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Biomedical subjects

T Xu

Publications and source records attributed to T Xu.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Effect of lower androgen levels on arteriosclerosis].

OBJECTIVE: To analyse the effect of lower androgen levels on risk factors for arteriosclerosis of men. METHODS: In 30 cases of primary prostate carcinoma (stage A), serum levels of testosterone (T), free testosterone (FT), dehydroepiandrosterone (DHEA), sex hormone-binding globulin (SHBG), prostatic specific antigen(PSA), triglyceride (TG), total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), apoprotein alpha 1 (APO alpha 1) and apoprotein beta(APO beta), insulin, plasma fibrinopeptide A (FPA), plasminogen activator inhibitor-1(PAI-1), fibrinogen were determined before and 1 week, 1,4,8 months after castration. RESULTS: T, FT, PSA decreased significantly 1 week after castration, and kept on decreasing afterwards. DHEA and SHBG were not changed. TG, fasting insulin and glucose, 2-hour insulin and glucose elevated significantly 1 month after castration. TG, LDL-C, FPA and PAI-1 elevated 4 months after castration. Insulin sensitive index(ISI) decreased significantly 1 month after operation (-4.4 +/- 0.4 vs. -3.5 +/- 0.4, P < 0.01). HDL-C, APO alpha 1, APO beta and fibrinogen were not changed. There was a negative linear correlation between FT and TG, TC, LDL-C, PAI-1, FPA, fasting insulin and glucose, 2 h insulin and glucose, so did T. CONCLUSION: Lower androgen levels have adverse effect on lipid metabolism, coagulative function and insulin sensitivity, which are related to arteriosclerosis of men.

Aged↗
PubMed2001

Detailed deletion mapping on chromosome region 9p21 in human periampullary neoplasms.

OBJECTIVE: To further define the extent of chromosome 9p21 deletion in periampullary neoplasms. METHODS: The loss of heterozygosity at 5 microsatellite polymorphic markers on chromosome 9p21 was detected by polymerase chain reaction (PCR), polyacrylamide gel electrophoresis (PAGE) and silver staining in 35 specimens of periampullary neoplasms and their matching blood samples. RESULTS: Fifty percent (4/8) of pancreatic cancer cases showed the loss of heterozygosity at one or more microsatellite loci, with the more frequent sites of D9S974 (37.5%) and D9S942 (28.6%), and some showing consecutive allelic loss. Sixty-two point five percent (5/8) of ampullary carcinoma cases showed loss of heterozygosity at one or more of the loci, frequent site of loss being D9S942 (42.9%) and the next most frequent being IFNA (37.5%) and D9S171 (37.5%). Loss of one locus was observed in 14.2% (1/7) of insulinoma. CONCLUSION: The minimal common region of chromosome deletion in periampullary neoplasms is defined between the D9S974 and D9S942 loci within a 15 kb interval in 9p21, suggesting the involvement of a novel tumor suppressor gene in their carcinogenesis.

Adolescent↗
PubMed2001

[The expression and clinical significance of proliferative antigen Ki-67 and apoptosis-antagonizing antigen Bcl-2 in non-Hodgkin's lymphoma].

OBJECTIVE: To evaluate the expression of proliferative antigen Ki-67 and apoptosis-antagonizing protein Bcl-2 as well as their clinical significance in non-Hodgkin's lymphoma (NHL). METHODS: Ki-67 antigen and Bcl-2 protein were measured by immunohistochemistry on paraffin -embedded slices in 35 cases of NHL. RESULTS: (1) The level of Ki-67 expression in low grade NHL was lower than that in high grade NHL (P < 0.01),while Bcl-2 expression in lower grade NHL was higher than that in high grade (P < 0.01). (2) The level of Bcl-2 expression in B cell NHL was higher than that in T cell NHL (P < 0.02), but there was no difference in the expression of Ki-67. (3) The level of Bcl-2 expression in remission group was lower than that in non-remission group after the first course of chemotherapy, but there was no significant difference in Ki-67 expression. (4) The survival time was longer in the group with Ki-67 < or = 20% than that in the group with Ki-67 > 20%, but there was no significant difference of survival time between the high and low expression group of Bcl-2. CONCLUSIONS: The level of Ki-67 and Bcl-2 expression was closely related with the grade of malignant and the prognosis of NHL. They were a pair of useful markers for understanding the generation and prognosis of NHL.

