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At least 253 records · Page 14Linked to original sources
PubMed1999

Potato performance in response to different mulches. 1. Nitrogen metabolism and yield.

This work evaluates the impact that the application of different mulches exerts on nitrogen (N) metabolism in roots and leaves and on yield of potato tubers (Solanum tuberosum var. Spunta). The parameters analyzed in this experiment were root temperature; nitrate reductase and nitrite reductase activities; concentrations of nitrates, ammonium, amino acids, proteins, and organic N; dry weight of roots and leaves; and tuber yield. Use of white polyethylene (T2) and white-black plastic (T3) promoted optimal root temperatures for plant growth (23-27 degrees C). Under these experimental conditions, plants showed the greatest efficiency in N utilization and the greatest yield in tubers. Considering the sensitivity of this plant to thermal stress, high root temperatures caused by black polyethylene (>31 degrees C) (T4) depressed N metabolism as well as yield, compared with the results of T2 and T3. Finally, clear polyethylene plastic (T1) caused more damage than did the absence of mulch (control, T0).

Nitrogen↗
PubMed1997

Self-assembling DNA-lipid particles for gene transfer.

PURPOSE: We have demonstrated that a heteromolecular complex consisting of cationic lipids and DNA can be prepared and isolated (1). Cationic lipids bind DNA through electrostatic interactions. However, when sufficient lipids are bound to DNA the physical and chemical properties of the complex are governed by hydrophobic effects. Here we describe an approach where this hydrophobic complex is used as an intermediate in the preparation of lipid-DNA particles (LDPs). METHODS: The approach relies on the generation of mixed micelles containing the detergent, n-octyl beta-D-glucopyranoside (OGP), the cationic lipid, N-N-dioleoyl-N, N-dimethylammonium chloride (DODAC), and selected zwitterionic lipids, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) or egg sphingomyelin (SM). RESULTS: When these micelles were prepared at low detergent concentrations (20 mM OGP) and combined with pCMV beta DNA, LDPs spontaneously formed. The mean diameter of these particles as measured by quasielastic light scattering was 55-70 nm, a result that was confirmed by negative stain electron microscopy. Further characterization of these LDPs showed that DNA within the particles was inaccessible to the small fluorochrome TO-PRO-1 and protected against DNase I degradation. LDPs could also be prepared in high concentrations of OGP (100 mM), however particles formed only after removal of OGP by dialysis. Particles formed in this manner were large (> 2000 nm) and mediated efficient transfection of Chinese hamster ovary cells. Transfection activity was greater when the lipid composition used consisted of SM/ DODAC. Small particles (< 100 nm) prepared of SM/DODAC were, however, inefficient transfecting agents. CONCLUSIONS: We believe that LDP formation is a consequence of the molecular forces that promote optimal hydrocarbon-hydrocarbon interactions and elimination of the hydrocarbon-water interface.

Animals↗
PubMed1985

Survey of wheelchair athletic injuries: common patterns and prevention.

Twelve hundred wheelchair athletes were surveyed to determine commonly experienced athletic injuries, sports participation and training patterns associated with injuries. Soft tissue trauma, blisters, lacerations, decubiti and joint disorders were the most commonly reported injuries of the 128 respondents. Over 70 per cent of all reported injuries occurred during wheelchair track, road racing and basketball. Common mechanisms of injury were also identified. A significantly higher number of reported injuries were associated with increased sports participation (p less than 001), with the 21-30 year-old age group (p less than .01), and with a high number of training hours per week (p less than .05). There was no significant relationship between number of reported injuries and disability type, National Wheelchair Athletic Association classification, or sex. Decubitus ulcers and temperature regulation disorders were identified as particular risks for the spinal cord injury population. Educating the athlete and coach in means to prevent injury is necessary to promote optimal performance and safe participation.

Adolescent↗
PubMed1999

A phase I study of paclitaxel for mobilization of peripheral blood progenitor cells.

