Purification and properties of a heat-resistant exotoxin produced byMacrophomina phaseolina (Tassi) Goid in culture

Summary A partially purified preparation of a water-soluble, heat-resistant, nonspecific exotoxin produced by a strain ofMacrophomina phaseolina, isolated fromPhaseolus mungo L. could reduce Cu⁺⁺ ions and produced a red colour with 2,4-dinitrophenyl hydrazine reagent. It caused inhibition of seed germination, wilting of cut seedlings, stunted growth of young seedlings and loss of permeability of the cell membrane. Seedlings ofP. mungo, grown in presence of the toxin showed a slight increase in the contents of protein and total RNA over control, but a significant increase in the specific activities of F-1, 6-BP aldolase and G-6-P isomerase.     

Einfluss des Schwefeldioxids auf den Gehalt freier Saccharide und Aminosäuren in Erbsen-Keimpflanzen

Summary The influence of gaseous 1% sulphur dioxide during 24, 48, 72 and 96 h on saccharide and amino acid content, has been studied on 14–15-day old green and etiolated pea seedlings. In roots and shoots of intoxicated seedlings of both sorts, there was found a marked decrease of sucrose and a marked increase of glucose and fructose content, most probably as a consequence of disturbed sucrose biosynthesis. In cotyledons, roots and shoots there was also found an increase of alanine and a decrease of glutamic acid content.     

In vivo continuous electrochemical determination of dopamine release in rat neostriatum]

Polarographic micro-electrodes (carbon fiber, o. d. 8 micron) implanted in the Rat caudate nucleus, allowed a practically continuous in vivo monitoring (one measurement every 5 sec.) of the extra-cellular concentration of dopamine released by striatal dopaminergic terminals. Administration of amphetamine produced a reproducible increase of the oxidation current. This effect was suppressed after the selective degeneration of the striatal dopaminergic terminals following the injection of 6-OHDA into the substantia nigra or after inhibition of the synthesis of the amine by alpha methyl-p-tyrosin. After 5 hrs. this drug produced a 70% decrease of the oxidation current.     

Adrenocortical metabolism and plasma corticosterone in soman intoxicated rabbits

The organophosphate neurotoxin soman produced impairments in adrenocortical RNA and protein metabolism. Fasciculate and reticular cell RNA and protein contents were suppressed with sublethal to acutely lethal dosages (20, 30 and 40 micrograms/kg, s.c.) during the acute excitatory phase of intoxication and at 6-8 h post injection. All three dosages produced ca 90% inactivation of plasma cholinesterase. A transient elevation of plasma corticosterone occurred with 20 micrograms/kg soman whereas there was a protracted increase with 30 micrograms/kg. Corticosterone was not significantly elevated with 40 micrograms/kg, but death occurred at 13 +/- 4 min. Thus, the magnitude and/or nature of soman-induced metabolic impairments does not appear to prevent adrenal activation.     

Central IL-1 differentially regulates peripheral IL-6 and TNF synthesis

Centrally given interleukin (IL)-1 is known to induce a rapid rises in blood IL-6. To extend this and to examine the mechanism by which this occurs, the effects of intracerebroventricular (icv) injection of human recombinant IL-1β on mRNA expression of IL-6 and tumour necrosis factor (TNF) in the spleen and liver were examined in rats. Icv injection of IL-1 produced a rapid rise of the tissue mRNA levels of IL-6 and TNF in both organs, prior to and/or in parallel with an increase in their serum levels. Pretreatment with chlorisondamine, a ganglionic blocking agent, inhibited the IL-6 responses, while it had little influence on the TNF responses. The results suggest that brain IL-1 induces peripheral production of IL-6, but not of TNF, through autonomic nervous system activation. Received 27 October 1997; received after revision 15 December 1997; accepted 12 January 1998     

Inhibitor of the oxidation of catechin released from the roots of corn seedlings

Summary When the specific activities of the catechin oxidases (catechin as the substrate) which were released from the roots of the seedlings of alfalfa, tomato, wheat, lettuce and corn were compared, it was found that the oxidizing activity was absent from the root exudate of corn seedlings. A 6.3 kDa protein was purified from the root exudate of corn seedlings and in the presence of this protein, the oxidation of catechin was inhibited. This inhibitor is responsible for the inability of the root exudate of corn seedlings to oxidize catechin.     

