Serum Concentrations of Vascular Endothelial Growth Factor, Stromal Cell-Derived Factor, Nitric Oxide and Endothelial DNA Proliferation in Development of Microvascular Pathology in Acute African Swine Fever.

There is significant evidence that pathology of the microcirculation occurs in African swine fever (ASF); however, the mechanisms by which it develops are largely unknown. In the present experimental infection study, we show that an increase in vascular permeability in the initial stages of acute ASF is dependent on viraemia and elevation of the concentration of serum nitric oxide (NO). Macrophages activated by ASF virus (ASFV) are stimulated to produce NO and simultaneously to sensitize the endothelial cells through the action of vascular endothelial growth factor Β (VEGFΒ), which is followed by an increase in VEGF-mediated endothelial permeability. In the later stages of disease, the endothelial cells undergo DNA proliferation, which may additionally provoke capillary leakage, point haemorrhages and migration of blood cells into tissues. The possible mechanism of a shift in the cell cycle from the G1 to S and G2 stages could be a direct effect of ASFV. The terminal stages of disease are characterized by triggering of compensatory mechanisms such as stimulation of the synthesis of stromal cell-derived factor-1.

Hemophagocytic lymphohistiocytosis in acute African swine fever clinic.

INTRODUCTION: Hemophagocytic lymphohistiocytosis (HLH) usually has been defined as the combination of a proliferation of cytologically benign, actively phagocytic macrophages in bone marrow, spleen, lymph nodes, etc. in association with fever, cytopenia, splenomegaly, and hypertriglyceridemia. HLH is often triggered by viral infection. The aim of this study was to ascertain the features of HLH involvement in African swine fever virus (ASFV) (genotype II) pathogenesis. METHODS: The serum levels of macrophage colony-stimulating factor (MCSF) and granulocyte-macrophage colony-stimulating factor (GMCSF), as well as the histological constitution (for hemophagocytic macrophages detection) of various organs of pigs infected with ASFV genotype II were investigated. The diagnosis of HLH was made according to universally accepted human criteria. RESULTS: The association of fever, cytopenias, splenomegaly, and hemophagocytosis was present in 87.5% of the infected pigs (absence of hyperthermia in one of eight pigs). Marked hypertriglyceridemia was observed at 3-4days post infection. Previously it was shown that ASFV induced a significant decrease in the level of fibrinogen from day 5 till the end of experiment. Progression of the HLH coincided with a temporary increase in the serum levels of MCSF levels (early stage of disease) and GMCSF levels (2-3 pays post infection). CONCLUSIONS: Hemophagocytic syndrome should be suspected in ASFV (genotypeII) infected pigs.

Characterization of the atypical lymphocytes in African swine fever.

AIM: Atypical lymphocytes usually described as lymphocytes with altered shape, increased DNA amount, and larger size. For analysis of cause of genesis and source of atypical lymphocytes during African swine fever virus (ASFV) infection, bone marrow, peripheral blood, and in vitro model were investigated. MATERIALS AND METHODS: Atypical lymphocytes under the influence of ASFV were studied for morphologic, cytophotometric, and membrane surface marker characteristics and were used in vivo and in vitro models. RESULTS: This study indicated the increased size, high metabolic activity, and the presence of additional DNA amount in atypical lymphocytes caused by ASFV infection. Furthermore, in atypical lymphocytes, nuclear-cytoplasmic ratio usually decreased, compared to normal lymphocytes. In morphology, they looking like lymphocytes transformed into blasts by exposure to mitogens or antigens in vitro. They vary in morphologic detail, but most of them are CD2 positive. CONCLUSIONS: Our data suggest that atypical lymphocytes may represent an unusual and specific cellular response to ASFV infection.

Properties of cells with increased resistance to some picornaviruses.

The resistance to picornaviral infection cells of susceptible lines has similar changes in the phenotype. They have decreased number of nucleoli and increased percentage of euploidy. Also the percentage of euploid cells those were resistant to the picornaviral infection increased in all highly transformed cultures. In resistant cells of all cultures has been found reduction of DNA. RNA amount also decreased both in nucleus and in cytoplasm. All these data correlated with the increased euploidy of the resistant population. The resistant cells had a less transformed phenotype, and decreased proliferative activity. Decreased nucleolar status became apparent by reduction of absolute and relative nucleolar indices. Consequently the reduction of viral titer (viral titters reduction) in resistant cells could be the direct result of diminished activity of the RNA synthesis machinery. It is important to note that the cells lose resistance while another type of virus, even from the same family, infects the culture once.

