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C Ansell

Publications and source records attributed to C Ansell.

7 recordsLinked to original sources
PubMed2004

Cements from nanocrystalline hydroxyapatite.

Calcium phosphate cements are used as bone substitute materials because they may be moulded to fill a void or defect in bone and are osteoconductive. Although apatite cements are stronger than brushite cements, they are potentially less resorbable in vivo. Brushite cements are three-component systems whereby phosphate ions and water react with a soluble calcium phosphate to form brushite (CaHPO4 x 2H2O). Previously reported brushite cement formulations set following the mixture of a calcium phosphate, such as beta-tricalcium phosphate (beta-TCP), with an acidic component such as H3PO4 or monocalcium phosphate monohydrate (MCPM). Due to its low solubility, hydroxyapatite (HA) is yet to be reported as a reactive component in calcium phosphate cement systems. Here we report a new cement system setting to form a matrix consisting predominantly of brushite following the mixture of phosphoric acid with nanocrystalline HA. As a result of the relative ease with which ionic substitutions may be made in apatite this route may offer a novel way to control cement composition or setting characteristics. Since kinetic solubility is dependent on particle size and precipitation temperature is known to affect precipitated HA crystal size, the phase composition and mechanical properties of cements made from HA precipitated at temperatures between 4 and 60 degrees C were investigated.

Bone Cements↗
PubMed1977

Metabolic acidosis and infant feeding.

Most cows' milk based formulae for infant feeding present a greater acid load to the infant than breast milk. To determine the effect of this difference the acid base state of 180 healthy term infants was measured on the sixth day of life and related to the type of feed. Those infants fed on cows' milk formula (SMA) had a mean pH of 7-34 +/- 0-05 and a base deficit of 8-8 +/- 3-1, while those fed on breast milk had a mean pH of 7-38 +/- 0-05 and a base deficit of 5-6 +/- 3-1. The difference between the two groups of infants was significant for both these measurements. Metabolic acidosis was defined as a base deficit greater than 10 mmol/l. Seventy-four per cent of the 34 infants who were acidotic at six days were bottle-fed. There was a significant correlation between the pH of the feed and the degree of acidosis in the infant as measured by the base deficit. The findings suggest that when breast milk is not available a pH-adjusted milk formula would be desirable for preventing and treating neonatal metabolic acidosis.

Acid-Base Equilibrium↗
PubMed1977

Electrolyte pH changes in Human Milk.

Milk samples from 100 lactating mothers in the 10 days following delivery have been analyzed for pH, sodium, and potassium. The sodium concentration was high in the first 5 days, mean 21 +/- 5 mmol/liter, but fell to a mean 15 mmol/liter by the end of the first week and 12 mmol/liter by the 10th day. A similar downward trend was shown for potassium with an initial mean concentration of 18.5 mmol/liter falling to 15 mmol/liter by the 10th day. The pH fluctuated widely from day to day through a range of 6.75-7.42 with a mean pH 7.09. Considerable variations were shown in individuals from day to day, and from the beginning to the end of feeds (Table 1). The relatively high sodium concentration in the first few days may be an important defense mechanism against dehydration and hyponatremia during a period of relative thirst and starvation. The variation in the pH and electrolyte content of human milk may be expected to have some influence on the acid-base and electrolyte status of the infant.

Female↗
PubMed1975

Milk for babies.

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Animals↗