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Biomedical subjects

J E Jordan

Publications and source records attributed to J E Jordan.

At least 55 records · Page 3Linked to original sources
PubMed1986

Xanthine oxidase-catalyzed crosslinking of cell membrane proteins.

Isolated erythrocyte membranes exposed to protease-free xanthine oxidase plus xanthine and ferric iron undergo lipid peroxidation and protein crosslinking (appearance of high molecular weight aggregates on sodium dodecyl sulfate (SDS) gel electrophoresis). Spectrin is more susceptible to crosslinking than the other polypeptides. Thiol-reducible bonds (disulfides) as well as nonreducible bonds are generated, the former type relatively rapidly (detected within 10-20 min) and the latter type more slowly (usually detected after 1 h). Reducible crosslinking is inhibited by catalase, but not by superoxide dismutase, desferrioxamine, butylated hydroxyltoluene, and mannitol; whereas nonreducible crosslinking, like free radical lipid peroxidation, is inhibited by all of these agents except mannitol. Zinc(II) also inhibits lipid peroxidation, but stimulates disulfide bond formation to the virtual exclusion of all other crosslinking. Our results indicate that disulfide formation is dependent on H2O2, but not O2- or iron. However, O2-, H2O2, and iron are all required for lipid peroxidation and nondisulfide crosslinking, suggesting the intermediacy of OH generated via the iron-catalyzed Haber-Weiss reaction. The possible role of malonaldehyde (MDA, a by-product of lipid peroxidation) in the latter type of crosslinking was examined. Solubilized samples of xanthine/xanthine oxidase-treated membranes showed a strong visible fluorescence (emission maximum 450 nm; excitation 390 nm). This resembled the fluorescence of membranes treated with authentic MDA, which forms conjugated imine linkages between amino groups. Fluorescence scanning of SDS gels from MDA-treated membranes showed a strong signal coincident with crosslinked proteins and also one in the low molecular weight, nonprotein region, suggestive of aminolipid conjugates. Similar scanning on xanthine/xanthine oxidase-reacted membranes indicated that all fluorescence is associated with the lipid fraction. Thus, nonreducible protein crosslinks in this system do not appear to be of the MDA-derived, Schiff base type.

Catalysis↗
PubMed1985

Lipid photooxidation in erythrocyte ghosts: sensitization of the membranes toward ascorbate- and superoxide-induced peroxidation and lysis.

The damaging effects of ascorbate (AH-) and superoxide (O-2) on resealed erythrocyte ghosts containing predetermined levels of lipid hydroperoxides (LOOHs) have been studied. Continuous blue light irradiation of membranes in the presence of protoporphyrin resulted in steadily increasing LOOH levels and enhanced release of a trapped marker, glucose 6-phosphate (G6P), after a 3- to 4-h lag. Neither superoxide dismutase (SOD) nor catalase inhibited these effects, ruling out O-2 and H2O2 as reactive intermediates. A 1-h light dose produced partially photoperoxidized ghosts, which, in the dark at 37 degrees C, released G6P no faster than unirradiated controls (approximately 7%/h). When xanthine oxidase plus xanthine (XO/X) was introduced as a source of O-2 and H2O2, the irradiated membranes lysed rapidly (t1/2 approximately 2 h). EDTA or SOD inhibited the reaction, whereas catalase had little or no effect. Unirradiated ghosts were not lysed by XO/X unless the system was supplemented with Fe(III), in which case total protection was afforded by SOD or catalase. In all experiments there was an excellent correlation between postirradiation lipid peroxidation (thiobarbituric acid reactivity) and G6P release. Similar observations were made with AH-. For example, dark incubation of photooxidized ghosts in the presence of 0.5 mM AH- resulted in rapid lysis (t1/2 approximately 1 h), which was stimulated approximately twofold by 50 microM Fe(III) and was inhibited by EDTA. By comparison, unirradiated ghosts showed no net peroxidation or lysis after 3 h exposure to Fe(III)/AH-. Neither SOD nor catalase protected against AH--stimulated damage. AH--promoted lipid peroxidation was inhibited by butylated hydroxytoluene, a lipophilic antioxidant, but was unaffected by 2,5-dimethylfuran or ethanol, singlet oxygen, and hydroxyl radical traps, respectively. These results suggest that a mechanism exists by which photogenerated LOOHs undergo redox metal-mediated reduction to alkoxy radicals (LO.), which trigger a burst of membrane-disrupting lipid peroxidation.

Ascorbic Acid↗
PubMed1985

Inhibitory effect of zinc(II) on free radical lipid peroxidation in erythrocyte membranes.

