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PubMed1998

Developing scholarship in athletic training.

OBJECTIVE: To outline the essential elements of scholarship, identify its role in the development of the athletic training profession, and encourage athletic trainers to increase scholarly activities. BACKGROUND: In the process of writing 2 manuscripts for the Journal of Athletic Training about how to write journal manuscripts, we felt something needed to be said concerning why one should write such manuscripts and how individual manuscripts should tie together to advance knowledge. This led us to search the scientific literature for information concerning scholarship and its attainment. Finding no comprehensive discussion on the topic, we then began to investigate components of scholarship and activities that lead to its attainment. DESCRIPTION: Scholarship, knowledge, truth, and theory are defined. The attributes or characteristics of a scholar delineated and discussed include seeking to establish truth and develop new knowledge, developing and refining theory, being focused in one's work, being honest about one's work, communicating ideas and stirring thinking, being open minded, and recognizing the difference between scholarship and pseudoscholarship. It is important to promote scholarship among undergraduate and graduate students; numerous suggestions are outlined. APPLICATION: Scholarship is essential to our survival as a profession. The guidelines presented here will help individuals examine and improve their scholarship.

Journal Article↗

PubMed2004

The human paracellin-1 gene (hPCLN-1): renal epithelial cell-specific expression and regulation.

Tubular reabsorption of Mg2+ is mediated by the tight junction protein paracellin-1, which is encoded by the gene PCLN-1 (CLDN16) and exclusively expressed in the kidney. Tubular Mg2+ reclamation is modulated by many hormones and factors. The aim of this study was to define regulatory elements essential for renal tubular cell-specific expression of human PCLN-1 (hPCLN-1) and to explore the effect of Mg2+ transport modulators on the paracellin-1 gene promoter. Endogenous paracellin-1 mRNA and protein were detected in renal cell lines opossom kidney (OK), HEK293, and MDCT, but not in the fibroblast cell line NIH3T3. A 7.5-kb hPCLN-1 5'-flanking DNA sequence along with seven 5'-deletion products were cloned into luciferase reporter vectors and transiently transfected into the renal and nonrenal cells. The highest levels of luciferase activity resulted from transfection of a 5'-flanking 2.5-kb fragment (pJ2M). This activity was maximal in OK cells, was orientation dependent, and was absent in NIH3T3 cells. Mg2+ deprivation significantly increased pJ2M-driven activity in transfected OK cells, whereas Mg2+ load decreased it compared with conditions of normal Mg2+. Deletion analysis along with electrophoretic mobility-shift assay demonstrated that OK cells contain nuclear proteins, which bind a 70-bp region between -1633 and -1703 of major functional significance. Deleting this 70-bp segment, which contains a single peroxisome proliferator-response element (PPRE), or mutating the PPRE, caused a 60% reduction in luciferase activity. Stimulating the 70-bp sequence with 1,25(OH)2 vitamin D decreased luciferase activity by 52%. This effect of 1,25(OH)2 vitamin D was abolished in the absence of PPRE or in the presence of mutated PPRE. We conclude that the PPRE within this 70-bp DNA region may play a key role in the cell-specific and regulatory activity of the hPCLN-1 promoter. Ambient Mg2+ concentration and 1,25(OH)2 vitamin D may modulate paracellular, paracellin-1-mediated, Mg2+ transport at the transcriptional level. 1,25(OH)2 vitamin D exerts its activity on the hPCLN-1 promoter likely via the PPRE site.

5' Flanking Region↗

PubMed2000

Molecular aspects of multiple myeloma.

