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Biomedical subjects

Y Cheng

Publications and source records attributed to Y Cheng.

At least 163 records · Page 9Linked to original sources
PubMed1998

Two alternatively spliced transcripts from the Drosophila period gene rescue rhythms having different molecular and behavioral characteristics.

The period (per) and timeless (tim) genes encode key components of the circadian oscillator in Drosophila melanogaster. The per gene is thought to encode three transcripts via differential splicing (types A, B, and C) that give rise to three proteins. Since the three per mRNA types were based on the analysis of cDNA clones, we tested whether these mRNA types were present in vivo by RNase protection assays and reverse transcriptase-mediated PCR. The results show that per generates two transcript types that differ only by the presence (type A) or absence (type B') of an alternative intron in the 3' untranslated region. Transgenic flies containing transgenes that produce only type B' transcripts (perB'), type A transcripts (perA), or both transcripts (perG) rescue locomotor activity rhythms with average periods of 24.7, 25.4, and 24.4 h, respectively. Although no appreciable differences in type A and type B' mRNA cycling were observed, a slower accumulation of PER in flies making only type A transcripts suggests that the intron affects the translation of per mRNA.

Alternative Splicing↗
PubMed1998

Voltage-sensitive dye RH421 increases contractility of cardiac muscle.

Voltage-sensitive dyes and imaging techniques have proved to be indispensable tools for use in in vitro electrophysiological studies. To avoid motion artifacts in optical recordings, electromechanical uncouplers such as 2,3-butanedione monoxime (BDM) are required. In this study, we sought to determine whether the voltage-sensitive dye RH421 had an effect on the contractility of heart muscle, either alone or in the presence of BDM. Ventricular contractility was studied in (i) isolated rat myocytes and (ii) Langendorff-perfused rat hearts under control conditions, and during perfusion with RH421 or RH421 + BDM. The following results were obtained. (i) The amplitude of cell shortening increased progressively from 6.24 +/- 0.64 to 9.95 +/- 1.02 microm during 15 min of superfusion with 5 microM RH421 (n = 11), and further increased to 12.54 +/- 0.97 microm during washout. In seven cells first perfused with 15 mM BDM and then with 15 mM BDM + 5 microM RH421, the amplitude of the cell shortening first decreased from 5.17 +/- 0.51 to 0.41 +/- 0.19 microm, then the amplitude increased to 2.63 +/- 0.25 microm. (ii) Left ventricular pressure (LVP) of the heart (n = 7) was reduced by 15 mM BDM from 60.7 +/- 2.5 to 2.8 +/- 0.5 mmHg (1 mmHg = 133.3 Pa). LVP increased to 12.8 +/- 1.1 mmHg during subsequent perfusion with 10 microM RH421 in the presence of BDM and did not change (LVP = 12.4 +/- 2.4 mmHg) during washout of the dye. Therefore, RH421 increased the contractility of rat hearts and isolated myocytes with and without BDM.

Animals↗
PubMed1998

[Histological evaluation of collagen-hydroxyapatite composite as osseous implants in the repair of mandibular defect].

To observe the collagen-hydroxylaptite composite in the repair of bone defect, ten minipigs were chosen to make a mandibular dafect measuring 2 cm in diameter and the composite was implanted, while the use of autogenous bone graft and the blank wese served as control. On the 4, 8, 12, 24 and 48 weeks after the operation, the animals were sacrificed and the samples were examined under light microscope. The result showed that: no infection or necrosis occurred. The composite coalesced with host bone and the outcome was similar to that of the autogenous bone graft. No foreign body giant cells or vacuum left from osteonecrosis was observed. It was suggested that the composite had the advantage of abundant supply, easy to handle and no harm. The biocompatibility was good and might be hopeful as a bone substitute.

Animals↗
PubMed1998

Inhibitory effect of trapidil on proliferation of cultured rat aortic smooth muscle cells induced by endothelin-1.

