The effect of L-2-amino-4-methoxy-trans-3-butenoic acid on serine hydroxymethyl transferase

The tumour growth inhibitor L-2-amino-4-methoxy-trans-3-butenoic acid (Ro07-7957) inhibits serine hydroxymethyltransferase in cytosolic extracts of Walker carcinoma non-competitively with respect to L-serine with an apparent inhibition constant similar to the K_m-value for L-serine. The kinetics of inactivation suggest that it reacts as an irreversible substrate analogue. Incubation of Walker cells with Ro07-7957 causes an increase in serine hydroxymethyltransferase activity which is most pronounced at concentration ≤LD₅₀. This increase in enzyme activity does not occur in the presence of cycloheximide. These results suggest that inhibition of serine hydroxymethyltransferase in intact cells is accompanied by an increase in enzyme biosynthesis and that the growth inhibitory property of Ro07-7957 does not involve interference with the conversion of serine to glycine.     

Specificity of Ethylcholine Mustard Aziridinium as an Irreversible Inhibitor of Choline Transport in Cholinergic and Noncholinergic Tissue

The sensitivity of choline transport to inhibition by ethylcholine mustard aziridinium (ECMA) was studied in several tissues. Choline transport was found to be inhibited irreversibly by ECMA in guinea pig and rat synaptosomes but not inhibited in erythrocytes or kidney slices. If this finding can be extended to other tissues ECMA sensitivity may provide a simple criterion for identifying the choline carrier associated with cholinergic tissue.     

Interaction between pathogenic and saprobic fungi isolated from soybean roots and seeds

A variety of interactions was recorded in culture between 11 saprobic fungi isolated from soybean (Glycine max) roots and seeds and the soybean pathogens Cercospora sojina, Colletotrichum truncatum, Macrophomina phaseolina, Phomopsis sojae, and Septoria glycines. The most active saprobes were Aspergillus terreus, Chaetomium cupreum, Epicoccum nigrum, Gliocladium roseum, Myrothecium roridum, Penicillium thomii, and Trichothecium roseum. Hyphal lysis of several fungal pathogens by Acremonium sp., C. cupreum and P. thomii was recorded perhaps because of parasitism by G. roseum and T. roseum. In greenhouse studies, seeds coated with G. roseum, P. thomii, and T. harzianum emerged significantly (P=0.05) more than those coated with A. terreus and the control. In field studies, seeds coated with a conidial suspension of A. terreus, G. roseum, P. thomii or Trichoderma harzianum produced a significantly greater stand than the control. The area of cotyledons covered with lesions caused by C. truncatum was significantly less on seeds coated with G. roseum, P. thomii and T. harzianum than the control.     

Different effects of supplied ammonium on glutamine synthetase activity in mustard (Sinapis alba) and pine (Pinus sylvestris) seedlings

The activity of glutamine synthetase (GS) in mustard ( Sinapis alba L.) and Scots pine ( Pinus sylvestris L.) seedlings was used as an index to evaluate the capacity to cope with excessive ammonium supply. In these 2 species GS activity was differently affected by the application of nitrogen compounds (NH₄⁺ or NO₃⁻). Mustard seedlings older than 5 days showed a considerable increase in GS activity after NH₄⁺ or NO₃⁻ application. This response was independent of the energy flux, but GS activity in general was positively affected by light. Endogenous NH₄⁺ did not accumulate greatly after nitrogen supply. In contrast, seedlings of Scots pine accumulated NH₄⁺ in cotyledons and roots and showed no stimulation of GS activity after the application of ammonium. In addition, root growth was drastically reduced. Thus, the pine seedlings seem to have insufficient capacity to assimilate exogenously supplied ammonium. NO₃⁻, however, did not lead to any harmful effects.     

Host plant recognition in monophagous weevils: specificity in feeding responses of Ceutorhynchus constrictus and the variable effect of sinigrin

Host plant relations of the monophagous weevil Ceutorhynchus constrictus Marsh. (Coleoptera: Curculionidae: Ceutorhynchinae) feeding on garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande (Cruciferae) were studied in the laboratory. Most other crucifers were rejected in choice tests using garlic mustard as a reference plant, but Brassica nigra, Sinapis alba and Thlaspi arvense were as acceptable as the host plant. Flowering plants of Descurainia sophia were acceptable while young plants of this species were not. The most important feeding stimulants in extracts of garlic mustard were uncharged, water soluble compounds. The most abundant glucosinolate in garlic mustard, sinigrin, was a feeding stimulant, too. However, the feeding stimulatory activity of sinigrin was only expressed in the presence of still unidentified uncharged compounds from garlic mustard leaves. Host plant relations in monophagous crucifer-feeding insects is discussed in relation to the distinctness of glucosinolate patterns found in their host plants.

