PubMed Health⌕ Search

Biomedical subjects

A M Steffan

Publications and source records attributed to A M Steffan.

53 records · Page 3Linked to original sources
PubMed1975

[A novel model of experimental toxic hepatitis/acute degenerative hepatitis induced by frog virus 3 (FV3) in the mouse (author's transl)].

The i.p. or i.v. injection of frog virus 3 (FV3) in mice produces a hepatitis which leads to the death of the animals within 24 h. This hepatitis is of a purely toxic nature since the virus does not develop at 37 degrees C. The toxic effect of the virus, which can be differentiated from the infectious effect, involves one or more structural proteins. The first pathological changes occur during the first few hours after the injection in the vicinity of the nuclei of the liver parenchyma cells in the form of changes in the chromatin and nucleoplasm. The inhibition of the synthesis of cellular macromolecules and of the function of nuclear enzymes points to the fact that it is the nucleus that is first and foremost attacked. Necrosis and biochemical disturbances in the vicinity of the cytoplasm appear later on. Premedication of the mice with a water-soluble silymarin salt leads to a distinct rise in the survival rate of the animals. The protective function of silymarin is dependent on the dose and on the duration of the premedication. The LD50 of FV3 in those mice which had previously been given silymarin, is approximately three times that of the animals which received no premedication.

Animals↗
PubMedDate not supplied

Phagocytosis, an unrecognized property of murine endothelial liver cells.

Impairment of the phagocytic capacities of Kupffer cells, as is found in Frog Virus 3 hepatitis of mice, allows the endothelial liver cells to take up intravenously inoculated latex particles of 1.0 micron diameter. In vitro experiments with cultivated endothelial cells isolated by collagenase perfusion of the liver and purified by centrifugal elutriation demonstrate that uptake occurs via a typical mechanism of phagocytosis involving pseudopodia. Ingestion of latex is inhibited by incubation of the cells at 4 degrees C and by treatment with cytochalasin B, whereas colchicine has no effect. These results demonstrate that: the Kupffer cells are not the only cells of the hepatic sinusoid capable of phagocytosis; and under conditions where the phagocytosis in Kupffer cells is impaired, the endothelial cells may participate in the clearance of large particles from the blood.

Animals↗
PubMedDate not supplied

Leukotrienes as mediators in frog virus 3-induced hepatitis in rats.

The role of leukotrienes was investigated in frog virus 3-induced hepatitis in rats. Frog virus 3 elicited an enhanced generation of cysteinyl leukotrienes in vivo as monitored by measurement of N-acetyl-leukotriene E4 as the major endogenous metabolite of cysteinyl leukotrienes secreted into rat bile. N-Acetyl-leukotriene E4 concentrations were elevated for more than 4 hr after frog virus 3 injection. In vitro experiments using cultured rat liver Kupffer cells of high purity indicated that these cells can produce and metabolize leukotrienes and are thus a possible source of leukotrienes elicited in vivo by frog virus 3. The selective 5-lipoxygenase inhibitor AA 861 and the dual inhibitor of arachidonate lipoxygenase and cyclooxygenase, BW 755C, reduced the hepatocellular injury after a high dose of frog virus 3 by about 50 and 80%, respectively, as judged from plasma activities of ALT and sorbitol dehydrogenase at 24 hr after frog virus 3 administration. Our in vivo and in vitro studies argue in favor of an important role of leukotrienes as mediators in frog virus 3 hepatitis in rats.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMedDate not supplied

Increase in the number of fenestrae in mouse endothelial liver cells by altering the cytoskeleton with cytochalasin B.

Endothelial cells of the hepatic sinusoid isolated from mice livers and maintained in culture display typical fenestrae grouped in sieve plates. Treatment with cytochalasin B led to no significant change in the mean diameter of the fenestrae but to an increase in their number and in the porosity of the cells (percentage of the cellular surface opened by the fenestrae) which attained up to 300% of that of the controls. Scanning electron microscopic observations of Triton-extracted cells revealed that these modifications were related to an alteration of the cytoskeleton. The effect of cytochalasin B could be reversed; 3 hr after removal of the drug, the cells recovered their original aspect with sieve plates scattered over their surface. These observations demonstrate that endothelial fenestrae are inducible structures and that the cytoskeleton seems to be involved in their formation.

