bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gravitropic responses of the Avena coleoptile in space and on clinostats. III. Hypogravity effects on coleoptile curvatures
Authors: Karlsson Christina , Johnsson Anders , Chapman David K. , Brown Allan H. 
Published: March 2003

The precise description of the gravitropic curvature response of plants is often difficult due to the presence of gravity when the response is recorded. Therefore, unambiguous results on the gravitropic reactions in differents segments of coleoptiles, the participation of auxin transport in the curvature development and the reactions to hypogravity stimulations can only be achieved in weightlessness. To answer these questions, curvatures of Avena coleoptiles at different distances from the apex were studied after transverse, hypogravity stimulations. The experiments were conducted in Spacelab on the Shuttle in earth orbit.Test plants were cultivated on 1.0 g‐centrifuges in Spacelab. The stimulation accelerations, were between 0.1 and 1.0 g, and duration varied between 2 and 130 min. All plant responses were recorded in weightlessness by a video cassette recorder for analysis.The gravitropic curvature started almost simultaneously in apical segments, and occurred later in the basal ones. After maximum response, the curvature in the top segments showed a clear autotropic reaction, that was not seen in the basal segments. Initial wrong‐way curvatures were recorded in the basal part of the coleoptiles at several g‐levels.The further down along the coleoptile, the later the occurrence of the maximum gravitropic curvature of each segment. For example, after a stimulus of 25 g min the maxima appeared to travel down the coleoptile with a speed of about 50 mm h−1 in the upper and 20 mm h−1 in the lower part of the coleoptiles. It is concluded that the basipetal auxin transport can contribute only marginally to the gravitropic curvature pattern due to its much lower transport rate. Local reactions control the curvature pattern in each segment (even if the basipetal auxin transport must add to the reactions).Extrapolations from stimulus response data curves allowed some determinations of threshold stimulation times for different segments along the coleoptiles. Data for the individual segments along the coleoptiles were not at variance with the reciprocity law.
Seasonal pattern of accumulation and effects of low temperatures on storage compounds in Trifolium repens
Authors: Bouchart V. , Macduff J. H. , Ourry A. , Svenning M. M. , Gay A. P. , Simon J. C. , Boucaud J. 
Published: March 2003

The seasonal pattern of concentrations of nitrogen, starch and vegetative storage protein (VSP) in stolons of Trifolium repens L. grown in the field were studied. Two different genotypes, cv. Aran and cv. Rivendel, differing in their morphology (stolon thickness and branching rate) but with similar growth rates, were used. Maximum concentrations of starch were found in summer whereas hydrolysis of starch took place throughout winter, suggesting that C storage is more important for winter survival than for promotion of early spring growth. On the other hand, VSP and nitrogen accumulated in autumn and early winter and then decreased when growth was resumed during early spring. For both cultivars, an inverse relationship was found between VSP concentration in stolons and mean air temperature, suggesting that VSP accumulation may be triggered by low temperature. Further experiments with plants grown under different regimes of temperature and daylength, suggested that VSP synthesis is stimulated by low root temperatures, with a slight synergistic effect of short daylength.The effects of root temperature on growth, N2 fixation, NH4+ uptake and N allocation within Trifolium repens L., were studied under controlled conditions. The shoot growth rate was greatly reduced when root temperatures were lowered from 12 to 6°C, while the rate of stolon growth was less affected. Low root temperatures inhibited N2 fixation more than it did NH4+ uptake, but the relative allocation of N to stolons was increased. Lowering root temperature also increased the accumulation of VSP in stolons. These results are discussed in terms of the mechanism associated with low temperature stimulation of VSP accumulation and its coupling with changes in the source/sink relations for allocation of N, between growth and storage.
Membrane lipid composition and restoration of photosynthesis during low temperature acclimation in Synechococcus sp. strain PCC 7942
Authors: Porankiewicz J. , Selstam E. , Campbell D. , Öquist G. 
Published: March 2003

