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PubMed1990

A dual electrophysiologic test for atrial antireentry and ventricular antifibrillatory studies. Effects of bethanidine, procainamide, and WY-48986.

We have developed a dual electrophysiologic test that allows measurement of both antireentry and antifibrillatory activities of potential antiarrhythmics in the same anesthetized dog. The reentry portion of the model was created surgically by a Y-shaped crushing around the tissue between the superior and inferior vena cava and tissue parallel to the AV groove. The pacing-induced tachycardia that results from circus movements around the tricuspid ring is very persistent in duration and regular in cycle length. The antifibrillatory activities were assessed by determination of the ventricular fibrillation threshold (VFT) using train-stimuli method. Control VFT was measured every 15-20 min in duplicate and followed by induction of atrial reentry. A drug was infused to intervene the atrial tachycardia. After the conversion of the arrhythmia (either by drug regimens or pacing), postdrug VFT was measured, again in duplicate. Bethanidine (20 mg/kg), procainamide (30 mg/kg), and WY-48986 (10 mg/kg), a Class III antiarrhythmic, were evaluated in this dual test. Bethanidine and procainamide prolonged the cycle length of atrial reentry to a greater extent than WY-48986. The atrial arrhythmias were consistently terminated by procainamide and WY-48986 whereas bethanidine converted the tachycardias in one of the five dogs studied. All three agents elevated VFT with bethanidine producing higher values than procainamide and WY-48986. In conclusion, the dual electrophysiologic testing system offers both economic and scientific advantages for the study of modes of action of antiarrhythmic agents.

Animals↗
PubMed2000

Loss of marrow reserve from dose-intensified chemotherapy results in impaired hematopoietic reconstitution after autologous transplantation: CD34(+), CD34(+)38(-), and week-6 CAFC assays predict poor engraftment.

Autologous hematopoietic stem cell transplantation (HSCT) is an increasingly successful modality for treating a variety of malignant disorders in the clinic. Experimental and clinical data suggest that prior exposure to cytotoxic agents that damage primitive stem cells results in impaired hematopoiesis after autologous HSCT. To further investigate the ability to predict for impaired hematopoiesis, we measured different stem/progenitor cell populations transplanted and time to engraftment. Patients with previously untreated, advanced-stage follicular lymphoma were treated in sequential prospective protocols with 6-8 cycles of standard-dose (SD) cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP), or four cycles of a higher-dose (HD) CHOP and granulocyte colony-stimulating factor, to induce remission prior to high-dose cyclophosphamide, total body irradiation, and autologous bone marrow transplantation (ABMT). Cryopreserved marrow samples obtained prior to ABMT were assayed for CD34(+), CD34(+)38(-), and cobblestone area-forming cell (CAFC) frequencies. Despite receiving similar numbers of nucleated cells at ABMT, HD-CHOP patients took significantly longer to attain platelet engraftment than the SD-CHOP patients. Marrow from the HD-CHOP patients contained significantly lower CD34(+), CD34(+)38(-), and week 6-8 CAFC frequencies than marrow from SD-CHOP-treated patients. Time to platelet engraftment was plotted against progenitor/stem cell numbers transplanted for each patient and threshold values were developed for all three stem/progenitor cell populations. These values were 0.5 x 10(6) CD34(+) cells/kg, 0.14 x 10(6) CD34(+)38(-) cells/kg, and 9500 week-6 CAFC/kg transplanted. Approximately 50% of patients received marrow progenitor/stem cell numbers above the threshold values and all engrafted without delay. However, transplantation of stem/progenitor cell numbers below threshold values did not uniformly predict for delayed platelet engraftment. These data provide further evidence for the association of low marrow reserve at ABMT, low numbers of stem/progenitor cells transplanted, and delayed hematopoietic recovery. However, there remains a group of patients who have rapid platelet engraftment after ABMT despite low numbers of progenitor/stem cells transplanted. These data suggest the presence of a crucial stem cell population not represented by the stem/progenitor cell populations studied in these experiments.

