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Biomedical subjects

X Su

Publications and source records attributed to X Su.

At least 37 records · Page 2Linked to original sources
PubMed2000

kappa -opioid receptor agonists modulate visceral nociception at a novel, peripheral site of action.

kappa-opioid receptor agonists (kappa-ORAs) have been shown to modulate visceral nociception through an interaction with a peripheral, possibly novel, kappa-opioid-like receptor. We used in the present experiments an antisense strategy to further explore the hypothesis that kappa-ORA effects in the colon are produced at a site different from the cloned kappa-opioid receptor (KOR). An antisense oligodeoxynucleotide (ODN) to the cloned rat KOR was administered intrathecally (12.5 microg, twice daily for 4 d) to specifically knock-down the cloned KOR. Efficacy of the KOR antisense ODN treatment was behaviorally evaluated by assessing the antinociceptive effects of peripherally administered kappa- (EMD 61, 753 and U 69,593), mu- (DAMGO) and delta- (deltorphin) ORAs in the formalin test. Intrathecal antisense, but not mismatch ODN blocked the actions of EMD 61,753 and U 69,593 without affecting the actions of DAMGO or deltorphin; a complete recovery of antinociceptive actions of the kappa-ORA EMD 61,753 was observed 10 d after the termination of antisense ODN treatment. In contrast, the ability of EMD 61,753 to dose-dependently attenuate responses of pelvic nerve afferent fibers to noxious colonic distension was unaffected in the same rats in which the antisense ODN effectively knocked-down the KOR as assessed in the formalin test. Additionally, Western blot analysis demonstrated a significant downregulation of KOR protein in the L4-S1 dorsal root ganglia of antisense, but not mismatch ODN-treated rats. The present results support the existence of a non-kappa-opioid receptor site of action localized in the colon.

Acetamides↗
PubMed2000

Structural basis for the fracture toughness of the shell of the conch Strombus gigas.

Natural composite materials are renowned for their mechanical strength and toughness: despite being highly mineralized, with the organic component constituting not more than a few per cent of the composite material, the fracture toughness exceeds that of single crystals of the pure mineral by two to three orders of magnitude. The judicious placement of the organic matrix, relative to the mineral phase, and the hierarchical structural architecture extending over several distinct length scales both play crucial roles in the mechanical response of natural composites to external loads. Here we use transmission electron microscopy studies and beam bending experiments to show that the resistance of the shell of the conch Strombus gigas to catastrophic fracture can be understood quantitatively by invoking two energy-dissipating mechanisms: multiple microcracking in the outer layers at low mechanical loads, and crack bridging in the shell's tougher middle layers at higher loads. Both mechanisms are intimately associated with the so-called crossed lamellar microarchitecture of the shell, which provides for 'channel' cracking in the outer layers and uncracked structural features that bridge crack surfaces, thereby significantly increasing the work of fracture, and hence the toughness, of the material. Despite a high mineral content of about 99% (by volume) of aragonite, the shell of Strombus gigas can thus be considered a 'ceramic plywood' and can guide the biomimetic design of tough, lightweight structures.

Animals↗
PubMed2000

A miniature integrated device for automated multistep genetic assays.

A highly integrated monolithic device was developed that automatically carries out a complex series of molecular processes on multiple samples. The device is capable of extracting and concentrating nucleic acids from milliliter aqueous samples and performing microliter chemical amplification, serial enzymatic reactions, metering, mixing and nucleic acid hybridization. The device, which is smaller than a credit card, can manipulate over 10 reagents in more than 60 sequential operations and was tested for the detection of mutations in a 1.6 kb region of the HIV genome from serum samples containing as few as 500 copies of the RNA. The elements in this device are readily linked into complex, flexible and highly parallel analysis networks for high throughput sample preparation or, conversely, for low cost portable DNA analysis instruments in point-of-care medical diagnostics, environmental testing and defensive biological agent detection.

DNA↗
PubMed2000

Extensive neurite outgrowth and active synapse formation on self-assembling peptide scaffolds.

