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Biomedical subjects

X Yu

Publications and source records attributed to X Yu.

At least 289 records · Page 16Linked to original sources
PubMed1997

Immobilized cells with endocellular enzymes improved by the permealizing and crosslinking treatment.

In order to achieve high activity of enzymatic catalysis, the method of permealizing and crosslinking treatment has been suggested for immobilizing cells with endocellular enzymes. Polyethene-polyamine and glutardehyde were used to enhance the activity and stability of E. coli having aspartase entrapped in k-carrageenan gel and intact P. dacunhae cells having aspartate-beta-decarbonoxylase. The strength and enlargement effects, which favor the performance of catalysis in a packed bed reactor and a membrane reactor, respectively, were also obtained from the experiment results.

Aspartate Ammonia-Lyase↗
PubMed1997

Body surface Laplacian mapping of bioelectrical activity.

A method is described to process and interpret multi-channel bioelectrical signals. The bioelectrical signals were recorded noninvasively over the body surface of human subjects at 120 sites. The body surface Laplacian maps were then constructed from the multi-channel bioelectrical potential measurement. The method was evaluated by means of computer simulations, and applied to imaging cardiac electrical activity. The present investigation suggests body surface Laplacian mapping provides an important means in interpreting bioelectrical signals.

Body Surface Potential Mapping↗
PubMed1997

Collecting duct carcinoma of the kidney.

OBJECTIVE: To describe the clinical, pathologic and immunohistochemical characteristics of collecting duct carcinoma (CDC) of the kidney. METHODS: Five cases of CDC (3 males and 2 females, aged 41 to 67 years) were identified between January, 1990 and December, 1994. Routine histopathologic study and immunohistochemical examinations of the surgical specimens were performed. RESULTS: Four patients underwent radical nephrectomy; 3 have been alive without evidence of recurrence for 3 months, 2 years and 2.5 years, respectively after the operation. Bone metastasis was noted 2 months after the operation in 1 case. One patient was submitted to simple nephrectomy because of extensive regional node involvement and died of lung metastasis 14 months after the surgery. Grossly, the tumors were usually grey-whitish in color and located in the renal medulla. Microscopically, the characteristic structure of tubulo-papillary pattern could be identified. Marked desmoplastic reaction was noted and atypical hyperplastic changes were found in the adjacent collecting ducts. Immunohistochemical studies revealed positive results to epithelial membrane antigen, high molecular weight cytokeratin and peanut agglutinin. CONCLUSION: CDC of the kidney is a rare disease with a poor prognosis. Radical nephrectomy is recommended even if the tumor is small.

Adult↗
PubMed1997

[Micro-particle image processing based on an artificial neuron network with fluid properties].

The form of macro-particle is a close successive region in two-valued micro-particle image, and the detection of microparticles is actually that of close successive regions. Accordign to this theory, this paper present a new technique for micro-particles detecting based on an artificial neuron network modeled on the diffusing behaviour of real visual system, which has fluid properties. The results of simulation on computer shew that this method is very effect.

Blood Cell Count↗
PubMed1997

[The research and application of uroflow rate measuring].

Using A/D converter acquiring uroflowrate is introduced in this paper. The uroflowrate curve is analysed and displayed by computer in real time. The programming of uroflowrate curve smoothing is presented.

Electronic Data Processing↗
PubMed1997

[The effect of wumingyi chongji on BMP content in callus].

A kind of Chinese herb medicine--Wumingyi chongji could promote fracture healing had been proved. In order to disclose the mechanism, a standard fracture model was produced in 50 healthy male Newzealand rabbits. The animals were randomly divided into experimental group and control group. Another 5 rabbits without operation act as nomal. By immunohistochemical study, the bone morphogenetic protein (BMP) content in callus was calculated by computerized interacive morphometry (CIM) in the 1st, 2nd, 3rd, 4th, 5th week after fracture. The results were: BMP in callus was much more than in nomal (P < 0.01); BMP in callus increased from the 1st week to the 3rd week, decreased from 4th week to 5th week, and was more in experimental group in the 1st and 2nd week than in the control group (P < 0.01). The highest BMP content appeared in the 2nd week in the experimental group, while in the 3rd week in the control group. It was concluded that Wumingyi chongji could promote osteoblast to synthetize BMP, BMP induce preosteoblast change into osteoblast. Thus the rate of fracture healing could be increased.

