Biomedical subjects

C Su

Publications and source records attributed to C Su.

At least 55 records · Page 3Linked to original sources

PubMed1999

Coagulase gene polymorphism of Staphylococcus aureus isolates from dairy cattle in different geographical areas.

The objectives of this study were to investigate the coagulase gene polymorphism of Staphylococcus aureus isolates obtained from bovine mastitic milk and to determine the resistance of predominant and rare coagulase genotypes to bovine blood neutrophil bactericidal activities. A total of 453 isolates were collected from four countries: the Czech Republic, France, Korea and the United States. The isolates were subtyped into 40 types by restriction fragment length polymorphism (RFLP) of the coagulase gene. Twenty-three strains from predominant and rare genotypes were evaluated for their ability to resist neutrophil bactericidal activities. There were significant (P < 0.01) differences in the average percent neutrophil killing of the predominant (16.7%) and rare (39.7%) genotypes when bacteria were opsonized with antiserum. The results indicate that the profiles of coagulase genotype differ among geographic locations, and only a few genotypes prevail in each location. In addition, the predominant genotypes were more resistant to neutrophil bactericidal activities than rare genotypes.

Animals↗

PubMed1999

A random coefficient degradation model with random sample size.

In testing product reliability, there is often a critical cutoff level that determines whether a specimen is classified as "failed." One consequence is that the number of degradation data collected varies from specimen to specimen. The information of random sample size should be included in the model, and our study shows that it can be influential in estimating model parameters. Two-stage least squares (LS) and maximum modified likelihood (MML) estimation, which both assume fixed sample sizes, are commonly used for estimating parameters in the repeated measurements models typically applied to degradation data. However, the LS estimate is not consistent in the case of random sample sizes. This article derives the likelihood for the random sample size model and suggests using maximum likelihood (ML) for parameter estimation. Our simulation studies show that ML estimates have smaller biases and variances compared to the LS and MML estimates. All estimation methods can be greatly improved if the number of specimens increases from 5 to 10. A data set from a semiconductor application is used to illustrate our methods.

Computer Simulation↗

PubMed1999

The proinflammatory cytokine, interleukin-1alpha, reduces glucocorticoid receptor translocation and function.

Proinflammatory cytokines have been shown to influence the expression and function of the glucocorticoid receptor (GR). Specifically, several studies have found that cytokines induce a decrease in GR function, as evidenced by reduced sensitivity to glucocorticoid effects on functional end points. To investigate the potential mechanism(s) involved, we examined the impact of the proinflammatory cytokine, interleukin-1alpha (IL-1alpha), on 1) GR translocation from cytoplasm to nucleus using GR immunostaining, 2) cytosolic radioligand GR binding, and 3) GR-mediated gene transcription in L929 cells stably transfected with the mouse mammary tumor virus-cholamphenicol acetyltransferase reporter gene. L929 cells were treated with IL-1alpha (100 and 1000 U/ml) for 24 h in the presence or absence of dexamethasone (Dex; 10 nM to 1 microM). IL-1alpha inhibited Dex-induced GR translocation and alone induced GR up-regulation. Pretreatment with IL-1alpha followed by Dex treatment for 1.5 h led to about 20% inhibition of Dex-induced GR-mediated gene transcription, whereas coincubation of IL-1alpha plus Dex for 24 h inhibited Dex-induced GR-mediated gene activity up to 42%. The latter effect was reversed by the IL-1 receptor antagonist. These results suggest that cytokines produced during an inflammatory response may induce GR resistance in relevant cell types by direct effects on the GR, thereby providing an additional pathway by which the immune system can influence the hypothalamic-pituitary-adrenal axis.

Animals↗

PubMed1999

Sensitization to the cytotoxicity of adriamycin by verapamil and heat in multidrug-resistant Chinese hamster ovary cells.

