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Biomedical subjects

P Goldman

Publications and source records attributed to P Goldman.

At least 37 records · Page 2Linked to original sources
PubMed1989

Thiol-mediated incorporation of radiolabel from 1-[14C]-methyl-4-phenyl-5-nitrosoimidazole into DNA. A model for the biological activity of 5-nitroimidazoles.

1-Methyl-4-phenyl-5-nitrosoimidazole (5NO), which has properties consistent with the biologically active form of a 5-nitroimidazole, was radiolabeled (1-[14C]-methyl) and shown to bind to DNA, but at a rate too slow to account for its bactericidal effect. In the presence of physiological intracellular concentrations of such thiols as glutathione, however, binding was enhanced by 2-3 orders of magnitude, which is quantitatively sufficient to account for the bactericidal effect of 5NO. That 5NO binding was greater for poly[d(G-C).d(G-C)] than for poly[d(A-T).d(A-T)] suggests that the reactive species binds to nucleophilic bases on DNA, a suggestion which is also supported by our finding of a thiol-dependent reaction to form an adduct between 5NO and aniline.

Bacteriophage lambda↗
PubMed1988

Mammalian cell toxicity and bacterial mutagenicity of nitrosoimidazoles.

It is currently believed that the biological activity of such therapeutic 5-nitroimidazoles as metronidazole is mediated by a short-lived, highly toxic species that arises from nitro group reduction. We found that the 5-nitroimidazole, 1-methyl-4-phenyl-5-nitroimidazole (5-NO2), is at least 1000-fold less cytotoxic for CHO cells and mutagenic for Ames tester strain TA100 than its homologous nitroso compound, 1-methyl-4-phenyl-5-nitrosoimidazole (5-NO). Such evidence, along with previous work showing a similar relative bactericidal potency of these compounds, is consistent with the labile nitrosoimidazole being a biologically active species of the nitroimidazole, and indicates that mammalian cells are very susceptible to such an active form. The high potency of both 5-NO and 1-methyl-4-nitroso-5-phenylimidazole (4-NO), in contrast to the lack of potency of 1-methyl-4-nitro-5-phenylimidazole (4-NO2) relative to 5-NO2, is additional evidence to support the suggestion that the activity of a nitroimidazole is determined mainly by the ease with which it is reduced.

Animals↗
PubMed1988

Alternative promoters and exons, somatic mutation and deregulation of the Bcl-2-Ig fusion gene in lymphoma.

The most common translocation in human lymphoma, the t(14;18)(q32;q21), generates heterogeneous 4.2-7.2 kb Bcl-2-immunoglobulin (Ig) chimeric mRNAs resulting from alternative Bcl-2 5' exons and varied Ig 3' untranslated regions (UT). The normal human Bcl-2 gene has a three exon structure with an untranslated first exon, a facultative 220 bp intron I, but an enormous 370 kb intron II. S1 protection and primer extension analysis defined initiation sites in exon II associated with classic promoter elements and a decanucleotide (ATG-CAAAGCA) homologous with Ig variable region enhancers. Multiple initiation sites were also found in a GC-rich region with Sp1 binding motifs in exon I. Most t(14;18) breakpoints cluster within the 3' UT of Bcl-2 implicating that event in gene deregulation. The Bcl-2 gene introduced into the Ig constant (C gamma) locus of SU-DHL-6 displayed somatic mutation. While Bcl-2--Ig mRNAs demonstrated an unaltered 2.5 h half-life, the Bcl-2--Ig gene revealed an inappropriately high rate of transcription for a mature B-cell. This indicates the translocated Bcl-2 allele has escaped normal control mechanisms.

Amino Acid Sequence↗
PubMed1988

Nitrosoimidazoles: highly bactericidal analogues of 5-nitroimidazole drugs.

