bluuebunny/crossref_metadata_2025_split huggingface dataset:
Basic fibroblast growth factor and epidermal growth factor downmodulate the growth of hematopoietic cells in long‐term stromal cultures
Authors: Dooley Douglas C. , Oppenlander Barbara K. , Spurgin Pam , Mead Jay H. , Novak F. Patrick , Plunkett Michael , Beckstead Jay , Heinrich Michael C. 
Published: February 2005

AbstractThe bone marrow microenvironment consists of stromal cells and extracellular matrix components which act in concert to regulate the growth and differentiation of hematopoietic stem cells. There is little understanding of the mechanisms which modulate the regulatory role of stromal cells. This study examined the hypothesis that mesenchymal growth factors such as basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) modulate stromal cell activities and thereby influence the course of hematopoiesis. Both bFGF and EGF were potent mitogens for marrow stroma. However, both factors proved to be inhibitory to hematopoiesis in primary log‐term marrow cultures. Inhibition was also observed when hematopoietic cells and bFGF or EGF were added to subconfluent irradiated stromal layers, demonstrating that the decline of hematopoiesis was not due to overgrowth of the stromal layer. Loss of hematopoietic support in bFGF and EGF was dose‐dependent. Removal of bFGF and EGF permitted stromal layers to regain their normal capacity to support hematopoiesis. In stroma‐free long‐term cultures, neither factor affected CFU‐GM expansion. Basic FGF slightly enhanced granulocyte‐macrophage colony forming unit (CFU‐GM) cloning efficiency in short‐term agarose culture. Basic FGF did not reduce the levels of interleukin‐6 (IL‐6), GM‐CSF, or G‐CSF released by steady state or IL‐1‐stimulated stroma. Similarly, the constitutive levels of steel factor (SF) mRNA and protein were not affected by bFGF. Basic FGF did not alter the level of TGF‐β1 in stromal cultures. We conclude that bFGF and EGF can act as indirect negative modulators of hematopoietic growth in stromal cultures. The actual mediators of regulation, whether bound or soluble, remain to be identified. © 1995 Wiley‐Liss, Inc.
Interferon‐γ and tumor necrosis factor‐α suppress both early and late stages of hematopoiesis and induce programmed cell death
Authors: Selleri Carmine , Sato Tadatsugu , Anderson Stacie , Young Nel S. , Maciejewski Jaroslaw P. 
Published: February 2005

AbstractIncreased expression of interferon gamma (IFN‐γ) and tumor necrosis factor alpha (TNF‐α) in bone marrow failure disorders suggests a possible pathophysiologic role of these cytokines in disease. In this study, we tested the action of TNF‐α and IFN‐γ on phenotypically and functionally defined stages of hematopoietic development using highly purified progenitor cell populations assayed in standardized culture systems. We hypothesized that the inhibitory effects of IFN‐γ and TNF‐α might be related to the induction of programmed cell death. In methylcellulose colony assays, IFN‐γ and TNF‐α inhibited the growth of early hematopoietic cells, including committed CD34+ CD38+ progenitor cells and phenotypically less mature CD34+CD38− cells, with 50% decreased colony formation occurring in the range of 750‐1,000 U/ml of IFN‐γ and 10–15 ng/ml of TNF‐α. More potent suppressive effects were observed in cultures supplemented with the combination of both cytokines than in cultures treated with IFN‐γ or TNF‐α alone. When used at these concentrations, IFN‐γ and TNF‐α inhibited growth of CD34+‐enriched long‐term culture‐initiating cells by 88% and 68%, respectively. IFN‐γ and TNF‐α triggered apoptosis of total bone marrow and CD34+ cells, recognized by the presence of a characteristic pattern of DNA degradation after low molecular weight DNA extraction, and by detection of apoptotic cells by the in situ terminal deoxynucleotidyl transferase assay. We speculate that chronic exposure of hematopoietic tissue to TNF‐α and IFN‐γ in vivo may result in broad depletion of the stem and progenitor cell pools. Death of these cells due to apotosis rather than transient inhibition of proliferation may be responsible for long‐lasting hematologic consequences. © 1995 Wiley‐Liss Inc.
Arachidonic acid release from NIH 3T3 cells by group‐I phospholipase A2: Involvement of a receptor‐mediated mechanism
Authors: Xing Mingzhao , Miele Lucio , Mukherjee Anil B. 
Published: February 2005

