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Biomedical subjects

Y Gu

Publications and source records attributed to Y Gu.

At least 253 records · Page 14Linked to original sources
PubMed1997

[Injury effects of nicotine on isolated rat common carotid artery].

OBJECTIVES: To investigate the injured effects of nicotine on isolated rat common carotid artery and to supply experimental proofs for vascular vessel and organ transplantation. METHODS: Asins relaxing and contractile functional test of isolated vascular vessel and scanning electron microscopy techniques, we observed the influence of nicotine on the contractile and the relaxing function of isolated artery and the intact of the intima. RESULTS: Lower concentrations of nicotine (6 x-10 mol/L-6 x 10(-6) mol/L) produced a concentration-dependent constrictor response of 18%-41% relative to those induced by norepinephrine (NE, 10(-7) mol/L), whereas removal of endothelium reduced nicotine-induced constrictions to 5%-21%. Higher concentrations of nicotine (6 x 10(-5) mol/L-6 x 10(-3) mol/L) not only injured contractile function of vascular smooth muscle but also caused severe damage to the intima. Various concentrations of nicotine all inhibited acetylcholine-induced relaxation response. CONCLUSIONS: Nicotine not only has cytotoxicity to vascular vessel but also results in vasoconstrictor effects which depend upon endothelium intact, probably by inhibiting the release of endothelium-derived relaxing factor.

Animals↗
PubMed1997

[Immunohistochemical study on myoglobin in electrocution].

We have studied the changes of myoglobin (MB) IN heart muscle cells from eight corpses died of electrocution. The changes were compared with that of the heart muscle cells died of fall. The results indicated that the immunohistochemical changes of Mb were as follows: (1) blocky separate from heart muscle cell; (2) drift away into the interval of the heart muscle. The Mb changes were small parts of an area separate from heart muscle cells in control. The authors emphasized these changes were the characteristics of oxygen deficiency of the heart by electrocution.

Adolescent↗
PubMed1997

[Effects of electric fields on the cellular structure of the regenerated nerve].

Eighty adult SD rats were randomly divided into four groups of 20 each: 1. local electrostimulation of nerve stump (Group LS); 2. electrostimulation of myeloneure (Group N); 3. electrostimulation of the denervated muscle (Group M); and 4. Control (Group C). 5 millimeters of the left sciatic nerve of the rat was excised and the severed nerve was bridged with a silicon tube. The gap between the stumps was about 10 millimeters. On the 3rd day and the 1st, 2nd, 3rd, 4th week after surgery, samples were taken and processed for microscopic examinations to observe the effects of electric fields on cellular structural development of regenerated axons, especially on the proliferation and migration of Schwann's cell and fibroblasts, etc. The number of the axon and capillary, the degree of axon maturity and myelinated axon proportion were also observed. The results showed that electrostimulation enhanced nerve regeneration by, 1. promoting the form of matrix bridge; 2. stimulating Schwann's cell and fibroblast migration and proliferation; 3. promoting vascularization of regenerating nerves; and 4. direct electrophoretic effects on structural protein of growth cone.

Animals↗
PubMed1997

[Clinical significance of changes of fibrillation potential amplitude following denervation of human skeletal muscle].

To evaluate the value of clinical application of examination of fibrillation potential amplitude, 110 patients, 97 males and 13 females, were examined and only the maximum fibrillation potential amplitudes were recorded in 420 muscles. The results showed that there was no significant difference between sexes, ages and sides. However, significant difference was evident between the groups of different frequency (1+ to 4+). The fibrillation potential amplitude was maximum at 3 to 4 months after denervation and still remained at relatively high level for years in certain patients. No significant difference was showed between the time groups in incomplete nerve injuries. Surgery did not affect the course of fibrillation potential amplitude change. It was suggested that the muscle cells sustained their property for years after denervation in some patients, thus it might explain that satisfactory result could be obtained from operative repair in some late cases. The changes of fibrillation potential amplitude might indicate that the changes from muscle denervation was still reversible and might be more accurate than traditional method of examination.

Action Potentials↗
PubMed1997

[Intraoperative extra strong electrical stimulation in the treatment of peripheral nerve injury].

