Search PubMed⌕ Search

Biomedical subjects

J L Born

Publications and source records attributed to J L Born.

At least 19 recordsLinked to original sources
PubMed1995

Inhibition of sarcoplasmic/endoplasmic reticulum calcium ATPases (SERCA) by polycyclic aromatic hydrocarbons in HPB-ALL human T cells and other tissues.

Polycyclic aromatic hydrocarbons (PAHs) are immunosuppressive chemicals found in the environment that have been shown to disrupt intracellular Ca2+ homeostasis and Ca(2+)-dependent signaling in human and murine lymphocytes. Many PAHs produce a rapid and sustained increase in intracellular free Ca2+ in lymphocytes. The mechanism of persistent Ca2+ perturbation remains undefined. In the present studies, ATP-dependent 44Ca2+ uptake into vesicles prepared from a 15,000g supernatant of HPB-ALL human T cell lysates was significantly inhibited by 0.1, 1, and 10 microM concentrations of the immunotoxic PAHs 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BAP), benz[a]anthracene, and 9,10-dimethylanthracene, but not by the less immunotoxic compounds anthracene (ANT) and benzo[e]pyrene (BEP). Ca(2+)-ATPase catalytic activity was determined by quantitating hydrolysis of ATP in the presence or absence of PAHs, with known ATPase inhibitors included as controls. Formation of inorganic phosphate was significantly decreased (> 65% of control at 10 microM) by DMBA and BAP, whereas ANT and BEP caused only a slight reduction in activity (10% of control at 10 microM). Anthracene partially reversed the inhibitory effect of DMBA and BAP on ATP hydrolysis when agents were coincubated. Both DMBA and BAP, but not ANT and BEP, inhibited the activity of all known SERCA-type Ca(2+)-ATPases, while not affecting either Na+, K(+)-ATPase activity or plasma membrane Ca(2+)-ATPase activities. These results demonstrate that immunotoxic and carcinogenic polycyclic aromatic hydrocarbons have a thapsigargin-like effect in human lymphocytes and SERCA-containing tissues from various species. Inhibition of SERCA activity may play an important role in altered Ca2+ homeostasis in lymphocytes and other tissues.

Adenosine Triphosphate↗
PubMed1994

Inhibition of humoral immunity and mitogen responsiveness of lymphoid cells following oral administration of the heterocyclic food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to B6C3F1 mice.

In these studies, the food promutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was evaluated for its immunotoxicity in B6C3F1 mice following oral 5-day dosing at total doses of 50 and 150 mg/kg. Results indicated that PhIP produced a dose-dependent suppression of the humoral immune response of spleen cells to sheep erythrocytes, with a 50% decrease in the number of PFC detected at the 150 mg/kg dose of PhIP. A 40-90% inhibition of the phytohemagglutinin (PHA) response of spleen cells, mesenteric lymph nodes (MLNs), and Peyer's patch (PP) lymphocytes was seen in the treatment groups. The lipopolysaccharide (LPS) response was somewhat more variable and less affected with 20-30% inhibition observed in the spleen and PPs, whereas PhIP increased the LPS response in the MLNs. There was no effect of PhIP on cell recovery or viability in any of the treatment groups. Flow cytometry analysis revealed a depletion of T cells (Thy 1.2+ cells) and a slight increase in B cells (Ly5+ cells) in the PPs. The percentage of B and T cells present in the spleen and MLNs was unaffected by PhIP. These results demonstrate that the oral administration of PhIP produces immunotoxicity to mice, especially to lymphoid tissues present in the GI tract (i.e., PPs), and demonstrates that T cell mitogen (PHA) responses in PPs are the most sensitive indicator of PhIP-induced immunotoxicity.

Administration, Oral↗
PubMed1994

Polycyclic aromatic hydrocarbons decrease intracellular glutathione levels in the A20.1 murine B cell lymphoma.

