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Biomedical subjects

Y Cheng

Publications and source records attributed to Y Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1995

A long-lasting increase and decrease in synaptic excitability in the rat lateral septum are associated with high and low shuttle box performance, respectively.

In a series of experiments with rats, using evoked field potentials, the influence of massed trial training in 2-way shuttle box avoidance and step-through passive avoidance tasks was studied on the synaptic excitability of the lateral septum (LS) neurons and on the induction of long-term potentiation in the lateral septum in vivo. The majority of rats that attained a high performance level in the shuttle box task exhibited, after the shuttle box training, a long-lasting enhancement of synaptic excitability of lateral septum neurons, whereas most of the rats with low performance in the shuttle box showed a long-lasting depression in the LS synaptic excitability. Both types of excitability changes disappeared within 24 h. Neither the first habituation session in the passive avoidance apparatus nor the subsequent one-trial learning in passive avoidance task had a marked influence on lateral septum synaptic excitability. Both high-performance and low-performance rats exhibited a long-term potentiation (LTP)-like potentiation of synaptic excitability of the lateral septum neurons after high frequency stimulation of the fimbria fibers although the amount of LTP in high performance rats was slightly higher than that in low performance animals.

Animals↗
PubMed1995

Nucleotide and deduced amino acid sequences of the M and S genome segments of a Swedish Puumala virus isolate.

The Swedish Puumala (PUU) virus strain Vindeln 83-L20, isolated from a bank vole trapped in 1983 near Vindeln, Västerbotten county, Sweden, was characterized by nucleotide sequence analysis. The coding region of the M segment was determined by PCR followed by direct sequencing and the entire S segment was characterized by cloning and nucleotide sequence analysis. The genomic organization was found to be very similar to that of other PUU virus strains regarding open reading frames, polypeptide sizes and potential glycosylation sites. According to phylogenetic analysis 83-L20 was found to represent a new lineage within the Puumala virus serotype in the Hantavirus genus. The M segment sequence of 83-L20 was found to be more closely related to the Finnish PUU virus strains than to strains from Central Europe or from Russia. The evolutionary origin of the S segment was not as clearly resolved since the branching points of all PUU virus strains in the phylogenetic tree were nearly the same.

Amino Acid Sequence↗
PubMed1995

Genetic variation in Tula hantaviruses: sequence analysis of the S and M segments of strains from Central Europe.

Hantavirus carried by the European common vole Microtus arvalis from Moravia (Czech Republic) was analyzed by RT-PCR-sequencing and by reactivity with a panel of monoclonal antibodies (MAbs). Sequencing of the full-length S segment and the proximal part of the M segment showed that the virus belonged to genotype Tula (TUL) we discovered earlier in Microtus arvalis from Central Russia. This finding supported the concept of host dependence of hantaviruses. Phylogenetic analyses suggested a similar evolutionary history for S and M genes of TUL strains; thus far there is no evidence for reassortment in TUL. Geographic clustering of TUL genetic variants was observed and different levels of the genetic variability were revealed resembling those estimated for another hantavirus, Puumala (PUU). Comparison of the deduced N protein sequence from Russia and from Moravia showed that genetic drift in TUL occurred not only by accumulation of point mutations but also by the deletion of a nucleotide triplet. It encoded Ser252 which was located within a highly variable hydrophilic part of the N protein carrying B-cell epitopes and presumably forming a loop. Analysis of naturally expressed TUL N-antigen derived from lung tissue of infected voles with MAbs indicated antigenic heterogeneity among TUL strains.

Amino Acid Sequence↗
PubMed1995

Persistence of Borrelia burgdorferi sensu lato in resolved erythema migrans lesions.

Erythema migrans skin lesions resulting from a tick bite and infection with Borrelia burgdorferi sensu lato eventually resolve, even without antibiotic therapy. The aim of the present study was to gauge the frequency of persistence of B. burgdorferi sensu lato in such lesions. Thus, the site of a previous lesion was biopsied and cultured in 48 patients: 39 with systemic or localized symptoms/signs and nine with no symptoms. B. burgdorferi sensu lato was isolated from biopsied skin from three symptomatic patients. Cultures of other tissues and fluids were negative. By genospecies-specific polymerase chain reaction (PCR) and pulsed-field gel electrophoretic (PFGE) analysis, two isolates were classified as Borrelia afzelii. The remaining isolate was a member of an unusual group of strains that type as B. burgdorferi sensu stricto by genospecies PCR but possess an atypical PFGE profile. All three patients had a dramatic clinical response to antibiotic treatment. These findings demonstrate the capacity of viable B. burgdorferi sensu lato organisms to persist in clinically normal-appearing skin at the site of a resolved erythema migrans rash for periods ranging from 2 months to 3.5 years. This observation may provide new insight into the organisms' ability to evade the host's immune response.

