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Objectives: A study is made of the influence of methodology on the analysis of cardiac cycle variability in terms of frequency and time domains., Methods: Twenty-five individuals were divided into three groups: 1) non-smokers (n = 10); 2) smokers (n = 8); and 3) non-smokers without guided respiratory frequency (n = 7). An analysis was made of RR variability during 5 min intervals in time domain (standard deviation, variation coefficient, and difference between maximum and minimum RR), and frequency domain (spectral analysis, Fast Fourier Transform algorithm using 5 types of data windows)., Results: On comparing the results obtained in the 25 individuals with the 5 data windows, significant differences were observed (ANOVA; p < 0.001) in maximum and total amplitudes of the spectrum (in absolute terms) in the low frequency band (0.04-0.15 Hz). No significant differences were found between the normalized values or between the low/high (0.15-0.40 Hz) frequency ratio: W1 = 1.63 +/- 0.30; W2 = 1.62 +/- 0.29; W3 = 1.65 +/- 0.31; W4 = 1.52 +/- 0.26, and W5 = 1.55 +/- 0.27 (X +/- SE). On averaging the RR intervals each 5 cycles, significant differences were encountered for great part of the parameters studied. No significant differences were encountered for great part of the parameters studied. No significant differences were noted between the non-smokers as regards the use or non-use of a metronome (low/high frequency ratio in group 1 = 1.85 +/- 0.39 vs group 3 = 1.78 +/- 0.43; NS). The linear regressions between the variability parameters in terms of time and frequency domains (absolute values), and age (group 1) were significant, with greater regression coefficients on using the linear transformation of an exponential model. On comparing groups 1 and 2, a non statistically significant trend towards smaller maximum and total amplitudes (absolute values) was noted in group 2 for both frequency bands., Conclusions: 1) The type of data window (Fourier analysis) introduces significant modifications of some parameters expressed in absolute values, but not between normalized values; 2) signal averaging greatly modifies the information obtained; 3) the decrease in variability parameters observed with age fits better to an exponential model; 4) no differences were detected on guiding or not respiratory frequency, and 5) smoking appears to induce a tendency towards reducing cardiac cycle variability.

Hamsters were experimentally infected with Leishmania garnhami and then treated for 10 days with N-methyl-glucamine antimoniate (Glucantime); 60 mg/kg/day by intramuscular (im) or intralesional (il) routes. Hydride generation-atomic absorption spectroscopy was used to determine the concentrations of SbIII and SbV in the blood serum and total Sb in the tissues of the hamsters from 1 to 30 days after initiation of the treatment. Serum concentrations of SbIII and SbV were always similar. Total Sb concentrations were significantly higher in the relatively parasite-rich spleen and lesion than in any other tissue, whether treatment had been given im or il. Reduction of SbV to SbIII is probably associated with decreasing size and healing of the leishmanial ulcers. Tissue Sb kinetics is related to Leishmania behaviour and attention is drawn to the use of antimonial pentavalent compounds for diseases, other than leishmaniasis, that can affect the heart, liver and/or spleen, such as Chagas disease.

Purpose: analyze the utility of transcatheter ablation with high-frequency currents to create different experimental models of altered cardiac automatism and conduction., Method: the results were obtained in six anesthetized dogs subjected to electrophysiological study after selectively applying transcatheter radiofrequency ablation to different zones of the specific cardiac conduction system. Ablation was carried out using conventional bipolar 7F catheter-electrodes. High-frequency currents (0.7 MHz) were emitted through the distal electrode, with variable intensity and duration according to the aim of the experiment. Anatomic (fluoroscopic) and electrophysiological criteria were used to position the electrode within the ablation zone., Results: selective radiofrequency application to the atrioventricular junction zone affords complete A-V blocks with escape rhythms located in the A-V node or His-Purkinje system, together with different degrees of infra- and intra-hisian and intranodal blocks. The modification of intranodal refractoriness and conduction without interrupting atrial pulse transmission may manifest atypical patterns with truncated nodal conduction curves. The abolition of sinus function through ablation in the zone of the sulcus terminalis makes it possible to obtain supraventricular subsidiary rhythms. The obtaining of intranodal complete blocks with supra-Hisian escape rhythms demonstrates phenomena such as the modulation of subsidiary automatism by non-transmitted atrial pulses, analyzed by constructing phase-response curves., Conclusion: transcatheter ablation using high-frequency currents is useful in demonstrating phenomena related to intranodal and His-Purkinje conduction, subsidiary pacemaker automatism or the modulation of automatism and conduction via non-transmitted pulses.

