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At least 811 records · Page 45Linked to original sources
PubMed2002

Downregulation of a chloroplast-targeted beta-amylase leads to a starch-excess phenotype in leaves.

A functional screen in Escherichia coli was established to identify potato genes coding for proteins involved in transitory starch degradation. One clone isolated had a sequence very similar to a recently described chloroplast-targeted beta-amylase of Arabidopsis. Expression of the gene in E. coli showed that the protein product was a functional beta-amylase that could degrade both starch granules and solubilized amylopectin, while import experiments demonstrated that the beta-amylase was imported and processed into pea chloroplasts. To study the function of the protein in transitory starch degradation, transgenic potato plants were generated where its activity was reduced using antisense techniques. Analysis of plants reduced in the presence of this beta-amylase isoform showed that their leaves had a starch-excess phenotype, indicating a defect in starch degradation. In addition, it was shown that the antisense plants degraded only 8-30% of their total starch, in comparison with 50% in the wild type, over the dark period. This is the first time that a physiological role for a beta-amylase in plants has been demonstrated.

Chloroplasts↗
PubMed1997

[Effect of hydroxyethyl starch solution on kidney function in surgical intensive care patients].

Hydroxyethyl starch is commonly used in resuscitation, anaesthesia and intensive care medicine. Increasing creatinine values in patients treated with hydroxyethyl starch have been described in some case reports. These have also been some clinical signs such as pain in the renal region, and swelling of kidney parenchyma, but no differential and sensitive parameters of renal function have supported these possible side effects of hydroxyethyl starch. Twenty-five patients were randomly allocated to a control and a treatment group. In the treatment group, patients received 12 ml per kg body-weight hydroxyethyl starch 10% (200/0.5) daily. A non-invasive diagnostic spectrum of renal function was performed. Specific tubular proteins (alpha 1-microglobulin, Tamm-Horsfall protein), glomerular parameters (immunoglobulin G, albumin), and the brush border enzyme acetyl-beta-glucosaminidase, were examined. Additionally, renal blood flow and glomerular filtration rate, Apache-II-score, breathing therapy, infusions, transfusion, and all medical interventions were documented. Both groups were comparable with regard to drug therapy. Apache-II-score, and fluid management. There were differences in tubular function between the two groups. Patients undergoing HES therapy showed increased excretion of alpha 1-microglobulin. Tamm-Horsfall-protein and of brush border enzyme acetyl-beta-glucosaminidase. No significant differences were detectable in glomerular functions (glomerular filtration rate, renal blood flow), albumin, and IgG. Correlates of tubular damage after hydroxyethyl starch therapy were seen in intensive care patients. Many influences of intensive therapy act on renal function, and further studies with larger cohorts are necessary. With regard to the documented localisation of the tubular damage in the HES group, colloid therapy with hydroxyethyl starch in renal dysfunction should be monitored carefully by means of sensitive markers.

Acute Kidney Injury↗
PubMed2004

Starch granule initiation is controlled by a heteromultimeric isoamylase in potato tubers.

Starch granule initiation is not understood, but recent evidence implicates a starch debranching enzyme, isoamylase, in the control of this process. Potato tubers contain isoamylase activity attributable to a heteromultimeric protein containing Stisa1 and Stisa2, the products of two of the three isoamylase genes of potato. To discover whether this enzyme is involved in starch granule initiation, activity was reduced by expression of antisense RNA for Stisa1 or Stisa2. Transgenic tubers accumulated a small amount of a soluble glucan, similar in structure to the phytoglycogen of cereal, Arabidopsis, and Chlamydomonas mutants lacking isoamylase. The major effect, however, was on the number of starch granules. Transgenic tubers accumulated large numbers of tiny granules not seen in normal tubers. These data indicate that the heteromultimeric isoamylase functions during starch synthesis to suppress the initiation of glucan molecules in the plastid stroma that would otherwise crystallize to nucleate new starch granules.

Cytoplasmic Granules↗
PubMed2003

Altered starch structure is associated with endosperm modification in Quality Protein Maize.