Adolescent↗
PubMed2001

[A study on the epidemiological characteristics and the preventive measures of rabies in Shanghai].

OBJECTIVE: To analyze the epidemiological characteristics and the preventive measures of rabies in Shanghai from 1950 to 2000. METHODS: Suspected cases of rabies were investigated epidemiologically and collection of samples to isolate the virus. RESULTS: The most highest morbidity of rabies was 1.98/100,000 in 1950. There had been neither case of rabies, nor the rabies virus positive identified in dogs between 1958 and 1988. The morbidity of rabies was 0 - 0.03/100,000 from 1989 to 2000. According to the data of 20 reported cases from 1985 to Sept. 2000, the mean incubation was 66.37 days, except one case of 14 years. The mean course of diseases was 4.55 days. Seventy percent of the cases did not receive any preventive measure. A hundred and ninety-four persons who were bitten by rabies virus positive dogs were timely treated and all of them survived. In recent years, there has been more than 50,000 persons bitten by dogs every year in Shanghai. The rate of rabies vaccine immunization was over 95%. The rate of anti-rabies serum immunization was over 20%. CONCLUSION: Rabies is a preventable disease even when persons were bitten by dogs with rabies virus positive. The important measure is to treat the wound timely, giving vaccine and anti-rabies serum injection. According to the regulation of dog control in Shanghai, the number of dogs be kept at the lowest level, immunizing all the registration dogs, and destroying the none-registration dogs are the most essential measures to be taken.

Animals↗
PubMed2001

[Differentiation of natural killer cells into two functional subsets: NKh1 and NKh2].

OBJECTIVE: To verify the presence of functional subsets of natural killer cells based on the cytokine production. METHODS: NK cells were purified and cultured in complete RPMI1640 medium in the presence of either IFN gamma + anti-IL-4(classical Th1 polarization) or IL-4 + anti-IFN gamma (classical Th2 polarization) for three days, and then were collected and detected for type I/type II cytokines by RT-PCR method. RESULTS: NK cells were purified from 15 healthy donors, over 70% purity of NK cells were determined by flow cytometry. NK cells in peripheral blood expressed high level of type I cytokines, mainly IFN gamma, but low level of type II cytokines such as IL-10 and IL-13, IL-4 was not produced by NK cells. Cells cultured in IFN gamma + anti-IL-4 condition exhibited significantly increased level of IFN gamma, unchanged IL-2, and decreased type II cytokines. Cells grew in IL-4 + anti-IFN gamma condition exhibited increased IL-10 and IL-13, and decreased IFN gamma expressions. CONCLUSIONS: Based on the cytokine production, NK cells may be divided into two functional subsets in the same manner as that of T lymphocytes(e.g. Th1/Th2): NKh1 and NKh2. The biological characterization and phenotypic marker are under investigate.

Cells, Cultured↗
PubMed2000

Mitochondria shape hormonally induced cytoplasmic calcium oscillations and modulate exocytosis.

