Inhibition of electron transport on the oxygen-evolving side of photosystem II by an antiserum to a polypeptide isolated from the thylakoid membrane.

A polypeptide fraction with the apparent molecular weight 11 000 was isolated from stroma-freed chloroplasts from Anthirrhinum majus. An antiserum to this polypeptide fraction inhibits photosynthetic electron transport in chloroplasts from Nicotiana tabacum. The relative degree of inhibition is pH dependent and has its maximum at pH 7.4. The maximal inhibition observed was 93%. The dependence of the inhibition on the amount of antiserum yields a sigmoidal curve which hints at a cooperative effect. A calculation of the Hill interaction coefficient gave the value of 10. The inhibition occurs on the water splitting side of photosystem II between the sites of electron donation of tetramethyl benzidine and diphenylcarbazide. Tetramethyl benzidine donates its electrons before the site where diphenylcarbazide feeds in its electrons. Analysis of the steady state level of the variable fluorescence also indicates that the inhibition site is on the water splitting side of photosystem II. Tris-washed chloroplasts are equally inhibited by the antiserum and the inhibition is also observed in the presence of an inhibitor of photophosphorylation like dicyclohexyl carbodiimide and in the presence of the uncoupler carbonylcyanide m-chlorophenyl hydrazone (CCCP) which means that the inhibitory action is directed towards the electron transport chain. Valinomycin which is supposed to affect the cation permeability of the thylakoid membrane has no influence on the inhibitory action of the antiserum. The same is valid for gramicidin. Methylamine on the other hand can induce a state in the thylakoids in which the antiserum is not effective. If the antibodies are already adsorbed prior to the methylamine addition then the high inhibitory effect by the antiserum remains unchanged upon addition of methylamine. From the experiments it follows that a component from the vicinity of photosystem II is accessible to antibodies that is, the component is located in the outer surface of the thylakoid membrane. It appears that the inhibitory effect is produced in the course of the light reaction.

Studies of enzymes involved in glycoprotein synthesis and degradation in diacetylbenzidine nephrosis.

Diacetylbenzidine was used to induce a nephrotic syndrome in female rats. Enzymes involved in glycoprotein metabolism were evaluated during an early stage of induced renal disease before extensive histologic changes occurred. The results show that lysosomal acid hydrolases are not activated or released to any measurable degree during the early stages of the disease. Minimal differences in the composition of glomerular basement membrane of nephrotic rats were found despite heavy proteinuria. Glomerular specific activities of certain glycoprotein:glycosyl transferases were depressed in nephrotic animals. A new viewpoint to explain the pathology of glomerular proteinuria is presented based on the phenomenon of sublethal autolysis affecting cell surface structure and function, of which activity levels of glycoprotein:glycosyl transferases are an example. Increased activities of glycosyl transferases and Na-D ATPase were noted in the cortex from nephrotic animals. These studies involving cortex indicate that the pathologic process is not confined to the glomerulus and may contribute information concerning Na+ transport in the nephrotic rat.

[Carcinogenic activity of a 4,4-diaminobiphenyl ester]. / O kantserogennoi aktivnosti 4,4-diaminodifenilovogo éfira

4,4'-diaminodiphenyl ether (dadpe) was injected subcutaneously (once a week) or given per orally (1-5 times a week) in rats in a dose of 25 mg/per rat and in mice of line CC57W in a dose of 5 mg/per mouse. Administration of the substance produced in mice and rats under study renal lesions of the nephrosis type with a nephritic component. In later stages of the experiment some rats showed adenomatous regeneration and formation of renal cysts, in one rat hypernephroid cancer of the kidney was observed. Tumors of different localizations were found in 44% of rats (in 7 of 16 animals), and in 57% of mice (in 8 of 14 animals) in experiments with peroral administration of the substance; in 18% of rats (in 7 of 39 animals) and in 33% of mice (in 3 of 9 animals) in experiments with subcutaneous injection of the substance. The results of the experiments have evidenced an insignificant blastomogenic action of 4,4'-diaminodiphenyl ether.