Secretory pathway of vitellogenesis in the liver of the cockerel as revealed by immuno-gold and computer-assisted digitization techniques

The hepatocytes of the brown trout (Salmo trutta fario): a stereological study of some cytoplasmic components with the breeding cycle

Sex differences exist in fish hepatocytes, but studies for characterizing their cytology throughout the breeding cycle are still scarce; suggesting changes, but most lacking quantitative data. To address this limitation, to complement baseline data generated from the brown trout model, and to prove that sex-specific seasonal changes exist, we made an unbiased stereological evaluation of the hepatocytic cytoplasm. Unprecedentedly for fish liver, the stereological design was exempt from model (biased) assumptions. Five (3 years old) animals per sex were studied in endogenous vitellogenesis, exogenous vitellogenesis, and spawning season end. Liver pieces for analysis were systematically sampled. Stereology was done in transmission electron microscopy (TEM) micrographs. Primary data generated relative volume estimates of the major cytoplasmic components. Such values were used for deriving absolute volumes (per cell and per liver). Lipid droplets did not show changes. As to other targets, trends at cell and liver levels were not always equal. If the hepatocyte was the reference space, the contents in mitochondria, dense bodies, glycogen, and cytosol changed seasonally, in both sexes. If taking the liver as the reference, changes attained the Golgi apparatus and rough endoplasmic reticulum (RER), besides dense bodies, glycogen (in females), and cytosol. The components volumes (namely per liver) were often positively (negatively for glycogen) correlated with the ovary weight, disclosing new associations and implications in fish. While also offering gold-standard data for backing morphofunctional correlations and pathology, we revealed a new process by which females increase the amount of RER and Golgi throughout vitellogenesis, breaking from the idea on how this event happens in fish.

Vitellogenin precursors in the liver of the oviparous lizard, Podarcis sicula

In reptiles, as in the other oviparous vertebrates, vitellogenin (VTG) synthesis is stimulated in the liver by ovarian estrogens. In this article, the presence of VTG precursors was detected in liver subcellular fractions of the oviparous lizard, Podarcis sicula, in the reproductive period. The rough endoplasmic reticulum (RER) and the smooth microsomal fraction (SMF), which includes smooth endoplasmic reticulum and Golgi complex, were separated by means of two different sucrose gradients. The successful separation was controlled at the electron microscope. The contents of the different compartments were extracted by means of n-octyl-beta-D-glucopiranoside detergent and subjected to SDS-PAGE. Western Blotting with homologous anti/VTG antibody revealed two immunoreactive proteins of about 84 and 70 kDa in the RER, and four proteins of about 180, 150, 60, 50 kDa in the SMF; all these proteins appeared phosphorylated and glycosylated. The differences in the molecular weight of these VTG precursors are discussed.