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Biomedical subjects

D Cohen

Publications and source records attributed to D Cohen.

At least 811 records · Page 45Linked to original sources
PubMed1967

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.

Electrocardiography↗
PubMed1967

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.

Journal Article↗
PubMed1967

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.

Journal Article↗
PubMed1967

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.

Journal Article↗