ADP-ribosyl Cyclase↗
PubMed2005

Reassessment of the cost-effectiveness of hormone replacement therapy in Sweden: results based on the Women's Health Initiative randomized controlled trial.

OBJECTIVES: The purpose of the study is to reassess the cost-effectiveness of hormone replacement therapy (HRT) based on new medical evidence found in the Women's Health Initiative (WHI). Within a model framework using an individual state transition model, the cost-effectiveness of 50- to 60-year-old women with menopausal symptoms is assessed based on a societal perspective in Sweden. METHODS: The model has a 50-year time horizon divided into a cycle length of 1 year. The model consists of the following disease states: coronary heart disease, stroke, venous thromboembolic events, breast cancer, colorectal cancer, hip fracture, vertebral fracture, and wrist fracture. An intervention is modeled by its impact on the disease risks during and after the cessation of therapy. The model calculates costs and quality-adjusted life years (QALYs) with and without intervention. The resulting cost per QALY gained is compared with the value of a QALY gained, which is set to SEK 600,000. The model requires data on clinical effects, risks, mortality rates, quality of life weights, and costs valid for Sweden. RESULTS: The cost-effectiveness ratios are estimated at approximately SEK 10,000, which is below the threshold value of cost-effectiveness. On the condition that HRT increases the quality of life weight more than 0.013 units, the therapy is cost-effective. CONCLUSIONS: In conclusion, given the new evidence in WHI, there is still a high probability that HRT is a cost-effective strategy for women with menopausal symptoms.

Cost-Benefit Analysis↗
PubMed1995

Colour Doppler myocardial imaging: potential applications in acquired and congenital heart disease.

Doppler myocardial imaging (DMI) is a new ultrasound technique which has been developed to allow colour Doppler imaging of cardiac structures as opposed to blood pool imaging. This is achieved by changing the velocity, filtering and threshold parameters of the standard colour Doppler algorithms. DMI parameters which can be measured are regional tissue velocity, acceleration and reflected Doppler energy. In addition, concomitant changes in the pulsed Doppler algorithms allow interrogation of instantaneous peak velocities during the cardiac cycle in the myocardial region in which the sample volume is placed. In both adult acquired heart disease and congenital heart disease, these new ultrasound parameters may provide new information on myocardial contractile function, diastolic function, myocardial perfusion and myocardial structure. The relative lack of image quality by chest wall attenuation inherent in the Doppler technique means that the methodology is potentially superior to standard grey-scale two-dimensional imaging in boundary detection and may prove to be of value in providing a robust boundary detection algorithm for use in volume calculations and in three-dimensional reconstruction of ventricular function.

Arrhythmias, Cardiac↗
PubMed1989

Circadian specificity in exercise training.

The purpose of this study was to determine whether metabolic and cardiorespiratory adaptations to exercise training are greater at the time of day of training than at another time. Twenty-seven subjects performed cycle ergometer tests in the morning (AM) and in the afternoon (PM) before and after a 6-wk period during which ten subjects trained regularly in the morning, seven subjects trained in the afternoon, and ten did not train. Training caused decreases in HR, VE, and rating of perceived exertion during submaximal exercise; a 7.7% increase (p less than 0.01) in VO2 max; and a 9.1% increase (p less than 0.01) in performance time. Adaptations (training effects) were independent of time of day of training for all variables except VO2 at the ventilatory threshold. Compared with each other, subjects who trained in the morning had relatively higher post-training thresholds in the morning, while subjects who trained in the afternoon had relatively higher values in the afternoon (p less than 0.05). This is evidence of circadian specificity in training and supports the notion of planning physical preparation to coincide with the time of day at which one's critical performance is scheduled.

Adult↗
PubMed2002

Effects of dinoseb on the life cycle of Daphnia magna: modeling survival time and a proposal for an alternative to the no-observed-effect concentration.

