Rhythm assimilation in the isolated canine heart under isovolumic conditions

Isolated canine heart has an expressed ability for autoregulation of bioelectrical and contractile functions irrespective of the neurohumoral factors influence on the work of the heart, and Frank-Starling law. Under the change of stimulation frequency, the autoregulation of heart functions is carried out as rhythm assimilation at organ (cell) level. The heart has a higher ability to bioelectrical rhythm assimilation rather than the mechanical rhythm assimilation. Incomplete rhythm assimilation is characterised by the alternation of contractions. The "Everything or nothing" law has no applicability to the work of the heart.     

Proteoglycan synthesis in the endothelium of embryonal vertebrate hearts: significance for the development of cardiovascular function

The endothelium of the embryonic heart is able to synthetize proteoglycans (PG) as it is the myocardium. In the extracellular matrix, PG form highly polymeric visco-elastic networks, which besides others act as shock absorber. That is apparently of evidence for the modulation of embryonic heart actions. Because during the embryonic period the large arteries are simple endothelial tubes without having an elastic-muscular wall. That means the typical "windkessel" function such as dumping of pulse waves or a continues pressure distribution is not existent. The embryonic vessels are perfused like rigid tubes. The continuous rhythmic flow pattern in the endothelial tubes, necessary for perfusion of the different organs, is apparently compensated by a high initial pressure level initiated by the heart. It is concluded that the continuity of the pressure profile is caused by intracardial PG. The endothelial synthesis of the PG of the heart decreases with increasing development of the muscular wall of the vessels and disappears completely post partum.     

Electrophysiological characteristics of cardiac function and the intensity of protein synthesis in cardiomyocytes during the arousal of susliks from hibernation

It has been demonstrated that during winter hibernation (body temperature 2-4 degrees C), the heart rate in ground squirrels is equal to 100 10-12 beats/min. At the initial stage of the arousal, while body temperature remains still low (9-10 degrees C), the heart rate may increase up to 160-200 beats/min. At this stage, practically all electrophysiological parameters of the heart correspond to those in active animals. These results may indicate the ability of "cold" heart in arousing ground squirrels to operate as a normothermic organ and reveal certain role of the heart in body warming. Significant increase of the intensity of protein synthesis in cardiomyocytes together with periodic changes in protein composition of their membranes were found during arousal which may account for regulation of the level of metabolism in cells and for adaptation of the latter to different temperatures.     

Significance of extracellular concentration of sodium ions in the protective effect during the "calcium paradox"]

Increasing of extracellular sodium concentration up to 200 mM diminishes heart damage under "calcium paradox". Phosphocreatine (10(-4) M) potentiates the effect of high sodium perfusion media; in this case myoglobin release from the myocardium is minimal (5-9% of control). An the same time, ATP and phosphocreatine concentrations and oxidation to phosphorylation coupling in mitochondria remain at a sufficiently high level. Elevation of osmotic pressure by the effect of 120 mM sucrose enhances heart damage under "calcium paradox" both in the presence and absence of phosphocreatine. The protective effects of superhigh (200 mM) sodium concentrations and phosphocreatine are completely reversed by strophanthin or decreasing K+ concentration down to 0.5 mM.     

Cardiac Troponin I in Non- Acute Coronary Syndrome Patients with Chronic Kidney Disease

Objective

The aim of this study was to assess the results of troponin I (cTnI) in non- acute Coronary Syndrome (ACS) patients with chronic kidney disease (CKD). We also examined the risk factors for elevated cTnI in non-ACS patients with CKD and whether stage 5 CKD modifies the associations of elevated cTnI and the risk factors in non-ACS patients with CKD.

Methods

A retrospective study was performed. Logistic regression models were used.

Results

293 non-ACS patients with CKD were included in the current study. 43.34% non-ACS patients with CKD have an elevated cTnI level and 5.12% have an elevated cTnT level in MI range. In CKD patients without ACS and heart failure, only 26.03% (38/146) patients have an elevated cTnT level. In adjusted analyses, age, diastolic blood pressure and congestive heart failure is associated with an elevated cTnI level in non-ACS patients with CKD. Congestive heart failure is associated with an elevated cTnI level in non-ACS patients with CKD (OR 2.30, 95% CI 1.08,4.88, P=0.03). Stage 5 CKD does not modify the association of congestive heart failure and an elevated cTnI level.

