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Biomedical subjects

P Goldman

Publications and source records attributed to P Goldman.

At least 19 recordsLinked to original sources
PubMed1992

Urinary organic acid profiles in obese (ob/ob) mice: indications for the impaired omega-oxidation of fatty acids.

As a means of generating an hypothesis to explain genetic obesity of the C57BL/6J ob/ob mouse, we used gas chromatography-mass spectrometry to compare the urinary organic acid profiles of obese (ob/ob) and lean (+/?) mice on both a chow and a chemically simplified diet. More than 60 peaks were found and quantified; 45 peaks were identified. No acid was excreted in greater amounts by lean mice and none was excreted exclusively by either lean or obese mice. When normalized to body weight (obese mice being 40% heavier) and to creatinine excretion (30% greater in obese mice), however, only the daily excretion of malate, 2-hydroxyglutarate, aconitate, 3-hydroxy-3-methylglutarate, oxalate, ethylmalonate, and 4-hydroxyphenylacetate were significantly greater in obese mice. When allowed to eat only an all-fat (Crisco) diet for 4 days, the excretion of adipate rose 10-fold in lean mice, but only threefold in obese mice. Adipate excretion by Zucker rats also increased on the Crisco diet, but was indistinguishable between lean and fatty rats, suggesting that omega-oxidation might be impaired in obese mice but not in fatty rats. This suggestion complements an earlier proposal that a comparative increase in ethylmalonate excretion, which was also characteristic of fatty Zucker rats, might be explained by an increased concentration of butyryl-CoA due to inadequate beta-oxidation. An impairment of omega-oxidation in the obese mouse may also explain why urinary 3-hydroxy-3-methylglutarate, which is derived from short chain products of beta-oxidation, is increased in obese mice but not in fatty rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acids↗
PubMed1992

Organic acid profiling in adipocyte differentiation of 3T3-F442A cells: increased production of Krebs cycle acid metabolites.

To try to find special metabolic characteristics of adipose tissue, we examined the organic acids released into the culture medium, which was changed every 48 hours, as 3T3-F442A mouse fibroblasts underwent differentiation to adipocytes under the influence of insulin and fetal calf serum. We identified 13 different organic acids, of which four (malate, fumarate, succinate, and 2-hydroxyglutarate) increased from threefold to 10-fold during an 18-day period of differentiation. After differentiation had occurred, the deletion of insulin from the culture medium resulted in a slight decrease in the concentration of malate, fumarate, and 2-hydroxyglutarate. Other acids were not affected, including 18 that we were unable to identify by gas chromatography-mass spectroscopy. No acid was found to be present only in the medium of either fibroblasts or adipocytes.

3T3 Cells↗
PubMed1991

Interaction of metronidazole with Escherichia coli deoxyribonucleic acid.

To define the characteristics of the reported binding of metronidazole to DNA, we isolated the DNA from hypoxic incubation mixtures that contained both [14C]metronidazole and metronidazole-susceptible strains of Escherichia coli. Thus, either [2-14C]metronidazole or [1',2'-14C]metronidazole was incubated with either wild-type E. coli (strain AB1157) or a DNA repair mutant (strain SR58) that is highly susceptible to metronidazole. Approximately 0.02% of the radiolabel in the metronidazole was found to be associated with DNA isolated from both strains of bacteria, a percentage similar to that found to be associated with DNA from mammalian sources in a variety of in vitro and in vivo experiments performed by other investigators. The bound radioactivity was not diminished, however, when a great excess of non-radiolabeled metronidazole was included in the incubation mixture, indicating that the binding we observed was probably due to impurities in the radiolabeled metronidazole. We also examined the binding to DNA of a possible surrogate for the partially reduced form of metronidazole, 1-methyl-4-phenyl-5-nitrosoimidazole (5NO), that has been described previously. The binding of the tritiated form of 5NO to DNA was also found to be undiminished by the addition of carrier 5NO (a finding which does not refute the hypothesis that 5NO may serve as a surrogate for the study of the active form of metronidazole). These studies do not exclude the binding to DNA of either metronidazole or a possible surrogate of its active functionality, but they indicate that if such binding occurs, it must be limited to very few sites on DNA and hence will be difficult to characterize.

