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U Wellner

Publications and source records attributed to U Wellner.

At least 19 recordsLinked to original sources
PubMed2001

[Influence of stable iodine on the uptake of the thyroid--model versus experiment].

AIM: The influence of physiological and pharmacological amounts of iodine on the uptake of radioiodine in the thyroid was examined in a 4-compartment model. This model allows equations to be derived describing the distribution of tracer iodine as a function of time. The aim of the study was to compare the predictions of the model with experimental data. METHODS: Five euthyroid persons received stable iodine (200 micrograms, 10 mg). I-123-uptake into the thyroid was measured with the Nal(Tl)-detector of a body counter under physiological conditions and after application of each dose of additional iodine. Actual measurements and predicted values were compared, taking into account the individual iodine supply as estimated from the thyroid uptake under physiological conditions and data from the literature. RESULTS: Thyroid iodine uptake decreased from 80% under physiological conditions to 50% in individuals with very low iodine supply (15 micrograms/d) (n = 2). The uptake calculated from the model was 36%. Iodine uptake into the thyroid did not decrease in individuals with typical iodine supply, i.e. for Cologne 65-85 micrograms/d (n = 3). After application of 10 mg of stable iodine, uptake into the thyroid decreased in all individuals to about 5%, in accordance with the model calculations. CONCLUSION: Comparison of theoretical predictions with the measured values demonstrated that the model tested is well suited for describing the time course of iodine distribution and uptake within the body. It can now be used to study aspects of iodine metabolism relevant to the pharmacological administration of iodine which cannot be investigated experimentally in humans for ethical and technical reasons.

Biological Transport↗
PubMed2000

[Effect of iodine application during radioiodine therapy in patients with impending therapy failure].

AIM: We investigated whether additional application of "cold" iodine after therapy with radioiodine could result in a prolongation of the effective half life of iodine-131 and would thus lead to an increase of the effective thyroid radiation dose. METHODS: Time-activity-curves after therapy with radioiodine were analysed in 25 patients (16 women, 9 men). Nine patients suffered from autonomously functioning thyroid nodules, 5 from autonomous multinodular goiter and 11 from Graves' disease. These patients had an effective half life shorter than 4 days resulting in an undertreatment of > 20% with respect to the desired effective thyroid radiation dose. 2-4 days after therapy with radioiodine all patients received "cold" iodine for three days in a dose of 3 x 200 micrograms per day. RESULTS: In 14 of the 25 patients an increase of the effective half life was observed. Patients with an autonomously functioning thyroid nodule showed a mean increase of the effective thyroid radiation dose of 40 +/- 44 Gy, patients with toxic multinodular goiter of 29 +/- 30 Gy and patients with Graves' disease of 37 +/- 37 Gy. CONCLUSION: Additional application of "cold" iodine after therapy with radioiodine can prolong the effective half life in selected patients. We suspect a correlation with the thyroid iodine pool. This will be the basis for further investigations hopefully resulting in a better patient preselection to determine who might respond to this therapy.

Adult↗
PubMed1998

[Exposure of relatives of patients after stationary radioiodine therapy by inhalation of 131I in their homes].

AIM: From a model of iodine metabolism exhalation coefficients shall become derived to calculate 131I exhalation by patients after a radioiodine treatment. The validity of these exhalation coefficients shall be reviewed by whole body activity measurements of relatives of patients, who inhaled the radioiodine exhaled by the patients in their homes. The exposure of relatives to patients of a nuclear medical ward after release by exhalation of iodine-131 is investigated. METHODS: Iodine 131I-activity of 17 relatives to patients who had to undergo a radioiodine therapy became measured in a whole body counter only a few days after release of the patient from the nuclear medical ward. The results of the measurements have been compared with the results of calculations according to the model of iodine metabolism. RESULTS: The calculated values of incorporated radioiodine in the relatives of the patient at time of measurement (Amodel) correlate with the measured whole body activity (AGK) according to the regression: Amodel = AGK -47.3 (r2 = 0.959). This relation holds if 2.1 micrograms of iodine become exhaled per day of the 60 micrograms of iodine which are the daily intake of iodine by food. The exposure of all relatives did never exceed 100 microSveff. Using the same model parameters the effective dose equivalent of the relatives to our patients rises up to 6.5 mSv under ambulant radio therapy condition. CONCLUSION: The daily exhalation of 131I is able to be calculated by a mathematical model of iodine metabolism. After staying of patients at least 3 days in a nuclearmedical ward the exposure of relatives of patients in their home does not exceed the value of 100 microSveff by inhalation of iodine-131. This are 10% of the limit of 1 mSveff according to the Recommendations of the Commission on Radiological Protection (ICRP 60). Radioiodine therapy outside of a hospital and "iodine therapy tourisme" of German patients to other countries cannot be accepted.

