Biomedical subjects

D Xie

Publications and source records attributed to D Xie.

At least 55 records · Page 3Linked to original sources

PubMed2000

[Precise map of allelic loss on chromosome 3p14 in nasopharyngeal carcinoma].

OBJECTIVE: To determine the precise allelic loss on chromosome 3p14 and discuss the possible relations between loss of heterozygosity (LOH) and EBV infection, clinical stage and clinic-pathology of nasopharyngeal carcinoma (NPC). METHODS: Six high dense microsatellite marker on chromosome 3p14 were selected to examine LOH in 32 cases of NPC. RESULTS: 23 of 32 (71.9%) tumors were deleted for at least one locus of six loci. High frequencies of LOH (> 40%) were observed at loci D3S1300(50.0%), D3S1313(46.4%) and D3S1312(44.4%). 12 cases showed LOH in one contiguous and nonrandom region. The smallest common deletion region seems likely to lie between D3S1313 and D3S1312. Relations between LOH on 3p14 and clinical stage and EBV infection were observed. The frequency of LOH was 70.0% in 30 cases of poor-differentiated squamous cell carcinoma. 2 cases of vesicular nucleus cell carcinoma had LOH at two loci. CONCLUSION: The high deletion rate on 3p14 in NPC indicates that there might be a putative tumor suppressor gene related to the development and progression of NPC.

Alleles↗

PubMed2000

[Mutations in the connexin 26 gene in patients with nonsyndromic hearing impairment].

OBJECTIVE: To determine the prevalence and characteristics of deafness-causing mutations in Connexin 26(Cx26, GJB2) gene in Chinese with nonsyndromic hearing impairment(NSHI). METHODS: Study subjects are all Chinese including 16 infants with sporadic congenital deaf-mutism, 39 patients with autosomal recessive hereditary hearing loss, 30 patients with autosomal dominant hereditary hearing loss and 100 normal adults. The subjects were screened for base variations by single-strand conformational polymorphism (SSCP) analysis of the amplified products of polymerase chain reaction (PCR). Those who were found have abnormal conformational band were sequenced. RESULTS: Five kinds of polymorphism were found in 15 cases of controls and six kinds of polymorphism in 10 patients. No mutation was found in Cx26 gene in Chinese with autosomal recessive NSHI. Heterozygous deletion AT at position 299-300 of Cx26 cDNA, which results in premature chain termination, was found in a pedigree with autosomal dominant hereditary nonsyndromic hearing loss. CONCLUSION: The prevalence of deafness-causing mutations in Cx26 gene in Chinese with autosomal recessive NSHI maybe is lower than that of other ethnic groups. Heterozygous deletion AT at position 299-300 of Cx26 cDNA can lead to autosomal dominant hereditary hearing loss (DFNA3).

Asian People↗

PubMed2000

[Neurofibromatosis type 2].

OBJECTIVE: To investigate the clinical characteristics and management strategies of bilateral acoustic neuromas. METHODS: The data of 7 patients with bilateral acoustic neuromas collected between 1990 to 1998 were retrospectively analyzed. RESULTS: Altogether 122 patients with acoustic tumors were treated from 1990 to 1998, in which 7 cases (5.8%, 6 male and 1 female) had bilateral acoustic neuromas. The age at onset of symptoms ranged from 13 to 60 years (average 29.1 years). Progressive hearing loss and tinnitus were the initial symptoms in 4 cases. Either strabismus, ptosis, headache or dysequilibrium was presented in 4 cases. Six cases complicated tumors in the central nervous system and/or other sites. Five cases had cafe au lait spots. One case had posterior subcapsular lenticular opacity. Four cases fell into severe (Wishart) type and 2 into mild (Gardner) type. The tumors were unilaterally removed in 4 patients through the retrolabyrinthine approach (1 case) or the retrosigmoid approach (3 cases). In these 4 patients, one died of central respiratory failure after the operation; two had contralateral tumor removal through retrosigmoid approach 3 weeks after the first surgery. One of the patients died of encephaledema after the surgery. No hearing impairment and facial nerve paralysis occurred in one case operated on through the retrolabyrinthine approach, whereas in those through retrosigmoid approach, 4 ears had hearing loss and 3 sides had facial nerve paralysis. CONCLUSION: The clinical characteristics and treatment strategies for bilateral acoustic neuromas are different from those of unilateral acoustic neuroma. Individualization of management is a prerequisite for the success of the treatment. To avoid injury to the VII and VIII cranial nerves, monitoring the nerve functions during the surgery is important.

