Stimulation of photosynthesis by carbonyl compounds and chelators

A number of carbonyl compounds including bicarbonate, ethylene carbonate, dimethylcarbonate, propylene carbonate, bis-pentamethylene urea, and glycidol, and several chelators were tested for their effect on photosynthetic reactions in isolated spinach chloroplasts. It was found that carbonyl compounds inhibited the DCMU-insensitive silicomolybdate reduction by photosystem II but stimulated the O₂ evolution associated with ferricyanide reduction in presence of DBMIB and the H₂O→methylviologen reaction. Many chelators behaved in the same manner except 1,10-phenanthroline which shows the opposite effect. The carbonyl compounds did not uncouple because they stimulated the proton gradients associated with noncyclic photophosphorylation, whereas some chelators, such as bathocuproine or bathophenanthroline inhibited the proton gradients 100%. Electron transport in presence of ADP and inorganic phosphate showed a stimulation of rates beyond that obtained in presence of an uncoupler. The data are discussed in terms of inhibition of cyclic electron flow around PS II which leads to increased electron transport rates toward PS I.     

Influence of sialic acid on cell surface properties in I-cell disease fibroblasts

Summary Fibroblasts derived from patients with I-cell disease have been shown to accumulate many natural substrates including a three to fourfold increase in sialic acid content compared to that found in normal fibroblasts. This diverse accumulation of storage material is due to a massive deficiency of multiple lysosomal hydrolases as they are preferentially excreted into the culture fluid. There is evidence that the I-cell plasma membrane itself is abnormal with respect to certain transferase activities and in its sensitivity to freezing and Triton X-100. In this study, we have shown that a neuraminidase-sensitive substrate, and perhaps others in I-cell fibroblasts, contribute to an increased electronegativity of the I-cell fibroblast surface and to the cells' sensitivity to freezing. We also found that neuraminidase treatment of I-cell fibroblasts before preservative freezing in liquid nitrogen enables the cells to adapt more easily to subculture upon thawing. This project was supported in part by National Institutes of Health (NIH) BRSG Grant RR-05493, NIH Grant 1-R01-HD-11453-01-A1, National Science Foundation Grant PCM 77-05733, and Maternal and Child Health Service Project 417. Georgirene D. Vladutiu is the recipient of Research Career Development Award 1K04 HD 00312-01A1 from the National Institutes of Health.     

Further studies on the metabolism of gibberellins (GAs) A9, A20 and A29 in immature seeds of Pisum sativum cv. progress No. 9

Seed maturation of Pisum sativum cv. Progress No. 9 proceeds more slowly in winter than in summer even when the parent plants are grown in greenhouse conditions with light-and heat-supplementation. For parent plants grown under summer and winter conditions the metabolism of [³H]GA₉ in cultured seeds is qualitatively different in seeds of equivalent age and qualitatively the same in seeds of equivalent weight. 13-Hydroxylation of [³H]GA₉[³H]GA₂₀ is restricted to early stages of seed development. 2-Hydroxylation of [³H]GA₉2-OH-[³H]GA₉ has only been observed at a stage of development after endogenous GA₉ has accumulated. 2-OH-GA₉ has been shown to be endogenous to pea and is named GA₅₁. H₂-GA₃₁ and its conjugate have not been shown to be present in pea and may be induced metabolites of [³H]GA₉. The metabolism of GA₂₀GA₂₉ is used to illustrate a technique of feeding [²H][³H]GAs in order to distinguish a metabolite from the same endogenous compound. The in vitro conversion of [³H]GA₂₀[³H]GA₂₉, and the virtual non-metabolism of [³H]GA₂₉ have been confirmed for seeds in intact fruits. These results are discussed in relation to the apparent absence of conjugated GAs in mature pea seeds.Abbreviations GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatography-mass spectrometry - GC-RC combined gas chromatography-radio counting - Me methyl ester - R_T etention time - SICM selected ion current monitoring - TLC thin layer chromatography - TMS trimethyl silyl ether The author is née Frydman     

Transfer of immunity to Plasmodium berghei by spleen and lymph node immune RNA.

The RNA from spleens and lymph nodes of Lewis rats immune to Plasmodium berghei protected A/J mice against a lethal challenge of the blood stages of P. berghei, NK65. The RNA was extracted by the hot phenol procedure from freshly removed spleens and lymph nodes. Protection was measured by survival and level of parasitemia as compared to controls. The levels of RNA administered were 10, 50, and 100 μg of RNA. There was observed 100% survival with 50 and 100 μg of immune spleen RNA. The maximum percentage of parasitemia was not reduced below that of the controls in the groups given immune RNA from lymph nodes, but was significantly reduced below that of the controls in the groups given immune RNA from spleens.     