The biochemical basis of modified kernel texture in Quality Protein Maize (QPM) is poorly understood. Proteomic analysis of several QPM lines indicated increased levels of granule-bound starch synthase I in the soluble nonzein protein fraction of these genotypes. Increased extraction of this enzyme reflected a change in starch structure, which was manifested as shorter amylopectin branches and increased starch-granule swelling. In mature kernels, these alterations in starch structure were associated with interconnections between starch granules that resulted in a vitreous kernel phenotype. Understanding the molecular basis for this previously uncharacterized starch structure will accelerate the development of QPM.

Amylopectin↗
PubMed2002

Intermediary glucan structures formed during starch granule biosynthesis are enriched in short side chains, a dynamic pulse labeling approach.

The formation of intermediary glucans, mature starch, and phytoglycogen was studied using leaves of Arabidopsis thaliana wild type and dbe mutant, which lacks plastidic isoamylase (Zeeman, S. C., Umemoto, T., Lue, W. L., Au-Yeung, P., Martin, C., Smith, A. M., and Chen, J. (1998) Plant Cell 10, 1699-1711). A new approach to the study of starch biosynthesis was developed based on "very short pulse" labeling of leaf starch through photosynthetic fixation of (14)CO(2). This allowed selective analysis of the structure of starch formed within a 30-s period. This time frame is shorter than the period required for the formation of a single crystalline amylopectin lamella and consequently permits a direct analysis of intermediary structures during granule formation. Analysis of chain length distribution showed that the most recently formed outer layer of the granules has a structure different from the mature starch. The outer layer is enriched in short chains that are 6-11 glucose residues long. Side chains with 6 glucose residues are the shortest abundant chains formed, and they are formed exclusively by transfer from donor chains of 12 glucose residues or longer. The labeling pattern shows that chain transfer resulting in branching is a rapid and efficient process, and the preferential labeling of shorter chains in the intermediary granule bound glucan is suggested to be a direct consequence of efficient branching. Although similar, the short chain intermediary structure is not identical to phytoglycogen, which is an even more highly branched molecule with very few longer chains (more than 40 glucose residues). Pulse and chase labeling profiles for the dbe mutant showed that the final structure is more highly branched than the intermediary structures, which implies that branching of phytoglycogen occurs over a longer time period than branching of starch.

Arabidopsis↗
PubMed1998

Resistant starch in the Italian diet.

Resistant starch (RS) has been defined as the sum of starch and starch-degradation products that reach the human large intestine (Champ, 1994), and it is now regarded as a sub-fraction of starch with a positive impact on colonic welfare and lipid metabolism. An early estimate of the RS intake in Europe gave an average value of approximately 4 g/d (Dyssler & Hoffem, 1994a). However, since no information is available for Italy, the aim of the present study was to estimate the intake of RS in the Italian diet by direct analysis of RS in a range of typical foods representing the main sources of starch intake in the country. The selection of representative foods and of food consumption data were based on published results of the National Food Consumption Study conducted during the 1980s by the National Institute of Nutrition on 10,000 households, using weighed-food records plus inventory methodologies (Saba et al. 1990; Turrini et al. 1991). Three main groups of foods were considered: cereals (pasta, rice, bread and bread products, and pastries), potatoes, legumes. Different commercial brands for each sample were purchased, according to the known presence on the market. Samples were prepared 'as eaten' and submitted to simulated chewing, followed by total and resistant starch determination using the enzymic procedure published as a result of the EC Concerted Action EURESTA (Champ, 1992). From these results, the estimated average intake of RS in Italy was found to be 8.5 g/d, with regional differences (from 7.2 g/d in the north-west to 9.2 g/d in the south) mainly due to the different consumption of some typical Italian starchy food (bread, pasta, legumes).

Bread↗
PubMed1989

Utilization of alpha-amylase (EC 3.2.1.1) resistant maize and pea (Pisum sativum) starch in the rat.

