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Biomedical subjects

Y Xie

Publications and source records attributed to Y Xie.

At least 217 records · Page 12Linked to original sources
PubMed1999

The N-end rule pathway is required for import of histidine in yeast lacking the kinesin-like protein Cin8p.

The N-end rule pathway is a ubiquitin-dependent proteolytic system whose targets include proteins bearing destabilizing N-terminal residues. We carried out a synthetic lethal screen for Saccharomyces cerevisiae mutants that require the N-end rule pathway for cell viability. A mutant thus identified, termed sln2, could not grow in the absence of Ubr1p, the recognition component of the N-end rule pathway, which was not essential for viability of the parental strain under the same conditions. Further analysis showed that inviability of sln2ubr1Delta cells could be rescued either by the HIS3 gene (which was absent from the parental strain) or by a high concentration of histidine in the medium. This defect in histidine uptake, exhibited by the sln2 mutant in the absence but not in the presence of Ubr1p, was traced to the gene HIP1, which encodes the histidine transporter. HIP1 was underexpressed in sln2 ubr1Delta cells, in comparison to either sln2 UBR1 or SLN2 ubr1Delta cells. Yet another property of the sln2 mutant was its inviability at 37 degrees C, which could not be rescued by either UBR1 or HIS3. This feature of sln2 allowed the cloning of SLN2, which was found to be a gene called CIN8, encoding a kinesin-like protein. Thus, either the N-end rule pathway or Cin8p must be present for the viability-sustaining rate of histidine import in S. cerevisiae auxotrophic for histidine. We consider possible mechanisms of this previously unsuspected link between kinesins, ubiquitin-dependent proteolysis, and the import of histidine.

Base Sequence↗
PubMed1999

Methanol-induced unfolding and refolding of cytochrome b5 and its P40V mutant monitored by UV-visible, CD, and fluorescence spectra.

In order to illustrate the structural importance of proline-40 of cytochrome b5 (Cyt b5), the P40V mutant gene was constructed. Unfolding and refolding of Cyt b5 induced by methanol was investigated by means of the UV-visible spectrum, circular dichroism, and the fluorescence spectrum. Methanol denaturation of Cyt b5 is a cooperative process, that is, the heme group dissociates from the heme pocket accompanied by unfolding of the polypeptide chain both in the secondary and tertiary structures. Substitution of proline by valine reduces the stability of the mutant under methanol denaturation. The unfolding process is almost reversible by dilution. During refolding, the denatured polypeptide must be folded to a more ordered structure prior to the heme capture. Pro40 plays an important role in modulating the protein's stability. The role of tyrosine in the unfolding and refolding of Cyt b5 is evaluated for the first time. A mechanism of methanol denaturation is also proposed.

Animals↗
PubMed1999

Activation of heat shock transcription factor 1 to a DNA binding form during the G(1)phase of the cell cycle.

The heat shock transcription factor (HSF) genes encode proteins that bind to the heat shock elements (HSE) of stress-inducible genes. We have observed the induction of HSF1, the ubiquitous member of the HSF family from a latent cytoplasmic state to a form competent to bind HSE during early G(1)in HeLa cells in the absence of stress. The induction of DNA-binding HSF1 coincided with a burst in cellular protein synthesis in early G(1)and inhibition of this translational peak prevented the formation of DNA binding-activated HSF1. A potential role for HSF1 in cell cycle regulation was suggested by the finding that cell lines stably overexpressing HSF1 showed an increased proportion of G(1)cells relative to other cell cycle phases. However, in contrast to the effects of heat shock, entry into G(1)did not lead to HSF1 hyperphosphorylation or increased activity of a heat shock promoter-reporter gene and did not cause the induction of heat shock protein 70 expression. Thus HSF1, previously implicated in the heat shock response is activated to a DNA binding from in G(1)under non-stress conditions and may play a role in G(1)regulation that does not involve the transcription of heat shock genes.

