Biomedical subjects

L Yu

Publications and source records attributed to L Yu.

At least 55 records · Page 3Linked to original sources

PubMed2001

Marginal Fermi liquid resonance induced by a quantum magnetic impurity in d-wave superconductors.

We consider a model of an Anderson impurity embedded in a d(x(2)-y(2))--wave superconducting state to describe the low-energy excitations of cuprate superconductors doped with a small amount of magnetic impurities. Because of the Dirac-like energy dispersion, a sharp localized resonance above the Fermi energy, showing a marginal Fermi liquid behavior ( omega ln omega as omega-->0), is predicted for the impurity states. The same logarithmic dependence of self-energy and a linear frequency dependence of the relaxation rate are also derived for the conduction electrons, characterizing a new universality class for the strong coupling fixed point. At the resonant energies, the spatial distribution of the electron density of states around the magnetic impurity is also calculated.

Journal Article↗

PubMed2001

Mutation analysis and the correlation between genotype and phenotype of Arg778Leu mutation in chinese patients with Wilson disease.

BACKGROUND: The defective gene (ATP7B) that causes Wilson disease (WD) codes for a putative copper-transporting P-type adenosine triphosphatase. After cloning of ATP7B, the spectrum of mutations and their clinical consequences have been investigated in patients with WD in different ethnic populations. However, the spectrum of mutations and the correlation of genotype-phenotype in the Chinese population have not been extensively studied. OBJECTIVE: To investigate the characterization of mutations of ATP7B and the correlation between genotype and phenotype in the Chinese population. METHODS: We studied 60 unrelated healthy Chinese and 65 unrelated Chinese families, including 84 patients with WD and 126 parents. Genomic DNA was prepared from peripheral blood leukocytes using a salt-precipitation method. Polymerase chain reaction single-strand conformation polymorphism and subsequent direct sequencing were used to identify the mutations and polymorphisms of ATP7B. Statistical analysis was performed using t test or chi(2) test. RESULTS: We identified 18 mutations (7 novel) and 11 polymorphisms (3 novel). The novel mutations are -36C-->T, Trp650ter, Gln914ter, 2810delT, Thr935Met, Arg1041Pro, and Glu1173Lys. The novel polymorphisms are 1168A-->G (Ile390Val), 2785A-->G (Ile929Val), and 3316G-->A (Val1106Ile). Two mutations, Arg778Leu and Thr935Met, are relatively frequent, representing 37.7% and 10.0% of patients, respectively. To our knowledge, we are the first to report the correlation between the genotype and phenotype of Arg778Leu. The result shows that Arg778Leu homozygotes are associated with the early onset of WD with hepatic presentation. CONCLUSIONS: The Arg778Leu and Thr935Met mutations are hot spots in the Chinese population. The features of mutations of ATP7B differ between the Chinese and Western ethnic populations. The Arg778Leu mutation has severe effects on the function of ATP7B. These findings are valuable for developing a fast and effective method to diagnose the presence of the WD gene.

Adolescent↗

PubMed2001

Long-term implantation test and tumorigenicity of polyvinyl alcohol hydrogel plates.

Two types of flat plates made from a polyvinyl alcohol (PVA) hydrogel with a water content of 80 and 20 (PVA-H80, PVA-H20), 20 x 10 x 1 mm in size, were subcutaneously implanted into each of 50 young, male Wistar rats. As a control, a sham operation was done on another set of 50 rats (Sham Op group). The shape and transparency of the PVA hydrogel were unchanged for up to 24 months. Tumors arose in 14 rats from the PVA-H80 group. In the PVA-H20 group, tumors appeared in 15 rats. The average tumor latency was 598 +/- 109 days in the PVA-H80 and 637 +/- 94 days in the PVA-H20. There was no difference in tumor incidence between the PVA-H20 and PVA-H80 groups (p < 0.05). In the Sham Op group, no malignant tumors appeared. Histopathologically, the tumors induced by hydrogel plates were malignant tumors resembling fibrosarcoma or malignant fibrous histiocytoma. This indicates that PVA hydrogel implants also induce solid state carcinogenesis at a similarly high rate to medical grade hydrophobic material reported in a previous study.

Absorbable Implants↗

PubMed2001

Determination of trimebutine maleate in rat plasma and tissues by using capillary zone electrophoresis.