Risk assessment is in urgent need of more accurate toxic effect endpoints than those currently in use, especially for low concentrations. Often such endpoints are estimated by analysis of variance, linear interpolation, or smoothing. As these statistical methods are not always satisfactory, some authors have proposed to describe the entire dose-response curves by fully formalized parametric regression models whose parameters have toxicological meaning. These models allow a better evaluation of pollutant effects, including inter- and extrapolation to any other than the measured effect values. Following this line, a four-parameter logistic regression model (standard model) was fitted to survival data of Daphnia magna under pesticide (dinoseb) stress. The heterogeneity of the variance was taken into account with a both-sides logarithmic transformation. Besides the standard model, a hormesis and a threshold model were tested too. These two others models have been described in the literature and might better represent the dose-response function we are looking for. All three models showed a good fit to our data, and the statistics gave no hints as to which model is the most appropriate. As no evidence was seen for hormesis or for the existence of a threshold concentration, we used the simplest, namely, the standard model, for most of our calculations. Model calculations allow the quantification of the effects on individuals' longevity as well as on mean survival time of the population. We used them to define a no-effect value, the statistical-no-effect concentration (SNEC). The SNEC is based on the confidence bands of the modeled regression and represents the highest value for which an effect is statistically not different from the control. The SNEC is an alternative to classical endpoints, like the no-observed-effect concentration (NOEC) or the low-effect concentrations (e.g., EC10, EC5, EC1).

2,4-Dinitrophenol↗
PubMed1995

Time evolution of the number of functional murine eccrine sweat glands after irradiation: a quantitative analysis of experimental data using a model of proliferative and functional organization.

The function of eccrine sweat glands in the beta-pad of the mouse foot after irradiation was followed over time. Graded doses of X-rays were given to the foot, either as single doses or in two equal fractions separated by a 24-h interval. A quantitative, non-invasive, functional assay was used allowing repeated evaluation of the animals. Sweat gland function was assessed once a week for the first 6 weeks, and at 8, 10, 14, 18, 28, 38 and 45 weeks after irradiation. The beta-pad of the unirradiated foot was used as a control. The function dropped to a nadir within 8-10 weeks after irradiation, whereafter it gradually recovered, reaching a stable level 20-25 weeks after irradiation. These data were analyzed using a mathematical model of proliferative and functional organization of the sweat pore. The model provides a description of the time evolution of pore function, and its basic features were as follows. The functional subunit is a single sweat pore, which will be assayed as functional provided that it contains a number of functional cells above a critical threshold. The functional cells are capable of self renewal (a so-called 'flexible' tissue), and the proportion of proliferating cells is subject to homeostatic control. Irradiation is assumed to transfer a certain fraction of the cells into a state with a limited probability of successful division. This fraction is assumed to have a linear-quadratic dependence on dose. The values of all free model parameters were optimized by a maximum-likelihood fit to the experimental data. With optimized parameter values, the initial decrease, nadir, and long-term level of tissue function estimated from the model were in close agreement with the experimental observations for all the 28 dose groups. Some of the estimated model parameters are: growth fraction 4.2 +/- 0.2%; cell cycle time, 0.95 +/- 0.04 days; number of functional cells in a single pore in the unirradiated animal, 9.9 +/- 0.5; and alpha/beta ratio, 4.3 Gy (95% confidence interval 3.1-5.0 Gy). It is concluded that the present model, despite its relative mathematical simplicity, provides a close description of the postirradiation kinetics of functional cells in the mouse sweat gland.

Animals↗
PubMed2004

Importance of DNA repair in tumor suppression.

