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PubMed1993

Structural study of the sugar chains of porcine factor VIII--tissue- and species-specific glycosylation of factor VIII.

The asparagine-linked sugar chains of blood coagulation factor VIII purified from porcine plasma were released as oligosaccharides by hydrazinolysis. These sugar chains were converted to radioactive oligosaccharides by reduction with sodium borotritide and separated into neutral and acidic fractions by paper electrophoresis. Most of the acidic oligosaccharides were converted to neutral ones by sialidase digestion, indicating that they are sialyl derivatives. The neutral and the sialidase-treated acidic oligosaccharides were fractionated by serial chromatography on immobilized lectin columns. Structural study of each oligosaccharide by sequential exoglycosidase digestion and by methylation analysis revealed that porcine factor VIII contains high mannose-type and bi-, tri-, and tetraantennary complex-type sugar chains. Sixty-seven percent of the complex-type sugar chains contained the Gal alpha 1-->3Gal group, and 23% of the biantennary complex-type sugar chains contained the bisecting N-acetylglucosamine residue. These structures were not detected in the sugar chains of human plasma factor VIII. An in vitro competition study of von Willebrand factor and anti-Gal antibody for binding to factor VIII revealed that von Willebrand factor prevented antibody binding to Gal alpha 1-->3Gal groups in porcine factor VIII sugar chains. This suggests that anti-Gal antibody present in human plasma may not interact with the sugar chains of therapeutic porcine factor VIII. Reverse-transcription polymerase chain reaction was used to identify porcine tissues producing FVIII mRNA. These studies revealed that the kidney is one of the major tissues expressing factor VIII which may contain the sugar chains with the bisecting N-acetylglucosamine residue.

Animals↗

PubMed1996

Sugars act as signal molecules and osmotica to regulate the expression of alpha-amylase genes and metabolic activities in germinating cereal grains.

The molecular mechanisms that initiate and control the metabolic activities of seed germination are largely unknown. Sugars may play important roles in regulating such metabolic activities in addition to providing an essential carbon source for the growth of young seedlings and maintaining turgor pressure for the expansion of tissues during germination. To test this hypothesis, we investigated the physiological role of sugars in the regulation of alpha-amylase gene expression and carbohydrate metabolism in embryo and endosperm of germinating rice seeds. RNA gel blot analysis revealed that in the embryo and aleurone cells, expression of four alpha-amylase genes was differentially regulated by sugars via mechanisms beyond the well-known hormonal control mechanism. In the aleurone cells, expression of these alpha-amylase genes was regulated by gibberellins produced in the embryo and by osmotically active sugars. In the embryo, expression of two alpha-amylase genes and production of gibberellins were transient, and were probably induced by depletion of sugars in the embryo upon imbibition, and suppressed by sugars influx from the endosperm as germination proceeded. The deferential expression of the four alpha-amylase genes in the embryo and aleurone cells was probably due to their markedly different sensitivities to changes in tissue sugar levels. Our study supports a model in which sugars regulate the expression of alpha-amylase genes in a tissue-specific manner: via a feedback control mechanism in the embryo and via an osmotic control mechanism in the aleurone cells. An interactive loop among sugars, gibberellins, and alpha-amylase genes in the germinating cereal grain is proposed.

Carbohydrates↗

PubMed1995

Improved strains of recombinant Escherichia coli for ethanol production from sugar mixtures.

Hemicellulose hydrolysates of agricultural residues often contain mixtures of hexose and pentose sugars. Ethanologenic Escherichia coli that have been previously investigated preferentially ferment hexose sugars. In some cases, xylose fermentation was slow or incomplete. The purpose of this study was to develop improved ethanologenic E. coli strains for the fermentation of pentoses in sugar mixtures. Using fosfomycin as a selective agent, glucose-negative mutants of E. coli KO11 (containing chromosomally integrated genes encoding the ethanol pathway from Zymomonas mobilis) were isolated that were unable to ferment sugars transported by the phosphoenolpyruvate-dependent phosphotransferase system. These strains (SL31 and SL142) retained the ability to ferment sugars with independent transport systems such as arabinose and xylose and were used to ferment pentose sugars to ethanol selectively in the presence of high concentrations of glucose. Additional fosfomycin-resistant mutants were isolated that were superior to strain KO11 for ethanol production from hexose and pentose sugars. These hyperproductive strains (SL28 and SL40) retained the ability to metabolize all sugars tested, completed fermentations more rapidly, and achieved higher ethanol yields than the parent. Both SL28 and SL40 produced 60 gl-1 ethanol from 120 gl-1 xylose in 60 h, 20% more ethanol than KO11 under identical conditions. Further studies illustrated the feasibility of sequential fermentation. A mixture of hexose and pentose sugars was fermented with near theoretical yield by SL40 in the first step followed by a second fermentation in which yeast and glucose were added. Such a two-step approach can combine the attributes of ethanologenic E. coli for pentoses with the high ethanol tolerance of conventional yeasts in a single vessel.