It is believed that metronidazole and related 5-nitroimidazoles are activated by reduction of the nitro group and that the active species has a nitrogen functionality of intermediate oxidation state. However, the preparation and isolation of the active forms of the 5-nitroimidazoles used therapeutically have proven elusive. To pursue this problem we have prepared both 1-methyl-4-phenyl-5-nitrosoimidazole (3) and 1-methyl-4-nitroso-5-phenylimidazole (5) from 4(5)-nitroso-5(4)-phenylimidazole (1). We have also prepared the homologous nitroimidazoles. Escherichia coli mutants with defects in DNA repair were found to be sensitive to both 1-methyl-4-phenyl-5-nitroimidazole (4) and metronidazole, but fairly resistant to 1-methyl-4-nitro-5-phenylimidazole (6), a finding in accord with the relative biological activity of 4- and 5-nitroimidazoles examined previously. In contrast, all three nitroso compounds are considerably more bactericidal than their analogous nitro compounds under both aerobic and anaerobic conditions, a finding that provides direct evidence that reduction of the nitro group is responsible for activation of the nitroimidazoles. Further evidence is also consistent with the possibility that the nitrosoimidazoles are themselves biologically active species derived from nitroimidazoles, although a more conservative interpretation is simply that they are more facilely converted to such active species.

Anti-Bacterial Agents↗
PubMed1988

Nitrate production and phagocyte activation: differences among Sprague-Dawley, Wistar-Furth and Lewis rats.

We have found that activated resident peritoneal macrophages from Wistar-Furth and Sprague-Dawley rats produce significantly more superoxide (2.2 +/- 0.4 and 3.6 +/- 0.8 nmol of cytochrome c reduced/10(6) cells/10 min respectively) than those from Lewis rats (1.0 +/- 0.3 nmol of cytochrome c reduced/10(6) cells/10 min). Similar results are found in macrophages elicited with intraperitoneal thioglycolate. Furthermore, nitrate excreted in the urine increased greatly when either Wistar-Furth or Sprague-Dawley rats are injected i.p. with iota carrageenan (0.25 g), a response that did not occur with Lewis rats. This strain difference in the manifestations of the inflammatory response correlates with previous observations that Wistar-Furth and Sprague-Dawley rats, but not Lewis rats, develop suture-line colonic tumors when the ureters and bladder base are implanted into the colon.

Animals↗
PubMed1987

5-Aminosalicylate: oxidation by activated leukocytes and protection of cultured cells from oxidative damage.

It has been postulated that oxygen radicals may play a role in the pathogenesis of inflammatory bowel disease. If so, then a drug like 5-aminosalicylate (5-ASA), which is used to treat such diseases, might work by interacting with oxygen-derived species. We found that activated mononuclear cells and activated granulocytes, as well as the products of the Fenton reaction, transformed [14C]5-ASA to a number of metabolites, among which we have characterized salicylate and gentisate. We also found that the lethal effect on cultured Chinese hamster ovary cells of adding either superoxide radical or hydrogen peroxide, components of the respiratory burst of activated white blood cells, was diminished by the addition of 100 micrograms/ml (0.65 mM) of 5-ASA. Thus, we have demonstrated that 5-ASA was oxidized by the oxidative burst of white blood cells and that 5-ASA protected cells from damage by oxygen-derived species, two findings which may offer an explanation for the role of 5-ASA in the treatment of inflammatory bowel disease.

Aminosalicylic Acids↗
PubMed1987

Chemical and biological properties of acetyl derivatives of the hydroxylamino reduction products of metronidazole and dimetridazole.

Metronidazole and related 5-nitroimidazoles undergo reduction of their nitro group apparently to produce such reactive species as 5-hydroxylaminoimidazoles. To define the role of these species we have sought ways to prepare them by the catalytic reduction of metronidazole, dimetridazole and flunidazole. Although their respective 5-hydroxylaminoimidazoles were too unstable to be isolated directly, their O,N-diacetyl derivatives were isolable. Of these, the diacetyl derivative of the hydroxylamine derived from dimetridazole, O,N-diacetyl-1,2-dimethyl-5-hydroxylaminoimidazole (DiacDMH), was used for further study. DiacDMH was converted to its monoacetyl derivative, N-acetyl-1,2-dimethyl-5-hydroxylaminoimidazole (AcDMH), by enzymatic deacylation. Both DiacDMH and AcDMH were examined for bactericidal activity against such strains as Bacteroides fragilis, Clostridium perfringens, and Escherichia coli strain SR58, which are known to be sensitive to dimetridazole, as well as a variety of other bacteria. No bactericidal activity was detected, even in the presence of deacetylating enzymes. As the 5-hydroxylaminoimidazole itself could not be shown to form in these bacterial incubations, it remains uncertain whether or not the hydroxylamino functionality of a 5-nitroimidazole has bactericidal activity.

