Changes In Carbohydrate Levels Research Articles

Target Metabolites to Slow Down Progression of Amyotrophic Lateral Sclerosis in Mice.

Microbial metabolites affect the neuron system and muscle cell functions. Amyotrophic lateral sclerosis (ALS) is a multifactorial neuromuscular disease. Our previous study has demonstrated elevated intestinal inflammation and dysfunction of the microbiome in patients with ALS and an ALS mouse model (human-SOD1G93A transgenic mice). However, the metabolites in ALS progression are unknown. Using an unbiased global metabolomic measurement and targeted measurement, we investigated the longitudinal changes of fecal metabolites in SOD1G93A mice over the course of 13 weeks. We further compared the changes of metabolites and inflammatory response in age-matched wild-type (WT) and SOD1G93A mice treated with the bacterial product butyrate. We found changes in carbohydrate levels, amino acid metabolism, and the formation of gamma-glutamyl amino acids. Shifts in several microbially contributed catabolites of aromatic amino acids agree with butyrate-induced changes in the composition of the gut microbiome. Declines in gamma-glutamyl amino acids in feces may stem from differential expression of gamma-glutamyltransferase (GGT) in response to butyrate administration. Due to the signaling nature of amino acid-derived metabolites, these changes indicate changes in inflammation, e.g., histamine, and contribute to differences in systemic levels of neurotransmitters, e.g., γ-Aminobutyric acid (GABA) and glutamate. Butyrate treatment was able to restore some of the healthy metabolites in ALS mice. Moreover, microglia in the spinal cord were measured by IBA1 staining. Butyrate treatment significantly suppressed the IBA1 level in the SOD1G93A mice. Serum IL-17 and LPS were significantly reduced in the butyrate-treated SOD1G93A mice. We have demonstrated an inter-organ communications link among microbial metabolites, neuroactive metabolites from the gut, and inflammation in ALS progression. The study supports the potential to use metabolites as ALS hallmarks and for treatment.

The Metabolic Response to Infection With Wolbachia Implicates the Insulin/Insulin-Like-Growth Factor and Hypoxia Signaling Pathways in Drosophila melanogaster

The endosymbiotic bacteria, Wolbachia, are best known for their ability to manipulate insect-host reproduction systems that enhance their vertical transmission within host populations. Increasingly, Wolbachia have been shown to depend on their hosts' metabolism for survival and in turn provision metabolites to their host. Wolbachia depends completely on the host for iron and as such iron has been speculated to be a fundamental aspect of Wolbachia-host interplay. However, the mechanisms by which dietary iron levels, Wolbachia, and its host interact remain to be elucidated. To understand the metabolic dependence of Wolbachia on its host, the possibility of metabolic provisioning and extraction, and the interplay with available dietary iron, we have used NMR-based metabolomics and compared metabolite profiles of Wolbachia-infected and uninfected Drosophila melanogaster flies raised on varying levels of dietary iron. We observed marked metabolite differences in the affected metabolite pathways between Wolbachia-infected and uninfected Drosophila, which were dependent on the dietary iron levels. Excess iron led to lipid accumulation, whereas iron deficiency led to changes in carbohydrate levels. This represents a major metabolic shift triggered by alterations in iron levels. Lipids, some amino acids, carboxylic acids, and nucleosides were the major metabolites altered by infection. The metabolic response to infection showed a reprogramming of the mitochondrial metabolism in the host. Based on these observations, we developed a physiological model which postulates that the host's insulin/insulin-like-growth factor pathway is depressed and the hypoxia signaling pathway is activated upon Wolbachia infection. This reprogramming leads to predominantly non-oxidative metabolism in the host, whereas Wolbachia maintains oxidative metabolism. Our data also support earlier predictions of the extraction of alanine from the host while provisioning riboflavin and ATP to the host.

