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Biomedical subjects

J Meng

Publications and source records attributed to J Meng.

At least 109 records · Page 6Linked to original sources
PubMed1996

A low molecular weight outer-membrane protein of Escherichia coli O157:H7 associated with adherence to INT407 cells and chicken caeca.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 and O26:H11 have been shown to produce a low mol.wt outer-membrane protein (OMP) that is unique to a few serotypes of E. coli. A mutant (A10) of E. coli O157:H7 strain HA1 deficient in the OMP was constructed by TnphoA mutagenesis and assayed for its adherent ability. Adherence of A10 to intestinal epithelial cells (INT407) was significantly less than that of its parent strain (HA1). Adherence of HA1 to INT407 cells was significantly decreased by treatment with a monoclonal antibody (4E8C12) that specifically binds to the OMP. When chickens were infected experimentally with E. coli O157:H7 strains, the average number of cfu of strain A10 recovered from chicken caeca was significantly less than those of strain HA1 and wild-type strain 932 at 14 and 21 days after peroral inoculation. These data suggest that the OMP of EHEC is associated with adherence of E. coli O157:H7 to epithelial cells in vitro and chicken caeca in vivo.

Animals↗
PubMed1996

Advanced glycation end products of the Maillard reaction in aortic pepsin-insoluble and pepsin-soluble collagen from diabetic rats.

Recent immunohistological studies using antibodies against advanced glycation end products (AGEs) have demonstrated the presence of AGEs in several tissues. By an enzyme-linked immunosorbent assay using the monoclonal anti-AGE antibody, the present study aimed to determine AGEs in pepsin-insoluble collagen (PIC) as well as in pepsin-soluble collagen (PSC) from the aortas of streptozotocin (STZ)-induced diabetic rats (at 4, 16, and 28 weeks after STZ injection) and those of age-matched control rats. Addition of EDTA to the immunoassay buffer has led us to successful determination of AGEs in the aortic PIC samples with following results: 1) in diabetic rats, there was a time-related increase in the AGE contents at 28 weeks (n = 9, 226.4 +/- 13.5 ng/mg collagen [mean +/- SE]), compared with that at 4 and 16 weeks (n = 6, 79.6 +/- 9.5 ng/mg collagen, and n = 8, 149.4 +/- 30.9 ng/mg collagen at 4 and 16 weeks, respectively; both P < 0.05, between 4 and 16 weeks and 28 weeks); 2) after 28 weeks of diabetes, the AGE contents in PIC of aortas were significantly higher in diabetic rats than in controls (n = 9, 226.4 +/- 13.5 ng/mg collagen vs. n = 8, 129.6 +/- 14.9 ng/mg collagen, P < 0.01, diabetic vs. control); and 3) the level of the AGE content was strongly correlated with the PIC/total collagen (TC) ratio (n = 45, r = 0.698, P = 0.0001). By treating the samples of PSC with alkaline solution, the AGE content of PSC was also determined. In the PSC fraction, the AGE levels in the diabetic rats tended to increase with time and to be higher than those of control rats at 28 weeks although these changes were not statistically significant (diabetic: n = 4, 19.4 +/- 9.7; n = 6, 22.3 +/- 6.2; n = 6, 39.6 +/- 10.8; control: n = 4, 19.7 +/- 9.8; n = 6, 22.9 +/- 7.3; n = 7, 30.7 +/- 7.2; at 4, 16, and 28 weeks, respectively). Compared with the AGE levels of PSC, those of PIC were about four to seven times and four to five times higher in diabetic and control rats, respectively (PIC versus PSC in diabetic or control rats, all P < 0.001, at 4, 16, and 28 weeks, respectively). These findings provide the first immunochemical evidence that AGE adducts are present in the materials extracted sequentially by pepsin and collagenase and that these adducts in PIC accumulated as a function of the increase in the aortic PIC/TC ratio.

Animals↗
PubMed1995

Specificity and binding affinity of an anti-crotoxin combinatorial antibody selected from a phage-displayed library.

A crotoxin-specific, monoclonal, high-affinity, single-chain antibody variable region (scFv) was generated by combinatorial methods using Pharmacia's Recombinant Phage Antibody System. A high-affinity clone, designated A10G, was selected, and its DNA sequence was determined. Protein A10G showed high reaction specificity, with only the closely related rattlesnake neurotoxins, concolor toxin and Mojave toxin, showing cross-reactivity out of eleven group II phospholipase A2s (PLA2s) screened. No group I PLA2s cross-reacted in enzyme-linked immunosorbent assays. The gene coding for A10G was subcloned into an expression vector, and the resulting expressed nonfusion protein, designated A10GPE, was renatured and purified to apparent homogeneity. Dissociation constants of A10G with intact crotoxin and crotoxin basic subunit were determined to be 7 x 10(-10) and 6.8 x 10(-9) M, respectively. When A10GPE was preincubated with either the basic subunit or intact crotoxin at molar ratios of up to 5:1, no inhibition of phospholipase activity was observed. Expressed protein, however, could partially neutralize the lethality of Mojave toxin, a crotoxin homolog, in mice.

