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Biomedical subjects

R E Taylor

Publications and source records attributed to R E Taylor.

At least 163 records · Page 9Linked to original sources
PubMed1974

Bovine gingival collagenase: demonstration and initial characterization.

A collagenase active against native collagen was found in culture fluids of bovine gingiva. The enzyme first appeared in the culture fluid after 1-2 days and could be harvested thereafter for at least 30 days. The collagenase attacked collagen fibrils and cleaved collagen in solution, resulting in reaction products 1/4 and 3/4 of the length of the original molecule. The enzyme was inhibited by serum, by EDTA and by cysteine. The molecular weight was estimated by gel filtration to be 63,000 daltons.

Animals↗
PubMed1974

Serum inhibition of gingival collagenase.

Collagenases derived from bovine and human gingiva are inhibited effectively by serum. In bovine and human serum fractionated by gel chromatography, alpha2-macroglobulin is the only significant inhibitor of gingival collagenase. alpha11-Antitrypsin inhibited collagenase only in very high concentration and was several hundred-fold less effective than alpha2-macroglobulin. Inhibition of gingival collagenase with alpha2-macroglobulin is accompanied by the formation of an enzyme-inhibitor complex, which has retained no collagenolytic activity.

Animals↗
PubMed1973

Calcium and potassium systems of a giant barnacle muscle fibre under membrane potential control.

1. Single barnacle muscle fibres from Megabalanus psittacus (Darwin) were internally perfused and the effects of various internal and external solutions on voltage clamp currents were examined.2. The usual internal solution was 180 mM-K(+) aspartate (osmotic pressure adjusted to 1000 m-osmole by adding sucrose). Fibres perfused with this solution gave an average resting potential of -55 +/- 5 mV (all potentials are referred to the external solutions as ground). Further increase in internal K concentration depolarized the fibres.3. With membrane current control the total capacitance, referred to apparent membrane surface area, was 21.2 +/- 2.4 muF/cm(2).4. Under normal conditions, with demonstrably good longitudinal space clamp control, voltage clamp currents associated with certain depolarizing pulses showed oscillations. These oscillations were reduced in frequency and magnitude by lowering the temperature from 20 to 10 degrees C, by eliminating the inward currents with external Ca-free saline or by reducing the outward currents with internal tetraethylammonium (TEA) or replacement of internal K by Cs.5. With a Na- and Ca-free, 60 mM-MgCl(2) solution outside depolarizing voltage clamp pulses produced only outward currents. On repolarization the current tail reversed direction at about -70 mV for pulses of less than 50 msec duration. For longer pulses this reversal potential was less negative, suggesting an accumulation of external, or depletion of internal K.6. Both the size of the outward currents and the rate at which they reached their maximum value increased with temperature. The activation energy for the rate constant was about 63 kJ/mole.7. Fibres bathed in Na- and Mg-free, 60 mM-CaCl(2) saline were excitable. After replacement of the internal K(+) with Cs(+) or adding 60 mM-TEA to the internal solution only sustained inward currents were recorded with depolarization.8. Sustained inward currents could be reduced by external application of 5 mM-LaCl(3). Tetrodotoxin was not effective even at a concentration of 1000 nM.9. The rate at which these inward currents reached a maximum value increased with increase in temperature of the bathing solution with an activation energy of the order of 42 kJ/mole.10. The reversal potential of the inward currents changed with the level of internal Ca ions. For a fibre perfused without ethyleneglycol-bis (beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA) this reversal potential was 175 mV (internal free Ca 5 x 10(-7)M), and was 196 mV for a fibre perfused with 20 mM-Tris EGTA (internal free Ca 0.26 x 10(-8)M).11. We propose an electrical equivalent circuit to account for most of the observed electrical properties of barnacle muscle fibres. In this model the Ca and the K system are located at different anatomical places and they interact through a series resistance.

Animals↗
PubMed1972

Collagenase: localization in polymorphonuclear leukocyte granules in the rabbit.

Polymorphonuclear leukocyte granules were submitted to zonal fractionation through a discontinuous sucrose gradient. Azurophilic and specific granules were enzymatically characterized by peroxidase and alkaline phosphatase activity, respectively. The enzymes formed modal distributions like those reported by others. Collagenase activity was consistently associated with the specific granules containing alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1970

Time course of the sodium influx in squid giant axon during a single voltage clamp pulse.

1. Sodium influx measurements were carried out on internally perfused squid giant axons under conditions of membrane potential control.2. The ratio ;measured extra sodium influx/calculated ionic influx from the inward current record' is close to unity and is independent of the duration of the rectangular pulse of membrane potential.3. The variation of the sodium permeability with time during the voltage clamp pulse is obtained by subtracting the sodium influx obtained from the ;tail' current record from the measured extra sodium influx.4. Evidence was obtained indicating that the measured change in sodium permeability during a sudden decrease of the membrane potential from its resting level involves two processes, namely, a transient increase in sodium permeability (activation), and a decrease in sodium permeability (inactivation).5. The extra influx of sodium during a voltage clamp pulse is not decreased by raising the internal sodium concentration from 0 to 100 mM, supporting the validity of the independence principle.

Animals↗
PubMed1970

Sodium and potassium conductance changes during a membrane action potential.

1. A method for turning a membrane potential control system on and off in less than 10 musec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current-voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin-Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.

Action Potentials↗