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Biomedical subjects

E R Morris

Publications and source records attributed to E R Morris.

At least 55 records · Page 3Linked to original sources
PubMed1982

Fragmentation and modification of iota-carrageenan and characterisation of the polysaccharide order-disorder transition in solution.

A procedure is described in detail by which the algal polysaccharide, iota-carrageenan, can be modified and fragmented to products of more regular structure and shorter chain length. Since most chains of this product can form uninterrupted helices they undergo the disorder-order transition without the gelation that is a feature of the behaviour of the natural polymer. The disorder-order transition becomes much sharper and occurs at higher temperatures with increasing chain length. The sign and magnitude of the accompanying shift in optical rotation can be estimated satisfactorily from the solid-state geometry of the helix using our semi-empirical method for correlating optical rotation with the conformations at glycosidic linkages. In solutions of the helical form, but not the coil form, cationic dyes such as methylene blue or acridine orange show induced optical activity and a changed visible spectrum which we attribute to binding and stacking on the helix. This also causes a shift in the temperature of the helix-coil transition. We discuss the possibility that the tendency of dyes to stack could drive polysaccharides into conformations that they would not otherwise adopt, with implications for their use as 'conformational probes'.

Carrageenan↗
PubMed1982

Phytate:zinc molar ratio, mineral, and fiber content of three hospital diets.

Phytate:zinc molar ratio, minerals, and fiber contents of regular, ovo-lacto vegetarian, and soy meat-substitute hospital diets were determined. The phytate:zinc molar ratio, minerals, and fiber contents of the soy meat-substitute diet were significantly higher than those of ovo-lacto vegetarian and regular hospital diets is within acceptable limits established by human and animal studies conducted by the USDA's Vitamin and Mineral Nutrition Laboratory.

Diet↗
PubMed1981

The inhibitory effect of bran on iron absorption in man.

The effects of whole wheat bran and its components on the absorption of nonheme dietary iron were measured using a double isotope technique in human volunteers. When 12 g bran was added to a light meal, absorption decreased by 51 to 74%; this inhibitory effect of bran was shown for meals of both high and low iron availability. Inhibition was not explained by monoferric phytate, the major form of iron in bran, because labeled iron from monoferric phytate was absorbed at least as well as the common pool of nonheme dietary iron. Furthermore, removal of phytate from bran by endogenous phytase did not in itself alter the inhibitory effect of the bran on iron absorption. Studies in which dephytinized bran was separated into a soluble, phosphate-rich fraction and an insoluble, high-fiber fraction indicated that the soluble fraction was more inhibitory than the insoluble fraction.

Adult↗
PubMed1980

Bioavailability to rats of iron and zinc in wheat bran: response to low-phytate bran and effect of the phytate/zinc molar ratio.

Low-phytate wheat bran was produced by enzymatic hydrolysis and extraction. Rat bioassay methods were utilized to determine bioavailability of iron and zinc in the low-phytate brans and to study the effect of dietary phytate/zinc molar ratio on zinc bioavailability when the phytate source was bran. Endogenous phytase activity hydrolyzed 80-100% of the phytate when wheat bran was incubated in water overnight. The relative biological values of the iron in raw bran and phytate-free bran were 98 and 113, respectively, compared to 100 for ferrous ammonium sulfate in a hemoglobin repletion assay. Low-phytate brans with phytate/zinc molar ratios of 8 or less were equivalent to zinc sulfate as dietary sources of zinc for growth of rats. Rats fed diets that contained wheat bran with zinc sulfate added to reduce the dietary phytate/zinc molar ratio from 40 or 50 to 20 grew at the same rate as rats fed a phytate-free diet, but femur zinc values were lower than those in the reference group. Gel filtration chromatography of extracts of raw and low-phytate brans suggested that zinc might be associated with phytate in wheat bran.

Animals↗
PubMed1980

Effect of dietary phytate/zinc molar ratio on growth and bone zinc response of rats fed semipurified diets.

In rats fed semipurified diets, bioavailability of dietary zinc was tested at different phytate/zinc molar ratios; growth and zinc in femurs were the criteria of adequacy. On diets with 10--12 ppm zinc, the growth of rats was not affected by phytate/zinc molar ratios of 12 or less if the level of dietary calcium was 0.75% but was depressed at ratios greater than 6 if the level of calcium was 1.75%. Phytate/zinc molar ratios greater than these did not depress growth if the dietary zinc concentration was at least 2.5 and 5 times the minimal requirement for growth at dietary calcium levels of 0.75 and 1.75%, respectively. At the maximum phytate/zinc molar ratio that did not depress growth, accumulation of zinc in femurs was depressed. Small increases in dietary calcium (from 0.75 to 0.87%) depressed growth of rats fed diets with 12 ppm zinc and a phytate/zinc molar ratio of 25. Preformed Zn3 and Zn6 phytate preparations were equivalent to ZnSO4.7H2O as dietary zinc sources. The data indicated that high dietary calcium per se reduced zinc bioavailability. The maximum phytate/zinc molar ratio that did not depress growth of young rats was greatly influenced by dietary calcium level and somewhat influenced by total dietary zinc concentration.

Animals↗
PubMed1979

Absorption of monoferric phytate by dogs.

Recent studies have shown that the iron in wheat is predominantly in the form of monoferric phytate (MFP). Unlike phytate complexed with two or more iron atoms, MFP is soluble at pH 7.0 and above and may therefore be a relatively available form of dietary iron. To examine this point, we tested iron absorption in adult dogs using a double radioisotope method and total body counting. When given without food, MFP was about one-half as available as ferrous sulphate at an iron-equivalent dose of 1.5 mg and only about one-seventh as available at a dose of 15 mg iron. When administered with food, MFP underwent complete isotopic exchange with the nonheme pool of dietary iron. When added to meals of either high or low iron availability in amounts that might be used for iron fortification, the absorption was the same for MFP iron as for the major pool of dietary inorganic iron.

Animals↗
PubMed1978

Blood glycoprotein from antarctic fish. Possible conformational origin of antifreeze activity.

High resolution 1H NMR and circular dichroism (CD) measurements have been performed on aqueous solutions of antarctic fish antifreeze glycoprotein. The carbohydrate contribution ot the observed CD spectrum has been estimated from closely analogous model compounds. The residual peptide contribution cannot be interpreted of the known spectral behaviour of alpha-helix, beta-sheet and random coil. Instead it resembles the CD spectrum of beta-structure in position, magnitude and spectral form, but is of opposite sign, indicating a specific but unusual peptide conformation, which we suggest may be stabilised by non-bonded interactions between the peptide backbone and the carbohydrate sidechains. Previous evidence which supports this interpretation is reviewed. NMR and CD measurements between -2 and +30 degrees C are consistent with conformational stability throughout the biologically relevant temperature range. The mechanism of the antifreeze activity is discussed in terms of the spatial and orientational correlations of sugar hydroxy groups and water in the liquid and solid states. The implication of an ordered peptide structure is explained by the comparison of the antifreeze glycoprotein with synthetic water-soluble polymers which also exhibit limited antifreeze properties.

Animals↗
PubMed1978

Fiber in the gastrointestinal tract.

It has long been recognized that fruit, vegetables, and cereal fiber alter bowel function. The right colon can be regarded as a fermenter and an absorbing organ, and the left colon is for continence. A rationale for the use of fiber based on physical chemical properties is discussed. On this basis, the use of coarse wheat bran, apples, oranges, and carrots is recommended to treat diverticular disease, spastic colon, and constipation.

Cellulose↗