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Results for “Radioactive Tracers”

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PubMed1991

Radioactive tracer techniques in the sequencing of glycoprotein oligosaccharides.

Complete sequencing of the oligosaccharide units of glycoproteins can be performed by conventional physical techniques if nanomole quantities of pure molecules are available. However, isolation of sufficient quantities of a glycoprotein may not be technically feasible (e.g., the analysis of biosynthetic intermediates, or rare molecules). Alternatively, partial structural analyses may answer the biological question at hand. In both instances, radioactive sugars can be used to metabolically label the oligosaccharide units of a glycoprotein, permitting substantial structural characterization. Several aspects of this approach are discussed in this overview, including selection of the labeled precursor, maximization of uptake and incorporation, determinants of the specificity of labeling, and general principles for the release and structural analysis of labeled oligosaccharides. Particular advantages include simplicity, ease of use without sophisticated instrumentation, and the fact that purification to radiometric homogeneity is sufficient. Radioactive tracer techniques cannot replace conventional approaches to sequencing oligosaccharides. However, they do provide a rapid, relatively simple approach to obtaining considerable information from limited amounts of material. For molecules such as short-lived biosynthetic intermediates, there is no substitute for these techniques. This approach has been responsible for the initial identification and characterization of many novel oligosaccharides of biological interest.

Animals↗
PubMed1993

A radioactive tracer technique to determine in vivo the number of fibers in the lungs of rats following their administration by intratracheal instillation.

A radioactive tracer technique is described which enables the total number of fibers present in the lungs of rats to be estimated following administration of the fibers by intratracheal instillation. The glass fiber used in the study was irradiated with thermal neutrons to induce radioactive 24Na. A suspension of the radioactive fiber was administered to eight rats by intratracheal instillation and to two additional rats by intraesophageal instillation. The 24Na radioactivity in the rats was counted in vivo at 24 and 48 hr after administration, after which they were killed. The amounts of fiber in the lungs, in the gastrointestinal tracts, and excreted in feces were estimated radiometrically. On average 93% of the administered fiber was accounted for. The lungs were digested with sodium hypochlorite solution and aliquots of the resulting digest filtered through membrane filters which were clear for examination by phase-contrast optical microscopy (PCOM). The numbers of fibers in the lungs, estimated by PCOM, were well correlated with the in vivo counting rates at 48 hr, indicating that the latter can be used to provide an accurate index of the number of fibers retained in the lung at that time.

Administration, Inhalation↗
PubMed1980

Radioactive tracers and the heart.

The most widely used tracer for the study of the heart muscle is thallium-201. The principal advantage of radioactive tracers in the study of the heart is that they tell us about regional as well as a overall function. In some cases a regional abnormality may be detected before the overall function of the heart is impaired.

Aortic Valve Insufficiency↗
PubMed1994

Estimation of metabolic flux rates in liver purine catabolism of tumour-bearing mice by computer simulation of radioactive tracer experiments.

Mouse hepatocytes from healthy control mice and from Ehrlich ascites tumour-bearing mice were used for tracer-kinetic studies of purine catabolism of liver cells during different periods of tumour growth. The dynamics of the radioactive tracers were modelled mathematically by a system of differential equations. Computer simulations, i.e. direct fitting of numerical solutions of these equations to the observed time-courses of metabolites and specific radioactivities, enables one to estimate unknown kinetic parameters of a simplified model of pathways of hepatic purine catabolism in tumour-bearing mice. There occurred great differences of metabolic flux rates between control hepatocytes, hepatocytes of mice during the proliferating period of tumour growth (6th day after inoculation of the tumour) and hepatocytes of mice during the resting period of tumour growth (12th day after inoculation of the tumour). The final purine degradation of hepatocytes prepared during the proliferating period was lower in comparison with that of control hepatocytes, but it was markedly higher in hepatocytes prepared during the resting period of tumour growth. The changes in hepatocyte purine catabolism during the proliferating period of tumour growth argue for transitions which aim at the maintenance of high purine nucleotide levels in the liver itself rather than for an increased nucleoside and nucleobase supply for the tumour. This suggestion is in accordance with the increased ATP level of the liver during the proliferating phase of tumour growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Migration of a particulate radioactive tracer from the vagina to the peritoneal cavity and ovaries.

