Interaction between radiation and drug damage in mammalian cells. V. DNA damage and repair induced in LZ cells by adriamycin and/or radiation

A multi-drug-resistant cell line selected in increasing concentrations of Adriamycin and designated LZ (J. A. Belli, Radiat. Res. 119, 88-100, 1989) is shown to exhibit a survival response characterized by radiation sensitivity and Adriamycin resistance. To determine if this response is due to alterations in either the initial levels of damage induced or the repair of DNA damage, LZ cells and the parental V79 cells were exposed to either radiation or Adriamycin and the damage and repair were measured with alkaline or nondenaturing filter elution. After exposure to radiation, induction and repair of both single-strand and double-strand breaks were equivalent. LZ cells exposed to 100 micrograms/ml Adriamycin for 1 h contained no measurable damage while the same treatment induced breaks and crosslinks in V79 cells. Pretreatment of LZ cells for 1 h with Adriamycin before irradiation did not alter either the initial levels of induced damage or the repair of strand breakage. These results suggest that (1) mechanisms other than differential induction and repair of strand breaks are responsible for the increased radiation sensitivity in LZ, and (2) the lack of Adriamycin-induced DNA damage in LZ is at least partially responsible for the increased cell survival after treatment.

Improved high-pressure liquid chromatographic-fluorometric assay for measurement of adenosine in plasma

A high-pressure liquid chromatographic system using fluorescence detection was characterized for the determination of adenosine levels in plasma from anesthetized cat, rat, dog, mouse, rabbit, and guinea pig. The optimal concentration of chloroacetaldehyde necessary to convert physiological levels of adenosine to its fluorescent derivative 1,N6-ethenoadenosine (ethenoadenosine) was in excess of 220 mM. As little as 0.2 pmol of ethenoadenosine could be measured, and detection was linear up to 200 pmol. Derivatization of adenosine into ethenoadenosine was highly dependent on temperature and time. However, ethenoadenosine showed thermal instability in that levels dropped sharply after 30 min at 100 degrees C, 2 h at 80 degrees C, and 24 h at 55 degrees C. Adenosine nucleotides were extracted from plasma samples with an efficiency of greater than 91% to prevent adenosine formation from ATP and AMP that would have otherwise occurred during the derivatization procedure. Plasma levels (microM) of adenosine in venous blood were 0.31 in dog, 0.54 in cat, 0.71 in guinea pig, 1.03 in mouse, 1.04 in rat, and 1.68 in rabbit. Plasma levels of adenosine in arterial blood were not significantly different from levels in venous blood. This method can be used to measure even very low levels of adenosine without interference from nucleotide breakdown.

[The effects of nifedipine, diltiazem, and Paeonia lactiflora Pall. on atherogenesis in rabbits]

The effects of nifedipine, diltiazem, and Paeonia lactiflora Pall (PLP) on serum lipids. Plasma lipid peroxides (LPO), TXB2, and 6-keto-PGF1 alpha in cholesterol-fed rabbits have been investigated. Oral administration of nifedipine (15 mg/kg.d), diltiazem (30 mg/kg.d), and PLP (5 g/kg.d) caused 60.8%, 45.2%, and 74.2% reduction in the area of atherosclerosis in the aorta respectively. The levels of plasma LPO and TXB2 and the contents of cholesterol, phospholipid, and calcium in the intimal-media of the aorta in the treated groups were significantly lower than those in the cholesterol group, but the level of plasma 6-keto-PGF1 alpha in the treated groups was significantly higher. The appearance of cholesterol-induced TXB2 elevation and 6-keto-PGF1 alpha decrease in the treated groups was delayed. There are positive correlation between plasma TXB2 and the followings: serum lipids, plasma LPO, and the content of calcium in the intimal-media of the aorta, and the percentage of area of lesion in the aorta, while plasma 6-keto-PGF1 alpha showed significantly negative correlation with the above data. TXB2/6-keto-PGF1 alpha was found to be positively correlated with the percentage of lesion area of the aorta. It was shown that Ca2+ metabolism plays an important role in thromboxane, prostaglandin, and LPO metabolism. In conclusion, the inhibition of LPO production and regulation of TXA2-PGI2 balance may be one of the main mechanisms of the antiatherogenic effects of calcium antagonists and PLP.

