Background Optical Density Research Articles

Subject: Methods

Oological material from two Kharkov Region colonies, Zmiyov and Chuguyev, of the black-headed gull Larus ridibundus were studied with the purpose to estimate population variability for the following traits: egg length (EL), egg width (EW), egg shape index (ESI), asymmetry value (AV), egg mass (EM) and egg shell background optical density (ESBOD). There were no significant differences between the two colonies for the characters studied, average character values in Kharkov population were respectively 52.4 mm, 37.0 mm, 0.707, 22.1 mm, 37.3 g, 84.1 cB, the corresponding coefficients of character variation being 3.82, 2.76, 3.90, 3.71, 7.24 and 15.70%. By using starch gel electrophoresis of egg whites, the polymorphism of an autosomal ovoglobulin locus G3 was revealed both in the Zmiyov and Chuguyev subpopulations with the frequencies of allele G3A 0.567 and 0.543, and of allele G3B 0.433 and 0.457, respectively. In the Zmiyov subpopulation, the polymorphism of an autosomal ovalbumin locus Ov was observed with the frequencies of allele OvA 0.896 and of allele OvB 0.104. Polymorphic types of egg white transferrin (locus Tf) were not found in the both subpopulations. With regard to values of population similarity and diversity (1), genetic similarity measure, r, was found to be 0.973 with identity criterion, I, 4.7 (P > .05) that testified to the insignificant differences between two subpopulations studied. Significant differences (P < .001) between the Zmiyov and Chuguyev subpopulations were observed by using values of population diversity, mean allele number, h (1.80 vs 1.50), and rare allele share (0.100 vs 0.012).

DEVELOPMENT OF A QUANTITATIVE ENZYME-LINKED IMMUNOSORBENT ASSAY FOR VITELLIN AND VITELLOGENIN OF THE BLUE CRAB CALLINECTES SAPIDUS

ABSTRACT Vitellin (Vn) and vitellogenin (Vg) were detected in the blue crab Callinectes sapidus by nondissociating polyacrylamide gel electrophoresis (PAGE). Vn was purified by gel filtration chromatography followed by PAGE, and anti-Vn immune serum was raised in rabbits. A slot blot analysis indicated that anti-Vn immune serum reacted with the ovarian homogenate from which Vn was isolated. In a double immunodiffusion test, single precipitin lines were found between the center well containing immune serum and surrounding wells containing purified Vn, ovarian homogenate, purified Vg, or female hemolymph. The precipitin lines were continuous, suggesting that the immune serum precipitated proteins of complete identity. Finally, a Western blot analysis revealed that immune serum specifically bound Vn and Vg. The IgG fraction was purified from anti-Vn immune serum and used to develop a quantitative enzyme-linked immunosorbent assay (ELISA). The Vn standard curve was linear over the range of 62.5-1,500 ng Vn. The sensitivity of the ELISA was 148 ng/ml. Male hemolymph yielded background optical density values, confirming the specificity of the assay. Serial dilutions of ovarian homogenate or female hemolymph produced sample titration curves that were parallel to the Vn standard curve. Thus, the ELISA is suitable for quantification of Vn and Vg in ovary and hemolymph, respectively.

Epizootic haematopoietic necrosis virus (EHNV): improved ELISA for detection in fish tissues and cell cultures and an efficient method for release of antigen from tissues

An improved antigen capture ELISA for the detection of epizootic haematopoietic necrosis virus (EHNV) is described. Affinity purified rabbit anti-EHNV immunoglobulin was used as capture antibody, enabling the detection of EHNV at a concentration of 10 3.5 TCID 50/ml cell culture supernatant. The sensitivity and specificity of the ELISA, determined by examination of clarified tissue homogenates from 55 infected fish and 348 uninfected fish in relation to virus isolation, were 81.2% and 98.9%, respectively. Specificity for redfin perch (Perca fluviatilis) tissue samples was 100%, however, high background optical density (OD) in samples from uninfected rainbow trout (Onchorhynchus mykiss) resulted in lower specificity (98.5%). Specificity for rainbow trout tissues was increased to 100% by testing clarified tissue homogenates that had been diluted 1:10. Sensitivity and specificity estimates for cell culture supernatants were 96.2% and 99.9% based on the results obtained for 158 infected and 355 uninfected samples. Incubation steps in the ELISA can be shortened to enable its completion in less than 4 h if a rapid qualitative diagnosis is required. Of eight methods of releasing EHNV from infected tissue that were evaluated, manual grinding of tissue with a fitted pestle in a 1.5-ml plastic disposable tube, followed by vortexing in the same tube with 3 mm diameter glass beads and clarification in a microcentrifuge was the most efficient. Samples from 150–200 individual fish could be prepared for ELISA and cell culture by a single operator in a day. Antigen capture ELISA can replace virus isolation as the method of choice for diagnosis of EHNV.

