Biomedical subjects

B Nowak

Publications and source records attributed to B Nowak.

At least 109 records · Page 6Linked to original sources

PubMed1996

Is there a risk for interaction between mobile phones and single lead VDD pacemakers?

Mobile phones may cause pacemaker interference. Patients with a single lead VDD pacemaker might be at special risk, since the atrial sensitivity is often programmed to low (high sensitivity) threshold values and the majority of patients are pacemaker dependent due to the underlying high degree AV block. We evaluated 31 patients with three types of single lead VDD pacemakers: 12 Unity, 292-07 (Intermedics, Inc.); 10 Thera VDD, 8948 or 8968i (Medtronic, Inc.); and 9 Saphir 600 (Vitatron, Inc.) for interference from a cellular mobile phone with a power of 2 W (D-net). For this purpose, atrial and ventricular sensitivity settings were programmed to their most sensitive values (A: 0.1-0.25 mV; V: 1.0 mV) and ventricular sensing was programmed to unipolar. With the ECG continuously monitored, the phone's extendable antenna was brought in direct contact with the patient's skin at the right sternal border, with the tip of the antenna in skin contact just below the clavicle, within 5 cm of the pacemaker connector. Then multiple phases of phone calls were performed, and the effects on the pacemakers recorded. In our group of patients with three different types of single lead VDD pacemakers, no interference could be detected using a 2-W mobile phone in the digital D-net. The programmed values remained unchanged after the interference test. Therefore, the risk of interference seems to be low for the VDD pacemakers tested, although our study design does not allow to entirely exclude the possibility of interference from a mobile phone.

Cardiac Pacing, Artificial↗

PubMed1996

Holter recordings with continuous marker annotations: a new tool in pacemaker diagnostics.

UNLABELLED: Pacemakers provide marker annotations to facilitate the interpretation of pacemaker electrocardiograms (ECGs) and can be used in cases of suspected pacemaker malfunction or to understand pacemaker behavior. Due to the need for a programmer, only short-term evaluations are possible. We evaluated a prototype Telemetry Data Logger (TDL) designed to continuously transfer markers from the pacemaker to a conventional Holter recorder. A miniaturized telemetry receiving coil was attached to patient's skin above the pacemaker, which was programmed to transmit markers continuously. The TDL, which receives and converts markers into eight positive and eight negative deflections, ranging from -2.5 to +2.5 mV in amplitude, was connected to one channel of a conventional Holter recorder (Tracker 2). We performed 20 Holters in 13 patients who had implanted VDDR or DDDR devices from the same manufacturer and evaluated three versions of software. Marker transmission was possible in all patients, producing Holter ECGs with complete marker annotations. Artifacts occurred < 4% of the time. A 50-ms rectangular pulse was optimal for marker interpretation. The device, which was easy to use and well accepted by the patients, assisted in the diagnosis of inappropriate pacemaker programming, even when the surface ECG seemed to show regular pacemaker function. In the presence of low quality surface ECGs, marker annotations allowed the assessment of pacemaker function. The capability to annotate the onset of special algorithms, like tachycardia termination algorithms or mode switching, facilitates interpretation of pacemaker behavior, enabling a reliable assessment of the appropriateness of such algorithms. CONCLUSION: The TDL effectively enables pacemaker markers to be inscribed onto a conventional Holter recording, facilitating the interpretation of pacemaker ECGs and the diagnosis of inappropriate pacemaker programming even when not discernible from the surface ECG alone.

Algorithms↗

PubMed1996

A simple method for preoperative assessment of the best fitting electrode length in single lead VDD pacing.

