Soil texture and climate limit cultivation of the arsenic hyperaccumulator Pteris vittata for phytoextraction in a long-term field study

Long term field studies are required to bridge gaps between research and practical application of arsenic phytoextraction with the arsenic-hyperaccumulating fern Pteris vittata. In a 4-year field study, we investigated the effects of nutrient application (compost, inorganic or organic nitrogen, inorganic or organic phosphorus) and soil texture (13 % and 35 % clay) on arsenic phytoextraction with P. vittata in moderately contaminated soils (74-79 mg As/kg in the 0-15 cm depth interval). We found the highest phytoextraction rates, 5 ± 1 kg As/ha/y, in a coarse-textured compost-amended soil after 2 years of phytoextraction. Phytoextraction rates decreased over time, likely due to decreased root growth in mature stands, indicating plants should be replaced every 2-3 years to maintain phytoextraction efficiency. Across soil textures, nitrogen or phosphorus application led to a 60 % decrease in mean frond arsenic concentrations, leading to mean phytoextraction rates 54 % lower than in control ferns. In the fine-textured soil, frond arsenic concentrations were 54 % lower than in the coarse-textured soil, and fewer ferns survived from year 3 to 4. Across soil textures, compost application increased fern survival. We show that phytoextraction with P. vittata is limited to specific soil and climate conditions, narrower than those under which P. vittata grows in the wild.

The Solution Structures and Interaction of SinR and SinI: Elucidating the Mechanism of Action of the Master Regulator Switch for Biofilm Formation in Bacillus subtilis

Bacteria have developed numerous protection strategies to ensure survival in harsh environments, with perhaps the most robust method being the formation of a protective biofilm. In biofilms, bacterial cells are embedded within a matrix that is composed of a complex mixture of polysaccharides, proteins, and DNA. The gram-positive bacterium Bacillus subtilis has become a model organism for studying regulatory networks directing biofilm formation. The phenotypic transition from a planktonic to biofilm state is regulated by the activity of the transcriptional repressor, SinR, and its inactivation by its primary antagonist, SinI. In this work, we present the first full-length structural model of tetrameric SinR using a hybrid approach combining high-resolution solution nuclear magnetic resonance (NMR), chemical cross-linking, mass spectrometry, and molecular docking. We also present the solution NMR structure of the antagonist SinI dimer and probe the mechanism behind the SinR-SinI interaction using a combination of biochemical and biophysical techniques. As a result of these findings, we propose that SinI utilizes a residue replacement mechanism to block SinR multimerization, resulting in diminished DNA binding and concomitant decreased repressor activity. Finally, we provide an evidence-based mechanism that confirms how disruption of the SinR tetramer by SinI regulates gene expression.

The Structure of the Biofilm-controlling Response Regulator BfmR from Acinetobacter baumannii Reveals Details of Its DNA-binding Mechanism

The rise of drug-resistant bacterial infections coupled with decreasing antibiotic efficacy poses a significant challenge to global health care. Acinetobacter baumannii is an insidious, emerging bacterial pathogen responsible for severe nosocomial infections aided by its ability to form biofilms. The response regulator BfmR, from the BfmR/S two-component system, is the master regulator of biofilm initiation in A. baumannii and is a tractable therapeutic target. Here we present the structure of A. baumannii BfmR using a hybrid approach combining X-ray crystallography, nuclear magnetic resonance spectroscopy, chemical crosslinking mass spectrometry, and molecular modeling. We also show that BfmR binds the previously proposed bfmRS promoter sequence with moderate affinity. While BfmR shares many traits with other OmpR/PhoB family response regulators, some unusual properties were observed. Most importantly, we observe that when phosphorylated, BfmR binds this promoter sequence with a lower affinity than when not phosphorylated. All other OmpR/PhoB family members studied to date show an increase in DNA-binding affinity upon phosphorylation. Understanding the structural and biochemical mechanisms of BfmR will aid in the development of new antimicrobial therapies.

Umbilical cord blood graft engineering: challenges and opportunities

We are entering a very exciting era in umbilical cord blood transplantation (UCBT), where many of the associated formidable challenges may become treatable by ex vivo graft manipulation and/or adoptive immunotherapy utilizing specific cellular products. We envisage the use of double UCBT rather than single UCBT for most patients; this allows for greater ability to treat larger patients as well as to manipulate the graft. Ex vivo expansion and/or fucosylation of one cord will achieve more rapid engraftment, minimize the period of neutropenia and also give certainty that the other cord will provide long-term engraftment/immune reconstitution. The non-expanded (and future dominant) cord could be chosen for characteristics such as better HLA matching to minimize GvHD, or larger cell counts to enable part of the unit to be utilized for the development of specific cellular therapies such as the production of virus-specific T-cells or chimeric-antigen receptor T-cells which are reviewed in this study.

A DNA mimic: the structure and mechanism of action for the anti-repressor protein AbbA

Bacteria respond to adverse environmental conditions by switching on the expression of large numbers of genes that enable them to adapt to unfavorable circumstances. In Bacillus subtilis, many adaptive genes are under the negative control of the global transition state regulator, the repressor protein AbrB. Stressful conditions lead to the de-repression of genes under AbrB control. Contributing to this de-repression is AbbA, an anti-repressor that binds to and blocks AbrB from binding to DNA. Here, we have determined the NMR structure of the functional AbbA dimer, confirmed that it binds to the N-terminal DNA-binding domain of AbrB, and have provided an initial description for the interaction using computational docking procedures. Interestingly, we show that AbbA has structural and surface characteristics that closely mimic the DNA phosphate backbone, enabling it to readily carry out its physiological function.

Chemical shift assignments and secondary structure prediction of the C-terminal domain of the response regulator BfmR from Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative pathogen responsible for severe nocosomial infections by forming biofilms in healthcare environments. The two-domain response regulator BfmR has been shown to be the master controller for biofilm formation. Inactivation of BfmR resulted in an abolition of pili production and consequently biofilm creation. Here we report backbone and sidechain resonance assignments and secondary structure prediction for the C-terminal domain of BfmR (residues 130-238) from A. baumannii.

Chemical shift assignments and secondary structure prediction of the master biofilm regulator, SinR, from Bacillus subtilis

Bacillus subtilis is a soil-dwelling Gram-positive bacterial species that has been extensively studied as a model of biofilm formation and stress-induced cellular differentiation. The tetrameric protein, SinR, has been identified as a master regulator for biofilm formation and linked to the regulation of the early transition states during cellular stress response, such as motility and biofilm-linked biosynthetic genes. SinR is a 111-residue protein that is active as a dimer of dimers, composed of two distinct domains, a DNA-binding helix-turn-helix N-terminus domain and a C-terminal multimerization domain. In order for biofilm formation to proceed, the antagonist, SinI, must inactivate SinR. This interaction results in a dramatic structural rearrangement of both proteins. Here we report the full-length backbone and side chain chemical shift values in addition to the experimentally derived secondary structure predictions as the first step towards directly studying the complex interaction dynamics between SinR and SinI.