AbstractGroup I pancreatic phospholipase A2 (PLA2 I) is primarily a digestive enzyme. Recently, however, in addition to its catalytic activity a receptor‐mediated function has been described for this enzyme. PLA2 I binding to its receptor induces cellular chemokinesis, proliferation, and smooth muscle contraction. This enzyme also induces the production of prostaglandin E2 in certain cells and may have a proinflammatory role. However, despite its ability to hydrolyze phospholipids in in vitro assays, PLA2‐I does not efficiently catalyze release of AA from intact cells. Here, we demonstrate that while short‐term exposure of NIH 3T3 cells to PLA2‐I is ineffective, exposure of 6 h or longer significantly increases the basal release of AA. Dose‐response curve of PLA2‐I‐induced AA release was saturable with an EC50 of 14.01 ± 1.36 nM (n = 3). [3H]‐AA was preferentially released over [3H]‐oleic acid by PLA2‐I, inactivated with 4‐bromophenacyl bromide, was fully capable of mediating AA release. These data suggest that a non‐catalytic, receptor‐mediated mechanism is involved in PLA2‐I‐induced AA release in NIH‐3T3 cells. This relase of AA is not dependent on protein kinase C or Ca2+ concentration. Comparison of the effect of PLA2‐I with those of ATP and platelet‐derived growth factor indicates that each of these agonists regulates AA release via independent pathways. Neither the basal enzymatic activity of the 85‐kDa cytosolic PLA2 nor the protein level of this enzyme was affected by treatment of cells with PLA2‐I. However, the increase in basal enzymatic activity of 85 kDa PLA2 due to protein kinase C activation was further enhanced by pretreatment of cells with PLA2‐I. We conclude that: (1) short‐term exposure of cells to PLA2 I does not cause measurable AA release; (2) release of AA from intact cells by this enzyme requires long‐term exposure; (3) AA release is not mediated by a direct catalytic effect of PLA2 I; and (4) AA release by PLA2 I is accomplished via a receptor‐mediated process. Taken together, these results raise the possibility that PLA2 I, in addition to its digestive function, may also contribute to aggravate preexisting inflammatory processes and/or to initiate new ones when chronic exposure of cells to this enzyme occurs. © 1995 Wiley‐Liss Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.
Expression and regulation of superoxide dismutase activity in human skin fibroblasts from donors of different ages
Authors: Allen P. G. , Keogh Bart P. , Gerhard Glenn S. , Pignolo Robert , Horton Joseph , Cristofalo Vincent J. 
Published: February 2005

AbstractWe have determined the activities, protein, and mRNA abundances as well as the level of transcriptional activation of two intracellular forms of the free radical metabolizing enzyme superoxide dismutase in 29 human skin fibroblast lines established from donors of different ages. SOD‐1 (a copper and zinc containing from of SOD) and SOD‐2 (a manganese containing form of the enzyme) activities were both observed to be significantly lower in cell lines derived from fetal skin than in lines established form postnatal skin (ages 17–94 years). The percent of total activity contributed by SOD‐1 decreased in an age‐associated manner from approximately 50% in the fetal lines to less than 20% in lines established from old tissue donors. All of the cell lines were screened to exclude the possibility that they contained a polymorphism known to influence SOD‐2 activity. Northern blot analysis revealed three SOD‐1 mRNA transcripts that were 0.5, 0.7, and 1.9 kb in length. Although SOD‐1 protein abundance was lower in fetal lines than in lines derived from postnatal donors, SOD‐1 mRNA abundance did not differ between fetal cells and cell lines derived from young donors. SOD‐2 protein abundance and mRNA abundance were both significantly lower in fetal lines than in postnatal lines. No postnatal age‐dependent differences were observed in any of the SOD‐2 parameters examined. Nuclear run‐on analysis revealed that fetal cell lines exhibited a lower level of transcriptional initiation for SOD‐1 than postnatal lines. The transcription of SOD‐2 was readily detected in postnatal lines, but undetectable in fetal lines. These results are consisten with multiple levels of control of SOD‐1 expression and with a strong transcriptional influence on SOD‐2 expression. © 1995 Wiley‐Liss Inc.
Contribution of increased glutathione content to mechanisms of oxidative stress resistance in hydrogen peroxide resistant hamster fibroblasts
Authors: Spitz Douglas R. , Kinter Michael T. , Roberts Robert J. 
Published: February 2005