For single lead VDD pacing, electrodes with various distances between the lead tip and the floating atrial dipole (AV distance) are available. Using different AV distances allows positioning of the atrial dipole in the mid- to high right atrium, regardless of the size of the right heart. In this position, reliable atrial sensing and rejection of ventricular far-field potentials can be expected. A simple test for the preoperative assessment of the best fitting AV distance in the individual patient was tested. We studied 24 consecutive patients prior to implantation of a VDD pacemaker. With the patient in supine position, a test electrode with an AV distance of 13 cm was taped onto the thorax. Under fluoroscopic control, it was moved until its course and projection onto the heart was equal to that of a ventricular lead. If fluoroscopy then showed a projection of the atrial dipole onto the mid- to high right atrium, a lead with a similar AV distance of 13 or 13.5 cm was used for implantation. If the atrial dipole projected itself too high or too low, a shorter or longer lead had to be implanted. The maximum time for the test was 2 minutes, and the maximum fluoroscopy time was 15 seconds. According to the test, a lead with an AV distance of 13 or 13.5 cm was implanted in 18 of 24 patients, and a lead with an AV distance of 15.5 or 16 cm was implanted in 6 of 24 patients. The atrial dipole could easily be positioned in the mid- to high right atrium in all patients, demonstrating a correct preoperative assessment of the best fitting AV distance. Intraoperatively, a P wave amplitude of 3.5 +/- 3.0 mV was measured. The described test allows a fast and reliable assessment of the best fitting electrode length in single lead VDD pacing.

Adult↗

PubMed1995

Soluble T cell receptors: detection and quantitative assay in fluid phase via ELISA or immuno-PCR.

To establish the concentration range in which soluble murine T cell receptors (sTCR), derived from the Th2 clone D10, exhibited biological activity, and to follow production and purification of D10 sTCR, we devised four quantitative immunoassays: three ELISA systems, and an immuno-PCR assay. The direct ELISA, employed hamster anti-TCR beta monoclonal antibody (H57), which detects all types of alpha beta TCR, regardless of their variable regions, and had a detection limit of about 6 ng/ml sTCR. The indirect sandwich ELISA employed anti-V beta 8 as capture antibody, and had a detection limit of 600 pg/ml. With the direct sandwich ELISA, that also employed anti-V beta 8, TCR concentrations as low as 100 pg/ml could be detected. The ELISA assays were specific for soluble alpha beta TCR, and showed no cross-reactivity when employing two control hamster anti-gamma delta TCR mAbs (GL3 and UC7), or with anti-TCR beta and monoclonal hamster IgG as a control antigen. Further, we demonstrated that in some assays where use of passive binding ELISA plates resulted in a high background, replacement with covalent binding ELISA plates resulted in an acceptable low background value. With the immuno-PCR assay, concentrations of sTCR as little as 0.8 pg/ml could be detected. In summary, the assays described here may prove valuable in investigating the occurrence and amount of sTCR in vitro and in vivo.

Animals↗

PubMed1995

Cardiac output in single-lead VDD pacing versus rate-matched VVIR pacing.

The importance of atrioventricular synchronous pacing compared with single-chamber rate-responsive pacing is still under discussion, especially for low-intensity workload representing daily life activities. We evaluated hemodynamics in single-lead VDD pacing versus VVIR pacing in 11 patients (8 men and 3 women, aged 58.6 +/- 13.8 years) with normal left ventricular function and a previously implanted single-lead VDDR pacemaker. A low-intensity steady-state treadmill test at 1 to 2.5 mph with a gradient of 2% to 4% was performed. Cardiac output was determined using a standard carbon dioxide rebreathing technique. Initially, the VDD mode was programmed, and after 5 minutes of exercise, cardiac output was measured in steady-state conditions. The pacemaker was then reprogrammed to the VVI mode at a rate 5 to 10 beats above the maximal atrial tracking rate to simulate rate-matched VVIR pacing (VVIRm). After 5 additional minutes of steady-state exercise, cardiac output was measured again. The maximal atrial rate in the VDD mode was 119 +/- 19 beats/min versus a programmed rate of 129 +/- 18 beats/min in the VVIRm mode. VDD pacing resulted in a significantly higher cardiac output than VVIRm pacing (10.6 +/- 1.9 vs 9.2 +/- 1.4 L/min; p < 0.002), with a mean difference of 1.6 +/- 1.2 L/min between the 2 modes. In the VDD mode, stroke volume (90.7 +/- 20.1 vs 71.6 +/- 13.0 ml; p < 0.001) and maximal oxygen uptake (1,183 +/- 264 vs 1,076 +/- 289 ml/min, p < 0.01) were also higher than in VVIRm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Cytotoxicity, metabolism, and mechanisms of action of 2',2'-difluorodeoxyguanosine in Chinese hamster ovary cells.