1. The extent of utilization of alpha-amylase (EC 3.2.1.1)-resistant retrograded starches in vivo was assessed in male Wistar rats (about 100 g body-weight). All animals were given a fibre-free semi-synthetic basal diet (SS) containing sucrose as the only carbohydrate source, ad lib., for 13 d. On day 14, after an overnight fast, rats were allocated to one of five dietary treatments (n 30):1, fibre-free basal SS diet; 2-5, basal SS diet supplemented with 100 g sucrose, Solka floc (cellulose), resistant maize starch (RCS) or resistant pea (Pisum sativum) starch (RPS)/kg diet. Animals allocated to each dietary treatment were divided into three groups of ten rats which were given the appropriate diet for 8 or 9, 17 or 18 and 29 or 30 d (8/9, 17/18 or 29/30 d groups respectively). Rats were fed on 12 g diet/d (treatment 1) or 13.2 g diet/d (treatments 2-5) for the first 20 d, and 14 or 15.4 g/d respectively until the end of the experiment. Rats fed on the supplemented basal diets were thus given 10% more food to allow for the addition of the test carbohydrate. Faecal carbohydrate excretion was determined at intervals in the 17/18 d groups. At the end of each experimental period animals were killed after consuming their daily food ration and small intestinal length, weight of caecal and ileal contents and tissue, and pH of caecal contents measured. The amount of carbohydrate in the caecal and ileal contents from the 8/9 and 17/18 d groups was determined. 2. Weights of ileal and caecal contents, caecal tissue and faecal output were significantly greater at all time points for rats fed on the resistant starches compared with those fed on basal and sucrose-supplemented diets. Values were higher for RPS-fed rats than for RCS-fed rats. 3. The quantity of carbohydrate recovered from ileal and caecal contents showed that both RCS and RPS were partially digested and absorbed as carbohydrate, but that RPS was digested to a lesser extent. 4. The concentration of carbohydrate decreased between the ileal and caecal sites when RPS and RCS were given but was essentially unchanged when cellulose was given. This is consistent with rapid fermentation of a fraction of these starches. 5. Faecal carbohydrate elimination in the 17/18 d groups fed on RCS and RPS declined with time, which suggested an adaptive response resulting in increased utilization of the starches. This adaptive response was slower in the RPS-fed rats than the RCS-fed rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Energy balance and energy values of alpha-amylase (EC 3.2.1.1)-resistant maize and pea (Pisum sativum) starches in the rat.

Apparent and partial digestible energy values for alpha-amylase (EC 3.2.1.1)-resistant, retrograde starches, isolated from cooked maize and pea starches (RMS and RPS respectively), were determined in male Wistar rats (about 180 g) during a 28-29 d balance period with ten animals per treatment. The starches were provided as supplements (100 g/kg diet) to a semi-synthetic basal diet (B), and their effects on the apparent digestibilities of nitrogen and fat, and on gains of live weight, fat and lean tissue were examined. Diet B alone was the control; sucrose (Su) and Solka-floc cellulose (SFC) were also examined for reference. Apparent digestibilities for Su, SFC, RMS and RPS were 1.0, 0.16, 0.98 and 0.89 respectively. Whereas the apparent digestibilities of gross energy, N and fat in the diet were unaffected by supplementation with Su, each was decreased by supplementation with SFC, RMS and RPS. Partial digestible energy values calculated from the intakes and faecal losses of energy in the basal and supplemented diets were 15, 12.4 and 0.8 kJ/g for RMS, RPS and SFC respectively. These values were smaller than corresponding apparent digestible energy values calculated from the apparent digestibility of the supplement and its gross energy value. Only the Su and starch supplements increased the intake of apparent digestible energy and the gain of live weight. Both starches and Su increased total energy (and fat) deposition to almost similar extents. It is concluded that the resistant starches contribute significant dietary energy, enhance growth and elevate fat deposition to extents almost similar to Su.

Animal Feed↗
PubMed1999

Wheat starch-containing gluten-free flour products in the treatment of coeliac disease and dermatitis herpetiformis. A long-term follow-up study.

