3,4-Dihydroxyxanthone dioxygenase from Arthrobacter sp. strain GFB100

Bacterial extradiol ring-fission dioxygenases play a critical role in the transformation of multiring aromatic compounds to more readily biodegradable aromatic or aliphatic intermediates. Arthrobacter sp. strain GFB100 utilizes an extradiol meta-fission dioxygenase, 3,4-dihydroxyxanthone dioxygenase (DHXD), in the catabolism of the three-ring oxygen heterocyclic compound xanthone. In this paper, we show that DHXD is a cytosolic enzyme, induced by growth on xanthone and maximally expressed during the stationary phase of growth. In addition, we characterize the DHXD activity in terms of its basic enzymological properties. 1,10-Phenanthroline and H2O2 treatments eliminated DHXD activity, indicating that the enzyme required Fe2+ ions for activity. Other divalent cations were either inhibitory or had no effect on activity. DHXD had a temperature optimum of 30 degrees C and a pH optimum of 7.0. DHXD followed typical saturation kinetics and had an apparent Km of 10 microM for 3,4-dihydroxyxanthone. The dye celestine blue served as a noncompetitive DHXD inhibitor (Ki, 5 microM). Several other structural analogs served neither as substrates nor inhibitors. DHXD was thermally labile at temperatures above 40 degrees C. The half-life for thermal DHXD inactivation was 5 min at 40 degrees C. DHXD activity was completely stable through one freeze-thaw cycle, and about 80% of the DHXD activity remained after 2 days of incubation at 0 degree C. The apparent tight binding of the Fe2+ cofactor to DHXD may be a factor contributing to the stability of this extradiol dioxygenase when it is stored.

Molecular location of a species-specific epitope on the hamster scrapie agent protein

Scrapie is a transmissible neurodegenerative disease of sheep and goats. An abnormal host protein, Sp33-37, is the major protein component of the scrapie agent and the only known disease- or agent-specific macromolecule. Two monoclonal antibodies (MAbs), 4H8 (immunoglobulin G2b [IgG2b]) and 6B11 (IgG1), produced by immunizing mice with the intact hamster 263K scrapie agent protein, Sp33-37Ha, were found to have species specificity similar to that reported previously for MAb 3F4 (IgG2a), which was produced by using PrP-27-30 as the immunogen (R. J. Kascsak, R. Rubenstein, P. A. Merz, M. Tonna-DeMasi, R. Fersko, R. I. Carp, H. M. Wisniewski, and H. Diringer, J. Virol. 61:3688-3693, 1987). These antibodies all bound to Sp33-37 derived from hamster but not from mouse cells. Competitive binding assays demonstrated that all three MAbs bound to the same or overlapping sites on Sp33-37Ha. The molecular location of the epitope for these antibodies was determined to within 10 residues by using an antigen competition enzyme-linked immunosorbent assay in which synthetic peptides spanning Sp33-37Ha residues 79 to 93 or 84 to 93 specifically inhibited binding of these antibodies to plates coated with purified Sp33-37Ha. A synthetic peptide with the mouse-specific sequence (83 to 92) that differed from the hamster sequence by substitution at two positions (MetHa-87----LeuMo-86 and MetHa-90----ValMo-89) did not inhibit antibody binding to Sp33-37Ha. MAb 3F4 binding to hamster Sp33-37 was eliminated by chemical modification of Sp33-37Ha with diethylpyrocarbonate or succinic anhydride and by cleavage with CNBr or trypsin. The effect of diethylpyrocarbonate on MAb 3F4 binding was not reversed by hydroxylamine treatment. MAb 3F4 binding was not affected by prolonged exposure of Sp33-37Ha to 70% formic acid or by boiling in sodium dodecyl sulfate. We conclude that the epitope for these MAbs is a linear determinant that includes Met-87, Lys-88, and Met-90 and that Met-90 is probably the major species-specific determinant.

