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Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 559 records · Page 31Linked to original sources
PubMed1995

Mouse thymus dendritic cells: kinetics of development and changes in surface markers during maturation.

The early thymus precursor population of adult mice has the capacity to generate T cells, B cells and dendritic cells (DC). These precursors were injected into the thymus of irradiated recipients in order to follow the kinetics of thymic DC development. The resultant cohort of T-lineage cells developing in the thymus was accompanied by a parallel cohort of DC, present at 10(3)-fold lower frequency. The intrathymic lifespan of these DC was as short as that of T-lineage thymocytes. As the thymic DC matured, some markers characteristic of the original precursor population gradually declined (Ly-5, c-kit, Sca-2) whereas markers characteristic of thymic DC appeared and were maintained (major histocompatibility complex class II, CD11c, NLDC-145 and CD8 alpha). Some thymic DC expressed the early B-cell marker BP-1, and BP-1 mRNA, throughout their maturation. The surface markers on thymic DC could be divided into two groups. Some markers, including class I and class II MHC, CD8 alpha and BP-1, appeared to be integral components of the DC surface. In contrast, other markers, including Thy-1, CD4 and CD8 beta, had probably been picked up from associated thymocytes.

Animals↗
PubMed1995

The phosphodiesterase secreted by prestalk cells is necessary for Dictyostelium morphogenesis.

Dictyostelium discoideum secretes a cyclic nucleotide phosphodiesterase to control cAMP levels during development. Three promoters control expression of the gene--one during vegetative growth, one during aggregation, and one which constrains phosphodiesterase synthesis to prestalk cells. In this report we show that the expression of phosphodiesterase (PDE) in prestalk cells is necessary for morphogenesis. A gene that codes for a specific glycoprotein inhibitor of the phosphodiesterase (Kd = 0.1 nM) was fused to the prestalk-specific promoter of the PDE gene. Transformants carrying multiple copies of this construct secreted inhibitor in 100-fold excess after the aggregation process had occurred. The first effect seen was an elongated tip, followed by a block in slug formation and an inability to culminate. Stalk and spores cells are produced but morphogenesis is uncoupled from cellular differentiation. Overproduction of inhibitor during earlier stages delayed aggregation, but did not affect fruiting body formation. A phosphodiesterase mutant was transformed with a plasmid that expresses PDE only during aggregation and not in prestalk cells. The defect in aggregation was rescued, but the defect in later development was not. The combined results indicate that PDE expression in prestalk cells is critical to morphogenesis. To ask whether the inhibitor gene under its normal regulation had a role in aggregation or later morphogenesis, it was destroyed by homologous recombination. The loss of the gene did not prevent development under the conditions used.

Amino Acid Sequence↗
PubMed1995

Regulation of Dictyostelium early development genes in signal transduction mutants.

The secreted cyclic nucleotide phosphodiesterase (PDE) and its glycoprotein inhibitor (PDI) are among the first genes expressed when Dictyostelium amoebae begin their development. We used a series of mutants with defects in signal transduction to ask whether cAMP receptors 1 and 3, G alpha2, G beta, adenylyl cyclase (ACA), or the protein kinase A catalytic subunit (PKAcat) are required for the initial appearance or later regulation of the PDE and the PDI transcripts. The PDE gene produces a 1.9-kb transcript during vegetative growth and then a 2.4-kb transcript during the early hours of development. Regulation of the 2.4-kb transcript in CAR1, G alpha2, G beta, and ACA mutants is similar to that of isogenic parental strains, although its level is reduced in strains that carry the CAR1 mutation. CAR1/CAR3 double mutants also produce less PDE transcript, but the PDE gene remains inducible by cAMP. The PKAcat mutant produces the 2.4-kb PDE transcript, but in this mutant the vegetative transcript is retained in development. CAR1 and CAR3 are not required for transcription of the PDI gene, but deleting CAR1 leads to overproduction of the PDI transcript. Induction or repression of the PDI gene does not require G alpha2, G beta, or ACA. PKAcat is required for synthesis of the PDI transcript. The results suggest a two-stage regulation of these early genes through a G alpha2/G beta-independent mechanism and an absolute dependence of PDI on the PKAcat.

Adenylyl Cyclases↗
PubMed1995

Bioextraction of soil boron by tall fescue.

