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C Maldonado

Publications and source records attributed to C Maldonado.

At least 19 recordsLinked to original sources
PubMed1992

A flow-cytometric method to study DNA fragmentation in lymphocytes.

A method to measure DNA fragmentation cell by cell in a cell population was implemented based on acridine orange procedure to determine DNA content of single cells by flow cytometry. Using this method it can be observed that the fragmentation process induced by irradiation in thymic cells occurs in a fraction of the population, thus indicating that this process is not evenly distributed over the total population, and that it corresponds to a fast phenomenon in which the cells suddenly lose DNA material.

Acridine Orange↗
PubMed1992

Ultrastructural and immunocytochemical study of the myoendocrine cells of the fish Hypostomus cordovae.

The myoendocrine cells of the heart of Hypostomus cordovae (Günther 1880), a teleost fish from South America, were investigated by electron microscopy and immunohistochemistry. By applying antibodies raised against synthetic cardiodilatin 99-126 (CDD/ANP 99-126), a specific labeling of this hormone was found in the heart of this fish, mainly in myoendocrine cells of atrial trabeculae, where specific secretory granules are stored. The distribution of secretory granules exhibited striking seasonal variations. In winter there were fewer differentiated myoendocrine cells, which were easily recognized by the presence of specific secretory granules, most of which occur clustered in perinuclear areas of the cells. By contrast, in summer the majority of the myocardic cells of the atrium are active endocrine cells. They contain abundant secretory granules widely scattered in the cytoplasm, many of them polarized toward the subendocardial aspect of the cell. The secretory granules can be easily differentiated from the Weibel-Palade granules of endothelial cells, the shape, size and content of which were typical at electron-microscopic level. In addition, these endothelial granules did not display CDD immunoreactivity. The presence of cardiodilatin in a fish such as Hypostomus cordovae further supports the view that cardiac hormones are present in many Vertebrates and may preserve analogous roles such as those reported in other species throughout the group.

Animals↗
PubMed1992

Conduction of early afterdepolarizations in sheep Purkinje fibers and ventricular muscle. An in vitro arrhythmia model.

To establish an arrhythmia generator model, a double-chambered bath was used in which sheep Purkinje fibers (PF) and ventricular muscle (VM) were placed. The conduction patterns of early afterdepolarization-induced triggered activations (TAs) were examined between normal segments bathed in unmodified Tyrode solution and abnormal segments bathed in ethylenediaminetetraacetate (3.3-5.0 mmol). Three types of preparations were used: PF-PF (n = 10), VM-VM (n = 5), and PF-VM (n = 13). Two types of spontaneous TAs appeared. One type was conducted to normal segments, inducing activations over the entire preparation, while the other type was not conducted. The conducting TAs had significantly more rapid mean dV/dt, larger amplitude, and higher peak transmembrane voltage as compared to nonconducting TAs. While conduction occurred in all PF-PF, VM-VM, and PF-VM preparations, conduction of TAs from abnormal segment VM to normal segment PF was impaired. A low plateau resulting from electrotonic transmission of depolarizing current from abnormal segments was recorded in normal segments near the border. This low plateau probably facilitated the transmission of TAs. In addition to spontaneous TAs, stimulated or spontaneous action potentials from NL were conducted to the not yet fully repolarized ABN and induced activations resembling TAs. These results may be relevant to clinical arrhythmias due to action potential prolongation. The arrhythmia may occur directly as a result of triggered activity or indirectly via slow conducting TAs, creating the possibility for reentry. This type of model may be useful for intervention studies, for example, by identifying agents that block abnormal segment to normal segment conduction.

Action Potentials↗
PubMed1992

Role of protein kinase-C in thymocyte apoptosis induced by irradiation.

The role of protein kinase C in radiation-induced death of thymocytes was studied. For this purpose murine thymocytes were irradiated and incubated for 6 h at 37 degrees C and afterwards the fraction of fragmented DNA was measured. Results indicate that radiation-induced DNA fragmentation can be prevented by adding the protein kinase C inhibitor H-7 or staurosporine to the thymocytes during incubation time. Incubation of irradiated cells with HA-1004, an inhibitor of cAMP-dependent protein kinase, with a minor effect on protein kinase C did not affect the DNA fragmentation induced by irradiation. Incubation of cells with phorboldibutyrate gave a dose-dependent induction of DNA fragmentation. This effect can be inhibited by staurosporine. These results suggest that radiation-induced DNA fragmentation is an active cellular process in which protein kinase C plays an important role.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Purkinje fibre-papillary muscle interaction in the genesis of triggered activity in a guinea pig model.