Persistence of rinderpest maternal antibodies in lambs

Rinderpest antibodies in 166 lambs of different ages, born to vaccinated ewes were studied with avidin-biotin enzyme-linked immunosorbent assay. The mean serum background optical density (OD) value in 20 colostrum deprived lambs and 50 unvaccinated adult sheep was 0.12. The OD values of 166 one to six month-old colostrum-fed lambs ranged from 0.08 to 0.64 and the pooled rinderpest positive serum was 1.44. A peak value of 0.64 was obtained in the first week which gradually declined to become negative for the presence of rinderpest maternal antibodies at around six months of age (OD=< 0.24). Primary vaccination of lambs of vaccinated ewes is therefore considered appropriate at six months of age for effective immunisation with least interference of maternally-derived antibodies.

Dual-lumen catheters: Quality control tests for radiopacity

A protocol utilizing a single-point densitometer was developed for the quality control (Q.C.) of the radiopacity of dual-lumen radiographic catheters where x-rays generated at 80 kVp are typically used. Catheter contrast, defined as the difference between catheter radiopacity and background optical density (O.D.) when an aluminum plate is imaged, forms the basic Q.C. parameter. When a given catheter is repeatedly measured, catheter contrast varies with a standard deviation of 0.013 O.D. units. The effects of minor background O.D. variations on contrast are significant, but empirically correctable. A variation in measured contrast of approx. 0.01 O.D. units is observed per 10 kVp energy variation. Aluminum plate thickness has a significant effect on the results; however, other details of the protocol geometry are less important. Variations due to catheter orientation were examined and imaging of packaged catheters was demonstrated.

TITER OF TOMATO SPOTTED WILT VIRUS IN THREE TOMATO SPECIES VARIES WITH THE LEAVES INOCULATED BUT NOT LIGHT INTENSITY

Three methods to inoculate Lycopersicon esculentum 'VF Pink' seedlings with tomato spotted wilt virus (TSWV) were compared. Treatments were 1) two inoculations by hand (rubbing leaves with a sterile cotton swab), 2) a single inoculation using a paint sprayer at 3.56 × 105 N· m-2, and 3) two spray inoculations. All three methods were effective (&gt;95% infection) under moderate temperatures in the spring, but hand inoculation was not effective under hot conditions in the summer. In another experiment, spray inoculation was used to compare effects of light intensity and the leaf inoculated on susceptibility of L.. hirsutum PI 127826, L. pimpinellifoliom LA 1580 and `VF Pink' to TSWV isolate 85-9. All three genotypes were susceptible under full sun and 60% shade cloth in the greenhouse. Inoculation of youngest leaves produced the highest virus titer. Background optical density for noninoculated plants differed between lower and upper leaves in the ELISA assay.

Background heat treatment studies in LR-115

Abstract The effects of pre-irradiation thermal treatment at 100 °C and etching time on background track density (BGTD) and/or optical density of different batches of LR-115 were studied in this paper. The energy range and efficiency for the registration of alphas from 1 to 5 MeV were also determined in thermally treated and untreated films. The BGTD in batches stored longer was higher than that of newer batches, as basically expected and contrary to some reported data by others. The BGTD was reduced to about less than 25% of its original value after thermal treatment of 1 to 6 hours at 100 °C. This treatment, however, showed no significant effect on the 85±10% efficiency within registration energy range of 1.2 to 3.8 MeV, which were determined in this study. Nevertheless, this treatment reduced track diameter or track etching rate over the above energy range by about 20%. In conclusion, even one hour of thermal treatment at 100 °C can be efficient for BGTD annealing without any significant effect on track registration characteristics.

