Modulation Of Entry Research Articles

Topic-specific Infobuttons Reduce Search Time but their Clinical Impact is Unclear

A Review of:
 Del Fiol, Guilherme, Peter J. Haug, James J. Cimino, Scott P. Narus, Chuck Norlin, and Joyce A. Mitchell. ‚Effectiveness of Topic-specific Infobuttons: A Randomized Controlled Trial.‛ Journal of the American Medical Information Association 15.6 (2008): 752-9.
 
 Objective – To assess whether infobutton links that direct users to specific content topics (‚topic links‛) are more effective in answering clinical questions than links that direct users to general overview content (‚nonspecific links‛).
 
 Design – Randomized control trial.
 
 Setting – Intermountain Healthcare, an integrated system of 21 hospitals and over 120 outpatient clinics located in Utah and southeastern Idaho.
 
 Subjects – Ninety clinicians and 3,729 infobutton sessions.
 
 Methods – To ensure comparable group composition, subjects were paired and randomly allocated to the study groups. Clinicians in the intervention group had access to topic links, while those in the control group had access to nonspecific links. All subjects at Intermountain Healthcare use a Web-based electronic medical record system (EMR) called HELP2 Clinical Desktop with integrated infobutton links. An Infobutton Manager application defines the content topics and resources; in this case, Micromedex® (Thomson Healthcare, Englewood, CO) provided access to the topic links. The medication order entry module, the most popular of the outpatient modules, was selected to test the two configurations of infobuttons. A focus group of seven HELP2 users aided the researchers in determining the most salient topics to be displayed as a part of the intervention group's user-interface. The study measured infobutton session duration, or time spent seeking information, the number of infobutton sessions conducted, and the outcome and impact of the information seeking. A post-session questionnaire displayed randomly in 30% of sessions measured outcome and impact. The study was conducted between May and November, 2007. This project was funded in part by the National Library of Medicine.
 Main Results – Subjects in the intervention group spent 17.4% less time seeking information than those in the control group (35.5 seconds vs. 43 seconds, p = 0.008). The intervention group used infobuttons 20.5% more often (22 sessions vs. 17.5 sessions, p = 0.21) than those in the control group, a difference that was not statistically significant. Twenty-five subjects answered the post-session survey at least once for a total of 115 (9.9%) responses out of 1,161 possible sessions. The information seeking success rate was equally high in both groups (87.2% intervention vs. 89.4% control, p = .099). Subjects reported high positive clinical impact (i.e., decision enhancement or learning) in 62% of successful sessions. Subjects conveyed a moderate or high level of frustration in 80% of responses associated with unsuccessful sessions.
 
 Conclusion – Topic links provide a slight advantage in the clinical decision-making process by reducing the amount of time spent searching. But while the session length difference between the control and intervention groups is statistically significant, it is less clear whether the difference is clinically meaningful. As previous studies have indicated, infobuttons are able to answer clinical medication questions with a high success rate. It is unclear whether topic links have a clinically significant impact, or rather, whether they are more effective than nonspecific links. The authors believe that the study results ‚should generalize to high-frequency, medication-related infobutton users in other institutions‛ (758).

Does initial treatment focus influence outcomes for depressed substance abusers?

Interventions for alcohol- and substance-dependent adults with comorbid depressive disorders are needed, but few have been empirically tested. In a randomized clinical trial of two psychotherapy interventions for these disorders, we examined whether initial focus of treatment was related to retention, substance use, and depression outcomes. Both interventions, integrated cognitive–behavioral therapy (ICBT; n = 105) and twelve-step facilitation ( n = 92), were delivered in group formats with entry points every 4 weeks at the beginning of three content-distinct modules. Entry module (i.e., initial treatment focus) was not related to percentage days abstinent, proportion of the sample abstinent, or depression symptoms for either intervention. This was true at both 12 and 24 weeks postbaseline. Furthermore, attendance was similar for both treatments, regardless of initial treatment focus, with a single exception in the ICBT condition. Our findings support the use of modular formats with multiple or rotating entry points for psychotherapy group interventions.

