Biomedical subjects

Z Xie

Publications and source records attributed to Z Xie.

At least 55 records · Page 3Linked to original sources

PubMed2001

Effects of uremic serum on isolated cardiac myocyte calcium cycling and contractile function.

BACKGROUND: Diastolic dysfunction occurs in patients with chronic renal failure. Moreover, serum from uremic patients contains one or more inhibitors of the plasmalemmal Na,K-ATPase (sodium pump). We hypothesized that a circulating substance present in uremic sera contributes to both sodium pump inhibition and diastolic dysfunction. METHODS: Serum samples were obtained from six patients with chronic renal failure and diastolic dysfunction. RESULTS: Their serum samples caused marked inhibition of Na,K-ATPase purified from dog kidney at all concentrations studied (all P < 0.01) and also impaired ouabain-sensitive rubidium uptake by myocytes isolated from Sprague-Dawley rats (P < 0.01). These cardiac myocytes were studied for their contractile function with video-edge detection and calcium metabolism with indo-1 fluorescence spectroscopy after exposure to these uremic sera. These uremic sera caused increases in myocyte fractional shortening (P < 0.01) as well as an increase in the time constant of relengthening (P < 0.01). Examining the calcium transient, the time constant for calcium recovery was also increased (P < 0.01). Exposure of these cells to sera from age- and sex-matched healthy subjects did not result in significant changes in contraction or calcium cycling. Extracts of uremic serum samples inhibited isolated Na,K-ATPase whereas extracts of normal serum samples did not. The effect of uremic serum extracts on contractile function and calcium cycling were quite similar to that of intact serum or the addition of ouabain. Co-incubation of uremic serum extract with an antibody fragment directed against digoxin markedly attenuated the inhibition of Na,K-ATPase activity and completely prevented any effects on calcium cycling or contractile function. CONCLUSION: These data show that one or more substances are present in uremic sera that acutely cause increased force of contraction and impaired recovery of cardiac myocyte calcium concentration as well as impaired relaxation. As these effects are similar to that seen with ouabain and can be prevented by co-incubation with an antibody fragment to digitalis, which also attenuates the sodium pump inhibitory effect, we suggest that this (these) substance(s) circulating in uremic sera and inhibiting the sodium pump also causes the acute diastolic dysfunction seen in our system.

Adult↗

PubMed2001

Evidence for an intrinsic toxicity of phosphatidylcholine to Sec14p-dependent protein transport from the yeast Golgi complex.

Yeast phosphatidylinositol-transfer protein (Sec14p) is essential for Golgi secretory function and cell viability. This requirement of Sec14p is relieved by genetic inactivation of the cytidine diphosphate-choline pathway for phosphatidycholine (PtdCho) biosynthesis. Standard phenotypic analyses indicate that inactivation of the phosphatidylethanolamine (PtdEtn) pathway for PtdCho biosynthesis, however, does not rescue the growth and secretory defects associated with Sec14p deficiency. We now report inhibition of choline uptake from the media reveals an efficient "bypass Sec14p" phenotype associated with PtdEtn-methylation pathway defects. We further show that the bypass Sec14p phenotype associated with PtdEtn-methylation pathway defects resembles other bypass Sec14p mutations in its dependence on phospholipase D activity. Finally, we find that increased dosage of enzymes that catalyze phospholipase D-independent turnover of PtdCho, via mechanisms that do not result in a direct production of phosphatidic acid or diacylglycerol, effect a partial rescue of sec14-1(ts)-associated growth defects. Taken together, these data support the idea that PtdCho is intrinsically toxic to yeast Golgi secretory function.

1-Phosphatidylinositol 4-Kinase↗

PubMed2001

AMADA: analysis of microarray data.

SUMMARY: AMADA is a Windows program for identifying co-expressed genes from microarray data. It performs data transformation, principal component analysis, a variety of cluster analyses and extensive graphic functions for visualizing expression profiles.

