[Coffee and health].
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Anxiety Disorders↗
Biomedical subjects
L Hirvonen
Publications and source records attributed to L Hirvonen.
Cardiac function in hypothermia.
Hypothermia retards cardiac contraction and prolongs the subphases of the cardiac cycle in varying degrees. Six anaesthetized beagle dogs were catheterized and cooled between ice bags until the aortic blood temperature was 25 degrees C and then rewarmed to normothermia. The speed of relaxation decreased to a half from its value in normothermia as indicated by the time constant of exponential isovolumic ventricular pressure fall and by the change in the negative dp/dt. It is suggested that retardation of relaxation is connected with temperature dependent changes in calcium kinetics. Decrease of cardiac output was mediated mainly by decreased stroke volume indicating sympathetic tone in spite of cold narcosis.
Animals↗
The cardiovascular effects of deconditioning after endurance training in rats.
The haemodynamic effects of endurance training and physical deconditioning were studied in anaesthetized rats using aortic and left ventricular pressure recordings and volume measurements by thermodilution method during isoproterenol and CaCl2 loads. The resting stroke volume was significantly larger in the training group (TG I, n = 10) than in the control group (CG I, n = 13). During the CaCl2 infusion stroke index, end-diastolic and end-systolic volumes increased in the TG I, but decreased in the CG I. Both isoproterenol and CaCl2 decreased systemic vascular resistance in the TG I, but increased it in the CG I. After a six-week deconditioning following training period (TG II, n = 10) stroke index, end-diastolic and end-systolic volumes decreased during CaCl2 and isoproterenol infusions similarly to the control deconditioning group (CG II, n = 12). These responses differed significantly from those observed in the TG I. Peripheral resistance increased in both the CG II and the TG II. Cardiac hypertrophy observed during training was partly reversed after the deconditioning period. In conclusion, endurance training improves the pumping performance of the rat heart by enhancing the diastolic filling of the left ventricle and decreasing peripheral resistance during inotropic load. Left ventricular contractility is not affected. A six-week deconditioning period after endurance training returns the haemodynamic changes to sedentary levels.
Animals↗
Anabolic steroids alter the haemodynamic effects of endurance training on the canine left ventricle.
The effects of six week, high-dose anabolic steroid treatment (methandienone, 1.5 mg/kg/day) on the changes in left ventricular function induced in dogs by endurance training were studied by a catheterization technique under anaesthesia. Pacing, isoproterenol and dextran infusions were used as loading tests (respectively). Dogs were randomized into an exercise group (EG, n = 7) and an exercise-steroid group (ESG, n = 7), the latter receiving anabolic steroids as well as participating in the training program. In a standardized submaximal exercise test, the heart rate of unanesthetized dogs was lower both in the EG (p less than 0.001) and in the ESG (p less than 0.01) after the training period than before it. In the EG the resting systemic vascular resistance (SVR) before haemodynamic interventions was lower (p less than 0.05) and left ventricular stroke work (SW) was higher (p less than 0.05) after the training period than before. In the ESG, left ventricular ejection fraction (EF) decreased with training and anabolic steroid treatment (p less than 0.05). After the training period isoproterenol increased the maximum velocity of the cardiac contractile element significantly more (p less than 0.05) in the EG than in the ESG. Also SW increased in the EG (29%, p less than 0.001), but not in the ESG (-11%, NS). Endurance training increased the left ventricular end-diastolic and stroke volumes during isoproterenol infusion, but this training effect was attenuated by simultaneous anabolic steroid treatment (p less than 0.05 between the groups in both cases). During the isoproterenol test SVR decreased less in ESG than in EG (p less than 0.05 between).(ABSTRACT TRUNCATED AT 250 WORDS)
Anabolic Agents↗
The effects of anabolic steroids and endurance training on systolic time intervals in the dog.