Adolescent↗

PubMed2000

[Effect of Al3+ on luminescence intensity of Tb in silica glasses].

The silica glasses doped with Tb3+ and Al3+ iones was synthesized through Sol-Gel process in this paper. The effect of Al3+ on luminescence properties of Tb3+ were studied. The results show that no obvious effect of Al3+ on the emission peak position of Tb3+, but the emission intensity of Tb3+ doped Al3+ by sol-gel process increased obviously for all samples. The emission intensity of 1% Al-99% SiO2 glass was 5 times larger than that of 100% SiO2 glass. We concluded that the relation between the energy levels of Tb3+ and the energy levels of Al3+ may be appropriate for the energy transfer, the function of Al3+ was to absorb efficiently energy and to transfer fully to Tb3+.

Aluminum↗

PubMed1999

Proline-Based P,N Ligands in Palladium-Catalyzed Asymmetric pi-Allyl Additions.

Excellent yields and at least 95 % ee can be achieved for the addition of dimethyl malonate to cycloalkenyl acetates by using a palladium complex of the new phosphanyldihydrooxazole ligand L as a catalyst (see scheme). The ligand L can be synthesized from commercially available trans 4-hydroxy-L-proline in four steps. BOC=tert-butoxycarbonyl.

Journal Article↗

PubMed1999

Genetic polymorphism of human O6-alkylguanine-DNA alkyltransferase: identification of a missense variation in the active site region.

O6-Alkylguanine-DNA alkyltransferase (AGT, EC 2.1.1.63) is a principle DNA repair protein in repairing O6-alkylguanine in DNA, a major premutagenic lesion produced by environmental and therapeutic alkylating agents. AGT plays a critical role in protecting cells against mutation and cytotoxicity induced by these alkylating agents. The existence of a large interindividual variation in human AGT activity level has been observed and we hypothesize that genetic polymorphism of AGT could be an important determinant for this variation. The present study reports the identification of a novel missense polymorphism in the human AGT gene. The polymorphic alteration occurs at codon 143 in exon 5, converting isoleucine (ATC) to valine (GTC). Because Ile143 is adjacent to the alkyl acceptor Cys145 of the AGT active site and is conserved among mammalian AGTs, amino acid substitution at this position may affect the function of AGT. The codon 143 polymorphism appears to be linked to another new polymorphic alteration at codon 178, which converts lysine (AAG) to arginine (AGG). Because it has been reported that human AGT can be truncated at position 176 without loss of activity, the codon 178 polymorphism may not affect AGT activity. The codon 143/178 polymorphism was found in two of 90 (2%) esophageal cancer patients residing in a high incidence area of China, but was not detected in 60 normal individuals residing in the same area. Six of 28 (210%) non-cancer Caucasian individuals, however, were found to carry this polymorphic allele, suggesting a significant ethnic difference in distribution of this codon 143/178 polymorphism between Chinese and Caucasian individuals. In addition, we confirmed the existence of a codon 84 genetic polymorphism previously identified in a Japanese population, which converts leucine (CTT) to phenylalanine (TTT). The distribution of codon 84 polymorphism was 16%, 20% and 36%, respectively, in the Chinese esophageal cancer patients, Chinese and Caucasian non-cancer individuals. Coexistence of codons 84 and 143/178 polymorphic alterations was found in one Caucasian individual. In all the Chinese (n = 150) and Caucasian (n = 28) samples examined, we were unable to detect a previously reported codon 160 polymorphism (Gly to Arg) which occurred in 10-25% of the Japanese individuals and was shown to affect the reaction of AGT with the drug O6-benzylguanine. The functional significance of the codon 143/178 genetic polymorphism of human AGT and its role in determining an individual's susceptibility to environmental alkylating carcinogens and response to alkylating chemotherapeutic drugs both remain to be studied.

