[The predictive value of the CHA2DS2-VASc score for in-hospital outcomes in patients with acute myocardial infarction: China PEACE-retrospective acute myocardial infarction study].

Objectives: This study aimed to evaluate the predictive value of the CHA2DS2-VASc score for in-hospital outcomes of patients with acute myocardial infarction (AMI). Methods: Data of 23 728 patients from the China patient-centered Evaluative Assessment of cardiac Events (China PEACE)Retrospective Acute Myocardial Infarction Study were analyzed retrospectively. The patients were categorized into 3 groups according to the CHA2DS2-VASc scores: the low score group (score 1-3), the middle score group (score 4-6) and the high score group (score 7-9). The in-hospital outcomes included major adverse cardiovascular events (MACE), death, death or withdrawal from treatment, reinfarction, ischemic stroke,etc. The CHA2DS2-VASc score was incorporated into multivariate Cox regression analyses to determine its independent impact on in-hospital outcomes. Receiver operating Characteristic (ROC) curves were constructed, and the area under the curve (AUC) was used to evaluate the predictive value of the CHA2DS2-VASc score for in-hospital mortality and death or withdrawal from treatment, respectively. Results: The patients had a median age of 66 (56,75) years, and 30.7% of them were females. Patients with higher CHA2DS2-VASc scores had a higher in-hospital mortality and more in-hospital complications (all P<0.001). After adjustment of baseline covariates, the subjects in the high score group were associated with high risks of in-hospital mortality (OR=6.13, 95%CI 4.77-7.87, P<0.001), death or treatment withdrawal (OR=6.43, 95%CI 5.16-8.00, P<0.001) and MACE (OR=4.94, 95%CI 4.06-6.01, P<0.001). The AUCs of the CHA2DS2-VASc score were comparable with those of the mini-global registry of acute coronary events(mini-GRACE)score in evaluation of in-hospital mortality (0.699 vs. 0.696, P=0.752) and the death or treatment withdrawal risk (0.708 vs. 0.713, P=0.489). Conclusions: The CHA2DS2-VASc score is an independent predictor of in-hospital outcomes for patients with AMI. Its predictive value was comparable with the mini-GRACE score, which could be used as a simple tool for early and rapid outcome evaluation for AMI patients.

[Expression of galectin-13 in allergic diseases involving airway, skin and mucous membranes].

To detect the expression of galectin-13 in allergic diseases and provide a new way for the diagnosis and treatment of allergic diseases. A retrospective analysis method was used to screen 216 patients with allergic diseases with house dust mites or aspergillus as allergens who visited the Department of Allergy and Department of Respiratory of Tongji Hospital attached Tongji Medical College, Huazhong University of Science and Technology from March 2018 to May 2021. These allergic diseases included allergic asthma, allergic bronchopulmonary aspergillosis, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, allergic urticaria. 25 subjects without underlying diseases were selected as healthy controls. The galectin-13 content in serum in each group were detected, and the Pearson correlation was used to determine the correlation between the galectin-13 content in serum in each group and blood eosinophil count, blood specific IgE, the score scale of allergic disease. The expression of Galectin-13 was increased in allergic asthma group (71.44±39.44) pg/ml, allergic bronchopulmonary aspergillosis group (100.10±47.62) pg/ml, allergic rhinitis group (54.11±24.81) pg/ml and dermatitis group (44.12±19.51) pg/ml. The expression of galectin-13 was not significantly increased in allergic urticaria group (32.75±10.29) pg/ml and the allergic conjunctivitis group (30.55±9.87) pg/ml. The galectin-13 content in serum, was positively correlated with blood eosinophil count(rs=0.54, P<0.001) and house dust mite specific IgE (rs=0.51, P<0.001) in allergic asthma group, and was positively correlated with blood eosinophil count(rs=0.63, P=0.025) and aspergillus fumigatus specific IgE (rs=0.58, P=0.046) in allergic bronchopulmonary aspergillosis group. It was positively correlated with blood eosinophil count (rs=0.52, P=0.000 2) and house dust mite specific IgE (rs=0.41, P=0.005) in allergic rhinitis group. In allergic conjunctivitis group, the expression of galectin-13 was positively correlated with conjunctivitis symptom score (rs=0.47, P=0.048). In atopic dermatitis group, the expression of galectin-13 was positively correlated with blood eosinophil count (rs=0.58, P<0.001) and house dust mite specificity IgE (rs=0.47, P=0.002). In allergic urticaria group, the expression of galectin-13 was not significantly correlated with blood eosinophil count or house dust mite specific IgE. Galectin-13 may be related to the occurrence and progress of allergic diseases and may be involved in the occurrence of eosinophilic inflammation.