Single and combined effects of heat and water stress and recovery on cotton (Gossypium hirsutum L.) leaf physiology and sucrose metabolism

High temperatures and water-deficit stress limit cotton production around the world. Their individual effects on plant physiology and metabolism have been extensively studied, however, their combination has received considerably less attention. To that end, growth chamber experiments were conducted using cotton (Gossypium hirsutum L.) cultivar ST5288B2F and the objectives were to discern physiological and metabolic alterations after heat and water stress application (single or combined) and recovery, during cotton's vegetative stage. Under water stress conditions, leaf physiological parameters were suppressed and changes in carbohydrate levels, due to alterations in sucrose-metabolizing enzymes activities, were observed. Heat stress alone increased carbohydrate content, and activities of sucrose-degrading enzymes, while leaf physiology remained unaffected. The combined stress did exacerbate decreases in leaf water potential and soluble acid invertase activity, but the rest of the responses were similar to those of water stress. After stress alleviation, leaf physiological parameters of water-stressed plants did not manage to recover and substantial decreases were observed in leaf starch levels and activities of sucrose-cleaving enzymes, while the majority of parameters of heat-shocked plants returned to control levels. Recovery of the plants subjected to the combined stress was comparable to that of water-stressed plants, but significant differences were observed in carbohydrate levels and sucrose synthase activity. Our study demonstrated that under combined stress and post-stress conditions, water stress was the dominant factor affecting cotton leaf physiology and sucrose metabolism, highlighting however, the unique responses of some traits that could not be deduced from the additive effects of the single stresses.

Metabolic footprinting revealed key biochemical changes in a brown fermented milk product using Streptococcus thermophilus

Ultra-performance liquid chromatography coupled with a quadrupole-time-of-flight mass spectrometryElevated Energy was used to investigate changes in the metabolite profile of brown milk and fermented brown milk produced using Streptococcus thermophilus S10. Samples were analyzed in both positive and negative electron ionization modes. Data were analyzed by multivariate statistical methods for biomarker metabolites that were differentially abundant in brown milk and fermented brown milk. We identified 43 differentially abundant metabolites based on mass spectrophotometry fragmentation patterns. These metabolites included peptides, AA, fatty acids and related metabolites, carbohydrate metabolites, vitamins, and nucleosides. Some of these metabolites are known to alter the sensorial quality of fermented dairy products. Thus, it is likely that some of the currently identified differentially abundant metabolites also contribute to the unique flavor, taste, and aroma of fermented brown milk. The bitterness and astringency of fermented brown milk are likely to be due to some of these peptides, whereas the sweetness and sourness could be a result of changes in carbohydrate levels. No previous study has analyzed metabolomics changes during fermentation of brown milk. Thus, our data are a valuable reference for future development and improvement of fermented brown milk products.

Root cultures of potato mutant lacking MSPI isoform, indispensable for photosynthetic light reactions, exhibit characteristics similar to intact plant roots

Potato (Solanum tuberosum) mutant (ST) lacking one isoform of manganese-stabilizing protein (MSPI) of photosystem II exhibited besides spontaneous tuberization also growth changes with strongly impaired root system development. Previous studies revealed marked changes in carbohydrate levels and allocation within ST plant body. To verify causal relationship between changed carbohydrate balance and root growth restriction we engaged dark grown sucrose-supplied root organ-cultures of ST plants to exclude/confirm shoot effects. Unexpectedly, in ST root cultures we observed large alterations in growth and architecture as well as saccharide status similar to those found in the intact plant roots. The gene expression analysis, however, proved PsbO1 transcript (coding MSPI protein) neither in ST nor in WT root-organ cultures. Therefore, the results point to indirect effects of PsbO1 allele absence connected possibly with some epigenetic modulations.

