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R A Reed

Publications and source records attributed to R A Reed.

36 records · Page 2Linked to original sources
PubMed1990

Crystallization and preliminary x-ray diffraction study of synthetic apolipoprotein E fragment (residues 129-169).

Apolipoprotein E is a plasma protein comprised of a lipid binding region (which together with other apoproteins maintains the structure of lipoprotein particles) and a receptor binding domain (which interacts with cellular receptors for control of triglyceride and cholesterol metabolism). A peptide, comprising residues 129-169 of human apolipoprotein E, which contains both a putative lipid-binding region and receptor binding domain, has been synthesized by solid phase techniques. Diffraction quality crystals of the synthetic apolipoprotein E fragment129-169 have been obtained at room temperature by vapor diffusion with polyethylene glycol in the presence of the nonionic detergent beta-octylglucoside. The crystals have been characterized with x-radiation as orthorhombic, space group I222 or I2(1)2(1)2(1), with unit cell dimensions a = 61.91, b = 30.84, and c = 42.79 A. There are eight molecules per unit cell, with one molecule (Mr = 4771) in each asymmetric unit. Precession photographs show that crystals diffract beyond 2.7-A resolution and are stable in the x-ray beam at room temperature for at least 200 h; thus, they can be used to collect three-dimensional data for a detailed crystallographic analysis.

Apolipoproteins E↗
PubMed1989

Effect of chain unsaturation on the structure and thermotropic properties of galactocerebrosides.

Differential scanning calorimetry (DSC) and x-ray diffraction have been used to study the effect of increasing chain-unsaturation on the structure and properties of the hydrated cerebrosides N-stearoyl, -oleoyl, and -linoleoyl galactosylsphingosine (NSGS, NOGS, and NLnGS, respectively). DSC of hydrated (70 wt% water) NSGS shows an endothermic transition at 85 degrees C (delta H = 18.0 kcal/mol NSGS) and a broad exothermic transition at 40-60 degrees C, the latter being dependent upon the previous cooling rate. X-Ray diffraction patterns recorded at 21, 61, and 86 degrees C provide evidence for interconversions between metastable and stable crystalline NSGS bilayer phases. The properties of the unsaturated-chain cerebrosides are more complex. Hydrated NOGS shows a single endothermic transition at 44.8 degrees C (delta H = 11.5 kcal/mol NOGS). However, incubation of NOGS at 49 degrees C for 24 h results in a second transition at 55.5 degrees C. By cycling NOGS between 0 and 49 degrees C complete conversion into this higher melting phase (delta H = 12.1 kcal/mol NOGS) is achieved. X-ray diffraction confirms a bilayer phase at all temperatures and delineates the conversions between a crystalline phase at 21 degrees C (bilayer period d = 56.5A), a second crystalline phase at 47 degrees C (d = 69.9A), and a liquid crystalline phase at 59 degrees C (d = 52.0A). The more unsaturated NLnGS shows two transitions, a sharp transition at 28 degrees C (delta H = 8.0 kcal/mol NLGS) and a broad, low-enthalpy transition at 42 degrees C (delta H = 0.4 kcal/mol NLGS). Again, incubation between the two transitions leads to a single transition at 44 degrees C (delta H = 9.3 kcal/mol NLGS). X-ray diffraction demonstrates conversions between two crystalline bilayer phases (d = 55.2A and d = 68.4A), and a liquid crystalline bilayer phase (d = 51.8A). Thus, increased unsaturation in the amide-linked fatty acyl chain of cerebrosides results in decreased chain-melting temperatures (NSGS greater than NOGS greater than NLnGS) and has marked effects on their structural properties.

Calorimetry, Differential Scanning↗
PubMed1988

Crystallization and preliminary x-ray diffraction study of cholera toxin B-subunit.