X-ray absorption fine structure investigation of the zinc transition metal binding site of Zn concanavalin A in solution and in the crystal

We report details on measurements by the X-ray absorption fine structure (XAFS) technique of the conformational changes around the transition metal binding site (S1) of the protein concanavalin A induced by crystallization when that site is occupied by Zn. A change from hexa- to tetracoordination occurs at the S1 site on crystallization when the calcium-binding site (S2) is occupied by a calcium atom. When the S2 site is unoccupied, the Zn is pentacoordinated both in solution and in the crystal. The average distance to the coordination shell increases with coordination number as expected. Conformational changes are detected up to 4.5 A from the Zn, the limit of sensitivity of the XAFS technique. When the Zn is hexacoordinated, the ligands around the Zn, as determined by XAFS, are consistent with the crystal structure determination results of five oxygens and one nitrogen. The atom that is released in the tetracoordinated Zn. decreases to five is an oxygen atom, and, in addition, the nitrogen is released in the tetracoordinated Zn. Thus, when S2 is emptied, the protein gains a ligand about the Zn site in the crystal and loses one in solution. These results provide direct evidence that the protein conformation can be altered by the intermolecular forces of crystallization.

Limitation to the use of the urinary S-/R-mephenytoin ratio in pharmacogenetic studies

The reproducibility of the S-/R-mephenytoin ratio was examined in urines stored at -20 degrees C over 2 years. Large changes in this ratio were observed in some urine samples stored for only a few months under these conditions. The changes observed in the S-/R-mephenytoin ratio are attributed to the decomposition of an acid labile metabolite of S-mephenytoin which is eliminated in the urine. The instability of this metabolite makes it desirable to process urine shortly after its collection in order to avoid inaccurate phenotype assignments based upon the urinary S-/R-mephenytoin ratio. If rapid processing of urines is impractical, additional methods are described for preventing improper phenotype assignment of subjects.

Phorbol myristate acetate and calcium ionophore A23187 modulate the accessory cell function of mouse dendritic cells

Dendritic cells (DC) comprise a small subpopulation of lymphoid cells, with distinct morphologic features, surface phenotypes and a potent accessory function in T cell-dependent immune responses. In the present study, we investigated the in vitro effects of a tumor promoter, phorbol myristate acetate (PMA), and calcium ionophore A23187 on the accessory cell function of mouse spleen DCs in the primary mixed lymphocyte reaction (1 degree MLR) and oxidative mitogenesis (OM). A multi-step purification procedure was used to procure a highly enriched DC population from mouse spleen. The accessory cell activity of the DCs so obtained was much stronger than that of M phi s in both MLR and OM. The effects of PMA, a protein kinase C (PKC) activator, on DC were dose-dependent. If pretreated with 50 ng/ml of PMA for 3 h, DC activity was enhanced by about two-fold; whereas 200 ng/ml decreased DC activity with an inhibition rate of about 50%. However, in the latter situation, a moderate increase in DC activity was seen in the early phase of the response. When pretreated with 0.5-1.0 mumol/L A23187 for 6-8 h, the accessory cell activity of DCs was twice as potent as that of the control, and the enhancing effect was sustained in both MLR and OM. Our results indicate that the function of DCs, a cell type with constitutively high accessory cell activity, can be further promoted by A23187 or a low dose of PMA. This is also circumstantial evidence of an up-regulation of DC activity via PKC activation and/or an increase in cytoplasmic calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of alpha adrenergic blockade during stellate ganglion stimulation on arrhythmias induced by acute myocardial ischemia in pigs