Cycloheximide↗
PubMed1999

Recombinant fusion protein and DNA vaccines against foot and mouth disease virus infection in guinea pig and swine.

In this study, we provide evidence that a recombinant fusion protein containing beta-galactosidase and a tandem repeat peptide of immunogenic dominant epitope of foot-and-mouth disease virus (FMDV) VP1 protein elicits high levels of neutralizing antibody and protects both guinea pigs and swine against infection. Vaccination with this fusion protein induced a FMDV-specific proliferative T-cell response and a neutralizing antibody response. The immunized guinea pigs and swine were protected against FMD type O virus infection. Two DNA plasmids expressing genes of foot-and-mouth disease were constructed. Both plasmids pBO1 and pCO1 contain a signal sequence of the swine immunoglobulin G (IgG) gene and fusion protein gene of pXZ84. The signal sequence and fusion protein gene were under the control of a metallothionein promoter in the case of the pBO1 plasmid and under the control of a cytomegalovirus immediate early promoter in the case of pCO1 plasmid. When pBO1 and pCO1 were inoculated intramuscularly into guinea pigs, both plasmids elicited a neutralizing antibody response and spleen cell proliferation increased following stimulation with FMDV antigen, but animals were not protected from viral challenge.

Animals↗
PubMed1999

Characterization of the repeat-tract instability and mutator phenotypes conferred by a Tn3 insertion in RFC1, the large subunit of the yeast clamp loader.

The RFC1 gene encodes the large subunit of the yeast clamp loader (RFC) that is a component of eukaryotic DNA polymerase holoenzymes. We identified a mutant allele of RFC1 (rfc1::Tn3) from a large collection of Saccharomyces cerevisiae mutants that were inviable when present in a rad52 null mutation background. Analysis of rfc1::Tn3 strains indicated that they displayed both a mutator and repeat-tract instability phenotype. Strains bearing this allele were characterized in combination with mismatch repair (msh2Delta, pms1Delta), double-strand break repair (rad52), and DNA replication (pol3-01, pol30-52, rth1Delta/rad27Delta) mutations in both forward mutation and repeat-tract instability assays. This analysis indicated that the rfc1::Tn3 allele displays synthetic lethality with pol30, pol3, and rad27 mutations. Measurement of forward mutation frequencies in msh2Delta rfc1:Tn3 and pms1Delta rfc1:Tn3 strains indicated that the rfc1::Tn3 mutant displayed a mutation frequency that appeared nearly multiplicative with the mutation frequency exhibited by mismatch-repair mutants. In repeat-tract instability assays, however, the rfc1::Tn3 mutant displayed a tract instability phenotype that appeared epistatic to the phenotype displayed by mismatch-repair mutants. From these data we propose that defects in clamp loader function result in DNA replication errors, a subset of which are acted upon by the mismatch-repair system.

Cell Cycle Proteins↗
PubMed1999

Palliative treatment of epidemic Kaposi sarcoma of the feet.

Limited information is available in the medical literature on epidemic Kaposi sarcoma (EKS) of the foot. Patients with EKS of the foot can experience severe discomfort that makes it difficult to ambulate and even wear shoes. Between 1985 and 1996, 36 patients with EKS of the foot were treated with palliative intent. Most patients were referred for radiation therapy because of foot discomfort or marked difficulty with ambulation. From the pool of 36 patients, data were available at completion of treatment for 46 sites, and at 1 month for 44 sites. Morbidity was assessed for 35 sites. The median follow-up time for the 44 sites with at least 1 month follow-up was 8 months. The most frequently used regimen was a novel fractionation schedule of three fractions a week at 3.5 Gy/fx to a total dose of 21.0 Gy. The overall response rate and complete response rate for the 44 sites with at least 1 month follow-up were 91% and 80%, respectively. The 46 treated sites evaluated at the completion of treatment had a complete response rate of only 13% and an overall response rate of 63%. Of the 35 sites assessed for acute toxicity, 63% experienced discomfort related to the radiation therapy. This discomfort usually resolved without intervention within 2 weeks of completion of radiation therapy. For patients with and without a history of opportunistic infections, complete responses were observed in 8 of 12 sites (67%) and 25 of 27 sites (93%), respectively (p = 0.06). Radiation therapy for EKS of the foot yields excellent response rates, comparable with responses seen in other cutaneous sites with EKS. Appropriate patient education and support are needed because initial responses to radiation therapy are often disappointing and pedal discomfort can be exacerbated transiently. However, the discomfort resolves and complete response occurs in most patients. The 3.5-Gy triweekly fractionation schedule is a convenient and effective regimen and minimizes treatment visits for patients with ambulatory discomfort. A history of opportunistic infections appears to be a poor prognosticator of response to radiation treatments.

