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Biomedical subjects

C Y Gao

Publications and source records attributed to C Y Gao.

At least 19 recordsLinked to original sources
PubMed2001

Surface coating of stearyl poly(ethylene oxide) coupling-polymer on polyurethane guiding catheters with poly(ether urethane) film-building additive for biomedical applications.

Three types of stearyl poly(ethylene oxide) (SPEO) with Mn of 2,300, 6,000 and 12,000 were synthesized; accordingly, three types of amphiphilic coupling-polymer SPEO-MDI-SPEO (MSPEO) were prepared by the reactions with 4,4'-methylene diphenyl diisocyanate (MDI). As the surface-modifying additives (SMA), MSPEOs were coated onto the outer wall of the medical guiding catheters. Due to the lack of stability, when coated, MSPEO blended with the film building agent (FBA), poly(ether urethane) (PEL). The process of coating was performed with a lifter. With invariable speed, the PU guiding catheter was vertically dipped into the coating mixture of SMA-MSPEO and FBA-PEL. The surface analysis was carried out by ATR-FTIR and contact angle measurements. It was proved that the surface enrichment of PEO on water interface was much higher than that on air interface. Three kinds of static clotting time tests, PRT, PT and TT, as well as the static platelet adhesion experiment were performed. The results indicated that the coated surface could resist the blood coagulation effectively. In order to test the blood compatibility of the coated catheters under a shear of blood flow, the dynamic experiment was performed with a closed-loop tubular system under a shear rate of 1,500 s(-1). The blood regular testing was carried out on the samples taken out at six different times (0, 5,10, 20, 30 and 60 min). The results were ideal. Finally, the SMA-MSPEO was proved to be non-acute-toxic by LD50 test.

Blood Coagulation↗
PubMed2001

Thalibealine, a novel tetrahydroprotoberberine--aporphine dimeric alkaloid from Thalictrum wangii.

A novel tetrahydroprotoberberine-aporphine dimeric alkaloid, (-)-thalibealine (1), was isolated from the roots of Thalictrum wangiii, and its structure established via spectroscopic analysis. Three other alkaloids were isolated, including the benzyltetrahydroisoquinoline-aporphine dimer (+)-thalmelatidine, the aporphine (+)-magnoflorine, and the protoberberine berberine. This is the first reported isolation of a tetrahydroprotoberberine-aporphine dimer from nature, as well as the first reported isolation of constituents from Thalictrum wangii.

Berberine Alkaloids↗
PubMed2001

Synthesis of thalprzewalskiinone, a revision of structure.

A direct comparison of the spectral data for synthetic 2-methyl-6,7-dimethoxy-3'-methoxy-4'-hydroxyoxobenzylisoquinoline iodide (1) and its positional isomer 2-methyl-6,7-dimethoxy-3'-hydroxy-4'-methoxyoxobenzylisoquinoline iodide (2) with the data obtained for the oxobenzylisoquinoline alkaloid thalprzewalskiinone revealed that the original structural assignment of the alkaloid as 1 was in error. These results mandate the revision of structure of thalprzewalskiinone to 2-methyl-6,7-dimethoxy-3'-hydroxy-4'-methoxyoxobenzylisoquinoline iodide (2).

Drugs, Chinese Herbal↗
PubMed2001

[Purification and biological activity of rh-leptin expressed in Escherichia coli].

The human leptin was successfully expressed with high level in E. coli under the control of PL promotor. The yield of recombinant protein was over 40% of total cellular protein and expressed as inclusion bodies. The recombinant human leptin (rh-leptin) was purified with gel filtration, anion-exchange and reverse chromatography. Refolding was achieved by gradually reducing denaturant using a diafiltration method. The refolded rh-leptin was characterized by SDS-PAGE, Western-blotting and its first 15 amino acid residues sequence of the N-terminal. The purified product was found to be biologically active, reducing the food intake and body weight gain upon testing in BALB/c mice.