[Control of staphylococcal skin infections in a nursery]

Outbreaks of skin infections due to Staphylococcus aureus continue to be a major problem in newborn nurseries. In this report, we described how the staphylococcal skin infections were controlled in the nursery during the last 5 1/2 years. An outbreak of staphylococcal skin infection (totally 29 cases) developed in January 1985, and declined dramatically to 3 cases in March of the same year when 3% hexachlorophene (HCP) bathing was used (period 1-January 1985 to March 1985). The infections increased to 30 cases in May when HCP bathing was discontinued and was replaced by baby soap baths (period 2-April 1985 to May 1985). Once again, HCP bathing (period 3-June 1985 to January 1987) was reinstituted and infection rate was reduced. After discontinuation of HCP (period 4-February 1987 to March 1987), another outbreak of staphylococcal skin infection reappeared. It was controlled again with HCP bathing (period 5-April 1987 to April 1988). Daily baby soap baths were continued during period 6 (May 1988 to October 1988), and skin infections increased again. Finally in period 7 (November 1988 to June 1990), daily baby soaps were reinstituted and a triple dye was applied daily to the cord and to the surrounding skin (1 inch diameter) until discharge. During this period, staphylococcal skin infections was reduced to 1-4 cases and no more outbreaks occurred. Our data confirmed that 3% HCP bathing of newborns reduced the infection rate of Staphylococcus aureus during an endemic period, and supported that triple dye may be an alternative to HCP for preventing staphylococcal skin infection in a newborn nursery.

Increased stability of nucleolin in proliferating cells by inhibition of its self-cleaving activity

Nucleolin is the major nucleolar phosphoprotein of exponentially growing eukaryotic cells and is presumably involved in pre-rRNA transcription and ribosome biogenesis. Monoclonal antibodies against nucleolin were selected by a differential dot-immunobinding assay. Nucleolin expression during T lymphocyte activation was monitored by the specific antibody. Results showed that nucleolin fluctuated in parallel to DNA synthesis. The intact 105-kDa nucleolin molecule was the major species in actively dividing cells, whereas the degraded forms were relatively abundant in nondividing cells. These results imply that stability of nucleolin molecule is cell proliferation-dependent. When affinity purified nucleolin containing undetectable contaminants was incubated at 37 degrees C, the majority of 105-kDa nucleolin was cleaved by 6 h and completely degraded within 24 h. This purified nucleolin was further separated from possible copurified protease, if any, on a reducing sodium dodecyl sulfate-polyacrylamide gel. After renaturation, the 105-kDa nucleolin immobilized in the gel was also cleaved at 37 degrees C. These data have confirmed that nucleolin protein autocatalyzes its own degradation. The self-cleaving activity of nucleolin was inhibited by nuclear extracts prepared from proliferating cells. Apparently, a proteolytic inhibitor(s) in the nuclei of proliferating cells stabilized the nucleolin molecule. It provides an unique regulatory mechanism for nucleolin expression.

Human and Escherichia coli cyclophilins: sensitivity to inhibition by the immunosuppressant cyclosporin A correlates with a specific tryptophan residue

The human T-cell protein cyclophilin shows high affinity for and is the proposed target of the major immunosuppressant drug cyclosporin A (CsA). Cyclophilin also has peptidyl prolyl cis-trans isomerase activity that is inhibited by CsA with an IC50 of 6 nM, while by contrast a homologous PPIase from Escherichia coli has been found to be much less sensitive to CsA, shown here to be 500-fold less potent at an IC50 of 3000 nM. This E. coli rotamase lacks the single highly conserved tryptophan residue of eukaryotic cyclophilins, and we show here that mutation of the natural F112 to W112 enhances E. coli rotamase susceptibility to CsA inhibition by 23-fold. Correspondingly, the human W121 mutations to F121 or A121 yield cyclophilins with 75- and 200-fold decreased sensitivity to CsA, while kcat/Km values of rotamase activity in a tetrapeptide assay drop only 2- and 13-fold, respectively. This complementary gain and loss of CsA sensitivity to mutation to or from tryptophan validate the indole side chain as a major determinant in immunosuppressant drug recognition and the separation of PPIase catalytic efficiency from CsA affinity.

[Candida arthritis: report of two cases]

Candida arthritis is extremely rare. However, there has been a steady increase in the incidence of candida arthritis during the last decade because of increasing candida infections in immunocompromised hosts, drug addicts, premature babies, and those who have received prosthetic joint operations or intraarticular injections of steroids. We report herein two cases of candida arthritis: a 27-year-old man with aplastic anemia and transfusional hemosiderosis, and a 60-year-old man with osteoarthritis who received repeated intra-articular injections of steroids. Definite diagnoses were made after repeated smear examinations of synovial fluids. In the first case, candida arthritis occurred about 2 weeks after an antecedent candidemia. Although the arthritis relapsed once due to inadequate antifungal treatment, it was finally successfully treated with systemic amphotericin B, oral ketoconazole and surgical drainage of the synovial fluid. In the second case, it took several months to make the diagnosis. The patient was also treated with amphotericin B, ketoconazole, and surgery with a satisfactory outcome. We conclude that since candida arthritis is a slow, less destructive joint infection, it can almost always be resolved. Also, late orthopedic complications can be avoided by early diagnosis and prompt treatment, including aggressive antifungal therapy, adequate drainage and necessary surgical intervention.

