A model is presented for the explosive cloud of particulates that produced the western trace of high radioactive ground contamination in the Chernobyl accident on 26 April 1986. The model was developed to reproduce measured dose rates and nuclide contamination and to relate estimated doses to observed changes in: (1) infrared emission from the foliage and (2) morphological and histological structures of individual pines. Dominant factors involved in ground contamination were initial cloud shape, particle size distribution, and rate of particle fallout. At time of formation, the cloud was assumed to be parabolical and to contain a homogeneous distribution of spherically shaped fuel particulates having a log-normal size distribution. The particulates were dispersed by steady winds and diffusion that produced a straight line deposition path. The analysis indicates that two clouds, denoted by Cloud I and Cloud II, were involved. Fallout from the former dominated the far field region and fallout from latter the region near the reactor. At formation they had a full width at half maximum of 1800 m and 500 m, respectively. For wind velocities of 5-10 m s(-1) the particulates' radial distribution at formation had a standard deviation and mode of 1.8 microm and 0.5 microm, respectively. This distribution corresponds to a release of 390 GJ in the runaway explosion. The clouds' height and mass are not uniquely determined but are coupled together. For an initial height of 3,600 m, Cloud I contained about 400 kg fuel. For Cloud II the values were, respectively, 1,500 m and 850 kg. Loss of activities from the clouds is found to be small. Values are obtained for the rate of radionuclide migration from the deposit. Various types of biological damage to pines, as reported in the literature, are shown to be mainly due to ionizing radiation from the deposit by Cloud II. A formula is presented for the particulate size distribution in the trace area.

A new immunometric two-site sandwich assay is introduced, in which a label-scavenging binding partner is added to the sample in addition to the analyte-binding partner, The scavenger binding partner binds excess label antibody, giving a signal proportional to the amount of excess label antibody in the sample solution. A set of two calibration curves is obtained from the two binding partners simultaneously, and a combination of the two signals gives an unambiguous determination of the analyte concentration, even for high analyte concentrations where the hook effect may occur. Two-particle immunofluorometric assays developed for placental alkaline phosphatase and human chorionic gonadotropin on the basis of this principle and yielding signals measured by flow cytometry gave rapid results (2 h) and had working ranges in excess of 5 and 6 orders of magnitude for the respective analytes.

The ability of serum factors to cross-link labeled mouse monoclonal antibody (mAb) of irrelevant specificity (mAb FN61, subclass IgG1) to different particle types coated with sheep IgG, bovine gamma-globulin, or mAb FN61 was measured simultaneously by flow cytometry. Significant interference with mAb FN61-coated particles was detected in 53 of 101 sera. Of the 30 sera showing the most pronounced interference, 23 were characterized by an even stronger cross-linking to particles coated with bovine gamma-globulin. These were designated type 1 sera. Seven sera, designated type 2, displayed a dominant interference with the mAb FN61-coated particles. The interference reaction in the two serum types was characterized by different kinetics, dependence on particle concentration, and response to blocking agents. The interference was minimized by addition of 500 micrograms of bovine gamma-globulin and 50 micrograms of mAb HH1 (IgG1) of irrelevant specificity per 10 microL of serum sample in a final assay volume of 100 microL.

The potential usefulness of alpha-particle radioimmunotherapy in the treatment of osteosarcoma was studied in vitro by using the monoclonal antibody TP-3 and cells of three human osteosarcoma cell lines (OHS, SAOS and KPDX) differing in antigen expression. Cell survival curves were established after treatment with (a) 211At-TP-3 of different specific activities, (b) 211At-labeled bovine serum albumin (BSA), (c) free 211At and (d) external-beam X rays. The three osteosarcoma cell lines showed similar survival curves, whether treated with external-beam X rays, 211At-BSA or free 211At. The D0's were lower for free 211At than for 211At-BSA. The survival curves for 211At-TP-3 treatment, on the other hand, differed significantly among the cell lines, suggesting that sensitivity to 211At-TP-3 treatment was governed by cellular properties other than sensitivity to external-beam X rays. The cellular property most important for sensitivity to 211At-TP-3 treatment was the antigen expression. Cell inactivation after 211At-TP-3 treatment increased substantially with increasing specific activity of the 211At-TP-3. At high specific activities, the cytotoxic effect of 211At-TP-3 was significantly higher than that of 211At-BSA. In conclusion, 211At-TP-3 has the potential to give clinically favorable therapeutic ratios in the treatment of osteosarcoma.