Adolescent↗
PubMed1995

Genotypic and phenotypic characterization of Borrelia burgdorferi isolated from ticks and small animals in Illinois.

We have characterized 33 isolates of Borrelia burgdorferi from northern Illinois (32 isolates) and Wisconsin (1 isolate) representing the largest series of midwestern isolates investigated to date. The techniques used for molecular analysis of strains included (i) genospecies typing with species-specific PCR primers, (ii) plasmid profiling by pulsed-field gel electrophoresis of total genomic DNA, (iii) large-restriction-fragment pattern (LRFP) analysis by pulsed-field gel electrophoresis of MluI-digested genomic DNA (J. Belfaiza, D. Postic, E. Bellenger, G. Baranton, and I. Saint Girons, J. Clin. Microbiol. 31:2873-2877, 1993), (iv) sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins, (v) microsequencing of high-performance liquid chromatography-purified peptides derived from proteins showing high levels of expression, (vi) amino acid composition analysis of proteins, and (vii) immunological analysis of proteins with a polyclonal antiserum of human origin. Five reference strains as well as two atypical tick isolates from California (DN127) and New York (25015) were included for comparison. All of the Illinois and Wisconsin isolates were typed as B. burgdorferi sensu stricto with genospecies-specific PCR primers. The isolates were found to be heterogeneous with regard to their plasmid and protein profiles. One isolate from Illinois possessed two large-molecular-size plasmids instead of the usual 49-kb plasmid. Fragment patterns resulting from MluI digestion of genomic DNA from the 33 isolates and strains DN127 and 25015 were separable into six distinct LRFPs, five of which have not previously been described. Strain 25015 and an isolate from Illinois (CT39) shared an unusual LRFP that is not typical of other B. burgdorferi sensu stricto strains, suggesting that they may represent a fifth species of B. burgdorferi sensu lato. Five of the 33 isolates and strains DN127 and 25015 showed high-level expression of proteins with molecular masses of approximately 22 kDa. Investigation of these proteins by microsequencing of individual peptides and total amino acid composition analysis indicated that the 22-kDa proteins expressed by the seven strains were polymorphic OspC proteins. By using a polyclonal serum of human origin, expression of OspC could be detected in all 33 Illinois and Wisconsin isolates.

Amino Acid Sequence↗
PubMed1995

[Sonographic diagnosis of ruptured corpus luteum with hemoperitoneum].

This article reports sonographic characteristics of a ruptured corpus luteum with hemoperitoneum in 44 cases. Sonographic findings were classified and compared with laparotomy and pathology. From sonographic imaging, it was found that the ruptured corpus luteum cyst was pathognomonic. There was a good correlation between ultrasound findings and surgical results when bleeding was over 100 ml. The sonographic value in diagnosis of ruptured corpus luteum with hemoperitoneum is discussed in detail.

Adult↗
PubMed1995

[Ultrasonic diagnosis of abnormalities of abdominal wall in fetuses].

Twelve cases of abnormal abdominal walls in fetuses are reported in this paper. Among them, there were 4 cases of umbilical hernia, 4 cases of a defective abdominal wall, 3 cases of diaphragmatic hernia and 1 case of a defective thoracic and abdominal wall. From the features of the sonographic picture, the reasons for misdiagnosis are discussed. From our analysis, the main points of differential diagnosis and the earliest time for making diagnosis are proposed. The diagnostic rate could be improved obviously by systemic and careful examination which is important for deciding the model and time of deliveries.

Abdominal Muscles↗
PubMed1995

[Percutaneous absorption of venenum bufonis in vitro].