Peri-prostatic adipose tissue measurements using MRI predict prostate cancer aggressiveness in men undergoing radical prostatectomy.

OBJECTIVES: To evaluate the effect of peri-prostatic adipose tissue (PPAT) measurements using preoperative MRI on the prediction of prostate cancer (PCa) aggressiveness in men undergoing radical prostatectomy (RP). METHODS: We performed a retrospective study on 179 consecutive patients receiving RP from June 2016 to October 2018. Clinical characteristics were collected. PPAT measurements including peri-prostatic fat area (PPFA) and peri-prostatic fat area to prostate area (PA) ratio (PPFA/PA) were calculated by MRI. Multivariable logistic regression analysis was performed to identify independent predictors of PCa lymph node metastasis (LNM). The predictive performance was estimated through ROC curves. Nomograms were created based on the predictors. RESULTS: Pathologic Gleason score positively correlated with digital rectal examination (DRE), PSA, PPFA/PA, P504S, and Ki-67 (all P < 0.05). ROC curves revealed that high PPFA and high PPFA/PA were associated with LNM (both P < 0.05). Multivariate analysis revealed that high PPFA/PA, pathologic Gleason score, pT stage, and Ki-67 were independently predictive of LNM. The nomograms were created and the C-index was 0.945. CONCLUSIONS: PPFA/PA is an independent predictor for LNM along with Gleason score, pT stage, and Ki-67. PPFA/PA may help predict LNM in men undergoing RP, thus providing adjunctive information for therapeutic strategy and prognosis.

The NAD(P)H:quinone oxidoreductase locus in human colon carcinoma HCT 116 cells resistant to mitomycin C.

Previously, we reported an association of mitomycin C resistance and a deficiency of NAD(P)H:quinone oxidoreductase (NQO1) in HCT 116-R30A cells, a subline derived from mitomycin C-sensitive HCT 116 cells. In HCT 116 cells, we found two mRNAs coding full-length cDNAs of NQO1 differing at codon 139, one with arginine (wild type), and one with tryptophan. Only the tryptophan 139 form of mRNA was detected in HCT 116-R30A cells. In addition, an exon 4 deleted mRNA of NQO1, a product of alternative splicing, was detected in both cell lines. Analysis by semiquantitative reverse transcription-PCR showed that NQO1 mRNA coding full-length cDNAs in HCT 116-R30A cells was 15% of that present in HCT 116 cells. A Mr 26,000 protein, representing the exon 4 deleted mRNA, was not detected by polyclonal anti-NQO1 in HCT 116 sublines. Recombinant plasmids of exon 4 deleted cDNA generated a Mr 26,000 protein without enzymatic activity in Escherichia coli but not in Cos7 cells. The function of exon 4 deleted mRNA is yet unknown. The rates of decay of all NQO1 mRNAs in HCT 116 and HCT 116-R30A cells were similar. DNA sequences of the promoter regions of the NQO1 gene (-837 bp) from both cell lines did not differ from each other or from the same region of the human liver NQO1 gene. Sequences of cis elements in the 837-bp region and mRNA stability could not account for the low expression of full-length mRNA in HCT 116-R30A cells. Southern blot analysis showed the size and the intensity of the NQO1 gene in the two cell lines to be similar. This result was confirmed by semiquantitative PCR analysis of a 450-bp fragment in the NQO1 gene containing codon 139 and the exon 4 region. Digestion of this PCR-amplified fragment by restriction enzyme MspI revealed that HCT 116 cells have two heterozygous NQO1 alleles, a wild-type and a tryptophan 139 form. The functional wild-type NQO1 allele was not detected in HCT 116-R30A cells. Sensitive and resistant cell lines each contained one normal and one abnormal chromosome 16. Loss of the wild-type NQO1 allele in HCT 116-R30A cells did not result from a loss of chromosome 16 or copies of the NQO1 gene. Alteration of factor(s) such as trans-acting factors and DNA methylation may be involved in the down-regulation of NQO1 in the mitomycin C-resistant HCT 116-R30A cells.

NAD(P)H:quinone oxidoreductase expression and mitomycin C resistance developed by human colon cancer HCT 116 cells.