AbstractAn H2O2‐resistant variant (OC14) of the HA1 Chinese hamster fibroblast cell line, which demonstrates cross resistance to 95% O2 and a 2‐fold increase in total glutathione content, was utilized to investigate mechanisms responsible for cellular resistance to H2O2‐ and O2‐toxicity. OC14 and HA1 cells were pretreated with buthionine sulfoximine (BSO) to deplete total cellular glutathione. Following BSO pretreatment, cells were either placed in 250 μM BSO to maintain the glutathione depleted condition and challenged with 95% O2, or challenged with hydroged peroxide in the absence of BSO. Total glutathione and the activities of CuZn superoxide dismutase, Mn superoxide dismutase, catalase, glutathione peroxidase, and glutathione transferase were evaluated immediately following the BSO pretreatment as well as following 39 to 42 hr of exposure to 250 μM BSO. BSO treatment did not cause significant decreases in any cellular antioxidant tested, except total glutathione depletion resulted in significant (P < 0.05) sensitization to O2‐toxicity and H2O2‐toxicity in both cell lines at every time point tested. However, glutathione depletion did not completely abolish the resistance to either O2‐ or H2O2‐toxicity demonstrated by OC14 cells, relative to HA1 cells. Also, glutathione depletion did not effect the ability of OC14 cells to metabolize extracellular H2O2. These data indicate that glutathione dependent processes significantly contribute to cellular resistance to acute H2O2‐ and O2‐toxicity, but are not the only determinants of resistance in cell lines. The contribition of aldehydes formed by lipid peroxidation in mechanisms involved with the sensitization to O2‐toxicity in glutathione depleted cells was tested by measuring the lipid peroxidation byproduct, 4‐hydroxy‐2‐nonenal (4HNE), bound in Schiff‐base linkages or in its free form in cell homogenates at 49 hr of 95% O2‐exposure. No significant increase in 4HNE was detected in glutathione depleted cells relative to glutathione competent cells, indicating that glutathione depletion does not sensitize these cells to O2‐toxicity by altering the intracellular accumulation of free or Schiff‐base bound 4HNE. © 1995 Wiley‐Liss Inc.
L‐fucose reduces collagen and noncollagen protein production in cultured cerebral microvessel endothelial cells
Authors: Yorek Mark A. , Conner Corinne E. , Spanheimer Robert G. 
Published: February 2005

AbstractL‐fucose is a monosaccharide which is present in low concentrations in normal serum but is increased in diabetes, cancer, and inflammatory diseases. The contribution that abnormal L‐fucose levels make to the progression of these disorders is unknown. In a previous study we showed that increased L‐fucose concentration reduced proliferation and proteoglycan production by cultured cerebral microvessel endothelial cells. In the present study we show that exposing cerebral microvessel endothelial cells for 2 weeks to medium containing an increased concentration of L‐fucose causes a significant decrease in collagen and to a lesser extent noncollagan protein production. The effect of L‐fucose on collagen and noncollagen protein production is concentration‐dependent: 1 mM L‐fucose causes a significant decrease in collagen production but has no effect on noncollagen protein production; a 5mM L‐fucose concentration causes a maximum decrease in both collagen and noncollagen protein production. This defect is unrelated to the reduction in myo‐inositol uptake caused by L‐fucose and is not prevented by aminoguanidine. Collagen production can be improved by restoring L‐fucose‐conditioned cells to normal medium. Culturing cells for 2 weeks in medium containing 10 mM L‐fucose resulted in a 50% decrease in collagen production, which was restored to 75% of control after cells were transferred to normal medium for 7 days. In contrast, noncollagen protein production was totally restored after 3 days in normal medium. Increasing levels of L‐fucose in serum of rats also resulted in a decrease in collagen production. Collagenase digestible incorporation of L‐[2,3,4,5‐3H]proline into protein of the articular cartilage from rats fed a diet containing 20% L‐fucose for 3 weeks was reduced by about 40% compared to rats fed a normal diet. The decrease in collagen production in L‐fucose fed rats was less than the reduction that occurred in streptozotocin‐induced diabetic rats. These data suggest that changes in L‐fucose concentration itself may be a factor in the regulation of collagen production. © 1995 Wiley‐Liss Inc.
Conservation and Divergence of Circadian Clock Operation in a Stress-Inducible Crassulacean Acid Metabolism Species Reveals Clock Compensation against Stress
Authors: Boxall Susanna F. , Foster Jonathan M. , Bohnert Hans J. , Cushman John C. , Nimmo Hugh G. , Hartwell James 
Published: February 2005

