Scientific and Public Perception of Plant Genetic Manipulation — A Critical Review

Scientific views on the importance and potential risks of plant genetic engineering are summarized and the ecological and economic consequences of the large scale release of engineered crops is discussed. The difference between scientific risk assessment and the public's perception of risk due to modification of the former by outrage factors is explained. Polls, media, and literature sources show that the public supports plant genetic engineering activity, but has some concerns. These concerns fall within two categories: (1) it is risky, (2) it is morally wrong. Polls show a lack of knowledge about GE by the public and that outrage factors play a major role; their effects on perception are described in detail. Ethical considerations also exercise a powerful influence over GE's acceptance, but the complementary roles of Religion and Science are emphasized. Different attitudes to nature are described and it is concluded that if the world is to be fed and life support systems sustained, active management of nature is required.

Lastly, the need for scientists to communicate with the public and the basis of effective presentation is discussed.     

The role of divalent cations in structure and function of murine adenosine deaminase.

For murine adenosine deaminase, we have determined that a single zinc or cobalt cofactor bound in a high affinity site is required for catalytic function while metal ions bound at an additional site(s) inhibit the enzyme. A catalytically inactive apoenzyme of murine adenosine deaminase was produced by dialysis in the presence of specific zinc chelators in an acidic buffer. This represents the first production of the apoenzyme and demonstrates a rigorous method for removing the occult cofactor. Restoration to the holoenzyme is achieved with stoichiometric amounts of either Zn2+ or Co2+ yielding at least 95% of initial activity. Far UV CD and fluorescence spectra are the same for both the apo- and holoenzyme, providing evidence that removal of the cofactor does not alter secondary or tertiary structure. The substrate binding site remains functional as determined by similar quenching measured by tryptophan fluorescence of apo- or holoenzyme upon mixing with the transition state analog, deoxycoformycin. Excess levels of adenosine or N6- methyladenosine incubated with the apoenzyme prior to the addition of metal prevent restoration, suggesting that the cofactor adds through the substrate binding cleft. The cations Ca2+, Cd2+, Cr2+, Cu+, Cu2+, Mn2+, Fe2+, Fe3+, Pb2+, or Mg2+ did not restore adenosine deaminase activity to the apoenzyme. Mn2+, Cu2+, and Zn2+ were found to be competitive inhibitors of the holoenzyme with respect to substrate and Cd2+ and Co2+ were noncompetitive inhibitors. Weak inhibition (Ki > or = 1000 microM) was noted for Ca2+, Fe2+, and Fe3+.     

鲫鱼后鳃体结构与功能的研究

本文对鲫鱼后鳃体的形态结构及其功能进行了初步研究。结果表明,鲫鱼后鳃体是一种内分泌腺体。腺体由滤泡组成,滤泡上皮包括二种颗粒细胞(亮细胞和暗细胞)和一种支持细胞。对不同性腺期的鲫鱼后鳃体的观察表明,后鳃体滤泡细胞随性腺发育增加高度,滤泡增生,腺体体积增大。而性腺成熟后期,后鳃体滤泡上皮有崩溃现象。揭示后鳃体可能与性腺发育有关。用免疫组织化学的非标记过氧化物酶技术对鲫鱼后鳃体进行激素降钙素的定性定位研究,观察到滤泡上皮的颗粒细胞发生阳性反应,由此证明颗粒细胞可分泌降钙素。     

Regulation of GABA Metabolism in Discrete Rabbit Brain Regions under Methoxypyridoxine—Regional Differences in Cofactor Saturation and the Preictal Activation of Glutamate Decarboxylase Activity1