Animals↗
PubMedDate not supplied

Multiplication of human immunodeficiency virus in primary cultures of human Kupffer cells--possible role of liver macrophage infection in the physiopathology of AIDS.

In primary cultures of Kupffer cells obtained from surgical biopsies of human liver by collagenase perfusion followed by centrifugal elutriation and infected with HIV, the virus multiplied abundantly, as attested by the appearance of a reverse transcriptase activity in the medium. Examined by electron microscopy, the cells were found to contain viral particles with typical features of Lentivirinae. Furthermore, the virus could be revealed by immunofluorescence using an HIV+ patient serum. HIV antibodies also neutralized the infectivity of the Kupffer cell-produced virus. Our results demonstrate that the cells constituting the largest fraction of fixed macrophages in the body may be infected by HIV, thereby suggesting that the Kupffer cells may play a role in the physiopathology of the disease, namely as a reservoir for the virus.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Morphological changes in lymph nodes and expression of VCAM1 and cytokines at the late stages of SIV-induced disease in rhesus monkeys.

Four patterns of structural alterations were found in lymph nodes (LNs) from rhesus monkeys 17 to 34 months after infection with simian immunodeficiency virus (SIV-mac251). SIV p27gag antigen and viral particles were localized either between the processes of follicular dendritic cells (FDCs) or in the cytoplasm of macrophages. In hyperplastic follicles, enlarged germinal centres contained numerous Ki67+ proliferating centroblasts which were rather rare in light zones occupied by the CD23+ FDC network. Involuted follicles contained a small number of Ki67+ centroblasts and the CD23 labelling was limited to a very small apical zone. A correlation was found between the morphological characteristics of the follicles (hyperplasia-involution) and the level of expression of the vascular cell adhesion molecule 1 (VCAM1) on FDCs. A gradient in VCAM1 intensity with no expression in the subcapsular-intermediary sinuses, low membrane labelling in the mantle and strong expression in the FDC network was observed. IL1 alpha+ and IL6+ (interleukin) cells (lymphocytes and macrophages) were detected in the mantle, the interfollicular area and the medulla of LNs. Expression of the tumour necrosis factor alpha and ultrastructural markers of interferon alpha production were found in a few FDC and macrophages. Our findings indicate a close relationship between the morphofunctional properties of FDC and the LN structure in SIV infection.

Animals↗
PubMedDate not supplied

Human endothelial cells isolated from the hepatic sinusoids and the umbilical vein display a different permissiveness for HIV1.

Endothelial cells are now considered as potential targets for HIV infection, together with other non-lymphoid cells. We previously demonstrated that endothelial cells isolated from the human liver sinusoids (SEC) are permissive for HIV1 in vitro (Steffan et al., 1992), whereas human umbilical vein endothelial cells (HUVEC) do not allow replication of seven HIV1 and HIV2 strains under the same infection conditions (Lafon et al., 1992). The aim of our work was to compare the permissiveness of SEC and HUVEC and to determine whether the lack of HIV replication in HUVEC, which do not possess CD4 receptors (Lafon et al., 1992), could be related to the absence of virus penetration. The bypass of the early events in the virus life cycle, including the stage of fusion, by transfection of HUVEC with the HTLV-IIIB provirus led to one cycle of viral replication. Moreover, a low level of viral replication was observed in HUVEC infected with the NDK HIV strain, known to penetrate its target cell in a CD4-independent fashion. These results indicate that the block of infection in HUVEC takes place during the early stages of the viral replicative cycle. However, given the low level of NDK replication in HUVEC (0.02% infected cells) in comparison with NDK-infected SEC (30 to 50% infected cells), the absence of the CD4 receptor on HUVEC may not be the only limiting factor for viral growth. Although these two types of endothelial cells display a very different permissiveness for HIV, the present data suggest that they could both serve as a viral reservoir.

