Search PubMed⌕ Search

Biomedical subjects

S Sell

Publications and source records attributed to S Sell.

At least 127 records · Page 7Linked to original sources
PubMed1986

Cloning of a cDNA encoding the rat placental glutathione S-transferase: overproduction of the mRNA in hepatocellular carcinomas.

Rat hepatocellular carcinomas and normal liver have been screened for mRNA sequences which are more abundant in the carcinomas than in livers. The screen was done by differential colony hybridization of a cDNA library constructed from the mRNA of a primary tumor induced by diethylnitrosamine (DEN). One cDNA was isolated which hybridizes to a 900 nucleotide mRNA present in abundance in six chemically induced rat hepatomas (both primary and transplantable), but is not detectable in normal adult or fetal (17 day) liver. The nucleotide sequence of this cDNA is identical to that reported by Suguoka et al. for the placental isoenzyme of rat glutathione S-transferase (GST-P) (Nucleic Acids Res. 13:6049). A comparison of the GST-P amino acid sequence with those of two liver GST isoenzymes (Yal and Yc) shows only 26% overall homology; however, this homology is concentrated in three regions of 50%, 68.2% and 34.5%. Genomic blotting experiments show that the overproduction of GST-P mRNA in three Morris hepatomas is not due to amplification of genomic DNA sequences hybridizing with the GST-P cDNA. However, hybridizing sequences are contained on at least 72 kb of genomic DNA, suggesting great complexity of the rat GST-P locus.

Amino Acid Sequence↗
PubMed1985

Purification and properties of the dnaJ replication protein of Escherichia coli.

The Escherichia coli dnaJ gene was originally discovered because mutations in it blocked bacteriophage lambda DNA replication. Some of these mutations were subsequently shown to interfere with bacterial growth at high temperature, suggesting that dnaJ is an essential protein for the host as well. The first step in purifying the dnaJ protein was to overproduce it at least 50-fold by subcloning its gene into the pMOB45 runaway plasmid. The second step was the development of an in vitro system to assay for its activity. A Fraction II extract from dnaJ259 mutant bacteria was shown to be unable to replicate lambda dv DNA unless supplemented with an exogenous source of wild-type dnaJ protein. Using this complementation assay we purified the dnaJ protein to homogeneity from the membrane fraction of an overproducing strain of bacteria. The purified dnaJ protein was shown to be a basic (pI 8.5), yet hydrophobic, protein of Mr 37,000 and 76,000 under denaturing and native conditions, respectively, and to exhibit affinity for both single- and double-stranded DNA. Using a partially purified lambda dv replication system dependent on the presence of the lambda O and P initiator proteins and at least the host dnaB, dnaG, dnaJ, dnaK, single-stranded DNA-binding protein, gyrase, RNA polymerase holoenzyme, and DNA polymerase III holoenzyme, we have shown that the dnaJ protein is required at a very early step in the DNA replication process.

Amino Acids↗
PubMed1985

Characterization, molecular cloning, and physical mapping of the Shope fibroma virus genome.

Five strains of Shope fibroma virus (SFV), a strain of rabbit myxoma virus, and a strain of vaccinia virus were compared by restriction endonuclease digestion of their viral DNAs. Restriction digest patterns revealed that SFV and rabbit myxoma, both members of the Leporipoxvirus genus, were distinct from vaccinia, an Orthopoxvirus. All strains of SFV examined had a high degree of nucleotide sequence homology as shown by conservation of restriction sites within their genomes. However, restriction patterns of SFV and myxoma were quite different from one another suggesting that the genomes from these two viruses of the Leporipoxvirus genus do not share a large, highly conserved region of homology as do the viruses belonging to the Orthopoxvirus genus. Restriction mapping identified inverted terminal repeats of approximately 12 kb in length. Restriction fragments representing all but 400 bp of the termini were cloned in plasmid vectors.

Animals↗
PubMed1985

alpha-Fetoprotein and albumin gene expression in brain and other tissues of fetal and adult rats.