Role of receptor polymorphism and glycosylation in syncytium induction and host range variation of ecotropic mouse gammaretroviruses

BackgroundWe previously identified unusual variants of Moloney and Friend ecotropic mouse gammaretroviruses that have altered host range and are cytopathic in cells of the wild mouse species Mus dunni. Cytopathicity was attributed to different amino acid substitutions at the same critical env residue involved in receptor interaction: S82F in the Moloney variant Spl574, and S84A in the Friend mouse leukemia virus F-S MLV. Because M. dunni cells carry a variant CAT-1 cell surface virus receptor (dCAT-1), we examined the role of this receptor variant in cytopathicity and host range.ResultsWe expressed dCAT-1 or mCAT-1 of NIH 3T3 origin in cells that are not normally infectible with ecotropic MLVs and evaluated the transfectants for susceptibility to virus infection and to virus-induced syncytium formation. The dCAT-1 transfectants, but not the mCAT-1 transfectants, were susceptible to virus-induced cytopathicity, and this cytopathic response was accompanied by the accumulation of unintegrated viral DNA. The dCAT-1 transfectants, however, did not also reproduce the relative resistance of M. dunni cells to Moloney MLV, and the mCAT-1 transfectants did not show the relative resistance of NIH 3T3 cells to Spl574. Western analysis, use of glycosylation inhibitors and mutagenesis to remove receptor glycosylation sites identified a possible role for cell-specific glycosylation in the modulation of virus entry.ConclusionVirus entry and virus-induced syncytium formation using the CAT-1 receptor are mediated by a small number of critical amino acid residues in receptor and virus Env. Virus entry is modulated by glycosylation of cellular proteins, and this effect is cell and virus-specific.

Drosophila Ebony Activity Is Required in Glia for the Circadian Regulation of Locomotor Activity

Previous studies suggest that glia may be required for normal circadian behavior, but glial factors required for rhythmicity have not been identified in any system. We show here that a circadian rhythm in Drosophila Ebony (N-beta-alanyl-biogenic amine synthetase) abundance can be visualized in adult glia and that glial expression of Ebony rescues the altered circadian behavior of ebony mutants. We demonstrate that molecular oscillator function and clock neuron output are normal in ebony mutants, verifying a role for Ebony downstream of the clock. Surprisingly, the ebony oscillation persists in flies lacking PDF neuropeptide, indicating it is regulated by an autonomous glial oscillator or another neuronal factor. The proximity of Ebony-containing glia to aminergic neurons and genetic interaction results suggest a function in dopaminergic signaling. We thus suggest a model for ebony function wherein Ebony glia participate in the clock control of dopaminergic function and the orchestration of circadian activity rhythms.

Experiences with an Interoperable Data Acquisition Platform for Multi-centric Research Networks Based on HL7 CDA

Today's increasing specialization of medicine necessitates the integration of telematic platforms for cross-institutional cooperation. In order to leverage the strengths of each cooperating institution a centralized unified storage using shared electronic patient records (EPRs) as well as secured remote data entry capabilities for supporting collaborative clinical research and care is essential. The objective of this project was to develop and introduce into routine use such a shared remote data entry (RDE) platform for the German multicentric Epidermolysis Bullosa (EB) network. An existing telematic application was extended by a remote data entry (RDE) module enabling the storage of structured data and pedigrees. HL7 Clinical Document Architecture (CDA) was chosen as a suitable standardized storage format that provides flexibility and future interoperability. Flexible data entry forms adaptable to distinct medical domains were implemented using XML-based technologies. A flexible and comprehensive EPR/RDE platform was successfully implemented in the German EB network. A set of specific data entry forms was created to fully cover the network's documentation needs. The platform has been in productive use since 2005. Standardized documentation by using HL7 CDA to store the medical research data as an EPR can contribute to high interoperability and an easier integration of heterogeneous health care information systems. Existing XML technologies offer a high degree of flexibility and adaptability to distinct medical domains. The ongoing development of standards (e.g. HL7 CDA R2) and interfaces (CDA/CDISC bridge) could further improve semantic and syntactic interoperability.

Epo Modulation of Cell Cycle Regulatory Genes Via PY343/STAT5 and PI3K Pathways in Primary Erythroblasts.

