Allometric relationships among body mass, MUZZLE-tail length, and tibia length during the growth of Wistar rats1

Abstract

PURPOSE:To investigate allometric relationships among body mass (BM), muzzle-tail length (MTL), and tibia length (TL) in Wistar rats and establish their growth rate change parameters. METHODS:Eighteen male and 18 female Wistar rats were studied from the 3rd to the 21st week of age. BM, MTL, and TL were measured daily, and relative growth was compared using allometry. RESULTS:A positive correlation between BM and MTL (p<0.05) and BM and TL (p<0.05) was observed. Males and females showed comparable curves; however, females had turning points at a younger age. The allometric relationship between BM and MTL presented a regular increase until reaching a mass of 351 g (males) and 405 g (females). BM and TL showed an initial increase until 185 g (males)and 182 g (females), and then reached a plateau that finished at 412 g (males) and 334 g (females), to display another increase. CONCLUSIONS:The allometric relationship of body mass with animal length and tibia length was comparable for male and female rats, with female rats maturing earlier. Animal longitudinal growth occurred in a single stage. In contrast, tibia length depicted two stages of accelerated growth with an intermediate period of deceleration.

Experimental proof that multivariate patterns among muscle attachments (entheses) can reflect repetitive muscle use

“…This interpretation is supported by the very similar PC2 scores of the left and right sides of most individuals, and especially the control specimens (both limbs unstimulated). This is consistent with the significant correlation found between PC2 scores and tibial length (Table 1), which is directly correlated with body mass in Wistar rats 28 . Two of the stimulated rats (individuals 2 and 4), showed considerable bilateral asymmetry on PC2, suggesting that other, multi-etiological, factors contributed to entheseal variability.…”

“…We then computed Pearson’s correlation coefficients, to test for the strength of association between each of the first two PCs and the volume of the muscle tibialis anterior (mm 3 ), tibial anterior cortical thickness (mm), and tibial maximum length (measured directly on the 3D models in mm) as a proxy for individual body size 28 . Three measurements of anterior cortical thickness were used, representing three distinct regions of the tibia, relying on the data published by Vickerton et al .…”

Undernutrition impairs the quality of growth plate and trabecular and cortical bones in growing rats

“…Our overall results show that undernutrition causes a harmful impact in weight increase and long bone growth. In our experiment the animals were followed up to 13 weeks of age but were still growing when they were euthanized 20 . Therefore, our results do not permit extrapolation of data to the end of the skeletal maturity, nor if these changes are reversible because we did not introduced a normal diet to the undernourished rats.…”

Efeitos da restrição alimentar sobre a cartilagem de crescimento e no tecido ósseo em tíbias de ratos

“…altamente resistente a condições adversas. Além de gerar custo relativamente baixo, apresentar um padrão de crescimento bem conhecido e bastante homogêneo, além da facilidade de manuseio(58,59). (redução da força máxima e rigidez), ou seja, as conexões entre o disco epifisário e a metáfise tornaram-se mais tênues ao cisalhamento e, provavelmente a outras forças que atuam no local como compressão, tração e envergamento.…”