Effects of genetically modified maize events expressing Cry34Ab1, Cry35Ab1, Cry1F,and CP4 EPSPS proteins on arthropod complex food webs

Four genetically modified (GM) maize (Zea mays L.) hybrids (coleopteran resistant, coleopteran and lepidopteran resistant, lepidopteran resistant and herbicide tolerant, coleopteran and herbicide tolerant) and its non‐GM control maize stands were tested to compare the functional diversity of arthropods and to determine whether genetic modifications alter the structure of arthropods food webs. A total number of 399,239 arthropod individuals were used for analyses. The trophic groups’ number and the links between them indicated that neither the higher magnitude of Bt toxins (included resistance against insect, and against both insects and glyphosate) nor the extra glyphosate treatment changed the structure of food webs. However, differences in the average trophic links/trophic groups were detected between GM and non‐GM food webs for herbivore groups and plants. Also, differences in characteristic path lengths between GM and non‐GM food webs for herbivores were observed. Food webs parameterized based on 2‐year in‐field assessments, and their properties can be considered a useful and simple tool to evaluate the effects of Bt toxins on non‐target organisms.     

Purification of bovine neurosecretory granule membranes by density gradient centrifugation

A procedure for the subfractionation of neurosecretory granules into membrane and content components is described. The procedure involves the hypotonic lysis of the secretory granule fraction and further purification of the membranes by centrifugation through a discontinuous sucrose gradient. The neurosecretory granule membranes represented 5.2% of the total proteins of the neurosecretory granule fraction and were highly enriched in cytochrome b561. Electron microscopic analysis of the purified membranes showed vesicles devoid of electrodense content.     

A tale of two plasticities: leaf hydraulic conductances and related traits diverge for two tropical epiphytes from contrasting light environments

We compared the effects of different light environments on leaf hydraulic conductance (K_leaf) for two congeneric epiphytes, the tank bromeliads Guzmania lingulata (L.) Mez and Guzmania monostachia (L.) Rusby ex Mez. They occur sympatrically at the study site, although G. monostachia is both wider ranging and typically found in higher light. We collected plants from two levels of irradiance and measured K_leaf as well as related morphological and anatomical traits. Leaf xylem conductance (K_xy) was estimated from tracheid dimensions, and leaf conductance outside the xylem (K_ox) was derived from a leaky cable model. For G. monostachia, but not for G. lingulata, K_leaf and K_xy were significantly higher in high light conditions. Under both light conditions, K_xy and K_ox were co‐limiting for the two species, and all conductances were in the low range for angiosperms. With respect to hydraulic conductances and a number of related anatomical traits, G. monostachia exhibited greater plasticity than did G. lingulata, which responded to high light chiefly by reducing leaf size. The positive plasticity of leaf hydraulic traits in varying light environments in G. monostachia contrasted with negative plasticity in leaf size for G. lingulata, suggesting that G. monostachia may be better able to respond to forest conditions that are likely to be warmer and more disturbed in the future.     

Isolation of N5N10 -Methylene Tetrahydrofolate Reductase From Bovine Brain

N⁵,N¹⁰ -methylene tetrahydrofolate reductase has been purified 100-fold from bovine brain. The initial fractionation with protamine sulfate and ammonium sulfate was followed by chromatography on DEAE-polyacrylamide gel (Bio Gel DM-30) and Sephadex G-200 as well as the selective adsorption and elution of the enzyme on calcium phosphate gel. The purified enzyme required FADH₂ and catalyzed the reduction of the methylene group of N⁵,N¹⁰ -methylene tetrahydrofolate to the methyl group of N⁵ -methyl tetrahydrofolate. The pH optimum of the bovine brain reductase occurred at a pK of 6.5. The enzyme proved quite unstable. Both air oxidation and prolonged periods of storage at -20° inactivated the enzyme.     

Rat relaxin: insulin-like fold predicts a likely receptor binding region

The amino acid sequences for the ovarian hormone relaxin, now determined for pig, rat and shark, indicate that the molecule may have an internal structure similar to that of insulin. The combined results from six secondary structure prediction methods applied to the sequences of both relaxin and insulin support the concept of a similar folding for the B chain between the disulphide bridges. Model building with a computer graphics system has shown that the rat relaxin sequence cannot be superimposed on the 2Zn insulin structure without close contacts occurring between the residues in the central core. However, the residues can be accommodated in the more open framework assumed by 4Zn insulin (molecule I). With the relaxin models built according to the insulin fold, surface residues shared by the three relaxin sequences (B9(Arg), B13(Arg), A13 and A14 (Lys or Arg)) all lie in a localized area on the molecule. This group of residues focuses attention on a larger area on the molecule's surface which may well be the receptor binding site.     

