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Biomedical subjects

E C Cameron

Publications and source records attributed to E C Cameron.

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

Dialysis encephalopathy and osteomalacic bone disease: a case-controlled study.

Nine patients on long-term hemodialysis with dialysis encephalopathy were studied, with sex matched control subjects for eight of the patients. Each patient with dialysis encephalopathy and control subject were contemporaries in a similar dialysis environment. Rib and other fractures were found in excess in the patients with dialysis encephalopathy (p less than 0.005 and p less than 0.01). These patients had less radiographic hyperparathyroid bone disease, and no more osteopenia as measured by metacarpal thickness than did their control counterparts. Severe osteomalacia was documented by bone biopsy in four of te patients. In a retrospective review of clinical, biochemical and pharmacologic differences, the patients with dialysis encephalopathy were significantly older at the start of dialysis (45.6 years versus 38.6 years, p less than 0.02) and had higher mean concentrations of blood urea nitrogen (BUN) and lower serum hemoglobin in the first year of dialysis than the control subjects. Blood pressure weight, creatinine, calcium, phosphate, alkaline phosphatase and a number of transfusions did not differ significantly. There was no difference in prescribed vitamin D and elemental aluminum in phosphate binders. This study demonstrates that patients with dialysis encephalopathy had more rib fractures without more parathyroid or osteopenic bone disease than did the control subjects and suggests that the etiology of dialysis encephalopathy and osteomalacia is multifactorial.

Adult↗
PubMed1981

Biochemical markers of bone turnover in Paget's disease.

The two most commonly used biochemical markers of bone turnover are the serum alkaline phosphatase and the urinary excretion of peptide-bound hydroxyproline, both of which are increased in Paget's disease. Serum alkaline phosphatase is assumed to be derived from osteoblasts during the process of bone formation, whereas small peptides containing hydroxyproline are excreted in the urine following the degradation of bone collagen. The alkaline phosphatase is probably the more useful measurement for diagnosis and for following response to treatment, whereas hydroxyproline, although very sensitive, presents technical difficulties in collection and measurement. Several other biochemical changes in Paget's disease indicate abnormal bone metabolism. These include increased urinary excretion of hydroxylysine and its glycosides derived from collagen, as well as the release into the circulation and subsequent urinary excretion of fragments of pro-collagen indicative of increased collagen formation. Proteins specific to bone, such as osteocalcin, are increased in serum, bone, such as osteocalcin, are increased in serum, as are various enzymes possibly derived from bone cells, including acid phosphatase and proline imino-peptidase. Treatment of Paget's disease results in a fall in urinary hydroxyproline before alkaline phosphatase. This indicates that drug treatment, whether with diphosphonates, calcitonin or mithramycin, has a primary action to inhibit bone resorption, with a subsequent adaptive reduction in bone formation rate.

Alkaline Phosphatase↗
PubMed1981

Sibling and parent--offspring correlation estimation with variable family size.

A method for estimating intrafamilial correlations under variable family sizes involving weightings of paired data points is introduced. Classical methods of intrafamilial correlation estimation and those in current use are outlined and critically analyzed. Extensions of the proposed estimation method to more general data structures are delineated.

Family↗
PubMed1981

The role of vitamin D metabolites in the osteomalacia of renal disease.

Osteomalacia is commonly found in patients with severe renal impairment. Its aetiology is multifactional and not simply due to deficient production of active metabolites of vitamin D. Decreased availability of calcium and phosphate and the accumulation of aluminium is some dialysis-treated patients are also important aetiological factors. The treatment of osteomalacia depends, in part, upon its accurate diagnosis, and identifying and reversing the underlying cause.

Calcium↗
PubMed1980

Acute interstitial nephritis associated with thiazide diuretics. Clinical and pathologic observations in three cases.

Renal failure insidiously developed in three patients treated with a combination of hydrochlorothiazide and triamterene five to 10 weeks after commencing therapy. All had normal renal function prior to therapy and none had preexisting renal disease. Two of the patients had eosinophilia and two had a fever. One patient was oliguric. Renal biopsy demonstrated acute interstitial nephritis histologically. Direct immunofluorescence did not disclose evidence of either immune complex or antitubular basement membrane antibody deposition. Withdrawal of the drug led to remarkable improvement with renal function returning to normal in two patients and near normal in the third. The sequence of events and the histologic findings strongly suggest that the acute interstitial nephritis was due to a drug-induced hypersensitivity reaction. Although hydrochlorothiazide appears to be the drug responsible for the reaction, certain observations suggest a possible potentiating role for triamterene.

Aged↗
PubMed1980

Hemodialysis patients with a unique mineralizing defect unresponsive to 1,25-dihydroxycholecalciferol. Dialysis osteomalacic syndrome.