Previous studies in this laboratory have shown that polycyclic aromatic hydrocarbons (PAHs) inhibit lymphocyte activation and alter intracellular Ca2+ homeostasis. Other investigators have demonstrated that intracellular Ca2+ may increase in lymphocytes following exposure to chemical oxidants or ionizing radiation. Cellular oxidants produce both a rise in intracellular Ca2+ and a decrease in intracellular levels of glutathione (GSH) in numerous cells and tissues. Therefore, the purpose of the present study was to determine whether PAHs alter intracellular levels of glutathione in lymphocytes. Using different, well-established glutathione assays, it was demonstrated in the A20.1 murine B lymphoma that PAHs induce a transient decrease in intracellular glutathione. A 10-25% decrease in reduced GSH was produced by benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene, benz(a)anthracene, and anthracene within 2-4 hr of exposure. Benzo(e)pyrene did not alter intracellular levels of glutathione in A20.1 cells. We conclude that glutathione depletion may contribute to cell injury in lymphocytes exposed to PAHs.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Persistence of calcium elevation in the HPB-ALL human T cell line correlates with immunosuppressive properties of polycyclic aromatic hydrocarbons.

The immunosuppressive synthetic methylated polycyclic aromatic hydrocarbon (PAH), 7,12-dimethylbenz[a]anthracene (DMBA), has been shown to cause both an immediate and a sustained elevation of free intracellular calcium (Ca2+) in human T cells. In the present studies, a series of anthracene- and pyrene-based PAHs were tested for rapid (3 min) and sustained (4 hr) Ca2+ mobilization in the HPB-ALL human T cell line measured by flow cytometry using Fluo-3 as a Ca2+ indicator. Immunosuppressive PAHs produced a sustained Ca2+ elevation for at least 4 hr, while weakly immunosuppressive PAHs caused only a transient increase in Ca2+. The immunosuppressive PAHs, DMBA, benzo[a]pyrene, dibenz[a,h]anthracene, and 9,10-dimethylanthracene, produced a sustained increase in intracellular Ca2+ in HPB-ALL cells. Those PAHs with moderate to minimal immunosuppressive properties (i.e., dibenz[a,c]anthracene, benz[a]anthracene, benzo[e]pyrene, and anthracene) produced small and transient Ca2+ mobilization responses in HPB-ALL cells. It appeared that methylation of anthracene at the 9,10-positions increased the duration of Ca2+ mobilization, whereas the addition of a benzene group in the "a" position was associated with a transient increase in Ca2+ levels. Genistein, a protein tyrosine kinase (PTK) inhibitor, partially inhibited the rapid and sustained PAH-induced Ca2+ mobilization responses, while the protein kinase C (PKC) inhibitors, staurosporine and calphostin C, had essentially no effect on PAH-induced Ca2+ elevation. It appears that the action of PAHs on PTKs is important in the rapid Ca2+ response of human T cells. However, additional biochemical mechanisms appear to be responsible for the sustained elevation of Ca2+ produced by PAHs in T cells. The results of these studies demonstrate that persistent elevation of intracellular Ca2+ by PAHs correlates with their known immunosuppressive properties.

Benzo(a)pyrene↗
PubMed1994

Characterization of induced pulpal hypoxia using 3H-misonidazole.

Tritiated misonidazole (3H-MISO) is a bioreductively activated marker which preferentially binds to cells with decreased oxygen tension (hypoxia). Detection of hypoxia may be an important indicator of metabolic imbalance. For 3H-MISO to be functional as a marker, normal oxygen (normoxic) levels must be distinguishable from increased hypoxic retention. This investigation characterized retention of 3H-MISO in: (a) normoxic pulp, (b) induced hypoxic pulp, and (c) reoxygenated hypoxic pulp. Rats were injected intraperitoneally with either 3H-MISO, unlabeled MISO, or saline, then divided into normoxic and hypoxic groups with appropriate controls. Normoxic animals were maintained at ambient pressure. Hypoxia was induced by placing animals in a hypobaric chamber at 0.5 atm. Pulps were then removed and prepared for liquid scintillation counting. Hypoxic pulps retained significantly more 3H-MISO than normoxic pulps (analysis of variance, p = 0.001). Hypoxic 3H-MISO retention was unaffected by subsequent, transient tissue reoxygenation. 3H-MISO detects changes in pulpal oxygen status that deviate from normal.