Some limitations in the use of plastic and dyed plastic dosimeters

Several practical plastic and dyed plastic dosimeters were examined under irradiation conditions similar to those used for radiation processing of materials. Cellulose triacetate, polymethyl methacrylate, polyvinyl chloride, dyed polymethyl methacrylate, dyed Cellophane and dyed Nylon were given fractionated and uninterrupted absorbed doses in the megarad range with 60Co γ-rays and 10 MeV electron beams. It was found that with some systems, differences in radiation response due to dose-rate and temperature dependence can cause large systematic errors in dose interpretation. Poor reproducibility of response may result from batch-to-batch differences or intra-batch variations in thickness, distribution of sensitizers and background optical density. When using these routine dosimeters, careful calibration of the response and monitoring of factors contributing to poor reproducibility are essential.

Influence of aerosol cloud height on the change in the atmospheric radiation balance due to aerosols

A radiative-convective atmospheric model for 35°N latitude in April is used to demonstrate the influence of aerosol cloud height on the change in the atmospheric radiation balance and temperature profile due to aerosols. Three different aerosol optical densities (0.065, 0.325 and 0.650) are considered as well as three mean aerosol cloud heights, corresponding to pressures of 958, 418 and 41.5 mb. In all cases considered, the surface temperature difference due to aerosols ranges between −3 and +0.4°K, with small magnitudes corresponding either to high aerosol clouds or to high surface albedo. The effect of surface albedo ω s is included by considering ω s, values of 0.07, 0.3 and 0.6. Aerosols at all heights produce two opposing effects in the atmosphere: 1. (1) they reduce the magnitude of the total radiative cooling of the atmosphere, resulting in an effective “heating” at the earth's surface, 2. (2) they increase the “reflectivity” of the earth-atmosphere system to solar radiation and thus reduce the amount of solar energy absorbed resulting in an effective “cooling” at the earth's surface. Effect (1) apparently results from a “trapping” of the radiation by the aerosol and the absorption of this radiation by O 3, H 2O and CO 2. A low-lying aerosol with an optical density ten times the present background value, when situated over a surface such as water ( ω s = 0.07) causes a 1.5 per cent decrease in the radiative cooling of the atmosphere relative to the present cooling rate. (The effect due to a low-lying aerosol having the background optical density τ = 0.065 was found to be negligible.) Accompanying the 1.5 per cent “heating” effect was a 3.8 per cent decrease in solar flux absorbed in the earth-atmosphere system. The combined heating and cooling produces a surface temperature difference of −3°K. For aerosols near the surface and over a reflecting surface such as snow ( ω s = 0.6) an aerosol optical density ten times the present background value produces a ~ 0.7 per cent decrease in the present value of the radiative cooling of the atmosphere. Accompanying this “heating” effect is a negligible decrease in the solar radiation flux absorbed in the earth-atmosphere system. The combined effect in this case results in a surface temperature increase of 0.4°K.

Galactose-1-phosphate uridyl transferase: A new manometric assay specially suited to erythrocyte studies in galactosaemia

Spectrophotometric assay of galactose-1-phosphate uridyl transferase, when applied to erythrocytes for studies relating to galactosaemia, is complicated by the high background optical density of the haemolysate. For this reason a sensitive manometric method for the assay of this enzyme has been developed. The reaction rate is followed continuously, and the enzyme measured under optimal kinetic conditions. The method is precise (C.V. = 5.4%) and the results correlate well ( r = 0.91) with the uridine diphosphoglucose consumption test.

Interference by Gastrografin with a spectrophotometric trypsin assay.

Small quantities of Gastrografin remaining in the intestinal tract some hours after introduction have been shown to cause falsely low trypsin values as determined by a spectrophotometric assay system. This interference is due first to the high absorbance of Gastrografin at 254 nm resulting in a falsely high background optical density. Secondly, Gastrografin inhibits esterase activity towards the synthetic substrate used in this assay. Gastrografin did not interfere with gelatin proteolysis by trypsin and did not affect amylase or lipase determination. Thus the instillation of Gastrografin into the duodenum before pancreatic function tests should be avoided when the trypsin content is to be determined spectrophotometrically.

Sensitive dual wavelength densitometer with suppression of the support introduced background optical density

An instrument for the direct photometric scanning of zones is described. The method involves the alternative flashing of two beams of light through the support. The wavelengths used are the peak of absorption and a selected reference at one of the sides of the absorption curve of the colored compound in the zone. This technique allows an inherent suppression of the background optical density of the support while maintaining full sensitivity and specificity. This results in a performance increase of about two orders of magnitude when sensitivity or precision are compared with single wavelength operating instruments.