We evaluated two homogeneous immunofluorometric assays (IFMAs) of alpha-fetoprotein (AFP) based on new macroporous acrylate particles combined with flow cytometry. The standard IFMA, requiring 1 h of incubation, provided a working range from 1.8 to > 900 kIU/L (CV < 10%) and a detection limit of 0.6 kIU/L. Use of overnight incubation and a lower particle concentration extended the working range by 1 decade in the lower end. Analytical recoveries for the standard IFMA varied between 97% and 108%. The slope and y-intercept of the regression line correlating measurements by the standard IFMA and a routine immunoradiometric assay were not significantly different from 1 and 0, respectively (P > 0.5), and the correlation coefficient was 0.996. High precision and warning of spuriously high measurements were obtained by including in each sample separate particle types for detecting instrument instability and measuring nonspecific binding only.

We present what is, to the best of our knowledge, the first detailed calculation of the reverse trapping force acting on a dielectric sphere when it is illuminated by a strongly focused laser beam. The calculation is carried out within the geometrical optics approximation. The phenomenon of laser trapping was discovered experimentally by Ashkin et al. [ Opt. Lett.11, 288 ( 1986)] and is of great practical interest in view of the possibility it offers for freely manipulating biological particles, such as viruses and bacteria, in a nondestructive manner. We support our calculations by a qualitative experiment that clearly shows the accessibility of the trapping effect in practice. We use, as an experimental improvement, an objective with a central field stop producing a conical dark field. This enhances the relative contribution from high-N.A. illumination and makes it easier to achieve optical trapping.

Hyperthermia has been reported to induce a dose-dependent reduction in the expression of melanoma-associated surface antigens. The objective of the present work was to study the mechanisms for the reduction in the expression of the p250 antigen recognized by the monoclonal antibody 9.2.27. Measurements at 37 degrees C showed that antibody binding induced a certain degree of modulation (internalization) of the melanoma-associated antigen. Masking of the antigen due to internalization and/or damage in situ, as well as shedding of the antigen, were measured after hyperthermia, and found to increase in a heat-dose-dependent manner, although for antigen masked this increase was not significant compared with control cells at 37 degrees C. The sum of antigen shed and masked after hyperthermia correlated with the overall reduction in antigen expression measured independently. During hyperthermia, antigen was shed and masked in approximately equal amounts. After the treatment, hyperthermia-induced shedding continued as a function of time and caused a further reduction in antigen expression, but masking did not differ from 37 degrees C controls.

Hyperthermia and photoactivated hematoporphyrin derivative induce a dose-dependent reduction in the expression of the p250 surface melanoma-associated antigen on the human FME cell line. Expression of this glycoprotein antigen was quantitated by immunofluorescence flow cytometry based on the monoclonal antibody 9.2.27. Decrease in antigen expression was followed by a transient increase above the level for untreated cells, before normalization occurred about one week after treatment. These treatment-induced changes in antigen expression could partly be explained by changes in protein synthesis. This conclusion was based on the following observations: Hyperthermia and photoactivated hematoporphyrin derivative both inhibited protein synthesis. The latter increased again rapidly to rates above normal until antigen expression reached normal level, whereupon the protein synthesis rate decreased to normal. Inhibition of protein synthesis by cycloheximide 1 day after heating, prevented the recovery of antigen expression, demonstrating that protein synthesis is necessary for resumption of normal antigen expression. The changes in both antigen expression and protein synthesis were dose-dependent, and the magnitude and duration of the changes increased with increasing dose. The time courses of the changes in protein synthesis after two different treatments which both inactivated two logs of cells were almost identical, as were the time courses after two lower heat doses inactivating one log of cells. These similarities were reflected in the changes in antigen expression. At the same time as protein synthesis reached its maximum and antigen expression resumed normal level, an increase in the Golgi apparatus was observed ultrastructurally, indicating an increased synthesis rate and transportation of glycoproteins to the cell surface.