High concentrations of soil B are detrimental to crop productivity in certain arid and semiarid regions of the western United States. Production of tall fescue on B-affected soils may be a viable strategy to reduce and maintain soil B concentrations at nontoxic levels for most agronomic crops. A 2-year field experiment was conducted to study B uptake in tall fescue (Festuca arundinacea) Schreb. cv. Au Triumph grown in soil containing potentially toxic levels of native soil B. The soil B concentrations (water-extractable B greater than 5 mg B liter-1) did not affect the dry matter (DM) yield of tall fescue. Boron concentrations in shoot tissue for both years ranged from 88 to 121 mg B kg-1 DM. whereas in root tissue, concentrations ranged from 50 to 60 mg B kg-1 DM. For both years of the study, soil samples were taken at depth of 0-45 and 45-90 cm at the beginning and end of the designated growing season and analyzed for water-extractable B. Summary data from all cropped plots at the two soil depths indicated that the mean water-extractable B concentrations were reduced by 35% after 2 years in the tall fescue plots, whereas losses of extractable B from bare plots did not exceed 13% for both years. Tall fescue apparently can be used as a component in an overall strategy to lower extractable soil native B levels in irrigated agriculture soils and potentially reduce leaching of B into shallow ground water.

Boron↗
PubMed1995

Selenium assimilation and differential response to elevated sulfate and chloride salt concentrations in two saltgrass ecotypes.

A comparative study of selenium (Se) assimilation under the influence of sulfate and chloride salt salinity was conducted on two saltgrass ecotypes. The inland saltgrass grows successfully on the soil contaminated with elevated Se concentrations at Kesterson, Merced County, California. The coastal saltgrass colonizes a tidal salt marsh in Bodega Bay on the coast of California. The saltgrass samples were grown in sand culture and irrigated with quarter concentration of modified Hoagland solution supplemented with different concentrations of Se with or without sulfate or chloride salt. The Bodega Bay plants exhibited greater tolerance to both the sulfate and chloride salinity than the Kesterson plants. The plants of both ecotypes accumulated about 90% of their total tissue Se in the nonprotein fraction. When sulfate was present in the irrigation solution, the Kesterson plants assimilated significantly less Se in its protein and nonprotein fractions than in the Bodega Bay plants. Under Se treatment, chlorosis symptoms were found on the leaves of the Bodega Bay plants, but not on the leaves of the Kesterson plants. The above results demonstrate that the two saltgrasses are distinct ecotypes in respect to their salinity tolerance and the ability of mitigation of selenium assimilation in the presence of sulfate.

California↗
PubMed1995

Transduction of hepatic allografts achieves local levels of viral IL-10 which suppress alloreactivity in vitro.

The application of gene therapy in transplantation might be targeted at immunoregulation within the donor graft. Viral IL-10 (vIL-10) down-regulates antigen presenting cells (APC) and effector functions in in vitro and in vivo models of alloreactivity. In the current study, we have constructed a replication-defective adenovirus bearing the cDNA encoding viral IL-10 and examined the level and chronicity of its expression in rat liver allografts up to 7 days after orthotopic transplantation. The results demonstrate that liver allografts may be efficiently transfected with adenovirus expressing viral IL-10. Detection of the recombinant viral cytokine was limited to the allograft without measurable levels in peripheral blood. In parallel, the effect of vIL-10 on mixed leukocyte reaction is also assessed using peripheral blood lymphocytes obtained from naive donor and recipient animals. Equivalent levels of viral IL-10 (5-10 ng/ml) achieved after adenovirus-mediated gene transfer suppress the in vitro alloreactivity of peripheral blood lymphocytes up to 70%. Adenovirus-mediated gene transfer of viral IL-10 offers the promise of effectively and favorably altering the alloreactive immune response.

Adenoviridae↗
PubMed1995

Mapping of the SLA complex class III region by pulsed field gel electrophoresis.

The fine order of genes in the class III region of the swine major histocompatibility complex (MHC), the SLA complex, was examined by pulsed field gel electrophoresis (PFGE) and Southern blot analysis. Four genes, C2, HSP70, TNF alpha, and CYP21, were analyzed. The CYP21, C2, and HSP70 genes were all located within a 200-kb NotI fragment. The C2, HSP70, and TNF alpha genes cohybridized to a 420-kb SalI fragment. The TNF alpha gene is linked to the class I region by a 390-kb NotI fragment. Combined with a previous study from our lab, the order of genes in the SLA complex is class II-class III [(CYP21/C4)-(Bf/C2/HSP70)-TNF alpha]-class I. The size of the class III region from CYP21 to TNF alpha is estimated to be 500 kb. This size and the order of the genes in the swine class III region are similar to those of human, mouse, goat, and rabbit, which confirms the high conservation of class III gene organization across species.

Animals↗
PubMed1995

In-hospital complications among survivors of admission for congestive heart failure, chronic obstructive pulmonary disease, or diabetes mellitus.

