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Biomedical subjects

M Potter

Publications and source records attributed to M Potter.

At least 91 records · Page 5Linked to original sources
PubMed1996

Antibodies to cholesterol: biological implications of antibodies to lipids.

Injection of silicone gel or silicone oil intraperitoneally into BALB/c mice induced the formation of antibodies that reacted by ELISA with highly purified crystalline cholesterol and, to a much lesser extent, antibodies that reacted with a phospholipid (dimyristoyl phosphatidylglycerol). Although IgM and IgG antibodies to cholesterol were detected, the titers of IgG antibodies were low when compared with IgM. The titers of IgM antibodies to cholesterol in certain sera exhibited activities that reached baseline values at dilutions as high as 1:5000, thus making them equivalent to titers that have been previously published for ascites fluid containing murine monoclonal antibodies to cholesterol. The antibodies to cholesterol induced by silicone compounds are indistinguishable in their binding to crystalline cholesterol from naturally-occurring antibodies to cholesterol in normal human serum. They are also indistinguishable from antibodies induced by a proposed vaccine to cholesterol that is currently in late preclinical development for prevention of hypercholesterolemia in humans. The anti-cholesterol vaccine, which consists of liposomes heavily laden with cholesterol as an antigen and lipid A as an adjuvant, induces antibodies that react with low density lipoproteins (LDL) and opsonize them for removal by liver macrophages. It appears that silicone gel or silicone oil causes recruitment and adsorption of cholesterol at the injection site, and also serves as an adjuvant that may have immunostimulant properties similar to lipid A for inducing antibodies to lipids. Antibodies to lipids such as cholesterol or phospholipids are not harmful to intact cell membranes because of steric hindrance from surrounding lipids and larger macromolecules that block binding of the antibodies.

Animals↗
PubMed1996

Plasmacytoma development in mice injected with silicone gels.

Silicone gels derived from commercially obtained implants induce plasmacytomas in 60-70% of highly susceptible BALB/cAn.DBA/2-Idh1-Pep3 congenic mice. In contrast, dimethylpolysiloxane (DMPS) silicone oils with viscosities of 5, 1000 and 12,500 cs fail to elicit these tumors. 1000 cs vinylmethylpolysiloxane is also inactive. Silicone gels, in contrast to the oils, induce a highly inflammatory silicone granuloma. Silicone gels contain chemical components not found in the oils. The chemical component responsible for inducing the permissive environment for plasmacytoma formation has not yet been identified. Silicone gels are well tolerated for long periods of time in mice without adverse effects other than plasmacytoma formation. The response to different gel preparations varies; some are associated with relatively rapid formation of plasmacytomas resembling that seen with pristane, while in others the plasmacytoma formation is extended nearly over a two year period.

Animals↗
PubMed1996

A "humanized" green fluorescent protein cDNA adapted for high-level expression in mammalian cells.

We constructed gfph, a synthetic version of the jellyfish Aequorea victoria green fluorescent protein (gfp) cDNA that is adapted for high-level expression in mammalian cells, especially those of human origin. A total of 92 base substitutions were made in 88 codons in order to change the codon usage within the gfp10 coding sequence so that it was more appropriate for expression in mammalian cells. We also describe a series of versatile recombinant adeno-associated virus and adenovirus vectors for delivery and expression of genes into mammalian cells and, using these vectors, demonstrate the efficient transduction and expression of the gfph gene in the human cell line 293 and also in vivo, within neurosensory cells of guinea pig eye. Cells infected with recombinant adeno-associated virus-GFPH can be readily sorted by fluorescence-activated cell sorting, suggesting that the newly designed gfph gene could be widely used as a reporter in many gene delivery technologies, including human gene therapy.

Amino Acid Sequence↗
PubMed1995

Differences between Burkitt's lymphomas and mouse plasmacytomas in the immunoglobulin heavy chain/c-myc recombinations that occur in their chromosomal translocations.