Quantitative measurement of messenger RNA (mRNA) for alpha-fetoprotein (AFP) and albumin in developing rat liver and in different fetal and adult tissues reveals a close correlation between the previously determined rate of protein synthesis and mRNA levels. mRNA for AFP and albumin exists in fetal intestine, lung, liver and kidney whereas there are no such transcripts in fetal brain or heart. There are no mRNA transcripts for AFP in any adult organs other than the liver. The lack of mRNA AFP in fetal brain tissue indicates that the AFP found in fetal brain cells is absorbed from the serum. This finding supports the hypothesis that AFP may serve as a carrier protein to deliver bound molecules, such as non-esterified fatty acids, to brain cells at a specific time during development.

Albumins↗
PubMed1985

Restricted changes in the adenovirus DNA-binding protein that lead to extended host range or temperature-sensitive phenotypes.

Human adenovirus fails to multiply efficiently in monkey cells owing to a block to late viral gene expression. Ad2hr400 through Ad2hr403 are a set of host range (hr) mutants which were selected for their ability to readily grow in these cells at 37 degrees C. The mutations responsible for this extended host range have previously been mapped to the 5' portion of the gene encoding the 72-kilodalton DNA-binding protein (DBP). DNA sequence analyses indicate that all four hr mutants contain the same alteration at coding triplet 130, which changes a histidine codon to a tyrosine codon. These results extend those of Anderson et al. (J. Virol. 48:31-39, 1983), which suggested that only this change in the DBP amino acid sequence can expand adenovirus host range to monkey cells. The hr phenotype does not appear to require phosphorylation of this tyrosine residue, since no phosphotyrosine was detected in DBP isolated from Ad2hr400-infected monkey cells. The hr mutants Ad2hr400 through Ad2hr403, however, are cold sensitive for growth in monkey cells. The mutant Ad2ts400, which was derived from Ad2hr400, represents a second class of hr mutants which can grow efficiently in monkey cells at 32.5 degrees C. The cold-resistant hr mutation of Ad2ts400 has previously been mapped to the 5' region of the DBP gene (map units 63.6 through 66). DNA sequence analysis of this region shows that this mutant contains the original hr alteration at coding triplet 130 as well as a second alteration at coding triplet 148, which changes an alanine codon to a valine codon. We suspect that the alterations at amino acids 130 and 148 change the structure of the amino-terminal domain of the DBP, allowing it to better interact with monkey cell components required for late viral gene expression. Ad2ts400 also contains a temperature-sensitive mutation which has previously been mapped to the 3' portion of the DBP gene (map units 61.3 through 63.6). Sequence analysis of this region indicates that the DBP coding triplet 413 has been altered. This change from a serine codon to a proline codon is the same alteration reported in the previously sequenced DBP mutants Ad5ts125 (W. Kruijer et al., Nucleic Acids Res. 9:4439-4457, 1981) and Ad5ts107 (W. Kruijer et al., Virology 124:425-433, 1983). Thus it appears that only a very limited number of changes in either the 5' or the 3' portion of the DBP gene can give rise to the hr or temperature-sensitive phenotypes, respectively.

Adenoviruses, Human↗
PubMed1985

Lack of correlation of methylation and alphafetoprotein and albumin gene expression during liver growth, in hepatocellular carcinomas, and during hepatocarcinogenesis.

Analysis of AFP and albumin genes fails to demonstrate a correlation of gene activity with the degree of gene methylation as determined by restriction endonuclease fragments obtained using the isoschizomer pair, Hpa II and Msp I. There is no difference in the methylation patterns of DNA from high and low producing tissues, such as fetal and adult liver for AFP, hepatoma 7777 and 9098 for AFP; adult lung, brain, kidney and liver for albumin; fetal liver and brain or heart for AFP, etc. Minor selective differences in gene methylation that correlate with AFP or albumin gene expression cannot be ruled out.

Albumins↗
PubMed1985

Connection of ductlike structures induced by a chemical hepatocarcinogen to portal bile ducts in the rat liver detected by injection of bile ducts with a pigmented barium gelatin medium.