Development of multidrug resistance to anticancer agents is a major limitation for the success of cancer chemotherapy. The chemosensitizer verapamil increases intracellular accumulation of drugs such as adriamycin in certain multidrug-resistant cell lines. When combined with verapamil, hyperthermia should be able to alter membrane permeability to adriamycin and to enhance the cytotoxicity of the drug. Verapamil increased the cytotoxicity of adriamycin in multidrug-resistant Chinese hamster ovary cells (CH(R)C5) but not in drug-sensitive cells (AuxB1). Hyperthermia (42 degrees C) alone clearly increased the cytotoxicity of adriamycin in AuxB1 cells. There was also a small increase in CH(R)C5 cells at 42 and 43 degrees C. In drug-resistant cells, the cytotoxicity of adriamycin increased considerably when verapamil was combined with heat. This effect was dependent on temperature and increased with time of incubation. At 37 degrees C, verapamil increased the uptake of adriamycin in CH(R)C5 cells, while drug efflux decreased. When verapamil was combined with hyperthermia, drug efflux decreased even further. These results led to an overall increase in intracellular accumulation of the drug. In drug-sensitive cells, hyperthermia increased both the uptake and efflux of adriamycin, but verapamil had no effect. Verapamil plus heat increased the cytotoxicity of adriamycin in drug-resistant cells, and this was accompanied by altered permeability of the membrane to the drug. Hyperthermia combined with verapamil could be beneficial by increasing the effectiveness of adriamycin in the elimination of multidrug-resistant cells in a localized target region.

Animals↗

PubMed1999

[Homozygous deletion of CDKN2/p16 gene in lung cancers].

OBJECTIVE: To study the relationship between CDKN2/p16 gene homozygous deletion and lung cancer progression. METHODS: Improved multiplex PCR technique was applied to detect deletion of CDKN2/p16 gene exon1 and exon2 in 89 cases of lung cancers. RESULTS: Gene deletion rate was increased by the improved PCR technique. Exon 1 and exon 2 deletion rates were 19.1% (17/89) and 22.5% (20/89) respectively, with total rate of exon1 and/or exon2 deletion 25.8% (23/89). Deletion of CDKN2/p16 gene occurred in non-small cell lung carcinoma (NSCLC) and was related to metastasis and progressive stage. CONCLUSION: Abnormality of CDKN2/p16 gene is a genetic factor for NSCLC susceptibility, and may play a role to some extent in NSCLC malignant progression.

Aged↗

PubMed1999

[Experimental study of interleukin-4 gene therapy for glioma].

OBJECTIVE: To study IL-4 gene therapy for glioma. METHODS: Using recombinant retrovirus vector, mIL-4 was transfected into psi 2 packaging cells and rat C6 glioma cells, respectively by lipofectamine. The IL-4 secretting cell clones psi 2 IL-4 and C6IL-4 were studied in vitro and in vivo. RESULTS: Apart from a decrease in cloning efficiency, no difference was observed between the transfected and the wild type glioma cells in proliferation and cell cycle in vitro. Tumorigenicity of subcutaneously and intracranially inoculated C6IL-4 was reduced. Tumor growth could be suppressed by perineoplastic inoculation of psi 2 IL-4 cells. CONCLUSION: IL-4 gene-modified C6 glioma has decreased tumorigenicity. Local production of IL-4 by psi 2 IL-4 cells can lead to regression of established glioma.

Animals↗

PubMed1999

[Study and application on the device of the drop volume of amniotic fluid in estimating fetal lung maturity].

A novel device of drop volume of amniotic fluid has been made to estimate fetal lung maturity. The design of the device is based on the principle that the surface tension of amniotic fluid is inversely proportional to the quantity of surfactant in the solution. The device measures the falling time of fluid drops from drop-tube and estimates the fetal lung maturity by using the method of comparison and electric-optic timing-counting. 148 samples of amniotic fluid were measured by the device and the data were compared with those obtained by biochemical method. The results demonstrate that this device has high stability and accuracy, and the rate of agreement between the two methods is as high as 93%.

Amniotic Fluid↗

PubMed1999

[Expression and identification of recombinant 22.6 kDa fusion protein of Schistosoma japonicum].

AIM: To obtain a large amount of purified 22.6 kDa antigen of Schistosoma japonicum (Sj22.6) in large quantity. METHODS: The sequence of the gene fragment encoding Sj22.6 was reformed by PCR and subcloned into plasmid vector pGEX-1 lambda T that coded for the 26 kDa GST antigen of Schistosoma japonicum (Sj26 GST). The recombinant plasmid was transformed into E. coli TG2 and then the positive recombinant clone was expressed by induction with IPTG. RESULTS: The recombinant Sj22.6/Sj26 GST fusion protein was expressed in 5.1% of total bacterial protein and was easy to be purified with glutathione sepharose 4B. Moreover, the purified recombinant Sj22.6 antigen could be cut off easily from the fusion protein with thrombin and had high immunogenicity. CONCLUSION: The purified recombinant Sj22.6 protein and Sj22.6/Sj26 GST fusion protein had the same immunological activity as the native Sj22.6 kDa protein.

