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Biomedical subjects

W Hofmann

Publications and source records attributed to W Hofmann.

At least 253 records · Page 14Linked to original sources
PubMed1985

Lung cancer incidence in a Chinese high background area--epidemiological results and theoretical interpretation.

A survey of inhabitant exposures arising from the inhalation of radon and thoron daughters, and lung cancer mortality has been carried out in two adjacent areas in Guangdong province, China, designated as the "high background" and the "control" area. Annual exposure rates are 0.38 WLM/yr in the high background, and 0.16 WLM/yr in the control area, while age-adjusted mortality rates are 2.7 per 10(5) living people of all ages in the high background, and 2.9 per 10(5) in the control area. From this data we conclude that we are unable to determine the excess lung cancer rate over normal fluctuations below a cumulative exposure of about 15 WLM. This conclusion is supported by lung cancer mortality data from an Austrian high background area.

China↗
PubMed1985

Binding of myosin subfragment 1 to glycerinated insect flight muscle in the rigor state.

The binding of rabbit muscle myosin subfragment 1 (S1) to glycerinated insect flight muscle fibers has been studied by low-angle x-ray diffraction, quantitative sodium dodecyl sulfate gel electrophoresis, quantitative interference microscopy, and electron microscopy. Changes induced in the rigor x-ray diffraction pattern are consistent with the idea that vacant myosin-binding sites on thin filaments are filled by exogenous S1. Electron microscopy indicates that S1 permeates and labels fibers and fibrils completely. Electron micrographs also show that cross-bridges are not displaced by exogenous S1 under the conditions used, and this is supported by the unchanged mechanical stiffness of the S1-labeled fibers. The amount of bound S1, as measured by gel electrophoresis and interference microscopy, together with the magnitude of the intensity changes in the x-ray diffraction pattern, is consistent with a thick filament structure that contains four molecules of endogenous myosin per 14.5 nm of its length, but does not agree well with earlier estimates of six myosins per crown. Lack of information on possible inhibition of S1-binding by factors other than the presence of cross-bridges, e.g., troponin, render uncertain calculations of the number of attached cross-bridges in the rigor state. However, it appears that at least 75% of the endogenous myosin heads are attached. Occupancy of binding sites on thin filaments after incubation with S1 is high, probably greater than 85%, so that x-ray scattering from those parts of the structure that adhere to the symmetry of the thin filaments can be treated as diffraction from S1-decorated thin filaments. In addition, we show in thin flared X cross sections that exo-S1 heads bind to actin with the geometry described in decorated actin by Taylor, K.A., and L.A. Amos.

Actins↗
PubMed1985

Analysis of human lung morphometric data for stochastic aerosol deposition calculations.

A stochastic lung model is proposed for aerosol deposition calculations. Airway geometry is selected randomly to reflect intrasubject variations in the human airway system. This may also be adjusted to take intersubject variations into account. The statistical analysis of the human airway geometry used is based on morphometric data measured at the Lovelace Inhalation Toxicology Research Institute. Average values and distributions of airway diameters and lengths, distributions of branching angles and criteria for termination of the pathway (when the alveolar region is reached) are presented. Correlations between the cross sections of tubes of succeeding generations and those between diameters and lengths of the same generation are also given.

Aerosols↗
PubMed1985

Health effects and risks from 222Rn in drinking water.

This paper presents an evaluation of the inhalation and ingestion doses from exposure to Rn and Rn progeny; an overview of the human and animal health-effects data; estimations of the cancer risks from Rn and Rn-progeny exposures; and suggested limits for Rn concentrations in drinking water and indoor air. We suggest that a rounded Rn-in-water concentration limit of 10,000 pCi/l can be supported by health-effects considerations alone, based on the conservative "tolerance dose" concept and other conservative assumptions regarding lung dose. A practical concentration limit (or action level) of 20,000 pCi/l has been derived by estimations of exposure distributions in the United States and in relation to current U.S. Environmental Protection Agency (EPA) standards for U-tailings-contaminated buildings. Research needed for resolution of the uncertainties in these estimates is suggested. We conclude that before a maximum contaminant level (MCL) for Rn in water can be firmly established, the broader issue of setting the MCL for Rn in indoor air must be addressed.

Air Pollutants, Occupational↗
PubMed1985

Thymoma. A clinicopathologic study of 98 cases with special reference to three unusual cases.