AIM: To study the effect of trapidil (Tra) on endothelin-1-induced proliferation of cultured rat aortic vascular smooth muscle cells (VSMC). METHODS: The [3H]TdR incorporation into DNA assay, the number of VSMC, and cell cycle distribution were measured. RESULTS: Pretreated with endothelin-1 100 nmol.L-1, cell number, [3H]TdR uptake, and cell mitogenic activity increased 134% +/- 23%, 210% +/- 70%, and 86% +/- 18%, respectively. This proliferation was inhibited by Tra 5, 50, 500 mumol.L-1. The inhibitory rates were 12%-48%, 35%-54% and 15%-47%, respectively. Tra did not influence the proliferation of VSMC without endothelin-1 pretreatment. CONCLUSION: Tra antagonized the proliferation of VSMC induced by endothelin-1.

Animals↗
PubMed1998

[Clinical application of photodynamic therapy combined with non-coherent light (red light) for treatment of port-wine stains].

OBJECTIVE: This is to report the clinical application of photodynamic therapy (PDT) combined with non-coherent light (red light) for the treatment of port wine stains (PWS). METHODS: Eleven cases with PWS have been treated with PDT combined with non-coherent light since Dec. 1995. RESULTS: The facial lesions of PWS in the 11 cases disappeared completely without any scarring. CONCLUSION: PDT combined with red light that has strong skin-penetrating ability and irradiation just after intravenous injection of photosensitizing drugs are effective to embolize the malformative vasculature in pink lesions, especially in dark purple lesions and purple lesions with proliferation.

Adolescent↗
PubMed1998

[Effects of static magnetic fields on free radical metabolism of human body].

The effects of static magnetic fields at 150 to 155 mT on the activities of superoxide dismutase (SOD) and the contents of maglonydiadehyde (MDA) in the serum and the activities of glutathione peroxidase (GSH-Px) in the whole blood were observed in the healthy volunteers. The results showed that the activities of SOD and GSH-Px were significantly increased, and the content of MDA was significantly decreased in short term at the observed magnitude of static magnetic fields. The results suggest that the function of the free radical metabolism of human body could be improved by static magnetic fields at that magnitude.

Adolescent↗
PubMed1998

[Cloning and secretory expression of staphylokinase in Streptomyces lividans].

OBJECTIVE: Construct a recombinant Streptomyces strain by which staphylokinase can be secretory expressed. METHODS: With the total DNA extracted from strains of Staphylococcus aureus isolated in clinic as template DNA, one 730 bp DNA fragment including secretory signal peptide sequence and structure gene of staphylokinase was amplified by PCR. After cloning into plasmid pUC19 and sequencing, this fragment was confirmed to have the same nucleotide sequence as that of staphylokinase gene reported before. Then the fragment was inserted into Streptomyces plasmid pIJ459 following strong promoter. Recombinant plasmid pIJ459SAK was transformed into S. lividans TK54. RESULTS: The 72 hours culture supernatant of the secretory-type genetic engineering strain that harbored pIJ459SAK was analyzed by 15% SDS-PAGE. One specific protein band with molecular weight about 16,000 can be seen after staining the gel with silver nitrate. The fibrinolytic activity of Staphylokinase can be also detected in the 72 hours culture supernatant in the fibrin-plate assay. CONCLUSIONS: Staphylokinase can be successfully secreted into fermentation culture by the recombinant Streptomyces strain.

Cloning, Molecular↗
PubMed1998

[Diagnostic imaging of adhesions of the temporomandibular joint].

OBJECTIVE: To study the image diagnostic criteria of adhesions of the TMJ. METHODS: 26 cases of intra-articular adhesions were collected from 103 cases with internal derangement of TMJ. The clinical examination, arthrographic findings and arthroscopic detections were compared. RESULTS AND CONCLUSION: The arthrographic findings showed that the lack, interruption and irregular joint margins of contrast material appeared in the superior space, the posterior band of disc appeared in the same relative position in both the closed and open views and intra-articular adhesion often associated with anterior disc displacement.

