The BsmI vitamin D receptor restriction fragment length polymorphism (bb) influences the effect of calcium intake on bone mineral density

Previous studies of the vitamin D receptor (VDR) polymorphisms and bone mineral density (BMD) have suggested that there may be differences in calcium absorption among groups of women with different VDR genotypes, and that the association may be stronger in younger women. To investigate the association between the VDR polymorphisms and BMD, this study was undertaken in the Framingham Study Cohort and a group of younger volunteers. Subjects from the Framingham Study (ages 69-90 years) included those who underwent BMD testing and who had genotyping for the VDR alleles (n = 328) using polymerase chain reaction methods and restriction fragment length polymorphisms with BsmI (B absence, b presence of cut site). A group of younger volunteer subjects (ages 18-68) also underwent BMD testing and VDR genotyping (n = 94). In Framingham Cohort subjects with the bb genotype, but not the Bb or BB genotypes, there were significant associations between calcium intake and BMD at five of six skeletal sites, such that BMD was 7-12% higher in those with dietary calcium intakes greater than 800 mg/day compared with those with intakes < 500 mg/day. The data also suggested that BMD was higher in persons with the bb genotype only in the group with calcium intakes above 800 mg/day. No significant differences were found in the Framingham Cohort for age-, sex-, and weight-adjusted BMD at any skeletal site between those with the BB genotype and those with the bb genotype regardless of 25-hydroxyvitamin D levels or country of origin. In the younger volunteers, BMD of the femoral neck was 5.4% higher (p < 0.05) in the bb genotype group compared with the BB group and 11% higher (p < 0.05) in males with the bb genotype compared with the BB group. There were no significant differences at the lumbar spine. In this study, the association between calcium intake and BMD appeared to be dependent upon VDR genotype. The findings of an association between dietary calcium intake and BMD only in the bb genotype group suggests that the VDR genotype may play a role in the absorption of dietary calcium. Studies that do not consider calcium intake may not detect associations between VDR genotype and BMD. In addition, the association between VDR alleles and BMD may become less evident in older subjects.     

Post-translational cleavage of a histone H1-like protein in the sperm of Mytilus

Starting with total RNA from spermatogenic cells of Mytilus trossulus and using random priming, we have cloned and sequenced the c-DNAs corresponding to two variants of the sperm-specific protein PLII* (phi 2B). DNA sequencing in conjunction with mass spectrometry and protein sequence data have allowed us to establish that of the three sperm-specific proteins present in the sperm of Mytilus (PL-II*(phi 2B), PL-III (phi 1), PL-IV (phi 3)), the first and the last one are the result of post-translational cleavage of a common precursor. This common precursor is a member of the histone H1 family, and it exhibits inter- and intraspecific microheterogeneity.     

Chondroma of the mandibular condyle: an example of a rare tumour

Chondromas are benign tumours of cartilage which are rare in the head and neck. We present a case report of a chondroma in the neck of condyle and demonstrate the value of multiplanar spiral CT and the limitations of 3D reconstruction.