We conducted a phase I trial to determine the dose and schedule of paclitaxel, when given together with filgrastim, which would optimally promote mobilization of stem cells with tolerable toxicity. Dose escalation began at 275 mg/m2 3 h infusion. Dose-limiting neuropathy was observed at the 300 mg/m2 dose level. A second dose escalation was conducted utilizing 24 h infusion schedules, beginning at 225 mg/m2. Dose escalation was continued by 25 mg/m2 increments to 300 mg/m2, at which dose neuropathy was again dose-limiting. The recommended dose and schedule of paclitaxel for the purpose of mobilization of stem cells, when given together with filgrastim, are 275 mg/m2 as a 24 h infusion. The median stem cell yield after this dose of paclitaxel was 6.6 x 10(6) CD34+ cells/kg/apheresis (range 3.6 x 10(6)-7.7 x 10(6)).

Adult↗
PubMed1997

The Evi-1 proto-oncogene encodes a transcriptional repressor activity associated with transformation.

The myeloid transforming gene Evi-1 encodes a protein with two zinc finger domains, designated ZF1 and ZF2, with distinct DNA binding specificities. For the first time we demonstrate that Evi-1 has transcriptional repressor activity which is directly proportional to the amount of Evi-1 protein in cells. Repression has been observed with two distinct promoters: the minimal HSV-1 tk promoter and a VP16 inducible adenovirus E1b minimal promoter. Optimal repression is DNA binding dependent and is mediated by either ZF1 or a heterologous GAL4 DNA binding domain (GAL4DBD) but is significantly less efficient through the ZF2 binding site. Both GAL4DBD/Evi-1 fusion and non-fusion proteins have been used to map the repressor activity to a proline-rich region located within amino acids 514-724 between the ZF1 and ZF2 domains. Constitutive expression of mutant proteins lacking the repressor domain are defective for transformation of Rat1 fibroblasts demonstrating that this region is required for the oncogenic activity of the Evi-1 protein. These studies show that the Evi-1 gene encodes a transcriptional repressor and has important implications for the mechanism of action of the Evi-1 protein both in development and in the progression of some myeloid leukaemias.

3T3 Cells↗
PubMed2002

Selenium deficiency increases the expression of inducible nitric oxide synthase in RAW 264.7 macrophages: role of nuclear factor-kappaB in up-regulation.

The inducible isoform of nitric oxide synthase (iNOS) is implicated in atherosclerosis, malignancy, rheumatoid arthritis, tissue and reperfusion injuries. A key determinant of the pro-oxidant versus protective effects of NO is the underlying redox status of the tissue. Selenoproteins, such as glutathione peroxidases (GPxs) and thioredoxin reductases, are key components of cellular defence and promote optimal antioxidant/oxidant balance. In this study, we have investigated the relationship between Se status, iNOS expression and NO production in Se-deficient and Se-supplemented RAW 264.7 macrophage cell lines. The cellular GPx activity, a measure of Se status, was 17-fold lower in Se-deficient RAW 264.7 cells and the total cellular oxidative tone, as assessed by flow cytometry with 2',7'-dichlorodihydrofluorescein diacetate, was higher in the Se-deficient cells than the Se-supplemented cells. Upon lipopolysaccharide (LPS) stimulation of these cells in culture, we found significantly higher iNOS transcript and protein expression levels with an increase in NO production in Se-deficient RAW 264.7 cells than the Se-supplemented cells. Electrophoretic mobility-shift assays, nuclear factor-kappaB (NF-kappaB)-luciferase reporter assays and Western blot analyses indicate that the increased expression of iNOS in Se deficiency could be due to an increased activation and consequent nuclear localization of the redox-sensitive transcription factor NF-kappaB. These results suggest an inverse relationship between cellular Se status and iNOS expression in LPS-stimulated RAW 264.7 cells and provide evidence for the beneficial effects of dietary Se supplementation in the prevention and/or treatment of oxidative-stress-mediated inflammatory diseases.

