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PubMed2001

Ripening-related changes in raspberry cell wall composition and structure.

Cell walls were prepared from the fruit of two cultivars of raspberry at three stages of ripening; green, white and red (ripe). The cultivars. Glen Clova and Glen Prosen, are subjectively classified, at harvest by growers, as soft and firm fruit, respectively. The cell walls were analysed for neutral sugar composition, uronic acid content, degree of methyl esterification, lignin and ferulic acid-derived dehydrodimers. Solid-state 31C NMR and diffuse reflectance infrared (DRIFT) spectra were acquired for the cell wall residues. For both cultivars the progression from green to white produced minimal changes, save for a reduction in pectin. NMR analyses indicated that the solubilized pectin was acetylated. Progression to the red (ripe) stage, in both cultivars, was accompanied by a reduction in the ordered cellulose and a dramatic reduction in pectin content and the degree of methyl-esterification. Significantly, the softer fruit (Glen Clova) exhibited greater reductions in both parameters, implicating increased pectin hydrolysis, as one of the main factors contributing to the difference in firmness between the cultivars. A relative increase in cell wall-associated protein was seen at the red stage. The nature and function of the protein(s) are, as yet unknown.

Cell Wall↗
PubMed1997

The effect of intestinal bacteria adherence on drug diffusion through solid films under stationary conditions.

PURPOSE: To study the in vitro and in vivo the role of surface bacterial adhesion on the diffusion of model drugs at stationary conditions. METHODS: Salicylic acid (SA) diffusion through ethyl cellulose (EC) films was measured in vitro in side-by-side diffusion cells with and without E. coli of intestinal origin. Insulin (I) release from paper strips coated or uncoated with pectin films, with or without antibiotic treatment, was measured in vivo in conscious rats after cecal implantation by comparing blood glucose levels at Tmax of the pharmacodynamic effect. RESULTS: During five hours of diffusion studies which were performed immediately following incubation of EC films with bacteria, the diffusion rate of SA throughout the films was 2.72-fold lower in the presence of bacteria compared with the diffusion rate in the control studies conducted without bacteria. The mean blood glucose levels dropped in the rat to 40.6 +/- 21.6% of glucose basal levels within 2.4 +/- 1.4 h when uncoated I solid carriers were used. Glucose levels did not change for pectin-coated dosage forms. After antibiotic treatment which prevented the formation of bacterial biofilm on the surface of the I solid dosage forms, blood glucose levels dropped to 22.0 +/- 4.7% and 50.9 +/- 20.5% of glucose basal levels within 7.4 +/- 2.6 h and 1.8 +/- 0.9 h for pectin uncoated or coated dosage forms, respectively. Maximum bacterial adherence occurred at stationary conditions (RPM = 0), while at maximum agitation (200 RPM), almost no adherence occurred. CONCLUSIONS: (a) Bacterial adherence shows down the diffusion rate of SA through EC films; (b) Under stationary conditions bacterial adherence may also interfere with drug release from biodegradable (pectin) films; (c) Successful functioning of biodegradable colon-specific delivery systems depends on agitation and surface friction in the lumen of the colon.

Animals↗
PubMed1995

Taurocholic acid adsorption during non-starch polysaccharide fermentation: an in vitro study.

The association of radiolabelled taurocholic acid with the solid fraction of a faecal fermentation mixture was measured. A human faecal inoculum was incubated with [24-14C]taurocholic acid and several non-starch polysaccharide sources (pectin, wheat bran, ispaghula (Plantago ovata) husk and seed), glucose or a substrate-free control. Portions of fermentation mixture were taken at 0, 3, 6, 21 and 24 h and centrifuged to acquire a supernatant fraction and a pellet containing the fermentation residue. 14C was measured in supernatant fractions and pellets at all time points. Volatile fatty acids (VFA) were measured at 0 and 24 h to confirm bacterial growth. Radioactivity in the pellet increased over time for all substrates. Glucose resulted in the greatest incorporation of taurocholic acid into the pellet, followed by pectin. At 24 h the proportion of the total radioactivity found in the pellet was 92% for glucose, 79% for pectin, 60% for wheat bran, 59% for ispaghula seed, 53% for ispaghula husk and 26% for the control (mean of duplicates). Glucose and pectin produced the greatest quantity of VFA at 24 h. VFA production was highly correlated with radioactivity in the pellet (r0.976, P < 0.005). These results suggest that the bile acid binding capacity of a faecal culture mixture may be strongly influenced by the fermentability of the available substrate and hence related to bacterial metabolic activity.

