The separation of proteins from plasma membranes of liver and two Morris hepatomas with different grades of differentiation (Morris hepatomas 7777 and 9121) is described. Size-exclusion high-performance liquid chromatography under non-denaturing conditions provides only poor separation and, with detergent-soluble fractions, unsatisfactory protein recovery. Much better results are obtained by ion-exchange chromatography. The amount of a 175 K protein in the membranes decreased in parallel with the increase in tumour malignancy. This protein appears during ion-exchange chromatography in a broad concentration range, between 0.1 and 0.3 M sodium chloride. Possible explanations for this phenomenon are discussed.

Animals↗

PubMed1986

The selectivity filter of voltage-dependent channels formed by phosphoporin (PhoE protein) from E. coli.

Phosphoporin, an Escherichia coli outer membrane-spanning protein re-incorporated in phospholipid planar bilayers generates aqueous channels similar to those of matrix porin. One phosphoporin trimer contains three pores which are induced simultaneously but fluctuate separately between open and closed states. Membrane potential shifts this two-state equilibrium in favour of closed channels. This negative resistance occurs at lower potentials than with matrix porin channels. The phosphoporin channel is poorly anion selective for small solutes. Polyphosphates and other phosphorylated molecules specifically inhibit phosphoporin pore conductance to small ions, a property which is specific to phosphoporin. There is an excellent correlation between the effect of such solutes measured in planar bilayers and their inhibitory effect on beta-lactam antibiotic uptake in vivo by phosphoporin. It is concluded that the phosphoporin channel contains a selectivity filter which is only efficient for larger molecules, most probably through basic residues.

Adenosine Triphosphate↗

PubMed1986

Uptake of natural and man-made radionuclides by lichens and mushrooms.

Due to the large absorbing surface of the mycelium that grows in the upper parts of the soil mushrooms take up higher amounts of 137Cs and 40K than lichens. Besides these nuclides only the long-lived radionuclides 125Sb and 60Co could be measured; but not the short-lived fission-products 144Ce, 95Zr and 95Nb which probably decayed before absorption into the mycelium. These nuclides, however, are present in lichens because of their surface structures which enable high foliar deposition. The 137Cs-content of lichens is probably due to absorption by the mycobiont and seems to be used to satisfy their potassium-requirements. Mushrooms on the other hand are characterized by a relatively stable potassium-content and a wide ranging 137Cs-content which depends on the availability in different substrates. Occasionally the natural radionuclides 238U and 226Ra could be detected in mushroom and lichen samples, showing no correlation with the natural radionuclide content of the soil.

Basidiomycota↗

PubMed1986

Insect iridescent virus type 6 induced toxic degenerative hepatitis in mice.

The toxic effect of insect iridescent virus type 6 - chilo iridescent virus - (CIV) was investigated using Balb/c mice (strain ByJ Ico and Kisslegg). The animals were inoculated with CIV intraperitoneally (1 X 10(9) to 9.2 X 10(11) TCID50/animal). The animals which were administered with 1 X 10(11) to 9 X 10(11) TCID50 of CIV per animal, developed acute clinical illness and died during 18 to 80 h post infection. Histopathological and electronmicroscopic examinations of the liver tissues of those animals which died and/or were sacrificed when moribund showed acute degenerative hepatitis leading to death. No evidence for viral replication was found in the liver cells affected. A mortality rate between 21.1% and 100% was recorded for CIV, depending on the strain and number of mice used and the dose of virus administered. The toxic effect of CIV was eliminated or reduced extensively using heat denaturation or treatment of CIV with sodium dodecylsulphate or proteinase K. This indicates that the nature of the factor causing toxic degenerative cell damage is a protein.

Animals↗

PubMed1986

[Lumbosacral computed tomography and lumbosacral functional myelography. Dosimetric comparison and comparison of indications].

The integral dose and organ dose produced by spinal lumbosacral CT and lumbosacral functional myelography were compared, using a phantom. The value of these methods of investigation is discussed.

Humans↗

PubMed1986

Biological variability influencing lung dosimetry for inhaled 222Rn and 220Rn decay products.

Particle deposition, clearance and dosimetry of inhaled short-lived 222Rn and 220Rn decay products in the human respiratory tract have been modeled by a stochastic compartment system, based on an already existing deterministic model (Ho82a). In order to allow for statistical uncertainties and biological variabilities, input parameters and transfer coefficients were described by truncated lognormal frequency distributions. Applying Monte Carlo techniques, a set of parameter values is selected randomly in an iterative manner from these prespecified distributions, yielding finally basal-cell doses as probability density distributions instead of single mean doses. The resulting highly skewed dose distributions illustrate the fact that a small percentage of individuals in an exposed population receives considerably higher doses than indicated by a deterministic mean value.

Animals↗

PubMed1986

Lung cancer risk at low doses of alpha particles.

A survey of inhabitant exposures arising from the inhalation of 222Rn and 220Rn progeny, and lung cancer mortality has been carried out in two adjacent areas in Guangdong Province, People's Republic of China, designated as the "high background" and the "control" area. Annual exposure rates are 0.38 working level months (WLM) per year in the high background, and 0.16 WLM/yr in the control area. In 14 yr of continuous study, from 1970 to 1983, age-adjusted mortality rates were found to be 2.7 per 10(5) living persons of all ages in the high background area, and 2.9 per 10(5) living persons in the control area. From this data, we conclude that we are unable to determine excess lung cancers over the normal fluctuations below a cumulative exposure of 15 WLM. This conclusion is supported by lung cancer mortality data from Austrian and Finnish high-background areas. A theoretical analysis of epidemiological data on human lung cancer incidence from inhaled 222Rn and 220Rn progeny, which takes into account cell killing as competitive with malignant transformation, leads to the evaluation of a risk factor which is either a linear-exponential or a quadratic-exponential function of the alpha-particle dose. Animal lung cancer data and theoretical considerations can be supplied to support either hypothesis. Thus we conclude that at our current stage of knowledge both the linear-exponential and the quadratic-exponential extrapolation to low doses seem to be equally acceptable for Rn-induced lung cancer risk, possibly suggesting a linear-quadratic transformation function with an exponential cell-killing term, or the influence of risk-modifying factors such as repair or proliferation stimuli.

China↗

PubMed1986