Structural requirements of alkyl acyldithiocarbazates for the uncoupling of oxidative phosphorylation in mitochondria

A structure-activity relationship study on the uncoupling of alkyl acyldithiocarbazates was carried out. Greater activity was observed with increasing alkyl chain length, the optimum being C₉. A further increase in alkyl chain length caused a decrease in the activity. Thione-thiol tautomeric forms with a dissociable proton were found to be of primary importance for the uncoupling and the role of the acyl group was auxiliary.The reactivity of the SH group of alkyl acyldithiocarbazates with an SH-reagent was very low. These compounds facilitated the valinomycin-induced swelling of non-respiring mitochondria and non-sonicated lecithin liposomes in isotonic potassium acetate solution.     

Effects of cyclic AMP and gibberellic acid on lettuce hypocotyl elongation and mechanical properties of its cell wall

Growth responses of lettuce seedlings to cyclic AMP and gibberellicacid were studied. Both cyclic AMP and sodium dibutyryl cyclicAMP significantly stimulated hypocotyl elongation, althoughelongation by cyclic AMP was smaller than that by gibberellicacid. Substances related to cyclic AMP, i.e. 5'-AMP, 5'-ADPand 5'-ATP, had no growth promoting effects. Examination of mechanical properties of the cell wall by a stress-relaxationtechnique indicated that both cyclic AMP and gibberellic acidcaused cell wall loosening when they stimulated hypocotyl elongation. (Received September 30, 1971; )     

Balanced ubiquitylation and deubiquitylation of Frizzled regulate cellular responsiveness to Wg/Wnt

Wingless (Wg)/Wnt has been proposed to exert various functions as a morphogen depending on the levels of its signalling. Therefore, not just the concentration of Wg/Wnt, but also the responsiveness of Wg/Wnt‐target cells to the ligand, must have a crucial function in controlling cellular outputs. Here, we show that a balance of ubiquitylation and deubiquitylation of the Wg/Wnt receptor Frizzled determines the cellular responsiveness to Wg/Wnt both in mammalian cells and in Drosophila, and that the cell surface level of Frizzled is regulated by deubiquitylating enzyme UBPY/ubiquitin‐specific protease 8 (USP8). Although ubiquitylated Frizzled underwent lysosomal trafficking and degradation, UBPY/USP8‐dependent deubiquitylation led to recycling of Frizzled to the plasma membrane, thereby elevating its surface level. Importantly, a gain and loss of UBPY/USP8 function led to up‐ and down‐regulation, respectively, of canonical Wg/Wnt signalling. These results unveil a novel mechanism that regulates the cellular responsiveness to Wg/Wnt by controlling the cell surface level of Frizzled.     

The Effects of Magnesium Deficiency on Molybdenum Metabolism in Rats

Our previous report indicated that magnesium (Mg) deficiency increased molybdenum (Mo) concentration in the rat liver, suggesting the possibility that Mg deficiency affects Mo metabolism. Growing male rats were given a control diet or a Mg-deficient diet for 4 weeks. Urine and feces were collected during the second and fourth weeks of the feeding trial. The liver, kidney, spleen, skeletal muscle, and blood were collected at the end of the feeding trial. Mg deficiency did not affect the apparent absorption of Mo, but it reduced urinary excretion of Mo. The retention of Mo tended to be higher in the Mg-deficient group than in the control group. Hepatic Mo concentration was higher in the Mg-deficient group than in the control group, but Mg deficiency did not affect Mo concentration in other tissues and plasma. Mg deficiency downregulated the mRNA expression of Mo transporter 2 (MOT2) in the liver, but not in the kidney. These results suggest that Mg deficiency decreases urinary Mo excretion, which is too slight to affect plasma Mo concentration, and that Mg deficiency selectively disturbs the homeostatic mechanism of Mo in the liver, which is not related to the mRNA expression of MOT2 in the liver.     

Macerating Activity of Streptomyces fradiae IFO 3439

Streptomyces fradiae IFO 3439 elaborated enzymes with macerating activity toward various plant tissues. The optimum pH of the macerating activity was about 8.0 when the crude enzyme preparation acted on disks of potato tuber or pieces of Ganpi (Wikstroemia sikokiana Fr. et Sav.) bark. Pectolytic activities in this preparation toward free pectin or poly-galacturonic acid were considerably lower than those of fungi or bacteria. However, when the crude enzyme preparation acted on native pectin in Ganpi bark, about 90 per cent of the galacturonic acid residues were recovered as the polygalacturonides having a still high degree of polymerization. These results suggested that the crude enzyme of S. fradiae solubilized Ganpi pectin, degrading it to only a very small extent.     

The Presence of Two Cd-Binding Components in the Roots of Water Hyacinth Cultivated in a Cd2+-Containing Medium

To find why water hyacinth accumulates the toxic heavy metalion Cd²⁺, the plant was cultivated in a mineral medium supplementedwith Cd²⁺. Cd accumulated in the roots against the concentrationgradient, mostly as a soluble form in the cytoplasm. Chromatographywith Sephadex G-25 and G-50 columns showed that the accumulatedCd was present in two forms with mol wt of 2,300 and 3,000.The components carrying Cd showed a high ratio of absorbanceat 254 nm to that at 280 nm, which suggests that they resemblemammalian Cd-thioneins. These components were not detected inthe roots of water hyacinth cultivated in the absence of Cd²⁺,indicating that they are formed in response to the Cd²⁺ supplement. (Received September 6, 1984; Accepted November 30, 1984)