We compared temperature acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 and two psbA inactivation mutants, R2K1 and R2S2C3, following shifts from 37 to 25°C. Wild‐type cultures incubated in the dark at 25°C showed no chill‐induction of lipid desaturation, probably because the lipid acclimation is dependent on photosynthesis. Incubation in the light at 25°C, however, induced considerable increases in membrane lipid desaturation, and within 24 h the monoenoic fatty acids increased from about 46 to about 57%. In parallel with this desaturation the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol (MGDG/DGDG) increased. Both of these lipid changes increase the repulsive forces of the hydrophobic chains of the membrane lipids and thereby alter the physical properties of the membrane. As expected, under irradiation this temperature shift also induced a reversible replacement of the constitutive photosystem II protein, D1:1, with an alternative stress form, D1:2. Photosynthesis decreased to 42% of the control level within the initial 2 h of cold incubation, but later recovered. The D1:2 protein accumulated to high levels between 2 and 4 h after the temperature shift, when desaturation of membrane lipids and MGDG/DGDG ratio had not yet increased significantly. Much of this accumulated D1:2 protein was in a higher molecular mass form, termed D1:2*, which is probably an unprocessed precursor form of the protein. In contrast to the wild‐type cells the psbA inactivation mutants, R2K1 and R2S2C3 did not accumulate any precursor form of D1 protein either at the optimal or low growth temperature.The R2S2C3 mutant strain expresses only the constitutive D1:1 protein and suffered severe photoinhibition following the temperature shift. Nevertheless, R2S2C3 eventually recovered some photosynthetic activity, induced lipid desaturation and slowly resumed growth at 25°C, thus demonstrating acclimation to the lower growth temperature.The R2K1 mutant synthesizes only the D1:2 stress form of D1 protein and maintained oxygen evolution at a high level (ca 70% of a control rate) after the low temperature shift. Chill‐induced lipid desaturation and increase in MGDG/DGDG ratio did proceed but, for unknown reasons the strain did not resume growth at the lower temperature. The physical properties of the membrane lipids were not the limiting factor for growth resumption.Our results demonstrate that in the wild‐type the chill‐induced desaturation of membrane lipids follows after the exchange of the two forms of the D1 proteins, but the D1 exchange results in accumulation of unprocessed D1:2* polypeptides until the lipid composition later acclimates. We also show that the lipid desaturation process in Synechococcus sp. strain PCC 7942 is dependent upon photosynthetic activity.
Preventing opportunistic infections in bone marrow transplant recipients
Authors: Dykewicz C.A. 
Published: March 2003

Abstract:In 1996, a Center for Disease Control and Prevention (CDC)‐sponsored working group began developing guidelines for preventing opportunistic infections (OIs) in bone marrow transplant (BMT) recipients. The purposes of the guidelines are to: a) summarize current data regarding the epidemiology of OIs in BMT recipients; b) produce an evidence‐based statement of recommended strategies for preventing OIs in BMT recipients; c) decrease the incidence, morbidity, and mortality of OIs in BMT recipients; and d) define directions for future OI prevention research. Each recommendation is given two ratings: one indicating the strength of the recommendation, and another indicating the strength of evidence supporting the recommendation. The target audience for the guidelines includes transplant and infectious disease physicians and BMT unit and clinic staff. The BMT OI guidelines include sections on viral, bacterial, fungal, protozoal, and helminth infections, immunization, infection control, and blood and stem cell safety. The disease‐specific sections address preventing exposure and disease among both adult and pediatric recipients of allogeneic and autologous BMTs. The immunization section addresses: a) immunization of BMT recipients, their household contacts, and health care workers; b) travel immunizations for BMT recipients; and c) passive immunization with immune globulin products. The infection control sections address room ventilation, isolation and barrier precautions, and prevention of nosocomial and other infections (e.g. infections acquired from visitors, plants, food, pets, construction sites, etc.). The blood safety section contains recommendations on preventing transmission of infections to BMT recipients from infected donated cells. After the guidelines are made available for public comment, they will be finalized and published in the Morbidity and Mortality Weekly Report and placed on the CDC web site (
Note).
Fluconazole in transplant recipients: options and limitations
Authors: Strahilevitz J. , Sugar A.M. , Engelhard D. 
Published: March 2003