Adult↗
PubMed1999

Removal of strontium by the chelating agent acetylamino propylidene diphosphonic acid in rats.

Studies of the effects of the chelating agent, calcium acetylamino propylidene diphosphonic acid (Ca-APDA), on the removal of radioactive strontium with two administration modalities were carried out in rats. The parenteral (intraperitoneal) administration of 150, 300, or 600 mg kg(-1) Ca-APDA was carried out for 3 d, 10 min after exposure of the animals to the strontium injection. On the first day post-treatment, the retention of strontium in the whole body decreased to 90.1%, 83.9%, and 35.1% that of the control level, respectively. The strontium deposited in femur of 600 mg kg(-1) Ca-APDA group was lowered to 28.4% of the control value. A single oral dose of 600 mg kg(-1) Ca-APDA administered simultaneously with, or 10 min after, oral administration of strontium, radionuclide retention in the whole body was reduced after 1 d to 42.9% and 31.9% of the control, respectively; meanwhile the strontium deposited in the femur was reduced to 16.9% and 29.3% of the control. In conclusion, the results indicate the efficacy of the new agent, Ca-APDA, to remove radioactive strontium from the body, or to inhibit the strontium intestinal absorption, in radio-strontium contaminated individuals.

Administration, Oral↗
PubMed1999

Small-angle x-ray scattering study of kinetics of spinodal decomposition in N-isopropylacrylamide gels.

We present synchrotron-based time-resolved small-angle x-ray scattering (SAXS) measurements of spinodal decomposition in a covalently cross-linked N-isopropylacrylamide gel. The range of wave numbers examined is well beyond the position of the maximum in the structure factor S(q,t). The equilibrium structure factor is described by the sum of a Lorentzian and a Gaussian. Following a temperature jump into the two phase region, the scattered intensity increases with time and eventually saturates. For early times the linear Cahn-Hilliard-Cook (CHC) theory can be used to describe the time evolution of the scattered intensity. From this analysis we found that the growth rate R(q) is linearly dependent on q(2), in agreement with mean-field theoretical predictions. However the Onsager transport coefficient Lambda(q) approximately q(-4), which is stronger than the q dependence predicted by the mean-field theory. We found that the growth rate R(q)>0, even though the wave numbers q probed by SAXS are greater than sqrt[2]q(m) where q(m) is the position of the peak of S(q,t), also in agreement with the mean-field predictions for a deep quench. We have also examined the range of validity of the linear CHC theory, and found that its breakdown occurs earlier at higher wave numbers. At later times, a pinning of the structure was observed. The relaxation to a final, microphase-separated morphology is faster and occurs earlier at the highest wave numbers, which probe length scales comparable to the average distance between crosslinks.

Journal Article↗
PubMed1999

The steroid promegestone is a noncompetitive antagonist of the Torpedo nicotinic acetylcholine receptor that interacts with the lipid-protein interface.