Abstract
One of the best-characterized physiological rhythms in plants is the circadian rhythm of CO2 metabolism in Crassulacean acid metabolism (CAM) plants, which is the focus here. The central components of the plant circadian clock have been studied in detail only in Arabidopsis (Arabidopsis thaliana). Full-length cDNAs have been obtained encoding orthologs of CIRCADIAN CLOCK-ASSOCIATED1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1 (TOC1), EARLY FLOWERING4 (ELF4), ZEITLUPE (ZTL), FLAVIN-BINDING KELCH REPEAT F-BOX1 (FKF1), EARLY FLOWERING3 (ELF3), and a partial cDNA encoding GIGANTEA in the model stress-inducible CAM plant, Mesembryanthemum crystallinum (Common Ice Plant). TOC1 and LHY/CCA1 are under reciprocal circadian control in a manner similar to their regulation in Arabidopsis. ELF4, FKF1, ZTL, GIGANTEA, and ELF3 are under circadian control in C3 and CAM leaves. ELF4 transcripts peak in the evening and are unaffected by CAM induction. FKF1 shows an abrupt transcript peak 3 h before subjective dusk. ELF3 transcripts appear in the evening, consistent with their role in gating light input to the circadian clock. Intriguingly, ZTL transcripts do not oscillate in Arabidopsis, but do in M. crystallinum. The transcript abundance of the clock-associated genes in M. crystallinum is largely unaffected by development and salt stress, revealing compensation of the central circadian clock against development and abiotic stress in addition to the well-known temperature compensation. Importantly, the clock in M. crystallinum is very similar to that in Arabidopsis, indicating that such a clock could control CAM without requiring additional components of the central oscillator or a novel CAM oscillator.
The Potassium Transporter AtHAK5 Functions in K+ Deprivation-Induced High-Affinity K+ Uptake and AKT1 K+ Channel Contribution to K+ Uptake Kinetics in Arabidopsis Roots
Authors: Gierth Markus , Mäser Pascal , Schroeder Julian I. 
Published: February 2005

Abstract
Potassium is an important macronutrient and the most abundant cation in plants. Because soil mineral conditions can vary, plants must be able to adjust to different nutrient availabilities. Here, we used Affymetrix Genechip microarrays to identify genes responsive to potassium (K+) deprivation in roots of mature Arabidopsis (Arabidopsis thaliana) plants. Unexpectedly, only a few genes were changed in their expression level after 6, 48, and 96 h of K+ starvation even though root K+ content was reduced by approximately 60%. AtHAK5, a potassium transporter gene from the KUP/HAK/KT family, was most consistently and strongly up-regulated in its expression level across 48-h, 96-h, and 7-d K+ deprivation experiments. AtHAK5 promoter-β-glucuronidase and -green fluorescent protein fusions showed AtHAK5 promoter activity in the epidermis and vasculature of K+ deprived roots. Rb+ uptake kinetics in roots of athak5 T-DNA insertion mutants and wild-type plants demonstrated the absence of a major part of an inducible high-affinity Rb+/K+ (K m approximately 15–24 μ m) transport system in athak5 plants. In comparative analyses, uptake kinetics of the K+ channel mutant akt1-1 showed that akt1-1 roots are mainly impaired in a major transport mechanism, with an apparent affinity of approximately 0.9 mm K+(Rb+). Data show adaptation of apparent K+ affinities of Arabidopsis roots when individual K+ transporter genes are disrupted. In addition, the limited transcriptome-wide response to K+ starvation indicates that posttranscriptional mechanisms may play important roles in root adaptation to K+ availability in Arabidopsis. The results demonstrate an in vivo function for AtHAK5 in the inducible high-affinity K+ uptake system in Arabidopsis roots.
A Genome-Wide Analysis of the Effects of Sucrose on Gene Expression in Arabidopsis Seedlings under Anoxia
Authors: Loreti Elena , Poggi Alessandra , Novi Giacomo , Alpi Amedeo , Perata Pierdomenico 
Published: February 2005

