Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

Effects of Mg(OH)2-fertilization on nutrient cycling in a heavily damaged Norway spruce ecosystem (NE Bavaria/FRG)

Main objective of this study was to test the effects of Mg(OH)₂-fertilization in a Norway spruce ecosystem showing severe symptoms of Mg-deficiency.The site is characterized by high atmospheric inputs with deposition rates of 1.25 kg H, 42 kg S, and 32 kg N per ha and year. The typic Dystrochrept derived from granite is acidified down to greater depths. The pH-values in soil solution of the organic surface layer and the upper mineral soil are around 3.5. Concentrations of Al, SO₄ ^2-, and especially NO₃ ^- and DOC are very high. The element balance indicates a significant influence of N-inputs and processes of N-turnover on the chemical status of the soil and probably on tree nutrition. Nitrification in the upper mineral soil leads to a transformation of a major part of NH₄ ⁺ into NO₃ ^-, which is quantitatively leached, resulting in an ecosystem-internal H⁺-production of 1.8 keq ha^-1yr^-1. NO₃ ^- and SO₄ ^2- govern the seepage output from the ecosystem.Mg(OH)₂ fertilization resulted in manifold increased Mg²⁺ concentrations in soil solution down to 70 cm soil depth and to a significant increase of pH down to 25 cm mineral soil depth. Nitrate concentrations were elevated after fertilization, but decreased within 15 months below the level of the control plot. As a mean over the whole experimental period, N-output was not increased by fertilization. Despite an elevated internal proton production due to nitrification, acid buffering in the soil was clearly increased, but enhanced Al-mobilization was not observed. Mg/Al- and Ca/H-ratios in soil solution indicate much more favourable conditions for fine root growth. Fertilization also increased the amount of exchangeable Mg down to 40cm mineral soil depth. Mg contents in current-year needles increased after three vegetation periods. Thirty months after application, only 10% and 4% of the fertilized Mg had left the organic surface layer and the mineral soil with seepage water output, respectively.     

Are polyphosphates or phosphate esters prebiotic reagents?

It is widely held that there was a phosphate compound in prebiotic chemistry that played the role of adenosine triphosphate and that the first living organisms had ribose-phosphate in the backbone of their genetic material. However, there are no known efficient prebiotic synthesis of high-energy phosphates or phosphate esters. We review the occurrence of phosphates in Nature, the efficiency of the volcanic synthesis of P₄O₁₀, the efficiency of polyphosphate synthesis by heating phosphate minerals under geological conditions, and the use of high-energy organic compounds such as cyanamide or hydrogen cyanide. These are shown to be inefficient processes especially when the hydrolysis of the polyphosphates is taken into account. For example, if a whole atmosphere of methane or carbon monoxide were converted to cyanide which somehow synthesized polyphosphates quantitatively, the polyphosphate concentration in the ocean would still have been insignificant. We also attempted to find more efficient high-energy polymerizing agents by spark discharge syntheses, but without success. There may still be undiscovered robust prebiotic syntheses of polyphosphates, or mechanisms for concentrating them, but we conclude that phosphate esters may not have been constituents of the first genetic material. Phosphoanhydrides are also unlikely as prebiotic energy sources. Correspondence to: S.L. Miller     

Direct application of carbendazim and propiconazole at field rates to the external mycelium of three arbuscular mycorrhizal fungi species: effect on 32P transport and succinate dehydrogenase activity

 The influence of the systemic fungicides propiconazole (Tilt 250E) and carbendazim (Bavistin) at field application rates on the functioning of three arbuscular mycorrhizal fungi was studied. Short-term fungal ³²P transport and succinate dehydrogenase (SDH) activity in external hyphae of Glomus intraradices Schenck and Smith, G. claroideum Schenck and Smith and G. invermaium Hall in symbiosis with pea (Pisum sativum L.) were measured. In the experimental system used, the hyphae grew into two root-free hyphal compartments (HCs). The fungicides were applied to each HC 24 days after sowing and ³²P was added to one HC of each pot. Four days later, the fungicide effect on fungal P transport was measured as the difference in ³²P content of treated and untreated plants. SDH activity in fungal hyphae was determined in the HCs given no ³²P. Carbendazim severely inhibited ³²P transport and SDH activity in external hyphae at an application rate of 0.5 μg g^–1 soil. The ergosterol inhibitor propiconazole affected none of these parameters. The fungicides had similar effects on all three fungal species, although P transport efficiency and SDH activity differed markedly between the fungi. Accepted: 12 December 1996     

Immunological characterization of a 36 kDa Fe deficiency specific peptide in barley roots

In a previous paper we reported that an acidic 36 kDa peptide is the most strongly induced peptide among several peptides induced by Fe deficiency in barley roots. In this paper, polyclonal antibodies were raised against the 36 kDa peptide. This peptide appeared in the roots of all the graminaceous species tested (barley, rye, wheat, oat, maize, sorghum and rice) in response to Fe deficiency. More of the peptide was found in the roots of graminaceous species which secrete higher amounts of mugineic acids (MAs) under Fe deficient nutrition status. Induction of the 36 kDa peptide was first observed on the third day of Fe deficiency, rising to a maximum value on the seventh day. The trend has a positive correlation with secretion of MAs during Fe deficiency. Further, resupply of Fe resulted in a decrease in peptide production on the second day, reaching a control level on the seventh day. The rate of decrease in peptide production was observed to be slower than that of MA secretion. Other nutrient stresses such as B excess, B deficiency, Cu excess, Cu deficiency, Mn excess, Mn deficiency, Zn excess and Zn deficiency induced far less of the peptide. The specific expression of the 36 kDa peptide in roots of graminaceous species under Fe deficiency suggested the positive association of the peptide with a specific Fe deficiency tolerance mechanism in graminaceous plants.     