Adult↗

PubMed1999

Real-time measurements of dark substrate catalysis.

We have developed a novel procedure to monitor the real-time cleavage of natural unmodified peptides (dark substrates). In the competition-based assay, the initial cleavage rate of a fluorogenic peptide substrate is measured in the presence of a second substrate that is not required to exhibit any optical property change upon cleavage. Using a unique experimental design and steady-state enzyme kinetics for a two-substrate system, we were able to determine both Km and k(cat) values for cleavage of the dark substrate. The method was applied to HIV-1 protease and to the V82F/I84V drug resistant mutant enzyme. Using two different substrates, we showed that the kinetic parameters derived from the competition assay are in good agreement with those determined independently using standard direct assay. This method can be applied to other enzyme systems as long as they have one substrate for which catalysis can be conveniently monitored in real time.

Amino Acid Sequence↗

PubMed1999

Drug resistance mutations can effect dimer stability of HIV-1 protease at neutral pH.

The monomer-dimer equilibrium for the human immunodeficiency virus type 1 (HIV-1) protease has been investigated under physiological conditions. Dimer dissociation at pH 7.0 was correlated with a loss in beta-sheet structure and a lower degree of ANS binding. An autolysis-resistant mutant, Q7K/L33I/L63I, was used to facilitate sedimentation equilibrium studies at neutral pH where the wild-type enzyme is typically unstable in the absence of bound inhibitor. The dimer dissociation constant (KD) of the triple mutant was 5.8 microM at pH 7.0 and was below the limit of measurement (approximately 100 nM) at pH 4.5. Similar studies using the catalytically inactive D25N mutant yielded a KD value of 1.0 microM at pH 7.0. These values differ significantly from a previously reported value of 23 nM obtained indirectly from inhibitor binding measurements (Darke et al., 1994). We show that the discrepancy may result from the thermodynamic linkage between the monomer-dimer and inhibitor binding equilibria. Under conditions where a significant degree of monomer is present, both substrates and competitive inhibitors will shift the equilibrium toward the dimer, resulting in apparent increases in dimer stability and decreases in ligand binding affinity. Sedimentation equilibrium studies were also carried out on several drug-resistant HIV-1 protease mutants: V82F, V82F/I84V, V82T/I84V, and L90M. All four mutants exhibited reduced dimer stability relative to the autolysis-resistant mutant at pH 7.0. Our results indicate that reductions in drug affinity may be due to the combined effects of mutations on both dimer stability and inhibitor binding.

Circular Dichroism↗

PubMed1999

mdm-2 expression correlates with wild-type p53 status in esophageal adenocarcinoma.