A simple and rapid capillary zone electrophoresis method was developed for the determination of trimebutine maleate in rat plasma and tissues. Rat plasma and tissue homogenates were mixed with acetonitrile containing internal standard, ephedrine hydrochloride, and then centrifuged. The supernatant was dried under a stream of nitrogen, and the residue was reconstituted in methanol-water (1:1). The electrophoresis was performed in uncoated capillary with 30 mmol/L phosphate buffer of pH 6.0 as the separation electrolyte. The applied voltage was 10 kV and the UV detection was set at 214 nm. The peak height ratio vs concentration in plasma or homogenates was linear over the range of 5-500 ng/mL and the limit of quantitation was 5 ng/mL. The intra- and inter-day precision was RSD < 14% and <15%. The accuracy was relative error (RE) within +/- 14%. This method was applied to studying the pharmacokinetics and tissue distribution after a single dose of trimebutine maleate was administrated to the rats. The T(max), AUC, C(max) and t(1/2) were 30 min, 7.8 x 10(2) (ng/mL) min, 39 ng/mL and 1.7 x 10(2) min. The drug distribution was found in a decreasing order of liver, kidney, spleen, lung and heart.

Animals↗

PubMed2001

Object-oriented approach to drug design enabled by NMR SOLVE: first real-time structural tool for characterizing protein-ligand interactions.

As a result of genomics efforts, the number of protein drug targets is expected to increase by an order of magnitude. Functional genomics efforts are identifying these targets, while structural genomics efforts are determining structures for many of them. However, there is a significant gap in going from structural information for a protein target to a high affinity (K(d) < 100 nM) inhibitor, and the problem is multiplied by the sheer number of new targets now available. nature frequently designs proteins in classes that are related by the reuse, through gene duplication events, of cofactor binding domains. This reuse of functional domains is an efficient way to build related proteins in that it is object-oriented. There is a growing realization that the most efficient drug design strategies for attacking the mass of targets coming from genomics efforts will be systems-based approaches that attack groups of related proteins in parallel. We propose that the most effective drug design strategy will be one that parallels the object-oriented manner by which nature designed the gene families themselves. IOPE (Integrated Object-Oriented PharmacoEngineering) is such an approach. It is a three-step technology to build focused combinatorial libraries of potential inhibitors for major families and sub-families of enzymes, using cogent NMR data derived from representatives of these protein families. The NMR SOLVE (Structurally Oriented Library Valency Engineering) data used to design these libraries are gathered in days, and data can be obtained for large proteins (> 170 kDa). Furthermore, the process is fully object-oriented in that once a given bi-ligand is identified for a target, potency is retained if different cofactor mimics are swapped. This gives the drug design process maximum flexibility, allowing for the more facile transition from in vitro potency to in vivo efficacy.

Binding Sites↗

PubMed2001

Rapid assays for detection of anti-islet autoantibodies: implications for organ donor screening.

The purpose of the current study was to develop and evaluate rapid assays for autoantibodies to GAD65 (GAA), ICA512bdc/IA-2 (ICA512AA), and insulin (microIAA, mIAA) as a potential tool for identification of cadaveric pancreas donors who were at high risk for developing diabetes. The study included 154 new onset diabetic, prediabetic, and healthy control subjects. Subjects were evaluated for all three autoantibodies in three separate assays: (1) standard (std) assay with a 24-h or 72-h incubation at 4 degrees C (combined GAA/ICA512AA or mIAA, respectively), (2) rapid assay with 1-h room temperature (RT) incubation, and (3) rapid assay with 2-h RT incubation. The serum samples from 777 organ donors were also evaluated for all three autoantibodies and all the positive samples from standard assay evaluated with the 1-h incubation assay. Simple linear regression analyses revealed excellent correlation between the standard assay and the rapid assays for all three autoantibodies, as follows: (1) GAA: std vs. 1 h (R2=0.85) and std vs. 2 h (R2=0.83), (2) ICA512AA: std vs. 1 h (R2=0.85) and std vs. 2 h (R2=0.84), and (3) mIAA: std vs. 1 h (R2=0.70) and std vs. 2 h (R2=0.64). Comparison of assay correlation rates between subject cohorts revealed no significant differences. Compared to their respective standard assays, the 1-h RT GAA assay missed 3.2% and identified an additional 1.3% of samples, the 1-h RT ICA512AA assay had no discordant samples, and the 1-h RT mIAA assay missed 7.1% and identified an additional 5.8% of samples. We analysed a series of 777 stored serum samples from cadaveric donors. Two of 777 (0.25%) were positive for two autoantibodies (both GAA and ICA512AA) and 23 of 777 (3.0%) one autoantibody (11 IAA; 12 GAA). The rapid analysis for all three autoantibodies could be completed in less than 3 h with comparable concordance rates to the more time-consuming standard assays, making these assays an attractive option for organ donor screening to identify potential pancreata for immunopathogenetic research.

