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Biomedical subjects

G Shi

Publications and source records attributed to G Shi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Manometric characteristics of the upper esophageal sphincter recorded with a microsleeve.

OBJECTIVES: We compared manometric recordings of the upper esophageal sphincter (UES) recorded with a miniature sleeve to those obtained using standard manometry. METHODS: The UES pressure of eight volunteer subjects was measured by station pull-through (SPT), by rapid pull-through (RPT), and with a microsleeve sensor for 30 min, followed by 15 min of esophageal acid infusion. Deglutitive UES relaxation recorded with a microsleeve and solid state sensor were compared. RESULTS: The UES pressure recorded with the microsleeve (25+/-9 mm Hg) was significantly less than that by SPT (114+/-18 mm Hg) or RPT (152+/-19 mm Hg), and was unaffected by acid infusion. Periods of low UES pressure were observed during long interswallow intervals (11+/-4, range 6-18 mm Hg). Deglutitive relaxation duration and intrabolus pressure measured with the microsleeve were less than those recorded by the solid state transducer. CONCLUSIONS: "Normal" UES pressure is heavily dependent on measurement technique; pressures obtained with a miniature sleeve are a fraction of those obtained by SPT or RPT. During periods of relative comfort with minimal swallowing, UES tone is approximately 10 mm Hg, similar to that during sleep. Volume modulation of deglutitive UES relaxation is demonstrable with a microsleeve, albeit with less precision than with a solid-state transducer.

Acids↗
PubMed2001

A novel procedure for pre-embedding double immunogold-silver labeling at the ultrastructural level.

Pre-embedding double immunogold-silver labeling using two ultrasmall gold conjugates has not been attempted previously because a means of distinguishing labels by conjugates of identical sizes was lacking. This study investigated the feasibility of creating a particle size segregation between two ultrasmall gold conjugates through sequential immunogold incubations and silver enhancements. Two primary antibodies, mouse anti-synaptophysin and rabbit anti-glial fibrillary acidic protein (GFAP), were used in the model system. Differentiation of the double labeling was achieved by incubating with one ultrasmall gold conjugate, followed by silver enhancement, and then incubating with the second ultrasmall gold conjugate, followed by additional silver enhancement. This resulted in two groups of silver-enhanced particles: smaller particles enhanced once and larger particles enhanced twice. Electron microscopic examination revealed two readily distinguished populations of gold-silver particles within the appropriate structures, with very little size overlap. The quality of the ultrastructure permitted identification of most subcellular organelles. This procedure provides for the first time a pre-embedding immunogold-silver labeling protocol that allows the precise subcellular co-localization of multiple antigens.

Animals↗
PubMed2001

[Expression of rasp21, C-myc, C-erbB-2, and AFP in 2-FAA induced experimental hepatocarcinogenesis].

OBJECTIVE: To investigate the distribution of oncogenes and their relationships in 2-FAA induced experimental hepatocarcinogenesis. METHODS: Rasp21, C-myc, C-erbB-2, and AFP were detected and analyzed by the SP method of immunohistochemistry. RESULTS: Some cells expressed rasp21, C-myc, and AFP in peripheral liver lobules and alternated hepatocyte foci in the early stage of the experiment. And with the formation and progression of hyperplastic hepatocytic nodules, expressed cells increased and often accompanied each other. Expression of C-erbB-2 appeared in the middle stage of the hepatocarcinogenesis. CONCLUSIONS: Expression of rasp21, C-myc, and AFP in the experimental hepatocarcinogenesis is an early molecule change, which may relate to the initiation of hepatocarcinogenesis and be considered to be one of the molecular bases for the morphogenesis of hepatocarcinogenesis. During the development of lesion, C-erbB-2 may have promoting effects. It is also clear that malignant transformation of hepatocyte needs the cooperation of multiple oncogenes.

2-Acetylaminofluorene↗
PubMed2001

[Weak signal detection in every heart cycle].

In this article, a new approach is introduced to lowering the myo-electronic noise in weak ECG signals. We use artificial neural network to make the noise be white, and then we adopt an adaptive filter of which the reference signal is achieved by extracting from other ECG cycle. The outcome is the reduction of both white noise and non-white noise in ECG signal. Satisfactory results have been achieved by using this method in the experiment of late potential detection.

Action Potentials↗
PubMed2001

[Effects of calcium on biological characteristics of wheat seedlings under ultraviolet-B radiation stress].

