Effects of CuDIPS and tween 80 on SJL/J tumorigenesis

Plasma copper and zinc levels were measured in SJL/J mice, an inbred strain characterized by a high, spontaneous incidence of reticulum cell sarcoma (RCS). The changes with age in mean concentrations of these metals were consistent with a physiological response that is required for remission of neoplasia. Treatment of SJL/J mice with a copper complex, Cu(II)(3,4-diisopropylsalicylate)₂ (Cu 3,5-DIPS), dissolved in a 10% Tween 80-saline solution revealed a decrease in survival and decline in the incidence of RCS at 52 wk of age. The toxic effects of Cu 3,5-DIPS therapy appeared to be related to the intraperitoneal route of administration and to extracellular deposition of collagen. The inhibitory effect on tumor development was not related to Cu 3,5-DIPS. Rather, Tween 80 was found to be the factor of importance.     

Several biotic and abiotic elicitors act synergistically in the induction of phytoalexin accumulation in soybean

Summary Plants often respond to microbial infection by producing antimicrobial compounds called phytoalexins. Plants also produce phytoalexins in response to in vitro treatment with molecules called elicitors. Specific elicitors, including a hexa--glucosyl glucitol derived from fungal cell walls, the pectin-degrading enzyme endopolygalacturonic acid lyase, and oligogalacturonides obtained by either partial acid hydrolysis or enzymatic degradation of plant cell walls or citrus polygalacturonic acid, induce soybean (Glycine max. L.) cytoledons to accumulate phytoalexins. The experiments reported here demonstrate that the elicitor-active hexa--glucosyl glucitol acts synergistically with several biotic and abiotic elicitors in the induction of phytoalexins in soybean cotyledons. At concentrations below 50 ng/ml, the hexa--glucosyl glucitol does not induce significant phytoalexin accumulation. When assayed in combination with either endopolygalacturonic acid lyase or with a decagalacturonide released from citrus polygalacturonic acid by this lyase, however, the observed elicitor activity of the hexa--glucosyl glucitol is as much as 35-fold higher than the sum of the responses of these elicitors assayed separately. A similar synergism was also demonstrated for the combination of the hexa--glucosyl glucitol with dilute solutions of sodium acetate, sodium formate, or sodium propionate buffers. These buffers are thought to damage or kill plant cells, which may cause the release of oligogalacturonides from the plant cell wall. The results suggest that oligogalacturonides act as signals of tissue damage and, as such, can enhance the response of plant tissues to other elicitor-active molecules during the initiation of phytoalexin accumulation.Supported by the United States Department of Energy DE-ACO2-84ER13161. This paper is number XXXI in a series, Host-Pathogen Interactions. The preceding paper, Host-Pathogen Interactions XXX is Characterization of elicitors of phytoalexin accumulation in soybean released from soybean cells by endopolygalacturonic acid lyase, by K. R. Davis, A. G. Darvill, P. Albersheim, and A. Dell. Zeitschrift für Naturforsschung, in press.     

Mechanism of proton-pumping in the cytochrome b/f complex

Several models have been proposed to interpret the mechanism of proton-pumping associated with the electron transfer reactions in the cytochrome b/f complex. Energetics considerations suggest that the proton pump is coupled to the oxidation of cytochrome b by plastoquinone. Experiments performed in living cells under anaerobic conditions suggest that proton-pumping can occur through two independent mechanisms. When the two b cytochromes are reduced prior to a flash illumination i.e. after a long dark anaerobic incubation (>10 minutes), proton-pumping is very likely associated with the reduction of a semiquinone by cyt b which occurs at a site close to the inner face of the membrane. The electrogenic phase is associated with the tranfer of protons via a transmembrane channel. This process is not inhibited by 2-n-nonyl-4-hydroxyquinoline N-oxide (NQNO). Under repetitive-flash or under aerobic conditions, proton-pumping occurs according to a modified Q-cycle mechanism, which is inhibited by NQNO.Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement     

Phenolic acid effects on peanut growth and oil production

Plants of peanut (Arachis hypogaea L. var. PG No. 1) were given two foliar sprays of phenolic compounds (H-acid, 1, 2, 4-acid, resorcinol and RD-Brown) at 100 and 200 ppm, 35 and 50 days after sowing. In treated plants, shelling %, yield (kg/ha), number of gynophores per plant and number of pods per plant were significantly greater than in the control. Oil content of kernels also showed a significant increase with all the phenolic compounds applied. These compounds increased the linoleic acid concentration so improving nutritional quality. The number of gynophores was significantly correlated with the number of pods per plant and yield per hectare. The effect of phenolic compounds on growth and development was independent of their structural configuration.     