The emerging clinical success of gemcitabine (2',2'-difluorodeoxycytidine) stimulated interest in the synthesis and evaluation of purine congeners. The cytotoxicity, metabolism, and mechanisms of action of the lead candidate, 2',2'-difluorodeoxyguanosine (dFdGuo), were studied in Chinese hamster ovary cells. Unlike the natural nucleoside deoxyguanosine (dGuo), dFdGuo was not a substrate for purine nucleoside phosphorylase. Wild-type Chinese hamster ovary cells and a mutant line deficient in deoxycytidine (dCyd) kinase were similarly affected by dFdGuo (50% inhibitory concentration, 7.5 and 6.5 microM, respectively), suggesting that unlike gemcitabine, dCyd kinase was not responsible for activation of dFdGuo. This was further confirmed by separation of nucleoside kinases (adenosine kinase, dGuo kinase, and dCyd kinase) of Chinese hamster ovary cells on DEAE-cellulose column chromatography. The kinase activity that phosphorylated dGuo also converted dFdGuo to its monophosphate, suggesting that dGuo kinase activated dFdGuo. Consistent with this result, coincubation with dGuo spared the dFdGuo-mediated toxicity; however, addition of up to 10 mM dCyd did not reverse the toxicity of dFdGuo. Intracellularly, dFdGuo was phosphorylated to its mono-, di-, and triphosphates; dFdGuo triphosphate (dFdGTP) was the major metabolite and accumulated to 45 microM after a 6-h incubation with 30 microM dFdGuo. The elimination of dFdGTP was monophasic with a t1/2 of about 6 h. Deoxynucleotides were decreased in cells incubated with dFdGuo, suggesting that ribonucleotide reductase was inhibited. dATP, which decreased 78% after a 4-h incubation with 30 microM dFdGuo, was most affected. dFdGuo was a potent inhibitor of DNA synthesis. Extension of a DNA primer over a defined template in the presence of dFdGTP revealed that dFdGTP was a good substrate for incorporation opposite C sites of the template by DNA polymerase alpha. dFdGTP incorporation caused DNA polymerase alpha to pause after the polymerization of one additional deoxynucleotide. This pattern of inhibition, which is shared by gemcitabine, distinguishes 2',2'-difluoronucleosides from arabinosylnucleosides which halt primer extension at the incorporation site. dGTP competed effectively with dFdGTP for incorporation by DNA polymerase alpha. The unique activation requirements and patterns of inhibition of DNA synthesis distinguish this promising new antimetabolite from other nucleoside analogues.

Adenosine Triphosphate↗

PubMed1995

Enzyme immunoassay for detection of antibodies against isolated flagella of Legionella pneumophila.

Flagella of Legionella pneumophila serogroup 1, strain Philadelphia (ATCC 33152), were isolated and used as antigen to detect antibodies by enzyme immunoassay (EIA) in sera of patients with significant titers against Legionella as determined by the indirect immunofluorescence assay (IFA). Healthy blood donors served as a control group. Whereas the sera of blood donors were negative in both assays, sera of patients showed two patterns of reactivity. Sera with elevated titers against Legionella pneumophila serogroup 1 or Legionella gormanii in IFA usually demonstrated high titers in EIA. However, high IFA titers against Legionella bozemanii were associated with low titers in EIA. The data show that flagella protein of Legionella pneumophila serogroup 1 strain Philadelphia is of limited value for the detection of antibodies against Legionella other than Legionella pneumophila serogroup 1, although in vitro studies revealed genus-specific epitopes. This might be due to unpredictable variabilities in the expression of flagella in vivo.

Antibodies, Bacterial↗

PubMed1995

Occurrence of heavy metals and sodium, potassium and calcium in human teeth.

Heavy metals and Na, Ca, and K were determined in human teeth during 1992/1993 in the Polish towns of Katowice and Istebna. In the relatively clean region of the southern part of Poland (Istebna) the content of heavy metals in the teeth of inhabitants was several times lower than in Katowice (Silesian industrial centre). Ratios of the concentration of Pb:Fe and Pb:Mn in teeth may be an indicator of the pollution. The analysis of the correlation matrix shows the differences in accumulation of metals in teeth for inhabitants of the two investigated towns. The differences of the mean concentration of metals Pb, Ni, Cd, Zn, Co, Mn, Cr, Na and Ca in teeth of inhabitants of Katowice and Istebna were significant (p < 0.05) according to Student's t-test for independent samples.

