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Biomedical subjects

R Baranowski

Publications and source records attributed to R Baranowski.

17 recordsLinked to original sources
PubMed2003

Direct observation of homoclinic orbits in human heart rate variability.

Homoclinic trajectories of the interbeat intervals between contractions of ventricles of the human heart are identified. The interbeat intervals are extracted from 24-h Holter ECG recordings. Three such recordings are discussed in detail. Mappings of the measured consecutive interbeat intervals are constructed. In the second and in some cases in the fourth iterate of the map of interbeat intervals homoclinic trajectories associated with a hyperbolic saddle are found. The homoclinic trajectories are often persistent for many interbeat intervals, sometimes spanning many thousands of heartbeats. Several features typical for homoclinic trajectories found in other systems were identified, including a signature of the gluing bifurcation. The homoclinic trajectories are present both in recordings of heart rate variability obtained from patients with an increased number of arrhythmias and in cases in which the sinus rhythm is dominant. The results presented are a strong indication of the importance of deterministic nonlinear instabilities in human heart rate variability.

Journal Article↗
PubMed2002

Gas chromatographic determination of prostaglandins.

Progress in separation and detection of prostaglandins and the other metabolites of arachidonic acid by means of GC-ECD, GC-MS, and GC-MS-MS in the course of the past fifteen years was reviewed. One discussed the problems of sample preparation, selection of proper chromatographic conditions, and detection modes available. Finally, applications of the methods developed to detection and quantification of prostanoids in biological material was presented.

Animals↗
PubMed2001

[Analysis of risk factors of the paroxysmal atrial fibrillation after valve replacement in patients with aortic stenosis].

UNLABELLED: Paroxysmal atrial fibrillation (PAF) is a frequent complication (10-60% of pts) after cardiac surgery. In our study we analyze the influence of clinical, echocardiographic and 24 h ecg parameters on the risk of postoperative PAF in 266 pts with aortic stenosis (88 women and 178 men; mean age 58 +/- 10). PAF was observed in 74 (28%) patients. Statistically significant factors of risk of PAF were (univariate analysis): age-relative risk 1.08 (1.04-1.11), history of PAF--4.3 (1.4-12.5), more than 100 supraventricular ectopic beats during 24 h ecg--2.9 (1.6-5.1), presence of SVT during 24 h ecg--2.6 (1.5-4.5) and presence of SVT > 140/min--relative risk 3.5 (1.8-6.7). Left atrium diameter and coronary artery bypass grafting during valve replacement had no impact on the risk of PAF. In multivariate analysis three factors remained significant--age, history of PAF and presence of SVT > 140/min during 24 h ecg. In discriminant analysis this model of 3 factors enabled the correct risk assessment in 72% of patients. CONCLUSIONS: 1. The factors that increase the risk of postoperative PAF in pts with aortic stenosis are: age, history of PAF and presence of SVT > 140/min during preoperative 24 h ecg. 2. Postoperative PAF is not related to left atrium diameter in this group of patients. 3. Coronary artery bypass grafting during aortic valve replacement does not increase the risk of PAF.

Adult↗
PubMed2000

Time-frequency analysis of the RT and RR variability to stratify hypertrophic cardiomyopathy patients.

The RT interval is a measure of the ventricular repolarization and is partially influenced by the sympathovagal balance. The analysis of the variation of the duration of the RT and RR intervals might bring new information about the arrhythmogenic vulnerability and autonomic imbalance. The RR signal and its spectral density (SD) are characterized by two different patterns during the sleep period. On the basis of this information, RT and RR sequences have been automatically classified into two patterns, R and N. In this work, we propose a methodology to define new variables that are able to distinguish patients with hypertrophic cardiomyopathy (HCM) who later developed sudden cardiac death (SCD) from HCM patients without such episode during the follow-up. These variables are based on the instantaneous frequency calculation using time-frequency representation of the RT and RR signals previously classified into R and N patterns. In this study, three spectral bands have been considered: low-frequency band (LF, 0-0.07 Hz), mid-frequency band (MF, 0.07-0.15 Hz), and high-frequency band (HF, 0.15-0.45 Hz). Then a suitable combination of mean energy and mean frequency of the RT and RR signals in the MF and HF bands has allowed HCM patients with SCD to be discriminated from HCM patients without SCD (P < 0.001).

Adult↗
PubMed1999

[Long-term follow-up of supraventricular tachyarrhythmia in adult patients with secundum atrial septal defect before and after surgery].

The frequency of arrhythmias was determined pre- and postoperatively in adult patients with secundum atrial septal defect. The study group consisted of 224 pts who had undergone surgical repair of ASD II in between 1987-1993. The mean postoperative follow-up was 7.5 y. The group (160 F, 64 M, aged 17-66 y) was divided on 3 subgroups: I--age under 20 y--27 pts, II--20-40 y--131 pts, III--over 40 y--66 pts. We analysed pre- and postoperative parameters: 1) arrhythmias in the 24-h Holter recording, 2) pulmonary hypertension (PASP-Doppler), 3) coexisting diseases, 4) functional class of heart failure (NYHA). Most common abnormalities found were supraventricular tachyarrhythmias (22.8 pre- and 40.6% postoperatively). There was significant increase in frequency of arrhythmias after surgery in the subgroups II and III. Arrhythmias were most frequent in patients with coexisting arrhythmogenic diseases.

