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Biomedical subjects

R B Mazess

Publications and source records attributed to R B Mazess.

At least 145 records · Page 8Linked to original sources
PubMed1980

Supranormal 25-hydroxyvitamin D and subnormal 1,25-dihydroxyvitamin D: their role in X-linked hypophosphatemic rickets.

Serum 25-hydroxyvitamin D (25-OH-D) and 1,25-dihydroxyvitamin D (1,25-(OH)2D) and bone mineral content by the photon-absorption technique were determined in eight patients with X-linked hypophosphatemic rickets treated for at least 24 months with oral sodium phosphate and high-dosage ergocalciferol (vitamin D2). Mean 25-OH-D2 level was 129.5 +/- 67.5 ng/mL (mean +/- SD); the level of 25-OH-D3 was 10.5 +/- 5.8 ng/mL. These values were significantly higher than in normal subjects (total 25-OH-D mean of 27 +/- 10 ng/mL). Serum 1,25-(OH)2D was 16.9 +/- 8.5 pg/mL (mean +/- SD) in the eight patients, significantly lower than 47 +/- 16 pg/mL in 27 age-matched controls. Values indicative of significant demineralization were found in seven of the eight phsophate-treated patients, who had no radiologic evidence of rickets. These results suggest that any theory of the pathogenesis of this disorder must account for inappropriate renal vitamin D metabolism and for renal hyperphosphaturia. The failure of high-dosage oral phosphate and ergocalciferol to fully correct demineralization may suggest a role for calcitriol (1,25-(OH)2D3) as a therapeutic agent.

Absorption↗
PubMed1980

Bone mineral status measured by direct photon absorptiometry in institutionalized adults receiving long-term anticonvulsant therapy and multivitamin supplementation.

The effects of long-term anticonvulsant drug therapy and multivitamin supplementation on bone mineral status were evaluated by direct photon absorptiometry in 53 adult residents of an institution for the mentally disturbed. Results demonstrated a similar amount of osteopenia for control subjects and those on anticonvulsant drugs. Average osteopenia was 8% for control subjects and 6% for subjects taking anticonvulsant drugs. Significant osteopenia was found in 25% of subjects taking anticonvulsant drugs and 20% of control subjects. Multivitamin supplementation had a beneficial effect on bone status in both subject groups. The use of anticonvulsant drugs had a significant effect on levels of alkaline phosphatase. Elevated alkaline phosphatase was found in 37% of subjects taking anticonvulsant drugs and 22% of control subjects. Hypocalcemia was found only in subjects taking anticonvulsant drugs (19%). Average calcium values were similar for both subject groups. Multivitamins were shown to have no significant effect on alkaline phosphatase or calcium values. Because both control subjects and those taking anticonvulsant drugs showed similar levels of osteopenia, factors other than anticonvulsant drug therapy appeared to adversely affect bone mineral status in this population. Conversely, multivitamin supplementation and the dietary control present in the institutionalized setting appear to have ameliorated the osteopenia commonly seen in anticonvulsant-treated populations without greatly modifying elevated alkaline phosphatase and hypocalcemia.

Adult↗
PubMed1980

Bone mineral status in growth hormone deficiency.

Bone mineral status was monitored by photon absorptiometry in 18 children with growth hormone deficiency. Before exogenous growth hormone therapy, bone mineral content, bone width, and BMC/BW were below predicted values. Delayed maturation, as assessed by skeletal age, accounted for approximately 35% of the deficit for these values. Height velocity doubled during therapy, and BMC, BW, and BMC/BW increased commensurate with height and weight increases so that the relative deficit was unchanged. The pathogenesis of relative osteopenia in growth hormone deficiency was not determined.

Adolescent↗
PubMed1979

Demineralization in cystic fibrosis detected by direct photon absorptiometry.

Bone mineral content, bone width, and their ratio were measured in patients with cystic fibrosis (CF) using monoenergetic photon absorptiometry. Serial measurements of the radius and ulna were made in 27 patients with CF and were compared with 968 age-matched controls. Demineralization was found in 37% of the boys and 63% of the girls. Patients under age 10 years had normal bone mineral content and nine of 15 patients aged 13 or older were demineralized (P less than .01). Demineralization correlated with the extent of weight reduction in patients (P less than .001). Patients most likely to be demineralized were adolescent girls. To our knowledge, this is the first report of bone mineral status of children with CF, and the results indicate that a sizable proportion of these patients may be demineralized without overt rickets.

Adolescent↗
PubMed1979

Heart rate recorder.

Explore the source record for details and available documents.

Electronics, Medical↗
PubMed1979

Longevity and age exaggeration in Vilcabamba, Ecuador.