CD4 Antigens↗
PubMedDate not supplied

Inhibition of HIV in vitro by antiviral drug-targeting using nanoparticles.

Nanoparticles are known to accumulate in the phagocytic cells of the mononuclear phagocyte system. Therefore, the use of this carrier system for the targeting of antiviral drugs to monocytes/macrophages (MO/MAC) is an attractive concept in the treatment of diseases involving MO/MAC, e.g. infection with HIV. In this study, the ability of macrophages isolated from peripheral blood of healthy blood donors to phagocytose and metabolize human serum albumin microspheres was investigated by transmission electron microscopy. Furthermore, nanoparticles manufactured using human serum albumin or polyhexylcyanoacrylate were loaded with nucleoside analogues (AZT and ddC) and tested for their ability to prevent HIV infection in MO/MAC cultures. Our results demonstrate the effectiveness of this drug-targeting system to one of the major target cells for HIV.

Antiviral Agents↗
PubMedDate not supplied

Signs of Kupffer cell involvement in productive simian immunodeficiency virus infection in monkey liver.

The livers of 21 rhesus monkeys inoculated with SIVmac251 were examined at 4 days to 39 months after infection. SIV antigens were detected in the cytoplasm of Kupffer cells (KC), macrophages and lymphocytes in two-thirds of the livers tested. The number of cells containing viral proteins substantially increased during the development of the disease, and KC were the main cell type displaying SIV proteins at an advanced stage of infection. Mature and immature lentiviral particles were found in cytoplasmic vacuoles or associated with worm-like structures in KC, indicating that SIV replication could occur within resident liver macrophages. Another sign of the permissiveness of KC was the formation of multinucleated giant cells within the hepatic sinusoids. Some of these cells containing 3-6 nuclei still retained ultrastructural features of KC. Most of them contained a high quantity of viral particles. Numerous lymphocytes displaying signs of apoptosis were taken up by KC, especially at the beginning of infection. Hyperplasia and hypertrophy of KC were noted in the course of SIV disease in the liver. The present data indicate that KC can be infected in vivo and may serve as a reservoir for SIV during the progression of the disease.

Animals↗
PubMedDate not supplied

Phagocytosis and degradation of human serum albumin microspheres and nanoparticles in human macrophages.

Nanoparticles and microspheres made from human serum albumin are biodegradable and, as a physiological material, less cytocidal than cyanoacrylates. Therefore, they should be a suitable carrier system for targeting drugs into cells of the mononuclear phagocyte system. Nevertheless, the process of phagocytic uptake and degradation of albumin particles by macrophages has so far not been documented in detail. For this reason the presented electron microscopical investigation was performed. To study both cellular particle uptake and intracellular degradation, human monocytes were isolated from the peripheral blood of healthy donors and cultivated in plastic plates. After maturation to macrophages, the cells were incubated with the particles for 2h, then washed with buffer and further cultivated for 1-7 days. After fixing with glutaraldehyde, the cells were prepared for electron microscopy. The process of incorporation was demonstrated to be phagocytosis, by scanning and transmission electron microscopy. The degradation of the microspheres was followed by transmission electron microscopy. The metabolism started some hours after particle uptake. After 3 days the process was almost terminated. After 7 days of cultivation only small numbers of intact microspheres were found in the cytoplasm.

Cells, Cultured↗
PubMedDate not supplied

[Rat Kupffer cells cultures and their applications to experimental hepatology (author's transl)].

Non-parenchymal cells were obtained by perfusion of rat liver with 0.05% collagenase followed by incubation at 37 degrees C of liver fragments in collagenase in a rotating water-bath. Kupffer cells were separated from endothelial cells by centrifugal elutriation and could be kept alive for several days. They had the same morphology as in vivo and retained the same properties of phagocytosis and pinocytosis. Rat Kupffer cells cultures could be used to investigate a number of unsolved problems of hepatic pathophysiology.

Animals↗