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Biomedical subjects

Z Wu

Publications and source records attributed to Z Wu.

At least 199 records · Page 11Linked to original sources
PubMed2000

An emergent mechanism of selective visual attention in Drosophila.

Due to the limited computational capacity of visual systems and the limited capacity to perform several mental operations at once, animals only select a small proportion of the stimuli available at any one time. It remains to be clarified how this process is related to the spatio-temporal dynamics of cell assemblies in the brain. By employing the flight simulator, selective visual attention behavior is studied in Drosophila. It has been found that for the visual objects presented, the tethered fruitflies display various attention patterns. Specifically, the learning memory mutants dunce and amnesiac possess attention patterns totally different from that of the wild-type fly. To explain these results from the viewpoint of dynamic cell assemblies, a neural network has been developed in which a possible link between the activity of cell assemblies, encoding of sensory information, and selective attention in Drosophila is proposed.

Animals↗
PubMed2000

Kinetics of propranolol uptake in muscle, skin, and fat of the isolated perfused rat hindlimb.

The tissue distribution kinetics of a highly bound solute, propranolol, was investigated in a heterogeneous organ, the isolated perfused limb, using the impulse-response technique and destructive sampling. The propranolol concentration in muscle, skin, and fat as well as in outflow perfusate was measured up to 30 min after injection. The resulting data were analysed assuming (1) vascular, muscle, skin and fat compartments as well mixed (compartmental model) and (2) using a distributed-in-space model which accounts for the noninstantaneous intravascular mixing and tissue distribution processes but consists only of a vascular and extravascular phase (two-phase model). The compartmental model adequately described propranolol concentration-time data in the three tissue compartments and the outflow concentration-time curve (except of the early mixing phase). In contrast, the two-phase model better described the outflow concentration-time curve but is limited in accounting only for the distribution kinetics in the dominant tissue, the muscle. The two-phase model well described the time course of propranolol concentration in muscle tissue, with parameter estimates similar to those obtained with the compartmental model. The results suggest, first that the uptake kinetics of propranolol into skin and fat cannot be analysed on the basis of outflow data alone and, second that the assumption of well-mixed compartments is a valid approximation from a practical point of view (as, e.g., in physiological based pharmacokinetic modelling). The steady-state distribution volumes of skin and fat were only 16 and 4%, respectively, of that of muscle tissue (16.7 ml), with higher partition coefficient in fat (6.36) than in skin (2.64) and muscle (2.79).

Adipose Tissue↗
PubMed2000

Amperometric glucose biosensor based on lipid film.

A novel glucose biosensor based on cast lipid film was developed. This model of biological membrane was used to supply a biological environment on the surface of the electrode, moreover it could greatly reduce the interference and effectively exclude hydrophilic electroactive material from reaching the detecting surface. TTF was selected as a mediator because of its high electron-transfer efficiency, and it was incorporated in the lipid film firmly. Glucose oxidase was immobilized in hydrogel covered on the lipid film. The effects of pH, operating potential were explored for the optimum analytical performance by using amperometric method. The response time of the biosensor was less than 20 s, and the linear range is up to 10 mmol l(-1) (corr. coeff. 0.9932) with the detection limit of 2 x 10(-5) mol l(-1). The biosensor also exihibited good stability and reproducibility.

Biosensing Techniques↗
PubMed2000

Direct coupling of transcription and mRNA processing through the thermogenic coactivator PGC-1.

Transcription and mRNA processing are coupled events in vivo, but the mechanisms that coordinate these processes are largely unknown. PGC-1 is a transcriptional coactivator that plays a major role in the regulation of adaptive thermogenesis. PGC-1 also has certain motifs characteristic of splicing factors. We demonstrate here that mutations in the serine- and arginine-rich domain and RNA recognition motif of PGC-1 interfere with the ability of PGC-1 to induce mRNAs of target genes. These mutations also disrupt the ability of PGC-1 to co-localize and associate with RNA processing factors. PGC-1 can alter the processing of an mRNA, but only when it is loaded onto the promoter of the gene. These data demonstrate the coordinated regulation of RNA transcription and processing through PGC-1.

