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S Sell

Publications and source records attributed to S Sell.

At least 163 records · Page 9Linked to original sources
PubMed1981

Rapid development of large numbers of alpha-fetoprotein-containing "oval" cells in the liver of rats fed N-2-fluorenylacetamide in a choline-devoid diet.

Fischer rats, fed 0.05% w/w N-2-fluorenylacetamide in a choline-devoid diet for 2 weeks, develop a massive infiltration of the liver by small "oval" cells. This occurs rapidly one week after feeding the diet for two weeks. All rats fed choline-devoid diet die within 5 weeks, with massive oval cell infiltration of the liver. Although similar changes occur in rats fed N-2 fluorenylacetamide in a choline-supplemented diet, their degree is much less. In rats fed a choline-devoid diet without N-2-fluorenylacetamide, proliferation of hepatocytes, but not of oval cells, is observed. Because the carcinogen-enhancing effects of choline-devoid diets seem to exceed those of partial hepatectomy, such diets may work by causing changes distinct from those induced by partial hepatectomy. Many oval cells contain alpha-fetoprotein, and the rapid oval cell increase is associated with an exponential increase in serum alpha-fetoprotein concentration. These observations suggest that a cellular change, not an alteration of gene expression in parenchymal cells, is the primary cause of hyper-alphafetoproteinemia during the course of chemical carcinogenesis in rats.

2-Acetylaminofluorene↗
PubMed1981

An immunohistologic study of Shope fibroma virus in rabbits: tumor rejection by cellular reaction in adults and progressive systemic reticuloendothelial infection in neonates.

The development of lesions in adult and neonatal New Zealand White rabbits following intradermal inoculation of Shope fibroma virus was studied by immunofluorescence for viral antigens. T-cells, and immunoglobulin. In adults a self-limiting local fibroxanthosarcomatous tumor was rejected within 10-12 days in association with a dense infiltration of T-cells. In neonates expanding skin lesions were associated with systemic presence of virus in the reticuloendothelial system. In surviving infected neonates, granulomas formed at the site of infection after 3 weeks. These reactions may have limited further dissemination of the virus. These results support the hypothesis that the progressive disease produced by Shope fibroma virus in neonatal rabbits may be due to the inability of the reticuloendothelial system to clear infectious virus.

Animals↗
PubMed1981

Individual rabbit peripheral blood lymphocytes reactive to anti-immunoglobulin and phytohemagglutinin or Concanavalin A identified by immunoelectronmicroscopic demonstration of endocytosis.

Individual rabbit lymphocytes reactive to phytohemagglutinin or Concanavalin A, and bearing membrane-associated surface immunoglobulin have been identified by electron microscopy. Endocytosis of lectin-lectin receptor complexes, which has previously been shown to be a marker for subsequent lectin-induced blast transformation was used as a marker for lectin reactivity. Surface immunoglobulin was detected by modified mixed antiglobulin (Coombs) technique. Lectin-reactive, sIg-bearing cells are well represented among lymphocytes from peripheral blood. Few of these cells, however, are found among lymphocytes isolated from spleen or popliteal lymph node. From these results it is suggested that some rabbit lymphocytes from peripheral blood share T cell (lectin reactivity) and B cell (bearing sIg) properties, or that reactivity to Con A is not an exclusive T cell property and sIg is not an exclusive property of B cells.

Animals↗
PubMed1981

Isolation of oval cells and transitional cells from the livers of rats fed the carcinogen DL-ethionine.

For the characterization of the metabolic and biologic properties of oval cells (i.e., cells emerging in the livers of rats treated with chemical carcinogens due to proliferation of bile ductular and/or duct cells) and transitional cells (i.e., cells having properties intermediate between those of oval cells and hepatocytes), these cells were isolated from the livers of Sprague-Dawley rats fed DL-ethionine for 4-5 weeks. The livers were dissociated into single cells by perfusion in situ with collagenase, and total cell suspensions were allowed to stand at unit gravity for 10 minutes to separate parenchymal (hepatocytes) from nonparenchymal cells. Nonparenchymal cells were centrifuged in linear gradients of Metrizamide (8-24% wt/vol), and 2-ml fractions were collected from the gradients. The cells in the fractions were defined by light microscopy, electron microscopy, and histochemical and immunofluorescence methods. A cell isolate was thus obtained consisting of Kupffer's cells (approximately 20%), bile ductular and/or duct cells and oval cells (approximately 30%), and transitional cells (approximately 50%). A twofold enrichment of bile ductular and/or duct cells and their derivatives was achieved over that found in the nonparenchymal cell fraction before isopyknic gradient centrifugation.