Adolescent↗

PubMed2001

Transient insulin autoantibody expression independent of development of diabetes: comparison of NOD and NOR strains.

NOD mice spontaneously develop anti-insulin autoantibodies associated with the subsequent development of diabetes. NOD mice that express insulin autoantibodies at 8 weeks of age have a diabetes risk exceeding 90%, while mice that do not express autoantibodies by 16 weeks have a risk of less than 20%. NOD female mice expressed insulin autoantibodies more often than male mice (13/15+ vs. 6/15+). Autoantibodies characteristically developed between 8 and 20 weeks and then for most mice became negative at diabetes onset in NOD mice. In the diabetes-free strain NOR mice, spontaneous expression of insulin autoantibodies was observed in less mice (female 8/15+, male 3/10+) compared to NOD mice. The expression of autoantibodies was transient in NOR mice and followed the same time-course as for NOD mice and they were all negative by 28 weeks (without progression to diabetes). No correlation was found in NOR mice between the levels of autoantibodies and insulitis. The program of insulin autoantibody expression is regulated over approximately 5 months for both NOD and NOR mice with only NOD mice developing diabetes, indicating that depending upon genetic combination, the presence of insulin autoantibodies does not always predict diabetes development. In addition, this data is not consistent with the hypothesis that the time-course of autoantibodies simply reflects the destruction of beta-cells with development of diabetes.

Animals↗

PubMed2001

Heterogeneity of type I diabetes: analysis of monozygotic twins in Great Britain and the United States.

AIMS: To determine the risk, hazard rate and factors affecting progression to diabetes in monozygotic twins of patients with Type I (insulin-dependent) diabetes mellitus. METHODS: Prospective analysis was done of two cohorts of non-diabetic monozygotic twins of patients with Type I diabetes from Great Britain (n = 134) and the United States (n = 53). RESULTS: The diabetes-free survival analysis was similar between both cohorts (p = 0.6). The combined survival analysis (n = 187, median follow-up = 17.7 years, range = 0.01-57) at 40 years of discordance estimated a 39% probability of diabetes for the initially discordant twin. Survival analysis with left truncation of data estimated that probability to be 50%. For twins who became concordant (n = 47), the median discordance time was 4.2 years (range 0.4 to 39), exceeding 15 years in 23.4%. Twins of probands diagnosed at 24 years of age or younger had a 38% probability of diabetes by 30 years of discordance, compared with 6% for twins of probands diagnosed after 24 years of age (p = 0.004). The twins of probands diagnosed before 15 years of age had the highest diabetes hazard rate in the first discordance year, decreasing thereafter. By survival analysis, diabetes risk was higher in twins who were heterozygous for DR3-DQ2 and DR4-DQ8 than in twins with neither DR3-DQ2 nor DR4-DQ8 (p < 0.05). CONCLUSION/INTERPRETATION: Monozygotic twins of patients with Type I diabetes from two different countries had similar rates of progression to diabetes. Whereas most twins did not develop diabetes, 25% of the twins who progressed did so after more than 14 years of discordance. An age-related heterogeneity was observed, with higher progression to diabetes for twins of patients diagnosed at a younger age.

Adolescent↗

PubMed2001

Opioid peptides alleviated while naloxone potentiated methamphetamine-induced striatal dopamine depletion in mice.

