Biomedical subjects

Y Cao

Publications and source records attributed to Y Cao.

At least 109 records · Page 6Linked to original sources

PubMed2001

Elimination of transcriptional interference between tandem genes in plant cells.

Plant cells are commonly transformed with two or more tandemly arranged genes, but how orientation affects their expression is not well understood. We investigated the amount of transcriptional interference occurring between two adjacent genes by cloning luciferase and green fluorescent protein (GFP) genes (promoter--coding sequence--terminator) in all possible orientations and expressing the genes in tobacco protoplasts. When two genes are oriented head-to-tail (-->-->), the expression of the downstream gene was reduced 80% by the upstream gene. When two genes are oriented tail-to-tail (--><--), the expression of the upstream gene was reduced 53% by the expression of the downstream gene. There was no interference when the orientation was head-to-head (<---->). Using a chemically inducible gene expression system, we showed that the downstream gene expression was reduced 71% by the induction of an upstream gene. Inserting a mammalian transcription blocker sequence eliminated the interference between the genes in tail-to-tail orientation. The interference in the head-to-tail orientation was eliminated by inserting a 2322-bp lambda phage DNA fragment. The terminators in gene constructs did not prevent the transcriptional interference, and the interference was eliminated by designing the orientation of genes and by placing a transcription blocker or a lambda phage sequence between genes.

Bacteriophage lambda↗

PubMed2001

Nucleotide sequence analysis of a transforming gene isolated from nasopharyngeal carcinoma cell line CNE2: an aberrant human immunoglobulin kappa light chain which lacks variable region.

A transforming gene, designated Tx, was isolated from a human nasopharyngeal carcinoma (NPC) cell line CNE2 by transfection and molecular cloning techniques. The Tx gene was analyzed using computer-based bioinformatics and compared with the known sequences in EMBL and GenBank databases. We found that Tx contains human immunoglobulin kappa light chain constant region, five intact joining regions J1-J5, five recombination signal sequences and an N-segment besides classic regulatory sequences such as TATA boxes, CAAT boxes, poly A signals, etc. Interestingly, Tx also contains several binding sites for nuclear transcription factors such as NF-kappaB, NF-IL6, TFIID, etc. In conclusion, there are only several base pairs mutations or deletions compared with normal Ig K JC gDNA fragment. In all, Tx is an aberrant human immunoglobulin kappa light chain that contains the constant region, five joining regions, which lacks the variable regions.

Genes, Immunoglobulin↗

PubMed2001

Gene therapy of scarring: a lesson learned from fetal scarless wound healing.

Cutaneous wounding in adult humans and higher vertebrate animals results in scar formation. In contrast, both human and animal fetuses, at early gestational ages, exhibit skin wound healing without scarring. This distinction suggests that the repair of adult wounds by skin regeneration, rather than by fibrosis, may be achieved if adult wounds can be modified to mimic the healing process of fetal wounds. The development of gene therapy offers the possibility to specifically enhance or block the gene expression of cytokines and extracellular molecules, and thus convert adult wound healing into a healing process more similar to tissue regeneration. This article reviews the characteristics of fetal wound repair focusing on cytokine profiles and the inflammatory response to dermal injury. Also included are new developments in gene transfer techniques as well as their application in wound healing. Finally, the authors propose possible strategies of wound gene therapy, to reduce wound scarring and to promote tissue regeneration.

Animals↗

PubMed2001

Modulation of recombinant small-conductance Ca(2+)-activated K(+) channels by the muscle relaxant chlorzoxazone and structurally related compounds.

