Overexpression of the mexC-mexD-oprJ efflux operon in nfxB-type multidrug-resistant strains of Pseudomonas aeruginosa

OprJ, overproduced in nfxB multidrug-resistant strains of Pseudomonas aeruginosa, and OprK, overproduced in the multidrug-resistant strain K385, were demonstrated to be immunologically cross-reactive using an OprJ-specific monoclonal antibody. Treatment of the purified proteins with trypsin or chymotrypsin yielded virtually indistinguishable digestion patterns, and the N-terminal sequence of two trypsin fragments was identical for both proteins, indicating that OprJ and OprK share identity. The N-terminal amino acid sequences were used to facilitate cloning of the oprJ gene on a 5kbp Kpnl fragment and a 10 kbp BamHl fragment. Nucleotide sequencing of portions of these fragments revealed that oprJ was the terminal gene in a putative three-gene operon, mexC-mexD-oprJ. The predicted mexC-mexD-oprJ gene products exhibit homology to the MexA-MexB-OprM components of the multidrug-resistance efflux pump of P. aeruginosa (43-46% identity). Consistent with an implied role for mexC-mexD-oprJ in drug efflux, the mexC-mexD-oprJ-hyperexpressing strain K385 showed reduced accumulation of a variety of antibiotics as compared with its parent strain, and this drug 'exclusion' was abrogated by energy inhibitors. The mexC and oprJ products are putative lipoproteins of a molecular mass of 40,707 and 51,742 Da, respectively, while mexD was predicted to encode a protein of 111 936 Da. Sequencing upstream of mexC revealed the presence of the nfxB gene transcribed divergently from the efflux genes. Overproduction of OprJ and the attendant multiple-antibiotic resistance of strain K385 was shown to result from a point mutation in nfxB, resulting in a H87-->R change in the predicted NfxB polypeptide. OprJ overproduction and multidrug resistance in K385 was reversed by the cloned nfxB gene, suggesting that nfxB encodes a repressor of mexC-mexD-oprJ expression. Consistent with this, the cloned nfxB gene repressed synthesis of a mexC-lacZ fusion in Escherichia coli. nfxB also repressed expression of a nfxB-lacZ fusion, indicating that NfxB negatively regulates its own expression. These data indicate that the multidrug resistance of nfxB strains is due to overexpression of an efflux operon, mexC-mexD-oprJ, encoding components of a second efflux pump in P. aeruginosa.

Role of mexA-mexB-oprM in antibiotic efflux in Pseudomonas aeruginosa

We have earlier described mexA-mexB-oprK, an operon involved in pyoverdine export in Pseudomonas aeruginosa, and suggested that the products of these genes also contribute to the active efflux of several antibiotics (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993). Recently the outer membrane component of this efflux system was shown to be OprM, rather than OprK (N. Gotoh and K. Poole, unpublished results). In the present study, the conclusion concerning the efflux activity of this system was confirmed and extended by the measurement of drug accumulation in intact cells. Thus, the steady-state accumulation levels of tetracycline and norfloxacin were increased in mexA and oprM null mutants. mexA and oprM null mutants also showed an increase in susceptibility to a wide variety of beta-lactam antibiotics and an increase in the steady-state accumulation level of benzylpenicillin, indicating that the MexA-MexB-OprM pump also effluxes beta-lactams. Furthermore, deenergization of the cytoplasmic membrane with a proton conductor always produced a strong increase in the accumulation level. Finally, a single-step mutant over-producing MexAB-OprM accumulated less tetracycline and chloramphenicol than the parent strain and was more resistant to a wide range of antimicrobial compounds, including beta-lactams. These results support the notion that these proteins contribute to the intrinsic resistance of P. aeruginosa through the multidrug active efflux process.

Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: resistance to tetracycline, chloramphenicol, and norfloxacin

Most strains of Pseudomonas aeruginosa are significantly more resistant, even in the absence of R plasmids, to many antimicrobial agents, including beta-lactams, tetracycline, chloramphenicol, and fluoroquinolones, than most other gram-negative rods. This broad-range resistance has so far been assumed to be mainly due to the low permeability of the P. aeruginosa outer membrane. The intrinsic-resistance phenotype becomes further enhanced in "intrinsically carbenicillin-resistant" isolates, which were often assumed to produce outer membranes of even lower permeability. It has been shown, however, that this hypothesis cannot explain the beta-lactam resistance of these isolates (D.M. Livermore and K.W.M. Davy, Antimicrob. Agents Chemother. 35:916-921, 1991). In this study, we examined the uptake of tetracycline, chloramphenicol, and norfloxacin by intact cells using strains showing widely different levels of intrinsic resistance. Their accumulation and the response to the addition of a proton conductor showed that even relatively susceptible strains of P. aeruginosa actively pump out these compounds from the cell and that the efflux activity becomes much stronger in strains showing higher levels of intrinsic resistance. We conclude that the efflux mechanism(s) are likely to contribute significantly to the intrinsic resistance of P. aeruginosa isolates to tetracycline, chloramphenicol, and fluoroquinolones, as does the low permeability of the outer membrane. This conclusion is supported by the observation that the hypersusceptibility to various agents of the mutant K799/61 (W. Zimmermann, Antimicrob. Agents Chemother. 18:94-100, 1980) was apparently caused by the lack of active efflux. Although the hypersusceptibility of this mutant has hitherto been assumed to be solely due to its higher outer membrane permeability, its outer membrane was shown to have a coefficient of permeability to cephaloridine that was not significantly different from that of the parent, resistant strain K799/WT. The strains with elevated intrinsic resistance overproduced two cytoplasmic membrane proteins and one outer membrane protein; at least two of these proteins appeared different from the proteins overproduced in the recently described mutant with a derepressed multidrug efflux system, MexA-MexB-OprK (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993).

Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: active efflux as a contributing factor to beta-lactam resistance

Wild-type strains of Pseudomonas aeruginosa are more resistant to various beta-lactam antibiotics as well as other agents than most enteric bacteria. Although resistance to compounds of earlier generations is explained by the synergism between the outer membrane barrier and the inducible beta-lactamase, it was puzzling to see significant levels of resistance to compounds that do not act as inducers or are not hydrolyzed rapidly by the chromosomally encoded enzyme. This intrinsic-resistance phenotype becomes enhanced in those strains with the so-called intrinsic carbenicillin resistance. In the accompanying paper (X.-Z. Li, D. M. Livermore, and H. Nikaido, Antimicrob. Agents Chemother. 38:1732-1741, 1994), we showed that active efflux played a role in the resistance, to various non-beta-lactam agents, of P. aeruginosa strains in general and that the efflux was enhanced in intrinsically carbenicillin-resistant strains. We show in this paper that, in comparison with the drug-hypersusceptible mutant K799/61, less benzylpenicillin was accumulated in wild-type strains of P. aeruginosa and that the accumulation levels were even lower in intrinsically carbenicillin-resistant strains. Deenergization by the addition of a proton conductor increased the accumulation level to that expected for equilibration across the cytoplasmic membrane. In intrinsically carbenicillin-resistant isolates, there was no evidence that either nonspecific or specific permeation rates of beta-lactams across the outer membrane were lowered in comparison with those of the more susceptible isolates. Furthermore, these carbenicillin-resistant isolates were previously shown to have no alteration in the level or the inducibility of beta-lactamase and in the affinity of penicillin-binding proteins. These data together suggest the involvement of an active efflux mechanism also in the resistance to beta-lactams. Hydrophilic beta-lactams with more than one charged group did not cross the cytoplasmic membrane readily. Yet one such compound, ceftriaxone, appeared to be extruded from the cells of more-resistant strains, although with this compound effects of proton conductors could not be shown. We postulate that wild-type strains of P. aeruginosa pump out such hydrophilic beta-lactams either from the periplasm or from the outer leaflet of the lipid bilayer of the cytoplasmic membrane, in a manner analogous to that hypothesized for multidrug resistance protein of human cancer cells (M.M. Gottesman and I. Pastan, Annu. Rev. Biochem. 62:385-427, 1993).

Gene amplification and high-level expression of human pro-urokinase cDNA in Chinese hamster ovary cells

Human Pro-Urokinase (Pro-UK) is expressed in CHO-DHFR- cells at high efficiency by co-transfecting the mouse dhfr gene and Pro-UK cDNA under the control of the SV40 late promoter. After gene co-amplification, the product level could reach 2-3 micrograms/10(6) cells/24 h in the presence of 5 x 10(-6) mol/L MTX, and the levels can be further raised to 3.5-4 micrograms/10(6) cells/24 h by PMA superinduction. The copy number of Pro-UK cDNA in the genomes of host cells is about 200-300 copies/cell. The Western blot analysis shows that the recombinant Pro-UK has similar molecular weight to its natural counterpart, and also the amidolytic activity of the product is determined by S-2444 assay.

