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Biomedical subjects

P Cheng

Publications and source records attributed to P Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cell cycle dysregulation by green tea polyphenol epigallocatechin-3-gallate.

Epidemiological, in vitro cell culture, and in vivo animal studies have shown that green tea or its constituent polyphenols, particularly its major polyphenol epigallocatechin-3-gallate (EGCG) may protect against many cancer types. In earlier studies, we showed that green tea polyphenol EGCG causes a G0/G1-phase cell cycle arrest and apoptosis of human epidermoid carcinoma (A431) cells. We also demonstrated that these effects of EGCG may be mediated through the inhibition of nuclear factor kappa B that has been associated with cell cycle regulation and cancer. In this study, employing A431 cells, we provide evidence for the involvement of cyclin kinase inhibitor (cki)-cyclin-cyclin-dependent kinase (cdk) machinery during cell cycle deregulation by EGCG. As shown by immunoblot analysis, EGCG treatment of the cells resulted in significant dose- and time-dependent (i) upregulation of the protein expression of WAF1/p21, KIP1/p27, p16 and p18, (ii) downmodulation of the protein expression of cyclin D1, cdk4 and cdk6, but not of cyclin E and cdk2, (iii) inhibition of the kinase activities associated with cyclin E, cyclin D1, cdk2, cdk4 and cdk6. Taken together, our study suggests that EGCG causes an induction of G1-phase ckis, which inhibit the cyclin-cdk complexes operative in G0/G1 phase of the cell cycle thereby causing a G0/G1-phase arrest of the cell cycle, which is an irreversible process ultimately resulting in an apoptotic cell death. We suggest that the naturally occurring agents such as green tea polyphenols which may inhibit cell cycle progression could be developed as potent anticancer agents for the management of cancer.

Apoptosis↗
PubMed2000

Genotypic, phenotypic, and modeling studies of a deletion in the beta3-beta4 region of the human immunodeficiency virus type 1 reverse transcriptase gene that is associated with resistance to nucleoside reverse transcriptase inhibitors.

Point mutations and inserts in the beta3-beta4 region of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) are associated with resistance to nucleoside analog inhibitors. This report describes HIV-1 strains from seven patients that were found to have a 3-bp deletion in the beta3-beta4 region of the RT gene. These patient strains also had a mean of 6.2 drug resistance-associated mutations in their RT genes (range, 3 to 10 mutations). The deletion was most frequently found in strains with the Q151M mutation. Nonnucleoside RT inhibitor mutations were found in six of seven strains. Culture-based drug sensitivity assays showed that deletion-containing isolates had reduced susceptibility to four to eight RT inhibitors. Site-directed mutagenesis experiments showed that the deletion alone conferred reduced susceptibility to nucleoside analogs. Changes in the three-dimensional models of the RT deletion mutants were consistently observed at the beta3-beta4 loop and at helices C and E in both the presence and the absence of dTTP. Loss of hydrogen bonds between the RT and dTTP were also observed in the RT deletion mutant. These results suggest that the deletion in the RT gene contributes to resistance to several nucleoside analogs through a complex interaction with other mutations in the RT gene.

Drug Resistance, Microbial↗
PubMed2000

Photo-cross-linkable oligonucleotide probes for in situ hybridization assays.

In situ hybridization techniques have been an important research tool since first introduced 30 years ago, and more recently clinical applications have been expanding greatly. Still, further improvements in the assay sensitivity and protocols that are amenable to routine clinical use are desired. We use a novel photo-cross-linking technology to irreversibly bind short oligonucleotide probes to the target sequence following a hybridization period. The cross-linking agent is incorporated into the backbone of the probe and is activated to react with pyrimidines in the opposite strand by near-UV (300-370 nm) irradiation. By locking the probe to the target, very stringent wash conditions can be used that would otherwise completely remove probes that are hybridized but not cross-linked to the target. Consequently, the probe-specific signal is maximized, while the background signal is minimized to the greatest extent possible with the stringency of the wash. The use of short, photo-cross-linkable probes presents a new strategy for maximizing the sensitivity of probe hybridization or signal amplification-based in situ techniques.

Base Sequence↗
PubMed2000

[Exploration on containers for medicinal measurement].