BACKGROUND: We investigated whether wheat starch-based gluten-free products are safe in the treatment of gluten intolerance. METHODS: The study involved 41 children and adults with coeliac disease and 11 adults with dermatitis herpetiformis adhering to a gluten-free diet for 8 years on average. Thirty-five newly diagnosed coeliac patients at diagnosis and 6 to 24 months after the start of a gluten-free diet and 27 non-coeliac patients with dyspepsia were investigated for comparison. Daily dietary gluten and wheat starch intake were calculated. Small-bowel mucosal villous architecture, CD3+, alphabeta+, and gammadelta+ intraepithelial lymphocytes, mucosal HLA-DR expression, and serum endomysial, reticulin, and gliadin antibodies were investigated. RESULTS: Forty of 52 long-term-treated patients adhered to a strict wheat starch-based diet and 6 to a strict naturally gluten-free diet; 6 patients had dietary lapses. In the 46 patients on a strict diet the villous architecture, enterocyte height, and density of alphabeta+ intraepithelial lymphocytes were similar to those in non-coeliac subjects and better than in short-term-treated coeliac patients. The density of gammadelta(+)cells was higher, but they seemed to decrease over time with the gluten-free diet. Wheat starch-based gluten-free flour products did not cause aberrant upregulation of mucosal HLA-DR. The mucosal integrity was not dependent on the daily intake of wheat starch in all patients on a strict diet, whereas two of the six patients with dietary lapses had villous atrophy and positive serology. CONCLUSION: Wheat starch-based gluten-free flour products were not harmful in the treatment of coeliac disease and dermatitis herpetiformis.

Adolescent↗
PubMedDate not supplied

The stability of ascorbic acid microencapsulated in granules of rice starch and in gum arabic.

Ascorbic acid (AA) was microencapsulated by spray drying, using gum arabic and rice starch as covering materials. The AA was dissolved in solutions of the wall material prior to processing. For the rice starch, gelatin was used as a binding agent and recovery was effected with calcium pectate. The morphology of the materials was analysed by optical and scanning electron microscopy, it thus being possible to verify the formation and evaluate the structural characteristics of the microcapsules. The capsules produced with gum arabic were smaller (d50% = 8.0 microns) and with a multimode particle size distribution, whilst uncovered starch capsules containing 1-2% gelatin presented a distribution mainly in the range of 5-40 microns. The capsules recovered with calcium pectate had average diameters 10-15 times greater than those obtained only by spray drying. The stability of the encapsulated materials was studied at room temperature (RH 60-65%) and at 45 degrees C (RH 60-65% and 90.7%). AA microencapsulated in gum arabic was shown to be as stable as free crystalline AA under environmental conditions, whereas that encapsulated in rice starch was less stable. Increasing the amount of the binding agent gelatin increased the stability of the uncovered starch encapsulated AA. Recovery with calcium pectate notably increased the stability of the starch encapsulated AA, as compared to the uncovered samples.

Ascorbic Acid↗
PubMed1998

Physiological effects of resistant starches on fecal bulk, short chain fatty acids, blood lipids and glycemic index.

OBJECTIVE: To assess the effects on fecal bulking, fecal short chain fatty acid (SCFA) production, blood lipids and glycemic indices of two different forms of resistant starch (RS2 and RS3) from a high-amylose cornstarch. METHODS: Twenty-four healthy subjects (12 men; 12 women) consumed four supplements taken for 2 weeks in random order separated by 2-week washout periods. The supplements were a low-fiber (control) and supplements providing an additional 30 g dietary fiber as wheat bran (high-fiber control) or the equivalent amount of resistant starch analyzed gravimetrically as dietary fiber from RS2 or RS3. Four-day fecal collections and 12-hour breath gas collections were obtained at the end of each period. Fasting blood was taken at the beginning and end of each period. Glycemic indices of supplements were also assessed. RESULTS: The wheat bran supplement increased fecal bulk 96+/-14 g/day compared with the low-fiber control (p<0.001) with the mean for both resistant starches also being greater (22+/-8 g/day) than the low-fiber control (p=0.013). On the resistant starch phases, the mean fecal butyrate:SCFA ratio, which has been suggested to have positive implications for colonic health, was significantly above the low-fiber control by 31+/-14% (p=0.035). Resistant starches did not alter serum lipids, urea or breath H2 or CH4. No significant differences in glycemic index were seen between the RS and control supplements. CONCLUSION: The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.

Adult↗
PubMed1993

[Effect of the starch sources barley, corn and potatoes and their ration portions on nutrient digestibility and energy utilization in ruminants. 3. Energy utilization in cattle].