Pituitary gonadotropes transduce hormonal input into cytoplasmic calcium ([Ca(2+)](cyt)) oscillations that drive rhythmic exocytosis of gonadotropins. Using Calcium Green-1 and rhod-2 as optical measures of cytoplasmic and mitochondrial free Ca(2+), we show that mitochondria sequester Ca(2+) and tune the frequency of [Ca(2+)](cyt) oscillations in rat gonadotropes. Mitochondria accumulated Ca(2+) rapidly and in phase with elevations of [Ca(2+)](cyt) after GnRH stimulation or membrane depolarization. Inhibiting mitochondrial Ca(2+) uptake by the protonophore CCCP reduced the frequency of GnRH-induced [Ca(2+)](cyt) oscillations or, occasionally, stopped them. Much of the Ca(2+) that entered mitochondria is bound by intramitochondrial Ca(2+) buffering systems. The mitochondrial Ca(2+) binding ratio may be dynamic because [Ca(2+)](mit) appeared to reach a plateau as mitochondrial Ca(2+) accumulation continued. Entry of Ca(2+) into mitochondria was associated with a small drop in the mitochondrial membrane potential. Ca(2+) was extruded from mitochondria more slowly than it entered, and much of this efflux could be blocked by CGP-37157, a selective inhibitor of mitochondrial Na(+)-Ca(2+) exchange. Plasma membrane capacitance changes in response to depolarizing voltage trains were increased when CCCP was added, showing that mitochondria lower the local [Ca(2+)](cyt) near sites that trigger exocytosis. Thus, we demonstrate a central role for mitochondria in a significant physiological response.

Animals↗
PubMed2000

Subunit D (Vma8p) of the yeast vacuolar H+-ATPase plays a role in coupling of proton transport and ATP hydrolysis.

To investigate the function of subunit D in the vacuolar H(+)-ATPase (V-ATPase) complex, random and site-directed mutagenesis was performed on the VMA8 gene encoding subunit D in yeast. Mutants were selected for the inability to grow at pH 7.5 but the ability to grow at pH 5.5. Mutations leading to reduced levels of subunit D in whole cell lysates were excluded from the analysis. Seven mutants were isolated that resulted in pH-dependent growth but that contained nearly wild-type levels of subunit D and nearly normal assembly of the V-ATPase as assayed by subunit A levels associated with isolated vacuoles. Each of these mutants contained 2-3 amino acid substitutions and resulted in loss of 60-100% of proton transport and 58-93% of concanamycin-sensitive ATPase activity. To identify the mutations responsible for the observed effects on activity, 14 single amino acid substitutions and 3 double amino acid substitutions were constructed by site-directed mutagenesis and analyzed as described above. Six of the single mutations and all three of the double mutations led to significant (>30%) loss of activity, with the mutations having the greatest effects on activity clustering in the regions Val(71)-Gly(80) and Lys(209)-Met(221). In addition, both M221V and the double mutant V71D/E220V led to significant uncoupling of proton transport and ATPase activity, whereas the double mutant G80D/K209E actually showed increased coupling efficiency. Both a mutant showing reduced coupling and a mutant with only 6% of wild-type proton transport activity showed normal dissociation of the V-ATPase complex in vivo in response to glucose deprivation. These results suggest that subunit D plays an important role in coupling of proton transport and ATP hydrolysis and that only low rates of turnover of the enzyme are required to support in vivo dissociation.

Adenosine Triphosphate↗
PubMed2000

CaV2.2 and CaV2.3 (N- and R-type) Ca2+ channels in depolarization-evoked entry of Ca2+ into mouse sperm.