An association between the resistance to mitomycin C (MMC) and a decrease of NAD(P)H:quinone oxidoreductase (NQO1) activity was reported for a MMC-resistant subline, HCT 116-R30A, derived from MMC-sensitive HCT 116 cells. Eight NQO1 cDNA clones were isolated from these two sublines by reverse transcription-PCR. Two clones, pDT9 from HCT 116 and pDT20 from HCT 116-R30A, are the full length of 274 amino acids. These two clones differ by a T to C substitution at nucleotide 464, which results in a replacement of arginine 139 by tryptophan in the enzyme. NQO1 of pDT9 and pDT20 was expressed in Escherichia coli, purified, and shown to have a protein subunit of M(r) 30,000. The change of amino acid 139 resulted in a shift of isoelectric pH from 9.5 to 8.35 and a 60% decrease of activity in reducing MMC. All of the other six clones differ from pDT9 by a deletion of exon 4. On Northern blot, we detected two mRNA species of NQO1 (1.2 and 2.7 kilobases) due to alternative polyadenylation in all sublines. MMC-resistant sublines showed 75-90% mRNA expression relative to HCT 116 cells. Reverse transcription-PCR amplification of cDNA fragment of nucleotide 298-617 revealed two full-length mRNAs in HCT 116 cells but only one full-length mRNA in HCT 116-R30A cells. An exon 4 deletion mRNA was detected in both sublines. The two full-length mRNAs may be from either alleles or chimeras of the same gene and the exon 4 deletion mRNA is a result of alternative splicing. On Western blot, we detected only one M(r) 30,000 protein in all sublines. A substantial decrease of this protein in MMC-resistant sublines (5% of HCT 116) explained the 95% decrease of their NQO1 activity. Transcriptional regulation and posttranscriptional modification may be responsible for the disparity of gene expression of NQO1 and the low concentration of NQO1 protein in MMC-resistant sublines. Reversal of MMC resistance and the recovery of NQO1 in two revertants further supports the hypothesis that cellular control of NQO1 can modulate the cytotoxicity of MMC.

Functional testing of putative oligopeptide permease (Opp) proteins of Borrelia burgdorferi: a complementation model in opp(-) Escherichia coli.

Studies of the protein function of Borrelia burgdorferi have been limited by a lack of tools for manipulating borrelial DNA. We devised a system to study the function of a B. burgdorferi oligopeptide permease (Opp) orthologue by complementation with Escherichia coli Opp proteins. The Opp system of E. coli has been extensively studied and has well defined substrate specificities. The system is of interest in B. burgdorferi because analysis of its genome has revealed little identifiable machinery for synthesis or transport of amino acids and only a single intact peptide transporter operon. As such, peptide uptake may play a major role in nutrition for the organism. Substrate specificity for ABC peptide transporters in other organisms is determined by their substrate binding protein. The B. burgdorferi Opp operon differs from the E. coli Opp operon in that it has three separate substrate binding proteins, OppA-1, -2 and -3. In addition, B. burgdorferi has two OppA orthologues, OppA-4 and -5, encoded on separate plasmids. The substrate binding proteins interact with integral membrane proteins, OppB and OppC, to transport peptides into the cell. The process is driven by two ATP binding proteins, OppD and OppF. Using opp-deleted E. coli mutants, we transformed cells with B. burgdorferi oppA-1, -2, -4 or -5 and E. coli oppBCDF. All of the B. burgdorferi OppA proteins are able to complement E. coli OppBCDF to form a functional Opp transport system capable of transporting peptides for nutritional use. Although there is overlap in substrate specificities, the substrate specificities for B. burgdorferi OppAs are not identical to that of E. coli OppA. Transport of toxic peptides by B. burgdorferi grown in nutrient-rich medium parallels borrelial OppA substrate specificity in the complementation system. Use of this complementation system will pave the way for more detailed studies of B. burgdorferi peptide transport than currently available tools for manipulating borrelial DNA will allow.

Racial/ethnic identity and amount and type of psychiatric treatment.