Solution structures of Mycobacterium tuberculosis thioredoxin C and models of intact thioredoxin system suggest new approaches to inhibitor and drug design

Here, we report the NMR solution structures of Mycobacterium tuberculosis (M. tuberculosis) thioredoxin C in both oxidized and reduced states, with discussion of structural changes that occur in going between redox states. The NMR solution structure of the oxidized TrxC corresponds closely to that of the crystal structure, except in the C-terminal region. It appears that crystal packing effects have caused an artifactual shift in the α4 helix in the previously reported crystal structure, compared with the solution structure. On the basis of these TrxC structures, chemical shift mapping, a previously reported crystal structure of the M. tuberculosis thioredoxin reductase (not bound to a Trx) and structures for intermediates in the E. coli thioredoxin catalytic cycle, we have modeled the complete M. tuberculosis thioredoxin system for the various steps in the catalytic cycle. These structures and models reveal pockets at the TrxR/TrxC interface in various steps in the catalytic cycle, which can be targeted in the design of uncompetitive inhibitors as potential anti-mycobacterial agents, or as chemical genetic probes of function.

Chemical crosslinking and LC/MS analysis to determine protein domain orientation: application to AbrB

To fully understand the modes of action of multi-protein complexes, it is essential to determine their overall global architecture and the specific relationships between domains and subunits. The transcription factor AbrB is a functional homotetramer consisting of two domains per monomer. Obtaining the high-resolution structure of tetrameric AbrB has been extremely challenging due to the independent character of these domains. To facilitate the structure determination process, we solved the NMR structures of both domains independently and utilized gas-phase cleavable chemical crosslinking and LC/MS(n) analysis to correctly position the domains within the full tetrameric AbrB protein structure.

Identification of BfmR, a response regulator involved in biofilm development, as a target for a 2-Aminoimidazole-based antibiofilm agent

2-Aminoimidazoles (2AIs) have been documented to disrupt bacterial protection mechanisms, including biofilm formation and genetically encoded antibiotic resistance traits. Using Acinetobacter baumannii, we provide initial insight into the mechanism of action of a 2AI-based antibiofilm agent. Confocal microscopy confirmed that the 2AI is cell permeable, while pull-down assays identified BfmR, a response regulator that is the master controller of biofilm formation, as a target for this compound. Binding assays demonstrated specificity of the 2AI for response regulators, while computational docking provided models for 2AI-BfmR interactions. The 2AI compound studied here represents a unique small molecule scaffold that targets bacterial response regulators.

Molecular docking and NMR binding studies to identify novel inhibitors of human phosphomevalonate kinase

Phosphomevalonate kinase (PMK) phosphorylates mevalonate-5-phosphate (M5P) in the mevalonate pathway, which is the sole source of isoprenoids and steroids in humans. We have identified new PMK inhibitors with virtual screening, using autodock. Promising hits were verified and their affinity measured using NMR-based (1)H-(15)N heteronuclear single quantum coherence (HSQC) chemical shift perturbation and fluorescence titrations. Chemical shift changes were monitored, plotted, and fitted to obtain dissociation constants (K(d)). Tight binding compounds with K(d)'s ranging from 6-60 μM were identified. These compounds tended to have significant polarity and negative charge, similar to the natural substrates (M5P and ATP). HSQC cross peak changes suggest that binding induces a global conformational change, such as domain closure. Compounds identified in this study serve as chemical genetic probes of human PMK, to explore pharmacology of the mevalonate pathway, as well as starting points for further drug development.

Clinical trials and tribulations--lessons from pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a dreadful disease that lacks adequate therapy. A number of treatment trials have been performed and have utilized a variety of primary efficacy endpoints. Endpoints that provide the most useful efficacy information are clinical endpoints that are directly related to how a patient feels, functions or survives. Unfortunately, there are no properly established patient-reported outcome measures or measures of functional status in IPF, making survival the most robust primary efficacy endpoint. Clinically meaningful events such as hospitalization can also provide important efficacy information. The use of non-validated surrogate endpoints as primary outcome measures often leads to uncertainty when interpreting trial results.

¹H, ¹³C, and ¹⁵N resonance assignments and secondary structure prediction of the full-length transition state regulator AbrB from Bacillus anthracis

The AbrB protein is a transcription factor that regulates the expression of numerous essential genes during the cells transition phase state. AbrB from Bacillus anthracis is, nototriously, the principal protein responsible for anthrax toxin gene expression and is highly homologous to the much-studied AbrB protein from Bacillus subtilis having 85% sequence identity and the ability to regulate the same target promoters. Here we report backbone and sidechain resonance assignments and secondary structure prediction for the full-length AbrB protein from B. anthracis.

P5-19-11: Tesetaxel, an Oral Taxane, as First-Line Therapy for Women with Metastatic Breast Cancer

Background

Parenteral taxanes (docetaxel, paclitaxel) are among the most active agents in treating metastatic breast cancer (MBC). However, their use is limited by inherent or acquired multidrug resistance, hypersensitivity, and neurotoxicity. Tesetaxel is an advanced-generation, orally available taxane that is formulated as a capsule for oral administration and has a long terminal half-life in plasma (∼180 hrs). Unlike standard taxanes, tesetaxel is not a substrate for P-glycoprotein (P-gp), a major cause of taxane resistance. The drug is highly concentrated in cells that overexpress P-gp. In taxane-resistant breast cancer xenografts (DU4475), tesetaxel induced a 94% reduction in tumor size, substantially exceeding the activity of docetaxel and paclitaxel (46% and 26%, respectively). Neurotoxicity was also substantially lower with tesetaxel compared with equi-myelotoxic doses of docetaxel. Among more than 350 patients (pts), there have been no occurrences of hypersensitivity reactions. An initial phase 2 study as 2nd-line therapy for pts with MBC who progressed after multidrug anthracycline-containing regimens showed a 38% partial response (PR) rate using tesetaxel Q3 wks at a dose of 27–35 mg/m2. We conducted a Phase 2, open-label, multicenter study of the efficacy and safety of tesetaxel as first-line therapy in women with MBC.

Methods: Eligible pts have Stage IV, HER2−negative MBC; ECOG PS 0–1; and adequate organ function. No prior chemotherapy is allowed (other than 1 regimen in the adjuvant setting). Tesetaxel was administered orally Q3 wks at a starting dose of 27 mg/m2 with escalation to 35 mg/m2 as tolerated. No premedication for potential hypersensitivity was used. RECIST response rate was the primary endpoint. A Simon min-max two-stage design was used with a target response rate of 30% in 25 pts.

Results: To date, 20 women have been enrolled and treated. The median age was 62 years (range, 45–78). Time from diagnosis was > 4 years in 5 pts and ≤ 4 years in 6; MBC was newly diagnosed in the remaining 9. Hormone receptor status was triple negative in 5 pts at diagnosis and 10 at the time of metastasis. The most common sites of metastasis were lung (13 pts) and bone (9). Prior treatment included hormonal therapy in 13 pts, adjuvant chemotherapy in 16 (most commonly, ACT), and radiotherapy in 9. Of 11 pts currently evaluable for response, PR was achieved in 6 (55%), with confirmation of response in 4 and an ongoing PR in 1 of the 2 pts with an unconfirmed PR. SD was observed in 2 and disease progression in 3. Neutropenia was the most common adverse event, affecting 50% of pts; Grade 3–4 occurrences were observed most often after escalation of the tesetaxel dose to 35 mg/m2. Single occurrences (Grade 1) of neuropathy and nail changes were reported. There were no occurrences of hypersensitivity.

Conclusions: Tesetaxel overcomes multiple disadvantages of standard parenteral taxanes and is highly active in 1st- and 2nd-line MBC. To date, overall response rates in these settings are 55% and 38%, respectively. In view of this, we have amended the trial to expand the initial cohort. Potential schedule-dependency will be examined in a future cohort with a newly developed weekly-times-3 schedule. Updated results in both cohorts will be presented.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-19-11.