Animals↗
PubMed2000

Tightly regulated, beta-estradiol dose-dependent expression system for yeast.

We have refined the regulated expression of UASGAL1, 10-driven genes in yeast by modifying a vector encoding the beta-estradiol inducible activator, GAL4.ER.VP16 (GEV). The expression of GEV was placed under the regulation of the low-level, constitutive MRP7 promoter, and beta-estradiol-regulated expression was monitored by the expression of an integrated UASGAL10-lacZ reporter and by immunoblot analysis of a UASGAL1-regulated gene product. Target gene expression regulated by low levels of GEV has several advantages over the standard galactose-inducible expression systems. (i) Most importantly, the target gene expression is undetectable in the absence of hormone; (ii) target gene expression is beta-estradiol dose-dependent, and variable levels of target gene expression from low to several hundred-fold induction can be achieved; and (iii) induction or depletion studies can be conducted independent of carbon source in gal4 delta strains. In addition, any UASGAL1,10 expression construct can be used without modification of the target gene or many gal4 delta host strains, and GEV vectors are compatible with other inducible yeast expression systems. This method may be useful to researchers investigating the functions of essential genes, dominant negative mutants, mitochondrial genes, and viral, plant, and mammalian genes in yeast assay systems.

Carbon↗
PubMed1999

Changes in cyclin dependent kinase expression and activity accompanying lens fiber cell differentiation.

Previous studies from this laboratory have shown that differentiating lens fiber cells contain two active cyclin dependent kinases (Cdks), Cdk1 and Cdk5. The present study was undertaken to explore the expression and regulation of six additional members of the Cdk family (Cdk2, Cdk3, Cdk4, Cdk6, Cdk7 and Cdk8) during lens differentiation. Differentiating lens fiber cells were separated from lens epithelial cells by microdissection of developing rat lenses [embryonic day 16 (E16) to postnatal day 8 (P8)] and Cdk expression was assessed by RT-PCR and immunoblotting. Two Cdks (Cdk3 and Cdk6) were not expressed in lens fiber cells or epithelial cells during this developmental period. In the lens epithelium, we detected proteins and mRNAs corresponding to all other Cdks examined (Cdk2, Cdk4, Cdk7, Cdk8) throughout this developmental period. Epithelial cells showed significant Cdk2 activity, which decreased with developmental age, but no significant activity was detected for Cdk4, Cdk7, or Cdk8. Fiber cells contained all four Cdk proteins and the corresponding Cdk mRNAs except for Cdk2 mRNA. None of the Cdks examined showed significant kinase activity in fiber cells. Immunoprecipitates of Cdk2 and Cdk4 from fiber cells contained p57(kip2), supporting the view that this Cdk inhibitor blocks the activity of these Cdks in lens fibers. In contrast, p57(kip2)did not co-immunoprecipitate with Cdk5 from lens fibers. These findings suggest that the differential affinity of p57(kip2)for members of the Cdk family may provide a mechanism for specific regulation of individual Cdks during fiber cell differentiation.

Animals↗
PubMed1998

pRb and p107 regulate E2F activity during lens fiber cell differentiation.

