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Biomedical subjects

R Dvorák

Publications and source records attributed to R Dvorák.

At least 19 recordsLinked to original sources
PubMed1999

[Electric programmed ventricular stimulation using a permanent cardiac pacing system--a noninvasive method in arrhythmia].

BACKGROUND: Complex forms of ventricular arrhythmias often occur in patients with an implanted permanent cardiac pacing system. Some of the pacemakers are provided with software which allows electrophysiological testing of the cardiac conduction system by coupling with an external diagnostic pacemaker via their programmer. This method is non-invasive. METHODS AND RESULTS: In a group of 26 patients (19 males, 7 females) with an implanted pacemaker (Paragon III, Synchrony III, Sensorithm--all Pacesetter) complex ventricular arrhythmias were observed (class Lown IVa and higher). In these patients the electrical stability of the myocardium was tested by the described method (protocol: incremental pacing 90-220 bpm, pacing drives 110 bpm and 140 bpm with 1-3 extrastimuli). Complex ventricular arrhythmias were induced in 42% patients (n = 11), in this subgroup 55% (n = 6) was non-sustained ventricular tachycardia, 36% (n = 4) sustained ventricular flutter, 9% (n = 1) sustained ventricular tachycardia. Patients with non-sustained ventricular tachycardia were treated with beta-blockers, in the others the effective therapy was selected according to electrophysiological testing (amiodarone in 4 patients, ICD in 1 patient). During a 24-month follow-up the overall mortality was 7.7% (n = 2), sudden death mortality was 3.8% (n = 1). CONCLUSIONS: Programmed ventricular stimulation performed by a permanent cardiac pacing system is a simple and above all non-invasive method with no need for fluoroscopy. It can be repeated several times. It is not possible to pace from the right ventricle outflow tract. This is the main disadvantage. Nevertheless, by using non-invasive risk stratification methods (echocardiography, signal averaged ECG, heart rate variability, baroreflex sensitivity, dispersion of QT interval) the patients in need of an invasive study can be identified. This method can be considered an alternative screening method and a standard part of the investigation of the algorithm in patients with a previously implanted pacemaker.

Arrhythmias, Cardiac↗
PubMed1998

Preferential silver reaction of nucleolar regions adjacent to fibrillar centers in ring shaped nucleoli of leukemic lymphocytes.

Silver stained proteins (SSPs) characteristic for interphasic nucleolus organizer regions (NORs) associated with fibrillar centers (FCs) and adjacent nucleolar regions of ring shaped nucleoli in leukemic lymphocytes exhibit a different sensitivity to the mild acid extraction including that with HCl. Such extractions permit a preferential visualization of fibrillar centers adjacent regions (FCARs) which are believed to represent sites of the ribosomal RNA (rRNA) transcription. The resistance of SSPs in FCARs to the extraction with HCl seems to be due to their binding to other components present in these regions. The extractibility of SSPs with HCl was influenced by the fixatives used. The largest resistance of SSPs to the extraction with HCl was noted after fixation with glutaraldehyde. In contrast, the largest extractibility of these proteins was observed after fixation with unbuffered formaldehyde.

B-Lymphocytes↗
PubMed1998

[Optimalization of rate adaptation using Holter functions in DDD/R pacemakers].

Introduction of the pacing rate adaptation according to the momentary metabolic needs added other programmable parametres which demand physician's attention during the initial postimplantation programmation and also in follow-up of pacemaker patients. The parametres setting is strictly individual with a need of feedback control. In some devices it is enabled by Holter functions as a part of pacemaker software. These methods were used to set the rate adaptive parametres in the group of 23 patients with implanted DDD/R pacemaker. The walking stress test was used. Model follow-up situations are presented in 3 case reports. Using Holter functions enables the physician to put patient's subjective complains in relation with actual heart rate--this is used to optimize the parametres of rate adaptation. The authors consider the Holter functions a necessary part of rate adaptive pacemaker software.

Aged↗
PubMed1997

[Selection and long-term effect of treatment in vasovagal neurocardiogenic syncope].