OBJECTIVE: Previous studies have attempted to characterise the genesis of triggered activity related to early afterdepolarisations. Little is known about their conduction behaviour. This study was designed to examine the origin and conduction behaviour of triggered activations to throw light on the pathogenesis of torsade de pointes. METHODS: Electrophysiological interactions related to triggered activations and early afterdepolarisations between papillary muscle and Purkinje fibres were studied in the guinea pig in a single chambered bath. EDTA (5 mM) in Tyrode's solution was used and microelectrodes were placed in both papillary muscle and Purkinje fibres. RESULTS: During early superfusion, marked prolongation of action potential duration and early afterdepolarisations occurred in Purkinje fibres but not in papillary muscle. In addition: (1) with prolongation of action potential duration and early afterdepolarisations in Purkinje fibres, triggered activations arose during phase 2 and were conducted to papillary muscle, where they induced activations; (2) the number of papillary muscle discharges increased with the increase in Purkinje fibre action potential duration in a linear correlation; (3) severing a segment of papillary muscle from Purkinje fibres eliminated these papillary muscle activations; (4) some triggered activations did not conduct to papillary muscle; these had smaller amplitude, slower rate of depolarisation (dV/dt), more positive activation voltage, and similar peak voltages compared to conducted triggered activations; (5) a low plateau resulting from electrotonic interaction was recorded at the Purkinje fibre-papillary muscle junction; this plateau may have facilitated conduction of triggered activations. CONCLUSIONS: In this preparation there was a disparity of effect on Purkinje fibre and papillary muscle. Prolongation of action potential duration and repetitive activations due to early afterdepolarisations originated in Purkinje fibres and were conducted to papillary muscle. Purkinje fibre-papillary muscle interactions are of interest in relation to torsade de pointes arrhythmias which are believed to arise from this mechanism.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Differentiation of endocrine myocardiocytes in the developing heart of the toad (Bufo arenarum Hensel).

The differentiation of endocrine myocardiocytes was investigated in the heart of developing toad Bufo arenarum Hensel, combining ultrastructural and immunocytochemical procedures. The distribution of immuno-reactive atrial natriuretic peptide (ANP) in the whole heart was appraised by light microscopy, applying biotin-streptavidin and immunofluorescence techniques. With the latter procedures ANP was first recognized at embryonic stage 22, in both atrium and ventricle. In the ensuing stages the ANP-reactivity became stronger in the atrium, while it became dimmer in the ventricle. At the end of the larval prometamorphic stage, atrial myocardiocytes acquired almost all the features of adult myoendocrine cells. At electron microscope level, small inclusions, about 110-120 nm in diameter, resembling secretory granules were found in myoendocrine cells beginning at embryonic stage 22. However, no immunogold labeling of ANP occurred until stage 25. The number of secretory granules diminished in the ventricles and increased in the atrium of the larval heart and at the end of the prometamorphic stage the atrial myoendocrine cells presented the ultrastructural characteristics of active secretory cells. The synthesis of ANP in larvae is enhanced at a critical period of development when the developing toad switches from an aquatic environment to terrestrial life. The cardiac hormones seem to play a key role in the regulation of the osmolarity of body fluids at this developmental stage.

Animals↗
PubMed1991

Radiation-induced surface IgG modulation: protein kinase C involvement.

Although radiation-induced loss of surface IgG (s-IgG) expression on murine B cells is known to be dependent on intact energy metabolism and integrity of the cytoskeleton, the exact mechanism of this radiation effect is not known. Evidence reported here shows that inhibition of protein kinase C (PKC) by H-7 impairs the radiation-induced s-IgG modulation, whereas addition of HA-1004, which preferently inhibits c-AMP-dependent protein kinase, shows only minor effects. On the other hand PMA, a PKC activator, mimics the radiation effect, and H-7 but not HA-1004 inhibits the PMA-induced loss of s-IgG expression. Therefore it is suggested that PKC is involved in the modulation of s-IgG induced by irradiation on B cells. The possibility of membrane participation in this event is discussed.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Defibrillation efficacy using two low-profile endocardial electrodes.

