[Structure and ultrastructure of osteoblasts and of the osteoid tissue in Paget's disease of bone (author's transl)]. / Structure et ultrastructure des ostéoblastes et du tissu ostéoïde dans la maladie osseuse de Paget.

Light and electron microscope studies of 64 biopsies from patients with Paget's bone disease reveal the structure of osteoblasts and osteoid tissue. The osteoblasts observed do not differ morphologically from those described in other bone diseases and the woven bone shows no specificity. These cells are possibly hyperactive and our observations show that such hyperactivity may be consequent to the increased and disorganized resorption of lamellar bone tissue by osteoclasts which are known to be abnormal. Osteoblasts do not appear to play any direct role in the pathogenesis of Paget's bone disease.

[Ultrastructural study of a case of monostotic fibrous dysplasia]. / Etude ultrastructurale d'in cas de dysplasie fibreuse monostotique.

Ultrastructural study of a case of fibrous dysplasia taken together with the rare data in the literature confirmed that the morphological characteristics of this lesion consist of a typical appearance of "woven bone", irregularly mineralised, containing osteocytes and bordered by osteoblasts, clearly distinct from fibroblasts. The cell elements are invariably endowed with a large microbrillary cytoplasmic brush, apparently made up of scleroproteins and showing the usual ultrastructural characteristics associated with low metabolic activity. The presence of myofibroblasts is unlikely. The numerous mastocytes seen by light microscopy show a large number of "rosette" granulation at electrom microscopy, which distinguishes them from the mastocytes seen in osseous modelling. These morphological data provide no decisive argument in favour of the truly dysplasic nature of this lesion.

[Action of calcitonin on osteoclasts in Paget's bone disease during long term treatment (author's transl)]. / Action de la calcitonine sur les ostéoclastes de la maladie de Paget au cours d'un tr,itement de longue durée.

Comparison of biopsies from patients with Paget's bone disease before and during long-term treatment with calcitonin reveals that the ration of bone-adherent osteoclasts to free osteoclasts is not modified by the hormone. Nor does treatment alter the average number of nuclei in osteoclasts. Under electron microscopy, all the cytological anomalies of osteoclasts in Paget's bone disease and, in particular, the characteristic nuclear inclusions, persist through treatment. Thus, although such osteoclasts do react to calcitonin as demonstrated by several authors, the specific morphological anomalies remain unaffected by the treatment. It is likely that the osteoclast in Paget's bone disease is an abnormal cell with peculiarities which may be related to the yet unknown etiology of the disease.