Burkitt's lymphomas (BLs) and mouse plasmacytomas (MPs) are characterized by chromosomal translocations juxtaposing the c-myc oncogene to one of the immunoglobulin loci. Here we describe illegitimate recombinations and the DNA sequence at the junction between c-myc and immunoglobulin heavy chain (IgH) regions in these B-cell lineage tumors. In 15 BLs and in 29 MPs, recombination products were amplified by PCR and sequenced. Molecular analysis of the IgH/c-myc junctions revealed the following characteristics: (a) rearrangements in BLs represent nearly reciprocal exchanges between c-myc and IgH switch sequences, whereas in MPs, several hundred bp of c-myc may be duplicated or deleted; (b) short homologies of up to 5 bp between immunoglobulin and c-myc sequences can be found at most junction sites in both tumors; and (c) pentameric sequences typically found in switch regions and V(D)J recognition motifs also occur frequently at the sites of recombination in c-myc.

Animals↗
PubMed1995

Persistence of immunoglobulin heavy chain/c-myc recombination-positive lymphocyte clones in the blood of human immunodeficiency virus-infected homosexual men.

We studied blood lymphocytes of human immunodeficiency virus (HIV)-seropositive and -negative homosexual men for the presence of T(8;14) translocations that recombine c-myc and immunoglobulin heavy-chain (IgH) mu/IgH alpha switch regions. Clones with T(8;14) translocations were detected in 10.5% (12/114) of the HIV-positive and in 2.0% of the 99 uninfected patients. The majority of recombinations were found at a single time point only. Four patients, however, harbored multiple (up to four) and persistent (up to 9 years) translocation-positive cell clones. No correlation between the presence of these aberrant lymphocytes and a later lymphoma could be established. The exon 1/intron 1 region of the recombined c-myc was investigated for the presence of point mutations and these were found in the nonpersistent clones. Additional alterations detected in these clones included duplications and a deletion in the c-myc gene. The pattern of base substitution indicates that they were introduced after the translocation event.

Base Sequence↗
PubMed1995

Nonrandom chromosomal change (trisomy 11) in murine plasmacytomas induced by an ABL-MYC retrovirus.

Trisomy of chromosome 11 (Ts11) is the second most frequent nonrandom chromosomal change in murine plasmacytomas (PCTs). The frequency of Ts11 is significantly higher in PCTs induced in pristane-conditioned mice infected by Abelson-murine leukemia virus (52%) compared to those induced by pristane alone (8.1%). Although the significance of Ts11 in mouse plasmacytomagenesis is not clearly understood it is hypothesized that a gene or genes located on chromosome (Chr) 11 may specifically promote the development of PCTs in which both oncogenes, c-myc and v-abl, are abundantly expressed. To test this assumption we induced PCTs by three highly effective plasmacytomagenic retroviruses: ABL-MYC, J3V1, and RIM. Nearly 90% of PCTs that arose in BALB/c, (BALB/c x DBA/2N)F1, BALB/c-nu/nu, and 5-month-old SCID mice infected with ABL-MYC virus were trisomic for Chr 11. In contrast, < 10% of PCTs induced by J3V1 or RIM retroviral constructs encompassing either v-myc and v-raf or c-myc and v-Ha-ras oncogenes, respectively, contained Ts11. We have also investigated whether the entire Chr 11 or any particular subregion is preferentially duplicated in the process of ABL-MYC plasmacytomagenesis. By inducing PCTs in F1 heterozygous mice that are carriers of reciprocal translocations involving Chr 11 we found that the duplicated chromosomal region is located distal to the T4Dn breakpoint (11B5 band) on the telomeric segment of Chr 11. The regular duplication of this chromosomal segment strongly suggests the presence of a gene or genes whose amplification is of critical importance for v-abl associated murine plasmacytomagenesis.

Animals↗
PubMed1995

Perturbation of B cell genesis in the bone marrow of pristane-treated mice. Implications for plasmacytoma induction.

A single injection of pristane was given i.p. to plasmacytoma-susceptible BALB/cAn mice. At intervals up to 6 mo thereafter, immunofluorescence labeling of intranuclear terminal deoxynucleotidyl transferase (TdT), cell surface B220 glycoprotein, cytoplasmic mu-chains of IgM (c mu), and surface mu-chains (s mu), together with mitotic arrest techniques, were used to quantitate the in vivo population dynamics of precursor B cells in the bone marrow. TdT-expressing pro-B cells (TdT+B220-, TdT+B220+), before the expression of mu-chains, showed sustained increases in both population size and the number of cells flowing through mitosis per unit time. In contrast, populations of pre-B cells (c mu + s mu -) and B cells (s mu +) were consistently depressed for long periods of time, including the phase of plasmacytoma formation. Precursor B cells in DBA/2 mice, a plasmacytoma-resistant strain, showed similar responses to pristane treatment. The results demonstrate that a single injection of pristane, which greatly increases the demand for macrophage activity in the peritoneal space, causes sustained distant alterations in B cell lymphopoiesis in the bone marrow; specifically, a prolonged increased proliferation of pro-B cells coupled with a depression and a exaggerated loss of pre-B cells and B cells. The protracted stress on B cell lymphopoiesis may be a predisposing factor in the subsequent development of c-myc-activating chromosomal rearrangements that play a critical role in plasmacytomagenesis.