Using the patch clamp technique we investigated the effects of the centrally acting muscle relaxant chlorzoxazone and three structurally related compounds, 1-ethyl-2-benzimidazolinone (1-EBIO), zoxazolamine, and 1,3-dihydro-1-[2-hydroxy-5-(triflu oromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS 1619) on recombinant rat brain SK2 channels (rSK2 channels) expressed in HEK293 mammalian cells. SK channels are small conductance K(+) channels normally activated by a rise in intracellular Ca(2+) concentration; they modulate the electrical excitability in neurons and neuroendocrine cells. When applied externally, chlorzoxazone, 1-EBIO, and zoxazolamine activated rSK2 channel currents in cells dialyzed with a nominally Ca(2+)-free intracellular solution. The activation was reversible, reproducible, and depended on the chemical structure and concentration. The order of potency was 1-EBIO > chlorzoxazone > zoxazolamine. Activation of rSK2 channels by chlorzoxazone, 1-EBIO, and zoxazolamine declined at higher drug concentrations. Zoxazolamine, when applied in combination with chlorzoxazone or 1-EBIO, partially inhibited the rSK2 channel current responses, suggesting a partial-agonist mode of action. 1-EBIO failed to activate rSK2 channel currents when applied to excised inside-out membrane patches exposed to a Ca(2+)-free intracellular solution. In contrast, 1-EBIO activated rSK2 currents in a concentration-dependent manner when coapplied to the patches with a solution containing 20 nM free Ca(2+). NS 1619 did not activate rSK2 channel currents; it inhibited rSK2 channel currents activated by the other three test compounds or by high intracellular Ca(2+). We conclude that chlorzoxazone and its derivatives act through a common mechanism to modulate rSK2 channels, and SK channel modulation in the brain may partly underlie the clinical effects of chlorzoxazone.

Benzimidazoles↗

PubMed2001

Effects of moxa-cone moxibustion at Guanyuan on erythrocytic immunity and its regulative function in tumor-bearing mice.

In the sarcoma S180 ascitic mice, the effects of moxa-cone moxibustion at Guanyuan (CV 4) on erythrocytic immunity and its regulative function were investigated. The results indicated that moxibustion at Guanyuan (CV 4) could significantly increase the decreased erythrocytic C3b receptor rosette forming rate (RBC-C3bRR), lower the raised erythrocytic immunocomplex rosette forming rate (RBC-ICR, P < 0.05 or P < 0.01), increase the decreased activity of erythrocytic immuno-accelerative factor, and reduce the increased activity of erythrocytic immunosuppressive factor (P < 0.05) in the tumor-bearing mice. This suggests that moxibustion at Guanyuan (CV 4) can strengthen erythrocytic immunity and promote its regulative function.

Acupuncture Points↗

PubMed2001

Metabolism of chlorpyrifos by human cytochrome P450 isoforms and human, mouse, and rat liver microsomes.

One of the factors determining the toxicity of chlorpyrifos (CPS), an organophosphorus (OP) insecticide, is its biotransformation. CPS can be activated by cytochrome P450 (CYP) through a desulfuration reaction to form chlorpyrifos-oxon (CPO), a potent anticholinesterase. CPS can also be detoxified by CYP through a dearylation reaction. Using pooled human liver microsomes (HLM), a K(m(app)) of 30.2 microM and V(max(app)) of 0.4 nmol/min/mg of protein was obtained for desulfuration, and a K(m(app)) of 14.2 microM and a V(max(app)) of 0.7 nmol/min/mg of protein was obtained for dearylation. These activities are lower than those obtained from rat liver microsomes. Gender differences in humans were also observed with female HLM possessing greater activity than male HLM. Use of human CYP isoforms expressed in human lymphoblastoma cells demonstrated that CYP1A2, 2B6, 2C9*1, 2C19, and 3A4 are involved in CPS metabolism. CYP2B6 has the highest desulfuration activity, whereas dearylation activity is highest for 2C19. CYP3A4 has high activity for both dearylation and desulfuration. The use of phenotyped individual HLM demonstrated that predictions of metabolic activation and/or detoxication could be made based on relative amounts of CYP2B6, 2C19, and 3A4 in the microsomes. Thus, individuals with high CYP2C19 but low 3A4 and 2B6 are more active in dearylation than in desulfuration. Similarly, individuals possessing high levels of CYP2B6 and 3A4 have the greatest potential to form the activation product. These differences between individuals suggest that differential sensitivities to CPS may exist in the human population.

Animals↗

PubMed2001

A 3D structural model of memapsin 2 protease generated from theoretical study.

AIM: To build a 3D structural model of memapsin 2 (M2) protease for theoretical study and drug design. METHODS: Structural alignment was performed based on multiple and pairwise sequence alignment of three templates. After the initial model was generated, energy minimization was completed by applying molecular mechanics method. Molecular dynamics (MD) technique was used to do further structural optimization. RESULTS: The 3D structural model of memapsin 2 was constructed. The model is reasonable according to several validation criteria. The active-site motifs of M2 are structurally supported by a beta-sheet rich domain and linked together with this domain through alpha helices. Tyr132 contained in beta-hairpin is a general characteristic of aspartic protease. The Calpha atom superimposing result is a direct verification that M2 is structurally unique but still belongs to the aspartic protease superfamily. CONCLUSION: The 3D-structure model from our study is informative to guide future molecular biology study about M2 and drug design based on database searching.

