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Biomedical subjects

A Hodgkinson

Publications and source records attributed to A Hodgkinson.

At least 19 recordsLinked to original sources
PubMed1985

Effects of oral ethinyl oestradiol and norethisterone on plasma copper and zinc complexes in post-menopausal women.

Orally administered ethinyl oestradiol increased the plasma total copper concentration and reduced the albumin concentration in post-menopausal women. Approximately 80% of the increase in copper was due to a rise in caeruloplasmin-bound copper and 20% to an increase in the amount of copper bound per gram of albumin. The plasma total zinc concentration was reduced, due partly to the decrease in albumin concentration and partly to a reduction in the amount of zinc bound per gram of albumin. Norethisterone had no significant effect on plasma copper but it reduced plasma zinc and albumin, though to a lesser extent than ethinyl oestradiol. When administered sequentially with ethinyl oestradiol, norethisterone diminished the effects of the former on plasma copper, zinc and albumin.

Administration, Oral↗
PubMed1984

Hypothesis. Biochemical changes at the menopause: possible role of the central nervous system.

Some of the biochemical changes which occur at the menopause can be attributed to an increased rate of loss of bone but others cannot be explained in this way. Data, collected through literature search, are presented which suggest that the rise in plasma phosphate concentration at the menopause is not due primarily to increased breakdown of bone but rather to the following sequence of events: progesterone deficiency----respiratory hypoventilation----mild respiratory acidosis and hypoxia----compensatory metabolic alkalosis----altered carbohydrate metabolism----rise in plasma phosphate concentration. Increases in the concentration of many plasma constituents occur at the menopause, which appear to be due to fluid loss and haemoconcentration. A possible cause of these changes is a reduced secretion of vasopressin by the pituitary gland as a result of oestrogen deficiency. Increases in the fasting urinary excretion of phosphate, sodium and magnesium also occur at the menopause. These changes cannot be attributed to increased bone loss but could be due to the effects of oestrogen deficiency on circadian rhythms in the hypothalamus.

Acid-Base Equilibrium↗
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↗
PubMed1976

Uric acid disorders in patients with calcium stones.

Plasma and uric acid levels were measured in 132 men with calcium-containing renal stones and in 24 healthy men of similar ages. Fasting resulted in a significant fall in the mean plasma uric acid level of normal subjects. Intermittent hyperuricaemia was observed in 7% of fasting patients. Intermittent hyperuricosuria was found in 17% of non-fasting patients but in only 2 to 6% of fasting subjects. Most of the uric acid abnormalities in patients with calcium stones therefore appear to be due to diet and may be prevented by reducing the consumption of purine-rich foods. A direct relationship was observed between uric acid excretion and urine flow at normal flow rates. It is suggested that the apparent increase in stone incidence, which occurs with rising living standards, may be due partly to increased consumption of purine-rich foods.

Adult↗
PubMed1975

Changes in the composition of urinary tract stones.

An increase in the average calcium oxalate content and decrease in average calcium phosphate content of stones received for analysis has been noted in a 9-year study. These changes appear to be due to a progressive increase in the number of patients with noninfected upper urinary tract stone and to the gradual elimination of phosphatic stones as a result of improved diagnosis and treatment. Some of the conditions associated with calcium phosphate stones are examined, particularly primary hyperparathyroidism, renal tubular acidosis, and medullary sponge kidney. These results further emphasize the importance of calcium oxalate in idiopathic stone disease and the need for a fuller understanding of the factors influencing calcium oxalate crystallization.

Acidosis, Renal Tubular↗