[Comparison of new convenient traditional Chinese medicine-decoction with traditional decoction]

Through determining the rate and speed of extracting and the contents of effective constituents, an experimental comparison was made of the new TCM-decoction with the traditional decoction. The result showed that the new one was better than the traditional one.

[A study of cerebral vasospasm after subarachnoid hemorrhage with transcranial Doppler]

Transcranial Doppler (TCD) was performed in 64 patients with subarachnoid hemorrhage (SAH) to detect the blood velocity in middle cerebral artery (MCA). Based on Poiseuille's principle, the increase of blood velocity was used as an indicator of cerebral vasospasm (CVS). It was found that 61.67% of the patients with SAH developed CVS, especially in the second week after SAH. The incidence of CVS in patients below 50 years old was higher than that in patients above 51 years old. The results showed that TCD is valuable in evaluation of CVS after SAH.

[Ovarian sex cord tumor with annular tubules--a report of 7 cases]

Seven cases of ovarian sex cord tumor with annular tubules are reported in this paper. All lesions occurred in the young (6-25 years of age with a mean of 15 years) without Poutz-Jeghers syndrome. Four cases had estrogenic hormonal imbalance and abdominal mass. Gross examination revealed that the tumors were unilateral with smooth surface. Except one, all showed varying degrees of cystic degeneration on section. The sections appeared as roe-like granular substance in a pale yellowish brown shade in the parenchymal region. Microscopic examination showed single or complex annular tubules with prominent basement membrane-like material around the tubules. Lipid in the cytoplasm and granulosa cell tumor-like differentiation were observed in isolated area of some cases. Ultrastructurally, Charcot-Battcher filaments were found in 1 case, indicating differentiation towards Sertoli's cells. The malignant potential of this tumor had been elucidated in the literature.

[Elimination of poison from Halitum violaceum by processing]

The contents of polysulphides in different forms of Halitum violaceum (unprocessed, processed with vinegar, calcinated and boiled with water) were determined indirectly by UV spectrophotometry. The results showed that the unprocessed forms are higher in the contents of polysulphides while the processed ones have little or no such contents at all. It is thus believed that the poisons can be eliminated from Halitum violaceum by processing, which helps to decrease or eliminate polysulphides and sulphides.

Autoantibodies to the major nucleolar phosphoprotein B23 define a novel subset of patients with anticardiolipin antibodies

Of 164 sera with antinucleolar antibodies, 7 (4.3%) were shown by Western blotting to react with a 37-kd polypeptide in a nuclear extract of HeLa cells and with the recombinant protein expressed by a complementary DNA clone encoding the major nucleolar protein B23. Six of the 7 sera (86%) had antibodies to cardiolipin (aCL), and the sample that was negative for aCL had had lupus anticoagulant on previous testing. All 7 patients had either systemic lupus erythematosus (SLE) or a variant of SLE, suggesting that anti-B23 identifies a subset of patients with SLE associated with a high frequency of aCL.

The nucleotide sequence of a human cDNA encoding the highly conserved nucleolar phosphoprotein B23

A cDNA clone containing the complete coding sequence for the human nucleolar phosphoprotein B23 was isolated from a Burkitt's lymphoma cDNA library by immunoscreening with human autoantibodies. The B23 clone contained a 1.3 kb cDNA insert encoding a polypeptide of 294 amino acids with a predicted molecular mass of 32,539 daltons. The deduced B23 amino acid sequence contained 2 acidic domains rich in aspartic and glutamic acid, a feature shared by a number of nuclear and nucleolar proteins. The human B23 amino acid sequence showed 98% homology with rat B23 and 68% homology with the Xenopus laevis nucleolar phosphoprotein, NO38 showing that the primary structure of B23 is highly conserved among these species.