The transition from a normal to cancerous cell requires a number of highly specific mutations that affect cell cycle regulation, apoptosis, differentiation, and many other cell functions. One hallmark of cancerous genomes is genomic instability, with mutation rates far greater than those of normal cells. In microsatellite instability (MIN tumors), these are often caused by damage to mismatch repair genes, allowing further mutation of the genome and tumor progression. These mutation rates may lie near the error catastrophe found in the quasispecies model of adaptive RNA genomes, suggesting that further increasing mutation rates will destroy cancerous genomes. However, recent results have demonstrated that DNA genomes exhibit an error threshold at mutation rates far lower than their conservative counterparts. Furthermore, while the maximum viable mutation rate in conservative systems increases indefinitely with increasing master sequence fitness, the semiconservative threshold plateaus at a relatively low value. This implies a paradox, wherein inaccessible mutation rates are found in viable tumor cells. In this paper, we address this paradox, demonstrating an isomorphism between the conservatively replicating (RNA) quasispecies model and the semiconservative (DNA) model with post-methylation DNA repair mechanisms impaired. Thus, as DNA repair becomes inactivated, the maximum viable mutation rate increases smoothly to that of a conservatively replicating system on a transformed landscape, with an upper bound that is dependent on replication rates. On a specific single fitness peak landscape, the repair-free semiconservative system is shown to mimic a conservative system exactly. We postulate that inactivation of post-methylation repair mechanisms is fundamental to the progression of a tumor cell and hence these mechanisms act as a method for the prevention and destruction of cancerous genomes.

Animals↗
PubMed2002

Determinants of metabolic cost during submaximal cycling.

The metabolic cost of producing submaximal cycling power has been reported to vary with pedaling rate. Pedaling rate, however, governs two physiological phenomena known to influence metabolic cost and efficiency: muscle shortening velocity and the frequency of muscle activation and relaxation. The purpose of this investigation was to determine the relative influence of those two phenomena on metabolic cost during submaximal cycling. Nine trained male cyclists performed submaximal cycling at power outputs intended to elicit 30, 60, and 90% of their individual lactate threshold at four pedaling rates (40, 60, 80, 100 rpm) with three different crank lengths (145, 170, and 195 mm). The combination of four pedaling rates and three crank lengths produced 12 pedal speeds ranging from 0.61 to 2.04 m/s. Metabolic cost was determined by indirect calorimetery, and power output and pedaling rate were recorded. A stepwise multiple linear regression procedure selected mechanical power output, pedal speed, and pedal speed squared as the main determinants of metabolic cost (R(2) = 0.99 +/- 0.01). Neither pedaling rate nor crank length significantly contributed to the regression model. The cost of unloaded cycling and delta efficiency were 150 metabolic watts and 24.7%, respectively, when data from all crank lengths and pedal speeds were included in a regression. Those values increased with increasing pedal speed and ranged from a low of 73 +/- 7 metabolic watts and 22.1 +/- 0.3% (145-mm cranks, 40 rpm) to a high of 297 +/- 23 metabolic watts and 26.6 +/- 0.7% (195-mm cranks, 100 rpm). These results suggest that mechanical power output and pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling, whereas pedaling rate (i.e., activation-relaxation rate) does not significantly contribute to metabolic cost.

Adult↗
PubMed1994

Who finds cervical laser therapy painful?

To identify women who find outpatient laser cervical surgery painful we designed a prospective observational study correlating surgical pain with multiple variables. The pain scoring systems were validated by comparing the subjective linear analogue score with an objective scoring method. The pain of surgery was compared with age, parity, acute anxiety scores, psychological state, premenstrual syndrome scores, phase of the menstrual cycle, contraceptive use, menstrual history, nature of the lesion, and intraoperative bleeding. Anxious women with no children suffered most. Nulliparity, acute preoperative anxiety, and a history of dysmenorrhea independently predict high pain scores. Young women and those using the combined oral contraceptive pill also find laser surgery more painful but this is because they are less likely to have delivered children and more likely to suffer from dysmenorrhea. Psychological state, premenstrual syndrome score, phase of the menstrual cycle, type of surgery, and perioperative bleeding have no predictive value. We suggest that nulliparous women and dysmenorrhea sufferers who are anxious about outpatient surgery but ambivalent about hospital admission should be offered cervical surgery under general anesthesia. Parous women who do not suffer from dysmenorrhea can be reassured that outpatient laser treatment should be tolerable.