Abstract
Exogenous sucrose (Suc) greatly enhances anoxia tolerance of Arabidopsis (Arabidopsis thaliana) seedlings. We used the Affymetrix ATH1 GeneChip containing more than 22,500 probe sets to explore the anaerobic transcriptome of Arabidopsis seedlings kept under anoxia for 6 h in presence or absence of exogenous Suc. Functional clustering was performed using the MapMan software. Besides the expected induction of genes encoding enzymes involved in Suc metabolism and alcoholic fermentation, a large number of genes not related to these pathways were affected by anoxia. Addition of exogenous Suc mitigated the effects of anoxia on auxin responsive genes that are repressed under oxygen deprivation. Anoxia-induced Suc synthases showed a lower induction in presence of exogenous Suc, suggesting that induction of these genes might be related to an anoxia-dependent sugar starvation. Anoxic induction of genes coding for heat shock proteins was much stronger in presence of exogenous Suc. Interestingly, a short heat treatment enhanced anoxia tolerance, suggesting that heat shock proteins may play a role in survival to low oxygen. These results provide insight into the effects of Suc on the anoxic transcriptome and provide a list of candidate genes that enhance anoxia tolerance of Suc-treated seedlings.
Factors influencing vascular plant diversity on 22 islands off the coast of eastern North America
Authors: McMaster Robert T. 
Published: February 2005

AbstractAim  The influence of physiographic and historical factors on species richness of native and non‐native vascular plants on 22 coastal islands was examined.Location  Islands off the coast of north‐eastern USA and south‐eastern Canada between 41° and 45° N latitude were studied. Island size ranges from 3 to 26,668 ha. All islands were deglaciated between 15,000 and 11,000 yr bp; all but the four New Brunswick islands were attached to the mainland until rising sea level isolated them between 14,000 and 3800 yr bp.Methods  Island species richness was determined from floras compiled or revised since 1969. Simple and multiple regression and rank correlation analysis were employed to assess the relative influence of independent variables on species richness. Potential predictors included island area, latitude, elevation, distance from the mainland, distance from the nearest larger island, number of soil types, years since isolation, years since deglaciation, and human population density.Results  Native vascular plant species richness for the 22 islands in this study is influenced most strongly by island area, latitude, and distance from the nearest larger island; richness increases with island area, but decreases with latitude and distance from the nearest larger island as hypothesized. That a similar model employing distance from the mainland does not meet the critical value of P confirms the importance of the stepping‐stone effect. Habitat diversity as measured by number of soil types is also an important predictor of native plant species richness, but at least half of its influence can be attributed to island area, with which it is correlated. Two historical factors, years since deglaciation and years since isolation, also appear to be highly correlated with native species richness, but their influence cannot be separated from that of latitude for the present sample size. Non‐native vascular plant species richness is influenced primarily by island area and present‐day human population density, although human population density may be a surrogate for the cumulative effect of several centuries of anthropogenic impacts related to agriculture, hunting, fishing, whaling, tourism, and residential development. Very high densities of ground‐nesting pelagic birds may account for the high percentage of non‐native species on several small northern islands.Main conclusions  Many of the principles of island biogeography that have been applied to oceanic islands apply equally to the 22 islands in this study. Native vascular plant species richness for these islands is strongly influenced by physiographic factors. Influence of two historical factors, years since deglaciation and years since isolation, cannot be assessed with the present sample size. Non‐native vascular plant species richness is influenced by island area as well as by human population density; human population density may be a surrogate for other anthropogenic impacts.