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Biomedical subjects

J E Porter

Publications and source records attributed to J E Porter.

16 recordsLinked to original sources
PubMed1992

A Ca(2+)-ATPase from rat parotid gland plasma membranes has the characteristics of an ecto-ATPase.

A Ca(2+)-ATPase with an apparent Km for free Ca2+ = 0.23 microM and Vmax = 44 nmol Pi/mg/min was detected in a rat parotid plasma membrane-enriched fraction. This Ca(2+)-ATPase could be stimulated without added Mg2+. However, the enzyme may require submicromolar concentrations of Mg2+ for its activation in the presence of Ca2+. On the other hand, Mg2+ could substitute for Ca2+. The lack of a requirement for added Mg2+ distinguished this Ca(2+)-ATPase from the Ca(2+)-transporter ATPase in the plasma membranes and the mitochondrial Ca(2+)-ATPase. The enzyme was not inhibited by several ATPase inhibitors and was not stimulated by calmodulin. An antibody which was raised against the rat liver plasma membrane ecto-ATPase, was able to deplete this Ca(2+)-ATPase activity from detergent solubilized rat parotid plasma membranes, in an antibody concentration-dependent manner. Immunoblotting analysis of the pellet with the ecto-ATPase antibody revealed the presence of a 100,000 molecular weight protein band, in agreement with the reported ecto-ATPase relative molecular mass. These data demonstrate the presence of a Ca(2+)-ATPase, with high affinity for Ca2+, in the rat parotid gland plasma membranes. It is distinct from the Ca(2+)-transporter, and immunologically indistinguishable from the plasma membrane ecto-ATPase.

Adenosine Triphosphatases↗
PubMed1992

Atypical alpha-1 adrenergic receptors on the rat parotid gland acinar cell.

Subtypes of alpha-1 adrenergic receptors on rat parotid gland acinar cell membranes were characterized using subtype selective alpha adrenergic receptor antagonists. The alpha-1 adrenergic receptor antagonist beta-iodo-[125I]-4-hydroxyphenyl-ethyl-aminomethyl-tetralone (125IBE) had an equilibrium dissociation constant for specific binding sites on these membranes of 0.241 +/- 0.03 nM and a total number of specific radioligand binding sites of 41 +/- 4 fmol bound/mg of protein. Displacement of 125IBE binding by subtype-selective alpha-1 adrenergic receptor antagonists 2-(2,6-dimethoxyphenoxyethyl)-aminomethyl-1,4-benzodioxane HCl (WB4101) and 5-methylurapidil fit best to biphasic competition curves. The high- and low-affinity inhibition equilibrium dissociation constant for WB4101 were 0.45 +/- 0.1 and 27 +/- 6 nM, respectively. Similarly, the high- and low-affinity inhibition equilibrium dissociation constants for 5-methylurapidil were 0.16 +/- 0.03 and 71 +/- 20 nM, respectively. These affinities for 125IBE binding sites suggest the presence of alpha-1A and alpha-1B adrenergic receptor subtypes on acinar cell membranes. The irreversible alpha-1 adrenergic receptor antagonist chloroethylclonidine was used to inactivate alpha-1B adrenergic receptors on acinar cell membranes. After treatment with chloroethylclonidine, saturation binding analysis demonstrated no change in the total number of 125IBE binding sites. In addition, competition curves for WB4101 and 5-methylurapidil again showed two sites of 125IBE displacement, with no change in antagonist affinities in membranes treated with chloroethylclonidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Calcium uptake in rat parotid gland secretory granules.

45Ca2+ uptake in isolated rat parotid secretory granules was examined in the presence of oxalate. Uptake of calcium was dependent on time, with the maximum occurring at 15 min. The uptake of calcium was dependent on adenosine-5'-triphosphate (ATP), and substitution of ATP with beta, gamma-methylene-ATP did not stimulate calcium uptake. Enzyme marker analysis indicated that mitochondria accounted for no greater than 3.0 +/- 0.2% of the observed ATP-dependent calcium uptake. Calcium uptake was blocked by the ATPase inhibitors tributyltin, IC50 = 12.2 +/- 0.6 nmol/L and 4-acetamido-4'-isothiocyano-2,2'-stilbene disulphonic acid (SITS), IC50 = 3.0 +/- 0.3 mumol/L. These results indicate that in the parotid secretory granule there is a calcium uptake mechanism that is dependent on the hydrolysis of ATP and is suppressed by two inhibitors of granule ATPase.

Adenosine Triphosphate↗
PubMed1990

Cost of a roller skating rink to the local accident and emergency department.

A 14 month retrospective study was undertaken to determine the cost implications of the opening of a roller skating rink to the local hospital accident and emergency department (A and E). A total of 398 patients attended following injury at the roller skating rink, of whom 384 were included in the study. The estimated cost of their injuries was determined by the hospital accounts department. The average cost per patient attending the A and E department following roller skating injury was about 100 pounds. The total cost to the A and E department of all injuries sustained at the rink over this period was 38,412 pounds. The cost implications of opening a roller skating rink for the A and E department are considerable. If proposals for self-budgeting are applied, A and E departments will have to seek additional funding if such leisure facilities are opened in their vicinity.

Adolescent↗