Adolescent↗
PubMed1998

[Forensic clinical identification in medical disputes].

46 cases of medical disputes were analyzed. The causes of medical disputes were analyzed and the features of forensic identification and medical compensation were discussed. Results showed that 37 cases had causality (cause and effect relation) between medical treatment and negative results. It is concluded that forensic medical identification can play an important role in the civil compensation of medical disputes.

Adolescent↗
PubMed1998

[Effects of prion protein on central nervous system and the mechanisms of action].

The following questions are discussed in this paper: (1) Can the bovine prion protein PrpRES infect a man? (2) What is the route of PrPRES infection? (3) In what condition the PrPRES may infect animals, (4) What are the normal functions of PrPc at the surface of neurons and neuroglia cells, (5) What is the structure of the prion protein, (6) What is possible mechanism of the PrPRES destroying neurons. Finally, the two possible mechanisms of the PrPRES to affect central nervous system are analysed. One is to destroy the normal function of the PrPC, the other is to raise the sensibility of the neuron to the free radical and increase the content of the oxygen radical.

Animals↗
PubMed1998

[Cloning and sequencing of fusion protein gene of recombinant GM-HBsAg].

GM-CSF is an effective adjuvant for immunology, it was used to improve the immunological function of antigen and to increase the anti-HBs responses. Through using polymerase chain reaction (PCR) technique, we amplified 384 bp and 846 bp gene fragments from GM-CSF and HBsAg. The products were extracted and purified; a 1230 bp gene fragment was obtained by T4 DNA linkage. This amplified product was cloned into pUC19 vector. The positive clones were screened and the inserted fragment was determined by restriction enzymes. The gene fragment length determined is 1230 bp, the sequence analysis showed that the gene fragment is GM-CSF-HBsAg gene. The successful construction of GM-HBsAg fusion protein gene provides basis for research of its biological activity and expression.

Base Sequence↗
PubMed1997

Control of mouse U1 snRNA gene expression during in vitro differentiation of mouse embryonic stem cells.

Early in mouse development, two classes of U1 RNAs, mU1a and mU1b, are synthesized, but as development proceeds, transcription of the embryo-specific mU1b genes is selectively down-regulated to a barely detectable level. We show here that during in vitro differentiation of mouse embryonic stem (ES) cells, both exogenously introduced and endogenous U1b genes are subject to normal developmental regulation. Thus, ES cells represent a convenient isogenic system for studying the control of expression of developmentally regulated snRNA genes. Using this system, we have identified a region in the proximal 5'flanking region, located outside the PSE element, that is responsible for differential transcription of the mU1a and mU1b genes in both developing cells and transiently transfected NIH 3T3 cells.

3T3 Cells↗
PubMed1997

Equilibrium and non-equilibrium conformations of peptides in lipid bilayers.

A synthetic, hydrophobic, 27-amino-acid-residue peptide 'K27', modelled on the trans-membrane domain of the slow voltage-gated potassium channel, IsK, has been incorporated into a lipid bilayer and its conformational properties studied using FT-IR spectroscopy. The conformation following reconstitution is found to be dependent on the nature of the solvent employed. When the reconstitution is conducted by solvent evaporation from a methanol solution, aggregates comprised of beta-strands are stabilised and their concentration is essentially invariant with time. By contrast, when trifluoroethanol is used, the initial conformation of the peptide is alpha-helical. This then relaxes to an equilibrium state between alpha-helices and beta-strands. The alpha-helix-to beta-strand conversion rate is relatively slow, and this allows the kinetics to be studied by FT-IR spectroscopy. The reverse process is much slower but again can be demonstrated by FT-IR. Thus, it appears that a true equilibrium structure can only be achieved by starting with peptide in the alpha-helical conformation. We believe this result should be of general validity for hydrophobic peptide reconstitution. The implications for conformational changes in membrane proteins are discussed.

Amino Acid Sequence↗
PubMed1997

The Drosophila protein Wunen repels migrating germ cells.