Animals↗

PubMed1999

[Studies on immunoprotection in mice after immunization with Schistosoma japonicum 22.6 kDa recombinant protein].

AIM: To evaluate the immunoprotective effect of Schistosoma japonicum recombinant 22.6 kDa (rSj22.6) and Sj22.6/Sj26 GST fusion protein. METHODS: The Sj22.6/Sj26 GST fusion protein was prepared by affinity chromatography using glutathione Sepharose 4B. The purified rSj22.6 could be cleaved easily from the fusion protein with Thrombin. 17 and 12 mice immunized with rSj22.6 and Sj22.6/Sj26 GST separately were each challenged with 40 +/- 1 S. japonicum cercariae. RESULTS: In BALB/c mice, the rSj22.6 and Sj22.6/Sj26 GST could induce 32.1 (P < 0.005) and 34.9% (P < 0.02) worm reduction, respectively, as well as 28.4% (P < 0.02) and 45.1% (P < 0.005) total egg reduction, respectively. CONCLUSION: Bpth rSj22.6 and Sj22.6/Sj26 GST fusion protein are partially effective against S. japonicum.

Animals↗

PubMed1998

A protein radical and ferryl intermediates are generated by linoleate diol synthase, a ferric hemeprotein with dioxygenase and hydroperoxide isomerase activities.

Linoleate diol synthase (LDS) was isolated as a hemeprotein from the fungus Gaeumannomyces graminis. LDS converts linoleate sequentially to 8R-hydroperoxylinoleate (8-HPODE) through an 8-dioxygenase by insertion of molecular oxygen and to 7S,8S-dihydroxylinoleate through a hydroperoxide isomerase by intramolecular oxygen transfer. Light absorption and EPR spectra of LDS indicated that the heme iron was ferric and mainly high spin. Oxygen consumption during catalysis started after a short time lag which was reduced by 8-HPODE. Catalysis declined due to suicide inactivation. Stopped flow studies with LDS and 8-HPODE at 13 degreesC showed a rapid decrease in light absorption at 406 nm within 35 ms with a first order rate constant of 90-120 s-1. Light absorption at 406 nm then increased at a rate of approximately 4 s-1, whereas the absorption at 421 nm increased after a lag time of approximately 5 ms at a rate of approximately 70 s-1. EPR spectra at 77 K of LDS both with linoleic acid and 8-HPODE showed a transient doublet when quenched after incubation on ice for 3 s (major hyperfine splitting 2.3 millitesla; g = 2.005), indicating a protein radical. The relaxation properties of the protein radical suggested interaction with a metal center. 8-HPODE generated about twice as much radical as linoleic acid, and the 8-HPODE-induced radical appeared to be stable. Our results suggest that LDS may form, in analogy with prostaglandin H synthases, ferryl intermediates and a protein radical during catalysis.

Electron Spin Resonance Spectroscopy↗

PubMed1998

Retinoblastoma, a tumor suppressor, is a coactivator for the androgen receptor in human prostate cancer DU145 cells.

The retinoblastoma protein may function as a tumor suppressor by controlling the progression of the normal cell cycle. Inactivation of Rb has been regarded as an important event in prostate carcinogenesis. However, the detailed mechanism of how Rb is linked to androgen-androgen receptor (A-AR), the major factor in promotion of prostate tumor growth, remains unclear. Using GST-Rb pull down assay and mammalian two-hybrid system, we report here that Rb can bind specifically to AR in an androgen-independent manner. Transient transfection assay demonstrates that cotransfection of AR and Rb can further induce AR transcriptional activity 4-fold in the presence of 1 nM dihydrotestosterone in DU145 cells. Interestingly, cotransfection of Rb and ARA70, the first identified AR coactivator, with AR can additively induce AR transcriptional activity 13-fold (from 5-fold to 64-fold). In conclusion, our discovery that Rb can function as a coactivator to induce AR transcriptional activity in prostate cells may represent the first data to link a negative growth regulatory protein function in a positive manner, by inducing the transcriptional activity of AR.

Cell Cycle↗

PubMed1998

Manganese lipoxygenase. Purification and characterization.

