Biomedical subjects

H Fischler

Publications and source records attributed to H Fischler.

4 recordsLinked to original sources

PubMed1985

Stimulation of skeletal-derived cell cultures by different electric field intensities is cell-specific.

Pulsed electric stimulation, coupled capacitively to different cell cultures of skeletal origin, caused immediate changes in the cellular levels of cyclic AMP and a later enhanced DNA synthesis. Changes both in cyclic AMP level and DNA synthesis were correlated with the strength of the applied electric field. Cultures of calvaria bone cells which contain mainly two cell types, parathyroid hormone responsive cells (osteoblast-like) and prostaglandin E2 responsive cells (fibroblast-like), respond to both low (13 V/cm) and to high (54 V/cm) electric field strength, with no response at intermediate (24 V/cm) field strength. Rat epiphyseal cartilage responded like bone cells both to low and high field intensities, while rat condylar cartilage responded only to the intermediate field strength. Moreover, subcultures of calvaria bone cells, which lost their osteoblastic phenotype expression during subculturing, were responsive only to low field strength. On the other hand, osteoblast-enriched cultures, derived from calvaria bone grown in low calcium, were responsive only to the high field strength. These findings suggest that the response to various electric field intensities is cell-specific and might be used as an additional parameter to characterize cell types. Our study points to the possibility that when exposing a whole organ to an electrical stimulation it is possible to affect specifically only one cell population out of the many cell types existing in the organ.

Animals↗

PubMed1979

Polarization properties of small-surface-area pacemaker electrodes--implications on reliability of sensing and pacing.

The polarization characteristics of Pt-Ir and Elgiloy small-surface-area (10-12.5 mm2) pacemaker electrodes were studied at AC linear (sensing) and DC non-linear (pacing) conditions. The electrodes' AC polarization impedance was approximately equal to the demand pacemaker's input impedance, which causes waveform distortions ofthe sensed R-wave potentials. The pacemaker's coupling capacitor adds to the distortion's effect. As a result of amplitude attenuation (up to approximately 50%) and slew rate changes, the pacemaker may fail to recognize the ventricular complexes, reverting to hazardous competitive pacing. The impact of the DC polarization elements and of the coupling capacitor on the effectiveness of pacing was examined. The deficiency of small area electrodes was pointed out, this being counter-balanced to some extent by their lower pacing thresholds. The necessity to ensure a sufficient safety margin between the pacing pulse and the stimulation threshold, to avoid possible reasons for creation of exit blocks, was stressed. In reducing the electrode surface, it is advisable not to step down below a 15-20 mm2 effective area for Pt-Ir, and a 40-50 mm2 area for Elgiloy.

Cardiac Pacing, Artificial↗

PubMed1979

Surface charge characteristics of cells from malignant cell lines and normal cell lines of the human hematopoietic system.

Cells from malignant and normal lines of human hematopoietic origin were studied for their surface charge characteristics with the use of the following criteria: 1) the electron microscopic appearance of cell membranes after labeling with cationized ferritin (CF) either before or after glutaraldehyde fixation, 2) electrophoretic mobility, 3) total sialic acid content, and 4) agglutinability with poly-L-lysine (PLL). CF induced a time-dependent redistribution of surface receptors in unfixed malignant cells but not in unfixed normal cells. After 10 seconds of labeling with CF, both normal and malignant unfixed cells showed a uniform and even labeling pattern. After 5 minutes of labeling, malignant cells exhibited a highly pronounced pattern of clusters and patches, as distinct from a random and even pattern exhibited by normal cells. Both normal and malignant cells after fixation exhibited an equivalent random and even labeling pattern with CF, independent of the duration of labeling. The malignant cells studied possessed less sialic acid, had a lower electric mobility, and were agglutinated more readily with PLL than were the normal cells.

B-Lymphocytes↗

PubMed1977

Surveillance of pacemaker patients by an automatic pacemaker function analyzer.

An external, simply operated, fail-safe, automatic pacemaker function analyzer (PFA) has been designed for routine examination of ambulatory patients in local medical clinics and for continual surveillance of hospitalized patients in cardiology units. The instrument provides a comprehensive test of the pacing system, including the battery, pulse generator, and electrodes (leads), during varying heart activity. In the recorded ECG from 92 pacemaker patients, the PFA recognized all but 0.29% of the QRS complexes and 0.21% of the pacing artifacts; no signals were incorrectly attributed to the QRS complex. With the PFA, 1171 pacemaker tests were performed on these patients. In all cases, the PFA judged the performance of the tested pacemakers in accordance with the predetermined criteria. The PFA can be integrated into a pacemaker-patient surveillance system within a general-purpose cardiac care unit.

Electrocardiography↗