Under simulated ultraviolet-B radiation (UV-B, 280-320 nm), effect of calcium on biological characteristics of wheat seedlings was studied with pot culture experiment. The results showed that the growth indexes of wheat seedlings on ground and underground in calcium concentration 2 mmol/L treated group were obviously reduced than that of wheat seedlings in control treated group (the descending range of 8.1%-36.1%) under UV-B stress (0.35 W/m2, 6 h per day, for 7 day). And the decreasing degree of growth indexes (3.2%-28.6%) for wheat seedlings in calcium concentration 6 mmol/L treated group were lower than in calcium concentration 2 mmol/L treated group. The experiment proved that calcium can mitigate the damage of ultraviolet-B radiation on wheat seedlings, and this effect was related to that calcium affected physiological and biochemical characteristics of wheat seedlings.

Calcium↗
PubMed2000

Catalytic center assembly of HPPK as revealed by the crystal structure of a ternary complex at 1.25 A resolution.

BACKGROUND: Folates are essential for life. Unlike mammals, most microorganisms must synthesize folates de novo. 6-Hydroxymethyl-7, 8-dihydropterin pyrophosphokinase (HPPK) catalyzes pyrophosphoryl transfer from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP), the first reaction in the folate pathway, and therefore is an ideal target for developing novel antimicrobial agents. HPPK from Escherichia coli is a 158-residue thermostable protein that provides a convenient model system for mechanistic studies. Crystal structures have been reported for HPPK without bound ligand, containing an HP analog, and complexed with an HP analog, two Mg(2+) ions, and ATP. RESULTS: We present the 1.25 A crystal structure of HPPK in complex with HP, two Mg(2+) ions, and AMPCPP (an ATP analog that inhibits the enzymatic reaction). This structure demonstrates that the enzyme seals the active center where the reaction occurs. The comparison with unligated HPPK reveals dramatic conformational changes of three flexible loops and many sidechains. The coordination of Mg(2+) ions has been defined and the roles of 26 residues have been derived. CONCLUSIONS: HPPK-HP-MgAMPCPP mimics most closely the natural ternary complex of HPPK and provides details of protein-substrate interactions. The coordination of the two Mg(2+) ions helps create the correct geometry for the one-step reaction of pyrophosphoryl transfer, for which we suggest an in-line single displacement mechanism with some associative character in the transition state. The rigidity of the adenine-binding pocket and hydrogen bonds are responsible for adenosine specificity. The nonconserved residues that interact with the substrate might be responsible for the species-dependent properties of an isozyme.

Adenosine Triphosphate↗
PubMed2000

Bolus transit assessed by an esophageal stress test in postfundoplication dysphagia.

INTRODUCTION: Dysphagia is common after Nissen fundoplication but the relationship between dysphagia and bolus transit is poorly defined. This study compared bolus transit of fundoplication patients to normal individuals. METHODS: Twelve fundoplication patients and 20 healthy volunteers rated their ability to swallow eight bolus consistencies from no difficulty (0) to extreme difficulty (3) to compute a dysphagia score (range = 0-24). A 16-lumen manometric assembly was positioned across the esophagogastric junction (EGJ) and subjects were imaged fluoroscopically in a supine posture while swallowing 5 cc liquid barium and a 5-cc marshmallow-like viscoelastic barium bolus. Videofluoroscopic images were analyzed for total esophageal transit time and the fraction of time required to cross the EGJ. Manometric tracings were analyzed for the intrabolus pressure proximal to the EGJ, intragastric pressure, and distal peristaltic amplitude for each bolus. RESULTS: Dysphagia scores for fundoplication patients were significantly higher (7.3 +/- 5.1, range = 1-17) than for normals (0.5 +/- 0.6, range = 0-2). This correlated with longer total transit times for liquids and solids (r = 0.60, P < 0.01) and a greater percentage of transit time attributable to the EGJ transit. Retrograde flow at the EGJ (escape of bolus proximally up the esophagus) and peristaltic dysfunction were more frequent in fundoplication patients. However, no differences existed in manometric parameters between groups. CONCLUSIONS: Fundoplication impairs both liquid and solid esophageal bolus transit. Dysphagia perceived by fundoplication patients correlated with increased transit time, particularly across the EGJ. Combined quantitative evaluation with manometry and fluoroscopy reveals functional defects in fundoplication subjects, which are not evident by either modality alone.

Adult↗
PubMed2000

Dissecting the nucleotide binding properties of Escherichia coli 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase with fluorescent 3'(2)'-o-anthraniloyladenosine 5'-triphosphate.