Carbohydrate Metabolism↗

PubMed1994

Individual differences in sugar intake predict the locomotor response to acute and repeated amphetamine administration.

Rats exhibit profound individual differences in their propensity to ingest sugar and in their locomotor response to AMP. Intrinsic variation in the responsiveness of mesolimbic dopamine mechanisms has been suggested to account for these individual differences. In light of this overlap, it might be expected that individual differences in one behavior would predict individual differences in the other. The present study determined whether individual differences in sugar intake would predict individual differences in the locomotor response to AMP. Male Wistar rats were divided into low and high feeders based on a median split of their sugar intake in response to saline administration and were subsequently tested for their locomotor response to either 1.0 or 1.75 mg/kg AMP in experiment 1. High sugar feeders exhibited significantly more locomotion than low sugar feeders in response to 1.75 mg/kg AMP. This difference was observed immediately after injection and continued for approximately 90 min. There was no difference between the two groups in their locomotor response to 1.0 mg/kg AMP. In experiment 2, rats receiving 1.0 mg/kg AMP in experiment 1 were tested for the development of behavioral sensitization with repeated AMP administrations. Rats were administered 1.0 mg/kg AMP across 5 test days, interspersed with days in which they received AMP treatment in their home cages to minimize conditioning effects. High sugar feeders exhibited greater behavioral sensitization than low sugar feeders with repeated AMP administration. Starting on test day 3, high sugar feeders exhibited significantly greater AMP-induced locomotor activity than low sugar feeders.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗

PubMed2006

Effect of sugar-induced senescence on gene expression and implications for the regulation of senescence in Arabidopsis.

There has been some debate whether leaf senescence is induced by sugar starvation or by sugar accumulation. External supply of sugars has been shown to induce symptoms of senescence such as leaf yellowing. However, it was so far not clear if sugars have a signalling function during developmental senescence. Glucose and fructose accumulate strongly during senescence in Arabidopsis thaliana (L.) Heynh. leaves. Using Affymetrix GeneChip analysis we determined the effect of sugar-induced senescence on gene expression. Growth on glucose in combination with low nitrogen supply induced leaf yellowing and changes in gene expression that are characteristic of developmental senescence. Most importantly, the senescence-specific gene SAG12, which was previously thought to be sugar-repressible, was induced over 900-fold by glucose. Induction of SAG12, which is expressed during late senescence, demonstrates that processes characteristic for late stages are sugar-inducible. Two MYB transcription factor genes, PAP1 and PAP2, were identified as senescence-associated genes that are induced by glucose. Moreover, growth on glucose induced genes for nitrogen remobilisation that are typically enhanced during developmental senescence, including the glutamine synthetase gene GLN1;4 and the nitrate transporter gene AtNRT2.5. In contrast to wild-type plants, the hexokinase-1 mutant gin2-1 did not accumulate hexoses and senescence was delayed. Induction of senescence by externally supplied glucose was partially abolished in gin2-1, indicating that delayed senescence was a consequence of decreased sugar sensitivity. Taken together, our results show that Arabidopsis leaf senescence is induced rather than repressed by sugars.

Anion Transport Proteins↗

PubMed1989

The sugar-chain heterogeneity of human gamma-glutamyl transferases from the reproductive system and kidney.

The sugar-chain heterogeneity of gamma-glutamyl transferase (gamma-GTP, EC 2.3.2.2) from the human reproductive system (seminal plasma, prostate and testis) and kidney was investigated using the serial lectin affinity technique and their properties were compared. According to the results of serial lectin affinity chromatography, a possible sugar chains of enzymes from reproductive system were mainly of the hybrid type without fucose linkages to the innermost GlcNAc and/or the biantennary complex type sugar chains and a few were of the multiantennary complex-type with branched GlcNAc (beta 1-4) Man and bisecting complex type sugar chains. On the contrary, the major sugar chains of kidney gamma-GTP were of the multiantennary complex type and/or bisecting complex type sugar chains. Results of isoelectric focusing showed the gamma-GTP bound multiantennary complex type sugar chains to be the most acidic glycoprotein. Moreover, the biantennary type sugar chains were slightly more acidic than the high mannose and/or hybrid type sugar chains, varying with the degree of sialylation.