With investigations on the influence of different starch origins (barley, maize and raw potatoes) and different portions of the starch origins in the rations (50, 25 and 10% of the net energy fat, cattle (NEFr) content of the rations) on the energy utilization of rations a contribution was made to the development of the energetic feed evaluation within Rostock NEF-system. The experiments were carried out with fattened oxen using the methods of total metabolism technique and duodenal passage measurement by means of reentrant fistula. The nutrition levels amounted to 1.7 and 1.1 of energy maintenance requirement. The utilization of metabolizable energy for deposition of the 9 rations-including 3 variants of starch origins barley, maize and raw potatoes with parts in the rations of 50, 25 and 10%--was measured as 65, 61 and 59%, 61, 60 and 58% as well as 59, 61 and 55%. The energy maintenance requirement amounted to 526 kJ ME/kg LM 0.75.d. The gradations of energy utilization are caused by the connection between energy concentration and utilization of rations in ruminants. With comparable parts of the rations the different starch sources had no relevant influence on the energy utilization of the rations. Despite a wide range of starch plus water soluble carbohydrates (WSC) intake between 896 and 3426 g/animal.d no correlation between the kind of digestion (fermentative or enzymatic) of starch and WSC and the energy utilization of the rations was measurable, because the part of the ruminal digestion amounted to 86.0 and 97.2%. The result presented for the energy and nitrogen metabolism measurements are in good agreement with results of former experiments with 92 rations.

Animal Feed↗
PubMed1999

Starch gelatinization under thermal stress.

The behavior under thermal stress of starch dispersed in water was studied by differential scanning calorimetry (DSC) to estimate the heat transported through the aqueous medium in gelatinization, and to characterize the range of gelatinization temperatures. In DSC scanning mode, the endotherm of 10% starch in aqueous dispersion showed the tracing of gelatinization at between 67 and 80 degrees C, having an onset at approximately 69 degrees C. In the isothermal mode, characteristically distinct isothermal heat flow profiles were revealed. It was hypothesized that the thermal influx proposed as being analogous to the diffusion process may affect the profiles. The profiles were transformed and nonlinearly fitted according to the square root of time model to characterize a so-called t-parameter, which was related to mean square displacement of molecular distribution. The t-parameter of starch in excess of water decreased compared to that of water only. The plot of difference in these t-parameters, expressed as delta, against temperature showed a dramatically decreased delta at the temperature between 66.7 and 75.2 degrees C, which coincided with the findings from scanning mode DSC. It was further hypothesized that the decreased delta may be due to the gelatinizing process. According to the theory of polymer solution, the critical temperature (theta) at 75.2 degrees C, where the free energy became theoretically negative, i.e., the starch became spontaneously dissolved, was drawn. This theta was located within the range of gelatinizing temperatures. It was deduced that starch polymer may have dissolved during gelatinization. The dissolution from acetaminophen tablets prepared by starch paste was lower compared with that of negative controls (without paste). Moreover, the paste prepared at gelatinizing temperature (70 degrees C) seemed to inhibit acetaminophen dissolution from tablet matrices more than that prepared at subgelatinizing temperature (50 degrees C).

Algorithms↗
PubMed2003

A novel amylose corn-starch dispersion as an aqueous film coating for tablets.

A novel aqueous coating dispersion of amylose-rich corn starch (Hylon VII) was evaluated in an aqueous film-coating process of tablets using an instrumented laboratory-scale pan-coating apparatus. The influence of two independent process variables, the coating temperature and the atomizing air pressure, on the properties of the coated tablets were investigated. The preuse stability of aqueous coating dispersion (i.e., amylose corn-starch precipitate) was studied using a powder X-ray diffraction (XRD) technique. The crystallinity of amylose starch in the coating dispersion was found to increase slightly during 9 months of storage (in a refrigerator 6 +/- 2 degrees C). The film coatings of an aqueous amylose-rich starch dispersion were successfully applied onto tablets without any significant drawbacks, such as nozzle blockage or related problems. It was found that the temperature in the coating pan had a significant influence on the film surface roughness, mechanical strength, and drug release in vitro. When the lowest coating temperature (30 degrees C) was used, rougher film coatings were obtained due to overwetting. At higher temperatures (up to 50-60 degrees C), lower surface roughness and higher mechanical strength values for the coated tablets were obtained. With the present amylose starch dispersion, the atomizing air pressure had a minor influence on the quality of the coating. Under appropriate coating conditions, a smooth tablet film coating was produced with this new, natural, and inexpensive amylose starch dispersion.

