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Biomedical subjects

Y Tang

Publications and source records attributed to Y Tang.

At least 91 records · Page 5Linked to original sources
PubMed2001

Crystal structure of the complex of concanavalin A and tripeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with the tripeptide molecule as the probe molecule showed electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the tripeptide complex was refined at 2.4-A resolution to an R-factor of 17.5%, (Rfree factor of 23.7%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residue of concanavalin A, 1 manganese ion, 1 calcium ion, 161 water molecules, 1 glutaraldehyde molecule, and 1 tripeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in a mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗
PubMed2001

Crystal structure of the complex of concanavalin A and hexapeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with a hexapeptide molecule as a probe molecule showed an electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the hexapeptide complex was refined at 1.93-A resolution, to an R-factor of 19% (Rfree factor of 25%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residues of concanavalin A, one manganese ion, one calcium ion, 95 water molecules, one glutaraldehyde molecule, one isopropanol molecule, and one hexapeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in the mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗
PubMed2001

A mimotope of pre-S2 region of surface antigen of viral hepatitis B screened by phage display.

To acquire the phage-displayed mimotopes which mimic the specificity of hepatitis B virus surface antigen (HBsAg), a random peptide library expressing linear peptide with 12 amino acids in length were used to screen with the serum from a hepatitis B virus infected patient in the recovery phase. After 3 rounds of biopanning, the positive phages were confirmed by competitive ELISA using HBsAg/P33. Two phagotopes were identified and one of them was confirmed as mimotope by competition experiment. Based on the mimotpe, a multiple antigenic peptide with four branches was synthesized by solid phase peptide synthesis. The antiginicity and specificity of the synthesized antigen was tested in BALB/c mice compared with the native epitope-based antigen. The results showed that the mimotope-based antigen could evoke higher titer of antibodies with the same specificity of the epitope-based antigen. Those findings indicate mimotopes can be used in antigen and vaccine design.

Animals↗
PubMed2001

The biomechanical, morphologic, and histochemical properties of the costal cartilages in children with pectus excavatum.

BACKGROUND/PURPOSE: The cause of the pectus excavatum (PE) remains unclear, although some results of research have indicated that the disturbance of the sternum or costal cartilage might be responsible for this deformity. But no decisive evidence has been gained. The authors have analyzed the biomechanical, morphologic, and histochemical properties of the cartilage in PE and intend to support the belief that the disturbance of the cartilage might contribute to the development of PE. METHODS: Thirty-eight specimens of the sixth cartilage were obtained at operation for the PE group (aged from 3 to 6 years; mean, 4.2 years). And 28 specimens of the control group (aged from 3 to 6 years; mean, 4.4 years) were gained from routine postmortem examinations in which the cause of death was unlikely to have affected the cartilage. The biomechanical test was carried out in a material testing machine (Shimadzu AG-10TA, Tokyo, Japan). The relation curve of load-deformation in tensile and compressive tests and the curve of load-time in the flexuous test were recorded automatically. The values of the ultimate strength and strain were calculated from this relation curve. The specimens also underwent H&E staining. The values of the area, circumference, mean diameter, maximal diameter, and morphologic factor of the cell and the nucleus of the cartilage in superficial and deep area were determined with the help of image analysis software (GT-2 model, China). The superficial zone (SZ) and deep zone (DZ) of the cartilage were examinated with electron microscopy (JEM-100SX, Japan). The distribution and intensity of type II collagen was shown by immunohistochemistry staining and analyzed with the image analysis software (GT-2 model, Huakang Co, Chengdu, China). The extent and distribution of proteoglycan were analyzed after Safranin-O and periodic acid shiff (PAS) staining. RESULTS: The mean strength of the costal cartilage in the experimental group was less than that in the control group in terms of tension, compression, and flexure (P <.05). The shape of the stress-strain curve for tension and compression in the experimental group was different from the control group. The fracture load in the experimental group was less than in the control group in tension (1.5 MPa versus 2.8 MPa) and in compression (.2 MPa versus 8.3 MPa). The time of fracture in experimental group was 30 seconds compared with 38 seconds in control group. No denaturation or necrosis could be found in light microscopical examination. There was no manifestation of hyperplasia or hypoplasia in the costal cartilage of the PE group. In SZ and DZ areas, the pattern and the number of mitochondria, endoplasmic reticulum, and Golgi in the experimental group were the same as the control group in transmission electron microscopy. Furthermore, the distribution and the number of proteoglycan in the 2 groups did not show a significant difference both in SZ and DZ areas. Although the distribution of the collagen in SZ areas was normal, this pattern was disturbed in DZ areas in the experiment group. The results of type II collagen immunohistochemistry examination was concordant with that change. No significant difference between control and experimental group could be seen in Safranin-O and PAS staining for proteoglycan. CONCLUSIONS: The biomechanical stability of the cartilage was decreased in the PE group. This might be caused by the disorderly arrangement and distribution of the collagen in the cartilage of PE patients. J Pediatr Surg 36:1770-1776.