Trichomonas vaginalis, Tritrichomonas foetus, and Trichomitus batrachorum: comparative proteolytic activity

At least four proteolytic activities were detected in the lysates of each of Trichomonas vaginalis, Tritrichomonas foetus, and Trichomitus batrachorum. These were HPAase, a dithiothreitol-dependent activity on hide powder azure; AZCase, a dithiothreitol-dependent activity on azocasein; and two distinct activities towards peptide nitroanilide derivatives--one was optimally active at pH 7 and stimulated by dithiothreitol; the other had no dithiothreitol requirement and was highly active at pH 5. HPAase and AZCase were active over a broad pH range. Overall, with respect to these four activities, T. batrachorum and T. vaginalis were quite similar. In contrast, T. vaginalis and T. foetus differed from one another in several respects, notably the level of HPAase activity and the properties of the dithiothreitol-independent activity. Multiple bands of proteinase activity were demonstrated with each species after electrophoresis of parasite extracts on polyacrylamide gels containing denatured haemoglobin. They appeared optimally at acid pH and in the presence of dithiothreitol. The proteinase band patterns of T. foetus were similarly complex (at least six bands), whereas T. batrachorum gave a much simpler pattern (three bands). The sensitivities to proteinase inhibitors suggested that all the activities were due to cysteine proteinases. The results show that there are some similarities in the proteolytic activities of all three trichomonad species, and that the two parasites of the urinogenital tracts of mammals possess additional features in common.     

The therapeutic significance of concomitant antitumor immunity

It is shown that progressive growth of the SA1 sarcoma in its semisyngeneic AB6F1 host results in the generation of concomitant immunity to growth of a tumor challenge implant, and in the generation of T cells in the spleen capable, on passive transfer, of causing regression of an established tumor in gamma-irradiated recipients, but not in normal recipients. T cells that passively transferred concomitant immunity against an established tumor were first generated around day 6 of tumor growth, reached peak numbers on day 9, and slowly decreased in number thereafter. They were of the Ly-1-2+ phenotype, in that they were functionally eliminated by treatment with monoclonal anti-Ly-2 antibody and complement, but not by treatment with anti-Ly-1 antibody and complement. The paradoxical ability of T cells from a donor with a relatively large tumor to cause the regression of a tumor in sublethally gamma-irradiated recipients is explained with reference to the facts that the recipient tumor was only half as large as the donor tumor at the time of passive transfer, and that the recipient was incapable of generating suppressor T cells that would function to inhibit the expression of adoptive immunity.     

Hypertriglyceridemia and the apolipoprotein CIII gene locus: lack of association with the variant insulin response element in Italian school children

Hypertriglyceridemia is a common metabolic disorder with a major inherited component. In some individuals the condition is suspected to occur as a result of overproduction of apolipoprotein (apo)CIII, a major constituent of triglyceride-rich lipoproteins. Population studies have established an association with the apoCIII gene but the identity of the causal mutation remains unknown. In the present study we have examined a series of six 5′ polymorphic nucleotides (G^–935 to A, C^–641 to A, G^–630 to A, deletion of T^–625, C^–482 to T, and T^–455 to C) that lie within the promoter region of the apoCIII gene for evidence of possible involvement in disease susceptibility. The polymorphic nucleotides at positions –455 and –482 reside within a negative insulin-response element. We show, in a community-based sample of 503 school children, that a DNA polymorphism (S2 allele) within the 3′-noncoding region of the apoCIII gene was associated with elevated apoCIII and triglyceride levels, but that the polymorphic nucleotides of the promoter were not. In addition, no obvious effect of any extended apoCIII promoter haplotype on plasma apoCIII or triglyceride levels, over and above that conferred by the presence of the S2 polymorphic nucleotide, was detected. These results demonstrate that none of the 5′ apoCIII polymorphisms can account for the association of the apoCIII gene locus with hypertriglyceridemia and, moreover, owing to linkage disequilibrium, raise the possibility that the region conferring susceptibility maps downstream, rather than upstream, of the apoCIII gene promoter sequences. Received: 8 January 1996 / Revised: 30 May 1996