5 patients are described who developed severe osteomalacia with spontaneous fractures after 2-4 years on dialysis. Phosphate control, vitamin D2 therapy and parathyroidectomy were ineffective. These individuals showed a hypercalcemic tendency but little histologic or radiographic evidence of osteitis fibrosa. After parathyroidectomy, the hypercalcemic tendency remained and bone biopsy revealed gross osteomalacia. A 6- to 12-month therapeutic trial with 1,25-dihydroxycholecalciferol (1,25[OH]2D3) in 3 did not arrest skeletal deterioration. 4 subsequently developed dialysis encephalopathy. These patients appear to have a unique mineralizing defect unresponsive to 1,25(OH)2D3. This "dialysis osteomalacic syndrome" may result from toxic substances associated with uremia or the hemodialysis regimen.

Adult↗
PubMed1979

Experience with 1,25-dihydroxycholecalciferol therapy in undergoing hemodialysis patients with progressive vitamin D2-treated osteodystrophy.

Six long-term hemodialysis patients with progressive skeletal deterioration during long-term pharmacologic vitamin D2 therapy were treated for six to 12 months with oral 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) to determine its therapeutic effectiveness in vitamin D2-unresponsive osteodystrophy. On bone biopsy, three of the patients had severe osteomalacia and three showed predominant osteitis fibrosa. Previous therapies, including phosphate binders and dialysis schedules, were maintained. The three patients with osteomalacia and the two with osteitis fibrosa showed clinical deterioration. There was no significant change in serum calcium, phosphate, alkaline phosphatase, bone densitometry, immunoreactive parathyroid hormone levels or bone histology. Roentgenograms showed multiple new fractures of ribs and femoral necks in the patients with osteomalacia and increased bone resorption in two of three patients with osteitis fibrosa. 1,25-(OH)2D3 dosage had to be decreased in all patients because of hypercalcemia with a mean tolerated dose of 0.22 microgram/day. In these patients, 1,25-(OH)2D3 was not effective therapy for progressive osteodystrophy unresponsive to pharmacologic vitamin D2.

Adult↗
PubMed1979

Spurious hypocalcemia in hemodialysis patients after heparinization. In-vitro formation of calcium soaps.

Patients on long-term hemodialysis via arteriovenous fistula received heparin when the fistula needle was inserted, before a sample of blood was obtained for chemical analysis. The resultant release of lipoprotein lipase activity in vivo and continued lipolytic activity in vitro sometimes produced sufficient free fatty acid to precipitate calcium soaps. The consequent spurious hypocalcemia was most frequently observed when the patients had chylomicronemia. This cause of apparent hypocalcemia was eliminated either by immediate analyses of the blood samples or by obtaining samples before systemic heparinization.

Arteriovenous Shunt, Surgical↗
PubMed1979

A prospective, controlled trial of six forms of hormone replacement therapy given to postmenopausal women.

This study was undertaken to investigate the effect of various forms of hormone replacement therapy (HRT) upon postmenopausal women while controlling as many variables as possible. It was felt that the age, duration of amenorrhoea and the general health of the patients should be as comparable as possible and that each patient should provide her own pretherapy and post-therapy control data. In addition, it was felt that any placebo effect should be investigated and the patients were therefore randomly allocated to placebo tablets or one of six available forms of HRT. The age/sex registers of two large general practices were scrutinized and all women between 49 and 54 years of age were asked to cooperate; for a variety of reasons only 56 women were suitable and willing to take part in the project, yielding 8 women for each of the seven possible therapy groups. Blood samples were taken at 7-day intervals three times before therapy was given and the mean of the three values was used as the control value. The women returned on day 21 of each subsequent therapy cycle for six consecutive months and finally three months after discontinuing therapy. From the data the following broad conclusions can be drawn: (i) some women have classic symptoms of hot flushes and sweating despite high endogenous oestrogen concentrations; (ii) vaginal cytology is a relatively poor indicator of endogenous oestrogen status; (iii) while follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations are reduced on HRT neither is decreased to anywhere near premenopausal values while prolactin is unaffected; (iv) plasma cholesterol levels are reduced on HRT, the pulse rate is slower and both systolic and diastolic blood pressure are reduced to a small but significant extent; (v) there is no adverse effect upon blood clotting; and (vi) most women experience significant or complete relief of symptoms on all forms of HRT as do some women taking a placebo. The combined preparations containing an oestrogen and progestogen produced vaginal bleeding in only 80 per cent of the women. Thus protection by regular endometrical shedding may not be afforded to all women. As vaginal bleeding is unacceptable to most women if they can achieve the same symptomatic relief without inducing menstruation, it is suggested that women have a low dose oestrogen preparation prescribed cyclically for 6 to 12 months. If therapy is to be maintained for a longer time, uterine curretage should be undertaken at regular intervals to exclude the possibility of endometrial carcinoma developing.

Climacteric↗
PubMed1979

Bone biopsy to diagnose hyperoxaluria in patients with renal failure.