Containers for measuring medicines, including Qian bi (coin dagger) . dao gui (knife dagger), san fen bi (3 - fen dagger) . wu fen bi (5 - fen dagger) and fang cun bi (square - ital dagger) are discussed on the basis of ancient literature records and unearthed relics. It is claimed that besides applied as a 5 - zhu coin, coin dagger can also be interpreted as the weight of 1 coin dagger. Knife dagger is a measuring container with a volume of 0.5 ml. Based on the fact that "1 - fen copper volume" measures 1.2 mil, it is suggested that a 3 - fen dagger equals 3.6 ml; while 5 - fen dagger, 6 ml. Being a flattened spoon, concave at its center, a square - cun dagger measures approximately 10 or approximately 18 ml.

China↗
PubMed2000

[Histologic study of the temporomandibular joints after ovariectomy in rats].

OBJECTIVE: To investigate histologic changes of the temporomandibular joints (TMJ) after ovariectomy in adult rats. METHODS: Sixty-eight female SD rats aged twenty weeks were assigned to 2 groups. One group underwent bilateral ovariectomies served as experimental group. The other underwent sham ovariectomy served as control group. The rats were killed at the intervals of 1, 2, 4, 8 and 12 weeks postoperatively. Histologic observation of the TMJ was performed in a synchronous manner by using light microscopy(LM), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The serum levels of estrogen and bone mineral density of femur were also determined. RESULTS: In the experimental group, the serum levels of estrogen were obviously decreased, and bone mineral density of femur was significantly decreased at 12 weeks postoperatively. No obvious histological changes of TMJ of rats were observed at 1 and 2 weeks after the ovariectomy, whereas thickness of the condylar cartilage was increased, with irregular shape of chondrocytes at 4 and 8 weeks postoperatively. A serial of degenerative changes in the TMJ was observed in osteoporotic rats at 12 weeks after the ovariectomy. CONCLUSIONS: Estrogen deficiency in rats may cause alterations of the TMJ, and osteoporosis may predispose to degenerative changes in the TMJ.

Animals↗
PubMed1999

Distinct roles for Galphai2, Galphai3, and Gbeta gamma in modulation offorskolin- or Gs-mediated cAMP accumulation and calcium mobilization by dopamine D2S receptors.

Previous studies have shown that a single G protein-coupled receptor can regulate different effector systems by signaling through multiple subtypes of heterotrimeric G proteins. In LD2S fibroblast cells, the dopamine D2S receptor couples to pertussis toxin (PTX)-sensitive Gi/Go proteins to inhibit forskolin- or prostaglandin E1-stimulated cAMP production and to stimulate calcium mobilization. To analyze the role of distinct Galphai/o protein subtypes, LD2S cells were stably transfected with a series of PTX-insensitive Galphai/o protein Cys --> Ser point mutants and assayed for D2S receptor signaling after PTX treatment. The level of expression of the transfected Galpha mutant subunits was similar to the endogenous level of the most abundant Galphai/o proteins (Galphao, Galphai3). D2S receptor-mediated inhibition of forskolin-stimulated cAMP production was retained only in clones expressing mutant Galphai2. In contrast, the D2S receptor utilized Galphai3 to inhibit PGE1-induced (Gs-coupled) enhancement of cAMP production. Following stable or transient transfection, no single or pair set of mutant Galphai/o subtypes rescued the D2S-mediated calcium response following PTX pretreatment. On the other hand, in LD2S cells stably transfected with GRK-CT, a receptor kinase fragment that specifically antagonizes Gbeta gamma subunit activity, D2S receptor-mediated calcium mobilization was blocked. The observed specificity of Galphai2 and Galphai3 for different states of adenylyl cyclase activation suggests a higher level of specificity for interaction of Galphai subunits with forskolin- versus Gs-activated states of adenylyl cyclase than has been previously appreciated.

Adenylate Cyclase Toxin↗
PubMed1999

Effects of serum of Kawasaki disease on PDGF expression in monocytes and on endothelial cell apoptosis.

