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Biomedical subjects

A Hodgkinson

Publications and source records attributed to A Hodgkinson.

At least 37 records · Page 2Linked to original sources
PubMed1982

Plasma electrolyte concentrations in women and the effects of oestrogen administration.

Age-related changes in the concentrations of the main plasma electrolytes and in the urinary excretion of some of these ions have been examined in 436 pre-menopausal and 117 post-menopausal women. The main changes up to the menopause were decreases in the mean plasma potassium, calcium and total protein concentrations, accompanied by increases in the renal excretion of calcium and inorganic phosphate. The decrease in plasma total calcium concentration was completely accounted for by the fall in albumin and globulin concentrations. The main changes observed at the menopause were increases in plasma sodium, total calcium, inorganic phosphate and magnesium concentrations, an increase in the plasma "anion gap" and increases in the renal excretion of sodium, magnesium and inorganic phosphate. All these changes were reversed by treatment with ethinyl oestradiol. The causes and significance of some of these changes are discussed, particularly the menopausal rises in plasma sodium concentration and in the plasma "anion gap".

Acid-Base Equilibrium↗
PubMed1982

A comparison of the effects of lactose and of two chemically modified waxy maize starches on mineral metabolism in the rat.

Diets containing 30% by weight of waxy maize starch, lactose monohydrate, acetylated distarch phosphate (EEC No. 1414) or acetylated distarch adipate (EEC No. 1422) were fed to weanling female Specified Pathogen-Free Sprague-Dawley rats for 1 yr and to similar 9-month-old rats for 34 wk. Behaviour and general health were unaffected by the different diets and there were no diet-related differences in food consumption. AT the end of the experiment with 9-month-old rats the mean body weight of the animals receiving lactose was significantly lower than that of the controls receiving starch. The animals receiving the modified starches were slightly but not significantly heavier than the controls at the end of both experiments. The main treatment-related changes in rats on the three test diets were (1) caecal enlargement, (2) increased urinary excretion of calcium, (3) increased renal calcification as measured by chemical analysis of renal tissue obtained at autopsy and (4) increased medullary and pelvic nephrocalcinosis as assessed histopathologically. Acetylated distarch adipate had a slightly greater effect on the above parameters than acetylated distarch phosphate but both modified starches had less effect than lactose. The calcium content of the kidneys, as measured by chemical analysis or histopathology, increased with age, even in the animals receiving the control diet. This change may be due to excessively high concentrations of calcium and phosphorus in all the diets, including the control diet. Cortico-medullary mineral deposits were not a feature in these studies possibly because the diets were not deficient in magnesium. The importance of correct dietary formulation in long-term toxicity studies is emphasized.

Animals↗
PubMed1982

Measurement of the fasting urinary hydroxyproline: creatinine ratio in normal adults and its variation with age and sex.

Conditions for the determination of the fasting urinary hydroxyproline: creatinine ratio (OHPr: Cr ratio) have been examined, using a resin-catalysed hydrolysis and automated colorimetric procedure for the determination of hydroxyproline. Feeding experiments with gelatin showed that hydroxyproline is rapidly absorbed and excreted in the urine and that a 12-hour (overnight) fast is sufficient to ensure correct and reproducible fasting OHPr: Cr ratios. The mean fasting OHPr: Cr ratio decreased slightly with increasing age in both men and premenopausal women but there was no significant difference between the sexes. There was, however, a significant increase in the mean ratio in postmenopausal women. The normal range of fasting OHPr: Cr ratios for men and premenopausal women was found to be 0.003--0.015.

Adolescent↗
PubMed1980

Solubility of calcium oxalate in human urine, simulated urine, and water.

The main factors that determine the amount of oxalate that can be held in solution in urine were found to be the ionic strength and the calcium and magnesium concentrations. Citrate seemed to be relatively unimportant at normal urine pH. Urea, pyrophosphate, chondroitin-4-sulphate, and chondroitin-6-sulphate were without effect at the concentrations normally found in urine.

