Diagnóstico radiográfico de la discordancia aurículo ventricular / Radiographic diagnosis of atrioventricular discordance

En un período de 10 años se diagnosticaron por angiocardiografía 21 pacientes con discordancia auriculoventricular. Veinte presentaron conexión ventriculoarterial discordante (transposición corregida de grandes vasos) y sólo uno tenía una doble salida del ventrículo anatómicamente derecho. Tres de los pacientes con transposición corregida de grandes vasos tenían dextrocardia y 17 levocardia con situs solitus, de los cuales 16 presentaron el aspecto típico descritos en la mayoría de estos casos, tanto en el telecardiograma como en el estudio contrastado. Otro paciente presentaba el tabique interventricular dispuesto horizontalmente. La anomalía asociada más frecuente fue la comunicación interventricular. Dos pacientes no presentaron anomalías asociadas y en uno de ellos el diagnóstico se hizo a los 47 años, al realizarse una coronariografía por sospecha de aterosclerosis coronaria. Teniendo en cuenta la posición del tabique interventricular y las anomalías asociadas más frecuentes en la discordancias auriculoventricular, se recomienda cuando se sospecha esta entidad comenzar el estudio contrastado con ventriculografía selectiva bilateral en las proyecciones frontal y lateral y recurrir después, si fuera necesario, a las vistas axiales e inyecciones en las aurículas, aorta y pulmonar

Atrial natriuretic factor controls salt gland secretion in the Pekin duck (Anas platyrhynchos) through interaction with high affinity receptors.

Marine birds possess supraorbital salt-secreting glands in addition to the kidneys as osmoregulatory organs to excrete a strongly hypertonic salt solution of mainly NaCl. Atrial natriuretic factor (ANF)-like peptides could be demonstrated immunocytochemically in duck atria, but not in the salt glands. To elucidate the putative role of bird-specific ANF (cANF) in the control of salt gland function, conscious saltwater-acclimated Pekin ducks received 15 pmol/min.kg BW cANF for 10 min at two states of salt gland activity. During steady state diuresis and salt gland secretion induced by systemic infusion of 1.0 ml/min isotonic Krebs-Ringer solution, cANF applied iv enhanced the secretion rate from 0.20 to 0.29 ml/min and the osmolality of secretion from 870 to 920 mosmol/kg. At threshold conditions of salt gland activity, cANF infused intracarotideally stimulated the secretion rate from 0.07 to 0.15 ml/min at elevated osmolality of 760 compared to 480 mosmol/kg. Mean arterial pressure and heart rate remained unchanged. Receptor autoradiography with [125I]Bolton-Hunter-cANF as ligand demonstrated specific binding sites throughout the salt gland tissue of both freshwater and saltwater ducks. Scatchard analysis using an enriched membrane fraction revealed high affinity (Kd = 0.9 nM) binding sites of 270 fmol/mg protein density. Displacement studies with unlabeled cANF and human ANF showed comparable Ki values for both peptides in freshwater and saltwater ducks. The combined results indicate an important role for cANF in the control of avian salt gland function.

Dynamics of atrial peptide secretion in the coronary circulation of the conscious dog.

The secretion of atrial natriuretic peptide by the heart is not simply the arterial-coronary sinus concentration difference times coronary blood flow, because only a small fraction of total coronary blood flow passes through the atria. We measured coronary sinus and arterial plasma atrial natriuretic factor (ANF) concentrations and blood flow to each part of the heart using the radioactive microsphere technique. Before acute volume expansion, the arterial-coronary sinus ANF difference was 305 +/- 23 pg/ml and rose to 1,009 +/- 220 pg/ml during volume expansion, whereas total coronary blood flow rose from 167 to 465 ml/min. Atrial blood flow rose from 2.9% to 4.6% of total coronary blood flow during volume expansion. ANF secretion rate increased from 51 to 469 ng/min. When divided by atrial weight, ANF secretion rate increased from 4.0 +/- 0.3 to 56 +/- 12 ng/min/g atrial tissue-in other words, from 0.3% to 3.7% of tissue ANF content each minute. Dividing by atrial blood flow indicated that the concentration of ANF leaving atrial tissue was 10,000 to 29,651 pg/ml, and the additional secretion of ANF was determined by the increase in coronary blood flow. Therefore, at least two mechanisms are responsible for altering coronary sinus ANF and circulating ANF: the release rate from atrial myocytes and the washout via changes in atrial blood flow.