Erythropoietin's essential role in late erythropoiesis is ascribed to survival effects on colony forming unit-erythroid-derived erythroblasts. However, several studies have pointed to possible Epo regulation of cell cycle factors, and proliferation. To investigate this issue, developmentally-staged KitposCD71high erythroblasts were prepared from murine marrow; were shown to proliferate in response to low-dose Epo (0.1U/ml); and were used in the Affymetrix 430 2.0 array-based discovery of Epo-modulated cell cycle regulatory genes. In keeping with certain prior studies, myelocytomatosis oncogene (c-Myc) was induced while cyclin-dependent kinase inhibitor 1B (p27) was inhibited several-fold. Beyond this, four select cell cycle progression factors were rapidly up-modulated up to five-fold by Epo: nuclear protein 1 (Nupr1), G1 to S phase transition 1 (Gspt1), early growth response 1 (Egr1) and Ngfi-A binding protein 2 (Nab2). B-cell leukemia 6 (Bcl6) in contrast, was down-modulated several-fold. Finally, among cyclins, D2 was up-modulated ~5-fold while G2 was selectively down-modulated 4- to 5-fold (All findings were confirmed by RT-PCR). Studies in erythroblasts expressing knocked-in minimal erythropoietin receptor (EpoR) alleles indicated EpoR proximal tyrosine-343 (PY343) regulation of cyclin D2 induction, and EpoR C-terminal regulation of cyclin G2 inhibition. Despite the capacity of a PY-null EpoR-HM allele to support steady-state erythropoiesis, EpoR-HM erythroblasts proved to be skewed in cell cycle phases, especially in G2/M (0.01% vs ~5% for wt-EpoR and EpoR-H alleles). For cyclin D2, cyclin G2, p27 and Bcl6, in silico models for promoter regulation are outlined which highlight Stat and Forkhead action. In summary, specific new evidence is provided for erythroblast cell cycle entry modulation by Epo (especially as elevated during anemia) via discrete EpoR subdomains, and nine selectively modulated cell cycle regulatory genes.

Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxin

A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca(2+)](c)), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na(+). Li(+) decreased the PTX-evoked rise in [Ca(2+)](c); replacement of Na(+) by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca(2+)](c) increase by PTX was strongly reduced after inhibition of the reverse operation of the Na(+)/Ca(2+) exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca(2+)-ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na(+)-dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na(+)/Ca(2+) exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space.

HCV and lipoproteins: Is oxLDL an Achilles' heel of the Trojan horse?

HCV and lipoproteins: Is oxLDL an Achilles' heel of the Trojan horse?

Local modulation of plus-end transport targets herpesvirus entry and egress in sensory axons

The core structures of many viruses move within cells by association with host cytoskeletal motor proteins; however, the mechanisms by which intracellular viral particles are transported toward sites of replication or the cell periphery at distinct stages of infection remain to be understood. The regulation of herpesvirus directional transport in sensory neurons was examined by tracking individual viral capsids within axons at multiple frames per s. After entry into axons, capsids underwent bidirectional and saltatory movement to the cell body independently of endosomes. A comparison of entry transport to a previous analysis of capsid axonal transport during egress revealed that capsid targeting in and out of cells occurs by modulation of plus-end, but not minus-end, motion. Entry transport was unperturbed by the presence of egressing virus from a prior infection, indicating that transport direction is not modulated globally by viral gene expression, but rather directly by a component of the viral particle.

275.Calmodulin-dependent nuclear import pathway of the testis-determining factor SRY

Modulation of the nuclear entry of transcription factors (TFs) and chromatin components is a means by which eukaryotic cells can regulate gene expression in response to extracellular signals and the cell cycle during differentiation and development. TFs and chromatin components access the nucleus through nuclear localisation sequences (NLSs), which mediate interaction with components of the cellular nuclear import machinery, such as members of the importin superfamily. The Ca2+-binding protein calmodulin (CaM ) has previously been shown to bind at or near NLSs in several nuclear-localising proteins that have important roles in testis development including the Y chromosome-encoded HMG-domain-carrying chromatin remodelling factor SRY, and related factor SOX9, both of which are key regulators of gonadal development. SRY function in the nucleus of somatic cells of the fetal gonad, in particular, is essential for development of a testis in males. Here we present new findings implicating a role for CaM in modulating SRY nuclear accumulation, whereby treatment of transfected cells with CaM antagonists significantly reduces nuclear accumulation of green fluorescent protein (GFP)-fusion proteins encoding either full length SRY or the SRY HMG domain alone. An in vitro nuclear transport assay using bacterially expressed fluorescent proteins showed similar results, with native gel electrophoresis/fluorimaging and fluorescence polarisation assays, indicating direct binding of CaM to the SRY HMG domain in Ca2+-dependent fashion. Since clinical mutations resulting in sex reversal occur within SRY's CaM-binding NLS, these results may shed new insight into CaM-dependent pathways of nuclear protein import, and how this may relate to testis development.

