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Biomedical subjects

G Cybulski

Publications and source records attributed to G Cybulski.

At least 19 recordsLinked to original sources
PubMed2006

Effect of adrenergic blockade on plasma adrenomedullin concentration during static handgrip in patients with heart failure.

Our previous study showed that static handgrip caused increases in the plasma adrenomedullin (ADM) both in patients with heart failure (HF) and healthy subjects. The present study was designed to determine the role of the sympathetic nervous system in mediating plasma ADM changes during handgrip in patients with HF. Twelve male HF patients (II class NYHA) treated with carvedilol, a non-selective adrenergic blocker (TC) and 12 patients untreated with carvedilol (UC) performed two 3-min bouts of static handgrip at 30% of maximal voluntary contraction, alternately with each hand. At the end of both exercise bouts and in 5 min of the recovery period, plasma ADM and catecholamines were determined. In addition, heart rate, blood pressure and stroke volume (SV) were measured. The baseline plasma ADM, noradrenaline (NA) and adrenaline (A) levels were similar in the two groups of patients, while SV was higher (P<0.05) in TC than in UC. During exercise plasma ADM concentrations were lower (P<0.05) in TC than in UC, but the handgrip-induced increases in plasma ADM did not differ between the groups. Plasma ADM correlated with NA concentrations (r = 0.764) and with SV (r = -0.435) and increases in plasma ADM expressed as percentage of baseline values correlated with those of plasma NA (r = 0.499), diastolic BP (r = 0.550) and total peripheral resistance (r = 0.435). The study suggests that the sympathetic nervous system may be involved in the stimulation of ADM secretion during static exercise either directly or by changes in the haemodynamic response.

Adrenergic beta-Antagonists↗
PubMed2006

Effect of 6-week endurance training on hemodynamic and neurohormonal responses to lower body negative pressure (LBNP) in healthy young men.

Endurance training is considered as a factor impairing orthostatic tolerance although an improvement and lack of effect have been also reported. The mechanisms of the changes and their relation to initial tolerance of orthostasis are not clear. In the present study, effect of moderate running training on hemodynamic and neurohormonal changes during LBNP, a laboratory test simulating orthostasis, was investigated in subjects with high (HT) and low (LT) tolerance of LBNP. Twenty four male, healthy subjects were submitted to graded LBNP (-15, -30 and -50 mmHg) before and after training. During each test heart rate (HR), stroke volume (SV) and blood pressure, plasma catecholamines, ACTH, adrenomedullin, atrial natriuretic peptide, and renin activity were determined. Basing on initial test, 13 subjects who withstood LBNP at -50 mmHg for 10 min were allocated into HT group and 11 subjects who earlier showed presyncopal symptoms to LT group. Training improved LBNP tolerance in six LT subjects. This was associated with attenuated rate of HR increase and SV decline (before training, at -30 mmHg deltaHR was 21 +/- 4 beats/min and deltaSV - -36+/- 8 ml while after training the respective values were 8 +/- 4 beats/min and -11+/- 6 ml). No differences in hemodynamic response were found in HT subjects and those from LT group whose LBNP tolerance was unchanged. In neither group training affected neurohormonal changes except inhibition of plasma ACTH rise in subjects with improvement of LBNP tolerance. It is concluded that some subjects with low orthostatic tolerance may benefit from moderate training due to improvement of cardiac function regulation.

Adrenocorticotropic Hormone↗
PubMed2005

Exercise training and 3-day head down bed rest deconditioning: exercise thermoregulation.

UNLABELLED: Bed rest (BR) deconditioning causes excessive increase of exercise core body tempera-ture, while aerobic training improves exercise thermoregulation. The study was designed to determine whether 3 days of 6 degrees head-down bed rest (HDBR) affects body temperature and sweating dynamics during exercise and, if so, whether endurance training before HDBR modifies these responses. Twelve healthy men (20.7+/-0.9 yrs, VO2max: 46+/-4 ml x kg(-1) x min(-1) ) underwent HDBR twice: before and after 6 weeks of endurance training. Before and after HDBR, the subjects performed 45 min sitting cycle exercise at the same workload equal to 60% of VO2max determined before training. During exercise the VO2, HR, tympanic (Ttymp) and skin (Tsk) temperatures were recorded; sweating dynamics was assayed from a ventilated capsule on chest. Training increased VO2max by 12.1% (p<0.001). Resting Ttymp increased only after first HDBR (by 0.22 +/- 0.08 degrees C, p<0.05), while exercise equilibrium levels of Ttymp were increased (p<0.05) by 0.21 +/- 0.07 and 0.26 +/- 0.08 degrees C after first and second HDBR, respectively. Exercise mean Tsk tended to be lower after both HDBR periods. Total sweat loss and time-course of sweating responses were similar in all exercise tests. The sweating threshold related to Ttymp was elevated (p<0.05) only after first HDBR. IN CONCLUSION: six-week training regimen prevents HDBR-induced elevation of core temperature (Ttymp) at rest but not during ex-ercise. The post-HDBR increases of Ttymp without changes in sweating rate and the tendency for lower Tsk suggest an early (<3d) influence of BR on skin blood flow.