Algorithms↗

PubMed2001

Highly frequent frameshift DNA synthesis by human DNA polymerase mu.

DNA polymerase mu (Polmu) is a newly identified member of the polymerase X family. The biological function of Polmu is not known, although it has been speculated that human Polmu may be a somatic hypermutation polymerase. To help understand the in vivo function of human Polmu, we have performed in vitro biochemical analyses of the purified polymerase. Unlike any other DNA polymerases studied thus far, human Polmu catalyzed frameshift DNA synthesis with an unprecedentedly high frequency. In the sequence contexts examined, -1 deletion occurred as the predominant DNA synthesis mechanism opposite the single-nucleotide repeat sequences AA, GG, TT, and CC in the template. Thus, the fidelity of DNA synthesis by human Polmu was largely dictated by the sequence context. Human Polmu was able to efficiently extend mismatched bases mainly by a frameshift synthesis mechanism. With the primer ends, containing up to four mismatches, examined, human Polmu effectively realigned the primer to achieve annealing with a microhomology region in the template several nucleotides downstream. As a result, human Polmu promoted microhomology search and microhomology pairing between the primer and the template strands of DNA. These results show that human Polmu is much more prone to cause frameshift mutations than base substitutions. The biochemical properties of human Polmu suggest a function in nonhomologous end joining and V(D)J recombination through its microhomology searching and pairing activities but do not support a function in somatic hypermutation.

3' Flanking Region↗

PubMed2001

Downregulation of cardiac myocyte Na(+)-K(+)-ATPase by adenovirus-mediated expression of an alpha-subunit fragment.

Cultured rat cardiac myocytes and A7r5 cells were transfected with an adenoviral vector used earlier for in vivo expression of functional alpha(2)-isoform of the catalytic subunit of rat Na(+)-K(+)-ATPase. Expressions of truncated forms of alpha(2), but little or no intact alpha(2), were detected, suggesting the rapid degradation of alpha(2) in these cultured cells. In neonatal myocytes normally containing the alpha(1)- and the alpha(3)-isoforms, expression of the alpha(2)-fragment led to 1) a significant decrease in the level of endogenous alpha(1)-protein and a modest decrease in alpha(3)-protein, 2) decreases in mRNAs of alpha(1) and alpha(3), 3) decrease in Na(+)-K(+)-ATPase function measured as ouabain-sensitive Rb(+) uptake, 4) increase in intracellular Ca(2+) concentration similar to that induced by ouabain, and 5) eventual loss of cell viability. These findings indicate that the alpha(2)-fragment downregulates endogenous Na(+)-K(+)- ATPase most likely by dominant negative interference either with folding and/or assembly of the predominant housekeeping alpha(1)-isoform or with signal transducing function of the enzyme. Demonstration of rise in intracellular Ca(2+) resulting from alpha(1)-downregulation 1) does not support the previously suggested special roles of less abundant alpha(2)- and alpha(3)-isoforms in the regulation of cardiac Ca(2+), 2) lends indirect support to proposals that observed decrease in total Na(+)-K(+)-ATPase of the failing heart may be a mechanism to compensate for impaired cardiac contractility, and 3) suggests the potential therapeutic utility of dominant negative inhibition of Na(+)-K(+)-ATPase.

Adenoviridae↗

PubMed2001

Signal-transducing function of Na+-K+-ATPase is essential for ouabain's effect on [Ca2+]i in rat cardiac myocytes.