OBJECTIVE: The purpose of this study was to examine the relationship of racial/ethnic identity to the amount and type of psychiatric treatment received by white, black, Latino, and Asian patients in the Los Angeles County mental health system. METHOD: The patients studied (N = 19,400) consisted of all adult inpatients and outpatients seen in all county mental health facilities between January 1983 and August 1988. Multiple regression analysis was used to test the relationship between race/ethnicity and four measures of treatment received: number of treatment sessions, treatment modality, treatment setting, and therapist's discipline. The covariates included in the analyses were age, sex, socioeconomic status, primary language, diagnosis, and measures of treatment when these were logical predictors and were not acting as dependent variables. RESULTS: Race/ethnicity did not have a consistent significant relationship to the treatment variables studied. However, diagnosis had a consistent and highly significant relationship to all four measures of treatment. A psychotic diagnosis was related to receiving more treatment sessions, greater use of medication, greater use of inpatient treatment, and less treatment by a professional therapist. Socioeconomic status and primary language also had consistent and significant relationships to three of the treatment variables. CONCLUSIONS: In considering modifications to the service delivery system, clinicians must evaluate whether the type of treatment provided to psychotic patients is the treatment of choice in terms of effectiveness and efficiency or whether it involves bias in service delivery. Similarly, the issue of bias in treatment of lower socioeconomic patients must be addressed.

Can test statistics in covariance structure analysis be trusted?

Covariance structure analysis uses chi 2 goodness-of-fit test statistics whose adequacy is not known. Scientific conclusions based on models may be distorted when researchers violate sample size, variate independence, and distributional assumptions. The behavior of 6 test statistics is evaluated with a Monte Carlo confirmatory factor analysis study. The tests performed dramatically differently under 7 distributional conditions at 6 sample sizes. Two normal-theory tests worked well under some conditions but completely broke down under other conditions. A test that permits homogeneous nonzero kurtoses performed variably. A test that permits heterogeneous marginal kurtoses performed better. A distribution-free test performed spectacularly badly in all conditions at all but the largest sample sizes. The Satorra-Bentler scaled test statistic performed best overall.

Synthesis and antitumor evaluation of a highly potent cytotoxic DNA cross-linking polyamine analogue, 1,12-diaziridinyl-4,9-diazadodecane.

A diaziridinylspermine analogue, 1,12-diaziridinyl-4,9-diazadodecane (NSC-667005), was synthesized as a bisalkylating agent with a polyamine backbone. DNA cross-linking was detected in the reaction of linearized pBR322 DNA with 1,12-diaziridinyl-4,9-diazadodecane at concentrations comparable with that required for cross-linking by two nitrogen mustard drugs, mechlorethamine and melphalan. A significant increase in life span of female CD2F1 mice bearing L1210 murine leukemia was observed after intravenous administration of 1,12-diaziridinyl-4,9-diazadodecane in doses of less than 2.7 mg/kg, given on days 1, 5, and 9 of treatment.

Community mental health services for ethnic minority groups: a test of the cultural responsiveness hypothesis.

This study investigated services received, length of treatment, and outcomes of thousands of Asian-American, African-American, Mexican-American, and White clients using outpatient services in the Los Angeles County mental health system. It tested the hypothesis that therapist-client matches in ethnicity and language are beneficial to clients. Results indicate that Asian Americans and Mexican Americans underutilized, whereas African Americans overutilized, services. African Americans also exhibited less positive treatment outcomes. Furthermore, ethnic match was related to length of treatment for all groups. It was associated with treatment outcomes for Mexican Americans. Among clients who did not speak English as a primary language, ethnic and language match was a predictor of length and outcome of treatment. Thus, the cultural responsiveness hypothesis was partially supported.

A covariance structure analysis of flicker sensitivity.

We tested whether linear structural models of the mechanisms underlying flicker sensitivity could reproduce the variance-covariance matrix of temporal contrast sensitivity data. Monocular sensitivities to frequencies between 2.5 and 45 Hz were measured for 124 subjects, ages 18-88 yr. Exploratory factor analyses revealed that both a two-mechanism and a three-mechanism model could adequately account for the data. Furthermore, confirmatory factor analyses and full structural equation models, using age as an explanatory variable, supported both models, with the three-factor model giving a somewhat better representation of the data. Parsimony favors the two-mechanism model. But patterns of loss associated with pre-exudative age-related maculopathy are more easily understood in terms of three underlying mechanisms.

Participation in and outcome of treatment for major depression among low income Asian-Americans.