Air Pollution, Indoor↗
PubMed1996

[Influence of physiological and pharmacological amounts of iodine on the 131I uptake of the thyroid gland--a model calculation].

AIM: The aim of this paper was to use a iodine metabolism model in order to analyze theoretically the different aspects of the iodine metabolism. METHOD: To perform this a three compartment model was developed. RESULTS: With this model we examined the influence of physiological and pharmacological iodine amounts on the iodine-131 uptake in the thyroid gland and additionally the excretion of Iodine-131 after radiotherapy. It can be said, that an in-patient admission for a duration of at least three days to perform a radiotherapy is sensible (wise) and a iodine-poor diet prior to the radiotherapy is of advantage. Regarding the iodine blockade of the thyroid gland after a reactor accident the effects (outcome) of the German recommendations were compared with the WHO-guidelines. CONCLUSION: The model of iodine metabolism is suited for analyses even if because of ethic or other limitations measurements at human beings are not possible.

Germany↗
PubMed1996

[Relationship between properties of 131I therapy and radioiodine kinetics].

AIM: The reason of unreproducible data under diagnosis and therapy with radioiodine should be elucidated. METHODS: The iodine content of the capsules was tested by a colorimetric method and by activation analysis. Radiochemical purity was determined by HPLC and by electrophoresis. Solubility of the capsules was investigated under different conditions. RESULTS: The iodine content of the capsules varied between 0.8 and appr. 100 micrograms/capsule. The radiochemical purity of the capsule iodine varied between 75% and 99.5% (main contamination: iodate). The solubility of the capsules differed. CONCLUSION: Additional non-radioactive iodine in the therapy capsules could be one reason of the reduced radioiodine-uptake under therapy.

Capsules↗
PubMed1994

[Benefit/risk considerations in diagnostic nuclear medicine].

The potential radiation risk carried out by diagnostic nuclear medicine has to be compared with the potential diagnostic and/or therapeutic benefit. An undifferentiated consideration of collective doses and risks is inappropriate. On the contrary, several factors have to be considered: the age of the patients, the prevalence of pathological test results, and the potential benefit from the diagnosis. This paper presents statistical data and individual examples. In many cases benefit exceeds risk substantially. On the other hand in some cases restrictions of diagnostic radiology or nuclear medicine should be considered.

Humans↗
PubMed1993

[The treatment of thyroid diseases using 131I in a special ward with a liquid waste storage plant].

This paper deals with the calculation of doses for organs of special interest under 131I treatment of thyroid diseases. Also the effective dose equivalent to the body of the patient, exclusive of the thyroid, is given. The ratio between the exposure by self-irradiation and the exposure from another patient in 2 m distance both having undergone 131I treatment with 50% uptake, is about 1000:1. Therefore positioning of a lead shield between two such patients in the same room is, from the point of view of radiation protection, unnecessary. A complete mathematical description of iodine distribution in a nuclear medicine ward and its liquid waste storage plant is given. The use in the authors' own department of these equations is demonstrated. Computer programs for additional calculations are available.

Humans↗
PubMed1990

Vitamin A deficiency increases noise susceptibility in guinea pigs.

