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Biomedical subjects

I Ostádalová

Publications and source records attributed to I Ostádalová.

At least 19 recordsLinked to original sources
PubMed2004

Low body weight and cardiac tolerance to ischemia in neonatal rats.

Adaptation to intermittent high altitude hypoxia (IHAH) increases tolerance of the isolated neonatal rat heart to ischemia and potentiates protection induced by ischemic preconditioning. In addition to the protective effect, IHAH significantly reduces growth of the animals. The aim of the present study was, therefore, to find out whether low body weight per se might influence cardiac sensitivity to oxygen deprivation. Low body weight was induced either by IHAH (barochamber, 8 h/day, 5000 m) from postnatal day 1 to 10 (HLBW), or by a higher number of sucklings per mother (14 instead of 8), again from postnatal day 1 to 10 (NLBW). Control animals (8 littermates per mother) were kept under normoxic conditions (Controls). The recovery of developed force following 40 min of global ischemia was measured in isolated hearts from 10-day-old rats by perfusing them in the Langendorff mode with Krebs-Henseleit solution at constant pressure, temperature and rate. Ischemic preconditioning was induced by three 3-min periods of global ischemia, each separated by 5-min periods of reperfusion. Low body weight in HLBW and NLBW groups was accompanied by increased hematocrit, and decrease in absolute heart weight (both wet and dry) and developed force. On the other hand, higher hydration, increased cardiac tolerance to ischemia and potentiation of protection by ischemic preconditioning were observed in HLBW rats only. This experimental group also exhibited the highest relative heart weight. It may be concluded that low body weight alone does not influence cardiac tolerance to ischemia in neonatal rats.

Altitude Sickness↗
PubMed1995

Reciprocal changes in the postnatal expression of the sarcolemmal Na+-Ca(2+)-exchanger and SERCA2 in rat heart.

The aim of this study was to examine the relationship between sarcolemmal Na(+)-Ca2+ exchangers and sarcoplasmic reticulum (SR) Ca(2+) -ATPase (SERCA2) expression and the developmental differences in cardiac Ca2+ handling. Postnatal steady-state mRNA and protein levels were analysed in rat ventricular myocardium by Northern and immunoblot analysis, respectively. This was compared to Na+ gradient-induced and SR oxalate-supported Ca2 transport in isolated membranes. Na(+)-Ca2+ exchanger mRNA declined by 75% between day 1 and 30, whereas SR Ca2+ ATPase mRNA levels increased by 97% during this period. The Na(+)-Ca2+ exchanger mRNA/Ca(2+)-ATPase mRNA ratio was found to be inversely related to post-natal age. The changes in mRNA levels were associated with corresponding developmental differences in the Ca2+ transport activities of the respective membrane proteins. In crude membranes, the Na(+)-dependent Ca2+ transport activity (at 75 microM Ca2+) declined gradually (P < 0.01; mean +/- S.E.) from 17.7 +/- 2.4 nmoles Ca2+/g wet tissue/2s at day 1-3 (n = 5) to a value of 4.2 +/- 1.1 at day 40 (n =4). Conversely, SR Ca2+ uptake increased (P < 0.01) 2.6-fold during this period. The inversely related changes in the post-natal expression and function of the Na(+)-Ca2+ exchanger and SR Ca(2+)-ATPase suggest a coordinated control at the pretranslational level of the cellular Ca2+ transport processes mediated by the two membrane proteins.

Aging↗
PubMed1995

Inotropic effect of increasing concentration of Ca2+ in the fetal rat heart with retinoic acid-induced malformations.

Cardiac malformations (pulmonary trunk stenosis, ventricular septal defect, and double outlet right ventricle) were induced by the administration of two doses of retinoic acid (RA) to Wistar rats on d 13 of pregnancy. Contractile performance of the isolated perfused rat heart and its inotropic response to Ca2+ (0.6-10.0 mmol.L-1) was studied in 20-d-old fetuses. The body weight of RA-exposed fetuses was significantly lower compared with controls. RA negatively influenced the contractile parameters of the fetal rat heart. The most pronounced effect was, except at a Ca2+ concentration of 2.5 mmol.L-1, observed at developed force at all other concentrations. Simultaneously, the sensitivity to Ca2+, expressed as the Ca2+ concentration at which 30% of maximum was attained, ws significantly lower in RA-exposed hearts. This implies that the malformed heart is more dependent on the extracellular sources of Ca2+.

