Magnetoencephalography: detection of the brain's electrical activity with a superconducting magnetometer

Measurements of the brain's magnetic field, called magnetoencephalograms (MEG's), have been taken with a superconducting magnetometer in a heavily shielded room. This magnetometer has been adjusted to a much higher sensitivity than was previously attainable, and as a result MEG's can, for the first time, be taken directly, without noise averaging. MEG's are shown, simultaneously with the electroencephalogram (EEG), of the alpha rhythm of a normal subject and of the slow waves from an abnormal subject. The normal MEG shows the alpha rhythm, as does the EEG, when the subject's eyes are closed; however, this MEG also shows that higher detector sensitivity, by a factor of 3, would be necessary in order to clearly show the smaller brain events when the eyes are open. The abnormal MEG, including a measurenment of the direct-current component, suggests that the MEG may yield some information which is new and different from that provided by the EEG.

Epidemiological studies of A-Hong Kong-68 virus infection in dogs

Experimental inoculation of dogs with the A/Hong Kong/68 influenzavirus resulted in subclinical infection. The virus was readily passed to contacts in the same cage when the latter were exposed in the same inoculation room 24 hours after experimental infection. Removing the site of contact to a noncontaminated room or delaying contact until 48 hours after experimental inoculation greatly reduced the possibility of infection in contact animals. A survey of 271 canine serum samples obtained after a human epidemic from different geographical areas of the USA and the United Kingdom showed that 5.9% of the samples were positive; no positive reactions were found among 111 pre-epidemic samples. These studies demonstrated the laboratory and natural susceptibility of dogs to the Hong Kong variant and suggest the possible role of dogs in the epidemiology of human influenza.

Automation of a hemagglutination-inhibition test for parainfluenza 3 antibodies in bovine sera

An automated hemagglutination-inhibition (HI) test for the "shipping fever" strain (SF-4) of parainfluenza 3 antibody in bovine sera was developed and compared to manual tube and microtiter test procedures. The automated system operating at 60 samples per hr provided the most test results per specified time period, and the manual tube test provided the least. The manual microtiter test and the automated system at 40 samples per hr, falling between the two above procedures, were comparable in the number of sera that could be titrated in 1 day by one technician. There was little difference between automated and manual test reproducibility when measured at the twofold titer one-dilution difference level. However, the automated system titrated a higher number of sera at the same titer on repeat runs than either of the manual test procedures. The automated one-quartile difference reproducibility (each twofold dilution subdivided into 4 units-"quartiles") was equal to the manual test one-dilution difference reproducibility. The standard deviation of the per cent variation from the mean of paired serum titers for 40-sample-per-hr runs ranged from +/-3.49 to +/-5.36%. The manual and automated systems were of comparable sensitivity in their detection of negative sera.

Magnetocardiography of direct currents: S-T segment and baseline shifts during experimental myocardial infarction

Magnetocardiograms with a bandwidth of 0 to 40 hertz were recorded from intact dogs undergoing myocardial infarction. This was done with a superconducting magnetometer in a magnetically shielded room. The purpose was to look for the steady currents of injury from the heart which supposedly produce much of the S-T segment shifts during infarction. These heart currents cannot be measured with surface electrodes because of direct-current interference from other sources, such as from the contact potential between electrode and skin. The magnetocardiograms showed both S-T segment shifts and direct currents as a result of infarction. However, they also showed that the S-T segment shifts were not produced by the direct currents. It is unlikely that these direct currents originated from the infarcted area, and their exact origin is not yet known.

On population growth in a randomly varying environment

If a population is growing in a randomly varying environment, such that the finite rate of increase per generation is a random variable with no serial autocorrelation, the logarithm of population size at any time t is normally distributed. Even though the expectation of population size may grow infinitely large with time, the probability of extinction may approach unity, owing to the difference between the geometric and arithmetic mean growth rates.

Measurements and a simplified interpretation of magnetocardiograms from humans

To understand and assess the magnetocardiograph, the magnetic field produced by electrical heart activity was mapped around the torsos of one abnormal and six normal heart subjects, at different times during QRS. The measurements are here presented in the form of instantaneous distributions of vector segments 6 cm from the skin, anteriorly. An electrical model is presented which explains the first-order features of these distributions. This model is a simple, rotating bipole heart source of changing strength which produces the same ion currents as measured with surface electrocardiograms and vectorcardiograms; these currents produce a time-changing magnetic field extending outside the torso. Further analysis of second-order details of the distributions can reveal information not obtainable with various forms of surface electrocardiography.

Magnetoencephalography: evidence of magnetic fields produced by alpha-rhythm currents

Weak alternating magnetic fields outside the human scalp, produced by alpha-rhythm currents, are demonstrated. Subject ard magnetic detector were housed in a multilayer magnetically shielded chamber. Background magnetic noise was reduced by signal-averaging. The fields near the scalp are about 1 x 10(-9) gauss (peak to peak). A course distribution shows left-right symmetry for the particular averaging technique used here.

Physiological effects of gibberellic Acid. X. The release of gibberellin-like substances by germinating barley embryos

Barley embryos, completely free from endosperm, were excised from germinating grain at various times and allowed to diffuse into an aqueous medium for varying lengths of time. At the end of this time, the embryos and ambient solutions were separately extracted. Gibberellin-like activity in the extracts was determined with the barley endosperm bioassay using seed from the same variety, harvest and treatment schedule as was employed for the embryo diffusion experiments. Gibberellin-like substances were released by embryos throughout the 60 hour germination period, though at no time during this period could sufficient activity be extracted from the embryos themselves to account for the observed release. Solvent partitioning and chromatography identified at least one major acidic component migrating at an Rf similar to that of GA(3).It is concluded that the endogenous gibberellin-like substance(s) originates within the embryo during germination, and that the release of this substance(s) is temporally consistent with, and quantitatively sufficient to account for the in vivo endosperm mobilization response syndrome. A gibberellin-like substance is undoubtedly the endosperm mobilizing hormone.

Magnetic fields around the torso: production by electrical activity of the human heart

A search was made outside the torso for fluctuating magnetic fields produced by the heart. Detector and subject were housed in a highly shielded enclosure. Magnetic signals with amplitudes of 10(-8) to 10(-7) gauss were detected synchronously with the electrocardiogram, confirming previous reports. A magnetocardiographic chest map, consisting of the magnetic field plotted against time at various spatial positions, shows genteral QRS and T-wave structure, as in the electrocardiogram; this structure varies with spatial position.

Barley Endosperm Bioassay for Gibberellins. II. Application of the Method

The use of the modified endosperm bioassay in conjunction with techniques for extracting and paper chromatographing extracts, and the application of statistical analyses to the results, is reported. The modified procedure has not altered the relative response to different gibberellins, though an analysis of many standard curves indicates that at least 1 feature of the bioassay system is still uncontrolled. A comparison of this bioassay with 15 others indicates that the endosperm response may have wide applicability in explorations of the physiological effects of gibberellins.

Barley endosperm bioassay for gibberellins. I. Parameters of the response system

Parameters of the bioassay based on the gibberellin-induced reducing sugar release of barley endosperm were investigated. Procedures for the rapid handling and processing of up to several hundred treatments without loss in sensitivity of the test are described, and the effects of variations in many aspects of the bioassay were assessed.In general, the variations in varieties, techniques, additives, conditions, and even gibberellins, all illustrate the stability, sensitivity, and adaptability of the hormone-induced response and emphasize its utility as a gibberellin bioassay.