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Biomedical subjects

J Zhao

Publications and source records attributed to J Zhao.

At least 541 records · Page 30Linked to original sources
PubMed1997

[Determination of solanesol in the extracts of tobacco leaves by high performance liquid chromatography (HPLC)].

Solanesol, a terpene compound mainly isolated from tobacco, is an important intermediate of medicines such as vitamin K2 and coenzyme Q10. This paper presents an HPLC method for the determination of solanesol in the extracts of tobacco leaves. Solanesol is separated completely on a Zorbax-SIL column, 250 mm x 4.6 mm i.d., by using a mixture of n-hexane, isopropyl ether and ethyl acetate (6:3:1) as mobile phase and determined refractometrically. The isopropyl ether makes the chromatographic peak sharp and the addition of ethyl acetate can prevent the column from blockade during the analysis, and the appropriate temperature (30 degrees C) is beneficial to the shortening of analysis time. This method is fast, accurate and reproducible. It has good linear relationship in the range of 0.2-4 microg. The results have shown that the average recovery is 96.4% and coefficient of variation is 2.8%.

Chromatography, High Pressure Liquid↗
PubMed1997

[Direct simultaneous determination of o, m, p-nitronethylbenzene in mixture using spectrophotometry combined with Kalman filter].

The basic principle of Kalman filter and its modified method, including forgetting factor and enhancing dimensions of vector, for the error correction of measurement model in spectrophotometric determination of multicomponents were introduced. Combining forgetting factor with enhancing dimensions of vector, the recursive effect of Kalman filter method was improved. The result of modified Kalman filter was compared with other three chemometric methods, including target transformation factor, iterative target transformation factor and artificial neural network. This method can apply to direct simultaneous determination of o, m, p-nitronethylbenzene in mixture without any preliminary chemical separation.

English Abstract↗
PubMed1997

[Femoral to radial artery pressure gradient in the patients undergoing coronary artery bypass graft under normothermic cardiopulmonary bypass].

Femoral to radial artery pressure gradient was evaluated in 14 patients undergoing coronary artery bypass graft under normothermic cardiopulmonary bypass (CPB). CPB was instituted at a flow rate of 2.6 l.min-1.m-2, using non-pulsatile pump and blood temperature of pump arterial line was controlled to maintain bladder temperature between 36 and 37 degrees C. Pressure gradients occurred 30 min after commencement of CPB and the mean gradients of systolic, diastolic and mean artery pressure were maximum all at the end of CPB (38 +/- 7 mmHg, 4 +/- 1 mmHg and 10 +/- 2 mmHg). These pressure gradients remained until the end of the surgery. Throughout the operation, nasopharyngeal and blood temperature remained unchanged, while mean palm temperature increased from 31.8 degrees C (after induction) to 34.6 degrees C (30 min after commencement of CPB) and thereafter remained between 33.3 and 33.9 degrees C. This increase in peripheral temperature might indicate that normothermic CPB was accompanied by peripheral vasodilatation. These results indicate that the magnitude of femoral to radial pressure gradient during normothermic CPB is similar to that during mild hypothermic CPB.

Aged↗
PubMed1997

Polymorphisms of vitamin D receptor gene and its association with bone mineral density and osteocalcin in Chinese.

OBJECTIVE: To explore the distribution frequencies of vitamin D receptor (VDR) gene polymorphisms in Chinese and the relationship between VDR genotypes and bone mineral density (BMD) or serum osteocalcin level in Chinese women. METHODS: Polymorphisms of VDR gene were analyzed by polymerase chain reaction (PCR) to amplify the DNA sequence and three restriction enzymes (namely BsmI, ApaI and TaqI) to digest the PCR products in 223 subjects. Some of the VDR genotypes were also confirmed by Southern hybridization analysis. BMD was measured at the spine and proximal femur by dual-energy X-ray absorptiometry (DEXA). Serum osteocalcin concentrations were determined by radioimmunoassay. RESULTS: Chinese had high frequencies of "b,a,T" alleles, 95%, 75% and 95% respectively, which were much different from Caucasians. "BB" or "AA" genotype had tendency for higher BMD at some sites in the group of young women, whereas in the group of postmenopausal women, "bb" or "aa" genotype had relationship with lower BMD at femoral neck and trochanter. Furthermore, no relationship were found between VDR genotypes and the serum osteocalcin level in Chinese women. CONCLUSIONS: Allele frequencies of VDR gene in Chinese are different from those in Caucasians. VDR gene polymorphisms are associated with BMD in Chinese, but in a different pattern from other reports. Further study on predicting function of VDR for osteoporosis is necessary.