Animals↗
PubMed1995

Effect of prenatal hypoxia on contractile performance and responsiveness to Ca2+ in the isolated perinatal rat heart.

The effect of prenatal hypoxic stress on the cardiac contractile function and responsiveness to calcium was studied in rats during the perinatal period. Pregnant rats were exposed to intermittent high altitude hypoxia from day 14 to 18 of pregnancy. Foetal hearts (prenatal day 22) and the hearts of offsprings (days 1, 4 and 7) were isolated and perfused in the Langendorff mode. Developed force of contraction (DF) as well as the rate of force development and fall were measured a) at the Ca2+ concentration of 1.25 mmol.l-1, b) under increasing Ca2+ concentration (from 0.6 to 10.0 mmol.l-1). Body and heart weights were significantly smaller in hypoxic than in matched control rats starting from day 1. The contractile performance of hypoxic hearts did not differ from controls. Their inotropic response to increasing Ca2+ concentrations was, however, significantly reduced on prenatal day 22 and postnatal day 7. Our results suggest that prenatal maternal hypoxia affects the cardiac inotropic responsiveness to Ca2+ even postnatally.

Animals↗
PubMed1993

Early postnatal development of contractile performance and responsiveness to Ca2+, verapamil and ryanodine in the isolated rat heart.

Contractile performance of the isolated perfused rat heart and its inotropic response to Ca2+, verapamil and ryanodine was studied in 1-, 2-, 4-, 7- and 12-day-old animals. Values of the developed force revealed two different phases: a slow decrease from day 1 to day 4 followed by a steep increase up to day 12. A similar biphasic time course was observed in the magnitude of the inotropic effect of Ca2+ (0.6-10.0 mmol.l-1): decrease from day 1 to day 4 followed by an increase up to day 7. The sensitivity to Ca2+ was, however, not changed. An analogous biphasic response was also observed during perfusion with the calcium antagonist verapamil (10(-9) to 3.3 x 10(-7) mol.l-1): the sensitivity to negative inotropic effect rose from day 1 to day 4 and then decreased at day 7 (values of IC50 were 170 +/- 61, 17 +/- 6 and 171 +/- 60 10(-9) mol.l-1 S.E.M. on day 1, 4 and 7, respectively). The contractile response to the inhibitor of calcium release from sarcoplasmic reticulum (SR)--ryanodine (10(-6) mol.l-1)--was surprisingly high already in 1-day-old animals (inhibition of contraction by more than 50%) indicating the presence of functionally active SR in the rat heart just after birth. Our data clearly shows that the early development of contractile function and inotropic responsiveness of the rat heart is not linear and changes dramatically during the first week of life.

Aging↗
PubMed1992

Effect of isoproterenol on 85Sr accumulation in the myocardium of the rat during postnatal ontogeny.

The aim of this study was to establish whether administration of toxic doses of isoproterenol (IPRO) increases the accumulation of strontium--a homologue element of calcium--in the rat heart during postnatal development. It has been shown that in 14-day-old animals 85Sr uptake was not increased; starting from the 30th day of postnatal life this parameter increases significantly up to adulthood.

Animals↗
PubMed1992

85Sr uptake by the chick embryonic heart: effect of high doses of isoproterenol.

The aim of the present study was to establish whether intraamnial administration of toxic doses of isoproterenol to chick embryos increases cardiac accumulation of strontium, the homologue element of calcium. It has been shown that the ability of embryonic tissues (blood, heart, and liver) to accumulate 85Sr decreases significantly during ontogeny. Administration of isoproterenol to chick embryos did not elevate the concentration of 85Sr in the heart. It seems, therefore, that isoproterenol-induced developmental changes in the chick embryonic myocardium are not necessarily due to intracellular calcium (as measured by 85Sr) overload.

Animals↗
PubMed1989

Effect of mercury on selenium binding to rat lens proteins in vitro.

The effect of mercury in the incubation medium on selenium influx, efflux and distribution was studied in eye lenses of 14-day-old rats. The presence of mercury did not affect the uptake of selenium into a water-soluble protein fraction but increased considerably its content in water-insoluble proteins and thus also the selenium influx into experimental lenses. The efflux from experimental lenses yielded significantly lower amounts of released selenium, most of the selenium being bound to proteins. In contrast, efflux experiments with control lenses showed most of the selenium to be in the medium in the form of free anions. The selenium content in experimental lenses decreased after the efflux only in the fraction of water-soluble proteins, while the decrease in control lenses was found in both fractions and was relatively higher in water-insoluble proteins. During both influx and efflux experiments the lenses of both groups released a small of proteins, but no difference found between the two groups.