The hypothesis that improved energy delivery and defibrillation efficacy can be achieved by using two widely separated endocardial electrodes and a cutaneous patch electrode was explored by positioning two 6.5 F electrodes (NuMed, Hopkinton, New York) with 5 cm platinum-iridium coils in the right ventricular apex (RVA) and the right ventricular outflow (RVO) in eight dogs. In another 12 dogs, an additional electrode was positioned in the RVA. A cutaneous patch (P) was placed at the cardiac apex. Biphasic pulses were delivered, the first pulse (6 ms) positive, the second negative (2 ms). The leading edge of the second was equal to the trailing edge of the first. RVO-/P+ and RVA-RVO-/P+ were compared with RVA-/P+ at a constant voltage setting required to achieve a 60% probability of success (P60) for RVA-/P+. At a constant voltage output, the probability of success for RVA-RVO-/P+ was significantly higher (81%) than RVO-/P+ (60%) or RVA-/P+ (67%) (p less than 0.03). The current delivered was greater for RVA-RVO-/P+ (9.9 +/- 2.3 amps) than for either RVA-RVO-/P+ (8.7 +/- 1.9 amps) or RVO-/P+ (9.0 +/- 2.0 amps) (p less than 0.0001). Similarly, the impedance was significantly lower for RVA-RVO-/P+ (66 +/- 12 omega) than for RVA-/P+ (75 +/- 12 omega) and RVO-/P+ (72 +/- 9.6 omega) (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of stress and beta 1 blockade on the ventricular depolarization gradient of the rate modulating pacemaker.

Prism-CLR is a closed loop, rate modulating pacemaker that uses ventricular depolarization gradient (Gd) to continuously adjust heart rate. Heart rate response to a formal mental stress protocol, esmolol (500 mcg/kg bolus, 75-125 mcg/kg/min infusion), and mental stress during esmolol infusion were studied in six patients to investigate if Gd and paced heart rate response are under direct beta-adrenergic control. Paced heart rates increased in response to mental stress in a physiological manner (P less than 0.001). Response to esmolol infusion was paradoxical, with increased paced heart rates during esmolol bolus and infusion (P less than 0.05). There was no significant alteration in either systolic or diastolic blood pressure during mental stress or esmolol infusion (P greater than 0.05). Paradoxical increase in paced heart rates during esmolol administration suggests a primary or secondary effect of esmolol to decrease the ventricular depolarization gradient. This hypothesis was supported in four dog studies in which direct Gd measurements were made during esmolol infusion. Mental stress during esmolol infusion resulted in significantly increased paced heart rates (esmolol effect) with blunted changes in heart rate in response to the mental stress. The results of this study suggest that the physiological rate response during mental stress is attributable to sympathetic autonomic response.

Adrenergic beta-Antagonists↗
PubMed1990

Protein kinase-C involvement in thymocyte apoptosis induced by hydrocortisone.

The involvement of protein kinase-C in thymocytes death induced by hydrocortisone was studied. Thymus cells were incubated 6 hr or in the presence of hydrocortisone, labeled with Acridine orange, and the DNA content of each nuclei was estimated by cytofluorimetry. The results indicate that hydrocortisone-induced DNA fragmentation can be prevented by adding the protein kinase-C inhibitor H-7 to the cell suspension. Incubation of the H-A 1004, an inhibitor of c-AMP-dependent protein kinase, with low effect on on protein kinase-C, did not interfere with the cortisone-mediated DNA fragmentation. Therefore, it can be concluded that protein kinase-C plays an important role in the process of lympholysis mediated by corticoids.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

Selective effects of tocainide in canine acute myocardial infarction.

