Estereologia do miocárdio em fetos humanos: estudo quantitativo das modificaçöes estruturais nos dois últimos trimestres de gestaçäo / Stereology of the Myocardium in Human Fetuses: Quantitative Study of the Structural Changes in the Last Two Trimesters of Gestation

RESUMO

Objetivo - Quantificar o miocárdio humano comparando o 2§ e 3§ trimestres gestacionais. Métodos - Fragmentos de miocárdio de 8 coraçöes de fetos humanos (sendo 4 do 2§ e 4 do 3§ trimestre) foram coletados e processados histologicamente. Quinze campos miocárdicos aleatórios de cada coraçäo foram quantificados para miócitos, tecido conjuntivo e vasos contando pontos-teste e intersecçöes . Resultados - As diferenças esterológicas para os miócitos, vasos e tecido conjuntivo, näo foram significantes comparando os 2 trimestres (p > 0,05). A densidade volumétrica foi miócitos (núcleos inclusive) = 75,6// no 2§ trimestre e 67,7// no 3§ trimestre; vasos = 3,7// no 2§ trimestre e 6,4// no 3§ trimestre; tecido conjuntivo (substância intersticial excluindo os vasos) de 20,6 a 25,9// do 2§ para o 3§ trimestres, respectivamente. Entretanto, a diferença das densidades volumétricas dos núcleos dos miócitos foi significante (p=0,004) e indicou reduçäo do 2§ para o 3§ trimestres, de 15,2 para 8,1// respectivamente. Conclusäo - Esses resultados sugerem que há reduçäo gradativa da síntese protéica nos 2 últimos trimestres gestacionais, sem alteraçäo quantitativa importante na composiçäo do tecido cardíaco, provavelmente relacionada à simultânea diminuiçäo da multiplicaçäo celular miocárdica

ABSTRACT

Purpose - Quantitative study of the human myocardial comparing the2nd and 3rd trimesters of gestation. Methods - Fragments of the myocardium were collected from 8 fetal human hearts (4 from 2nd and 4 from 3rd trimesters) and prepared by histological methods. Fifteen random fields from each region were analyzed considering independently myocytes, connective tissue and vessels. Stereological determinations were possible by counting test-points and intersections on a multipurpose test lattice (M42). Results - Stereological differences between last 2 trimesters of gestation were not significant (p>0,05). The volume density was myocyte (including nucleus)=75.6% in 2nd trimester and 67.7% in 3rd trimester; vessels=3.7% in 2nd trimester and 6.4% in 3rd trimester; connective tissue (interstitial substance without vessels) = 20.6 to 25.9% for 2nd and 3rd trimesters respectively. However, considering the nuclei of the myocytes differences between last 2 trimesters were significant (p=0.004). The volume density of the nuclei had a reduction from 2nd to 3rd trimesters (from 15.2 to 8.1% respectively). Conclusion - This result suggests decreasing synthesis of proteins from nucleus of myocyte in the last 2 gestational trimesters, but without quantitative important changes in the cardiac tissue, probably in relation to the reduction of the myocardial cellular multiplication