The effects of administration of anabolic steroids (SG, n = 6), endurance training (EG, n = 7) and a combination of steroid administration (Methandienone R) and training (ESG, n = 7) on systolic time intervals (STI) in the dog heart were compared with control dogs (CG, n = 7) by a catheterization technique. Isoproterenol infusion was used as a positive inotropic load. Physical performance was checked with submaximal exercise test, a 30 beats min-1 decrease in heart rate response was considered a sufficient training effect. During isoproterenol infusion, exercise was found to enhance the pump performance of left ventricle and increased stroke volume was related to shortened pre-injection period (PEP) (P less than 0.05), whereas steroid administration failed to induce any significant differences in PEP or PEP/LVET (LVET = left ventricular ejection time) when compared with CG. However, when steroid administration was combined with endurance training, both PEP and PEP/LVET were lengthened significantly in comparison with EG (P less than 0.05 and P less than 0.01, respectively). In conclusion, it seems that the anabolic steroids affected the STIs only, when their administration was combined with endurance training.
Anabolic Agents↗
Hemodynamic effects of endurance training on canine left ventricle.
To investigate the effects of endurance training on myocardial performance seven beagle dogs (exercise group, EG) were trained by treadmill running for 6-7 wk. Before and after experimental period the EG and control group (CG, n = 7) underwent a standard submaximal exercise test (SMT), and hemodynamic status was checked during anesthesia by catheterization technique exposing the animals to different loadings: pacing, volume loading, and isoproterenol infusion. The increase of heart rate during SMT was about 30 beats/min less in the EG than in the CG. A highly linear relationship between stroke work and end-diastolic volume was observed within the groups (for EG r = 0.953, for CG r = 0.846), but the slope of the regression line obtained for EG appeared to be significantly (P less than 0.001) greater. In EG isoproterenol induced increases in end-diastolic (27%), end-systolic (37%), and stroke volumes (19%), but, on the contrary, decreases of these volumes in CG (19, 15, and 22%, respectively); ejection fraction remained unchanged for both EG and CG. Ventricular stroke work was significantly greater in EG. Systemic vascular resistance decreased in EG in every loading test. The results indicate an improved pump performance, which is related not only to the heterometric autoregulatory adjustments, but also to extracardial adaptations.
Animals↗
Time constant of isovolumic pressure fall in the intact canine left ventricle.
The two standard methods of computation of the time constant of the isovolumic single exponential decay of the left ventricular pressure were compared in anaesthetised, artificially ventilated, closed chest dogs in 87 experiments. In 23 additional experiments, carried out under basal steady state conditions, the time constant attained a mean (SD) value of 32(5) ms when computed according to the method with zero pressure asymptote assumption (Tz) and 39(7) ms when estimated according to a fit with variable pressure asymptote (Tv). Phenylephrine infusion significantly prolonged Tz from 31(6) to 46(12) and Tv from 39(7) to 92(52) ms. The increase in Tv was significantly greater than that in Tz. Propranolol increased Tv by 50% but Tz remained unaltered. Isoproterenol significantly decreased Tz from 33(2) to 18(3) and Tv from 38(3) to 29(3) ms. The decrease in Tz was significantly greater than that in Tv. Calcium chloride and atrial pacing decreased time constants, but volume loading by dextran infusion did not affect them. With regard to the whole material, the linear regression analysis yielded 0.776 as the coefficient of correlation between Tz and Tv. The two methods of time constant calculation appeared to diverge significantly always when changes in afterload or sympathetic activity were involved. These results indicate the dependence of relaxation on afterload but the independence on preload or ejection timing. In the light of these results the zero pressure asymptote method is recommended for the time constant computation as the practical choice when relaxation of the intact left ventricle is assessed.
Animals↗
Electromechanical delay in the intact dog heart.