Pulmonary fibrosis is associated with an elevated risk of thromboembolic disease

Recent epidemiological studies have suggested an increased risk of venous thromboembolism (VTE) in lung fibrosis. Large-scale epidemiological data regarding the risk of VTE in pulmonary fibrosis-associated mortality have not been published. Using data from the National Center for Health Statistics from 1988-2007, we determined the risk of VTE in decedents with pulmonary fibrosis in the USA. We analysed 46,450,489 records, of which 218,991 met our criteria for idiopathic pulmonary fibrosis. Among these, 3,815 (1.74%) records also contained a diagnostic code for VTE. The risk of VTE in pulmonary fibrosis decedents was 34% higher than in the background population, and 44% and 54% greater than among decedents with chronic obstructive pulmonary disease and lung cancer, respectively. Those with VTE and pulmonary fibrosis died at a younger age than those with pulmonary fibrosis alone (females: 74.3 versus 77.4 yrs (p<0.0001); males: 72.0 versus 74.4 yrs (p<0.0001)). Decedents with pulmonary fibrosis had a significantly greater risk of VTE. Those with VTE and pulmonary fibrosis died at a younger age than those with pulmonary fibrosis alone. These data suggest a link between a pro-fibrotic and a pro-coagulant state.

NMR dynamics investigation of ligand-induced changes of main and side-chain arginine N-H's in human phosphomevalonate kinase

Phosphomevalonate kinase (PMK) catalyzes phosphoryl transfer from adenosine triphosphate (ATP) to mevalonate 5-phosphate (M5P) on the pathway for synthesizing cholesterol and other isoprenoids. To permit this reaction, its substrates must be brought proximal, which would result in a significant and repulsive buildup of negative charge. To facilitate this difficult task, PMK contains 17 arginines and eight lysines. However, the way in which this charge neutralization and binding is achieved, from a structural and dynamics perspective, is not known. More broadly, the role of arginine side-chain dynamics in binding of charged substrates has not been experimentally defined for any protein to date. Herein we report a characterization of changes to the dynamical state of the arginine side chains in PMK due to binding of its highly charged substrates, ATP and M5P. These studies were facilitated by the use of arginine-selective labeling to eliminate spectral overlap. Model-free analysis indicated that while substrate binding has little effect on the arginine backbone dynamics, binding of either substrate leads to significant rigidification of the arginine side chains throughout the protein, even those that are >8 A from the binding site. Such a global rigidification of arginine side chains is unprecedented and suggests that there are long-range electrostatic interactions of sufficient strength to restrict the motion of arginine side chains on the picosecond-to-nanosecond time scale. It will be interesting to see whether such effects are general for arginine residues in proteins that bind highly charged substrates, once additional studies of arginine side-chain dynamics are reported.

Substrate induced structural and dynamics changes in human phosphomevalonate kinase and implications for mechanism

Phosphomevalonate kinase (PMK) catalyzes an essential step in the mevalonate pathway, which is the only pathway for synthesis of isoprenoids and steroids in humans. PMK catalyzes transfer of the gamma-phosphate of ATP to mevalonate 5-phosphate (M5P) to form mevalonate 5-diphosphate. Bringing these phosphate groups in proximity to react is especially challenging, given the high negative charge density on the four phosphate groups in the active site. As such, conformational and dynamics changes needed to form the Michaelis complex are of mechanistic interest. Herein, we report the characterization of substrate induced changes (Mg-ADP, M5P, and the ternary complex) in PMK using NMR-based dynamics and chemical shift perturbation measurements. Mg-ADP and M5P K(d)'s were 6-60 microM in all complexes, consistent with there being little binding synergy. Binding of M5P causes the PMK structure to compress (tau(c) = 13.5 nsec), whereas subsequent binding of Mg-ADP opens the structure up (tau(c) = 15.6 nsec). The overall complex seems to stay very rigid on the psec-nsec timescale with an average NMR order parameter of S(2) approximately 0.88. Data are consistent with addition of M5P causing movement around a hinge region to permit domain closure, which would bring the M5P domain close to ATP to permit catalysis. Dynamics data identify potential hinge residues as H55 and R93, based on their low order parameters and their location in extended regions that connect the M5P and ATP domains in the PMK homology model. Likewise, D163 may be a hinge residue for the lid region that is homologous to the adenylate kinase lid, covering the "Walker-A" catalytic loop. Binding of ATP or ADP appears to cause similar conformational changes; however, these observations do not indicate an obvious role for gamma-phosphate binding interactions. Indeed, the role of gamma-phosphate interactions may be more subtle than suggested by ATP/ADP comparisons, because the conservative O to NH substitution in the beta-gamma bridge of ATP causes a dramatic decrease in affinity and induces few chemical shift perturbations. In terms of positioning of catalytic residues, binding of M5P induces a rigidification of Gly21 (adjacent to the catalytically important Lys22), although exchange broadening in the ternary complex suggests some motion on a slower timescale does still occur. Finally, the first nine residues of the N-terminus are highly disordered, suggesting that they may be part of a cleavable signal or regulatory peptide sequence.

Differential glucose uptake in retina- and brain-derived endothelial cells

Microangiopathy is a systemic complication of diabetes that is especially severe in the retinal microcirculation. The objective of this study was to compare glucose uptake and glucose transporter expression between retinal endothelial cells and the closely related endothelial cells derived from the cerebral microcirculation. Endothelial cells isolated from bovine brain, bovine retinal, and rat heart microvessels were cultured in the presence of control (5 mM) and high levels of (30 mM) d-glucose for 1-5 days. Glucose uptake by cultured endothelial cells was determined by measuring the uptake of [(3)H]deoxy-d-glucose and glucose transporter protein expression was assessed by Western blot. Our results showed that glucose uptake was significantly (P < 0.001) higher in brain- and heart-derived endothelial cells than in retinal endothelial cells at both physiologic and high concentrations of glucose. High levels of glucose caused a significant (P < 0.05) decrease in glucose uptake in brain-derived and heart endothelial cells but had no effect on retinal endothelial cells. Similarly, in response to high glucose levels there was a significant (P < 0.01) down regulation of GLUT-1 in brain-derived endothelial cells but not in retinal endothelial cells. These results suggest that despite a low basal level of glucose uptake the inability of retinal endothelial cells to down regulate glucose uptake in the presence of high glucose levels could make them especially sensitive to the deleterious effects of hyperglycemia in diabetes.

Regulation of muscle GLUT-4 transcription by AMP-activated protein kinase

Skeletal muscle GLUT-4 transcription in response to treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), a known activator of AMP-activated protein kinase (AMPK), was studied in rats and mice. The increase in GLUT-4 mRNA levels in response to a single subcutaneous injection of AICAR, peaked at 13 h in white and red quadriceps muscles but not in the soleus muscle. The mRNA level of chloramphenicol acyltransferase reporter gene which is driven by 1,154 or 895 bp of the human GLUT-4 proximal promoter was increased in AICAR-treated transgenic mice, demonstrating the transcriptional upregulation of the GLUT-4 gene by AICAR. However, this induction of transcription was not apparent with 730 bp of the promoter. In addition, nuclear extracts from AICAR-treated mice bound to the consensus sequence of myocyte enhancer factor-2 (from -473 to -464) to a greater extent than from saline-injected mice. Thus AMP-activated protein kinase activation by AICAR increases GLUT-4 transcription by a mechanism that requires response elements within 895 bp of human GLUT-4 proximal promoter and that may be cooperatively mediated by myocyte enhancer factor-2.