Animals↗
PubMed1995

Induction of plasmacytomas in genetically susceptible mice with silicone gels.

Silicone gels injected intraperitoneally into strains of mice related to BALB/c develop plasmacytomas in approximately the same numbers and with similar phenotypes as previously obtained with pristane. Silicone gels produce few side effects and are well tolerated for long periods. Silicone gels contain several components that are potentially biologically active: residual vinyl groups and platinum. Microscopic and histological evidence suggests the silicone gel is degraded over a long period of time. Preliminary studies with long chain liquid dimethylpolysiloxanes with viscosities of 1000 cSt and 12,500 cSt have not produced plasmacytomas as yet. The plasmacytomagenic action of the gel appears to be due to the release of liquids from the gel matrix.

Animals↗
PubMed1995

Genomic instability in B-cells and diversity of recombinations that activate c-myc.

Genetic rearrangements activating the proto-oncogene c-myc comprise a mandatory oncogenic step in plasma cell tumor development in BALB/cAnPt mice. In the majority of plasmacytomas, c-myc activating rearrangements take the form of reciprocal chromosomal translocations t(12;15) that juxtapose c-myc to the immunoglobulin heavy chain alpha locus (IgH alpha) in particular the switch alpha region (S alpha). The genetic basis for the prevalence of S alpha/c-myc recombinations in BALB/cAnPt plasmacytomas is not known but may be related to a hypothetical regional genomic instability of the c-myc and IgH alpha loci in BALB/cAnPt mice. We wished to test whether the genomic instability of both loci might be revealed by the diversity of genetic recombinations that can be observed in IgH alpha and c-myc. We employed PCR methods to detect new recombinations of c-myc and IgH alpha in the preneoplastic stage of plasma cell tumor development and found that c-myc can be joined to more genes or genomic regions than known before. This is indicative but does not formally prove a particular genomic instability of c-myc and IgH alpha in BALB/cAnPt B cells. Since defective DNA repair provides a mechanistic explanation for genomic instability, we measured the efficiency of repair in IgH alpha and c-myc using an assay that quantitates the removal of UV-induced pyrimidine dimers within specific genomic regions. We used plasmacytoma XRPC 24 as a model system and found that both IgH alpha and c-myc were poorly repaired, whereas c-abl, a proto-oncogene not related to conventional pristane-induced plasmacytoma-genesis, was efficiently repaired.

Animals↗
PubMed1995

Illegitimate recombinations between c-myc and immunoglobulin loci are remodeled by deletions in mouse plasmacytomas but not in Burkitt's lymphomas.

Recombinations between c-myc and immunoglobulin loci are a hallmark of Burkitt's lymphomas and mouse plasmacytomas. Analyzing the fine structure of these illegitimate rearrangements has revealed differences between the recombinations in these two tumors. Recombinations are nearly reciprocal in Burkitt's lymphomas, whereas in most BALB/c plasmacytomas large stretches of c-myc sequences have been deleted. The recombinations detected during preneoplastic development of plasmacytomas, in contrast, have most of the c-myc sequences retained on either one of the translocated chromosomes. We conclude that initial recombination structures are subjected to secondary changes in mouse plasmacytomas. In Burkitt's lymphomas the primary recombination sequence is preserved in tumor cells.

Animals↗
PubMed1994

Differences in the molecular structure of c-myc-activating recombinations in murine plasmacytomas and precursor cells.

