Food Versus Biofuels: Environmental and Economic Costs

The rapidly growing world population and rising consumption of biofuels intensify demands for both food and biofuels. This exaggerates food and fuel shortages. The use of food crops such as corn grain to produce ethanol raises major nutritional and ethical concerns. Nearly 60% of humans in the world are currently malnourished, so the need for grains and other basic foods is critical. Growing crops for fuel squanders land, water and energy resources vital for the production of food for human consumption. Using corn for ethanol increases the price of US beef, chicken, pork, eggs, breads, cereals, and milk more than 10% to 30%. In addition, Jacques Diouf, Director General of the UN Food and Agriculture Organization, reports that using food grains to produce biofuels is already causing food shortages for the poor of the world. Growing crops for biofuel not only ignores the need to reduce fossil energy and land use, but exacerbates the problem of malnourishment worldwide.     

Energy conservation in whole cells of the methylotrophic bacterium Methylophilus methylotrophus

Respiratory chain phosphorylation has been investigated in the methylotrophic bacterium Methylophilus methylotrophus following the addition of oxidisable substrates to aerobic, whole cell suspensions. Initial-rate experiments showed that ATP synthesis occurred at the overall expense of AMP and inorganic phosphate via the sequential action of the ATP phosphohydrolase and adenylate kinase; some of the nascent ATP was rapidly used to synthesis nonadenine nucleoside triphosphates. After being corrected for ATP turnover, Pi/O quotients of 0.46 to 0.54, 0.77 and 1.37 nmol/ng-atom O were obtained for the oxidation of methanol dehydrogenase-linked substrates (methanol, ethanol and acetaldehyde), duroquinol and formate (NAD⁺-linked) respectively. These values were proportional to the H⁺/O and/or K⁺/O quotients exhibited by these substrates, and yielded an average H⁺/ATP (H⁺/Pi) quotient of 4.2 ng-ion H⁺/nmol. Steady-state experiments showed that the extent of cellular energisation varied with the respiration rate but was always in the order methanol > duroquinol > acetaldehyde, thus indicating that under these longer-term conditions methanol was completely oxidised to yield PQQH₂ and 2NAD(P)H. These results are discussed in terms of the various reactions which lead to the generation or utilisation of the protonmotive force in this organism.Abbreviations FCCP carbonylcyanide p-trifluoromethyxyphenyl-hydrazone - bulk phase, transmembrane electrochemical potential difference of protons ( ) - pH bulk phase, transmembrane pH difference (pH_in–pH_out) - bulk phase, transmembrane electrical potential difference (_in - _out) - [P] concentration of anhydride phosphate bonds in adenine nucleotides (2[ATP]+[ADP]) - FPLC fast protein liquid chromatography - PQQ pyrroloquinoline quinone - Gp phosphorylation potential     

Energy allocation rules inDaphnia magna: clonal and age differences in the effects of food limitation

Summary The allocation of energy to carapace formation, respiration, growth, and reproduction were examined in two parthenogenetic clones ofDaphnia magna (Cladocera) cultured at two levels of food (Chlorella) concentration. Clonal differences in energy allocation were more apparent at high ration (1.5 g C mL^-1) than at low ration (0.3 g C mL^-1). These differences included respiratory and molting costs, and the timing of energy allocation to growth and reproduction. A comparison of active vs. anesthetized animals revealed that the interclonal difference in respiration rate was the result of a difference in activity level. In both clones mass-specific rates of respiration, growth, and brood production all decreased at low vs. high ration levels, whereas mass-specific molt-loss rate increased. Lowered food concentration decreased the relative allocation of energy to growth and reproduction, but increased allocation to maintenance (respiration and carapace formation). These allocation responses to food limitation indicated that for both clones the highest energy priority was carapace formation. However, the relative priority of respiration, growth and reproduction varied with age and clone. In juveniles (instars 1–4) the priority ranking of growth was essentially equal to that of respiration, whereas respiration always had higher priority in adults (instars 5–9). All three possibilities for the relative ranking of growth and reproduction (i.e., growth>reproduction, growth=reproduction, and reproduction>growth), as specified by different models in the literature, were observed depending on age and clone. The energy allocation rules were also shown to vary between other daphniid species. Furthermore, metabolic responses to chronic food limitation may be different from responses to acute food deprivation. In this study, one clone showed a greater decrease in respiration rate as a result of lifetime food limitation than did the other, but the opposite was true when these clones were exposed to 48 h of starvation. These differences in allocation rules and in acute vs. chronic responses may have to be considered when using physiological data to modelDaphnia populations.     

