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G C Schofield

Publications and source records attributed to G C Schofield.

At least 19 recordsLinked to original sources
PubMed1979

Microspectrofluorometric studies on the formaldehyde-induced reaction product of 5-hydroxytryptamine.

A new model incorporating Sephadex G-25 as an inert carrier has been developed for studying the reaction between biogenic amines and formaldehyde vapour. Both the fluorescence yield and the spectral characteristics of the 5-HT formaldehyde reaction product are influenced appreciably by the relative humidity at which paraformaldehyde is equilibrated, the duration of the reaction, the glycine concentration and pH of the suspending solution and the duration of exposure to ultraviolet light. It is concluded that care should be exercised in attempting to identify or quantify 5-HT on the basis of microspectrofluorometric analysis.

Animals↗
PubMed1979

Changes in membrane surface areas in mouse parietal cells in relation to high levels of acid secretion.

Levels of gastric acid secretion which may be maximal for the mouse were recorded following treatment with histamine and carbachol. A 30-fold increase over control levels was obtained in perfused animals, corresponding to a fourfold increase over highest levels recorded previously for stimulated mice. Stereological methods were used to estimate surface areas of membrane compartments of parietal cells in control and stimulated animals. Estimates of relative changes in membrane surface areas using a surface ratio method in this case substantiated changes detected by calculating surface densities. Main changes in membrane compartments of parietal cells from animals showing maximal acid secretion were a fourfold increase in free (luminal) surface, a 50% increase approximately in lateral and basal membrane, and a 90% reduction approximately in the tubulovesicular membrane compartment. Following withdrawal of secretagogues, acid secretion usually returned to control levels within 3 hours, but complete reconstitution of the tubulovesicular compartment was not seen within any survival period up to 5 hours. Reappearance of tubulovesicular elements first occurred shortly after the peak of a secretory response in focal cytoplasmic areas containing spherical and indented coated vesicles, and also numerous concentric membrane profiles not previously described in parietal cells. The way in which movement of membrane from the tubulovesicular compartment to the free surface occurs is not yet clear. However, reconstitution of the tubulovesicular compartment during a fall in acid secretion appears to involve movement of membrane from the free surface through coated vesicles, and their progression through indented forms and concentric membrane profiles to vesicles of the tubulovesicular compartment.

Animals↗
PubMed1974

Studies on the depletion and accumulation of microvilli and changes in the tubulovesicular compartment of mouse parietal cells in relation to gastric acid secretion.

Gastric parietal cells in mice present a spectrum of microscopic appearances due mainly to variations in the abundance of the tubular and vesicular component of the cytoplasm and in the size and number of microvilli lining the intracellular canaliculi. Differences in the range of forms among parietal cells of fasting versus fed mice were not especially striking, but cells with very numerous tubules and vesicles were more common after fasting. However, in mice treated with drugs or hormones that induce acid secretion, parietal cells were more uniform in appearance. There was a marked reduction of these cytoplasmic membranes and a concomitant increase in both the number and size of microvilli. Measurements of acid secretion in control animals and in animals treated with acid secretagogues indicated hydrogen ion secretion contemporaneous with depletion of the cytoplasmic tubulovesicular membranes and with increase of the microvilli. In mice with inhibited acid secretion, parietal cells showed an accumulation of cytoplasmic tubules and vesicles and reduction in the numbers of microvilli. Stereological methods were used to quantitate 10 different parietal cell compartments. Tracer studies with lanthanum did not reveal continuity between the tubules and the plasma membrane. However, there were regions of close apposition between the tubulovesicular membranes and the cell membrane of the canaliculus, and instances where cytoplasmic tubules extended from the cell into the core of enlarged microvilli.

Animals↗