Animals↗
PubMed1988

Effect of isoprenaline on 85Sr accumulation in the myocardium of the adult rat.

The administration of a single dose of isoprenaline to adult male rats stimulated 85Sr uptake by their blood, liver and myocardium. Whereas the 85Sr concentration in the blood and liver rose by only 36% and 42% respectively, the increase in the various compartments of the heart was 5-7 times this value. This finding is also documented by the increase in the ratio of the 85Sr concentration in the heart and blood. The increase observed in 85Sr accumulation in the myocardium is comparable to the repeatedly described changes which occur in radioactive calcium after the administration of isoprenaline.

Animals↗
PubMed1988

Selenium metabolism in rats after administration of toxic doses of selenite.

We studied organ concentration, excretion and excreted forms of selenium in young and adult rats after a single s.c. injection of a sublethal dose of 75Se-selenite. In the young about a 10-fold higher concentration of 75Se in blood, liver, kidneys and In the young, about a 10-fold higher concentration of 75Se in blood, liver, kidneys and heart was found at all the experimental intervals studied (1-7 days). The highest 75Se concentration in the young was in the liver while in the adults it was found in the kidneys. The spectrum of radioselenium metabolites in the urine was the same in both groups. However, the main product excreted by young rats was 75Se-glutathione selenotrisulphide and an unidentified neutral substance while it was the trimethylselenonium ion in the adults. Ontogenetic differences in selenium metabolism could be one of the factors underlying the differences in the response of the young and the adult rats to toxic doses of selenite.

Aging↗
PubMed1987

Calcium antagonists and the developing heart.

Ontogenetic differences in cardiac sensitivity to calcium antagonists were studied in chick embryonic and postnatal immature rat heart. It has been found that verapamil exhibits no protective effect on isoprenaline-induced changes of the chick embryonic heart. Furthermore, it increased the mortality of experimental embryos. The mortality of verapamil-treated rats was age-dependent, increasing with decreasing age of animals. Similarly, the intensity of negative inotropic response of the isolated right ventricular myocardium and isolated perfused rat heart was significantly greater in the youngest age groups. These results point to the possible negative consequences of the clinical use of calcium antagonists during the early phases of ontogeny.

Age Factors↗
PubMed1985

Age dependence of selenite uptake in rat eye lenses.

75Se-selenite was administered to young and adult rats in subcutaneous injection or added into the medium in which eye lenses were incubated. The 75Se uptake in lenses of the young was significantly higher in comparison with adults both in vivo and in vitro. The in vivo 75Se uptake, referred to unit of lens weight, was almost 500 times higher in young animals while in vitro it was only five times higher, which apparently reflects the age-dependent differences in the structure and function of membranes and/or system barriers.

Aging↗
PubMed1984

Nutritional dependence of the incidence of selenite-induced cataracts in rats.

The protective effect of premature weaning on the incidence of selenite-induced cataracts in young rats can be abolished by the timely administration of the main components of nourishment, including water. The results suggest that water which is a common factor of all supplemented nutrients could play an important role in the development of selenium cataract.

Animals↗
PubMed1983

Delimitation of the period of sensitivity to the cataractogenic action of selenite in rats.

The period when selenite is able to induce cataracts begins on the 2nd and ends on the 17th day of postnatal life. Higher doses of selenite do not change the beginning of the cataractogenic period but may induce rare cataracts (up to 17%) when given on the 18th and 19th day of life. The lethal effect of selenite, which predominantly depends on the administered dose, is significantly lowered during the period of selenite-induced cataractogenesis.

Age Factors↗
PubMed1982

Ontogenic changes in selenite metabolism in rats.

Radioselenium concentration and excretion was studied after administration of 75SE-labelled selenite to male rats during ontogeny. The concentration of radioselenium in individual organs decreases with increasing age. The largest differences between young and adults were in the quantity and quality of excreted substances. During 2 h after the administration of 20 mumol selenite/kg young rats excreted 2.4% of the dose, essentially in the urine only, whilst adults excreted a total of 11%, distributed equally in breath and urine. The part excreted as methylated metabolites was 0.1% of the administered dose in young and 6.3% in adult rats. These results support the hypothesis that the differences in the sensitivity to the toxic action of selenite between young and adult rats can be due to ontogenic differences in selenium metabolism.

Aging↗