Abstract:Fluconazole is currently a first‐line agent used for therapy of non‐critically ill patients with candidal infection. Its efficacy, the availability of an oral formula, and its relatively low toxicity make it a very attractive drug for use in many clinical situations. The advisability of prophylaxis and empirical treatment in transplant patients is a difficult issue for the following reasons: the potential emergence of resistance to the azoles, the lack of solid data establishing its advantage over placebo and/or oral nonabsorbable antifungal agents in some of the clinical conditions encountered, its ineffectiveness against molds, and its cost. Judicious use of fluconazole where its efficacy has been well established would provide the best therapy for patients and would limit the emergence of potential pathogens. As new antifungal agents are approved for clinical use, appropriate clinical trials will need to be designed and conducted in order for clinicians to make rational decisions in selecting the most appropriate drug for the specific indication. Prophylaxis and treatment with fluconazole in various transplant situations is reviewed.
The use of itraconazole as prophylaxis against invasive fungal infection in blood and marrow transplant recipients
Authors: Boyle B.M. , McCann S.R. 
Published: March 2003

Abstract:Invasive fungal infections play a key role in contributing to morbidity and mortality in patients undergoing treatment for haematological malignancies and related diseases. Risk factors for development of invasive fungal infections after blood or bone marrow transplantation include the use of broad‐spectrum antibiotics, steroids, mismatched or unrelated donor transplant, right atrial catheters, and prolonged or profound neutropenia. Previous attempts at use of oral itraconazole as antifungal prophylaxis in the setting of chemotherapy‐induced neutropenia were unsuccessful because of its poor absorption in capsule form. Itraconazole‐cyclodextrin is well absorbed even in the presence of chemotherapy‐induced neutropenia. Plasma levels of 250–500 ng/ml are required for prophylaxis. Studies to date show a favourable outcome in patients receiving itraconazole as prophylaxis against invasive fungal infections, although many studies looked at small numbers of patients and the incidence of invasive fungal infection in the control groups was low, prohibiting meaningful statistical evaluation. Fungi differ in their sensitivity to antifungal agents, and itraconazole is not the agent of choice in all patients. With the widespread use of antifungal prophylaxis, the possibility of resistance to antifungal agents and an increase in the number of invasive fungal infections caused by ubiquitous fungi previously considered nonpathogenic must be considered as potential problems.
Significant post‐transplant hypogammaglobulinemia in six heart transplant recipients: an emerging clinical phenomenon?
Authors: Corales R. , Chua J. , Mawhorter S. , Young J.B. , Starling R. , Tomford J.W. , McCarthy P. , Braun W.E. , Smedira N. , Hobbs R. , Haas G. , Pelegrin D. , Majercik M. , Hoercher K. , Cook D. , Avery R.K. 
Published: March 2003

Abstract:Background:The recent development of powerful agents such as mycophenolate mofetil and tacrolimus has altered current regimens for the prevention and treatment of allograft rejection. Questions have been raised about these newer regimens in terms of susceptibility to opportunistic infections and effects on host defenses. Severe hypogammaglobulinemia has been infrequently described in solid organ transplant recipients, but has been recently noted in six heart transplant recipients at one center, of whom five were receiving a combination of tacrolimus, mycophenolate mofetil, and prednisone.Methods:Case summaries of six recent heart transplant recipients with total immunoglobulin G (IgG) levels of less than 310 mg/dl, five of whom had cytomegalovirus (CMV) infection and three of whom had multiple infections includingNocardia, invasiveTrichophyton, andAcinetobacterbacteremia. Previous literature was reviewed with the aid of a Medline search using the search terms hypogammaglobulinemia; kidney, liver, heart, lung, and organ transplantation; mycophenolate mofetil; tacrolimus; cyclosporine; azathioprine; and nocardiosis.Results:We here report six cardiac transplant recipients seen over a period of one year who were found to have immunoglobulin G levels of 310 mg/dl or below (normal: 717–1400 mg/dl). The first five patients were diagnosed because of evaluation for infections; the sixth, who was asymptomatic with an IgG level of 175, was found during screening for hypogammaglobulinemia instituted as a result of these first five patients. All six patients had received steroid pulses for rejection; all received mycophenolate mofetil; and 5/6 had been switched from cyclosporine to tacrolimus because of steroid‐resistant rejection. Transient neutropenia (absolute neutrophil count less than 1000) was observed in 2/6; 3/6 had received OKT3 therapy for refractory rejection. These six patients were treated with a combination of antimicrobials, immunoglobulin replacement, and decrease in immunosuppressive therapy.Conclusions:The finding of unexpected hypogammaglobulinemia and concomitant infectious complications in six heart transplant recipients highlights a possible complication in a subset of patients receiving newer immunosuppressive agents. A larger prospective study is underway to determine risk factors for development of post‐transplant hypogammaglobulinemia and to assess pre‐transplant immune status of these recipients. Monitoring of immunoglobulin levels in high‐risk patients receiving intensified immunosuppressive therapy for rejection may help to prevent infectious complications.
Effects of immunosuppression and organ transplantation on the natural history and immunopathogenesis of hepatitis C virus infection
Authors: McCaughan G.W. , Zekry A. 
Published: March 2003