We examined the in vivo electrophysiologic effects of tocainide in canine acute myocardial infarction. We compared the effects of tocainide in infarcted and non-infarcted zones. The left anterior descending coronary artery of 8 dogs was ligated and bipolar ventricular electrograms were recorded from a needle electrode placed transmurally in the infarcted zone and from electrodes in the non-infarcted zone. Conduction intervals were measured from the onset of the limb lead QRS to the major deflection of the recorded electrograms in the infarcted and non-infarcted zones. Effective refractory periods were also determined. Measurements were made before, during and after intravenous infusion of tocainide in therapeutic doses 2 hours after infarct. Tocainide prolonged conduction intervals by 26-31% in the infarcted zone at peak (P less than 0.001), but by only 6% in the non-infarcted zone. Similarly, tocainide prolonged the effective refractory period by 27% (P less than 0.001) on the infarcted, but by 8% the non-infarcted zone. Tocainide had very slight effects on QRS duration. The present study shows that tocainide had selective effects in the infarcted zone on both conduction and effective refractory period. These selective effects may explain its antiarrhythmic effects in acute myocardial infarction.

Animals↗
PubMed1990

Low energy partial ablation of the atrioventricular node junction in the dog using a suction-ablation catheter.

A suction electrode catheter was used for low energy, partial ablation of the atrioventricular (AV) node junction in 12 dogs. In 10 dogs, partial injury of the AV node was induced. In six dogs, delivered energy was measured precisely with use of a specially designed electronic circuit. The total energy required for partial ablation was 225 +/- 91 J. The increase in PR (p less than 0.0001) and AH (p less than 0.001) intervals was proportional to the energy delivered. After ablation, the PR interval increased from 98 +/- 10 to 154 +/- 33 ms (p less than 0.004) and the AH interval from 59 +/- 8 to 102 +/- 16 ms (p less than 0.004). There was no significant change in QRS, QTc, HV or RR intervals. AH and PR intervals were significantly prolonged at 3, 7 and 14 days after ablation (p less than 0.05). Anterograde conduction was significantly altered in 10 dogs. Anterograde AV node effective refractory period increased from 157 +/- 14 to 214 +/- 45 ms (p less than 0.005). Anterograde AV node Wenckebach cycle length increased from 196 +/- 30 to 244 +/- 44 ms (p less than 0.002). Retrograde conduction was assessed in three dogs. Retrograde AV node effective refractory period increased from 156 +/- 21 to 260 ms in two dogs, with complete retrograde block in the third. These changes persisted for up to 2 weeks. Pathologic changes were limited to the region of the AV node. In four dogs adherent thrombus without pulmonary emboli was noted. Partial focal injury to the AV node is feasible in the canine model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

From food basket to food security. The food factor in nutritional surveillance.

One important indicator of nutritional surveillance is the one devoted to monitor food security. The experience toward the development of one of such indicators is presented. This includes the development of a food basket, defined as the group of foods that meet the characteristics such as is now consumed by important population segments of the community; it contributes a substantial portion of the calories and proteins purchased, and is responsible for an important proportion of the food budget. The concept implies a dynamic food basket, the quantities of which are calculated in a way that simulates the behavior of the consumer and the best nutrition knowledge. For this purpose we use linear program techniques. A measure of the risk of being unable to buy the foods needed for a family is presented, and is used as a proxy for food security risk. In the appendix, the mathematical expressions of the model used for a linear program is also presented.

Colombia↗
PubMed1988

Dextrorotatory isomer of sotalol: electrophysiologic effects and interaction with verapamil.

The dextrorotatory isomer of sotalol (d-sotalol) has class III antiarrhythmic properties with known action potential duration (APD) prolonging effects, and is largely devoid of beta-adrenergic blocking activity. We studied its electrophysiologic effects and the mechanism of its APD prolonging effects in sheep Purkinje fibers by means of standard microelectrode techniques. At all concentrations (10(-6) to 10(-4) mol/L), d-sotalol had no effect on Vmax. At 10(-6) mol/L, d-sotalol had no effect on APD. A concentration-dependent effect of 10(-5) to 10(-4) mol/L d-sotalol was found on APD. At peak effect, APD was prolonged by 56% and 49% at 50% (APD50) and 90% (APD90) of repolarization (p less than 0.01). Early afterdepolarizations (EADs) were noted at high concentration of d-sotalol (10(-4) mol/L). These EADs were increased in number by epinephrine. To assess the mechanism of APD prolongation, verapamil (2.0 X 10(-6) mol/L) was added before and after d-sotalol treatment. In the presence of verapamil, no APD prolongation was observed even at the highest d-sotalol concentration (10(-4) mol/L). Next, during APD prolongation at the highest d-sotalol concentration, we added verapamil, noticing a remarkable shortening of APD. In addition, d-sotalol-induced EADs disappeared with addition of verapamil. Thus (1) verapamil blocks d-sotalol-induced APD prolongation and EADs and (2) this may be consistent with a mechanism via slow inward current.