Animals↗
PubMed1997

[The value of electronystagmography in differential diagnosis of vertigo].

Findings of electronystagmography (ENG) in 645 patients with vertigo were analysed. Two hundred and twelve cases showed vestibular peripheral vertigo, 394 cases vestibular central vestigo, and 39 cases other types of vertigo. The ENGs in patients with vestibular peripheral vertigo were charazterized mainly by the vestibular abnormal caloric responses, spontaneous and benign positional nystagmuses were also obsedrved at the same time. Different degrees and various combinations of the abnormal responses shown in optokinetic central test were the most characteristic of ENG in patients with vestibular central vertigo. The results suggest that ENG is particularly useful for differentiating peripheral and central vertigo.

Adolescent↗
PubMed1996

Synthetic hydrophobic peptides are substrates for P-glycoprotein and stimulate drug transport.

P-Glycoprotein functions as an ATP-driven active efflux pump for many natural products and chemotherapeutic drugs. Hydrophobic peptides have been shown to block drug uptake by P-glycoprotein, indicating that they might be transport substrates. The present study examines the interaction of the synthetic peptide series NAc-LnY-amide with the multidrug transporter. Several peptides in this series caused up to 3.5-fold enhancement of colchicine accumulation in membrane vesicles from multidrug resistant (MDR) cells, which suggests the existence of novel interactions between the binding sites for peptides and drug. Peptides did not stimulate vinblastine transport, which was inhibited as expected for competing substrates. These peptides displayed modest stimulatory effects on the ATPase activity of P-glycoprotein. None blocked azidopine photoaffinity labelling, showing that they probably occupy a binding site separate from that for the drug. Studies with 125I-labelled NAc-LLY-amide showed that it was transported by P-glycoprotein in both membrane vesicles and reconstituted proteoliposomes. Uptake of the peptide was rapid, saturable, osmotically sensitive and occurred against a concentration gradient. The enhancing effect of NAc-LLY-amide on colchicine transport was reciprocated, i.e. colchicine greatly increased the transport of labelled peptide by P-glycoprotein. Peptide transport was also modulated, both positively and negatively, by other MDR spectrum drugs. It is concluded that linear hydrophobic peptides are indeed transported by P-glycoprotein, and some have interactions with drug substrates that result in mutual stimulation of transport.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Increased amyloid-beta42(43) in brains of mice expressing mutant presenilin 1.

Mutations in the genes encoding amyloid-beta precursor protein (APP), presenilin 1 (PS1) and presenilin 2 (PS2) are known to cause early-onset, autosomal dominant Alzheimer's disease. Studies of plasma and fibroblasts from subjects with these mutations have established that they all alter amyloid beta-protein (beta APP) processing, which normally leads to the secretion of amyloid-beta protein (relative molecular mass 4,000; M(r) 4K; approximately 90% A beta1-40, approximately 10% A beta1-42(43)), so that the extracellular concentration of A beta42(43) is increased. This increase in A beta42(43) is believed to be the critical change that initiates Alzheimer's disease pathogenesis because A beta42(43) is deposited early and selectively in the senile plaques that are observed in the brains of patients with all forms of the disease. To establish that the presenilin mutations increase the amount of A beta42(43) in the brain and to test whether presenilin mutations act as true (gain of function) dominants, we have now constructed mice expressing wild-type and mutant presenilin genes. Analysis of these mice showed that overexpression of mutant, but not wild-type, PS1 selectively increases brain A beta42(43). These results indicate that the presenilin mutations probably cause Alzheimer's disease through a gain of deleterious function that increases the amount of A beta42(43) in the brain.

Amyloid beta-Peptides↗
PubMed1996

Chemiluminescence enzyme immunoassay using bacterial magnetic particles.