We showed before that Na+-K+-ATPase is also a signal transducer in neonatal rat cardiac myocytes. Binding of ouabain to the enzyme activates multiple signal pathways that regulate cell growth. The aims of this work were to extend such studies to adult cardiac myocytes and to determine whether the signal-transducing function of Na+/K+-ATPase regulates the well-known effects of ouabain on intracellular Ca2+ concentration ([Ca2+]i). In adult myocytes, ouabain activated protein tyrosine phosphorylation and p42/44 mitogen-activated protein kinases (MAPKs), increased production of reactive oxygen species (ROS), and raised both systolic and diastolic [Ca2+]i. Pretreatment of myocytes with several Src kinase inhibitors, or overexpression of a dominant negative Ras, antagonized ouabain-induced activation of MAPKs and increases in [Ca2+]i. Treatment with PD-98059 (a MAPK kinase inhibitor) or overexpression of a dominant negative MAPK kinase 1 also ablated the effect of ouabain on MAPKs and [Ca2+]i. N-acetyl-cysteine, which blocks the effect of ouabain on ROS, did not prevent the ouabain-induced rise in [Ca2+]i. Clearly, the activation of the Ras/MAPK cascade, but not ROS generation, is necessary for ouabain-induced increases in [Ca2+]i in rat cardiac myocytes.

Age Factors↗

PubMed2001

Coronary reperfusion following ischemia: different expression of bcl-2 and bax proteins, and cardiomyocyte apoptosis.

The aim of this work was to examine factors that could be involved in the occurrence of apoptosis in rat hearts subjected to coronary occlusion followed by reperfusion. To this end, we studied the expression of the pro- and anti-apoptotic factors, bax and bcl-2, respectively, in reperfused ischemic hearts and in hearts injected with bFGF or saline. In anesthetized rats the left coronary artery was occluded for 45 min, the anesthesia withdrawn and the occlusion removed to allow reperfusion; in sham-operated rats the occlusion was omitted. After 4 hours the rats were decapitated and the heart excised. Sections from the left ventricle were stained with anti-bcl-2-antibody and anti-bax-antibody using the TUNEL method which detects apoptosis. Fragmentation of DNA isolated from reperfused ventricles was examined by agarose electrophoresis. In reperfused hearts no bcl-2 staining was observed in the discrete area in which many cardiomyocyte nuclei were stained by the TUNEL method; outside this area staining for bcl-2 was more marked than in sham-operated rats. Sections from reperfused hearts were stained for bax protein over a wide area including the apoptotic region; sham-operated hearts showed little reaction. Staining for bcl-2 was demonstrable in some nuclei in hearts from saline-injected rats; the numbers were unaffected by i. v. bFGF. Ischemia/reperfusion increases the overall expression of both bcl-2 and bax proteins, but bcl-2 is lost from the reperfused area as indicated by TUNEL staining. Accordingly, the ratio of bcl-2 to bax was reduced in the reperfused area, indicating a pro-apoptotic trend. The marked increase in bcl-2 outside the reperfused area could be a mechanism with which to salvage surviving cardiomyocytes.

Animals↗

PubMed2001

Relics: penguin population programs.

What has been responsible for the increase in Chinstrap penguin populations during the past 40 years in maritime Antarctica? One view ascribes it to an increase in availability of their prey brought on by the decrease in baleen whale stocks. The contrary opinion, attributes it to environmental warming. This causes a gradual decrease in the frequency of cold years with extensive winter sea ice cover. A number of penguin monitoring programs are in progress and are expected to provide some answers to these questions. Unfortunately, it is not easy to distinguish natural variability from anthropogenic change since penguins are easily accessible predators of krill and the feeding range of the penguins has almost overlapped with the krill fishery in time and space in the last four decades. Therefore it is important to reconstruct the change of ancient penguin abundance and distribution in the absence of human activity. Many efforts have focused on surveying the abandoned penguin rookeries, but this method has not been able to give a continuous historical record of penguin populations. In several recent studies, ancient penguin excreta was scooped from the penguin relics in the sediments of the lake on penguin rookery, Ardley Island, maritime Antarctica. In these studies, penguin droppings or guano soil deposited in the lake and changes in sediment geochemistry have been used to calculate penguin population changes based upon the geochemical composition of the sediment core. The results suggest that climate change has a significant impact on penguin populations.