BACKGROUND: Syncope state performed by transient loss of consciousness connected with a postural tone decrease present still an important therapeutical problem. The authors use HUT testing for discovering of vasovagal etiology of a syncope. The aim of the study was to find out the optimal medication in treatment and prevention of VVS by repeated HUT drug testing in a group of positive patients. METHODS AND RESULTS: We examined a group of 300 patients (172 female and 128 male) age 35.26 +/- 13.47 years with an anamnesis of recurrent syncopes by HUT test. In 83 patients (27%) we set up a diagnosis of VVS. Thirteen patients (15.66%) were only followed without medication. The rest of the group (70 patients, 84.34%) started with a therapy. Testing was performed by repeated HUT according to the "Westminster protocol". HF and BP were measured by FINAPRESS 2,300 made by Ohmeda. The effective therapy was found in 64 patients (91.43%) of the group. For various reasons the therapy was changed and retested in 9 patients (14.06%). Beta1 selective beta-blockers were used in 51 patients (80.96%) theophyllin in 5 patients (7.94%), etilephrin in 6 patients (9.52%) and clonidine in 1 patient (1.59%). CONCLUSIONS: The therapy of VVS should be set-on according to the effective drug selection by serial drug testing in repeated HUT tests. The article shows a high predictive value of negative HUT test for a long term effect of tested therapy.

Adult↗
PubMed1997

[Significance of vegetative nerve tone in patients with vasovagal neurocardiogenic syncope].

The timely provided and precise diagnostic of the syncopal states as well as their causal therapy is a main subject of many medical branches interest within last time. Our work was concentrated on a vasovagal neurocardiogenic syncope. The definition of the vegetative nervous tonus participation on its development by a method of evaluation of the heart rate variability as well as the review of a possibility to the application of quantification these results to a prediction of vasovagal reaction, respective of its malignant variant, was the main aim of our effort. Our results enable a conclusion, that the observation of aquiet autonomic nervous tonus does not represent a contribution to a differential diagnostics of syncope of uncleared etiology with a suspicion on vasovagalous neurocardiogenous syncope, because the basal vagal tonus does not allow the forecast of head upright tilt table testing results as well as determination of the type of respectively provocated vasovagal neurocardiogenic syncope. However, a correlation between an actual reactive vageous tonus surveyed by the SD index for patients with vasovagal neurocardiogenic syncope of the type I and IIa in comparison with healthy persons, was found out. It allows to draw a conclusion, that the vasovagal neurocardiogenic syncope is not homogeneous nosological unit, what results in efforts to it's more detailed classification.

Adult↗
PubMed1996

[Head-upright tilt table test: a new method for diagnosis of vasovagal neurocardiogenic syncope].

The head upright tilt table test (HUT) has been unambiguously included into the screening algorithm of syncopes. The HUT is based on exposing patients to orthostatic stress. This easy, cheap and safe test makes it possible to diagnose neurally-mediated vasovagal syncope (NMS). The pathophysiology of the NMS is based on the hypercontractility of the myocardium, when with the body being orthostatic, the venous return to the heart is lower and then followed by protecting mechanism--vasodilatation and bradycardia--both controlled by the CNS. Nowadays there is a tendency to integrate examination schedules of the HUT and all possible types of responses have been defined.

Humans↗
PubMed1996

[The effect of experimental metabolic stress on ovulation and blood progesterone levels in cows].

The effect of a long run subclinic metabolic stress of acidotic and alkalotic nature was examined with respect to the course of cloprostenol induced estrus, ovulation and progesterone levels in blood and milk. The stress of acidotic nature was induced by widening the ratio of digestible crude protein to total dietary energy to the value 1:8.1 in 11 cows, while the alkalotic stress was due to narrowing the nutrient ratio to 1:2.81 in eight cows. Control group with the nutrient ratio 1:4.5-5 comprised 11 cows. The stress of acidotic nature was accompanied by ovulation disorders in 4 out of 11 cows (36.4%), in the group with the stress of alkalotic type it was in 2 out of 8 animals (25%). No ovulation disorders were observed in control group. Within 7 days after estrus, the average progesterone levels were 1.26 +/- 0.84 ng/ml in the blood of cows with stress of acidotic type, 3.48 +/- 2.99 in cows with stress of alkalotic type and 3.12 +/- 1.98 ng/ml in control cows. The differences between acidotic stress and control were statistically significant (P < 0.05). During the whole pregnancy (18 to 276 days), average progesterone levels were lowest in the group subjected to stress of acidotic nature. They ranged from 1.9 to 3.8 ng/ml with the average value 2.65 +/- 1.40 ng/ml. In the group with stress of alkalotic type they ranged from 2.55 to 5.43 ng/ml with the average value 3.67 +2- 2.29 ng/ml. In this control group, they ranged from 4.00 to 8.68 ng/ml with the average value 5.62 +2- 2.24 ng/ml. Variations in cortisol concentrations indicated a certain stressing effect of feeding rations on the internal environment of dairy cow organisms and activation of compensatory mechanisms.