New evidence in support of zinc's role as a membrane antioxidant is presented. Human erythrocyte membranes in buffered saline underwent catalase- and superoxide dismutase-inhibitable lipid peroxidation when incubated with xanthine, xanthine oxidase, and Fe(III). Free radical mediated peroxidation was measured in terms of thiobarbituric acid reactivity and iodometric determination of lipid hydroperoxides. Whereas Ca(II) had relatively little effect on lipid peroxidation, Zn(II) strongly inhibited the reaction and suppressed peroxidation-dependent lysis of resealed membranes. Inhibition of lipid peroxidation was essentially complete in the presence of 0.1 mM Zn(II), a concentration equivalent to that of added Fe(III). By contrast, Zn(II) had no effect on rose bengal-photosensitized lipid peroxidation, a predominantly nonradical, singlet oxygen-driven process. Zinc(II) also interfered with xanthine/xanthine oxidase/iron-induced peroxidation of Triton X-100-dispersed membranes, but had no effect if EDTA was present. Trivial reasons for inhibition, for example, inactivation of xanthine oxidase or complex formation with O2-, were ruled out by showing that the rate of reduction of cytochrome c by xanthine/xanthine oxidase is not affected by Zn(II). We speculate that Zn(II) acts by interfering with the redox cycling of iron, possibly by competing with the latter for membrane binding sites.

Calcium↗
PubMed1983

Effect of cimetidine on phenytoin serum levels.

Cimetidine, 300 mg p.o. four times a day, was administered for 5 days to nine epileptics who were stabilized while receiving phenytoin. Five patients had statistically significant increases in phenytoin serum levels, including two who became clinically toxic. One patient had a statistically significant decrease in phenytoin serum concentration. A relationship was not found between cimetidine levels and change in phenytoin serum levels. Cimetidine can cause significant changes in phenytoin serum levels which may be manifested clinically.

Cimetidine↗
PubMed1983

Multiple congenital defects: report of a case.

An unusual case history is presented in which a 4-year-old Oriental boy, born with multiple congenital defects primarily affecting anatomic structures in the midline, was treated by an oral surgeon, restorative dentist, and others. The defects included cleft palate, two complete and separate tongues, missing and decayed teeth, and an aortic abnormality. Treatment procedures included restoring the teeth, uniting the two tongues, lip repair, and fabrication of an obturator to close the palatal defect.

Abnormalities, Multiple↗
PubMed1982

Purification of rat liver phosphorylase kinase.

A rapid method for the purification of rat liver phosphorylase kinase 30,000-fold over homogenate values is described. The method allows the isolation of a near homogeneous preparation of phosphorylase kinase initially associated with the glycogen pellet to be accomplished within 24 h. The enzyme has Mr (apparent) = 1.3 million by gel filtration and is composed of subunits similar in size to those of skeletal muscle phosphorylase kinase. The enzyme is phosphorylated by the cAMP-dependent protein kinase: phosphate is incorporated into two of the subunits (Mr = 140,000 and Mr = 116,000) and is closely paralleled by activation of the enzyme. The enzyme is partially inhibited by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and is stimulated by 10(-8)-10(-6) M Ca2+. The pH optimum of the nonactivated enzyme is 7.0. Activation by cAMP-dependent protein kinase does not appear to alter the Ca2+ sensitivity of the enzyme. However, it results in a large increase in activity at pH 7 through 8, but not at pH below 6.5. Purified rat liver phosphorylase kinase thus shows many similarities to purified skeletal muscle phosphorylase kinase, but differs in respect to its incomplete inhibition by ethylene glycol bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid and to the effects of phosphorylation by cAMP-dependent protein kinase on its pH activity profile and Ca2+ sensitivity.

Animals↗
PubMed1981

Rat liver phosphorylase kinase. Stimulation by heparin.

Rat liver phosphorylase kinase activity was increased up to 7-fold by low concentrations of heparin, but other glycosaminoglycans were relatively ineffective. A half-maximal effect was seen with 0.5 units of heparin/ml, corresponding to 150 nM. The stimulation was rapid, i.e. occurring within 15 s, and was prevented or reversed by addition of the heparin-binding protein antithrombin III. The action of heparin was also sharply reduced by prior activation of the enzyme by MgATP. In the absence of heparin, the time course of the phosphorylase kinase reaction was concave upward, whereas in the presence of heparin, a constant rate was seen. The stimulatory effect of heparin was inversely proportional to the concentration of phosphorylase b. The data suggest that heparin reversibly stimulates a low activity form of liver phosphorylase kinase to a degree similar to that found with activation by phosphorylation.