Conclusion

43.34% non-ACS patients with CKD and 26.03% CKD patients without ACS and congestive heart failure have an elevated cTnI level. Congestive heart failure is associated with an elevated cTnI level in non-ACS patients with CKD. Stage 5 CKD does not modify the association of congestive heart failure and an elevated cTnI level.     

Myogenic origin of the hypotension induced by rapid changes in posture in awake dogs following autonomic blockade

The "push-pull" effect denotes the reduced tolerance to +G(z) (hypergravity) when +G(z) stress is preceded by exposure to hypogravity, i.e., fractional, zero, or negative G(z). The purpose of this study was to test the hypothesis that an exaggerated, myogenically mediated rise in leg vascular conductance contributes to the push-pull effect, using heart level arterial blood pressure as a measure of G tolerance. The approach was to impose control (30 s of 30 degrees head-up tilt) and push-pull (30 s of 30 degrees head-up tilt immediately preceded by 10 s of -15 degrees head-down tilt) gravitational stress after administration of hexamethonium (5 mg/kg) to inhibit autonomic ganglionic neurotransmission in seven dogs. Cardiac output or thigh level arterial pressure (myogenic stimulus) was maintained constant by computer-controlled ventricular pacing. The animals were sedated with acepromazine and lightly restrained in lateral recumbency on a tilt table. Following the onset of head-up tilt, the magnitude of the fall in heart level arterial pressure from baseline was -11.6 +/- 2.9 and -17.1 +/- 2.2 mmHg for the control and push-pull trials, respectively (P < 0.05), when cardiac output was maintained constant. Over 40% of the exaggerated fall in heart level arterial pressure was attributable to an exaggerated rise in hindlimb vascular conductance (P < 0.05). Maintaining thigh level arterial pressure constant abolished the exaggerated rise in hindlimb blood flow. Thus a push-pull effect largely attributable to a myogenically induced rise in leg vascular conductance occurs when autonomic function is inhibited.     

Distribution of the 14C-hydrated analog of phenazepam in the organs and tissues of mice

The absorption kinetics of hydrated phenazepam analog into the liver, spleen, brain, kidney, blood, lungs, heart, skeletal and fat tissues is studied at 0.25-24 hour intervals after its intraperitoneal (i/p) administration to mice. Drug concentration in the above mentioned organs was maximal 0.5-1 hour later. The decrease of the drug and its metabolite level in the organs under study is a biexponential process, consisting of "quick" (1-6 hours) and "slow" phases. The rate of absorption of hydrated phenazepam analog into the organs and tissues and its elimination is lower than that of phenanzepam.     

Adrenocorticotropin production by the intermediate lobe of the rat pituitary

Summary Tissue from the four chambers of the heart of the plaice (Pleuronectes platessa, L.) has been examined in the electron microscope in order to describe the morphology of the heart at a fine structural level.The sinus venosus is a thin walled chamber between 60–90 thick consisting of a connective tissue matrix in which are situated the plexus of the parasympathetic cardiac ganglion and localised bundles of myocardial cells. The myocardial cells do not form a continuous layer but are associated in particular with the region of the cardiac ganglion and are innervated by it.The sino-auricular junction has hitherto been described as a pacemaker region but the myocardial cells in this region are identical in morphology to myocardial cells in other parts of the heart. There is a large complex of nerves, derived from the cardiac plexus, that runs around the junction before branching to innervate the auricle.The myocardial tissues consist of an outer layer of myocardium forming the wall of the heart and a profusion of trabeculae. The endocardium invaginates into the endocardium to divide up the cells into populations of approximately 25 cells in profile. There is no well-defined coronary blood supply although capillaries are occasionally seen. The myocardial cells themselves are small in diameter (3.5–5.5 ) and show some primitive features which are: a short sarcomere (1.4–2.0 ), the absence of any sarcoplasmic reticulum, and very scarce fasciae occludentes. In the atrium in particular, there are many groups of 1500 Å membrane-bound, dense-cored vesicles in the myocardial cells. Ventricular cells contain more myofilaments and mitochondria than do atrial cells and have many vesicles of 0.1–0.3 diameter whose function and contents are unknown.Connective tissue is very evident in the plaice heart, being an integral part of the sinus venosus and the auriculo-ventricular junction and being the sole constituent of the auriculoventricular valve and the bulbus arteriosus.This investigation was carried out during the tenure of an S. R. C. studentshyp awarded to R. M. S.     