A new type of self-assembling peptide (sapeptide) scaffolds that serve as substrates for neurite outgrowth and synapse formation is described. These peptide-based scaffolds are amenable to molecular design by using chemical or biotechnological syntheses. They can be tailored to a variety of applications. The sapeptide scaffolds are formed through the spontaneous assembly of ionic self-complementary beta-sheet oligopeptides under physiological conditions, producing a hydrogel material. The scaffolds can support neuronal cell attachment and differentiation as well as extensive neurite outgrowth. Furthermore, they are permissive substrates for functional synapse formation between the attached neurons. That primary rat neurons form active synapses on such scaffold surfaces in situ suggests these scaffolds could be useful for tissue engineering applications. The buoyant sapeptide scaffolds with attached cells in culture can be transported readily from one environment to another. Furthermore, these peptides did not elicit a measurable immune response or tissue inflammation when introduced into animals. These biological materials created through molecular design and self assembly may be developed as a biologically compatible scaffold for tissue repair and tissue engineering.

Amino Acid Sequence↗
PubMed2000

[Effect of sepia on intracellular Ca2+ concentration, nuclear Ca2+/Mg(2+)-ATPase activities and c-jun expression in H22 cancer cells].

The effect of sepia on the intracellular Ca2+ concentration, nuclear Ca2+/Mg(2+)-ATPase activities and the expression of c-jun were studied in H22 cancer cells by using fluorescent probe and immunohistochemical method. The results showed that intracellular Ca2+ concentration decreased 69% and 79%, nuclear Ca2+/Mg(2+)-ATPase activities diminished 21% and 37%, c-jun expression decreased obviously. The results suggested that sepia probably diminished the intracellular Ca2+ concentration, affected Ca(2+)-dependent nuclear Ca2+/Mg(2+)-ATPase activities, thus reduced the amount of Ca2+ transporting into nuclei, so lessened the promoting effect of Ca2+ on c-jun expression, and therefore inhibited cellular differentiation and proliferation. This might be one of the possible anti-cancer mechanisms of sepia.

Animals↗
PubMed2000

A novel topology model of the human Na(+)/H(+) exchanger isoform 1.

The membrane topology of the human Na(+)/H(+) exchanger isoform 1 (NHE1) was assessed by substituted cysteine accessibility analysis. Eighty-three cysteine residues were individually introduced into a functional cysteineless NHE1, and these mutants were expressed in the exchanger-deficient PS120 cells. The topological disposition of introduced cysteines was determined by labeling with a biotinylated maleimide in the presence or absence of preincubation with the membrane-impermeable sulfhydryl reagent, 2-trimethylammoniumethyl-methanethiosulfonate in streptolysin O-permeabilized or nonpermeabilized cells. We proposed a new model for the topology of NHE1 that is significantly different from the model derived from hydropathy analysis. In this model, NHE1 is composed of 12 transmembrane segments (TMs) with the N and C termini located in the cytosol. The large, last extracellular loop in the membrane domain of the original model was suggested to comprise an intracellular loop, a new transmembrane segment (TM11), and an extracellular loop in the new model. Interestingly, cysteines at 183 and 184 and at 324 and 325 mapped to intracellular loops connecting TMs 4 and 5 (IL2) and TMs 8 and 9 (IL4), respectively, were accessible to sulfhydryl reagents from the outside. Furthermore, exchange activities of two mutants, R180C and Q181C, within IL2 were markedly inhibited by external MTSET. These data suggest that part of IL2 or IL4 may be located in a pore-lining region that is accessible from either side of the membrane and involved in ion transport.

Amino Acid Sequence↗
PubMed2000

Significant role for Fas in the pathogenesis of autoimmune diabetes.

