Tooth morphology, implantation and replacement system of Hoplias malabaricus (Teleostei, Characiformes, Erythrinidae) / Morfologia, implantação e sistema de substituição dentária do Hoplias malabaricus (Teleostei, Characiformes, Erythrinidae)

The oropharyngeal cavity of Hoplias malabaricus, an ichthyophagous freshwater fish, is anatomically adapted to predation. Macroscopic and microscopic analyses were conducted in order to study the morphology and system of implantation and replacement of teeth. The results showed that this teleost has conical and caniniform teeth, with an orthodentin crown covered by an enameloid cap and a vascularised orthodentin in the root. With regard to the implantation system, there is a junction between the tooth and the bone tissue, as a typical physiological dental ankylosis. The teeth are replaced by a resorption process of multinucleated giant cells that actively eliminate the dentin and bone tissue.

A cavidade orofaríngea do Hoplias malabaricus, um peixe de água doce ictiófago, é anatomicamente adaptado à predação. Análises macroscópica e microscópica foram realizadas com o objetivo de estudar a morfologia e o sistema de implantação e substituição dentária. Os resultados mostraram que este teleósteo apresenta dentes cônicos e caniniformes, com coroa de ortodentina coberta por capuz enamelóide e ortodentina vascularizada na raiz. Em relação ao Sistema de implantação, existe uma junção entre o dente e o tecido ósseo, semelhante a uma anquilose dentária fisiológica típica. Os dentes são substituídos por um processo de reabsorção por células gigantes multinucleadas que ativamente eliminam a dentina e o tecido ósseo.

Tooth morphology, implantation and replacement system of Hoplias malabaricus (Teleostei, Characiformes, Erythrinidae).

The oropharyngeal cavity of Hoplias malabaricus, an ichthyophagous freshwater fish, is anatomically adapted to predation. Macroscopic and microscopic analyses were conducted in order to study the morphology and system of implantation and replacement of teeth. The results showed that this teleost has conical and caniniform teeth, with an orthodentin crown covered by an enameloid cap and a vascularised orthodentin in the root. With regard to the implantation system, there is a junction between the tooth and the bone tissue, as a typical physiological dental ankylosis. The teeth are replaced by a resorption process of multinucleated giant cells that actively eliminate the dentin and bone tissue.

Allometric analysis of the postnatal development of the Syrian golden hamster pancreas.

The objective of the present study was to analyse allometrically the growth of the Syrian golden hamster pancreas during days 2 to 70 of postnatal development. Body and pancreatic mass were determined, followed by stereological determination of the absolute volume of each morphological compartment of the pancreas. The marked pancreatic growth, by 4360%, was due to an increase in the absolute volume of all morphological compartments, mainly the acini which showed an increase of 10 431%. Bivariate allometric analysis of pancreatic mass and morphological compartmental volume in relation to body mass gain showed: (1) a biphasic pattern for pancreatic mass, acinar volume, excretory duct volume and stromal volume, with the first phase being observed from 2 to 21 days of age and the second from 21 to 70 days of age, with allometry coefficients of 1.537-0.513, 1.770-0.543, 1.651-0.506 and 0.967-0.258, respectively, and (2) a monophasic pattern from 2 to 70 days for intercalated duct volume and islet volume, with allometry coefficients of 0.913 and 1.727, respectively. These results show that during the growth of the pancreas in relation to that of the body some structures - acini and excretory ducts - follow the growth pattern of the organ, while others - intercalated ducts and islets - show a different pattern. This may be related to the genetic growth characteristics of each compartment itself or to some relationship between compartments during some stage of the ontogenetic development of this organ.

Morphometric and allometric study of the mouse exocrine pancreas growth during the postnatal life.

Postnatal mouse pancreas growth was submitted to allometric analysis by the Wald nonparametric method, modified by Bartlett. The body and gland mass were obtained and the total cell number and the absolute compartmental volumes of acini, ducts and stroma were evaluated by morphometric methods. The allometric coefficients were calculated for the growths between the following parameters: a) pancreatic mass and body mass; b) acinar compartmental volume and body mass; c) ductal compartmental volume and body mass; d) stroma volume and body mass; e) total cell number and body mass; and f) acinar volume and stroma volume. The results of these analysis showed that the pancreatic mass, total cell number and stroma volume exhibited statistically significant allometric growths with a monophasic pattern and allometric coefficients of 1.56, 1.27 and 1.29, respectively, for the periods of 2 to 70, 2 to 28 and 2 to 70 days of age; while the growth of compartmental acinar volume in relation to body mass and compartmental stroma volume was biphasic. In the first case, the 1st phase occurred between 2 to 14 days (K = 1.09) and the 2nd phase between 14 to 70 days (K = 1.44) and in the second case, the 1st and 2nd phases occurred, respectively, between 2 to 28 days (K = 1.31) and 28 to 70 days (K = 0.79) of age. The growth of ductal volume in relation to body mass was also biphasic with a 1st phase between 2 to 14 days (K = 0.88) and a 2nd phase between 14 to 70 days (K = 1.07). These results permitted us to conclude that the growth of the mouse pancreas is allometrically associated with the growth of body mass.