As sperm prepare for fertilization, surface Ca(2+) channels must open to initiate required, Ca(2+)-mediated events. However, the molecular identity and functional properties of sperm Ca(2+) channels remain uncertain. Here, we use rapid local perfusion and single-cell photometry to examine the kinetics of calcium responses of mouse sperm to depolarizing stimuli. The linear rise of intracellular [Ca(2+)] evoked by approximately 10-s applications of an alkaline high [K(+)] medium directly reports activity of voltage-gated Ca(2+) channels. Little response occurs if external Ca(2+) is removed or if external or internal pH is elevated without depolarization. Responses are inhibited 30-40% by 30-100 micrometer Ni(2+) and more completely by 100-300 micrometer Cd(2+). They resist the dihydropyridines nitrendipine and PN200-110, but 1-10 micrometer mibefradil inhibits reversibly. They also resist the venom toxins calciseptine, omega-conotoxin MVIIC, and kurtoxin, but omega-conotoxin GVIA (5 micrometer) inhibits approximately 50%. GVIA also partially blocks transient, low voltage activated Ca(2+) currents of patch-clamped spermatids. Differential sensitivity of sperm responses to Ni(2+) and Cd(2+) and partial blockade by GVIA indicate that depolarization opens at least two types of voltage-gated Ca(2+) channels in epididymal sperm examined prior to capacitation. Involvement of a previously undetected Ca(V)2.2 (N-type) channel, suggested by the action of GVIA, is substantiated by immunodetection of Ca(2+) channel alpha(1B) subunits in sperm and sperm extracts. Resistance to dihydropyridines, calciseptine, MVIIC, and kurtoxin indicates that Ca(V)1, Ca(V)2.1, and Ca(V)3 (L-, P/Q-, and T-type) channels contribute little to this evoked response. Partial sensitivity to 1 micrometer mibefradil and an enhanced sensitivity of the GVIA-resistant component of response to Ni(2+) suggest participation of a Ca(V)2.3 (R-type) channel specified by previously found alpha(1E) subunits. Our examination of depolarization-evoked Ca(2+) entry indicates that mature sperm possess a larger palette of voltage-gated Ca(2+) channels than previously thought. Such diversity may permit specific responses to multiple cues encountered on the path to fertilization.

Animals↗
PubMed2000

Exocytotic mechanism studied by truncated and zero layer mutants of the C-terminus of SNAP-25.

The highly conserved SNARE proteins, SNAP-25, syntaxin and synaptobrevin, form a tight ternary complex, which is essential for exocytosis. Crystallization of this complex revealed a four-helix bundle with an unusual hydrophilic layer (zero layer) in its center. In order to evaluate the role of this layer in different kinetic components of secretion, we used the Semliki Forest virus (SFV) system to infect adrenal chromaffin cells with SNAP-25 Q174L, a point mutant in the zero layer. Using combined flash photolysis of caged calcium and membrane capacitance measurements, we investigated its effect on the exocytotic burst and sustained phase of exocytosis with high time resolution. Cells expressing SNAP-25 Q174L displayed a selective reduction in the sustained phase, while the two components of the exocytotic burst remained unaffected. Furthermore, the exocytotic response to the second flash was significantly reduced, indicating a decrease in refilling kinetics. We therefore conclude that the zero layer is critical for the formation of SNARE complexes, but that it plays no role in the dynamic equilibrium between the two exocytosis-competent vesicle pools.

Amino Acid Substitution↗
PubMed2000

Drosophila in cancer research. An expanding role.

In recent years, Drosophila researchers have developed powerful genetic techniques that allow for the rapid identification and characterization of genes involved in tumor formation and development. The high level of gene and pathway conservation, the similarity of cellular processes and the emerging evidence of functional conservation of tumor suppressors between Drosophila and mammals, argue that studies of tumorigenesis in flies can directly contribute to the understanding of human cancer. In this review, we explore the historical and current roles of Drosophila in cancer research, as well as speculate on the future of Drosophila as a model to investigate cancer-related processes that are currently not well understood.

Animals↗
PubMed2000

Cellular localization of serotonin(2A) (5HT(2A)) receptors in the rat brain.

