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Biomedical subjects

J Zerwekh

Publications and source records attributed to J Zerwekh.

12 recordsLinked to original sources
PubMed1996

Porous ceramics as bone graft substitutes in long bone defects: a biomechanical, histological, and radiographic analysis.

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evaluation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight-bearing was achieved.

Animals↗
PubMed1996

The importance of the dura in craniofacial surgery.

The hypothesis of this study is that craniofacial procedures that rely on devascularization of cranial bone are successful largely because of the unique environment that the dura offers. This hypothesis was tested by sequentially labeling animals with tetracycline and studying the healing of cranial bone grafts when replaced immediately and when subjected to room air exposure for 90 minutes and contrasting healing in mature and immature animals. Bilateral parietal bone flaps were harvested from guinea pigs. On one side, the bone was replaced as a control, and on the other side, the dura was resected prior to replacing the bone flap. The animals were divided into four groups of five animals each. The first and second groups were immature animals (3 to 4 weeks of age), and the third and fourth groups were mature animals (4 to 6 months of age). In the first and third groups, the bone flaps were replaced immediately, and in the second and fourth groups, the bone flaps were exposed to room air for 90 minutes, since this has been shown to destroy surface osteocytes and simulates extreme exposure conditions that could occur in clinical situations. Sequential marking with tetracycline was performed to study the mineralization rate and overall matrix formation. Significantly decreased mineralization rates occurred in bone flaps not in contract with dura. In those bone flaps exposed to room air for 90 minutes, healing occurred only on the side where dura was present. The clinical implications of the importance of the dura in craniofacial procedures are discussed.

Aging↗
PubMed1994

Limited risk of kidney stone formation during long-term calcium citrate supplementation in nonstone forming subjects.

The physiological and physicochemical effects of long-term calcium citrate supplementation (25 mmol. calcium per day) were assessed in 7 normal premenopausal women. Calcium citrate increased urinary calcium from 3.27 +/- 0.42 mmol. per day (standard deviation) before treatment to 5.16 +/- 0.75 mmol. per day after 1-month of treatment (p < 0.0125). After 3 months of treatment urinary calcium decreased from the 1-month value to 4.54 +/- 0.67 mmol. per day (p < 0.0125) but remained higher than the pretreatment value (p < 0.0125). Fractional intestinal calcium absorption and serum 1,25-dihydroxyvitamin D levels decreased marginally at 1 month of calcium citrate therapy, from 0.457 +/- 0.092 to 0.374 +/- 0.035 (p < 0.05) and from 103 +/- 7 to 77 +/- 14 pmol./l. (p < 0.05), respectively. After 3 months of treatment fractional intestinal calcium absorption decreased further to 0.341 +/- 0.061 (p < 0.0125 compared to pretreatment), whereas serum 1,25-dihydroxyvitamin D remained unchanged at 82 +/- 14 pmol./l. Calcium citrate treatment decreased urinary phosphorus levels significantly from 18.9 +/- 3.3 to 15.0 +/- 2.5 mmol. per day (p < 0.0125) and 14.0 +/- 2.5 mmol. per day (p < 0.05) at 1 and 3 months, respectively. Mean urinary oxalate decreased by 15 to 20% and urinary citrate increased marginally during treatment. Urinary saturation of calcium oxalate and brushite did not change during calcium citrate therapy, except at 1 month when the saturation of calcium oxalate increased marginally. The inhibitory activity of urine against spontaneous nucleation of calcium oxalate and brushite (formation product) did not change during treatment. In conclusion, long-term calcium citrate supplementation in normal subjects does not increase the propensity for crystallization of calcium salts in the urine. This protective effect is probably due to the attenuated increase in urinary calcium excretion (from a decrease in fractional intestinal calcium absorption), a decrease in urinary phosphorus and an increase in urinary citrate.

Adult↗
PubMed1987

Developing a solid base for a cost accounting system.

Henry Ford Hospital recently conducted a procedural costing study to determine if more accurate costs for various institutional procedures could be developed. The hospital conducted the study in two phases. The first phase looked at a specific department while phase two took a broader approach and covered the entire institution. This article examines the department-specific phase in which the diagnostic radiology department was selected as the participant. The study concluded that by allocating costs to the procedural level using relative value units and feeding this information into the case-mix system, departmental costs could be accurately identified.

Accounting↗
PubMed1980

Effect of 1,25-(OH)2D3 on jejunal absorption of magnesium in patients with chronic renal disease.