Identifying physicians likely to benefit from depression education: a challenge for health care organizations

BACKGROUND

Few methods exist to identify physicians who might benefit from depression education.

OBJECTIVES

To develop a measure of physicians' confidence or self-efficacy in caring for depressed patients and assess it's reliability and validity.

RESEARCH DESIGN

A national sample of primary care physicians were surveyed and exploratory factor analysis (EFA) was used to identify factors underlying physicians' responses to 26 items. We named the factors, selected items with factor loadings > or = 0.50 for final scales, and tested a priori hypotheses about self-efficacy.

SUBJECTS

1) Random cross-sectional sample of family physicians, internists, obstetrician-gynecologists, and pediatricians (n = 5,369) and 2) 49 general internists and family physicians participating in a prepost evaluation of a depression workshop.

RESULTS

In the national sample, 3,712 physicians were eligible and 2,104 responded. Forty-six percent were female, and 51% were family physicians and general internists. EFA identified 5 factors, the first of which was called Self-Efficacy (4 items, alpha = 0.86). More family physicians (64%) had confidence (self-efficacy) in caring for depressed patients compared with general internists (33%), obstetrician-gynecologists (16%), and pediatricians (6%) (P < 0.001). Few physicians intended to change their care of depressed patients (10%) or take CME on depression (24%). Of the 49 physicians attending a depression workshop, 76% reported high self-efficacy after the workshop versus 50% before it (P = 0.013).

CONCLUSIONS

This study supports the reliability and validity of the Self-Efficacy scale as one method to identify physicians who might benefit from interventions. New approaches are needed because physicians are unlikely to change.

Insulin-mediated GLUT4 translocation is dependent on the microtubule network

The GLUT4 facilitative glucose transporter is recruited to the plasma membrane by insulin. This process depends primarily on the exocytosis of a specialized pool of vesicles containing GLUT4 in their membranes. The mechanism of GLUT4 vesicle exocytosis in response to insulin is not understood. To determine whether GLUT4 exocytosis is dependent on intact microtubule network, we measured insulin-mediated GLUT4 exocytosis in 3T3-L1 adipocytes in which the microtubule network was depolymerized by pretreatment with nocodazole. Insulin-mediated GLUT4 translocation was inhibited by more than 80% in nocodazole-treated cells. Phosphorylation of insulin receptor substrate 1 (IRS-1), activation of IRS-1 associated phosphatidylinositide 3-kinase, and phosphorylation of protein kinase B/Akt-1 were not inhibited by nocodazole treatment indicating that the microtubule network was not required for proximal insulin signaling. An intact microtubule network is specifically required for insulin-mediated GLUT4 translocation since nocodazole treatment did not affect insulin-mediated GLUT1 translocation or adipsin secretion. By using in vitro microtubule binding, we demonstrated that both GLUT4 vesicles and IRS-1 bind specifically to microtubules, implicating microtubules in both insulin signaling and GLUT4 translocation. Vesicle binding to microtubules was not mediated through direct binding of GLUT4 or insulin-responsive aminopeptidase to microtubules. A model microtubule-dependent translocation of GLUT4 is proposed.

Primary care pediatricians' roles and perceived responsibilities in the identification and management of depression in children and adolescents

OBJECTIVE

To describe primary care pediatricians' 1) approach to the identification and management of childhood and adolescent depression and 2) perception of their skills, responsibilities, and barriers in recognizing and managing depression in children and adolescents.

DESIGN AND METHODS

National cross-sectional survey of randomly selected primary care pediatricians that assessed the management of recalled last case of child or adolescent depression, attitudes, limitations to care from barriers and skills, and willingness to implement new educational or intervention strategies to improve care.

RESULTS

There were 280 completed surveys about child and adolescent depression (63% response rate). Pediatricians overwhelmingly reported it was their responsibility to recognize depression in both children and adolescents (90%) but were unlikely to feel responsible for treating children or adolescents (26%-27%). Those with most of their practice in capitated managed care were less likely to feel responsible for recognizing depression in either children or adolescents. Forty-six percent of pediatricians lacked confidence in their skills to recognize depression in children, and few of them (10%-14%) had confidence in their skills in different aspects of treatment with children or adolescents. Diagnostic, assessment, and management details for their last recalled case of depression in a child or adolescent were provided by 248 of these pediatricians. In addition to referring 78%-79% of the cases to mental health care professionals, 77% of pediatricians provided a wide range of brief interventions. Only 19%-20% prescribed medication. Major factors cited that limited their diagnosis or management were time (56%-68%) and training or knowledge of issues (38%-56%). Fewer pediatricians noted limitations due to insurer or financial issues (8%-39%) or patient issues (19%-31%). The 35% of pediatricians who were motivated to change their recognition and management of suspected depression were significantly more interested in implementing in the future a variety of new strategies to improve care.

CONCLUSION

Primary care pediatricians felt responsible for recognizing but not for treating child and adolescent depression. Although the lack of confidence and lack of knowledge and/or skills and time issues are major barriers that limit pediatricians in their treatment of childhood and adolescent depression, pediatricians varied in their readiness to change, with some being more willing to implement new strategies to care for depression. Educational and practice interventions need to focus on how to assist all pediatricians in diagnosis and to prepare these motivated pediatricians to manage depression in primary care settings.

Persistent increase in children's sun protection in a randomized controlled community trial

BACKGROUND

Reducing sun exposure during childhood may prevent skin cancer later in life. Sun protection increased immediately following implementation of the SunSafe multicomponent, community-based intervention delivered in 1996 through schools, day care centers, primary care offices, and beach recreation areas. Whether sun protection levels would remain higher than preintervention levels the following summer was unknown.

METHODS

A randomized controlled trial based in 10 New Hampshire towns addressed children's use of protective clothing, shade, and sunscreen at freshwater beach areas. The intervention was provided initially between March and May 1996. A brief project follow-up contact was provided to schools, day care centers, beaches, and primary care offices between March and May 1997 to restock intervention materials and to answer questions. Observations of 1490 children during June through August of 1997 were compared with observations made prior to any intervention between June and August of 1995.

RESULTS

In intervention towns, the proportion of children using at least some sun protection increased by 0.15 from 0.58 in 1995 to 0.73 in 1997 while the proportion in control towns increased by 0.03 (P = 0.033). This increase was due to more use of sunscreen, but not more use of protective clothing or shade. In 1997, care-givers of children in intervention towns reported receiving more sun protection information from school and health care sources than control town caregivers (62% versus 33%, P < 0.006).

CONCLUSIONS

In intervention communities, a higher proportion of children used sun protection in 1997 than at baseline. Increases from 1995 to 1997 were similar in magnitude to short-term increases between 1995 and 1996 that we have been previously reported.