V-C horizontal diffusion cell and HPLC determination have been used to study the effect of 1,2-propanediol and azone on the percutaneous absorption Venenum Bufonis. The contents of resibufogenin have been determined through mouse skin in vitro by HPLC. The results indicate that the contents get increased when 1,2-propanediol is added and that azone can shorten the lag time of percutaneous absorption of resibufogenin through mouse skin in vitro.

Amphibian Venoms↗
PubMed1995

[Research on the relationship between estrogen receptor, progesterone receptor, cell proliferation associated antigen in uterine leiomyoma and nuclear body density of myoma, serum reproductive hormone concentrations].

OBJECTIVE: To study the role of sex hormones in the pathogenesis of uterine leiomyoma in order to provide theoretical basis for medical treatment. METHODS: Estrogen Receptor (ER), progesterone receptor (PR) and cell proliferation associated antigen (Ki-67) contents of both normal uterine myometrium and leiomyoma were quantitatively analysed by ABC method and image analyser system (IAS) in 30 and 19 specimens obtained during hysterectomy respectively. Nuclear body density were also measured in 8 of them under electronic microscope. Serum luteinizing hormone (LH), follicular stimulating hormone (FSH), estradiol (E2) and progesterone (P) concentrations were determined by radioimmunoassay in 22 cases on the operation day. 21 age-matched normal cycling women served controls. RESULTS: Contents of ER, PR, Ki-67 and the number, volume densities of nuclear body were significantly higher in leiomyoma than those in normal myometrium (P < 0.01, P < 0.05). ER,PR contents of the two tissues in proliferative phase were greater than those in secretory phase, (P < 0.05), while Ki-67 contents were the opposite (P < 0.01). ER, PR contents of leiomyoma did not correlate with serum E2 and P concentrations, but correlate negatively with serum LH and FSH levels (P < 0.050). Ki-67 contents correlated positively with serum P levels and also showed inverse correlation with serum LH. FSH concentrations (P < 0.05). ER of leiomyoma positively correlated with density of nuclear body (P < 0.05). CONCLUSION: High ER, PR and Ki-67 contents in leiomyoma, may be the result of local high E2, P concentrations, and cause growth and development of leiomyoma. High Ki-67 content in secretory phase may indicate that progesterone has a synergistic effect in the pathogenesis of leiomyoma.

Adult↗
PubMed1994

A physical map of the Myxococcus xanthus chromosome.

A physical map of the 9.2-Mbp Myxococcus xanthus DK1622 chromosome at a resolution of 25 kbp was constructed by using a strategy that is applicable to virtually all microorganisms. Segments of the chromosome were used as hybridization probes to subdivide a yeast artificial chromosome (YAC) library into groups of linked clones. The clones were aligned by comparing their EcoRI restriction patterns. The groups of YAC clones ("contigs") were oriented and aligned with the genomic restriction map by means of common genetic and physical markers such as rare restriction sites and transposon insertions. Over 95% of the genome is represented by cloned DNA. Sixty genetic loci including > 100 genes, many of which play a role in fruiting body development, have been mapped in this way. Additional genes can now be located on the chromosome map by hybridization of their sequences to the ordered set of YAC chromosomes. The mapped genetic loci account for approximately 2% of the genome.

Base Sequence↗
PubMed1994

Organization of the mouse GP42/Basigin gene: a member of the Ig superfamily.

We have mapped and sequenced the GP42/Basigin gene isolated from a Balb/C mouse genomic library. The genomic organization and upstream, putative regulatory, regions of this gene have not been previously reported. Our data show that exon 5 of the GP42/Basigin gene encodes the carboxy proximal half of the second Ig-like domain, the highly conserved transmembrane region and a portion of the cytoplasmic tail. This inclusion of Ig-like and other functional domains in a single exon is unusual. Splice junction analysis indicates that two reported alternate GP42/Basigin cDNA isoforms are likely due to cloning artifacts. In addition, we find that GP42/Basigin is polymorphic in mice. Our data also support the proposal that the transmembrane domain and portions of the cytoplasmic region of GP42/Basigin have been evolutionarily conserved.

Amino Acid Sequence↗
PubMed1994

Oxidative mechanisms involved in kainate-induced cytotoxicity in cortical neurons.