Amino Acid Substitution↗
PubMed2000

The genetic analysis of F1 hybrid larvae between female Trichinella spiralis and male Trichinella britovi.

Hybrids between female Trichinella spiralis and male Trichinella britovi were constructed. Then, hybrid genotype was characterized by DNA markers including mitochondrial cytochrome c oxidase subunit I (CO I) gene, the gene encoding the 43-kDa excretory-secretory (ES) protein, and genomic DNA fragments specific for T. spiralis and T. britovi identified from random amplified polymorphism DNA (RAPD). PCR-restriction fragment length polymorphism (PCR-RFLP) analysis of the mitochondrial CO I gene revealed that all hybrids carried a T. spiralis pattern. The same analysis of the gene encoding the 43-kDa ES protein showed that each hybrid carried both T. spiralis and T. britovi gene type simultaneously. In the analysis of genomic DNA using RAPD-derived PCR primers, some hybrids carried T. spiralis and T. britovi-specific RAPD markers, while others carried the RAPD marker of T. spiralis only.

Animals↗
PubMed2000

Five types of nuclei present in the capsule of Trichinella spiralis.

This study describes morphological changes during capsule formation of Trichinella spiralis with emphasis on nuclei within the capsule. The nuclei of the pre-existing muscle cell may become hypertrophied or degrade soon after the entrance of newborn larvae. Cytoplasm associated with these hypertrophied nuclei was basophilic in H&E staining and composed of mitochondria and rough endoplasmic reticulum. Satellite cells underwent cell division and joined to the nurse cell. These nuclei may also become hypertrophied or degrade. Cytoplasm associated with nuclei of satellite cell origin was eosinophilic in H&E staining and composed of mitochondria, polysomes, and smooth and rough endoplasmic reticulum. Eosinophilic cytoplasm (of satellite cell origin) became prevalent in the capsule as capsule formation proceeded. Infiltrated cells were observed within the capsule. Thus this study showed diversity of nuclei in the capsule of Trichinella.

Animals↗
PubMed2000

Ribozyme-mediated resistance to rice dwarf virus and the transgene silencing in the progeny of transgenic rice plants.

A hammerhead ribozyme (Rz) with long hybridizing arms targeting the mRNA of rice dwarf virus (RDV) segment 5 and a mutated nonfunctional ribozyme (mRz) were constructed. As predicted, Rz transcribed in vitro cleaved the target mRNA of RDV segment 5 into two fragments of 138 and 238 nucleotides in length. The Rz and mRz genes were each placed under the control of the CaMV 35S promoter and used to transform Japonica rice variety 'Tongling No. 1' via Agrobacterium tumefaciens. A total of 32 independent lines containing Rz or mRz was obtained as demonstrated by Southern blot analysis. Challenge inoculation with RDV viruliferous leafhoppers (Nephotettix cincticeps) showed that T1 plants containing the Rz transgene displayed high resistance or delayed and attenuated viral symptoms. In contrast, transgenic lines expressing mRz showed severe symptoms similar to the control plants transformed with the vector alone. These results suggest that Rz confers RDV resistance in transgenic rice. Genomic DNA PCR analysis confirmed that all of the examined T6 progeny plants contained the Rz transgene. However, accumulation of the Rz transcripts was detectable by RT-PCR only in the plants that were resistant to RDV. This suggested that loss of RDV resistance in progeny plants containing the Rz transgene may result from silencing of the Rz transgene.

Base Sequence↗
PubMed2000

Immune reconstitution following high-dose chemotherapy with stem cell rescue in patients with advanced breast cancer.

The present study examines the nature of humoral and cellular immune reconstitution in 28 patients with advanced breast cancer following high-dose chemotherapy with stem cell rescue. Patients underwent testing of T, B, NK and dendritic cell function at serial time points until 1 year post transplant or until the time of disease progression. Abnormalities in T cell phenotype and function were observed following high-dose chemotherapy that persisted for at least 6-12 months. The vast majority of patients experienced an inversion of the CD4/CD8 ratio and demonstrated an anergic response to candida antigen. Mean T cell proliferation in response to PHA and to co-culture with allogeneic monocytes was significantly compromised. In contrast, mean IgG and IgA levels were normal 6 months post transplant and NK cell yields and function were transiently elevated following high-dose chemotherapy. Dendritic cells generated from peripheral blood progenitors displayed a characteristic phenotype and were potent inducers of allogeneic T cell proliferation in the post-transplant period. The study demonstrates that patients undergoing autologous transplantation for breast cancer experience a prolonged period of T cell dysfunction. In contrast, B, NK, and DC recover more rapidly. These findings carry significant implications for the design of post-transplant immunotherapy.

