A Monte Carlo simulation of Auger cascades

The energy imparted to biological tissue after the decay of incorporated Auger emitters stems from two sources: (a) energy deposition by the Auger and Coster-Kronig electrons and (b) the charge potential which remains on the multiple ionized atom after the end of the cascade. For the numerical assessment of both the kinetic energy of the released electrons and the charge potential, a new and--for purposes of microdosimetry--precise method is presented. Based on relativistic Dirac-Fock calculations and a rigorous bookkeeping, this method provides a perfect energy balance of the considered atomic system when applied to Monte Carlo simulations of Auger cascades. By comparing the results for charge distribution for krypton and iodine with experimental data and the electron spectrum of 125I with theoretical data, it can be shown that the approach followed in this work is reasonable and appropriate for the determination of the energy deposited by incorporated Auger emitters in small volumes of condensed matter. The total energy deposited by 125I in a volume of 20-nm diameter is 2.03 keV which is made up by multiple ionization (1.07 keV) and energy deposition by the emitted Auger electrons (0.96 keV).     

Morphological changes in the central canal of the cat after kaolin injection into the cisterna magna

40 adult cats were made hydrocephalic by intracisternal injection of 200 mg Kaolin. 34 survived between 24 hours to 4 months. In 19 cases a ventriculostomy was carried out, whereby in 13 animals a contrast filling of the central canal occurred. The contrast medium injected into the ventricles entered the external CSF-space in the lumbo-sacral junction of the filum terminale. Light- and electron-microscopic studies showed adaptive structural changes of the central canal epithelium in the early stages. In later stages massive destructions of ependyma and spinal cord parenchyma were found.     

Secretory phenomena at the ependyma of the sulcus hypothalamicus Monroi of the fetal rat. A histochemical and electron microscopic study

In a localized area above the sulcus hypothalamicus Monroi ventriculi tertii of the rat ependymal structures are observed, which only occur between the 18th and 20th day of gestation. They were investigated with the aid of lightmicroscopic, ultrastructural and histochemical technics. The surface of the ventricular wall is rendered irregular by protrusions and deposits. Neurosecretory stains and histochemical examination give no positive results. Apical parts of the ependymal cells are fingershaped, dome-like and of spheric appearance. The equipment of the protrusions with organels is variable. Some of them contain a fine granular ground plasma, polyribosomes and occasional profiles of the endoplasmatic reticulum. Others are impacted with optic empty or substantial vacuols. Vacuols merging in the cellular membrane evacuate their content into the ventricular space. Multivesicular bodys engorged with vesicles are together with those, which lie empty in the ventricular cavity. Empty, buddle like and frequently folded membrane protrusions suggest that cellular content has been delivered into the ventricle.     

Cellular and nuclear volume of human cells during the cell cycle

Summary The volumes of whole cells and nuclei of cultured human cells were studied at different times after synchronization of growth using the Coulter counter and scanning microphotometry. It was found that the increase in cell volume is compatible with both linear or exponential growth during the cell cycle. The growth of the nuclear volume is not correlated with the beginning of the DNA synthesis. The nuclear volume starts to increase already 6 h prior DNA synthesis. The data also indicate that the nuclear volume growth could proceed in two stages. The relation of this result to radiation sensitivity is discussed.This research was carried out under contract no. 215-76-10-BIO-D, Radiation Protection programme of the Commission of the European Community (Publication no. BIO 1747)     

Neutron scattering and energy deposition spectra

Summary The influence of neutron scattering in the wall of a spherical proportional counter on the energy deposition spectra and the absorbed dose is investigated. Event probabilities, and frequency and dose-averaged deposited energies are calculated with and without scattering contribution and compared. The change of absorbed dose due to attenuation of the primary neutron flux is also evaluated.Contribution No. 1157 of the Biology Programme, Directorate General XII of the Commission of the European Communities.     

Two-dimensional electrophoresis of soybean root plasma membrane proteins solubilized by SDS and other detergents

Proteins solubilized from enriched soybean root plasma membrane with sodium dodecyl sulphate (SDS) and selected non-denaturing detergents (octyl-β-d-glucopyranoside, Zwittergent 312, Zwittergent 314, Zonyl FSK, and Nonidet P-40) were electrophoresed in two-dimensions by standard procedures. The basic electrophoretogram ‘fingerprint’ was similar for all detergents tested. However, differences in the total number of polypeptides resolved and the presence or absence of certain polypeptides on specific two-dimensional gels indicated some selectivity. Of all detergents tested, SDS solubilized the most polypeptides (ca 95) and provided the best resolution. The other detergents solubilized 50–80 polypeptides with varying resolution. Of those tested, octyl-β-d-glucopyranoside consistently provided the best balance between the number of polypeptides resolved (ca 70) and the level of resolution. The results suggest that selected detergents may prove useful in plant plasma membrane studies which require non-denaturing conditions.