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Biomedical subjects

J D Stuart

Publications and source records attributed to J D Stuart.

16 recordsLinked to original sources
PubMed1992

Effects of neural transplantation on seizures in the immature genetically epilepsy-prone rat.

To study the hypothesis that neural transplantations can alter seizure susceptibility in a genetic animal model of epilepsy, 93 pubescent genetically epilepsy-prone rats with stage 9 seizures received either bilateral inferior colliculi (N = 21) or lateral ventricle (N = 42) transplants or sham transplants (N = 30). The grafts consisted of embryonic locus ceruleus, neocortical, or cerebellar tissue. Starting 2 days after the transplantation the rats were subjected to audiogenic stimulations every other day for 61 days. Latency to the running and tonic phase, seizure severity score, and duration of the tonic and clonic phase were compared in the neural transplant and sham-operated controls. Rats that received transplants had a longer latency to the tonic phase and a shorter duration of the clonic phase than the controls. At age 110 days the rats had electrodes implanted bilaterally into the angular bundle and were kindled. No difference in kindling rate was found between the rats that received neural grafts and the sham-operated controls. Cerebrospinal fluid concentration of norepinephrine was not altered by the transplants. This study demonstrates that the anticonvulsant effects of neural transplants, using the genetically epilepsy-prone model of epilepsy, are mild.

Acoustic Stimulation↗
PubMed1990

Single-donor fibrin glue for hand burns.

Early tangential excision sometimes results in considerable blood loss, prolonged operative time, and partial loss of the graft secondary to hematoma formation. Previous reports document positive hemostatic effects and improved skin fixation with fibrin "glue." The commercial preparation used in Europe, however, has not been approved by the United States Food and Drug Administration because of the high risk of hepatitis and human immunodeficiency virus transmission. Using a method developed at the University of Virginia, we applied single-donor fibrin glue as an adjunct in early excision and grafting in 16 patients (26 hands). The overall graft take was 99%. In all patients, better adherence of the split-thickness graft to the recipient bed, during and immediately after application, was noted. We have observed no negative effects with regard to infection or healing. We recommend the use of single-donor fibrin glue to reduce operative blood loss, improve survival and ease of graft application, and possibly to accelerate healing.

Adult↗
PubMed1989

Nerve compression syndromes of the lower extremity.

Nerve compression syndromes of the lower extremity present a challenge in differential diagnosis. Compression of the common peroneal nerve occurs relatively frequently; compression of the sciatic nerve occurs infrequently. The pattern of weakness helps distinguish lumbar root entrapment from peripheral compression syndromes. Compression syndromes must also be differentiated from diabetic, alcoholic or vasculitic neuropathy. Recovery correlates with the degree and duration of nerve injury. Thus, early diagnosis and treatment are important.

Diagnosis, Differential↗
PubMed1987

Improvement in the resolution of o-phthalaldehyde derivatized amino acids by applying gradient steepness optimization to five reversed-phase columns of different lengths and particle sizes.

Twenty-two o-phthalaldehyde (OPA) derivatized amino acids were separated on five different reversed-phase, octadecyl columns. Each column was packed with the same type of spherical silica on which matched bonding chemistry had been performed. Columns of 250, 150 or 50 mm x 4.5 mm I.D. were packed with 5 microns particles, and columns of 100 or 50 mm x 4.5 mm I.D. were packed with 3 microns particles. Snyder's linear solvent strength gradient optimization method was used to determine the optimum gradient steepness by maximizing the resolution of four pairs of adjacent OPA-derivatized amino acids. An asymptotic dependence of improvement in resolution with increase in gradient time was obtained for each pair of compounds on each column. For short (50 mm) columns, resolution of very closely eluting compounds required the use of gradient steepness parameters as low as 0.05 and 0.02, due to the low efficiencies intrinsic to these short column lengths.

Amino Acids↗
PubMed1987

Pediatric burns.

Burns are the second most common cause of death in childhood. More than half of pediatric burns are partial-thickness scald burns; the majority occur in the kitchen. Generally, minor burns may be treated on an outpatient basis, while moderate burns are treated in a community hospital. Children with major burns should be transferred to a regional burn unit as soon as possible after stabilization, provision of fluids and, if necessary, intubation.

Age Factors↗
PubMed1985

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. II. Retention behavior, quantitative structure-retention relationships and octanol-water partition coefficients.

The retention behavior of methoxy-substituted p-benzoquinones and the corresponding hydroquinones in reversed-phase chromatography was examined on octylsilica and two octadecylsilica stationary phases and with five hydroorganic mobile phases containing acetonitrile, methanol or tetrahydrofuran and additionally in most cases (NH3OH)3PO4 used as a reducing and buffering agent. The retention order of benzoquinones and hydroquinones was the same on each stationary phase with either methanol or acetonitrile as the organic modifier. On the other hand, minor differences in the retention order were observed with the various stationary phases. In all cases, satisfactory quantitative structure-retention relationships (QSRRs) were found and the data suggest that the differences in the retention behaviour of octadecylsilicas used in this study are silanophilic interactions which, together with solvophobic interaction contribute to the retention of these eluites. Further analysis showed that QSRRs of sterically crowded molecules must take into account reduced surface area available for binding. The retention data obtained with use of aqueous tetrahydrofuran as mobile phase failed to give rise to satisfactory QSRRs. This was attributed to selective solvation of eluite by tetrahydrofuran and/or nearly equipotent binding of eluite and tetrahydrofuran to stationary phase.