Abstract:The hepatitis C virus (HCV) is recognized as the leading cause for parenterally transmitted hepatitis. It is characterized by a high propensity to chronicity. Several efforts have been directed towards understanding the natural history of chronic HCV infection and the immunopathogenic pathways involved in mediating liver injury in the non‐immunosuppressed and immunosuppressed states. In the non‐immunosuppressed setting, liver damage seems to be largely immune mediated. In contrast, in the non‐immunosuppressed state, there are several other factors that may modify the natural course of the infection and play a role in mediating liver injury. In this review we will address the natural history, virological and immunological aspects of HCV infection. Also, the role played by immunosuppression and organ transplantation in modifying the course of the infection and the pathogenesis of liver injury will be discussed.(Note)
High avidity antibodies to fetal pig pancreas endocrine cells transfer rejection but are not normally generated to fetal pig pancreas xenografts
Authors: Fox Annette , Mountford Joanne , Braakhuis Andrea , Harrison Leonard C. 
Published: March 2003

Fox A, Mountford J, Braakhuis A, Harrison LC. High avidity antibodies to fetal pig pancreas endocrine cells transfer rejection but are not normally generated to fetal pig pancreas xenografts. Xenotransplantation 2002; 9: 382–392. © Blackwell Munksgaard, 2002Previous studies on the contribution of T cell‐dependent antibody (Ab) to non‐vascular xenograft rejection have yielded conflicting results, being confounded by the presence of recipient T cells and the use of different tissues and immunizing regimens to generate Ab. In the present study, the effect of adoptive transfer of Ab on fetal pig pancreas (FPP) and pig PK15 cell xenografts was examined in T cell‐deficient severe combined immune deficiency (SCID) mice. T cell‐dependent Abs raised by hyperimmunization with different cell types and by FPP transplantation were compared.Ab raised by hyperimmunization with pig thymocytes exhibited strong binding to pig thymocytes and PK15 cells but did not transfer FPP rejection. IgG1 and IgM, but not IgG3, Abs bound strongly to FPP exocrine and connective tissue, whereas binding to endocrine cells in vitro and in vivo was weak or absent. This pattern of Ab binding was similar to that observed after transplanting FPP into BALB/c mice. Furthermore, serum recovered from BALB/c mice 20 days after FPP transplantation bound strongly to non‐endocrine but not endocrine cells and did not transfer FPP rejection. In contrast, serum from mice hyperimmunized with PK15 cells bound strongly to PK15 cells and transferred rejection of intraperitoneal PK15 cells. Furthermore, this serum contained IgG1 and IgM Abs that bound strongly, and IgG3 Abs that bound weakly, to endocrine cells in FPP, and also transferred rejection of FPP in SCID mice. These results indicate that endocrine cells express low concentrations of xenoreactive Ab epitopes and that high Ab concentrations and/or high avidity Abs are required for sufficient endocrine cell binding to cause damage and rejection in the immunodeficient mouse model. Such Abs are not elicited by transplanting FPP into immunocompetent mice. Nevertheless, a contribution of Ab to rejection in immunocompetent mice cannot be excluded.
Promotion of xenogeneic hematopoietic chimerism in rodents by mononuclear phagocyte depletion
Authors: Cheng J. , Glaser R. M. , Kruger‐Grey H. , White‐Scharf M. E. , Cooper D. K. C. , Thall A. D. 
Published: March 2003