Regulation of K+ currents by CO in carotid body type I cells and pulmonary artery smooth muscle cells.

Potassium channels are a diverse group of proteins that control membrane excitability and their regulation can influence cell signalling through the modulation of calcium entry. A subset of these channels appears to be particularly sensitive to oxygen tension and these play an important role in the regulation of arterial blood gas tensions. In pulmonary arterial smooth muscle cells, K+ channel activity is linked to contractile tone. Factors that regulate the activity of these channels therefore have a major influence upon blood vessel diameter and therefore on pulmonary artery (PA) blood pressure, thus altering regional ventilation -perfusion ratios in the lung. In carotid body (CB) type I cells, K+ channel activity is linked to the secretion of a variety of putative neurotransmitter and regulation of these channels therefore influences carotid sinus nerve activity and thus cardiorespiratory control. In both systems, hypoxia decreases the activity of a variety of K+ channels, some of which regulate the resting membrane potential. In CB type I cells and in PA smooth muscle cells, hypoxia decreases the activity of the TASK-1 channel (a background K+ channels in type one cells and probably KN channels in PA (Gurney et al.2002)), large conductance Ca2+-activated (BKca) channels and/or voltage-activated (Kv) channels depending on species and experimental conditions (Lopez-Barneo et al.2001).

Modulation of entry of enveloped viruses by cholesterol and sphingolipids (Review).

Enveloped animal viruses infect host cells by fusion of viral and target membranes. This crucial fusion event occurs either with the plasma membrane of the host cells at the physiological pH or with the endosomal membranes at low pH and is triggered by specific glycoproteins in the virus envelope. Both lipids and proteins play critical and co-operative roles in the fusion process. Interactions of viral proteins with their receptors direct which membranes fuse and viral fusion proteins then drive the process. These fusion proteins operate on lipid assemblies, whose physical and mechanical properties are equally important to the proper functioning of the process. Lipids contribute to the viral fusion process by virtue of their distinct chemical structure, composition and/or their preferred partitioning into specific microdomains in the plasma membrane called 'rafts'. An involvement of lipid rafts in viral entry and membrane fusion has been examined recently. However, the mechanism(s) by which lipids as dynamic raft components control viral envelope-glycoprotein-triggered fusion is not clear. This paper will review literature findings on the contribution of the two raft-associated lipids, cholesterol and sphingolipids in viral entry.

Corticosterone increases serotonin type-3 receptor mRNA in rat pheochromocytoma-12 cells

Serotonin type-3 (5-HT3) receptors are cation permeable membrane receptors which are involved in modulation of calcium entry in neuronal cells. Along with other ion-channels such as the N-methyl- d-aspartate receptor, it appears to be a target for the actions of ethanol and has been the focus of considerable work in this regard. Since in animals, ethanol exposure results in elevations of corticosteroids in both acute and chronic conditions, we studied the effects of both ethanol and corticosteroid exposure on 5-HT3 gene expression in an in situ pheochromocytoma-12 (PC12) cell model. We found that ethanol exposure alone (80 mM×4 days) did not significantly alter target gene expression. Corticosterone (CORT) (50, 150, and 300 ng/ml) resulted in significant increases in 5-HT3 expression which were attenuated by mifeprestone (50 ng/ml). Ethanol in combination with CORT did not significantly alter the increase in 5- HT3 mRNA seen with CORT alone. We conclude that in PC12 cells, exposure to CORT at physiologically relevant concentrations increases 5-HT3 gene expression.

Anticarcinogenic effect of FTY720 in human prostate carcinoma DU145 cells: modulation of mitogenic signaling, FAK, cell-cycle entry and apoptosis.