Changes in carbohydrate levels and relative water content (RWC) to distinguish dormancy phases in sweet cherry

Perennial trees require chilling, i.e. a period of cold temperature in the winter, for flowering next spring; sweet cherry is particularly prone to lack of chilling. The objective of this study is to identify possible transition points to clearly distinguish dormancy phases by relating carbohydrate and relative water content (RWC) in reproductive buds to concomitant chilling fulfilment.This contribution proposes the use of four transition points between the dormancy phases and their characterization in terms of carbohydrates, water contents in combination with chilling values and may allow upscaling to other dormancy studies in trees; two groups of cherry varieties were defined based on their different initial sorbitol and starch level in the autumn. The first separation between para- and (deep) d-endo-dormancy is characterized as a transition from a decrease (variety group 1) or a constant level (variety group 2) to a sharp increase in hexoses and sorbitol and a drop of starch content. The second transition point (d-endo- to f-endo-dormancy) is characterized as the changes in both hexoses (increase) and starch (decrease) terminate and ca. 650 Chilling Hours (CH), i.e. insufficient chilling in the concomitant forcing experiment with cut branches. This third transition point (f-endo- to eco-dormancy) was characterized by ca. 1000 CH, the minimum chilling requirement and restrained flowering (cut branches). The fourth transition point (forcing initiation) marked an increase in water content at ca. 1550 CH, optimum chilling for cherry and coincided with natural flowering.A ratio of hexoses (glucose plus fructose) to starch content (<2:1) appeared to be a potential indicator of the beginning of chilling (para-dormancy) and a ratio of 14–20:1 typical for endo-dormancy, whereas the release from dormancy was associated with a decline to less than 10:1 at the end of winter (eco-dormancy).To our knowledge, this is the first time that transition points are identified based on constituents (carbohydrates and relative water content) in floral buds related to current chilling status and dormancy phases and are also presented in a schematic diagram. The understanding of these changes in relative water content and carbohydrate levels may contribute to manage insufficient chilling in the orchard and support climate change studies with trees.

Defence response of Sitka spruce before and after inoculation with Heterobasidion annosum: 1H NMR fingerprinting of bark and sapwood metabolites

Metabolite fingerprinting of Sitka spruce (Picea sitchensis) bark and sapwood was carried out by (1)H nuclear magnetic resonance after wounding and artificial inoculation with the white rot fungus Heterobasidion annosum sensu stricto. The aim was to determine whether metabolites would differ in clones showing differing levels of susceptibility to H. annosum, in the fungal as compared with the control treatment (wounding, no fungus) and the reference (healthy sample collected at 0 days), at two different locations on the host, and at different sampling times (3 and 43 days after treatment). The results suggested that different metabolic processes occur in bark and sapwood after wounding and fungal inoculation, compared with healthy samples collected before treatment: In bark, greater peaks were elicited in the aromatic region whereas, in sapwood, lower amounts of all metabolites were observed in inoculated samples, compared with healthy samples. Multivariate statistical analysis carried out with analysis of variance-principal component analysis showed highly significant effects of reference, location, and time (PC1), and significant effects of clone and fungus. Differences between clones were apparent in sapwood but not in bark and were due to peaks in the aliphatic and carbohydrate regions. Over time, in bark, there was a decrease in carbohydrate peaks, followed by an increase in aliphatic and aromatic peaks. Sapwood, by contrast, showed a decrease in all peaks, followed by an increase in carbohydrate and aliphatic peaks. Changes in carbohydrate levels were observed within the lesion compared with the more distal location in both bark and sapwood.

Changes in carbohydrate levels and their metabolic enzymes in leaves, phloem sap and mesocarp during cucumber ( Cucumis sativus L.) fruit development

Levels of carbohydrates and activities of metabolic enzymes were examined in leaves (source), phloem sap (flow) and mesocarp tissues (sink) in the course of cucumber ( Cucumis sativus L.) fruit development, from 2 days before anthesis to 20 days after anthesis. While total sugar levels increased in all the three sampling organs, starch levels declined in leaves and mesocarp tissues as fruit development progressed. Glucose and fructose were the primary contributors to the soluble sugar pools in mature leaves. Stachyose was found as the most important component of the phloem sap extracts, followed by sucrose and raffinose. However, the primary sugars accumulated in mesocarp tissues were glucose and fructose, not stachyose or sucrose. Activities of sucrose synthesizing enzymes (sucrose phosphate synthase plus sucrose synthase in the synthesizing direction) exceeded that of sucrose degrading enzymes (acid invertase, neutral invertase plus sucrose synthase in the degrading direction) in leaves, which might cause a sucrose pool utilized in raffinose and stachyose biosynthesis. While alkaline a-galactosidase form I activity declined, stachyose synthase activity showed a rapid increase until 12 days after anthesis and only subsequently decreased in leaves. Activities of sucrose degrading enzymes were always much higher than that of sucrose synthesizing enzymes in mesocarp tissues. Thus, sucrose accumulation could not occur in mesocarp tissues. While stachyose synthase activity steadily decreased, alkaline a-galactosidase form I activity showed a moderate increase before decrease in mesocarp tissues. The relationship between levels of soluble sugars and activities of relative enzymes was also discussed.