Identification of a 30-base pair regulatory element and novel DNA binding protein that regulates the human GLUT4 promoter in transgenic mice

We have previously demonstrated that the important cis-acting elements regulating transcription of the human GLUT4 gene reside within 895 base pairs (bp) upstream of the transcription initiation site (Thai, M. V., Guruswamy, S., Cao, K. T., Pessin, J. E., and Olson, A. L. (1998) J. Biol. Chem. 273, 14285-14292). Our studies demonstrated that an MEF2 binding site within this region was necessary, but not sufficient, for GLUT4 promoter function in transgenic mice. We have identified a second regulatory element (Domain I) that functions cooperatively with the MEF2 domain in regulating GLUT4 transcription. Using a yeast-one hybrid screen, we obtained a partial cDNA and generated an antibody directed against a protein binding specifically to Domain I. Sequence analysis of the partial cDNA indicates that the protein binding to Domain I is a novel protein. The antibody specifically labels two proteins of approximately 70 and 50 kDa in Western blot analysis. These molecular masses correspond to Domain I binding proteins identified by UV-cross-linking nuclear extracts to a Domain I probe. The antibody raised against the Domain I binding protein inhibited formation of a Domain I-protein complex in electrophoretic mobility shift assays. We conclude that we have identified an authentic, novel, Domain I binding protein required for transcriptional regulation of the human GLUT4 promoter.

A national general pediatric clerkship curriculum: the process of development and implementation

OBJECTIVE

To describe a new national general pediatrics clerkship curriculum, the development process that built national support for its use, and current progress in implementing the curriculum in pediatric clerkships at US allopathic medical schools. CURRICULUM DEVELOPMENT: A curriculum project team of pediatric clerkship directors and an advisory committee representing professional organizations invested in pediatric student education developed the format and content in collaboration with pediatric educators from the Council on Medical Student Education in Pediatrics (COMSEP) and the Ambulatory Pediatric Association (APA). An iterative process or review by clerkship directors, pediatric departmental chairs, and students finalized the content and built support for the final product. The national dissemination process resulted in consensus among pediatric educators that this curriculum should be used as the national curricular guideline for clerkships. MONITORING IMPLEMENTATION: Surveys were mailed to all pediatric clerkship directors before dissemination (November 1994), and in the first and third academic years after national dissemination (March 1996 and September 1997). The 3 surveys assessed schools' implementation of specific components of the curriculum. The final survey also assessed ways the curriculum was used and barriers to implementation.

OUTCOMES

The final curriculum provided objectives and competencies for attitudes, skills, and 18 knowledge areas of general pediatrics. A total of 216 short clinical cases were also provided as an alternative learning method. An accompanying resource manual provided suggested strategies for implementation, teaching, and evaluation. A total of 103 schools responded to survey 1; 84 schools to survey 2; and 85 schools responded to survey 3 from the 125 medical schools surveyed. Before dissemination, 16% of schools were already using the clinical cases. In the 1995-1996 academic year, 70% of schools were using some or all of the curricular objectives/competencies, and 45% were using the clinical cases. Two years later, 90% of schools surveyed were using the curricular objectives, 88% were using the competencies, 66% were using the clinical cases. The extent of curriculum use also increased. Schools using 11 or more of the 18 curriculum's knowledge areas increased from 50% (1995-1996) to 73% (1996-1997).

CONCLUSION

This new national general pediatric clerkship curriculum developed broad support during its development and has been implemented very rapidly nationwide. During this period the COMSEP and the APA have strongly supported its implementation with a variety of activities. This development and implementation process can be a model for other national curricula.

Sun protection counseling for children: primary care practice patterns and effect of an intervention on clinicians

OBJECTIVES

To describe current primary care sun protection advice for children and assess the effect on clinicians of an intervention to enhance their sun protection advocacy.

SETTING

Primary care practices caring for children in New Hampshire with special attention to clinicians serving 10 towns that were involved in a randomized controlled trial of the multicomponent SunSafe intervention involving schools, recreation areas, and primary care practices.

DESIGN/INTERVENTION

A statewide survey of all primary care clinicians serving children addressed their self-reported sun protection advocacy practices. Clinicians in 10 systematically selected rural towns were involved in the subsequent intervention study. The primary care intervention provided assistance to practices in establishing an office system that promoted sun protection advice to children and their parents during office visits.

MAIN OUTCOME MEASURES

Sun protection promotion activities of primary care clinicians as determined by their self report, research assistant observation, and parent interviews.

RESULTS

Of 261 eligible clinicians responding to the statewide survey, about half provide sun protection counseling "most of the time" or "almost always" during summer well care visits. Pediatricians do so more often than family physicians. Clinicians involved in the intervention increased their use of handouts, waiting room educational materials, and sunscreen samples. Compared with control town parents, parents in intervention towns reported an increase in clinician sun protection advice.

CONCLUSIONS

The SunSafe primary care intervention increased sun protection counseling activities of participating clinicians. A single-focus preventive service office system is feasible to include in community interventions to promote sun protection.

Expression of a prenylation-deficient Rab4 interferes with propagation of insulin signaling through insulin receptor substrate-1

Rab proteins are small GTP-binding proteins of the Ras superfamily that function in the regulation of vesicle transport processes. The Rab4 isoform has been implicated in insulin action. For instance, overexpression of a prenylation-deficient form of Rab4 has been shown to inhibit insulin-dependent GLUT4 translocation. Other steps affected by Rab4 in the cascade of events resulting from insulin receptor activation have not been elucidated. In the present studies, we measured effects on insulin-signaling proteins in 3T3-L1 adipocytes transiently expressing cytoplasmic forms of Rab4 and Rab5. Expression of a mutant Rab4 lacking a prenylation site resulted in reduced insulin-dependent phosphorylation ofcytoplasmic and internal membrane-associated insulin receptor substrate-1, leading to decreased insulin receptor substrate-1-associated phosphatidylinositol 3'-OH kinase activation and decreased Akt activation. These effects were not observed upon introduction of a similar mutant form of Rab5. These data indicate that Rab4 or a Rab4-associated protein is involved at one or more steps in propagating the insulin signal, in addition to any role it may play in the regulation of GLUT4 vesicle translocation. Our results support models of insulin signaling in which regulation of internal membrane trafficking plays a role in transduction of the insulin signal.

Osmotic shock inhibits insulin signaling by maintaining Akt/protein kinase B in an inactive dephosphorylated state

We have previously reported that insulin and osmotic shock stimulate an increase in glucose transport activity and translocation of the insulin-responsive glucose transporter isoform GLUT4 to the plasma membrane through distinct pathways in 3T3L1 adipocytes (D. Chen, J. S. Elmendorf, A. L. Olson, X. Li, H. S. Earp, and J. E. Pessin, J. Biol. Chem. 272:27401-27410, 1997). In investigations of the relationships between these two signaling pathways, we have now observed that these two stimuli are not additive, and, in fact, osmotic shock pretreatment was found to completely prevent any further insulin stimulation of glucose transport activity and GLUT4 protein translocation. In addition, osmotic shock inhibited the insulin stimulation of lipogenesis and glycogen synthesis. This inhibition of insulin-stimulated downstream signaling occurred without any significant effect on insulin receptor autophosphorylation or tyrosine phosphorylation of insulin receptor substrate 1 (IRS1). Furthermore, there was no effect on either the insulin-stimulated association of the p85 type I phosphatidylinositol (PI) 3-kinase regulatory subunit with IRS1 or phosphotyrosine antibody-immunoprecipitated PI 3-kinase activity. In contrast, osmotic shock pretreatment markedly inhibited the insulin stimulation of protein kinase B (PKB) and p70S6 kinase activities. In addition, the dephosphorylation of PKB was prevented by pretreatment with the phosphatase inhibitors okadaic acid and calyculin A. These data support a model in which osmotic shock-induced insulin resistance of downstream biological responses results from an inhibition of insulin-stimulated PKB activation.

