Detection of Ehrlichia chaffeensis in human tissue by using a species-specific monoclonal antibody

A mouse monoclonal antibody (MAb 1A9) was produced and used in detection of Ehrlichia chaffeensis in human tissues including kidney, liver, and lung by using an indirect immunohistologic stain. MAb 1A9 was specific to E. chaffeensis and did not react with other bacteria, including Ehrlichia canis, which is the organism most closely related to E. chaffeensis. It reacted with an epitope present in two surface proteins of E. chaffeensis with molecular masses of 29 and 27 kDa. E. chaffeensis was easily detected in human tissue by immunohistology with MAb 1A9. This study demonstrates that our MAb can provide a specific and simple method for detection of E. chaffeensis in clinical specimens for establishing an etiologic diagnosis of human ehrlichiosis; it may also provide a tool for the investigation of immunopathologic characteristics in infected patients.

Regulation of Defense-related Gene Expression during Plant-Pathogen Interactions

Plants have evolved a broad array of defense mechanisms involved in disease resistance. These include synthesis of phytoalexin antibiotics and proteinase inhibitors, deposition of cell wall materials, and accumulation of hydrolytic enzymes such as chitinases. Resistance appears to depend on the ability of the host to recognize the pathogen rapidly and induce these defense responses in order to limit pathogen spread. Application of molecular technologies has yielded significant new information on mechanisms involved in pathogen recognition, signal transduction, and defense-related gene activation, and is leading to novel strategies for engineering enhanced disease resistance. We are using these approaches to analyze regulation of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), a key enzyme mediating the production of terpenoid defense compounds. This enzyme is encoded by four genes in tomato; hmg2 gene expression is specifically associated with responses to pathogen or defense elicitors. Transgenic plants containing DNA constructs that fuse the hmg2 promoter to a reporter gene have been used to analyze both tissue specificity and patterns of defense-related expression. Because this gene is rapidly induced in tissues directly surrounding the site of ingress by a variety of pathogens, it may serve as a valuable tool in engineering new disease-resistance mechanisms.

Functional reconstitution of drug transport and ATPase activity in proteoliposomes containing partially purified P-glycoprotein

P-glycoprotein, the multidrug transporter, is proposed to act as an ATP-driven drug efflux pump. We previously reported the partial purification of P-glycoprotein from multidrug-resistant cells (Doige, C. A., Yu, X., and Sharom, F. J. (1992) Biochim. Biophys. Acta 1109, 149-160). We now report the reconstitution of this preparation into phospholipid bilayers using rapid detergent removal by gel filtration chromatography. The resulting proteoliposomes displayed ATP-dependent [3H]colchicine uptake over a time period of 0-4 min. No drug uptake was observed for liposomes of lipid alone, or liposomes reconstituted with a similar extract from drug-sensitive cells. Drug uptake was osmotically sensitive, and abolished by detergent permeabilization, indicating that it represented true transport into the vesicle lumen. Steady-state levels of drug uptake increased with drug concentration, approaching saturation at approximately 150 microM colchicine, with half-maximal accumulation at 50 microM. Drug was accumulated actively against a 5.6-fold concentration gradient. Multidrug resistance spectrum drugs and chemosensitizers inhibited colchicine uptake by P-glycoprotein proteoliposomes, whereas cytosine arabinoside and methotrexate had no effect. Reconstituted liposomes showed high levels of ATPase activity, which was stimulated over 2-fold by verapamil and trifluoperazine. These results suggest that P-glycoprotein functions as an active drug transporter with constitutive ATPase activity.

Expression of monocyte chemoattractant protein 1 in human inflamed gingival tissues

Gingival inflammation is initiated by bacterial colonization on the tooth surface. It is characterized by infiltration of mononuclear cells, a common feature of many forms of chronic inflammation. Monocyte chemoattractant protein 1 (MCP-1) is the predominant monocyte chemoattractant secreted by a variety of different cells in vitro. For this report, we examined MCP-1 expression in bacterially induced gingival inflammation by immunohistochemistry and in situ hybridization. The cell types expressing MCP-1 are identified as vascular endothelial cells and monocytes/macrophages. Correlation analysis shows that the number of cells expressing MCP-1 is related to the degree of inflammation. Our finding that MCP-1 is expressed in inflamed gingival tissue suggests that MCP-1 plays an important role in the recruitment of monocytes and amplification of inflammatory signals in bacterially induced inflammation.