Stimulation of induction or inhibition of crown-gall tumor development by RNA-fragments U2. Interference by auxin]

RNA-fragments U2 obtained by mild degradation with RNase U2 of ribosomal RNA containing A and G nucleotides in excess are capable of exhibiting either a stimulatory effect on the induction of Crown-gall tumors or an inhibitory action on their subsequent development. These different effects are dependent on the moment at which RNA-fragments were introduced into wounded Pea seedlings infected by Agrobacterium tumefaciens B6. The results obtained in vitro and in vivo suggest that an interaction between auxin and RNA-fragments U2 may take place, either increasing the tumor induction or inhibiting the proliferation of tumourous cells.     

Plants are better protected against spider-mites after exposure to volatiles from infested conspecifics

When infested by herbivorous mites, cotton seedlings produce volatile cues that elicit attraction of predatory mites. Experiments were carried out to elucidate how downwinduninfested conspecific seedlings are affected by these volatiles. It was found that the rate of oviposition of herbivorous mites was reduced on seedlings exposed to volatiles from infested seedlings. Moreover, predatory mites were attracted by exposeduninfested seedlings. These results strongly suggest that uninfested plants are better protected against herbivore attack when exposed to airborne chemicals released by their infested neighbours.     

Reflex motility of the stomach evoked by electrical stimulation of the hepatic vagus nerve

Summary Electrical stimulation of the cranial end of the cut hepatic branch of the vagus nerve produced an increase in the motility of the empty stomach in the rat, whereas systemic injection of insulin produced a gradual increase in the motility.Acknowledgment. The authors are indebted to Dr K. Yamaguchi and Prof. A. Niijima for their encouragement of the project.     

Effect of benzatropine on the O-methylation of striatal dopamine]

After treatment by nialamid, benztropine administered to Rats produced an increase in the level of 3-O-methyldopamine in the corpus striatum. It produced a slight increase in the level of striatal dopamine and no change in the level of norepinephrine. The monoamine oxydase and catechol-O-methyltransferase activities of remaining brain showed no variations by benztropine. The results suggest the possible involvement of striatal dopamine and its extraneuronally catabolism in the antiparkinsonian effect of benztropine.     

Comparative study of oxalate oxidase in three genotypes ofSorghum vulgare

Summary The presence of an oxalate oxidase (EC 1.2.3.4) has been demonstrated in 15,000×g supernatants prepared from 10-day-old seedlings of three genotypes ofSorghum vulgare: grain sorghum hybrid (CSH-5), grain-cum-forage sorghum (PC-6) and forage sorghum (PC-1). The specific activity of the enzyme in the different tissues of seedlings was found to be present in the order leaves > stems > roots in PC-6 and PC-1, but this order was reversed in CSH-5. A comparison of the different properties of the leaf enzyme of these three genotypes of sorghum revealed that the enzyme has maximum activity in the acidic pH range from 4.0 to 5.0 and in the temperature range from 37°C to 40°C. The enzyme was stimulated by Cu²⁺ and Fe²⁺. The rate of H₂O₂ formation in the enzyme reaction was linear up to 5 min and was stoichiometrically related to oxalate consumption. The enzyme is unaffected by Na⁺ at physiological concentration (0.15 M). The superiority of this enzyme over moss and other plant enzymes for enzymic determination of urinary oxalate is discussed.     

Enemy-induced dispersal in a parasitic wasp

Females of the parasitic waspAphidius uzbekistanicus, a specialist aphid primary parasitoid, react to the presence of their specialist hyperparasitoid enemyAlloxysta victrix by leaving the area. The wasps leave to increase their reproductive success, because only their offspring, but not the wasps themselves, are threatened by enemy attack. Furthermore, this dispersal is elicited through the action of volatile chemical cues produced by the hyperparasitoids. We provide evidence for 6-methyl-5-hepten-2-one being one of the volatiles eliciting dispersal. The tendency of the wasps to leave areas which are being colonized by their enemies reduces their efficiency as aphid antagonists.     