98 thymomas were assessed in respect to clinical manifestations, gross and histologic pathological findings and clinicopathologic correlations. 34% of patients were asymptomatic and thymoma was detected fortuitously. The most common presenting symptoms were related to myasthenia gravis, symptoms due to pressure on mediastinal structures were next in frequency. The symptom-diagnosis interval ranged from 0 to 120 months with a median of 4,5 months and was longer in invasive thymomas (median 6 months) than in noninvasive thymomas (median 2 months). 52% of thymomas were encapsulated and showed no cytologic atypia and were therefore classified as benign encapsulated thymomas. 26% showed gross invasion of peripheral structures and 3% were thymic carcinomas on histologic grounds. Histologically 55% of thymomas were epitheloid cell type, 17% spindle cell type and 20% mixed type thymomas. Epidermoid type thymoma occurred in 3% of the cases. 3 cases showed some unusual morphologic feature: one was localized intrapulmonal, another had an outspread like a mesothelioma, and the third was a basaloid carcinoma with unusual goblet cell metaplasia. In the three cases immunohistological methods were used as a diagnostic tool. The lectins UEA-I, PNA and HPA and an anti-keratin allowed the diagnosis of epithelioma (in 2 cases) and showed some more cellular and structural differentiations (in 1 case).

Adolescent↗
PubMed1984

Cryo-electron microscopy of vitrified insect flight muscle.

Frozen hydrated sections of vitrified unstained insect flight muscle in the rigor and relaxed states were studied by cryo-electron microscopy. High resolution images with good contrast were obtained. As judged from direct images and from the comparison of optical diffractograms with X-ray diffraction patterns obtained from glycerinated muscle fibres, the vitrified specimen is well preserved. Preparation artifacts encountered in conventional plastic sections are avoided. The preservation of the relaxed structure also seems better than in freeze-etched replicas as the 14.5 nm repeat of crossbridges on thick filaments is easily visible.

Animals↗
PubMed1984

Lymphoepithelial carcinoma (Schmincke type) as a derivate of the tonsillar crypt epithelium.

Ten tumours of tonsillar or epipharyngeal localization showing the histological picture of "lymphoepithelial carcinoma" (Schmincke 1921) were examined immunohistochemically using Peanut lectin, Ulex europaeus lectin-I and an antiserum to S-100 protein. The findings suggest a close relationship of this type of carcinoma to the normal tonsillar crypt epithelium. The majority of tumour cells are UEA-I-positive and PNL-negative, as is the crypt epithelium, while oral mucosa is both PNL- and to a lesser extent UEA-I-reactive. Tumour areas expressing this pattern contain a large number of asteroid-shaped PNL-positive histiocytes and arachnoid-shaped histiocytes reacting with anti-S-100 protein; both cell types being probably identical and representing typical elements of the normal tonsillar crypt epithelium. Consequently, the WHO-term "nasopharyngeal carcinoma, undifferentiated type" seems to be inadequate for this type of tumour.

Carcinoma, Squamous Cell↗
PubMed1984

Some comments on the concepts of dose and dose equivalent.

Although dose is the simplest and most widely used measurement of a radiation field, it does not always lead to an unambiguous estimate of response. This is reflected in the very wide range of relative biologic effectiveness (RBE) values for biological systems. The ambiguity arises from the focus on energy deposition as the source of biological effect, whether in macroscopic or microscopic volumes. The properties of the biological detector play a role equally important to the properties of the radiation field in their interaction. To predict even the most experimentally accessible biological response, cell killing, we must know the probability per unit path length for generating the observed end point. Especially for high LET radiations we need the action across sections and the particle-energy spectrum. No one parameter reduction of a radiation field can predict biological effect. For cell killing such a prediction can be made, however, from a two-parameter reduction of the interaction between the radiation field and a specific cell line and a specific ambience of the survival curve for the specific radiation field. The determination of these two parameters leads to a suggested new procedure for evaluating the dose equivalent.

Cell Survival↗
PubMed1984

CAT scan and immunohistochemical findings in a case of cerebral thromboangiitis obliterans (Buerger's disease).

Immunohistochemical examinations were carried out in a case of thromboangiitis obliterans. A 26-year-old man developed 4 brain infarctions which could be demonstrated by CAT scan. He suffered from a left-sided hemiparesis, major epileptic seizures, and an ischemic optic neuritis. Immunologic studies supported a diagnosis of cerebral thromboangiitis obliterans (CTAO). The serum anti-elastin titer as well as IgE were considerably increased and a biopsy of the temporal artery showed immunohistochemical signs of an acute inflammatory vessel disease. After the diagnosis of CTAO had been made, the patient was treated with azathioprine and dexamethasone. In cases of young stroke patients, a temporal biopsy is important in confirming the diagnosis.

Adult↗
PubMed1984

[Staging of metastasized bladder cancer using parietocystotomography].

To date no diagnostic procedure has been able accurately to stage carcinomas of the urinary bladder. Parietocystotomography by means of instillation of air and nitrous oxide was used in an attempt to distinguish between the tumour infiltration stages T3A , T3B and T4 and to depict them radiologically. Using this method it is possible to achieve a high degree of concurrence between radiological findings and the pathological-anatomical substrate. The methods, results achieved and the limits of the procedure are demonstrated.

Aged↗