Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 58-year-old man was initially seen with fatigue and weight loss. Laboratory examination detected hypercalcemia, elevated 1,25-dihydroxycholecalciferol levels, low parathyroid hormone (PTH) concentrations, and subperiosteal bone resorption. The patient underwent subtotal parathyroidectomy for presumed hyperparathyroidism, but serum calcium and 1,25-dihydroxycholecalciferol levels remained elevated following surgery. Search for another cause of the hypercalcemia disclosed enlarged para-aortic lymph nodes, biopsy specimens of which demonstrated Hodgkin's disease. After treatment of the patient with two cycles of chemotherapy with mechlorethamine hydrochloride, vincristine sulfate, procarbazine hydrochloride, and prednisone, serum calcium, 1,25-dihydroxycholecalciferol, and PTH levels normalized. We speculate that the humoral hypercalcemia in this patient resulted from tumor production of 1,25-dihydroxycholecalciferol.
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PMID:Humoral hypercalcemia in Hodgkin's disease. Association with elevated 1,25-dihydroxycholecalciferol levels and subperiosteal bone resorption. 383 28

We have studied periodic as well as aperiodic behavior in the self-sustained oscillations exhibited by the Hodgkin-Huxley type model of Chay, T. R., and J. Keizer (Biophys. J., 1983, 42:181-190) for the pancreatic beta-cell. Numerical solutions reveal a variety of patterns as the glucose-dependent parameter kCa is varied. These include regimes of periodic beating (continuous spiking) and bursting modes and, in the transition between these modes, aperiodic responses. Such aperiodic behavior for a nonrandom system has been called deterministic chaos and is characterized by distinguishing features found in previous studies of chaos in nonbiophysical systems and here identified for an (endogenously active) excitable membrane model. To parallel the successful analysis of chaos in other physical/chemical contexts we introduce a simplified, but quantitative, one-variable, discrete-time representation of the dynamics. It describes the evolution of intracellular calcium (which activates a potassium conductance) from one spike upstroke to the next and exhibits the various modes of behavior.
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PMID:Bursting, beating, and chaos in an excitable membrane model. 388 58

A physically based theory of ionic currents associated with nervous activity is extended to provide a model of electrical activity in the cortex and its immediate neighbourhood. It is shown that the most significant variations of potential in the extracellular fluid are associated with fluctuations in density of calcium and potassium ions. Nervous activity may activate a calcium resonance at the external surface of a neural membrane, which in turn excites a potassium resonance. The resulting variations of electrical potential are sufficient to account for the event related potentials observed in the extracellular fluid. In addition, it is found that periodic variations of potential associated with the potassium resonance may be initiated by metabolic changes in ion concentrations and are in close correspondence with those identified experimentally with the alpha- and beta-rhythms. It is shown how to determine the effective conductance of the neural membrane from ionic theory, with a result comparable to that assumed by Hodgkin & Huxley, under the conditions of the voltage clamp.
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PMID:Extracellular fields within the cortex. 403 63

The relationship between inward current and contraction was studied with double sucrose gap technique and measurement of contraction of the small muscular bundle in circular muscle from the fundus of guinea pig stomach. In voltage-clamped circular muscle, an inward current observed during depolarizing potential step was sensitive to Cd2+ or low external Ca2+ and had two components: a transient and a steady-state ones. Inactivation of this current was both voltage-dependent and Ca-current-dependent. Transient inward current activated phasic contraction, while the steady-state current activated tonic contraction. The voltage--dependence of the steady-state inward current was estimated with the Hodgkin--Huxley equation.
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PMID:[Calcium current and electromechanical coupling in the smooth muscle cells of the stomach]. 404 29

Alternating current threshold excitation of space-clamped squid giant axons was measured as a function of frequency, external calcium concentration, temperature (from 10 degrees to 35 degrees C), and hyper- and depolarizing steps. In normal axons there is usually an optimum frequency at about 120 Hz, at which the threshold is a minimum. The threshold rises at both lower and higher frequencies to give a resonance curve. Low calcium causes an increase in optimum frequency, a decrease in current threshold, and an increase in sharpness of tuning in both real axons and axons computed according to the Hodgkin-Huxley formulation; high calcium causes opposite effects. An increase in temperature causes an increase of optimum frequency, an increase in sharpness of tuning, and an increase in threshold current in both real and computed axons. The Q(10) for the effect of temperature upon optimum frequency is 1.8 in real and computed axons at moderate temperatures. Hyperpolarization causes (a) a decrease in optimum frequency, (b) a decrease in sharpness of tuning, and (c) an increase in threshold. Depolarization causes opposite effects.
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PMID:Effect of calcium, temperature, and polarizing currents upon alternating current excitation of space-clamped squid axons. 509 81