Adsorption↗
PubMed2000

Dietary carbohydrates affect caecal fermentation and modify nitrogen excretion patterns in rats. I. Studies with protein-free diets.

In a two-factorial experiment on 96 young male rats, the effects of substituting 10% raw potato starch (PS), pectins (PEC), or cellulose (CEL) for corn starch (CS) were studied using an unsupplemented protein-free (PF) diet or a PF diet supplemented either with DL-methionine or urea. The pH and the short chain fatty acids (SCFA) content in caecal digesta, as well as caecal digesta and tissue weights were determined and used as the criteria of caecal fermentation intensity. Blood urea level, amount of N excreted via faeces and urine, DAPA content, and amino acid composition of faecal protein were analyzed as indices of protein metabolism. A 10-day adaptation period to the carbohydrates fed with the casein diet preceded the experimental period of feeding the respective carbohydrates with protein-free diets. Dietary carbohydrates significantly influenced total and individual SCFA content in caecal digesta, as well as other parameters related to the intensity of fermentation. Potato starch and pectins were more intensively fermented than cellulose. Supplementation of the PF diet with methionine and urea affected only caecal isobutyric and valeric acid content in a way dependent on the carbohydrates present in the diet. Carbohydrates significantly altered the routes of N excretion. Faecal excretion was increased by all carbohydrates studied compared to corn starch, pectins had the most marked effect. Urinary excretion was significantly increased by cellulose (as compared with the PEC and PS groups) and decreased by pectins as compared with all other groups. There was an interaction between the effects of carbohydrates and type of protein-free diet on faecal and urinary excretion. The sum of amino acids in faecal protein was the lowest on the PEC diet, but the amino acid composition expressed as a per cent of total amino acid content was similar in all groups. It can be concluded that dietary carbohydrates alter the excretion patterns of endogenous nitrogen in rats in different ways and that this effect is related to the intensity of their fermentation in the hind gut.

Animals↗
PubMed1987

Fiber supplementation results in expanded proliferative zones in rat gastric mucosa.

The effects of three different fibers on gastric fundic mucosal morphometrics and cytokinetics were compared by feeding defined diets to 40 male Sprague-Dawley rats for 4 wk. Groups of 10 rats each were fed a fiber-free diet as a control or the same diet uniformly diluted with either 20% oat bran, 10% pectin, or 10% guar. Fiber supplementation expanded the zone of proliferating cells by 58% with the guar-supplemented diet (p less than 0.05), 101% with oat bran (p less than 0.05), and 150% with pectin (p less than 0.01) compared with controls. Expansion was due to a downward shift in proliferating cells towards the muscularis mucosa of the oat bran and pectin groups (p less than 0.01) while pectin also expanded the proliferative zone toward the mucosal surface (p less than 0.05). Because expanded proliferative zones have been shown to precede and accompany neoplastic transformation, these data suggest a potentially negative effect of dietary fiber on the gastric mucosa.

Animals↗
PubMed1981

Effects of tomato pomace and mixed-vegetable pomace on serum and liver cholesterol in rats.

The effects of tomato pomace and mixed-vegetable pomace, vegetable processing by-products, on serum and liver cholesterol were compared against pectin, wheat bran, cellulose, and lignin. Male Sprague-Dawley rats (100 g) were fed high sucrose, semi-purified diets containing basal (0), 5% or 10% of the fiber source and either 0, 0.5% cholesterol or 0.5% cholesterol + 0.125% sodium cholate. After 28 days, there were highly significant differences (P less than 0.001) in serum and liver cholesterols due to fiber source, dietary cholesterol and the interaction. The effect of fiber source level was significant (P less than 0.05) for liver cholesterol only. Pectin groups had serum and liver cholesterol levels lower (P less than 0.05) than the others. At the 10% level, tomato pomace, wheat bran and lignin (Indulin AT) groups had serum cholesterols higher (P less than 0.05) than basal; the mixed-vegetable pomace and cellulose groups were not different from basal. Liver cholesterols of tomato pomace, mixed-vegetable pomace, wheat bran and lignin groups were not different at the 10% level, but were higher than the pectin, cellulose and basal groups (P less than 0.05). In a second experiment, serum cholesterols of rats fed pectin were lower (P less than 0.05) than for those fed cellulose or two types of lignin (Indulin AT, Reax 27).