Amino Acid Sequence↗

PubMed2001

Isolation and characterization of a Xenopus gene (XMLP) encoding a MARCKS-like protein.

We have identified a cDNA coding for a Xenopus MARCKS-like protein (XMLP) from a cDNA library prepared from activin-treated ectoderm. Using whole-mount in situ hybridization and RT-PCR, we found XMLP maternal transcripts during the cleavage stages. After MBT, the signals were restricted to the neural plate. Subsequently XMLP was expressed predominantly in the brain, somites and pronephros. Ectopic expression of XMLP resulted in eye and axis defects and in a change of the expression pattern of Krox 20, a neural marker for rhombomeres 3 and 5. Injected XMLP caused apoptosis. It was characterized by loss of intercellular adhesion contacts, transient plasma membrane ruffling at gastrula, and epithelial disruption attailbud stage. Overexpression of mutant XMLPs showed that this phenotype was correlated with its putative PSD domain and glycine at position 2. The embryos injected with a morpholino oligo complementaryto XMLPmRNA showed malformations of the anterior axis and eye defects. Extirpation experiments indicated that the phenotypes might be correlated with disturbed morphorgenetic movements rather than an inhibition of induction process. Overexpression of XCYP26 resulted in a shift of the expression pattern of XMLP. In the early tailbud stage (stage 20) the signal stripe in the XCYP26 injected half of the embryo got diffuse or even disappeared. This observation suggests that retinoic acid plays an important role in the regulation of XMLP. Our results suggest that XMLP might participate in pattern formation of the embryonic axis and the central nervous system.

Amino Acid Sequence↗

PubMed2001

[Analysis on landscape ecology literatures in China during recent ten years].

Landscape ecology has achieved great progress since its introduction to China in early 1980s. Based on 619 collections of literatures and 14 collections of books, this paper has all the literatures and books classified, arranged in order and counted on different special subject. According to the results of classified statistics, the authors discuss and analyze how landscape ecology research was going in China during 1990s. Moreover, this paper can also provide scientific basis for those who want to grasp and keep abreast of current focus and trend of landscape ecology in China.

China↗

PubMed2001

[An experimental study of tissue engineered autologous cartilage by using an injectable polymer].

OBJECTIVE: To investigate the proper cell density of tissue engineered autologous cartilage to indicate the clinical application. METHODS: The chondrocytes, isolated from mini swines' ears, were mixed with an injectable biocompatible matrix(Pluronic F127) to make the cell suspensions with the densities of 10,20, 30,40,50,60,70 x 10(6)/ml. The chondrocyte-polymer complex was injected into the subcutaneous tissue of the swines' abdomens. Each specimen was harvested and evaluated with body-mass, histological examination, and glycosaminoglycan content and type II collagen tests after 6 weeks in vivo. RESULTS: The histological examination had showed that the neo-cartilage was solid, homogenous cartilage when using 50 million chondrocytess/cc for 6 weeks. The samples with the 10 and 30 million chondrocytes/cc showed that the area of the cartilage was incomplete and separated by the remnant polymer. The mass of the samples was ranged from 30-110 mg after 6 weeks. The glycosaminoglycan content was lower from 5.8 to 9.0 percent, compared to the 9.2 percent of the normal auricular cartilage. Western-Blot had presented the type II collagen in all samples. CONCLUSION: This study has demonstrated that the qutologous cartilage could be generated by using tissue engineering technique, with the histological characteristics similar to natural cartilage. Fifty million chondrocytes per cc could yield the best quality cartilage in 6 weeks.

Animals↗

PubMed2001

[Study on anti-HBV effects by antisense oligodeoxynucleotides in vitro].

OBJECTIVE: To study the inhibition effect of anti-HIV oligodeoxy-nucleotides on HBV X gene. METHODS: Three antisense phosphorothioate oligodeoxy-nucleotides(AsON) complementary to the initiator of X, DR2, EN II respectively, were synthesized and tested for their anti-HBV activity on HepG2.2.15 cells with ELISA methods. RESULTS: When the best effect concentration of AsON was 10 mumol/L, the inhibition rates on HBsAg of three AsON were 57%, 60% and 52% respectively, and on HBeAg were 56%, 45% and 56% respectively. There were two inhibition peaks at different times. There was no inhibition effect treated by random control (< 12%). Using the 3-(4,5-dimethythiazol-xyl)-2,5-diphnyl tetrazolium bromide method, there was no cytotoxicity at 40 mumol/L of AsON. CONCLUSION: AsONs on three key region of X gene were effective drugs to inhibit the expression of HBV.