The authors describe a ventricular arrhythmia observed in 14 patients between 1972 and 1991, and 9 cases in the literature. The patients were hospitalised for investigations of syncope related to torsades de pointes. They were characterised by the very short coupling interval to the initiating extrasystole (average: 245 ms), by the young age of the patients (average: 34.6 years) and by the absence of overt cardiac disease. The resting electrocardiogrammes were normal, especially ventricular repolarisation. Some recordings showed isolated ventricular extrasystoles with short coupling intervals. Quite often, a family history of sudden death was obtained. These episodes of ventricular arrhythmia may degenerate to ventricular fibrillation. Pharmacological and electrophysiological investigations did not show any consistent characteristic electrophysiological behaviour. Investigations of autonomic nervous system function showed a decrease in global sinus rhythm variability and an increased sympathetic over parasympathetic activity. The clinical outcome of these patients is unpredictable with present methods. From a therapeutic point of view, Class I antiarrhythmics, betablockers and amiodarone were ineffective. Verapamil showed an electrocardiographic improvement by increasing the coupling interval of the extrasystoles and decreasing or even suppressing some repetitive forms, but without preventing recurrences. The indications for an implantable automatic defibrillator should be considered in this group of patients. These patients have clinical and electrocardiographic abnormalities which are sufficiently coherent for them to constitute a new pathological entity which the authors suggest calling "torsades de pointes with a short coupling interval".

Although transcatheter radiofrequency modification of the atrioventricular (AV) node has been proposed as curative treatment in AV nodal reentry tachycardias, its role for the control of the ventricular rate in atrial tachyarrhythmias remains unclear. The aim of this study was to analyze the acute effect of radiofrequency current on AV nodal conduction and refractoriness, and to compare it with the effects of two antiarrhythmic drugs such as amiodarone (class III) and flecainide (class I). Twenty-one dogs were studied: (1) radiofrequency group (5 W for less than 45 seconds; 2 to 12 discharges; seven dogs); (2) amiodarone group (5 mg/kg intravenously; seven dogs); and (3) flecainide group (2 mg/kg intravenously; seven dogs). The following parameters were measured under basal conditions and after each procedure: AH interval, AV nodal functional refractory period, Wenckebach cycle length, minimum R-R interval during atrial fibrillation, and fitting of AV nodal function curve to a hyperbolic equation using its linear transformation. The AV nodal effective refractory period could not be calculated in any dog in the basal study because it was shorter than the atrial functional refractory period.(ABSTRACT TRUNCATED AT 250 WORDS)

The principle of flow injections analysis (FIA) is briefly described, along with some of its advantages for analytical measurements. A review of the development, current status and application of FIA coupled with optical or electrochemical techniques for the determination of various elements in body fluids is presented. Further, the analytical potential of FIA for the determination of elements in biological materials is then summarized and trends in the methodology are given brief consideration.

The effects of acute and chronic administration of lithium (Li) on the basal levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxy-indoleacetic acid (5-HIAA), and the amphetamine-induced DA increase were assessed in the Nucleus Accumbens (NAC) and Prefrontal Cortex (PFC) by brain dialysis in freely-moving rats. Acute Li (2 meq/L) was locally administered by reverse dialysis. Chronic Li (2 meq/kg) was intragastrically administered for 14 days. No effect was observed after acute Li administration. However, after chronic Li administration, the basal levels of DOPAC and the amphetamine-induced DA increase in the NAC were significantly higher in the Li-treated rats than in the saline-treated controls. In the PFC, while the amphetamine-induced DA increase was not affected by chronic Li, the basal levels of DA and DOPAC were significantly decreased after Li administration. The effects of chronic Li in the NAC could be due to increased synthesis and/or decreased release of DA, whereas in the PFC the effects could be due to a decreased synthesis of DA. The absence of effects of acute Li administration is in agreement with the therapeutic inefficacy of the acute use of the cation. The changes observed after chronic treatment in the NAC and the PFC could be related to the effects of Li on mood disorders and cognitive functions, respectively.