Comparative multiparametric analysis of HeLa and RD cell culture reactions to solcoseryl.

Reactions of continuous HeLa and RD cell cultures and their nuclear and nucleolar apparatus to addition of solcoseryl into the medium were studied. The monolayer density, proliferation activity, percentage of dead cells, RNA and DNA content in the nuclei and nucleoli, number of nucleoli in the nuclei, cell distribution in the population by the number of nucleoli in the nuclei, volume and complete surface area of the nuclei and nucleoli, and the nucleolar/nuclear ratio were evaluated. The cultures differently reacted to solcoseryl in the medium at the population and cellular levels of their organization. By the results of multiparametric analysis of the reactions of cells and their nuclear and nucleolar apparatus, solcoseryl can be referred to bioactive substances with characteristics of a factor regulating cell population growth.

Comparison of impact of EMCV replication on the nuclear apparatus of NIH 3T3 and HEp-2 cells.

We have investigated differences between the actions of encephalomyocarditis virus (EMCV) on cytometric indices in cultured NIH 3T3 and HEp-2 cells, which are characterized by different levels of transformation. HEp-2 cells surviving 48 h after EMCV infection showed lower nuclear ploidy, reduced nuclear area, fewer nucleoli and a higher percentage of euploid cells. There was a significant increase of nucleolar/nuclear DNA 6-24 h after EMCV infection. However, EMCV had markedly different effects on NIH 3T3 cells: there was a consistent increase in population ploidy, but the average number of nucleoli and the number of euploid cells in the population remained constant. The nucleolar/nuclear DNA ratio was almost unchanged. These different viral effects might be explained by the contrasting levels of differentiation of the cultured cell lines. The number of nucleoli does not depend on the amount of nuclear DNA in either viral-infected or intact cells but on the euploidy-to-aneuploidy ratio. The ratio of the sums of the nucleolar perimeters to the nuclear perimeter increases linearly with the number of nucleoli per nucleus in both intact and virus-infected cells. In both cell lines, the amount of DNA per nucleolus decreases as the number of nucleoli increases.

Morphometry of nuclear and nucleolar structures in a CaCo-2 cell line.

The number of the nucleoli in a CaCo-2 cell nucleus does not generally depend on the quantity of DNA in the nucleus, but nucleolar DNA content is directly proportional to total nuclear DNA. However, in multinucleolar cells (three or more nucleoli), the nucleolar DNA content increases after 96 h incubation in culture without concomitant quantitative changes in nuclear DNA. The percentage of multinucleolar cells and the average number of nucleoli per nucleus increase with increasing incubation time. After 72 and 96 h in culture, multinucleolar cells show distinctive morphologies. The ratio of the sum of nucleolar perimeters to the nuclear perimeter increases linearly when the number of nucleoli in a nucleus increases, but there is no concomitant increase in total nucleolar area or DNA content, except in the 72 and 96 h populations. When the number of nucleoli in CaCo-2 cells increases after 48 and 60 h in culture, the amount of DNA per nucleolus decreases.

New indices in morphometry of nuclear structure in the NIH 3T3 cell line.

We analyzed the connection of changes in nucleus ploidy with changes in nucleolar apparatus of NIH 3T3 cells. The quantity of nucleoli does not depend on the quantity of nucleolar DNA, but instead depends on euploidy: the majority of euploid cells have 1-3 nucleoli. The quantity of DNA in the nucleolus is correlated with the quantity of nucleolar DNA, and does not depend on ploidy changes. The nucleolar area has a tendency to increase in line with an increase in their numbers in the nucleus. The relationship of the quantity of DNA in the nucleolus with that of the nucleus is stable. During the process of increase in the number of nucleoli in a nucleus, there is a corresponding decrease in the quantity of DNA in each nucleolus, and there is likewise no increase in the sum of nucleolar DNA. The ratio of sums of the nucleolar perimeters to nuclear perimeter is a significant factor, which increases linearly along with an increase in the number of nucleoli in a nucleus.