Adult↗
PubMed1997

[The development and efficacy tests for the autoclave indicator tape].

The paper describes the development and efficacy teats for the autoclave indicator tape which has specially effects on temperature of pressure steam, time of persistence and air of remainder in the autoclave, and quick, simple and advanced charater for indirectly testing the quality of autoclave sterilization.

Indicators and Reagents↗
PubMed1997

[Clinical significance of detection of PML-RAR alpha fusion gene of APL during differentiation therapy with ATRA].

OBJECTIVE: To characterize of the expression patterns of PML-RAR alpha fusion gene during differentiation therapy with ATRA. METHODS: A "neated" RT/PCR was established and subsequently used to study on 74 Acute Promyelocytic Leukemia (APL). RESULTS: Two major isoforms (type S and L) were detected in leukemia cells from 44 novel patients with APL. 19 of 44 (43.2%) patients with type S isoforms were accompanied with poor prognosis. 15 cases were detected sequentially by the RT/PCR method for dynamic observation of MSD during postremission therapy with ATRA and chemotherapy alternatly. The positive rate was 46.7% in 6 months after CR, then the positive rate curve tended to down wards gradually from 33.5% (12 months after CR) to 26.7% (24 months after CR), 11.1% (36 months after CR), 8.3% on 48 months after CR. Other 30 cases of APL which are long-term survivals and received the same postremission program were detected by the RT/PCR method. The expression of the fusion gene reversed positivty in two cases on 56 and 60 months respectively, then both relapsed. One case was detected regularly once a year for 3 times. In another case, the fusion gene was detectable whoever was no any abnormal evidence in peripheral blood and bone marrow 26 cases were negative and had a long-term survival CCR of 47-114 months (medium 66). CONCLUSION: The detection of RT/PCR PML-RAR alpha fusion gene plays an important role in clinical diagnosis, evaluation of prognosis and prediction of relapse in APL.

Adolescent↗
PubMed1996

Beta-secretase processing of the beta-amyloid precursor protein in transgenic mice is efficient in neurons but inefficient in astrocytes.

Alzheimer's disease is characterized by the extracellular deposition of beta-amyloid peptide (Abeta) in cerebral plaques and evidence is accumulating that amyloid is neurotoxic. Abeta is derived from the beta-amyloid precursor protein (APP). Proteolytic processing of APP by the enzyme, beta-secretase, produces the N terminus of Abeta, and releases a secreted ectodomain of APP (beta-s-APP). To develop animal models for measuring beta-secretase activity in specific brain cells in vivo, we have targeted the expression of the full-length human APP to either neurons or astrocytes in transgenic mice using the neuron- specific enolase (NSE) promoter or a modified glial fibrillary acidic protein (GFAP) gene, respectively. The APP cDNAs expressed were mutated (KM to NL at 670/671) to encode amino acid substitutions that enhance amyloidogenic processing in vitro. Western analyses revealed abundant production of beta-s-APP in the brains of NSE-APP mice and enzyme-linked immunosorbent assay analyses showed production of Abeta in fetal primary mixed brain cultures and brain homogenates from these transgenic animals. Because the NSE promoter drives expression primarily in neurons, this provides in vivo evidence that the beta-secretase cleavage necessary for generation of beta-s-APP and Abeta is efficiently performed in neurons. In contrast, only little beta-s-APP was detected in brain homogenates of GFAP-APP mice, indicating that astrocytes show very little beta-secretase activity in vivo. This provides strong in vivo evidence that the major source of Abeta in brain is from neurons and not from astrocytes.

Amyloid Precursor Protein Secretases↗
PubMed1996

Abrogation of transforming growth factor-beta type II receptor stimulates embryonic mouse lung branching morphogenesis in culture.

