The geomagnetic field: a factor in cellular interactions? I. Magnetism and Schwann cell-axon interaction in the peripheral nerves of the newborn rat.

Axonal ensheathment and myelination, one form of axon-sheath cell interaction, was studied under normal earth magnetism, in the absence of terrestrial magnetic field, and under a 5 G (0.0005 T) magnetic field. Results indicate that the geomagnetic field is necessary for the fundamental biological activity of axonal ensheathment and myelination. The exact mechanism of action remains obscure.

Fragmentation of bandpass-filtered QRS-complex of patients prone to malignant arrhythmia.

The structure of high-frequency components of electric and magnetic signals from the heart during the depolarisation phase is investigated. After averaging and broadband filtering with a binomial bandpass filter (37 Hz-90 Hz), the fragmentation of the QRS-complex is quantified. The number of extrema M and a new score value S are calculated from the signals of three electrical leads and one magnetic lead of 23 healthy subjects, 23 patients with coronary heart disease (CHD) without reported event of ventricular tachycardia or fibrillation at the time of measurement, and eight patients with CHD who have suffered from malignant tachycardia. For the parameter M, the sensitivity and specificity for healthy subjects against patients with CHD and ventricular tachycardia for the magnetic lead (the best electric lead) are 100% (75%) and 100% (100%). For the magnetic lead (best electric lead) and parameter S, the sensitivity and specificity are 100% (75%) and 95.6% (100%).

Beat to beat surface recording and averaging of His-Purkinje activity in man.

A non-invasive technique has been used to record the electrical activity of the His-Purkinje System (HPS) on the body surface involving shielding, high gain band pass filtering and averaging of bipolar chest ECGs (V6-V6R). The measurements were made in the Berlin Magnetically Shielded Room (BMSR) which reduces the background noise level (almost white) to less than 0.4 microVrms (measured for a bandwidth between 0.1 Hz and 300 Hz), so that individual HPS body surface signals were limited only by patient inherent noise. Signal amplitudes greater than 1 microV were detectable in single beats. In addition, for best resolution, signal averaging was accomplished with software triggers referred to either the QRS complex or the P wave. A P-wave trigger is of most interest in clinical use because averaging techniques, even in the case of A-V blocks of different degree, can be applied.

Late potential-like deflections in the ST segment of normal subjects.

Irregular high frequency deflections of low amplitude have been found within the ST segment immediately following the QRS complex and in the T wave of high resolution bipolar recordings (lead V4-V7) in single beats as well as in averages of 100 beats. The signals in the T wave, found in six out of 22 normal subjects, coincide with the apex of the T wave in standard lead II. Their amplitude depends on the phase of the respiratory cycle. They were most pronounced during expiration. The occurrence of these signals depends on the position of the electrodes relative to the position of the equivalent current dipole, which is determined from simultaneous magnetocardiographic measurements. When electrode V4 is systematically shifted these signals vanish or increase, respectively become measurable.