Preparation of monoclonal antibodies against brain natriuretic peptide and their application to radioimmunoassay and passive immunization.

Two monoclonal antibodies (mAbs) directed toward brain natriuretic peptide (BNP), KY-BNP-I and KY-BNP-II, have been produced. Both mAbs against BNP possessed high affinities for BNP, with association constants (Ka) of 4.0 X 10(9) M-1 (KY-BNP-I) and 2.0 X 10(10) M-1 (KY-BNP-II). With these mAbs, specific RIAs for BNP have been established. The least detectable quantities of BNP were 5 pg/tube (KY-BNP-I) and 1 pg/tube (KY-BNP-II). Cross-reactivities of alpha-human and rat atrial natriuretic polypeptides were less than 0.001%. These RIAs detected BNP-like immunoreactivity (BNP-LI) not only in the porcine brain but also in the canine brain, with the highest concentration in the medulla oblongata. These RIAs also detected BNP-LI in both the porcine and canine hearts and in the porcine plasma. The iv pretreatment of purified mAb[KY-BNP-II] almost completely blocked the hypotensive action of iv administered BNP in rats, with the concomitant suppression of BNP-induced increase of the plasma cyclic GMP level. These results indicate that our mAbs against BNP will serve as a useful tool for the elucidation of the physiological and pathophysiological significance of BNP as a neuropeptide and as a hormone.

Histamine H1-receptor in heart: unique electrophoretic mobility and autoradiographic localization.

Histamine H1-receptors, visualized in the guinea pig heart by autoradiography using [125I]iodobolpyramine as a specific probe, are abundant in the nodal tissue and cardiac vessels but also occur heterogeneously in the myocardium. Following photoaffinity labeling with [125I]iodoazidophenpyramine and electrophoresis, the ligand binding domain of the heart H1-receptor was shown to be present on a major 68-kDa and a less abundant 54- to 58-kDa protein. The 68-kDa protein displayed a molecular size higher in heart than in all other tissues (56 kDa). This indicates the existence of at least two isoforms of the H1-receptor; the cardiac isoform, however, was pharmacologically indistinguishable from the common isoform studied in cerebellar membranes using available ligands. Its distinct electrophoretic properties suggest that the cardiac isoform may have a unique function.

Partial agonist effects on the interaction between the atrial muscarinic receptor and the inhibitory guanine nucleotide-binding protein in a reconstituted system.

The mechanism of action of the partial muscarinic agonist pilocarpine was analyzed in a reconstituted system consisting of the purified porcine atrial muscarinic receptor and the purified porcine atrial inhibitory guanine nucleotide-binding protein, Gi. When GTPase activity was measured as a function of receptor.agonist complex concentration at saturating concentrations of either the full agonist carbachol or pilocarpine, both ligands gave similar values of kcat (4.3 +/- 0.2 min-1 for carbachol and 5.4 +/- 0.7 min-1 for pilocarpine); however, the observed dissociation constant for the ligand.receptor complex binding to Gi was about 4-fold lower for carbachol (0.81 +/- 0.19 nM) than for pilocarpine (3.02 +/- 0.83 nM). These results suggested that, in this system, the reduced activity of the partial agonist compared with the full agonist was the result of a decrease in affinity of the receptor.ligand complex for Gi, as opposed to differences in their relative abilities to activate the guanine nucleotide-binding protein. Several analogues of oxotremorine were also tested to determine their effects on the GTPase activity of Gi. Results from these studies indicate that the reconstituted system may be useful in determining structure-function relationships for muscarinic agonists with regard to receptor.Gi interactions.