Parallelization of the EM algorithm for 3-D PET image reconstruction

The EM algorithm for PET image reconstruction has two major drawbacks that have impeded the routine use of the EM algorithm: the long computation time due to slow convergence and a large memory required for the image, projection, and probability matrix. An attempt is made to solve these two problems by parallelizing the EM algorithm on multiprocessor systems. An efficient data and task partitioning scheme, called partition-by-box, based on the message passing model is proposed. The partition-by-box scheme and its modified version have been implemented on a message passing system, Intel iPSC/2, and a shared memory system, BBN Butterfly GP1000. The implementation results show that, for the partition-by-box scheme, a message passing system of complete binary tree interconnection with fixed connectivity of three at each node can have similar performance to that with the hypercube topology, which has a connectivity of log(2) N for N PEs. It is shown that the EM algorithm can be efficiently parallelized using the (modified) partition-by-box scheme with the message passing model.

Identification of a human stomach alcohol dehydrogenase with distinctive kinetic properties

A new form of alcohol dehydrogenase, designated mu-alcohol dehydrogenase, was identified in surgical human stomach mucosa by isoelectric focusing and kinetic determinations. This enzyme was anodic to class I (alpha, beta, gamma) and class II (pi) alcohol dehydrogenases on agarose isoelectric focusing gels. The partially purified mu-alcohol dehydrogenase, specifically using NAD+ as cofactor, catalyzed the oxidation of aliphatic and aromatic alcohols with long chain alcohols being better substrates, indicating a barrel-shape hydrophobic binding pocket for substrate. mu-Alcohol dehydrogenase stood out in high Km values for both ethanol (18 mM) and NAD+ (340 microM) as well as in high Ki value (320 microM) for 4-methylpyrazole, a competitive inhibitor for ethanol. mu-Alcohol dehydrogenase may account for up to 50% of total stomach alcohol dehydrogenase activity and appeared to play a significant role in first-pass metabolism of ethanol in human.

Mutagenesis of a nucleotide-binding site of an anion-translocating ATPase

The ars operon of the conjugative R-factor R773 confers resistance to arsenicals by coding for an anion pump for extrusion of arsenicals from cells of Escherichia coli. The operon encodes three structural genes arsA, arsB, and arsC. The anion pump requires only two polypeptides, the ArsA and ArsB proteins. Purified ArsA protein exhibits oxyanion-stimulated ATPase activity and was demonstrated to bind ATP by photoaffinity labeling with [alpha-32P]ATP. Analysis of the amino acid sequence deduced from the nucleotide sequence of the arsA gene suggests that the ArsA protein contains two potential nucleotide binding folds, one in the N-terminal half and one in the C-terminal half of the protein. A combination of site-directed and bisulfite mutagenesis was used to alter the glycine-rich region of the N-terminal putative nucleotide-binding sequence G15KGGVGKTS23. Four mutant proteins (G18----D, G18----R, G20----S, and T22----I) were analyzed. Strains bearing the mutated plasmids were all arsenite sensitive and were unable to extrude arsenite. Each purified mutant protein lacked oxyanion-stimulated ATPase activity and ATP binding. These results suggest that the N-terminal sequence is part of a nucleotide-binding domain required for catalysis.

Mandibular fractures in children-immediate reduction and fixation with orthodontic resin

Mandibular fractures are not common in children. In Chang Gung Memorial Hospital from 1983 to 1987, we had 354 mandibular fractures but only 12 cases happened to children under 10 years old. Mandibular fractures in children under 10 years cannot be treated in the same way as patient with permanent teeth since possibly neither intermaxillary, nor interosseous fixation can be applied. Complication have been observed in 3 (25%) of these 12 patients, including malocclusion, infection and open bite. In 1988, orthodontic resin was adopted as the fixation material after immediate reduction in three cases. There is no complication and the patients have had a better postinjury quality of life compared with those patients treated from 1983 to 1987. The importance of immediate reduction for mandibular fracture in children and the application of resin cap splint are stressed.