Primary hyperoxaluria is a rare congenital disorder characterized by large quantities of urinary oxalate with resultant nephrocalcinosis and nephrolithiasis and by deposits of calcium oxalate in other organs. Renal failure occurs early in life. Reports of unsuccessful renal transplantation attempts in this disorder underscore the need for antemortem diagnosis. Percutaneous bone biopsy is a relatively new procedure that is easily done at bedside, safe, and of potentially high yield in the demonstration of tissue oxalate. Three cases presented here show the characteristic histologic picture seen in this disease. In one case, the diagnosis was established by bone biopsy.

Adolescent↗
PubMed1977

Cortical thickness measurements and photon absorptiometry for determination of bone quantity.

Reproducibility of estimates of cortical bone quantity in the appendicular skeleton by two methods was studied in healthy individuals and patients undergoing long-term hemodialysis. Repeated measurements of cortical thickness (CT) at the midpoint of the second metacarpal were taken from single radiographs of both hands by two independent observers. Repeated measurements by the same observer were more reproducible and the degree of reproducibility was far greater in healthy subjects than in dialysis patients. Repeated measurements were made of bone mineral content (BMC) and bone width (W) of the distal radius by photon absorptiometry. Repeated BMC/W determinations were highly reproducible in both healthy subjects and dialysis patients. High correlation was found between BMC and cross-sectional cortical area and between both simple cortical thickness and cortical area/width. Thus the photon absorptiometric technique is superior for the serial monitoring of bone quantity, particularly in patients with uremic osteodystrophy, but results obtained by the two methods in group studies should be comparable.

Adult↗
PubMed1974

Measurement of bone mineral content in vivo using photon absorptiometry.

Progress in evaluating treatment of systemic bone disease has been hampered in the past by lack of precise in vivo quantitative techniques. Recently a method has been developed for measurement of bone mineral content (BMC), based on bone absorption of low-energy monochromatic radiation. This paper discusses a technique of photon absorptiometry using (125)l as a collimated point source. The technique is simple, with accuracy and precision within 2%.BMC and bone width (W) were measured in the distal radius of 359 normal subjects ranging in age from 5 to 82 years. A "normal" curve of BMC/W with age as the independent variable was then obtained from this population and was constructed for each sex. A positive correlation of BMC/W with height and body weight was found in a group of normal males.A series of patients with osteoporosis or malabsorption, or undergoing hemodialysis or steroid treatment, was then assessed in order to demonstrate changes in BMC/W that may occur secondary to disease or disturbances in calcium metabolism. Many of these patients were found to have a BMC/W below the normal mean value for their age and sex.

Adolescent↗
PubMed1971

A Nonproteolytic "Trypsin-like" Enzyme: Purification and Properties of Arachain.

By the use of the proteolytic substrates benzoyl-dl-arginine-p-nitroanilide and benzoyl-l-arginine ethyl ester the enzyme arachain has been purified 325-fold from acetone powders of ungerminated peanuts. The pH optimum for the hydrolysis of benzoyl-dl-arginine-p-nitroanilide was 8.1 in tris buffer, and for benzoyl-l-arginine ethyl ester was 7.5 using N - 2 - hydroxyethylpiperazine - N' - 2 - ethanesulfonic acid buffer. The purest fraction showed one main band with one to three minor bands on disc gel electrophoresis. The major protein component had an S(20,w) of 6.20. The energy of activation for the hydrolysis of benzoyl-dl-arginine-p-nitroanilide was calculated to be 16 kilocalories. The Michaelis constant for benzoyl-dl-arginine-p-nitroanilide was 10 micromolar and for benzoyl-l-arginine ethyl ester was 110 micromolar. The enzyme showed essentially no activity with casein, dimethyl casein, or bovine serum albumin as substrates. A large number of peptides were hydrolyzed by the enzyme, only l-leucyl-l-tyrosine being resistant of the peptides tested. The results suggest that arachain is not a "trypsin-like" protease but is a peptide hydrolase.

Journal Article↗
PubMed1968

Regulation of starch biosynthesis in plant leaves: activation and inhibition of ADPglucose pyrophosphorylase.

The ADPglucose pyrophosphorylases of 7 plant-leaf tissues were partially purified and characterized. In all cases the enzymes showed stability to heat treatment at 65 degrees for 5 minutes in the presence of 0.02 m phosphate buffer, pH 7.0. The leaf ADPglucose pyrophosphorylases were activated 5 to 15-fold by 3-phosphoglycerate. Fructose-6-phosphate and fructose 1, 6-diphosphate stimulated ADPglucose pyrophosphorylase to lesser extents. The A(0.5) (conc of activator required to give 50% of the observed maximal activation) of 3-phosphoglycerate for the barley enzyme was 7 x 10(-6)m while for the sorghum enzyme it was 3.7 x 10(-4)m. Inorganic phosphate proved to be an effective inhibitor of ADPglucose synthesis. The I(0.5) (conc of inhibitor that gave 50% inhibition of activity for the various leaf enzymes varied from 2 x 10(-5)m (barley) to 1.9 x 10(-4)m (sorghum). This inhibition was reversed or antagonized by the activator 3-phosphoglycerate. These results form the basis for an hypothesis of the regulation of leaf starch biosynthesis.

Glucosyltransferases↗