A zone phenomenon and a progressive reaction occurring with a radioactive hemolysin,sodium erucate,I 131

Sodium erucate reacts progressively (i.e., once the reaction is started in a time which is so short that the lysin is in contact with the red cells for 30 seconds, it cannot be stopped even by being diluted 10-fold) with human red cells at pH 7. At the same time, systems containing the lysin and human red cells show a zone phenomenon, lysis occurring most readily in a certain concentration of lysin but more slowly in larger or smaller concentrations. Sodium erucate-I¹³¹ can be used to investigate both the zone phenomenon and the progressive character of the reaction. As regards the former, large concentrations of the lysin react relatively poorly with the red cell surfaces and the resistance of the red cells is relatively high. This may be due to the presence of an admixed inhibitor or to the development of an inhibitory state. The lysin is taken up and fixed by material in the red cell surface, so that the "internal phase" of lysin attached to the cell surfaces is so firmly fixed that a 10-fold dilution has no effect on it. It follows that lysis in these systems is progressive, as it is found to be.     

Nucleotide sequence of a plasmid-encoded hemolysin determinant and its comparison with a corresponding chromosomal hemolysin sequence

Abstract The complete sequence of the plasmid pHly152-encoded hemolysin ( hly ) determinant of Escherichia coli is presented and compared with a recently sequenced chromosomal hly determinant [1]. High sequence homology between the two hly determinants is observed withìn all four structural genes, hlyC, A, B and D , but little sequence similarities are found in the 3'- and 5'-noncoding flanking regions. In addition, the noncoding region upstream of hlyC which carries the promoter for hlyC, A and B , was sequenced for several chromosomal hly determinants. The comparison of these sequences indicates three distinct classes of promoter regions which share common putative −10 and −35 boxes at roughly the same location relative to the start of hlyC .     

Hemolysis considered as a progressive reaction in a heterogeneous system

It is demonstrated, without the use of special assumptions, that red cells are heterogeneous with respect to their resistance to at least certain lysins, that the reaction between the cell components and the lysin is virtually irreversible in some cases but reversible, although to different extents, in others, and that the lysin initiates a process in the cell which is not adequately described by the terms reversible and irreversible, but rather by the term progressive. Progressive reactions, i.e. reactions which cannot be stopped once they are well under way, may be looked for in systems which have structure, and in which local reactions occurring at strategic points lead to disproportionate results.     

A mutant hemolysin with lower biological activity produced by a mutant Vibrio parahaemolyticus

Abstract A mutant toxin (m-TDH) of thermostable direct hemolysin (Vp-TDH) of Vibrio parahaemolyticus w was isolated from the culture of a strain of this organism mutagenized with N -methyl- N '-nitro- N -nitrosoguanidine. Although the m-TDH had a molecular structure similar to the native Vp-TDH, the m-TDH retained only about 7% residual hemolytic activity of the native toxin. Furthermore, other biological activities of m-TDH, such as lethality in mice and enterotoxicity in rabbit ileal loops, were also weakened. The m-TDH was immunologically indistinguishable from the native Vp-TDH. These results suggest that the m-TDH is only slightly different in structure from the native Vp-TDH. Also, the mutagenized site in m-TDH, which is not immunogenic, seems to be involved in expressing not only hemolytic activity but also lethal and enterotoxic activity.     

A framework for including enhanced exposure to naturally occurring radioactive materials (NORM) in LCA

Purpose

Despite advances in the development of impact categories for ionising radiation, the focus on artificial radionuclides produced in the nuclear fuel cycle means that the potential impacts resulting from increased exposure to naturally occurring radioactive materials (NORM) are still only covered to a limited degree in life cycle assessment (LCA). Here, we present a potential framework for the inclusion of the exposure routes and impact pathways particular to NORM in LCA.

Methods

We assess the potential magnitude of enhanced NORM exposure, particularly in light of the potential use of NORM residues in building materials, and set out the potential exposure routes that may exist. We then assess the current state of the art, in terms of available fate, exposure and damage models, both within and outside of the LCA sphere. Finally, these exposure routes and modelling techniques are combined in order to lay out a potential framework for NORM assessment in LCA, both in terms of impact on humans and ecosystems.