Acid-Base Imbalance↗
PubMed1995

[Neural syncope--a current therapeutic problem].

Syncope, a state performed by transient loss of consciousness connected with postural tone decrease present still an important therapeutical problem. It can vary from a benign physiological body reaction to a life-limiting situation. The authors of the article present HUT-testing to be a simple, useful and safe method for discovering vasovagal mechanism of the syncope. They notice the experiences with treatment according to the HUT results. The most frequent types of therapy are the pharmacological and the pacing ones, when the former is appropriate for I and III class of VVS the latter then for the II. class. There are some big studies in progress now which should bring more information about this clinical problem.

Humans↗
PubMed1994

[The role of the HUT test (head upright tilt table test) in patients with syncope of uncertain etiology].

UNLABELLED: The authors have examined 73 patients at the mean age of 36.8 +/- 15.3 (M:34, F:39). All the pts have suffered from recurrent presyncopes or syncopes the etiology of which has not been diagnosed by previous internal, neurological or psychiatric examination. Before the HUT the patients have undergone a complete cardiological examination. The HUT has been carried out according to the modificated Westminster protocol, the blood pressure and the heart rate have been monitored continuously. The end-point of the HUT has been a presyncope or a syncope, viewed as positive. The positive pts have been divided into 4 groups according to the changes of their blood pressure and heart rate during a presyncope or a syncope-mixed, cardioinhibitory A, cardioinhibitory B and vasodepressor responses. Out of 73 pts there have been 27 pts (37%) with positive responses and 46 (63%) with negative responses. The mixed type has been achieved in 12 pts, cardioinhibitory A-in 5 pts, cardioinhibitory B-in 2 pts, vasodepressoric in 8 pts. The mean time needed for positive response during the native HUT has been 17.7 +/- 11 min, after activating with isoproterenol for 2.6 +/- 1 min. The achieved results correlate with data in medical literature. The test activated with isoproterenol increases its sensitivity. There have not been any complications marked within the examined group. CONCLUSION: The HUT has been unambiguously included into screening algorithms of syncopes as an easy, cheap, safe examination with good sensitivity and specificity.

Adult↗
PubMed1993

Experimental thyroiditis in guinea pigs and rabbits. Immunization with thyroglobulin and bovine thyroid gland suspension.

Morphological changes in the thyroid glands of the guinea pigs with autoimmune thyroiditis (EAT) experimentally induced by thyroglobulin (TGL) or immunization by the suspension of thyroid gland cells with CFA manifested mainly by atrophy and alterations of follicular cells, fibrotic tissue changes, formation of inflammatory lymphoplasmocytic infiltrations, multiplication of C-cells and by the increase in the proportion of lymphocytes with activated nucleoli in the tissue. The antigenic effects of TGL differed from those of the cell suspension; the effects of TGL participated especially in the formation of the infiltrates, the effects of cell suspension participated in the diapedesis of mononuclears and in the multiplication of C-cells. The findings correspond to the principal findings in human autoimmune lymphocytic thyroiditis. In an electron microscope, strongly dilated cisterns of endoplasmic reticulum (ER) and multiplied mitochondria in the cytoplasm of altered follicular cells were found. The wall of the follicles exhibited fully intact or altered C-cells. The latter had a large number of granules in cytoplasm with an unusually clear medullary substance. In the rabbit thyroid glands no morphological changes were observed following the immunization with both antigens. TGL antibodies examined immunohistochemically in the sera were present in all the sera of guinea pigs immunized with TGL and CFA. The antibodies determined by dot immunodetection were present in the sera of all guinea pigs immunized with TGL+CFA, the titres reached the level of 1:81 to 1:729; the highest titres were observed in the guinea pigs following the immunization by dose of 7.7 mg/kg after 12 weeks of immunization.

