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Results for “Beta Particles”

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At least 1,711 records · Page 95Linked to original sources
PubMed1989

Experimental study on relative biological effectiveness of tritium and risk estimates of genetic damage.

The relative biological effectiveness (RBE) and the genetic effect of tritium internal exposure compared with those of Co-60 gamma rays external exposure are studied in mice. Two different irradiation models are used: 1) irradiation by single intake of tritium, or by Co-60 gamma rays external exposure with gradually decreasing doses simulating the exponential decreasing function of tritium in the mouse body; 2) irradiation by continual intake of tritium, or by Co-60 gamma rays external exposure at constant dose rates. The biological effective end points observed in this study are dominant lethal mutations, dominant skeleton mutations, survival rates of primary oocytes and spermatogonia and chromosome aberrations in spermatocytes. The experimental results show that the RBE values of tritium would be 2.24 to 2.99 in the dose range of 0.02-0.06 Gy/day. The risk estimates of genetic damage from dominant skeleton mutations are 10959/10(6). Gy for tritium beta rays and 3605/10(6). Gy for Co-60 gamma rays.

Animals↗
PubMed1989

[Thermotolerance of tumors MA737 and LA795 of mice].

The effects of splitted heating of tumor, alone or in combination with local radiation, were studied on mouse mammary cancer MA737 in JB 2 mice and lung cancer LA795 in 739 mice. Hyperthermia was done by immersing the tumor-bearing foot into a water bath at 44 +/- 0.2 degrees C. When combined with radiation, 8 Mev beta irradiation from a linear accelerator was given. The response was assessed by tumor growth retardation calculated according to a special computer program. A priming dose of 5 to 6-minute exposure to 44 degrees C was followed, after various time intervals (1, 4, 5, 24 hr), by a longer exposure. Thermotolerance was induced in these two animal tumor models. Tolerance to heat, however, did not affect the combined effect of hyperthermia and radiation. Electron microscopic examination of the treated tumors confirmed the synergistic killing effect of the combined treatment.

Animals↗
PubMed1989

[Radiation pathomorphosis of malignant melanoma of the uveal tract of the human eye].

The paper describes peculiarities of changes in uveal melanomas after beta application. It is shown that the degree of changes depends on the intensity of action, the cellular type of the tumor and the degree of its pigmentation. The most radiosensitive proved to be spindle cell B, mixed and epithelioid melanomas. Less radiosensitive are pigmented tumourous cells. The most intensive postradiation changes, were characterized by development of long-term existence of coagulation necrosis, growing of cellular polymorphism, hyperploidy, polynucleosis, appearance of apoptosis. The study of the reaction of monolayer culture of uveal melanomas on beta application has confirmed different radiosensitivity of melanoma cells of a different kind as well as has revealed that the growing of cellular polymorphism is a morphologic manifestation of a postradiation degeneration. The degree of postradiation changes correlated with the duration of monolayer culture of the tumor.

Beta Particles↗
PubMed1989

[The potential for organ-preserving treatment in large uveal melanoma].

As compared with enucleation, organ-preserving treatment (photocoagulation, local excision, radiotherapy) of uveal melanoma doesn't worsen the prognosis for the patient's life. However, it was used chiefly for tumors of stages T1-T2, the prominence of the tumor not exceeding 4-5 mm. The purpose of the present communication was a study of the possibility of organ-preserving beta radiotherapy for treatment of uveal melanomas T3, the prominence of the tumor exceeding 5 mm. A new Soviet beta applicator (ruthenium-106, rhodium-106) was used for treatment of 21 patients with melanoma T3N0M0, who had refused enucleation. Average summary doses on the surface of the sclera were 1561 +/- 41 Gr. Clinical results (the follow-up period ranging from 12 to 20 months) were the following: total resorption of the tumor--3 cases; the volume of the tumor reduced by 1/2 and more--9 cases, by less than 1/2--7 cases; the size of the tumor remained unchanged--2 cases. Enucleation was made in 2 patients 3 and 4 months after radiation. The results obtained have shown beta therapy to be effective in some cases of uveal melanoma T3, this allowing to widen indications to organ-preserving treatment.

Beta Particles↗
PubMed1989

[Characteristics of the immune status of patients with uveal melanoma during the performance of organ-preserving treatment].

The paper presents data about changes in the immune status of patients with uveal melanoma in the process of organ-preserving treatment. The presence of 2 types of reaction on the treatment are shown. They are characterized by intensification or depression of the cellular immunity, in particular of its T-cellular link. The type of reaction depends on the initial state of the immune reactivity of the body, the size of the tumor and the type of the injurious factor. The increase of immune reactivity correlates with the best clinical outcomes of the treatment. This allows to use the determination of the immune status in prognosticating the outcome of treatment.

