Sulphate influx in wheat and barley roots becomes more sensitive to specific protein-binding reagents when plants are sulphate-deficient

When young wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) plants were deprived of an external sulphate supply (-S plants), the capacity of their roots to absorb sulphate, but not phosphate or potassium, increased rapidly (derepression) so that after 3–5 d it was more than tenfold that of sulphate-sufficient plants (+S plants). This increased capacity was lost rapidly (repression) over a 24-h period when the sulphate supply was restored. There was little effect on the uptake of L-methionine during de-repression of the sulphate-transport system, but S input from methionine during a 24-h pretreatment repressed sulphate influx in both+S and-S plants.Sulphate influx of both+S and-S plants was inhibited by pretreating roots for 1 h with 4,4rc="/content/xj0rj606445r8187/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-diisothiocyanatostilbene-2,2rc="/content/xj0rj606445r8187/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-disulphonic acid (DIDS) at concentrations > 0.1 mol · m^-3. This inhibition was substantially reversed by washing for 1 h in DIDS-free medium before measuring influx. Longer-term pretreatment of roots with 0.1 mol·m^-3 DIDS delayed de-repression of the sulphatetransport system in-S plants but had no influence on+S plants in 3 d.The sulphydryl-binding reagent, n-ethylmaleimide, was a very potent inhibitor of sulphate influx in-S roots, but was much less inhibitory in +S roots. Its effects were essentially irreversible and were proportionately the same at all sulphate concentrations within the range of operation of the high-affinity sulphate-transport system. Inhibition of influx was 85–96% by 300 s pretreatment by 0.3 mol·m^-3 n-ethylmaleimide. No protection of the transport system could be observed by including up to 50 mol·m^-3 sulphate in the n-ethylmaleimide pre-treatment solution. A similar differential sensitivity of-S and+S plants was seen with p-chloromercuriphenyl sulphonic acid.The arginyl-binding reagent, phenylglyoxal, supplied to roots at 0.25 or 1 mol·m^-3 strongly inhibited influx in-S wheat plants (by up to 95%) but reduced influx by only one-half in+S plants. The inhibition of sulphate influx in-S plants was much greater than that of phosphate influx and could not be prevented by relatively high (100 mol·m^-3 sulphate concentrations accompanying phenylglyoxal treatment. Effects of phenylglyoxal pretreatment were unchanged for at least 30 min after its removal from the solution but thereafter the capacity for sulphate influx was restored. The amount of rc="/content/xj0rj606445r8187/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">newrc="/content/xj0rj606445r8187/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> carrier appearing in-S roots was far greater than in+S roots over a 24-h period.The results indicate that, in the de-repressed state, the sulphate transporter is more sensitive to reagents binding sulphydryl and arginyl residues. This suggests a number of strategies for identifying the proteins involved in sulphate transport.Abbreviations DIDS 4,4rc="/content/xj0rj606445r8187/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-diisothiocyanatostilbene-2,2rc="/content/xj0rj606445r8187/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-disulphonic acid - NEM n-ethylmaleimide - PCMBS p-chloromercuriphenyl sulphonic acid     

Sensitivity of the cell cycle to TGFβ1 does not correlate with transformation of a rat liver epithelial cell line

The effects of TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 on cell cycle events in a rat liver derived epithelial cell line (BL9) and in two in vitro transformants of this line were studied by flow cytometry. Using either ethidium bromide staining or the incorporation of bromodeoxyuridine to evaluate DNA synthesis it was shown that TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 prevented the entry of G0/G1 phase BL9 cells into S phase. TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 did not exert its inhibitory effect(s) on DNA synthesis by the modulation of early events in the cell cycle. The tumorigenic transformed BL9 cell lines gave contrasting responses to the effects of TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1. DNA synthesis in a BL9 cell line derived by transfection with an active N-ras oncogene was unaffected by TFGrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 and thus appeared refractory to its growth controlling effects. On the other hand cells from a BL9 cell line derived by in vitro transformation with activated aflatoxin B₁ retained their sensitivity to the effects of TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1. Thus the loss of the inhibitory effect of TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 on DNA synthesis is not obligatory for the malignant transformation of rat liver epithelial cells.Abbreviations TGFrc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 transforming growth factor rc="/content/r583213mmx833652/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">1 - BSA bovine serum albumin - FBS foetal bovine serum - BrdUrd bromodeoxyuridine - PI propidium iodide - PBS phosphate buffered saline     

