Effects of sera from scalded rats on epithelial liver cells in vitro

Visualizing the expression of a human growth hormone (hGH) transgene in the liver: intrahepatic regional and intracellular differences of expression are associated with morphological alterations and hepatocellular proliferation

Growth hormone acts directly on liver cells; it binds to its receptor and induces a multitude of intracellular events leading, for example, to the production of insulin-like growth factor-1 (IGF-1). While much is known about the biochemical side of these events, their structural correlates are less well examined. Here, we examined livers of transgenic mice (TM) expressing human GH, in an attempt to correlate at the cellular level the site of GH gene expression with effects on morphology and mitotic behavior of liver cells within the hepatic architecture. Using in situ hybridization histochemistry we observed a striking expression pattern of the hGH gene in hepatocytes near the periportal spaces. In the same regions, the hGH protein, but no IGF-1 immunoreactive product, was detected using immunohistochemical methods. In the sections of TM livers, 6.8-31.9% of cells were hGH-immunoreactive. However, the cellular hGH staining pattern was not homogeneously distributed in the immunoreactive cells. Two main patterns became obvious. In the majority of the immunoreactive cells a cytoplasmic stain was present. These cells exhibited normal liver cell features and were not enlarged (type I). In the other group (type II), the staining was stronger and concentrated, sometimes punctuate, and often confined to cytoplasmic compartments which were in a perinuclear position. The latter staining pattern was generally seen in morphologically altered cells, which were enlarged and possessed intranuclear inclusions and invaginations. In the the periportal regions, mitotically active hepatocytes were evident, but these cells, as judged from immunocytochemistry, apparently did not express the transgene. In conclusion, different staining patterns for hGH may indicate different levels of transgene expression, which could be associated with difficulties in the cells with regard processing and/or secreting the hormone. In addition to the endocrine actions implied by the high hGH levels in the peripheral circulation of these TM, intracrine actions are also suggested (type II staining pattern), but para- and autocrine loops are possible as well (type I staining pattern). Whether IGF-1 is involved, and the mechanism underlying hepatocyte cell proliferation, remain to be examined.

Acute effects of rat growth hormone (GH), human GH and prolactin on proliferating rat liver cells in vitro: a study of mitotic behaviour and ultrastructural alterations

Examination of livers from transgenic mice over expressing human growth hormone (hGH) revealed numerous alterations including a striking incidence of mitotic figures. The reason for increased proliferation is unclear, but could be related to effects of hGH, which is also acting as a lactogen in rodents. In order to identify some of the actions of GH, we have examined the effects of rat and human GH and rat prolactin on proliferation, as well as on morphological differentiation of normal rat liver cells in vitro. These cells, isolated from a 20-day-old rat, proliferate in culture, incorporate BrdU and are thus strikingly different from primary cultures of isolated hepatocytes, which typically are non-proliferating cells. Monolayers of these cells were treated with rat prolactin (rPRL), rat growth hormone (rGH), rPRL and rGH in combination, or hGH, for 24 hr. Subsequently, mitotic figures were counted and the cultures were processed for transmission electron microscopy. The incidence of mitotic figures was significantly increased by rPRL (27.4%) versus control (19%), while rGH (13%) and hGH (9.6%) significantly decreased proliferation. In controls, 2% of the proliferating cells were in prophase, approximately 12% in metaphase and approximately 15% in telophase. In contrast, rPRL caused a significant increase in the number of cells in prophase (14%) and reduced the number of cells in the other mitotic stages. hGH and rGH reduced the overall number of mitotic figures. Unexpectedly, the effects of rGH plus rPRL were different from the effect of hGH. In addition, each treatment caused distinct morphological changes of liver cell organelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of human growth hormone on liver cells in vitro: a comparison with livers of mice transgenic for human growth hormone

We have examined the effects of human growth hormone (hGH), in concentrations comparable to those measured in plasma of transgenic mice expressing foreign GHs, on rat liver cells in culture. This treatment produced, within 24 and 48 hr, extreme heterogeneity in liver cell size, enlargement of nuclei, increase in the numbers of large nucleoli and nuclear protrusions, as well as appearance of numerous lipid droplets and accumulation of glycogen. These changes most likely indicate massive metabolic alterations and resemble changes present in vivo in the livers of mice transgenic for hGH and other foreign GHs. Since morphological alterations in vitro were apparent within 24 hr, we conclude that GH acutely and directly affects liver cell morphology and function in vitro and that the pathological lesions in vivo in the livers of transgenic mice are very likely a consequence of GH action.

The decay of autoradiographic grain number over crypt base columnar cells in murine ileum as a measure of their generation time

The decay in the number of grains over [3H]-thymidine labelled crypt base columnar cells (BCC) in autoradiographs of the ileum of BDF1 mice has been studied. The results revealed that using the conventional grain count halving (GCH) method it is possible to obtain an estimation of the generation time (Tc) of the proliferative BCC cells in the Paneth cell zone (PC-zone) of 18.8 +/- 0.74 h. This lies within the range obtained by the percent labelled mitoses (PLM) method, but is shorter than most values obtained by stathmokinetic methods. The present data show no evidence for a shortening of the cell cycle 3 days after irradiation (8 Gy) which is contrary to some earlier observations. Some reasons for this discrepancy are discussed. The comparatively high labelling index of the BCC allows a larger amount of data to be easily collected, compared with the PLM technique, and correction factors which take into account the complicated shape of the bottom of the crypt are not required.

Vertical sections of cultivated anchorage-dependent cells for electron microscopy

A method is described for electron microscopic preparation of cultivated cells for vertical sections using the test chamber system TCSC-1. The cells are cultivated on a special foil. They can be fixed and embedded directly in the chamber. After polymerization of the resin, the foil can be easily taken off and a second resin layer is poured upon the embedded cells. Then distinct cells can be marked under an inverted light microscope. The bilayer of the resin allows optimal conditions for vertical sections of anchorage-dependent cells.