The effects of serum of patients with Kawasaki disease on the platelet derived growth factor-B (PDGF-B) chain protein expression in monocytes were studied by immunocytochemical method and the effects of the serum on the endothelial cellular (EC) apoptosis were observed by flow cytometric technique. It was found that the serum of patients with Kawasaki disease induced significantly the expression of PDGF-B chain protein. Likewise, EC apoptosis was increased significantly in the experimental group as compared with the control group (P < 0.01). The results suggest that PDGF in monocytes increase and EC apoptosis play an important role in the development of coronary artery complication in Kawasaki disease.

Apoptosis↗
PubMed1999

Ion transport across the cecum in normal and colitic mice.

This study was conducted to determine the ion transport mechanisms in the normal mouse cecum and compare them to an inbred mouse model of colitis. The Ussing chamber-voltage clamp technique was used to monitor the short circuit current (I(sc)). The basal I(sc) in the normal cecum was 82.6 +/- 5.8 microA/cm2. It was not affected by bumetanide, 9-anthracene carboxylate, amiloride, and phenamil or by removal of Cl- ions; but was abolished by the removal of Na+ ions. Flux measurements revealed the presence of neutral NaCl transport. In the colitic cecum, the basal current was significantly higher than the normal cecum. Basal current in the normal cecum was due primarily to Na+ absorption through a Na+ channel, while in the colitic cecum it was due to Cl- ion secretion. cAMP addition in colitic cecum did not increase Cl- secretion, further suggesting that the tissue is already secreting at a maximal rate.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

TATA-driven transcriptional initiation and regulation of the rat serotonin 5-HT1A receptor gene.

The transcriptional initiation and regulation of the rat serotonin 5-HT1A receptor gene were characterized. By three types of analyses, a single brain-specific site of transcriptional initiation was localized to -967 bp upstream of the translation initiation codon that is utilized both in hippocampus and in the rat raphe RN46A cell line. This major site of transcriptional initiation was located 58 bp downstream from a consensus TATA element, suggesting TATA-driven transcription of the rat 5-HT1A receptor. To identify the promoter activity of the receptor gene, progressive 5' deletions of the -2,719/-117-bp fragment of the 5-HT1A promoter linked to luciferase gene were transfected into 5-HT1A-negative (pituitary GH4C1, L6 myoblast, and C6 glioma) and 5-HT1A-positive (septal SN-48 and raphe RN46A) cell lines. Enhancer regions were identified within a fragment between nucleotides -426 and -117 that selectively enhanced transcription in 5-HT1A-positive cells. A nonselective enhancer/promoter that mediated expression in all cell lines was located upstream between -1,519 and -426 bp in a DNA segment containing consensus TATA, CCAAT, SP-1, and AP-1 elements as well as a poly-GT26 dinucleotide repeat. Strong repression of transcription in all cell lines was conferred by the region upstream of -1,519 bp that contains a 152-bp DNA segment with >80% identity to RANTES, tumor necrosis factor-beta, and other immune system genes. Our results indicate that TATA-driven expression of the 5-HT1A receptor is regulated by a novel proximal tissue-specific enhancer region, a nonselective promoter, and an upstream repressor region that is distinct from previously identified neuron-specific repressors.

Animals↗
PubMed1999

Subspecies-dependent regulation of Bacillus thuringiensis protoxin genes.

Bacillus thuringiensis accumulates, primarily during sporulation, large quantities of insecticidal protoxins which are deposited as crystalline, intracellular inclusions. Most subspecies contain several plasmid-encoded cry genes, each of which has a unique specificity. The overall toxicity profile of a subspecies depends not only on the array of cry genes present but also on the relative expression of the genes. In general, transcription depends on sporulation-specific sigma factors, but little is known about regulation of expression of the individual genes. In order to determine whether expression of a particular cry gene varies in different subspecies, lacZ fusions to the cry promoters of two protoxin genes (cry1 class) were constructed. Protoxin accumulation and mRNA contents were also measured by performing immunoblotting and Northern analyses, respectively. The expression of a cry1Ab-lacZ fusion, but not the expression of a cry1C-lacZ fusion, was three to four times lower in B. thuringiensis subsp. aizawai strains than in B. thuringiensis subsp. kurstaki or B. thuringiensis subsp. tolworthi. Also, the Cry1Ab antigen and steady-state mRNA contents of B. thuringiensis subsp. aizawai were lower. The regulation of the genes must involve regions upstream of the promoters which are unique to each cry gene since (i) mutations in the upstream region of the cry1Ab gene resulted in enhanced expression in B. thuringiensis subsp. aizawai and (ii) no differences were found when the lacZ fusions contained the cry1Ab promoters but no upstream sequences. The capacity to regulate each of the protoxin genes must be a factor in the overall protoxin composition of a subspecies and thus its toxicity profile.