Role of the N-terminal region of the A chain in beta 1-bungarotoxin from the venom of Bungarus multicinctus (Taiwan-banded krait)

The N-terminal rc="/content/u0130747188m342r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-amino groups of rc="/content/u0130747188m342r/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">₁-bungarotoxin (rc="/content/u0130747188m342r/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">₁-Bgt) fromBungarus multicinctus venom were modified with trinitrobenzene sulfonic acid and the modified derivative was separated by high performance liquid chromatography. The trinitrophenylated (TNP) derivative contained two TNP groups at the rc="/content/u0130747188m342r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-amino groups of A chain and B chain and showed a marked decrease in enzymatic activity. Methionine residues at positions 6 and 8 of the A chain were oxidized with chloramine T or cleaved with cyanogen bromide to remove the N-terminal octapeptide. Oxidation of methionine residues and removal of the N-terminal octapeptide caused a precipitous decrease in enzymatic activity, whereas antigenicity remained unchanged. The presence of dihexanoyllecithin influenced the interaction between rc="/content/u0130747188m342r/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">₁-Bgt and 8-antilinonaphthalene sulfonate (ANS) and revealed that rc="/content/u0130747188m342r/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">₁-Bgt consists of two types of ANS-binding sites, one at the substrate binding site of the A chain and the other might be at the B chain. The modified derivatives still retained their affinity for Ca²⁺ and ANS, indicating that the N-terminal region is not involved in Ca²⁺ and substrate binding. A fluorescence study revealed that the rc="/content/u0130747188m342r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-amino group of the A chain was in the vicinity of substrate binding site and that the TNP rc="/content/u0130747188m342r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-amino groups were in proximity to Trp-19 of the A chain. In addition, the study showed that the N-terminal region is important for stabilizing the architectural environment of Trp-19. The results, together with the proposal that Trp-19 of the A chain is involved in substrate binding, suggest that the N-terminal region of the A chain plays a crucial role in maintaining a functional active site for rc="/content/u0130747188m342r/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">₁-Bgt.     

Transient states of geosmin,pigments, carbohydrates and proteins in continuous cultures of Oscillatoria brevis induced by changes in nitrogen supply

Transitions in the growth limiting factor from light (I) to nitrogen (N) and vice versa caused changes in geosmin production, protein and carbohydrate content, and the synthesis of pigments such as chlorophyll a (Chl a), phycobiliproteins (PBPs), and rc="/content/h3276r761418740u/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-carotene of the cyanobacterium Oscillatoria brevis. Following Irc="/content/h3276r761418740u/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">N transition the first 150h, the decrease in protein content was compensated for by an increase of carbohydrates, and thereby, a constant biomass level was maintained in this period. Thereafter, biimass dropped to 15% of its initial level. A decrease in geosmin and pigment content was observed during transition from Irc="/content/h3276r761418740u/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">N-limited growth. However, geosmin increased relative to phytol (Chl a) and rc="/content/h3276r761418740u/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-carotene which may indicate that a lowered demand for phytol and rc="/content/h3276r761418740u/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-carotene during N-limited growth allows isoprenoid precursors to be directed to geosmin rather than to pigment synthesis. Synthesis of Chl a and rc="/content/h3276r761418740u/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-carotene at the expense of geosmin was suggested for the observed start of increase in geosmin production only at the time that Chl a and rc="/content/h3276r761418740u/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-carotene had reached their I-limited steady state. Transition from nitrogen to light limited growth caused an acceleration of metabolism shown by a rapid decrease in carbohydrate content accompanied by an increase in protein content. The growth rate of the organisms temporarily exceeded the dilution rate of the culture and the biomass level increased 6-fold. Due to the only modest changes in geosmin production (2-fold) compared to changes in biomass level (6-fold) during I-or N-limited growth, environmental factors seem to have limited effect on geosmin production.Abbreviations Chl a chlorophyll a - dry wt dry weight; - I-limited light-limited - N-limited nitrogen-limited - PBP phycobiliprotein This research was performed at the Department of Microbiology, University of Amsterdam, with finacial support provided by the Royal Norwegian Ministry of Foreign Affairs and the Royal Norwegian Council for Scientific and Industrial Research     

The intrinsic rates of increase of insects of different sizes

ABSTRACT.