Analysis of the effect of morphine and promedol on uptake and release of noradrenaline by myocardial tissue]

A study was made of the effect of morphine and promedol on the content, uptake, and release of norepinephrine (NE) on rat myocardium. Promedol proved to decrease the NE level in the myocardium. Morphine failed to influence the release of the NE-14C from the isolated perfused heart, whereas promedol increased it significantly, altering both the "slow" and the "rapid" release of the mediator. Promedol failed to influence the uptake of NE-14C by the perfused heart, whereas morphine decreased it significantly. The competition between morphine and NE was characterized by the effect of incomplete inhibition: morphine and NE produced reciprocal effects on the affinity of one another to the receptor, and their interaction depended on the ratio of the concentrations of these drugs.     

Regulation of cardiolipin biosynthesis in the heart

Cardiolipin is one of the principle phospholipids in the mammalian heart comprising as much as 15–20% of the entire phospholipid phosphorus mass of that organ. Cardiolipin is localized primarily in the mitochondria and appears to be essential for the function of several enzymes of oxidative phosphorylation. Thus, cardiolipin is essential for production of energy for the heart to beat. Cardiac cardiolipin is synthesized via the cytidine-5-diphosphate-1,2-diacyl-sn-glycerol pathway. The properties of the four enzymes of the cytidine-5-diphosphate-1,2-diacyl-sn-glycerol pathway have been characterized in the heart. The rate-limiting step of this pathway is catalyzed by the phosphatidic acid: cytidine-5-triphosphate cytidylyltransferase. Several regulatory mechanisms that govern cardiolipin biosynthesis in the heart have been uncovered. Current evidence suggests that cardiolipin biosynthesis is regulated by the energy status (adenosine-5-triphosphate and cytidine-5-triphosphate level) of the heart. Thyroid hormone and unsaturated fatty acids may regulate cardiolipin biosynthesis at the level of three key enzymes of the cytidine-5-diphosphate-1,2-diacyl-sn-glycerol pathway, phosphatidylglycerolphosphate synthase, phosphatidylglycerolphosphate phosphatase and cardiolipin synthase. Newly synthesized phosphatidic acid and phosphatidylglycerol may be preferentially utilized for cardiolipin biosynthesis in the heart. In addition, separate pools of phosphatidylglycerol, including an exogenous (extra-mitochondrial) pool not derived from de novo phosphatidylglycerol biosynthesis, may be utilized for cardiac cardiolipin biosynthesis. In several mammalian tissues a significant number of studies on polyglycerophospholipid biosynthesis have been documented, including detailed studies in the lung and liver. However, in spite of the important role of cardiolipin in the maintenance of mitochondrial function and membrane integrity, studies on the control of cardiolipin biosynthesis in the mammalian heart have been largely neglected. The purpose of this review will be to briefly discuss cardiolipin and cardiolipin biosynthesis in some selected model systems and focus primarily on current studies involving the regulation of cardiolipin biosynthesis in the heart. (Mol Cell Biochem 159: 139–148, 1996)Abbreviations CL cardiolipin - PG phosphatidylglycerol - PA phosphatidic acid - CTP cytidine-5triphosphate - CDPDG cytidine-5'-diphosphate-1,2-diacyl-sn-glycerol - CMP cytidine-5monophosphate - lysoPG lysophosphatidylglycerol - monolysoCC monolysoCcardiolipin - BMP bis(monoacylglycerol)phosphate - ATP adenosine-5-triphosphate - ADP adenosine-5-diphosphate - PGP phosphatidylglycerol phosphate - DNA deoxyribonucleic acid - STZ streptozotocinM     

Control of cardiac response under aversive stimulation

The relative heart rate effects of biofeedback training, deep muscle relaxation, and a no-feedback/music procedure were compared during two criterion situations. The first consisted of a 25-min training period during which subjects received the assigned treatments. The second consisted of the pre- to posttraining reductions in heart rate reactivity to a series of aversive tone-shock trials. On the first criterion, the heart rate decreases of the feedback and no-feedback/music groups were not clearly distinguishable; however, both groups fell significantly below the muscle-relaxation group. By contrast, on the second criterion, the three groups were clearly distinguishable, with feedback subjects evidencing the most heart rate control, followed by the muscle-relaxation and no-feedback/music groups, respectively. On the segment of the posttraining aversive trials conducted in the absence of the feedback signal, transfer of heart rate control was incomplete for feedback subjects, but still remained below the level of the other two groups. Training effects were more pronounced on tonic than on phasic heart rate changes. The difference between the two criterion situations suggests the possible need for and feasibility of employing a situational arousal methodology in evaluating the extent and limitation of physiological training procedures.     