[The topographic characteristics and changes in the ontogeny of light-chain myosin in the human myocardium]. / Izuchenie topograficheskikh osobennostei i izmenenii v ontogeneze legkikh tsepei miozina v miokarde cheloveka.

Pattern of myosin light chain in human atrium and ventricles was studied using two-dimensional electrophoresis. Minor fraction was found in ventricles and atria of adult man that coincided in molecular weight, isoelectric point and staining specificity with fetal myosin light chain. The 23 kDa and 24 kDa fractions of auricles were not detected in ventricles.

Rapid isolation and chemical synthesis of two porcine cardiodilatins, the cardiac hormone precursor and related fragment.

To evaluate the chemically synthesized materials, two cardiodilatins, CDD-126 and CDD-88/CDD(39-126), a precursor of atrial hormone and a related fragment, were isolated from porcine atria by immunoaffinity chromatography or alginic acid adsorption followed by an ion exchange high performance liquid chromatography. The chemical synthesis was carried out using an automated peptide synthesizer. After cleavage and refolding, the crude CDDs were directly characterized by the novel method of primary structure determination using electroblotting and microsequencing. The purified synthetic CDDs were identical with the natural ones in physicochemical and immunochemical properties, as well as their biological actions both in vivo and in vitro.

Localization and characterization of the N-terminal fragment of atrial natriuretic factor (ANF) precursor in the frog heart.

The localization of the N-terminal fragment of the atrial natriuretic factor (ANF) precursor in the heart of the frog Rana ridibunda was examined by the indirect immunofluorescence and the immunogold techniques using an antiserum directed against synthetic rat ANF (Asp11-Ala37). At the optic level, positive material was found in most atrial myocytes. Staining of consecutive sections of frog heart with antibodies against N-terminal and C-terminal regions of the proANF molecule showed that both peptides are contained in the same cardiocytes. In the rat atrium, antibodies against the N-terminal ANF region induced a more intense labeling than in the frog atrium. Electron microscopic studies indicated that all secretory granules present in frog atrial cardiocytes contain N-terminal ANF-like immunoreactive material. The positive material localized in frog atrium was characterized by gel filtration and radioimmunological detection. Serial dilutions of frog atrial extracts exhibited displacement curves which were parallel to that obtained with synthetic human ANF (Asn1-Asp30). Sephadex G-50 gel chromatography of the immunoreactive material showed that the N-terminal ANF-like immunoreactivity eluted in a single peak corresponding to high molecular weight material. These results indicate that the N-terminal fragment of frog proANF is immunologically and biochemically related to the homologous mammalian peptide.

Isolation and identification of human brain natriuretic peptides in cardiac atrium.

By using a radioimmunoassay (RIA) system newly established for human brain natriuretic peptide (BNP), a high concentration of immunoreactive (ir-) human BNP (hBNP) has been found in cardiac atrium (1). Two molecular forms of ir-hBNP of 4K and 13-15K were isolated from atrial extracts by using anti-hBNP IgG immunoaffinity chromatography and reverse phase high performance liquid chromatography (HPLC). By microsequencing, the peptides were determined to be a pro-hBNP (gamma-hBNP) and its C-terminal 32-amino acid peptide (hBNP-32). Based on these results, in cardiac atrium, hBNP is found to be processed in a pathway similar to that of porcine BNP (pBNP) but distinct from that of rat BNP, although low MW hBNP-32 is a major form in contrast to pBNP which exists as a high MW gamma-pBNP.

Characterization of immunoreactive brain natriuretic peptide in human cardiac atrium.

Based on cDNA sequence data for human brain natriuretic peptide (BNP) precursor (1), a radioimmunoassay (RIA) system highly specific to human BNP (hBNP) was developed and used to characterize immunoreactive (ir-) hBNP in cardiac atrium. Gel filtration of ir-hBNP in atrium indicated that ir-hBNP was mainly comprised of two molecular forms of 13-15K and 4K. In reverse phase high performance liquid chromatography (HPLC), the low molecular weight (MW) ir-hBNP emerged as a single peak at an elution time identical to that of synthetic hBNP-32. The high MW ir-hBNP was also eluted as a single peak. On the other hand, tissue concentrations of ir-hBNP in cardiac atria were found to be 9.98-593.22 pmol/g in 13 specimens, being about 1/150 the concentration of ir-human atrial natriuretic peptide (hANP). These results demonstrate that hBNP is present as a peptide in human heart, suggesting that hBNP is secreted from heart and functions together with hANP as a hormone.