During growth arrest and differentiation, activity of the E2F family of transcription factors is inhibited by interactions with pRb and the related proteins, p107 and p130. To determine which members of the E2F and pRb families may contribute to growth arrest as lens epithelial cells differentiate into fiber cells, we examined the expression of individual E2F species and characterized the E2F protein complexes formed in rat lens epithelia and fibers. RT/PCR detected all five known members of the E2F family in lens epithelial cells, but only E2F-1, E2F-3, and E2F-5 in fiber cells. Proteins extracted from lens epithelia of newborn rats formed at least two specific complexes with an E2F consensus oligonucleotide. Proteins from lens fiber cells formed three specific complexes, one of which comigrated with an epithelial cell complex. Incubation of epithelial and fiber cell extracts with an antibody specific for p107 demonstrated that two fiber cell complexes and one epithelial cell complex contained p107. Although the remaining fiber cell complex did not react with antibodies to pRb or p130 in this assay, a strong reaction with pRb antibody was observed when the electromobility shifted complexes were subsequently immunoblotted (shift/Western assay). Immunocytochemistry confirmed that pRb protein is present in the nuclei of both epithelial cells and fiber cells. Immunoblotting of whole cell extracts with pRb antibody showed multiple, phosphorylated forms of pRb in the epithelial cells, but predominantly hypophosphorylated pRb in the fiber cells. None of the complexes formed with E2F were recognized exclusively by the p130 antibody, although the previously identified p107 complexes reacted weakly. The absence of p130/E2F complexes was correlated with the presence of multiple ubiquitinated forms of p130, especially in the fiber cells. Thus, although p130/E2F complexes are implicated in the terminal differentiation of many cell types, in differentiating lens fiber cells pRb and p107 seem to be the primary regulators of E2F activity.

Animals↗
PubMed1997

Expression of Cdk5, p35, and Cdk5-associated kinase activity in the developing rat lens.

We have investigated the expression of Cdk5 and its regulatory subunit, p35, in the developing rat lens from embryonic day 16 (E16) to postnatal day 8 (P8). Reverse transcription and polymerase chain reaction (RT/PCR) detected Cdk5 and p35 mRNA expression in lens epithelial cells and in differentiating lens fibers throughout this developmental period. Subsequent sequencing of the RT/PCR products confirmed their identifies. In sity hybridization with Cdk5 and p35 riboprobes showed especially high expression of both mRNAs in the newly formed lens fiber cells in the bow region of the lens. Immunocytochemistry at E18 showed that Cdk5 was present in the cytoplasm of lens epithelial cells and fiber cells, with especially strong immunostaining at the anterior ends of the fibers. Fiber cells in the final stages of maturation, immediately prior to nuclear degeneration, showed positive staining for Cdk5 in the nucleus. Immunoprecipitation of proteins with Cdk5 antibody followed by immunoblotting with either N-terminal specific or C-terminal specific p35 antibodies demonstrated that p35 is complexed with Cdk5 in lens epithelial cells and lens fibers. Immunoprecipitates of Cdk5 from epithelia and fibers showed kinase activity in vitro using histone H1 as a substrate. These findings demonstrate that p35/Cdk5 activity is not restricted to neurons and raise the possibility that this kinase may play a role in lens fiber cell differentiation.

Amino Acid Sequence↗
PubMed1997

Cyclins, cyclin-dependent kinases and differentiation.

Cyclin-dependent kinases and their regulatory subunits, the cyclins, are known to regulate progression through the cell cycle. Yet these same proteins are often expressed in non-cycling, differentiated cells. This review surveys the available information about cyclins and cyclin-dependent kinases in differentiated cells and explores the possibility that these proteins may have important functions that are independent of cell cycle regulation.

Animals↗
PubMed1997

Patterns of recovery in the Guillain-Barre syndromes.

Clinical, electrodiagnostic, and pathologic studies indicate that the Guillain-Barre syndromes (GBSs) include both primary demyelinating and primary axonal forms. The axonal forms are usually thought to have a poorer prognosis, with less chance for rapid or complete recovery. In northern China, epidemics of one axonal form, acute motor axonal neuropathy (AMAN), occur annually in the summer. Autopsy studies in some fatal cases have demonstrated wallerian-like degeneration of motor roots and motor fibers in the peripheral nerves. Recovery of such patients would require axonal regeneration along the entire length of the nerve fiber. In a 2-year prospective study of GBS at a single hospital in northern China, 42 patients were classified as having either AMAN (32 patients), acute inflammatory demyelinating polyneuropathy (AIDP) (8 patients), or as undetermined (2 patients) by electrodiagnostic criteria. Their recoveries were monitored clinically. The recovery times of AMAN and AIDP patients were similar: the median time to regain the ability to walk 5 meters with assistance was 31 days for patients classified as having AMAN and 32 days for those classified as having AIDP. These rapid recovery times are incompatible with severe wallerian degeneration of the ventral roots and motor nerve fibers. The rapid recoveries observed in AMAN patients could be explained by relatively quickly reversible immune-mediated changes at nodes of Ranvier in motor fibers, by degeneration and regeneration of intramuscular motor nerve terminals, or both.