A community-based randomized trial encouraging sun protection for children

OBJECTIVE

We evaluated the impact of an intervention promoting sun protection behavior among children 2 to 11 years of age through schools and day care centers, primary care practices, and recreation areas.

METHODS

Ten towns in New Hampshire were paired, then assigned randomly to intervention or control status. The multicomponent SunSafe intervention was provided to children and caregivers through primary care practices, day care centers, schools, and beach recreation areas. Training support and materials were provided by the SunSafe project, but project staff had no direct contact with children or parents in providing the intervention. All intervention components promoted the same message: avoid the sun between 11 AM and 3 PM, cover up using hats and protective clothing, use sun block with a sun protection factor >/=15, and encourage sun protection among family and friends. The impact of the intervention was determined by observing children's sun protection behavior at the beach during baseline compared with 1 year later. The primary outcomes of interest were changes in the proportion of children per town using at least some sun protection and changes in the proportion of children fully protected. Children were clustered by town, with the town thus being the unit of analysis. The primary care practice component included one practice meeting for clinicians and staff at which project staff presented background on skin cancer and how to promote its prevention; a sun protection office system manual based on our previous work, which provided specific direction on how to share responsibility among office staff and clinicians in carrying out routines that promote sun protection; and educational posters, pamphlets, and self-adhesive reminder notes designed to enhance sun protection counseling. SunSafe removable tattoos and stickers were offered to children at well-child and illness visits during the summer months. Schools each received three project staff visits: a brief visit with the principal to describe the intervention and to answer questions; an in-service program to educate teachers about skin cancer and to introduce curricular materials; and help with one parent outreach program. Larger day care centers each received one project staff visit. An additional six smaller day care centers received curricular materials through the mail but no visits. Two similar sets of curricular materials were used, one for grade schools and the other for preschools and day care centers. Both emphasized the importance of sun protection rather than the danger of skin cancer. Materials emphasized dynamic activities modeled after the "Slip, Slop, Slap" and "SunSmart" programs and included new material developed to suit regional needs. Both manuals offered structured plans but also provided a variety of activities from which teachers could choose. Teachers agreed to devote a minimum of two class periods to these materials. For recreation areas, lifeguards in each of the intervention communities attended an in-service meeting, during which background about skin cancer prevention was presented by project staff. The project also provided displays about the ultraviolet (UV) light index and about sun protection to be posted at each beach. Subsequently, project staff called beach staff in each community each morning with the predicted UV index for the day to post on the display. Educational pamphlets about the UV index and free sun-block samples were available to beachgoers through the lifeguards. One brief follow-up visit by project staff was made to each beach area to provide reinforcement.

RESULTS

We observed 1930 children. Use of some sunscreen on at least one body area increased in all 5 intervention towns compared with paired control towns. In intervention towns, this mean proportion increased from 0.56 of those observed at baseline to 0.76 of those observed postintervention, with a minimal increase among control town children. (ABSTRACT TRUNCATED

Myocyte enhancer factor 2 (MEF2)-binding site is required for GLUT4 gene expression in transgenic mice. Regulation of MEF2 DNA binding activity in insulin-deficient diabetes

We have previously demonstrated that important regulatory elements responsible for regulated expression of the human GLUT4 promoter are located between -1154 and -412 relative to transcription initiation (Olson, A. L., and Pessin, J. E. (1995) J. Biol. Chem. 270, 23491-23495). Through further analysis of this promoter regulatory region, we have identified a perfectly conserved myocyte enhancer factor 2 (MEF2)-binding domain (-CTAAAAATAG-) that is necessary, but not sufficient, to support tissue-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice. Biochemical analysis of this DNA element demonstrated the formation of a specific DNA-protein complex using nuclear extracts isolated from heart, hindquarter skeletal muscle, and adipose tissue but not from liver. DNA binding studies indicated that this element functionally interacted with the MEF2A and/or MEF2C MADS family of DNA binding transcription factors. MEF2 DNA binding activity was substantially reduced in nuclear extracts isolated from both heart and skeletal muscle of diabetic mice, which correlated with decreased transcription rate of the GLUT4 gene. MEF2 binding activity completely recovered to control levels following insulin treatment. Together these data demonstrated that MEF2 binding activity is necessary for regulation of the GLUT4 gene promoter in muscle and adipose tissue.

Regulation of glucose transporters GLUT-4 and GLUT-1 gene transcription in denervated skeletal muscle

Because GLUT-4 expression is decreased whereas GLUT-1 expression is increased in denervated skeletal muscle, we examined the effects of denervation on GLUT-4 and GLUT-1 gene transcription. The right hindlimb skeletal muscle of male transgenic mice containing sequential truncations (2,400, 1,639, 1,154, and 730 bp) of the human GLUT-4 promoter linked to the chloramphenacol acyl transferase (CAT) gene was denervated, and the contralateral hindlimb was sham operated. RNase protection analysis revealed that after 72 h denervation decreased CAT mRNA and GLUT-4 mRNA levels 64-85%, respectively (P < 0.05), in the gastrocnemius muscles. In contrast, denervation of the right hindlimb of male rats increased GLUT-1 gene transcription and GLUT-1 mRNA levels by 94 and 213%, respectively (P < 0.05). In conclusion, GLUT-4 transcription is decreased but GLUT-1 transcription is increased in denervated skeletal muscle, suggesting that the effects of denervation on GLUT-4 and GLUT-1 expression are, in part, transcriptionally mediated. Furthermore, these data indicate that a DNA sequence regulated by denervation is located within 730 bp of the 5'-flanking promoter region of the human GLUT-4 gene.

Osmotic shock stimulates GLUT4 translocation in 3T3L1 adipocytes by a novel tyrosine kinase pathway

Similar to insulin, osmotic shock of 3T3L1 adipocytes stimulated an increase in glucose transport activity and translocation of GLUT4 protein from intracellularly localized vesicles to the plasma membrane. The docking/fusion of GLUT4 vesicles with the plasma membrane appeared to utilize a similar mechanism, since expression of a dominant interfering mutant of syntaxin-4 prevented both insulin- and osmotic shock-induced GLUT4 translocation. However, although the insulin stimulation of GLUT4 translocation and glucose transport activity was completely inhibited by wortmannin, activation by osmotic shock was wortmannin-insensitive. Furthermore, insulin stimulated the phosphorylation and activation of the Akt kinase, whereas osmotic shock was completely without effect. Surprisingly, treatment of cells with the tyrosine kinase inhibitor, genistein, or microinjection of phosphotyrosine antibody prevented both the insulin- and osmotic shock-stimulated translocation of GLUT4. In addition, osmotic shock induced the tyrosine phosphorylation of several discrete proteins including Cbl, p130(cas), and the recently identified soluble tyrosine kinase, calcium-dependent tyrosine kinase (CADTK). In contrast, insulin had no effect on CADTK but stimulated the tyrosine phosphorylation of Cbl and the tyrosine dephosphorylation of pp125(FAK) and p130(cas). These data demonstrate that the osmotic shock stimulation of GLUT4 translocation in adipocytes occurs through a novel tyrosine kinase pathway that is independent of both the phosphatidylinositol 3-kinase and the Akt kinase.