A linoleic acid (13R)-lipoxygenase was purified to homogeneity from the culture medium of Gäumannomyces graminis, the take-all fungus, by hydrophobic interaction, cation exchange, lectin affinity, and size-exclusion chromatography. The purified dioxygenase lacked light absorption between 300 and 700 nm. Gel filtration indicated an apparent molecular mass of approximately 135 kDa in 6 M urea and approximately 160 kDa in buffer. SDS-polyacrylamide gel electrophoresis (PAGE) showed that the enzyme was heterogeneous in size and consisted of diffuse protein bands of 100-140 kDa. Treatment with glycosidases for N- and O-linked oligosaccharides yielded a distinct protein of approximately 73 kDa on SDS-PAGE. Atomic emission spectroscopy indicated 0.5-1.0 manganese atom/enzyme molecule. The isoelectric point was approximately 9.7, and the enzyme was active between pH 5 and 11 with optimum activity at pH 7. 0. For molecular oxygen, Km was 30 microM and Vmax 10 micromol mg-1min-1; for linoleic acid, Km was 4.4 micromol, Vmax 8.2 micromol mg-1min-1, and the turnover number 1100 min-1. The enzyme oxidized linolenic acid twice as fast as linoleic acid. The main products were identified by mass spectrometry as 13-hydroperoxy-(9Z,11E, 15Z)-octadecatrienoic and 13-hydroperoxy-(9Z,11E)-octadecadienoic acids, respectively. After reduction of the hydroperoxide, steric analysis of methyl 13-hydroxyoctadecadienoate by chiral high performance liquid chromatography yielded one enantiomer (>95%), which co-eluted with the R-stereoisomer of methyl (13R, 13S)-hydroxyoctadecadienoate. Arachidonic and dihomogammalinolenic acids were not substrates, while oxygen consumption, UV analysis, and mass spectrometric analysis indicated that gamma-linolenic acid was oxygenated both at C-11 and C-13. The enzyme was active at 60 degreesC and after treatment with 6 M urea. It was strongly inhibited by 10-50 microM concentrations of eicosatetraynoic acid and a lipoxygenase inhibitor (N-(3-phenoxycinnamyl)acetohydroxamic acid), but many other lipoxygenase inhibitors (100 microM) were without effect. We conclude that, after deglycosylation, the enzyme has the same size on SDS-PAGE as mammalian and marine lipoxygenases, but it differs from all previously described lipoxygenases in three ways. It is secreted, it forms (13R)-hydroperoxy-(9Z, 11E)-octadecadienoic acid, and it contains manganese.

Ascomycota↗

PubMed1998

Manganese lipoxygenase. Discovery of a bis-allylic hydroperoxide as product and intermediate in a lipoxygenase reaction.

Linoleic acid was incubated with manganese lipoxygenase (Mn-LO) from the fungus Gäumannomyces graminis. The product consisted of (13R)-hydroperoxy-(9Z,11E)-octadecadienoic acid ((13R)-HPOD) and a new hydroperoxide, (11S)-hydroperoxy-(9Z,12Z)-octadecadienoic acid ((11S)-HPOD). Incubation of (11R)-[2H]- and (11S)-[2H]linoleic acids with Mn-LO led to the formation of hydroperoxides that largely retained and lost, respectively, the deuterium label. Conversion of the (11S)-deuteriolinoleic acid was accompanied by a primary isotope effect, which manifested itself in a strongly reduced rate of formation of hydroperoxides and in a time-dependent accumulation of deuterium in the unconverted substrate. These experiments indicated that the initial step catalyzed by Mn-LO consisted of abstraction of the pro-S hydrogen of linoleic acid to produce a linoleoyl radical. (11S)-HPOD was converted into (13R)-HPOD upon incubation with Mn-LO. The mechanism of this enzyme-catalyzed hydroperoxide rearrangement was studied in experiments carried out with 18O2 gas or 18O2-labeled hydroperoxides. Incubation of [11-18O2](11S)-HPOD with Mn-LO led to the formation of (13R)-HPOD, which retained 39-44% of the 18O label, whereas (11S)-HPOD incubated with Mn-LO under 18O2 produced (13R)-HPOD, which had incorporated 57% of 18O. Furthermore, analysis of the isotope content of (11S)-HPOD remaining unconverted in such incubations demonstrated that [11-18O2](11S)-HPOD suffered a time-dependent loss of 18O when exposed to Mn-LO, whereas (11S)-HPOD incorporated 18O when incubated with Mn-LO under 18O2. On the basis of these experiments, it was proposed that the conversion of (11S)-HPOD into (13R)-HPOD occurred in a non-concerted way by deoxygenation into a linoleoyl radical. Subsequent reoxygenation of this intermediate by dioxygen attack at C-13 produced (13R)-HPOD, whereas attack at C-11 regenerated (11S)-HPOD. The hydroperoxide rearrangement occurred by oxygen rebound, although, as demonstrated by the 18O experiments, the oxygen molecule released from (11S)-HPOD exchanged with surrounding molecular oxygen prior to its reincorporation.