These studies were performed to see if jejunal malabsorption of magnesium in patients with chronic renal disease was influenced by therapy with 1 alpha, 25-dihydroxyvitamin D3 [1,25-(OH)2D3; 2 microgram/day by mouth for 7 days]. This treatment restored normal serum concentrations of the vitamin D metabolite from 0.9 +/- 0.2 to 4.2 +/- 0.6 ng/dl. Jejunal absorption of magnesium, measured by a triple-lumen constant-perfusion technique, was enhanced in each of the seven patients by this therapy. The mean value rose from 0.04 +/- 0.02 to 0.13 +/- 0.02 mmol . 30 cm-1 . h-1. This last value is similar to the magnesium absorption rate in untreated normal subjects. These results demonstrate that magnesium absorption in the human jejunum is dependent on vitamin D, and they show that 1 alpha,25-dihydroxyvitamin D3 therapy in patients with chronic renal failure is associated with an enhanced jejunal absorption of magnesium.

Adult↗
PubMed1980

Effect of growth hormone administration: reciprocal changes in serum 1 alpha,25-dihydroxyvitamin D and intestinal calcium absorption.

The mechanism by which GH stimulates intestinal calcium absorption was explored. In this study, seven children with idiopathic GH deficiency were studied before and during GH therapy while they were maintained on the same metabolic diet. After 5-14 months of GH administration, fractional intestinal calcium absorption increased from 0.364 +/- 0.114 to 0.449 +/- 0.159 (P less than 0.01), and serum 1,25-dihydroxyvitamin D decreased from 63.7 +/ 19.3 to 46.7 +/ 17.8 pg/ml (P less than 0.025). Serum immunoreactive parathyroid hormone, urinary cAmp, serum 24,25-dihydroxyvitamin D, and 25-hydroxyvitamin D did not change significantly. The data suggest that GH does not directly influence parathyroid hormone or vitamin D metabolism. The possibility that relative intestinal resistance to 1,25-dihydroxyvitamin D exists in patients with GH deficiency is considered.

Adolescent↗
PubMed1979

Effect of phenytoin on bone and vitamin D metabolism.

Calcium and vitamin D metabolism were evaluated in 5 adult epileptic patients before and during treatment with phenytoin. Significant decreases occurred in serum concentrations of calcium, albumin, and 25-hydroxy-cholecalciferol. The decreases in serum calcium paralleled those in serum albumin. Significant increases occurred in serum alkaline phosphatase and 1 alpha, 25-dihydroxycholecalciferol, in urinary hydroxyproline, and in the fractional gastrointestinal absorption of calcium. Urinary cyclic adenosine monophosphate and serum parathyroid hormone did not change. The results suggest that the bone disease resulting from phenytoin therapy may be associated with a deficiency of 25-hydroxycholecalciferol and not of 1 alpha, 25-dihydroxycholecalciferol, and that reduced gastrointestinal absorption of calcium or changes in parathyroid function may not be necessary for the development of bone disease.

Adult↗
PubMedDate not supplied

Transcending life: the practice wisdom of nursing hospice experts.

In philosophy and theology, to transcend is to go beyond the limits of lived human experience. Hospice workers accompany people who are traveling beyond the limits. "Whoever would be a companion to the dying, therefore, must enter into their darkness, go with them at least part way along their lonely and frightening road." This paper explores the requisite hospice practice competencies of caring spiritually and guiding letting go, as identified in a qualitative analysis of the practice stories of 32 hospice nurse experts working with people nearing death. Spirituality has been described as the essence of personhood, the longing for meaning in existence, experience of God, experience of ultimate values, and trust in the transcendent. Its ultimate end is union or connection with a reality more enduring than the individual self. In contrast, spiritual distress is manifested as alienation and disconnection. The reality of the dying process involves a progressive series of disconnections from life, which requires the process of letting go. Thus, transcending life involves both the need to detach and separate from life as it has been lived. One home visiting hospice nurse has described dying as a spiritual process of both reflecting and detaching. Nagai-Jacobsen and Burkhardt identify three goals of caring spiritually: Fostering personal integrity; Promoting interpersonal connection; Supporting personal search for meaning. O'Connor describes hospice spiritual care promoted through the practice of presence, compassion, hopefulness, and the affirmation of life as fruitful. Stiles has completed the only published qualitative description of hospice nursing as spiritual care.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude to Death↗