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Biomedical subjects

H M Burt

Publications and source records attributed to H M Burt.

51 records · Page 3Linked to original sources
PubMed1991

High-performance liquid chromatographic analysis of oxytetracycline in chinook salmon following administration of medicated feed.

A high-performance liquid chromatographic assay was developed to detect oxytetracycline (OTC) in chinook salmon muscle tissue. A solid-phase extraction protocol was used to recover OTC and the internal standard, epitetracycline hydrochloride, from the salmon tissue samples. OTC was analyzed using a mobile phase of methanol-0.02 M phosphate buffer, pH 2.25 (60:190), an ultraviolet detection wavelength of 365 nm and 250 mm x 4.6 mm I.D. Ultrasphere ODS column. A linear calibration curve (r2 = 0.999) of OTC in salmon muscle tissue from 0.05 to 3.0 ppm was obtained. Using a signal-to-noise ratio of 5:1, the OTC detection limit was 0.5 ppm in salmon muscle tissue. OTC recovery (74.4%) and intra-assay variability (2.3%) were optimized for salmon muscle tissue. An in vivo feeding study was performed by administrating OTC-medicated feed for a period of 10 days, followed by a 42-day sampling period. The half-life for the elimination of OTC in chinook salmon muscle tissue was found to be 5.4 days.

Animal Feed↗
PubMed1991

Crystal-induced inflammation: studies of the mechanism of crystal-membrane interactions.

Studies of the interactions of monosodium urate monohydrate (MSUM) crystals and calcium pyrophosphate dihydrate triclinic (CPPD) crystals with biomembranes have been reviewed. Crystal-membrane binding and crystal-induced membranolysis have been studied using human erythrocytes as a model membrane system. The extent of MSUM-membrane binding was determined by incorporating a hydrophobic, fluorescent probe into the membranes, centrifugation to separate free membranes from membranes with bound crystals and quantitation of free membranes by measuring the total fluorescence intensity. The ability of MSUM and CPPD to hemolyse red cells was used as a measure of the membranolytic potential of the crystals. Fluorescence polarization studies showed that MSUM-membrane binding resulted in fluidization of the membrane. Cross-linking of the membrane proteins of the erythrocyte or the presence of divalent cations in the incubation medium inhibited MSUM induced hemolysis. These findings were explained by hypothesizing a "pore" model mechanism for MSUM induced membranolysis as follows. Binding of crystals to membranes induces the redistribution of transmembrane proteins into clusters or aggregates leading to "pore" formation. The "pores" permit the leakage of low molecular weight soluble compounds and ions acoss the membrane which is followed by osmotic rupture of the membrane.

Arthritis↗
PubMed1990

High-performance liquid chromatographic analysis of Romet-30 in salmon following administration of medicated feed.

A sensitive and selective high-performance liquid chromatographic assay was developed for the simultaneous quantitation of sulphadimethoxine (SDM) and ormetoprim (OMP) in chinook salmon muscle tissue. SDM and OMP were extracted from tissue samples using a solid-phase extraction technique. Resolution of both drugs was accomplished using an Ultrasphere ion-pair column (250 x 4.6 mm I.D.) and a mobile phase of acetonitrile-methanol-0.1 M phosphate buffer, pH 4 (17:10:73) with ultraviolet detection at 280 nm. The calibration curve in salmon muscle tissue was linear over the concentration range 0.2-20 ppm for both SDM (r2 = 0.9974) and OMP (r2 = 0.9956). The minimum detectable quantity of SDM and OMP in salmon muscle tissue was 0.2 ppm at a signal-to-noise ratio of 5:1. An in vivo feeding experiment was undertaken where chinook salmon were administered Romet-30-medicated feed for a 10-day period, followed by a 42-day wash-out period. The rate of tissue uptake and decline of SDM and OMP was shown to differ.

Administration, Oral↗
PubMed1990

Role of membrane proteins in monosodium urate crystal-membrane interactions. I. Effect of pretreatment of erythrocyte membranes with glutaraldehyde and neuraminidase.

Intact human erythrocytes were pretreated with glutaraldehyde, neuraminidase or a combination of both treatments, incubated with monosodium urate monohydrate (MSUM) crystals and the percent hemolysis values determined by measuring hemoglobin release from the cells. The binding of MSUM crystals to pretreated erythrocyte membranes was also quantitated. Neuraminidase treated cells gave higher percent hemolysis values than untreated cells due primarily to the increased binding of MSUM to neuraminidase treated erythrocyte membranes. Pretreatment of red cells with glutaraldehyde up to a maximum concentration of 0.015% inhibited MSUM induced hemolysis but the binding of MSUM to glutaraldehyde treated and untreated cell membranes was the same. We propose a "pore" model for MSUM induced hemolysis.