Cheng J, Glaser RM, Kruger‐Grey H, White‐Scharf ME, Cooper DKC, Thall AD. Promotion of xenogeneic hematopoietic chimerism in rodents by mononuclear phagocyte depletion. Xenotransplantation 2002; 9: 402–409. © Blackwell Munksgaard, 2002The successful establishment of tolerance toward pig tissues in primates through hematopoietic progenitor cell engraftment is restricted by the rapid disappearance of these cells in the recipient following infusion. We developed and tested the hypothesis that phagocytes of the reticuloendothelial system are responsible for the rapid clearance of infused pig hematopoietic cells using a mouse model. Mice received non‐myeloablative conditioning and, on various days, were injected with medronate‐encapsulated liposomes (M‐L) or control blank liposomes, followed by the intravenous infusion of miniature swine hematopoietic cells. M‐L were well‐tolerated in mice (n=100) at levels that deplete mononuclear phagocytes. Depletion of mononuclear phagocytes in normal Balb/c mice as well as in severe combined immune deficient mice increased the accumulation of pig hematopoietic cells in the bone marrow (BM) by 10‐fold when measured 24 h after the infusion of the cells. Colony‐forming unit analysis showed an increased accumulation of pig hematopoietic progenitors in the BM of mice that were infused with medronate‐liposomes. We conclude that depletion of mononuclear phagocytes by M‐L has the potential to lower the barrier to the establishment of mixed chimerism and tolerance induction in xenotransplantation.
Regulation of IL‐4 production in mast cells: a paradigm for cell‐type‐specific gene expression
Authors: Weiss Deborah L. , Brown Melissa A. 
Published: March 2003

Summary: The role of interleukin (IL)‐4 as an important immunomodulatory cytokine is well established. IL‐4 exhibits a highly restricted pattern of expression by cells of distinct lineages. The cell types that produce IL‐4 are located in anatomically distinct locations (e.g. circulating T cells vs. fixed tissue mast cells) and thus have access to different IL‐4‐responsive target cells. In addition, these cells appear to regulate IL‐4 expression in cell‐type‐specific ways. These findings suggest that an understanding of IL‐4 gene regulation in T and mast cells could provide the means to specifically control IL‐4 release in a lineage‐ and site‐specific manner. In this article we review the current knowledge regarding the cell‐type specific regulation of IL‐4 gene expression in mast cells and compare this to what has been defined in T cells. We show that there are distinct yet parallel events that control developmentally determined chromatin modifications, allowing accessibility of the locus, and provide the potential for transcription. In differentiated cells, a subset of unique cell activation signals initiates the cascade of events that lead to transcriptional activation of the IL‐4 gene.This work was supported by the National Science Foundation (DLW), the National Institutes of Health and the Multiple Sclerosis Society (MAB). We appreciate the technical and intellectual contributions of many colleagues including Doris Powell, John Hural, Tammy Nachman, Ben Hock, David Tara, Greg Henkel, Susan Lee, Millie Kwan, Melanie Sherman and Ginny Secor.
DNA methylation: an epigenetic pathway to cancer and a promising target for anticancer therapy
Authors: Worm Jesper , Guldberg Per 
Published: March 2003

AbstractThe unique properties of a cancer cell are acquired through a stepwise accumulation of heritable changes in the information content of proto‐oncogenes and tumor suppressor genes. While gain, loss, and mutation of genetic information have long been known to contribute to tumorigenesis, it has been increasingly recognized over the past 5 years that ‘epigenetic’ mechanisms may play an equally important role. The main epigenetic modification of the human genome is methylation of cytosine residues within the context of the CpG dinucleotide. De novo methylation of ‘CpG islands’ in the promoter regions of tumor suppressor genes may lead to transcriptional silencing through a complex process involving histone deacetylation and chromatin condensation, and thus represents a tumorigenic event that is functionally equivalent to genetic changes like mutation and deletion. DNA methylation is interesting from a diagnostic viewpoint because it may be easily detected in DNA released from neoplastic and preneoplastic lesions into serum, urine or sputum, and from a therapeutic viewpoint because epigenetically silenced genes may be reactivated by inhibitors of DNA methylation and/or histone deacetylase. A better understanding of epigenetic mechanisms leading to tumor formation and chemoresistance may eventually improve current cancer treatment regimens and be instructive for a more rational use of anticancer agents.