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Biomedical subjects

J Meng

Publications and source records attributed to J Meng.

At least 37 records · Page 2Linked to original sources

Identification and characterization of the neutralization epitope(s) of the hepatitis E virus.

The neutralization epitope(s) of the hepatitis E virus (HEV) was studied by an in vitro neutralization assay using antibodies obtained by immunization of mice with 51 overlapping 30-mer synthetic peptides spanning the region 221-660 amino acids (aa) of the HEV open reading frame 2 encoded protein (pORF2) and 31 overlapping recombinant proteins of different sizes derived from the entire pORF2 of the HEV Burma strain. Antibodies against synthetic peptides and short recombinant proteins of approximately 100 aa did not neutralize HEV, suggesting the HEV neutralization epitope(s) is conformation-dependent. However, one recombinant protein of approximately 400 aa in length comprising the pORF2 sequence at position 274-660 aa as well as all truncated derivatives of this protein containing region 452-617 aa elicited antibodies, demonstrating HEV neutralizing activity. These findings establish for the first time that the minimal size fragment, designated pB166, that can efficiently model the neutralization epitope(s) is 166 aa in length and is located at position 452-617 aa of the HEV pORF2. Additionally, antibodies against pB166 were found to cross-neutralize three different HEV genotypes, suggesting that a common neutralization epitope(s) may exist within the different HEV genotypes. Thus, recombinant proteins constructed in this study may be considered as potential candidates for the development of an HEV subunit vaccine as well as for the development of highly sensitive and specific diagnostic tests.

Antibodies, Viral↗

Two-component molecular crystals from N-heteroaromatics and nitrobenzoic acids.

Five two-component molecular crystals, benzimidazolium 3-nitrobenzoate, C(7)H(7)N(2)(+).C(7)H(4)NO(4)(-), (I), benzimidazolium 4-nitrobenzoate, C(7)H(7)N(2)(+).C(7)H(4)NO(4)(-), (II), 1H-benzotriazole-3-nitrobenzoic acid (1/1), C(6)H(5)N(3).C(7)H(5)NO(4), (III), imidazolium 3-nitrobenzoate, C(3)H(5)N(2)(+).C(7)H(4)NO(4)(-), (IV), and imidazolium 4-nitrobenzoate, C(3)H(5)N(2)(+).C(7)H(4)NO(4)(-), (V), were prepared with the aim of making chiral crystals. Only (I) crystallizes in a chiral space group. The molecules of (I) and (II) are linked by hydrogen bonds to form 2(1) spiral chains. In (III), (IV) and (V), macrocyclic structures are formed from two acid and two base components, by an alternate arrangement of the acid and base moieties.

Journal Article↗

Isolation and characterization of two novel forms of the human prolactin receptor generated by alternative splicing of a newly identified exon 11.

We have identified a novel exon 11 of the human prolactin receptor (hPRLR) gene that is distinct from its rodent counterparts and have demonstrated the presence of two novel short forms of the hPRLR (S1(a) and S1(b)), which are derived from alternative splicing of exons 10 and 11. S1(a) encodes 376 amino acids (aa) that contain partial exon 10 and a unique 39-aa C-terminal region encoded by exon 11. S1(b) encodes 288 aa that lack the entire exon 10 and contains 3 amino acids at the C terminus derived from exon 11 using a shifted reading frame. These short forms, which were found in several normal tissues and in breast cancer cell lines, were expressed as cell surface receptors and possessed binding affinities comparable with the long form. Unlike the long form, neither short form was able to mediate the activation of the beta-casein gene promoter induced by prolactin. Instead they acted as dominant negative forms when co-expressed with the long form in transfected cells. Due to a marked difference in the cellular levels between the two short forms in transfected cells, S1(b) was more effective in inhibiting the prolactin-induced activation of the beta-casein gene promoter mediated by the long form of the receptor. The low cellular level of S1(a) was due to its more rapid turnover than the S1(b) protein. This is attributable to specific residues within the C-terminal unique 39 amino acids of the S1(a) form and may represent a new mechanism by which the hPRLR is modulated at the post-translational level. Since both short forms contain abbreviated cytoplasmic domains with unique C termini, they may also exhibit distinct signaling pathways in addition to modulating the signaling from the long form of the receptor. These receptors may therefore play important roles in the diversified actions of prolactin in human tissues.