The effects of alpha-adrenergic receptor blockade during stellate ganglion stimulation on arrhythmias induced by repeated coronary artery occlusion in pigs under spontaneous breathing were studied. Prazosin, alpha 1-receptor blocker, did not have any effect on the early ischemic dysrhythmia. Yohimbine, which selectively blocks alpha 2-receptor, significantly increased the number of premature ventricular complexes (19 +/- 3----32 +/- 2 PVC; P less than 0.01), but produced no effects on the percentage of appearance of ventricular fibrillation (VF) and ventricular tachycardia (VT). However, nonselective alpha-receptor blocker phentolamine significantly reduced the number of premature ventricular complexes (30.5 +/- 4.5----11 +/- 3 PVC; P less than 0.05), but did not affect the frequency of occurrence of VF and VT. The above results show that alpha-adrenergic mechanisms do not play any important role in the genesis of arrhythmias during ischemia in the pig model.

The effects of perfusion of lateral ventricle with CaCl2 on the febrile response and cAMP content in plasma and cerebrospinal fluid during LP-induced fever

Artificial cerebrospinal fluid (c.s.f.) containing 40 mmol/L excess calcium was perfused through the lateral ventricles of New Zealand white rabbits in order to reduce the Na+/Ca++ ratio in the brain and the effects on both the febrile response and adenosine cyclic monophosphate (cAMP) concentration in plasma and c.s.f. during leucocytic pyrogen (LP)-induced fever were observed. The results showed that cAMP concentration in c.s.f. increased significantly during LP-induced fever while the cAMP level in Plasma remained unchanged, and the perfusion of artificial c.s.f. containing 40 mmol/L excess calcium can significantly inhibit not only the febrile response but also the increase in c.s.f. cAMP level, while there appears no effect on plasma cAMP concentration, thus demonstrating that the increase of Na+/Ca++ ratio causing the increase of cAMP content in the brain may be an essential link in the pathogenesis of LP-induced fever.

Endothelin-1 stimulates the release of arachidonic acid and prostaglandins in rabbit iris sphincter smooth muscle: activation of phospholipase A2

We have investigated the effects of endothelin-1 (ET1) on phospholipid hydrolysis and 3H-arachidonic acid (AA) release and prostaglandin synthesis in the rabbit iris sphincter smooth muscle. ET1 actions are concentration- and time dependent with an EC50 for AA release of 1 nM and t1/2 value of 1.5 min. We have identified the AA metabolites released by ET1, employing HPLC, as both cyclooxygenase and lipoxygenase products. The AA released by ET1 appears to derive mainly from the phosphoinositides through phospholipase A2, rather than phospholipase C activation. A key role for phospholipase A2 in AA release in the sphincter muscle is supported by the following observations. (1) Pretreatment of the labeled sphincter with the phorbol ester, PDBu (100 nM) inhibited ET1-stimulated IP3 formation, but it potentiated ET1-stimulated AA release. (2) Pretreatment of the labeled tissue with isoproterenol (5 M) inhibited ET1-stimulated IP3 production without altering AA release. (3) The potency for ET1-stimulated AA release (EC50 = 1 nM) was much higher than that for IP3 formation (EC50 = 45 nM). (4) There were considerable increases, rather than decreases, in 1, 2-diacyl-glycerol formation (1.2-folds) and its phosphorylated product, phosphatidic acid (2.6-folds) by ET1. It is concluded that in the rabbit iris sphincter ET1 is a potent agonist for AA release and eicosanoid synthesis and that AA is released from phosphoinositides mainly through activation of phospholipase A2.

Characterization of prominent protein antigens from mycobacteria

Detailed analysis of mycobacterial proteins originally identified by their prominent interaction with the host immune system reveals a number of interesting biochemical characteristics. M. tuberculosis antigens with molecular weights of 71, 65 and 12 kilodaltons (kD) belong to highly conserved heat shock protein families. A group of closely related antigens with molecular weights around 30 kD are major secreted antigens which share the ability to bind to fibronectin. Antigens with molecular weights of 38 kD and 19 kD are probably lipoproteins with a role in nutrient transport, while the 23 kD antigen is the superoxide dismutase enzyme of M. tuberculosis. It is anticipated that further studies along these lines will generate information of importance to the understanding of the lifestyle of mycobacteria in vivo and also to the elucidation of immune mechanisms in mycobacterial disease.

