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Biomedical subjects

E J Murphy

Publications and source records attributed to E J Murphy.

68 records · Page 4Linked to original sources
PubMed1990

Purification of plasmalogens using Rhizopus delemar lipase and Naja naja naja phospholipase A2.

Bovine heart ChoGpl (choline glycerophospholipid) and bovine brain EtnGpl (ethanolamine glycerophospholipid) contain diacyl, alkenylacyl and alkylacyl analogs. Purification of plasmalogens was achieved using R. delemar lipase and N. naja naja phospholipase A2 digestion. The R. delemar lipase hydrolyzes the acyl bond at the 1-position of 1,2-diacyl glycerophospholipids. The N. naja naja phospholipase A2 has greater activity with diacyl and alkylacyl than with alkenylacyl glycerophospholipids. These enzymes were mainly used to remove diacyl and alkylacyl analogs respectively. When the diacyl types were removed by double incubation with R. delemar lipase, the plasmalogen content was 94.2% +/- 0.21% (mean +/- S.E.M., n = 4) for PlsCho (plasmenylcholine) and 94.9% +/- 0.19% (mean +/- S.E.M., n = 3) for PlsEtn (plasmenylethanolamine). Recoveries were 74% and 88% respectively. These partially purified plasmalogens were treated with N. naja naja phospholipase A2. Finally, 97.7% +/- 0.24% (mean +/- S.E.M., n = 4) and 98.8% +/- 0.27% (mean +/- S.E.M., n = 3) pure plasmalogens were obtained for PlsCho and PlsEtn respectively. Plasmalogens were recovered in an overall yield of 7.7% +/- 0.7% (mean +/- S.E.M., n = 4) and 10.2% +/- 1.2% (mean +/- S.E.M., n = 3) for PlsCho and PlsEtn.

Animals↗
PubMed1989

Solubilization, purification and characterization of lysoplasmalogen alkenylhydrolase (lysoplasmalogenase) from rat liver microsomes.

Alkenylhydrolase (EC 3.3.2.2; EC 3.3.2.5) has been purified 200-fold to a specific activity of 8.0 mumol/min per mg from rat liver microsomes with 51% of the activity recovered. Purification was accomplished by solubilization of the membrane-associated enzyme with octylglucoside and chromatographic resolution on sequential DEAE cellulose and hydroxylapatite (HPLC) columns in the presence of octylglucoside. The partially purified enzyme, specific for the 2-deacylated plasmalogen, lysoplasmalogen (1-alk-1'-enyl-sn-glycero-3-phosphocholine or -ethanolamine), had no hydrolytic activity with intact plasmalogens or 1-acyl-sn-glycero-3-phosphoethanolamine. Kinetic analyses of enzymic activity demonstrated apparent Km values of 5.5 and 42 microM for 1-alk-1'-enyl-sn-glycero-3-phosphocholine and 1-alk-1'-enyl-sn-glycero-3-phosphoethanolamine, respectively. The Vmax values were 11.7 and 13.6 mumol/min per mg with the choline and ethanolamine substrates, respectively. The optimal pH range was between 6.6 and 7.1 with both substrates; the energy of activation for the purified enzyme was 15,200 cal. The enzyme required no cofactors and was unaffected by low millimolar concentrations of Ca2+, Mg2+, Mn2+ or EDTA. It was inhibited by the sulfhydryl-reacting reagent, p-chloromercuribenzoate. Mono- or diradylglycerophospholipids or sphingomyelin did not affect the enzymic activity at 37 degrees C. Activity of the purified enzyme, destroyed by freezing at -20 degrees C, was preserved if stored at this temperature in the presence of 300-600 microM diradylglycerophosphocholine or 50% glycerol. A continuous spectrophotometric assay, adapted in our laboratory for the assay of liver alkenylhydrolase, facilitated this purification. This is the first reported purification of alkenylhydrolase.

Animals↗
PubMed1989

Phospholipid bilayer contribution to 31P NMR spectra in vivo.

The magnetic field-dependent phosphodiester (PDE) signal found in 31P NMR spectra of liver and brain has been studied using saturation transfer and proton decoupling techniques. This PDE component, which accounts for as much as 45% of the signal in vivo, has been identified as primarily phospholipid bilayer with a small contribution from a motionally averaged macromolecule(s).

Animals↗
PubMed1988

Preliminary results on phosphorus-31 nuclear magnetic resonance evaluation of human uveal melanoma in enucleated eyes.

Clinical evaluation of uveal melanomas by nuclear magnetic resonance (NMR) techniques depends on ascertaining how these tumors characteristically appear in NMR images and spectra. The authors have determined NMR characteristics of suspected uveal melanomas by phosphorus-31 (31P) NMR spectroscopy of freshly enucleated human eyes. Nuclear magnetic resonance examination was performed at 8.45 Tesla within 90 minutes after enucleation. Enucleated eyes were maintained at 4 degrees C in tissue culture medium during the 30 minutes required for transport. Nuclear magnetic resonance spectra were obtained within 10 minutes, a clinically acceptable time, using a two-turn 31P surface coil. Spectral parameters included 10-kHz spectral width, 1024 data points, and 0.5-second recycle delay. Phosphorus-31 NMR spectroscopy allowed differentiation of choroidal melanomas from normal ocular structures. Differentiating features include significant peaks in tumor spectra due to the phosphodiesters glycerol 3-phosphoryl ethanolamine (GPE) and glycerol 3-phosphorylcholine (GPC), and the phosphomonoesters phosphorylethanolamine (PE) and phosphorylcholine (PC). These preliminary data are encouraging and suggest that clinical trials at the lower magnetic field strengths available in NMR imaging systems seem feasible and warrant investigation.