Mutations in the N-terminal region of human immunodeficiency virus type 1 matrix protein block intracellular transport of the Gag precursor

The matrix domain of human immunodeficiency virus type 1 Gag polyprotein was studied for its role in virus assembly. Deletion and substitution mutations caused a dramatic reduction in virus production. Mutant Gag polyproteins were myristoylated and had a high affinity for membrane association. Immunofluorescence staining revealed a large accumulation of mutant Gag precursors in the cytoplasm, while wild-type Gag proteins were primarily associated with the cell surface membrane. These results suggest a defect in intracellular transport of the mutant Gag precursors. Thus, in addition to myristoylation, the N-terminal region of the matrix domain is involved in determining Gag protein transport to the plasma membrane. Wild-type Gag polyproteins interacted with and efficiently packaged mutant Gag into virions. This finding is consistent with the hypothesis that intermolecular interaction of Gag polyproteins might occur in the cytoplasm prior to being transported to the assembly site on the plasma membrane.

Dentin bonding system shelf life and bond strength

The purpose of this study was to assess the shelf life of dentin bonding systems by means of bond strength testing. The systems evaluated were Mirage-Bond, All-Bond and Tenure. Specimens were tested immediately, and 1, 2, 3, 4, 5 and 12 months after opening the kits. Flat dentin surfaces were created on 210 extracted human molars that had been stored in saline. Ten specimens were prepared for each dentin bonding system at each shelf time. Each material was prepared and placed following the manufacturer's instructions. Prisma MicroFine resin composite was then placed. Shear bond strength testing was conducted using a universal testing machine. A two-way ANOVA indicated a significant interaction between bonding system and storage time (F = 2.28, P = 0.01). Multiple comparison tests indicated statistically significant bond strength differences by storage time for All-Bond and Mirage-Bond. In addition, a comparison of bonding systems at each storage time revealed significant differences at three of the seven times. These results suggest that shelf life for two of the three dentin bonding systems may be significantly shorter than currently presumed.

Sustained root culture for generation and vegetative propagation of transgenic Arabidopsis thaliana

Excised roots of wild-type and nitrate-reductase deficient mutant Arabidopsis thaliana (L.) HEYNH. can be propagated as sustained root cultures in liquid medium. Culture initiation from a single seedling required a two-day indoleacetic acid treatment at 0.05 mg/l concentration. Indoleacetic acid facilitated subculture but was not essential for sustained growth. This procedure has allowed the clonal propagation of roots derived from individual wildtype and mutant seedlings for more than 21 months. The cultured roots retained their shoot regeneration ability; however, a controlled desiccation treatment was required to restore it to the level of freshly excised roots. The chromosome number remained diploid and no evidence for the accumulation of recessive mutations was observed. The cultured roots are competent for Agrobacterium-mediated transformation. The sustained root culture technology allowed the maintenance of transgenic tissues in which expression of a dominant, seed-lethal gene (seed-specific pea vicilin promoter fused to diphtheria toxin A chain gene) precluded generative propagation.

Protective effect of Salmonella typhimurium Re-LPS antiserum

There is increasing evidence that antiserum to LPS can reduce the morbidity and mortality of Gram-negative bacterial infections. We report that antiserum to S. typhimurium SL 1102 (Re mutant strain) has excellent cross-protective activity. Antisera to these bacteria and to their Re-LPS were prepared in rabbits immunized with heat-killed bacterial cells and with Re-LPS preparations. Re-LPS antibody titers were tested by immune hemagglutination (IHA) and by ELISA. These antisera were found to be capable of protecting ICR mice against lethal challenge with S-type S. typhimurium 50014 (100 LD50), E. coli 0111:B4 (32 LD50), Pseudomonas aeruginosa (8 LD50) and Klebsiella pneumonia (16 LD50). We used gastric mucin (5%) as a virulence enhancing agent for the bacterial challenges. The IHA titer of antibody to the homologous strain proved to be much higher than that of other strains. Protection by the sera was 75-100%, 25% and 0% when injected 24, 48 or 72 h before the challenge, respectively. The survival rate was more than 50% when the antiserum was injected 5-7 h after challenge with a ten-fold or higher lethal dose. No protection was observed against such high challenge when the serum was injected later. According to these results, Re-LPS antiserum provides better protection than S-type specific antisera.