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Zusammenfassung Ceutorhynchus constrictus Marsh. (Coleoptera: Chrysomelidae: Ceutorhynchinae) ist ein monophager Rüsselkäfer, der an Knoblauchhederich frisst. Das Wirtswahl-Verhalten dieses Käfers ist im Labor untersucht worden. Die meisten Crucifiren waren im Wahlversuche nicht akzeptiert, wenn Knoblauchhederich als Vergleichspflanze vorhanden war. Von Brassica nigra, Sinapis alba, und Thlaspi arvense wurden im Vergleich gleiche Mengen verzehrt wie von der Wirtspflanze. Blühende Descurainia sophia Pflanzen wurden, im Gegensatz zu Jungpflanzen der gleichen Art, angenommen. Die wichtichsten Phagostimulanten in Extrakten von Knoblauchhederich-Blättern waren ungeladene, wasserlösliche Substanzen. Das häufigste Glukosinolat im Knoblauchhederich, Sinigrin, war auch ein Phagostimulant. Doch war die phagostimulierende Wirkung von Sinigrin nur in Kombinationen mit noch nicht identifizierten, ungeladenen Substanzen aus Knoblauchhederich-Blätter nachweisbar. Wirtspfanzen-Beziehungen von monophagen Insekten werden diskutiert im Zusammenhang mit der Eigenart des Glukosinolat-Inhaltes ihrer Wirtspflanzen.

     

Dose- and time-dependent hippocampal cholinergic lesions induced by ethylcholine mustard aziridinium ion: Effects of nerve growth factor,GM1 ganglioside,and vitamin E

Ethylcholine mustard aziridinium ion (ECMA) was infused intracerebroventricularly (icv) to rats followed by measurement of two markers of presynaptic cholinergic neurons, choline acetyltransferase (ChAT) activity and high affinity choline transport (HAChT), in the hippocampus and cortex. Bilateral icv administration of 1, 2, or 3 nmol of ECMA per side produced dose-dependent reductions in each marker in the hippocampus, but not in the cortex, one week after treatment. Reductions of 52% and 46% for ChAT activity and HAChT, respectively, were produced in the hippocampus by 3 nmol ECMA. Measurement of these two markers at different times after icv infusion of 2 nmol ECMA/ventricle revealed that the activity of ChAT was reduced to a greater extent than was HAChT in the hippocampus 1 day and 1, 2, 4, and 6 weeks after treatment. The maximal reductions of ChAT activity and HAChT (61% and 53%, respectively) were reached between 1 and 2 weeks after ECMA administration. There was no evidence of regeneration of either marker at 4 or 6 weeks posttreatment. HAChT and ChAT activity in the cortex were not altered at any of the posttreatment times examined.ECMA-induced deficits in hippocampal ChAT activity and HAChT were not counteracted by the following treatments: (i) daily administration of GM₁ ganglioside (10 mg/kg, intraperitoneally (ip)) from the day prior to infusion of ECMA until 2 weeks later; (ii) daily administration of GM₁ ganglioside between 2 and 6 weeks after infusion of ECMA; and (iii) icv administration of nerve growth factor (NGF) twice per week for 2 weeks after ECMA treatment. Since similar treatments with NGF and GM₁ ganglioside ameliorate lesions induced by other methods, these results indicate that the mechanism of lesion formation and the surviving cellular components influence the functional effects of neurotrophic factors. In contrast to the above results, treatment with vitamin E significantly attenuated ECMA-induced deficits of ChAT activity and HAChT. Further studies of the effects of vitamin E on the development of ECMA-induced deficits may help to elucidate the mechanism action of ECMA.     

High frequency of plant regeneration from hypocotyl explants of Brassica carinata A. Br.

An efficient tissue culture system for high frequency of plant regeneration from hypocotyl explants of Brassica carinata was developed via manipulation of culture medium and selection of explants. Explants grown on medium containing combinations of 2 mg l^-1 BA and 0.01 mg l^-1 NAA or 4 mg l^-1 kinetin and 0.01 mg l^-1 2,4-D regenerated shoots at 100% frequency. High frequency shoot regeneration occurred only from explants originating from 6 to 7-day-old but not younger or older seedlings. Explants showed higher regeneration capacity at the distal end than the proximal end, and the upper segment was more regenerative than the lower segment of hypocotyl. Regenerants were rooted on half-strength growth regulator-free medium, acclimatized and developed into normal, fertile plants.Abbreviations BA benzyladenine - 2-4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - MS Murashige & Skoog     