In this report we describe a radionuclide procedure designed to evaluate the migration of a particulate radioactive tracer from the vagina to the peritoneal cavity and ovaries, as well as the determination of the patency of the pathways between these two extremes of the female reproductive system. 99mTc-labelled human albumin microspheres (99mTc-HAM) were deposited in the posterior fornices of 24 patients a day before they were to undergo different gynaecological operations. During this period sequential images were obtained and after the operation radioactivity levels in the removed organs and tissues were counted with a scintillation detector. In 14 out of 21 cases, the ovaries and fallopian tubes were counted separately from the uterus. Nine were positive (radioactivity levels were sufficiently high in the tubes and ovaries) and 5 were negative (no substantial radioactivity levels could be detected in either the tubes or the ovaries). The 5 negative results all occurred in patients with proved tubal damage as a result of previous infection. All the results were either true positive or true negative, providing evidence of migration, or obstruction, of 99mTc-HAM from the vagina through the uterus and tubes to the peritoneal cavity and ovaries.

Adult↗
PubMed1983

Studies on the percutaneous absorption of paeonol in experimental animals by a radioactive tracer technique.

Studies on in vivo percutaneous absorption of paeonol (2-hydroxy-4-methoxyacetophenone: I) in rabbits, guinea pigs, and rats were carried out by a radioactive tracer technique. Hydrophilic ointment (specific activity: 376 Bq (0.01016 microCi)/mg) containing I[carbonyl-14C] was applied for 24 h by occlusive dressing treatment on the shaven back of experimental animals. Then, the 14C-activity in urine, which is the dominant excretion route, was determined for 8 days. Percentage excreted within 24 h after application to rabbits, guinea pigs, and rats were 42.8%, 46.5% and 52.0%, respectively. Urinary metabolites were identified as 2,5-dihydroxy-4-methoxyacetophenone, resacetophenone, and substrate I in all the case.

Acetophenones↗
PubMed1985

Model identification and estimation of organ-function parameters using radioactive tracers and the impulse-response function.

Examination of the input-output events in functioning organs by the use of the impulse-response function (IRF) for a radioactive tracer is gaining more and more ground in nuclear medicine. This study summarizes the development of deconvolution analysis, laying special stress on the 'model-free' approach. System linearity and time invariance are discussed, and means of eliminating noise in IRFs originating from the input and organ-time-activity curves are outlined. Typical IRFs are illustrated by flow diagrams, time-domain curves, and their representation by Laplace transforms. The cases of nondiffusible and diffusible tracers as well as parenchymally extracted and transported substances are discussed. Methods for the derivation of models and for the calculation of physiologically important parameters from the IRFs are suggested.

Heart↗
PubMed2006

Methylene blue dye versus combined dye-radioactive tracer technique for sentinel lymph node localisation in early breast cancer.

AIM: The study compared the accuracy and success rate of two techniques, methylene blue alone versus combined methylene blue and radioactive colloid in sentinel lymph node localisation in the management early breast cancer. METHODS: Three hundred and twenty-nine patients with tumours less than 2 cm on ultrasound assessment were prospectively evaluated. One hundred and seventy-three patients (Group A) underwent sentinel lymph node localisation using 1 ml of 1% methylene blue. A combined technique of both methylene blue and radioactive colloid was used in 156 patients (Group B). Application of both was subdermal and subareolar. Sentinel lymph nodes were examined by standard microscopy. Patients underwent breast conservation surgery or mastectomy and sentinel node guided four node axillary sampling+/-clearance. RESULTS: In Group A, the sentinel lymph node identification rate was 96.5%. The negative predictive value was 96.3%, with false negative of 3.7% and accuracy of 87.4%. In group B the identification rate for sentinel lymph node was 98.7%, with false negative of 4.1%, negative predictive value of 96%, and accuracy of 83.8%. CONCLUSION: Sentinel lymph node localisation using methylene blue or combined dye and radioactive tracer technique predicts the axillary lymph node status in early breast cancer with comparable success rates, accuracy and false negative rates. The combined technique facilitates quicker identification of sentinel lymph node; however the dye technique alone can be used successfully in centres without nuclear medicine facilities.

Axilla↗
PubMed2004

Failure in the detection of the sentinel lymph node with a combined technique of radioactive tracer and blue dye in a patient with cancer of the vulva and a single positive lymph node.

BACKGROUND: In early stage vulvar cancer, the sentinel lymph node procedure with a radioactive tracer appears to be a promising new diagnostic tool to predict lymph node status. No detection failures have been published so far in vulvar cancer. We recently experienced failure in the detection of the sentinel lymph node in a patient with a positive lymph node. CASE: A 75-year-old patient with a clinical T2N0M0 squamous cell carcinoma replacing the clitoris underwent a sentinel node procedure. A sentinel node was detected only at one groin. An exploration of the other groin showed a positive lymph node totally replaced by tumor. CONCLUSION: In the case we present, stasis of the lymph flow might be the leading cause of the failure of the sentinel lymph node procedure.

Aged↗