Multiple myeloma (MM) is a B-cell neoplasm characterized by bone marrow infiltration with malignant plasma cells, which synthesize and secrete monoclonal immunoglobulin (Ig) fragments. Despite the considerable progress in the understanding of MM biology, the molecular basis of the disease remains elusive. The initial transformation is thought to occur in a postgerminal center B-lineage cell, carrying a somatically hypermutated Ig heavy chain (IGH) gene. This plasmablastic precursor cell colonizes the bone marrow, propagates clonally and differentiates into a slowly proliferating myeloma cell population, all under the influence of specific cell adhesion molecules and cytokines. Production of interleukin-6 by stromal cells, osteoblasts and, in some cases, neoplastic cells is an essential element of myeloma cell growth, with the cytokine stimulus being delivered intracellularly via the Jack-STAT and ras signaling pathways. While karyotypic changes have been identified in up to 50% of MM patients, recent molecular cytogenetic techniques have revealed chromosomal abnormalities in the vast majority of examined cases. Translocations mostly involve illegal switch rearrangements of the IGH locus with various partner genes (CCND1, FGFR3, c-maf). Such events have been assigned a critical role in MM development. Mutations in coding and regulatory regions, as well as aberrant expression patterns of several oncogenes (c-myc, ras) and tumor suppressor genes (p16, p15) have been reported. Key regulators of programmed cell death (BCL-2, Fas), tumor expansion (metalloproteinases) and drug responsiveness (topoisomerase II alpha) have also been implicated in the pathogenesis of this hematologic malignancy. A tumorigenic role for human herpesvirus 8 (HHV8) was postulated recently, following the detection of viral sequences in bone marrow dendritic cells of MM patients. However, since several research groups were unable to confirm this observation, the role of HHV8 remains unclear. Translation of the advances in MM molecular biology into novel therapeutic strategies is essential in order to improve disease prognosis.

Apoptosis↗

PubMed2005

Development of the Diabetes Indicators and Data Sources Internet Tool (DIDIT).

Developing a Web-based tool that involves the input, buy-in, and collaboration of multiple stakeholders and contractors is a complex process. Several elements facilitated the development of the Web-based Diabetes Indicators and Data Sources Internet Tool (DIDIT). The DIDIT is designed to enhance the ability of staff within the state-based Diabetes Prevention and Control Programs (DPCPs) and the Centers for Disease Control and Prevention (CDC) to perform diabetes surveillance. It contains information on 38 diabetes indicators (measures of health or factors associated with health) and 12 national- and state-level data sources. Developing the DIDIT required one contractor to conduct research on content for diabetes indicators and data sources and another contractor to develop the Web-based application to house and manage the information. During 3 years, a work group composed of representatives from the DPCPs and the Division of Diabetes Translation (DDT) at the CDC guided the development process by 1) gathering information on and communicating the needs of users and their vision for the DIDIT, 2) reviewing and approving content, and 3) providing input into the design and system functions. Strong leadership and vision of the project lead, clear communication and collaboration among all team members, and a commitment from the management of the DDT were essential elements in developing and implementing the DIDIT. Expertise in diabetes surveillance and software development, enthusiasm, and dedication were also instrumental in developing the DIDIT.

Diabetes Mellitus, Type 2↗

PubMed2002

Essential role of ferritin Pfr in Helicobacter pylori iron metabolism and gastric colonization.

The reactivity of the essential element iron necessitates a concerted expression of ferritins, which mediate iron storage in a nonreactive state. Here we have further established the role of the Helicobacter pylori ferritin Pfr in iron metabolism and gastric colonization. Iron stored in Pfr enabled H. pylori to multiply under severe iron starvation and protected the bacteria from acid-amplified iron toxicity, as inactivation of the pfr gene restricted growth of H. pylori under these conditions. The lowered total iron content in the pfr mutant, which is probably caused by decreased iron uptake rates, was also reflected by an increased resistance to superoxide stress. Iron induction of Pfr synthesis was clearly diminished in an H. pylori feoB mutant, which lacked high-affinity ferrous iron transport, confirming that Pfr expression is mediated by changes in the cytoplasmic iron pool and not by extracellular iron. This is well in agreement with the recent discovery that iron induces Pfr synthesis by abolishing Fur-mediated repression of pfr transcription, which was further confirmed here by the observation that iron inhibited the in vitro binding of recombinant H. pylori Fur to the pfr promoter region. The functions of H. pylori Pfr in iron metabolism are essential for survival in the gastric mucosa, as the pfr mutant was unable to colonize in a Mongolian gerbil-based animal model. In summary, the pfr phenotypes observed give new insights into prokaryotic ferritin functions and indicate that iron storage and homeostasis are of extraordinary importance for H. pylori to survive in its hostile natural environment.

Animals↗

PubMed1989

Biochemical properties of metallothionein isoforms from bovine hippocampus.