[Existence of phencyclidine receptor in guinea pig atria].

[3H]-PCP was used in receptor binding studies on membrane preparation from guinea pig atria. It was found that this binding was specific, saturable, reversible and stereoselective. Scatchard plots revealed that guinea pig atria had two different affinity binding sites. The high affinity constant (Kd1) and low affinity constant (Kd2) were 12.15 +/- 0.414 nmol/l and 561.23 +/- 121.36 nmol/l, respectively; the maximum bindings (Bmax) were 0.71 +/- 0.029 pmol/mg protein (Bmax1) and 1.047 +/- 0.099 pmol/mg protein (Bmax2), respectively. The displacement analysis revealed that the [3H]-PCP binding was inhibited by the ligands of both PCP and sigma receptors, while the inhibition of PCP ligands was larger than of sigma ligands. Etorphine, an agonist of opioid receptors, failed to inhibit the binding of [3H]-PCP. The results mentioned above show the existence of a specific PCP receptor in guinea pig atria. The autoradiographic analysis of guinea pig right atria was shown that there was autoradiographic localization of [3H]-PCP on atria of guinea pig with homogeneous distribution, suggesting that the distribution of PCP receptor in atria was homogeneous relatively.

Isolation and sequence determination of human brain natriuretic peptide in human atrium.

We isolated human brain natriuretic peptide (human BNP) from the human atrium. Sequence analysis has revealed that it is a 32-amino-acid peptide with the sequence S-P-K-M-V-Q-G-S-G-C-F-G-R-K-M-D-R-I-S-S-S-S-G-L-G-C-K-V-L-R-R-H, which is identical to the C-terminal sequence (77-108) of the human BNP precursor deduced from the cDNA sequence. The sequence of human BNP (77-108) is preceded by Pro75-Arg76 in the human BNP precursor, which is the same processing signal as Pro97-Arg98 of the precursor of atrial natriuretic peptide (ANP). The processing of the BNP precursor occurs in the cardiocyte, although that of the ANP precursor in the cardiocyte is unclear at present.

Interaction of lead acetate with atrial natriuretic factor in rats.

Lead exposure alters cardiovascular function and has been implicated in the etiology of hypertension. Therefore it was of interest to study the short term effect of lead treatment on atrial natriuretic factor (ANF), a hormone which produces vascular smooth muscle relaxation and natriuresis. Male Sprague Dawley rats were randomly divided into 5 groups containing 4 animals each and injected intraperitoneally with normal saline (control), 0.01, 0.1, 0.5 or 1.0 mg/kg of body weight with lead acetate solution twice a day for 7 days, and then maintained for a period of 30 days. During this period water consumption and urine volume were measured daily. At the end of the 30 day period, immunoreactive levels of ANF in hypothalamus, atria and plasma were measured by radioimmunoassay. Lead treatment did not alter water consumption, but significantly decreased urine output. At all doses, lead produced a decrease in hypothalamic content of ANF and slightly increased atrial levels. The content of ANF in plasma was decreased. The changes in ANF content indicate that lead interacts with the hormonal regulation of the cardiovascular system and these observations may relate to the cardiovascular toxicity of this heavy metal.

Relationship between alterations in atrial and ventricular histamine content and cardiac function during cardiac anaphylaxis of isolated guinea pig hearts.