Cross-Linking Reagents↗
PubMed1990

Role of membrane proteins in monosodium urate crystal-membrane interactions. II. Effect of pretreatments of erythrocyte membranes with membrane permeable and impermeable protein crosslinking agents.

Intact, human erythrocytes were pretreated with membrane permeable, dimethyl adipimidate (DMA) and dimethyl suberimidate (DMS) and membrane impermeable 3,3' dithiobis (sulfosuccinimidylpropionate) (DTSSP) protein crosslinking agents and incubated with monosodium urate monohydrate (MSUM) crystals. The percent inhibition of lysis values for pretreated cells relative to untreated cells were determined. All 3 agents caused a concentration dependent inhibition of MSUM induced hemolysis that was not due to a decrease in MSUM binding to the pretreated membranes. It was proposed that the inhibition of lysis was due to crosslinking of integral and cytoskeletal membrane proteins, resulting in a reduced mobility of the proteins, inhibition of lateralization of integral proteins into aggregates and decreased "pore" formation in the membrane.

Cell Membrane Permeability↗
PubMed1989

Calcium pyrophosphate and monosodium urate crystal interactions with neutrophils: effect of crystal size and lipoprotein binding to crystals.

"Small" (between 75-98% of crystals less than or equal to 10 microns) and "large" (between 81-93% of crystals greater than 10 microns) size fractions of monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate triclinic (CPPD) crystals were incubated with human neutrophils and crystal induced neutrophil cytolysis monitored by measuring the release of lactate dehydrogenase. "Small" size fractions of MSUM and CPPD gave higher percent lysis values than "large" crystals. The binding of high density lipoproteins (HDL) and low density lipoproteins (LDL) to the crystals was quantitated. HDL and LDL bound in significant amounts to both CPPD and MSUM and strongly inhibited CPPD and MSUM induced neutrophil cytolysis. We propose that HDL and LDL bound to MSUM and CPPD may play important roles in the regulation of gouty inflammation.

Apolipoproteins↗
PubMed1988

Monosodium urate monohydrate crystal induced changes in membrane fluidity: a fluorescence polarization study.

The hydrophobic fluorophore 1,6-diphenyl-1,3,5-hexatriene was incorporated into erythrocyte ghosts. After incubation of the labelled ghost membranes with monosodium urate monohydrate (MSUM) crystals, low speed centrifugation was used to separate ghosts bound to MSUM from "free" ghosts. The fluorescence anisotropy of ghosts with bound crystals was significantly lower than for free ghosts, indicative of an increased membrane fluidity. Possible mechanisms for the fluidization of ghosts membranes after MSUM binding and the relationship of this to cellular membranolysis are discussed.

Crystallization↗
PubMed1987

Ion-exchange resins as potential phosphate-binding agents for renal failure patients: effect of the physicochemical properties of resins on phosphate and bile salt binding.

The effect of resin type, degree of cross-linking, bead size, and surface area on the phosphate and bile salt binding characteristics of five strongly basic Dowex anion-exchange resins in the chloride form was studied. The maximum uptake of phosphate (expressed as uptake of phosphorus) from sodium phosphate solutions was 137, 82, 86, 138, and 76 mg of phosphorus per gram of dry Dowex resins XF 43311, XY 40013, XF 43254, XY 40011, and XY 40012, respectively. The presence of simulated gastric or intestinal fluids resulted in small but insignificant alterations in phosphorus uptake by the resins. The resins all bound similar amounts of phosphorus and taurocholate (80-100% of the total phosphorus and taurocholate in solution) at physiological concentrations of phosphate and bile salt. Dowex resins XY 40013 and XF 43254, with identical physicochemical properties, but different bead sizes and surface areas, bound similar amounts of the bile salt sodium taurocholate at all taurocholate concentrations, indicating that binding was not restricted to the surface sites on the resin bead. The 2% cross-linked resins bound 3-4 times more taurocholate than the 8% cross-linked resins (at high taurocholate concentrations); the smaller pore size of the latter resins probably presents a greater mechanical exclusion barrier than the larger pore size of the 2% cross-linked resins.

Anions↗
PubMed1987

Characterization and membranolytic effects of triclinic calcium pyrophosphate dihydrate crystals.

The effects of incubation time and buffers of differing phosphate concentration on the ability of well characterized, synthetic triclinic calcium pyrophosphate dihydrate (CPPD) crystals to cause hemolysis of erythrocytes were determined. Maximum hemolysis was attained between 8-11 h; the percent hemolysis was 79% at a high crystal concentration of 50 mg/ml. The percent hemolysis values decreased with increasing phosphate concentration, which may have been due to adsorbed phosphate ions partially masking or protecting the erythrocyte membrane from a binding interaction with CPPD crystals. CPPD crystals possessed a significant negative surface potential, and we postulate that the CPPD crystal-membrane interaction may be mediated via an electrostatic mechanism.

