Effects of Triton X-100 on acid phosphatases with different substrate specificities

Summary The effect of Triton X-100 on the activities of acid phosphatases from wheat germ, potato and human prostate was tested using -glycerophosphate, p-nitro-phenyl phosphate and naphthol AS BI phosphate as substrates. There was little effect on -glycerophosphatase activity at the concentrations of Triton X-100 tested. However at low concen trations of the detergent there was a stimulation of the activities of p-nitrophenyl phosphatase and naphthol phosphatase which were inhibited with the higher concentrations. Triton X-100 was found to enhance colour production between naphthol AS BI and fast red violet LB.Further evidence is presented confirming the presence of more than one acid phosphatase from each of the sources employed.     

Application ofVerticillium lecanii for the control ofAphis gossypii by a low-volume electrostatic rotary atomiser and a high-volume hydraulic sprayer

Verticillium lecanii (Fungi: Deuteromycete) blastospores were applied to a chrysanthemum crop by an ULV electrostatically charged rotary atomiser (APE-80). The deposition of spores and subsequent control ofAphis gossypii were compared to high volume hydraulic application. A full rate treatment (2×10¹³ blastospores per ha.) was applied by the APE-80 at week 1 and reduced spore rates of 1/6^th and 1/12^th applied by both the APE-80 and the hydraulic sprayer once and twice a week respectively for weeks 1 to 6. Untreated plots served as controls. Initial deposits of spores were higher with the electrostatic sprayer and better distributed with respect to the position of the target aphids. Significantly lower aphid populations were recorded on the electrostatically treated plots in week 4. The single full rate treatment had significantly fewer aphids than the untreated plots from week 3 and all treatments had significantly fewer aphids than the untreated plots from week 5 onwards. The proportion of the aphid population killed byV. lecanii was higher on the electrostatically treated plots until week 6.      

Age determination of Antarctic krill using fluorescence and image analysis of size

Summary The ages of 252 mature female krill, collected from Prydz Bay in January 1985, were determined using length frequency analysis and the fluorescent age pigment (FAP) technique. Results of both methods suggest 6 years classes for adult krill. Correspondence between the ages determined by the two techniques is generally within one year. The animals were also analyzed by a computerized image analysis system, which recorded a large suite of size and shape parameters. The accuracy of discriminant functions constructed to relate the image analysis parameters to age approached 90% for the ages defined by length frequency, and 52% for physiological age.     

Studies on the biosynthesis and metabolism of the phytoalexin lubimin and related compounds in Datura stramonium L.

Arachidonic acid, cellulase, CuSO₄, a sonicate of Phytophthora infestans mycelium and a spore suspension of Penicillium chrysogenum all elicited the formation of the sesquiterpenoid phytoalexins lubimin, 3-hydroxylubimin and rishitin in fruit cavities of Datura stramonium. 3-Hydroxylubimin was the predominant phytoalexin formed after treatment of the fruits with arachidonic acid, cellulase and the P. infestans preparation. Copper sulphate was a potent elicitor of lubimin but not 3-hydroxylubimin. The fungus P. chrysogenum metabolized lubimin and 3-hydroxylubimin to 15-dihydrolubimin and 3-hydroxy-15-dihydrolubimin respectively, both in fruit cavities inoculated with spores of this fungus and in pure culture. The 15-dihydrolubimin formed in the fruits by the fungus was further metabolized (by the fruits) to both isolubimin and 3-hydroxy-15-dihydrolubimin. The precursor-product relationships between all of the subject compounds was investigated by feeding experiments with ³H-labelled compounds. 2-Dehydro-[15-³H₁]lubimin was rapidly and efficiently incorporated into lubimin and may be the direct precursor of lubimin in planta. 3-Hydroxy[2-³H₁]lubimin was incorporated into the nor-eudesmane rishitin but 10-epi-3-hydroxy[2-³H₁]lubimin was not. An updated scheme for the biosynthesis and metabolism of lubimin and related compounds in infected tissues of solanaceous plants is presented.We thank Mr Vic Swetez for the provision of plant material, Mrs Margaret Huffee for technical assistance, Dr David Ewing for help with obtaining NMR spectra, and the Agricultural and Food Research Council for financial support.     

Short-term changes in carbon-isotope discrimination identify transitions between C3 and C4 carboxylation during Crassulacean acid metabolism

Short-term measurements of instantaneous carbon-isotope discrimination have been determined from mass-spectrometric analyses of CO₂ collected online during gas exchange for the epiphytic bromeliad Tillandsia utriculata L. Using this technique, the isotopic signature of CO₂ exchange for each phase of Crassulacean acid metabolism (CAM) has been characterised. During night-time fixation of CO₂ (Phase I), discrimination () ranged from 4.4 to 6.6, equivalent to an effective carbon-isotope ratio (¹³C) of –12.3 to –14.5 versus Pee Dee Belemnite (PDB). These values reflected the gross photosynthetic balance between net CO₂ uptake and refixation of respiratory CO₂, characteristic of CAM in the Bromeliaceae. When for the relative proportion of external (p _a ) and internal (p _i) CO₂ is taken into account, calculated p _i/p _a decreased during the later part of the dark period from 0.68 to 0.48. Measurements of during Phase II, early in the light period, showed the transition between C₄ and C₃ pathways, with carboxylation being increasingly dominated by ribulose bisphosphate carboxylase (Rubisco) as increased from 10.5 to 21.2 During decarboxylation in the light period (Phase III), CO₂ leaked out of the leaf and the inherent discrimination of Rubisco was expressed. The value of calculated from on-line measurements (64.4) showed that the CO₂ lost was considerably enriched in ¹³C, and this was confirmed by direct analysis of the CO₂ diffusing out into a CO₂-free atmosphere ( ¹³C = + 51.6 versus PDB). Instantaneous discrimination was characteristic of the C₃ pathway during Phase IV (late in the light period), but a reduction in showed an increasing contribution from phosphoenolpyruvate carboxylase. The results from this non-invasive technique confirm the observations that double carboxylation involving both phosphoenolpyruvate carboxylase and Rubisco occurs during the transient phases of CAM (II and IV) in the light period.Abbreviations and Symbols CAM Crassulacean acid metabolism - H⁺ (dawn-dusk) variation in titratable acidity - ¹³C carbonisotope ratio of plant organic material, relative to Pee Dee Belemnite (vs. PDB) - discrimination against ¹³CO₂, - p _i, p _a internal, external partial pressures of CO₂ - Rubisco ribulose1,5-bisphosphate carboxylase - PAR photosynthetically active radiation - PEPCase phosphoenolpyruvate carboxylase We are grateful for financial support in respect of research grants (GR3/5360, GR3/6419) and a studentship awarded by the Natural Environment Research Council, UK.     

Class I major histocompatibility complex cDNA clones from sheep thymus: alternative splicing could make a long cytoplasmic tail

To investigate the class I major histocompatibility complex (MHC) genes expressed in the young sheep thymus, a cDNA library was screened with a human HLA-B7 cDNA probe under conditions of relaxed stringency. Thirteen clones were isolated and found by partial sequences to fall into five classes, requiring the expression of at least three loci. One sequence was found six times, almost half of the total, and may thus represent the major message expressed in the young sheep thymus. One of the clones was found to have failed to excise the intron between cytoplasmic exons 7 and 8, leading to the predicted synthesis of a cytoplasmic domain 23 amino acids longer than the other sheep sequences, and 15 amino acids longer than any cytoplasmic domain previously described. The sequences of all the clones were found to be most similar to bovine, and least similar to mouse class I MHC sequences.The nucleotide sequence data reported in this paper have been sunmitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M 34672-6.