Energy source utilization by embryos and larvae of the muricid snail Chorus giganteus (Lesson, 1829)

The muricacean snail Chorus giganteus presents intracapsular development and the occurrence of nurse eggs that are ingested by the early encapsulated embryos indicate both that these snails develop through a lecitotrophic type of development and that reserves would be sufficient to support settlement and metamorphosis. In order to get more information about the use of energy resources, the dynamics of biochemical components throughout development at three temperatures (9, 12 and 15 °C) and the energetic cost of free-swimming life and metamorphosis are described. The uptake of 3H-alanine, as representative of dissolved organic matter, by embryo and larval stages is also investigated. While protein levels increased at all temperature conditions after ingestion of nurse eggs, lipids only increased when embryo and larvae were reared at 15 °C, and no change in carbohydrate levels was detected at any of the temperatures. The RNA/DNA indexes showed no significant differences with temperature at any stage of development but decreased along with the development of individuals. After hatching, organic matter and energy content of juveniles steadily decreased. Individuals at any of the developmental stage showed to be able to uptake alanine from seawater; the aminoacid uptake capacity increased along with intracapsular development. Uptake of alanine showed to be an active process and to follow Michaelis–Menten kinetics. This would be the first report about dissolved organic matter uptake by encapsulated development stages of any marine invertebrate species and let conclude that these larvae have the ability to obtain exogenous food in a dissolved form and to incorporate it into metabolizable compounds.

Low night temperatures change whole-plant physiology and increase starch accumulation in Chrysanthemum morifolium

SummaryOvernight changes in carbohydrate levels and the uptake of 15NO3–, photosynthesis, and plant morphology were investigated in Chrysanthemum morifolium with the aim of identifying the first limiting factor to influence plant growth and maintenance at low night temperatures. Plants were grown in long-day conditions in an aerated nutrient solution culture system placed in three identical climate chambers. Night/day temperature treatments were 18°/18°C (control), 12°/18°C, and 8°/18°C, respectively. Chrysanthemum morifolium had the same dry matter (DM) production in the three treatments; however, plants grown with low night temperature treatments formed fewer leaves and their total leaf area decreased. In contrast, low night temperatures increased leaf DM content at the expense of root DM content. This was explained, in part, by starch accumulation, which occurred because the starch synthesised during the photoperiod did not disappear during the dark period. Low night temperatures decreased the N concentration in plants; however, this reduction was limited and explained, in part, by starch accumulation in the leaves. Daily plant NO3– uptake was not affected by low night temperatures, although the NO3– uptake rate was lower during the night when plants were grown at 8°C, possibly due to a decrease in transpiration. Furthermore, low night temperatures had no effect on stem length, in contrast to previous literature. No explanation could be found; however, the short duration of the experiment might explain this. The present results provide new information on the limits for growing chrysanthemums and other floricultural crops in a dynamic climate-control system with low temperatures during the night, and in other periods when plants are less active.

