Biomedical subjects

R L Lyster

Publications and source records attributed to R L Lyster.

13 recordsLinked to original sources

PubMed1992

Effect of calcium on the stability of mares' milk lysozyme.

The three aspartic acid residues that form part of the Ca-binding site of mares' milk lysozyme have apparent pK values of 4.9, 4.3 and 4.1. The fluorescence of tryptophan has been used to compare the denaturation of mares' milk lysozyme by guanidinium chloride at various concentrations of Ca with that of hens' egg-white lysozyme (EC 3.2.1.17) and alpha-lactalbumin. Fluorescence revealed an intermediate stage in the denaturation of mares' milk lysozyme. The Ca-free form of mares' milk lysozyme is slightly more stable than that of alpha-lactalbumin, but its interaction with Ca is similar to that of alpha-lactalbumin, since only the native state binds Ca. Three-state models of denaturation can usefully be displayed on a ternary diagram.

Animals↗

PubMed1991

31P nuclear magnetic resonance spectra of milk from various species.

The 31P nuclear magnetic resonance spectra of milk from goats, sheep, a rabbit, a baboon and a human were examined and compared with the spectrum of cows' milk. Most of the peaks observed could be assigned to phosphorus compounds already known to be present in such milks. However, rabbit milk was found to contain unexpectedly large amounts of phosphate esters, and to have only low levels of alkaline phosphatase (EC 3.1.3.1) activity. In addition, an unknown compound was detected in baboon milk and in some samples of sheep and goat colostrum. This compound was not identified, but may be a mixed anhydride such as 1,3 diphosphoglyceric acid. The results show that changes during lactation may be followed by 31P nuclear magnetic resonance and that the technique may be of value in authentification of samples.

Animals↗

PubMed1988

The disaggregation of calcium-depleted casein micelles.

The effect of depletion of Ca2+ on the composition and size distribution of casein micelles in milk has been examined using chemical analysis, size exclusion chromatography, fast protein liquid chromatography, turbidimetry and photon correlation spectroscopy. Partial removal of Ca2+ by EDTA and subsequent dialysis resulted in disaggregation of some of the casein micelles; as the EDTA concentration increased, the proportions of Ca2+ and phosphate relative to protein in the micelles remaining intact decreased. However, the composition of the intact micelles, with respect to the different caseins, and the number-frequency size distribution were essentially unchanged.

Animals↗

PubMed1985

The 31P nuclear magnetic resonance spectrum of cows' milk.

The 31P nuclear magnetic resonance spectrum of liquid milk was examined. Of the three peaks observed, the two larger were assigned to inorganic phosphate (Pi) and the seryl phosphate (SerP) residues of casein; the third peak was assigned to a phosphodiester, which is probably glycerophosphoryl choline. The pH-dependences of the chemical shifts of the Pi and SerP were measured with and without added EDTA, and the results confirm the assignments. The width of the Pi peak in milk is significantly greater than in similar solutions lacking casein, probably because of binding to, or chemical exchange with, the casein micelle. Most of the SerP residues in milk are not sufficiently mobile to have been detected in these experiments but a significant fraction of SerP residues is able to move freely and can be titrated.

Animals↗

PubMed1984

Nature of micellar calcium phosphate in cows' milk as studied by high-resolution electron microscopy.

The nature of the inorganic calcium phosphate in the casein micelle of cows' milk has been studied by high-resolution electron microscopy. No periodic lattice spacings could be imaged, and diffraction patterns were of the diffuse amorphous type. Short-range order of less than 15 A may be present, but the results indicate that there is no long-range order in micellar calcium phosphate.

Animals↗

PubMed1980

A human milk formula.

In view of the possible deficits in the energy value and protein content of human milk when used for feeding low birth weight preterm neonates, a method has been devised suitable for use in a human milk bank for making milk formulae from human milk products. Human milk formula (HMF) is produced by adding, to whole human milk, human cream, obtained by separation by centrifugation, together with salt-free and lactose-free human milk protein, extracted by simple dialysis and freeze-drying. This human milk formula is, therefore, enriched in energy, human milk fat, protein and salts (which may be added), to approach the current concept of an ideal milk formula(e) for preterm infants. In addition, the increased concentration of antimicrobial proteins achieved in HMF may offset any losses in these proteins caused by pasteurisation.

Dietary Fats↗

PubMed1979

The equilibria of calcium and phosphate ions with the micellar calcium phosphate in cow's milk.

Calorimetric measurements of the heat of solution of micellar Ca phosphate suggest that this material more closely resembles OH-apatite than amorphous Ca phosphate or any other crystalline form. Preliminary computer calculations of the ionic equilibria of milk salt solutions indicate that, over a wide range of pH and temperature, such solutions are supersaturated with respect to OH-apatite and to various other Ca salts under certain conditions.

Animals↗

PubMed1978

Creamatocrit: simple clinical technique for estimating fat concentration and energy value of human milk.

A simple micromethod has been devised for estimating the fat and energy content of human milk based on the centrifugation of milk in a haematocrit centrifuge. The percentage of cream, or "creamatocrit," is read from the haematocrit capillary tube and is linearly related to the fat and energy content. The technique, which is rapid and cheap, may be used in clinical practice, in research, and in epidemiological studies.

Centrifugation↗

PubMed1976