Adult↗
PubMed2000

Regulation of adipogenesis and energy balance by PPARgamma and PGC-1.

There has been a great deal of recent progress in our understanding of the transcriptional control of adipogenesis. Current data suggest that fat cell differentiation involves an interplay between the C/EBP family of transcription factors and PPARgamma. The thermogenic program of brown fat cells may also include a contribution from a new coactivator, PGC-1. Recent data suggests that this coactivator is responsible for activation of thermogenesis and oxidative metabolism in both brown fat and muscle. The PGC-1 dependent program includes both mitochondrial biogenesis and tissue-specific expression of uncoupling proteins.

Adipocytes↗
PubMed2000

Simultaneous quantitative determination of norgestrel and progesterone in human serum by high-performance liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization.

A selective, reliable and rapid method for the simultaneous determination of progesterone and norgestrel concentrations in human serum after taking oral contraceptive tablet has been developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) with atmospheric pressure chemical ionization (APCI) interface. The norethisterone was used as the internal standard. Selected transitions of m/z 313/245 for norgestrel, m/z 315/97 for progesterone and m/z 299/109 for norethisterone were monitored using multiple reaction monitoring (MRM) mode for quantitation. The assay was linear over the concentration range of 0.2-50 ng mL-1 for norgestrel and progesterone. The lower level of quantitation in human serum was obtained at 0.2 ng mL-1 for both norgestrel and progesterone using optimum tuning parameters. The intra-assay precision and inter-assay precision do not exceed 10 and 9%, respectively. The method has been applied to the determination of norgestrel and progesterone in serum of female volunteers.

Adult↗
PubMed2000

Distinct effects of Vibrio cholerae haemagglutinin/protease on the structure and localization of the tight junction-associated proteins occludin and ZO-1.

Vibrio cholerae produces a little-studied cytotoxin, haemagglutinin/protease (HA/P), in addition to several better-characterized enterotoxins, i.e. cholera toxin (CT), zonula occludens toxin (ZOT) and accessory cholera enterotoxin (Ace). We have found recently that HA/P perturbs the barrier function of Mardin-Darby canine kidney epithelial cell line I (MDCK-I) by affecting the intercellular tight junctions (TJs) and the F-actin cytoskeleton. In the present study we have assessed more specifically how TJs are affected by HA/P by investigating the cellular localization and biochemical integrity of two well-characterized TJ-associated proteins, occludin and ZO-1. Western blot analysis showed that occludin bands of 66-85 kDa were digested by HA/P to two predominant bands of around 50 kDa and 35 kDa, and that this degradation was greatly attenuated when the specific bacterial metalloproteinase inhibitor Zincov was co-administered. Trypsin, on the other hand, did not degrade occludin when it was applied in the same way, suggesting that the degradation of occludin by HA/P is an early and specific event. The other TJ-associated protein ZO-1 was not degraded by HA/P in parallel experiments, suggesting the selectivity of HA/P-associated protein degradation. Moreover, immunofluorescence labelling and confocal microscopy showed that ZO-1, but not occludin, around cell-cell boundaries was rearranged by HA/P treatment. Since ZO-1 is located on the inside of the plasma membrane and is directly associated with occludin, the results indicate that breakdown of occludin may send signals to ZO-1 that affect its organization and the structure of the F-actin cytoskeleton. Our finding that the zinc-containing metalloprotease of V. cholerae specifically degraded occludin suggests that specific degradation of important host proteins by bacterial zinc-containing metalloproteases may be an important mechanism in microbial pathogenesis.

Animals↗
PubMed2000

Test method: GH.