Delta opioid peptide [D-Ala2, D-Leu5] enkephalin (DADLE) can partially reverse long-term loss of striatal dopamine transporters induced by multiple doses of methamphetamine via an unknown mechanism. This study was designed to examine the modulating effects of three opioid ligands, DADLE, Leucine enkephalin (L-enk), and naloxone, on the long-lasting dopamine depletion produced by 4 cumulative doses of methamphetamine. Both DADLE (at a dose of 18 mg/kg) and L-enk (100 microg/kg x 2) effectively attenuated methamphetamine-induced dopamine depletion in the striatum while their protective effects were not blocked by coadministration of naloxone. In contrast, naloxone (10 mg/kg x 2) alone potentiated the long-lasting dopamine depletion produced by methamphetamine. Moreover, none of the treatments with DADLE (18 mg/kg), L-enk (100 microg/kg), or naloxone (10 mg/kg) alone affected body temperature. These results suggest that the opioid ligands may, directly or indirectly, modulate this methamphetamine-induced dopamine neurotoxicity in the nigrostriatal system via a temperature-independent mechanism.

Animals↗

PubMed2001

Mucosal pathophysiology and inflammatory changes in the late phase of the intestinal allergic reaction in the rat.

Relatively little information exists concerning the late phase of the allergic reaction in the gastrointestinal tract. Here, we characterized jejunal mucosal pathophysiology and inflammation after oral antigen challenge of sensitized rats, and examined the role of mast cells in events after challenge. Sprague-Dawley rats, mast cell-deficient (Ws/Ws), and +/+ control rats were sensitized to horseradish peroxidase, and challenged intragastrically with antigen 14 days later. Jejunal segments were obtained at 0.5 to 72 hours after challenge for functional assessment in Ussing chambers and for morphological assessment by light and electron microscopy. Intestine from sensitized Sprague-Dawley rats demonstrated enhanced ion secretion and permeability at all times after challenge. Electron microscopy revealed abnormal mitochondria within enterocytes and disruption of the epithelial basement membrane associated with influx into the mucosa of mast cells, eosinophils, neutrophils, and mononuclear cells. Many inflammatory cells appeared activated. In contrast, antigen-challenged Ws/Ws rats demonstrated no functional changes or inflammatory cell infiltrate. We conclude that oral antigen challenge of sensitized rats induces sustained epithelial dysfunction. Mast cells mediate both epithelial pathophysiology and recruitment of additional inflammatory cells that may contribute to persistent pathophysiology and symptoms.

Animals↗

PubMed2001

Free radical scavenging properties of conjugated linoleic acids.

Conjugated linoleic acids (CLA) were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH.) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR results demonstrated that CLA directly reacted and quenched free DPPH radicals in benzene, while spectrophotometric analysis showed the radical scavenging capacity of CLA in ethanol. Dose and time effects of CLA-DPPH. reactions were observed in both tests. The ED(50) of CLA was 18 mg/mL under experimental conditions. CLA are much weaker radical scavengers as compared to vitamin E, vitamin C, and BHT. Kinetics of CLA-DPPH. reactions was different to that of linoleic acid (LA)-DPPH. reactions. CLA reacted and quenched DPPH radicals at all tested levels without a lag phase, while LA had a lag phase and showed no radical quenching activity at levels of 5-80 mg/mL in 30 min. These data indicated that CLA can provide immediate protection against free radicals, but LA cannot.

Electron Spin Resonance Spectroscopy↗

PubMed2001

Synthesis and reactivity of potential toxic metabolites of tamoxifen analogues: droloxifene and toremifene o-quinones.

Tamoxifen remains the endocrine therapy of choice in the treatment of all stages of hormone-dependent breast cancer. However, tamoxifen has been shown to increase the risk of endometrial cancer which has stimulated research for new effective antiestrogens, such as droloxifene and toremifene. In this study, the potential for these compounds to cause cytotoxic effects was investigated. One potential cytotoxic mechanism could involve metabolism of droloxifene and toremifene to catechols, followed by oxidation to reactive o-quinones. Another cytotoxic pathway could involve the oxidation of 4-hydroxytoremifene to an electrophilic quinone methide. Comparison of the amounts of GSH conjugates formed from 4-hydroxytamoxifen, droloxifene, and 4-hydroxytoremifene suggested that 4-hydroxytoremifene is more effective at formation of a quinone methide. However, all three substrates formed similar amounts of o-quinones. Both the tamoxifen-o-quinone and toremifene-o-quinone reacted with deoxynucleosides to give corresponding adducts. However, the toremifene-o-quinone was shown to be considerably more reactive than the tamoxifen-o-quinone in terms of both kinetic data as well as the yield and type of deoxynucleoside adducts formed. Since thymidine formed the most abundant adducts with the toremifene-o-quinone, sufficient material was obtained for characterization by (1)H NMR, COSY-NMR, DEPT-NMR, and tandem mass spectrometry. Cytotoxicity studies with tamoxifen, droloxifene, 4-hydroxytamoxifen, 4-hydroxytoremifene, and their catechol metabolites were carried out in the human breast cancer cell lines S30 and MDA-MB-231. All of the metabolites tested showed cytotoxic effects that were similar to the parent antiestrogens which suggests that o-quinone formation from tamoxifen, droloxifene, and 4-hydroxytoremifene is unlikely to contribute to their cytotoxicity. However, the fact that the o-quinones formed adducts with deoxynucleosides in vitro implies that the o-quinone pathway might contribute to the genotoxicity of the antiestrogens in vivo.