Effects of anions on the Ca2+, H+ and electrical gradients formed by the sarcoplasmic reticulum ATPase in reconstituted proteoliposomes

The chaotropic character of several ions determines their partition on membrane interfaces with aqueous media as predicted by the Hofmeister series. However, specific characteristics of each individual ion determine its ability to cross the membrane and to influence Ca2+, H+ and electrical gradients produced by the sarcoplasmic reticulum (SR) Ca2+ pump in reconstituted proteoliposomal vesicles. Specific effects of this kind may be relevant to a variety of biological systems, including the excitation-contraction coupling of muscle fibers in which SR plays a prominent role.

DNA conformation induced by the bacteriophage T4 UvsX protein appears identical to the conformation induced by the Escherichia coli RecA protein

The study of homologous genetic recombination has been dominated by the RecA protein of Escherichia coli, which is involved in DNA recombination and repair, as well as phage induction, in vivo. The active form of the RecA protein is a helical filament formed on DNA in the presence of ATP, and within this filament, the DNA is extensively stretched to about 5.1 A rise per base-pair and untwisted to about 19 base-pairs per turn. The bacteriophage T4 UvsX protein is only weakly homologous to RecA, but it has very similar ATP-dependent DNA binding and strand-exchange activities. We can now show that the UvsX protein forms helical filaments that are very similar to those made by RecA, and induces the same extended DNA conformation within these filaments that is induced by RecA. This implies that the unusual conformation of DNA in the RecA filament may be a universal structure in homologous recombination.

Vpx of simian immunodeficiency virus is localized primarily outside the virus core in mature virions

Human immunodeficiency virus type 2 and the related simian immunodeficiency virus (SIV) contain a unique regulatory gene, vpx. The Vpx protein is packaged in mature virions and is required for efficient viral replication in peripheral blood lymphocytes and macrophages. To study the localization of Vpx in mature virions, conical and bar-shaped core structures of SIV from macaques (SIVmac) were purified. The SIVmac core has a density of approximately 1.25 g/cm3, compared with 1.16 g/cm3 for an intact virion. The relative proportions of major capsid protein (p27) and reverse transcriptase activity were similar for intact virions and core structures. The majority of matrix protein (p14) was removed from the purified core structure, suggesting its association with the viral membrane. Similarly, most of the Vpx protein was absent from the purified core structure. This result suggests that as with the matrix protein, the majority of Vpx proteins are localized outside the virus core. The localization of Vpx suggests that it may be involved in virus entry such as penetration or uncoating.

[Fermentation of engineered strain producing cholera toxin B subunit]

Studies indicate that the cholera B subunit could be synthesized efficiently in corn steep liquor by engineered E. coli strain MM2. We have also determined the optical density, pH and the yield of B subunit kinetically during fermentation. Corn steep liquor medium has advantages in low cost, simplicity in technological process and high yield of B subunit which can reaches 40 micrograms/ml in 50L fermentative tank.

Shear strength and microleakage of light-cured glass ionomers

Bond to dentin and marginal integrity of three light activated glass ionomer cements were evaluated, and compared to a traditional chemical-cured glass ionomer cement. Results indicated no significant difference in shear bond strength among the glass ionomer cements tested. However, there was a significant difference among glass ionomer cements in bond strength variability, with coefficients of variation ranging from 55 to 102%. A discrepancy between manufacturers' instructions and optimum curing times is one possible explanation for these results. There were also no significant differences in microleakage among glass ionomer cements. Most samples exhibited minimal or no microleakage.