In order to enhance the therapeutic effectiveness of peripheral nerve injury, intraoperative extrastrong electrical stimulation was used in peripheral nerve surgery. In 16 cases of incomplete peripheral rnerve injuries or poorly regeneratedn erves, continuous intraoperative electrophysiological monitoring was used for guidance of neurolysis. Meanwhile, extrastong electrical stimulation was applied. The latency and amplitude before and after electrical stimulation were recorded and the extent of improrement was compared. In all cases, the latency and amplitude were improved after neurolysis and electrical stimulation. Clinical follow-up also showed that the function of corresponding innorvated muscle was improved. Continuous intraoperative extrastrong electrical stimulation could be used as an practical measure to increase the effectiveness of peripheral nerve treatment.

Adolescent↗
PubMed1996

Processing and activation of CMH-1 by granzyme B.

Granzyme B plays an essential role in cytotoxic T lymphocyte (CTL)-mediated cell killing. Recent studies suggest that granzyme B may exert its effect by cleaving and activating CPP32, a member of the interleukin-1 beta-converting enzyme/Ced-3 family of cysteine proteases. We have examined the processing and activation of CMH-1, a close homologue of CPP32, by granzyme B in vitro. We have found that granzyme B specifically cleaves CMH-1 at Asp198-Ser199 between the p20 and p12 and activates the cysteine protease. Cleavage between p20 and the prosequence of CMH-1 at Asp23-Ala24 is autocatalytic and is not required for CMH-1 activity in vitro. The cleavage and activation of CMH-1 by granzyme B in vitro sugge st that, in addition to CPP32, CMH-1 may also play a role in CTL-mediated cell killing.

Amino Acid Sequence↗
PubMed1996

Crystallization and preliminary X-ray diffraction studies of recombinant staphylokinase.

Staphylokinase, a fibrin-specific plasminogen activator, was highly expressed in Escherichia coli and purified by ion-exchange and gel-filtration chromatography. The purified recombinant staphylokinase was fully active and readily crystallized against 1.2 M sodium citrate in 100 mM Tris-HCl buffer at pH 8.0 using the hanging-drop method. Crystals of staphylokinase diffract to better than 2.2 A resolution. The crystal belongs to the tetragonal space group P4(1)2(1)2 or its enantiomorph with unit-cell parameters a = b = 67.5, c = 150.1 A. There are two molecules in the asymmetric unit. In this paper, we described the first crystallization of a kind of plasminogen activator and present the results of preliminary X-ray diffraction data from the native protein.

Journal Article↗
PubMed1996

Identification and characterization of CPP32/Mch2 homolog 1, a novel cysteine protease similar to CPP32.

We have identified and characterized a novel cysteine protease named CMH-1 that is a new member of the interleukin 1 beta converting enzyme (ICE) family of proteases with substrate specificity for Asp-X. CMH-1 has the highest similarity to CPP32 (52% amino acid identity) and MCH2 (31% identical). CMH-1 shares conserved amino acid residues that form the core structure of ICE as well as those residues involved in catalysis and in the P1 aspartate binding. Overexpression of CMH-1 in COS cells resulted in the processing of CMH-1 and the induction of apoptosis of transfected cells. Coexpression of CMH-1 with poly(ADP-ribose) polymerase (PARP) also resulted in a specific cleavage of PARP. Purified recombinant CMH-1 cleaved PARP but not interleukin 1 beta precursor in vitro.

Amino Acid Sequence↗
PubMed1996

Identification of FMR2, a novel gene associated with the FRAXE CCG repeat and CpG island.

Five folate-sensitive fragile sites have been identified at the molecular level to date. Each is characterized by an expanded and methylated trinucleotide repeat CGG (CCG). Of the three X chromosome sites, FRAXA, FRAXE and FRAXF, the former two are associated with mental retardation in their expanded forms. FRAXA expansion results in fragile X syndrome due to down regulation of expression of the FMR1 gene, which carries the hypermutable CGG repeat in the 5' untranslated portion of its first exon. Mild mental retardation without consistent physical findings has been found associated with expanded CCG repeats at FRAXE. We have identified a large gene (FMR2) transcribed distally from the CpG island at FRAXE, and down-regulated by repeat expansion and methylation. The gene is novel, expressed in adult brain and placenta, and shows similarity with another human protein, MLLT2, expressed from a gene at chromosome 4q21 involved in translocations found in acute lymphoblastic leukaemia (ALL) cells. Identification of this gene will facilitate further studies to determine the role of its product in FRAXE associated mental deficiency.