Adult↗
PubMed1994

Saliva electrolytes as a useful tool for anaerobic threshold determination.

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 min, until capillary blood lactate exceeded 4 mmol.l-1. A maximal test for maximum O2 uptake (VO2max) determination (initial load of 100 W and load increases of 50 W per 2 min) was also performed. Saliva and blood samples were obtained only in the submaximal test. Saliva threshold (Thsa) was defined as the point at which the first increase in either Cl- or Na+ occurred. Catecholamine threshold (Thca) was defined as the point at which a nonlinear increase occurred in either adrenaline or noradrenaline. The lactate (Thla) and ventilatory (Thve) thresholds were determined according to published criteria. No significant differences were found between Thsa values and the other methods of threshold determination. A high correlation was found between Thsa and Thla (r = 0.82, P < 0.01), and Thsa and Thca (r = 0.75, P < 0.05). These results support the validity of Thsa as a new method for noninvasive determination of the anaerobic threshold.

Adult↗
PubMed2006

The prey-dependent consumption two-prey one-predator models with stage structure for the predator and impulsive effects.

In this paper, we consider the prey-dependent consumption two-prey one-predator models with stage structure for the predator and impulsive effects. By applying the Floquet theory of linear periodic impulsive equation, we show that there exists a globally asymptotically stable pest-eradication periodic solution when the impulsive period is less than some critical value, that is, the pest population can be eradicated totally. But from the point of ecological balance and saving resources, we only need to control the pest population under the economic threshold level instead of eradicating it totally, and thus, we further prove that the system is uniformly permanent if the impulsive period is larger than some critical value, and meanwhile we also give the conditions for the extinction of one of the two preys and permanence of the remaining species. Thus, we can use the stability of the positive periodic solution and its period to control insect pests at acceptably low levels. Considering population communities always are imbedded in periodically varying environments, and the parameters in ecosystem models may oscillate simultaneously with the periodically varying environments, we add a forcing term into the prey population's intrinsic growth rate. The resulting bifurcation diagrams show that with the varying of parameters, the system experiences process of cycles, periodic windows, periodic-doubling cascade, symmetry breaking bifurcation as well as chaos.

Animals↗
PubMed2001

Multistationarity, the basis of cell differentiation and memory. II. Logical analysis of regulatory networks in terms of feedback circuits.

Circuits and their involvement in complex dynamics are described in differential terms in Part I of this work. Here, we first explain why it may be appropriate to use a logical description, either by itself or in symbiosis with the differential description. The major problem of a logical description is to find an adequate way to involve time. The procedure we adopted differs radically from the classical one by its fully asynchronous character. In Sec. II we describe our "naive" logical approach, and use it to illustrate the major laws of circuitry (namely, the involvement of positive circuits in multistationarity and of negative circuits in periodicity) and in a biological example. Already in the naive description, the major steps of the logical description are to: (i) describe a model as a set of logical equations, (ii) derive the state table from the equations, (iii) derive the graph of the sequences of states from the state table, and (iv) determine which of the possible pathways will be actually followed in terms of time delays. In the following sections we consider multivalued variables where required, the introduction of logical parameters and of logical values ascribed to the thresholds, and the concept of characteristic state of a circuit. This generalized logical description provides an image whose qualitative fit with the differential description is quite remarkable. A major interest of the generalized logical description is that it implies a limited and often quite small number of possible combinations of values of the logical parameters. The space of the logical parameters is thus cut into a limited number of boxes, each of which is characterized by a defined qualitative behavior of the system. Our analysis tells which constraints on the logical parameters must be fulfilled in order for any circuit (or combination of circuits) to be functional. Functionality of a circuit will result in multistationarity (in the case of a positive circuit) or in a cycle (in the case of a negative circuit). The last sections deal with "more about time delays" and "reverse logic," an approach that aims to proceed rationally from facts to models. (c) 2001 American Institute of Physics.