Adolescent↗
PubMed1996

Expression of alternatively spliced PCTAIRE-1 mRNA in PC12 cells and neonatal rat brain.

A rat PCTAIRE-1 cDNA clone was isolated by immunoscreening of a PC12 cDNA library, followed by 5' RACE (rapid amplification of cDNA ends) to determine the 5' end. The rat PCTAIRE-1 cDNA sequence is 96% identical to mouse PCTAIRE-1 and contains an alternatively spliced exon of 131 bp near the 5' end. Although a mouse cDNA containing this exon has been reported, examination of several mouse cell lines provided no evidence for expression of the corresponding mRNA (Okuda et al., 1992). In contrast, reverse transcription and polymerase chain reaction (RT/PCR) across this region using RNA from proliferating, differentiated, and apoptotic PC12 cells demonstrated that alternatively spliced forms of PCTAIRE-1 mRNA with and without this exon are expressed. Both forms of PCTAIRE-1 mRNA are also expressed in vivo in neonatal rat brain, although other tissues examined contained only the form lacking the alternatively spliced exon. In the absence of the alternatively spliced exon PCTAIRE-1 mRNA contains an open reading frame of 1488 bp, corresponding to a 55-kDa protein that is 97% identical to mouse PCTAIRE-1 protein. When the alternatively spliced exon is present, this open reading frame is terminated by a stop codon and a second open reading frame is initiated, predicting a second PCTAIRE-1 protein of 52 kDa. The two predicted PCTAIRE-1 proteins are identical downstream of the splice site, but share no homology at their N-terminal ends.

Alternative Splicing↗
PubMed1996

Pathology of the motor-sensory axonal Guillain-Barré syndrome.

The concept of a severe motor-sensory neuropathy of acute onset caused by an immune attack on the axon ("axonal" Guillain-Barré syndrome) has been advanced primarily based on electrodiagnostic and limited pathological data, but remains controversial. At autopsy some cases demonstrate unusually severe inflammatory demyelinating neuropathy. There are conflicting data about whether antecedent Campylobacter jejuni infection is associated with "axonal" Guillain-Barré syndrome. We report 4 individuals from Hebei Province, China, who died 7, 7, 18, and 60 days after onset of a syndrome diagnosed clinically as Guillain-Barré syndrome. High titers of antibodies recognizing C. jejuni, consistent with recent infection, were found in the 2 patients tested. At autopsy the 3 with early disease had ongoing wallerian-like degeneration of fibers in the ventral and dorsal roots and in the peripheral nerves, with only minimal demyelination or lymphocytic infiltration. All 3 had numerous macrophages in the periaxonal space of myelinated internodes, and rare intraaxonal macrophages as well. Examination of the patient having the syndrome for 60 days confirmed the extensive loss of large fibers in the spinal roots and nerves, and the paucity of demyelination and remyelination. These observations confirm predictions that some patients with severe motor-sensory Guillain-Barré syndrome, as defined clinically, have predominantly axonal lesions of both motor and sensory fibers, even in the early stages of the disease, and that axonal Guillain-Barré syndrome can follow C. jejuni infection. The pathology supports the possibility that such cases of motor-sensory axonal Guillain-Barré syndrome represent the most severe end of a spectrum of immune attack directed toward epitopes on the axon.

Acute Disease↗
PubMed1995

Cyclin B, p34cdc2, and H1-kinase activity in terminally differentiating lens fiber cells.