In Search of Sustainable Land Use and Food Security in the Arid Hillside Regions of Central America: Putting the Horse Before the Cart

This article is based on a 2003 case study of the Special Program for Food Security in two dry, upland regions of Honduras and Nicaragua. In particular the research sought to identify factors influencing farmers’ interest in various “best practices” being promoted as alternatives to the use of fire in cropping and ranching systems. The economic feasibility and/or affordability of several of these practices are questionable in light of most farmers’ priorities, risk concerns, or limited resources. The technical feasibility of several of the practices is unclear, at least in the marginal agroecological environments in which most of the farmers in these regions operate. The study highlights the weaknesses of agricultural development initiatives designed without a sufficient understanding of existing agricultural strategies and their purposes. It also reveals the limitations of technological approaches to problems of food insecurity and land degradation, and the need for broader, more integrated rural development strategies. The findings support critiques regarding the biases of many development professionals that may prevent them from giving sufficient attention to local knowledge and perspectives.

Axonal Transport of Glycoconjugates in the Rat Visual System

Long-Evans rats at 45 days of age were injected intraocularly with 25 mu Ci of [3H]glucosamine. Incorporation of radioactivity into retinal gangliosides, glycoproteins, and glycosaminoglycans (GAGs) was determined at various times after injection. Portions of all three classes of radioactive macromolecules were committed to rapid axonal transport in the retinal ganglion cells. With respect to gangliosides about 60% of those synthesized in the retina were retained in that structure, 30% were committed to transport to regions containing the nerve terminal structures (lateral geniculate body and superior colliculus), and about 10% were deposited in stationary structures of the axons (optic nerve and tract). With the exception of ganglioside GD3 the molecular species distribution of gangliosides synthesized in the retina matched that committed to transport. In contrast to gangliosides a smaller fraction of newly synthesized retinal glycoprotein (less than 12% of that synthesized in the retina) was committed to rapid transport to nerve ending regions and only about 0.5% was retained in the nerve and tract. The molecular-weight distribution of glycoproteins committed to transport differed quantitatively from that of the retina. With respect to GAGs an even smaller portion (1-2%) of that synthesized in the retina was committed to rapid transport; of this portion almost all was recovered in nerve terminal-containing structures. A constant proportion of each retinal GAG species was transported to the superior colliculus. We suggest that most of the retinal gangliosides are synthesized in neurons and preferentially in ganglion cells (possibly a function of the large surface membrane area supported by these cells). Subcellular fractionation experiments indicated that transported gangliosides, glycoproteins, and GAGs may be preferentially distributed into different subcellular compartments.     

Axonal Transport of the Ca2+-Dependent Protein Modulator of 3'':5''-Cyclic-AMP Phosphodiesterase in the Rabbit Visual System

Water-soluble proteins were extracted from individual retinas, optic nerves, combined optic tracts and lateral geniculate bodies, and superior colliculi of rabbits at 1, 3, and 18 days after injection of [3H]leucine into the right eye. The Ca2+-dependent protein modulator of 3':5'-cyclic-AMP phosphodiesterase (calmodulin) was isolated from these samples by a two-step polyacrylamide gel electrophoresis procedure. An analysis of the radioactivity incorporated into the total soluble proteins and the calmodulin revealed that most of the calmodulin was axonally transported at a slow rate (2--4 mm/day) and represented about 0.45% of the total transported soluble protein.     

花生下胚轴组织H~ 分泌与质膜氧化还原系统的某些特性

花生幼苗下胚轴细胞表面存在氧化NADH与还原Fe(CN)_6~(3-)的氧化还原系统(redox system),它的活性随反应介质pH的上升而增加,氧是该系统的天然电子受体,受DCCD抑制。在NADH与Fe(CN)_6~(3-)被氧化与还原的同时,组织的H~ 分泌明显受到促进,并随反应介质pH上升而增加。质膜H~ -ATPase专一抑制剂Na_3VO_4(0.1 mmol/L)对组织H~ 分泌抑制绝对量基本上不受介质pH的影响,表明质膜H~ -ATPase与redox system共同参与该组织的H~ 分泌,部分redox system支配的H~ 分泌是依赖氧的。     

Regulation of Lactose Transport by the Phosphoenolpyruvate-Sugar Phosphotransferase System in Membrane Vesicles of Escherichia coli