OBJECTIVE: To determine the frequency of hospital complications among survivors of inpatient treatment for congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), or diabetes mellitus (DM). DESIGN: Retrospective cohort study. SETTING: Nine Veterans Affairs hospitals in the southern United States. PATIENTS: 1,837 men veterans discharged alive following hospitalization for CHF, COPD, or DM between January 1987 and December 1989. This patient population represents a subset of cases gathered to study the process of care in the hospital and subsequent early readmission; thus, veterans who died in the hospital were not included. MEASUREMENTS: Medical record review to record the occurrence of any of 30 in-hospital complications such as cardiac arrest, nosocomial infections, or delirium (overall agreement between two reviewers = 84%, kappa = 0.37). RESULTS: Complications occurred in 15.7% of the CHF cases, 13.1% of the COPD cases, and 14.8% of the DM cases. Hypoglycemic reactions were the most frequent individual adverse events in the CHF and DM cases (3.6% and 11.4% of the cases, respectively), and theophylline toxicity was most frequent among the COPD cases (4.9%). Patient age, the presence of comorbid diseases, and the Acute Physiology Score (APS) of APACHE II were associated with complication occurrence. For each disease, the patients who had a complication had significantly longer mean hospital stays than did the patients who did not have complications (14.6 to 14.9 days vs 7.2 to 8.2 days, p < 0.01). CONCLUSIONS: Complications are frequent among patients discharged alive with CHF, COPD, or DM. The patients who experienced complications were more ill on admission and had longer hospital stays.

APACHE↗
PubMed1995

The molecular biology of androgenic 17 beta-hydroxysteroid dehydrogenases.

The enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) catalyzes the 17 beta-oxidation/reduction of C18- and C19-steroids in a variety of tissues. Three human genes encoding isozymes of 17 beta-HSD, designated 17 beta-HSD types 1, 2 and 3 have been cloned. 17 beta-HSD type 1 (also referred to as estradiol 17 beta-dehydrogenase) catalyzes the conversion of estrone to estradiol, primarily in the ovary and placenta. The 17 beta-HSD type 2 is expressed to high levels in the liver, secretory endometrium and placenta. The type 2 isozyme catalyzes the oxidation of androgens and estrogens equally efficiently. Also, the enzyme possesses 20 alpha-HSD activity demonstrated by its ability to convert 20 alpha-dihydroprogesterone to progesterone. Testicular 17 beta-HSD type 3 catalyzes the conversion of androstenedione to testosterone, dehydroepiandrosterone to 5-androstenediol and estrone to estradiol. The 17 beta-HSD3 gene is mutated in male pseudohermaphrodites with the genetic disease 17 beta-HSD deficiency.

17-Hydroxysteroid Dehydrogenases↗
PubMed1995

Effect of ischemia on growth factor enhancement of incisional wound healing.

BACKGROUND: Several growth factors have been shown to enhance incisional wound healing in different models, but the models have been difficult to compare, and the effects under ischemic conditions are unknown. METHODS: An ischemic model was developed by selective interruption of the rabbit ear circulation and placement of dorsal incisions. The model was defined during a 28-day period by use of serial blood gas analysis, breaking strength measurement, and histologic analysis. In a separate experiment, incisions were treated with topical growth factors with the contralateral ear serving as paired controls, and the wounds were evaluated similarly. RESULTS: The ischemic ears were more hypoxic than controls through day 14 after wounding (48.5 versus 41 mm Hg, p < 0.03), and healing was impaired through day 28 (3.21 versus 1.90 newtons, p < or = 0.001). Transforming growth factor-beta (1 microgram) and Kaposi's fibroblast growth factor (20 micrograms) increased breaking strengths under both normal (3.03 versus 2.41 and 2.83 versus 2.47 newtons, respectively; p < 0.05) and ischemic conditions (1.40 versus 1.11 and 1.56 versus 1.23 newtons, respectively; p < 0.05). Platelet-derived growth factor-BB (10 micrograms) was effective only under normal conditions (2.67 versus 2.15 newtons, p < 0.02), whereas basic fibroblast growth factor (20 micrograms) was ineffective under both conditions. CONCLUSIONS: The rabbit ear incisional model is a reproducible ischemic incisional model allowing comparison of growth factor effects under ischemic and nonischemic conditions. Transforming growth factor-beta and Kaposi's fibroblast growth factor are both effective under ischemic conditions, whereas basic fibroblast growth factor and platelet-derived growth factor-BB are not, suggesting that ischemia is an important parameter affecting growth factor actions.

Animals↗
PubMed1995

Vapor pressure response to denaturant and water in E10 blends.

On December 16, 1993, the U.S. Environmental Protection Agency (EPA) released the final rule on reformulated gasoline (RFG). This rule will affect the composition of as much as 45% of the gasoline used in the United States by the summer of 1995. The acceptance of any gasoline component lies in its ability to contribute to the RFG program's environmental goals. This study was conducted to determine the effect of water and ethanol denaturant on gasoline Reid vapor pressure (RVP) for which little quantitative data are available. This paper addresses two new areas where environmental goals may be achieved while maintaining the use of ethanol-blended gasolines within ozone nonattainment areas.