The membrane systems of the cardiac muscle cell of Euchaeta norvegica Boeck (Crustacea,Copepoda)

Summary The membrane systems of the cardiac muscle cell of the copepod Euchaeta norvegica Boeck are described. The heart wall, which is between 0.12 and 1.36 m thick, consists of an epicardium and a single layer of muscle cells. Invaginations of the sarcolemma forming transverse tubules have been found at all levels of the sarcomere with the exception of the H-band level. The longitudinal tubules of the same system are closely associated with the sarcoplasmic reticulum to form interior couplings at the A-I level of the sarcomere. Triadic couplings at the Z band level were not seen in E. norvegica, but peripheral couplings were demonstrated. Nexuses were found in the intercalated discs.     

Leptomeric fibrils and T-tubule desmosomes in the Z-band region of the mouse heart papillary muscle

Summary The papillary muscle of the heart of adult white mice is investigated. Intrafibrillarly located leptomeric fibrils, frequently encountered in the Z-band region of the myofibrils. The leptomeric fibrils are always running in a transverse direction and often in close proximity to the transverse tubules (which are also located at this level). There seems to be a close connection between the dense striae of the leptofibrils and the Z-bands of ordinary myofibrils. The leptomeric fibrils are spindle-shaped and have a length varying between 0.6 and 1.2 m. The banding periodicity of the fibrils is approximately 0.16 m.Occasionally desmosomes are observed in the T-tubule system.     

Effect of gradual reperfusion on the restoration of the pump function and energy stores of the heart after ischemia

The contractile and pump function of guinea pig hearts was evaluated 40 min after total normothermic ischemia and 30 min reperfusion. A half of the hearts was reperfused with rapid mode restoration of the preischemic coronary flow ("sudden" reperfusion, SR), while the other half was reperfused with gradual mode restoration (GR) of coronary flow by 2 ml/min each 4 min till the initial level. The cardiac output and external work after SR constituted 49 and 28 of initial values, while after GR-87 and 71%, respectively. A distinct rise in minimal diastolic left ventricular pressure in the former group indicates a deteriorated filling of the heart. The total pool of adenine nucleotides and ATP content remained almost unchanged after GR: while after SR they decreased to 61 and 54% of the initial level, and myocardial lactate content was three times higher. The beneficial effect of GR seems to be due to better preservation or restoration of ATP content and more profound relaxation of the heart.     

Innervation of heart and alary muscles in Sphinx ligustri L. (Lepidoptera)

Summary The origin and orientation of the heart nerves in Sphinx ligustri and Ephestia kuehniella were investigated by scanning electron microscopy using a special technique which involved pinning the dissected specimens on a stabilizing metal pad. The heart and alary muscles in Sphinx particularly their caudal extremity were also examined by transmission electron microscopy. The alary muscles form an incomplete sheath around the heart with a mainly longitudinal fibre orientation, e.i. antagonistically to the fibres of the heart itself. The heart and alary muscles are multiterminally innervated by branches of the transverse segmental nerves. All branches contain a single electron lucent axon; the thickest branches also possess several neurosecretory axons. Swellings of the segmental nerves may indicate the position of nerve cell bodies. There are no lateral heart nerves. Only one type of neuromuscular junction is abundant in the alary muscles but less frequently found in the heart. The terminals originate from the central axon only. They are capped by glial cells, which interdigitate with the muscle cells. They penetrate into the T-system toward the Z-discs and form a complex intercellular space system. Exocytosis of dense-cored vesicles into this perisynaptic reticulum seems likely. Sites of neurohaemal release are distributed along the nerve branches and special nerve endings occur at the level of the ostia. The possible nervous influence upon heart activity is discussed.The transmission electron microscopic part of this investigation was supported by a research scholarship from the Deutsche Forschungsgemeinschaft     