Acquired resistance of Nocardia brasiliensis to clavulanic acid related to a change in beta-lactamase following therapy with amoxicillin-clavulanic acid

Previous studies have demonstrated that Nocardia brasiliensis is susceptible to amoxicillin-clavulanic acid and that its beta-lactamases are inhibited in vitro by clavulanic acid. A cardiac transplant patient with disseminated infection caused by N. brasiliensis was treated with this drug combination with good response, but relapsed while still on therapy. The relapse isolate was found to be identical to the initial isolate by using genomic DNA restriction fragment patterns obtained by pulsed field gel electrophoresis, but it was resistant to amoxicillin-clavulanic acid. On isoelectric focusing, the beta-lactamase from the relapse isolate exhibited a shift in the isoelectric point (pI) of its major band from 5.10 to 5.04 compared with the enzyme from the pretreatment isolate. As determined by using values of the amount of beta-lactamase inhibitor necessary to give 50 +/- 5% inhibition of beta-lactamase-mediated hydrolysis of 50 microM nitrocefin, the beta-lactamase of the relapse isolate was also 200-fold more resistant than the enzyme from the pretreatment isolate to clavulanic acid and was more resistant to sulbactam, tazobactam, cloxacillin, and imipenem. The beta-lactamase of the relapse isolate exhibited a 10-fold decrease in hydrolytic activity for cephaloridine and other hydrolyzable cephalosporins compared with that for nitrocefin. Acquired resistance to amoxicillin-clavulanic acid in this isolate of N. brasiliensis appears to have resulted from a mutational change affecting the inhibitor and active site(s) in the beta-lactamase.

Genetic analysis of superoxide dismutase, the 23 kilodalton antigen of Mycobacterium tuberculosis

The gene encoding a 23 kilodalton protein antigen has been cloned from Mycobacterium tuberculosis by screening of a recombinant DNA library with monoclonal antibodies. The product of the gene has been identified as the superoxide dismutase (SOD) of M. tuberculosis on the basis of sequence comparison and by expression of the recombinant protein in a functionally active form. The derived amino acid sequence of M. tuberculosis SOD reveals a close similarity to manganese-containing SODs from other organisms, in spite of the fact that previous studies using the purified enzyme have identified iron as the preferred metal ion ligand. SOD is present in the extracellular fluid of logarithmic-phase cultures of M. tuberculosis, but the structural gene is not preceded by a signal peptide sequence. Insertion of the M. tuberculosis SOD gene into a novel shuttle vector demonstrated the mycobacteria but is ineffective in Escherichia coli.

Inhibition of Plasmodium falciparum dihydropteroate synthetase and growth in vitro by sulfa drugs

The Michaelis-Menten inhibitory constants (Kis) and the concentrations required for 50% inhibition of the Plasmodium falciparum dihydropteroate synthetase were determined for six sulfa drugs. These drugs inhibited the in vitro growth of P. falciparum (50% lethal concentration) at concentrations of 30 to 500 nM; these concentrations were 100 to 1,000 times lower than the concentrations required for 50% inhibition and Kis (6 to 500 microM). The uptake of p-aminobenzoic acid was not inhibited by the sulfa drugs. However, infected erythrocytes took up more labeled sulfamethoxazole than did uninfected erythrocytes. Thus, the concentration of sulfa drugs by malaria parasites may explain how sulfa drugs inhibit in vitro growth of parasites through the inhibition of dihydropteroate synthetase.