Antigen-induced histamine release from sensitized cardiac tissue has been shown to contribute significantly to the increases in atrial rate, atrioventricular nodal conduction, and ventricular contractile force that occur during cardiac anaphylaxis. These findings suggest that there might be a strong negative correlation between changes in these variables and the residual histamine content in the tissue after the anaphylactic reaction. In the present study using isolated hearts of passively sensitized guinea pigs, antigen challenge evoked transient increases in atrial automaticity, P-R intervals, vascular resistance, and left ventricular pressure. The histamine content of atrial and ventricular tissue from antigen-challenge hearts (1,475 +/- 296 and 4,543 +/- 360 ng/g, respectively) was significantly less than that of nonchallenged hearts (2,652 +/- 335 and 6,298 +/- 251 ng/g, respectively). Significant correlations found were between the residual histamine content of the ventricular tissue or the total histamine released and the magnitude of the antigen-induced increase in left ventricular systolic pressure. These findings suggest that antigen-induced increases in left ventricular systolic pressure can be used as an index of the local ventricular histamine release. The lack of significant correlations between local residual histamine levels and changes in atrial rate, P-R intervals, or coronary vascular resistance suggests that complicated interactions between histamine and other mediators or factors may be involved in the antigen-induced chronotropic, dromotropic, and vasoconstrictive alterations in these preparations.

A new approach to the direct detection of free radicals in the intact myocardium.

A new method for the direct ESR detection of free radicals in rat myocardial tissue is described. Isolated rat atria are continuously monitored for heart rate and contractile force; at the end of the experimental period the beating organs are inserted into quartz ESR tubes and immediately frozen in liquid nitrogen. Spectra obtained from these preparations show the presence of very weak radical signals. When ESR spectra are recorded on samples obtained from pools of rat atria pulverized under liquid nitrogen, the radical lines are markedly stronger than those observed for intact organs; contaminating metals are also frequently detected. These findings indicate that crushing or grinding procedures carried out under liquid nitrogen produce artifactual ESR active species. The new method described in the present paper does not involve mechanical interventions and therefore should yield reliable artifact-free results.

Distribution and molecular forms of brain natriuretic peptide in porcine heart and blood.

Although brain natriuretic peptide (BNP) is a novel natriuretic peptide originally identified in porcine brain, recent investigation has verified the presence of BNP in porcine heart. In order to identify BNP as a circulating hormone, we analyzed the regional distribution and molecular form of immunoreactive (ir-) BNP in heart and blood. Tissue concentration of ir-BNP was high in atrium, but low in ventricle, in a manner similar to that of atrial natriuretic peptide (ANP). However, the concentration of ir-BNP in atrium was only about 1/50 that of ir-ANP. In plasma, ir-BNP was found at a concentration of 1-3 fmol/ml, which was about 1/20 that of ir-ANP. Both ir-BNP and ir-ANP were present as low molecular weight forms. Three forms of ir-BNP of about 3K daltons, including BNP-26, BNP-29 and BNP-32, are thought to circulate in blood.

Distribution and molecular forms of brain natriuretic peptide in the central nervous system, heart and peripheral tissue of rat.

The amino acid sequence of rat brain natriuretic peptide (rBNP) precursor has recently been deduced by the cDNA cloning method (1). In the present study, a radioimmunoassay (RIA) system for rBNP was newly established, and regional distribution of rBNP in the central nervous system, heart and other peripheral tissue of rat was investigated. In heart, especially in cardiac atrium, a high concentration of immunoreactive (ir-) rBNP was detected and identified as rBNP-45 and gamma-rBNP. No significant amount of ir-rBNP was found in other tissues examined including the central nervous system. Especially in brain, no ir-rBNP was detected, while ir-rat atrial natriuretic peptide (rANP) was observed at a relatively high concentration. These results demonstrate a sharp contrast between rat and porcine brains in ir-BNP distribution.

[An experimental investigation on application of silver-intensification technique to immunoelectron microscopy with colloidal gold probe].

The value of silver-intensification technique to immunoelectron microscopy being displayed with colloidal gold probe was evaluated through ultrastructural study on localization of cardionatrin in the atrial cardiocytes of rat. The results indicate that this technique is simple and feasible. It enables rapid screening of positively labelled sites at low magnification, and more information will be available. Further more, it offers better contrast and this technique may be of practical value.