Alternative Splicing↗

Expression in Spodoptera frugiperda (Sf21) insect cells of BT-R(1), a cadherin-related receptor from Manduca sexta for Bacillus thuringiensis Cry1Ab toxin.

The cadherin-related receptor of Manduca sexta, BT-R(1), for the Cry1A family of Bacillus thuringiensis insecticidal toxins, was expressed in cultured Spodoptera frugiperda (Sf21) insect cells utilizing the expression vector deltaOp-gp64. Recombinant BT-R(1) was released by the Sf21 cells in soluble form into the culture medium and represents approximately 58% of total BT-R(1) produced by the cells. The soluble protein was purified by affinity chromatography using Cry1Ab toxin coupled to Sepharose 4B. The apparent molecular mass of purified soluble recombinant BT-R(1) is 195 kDa. Radiolabeled toxin bound to purified soluble BT-R(1) with a K(d) value of 1.1 nM, which is similar to that of both membrane-bound BT-R(1) in Sf21 cells and natural BT-R(1) from M. sexta larval midgut tissue. Binding of radiolabeled toxin to soluble BT-R(1) was competitively inhibited by unlabeled Cry1Ab toxin but not by other Cry toxins as was observed also for membrane-bound BT-R(1). The recombinant soluble protein was stable in culture medium for at least 3 days at 27 degrees C and for 7 days at 4 degrees C and exhibited toxin-binding properties similar to the natural protein. Apparently, neither membrane association nor the extent of glycosylation influences the binding affinity and specificity of BT-R(1). Approximately 1 mg of purified BT-R(1) was obtained per liter of insect cell culture supernatant, representing approximately 2 x 10(9) Sf21 cells.

Animals↗

Glycoxidation-modified macrophages and lipid peroxidation products are associated with the progression of human diabetic nephropathy.

The aim of this study is to investigate the role of glomerular macrophages activated by glycoxidation and lipid peroxidation products in the progression of glomerular lesions in diabetic nephropathy. Renal biopsy samples from 43 patients with diabetes (age, 54 +/- 14 years) and 10 control cases were immunohistochemically examined for the expression of carboxymethyllysine (CML), a representative glycoxidative product; oxidized phosphatidylcholine (Ox-PC), a representative lipid peroxidation product; leukocyte common antigen (LCA); CD68; and macrophage scavenger receptor (MSR) class A. The severity of the diffuse lesions in each glomerulus was histologically graded from 0 to IV. When grade II and III lesions had Kimmelstiel-Wilson (KW) nodules, they were placed in a new category called grade III with KW nodules. The number of cells positive for CML, Ox-PC, LCA, CD68, and MSR was compared in different grades. The number of macrophages per glomerulus increased with the glomerular lesion grade and was highest in grade III with KW nodules. Conversely, the number of lymphocytes did not parallel the grade of glomerular lesions. Almost 50% of macrophages contained CML, and more than 40% of those were observed in exudative lesions, tuft adhesions, and at the periphery of KW nodules. Ox-PC accumulated in 50% of CML-positive macrophages, which coexpress MSR. Macrophages positive for CML and Ox-PC increased with the grade. Glomerular macrophages may be activated by glycoxidative and lipid peroxidation products through MSR and may have a role in the development of human diabetic glomerulosclerosis.

Adolescent↗

Reawakening the dragon: changing patterns of opiate use in Asia, with particular emphasis on China's Yunnan province.

Asian countries adjacent to the Golden Triangle and their neighbors have witnessed an evolution in "drug abuse" from traditional opium smoking to heroin eating, smoking, and finally heroin injection. A recent study of 630 heroin users was conducted in China's Yunnan Province, located close to the Golden Triangle. Data collected between August 1997 and February 1998 indicate injecting heroin users, in comparison to noninjectors, were more likely to have used drugs for a longer period of time, and to use drugs more frequently everyday. Other major differences existed between urban and rural subjects, especially highlighting differences between men and women. Women comprised a much higher proportion of urban subjects than rural subjects. Rural injectors were much more likely to be male, but urban injectors were almost evenly split between men and women. The emerging epidemic of heroin use in China and the continuing substance abuse problem in the United States provide an opportunity for collaborative research of mutual benefit.