Adolescent↗

PubMed1995

[Atrial sensing by a new VDD pacemaker].

VDD stimulation is an alternative to DDD pacing due to the possibility of p-wave synchronous ventricular pacing without the need of an atrial lead. Mainly, the reliability of the system depends on the atrial sensing. In 22 patients the intraoperative atrial amplitude and, postoperatively, the atrial sensing threshold were measured. Furthermore, the stability of the atrial sensing threshold during follow-up was proven. The mean atrial amplitude was intraoperative by 2.4 +/- 1.2 (1.0-6.8) mV. The measurement of the atrial sensing threshold in the first 5 postoperative days showed a mean value of 1.02 +/- 0.49 (0.3-1.6) mV. The measurements of the mean atrial sensing threshold after 30, 90, and 180 days showed no statistical differences. Intraindividual variance was shown in 17/20 patients (0.55 +/- 0,42; 0.15-1.05 mV). Seventeen of the 22 patients were programmed with an atrial sensing threshold of 0.3 mV. In five patients the atrial sensing threshold was programmed at less than 0.3 mV in order to reach a twofold atrial sensitivity. Despite a programmed atrial sensitivity of 0.1 mV and isometric conditions no atrial oversensing occurred. The postoperative atrial sensing thresholds of the VDD system investigated were significantly lower than the intraoperatively measured atrial amplitudes. The mean atrial sensing threshold did not change during the follow-up period. The variation which did occur was within individual variation at different return visits.

Aged↗

PubMed1995

Modulation of the cellular metabolism of cytarabine and fludarabine by granulocyte-colony-stimulating factor during therapy of acute myelogenous leukemia.

Previous in vitro investigations demonstrated that human leukemia cells, when incubated with hematopoietic growth factors such as granulocyte-colony-stimulating factor (G-CSF), augment the accumulation of the triphosphate 1-beta-D-arabinofuranosylcytosine (ara-C cytarabine). To test whether G-CSF infusion prior to ara-C infusion would biologically modulate the accumulation of ara-9-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP) and other ara nucleotides in the leukemia blasts during therapy, protocols were designed to infuse G-CSF prior to fludarabine (9-beta-D-arabinofuranosyl-2-fluoroadenine monophosphate) and ara-C to increase the accumulation of the active triphosphates [9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-triphosphate (F-ara-ATP) and ara-CTP] in acute myelogenous leukemia (AML) blasts during therapy. To complement these in vivo studies, ex vivo accumulation of ara-CTP was also investigated before and after G-CSF infusion. Patients (n = 5) treated on the fludarabine/ara-C/G-CSF regimen received a 30 mg/m2 dose of fludarabine followed by a 2 g/m2 dose of ara-C infused i.v. for 4 h. Beginning at 24 h, and every day, patients received a 6-h infusion of 400 microgram/m2 G-CSF. At 48 h, the fludarabine and ara-C couplet was repeated. Comparison of F-ara-ATP pharmacokinetics in circulating AML cells of patients on the fludarabine/ara- C/G-CSF regimen demonstrated that the area under concentration time curve (AUC) of F-ara-ATP increased significantly (median, 1.4-fold; range, 0.9-1.5; P = 0.045) after G-CSF infusion. This was due to an increased rate of F-ara-ATP accumulation by AML cells. The AUC of ara-CTP, on the other hand, was not affected (median, 1.0-fold; range, 1.0-1.2; P = 0.571) after G-CSF infusion. Because fludarabine potentiates the accumulation of ara-CTP, the effect of G-CSF on ara-CTP metabolism may not be evident in the AML blasts of patients on the fludarabine/ara-C/G-CSF regimen. To determine the effect of G-CSF when ara-C was infused alone, four additional patients were treated on a pilot protocol in which ara-C (2 g/m2) was infused on days 1 and 3 and G-CSF on day 2. The AUC of ara-CTP accumulation in these patients decreased by a median of 48% after G-CSF infusion. Consistent with these in vivo investigations, ex vivo ara-CTP accumulation was decreased in the AML blasts after G-CSF infusion. Based on these data it could be concluded that (a) infusion of G-CSF before fludarabine augmented the rate of F-ara-ATP synthesis in circulating AML blasts during therapy, suggesting that G-CSF may benefit fludarabine therapy by biological modulation; (b) G-CSF did not increase ara-CTP accumulation, rather it may have caused it to decrease; and (c) these data imply that when G-CSF and ara-C are used in combination, administration of fludarabine prior to ara-C may maintain the ara-CTP AUC.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1994

[Duodenal tuberculosis. A rare cause of a covered perforation in the duodenal bulb].