Journal Article↗
PubMed1986

Aerobic capacity during two-arm and one-leg ergometric exercise.

Previous studies have shown that maximal oxygen uptake (VO2 max) measured during two-arm cranking and one-leg cycling is about 70-78 per cent of VO2 max measured during two-leg cycling. The present study investigated the maximal physiological responses of eight healthy untrained males during two-arm, one-leg, and two-leg ergometric exercise. Two-arm cranking and one-leg cycling were found to be 55 and 66 per cent of two-leg VO2 max, respectively. The % VO2 max at which the anaerobic threshold occurred during the two-arm and one-leg exercise conditions were 57 and 68 per cent, respectively. These findings suggest that when the active muscle mass is limited, a progressive exercise test using one leg may elicit a higher VO2 max than with two arms.

Adult↗
PubMed1996

Control of the respiratory cycle in conscious humans.

We studied in conscious humans the relative strength of mechanisms controlling timing and drive components of the respiratory cycle around their resting set points. A system of auditory feedback with end-tidal PCO2 held constant in mild hyperoxia via an open circuit was used to induce subjects independently to change inspiratory time (TI) and tidal volume (VTI) over a wide range above and below the resting values for every breath for up to 1 h. Four protocols were studied in various levels of hypercapnia (1-5% inspired CO2). We found that TI (and expiratory time) could be changed over a wide range (1.17 - 2.86 s, P < 0.01 for TI) and VTI increased by > or = 500 ml (P < 0.01) without difficulty. However, in no protocol was it possible to decrease VTI below the free-breathing resting value in response to reduction of auditory feedback thresholds by up to 600 ml. This applied at all levels of chemical drive studied, with resting VTI values varying from 1.06 to 1.74 liters. When reduction in VTI was forced by the more "programmed" procedure of isocapnic panting, end-expiratory of volume was sacrificed to ensure that peak tidal volume reached a fixed absolute lung volume. These results suggest that the imperative for control of resting breathing is to prevent reduction of VTI below the level dictated by the prevailing chemical drive, presumably to sustain metabolic requirements of the body, whereas respiratory timing is weakly controlled consistent with the needs for speech and other nonmetabolic functions of breathing.

Acoustic Stimulation↗
PubMed1993

Maximal oxygen uptake and aerobic-anaerobic transition on treadmill and bicycle in triathletes.

The maximal aerobic capacity and the aerobic-anaerobic transition were analyzed on 14 triathletes performing an incremental work load on a bicycle ergometer and on horizontal or inclined treadmills. To compared the cardiorespiratory responses between cycling and running, the subjects were divided into 2 groups of 7 with similar aerobic capacity determined from cycle runs. The first group ran on horizontal treadmill while the second group performed similar exercise on inclined treadmill at constant grade (1.5%). Heart rate was recorded by electrocardiogram. Oxygen uptake (VO2), CO2 production (VCO2), respiratory frequency, and pulmonary ventilation were monitored at 30 s intervals through a Rudolph valve connected to a calibrated Oxycon V. Tidal volume, respiratory exchange ratio, equivalent O2 and CO2 were calculated from on-line computer. Aerobic and anaerobic thresholds were determined by a non-invasive method from pulmonary ventilation curves. The results showed that maximum oxygen uptake (VO2max) did not differ between the 2 types of ergometers. Pulmonary ventilation, heart rate and VO2 recorded at aerobic and anaerobic thresholds depended on the mode of exercise and reached the highest values on inclined treadmill. The amount of muscle mass, the type and the distribution of active motor units involved in each exercise test might be at the origin of these differences. This indicates that, when assessing a training program from anaerobic threshold values, it is necessary to take into consideration the type of ergometer used and the protocol performed.