Acquired Immunodeficiency Syndrome↗

Readmission to the intensive care unit after liver transplantation.

OBJECTIVE: We undertook this study to understand the factors at our transplant center that contribute to patients' return to the ICU after their liver transplant and their initial discharge from that unit. Patients who, after liver transplantation, fail discharge from the Intensive Care Unit (ICU) and must be readmitted to that unit may well utilize many more resources than those patients who are well enough to stay out of the ICU. DESIGN: A retrospective review of a prospectively maintained liver transplant research database followed by a retrospective review of (a subgroup) patient charts and contemporaneous controls. SETTING: A large metropolitan tertiary care center and adult liver transplant center. PATIENTS: A total of 1,197 consecutive adult patients who underwent their initial liver transplantation from 1984 to 1996. INTERVENTION: Readmission to the intensive care unit after adult liver transplantation and discharge from that unit. MAIN RESULTS: Only recipient age, pretransplant synthetic function labs (protime and albumin), bilirubin levels, and intraoperative blood product requirements could be statistically linked to the group requiring ICU readmission. The primary etiology for ICU readmission was cardiopulmonary deterioration. Readmission was associated with significantly lower patient and graft survivals. A detailed review of 23 patients transplanted from October 1994 to June 1996 was made, with special emphasis on cardiopulmonary status (hemodynamics, respiratory variables, and chest radiograph findings). This subgroup was compared with 30 temporally matched controls who were not readmitted to the ICU. Intravascular fluid overload and lower inspiratory capacity were significant factors related to ICU readmission. Readmitted patients had a longer hospitalization with higher hospital charges than the control group. CONCLUSIONS: We conclude that the most important means of preventing ICU readmission in liver transplantation patients is to optimize cardiopulmonary function and status. Close monitoring of fluid balance to avoid hypervolemia is essential. Readmitted patients have a greater resource utilization and have lower survival rates.

Adult↗

Identification and expression of cephamycinase bla(CMY) genes in Escherichia coli and Salmonella isolates from food animals and ground meat.

Twenty-one Salmonella and 54 Escherichia coli isolates, recovered from food animals and retail ground meats, that exhibited decreased susceptibilities to ceftiofur and ceftriaxone were shown to possess a bla(CMY) gene. The bla(CMY-4) gene was identified in an E. coli isolate recovered from retail chicken and was further shown to be responsible for resistance to cephalothin, ampicillin, and amoxicillin-clavulanic acid and elevated MICs of ceftriaxone, cefoxitin, and ceftiofur.

Animals↗

Availability of glutamate and arginine during acid challenge determines cell density-dependent survival phenotype of Escherichia coli strains.

The cell density-dependent acid sensitivity phenotypes of Escherichia coli strains K-12 and O157:H7 were examined with reference to three possible mechanisms of acid resistance. There was no evidence of any diffusible substance released from dead cells which could influence the cell density-dependent acid survival phenotype. Instead, cell density-dependent acid survival phenotype was associated with induction of glutamate- and arginine-decarboxylase acid survival pathways and concomitant availability of glutamate and arginine during acid challenge.

Arginine↗

Prevalence of Campylobacter spp., Escherichia coli, and Salmonella serovars in retail chicken, turkey, pork, and beef from the Greater Washington, D.C., area.

A total of 825 samples of retail raw meats (chicken, turkey, pork, and beef) were examined for the presence of Escherichia coli and Salmonella serovars, and 719 of these samples were also tested for Campylobacter spp. The samples were randomly obtained from 59 stores of four supermarket chains during 107 sampling visits in the Greater Washington, D.C., area from June 1999 to July 2000. The majority (70.7%) of chicken samples (n = 184) were contaminated with Campylobacter, and a large percentage of the stores visited (91%) had Campylobacter-contaminated chickens. Approximately 14% of the 172 turkey samples yielded Campylobacter, whereas fewer pork (1.7%) and beef (0.5%) samples were positive for this pathogen. A total of 722 Campylobacter isolates were obtained from 159 meat samples; 53.6% of these isolates were Campylobacter jejuni, 41.3% were Campylobacter coli, and 5.1% were other species. Of the 212 chicken samples, 82 (38.7%) yielded E. coli, while 19.0% of the beef samples, 16.3% of the pork samples, and 11.9% of the turkey samples were positive for E. coli. However, only 25 (3.0%) of the retail meat samples tested were positive for Salmonella. Significant differences in the bacterial contamination rates were observed for the four supermarket chains. This study revealed that retail raw meats are often contaminated with food-borne pathogens; however, there are marked differences in the prevalence of such pathogens in different meats. Raw retail meats are potential vehicles for transmitting food-borne diseases, and our findings stress the need for increased implementation of hazard analysis of critical control point (HACCP) and consumer food safety education efforts.