Adult↗

PubMed1976

Sugar binding to purified fractions from bovine taste buds and epithelial tissue. Relationships to bioactivity.

Binding of various sugars was compared in purified subfractions of taste buds isolated from bovine circumvallate papillae and of non-taste bud-bearing epithelium isolated from tissue surrounding these papillae. Binding of 14C-labeled sugars was greater in purified subfractions obtained from taste bud than from non-taste bud-bearing tissue and was, in general, greater in those taste bud subfractions in which a greater membrane purification was achieved. Binding specificity of the 14C-labeled sugars sucrose, fructose, glucose and of 14C-labeled cyclamate and saccharine was measured by competition of each 14C-labeled sugar or synthetic sweetener with its unlabeled homologous sugar in P4(B) taste bud subfractions; this binding, as shown for sucrose, was reversible and temperature dependent. Essentially no competition of the 14C-lageled sugars sucrose, fructose, glucose or 14C-labeled cyclamate and saccharine by their respective unlabeled homologues occurred in epithelial tissue P4(B) subfractions; this binding was not reversible. Binding specificity was further observed by the competition of 14C-labeled sucrose, fructose and glucose with each unlabeled sugar for binding sites on P4(B) taste bud subfractions; unlabeled sucrose was more effective in competing with each 14C-labeled surgar than was unlabeled fructose or glucose. The relatively non-sweet sugar lactose did not compete with 14C-labeled lactose in P4(B) subfractions from either taste bud or non-taste bud-bearing epithelial tissue. Binding of 14C-labeled sucrose in purified P4(B) bud subfractions was inhibited by increased concentrations of unlabeled sucrose, phospholipase C, neuraminidase, EDTA, NaCl and urea. Dissociation constants for sugar or synthetic sweetener binding were low (approx. 10(-3) M) but in a rank order (sucrose greater than fructose greater than glucose greater than saccharine) consistent with preference and electrophysiological responses in cow. The cow is behaviorally indifferent to saccharine and lactose consistent with the data obtained in the present study.

Animals↗

PubMed1977

Studies on lectins. XXXI. Determination of dissociation constants of lectin. Sugar complexes by means of affinity electrophoresis.

A modification of affinity electrophoresis in polyacrylamide gels containing immobilized sugar residues is described. The immobilization of sugar residues is achieved by addition of a water soluble O-glycosyl polyacrylamide copolymer to the polymerization mixture, which serves for the preparation of gels for commonly used discontinuous polyacrylamide gel electrophoresis. The electrophoretic mobility of lectins in affinity gels containing specific immobilized sugar decreases with increasing sugar concentration. The addition of free sugar into the affinity gel abolishes retardation of the electrophoretic mobility caused by immobilized sugar. The relationship between electrophoretic mobility of lectins and concentration of immobilized and free sugar was used for the calculation of dissociation constants of the various complexes lectin-immobilized sugar and lectin-free sugar.

Electrophoresis, Polyacrylamide Gel↗

PubMed1987

Stabilization of phosphofructokinase with sugars during freeze-drying: characterization of enhanced protection in the presence of divalent cations.

Phosphofructokinase purified from rabbit skeletal muscle is fully inactivated after freeze-drying and dissolution. The addition of trehalose or maltose to the enzyme solution prior to freeze-drying results in a recovery of up to 80% of the original activity. Slightly less stabilization is imparted by sucrose, whereas glucose and galactose at concentrations up to 500 mM are relatively ineffective at protecting phosphofructokinase. Addition of ionic zinc to enzyme-sugar mixtures prior to freeze-drying greatly enhances the stabilization imparted by the above sugars. This effect is not simply due to the summation of the individual protective capacities of zinc and the sugar. Zinc alone affords no protection, but a high degree of stabilization is achieved when zinc is added to a sugar solution, even when the sugar is at a concentration at which, by itself, it is totally ineffective. In the presence of a constant sugar concentration (100 mM), freeze-dry stabilization of phosphofructokinase is increased as the concentration of zinc is increased. When the zinc concentration is held constant (0.9 mM) and the sugar concentration varied, the maximum stabilization is noted with less than 200 mM sugar. At higher solute concentrations the degree of enhancement decreases such that with 500 mM sugar the addition of zinc results in only a slight increase in protection. Several other organic solutes (proline, 4-hydroxyproline, glycine, trimethylamine N-oxide, glycerol and myo-inositol) that afford cryoprotection to phosphofructokinase, an effect enhanced by the addition of zinc, do not stabilize the enzyme during freeze-drying, even if zinc is present. The addition of ionic copper, cadmium, nickel, cobalt, calcium and manganese to trehalose-phosphofructokinase solutions prior to freeze-drying also increases the percentage of activity recovered after dissolution. Magnesium is ineffective in this respect.