Programmed cell death represents an important pathogenic mechanism in various autoimmune diseases. Type I diabetes mellitus (IDDM) is a T cell-dependent autoimmune disease resulting in selective destruction of the beta cells of the islets of Langerhans. beta cell apoptosis has been associated with IDDM onset in both animal models and newly diagnosed diabetic patients. Several apoptotic pathways have been implicated in beta cell destruction, including Fas, perforin, and TNF-alpha. Evidence for Fas-mediated lysis of beta cells in the pathogenesis of IDDM in nonobese diabetic (NOD) mice includes: 1) Fas-deficient NOD mice bearing the lpr mutation (NOD-lpr/lpr) fail to develop IDDM; 2) transgenic expression of Fas ligand (FasL) on beta cells in NOD mice may result in accelerated IDDM; and 3) irradiated NOD-lpr/lpr mice are resistant to adoptive transfer of diabetes by cells from NOD mice. However, the interpretation of these results is complicated by the abnormal immune phenotype of NOD-lpr/lpr mice. Here we present novel evidence for the role of Fas/FasL interactions in the progression of NOD diabetes using two newly derived mouse strains. We show that NOD mice heterozygous for the FasL mutation gld, which have reduced functional FasL expression on T cells but no lymphadenopathy, fail to develop IDDM. Further, we show that NOD-lpr/lpr mice bearing the scid mutation (NOD-lpr/lpr-scid/scid), which eliminates the enhanced FasL-mediated lytic activity induced by Fas deficiency, still have delayed onset and reduced incidence of IDDM after adoptive transfer of diabetogenic NOD spleen cells. These results provide evidence that Fas/FasL-mediated programmed cell death plays a significant role in the pathogenesis of autoimmune diabetes.

Adoptive Transfer↗
PubMed2000

Allelic modifications of the cg2 and cg1 genes do not alter the chloroquine response of drug-resistant Plasmodium falciparum.

The determinant of chloroquine resistance (CQR) in a Plasmodium falciparum cross was previously mapped by linkage analysis to a 36 kb segment of chromosome 7. Candidate genes within this segment have been previously shown to include two genes, cg2 and cg1, that have complex polymorphisms linked to the CQR phenotype. Using DNA transfection and allelic exchange, we have replaced these polymorphisms in CQR parasites with cg2 and cg1 sequences from chloroquine sensitive parasites. Drug assays of the allelically-modified lines show no change in the degree of CQR, providing evidence against the hypothesis that these polymorphisms are important to the CQR phenotype. Similarly, no change was found in the degree to which verapamil or other chloroquine sensitizers reverse CQR in the transformants. These results and the high though not complete degree of association of CQR with cg2 and cg1 polymorphisms in field isolates suggest involvement of another nearby gene in the P. falciparum CQR mechanism.

Alleles↗
PubMed2000

Canine thyrotropin beta-subunit gene: cloning and expression in Escherichia coli, generation of monoclonal antibodies, and transient expression in the Chinese hamster ovary cells.

The gene encoding the mature beta subunit of canine thyroid stimulating hormone (cTSH beta) was cloned, sequenced and expressed in Escherichia coli and in Chinese hamster ovary (CHO) cells, and monoclonal antibodies against the recombinant cTSH beta purified from E. coli were generated. The gene fragment that encodes mature TSH beta was cloned from the canine genomic DNA by direct polymerase chain reaction (PCR) using primers that were designed based on the consensus sequences from other species. The resulting 891 basepairs (bp) of genomic DNA consisted of two coding exons of the canine TSH beta gene and an intron of 450 bp. The two exons, which encode the mature cTSH beta subunit, was joined together by an overlap PCR and was expressed in E. coli as 6xHis-tagged protein. The purified recombinant cTSH beta with a molecular weight of about 15 kDa was recognized by the polyclonal antibodies prepared against the native canine TSH in Western blot. Monoclonal antibodies were raised against the purified cTSH beta and subsequently characterized. For transient expression in CHO cells that are permanently transfected with the bovine common alpha gene, a 60-oligonucleotide signal peptide coding sequence was added to the 5' end of the cTSH beta gene before it was cloned into the mammalian expression vector pRSV and used to transfect CHO cells. The medium from these transfected cells, presumably containing the bovine alpha and canine TSH beta in heterodimeric confirmation, exhibited TSH bioactivity as indicated by the stimulation of cAMP production in the cultured FRTL-5 thyrocytes.

Amino Acid Sequence↗
PubMed2000

Piezoelectric quartz crystal based label-free analysis for allergy disease.