Animals↗

Identification and characterization of integron-mediated antibiotic resistance among Shiga toxin-producing Escherichia coli isolates.

A total of 50 isolates of Shiga toxin-producing Escherichia coli (STEC), including 29 O157:H7 and 21 non-O157 STEC strains, were analyzed for antimicrobial susceptibilities and the presence of class 1 integrons. Seventy-eight (n = 39) percent of the isolates exhibited resistance to two or more antimicrobial classes. Multiple resistance to streptomycin, sulfamethoxazole, and tetracycline was most often observed. Class 1 integrons were identified among nine STEC isolates, including serotypes O157:H7, O111:H11, O111:H8, O111:NM, O103:H2, O45:H2, O26:H11, and O5:NM. The majority of the amplified integron fragments were 1 kb in size with the exception of one E. coli O111:H8 isolate which possessed a 2-kb amplicon. DNA sequence analysis revealed that the integrons identified within the O111:H11, O111:NM, O45:H2, and O26:H11 isolates contained the aadA gene encoding resistance to streptomycin and spectinomycin. Integrons identified among the O157:H7 and O103:H2 isolates also possessed a similar aadA gene. However, DNA sequencing revealed only 86 and 88% homology, respectively. The 2-kb integron of the E. coli O111:H8 isolate contained three genes, dfrXII, aadA2, and a gene of unknown function, orfF, which were 86, 100, and 100% homologous, respectively, to previously reported gene cassettes identified in integrons found in Citrobacter freundii and Klebsiella pneumoniae. Furthermore, integrons identified among the O157:H7 and O111:NM strains were transferable via conjugation to another strain of E. coli O157:H7 and to several strains of Hafnia alvei. To our knowledge, this is the first report of integrons and antibiotic resistance gene cassettes in STEC, in particular E. coli O157:H7.

Animals↗

Carboxymethyllysine in dermal tissues of diabetic and nondiabetic patients with chronic renal failure: relevance to glycoxidation damage.

Carboxymethyllysine (CML) is currently recognized as a major advanced glycation end product and a marker for glycoxidation. Plasma CML levels are increased in patients with chronic renal failure (CRF). However, significance and mechanism of CML accumulation in these patients are poorly understood. The objective of the present study was to analyze CML in soluble and collagen-binding fractions of the dermis to investigate CML deposition and formation and collagen damage related to CML accumulation in patients with CRF. Skin samples (among them autopsy samples) were obtained from 33 subjects: 8 nondiabetic CRF patients, 7 diabetic predialysis patients with CRF (CRF-DM), 7 hemodialysis patients, and 11 control subjects without either CRF or DM. The dermal samples were extracted sequentially by phosphate-buffered normal saline, pepsin, and collagenase. The extracts were referred to as the soluble fraction and the proteinase-extracted fraction (including pepsin-extracted and collagenase-extracted fractions). Our ELISA assay for CML in dermal collagen from predialysis patients with CRF (CRF and CRF-DM groups) demonstrated that the levels of CML in both the soluble fraction (containing soluble CML which was mainly determined by serum clearance) and the structural collagen-binding proteinase-extracted fraction (in which high CML levels could be a strong indication of in situ formation) were increased and could not be completely reduced after hemodialysis in CRF-DM and CRF groups. These results suggest that accumulation of CML may be due to both a low serum clearance and/or increased in situ CML formation in CRF. CML contents in the proteinase extracted fraction inversely correlated with the susceptibility of collagen to extraction by proteinases (n = 33, r = -0.59, p < 0.001). Our results provide the first biochemical evidence that CML level is increased in both the soluble and collagen-binding fractions and that increased CML level resulted in increased fractions of proteinase-resistant collagen in dermal extracts of patients with CRF.