Antibody Formation↗
PubMedDate not supplied

[Macrophage lipoprotein metabolism].

In this review, attention has been focused on specific receptors on macrophages where mechanisms allow macrophages to take up and digest cholesterol-containing lipoproteins. These receptor-mediated mechanisms differ from those in other cell types like fibroblasts and smooth muscle cells. There are at least two types of lipoprotein receptors on macrophages: "scavenger" receptors and beta-VLDL receptors. Modified low-density lipoproteins are recognized by non-regulated "scavenger" receptors. Poorly regulated receptor mechanism for beta-VLDL particles enriched in cholesterol esters are operative in humans with familial dysbetalipoproteinemia. Macrophage cholesterol esters are processed by cholesterol-ester cycle. Without an available cholesterol acceptor in extracellular fluid, free cholesterol is re-esterified which may result in an accumulation of cholesterol in the macrophages and hence, in the arterial wall. The scavenging of cholesterol by macrophages appears to be a protective mechanism against "foam cell" formation in atherosclerosis.

Humans↗
PubMed1989

A system for on-line detection and resolution of radiolabeled DNA molecules and its application to automated DNA sequence analysis.

We describe a system for the real-time detection of radioactively labeled DNA molecules in gel matrix, and we demonstrate the application of this system to DNA sequence analysis. DNA sequencing reactions prepared by the Sanger chain termination method are resolved by electrophoresis on 8% polyacrylamide gels. During electrophoresis the 32P-labeled DNA fragments are detected by solid state detectors positioned 22 cm from the top surface of the gel. This system is able to resolve a DNA sequence of 300 bases or greater. Optimized protocols that allow sequence information to be obtained from single stranded and double-stranded templates are described. A linear relationship exists between the input dpm and the integrated peak values over a 20-fold range indicating that accurate DNA quantitation is also possible using this system.

Automation↗
PubMed1989

Cell death (apoptosis) in mouse intestine after continuous irradiation with gamma rays and with beta rays from tritiated water.

Apoptosis is a pattern of cell death involving nuclear pycnosis, cytoplasmic condensation, and karyorrhexis. Apoptosis induced by continuous irradiation with gamma rays (externally given by a 137Cs source) or with beta rays (from tritiated water injected ip) was quantified in the crypts of two portions of mouse bowel, the small intestine and descending colon. The time-course change in the incidence of apoptosis after each type of radiation could be explained on the basis of the innate circadian rhythm of the cells susceptible to apoptotic death and of the excretion of tritiated water (HTO) from the body. For 6-h continuous gamma irradiation at various dose rates (0.6-480 mGy/h) and for 6 h after injection of HTO of various radioactivities (0.15-150 GBq per kg body wt), the relationships between dose and incidence of apoptosis were obtained. Survival curves were then constructed from the curves for dose vs incidence of apoptosis. For the calculation of the absorbed dose from HTO, the water content both of the mouse body and of the cells was assumed to be 70%. One megabecquerel of HTO per mouse (i.e., 40 MBq/kg body wt) gave a dose rate of 0.131 mGy/h. The mean lethal doses (D0) were calculated for gamma rays and HTO, and relative biological effectiveness values of HTO relative to gamma rays were obtained. The D0 values for continuous irradiation with gamma rays were 210 mGy for small intestine and 380 mGy for descending colon, and the respective values for HTO were 130 and 280 mGy, indicating the high radiosensitivity of target cells for apoptotic death. The relative biological effectiveness of HTO relative to 137Cs gamma rays for cell killing in both the small intestine and the descending colon in the mouse was 1.4-2.1.

Animals↗
PubMed1989

The response of murine intestinal crypts to short-range promethium-147 beta irradiation: deductions concerning clonogenic cell numbers and positions.

An exteriorized loop of mouse intestine was exposed to 147Pm low-energy electrons, where the dose rate decreased by a factor of 5 from the base of the crypt to the top of the proliferative zone. A crypt survival curve was obtained, expressed in terms of exposure time. The shape of the curve was interpreted in terms of survival parameters for colony-forming cells (clonogens) derived using 137Cs gamma rays and the depth-dose curve measured for 147Pm electrons. It is concluded that the shape of the crypt survival curve using 147Pm electrons is inconsistent with the notion of either the presence of a large number of clonogens or a small number near the top of the proliferative zone. A computer fitting procedure showed that the best agreement between predicted and observed curves was achieved with 2.7 +/- 0.5 clonogens at cell position 5.6 +/- 0.6, in the putative stem-cell zone.