6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphate from ATP to 6-hydroxymethyl-7, 8-dihydropterin, the first reaction in the folate biosynthetic pathway. Like other enzymes in the folate pathway, HPPK is an ideal target for development of antimicrobial agents because the enzyme is essential for microorganisms but is absent from humans and animals. Using 3'(2')-o-anthraniloyladenosine 5'-triphosphate as a fluorescent probe, a fluorometric competitive binding assay has been developed for measuring the dissociation constants of various compounds that bind to the ATP site of HPPK. The fluorometric assay has been used to determine the nucleotide specificity and dissect the energetics of the binding of MgATP. The order of affinity of various nucleoside triphosphates for HPPK is MgATP>MgGTP>MgITP>MgXTP approximately MgUTP approximately MgCTP. The affinity of MgATP for HPPK (K(d)=2.6+/-0.06 microM) is 260-fold higher than that of MgGTP and more than 1000-fold higher than those of the other nucleoside triphosphates, indicating that HPPK is highly specific with respect to the base moiety of the nucleotide. The affinity of ATP for HPPK in the presence of Mg(2+) is 15 times that in the absence of Mg(2+), indicating that the metal ion is important for the binding of the nucleotide. Removal of the gamma-phosphate from MgATP reduces its affinity for HPPK by a factor of approximately 21. The affinity of AMP for HPPK is about one third that of ADP and almost the same as that of adenosine. The result suggests that among the three phosphoryl groups of MgATP, the gamma-phosphoryl group is most critical for binding to HPPK and the alpha-phosphoryl group contributes little to the binding of the nucleotide. The affinity of MgATP is 18 times that of MgdATP, indicating that the 2'-hydroxyl group of MgATP is also important for binding. van't Hoff analysis suggests that binding of MgATP is mainly driven by enthalpy at 25 degrees C and the entropy of binding is also in favor of the formation of the HPPK.MgATP complex.

Binding, Competitive↗
PubMed2000

Increased frequency of transient lower esophageal sphincter relaxation induced by gastric distention in reflux patients with hiatal hernia.

BACKGROUND & AIMS: This study aimed to determine if hiatal hernia influences vulnerability to reflux and transient lower esophageal sphincter relaxation (tLESR) during gastric distention in patients with gastroesophageal reflux disease (GERD). METHODS: Eight normal subjects and 15 patients with GERD were studied. A metal clip attached to the squamocolumnar junction (SCJ) was beneath the hiatus in all control subjects. Eight GERD patients with >/=1-cm SCJ-hiatus separation were considered hernia patients, and 7 with <1-cm separation were considered nonhernia patients. Manometry and esophageal pH were recorded for 30 minutes, after which the stomach was loaded with acid dextrose and the recording continued for 2 hours with intragastric air infusion of 15 mL/min. RESULTS: Baseline reflux was comparable among groups. Gastric distention increased the frequency of reflux by the tLESR mechanism in all groups. Controls and nonhernia patients had median increases of 4.0 and 4.5 in tLESR frequency, respectively, and hernia patients had a median increase of 9.5/h. tLESR frequency was highly correlated with the SCJ-hiatus separation (r = 0.76; P < 0.001). CONCLUSIONS: Gastric air infusion was a potent stimulus for tLESR and reflux. The resultant tLESR frequency was directly proportional to the separation between the SCJ and hiatus, suggesting that the perturbed anatomy associated with hiatal hernia predisposed to eliciting tLESRs in patients with GERD.

Acids↗
PubMed2000

Esophagogastric junction pressure topography after fundoplication.

OBJECTIVES: This study compared the pressure topography after laparoscopic Nissen fundoplication to that of normal subjects and patients with hiatal hernia and reflux disease. METHODS: Seven patients with fundoplication, 7 normal subjects and 7 patients with hiatal hernia, were studied. The squamocolumnar junction and intragastric margin of the esophagogastric junction (EGJ) were marked with metal clips. Axial and radial characteristics of EGJ pressure were mapped relative to the hernia and clipped during concurrent fluoroscopy and manometry. Responses to inspiration and abdominal compression were also analyzed. RESULTS: Fundoplication modifies the EGJ by restoration of the hiatal component of EGJ pressure and elongation of the subdiaphragmatic component. Maximal EGJ pressure after fundoplication is mainly dependent on the extrinsic effect of the hiatal canal that compresses the esophagus; the resultant length of the EGJ reflects the length of the fundic wrap. Integrity of the EGJ after fundoplication is independent of the intrinsic lower esophageal sphincter itself. CONCLUSIONS: Fundoplication alters the pressure topography of the EGJ by reducing the hiatal hernia, tightening the hiatal orifice, and constructing a subdiaphragmatic wrap of variable length. Each effect depends on different technical aspects of the surgery with the potential of substantial variability in the resultant pressure topography.