Several immunohistochemical studies showed that p53 protein is expressed in 50 to 80% of esophageal adenocarcinomas (EAs). Mutations of this tumor suppressor gene are present in 40 to 70% of EAs, so it is possible that p53 expression might occur as a result of mechanisms other than gene mutation. The human homologue of the murine double minute-2 gene (mdm-2) is a known regulator of p53 activity, and its expression results in stabilization of the wild-type p53 protein and loss of its tumor suppressor function. In this study, we evaluated the frequency of mdm-2 amplification and expression in EA and investigated the relationship between mdm-2 expression and p53 mutation. Thirty-three resection specimens of EAs and associated Barrett's esophagus were evaluated by immunohistochemical methods for p53 and mdm-2 expression. Sixteen of these cases were also evaluated for p53 mutations with use of polymerase chain reaction, single-strand conformational polymorphism, and DNA sequencing and for mdm-2 amplification with a differential polymerase chain reaction-based amplification analysis. Overexpression of p53 was present in 23 EAs (70%), and 18 EAs (55%) overexpressed mdm-2. p53 mutation was observed in 7 (43%) of 16 cases, whereas mdm-2 gene amplification was not detected in any. To summarize, we found substantial discordance of p53 immunohistochemical features and mutation in EA. Significant expression of mdm-2 occurred only in cases with wild-type p53, whereas all of the cases with p53 mutation showed little if any expression of mdm-2. Also, mdm-2 expression in cases with p53 overexpression but without p53 mutation exceeded mdm-2 expression in cases with p53 overexpression and p53 gene mutation. In cases without p53 mutation, overexpression of mdm-2 occurred in 50% of cases and might be responsible for stabilization of p53 protein and possible loss of tumor suppressor function.

Adenocarcinoma↗

PubMed1999

[Utilization of a pedicled labial flap, single or double face, for the management of post-obstetric urethral damage].

Reported here is our experience with a single or double-face new procedure using a pedicled labial flap for urethral reconstruction in patients treated for extensive urethral damage after obstetrical injury. Between January 1992 to July 1997, 56 cases of urethral damage on African female patients, with an average age of 18 years old, were treated by pedicled labial urethroplasty. This procedure was done by using a single or double-face pedicled flap obtained from the major or minor labia. The flap was then introduced as in a tunnel beneath the vaginal epithelium reaching the damaged urethra. A variety of techniques were proposed: patch for sufficient lengthening (27 cases), tubularized flap allowing complete reconstruction of the urethra (18 cases) and the double-face urethroplasty (11 cases). Good quality urine continence was obtained by using the sub urethral Martius'sling procedure. In 11 cases, we combined the treatment with a colposuspension procedure. The average follow-up was 23 months (ranging from 5 to 47 months). The global success was 82% (52 patients treated). Recovery of normal miction and absence of urinary leak was obtained in 36 cases (69%). While 7 moderate failures occurred (13%), 9 cases were considered complete failures (17%). In view of the high success rate, we consider that the one-stage procedure by the use of a single or double face pedicled labial flap is a choice treatment and highly suitable for the management of extensive urethral cervical damage after obstetrical injury.

Adolescent↗

PubMed1999

Effect of cytokines on in vitro bone resorption by cells isolated from giant cell tumor of bone.

OBJECTIVE: To investigate the effect of cytokines on in vitro bone resorption by cells isolated from giant cell tumor of bone. METHODS: Mononuclear stromal cells and multinucleated giant cells (MGC) were isolated from 11 cases of giant cell tumor of bone (GCT) and their bone resorption capability in an in vitro cell-bone resorption model were tested. Expressions of some cytokines were detected by immunohistochemistry, Western blotting analysis and Enzyme-linked immunoabsorbent assay (ELISA) in the GCT. RESULTS: The results showed that MGCs of GCT had capability to resorb bone matrix directly. Fibroblast-like stromal cells (FC) could not only resorb bone matrix directly, but also secret unknown factors to facilitate bone resorption of MGC. Exogenous TNF-alpha could significantly increase the bone resorption by both kinds of stromal cells, while exogenous IL-1 did not. Expression rate of M-CSF and level of TNF-alpha in GCT were higher than in osteosarcoma and normal serum. CONCLUSIONS: The characteristic bone resorption behavior of GCT might be caused by its three major cell components. The M-CSF and TNF-alpha could promote their bone resorption capability.

Animals↗

PubMed1999

[Differential diagnosis in patients with tuberculous meningitis and cryptococcal meningitis].