Effect of different temperature regimes on reproductive conditioning in the scallop Argopecten purpuratus

Adult Argopecten purpuratus were conditioned under four different temperature regimes and their gonadal development and quality of the resulting offspring evaluated. Biochemical composition of muscle and gonad, during laboratory conditioning at the different treatments, was also examined. Spawned-out individuals were obtained from commercial culture centers for experimentation. Test groups of scallops were independently maintained at: (a) 15 °C, (b) 19 °C, (c) 15 °C in the first stage, raised to 19 °C in the second stage, and (d) 19 °C in the first stage decreasing to 15 °C in the second stage. Scallops were maintained in seawater which was changed daily, provided with aeration, and were continuously fed a diet consisting of 50% Isochrysis galbana (var. T-iso) and 50% Chaetoceros gracilis. The daily ration was equivalent to 6% of the dry biomass of the scallops. Animals were maintained under a constant photoperiod of 12-h light and 12-h dark. Progress of gonadal recovery was followed by periodic determination of gonadosomatic index (GSI) and histological analysis. The highest percentage of scallops attaining spawning condition and highest values for GSI was obtained from animals conditioned under the constant 15 °C regime. The group started at 15 °C and raised to 19 °C showed the most variable pattern of maturation. Of the major biochemical components of the adductor muscle, lipids and proteins changed most during conditioning under any of the temperature regimes; changes in carbohydrate levels in this tissue were only detected for scallops maintained at a constant temperature. Changes in protein levels, depending on the time and temperature of conditioning, were detected in the gonad. Based on quality indicators used in this study, including fecundity, egg size, biochemical composition, and “D” larvae survival, the best physiological conditioning for the reproductive process was obtained in scallops, which were conditioned at a constant temperature of 15 °C, and at an initial temperature of 19 °C and then decreased to 15 °C. Results showed an inverse relationship between temperature and conditioning success and the importance of maintaining stable temperatures during the laboratory conditioning process which permitted adequate accumulation and use of nutritional reserves required to produce highly viable larvae.

Induction of 1-FEH in mature chicory roots appears to be related to low temperatures rather than to leaf damage.

Large-scale inulin production from chicory roots (Cichorium intybus L.) is hampered by the induction of 1-FEH activity (fructan 1-exohydrolase) and concomitant fructose production in autumn, coincident with a period with low night temperatures that cause leaf damage. To understand whether leaf damage per se is sufficient for 1-FEH induction and fructan breakdown, we defoliated mature chicory plants at a preharvest stage (September 10) and investigated the changes in carbohydrate levels and 1-FEH activities. Also, the activities of 1-SST (sucrose:sucrose 1-fructosyl transferase, EC 2.4.1.99), 1-FFT (fructan:fructan 1-fructosyl transferase, EC 2.4.1.100), and acid invertase (EC 3.2.1.26) were determined. Defoliation did not result in a prompt fructan breakdown and increase in 1-FEH activity, but after 10 days fructan breakdown and 1-FEH activities became higher in the defoliated plants. Defoliation resulted in a sharp decrease in 1-SST activity over the first 24 h. Afterwards, root 1-SST activities of defoliated plants remained at a lower level than in control plants. 1-FFT and invertase activities were not affected by defoliation. It can be concluded that defoliation of plants at the preharvest stage by itself did not induce the same rapid changes as observed in naturally induced October roots by low temperature (harvest stage). Taken together with our finding that 1-FEH is not induced in chicory roots when plants are transferred to the greenhouse early autumn (minimal temperature 14°C), we conclude that low temperatures might be essential for 1-FEH induction.

Carbohydrates as related to the heat-induced chilling tolerance and respiratory rate of ‘Fortune’ mandarin fruit harvested at different maturity stages

