George Kollmann

The nature of the membrane injury in irradiated human erythrocytes.

The mechanism of the radiation-induced increase in sodium accumulation of erythrocytes was studied by chemically altering the cell surface and the cell interior. Agents such as PCMBS and GED, which block surface sulfhydryl groups, mimicked the radiation effect but, when employed with radiation, reduced the radiation effect. Papain, which increased the surface sulfhydryl groups, increased the radiation effect. Trypsin and neuraminidase, which did not alter surface sulfhydryl groups, did not alter the radiation effect. Agents that altered the heme (nitrite, carbon monoxide, nitrogen) or globin (

The Mechanism of Radiation Hemolysis in Human Erythrocytes

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The mechanism of action of AET. IV. The distribution and the chemical forms of 2-mercaptoethylguanidine and bis(2-guanidoethyl) disulfide in protected mice.

) of hemoglobin inside the cells did not alter the radiation effect. The measurement of sulfhydryl groups on the cells showed decrease on irradiation. Reversal of PCMBS effect on sodium accumulation was observed with GSH and MEG and correlated with the removal by these agents of a small amount of the PCMBS from the cells. Reversal of of radiation effect on sodium accumulation was observed with B...

MECHANISM OF THE PROTECTIVE ACTION OF GED AGAINST RADIATION DAMAGE TO DNA.

Human bank blood erythrocytes were given hemolyzing (16 to 50 kR) exposures of60 Co gamma rays, suspended in various media, and maintained at 5°C for 20 hours. Hemolysis occurred in isotonic NaCl but was prevented or reduced in isotonic choline chloride and in hypertonic NaCl or KCl. Prior to hemolysis in isotonic NaCl, the cells rapidly lost potassium and accumulated sodium. Although irradiated suspensions of cells in choline chloride did not hemolyze, they lost potassium. 2-Mercaptoethylguanidine (MEG) and reduced glutathione (GSH), which does not enter cells, reduced hemolysis and potassium loss when added to the suspensions before irradiation. Radiation caused a marked decrease in membrane sulfhydryl groups. Blockage of membrane sulfhydryl groups by p-chloromercuribenzoate (FCMB) and p-chloromercuribenzene sulfonate (PCMBS), which does not enter the cells, mimicked radiation by causing potassium loss and hemolysis. PCMBS-induced hemolysis was prevented by suspension of the cells in isotonic choline ch...

The mechanism of action of AET. VI. The protection of proteins against ionizing radiation by GED.

The distribution and chemical nature of the protective agent in the various tissues of 8- to 10-week-old C57BL/6J male mice given a protective dose of MEG-S/sup 35/ and GEDS/sup 35/ were studied. Results were obtained at 20 minutes after an intraperitoneal (i.p.) injection of 140 and 280 mg of MEG per kilogram and at 20, 60, and 120 min after an i.p, injection of 140 mg of GED per kilogram. Protein-bound S/sup 35/, GED, taurocyamine, guanidoethanesulfinic acid, MEG, and sulfate were identified in the serum, tissues, and excreta. Several unknown compounds were also observed. Concentrations of protein-bound S/ sup 35/ and GED decreased at 120 minutes after GED administration and correlated best with protection of the mice. All products increased in the tissues at the higher dose of MEG. Some differences in the concentrations of products were noted on comparison of MEG with GED-treated animals. The relation of the results to the mechanisms of action of MEG and GED is discussed. (auth)

Pitfalls in the application of digoxin determinations.

The specific viscosity was measured in unirradiated and irradiated solutions of highly polymerized salmon sperm DNA alone and containing bis(2-guanidoethyl) disulfide (GED), oxidized glutathione (GSSG), cystamine, cadaverine, agmatine, and pentamethylene diguanidine (PMDG). Radiation-induced decrease in viscosity was almost completely prevented by 10-3 M GED up to 100 kR, at which dose the viscosity of the unprotected DNA solution approximated that of the solvent. When viscosity was measured at 90°C to study the effect on single strands, radiation effect and GED protection of DNA were demonstrated with doses as low as 100 to 200 R. GED had to be present during irradiation for protection but could be removed by dialysis after irradiation without loss of protection. Equilibrium dialysis demonstrated binding of GED to DNA. Other disulfides, GSSG, and cystamine showed less binding to DNA and also showed less protection. The diamine cadaverine and the diguanidine PMDG were bound to DNA equally well as cystamin...

