The ultrastructure of the liver parenchyma of the immature fowl (Gallus domesticus)

Exoerythrocytic development of Plasmodium gallinaceum in the White Leghorn chicken

Plasmodium gallinaceum typically causes sub-clinical disease with low mortality in its primary host, the Indian jungle fowl Gallus sonnerati. Domestic chickens of European origin, however, are highly susceptible to this avian malaria parasite. Here we describe the development of P. gallinaceum in young White Leghorn chicks with emphasis on the primary exoerythrocytic phase of the infection. Using various regimens for infection, we found that P. gallinaceum induced a transient primary exoerythrocytic infection followed by a fulminant lethal erythrocytic phase. Prerequisite for the appearance of secondary exoerythrocytic stages was the development of a certain level of parasitaemia. Once established, secondary exoerythrocytic stages could be propagated from bird to bird for several generations without causing fatalities. Infected brains contained large secondary exoerythrocytic stages in capillary endothelia, while in the liver primary and secondary erythrocytic stages developed primarily in Kupffer cells and remained smaller. At later stages, livers exhibited focal hepatocyte necrosis, Kupffer cell hyperplasia, stellate cell proliferation, inflammatory cell infiltration and granuloma formation. Because P. gallinaceum selectively infected Kupffer cells in the liver and caused a histopathology strikingly similar to mammalian species, this avian Plasmodium species represents an evolutionarily closely related model for studies on the hepatic phase of mammalian malaria.

Ultrastructure of in situ perfusion-fixed avian liver, with special reference to structure of the sinusoids

Broiler chicken and laying hen livers were fixed using a simple technique of in situ puncture perfusion of cacodylate-buffered fixative, which allowed characterisation of the fine structure of hepatic parenchyma, hepatocytes, bile ductules, and, in particular, the sinusoidal cells including endothelial, Kupffer, and Ito cells. Sinusoidal endothelial cells with their bulging perinuclear cytoplasm, evident in both transmission and scanning electron micrographs, were easily distinguishable from Kupffer cells, which possessed numerous pseudopodia. Bile ductular epithelium and hepatocytes of the laying hens contained large amounts of lipid. The ultrastructural characteristics of intercalated cells (putative extra-sinusoidal macrophages of chicken liver) are described and their possible role as precursors of Kupffer cells is discussed.

Development of the liver in the chicken embryo. I. Hepatic cords and sinusoids

Hemopoiesis in the liver of the chicken embryo begins on day 7 of incubation (Hamburger and Hamilton Stage 30) and peaks on day 14 (Stage 40). During this time frame, the differentiation of hepatic cells was examined by light microscopy, transmission and scanning electron microscopy, and morphometry. The avian liver is a closely packed mass of dendriform cords and discontinuous sinusoids. Hepatocytes are pyramidal in shape, and they ring the bile canaliculi which run through the centers of the cords. Semithin sections, made possible by infiltration and embedding in glycol methacrylate, were stained with hematoxylin and eosin to assess the general architecture of the organ and the lipid content of the hepatocytes and by the periodic acid-Schiff reaction and hematoxylin to visualize the cytoplasmic stores of glycogen. The number of hepatocytes with demonstrable glycogen fluctuates erratically in early hemopoiesis, and the proportion of glycogen-containing cells progressively increases as hemopoiesis climbs to a peak. Most differentiating hepatocytes are devoid of lipid droplets until Stages 39 and 40. From Stage 30 to 35, hepatocyte volume falls to its lowest value. Subsequently (Stages 36 to 40), cell volume increases and hepatocytes achieve a relatively uniform size. Ultrastructural changes in the differentiating hepatocytes, including alterations to the mitochondria, endoplasmic reticulum, and Golgi apparatus, are documented. These morphological and morphometric findings on the prehepatocyte population and hepatic vasculature cover 2 of the 3 elements deemed critical to hepatic hemopoiesis in many vertebrates.

Ultrastructure of turkey hepatocytes

Hepatocytes of normal male and female turkey livers perfused in situ with a fixative containing 4% glutaraldehyde in 0.05 M phosphate buffer (pH 7.4) were examined by electron microscopy. The hepatocytes, arranged in two-cell-layered plates, were polygonal and had three spatially different surfaces. The vascular surface was formed by microvilli, which at times projected into the sinusoids past the space of Disse. The interhepatocytic surfaces were closely applied and contained an occasional gap junction. The biliary surface participated in bile canaliculus formation and had short, regular microvilli. Tight junctions and adherens junctions were close to the canalicular lumen. The hepatocyte nucleus was located towards the vascular pole. The cytoplasm of hepatocytes of the females had many lipid droplets. The pleomorphic mitochondria, with relatively electron dense matrices were surrounded by one or, rarely, two profiles of flattened rER. Golgi complex was often observed in the vicinity of the nucleus, whereas the centrioles were located in the pericanalicular area of the biliary pole, which was rich in microtubules. These microtubules were extremely long, at times covering a substantial distance between the Golgi complex and bile canaliculi; microtubules occasionally formed bundles near the biliary pole. Small vesicles in close proximity of the microtubules were frequently observed. The spatial relationship between Golgi complex, microtubules, vesicles, and centrioles at the biliary pole of the hepatocyte appears to support the concept that the bile secretory mechanism in avian hepatocytes may involve a centrioles-microtubules-vesicles-Golgi complex system.

Studies on the liver of Xenopus laevis. I. The ultrastructure of the parenchymal cell

The liver of Xenopus laevis was examined with electron microscopy. Its structure was found to be markedly different from that of mammals, particularly regarding the morphology of the hepatocytes to be classified as typical. It was established that the main function of such a cell is the storage of glycogen, and further that it possesses only scant organelles and other inclusions. Since this type of cell was found most frequently in the liver of untreated animals, it was designated as normal cell. The fact appears noteworthy that in the normal liver of Xenopus laevis an abundance of cell types occur which are otherwise found to be proliferated under experimental conditions, e.g. cells with pronouncedly augmented RER, enlarged Golgi complexes, increased lipid inclusions etc. This high number of divergent hepatocytes and the fact that all intermediate stages between the individual extremes are present and not to be accounted for by the position of the cell within the liver was interpreted as being the expression of a cyclic passage of the various stages of activity. It is of special interest that augmented degradation of glycogen in the liver cell takes place only during vitellogenesis. Acute and chronic hunger, as well as adaptation to cold, hardly affect the morphology of the normal cell, especially as far as the glycogen is concerned. The possible causes for this are discussed.

The liver parenchyma and foreign compound metabolism in red-winged blackbird compared with rat

1. Aniline p-hydroxylase, aminopyrine N-demethylase, and p-nitroanisole O-demethylase activities were measured in liver microsomes prepared from the red-winged blackbird (Agelaius phoeniceus) and compared with analogous preparations from rat. All had lower activities in birds than in rats, when expressed in terms of microsomal protein. 2. Hepatic parenchyma of the bird was observed by electron microscopy to contain less endoplasmic reticulum than that of rat. This morphological difference may partially explain the species difference in enzyme activities. 3. Cytochrome P-450 levels were not sex-dependent in the red-winged blackbird, unlike rat, but the opposite was true for the rate of hydroxylation of aniline. 4. There was no species difference in the activity of aniline p-hydroxylase when expressed in terms of activities per unit of cytochrome P-450, but the activity of p-nitroanisole O-demethylase was higher in red-winged blackbird than in rat; the reverse may be true for the activity of aminopyrin N-demethylase.