Animals↗

PubMedDate not supplied

Incorporation of radiolabelled sugars into synaptic junctional macromolecules from chick brain.

Individual radiolabelled sugars ([1-14C]-L-fucose, [U-14C]-D-galactose, [U-14C]-D-mannose, [U-14C]-D-glucose and [U-14C]-D-glucosamine) were injected intraventricularly into the forebrains of day-old chickens, and the relative incorporation, after 6 hr, into the glycoprotein sugars, aglycosyl protein, glycolipid sugars and aglycosyl lipid assessed. In addition, the relative total and specific activities of the individual glycoprotein sugars was also determined. Exclusive labelling of glycoprotein sugars (and of the fucose within these oligosaccharides) using fucose as precursor was confirmed, while optimal labelling of glycolipid sugars was achieved using the precursor mannose. Galactose, mannose, glucose and glucosamine were converted to varying degrees to other sugars and non-sugar precursors prior to incorporation. Glucosamine gave rise to the most even distribution of radioactivity among the glycoprotein sugar residues. The highest relative specific activities of the glycoprotein oligosaccharides were achieved using fucose and glucosamine as precursors.

Acetylgalactosamine↗

PubMed2005

Syntheses and biological activities of daunorubicin analogs with uncommon sugars.

To study the effects of the sugar structure on the activity of anthracycline against cancer cells, six daunorubicin analogs containing different uncommon sugars were synthesized. Their cytotoxicities were tested against colon cancer cells by MTS assay. The results showed that the aglycon without sugar moiety has 70-100-fold lower activity against cancer cells than daunorubicin derivatives with various uncommon sugars. It suggests that the sugar structure in daunorubicin plays a critical role in determining its anticancer activity. In the compounds with various sugars, the 4'-OH of the sugar is an important determinant for their activity, while the axial-3'-substituent in the sugar interferes with the binding of daunorubicins to DNA. Therefore, 2,6-dideoxy sugars are a better choice for generating biologically active daunorubicin analogs than 6-deoxysugars, 2,3,6-trideoxysugars, or 2,3,4,6-tetradeoxysugars.

Cell Line, Tumor↗

PubMed2005

Dual sugar gut-permeability testing on blood drop in animal models.

BACKGROUND: Intestinal permeability is determined by measuring nonmetabolized sugars. In animals, intestinal permeability is determined in urine, using cumbersome and expensive metabolic cages. We developed an HPLC method for determining concentrations of lactulose (L) and L-rhamnose (R) in blood-drop of rabbits and mice, and we compared these results with the procedure based on sugars excreted in urine. We measured the intestinal permeability induced by a fragment (DeltaG) of the zonula occludens toxin which opens the paracellular pathway. METHODS: The animals received sugar solution and later received the same solution+DeltaG. Five-hour urine collection and timed blood tests were performed after ingestion of sugars. Sugars were measured with HPLC, and the percentage of recovered sugars was expressed as L/R ratio. RESULTS: At 60 min after administration of sugars, the mean L/R ratio for rabbits and mice was 0.026 and 0.052, respectively. At 60 min after administration of sugars+DeltaG, the mean L/R ratio for rabbits and mice was 0.22 and 0.53. The mean L/R ratio in the urine was 0.023 at basal condition and 0.25 after DeltaG ingestion. CONCLUSIONS: Testing small serum samples for sugar permeability is effective for monitoring changes in permeability of the gut in animals. This cheap simple method allows us to measure in vivo the biological activity of other molecules which modulate the paracellular pathway.

Animals↗

PubMed2005

A solid-state NMR study of molecular mobility and phase separation in co-spray-dried protein-sugar particles.