Vague upper abdominal pain, weight loss (10 kg) and recurrent bouts of fever had been present for several months in a 77-year-old woman. Abdominal ultrasonography in the region of the head of the pancreas and duodenum had demonstrated several lymphomas, some of them with "air streaking". This finding suggested penetration from the duodenum to neighbouring lymph nodes. Plain film of the abdomen did not show free air, but at gastroscopy a covered perforation into the surrounding lymph nodes was found. At first lymphoma or Crohn's disease were considered in the differential diagnosis. But the finding of acid-fast bacteria in a biopsy from the pelvic crest suggested intestinal tuberculosis with dissemination. This diagnosis was confirmed by the direct demonstration of Mycobacterium tuberculosis in gastric juice. Under tuberculostatic treatment with daily 0.3 g isoniazid, 0.45 g rifampicin, 0.8 ethambutol and 1.5 g pyrazinamide, as well as 50 mg prednisolone to prevent stricture, the size of the tuberculous ulcer had markedly decreased within 2 weeks. Follow-up gastroscopy after 6 months showed almost complete healing without stricture. However rare, gastrointestinal tuberculosis should not be forgotten in the differential diagnosis because it can imitate a large variety of gastrointestinal diseases.

Aged↗

PubMed1994

Quantification of topoisomerase-DNA complexes in leukemia cells from patients undergoing therapy with a topoisomerase-directed agent.

Several clinically important drugs utilized in cancer chemotherapy inhibit type I (Topotecan) or type II (amsacrine, etoposide) DNA topoisomerases by stabilizing the formation of DNA-topoisomerase complexes (topoisomerase-DNA cross-links). In various cell lines, the magnitude of drug-induced DNA-protein cross-link production correlates with the magnitude of cytotoxicity induced by the drugs. We developed a simple filter-binding assay that can measure drug-induced DNA-protein cross-links in leukemia cells obtained directly from patients because the assays most widely used for assessment of drug-induced DNA-protein cross-links in cells [sodium dodecyl sulfate (SDS)/KCl precipitation and alkaline elution] are not readily applicable for use on patient material. HL-60 human leukemia cells or freshly isolated patients' leukemia cells were incubated with Topotecan, etoposide, or amsacrine; lysed with SDS; and applied to nitrocellulose filters in a low-salt buffer. DNA is retained on the filter only if it is covalently bound to protein. The amount of DNA retained on the filter is quantified by hybridization to the alu sequence of DNA, which is distributed ubiquitously in the human genome. Using radiolabeled cells, we compared the filter-binding assay directly with the SDS/KCl precipitation assay in the detection of etoposide- or amsacrine-induced DNA-protein cross-links in HL-60 cells and amsacrine-resistant HL-60/AMSA cells. Both the SDS/KCl precipitation assay and the filter-binding assay detected etoposide-induced DNA-protein cross-links in HL-60 and HL-60/AMSA cells and detected a greater frequency of amsacrine-induced DNA-protein cross-links in HL-60 cells than in HL-60/AMSA cells. The filter-binding assay detected DNA-protein cross-links in freshly isolated leukemia cells exposed to Topotecan in vitro. The ratios of DNA retention for Topotecan-treated versus untreated cells from leukemia patients ranged from 1.8 to 11.5. The heterogeneity of this detected cross-linking was as might be expected if the assay were predictive of the antileukemic action of Topotecan, which is variable. This new filter-binding technique may be useful for predicting the sensitivity of individual patients' tumors to drugs that inhibit type I or type II DNA topoisomerases.

Amsacrine↗

PubMed1994

Echocardiographic visualization of anomalous left main coronary arteries originating from the right sinus of Valsalva.