Antigens, Bacterial↗
PubMed1999

Analysis of two IL-4 promoter polymorphisms in a cohort of atopic and asthmatic subjects.

The Th2 cytokine interleukin 4 (IL-4) has been identified as having a central role in driving the inflammatory immune responses which are present in atopic airway disease. This study examined the distribution of two putative IL-4 promoter polymorphisms (-285 C-T and -81 A-G) in groups of patients with severe and moderate asthma, non-asthmatic atopy and control subjects. Neither polymorphism was identified in any of the samples tested. The data suggest that either the polymorphisms are present at very low frequencies or are artefacts of the B cell lines from which they were identified.

Adult↗
PubMed1999

[The observation of mycology and clinical efficacy in 325 cases with otomycosis].

OBJECTIVE: To study otomycosis of pathogenic fungi, antifungal susceptibility test and clinical efficacy. METHOD: The study was performed as follows: 1) culture of pathogenic fungi and fungus identification in 110 cases. 2) antifungal susceptibility test with Etest strip by ketoconazole (KE), itraconazole (IT), Fluconazole (FC), Fluorocytosine (FL), and amphotericinum B (AP). 3) Topical application of doktarin ps cream (DC), ketoconazole cream (KEC), clotrimazole ung (CU), and thymol alcohol (TA) were performed in 4 groups and the intermittent impulsive treatment in who failed to respond to local treatment were performed too. RESULT AND CONCLUSION: 1) Chiefly, otomycosis of pathogenic fungi were aspergillus (79%) and candida albicans (8%) and penicillium citrinum (5%). 2) Antifungal susceptibility test showed that aspergillus were sensitive to KE and IT, but not sensitive to KE and FL, and candida albicans were sensitive to KE, IT, FC, FL and AP all; P. citrinum was sensitive to AP, FL and KE but not to FC. 3) Effective rate of topical application on 4 groups were 97.6%, 97.5%, 90.0% and 80.0% respectively. Comparing the results between compound azoles drugs and TA, there was a statistical significant difference (P < 0.05), the efficacy of compound azoles is better than that of TA. The effective rate of systematic intermittent impulsive treatment in 30 cases failed to respond to local treatment were 100%.

Adolescent↗
PubMed1998

A monoclonal antibody selected for probing the folding of staphylococcal nuclease and its N-terminal fragments.

Monoclonal antibody McAb2C9 against Staphylococcal nuclease (SNase R) and its N-terminal fragments was produced and characterized. It was observed that the intact enzyme SNase R and its seven fragments (SNR141, SNR135, SNR121, SNR110, SNR102, SNR79 and SNR52) differed in their interactions with McAb2C9. However, the fragments with weak immunoreactivity, such as SNR141 and SNR110, increased ability reacting with McAb2C9 in their partially unfolded state. It suggests that the differences of immunoreactivity among the fragments are due to diverse extent of the exposure of the specific epitope and the conformation of the peptide fragment. The monoclonal antibody McAb2C9 could be a useful probe to investigate the mechanism of folding of SNase R and its N-terminal fragments.

Animals↗
PubMed1998

Kawasaki disease on PDGF expression and VSMC proliferation.

The effect of serum of patients with Kawasaki disease (KD) on expression of platelet-derived growth factor (PDGF) B chain protein in vascular endothelial cells (VEC) was studied by immunocytochemical method. Meanwhile, the effects of the endothelial cell conditioned media (ECM) on expression of PDGF receptor mRNA in vascular smooth muscle cells (VSMC) and on cell cycle of VSMC were investigated by the methods of nucleic acid hybridization and flow cytometry (FCM). The results showed that the serum of patients with KD induced the expression of PDGF-B chain protein significantly. ECM significantly promoted the expression of PDGF receptor mRNA and induced the proliferation of VSMC. These data suggest that the activation of PDGF-PDGF receptor may play a role in the pathogenesis of coronary complication of KD.