Adolescent↗
PubMed1993

[Coronary ultrasonography. More exact than coronary angiography? Description of two case histories].

Coronary angiography as the "golden standard" in diagnostic imaging, guiding and assessing the results of interventional therapy has well known limitations inherent to the two dimensional imaging of three dimensional structures. Intravascular ultrasonography provides cross-sectional images of coronary artery, allowing an accurate calculation of cross-sectional luminal area and assessment of the degree of eccentricity of plaque and its structure including fissures, dissections and intracoronary thrombi. Case 1: Coronary angiography was performed in a 60 y. male patient with unstable angina revealing only a 40% stenosis in proximal LAD. The inconsistency of clinical presentation with angiography findings led to perform an intravascular ultrasound (IVUS) examination of LAD. The angiographic 40% stenosis was found to be over 80% on IVUS. Subsequent PTCA procedure led to a good IVUS and clinical result with no obvious changes in angiography. Case 2: PTCA of 80% Cx stenosis was performed with good immediate angiographic result, without dissection nor residual stenosis. However, IVUS immediately after PTCA assessed a dissection of the plaque with a flap protruding into the lumen. The patient was sent back to coronary angiography several hours later with clinical and ecg symptoms of acute myocardial ischemia. An important, occlusive dissection was found at the PTCA site. Angioplasty was performed again restoring a wide lumen at intervention site. IVUS was able to clarify the ambiguous angiographic findings with an important impact on interventional therapy. The immediate results of invasive procedures were readily and safely assessed by intravascular ultrasound.

Aortic Dissection↗
PubMed1992

[Increased tension on the sympathetic nervous system in arrhythmogenic right ventricular dysplasia. Participation in etiopathogenesis?].

UNLABELLED: To evaluate the suspected role of sympathetic nerve tone in pathogenesis of arrhythmogenic right ventricle dysplasia (ARVD), noradrenaline (NOR) and adrenaline (AD) plasma levels were determined by radioenzymatic method in 10 pts with ARVD (mean age 36 y, VT-8 pts, syncope-5) at rest and during peak exercise. 9 healthy men (mean age 28 y) served as control. RESULTS: [table: see text] CONCLUSION: Significant increase of norepinephrine serum level during peak exercise suggests essential role of sympathetic nerve tone in pathogenesis of ARVD.

Adult↗
PubMed1990

[Ambulatory 24-hour blood pressure monitoring in patients with resistant hypertension].

The aim of the study was to assess the usefulness of 24-hour blood pressure (BP) and heart rate (HR) monitoring in patients with "resistant" hypertension. 30 patients (44.1 +/- 9.9 years) with diastolic BP 100 mm Hg or more in spite of treatment with three or more antihypertensive drugs were studied. Ambulatory recording of BP and HR was performed by means of Del Mar Avionics monitoring system 9000. Mean recording time was 21.5 hours and mean number of measurements during one recording--56.7. Mean ambulatory systolic and diastolic BP values were significantly lower than mean value of three casual measurements (146.0 +/- 24.6 vs 171.5 +/- 21.2 mm Hg for systolic and 97.2 +/- 11.3 vs 110.4 +/- 7.5 mm Hg for diastolic BP p less than 0.01) In 14 (46.6%) systolic BP and in 10 patients (33.3%) diastolic BP were normal. The patients with normal and abnormal ambulatory BP recordings did not differ in regard to age and mean clinic BP levels. However, patients with abnormal ambulatory BP recordings were more often overweight and showed a greater frequency of left ventricular hypertrophy and family history of hypertension and its complications. The results of the study show that ambulatory BP monitoring may be of value in assessing the response to antihypertensive treatment in patients with so called resistant hypertension as judged on the basis of clinic pressure.

Adult↗
PubMed1988

Effects of triiodothyronine replacement on the anemia of chronic renal failure.

Patients and/or experimental animals with chronic renal failure have decreased serum levels of triiodothyronine (T3), a hormone well known for its erythropoietic activity. The following studies were designed in order to determine whether this observed abnormality in T3 metabolism is an important contributory factor to the etiology of the anemia of uremia. Groups of rats were made chronically uremic by a standard 5/6 nephrectomy technique and received slightly above physiological doses of T3 either by intermittent S.C. injections (twice daily) or by continuous infusion from intraperitoneally implanted osmotic minipumps. After 2 weeks of such treatment, and despite a normalization of serum T3 levels, there were no significant changes in the hematocrit, individual red cell mass, or serum erythropoietin levels of the uremic animals given T3 compared to control rats. We conclude that (1) the decreased serum T3 levels observed in uremia are not an important contributory factor to the pathogenesis of the anemia, and (2) treatment with replacement doses of T3 does not result in significant improvement of erythropoiesis.

Anemia↗
PubMed1986

The effects of locally applied capsaicin on conduction in cutaneous nerves in four mammalian species.