The abuse of recombinant human growth hormone in sports is considered to be a widespread phenomenon, but until today all our knowledge thereof is based on rumor, anonymous surveys or accidental observations by customs officers. Although growth hormone (GH) is listed as a prohibited class E substance by the International Olympic Committee (IOC) no official test for the detection of GH abuse is implemented. Because of the high degree of identity in the amino acid sequence between recombinant and endogenous GH and because of the pulsatile nature of GH secretion, as well as inter-individual variations, it was believed to be undetectable. Recently, new proposals have been made to overcome this problem. On the basis of differential immunoassays it is possible to determine the relative content of GH isoforms in the circulation and thus to detect the application of recombinant GH. Furthermore, changes in GH dependent parameters after the administration of recombinant GH have been shown to be a possible indicator of GH abuse.

Biomarkers↗
PubMed2000

Transcriptional regulation of the MHC II gene DRA in untransformed human thyrocytes.

MHC class II molecules are heterodimeric, polymorphic transmembrane glycoproteins physiologically expressed on cells of the immune system and pathologically expressed on the affected target cells of autoimmunity. Their function is to present processed peptides to antigen-specific CD4(+) T cells. To understand the molecular mechanism of the regulation of class II genes in autoimmune target cell thyrocytes, we investigated the transcriptional regulation of DRA on untransformed, differentiated human thyroid cells following IFN-gamma stimulation, which is potentially relevant to the inappropriate class II expression found in Graves' disease. Data from this study show that IFN-gamma enhances a promoter Y box binding protein and induces an X box binding protein in untransformed thyrocytes, but not in SV-40-transfected thyrocytes. Initial characterization of the proteins has indicated that the Y box binding protein is approximately 132 kDa in size while the X box binding protein binds to the X2 region and is approximately 116 kDa. The X box binding protein may correspond to poly(ADP-ribose) polymerase, a recently described component of the X2 box binding protein, X2BP. In addition, the signal transducer and activator of transcription 1alpha protein (STAT1alpha) is also induced by IFN-gamma in these cells. These results further suggest that there are differences in class II gene regulation between differentiated cells and transformed cell lines.

Base Sequence↗
PubMed2000

Genomic analysis of Blastocystis hominis strains isolated from two long-term health care facilities.

The genotype Blastocystis hominis is highly polymorphic. Therefore, a genetic marker would be a powerful tool for the identification or classification of B. hominis subtypes and could be used as a means to resolve the transmission route or origin of the parasite. To this end, 32 B. hominis isolates were collected from patients and/or staff members of two long-term health care facilities (facilities A and B), and these organisms were subjected to genotype analysis based on diagnostic PCR primers and restriction fragment length polymorphism (RFLP) of small subunit rRNA gene (rDNA). Based on PCR amplification using diagnostic primers which were developed from randomly amplified polymorphic DNA analysis of known strains of B. hominis, the 32 isolates of B. hominis were classified into three different subtypes. Thirty isolates, including twenty-four that were isolated from patients and a staff member, from facility A and all isolates isolated from six patients from facility B showed the same genotype. Two of six patients of facility B had been transferred from facility A, and these two patients also had the same-genotype B. hominis that corresponded to 24 isolates from facility A. This genotype strain may have been transmitted by these two patients from facility A to facility B, suggesting human-to-human transmission. In contrast, 2 of 26 isolates from facility A showed distinct genotypes, suggesting that the colonization by these two isolates is attributable to another infectious route. These different subtypes were subjected to RFLP analysis, and the RFLP profiles were correlated with the results obtained by diagnostic PCR primers. This study presents the first molecular evidence of possible human-to-human B. hominis infection between and/or among two small communities.

Animals↗
PubMed2000

p38 and extracellular signal-regulated kinases regulate the myogenic program at multiple steps.