The serotonin(2A) (5HT(2A)) receptors have been shown to play an important role in several psychiatric disorders, including depression, schizophrenia, and alcoholism. This immunohistochemical study examined the cellular localization of 5HT(2A) receptors in various rat brain structures (olfactory, striatum, cortex, hippocampus, and amygdala). The colocalization of 5HT(2A) receptors in astrocytes was performed by double-immunofluorescence staining of 5HT(2A) receptors and of glial fibrillary acidic protein (GFAP) using confocal laser microscopy. 5HT(2A) receptor immunolabeling was observed in olfactory bulbs, neostriatum, hippocampus, amygdala, and neocortex. Somata and dendrites of pyramidal cells in the frontal cortex (layer V) were densely labeled with 5HT(2A) receptors. In several other brain structures (hippocampus, amygdala, striatum, olfactory structures), 5HT(2A) receptor immunolabeling was found in cell bodies and processes of neurons. 5HT(2A) receptor immunolabeling was also observed in GFAP-positive cells of the various brain structures we investigated (layers I/VI of the neocortex, corpus callosum, hippocampal fissure and hilus, and amygdala). These results indicate that 5HT(2A) receptors are expressed in neurons and astrocytes and suggest the possibility that not only neuronal but also glial 5HT(2A) receptors have functional implications in psychiatric disorders.

Amygdala↗
PubMed2000

F1 and F0 connections in the bovine mitochondrial ATP synthase: the role of the of alpha subunit N-terminus, oligomycin-sensitivity conferring protein (OCSP) and subunit d.

We have studied the functional effect of limited proteolysis by trypsin of the constituent subunits in the native and reconstituted F1F0 complex and isolated F1 of the bovine heart mitochondrial ATP synthase (EC 3.6.1.34). Chemical cross-linking of oligomycin-sensitivity conferring protein (OSCP) with other subunits of the ATP synthase and the consequent functional effects were also investigated. The results obtained show that the alpha subunit N-terminus is essential for the correct, functional connection of F1 to F0. The alpha-subunit N-terminus contacts OSCP which, in turn, contacts the F0I-PVP(b) and the F0-d subunits. The N-terminus of subunit alpha, OSCP, a segment of subunit d and the C-terminal and central region of F0I-PVP(b) subunits are peripherally located with respect to subunits gamma and delta which are completely shielded in the F1F0 complex against trypsin digestion. This qualifies the N-terminus of subunit alpha, OSCP, subunit d and F0I-PVP(b) as components of the lateral element of the stalk. These subunits, rather than being confined at one side of the complex which would leave most of the central part of the gamma subunit uncovered, surround the gamma and the delta subunits located in the central stalk.

Adenosine Triphosphatases↗
PubMed2000

[The effects of distalization of upper molars in Class II malocclusion by pendulum appliance].

OBJECTIVE: To study the mechanics of Pendulum appliance, and its effects on craniofacial and dentoalvaolar structure. METHODS: 16 class II malocclusion patients (13 females and 3 males) were selected as the subjects, aged from 9.3 to 22.8 years(13.6 on average). All the patients were treated with Pendulum appliance. The duration for distolization of upper molars was from 1 to 6 months(3.7 months on average). Cephalomatric analysis was used. RESULTS: 1. The upper molar was distalized by 3.59 mm per side with mainly tilting movement. 2. Incisors moved mesially by 3.28 mm per side (tilting movement). 3. Anterior overjet was increased by 1.56 mm after treatment and more than 6 mm space was created per side. 4. The upper molars extruded slightly by 0.69 mm. 5. The width of upper arch was increased by 2.03, 1.66, 1.10 mm at molar, premolar and canine region respectively. 6. The Pendulum appliance had less effects on craniofacial structure because of short treatment time. CONCLUSIONS: The Pendulum appliance can distalize the upper molars effectively without patients' active cooperation. However, it should be cautions in using the appliance because of its side effects on tilting of molars and mesial movement of incisors.

Acrylic Resins↗
PubMed2000

[Study on the relations between HLA-DRB 1 alleles and Helicobacter pylori infection].