Results and discussion

Increased exposure to NORM radionuclides can result either from their release to the environment or their proximity to humans as they reside in stockpiles, landfills or products. The exposure route via products is considered to be increasingly significant in light of current attempts to incorporate technologically enhanced NORMs (TENORM) including bauxite residue into building materials, by groups such as the ETN-MSCA REDMUD project. Impact assessment models for NORM exposure are therefore required to avoid potential burden shifting in the assessment of such TENORM products. Models describing the fate of environmental releases, the exhalation of radon from building products and the shielding effects on landfills/stockpiles are required to assess potential exposure. Subsequently, models relating exposure to radiation sources and the effective internal and external dose received by receptors are required. Finally, an assessment of the damage caused to the receptors is desirable.

Conclusions

A sufficient suite of currently existing and internationally recognised models exist that can, with varying degrees of modification, form the building blocks of a comprehensive NORM characterisation method for LCA. The challenge ahead lies in consolidating these models, from disparate fields, into a coherent and generally applicable method for the assessment of enhanced NORM exposure in LCA.

     

Conformational analysis of bacitracin A, a naturally occurring lariat

The proton nmr spectra of bacitracin A in H2O and DMSO-d6 have been assigned and the conformational behavior of the peptide in the two solvents has been compared. Although bacitracin A shows a conformational equilibrium between at least two conformations differing in the relative position of the cyclic and linear domains of the molecule, the spectra in water can be interpreted in terms of a preferred conformation in which the linear part is folded over the cyclic moiety and a turn is present around Ile(8)-DPhe(9).     

131I thyroid activity and committed dose assessment among family members of patients treated with radioactive iodine

Radiation and Environmental Biophysics - The main goal of the present study was estimation of an internal contamination of 131I among family members of patients treated with radioactive iodine....     

Properties of a hemolysin related to the thermostable direct hemolysin produced by a Kanagawa phenomenon negative, clinical isolate of Vibrio parahaemolyticus

A hemolytic toxin (Vp-TRH) produced by a Kanagawa phenomenon negative, clinical isolate of Vibrio parahaemolyticus was further characterized. The purified Vp-TRH showed various biological activities, such as fluid accumulation in rabbit ileal loops, increase of rabbit skin vascular permeability, and cardiotoxicity on cultured myocardial cells, all of which are essentially similar to the activities found with thermostable direct hemolysin (Vp-TDH), a pathogenic toxin produced by Kanagawa phenomenon positive V. parahaemolyticus. Immunological similarities of Vp-TRH not only to Vp-TDH but also to hemolytic toxins produced by Vibrio hollisae and Vibrio cholerae non-O1, both of which are also enteropathogens closely related to V. parahaemolyticus, were demonstrated. The amino acid composition and sequence of N-terminal amino acids of Vp-TRH were determined. These results suggest that Vp-TRH has biological and immunological characters similar to Vp-TDH, although they are distinct molecules.     

The inhibition of hemolysis,as studied by the technique used for investigating progressive reactions,and by a technique using radioactive hemolysins

Inhibition of hemolysis by plasma has been studied in systems containing saponin, digitonin, and sodium lauryl sulfate, using the methods developed for the study of the kinetics of progressive reactions. The results are that the progressive nature of the hemolytic reaction in saponin systems becomes less when the inhibitor is added, that the addition of inhibitor to digitonin systems has no effect on the final result although the velocity of the progressive reaction is reduced, and that the effect of plasma in lauryl sulfate systems is intermediate between the effects in saponin systems and digitonin systems. A simple explanation is that the lysin is very strongly fixed, to form an internal phase, to the cell surfaces in digitonin systems, less strongly in laurate systems, and still less strongly in saponin systems. To answer the question as to whether, in a system in which some of the lysin forms as internal phase, the addition of an inhibitor results in a redistribution of the lysin between the internal phase and the bulk phase, sodium lauryl sulfate-S³⁵ and sodium cetyl sulfate-S³⁵ were prepared, and their distribution between the internal phase and the bulk phase was measured before and after the addition of plasma, the lysins being added to the cells either before or after the addition of the inhibitor. The results show that there is a large uptake of these lysins at the red cell surfaces when they are added first, and that the subsequent addition of plasma greatly reduces the quantity of lysin held in the internal phase. Further, if the inhibitor is added first and the lysin subsequently, the internal lysin phase is very incompletely formed. Serum albumin, used in place of plasma, gives essentially similar results.