Molecular biology of carbon-phosphorus bond cleavage. Cloning and sequencing of the phn (psiD) genes involved in alkylphosphonate uptake and C-P lyase activity in Escherichia coli B

Whereas bacteria such as Escherichia coli have been known for some time to cleave carbon-phosphorus (C-P) bonds in unactivated alkylphosphonates, the enzymes responsible for C-P lyase activity have resisted detection or purification. Genes from E. coli B that support growth on alkylphosphonates as the sole phosphorus source have now been cloned (B. L. Wanner and J. A. Boline, unpublished data). Deletion analysis demonstrated that at least 13 kilobases of DNA information is required for E. coli to express the phosphonate utilization phenotype (Phn+). The complete nucleotide sequence of 15,611 bases has been determined, and the gene structures were examined. Seventeen open reading frames (phnA to phnQ) were identified in one transcriptional direction and five open reading frames in the divergent direction. Sequence homology searches identify PhnC, PhnK, PhnL, and, possibly, PhnN proteins as members of nucleotide-binding proteins of the binding protein-dependent transport systems. Candidates for other membrane components and regulatory proteins are also identified. A Pho box-like promoter sequence is also found upstream of the gene cluster starting at phnA, which is consistent with the observation of phosphate regulation of the Phn+ response. Fourteen repetitive extragenic palindromic sequences are found in the phn DNA: 10 exist in the extragenic region between phnA and phnB, two between phnD and phnE, and two between phnK and phnL. An unusual finding is that one of the repetitive extragenic palindromic sequences actually overlaps with the reading frame of the phnE gene.

Cloning, expression, and purification of human cyclophilin in Escherichia coli and assessment of the catalytic role of cysteines by site-directed mutagenesis

The cDNA encoding human cyclophilin from the Jurkat T-cell lymphoma line has been cloned by the expression cassette polymerase chain reaction and sequenced, and an expression vector has been constructed under control of the tac promoter for efficient expression in Escherichia coli. Active cyclophilin is produced at up to 40% of soluble cell protein, facilitating a one-column purification to homogeneity. Wild-type cyclophilin was characterized for binding of the potent immunosuppressant agent cyclosporin A (Kd = 46 nM) by tryptophan fluorescence enhancement and for inhibition (IC50 = 19 nM) of cyclophilin's peptidyl-prolyl cis-trans isomerase (rotamase) activity. With N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as the substrate, recombinant human cyclophilin has a high catalytic efficiency; kcat/Km is 1.4 X 10(7) M-1.S-1 at 10 degrees C. To test the prior suggestion that a cysteine residue may be essential for catalysis and immunosuppressant binding, the four cysteines at positions 52, 62, 115, and 161 were mutated individually to alanine and the purified mutant proteins were shown to retain full affinity for cyclosporin A and equivalent catalytic efficiency as a rotamase. Clearly the cysteines play no essential role in catalysis or cyclosporin A binding. These results rule out the recently proposed mechanism [Fischer, G., Wittmann-Liebold, B., Lang, K., Kiefhaber, T. & Schmid, F. X. (1989) Nature (London) 337, 476-478)] involving the formation of tetrahedral hemithioorthoamide. Whereas mechanisms that embody other tetrahedral intermediates may be operative, an alternative mechanism is considered that involves distortion of bound substrate with a twisted (90 degrees) peptidyl-prolyl amide bond.

[Effects of anisodamine on blood coagulation, fibrin and thrombosis in rabbits]

Anisodamine at dose of iv 10 and 20 mg/kg prolonged plasma prothrombin time, bleeding time and coagulation time, and showed positive reaction of plasma protamine paracoagulation test in conscious rabbits. The drug prolonged the thrombin time and reduced the contend of plasma fibrin. Anisodamine markedly inhibited blood platelet aggregation both in vitro and in vivo, dose-dependently. The extracorporeal thrombosis time was prolonged, the length and weight of thrombus was decreased after iv anisodamine 20 mg/kg. These results suggest that anisodamine has inhibitory action thrombosis and blood coagulation.