Adult↗
PubMed2005

Hemodynamic and neuroendocrine predictors of lower body negative pressure (LBNP) intolerance in healthy young men.

Exposure to LBNP results in body fluid shift to lower extremities similarly as under influence of orthostatic stress. In susceptible persons it leads to syncope. For better understanding why certain individuals are more susceptible to orthostatic challenges it seemed necessary to collect more data on hemodynamic and neuroendocrine adjustments occurring before onset of presyncopal symptoms Accordingly, in this study heart rate (HR), blood pressure (BP), stroke volume (SV), cardiac output (CO), hematocrit, plasma catecholamines, adrenomedullin, ACTH and plasma renin activity (PRA) were measured in 24 healthy men during graded LBNP (-15, -30 and -50 mmHg). Thirteen subjects completed the test (HT group) whereas 11 had presyncope signs or symptoms at -30 mmHg or at the beginning of -50 mmHg (LT group). Comparison of these groups showed that LT subjects had lower baseline total peripheral resistance and higher plasma adrenomedullin. During LBNP plasma catecholamine and PRA increases were even greater in LT than in HT group while plasma adrenomedullin elevations were similar in both groups. Plasma ACTH increased only in LT group following presyncope symptoms. Low tolerant group showed more rapid decline of SV and CO than HT subjects from the beginning of LBNP. It is suggested that measurements of SV at the level of LBNP which did not evoke any adverse symptoms may be of predictive value for lower orthostatic tolerance.

Adrenocorticotropic Hormone↗
PubMed2004

Stroke volume and systolic time intervals: beat-to-beat comparison between echocardiography and ambulatory impedance cardiography in supine and tilted positions.

The aim of the study was to compare stroke volume (SV), ejection time (ET) and pre-ejection period (PEP) measurements obtained using a central haemodynamics ambulatory monitoring device based on impedance cardiography (ICG), in supine and tilted positions (60 degrees), with pulsed Doppler echocardiography as a non-invasive reference method. The Holter-type ICG device was used for off-line, beat-to-beat, automatic determination of SV, ET and PEP. ICG data were compared with those obtained simultaneously using pulsed Doppler echocardiography in the ascending aorta from a suprasternal projection, 1 min before and 10 min after tilting. The tests were performed in 13 young, healthy subjects (six men and seven women, aged 23-33 years). Linear regression between the measured values obtained for all subjects was described by the following formulas: SVicg= 13.9 + 0.813 x SVecho (r = 0.857, SEE = 9.03, n = 496), ETicg = 16.8 + 0.987 x ETecho (r = 0.841, SEE=21.3, n = 496), PEPicg= 22.8 + 0.890 x PEPecho (r = 0.727, SEE = 14.6, n = 496). The data showed that ambulatory impedance cardiography gives useful absolute values of SV and systolic time intervals measured in supine and tilted positions.

Adult↗
PubMed2003

Early effects of short-term aerobic training. Physiological responses to graded exercise.

AIM: The aim of this study was to find out how early the moderate training effects appear and to check the hypothesis that familiarization with exercise protocol may contribute to an early physiological responses to training in previously sedentary subjects. METHODS: Twelve male, sedentary volunteers (22.0+/-0.7 yrs) were submitted to 3 weeks of a bicycle ergometer training, consisting of 45 min of exercise (at 70% VO(2)max), 3-4 times a week. The subjects performed 4 incremental exercise tests until volitional exhaustion: 2 before training (C1 and C2), and then after 1 (T1) and 3 (T3) weeks of training. During exercise HR, VO(2), electrical activity (EMG) of rectus femoris, biceps femoris, soleus and trapezius muscles were recorded and blood samples were taken for blood lactate (LA) determination. RESULTS: Already after 1 week of training HR decreased (p<0.05) with a further decline after 3 weeks the training (p<0.01). Maximal work load after 3 weeks of training increased to 277+/-10.4 W vs 250+/-9.5 W (p<0.05), VO(2)max achieved higher values than in C1 and C2 tests (p<0.05) and LA and EMG thresholds were elevated (p<0.05). CONCLUSION: A decrease in the resting and submaximal heart rate is the earliest effect of increased physical activity. Familiarization to exercise protocol decreased EMG of biceps femoris and soleus muscles during exercise, but did not influence that of rectus femoris muscle the most engaged during cycling.