We report on two patients in whom the anomalous left main coronary artery arising from the right sinus of Valsalva with a septal course could be visualized by transthoracic echocardiography. It appeared as a small echo-free space, anterior to the aorta in the short parasternal axis. If the left main coronary artery arises anomalously from the right sinus of Valsalva, it can take four different courses until it branches into the left anterior descending and the circumflex coronary artery. The course between aorta and pulmonary trunk can be differentiated into an interarterial and a septal course using angiographic criteria. The interarterial course is a potentially life-threatening anomaly due to a high rate of myocardial infarction and sudden cardiac death. Echocardiography alone seems not to be able to distinguish between the potentially life-threatening interarterial and the benign septal course, as in our patients.

Coronary Angiography↗

PubMed1994

[Cor triatriatum sinistrum and atrial septal defect].

The cor triatriatum sinistrum is a rare congenital malformation. Frequently, the patients become symptomatic in infancy with clinical signs of severe congestive heart failure. We report on an adult patient with only mild symptoms with cor triatriatum sinistrum and atrial septal defect. The embryological basis of the disorder and the hemodynamic conditions which permitted this patient to remain symptom free for a long period are discussed.

Atrial Function, Left↗

PubMed1993

High rate of late dislodgements of an active fixation atrial lead.

Between May 1985 and May 1991 we implanted 115 DFH-leads as unipolar atrial leads. The active fixation mechanism of this electrode consists of two sickle-shaped anchoring hooks which are placed at a distance of 0.9 mm parallel to the distal flat end of the electrode. All leads were affixed to the free wall of the right atrium. One hundred eight leads (93.9%) were implanted for dual chamber pacing and seven leads (6.1%) for single chamber atrial pacing. Parameters measured at implantation were (mean values): stimulation threshold 1.06 +/- 0.42 V at 0.5 msec pulse width, P wave amplitude 5.12 +/- 2.04 mV, and lead impedance 560 +/- 76.1 Ohms. Within the first week after implantation, three early dislodgements occurred (2.6%). The follow-up period averaged 30.4 +/- 16.2 months (range 2-76 months). During this time, 14 late macrodislodgements (12.2%) occurred after a mean period of 18.4 months (range 2-59 months). All of them required reoperation. The active fixation mechanism of the DFH-lead appears to be unreliable, if implanted in the free wall of the right atrium for dual chamber pacing.

Adult↗

PubMed1993

[25 year assessment of occupational exposure to x-rays in Poland].

The paper describes the organization and methods for assessment of occupational exposure of X-ray workers. The results of the dose measurements carried out during 1966-1991 at the Institute of Occupational Medicine in Lodz are discussed. In 1991 the measurements concerned about 25,500 persons employed in 2600 institutions. About 99.5% of the monitored population receives annual dose equivalent below 0.1 of the limit i.e. below 5 mSv. Doses exceeding the annual limit occur very rarely--a few cases a year.

Air Pollutants, Radioactive↗

PubMed1993

[Conservative or surgical treatment of metacarpal fractures].

A total of 146 patients with 150 closed metacarpal fractures were treated between 1980 and 1981, and 109 patients with 113 metacarpal fractures (75%) were followed up (follow up 7.3 years). After conservative treatment, the functional results were good to excellent in 92.7%, while 5.8% had satisfactory and 1.5% poor functional results. After operative treatment 81.5% had good or excellent functional results, 14.8% satisfactory results and 3.7%, poor functional results. The radiological result did not correspond with the functional result. Angulation of the Ist-IVth metacarpal bones by up to 20 degrees of the Vth metacarpal bone by up to 50 degrees, and even shortening by up to 8 mm had no detrimental influence on the functional results. Axial rotational deviation of the Vth metacarpal bone by up to 15 degrees was tolerated. Joint fractures with a 1 mm step could also be treated by conservatively means.

Adult↗

PubMed1992

Nuclear spin-lattice relaxation in transition metal compounds with local tetragonal symmetry.

We report on the various contributions to the total spin-lattice relaxation rate in metallic materials with local tetragonal symmetry. The analytical formulae are given in the tight-binding approximation. The calculations show the relation between various partial electron densities of states and corresponding contributions to the relaxation rates. The presented formulae can be used to compare theoretically calculated electron band structure parameters with those obtained from NMR spin-lattice relaxation time measurements.

Electrons↗