Animals↗
PubMed2003

Keratinocyte adherens junctions initiate nuclear signaling by translocation of plakoglobin from the membrane to the nucleus.

Because changes in cell-cell adhesion have profound effects on cellular behavior, we hypothesized a link between the adhesion and signaling functions of plakoglobin and beta-catenin. To investigate the existence of adherens-junction-mediated signaling, we used peroxovanadate to tyrosine phosphorylate plakoglobin and beta-catenin and to dissociate adherens junctions. The distribution of plakoglobin and beta-catenin was determined by immunofluorescence, western blot analysis, pulse-chase radiolabeling, and biochemical subcellular fractionation. Coimmunoprecipitation studies from nuclear fractions, gel-shift assays, and transient transfections with T cell factor (TCF)/lymphoid enhancer factor (LEF) optimized promoter reporter constructs were used to investigate the ability of plakoglobin and beta-catenin that had redistributed from the membrane to the nucleus to form functional transcriptional regulatory complexes with TCF/LEF family member transcription factors. Tyrosine phosphorylation of plakoglobin and beta-catenin resulted in their rapid translocation from the cell membrane to the nucleus. Nuclear translocation was associated with increased plakoglobin and decreased beta-catenin binding to nuclear TCF/LEF and downregulation of gene transcription from TCF/LEF reporter constructs. These results are consistent with a signaling pathway initiated by structural changes in the adherens junction in which adherens-junction-derived plakoglobin regulates nuclear transcription by antagonizing the binding of beta-catenin to TCF/LEF proteins.

Adherens Junctions↗
PubMed1999

Histological comparison of postoperative wound care regimens for laser resurfacing in a porcine model.

BACKGROUND: The use of short-pulsed CO2 lasers for skin resurfacing is routinely performed, but few studies have examined postsurgical care. OBJECTIVE: To determine which postoperative treatments are most beneficial in promoting optimal healing after laser resurfacing. METHODS: Four pigs received laser resurfacing. The laser sites were randomly left untreated or treated with petroleum-based ointment or dressed with 1 of the following occlusive dressings: hydrocolloid, hydrogel or foam. Biopsies were taken from each treatment group on Days 2, 3, 4, 5, 8, 12, and 19. All samples were stained with hematoxylin and eosin. Each histological slide was evaluated by a blinded investigator. RESULTS: Differences were observed between treatment groups in the amount of cellular infiltrate, presence of necrotic tissue, progression of the epidermal sheet, maturation of the epidermis, presence of rete ridges, and appearance of new collagen. CONCLUSION: Postoperative treatments after laser resurfacing vary in their ability to influence the quality of healing.

Animals↗
PubMed2003

Binding studies of the enzyme (factor IXa) with the cofactor (factor VIIIa) in the assembly of factor-X activating complex on the activated platelet surface.

Activated platelet membranes expose binding sites for the enzyme factor (F)IXa, the substrate (FX) and the cofactor (FVIIIa) that colocalize to assemble the FX-activating complex and promote optimal rates of FX activation. To determine the stoichiometry and affinity of binding to activated platelets, coordinate, equilibrium binding studies with enzyme (125I-FIXa) and cofactor (131I-FVIII or 131I-FVIIIa) were carried out in the presence of saturating concentrations of substrate (FX). Results of these studies indicate that in the presence of FX (1.5 micro m), the enzyme (active-site-inhibited Glu-Gly-Arg-FIXa, EGR-FIXa) and procofactor (FVIII) bind to an equal number (approximately 700 sites/platelet) of receptors whereas the active cofactor (FVIIIa) binds an additional approximately 500 high-affinity FVIIIa binding sites per platelet (Kd approximately 0.8 nm). With excess zymogen (FIX) to block shared FIX/FIXa-binding sites, the stoichiometry of 125I-FIXa and 131I-FVIIIa binding was 1:4. These FIXa/FVIIIa binding studies together with previously reported evidence of the coordinate binding of FVIIIa and FX to equivalent numbers of binding sites on activated platelets provide strong evidence to support the conclusion that FVIIIa comprises the receptor that presents FX to FIXa for efficient catalysis on the activated platelet membrane.