We have evaluated the effect of a heat-conditioning treatment (3 days at 37 °C) on respiratory rate, soluble carbohydrate and starch content of ‘Fortune’ mandarin fruit harvested at different maturity stages and stored at a chilling (2 °C) and a non-chilling (12 °C) temperature. The treatment was highly effective, increasing the tolerance of detached ‘Fortune’ fruit to chilling injury (CI). Changes in carbohydrate levels in response to the high temperature treatment, and during exposure of the non-conditioned and heat-conditioned fruit to 2 and 12 °C, appear to be mainly related to the consumption of carbohydrate reserves for respiration. The highest respiratory rate was found in fruit exposed to 37 °C. The respiration of non-conditioned fruit stored at 2 °C was lower than that of control fruit stored at 12 °C. Therefore, anomalous high respiratory activity did not occur during chilling in ‘Fortune’ mandarins. Sucrose appeared to be the most accessible sugar as a respiratory substrate in non-conditioned fruit. No relationship between the susceptibility to CI and changes in carbohydrates during storage of non-conditioned fruit at 2 °C was found. The heat treatment prevented the decline in sucrose content during chilling. After 30 days at 2 °C, the sucrose content of non-conditioned fruit harvested in December, January and March was about 79, 57 and 68% that of their respective heat-conditioned fruit. In contrast, heating the fruit favoured the loss of glucose, fructose and starch in fruit kept at 2 °C. These data suggest that sucrose but not glucose, fructose or starch could be involved in the heat-induced chilling tolerance of citrus fruit detached from the tree. The effect of the heat treatment preventing sucrose decline during storage of fruit at 2 °C was less relevant in fruit from December than in those harvested later in the season, although it was very effective in protecting fruit harvested at all maturity stages against chilling. Therefore, sucrose appears not to be a limiting factor for the heat-induced chilling tolerance in citrus fruit.

Incidence of Fusarium spp. in Asparagus Spears.

Fusarium proliferatum and F. oxysporum have been identified as causal agents of asparagus decline in the field and have been associated with reduction in spear quality (1,2). Our objective was to determine the origin and incidence of spear infection by these fungi during the cropping years 1994 to 1997. From 15 to 40 asparagus samples were randomly selected from the field, packing houses, and retail markets and assayed for Fusarium spp. Collections were made in California, Connecticut, Peru, Mexico, and Australia. The number of samples varied between sampling sites and for the time of harvest season. One Mexican collection site was sampled at the beginning, mid-point, and end of the harvest season to evaluate influence of decreasing carbohydrate levels and increasing temperatures on infection and growth of the fungi. Isolations included sections (5 to 6 cm) from the basal and terminal portions of the spear to evaluate postharvest growth in the spear. Fusarium spp. were recovered from spear samples that included all geographical sampling locations (mean 45%, range 20 to 90%). F. proliferatum was the dominant species isolated consistently from the desert areas regardless of harvest period. The frequency of F. oxysporum isolation ranged from 2 to 32% with no correlation to time or location of sampling. Basal sections were more frequently infected (94%) than terminal portions of the spear (less than 6%). No major differences in the percentage of infected spears were found in collection sites regardless of country sampled. There were differences in the incidence of infection between harvest sample dates. Spears sampled late in the harvest period were 57% more infected than spears of early or mid-season collections. Samples from the same fields, regardless of whether collected directly from the field, from packing sheds, or from the retail market, had higher infection rates later in the harvest season compared with earlier harvests. This may be attributable to warmer temperatures, changes in levels of carbohydrates, or other physiological factors. Spears harvested from the field that were infected with both Fusarium spp. had a greater incidence of infection than spears recovered from packing houses or from retail sources. This supports the theory that the source of spear infection is diseased crowns and not postharvest sources. Isolates from the spears of both Fusarium spp. were found to be pathogenic when challenged to asparagus seedlings.

Drought-induced male sterility in rice: changes in carbohydrate levels and enzyme activities associated with the inhibition of starch accumulation in pollen

Drought-induced male sterility in rice: changes in carbohydrate levels and enzyme activities associated with the inhibition of starch accumulation in pollen

Drought-induced male sterility in rice: Changes in carbohydrate levels and enzyme activities associated with the inhibition of starch accumulation in pollen