Animals↗
PubMed1981

Analysis of the presenting features of adult acute leukemia: the French-American-British classification.

The authors have performed a clinical and statistical analysis of the presenting features of adult acute leukemia classified according to the French-American-British (FAB) hematopathologic criteria. Observations were made on 70 variables of history, physical examination, and laboratory examination recorded for 195 patients seen during a recent six year interval. The incidence of each category as determined by consensus of three observers was L1, 9%; L2, 17%; L3, 3%; M1, 21%; M2, 22%; M3, 5%; M4, 21%; M5, 4%; and M6 1%. there were recurring features of each FAB category and for aggregated categories (myeloid, lymphoid). Some groups such as L1, M3, M4, and M5 were characterized by many distinctive characteristics. In contrast, the L2, M1, and M2 categories had few distinctive characteristics, although L3 shared many features with the other lymphoid groups. The distinctness of the categories was quantitated by stepwise discriminant analysis. Using only a few computer-selected clinical variables, the authors classified patients into the correct FAB category with an accuracy of over 65% for some groups. The accuracy in discriminating between lymphoid and myeloid groups, the important therapeutic distinction, was 82%. This study demonstrates that many of the categories defined by the FAB criteria have characteristic clinical features at presentation.

Adult↗
PubMed1981

Acute chlordecone toxicity in rats: a relationship between tremor and ATPase activities.

Since we have demonstrated that ATPase system was sensitive to chlordecone, it was decided to examine the relationship between physiological and biochemical responses to this neurotoxin. Male Sprague-Dawley rats were fed with chlordecone by gastric intubation at 10, 25 and 50 mg/kg/day for three days. Control rats received 0.3 ml of corn oil. Complete body movements (including tremors) were monitored for a period of 12 hr at 24, 48 and 72 hr after treatment by a piezoelectric crystal attached to the bottom of a plastic rodent cage. The output of the crystal was recorded by a Grass model of EEG machine and magnetic tape. For biochemical study chlordecone treated rats were killed, the brain synaptosomes were prepared and Na+-K+ ATPase, oligomycin-sensitive and insensitive Mg2+ ATPases were determined. Rats receiving chlordecone showed an increased tremor activity which was significant and dose- dependent with a correlation coefficient of the regression line of 0.96. The onset of tremors was evident as early as 2 hr in 50 mg/kg dosed rats. Behavioral abnormalities include startling response to external stimuli like sound, etc. The brain synaptosomal Na+-K+ and oligomycin-sensitive Mg2+ ATPases were significantly decreased in chlordecone treated rats as compared to controls and the decrease was dose-dependent. A linear relationship was observed between the decreases in ATPase activities and physiological (tremor) activity with an r value of 0.96. These results suggest that the inhibition of ATPase system in brain may be related to the production of the neurotoxic symptoms.

Adenosine Triphosphatases↗
PubMed1980

Cortical independence of type I and II barbiturate spindles.

Two varieties of barbiturate-induced EEG spindles are recognized. Type I originates subcortically but recent data suggest that type II spindles are triggered by type I at the cortical level. This is based on a temporal relationship between the two spindle types in the gross electrocorticogram. In the present study no such relationship could be found except possibly in light anesthesia. These results fail to confirm the only data supporting a cortical mechanism underlying type II spindles.

Anesthesia↗
PubMed1980

A cineradiographic study of chin marker positioning: implications for the strain gauge transduction of jaw movement.

Three normal adult subjects were filmed using lateral-view, high-speed cineradiography to measure the amount of movement of external skin points on the jaw relative to the underlying jaw bone. Metal markers were secured to the skin to simulate cantilever beam attachment points commonly utilized in the strain gauge transduction of jaw movements. Standard deviations of chin marker movement relative to the jaw ranged from 0.52 to 1.28 mm in an anterior-posterior direction and 0.67 to 2.31 mm in a superior-inferior direction. Lower lip and chin marker positions were highly correlated in the superior-inferior direction. Chin marker positions tended to be more superior and, in one subject, more anterior for labial than for nonlabial different contexts. The degree of variability was not systematically different for the two different contexts.

Adult↗
PubMed1979

The recordings and cerebral properties of unaveraged electroretinograms in routine EEG's.

The occurrence of single unaveraged ERG activity in routine EEG's is documented in this report. The ERG activity is focal at Fp1 or Fp2 and often restricted to these electrodes. Mean values of latency and amplitude are 51.5 mSec and 31.8 uv. Significant differences with age, sex and light intensity are shown identical to those of corneally-recorded ERG's.

Adolescent↗