The mammalian hippocampi not only contain high concentrations of zinc, but also exhibit regional variation in this essential element, with concentrations being highest in the hilar region and lowest in the fimbria. For example, the concentration of zinc in the mossy fiber axons has been estimated to approach 300-350 microM. Since "free" zinc is an extremely neurotoxic substance with an inherent ability to inhibit an extensive number of sulfhydryl-containing enzymes and receptor sites, we hypothesized that low-molecular weight zinc binding protein may exist in the hippocampus in order to regulate the steady-state concentration of zinc. In an attempt to investigate this hypothesis and the dynamic metabolism of zinc, we have searched for and have identified a metallothionein-like protein in bovine hippocampus which exhibits an elution volume (Ve/Vo) of 2.0 on gel filtration chromatography and which produces two isoforms, which on a reverse phase high performance liquid chromatography, show retention times of 15.70 min and of 16.37 min, respectively. The hippocampal metallothionein isoform II contains a cysteine to zinc ratio of 2.8 to 1.0, has an apparent molecular weight of 9,500 daltons and, as judged by studies involving UV spectral analysis, lacks aromatic amino acids, but possesses metallomercaptide bonds. The results of these studies suggest that the metallothionein may play an essential role in regulating the transport and/or accumulation of zinc in the hippocampus.

Animals↗

PubMed2002

Waste management options in southern Europe using field and experimental data.

The applicability of the Waste Management Hierarchy concept that appeared to be an essential element in current national environmental policies was investigated in the case of a region in Southern Europe. The waste generation profile that determines the appropriateness of different waste management options was created after a 1-year municipal waste sampling investigation conducted in the Municipality of Pilea in Northern Greece. The paper describes the results of (1) the sampling method, which was conducted four times during 1 year (once per season) in selected areas of the city, (2) the qualitative analysis of the collected samples and (3) the waste treatment, which consisted of drying, grinding, calorific value measurement, incineration and chemical analysis of the collected samples. Comparative analysis between the above mentioned data and on past data derived from investigations conducted in other Greek regions with similar characteristics to those of Pilea were used to identify and discuss future trends in the composition of generated waste over time. An analysis of the current waste management status in Greece as well as the feasibility of implementing a comprehensive management approach is assessed taking into account guidelines set worldwide to promote renewable energy sources use. It is concluded that recycling, perhaps the most positively received of all waste management practices, is going to be an essential part of contemporary waste management strategies, composting can play an important role, while incineration seems to be a conditionally feasible solution.

Conservation of Natural Resources↗

PubMed1986

IgE antibody and resistance to infection. II. Effect of IgE suppression on the early and late skin reaction and resistance of rats to Schistosoma mansoni infection.

Most helminth parasites induce a strong IgE antibody and elevated eosinophil response in their mammalian hosts and a number of in vitro studies have suggested that IgE, possibly in association with eosinophils, may be an essential element of the host protective immunity against helminth infections. To assess the role of IgE in protective immunity, we examined the effect of suppressing the IgE antibody response on rat immunity to Schistosoma mansoni. Suppression was achieved in neonates by injections of rabbit anti-epsilon chain gamma-globulins, control rats received injections of unspecific gamma-globulins. IgE suppression caused a marked reduction of the inflammatory reaction that developed in the skin of immune rats at the site of a cercarial challenge: the early (30 to 60 min) wheal and flare reaction was abolished, and the late cutaneous reaction (6 to 18 h) associated with intense pruritus, edema and local eosinophilia was greatly reduced. This shows that IgE was critical to the recruitment of effector cells and molecules in the skin during the first 24 h following parasite invasion. Worms were recovered 18 to 30 days after a primary infection and 18 days after a challenge infection from IgE-suppressed and control rats. IgE-suppressed rats cured a first infection as rapidly as the control rats; however, they were two to three times less efficient than the controls at eliminating a second or a third challenge. These observations demonstrate that IgE antibodies are essential for the full development of rat acquired protective immunity against Schistosoma mansoni.

Animals↗

PubMed2002

[Internal fixation of proximal humerus fracture by "palm tree" pinning].