Aged↗

Benign nephrosclerosis: incidence, morphology and prognosis.

AIMS: Study of benign nephrosclerosis (BNS) is often mixed up with IgA nephritis (IgAN) associated with hypertension or thin basement membrane disease (TBMD). Here we examined the clinicopathological features, incidences and prognosis of decompensated BNS. MATERIALS AND METHODS: BNS was identified in 590 (8.3%) adult cases among 7,108 renal biopsies of a mean age of 56.5 years (male: female ratio = 2.5:1). The post-biopsy follow-up period ranged from 3 to 22 years (10.1 +/- 4.6 years). RESULTS: Patients with progressive BNS were more likely to develop end-stage renal disease within 5 years of biopsy. Poor prognostic factors included poor or no control of arterial blood pressure by anti-hypertensive drugs, global glomerulosclerosis (GS) (> or = 41%) at biopsy, presence of collapsed glomeruli and/or segmented or semi-global GS. Tubulointerstitial damage, glomerular hypertrophy and loop dilatation were secondary to GS. Gender, duration of HT and onset of HT to biopsy were not significant factors. CONCLUSION: GS in BNS is due to ischemia induced by luminal narrowing or obstruction of preglomerular vessels, and glomerular HT due to loss of autoregulation in preglomerular vessels (irregularly shaped atrophic or segmented medial smooth muscle cells, with expansion of extracellular matrix with or without fibrous intimal thickening). GS resulted in luminal dilatation. Both pathological changes affecting the glomerulus may occur in the same kidney and different nephron units.

Female↗

Cellular depolarization of neurons in the locus ceruleus region of the guinea pig associated with the development of tolerance to opioids.

These experiments were designed to test two hypotheses: 1) the tolerance induced by morphine pellet implantation in guinea pigs will result in subsensitivity of cells in the locus ceruleus (LC), not only to morphine, but to another agonist acting on a different receptor and transduction system, namely the gamma-aminobutyric acid(A) receptor agonist, muscimol; and 2) The nonspecific (heterologous) tolerance would be associated with a partial depolarization of the tolerant cells and a decrease in the contribution of electrogenic Na(+)/K(+) pumping. Extracellular recording from LC neurons in brain slices from animals implanted with either morphine or placebo pellets established that the tolerant preparations were subsensitive to both morphine and muscimol. Immunocytochemical analysis identified the alpha(3)-subunit as the primary isoform of the Na(+)/K(+) pump in the cells under investigation. Whole-cell patch clamp recording of neurons in brain slices demonstrated that, with electrodes containing 20 mM Na(+) (approximating [Na](i)), tolerant cells were significantly depolarized by a mean of 6.7 mV. Dialysis with antibody specific for the alpha(3)-isoform from patch pipettes produced depolarization of both control and tolerant cells. However, the depolarizing effect of the antibody was less in tolerant cells, suggesting a lesser degree of electrogenic Na(+) pumping. Furthermore, the presence of antibody reduced the membrane potentials of tolerant and placebo cells to equal values, suggesting that the diffusion potentials were not different. In contrast, antibody specific for the alpha(1)-subunit isoform in the pipettes had no effect on membrane potential in either control or tolerant cells. In conclusion, both hypotheses were supported.

Animals↗

Detection and characterisation of swine hepatitis E virus in New Zealand.

The objectives of the present study were to establish the presence of hepatitis E virus (HEV) in New Zealand pigs, first by testing for HEV antibody in pig herds throughout New Zealand to measure the herd prevalence, then by attempting to amplify HEV genomic sequences by PCR. Antibody was measured by two independently designed ELISA serology tests. HEV RNA fragments were amplified by RT-PCR of nucleic acid extracted from faeces of 10-12-week-old piglets using primers targeting ORF1, ORF2, and ORF2/3. PCR products were subject to phylogenetic analysis. Antibody to HEV was found throughout New Zealand pig herds as well as in the different age groups within the herds. Twenty herds from 22 tested were positive for HEV antibody (91% herd prevalence). Phylogenetic analysis of the amplified sequences placed this New Zealand strain of HEV closest to the human European strain It-1 (AF 110390) and U.S. swine strain (AF 082843) with 88% and 83% similarity respectively in ORF1. It was concluded that HEV is widely distributed in the New Zealand pig population. Phylogenetic analysis shows that this is a new HEV strain, grouping most closely with the United States/European cluster, which includes HEV strains of both human and swine origin.