Assessment of metals in reconstituted metallothioneins by electrospray mass spectrometry

A method has been developed that combines electrospray ionization mass spectrometry with pH control to provide analysis of metals in native or reconstituted metallothioneins. These metalloproteins cooperatively bind seven divalent metal ions, most commonly Zn2+ and Cd2+. Since the protein is denatured and metal ions are lost below pH3, the pH of the electrospray solution is critical to successful results. The metal-free apoprotein was detected with its most abundant ions in a charge state of 6+, while the folded metallothionein-metal complexes were observed with lower charge states. The retention of seven metals in the molecular ions detected is consistent with the hypothesis that metallothionein retains its conformation in the gas phase. This mass spectrometric technique can be used to determine rapidly and accurately how many and what cations are incorporated per molecule of protein. Information about molar distributions and estimates of relative abundances of various complexes in the sample can be acquired in a single measurement.

The LexA repressor binds within the deep helical groove of the activated RecA filament

The RecA protein of Escherichia coli, as a result of DNA damage, catalyzes the cleavage of its own repressor, the LexA protein, and thereby initiates the SOS response. Using a non-cleavable LexA mutant, we have obtained a co-complex of both the RecA and LexA proteins on DNA. Mass analysis using scanning transmission electron microscopy suggests that the site size of the LexA repressor on RecA is two, which would be consistent with a nearest-neighbor exclusion model for binding. Three-dimensional reconstruction of electron micrographs of these filaments shows that the LexA protein is bound in the deep groove of the RecA filament, with two strong regions of contact that span adjacent RecA protomers within the filament. One contact is consistent with a proposed LexA binding site in the RecA crystal structure. The other contact maps onto a region that has been postulated to be a second DNA-binding site within RecA, which can explain the inhibition of RecA cleavage of LexA by excess DNA.

A virion-specific inhibitory molecule with therapeutic potential for human immunodeficiency virus type 1

A potential new approach for gene therapy against human immunodeficiency virus type 1 (HIV-1) infection is the design of a nonstructural gene-based virion-specific inhibitory molecule that is packaged with virus to destroy its infectivity. We tested this approach for HIV-1 by using Vpx, a virion-associated protein of HIV-2 and simian immunodeficiency virus. Vpx was incorporated into HIV-1 virions and the resulting cell-free virus lost infectivity in CD4+ human T cells. This demonstrates the therapeutic potential of an accessory gene-based virion-specific inhibitory molecule. Vpx and its derivatives can be regarded as a new class of anti-HIV-1 molecule.

H+ countertransport and electrogenicity of the sarcoplasmic reticulum Ca2+ pump in reconstituted proteoliposomes

The Ca2+ transport adenosine triphosphatase of sarcoplasmic reticulum was reconstituted in unilamellar liposomes prepared by reverse-phase evaporation. The size of the resulting proteoliposomes was similar to that of native sarcoplasmic reticulum vesicles, but their protein content was much lower, with a protein/lipid ratio (wt/wt) of 1:40-160, as compared with 1:1 in the native membrane. The proteoliposomes sustained adenosine triphosphate-dependent Ca2+ uptake at rates proportional to the protein content (1-2 mumol Ca2+/mg protein/min), reaching asymptotic levels corresponding to a lumenal calcium concentration of 10-20 mM. The low permeability of the proteoliposomes permitted direct demonstration of Ca2+/H+ countertransport and electrogenicity by parallel measurements in the same experimental system. Countertransport of one H+ per one Ca2+ was demonstrated, and inhibition of the Ca2+ pump by lumenal alkalinization was relieved by the H+ ionophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone. Consistent with the countertransport stoichiometry, net positive charge displacement was produced by Ca2+ transport, as revealed by a rapid oxonol VI absorption rise. The initial rise and the following steady-state level of oxonol absorption were highest when SO4(2-) was the prevalent anion and lowest in the presence of the lipophilic anion SCN-. The influence of anions was attributed to potential driven counterion compensation. The absorption rise was rapidly collapsed by addition of valinomycin in the presence of K+. Experimentation with Ca2+ and H+ ionophores was consistent with a primary role of Ca2+ and H+ in net charge displacement. The estimated value of the steady-state electrical potential observed under optimal conditions was approximately 50 mV and was accounted for by the estimated charge transfer associated with Ca2+ and H+ countertransport under the same conditions.