Adult↗
PubMed2000

[Expression of the gene encoding human leukocyte differentiation antigen 5D4].

OBJECTIVE: To make sure that 5D4 cDNA is a full length cDNA and to prepare antigens to make monoclonal antibodies against different epitopes in 5D4 protein. METHODS: Recombinant expression vectors pGEX-5X-3-5D4 (full length) and pGEX-5X-3-5D4 (5'fragment) were constructed. 5D4 polypeptides were expressed in Escherichia coli DH5 alpha. 5D4 mRNA expression was detected in various tissues and cell lines with Northern blot assay and RT-PCR. RESULTS: Northern blot demonstrated five mRNA transcripts of 1.9, 2.4, 3.9, 4.5, and 10.0 kb in length existing and expressing of various extent in various tissues. The 1.9 kb mRNA transcript was observed only in the spleen and the small intestinal tissues. The expression of 5D4 mRNA was different in various cell lines. 5D4 polypeptides were expressed in Escherichia coli DH5 alpha. CONCLUSION: The 1,846 bp 5D4 cDNA is a full length cDNA. A full length 5D4 protein and a 5D4 polypeptide which is the NH2 side to the transmembrane region fused with GST with a molecular weight of 66,000 and 60,000 expressing in Escherichia coli DH5 alpha.

Antigens, CD↗
PubMed2000

[Effect of 6A8 alpha-mannosidase expression on the proliferative response of human B cell line 3D5].

OBJECTIVE: To study the effect of 6A8 alpha-mannosidase expression on the proliferative response of human B cell 3D5. METHODS: Recombination of adeno-associated virus vector(rAAV) mediated delivery of sense 6A8 DNA or antisense 6A8 DNA into 3D5 cells, and monoclonal antibody 6A8 alpha staining and Con A binding assay for determination of the change of 6A8 alpha-mannosidase expression, MTT assay for proliferation detection of 3D5 cells driven by Staphylococcus aureus crude cell suspension formalin-fixed (SAC), lower molecular weight B cell growth factor (LMW-BCGF), or rIL-6. RESULTS: The expression of 6A8 alpha-mannosidase was enhanced in sense 6A8-transduced cells and reduced in antisense 6A8-transduced cells. In comparison with the wild type and the mock-transduced cells, the proliferative response of the sense 6A8-transduced cells to SAC stimulation was enhanced (P < 0.05). However, transduction with antisense 6A8 did not affect the response. In addition, transduction with either sense or antisense 6A8 had no effect on proliferation of 3D5 cells induced by LMW-BCGF or IL-6. CONCLUSION: The proliferative response to SAC stimulation was enhanced in the 3D5 cells with enhanced expression of 6A8 alpha-mannosidase. Either enhancement or reduction of 6A8 alpha-mannosidase expression had no effect on proliferation induced by LMW-BCGF or IL-6.

B-Lymphocytes↗
PubMed2000

[Effect of 5,7-dihydroxytryptamine on the distribution pattern of calcitonin gene-related peptide in different motoneuron pools].

OBJECTIVE: The effect of 5,7-dihydroxytryptamine (5,7-DHT) on distribution pattern of calcitonin gene-related peptide (CGRP) in different motoneuron pools was studied in rats. METHODS: Cholera toxin B subunit coupled with colloidal gold (CB-Au) retrograde labeling combined with CGRP immunocytochemistry technique was mainly used. RESULTS: In control group, there was a different distribution pattern of CGRP-LI content in soleus motoneuron (SOL-Mn) and extensor digitorum longus motoneuron (EDL-Mn) pools. SOL-Mn pools had a higher ratio of neurons lacking CGRP-LI/weak CGRP-LI and a lower proportion of strongly CGRP-LI labeled ones. Comparing with control, there was a marked shift to increasing of CGRP-LI content in SOL-Mn pool and slight decrease in EDL-Mn pools 14 days after 5,7-DHT. All the SOL-Mns were CGRP-LI positive and the ratio of CGRP-LI strongly positive Mns significantly increased (P < 0.001) while 5,7-DHT did not increase the ratio of CGRP-LI strongly positive Mn in EDL-Mn pool. CONCLUSIONS: Except muscular motor activity, the different distribution pattern of CGRP-LI content in SOL-Mn and EDL-Mn pools is related to different 5-HT inputs. SOL-Mns may receive more 5-HT inputs.

