during heavy but not moderate exercise

The aim of this study was to examine the effects of low carbohydrate (CHO) availability on heart rate variability (HRV) responses during moderate and severe exercise intensities until exhaustion. Six healthy males (age, 26.5 +/- 6.7 years; body mass, 78.4 +/- 7.7 kg; body fat %, 11.3 +/- 4.5%; (V) over dotO(2max), 39.5 +/- 6.6 mL kg(-1) min(-1)) volunteered for this study. All tests were performed in the morning, after 8-12 h overnight fasting, at a moderate intensity corresponding to 50% of the difference between the first (LT(1)) and second (LT(2)) lactate breakpoints and at a severe intensity corresponding to 25% of the difference between the maximal power output and LT(2). Forty-eight hours before each experimental session, the subjects performed a 90-min cycling exercise followed by 5-min rest periods and subsequent 1-min cycling bouts at 125% (V) over dotO(2max) (with 1-min rest periods) until exhaustion, in order to deplete muscle glycogen. A diet providing 10% (CHO(low)) or 65% (CHO(control)) of energy as carbohydrates was consumed for the following 2 days until the experimental test. The Poicare plots (standard deviations 1 and 2: SD1 and SD2, respectively) and spectral autoregressive model (low frequency LF, and high frequency HF) were applied to obtain HRV parameters. The CHO availability had no effect on the HRV parameters or ventilation during moderate-intensity exercise. However, the SD1 and SD2 parameters were significantly higher in CHO(low) than in CHO(control), as taken at exhaustion during the severe-intensity exercise (P < 0.05). The HF and LF frequencies (ms(2)) were also significantly higher in CHO(low) than in CHO(control) (P < 0.05). In addition, ventilation measured at the 5 and 10-min was higher in CHO(low) (62.5 +/- 4.4 and 74.8 +/- 6.5 L min(-1), respectively, P < 0.05) than in CHO(control) (70.0 +/- 3.6 and 79.6 +/- 5.1 L min(-1), respectively; P < 0.05) during the severe-intensity exercise. These results suggest that the CHO availability alters the HRV parameters during severe-, but not moderate-, intensity exercise, and this was associated with an increase in ventilation volume.