A soluble chloroplast protein catalyzes ribulosebisphosphate carboxylase/oxygenase activation in vivo

Ribulosebisphosphate carboxylase/oxygenase (EC 4.1.1.39) (rubisco) must be fully activated in order to catalyze the maximum rates of photosynthesis observed in plants. Activation of the isolated enzyme occurs spontaneously, but conditions required to observe full activation are inconsistent with those known to occur in illuminated chloroplasts. Genetic studies with a nutant of Arabidopsis thaliana incapable of activating rubisco linked two chloroplast polypeptides to the activation process in vivo. Using a reconstituted light activation system, it was possible to demonstrate the participation of a chloroplast protein in rubisco activation. These results indicate that a specific chloroplast enzyme, rubisco activase, catalyzes the activation of rubisco in vivo.     

Effects of the S-adenosylhomocysteine hydrolase inhibitors 3-deazaadenosine and 3-deazaaristeromycin on RNA methylation and synthesis

The effects of 3-deazaaristeromycin and 3-deazaadenosine on RNA methylation and synthesis were examined in the mouse macrophage cell line, RAW264. S-Adenosylhomocysteine accumulated in cells incubated with 3-deazaaristeromycin while S-3-deazaadenosylhomocysteine was the major product in cells incubated with 3-deazaadenosine and homocysteine thiolactone. RNA methylation was inhibited to a similar extent by the accumulation of either S-adenosylhomocysteine or S-3-deazaadenosylhomocysteine, with S-adenosylhomocysteine being a slightly better inhibitor. In mRNA, the synthesis of N6-methyladenosine and N6-methyl-2'-O-methyladenosine were inhibited to the greatest extent, while the synthesis of 7-methylguanosine and 2'-O-methyl nucleosides were inhibited to a lesser extent. Incubation of cells with 100 microM 3-deazaaristeromycin or with 10 microM 3-deazaadenosine and 50 microM homocysteine thiolactone produced little inhibition of mRNA synthesis, even though mRNA methylation was inhibited. In contrast, mRNA synthesis was greatly inhibited by treatment of cells with 100 microM 3-deazaadenosine and the inhibition of synthesis was not correlated with an inhibition of methylation.     

Potential of Agrotis ipsilon nucleopolyhedrovirus for suppression of the black cutworm (Lepidoptera: Noctuidae) and effect of an optical brightener on virus efficacy.

Studies were performed in the laboratory, greenhouse and field to assess the potential of Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) and a viral enhancing agent, M2R, for suppression of Agrotis ipsilon (Hufnagel). In laboratory droplet feeding bioassays, AgipMNPV was shown to be highly active against third-instar A. ipsilon. The optical brightener M2R significantly reduced LD50 estimates by approximately 160-fold, but had no direct effect on survival time estimates. In greenhouse trials, spray and bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings caused by third-instar A. ipsilon. In two sets of replicated field trials, bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings by third-instar A. ipsilon. However, there were no beneficial effects attributable to the inclusion of M2R in AgipMNPV formulations under greenhouse or field conditions. It seems likely that in an appropriately designed pest management program AgipMNPV could be used to suppress field populations of early and mid-instar A. ipsilon.     

Homologies between paraflagellar rod proteins from trypanosomes and euglenoids revealed by a monoclonal antibody

A Nonidet P 40 insoluble fraction was isolated from Trypanosoma brucei and was used to raise a monoclonal antibody (5E9). The antigen was localized by indirect immunofluorescence in the flagellum of T. brucei and of two species of euglenoids, Euglena gracilis and Distigma proteus. In immunoblot analysis, 5E9 appeared to bind to paraflagellar rod proteins PFR1 and PFR2 of T. brucei (72000 and 75000 mol. wt.) and of E. gracilis (67000 and 76000 mol. wt.). The presence of a common epitope in paraflagellar rod proteins from species of trypanosomes and euglenoids shows that despite distinct structures of the rods some identical domain exists in the proteins that could be involved in their supramolecular assembly into a similar organelle. The antigenic determinant defined by 5E9 was also shown to be present in a 87000 molecular weight polypeptide located in the proximal part of the flagellum of Crithidia oncopelti in which a paraflagellar rod is not detectable at the ultrastructural level.     

Pectolytic clostridia isolated from sugar beet pulp silages in Italy

Twenty-eight strains of pectolytic clostridia were isolated from sugar beet pulp silages. Seventeen non-pigmented strains were presumed to be Clostridium acetobutylicum ; the remaining 11 pigmented strains were similar to Cl. felsineum. The addition of molasses to sugar beet pulps favoured the growth of other bacteria, particularly lactic acid organisms, whereas pectolytic clostridia were only occasionally found. The pectolytic clostridia promoted the structure loss of simulated silages. The use of molasses in sugar beet pulp ensiling was suggested to prevent texture loss of the ensiled mass.     

The relationship of hormone-sensitive and hormone-insensitive phosphatidylinositol to phosphatidylinositol 4,5-bisphosphate in the WRK-1 cell

We have previously characterized two distinct pools of phosphatidylinositol (PI) in the WRK-1 rat mammary tumor cell, one whose metabolism is enhanced in response to vasopressin and another which is insensitive to hormonal manipulation. The purpose of the present study was to examine the relationship between cellular phosphatidylinositol 4,5-bisphosphate (PIP2) and each of the two PI pools. We have found that in WRK-1 cells, vasopressin induces the rapid loss of PIP2 and the accumulation of inositol phosphates. By making use of kinetic differences in 32Pi uptake into the two pools of PI and assessing radioactivity levels in the 1-phosphate of PIP2, we have determined that hormone-sensitive PI is the precursor of approximately 60% of the cellular PIP2; the remainder is synthesized from the hormone-insensitive pool. Additional data indicate that PIP2 derived from hormone-sensitive PI is likewise hormone-sensitive, while that synthesized from hormone-insensitive PI remains stable over a long period of time and is not affected by the presence of vasopressin.     

Ligand-induced association of rat lymphocyte membrane proteins with the detergent-insoluble lymphocyte cytoskeletal matrix

There are two classes of membrane protein capping on the basis of ligand requirements. Surface immunoglobulin (Slg), the prototype of the first class, requires a single ligand for cap induction. RT1 (rat histocompatibility proteins) requires two antibodies for cap induction. The lateral mobility of Slg is relatively restricted compared with RT1. These differences may be due to differential interaction with the cytoskeleton. After ligand binding 71% of Slg becomes detergent insoluble and is associated with the lymphocyte cytoskeletal matrix. The insolubilization occurs at 4 degrees C and is not inhibited by sodium azide or cytoskeleton-active drugs. The insolubilized ligand-receptor complex can be solubilized by a cytoskeleton destabilizing buffer. In contrast, only 20% of RT1 becomes associated with the lymphocytic cytoskeleton after ligand binding. The ligand-induced receptor-cytoskeleton interaction influences capping behavior and may play a role in cell activation.     

Measurement of cerebral blood flow by transcranial Doppler ultrasonography in children presenting with autistic behavior. Preliminary results

Transcranial Doppler ultrasonographic recordings of the middle cerebral arteries were performed on eight children with autistic behavior compared to eight controls. Blood flow measurements were assessed at rest and during auditory and visual stimulations. The main result was obtained during the auditory stimulations and concerned the left artery blood flow which is lower in autistics than in controls in these conditions (p less than .02). This result confirms the possibility of a left hemisphere dysfunctioning in autistics and may be related to clinical features as language disabilities and paradoxical reactivity to auditory stimuli.