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Biomedical subjects

W Hofmann

Publications and source records attributed to W Hofmann.

At least 289 records · Page 16Linked to original sources
PubMed1982

Mathematical model for the postnatal growth of the human lung.

Theoretical particle deposition studies for children and youths in practical health physics or medical aerosol therapy require detailed information on alterations of anatomical as well as physiological parameters during postnatal growth. Based on the commonly used anatomical model A of Weibel, assuming regular dichotomy, for an adult human lung, a mathematical model was developed for the calculation of airway parameters, such as geometrical dimensions and number of airways as functions of age. Sometimes widely scattered experimental data obtained by different authors were fitted to analytical functions by a multiregressional procedure. Due to the lack of these data for most of the generations of the anatomical model, theoretical considerations had to be applied. For changes of respiration parameters with progressing age, e.g., tidal volume or respiratory frequency, also experimental data were used. The results of these calculations can then serve as a base for the determination of deposition probabilities in different regions of the human respiratory tract.

Adolescent↗
PubMed1982

Dose calculations for the respiratory tract from inhaled natural radioactive nuclides as a function of age--II. Basal cell dose distributions and associated lung cancer risk.

Dose calculations for inhaled radon decay products presented in Part I (Ho79) have revealed that the doses to tracheobronchial and pulmonary compartments of the ICRP lung model are significantly dependent on age. From a consideration of the nonuniform dose distribution within the tracheobronchial region, doses are now calculated for the bronchial epithelium basal cells which are commonly regarded as the critical target for the induction of lung cancer. For the simulation of deposition and clearance mechanisms a refined mathematical model for postnatal growth of the human respiratory tract was developed on the basis of the Weibel model A. A reference atmosphere of 1 pCi/l for each nuclide with a mean respiratory minute volume, corresponding to a mean physical activity, was used to determine doses for the basal cells in different generations of the tracheobronchial tree as functions of age. The results obtained show again a strong dependence on age. In general a continuous decrease of dose with increasing age can be seen, with distinct differences between the various generations. If, however, the physical activity distribution and the ratio for the decay products as already defined in Part I are used, maximum dose values appear again in all generations at the age of about six years. Application of data on the relative risk of the induction of various malignancies versus age, taken from the BEIR report, results in even more pronounced dose maxima with a significantly higher radiation risk for children between birth and ten years of life of about one order of magnitude as compared to adults.

Adolescent↗
PubMed1982

Distribution and retention of 239Pu in the tree shrew (Tupaia belangeri) following intramuscular injection.

The retention of intramuscularly injected monomeric 239Pu has been studied in the tree shrew (Tupaia belangeri), a primitive prosimian species. Data for the first 2 yr are presented. Resorption from the injection site is rapid, and the main depository organs are skeleton and liver with approximately 50 and 20% of the absorbed dose, respectively. The half life of retention in skeleton is approximately 500-600 days and in liver approximately 150 days, these half lives are compared to data for the retention of transuranium elements in other animal species. Indications of liver lesions were found in 5 animals and 1 animal died at day 790 with an osteosarcoma.

Animals↗
PubMed1982

[Bacterial spectrum and pathogen resistance in chronic primary and secondary pyelonephritis].

The analysis of 168 patients with chronic infections of the urinary tract served to clarify whether different findings are obtained concerning the spectrum of germs and resistance in cases of primary, secondary monoinfected and secondary superinfected pyelonephritis. It was found that in cases of secondary obstructive pyelonephritis the degree of chemotherapeutic sensitivity is reduced and especially where problem germs (proteus, pseudomonas, Klebsiella) are concerned therapy will hardly be successful except by means of aminoglycosides. In this context the recognition and senitation of multifactorial urological primary diseases which cause infection are of special importance.

Anti-Bacterial Agents↗
PubMed1982

[Experimental Klebsiella pneumonia (author's transl)].

Experimental pneumonia was investigated by light microscopic, electron microscopic and morphometric methods in mice infected with the problem spore Klebsiella pneumoniae. In the early stage (2 to 7 hours post infection) we found Klebsiellae and aggregates of platelets in the pulmonary capillaries, but we could not establish significant structural alterations with morphometric methods. The ultrastructural investigation revealed alterations of the alveolar lining cells and the endothelial cells of capillaries and an infiltration of the interalveolar septula with polymorphonuclear and mononuclear leucocytes. These early changes were followed by an intraalveolar infiltration with inflammatory cells. Complement activation is considered as a trigger of the initial inflammatory reaction. The results of our study indicate that bacterial pneumonia starts in the interalveolar septula and secondary involves the alveolar spaces. A restitutio ad integrum of the lung develops 11 days post infection.

Animals↗