Viral etiology of cervical carcinoma. Human papilloma virus and herpes simplex virus type 2

The possible role of human papilloma virus (HPV) and herpes simplex virus type 2 (HSV-2) in the viral etiology of cervical carcinoma was investigated a series of cervical lesions were studied for the presence of HPV and HSV-2 DNA sequences as well as HPV and HSV-2 antigens by DNA dot blot hybridization technique and high-specificity PAP staining method. The results obtained were correlated with the histologic diagnosis. HPV 16 DNA sequences detected in cervical carcinoma biopsies were 43%, whereas HSV-2 DNA sequences were only 8%. HPV antigens detected in cervical dysplasia were 31%, whereas those detected in cervical carcinoma and cervicitis were the least. HSV-2 antigens were detected in chronic cervicitis, dysplasia and cervical carcinoma. The difference in positive rate between the cervical carcinoma and cervicitis groups was statistically significant, (chi-square test, P less than 0.01). No HPV DNA and HSV-2 DNA sequences were found in the same specimen, although both HPV DNA sequences and HSV-2 antigens were found in the same sample in some cases. The results indicate that the viral etiology of cervical carcinoma may be multifactorial. Both HSV-2 and HPV may be associated with cervical carcinoma, but the mechanisms involved are different. HSV-2 and HPV may act synergistically in the development of cervical carcinoma.

[A case of hepatoid adenocarcinoma of the stomach]

A patient, male, 57 years old, with hepatoid adenocarcinoma of the stomach is reported. Chief complaint was right upper abdominal mass and anorexia for 11 months. The patient's serum AFP level was found to be elevated (652.8 ng/ml) and a mass was observed in left hepatic lobe by isotope scan. It was diagnosed as primary hepatic carcinoma. A large ulcerative tumor (14 x 13 x 0.8 cm) in gastric pylorus-antrum and liver metastasis were found by autopsy. Histologically, the tumor, diagnosed as hepatoid adenocarcinoma of the stomach by pathology, was composed of two but closely related to well differentiated tubular papillary adenocarcinoma and differentiated hepatoid adenocarcinoma. Histogenesis, production of AFP and its significance, and clinicopathologic characteristics of this tumor are discussed with review of literature.

Synergistic effect of hydroxyurea and excessive thymidine on the expression of the common fragile sites at 3p14 and 16q23

There is a synergistic effect between hydroxyurea (HU) and high concentrations of thymidine (TdR) on the induction of the common fragile sites at 3p14 and 16q23. The frequencies of expression of these fragile sites were significantly higher than in the controls when excessive TdR (0.5 mM) and HU (4 mM) were added into lymphocyte cultures in MEM medium 24 h and 2 h before harvest. Two conditions for the maximum expression of common fragile sites, such as fra(3)(p14), fra(16)(q23) are discussed. The TdR-HU fra(3)(p14)-inducing system might be modified effectively and consistently to improve the prenatal diagnosis of the fragile X syndrome.

The effect of hydroxyurea on the expression of the common fragile site at 3p14

Hydroxyurea (HU) is an inhibitor of DNA synthesis, which can inhibit the enzyme ribonucleotide reductase, reduce the syntheses of all four deoxyribonucleoside diphosphates (dNDP), and disturb the balance of the dNTP pool. We have studied the effect of HU on the common fragile site at 3p14 (FRA3B) and have found that G2 treatment with HU increased not only the frequency of chromosomal aberration but also the expression of FRA3B in both complete and folate deficient media. There is a synergistic effect between HU and growth in folate deficient medium on the induction of FRA3B. Our results suggest that the inhibition of DNA repair, including the inhibition in G2 phase, plays an important role in the expression of FRA3B, supporting other authors' data on the effect of other DNA repair inhibitors, such as aphidicolin, caffeine, 1-beta-D-arabinofuranosylcytosine, and 5-fluorodeoxyuridine, on the expression of FRA3B.

The effect of 1-beta-D-arabinofuranosyl-cytosine on the expression of the common fragile site at 3p14

The effect of the G2-treatment of 1-beta-D-arabino-furanosyl-cytosine (araC) on the expression of the common fragile site at 3p14 (FRA3B) was studied. A significantly increased frequency of FRA3B induced by G2 treatment of araC was found in the lymphocytes grown in folate-deficient medium (positive rate 100%). A relatively low frequency of FRA3B was also induced in the cultures with folate in four of the seven subjects. There is a synergistic effect between araC and growth in folate-deficient medium on the induction of FRA3B. The results suggest that the DNA lesions related to the expression of FRA3B induce the long-patch repair and that the low DNA polymerase alpha activity and inefficient repair process during G2 phase is involved in the expression of FRA3B.