Analysis of Variance↗
PubMed1993

Enhanced tumor imaging with pokeweed mitogen.

Traditional tumor imaging with biotracer techniques relies solely on the target specificity of the biomolecule. We hypothesize that specific imaging is possible by altering the rate of tissue clearance (both normal and aberrant) of any given radiotracer. Pokeweed mitogen (PWM) as a biomodulator, represents a class of molecules which regulate cellular differentiation and cell-cell interactions and, as part of these mechanisms alter tissue clearance rates (both normal and aberrant). Utilizing the B-16/C57BL/6 model, 7 days post-transplantation (which represents log phase growth of the tumor), 10 animals were imaged following an i.v. injection of 1-2 mCi 99mTc-PWM in order to visualize the tumors and determine the optimal imaging kinetics. A specific tumor image is achieved between 120 and 240 min post-injection. In addition, tumor imaging studies using a non-tumor-specific biomolecule were conducted by injecting 19 animals i.v. with 1-2 mCi of 99mTc-human serum albumin (HSA). Twelve of these animals were given 10 micrograms of PWM i.p. at various intervals prior to the 99mTc-HAS administration. Imaging and biodistribution studies were performed at various intervals up to 2 h post-99mTc-HSA injection. A 32-59% increase in the tumor-to-muscle ratio was observed in the PWM-treated animals relative to the non-treated controls. To further investigate the PWM-induced tissue clearance alteration hypothesis, tissue clearance studies using 99mTc-diethylenetriaminepentaacetic acid (DTPA) were conducted in non-tumor bearing ICR mice and the B-16/C57BL/6 tumor bearing animals. 99mTc-DTPA normal tissue clearance rates were significantly increased in the PWM treated animals relative to the non-treated controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Metabolism and radiosensitization of 4,5-dimethylmisonidazole, a ring-substituted analog of misonidazole.

4,5-Dimethylmisonidazole (DMM) is a ring-substituted derivative of the 2-nitroimidazole, misonidazole. 2-Nitroimidazoles are able to sensitize radioresistant hypoxic cells, and to kill them outright through bioreductive metabolism. The toxic process is believed to reflect the consequences of reductively activated drugs forming adducts with cellular (macro)molecules. Both this process and the radiosensitizing activity are thought to correlate with the electron affinity of radiosensitizing agents. In the present study, methyl groups were added to the imidazole ring of misonidazole in order to hinder adduct formation with cellular molecules after reductive-activation of the compound. It was anticipated that this would substantially decrease the hypoxic-cell toxicity of the parent drug. The presence of the two methyl groups reduced the half-wave reduction potential of DMM by about 70 mV, so we expected that its radiosensitizing ability would also decrease. In direct comparison with misonidazole, DMM, at equimolar concentrations, showed dramatically reduced binding to cellular macromolecules under bioreductive conditions, both in vivo, using a liver perfusion system, and in vitro, using tissue culture cells incubated under extreme hypoxia. However, DMM was only moderately less toxic than the parent compound, and showed greatly diminished radiation sensitization capacity. Since the decrease in toxicity was much less than expected, and the decrease in radiosensitization was much more than expected, this compound may be an important drug for continuing studies on the mechanisms of radiation sensitization, binding and cytotoxicity caused by electron affinic drugs.

Animals↗
PubMed1992

Covalent binding of 7,12-dimethylbenz[a]anthracene to lymphoid and nonlymphoid tissues following oral administration to B6C3F1 mice.