Space-clamped squid axons treated with low calcium and computed Hodgkin-Huxley (HH) axons were stimulated by steps of superthreshold current from 101 to 400% of the rheobasic value over a temperature range of 5-27 degrees C. The natural frequency of sustained repetitive firing of real and computed axons depended weakly upon stimulus intensity and strongly upon temperature, with a Q(10) of 2.7 (experimental) and 2.6 (computed). For real axons, but not the computed axon, the intervals between the first two spikes were shorter than between subsequent spikes. Constant spike frequencies from 75 Hz at low intensities and temperatures to 330 Hz at high intensities and temperatures were soon achieved. Subthreshold and superthreshold responses were sometimes intermixed in a train of responses from a real axon responding to a constant step of current, but not predicted by HH. The time interval following a spike was always longer than that following a subthreshold oscillation in slightly decalcified real axons, as Huxley and FitzHugh also found for computed axons. There was a bias toward spikes at the beginning of the train and toward subthreshold responses later on. Some repeated patterns were found, every second, third, or fourth response being a spike. Neither the HH equations nor the computed or experimental threshold behaviors show a critical temperature to support a membrane phase transition.
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PMID:Oscillation and repetitive firing in squid axons. Comparison of experiments with computations. 541 Apr 85

Single giant axons from the lobster circumesophageal connective were studied using the sucrose gap voltage-clamp technique. The axon area in the gap was bathed in acridine orange for several minutes and then rinsed for several minutes. Subsequent illumination resulted in progressive prolongation of electrically stimulated action potentials to durations of 150 msec. The prolongation was accompanied by an increase in threshold. Currents in voltage clamp were altered such that transient current inactivation was greatly slowed. The turn on of transient current was somewhat slowed, the voltage at which peak transient current could be obtained was shifted to more positive internal potentials, and transient current at all potentials was decreased. Steady-state current was similarly affected. Low calcium following illumination partially counteracted some of the changes, but not the slowing of inactivation. Low calcium increased the duration of prolonged action potentials. Selective alteration of parameters in the Hodgkin-Huxley equations brought about a qualitative match between computations and data.
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PMID:Light-induced changes in dye-treated lobster giant axons. 567 18

The temperature dependence of the oscillatory behavior of experimental and computed axons was compared. In the experimental study of space-clamped giant axons of the squid, small oscillations after a single threshold spike were measured using the double glucose gap over the temperature range 10 degrees -30 degrees C during treatment with three concentrations of external CaCl(2) solutions. Calcium concentration had little effect on frequency, as was found also by Huxley in his computations at 18.5 degrees C for a fiber at rest. The Q(10) both for the experimental and for the computed axon of FitzHugh was 2.25. The experimental measurements of the frequency of oscillations near threshold agree extremely well with the Hodgkin-Huxley calculations.
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PMID:Temperature dependence of oscillation in squid axons: comparison of experiments with computations. 578 Jul 9

Voltage clamp studies with the squid giant axon have shown that changes in the external calcium concentration (Frankenhaeuser and Hodgkin, 1957) shift the sodium and potassium conductance versus membrane potential curves along the potential axis. Taylor (1959) found that procaine acts primarily by reducing the sodium and, to a lesser extent, the potassium conductances. Both procaine and increased calcium also delay the turning on of the sodium conductance mechanism. Calcium and procaine have similar effects on lobster giant axon. In addition, we have observed that the magnitude of the response to procaine is influenced by the external calcium concentration. Increasing external calcium tends to reduce the effectiveness of procaine in decreasing sodium conductance. Conversely, procaine is more effective in reducing the membrane conductance if external calcium is decreased. The amplitude of the nerve action potential reflects these conductance changes in that, for example, reductions in amplitude resulting from the addition of procaine to the medium are partially restored by increasing external calcium, as was first noted by Aceves and Machne (1963). These phenomena suggest that calcium and procaine compete with one another with respect to their actions on the membrane conductance mechanism. The fact that procaine and its analogues compete with calcium for binding to phospholipids in vitro (Feinstein, 1964) suggests that the concept of competitive binding to phospholipids may provide a useful model for interpreting these data.
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PMID:Competitive action of calcium and procaine on lobster axon. A study of the mechanism of action of certain local anesthetics. 596 53

Instead of the single-channel pore proposed earlier [Wooldridge, D. E. (1984) Proc. Natl. Acad. Sci. USA 81, 5609-5612] for the transit of conductance ions through the neural membrane, a pore with a second channel for "influence ions" of calcium or magnesium is considered in this paper. By entering trapping centers at the closed inner ends of the new channels, the influence ions are postulated to alter the rates of chemical reactions that change the configurational state of the gates guarding the inner ends of the nearby conductance channels. This makes the permeability of the conductance channels strongly dependent on voltage. Using a four-state reaction scheme for both the sodium and potassium pore systems, a computer model of the membrane conductance is constructed. When suitable values are assigned to its parameters, the model closely reproduces the results of the Hodgkin-Huxley voltage-clamp and action potential experiments.
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PMID:A "convertible pore" model of neural membrane conductance. 609 78


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