Adaptation, Physiological↗
PubMed2003

Influence of age on the immediate heart rate response to the active orthostatic test.

Dynamics of the heart rate changes following standing up from the supine position was investigated in 41 healthy men aged 20 to 59 years, classified according to the age into three groups: (22 to 26 yrs, n = 14), (33 to 49, yrs, n = 13) and (51 to 59 yrs, n = 14). The protocol consisted of twice repeated sequence: lying down-standing up-lying down. The subjects remained in each position for 8 minutes. The average and beat-to-beat heart rate (HR) were continuously calculated using the specialized computer program analysing ECG. The initial response was analysed using both the indices known from literature and newly introduced by the authors. The high reproducibility of the response was observed and the correlations between the indices were analysed. The relationship between the indices characterising the pattern of the response and age were analysed using the linear regression model. Most of these indices showed a tendency towards attenuation of the HR response with age. The closest correlation with age was found for the index characterising the initial increase of HR after standing up (r = -0.610, p < 0.001). There were no correlations between the indices of HR response to standing up and the height or body mass of the healthy subjects.

Adult↗
PubMed2002

Effect of static handgrip on plasma adrenomedullin concentration in patients with heart failure and in healthy subjects.

Adrenomedullin (ADM) release is enhanced in pheochromocytoma, chronic heart failure (HF), hypertension and renal diseases. This study was designed to test the hypothesis that ADM secretion increases also in response to acute stimuli, such as static effort and to compare plasma ADM response to this stimulus in patients with chronic HF and healthy persons. Eight male HF patients (II/III class NYHA) and eight healthy subjects (C) performed two 3-min bouts of static handgrip at 30% of maximal voluntary contraction, alternately with each hand without any break between the bouts. At the end of both exercise bouts and in 5 min of the recovery period, plasma ADM and catecholamines were determined. In addition, heart rate, blood pressure, and stroke volume (SV) were measured. The baseline plasma ADM and noradrenaline levels were higher, whilst plasma adrenaline and SV were lower in HF patients than in C group. The 1st exercise bout caused an increase in plasma ADM from 3.32 +/- 0.57 to 4.98 +/- 0.59 pmol l(-1) (p<0.01) in C and from 6.88 +/- 0.58 to 7.80 +/- 0.43 pmol x l(-1) (p<0.02) in HF patients. The 2nd exercise bout did not produce further elevation in plasma ADM and during recovery the hormone concentration declined to pre-exercise or lower values. There were no differences between groups in exercise-induced increases in plasma ADM. Plasma ADM correlated with SV (r = -0.419) and with noradrenaline concentrations (r = 0.427). It is concluded that static exercise causes the short-lasting increase in plasma ADM concentration which is similar in healthy subjects and in patients with mild heart failure.

Adrenomedullin↗
PubMed2001

Effects of 3-day bed rest on physiological responses to graded exercise in athletes and sedentary men.

To test the hypotheses that short-term bed-rest (BR) deconditioning influences metabolic, cardiorespiratory, and neurohormonal responses to exercise and that these effects depend on the subjects' training status, 12 sedentary men and 10 endurance- and 10 strength-trained athletes were submitted to 3-day BR. Before and after BR they performed incremental exercise test until volitional exhaustion. Respiratory gas exchange and heart rate (HR) were recorded continuously, and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate concentration ([LA]), epinephrine concentration ([Epi]), norepinephrine concentration ([NE]), plasma renin activity (PRA), human growth hormone concentration ([hGH]), testosterone, and cortisol determination. Reduction of peak oxygen uptake (VO(2 peak)) after BR was greater in the endurance athletes than in the remaining groups (17 vs. 10%). Decrements in VO(2 peak) correlated positively with the initial values (r = 0.73, P < 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased in the endurance athletes from 71 to 60% VO(2 peak) (P < 0.001); they also had an earlier increase in [NE], an attenuated increase in [hGH], and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion, reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes.

Adult↗
PubMed2000

Cardiovascular, metabolic and plasma catecholamine responses to passive and active exercises.