Sodium, potassium, chloride, calcium, inorganic phosphorus (Pi) and magnesium contents in the serum of 75 myocardiopathic chagasic patients together with that in 29 healthy controls were determined. Blood samples were taken by catheterization from the superior cava vein (SCV), coronary sinus (CS), pulmonary artery (PA) and a peripheral artery, usually the femoral (FA). The results show that the average serum sodium, potassium, chloride, calcium and PI were invariably different in most samples, except the levels of potassium in SCV and Pi levels in FA. The serum concentration of magnesium was significantly different only in the blood of CS. In general one can observe that in the chagasic patients the serum sodium, chloride and calcium tend to diminish while serum potassium, Pi and magnesium tend to increase, especially in CS blood. The coronary gradient indicates that sodium, chloride and calcium tend to deposit in heart tissues, whereas the other elements (potassium, magnesium and Pi) tend to be released from this tissue. The systemic and peripheric gradients suggest that the chemical elements under study tend either to deposit in/or be released from different tissues depending on the course of development of the chagasic myocardiopathy.

A case of acute poisoning by oral ingestion of fenthion is reported. Plasma cholinesterase activity and fenthion whole blood concentration were thoroughly evaluated during the therapeutic intervention that consisted in administration of atropine, toxogonine and fresh plasma. Correlation studies between clinical signs, cholinesterase activity and fenthion levels revealed that pChE activity was not as helpful as the patient's clinical status in determining when the atropine infusion could be stopped. Moreover pChE was also useless in signaling sudden relapses. It is concluded, based on this case, that supportive care combined with antidotal therapy remains the cornerstone of treatment specially in severe acute poisoning cases.

The present study describes the effect of high doses of vitamin K3 (8-30 mg/kg) administered daily by intramuscular injection during seven days; on blood smear, red blood cells (RBC) and concentration of hemoglobin (Hb) counts, value of hematocrit (Ht), mean corpuscular hemoglobin concentration (MCHC), reticulocyte and erythroblast counts, total and differential counting of leukocytes (WBC) and total and fractionated serum bilirubin concentration of albino male rats. Results were then compared with findings in normal rats treated with the same doses of sodium bisulfite. In animals treated with vitamin K3 a statistically significant decrease in the number of erythrocytes and in the concentration of Hb, Ht and MCHC was found together with a concomitant increase of erythroblast and reticulocyte counting. In regard to the blood smear, it was observed that erythrocytes vary in their hemoglobin content, size, shape and in their staining properties (polychromatophilia) where as the leukocytes were found to be morphologically normal, but in an increased number. Lymphocytes occasionally showed azurophil granules. Platelets assumed irregular shape and in normal amounts. The leukocytes count showed leukocytosis with marked neutrophilia, eosinophilia, lymphocytosis and monocytosis. Also, the presence of clinical jaundice with an increase of the serum "indirectly-reacting" bilirubin was also observed. These findings indicate that hypervitaminosis K3 induces a marked hemolytic microcytic hypochromic anemia and changes in the white blood cells count. Further studies will be pursued in order to obtain a better understanding of the causes and/or the mechanisms that induce these alterations in the blood cells.

Two experiments are reported here. First, the effect of lithium chloride (1, 2 and 4 mEq/kg IP for 21 days) on body weight was assessed in female and male rats. Food intake was measured in the rats treated with 2 mEq/kg. All the doses tested significantly increased body weight in female rats. A linear relationship between body weight gain and lithium dose was also observed. In contrast, in male rats, the low doses of lithium (1 and 2 mEq/kg) did not affect body weight, whereas the high dose (4 mEq/kg) decreased body weight. These results confirm previous reports on a sex-dependent effect of lithium on body weight in rats. In the second experiment, body weight and food intake were assessed in female rats treated with lithium alone, or in combination with insulin or sulpiride, a D2 dopamine receptor blocker. It was found that the effect of lithium on body weight and feeding was additive to the effects of sulpiride and insulin. These findings are indirect evidence that lithium enhances body weight in rats by a different mechanism than the one described for sulpiride or insulin.

Blood serum selenium levels were measured in healthy subjects of six districts located throughout the province of Mérida, Venezuela. There were either high (87-115 micrograms/L) or low (58-72 micrograms/L) serum selenium-containing districts. Serum selenium in males from three districts were statistically significantly lower (p less than 0.001) than in females. There was a general tendency for serum selenium to increase with age. On the average, a reduction in cancer was observed in the districts with high serum selenium content. Further, serum selenium was lower in male patients from the Mérida district with cancer disease. Association between selenium in soil and in the blood serum of healthy subjects has been observed.