17,21-Dimethyl-19-nor-pregn-4,9-diene-3,20-dione (promegestone) was used to characterize the mechanism of inhibition of nicotinic acetylcholine (ACh) receptors (AChR) by progestin steroids. Promegestone reversibly inhibited ACh-induced currents of Torpedo AChRs expressed in Xenopus oocytes. Between 1-30 microM promegestone produced a concentration-dependent enhancement of the equilibrium binding affinity of [3H]ACh to Torpedo AChR-rich membranes. For AChRs in the presence of agonist (desensitized state) promegestone was a more potent inhibitor of the binding of the noncompetitive antagonist [3H]phencyclidine (IC50 = 9 microM) than of [3H]histrionicotoxin (IC50 approximately 100 microM). To identify AChR domains in contact with the steroid, AChR-rich membranes equilibrated with [3H]promegestone were irradiated at 312 nm, and 3H-labeled amino acids were identified by amino-terminal sequencing of fragments isolated from subunit proteolytic digests. Within AChR alpha-subunit, 70% of 3H was covalently incorporated in a 10-kDa fragment beginning at Asn-339 and containing the M4 membrane spanning segment, and 30% was in a 20-kDa fragment beginning at Ser-173 and containing the M1-M3 segments. Fragments containing the M2 channel domains as well as the M4 segments were isolated from proteolytic digests of AChR subunits and subjected to amino-terminal sequence analysis. No evidence of [3H]promegestone incorporation was detected in any of the M2 segments. The amino acids in the M4 segments labeled by [3H]promegestone were among those previously shown to be in contact with the lipid bilayer (). These results indicate that the steroid promegestone is an AChR noncompetitive antagonist that may alter AChR function by interactions at the lipid-protein interface.

Acetylcholine↗
PubMed1999

A comparative study on the treatment of migraine headache with combined distant and local acupuncture points versus conventional drug therapy.

UNLABELLED: According to Chinese medicine, the differential diagnosis of migraine headache may be classified based on the state of the viscera, channels and collaterals. In this study, acupuncture treatment prescriptions combining distant and local acupoints were selected according to the differential diagnosis. Sixty-four patients were divided into two equal groups: one group received acupuncture, and the other group underwent conventional drug treatment. RESULTS: The efficacy rates in the acupuncture and control groups were as follows, respectively: Cure: 75% versus 34.4%, marked improvement: 18.8% versus 28.1%, no effect: 6.3% versus 37.5%. The overall effective rates for the acupuncture and control groups were 93.8% and 62.5%, respectively, indicating a significantly greater effect in the acupuncture group (P < 0.01, x = 13.475).

Acupuncture Therapy↗
PubMed1999

[A nasopharyngeal carcinoma negatively related EST on 7q32].

To isolate and clone the tumor suppressor gene on chromosomal region 7q32 that corelated with the occurrence of human NPC, we detected the genotype of polymorphic microsatellite markers on 7q32 in 24 nasopharyngeal carcinoma biopsies and matched normal lymphocyte DNA. LOH was found in 30% biopsies. Using differential RT-PCR and Northern hybridization we compared the expression level of 20 EST on 7q32 between NPC cell line HNE1 and primary culture of normal nasopharyngeal epithelial cell, and found AA070437 EST expressed high in primary culture of normal nasopharyngeal epithelial cell, but very low in HNE1. Differential RT-PCR (dRT-PCR) analysis showed that the expression level of AA070437 was lower in 30.7% NPC biopses than in normal cell. Differential PCR (dPCR) showed that allelic loss of AA070437 was observed in 29.1% NPC biopses. This EST is a part of sequence of a new gene compared with GeneBank database. Our results showed that AA070437 EST negatively related with the occurrence of human NPC is a candidate of tumor suppressor gene of NPC on 7q32.

Base Sequence↗
PubMed1999

Efficacy of adenovirus-mediated CD/5-FC and HSV-1 thymidine kinase/ganciclovir suicide gene therapies concomitant with p53 gene therapy.