Eight healthy male volunteers (aged 19.6+/-3.0 years) were submitted to the unloaded active (AE) and passive (PE) cycling exercise-tests performed on an adapted cycle ergometer at a pedalling rate of 50 rpm. Intensity of active exercise was about 10% of VO2 max. In the PE exercise test the ergometer was moved electrically. During both tests the systolic time intervals (STI), stroke volume (SV), heart rate (HR), blood pressure (BP), oxygen uptake (VO2), rating of perceived exertion (RPE), electrical muscle activity (EMG), plasma adrenaline (A), noradrenaline (NE) and blood lactate (LA) concentrations were measured. Exercise induced changes in VO2, RPE and EMG were significantly higher during AE than PE. Shortening of the pre-ejection period (PEP) and diminishing of the PEP to ejection time (ET) ratio were similar in both types of exercise, whereas HR increased only during AE. A significant increase in cardiac output (p<0.01) resulted from increased SV (p<0.01) during PE and from increased HR (p <0.01) during AE. MAP increased only during PE and it was higher than at rest and during AE (p<0.01). Absence of changes in SV and MAP during AE may be considered as a secondary effect of the decrease in TPR. Plasma catecholamines did not increase above resting values in either type of exercise. Blood LA concentration increased during both PE and AE but it reached higher values (p<0.01) after the latter test. The present data suggest that the inotropic state depends on the mechanoreflexes originated in skeletal muscles. However, contribution of changes in preload to shortening of PEP can not be excluded.

Adult↗
PubMed1999

The influence of endurance training on the transient haemodynamic response to orthostatic manoeuvre.

Several investigations demonstrated that aerobic fitness is associated with a tendency towards orthostatic hypotension whereas other reports did not show any differences in cardiovascular adjustment to orthostatic challenges between endurance trained and sedentary subjects. In the present work, the time course of changes in heart rate (HR), systolic time intervals (STI), stroke volume (SV), cardiac output (CO) and blood pressure was studied during 8 minutes following standing up from supine position in 7 healthy volunteers before and after 10 weeks of endurance training on bicycle ergometer. Impedance cardiography was used for measurement of cardiac postural responses. The training program applied in this study increased the subjects' aerobic capacity (VO2max) by approx. 18%. After training, the steady-state supine HR and contribution of the pre-ejection period and ejection time to the total R-R interval in ECG were lowered while SV was significantly increased. No significant training-induced changes were found in magnitude and time-courses of HR, STI, SV and CO changes following standing up. Diastolic blood pressure during standing was greater after than before training. It is concluded that the short-time endurance training does not affect adversely cardiovascular orthostatic response and may even improve orthostatic tolerance due to the augmentation of diastolic blood pressure response.

Adult↗
PubMed1996

Influence of age on the immediate cardiovascular response to orthostatic manoeuvre.

The dynamics of cardiovascular changes following standing up from the supine position were investigated in 41 healthy men aged 20-59 years, classified into three groups: (22-26 years, n = 14), (33-49 years, n = 13) and (51-59 years, n = 14). The protocols consisted of a sequence repeated twice lying down-standing up-lying down. The initial period supine was for 20 min and then the subjects remained in each position for 8 min. Stroke volume, cardiac output (CO), ejection time (ET), pre-ejection period and heart rate (HR) were continuously calculated using automated impedance cardiography and electrocardiography. Blood pressure was measured by the auscultation method. The patterns of HR and haemodynamic orthostatic response were shown to be highly reproducible. Most of the indices characterizing the amplitude and rate of cardiovascular changes following standing up showed a tendency towards attenuation with age. However, only the indices of HR, CO and ET responses correlated significantly with age. The strongest relationships with age were observed in the sudden increase in HR (r = -0.61, P < 0.01), the transient increase in CO (r = -0.45, P < 0.001), and the rapid decrease in ET (r = 0.42, P < 0.01) after standing up. A few indices of HR and haemodynamic response also showed weak correlations with the subjects' heights and body masses.

Adult↗
PubMed1994

Noninvasive determination of local wavespeed and distensibility of the femoral artery by comb-excited Fourier velocity-encoded magnetic resonance imaging: measurements on athletic and nonathletic human subjects.