Calcium↗
PubMed1979

Vitamin D and magnesium absorption in man.

1. The effects of vitamin D and its hydroxylated derivatives on calcium and magnesium absorption have been examined in 47 balance studies on patients with various disorders of calcium or bone metabolism. 2. Vitamin D significantly increased the mean net absorption of calcium and also the calcium balance. The mean net absorption of magnesium was also significantly increased although the rise was much less than that of calcium and the mean magnesium balance was unaffected. 3. It is suggested that the slight effect of vitamin D on magnesium absorption may be incidental to its stimulation of active calcium transport, since the latter system has weak affinities for other alkaline earth ions including strontium, barium and magnesium.

Absorption↗
PubMed1979

Effects of calcium deprivation and orchidectomy on bone composition in the rat.

The effects of calcium deprivation and of orchidectomy, separately and combined, on body growth and bone composition have been examined in mature male rats. Calcium deprivation had no significant effect on the rate of body growth but femoral bone weight, bone ash weight and total calcium and phosphorus contents of the femora were reduced while the water content increased. However, there were no significant changes in the ratio of bone weight to body weight, in the amounts of calcium or phosphorus per unit weight of bone, or in the ratio of calcium to phosphorus in the bone. Orchidectomy reduced the rate of body growth, the mean weight of the femora and the ratio of bone weight to body weight. There was a 60% decrease in bone water and a 30--35% reduction in the calcium and phosphorus content of the femora but the amounts of ash, calcium and phosphorus per unit weight of bone fell by only 6--10%. The combination of orchidectomy and calcium deprivation had no greater effect on body weight, bone weight or bone composition than had orchidectomy alone. It is concluded that calcium deprivation and orchidectomy both cause osteoporosis in mature rats but the effects of orchidectomy are more severe than those of calcium deprivation and there appears to be some demineralization of the bone remaining after orchidectomy.

Animals↗
PubMed1979

Composition of urinary tract calculi from some developing countries.

The composition of 142 calculi from Sudan, Thailand, Indonesia and Saudi Arabia has been determined by qualitative and quantitative chemical analysis. Calcium oxalate was the commonest constituent of both kidney and bladder stones, followed by magnesium ammonium phosphate, ammonium acid urate, calcium phosphate, uric acid and cystine in that order. Calcium oxalate was also the main constituent of the nucleus of most kidney and bladder stones, calcium phosphate, magnesium ammonium phosphate, and ammonium acid urate occurring most frequently in the outer layers of the stones. Most endemic bladder stones appear to originate as aggregates of calcium oxalate crystals in the kidney, which subsequently descend to the bladder, where they may acquire secondary deposits of calcium phosphate, magnesium ammonium phosphate or ammonium acid urate.

Adolescent↗
PubMed1978

Evidence of increased oxalate absorption in patients with calcium-containing renal stones.

1. The possible roles of the diet and of intestinal absorption in the increased excretion of oxalate by patients with renal calcium stones have been studied. 2. Dietary surveys showed that the mean daily intake of oxalic acid by stone-formers was not significantly different from that of non-stone-formers. 3. The mean urinary excretion of oxalate, expressed as an oxalate/creatinine molar ratio, was significantly reduced by fasting, the change being more marked in the stone-formers than in the normal subjects. Moreover, fasting abolished the difference in mean oxalate/creatinine ratios between stone-formers and control subjects. 4. These results are compatible with the hypothesis that the small increases in urinary oxalate excretion which occur in some idiopathic calcium oxalate stone-formers are due to increased absorption of oxalate from the intestine, which may be due to a reduction in intraluminal calcium concentration.

Adult↗
PubMed1978

Effect of oophorectomy and calcium deprivation on bone mass in the rat.