Adult↗
PubMed1996

Susceptible chiasmate configurations of chromosome 21 predispose to non-disjunction in both maternal meiosis I and meiosis II.

The cause of non-disjunction of chromosome 21 remains largely unknown. Advanced maternal age is associated with both maternal meiosis I (MI) and meiosis II (MII) non-disjunction events. While reduced genetic recombination has been demonstrated in maternal MI errors, the basis for MII errors remains uncertain. We studied 133 trisomy 21 cases with maternal MII errors to test the hypothesis that segregation at MII may also be influenced by genetic recombination. Our data support a highly significant association: MII non-disjunction involves increased recombination that is largely restricted to proximal 21q. Thus, while absence of a proximal recombination appears to predispose to non-disjunction in MI, the presence of a proximal exchange predisposes to non-disjunction in MII. These findings profoundly affect our understanding of trisomy 21 as they suggest that virtually all maternal non-disjunction results from events occurring in meiosis I.

Adult↗
PubMed1996

Tau is widely expressed in rat tissues.

The microtubule-associated protein tau, a major component of paired helical filaments in Alzheimer's disease, had been thought to be a neuron-specific protein. We investigated various rat tissues using both reverse transcriptase-coupled polymerase chain reaction and immunoblotting. tau was found to be widely expressed in many tissues besides the nervous system: at relatively high levels in the heart, skeletal muscle, lung, kidney, and testis and at low levels in the adrenal gland, stomach, and liver. In terms of the tau isoform expression, tissues fall into three classes: those expressing predominantly small tau, those expressing predominantly big tau, and those expressing both at comparable levels. The phosphorylation state of tau varied among the tissues, as shown by differences in the extents of changes in the reactivities with Tau 1 and electrophoretic mobilities after dephosphorylation. It is notable that tau in many nonneural tissues was highly phosphorylated at Ser396 (according to the numbering of the 441-residue human tau isoform). Thus, tau is widely expressed in rat tissues.

Animals↗
PubMed1996

Role of inhibitory CDC2 phosphorylation in radiation-induced G2 arrest in human cells.

The activity of the mitosis-promoting kinase CDC2-cyclin B is normally suppressed in S phase and G2 by inhibitory phosphorylation at Thr14 and Tyr15. This work explores the possibility that these phosphorylations are responsible for the G2 arrest that occurs in human cells after DNA damage. HeLa cell lines were established in which CDC2AF, a mutant that cannot be phosphorylated at Thr14 and Tyr15, was expressed from a tetracycline-repressible promoter. Expression of CDC2AF did not induce mitotic events in cells arrested at the beginning of S phase with DNA synthesis inhibitors, but induced low levels of premature chromatin condensation in cells progressing through S phase and G2. Expression of CDC2AF greatly reduced the G2 delay that resulted when cells were X-irradiated in S phase. However, a significant G2 delay was still observed and was accompanied by high CDC2-associated kinase activity. Expression of wild-type CDC2, or the related kinase CDK2AF, had no effect on the radiation-induced delay. Thus, inhibitory phosphorylation of CDC2, as well as additional undefined mechanisms, delay mitosis after DNA damage.

CDC2 Protein Kinase↗
PubMed1996

Human endometrial expression of granulocyte colony-stimulating factor (G-CSF) and its receptor, stimulation of endometrial G-CSF production by interleukin-1 beta, and G-CSF inhibition of choriocarcinoma cell proliferation.

