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Biomedical subjects

R E Taylor

Publications and source records attributed to R E Taylor.

At least 145 records · Page 8Linked to original sources
PubMed1977

Proteins of the periodontium. Characterization of the insoluble collagens of bovine dental cementum.

Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([alpha1(I)]2alpha2) accounted for more than 90% of the organic matrix, while Type III collagen ([alpha1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from alpha1(I) and alpha2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.

Amino Acids↗
PubMed1976

Activation of fibroblast procollagenase by mast cell proteases.

Proteases capable of activating procollagenase from gingiva and from fibroblast and macrophage monolayer cultures were harvested from homogenates of canine tumor mast cells. The mast cell proteases lysed casein and Azocoll but not native collagen. In low salt concentrations the enzymes existed at high molecular weight complexes, which were dissociated by increasing the salt concentration above 1.0 M (NaCl, KCl). Gel filtration in 1.4 M KCl separated the protease activity into three peaks, all of which activated procollagenase. Two of the enzymes showed substrate specificities (hydrolysis of p-tosyl-L-arginine methyl ester and benzoyl-tyrosine ethyl ester) and reactive center reactivities similar to pancreatic trypsin and chymotrypsin. Based on gel filtration, apparent molecular weights of 160 000 (p-tosyl-L-arginine methyl ester esterase), 90 000 (main procollagenase activator) and 36 000 benzoyl-tyrosine ethyl ester esterase) were determined. Activation of procollagenase resulted in a 18-20 000 decrease of the molecular weight. The activation was directly related to the amount of activator added within certain limits. Further addition of activator resulted in proteolytic inactivation of collagenase.

Animals↗
PubMed1976

Synthesis and release of procollagenase by cultured fibroblasts.

An inactive collagenase was harvested from both serum-free and serum-supplemented fibroblast monolayer cultures in periods of active collagen synthesis. The latent collagenase did not hydrolyze collagen and did not bind the potent collagenase inhibitor alpha2-macroglobulin. Activation with trypsin imparted to the enzyme the ability to hydrolyze collagen at neutral pH in a typical manner and to form an inhibited complex with alpha2-macroglobulin. The molecular weights, determined by calibrated gel filtration, were 78,000 and 60,000 for the latent and active enzymes, respectively. The data indicate that collagenase is released from the cells in inactive form, as a zymogen.

Amino Acids↗
PubMed1976

Procollagenase from bovine gingiva.

1. Collagenase (EC 3.4.24.3) is released from bovine gingival explants in vitro as a zymogen. The zymogen does not hydrolyze collagen and does not form a complex with alpha2-macroglobulin (alpha2-M). It elutes in gel filtration with an apparent molecular weight of approx. 80 000. 2. Incubation of the zymogen with trypsin results in a 15 000-20 000 dalton decrease in molecular weight and imparts to the enzyme the ability to hydrolyze collagen and to form a complex with alppha2-M. 3. The zymogen can be completely separated from the active enzyme to alpha2-M. Likewise, the zymogen can be harvested from cultures supplemented with serum.

Animals↗
PubMed1976

Rabbit alveolar macrophage collagenase: evidence of polymeric forms.

Collagenase harvested in vitro from rabbit alveolar macrophages eluted in gel chromatography corresponding to apparent molecular weights of 45 000, 85 000, and 165 000. Reversible changes from one molecular weight to another in low salt concentration and predominance of the 45 000 species in salt concentrations above 1.0 M (NaCl, KCl) suggest that the higher molecular weights represent polymeric forms of collagenase.

Animals↗
PubMed1975

Proteins of the periodontium. Identification of collagens with the [alpha1(I)]2alpha2 and [alpha1(III)]3 structures in bovine periodontal ligament.

Insoluble collagen was prepared from bovine periodontal ligament. Isolation and characterization of CNBr peptides originating from the alpha1(I), alpha2, and alpha1(III) chains showed that the tissue contained both type I and type III collagens. Further evidence for the presence of type III collagen was obtained by the isolation of alpha1(III) chains from pepsin-treated ligament collagen, with properties similar to those of human alpha1(III) chains. Estimates based on the amounts of certain CNBr peptides indicated that about one-fifth of the collagen of periodontal ligament is type III, the remainder being type I collagen.

Amino Acids↗
PubMed1975

The rate of action of tetrodotoxin on sodium conductance in the squid giant axon.

When tetrodotoxin is applied to or washed away from the squid giant axon, the rates at which the sodium conductatnce is blocked and unblocked are an order of magnitude smaller than those reported for the isolated node of Ranvier. This slowing is to be expected if in squid the tetrodotoxin binding sites act as a saturable sink in series with the barrier to free diffusion imposed by the presence of the Schwann cell. A comparison has been made between the rates observed experimentally and those calculated for a computer model of the system, in order to estimate the apparent density in the membrane of both specific and non-specific tetrodotoxin binding sites. The figure thus obtained for the number of sodium channels in the squid giant axon, several hundred per square micrometre, agrees well with those derived from other lines of argument.

