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Biomedical subjects

R E Taylor

Publications and source records attributed to R E Taylor.

At least 19 recordsLinked to original sources
PubMed1979

Modification of permeability of frog perineurium to [14C]-sucrose by stretch and hypertonicity.

An in vitro method has been developed to determine quantitatively the permeability of the perineurium to radiotracers at room temperature. The permeability to [14C]sucrose of the isolated perineurium of the sciatic nerve of the frog, Rana pipiens, was measured at rest length, when the perineurium was stretched and after the perineurium had been subjected to hypertonic treatment. Mean permeability at rest length was calculated to be 5.6 +/- 0.27 (S.E.M., n = 45) X 10(-7) cm/sec, and both stretch and hypertonic treatment increased the permeability. A 10% stretch increased permeability reversibly, whereas a 20% stretch or immersion of the perineurium in a hypertonic bath increased permeability irreversibly. Altered permeability under these conditions might be related to changes in the ultrastruct of tight junctions in the perineurium.

Animals↗
PubMed1979

Simple and rapid high-pressure liquid chromatographic determination of papaverine in plasma.

A rapid and sensitive high-pressure liquid chromatographic (HPLC) assay is described for the quantification of papaverine in plasma. A paired-ion, reversed-phase system was employed with detection at 254 nm. This procedure yielded reproducible results with a sensitivity of 2 ng/ml. Total extraction and quantification time was less than 1 hr. The suitability of this procedure for plasma sample analysis from a bioavailability study was demonstrated.

Biological Availability↗
PubMed1978

Temperature effects on gating currents in the squid giant axon.

The effects of temperature (3 degrees-26 degrees C) on the nonlinear components of the displacement current were measured in internally perfused, voltage clamped squid axons. Steps of potential were applied from a holding potential of -70mV (outside ground) to values from -130 to +70mV and either the current or its integral (charge) was recorded as a function of time. For that component of the charge movement not linearly related to voltage, the total charge moved in a few milliseconds (about 1,500 electronic charges/micron2) between saturation limits (e.g. -100mV to +50mV) showed an apparent increase of 13 +/- 5% for a 10 degrees C rise in temperature. Attempts to fit the falling phase of the gating current (or charge) with the sum of two exponentials showed temperature effects on both components but there was considerable scattering. At short times, records for current or charge made at 16 degrees C, expanded by a factor alpha, superimposed on those made at 6 degrees C for alpha about 1.6. For long times alpha was about 2.3.

Axons↗
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↗