TGF-beta1 is a known inhibitor of branching morphogenesis when added exogenously to mouse embryonic lungs in culture. However, the issue of whether endogenous TGF-beta signaling has a function in the process of lung organogenesis is not completely resolved. We utilized immunoperturbation and antisense oligodeoxynucleotide inhibitory strategies to abrogate TGF-beta type II receptor function in embryonic mouse lungs undergoing branching morphogenesis in serumless explant culture. Antisera directed against a TGF-beta type II receptor N-terminal peptide that perturbs TGF-beta ligand-receptor binding increased branching by 70%. Similarly, antisense TGF-beta type II receptor oligodeoxynucleotides (40 microM) resulted in a 58% increase in branching, compared to scrambled and mismatched sequence controls, while TGF-beta, type II receptor mRNA and its protein expression levels were suppressed by 95 and 84%, respectively. Addition of exogenous TGF-beta1 did not overcome the stimulatory effects either of TGF-beta type II receptor immunoperturbation or of antisense oligodeoxynucleotide treatment on lung branching morphogenesis. Using in situ hybridization and immunohistochemistry, both TGF-beta type II receptor mRNA and protein were localized to the epithelium lining the developing airways, and to the surrounding mesenchyme, indicating that TGF-beta type II receptor is an important regulator of epithelial-mesenchymal interaction. Exogenous TGF-beta1 decreased cyclin A mRNA levels in control embryonic lung explants, while TGF-beta type II receptor antisense oligodeoxynucleotides prevented the downregulation of cyclin A mRNA expression by exogenous TGF-beta1. In addition, PCNA immunostaining of the primitive bronchial epithelium was increased in the presence of TGF-beta type II receptor antisense oligodeoxynucleotides either alone or together with exogenous TGF-beta1, whereas TGF-beta1 alone decreased PCNA staining. Thus, abrogation of TGF-beta type II receptor expression prevented TGF-beta1-induced epithelial cell G1 arrest. These results demonstrate, for the first time, that abrogation of the TGF-beta type II receptor stimulates embryonic lung organogenesis in culture and reverses the negative influence of endogenous TGF-beta signaling upon epithelial cell cycle progression.

Animals↗
PubMed1996

Purification of the Saccharomyces cerevisiae cleavage/polyadenylation factor I. Separation into two components that are required for both cleavage and polyadenylation of mRNA 3' ends.

The cleavage/polyadenylation factor I (CF I) is one of four factors required for mRNA 3' end formation in the yeast Saccharomyces cerevisiae. Here we describe the purification of CF I and its separation into two components, CF IA and CF IB. Both components are needed to reconstitute CF I activity in cleavage and poly(A) addition. CF IA consists of a complex of four polypeptides of 76, 70, 50, and 38 kDa, and CF IB is a single 73-kDa polypeptide. The 76- and 38-kDa subunits of CF IA correspond to the previously identified RNA14 and RNA15 proteins. The RNA14 protein, but not the 70- or 50-kDa proteins, coimmunoprecipitates with the RNA15 protein, indicating that RNA14 and RNA15 proteins exist in a tight complex. RNA15 is the only subunit of CF I that can be cross-linked to pre-mRNA.

Chromatography, Ion Exchange↗
PubMed1996

Elimination of potential sites of glycosylation fails to abrogate complement regulatory function of cell surface CD59.

CD59 is a glycosylphosphatidylinositol-anchored membrane glycoprotein that serves as the principle cellular inhibitor of the C5b-9 membrane attack complex (MAC) of human complement. Approximately 50% of the total apparent mass of CD59 is attributable to glycosylation of a single Asn (Asn18). The deduced amino acid sequences of CD59 homologues identified in Old and New World primates as well as in rat reveal that the motif for N-linked glycosylation at the residue corresponding to Asn18 of human CD59 is invariably conserved, despite considerable sequence divergence elsewhere in the protein. Such conservation suggests that the post-translational modification at Asn18 has importance for either expression or normal function of CD59 at the cell surface. In this study, we specifically examined how deletion or transposition of the site of N-linked glycosylation in the CD59 polypeptide affects its MAC inhibitory function. Our data demonstrate that the inhibitory potency of CD59 is unaffected when glycosylation is transposed from Asn18 to another site in the polypeptide. Furthermore, we show that CD59 retains normal MAC regulatory function when mutated to eliminate all potential sites for N-linked glycosylation. These data suggest that the MAC inhibitory function of CD59 is entirely provided by residues exposed at the surface of the core polypeptide and that this core structure is not influenced by glycosylation at Asn18.

Amino Acid Sequence↗
PubMed1996

Fusion of liposomes due to transient and lasting perturbation induced by synthetic amphiphilic peptides.

