Molecular aspects of tibial dyschondoplasia in the chicken: I. Expression of calbindin-D28k gene

Tibial dyschondroplasia 40 years later

Tibial dyschondroplasia is a disease of rapid growth rate that occurs in many avian species. It is characterized by an avascular lesion in which the life span of the growth plate chondrocyte is essentially doubled. A characteristic pattern of gene expression and gene product localization has emerged that mimics the pattern observed with endoplasmic reticulum (ER) stress in growth plate chondrocytes. This activates a cell-survival mechanism called autophagy. The initial phases of this mechanism appear to originate in the avascular transition zone of the growth plate. Because specific genes and gene products are associated with autophagy and ER stress, it should now be possible to identify the mechanisms involved in the development of this cartilage abnormality. The potential biochemical pathways responsible for initiating ER stress are discussed.

Lead in young herring gulls: paradoxical effects of exercise on tissue concentrations

Exposure to lead prenatally and early in life affects physiological, behavioral, and intellectual development in humans and other animals. The movement and storage of lead within tissues and organs and its elimination from the body influence the amounts reaching sensitive target organs such as the developing brain. In this study, young herring gulls, Larus argentatus, were used to examine the effect of mild exercise on the deposition of lead in bone, to clarify possible differences between free-ranging birds in nature and confined birds in the laboratory. Forty 2-day-old chicks were randomly assigned to one of four groups: lead treatment with and without exercise, and controls with and without exercise. Chicks in the lead treatment group received a single intraperitoneal injection of lead acetate solution (100 mg/kg); weight-matched control chicks were injected with an equal volume of isotonic saline at the same age. Chicks in the exercise groups were taken outside and encouraged to move about for 2.5 h/d; others were confined in standard cages. Chicks were sacrificed at 45 d of age and lead was analyzed by graphite furnace atomic absorption. The interaction of exercise and lead dose significantly influenced the amount of lead in the three bones examined (rib, humerus, tibiotarsus), but not in the other tissues. For the lead-treated birds, mean bone lead levels were lower in the exercised versus nonexercised birds, while the reverse was true for control chicks. The data suggest that lead storage can be partly ameliorated by exercise, that young chicks would be the most affected by lead, and that older chicks that move and have larger territories in which to move may suffer lesser effects than those in dense territories.

Discondroplasia tibial: mecanismos de lesão e controle

A discondroplasia tibial (DT) é atribuída a uma assincronia no processo de diferenciação dos condrócitos, levando à formação de uma camada de condrócitos pré-hipertróficos e de uma cartilagem na tíbia proximal que não é calcificada, mas é resistente à invasão vascular. Além disso, tem sido proposto que, na discondroplasia tíbial, a etapa final do processo de calcificação não ocorre devido ao fato de que os efetores de alguns genes, relacionados com o mecanismo de calcificação do disco de crescimento podem apresentar algumas de suas propriedades químicas ou biológicas alteradas e/ou não serem expressos. Nesse sentido, a compreensão do mecanismo de ação e o papel das biomoléculas e dos minerais relacionados com a discondroplasia tibial poderão contribuir para o conhecimento de doenças do tecido ósseo e estabelecer estratégias de prevenção e tratamento.