Animals↗

PubMed2001

Structure of the N-terminal region of Haemophilus influenzae H10017: implications for function.

Haemophilus influenzae is a gram-negative pathogen that causes infections ranging from asymptomatic colonization of the human upper respiratory tract to serious invasive diseases such as meningitis. Although the genome of Haemophilus influenzae has been completely sequenced, the structure and function of many of these proteins are unknown. H10017 is one of these uncharacterized proteins. Here we describe the three-dimensional solution structure of the N-terminal portion of H10017 as determined by NMR spectroscopy. The structure consists of a five-stranded antiparallel beta-sheet and two short alpha-helices. It is similar to the C-terminal domain of Diphtheria toxin repressor (DtxR). The C-terminal portion of H10017 has an amino acid sequence that closely resembles pyruvate formate-lyase--an enzyme that converts pyruvate and CoA into acetyl-CoA and formate by a radical mechanism. Based on structural and sequence comparisons, we propose that the C-terminus of H10017 functions as an enzyme with a glycyl radical mechanism, while the N-terminus participates in protein/protein interactions involving an activase (iron-sulfur protein) and/or the substrate.

Acetyltransferases↗

PubMed2001

Systemic administration of TerplexDNA system: pharmacokinetics and gene expression.

PURPOSE: The aim of this study is to extend our previous studies to investigate the TerplexDNA synthetic gene carrier system in pharmacokinetics, biodistribution, and gene expression in major organs after systemic administration. METHODS: The stability of the TerplexDNA system was analyzed in vitro with a serum incubation assay. The TerplexDNA PK/PD studies were conducted by quantitation of Terplex/radiolabeled DNA [CTP alpha-32P] complexes after rat-tail vein injection. The effect of the TerplexDNA system on gene expression in mouse major organs was analyzed by measuring luciferase activities after systemic administration. RESULTS: The TerplexDNA gene carrier showed significantly longer retention in the vascular space than naked plasmid DNA alone. At early time points (1 h postvenous injection), the lung was the major organ of the TerplexDNA distribution, followed by the liver as a major distribution organ at later time points (24 h postinjection). The major organs of transgene expression after intravenous injection were the liver and heart. CONCLUSION: The TerplexDNA system has the potential for in vivo applications due to its higher bioavailability of plasmid DNA in the tissues, and due to its organ specific distribution.

Algorithms↗

PubMed2001

Cloning of human myeloid-associated differentiation marker (MYADM) gene whose expression was up-regulated in NB4 cells induced by all-trans retinoic acid.

A full-length cDNA of 3192 bp isolated from human bone marrow cDNA library was predicted an ORF encoding 298 amino acids. The deduced protein, containing seven putative transmembrane segments and sharing 75.8% amino acid identity with mouse Myadm protein, was named as human MYADM. The results of Northern blot analysis showed that MYADM was ubiquitously expressed in 15 of 16 adult tissues tested, except thymus. To determine whether the novel human gene was involved in hematopoietic differentiation process as mouse Myadm did, we examined the mRNA expressive abundance of this gene between normal bone marrow cells and peripheral blood leukocytes, and detected the expression change in NB4 cells induced by all-trans retinoic acid at different induce time by the semi-quantitative RT-PCR. The results showed that the expression of the novel gene was not only significantly higher in peripheral blood leukocytes than in bone marrow cells, but also significantly up-regulated when the NB4 cells(derived from a patient with acute promyelocytic leukemia) were induced by all-trans retinoic acid (ATRA) for 48hr. It is suggested that human MYADM was also associated with the differentiation of hematopoietic cells or acute promyelocytic leukemia cells. In addition, MYADM was mapped to human chromosome 19q 13.33-q 13.4 by Radiation Hybrid mapping, and it consists of 3 exons and 2 introns and spans a 7.1-Kb genomic region.