Animals↗
PubMed1981

Cell-mediated immune response to Shope fibroma virus-induced tumors in adult rabbits.

The parameters of cell-mediated immune responses of adult rabbits infected with Shope fibroma virus (SFV) were characterized by measurement of the size of local draining nodes, number of cells per lymph node, mitogen responses of lymphocytes, and kinetics of virus-specific cell-mediated lymphocytotoxicity (CML). In addition, the cytolytic effector population was characterized. After intradermal injections, tumors appeared within 3-4 days, reached maximum size in 10-12 days, and then regressed completely with 24 days. The size of local popliteal lymph nodes, in particular the diffuse cortex (paracortex), and the number of cells per node increased during tumor growth but then declined as the tumor regressed. Maximum specific CML to SFV-infected kidney cell monolayers (RK-13) occurred 10 days after inoculation of SFV and correlated with the initiation of tumor regression. Adult cytotoxic lymphocytes passed through nylon wool, and most of their activity was removed by treatment with antithymocyte globulin plus complement. Cytotoxic T-cells from SFV tumor-bearing rabbits killed only targets infected with SFV and not targets uninfected or infected with vaccinia virus. Therefore, T-cell-mediated virus-specific CML appeared as a major immune effector mechanism that correlated with tumor regression. However, antibody-dependent cell-mediated and NK cytotoxicity were also demonstrable. The presence of different cell-mediated cytotoxic mechanisms suggested a heterogeneity of effector mechanism.

Animals↗
PubMed1980

Molecular mechanisms of control of albumin and alphafetoprotein production: a system to study the early effects of chemical hepatocarcinogens.

The cellular mechanism of control of alphafetoprotein (AFP) and albumin (ALB) production during normal and pathologic permissive states is being examined using complementary DNA probes. AFP is the major serum protein for most of fetal life, but normally is produced in very small amounts in the adult. AFP production recurs in the adult during restitutive proliferation of the liver following partial hepatectomy or chemical injury, early after the exposure to chemical carcinogens and in animals with hepatocellular or yolk sac carcinomas. AFP production is roughly proportional in each case examined so far to the amount of mRNA available. On the other hand, there appears to be no difference in the gene number or gene organization in permissive or non-permissive states and there is no evidence of selective degradation of AFP or AFP (and ALB) production is probably at the level of gene transcription. Understanding of how carcinogens act to permit expression of the AFP gene may lead to important insights into carcinogenic mechanisms.

Albumins↗
PubMed1980

Host response to Treponema pallidum in intradermally-infected rabbits: evidence for persistence of infection at local and distant sites.

Intradermal infection of rabbits with Treponema pallidum imitiates rapid and active cellular response at the site of injection. During the first 2 weeks following infection, there is a marked increase in the numbers of organisms at the site of infection. Systemic dissemination of treponemes occurs during the early stage of infection, presumably before the immune response is fully mobilized. The mononuclear infiltration, which is apparent at the lesion site one week postinfection, becomes more pronounced at 2 weeks. The infiltrating cells are predominantly T lymphocytes and macrophages. By 4 weeks postinfection, most of the organisms have been cleared from the primary site; however, low numbers of treponemes survive locally and in distant tissues. Thus, whereas infection with T. pallidum appears to activate immune mechanisms which are capable of clearing most of the organisms from the primary lesion, some organisms are able to evade these mechanisms and persist in vivo.

Animals↗
PubMed1980

Characterization of lymphocyte responsiveness in early experimental syphilis. I. In vitro response to mitogens and Treponema pallidum antigens.