By examination of compound action potentials in the saphenous nerve of the anaesthetized rat it has been shown that capsaicin causes a rapid, dose-dependent, failure of conduction in many C-fibres when applied directly to the nerve. A large reduction in C-fibre conduction occurs with concentrations as low as 110 microM. After a 15-30 min exposure to capsaicin, only partial recovery occurs in 1 h. Similar block of C-fibre conduction occurs in the ferret. However, only smaller, reversible, reductions in C-fibre conduction were seen in the guinea-pig and rabbit, even at the highest concentration of capsaicin used (33 mM). A small reduction in the A delta component of the compound action potential occurred in all four species. In the rat and ferret the effects were much less than those on C-fibres. At high doses, small reversible effects were also seen on the fastest conducting A alpha beta component of the compound action potential in the rat, rabbit and guinea-pig; no effects were seen on the A alpha beta fibres in the ferret. Decreases in amplitude of the compound action potential were accompanied by some slowing of conduction in most cases. The slowing was less than 5% except for the rat A alpha beta and C-fibres and the ferret C-fibres where 9-15% changes occurred at the highest doses of capsaicin. Opening the connective tissue sheath of the nerve did not significantly increase the effectiveness of capsaicin.

Action Potentials↗
PubMed1985

Receptive field size of hair follicle afferents in rats treated neonatally with capsaicin.

Receptive field parameters of G- and D-hair units were investigated in adult rats given capsaicin as neonates. An air jet stimulator mounted on a two-way micromanipulator was used for accurate mapping of receptive fields. Diameters of G- and D-hair unit receptive fields were similar in both control and treated groups averaging 2.14 and 2.44 mm respectively with a 1.5 X threshold stimulus. It is concluded that the reported expansion of rat spinal cord cutaneous receptive fields following capsaicin treatment does not have any significant peripheral component.

Animals↗
PubMed1979

Functional characterization of drug-induced experimental papillary necrosis.

The functional expression of papillary necrosis was investigated with a model of drug-induced papillary necrosis. Bromoethylamine hydrobromide (BEA) administration to rats uniformly resulted in the development of papillary necrosis. All studies were performed 24 hours after BEA administration with the exception of the electrolyte balance studies, which were performed during the 72 hours after the induction of papillary necrosis. GFR was not different between BEA-treated and sham rats. BEA-treated rats had a significantly lower maximal urine osmolality and free water reabsorption than did sham rats. Renal tissue concentrations of sodium, potassium, and water were not different between BEA-treated and sham rats. During water diuresis, free water clearance was not significantly different between the two groups. During sodium bicarbonate administration, maximal bicarbonate reabsorption and urine-blood Pco2 gradient (at comparable urine bicarbonate concentrations) were not significantly different between the two groups. During sodium sulfate infusion, there was no difference in minimum urine pH, ammonium excretion, and net acid excretion between chronically acidotic BEA-injected and sham rats. In rats on "zero" sodium intake, BEA administration resulted in a significant increase in urine flow and sodium excretion, whereas sham rats remained in sodium balance. In rats with restriction of both sodium and chloride, BEA administration resulted in a significant wastage of sodium, chloride, and calcium. There was no difference in potassium excretion between BEA-treated and sham rats during hydropenia, bicarbonate administration, sodium sulfate infusion, or ingestion of a normal potassium diet. When potassium intake was restricted to "zero," BEA-treated rats developed potassium wastage; when potassium intake was increased to 21 mEq/day, BEA-treated rats had a significantly lower potassium excretion than did sham rats. These findings may result from alterations in collecting duct transport, but damage to deep medullary structures may also contribute.

Animals↗
PubMed1976

Effect of renin on extrarenal erythropoietin production.

Extracts containing renal erythropoietic factor (REF) and others which contain renin reportedly enhance erythropoietin (Ep) titers in the plasma of hypoxic nephrectomized rats. Studies reported here were designed to elucidate the mechanism by which renin increases Ep production in the anephric rat. Injection of a renal extract containing renin significantly raised the blood pressure of anephric rats, and when it was injected just prior to exposure to hypoxia and 15 hour postnephrectomy, the resultant plasma Ep level exceeded that observed in rats exposed to the same hypoxic conditions immediately postnephrectomy. In contrast rats made hypoxic 15 hours after nephrectomy, but not given renin, had plasma Ep levels which were lower than those of anephric rats made hypoxic immediately postoperatively. When renin was injected immediately after nephrectomy or into normal rats, it failed to stimulate Ep production. When diazoxide was injected with the renin extract into hypoxic nephrectomized rats, the vasopressor effect of renin was abolished for 4 hours, and the plasma Ep levels were significantly lower than those of hypoxic nephrectomized animals injected only with renin, Injection of angiotensin II into anephric, hypoxic rats had an effect comparable to that of renin on extrarenal Ep roduction. REF was not detectable in the renin preparation. These results are best explained by the concept that renin and angiotensin increase extrarenal Ep production by causing vasoconstriction and consequently hypoxia in extrarenal sites of Ep production. Also of interest is the finding that plasma EP levels of rats, injected with renin and made hypoxic 15 hours postnephrectomy, are higher than those previously reported to occur in anephric rats.

Angiotensin II↗