This work presents a piezoelectric (Pz) quartz crystal based label-free quantification of total IgE and allergen-specific IgE in human sera for allergy testing. An evaluation of the different brands of crystals was first initiated with respect to variability in mass sensitivity, frequency measurement reliability and stability, and surface roughness. Thereafter, for total IgE quantification. a direct assay format was adopted. By means of thioctic acid (TA) and coupling reagents, anti-human IgE antibodies were immobilized on AT-cut Pz crystals (10 MHz). The modified crystals could detect serum IgE directly corresponding to a downward frequency shift. The results showed that silver-coated crystals as compared with their gold-coated counterparts provided approximately 1.5 times higher mass detection sensitivity for total IgE in the range of 5-300 IU/ml with a linear regression line, y = 1.8957 x + 1.5603, R2 = 0.995. For the detection of allergen-specific IgE, a sandwiched assay format was used. As the allergen-modified sensor surface captured various classes of associated antibodies (IgE, IgG, etc) and interfering serum proteins as well, the initial frequency shift downwards caused by sera sample incubation would not be proportional to specific IgE levels. Thus, following sample incubation, a second incubation step with secondary anti-human IgE was added to recognize IgE from other bound substances. The frequency shift after secondary antibody binding reflected the amount of allergen-specific IgE proportionally. Compared with 10 MHz crystals, the 20 MHz counterparts provided approximately four times higher mass detection sensitivity for allergen specific IgE in the range of 0.15-17.5 IU/ml with a linear regression line, y = 50.525 x + 107.777, R2 = 0.954. Total IgE and allergen specific IgE assay results of real patients' sera using the Pz sensors agreed well with those obtained by commercially available test kits with correlation coefficient 0.96-0.98. The possibility of regenerating the quartz crystals for further re-use was also dealt with.

Allergens↗
PubMed2000

Disposable, low cost, silver-coated, piezoelectric quartz crystal biosensor and electrode protection.

The use of a commercial, silver-coated, piezoelectric quartz crystal as a disposable, low cost and reliable immunosensor is presented. The protection of the silver electrode from undesirable oxidation was achieved by polystyrene or carboxy-poly(vinyl chloride) (PVC-COOH) modification. In addition to serving as protection for the electrode, polymer films provided a substrate for antibody immobilization by either physical adsorption or covalent linkage. Polystyrene modification showed an additional advantage of improvement of surface smoothness. The atomic force microscope (AFM) and scanning electron microscope (SEM) were used to evaluate the morphologies of polymer films obtained by dip or drop coating techniques. It was found that drop coating provided more significant improvement in surface smoothness than dip coating, and the resulting sensor surfaces were more suitable for in situ liquid phase assay. Although PVC-COOH-modified sensors were not suitable for liquid phase assay because of the high surface roughness, the covalent linkages (amide bonds) between antibodies and -COOH groups in the polymer film offered better sensor performance in ex situ assay in terms of a higher antibody binding capacity and better antigen detection sensitivity.

Biosensing Techniques↗
PubMed2000

Peripheral opioid modulation of visceral pain.

Opioids are widely and successfully used for control of pain, including pain arising from the viscera. Constipating, sedating, respiratory depressant and other effects of opioids, however, often limit their long-term use in the treatment of a variety of visceral pain states. Accordingly, understanding visceral pain mechanisms and its modulation is important to developing improved strategies for pain control.

Analgesics, Opioid↗
PubMed2000

Effects of intracolonic opioid receptor agonists on polymodal pelvic nerve afferent fibers in the rat.

We studied the effects of intracolonic administration of opioid receptor agonists (ORAs) on responses of pelvic nerve afferent fibers to colorectal distension (CRD) and heat. Single-fiber recordings were made from the decentralized S1 dorsal rootlet in the rat. An approximately 7-cm length of descending colon was isolated in situ to permit intracolonic perfusion with Krebs solution, which, when the outflow was clamped, was used to distend the colon. Responses to noxious CRD (40 mmHg, 30 s) were tested after intracolonic instillation of mu-, delta- or kappa-ORAs. Intracolonic administration of the kappa-ORAs EMD 61,753 (n = 5/12) and U62,066 (n = 8/11), but not either the mu-ORA fentanyl or the delta-ORA SNC-80, concentration-dependently inhibited responses of afferent fibers. For fibers unaffected by intracolonic administration of EMD 61,753 or U62,066, intra-arterial administration of kappa-ORAs was effective. Forty-one of 54 mechanosensitive fibers also responded to intracolonic instillation of heated Krebs solution (50 degrees C). Intra-arterial injection of fentanyl or SNC-80 did not attenuate responses to heat. Either intracolonic or intra-arterial administration of EMD 61,753 or U62, 066, however, inhibited afferent fiber responses to heat. These results document that mechanical and thermal sensitivity of polymodal pelvic nerve afferent fibers innervating the rat colon can be inhibited peripherally by intracolonic instillation of kappa-ORAs.