The extracellular signals which regulate the myogenic program are transduced to the nucleus by mitogen-activated protein kinases (MAPKs). We have investigated the role of two MAPKs, p38 and extracellular signal-regulated kinase (ERK), whose activities undergo significant changes during muscle differentiation. p38 is rapidly activated in myocytes induced to differentiate. This activation differs from those triggered by stress and cytokines, because it is not linked to Jun-N-terminal kinase stimulation and is maintained during the whole process of myotube formation. Moreover, p38 activation is independent of a parallel promyogenic pathway stimulated by insulin-like growth factor 1. Inhibition of p38 prevents the differentiation program in myogenic cell lines and human primary myocytes. Conversely, deliberate activation of endogenous p38 stimulates muscle differentiation even in the presence of antimyogenic cues. Much evidence indicates that p38 is an activator of MyoD: (i) p38 kinase activity is required for the expression of MyoD-responsive genes, (ii) enforced induction of p38 stimulates the transcriptional activity of a Gal4-MyoD fusion protein and allows efficient activation of chromatin-integrated reporters by MyoD, and (iii) MyoD-dependent myogenic conversion is reduced in mouse embryonic fibroblasts derived from p38alpha(-/-) embryos. Activation of p38 also enhances the transcriptional activities of myocyte enhancer binding factor 2A (MEF2A) and MEF2C by direct phosphorylation. With MEF2C, selective phosphorylation of one residue (Thr293) is a tissue-specific activating signal in differentiating myocytes. Finally, ERK shows a biphasic activation profile, with peaks of activity in undifferentiated myoblasts and postmitotic myotubes. Importantly, activation of ERK is inhibitory toward myogenic transcription in myoblasts but contributes to the activation of myogenic transcription and regulates postmitotic responses (i.e., hypertrophic growth) in myotubes.

Animals↗
PubMed2000

Milk production, reproductive performance, and fecal excretion of phosphorus by dairy cows fed three amounts of phosphorus.

Milk production was measured and phosphorus (P) excretion in feces was estimated in dairy cows fed three amounts of P. A basal diet was formulated to contain 0.31% P (DM basis). Sodium monophosphate replaced corn in the basal diet to give two additional diets containing 0.40 and 0.49% P. The diets were fed to eight, nine, and nine multiparous Holsteins from the beginning to the end of lactation. Milk yields for the 308-d lactation were 10,790, 11,226, and 11,134 kg for the three treatments, respectively. The lowest milk yield resulted from decreased milk production during late lactation with the 0.31% P group. Reproductive performance of the cows was not related to dietary P content. Fecal P concentration, determined in wk 2, 4, 6, 8, 23, and 40 of lactation, increased as dietary P intake was increased. Cows fed the lowest P diet conserved P by minimizing P excretion in feces and urine, whereas cows in the other two treatments excreted more P through these routes. A reduction in dietary P from 0.49 to 0.40% reduced fecal P excretion by 23%. Apparent P digestibilities of less than 40% are indicative of surplus dietary P. Feeding 0.40% P appeared sufficient to maintain P balance and the level of milk production achieved in this experiment. An example is given which illustrates the relationship between dietary and fecal P.

Animals↗
PubMed2000

Milk production during the complete lactation of dairy cows fed diets containing different amounts of protein.

Milk production response to four different amounts of protein supplementation was measured in a complete lactation study utilizing 58 multiparous Holstein cows treated with bovine somatotropin. The four treatments were as follows (the first number is the dietary crude protein content (% of dry matter) during the first 16 wk of lactation and the second number is the protein content for wk 17 to 44 of lactation): 15.4-16.0, 17.4-16.0, 17.4-17.9, and 19.3-17.9. Diets were formulated to maximize the supply of amino acids to the intestine. High moisture ear corn was finely ground to promote ruminal fermentation and microbial protein synthesis, and roasted soybeans and expeller processed soybean meal were used as the protein supplements to provide relatively high amounts of rumen-undegradable protein. Alfalfa silage and corn silage (3:2) provided the forage. Milk production for the 308-d lactation for each of the treatment groups was 10,056, 10,831, 11,095, and 11,132 kg. Cows of this production level fed diets similar to those used in this experiment benefit from dietary protein of approximately 17.5% during the first 30 wk of lactation. A reduction in dietary protein to 16% can be made around wk 30 of lactation. This amount of dietary protein should, with prevailing feed prices, be compatible with maximum profit and a moderate amount of nitrogen excretion to the environment.

Amino Acids↗