Calcium Pyrophosphate↗
PubMed1986

Growth of monosodium urate monohydrate crystals: effect of cartilage and synovial fluid components on in vitro growth rates.

The effects of cartilage and synovial fluid components such as proteoglycans, chondroitin sulphate, hyaluronic acid, phospholipids, and albumin on the growth kinetics of monosodium urate monohydrate (MSUM) crystals were investigated. MSUM seed crystals were added to supersaturated sodium urate solutions, and the rate of decrease in the concentration of growth medium was used as a measure of the growth rate. A second order dependence of growth rate on supersaturation was found, and growth rate constants were determined with an integrated form of the growth equation. The additives, hyaluronic acid, proteoglycan monomer and aggregate, and phosphatidylserine, had no significant effect on the growth rate constant. Chondroitin sulphate and phosphatidylcholine increased the growth rate constant, possibly by promoting further nucleation in the growth medium. Albumin significantly inhibited MSUM crystallisation. The possible implications of these findings on in vivo MSUM crystallisation are discussed.

Albumins↗
PubMed1986

A spin label study of the membranolytic effects of crystalline monosodium urate monohydrate.

The nature of the membranolytic interaction between monosodium urate monohydrate (MSUM) crystals and phospholipid membranes was studied using electron spin resonance. Two spin probe molecules were incorporated into intact human erythrocytes and incubated with MSUM crystals. The apparent increased fluidity of 5-doxyl stearic acid incorporated erythrocytes after a 2 h incubation with MSUM was probably due to an electrostatically induced redistribution of probe from the outer more rigid layer to the fluid inner leaflet via a flip-flop mechanism. It was suggested that the MSUM induced redistribution of cationic amphiphilic probe population in the whole erythrocyte was also due to an electrostatic interaction between negatively charged MSUM crystals and positively charged probe. Possible mechanisms of MSUM induced membranolysis are discussed.

Crystallization↗
PubMed1986

Membranolytic effects of monosodium urate monohydrate: influence of grinding.

The effect of grinding on the membranolytic interaction between monosodium urate monohydrate (MSUM) crystals and intact erythrocyte membranes was studied. Crystals were ground for between 1-72 h, and percent hemolysis and zeta potentials determined. A cationic amphiphilic probe (CAT12) was incorporated into the erythrocyte membrane and incubated with MSUM. Increasing grinding times caused a decrease in both the crystallinity and zeta potential of the samples, a decrease in percent hemolysis values and a change in the distribution of free and bound spin label populations. The probe redistribution is thought to be due to an electrostatic interaction between negatively charged MSUM and the CAT12 probe.

Crystallization↗
PubMed1983

Membranolytic effects of crystalline monosodium urate monohydrate.

We studied the effect of heat treatment and subsequent rehydration of heated monosodium urate monohydrate (MSUM) crystals on the physicochemical characteristics and ability of the crystals to cause hemolysis of erythrocytes (measure of membranolytic potential). MSUM crystals dehydrated slowly on heating at 200 degrees from 1-5 h and rehydration to 100% monohydrate was complete within 30 min. Heating at 250 degrees for 2 h caused rapid dehydration to anhydrous MSU and rehydration was incomplete up to 17 h. Zeta potential and percent hemolysis of MSUM crystals decreased after heating and rehydration. This reduction in percent hemolysis may be due to the reduction in surface potential (measured as zeta potential) of the crystals.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

In vitro studies using ion exchange resins as potential phosphate binders for renal failure patients.

The uptake of phosphate [expressed as phosphorus (P)] by the anion exchange resins, Dowex 1-X8, Dowex SBR, and Bio-Rex 5, aluminum hydroxide, and sucralfate tablets was evaluated. The maximum uptake capacities (in mg P per gram of "wet" resin or solid) were 56, 49, and 84 mg for Dowex SBR, Dowex 1-X8, and Bio-Rex 5 resins, respectively, and 164-168 mg for aluminum hydroxide and sucralfate. At a concentration of P considered to approximate that encountered in the stomach (0.3 mg/ml), Bio-Rex 5 resin, aluminum hydroxide, and sucralfate bound similar amounts of P. Physiologic concentrations of bicarbonate or chloride and simulated gastric or intestinal fluids caused small changes in P uptake by Bio-Rex 5 resin. The resins bound large quantities of taurocholic (TA) and glycocholic (GA) acids. However, when Bio-Rex 5 was converted to the taurocholate form, it bound the same amount of P as the original chloride-form resin, and the binding of TA was prevented.

Aluminum↗