The radiolabeled anti-T cell antibody T101 can be used for specific tumor localization, but unlabeled T101 produces limited cytotoxicity in patients. We thus studied the in vitro cytotoxic effects of T101 labeled with 125I, a radionuclide known for its short-range, high- linear-energy electrons. We showed that 125I-T101 could be readily prepared at high specific activity with high immunoreactivity. Human malignant T cell lines HUT 102, MOLT-4, and HUT 78 were found to differ in the number of T65 determinants (the antigen recognized by T101) and the sensitivity to external x-ray radiation, which were of significance for the cytotoxicity of 125I-T101 in vitro. The cytotoxic effects of 125I-T101 were also found to be dose dependent and increased with exposure time under frozen conditions. As controls, unlabeled T101 had no cytotoxic effect, while free Na 125I or the 125I-labeled irrelevant antibody 9.2.27 exerted minor cytotoxicity. In HUT 102 and MOLT-4, more than 3 logs' cell killing was achieved within four weeks. Because considerable cytotoxicity was demonstrated in vitro by 125I-T101 on T65- positive malignant cells, and because low-dose 111In-T101 can be used successfully for tumor localization, future trials using 125I-T101 at high specific radioactivity may improve therapeutic results in patients with T65-positive malignancies.

Exponentially growing melanoma cells of the line FME were incubated with hematoporphyrin derivative (HpD) for 1 and 18 h and subsequently exposed to light in the presence of HpD. Quantitative changes in the expression of the melanoma-associated surface antigen p250 recognized by the monoclonal antibody 9.2.27 were studied by flow cytometry. Treatment with HpD and light resulted in no immediate changes in the antigen expression. However, a few hours after light exposure a significant reduction in antigen expression was observed. For cells incubated with HpD for 1 h, the minimum expression of the antigen was observed 6 h after the irradiation, and the duration of the reduced expression was almost dose independent. On the other hand, the duration of the reduced antigen expression increased strongly with light dose for cells incubated with HpD for 18 h. In both cases antigen expression decreased exponentially with the product of drug concentration and light dose, indicating that there is no rapid mechanism by which the cells can repair the damage which leads to reduced antigen expression. Days were needed before the cells expressed a normal level of the antigen. A slight overshoot of the level of antigen expression above that for untreated cells was observed 2-5 days after light exposure depending on the incubation conditions with HpD and the light dose. At a given cell survival level (greater than 0.1), the decrease in antigen expression was more pronounced on cells incubated with HpD for 1 h than on cells incubated with the drug for 18 h.

Quantitative changes in the expression of three melanoma-associated antigens on human FME cells were studied by means of flow cytometry as a function of time after exposure to hyperthermia (42 degrees C for 1, 2, and 3 h; 43.5 degrees C for 1 and 2 h; 45 degrees C for 20 min). The expression of the three different surface antigens p250, p210, and p97a recognized by the monoclonal antibodies 9.2.27, 5.1, and 4.1, respectively, underwent qualitatively similar changes after hyperthermia. The antigen expression was reduced immediately after end of the treatment and decreased further to reach a minimum 1 day after treatment. Then the antigen expression gradually increased and reached a maximum above the level for unheated cells before it returned to this level about 1 wk after hyperthermia. The magnitude of these effects increased with increasing temperature and with increasing heating time at a given temperature. Quantitatively there were individual variations for the three different antigens. A positive correlation was found between the surviving fraction of the cells and the minimum level of antigen expression, indicating that different heat treatments which inactivated the same number of cells induced the same reduction in antigen expression. The demonstrated therapy-induced changes in antigen expression may be of importance for the use of monoclonal antibodies in diagnostic imaging of tumor tissue after hyperthermia or as therapeutic agents in combination treatments involving hyperthermia.

The anti-melanoma antibody 9.2.27 localizes to melanoma cells when administered i.v. to melanoma patients, but high doses of this antibody alone have no specific cytotoxic effect in vivo. To determine whether radiolabeled antibodies would exhibit specific antimelanoma cytotoxicity in vitro, cell survival curves were established for NCl-N892 human melanoma cells treated with 125I-labeled 9.2.27 monoclonal antibody. The binding capacity per cell was 5 X 10(5) molecules of 9.2.27 immunoglobulin G, and the association constant of binding was 10(10) M-1. Antibody preparations with specific radioactivities of 9-80 microCi/micrograms were used. Colony-forming ability after in vitro exposure to 125I-9.2.27 was determined by a 1-h antibody incubation at saturating concentrations, washing, and cell freezing for various exposure durations. Colony survival was dose dependent, varying with the radioactivity per cell and the exposure time. The survival curves demonstrated no shoulder effect and had a 37% incremental survival dose of 0.5-0.9 X 10(5) decays/cell. Selective killing of melanoma cells was demonstrated in experiments where NCl-N417 lung cancer cells were mixed with the melanoma cells prior to antibody treatment. The NCl-N417 cells did not express the melanoma-associated antigen, were more sensitive to conventional external irradiation than were the melanoma cells, and could easily be distinguished from them by different growth morphology. In spite of a growth advantage for the melanoma cells in the clonogenic assay, the antigen-negative lung cancer cells selectively survived the treatment and were the only surviving cells after 15 days of exposure.