Animals↗

PubMed2001

Ouabain interaction with cardiac Na/K-ATPase reveals that the enzyme can act as a pump and as a signal transducer.

Na/K-ATPase hydrolyzes ATP to maintain the transmembrane gradients of Na+ and K+ found in most mammalian cells and is inhibited specifically by cardiac glycosides such as ouabain. Recently, we have shown that partial inhibition of Na/K-ATPase by non-toxic concentrations of ouabain causes hypertrophic growth and transcriptional regulation of several growth-related marker genes in neonatal rat cardiac myocytes. These ouabain effects involve the activation of multiple signal transduction pathways, including the activation of Src kinase and tyrosine phosphorylation of the epidermal growth factor receptors and other proteins, followed by the activation of Ras, the Ras/Raf/MEK/MAPK cascade, and increased production of reactive oxygen species. The gene regulatory actions of ouabain, like its classical effect on cardiac contractility, are dependent on the net influx of Ca2+ and rise in [Ca2+]i, indicating that the latter is a shared second messenger for the ouabain effects on cardiac contractility and growth. Significantly, the effects of ouabain on several early signaling events including stimulation of tyrosine phosphorylation and production of reactive oxygen species are independent of changes in intracellular Na and Ca2+ concentrations. Taken together, these new findings have led us to propose that when ouabain binds to Na/K-ATPase, it converts the enzyme to a signal transducer and initiates multiple gene regulatory pathways through either direct or indirect interactions with tyrosine kinases in cardiac myocytes.

Animals↗

PubMed2001

[Fluoride emission from different soil minerals at high temperatures].

The emission characteristics of fluoride pollutants from montmorillonite, kaolinite, vermiculite, geothite and allophane were studied to elucidate the mechanism of fluoride-releasing from soils during brick and tile making at high temperatures from 300 degrees C to 1000 degrees C. The rate of fluoride emission varied with temperature, mineral type, heating time, specific surface area and cations added to minerals. The escape of crystalline water resulting from crystal lattice collapse at a certain high temperature was found to affect the rate of fluoride emission. Calcium compounds could decrease fluoride emission rate from montmorillonite. At 800 degrees C, the rate of fluoride emission from Ca-treated montmorillonite decreased by 59.6% compared to untreated montmorillonite. The order for fluoride-fixing capacity of the 5 calcium compounds at 800 degrees C was as follows: CaCO3 > CaO > Ca3(PO4)2 > Ca(OH)2 > CaSO4.

Aluminum Silicates↗

PubMed2001

[Characteristics of N2O emissions from vegetal soils on Fildes peninsula, Antarctica].

The N2O fluxes from the vegetal soils were first measured on the Fildes peninsula, Antarctica, and the total N2O emission was also estimated in the summer 2 months. The daily variations of N2O fluxes appeared single-peak trend under the sunshine or rainy weather conditions but they were irregular under the snow weather conditions and inconsistent with the atmospheric temperatures. The seasonal variations of the N2O fluxes were affected by the temperature and rainfall. The conditions during the transitions between dry and wet seasons improved the N2O emission. The total N2O emissions from moss and lichen soils were 3.7152 kg and 2.5344 kg, respectively. It follows that the vegetal soils are the sources for the atmospheric N2O on the Fildes peninsula, Antarctica.

Antarctic Regions↗

PubMed2001

[Measurement of CO2 concentration in the areas with vegetation cover on the Fildes peninsula, Antarctica].

The average CO2 concentration was above 473.5 mg.m-3 in the areas covered by moss or lichen, greatly higher than the global average CO2 concentration, implying that these areas may be one of the atmospheric CO2 sources. Abnormally high CO2 concentration was relative with vegetal physiological and ecological characters. In the areas covered by moss, the daily variation of the CO2 concentrations was affected by sunshine and temperature and it was also different under the conditions of the different weathers. Sunshine was the main factors influencing the CO2 concentration. The seasonal variation of the CO2 concentration was negatively correlated with atmospheric temperature and positively with rainfall and air relative humidity. This article first presents the variations of CO2 concentration and its influential factors under the Antarctic environmental conditions, which also presents new information for the further study to the Antarctic greenhouse gases.