The hypothalamic somatostatinergic pathways mediate feeding behavior in the rat

The level of somatostatin in the hypothalamus was higher in satiated rats than in hungry rats. Elevating hypothalamic somatostatin levels by administering somatostatin into the hypothalamus produced a decrease in food intake, whereas lowering hypothalamic somatostatin levels by administering cysteamine into the peritoneal cavity produced an increase in food intake in rats.     

Effects of retinoic acid on the fibrinolytic activity of HL 60 human promyelocytic leukemia cells

Summary Fibrinolytic activity of HL 60 human leukemic cells was found to increase in parallel with myeloid differentiation following retinoic acid but not dimethylsulfoxide treatment. However, both retinoic acid and dimethylsulfoxide produced an increase in acid phosphatase and a decrease in muramidase.     

Rosette formation by human T and B lymphocytes in the presence of adrenergic and cholinergic drugs.

It was shown that adrenergic drugs, which increase the intracellular levels of cAMP, inhibit the rosette formation by T-lymphocytes, but stimulate the rosettes produced by B-lymphocytes. Cholinergic drugs, which increase the levels of cGMP, on the contrary, stimulate the formation of rosettes by T-lymphocytes but inhibit those produced by B-lymphocytes.     

Effect of dipyridamole on human platelet phospholipids

Summary The effect of dipyridamole on platelet phospholipids has been studied. After the platelet incubation with dipyridamole, a 38% reduction in the concentration of the sphingomyelin and a 21% increase in phosphatidyl choline were produced.     

Rosette formation by human T and B lymphocytes in the presence of adrenergic and cholinergic drugs

Summary It was shown that adrenergic drugs, which increase the intracellular levels of cAMP, inhibit the rosette formation by T-lymphocytes, but stimulate the rosettes produced by B-lymphocytes. Cholinergic drugs, which increase the levels of cGMP, on the contrary, stimulate the formation of rosettes by T-lymphocytes but inhibit those produced by B-lymphocytes.Acknowledgments. This investigation was supported by Grant from National Council for Scientific and Technological Development (CNPq), Rio de Janeiro, Brazil.     

Effect of dipyridamole on human platelet phospholipids.

The effect of dipyridamole on platelet phospholipids has been studied. After the platelet incubation with dipyridamole, a 38% reduction in the concentration of the sphingomyelin and a 21% increase in phosphatidyl choline were produced.     

Melatonin biosynthesis in the mammalian pineal gland

Rhythmic production of melatonin by the mammalian pineal occurs in response to noradrenergic stimulation which produces a cascade of biochemical events within the pinealocyte. In the rat, massive changes in NAT activity result from an increase in intracellular c-AMP levels produced by a synergistic interaction whereby an alpha 1 activation amplifies beta-adrenergic stimulation. The intracellular events mediating this effect are described. A major aspect of the temporal control of melatonin production is the programmed down-regulation of responses to noradrenergic stimulation once the initial surge of c-AMP is produced. Noradrenergic activation of the gland also influences other enzymic functions, including tryptophan hydroxylase and HIOMT activities, and produces a dramatic increase in intracellular c-GMP levels. Other neurotransmitters and neuropeptides, e.g. VIP, may also influence pineal function and comparisons are made between the rat, the subject of the bulk of experimental studies, and other species.     

Amylin given by central or peripheral routes decreases gastric emptying and intestinal transit in the rat

The effect of rat amylin on gastric emptying and intestinal transit in the rat was examined. Amylin administered intracerebroventricularly (1, 2, 2.5 or 4 g/rat) produced the maximal decrease in gastric emptying and intestinal transit at the dose of 2.5 g/rat. Higher doses produced a lower effect. Peripheral administration (25, 50 or 100 g/kg) produced dose-dependent effects. Pre-treatment with neostigmine blocked the effect of amylin when it was centrally injected, while the effect of amylin given peripherally was partially reduced. Pre-treatment with domperidone decreased the inhibitory effect of peripherally injected amylin, but no effect was observed when the peptide was centrally injected.