Amino Acid Sequence↗

PubMed2001

Identification of human, mouse and rat PPP1R14A, protein phosphatase-1 inhibitor subunit 14A, & mapping human PPP1R14A to chromosome 19q13.13-q13.2.

Three novel cDNAs encoding putative protein phosphatase-1 inhibitory protein (PPP1R14A) were isolated from human, mouse and rat. The human, mouse and rat PPP1R14A proteins were all of 147 amino acids sharing about 90% sequence identity to porcine CPI17, an inhibitor of protein phosphatase-1 holoenzyme. The protein sequence 33RHARVTVK40, which is important for the inhibitory potency of porcine CPI17, was conserved in mammalian PPP1R14A. Northern blot analysis showed that human PPP1R14A was highly expressed as a 600 bp transcript in heart, prostate, testis, ovary, colon, small intestine and pancreas, lowly in brain, placenta, skeletal muscle and spleen and lung. The distribution of mouse and rat PPP1R14A was more specific and different from that of human PPP1R14A, abundant in lung, moderate/abundant in testis, moderate in brain and low in heart. In addition, we mapped human PPP1R14A to chromosome 19q13.13-q13.2 by radiation hybrid mapping, and determined that the human PPP1R14A gene spanned a 5.1-kb region and consisted of four exons and three introns.

Amino Acid Sequence↗

PubMed2001

Augmentation of myocardial transfection using TerplexDNA: a novel gene delivery system.

Gene therapy is a potential new strategy for the treatment of cardiovascular disease. The most efficacious method of gene delivery remains a key hurdle to effective gene therapy. We present the application of a novel, nonviral gene delivery system (TerplexDNA) to augment myocardial transfection. The hearts of New Zealand white rabbits were injected with reporter genes, luciferase cDNA or beta-galactosidase cDNA, either as naked plasmid DNA or plasmid DNA complexed with stearyl-poly(L-lysine)-low density lipoprotein (TerplexDNA). Three day left heart myocardial cell lysates produced 44571 +/- 8730 RLU (RLU = total light units/mg protein) for the TerplexDNA luciferase rabbits versus 1638 +/- 567 RLU for the naked luciferase rabbits (P = 0.002). Thirty days after injection, myocardial lysates produced 677 +/- 52 RLU for the TerplexDNA luciferase hearts versus 18 +/- 3 RLU for the naked luciferase hearts (P = 0.002). Histologic analysis of the hearts transfected with beta-galactosidase showed that TerplexDNA increased the area and depth of transfection compared with the naked plasmid DNA alone. The hearts of Sprague-Dawley rats were injected in a similar fashion and analyzed at 1, 3, 5, 10, 15, 25 and 30 days after injection. The naked luciferase injected hearts showed transient elevation of luciferase activity to day 5 but fell back to baseline levels after that time-point. The TerplexDNA luciferase injected hearts had significantly elevated luciferase activity to 30 days. The Terplex gene delivery system significantly augments myocardial transfection compared with a naked plasmid DNA system alone. The advantage in transfection efficiency appears to be related to the unique properties of the TerplexDNA carrier molecule. The TerplexDNA delivery system represents a novel means to augment transfection of the myocardium.

Animals↗

PubMed2001

Detection of immunomagnetically captured Escherichia coli O157:H7 by antibody-conjugated alkaline phosphatase.

A rapid and sensitive detection process for Escherichia coli O157:H7 was developed using alkaline phosphatase (APase)-labeled anti-E. coli O157 antibodies to tag the targeted bacteria. Immunomagnetic beads or antibody-labeled streptavidin-coated magnetic beads were then used to capture the APase-tagged E. coli. Immunomagnetically captured bacteria were washed and distributed into microplates or optical cuvettes. The enzyme-catalyzed hydrolysis of p-nitro-phenol phosphate in alkaline solutions was then followed. Less than 1000 cfu/ml of E. coli O157:H7 could be detected. This approach was applied to detect the bacteria artificially spiked in beef hamburgers. Less than 1 cfu/g of E. coli O157:H7 produced a significant response after cultural enrichment for 4-6 h at 37 degrees C.

Alkaline Phosphatase↗