A sensitive method for the colorimetric determination of urea

A method is described for the direct colorimetric determination of urea in biological fluids. The method depends on the reaction (first described by Wheatley, 1948) between urea, diacetylmonoxime, and phenylanthranilic acid in the presence of controlled amounts of oxidant; chloride ions are included to sensitize the reaction; manganous ions stabilize the resultant colour; and phosphate enables reasonable reproducibility to be achieved.     

A simple and sensitive method for the determination of blood group antigens in secretions.

A simple method for the determination of ABH blood group antigens in secretions has been developed. Blood group ABH specific monoclonal antibodies were covalently bound to blue dyed microspheres of acryl polymer with a diameter of 2.2 microns. The dyed microspheres coated with anti-A, -B and -H antibodies were found to be agglutinated specifically on a plastic microtiter plate by the corresponding blood group antigens secreted in saliva. The agglutination reactions with saliva samples were also observed rapidly and conveniently in a glass capillary tube which contained the same antibody immobilized dyed microspheres. The procedure provides a simple and sensitive method for the determination of blood group antigens through the visible agglutination reaction of dyed microspheres despite the invisibility of the antigens.     

The L.A.I. microtest: A rapid and sensitive procedure for the demonstration of cell-mediated immunity in vitro

A new microtest for cell-mediated immunity is described, which is based on the elaboration of a diffusible factor from sensitized lymphocytes following contact with specific antigen. The factor inhibits the adherence of neighbouring leucocytes to plastic surfaces. Production of the factor ablated by pretreatment of lymphocytes with Theta-antiserum. It is suggested that the factor may be a new lymphokine, leucocyte adherence inhibition factor (LAIF).     

An automated apparatus for the determination of visual thresholds in turtles.

An automated apparatus is described that permits precise and reliable measurements of visual thresholds in turtles using a conditioned avoidance technique. The entire sequence of stimulus management and the collection of response data are under programmed control.     

A sensitive radioimmunoassay for the determination of antibodies to mouse hepatitis virus

A solid-phase radioimmunoassay is described for the detection of antibodies to mouse hepatitis virus. Viruses were purified by velocity and isopycnic gradient centrifugation and 96-well plastic plates were coated with viral antigens. To allow the detection of most serotypes of low titered antisera, a pool of antigens from several viral serotypes were employed. The second antibody, an affinity-purified goat antimouse immunoglobulin, detects IgG, IgM and IgA antibodies. This assay is more sensitive than either the plaque reduction assay or the commercially available enzyme-linked immunosorbant assay and proved to be useful for screening mouse colonies for the presence of mouse hepatitis virus, following seroconversion in experimental animals and in the production of monoclonal antibodies to both structural and nonstructural proteins.     

A simplified procedure for the fluorometric determination of histamine in rat stomach

Histamine and be determined fluorometrically by the use ofo-phthaldialdehyde. Over the years, the fluorometric procedure has been made more sensitive and more specific through modifications of the reaction conditions. As a consequence the method now allows the direct measurement of histamine in crude trichloroacetic acid extracts of rat gastric mucosa and peritoneal mast cells. This conclusion is corroborated by the results of high performance liquid chromatography of theo-phthaldialdehyde-induced fluorophores in the extracts.     

A sensitivity-guided algorithm for automated determination of IMRT objective function parameters

Optimizing intensity-modulated radiotherapy (IMRT) plans involves tradeoffs that balance normal-tissue objectives against each other and against tumor objectives. Adjusting the parameters that determine the appropriate contributions of individual anatomic structures to the objective functions through trial and error is time consuming and may not produce the best achievable plans. We have developed a sensitivity-guided parameter optimization (SGPO) method to assist in the automatic determination of parameters to drive the IMRT optimization to better achieve, or even exceed, specified planning goals. The method is based on the trade-off relationships among multiple objectives: In a globally optimal plan (or within a convex subspace of the plan objectives), any attempt to improve the achievement of goals for a structure will result in sacrificing the goals for at least one other structure. However, different objectives may have different sensitivities to the overall goal of an IMRT plan. For instance, changes in dose distribution, hence the subscore corresponding to an objective for a given normal structure, may minimally impact the target dose distribution. Stated differently, the target coverage is insensitive to the changes in dose distribution of the specific normal structure. A lung cancer treatment plan designed with the SGPO method was used to demonstrate that IMRT plans could be designed to favor a structure with the highest target sensitivity and spare the structures with the least target sensitivity without compromising the target coverage. Using one case each of prostate and paranasal sinus cancers, we also demonstrated that several alternative optimal solutions could be designed with the SGPO algorithm favoring different structures. Finally, we applied the method to eight oropharyngeal cancer cases to obtain objective function parameters that satisfied the Radiation Therapy Oncology Group RTOG-H-0022 protocol. The eight plans optimized using the computer-generated objective function parameters met the protocol's scoring criteria with no or only minor protocol violations. Our preliminary study indicates that the SGPO method may be an effective and practical way to improve IMRT planning.     

An automated scoring procedure for the micronucleus test by image analysis

The micronucleus assay (MNT) in human lymphocytes is frequently used to assess chromosomal damage as a consequence of environmental mutagen exposure, to assess the effect of mutagens or to search for reduced DNA repair capacity after a mutagenic challenge. We have established an automated scoring procedure for the cytokinesis blocked MNT based on computerized image analysis (Metasystems Metafer 4 version 2.12). To evaluate the results we used the reproducibility of counts, established a dose-response curve for gamma-irradiation and used the ability of the system to differentiate between breast cancer patients and controls as a biological reference, a difference which we had observed before by visual counting. Blood cultures were irradiated with gamma-rays (2 Gy) at the beginning and treated with cytochalasin B during the last 24 h. The slides were stained with Giemsa for visual counting and with DAPI for automated analysis. Our test sample consisted of 73 persons (27 with breast cancer and 26 female and 20 male controls). A comparison between visual counting (controls, mean MN frequency 313) and automated counting (mean MN frequency 106) in slides from the same culture revealed a large drop for the automated counts. However, the automated counts were as reproducible as the visual counts [coefficient of variation (CV) on the sample approximately 20%; CV on repeated counts of the same slides approximately 5%] and both counts were highly correlated. Furthermore, the discrimination between cases and controls improved for automated counting of slides from the same cultures [visual odds rato (OR) < or = 4.0, P = 0.009; automated OR > 16, P < 0.0001], with a strong dependence on the set of parameters used. This improvement was confirmed in a validation sample of an additional 21 controls and 20 cases (OR = 11, P = 0.0018) performed as a prospective or diagnostic test.     

A simple procedure for determination of the dead time of a stopped-flow instrument

The reducing reaction of 2,6-dichlorophenolindophenol by L-ascorbic acid was used to determine the dead time of a stopped-flow instrument. Because this reaction is irreversible, the dead time could be determined by a simple graphical analysis. The dead time values determined by the present method were comparable to those by other methods previously reported.     

Towards an automated procedure for the quantitative cytological screening of cervical neoplasms

Integrating microdensitometry has been used to quantify the glycoprotein, epithelial membrane antigen (EMA), which is frequently expressed on the cytoplasmic membrane of neoplastic cells of the cervix uteri. The technique was able to identify and quantify the antigen over a wide concentration range and could also be semi-automated using a microcomputer interfaced to the microdensitometer and programmed with the simple high level language BASIC.     

An automated method for serum bilirubin determination

A method for the determination of both direct and indirect serum bilirubin on the AutoAnalyzer is described which has a number of advantages over the automated method that is currently recommended. It gives total bilirubin results which are similar to those obtained with the equivalent manual method and direct bilirubin results which are usually about 10% lower.