Autoradiography↗
PubMed2001

Cerebral venous thrombosis in young adults: 2 Case reports.

Cerebral venous thrombosis (CVT) is a disease with multiple known etiologies that present with a remarkably wide spectrum of clinical signs and symptoms. We present a case of a 34-year-old man with a history of meningeal symptoms for 1 week after receiving a lumbar injection for lower back pain. He subsequently developed dense right hemiplegia and global aphasia. Head magnetic resonance imaging revealed superior sagittal sinus thrombosis. The patient was started on intravenous heparin but deteriorated neurologically. Urokinase infusion directly into the superior sagittal sinus was performed, with striking functional and neurologic improvement. Lupus anticoagulant was positive. We also present the case of a 24-year-old pregnant woman who developed an acute onset of meningeal symptoms and resultant left hemiparesis. Head magnetic resonance angiography revealed thrombosis of right transverse and sigmoid sinuses. Protein S deficiency was found. She was started on intravenous heparin, then enoxaparin, with improvement in symptoms. These cases demonstrate that CVT can be a cause of stroke in young patients with hypercoagability disorders, and a heightened awareness of CVT will promote optimal medical care and functional outcomes. Excellent functional recovery is likely with early recognition and treatment of the underlying etiology, as well as successful lysis of the clot.

Adult↗
PubMed2000

Vitamin D therapy in patients with chronic renal disease: the role of the renal dietitian.

Chronic renal failure causes decreased vitamin D production, which profoundly alters parathyroid hormone (PTH) metabolism, and calcium and phosphorus balance. Correcting this deficiency is an important strategy in managing secondary hyperparathyroidism (SHPT) and helping to restore mineral balance. However, hypercalcemia and hyperphosphatemia are common side effects that hamper vitamin D hormone therapy by increasing dietary calcium and phosphorus absorption. This limitation has led to the development of D-hormone analogs that retain the ability to suppress PTH levels without causing drastic changes in calcium and phosphorus metabolism. These analogs have the potential to advance the management of SHPT. Renal dietitians can play a leading role in ensuring successful management of SHPT by participating in early patient intervention for abnormal mineral and vitamin D metabolism, by encouraging long-term phosphorus control, and by updating and implementing clinical protocols that promote optimal hormone levels (D and PTH), mineral levels (phosphorus and calcium), and nutritional factors.

Dietetics↗
PubMed2002

Obesity and the risk of heart failure.

BACKGROUND: Extreme obesity is recognized to be a risk factor for heart failure. It is unclear whether overweight and lesser degrees of obesity also pose a risk. METHODS: We investigated the relation between the body-mass index (the weight in kilograms divided by the square of the height in meters) and the incidence of heart failure among 5881 participants in the Framingham Heart Study (mean age, 55 years; 54 percent women). With the use of Cox proportional-hazards models, the body-mass index was evaluated both as a continuous variable and as a categorical variable (normal, 18.5 to 24.9; overweight, 25.0 to 29.9; and obese, 30.0 or more). RESULTS: During follow-up (mean, 14 years), heart failure developed in 496 subjects (258 women and 238 men). After adjustment for established risk factors, there was an increase in the risk of heart failure of 5 percent for men and 7 percent for women for each increment of 1 in body-mass index. As compared with subjects with a normal body-mass index, obese subjects had a doubling of the risk of heart failure. For women, the hazard ratio was 2.12 (95 percent confidence interval, 1.51 to 2.97); for men, the hazard ratio was 1.90 (95 percent confidence interval, 1.30 to 2.79). A graded increase in the risk of heart failure was observed across categories of body-mass index. The hazard ratios per increase in category were 1.46 in women (95 percent confidence interval, 1.23 to 1.72) and 1.37 in men (95 percent confidence interval, 1.13 to 1.67). CONCLUSIONS: In our large, community-based sample, increased body-mass index was associated with an increased risk of heart failure. Given the high prevalence of obesity in the United States, strategies to promote optimal body weight may reduce the population burden of heart failure.