Recent evidence has suggested that tumor cells having a wild-type p53 status are more sensitive to chemotherapeutic agents and radiation than cells that lack functional p53. The heightened sensitivity of wild-type p53 cells is thought to be attributable to their propensity to undergo p53-mediated apoptosis after insult. Given that suicide gene therapy is essentially tumor-targeted chemotherapy, we examined the hypothesis that coexpression of wild-type p53 could enhance the efficacy of adenovirus-mediated suicide gene therapy. Human Hep3B and SK-OV-3 cells, which are null for p53, were infected with a pair of replication-deficient adenoviruses that expressed a cytosine deaminase/herpes simplex virus thymidine kinase (CD/HSV-1 TK) fusion gene without (fusion gene nonreplicative adenovirus, FGNR) or with (FGNRp53) the wild-type human p53 gene. The sensitivity of cells to the CD/5-fluorocytosine (CD/5-FC) and HSV-1 TK/ ganciclovir (GCV) enzyme/prodrug systems was determined in vitro and in vivo. Coexpression of p53 did not enhance the cytotoxicity of either the CD/5-FC or HSV-1 TK/GCV system in vitro. The failure to observe an effect of p53 could not be explained on the basis of insufficient or transient p53 expression, because FGNRp53-infected cells growth arrested in G1, induced Bax, and underwent apoptosis at an increased rate after prodrug treatment, particularly when the adenovirus E1A protein was present. Intratumoral injection of FGNRp53 concomitant with single or double pro-drug therapy resulted in a tumor growth delay that was equal to or less than that observed with the FGNR virus. Our results indicate that coexpression of p53 may not necessarily improve the efficacy of adenovirus-mediated CD/ 5-FC and HSV-1 TK/GCV suicide gene therapies in vivo.

Adenoviridae↗
PubMed1999

Expression of Bcl-2 family proteins during chemotherapeutic agents-induced apoptosis in the hepatoblastoma HepG2 cell line.

This study demonstrates that two anticancer drugs, taxol and doxorubicin (Dox), can kill human hepatoblastoma HepG2 cells in a dose-dependent manner via the induction of apoptosis. Characteristic events, including externalization of phosphatidylserine, cytoplasmic shrinkage, chromatin condensation and DNA degradation, were observed in a large majority of the drug-treated cells. DNA fragmentation showed that a ladder of DNA fragments of approximately 200 bp multiples was observed in taxol-treated, but not in Dox-treated, cells. In addition, the expression patterns of Bcl-2 family members during taxol or Dox treatment were investigated. Results from Western blot analysis indicated that HepG2 cells did not express either the death repressor Bcl-2, or the death promoters Bcl-XS and Bax. However, during the apoptotic process one death repressor, Bcl-XL, and two death promoters, Bak and Bad, were expressed. The expression levels of Bcl-XL and Bak remained unchanged, whereas the level of Bad was down-regulated. As the ratio between death repressors and death promoters in the Bcl-2 family will determine the sensitivity of cells to apoptotic stimuli, the findings suggest that the changed expression patterns of Bcl-2 family proteins caused by anticancer drugs in liver cancer cells may be involved in chemoresistance.

Antineoplastic Agents↗
PubMed1999

[Anatomical basis for the newly developed facelifting].

OBJECTIVE: To investigate the relationship between the SMAS and the facial nerve divisions in the cheek area. METHOD: We dissected 12 cadaver heads(24 sides). RESULTS: 1. SMAS distributed over the middle face. It became thinner as it extended forward and there was a small aperture lateral to the mouth. The branches of facial nerve lay directly beneath the parotidomassetric fascia after emerging from the parotid gland. 2. The frontal branch penetrated the deep fascia to the SMAS at about 0.5 cm below the zygomatic arch. 3. Some buccal branches went through the cheek fat pad while the others lay on its surface directly under the thin SMAS. 4. There was constantly a zygomatic ramus went into the upper one third of the zygomaticus. It innervated the lower and lateral orbicularis oculi muscle in 9 of 24 sides (37.5%) of the cadaver heads, zygomaticus major and minor and orbicularis oculi muscle in 8 of 24 sides (33.3%), and the zygomaticus major and minor in 7 of 24 sides (29.2%). CONCLUSION: During facelifting, wide dissection of the SMAS should be done directly above the parotidomassetric fascia and 0.5 cm below the zygomatic arch. While approaching the middle face, the dissection should be limited to the lower two third of the zygomaticus, followed by elevating the zygomatic fat. The authors dissect the nasolabial fold through the lower eyelid incision, then the dissection should go downwards, under the orbicularis oculi muscle, to the nasolabial area. In a clinical situation, care must be taken not to damage the facial nerve trunk, and dissection of the upper one third of the zygomaticus should be avoided.

