150 Abstracts from the Bone and Tooth Society.

most of the bovine PTH gene sequence complementary to the bound mRNA. This cDNA probe had been labeled with 32P by the nick translation procedure and after extensive washing to remove nonspecifically bound radioactivity, the filters were exposed to x-ray film at -70°C. After autora- diography, the intensities of the resulting hybrid bands or dots were scanned by densitometer and their relative ab- soibancies compared. A PTH mRNA band of approximately 800-900 bases in size was obtained on the agarose gel blot. This assay is currently being using to investigate the effect of low (0.5/mM) or high (5/mM) calcium concentrations on levels of PTH mRNA in bovine parathyroid tissue cultured over short periods (hours) as well as long periods (days). We are also using the PTH mRNA assay with a specific human PTH cDNA probe to detect the presence of PTH- related mRNA sequences in tumors from patients with hy- percalcemia associated with cancer.

PERINATAL VITAMIN 0 SUPPLY IN THE RAT

M.R. Clements and D.R. Fraser

University of Cambridge and Medical Research Council, Dunn Nutritional Laboratory, Cambridge C64 IXJ

The relative contributions of prenatal and postnatal supplies of vitamin D to newborn rats were investigated by a double- isotope technique. Vitamin D-deficient female rats were given depot injections of 3H-D, or 14C-D, prior to mating.3 H-dosed rats were killed during gestation on days 14, 17, 19, and 21, and total lipid from individual fetuses was chro- matographed to determine the distribution of metabolites. Total vitamin D content of fetuses increased rapidly during the last third of gestation, with a linear increase in concen- tration from days 14 to 19. During this period, t,,, of 3H in maternal plasma fell from 35.9 to 2.1 days, suggesting that specific mechanism was transferring vitamin D molecules into the fetuses. At birth the major metabolite in the pups was 250HD, (57.7 i 1.2%) with significant amounts of unchanged D, (10.1 f 0.8%) and 24,25 (OH),D, (22.5 + 0.9%). Immediately after birth, pups from 3H- and from 14C-labeled mothers were exchanged and later killed after various periods of suckling. Total lipid extracts were chro- matographed and analyzed for 3H and 14C content, to de- termine the relative contributions of vitamin D supplied be- fore birth via the placenta and after birth in milk. The vitamin D received in utero fell rapidly from 62.2/pmol/pup at birth to 3,4/pmol/pup at 3 weeks. However the total vitamin D content of the pups declined more gradually to 385/pmol/ pup over this period as the prenatal vitamin D was partially replaced by that from milk. These results demonstrate, for the first time in mammals, the existence of a specific transfer mechanism that allows the fetus to accumulate vitamin D from the mother during the last third of gestation. This supply of vitamin D in utero, rather than from milk, is the main determinant of vitamin D status during the first IO days after birth.

We report 2 years experience of providing a service to cli- nicians for the assay of serum levels of 25-hydroxyvitamin D. Over this period 420 assays were performed, In the further investigation of patients with possible osteo- mafacia or rickets, the assay was particularly valuable in excluding significant osteomalacia underlying a patient’s symptoms. In addition, patients whose biochemical findings were already disturbed, for example, by Paget’s disease of bone or by chronic liver disease, could be further investi- gated in this way to obtain an independent indication of vitamin D deficiency. As a result, the number of patients in this area submitted to a bone biopsy has decreased sub- stantially. In the follow-up of patients with osteomalacia and of patients with malabsorption the assay was useful for en- suring adequacy of replacement therapy. Measurement of serum 25-hydroxyvitamin D was found to be of little value in the clinical management of patients with hypoparathyroidism of pseudohypoparathyroidism. Sub- stantial overlap was found between patients with high, nor- mal, or low serum calcium levels. High levels of 25-hydroxyvitamin D were found in patients with vitamin D intoxication, but in none of the patients in this series was the diagnosis made for the first time in this way. Clearly, however, the assay is valuable in the diagnosis of vitamin D intoxication.

POLYMORPHIC VARIANTS OF THE HUMAN TYPE II COLLAGEN GENE

B. Sykes, D. Ogilvie, P. Wordsworth*, and R. Smith*

N&e/d Department of Pathology, John Radcliffe Hospital, Headington, and *N&field Orihopaedic Centre, Headington, Oxford

The human structural gene coding for a, (11) collagen on chromosome 12 is contained within a 37kb genomic cosmid clone. Using this cosmid, or subclones derived from it, as hybridization probes we have studied the fragmentation pat- tern of the gene by different restriction endonucleases. Some enzymes (Hpa I, Hind Ill, Pvu II) reveal naturally oc- curring variants at the enzyme recognition site. Other en- zymes (eg Eco Rl) reveal length differences in a region beyond the 3’-end of the gene. Both site and length variants can be used as genetic linkage markers to test the gene as the mutant locus for any inherited disease. We present evi- dence about its involvement in different clinical types of osteogenesis imperfects.

THE LOCALIZATION OF PARATHYROID TUMORS BY COMPUTED TOMOGRAPHY

J.E. Adams and P.H. Adams*

Departments of Diagnostic Radiology and *Medicine, fti;rs; of Manchester, Oxford Road, Manchester

CLINICAL VALUE OF ASSAYS OF SERUM PS-HYDROXYVITAMIN D

C.R. Paterson and J. Burns

Department of Biochemical Medicine, Ninewells Hospital and Medical School, Dundee DDI 9SY

Several imaging techniques have been used in the preop- erative localization of parathyroid tumors. Few have proved successful in clinical practice. The most reliable is a combination of arteriography and venous sampling, but this is technically difficult, time consuming, and potentially hazardous. The introduction of general purpose computed tomography