Discussing possible standards of natural radioactivity in building materials

Summary This paper discusses different possibilities of deriving reference values for the natural radioactivity concentrations in building materials to estimate possible additional radiation exposure for the population. Based on comprehensive experimental and theoretical investigations the consequences of the resulting hypothetical reference activity concentrations in building materials, applying different dose limits, were examined. The calculation of the activity concentration standards was performed for standard conditions obtained by earlier studies on exhalation of Radon-222 and Radon-220 from building materials.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday     

Western equine encephalitis in avian populations in North Dakota, 1975

The involvement of wild birds in western equine encephalitis (WEE) and St. Louis encephalitis (SLE) virus activity in the Red River valley area of North Dakota (USA) during a WEE epidemic was investigated in August 1975. Free-ranging birds were captured with mist nets and nestlings by hand. Virologic and serologic results indicated that a similar rate of WEE virus activity occurred throughout Richland County and between permanent and summer resident birds. The rate of SLE virus activity in the birds of Richland County was lower than for WEE virus, but the SLE antibody prevalence was greater in rural areas than within urban locations. Seven of the nine WEE virus isolations were from nestling birds of four different species; the remaining two from adults of two different species. Overall prevalence of neutralizing (N) antibody against WEE virus was 5% in nestling and 14% in adult birds but was the opposite for N antibody against SLE virus, 17% in nestling and 5% in adult birds. Differences between the two viruses in the presence and persistence of maternal N antibody or differential mortality in nestling birds may have caused the disparity in antibody prevalences.     

Influence of phloem transport, N-fertilization and ion accumulation on sucrose storage in the taproots of fodder beet and sugar beet

To investigate the factors governing the accumulation of sucroseand amino acids in the taproots of sugar beet, their contentswere measured in the leaves, phloem sap and the taproots ofsugar beet, fodder beet and a hybrid between both, grown oneither 3.0 or 0.5 mM nitrate. In the taproots the contents ofmalate, citrate and inorganic ions were also determined. Forthe high sucrose accumulation in sugar beet as compared to theother varieties three factors were found. (a) In sugar beet,less amino acids and more sucrose are taken up into the phloemthan in fodder beet. (b) In sugar beet, the sucrose and aminoacid syntheses are less sensitive to the nitrate concentrationsthat are required for optimal plant growth than in other varieties.In fodder beet, upon raising the nitrate concentration from0.5 mM to 3 mM, the synthesis and storage of sucrose is decreasedand that of amino acids increased. The corresponding valuesin sugar beet (0.5 mM) are similar to those in fodder beet andare not much affected by an increase of nitrate. (c) The sucroseaccumulation is limited by the accumulation of inorganic ionsin the taproots. The sucrose content in the taproots is negativelycorrelated to the total ion content. Whereas sucrose representstwo-third of all solutes in the taproots of sugar beet, it amountsto only one-third of the solutes in fodder beet taproots. Key words: Amino acids, Beta vulgans L, phloem sap, potassium, sucrose storage, sugar beet, taproots, transport     

Molekularbiologie der Mukoviszidose

Mukoviszidose ist eine angeborene Funktionsstörung der exokrinen Körperdrüsen. Sie kommt bei etwa 1 : 2500 Lebendgeborenen in der weißen Bevölkerung Europas und Nordamerikas vor und gehört damit zu den häufigsten lebensbedrohlichen Erbkrankheiten des Menschen. Dennoch sind vollständige Beschreibungen des Krankheitsbildes erst seit etwas mehr als fünfzig Jahren bekannt. Die bei den meisten Mukoviszidosekranken auftretenden fibrotischen Veränderungen (Fibrose - Vermehrung des Bindegewebes) der Bauchspeicheldrüse haben zu der Bezeichnung cystic fibrosis of the pancreas geführt, so daß auch der Name zystische Fibrose (cystic fibrosis, CI) heute synonym gebräuchlich ist. Wir wollen im folgenden in kurzer Form auf die Symptome und Ursachen der Erkrankung eingehen. Eine ausführlichere Darstellung der Mukoviszidose und ihrer molekularbiologischen Grundlagen mit zahlreichen Literaturhinweisen ist kürzlich aktualisiert und erweitert worden [21].     

Escherichia coli K12 does not colonize the gastrointestinal tract of Fischer-344 rats

Summary The colonizing potential ofEscherichia coli K12 containing a vector coding for somidobove (bovine somatotropin) was determined. Treated male and female Fischer-344 rats were given a single oral gavage inoculum of sucrose with/without tetracycline (15 g/ml). Untreated control animals received similar drinking water regimes. All animals survived until termination. There were no clinical signs of toxicity observed and no treatment-related effect upon body weight, food consumption, or efficiency of food utilization. Fresh fecal samples were collected from each rat every 24 h following inoculation and the population of the marked strain was quantitated until no bacterial colonies were observed for two consecutive days. While all inoculated rats were positive at 24 h, by 72 and 96 h all had become negative for the test (marked) strain, as were the corresponding control group throughout the test. The frozen stock of the marked strain used as the positive control demonstrated that the agar plates were selective for the test strain. Fourteen days following inoculation, all groups of rats were killed and the gastrointestinal tracts removed and treated to recover the marked strain. There was no evidence of the marked strain in the gastrointestinal tract of any rat from any group. Thus, theE. coli K12 host/vector system used in this experiment does not colonize the gastrointestinal tract of Fischer-344 rats.     

Conjugative plasmid transfer in gram-positive bacteria.