This study examined the relationship of four aspects of psychiatric treatment (use of medication, client-therapist ethnic match, treatment in an Asian-specific clinic, and professional therapist) to participation in treatment and outcome of treatment in low income Asian-American clients (n = 273) of the Los Angeles County mental health system who were diagnosed with major depression. Based on cultural responsiveness theory, the study tested the hypothesis that use of medication in treatment would have the greatest effect on participation and outcome followed, in order, by client-therapist ethnic match, treatment in an Asian-specific clinic, and treatment by a professional therapist. The hypotheses were largely supported: treatment with medication had a significant relationship to total number of treatment sessions (participation) and improvement in the admission-discharge Global Assessment Scale (GAS) score (outcome). Treatment by a therapist of the same ethnicity as the client and treatment in an agency designated to provide services to Asian clients both had significant relationships to the number of treatment sessions but not to GAS score improvement. Four covariates included in the analysis and treatment by a professional therapist had no relationship to either of the dependent variables.

Public outpatient mental health services: use and outcome among Asian Americans.

Use of public outpatient mental health services and treatment outcomes were studied among Chinese, Japanese, Filipino, Korean, and Southeast-Asian Americans in Los Angeles County. Filipinos were underrepresented in the system, whereas Southeast Asians were overrepresented and had higher utilization rates, but showed less improvement, than did the other groups. The influence of therapist-client ethnic match and of clinicians' professional status were assessed, and recommendations are made for further research based on present findings.

Helicobacter pylori urease: properties and role in pathogenesis.

Urease (urea amidohydrolase, EC 3.5.1.5) catalyzes the hydrolysis of urea to yield ammonia and carbon dioxide. Research on this enzyme has gained momentum since the discovery of Helicobacter pylori as a causative agent of human gastritis. The remarkably high urease activity of each organism has served as the basis of diagnostic tests for the presence of the organism in the urease biopsy test and urea breath test. Urease undoubtedly plays a central role in H. pylori pathogenesis. Hydrolysis of urea with generation of ammonia may enable survival of this acid-sensitive organism in the gastric mucosa. Ammonia generated by urea hydrolysis may also produce severe cytotoxic effects within gastric epithelium. The enzyme also elicits a strong immune response during acute infection, suggesting that this abundant antigen is readily available to the immune system. An increase in serum IgG titer is predictive of ongoing infection. Much progress has been made with regard to the molecular biology of urease. The high molecular weight protein (estimated by several investigators to be 300-520 kDa) has been purified, revealing two distinct subunits of 29.5 kDa and 66 kDa, a unique subunit structure as compared with other microbial ureases. However, amino acid sequences are nevertheless well conserved when compared with other bacterial ureases and that of the jack bean, Canavalia ensiformis. Furthermore, genes encoding urease of H. pylori have been cloned, sequenced, and amplified by the polymerase chain reaction.

Purification and N-terminal analysis of urease from Helicobacter pylori.

Urease of Helicobacter pylori (formerly Campylobacter pylori) is believed to represent a critical virulence determinant for this species. Ammonia generated by hydrolysis of urea may protect the acid-sensitive bacterium as it colonizes human gastric mucosa. An H. pylori strain, cultured from a gastric biopsy of a patient with complaints of abdominal pain and a history of peptic ulcer disease, was isolated on selective medium and cultured in Mueller-Hinton broth supplemented with 4% fetal calf serum. Whole cells were ruptured by French pressure cell lysis, and soluble protein was chromatographed on DEAE-Sepharose, phenyl-Sepharose, Mono-Q, and Superose 6 resins. Purified urease represented 6% of the soluble protein of crude extract, was estimated to have a native molecular size of 550 kilodaltons (kDa), and was composed of two distinct subunits of apparent molecular sizes of 66 and 29.5 kDa. On the basis of subunit size, a 1:1 subunit ratio as measured by scanning densitometry of Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels, and estimated native molecular size, the data are consistent with a stoichiometry of (29.5 kDa-66 kDa)6 for the structure of the native enzyme. Km for urea was estimated at 0.2 mM. By N-terminal analysis, the 29.5-kDa subunit of H. pylori urease was found to share significant amino acid sequence similarity with the smallest of three subunits of the Proteus mirabilis and Morganella morganii ureases, as well as to the amino terminus of the unique jack bean subunit. The 66-kDa subunit also shared up to 80% similarity with the largest of three subunits of P. mirabilis, M. morganii, and Klebsiella aerogenes ureases and to internal sequences (amino acids 271 to 285) of the jack bean urease subunit. Thus, the amino acid sequence is conserved among ureases with one, two, and three distinct subunits, suggesting a common ancestral urease gene. Also, urease subunits of M. morganii and jack bean were specifically recognized by antisera raised against the 66-kDa subunit of H. pylori urease, demonstrating that at least some antigenic determinants were conserved among ureases from different species.