Air↗

PubMed2001

[Does response of rape to La and critical concentration of La in red earth].

The effects of different concentration of La added in red soil on the growth, yield, content of chlorophyll and peroxidase(POD) activity of rape were studied by pot experiments. The results showed that the growth and yield of rape could be improved by low concentration of La3+, however there was no significant difference between the treatment and the control, and inhibited when the dose were more than 300 mg kg-1 and killed after 600 mg.kg-1 La was added. The decrease of chlorophyll content and chlorophyll a/b was observed when the exogenous concentration of La was more than 15 mg.kg-1. POD activity increased gradually with increasing concentration and prolonging reaction. The feasible application level of La was suggested to be below 15 mg.kg-1.

Chlorophyll↗

PubMed2001

Endocytic routes of exogenous antigen in murine dendritic cells and macrophages.

OBJECTIVE: To compare the endocytic routes of exogenous antigen between murine dendritic cells (DCs) and macrophages (M phi s). METHODS: Murine bone marrow-derived DCs and peritoneal M phi s were pulsed with horseradish peroxidase (HRP)-5 nm colloidal gold for 10 minutes, then grouped and chased for 0-120 minutes in culture medium. Intracellular distribution of 5 nm colloidal gold was explored by means of the cellular enzymatic-chemistry of acid phosphatase and MHC II immuno-cytochemistry under electron microscope. RESULTS: After 10 minutes of pulse with HRP-5 nm colloidal gold and 30 minutes of chase, most HRP-5 nm gold particles internalized by DCs entered into MHC class II compartments (M II Cs), and a small portion entered into acid phosphatase-positive lysosomes. In contrast to DCs, most M phi s lysosomes were accessed by HRP-5 nm gold particles, and a small portion of HRP-5 nm gold particles entered into M II Cs. After 60 minutes of chase, 5 nm gold particles could hardly be seen within M phi s, whereas most 5 nm gold particles were still retained in DCs. CONCLUSIONS: The endocytic route of exogenous antigen in DCs seems to be different from that in M phi s. Antigens taken by M phi s mainly enter into lysosomes within 30 minutes. In the case of DCs, most internalized antigens enter into M II Cs, which may be related to their unique antigen-presenting function. In addition, M phi s seem to have more powerful capacity to scavenge exogenous antigen than DCs.

Acid Phosphatase↗

PubMed2001

[Transfer and expression of tyrosinase gene of Pseudomonas maltophilia in Pseudomonas pseudoalcaligenes].

Pseudomonas pseudoalcaligenes is a notably killing maggots bacterium, which was isolated from natural dead maggots in the manure pits in the countryside of Yancheng. It easily die from effect of ultra-violet ray when it is exposed in the sun. Antiradiation effect of melanin is quite strong. Mel gene of P. maltophilia AT18 has been introduced into P. pseudoalcaligenes, and enabled it the ability of producing melanin steadily. Southern hybridization studies confirmed that the small fragment cloned in the P. pseudoalcaligenes comes from P. maltophilia DNA. SDS-PAGE analysis also revealed that an additional protein of 18 kD, which was equal to the size of the putative tyrosinase according to mel fragment, was exressed in the P. pseudoalcaligenes recombinant carrying the mel gene, The results of assay show that antiradiation effect of recombinant is quites strong, the effect time of killing maggats is longer than the recipient, the recombinant can't infect animals and fowls.

DNA, Bacterial↗

PubMed2001

[A multi-centered clinical study an domestic intravenous Turbutalin sulfate in the treatment of asthma and chronic asthmatic bronchitis].