Antiviral Agents↗

PubMed2001

[Role of endogenous cholinergic nerve in esophageal dysmotility with reflux esophagitis].

OBJECTIVE: To study the role of endogenous cholinergic nerve in esophageal dysmotility with reflux esophagitis in a feline model. METHODS: In 16 healthy cats under ketamine anesthesia (20 mg/kg), the abdominal parts of lower esophageal sphincter were cut open to establish the animal model for reflux esophagitis; esophageal motility was measured respectively preoperation and post-esophagitis. The activities of choline acetyltransferase (CHAT) and acetylcholinesterase(ACHE) in medial and distal esophageal body muscle was measured respectively with spectrophotometry, and compared to the normal cats(n = 8). RESULTS: Reflux esophagitis can make distal esophageal peristaltic amplitude decrease, the distal esophageal peristaltic amplitude of cats with reflux esophagitis [above LES 1 cm: (22.65 +/- 16.53) mm Hg; above LES 3 cm:(39.94 +/- 14.78) mm Hg, P < 0.0001] was significantly lower than that of normal cats [above LES 1 cm: (63.71 +/- 21.34) mm Hg; above LES 3 cm: (73.65 +/- 23.42) mm Hg] and the conducting velocity of distal esophagus was slower than that of normal cats [(1.04 +/- 0.36) cm/s vs (1.39 +/- 0.46) cm/s, P < 0.05]. In the esophagus of reflux esophagitis group, CHAT activity was lower in the model, especially in the distal part [(81.01 +/- 22.03) U/g vs (230.13 +/- 30.10) U/g, P < 0.0001] and ACHE activity remains unchanged. CONCLUSION: CHAT activity and pressure level were lower in the distal esophagus with reflux esophagitis compared to the normal cats. This study supported that reflux esophagitis can results in dysmotility of the distal esophagus and the abnormality of endogenous cholinergic innervation is one of the important mechanisms as far as the disorder of esophageal movement in reflux esophagitis.

Acetylcholinesterase↗

PubMed2001

LMP1 activates NF-kappa B via degradation of I kappa B alpha in nasopharyngeal carcinoma cells.

OBJECTIVE: To elucidate the mechanisms by which Epstein-Barr virus-encoded latent membrane protein 1 activates NF-kappa B in nasopharyngeal carcinoma cells. METHODS: A tetracycline-regulated LMP1-expressing nasopharyngeal carcinoma cell line, Tet-on-LMP1-HNE2, was used as the cell model. The kinetics of the expression of proteins, including LMP1, I kappa B alpha and I kappa B beta, was analyzed by Western blotting. The subcellular localization of NF-kappa B (p65) was detected by indirect immunofluorescence assay. The NF-kappa B transactivity was studied by transient transfection and reporter gene assay. RESULTS: I kappa B alpha was phosphorylated and degraded after the inducible expression of LMP1, although the total protein levels remained stable. The steady-state level of total I kappa B beta protein may have resulted from the initiation of an autoregulation loop after the activation of NF-kappa B. No change in the I kappa B beta level was detected. NF-kappa B (p65) was translocated from the cytoplasm to the nucleus following degradation of I kappa B alpha. After the introduction of the dominant-negative mutant of I kappa B alpha (Del 71) into Tet-on-LMP1-HNE2 cells, both nuclear translocation and transactivation of NF-kappa B induced by LMP1 was significantly inhibited. CONCLUSIONS: The results indicated that in nasopharyngeal carcinoma cells, LMP1 activated NF-kappa B via phosphorylation and degradation of I kappa B alpha, but not I kappa B beta. The dominant-negative mutant of I kappa B alpha (Del 71) could completely inhibit both the nuclear translocation and transactivation of NF-kappa B induced by LMP1.

Biological Transport↗

PubMed2001

In-vitro cultivation of normal human oral keratinocytes.