Cholera toxin binds to its ganglioside GM1 receptor via its B-subunit, a pentameric assembly of identical subunits (Mr = 11,600). Diffraction quality crystals of cholera toxin B-subunit have been obtained at room temperature by vapor diffusion with polyethylene glycol in the presence of the nonionic detergent beta-octyl glucoside. The crystals have been characterized with x-radiation as monoclinic, space group P21, with unit cell dimensions a = 39.0 A, b = 94.3 A, c = 67.5 A, beta = 96.0 degrees. There are two molecules per unit cell, with one molecule (Mr = 58,000) in each asymmetric unit. Precession photographs (micron = 13 degrees) show that crystals diffract beyond 3.3-A resolution and are stable in the x-ray beam at room temperature for at least 40 h; thus, they can be used to collect three-dimensional crystallographic data.

Cholera Toxin↗
PubMed1987

Interaction of cholera toxin with ganglioside GM1 receptors in supported lipid monolayers.

Lipid monolayers formed at the air-water interface containing the ganglioside GM1 in egg yolk phosphatidylcholine have been transferred according to the Langmuir-Blodgett technique to glass cover slips coated with octadecyl- or hexadecyltrichlorosilane and carbon-coated electron microscope grids. Monolayer transfer has been demonstrated with fluorescence microscopy, by the transfer of a fluorescent phospholipid analogue, N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylethanolamine or Lucifer yellow labeled GM1 (LY-GM1), incorporated into the lipid monolayer. Incubation of supported monolayers with solutions of fluorescein-labeled cholera toxin (FITC cholera toxin) resulted in specific binding of the toxin to monolayers containing GM1, as revealed by fluorescence microscopy. Lateral diffusion coefficients were measured for both the receptor (LY-GM1) [(3.9 +/- 2.1) X 10(-8) cm2/s] and the receptor-ligand complex (GM1-FITC cholera toxin) [(8.9 +/- 3.2) X 10(-9) cm2/s] according to the technique of fluorescence recovery after photobleaching. In separate studies, GM1-containing monolayers transferred to electron microscope grids were incubated with solutions containing unlabeled cholera toxin, followed by negative staining with uranyl acetate. Electron microscopy revealed patches of stained cholera toxin molecules (diameter approximately 70 A) in crystalline, two-dimensional hexagonal arrays. Optical diffraction and image reconstruction showed the arrangement of the cholera toxin molecules in a planar hexagonal cell, a = 81 A. These initial reconstructions give structural information to a resolution of approximately 30 A and indicate a doughnut-shaped molecule with a central aqueous channel.

Animals↗
PubMed1987

Structure and metastability of N-lignocerylgalactosylsphingosine (cerebroside) bilayers.

Differential scanning calorimetry (DSC) and X-ray diffraction have been used to study hydrated N-lignocerylgalactosylsphingosine (NLGS) bilayers. DSC of fully hydrated NLGS shows an endothermic transition at 69-70 degrees C, immediately followed by an exothermic transition at 72-73 degrees C; further heating shows a high-temperature (Tc = 82 degrees C), high-enthalpy (delta H = 15.3 kcal/mol NLGS) transition. Heating to 75 degrees C, cooling to 20 degrees C and subsequent reheating shows no transitions at 69-73 degrees C; only the high-temperature (82 degrees C), high-enthalpy (15.3 kcal/mol) transition. Two exothermic transitions are observed on cooling; for the upper transition its temperature (about 65 degrees C) and enthalpy (about 6 kcal/mol NLGS) are essentially independent of cooling rate, whereas the lower transition exhibits marked changes in both temperature (30----60 degrees C) and enthalpy (2.2----9.5 kcal/mol NLGS) as the cooling rate decreases from 40 to 0.625 Cdeg/min. On reheating, the enthalpy of the 69-70 degrees C transition is dependent on the previous cooling rate. The DSC data provide clear evidence of conversions between metastable and stable forms. X-ray diffraction data recorded at 26, 75 and 93 degrees C show clearly that NLGS bilayer phases are present at all temperatures. The X-ray diffraction pattern at 75 degrees C shows a bilayer periodicity d = 65.4 A, and a number of sharp reflections in the wide-angle region indicative of a crystalline chain packing mode. This stable bilayer form converts to a liquid-crystal bilayer phase; at 93 degrees C, the bilayer periodicity d = 59.1 A, and a diffuse reflection at 1/4.6 A-1 is observed. The diffraction pattern at 22 degrees C represents a combination of the stable and metastable low-temperature bilayer forms. NLGS exhibits a complex pattern of thermotropic changes related to conversions between metastable (gel), stable (crystalline) and liquid-crystalline bilayer phases. The structure and thermotropic properties of NLGS are compared with those of hydrated N-palmitoylgalactosylsphingosine reported previously (Ruocco, M.J., Atkinson, D., Small, D.M., Skarjune, R.P., Oldfield, E. and Shipley, G.G. (1981) Biochemistry 20, 5957-5966).