The membrane-fusion activities of amphiphilic peptides of H-(Leu-Aib-Lys-Aib-Aib-Lys-Aib)n-Ala-N(C18H37)2 (n = 1, P7D and n = 3, P21D) immobilized on liposome were investigated. P7D, which takes a random conformation, induced fusion of DPPC SUV, but P7D immobilized on the DPPC SUV did not show the fusion activity. On the other hand, P21D showed a high activity of membrane fusion either in the free peptide or in the immobilized state. CF-Leakage experiments revealed that the peptides caused a transient perturbation of the membrane structure on binding to the membrane. A lasting and steady perturbation was also caused by P21D embedded in the membrane, which was indicated by EU3+ permeation through the membrane. This type of membrane perturbation was very slight in the case of P7D embedded in the membrane. A conclusion was reached that the different activities in the membrane fusion are based on the transient perturbation in the membrane at the peptide binding to the membrane surface as well as the steady perturbation caused by the peptide embedded in the membrane.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1996

Receptor affinity of neurotensin message segment immobilized on liposome.

Neurotensin derivatives having a dioctadecyl group were synthesized and immobilized on DMPC liposome to construct a multivalent-ligand system. The derivatives are Ac-Glu[N(C18H37)2]-(Sar-Sar-Pro)n-Arg-Arg-Pro-Tyr-Ile-Leu-OH (D3nNT, n = 0,1,2,3), where a dioctadecyl group was connected to the N-terminal side of neurotensin 8-13 fragment directly or through a hydrophilic and flexible spacer chain of different lengths. The derivatives were spontaneously immobilized on DMPC liposome upon incubation overnight. The receptor affinity of the derivatives increased significantly upon immobilization on liposome. The maximum affinity was obtained by D9NT immobilized on DMPC liposome at the molar ratio of DMPC and D9NT of 200. This affinity is slightly better than the neurotensin 8-13 fragment, the message segment of the derivatives. The fluorescent microscopy using rhodamine-labelled liposome revealed that the multivalent-ligand system binds to specific receptors without dissociation of the derivative from DMPC liposome.

Amino Acid Sequence↗
PubMed1996

p53 binds to a novel recognition sequence in the proximal promoter of the rat muscle creatine kinase gene and activates its transcription.

The rat muscle creatine kinase (CKM) gene promoter is unusual since it is one of the few cellular promoters containing a p53 response element which is located proximally (bp -168 to -57) to the transcription start site. We have previously shown that p53wt transactivates transcription in vivo of rat CKM, in CV-1 monkey kidney cells, through this 112 bp promoter-proximal fragment which contains at least five degenerate p53-binding elements. In this report, we employed the gel-shift assay and demonstrated that recombinant, immunoaffinity-purified mouse p53wt binds to this 112 bp CKM sequence and activates the in vitro transcription of the proximal CKM promoter by nuclear extracts from CV-1 cells. Also, a competitor plasmid containing this 112 bp CKM fragment interferred with the in vivo transactivation of CKM by p53. This CKM fragment, when cloned upstream of the rat brain creatine kinase (CKB) promoter, mediated the p53 transactivation of CKB. Analyses of p53wt and a series of missense mutants (altered in conserved region II of p53) showed that binding of p53 to the CKM promoter was required but was not sufficient for transactivation. The results are discussed in relation to the possible role of p53wt in the expression of CKM in cell types which may not express the myogenic transcription factors.

Animals↗
PubMed1996

Determination of the cannabinoid receptors in mouse x rat hybridoma NG108-15 cells and rat GH4C1 cells.

The cannabinoid receptors expressed in the mouse neuroblastoma X rat glioma NG108-15 cell and the rat pituitary tumor GH4C1 cell were determined by polymerase chain reaction, dideoxysequencing and pharmacologically. The CB1 but not the CB2 or CB1A cannabinoid receptor was found in both cell lines. The cDNA identified in GH4C1 cells corresponds to the rat CB1 receptor. Interestingly, NG108-15 cells express two distinct cDNAs, one corresponds to the rat and the other to the mouse CB1 receptor. The newly developed CB1 receptor selective antagonist SR141716A was found to reverse cannabinoid agonist (WIN55212-2 or CP55940)-induced adenylyl cyclase inhibition. These results provide more direct evidence that the CB1 receptor is mediating the pharmacological actions of cannabinoids in NG108-15 and GH4C1 cells.