Newly found metaplastic ductlike structures that form in the liver of rats exposed to carcinogens are connected to preexisting bile ducts. Male Fischer rats fed a diet of N-2-acetylaminofluorene in a choline-deficient diet (CDAAF) develop a massive proliferation of oval cells which appear to differentiate into bile-ductlike structures. However, unlike normal or proliferating bile ducts, these ductlike structures contain alpha-fetoprotein (AFP) and albumin, which are markers for proliferating hepatocytes and some hepatocellular carcinomas. Bile duct injections with a green pigmented barium gelatin medium filled the lumens of the ductlike structures and typical ductlike structures induced by the CDAAF diet, as well as the proliferating bile ducts induced by the noncarcinogenic alpha-naphthylisothiocyanate (ANIT), and the ducts in the normal controls. AFP was present in the ductlike structures in the rats fed AAF, but not in the bile ducts of animals fed ANIT. These studies suggest that most, if not all, of the ductlike structures produced during chemical hepatocarcinogenesis are derived from bile ducts, yet have the capacity to produce AFP and albumin.

2-Acetylaminofluorene↗
PubMed1985

Reinfection of chancre-immune rabbits with Treponema pallidum. I. Light and immunofluorescence studies.

Inoculation of infectious Treponema pallidum into the skin of chancre-immune rabbits results in a limited inflammatory response. Intact organisms are identifiable by immunofluorescence in the dermis of the infection site for 1-2 days. By Day 3 structurally intact T pallidum are seen localized in hair follicles, erector pili muscles, and cutaneous nerves, while inflammatory cells containing fluorescent (T pallidum) fragments are seen in the dermis. After Day 6 intact organisms are no longer found. It is proposed that hair follicles, erector pili muscles, and particularly nerves may provide relatively protected sites for T pallidum, and that T pallidum may migrate within nerves. Clearance of organisms from the infected site appears to be mediated by phagocytosis and digestion by macrophages as a result of an accelerated delayed hypersensitivity response, but antibody-mediated destruction and T pallidum migration may also be involved.

Animals↗
PubMed1984

Immunologic dysfunction during viral oncogenesis. II. Inhibition of cellular immunity to viral antigens by malignant rabbit fibroma virus.

The ability of two related viruses--Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV)--to induce virus-specific immune responses in lymphocytes of recipient animals was studied. SFV produces a benign local tumor which regresses in 12-14 days. Using an assay for virus-induced lymphocyte blastogenesis lymphocytes reactive to SFV were detected, both in rabbits bearing SFV-induced tumors and in rabbits whose SFV-induced tumor had regressed. These virus-reactive cells were detected in peripheral blood and spleen, and in lymph nodes draining the primary tumor. In contrast, MV produces a disseminated tumor and eventual death. MV does not induce detectable blastogenic responses in lymphocyte populations. SFV and MV are antigenically cross reactive: rabbits immune to SFV do not develop MV-induced tumors, and antisera to each virus neutralize both equally. Lymphocytes from SFV-infected rabbits proliferate in vitro in response to MV that has been inactivated by ultraviolet light (uv/MV) but not to infectious MV. In contrast, lymphocytes from rabbits infected with MV do not respond to uv-inactivated MV or to SFV. Thus, infectious MV inhibits the development of normal blastogenic responses in vivo and prevents the expression of those responses in lymphocytes from MV-resistant, SFV-immune rabbits in vitro. The relevance of this impairment to the differences in the clinical courses of SFV- and MV-induced tumors is discussed.

Animals↗
PubMed1984

Experimental neonatal syphilis. II. Immunological responses of neonatal rabbits to intradermal inoculation with Treponema pallidum (Nichols strain).

The immunological competence of neonatal rabbits inoculated intradermally with Treponema pallidum was examined. Both cellular responses and the production of humoral antibody to specific T. pallidum antigens and to nonspecific antigens or mitogens were investigated. In blast transformation assays, splenic and popliteal lymph node lymphocytes from neonates inoculated with virulent T. pallidum responded to T. pallidum antigens in a manner similar to or greater than inoculated adult rabbits. Splenic and popliteal lymph node lymphocytes from both uninoculated and T. pallidum-inoculated neonate and adult animals showed consistent and similar responses to concanavalin A. Both neonate and adult animals inoculated with heat-killed T. pallidum also responded but to a significantly lesser degree. Immunofluorescent examination of skin sections from the site of inoculation of adult and neonatal animals revealed 1) that the early infiltrate was composed predominantly of T cells, 2) diffuse antibody staining with rare B cells, and 3) fewer treponemes with significant fragmentation in neonates as compared to adult controls. Antibody production by neonates inoculated with virulent T. pallidum was delayed 4 to 6 weeks postinoculation as measured by the fluorescent Treponemal antibody absorption and Venereal Disease Research Laboratory (VDRL) test procedures, respectively. Antibody was not detected among neonates inoculated with heat-killed treponemes during a 6-week observation period and only low levels of VDRL antibody were detected in a few adult control animals. Evidence for incomplete resistance of neonatal rabbits to the intradermal inoculation of Treponema pallidum was provided.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Polymorphism of rat alphafetoprotein and albumin genes.