Animals↗
PubMed1989

[Cell kinetic analysis with flow cytometry as a disdifferentiation mechanism in human neuroblastoma cells in vitro].

The established cell line NB6 (human neuroblastoma) was perturbed in vitro, in order to evaluate the disdifferentiation mechanism of malignant neoplastic cells during cultivation. The methods for perturbation were as follows: 1) 50%-cell removal from dishes; 2) 0.1 mg/ml of vincristine (VCR) contact; and 3) 10Gy of beta-radiation. Specimens were harvested every 24 hours until 72 hours, simultaneously stained for DNA and RNA with acridine orange (AO), and cell kinetically analyzed for DNA/RNA/cell-distribution with the aid of flow cytometry (FCM). Thus disdifferentiated cells and/or newly cell cycle traversing cells, were evaluated. The new subpopulations were considered to be recruited from G1A and/or Gq (Darzynkieowicz et al.) into the cell cycle after perturbations. Cells of the new subpopulations had smaller volume compared with the control cells. Furthermore, in the current study, newly cell cycle traversing cells of NB6 appeared to have a disturbed cell cycle traverse in G2B phase from the clonological changing patterns of FCM cytograms. These new subpopulations were revealed to be able to passage up to five or six times. Though it was impossible to make them appear, these new cycling subpopulations might be capable of remaining as permanent clones in vitro.

Beta Particles↗
PubMed1989

Beta dose point kernels for radionuclides of potential use in radioimmunotherapy.

Beta dose point kernels for 32P, 67Cu, 90Y, 131I, 186Re, and 188Re nuclides appropriate for radioimmunotherapy are calculated based upon Monte Carlo results. The calculations are shown to differ significantly from values based upon solutions to the electron transport equation. Agreement with experiment for 32P is found to be improved for the former as compared with the latter. Values of the scaled dose point kernels are tabulated at 4% intervals of the continuous slowing down approximation range for each of the six radionuclides. Beta dose distributions are also tabulated at corresponding distances from the source. This data may be used to calculate the spatial dose distribution expected following administration of radiolabeled monoclonal antibodies, aiding in optimum selection of the appropriate radionuclide. Parameters for functions providing analytic representation of the calculated scaled dose point kernels of individual beta groups are presented.

Beta Particles↗
PubMed1989

[Optimization of methodology and extension of indications for beta therapy of neoplasms of the eyelids, conjunctiva and cornea].

The paper offers a theoretical foundation and results after clinical approbation of the method developed by the authors for beta therapy by enlarged single doses using, if necessary, a speeded-up fractionating and split courses of radiation. Beta therapy was used in 220 patients with tumors of the eye lids, conjunctiva and cornea, single doses of radiation, 40 Gr daily or each other day. By their morphologic type the tumors were mostly malignant epithelial and pigmented new-formations (sarcoma, melanoma). In the follow-up period, from 1 to 6 years, the following results were recorded: the treatment proved effective for epithelial tumors in 97%, melanocytic--in 73%; recurrences appeared in 3%; the number of postradiation complications made up 6.6%, of them disturbances in visual functions--2%: death from metastases in melanoma--8.7% of cases. The proposed method of radiation allowed to increase indications for beta therapy of this pathology to 5-6 mm of the tumor protrusion, to decrease the number of complications and terms of treatment. As a result of computer analysis of clinical results, a new method for calculation of optimal summary doses of beta radiation was worked out, that can be used by practitioners in conducting beta therapy for tumors of the eye lids, conjunctiva and cornea.

Beta Particles↗
PubMed1978

Cathodoluminescence technique combined with blue light fluorescence microscopy for the investigation of the transport of molecules through the extravascular space of mammalians.

The mechanisms of transport of molecules across the extravascular spaces represent an open problem. Vital microscopic results with marked proteins using the blue light luminescence technique indicate a movement of fluid along the connective tissue fibres. Furthermore, the findings suggest that the elastic fibres play an important role in this movement. It may also be possible to elucidate the extravascular pathway for molecules by means of the cathodoluminescence technique in the scanning electron microscope. The investigations were performed using the mesentery of mammalians anaesthetized by Nembutal. The biological material for cathodoluminescence applications was selected from animals without injection of luminescent dye as well as with animals following intravenous injection of marked proteins. Two techniques, critical point drying and freeze drying, were used in the preparation. Stained and unstained tissues were investigated in the scanning electron microscope with a special cathodoluminescence detector system. Simultaneously observations of the tissue surfaces were performed by means of the secondary electron or backscattered electron mode. The results obtained agree with the findings observed by the blue light fluorescence microscopy and confirm the concept of an extravascular fluid pathway along the elastic fibres in the tissue.

Animals↗