[Relationship of chest roentgenographic features and outcome in meconium aspiration syndrome]

Aspiration of meconium may produce respiratory distress of various severity and outcome. It is the purpose of this study to evaluate the relationship between roentgenographic feature of initial chest roentgenogram (less than 10 hours old) and outcome in infants with meconium aspiration syndrome (MAS). We analyzed retrospectively the clinical data and initial chest roentgenograms of 65 infants who had MAS and who were admitted to NICU of Mackay Memorial Hospital in 1987. The incidence and the mortality rate in this hospital were 0.33% and 15.4% respectively. Infiltration was seen in 52, consolidation or atelectasis in 18, hyperinflation in 17, air leak in 11, and cardiomegaly in 4. The outcome was similar between infants with the first four features. Four infants with cardiomegaly also had other types of roentgenographic feature and PH value of initial blood gas less than 7.0, which means that their poor outcome was influenced by multiple factors. From this observation we concluded that the initial chest roentgenogram is a useful aid for the diagnosis and treatment of MAS, but it is not suitable for predicting the outcome of infants with MAS.

Incremental algorithm-a new fast backprojection scheme for parallel beam geometries

A fast backprojection scheme for parallel beam geometries is proposed. Known as the incremental algorithm, it performs backprojection on a ray-by-ray (beam-by-beam) basis rather than the pixel-by-pixel backprojection in the conventional algorithm. By restructuring a conventional backprojection algorithm, the interdependency of pixel computations (position and value) is transformed to a set of incremental relations for a beam, where a beam is a set of pixels enclosed by two adjacent rays in 2-D computed tomography (CT), and a set of voxels enclosed by four adjacent rays in 3-D CT. To minimize the overhead of searching for the next pixels, a searching flow technique has been developed to implement the first-order and second-order incremental relations for 2-D and 3-D CTs, respectively. The values of all the pixels in each beam (except the first pixel) are computed with additions only, the key idea of the proposed backprojection scheme. The incremental algorithm has been implemented on two different machines and compared to B.F. Shepp and L.A. Logan's (1974) algorithm. The present implementation results show the superiority of this approach over the conventional algorithm.

Altered imino diacid synthesis and transcription in crown gall tumors with transposon Tn5 insertions in the 3' end of the octopine synthase gene

Octopine synthase encoded by the T-DNA (transferred DNA) locus ocs synthesizes N2-(D-1-carboxyethyl)-L-amino acids in octopine-type crown gall tumors. So far, derivatives of only basic amino acids have been isolated. We have detected a glutamine derivative and called it heliopine. Tumors induced by several Ti plasmids with transposon Tn5 insertions in the 3' end of ocs still synthesized small quantities of N2-(1-carboxyethyl)-arginine and N2-(1-carboxyethyl)-glutamine. In addition, N2-(1,3-dicarboxypropyl)-asparagine, which is absent in wild-type octopine tumors, was detected in these tumors. These three imino diacids (octopine, heliopine, and asparaginopine, respectively, or their isomers) were undetectable in tumors induced by Ti plasmids harboring deletions of the ocs gene. Poly(A)+ RNAs which hybridize to the ocs sequence can also be detected in the ocs::Tn5 tumors; these RNAs, however, were heterogeneous in size and shorter in length than the normal ocs mRNA. These results indicate that mutant ocs products synthesize imino diacids in these ocs::Tn5 tumors.

Intracranial hemorrhage in the hemophiliacs

Five of 34 hemophiliac children suffered from nine episodes of intracranial hemorrhage (ICH) from hemophilia A, and another 3 were B hemophiliacs. Diagnoses were confirmed by computed tomographic scan in all nine episodes. The ages of the patients with ICH ranged from 3 months to 4 1/2 years. The most frequent presenting symptoms were headache and vomiting, followed by focal neurological deficits. Eight of 9 episodes had bleeding in multiple regions. All the patients received immediate replacement therapy had recovered without surgical intervention. The duration of treatment was 10 +/- 2 days. All the patients survived and only one of them had neurological sequela as left hand paresis. From this observation we suggest that the treatment of suspected ICH in hemophiliacs should include prompt replacement therapy for either trauma or neurological symptoms in the absence of trauma history, documentation of ICH by computed tomographic scan, and prolonged replacement therapy and control of increased intracranial pressure in hemophiliacs with documented ICH.