Animals↗
PubMed1989

Independent effects of fiber and protein on colonic luminal ammonia concentration.

The potential interactive effects of protein and fiber on cecal and colonic surface areas, colonic luminal ammonia concentrations, luminal pH and blood indices of nitrogen metabolism were tested using two levels of protein (8% and 24%) and two types of fiber (8% pectin or cellulose). Pectin supplementation resulted in larger cecal surface areas and longer large intestines than those of rats fed fiber-free or cellulose-supplemented diets. All high protein diets resulted in total large bowel luminal ammonia (NH3 + NH4+) concentrations that were twice as high as their low protein counterparts (P less than 0.05). The effect of fiber on ammonia concentration depended on the fiber type. In the distal colon, pectin-fed animals had three times the ammonia concentration of the fiber-free animals, and 4-5 times the ammonia concentration of the cellulose-fed animals (P less than 0.001). Blood urea nitrogen values were higher in the high protein than in the low protein groups (P less than 0.05), and highest in the high protein/pectin animals (P less than 0.01). This study clearly demonstrates that luminal ammonia concentration is dependent upon both protein level and fiber type, and that a fermentable fiber (pectin), rather than decreasing colonic ammonia concentrations, actually increases them several-fold.

Ammonia↗
PubMed1992

Soluble dietary fiber and cholesterol influence in vivo hepatic and intestinal cholesterol biosynthesis in rats.

Ninety-six male Sprague-Dawley rats were randomly assigned to eight dietary treatments. Rats were fed, with ad libitum access, diets containing 10% dietary fiber as cellulose (control), pectin, psyllium or oat bran with or without 0.3% added cholesterol for 3 wk. Among cholesterol-fed rats, liver total cholesterol was significantly lower in rats fed diets supplemented with either pectin or psyllium compared with those fed cellulose. In contrast, rats fed oat bran with cholesterol had significantly higher liver cholesterol concentrations compared with cellulose-fed animals. Liver total lipid concentrations were significantly lower in groups fed pectin and psyllium with or without dietary cholesterol compared with cellulose-fed controls. Pectin feeding with or without dietary cholesterol significantly lowered plasma total cholesterol compared with cellulose feeding. Oat bran had no effect on plasma total cholesterol compared with control diets. Hepatic sterol synthesis was significantly greater for animals fed soluble dietary fibers compared with those fed cellulose, but the effect on intestinal sterol synthesis was less pronounced.

Animals↗
PubMed2000

Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of beta-carotene to vitamin A in mongolian gerbils.

Current dietary guidelines recommend a decrease in fat intake and an increase in fiber consumption. Decreased bioavailability (BV) of carotenoids is thought to be associated with both of these recommendations. A 2 x 4 factorial design was used to test the effects of dietary fat level at 10 or 30% of total energy and fiber type using no fiber, silica, citrus pectin or oat gum (7 g/100 g) on beta-carotene (betaC) BV in 4- to 5-wk-old Mongolian gerbils. We assessed BV as both accumulation of betaC and bioconversion of betaC to vitamin A (VA) in tissues. A VA- and betaC-deficient diet was fed for 1 wk followed by one of eight isocaloric, semipurified diets supplemented with carrot powder [ approximately 1 microgram betaC, 0.5 microgram alpha-carotene (alphaC)/kJ diet] for 2 wk (n = 12/group). Increasing dietary fat resulted in higher VA (P: = 0.074) and lower betaC (P: = 0.0001) stores in the liver, suggesting that consumption of high fat diets enhances conversion of betaC to VA. The effect of soluble fiber on hepatic VA storage was dependent on fiber type. Consumption of citrus pectin resulted in lower hepatic VA stores and higher hepatic betaC stores compared with all other groups, suggesting less conversion of betaC to VA. In contrast, consumption of oat gum resulted in hepatic VA and betaC stores that were higher (P = 0.012) and lower (P = 0.022), respectively, than those of citrus pectin-fed gerbils. The level of dietary fat consumed with soluble fiber had no interactive effects on hepatic VA, betaC or alphaC stores. Results demonstrate that betaC BV is independently affected by dietary fat level and type of soluble fiber, and suggest that these dietary components modulate postabsorptive conversion of betaC to VA. This study confirms the negative effects of citrus pectin on betaC BV, and suggests that oat gum does not adversely affect betaC BV.