Acetylation↗
PubMed1987

Formation of an amino reduction product of metronidazole in bacterial cultures: lack of bactericidal activity.

To investigate whether the amino reduction product of metronidazole has antibacterial activity, 5-amino-1-beta-hydroxyethyl-2-methylimidazole (AMN) was synthesized and tested against Bacteroides fragilis and Escherichia coli strain SR58, both of which are known to be sensitive to metronidazole. Neither of these strains was found to be sensitive either to AMN or to the equivalent amine derived from dimetridazole, 5-amino-1,2-dimethylimidazole. Both of these amines are relatively stable in the presence of bacteria, making it possible to examine the bacterial reduction of radiolabeled metronidazole in the presence of AMN. This experiment indicated that at least 17% of the metronidazole that disappeared under the reducing conditions of the bacterial medium was converted to AMN. We conclude, therefore, that AMN forms during the activation of metronidazole by bacterial reduction but is not a bactericidal form of metronidazole.

Bacteroides fragilis↗
PubMed1987

Mechanism of the t(14;18) chromosomal translocation: structural analysis of both derivative 14 and 18 reciprocal partners.

To elucidate the mechanism of the t(14;18)(q32;q21) chromosomal translocation found in follicular lymphoma, we examined the structure of both derivative (der) chromosomal breakpoints as well as their germ-line predecessors. We noted that chromosome segment 18q21 was juxtaposed with immunoglobulin heavy (H) chain gene diversity (DH) regions on all five der(18) chromosomes we examined, and we confirmed the juncture with immunoglobulin H-chain gene joining (JH) regions on the der(14) chromosome. However, the t(14;18) was not fully reciprocal in that chromosome 14 DNA between the DH and JH regions was deleted. Furthermore, extra nucleotides, reminiscent of "N" segments, were present at the der(14) and possibly der(18) junctions. This indicates that despite the mature B-cell phenotype of follicular lymphoma, the t(14;18) occurs during attempted DH-JH joining, the earliest event in immunoglobulin rearrangement in a pre-B-cell. Our detailed analysis of the germ-line 18q21 region indicated that most breakpoints clustered within a 150-base-pair major breakpoint region. However, we found no evidence for evolutionarily conserved immunoglobulin-like recombinational signals at 18q21, arguing against a role for immunoglobulin recombinase in chromosome 18 breakage. Instead, a direct repeat duplication of chromosome 18 sequences was discovered at both chromosomal junctures, typical of the repair of a naturally occurring staggered double-stranded DNA break. These results prompt a translocation model with illegitimate pairing of a staggered double-stranded DNA break at 18q21 and an immunoglobulin endonuclease-mediated break at 14q32 and with N-segment addition, repair, and ligation to generate der(14) and der(18) chromosomes.

Base Sequence↗
PubMed1987

T cell receptor alpha-, beta-, and gamma-genes in T cell and pre-B cell acute lymphoblastic leukemia.

We examined alpha-, beta-, and gamma-T cell receptor (TCR) gene activation within acute lymphoblastic leukemias (ALLs) that represent early stages of B and T cell development. We wished to determine if TCR rearrangement and expression was lineage restricted, showed any developmental hierarchy, or could identify new subsets of T cells. Rearrangement of gamma and beta TCR genes occurred early in development but in no set order, and most T-ALLs (22/26) were of sufficient maturity to have rearranged both genes. T-ALLs preferentially rearranged C gamma 2 versus the C gamma 1 complex; no preference within the beta locus was apparent. Once rearranged, the beta TCR continued to be expressed (11/13), whereas the gamma TCR was rarely expressed (3/14). The alpha TCR was expressed only in more mature T-ALLs (8/14) that usually displayed T3. The 3A-1 T cell associated antigen appeared earliest in development followed by T11 and T3. Within pre-B cell ALL a higher incidence of lineage spillover was noted for gamma TCR rearrangements (8/17) than for beta rearrangements (3/17). This also contrasts with the only occasional rearrangement of immunoglobulin (Ig) heavy chains (3/25) in T-ALL. However, in pre-B ALL the pattern of gamma TCR usage was distinct from that of T cells, with the C gamma 1 complex utilized more frequently. Almost all ALLs could be classified as pre-B or T cell in type by combining Ig and TCR genes with monoclonal antibodies recognizing surface antigens, although examples of lineage duality were noted. Unique subpopulations of cells were discovered including two genetically uncommitted ALLs that failed to rearrange either Ig or TCR loci. Moreover, two T lymphoblasts were identified that possessed the T3 molecule but failed to express alpha plus beta TCR genes. These T-ALLs may represent a fortuitous transformation of T cell subsets with alternative T3-Ti complexes.