PURPOSE OF THE STUDY: Fractures of the proximal humerus are increasingly frequent. Conservative treatment is most often proposed, but surgery must be performed when the displacement is significant and/or when the fracture is unstable. Osteoporosois and comminution are two essential elements for deciding on the surgical technique. MATERIAL AND METHODS: This retrospective study included 31 patients who underwent pinning from the deltoid V according to the Kapandji procedure. There were 19 females and 12 males. Mean age was 61 years. There was a fracture of one of the tuberosities in 12 cases and significant metaphyseal comminution in 8. RESULTS: Mean follow-up was 26 months. Outcome was excellent or good in 22 cases (70.9%), fair in 4 (12.9%), and poor in 5 (16.2%). Fifteen complications were noted (48.4%): material displacement 8 cases, reflex sympathic dystrophy 3 cases, radial nerve palsy 2 cases, head osteonecrosis 1 case, and humeral fracture at the site of insertion of the K wires 1 case. DISCUSSION: At the present time, there is no consensus for the surgical management of fractures of the proximal humerus, including proximal metaphyseal fracture with or without fracture of one of the tuberosities. Closed reduction and pinning is not really an invasive procedure, and does not injure the rotator cuff. Surgical approach at the level of the deltoid V according to the Kapandji technique avoids elbow pain and stiffness. The procedure requires a fluoroscan and experience to obtain satisfactory divergence of the K wires in the humeral head, an essential technical point. This procedure cannot be recommended for elderly patients whose bone quality is too poor to obtain good fixation of the K wires.

Adolescent↗

PubMed2000

Mesenchymal cells expressing bone morphogenetic protein receptors are present in the rheumatoid arthritis joint.

OBJECTIVE: To evaluate the presence of cells of an early mesenchymal lineage, as judged by the expression of bone morphogenetic protein receptors (BMPRs), in the joints of normal individuals and patients with rheumatoid arthritis (RA). METHODS: Synovial fluids, single cell suspensions of cultured fibroblast-like synoviocytes (FLS), and synovial tissues were examined by immunohistology with antibodies to BMPR type IA (BMPRIA), BMPRIB, and BMPRII and then quantified using computerized image analysis. Other antibodies were evaluated by cytofluorography. RESULTS: In primary cultures of joint effusions from patients with RA and other forms of inflammatory arthritis, there were large adherent cells with the appearance of either fibroblasts or stromal cells that stained with antibodies to mesenchymal elements-CD44, type I collagen, alpha-actin, and vimentin-but not with antibodies to hematopoietic markers. These cells proliferated rapidly, expressed BMPRIA and BMPRII, and soon became the predominant cells in culture. They were retained through multiple passages and persistently displayed surface vascular cell adhesion molecule 1. Immunohistochemical analysis of cultured RA FLS (passages 3, 4, and 6; n = 6) revealed that 11.6% were BMPR-positive, while only 2.0% of osteoarthritis FLS (passage 4; n = 3) were BMPR-positive, and 1 normal synovial culture had no BMPR-positive cells. In all RA synovial membranes examined (n = 9), BMPRI- and BMPRII-expressing cells were identified in the intimal lining and were also scattered in the subintima. These cells constituted approximately 25% and approximately 7% of the cells in each area, respectively. Double immunostaining showed no coexpression of BMPR-positive cells with CD68, CD34, or CD3. Cells expressing BMPR were not seen in any normal synovial samples (n = 4). Strong staining for BMPR was identified on cells at the invasive front of the pannus and at sites of cartilage erosion. CONCLUSION: The inflamed RA joint contains BMPR-positive mesenchymal cells. Their origin is still speculative, but since their counterparts in the bone marrow are essential for osteoclastogenesis, support lymphocyte development and maturation, and protect T cells and B cells from programmed cell death, the BMPR-positive cells may be essential elements in the pathogenesis of RA and other inflammatory forms of chronic synovitis.

Arthritis, Rheumatoid↗

PubMed2006

Effects of Cd2+ on K+, Ca2+ and N uptake in two halophytes Sesuvium portulacastrum and Mesembryanthemum crystallinum: consequences on growth.