OBJECTIVE: To establish a method for culturing normal human oral keratinocytes. METHODS: Specimens obtained from healthy humans undergoing oral surgery were dissociated into single cell suspensions by dispase and trypsin. The cells were grown in serum-free medium. Morphological characteristics were studied under light microscope and electron microscope. Cytokeratins were shown by immunohistochemistry. RESULTS: Cells could be maintained in culture up to 4-5 passages or 30-50 days. Electron microscope revealed that there were desmosomes and tonofibrils in the oral keratinocytes. The cells showed positive staining for cytokeratin antibody. CONCLUSION: Human oral keratinocytes have been successfully grown in serial culture.

Cell Culture Techniques↗

PubMed2001

The regulatory action of Radix Astragali on M-cholinergic receptor of the brain of senile rats.

The changes in density of M-cholinergic receptors in different areas of senile rats and the regulatory action of Huang Qi ([symbol: see text] Radix Astragali, a drug for warming yang and replenishing qi) were observed by autoradiography. The results showed that the gray scale displayed in brain sections was clear and mainly distributed in the cortex, hippocampus and striate body, while that due to nonspecific combination was negligible. The gray scale in the cortex, hippocampus and striate body of the experimental group was markedly lower than that in the young control rats, decreased respectively by 24.87%, 14.12% and 12.76% (all P < 0.05); but it was obviously higher than those in the senile control rats, increased respectively by 24.15%, 14.38% and 13.47% (P < 0.05). The data indicate that Huang Qi ([symbol: see text]Radix Astragali) may up-regulate the decreased density of M-cholinergic receptors in the brain of senile rats.

Aging↗

PubMed2001

Transforming growth factor-alpha promotes mouse blastocyst outgrowth and secretion of matrix metalloproteinases.

OBJECTIVE: To study the effect of transforming growth factor-alpha (TGF-alpha) on early stage of embryo implantation. METHODS: Mouse blastocysts were cultured in vitro in medium containing various concentrations of TGF-alpha. Blastocyst implantation capacity was evaluated by calculating the percentage of embryos with attachment or outgrowth. Matrix metalloproteinases (MMPs) secretion of blastocysts was observed using gelatin zymography. RESULTS: There was no significant difference in the percentage of attachment between control and TGF-alpha treated groups, but the percentage of outgrowth of TGF-alpha treated groups was significantly higher than that of the control group after 24 h culturing. Gelatin zymography showed that blastocysts cultured in TGF-alpha treated groups started secreting MMPs earlier than those in the control group. CONCLUSION: TGF-alpha is involved in regulating the mouse embryo implantation process by promoting blastocyst outgrowth and secreting matrix matalloproteinases.

Animals↗

PubMed2001

[Expression of a snake venom plasminogen activator TSV-PA in insect cells].

A snake venom gene TSV-PA was inserted into the donor plasmids pFastBacHTa and expressed in Tn-5B1-4 cells. SDS-PAGE analysis revealed that the molecular weight of expressed product of TSV-PA were 33 kD. It was also proved by Western blot. The result of enzyme activity showed that TSV-PA protein expressed in insect cells had a higher activity.

Animals↗

PubMed2001

[An experimental study of repairing nerve gap with acellular basal lamina tubes].

OBJECTIVE: To develop an effective new material for repair of nerve defects. METHODS: The 4-week pre-degenerative and normal sciatic nerve segments of SD rats were extracted with the detergent lysophosphatidylcholine, which resulted in acellular nerve basal lamina tubes, called EDNG (extracted degenerative nerve grafts) and ENG (extracted normal nerve grafts) respectively. The morphology of the acellular nerve basal lamina tubes was revealed by conventional histological examinations, transmission electron microscopy and immunohistochemistry method. The basal lamina tubes, as allografts, were used to repair a 15 mm-gap of sciatic nerve in Wistar rats. In the control group nerve autografts (NAG) was applied. Evaluation included general observation, electromyographic examination, muscle measurement and histological observation of serial sections at 12 weeks after surgery. RESULTS: The EDNG had more ideal frame, better resilience than ENG. There was no any cell debris in EDNG, whereas in the inner wall of the tubes immunohistochemical analysis revealed clear positive staining and strong immunoreactivity of laminin under immunoelectron microscopy. After peripheral nerves were repaired, all the animals of the three groups had restoration of function to a certain extent. The result of the NAG group was the best, the EDNG group was the next and the ENG group was the inferior. CONCLUSION: This new material offers a possible solution to repair of a short defect of a peripheral nerve.

Animals↗