OBJECTIVE: In order to study the relation between human leukocyte antigen (HLA) DRB1 alleles and Helicobacter pylori (Hp) infection. METHODS: Hp-IgG antibody from 46 gastric cancer (GC), 75 esophageal cancer and 100 population-based controls were identified by Hp-IgG quantitative enzyme immunoassay. Biotest HLA-DRB enzyme linked probe hybridization assay kit (low resolution) was used to identify DRB1 alleles. RESULTS: (1) Frequency of DRB1 * 08 was significantly higher in Hp-IgG positive group than in Hp-IgG negative group (13.1% vs 4.4%, chi(2) = 11.14, P < 0.001). Frequency of DRB1 * 12 was significantly lower in Hp-IgG positive group than in Hp-IgG negatives (5.4% vs 11.3%, chi(2) = 4.49, P < 0.05). (2) Frequency of DRB1 * 02 in GC was significantly higher than that of controls. Frequency of DRB1 * 07 in GC was significantly lower than that of controls. However, neither the frequency of DRB1 * 02 between Hp-IgG positive and Hp-IgG negative groups nor the frequency of DRB1 * 07 between Hp-IgG positive and Hp-IgG negative groups showed significant differences in GC and controls. CONCLUSIONS: (1) HLA-DRB1 * 08 might serve a genetic risk factor for Hp infection while DRB1 * 12 might play a role of protecting effect against Hp infection. (2) DRB1 * 02 might be a genetic risk factor for GC while DRB1 * 07 might play a role of protecting effect against GC. However, the relations between DRB1 * 02, DRB1 * 07 and GC were not associated with Hp infection.

Alleles↗
PubMed2000

[Morphological changes in canine heart after electrical injury].

OBJECTIVE: To observe the histomorphological changes in canine heart after electrical injury. METHODS: Light and electronic microscopes (LM, EM) were employed to observe the histomorphological changes in canine heart after electrical injury. RESULTS: There were swelling and deformation of pacemaker cells (p cells) and mitochondrial swelling and vacuolization in cardiac conduct system. The cardiac muscle cells in the atrial and the ventricular walls exhibited obvious swelling and deformation, blurred cross striation, intracytoplasmic structural destruction of myofibrils, messy microfilaments, mitochondrial swelling, vacuolization and even dissolution. Furthermore, there was also breaking and expanding of the intercalated disk between adjacent cardiac muscle cells. The gap junctions at sites of intercalated disk were disrupted. CONCLUSION: The pathomorphological characteristics of cardiac histological changes after electrical injury were similar to those of acute myocardial infarction.

Animals↗
PubMed2000

Present and future technologies of tooth whitening.

Dental stains can be broadly classified as intrinsic or extrinsic. Intrinsic stains are a result of defects in tooth development, fluorosis, or acquired through the use of tetracycline. Extrinsic stains are localized mainly in the pellicle and are generated by the reaction between sugars and amino acids or acquired from the retention of exogenous chromophores in the pellicle. Three clinical methods are currently used for measuring stain removal and tooth whitening in the development of new whitening technologies: Lobene Stain Index, Shade Guide Color Change, and Minolta ChromaMeter. Professional tooth whitening products rely on proven technologies--35% hydrogen peroxide for in-office power bleaching or 10% to 15% carbamide peroxide for at-home bleaching--to reduce intrinsic stain and change the inherent tooth color. Over-the-counter tooth whitening products use a combination of surfactants, abrasives, anticalculus agents, and low levels of hydrogen peroxide to reduce extrinsic stain and help maintain tooth whiteness after professional treatment. Future technologies for whitening teeth could involve the use of activating agents to enhance the performance of hydrogen peroxide and natural enzymes.

Color↗
PubMed2000

[Study of chromosome pellicle by indirect immunoflourescence method and antigen analysis in Vicia faba].

The autoimmune antiserum specific to pellicle of human metaphasic chromosomes from a lupus patient was used to stain metaphasic chromosome Vicia faba by means of indirect immunoflourescence method. It was found that the pellicles of vicia metaphasic chromosomes was positively stained. The antigen of Vicia faba recognized by the antiserum was also examined by PAGE of total cell lysate and western blotting.

Antigens↗