Ascomycota↗

PubMed1998

A simple method to enrich mRNA from total prokaryotic RNA.

Isolation of prokaryotic mRNA by the poly(dT) method has been difficult, primarily due to the great instability of the poly(A) sequence in its mRNA. We developed a simple method to remove rRNA from total RNA of Staphylococcus aureus by cloning a PCR-amplified S. aureus rRNA gene fragment into a plasmid, and then synthesizing biotin-labeled antisense rRNA to subtract rRNA. By using this method, S. aureus rRNA is significantly reduced and mRNA is enriched. This method may be used to prepare prokaryotic mRNA for many molecular biology applications.

Cloning, Molecular↗

PubMed1998

Analysis of novel hydroperoxides and other metabolites of oleic, linoleic, and linolenic acids by liquid chromatography-mass spectrometry with ion trap MSn.

Linoleate is oxygenated by manganese-lipoxygenase (Mn-LO) to 11S-hydroperoxylinoleic acid and 13R-hydroperoxyoctadeca-9Z,11E-dienoic acid, whereas linoleate diol synthase (LDS) converts linoleate sequentially to 8R-hydroperoxylinoleate, through an 8-dioxygenase by insertion of molecular oxygen, and to 7S,8S-dihydroxylinoleate, through a hydroperoxide isomerase by intramolecular oxygen transfer. We have used liquid chromatography-mass spectrometry (LC-MS) with an ion trap mass spectrometer to study the MSn mass spectra of the main metabolites of oleic, linoleic, alpha-linolenic and gamma-linolenic acids, which are formed by Mn-LO and by LDS. The enzymes were purified from the culture broth (Mn-LO) and mycelium (LDS) of the fungus Gaeumannomyces graminis. MS3 analysis of hydroperoxides and MS2 analysis of dihydroxy- and monohydroxy metabolites yielded many fragments with information on the position of oxygenated carbons. Mn-LO oxygenated C-11 and C-13 of 18:2n-6, 18:3n-3, and 18:3n-6 in a ratio of approximately 1:1-3 at high substrate concentrations. 8-Hydroxy-9(10)epoxystearate was identified as a novel metabolite of LDS and oleic acid by LC-MS and by gas chromatography-MS. We conclude that LC-MS with MSn is a convenient tool for detection and identification of hydroperoxy fatty acids and other metabolites of these enzymes.

Chromatography, Liquid↗

PubMed1998

Comparison of recombinant human PDE4 isoforms: interaction with substrate and inhibitors.

Four cyclic-nucleotide phosphodiesterase (PDE) genes belonging to the PDE4 family (PDE4A, 4B, 4C and 4D) have been identified. All four isogenes, including several deletions and alterations of the amino, carboxyl and central catalytic domains, were expressed in insect cells. Lysates were characterised for enzyme activity by using the Km for substrate and the EC50 for activation by the cofactor Mg2+. The catalytic domain alone appears to be sufficient for the normal enzymatic function of PDE4 proteins. Substrate affinity varied by less than 2-fold between catalytic-domain forms of the PDE4A, 4B and 4D isogenes and the long forms (PDE4A5, PDE4B1 and PDE4D3). The affinity for Mg2+ varied by less than 4-fold between long and catalytic-domain forms of PDE4A and 4B. The catalytic-domain form of PDE4D, however, had a 12-fold lower affinity for Mg2+ that was restored by including a portion of the amino-terminal domain, upstream conserved region-2 (UCR2). This result suggests that the Mg2+-binding site of PDE4D involves the UCR2 region. Inhibition of the PDE4 proteins by synthetic compounds is apparently affected differently by the domains. For PDE4B, the catalytic domain is sufficient for interactions with the inhibitors studied: IBMX, trequinsin, rolipram, TVX 2706, RP 73401 and RS-25344. For PDE4D the catalytic-domain form is less sensitive than the long form to inhibition by RS-25344, rolipram and TVX 2706, by 1463-, 11-and 12-fold, respectively. Addition of UCR2 to the catalytic-domain form of PDE4D restored all the lost sensitivities. The catalytic-domain form of PDE4A showed a reduced inhibitor affinity with RS-25344 and TVX 2706 by 77- and 90-fold, respectively. Both catalytic-domain and long forms of PDE4 isogenes interacted with equal affinity with the non-specific inhibitors IBMX and trequinsin, as well as the very potent PDE4-specific inhibitor RP 73401. Other potent and specific PDE4 inhibitors, such as rolipram, RS-25344 or TVX 2706, appear to utilize non-catalytic domain interactions with PDE4D and 4A to supplement those within the catalytic domains. These observations suggest a different relation between amino and catalytic domains in PDE4D relative to PDE4B. We therefore propose a model to illustrate these isogene-specific PDE4 domain interactions with substrate, inhibitors and the co-factor Mg2+. The model for PDE4D is also discussed in relation to changes in the activation curve for Mg2+ and sensitivity to RS-25344 that accompany phosphorylation of the long form by protein kinase A.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