Lymphoid cells from spleens and lymph nodes of rabbits infected with T. pallidum respond by proliferation to concanavalin A (Con A) and T. pallidum antigens. Spleen cell responsiveness to treponemal antigens appears 6 days after infection, is 100 to 600 fold higher than the response of uninfected control rabbits, and is maintained throughout the 31-day observation period. Specifically responding cells in the inguinal and popliteal lymph nodes of infected animals are demonstrable on day 10, and the magnitude of the response increases throughout the observation period. Specific responsiveness to T. pallidum antigens in vitro is enhanced in purified T cell populations and is abolished by treatment with goat anti-rabbit thymocyte serum and complement. The response of spleen and lymph node cells to Con A is unaffected during syphilitic infection. These results are consistent with a role for T cell-mediated specific immunity to treponemal antigens early after infection and do not support a hypothesis of depressed cellular immunity during syphilitic infection.

Animals↗
PubMed1980

Characterization of lymphocyte responsiveness in early experimental syphilis. II. Nature of cellular infiltration and Treponema pallidum distribution in testicular lesions.

The nature of the cellular infiltration and the distribution of Treponema pallidum during rabbit testicular infection were examined by immunofluorescence and light microscopy. Low numbers of treponemes are demonstrable in the perivascular regions on day 3 post-infection. On days 6, 10, and 13, large numbers of organisms are found in the interstitial spaces. The treponemes do not appear to invade the walls or lumina of the seminiferous tubules, although tubular atrophy is obvious. On days 17, 24 and 31, treponemes are no longer identifiable by immunofluorescence in infected testicles. The cellular infiltration, which is apparent on day 6, reaches its peak on day 13, corresponding to the amount of swelling observed grossly. The infiltrate is primarily lymphocytic, but macrophages are also observed during the peak cellular response. These cells are located, as are the treponemes, in the interstitial spaces. The lymphocytes are demonstrated by specific immunofluorescence to be predominantly T cells. The peak T cell infiltration in the infected testicle is followed rapidly by the disappearance of the organisms from that organ. Thus, it is postulated that infiltration by specifically sensitized T cells results in the clearance of large numbers of T. pallidum from infected tissues.

Animals↗
PubMed1980

Heterogeneity of alpha-fetoprotein(AFP) and albumin containing cells in normal and pathological permissive states for AFP production: AFP containing cells induced in adult rats recapitulate the appearance of AFP containing hepatocytes in fetal rats.

The cellular localization of alpha-fetoprotein (AFP) and albumin (ALB) in permissive states for AFP synthesis has been examined. The cells containing AFP associated with permissive states in the adult are similar in appearance to cells that are present during the development of fetal liver. In fetal liver, AFP is seen in most developing hepatocytes ranging from small 'oval' like cells to larger dividing hepatocytes and in cells organized in glandular structures. Following exposure to some chemical hepatocarcinogens, AFP can also be seen in small 'oval' cells, ductal-like cells, and larger atypical hepatocytes that form glandular-like structures. Following partial hepatectomy or galactosamine-induced live injury, AFP is seen in a few large parenchymal cells usually containing identifiable chromatin Cells which contain AFP almost always contain ALB as well, but for each cell type there are many more ALB containing cells than AFP containing cells. ALB and AFP containing hepatoma cells are more frequently located adjacent to tumor vessels and AFP production by hepatoma 777 in vitro is associated with the growth state of the tumor. The AFP containing cells that are seen during restitutive proliferation most likely arise from deregulation of proliferating adult hepatocytes. The non-hepatoma AFP containing cells that appear early during carcinogenesis may arise in the adult by retrodifferentiation of hepatocytes or by proliferation of stem cells. These morphologically different AFP containing cells may or may not be precursors of the hepatocellular carcinomas which develop later.

Albumins↗
PubMed1980

A histopathologic and immunologic study of the course of syphilis in the experimentally infected rabbit. Demonstration of long-lasting cellular immunity.