Biomechanical Phenomena↗
PubMed2001

In vitro affinity maturation of human IgM antibodies reactive with tumor-associated antigens.

Human lymphocytes secreting tumor cell-specific IgM antibodies were enriched in vitro following the stimulation of allogeneic human splenocytes from nontumor-bearing donors with cytostatic tumor cells or tumor cell plasma membrane fractions. The antibodies were generally of the IgM class and displayed low intrinsic affinity (K(d) > 100 nM). Nonetheless, the avidity arising from multivalent binding sites permitted the identification of multiple monoclonal antibodies (MAbs) displaying specificity for cultured tumor cells. Five antibodies were cloned from the B cells and two of these were expressed as human Fabs with IgG(1) constant regions. Although the avidity of the human IgM antibodies was sufficient to permit detection in the original screening, the monovalent Fabs displayed low binding activities, consistent with their low intrinsic affinity. Thus, in vitro affinity maturation was used to rapidly generate multiple variants of both antibodies displaying greater than 100-fold higher affinity. Two of the antibodies were characterized further and shown to have distinct specificities. One of the targets, LH11238, is associated both with the plasma membrane and with lysosomes and is rapidly internalized following incubation of the antibody with intact live cell monolayers. The second antigen, designated LH13, is a secreted antigen that has been enriched 200-fold from conditioned media and consists of two reactive bands at 42 and 45 kDa on denaturing Western blots. The stimulation and enrichment of human lymphocytes in culture coupled with rapid in vitro affinity maturation of low affinity antibodies potentially enables the discovery of human antibodies to a broader range of epitopes, including those that might be of greater therapeutic relevance.

Amino Acid Sequence↗
PubMed2001

Is elevation of carbon dioxide concentration beneficial to seedling photosynthesis in the understory of tropical rain forests?

Cuttings of the southeast Asian tropical rain forest tree species, Pongamia pinnata (L.) Pierre were raised in growth chambers providing a photosynthetic photon flux density (PPFD) of 60 micromol m(-2) s(-1) with either a low or a high red:far-red light ratio (LR and HR, repectively). The chambers were supplied with air containing CO(2) at a concentration of either 400 (LR4 and HR4, respectively) or 800 micromol mol(-1) (HR8 and LR8, respectively). After 4 months, leaf morphology and photosynthetic characteristics were determined. Relative to HR4, the LR4 treatment increased leaf area and total chlorophyll concentration (Chl) by 24 and 25%, respectively, but reduced leaf mass per unit area (LMA) by 19%. Elevated [CO(2)] significantly increased leaf area and LMA but did not affect Chl of LR or HR plants. Leaf nitrogen concentration was unaffected by the red:far-red light ratio but decreased significantly in seedlings in the elevated [CO(2)] treatment. Photosynthesis measured in situ under the growth conditions of ambient light and [CO(2)] (A(amb)) was 30% lower on an area basis and 14% lower on a mass basis in LR4 plants than in HR4 plants. Elevated [CO(2)] reduced the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase and thus decreased light-saturated photosynthetic rate in both HR and LR plants. Elevated [CO(2)] increased mean leaf area and decreased respiration rates in both LR and HR plants. The LR8 plants had significantly higher A(amb) than LR4 plants, but similar A(amb) to HR8 plants.

Carbon Dioxide↗
PubMed2001

Norepinephrine modulates myelopoiesis after experimental thermal injury with sepsis.