Relationship of ethnicity to psychiatric diagnosis.

The purpose of this study was to determine the relationship of ethnic identity to psychiatric diagnosis in white, black, Latino, and Asian clients of the Los Angeles County mental health system. The sample (N = 26,400) consisted of adult inpatient and outpatient clients seen in county mental health facilities between January 1983 and August 1988. Logistic regression analysis was used to determine the relationship of ethnicity to diagnosis in both outpatient and inpatient samples. The covariates included in the analysis were age, gender, socioeconomic status, and primary language. Ethnicity had a significant and consistent relationship to diagnosis in both outpatient and inpatient samples, with black and Asian clients having a greater proportion of psychotic diagnoses than whites, and Latinos a lesser proportion than whites. None of the covariates included in the analysis had a consistent relationship to diagnosis. Whites and Asians received more diagnoses of major affective disorders than blacks or Latinos; blacks and Asians received more diagnoses of schizophrenia and other psychoses than whites, and Latinos received fewer of these diagnoses than whites. Substance abuse was lower for Asians than for the other three groups. Based on the findings, it was concluded that there continues to be a difference in psychiatric diagnosis that is related to ethnicity. Clinical practice issues and recommendations for further research are considered in relationship to these findings.

Update on the prevention, diagnosis, and treatment of Lyme disease.

With our better understanding of Lyme disease, we now know it is not the "great imitator" of disease it once was thought to be. Limited, identifiable syndromes can be related to Lyme disease. Most of the disease's manifestations resolve without treatment. Treatment with standard antibiotics is very effective at preventing the development of long-term sequelae. The Lyme disease vaccine is safe and effective at preventing transmission of Lyme disease. Future improvements in the care of patients with Lyme disease should focus on identifying the etiology and most effective therapies for patients with posttreatment chronic Lyme disease syndrome, determining the safety and efficacy of vaccination in children, and developing second generation vaccines with improved efficacy and dosing schedules, possibly through the addition of antigens expressed in the human host.

Host-pathogen interactions in the immunopathogenesis of Lyme disease.

The immunopathogenesis of Lyme disease is complicated and requires a thorough understanding of the interaction among the causative organism, Borrelia burgdorferi, its tick vector, and its mammalian hosts. In vitro, animal and human studies have shown that the organism is capable of adapting to and utilizing elements from its environment to establish infection and persist despite a inducing a strong immune response. Indeed, the immune response may be responsible for many of the symptoms associated with Lyme disease. It appears that humoral immunity plays the greatest role in clearance of the organism. Cytokines released by Th 1 or Th 2 subsets of CD4+ cells have been shown to play an important role in determining outcome of the disease in animal models possibly through their effects on immunoglobulin class switching. In the small percentage of patients who have treatment resistant chronic Lyme disease, autoimmune mechanisms may play a role in persistent disease.

Expression of catalytically active recombinant Helicobacter pylori urease at wild-type levels in Escherichia coli.

The genes encoding Helicobacter pylori urease, a nickel metalloenzyme, have been cloned and expressed in Escherichia coli. Enzymatic activity, however, has been very weak compared with that in clinical isolates of H. pylori. Conditions under which near wild-type urease activity was achieved were developed. E. coli. SE5000 containing recombinant H. pylori urease genes was grown in minimal medium containing no amino acids, NiCl2 was added to 0.75 microM, and structural genes ureA and ureB (pHP902) were overexpressed in trans to the complete urease gene cluster (pHP808). Under these conditions, E. coli SE5000 pHP808/pHP902) expressed a urease activity up to 87 mumol of urea per min per mg of protein (87 U/mg of protein), a level approaching that of wild-type H. pylori UMAB41 (100 U/mg of protein), from which the genes were cloned. Poor catalytic activity of recombinant clones grown in Luria broth or M9 medium containing 0.5% Casamino Acids was due to chelation of nickel ions by medium components, particularly histidine and cysteine. In cultures containing these amino acids, 63Ni2+ was prevented from being transported into cells and was not incorporated into urease protein. As a consequence, M9 minimal medium cultures containing histidine or cysteine produced only 0.05 and 0.9%, respectively, of active urease produced by control cultures containing no amino acids. We conclude that recombinant H. pylori urease is optimally expressed when Ni2+ transport is not inhibited and when sufficient synthesis of urease subunits UreA and UreB is provided.