The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing...
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The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing voltage-clamp pulses of identical size. Since 1. the integrals of the "on" and "off" current transients were found to be equal and opposite, 2. the change displaced reached saturation (about 140-10-minus 15 C/node) when the internal potential was taken to a sufficiently positive value during the depolarizing pulses and, 3. the size of the charge transferred was unaffected by temperature although its time constant had a large temperature coefficient (Q10 = 2.4), these currents to our opinion must result form charge movements confined to the membrane and, therefore, can be considered as non-liner displacement currents. The steady-state rearrangement of the charges is consistent with a Boltzmann distribution of charges (effective valence z = 1.65) between two configurations characterized by different energy levels. The midpoint potential of the distribution curve is -33.7mV and its maximum slope, kT/ZE, is 14.9 mV. Following changes in membrane potential the charges undergo a first order transition between these states. We propose that these displacement currents arise from a redistribution of the charges involved in the sodium gating system.
The usefulness of a digital computer system for acquisition, manipulation and display of nuclear medicine or other medical two-dimensional images is enhanced by fast data acquisition of 80 000 cps in list mode (128 &#...
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The usefulness of a digital computer system for acquisition, manipulation and display of nuclear medicine or other medical two-dimensional images is enhanced by fast data acquisition of 80 000 cps in list mode (128 × 128) and 300 000 cps in histogram mode (64 × 64) with 3μsec pulse pair resolution and dual isotope handling capabilities. Speed and ease of operation are important developments which lead to practical clinical application of research developments such as brain and heart blood-flow studies, Fresnel hologram reconstruction, three-dimensional reconstruction from multiple camera views, and display of functional images such as lung, heart, and kidney uptake and clearance rates.
A versatile system has been developed for off-line computerized quantitation of uterine contractility. It includes tabulation and display of intensity, frequency, resting tone, uterine activity, cumulative area below ...
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A versatile system has been developed for off-line computerized quantitation of uterine contractility. It includes tabulation and display of intensity, frequency, resting tone, uterine activity, cumulative area below the pressure curve, and average intrauterine pressure. Its advantages and drawbacks are compared with the conventional method and with an automated on-line labor surveillance system.
Thirty consecutive patients with acute myocardial infarction had continuous magnetic tape recording of their electrocardiograms (lead II) for the period of their stay in the coronary care unit. Analysis of the 24 hour...
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Thirty consecutive patients with acute myocardial infarction had continuous magnetic tape recording of their electrocardiograms (lead II) for the period of their stay in the coronary care unit. Analysis of the 24 hour tape recordings was implemented on a Honeywell model 316 digital computer. In the first 24 hours after admission to the coronary care unit, 12 of the 30 patients (40 percent) exhibited nonparoxysmal junctional tachycardia; in 5 the arrhythmia was not recognized by conventional monitoring techniques. For the subsequent 3 days, the incidence rate of the arrhythmia was 13 percent for the first 48 hours and 3 percent for 72 hours. Although the mortality rate in patients with nonparoxysmal junctional tachycardia was greater than in patients not demonstrating the arrhythmia (33 versus 6 percent), there was a greater percentage of patients with anterior infarction in the former group; therefore, mortality may have been related to site of infarction rather than being reflective of the arrhythmia or its associated pathophysiologic state. Of possible significance is the association of a greater degree of sinus arrhythmia with nonparoxysmal junctional tachycardia. The incidence of nonparoxysmal junctional tachycardia in this group of patients was greater than previously reported. It is possible that computer tape analysis may have provided more accurate recognition of the arrhythmia and, thus, more realistic incidence data. The association of nonparoxysmal junctional tachycardia with sinus arrhythmia could only have been recognized by computer technique. The computer system is not a diagnostic system but rather a tape review method.
A mathematical interpretation of the molecular biological facts is attempted and a hybrid automaton model of the genetic system and the continuous biochemical one is considered. For the continuous system under the con...
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A mathematical interpretation of the molecular biological facts is attempted and a hybrid automaton model of the genetic system and the continuous biochemical one is considered. For the continuous system under the control of the genetic one, one may take the KM (kinematic machine) of von Neumann. Thus the total system of the molecular automaton, the genetic information of DNA and the hybridized continuous system or KM may make a self-reproducing automaton. This idea is applied to the cell cycle, G 1 , S, G 2 and M, during which duplication of DNA and cell division takes place, and a computer simulation is tried. The change of the continuous system may be interpreted as the response to the digital information, which may be the permanent genetic one as well as a temporal one like the open or closed state. This change is a kind of DA conversion. Then the digital feedback from the continuous system to the temporal state of the operons may be a kind of AD (analogue-digital) conversion, and the combination of the DA and the AD conversion may correspond to a delay unit which is necessary for the molecular automaton. As there are difficulties in determining the system parameters of the continuous system in the living state, the continuous changes are again replaced by the delay units of various intervals corresponding to the DA and the AD conversions and thus an automaton model having various delay constants is considered for the case of a cell cycle. For this automaton theory a chemico-physical interpretation of the concept of information is given, i.e. the information is an indirect action affecting the free energy of activation of the rate processes. Then the fluxes of the rate processes correspond to the response to the information.
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