Previous studies have shown that 7,12-dimethylbenz[a]anthracene (DMBA) is cytotoxic to various murine lymphoid tissues, including the spleen, thymus, mesenteric lymph nodes (MLNs), and Peyer's patches (PPs). In the present studies, we measured the amount of covalent binding of [3H]DMBA to lymphoid and nonlymphoid tissues and correlated these findings with the overall levels of [3H]DMBA (and derived substances) present in various tissues following a single oral administration to mice. Results show that [3H]DMBA was taken up relatively rapidly from the GI tract and that it was nearly completely eliminated within 24 hr via the feces. Peak plasma levels were obtained approximately 6 hr after gavage, and most organs (including brain, heart, liver, lung, kidney, spleen, and thymus) achieved their peak level of DMBA at this time. Maximal concentrations of DMBA were detected in gut-associated lymphoid tissues (i.e., PPs and MLNs) at 4 hr, during which time covalent binding of [3H]DMBA was also maximal. The time course for covalent binding was different in the liver, lung, thymus, and spleen, peaking at 6-12 hr. The amount of covalent binding of [3H]DMBA and derived metabolites in the spleen was more than twice that seen in the other tissues examined. Since the spleen has previously been found to be less sensitive to DNA fragmentation induced by DMBA than the PPs, these results suggest that covalent binding may not be the primary determinant of lymphotoxicity in these organs.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

An updated pKa listing of medicinal compounds.

A tabulated listing of pKa values is presented for 87 medicinal compounds commercially marketed since 1978. Medicinal compounds are listed alphabetically under their respective generic name. The pKa values reported are listed as either acid or base depending upon the ionization characteristics of the functional group corresponding to the respective pKa value.

Bibliographies as Topic↗
PubMed1985

Comparative distribution of misonidazole and its amine metabolite in female Swiss Webster mice.

The distribution of misonidazole and its terminal reduction product 1-(2-amino-1-imidazolyl)-3-methoxy-2-propanol (miso-amine) were compared in female Swiss Webster mice to determine if either misonidazole or miso-amine is distributed to peripheral nerves. Female Swiss Webster mice received a 100 mg/kg (5 microCi/mumole) i.p. dose of either 3H-misonidazole or 3H-miso-amine and the distribution of radioactivity was determined in various tissues including sciatic nerves and other myelinated nerves. Urine from misonidazole treated animals contained both miso-amine and misonidazole (8.4 and 20.4%, respectively, of the total radioactivity in the urine). Misonidazole produced higher initial tissue concentrations of radioactivity than did miso-amine. The relative tissue concentrations of radioactivity produced by misonidazole or miso-amine were similar, although not identical, 48 hours after administration of the drugs. Both sciatic and other myelinated nerves were found to retain radioactivity following the administration of either misonidazole or miso-amine.

Animals↗
PubMed1985

Binding of misonidazole to hypoxic cells in monolayer and spheroid culture: evidence that a side-chain label is bound as efficiently as a ring label.

The binding of ring-labelled and side-chain labelled misonidazole to hypoxic cells in monolayer and spheroid cultures of mammalian cells has been compared. The kinetics and patterns of binding for the two labelled compounds are indistinguishable. This finding has implications for the mechanism of binding and for the design of misonidazole analogues which might be used to identify hypoxic zones in tumours.

Animals↗
PubMed1984

Metabolism and excretion of [3H]misonidazole by hypoxic rat liver.

Our investigation was initiated to determine if misonidazole's biological activity is related to hypoxia-dependent, reductive biotransformation to form reactive metabolites. This study was facilitated by the synthesis of [3H]misonidazole and by use of the isolated perfused rat liver as a model system for hypoxic tissue. The perfused rat liver was verified as an appropriate model system to study misonidazole (MISO) metabolism. This was done by demonstrating that the perfused liver produced the same metabolites as those isolated from rats given MISO, albeit reductive metabolism was much less in rats. Reductive metabolism of MISO by perfused livers was enhanced (estimated by measuring the rate of 1-[2-aminoimidazol-1-yl]-3-methoxy-2-propanol production) by hypoxic conditions. Formation of a MISO-derived glutathione conjugate (MISO-GSH) and covalent binding of MISO-derived radioactivity to tissue protein was also enhanced by hypoxia. Depletion of hepatic GSH with diethyl maleate increased the extent of covalent binding to protein under both aerobic and hypoxic conditions, and greatly diminished the formation of MISO-GSH. These results support the hypothesis that hypoxic conditions facilitate reductive metabolism of MISO to an alkylating agent, and that GSH plays an intervening role in the alkylation reaction.