Solar protection of children at the beach

BACKGROUND

Excessive sun exposure during childhood has been associated with subsequent development of skin cancers. Children have been advised to avoid sun exposure, use protective clothing, and apply sunscreen lotions, but how completely these recommendations are followed has not been studied.

OBJECTIVE

To determine the extent of sun protection among children visiting lake beaches, the methods used, and the characteristics associated with more protection.

DESIGN

Direct observations of children were linked with concurrent care giver/parent interviews.

SUBJECTS/SETTING

A total of 871 children 2 to 9 years of age and their parents/care givers at freshwater beaches in 10 small New Hampshire towns during July and August 1995.

OUTCOME MEASURES

Protection of the head, torso, and legs according to method used (hats, shirts, pants, sunscreen, or shade).

RESULTS

Fifty-four percent of children were protected by at least one method for all three body surface regions, although 17% had no protection for any region. Sunscreen was used either alone or in combination with clothing for at least one region in 79%. Hats were used by 3%, shirts by 22%, and pants to the knee by 49%. Only 12% of observed children were in the shade. The region that was protected most often was the legs for boys (due to swim suit styles) followed by the torso for both sexes. The region most often unprotected was the legs for girls followed closely by the face for both boys and girls. Girls were significantly more likely to have no protection (31.2% female vs 7% male, chi2 83.3) due to better leg protection from swim trunks to the knees popular with boys. Full protection of all three regions was more common for children younger than 5 (odds ratio [OR] = 1.8, 95% confidence interval, [CI] 1.3-2.5), for children perceived to usually or always burn (OR = 2.0, 95% CI 1.4-2.7), for children whose parents had more than a high school education (OR = 1.8, 95% CI 1.3-2.5), and if the parents indicated receiving sun protection information from a school or clinician during the previous year (OR = 1.7, 95% CI 1.2-2.3). Approximately 51.6% of parents recalled receiving childhood solar protection advice in the past year from either their physician, a nurse, or a school/day care setting.

CONCLUSIONS

Sunscreen provided the most common form of solar protection. Hats and shade were used rarely, and shirts were also underused. Although the sun protection of these children visiting the beach was substantial, nearly half were still not fully protected. Clinician advice within the past year was associated with better protection. Clinicians could increase their influence by providing more specific counseling about how to achieve full protection. Use of multiple methods of protection rather than just sunscreen and full protection rather than protection for just one or two body regions should be emphasized. It is helpful to remind families to protect the regions most frequently omitted from protection: girls' legs and boys' and girls' faces. Advice can be enhanced with patient education materials such as included in the "Slip" (on a shirt), "Slop" (on sunscreen), and "Slap" (on a hat) program developed in Australia and available through the American Cancer Society.

Syntaxin 4, VAMP2, and/or VAMP3/cellubrevin are functional target membrane and vesicle SNAP receptors for insulin-stimulated GLUT4 translocation in adipocytes

Introduction of the cytoplasmic domain of syntaxin 4, using either recombinant vaccinia virus or single-cell microinjection, resulted in an inhibition of insulin-stimulated GLUT4 but not GLUT1 translocation to the plasma membrane. This was specific for syntaxin 4, since neither the expression of syntaxin 3 nor the expression of a syntaxin 4 mutant in which the vesicle-associated membrane protein (VAMP) binding site was deleted had any significant effect. Consistent with the requirement for a functional VAMP binding site, expression of the cytoplasmic domains of VAMP2 or VAMP3/cellubrevin also resulted in an inhibition of insulin-stimulated GLUT4 translocation. In addition, immunoprecipitation of the expressed syntaxin 4 cytoplasmic domain resulted in an insulin-stimulated increase in the coimmunoprecipitation of GLUT4-containing vesicles. Together, these data demonstrate that syntaxin 4, VAMP2, and/or VAMP3/cellubrevin can function as target membrane and vesicle SNAP receptors, respectively, for insulin-responsive GLUT4 translocation to the plasma membrane.

Structure, function, and regulation of the mammalian facilitative glucose transporter gene family

The facilitative transport of glucose across the plasma membranes of mammalian cells is catalyzed by a family of glucose transport proteins (GLUT). Four glucose transport proteins and a fructose transport protein have been identified. These transport proteins have unique tissue distributions and biochemical properties under- lying specific physiologic functions. GLUT1, the first GLUT isoform identified, is expressed at highest levels in the endothelial of barrier tissues such as blood vessels and the blood-brain barrier. GLUT2, found predominantly in liver, intestine, kidney, and pancreatic beta-cells, is a low-affinity glucose transport protein that is part of the glucose sensor in pancreatic beta-cells and facilitates either glucose uptake or efflux from the liver depending on the nutritional state. GLUT3 is the glucose transporter responsible for maintaining an adequate glucose supply to neurons. GLUT4 is the insulin-regulated glucose transporter found in adipose tissues, heart muscles, and skeletal muscles that is responsible for insulin-regulated glucose disposal.

Reversal of flow in the left pulmonary artery after cavopulmonary connection

The postoperative course of a 15-month-old girl who underwent a bilateral bidirectional cavopulmonary connection was complicated by a left chylothorax and left hemidiaphragm paralysis. Two-dimensional and Doppler echocardiography revealed complete flow reversal in the left pulmonary artery. This flow abnormality was confirmed by angiography. Multiple aortopulmonary collaterals had also developed and were coil embolized at the time of catheterization. Coil embolization of the collaterals, combined with relief of the chylothorax and diaphragmatic plication, reestablished forward flow in the left pulmonary artery.

Preventive health care for children

This article discusses immunization, development, vision, blood pressure, dentition, behavioral, and environmental screening for preschool children. The authors then discuss screening for children in the early school years. Injury and violence prevention and topics of sexuality for the preadolescent are also presented.

Transcriptional regulation of the human GLUT4 gene promoter in diabetic transgenic mice

We previously reported that 2400 base pairs (bp) of 5'-flanking DNA is sufficient for tissue-specific and hormonal/metabolic regulation of the human GLUT4 gene in transgenic mice (Liu, M.-L., Olson, A. L., Moye-Rowley, W. S., Buse, J. B., Bell, G. I., and Pessin, J. E. (1992) J. Biol. Chem. 267, 11673-11676). To further define the DNA sequences required for GLUT4 expression, we generated transgenic mice carrying 1975, 1639, 1154, 730, and 412 bp of the GLUT4 5'-flank (hG4) fused to the chloramphenicol acetyltransferase (CAT) reporter gene. The 1975-hG4-CAT, 1639-hG4-CAT, and 1154-hG4-CAT constructs were expressed in a tissue-specific manner identical to the endogenous murine GLUT4 mRNA. Regulation of these reporter gene constructs in insulin-deficient diabetes also paralleled the endogenous gene. In contrast, 730-hG4-CAT was expressed at high levels only in skeletal muscle and at low levels in all of the other tissues examined. Additionally, expression of 412-hG4-CAT was completely unrestricted. Neither the 730-hG4-CAT nor the 412-hG4-CAT reporter genes displayed any insulin-dependent regulation. These data demonstrate that a skeletal muscle-specific DNA element is located within 730 bp of the GLUT4 5'-flanking DNA but that 1154 bp is necessary to direct the full extent of tissue-specific and insulin-dependent regulation of the human GLUT4 gene in transgenic mice.

