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Biomedical subjects

W E Harris

Publications and source records attributed to W E Harris.

At least 37 records · Page 2Linked to original sources
PubMed1984

Phosphorylation states of the (Na+ + K+)-transporting ATPase in preparations from lamb kidney and electric-eel (Electophorus electricus) electric organ.

Phosphorylation states of the (Na+ + K+)-transporting ATPase were studied in highly purified preparations isolated from electric-eel electric organ and from lamb kidney. The steady-state level of phosphorylated lamb kidney enzyme, obtained by reaction with [gamma-32P]ATP, was not appreciably reduced in the presence of ADP unless oligomycin was present. The phosphorylated form of the electric-eel electric-organ enzyme was reduced by at least 95% under the same conditions, suggesting that the E1P state in the kidney enzyme is more transitory than that in electric organ. The level of phosphorylation from [32P]Pi was higher in the lamb kidney preparation than in the electric-organ preparation, and the difference in stimulation of phosphorylation by ouabain in the two preparations was striking. Ouabain increased the level of phosphorylation by 35% in the kidney preparation and 734% in the electric-organ preparation. The E2P state seems to be stabilized by ouabain in the latter preparation. These findings, as well as the different reactivities of the thiol groups to blocking reagents in these preparations, suggest that the tertiary structure in the enzyme isolated from these two sources is different.

Adenosine Triphosphate↗
PubMed1983

Incorporation of cis-parinaric acid, a fluorescent fatty acid, into synaptosomal phospholipids by an acyl-CoA acyltransferase.

The cis-isomer of parinaric acid, a naturally occurring C-18 polyene fatty acid, was incubated with brain subcellular fractions and the polarization of fluorescence increased in a time dependent manner. Greatest increases occurred in synaptosomal and microsomal membranes. This increase in polarization of fluorescence was found with the cis, but not the trans, isomer of parinaric acid and required Mg2+ or Ca2+ and was stimulated by coenzyme A and ATP. Synaptosomes were incubated with cis-parinaric acid and lipids were extracted and examined by high performance liquid chromatography. The highest incorporations of cis-parinaric acid were found in phosphatidylcholine (71%) and phosphatidylethanolamine (20%) while only traces were found in phosphatidylserine and phosphatidylinositol. [3H]Oleic acid was also incorporated into membrane phospholipids and unlabeled oleic acid blocked incorporation of cis-parinaric acid. It is proposed that cis-parinaric acid, like fatty acids normally found in brain, is incorporated into membrane phospholipids by an acyl-CoA acyltransferase. The presence of this enzyme in nervous tissue may make it possible to easily introduce fluorescent fatty acid probes into membrane phospholipids and to thereby facilitate study of membrane-mediated processes.

Animals↗
PubMed1982

Unusual cervical resorption after reinjury.

The root canal of a maxillary central incisor apparently completely calcified after an injury. Eight years later, this tooth was injured again and massive resorption developed. The resorption began as an unusual pattern of cervical destruction, and ultimately the entire root apparently was destroyed. However, the tooth was still serving satisfactorily without other symptoms seven years after the reinjury--15 years after the original injury. Calcification of the pulp space can develop in a tooth and the root structure can be resorbed in a tooth after an injury. Therefore a similar stimulus can produce opposite responses, in this instance in the same tooth at different times. Luxation of teeth is a treatable injury, and replantation of luxated teeth is an acceptable technique that can result in long-term retention of the replanted tooth. Replantation of the patient's own tooth is usually preferred to artificial replacement of the luxated tooth at the time of injury. Interceptive endodontic care for a tooth that has been traumatized and in which the pulp space appears on the radiograph to be calcifying is probably best for the patient.

Adolescent↗
PubMed1980

Organization of thiol groups of electric-eel electric-organ sodium-plus-potassium ion-stimulated adenosine triphosphatase studied with bifunctional reagents.