Analysis of Variance↗
PubMed2005

Polymorphism and modulation of cell wall esterase enzyme activities in the chicory root during the growing season.

Pectins are major components of the primary plant cell wall. They can be both methylesterified and acetylesterified and de-esterification occurs by specific esterases. Proteins extracted by NaCl treatment from root cell walls of two chicory varieties (Cichorium intybus L. cv. Nausica and Arancha) sampled in an experimental field every 2 weeks between July 2002 and January 2003 were analysed by isoelectrofocalization, semi-denaturing SDS-PAGE, and quantitative assays for their esterase activity. Zymograms showed that chicory root pectin methylesterases belong to a multigene family. The isoelectric points of the pectin methylesterase isoforms ranged from pI 3.8 to pI 9.0. Concerning acetylesterases, only acidic isoforms between pI 4.1 and pI 5.2 were observed, but a large polymorphism of this class of enzymes could be identified in one variety. The results indicate that the root pectin methylesterase activity of the Nausica variety was correlated with ambient temperature, while no significant effect of temperature could be detected on any acetylesterase isoform.

Acetylesterase↗
PubMed1996

Postmortem perianal findings in children.

The postmortem finding of anal dilation or an exposed pectinate line in children who have died under suspicious circumstances continues to raise the concern of possible sexual abuse. The following multicenter, collaborative study was designed to help address that question. Sixty-five subjects, ranging in age from birth to 17 years, were autopsied at three different sites. A standard protocol along with 35-mm cameras were used to record the results. Thirty-eight (58%) subjects were boys, and 27 (42%) were girls. Forty-two (65%) were white, 10 (15%) African-American, five (8%) Asian, three (5%) white Hispanic and five (8%) other. Fifty-seven (88%) were in Tanner stage I of secondary sexual development. Thirty-four (52%) died of natural causes, 26 (40%) from accidental injuries, three (5%) from other causes, and four (6%) as a result of a homicide. Forty-eight subjects (74%) had some dilation of the anal sphincters. In 21 children (32%), the entire anal canal, including the rectal ampulla, could be visualized. In another 21 (32%) subjects, the pectinate line was exposed. Only the outer portion of the anal canal opened in six children (10%), whereas 17 (26%) had no dilatation of the anus. Anal laxity led to flattened skin folds in 50 (77%), a shallow anal canal in 40 (62%), the exposure of both the pectinate line in 38 (59%), and the anal mucosa in 24 (37%). Venous congestion was present in 14 (22%), venous pooling in three (5%), erythema in six (9%), and increased pigmentation in eight (12%). Funneling was found in two (3%). Blood was present in three (5%), and an abrasion was discovered in one (2%). No fissures, lacerations, hemorrhoids, or scars were found in any of the children. Anal orifice size varied with the age of the child, the amount of traction applied to the buttocks, and a history of a CNS injury at the time of death. It is suggested, finally, that anal dilatation alone cannot be used a marker for prior sexual abuse and the exposure of the pectinate line should not be confused with tears or fissures of the anal verge. Further studies of children known to have been sodomized prior to death are required.

Anal Canal↗
PubMed1993

Cell Wall Metabolism in Ripening Fruit (VI. Effect of the Antisense Polygalacturonase Gene on Cell Wall Changes Accompanying Ripening in Transgenic Tomatoes).

