Heterometric regulation and calcium sensitivity of the infarcted rat heart.

1. The surviving hypertrophied muscle remaining after myocardial infarction in rats is less sensitive to extracellular Ca2+ than the normal myocardium. Since the inotropic effect of Ca2+ is modulated by sarcomere length, the present study was undertaken to determine if Ca2+ desensitization of infarcted left ventricles (LV) can be modulated by increasing the diastolic pressure (DP).

Time course of changes in heart rate and sympathetic tone after coronary artery ligation in rats.

The purpose of this study was to investigate the changes of heart rate (HR) and sympathetic tone occurring after myocardial infarction. Male rats (200-250 g) were submitted to ligation of the anterior branches of the left coronary artery to produce infarction (INF, N = 26) or to sham surgery (SO, N = 24). Groups of animals (N = 6-8) were studied 1,3,7 and 15 days later.

Post-rest contractions of amphibian cardiac muscle.

Post-rest potentiated contractions have been reported to be more dependent on Ca2+ stored in intracellular sites than on transmembrane Ca2+ influx. The phenomenon was examined using toad ventricular strips contracting isometrically and superfused with Ringer solution. Toad ventricular strips did not present post-rest potentiation, a fact that may be explained by the reduced volume of the sarcoplasmic reticulum in the amphibian myocardium.

Changes in performance of the surviving myocardium after left ventricular infarction in rats.

Study Objective: The aim was to investigate left ventricular performance of infarcted hearts during scar formation and development of hypertrophy in the surviving myocardium.

Design: Hearts were perfused according to the Langendorff technique and left ventricular function curves were obtained by inserting a distensible balloon into the ventricular cavity. The isovolumetric systolic pressure was measured as diastolic pressure was changed from 0 to 25 mm Hg and during inotropic interventions produced by Ca and isoprenaline.

Local activation of contraction in isolated rat ventricular myocytes.

The aim of this paper was to examine whether contraction (which is thought to result from Ca-induced release of Ca2+ from the sarcoplasmic reticulum) can propagate along a cardiac cell. The experiments were performed on isolated rat ventricular cardiac myocytes. Two techniques were used to initiate contraction in a localized region of the cell.

Characterization of human cDNA and genomic clones for glial fibrillary acidic protein.

Both a partial cDNA clone and a complete genomic clone have been isolated for human gfa, the gene encoding the major component of astrocyte intermediate filaments, glial fibrillary acidic protein (GFAP). The nucleotide sequence of the entire coding region and 102 bp of the 5' flanking DNA was determined. The mRNA start site was identified by primer extension and probe protection experiments, and a novel in vitro transcription and translation procedure was then used to establish that the first ATG in the mRNA initiates GFAP synthesis.

Neural control of glutamine synthetase activity in rat skeletal muscles.

The mechanism of glutamine synthetase induction in rat skeletal muscle after denervation or limb immobilization was investigated. Adult male rats were subjected to midthigh section of the sciatic nerve. At 1, 2, and 5 h and 1, 2, and 7 days after denervation, rats were killed and denervated, and contralateral control soleus and plantaris muscles were excised, weighted, homogenized, and assayed for glutamine synthetase.

Left ventricular length dependent activation in the isovolumetric rat heart.

Study Objective: The aim of the study was to examine, in a whole heart preparation, the relationship between length changes in cardiac muscle and tension development and length dependent activation.

Design: Rat hearts were perfused by the Langendorff technique and isovolumetric pressure changes in the left ventricle, produced by increasing diastolic pressures (0, 5, 10, 15, 20, 25 mm Hg), were studied at different calcium concentrations (0.5, 1.

Myocardial depression produced by unilateral nephrectomy in rats.

Previous experiments using 15 days renovascular hypertensive rats and their sham operated uninephrectomized controls suggested a decrease in contractile force developed by the papillary muscles from uninephrectomized rats. Because of the implications of such findings two sets of experiments were performed. The first set 15 days after operations, compared four groups of Wistar male rats: uninephrectomized, sham operated controls and renovascular hypertensive 1K1C and 2K1C.

Neuron-glial interactions involved in the regulation of glutamine synthetase.

Cocultures of rat cortical astrocytes with cerebellar granule cell neurons, but not a variety of other cell types tested, resulted in an induction of glutamine synthetase (GS) mRNA over the basal levels expressed in pure astrocyte cultures. This induction involved both contact- and noncontact-mediated events and may be a result of astroglial differentiation promoted by interactions with the primary neurons. Astrocytes grown in the presence of the granule neurons (but not the other cell types tested) exhibited a more complex, process-bearing morphology typical of more differentiated cells.

The ontogeny and localization of glutamine synthetase gene expression in rat brain.

A 2.4 kb cDNA clone containing the coding sequence for glutamine synthetase (GS) was isolated from a rat brain cDNA library, and a probe constructed from this cDNA was utilized in Northern analysis of total RNA to study the tissue distribution and the ontogeny of GS mRNA expression in the rat brain from embryonic day 14 (E14) to adulthood. The levels of GS mRNA were highest in the brain, followed by kidney and liver.