1. The effects of a low calcium diet and of oophorectomy, separately and together, on cortical and trabecular bone mass, have been examined in mature female rats. 2. Calcium deprivation caused a significant decrease of weight, cortical cross-sectional area and ratio of cortical to total area in the femur, it significantly reduced the volume of trabecular bone and increased the percentage of osteoid surface in the tail vertebrae, and in addition increased the urinary excretion of phosphate and, initially, of hydroxyproline. 3. Oophorectomy caused similar though smaller changes in trabecular bone and urine, whereas the effects of oophorectomy on cortical bone were greater on a low calcium intake than on a normal intake. 4. The ash weight of the femora, expressed as a percentage of the total dry weight, was unaffected by calcium deprivation or oophorectomy alone but was significantly reduced when the two occurred together. 5. The percentage of resorption surfaces in the vertebrae tended to increase on the low calcium diet and after oophorectomy on the normal diet but decreased after oophorectomy on a low calcium diet. 6. It is concluded that oophorectomy and calcium deficiency each reduce bone mass in the adult rat but the greatest effect is seen when they are combined.

Animals↗
PubMed1978

Oxalic acid metabolism in the rat.

Feeding experiments indicated that approximately 15% of dietary oxalate is adsorbed in the rat intestine and that dietary oxalate accounts for about one third of the oxalic acid normally excreted in rat urine. Oxalate excretion increased by about 40% when a low calcium diet was fed, decreased by 65% when a low protein diet was fed and increased by 100% when a high protein diet was fed. Fasting for 24 hours resulted in a fall in calcium excretion but phosphate and creatinine excretion increased. Oxalate excretion also tended to increase. Between 60% and 70% of activity was recovered in the urine, faeces and body tissues after 14C-oxalic acid had been administered intraperitoneally. Recoveries of 14C-labeled compounds as urinary 14C-oxalic acid decreased in the following order: glyoxylic acid greater than ascorbic acid greater than citric acid greater than glycollic acid greater than tryptophan greater than hydroxyproline greater than glycine. It is suggested that conversion of citrate to oxalate in the rat may occur via the "glyoxylate cycle." It is concluded that a higher proportion of dietary oxalate is absorbed in the rat intestine compared with man, and that dietary oxalate accounts for a higher proportion of urinary oxalate in the rat than in man. Intestinal secretion and bacterial degradation of oxalate also appear to be proportionately greater in the rat than in man.

Animals↗
PubMed1978

The effect of oophorectomy on plasma oestrone and androstenedione levels in the rat.

Plasma oestrone and androstenedione levels have been measured in oophorectomized and sham-operated rats by means of radioimmunoassay. The mean oestrone level in the oophorectomized animals was approximately two-thirds of that in the intact animals while the androstendione levels were about half of those in the intact rats. A direct relationship was observed between the plasma oestrone and androstenedione levels in the control animals and to a lesser extent in the oophorectomized animals. The results indicate that approximately 50% of circulating androstenedione and 30% of circulating oestrone originate in the ovaries in the female adult rat.

Androstenedione↗
PubMed1977

Seasonal variations in the composition of urine from normal subjects: a longitudinal study.

The volume, pH and composition of 24-h urine samples, collected by 13 healthy male adults, were followed over a period of one year. Significant and systematic variations in urine pH, calcium, phosphate, oxalate, uric acid, potassium and magnesium were observed. A significant but non-sinusoidal variation in sodium excretion was found but there were no significant changes in urinary volume, creatinine or hydroxyproline. Many of the observed changes could be attributed to variations in the pattern of food consumption throughout the year but calcium, phosphate and oxalate were exceptions in that seasonal variations in these parameters appeared to be due to the effects of sunlight (or vitamin D) rather than to the diet.

Adult↗
PubMed1977

Composition of urinary tract calculi in children of different ages.

The composition of urinary tract calculi in children in relation to their age has been examined and comparisons have been made with other published series. It is concluded that paediatric stone disease can be divided into two main types: (1) infection stones, composed largely of magnesium ammonium phosphate and occurring mainly in children under 5 years of age, (2) calcium stones, occurring mainly in older children.

Adolescent↗