Animals↗
PubMed1998

HSP60, HSP70 in the pathogenesis of Kawasaki disease: implication and action.

HSP60, HSP70 in plasma of 11 cases of Kawasaki diseases (KD) and 23 healthy children were determined. The two groups were controlled for age. Determination of HSP60, HSP70 was conducted in lymphocytes of 14 cases of KD and 26 healthy children. The results were compared with those of 12 patients with febrile diseases and 10 patients with tuberculosis. Our results showed that except a significant difference in plasma HSP70 found between acute phase and convalescent phase of KD (P < 0.01), no significant difference was found in HSP60, HSP70 among all groups (P > 0.05). The differences in HSP60, HSP70 in lymphocytes were relatively obvious among all groups. The levels of HSP60, HSP70 in acute phase of KD were significantly higher than those in convalescent phase or in healthy controls (P < 0.01). The levels of HSP60 in KD were significantly higher than those of patients with febrile diseases. HSP60 of KD children was significantly lower than those of children with tuberculosis (P < 0.01). The findings showed that HSP60, HSP70 might contribute to the pathogenesis of KD. Determination of HSP60, HSP70 in lymphocytes is of help in the diagnosis of KD.

Chaperonin 60↗
PubMed1998

Variation in kinematics and dynamics of the landing flights of pigeons on a novel perch

Pigeons made 10 flights to a novel perch. Kinematic measurements of these flights were obtained from video recordings, and the forces exerted on the perch on each landing were measured. There was wide variation (20-fold range) in the kinetic energy of the pigeons just before landing, arising almost entirely from variation in horizontal velocity. The maximum force exerted on the perch varied in magnitude from approximately twice to eight times the pigeons' body weight, and in direction from 40 to 90 below the horizontal. In landings with high final kinetic energy, the maximum force exerted on the perch was larger and was applied at a shallower angle than in those with low final kinetic energy. Landing flights with high final kinetic energy showed straighter trajectories and a larger peak deceleration during the last 300 ms of approach flight than those with low final kinetic energy, which had downward-curving trajectories and a more prolonged and steady pattern of deceleration. Mean final kinetic energy was lower in the first two landings made on the perch than in subsequent landings, indicating that pigeons are more likely to adopt a slow, downward-curving approach to a novel perch and a fast, straight approach to a familiar one.

Journal Article↗
PubMed1997

Stable transfection of nonosteogenic cell lines with tissue nonspecific alkaline phosphatase enhances mineral deposition both in the presence and absence of beta-glycerophosphate: possible role for alkaline phosphatase in pathological mineralization.

It is documented that alkaline phosphatase (AP) plays an important role in bone mineralization. Considering that TN-AP is expressed in periodontal ligament fibroblasts, renal epithelial cells, and vascular endothelial cells, and that TN-AP is both a calcium-/phosphate-binding protein and a phosphohydrolytic enzyme, we hypothesize that membrane-bound AP also plays an important role in the initiation of physiological and pathological mineralizations in tissues other than bone and cartilage. To test this hypothesis, nonosteoblast cell lines, including a fibroblast line, a renal epithelial line, and a capillary endothelial line, were stably transfected to express high levels of rat bone AP on their cell surfaces. These rat bone AP-expressing cells were then cultured on filter membranes in the presence or absence of beta-glycerol phosphate. von Kossa staining for calcium phosphate and transmission electron microscopy with electron diffraction analysis for minerals were employed to investigate the effect of membrane AP on extracellular calcium phosphate mineralization. Our results indicated that AP expression on these nonosteoblast-like cell surfaces have induced extracellular hydroxyapatite (HAP) mineralization. Our findings support the concept that membrane-bound AP contributes to extracellular apatitic mineralization by mechanisms that do not necessarily involve its hydrolase activity. They also suggest that AP might be important for the initiation of pathological mineralization in nonosteogenic tissues.

Alkaline Phosphatase↗