Animals↗

[Fluorescence enhancement and laser behavior of Rhodamine 6G in micell].

Fluorescence of Rhodamine 6G in aqueous solution is effectively enhanced by using anionic sodium dodecylsulfate (SDS) surfactant. When the concentration of Rhodamine 6G is 5.47 x 10(-7) mol.L-1 and 5.47 x 10(-4) mol.L-1, maximal enhancement ratio can be 1.95 and 9.7, respectively. In the latter case, using SDS can reduce the threshold and improve the energy conversion efficiency of the dye laser of Rhodamine 6G. In the absence of SDS, the laser threshold power density is near 65 MW.cm-2. While in the present of SDS, the threshold is reduced to 0.8 MW.cm-2. The laser energy conversion efficiency can reach 25% when the pumping power density is 65 MW.cm-2. We also observed the red shifts of absorption spectrum, fluorescence spectrum and the dye laser spectrum in the present of SDS. The physical mechanism of the phenomena is discussed.

Fluorescence↗

Increased glycoxidation and lipoperoxidation in the collagen of the myocardium in hemodialysis patients.

OBJECTIVE: The purpose of this study was to examine the glycoxidation and lipoperoxidation products in the collagen of the myocardium in hemodialysis (HD) patients and age-matched control subjects. METHODS: Cardiac samples from 15 autopsied subjects (HD, n=6; control, n=9) were sequentially extracted with 0.9% NaCl and collagenase to obtain two fractions [soluble fraction (SF) and collagenase soluble fraction (CSF)]. The glycoxidation and lipoperoxidation products of these two fractions were measured by pentosidine-linked fluorescence (lambda(ex), 335; lambda(em), 385) and malondialdehyde (MDA)-linked fluorescence (lambda(ex), 390; lambda(em), 460), respectively. RESULTS: Both pentosidine- and MDA-linked fluorescence were found to have significantly increased more in the collagenase soluble fraction (CSF) extracted form the anterior and posterior wall in HD patients than in the controls (P<0. 05, control, n=9 vs. HD, n=6). Interestingly, the level of the lipid peroxides strongly correlated with that of the glycoxidation product in CSF (both P<0.0001 for the anterior and posterior wall). In contrast, in SF, which did not contain matrix collagen, neither significant difference nor correlation in the levels of pentosidine- and MDA-linked fluorescence was observed in these two groups. CONCLUSION: the present study provides the first biochemical evidence for an increase in glycoxidation and a close link between glycoxidation and lipoperoxidation in the collagen of the myocardium in hemodialysis patients. These findings suggest that these two spontaneous chemical reactions in the collagen matrix of myocardium may synergistically contribute to cardiac damage in hemodialysis patients.

Aged↗

Genomic typing of Escherichia coli O157:H7 by semi-automated fluorescent AFLP analysis.

Escherichia coli serotype O157:H7 isolates were analyzed using a relatively new DNA fingerprinting method, amplified fragment length polymorphism (AFLP). Total genomic DNA was digested with two restriction endonucleases (EcoRI and MseI), and compatible oligonucleotide adapters were ligated to the ends of the resulting DNA fragments. Subsets of fragments from the total pool of cleaved DNA were then amplified by the polymerase chain reaction (PCR) using selective primers that extended beyond the adapter and restriction site sequences. One of the primers from each set was labeled with a fluorescent dye, which enabled amplified fragments to be detected and sized automatically on an automated DNA sequencer. Three AFLP primer sets generated a total of thirty-seven unique genotypes among the 48 E. coli O157:H7 isolates tested. Prior fingerprinting analysis of large restriction fragments from these same isolates by pulsed-field gel electrophoresis (PFGE) resulted in only 21 unique DNA profiles. Also, AFLP fingerprinting was successful for one DNA sample that was not typable by PFGE, presumably because of template degradation. AFLP analysis, therefore, provided greater genetic resolution and was less sensitive to DNA quality than PFGE. Consequently, this DNA typing technology should be very useful for genetic subtyping of bacterial pathogens in epidemiologic studies.

Animals↗