OBJECTIVE: To search for the main differential points in clinical and CSF changes between patients with tuberculous meningitis (TBM) and cryptococcal meningitis (CCM). METHODS: Fifty three cases of TBM and 55 cases of CCM who admitted to hospital from February 1983 to December 1997 were investigated retrospectively. Main symptoms, signs and CSF changes before administration of specific antibiotics were compared. RESULTS: 9%(5/53) TBM and 49% (27/55) CCM patients had headache without fever at the onset. The incidences of symptoms of failing eyesight, hearing loss and paralysis of extremities were 13% (7/53) and 36%(20/55), 2% (1/53) and 16% (9/55), and 19% (10/53) and 0 in TBM and CCM patients respectively. The rate and the degrees of optic papilla edema in CCM patients (66%, 16/36 slight, 13/36 moderate, and 7/36 serious) were significantly higher and more serious than that in TBM (15%, 8/8 slight). The patients with initial CSF pressure over 400 mm H2O were 11% and 90% in TBM and CCM. All but 20 CCM patients had elevation of CSF protein content, and 45% (24/53) TBM and 9%(5/55) CCM were > 2 g/L. CONCLUSIONS: This study shows that the most important differences between TBM and CCM are: headache not accompanied by fever at the onset, failing eyesight, striking elevation of initial CSF pressure, moderately and serious degree of optic papilla edema, normal CSF protein content occurs usually in CCM more than those in TBM patients. On the other hand, striking elevation of CSF protein content (> 2 g/L) occurs usually in TBM patients.

Adolescent↗

PubMed1999

[Component in diphtheria-pertussis-tetanus-hepatitis B vaccine].

OBJECTIVE: To study immunogenecity of yeast-derived recombinant hepatitis B (YHB) component in diphtheria-pertussis-tetanus-YHB vaccine (DPTw-YHB). METHODS: Immunogenecity of tetra-valent DTPw-YHB vaccine and mono-valent recombinant YHB vaccine, and that of the tetra-valent vaccine with varied YHB component were compared. The efficiency and stability of recombinant YHB in the tetra-valent vaccine stored at 2 - 8 degrees C for 18 months were determined. RESULTS: The efficiency of recombinant YHB in the tetra-valent vaccine enhanced significantly in mice, as compared with that of mono-valent recombinant YHB vaccine, with an average mouse ED(50) of 1:2.0 - 1:3.1. There was no significant difference in efficiency of the tetra-valent vaccine with varied recombinant YHB component. Recombinant YHBin the DPTw-YHB tetra-valent vaccine still kept good stability stored at 2 - 8 degrees C for 18 months. CONCLUSION: Recombinant YHB in the tetra-valent vaccine was more immunogenic than the mono-valent YHB vaccine. No interference and inhibition of DPTw to recombinant YHB was found, indicating good compatibility between DPTw and YHB.

Animals↗

PubMed1999

[The effects of muscarinic and nicotinic receptor antagonists on compound action potentials in the cochleae of gerbils].

To explore the mechanism of the medial olivocochlear(MOC) efferents and their neurotransmitter acetylcholine in regulating the cochlear mechanics and the auditory afferent activities, the effects of contralateral noise(CLN) and muscarinic(M) and nicotinic(N) receptor antagonist on the compound action potential(CAP) of the cochleae of gerbils were observed in our studies. The results showed that the CAP was significantly inhibited by CLN, and the suppressive effect of CLN on CAP was eliminated either by atropine or by gentamycin. These results support that MOC efferents play their physiological effect via both M and N receptors.

Action Potentials↗

PubMed1999

[Protective effect of Radix Salvia Miltiorrhizae on radiation damage of the cochlea].