Similarity of the yeast RAD51 filament to the bacterial RecA filament

The RAD51 protein functions in the processes of DNA repair and in mitotic and meiotic genetic recombination in the yeast Saccharomyces cerevisiae. The protein has adenosine triphosphate-dependent DNA binding activities similar to those of the Escherichia coli RecA protein, and the two proteins have 30 percent sequence homology. RAD51 polymerized on double-stranded DNA to form a helical filament nearly identical in low-resolution, three-dimensional structure to that formed by RecA. Like RecA, RAD51 also appears to force DNA into a conformation of approximately a 5.1-angstrom rise per base pair and 18.6 base pairs per turn. As in other protein families, its structural conservation appears to be stronger than its sequence conservation. Both the structure of the protein polymer formed by RecA and the DNA conformation induced by RecA appear to be general properties of a class of recombination proteins found in prokaryotes as well as eukaryotes.

Improved shoot multiplication of mature hazelnut (Corylus avellana L.) in vitro using glucose as a carbon source

Shoot cultures established from mature trees of hazelnut (Corylus avellana L.) cvs. Nonpareil and Tonda Gentile Romana were used to determine the effects of basal media, carbon sources and concentrations, pH and cytokinins on shoot multiplication. All factors except pH affected the multiplication rate. Shoot multiplication was the best on a modified Driver and Kuniyuki medium for Paradox walnut (DKW) supplemented with 6-benzylaminopurine (BA) (1.5-3 mg/l). Plants grown on 3% glucose or fructose medium produced more and longer shoots than those on sucrose. The general appearance and growth habit of shoots were better on medium with glucose than fructose. 'Nonpareil' shoots elongated better than those of 'Tonda Gentile Romana.' Changes in medium pH from 4.7 to 5.7 did not significantly affect the multiplication rate. More than 10 genotypes propagated well on modified DKW medium with glucose. This is the first report of the effect of carbon sources on shoot multiplication of hazelnut and provides a basis for further research in the improvement of hazelnut micropropagation.

Shared nuclear protein binding sites in the upstream region of the rat opsin gene

DNase I protection and gel retardation assays have identified two sequences 5' to the rat opsin gene that interact with nuclear proteins from retina but not from a number of neuronal and non-neuronal tissues. These sites, Ret 2 and Ret 3, are over 1200 base pairs apart but seem to interact with the same protein(s). Synthetic oligonucleotides corresponding to each site were able to inhibit complex formation in a gel retardation assay using an oligonucleotide corresponding to the other site. The proteins binding to the Ret 2 and Ret 3 sites co-eluted in both ion exchange and gel filtration chromatography. The protein(s) were also present at adult levels at birth, suggesting that they may represent differentiation products expressed in the proliferating retinal epithelium.

The effects of lipids and detergents on ATPase-active P-glycoprotein

We previously isolated and characterized a partially purified preparation of ATPase-active P-glycoprotein, the multidrug transporter (Doige, C.A., Yu, X. and Sharom, F.J. (1992) Biochim. Biophys. Acta 1109, 149-160). The effect of various detergents and membrane phospholipids on the ATPase activity of P-glycoprotein has now been investigated. P-Glycoprotein ATPase activity was most stable in CHAPS, with over 50% of the activity retained at a concentration of 8 mM. Octyl glucoside in the low mM range also supported the ATPase, while deoxycholate destroyed all activity at 1 mM. Digitonin and SDS inhibited ATPase activity at very low concentrations. Triton X-100 at 2-10 microM stimulated the ATPase almost 2-fold, while higher levels inhibited activity. Although P-glycoprotein ATPase was sensitive to thermal inactivation, full activity was preserved in the presence of asolectin, but not phosphatidylcholine species. Further studies revealed that asolectin, both saturated and unsaturated phosphatidylethanolamines, and phosphatidylserine, were best able to maintain ATPase activity at 23 degrees C. Saturated phosphatidylethanolamine species activated P-glycoprotein ATPase up to 40% at 23 degrees C, and 80% at 4 degrees C. Following detergent delipidation, various lipids were able to restore P-glycoprotein ATPase activity. Unsaturated phosphatidylcholine and phosphatidylserine were most effective, while saturated species were not able to restore catalytic activity. These results indicate that membrane lipids are necessary for catalytic activity of the ATPase domains of P-glycoprotein. P-Glycoprotein has well-defined lipid preferences, with saturated phosphatidylethanolamines both activating the ATPase and providing protection from thermal inactivation, while fluid lipid mixtures are able to restore activity following delipidation.