The local distensibility of arteries is of interest because distensibility varies from artery to artery, may be altered by disease to different extents in different arteries, and may be modified by physiological or pharmacological means. Using magnetic resonance imaging (MRI) we have measured local arterial wavespeed in the femoral artery in healthy human subjects and calculated local arterial distensibility. We acquired 2-D coronal and sagittal MR phase contrast angiograms of the femoral artery. We used a novel imaging technique, comb-excited Fourier velocity-encoded MRI, to obtain simultaneous measurements of arterial blood velocity at two stations 14 cm apart on the femoral artery. The separation of the two stations divided by the delay between the onset of forward flow at the two stations was used to calculate the wavespeed. The measurements were made on 16 healthy men (8 athletes, 8 non-athletes) in the age range 20-30 years, who were scanned with the use of ECG gating and an extremity coil in a 1.5 Tesla scanner (GE Medical Systems, Milwaukee, WI). By systematically altering the delay between the R-wave and data acquisition, a temporal resolution of 2-4 ms was achieved. The onset of forward flow at each station was determined from a least-squares fit to the data for 30% of the maximum velocity during the cardiac cycle. Average femoral artery wavespeed was 7.7 m/s +/- 1.2 in the athletes and 11.5 m/s +/- 1.1 in the non-athletes (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

A comparison between the automatized impedance cardiography and pulsed-wave Doppler echocardiography methods for measurements of stroke volume (SV) and systolic time intervals (STI).

Stroke volume (SV) and systolic time intervals (STI) were measured automatically using impedance cardiography signals (ICG) and compared with those obtained by pulsed-wave Doppler echocardiography using the apex approach. The comparison was made in 9 healthy male subjects, mean age 24.9 +/- 12.2 years, using recordings of 10 heart cycles simultaneously obtained by the two methods. During measurements the subjects rested in the supine position. There were no differences between mean values of SV determined by the two methods as well as between mean values of ejection time (ET) (p > 0.8 and p > 0.9, respectively). The pre-ejection period (PEP) estimated by ICG was 22 ms longer than that determined by echocardiography (p < 0.001). The relationship between SV values measured by impedance cardiography (SVA) vs those calculated by echocardiography (SVE) was found to be close to the line of identity in the range of measurements. The regression equation for SV was: SVA = 0.784.SVE + 15 (r = 0.69, p < 0.001, SEE = 10.7 ml). We conclude that automatic determination of SV and ET from ICG signals provides results comparable in absolute values with those obtained by the pulsed wave Doppler ultrasonocardiography using the apex approach for subjects remaining in the supine position.

Adult↗
PubMed1992

Neuromuscular stimulation in spinal cord injury: I: Restoration of functional movement of the extremities.

The spinal cord injured patient has been the focus of clinical and research efforts to restore functional movement and obtain therapeutic benefits by electric stimulation of upper-motor-neuron paralyzed muscles. Our review articles treat developments in this field from 1983 to 1990. Efforts have been directed to restoring hand function, standing, and walking (covered in part I), as well as prevention of secondary complications through ventilatory function, bladder function, and achieving therapeutic effects of electric stimulation (covered in Part II). The technology for hand function, standing, and walking is used primarily in the research laboratory, as clinical applications are minimal. Much work remains to be done to solve the difficult problems associated with applying this promising technology to spinal cord injury.

Electric Stimulation Therapy↗
PubMed1991

Endurance training slows down the kinetics of heart rate increase in the transition from moderate to heavier submaximal exercise intensities.

To find out whether endurance training influences the kinetics of the increases in heart rate (fc) during exercise driven by the sympathetic nervous system, the changes in the rate of fc adjustment to step increments in exercise intensities from 100 to 150 W were followed in seven healthy, previously sedentary men, subjected to 10-week training. The training programme consisted of 30-min cycle exercise at 50%-70% of maximal oxygen uptake (VO2max) three times a week. Every week during the first 5 weeks of training, and then after the 10th week the subjects underwent the submaximal three-stage exercise test (50, 100 and 150 W) with continuous fc recording. At the completion of the training programme, the subjects' VO2max had increased significantly (39.2 ml.min-1.kg-1, SD 4.7 vs 46 ml.min-1.kg-1, SD 5.6) and the steady-state fc at rest and at all submaximal intensities were significantly reduced. The greatest decrease in steady-state fc was found at 150 W (146 beats.min-1, SD 10 vs 169 beats.min-1, SD 9) but the difference between the steady-state fc at 150 W and that at 100 W (delta fc) did not decrease significantly (26 beats.min-1, SD 7 vs 32 beats.min-1, SD 6). The time constant (tau) of the fc increase from the steady-state at 100 W to steady-state at 150 W increased during training from 99.4 s, SD 6.6 to 123.7 s, SD 22.7 (P less than 0.01) and the acceleration index (A = 0.63.delta fc.tau-1) decreased from 0.20 beats.min-1.s-1, SD 0.05 to 0.14 beats.min-1.s-1, SD 0.04 (P less than 0.02). The major part of the changes in tau and A occurred during the first 4 weeks of training. It was concluded that heart acceleration following incremental exercise intensities slowed down in the early phase of endurance training, most probably due to diminished sympathetic activation.

Adult↗