A comparative study of the analytical performance of fluorimetric spectrophotometric, atomic absorption spectrometric, flow injection analysis with atomic absorption spectrometric, flow injection analysis with atomic absorption spectrometric detection, hydride generation with atomic absorption spectrometric detection and hydride generation with molecular emission cavity analysis detection methods has been carried out for the determination of selenium in biological materials. Based on results concerning detection limit, linearity and sensitivity, only the fluorimetric and hydride generation with atomic absorption spectrometric detection methods were suitable for the determination of selenium in biological materials. Whereas, the spectrophotometric, flame absorption spectrometric flow injection-atomic absorption spectrometric and hydride generation with molecular emission cavity detection, due to its worse detection limits and poorer sensitivities, were found to be unsuitable for the determination of selenium in such matrices. The accuracy of the fluorimetric and hydride generation with atomic absorption spectrometric detection methods were tested by using NBS standard reference materials.

Chronic administration of lithium displays therapeutic and prophylactic effects in bipolar affective disorders, but its mechanism of action remains unknown. Several studies in animals and humans strongly suggest that central serotonergic neurons might be involved in lithium effects. In the experiments reported here microdialysis with removable probes and high pressure liquid chromatography and electrochemical detection were used to assess the amphetamine-induced release of serotonin (5-HT) and the 5-hydroxy-indoleacetic acid (5-HIAA) levels in the perifornical hypothalamus (PFH) and hippocampus (HP) of freely moving rats before and after chronic lithium chloride administration (2 meq/kg, as intragastric daily injections for 14 days). The serum lithium levels were 0.66 +/- 0.08 meq/l. After lithium treatment, the amphetamine-induced 5-HT release was significantly enhanced in the PFH but not so in the HP. Basal levels of 5-HIAA in the control group decreased but remained unchanged in the lithium group in the PFH. No change of basal levels of 5-HIAA was observed in the HP. The effect of lithium on the PFH could be related to the improvement of the autonomic and cyclic symptoms of patients with manic depressive disorders undergoing lithium therapy.

The gas exchange and water relations of the hemiparasite Pthirusa maritima and two its mangrove host species, Conocarpus erectus and Coccoloba uvifera, were studied in an intertidal zone of the Venezuelan coast. Carbon uptake and transpiration, leaf osmotic and total water potential, as well as nutrient content in the xylem sap and leaves of mistletoes and hosts were followed through the dry and wet season. In addition, carbon isotope ratios of leaf tissue were measured to further evaluate water use efficiency. Under similar light and humidity conditions, mistletoes had higher transpiration rates, lower leaf water potentials, and lower water use efficiencies than their hosts. Potassium content was much higher in mistletoes than in host leaves, but mineral nutrient content in the xylem sap of mistletoes was relatively low. The resistance of the liquid pathway from the soil to the leaf surface of mistletoes was larger than the total liquid flow resistance of host plants. Differences in the daily cycles of osmotic potential of the xylem sap also indicate the existence of a high resistance pathway along the vascular connection between the parasite pathway along the vascular connection between the parasite and its host. P. maritima mistletoes adjust to the different physiological characteristics of the host species which it parasitizes, thus ensuring an adequate water and carbon balance.

Ten anesthetized dogs were studied in an attempt to provoke partial alterations in atrioventricular (AV) conduction by high-frequency current (HFC) transcatheter ablation. A discharge power (10 to 15 W) was used for less than 5 seconds after reaching complete AV block (CAVB). The catheter was placed within an area having an A/V ratio = 1 with His bundle deflection. If following discharge, no appreciable lengthening an AH, AV nodal block cycle length (Wenckebach point, WP), and/or functional nodal refractory period (FRPAVN) was observed, the procedure was repeated. Four dogs (group I) were killed immediately, and the other six (group II) after 2 to 4 weeks. The AH interval, WP, and FRPAVN were found to prolong significantly following HFC, without variations in HV interval. In group II, two dogs progressed to CAVB, whereas the other four maintained 1:1 AV conduction with AH, WP, and FRPAVN greater than before the power discharge. In conclusion, HFC is an efficient technique to induce partial alterations in AV conduction, since the discharge can be adjusted and the ablation can be localized to specific regions.