One of the limits of Cd2+-phytoextraction is the high toxicity of this metal to plants. Growth restriction, chlorosis and necrosis are usually accompanied with a large disturbance of the uptake of essential elements. This work aims to study the effects of cadmium (Cd2+) on potassium (K+), calcium (Ca2+) and nitrogen (N) acquisition, and their consequences on growth in two halophytes species: Sesuvium portulacastrum and Mesembryanthemum crystallinum. Seedlings were grown for 30 days in split-root conditions. One half of the root system was immersed in complete nutrient solution (Basal medium (B)) supplemented with 100 microM Cd2+, and the other half was immersed in a Cd2+-free medium, containing all nutrients (B/Cd plants) or deprived of potassium ((B-K)/Cd) or calcium ((B-Ca)/Cd) or nitrogen ((B-N)/Cd). Using this approach, we demonstrated that K+ and Ca2+ uptake was impaired in roots exposed to Cd2+. Concerning N, we noticed no indication of uptake inhibition by Cd2+. However, restriction of K+ uptake by roots was compensated by an increase in the K+-use efficiency, so that growth was not inhibited. Calcium uptake was strongly limited by Cd2. This inhibition was accompanied by a reduction in growth of ((B-Ca)/Cd) plants. Thus, we conclude that Cd2+ limits growth of both halophytes through restriction imposed on Ca2+ uptake. We suggest that the increase of Ca2+ availability in soils could improve the growth of both species in the presence of Cd2+. This would be essential for improving their utility for extraction of this metal by from salty contaminated soils.

Aizoaceae↗

PubMed2005

A single PDZ domain protein interacts with the Menkes copper ATPase, ATP7A. A new protein implicated in copper homeostasis.

The homeostatic regulation of essential elements such as copper requires many proteins whose activities are often mediated and tightly coordinated through protein-protein interactions. This regulation ensures that cells receive enough copper without intracellular concentrations reaching toxic levels. To date, only a small number of proteins implicated in copper homeostasis have been identified, and little is known of the protein-protein interactions required for this process. To identify other proteins important for copper homeostasis, while also elucidating the protein-protein interactions that are integral to the process, we have utilized a known copper protein, the copper ATPase ATP7A, as a bait in a yeast two-hybrid screen of a human cDNA library to search for interacting partners. One of the ATP7A-interacting proteins identified is a novel protein with a single PDZ domain. This protein was recently identified to interact with the plasma membrane calcium ATPase b-splice variants. We propose a change in name for this protein from PISP (plasma membrane calcium ATPase-interacting single-PDZ protein) to AIPP1 (ATPase-interacting PDZ protein) and suggest that it represents the protein that interacts with the class I PDZ binding motif identified at the ATP7A C terminus. The interaction in mammalian cells was confirmed and an additional splice variant of AIPP1 was identified. This study represents an essential step forward in identifying the proteins and elucidating the network of protein-protein interactions involved in maintaining copper homeostasis and validates the use of the yeast two-hybrid approach for this purpose.

Adenosine Triphosphatases↗

PubMed2001

A method for in vitro determination of calcium, iron and zinc availability from first-age infant formula and human milk.

A method for in vitro determination of available calcium, iron and zinc content from infant food after digestion was evaluated. This method introduced an intraluminal digestive phase, adapted to the gastrointestinal conditions of infants younger than 6 months of age, prior to continuous flow dialysis of the resultant gastric digest. Precautions handling the method were discussed and enzymatic parameters were defined. Ruggedness of the method was determined from the availability of calcium, iron and zinc at different gastrointestinal conditions. Availability of all three elements was higher at gastric pH of 2 (20.0 +/- 1.1% for calcium, 4.06 +/- 0.66% for iron and 17.5 +/- 1.3% for zinc), than from the normal procedure (pH 4) (15.6 +/- 1.2% for calcium, 1.18 +/- 0.26% for iron and 8.2 +/- 0.9% for zinc). At pH 5, however, calcium availability appeared to be lower (11.7 +/- 1.0%) (P < 0.05). The intestinal pH also had a major influence on the availability. At low intestinal pH (5.5), availability was 40.5 +/- 2.3% for calcium, 3.01 +/- 0.58% for iron and 26.8 +/- 1.8% for zinc, which was higher compared with the normal procedure (P < 0.05). Moreover, other factors, such as digestion time, mixing and filtration pressure, also affected the availability. Recovery tests yielded mean values of 94 +/- 3% for calcium, 109 +/- 9% for iron and 106 +/- 4% for zinc. Mean intra- and inter-batch precision of the availability procedure was 4.1 CV% and 6.6 CV% for calcium, 14.5 CV% and 19.2 CV% for iron, and 4.0 CV% and 13.6 CV% for zinc. The method provides adequate accuracy, acceptable precision and good recovery. It offers the advantage of being simple, rapid and inexpensive, since it takes only 1 day to run the whole availability procedure (including four replicates per sample), and the low costs of the dialysis equipment. It can therefore be considered as suitable for predicting the availability of essential elements from foods used during the first months of infancy.

