What Is an Autoradiograph?

Autoradiography is a technique for locating radioactive molecules in a specimen using the principle that radioactivity can make photographic emulsions and films sensitive.

Autoradiography is a technique for locating radioactive molecules in a specimen using the principle that radioactivity can make photographic emulsions and films sensitive. Radioisotopes emit ionizing radiation during the decay process, and the radiation can sensitize the photographic latex. After the latex is in contact with the specimen, the silver bromide colloid at the site where the radioactive material is present is reduced, resulting in the precipitation of silver particles, thereby showing the site where the radioactive material is present. ^[1]

In the application of this technology, compounds containing radioactive isotopes are first introduced into the body, and after a certain period of time, their tissues are removed, made into sections or smears, and then brought into contact with photographic latex. Because the alpha particles and beta particles produced by radioactive elements can interact with visible light on a photographic latex, development and fixation using ordinary photographic techniques can obtain the correct position of the radioisotope. The content of radioactive material was measured according to the degree of blackening effect of radioactive elements on the latex, that is, the number of black silver particles on the latex. In autoradiography, commonly used isotopes are hydrogen 3, carbon 14, phosphorus 32, sulfur 35, iodine 131, iodine 125, and the like. ^[2]

The first step of the autoradiographic operation is to prepare a radioisotope-labeled compound, usually an isotope that emits low-energy beta rays, such as ¹⁴ C, ³ H, and the like. The labeled compound is then absorbed by biological tissues or cells and participates in biological metabolism. The tissue containing the labeled compound is made into sections, placed on a slide, and a thin layer of latex is coated on the surface of the section, and placed in a dark box for a certain period of time to perform radioactive "exposure". Finally, according to the process of processing photographic negatives, after development and fixing, silver particles reduced by radiation are displayed. Since the radioactive compound in the section coincides with the precipitation of the silver particles, the silver particles can indicate the location of the radioactive compound. In some cases, the section can be stained to make the marked part clear. Autoradiography can be used to prepare specimens for optical microscope observation and electron microscope observations. The resolution is about 0.1 m. In the process of autoradiographic specimen processing, since the latex coating step must be performed in a tight dark room to avoid interference from natural light, increase the background, and reduce the self-development effect.

Autoradiography is mainly used to track the distribution and dynamic changes of labeled compounds. Autoradiography is also an important means of gene mapping, the so-called in situ hybridization technique. RNA and the DNA sequence (gene) that it encodes have a complementary base-pairing relationship at the molecular level, so they can combine with each other to form a DNA-RNA molecular hybrid. If radioactively labeled RNA is interacted with a cell slice, the RNA can be bound to complementary DNA fragments in the chromosome. After this slice is subjected to autoradiography, the specific chromosomal site where the RNA gene exists Provide valuable information for genetics and genetic engineering. ^[1]

Autoradiography has a history of more than 100 years, but in terms of breadth of application and depth of problem solving, it has developed particularly rapidly in the past 20 years. Autoradiography can be divided into 4 different levels: overall level, tissue level, cell level and molecular level. The outstanding advantages of autoradiography are: intuitive results, realistic records, and avoiding personal prejudice in interpretation; autoradiography can unify morphology, function, and metabolism to study the dynamic changes in the body. This is its It is unique because it is called a modern functional morphology method; it has high sensitivity and can even record count rates as low as once a day; it is easy to operate. Because of the above-mentioned advantages of autoradiography, especially in recent years due to the improvement of latex and the application of ³ H-labeled compounds, the resolution of autoradiography has reached below 0.1 m using an electron microscope and 1 m under an optical microscope. There are also many improvements in the technical methods of imaging, so they are widely used in biological and medical research. ^[3]

For images obtained by a general photographic process, development and fixing are required to obtain a fixed image.