Stabilization of tubulin mRNAs by insulin and insulin-like growth factor I during neurite formation.

Neurotrophic factors may increase axon and dendrite growth in part by regulating the content of cytoskeletal elements such as microtubules, which are comprised of tubulin subunits. The mechanism by which insulin, insulin-like growth factors (IGFs), and nerve growth factor (NGF) can increase the relative abundance of tubulin mRNAs as a prelude to neurite formation was studied. Insulin significantly increased the abundance of tubulin mRNAs relative to total RNA in cultured human neuroblastoma SH-SY5Y cells.

[Anesthesia of horses in the standing position].

Painful interventions can be performed on horse in standing position by means of sedative analgesia, also called standing-position anaesthesia. Combinations of anaesthetics are quite often used, in that context, for the purpose of producing analgetic effects stronger and more reliable than those that would be obtainable from one anaesthetic alone. The following combinations were comparatively tested for their analgetic and sedative effects and their effects upon the organism: Chloralhydrate with Ursonarkon (oxazolidone), Chloralhydrate with Rompun (xylazine), Chloralhydrate with morphine hydrochloride, Chloralhydrate with morphine hydrochloride and Ursonarkon, local anaesthesia in conjunction with sedation by Ursonarkon.

Effect of urea on the mechanical and electrical activity of the perfused rat heart.

The mechanical and electrical activities of Langendorff perfused isolated hearts from albino female rats were studied before and after the addition of 17 mM urea to the medium. The effect of urea on the osmolarity of the perfusing solution was evaluated by also carrying out the measurement in 17 mM saccharose. The rate of the spontaneously beating hearts did not change after urea or saccharose treatment.

The relationship between extracellular calcium and isovolumic systolic pressure in the Langendorff-perfused rat heart.

The relationship between extracellular calcium concentration and isovolumic systolic pressure developed by left ventricles was studied in Langendorff-perfused rat hearts. At diastolic pressure lower than 15 mmHg the isovolumic systolic pressure increased when external calcium was changed from 0.5 to 1.

Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles.

The regulation of glutamine synthetase expression by dexamethasone was studied in rat skeletal muscles. Daily administration of dexamethasone caused striking enhancement of glutamine synthetase activity in plantaris, soleus, and diaphragm muscles. Northern blot analysis revealed that the dexamethasone-mediated increase of glutamine synthetase activity was associated with dramatically increased levels of glutamine synthetase mRNA.

Depression of myocardial force development after urea treatment.

Left ventricle papillary muscles from Wistar male rats were studied before, during and after urea treatment. Urea was used at a concentration (17 mM) equivalent to a plasma level of 100 mg/dl. To verify whether these effects were produced by an increase in osmolarity, the study was repeated using 17 mM saccharose.

Effects of nifedipine on blood pressure and heart rate in conscious neurogenic hypertensive rats.

The effects of nifedipine (15 micrograms/kg, i.v.) on mean blood pressure (MBP) and heart rate were studied in neurogenic hypertensive rats (NHR), compared with renovascular hypertensive (RHR), and control (CR) rats.

The effect of verapamil on potentiated rest contractions in the rat ventricular myocardium.

The effects of verapamil (0.3 to 30 microM) on potentiated rest contractions (PRC) were studied in isometric contractions of left ventricular papillary muscles of the rat. The post-rest potentiation was studied after rest periods of 5, 10, 15, 30, 60 and 120 s.

Enhanced inotropic response to isoproterenol in acute sinoaortic denervated rat heart.

The effects of acute sinoaortic baroreceptor denervation were studied in left ventricle papillary muscles obtained from rats after 3 days of sinoaortic denervation (SAD) and compared to sham-operated controls (SO). SAD and SO muscles developed similar force (F) and rate of force development (dF/dt). To test changes in beta-adrenoceptor sensitivity, isoproterenol (IPA) was used in four doses (0.

Mechanical behavior of rest contractions in cardiac muscle.

The effects of increasing rest periods on rest contractions and rest potentiation were analysed on isometric contractions of guinea pig papillary muscles at room temperature. Rest contraction amplitude is dependent on pause duration and potentiated for short pauses, which decreases as the rest period increases. their inotropic state is also dependent on the inotropic state of steady state control contractions.

Right ventricular contractility depression in chronically infarcted rats.

We studied the in vitro mechanical performance of right ventricular strips obtained from male albino rats submitted to left coronary ligation for 30 days. The infarcted rats developed significant right ventricle hypertrophy together with a reduction of the isometric tension when compared to controls. The reduction was maintained even under positive inotropic intervention, i.

Electrophysiological effects of labetalol on canine atrial, cardiac Purkinje fibres and ventricular muscle.

1. Using conventional microelectrode techniques for the intracellular recordings of the membrane potential, the effects of labetalol were studied on cardiac Purkinje, atrial and ventricular muscle fibres of the dog. 2.