Role of herpes simplex virus type 1 UL46 and UL47 in alpha TIF-mediated transcriptional induction: characterization of three viral deletion mutants

The transcriptional induction of the alpha or immediate-early gene class of herpes simplex virus type 1 effected by the alpha trans-induction factor (alpha TIF, ICP25, VP16, Vmw65) requires an alpha-specific cis-acting site. Increased transcription does not result from the direct, independent binding of alpha TIF, but rather from an alpha TIF-dependent formation of a protein-DNA complex containing, in addition to alpha TIF, at least one host cell factor. One of the host factors is a POU domain protein which recognizes an octamer element in the alpha-specific consensus. There is evidence that alpha TIF may drive the formation of multiple protein-DNA complexes containing a POU protein and additional host factors. Previously, the gene products of UL46 and UL47 have been implicated in modulating the alpha TIF-dependent transcriptional induction of alpha genes. Our current studies have extended these analyses from a transient-expression system to a series of viral deletion mutants. In these studies we demonstrate that neither UL46- nor UL47-encoded gene product, either separately or in combination, is required for viral growth in cell culture. The absence of UL47 reduces by up to 80% the ability of the virus to induce an alpha-regulated thymidine kinase reporter gene resident in 143TK- cells. Autoradiograms of [35S]methionine pulse-labeled infected cell proteins, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, show that deleting UL46 and/or UL47 has no discernable effect on the synthesis of alpha TIF or alpha TIF-containing proteins. Subsequent Western immunoblot analysis, with rabbit anti-alpha TIF antibodies made to an alpha TIF-Staphylococcus aureus protein A fusion, demonstrated that the accumulation and steady-state levels of alpha TIF or alpha TIF-containing proteins was indistinguishable from that of the thymidine kinase-negative isogenic parental virus, R delta 305.

[Scavenging of probimane on semiquinone free radical formation by doxorubicin in rat heart]

Probimane, dl-bis (4-morpholin-methyl 3,5-dioxopipweazin-1-yl) propane first synthesized in China, is a dioxopiperazin compound with antineoplastic, antimetastatic and radiopotentiating activities. In order to evaluate the mechanisms of cardiotoxicity protective action of probimane, the free radical induced by doxorubicin were analysed by electron spin resonance (ESR) techniques. Our studies showed that doxorubicin stimulated the formation of semiquinone free radicals in the rat heart homogenate and heart cell mitochondria systems, and probimane inhibited the free radical formation in both systems, with the dose-dependent and time-dependent responses. The inhibitory rates of doxorubicin free radical formation in rat heart homogenate system by probimane 0.6 mmol.L-1 at time of 3, 5, 10, 15, 30, 45 and 60 min were 44.6%, 43.0%, 51.5%, 74.3%, 68.1%, 56.1% and 39.9% respectively. The inhibitory rates of semiquinone free radical formation in mitochondria system by probimane at the concentration of 0.02, 0.06, 0.6, 1.2 and 2.4 mmol.L-1 were 17.07%, 29.87%, 63.95%, 64.62% and 83.64%, respectively. Probimane had no effect on NADH2, but inhibited NADH dehydrogenase activity at higher concentration.

Diffusion of water in rhyolitic glasses

Water dehydration experiments on rhyolitic glasses have been carried out at 400-550 degrees C under a N2 atmosphere. Concentration profiles of both H2O molecules and OH groups were measured by Fourier transform infrared spectroscopy. As found in previous studies of water diffusion in rhyolitic melts, the measured total water concentration profiles do not match expectations based on a single constant diffusion coefficient for total water. The diffusion of total water is described by considering the diffusion of both H2O molecules and OH groups and the reaction between them. The concentration relationship between the two species has been obtained from direct infrared measurement on quenched experimental charges. The quench is inferred to be rapid enough to preserve concentrations of both species at experimental temperature based on experimental results designed to examine reaction kinetics. The measured species concentrations along diffusion profiles show that local equilibrium between H2O and OH is approximately reached at high temperatures and high water contents. However, at lower water content or lower temperature, local equilibrium is not reached. In treating the diffusion problem, this disequilibrium effect is partially compensated by using empirical relationships between H2O and OH concentrations based on measurements, instead of using an equilibrium relationship. It is thus possible to obtain diffusion coefficients for both species from their concentration profiles. The diffusion coefficient of OH is found to be negligible compared to that of H2O at 403-530 degrees C (DOH < 0.02 DH2O and could be much smaller); i.e., H2O is the dominant diffusing species even at total water concentration as low as 0.2 wt%. The variation of OH concentration along the diffusion profile is inferred to be due to the local interconversion between OH groups and H2O molecules; the reaction also provides the diffusing H2O species. DH20 values are found to vary by less than a factor of 2 over a total water concentration range of 0.2 to 1.7 wt%. This simple model, coupled with the assumption of local equilibrium between H2O and OH, yields a very good fit to the data from diffusion-couple experiments of LAPHAM et al. (1984) at 850 degrees C. When our data are combined with DH2O obtained from that fit, DH2O (in m2/s) is given by: ln DH2O = (-14.59 +/- 1.59) - (103000 +/- 5000) / RT; 673 K < or = T < or = 1123 K, where T is temperature in K and R is the gas constant in J K-1 mol-1. This equation also approximates well DH2O values calculated from previous measurements of concentration-dependent bulk water diffusion coefficients of KARSTEN et al. (1982). The diffusion of H2O is also compared to the diffusion of the noble gas elements. The activation energy for diffusion in rhyolitic glasses is well correlated with neutral species radii of He, Ne, H2O, and Ar. This supports the contention that the diffusing species for "water" is neutral molecular H2O. The role of speciation may also be important in understanding the diffusion of many other multi-species components, and the effect can be treated in a similar fashion as that during water diffusion.