• 1 A negative relationship between intrinsic rate of increase, r, and body size has only clearly been shown using data for species drawn from a number of phyla and covering several orders of magnitude in size. Analyses for more closely related species are equivocal.
• 2 Data for ninety-one species of insects, from nine orders, were used to examine the correlation between intrinsic rate of increase and size.
• 3 Intrinsic rate of increase was negatively correlated with both length and weight across orders, but no relationship could be shown within orders.
• 4 Generation times were positively related to body size, but there was no relationship between net reproductive rate (R_Q) and size.
• 5 These results support the hypothesis that documented relationships between species size and colonization success in insects could be a consequence of the scaling of intrinsic rate of increase with size.

     

2-Aminopurine and 5-bromouracil induce alleviation of type I restriction in Escherichia coli: Mismatches function as inducing signals?

Summary The EcoK restriction of unmodified phage rc="/content/lvw54535r2w63283/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0"> is 1000-fold alleviated in Escherichia coli grown in the presence of base analogs 2-aminopurine (2AP) and 5-bromouracil (5BU). 2AP treatment of bacteria affects specificially the type I restriction systems (EcoA, EcoB, EcoD and EcoK) and does not influence type II (EcoRI) and type III (EcoP1) restriction. 2AP-induced alleviation of restriction occurs in bacteria which are deficient in the SOS response (recA and lexA) and mismatch repair (mutH, mutL and mutS) and can be distinguished from the alleviation of restriction observed in dam ^- strains. We suggest that mismatches induced by 2AP and 5BU may function as an inducing signal for the alleviation of restriction observed in the presence of base analogs.     

Tree-ring analysis and conifer growth responses to increased atmospheric CO2 levels

Summary Tree-ring data of naturally grown connifers were analyzed to evaluate the possibility of enhanced tree growth due to increased atmospheric CO₂. Tree cores were obtained from 34 sites in four different climatic regions in the northern hemisphere. In each of the four regions, the sampling sites were located along ecological gradients between the subalpine treeline and low elevations and, sometimes, the arid forest border. Growth trends after 1950, when the atmospheric CO₂ concentration increased by more than 30 rc="/content/w648r2364h106347/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">l·l^-1 indicate an increase in ring-widths at eight of the 34 sites. These chronologies were from sites which moderate temperature or water stress. In four cases the growth increase in the post-1950 period coincided with favorable climatic conditions. In the remaining four cases, the growth increase exceeded the upper bound response expected from CO₂ enrichment experiments with seedling conifer species. Therefore, increased growth in any of the tree-ring chronologies examined could not be solely attributed to higher atmospheric CO₂ concentrations.Major financial supporters: Swiss National Science Foundation (application no. 1.869-0.83); Swiss Federal Institute of Forestry Research, 8903 Birmensdorf, Switzerland; other financial supporters: Carbon Dioxide Research Division, U.S. Department of Energy under subcontract no. 11X-57507V with Martin Marietta Energy Systems, IncOperated by Martin Marietta Energy Systems, Inc., under contract DE-AC05-840R21400 with U.S. Department of Energy     

Expression sites and developmental regulation of genes encoding (1→3,1→4)-β-glucanases in germinated barley