In order to evaluate the preventive and therapeutic effects of Radix Salvia Miltiorrhizae on radiation damage of the cochlea, guinea pigs were divided into 3 groups. Group 1 was treated by radiation added with Radix Salvia Miltiorrhizae. Group 2 was radiated alone, and Group 3 was control. Group 1 and Group 2 were radiated with a single dose of gamma radiation(60 Gy). Morphological and functional observation of the cochleae was performed in two weeks after radiation. The result showed that the changes of complex action potential(CAP) and the cochlear structure were slight in Group 1, but obvious changes were found in Group 2. There was a significant difference in CAP response threshold and incidence of the cochlear hair cell loss between Group 1 and Group 2 (P < 0.01). These results suggest that Radix Salvia Miltiorrhiza may prevent radiation-induced cochlea damage. Its protective mechanisms may be cleaning free radicals, blocking calcium channel and improving microcirculation of the cochlea.

Animals↗

PubMed1999

[Traumatic perilymphatic fistula of round and oval windows (four cases reported)].

OBJECTIVE: To explore the diagnosis and treatment to traumatic perilymph fistula (PLF) of round and oval window. METHOD: Traumatic PLF was diagnosed by the traumatic history of head, neck and ear, the examinations of auditory and vestibular function, and the exploratory tympanotomy. The PLF of round and oval windows were repaired by fascia graft or tragus perichondrium and gelform. Four cases with traumatic PLF of round and oval window were reported in this paper, which included 2 cases hitten by hand, 1 by brick, 1 insulted by middle ear surgery. Exploratory tympanotomy was performed from one and half to nine months after injury. One case was misdiagnosed as Meniere's disease before confirming PLF. Exploration and repair of PLF underwent in all cases. RESULT: The symptom of vertigo relieved in all cases after surgery, while the hearing recovery was not evident. CONCLUSION: 1. Traumatic PLF is unrare, hence, traumatic PLF should be alerted if patients suffer from vertigo and hearing impairment after head and ear injury. 2. The features with vertigo attacks, fluctuating hearing loss and tinnutis should be distinguished from Meniere's disease. 3. Early exploratory tympanotomy and repair of PLF are effective for relieving vertigo and improving hearing.

Adult↗

PubMed1999

[The submucosal structure of the endolymphatic sac of guinea pigs].

OBJECTIVE: To investigating the submucosal structure of the endolymphatic sac (ES), so as to analyse the role of ES in the function of inner ear. METHOD: The temporal bone of the guinea pigs were cleared in methyl salicylate and inspected under a stereomicroscope. The ultrastructure of endolymphatic sac has been observed by transmission electron microscope. RESULT: The extensive vascular system around the sac and has compact contact with sinus sigmoid. Its submucosal space comprises both arterioles and venules, as well as lymphatic sinus. CONCLUSION: The result suggests that the ES is a very metabolically active structure and has a pressure regulating function. The disturbance of endolymphatic resorptive function seems to result endolymphatic hydrops after the vascular supply poverty of endolymphtic sac. It's may be the causative factor of Meniere's disease.

Animals↗

PubMed1999

[Hair cell apoptosis and hearing loss of perilymphatic fistula].

OBJECTIVE: To investigate the effect of hair cell apoptosis on hearing loss of perilymphatic fistula (PLF) in guinea pig. METHOD: Twenty-five guinea pigs with light microscope and TdT mediated biotin dUTP nick-end labelling (TUNEL) techniques. The ECochG and ABR were measured and the data analyzed with statistics. RESULT: 1. The apoptosis of hair cell was not revealed in 0-hour-group and 2-hour-group of PLF. Following the time of PLF was longer, the apoptosis of hair cell was more increased. The apoptosis of hair cell was demonsted in 1-day-group (1 case, 17%), 2-day-group (4 case, 67%) and 7-day-group (4 case, 80%); 2. The amplication of AP was reduced after operation induced PLF. The CAP of experimental ear was significantly higher than that of control ear (P < 0.01) in 1-day-group, 2-day-group and 7-day-group. CONCLUSION: 1. Apoptosis of hair cell was appeared in PLF; 2. The apoptosis of hair cell may be one of morphological evidence in hearing loss of PLF.

Animals↗