Calorimetry, Differential Scanning↗
PubMed1981

Multiple systems organ failure: III Contrasts in plasma amino acid profiles in septic trauma patients who subsequently survive and do not survive-effects of intravenous amino acids.

The response of the plasma substrate and hormone profile of survivor and nonsurvivor septic trauma patients to varying rates of amino acid infusion (IVAA) were contrasted. When IVAA=0 levels of most plasma amino acids (except aspartate, tryptophan, cysteine, and proline) were lower in nonsurvivors. At IVAA=1 to 100, however, 11 of 20 plasma amino acids were significantly (p less than or equal to 0.05) higher in nonsurvivors: only glutamate was significantly lower (p less than or equal to 0.001) and valine, isoleucine, and arginine on average lower. At IVAA less than or equal to 101 to 200, only alanine, methionine, tyrosine, and phenylalanine were significantly (p less than or equal to 0.005) higher in nonsurvivors; isoleucine was significantly (p less than or equal to 0.02) lower. The sharp increase in methionine and decrease in tryptophan in nonsurvivors with IVAA was particularly marked. Polynomial regression analysis showed that urea increased significantly with IVAA in both patient groups, while free fatty acids and cortisol decreased only in nonsurvivors. Insulin increased with IVAA only in survivors, glucagon only in nonsurvivors. Triglycerides, glycerol, acetoacetate, beta OH butyrate, and glucose appeared to show no significant response to IVAA in either patient group. The data are consistent with increased peripheral protein catabolism and branched-chain amino acid oxidation in association with decreased tissue uptake of conventional energetic fuels. These results may be interpreted to be consistent with an impairment of mitochondrial translocase systems.

Adolescent↗
PubMedDate not supplied

The use of inferior vena cava filters in pediatric patients for pulmonary embolus prophylaxis.

PURPOSE: To report our experience with inferior vena cava (IVC) filters in pediatric patients. METHODS: Over a 19-month period, eight low-profile percutaneously introducible IVC filters were placed in four male and four female patients aged 6-16 years (mean 11 years). Indications were contraindication to heparin in six patients, anticoagulation failure in one, and idiopathic infrarenal IVC thrombosis in one. Six of the eight devices placed were titanium Greenfield filters. One LGM and one Bird's Nest filter were also placed. Two of the filters were introduced via the right internal jugular vein by cutdown, and the remainder were placed percutaneously via the right internal jugular vein or the right common femoral vein. Patients received follow-up abdominal radiographs from 2 to 13 months after IVC filter placement. RESULTS: All filters were inserted successfully without complication. Three of the patients died during the follow-up period: two due to underlying brain tumors at 2 and 12 months and a third at 6 weeks due to progressive idiopathic renal vein and IVC thrombosis. The remaining five patients were all alive and well at follow-up without evidence of IVC thrombosis, pulmonary emboli, or filter migration. CONCLUSION: IVC filter placement using available devices for percutaneous delivery is technically feasible, safe, and effective in children.

Adolescent↗
PubMedDate not supplied

In vitro flow phantom analysis and clot-capturing ability of incompletely opened Vena Tech-LGM vena caval filters.