OBJECTIVE: To determine whether thermal injury and sepsis cause an increase in bone marrow norepinephrine release and whether such a release influences bone marrow monocytopoiesis. SUMMARY BACKGROUND DATA: The authors previously demonstrated enhanced bone marrow monocytopoiesis after burn with sepsis. They also showed that physiologic stress and bacterial challenge without injury could lead to a dynamic release of norepinephrine from the bone marrow compartment. In this study, they sought to determine the potential cause-and-effect relationship of bone marrow norepinephrine release on increased monocytopoiesis after burn sepsis. METHODS: Norepinephrine release from bone marrow was determined by traditional pulse-chase methods. Tissue and bone marrow norepinephrine content was ablated by chemical sympathectomy with 6-hydroxydopamine treatment. Clonogenic potential in response to colony-stimulating factors was determined in total nucleated bone marrow cells. Dual color flow cytometry was used to document the distribution pattern of monocyte progenitors. RESULTS: Burn sepsis induced increased norepinephrine release in bone marrow, spleen, and heart. Colony-forming assays demonstrated an increase in responsive colonies, which was significantly attenuated when norepinephrine content was reduced in animals before burn sepsis. Flow cytometric analysis of early and late monocyte progenitors showed a significantly altered distribution profile of monocyte progenitors in norepinephrine-depleted mice compared with norepinephrine-intact mice. Abrogation of bone marrow norepinephrine content resulted in a 62% survival rate in burn septic mice compared with no survivors in norepinephrine-intact mice. CONCLUSIONS: These data suggest that enhanced bone marrow norepinephrine release after burn sepsis may play a role in bone marrow monocytopoiesis, thus contributing to the sustenance of inflammation.

Animals↗
PubMed2001

Management of urethritis in health maintenance organization members receiving care at a multispecialty group practice in Massachusetts.

BACKGROUND: Cost containment has led to a concern that health maintenance organization-insured patients presenting with complaints of urethritis may be treated without being tested. GOAL: To determine the proportion of men presenting with symptoms of urethritis who are tested for Chlamydia trachomatis and Neisseria gonorrhoeae. STUDY DESIGN: Reviews were performed on 196 randomly selected patient records with an outpatient visit and a diagnostic code consistent with urethritis between 1995 and 1997. Data were collected on demographics, diagnostic testing, and treatment. RESULTS: Diagnostic testing for C trachomatis and N gonorrhoeae was performed, respectively, in 92.3% and 83.2% of the men presenting at an initial visit with complaints of urethritis. Altogether, 98.2% of the patients who met the Centers for Disease Control criteria for documenting urethritis were tested for C trachomatis and N gonorrhoeae. CONCLUSION: Diagnostic testing for C trachomatis and N gonorrhoeae is nearly universal in this multispecialty group practice setting, facilitating surveillance and public health efforts.

Chlamydia Infections↗
PubMed2001

Brain volume changes on longitudinal magnetic resonance imaging in normal older people.

BACKGROUND AND PURPOSE: The purpose of this study is to investigate the longitudinal age-related changes in human brain volume using stereological methods. METHODS: Sixty-six older participants (34 men, 32 women, age [mean +/- SD] 78.9 +/- 3.3 years, range 74-87 years) with normal baseline and follow-up examinations underwent 2 MRIs (magnetic resonance imaging) of the brain on average 4.4 years apart. The volumes of the cerebrum (defined as cortex, basal ganglia, thalamus, and white matter), lateral ventricles, and cerebellum were estimated on the 2 MRIs using an unbiased stereological method (Cavalieri principle). RESULTS: The annual decrease (mean +/- SD) of the cerebral volume was 2.1% +/- 1.6% (P < .001). The average volume of the lateral ventricles on the second MRI was increased by 5.6% +/- 3.6% per year (P < .001). The average volume of the cerebellum on the second MRI was decreased by 1.2% +/- 2.2% per year (P < .001). Even though the average cerebral volume was significantly different between men and women on initial MRI and second MRI, the percentage change of the age-related cerebral volume decrease in male and female brains between initial MRI and second MRI were identical. CONCLUSIONS: The findings showed that there was age-related atrophy of cerebrum and cerebellum and age-related disproportional enlargement of lateral ventricles in normal older men and women.

Aged↗
PubMed2001

Evaluation of biosite triage Clostridium difficile panel for rapid detection of Clostridium difficile in stool samples.

One hundred two stool samples were tested by both the rapid Triage Clostridium difficile Panel (Triage Panel) and the cytotoxin cell culture assay. Five samples positive by both the C. difficile toxin A (Tox A) and common antigen components of the Triage Panel had cytotoxin titers of > or =10,000. Twenty-three samples were Triage Panel Tox A negative but common antigen positive. Ten of these had cytotoxin titers of 10 to 1,000, but 13 were cytotoxin negative. Bacterial isolates obtained from 8 of these 13 specimens were analyzed for Tox A and B genes by PCR, and only two contained toxigenic bacteria. Thus, the majority of samples positive only for C. difficile common antigen contained nontoxigenic bacteria. A Triage Panel Tox A-positive result indicated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 33.3, 100, 100, and 88.2%, respectively. A Triage Panel common antigen-positive result indicated a sensitivity, specificity, PPV, and NPV of 100, 82.7, 53.6, and 100%, respectively. The high NPV of the Triage Panel common antigen, together with rapid reporting of results, should prove useful in avoiding unnecessary use of contact precautions and antibiotic treatment for C. difficile-negative patients. However, with Triage Panel common antigen-positive patients, a sensitive cytotoxin assay should be used to distinguish true cytotoxin-positive patients from C. difficile carriers.