Coevolution of immunoglobulin heavy- and light-chain variable-region gene families.

The gene families encoding the immunoglobulin variable regions of heavy (VH) and light (VL) chains in vertebrates are composed of many genes. However, the gene number and the extent of diversity among VH and VL gene copies vary with species. To examine the causes of this variation and the evolutionary forces for these multigene families, we conducted a phylogenetic analysis of VH and VL genes from the species of amniotes. The results of our analysis showed that for each species, VH and VL genes have the same pattern of clustering in the trees, and, according to this clustering pattern, the species can be divided into two groups. In the first group of species (humans and mice), VH and VL genes were extensively intermingled with genes from other organisms; in the second group of species (chickens, rabbits, cattle, sheep, swine, and horses), the genes tended to form clusters within the same group of organisms. These results suggest that the VH and VL multigene families have evolved in the same fashion: they have undergone coordinated contraction and expansion of gene repertoires such that each group of organisms is characterized by a certain level of diversity of VH and VL genes. The extent of diversity among copies of VH and VL genes in each species is related to the mechanism of generation of antibody variety. In humans and mice, DNA rearrangement of immunoglobulin variable, diversity, and joining-segment genes is a main source of antibody diversity, whereas in chickens, rabbits, cattle, sheep, swine, and horses, somatic hypermutation and somatic gene conversion play important roles. The evolutionary pattern of VH and VL multigene families is consistent with the birth-and-death model of evolution, yet different levels of diversifying selection seem to operate in the VH and VL genes of these two groups of species.

Animals↗

PubMed1998

The immunohistological diagnosis of E. coli O157:H7 colitis: possible association with colonic ischemia.

OBJECTIVE: E. coli O157:H7 may cause hemorrhagic colitis resembling ischemic colitis. Diagnosis is usually made by finding sorbitol-negative colonies on MacConkey agar that react with O157 and H7 antisera. Most ischemic colitis is idiopathic, but some may be caused by E. coli O157:H7, inasmuch as this organism can produce fibrin thrombi in colon vasculature. The objectives of this study were to determine whether E. coli O157:H7 infection can be diagnosed retrospectively from paraffin blocks of colon sections and whether an association exists between E. coli O157:H7 infection and colonic ischemia. METHODS: Paraffin-embedded sections of normal colon (n = 2) and various colitides [ischemic (n = 11), E. coli O157:H7 (n = 2), IBD (n = 8) and pseudomembranous (n = 3)] were used. Sections were deparaffinized, rehydrated, incubated with 3% peroxide in methanol, rinsed, and incubated with peroxidase-labeled antibody isolated from goats immunized with whole E. coli O157:H7. Sections were stained with peroxidase chromagen reagent and counterstained with hematoxylin. Coarse, granular, orange-brown staining was considered positive. To determine the localization of the chromagen deposits, three cases that stained positive, including one of the culture-proved E. coli O157:H7 colitis and two of colonic ischemia, were processed for electron microscopy. RESULTS: Both cases (100%) of E. coli O157:H7 colitis and three of 11 (27.3%) cases of ischemic colitis stained positive by light microscopy. In one culture-proved case, electron microscopy demonstrated staining of bacillary structures; in two cases of colonic ischemia, extensive deposits of chromagen material were present that were associated neither with inflammatory cells nor with bacterial forms. CONCLUSIONS: Immunoperoxidase staining of archival sections may be used to diagnose E. coli O157:H7 infection. An etiological role for this organism is possible in some cases of colonic ischemia.

Aged↗