Acetamides↗
PubMed2000

Mechanosensitive potassium channels in rat colon sensory neurons.

Single-channel recording techniques were used to characterize mechanosensitive channels in identified (1.1'-dioctadecyl-3,3,3', 3'-tetramethylindocarbocyanine methanesulfonate labeled) colon sensory neurons dissociated from adult S1 dorsal root ganglia. Channels were found in 30% (7/23) of patches in a cell-attached configuration and in 43% (48/111) of excised inside-out patches. Channels were highly selective for K(+), had a slope conductance of 54 pS in symmetrical solutions, and were blocked by tetraethylammonium, amiloride, and benzamil. Channels were also seen under Ca(2+)-free conditions. Gadolinium (Gd(3+)), a known blocker of mechanosensitive ion channels, did not block channel activity. Tetrodotoxin and 4-aminopyridine were also ineffective. The cytoskeletal disrupters colchicine and cytochalasin D reduced the percentage of patches containing mechanosensitive channels. These results indicate that rat colon sensory neurons contain K(+)-selective mechanosensitive channels that may modulate the membrane excitability induced by colonic distension.

4-Aminopyridine↗
PubMed2000

[Analysis of chromosomal karyotypes in 300 fetal blood samples during the second and third trimesters of gestation].

OBJECTIVE: To analyze the fetal chromosomal karyotypes from the blood samples obtained by cordocenteses during the second and third trimesters, and to investigate the types of chromosomal abnormalities, as well as the relationship between the abnormal karyotypes and the indications of prenatal diagnosis. METHODS: Cordocenteses were performed in 300 pregnant women with different indications for prenatal diagnosis during the 18 to 38 gestational weeks, and fetal chromosomal karyotypes were examined. RESULTS: Twenty three chromosomal abnormalities(7.7%) were checked out. In the second trimester, there were 15 abnormalities in 174 samples(8. 6%); whereas in the third trimester, it was 8 out of 126(6.3%), P=0. 77. Trisomy, the leading abnormality, consisted of 60.9%(14/23) of all abnormalities and 9 out of 14 were trisomy 21, which was 39. 1%(9/23). In those aged over 35 years, trisomy 21 was detected in 5 of 92(5.4%), and in the age under 35 years, it was 4 out of 208(1. 9%), P=0.26. Thirty three women had the history of giving a birth of trisomy 21 previously, this time, however, no one was recurrent. Highest chromosomal aberration rate, 26.3%(5/19), was detected in the fetuses with intrauterine growth retardation(IUGR), and all were trisomy. Balanced translocation was found in 5 fetuses (1 associated with Robertsonian translocation), which was 21.7%(5/23). CONCLUSION: During the second and third trimesters, the rate of chromosomal abnormality is 7.7% in those fetuses who have maternal indications for prenatal diagnosis. trisomy, especially trisomy 21, is the most common abnormal karyotype found in these periods and in advanced maternal age, as well as in severe IUGR.

Adult↗
PubMed2000

[Determination of S-100 beta protein in cerebrospinal fluid of patients with metastatic carcinoma to central nervous system].

OBJECTIVE: To investigate the concentration of S-100 beta protein in cerebrospinal fluid (CSF) for 25 patients with metastatic carcinoma to central nervous system (CNS), and to evaluate its clinical value. METHODS: S-100 beta protein of CSF was measured by ELISA for 25 patients with metastatic carcinoma to CNS and 20 patients without any CNS disease (control group). The patients were divided into three categories according to severity of disease: severe group, moderate group and mild group. Meanwhile, CSF cytology was also detected. RESULTS: The level of S-100 beta protein of all patients was higher than that of control group (P < 0.01), and severe group > moderate group (P < 0.01) > mild group (P < 0.01). The percentage of CSF lymphocyte in severe group was lower than that of mild group and control group (P < 0.05 and P < 0.01). CONCLUSIONS: CSF S-100 beta protein level of patients with metastatic carcinoma may be related to the severity of their brain insult.

Adolescent↗