B-Lymphocytes↗
PubMed1987

Expression of Bcl-2 and Bcl-2-Ig fusion transcripts in normal and neoplastic cells.

We examined the expression of the Bcl-2 gene at chromosome segment 18q21, that is translocated into the Ig heavy chain gene locus in t(14;18) bearing lymphomas. Bcl-2, while B cell associated, is expressed in a variety of hematopoietic lineages including T cells. Bcl-2 mRNA levels are high during pre-B cell development, the time at which the t(14;18) translocation occurs, but are down regulated with maturation. Like certain other oncogenes, Bcl-2 is quiescent in resting B cells but up-regulated with B cell activation. Mature B cell lymphomas with a t(14;18) have log-folds more mRNA than matched counterparts without the translocation. A sensitive S1 protection assay revealed that all transcripts in t(14;18) B cells were Bcl-2-Ig fusion mRNAs and originated from the translocated allele. Thus, there is a marked deregulation of Bcl-2 when it is introduced into the Ig locus in t(14;18) lymphomas.

B-Lymphocytes↗
PubMed1986

Immune regulation of the L5178Y murine tumor-dormant state. I. In vivo and in vitro effects of prostaglandin E2 and indomethacin on tumor cell growth.

Immunization and intraperitoneal challenge of DBA/2 mice with L5178Y lymphoma cells results in the suppression and maintenance of the L5178Y cells in a tumor-dormant state in the peritoneal cavity for many months. Cell-mediated immune responses involving lymphocytes and macrophages are involved in maintenance of the tumor-dormant state. Macrophages that have increased immunosuppressive activity and that produce increased amounts of PGE2 appear in the peritoneal cavity of tumor-dormant mice before the breakdown of the tumor-dormant state and formation of ascitic tumors. We report here that the tumor-dormant state can be terminated with formation of ascitic tumors by treatment of tumor-dormant mice with PGE2. Treatment with indomethacin results in inhibition of tumor cell growth and elimination of all recoverable tumor cells. Cultures of peritoneal cells (PC) from mice harboring L5178Y cells in a tumor-dormant state were used to analyze the PGE2 and indomethacin effects. Tumor cells did not grow out in the high-cell density PC cultures prepared from many tumor-dormant mice, but addition of PGE2 to these cultures resulted in tumor cell growth. The tumor cell growth that did occur in the PC cultures from some tumor-dormant mice was associated with PGE2 production by the associated host cells, and the addition of indomethacin to these cultures inhibited both PGE2 synthesis and tumor cell growth. Removal of plastic-adherent cells from the PC cultures eliminated the restraint on tumor cell growth. These experiments suggest that L5178Y tumor cells are maintained in a tumor-dormant state by host peritoneal cells, which are under PGE2 regulation.

Animals↗
PubMed1986

Studies on avian erythrocyte metabolism. XIV. Effect of CO2 and pH on P50 in the chicken.

The O2 affinity (P50) of erythrocyte suspensions from 18-day chick embryos, from 2-, 5-, 8-, and 14-day chicks, and from mature chickens decreased with increasing concentrations of either CO2 or H+, particularly at a pH near 7.4 and at 37 degrees C. A greater effect on delta P50's was observed from increasing H+ concentration from pH 8.0 to 6.8 in cell suspensions from 18-day embryos (28.8 Torr at 0% CO2) and adult chickens (55.1 Torr at 0% CO2) than from increases in CO2 concentration at any given pH. The Bohr effect (delta log P50/delta pH) in the absence of CO2 was -0.508 and -0.479 for cell suspensions from 18-day chick embryos and adult birds, respectively. The specific effect of CO2 on the Bohr effect, regardless of the CO2 concentration, indicates that the delta P50/0.1 pH is approximately 1.35 and 2.45 Torr for the embryo and adult chicken blood. These results indicate that increasing H+ and CO2 concentrations markedly affect the P50 of chicken blood and that even subtle changes in either could play a significant role physiologically in regulating blood P50 in birds.

Animals↗
PubMed1986

[Not Available].

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France↗