Molecular mobility and physical form of co-spray-dried sugar-lysozyme formulations were evaluated. Co-spray-dried trehalose:lysozyme and sucrose:lysozyme formulations in 1:9, 1:1 and 9:1 ratios (w:w) were stored at 0% RH and 75% RH for 5-6 days. Molecular mobility and physical form of the co-spray-dried formulations after storage were determined by using 13C and 1H solid-state NMR as well as X-ray powder diffractometry. The results showed that increasing sugar content in co-spray-dried formulations stored at 0% RH decreased molecular mobility of the amorphous formulations indicating a close association of the protein and sugar. Exposure of sugar-lysozyme 1:1 and 9:1 formulations to 75% RH led to separation of sugar and protein phases, where the sugar phase was crystalline. The intimate sugar-lysozyme interaction of the formulations stored at 0% RH and the phase separation of the sugar-rich formulations stored at 75% RH were also confirmed by using 13C solid-state NMR spin-lattice relaxation time-filter (T1-filter) measurements. The propensity of sucrose and trehalose to crystallise was similar; however, the results suggest that part of the sugar in the phase-separated formulations remained amorphous and in close association with lysozyme.

Carbohydrates↗

PubMed2000

Probing sugar translocation through maltoporin at the single channel level.

Sugar permeation through maltoporin of Escherichia coli, a trimer protein that facilitates maltodextrin translocation across outer bacterial membranes, was investigated at the single channel level. For large sugars, such as maltohexaose, elementary events of individual sugar molecule penetration into the channel were readily observed. At small sugar concentrations an elementary event consists of maltoporin channel closure by one third of its initial conductance in sugar-free solution. Statistical analysis of such closures at higher sugar concentrations shows that all three pores of the maltoporin channel transport sugars independently. Interestingly, while channel conductance is only slightly asymmetric showing about 10% higher values at -200 mV than at +200 mV (from the side of protein addition), asymmetry in dependence of the sugar binding constant on the voltage polarity is about 20 times higher. Combining our data with observations made with bacteriophage-lambda we conclude that the sugar residence time is much more sensitive to (and is decreased by) voltages that are negative from the intra-cell side of the bacterial membrane.

Bacterial Outer Membrane Proteins↗

PubMed1996

Salicylic acid-independent induction of pathogenesis-related protein transcripts by sugars is dependent on leaf developmental stage.

Soluble sugars have been found to regulate a number of genes involved in functions associated with sink metabolism, defense reactions and photosynthesis. As viruses and pathogens induce the expression of pathogenesis-related (PR) protein genes and have also been reported to lead to localized sugar accumulation in leaves, it was investigated whether a salicylic acid-independent but sugar-dependent pathway for PR-protein gene induction may exist in plant cells. Leaf discs of tobacco plants were floated on different sugar solutions, transcript accumulation and salicylic acid (SA) levels were subsequently determined. PR-Q and PAR-1 transcripts were found to be inducible by glucose, fructose and sucrose. No significant change in SA content could be detected, following incubation. On the other hand, SAR8.2 transcripts were repressed by elevated levels of soluble sugars and sorbitol, respectively, suggesting sensitivity to turgor pressure. Since leaves undergo sink to source transition during growth, sugar responsiveness was investigated in leaves of different developmental stages. Interestingly, induction of PR-Q and PAR-1 by soluble sugars was essentially restricted to fully expanded leaves and was independent of plant age. Induction by salicylate was not confined to the source capacity of a leaf but was dependent on the age of the respective leaf. Repression of transcripts encoding photosynthetic genes (ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcS) and chlorophyll a/b binding protein (cab) by soluble sugars were largely independent from the leaf developmental state. These findings hint to the possibility of salicylic acid-independent defense reactions of plants against pathogens by induction of a set of PR proteins in source leaves. Furthermore, the data suggest different mechanisms for the induction of PR-protein genes and the repression of photosynthetic genes by soluble sugars.

Carbohydrate Metabolism↗

PubMed2000

Influence of sugar supplementation of the extender on motility, viability and acrosomal integrity of dog spermatozoa during freezing.