Cell walls of tomato (Lycopersicon esculentum Mill.) fruit, prepared so as to minimize residual hydrolytic activity and autolysis, exhibit increasing solubilization of pectins as ripening proceeds, and this process is not evident in fruit from transgenic plants with the antisense gene for polygalacturonase (PG). A comparison of activities of a number of possible cell wall hydrolases indicated that antisense fruit differ from control fruit specifically in their low PG activity. The composition of cell wall fractions of mature green fruit from transgenic and control (wild-type) plants were indistinguishable except for trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid (CDTA)-soluble pectins of transgenic fruit, which had elevated levels of arabinose and galactose. Neutral polysaccharides and polyuronides increased in the water-soluble fraction of wild-type fruit during ripening, and this was matched by a decline in Na2CO3-soluble pectins, equal in magnitude and timing. This, together with compositional analysis showing increasing galactose, arabinose, and rhamnose in the water-soluble fraction, mirrored by a decline of these same residues in the Na2CO3-soluble pectins, suggests that the polyuronides and neutral polysaccharides solubilized by PG come from the Na2CO3-soluble fraction of the tomato cell wall. In addition to the loss of galactose from the cell wall as a result of PG activity, both antisense and control fruit exhibit an independent decline in galactose in both the CDTA-soluble and Na2CO3-soluble fractions, which may play a role in fruit softening.

Journal Article↗
PubMed1996

Alterations in Structural Polysaccharides during Liquefaction of Tomato Locule Tissue.

The locule tissue of tomato (Lycopersicon esculentum, Mill.) undergoes extensive liquefaction during ripening. In this study, the solubility, molecular mass, and glycosyl composition of locule pectic and alkali-soluble polysaccharides were examined with the aim of identifying features contributing to the unique properties of this tissue. Ethanol-insoluble solids were prepared from de-seeded locule tissue from tomato fruit at the immature green (IMG), mature green, and breaker stages of development. Ethanol-insoluble pectins were extracted sequentially in H2O, 50 mM trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid, 50 mM Na2CO3, and 4 M KOH. At the IMG stage, nearly 85% of the locule pectins were solubilized by water, trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid, and Na2CO3 solutions. Solubility increased only slightly with further locule development. The noncovalently associated polymers were of high molecular mass throughout liquefaction. Polymers extracted in mild alkali were of considerably lower molecular mass. Locule pectins in IMG fruit were heavily glycosylated with galactose, arabinose, and xylose. All pectin classes exhibited similar deglycosylation trends during liquefaction. Locule hemicelluloses were rich in glucose, xylose, and arabinose. These polymers collectively showed molecular mass downshifts with minimal compositional changes during liquefaction. The KOH-soluble material also included xylose-rich acidic polymers not matching the neutral sugar profile of the noncovalently associated pectic polymers.

Journal Article↗
PubMed1981

pH-Dependent Interactions between Pea Cell Wall Polymers Possibly Involved in Wall Deposition and Growth.

In an effort to detect a pH-dependent release of polymers such as xyloglucans, thought to be involved in auxin-induced cell wall expansion during growth, radioactively labeled cell walls from pea stem tissue were incubated at different pH values, and changes in water-soluble, ethanol- or trichloroacetic acid-insoluble components were determined. This revealed the occurrence, at neutral pH, of a time- and pH-dependent binding of soluble pectin, in the walls, to a heat-labile, presumably protein, wall component, yielding a trichloroacetic acid-insoluble pectin-protein complex. This reaction, which can also be observed between polymers in water extracts of cell walls, is inhibited at low pH and by Ca(2+), and appears to be of a physical, possibly lectin-like, nature. Progressive binding of pectin or of the pectin-protein complex to the insoluble wall structure is also observed. These reactions may be involved in wall assembly during its deposition, and may participate in, or be analogous to pH-dependent physical interactions that participate in, wall extension during cell growth.

Journal Article↗
PubMed1988

Products Released from Enzymically Active Cell Wall Stimulate Ethylene Production and Ripening in Preclimacteric Tomato (Lycopersicon esculentum Mill.) Fruit.