Despite the high frequency of prostate cancer, therapeutic options for advanced disease are limited to chemotherapy, radiation or hormonal therapy and eventually fail in all patients. Therefore, alternative approaches need to be developed. We previously reported that FTY720, a metabolite from Isaria sinclarii, is a unique antitumor agent for an androgen-independent prostate cancer cell line and requires caspase-3 activation in apoptosis. In our study, we have evaluated the effect of FTY720 on a family of mitogen-activated protein kinases (MAPKs), focal adhesion kinase (FAK), mitochondrial transmembrane potential, caspase-9 and caspase-8 and analyzed the expression of some cell-cycle regulator proteins in DU145 cells in order to understand the various antitumor effects of FTY720. Apoptosis was quantified by phosphatidylserine exposure. Activation of MAPKs, cleavage of caspase-9 and caspase-8, status of cyclin-dependent kinases (CDKs) and Cip1/p21, a cyclin-dependent kinase inhibitor, were evaluated by Western blot analysis, in addition to FAK and phospho-FAK immunoprecipitation and cell-cycle analysis by FACScan. We found that in DU145 cells, 40 microM FTY720 caused activation of p38 MAPK and the upstream kinase MKK3/MKK6 but not SAPK/JNK. Mitochondrial transmembrane potential, FAK and ERK1/2 were reduced while caspase-9 and caspase-8 were cleaved. The p38-specific inhibitor had no effect on apoptosis induced by FTY720, whereas z-VAD.FMK, a broad-spectrum caspase inhibitor, did not inhibit the p38 MAPK activation. An amount of 20 microM FTY720 resulted in G(1) arrest and a decrease of CDK2 as well as CDK4, whereas it induced Cip1/p21. FTY720 may exert anticarcinogenic effects against prostate cancer cells possibly involving modulation of mitogenic signaling, cell-cycle regulators, induction of G(1) arrest and apoptotic death in DU145 cells.

Traumatic Axonal Injury Induces Calcium Influx Modulated by Tetrodotoxin-Sensitive Sodium Channels

Diffuse axonal injury (DAI) is one of the most common and important pathologies resulting from the mechanical deformation of the brain during trauma. It has been hypothesized that calcium influx into axons plays a major role in the pathophysiology of DAI. However, there is little direct evidence to support this hypothesis, and mechanisms of potential calcium entry have not been explored. In the present study, we used an in vitro model of axonal stretch injury to evaluate the extent and modulation of calcium entry after trauma. Using a calcium-sensitive dye, we observed a dramatic increase in intra-axonal calcium levels immediately after injury. Axonal injury in a calcium-free extracellular solution resulted in no change in calcium concentration, suggesting an extracellular source for the increased post-traumatic calcium levels. We also found that the post-traumatic change in intra-axonal calcium was completely abolished by the application of the sodium channel blocker tetrodotoxin or by replacement of sodium with N-methyl-d-glucamine. In addition, application of the voltage-gated calcium channel (VGCC) blocker omega-conotoxin MVIIC attenuated the post-traumatic increase in calcium. Furthermore, blockade of the Na(+)-Ca(2+) exchanger with bepridil modestly reduced the calcium influx after injury. In contrast to previously proposed mechanisms of calcium entry after axonal trauma, we found no evidence of calcium entry through mechanically produced pores (mechanoporation). Rather, our results suggest that traumatic deformation of axons induces abnormal sodium influx through mechanically sensitive Na(+) channels, which subsequently triggers an increase in intra-axonal calcium via the opening of VGCCs and reversal of the Na(+)-Ca(2+) exchanger.

HCO 3− ions modify the role of PKC isoforms in the modulation of rat mast cell functions

PKC and the intracellular calcium signal are two well-known intracellular signaling pathways implicated in the induction of mast cell exocytosis. Both signals are modified by the presence or absence of HCO 3 − ions in the external medium. In this work, we studied the regulation of the exocytotic process by PKC isozymes and its relationship with HCO 3 − ions and PKC modulation of the calcium entry. The calcium entry, induced by thapsigargin and further addition of calcium, was inhibited by PMA, a PKC activator, and enhanced by 500 nM GF109203X, which inhibits Ca 2+-independent PKC isoforms. PMA inhibition of the Ca 2+ entry was reverted by 500 and 50 nM GF109203X, which inhibit Ca 2+-independent and Ca 2+-dependent isoforms, respectively, and Gö6976, a specific inhibitor of Ca 2+-dependent PKCs. Thus, activation of Ca 2+-dependent and Ca 2+-independent PKC isoforms inhibit Ca 2+ entry in rat mast cells, either in a HCO 3 −-buffered or a HCO 3 −-free medium. PMA, GF109203X, Gö6976 and rottlerin, a specific inhibitor of PKC δ, were also used to study the role of PKC isoforms in the regulation of exocytosis induced by thapsigargin, ionophore A23187 and PMA. The results demonstrate that Ca 2+-dependent PKC isoforms inhibit exocytosis in a HCO 3 −-dependent way. Moreover, Ca 2+-independent PKC δ was the main isoform implicated in promotion of Ca 2+-dependent mast cell exocytosis in the presence or absence of HCO 3 −. The role of PKC isoforms in the regulation of mast cell exocytosis depends on the stimulus and on the presence or absence of HCO 3 − ions in the medium, but it is independent of PKC modulation of the Ca 2+ entry.