Terminal differentiation of lens fiber cells is marked by chromatin condensation, abrupt dissolution of the nuclear lamina, vesicularization of the nuclear membrane, and complete degradation of the nucleus and other organelles. Since these events resemble the chromosomal condensation and nuclear envelope breakdown associated with mitosis, we investigated whether a similar biochemical mechanism might be involved by testing for the presence of cyclin B/p34cdc2 complexes and p34cdc2-associated histone kinase activity in differentiating lens fiber cells. A coupled reverse transcription/polymerase chain reaction using RNA from E7, E15, or E20 embryonic chicken lens fibers amplified a cyclin B product of the expected size, whose identity was confirmed by sequencing. In situ hybridization showed that cyclin B mRNA was present in nucleated lens fiber cells at E19. Immunoblotting of proteins isolated from E6 or E15 lens fibers by p13-agarose affinity chromatography with anti-cyclin B antibody detected the 45-kDa cyclin B protein, while immunoblotting with anti-PSTAIRE antibody detected a single, 34-kDa band, identified as p34cdc2. The p13-affinity purified fraction from E6 or E15 lens fibers showed histone H1 kinase activity in vitro. Immunocytochemistry of E6 lenses with anti-chicken cyclin B antiserum showed positive staining in the nuclei of postmitotic annular pad and fiber cells. These results demonstrate that cyclinB/p34cdc2 complexes and p34cdc2-associated histone kinase activity are present in postmitotic, differentiating lens fiber cells and support the possibility that phosphorylation of specific nuclear substrates by p34cdc2 may play a role in the denucleation of lens fiber cells.

Animals↗
PubMed1995

Induction of cyclin B and H1 kinase activity in apoptotic PC12 cells.

The present study examines whether cyclin B may be involved in apoptosis of neuronally differentiated PC12 cells following withdrawal of NGF. Cyclin B mRNA increased approximately 10-fold 4 days after NGF withdrawal, as indicated by competitive RT/PCR. Sequencing of the PCR product confirmed that it was derived from cyclin B mRNA. Cyclin B protein increased in parallel with cyclin B mRNA, as shown by immunoblotting. Immunoprecipitation with anti-cyclin B antibody demonstrated that cyclin B was associated with H1K activity, which reached a maximum 5 days after NGF withdrawal. When proteins immunoprecipitated with anti-cyclin B antibody were immunoblotted with anti-PSTAIR antibody, a protein with apparent molecular weight of 34 kDa was detected. This protein was identified as p34cdc2 on the basis of immunoreactivity with antibody against the C-terminal portion of mouse p34cdc2. Since cyclin B/p34cdc2 complexes are known to catalyze chromosomal condensation and nuclear envelope breakdown during mitosis, these results suggest that cyclin B/p34cdc2 may play some role in the nuclear changes accompanying apoptosis of PC12 cells.

Animals↗
PubMed1995

Guillain-Barré syndrome in northern China. The spectrum of neuropathological changes in clinically defined cases.