Body Mass Index↗
PubMed2003

The transition from paediatric to adult health care services for young adults with a disability: an ethical perspective.

Young children with disabilities and their carers or parents tend to form a long-term dependent relationship with a paediatrician throughout childhood. At some stage when the young person with a disability reaches early adulthood, the relationship is severed. This paper draws upon recent research undertaken by the authors that describes the difficulties experienced by young people with disabilities as they go through the transition from paediatric care to adult mainstream health care services. The purpose of this article is to present the argument that the dependent, paternalistic relationship that tends to exist between young people with disabilities (and/or their carers) and paediatricians throughout childhood does not facilitate the successful negotiation of adult mainstream health care services, nor optimally promote the well-being of these young people with disabilities. It is proposed that the promotion of autonomy (or self-determination) via a well planned transition program will increase the likelihood that young adults with disabilities and/or their carers will be empowered to successfully negotiate the current mainstream health care system in Australia, and will enhance the well-being of young adults with disabilities.

Adolescent↗
PubMed2006

Signals from OX40 regulate nuclear factor of activated T cells c1 and T cell helper 2 lineage commitment.

T cell helper type 2 (Th2) differentiation is driven by a source of IL-4 receptor (IL-4R) that mobilizes IL-4R signaling pathways and the transcription factor GATA-3. Naïve CD4 cells can secrete IL-4 independently of IL-4R signals, but how this secretion is regulated is not understood. Here we demonstrate that costimulation through the tumor necrosis factor receptor family molecule OX40, in synergy with CD28, is essential for high levels of nuclear factor of activated T cells c1 to accumulate in the nucleus of a recently activated naïve T cell. This action is not dependent on either IL-4R or IL-2R signals and results in OX40 controlling initial naïve T cell IL-4 transcription. OX40 signals subsequently enhance nuclear GATA-3 accumulation through an IL-4R-dependent action, leading to Th2 differentiation. These data show that, in the absence of an exogenous source of IL-4, OX40 provides a critical synergistic and temporal signal with other noncytokine receptors to modulate nuclear factor of activated T cells c1 and to promote optimal Th2 generation.

Active Transport, Cell Nucleus↗
PubMed2003

Differential regulation of midbrain dopaminergic neuron development by Wnt-1, Wnt-3a, and Wnt-5a.

The Wnts are a family of glycoproteins that regulate cell proliferation, fate decisions, and differentiation. In our study, we examined the contribution of Wnts to the development of ventral midbrain (VM) dopaminergic (DA) neurons. Our results show that beta-catenin is expressed in DA precursor cells and that beta-catenin signaling takes place in these cells, as assessed in TOPGAL [Tcf optimal-promoter beta-galactosidase] reporter mice. We also found that Wnt-1, -3a, and -5a expression is differentially regulated during development and that partially purified Wnts distinctively regulate VM development. Wnt-3a promoted the proliferation of precursor cells expressing the orphan nuclear receptor-related factor 1 (Nurr1) but did not increase the number of tyrosine hydroxylase-positive neurons. Instead, Wnt-1 and -5a increased the number of rat midbrain DA neurons in rat embryonic day 14.5 precursor cultures by two distinct mechanisms. Wnt-1 predominantly increased the proliferation of Nurr1+ precursors, up-regulated cyclins D1 and D3, and down-regulated p27 and p57 mRNAs. In contrast, Wnt-5a primarily increased the proportion of Nurr1+ precursors that acquired a neuronal DA phenotype and up-regulated the expression of Ptx3 and c-ret mRNA. Moreover, the soluble cysteine-rich domain of Frizzled-8 (a Wnt inhibitor) blocked endogenous Wnts and the effects of Wnt-1 and -5a on proliferation and the acquisition of a DA phenotype in precursor cultures. These findings indicate that Wnts are key regulators of proliferation and differentiation of DA precursors during VM neurogenesis and that different Wnts have specific and unique activity profiles.