In Drosophila, germ cells migrate in embryonic development from the lumen of the developing gut towards the overlying mesoderm, where they enter the gonads. The gene wunen is responsible for guiding the germ cells early in this process. Here we report that the protein Wunen has two properties that allow it to use repulsion to guide the germ cells. Wunen can transform a permissive cellular environment into a repulsive one, and is expressed in the gut in a pattern that guides germ cells towards the mesoderm. Wunen shows strong similarity to the enzyme type 2 phosphatidic acid phophatase (PAP2)4, suggesting that it is involved in lipid metabolism.

Amino Acid Sequence↗
PubMed1997

Marked age-dependent neuroprotection by brain-derived neurotrophic factor against neonatal hypoxic-ischemic brain injury.

Hypoxic-ischemic brain injury in survivors of perinatal asphyxia is a frequently encountered clinical problem for which there is currently no effective therapy. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), can protect responsive neurons against cell death in some injury paradigms. While the role of BDNF in hypoxic-ischemic brain injury is not clear, evidence suggests that BDNF may have different effects in the developing, as opposed to the adult, brain. We found that a single intracerebroventricular (ICV) injection of BDNF resulted in rapid and robust phosphorylation of trk receptors in multiple brain regions in the postnatal day (PD) 7 rat brain. BDNF also markedly protected against hypoxic-ischemic brain injury at PD7. It protected against 90% of tissue loss due to hypoxic-ischemia when given just prior to the insult and against 50% of tissue loss when give after the insult. In contrast, ICV injection of BDNF in PD21 and adult rats resulted in little trk phosphorylation and less dramatic protection against unilateral hypoxic-ischemic injury at PD21. Because of its potent neuroprotective actions in the developing brain, BDNF may be a potential treatment for asphyxia and other forms of acute injury in the perinatal period.

Age Factors↗
PubMed1997

The use of electron tomography for structural analysis of disordered protein arrays.

A method based on Fourier transforms is described for obtaining a 3-D reconstruction from a paracrystalline object with static disorder. The method is derived from the standard methods used in 3-D reconstruction of 2-D crystals except that all of the Fourier coefficients are used and not just the sampled data from the periodic lattice. Thus, not only is the spatially ordered part of the structure visualized in 3-D, but also the spatially disordered part. Application of the method to 3-D reconstructions Application of the method to 3-D reconstructions of insect flight muscle is described as well as prospects for extension of the method to radiation-sensitive specimens.

Algorithms↗
PubMed1997

Contraceptive practices of women requesting termination of pregnancy: a study from China.

In order to develop a program for prevention of unwanted pregnancies, we conducted a survey of contraceptive practices and reasons for contraceptive failures of 1520 women seeking abortion at eight large hospitals in Zheng Zhou City, Henan Province, P.R. China, during the period from March 1996 to May 1996. The most frequent cause of the unplanned pregnancy was contraceptive failure (71.9%) 61.7% (938) of these current pregnancies were potentially predictable by virtue of nonuse of contraception (427) or by recognition of contraceptive failures (511). Among the contraceptive failures, the proportion of condom mishaps was the highest (29.7%), next was IUD failures (23.5%), then rhythm miscalculation (15.9%). Most of abortion seekers (77.1%) used some contraceptive methods previously. But only 19.7% of them used a contraceptive method at the first sexual intercourse. Among 1520 abortion seekers. 57.6% had used condoms previously; 50.9% of the condom users had at least one instance of condom mishap. The rhythm method had been used by 31.7% of abortion seekers previously; 59.1% of the rhythm users had at least one instance of rhythm failure. Of the 16.8% of abortion seekers who had used pills, 58.0% of them had pill failures Among condom and pill failures, most of them (46.4% condom users and 56.0%, pill users) belonged to the users failure category (poor compliance). Of those seeking abortion 56.4% had experienced at least one instance of previous abortion; 5.3% had experienced previous abortions at least two times. Emergency contraception had been utilized by only 10 subjects prior to this current pregnancy.

Abortion, Induced↗