The expression of a melanoma-associated antigen, recognized by the monoclonal antibody 9.2.27, has been studied in the human FME melanoma cell line, grown as a monolayer under various conditions in vitro and as tumours in athymic mice. Two-parameter flow cytometric measurements of DNA and immunofluorescence showed that the antigen expression was uniform throughout the cell cycle. Highest expression of the melanoma-associated antigen was found in cultures in which the medium was frequently renewed (4 times in 6 days) and no contact inhibition was present. In comparison, the antigen expression of cells subjected to medium starvation (6 days without medium renewal) was reduced to 44%, and the cell size, as measured by forward angle light scatter, to 82% of the values found for optimally growing cells. Intermediate conditions, such as scanty medium supply or contact inhibition of growth, gave smaller effects. Two-parameter measurements of cell size and immunofluorescence demonstrated a positive correlation between cell size and antigen expression. The reduction in cell size, therefore, could explain part, but not all, of the reduction in antigen expression on medium-starved and contact-inhibited cells. The antigen expression on FME cells grown as xenografts in athymic mice varied between individual tumours and was lower than on cells from optimal in vitro growth. Due to smaller cell size, the antigen density was, however, comparable to that on cells from optimal in vitro growth.

The stability of expression of a membrane antigen on human FME melanoma cells was investigated by means of flow cytometric cell sorting and analysis. The melanoma-associated 250 kd antigen was strongly expressed on all cells, as recognized by binding of the monoclonal antibody 9.2.27. By flow cytometric cell sorting, cells of high and low antigen expression were isolated, and the difference in antigen expression between the two populations was examined as a function of time in culture. Immediately after sorting, the median fluorescence intensities of the two populations differed by a factor of 2.7. After the first few days in culture, much of the range in antigen expression of the parent population was regenerated. However, a lasting difference in antigen expression was established, corresponding to 50% higher density of antigen on the cells sorted for high fluorescence intensity, compared to those sorted for low intensity. After trypsin treatment, which removed the antigen from the cell surface, normal antigen expression was regained after 2-3 days in culture, with the same difference between the two populations as before the trypsin treatment. The stability of the established difference in antigen expression between the two sorted subpopulations indicates that expression of this antigen is a precisely controlled, heritable characteristic of the FME melanoma cells.

Most papillary carcinomas of the thyroid run a surprisingly indolent clinical course, and even widespread lymph node metastases in the neck are not a bad prognostic omen. A small group behaves in a far more aggressive fashion and kills through local invasion of adjacent structures or blood borne metastases. This paper deals with a papillary carcinoma which does not fit into any of these groups. Following hemithyroidectomy for papillary carcinoma in 1970 the patient, a woman aged 70 years, lived comfortably for nine years until she died of what appeared to be an unrelated cause. During these nine years, papillary carcinoma metastases were removed at irregular intervals from unusual locations such as the thoracic wall, both groins, and the thigh. Gross examination, light and electron microscopy, and freeze-etching, all failed to distinguish this tumor from conventional papillary carcinomas. Morphometry showed that the nuclei were significantly larger than those found in other papillary carcinomas, and conventional and flow cytometric DNA analysis proved that the primary tumor and the metastases contained mainly tetraploid cells. One lymph node metastasis had even larger nuclei than the others and also a different, bizarre DNA distribution pattern. This study also showed that the ground glass appearance of the nuclei of papillary thyroid carcinomas does not depend on hypodiploid DNA values. Of about 70 cases of papillary thyroid carcinomas in the world literature studied by conventional or flow cytometric DNA analysis, this case is the only one with tetraploid DNA values. It is therefore tempting to correlate this tetraploidy to its peculiar biologic behavior.