Abstract: The activities of the enzymes of the GABA system, glutamate decarboxylase (GAD) and GABA-transaminase, were measured in discrete regions of the rabbit brain before the onset and during the course of sustained epileptiform seizures induced by the vitamin B₆, analogue methoxypyridoxine (MP). GAD activities were measured in a reaction mixture alternatively containing the cofactor pyridoxal-5′-phosphate (PLP) in excess or containing no PLP (holoenzyme of GAD). A comparison between these two estimations showed that the apoenzyme of GAD is only partially saturated with cofactor and that the degree of saturation varied from brain area to brain area, being highest in cerebellar cortex and lowest in substantia nigra. Holoenzyme activity fell steeply after administration of 100 mg/kg MP. The regional degree of enzyme inhibition by MP was a function of the saturation of the apoenzyme with cofactor; i.e., a low rate of saturation resulted in a high degree of inhibition, and vice versa. That GAD from the regio inferior of the hippocampus did not fit into the scheme (strong inhibition is present although the degree of saturation is high) is discussed in view of the role of the hippocampus in seizure genesis and generalization. Inhibition of GAD activity by MP was completely reversible in vitro by excess PLP. Before the onset of seizures but not during their course, apoenzyme activity surpassed control levels. This preictal activation is significant in regio inferior of hippocampus, in superior colliculus, and in cerebellar cortex. GABA-transaminase activities were not significantly altered. The present study demonstrates that only investigation during the preictal period and in regional brain areas can reveal changes specific for the drug and perhaps representing the cause for seizure development, without being masked by additional alterations resulting from the severe functional and metabolic derangement during the ictal events. Thereby, it was disclosed that a decrease in vivo in the level of the enzyme product, GABA, is able to activate GAD.     

The role of dietary copper,manganese, selenium,and vitamin E in lipid peroxidation in tissues of the rat

The role of dietary Cu and Mn in maintaining tissue integrity, through the effects of these metals on activity of the superoxide dismutase (SOD) enzyme, and their interactions in peroxidative pathways involving Se and vitamin E was investigated. Weanling rats were fed diets deficient in Mn, Cu, Se, and/or vitamin E for 35 days, in a factorial experimental design. Dietary effects on peroxidation, measured in mitochondrial fractions prepared from liver and heart tissue, were compared with changes in the activities of glutathione peroxidase and the Cu and MnSOD enzymes. Decreased heart MnSOD and CuSOD activities, resulting from dietary Mn and Cu deficiencies, were both associated with increased peroxidation. Adequate Se (and glutathione peroxidase activity) prevented the peroxidation associated with either of these deficiencies, but was ineffective with a combined Cu−Mn deficiency. These effects of Se were only observed in tissue lacking glutathione transferase activity. Effects of Cu, Mn, and Se on peroxidation appeared to be present at both levels of vitamin E, although in both tissues, vitamin E deficiency greatly increased the overall peroxidation. Comparison of these in vitro peroxidation results with the deficiency associated lesions observed in vivo indicates that changes in SOD activities and peroxidation pathways may be the dominant cause of these lesions in only some cases. In others, the roles of Cu and Mn in different metabolic pathways appear to be of greater importance.     

Evidence for the formation of methoxyl groups of ferulic and sinapic acids in Bambusa by the same O-methyltransferase

The two methylation reactions, i.e. caffeate to ferulate (FA) and 5-hydroxyferulate to sinapate (SA), in the biosynthesis of guaiacyl and syringyl lignins in angiosperms were demonstrated to be catalyzed by the same enzyme in bamboo. This follows from the facts that: the ratio (SA/FA) obtained for O-methyltransferase remains constant during purification of the enzyme; chromatography on DEAE-cellulose, Sephadex G100 and G200, and analyses by polyacrylamide gel electrophoresis and isoelectric focusing in pH gradients showed that the two methylating activities belonged to a single enzyme protein; caffeate and 5-hydroxyferulate compete each other in the formation of the enzyme-substrate complex, the latter substrate showing greater affinity for the enzyme. Thus, feedback control may operate at the methylation step, caffeate to FA, in biosynthesis of angiosperm lignin.     