Regional alterations of thiamine phosphate esters and of thiamine diphosphate-dependent enzymes in relation to function in experimental Wernicke's encephalopathy

Thiamine phosphate esters (thiamine monophosphate-TMP; thiamine diphosphate-TDP and thiamine triphosphate-TTP) were measured as their thiochrome derivatives by High Performance Liquid Chromatography in the brains of pyrithiamine-treated rats at various stages during the development of thiamine deficiency encephalopathy. Severe encephalopathy was accompanied by significant reductions of all three thiamine phosphate esters in brain. Neurological symptoms of thiamine deficiency appeared when brain levels of TMP and TDP fell below 15% of normal values. Activities of the TDP-dependent enzyme -ketoglutarate dehydrogenase were more severely reduced in thalamus compared to cerebral cortex, a less vulnerable brain structure. On the other hand, reductions of TTP, the non-cofactor form of thiamine, occurred to a greater extent in cerebral cortex than thalamus. Early reductions of TDP-dependent enzymes and the ensuing metabolic pertubations such as lactic acidosis impaired brain energy metabolism, and NMDA-receptor mediated excitotoxicity offer rational explanations for the selective vulnerability of brain structures such as thalamus to the deleterious effects of thiamine deficiency.     

HeteroTOCSY-based experiments for measuring heteronuclear relaxation in nucleic acids and proteins

Summary While both ³¹P and ¹¹³Cd are present at locations of interest in many different macromolecular systems, heteronuclear-detected relaxation measurements on these nuclei have been restrained by limitations in either resolution or signal-to-noise ratio. We have developed hetero TOCSY-based methods to overcome both of these problems. Two-dimensional versions of these experiments were utilized to measure ³¹P T₁ and T₂ values in DNA oligonucleotides; the additional resolution offered by a second dimension allowed determination of these values for most of the ³¹P resonances in a DNA dodecamer. The results from the experiments indicated that there was little significant variation in T₁ values for the different phosphates in the DNA dodecamer; however, the T₂ values showed a clear pattern, with lower values in the interior of the sequence than at the ends of the helix. Furthermore, a significant correlation between ³¹P chemical shifts and T₂ values was observed. One-dimensional, frequency-selective versions of these experiments were also developed for use on systems containing a smaller number of heteronuclear spins. These methods were applied to investigate the heteronuclear relaxation properties of ¹¹³Cd in ¹¹³Cd₂LAC9(61), a Cys₆Zn₂ DNA-binding domain. Data from the experiments confirm biochemical evidence that more significant differences occur in the metal-protein interactions between the two metal-binding sites than has been previously identified for proteins containing this motif.     

Effects of vesicular-arbuscular mycorrhiza on Tagetes erecta and Zinnia elegans

 Seeds of Tagetes erecta and Zinnia elegans were planted in soil inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus etunicatum. This procedure produced positive effects on both Tagetes and Zinnia compared with the control: faster flowering and an increased number of flowers. Shoot height, shoot and root dry weights and percentage infected root length were also measured. The reactions of these plants to mycorrhizal infection were shown to be independent of changes in the phosphorus, potassium and sodium contents of the plants. Accepted: 1 August 1995     

氮磷对污水净化中藻类叶绿素含量的影响

在室内模拟生物净化槽中比较研究了氮磷对污水中藻类叶绿素含量和污水净化的影响。污水中磷含量均为７ｍｇ／Ｌ左右,氮含量分别为７７．４、４４．４、２４．８和１３．５ｍｇ／Ｌ,结果发现ＴＮ／ＴＰ＝７７．４／７．０１ｍｇ／Ｌ组,污水经７ｄ净化,藻类叶绿素含量最高,污水净化效果较好。四个实验组比较,叶绿素含量随ＴＮ／ＴＰ比例的上升而上升,呈显著正相关。     

Guanosine triphosphate catabolism in purine nucleoside phosphorylase deficient human B lymphoblastoid cells

GTP catabolism induced by sodium azide or deoxyglucose was studied in purine nucleoside phosphorylase (PNP) deficient human B lymphoblastoid cells. In PNP deficient cells, as in control cells, guanylate was both dephosphorylated and deaminated but dephosphorylation was the major pathway. Only nucleosides were excreted during GTP catabolism by PNP deficient cells and the main product was guanosine. The level of nucleoside excretion was largely affected by intracellular orthophosphate (P_i) level. In contrast, normal cells excreted nucleosides only at low P_i level while at high P_i levels, purine bases (guanine and hypoxanthine) were exclusively excreted. PNP deficiency had no effect on the extent of GMP deamination.