Novel metabolism of several beta zero-thalassemic beta-globin mRNAs in the erythroid tissues of transgenic mice

Mice that are transgenic for human beta zero-thalassemic beta-globin alleles were generated in order to study how beta zero-thalassemic mutations affect beta-globin RNA metabolism in erythroid tissues. Three thalassemic alleles were studied, each of which harbors either a frameshift or a nonsense mutation. These mutations result in the premature termination of beta-globin mRNA translation and an abnormally low level of beta-globin mRNA in the peripheral blood of thalassemic patients. Comparative studies of mice that express any of the beta zero-thalassemic transgenes with mice that express a normal human beta-globin transgene demonstrated that all three thalassemic mRNAs are metabolized in erythroid tissues abnormally. RNA blotting and S1 nuclease transcript mapping revealed for each thalassemic transgene that (i) the full-length mRNA is abnormally short-lived and (ii) in addition to full-length mRNA, three more stable yet smaller RNAs are present. These smaller RNAs are polyadenylated and lack the mRNA 5' end.

Intravenous sulbactam/ampicillin in the treatment of pediatric infections

A total of 82 patients involving 83 episodes of proven or presumed bacterial infection were treated with sulbactam/ampicillin. These included 36 cases of soft tissue infection or abscess, four cases of joint or bone infection, 20 cases of respiratory tract infection (17 cases of pneumonia, two of otitis media, and one of tonsillitis), 15 urinary tract infections, three cases of enterocolitis, one case of infective endocarditis, two cases of septicemia, and two of peritonitis. The causative pathogen was isolated in 48 cases (49 infections). These pathogens included Staphylococcus aureus 13 cases, Staphylococcus epidermidis one, Streptococcus pyogenes two, Streptococcus pneumoniae two, Viridans group streptococcus two, peptostreptococcus one, Haemophilus influenzae one, Escherichia coli 12, Enterobacter cloacae three, Proteus mirabilis one, Acinetobacter calcoaceticus one, Salmonella spp. two, Shigella sonnei one, Bacteroides fragilis one, and polymicrobial infections of various combinations in five cases. No bacterial pathogens were isolated in 34 infections, 14 cases of pneumonia and 15 soft tissue infections. Sulbactam/ampicillin was given by intravenous bolus in a dosage range of 75-450 mg/kg/day in four divided doses for variable periods of time depending on the type and severity of the infection. Of a total of 83 episodes of infections, 80 (96.4%) cases were either cured or improved. Bacteriologic eradication also occurred in 46 (93.9%) of 49 infections. Side effects were diarrhea in two patients, acute hemolytic anemia in one patient, and transient elevations in SGOT and leukopenia in one patient. Side effects disappeared upon completion of treatment. Sulbactam/ampicillin is a safe and effective antibiotic for the treatment of common pediatric infections.

A new compound, withangulatin A, promotes type II DNA topoisomerase-mediated DNA damage

Withangulatin A, a new compound with a known chemical structure and from the antitumor Chinese herb Physalis angulata L, was found to act on topoisomerase II to induce topoisomerase II-mediated DNA damage in vitro. It has two effective dosage ranges of approximate 0.5 and 20 microM, with about one-third the activity of 20 microM VM-26.

Decreased resistance to Listeria monocytogenes in mice following vanadate exposure: effects upon the function of macrophages

We have previously demonstrated that ammonium metavanadate has a broad immunomodulating effect in mice after subchronic exposure. Because host resistance to pathogenic Listeria monocytogenes and in vitro phagocytic activity of harvested peritoneal macrophages (PEM) were strongly affected by vanadate treatment, we investigated the effect of vanadate on the functional role of resident PEM in active listeriosis in the mouse. Vanadium treatment results in altered patterns of clearance of the organism from the peritoneal cavity, liver and spleen. The total in vitro phagocytic uptake of Listeria by PEM was consistently decreased as a function of infection period. Similarly, intracellular killing of Listeria was decreased although the PEM from the vanadate-treated and control mice were more bacteriostatic than bactericidal. Population distributions of Listeria within infected PEM were not affected by host pretreatment with vanadate. Vanadate exposure interferes with both the uptake and ultimate intraphagolysosomal killing of Listeria. These results were expected in light of our previous studies of the effects of vanadate on PEM superoxide production, and hexose monophosphate shunt and glutathione redox cycle activity. The results provide additional information for the development of a mechanism to explain why workers exposed to vanadium-containing dusts have increased susceptibility to bacterial respiratory diseases.