Stimulation of acid invertase activity by indol-3yl-acetic acid in tissues undergoing cell expansion

The soluble acid invertase activity of young, excised P. vulgaris internodal segments fell when they were incubated in water, and their elongation ceased within 6–7 h. IAA (10 M) promoted segment elongation and stimulated an increase in the specific activity of acid invertase to a level greater than that originally present. The rate of segment elongation in the presence of IAA was closely and positively correlated with the specific activity of the enzyme. Optimum concentration of IAA for both elongation and stimulation of invertase activity was 10 M. Concurrent protein synthesis was necessary for these responses to IAA. Segments cut from mature, fully-elongated internodes did not responsd to IAA.Inclusion of Ca²⁺, vanadate or mannitol in the incubation medium abolished IAA-induced segment elongation but did not inhibit the stimulation of acid invertase activity by IAA. Auxin-induced elongation and acid invertase activity were both substantially increased in the presence of up to 25 mM D-glucose or up to 50 mM sucrose. Inclusion of either sugar in the medium considerably increased tissue hexose concentrations. Under some circumstances cell growth and invertase synthesis may compete for available hexose substrate.It is concluded that IAA-induced promotion of acid invertase in P. vulgaris internodal segments is not simply an indirect consequence of removal of end-product (hexose) during IAA-induced cell growth and that a more direct action of IAA on enzyme turnover is involved.     

Backbone side-chain interactions in peptides

IR, ¹H-NMR and X-ray experiments have been carried out on dipeptides with the Pro-Asp and Pro-Asn sequences protected on both ends by amide groups. The Pro-Asp dipeptide was investigated for the carboxylic, methyl ester and carboxylate forms of the Asp residue.In solution, all dipeptides are found to accommodate almost exclusively the I-turn conformation stabilized by an interaction between the Asp or Asn-NH and CO bonds. The I-turn percentage roughly parallels the basicity of the Asp or Asn side substituent, and decreases from Asp^- to Asn, and to Asp or Asp (OMe).The I-turn, stabilized by the interaction involving the Asp-CO site, is retained in the crystal structure of the Pro-Asp(OMe) dipeptide. The Pro-Asp and Pro-Asn dipeptides assume a II-turn conformation in the solid state and the polar Asp or Asn side-groups are involved in a complex network of intermolecular interactions.     

Cross reactivity and enzyme sensitivity of immunoaffinity purified Sm/RNP antigens

Immunoaffinity purified Sm/RNP antigens from buffalo and goat liver were studied to determine the role of RNA and proteins towards the antigenicity of Sm and RNP antigens. A more direct approach using enzyme-linked immunosorbent assay on nylon beads has been utilized to look into the problem. The effect of enzyme treatment and the role of RNA and protein fractions in influencing antigenicity have been described. RNA seems to be involved in the maintenance of RNP specific polypeptides in suitable conformation so as to keep them in solution. Removal of RNA leads to insolubilization of RNP specific polypeptides. Antibodies to Sm and RNP antigens have been shown to cross react with poly A containing heterogeneous nuclear ribonucleoprotein with no cross reactivity with thymus RNA or DNA.     

Prevention of aortic lesions and hyperlipidaemia by alfalfa seed extract in cholesterol fed rabbit

Extract of alfalfa seed (ethanolic 50 % v/v) prevents the development of plaque formation and hyperlipidaemia in cholesterol fed rabbits. It inhibits the elevation of serum total cholesterol, triglycerides, phospholipids, LDL-cholesterol and total cholesterol/phospholipid ratio, while HDL-cholesterol/total cholesterol ratio increases, which is associated with a reduced incidence of atherosclerosis. Further reduction in total cholesterol and phospholipid contents of liver and heart muscle are suggestive of a beneficial role of the seed extract. The possible mechanisms of action are discussed.     

Fibrinolysis: Its initiation and regulation

Fibrinolytic system is one of the major proteolytic pathways in vivo and primarily responsible for dissolution of thrombi. Two enzymes are primarily involved in this proteolytic system; plasminogen activator (PA) and plasmin. Plasmin is formed by a limited proteolysis of plasminogen by PA, which is mainly synthesized by and secreted from vascular endothelial cells. This proteolytic process proceeds physiologically only on the surface of fibrin. Thus, initiation and progression of the fibrinolytic process depend on the function of endothelial cells and fibrin formation. Endothelial cells may also synthesize and excrete PA inhibitor (PAI) which inhibits immediately, PA once released. The rates of synthesis and excretion of PA and PAI by endothelial cells are regulated by various factors. Among them, thrombin stimulates the release of PA whereas activated protein C may decrease the release of PAI. Thus, both enzymes enhance fibrinolytic potential. PA which has escaped from inhibition by PAI binds to fibrin. ₂-Plasmin inhibitor (₂PI) inhibits the binding of plasminogen to fibrin, thereby suppressing this fibrin-associated plasminogen activation. A part of ₂PI is cross-linked to fibrin by activated factor XIII when fibrin is formed, and the ₂PI thus cross-linked to fibrin inhibits in situ plasmin formed on fibrin. Thus, ₂PI as well as PAI plays a central role in inhibition of fibrinolysis.     

Facile synthesis of 2′-substituted lactoses

Isopropylidenation of lactose with 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid gave two products, which were identified by¹H- and¹³C-NMR as 2,35,63,4-tri-O-isopropylidenelactose dimethyl acetal (1) and its 6-O-(2-methoxy)-isopropyl derivative (2). These products were used for the synthesis of 2-O-methyllactose (7), 2,6-di-O-methyllactose (9) and 2-O-benzyllactose (13).