The translocation of c-myc on chromosome (chr.) 15 to an immunoglobulin heavy-chain switch region on chr. 12 is the critical oncogenic step in pristane-induced plasmacytoma (PCT) development in BALB/cAnPt mice. Applying a recently developed PCR method, we have been able to detect the most commonly occurring illegitimate recombinations between alpha-chain switch region (S alpha) and c-myc in preneoplastic B cells residing in mesenteric oil granuloma (OG) tissues 7-30 days postpristane. In this study, we compare the nucleotide sequences at the S alpha/c-myc breaksites on both the c-myc-activating chr. 12+ and the reciprocal chr. 15- from eight transplanted PCTs, seven primary PCTs, and five OGs that contained six B-cell clones. These junction sequences revealed a remarkable diversity of S alpha/c-myc recombinations. In nine cases--four PCTs and five B-cell clones--nearly precise reciprocal exchanges with a loss of only 3-35 bp in c-myc were found. Large deletions in c-myc that removed 369-878 bp were observed in seven PCTs but not in early B cells. Duplications of c-myc ranging from 103 to 229 bp were also restricted to PCTs and noticed in four cases. Clonally related but different reciprocal recombinations, 38 bp apart on chr. 12+ and 15 bp apart on chr. 15-, were isolated from two different specimens of the same OG tissue from a BALB/c mouse 30 days postpristane. A second OG from another 30-day mouse yielded four recombinational fragments--two clonally related chr. 12(+)-specific fragments and two chr. 15(-)-specific fragments--one of which carried a 143-bp insertion of a microsatellite at the breaksite. We suggest that the initial recombinational break-point regions between S alpha and c-myc in plasmacytoma precursor cells at the time of immunoglobulin heavy-chain switching are intrinsically labile and characterized by a persisting instability of c-myc, which can result in large secondary deletions of c-myc.

Animals↗
PubMed1994

Induction of plasmacytomas with silicone gel in genetically susceptible strains of mice.

BACKGROUND: Plasmacytomas can be induced in high frequency in susceptible strains of mice by the intraperitoneal introduction of plastics or paraffin oils, including the chemically defined oil pristane (2,6,10,14-tetramethylpentadecane). These materials persist in the peritoneal cavity, where they induce chronic inflammation during the long periods before plasmacytomas develop. Such plasmacytomas appear to arise from B cells carrying chromosomal translocations that affect c-myc transcription. PURPOSE: Because silicone gels are in widespread medical use and share many of the characteristics of other materials known to be inducers of plasmacytomas, we wished to determine their capacity to induce plasmacytomas in mice. METHODS: In a series of parallel experiments, corn oil, pristane, silicone oil (dimethylpolysiloxane), or silicone gel from commercially obtained mammary implants was injected intraperitoneally into plasmacytoma-susceptible BALB/cAnPt-A and congenic BALB/cAnPt.DBA/2-Idh1-Pep3 mice, as well as into plasmacytoma-resistant C57BL/6N, C3H/HeJ, DBA/2N, and (BALB/c x DBA/2)F1 mice. Mice were examined at least once every 2 weeks for signs of abdominal tumor or weight loss and screened every 4-6 weeks for peritoneal plasmacytoma cells by peritoneal lavage. Tissues were examined by histologic and immunohistochemical techniques. Metaphase chromosome spreads were made from ascitic plasmacytomas without Colcemid treatment, and metaphase plates were G-banded according to standard techniques. The t(12;15) or t(6;15) translocation chromosomes were identified under the microscope in at least five metaphase plates of high banding quality. Mice were autopsied 125-400 days after the injection of test material. Gas chromatography and mass spectrometry were utilized to determine the composition of the silicone oil and silicone gel used in the injections. RESULTS: The silicone gels tested induced plasmacytomas in BALB/cAnPt-A and BALB/cAnPt.DBA/2-Idh1-Pep3 mice. Neither corn oil used as a control nor 1000-centistoke or 12,500-centistoke dimethylpolysiloxane induced plasmacytomas in these mice. The plasmacytomas were transplantable in syngeneic hosts. Cytogenetic studies of 41 silicone-induced plasmacytomas showed that 30 had t(12;15) translocations, eight had t(6;15) translocations, and three had no translocations. CONCLUSIONS: The silicone gels used in mammary implants, which contain a complex mixture of different siloxanes, induced peritoneal plasmacytomas in genetically susceptible mice. Silicone gels provide new chemically defined materials that are effective inducers of plasmacytomas in BALB/cAnPt-A and BALB/cAnPt.DBA/2-Idh1-Pep3 mice. Further studies will be required to determine which of the components of these gels are the active materials.

Animals↗