It has been shown recently that Vena Tech-LGM (B. Braun Vena Tech, Evanston, IL) filters inserted into the inferior vena cava via the jugular route may be deployed sometimes in an incompletely opened (IO) position. The flow characteristics and clot capturing ability of IO Vena Tech-LGM filters are not clearly understood. Using a vena cava flow phantom, the clot-capturing abilities of the IO and opened Vena Tech-LGM filters were assessed. For 5 x 5-mm clots, the IO Vena Tech-LGM filter captured only 40% of thrombi compared with a 90% capture rate for the opened filter. The capture rates were 90 and 100% for the IO and opened filter, respectively, for larger 5 x 15-mm clots. It was found that the IO filter could capture 2-7 x 25 mm thrombi prior to the development of a turbulent bypass channel which prevented subsequent clot capture. Using 5 x 15 mm clots, this same phenomenon occurred with the capture of 6 and 11 thrombi by the IO and opened Vena Tech-LGM filters, respectively. Our results suggest a significantly reduced filtering efficiency for the IO Vena Tech-LGM device. However, there is a high rate of clot capture with the opened Vena Tech-LGM filter.

Efficiency↗
PubMedDate not supplied

Microcatheter embolization of non-neurologic traumatic vascular lesions.

PURPOSE: The authors report their experience over a 28-month period with embolization of 23 non-neurologic traumatic vascular lesions in 21 patients with use of a coaxial microcatheter coil delivery system. PATIENTS AND METHODS: The injuries included pseudoaneurysms (n = 17), arteriovenous fistulas (n = 3), and sites of extravasation (n = 3) and were caused by gunshot, shotgun, and stab wounds, as well as motor vehicle accidents and iatrogenic trauma. All microcatheter embolizations except one were performed with 2.2-F Tracker-18 catheters inserted coaxially through 5.0-5.5-F guiding catheters. In one case, a coaxial 3-F Teflon catheter was used. In all cases platinum microcoils (almost all non-fibril) and/or straight platinum embolization wires (with fibrils) were used. RESULTS: Twenty-one (91%) of 23 vascular lesions were successfully occluded with use of the microcatheter system. The two cases in which microcatheter embolization failed were successfully managed by using larger catheters and steel coils. Two patients with hepatic vascular lesions (one site of extravasation and a pseudoaneurysm) and one patient with a lower extremity arteriovenous fistula required two procedures each for successful treatment. Procedures were life-saving in at least two patients. Two lesions recurred during follow-up ranging from 3 days to 17 months. Both of these recurrences were successfully treated with transcatheter embolization, in one case with use of microcatheters. CONCLUSION: Microcatheter embolization with platinum coils and wires is an effective means for treating traumatic vascular lesions. A coaxial microcatheter system allows for easier, more rapid coil/wire delivery to smaller, spasm-prone arteries in such cases.

Adult↗
PubMedDate not supplied

Prevalence of infection following hepatic chemoembolization with cross-linked collagen with administration of prophylactic antibiotics.

PURPOSE: The authors present their experience with 494 hepatic chemoembolization (HCE) procedures in 236 patients with administration of a mixture of cross-linked collagen and chemotherapeutic agents. The prevalence of infectious complications was compared in patients who did and did not receive prophylactic administration of antibiotics as part of the HCE procedure. PATIENTS AND METHODS: Fourteen HCE procedures in nine patients were performed without prophylactic antibiotics (PA). These patients underwent embolization with cross-linked collagen alone or with low-dose cisplatinum. All of the remaining 480 procedures in 227 patients were performed with PA. RESULTS: One of the nine patients (11%) who did not receive PA experienced fatal sepsis within 24 hours of HCE. Of the 227 patients who did receive antibiotics, six (2.6%) developed hepatic abscess and no fatal sepsis was encountered. CONCLUSION: Use of PA decreases the prevalence of infectious complications following HCE.

Adult↗