Development is essentially a redox process. Development starts from the development center. First, the developer (reducing agent) emits electrons and oxidizes itself. The silver ions (oxidants) in the silver bromide crystals then accept electrons and are reduced to silver atoms. The actual process is roughly that the silver australian crystal first adsorbs bromine ions and forms a negative charge layer. A potassium positive ion is adsorbed outside the negative charge layer, and a positive charge layer is formed. In this way, an electric double layer having a certain electrostatic potential is formed between the surface of the silver bromide crystal and the solution. During the development process, the developer must pass through the electric double layer and adsorb to the surface of the silver bromide crystal in order to start the development process. The electrode theory believes that the development center on the surface of the silver crystal of Aussie is because of the silver micro-spots, so it absorbs less bromine ions, and its electric double layer is weak. In this way, the negatively charged developer is easily adsorbed on the development center. Silver micro-spots have good electrical conductivity. Electrons enter the silver bromide crystals from the developer through the silver micro-spots and neutralize with silver ions to form silver atoms. The above process can be summarized into three basic steps, that is, the developer adsorbs on the surface of the photosensitized silver bromide crystal; the developer releases electrons, and the electrons are transferred to the development center; the electrons are combined with silver ions in the silver bromide crystal to form silver atoms, Deposited in the development center. In order to meet the development conditions, the pH value and bromine ion concentration of the developer must be controlled.

After development, there is still a considerable amount of silver halide in the emulsion layer that has not been reduced to atomic silver. The basic role of the fixing process is to dissolve the unsensitized silver halide remaining in the emulsion layer from the emulsion layer and make the image formed by development. During the fixing process, the fixer sodium thiosulfate reacts with the silver halide to form a complex of water-soluble silver, but does not dissolve the reduced metallic silver.

Multiple myeloma (MM) is a B-cell malignant tumor that is common in middle-aged and elderly people. It is characterized by the accumulation of a large number of malignant plasma cells in the bone marrow and secretion of monoclonal immunoglobulins. The clinical manifestations of myeloma are complex, and there are many factors that affect the prognosis, and the survival period varies from months to decades. Traditional prognostic indicators include age, plasma cell index, 2-microglobulin (2-MG), and molecular cytogenetics. In recent years, it has been reported in the literature that absolute lymphocyte count (ALC) has also become one of the prognostic factors of malignant hematological diseases. ^[4] At the same time, studies have confirmed that patients with diffuse large B-cell lymphoma and follicular lymphoma with lower ALC at the onset have shorter survival and poorer prognosis, but there are studies on the correlation between ALC and MM prognosis at home and abroad. less. Therefore, this article retrospectively analyzes 102 cases of newly diagnosed MM patients, analyzes the correlation between ALC and various clinical characteristics and other prognostic factors of patients, and infers the feasibility and clinical application value of ALC as a prognostic indicator of MM.

Autoradiography research subjects

A total of 102 newly diagnosed patients with MM who were admitted to the Tumor Hospital of Tianjin Medical University from December 2007 to February 2012 were collected. For disease diagnosis and staging, refer to "Diagnosis and Efficacy Criteria for Hematology" (third edition) edited by Zhang Zhinan. There were 63 males and 39 females with a median age of 60 (33-83) years. Durie-Salmon (DS) staging: 42 cases of stage I and II, 60 cases of stage 111. International staging system (ISS) staging method: 56 cases of stage I and II, 46 cases of 111 stage. According to the type of M eggs, they were divided into 45 cases of IgG type, 28 cases of IgA type, 8 cases of K light chain type, 15 cases of light chain type, 3 cases of non-secretion type, and 3 cases of plasma cell autohematopathy. Grouped according to renal function: 80 cases in group A and 22 cases in group B.

Autoradiography

A retrospective analysis was performed on 102 patients with myeloma. The age, sex, ALC, lactate dehydrogenase (LDH), albumin (ALB), 2-MG, creatinine (Cr) and their overall survival (overall sur -vival, OS) were grouped by the median of the corresponding ALC, and the correlation between ALC and other clinical indicators was calculated.

Autoradiography follow-up

The follow-up deadline is February 29, 2012. The overall survival time was calculated from the time of diagnosis to death or the last follow-up. All patients who were lost to follow-up were calculated to the date of the last follow-up, and were treated as truncated data. The follow-up method used telephone follow-up.

Statistical analysis of autoradiography

Statistical analysis was performed using SPSS10.5 statistical software package. The count data between groups were tested by ² and the measurement data were analyzed by t test. The Kaplan-Meier method was used to estimate the survival probability, and the results were tested for significance using the Log-rank method. P <0.05 was considered statistically significant. ^[5]