Biomedical subjects

L Donnan

Publications and source records attributed to L Donnan.

4 recordsLinked to original sources

PubMed1997

Bone biology.

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite and amorphous calcium phosphate crystals deposited in an organic matrix. Bone has two main functions. It forms a rigid skeleton and has a central role in calcium and phosphate homeostasis. Bone modelling is the process associated with growth and re-shaping of bones in childhood and adolescence. This is distinguished from bone remodelling, which describes the lifelong process whereby skeletal tissue is continually being resorbed and replaced in order to maintain skeletal integrity, shape and mass. Bone remodelling is controlled by systemic hormones and cytokines and is an integral part of the calcium homeostatic system. The maintenance of a normal, healthy skeletal mass depends on interactions between osteoblasts, osteoclasts and constituents of the bone matrix to keep the process of bone resorption and formation in balance. The factors, local and systemic, which regulate these processes are discussed.

Animals↗

PubMed1996

Idiopathic chondrolysis of the hip.

A case of idiopathic chondrolysis of the hip is described in a 12 year old female who has the characteristics of arthroophthalmopathy (Stickler's syndrome). This common connective tissue dysplasia may go unrecognized and is possibly an aetiological factor in the development of this disease process. A review of the literature is presented.

Cartilage Diseases↗

PubMedDate not supplied

Cell cycle control by timer and sizer in Chlamydomonas.

Conservation of cell cycle control mechanisms is indicated by the presence of functionally homologous division control genes in unrelated yeasts and by the nonspecific action of oncogenes, but it remains uncertain what property of a growing cell results in the initiation of events leading to division. Response to a critical size is indicated by the longer growth period of smaller cells prior to division, which is consistent with deferment of division events until a minimum size is attained; however, in the same cell types faster growing cells are larger and this is more easily explained if division follows a timed period during which faster growing cells grow more, as is postulated for mammalian cells. Therefore, either time- or size-dependent controls might be the sole significant mechanism; we report here, however, that both controls do function in Chlamydomonas since cycle duration is under timer control and cell size determines the number of division rounds committed at the end of each cycle, and hence whether 2, 4, 8 or 16 daughter cells are formed.

Biological Clocks↗

PubMedDate not supplied

Posterior dislocation of the humeral head in association with obstetric paralysis.

Twelve children with obstetric paralysis were diagnosed as having a posterior dislocation of the humeral head. The diagnosis was suspected on clinical grounds and confirmed by computed tomography (CT) scans in all cases. All 12 patients were treated with open reduction via an anterior approach. The age range at the time of surgery was from 7 months to 7 years (average, 2 years and 3 months). All patients were immobilized in a shoulder spica for 6 weeks and a further 6 weeks in an orthosis. All patients were examined by CT scans in the postoperative period, which confirmed a satisfactory reduction in all cases. With a minimal follow-up of 12 months, there have been no redislocations. This article demonstrates that dislocation of the shoulder in association with obstetric paralysis is not rare, as previously described, and shows that once diagnosed, the dislocation can be satisfactorily treated by a single anterior open reduction of the shoulder.

Child↗