PROBLEM: To investigate the expression, regulation thereof, and actions of human endometrial granulocyte colony-stimulating factor (G-CSF). METHODS: Endometrial expression of messenger ribonucleic acids for G-CSF and its receptor were studied using reverse transcriptase-polymerase chain reaction. In tissue culture, endometrial G-CSF protein production, baseline and in response to interleukin-1 beta, was determined by enzyme-linked immunosorbant assay of the conditioned media. G-CSF effects on proliferation of three choriocarcinoma cell lines were determined. RESULTS: In vivo, human endometrium expressed messenger ribonucleic acids for G-CSF and its receptor throughout the menstrual cycle, and endometrium expressed G-CSF protein in vitro. Interleukin-1 beta stimulated endometrial G-CSF protein production in time and dose dependent manners. G-CSF inhibited proliferation of two choriocarcinoma cell lines. CONCLUSIONS: These results suggest that 1) G-CSF may have physiologic roles in the endometrium throughout the menstrual cycle; 2) endometrial G-CSF protein production is stimulated by interleukin-1 beta; and 3) that G-CSF may, in part, mediate local actions of interleukin-1 beta and modulate trophoblast proliferation.

Adult↗
PubMed1996

Host DNA can interfere with detection of Borrelia burgdorferi in skin biopsy specimens by PCR.

It is demonstrated that a diagnostic PCR for Borrelia burgdorferi can be inhibited in the presence of more than 500 ng of host (monkey skin) DNA. The inhibitor is the host DNA itself. An acceptable value for analytical sensitivity can be obtained by diluting the skin-B. burgdorferi proteinase K lysate to a level below the inhibitory concentration of the host DNA. Dilution of the lysate may obviate the need for further DNA purification.

Animals↗
PubMed1996

The decidual prolactin receptor and its regulation by decidua-derived factors.

Decidualization of the endometrial stroma in the rat gives rise to two different cell populations, located either mesometrially or antimesometrially in the uterus. We have previously shown that the rat decidua is the site of production and action of a PRL-like hormone. In this investigation we examined, using reverse transcription-PCR, whether and which type of PRL receptor (PRL-R) messenger RNA (mRNA) is expressed in the decidua, whether the receptor is confined only to one cell population, and whether the PRL-R expression is regulated by decidua-derived factors. The results indicate that the uterus of pseudopregnant rats does not express the PRL-R and that decidualization does not trigger a rapid appearance of PRL-R mRNA. It is only 3 days after the induction of decidualization that the long form of the PRL-R was first expressed. Thereafter, mRNAs for both the short (PRL-RS) and the long (PRL-RL) form became detectable in both antimesometrial and mesometrial decidua, although PRL-RL mRNA was much more abundant than PRL-RS. As development proceeded, PRL-R mRNA decreased and disappeared specifically from the antimesometrial decidua, whereas the mesometrial decidua continued to express this receptor mRNA. Concomitant with down-regulation of the PRL-R in the antimesometrial tissue was a rather abrupt expression of activin A. In contrast, the mesometrial tissue that maintained high levels of PRL-R mRNA expressed little activin A, but produced an activin-binding protein, alpha(2)-macroglobulin (alpha(2)MG). To determine whether activin A and alpha(2)MG regulate PRL-R expression, antimesometrial and mesometrial cells were separated by elutriation and maintained in culture in the presence or absence of activin A, alpha(2)MG, or follistatin. Just after cell separation, both cell populations expressed PRL-R, but not activin A. Within 6 h, activin A mRNA and protein became highly expressed in the mesometrial cells, whereas PRL-RL mRNA became undetectable. In contrast, activin A mRNA was at very low levels in the antimesometrial cells, and no activin A protein could be detected in the medium for at least 12 h. In these cells PRL-RL mRNA remained elevated. Addition of activin A to antimesometrial cells caused a marked down-regulation of PRL-RL mRNA expression, whereas addition of alpha(2)MG and follistatin to mesometrial cells prevented the disappearance of PRL-R. In summary, the results of this investigation 1) indicate that decidualization of the endometrial stroma induces the appearance of both forms of the PRL-R mRNAs; 2) show differential expression of the PRL-R mRNA in the two-cell population forming the decidua; 3) establish that this differential expression is due to two key decidual molecules, activin A and alpha(2) macroglobulin; and 4) demonstrate that activin A can cause the decidual cells to lose the PRL-R and that the disappearance of the decidual PRL-R can be prevented by addition to the culture of two activin binding proteins, follistatin and alpha(2) MG.

Activins↗