Action Potentials↗
PubMed1987

Cibenzoline for high-frequency ventricular arrhythmias: a short-term comparison with quinidine and a long-term follow-up.

Cibenzoline, a new class I antiarrhythmic drug, was compared with quinidine in an open crossover study of 20 patients with frequent (greater than 30/hr) premature ventricular depolarizations (PVDs). Eight patients treated with cibenzoline experienced more than 75% reduction in PVD frequency. Cibenzoline completely suppressed ventricular couplets in eight of 17 patients and inhibited ventricular tachycardia (VT) in four of 13 patients. Only four patients (20%) responded to quinidine with a similar reduction in PVDs. Quinidine completely suppressed ventricular couplets in eight of 17 patients and episodes of VT in six of 13 patients. Cibenzoline prolonged PR, QRS, and QTc intervals. Eight patients who had shown more than a 75% reduction of PVDs were treated with cibenzoline for an extended period. At the end of three months, only five of eight patients continued to have 75% or greater reduction of PVDs. At the end of six and 12 months, four of five patients continued to have 75% or greater reduction of PVDs. Cibenzoline was similarly effective in suppressing complex arrhythmias. Thus, cibenzoline was only slightly superior to quinidine in suppressing ventricular arrhythmias. With long-term use of cibenzoline, significant PVD suppression was noted at the end of three months but not afterward.

Adult↗
PubMed1987

Myotonic dystrophy: ambulatory electrocardiogram, electrophysiologic study, and echocardiographic evaluation.

Myotonic dystrophy is frequently associated with functional and anatomic derangements in the myocardium. Ten myotonic dystrophy patients (seven men and three women, ages ranging from 35 to 58 years) were evaluated with a 12-lead ECG, 24-hour Holter monitor recording, invasive electrophysiologic studies, and echocardiographic examination. Nine patients displayed abnormalities in the conduction system. ECG and Holter monitor abnormalities were first-degree atrioventricular block (n = 8), second-degree atrioventricular block (n = 1) (Wenckebach type), complete left bundle branch block (n = 2), left anterior fascicular block (n = 5), left posterior fascicular block (n = 1), sinus bradycardia (n = 6), sick sinus syndrome (n = 2), frequent premature ventricular complexes (n = 4), and ventricular tachycardia (n = 2). Electrophysiologic study abnormalities included AH interval less than or equal to 140 msec (n = 7), AH interval greater than 140 msec (n = 3), HV interval greater than 60 msec (n = 9), and ventricular tachycardia induction (n = 1). Echocardiographic examination revealed mitral valve prolapse (n = 6). We conclude that diffuse conduction abnormalities were seen in a majority of our patients with myotonic dystrophy. Ventricular arrhythmias, including ventricular tachycardia, were seen in some of these patients, and mitral valve prolapse was a frequent finding.

Adult↗
PubMed1985

Late potentials in normal subjects and in patients with ventricular tachycardia unrelated to myocardial infarction.

Fifty normal male and female athletes, or athletically active subjects, were evaluated, and a search for low-amplitude late potentials in the terminal part of ventricular activation was performed. Recordings from 3 normal men met the definition of abnormal late potentials, and were indistinguishable by present analytic techniques from those encountered in patients who have ventricular tachycardia (VT) after myocardial infarction (MI). Of 24 patients studied, 11 had VT, but only 2 had had an MI, which occurred in the remote past. Another patient had 1 narrowed coronary artery on arteriography. Group differences could be demonstrated using amplitudes and durations of late potentials, but late potentials generally did not prove the impressive marker of the patient with VT, which other workers, as well as ourselves, have encountered in patients after MI. Late potentials were an impressive marker in a subset of the VT group in whom cardiomegaly developed. Thus, the absence of late potentials is an effective marker in the normal subject, but the presence of late potentials is not an effective marker in identifying the patient with non-MI-related, nonsustained VT before development of cardiomegaly.

Action Potentials↗