Calcium and plant organelles

Abstract. The role of intracellular organelles in the regulation of cytosolic Ca²⁺ levels and whether changes in these levels affect organelle metabolism is considered. We have assessed the biochemical properties of the Ca²⁺ transporting systems in mitochondrial, chloroplast and microsomal fractions. It is proposed that although all of these organelles can transport Ca²⁺ to varying extents it would appear that in some tissues at least mitochondria do not play a significant role in the maintenance of cytosolic Ca²⁺. The most important Ca²⁺ transporting systems are probably the ATP dependent Ca²⁺ extrusion across the plasma membrane and Ca²⁺ uptake by endoplasmic reticulum, as well as light driven Ca²⁺ uptake by chloroplasts. Changes in cytoplasmic [Ca²⁺] do appear to regulate the activity of NAD kinase in chloroplasts, the mitochondrial external NADH dehydrogenase and intra-mitochondrial glutamate dehydrogenase, all of which play a key role in plant cell metabolism. Since some of these enzymes are affected by primary stimuli such as light or hormones, it is concluded that Ca²⁺ may act as a second messenger mediating some of the primary responses.     

Change in behaviour of the cockroach, Periplaneta americana, after being stung by the sphecid wasp Ampulex compressa

The solitary wasp Ampulex compressa Fabr. (Sphecidae: Hymenoptera) stings the cockroach first in the thorax and then in the neck toward the suboesophageal ganglion. The first sting results in a short lasting and completely reversible paralysis. The second sting causes an irreversible change in the behaviour: undisturbed cockroaches seem to be lethargic, and if stimulated they are able to run with speeds that equal that of control animals.

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Résumé La guêpe solitaire aculéate, Ampulex compressa Fabr. n'inflige en général à sa proie, la blatte Periplaneta americana L., que deux piqûres: l'une thoracique au niveau d'un patte prothoracique; la seconde dans le cou, au niveau du ganglion sousoesophagien. La première piqûre provoque une paralysie immédiate, complètement réversible en moins d'une minute. Les piqûres doubles provoquent également une paralysie, mais réversible dans un délai de plusieurs minutes. Au surplus, la deuxième piqûre influence irréversiblement le comportement de la blatte, qui présente un état léthargique mais est tout à fait capable de se déplacer rapidement après une stimulation des mécanorécepteurs cercaux par un léger souffle d'air au niveau du cerque.

     

Relative motion inAmoeba proteus in respect to the adhesion sites. I. Behavior of monotactic forms and the mechanism of fountain phenomenon

Summary The unbranched ectoplasmic cylinder of monotacticA. proteus is always retracted toward the cell-substrate attachment sites. The retraction velocity increases from the adhesion sites toward any free distal body end in a linear way, which indicates the uniform contractility of the whole cylinder. Therefore, in the cells frontally attached all the ectoplasm moves forward, and in those adhering by the tail the whole ectoplasmic tube moves backward producing the full fountain phenomenon. With cell attachment at the middle body regions, which is most typical for normal locomotion, the whole ectoplasm is centripetally retracted from both body poles toward the adhesion zone, producing then the tail retraction in the posterior and incomplete fountain in the anterior body part. In unattached amoebae the whole peripheral tube is retracted toward its geometrical centre which coincides with its posterior closed end, producing therefore also a full fountain. It is generalized that the fountain arises always between an unattached front and the nearest attachment point behind its manifestation zone. The photographic records of movement and longitudinal velocity profiles of ectoplasmic retraction are identical on both sides of the attachment points, suggesting the same mechanism for the fountain movement as for the tail withdrawal. It is concluded therefore that not the axial endoplasmic arm of the fountain is active, but its peripheral arm built of the ectoplasm.All elements complicating the cell contour, as the constriction rings and ephemeral lateral pseudopodia, do not change their position in respect to the ectoplasmic material, but move together with it in respect to the substrate, i.e., the cytoskeleton moves as a whole. Loose glass rods attached by adhesion to cell surface also precisely follow the cytoskeleton movements, being transported toward the main locomotory adhesion zone established on the firm substrate, although the cell membrane as such behaves differently. It suggests a direct connection between the adhesion sites and the cytoskeleton.Study supported by Research Project II. 1 of the Polish Academy of Science.I dedicate this paper to the memory of Reginald J. Goldacre, deceased in December 1983, who twenty years ago introduced me to the study of amoebae.