Choroid Neoplasms↗
PubMed1987

Proton and sodium 23 magnetic resonance imaging of human ocular tissues. A model study.

Clinical evaluation of uveal melanomas by magnetic resonance imaging (MRI) techniques depends on developing an understanding of the appearance of these tumors in magnetic resonance (MR) images. We have determined MR characteristics of uveal melanomas by proton (1H) and sodium 23 MRI of freshly enucleated human eyes at 1.5 tesla. The MR images were obtained using two-turn proton and 23Na surface coils, designed to both transmit and receive the radiofrequency signal. Proton MRI techniques included saturation recovery and spin echo; the gradient-recalled echo technique was used for 23Na MRI. Proton and 23Na MR images provide complementary information; contrast between intraocular tumors and vitreous, lens, or subretinal hemorrhage may be varied by using MR pulse sequences that emphasize tissues based on T1, T2, proton, or sodium density values. A combination of proton and 23Na MRI provides differentiation between normal ocular structures and intraocular tumors, as well as associated complications, such as retinal detachments and subretinal hemorrhages.

Eye↗
PubMed1987

Measurement of lactate accumulation by in vivo proton NMR spectroscopy during global cerebral ischemia in rats.

In vivo 1H NMR spectral editing techniques were used to monitor cerebral lactate production during remotely controlled temporary forebrain ischemia in rats. The lactate/N-acetylaspartate (NAA) ratio correlated with survival after ischemia and subsequent reperfusion. The lactate/NAA ratio that predicted death after ischemia in rats was estimated to be approximately 1.3.

Animals↗
PubMed1979

Lung expansion, airway pressure transmission, and positive end-expiratory pressure.

Transmission of airway pressure to the intrapleural space and change in functional residual capacity by positive end-expiratory pressure (PEEP) were measured in ten anesthetized swine. Measurements and calculations were performed with varying lung and chest wall compliances. When both compliances were normal, approximately half of the applied airway pressure was transmitted. Aspiration of hydrochloric acid reduced lung compliance approximately fourfold and decreased airway pressure transmission. Increased thoracic compliance also reduced airway pressure transmission. When acid aspiration reduced lung compliance and sternotomy simultaneously increased thoracic compliance, pressure transmission was maximally reduced. Decreases in either thoracic or lung compliance reduced the volume-expanding effects of PEEP. Positive end-expiratory pressure was least effective when thoracic and lung compliances were reduced simultaneously. Careful assessment of both lung and thoracic compliances may be helpful in treating patients requiring elevated airway pressure.

Animals↗
PubMed1976

External pterygoid myotomy for recurrent mandibular dislocation. Review of the literature and report of a case.

Dislocation of the temporomandibular joint is a condition that requires immediate attention. Several conservative methods are effective in the treatment of the acute episode, but surgical treatment is indicated for chronic dislocation. Many, sometimes conflicting, procedures have been proposed for the surgical treatment of chronic dislocation. Comprehensive review and analysis of the literature reveals that this confusion is generated by a poor understanding of the etiology of chronic dislocation. External pterygoid myotomy is recommended as the surgical treatment of choice since it eliminates the forces responsible for pulling the mandible into the dislocated position. A case is presented to demonstrate the effectiveness of this procedure.

Cartilage, Articular↗
PubMedDate not supplied

Mechanisms of hypoxic and ischemic injury. Use of cell culture models.

Cell cultures are useful tools to study the mechanisms involved in cell death following hypoxia or ischemia. By manipulating the extracellular environment, conditions that closely mimic the conditions that are thought to occur in vivo can be produced. These conditions permit study of cell's reaction to the trauma under specific conditions. Monitoring of the extracellular pH and ionic environment in cell cultures is much easier than in vivo. Further, metabolites produced by injured cells can be quantitated easier from cultures than from tissues in vivo. Cell cultures have recently been used to examine in detail the neurotoxicity of glutamate. Intracellular Ca2+ increases appear to be involved in the mechanisms of neurotoxic cell death. This Ca2+ entry appears to be through the NMDA receptor's Ca2+ channel. Ischemic and hypoxic injury produced by mechanisms other than glutamate neurotoxicity appear to involve increases in intracellular Ca2+ by releasing internal Ca2+ stores or by the influx of extracellular Ca2+. This Ca2+ entry may be through voltage-gated channels of the NMDA channel, or may be attributable to membrane perturbations. Through the use of cell cultures, each of the mechanism's involvement in the injury can be delineated.

Animals↗