Animals↗
PubMed1984

Delayed sequelae of pituitary irradiation.

Since 1958, 781 patients at Lawrence Berkeley Laboratory have received helium-particle stereotactic radiosurgery to the adenohypophysis. Autopsy findings in 15 of these patients are reported. Ten patients received pituitary radiation (average dose, 116 Gy in six fractions) for progressive neovascularization retinopathy due to diabetes mellitus. Evidence of a time-dependent course of progressive fibrosis in their pituitary glands was found. Five patients were treated for eosinophilic adenomas. Although they had lower average doses of radiation (56 Gy in six fractions), their pituitary glands showed cystic cavitation of the adenomas. The adenomas thus appeared more radiosensitive than the normal pars anterior, which, in turn, was more radiosensitive than the adjacent neurohypophysis. No significant radiation changes were found in the surrounding brain or cranial nerves. The endocrine organs under pituitary control showed varying degrees of atrophy, and clinical tests revealed progressive hypofunction. It was concluded that charged-particle therapy produced a sharply delineated focal radiation lesion confined to the pituitary gland but did not cause injury to the critical structures of the surrounding central nervous system.

Acromegaly↗
PubMed1983

Influence of hypoxia on the metabolism and excretion of misonidazole by the isolated perfused rat liver--a model system.

The isolated perfused rat liver was evaluated as a model system for the characterization of misonidazole metabolism under hypoxic conditions. Misonidazole metabolism by livers perfused under aerobic conditions was also examined. The clearance of misonidazole was more than three times greater under anaerobic compared to aerobic conditions (4.94 +/- 1.56 vs 1.27 +/- 0.22 ml/min; means +/- S.D., N = 3). Misonidazole metabolites were detected only in the bile. Analysis of these metabolites by reverse-phase high performance liquid chromatography (HPLC) demonstrated that misonidazole metabolism was also qualitatively changed when anaerobic conditions were employed. Misonidazole beta-glucuronide was the major metabolite detected under aerobic conditions, but it was a minor metabolite in anaerobically perfused livers. The three major metabolites produced under anaerobic conditions were not characterized, but desmethyl misonidazole (RO-07-9963) and the 2-amino-imidazole derivative of misonidazole (1-[2-aminoimidazol-1-yl]-3-methoxy-2-propanol) were excluded as possible structures.

Animals↗
PubMed1981

Growth of human malaria parasites in biotinylated erythrocytes.

The adaptation of the biotin-avidin system for the analysis of membrane pathobiology in Plasmodium falciparum malaria is described. Biotin was linked covalently via the succinimide ester derivative (biotinyl-N-hydroxysuccinimide ester, BNHS) to intact human erythrocytes, prior to inoculation and in vitro cultivation of falciparum parasites. Growth experiments indicated that incubation concentrations of less than 1.0 mg BNHS/1.0 ml erythrocyte packed cell volume could yield biotinylated erythrocytes capable of sustaining parasite growth at levels comparable to control cultures. Using a synthesized [14C]BNHS compound at optimal incubation concentration, it was determined that 1.32 X 10(-4) mmol [14C]BNHS were bound per 1.0 mg of erythrocyte stromal protein. In addition, analysis of [14C]biotinylated red blood cell ghost preparations by polyacrylamide gel electrophoresis demonstrated that band 3 (a heterogeneous glycoprotein) was the principal site of membrane labeling. Approximately 77% of total membrane-associated [14C]BNHS was localized to this polypeptide. The unique properties of the specific, ligand-protein interaction of the biotin-avidin complex suggest that the biotinylation procedure described in this report will provide a useful analytical tool in host cell-plasmodial parasite, membrane studies.

Animals↗