Antigens, Bacterial↗
PubMed2001

Rapid definition of five novel HLA-A*3002-restricted human immunodeficiency virus-specific cytotoxic T-lymphocyte epitopes by elispot and intracellular cytokine staining assays.

Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) play a major role in control of viral replication. To understand the contribution of this antiviral response, an initial step is to fully define the specific epitopes targeted by CTL. These studies focused on CTL responses restricted by HLA-A*3002, one of the HLA-A molecules most prominent in African populations. To avoid the time-consuming effort and expense involved in culturing CTL prior to defining epitopes and restricting alleles, we developed a method combining Elispot assays with intracellular gamma interferon staining of peripheral blood mononuclear cells to first map the optimal epitopes targeted and then define the HLA restriction of novel epitopes. In two A*3002-positive subjects whose CTL responses were characterized in detail, the strongest response in both cases was to an epitope in p17 Gag, RSLYNTVATLY (residues 76 to 86). Using this method, CTL epitopes for which there were no motif predictions were optimized and the HLA restriction was established within 48 to 72 h of receipt of blood. This simple and convenient approach should prove useful especially in the characterization of CTL responses specific to HIV and other viruses, particularly in localities where performing cytotoxicity assays would be problematic.

Amino Acid Sequence↗
PubMed2001

Smad proteins and hepatocyte growth factor control parallel regulatory pathways that converge on beta1-integrin to promote normal liver development.

Smads serve as intracellular mediators of transforming growth factor beta (TGF-beta) signaling. After phosphorylation by activated type I TGF-beta receptors, Smad proteins translocate to the nucleus, where they serve as transcription factors and increase or decrease expression of TGF-beta target genes. Mice lacking one copy each of Smad2 and Smad3 suffered midgestation lethality due to liver hypoplasia and anemia, suggesting essential dosage requirements of TGF-beta signal components. This is likely due to abnormal adhesive properties of the mutant hepatocytes, which may result from a decrease in the level of the beta1-integrin and abnormal processing and localization of E-cadherin. Culture of mutant livers in vitro revealed the existence of a parallel developmental pathway mediated by hepatocyte growth factor (HGF), which could rescue the mutant phenotype independent of Smad activation. These pathways merge at the beta1-integrin, the level of which was increased by HGF in the cultured mutant livers. HGF treatment reversed the defects in cell proliferation and hepatic architecture in the Smad2(+/-); Smad3(+/-) livers.

Active Transport, Cell Nucleus↗
PubMed2001

Single-dose and steady-state pharmacokinetic and pharmacodynamic evaluation of therapeutically clinically equivalent doses of inhaled fluticasone propionate and budesonide, given as Diskus or Turbohaler dry-powder inhalers to healthy subjects.

Direct comparisons of the pharmacokinetic (PK) and systemic pharmacodynamic (PD) properties of inhaled corticosteroids after single and multiple dosing in the same subjects are scarce. The objective of this study was to compare thePK/PDproperties of clinically equivalent, single, and multiple doses of dry-powder formulations of inhaled fluticasone propionate (FP 200 and 500 microg via Diskus) and budesonide (BUD, 400 and 1,000 microg via Turbohaler). Fourteen healthy subjects completed a double-blind, double-dummy, randomized, placebo-controlled, five-way crossover study consisting of a single dose administered at 8 a.m. on day 1 followed by 4 days of twice-daily dosing at 8 a.m. and 8 p.m. on days 2 to 5. Serum concentrations of FP and BUD were measured using validated liquid chromatography/ mass spectrometry assays. The 24-hour cumulative cortisol suppression (CCS) in serum was monitored as the pharmacodynamic surrogate marker. Peak serum concentrations following single and multiple dosing were observed 10 to 30 minutes after inhalation for BUD and 30 to 90 minutes afterinhalation of FP with no influence of dose ordosingregimen. After a single dose of 1000 microg BUD and 500 microg FP the median estimates of terminal half-life and mean residence time were 3.5 and 3.9 hours for BUD and 10.1 and 12.0 hours for FP, respectively. Using previously reported intravenous data, the mean absorption times (MAT) were calculated to be around 2 hours and 7 hours for BUD and FP respectively. On average, the area under the curve (A UC) at steady state (day 5) was up to 30% higher for BUD compared to that over a 12-hour period following the first dose on day 1, whereas A UC estimates were 50% to 80% higherforFP at steady state, indicating accumulation. However, the steady-state Cmax values were seven to eight times and AUC values three to four times higher for BUD than for FP. Comparison of active treatment data with placebo showed that CCS after a single dose was not pronounced for any of the doses/drugs studied. On day 5, both doses of BUD caused statistically significant suppression (CCS of 19% for the 400 microg dose and 36% for the 1,000 microg dose). For FP only the high dose had a statistically significant effect on serum cortisol (CCS of 14% for the 200 microg dose and 27% for the 500 microg dose). Compared to BUD, FP has slower pulmonary absorption and slower elimination kinetics. However, following inhalation of therapeutically equipotent, multiple twice-daily doses in healthy subjects, the systemic effects of FP delivered via Diskus on AUC24 serum cortisol were relatively low and similar to those of BUD delivered via Turbohaler.