Amino Acid Sequence↗
PubMed1995

Cloning and nucleotide sequence of a gene upstream of the eaeA gene of enterohemorrhagic Escherichia coli O157:H7.

A DNA segment located immediately upstream of the eaeA gene of enterohemorrhagic Escherichia coli O157:H7 strain HA1 was cloned and sequenced. This segment contained an open reading frame encoding a predicted protein of 156 amino acids. A database search identified similar open reading frames upstream of the eaeA gene in two other bacterial pathogens, i.e. enteropathogenic E. coli and Citrobacter freundii. The predicted amino acid sequence of the enterohemorrhagic E. coli protein shared 96.8% and 94.2% identity with the enteropathogenic E. coli and C. freundii sequences, respectively. Because the open reading frame is located within the locus of enterocyte effacement region of the E. coli chromosome, a 'hot spot' for insertion of virulence factor genes, and shares high sequence homology with attaching and effacing EPEC and C. freundii, this protein may be associated with pathogenicity of E. coli O157:H7.

Amino Acid Sequence↗
PubMed1995

Nonenzymatic glycation and extractability of collagen in human atherosclerotic plaques.

The relationship between the extractability of collagen by enzymatic digestion and the degree of nonenzymatic glycation of collagen was examined in the aorta and skin from 38 subjects without diabetes mellitus (mean age: 62.3 +/- 20.2 years). Samples were obtained from the aortic media (M), lesion-free intima (I), atherosclerotic intima (A) and dermis of the skin (S). Collagen was extracted first by incubation with 1/50 (enzyme/substrate weight ratio) pepsin at 4 degrees C for 24 h (P-fraction) and then by incubation with 1/10 (enzyme/substrate weight ratio) pepsin at room temperature for 24 h (EP-fraction). The pepsin-insoluble precipitates were digested by incubation with 270 units of bacterial collagenase at 37 degrees C for 24 h (PIS-fraction). Collagen contents, ketoamines and collagen-linked fluorescence (CLF) were measured in each fraction. The amount of ketoamines and the level of CLF correlated inversely with the susceptibility of collagen to pepsin digestion in various tissues, including M, I, A and S. These values were highest in both the P- and EP-fractions of M, which contained the least amount of collagen extracted by pepsin digestion. In contrast, they were lowest in S, where the concentration of collagen extracted by pepsin digestion was greatest among all of the tissue samples. Atherosclerotic intima (A) and aortic media (M) showed an age-related increase in the total amount of collagen digested with pepsin and collagenase, which depended mainly on an increase in the content of pepsin-insoluble collagen. Although the total amount of collagen did not increase with advancing age in I or S, collagen in I and S became progressingly resistant to pepsin digestion. These results suggest that the age-related decrease in the susceptibility of collagen to pepsin digestion may be due to nonenzymatic glycation in atherosclerotic lesions as well as normal tissues, including the aortic media, lesion-free intima and skin. The level of CLF significantly increased with age in the P-fraction and/or EP fraction of M, I and S. However, there was no relationship between the level of CLF and the subject's age in A. Thus, the accumulation of advanced glycation endproducts (AGEs) on collagen fibers may be partially responsible for the increase in collagen matrix in atherosclerotic lesions of subjects without diabetes mellitus.

Adolescent↗
PubMed1995

Selective inhibitors of 5-lipoxygenase reduce CML blast cell proliferation and induce limited differentiation and apoptosis.

Inhibitors of the arachidonic acid metabolizing enzyme, 5-lipoxygenase, reduce the rate of proliferation of chronic myelogenous leukemia blast cells. The inhibitory agents studied were ETYA, A63162 and SC41661A. These reagents induced differentiation of cultured chronic myelogenous leukemia cells from blast to promyelocytic morphology. Promyelocytic cells then underwent apoptosis, which was identified by nuclear and cytoplasmic morphological features and by DNA laddering. Proliferation of monoblastoid U937 and myelomonocytic HL60 cell lines, known to contain 5-lipoxygenase and synthesize leukotrienes, was reduced by these inhibitors. U937 cells cultured with ETYA, A63162 or SC41661A for 48 h exhibited apoptosis as assessed by DNA laddering and morphology. Characteristic ultrastructural changes of apoptosis were seen at 120 h. MK886, an inhibitor of 5-lipoxygenase with a mechanism of action distinct from oxidation/reduction reagents, at 20-40 microM also inhibited CML and U937 cell proliferation and induced apoptosis, as shown by DNA laddering and ultrastructure.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1995

Molecular characterisation of Escherichia coli O157:H7 isolates by pulsed-field gel electrophoresis and plasmid DNA analysis.