Amino Acid Sequence↗
PubMed1996

Electrophysiological properties of morphologically distinct cells isolated from the rabbit atrioventricular node.

1. Experiments were conducted using the whole-cell patch clamp technique to determine the electrophysiological properties and ionic currents of ovoid and rod-shaped single isolated calcium-tolerant rabbit atrioventricular (AV) nodal cells. 2. Action potential morphologies observed in these cells were similar to those obtained previously from intracellular recordings of intact atrioventricular nodal preparations: ovoid cells had N- or NH-like action potential configurations (see below), whereas rod-shaped cells had AN-like configurations. 3. Action potential restitution in AV nodal cells was characterized by a progressive increase in overshoot potential, maximal upstroke velocity (Vmax) and action potential duration, as well as a decrease in latency from stimulus to Vmax. In rod-shaped cells, premature stimuli could induce regenerative membrane responses before full action potential repolarization, whereas ovoid cells showed only post-repolarization refractoriness. In ovoid cells stimulated at the low stimulus intensities there was no shortening of the action potential duration and the most premature action potentials were often prolonged. 4. The quasi-steady-state current-voltage relationship of ovoid cells was significantly steeper, at both depolarized and hyperpolarized potentials, than that of either the rod-shaped AV nodal cells or atrial cells. The rod-shaped AV nodal cells and the atrial cells had similar current-voltage (I-V) relationships in the positive potential range, but the I-V curves crossed over at potentials of about-90 mV. 5. A hyperpolarization-activated inward current (I(f)) was apparent in the range between -60 and -90 mV in 95% of the ovoid cells (n = 75), whereas in 88% of rod-shaped cells (n = 16) I(f) was activated at more negative potentials. The magnitude of I(f) in ovoid cells, measured at -100 mV, was approximately 25 times that in rod-shaped cells. 6. A rapid inward current (INa) greater than 1 nA was found in all rod-shaped cells (n = 16) but in only 30% of ovoid cells (n = 75). A transient outward current (I(to)) was found in 93% of rod-shaped cells (n = 14) and in 42% of ovoid cells (n = 54). The combination of I(to) and INa was found in 93% of rod-shaped cells but in only 24% of ovoid cells. 7. These results suggest that there are at least two populations of isolated AV nodal cells with distinct action potentials and ionic current profiles that may contribute to the complex electrophysiological properties observed in the intact AV node.

Action Potentials↗
PubMed1996

The role of the four Ca2+ binding sites of troponin C in the regulation of skeletal muscle contraction.

In order to study the role of the Ca2+-specific sites (I and II) and the high affinity Ca2+-Mg2+ sites (III and IV) of TnC in the regulation of muscle contraction, we have constructed four mutants and the wild type (WTnC) of chicken skeletal TnC, with inactivated Ca2+ binding sites I and II (TnC1,2-), site III (TnC3-), site IV (TnC4-), and sites III and IV (TnC3,4C-). All Ca2+ binding site mutations were generated by replacing the Asp at the X-coordinating position of the Ca2+ binding loop with Ala. The binding of these mutated proteins to TnC-depleted skinned skeletal muscle fibers was investigated as well as the rate of their dissociation from these fibers. The proteins were also tested for their ability to restore steady state force to TnC-depleted fibers. We found that although the NH2-terminal mutant of TnC (TnC1,2-) bound to the TnC-depleted fibers (with a lower affinity than wild type TnC (WTnC)), it was unable to reactivate Ca2+-dependent force. This supports earlier findings that the low affinity Ca2+ binding sites (I and II) in TnC are responsible for the Ca2+-dependent activation of skeletal muscle contraction. All three COOH-terminal mutants of TnC bound to the TnC-depleted fibers, had different rates of dissociation, and could restore steady state force to the level of unextracted fibers. Although both high affinity Ca2+ binding sites (III and IV) are important for binding to the fibers, site III appears to be the primary determinant for maintaining the structural stability of TnC in the thin filament. Moreover, our results suggest an interaction between the NH2- and COOH-terminal domains of TnC, since alteration of sites I and II lowers the binding affinity of TnC to the fibers, and mutations in sites III and IV affect the Ca2+ sensitivity of force development.

Animals↗