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.

Application of cell culture toxicity tests to the development of implantable biosensors

Cell culture toxicity testing methods were modified and applied to the development of implantable glucose microsensors, and positive and negative control materials suitable for the microsensor assessment were established. The location, source and degree of the toxic effect in a multi-component biosensor was spatially visualized with cell monolayers. A freshly prepared sensor showed moderate toxicity, mainly as a result of the presence of glutaraldehyde and the residual solvents in the polymer layers. However, it was possible to reduce the toxicity by removing the leachable toxic substances through extraction in phosphate buffer, and a non-toxic sensor was readily obtained.

Heating patterns generated by phase modulation of a hexagonal array of interstitial antennas

In this paper, we investigate an array of six interstitial microwave antennas used for hyperthermia cancer treatment. The purpose is to generate both uniform and controlled nonuniform heating patterns in biological tissue by phase modulating the signals applied to each antenna. The array consists of six antennas positioned on the corners of a hexagon. The distance between two diagonal antennas is 4 cm. The distributions of absorbed power per unit mass within the array are computed, and then converted into temperature distributions through a thermal conduction simulation. The SAR and temperature patterns are presented in both the lateral plane (perpendicular to the antennas) and the axial plane (parallel with the antennas). By proper phase modulation of microwave signals applied to each antenna, a uniform heating pattern can be produced within the entire array volume. Also, a peripheral heating pattern may be generated around the array; again, by using the proper phase modulation. The modulation schemes for generating both types of heating patterns are discussed.

Diffusion of a multi-species component and its role in oxygen and water transport in silicates

An important but poorly understood factor that affects diffusion rates is the role of speciation during diffusion of a multi-species component. The diffusion of such a component is complicated by the different diffusion coefficient of each species and the interconversion reactions among the species. These complexities can be treated by a diffusion equation that incorporates the diffusive fluxes of all species contributing to the concentration of the component. The effects of speciation on the diffusion of the component can be investigated experimentally in some simple cases by measuring concentration profiles of all species developed during diffusion experiments or by studying some of their other consequences. Experimental data on water diffusion in rhyolitic glasses indicate that although dissolved water is present as two species, H2O molecules and OH groups, molecular H2O is the dominant diffusing species at very low to high water concentrations. This explains the apparently complex behavior of water diffusion. Experimental data on oxygen diffusion in some silicates using 18O tracers in the form of H2(18O) are consistent with the idea that 18O transport is dominated by diffusion of H2O molecules even at lower water contents (ppm or less). This explains why oxygen transport depends on the presence of water and generally depends on water fugacity linearly. For this mode of oxygen transport, there is a simple theoretical relationship between the effective total oxygen diffusion coefficient and the total water diffusion coefficient that is a function of only the water concentration of the silicate at low water content. This relationship appears to describe quantitatively the existing data over a wide range in water contents and diffusion coefficients in several phases.

Identification of T-cell epitopes of autoantigens using recombinant proteins; studies on experimental autoimmune myasthenia gravis

In the Lewis rat, T-cell lines from animals immunized with native or denatured Torpedo nAChR recognize the Torpedo-derived recombinant protein T alpha X1 omega (alpha-2-200) but not the equivalent mouse- or chick-derived recombinant proteins X4 omega or C alpha X1 omega (alpha 6-216 and alpha 35-216, respectively). T-cell lines derived from animals immunized with T alpha X1 omega, X4 omega or C alpha X1 omega are specific for the homologous protein. This lack of cross-species reactivity suggests caution in the use of Torpedo nAChR-selected lines generated from human patients. Proteolysis and fractionation of the products by reverse-phase HPLC was effective in localization of a T-cell epitope of X4 omega, a mouse-derived recombinant protein. With Lewis rats, the major epitope of T alpha X1 omega is alpha 97-112. However, the major epitope of the mouse-derived protein, X4 omega, as determined by proteolytic digestion and fractionation of the products by reverse-phase HPLC, is alpha 14-22. This shift in T-cell epitope between closely related proteins may result from the conservation of sequence of alpha 97-112 between mammalian species.

Immunological heterogeneity of autoreactive T lymphocytes against the nicotinic acetylcholine receptor in myasthenic patients

The response of human T lymphocytes against the nicotinic acetylcholine receptor (AChR) was studied in five patients with myasthenia gravis (MG) and in six healthy donors using either native Torpedo AChR or recombinant protein derived from the mammalian AChR alpha subunit (X4, residues 6-216 of mouse AChR alpha subunit). The present study demonstrates that (a) AChR-specific T helper cell lines can be generated from MG patients [either from peripheral blood lymphocytes (PBL) or from thymocytes] as well as from PBL of normal controls, (b) lymphocytes from MG patients, but not from controls, recognize the mammalian AChR but not the Torpedo receptor, (c) in humans, the HLA-DR2-associated T cell epitope is probably located in the region of residues 162-216 of the AChR alpha subunit and (d) there is a considerable heterogeneity of autoreactive T cell responses: (i) T cell lines from different HLA-type donors have distinct epitope profiles; (ii) the epitope specificity of the PBL-derived T cell line is different from that of the thymocyte-derived line; (iii) the epitope specificities of patient-derived T cell lines are different from those generated from normal controls who share the same HLA phenotype.

[The augmenting effect of selenium(Se) on cell-mediated immunity. III. Se enhances delayed-type hypersensitivity reaction by promoting antigen presentation]

Delayed-type hypersensitivity reaction (DTH) to TNCB in TNCB-primed mice was increased when mice was treated with sodium selenite. In vitro studies showed that primed T cells proliferated more vigorously when TNP-conjugated spleen adherent cells (SAC) from Se-treated mice were the stimulators as compared with SAC of untreated controls. TNP-conjugated SAC treated in vitro with sodium selenite were even stronger stimulators than SAC treated in vitro. The results indicate that Se enhances DTH by promoting antigen presentation.