Systematic age exaggeration was found after age 70 in an Equadorian population noted for extreme longevity. Extreme ages (over 100 years) were either incorrect or unsubstantiated. There was no evidence of increased longevity in the Vilcabamba population.

Adult↗
PubMed1979

The effect of immediate and delayed cold immersion on burn edema formation and resorption.

Massive wound edema after a burn may impair healing and help to convert partial to full-thickness injury. Cold treatment (usually by immersion) has been reported to decrease wound edema and is useful in first-aid treatment of burns. Reliable quantitative data have been lacking and frequently a superficial burn has been studied. Since cold by decreasing peripheral blood flow could actually be harmful to a deep burn, especially if applied late, we measured the effect of cold immediately and 2 minutes postburn on edema formation and resorption in a deep second-degree burn in sheep hindlimbs. We used Dichromatic Absorptiometry, a noninvasive, reliable method for measuring tissue fluid, to quantitate edema. Immediate application of cold by immersion in 15 degrees C saline for 30 minutes reduced the edema of a deep second-degree burn and did not impair resorption rate compared with control limbs, fluid content returning to baseline after 1 week. Cold treatment beginning 2 minutes after the burn did not decrease edema formation and did impair resorption. Fifteen per cent of the edema fluid was still present 1 week postburn, suggesting further injury to the burn wound vasculature with use of cold immersion 2 minutes postburn.

Animals↗
PubMed1978

Reduction of serum-1, 25-dihydroxyvitamin-D3 in children receiving glucocorticoids.

Serum-1,25-dihydroxyvitamin-D3 (1,25-[OH]2D3) was subnormal in children receiving long-term glucocorticoid treatment for various glomerular diseases, including nephrotic syndrome. In children with chronic glomerulonephritis not treated with glucocorticoids who had similar serum-creatinine with glucocorticoids who had similar serum-creatinine concentrations, serum-1,25-dihydroxyvitamin-D3 concentrations resembled those in healthy controls, indicating that glomerular renal disease per se does not account for reduced serum-1,25(OH)2DE concentrations in steroid-treated patients. The reduction in concentration of this most active vitamin-D metabolite correlated with the dose of steroid administered and with reduction in forearm bone mineral content measured by the photon absorption technique. Reduced serum-1,25-(OH)2D3 concentration may be important in the pathogenesis of steroid-induced osteopenia.

Administration, Oral↗
PubMed1978

Increased growth after long-term oral 1alpha,25-vitamin D3 in childhood renal osteodystrophy.

We evaluated oral 1,25-vitamin D3 for as long as 26 months in six prepubescent children with renal osteodystrophy previously treated with vitamin D2. Therapy was given at 14 to 41 ng per kilogram per day to correct hypocalcemia and reverse bone disease. Serum levels of 1,25-vitamin D3 were initially reduced at 15 +/- 5 pg per milliliter (mean +/- S.E.M.) and after treatment rose to 54 +/- 13. Serum calcium rose from 7.5 +/- 1.6 mg per deciliter (mean +/- S.D.) to 9.8 +/- 0.6 after one month (P less than 0.02). Alkaline phosphatase activity fell from 536 +/- 298 to 208 +/- 91 IU per liter after 12 months (P less than 0.05). Serum immunoreactive parathyroid levels fell from 900 +/- 562 microliter eq per milliliter 411 +/- 377. Healing of rickets and subperiosteal erosions was found. Remineralization of bone was demonstrated by the photon absorption technic. In four patients growth velocity, evaluated for 12 months before and after therapy, increased from 2.6 +/- 0.8 to 8.0 +/- 3.2 cm per year. Growth velocity per year increased from less than third percentile in each to the 10th to 97th percentile after therapy. Height increment ranged from 27 to 113 per cent of that expected for change in chronologic age and 40 to 114 per cent expected for change in bone age after therapy. This trial demonstrates that oral 1,25-vitamin D3 can reverse renal bone disease and increase growth in uremic children.

Administration, Oral↗
PubMed1978

Effect of prednisone on growth and bone mineral content in childhood glomerular disease.

Children with acquired glomerular disease were divided into two groups: Group 1 patients received short-term daily or long-term alternate-day prednisone (up to 2.7 mg/kg/48 hr); group 2 patients received no corticosteroids. Height, bone mineral content (BMC), and bone density were evaluated in the two groups and compared to those of 800 sex- and age-matched controls; BMC and bone density were assessed by the photon absorption technique. Significant demineralization was present in 18 of 25 prednisone-treated and none of the 17 nonprednisone-treated patients (P less than .001). Group 1 patients were 5.3 +/- 0.7% shorter than controls, while group 2 patients were only 1.9 +/- .8% shorter (P less than .02). Height velocity was 2.6 +/- 0.8 cm/yr in group 1 and 5.1 +/- 0.8 cm/yr in group 2 patients (P less than .05). When prednisone therapy was discontinued, six patients had an increase in height and BMC toward normal values. This study suggests that BMC and height velocity are correlated. Both appear to be influenced by alternate-day prednisone therapy rather than by glomerular disease per se.