The effect of vitamin A deficiency in guinea pigs on noise-induced temporary threshold shift (TTS) was evaluated after short (15 min) acoustic overstimulation with a moderate (90 dB) broad-band white noise. Some guinea pigs were fed ad libitum a purified diet deficient in vitamin A (VAD group) until biochemical signs of deficiency occurred. A second, control group (VA group) received the same diet as well as 100 IU vitamin A daily by pharyngeal tube. Cochlear potentials were recorded by special computerized equipment using implanted electrodes. Before acoustic stimulation, a baseline value was determined with a test stimulus [90 dBA (A-filter according to usual DIN instructions)] corresponding to that for TTS measurements. Noise-induced changes were determined by calculating the changes in latency and amplitude of the N1-signal of the compound action potential (CAP) at various times (1, 3, 5, 7, 11 min) after termination of acoustic stimulation in comparison with baseline values. Statistical analysis of the CAP data showed that the VAD group had significantly smaller amplitudes and increased latency of the N1-potential after acoustic stimulation and that the VA group did not show a significant change in amplitude or latency. The reduction in N1-amplitude and N1-latency in the VAD group reflects changes in inner ear hair cell activity. We conclude that vitamin A deficiency increases the sensitivity of the inner ear to noise and that this increased sensitivity increases the probability of noise-induced hearing loss.

Acoustic Stimulation↗
PubMed1989

[A pharmacokinetic approach to studying the uptake of 137Cs by children following the reactor accident at Chernobyl].

The course of 137Cs content of children after the reactor accident of Chernobyl measured by means of a whole-body counter could be reconstructed theoretically by a pharmacokinetic model. The children of the kindergarten of the hospital of the University of Cologne accumulated during the vegetation periods 1986/87 (I) 86.9, 1987/88 (II) 114.4 and 1988/89 (III) 24.4 Bq 137Cs per kg body weight.

Accidents↗
PubMed1986

Vitamin A and ciliated cells. I. Respiratory epithelia.

To estimate the role of vitamin A on ciliated cells we investigated whether ciliated cells undergo any alteration during vitamin A deficiency. The epithelia examined include the ciliated cells of the respiratory tract and the ciliated sensory cells of the inner ear, the tongue, and the olfactory cells. This part of the paper will describe the ciliated epithelium of the tracheobronchial tract and its relation to vitamin A status. During vitamin A deficiency a partial loss of ciliae can be observed before any squamous metaplasia (which usually occurs during longer lasting vitamin A deficiency) develops. The scanning electron microscopic data illustrate the altered surface of the epithelium during vitamin A deficiency better than transmission electron microscopy.

Animals↗
PubMed1986

Kinetic models of metabolism.

The model structure established here can be applied to tracer kinetics, pharmacokinetics and to non-equilibrium responses. Furthermore the possible and impossible pathways of metabolism can be determined directly leading to a special model version corresponding to a special kinetic problem.

Humans↗
PubMed1985

Vitamin A deficiency and sensory function.

Morphological investigation of tongue, olfactory epithelia, trachea and inner ear in vitamin A deficiency are reported. The results support assumptions concerning the loss of sensory function as been at least a secondary effect of alterations of the neighbourhood of the sensory cells caused by vitamin A deficiency. Taste buds are hindered in function by a dense layer of squamous cells and olfaction is decreased by atrophy of the surrounding respiratory epithelium. Inner ear functionality seems to be affected by vitamin A status via a stabilizing effect on the endolymph-perilymph barrier.

Animals↗
PubMed1984

The influence of elevated iodide supply on the autonomously functioning thyroid gland.

A pharmacokinetic two-compartment model of iodine metabolism has been established on the basis of data from the literature and our own experimental investigations. By this model it is possible to estimate the effects either of prolonged elevation of iodide supply or of a single administration of a high dose of inorganic iodide in the presence of autonomously functioning thyroid tissue. Prolonged elevation of iodide supply in regions of iodine deficiency will cause manifest hyperthyroidism in many cases of thyroidal autonomy (cases with facultative hyperthyroidism). The administration of a single high dose of iodide, as it is proposed for the situation of an accident in a nuclear power station (100 mg NaI) in order to reduce the radiation burden to the surrounding population, carries almost no risk in cases of thyroid autonomy.

Disaster Planning↗