[Antimutagenicity screening of water extracts from 102 kinds of Chinese medicinal herbs]

Our observation shows that out of 102 kinds of Chinese medicinal herbs tested, 17 have remarkable antimutagenic effect on the mutation induced by aflatoxin B1, in Ames test. Among the 17 herbs Glycyrrhiza uralensis, Bupleurm chinense, Portulaca grandiflora and Cnidium monnieri have been found in other tests to be effective against mutagenesis induced by cyclophosphamide in mice.

Beta-lactamase as a probe of membrane protein assembly and protein export

The enzyme TEM beta-lactamase constitutes a versatile gene-fusion marker for studies on membrane proteins and protein export in bacteria. The mature form of this normally periplasmic enzyme displays readily detectable and distinctly different phenotypes when localized to the bacterial cytoplasm versus the periplasm, and thus provides a useful alternative to alkaline phosphatase for probing the topology of cytoplasmic membrane proteins. Cells producing translocated forms of beta-lactamase can be directly selected as ampicillin-resistant colonies, and consequently a beta-lactamase fusion approach can be used for positive selection for export signals, and for rapid assessment of whether any protein expressed in Escherichia coli inserts into the bacterial cytoplasmic membrane. The level of ampicillin resistance conferred on a cell by an extracytoplasmic beta-lactamase derivative depends on its level of expression, and therefore a beta-lactamase fusion approach can be used to directly select for increased yields of any periplasmic or membrane-bound gene products expressed in E. coli.

The oxidative inactivation of mitochondrial electron transport chain components and ATPase

Bovine heart submitochondrial particles (SMP) were exposed to continuous fluxes of hydroxyl radical (.OH) alone, superoxide anion radical (O2-) alone, or mixtures of .OH and O2-, by gamma radiolysis in the presence of 100% N2O (.OH exposure), 100% O2 + formate (O2- exposure), or 100% O2 alone (.OH + O2- exposure). Hydrogen peroxide effects were studied by addition of pure H2O2. NADH dehydrogenase, NADH oxidase, succinate dehydrogenase, succinate oxidase, and ATPase activities (Vmax) were rapidly inactivated by .OH (10% inactivation at 15-40 nmol of .OH/mg of SMP protein, 50-90% inactivation at 600 nmol of .OH/mg of SMP protein) and by .OH + O2- (10% inactivation at 20-80 nmol of .OH + O2-/mg of SMP protein, 45-75% inactivation at 600 nmol of .OH + O2-/mg of SMP protein). Importantly, O2- was a highly efficient inactivator of NADH dehydrogenase, NADH oxidase, and ATPase (10% inactivation at 20-50 nmol of O2-/mg of SMP protein, 40% inactivation at 600 nmol of O2-/mg of SMP protein), a mildly efficient inactivator of succinate dehydrogenase (10% inactivation at 150 nmol of O2-/mg of SMP protein, 30% inactivation at 600 nmol of O2-/mg of SMP protein), and a poor inactivator of succinate oxidase (less than 10% inactivation at 600 nmol of O2-/mg of SMP protein). H2O2 partially inactivated NADH dehydrogenase, NADH oxidase, and cytochrome oxidase, but even 10% loss of these activities required at least 500-600 nmol of H2O2/mg of SMP protein. Cytochrome oxidase activity (oxygen consumption supported by ascorbate + N,N,N',N'-tetramethyl-p-phenylenediamine) was remarkably resistant to oxidative inactivation, with less than 20% loss of activity evident even at .OH, O2-, OH + O2-, or H2O2 concentrations of 600 nmol/mg of SMP protein. Cytochrome c oxidase activity, however (oxidation of, added, ferrocytochrome c), exhibited more than a 40% inactivation at 600 nmol of .OH/mg of SMP protein. The .OH-dependent inactivations reported above were largely inhibitable by the .OH scavenger mannitol. In contrast, the O2(-)-dependent inactivations were inhibited by active superoxide dismutase, but not by denatured superoxide dismutase or catalase. Membrane lipid peroxidation was evident with .OH exposure but could be prevented by various lipid-soluble antioxidants which did not protect enzymatic activities at all.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of chronic caffeine administration on peripheral adenosine receptors

Rat platelets and adipocytes were used as models to investigate alterations of the A2- and of the A1-adenosine receptor-adenylate cyclase system of peripheral cells caused by chronic caffeine administration. The maximum effects of 5'-N-ethylcarboxamidoadenosine (NECA) to stimulate adenylate cyclase activity in suspensions of platelet membranes and to inhibit aggregation were significantly greater with platelets from caffeine-treated rats than from control rats. The effects of 1 to 100 nM prostaglandin E1 to inhibit platelet aggregation and to stimulate adenylate cyclase activity in platelet membranes were also significantly greater with caffeine-treated than with control rats. These data suggest that the increased ability of NECA to inhibit platelet aggregation after chronic caffeine ingestion was a result of increased cyclic AMP accumulation induced by this agonist. The increased stimulatory effect of NECA on adenylate cyclase in platelet membranes could be due to an increased A2-adenosine receptor number and/or an increased functional coupling between A2-adenosine receptor and stimulatory guanine nucleotide binding proteins. In contrast, although A1-receptor number was 37% higher in fat cell membranes from caffeine-treated rats than in those from control rats, increased A1-adenosine receptor-mediated inhibition of lipolysis and of adenylate cyclase was not detected. Thus, chronic caffeine consumption causes alterations in the response of some but not all peripheral cell types to agonists of adenosine receptors.