Analysis of Variance↗

PubMed1997

Loss of endothelial barrier function requires neutrophil adhesion.

BACKGROUND: The inflammatory response is characterized by cytokine-induced up-regulation of endothelial adhesion molecules followed by polymorphonuclear neutrophil (PMN) adhesion and breakdown of tight junctions between cells. The purpose of this investigation was to determine whether PMN adhesion is an essential element in the alteration of endothelial permeability or whether cytokines alone can produce this change. METHODS: Human umbilical vein endothelial cells (HUVECs) were exposed to formylated met-leu-phe-activated PMNs. In a second series of experiments, PMNs were contained in a microporous membrane that allowed passage of secreted cytokines but not cells. Permeability was quantified by using transendothelial electrical resistance (TEER, ohm.cm2,) whereas expressions of two cell adhesion molecules (endothelial leukocyte adhesion molecule-1 [ELAM-1] and intercellular adhesion molecule-1 [ICAM-1]) were measured by flow cytometry (% shift). Cytokine production was monitored with enzyme-linked immunosorbant assays (picograms per milliliter). RESULTS: Stimulated PMNs secreted comparable amounts of cytokines whether allowed access to HUVECs or trapped in a microporous membrane (interleukin-1 alpha, 5.88 +/- 2.38 versus 3.65 +/- 1.84 pg/ml; tumor necrosis factor-alpha, 10.27 +/- 3.21 versus 6.61 +/- 1.82 pg/ml). Up-regulation of ELAM-1 and ICAM-1 was observed whether PMNs were free or restricted (52.97% +/- 2.14% versus 75.32% +/- 4.19% and 71.66% +/- 7.37% versus 73.66% +/- 4.32%, respectively). TEER was unchanged in controls and when PMNs were membrane restricted. In contrast, TEER decreased precipitously (51% +/- 5.9% of control, p < 0.05) if PMNs were allowed access to HUVECs. CONCLUSIONS: Cytokine secretion by PMNs is independent of endothelial contact and is sufficient to upregulate adhesion molecules. However, PMN adhesion is essential for the loss of endothelial barrier function, which leads to diapedesis of activated PMNs and eventual tissue injury.

Cell Adhesion↗

PubMed1991

Mononuclear cell adherence induces neutrophil chemotactic factor/interleukin-8 gene expression.

The accumulation of polymorphonuclear cells (PMN) in tissue is an essential element of the inflammatory response that is important in host defense. Adherence to endothelium constitutes the first step in PMN migration from the vascular compartment to the interstitium. We demonstrate that human peripheral blood mononuclear cells (PBMC) adherent to plastic can result in expression of interleukin-8 (IL-8), a potent PMN chemoattractant and activating cytokine. Northern blot analyses showed PBMC adherent to plastic expressed IL-8 steady-state mRNA levels by 30 min, peaked at 8 h, and then decreased over the next 16 h. In contrast, nonadherent PBMC (cultured in teflon chambers) expressed less than 25% of the maximal IL-8 steady-state mRNA levels as compared with adherent PBMC. Adherent PBMC-associated IL-8 determined by immunochemistry, supernatant chemotactic bioactivity, and extracellular antigenic IL-8 paralleled IL-8 mRNA expression. Antigenic and bioactive IL-8 were significantly apparent by 4-8 h, respectively, and increased significantly to maximal levels by 24 h. Furthermore, adherent PBMC IL-8 gene expression was suppressed by either concomitant treatment with actinomycin-D or cycloheximide, yet specific neutralizing antibodies directed against either IL-1 beta or tumor necrosis factor (TNF)-alpha failed to alter adherence-induced steady-state IL-8 mRNA levels. These data support the hypothesis that PBMC adherence is an important signal for the production of IL-8, and may be essential to the development of the inflammatory response through the elicitation of PMN.

Blood Proteins↗

PubMed2004

Cesium toxicity in Arabidopsis.

