Ultrastructural morphometric study on developing acinar cells of the rat pancreas and parotid gland

Abstract

The fraction of cellular volume occupied by the cytoplasm has been assessed by point-counting volumetry in 0.5-μm araldite sections. Measurement of the transection radius of the nuclei of acinar cells allowed the assessment of the mean nuclear volume according to the method of Bach. With these data, the cytoplasm volume was calculated in cubic micrometers. Ultrastructural morphometric data were obtained by means of superimposing on the electron photomicrographies (× 21,000 or × 28,500) a test system of 84 evenly spaced segments according to Weibel et al. The analysis of the values obtained for the pancreas and parotid gland allowed for the supposition that the process of maturation in the rat, either for the pancreas or the parotid gland, occurs simultaneously with the mitotic process, this last being held as the predominating one in the first 3–4 postnatal weeks. The cytodifferentiation process becomes more marked in the last phases studied and on the 40th day it already shows parameters held as similar to those of the adult animal.

Ultrastructural Studies on Developing Parotid Gland of the Rat at Early Postnatal Periods

“…During this period the relative rise in cell size and thereby in the quantity of cytoplasmic organelles is the highest of all ontogenetic development. FERRAZ DE CARVALHO et al (1978) showed morphometrically that between days 10-40 the total surface of the rough endoplasmic BIGNARDI (1961) studying histochemically the early postnatal evolution of the rat parotid gland observed in 5-day-old rats another cell type containing clear secretory granules exhibiting PAS and Alcian blue positive materials. These observations were confirmed by LAWSON (1970) in rats of 3-4 days of age.…”

Developmental change of Ca2+-ATPase activity on plasma membrane of rat pancreas during perinatal period.

“…Although no strong evidence has been available to indicate the direct relationship of this ATPase activity to plasma membrane Ca2+-flux, in the present study the cytochemical demonstration of the perinatal change of Ca2+-ATPase activity strongly suggests that the association of this activity with the pancreatic exocrine secretory function. By many morphological and biochemical studies (5,9,11,16,25,26,30,33,39,40), it has been shown that secretory function in rat pancreas starts just after birth and increasingly develops till weaning period (ca. 20 days old).…”

“…The developmental change of rat pancreatic exocrine cells has been extensively studied by both biochemical (11,25,27,30,34) and morphological approaches (5,21,25,26,33,39). Term fetal rats (22 day gestation) have fully developed morphological feature of pancreatic exocrine cells (5,21,25,26,33,39), and intracellular synthesis of secretory enzymes such as amylase, chymotrypsinogen, trypsinogen and lipase is almost at adult level (11,25,27,30,34).…”

“…Term fetal rats (22 day gestation) have fully developed morphological feature of pancreatic exocrine cells (5,21,25,26,33,39), and intracellular synthesis of secretory enzymes such as amylase, chymotrypsinogen, trypsinogen and lipase is almost at adult level (11,25,27,30,34). However, it seems that the secretory function of exocrine cells is still immature at the time of birth.…”

Exocrine glands and protein secretion: a stereological viewpoint

“…Doubling times of 4.7 to 4.9 days for each cell type were similar to estimates derived from labelling indices and confirmed that acinar cell increase did not occur at the expense of ductal elements. In a study of the development of the rat pancreas and parotid from 17 days in titer0 to 40 days post partum Ferraz de Carvalho et al (1978) showed that cytoplasmic volume in the pancreatic acinar cell trebled in this period. From birth the cells mainly got larger without major changes in the volume proportions of the organelles, except for secretion granules which increased.…”