Expression sites of genes encoding (1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">3,1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">4)-rc="/content/t7845513235851r1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucan 4-glucanohydrolase (EC 3.2.1.73) have been mapped in germinated barley grains (Hordeum vulgare L.) by hybridization histochemistry. A³²P-labelled cDNA (copy DNA) probe was hybridized to cryosections of intact barley grains to localize complementary mRNAs. No mRNA encoding (1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">3,1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">4)-rc="/content/t7845513235851r1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucanase is detected in ungerminated grain. Expression of (1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">3,1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">4)-rc="/content/t7845513235851r1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucanase genes is first detected in the scutellum after 1 d and is confined to the epithelial layer. At this stage, no expression is apparent in the aleurone. After 2 d, levels of (1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">3,1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">4)-rc="/content/t7845513235851r1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucanase mRNA decrease in the scutellar epithelium but increase in the aleurone. In the aleurone layer, induction of (1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">3,1rc="/content/t7845513235851r1/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">4)-rc="/content/t7845513235851r1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucanase gene expression, as measured by mRNA accumulation, progresses from the proximal to distal end of the grain as a front moving away from, and parallel to, the face of the scutellum.Abbreviations cDNA copy DNA - RNase ribonuclease     

Anaerobic degradation of trans-cinnamate and ω-phenylalkane carboxylic acids by the photosynthetic bacterium Rhodopseudomonas palustris: evidence for a β-oxidation mechanism

The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and rc="/content/t846t1801r316232/xxlarge969.gif" alt="ohgr" align="BASELINE" BORDER="0">-phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO₂ dependence for growth on acids with greater side-chain lengths. Here, CO₂ was presumably acting as a redox sink for the disposal of excess reducing equivalents. Growth on benzoate did not require the addition of exogenous CO₂. Aromatic acids with an odd number of side-chain carbon atoms (3-phenylpropionate, 5-phenylvalerate, 7-phenylheptanoate) gave greater apparent molar growth yields than those with an even number of side-chain carbon atoms (4-phenylbutyrate, 6-phenylhexanoate, 8-phenyloctanoate). HPLC analysis revealed that phenylacetate accumulated and persisted in the culture medium during growth on these latter compounds. Cinnamate and benzoate transiently accumulated in the culture medium during growth on 3-phenylpropionate, and benzoate alone accumulated transiently during the course of trans-cinnamate degradation. The transient accumulation of 4-phenyl-2-butenoic acid occurred during growth on 4-phenylbutyrate, and phenylacetate accumulated to a 1:1 molar stoichiometry with the initial 4-phenylbutyrate concentration. It is proposed that the initial steps in the anaerobic degradation of trans-cinnamate and the group of acids from 3-phenylpropionate to 8-phenyloctanoate involves rc="/content/t846t1801r316232/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-oxidation of the side-chain.Abbreviation 3-PP 3-phenylpropionic acid - 4-PB 4-phenylbutyric acid - 5-PV 5-phenylvaleric acid - 6-PH 6-phenylhexanoic acid - 7-PH 7-phenylheptanoic acid - 8-PO 8-phenyloctanoic acid - 4-P2B 4-phenyl-2-butenoic acid - GC/MS Gas chromatography/Mass spectrometry - HPLC High-pressure liquid chromatography     

Effect of interferon γ on the sensitivity of bovine-papilloma-virus(BPV1)-transformed cell lines to cell-mediated cytotoxicity

Summary The effect of interferon rc="/content/u07l638488636r35/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> (IFNrc="/content/u07l638488636r35/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">) on the immunogenicity and immunosensitivity of mouse cell lines transformed by bovine papillomavirus type 1 (BPV1) DNA was examined in a syngeneic mouse model. The overnight incubation of BPV1-transformed cell lines with 100 IU/ml IFNrc="/content/u07l638488636r35/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> did not affect their ability to induce the generation of cytotoxic effector cells but it clearly increased their sensitivity to lysis by interleukin-2-induced lymphokine-activated killer (LAK) cells and by nonspecific LAK-type effector cells induced by BPV-1-transformed cell lines. The treatment of two allogeneic lymphoid tumour cell lines, P815X2 and YAC-1, with IFNrc="/content/u07l638488636r35/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> either decreased or had no effect on their sensitivity to LAK-cell-mediated lysis.