Enzymically active cell wall from ripe tomato (Lycopersicon esculentum Mill.) fruit pericarp release uronic acids through the action of wall-bound polygalacturonase. The potential involvement of products of wall hydrolysis in the induction of ethylene synthesis during tomato ripening was investigated by vacuum infiltrating preclimacteric (green) fruit with solutions containing pectin fragments enzymically released from cell wall from ripe fruit. Ripening initiation was accelerated in pectin-infiltrated fruit compared to control (buffer-infiltrated) fruit as measured by initiation of climacteric CO(2) and ethylene production and appearance of red color. The response to infiltration was maximum at a concentration of 25 micrograms pectin per fruit; higher concentrations (up to 125 micrograms per fruit) had no additional effect. When products released from isolated cell wall from ripe pericarp were separated on Bio-Gel P-2 and specific size classes infiltrated into preclimacteric fruit, ripening-promotive activity was found only in the larger (degree of polymerization >8) fragments. Products released from pectin derived from preclimacteric pericarp upon treatment with polygalacturonase from ripe pericarp did not stimulate ripening when infiltrated into preclimacteric fruit.

Journal Article↗
PubMed1979

The effects of dietary fibre on glucose tolerance in healthy males.

Previous studies have shown that the addition of non-absorbable carbohydrate (NAC) to test meals decreases the glucose and and insulin response both in normal and diabetic subjects. However, these studies appear to have used brain in the basic test meal without a knowledge of the effect of bran itself or of the added NAC alone. In the present investigation bran alone, pectin alone, guar alone and pectin with guar have been studied. Guar alone added to the test meal significantly lowered blood glucose at 90 minutes. Pectin alone did not have a significant effect. Pectin and guar together resulted in a blood glucose lower at 30 minutes and greater at 120 minutes. No significant changes in insulin response were noted to our study. It appears that NAC alters the glucose response to a given meal, but the extent to which this occurred in the present study was less than in previous studies. The differences may reflect synergism between bran and other NAC's to lower blood glucose response after a meal.

Adult↗
PubMed1995

Pectinolytic enzymes of anaerobic fungi.

Pectinolytic enzymes of four rumen fungi have been described. Three fungal species were monocentric Neocallimastix spp. H15, JL3 and OC2, and one isolate was a polycentric strain of Orpinomyces joyonii, A4. They differed in degree of pectin degradation and utilization. Only the strain Neocallimastix sp. H15 and partially Orpinomyces joyonii A4 were able to utilize pectin to a higher extent. The most important pectinolytic activity in all these isolates represented pectin lyase (EC 4.2.2.10) and polygalacturonase (EC 3.2.1.15). Their specific activities were in the range of 100-900 and 10-450 micrograms galacturonic acid h-1 mg protein-1 for pectin lyase and polygalacturonase, respectively. Polygalacturonase, located mainly in the endocellular fraction, was inhibited by calcium ions and had the main pH optimum at pH 6.0. All strains produced pectate lyase (EC 4.2.2.2). None of the strains tested produced pectinesterase (EC 3.1.1.11).

Animals↗
PubMed1981

Pectic Enzyme Activities of Bacteria Associated with Rotted Onions (Allium cepa).

The aerobic bacteria associated with soft rot in onions (Allium cepa) were isolated and identified as a Vibrio sp., Micrococcus epidermidis, Pseudomonas cepacia, an Acinetobacter sp., a Xanthomonas sp., Bacillus polymyxa, and Bacillus megaterium. With the cup-plate assay method, no pectin hydrolase could be detected from any of these isolates when they were cultured in pectin medium, but lyase and pectinesterases were detectable. Onion tissue cultures showed pectin hydrolase activity for P. cepacia and B. polymyxa and lyase and pectinesterase activities for all of the isolates, usually at higher levels of activity than those of the pectin medium culture filtrates. In both culture media, Vibrio sp. showed the highest lyase and pectinesterase activities. In the viscometric test, all of the isolates achieved at least a 50% decrease in viscosity for lyase enzyme, with M. epidermidis and Vibrio sp. recording viscosity decreases as high as 83%. The ability to cause soft rot in onion bulbs was demonstrated by P. cepacia and Xanthomonas sp. Benzoic acid at a concentration of 0.8 mg/ml caused total suppression of enzyme production, whereas sodium benzoate at this concentration reduced pectinesterase production by 71% and lyase production by 72%. The possible use of these preservatives in the control of soft rot in onions is noted.

Journal Article↗