Animals↗
PubMed1993

[The ovarian response and conception rate in cows during experimental nitrate loading].

The effects of potassium nitrate were investigated on ovarian activity, especially on ovarian activity, especially on follicle ripening and ovulation, conception rate and progesterone levels in the milk of cows with cloprostenol-induced oestrus (Oestrophan Spofa) at a rate of 500 micrograms i.m. Potassium nitrate was administered at an amount of 150 g per head/day, and this amount increased by 50 g every other fortnight to the total rate of 300 g per head/day. In a group of 11 cows exposed to potassium nitrate load, clinical examination of ovaries on day 8 after oestrus revealed the presence of CL in seven cows (63.6%), persisting follicles in two cows, and two cows did not have any CL or follicles (Tab. I). After the first insemination three cows got in calf (27.3%), and after all inseminations it was 10 cows in total (90.9%) on average in 24.4 days after cloprostenol administration, with SP 96.7 days and insemination index 1.7. No ovulation disorders were found in the control group. All five cows got in calf after the first insemination in three days after cloprostenol administration with SP 61.5 days and insemination index 1.0 (Tab. II). The progesterone levels in milk were 22.3 and 21.1 ng/ml before the second administration of cloprostenol, 2.7 and 2.1 ng/ml in oestrus and at the time of A.I., and 16.6 in eight days after insemination in cows exposed to nitrate load, and finally 21.7 ng/ml in the control group (Tab. III). Ovulation disorders were easily detectable by a clinical check of ovaries on day 8 after oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[The ovarian response and fertility in cows with acidosis induced by acetic acid].

The effects of acetic acid administered at an amount of 300 to 600 g (5 to 10 mol) to the rumen of breeding cows, were investigated on ovulation, conception and progesterone levels in the blood and milk of cows with cloprostenol-induced (Oestrophan Spofa) oestrus at a dose of 500 micrograms i.m. In the group of 15 cows exposed to the acetic acid load five cows got in calf after the first insemination (33.3%), and 12 cows (80.0%) after all inseminations in 37.6 days after cloprostenol administration, with the insemination index 1.67 (Tab. I). In the control group (five cows) four cows (80.0%) got in calf after the first insemination, in total all five breeding cows got in calf in 20.6 days after cloprostenol administration, with the insemination index 1.2. In the experimental group of 15 cows a clinical examination of ovaries on day 7 after insemination revealed ovulation disorders in eight cows, that means in 53.3% of the animals (Tab. II). No ovulation disorders were observed in the control group of five cows. Progesterone levels in the blood showed high variability (Tab. III). In the group of cows administered acetic acid they were by more than a half lower (1.49; 0.67; 1.53 per ml) on days 7, 14 and 21 after insemination in comparison with the control group (3.35; 2.5; 3.38 ng per ml). The average progesterone levels in milk (Tab. IV) were 1.27 and 1.53 on day 7, 6.74 and 7.27 on day 14 and 3.52 and 11.85 ng per ml on day 21, respectively, the higher values apply to the control. It was not possible to evaluate reliably from the progesterone levels in the blood and milk if ovulation took place and if the corpus luteum was developing (Tab. V and VI). The clinical control of ovaries on days 7 and 8 after oestrus and insemination was more reliable to determine the ovulation disorders than the progesterone determination in the blood and milk of cows.

Acetates↗
PubMed1991

Bacterial endotoxins: comparison of mitogenic, polyclonal, antibody-inducing and toxicity activities.