DNA Repair↗
PubMed1991

Effect of the intestinal flora on the urinary organic acid profile of rats ingesting a chemically simplified diet.

In order to estimate the influence of gut bacteria on animal metabolism, the excretion of organic acids, as monitored by gas-liquid chromatography, was compared in the urines of conventional and germ-free rats. Rats were maintained on a chemically simplified diet in order to minimize the effect of strictly exogenous compounds on the organic acid profile. Initial analysis of the excretion rates of 68 compounds, found reproducibly in the profile, indicated significant day-to-day and rat-to-rat variation, suggesting that haphazard comparison of experimental groups of animals might yield spurious differences with no biological significance. When repeated measures of the profile were analysed by a random effects analysis of variance model, no compound was found exclusively in the urine of either conventional or germ-free rats. Nevertheless, tricarballylate was significantly higher and both tartronate and vanillate significantly lower in conventional rat urine. The flora was implicated in these differences because caecal contents of conventional rats were found to convert such tricarboxylic acids as cis- and trans-aconitate to tricarballylate and to cause the dissimilation of both vanillate and tartronate, the latter compound being of dietary origin.

Analysis of Variance↗
PubMed1991

The resource utilization group system: its effect on nursing home case mix and costs.

Using data from 1985 and 1986, we examine how New York state's prospective payment system affected nursing homes. The system, called Resource Utilization Group (RUG-II), aimed to limit nursing home cost growth and improve access to nursing homes by "heavy-care" patients. As in Medicare's prospective hospital reimbursement system, payments to nursing homes were based on a "price," rather than facility-specific rates. With respect to cost growth, we observed considerable diversity among homes. Specifically, those nursing homes most financially constrained by the RUG-II methodology exhibited the slowest rates of cost growth; we observed higher cost growth among the homes least constrained. This higher rate of cost growth raises a question about the desirability of using a pricing methodology to determine nursing home payment rates. In addition to moderating cost growth, we also observed a significant change in the mix of patients admitted to nursing homes. During the first year of the RUG-II program, nursing homes admitted more heavy-care patients and reduced days of care to lighter-care patients. Thus, through 1986, the RUG-II program appeared to satisfy at least one of its major policy objectives.

Aged↗
PubMed1990

Urinary organic acid profiles in fatty Zucker rats: indications for impaired oxidation of butyrate and hexanoate.

The urinary excretion of 45 organic acids, monitored by gas-liquid chromatography, was compared in fatty (fa/fa) and lean (Fa/?) Zucker rats maintained on a chemically simplified diet. At the age of 6, 16, and 22 weeks, fatty rats excreted more of the various organic acids than their lean counterparts. However, the greatest difference was in the excretion of ethylmalonate, even when excretion data were normalized to body weight. The next highest excretion difference was in adipate and an unknown compound, and the third highest in pyruvate. A second group of rats examined at 7 weeks also excreted an excess of these four acids, as well as glucuronate and indole-3-acetate. The excessive excretion of ethylmalonate and adipate, which is characteristic of human genetic defects in short- and medium-chain fatty acid oxidation, suggested that the oxidation of butyrate and hexanoate might be impaired in the fatty rat. Thus, as a test of their capacity to oxidize medium- and short-chain fatty acids, two groups of fatty and lean rats were transferred to diets enriched with either trioctanoylglyceride, a medium-chain triglyceride (MCT), or sodium butyrate, a short-chain fatty acid. Both lean and fatty rats on the MCT diet, but only the lean rats on the butyrate-enriched diet, increased their excretion of adipate. However, on both the MCT and butyrate diet, ethylmalonate excretion increased only in lean rats, almost reaching amounts found previously in fatty rats. These results suggest that the fatty rat has an impairment of the beta-oxidation of butyrate and hexanoate, a defect that might increase intracellular concentrations of butyryl-CoA, the optimal primer for the synthesis of long-chain fatty acids.

Acids↗
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↗