A novel chemiluminescence enzyme immunoassay using bacterial magnetic particles (BMPs) has been developed for highly sensitive and rapid detection of immunoglobulin G. Antibody was immobilized onto BMPs using the heterobifunctional reagents sulfosuccinimidyl 6-[3'-(2-pyridyldithio) propionamido]hexanoate (sulfo-LC-SPDP) and sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC). For the highly sensitive immunoassay method using these BMPs, a good relationship was obtained between the luminescence intensity and mouse IgG concentration in the range of 1-10(5) fg/mL. Furthermore, in order to reduce assay time and to simplify operations, a rapid chemiluminescence enzyme immunoassay method has been developed. The rapid method was completed in 10 min. A linear relationship was obtained between the luminescence and mouse IgG concentration in the range of 10-1000 ng/mL.

Alkaline Phosphatase↗
PubMed1996

Identification of two DNA-binding sites on the globular domain of histone H5.

The nature of the complexes of histones H1 and H5 and their globular domains (GH1 and GH5) with DNA suggested two DNA-binding sites which are likely to be the basis of the preference of H1 and H5 for the nucleosome, compared with free DNA. More recently the X-ray and NMR structures of GH5 and GH1, respectively, have identified two basic clusters on opposite sides of the domains as candidates for these sites. Removal of the positive charge at either location by mutagenesis impairs or abolishes the ability of GH5 to assemble cooperatively in 'tramline' complexes containing two DNA duplexes, suggesting impairment or loss of its ability to bind two DNA duplexes. The mutant forms of GH5 also fail to protect the additional 20 bp of nucleosomal DNA that are characteristically protected by H1, H5 and wild-type recombinant GH5. They still bind to H1/H5-depleted chromatin, but evidently inappropriately. These results confirm the existence of, and identify the major components of, two DNA-binding sites on the globular domain of histone H5, and they strongly suggest that both binding sites are required to position the globular domain correctly on the nucleosome.

Amino Acid Sequence↗
PubMed1996

The hexameric E. coli DnaB helicase can exist in different Quaternary states.

The DnaB protein is the primary replicative helicase in Escherichia coli, and the active form of the protein is a hexamer. It has been reported that the protein forms a ring with strong 3-fold symmetry, which was suggested to be a trimer of dimers. We show that under different conditions, using either ATP, ATP gamma S, AMP-PNP or ADP as nucleotide cofactors, we always find two different forms of the DnaB ring; one with a 3-fold symmetry and one with 6-fold symmetry. We have used scanning transmission electron microscopy for mass analysis, and have found that both forms are hexamers, excluding the possibility that the 3-fold form is in fact a trimer of the 52 kDa monomer. We have also found rings that are in an intermediate state between these two. The existence of hexamers in discrete states shows that the transitions between these states must be cooperative. These observations suggest that there may be an equilibrium between two different conformations of the hexameric ring. The role of these two states in the mechanism of helicase action remains to be determined.

Adenosine Diphosphate↗
PubMed1996

Subcellular metabolite transport and carbon isotope kinetics in the intramyocardial glutamate pool.

The pathophysiological state of the cell must be translated into the mitochondria to meet the demands for oxidative energy production. Metabolite exchange across the mitochondrial membrane provides this communication and was observed with 13C NMR spectroscopy of hearts oxidizing [2-13C]-butyrate at normal or high cytosolic redox state. Previous NMR observations of 13C turnover within the glutamate pool of intact tissues have indicated its relationship with metabolic flux through the tricarboxylic acid (TCA) cycle, but the direct influence of isotope exchange between the TCA cycle intermediates in the mitochondria and the cytosolic glutamate pool has been much less considered. This current study was designed to determine whether the physical transport of metabolites across the mitochondrial membrane of intact heart tissues could be discerned as a rate determinant for isotope turnover in the NMR-detectable glutamate pool. 13C entry into glutamate provided measures of TCA cycle flux and the interconversion between mitochondrial intermediates and cytosolic glutamate. The influence of the malate-aspartate shuttle activity was examined by comparing two groups of hearts: one group oxidizing 2.5 mM [2-13C]-butyrate (n = 5) and the other oxidizing 2.5 mM [2-13C]butyrate in the presence of a lactate (2.5 mM)-induced elevation in the cytosolic redox to stimulate shuttle activity (n = 5). High redox state did not affect TCA cycle flux but increased the rate of interconversion between alpha-ketoglutarate and glutamate from 3.1 +/- 0.2 mumol min-1 (g dry)-1 to 14.3 +/- 2.0. High resolution 13C NMR spectra of tissue extracts confirmed that the exogenous lactate did not contribute as a carbon source for the formation of either the TCA cycle intermediates or glutamate. In both groups, over 95% of the acetyl-CoA was derived from the short-chain fatty acid butyrate, irrespective of the presence of lactate. Additional hearts perfused with unlabeled butyrate and [3-13C]lactate showed no label entry into glutamate, but rather the formation of [3-13C]alanine, indicating the net reverse flux through lactate dehydrogenase to increase NADH production. Thus, the addition of lactate served only to augment cytosolic redox state to drive the malate-aspartate shuttle. The dynamic-mode acquisition of 13C NMR data from intact hearts, oxidizing [2-13C]-butyrate with or without additional lactate, demonstrated the influence of malate-aspartate shuttle activity on the 13C enrichment rates within glutamate. These data indicate metabolic communication between the mitochondria and cytosol in response to the physiological state of intact tissues.