Adult↗
PubMed1995

Generation of human auditory steady-state responses (SSRs). I: Stimulus rate effects.

Auditory evoked responses were recorded in 16 normally hearing subjects in order to investigate the mechanisms underlying the generation of the 40 Hz steady-state response (SSR). In the first part of our study, auditory potentials were evoked by 0.1 ms clicks presented at 105 dB p.e. SPL with repetition rates of 7.9 (to obtain middle latency response, MLR), 20, 30, 40, 50, 60 Hz. In each subject predictions of the responses recorded at stimulus repetition rates of 30, 40, 50, 60 Hz were synthesized by superimposing MLRs at suitable time intervals. The calculated mean amplitude/rate and phase/rate functions behaved similarly for the recorded and predicted curves, showing the highest amplitude at 40 Hz and a linear increase of phase values when increasing the stimulus rate. Nevertheless the synthetic curves closely predicted amplitude and phase values of the recorded responses only at 40 Hz. At frequencies below 40 Hz, the mean amplitude of the predicted curve was lower than that of the recorded one while at frequencies above 40 Hz the mean amplitude was higher. Predicted phase values were found lagging at 30 Hz, and leading at 50 Hz and 60 Hz in comparison to phase values calculated on the recorded responses. Our findings suggest that a model based on the linear addition of transient MLRs is not able to adequately predict steady-state responses at stimulus rates other than at 40 Hz. Other mechanisms related to the recovery cycle of the activated system come into play in the steady-state response generation causing a decrease in amplitude and an increase in phase lag when increasing the stimulus repetition rate.

Acoustic Stimulation↗
PubMed1991

Circulating leucocyte and lymphocyte subpopulations before and after intensive endurance exercise to exhaustion.

Seventeen healthy cyclists [age 20.8 (SD 4.8) years; body mass 68.3 (SD 7.7) kg; body fat, 11.4 (SD 2.6) %; height, 179.1 (SD 5.9) cm; VO2max, 60.9 (SD 7.4) ml.kg-1.min-1] conducted intensive endurance exercise to exhaustion (stress test, ST) on a cycle ergometer at 110% of their individual anaerobic threshold [Than,individual; exercise intensity, 3.97 (SD 0.6) W.kg-1; duration, 23.9 (SD 8.3) min; maximal lactate concentration, 7.39 (SD 2.59) mmol.l-1]. The distribution of leucocyte subpopulations was measured flow cytometrically: before, immediately after (0), 5 (+5), 30 (+30) and 60 (+60) min after ST. The lymphocytes (0 min) and granulocytes (+60 min) were mainly responsible for the increase of leucocytes. Lymphocytes were significantly lower at +30 and +60 min than before. CD3-CD16/CD56+ (+480%) and CD8(+)-lymphocytes (+211%) increased at 0 min more than the other lymphocyte subpopulations (CD(3+)-cells, +100%; CD(4+)-cells, +56%; CD(19+)-cells, +64%). CD3-CD16/CD(56+)- and CD(8+)-cells also were mainly responsible for the decreased values of lymphocytes at +30 min and +60 min compared to before. At 0 min naive CD(8+)-cells (CD45RA+, CD45RO-) increased more than memory CD(8+)-cells (CD45RA-, CD45RO+). Changes of naive and memory CD(4+)-cells did not differ. All lymphocyte subpopulations, in particular CD(8+)- and CD3-CD16/CD(56+)-cells, decreased rapidly between 0 min and 5 min. We conclude that an intensive endurance exercise to exhaustion causes a mobilisation of lymphocytes, especially of natural killer cells (CD3-CD16/CD56+) and naive, unprimed CD(8+)-cells (CD45RA+, CD45RO-) which may be transported to injured muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