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R K Crane

Publications and source records attributed to R K Crane.

At least 37 records · Page 2Linked to original sources
PubMed1976

Studies on the transport of aliphatic glucosides by hamster small intestine in vitro.

It has been found (1) that glucosides with a long alkyl chain (2-18 carbon atoms) as the aglycone can be transported by carrier-mediated processes in the hamster small intestine in vitro, (2) that these glucosides interact with the glucose carrier, and (3) that they compete with glucose and analogs for the binding to the carrier. The are Na+- and phlorizin-insensitive components of uptake for the long chain alkyl glucosides which suggest additional interactions or uptake processes.

Animals↗
PubMed1975

Response of transmural electrical parameters across in vitro everted sacs of hamster jejunum to variations in oxygenation rate.

1. The response of the electrical potential difference, short circuit current, and resistance across everted sacs of hamster jejunum to variations in the mucosal solution gassing rate was investigated. 2. Contrary to previous reports by others, it was found that the potential difference responds to increases in mucosal solution gassing rate by increasing in magnitude during the first 20 min of incubation. 3. The increases in potential difference were parallelled by increases in short circuit current but not by changes in resistance. 4. Increases in mucosal solution gassing rate increased epithelial cell O2 availability and this effect was determined to be due to increased stirring by gas bubbles. From the data, it was deduced that the minimum thickness of the mucosally located functional unstirred layer is between 0.08 and 0.16 cm when less than the full magnitude of electrical activity is observed across the everted sac preparation. 5. Serosal N2 or O2 had little or no effect on electrical parameters under maximum mucosal oxygenating conditions but dramatically affected these parameters when less than maximum mucosal oxygenating conditions were used. 6. Qualitative variations in the magnitude of the short circuit current across this preparation with respect to Cl- dependence were demonstrated. These variations were dependent upon the level of O2 availability, being apparent at high levels of O2 and absent at low levels. 7. It is concluded that the thickness of mucosally located unstirred layers can determine the O2 availability to the mucosa of everted sacs of hamster jejunum and thereby influence the observable magnitude and pattern of ionic dependence of the short circuit current across this preparation.

Animals↗
PubMed1975

An analysis of the D-glucose influx kinetics of in vitro hamster jejunum, based on considerations of the mass-transfer coefficient.

1. A study designed specifically to investigate the effects of unstirred layers on the apparent glucose-influx kinetics of hamster jejunum was conducted. 2. The apparent V was 12.81, 10.71, 9.75, 10.17 and 9.33 mumol/cm-2 - h while the apparent Km was 7.42, 3.95, 1.87, 0.93 and 0.5 mM, respectively, when the rate of shaking the incubation flasks was 40, 80, 120, 160 and 200 cycles/min. 3. Extrapolation of the slope and reciprocal intercept of Lineweaver-Burke plots of the data to infinite shaking rate is mathematically justified to yield the slope and intercept of a Lineweaver-Burk plot which is uncomplicated by unstirred layers. These extrapolations were found to have a regression coefficient = 1 when plotted as (intercept)-1 or slope = b0 + b1b-(shake)-2 where b = 2.764 for the slope plot and 6.626 for the (intercept)-1 plot. From the values of b0 one obtains a Km of 0.41 and a V 0f 0.35 which should represent the true kinetic parameters for glucose influx into this tissue under the experimental conditions employed. 4. Values of the theoretical flux expected on a basis of unstirred-layer thickness which was calculated from the relation Cb (for J = V/2) = Km + 0.5 V/Kd agreed with the experimental values of J in some instances but the 95% confidence interval of the theoretical and experimental values did not overlap in many instances at low shaking rates and low concentrations of glucose. 5. A factor theta representing the error between the theoretical and experimental values was found to fit the relationship 1n(theoretical J) = - 3.8 + 5.77 (1/theta) with a regression coefficient of 0.98 and was proposed to be due to one or more of the following parameters: (1) a villus tip to base gradient of transport (influx) activity; (2) a dependence of brush-border influx area on substrate concentration in the bulk incubation media; and (3) an end-product inhibition of the overall transport rate. 6. It is apparent from the data that the flux of glucose across the unstirred layer is ordinarily the rate-limiting step in the trans-brush-border transport of this sugar by hamster jejunum when less than saturating concentrations of glucose are used. At high shaking rates the contribution of the unstirred layer is reduced.

Animals↗
PubMed1975

Enzymes of the human intestinal brush border membrane. Identification after gel electrophoretic separation.

The postition of a number of human intestine brush border membrane enzyme activities in polyacrylamide gels after electrophoresis has been determined. These activities are, in order from the origin, maltase/glucoamylase, lactase/phlorizin hydrolase, maltase/sucrase/isomaltase, enteropeptidase, trehalase and gamma-glutamyl-transferase. Leucylnaphthylamide hydrolyzing activity was inactivated by sodium dodecylsulfate and its position was not determined. The positions of the activities have been correlated with the positions of protein bands previously determined. One such band situated between enteropeptidase and alkaline phosphatase has not been identified.

Alkaline Phosphatase↗
PubMed1975

Modification of an assay for trypsin and its application for the estimation of enteropeptidase.

A sensitive method for the estimation of trypsin and enteropeptidase is described. The use of alpha-N-benzoyl-DL-arginine-p-nitroanilide as substrate in combination with the Bratton-Marshall reaction increased the sensitivity of an established method to a degree which permits the determination of enteropeptidase at considerably lower activity levels than heretofore such as those expected in brush border membrane preparations from peroral biopsies of human small intestine.

Anilides↗