Male reproductive development of rice (Oryza sativa L.) is very sensitive to drought. A brief, transitory episode of water stress during meiosis in pollen mother cells of rice grown under controlled environmental conditions induced pollen sterility. Anthers containing sterile pollen were smaller, thinner, and often deformed compared to normal anthers of well-watered plants. Only about 20% of the fully developed florets in stressed plants produced grains, compared to 90% in well-watered controls. Water stress treatments after meiosis were progressively less damaging. Levels of starch and sugars and activities of key enzymes involved in sucrose cleavage and starch synthesis were analyzed in anthers collected at various developmental stages from plants briefly stressed during meiosis and then re-watered. Normal starch accumulation during pollen development was strongly inhibited in stress-affected anthers. During the period of stress, both reducing and non-reducing sugars accumulated in anthers. After the relief of stress, reducing sugar levels fell somewhat below those in controls, but levels of non-reducing sugars remained higher than in controls. Activities of acid invertase and soluble starch synthase in stressed anthers were lower than in controls at comparable stages throughout development, during as well as after stress. Stress had no immediate effect on ADP-glucose pyrophosphorylase activity, but had an inhibitory aftereffect throughout post-stress development. Sucrose synthase activity, which was, relatively speaking, much lower than acid invertase activity, was only slightly suppressed by stress. The results show that it is unlikely that pollen sterility, or the attendant inhibition of starch accumulation, in water-stressed rice plants are caused by carbohydrate starvation per se. Instead, an impairment of enzymes of sugar metabolism and starch synthesis may be among the potential causes of this failure.

Crypt/villus site of substrate-dependent regulation of mouse intestinal glucose transporters.

The intestinal epithelium is in a constant state of turnover, with cells differentiating at the crypts and then migrating toward the tips of the villi. Does substrate-dependent regulation of intestinal Na+/D-glucose cotransporters occur only in crypt cells, or can transport activity be subsequently reprogrammed in mature enterocytes? We used in situ, glucose-protectable specific phlorizin binding to determine site density of brush border glucose transporters in enterocytes fractionated along the crypt/villus axis of mice that were killed shortly after drastic changes in carbohydrate levels of their diets. Dietary carbohydrate-induced changes in site density of specific phlorizin binding initially appeared only in crypt cells before spreading, over the course of several days, to the villus tips. Thus, only crypt cells perceive the signal for glucose transporter regulation, and the observed time lag of diet-induced changes in intestinal glucose uptake is due mainly to cell migration times.

Available carbohydrates of cereal grains as affected by storage and insect infestation

Total soluble sugar, reducing sugar, non-reducing sugar and starch contents of wheat, maize and sorghum grains were affected adversely at 25, 50 and 75% insect infestation caused by Trogoderma granarium Everts and Rhizopertha dominica Fabricius, separately and mixed population. R. dominica caused significant (P < 0.05) reduction in available carbohydrates at 50 and 75% infestation levels whereas T. granarium achieved similar effect at 75%. Mixture of both insect species caused intermediate losses. Storage of cereal grains up to 4 months resulted in substantial increase in sugars and decrease in starch content, but storage for a shorter period of time did not cause any significant changes in levels of carbohydrates.

Changes in Starch, Sugar, and Abscisic Acid Contents Associated with Second Growth in Tubers of Potato ( Solanum tuberosum L.) One-leaf Cuttings

Summary Tuberized one-leaf cuttings of potato ( Solanum tuberosum L.) were kept under conditions inducing tuber regrowth (35 °C, leaf removed) or conditions allowing normal tuber growth (20 °C, leaf removed). The level of starch decreased substantially under conditions that induced tuber regrowth with a concomitant rise in the levels of sucrose and glucose. As a result, water was taken up and the dry matter content of the tubers decreased. Immediately after leaf removal, the level of ABA in the tubers decreased significantly in both treatments. It remained low under conditions that induced regrowth, whereas in the control treatment the level of ABA increased again. The changes in carbohydrate levels and in ABA content between the two treatments both preceded the occurrence of visible second growth, but the carbohydrate differences occurred first.

Correlated changes in carbohydrate levels and associated enzyme activities during development and senescence of ray florets inChrysanthemum

Changes in fresh and dry weight, content of sugars and starch and activities of α-amylase and acid invertase were determined during various stages of ray floret development and senescence inChrysanthemum. Total and reducing sugars increased until the ray florets attained their maximal expansion, peak fresh and dry weights. This coincided with the highest activity of invertase. Starch content and maximal activity of α-amylase declined much earlier. It is presumed that invertase rather than α-amylase plays a major role in the expansion of ray florets inChrysanthemum. Senescing stages of ray floret are characterized by decrease in fresh and dry weights and loss of metabolites and a marked decline in the activities of both invertase and α-amylase.