Amylose↗
PubMed1983

Factors affecting starch digestibility and the glycemic response with special reference to legumes.

Large differences exist in the degree to which different starch containing foods affect the blood glucose levels of both normal volunteers and diabetics. These differences appear to relate to the digestibility of the starch and the factors determining this, including: the interaction of starch with fiber, antinutrients (eg, phytate) and protein in the food, together with the nature of the starch itself and its physical form (eg, raw or cooked, ground or whole). In this respect legumes exemplify a class of foods, high in fiber, protein and antinutrients, with a starch which is digested slowly in vitro. They also produce relatively small blood glucose rises after consumption by both normals and diabetics and in the longterm result in improved diabetic control. Identification of more such foods and further understanding of factors determining starch digestibility will allow greater therapeutic use of diet in the management of diabetics and disorders of carbohydrate metabolism.

Animals↗
PubMed1988

Starch absorption by healthy man evaluated by lactulose hydrogen breath test.

The amounts of hydrogen produced from starch and lactulose were compared to assess the accuracy of the hydrogen breath test with lactulose as standard to quantify starch malabsorption. The mean amounts of hydrogen produced from starch and lactulose were not different in fecal homogenates and in breath excretion after carbohydrate infusions into the cecum. Known amounts of starch infused into the cecum of 18 subjects were compared with amounts calculated from the total excess excretion of hydrogen in breath computed in relation to hydrogen production after the ingestion of 10 g lactulose; calculated amounts were 3.6 +/- 1.0, 9.9 +/- 1.3, and 22.0 +/- 3.4 g for the infusion of 5, 10, and 25 g of starch, respectively. The lactulose hydrogen breath test based on total excess hydrogen volume provides a valid measurement of the mean amount of starch metabolized in the colon in a group of subjects. However, large individual variations preclude its use in a given subject.

Absorption↗
PubMed1989

Insulin and glycemic responses in healthy humans to native starches processed in different ways: correlation with in vitro alpha-amylase hydrolysis.

The aim of the study was to elucidate how extracted starches submitted to food processing (or not) can influence plasma insulin and glucose responses in healthy subjects. Native starches from wheat, manihot, smooth peas, or mung beans were tested either raw, as starch gels (boiled and cooled), or cooked and cooled after a preliminary industrial processing: extrusion cooking for wheat, tapioca for manihot, and noodles for mung beans. Eighteen healthy subjects randomly assigned received three different starches under one form of conditioning. All products were submitted to in vitro alpha-amylolysis. Raw manihot starch produced the lowest (p less than 0.05) metabolic responses. Cooking significantly (p less than 0.01) increased plasma responses. However, cooked mung bean noodles gave metabolic responses similar to those of raw products. Close correlations were found between percentages of in vitro starch hydrolysis at 30 min and mean areas under the glycemic curves and the insulinemic curves (r = 0.95, p less than 0.001).

Adult↗
PubMed1995

Food processing and maize variety affects amounts of starch escaping digestion in the small intestine.

Two meals which differed greatly in resistant starch (RS) concentration, but otherwise had similar macronutrient composition (including nonstarch polysaccharides), were fed for breakfast to five subjects with ileostomies. The high-RS meal included bread made from high-amylose maize, uncooked green banana flour, and coarsely ground uncooked wheat. The low-RS meal contained bread made from low-amylose maize, cooked green banana flour, and cooked wheat. The effluent produced over 14 h was analyzed for the total amount of starch escaping digestion. In the low-RS meal 51.8 +/- 6.2 g (mean +/- SD) starch was consumed and 2.4 +/- 0.6 g recovered in the effluent, while for the high-RS meal a total of 52.7 +/- 8.8 g starch was fed and 19.9 +/- 5.2 g recovered in the effluent. The ileostomy results provided additional validation of an in vitro resistant starch assay. Scanning electron micrographs of effluent from one subject who consumed the high-amylose bread revealed that many intact starch granules escaped digestion in the small intestine.

Adult↗