In our previous experiments, evidence of free radical formation has been demonstrated in gerbil brain after kainic acid (KA) administration. In the present study, the mechanisms involved in KA-induced free radical formation and subsequent cell degeneration were investigated using high density cortical neuron cultures. A free radical trapping agent, alpha-phenyl-N-tert- butyl-nitrone (PBN), as well as the combined action of superoxide dismutase and catalase attenuated KA neurotoxic effect. Calpain-induced xanthine oxidase (XO) activation may play an important role in KA excitotoxicity since calpain inhibitor I as well as allopurinol, a selective XO inhibitor, significantly protected the cortical neurons from KA-induced cell death. However, XO activation may not be the only source producing free radicals, other free radical generating systems such as nitric oxide synthase may also play a role in KA insult.

Allopurinol↗
PubMed1994

A novel cyclic AMP response element, CACTTGATC, mediates forskolin induction of the myelin basic protein promoter in the rat Schwannoma line, D6P2T.

The rat Schwannoma cell line D6P2T constitutively expresses the mRNA encoding the major myelin protein, P0, but only expresses the mRNA encoding myelin basic protein (MBP) after exposure to forskolin or other substances that raise the levels of intracellular cyclic AMP. In this study we have investigated the molecular basis for forskolin induction of MBP transcription in D6P2T cells. We have found that a 9-bp sequence element, CACTTGATC, located between nucleotides -85 and -77 in the MBP promoter, is necessary for forskolin induction of chloramphenicol acetyltransferase (CAT) expression after transient transfection of MBP promoter-CAT fusion constructs into D6P2T cells. Although similar DNase I footprints, one of which is located within the above 9-bp sequence element, are produced by nuclear extracts prepared from both forskolin-treated and untreated cells, this same sequence can be shown to interact with a forskolin-inducible protein complex using an electrophoretic mobility shift assay. In addition, mutation of this 9-bp sequence abolishes both formation of this new protein--DNA complex and forskolin-inducible CAT expression from the heterologous SV40 promoter. Finally, we have shown that the appearance of this forskolin-inducible protein--DNA complex precedes that of MBP mRNA. Taken together, these data strongly support the notion that the induction of MBP transcription by forskolin in D6P2T cells is mediated by the binding of a forskolin-inducible protein complex to the MBP promoter sequence CACTTGATC.

Animals↗
PubMed1994

Effects of extracellular ATP on Fe(2+)-induced cytotoxicity in PC-12 cells.

Extracellular ATP is known to cause a variety of changes, including the alteration of ion fluxes, cell growth, and other physiological activities. Recently, it has been suggested that ATP acts as an excitatory synaptic transmitter, which may produce a Ca2+ influx via the activation of a P2y purinoceptor. Rat pheochromocytoma (PC-12) cells are known to resemble rat sensory neurons and to possess a P2y purinoceptor. In this study, we demonstrated that extracellular ATP dose-dependently increased PC-12 cell death in the presence of ferrous ions. Voltage-sensitive calcium channel blockers and calpain and xanthine oxidase inhibitors were found to be effective at protecting PC-12 cells from Fe2+/ATP-induced lipid peroxidation and cell death. These results suggest that xanthine oxidase activation induced by calpains and subsequent free radical formation may be responsible for Fe2+/ATP-induced neuronal cell death.

Adenosine Triphosphatases↗
PubMed1994

Extended-spectrum beta-lactamases in clinical isolates of Enterobacter gergoviae and Escherichia coli in China.

Resistance to ceftazidime, detected in isolates of Escherichia coli 5518 and Enterobacter gergoviae 3773 from our hospital, was transferred, together with resistance to aminoglycosides, trimethoprim, sulfonamide, and other beta-lactam antibiotics, by conjugation to E. coli JP559. Both E. coli transconjugants were resistant to ampicillin, all cephalosporins, and aztreonam but remained susceptible to cefoxitin and imipenem. The enzymes of the two transconjugant strains readily hydrolyzed cephalosporins in a spectrophotometric assay. Hybridization results suggested that the extended-spectrum beta-lactamase produced by E. coli 5518 was a non-TEM, non-SHV enzyme, the origin of which is currently unknown. The beta-lactamase produced by E. gergoviae 3773 was of the SHV type and was further proved to be SHV-2 by DNA sequencing. Thus, extended-spectrum beta-lactamases are occurring in China as well as in other parts of the world.

Cloning, Molecular↗