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Biomedical subjects

S B Thomas

Publications and source records attributed to S B Thomas.

At least 37 records · Page 2Linked to original sources
PubMed1989

Serum osteocalcin and bone mineral metabolism following successful renal transplantation.

Serum osteocalcin (bone gla protein, BGP), a vitamin K-dependent non-collagenous bone protein and its relationship to other markers of bone and mineral metabolism were studied cross-sectionally in varying numbers of patients before and over 240 days following renal transplantation. Marked elevation of serum creatinine (11.9 +/- 0.76 mg/dl), osteocalcin (216.9 +/- 7 ng/ml), parathyroid hormone (PTH, mid-molecule fragment) (24.5 +/- 3.6 ng/ml), alkaline phosphatase (255.2 +/- 54.7 IU/l) and phosphorus (5.6 +/- 0.3 mg/dl) were noted preoperatively. Serum calcium levels remained normal throughout the study period while phosphate levels normalized within one week after transplantation. PTH levels progressively decreased postoperatively over the study period but were still elevated well above normal. Serum osteocalcin decreased to near normal values at 60-90 days after surgery. Both PTH and alkaline phosphatase correlated significantly with osteocalcin preoperatively and postoperatively. The relatively depressed values of osteocalcin in the face of still elevated PTH levels post-transplantation was attributed to the effect of immunosuppressive corticosteroid therapy. The significant correlation between PTH and osteocalcin suggests that osteocalcin may be as or more sensitive a measurement of bone turnover than alkaline phosphatase pre- and post-transplantation.

Adolescent↗
PubMed1988

Serum bone gla protein and the vitamin D endocrine system in the oophorectomized rat.

Because of the importance of estrogen in osteoporosis, the effects of decreased estrogen production using sensitive measurements of bone mineral metabolism were studied in oophorectomized rats. Serum levels of ionized calcium, bone gla protein (BGP), vitamin D metabolites (25-hydroxyvitamin D and 1,25-dihydroxyvitamin D), and estradiol were measured before and serially for 6 weeks after oophorectomy in the rat. In addition, static and dynamic indices of bone histomorphometry were determined after double tetracycline labeling. Fifty Sprague-Dawley female rats (approximately 250 g) were studied. Twenty-five rats underwent oophorectomy (O), while the remaining rats were sham operated. Estrogen deficiency was noted in the O group within a week after surgery (estradiol, 2.45 +/- 0.78 vs. 27.9 +/- 4.15 pg/ml; P less than 0.05). Serum ionized calcium levels, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and PTH levels did not differ between the two groups during the length of the study. Serum BGP levels were the same in both groups until the second week postoophorectomy, after which BGP remained significantly elevated in the O animals (121.7 +/- 5.95 vs. 76.7 +/- 3.87; P less than 0.001). Bone histomorphometry revealed increased osteoid volume (4.4 +/- 0.9% vs. 2.3 +/- 0.7%), osteoblast surface (26.5 +/- 2.4% vs. 3.2 +/- 1.2%), tetracycline surface (18.9 +/- 4.1% vs. 6.8 +/- 2.2%), as well as osteoclast surface (8.2 +/- 1.4% vs. 2.5 +/- 2%) in all O animals compared with those in the sham-operated group. These data indicate that oophorectomy and decreased estrogen result in increased bone turnover with elevated BGP levels. The marked BGP elevation within 2 weeks postoophorectomy suggests that estrogen withdrawal results in rapid altered bone mineral metabolism. The lack of concomitant increase in circulating PTH levels suggests that other factors may be mediating the bone loss following surgical oophorectomy.

Animals↗
PubMed1986

Serum bone gla protein (BGP) and other markers of bone mineral metabolism in postmenopausal osteoporosis.

Bone gla protein, the vitamin K-dependent protein synthesized by osteoblasts and measured in blood by radioimmunoassay, has been used as an index of the rate of bone turnover. The relationship of bone gla protein with other markers of bone mineral metabolism was determined in 31 untreated postmenopausal women with the osteoporotic syndrome. In addition to serum osteocalcin (BGP) we measured parathyroid hormone (PTH) (carboxyl and mid-molecule fragments), 25(OH)D, alkaline phosphatase, estradiol (E2), estrone (E1), dietary calcium intake, 24 hour urinary calcium excretion, and bone mineral density by CT scan of the lumbar vertebrae. Significant osteopenia was present on CT in untreated postmenopausal osteoporotic women (bone density in 18 out of 31 was below the critical value of 60 mg/cm3). Serum BGP correlated positively with CT scan (r + 0.647, P less than 0.001). CT and age were negatively correlated (r - 0.661, P less than 0.001) while CT and E2 showed a positive correlation (r + 0.554, P less than 0.01). Unexpectedly, BGP and age revealed a significant negative correlation (r - 0.421, P less than 0.05). These findings suggest a state of low bone turnover in this group with untreated postmenopausal osteoporosis.

Adult↗
PubMed1986

Tissue expansion: dividend or loan?

Epidermal mitotic activity during tissue expansion has been assessed in the guinea pig using tritiated thymidine and other confirmatory techniques. Implant inflation results in a threefold elevation of epidermal mitotic activity within 24 hours, followed by a gradual return to normal baseline over 2 to 5 days. Implant deflation, conversely, causes a transient decrease in epidermal mitotic activity. Neither of these phenomena has been previously described. It confirms previous animal studies which illustrate the highly responsive nature of the epidermis to physical stimuli and supports the view that tissue expansion is a highly useful manipulation of normal physiologic processes.

Animals↗
PubMed1977

The phospholipid-dependence of uridine diphosphate glucuronyltransferase. Phospholipid depletion and re-activation of guinea-pig liver microsomal enzyme.

More than 80% of the phospholipid component of guinea-pig liver microsomal membranes (prepared with 154mM-KCl) was removed by treatment with phospholipase A followed by extraction of the lysophosphatides and fatty acids produced with albumin. Delipidation strongly inactivated the highly active UDP-glucuronyltransferase of these preparations and activity was restored by mixtures of phosphatidylcholine and lysophosphatidylchlone. However, small quantities of lysophosphatides were still associated with the delipidated fractions after extraction with albumin and might have influenced the inactivation and re-activation observed. To eliminate these uncertainties, microsomal proteins and phospholipids were separated by gel filtration on Sephadex G-150 in the presence of cholate. This technique also strongly inactivated the enzyme but did not generate membrane-active phospholipid degradation products. High transferase activity was again restored to the delipidated protein by choline glycerophosphatides. These results confirm the view that the fully active form of microsomal UDP-glucuronyltransferase is phospholipid-dependent.

Animals↗