OBJECTIVE: This multi-centered clinical trial was designed to assess the efficacy and safety of domestic intravenous Turbutalin Sulfate in the treatment of asthma and chronic asthmatic bronchitis. METHODS: Bricanyl was used as control. A total of 120 patients were included in this randomized controlled study. The two medications, both at a dose of 0.25 mg intravenous drip, were given three times a day for 3-5 days. RESULTS: The two drugs' clinical excellent rates were 66.7% and 73.3%; overall efficacy rates were 98.3% and 100.0%, respectively. Their pulmonary functional excellent rates were 78.4% and 76.6%; overall effect rates were 88.3% and 90.0%, respectively. Composite curative evaluation showed that the two drug's composite excellent rates were 61.6% both; their overall efficacy rates were 88.3% and 90.0%, respectively. All of these showed no significant difference (P > 0.05). The incidence rates of adverse side effects of the two groups were 13.5% and 15.0%, respectively; most of them were mild and tolerable. CONCLUSION: Domestic intravenous Terbutalin Sulfate is effective and safe in treating asthma and chronic asthmatic bronchitis.

Adolescent↗

PubMed2000

Requirements and effects of palmitoylation of rat PLD1.

Rat brain phospholipase D1 (rPLD1) has two highly conserved motifs (HXKX(4)D), denoted HKD, located in the N- and C-terminal halves, which are required for phospholipase D activity. The two halves of rPLD1 can associate in vivo, and the association is essential for catalytic activity and Ser/Thr phosphorylation of the enzyme. In this study, we found that this association is also required for palmitoylation of rPLD1, which occurs on cysteines 240 and 241. In addition, palmitoylation of rPLD1 requires the N-terminal sequence but not the conserved C-terminal sequence, since rPLD1 that lacks the first 168 amino acids is not palmitoylated in vivo, while the inactive C-terminal deletion mutant is. Palmitoylation of rPLD1 is not necessary for catalytic activity, since N-terminal truncation mutants lacking the first 168 or 319 amino acids exhibit high basal activity although they cannot be stimulated by protein kinase C (PKC). The lack of response to PKC is not due to the lack of palmitoylation, since mutation of both Cys(240) and Cys(241) to alanine in full-length rPLD1 abolishes palmitoylation, but the mutant still retains basal activity and responds to PKC. Palmitoylation-deficient rPLD1 can associate with crude membranes; however, the association is weakened. Wild type rPLD1 remains membrane-associated when extracted with 1 m NaCl or Na(2)CO(3) (pH 11), while rPLD1 mutants that lack palmitoylation are partially released. In addition, we found that palmitoylation-deficient mutants are much less modified by Ser/Thr phosphorylation compared with wild type rPLD1. Characterization of the other cysteine mutations of rPLD1 showed that mutation of cysteine 310 or 612 to alanine increased basal phospholipase D activity 2- and 4-fold, respectively. In summary, palmitoylation of rPLD1 requires interdomain association and the presence of the N-terminal 168 amino acids. Mutations of cysteines 240 and 241 to alanine abolish the extensive Ser/Thr phosphorylation of the enzyme and weaken its association with membranes.

Animals↗

PubMed2000

Weakly coordinating nature of a carborane cage bearing different halogen atoms. Synthesis and structural characterization of icosahedral mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I).

Mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I), have been prepared by treatment of [Me3NH][1-H-CB11H5X6] (X = Cl, Br, I) with proper halogenating reagents at 180-220 degrees C in a sealed tube in high yield. These new anions are fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some are further confirmed by single-crystal X-ray analyses. The weakly coordinating nature of these anions is probed by 29Si chemical shifts of the resulting Pri3Si(1-H-CB11Y5X6) compounds. The results suggest that the coordinating ability of these anions is mainly dependent on the substituents at 7-12 positions (namely, X atoms), and the contribution from the upper belt substituents Y is relatively small. These suggestions are consistent with the results obtained from the structural study of silver salts of mixed halo- and perhalocarborane anions.

Journal Article↗