ATP-Binding Cassette Transporters↗
PubMed1996

Multiplet structure of 13C NMR signal from glutamate and direct detection of tricarboxylic acid (TCA) cycle intermediates.

For the first time, 13C NMR signals are shown from 13C-enriched, low-level tricarboxylic acid (TCA) cycle intermediates from extracts of normal cardiac tissue. As the low tissue content of the key intermediates alpha-ketoglutarate (alpha-KG) and succinate (SUC) in normal, well perfused tissues has until now precluded direct NMR detection from intact tissues and tissue extracts, 13C NMR signal from glutamate has generally been used to infer the isotopomer patterns of intermediates that are in chemical exchange with glutamate. However, the required assumptions regarding intracellular compartmentation for such indirect analysis have not been previously tested, as glutamate is largely cytosolic while the TCA cycle enzymes are located in the mitochondria. Chromatographic isolation of alpha-KG and SUC from heart tissue extracts allowed isotopomer analysis to be performed for comparison with that of glutamate. At steady state, a direct relationship between glutamate and alpha-ketoglutarate isotopomers was found, but succinate isotopomers matched those of glutamate only in hearts that displayed negligible contributions from the oxidation of unlabeled endogenous carbon sources.

Animals↗
PubMed1996

Chemical versus isotopic equilibrium and the metabolic fate of glycolytic end products in the heart.

Recent studies of isotope exchange across lactate dehydrogenase (LDH) and alanine aminotransferase (AAT) in hearts call into question whether both reactions are in equilibrium. To compare the oxidative and non-oxidative fates of glycolytic end products, isolated rabbit hearts were perfused with 5 mM [2-13C] glucose and 2.5 mM [3-13C] pyruvate: with (n = 6) and without (n = 7) stimulation of pyruvate oxidation using dichloroacetate (DCA), and during normal perfusion or hypoxia (n = 7/n = 6, +/- DCA). 13C NMR spectroscopy of intact hearts confirmed a steady-state enrichment level in both alanine and lactate. 1H- and 13C-NMR spectroscopy of tissue extracts identified the fractions of lactate, alanine and glutamate pools formed from each exogenous substrate. Glycolysis from glucose accounted for 22 +/- 7% of lactate formed and 10 +/- 2% of alanine formed in control hearts, and 16 +/- 2% lactate and 15 +/- 2% alanine in hypoxic hearts (mean +/- S.E.M.). In contrast, exogenous pyruvate formed 36 +/- 5% of the lactate pool, and 86 +/- 3% of the alanine pool in controls and 47 +/- 3% of lactate and of 67 +/- 3% alanine during hypoxia. [2(-13)C] glucose did not contribute to oxidative energy production via the TCA cycle as determined from low 13C enrichment of glutamate C5 from glucose (< 2%), while [3-13C] pyruvate accounted for 84 +/- 7% of labeled glutamate C4. Thus, exogenous pyruvate out-competed the metabolism of glucose, indicating low glycolytic activity. At 40 min, 96 +/- 2% of the total alanine was labeled from either glucose or pyruvate, confirming equilibrium at AAT. However, only 55 +/- 10% of total lactate was labeled, suggesting that the LDH reaction is not in rapid equilibrium within the myocardium.

Animals↗