In this study, the lithium concentration in the blood sera of 85 patients with endemic goiter was evaluated. The results were compared with those obtained in 114 normal subjects. The lithium concentration in the blood sera of the patients with endemic goiter was 74.00 +/- 2.88 micrograms/dl compared with 39.00 +/- 0.19 micrograms/dl detected in normal subjects. Based on these findings, a possible explanation to the values obtained is given.

The effect of hypervitaminosis A on the content of sodium, potassium, magnesium, iron, zinc and copper in rat serum was studied. Results were compared to findings in non-treated animals. The serum content of potassium, magnesium and copper increased significantly, while the content of sodium, zinc and iron decreased significantly in the treated animals, when compared to the values obtained with untreated animals. Possible mechanisms for these changes are discussed, and we conclude that high doses of vitamin A cause a marked change in the serum content on the measured cations.

Copper, zinc and iron concentrations were determined in blood serum and parotid saliva of patients with various otorhinolaryngological disorders such as sinusitis, rhinitis, otitis and amygdalitis. Comparing results between individuals of control group and patients significant differences were observed in concentrations of the metals studied as a result of the different infections diseases.

Zinc, iron and copper content in serum of 75 myocardiopathic chagasic patients together with that in 29 healthy controls were determined. Blood samples were taken by catheterization from the superior cava vein, coronary sinus, pulmonary artery and a peripheral artery, usually the femoral. In general, serum zinc and iron levels tend to diminish in chagasic patients, while serum copper levels tend to increase. The coronary, systemic and peripheric gradients indicate that all these metal elements tend to deposit in heart tissue. Although zinc and iron tend to be deposited also in liver and other tissues, copper is released from them into the blood stream. Further studies should determine the requirement of these metal species in heart and other tissues of experimental animals in order to obtain more conclusive information about the cause of the serum metal impairment observed here.

The linear correlation of the circadian rhythms (CR) of heart rate (HR) with those of ventricular extrasystole (VE) is analyzed by electrocardiographic ambulatory monitoring in 32 patients: 22 with ischemic post-infarction cardiopathy (group A) and ten free of structural cardiopathy (group B). Variability expressed as the coefficient of ventricular extrasystole variation (100 x standard deviation/mean) presented an inverse correlation with the number of recording extrasystoles. Linear correlation between HR and VE was statistically significant in 72% of recordings in group A, and in 60% in group B. The percentage of cases with significant linear correlation was greater on analyzing the three-minute periods than with the longer periods. When the cases analyzed presented over 200 extrasystoles, the percentage with significant linear correlation between HR and extrasystole was greater in group A than in group B. The circadian rhythm of the ventricular extrasystoles using interpolation of a cosinor function was significant in 50% of group A cases, and in 60% of group B. The achrophases were diurnal in group B, but only in 45% of cases in group A, two correspondence models being found between the CR achrophases and the inverse linear correlation between HR and VE.

Lead content in head hair of 53 gas station workers together with an equal number of normal controls was determined. Samples of hair were washed with ethanol and water and microwave-aided wet digested prior to the determination of lead by flow injection/atomic absorption spectrometry. The lead content in hair of the gas station workers (48.7 +/- 17.5 micrograms/g) was significantly higher than that of the normal controls (17.2 +/- 8.1 micrograms/g). The effects of washing and sample digestion procedures, head sampling site, hair color, age, smoking habits and duration of exposure to the metal are discussed.

The effect of eight doses of 10,000, 20,000 and 30,000 UI of vitamin D2 administered every other day to three groups of rats, on the activities of some enzymes in the animals' liver was evaluated. In general terms, findings revealed a decrease in the activities of glucose-6-phosphatase, phosphorylase and arginase. Likewise, an increase of the activities of maltase and of glutamic oxaloacetic and glutamic pyruvic transaminases was observed. Furthermore, the activities of cholinesterase and alpha-amylase also varied depending on the vitamin D2 doses administered.

A simple and reliable method for the measurement of sodium and potassium in blood serum without any sample dilution by using flow injection and atomic absorption spectrophotometry is described. A sample throughout of 100 measurements per hour is possible. Matrix problems have not been encountered. The coefficient of variation for within-run determinations is about 1,14 and 2,36% for sodium and potassium, respectively, in serum samples (n = 10). The method is easily adaptable to pediatric research, because of the low required sample volume of 5 microliter.