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Biomedical subjects

W Shaw

Publications and source records attributed to W Shaw.

At least 55 records · Page 3Linked to original sources
PubMed1982

Comparison of continuous and interrupted suture techniques in microvascular anastomosis.

A comparison of the continuous and the interrupted suture techniques, ten procedures each, was performed upon dogs using high frequency pulsed Doppler ultrasonography to monitor blood velocity. No statistically significant differences in the blood velocity profile were found between the two techniques. The pulsatility of the vessels after anastomosis was similar for both techniques. At follow-up examination, mean being 13 weeks, the patency rate was 100 per cent as demonstrated arteriographically for both the continuous and the interrupted techniques with statistically no significant difference in the blood velocity profile. The speed and the ease of completing a continuous anastomosis and its lack of significant hemodynamic differences compared with the interrupted technique speak well for the preferential use of the continuous suture technique.

Angiography↗
PubMed1982

Theoretical and mathematical conditions for use of linearization methods for saturation-type radioassay data.

The algebraic equivalency of nine different methods for the linearization of saturation-type radioassay data was previously demonstrated mathematically to hold under the assumption that the antibody is saturated with ligand. Although compete saturation with antibody never occurs, a good approximation to a saturation condition occurs when the product of the labeled ligand and the affinity constant is 100 or more. The mathematical basis for determining when methods for the linearization of saturation-type radioassay data are valid is derived from a development of the first-order mass action law applied to ligand-antibody reactions.

Antibody Affinity↗
PubMed1981

Adaptation of EMIT procedures for maximum cost effectiveness to two different centrifugal analyzer systems.

We have adapted commercial immunoassay (EMIT) procedures for dilantin, phenobarbital, theophylline, carbamazepine, tobramycin, disopyramide, quinidine, procainamide, N-acetyl procainamide, and mysoline to two different centrifugal analyzers (Centrifichem and Multistat) using maximum dilutions of reagents to reduce reagent costs to approximately one-tenth of that incurred using the manufacturer's protocol. This savings due to the dilutions of reagents was primarily because of the ability to prolong the reaction time to achieve acceptably large absorbance changes over the absorbance measurement period. Correlation coefficients between values for drugs analyzed by these modified EMIT protocols and values obtained by other methods ranged from 0.927 to 0.994. Within-run precision and recovery values for these drugs were also entirely acceptable. We found that premature mixing of reagents in the rotors of the Multistat system and variable delivery of reagent in the Centrifichem 400 system were both caused by the surfactant in the EMIT buffer. The former problem is being resolved by the manufacturer; the latter problem was resolved by siliconizing the reagent pipet tips.

Centrifugation↗
PubMed1977

Linearization of data for saturation-type competitive protein binding assay and radioimmunoassay.

Most of the commonly-performed competitive protein-binding radioassay methods utilized in the clinical laboratory are based on the principle of saturation analysis. Although many different methods for linearization of saturation-type assays have been proposed, the algebraic equivalency of all of these methods has not been adequately documented. In this manuscript we have shown the physical and mathematical basis for various methods for linearlization of saturation type assays and the algebraic equivalency of these linearization methods. We have also shown that key parameters such as slope and intercept may be dependent on different components of the assays system with differnt linearization methods. An understanding of these key parameters can help the analyst to evaluate changes in these key parameters and to integrate these parameters in a complete quality control system.

Binding, Competitive↗
PubMed1977

The changes produced by presurgical orthopedic treatment of bilateral cleft lip and palate.

A serial cephalometric analysis (with the aid of metallic implants) and an analysis of the models of 10 children with complete bilateral clefts, who received presurgical orthopedic treatment, was done. It revealed that such therapy can successfully reduce the protrusive deformity of the premaxilla, when forward growth of this structure is restrained so as to allow the remainder of the face to "catch up." Our other observations include the accentuation of the columella during treatment, but an absence of growth at the cleft margins. Orthopedic treatment which fails to achieve the desired aims in 12 weeks of active therapy should be discontinued then in favor of such surgical setback as may be necessary to allow a satisfactory lip repair.

Cephalometry↗
PubMed1977

Factors affecting T3 and T4 proficiency testing.

Problem areas within a proficiency testing (PT) program are performance evaluation and sample stability. The different units used in the various T3 uptake methodologies make performance evaluation complex. To facilitate this evaluation, a normalization method for T3 uptake performance evaluation has been developed. Sample stability studies for T3 uptake indicate that, at room temperature, sample values increase after storage for about seven days. Room temperature sample stability studies for T4 using a competitive protein binding (CPB) method indicate that the apparent T4 content of pooled serum increases after about one week. Fatty acids are shown to be an interfering substance in the T4 CPB method as well as the T4 radioimmunoassay (RIA) method. This interference increases with a decrease in carbon chain length from C18 to C12 and with an increase in unsaturation of fatty acids. The B/B0 ration for arachidonic acid at a concentration of 0.48 micronMoles per tube is 17.4 in a CPB method and 87.1 in a radioimmunoassay method indicating that the greater effect is in the CPB method. The increase in T3 uptake values are probably also due to the interfering effect of fatty acids.