Animals↗
PubMed1975

Simultaneous measurements of magnesium, calcium and sodium influxes in perfused squid giant axons under membrane potential control.

1. Giant axons from the squids Dosidicus gigas, Loligo forbesi and Loligo vulgaris were internally perfused with 550 or 275 mM KF plus sucrose and bathed in artificial sea water containing 45Ca, 28Mg or mixtures of 45Ca-28Mg or 45Ca-22Na. Resting influxes and extra influxes during voltage-clamp pulses were measured by collecting and counting the internal perfusate. 2. For Dosidicus axons in 10 mM-CaCl2 the resting influx of calcium was 0-016 +/- 0-007 p-mole/cm2 sec and a linear function of external concentration. For two experiments in 10 and 84-7 mM-CaCl2, 100 nM tetrodotoxin had no effect. Resting calcium influx in 10 mM-CaCl2 was 0-017 +/- 0-013 p-mole/cm2 sec for Loligo axons. 3. With 55 mM-MgCl2 outside the average resting magnesium influx was 0-124 +/- 0-080 p-mole/cm2 sec for Loligo axons. Discarding one aberrant point the value is 0-105 +/- 0-046 which is not significantly different from the resting calcium influx for Dosidicus fibres in 55 mM-CaCl2, given as 0-094 p-mole/cm2 sec by the regression line shown in Fig. 1. In two experiments 150 nM tetrodotoxin had no effect. 4. With 430 mM-NaCl outside 100 nM tetrodotoxin reduced the average resting influx of sodium in Dosidicus axon from 27-7 +/- 4-5 to 25-1 +/- 6-2 p-mole/cm2 sec and for Loligo fibres in 460 mM-NaCl from 50-5 +/- 4 to 20 +/- 8 p-mole/cm2 sec. 5. Using depolarizing pulses of various durations, the extra calcium influx occurred in two phases. The early phase was eliminated by external application of tetrodotoxin. The results of analysis are consistent with, but do not rigorously demonstrate, the conclusion that the tetrodotoxin sensitive calcium entry is flowing through the normal sodium channels (cf. Baker, Hodgkin & Ridgway, 1971). 6. Measurements of extra influxes using 22Na and 45Ca simultaneously indicate that the time courses of tetrodotoxin sensitive calcium and sodium entry are similar but not necessarily identical. It is very doubtful that any significant calcium entry occurs before the sodium or is involved in the activation of the sodium system. 7. These measurements confirm for Loligo, as previously shown for Dosidicus axons, that the magnitude and time course of the sodium entry during a depolarizing pulse deduced from electrical measurements is the same as that measured with 22Na. 8. Using 28Mg, or mixtures of 45Ca and 28Mg, we observed a single phase of magnesium entry which was insensitive to external tetrodotoxin or internal tetraethyl ammonium. The magnitude of the magnesium influx was considerably greater than the calcium extra entry and large enough to have been detected in the experiments of Meves & Vogel (1973) if it represented current. 9. We suggest the possibility that the calcium and magnesium extra influxes, after external treatment with tetrodotoxin, during a depolarizing pulse, do not contribute to the measured current.

Animals↗
PubMed1975

Production and measurement of exophthalmos-producing factor in guinea pigs.

Although the extent of proptosis in exophthalmic Graves' disease has been measured directly and shown to correlate with serum content of a bioassayable exophthalmus-producing factor (EPS;1), a comparable relationship in an experimental model has not been reported. Progressive exophthalmos, measured from photographs and expressed as a ratio of intercorneal distance to intersupraorbital ridge distance, was produced in male guinea pigs when thyroid status was altered either by surgical thyroidectomy supplemented with 131-I treatment or by the administration of 6-propyl-2 thiouracil (0.1% in chow). In both groups, at time of sacrifice, serum content of EPF estimated by a modified goldfish bioassay using a known exophthalmogeric TSH preparation (Ambinon, Organon-Oss) as standard was positively correlated (r equals 0.804) with the terminal degree of exophthalmos. Daily replacement therapy with T4 (15mug/kg body wt) failed to alter significantly the exophthalmos which developed, even when replacement was initiated prior to the alterations of thyroid gland function; this observation tends to eliminate thyroid hormone deficiency per se as the causal event in exophthalmos. T4 treatment did, however, reverse or prevent the rises in serum TSH levels (McKenzie bioassay) thus dissociating TSH activity from EPF activity in the guinea pig. Treatment of guinea pigs with synthetic TRH (0.5, 1.0 OR 10 mug/kg body wt) for 21 days failed to produce demonstrable exophthalmos or assayable EPF levels although plasma TSH was significantly elevated.

Animals↗