Inoculation of the causative agent of syphilis, Treponema pallidum into the testes of rabbits initiated the following sequence of events: 1) a rapid proliferation of organisms in the interstitial tissues of the testes, reaching a maximum at about 10-11 days after infection; 2) systemic spread of organisms primarily in the lymphoid organs; 3) a prompt immune response manifested by hyperplasia of T cell domains in draining lymph nodes and spleen, blast transformation responses of lymphoid cells to sonicates of T pallidum, the appearance of serum antibody, and the marked infiltration of the infected areas of the testes by T cells; 4) essential clearing of organisms identified by immunofluorescence from the infected site 10-14 days after infection associated with evolution of the inflammatory response from primarily a T cell infiltrate to a larger mononuclear cell type, and the immunofluorescent identification of presumptive T pallidum antigen in macrophages; 5) interstitial fibrosis or resolution 17-21 days after infection so that examination of infected testes from 1 to 24 months later reveals foci of tubular atrophy and fibrosis of varying size, alternating with regenerated tubules, separated by interstitial areas with only minimal fibrosis. During the long period of latency there is no evidence of atrophy or hypoplasia of the lymphoid organs and long-lasting T cell memory with regard to T pallidum sonicates is demonstrable. Reinfection of previously inoculated rabbits indicates partial protection at 25 days after infection followed by essentially complete protection after 55 days. It is concluded that there is a prompt and long-lasting immune response to T pallidum in experimentally infected rabbits. The main mechanism for destruction of infecting organisms appears to be T-cell-initiated macrophage-mediated destruction, but a role for antibody dependent phagocytosis cannot be ruled out. The reason that some organisms may survive in various body organs remains unknown, but possible explanations are presented.

Animals↗
PubMed1979

Control of albumin and alpha-fetoprotein expression in rat liver and in some transplantable hepatocellular carcinomas.

Albumin and alpha-fetoprotein production by rat liver and by four selected transplantable hepatocellular carcinomas is compared to the messenger RNA present in these tissues. Albumin and alpha-fetoprotein were measured by radioimmunoassay of serum concentration, immunofluorescence, and in vitro incorporation of labeled amino acids into proteins specifically precipitated by antisera. The number of mRNA molecules per cell was calculated from the hybridization of specific cDNA probes to polysomal mRNA and by translational activity of polysomal RNA in a wheat germ system. The amount of albumin and alpha-fetoprotein produced by the different tissues is directly related to the number of functional mRNA molecules per cell for each protein.

Animals↗
PubMed1979

Changes in expression of albumin and alpha-fetoprotein genes during rat liver development and neoplasia.

Albumin mRNA was isolated and purified from rat liver polysomes by a combination of immunoprecipitation of specific polysomes, poly(U)-Sepharose 4B chromatography, and fractionation of the resulting poly(A)-containing RNA on a sucrose gradient. alpha-Fetoprotein (AFP) mRNA was isolated from Morris hepatoma 7777 by a similar procedure. The purity of the mRNA preparations was determined by analytical gel electrophoresis under denaturing conditions, analysis of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the polypeptides synthesized in a wheat germ cell-free system, and the kinetics of hybridization to cDNA transcribed from albumin mRNA and AFP mRNA. The albumin mRNA possessed a chain length of approximately 2265 nucleotides and the AFP mRNA possesed a length of approximately 2235 nucleotides when examined under stringent denaturing conditions on agarose gels containing 10 mM methylmercury hydroxide. Analysis of poly(A) content by a hybridization assay with [3H]poly(U) revealed the presence in albumin mRNA of a poly(A) region containing approximately 100 adenosine residues. The AFP mRNA preparation was found to contain an average poly(A) tract of approximately 190 bases. Thus, albumin mRNA appears to contain approximately 330 untranslated nucleotides, and AFP mRNA appears to contain a similar number (approximately 285) of noncoding, nonpoly(A) bases. The purified albumin and AFP mRNA's were used as templates for synthesis of full-length cDNA hybridization probes. Both of the probes selectively hybridized to their templates with kinetics expected for single RNA species the sizes of albumin and AFP mRNA. ROt analysis was used to quantitate albumin and AFP mRNA sequences during normal liver postnatal development and liver oncogenesis. The number of polysomal AFP mRNA molecules per liver was found to drastically decrease during the first weeks of postnatal life, concomitant with a decline in the AFP synthetic capacity of the livers and in the serum concentrations of AFP. During this period, the concentration of albumin mRNA molecules per cell in the liver remained at high, approximately constant levels. In Morris hepatoma 7777, the concentration of AFP-specifying sequences was at least 10(3)-fold higher than that found in normal adult liver, whereas the content of albumin nRNA was four- to five-fold lower. These changes in concentration of albumin and AFP mRNA sequences closely correlated with a parallel variation in the specific protein synthetic capacity of the tissues.

Animals↗