The Distribution and Metabolism of the Radiation Protective Agent Aminopentylaminoethylphosphorothioate in Mice

Studies on the distribution and metabolism of the radiation-protective agents 2-mercaptoethylguanidine (MEG) and bis(2-guanidoethyl) disulfide (GED) in mice have shown that, after administration of either agent, the major chemical forms found in the tissues at the time when the animal is protected are proteinbound agent and free GED (1). Moreover, the tissue concentrations of these two chemical forms are the only ones that correlate with protection in the animals studied at 20 minutes (protected) and 120 minutes (no longer protected) after intraperitoneal administration of the protective agents. These results suggest that further studies on the mechanism of protection by MEG and GED be directed at the mechanism of action of protein-bound agent and free GED. Most of the protein-bound agent in MEGor GED-treated animals is MEG in mixed disulfide linkage with protein sulfhydryl groups. This form readily results from the reaction

A comparison of methods for labelling DNA for use in the radioimmuno assay of DNA-antibodies

The radioimmunoassay of digoxin is one of the most important services of the nuclear medicine laboratory. Precision and accuracy in the performance of the test are especially critical. A number of commerical kits are available and reliable. Pitfalls to be avoided includelimited availability or delay in performance of the assay; failure to consider senitizing factors; drawing the blood sample too soon after a digoxin dose; failure to consider desensitizing factors; forgetting that renal function is a major determinant of blood and tissue digoxin levels; assuming patient compliance and uniform intestinal absorption (bioavailiability with all digoxin preparations in all patients; attempting to interpret digoxin levels without the necessary clinical information; and failure to deliver the result to the proper person. If one avoids these pitfalls, and important service will be rendered in the evaluation of the patient requiring digitalis therapy.

Further Studies on Protection of DNA against Ionizing Radiation

Abstract : Aminopropylaminoethyl-phosphorothioate (WR-2721) is the least toxic and most effective of the phosphorothioate class of radiation protective agents. In order to investigate the mechanism of action of this agent, distribution and metabolism studies were carried out using 35S-labelled WR-2721. In mice given WR-2721 intraperitoneally, tissue analysis showed only the unchanged compound and the protective agent bound to proteins by mixed disulfide bond. Concentration of the latter form correlated best with the time course of protection. Dephosphorylation to yield the thiol form of WR-2721, necessary for mixed disulfide formation on tissue proteins, was best demonstrated in the kidneys, both in vivo and in vitro, but also occurs in other tissues. Preliminary studies with the disulfide and thiol forms of WR-2721, which are less protective and more toxic than the phosphorothioate, suggest that the presence of the phosphate is necessary to mask the sulfhydryl group during transport to the target site. Formation of a mixed disulfide with tissue protein sulfhydryl groups at the target site appears to yield the final necessary condition for radiation protection. (Author)

MECHANISM OF ACTION OF RADIATION PROTECTIVE AGENTS: IN VIVO DISTRIBUTION AND METABOLISM OF CYSTEAMINE-S-PHOSPHATE (MEAP).

Abstract The radioimmunoassay for DNA-antibodies in systemic lupus erythematosus is assessed with DNA labelled with 125 I via chemical iodination on one hand ( 125 I-DNA), and with DNA containing [ 125 I]iododeoxyuridine via biological incorporation on the other ([ 125 IUdR]DNA). The results show that chemical iodination labels protein impurities in the DNA and reduces the difference in binding of normal vs lupus sera. 125 IUdR-DNA is a superior product since no label is introduced in proteins. The binding of 125 I-DNA by normal sera ranges from 5 to 20% and from 40 to 70% lupus sera. The same sera yield values of 0–3% for normal and 92–98% for lupus with 125 IUdR-DNA. The latter allows a sharper discrimination between normal and slightly elevated values, as in patients under treatment.