The distribution of glutathione in the rat liver lobule.

A quantitative cytochemical method was developed for measuring the GSH (reduced glutathione) content of hepatocytes in different regions of the rat liver lobule. Use of this method enabled us to show that GSH is not evenly distributed within the rat liver lobule. The hepatocytes located within 100 micrometer of the central vein contain much less GSH than do those in other regions of the rat liver lobule. We suggest that this partially explains the peculiar susceptibility of these cells to electrophilic attack by toxic metabolites formed via the microsomal cytochrome P-450 system.     

Changes in glycan distribution within the porcine interhaemal barrier during gestation

Changing patterns of glycan distribution are described in porcine placentae at 15, 19, 26, 43, 58, 69 and 109 days gestation, using a carefully selected panel of lectins that allowed partial analysis of saccharide classes and sequences. The lectins used were from Galanthus nivalis, Pisum sativum, Phaseolus vulgaris (leukohaemagglutinin), Triticum vulgaris, Tetragonolobus purpureus, Ulex europaeus-1, Arachis hypogaea, Erythrina cristagalli, Glycine max, Maclura pomifera, Wisteria floribunda, Dolichos biflorus, Maackia amurensis, Sambucus nigra and Limax flavus. During the course of gestation the trophoblast developed from a smooth to a deeply folded membrane, while enlarging fetal and maternal capillaries grew closer to each other. The fetomaternal interface expressed many classes of saccharide, both O-and N-linked, but failed to bind DBA, MAA and SNA. Many granules were present in the maternal epithelium, and a striking feature was the appearance of staining with DBA and UEA-1 by day 43. This stage of pregnancy was also associated with changes in trophoblast glycan expression, with a diminution in staining intensity of AHA, MPA and LTA, but an increased intensity with ECA, SBA and WFA. Changes in lectin binding throughout gestation are correlated with previous ultrastructural findings and their relevance to the immunological and functional aspects of pregnancy is discussed.     

Differential distribution of B16F10 melanoma cells in the liver lobule

The distribution pattern and the number of tumor cells arrested in the liver were studied in mouse livers. Mice were perfused intravascularly with a suspension of B16F10 melanoma cells. The animals were sacrificed at 0, 1, 5, and 20 min after tumor cell perfusion. The pattern of tumor cell distribution was studied by morphological methods, and by a combined method of fluorescent-tumor cell labelling and histochemical succinate dehydrogenase activity on frozen sections, in order to define the localization of tumor cells arrested in the liver lobule. The results show that the tumor cells have an exclusive distribution in the periportal regions of the liver lobule (identified as the high succinate dehydrogenase activity areas), and that the cells are not arrested in the pericentral regions (identified as the low succinate dehydrogenase activity areas). In addition, indomethacin treatment (2 mg/kg/day) induced an increase in the number of melanoma cells arrested in the liver, but a different distribution with respect to controls was not observed. These results show that periportal regions of the liver lobule constitute a particular domain in which the B16F10 melanoma cells present a special retention ability that can be modulated by indomethacin treatment.     

Mechanism of adaptive increase of respiratory enzymes in rat liver mitochondria during obstructive jaundice

In order to elucidate the response of mitochondria to obstructive jaundice, we have examined the effects of common bile duct ligation on rat liver mitochondria. Although oxidative phosphorylation, especially respiratory control, of mitochondria was disturbed after the ligation, specific enzymic activities and subunit contents of the respiratory enzymes in mitochondria were significantly increased one week after the ligation. The immunostain for ubiquinol-cytochrome c oxidoreductase confirmed the increase in the subunit amounts in hepatocytes. This increase was associated with the increase in specific contents of DNA in mitochondria. These results suggest that mitochondrial biosynthesis is stimulated during obstructive jaundice.     

Dynamics of bacterial growth and distribution within the liver during Salmonella infection

Salmonella enterica causes severe systemic diseases in humans and animals and grows intracellularly within discrete tissue foci that become pathological lesions. Because of its lifestyle Salmonella is a superb model for studying the in vivo dynamics of bacterial distribution. Using multicolour fluorescence microscopy in the mouse typhoid model we have studied the interaction between different bacterial populations in the same host as well as the dynamic evolution of foci of infection in relation to bacterial growth and localization. We showed that the growth of Salmonella in the liver results in the spread of the microorganisms to new foci of infection rather than simply in the expansion of the initial ones. These foci were associated with independently segregating bacterial populations and with low numbers of bacteria in each infected phagocyte. Using fast-growing and slow-growing bacteria we also showed that the increase in the number of infected phagocytes parallels the net rate of bacterial growth of the microorganisms in the tissues. These findings suggest a novel mechanism underlying growth of salmonellae in vivo with important consequences for understanding mechanisms of resistance and immunity.     

Topographic distribution of dividing hepatocytes in the regenerating liver lobule in the period of maximum mitotic activity

Topographic distribution of dividing hepatocytes was studied in the liver lobule after hepatectomy performed at 10-11.30 a. m. The studies were conducted 20-32 h after surgery during the first increase in mitotic activity. It has been established that dividing hepatocytes appear simultaneously in all lobule areas, i. e. that all the hepatocytes are capable of responding to regenerating stimuli. However, further behaviour of dividing hepatocytes becomes different. It is concluded that hepatocytes from outer and intermediate lobule areas possess a more pronounced proliferative potential during peak mitotic activity after partial hepatectomy.     

