Biomedical subjects

M Kao

Publications and source records attributed to M Kao.

39 records · Page 3Linked to original sources

PubMed1975

A simple radioimmunoassay for unconjugated estriol in pregnancy plasma.

A simple and specific radioimmunoassay (RIA) for the measurement of plasma or serum unconjugated estriol (E3) in pregnancy is described for general laboratory use. Two different antibodies utilized had low cross-reaction to estrone (E1) and estradiol-17 beta (E2). With either of these antibody reagents, a method was designed that requires only an extraction step using a specific solvent mixture of ethyl acetate and n-hexane (3:2, v/v), one-hour incubation with working antibody, and separation of bound from free E3 by ammonium sulfate. Standard curves useful in the range of 0 to 2,000 pg. were obtained. This assay, requiring only 0.05 ml. of plasma, can be completed within 4 hours. The sensitivity of this RIA was 10 pg. The intra- and interassay coefficients of variation (CV) were 5.0 and 9.4 per cent, respectively. When E3 determinations by this method are compared with RIA values by a more complicated technique using Celite column chromatography, the results are not significantly different. There was a good correlation between our RIA and a standard urine E3 determination (n = 137, r = 0.82, p less than 0.001). Using our simplified method, the mean plasma E3 during pregnancy were 1.0 +/- 0.6 ng. per milliliter at 10 weeks, 2.3 +/- 0.6 ng. per milliliter at 20 weeks, 6.5 +/- 1.4 ng. per milliliter at 30 weeks, and 16.5 +/- 5.1 ng. per milliliter at term. Since the serum RIA reflects changes in free E3 which has a shorter half-life than conjugated E3, this rapid and simple method is attractive as an approach to monitor fetal-placental function.

Estriol↗

PubMed1975

Parallel radioimmunoassay for plasma cortisol and 11-deoxycortisol.

We describe a direct, rapid, and specific procedure for the parallel radioimmunoassay for cortisol and 11-deoxycortisol in plasma. The plasma sample is used directly, after heat inactivation of the natural cortisol-binding protein. The radioimmunoassay utilizes antibodies generated in rabbits by steroids congugated at their 3-oxo position to thyroglobulin. Ammonium sulfate is used to separate bound and free steroids. Our cortisol antibody and an 11-deoxycortisol antibody obtained elsewhere cross reacted negligibly with each other or with other steroids that might be present in plasma. Radioimmunoassays were therefore developed for both steroids in only 1.25 mul of plasma. The intra- and inter-assay coefficients of variation for both steroids were less than 10%, with a sensitivyt of 4 mug/liter. Steroid values obtained by a competitive protein binding method were consistently higher than those of the present method, suggesting that the former is measuring total corticosteroids. This simple approach requires only 4 h for the specific measurement of both cortisol and 11-deoxycortisol in 20 samples of plasma.

17-Hydroxycorticosteroids↗

PubMedDate not supplied

Electron dose calculation using multiple-scattering theory: thin planar inhomogeneities.

In this article in our series on electron dose calculation using multiple-scattering theory, we apply the Fermi-Eyges theory to the problem of a thin planar inhomogeneity present in an otherwise-layered medium. We derive expressions for the distribution function P and the location distribution L (which multiplied by the restricted mass collision stopping power is the dose directly deposited by the primary electrons) for various types of incident beams: a completely arbitrary distribution, a Gaussian point source, a pencil beam, an isotropic point source, and a broad parallel beam. We show how divergent-beam dose distributions can be determined from parallel-beam calculations, through use of equivalent configurations dependent upon the depth of dose calculation. Also, we indicate how this work can be applied to the design of wedges (or "compensators") for beam shaping to provide desired dose distributions or to match juxtaposed radiation fields. Explicit formulas for thin plates are then worked out, and we examine the appearance of hot and cold spots distal to the edge of a localized inhomogeneity, for thin half-slabs and for narrow strips. Finally, considering the case of a thin straight wedge-shaped inhomogeneity, we theoretically discover the phenomenon of a "focused hot spot" without an accompanying cold spot, and suggest the design of a "multiple-scattering lens".

Electrons↗