A computer method was developed for the determination of electromechanical delay defined as the time between the onset of Q-wave and the onset of the left ventricular systolic pressure rise. It was validated for heart catheterization studies on 56 intact anaesthetized beagle dogs in 86 sessions. The mean basal value of the electromechanical delay was 22 +/- 4 msec. Heart rate, contractility, preload and afterload were changed by atrial pacing and by infusions of calcium chloride, isoproterenol, propranolol, dextran and phenylephrine. Increase of heart rate by pacing from the spontaneous rate of 90 per min to 240 per min prolonged the electromechanical delay from 21 +/- 5 to 33 +/- 14 msec (P less than 0.001). Otherwise the duration of electromechanical delay changed independently of the heart rate. If it changed, the direction of the change followed that of the pre-ejection period. Its proportion of the pre-ejection period varied from 26 to 52%. The electromechanical delay shortened when a positive inotropic effect was noticed or the presystolic fibre length increased.
Animals↗
Electrocardiogram of the reindeer, Rangifer tarandus tarandus.
Electrocardiograms were recorded for 50 Finnish reindeer of age 1 day to 9 years, using standard and unipolar extremity leads in the frontal plane. The range of heart rate was 40-250 beats per minute. Atrial and ventricular depolarization times were 5-10 ms shorter in newborn calves than in other reindeer, and showed only minor variance with respect to heart rate. The duration of depolarization was dependant on heart rate, and was more rapid in young calves. A-V conduction time decreased with increasing heart rate. The mode of the QRS vector was 280-290 degrees, and the mode of the T vector 200-230 degrees in the older animals, but 100-120 degrees in young calves. The main deflection in the QRS complex was S in the leads II, III and aVF.R was dominant in aVL and I.
Age Factors↗
Observations on circulatory adjustment in newborn reindeer and elk.
Haemodynamics of two reindeer (18 h and 4 days old) and one elk (1 week old) calves were studied by catheterization and angiography. Early closure of foetal shunts, high cardiac output and large ejection fractions were observed in all three animals. Pulmonary arterial blood pressure decreased to the full-grown level during the first days of life in the reindeer. Electrocardiography showed cranial-orientated QRS vector in both species. The cardiovascular system of the Cervidae is well developed at birth and adapts rapidly during the neonatal period.
Age Factors↗
Renography in the foetal and newborn lamb.
Hippuran renography indicates kidney function as reflected in a substance handled mainly by the tubules. The working conditions of the kidneys undergo a fundamental change at birth with the cessation of placenta circulation, and these organs become responsible for waste elimination. 131I-hippuran renography was performed on foetal and newborn lambs using a gamma camera and a computer. The intervals of the maximum- and half-time renal activity were determined. These decreased by a half from mean foetal value of Tm=7 mi and T12=19 min in 1 to 1.5 days and reached the full-grown level in 2 to 5 weeks. No sudden change occurred as a result of the first breath.
Animals↗
Smoking and the subjective health condition among Finnish military conscripts.
Information on smoking habits and a subjective self-estimate of general state of health was collected by means of a questionnaire from 400 conscripts in Northern Finland. The data were treated by factor analysis. Long-term fatigue, frequent headache, insomnia and occasional depression were less frequent among non-smokers than among smokers.
Depression↗
Disappearance of tracheobronchial fluid at birth in the lamb.
Bronchography was performed in lambs before, during and after the first breath. Swallowing of the contrast medium containing tracheobronchial fluid was observed before the first breath. Intratracheal pressure changes ranging up to 20 mmHg were observed during respiratory movements which did not open the alveoli. The lamb did not start breathing as long as the snout was covered although there was a direct connection between the trachea and atmospheric air through a tracheostomy. When the snout was uncovered a lamb in good condition drew its first breath and the spreading of the contrast material into the peripheral parts of the lungs was almost explosive. The diameter of the tracheobronchial tree widened as a result of the initiation of respiration. It is suggested that both swallowing in the pharynx and absorption into the blood circulation below the larynx play an essential role in the disappearance of the tracheobronchial fluid. Intrauterine aspiration seems less probable in the light of these observations.
Animals↗
Survival of rats after combined injuries of whole-body LD50/30 days irradiation, uncomplicated tibial fracture, and cold exposure.
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Animals↗
[Tobacco smoking and educational achievement].
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Educational Measurement↗
[Neurovegetative problems in newborn infants].
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Animals↗