Conjugative transfer of bacterial plasmids is the most efficient way of horizontal gene spread, and it is therefore considered one of the major reasons for the increase in the number of bacteria exhibiting multiple-antibiotic resistance. Thus, conjugation and spread of antibiotic resistance represents a severe problem in antibiotic treatment, especially of immunosuppressed patients and in intensive care units. While conjugation in gram-negative bacteria has been studied in great detail over the last decades, the transfer mechanisms of antibiotic resistance plasmids in gram-positive bacteria remained obscure. In the last few years, the entire nucleotide sequences of several large conjugative plasmids from gram-positive bacteria have been determined. Sequence analyses and data bank comparisons of their putative transfer (tra) regions have revealed significant similarities to tra regions of plasmids from gram-negative bacteria with regard to the respective DNA relaxases and their targets, the origins of transfer (oriT), and putative nucleoside triphosphatases NTP-ases with homologies to type IV secretion systems. In contrast, a single gene encoding a septal DNA translocator protein is involved in plasmid transfer between micelle-forming streptomycetes. Based on these clues, we propose the existence of two fundamentally different plasmid-mediated conjugative mechanisms in gram-positive microorganisms, namely, the mechanism taking place in unicellular gram-positive bacteria, which is functionally similar to that in gram-negative bacteria, and a second type that occurs in multicellular gram-positive bacteria, which seems to be characterized by double-stranded DNA transfer.     

Interactions of VirB9, -10, and -11 with the membrane fraction of Agrobacterium tumefaciens: solubility studies provide evidence for tight associations.

The eleven predicted gene products of the Agrobacterium tumefaciens virB operon are believed to form a transmembrane pore complex through which T-DNA export occurs. The VirB10 protein is required for virulence and is a component of an aggregate associated with the membrane fraction of A. tumefaciens. Removal of the putative membrane-spanning domain (amino acids 22 through 55) disrupts the membrane topology of VirB10 (J. E. Ward, E. M. Dale, E. W. Nester, and A. N. Binns, J. Bacteriol. 172:5200-5210, 1990). Deletion of the sequences encoding amino acids 22 to 55 abolishes the ability of plasmid-borne virB10 to complement a null mutation in the virB10 gene, suggesting that the proper topology of VirB10 in the membrane may indeed play a crucial role in T-DNA transfer to the plant cell. Western blot (immunoblot) analysis indicated that the observed loss of virulence could not be attributed to a decrease in the steady-state levels of the mutant VirB10 protein. Although the deletion of the single transmembrane domain would be expected to perturb membrane association, VirB10 delta 22-55 was found exclusively in the membrane fraction. Urea extraction studies suggested that this membrane localization might be the result of a peripheral membrane association; however, the mutant protein was found in both inner and outer membrane fractions separated by sucrose density gradient centrifugation. Both wild-type VirB10 and wild-type VirB9 were only partially removed from the membranes by extraction with 1% Triton X-100, while VirB5 and VirB8 were Triton X-100 soluble. VirB11 was stripped from the membranes by 6 M urea but not by a more mild salt extraction. The fractionation patterns of VirB9, VirB10, and VirB11 were not dependent on each other or on VirB8 or VirD4. The observed tight association of VirB9, VirB10, and VirB11 with the membrane fraction support the notion that these proteins may exist as components of multiprotein pore complexes, perhaps spanning both the inner and outer membranes of Agrobacterium cells.     

Thorotrast kinetics and radiation dose

Summary As a presupposition for estimating the mean tissue dose from intravascularly injected Thorotrast results of investigations on tissue distribution and steady state activity ratios of²³²Th and daughters in Thorotrast patients were compiled and are presented as best estimates. Special emphasis has been given to the non-uniformity of Thorotrast distribution on the organ 2and cellular level on the basis of results from animal experiments. Moreover, the variation widths of the mean tissue doses were calculated from the individual standard errors of the mean Thorotrast tissue distribution and activity ratios.According to the results of Thorotrast tissue distribution analyses about 97% of intravascularly injected colloidal ThO₂ are retained by the organs of the reticulo-endothelial-system (RES) of the average Thorotrast patient (liver: 59%; spleen: 29%; bone marrow: 9%). Only 0.7 and 0.1% are distributed within the lungs and the kidneys, respectively. The fractional retention of²³²Th in the marrow-free skeleton proved to be 2% on the average. Considering in addition the results on the steady state activity ratios between²³²Th and its daughters and self-absorption of-energy in Thorotrast agglomerates the mean annual tissue doses to the liver, spleen, red bone marrow, lungs (respiratory zone), and cells on bone surface, e.g., from 30 ml intravascularly injected Thorotrast are about 30 (10–70), 80 (30–200), 10 (4–27), 4.5 (1.8–11.3), and 15 (6–38) rad. The variation widths of the mean tissue doses given in brackets are based upon an average individual standard error of the mean Thorotrast tissue distribution and activity ratios of 150%. The data on mean tissue doses, however, do not include variations of the dose due to macroscopic inhomogeneities of Thorotrast distribution on the organ level, which in the liver may go up to a factor of 50. Contrary to the mean tissue dose the local annual dose, i.e., the dose to cells adjacent to the surface of 0.1–50 µm Thorotrast aggregates is between 40 and 40,000 rad.Paper presented on the occasion of a WHO meeting of a Scientific Group on the Long-Term Effects of Radium and Thorium in Man. Geneva, Sept. 12–16, 1977Dedicated to Prof. Dr. med. F. Sommer, Homburg/Saar, on the occasion of his 65th birthday