In situ visualization of the intracellular Ca2+ dynamics at the border of the acute myocardial infarct

Ischemic insult to the heart produces myocyte Ca²⁺ ([Ca²⁺]_i) overload. However, little is known about spatiotemporal changes in [Ca²⁺]_i within the ischemic heart in situ at the cellular level. Using real-time confocal microscopy, we successfully visualized [Ca²⁺]_i dynamics at the border zone on the subepicardial myocardium of the heart 2 h after coronary ligations followed by loading with fluo 3/AM. Three distinct regions were identified in the acute infarcted heart. In intact regions, the myocytes showed spatially uniform Ca²⁺ transients synchronously to QRS complex in the electrocardiogram. The myocytes at the infarcted regions showed no fluorescence intensity (FI). At the border zones between the intact and infarcted regions, Ca²⁺ waves emerged sporadically and randomly, instead of Ca²⁺ transients, at a mean frequency of 11.5 ± 8.5 min/cell with a propagation velocity of 151.0 ± 35.7 m/sec along the longitudinal axis of the individual myocytes. In addition, some myocytes within the border zone exhibited homogeneously high static FI, indicating severe Ca²⁺ overload. In summary, we provided the first direct evidence of abnormal [Ca²⁺]_i dynamics in acute infarcted hearts at the cellular level. The observed diversity in spatiotemporal [Ca²⁺]_i dynamics at the border zone may contribute to the arrhythmias or contractile failure in acute myocardial infarction.     

A causal analysis of the heart curvatures in the chicken embryo

Summary By means of grafts of the heart tube of the chicken embryo (before incurvation), we tried to clear up those factors which determine the curvatures. The heart tube, cultivated or grafted, possesses in itself the property of incurvation but it is manifested only if it is developed in a medium or a cavity similar to the pericardiac cavity. This property cannot manifest itself in the thickening of the tissues such as the embryonic mesenchyme. The curvatures which are formed, that is to say the morphogenesis (in the coelomic grafts) is always imperfect and cannot be compared to those of a normal heart in the same stage of development. The ventricle and the heart bulb can be recognized many times, but not the atrium or the venous sinus. The retrocardiac tissue and the endoderm of the anterior intestinal portal are factors necessary for a normal morphogenesis, as the grafts accompanied by these tissues give rise to better morphogenesis and one can recognize all the fundamental portions of the heart. In these cases a liver is almost always differentiated, originating with the graft. The blood flow has no influence for some time in the heart morphogenesis but it does in the structure of the heart. Only in those cases in which circulation exists are the endocardium and the myoepicardium formed, with their typical structure. The morphogenesis and the heart structure are, to a certain point, independent processes during these stages of development and are due to different factors.This investigation was supported in part, by a grant from the Pfizer, s. A.     

Importance of RR-interval variability in stress test

Cardiac rhythmogram (CRG) variability at the early stage of loading and recovery periods has a number of parameters associated with the functional state of subjects. These parameters can be estimated by measuring the probability of pairs of RR intervals with certain length differences (pNNx). At the same time, each of these parameters has its own diagnostic role, such as the binary marker of adaptation reserves (pNN15), loading tolerance level (pNN5, 10) and a criterion for the training level (pNN10, 15). The pNNx coupling with the endured load power and the dynamics of heart rate (HR) is to a great extent determined by the mixed endurance level. Higher pNNx values correspond with the predominant load and lower heart rate, regardless of the period. Physiological relevance of pNNx is determined by their behavior, diagnostic role, the sensitivity of each argument (x), and the level of aerobic/anaerobic endurance of a subject.     

Psychophysiological and Some Functional Markers of Mental Workload in Young Men

The emotional state of a person affects both the central level and the peripheral indices of the autonomic nervous system, particularly those of the regulation of the heart rate. Our study showed that boys with a higher level of anxiety had higher values of the latent period of the P300 evoked potential and lower indices of short-term auditory memory. Changes in the temporal and spectral components of heart rate variability under the conditions of mental workload indicate that the neurohumoral regulation of the heart rate is shifted toward the suprasegmental influences, including pituitary–hypothalamic and cortical influences.