Restriction endonuclease digestion using Hind III and Msp I and Southern blot analysis of DNA from the liver of three inbred rat strains and one outbred strain using cDNA probes yields two banding patterns for the alphafetoprotein and albumin genes. Buffalo and Fischer DNA have one pattern whereas ACI had a different pattern for both genes. Sprague Dawley DNA contains fragments of both patterns suggesting heterozygosity in some individuals of this strain. These polymorphisms do not appear to be associated with any structural or biological differences in the proteins resulting from expression of these genes.

Albumins↗
PubMed1984

Strain differences in Shope fibroma virus. An immunopathologic study.

The pathogenic effects of plaque-purified Boerlage and Patuxent strains of Shope fibroma virus (SFV) in neonatal rabbits are compared with results of previous reports which used nonpurified SFV. Clinically, the Boerlage strain produced large tumors; whereas the same dose of Patuxent strain SFV induced much smaller tumors locally. Neither virus caused metastatic or extensively invasive local spread in our study. Some Patuxent recipients died of respiratory infections prior to sacrifice. However, both groups of rabbits handled the tumor well; the tumor began regressing 15-20 days after inoculation. Histologically, the tumors produced by those viruses were identical. Patuxent strain recipients were otherwise normal. Boerlage strain recipients showed increased persistence of extramedullary hematopoiesis and scattered foci of parenchymal necrosis in their livers. They also showed considerable cell death in thymic lobules. In rabbits given Patuxent strain SFV, virus antigens were detected only in the tumor by immunohistologic examination. Boerlage viral antigens were found in the tumor and overlying skin. We also detected virus systemically in Boerlage recipients: it was present in fixed tissue phagocytes in the spleen and liver and also in parenchymal cells of the lungs, liver, and kidney. Boerlage strain SFV recipients also showed detectable virus in their thymus, both at the periphery of the thymic lobules and in the connective tissue separating thymic lobules from each other. Despite the disseminated nature of the infection, rabbits that received the latter strain fared as well as those receiving Patuxent strain SFV.

Animals↗
PubMed1984

Antigenic complexity of Treponema pallidum: antigenicity and surface localization of major polypeptides.

The protein structure of Treponema pallidum was characterized by two-dimensional electrophoresis (2DE), consisting of isoelectric focusing (IEF, pH 5 to 7) in the first dimension and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the second dimension. Up to 85 major polypeptide species could be detected in the organisms in 2DE gels by Coomassie Blue staining. The antigenicity of the individual polypeptides was determined by transferring the 2DE pattern to nitrocellulose paper and utilizing a sensitive immunoperoxidase procedure to demonstrate the reactivity of immunoglobulins in sera obtained from rabbits infected intratesticularly at least 6 mo previously. The infected rabbit serum reacted with virtually every major polypeptide detectable by protein staining techniques, indicating that infected rabbits produce antibodies against nearly all major T. pallidum proteins at the time when the animals exhibit systemic resistance to reinfection. Surface radioiodination of freshly purified T. pallidum by an Iodogen procedure yielded preferential labeling of a major polypeptide with an apparent m.w. of 39,000. The results of this study indicate that the antigenic complexity of T. pallidum is much greater than described previously. The 39-kd polypeptide appears to be a major surface constituent of T. pallidum and as such may play an important role in the induction of immunity to syphilis.

Animals↗
PubMed1984

Light- and electron-microscopic autoradiographic analysis of proliferating cells during the early stages of chemical hepatocarcinogenesis in the rat induced by feeding N-2-fluorenylacetamide in a choline-deficient diet.