Blood Preservation↗
PubMed1976

Optimization of T assay: a model study.

Factors involved in the optimization of competitive binding radioassays have been analyzed using a thyroxine (T4) radioassay as a model system. The effects of kinetic errors are minimized by the use of the lowest possible incubation temperature for the separation step and by the use of labeled T4 of high purity (which is not consistently available from commerical sources). The use of labeled T4 containing significant quantities of labeled triiodothyronine (T3) can lead to a marked increase in bias and a decrease in precision with relatively small errors in the separation step due to the relatively short half-life of the T3-binder complex. The determination of the dissociation rate constant (not to be confused with the affinity constant) allows one to make useful estimates of the tolerances that can be allowed in the separation step in order to achieve a desired level of accuracy and precison.

Evaluation Studies as Topic↗
PubMed1976

An evaluation of three commercially prepared anion-exchange resin columns for separation of tetraiodothryonine in serum.

Three different commercially prepared anion-exchange resin columns for thyroxine (T4) separation from serum for the "T4 by column" assay were evaluated using the protocol of the supplier. The claims by the suppliers for the distribution and recovery of T4 in the first and second thyroxine-containing eluates were experimentally evaluated by the addition of a tracer quantity of purified [125I]T4. The average experimentally determined elution ratios of recoverable T4 (sum of T4 in first and second eluates) with these commercial columns were: Bio-Rad, 92.2:7.8 (90:10 claimed); Oxford, 87.8:12.2 (94:6 claimed); and Curtis Nuclear, 88.7:11.3 (80:20 claimed). The percent recoveries of T4 in the first thyroxine-containing eluate were: Oxford, 82.3 + 9.70 (x +/- 1 S.D.); Bio-Rad, 91.75 +/- 2.09; and Curtis Nuclear, 74.20 +/- 6.14. Mean serum T4 values obtained by the column method with all commercial columns tested were lower than competitive protein binding radio-assay (CPBR) values if the former values were not corrected for recovery. When individual recovery correction factors were applied to column results, improved correlation and better correspondence of "T4 by column" mean values with the CPBR values were noted. It is concluded that the largest part of the total variability of the "T4 by column" assay is contributed by the chromatographic step when the colorimetric step is performed with an automated technique.

Anion Exchange Resins↗
PubMed1976

Interference of fatty acids in the competitive protein-binding assay for serum thyroxine.

An increase in apparent thyroxine values obtained by competitive protein-binding assay on storage of sera is well documented. We find that the major source of this positive bias is probably the unsaturated nonesterified fatty acids. Nonesterified fatty acids cause a positive basis in the competitive protein-binding assay for serum thyroxine because they inhibit the binding of radioactive thyroxine by the serum-binding reagent (probably thyroxine-binding globulin). This inhibition by fatty acids may be due to the formation of a fatty acid/thyroxine complex. The degree of inhibition caused by the fatty acids depends on the length of the carbon chain of the fatty acid and the degree of saturation. Short-chain fatty acids are more potent inhibitors of thyroxine binding than those with a longer chain, and unsaturated fatty acids are more potent inhibitors of thyroxine binding than are saturated fatty acids. The polyunsaturated fatty acid, arachidonic acid, was the most potent inhibitor of all the fatty acids tested. Triglycerides (triacylglycerols) insignificantly inhibit thyroxine binding in this assay.

Binding, Competitive↗
PubMed1975

Purification from human plasma of a heparin-released lipase with activity against triglyceride and phospholipids.

A triglyceride lipase different from lipoprotein lipase, but measurable only after intravenous heparin injection, has been isolated from human plasma by sequential use of heparin-Sepharose and concanavalin A-Sepharose affinity chromatography. Using these procedures, phospholipase A1 activity was found to chromatograph identically with the triglyceride lipase. The constancy of the ratio of activities after isoelectric focusing (pI 4.1) and during thermal deactivation indicates that this enzyme has hydrolase activity against both triglycerides and phospholipids. This conclusion was supported further by the homogeneity of the protein as indicated by sodium dodecyl sulfate polyacrylamide gel electrophoresis.

Heparin↗
PubMed1975

Caecal rupture due to colonic ileus.

Caecal rupture due to colonic ileus is rare and has a mortality rate of 43 per cent. Three new cases are presented and the 18 previously reported cases are reviewed. The disease has always occurred in association with another illness, has usually afflicted patients over the age of 55 and has only resulted when the caecum was at least 9 cm in diameter. The technique of 'blow-hole' caecostomy, a method for decompressing the distended caecum, is described.

Adult↗