Benzoquinones↗
PubMed1984

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. I. Interplay of on-column redox reaction and the chromatographic retention process.

Chromatograms exhibiting unusual elution profiles were obtained in the reversed-phase chromatography of methoxy-substituted hydroquinones with hydro-organic mobile phases. The dependence of the elution profiles on the flow-rate and the mass of injected sample indicated that peaks were caused by the interplay of the chromatographic retention process and the concomitant oxidation of hydroquinones in the chromatographic column. The reaction was first investigated in free solution and the first-order rate constants and equilibrium constants were estimated for the oxidation of 2-methoxy-, 2,5-dimethoxy-, 2,6-dimethoxy-, 2,3,5-trimethoxy- and 2,3,5,6-tetramethoxyhydroquinones. The effect of Fe3+ and Cu2+ on the oxidation of 2,6-dimethoxyhydroquinone was also examined and it was found that Fe3+ caused a ten-fold increase in the reaction rate. The oxidation of 2-methoxy- and 2,6-dimethoxyhydroquinones in the chromatographic column showed first-order and zerothorder kinetic behavior at low and high sample loads, respectively. Such change in reaction order is typical for heterogeneous reactions that follow Langmuir-Hinshelwood kinetics and suggests the existence of catalytically active sites on the silica. Upon purging the columns with EDTA, on-column oxidation of the hydroquinones was attenuated so that no reaction zones appeared on the chromatogram. Subsequent loading of the column with Fe3+, however, gave rise to broad reaction zones and possibly to total conversion of the hydroquinones to benzoquinones in the column. In all cases investigated the rate of oxidation was much higher in the column than in free solution. On the basis of the results obtained here, heavy mental-catalyzed reaction at the stationary phase surface is proposed to be the dominant mechanism for the oxidation reaction examined here.

Benzoquinones↗
PubMed1982

HPLC analysis of underivatized fatty acids in margarines.

The composition of the underivatized fatty acids in margarines was determined by high performance liquid chromatography (HPLC). A 50-min analysis gave not only the distribution of the cis- and trans-isomers of the 18 carbon-length, but also a quantitative measure of seven of the underivatized fatty acids studied. High concentrations of the essential fatty acid, linoleic acid, were found in the four margarine samples. Results of the quantitation, reproducability of the HPLC analysis, and stability of the standards are discussed. It was found that the developed HPLC analysis was able to adequately separate the geometric isomers, linoleic acid (18:2 delta 9c, 12c) from linolelaidic acid (18:2 delta 9t, 12t). However, a mixture of the other two isomers, 18:2 delta 9c, 12t and 18:2 delta 9c, 12c coeluted together between the peaks due to the 18:2 delta 9c, 12c and 18:2 delta 9t, 12t isomers. This study did not attempt to separate the various positional isomers of underivatized fatty acids.

Chromatography, High Pressure Liquid↗
PubMed1977

Effect of antacids on absorption of clorazepate.

The effect of a magnesia and alumina antacid suspension on the absorption of clorazepate dipotassium was studied in 15 normal healthy adult subjects who ingested a 15-mg dose of clorazepate alone or with single or multiple doses of antacid. The results of this three-period randomized complete crossover study showed a trend of initially slower absorption and lower peak nordiazepam plasma levels when administered with the antacid suspension. However, there were no significant differences among treatments in the extent of absorption as measured by the area under the plasma level-time curves. Clorazepate plasma levels were of relatively short duration and similar for all treatments. The urinary excretion pattern was likewise comparable with conjugated oxazepam, the major species measured. Plasma elimination half-lives of nordiazepam and clorazepate were not affected by the antacid treatments.

Adult↗
PubMed1977

Fluorescent assay of total serum cholesterol, with use of gas-liquid chromatography to study saponification efficiency.

We describe a fluorescent determination of total cholesterol in serum for which the accuracy and precision are comparable to that for the method of Abell-Kendall, a method of generally accepted accuracy. By the use of quality reagents and the rigorous exclusion of water, the strong fluorophor that develops on reacting concentrated sulfuric acid with cholesterol can be used to quantitatively determine the total cholesterol in serum. We used gas-liquid chromatography to monitor the extent of saponification of the cholesterol esters, because we found them to have fluorescent efficiencies that differed from that of free cholesterol. Sodium methoxide in methanol/methylene chloride (1/3 by vol) was shown by gas-liquid chromatography to very effectively saponify the cholesterol esters in serum.

Cholesterol↗
PubMedDate not supplied

Application of single-donor fibrin glue to burns.

Early tangential excision and immediate grafting of the burn-injured patient has been shown to be effective. Along with the use of this technique, however, comes the potential for significant blood loss, prolonged operative time, and partial loss of graft due to underlying hematoma formation. Based on experience using a pooled fibrinogen preparation, European and Japanese surgeons have provided evidence for the positive hemostatic and skin transplant fixation effects of fibrin glue. This commercial preparation, however, has not been approved by the U.S. Food and Drug Administration for use in the United States because of high risk of hepatitis and HIV transmission. Using a method of preparing highly concentrated fibrinogen utilizing standard blood bank techniques developed at the University of Virginia, we have applied single-donor fibrin glue as an adjunct in the early excision and grafting of 26 patients. Since we have been using fibrin glue, we have noted a marked reduction in operative blood loss and time involved in obtaining hemostasis. Additionally, we have found the application of the grafts to be facilitated by the "stickiness" of the recipient bed. In follow-up, grafts applied utilizing the fibrin glue technique have proceeded to uncomplicated wound healing with an overall 98% graft take.

Adult↗