Abstracts from the Bone and Tooth Society Meeting 261

IIIa antigens may thus play a role in fibrinogen binding by osteoclasts. By analogy with platelets, fibrinogen may be necessary for aggregation of osteoclast precursors or osteoclast binding to the bone surface. Alternatively, plasminogen activator, which is known to be secreted by osteoblasts, may act either on fibrinogen or one of the platelet antigens expressed by osteoclasts, to influence osteoclast function.

P2. Bone cell viability in vitro as a function of age CE Evans, CSB Galasko Department of Ortkopaedic Surgery, Clinical Sciences Building, Hope Hospital, Eccles Old Road, Salford M6 8HD

Using the explant method, we have cultured cells from fragments of human trabecular bone, removed at surgery. We studied the proliferation rates of bone cells from primary bone cultures obtained from over 80 patients, aged from 2-87 years, as well as alkaline phosphatase, total protein and osteocalcin production. A skin biopsy was taken at the same time and skin fibroblasts cultured.

Proliferation rates were assessed using three criteria: uptake of 3H thymidine, cell numbers after 48 hours incubation and time taken to form a confluent mono- layer. Cell numbers at confluence were also counted. We found that, whilst none of the proliferation assays showed changes with chronological age or time in vitro, a significant decrease was seen in cell number at confluence, as the age of the donor increased. Alkaline phosphatase activity showed an upward trend in cells from female donors over 60 years of age, but no such trend was seen in males. Total protein and osteocalcin synthesis showed no age-related changes. These results suggest that age-related osteoporosis may be cell- mediated.

P3. Rate of movement of cultured osteoclasts: species and size variation CS Morris and SJ Jones Department ofAnatomy, University College London, Gower Street, London WClE 6BT

Osteoclasts (0~s) locomote in vivo and in vitro, both during and between resorptive activity. Adhesion structures of cultured chick Ocs are similar on bone and plastic (Zambonin Zallone, 1986) although the rate of movement on plastic exceeds that on bone, especially if resorption ensues. The rate of locomotion (and resorption) may be related to cell size, and this is of interest clinically, since large Ocs are a feature of some bone pathologies e.g., Paget’s disease. Ocs were isolated from chick and rat long bones and cultured in MEM plus 10% FCS on plastic and observed during their first 24 hours after seeding, either by automatic photographic recording at 10 or 30 minute intervals, or by video- recording. Enlargements of these were analysed using stereomorphometry programs on an Apple IIC computer, and the movements of the cells within a sequence calculated.

The rates of movement were of the order previously reported for rabbit Ocs (Ferrier et al, 1986). However,

larger Ocs (both in terms of nuclei numbeb and plan area) had a significantly faster mean velocity than smaller ones in both rat and chick cultures: e.g., Ocs with <5 nuclei moved 15.7+%4ym/30 min; >4 nuclei 26.98+12.5pm/30 min (mean rates). The rates of movement fluctuated, peaking every 6 hours, the first peak velocity occurring earlier in chick (74% before 1 hour) than rat (325% before 1 hour) Ocs, although rat cells adhered and spread sooner. The mean rate of movement and rate for a given size were also greater for chick Ocs. Osteoblastic cells in the same cultures moved 2 to 3 times more slowly. Thus cell size, as well as species variation, is an important factor in studies of osteoclast function.

P4. Plasma immunoreactive parathyroid hormone (PTH) concentration in the detection of ok&eomalacia (OM) in asian out-patients JA Nisbet,* AM Flanagan,t L Ang,$ KW Colston,* TJ Chambers,t JB EastwoodS and JD Maxwell+ *Department of Chemical Pathology, tDepartment of Histopatkology, SDepartment of Medicine, St GeorgeS Hospital and Medical School, London SW17

Since plasma 25-OH vitamin D is low in over 20% of healthy British Asians, we were interested to investigate whether elevated plasma PTH concentrations might be more useful as an indication of clinically significant vitamin D deficiency (osteomalacia) in this at-risk population.

In a prospective study of 125 adult Asian out-patients, bone biopsy was offered to those who hadNan abnormal discriminant score (derived from clinical features indicating a high risk of OM) or who had hypocalcaemia, elevated bone alkaline phosphatase, subnormal 25-OH vitamin D or elevated PTH using an N-terminal assay. 23 of 25 eligible patients consented to iliac bone biopsy following tetracycline labelling. Undecalcified sections were examined for evidence of OM.

6 patients had unequivocal OM and 8 had normal biopsies. The remaining 9 were judged to be borderline on the basis of elevation of trabecular surface covered by osteoid but no increase in the volume of osteoid.

The mean PTH of the patients with unequivocal OM was more than double that of the normals; the mean of those with borderline histology was similar to that of the normals. Overall, there was a significant inverse relation between PTH and plasma calcium but none between PTH and plasma 25-OH vitamin D.

Plasma PTH was more useful than plasma calcium, phosphate, alkaline phosphatase and 25-OH vitamin D in the detection of OM. It was also more useful than the clinical discriminant score, 5 out of 6 elevated PTH values being in the OM group. The discriminant score, however, was abnormal in all 6 patients with OM but also in 4 of the 8 with normal histology.