The reactions of three bifunctional thiol-blocking reagents of differing cross-linking spans and two monofunctional thiol-blocking reagents with the Na+ + K+-stimulated ATPase of the electric-eel electric organ were examined. 1,5-Difluoro-2,4-dinitrobenzene with a cross-linking span of 0.3--0.5 nm (3--5 A) and high solubility in non-polar solvent was the most efficient inhibitor of enzyme activity; thus essential thiol groups exist in a non-polar environment and are approx. 0.3--0.5 nm (3--5 A) from their nearest thiol-group neighbours. Ligands promoting phosphorylation of the Na+ + K+-stimulated ATPase decreased the number of thiol groups bridged by 1,5-difluoro-2,4-dinitrobenzene and by 4,4'-difluoro-3,3'-dinitrodiphenyl sulphone [0.7--1.0 nm (7--10 A) span]. Phosphorylation is associated with a conformational change in the enzyme.

Animals↗
PubMed1977

Conformational changes of purified (Na+ + K+)-ATPase detected by a sulfhydryl fluorescence probe.

The fluorescent sulfhydryl reagent S-mercuric-N-dansyl cysteine (Dn-Cys-Hg+) has been used to label a purified preparation of the (Na+ + K+)-ATPase obtained from the electric organ of Electrophorous electricus. The labelled (Na+ +K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3), although reversibly inhibited, was capable of undergoing conformational changes associated with the active enzyme that could be monitored fluorometrically. The presence of ligands (Na+ + Mg2+ + ATP or Mg2+ + Pi) which are known to convert the enzyme from the E-1 state to the E-2-P state brought about large (97--100%) increases in fluorescence of the dimethylaminonaphthalene sulfonyl (Dn) label. An E-2 state could be achieved by the addition of Mg2+ which caused only a 32.3% increase in fluorescence over the E-1 state. Neither AMP nor TTP with or without Mg2+ or Na+ or Pi added without Mg2+ had any effect on the Dn fluorescence. If the enzyme was denatured, no fluorescence changes were observed. Small changes in the polarization of fluorescence of the Dn moiety were observed under all the conditions used. These small polarization changes and the large increases in the fluorescence intensity suggest that the enzyme can change conformational states in the presence of appropriate ligands and these conformational changes may take place in a relatively limited region of the protein's structure.

Adenosine Triphosphatases↗
PubMed1977

Interactions between fluorescent labeled phosphatidyl serine and cations.

Phosphatidyl serine (PS) was reacted with dimethylaminoanphthalenesulfonyl (DNS) chloride to produce a fluorescent phospholipid derivative (DNS--PS). By comparison of the emission maximum of the fluorochrome in solvents of varying dielectric constants and in aqueous suspension it was concluded that the DNS moiety of sonicated DNS--PS micells was within the glycerol region of the lipid. Addition of CaC12 to aqueous suspensions of DNS--PS micells caused a shift in the emission maximum from 524 nm to 490 nm, a two-fold increase in the relative fluorescence and an increase in the polarization of fluorescence and finally aggregation. MgC12 produced similar but smaller changes in the fluorescence parameters. In the presence of calcium the thermal transition of the fatty acid tail region could be monitored as an increase in the fluorescence intensity of the DNS group. Without calcium an almost linear decrease in relative fluorescence was observed. These data suggested that calcium caused the fluorochrome to be shifted from the glycerol region of the lipid structure into the fatty acid tail region. These observations indicate how the conformation of a biological membrane might be altered by the interaction between acidic phospholipids and calcium.

Binding Sites↗
PubMed1977

Occlusal migration of a filled root: report of case.

A mandibular premolar was treated by root canal therapy. The root migrated 11 mm in an occlusal direction beneath the anterior retainer of a fixed partial denture during eight years after treatment. Caries occurred at the junction of the root and the anterior retainer; and, as caries continued, the root apparently migrated to compensate for the lost tooth structure.

Bicuspid↗