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.     

Effect of Protease Inhibitors on Early Events of Apoptosis

Proteolysis is an early event of apoptosis which appears to be associated with activation of the endonuclease which is responsible for internucleosomal DNA cleavage. The present study was designed to reveal the possible role of proteolysis in other early events, such as chromatin condensation, nuclear breakdown, and destabilization ofin situDNA double-stranded structure. Apoptosis of human leukemic HL-60 cells and rat thymocytes was induced by different agents, including DNA topoisomerase inhibitors, an RNA antimetabolite, and the glucocorticosteroid, prednisolone. DNA degradation was evaluated by pulsed field and conventional gel electrophoresis and by the presence ofin situDNA strand breaks. DNA stability was estimated by the measure of its sensitivityin situto denaturation. Chromatin condensation, nuclear breakdown, and other morphological changes were monitored by interference contrast and UV microscopy following cell staining with the DNA-specific fluorochrome 4′,6-diamidino-2-phenylindole. Several irreversible or reversible serine protease inhibitors prevented internucleosomal DNA degradation, nuclear breakdown, and destabilization of DNA double-stranded structure. The effective inhibitors, however, did not prevent the onset of chromatin condensation, nor the loss of the fine structural framework, nor the initial step of DNA cleavage generating DNA fragments of ≥50 kb in size. The data indicate that in both cell systems the activity of proteases sensitive to the inhibitors tested is needed for internucleosomal DNA cleavage to occur. The data also suggest that these proteases may be involved in dissolution of the nuclear envelope. Because nuclear matrix proteins and histones stabilize DNAin situ,and the decrease in DNA stability which occurs during apoptosis is precluded by the inhibitors, it is likely that serine proteases may degrade DNA stabilizing proteins. The activity of these proteases, however, appears needed neither for DNA cleavage to ≥50-kb fragments nor for the onset of chromatin condensation which is associated with dissolution of the structural framework of the nucleus.     

Sulfation of hypertensive and hypotensive drugs by monkey brain phenol sulfotransferase

The substrate specificity and affinity of two forms of phenol sulfotransferase (PST) from Rhesus macaque brain cortex were studied. Catecholamines, their methylated metabolites (normetanephrine, metanephrine) and methylated precursor, -methylDOPA, were examined as substrates for both the cationic (PST I) and the anionic (PST II) forms of the enzyme. Sulfation of hypertensive drugs (phenylephrine, octopamine, metaraminol), hypotensive drugs (-methylDOPA, minoxidil), and related agents without a free hydroxy group on the benzene ring were also studied. Results indicated that both PST forms sulfated -methylDOPA and minoxidil, but only PST II transferred the sulfate group to catecholamines and most of the adrenergic agents examined.     

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.     

THE RELATIONSHIPS BETWEEN THE PRIMARY VASCULAR SYSTEM AND PHYLLOTACTIC PATTERNS OF ANAGALLIS ARVENSIS (PRIMULACEAE)

The various primary vascular systems of shoots of Anagallis arvensis L. (Primulaceae) can be distinguished in relation to the number of leaves (two, three, or four) at each node. In this study, shoot segments (single intemodes and the nodes above them) were examined. The arrangement of segments within shoots was also recorded. The vasculature forms a closed system with the number of sets of bundles usually equal to twice the number of leaves. Irregularities are found in the following features of the system: the number of bundles composing leaf half-traces; occurrence of anastomosing bundles; the number of intemodes through which bundles extend; levels of leaf attachment to the stem at the node; and distribution of parenchyma within the vascular cylinder, which determines the number of bundles in sets and the number of bundle sets. The irregularities occur with different frequencies for segments exhibiting different phyllotactic patterns. Comparison of these frequencies leads to the following conclusions: anastomosing bundles occur only in decussate or trimerous shoot segments, whereas sets of bundles united within intemodes and displaced leaves occur only in tetramerous or trimerous ones; decrease of the number of bundles per leaf and displacement of leaves at the nodal level are correlated; variation between segments exhibiting the same phyllotactic pattern is greatest for trimerous, less for tetramerous, and least for decussate segments; the vascular system of decussate shoot segments is more stable than that of the other systems; and trimerous segments seem to be intermediate between the other two segment types.     

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