Administration, Inhalation↗
PubMed2001

Adipocyte-specific reduction of phosphodiesterase 3B gene expression and its restoration by JTT-501 in the obese, diabetic KKAy mouse.

OBJECTIVE: Phosphodiesterase (PDE) 3B is a key enzyme involved in the anti-lipolytic action of insulin in adipocytes. PDE3B activation results in a reduced output of free fatty acids (FFA), whereas elevated serum FFA is known to cause insulin resistance. We have recently reported that reduced PDE3B gene expression is restored by treatment with pioglitazone, in the adipose tissues of obese, insulin-resistant diabetic KKAy mice. To determine whether the altered PDE3B gene expression is specific for adipocytes, the expression of this gene in liver and epididymal fat tissues of KKAy mice was examined. The effect of JTT-501, another peroxisome proliferator-activated receptor (PPAR)gamma ligand, which is different from thiazolidinedione, was also examined. METHODS: PDE3B mRNA and protein were quantified by an RNase protection assay and Western blotting respectively. Membrane-bound PDE activities were also measured. RESULTS: In adipose tissues of KKAy mice, PDE3B mRNA, protein and membrane-bound PDE activity were reduced to 47%, 57% and 51% respectively relative to those in C57BL/6J control mice. JTT-501 increased PDE3B mRNA, protein and membrane-bound PDE activity by 2.2-, 1.6- and 1.7-fold respectively over those of untreated KKAy mice. In the liver, PDE3B gene expression remained unchanged in KKAy mice, and was not affected by JTT-501. JTT-501 reduced the elevated levels of serum insulin, glucose, FFA and triglyceride in KKAy mice. CONCLUSIONS: PDE3B gene expression was specifically reduced in the adipose tissues of KKAy mice. JTT-501 restored this reduced gene expression with an accompanying improvement in elevated serum FFA and insulin resistance.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

[The influence of hyaluronic acid and basic fibroblast growth factor on the proliferation of ligamentous cells].

OBJECTIVE: To observe the effects of hyaluronic acid (HA) and basic fibroblast growth factor (bFGF) on the proliferation of the cells from medial collateral ligament (MCL) and anterior cruciate ligament (ACL) cells. METHODS: The MCL cells and ACL cells of mature New Zealand white rabbit were cultured, while HA, bFGF or HA and bFGF were added to the cell culture media, the cellular proliferation was assayed by MTT method. RESULTS: HA only had no effect on the preoliferation of ACL cells, but had a small stimulatory effect on the proliferation of MCL cells. The addition of 1 ng/ml bFGF enhanced the proliferation of both MCL and ACL cells significantly, and this enhancement was maximal in the concentration of 50 ng/ml. However, the enhancement of proliferation of MCL and ACL cells could be achieved when the combination of HA in concentration of 100 micrograms/ml and bFGF in concentration of 100 ng/ml. CONCLUSION: It is evident that bFGF can enhance the proliferation of the ligament cells. HA can maintain the normal growth of ACL cells with no effect on the proliferation of the cells, while HA has a small stimulatory effect on the proliferation of MCL cells. However, when bFGF is coordinated with HA, more improvement of cellular proliferation can be achieved. HA can be used as a potential carrier for bFGF to enhance the healing of ligamentous tissue injuries.

Animals↗