Mathematical modeling of the circulation in the liver lobule

In this paper, we develop a mathematical model of blood circulation in the liver lobule. We aim to find the pressure and flux distributions within a liver lobule. We also investigate the effects of changes in pressure that occur following a resection of part of the liver, which often leads to high pressure in the portal vein. The liver can be divided into functional units called lobules. Each lobule has a hexagonal cross-section, and we assume that its longitudinal extent is large compared with its width. We consider an infinite lattice of identical lobules and study the two-dimensional flow in the hexagonal cross-sections. We model the sinusoidal space as a porous medium, with blood entering from the portal tracts (located at each of the vertices of the cross-section of the lobule) and exiting via the centrilobular vein (located in the center of the cross-section). We first develop and solve an idealized mathematical model, treating the porous medium as rigid and isotropic and blood as a Newtonian fluid. The pressure drop across the lobule and the flux of blood through the lobule are proportional to one another. In spite of its simplicity, the model gives insight into the real pressure and velocity distribution in the lobule. We then consider three modifications of the model that are designed to make it more realistic. In the first modification, we account for the fact that the sinusoids tend to be preferentially aligned in the direction of the centrilobular vein by considering an anisotropic porous medium. In the second, we account more accurately for the true behavior of the blood by using a shear-thinning model. We show that both these modifications have a small quantitative effect on the behavior but no qualitative effect. The motivation for the final modification is to understand what happens either after a partial resection of the liver or after an implantation of a liver of small size. In these cases, the pressure is observed to rise significantly, which could cause deformation of the tissue. We show that including the effects of tissue compliance in the model means that the total blood flow increases more than linearly as the pressure rises.     

Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.     

Distribution of mitoses within a lobule of the rat liver in recovery after various types of injuries]

The distribution of mitotic activity inside the rat's liver lobe was found to depend on the time that elapsed after the injury. At the early stages, the maximal quantity of mitotic figures in hepatocytes was observed along the periphery of the lobe, being less in the middle parts. At the later stages, mitotic figures were noted around the central veins. With the prolonged injury of the liver, the maximal amount of dividing hepatic cells was localized in the middle sections of the liver.     

Differential distribution of the lipoxygenase pathway enzymes within potato chloroplasts

The lipoxygenase pathway is responsible for the production of oxylipins, which are important compounds for plant defence responses. Jasmonic acid, the final product of the allene oxide synthase/allene oxide cyclase branch of the pathway, regulates wound-induced gene expression. In contrast, C6 aliphatic aldehydes produced via an alternative branch catalysed by hydroperoxide lyase, are themselves toxic to pests and pathogens. Current evidence on the subcellular localization of the lipoxygenase pathway is conflicting, and the regulation of metabolic channelling between the two branches of the pathway is largely unknown. It is shown here that while a 13-lipoxygenase (LOX H3), allene oxide synthase and allene oxide cyclase proteins accumulate upon wounding in potato, a second 13-lipoxygenase (LOX H1) and hydroperoxide lyase are present at constant levels in both non-wounded and wounded tissues. Wound-induced accumulation of the jasmonic acid biosynthetic enzymes may thus commit the lipoxygenase pathway to jasmonic acid production in damaged plants. It is shown that all enzymes of the lipoxygenase pathway differentially localize within chloroplasts, and are largely found associated to thylakoid membranes. This differential localization is consistently observed using confocal microscopy of GFP-tagged proteins, chloroplast fractionation, and western blotting, and immunodetection by electron microscopy. While LOX H1 and LOX H3 are localized both in stroma and thylakoids, both allene oxide synthase and hydroperoxide lyase protein localize almost exclusively to thylakoids and are strongly bound to membranes. Allene oxide cyclase is weakly associated with the thylakoid membrane and is also detected in the stroma. Moreover, allene oxide synthase and hydroperoxide lyase are differentially distributed in thylakoids, with hydroperoxide lyase localized almost exclusively to the stromal part, thus closely resembling the localization pattern of LOX H1. It is suggested that, in addition to their differential expression pattern, this segregation underlies the regulation of metabolic fluxes through the alternative branches of the lipoxygenase pathway.     

Changes in the activity of antioxidizing enzymes during spermatogenesis

A study was made of variation in the activity of the antioxidant defense system enzymes superoxide dismitase (SOD), glutathione peroxidase, (GP) and glutathione-S-transferase (GT) in the cells of mouse spermatogenic epithelium. The cells were fractionated in the gradient of human serum albumin using the STAPUT system. SOD activity was comparable to that in liver cells, that of GP was one order to magnitude lower, and that of GT one order of magnitude higher than in the liver. Differentiation of spermatogenic cells demonstrated phase variations in the activity of these enzymes, with a maximum seen at the stage of late pachytene spermatocytes. SOD, GP and GT activities were discovered to be reduced in postmeiotic cells (early spermatid fractions) by 2.8-3.5; 1.9-2.3 and 4.2-5.6 times, respectively. That reduction was followed by activation of the enzymes at the late stages of spermiogenesis.     

Changes of gamma-glutamyltranspeptidase activity in the rat during development and comparison of the fetal liver, placental and adult liver enzymes

Changes in the activity of gamma-glutamyltranspeptidase (GGT, EC 2.3.2.2) during development in rats were investigated. The activity of GGT in fetal liver increased rapidly immediately before birth, reached a maximum at birth and then decreased rapidly within a week after birth to nearly the level in adult rat liver. In contrast, placental GGT showed higher activity at an early stage (from day 13 to day 15) of the gestation period, but the activity decreased in the last part of fetal life. The activity in the amniotic fluid increased significantly just before birth, in parallel with the increase of activity in the fetal liver. No change of activity in the uterine wall was observed throughout gestation. The kinetic and immunological properties of partially purified GGTs from fetal liver and placenta were almost identical with those of adult liver GGT. However, the activity of soluble GGT in fetal liver was less effectively inhibited by antibody against adult kidney GGT. Thus, it is likely that at least one isozyme of GGT is present in the soluble fraction of fetal liver.