Continuous-flow plasmapheresis in management of severe rhesus disease.

Eight patients with severe rhesus disease and expected fetal loss were treated by intensive plasmapheresis using a continuous-flow cell separator. Plasmapheresis was started at 16-27 weeks'' gestation, and continued until planned intrauterine transfusion or until the infant was delivered or the rhesus disease became uncontrolled again. Altogether 24 to 2371 of plasma was exchanged over periods ranging from seven to 16 weeks. In seven of the eight patients the anti-D concentration fell during the period of plasmapheresis. Amniotic fluid spectrophotometry values remained below those recorded in the preceding pregnancy in six out of seven women. In five patients an attempt was made to control the rhesus disease by plasmapheresis alone, and two of these women delivered infants who survived. In the other three cases the infants died, one from the idiopathic respiratory distress syndrome and the other two in utero. These preliminary findings suggest that intensive plasmapheresis with a cell separator may reduce fetal haemolysis is delivered. Nevertheless, plasmapheresis may best be used to reduce haemolysis until intrauterine transfusions may be given more safely after 30 weeks'' gestation.     

Transmembrane ferricyanide reduction in tobacco callus cells

Transmembrane ferricyanide reduction in whole cells of normal and of transformed tobacco (Nicotiana tabacum) callus tissue was compared. It was found that low concentrations of indoleacetic acid (IAA, 0.1 μM), gibberellic acid (GA, 0.3 μM), and benzyl adenine (BA, 0.03 μM) stimulate external ferricyanide reduction in normal tobacco callus cells, but inhibit this reaction up to 67% in transformed cells when hormones are applied to cells 10 min prior to assay. Higher concentrations of these growth regulators (1 μM or greater) inhibit transmembrane ferricyanide reduction in both types of cells, with the exception of IAA, giving an initial stimulation of the rate (12%), followed by 24% inhibition after 2 min. The observed external ferricyanide reduction by whole tobacco callus cells may be explained on the basis of a transplasmalemma redox system, which may be associated with the iron metabolism of these cells.     

Calmodulin antagonists inhibit electron transport in photosystem II of spinach chloroplasts

Chlorpromazine, phenothiazine and trifluoperazine, known as calmodulin antagonists, inhibit electron transport in Photosystem II of spinach chloroplasts in concentrations from 20–500 μM. The inhibition site is located on the diphenyl carbazide to indophenol pathway in Tris-treated chloroplasts, indicating that water oxidation is not affected by these drugs. Ca²⁺ ions, bound to chloroplast membranes before the addition of calmodulin antagonists, can protect against inhibition up to 25% of the electron transport rate. In presence of A23187, the Ca²⁺-specific ionophore, Ca²⁺ ions provide less protection against inhibition by the 3 calmodulin antagonists used. A possible role of a calmodulin-like protein in spinach chloroplasts is postulated.     

Ca2+ and calmodulin antagonists inhibit the proton gradients associated with non-cyclic and cyclic photophosphorylation in spinach chloroplasts

The synthesis of benzylpenicillin (BP) after mixing phenyl-acetyl-glycine(PAG), 6-aminopenicillanic acid (6-APA) and free or immobilized penicillin amidase (E.C.3.5.1.11.) was studied as a function of pH and ionic strength. Before the final equilibrium was reached a kinetically controlled synthesis of BP was observed. Then a transient maximum concentration in BP much larger than the final equilibrium content was synthesized in the acyl-transfer process. The factors influencing this maximum have been analyzed. Increasing ionic strength markedly decreased the maximum in BP and the rate of deacylation of phenyl-acetyl-penicillin amidase by 6-APA. The change was largest when the enzyme was immobilized in a positively charged support, where at low ionic strength the concentration of 6-APA around the enzyme is larger than the bulk concentration due to the partitioning of charged solutes.     

Chromosome replication in aging human diploid fibroblasts

The patterns of termination of DNA replication in human embryonic MRC-5 fibroblasts at four passage levels have been examined by autoradiography. Only chromosome 9 showed statistically significant differences in the time of replication among cultures of different ages. This chromosome terminated replication earlier at later passages than at earlier passages, primarily because of differences in the time of replication of the centromere region. Because very few differences were observed at different passage levels, we conclude that changes in the order of chromosome replication are unlikely to contribute to the phenomenon of in vitro senescence.