The mitogenic effects on mouse spleen lymphocytes were determined in a large series of commercially available and laboratory-prepared lipopolysaccharides (LPS) obtained from Escherichia, Salmonella, Serratia and Shigella species; part of these LPS preparations was chemically modified prior to testing. In order to establish whether the degree of mitogenic activity corresponds with other biological effects of these preparations, polyclonal activity, capability to induce specific antibody formation and toxicity were determined for selected LPS's with different mitogenic effects. Some of the detoxication procedures used succeeded in reducing the toxicity of LPS while preserving its high mitogenic activitione of the Fe-detoxified preparations of LPS (from the R-form of Shigella dysenteriae serovar 1) exhibited a medium-degree efficacy in all parameters studied. Generally, there was no correlation between the degree of mitogenic activity and the polyclonal and antibody-inducing activities, but in some instances polyclonal activity did correlate with the antibody-inducing activity.

Animals↗
PubMed1991

Pathogenesis of experimental combined infections with Isospora suis and rotavirus in conventional and gnotobiotic piglets.

51 gnotobiotic and 63 conventional, one-, or two-days-old piglets were divided into five groups and infected orally either with Isospora suis or rotavirus alone, or with both agents simultaneously or successively with alternative sequences and various intervals. 15 gnotobiotic and 10 conventional piglets served as controls. The development of small intestinal lesions after infection with I. suis was biphasic. The dominant alteration resulting from rotavirus infection was villus atrophy, considerably more pronounced and extensive in gnotobiotic than in conventional piglets. Synergistic action of I. suis and rotavirus was manifested both clinically, and morphologically. This action culminated at the time of the actual, or presumed development of merogony of I. suis, i.e. on DPI 3 to 5. The action develops only if the intestinal epithelium is damaged functionally and morphologically by a preceding rotavirus infection. It is concluded that the synergistic action is based on a competition of rotavirus and I. suis for mature, enzymatically active absorptive cells.

Animals↗
PubMed1991

[The effect of clover silage treated with acrylic acid on selected indicators of metabolism in cows around the time of parturition and the status of their calves].

A trial was conducted with 16 cows divided into control and test group (eight cows in either); since day 57.6 +/- 21.1 before parturition, test cows were given feed rations for 107 days which contained 16.0 kg clover-grass silage a day, treated with 3 l acrylic acid per t ensiled matter. Control group of cows was administered feed rations containing silage treated with 4 l formic acid per 1 t ensiled matter from day 55.5 +/- 21.9. In the blood (plasma) of test cows the alkaline phosphatase activity was increasing gradually, in the time after parturition a tendency of lower glucose (P 0.05 to 0.01), thyroxine and triiodothyronine concentrations was observed, and the phagocytal activity of leucocytes and its index decreased. The levels of ketone bodies and aspartate aminotransferase activity were found to be higher. In this period in urine the pH value and net acid-base output were lower, while the inorganic phosphorus concentration was higher. No difference were observed in colostrum density, liveweight of born calves and in the target metabolic parameters in the blood (plasma) of calves. In the 30-day period of investigation the cows of test group gave an average daily milk yield lower by 1.5 l (in comparison with control cows). The residues of acrylic acid (method sensitivity of 1.0 mg acrylic acid in 1 l sample) were not detected in their colostrum and milk.

Acrylates↗
PubMed1990

Preclinical screening and analysis of the immunotoxic and immunomodulatory activity using a multiple immunoassay (MIA) in mice.

Screening and analysis of immunotoxic and immunomodulatory activity has become an integral component in preclinical studies of pharmaceuticals and xenobiotics. In an attempt to replace laborious and expensive batteries of assays used at present we developed a multiple immunoassay (MIA) enabling the determination, in a single mouse, of: the weight of the thymus, spleen and a group of lymph nodes; delayed type hypersensitivity and antibody response to SRBC; phagocytic activity of peritoneal macrophages and the responsiveness of spleen lymphocytes to "T" (PHA, ConA) and "B" (LPS) mitogens in vitro. The MIA responsiveness to two prototype immunostimulators (Thymostimulin and Listeria factor Ei) was tested at two time periods after antigenic stimulation, not only in normal mice, but also in animals with selectively depressed T-systems (anti-Thy1.2 monoclonal antibody) and B-systems (cyclophosphamide); in both dexamethasone-treated and irradiated animals. The findings indicate, that this MIA is capable of reflecting both immunosuppressive and immunostimulatory activities of the tested agents and permits partial insight into the mechanisms underlying these activities.

Adjuvants, Immunologic↗