Foods of bovine origin have been identified as sources of Escherichia coli O157:H7. Genomic DNA of E. coli O157:H7 isolates from patients (six isolates), food samples (18 isolates from ground beef and six isolates from raw milk) and calf faecal samples (31 isolates) were characterised by pulsed-field gel electrophoresis (PFGE) and plasmid DNA analysis. These isolates originated from different locations in the USA during 1992 and 1993. Twenty-one distinct genomic profiles were generated from the 61 isolates by PFGE after digestion with the endonuclease XbaI. Four genomic profiles were identified among five patient isolates and the remaining patient isolate was not typable. Five different profiles were detected amongst the isolates from ground beef, one of which was associated with 13 ground beef isolates from an outbreak in the Pacific Northwest of the USA in 1993. The PFGE profile of five calf isolates from Washington and Wisconsin was identical to the profile of the ground beef isolates from the outbreak, suggesting that these isolates were related. Similarly, one PFGE profile accounted for three isolates from calf faeces and one from ground beef. Six raw milk isolates from Georgia were indistinguishable both from each other and from one isolate from calf faeces. Fourteen genomic profiles were identified among 31 calf faecal isolates from 18 different herds in 11 states. Only five plasmid profiles were identified among the 61 isolates. PFGE was shown to be a useful typing technique for E. coli O157:H7.

Animals↗
PubMed1995

Disability glare: effects of temporal characteristics of the glare source and of the visual-field location of the test stimulus.

One of the main early complaints of cataract patients, even when these patients exhibit only mild glare problems as measured by standard tests, is that glare impairs their night driving. To provide a better measure of the patients' impairment, glare tests should include measurements of the glare effect in conditions more similar to those found in night driving. During night driving the ambient light is very low, and oncoming headlights present a transient temporal pattern. Furthermore, the objects of interest often appear initially in the peripheral visual field. Thus three important characteristics of glare in night driving are that the ambient illuminance is in the scotopic-mesopic range, the detection stimulus is in the periphery, and the glare source is transient. Most of the current glare testers measure glare only at photopic levels, and all the glare tests that we know of use only steady sources of glare with foveal discriminations. All these conditions are dealt with. The transient glare source raised thresholds by 0.5-0.75 log unit more than the steady glare source, and the transient glare effect was more pronounced and more long lasting in the periphery. Standard glare testers seriously underestimate disability glare effects in everyday life.

Adaptation, Ocular↗
PubMed1995

[Aging of aorta and atherosclerosis--role of nonenzymatic glycation of collagen].

In order to clarify the role of the nonenzymatic glycation of the collagen matrix in aging of the aorta and atherogenesis, we studied the relation between ketoamine or advanced glycation end-products (AGEs) and the solubility of collagen in human skin and aorta. AGEs were measured as a collagen-linked fluorescence (excitation wavelength: 370 nm. emission wavelength: 440 nm). There was a positive correlation between the level of AGEs and subjects' age in skin and aortic media. Collagen became more insoluble with increase in the amount of ketoamine and AGEs. Collagen was more resistant to pepsin digestion in atherosclerotic intima than in other tissues including aortic media, lesion-free intima and skin. Diabetic rats showed an accumulation of collagen in aortic media at 28 weeks after an injection of streptozotocin. Moreover, they increased the percentage of insoluble collagen to total collagen and the amount of AGEs binding to insoluble collagen in aortic media. In contrast, the amount of ketoamine of insoluble collagen was increased in diabetic rats at 16 weeks as compared to control. There was no difference in DNA contents of cultured smooth muscle cells between glycolaldehyde-modified and non-modified matrices. However, the activity of type I collagenase (inactive form) of smooth muscle cells decreased on glycolaldehyde-modified type I collagen as compared to that on non-modified collagen. These results suggest that AGEs contribute to the accumulation of collagen in atherosclerotic lesions and aged aorta through the insolubility of collagen and the inhibition of collagenase activity of smooth muscle cells.

Adult↗
PubMed1995

[Determination of primaquine and hepatic targeting neoglycoalbumin-primaquine in whole blood and liver of mouse by normalphase high-performance liquid chromatography].