Adolescent↗
PubMed1978

Photon absorptiometry of soft tissue and fluid content: the method and its precision and accuracy.

Dichromatic absorptiometry (DA) is a new, non-invasive method for determining soft tissue (STC) and fluid content (FC), and their changes. The technique uses linear transmission scans made across the limbs with a congruent 125I and 241Am dual-photon source and a NaI(TI)--PMT detector. Patient measurements could be made at the bedside with the mobile system. Factors affecting the precision and accuracy were evaluated theoretically and experimentally. Repositioning and subject motion were the greatest sources of variation and limited the precision to 2--3% in normals and 3--7% in patients; instrumental variation was 0.5%. The accuracy was 4% for typical (p10%) fluid changes observed in vivo. The ease, simplicity and small errors of the technique suggest its utility in monitoring the time course and degree of fluid changes in patients.

Americium↗
PubMed1978

The study of burn wound edema using dichromatic absorptiometry.

Burn wound edema is a source of major morbidity and mortality. To quantitatively study this edema, we have devised a noninvasive method called Dichromatic Absorptiometry (DA) which is precise (2-3%) and accurate (r equal to 0.99) in measuring changes in tissue fluid. A scanning technique using a dual photon source, 125I and 241Am, is used. The variable attenuation of the two photon energies allows for selective mass measurements of fluid, protein, lipid, and bone. In limbs with thermal injury the correlation of DA changes in fluid mass with circumference was (r equal to 0.97), but DA was more sensitive. In deep second- and third-degree burns, edema formation was maximum between 12 and 18 hours postburn with 80% of maximum already present at 4 hours. Resorption was complete by 1 week in second-degree burns, but significantly delayed in third-degree burns. Superimposed infection produced persistent edema.

Absorption↗
PubMed1978

Bone mineral in Vilcabamba, Ecuador.

Bone mineral content was measured by photon absorptiometry of the radius in an Ecuadorian population noted for longevity and for rarity of fractures and spinal curvature in the elderly. Bone mass, after covariance adjustment for age, height, weight, and bone width, was 15% below values for U.S. whites, indicating that the rarity of skeletal problems was not due to high bone mass or diminution of aging bone loss.

Adolescent↗
PubMed1977

Soft-tissue fluid determination by dichromatic absorptiometry.

Dichromatic absorptiometry (DA) in a noninvasive method for individually determining the amount of lipid, bone mineral, and protein and water present in a mixture by differential attenuation of radiation beams emitted from a dual photon source. The physics involved permit these components to be determined extremely accurately and precisely. The present study investigated the ability of DA limb scans to measure changes in total body water produced in dogs and in patients. Dichromatic absorptiometry was determined to be a valid method of measuring changes in total body water content as reflected by limb fluid content changes. Precision was limited by the accuracy in positioning the limb for repeated scanning. Dichromatic absorptiometry has the potential of becoming a clinically useful instrument for measuring fluid content changes in limbs produced either by changes in total body water content or by conditions causing limb edema.

Animals↗
PubMed1977

Bone mineral status measured by direct photon absorptiometry in childhood renal disease.

Bone width (BW), bone mineral content (BMC), and their ration (BMC/BW ratio) were measured in renal patients using direct photon absorptiometry. Serial measurements were made on the radius and ulna in 74 children with renal diseases. Values were compared to age-, sex-, height-, and weight-matched controls. The SD from the mean in normal subjects is +/- 10%. Significant demineralization (greater than -2 SD) was found in 42% of all patients and in 75% with tubulointerstitial disease. Twelve patients with nephrotic syndrome and two with systemic lupus erythematosus, all of whom were receiving prednisone therapy and had a serum creatinine level less than 1.0 mg/dl, and three treated with anticonvulsants had significant demineralization. Severe demineralization (greater than -3 SD) was found in four rachitic patients with tubulointerstitial disease. Normal mineralization was present in 32 patients with various primary glomerular diseases, seven of whom had a serum creatinine level greater than 1.5 mg/dl. BMC declined with daily prednisone therapy but increased with alternate-day dosage in seven patients. This study suggests that demineralization is more common in patients with tubulointerstitial disease and in patients with primary glomerular disease who are receiving prednisone (16 patients) or anticonvulsants. Photon absorptiometry appeared more useful than conventional radiographic evaluation in assessing skeletal involvement in childhood renal disease.

Adolescent↗