Adult↗
PubMed1999

[The distribution of the frontal branch of the facial nerve and its significance in facelift].

OBJECTIVE: To further understand the distribution and course of the frontal branch of the facial nerve in the temporal and zygomatic areas. METHODS: Facial dissection was performed on 9 cadaver heads(18 sides). RESULTS: It was found that the frontal of the facial nerve had 3 to 7 divisions (average 5) instead of one. The divisions of the frontal branch showed no constant course and distributed nearly all over the zygomatic arch. We divided the zygomatic arch into 3 equal parts and found that the middle third had the highest density of the branch distribution, accounting for 44.44% of the total divisions; the anterior third and the lateral third possessed 38.89% and 16.66% of the total divisions respectively. These divisions entered deeply into the temporoparietal fascia(the superficial temporal fascia). The divisions in the anterior third of the zygomatic arch innervate the lower and lateral orbicularis oculi muscle; the divisions in the middle third innervate the lateral orbicularis oculi muscle and the frontal muscle; the divisions in the lateral third innervate the frontal muscle and the anterior auricularis. CONCLUSION: We recommend discriminating the layers of the soft tissue over the zygomatic arch, not limiting the dissection range of the zygomatic arch to avoid damaging the nerve divisions while doing subperiosteal dissection of the zygomatic arch in facelifting.

Adult↗
PubMed1999

[Ethanol-induced gastric mucosal injury and the protection of taurine against the injury in rats].

40 SD rats were randomly divided into control group, ethanol-induced injury group and taurine protective group for the measurement of the contents of endothelin (ET), nitric oxide synthetase (NOS), somatostatin (SS) and vasoactive intestinal peptide (VIP). The results are as follows. The gastric mucosa was damaged by 75% ethanol, being aggravated with prolonged application time, as shown by a significant increase of the ET content and decreases of the contents of NOS, VIP and SS in the gastric mucosa. In the taurine group, decrease of ET content and increase of the contents of NOS, SS and VIP in the gastric mucosa were observed. Apparently, the changes in ET, NOS, SS and VIP contents of gastric mucosa serve as reliable indices in the pathogenesis by ethanol and protective effect by taurine.

Animals↗
PubMed1999

[Vascular endothelial growth factor in non-small cell lung carcinoma expression and its significance].

OBJECTIVE: To clarify the relationship between the expression of vascular endothelial growth factor (VEGF) and the angiogenesis, invasion, prognostic value in non-small cell lung cancer. METHODS: Immunohistochemistry. RESULTS: 53 patients with NSCLC after radical resection were evaluated. A significantly higher microvessel density (MVD) was observed in the tumors with high expression of VEGF compared with that of the low expression (P < 0.001). 29 patients (80%, 29/33) with the high expression of VEGF showed lymph node metastasis and 4 patients (27%, 4/15) unlymph node metastasis (P < 0.001). By Cox's proportional hazard model analysis, the expression of VEGF was considered an independent predictor for the prognosis of NSCLC. CONCLUSIONS: The expression of VEGF has a significant correlation among MVD, growth, invasion, and lymph node metastasis. The patient with the tumor of the higher expression of VEGF and MVD may have poor prognosis. VEGF may be an independent predictor of prognosis.

Adenocarcinoma↗