Dilazep-induced vasodilation is mediated through adenosine receptors

Administration of dilazep, an inhibitor of adenosine uptake, significantly reduced systemic arterial blood pressure and increased superior mesenteric arterial conductance without affecting the plasma adenosine levels of femoral arterial or portal venous blood. Administration of a bolus dose of 8-phenyltheophylline (8-PT), an antagonist of adenosine receptors, blocked adenosine-mediated autoregulation of the superior mesenteric artery. After the blockade of adenosine receptors by 8-PT, dilazep did not produce vasodilation. These data suggest that dilazep has a vasodilating effect in vivo that is mediated by adenosine.

Sequence of a HeLa cDNA provides the DNA binding domain and carboxy terminus of HE47: a human helix-loop-helix protein related to the enhancer binding factor E47

In order to identify cDNA encoding regulators of gene expression, a HeLa lambda gt11 expression library was screened with a DNA segment containing multiple copies of a sequence spanning the AP4 site in the simian virus 40 control region. We identified a partial cDNA encoding HE47, a sequence-specific DNA binding protein. The HeLa clone overlaps with a previously reported human B-cell partial cDNA encoding E47. The HeLa cDNA includes the HE47 DNA binding domain, its carboxy terminus, and the 3' untranslated region of its mRNA.

Prediction of heating patterns of a microwave interstitial antenna array at various insertion depths

Measurements made on the interstitial microwave antennas used for hyperthermia cancer therapy indicate that the heating patterns vary with the insertion depths (defined as the distance from the antenna tip to air-tissue interface). The antennas are made of thin coaxial cables with a radiation gap or gaps on the outer conductor. The antennas are inserted into small polypropylene catheters implanted in the tumour volume. This type of antenna may be simulated as an asymmetric dipole with one arm being the tip section consisting of the expanded extension of the inner conductor, and the other arm being the section of the outer conductor from the gap to the insertion point (air-tissue interface). We use four of the antennas to form a 2 cm x 2 cm array. The antennas are positioned on the corners of a 2 cm square. Measurements on both single antennas and multi-antenna arrays show that the maximum heating is not stationary with position along the antenna when the depth of insertion is changed. This paper investigates the theoretical prediction of the changes in heating patterns of interstitial microwave antennas at different insertion depths. Each of the antennas in the array is simulated as an asymmetric dipole. The SAR (specific absorption rate) is computed by using the insulated dipole theory. The temperature distribution in absence of perfusion is obtained through a thermal simulation routine to convert the SAR pattern into the temperature pattern. Excellent qualitative agreement is found between the theoretical heating pattern and the measured pattern in a non-perfused phantom on a 2 cm x 2 antenna array. Since the insertion depths of the interstitial antennas are different from patient to patient, it is recommended that simulation of the heating be done before treatments, to confirm the delivery of power to the target region.