Presenilin-Mediated Modulation of Capacitative Calcium Entry

We studied a novel function of the presenilins (PS1 and PS2) in governing capacitative calcium entry (CCE), a refilling mechanism for depleted intracellular calcium stores. Abrogation of functional PS1, by either knocking out PS1 or expressing inactive PS1, markedly potentiated CCE, suggesting a role for PS1 in the modulation of CCE. In contrast, familial Alzheimer's disease (FAD)–linked mutant PS1 or PS2 significantly attenuated CCE and store depletion–activated currents. While inhibition of CCE selectively increased the amyloidogenic amyloid β peptide (Aβ42), increased accumulation of the peptide had no effect on CCE. Thus, reduced CCE is most likely an early cellular event leading to increased Aβ42 generation associated with FAD mutant presenilins. Our data indicate that the CCE pathway is a novel therapeutic target for Alzheimer's disease.

Radiation safety system of the B-Factory at the Stanford Linear Accelerator Center.

The radiation safety system of the B-Factory accelerator facility at the Stanford Linear Accelerator Center is described. The radiation safety system, which is designed to protect people from prompt radiation exposure due to beam operation, consists of the access control system and the radiation containment system. The access control system prevents people from being exposed to the very high radiation levels inside a beamline shielding enclosure. The access control system consists of barriers, a standard entry module at every entrance, and beam stoppers. The radiation containment system prevents people from being exposed to the radiation outside a shielding enclosure due to either normal or abnormal operation. The radiation containment system consists of power limiting devices, shielding, dump and collimator, and an active radiation monitoring system. The inter-related elements for the access control system and radiation containment system, as well as the associated interlock network, are described. The policies and practices used in establishing the radiation safety system are also compared with the regulatory requirements.

Modulation of phosphate uptake and amphotropic murine leukemia virus entry by posttranslational modifications of PIT-2.

PIT-2 is a type III sodium phosphate cotransporter and the receptor for amphotropic murine leukemia viruses. We have investigated the expression and the functions of a tagged version of PIT-2 in CHO cells. PIT-2 remained equally abundant at the cell surface within 6 h following variation of the phosphate supply. In contrast, the efficiency of phosphate uptake and retrovirus entry was inversely related to the extracellular phosphate concentration, indicating that PIT-2 activities are modulated by posttranslational modifications of cell surface molecules induced by phosphate. Conformational changes of PIT-2 contribute to both activities, as shown by the inhibitory effect of sulfhydryl reagents known as inhibitors of type II cotransporters. A physical association of PIT-2 with actin was demonstrated. Modifications of the actin network were induced by variations of the concentrations of extracellular phosphate, cytochalasin D, or lysophosphatidic acid. They revealed that the formation of actin stress fibers determines the cell surface distribution of PIT-2, the internalization of the receptor in response to virus binding, and the capacity to process retrovirus entry. Thus, the presence of PIT-2 at the cell surface is not sufficient to ensure phosphate transport and susceptibility to amphotropic retrovirus infection. Further activation of cell surface PIT-2 molecules is required for these functions.

Joint Limiting Values of N, Mean, and SD

A graphical Win32 computer program for variance function estimation (1) is currently under development in this department, and design of the data entry module produced an interesting “impossible values” issue. The program incorporates two distinct data entry spreadsheets: (a) a grid for entering or importing sets of raw replicated measurements (e.g., runs of QC or other precision results), and (b) a grid for entering sets of values of N, mean, and SD (e.g., to allow estimation of a variance function from the summarized precision data often found in the literature). Restricting raw measurements to a sensible laboratory oriented range (e.g., 0–10) is a simple matter, but …