5,7-Dihydroxytryptamine↗
PubMed2000

[The multicolour three-photon resonant ionization spectrum studies in uranium atom].

The multicolour three-photon resonant ionization spectra of 238U were measured by using the pulsed dye lasers system synchronously pumped by a frequency doubled Nd:YAG-laser 532 nm output(operated at 10 Hz), a device for atomic beam of U, time-of-flight mass spectrometer and boxcar integrator. The dye laser pulses have a 6 ns duration. Beams from the dye lasers, which have the same polarization direction and are focused by lenses, entered an interaction chamber through opposite windows on a common axis and spatially overlapped the U atomic beam. The optical pulse from dye laser DL2 was delayed to arrive at the interaction region 8 ns after the pulse from dye laser DL1; in the same way, the pulse from DL3 was delayed 8 ns after from DL2. The atomic beam device was made from stainless steel. We generated the U vapor by heating solid U in a graphite crucible by e-type electron-field on first excited states were studied in uranium atom. The question how to determine single-colour, two-colour and three-colour three-photon resonant ionization peak in the three-colour three-photon resonant ionization spectra diagram were solved.

English Abstract↗
PubMed2000

[Identification of high-lying odd energy levels of uranium by resonant ionization mass spectrometry].

Single-colour and two-colour multiphoton resonant ionization spectra of uranium atom were studied extensively with a Nd:YAG laser-pumped dye laser atomic beam apparatus time-of-flight mass spectrometer in our laboratory. The energy locations of high-lying odd-parity levels in the region 33,003-34,264 cm-1, measured by a two-colour three-step ionization technique, were reported here. The angular momentum quantum number J was uniquely assigned for these levels by using angular momentum selection rules.

Lasers↗
PubMed1999

Differential asparagine-linked glycosylation of voltage-gated K+ channels in mammalian brain and in transfected cells.

Glycosylation of ion channel proteins dramatically impacts channel function. Here we characterize the asparagine (N)-linked glycosylation of voltage-gated K+ channel alpha subunits in rat brain and transfected cells. We find that in brain Kv1.1, Kv1.2 and Kv1.4, which have a single consensus glycosylation site in the first extracellular interhelical domain, are N-glycosylated with sialic acid-rich oligosaccharide chains. Kv2.1, which has a consensus site in the second extracellular interhelical domain, is not N-glycosylated. This pattern of glycosylation is consistent between brain and transfected cells, providing compelling support for recent models relating oligosaccharide addition to the location of sites on polytopic membrane proteins. The extent of processing of N-linked chains on Kv1.1 and Kv1.2 but not Kv1.4 channels expressed in transfected cells differs from that seen for native brain channels, reflecting the different efficiencies of transport of K+ channel polypeptides from the endoplasmic reticulum to the Golgi apparatus. These data show that addition of sialic acid-rich N-linked oligosaccharide chains differs among highly related K+ channel alpha subunits, and given the established role of sialic acid in modulating channel function, provide evidence for differential glycosylation contributing to diversity of K+ channel function in mammalian brain.

Animals↗
PubMed1999

Esophageal sensitivity and symptom perception in gastroesophageal reflux disease.

Patients with gastroesophageal reflux disease (GERD) experience a wide spectrum of symptoms, varying both in quality and severity. This review summarizes clinical observations of esophageal sensitivity and symptom perception in GERD patients. The Bernstein test, although lacking standardization, remains a useful tool in determining esophageal sensitivity to acid stimuli. Ambulatory 24-hour pH monitoring with symptom event marking and subsequent symptom-reflux correlation between acid reflux events and esophageal symptomatology now provides an alternative method for establishing esophageal acid sensitivity. The intraesophageal balloon distention test (IEBD) was developed to assess esophageal sensitivity to mechanical stimuli. Variants of each of these tests have been applied to the evaluation of uncomplicated GERD patients and patients with esophagitis and Barrett's metaplasia, who generally demonstrate less esophageal sensitivity than the former group. Studies using these methods have demonstrated increased esophageal sensitivity in patients with esophageal chest pain and have also identified a subset of patients with esophageal symptoms yet normal esophageal acid exposure, a condition referred to as "hypersensitive esophagus." The Bernstein test, 24-hour pH monitoring with symptom assessment, and IEBD have each contributed to our understanding of esophageal pain syndromes; it is hoped that future work in this area will lead to improved and more specific therapy for these patients.

Chest Pain↗