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Biomedical subjects

D V Becker

Publications and source records attributed to D V Becker.

At least 37 records · Page 2Linked to original sources
PubMed1987

Reactor accidents. Public health strategies and their medical implications.

In a reactor accident with release of radioactivity, the major potential public health risks are likely to result from radioiodines, particularly iodine 131, which can be readily volatilized and dispersed. They are rapidly absorbed and concentrated by the thyroid, which could result in substantial thyroidal radiation. Although some forms of radiation can cause thyroid cancer in humans, 131I has not been shown to do so, and 40 years of safe experience with this radionuclide in routine clinical thyroid testing and treatment has been reassuring. Nevertheless, since 131I has been shown to cause thyroid neoplasms in animals, efforts to minimize unwarranted exposure seem advisable. Potassium iodide, administered at an appropriate time, will effectively block thyroid uptake, but it has potential toxicity and may be difficult to distribute effectively and safely on a large scale in an emergency. Evaluation of the risks and benefits of potassium iodide use is essential to establishing sound public health policy but awaits additional scientific information.

Accidents↗
PubMed1987

Autonomy of growth and of iodine metabolism in hyperthyroid feline goiters transplanted onto nude mice.

Hyperthyroidism caused by nodular goiters is a common disease of aging cats. Growth and iodine metabolism were studied by autoradiography in normal and hyperfunctioning thyroid tissue obtained from cats injected with 125I before surgery, and in xenografts, grown in nude mice, after double-labeling with 131I and [3H]thymidine. Hyperthyroid cat goiters contain single or multiple hyperplastic nodules, consisting of highly cellular tissue with an iodine metabolism exceeding that of the surrounding normal tissue. Xenografts of hyperplastic hot tissue in thyroxine-treated nude mice retain their original histologic pattern and continue to accumulate radioiodine intensely. Autoradiographs assessed for [3H]thymidine incorporation reveal autonomously proliferating follicular cells within the hyperplastic foci but not within the normal tissue. Administration of sera from donor cats into host mice fails to stimulate the xenografts. Neither hyperfunction nor growth of toxic cat goiters depends on extrathyroidal stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells.

Animals↗
PubMed1984

The use of iodine as a thyroidal blocking agent in the event of a reactor accident. Report of the Environmental Hazards Committee of the American Thyroid Association.

In the event of a nuclear reactor accident, radioactive materials could be released into the environment: radioisotopes of iodine could constitute a major component of such a release. Upon such exposure, radioiodines could enter the body and accumulate in an unprotected thyroid gland where they would remain for varying periods of time. A number of methods have been proposed to protect those at risk of exposure. Administration of thyroid-blocking agents (such as potassium iodide) to exposed populations could be effective, but their use has raised a number of questions since there are considerable gaps in the scientific information available about the possible effects of low-level radiation from radioiodine. In addition, there are only limited data available about potential toxic side effects of potassium iodide distributed widely to large, unsupervised populations. Concern about these issues led the American Thyroid Association to appoint a committee of its members with special interest and competence in these areas to review the problems in detail and develop an advisory statement on the questions at issue for those to whom this matter might be of concern.

Accidents↗
PubMed1983

Feline hyperthyroidism: pretreatment clinical and laboratory evaluation of 131 cases.

Hyperthyroidism was diagnosed in 131 cats during a 3 1/2-year period. The cats ranged in age from 6 to 20 years; there was no breed or sex predilection. The most frequent clinical signs included weight loss, polyphagia, increased activity, polydipsia, polyuria, and vomiting. Common serum biochemical abnormalities included high values for alkaline phosphatase activity (75%), lactate dehydrogenase activity (66%), aspartate transaminase activity (66%), and alanine transaminase activity (54%). Electrocardiographic changes included tachycardia (greater than or equal to 240 beats/min) and increased R-wave amplitude in lead II (greater than or equal to 0.9 mV) in 66% and 29% of the 131 cats, respectively. Thoracic radiography in 82 cats revealed cardiomegaly in 40 (49%) of these cats; 16 cats with congestive heart failure also had pulmonary edema or pleural effusion. In 5 cats with markedly increased fecal volume, mean 48-hour fecal fat content was significantly greater than normal, with daily fat excretion 2 to 15 times the upper limit of normal. Base-line serum thyroxine concentrations were increased above normal range in all cats, whereas triiodothyronine concentrations were increased in 127 (97%) of the 131 cats. In 11 cats tested, mean thyroxine concentration did not increase significantly after thyroid-stimulating hormone administration. Mean 24-hour percentage of thyroid radioiodine uptake in 32 hyperthyroid cats was significantly higher (39.1%) than normal (9.2%). Thyroid scans, performed on 126 cats, showed enlargement and increased radionuclide accumulation in 1 thyroid lobe in 36 (29%) and both lobes in 90 (71%) of the cats.

Adenocarcinoma↗
PubMed1981

Thyroid suppression and stimulation testing: The place of scanning in the evaluation of nodular thyroid disease.

In the past, T3 suppression testing was often required to confirm the presence of autonomous thyroid function in patients with borderline clinical and laboratory findings suggestive of hyperthyroidism or in euthyroid patients with the stigmata of Graves' disease. Similarly, TSH stimulation testing was used to document the presence of "low thyroid reserve" in patients with borderline clinical and laboratory findings suggestive of hypothyroidism. The current availability of radioimmunoassays for triiodothyronine (T3) and thyrotorpin (TSH) plus the ability to evalate pituitary responsiveness by performing a TRH stimulation test permits a definitive diagnosis to be made in the majority of borderline situations without recourse to the more cumbersome suppression and stimulation tests. Suppression and stimulation thyroid scanning retain a unique position in the evaluation of localized areas in increased uptake of radionuclide (hot nodules), especially in patients who are euthyroid. Proof that such nodules are autonomously functioning thyroid adenomas (AFTN) greatly decreases the possibility that they represent malignant thyroid tumors. Suppression and stimulation scanning have a more limited role in the evaluation of patients with hyperthyroidism arising in a multinodular goiter, where TSH stimulation scanning may help to differentiate between toxic multinodular goiter and Graves' disease arising in a preexisting goiter.

Diagnosis, Differential↗
PubMed1975

The iodine requirement and influence of iodine intake on iodine metabolism and thyroid function in the adult beagle.

Various aspects of iodine metabolism were studied in adult beagles maintained at iodine intake levels ranging from 480 to 20 mug/day. On the basis of changes in radioiodine metabolism, the minimum daily iodine requirement of the adult beagle was found to be 140 mug. Although striking changes were observed in radioiodine metabolism when iodine intake was reduced to 90mug/day, serum T4 and T3 levels were unaffected. Marked reductions in serum T4 occurred in dogs restricted to an iodine intake of 50 or 20 mug/day, but even at these low levels of iodine intake there were only slight reductions in serum T3 concentration and a eumetabolic state was maintained. Prolonged iodine deficiency (8-12 months) resulted in variable patterns of thyroid histology, which were related to differences in thyroidal 127I content and in the rate of release of radioiodine from the thyroid. The heterogeneity in thyroid morphology and iodine kinetics did not, however, have a significant effect on serum T4 and T3 levels.

Animals↗