Animals↗
PubMed2002

A novel set of Wnt-Frizzled fusion proteins identifies receptor components that activate beta -catenin-dependent signaling.

Wnt proteins initiate the canonical (beta-catenin-regulated) signaling cascade by binding to seven-transmembrane spanning receptors of the Frizzled (Fz) family together with the coreceptors LRP5 and -6, members of the low density lipoprotein receptor-related protein family (LRP). Several reports have shown physical and functional associations between various Wnt, LRP, and Frizzled molecules; however, the underlying mechanisms for selectivity remain poorly understood. We present data on a novel set of Wnt-Fz fusion constructs that are useful for elucidating mechanisms of Wnt signal transduction specificity in both Xenopus embryos and 293T cells. In 293T cells, coexpression of several Wnt-Fz fusion proteins with LRP6, but not LRP5, significantly activated a Wnt-responsive promoter, Optimized TOPFlash. Interestingly, Wnt proteins from both the Wnt1 and Wnt5A classes, when fused to the same Frizzled, can synergize with LRP6 to activate signaling and induce secondary axes in Xenopus embryos. However, when several Wnt-Fz constructs containing different Frizzled molecules were tested, it was found that all Frizzled molecules are not equivalent in their ability to activate the canonical Wnt pathway in this context. The data suggest that the distinction between the two Wnt classes lies not in intrinsic differences in the molecules but via the Frizzled molecules with which they interact.

Animals↗
PubMed2005

Nuclear localization and mitogen-activated protein kinase phosphorylation of the multifunctional protein CAD.

CAD is a multifunctional protein that initiates and regulates mammalian de novo pyrimidine biosynthesis. The activation of the pathway required for cell proliferation is a consequence of the phosphorylation of CAD Thr-456 by mitogen-activated protein (MAP) kinase. Although most of the CAD in the cell was cytosolic, cell fractionation and fluorescence microscopy showed that Thr(P)-456 CAD was primarily localized within the nucleus in association with insoluble nuclear substructures, including the nuclear matrix. CAD in resting cells was cytosolic and unphosphorylated. Upon epidermal growth factor stimulation, CAD moved to the nucleus, and Thr-456 was found to be phosphorylated. Mutation of the CAD Thr-456 and inhibitor studies showed that nuclear import is not mediated by MAP kinase phosphorylation. Two fluorescent CAD constructs, NLS-CAD and NES-CAD, were prepared that incorporated strong nuclear import and export signals, respectively. NLS-CAD was exclusively nuclear and extensively phosphorylated. In contrast, NES-CAD was confined to the cytoplasm, and Thr-456 remained unphosphorylated. Although alternative explanations can be envisioned, it is likely that phosphorylation occurs within the nucleus where much of the activated MAP kinase is localized. Trapping CAD in the nucleus had a minimal effect on pyrimidine metabolism. In contrast, when CAD was excluded from the nucleus, the rate of pyrimidine biosynthesis, the nucleotide pools, and the growth rate were reduced by 21, 36, and 60%, respectively. Thus, the nuclear import of CAD appears to promote optimal cell growth. UMP synthase, the bifunctional protein that catalyzes the last two steps in the pathway, was also found in both the cytoplasm and nucleus.

Active Transport, Cell Nucleus↗
PubMed1985

Preparing the medically compromised patient for surgery.

Preparing the medically compromised patient for surgery requires identifying and treating preoperative risk factors and anticipating postoperative complications. Preoperative evaluation of all patients should include careful screening for bleeding disorders and prior anesthetic complications and assessment of nutritional status. In addition, patients with preexisting cardiac, pulmonary, and endocrine problems must be identified, since these problems represent the greatest risk factors for postoperative complications. Perioperative care is more effective when directed at specific organ systems. Communication among internists, anesthesiologists, and surgeons promotes optimal treatment for surgical patients with medical illness.

Cardiovascular Diseases↗