Effect of nitrogen and chlormequat chloride on the seed yield and oil content of mustard (Brassica juncea L. Czern & Coss)

The growth of mustard was increased significantly when treated with up to 80 kg N ha^–1 (N₈₀). Spraying with (2-chloroethyl) trimethylammoniumchloride (chlormequat chloride) increased seed yield and seed protein content. Spraying nitrogen fertilized plots with chlormequat chloride, increased leaf area, leaf area ratio, leaf area duration, number of siliquae plant^–1, number of seeds siliqua^–1 and length of siliqua. Reducing, non-reducing and total sugars in the leaves at 80 days after sowing were also affected significantly. Chlorophyll a, b and total chlorophyll were little affected. The number of siliquae plant^–1 was highly correlated with seed yield in both the seasons of experimentation. The correlation coefficient value () was 0.586 in 1982/83 and 0.912 in 1983/84.The total accumulation of nutrients, i.e. nitrogen, phosphorus and potassium in seed and straw was significantly affected by N₈₀ × chlormequat chloride interaction.     

Location in Muscarinic Acetylcholine Receptors of Sites for [3H]Propylbenzilcholine Mustard Binding and for Phosphorylation with Protein Kinase C

Muscarinic acetylcholine receptors purified from porcine cerebra or atria were covalently labeled with [3H]propylbenzilylcholine mustard ([3H]PrBCM), and then the labeled receptors were subjected to limited hydrolysis with trypsin, V8 protease, and lysyl endopeptidase, followed by analysis involving sodium dodecyl sulfate-polyacrylamide gel electrophoresis, fluorography, autoradiography, or immunostaining. The labeled peptides were located on the basis of their reactivity with antibodies raised against three synthetic peptides with partial sequences of the m1 or m2 receptor, and of their sensitivity to endoglycosidase F, which was taken as evidence that they contain glycosylation sites near the N terminus. The [3H]PrBCM-binding site in both cerebral and atrial receptors was found to be located between the N terminus and the second intracellular loop, because the size of the smallest deglycosylated peptide that contained both the [3H]PrBCM-binding and glycosylation sites was approximately 16 kDa. Cerebral receptors were 32P-phosphorylated with protein kinase C, and the major phosphorylation sites in cerebral muscarinic receptors were found to be located in a C-terminal segment including a part of the third intracellular loop, because a 32P-labeled peptide of 12-14 kDa reacted with anti-(m1 C-terminal peptide) antiserum. The presence of an intramolecular disulfide bond, probably between Cys 98 and Cys 178 in the first and second extracellular loops, respectively, was suggested by the finding that a peptide of approximately 17 kDa containing the [3H]PrBCM-binding site, but not the glycosylation sites, was partly converted to a peptide of approximately 12 kDa on treatment with beta-mercaptoethanol.     

Plant regeneration from cotyledon protoplasts of Brassica carinata

Protoplasts isolated from cotyledons of Brassica carinata, underwent sustained division when cultured at 5.0 × 10⁴ ml^-1 in modified 8p medium (KM8P) with 1.0% (w/v) Seaplaque agarose. Cell colonies produced callus when agarose droplets, in which the protoplasts were embedded, were transferred to K8 medium with 0.6% (w/v) Sigma Type I or Type VII agarose at day 16, giving a plating efficiency of 1.6%. Seventy percent of the protoplast derived-tissues produced shoot buds after subculture to MS medium containing 3.0% (w/v) sucrose, 1.125 mgl^-1 BAP, 0.035 mgl^-1 GA and 0.6% (w/v) Type I agarose, resulting in shoot formation from 1.1% of the protoplasts originally plated. Protoplast-derived colonies transferred to hormone-free MS medium with 1.0% (w/v) sucrose and 0.6% (w/v) Type I agarose produced roots. The latter gave rise to shoots after excision from the parent callus and culture on MS medium with 3.0% sucrose, 0.225 mgl^-1 BAP, and 0.6% (w/v) Type I agarose. Shoots regenerated directly from protoplast-derived calli, or indirectly from roots, developed prolific root systems when placed on hormone-free MS medium with 1.0% (w/v) sucrose and 0.6% (w/v) Type I agarose.Abbreviations BAP 6-benzylaminopurine - CH casein hydrolysate - 2,4-D 2,4-dichlorophenoxyacetic acid - GA gibberellic acid - K kinetin - NAA -naphthaleneacetic acid - MES 2(N-morpholino)ethanesulphonic acid, 2,iP-6(,-dimethylallyamino) purine - IAA indole-3-acetic acid - Z zeatin - ZR zeatin riboside