Air Pollutants↗
PubMed1995

The G protein beta subunit is essential for multiple responses to chemoattractants in Dictyostelium.

Increasing evidence suggests that the beta gamma-subunit dimers of heterotrimeric G proteins play a pivotal role in transducing extracellular signals. The recent construction of G beta null mutants (g beta-) in Dictyostelium provides a unique opportunity to study the role of beta gamma dimers in signaling processes mediated by chemoattractant receptors. We have shown previously that g beta- cells fail to aggregate; in this study, we report the detailed characterization of these cells. The g beta- cells display normal motility but do not move towards chemattractants. The typical GTP-regulated high affinity chemoattractant-binding sites are lost in g beta- cells and membranes. The g beta- cells do not display chemoattractant-stimulated adenylyl cyclase or guanylyl cyclase activity. These results show that in vivo G beta links chemoattractant receptors to effectors and is therefore essential in many chemoattractant-mediated processes. In addition, we find that G beta is required for GTP gamma S stimulation of adenylyl cyclase activity, suggesting that the beta gamma-dimer activates the enzyme directly. Interestingly, the g beta- cells grow at the same rate as wild-type cells in axenic medium but grow more slowly on bacterial lawns and, therefore, may be defective in phagocytosis.

Adenylyl Cyclases↗
PubMed1995

Altered selenium-binding protein levels associated with selenium resistance.

Our previous studies have sought to elucidate the mechanism by which selenium inhibits cell growth since the mechanisms involved may be relevant to the chemopreventive properties of selenium. In a previous report, we described the isolation of a selenium-resistant cell line, B19, from a selenium-sensitive parental cell line, C57. In this report we identify biochemical changes that may be responsible for conferring selenium resistance. Altered selenium uptake and intracellular glutathione concentrations were eliminated as possible modes of resistance since these two parameters were similar between the two cell lines. However, when the selenium-containing protein complements of the two cell lines were compared by labelling with [75Se]selenite, both increases and decreases in a number of selenium-labelling proteins were found in the B19 cells. The most striking differences were the presence of two 72 kDa selenium-labelling proteins in B19 cells which could not be detected in C57 cells. The levels of a number of mRNAs encoding antioxidant or detoxification enzymes were also compared between the two cell lines but only minor changes were found. This work suggests that further analysis of the 72 kDa selenium-labelling proteins may reveal insights into the mechanisms of growth inhibition by selenium.

Animals↗
PubMed1995

The selenium metabolite selenodiglutathione induces cell death by a mechanism distinct from H2O2 toxicity.

Our previous studies have implicated the selenium metabolite selenodiglutathione (SDG) in the growth inhibitory effects of selenite in vitro. Other work has suggested that reactive oxygen species, the superoxide anion and hydrogen peroxide, may be implicated in selenite toxicity. In this study the mechanism of growth inhibition by SDG and H2O2 has been compared in a mammary cell line, C57. Both SDG and H2O2 had a rapid effect on C57 cells and markedly reduced cloning efficiency within 1 h. However, the mechanisms involved seem to be different, as judged by the following observations: (i) An SDG-resistant cell line (B19) derived from C57 cells is cross-resistant to selenite, but not H2O2; (ii) SDG reduces the levels of the mRNAs for phospholipid hydroperoxide glutathione peroxidase and cytosolic glutathione peroxidase, whereas H2O2 has no effect; (iii) SDG induces both 560 kb and 50 kb DNA fragments, whereas H2O2 only induces 560 kb DNA fragments. This is of interest, since formation of high molecular weight DNA fragments has been recognized as a characteristic of apoptosis.

Animals↗
PubMed1995

Alternatively spliced forms in the carboxy-terminal domain of the p53 protein regulate its ability to promote annealing of complementary single strands of nucleic acids.

The carboxy-terminal domain of the p53 protein comprising amino acid residues 311 to 393 is able to promote the reassociation of single-stranded RNA or DNA into duplex hybrids. This domain is as efficient as the intact p53 protein in both the rate and the extent of the double-stranded product produced in this reaction. Both wild-type and mutant p53 proteins from cancerous cells carry out this reaction. The monoclonal antibody PAb421, which detects an epitope between residues 370 and 378, blocks the ability of p53 to reassociate single strands of RNA or DNA. Similarly, the alternative splice form of the murine p53 protein, which removes amino acid residues 364 to 390 and replaces them with 17 new amino acids, does not carry out the reassociation reaction with RNA or DNA. This is the first indication of functionally distinct properties of the alternative splice forms of p53. These results suggest that this splice alternative can regulate a p53-mediated reaction that may be related to the functions of this protein.

Alternative Splicing↗