Characterization of 5'-heterogeneity of the rat GLUT4/muscle-adipose glucose transporter gene product

To examine the mechanisms responsible for tissue-specific, nutritional, and metabolic regulation of the GLUT4/muscle-adipose specific glucose transporter, we isolated and characterized the properties of the rat GLUT4 gene. Examination of the sequenced 2.5-kilobase flanking DNA revealed substantial identity with that of the mouse and human GLUT4 genes, with the greatest degree of sequence identity within the proximal 1000 basepairs up-stream of the GLUT4 open reading frame. Primer extension analysis identified a unique single transcription initiation site 176 basepairs up-stream from the start of translation. However, ribonuclease mapping revealed the presence of a previously undescribed alternatively spliced form of GLUT4 messenger RNA. Approximately 75% of the GLUT4 transcripts consisted of a fully spliced messenger RNA, and 25% was expressed as an unspliced intron-containing species. The ratios of 5' spliced and unspliced messages were invariant in adipose, cardiac, and skeletal muscle tissues. In vitro translation of reporter constructs containing both the spliced and unspliced leader demonstrated a functional difference between these two transcripts, with the unspliced form translated approximately 5-fold more than the fully spliced species. These data demonstrate the presence of 5'-heterogeneity of the GLUT4 transcripts, which underlies differences in translational efficiency in vitro.

Myocyte enhancer factor 2 (MEF2) binding site is essential for C2C12 myotube-specific expression of the rat GLUT4/muscle-adipose facilitative glucose transporter gene

We have cloned and characterized the rat GLUT4 gene in order to identify the cis-DNA elements responsible for tissue-specific GLUT4 expression. In this study, a variety of luciferase reporter gene constructs were transiently transfected into C2C12 myoblasts and myotubes as a model for skeletal muscle differentiation. These data identified a 103-base pair fragment, located from -522 to -420 relative to the transcription initiation site, that was sufficient to account for GLUT4 C2C12 myotube-specific expression. This fragment was operationally defined as an enhancer since it conferred myotube-specific expression in the context of both the minimal native GLUT4 or the heterologous thymidine kinase promoters in an orientation-independent manner. Further, mutagenesis of this fragment demonstrated that a sequence analogous to the muscle creatine kinase myocyte enhancer factor 2 (MEF2) binding site (-466 and -457) was required for transcriptional activation. Electrophoretic mobility gel shift assays demonstrated specific binding activity to the GLUT4 MEF2 sequences which directly correlated with functional expression. Although this element was capable of directing myotube-specific expression when cloned as multiple copies into luciferase reporter gene constructs, the MEF2 sequence alone was insufficient to enhance GLUT4 expression. These data demonstrated that GLUT4 muscle-specific expression is conferred by a 103-base pair DNA sequence located between -522 and -420 of rat GLUT4 gene. This region encompasses a MEF2 binding site which was necessary, but not sufficient, for transcriptional activation.

Depressive symptoms and work role satisfaction in mothers of toddlers

OBJECTIVE

To determine the incidence of depressive symptoms in mothers of toddlers in community pediatric practice. The interaction of employment and work role satisfaction with depressive symptoms was also investigated.

SUBJECTS AND METHODS

Depression screening measures were completed by 233 mothers of toddlers (aged 12 to 24 months) at health supervision visits in two community pediatric practices in New Hampshire. Depression was evaluated with a depressive symptom screening inventory modified by Barrett, Oxman, and Gerber from the Hopkins Symptom Checklist for use in primary care population. Data were obtained on parents' socioeconomic variables, hours worked, and whether the mother was satisfied with her current role of being employed or not employed.

RESULTS

Depressive symptoms were present in 42% of mothers. Rates of depressive symptoms were similar in employment groups but varied significantly with work role satisfaction. When both employment and satisfaction were considered, mothers who were dissatisfied were 3.7 times more likely to be depressed. After controlling for work role satisfaction, mothers working part time were half as likely to be depressed as mothers working full time and not employed.

CONCLUSION

Depressive symptoms are a major problem for mothers of toddlers in middle class pediatric practice. Work role satisfaction and employment status together are related to depressive symptoms.

In vivo association of Grb2 with pp116, a substrate of the T cell antigen receptor-activated protein tyrosine kinase

Numerous recent studies have implicated the src homology 2 and 3 domain-containing protein, Grb2, in coupling protein tyrosine kinase signaling pathways with the Ras signaling pathway. Ligation of the T cell antigen receptor results in the activation of both a PTK, and Ras; therefore, we investigated whether Grb2 may serve a similar function in T cells. Here we report that a GST/Grb2 fusion protein associates with several tyrosine phosphoproteins from lysates of T cell antigen receptor-stimulated Jurkat T cells. Two of these proteins, pp36 and pp116, bind to the Grb2 fusion protein with high affinity. Through the use of mutated Grb2 fusion proteins, we demonstrate that pp116 binds the amino-terminal src homology 3 domain of Grb2, the same domain of Grb2 thought to be primarily responsible for its interaction with SOS. We demonstrate further that pp116 associates with Grb2 in vivo, and we provide evidence that in the Jurkat T cell line Grb2 may exist complexed with either pp116 or with SOS.

Regulation of c-fos expression in adipose and muscle tissue of diabetic rats

Insulin treatment of control rats demonstrated a marked 8-fold transient increase (15 min) in c-fos mRNA in white adipose tissue, which returns to basal levels by 5 h. Similarly, insulin treatment resulted in a rapid 9-fold increase in cardiac muscle c-fos mRNA, which also returned to control values by 1 h. By contrast, insulin treatment resulted in only a small increase in c-jun mRNA levels in both adipose tissue and cardiac muscle. Similarly, the expression of c-jun mRNA was only slightly responsive to insulin in these tissues from streptozocin-induced insulin-deficient diabetic rats. However, insulin treatment of insulin-deficient diabetic rats resulted in a prolonged increase in c-fos message levels in adipose tissue without any significant change in the time course of c-fos mRNA induction/repression in cardiac muscle. These data demonstrate that in contrast to c-jun, c-fos is transiently increased in both cardiac muscle and adipose tissue by insulin treatment. Furthermore, transrepression of the c-fos gene is specifically attenuated in adipose tissue of insulin-deficient diabetic rats, but not in cardiac muscle.

Cognitive coping strategies of children with chronic illness

Children with chronic illness need to adapt to more stresses than do healthy children. Research highlights the problems of children with chronic illnesses but not how they cope in response to the stress created by these problems. Cognitive appraisal of a stressor and of response options is an important aspect of coping. Our cross-sectional study investigated whether children with chronic illness used cognitive strategies for coping as often as did healthy children. One hundred seventy five children from summer camps with juvenile arthritis, asthma, or diabetes were compared with 145 healthy school children. Spontaneous responses to common painful and stressful events were categorized into coping or catastrophizing ideation. Data on anxiety, disease severity, and other sociodemographic variables were obtained. Coping strategies were reported by 64% of children with chronic illness and 63% of healthy children and varied significantly with age (p < .05) in both groups. Children with different chronic illnesses performed similarly except for a trend among children with severe juvenile rheumatoid arthritis who had higher rates of coping. For the individual stressful events, the rate of coping varied from 46% to 86%. The highest rates of coping responses were found with the child's recent personal stressful event where adolescents with chronic illness were twice as likely to offer more complex coping responses. More children with chronic illness than healthy children offered coping strategies in response to venipuncture (p < .001) but not to dental injection. Children with chronic illness report coping as their predominant strategy for adapting to common painful and stressful events.(ABSTRACT TRUNCATED AT 250 WORDS)