Influence of different sugars supplemented to the extender on the motility, viability and intact acrosome rates of dog spermatozoa during dilution, equilibration and freezing was studied. The ejaculate was divided into 10 aliquots, which were diluted 1:3 with TRIS-citric acid extender containing 240 mMTRIS, 63 mM citric acid, 8% (v/v) glycerol, 20% (v/v) egg yolk and 70 mM sugar, which was either fructose, galactose, glucose, xylose (monosaccharide), lactose, trehalose, maltose, sucrose (disaccharide) or raffinose (trisaccharide). No sugar was added to the extender in the control group. Extended semen samples were cooled to 5 degrees C over 45 min, packaged in 0.25-mL straws, equilibrated for 2 h at 5 degrees C and frozen in liquid nitrogen vapor. Samples were thawed by placing straws into 37 degrees C water for 30 sec. Motility, viable sperm and intact acrosome rates decreased gradually in all groups after equilibration and consecutively freezing (P<0.001). The type of sugar significantly effected motility, viability and acrosomal integrity during equilibration and freezing (P<0.05). Galactose, lactose, trehalose, maltose and sucrose reduced damaged acrosome percentages in equilibrated samples (P<0.05). Sugar supplementation did not enhance motility and viability during equilibration. The disaccharides, except lactose, reduced post-thaw dead sperm and/or damaged acrosome percentages without promoting post-thaw motility (P<0.01), whereas monosaccharides, especially fructose and xylose, improved motility (P<0.05) along with viability and intact acrosome rates (P<0.05). Trehalose, xylose and fructose significantly increased total active sperm rates (motility x live sperm rate x normal acrosome rate) compared to other sugars (P<0.01) and control (P<0.0001) in frozen thawed samples. Therefore, sugar supplementation of the extender influenced post-equilibration and post-thaw sperm quality, and the type or locality of protective impact of the sugar on dog spermatozoa vary according to type of the sugar.

Acrosome↗

PubMed1983

Sugars and dental decay.

Sugar is the principal cause of the most common disease in industrialised countries, dental caries. The sugars implicated in dental caries, in decreasing order of cariogenicity, are sucrose, glucose, and fructose; brown sugars are as cariogenic as white. The level of sugar consumption at which most of the population will not get dental caries is 15 kg/person/year. The goal should therefore be to reduce consumption to this level and below. The following policies should be introduced to achieve this goal: sugars should not be added to dietary items such as baby foods; a range of acceptable sugar-free snacks and drinks should be developed; non-cariogenic sweeteners should be substituted for added sucrose and glucose in foods, confections, and drinks; sugar-containing foods should be modified to make them less cariogenic; and the levels of added sugars in commonly used foods should be reduced. The transmission to the public of information on sugars and dental health should be improved.

Dental Caries↗

PubMed2000

Interactions of dietary protein and carbohydrate determine blood sugar level and regulate nutrient selection in the insect Manduca sexta L.

The non-homeostatic regulation of blood sugar concentration in the insect Manduca sexta L. was affected by nutritional status. Larvae maintained on diets lacking sucrose displayed low concentrations of trehalose, the blood sugar of insects, which varied from 5 to 15 mM with increasing dietary casein level between 12.5 and 75 g/l. These insects were glucogenic, as demonstrated by the selective 13C enrichment of trehalose synthesized from [3-13C]alanine, and de novo synthesis was the sole source of blood sugar. The distribution of 13C in glutamine established that following transamination of the 13C substituted substrate, [3-13C]pyruvate carboxylation rather than decarboxylation was the principal pathway of Pyr metabolism. The mean blood trehalose level was higher in insects maintained on diets with sucrose. At the lowest dietary casein level blood trehalose was approximately 50 mM, and declined to 20 mM at the highest casein level. Gluconeogenesis was detected in insects maintained on sucrose-free diets at the higher protein levels examined, but [3-13C]pyruvate decarboxylation and TCA cycle metabolism was the principal fate of [3-13C]alanine following transamination, and dietary carbohydrate was the principal source of glucose for trehalose synthesis. Feeding studies established a relationship between nutritional status, blood sugar level and dietary self-selection. Insects preconditioned by feeding on diets without sucrose had low blood sugar levels regardless of dietary casein level, and when subsequently given a choice between a sucrose diet or a casein diet, selected the former. Larvae preconditioned on a diet containing sucrose and the lowest level of casein had high blood sugar levels and subsequently selected the casein diet. Larvae maintained on the sucrose diet with the highest casein level had low blood sugar and self-selected the sucrose diet. When preconditioned on diets with sucrose and intermediate levels of casein, insects selected more equally between the sucrose and the casein diets. It is concluded that blood sugar level may be intimately involved in dietary self-selection by M. sexta larvae, and that in the absence of dietary carbohydrate, gluconeogenesis provides sufficient blood sugar to ensure that larvae choose a diet or diets that produce an optimal intake of dietary protein and carbohydrate.

Alanine↗