Proliferating cells that appear after feeding the hepatocarcinogen N-2-fluorenylacetamide in a choline-deficient diet were identified by autoradiographic electron and light microscopy. Labeled cells are first seen as nondescript periductular cells 1 day after feeding carcinogen. Proliferation of duct lining cells begins at 2-3 days. For the next three weeks there is proliferation and extension of a mixture of nondescript cells and cells with a duct like appearance from the portal zone into the adjacent liver. By 3-4 weeks the entire liver lobule contains this new cell population. At 3 weeks more differentiated duct like structures are seen at the edge of the advancing new cell population. Newly appearing duct like cells differ from normal duct cells in that they contain AFP and albumin. It is concluded that the new cell population may arise from duct cells or periportal "stem" cells, or both.

2-Acetylaminofluorene↗
PubMed1983

Comparison of oval cells induced in rat liver by feeding N-2-fluorenylacetamide in a choline-devoid diet and bile duct cells induced by feeding 4,4'-diaminodiphenylmethane.

Oval cells and duct-like structures produced in the livers of rats fed N-2-fluorenylacetamide in a choline-devoid diet differ from bile ducts produced after feeding 4,4'-diaminodiphenylmethane. Rapid elevations of serum alpha-fetoprotein (AFP) occur after feeding N-2-fluorenylacetamide in a choline-devoid diet; no elevations of AFP are seen during 4,4'-diaminodiphenylmethane feeding. The duct-like structures associated with oval cells frequently contain AFP and albumin and are faintly delineated by laminin, whereas normal bile ducts and ducts induced by 4,4'-diaminodiphenylmethane do not contain AFP or albumin and are delineated by an intensely staining layer of laminin. Zones of oval cell proliferation label intensely for fibronectin, whereas zones of bile duct proliferation label much less intensely. It is concluded that the "tubuloform degeneration" seen after carcinogen exposure does not necessarily represent differentiation to true bile duct structures and that oval cells may neither derive from nor differentiate into bile ducts. Oval cells have characteristics more like fetal hepatocytes than ductular cells and may represent a "stem cell"-like population with potential for loss of growth control and malignant transformation.

2-Acetylaminofluorene↗
PubMed1983

Demonstration of Treponema pallidum in a cutaneous gumma by indirect immunofluorescence.

Treponema pallidum was demonstrated in a cutaneous, tertiary syphilitic lesion by indirect immunofluorescence microscopy, but not by darkfield microscopy illumination or silver stain. The numerous organisms observed by this method may help explain the histologically vigorous tissue reaction in tertiary syphilis, despite the scarcity of organisms demonstrable by other methods.

Aged↗
PubMed1983

Immunologic dysfunction during viral oncogenesis. I. Nonspecific immunosuppression caused by malignant rabbit fibroma virus.

Malignant rabbit fibroma virus (MV) is a potent oncogenic poxvirus that produces a rapidly progressive syndrome of disseminated myxosarcoma, immunosuppression, and fatal gram-negative infection. MV is probably a recombinant between Shope fibroma virus (SFV) and rabbit myxoma virus, and is capable of preventing or aborting the in vitro proliferative responses of rabbit lymphocytes to B and T lymphocyte mitogens. Proliferative responses to sheep erythrocytes (SRBC) are similarly affected, although MV does not alter ongoing antibody responses to SRBC. Splenic lymphocytes from MV tumor-bearing rabbits suppress antibody and proliferative responses to SRBC when added to lymphocytes from SRBC-primed rabbits. Finally, lysates of cultured splenic lymphocytes from rabbits given MV suppress both proliferative and antibody-forming responses to SRBC. When MV is removed from these lysates by UV inactivation or by centrifugation, the suppressive activity remains. We therefore conclude that MV induces immunologic unresponsiveness in rabbits by at least two mechanisms. First, a direct suppressive effect of added virus on in vitro lymphocyte proliferation is seen. There is no effect in this situation if an antibody response is already in progress. Second, spleen cells exposed to MV in vivo produce one or more soluble factors capable of suppressing both proliferative and antibody responses of normal lymphocytes.

Animals↗