Study of mandibular head volume in rats submitted to occlusal alterations.

The possible alterations caused by occlusal modifications in mandibular head volume were studied in rats by morphometric techniques. The results permitted the authors to conclude that, within the conditions of the experiments, the total volume of the mandibular head was unchanged, although alterations in the direction of growth may occur.

Morphometric study of the mandibular condyle of the rat during postnatal development.

A morphometric technique for the use of the temporomandibular joint (TMJ) of the rat as an experimental model was developed to study TMJ growth from birth to 120 days of age. Experimental conditions for the reduction and embedding of the specimen, as well as for data collection were standardized. Morphometric data were obtained from projected drawings and the areas occupied by the various structures were determined by counting points with a specially constructed integration grid. The areas occupied by the layers making up the mandibular condyle remained relatively constant, forming an architectural pattern from the 30th postnatal day on. Between the 10th and 30th day they underwent modifications interpreted to be functional adaptations conditioned by changes in the animal's feeding habits.

Relative growth of the condylar cartilage of the rat mandibular head during postnatal life.

In a study using morphometric techniques, the changes in area undergone by the various constituting layers of the condylar cartilage of the mandibular head of normal rats were examined, the cell/cartilage matrix ratios were determined, and the relative growth of the various cartilage layers was analyzed during postnatal life. The approximate 15% decrease of the cell contingent, the approximate 48% increase in cartilage matrix, the abrupt changes in the descriptive curve around the 15th to 20th d of postnatal life and the analysis of the relative growth pattern of the fibrous, embryogenic, cartilage, and hypertrophic cartilage layers were related to the functional adaptations which regulate the growth of the mandible condyle by a direct or indirect action on the temporal-mandibular articulation system.

Distribution of A, B, and mixed pancreatic islets in two bird species (Anas platyrhincus Gallus gallus, Linné, 1758)--a morphometric study.

The structural configuration of the duck and chicken pancreas was studied using a morphometric technique and 3 different sampling types. The distribution and percentage of the various types of pancreatic islets are reported. Contrary to reports by other investigators, a larger proportion of type A islets was observed in each of the pancreatic lobes, and the established conclusion that A cells are present only in the splenic portion of the organ was not confirmed.