Cesium (Cs) is chemically similar to potassium (K). However, although K is an essential element, Cs is toxic to plants. Two contrasting hypotheses to explain Cs toxicity have been proposed: (1) extracellular Cs+ prevents K+ uptake and, thereby, induces K starvation; and (2) intracellular Cs+ interacts with vital K(+)-binding sites in proteins, either competitively or noncompetitively, impairing their activities. We tested these hypotheses with Arabidopsis (Arabidopsis thaliana). Increasing the Cs concentration in the agar ([Cs](agar)) on which Arabidopsis were grown reduced shoot growth. Increasing the K concentration in the agar ([K](agar)) increased the [Cs](agar) at which Cs toxicity was observed. However, although increasing [Cs](agar) reduced shoot K concentration ([K](shoot)), the decrease in shoot growth appeared unrelated to [K](shoot) per se. Furthermore, the changes in gene expression in Cs-intoxicated plants differed from those of K-starved plants, suggesting that Cs intoxication was not perceived genetically solely as K starvation. In addition to reducing [K](shoot), increasing [Cs](agar) also increased shoot Cs concentration ([Cs](shoot)), but shoot growth appeared unrelated to [Cs](shoot) per se. The relationship between shoot growth and [Cs](shoot)/[K](shoot) suggested that, at a nontoxic [Cs](shoot), growth was determined by [K](shoot) but that the growth of Cs-intoxicated plants was related to the [Cs](shoot)/[K](shoot) quotient. This is consistent with Cs intoxication resulting from competition between K+ and Cs+ for K(+)-binding sites on essential proteins.

Arabidopsis↗

PubMed1993

Role of the Q10 class I regulatory element region 1 in controlling tissue-specific expression in vivo.

The MHC class I regulatory element (CRE) region 1 has been previously described as a positive cis-acting regulatory element essential for class I gene expression. We have generated transgenic mice (CBA x C57BL/6) with the MHC class I gene H-2Dd driven by two different 400-bp promoter regions of Q10, a nonpolymorphic MHC class I gene expressed in the liver, kidney, and fetal yolk sac. One transgene contained the wild-type Q10 promoter (Q10WT/Dd). The second construct (Q10M3/Dd) had 2 bp substitutions introduced in region 1 of the CRE that reconstituted the CRE inverted repeat present in classical class I genes. Mice containing the wild-type Q10/Dd gene expressed membrane-bound H-2Dd molecules in a tissue-restricted expression pattern similar to that observed for endogenous Q10. In mice containing the mutant construct (Q10M3/Dd), H-2Dd was also expressed in the thymus, a tissue not normally associated with Q10 expression but, surprisingly, the Dd was not expressed in other lymphoid tissues. Furthermore, thymic expression was greatest on double positive (CD4+ CD8+) thymocytes. Thymic Dd expression was correlated with the presence of what appears to be a previously unidentified transcription factor in thymocytes that is capable of interacting with the CRE-inverted repeat. These results show that the mutations in region 1 altered the tissue-specific regulation of the Q10 promoter in vivo, although an intact inverted repeat did not restore the ubiquitous pattern of expression characteristic of classical class I genes. Thus, these results indicate that elements in addition to CRE region 1 in the Q10 promoter region serve to limit ubiquitous tissue expression.

Animals↗

PubMed1995

Cloning of the cDNA encoding human C/EBP gamma, a protein binding to the PRE-I enhancer element of the human interleukin-4 promoter.

The positive regulatory element-I (PRE-I) is a strong enhancer element essential for expression of the human interleukin-4 (IL-4)-encoding gene. In order to identify transcription factors binding to PRE-I, we screened a cDNA expression library from human Jurkat T-cells. A cDNA encoding the human CCAAT/enhancer binding protein-gamma (hC/EBP gamma) was cloned. The deduced amino acid (aa) sequence of HC/EBP gamma contains 150 aa with high homology to mouse Ig/EBP-1 and rat C/EBP gamma. The mRNA of hC/EBP gamma is expressed at a high level in Jurkat T-cells in three forms generated via differential polyadenylation. DNA-binding experiments with recombinant protein produced in bacteria demonstrate that hC/EBP gamma binds to PRE-I, but not to unrelated DNA fragments. Our data also show that hC/EBP gamma may cooperate with Fos to bind PRE-I.

Amino Acid Sequence↗