Regulation of lactose uptake by the phosphoenolpyruvate-sugar phosphotransferase system (PTS) has been demonstrated in membrane vesicles of Escherichia coli strain ML308-225. Substrates of the phosphotransferase system inhibited D-lactate energized uptake of lactose but did not inhibit uptake of either L-alanine or L-proline. This inhibition was reversed by intravesicular (but not extravesicular) phosphoenolpyruvate. Lactose uptake was also inhibited by enzyme III^glc preparations that were shocked into the vesicles, and this inhibition was reversed by phosphoenolpyruvate. Intravesicular HPr and enzyme I stimulated methyl α-glucoside uptake but did not inhibit or stimulate lactose accumulation. Vesicles maintained at 0°C for several days partially lost 1) the ability to take up lactose, 2) the ability to accumulate PTS substrates, and 3) PTS-mediated regulation. Phosphoenolpyruvate addition restored all of these activities. These results support a mechanism in which the relative proportions of phosphorylated and nonphosphorylated forms of a phosphotransferase constituent regulate the activity of the lactose permcase.     

Immunohistochemical Localization of Glycogen Phosphorylase Isozymes in the Rat Gastrointestinal Muscle Layers and Enteric Nervous System

Glycogen represents the major brain energy reserve though its precise functions are still under debate. Glycogen has also been found in different cell types of the enteric nervous system (ENS), the largest and most complex component of the peripheral nervous system. In the present work we have demonstrated, by application of isozyme-specific antibodies, the presence of isozymes of glycogen phosphorylase (GP), one of the major control sites in glycogen metabolism, in the rat ENS. Immunohistochemistry revealed that isoform BB (brain) is the predominant isozyme expressed in enteric glial cells (EGC) and rare neurons of the myenteric and submucosal plexuses. Isoform MM (muscle) appears in cells which are, according to their location and morphology, probably interstitial cells of Cajal (ICC). In addition, both GP isoforms are expressed in longitudinal and circular intestinal smooth muscle layers. As GP BB is mainly regulated by the cellular AMP level, a special function of glycogen in the energy supply of neural gut functions is suggested.     

The Role of Plastids and Assimilate Transport System in the Control of Plant Development

Phylogenetic and ontogenetic relationships between the plastids, cell endoplasmic reticulum, and plant transport communication have been reviewed. The initiating role of plastids (endosymbionts) in the origin of endoplasmic reticulum (buffer zone of endosymbiogenesis) has been shown, as well as a similar role of endoplasmic reticulum in the development of transport communication of xylem and phloem. Plastids, sugars and transport system for their distribution can be interpreted as leading sections in the mechanism of developmental control: gene expression of nuclear genome and genome of organelles, cell and tissue differentiation, and plant morphogenesis. The conflict between the bulk of plant genome and low percentage of its realization is explained as a result of limitation of the nuclear genome realization by plastid genome. The concept of development as applied to plant ontogenesis has been critically analyzed. The possibilities of the concept correction by with the help of symbiogenetic hypothesis are discussed.__________Translated from Ontogenez, Vol. 36, No. 3, 2005, pp. 165–181.Original Russian Text Copyright © 2005 by Gamalei.     

Evidence for the Functional Association of Enzyme I and HPr of the Phosphoenolpyruvate-Sugar Phosphotransferase System With the Membrane in Sealed Vesicles of Escherichia coli

Several independent assay procedures were used to estimate the activities of the enzyme constituents of the phosphoenolpyruvate-sugar phosphotransferase system (PTS) in osmotically shocked bacterial membrane vesicles. The soluble enzymes of the system were found to be in association with the membrane by several criteria. Phosphoenolpyruvate-dependent sugar phosphorylation was catalyzed by this membrane-bound enzyme system far more efficiently than by a mixture of the individual enzymes at corresponding concentrations. By contrast, the rates of the phosphoryl exchange reactions catalyzed by enzyme I and the enzyme II complexes were essentially the same for the associated and dissociated forms of the system. Functional association of the PTS-enzyme complex was stabilized by Mg⁺⁺ and phosphoenolpyruvate and could be destroyed by detergent treatment, sonication, or by passage of the vesicle preparation through a French pressure cell. These results lead to the possibility that in the intact bacterial cell the soluble enzymes of the phosphotransferase system exist, in part, as peripheral membrane constituents associated with the integral membrane enzyme II complexes.