The pathology of the Guillain-Barré syndrome remains controversial, and autopsied cases available for study by contemporary techniques are uncommon. Large numbers of cases clinically diagnosed as Guillain-Barré syndrome occur in northern China. In this study we examined the neuropathological changes in 12 autopsied cases from Hebei Province, China. Eleven died early in the course of their disease. In all cases tissue was specially handled and fixed for electron microscopy and for immunocytochemistry. Three of these 12 cases had typical acute inflammatory demyelinating polyneuropathy (AIDP) with lymphocytic infiltration and macrophage-mediated demyelination, reproducing the pathological picture most often reported in Guillain-Barré syndrome in North America, Europe, and Australia. Six cases had predominantly axonal involvement, characterized by Wallerian-like degeneration of nerve fibres, with only minimal demyelination and with minimal inflammation in five. Three cases, even though paralysed at the time of death, had only very mild changes in the spinal roots and sciatic nerves. Within the group of six predominantly axonal cases, there were important differences both in the severity of the abnormalities and in the classes of fibres involved. Three cases had extensive Wallerian-like degeneration of sensory as well as motor fibres [acute motor-sensory axonal neuropathy (AMSAN)], while in the other three cases the fibre degeneration affected the motor nerve fibres almost exclusively. These latter cases establish a structural basis for the clinical and electrophysiological picture termed the acute motor axonal neuropathy (AMAN) pattern. In both the AMAN and the AMSAN patterns, a prominent feature was the presence of macrophages within the periaxonal space, surrounding or displacing the axon, and surrounded by an intact myelin sheath. These studies show that the early pathological changes in cases clinically diagnosed as the Guillain-Barré syndrome are diverse and not restricted to the well-known pattern of AIDP, and that the predominant pathological patterns may differ in different parts of the world. The differences in pathological findings between acute inflammatory demyelinating polyneuropathy and the axonal patterns are likely to reflect differences in the pathogenetic mechanisms. The periaxonal macrophages in the axonal patterns suggest that an important epitope may be localized to the axolemma or periaxonal space. The mild cases indicate that severe paralysis can occur early in Guillain-Barré syndrome without prominent structural changes along the nerve, suggesting that physiological block or nerve terminal changes may be implicated.

Acute Disease↗
PubMed1995

Guillain-Barré syndrome in northern China. Relationship to Campylobacter jejuni infection and anti-glycolipid antibodies.

Guillain-Barré syndrome has been considered to be primarily an acute inflammatory demyelinating polyneuropathy (AIDP). Our experience with Guillain-Barré syndrome in northern China differs from the traditional concept. Electrophysiologically and pathologically, most of our patients have motor axonal degeneration with minimal cellular inflammation, which we have termed 'acute motor axonal neuropathy' (AMAN). The current studies were undertaken to characterize prospectively the clinical, electrophysiological, and serological features of Guillain-Barré syndrome, defined clinically, in northern China. In 1991 and 1992, we characterized by electrodiagnostic criteria 129 Chinese patients with Guillain-Barré syndrome. The AMAN form was present in 65% of patients, the AIDP form in 24% and 11% were unclassifiable. For the 38 patients who presented from January to October, 1992, we performed serological assays for antibodies to Campylobacter jejuni and to glycolipids. Of these 38 patients, 55% had AMAN, 32% had AIDP and 13% were unclassifiable. Sixty-six percent of the 38 had serological evidence of recent C. jejuni infection as compared with 16% of village controls (P = 0.001). Seventy-six percent of AMAN patients and 42% of AIDP patients were seropositive. IgG anti-GM1 antibodies were more frequent in Guillain-Barré syndrome patients compared with village controls (42% versus 6%; P < 0.01). However, no statistically significant correlations were found between the pattern of disease, AMAN or AIDP, anti-glycolipid antibodies, or C. jejuni antibodies. Based on electrophysiological criteria, Guillain-Barré syndrome in northern China can be divided into two predominant forms: AIDP and AMAN. The AMAN form is more common and predominates in the yearly summer outbreaks of Guillain-Barré syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

[Responses of toad spinal ganglion neurons to repetitive stimulation of their central and peripheral processes].

Intracellular recordings were made from 48 toad dorsal root ganglion neurons in vitro while electrical stimulation was delivered respectively to their dorsal root or sciatic nerve input. The average conduction velocities were respectively 12 m/s and 15 m/s. With progressively increasing frequency of stimulation, 30% of the recorded cells showed simultaneous decrease of amplitude, wave decomposition and dropping of propagated response to both inputs while 70% of the cells showed more or less different patterns of degradation of the various parameters. Complete failure of neurons to follow the inputs occurred respectively at 126 and 323 Hz. Evidently the dorsal root ganglion neurons reported in the present work pertain to type A neuron with central processes smaller in diameter than peripheral ones A possible mechanism underlying the different changes is discussed.

Animals↗