We have developed a method to estimate primaquine (PQ) and hepatic targeting antimalarial agent neoglycoalbumin-primaquine (NGA PQ) in whole blood and liver of mice by sensitive and selective high-performance liquid chromatography. The primaquine was extracted out with ether from the basified biological samples in the PQ diphosphate group or from the samples which were acidic hydrolyzed then basified in NGA-PQ group. The extracts were evaporated under N2 then dissolved in the mobile phase. A linear chain analogue of primaquine was used as the internal standard. The samples were injected into the normal phase silica column with chloroform: methanol:ammonia solution (86.8:12.5:0.7,V/V/V) as mobile phase and detected at 254 nm. The average recovery of the method was 100.09 +/- 3.46 (mean +/- s)%; the CV of within-day and between-day were 2.7%-6.13% (n = 5) and 8.32%-13.56% (n = 9) respectively; in PQ group and NGA-PQ group, the PQ concentrations ranged from 10-20,000 ng/ml blood or 1g. liver respectively, and they all yielded a good linear relationship with the peak height ratios. No endogeneous interference was found in chromatograms of biological samples.

Animals↗
PubMed1995

Cross-reactive immunity against different strains of the hepatitis E virus transferable by simian and human sera.

Monkey infection with the hepatitis E virus induces protection. We confirm the humoral nature of this immunity and show that protection is effective against the homologous strain, as well as against heterologous strains isolated from Asian and African countries. However this immunity is incomplete since only the clinical disease seems to be prevented, while the virus is still excreted in stools and can even appear in blood as well after serotherapy as previous acute or occult infections. We obtained also a preliminary evidence that convalescent human sera are also efficient for the passive protection, indicating that seroprophylaxis of HEV hepatitis in pregnant women (20% of mortality during the 3rd trimester of pregnancy) should be attempted in the case of epidemics.

Animals↗
PubMed1994

Primitive fossil rodent from Inner Mongolia and its implications for mammalian phylogeny.

The evolutionary origin of rodents is obscured by the group's sudden and highly transformed first appearance in the fossil record in the latest Paleocene. We report here the discovery of nearly complete dental remains of an extraordinary new primitive rodent from strata of transitional Paleocene-Eocene age in Inner Mongolia, China. The strikingly conservative morphological features of this taxon, Tribosphenomys minutus, gen. et sp. nov., substantially modify previous ideas about the ancestral rodent morphotype, which in turn has important implications for understanding the origin of rodents and their relationship to other eutherian mammals. This new fossil, in conjunction with recent morphological and molecular evidence confirming rodent monophyly, indicates the need for a reassessment of phylogenetic affinities among gliriform eutherians. Our results indicate a sister-group position of the new taxon to other rodents, and support the alliance of lagomorphs (rabbits) and rodents (cohort Glires). They also suggest that paraphyly of an extinct assemblage, the 'Eurymylidae', and reveal an unexpectedly complex pattern of character evolution near the ancestry of Rodentia.

Animals↗
PubMed1994

Liver tissue damage by ultrasound in combination with the photosensitizing drug, Photofrin II.

We have investigated whether ablation of normal rat liver by ultrasound can be enhanced after administration of a photosensitizing agent (Photofrin II). After laparotomy and administration of Photofrin II (30 mg/kg), ultrasound (210 kHz, 1.3 W/cm2) was directed directly to the surface of the liver for a total duration of 3 min by a plane type unfocused transducer (6 mm x 6 mm). The depth of tissue damage was histologically compared to rats exposed to ultrasound alone. The mean maximum lesion depth on rats applied with ultrasound and Photofrin II was 5.7 +/- 0.9 mm (mean +/- SD) whereas in rats treated with ultrasound alone this was 3.0 +/- 0.4 mm. There was a significant difference between the two groups (P < 0.05). The present study suggests the possible use of a photosensitizing agent as an enhancer for the treatment of liver tumors by ultrasound.

Animals↗
PubMed1994

Synthesis of 2-[18F]fluoro-2-deoxy-L-glucose and positron emission tomography studies in monkeys.

2-[18F]Fluoro-2-deoxy-L-glucose was synthesized from its trifluoromethanesulfonyl precursor. The precursor was prepared by selective acetylation and triflation of L-mannose. L-Mannose was first treated with acetic anhydride in the presence of a catalytic amount of perchloric acid and then reacted with phosphorus tribromide followed by aqueous sodium acetate to produce pure 1,3,4,6-tetra-O-acetyl-a-L-mannopyranose in 32% yield. This compound was treated with trifluoromethanesulfonic anhydride and pyridine in methylene chloride to form 1,3,4,6-tetra-O-acetyl-O-tritrifluoromethanesulfonyl-a-L-mannopyra nose in 77% yield. Nucleophilic substitution of the triflate with 18F-in the presence of Kryptofix 2,2,2 followed by acid hydrolysis produced 2-[18F]fluoro-2-deoxy-L-glucose with a radiochemical yield of 20-30% (EOS) within 90 min. Biodistribution studies in rats and PET imaging in Rhesus monkeys demonstrated that this sugar analog distributes in the extracellular space of most organs but is excluded from the CNS.

Animals↗