Cancer registries fear collapse. BUPA wants to ensure systematic transfer of data.
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Humans↗
Biomedical subjects
V Warren
Publications and source records attributed to V Warren.
WIN 17317-3, a new high-affinity probe for voltage-gated sodium channels.
The iminodihydroquinoline WIN 17317-3 was previously shown to inhibit selectively the voltage-gated potassium channels, K(v)1.3 and K(v)1.4 [Hill, R. J., et al. (1995) Mol. Pharmacol. 48, 98-104; Nguyen, A., et al. (1996) Mol. Pharmacol. 50, 1672-1679]. Since these channels are found in brain, radiolabeled WIN 17317-3 was synthesized to probe neuronal K(v)1 channels. In rat brain synaptic membranes, [(3)H]WIN 17317-3 binds reversibly and saturably to a single class of high-affinity sites (K(d) 2.2 +/- 0.3 nM; B(max) 5.4 +/- 0.2 pmol/mg of protein). However, the interaction of [(3)H]WIN 17317-3 with brain membranes is not sensitive to any of several well-characterized potassium channel ligands. Rather, binding is modulated by numerous structurally unrelated sodium channel effectors (e.g., channel toxins, local anesthetics, antiarrhythmics, and cardiotonics). The potency and rank order of effectiveness of these agents in affecting [(3)H]WIN 17317-3 binding is consistent with their known abilities to modify sodium channel activity. Autoradiograms of rat brain sections indicate that the distribution of [(3)H]WIN 17317-3 binding sites is in excellent agreement with that of sodium channels. Furthermore, WIN 17317-3 inhibits sodium currents in CHO cells stably transfected with the rat brain IIA sodium channel with high affinity (K(i) 9 nM), as well as agonist-stimulated (22)Na uptake in this cell line. WIN 17317-3 interacts similarly with skeletal muscle sodium channels but is a weaker inhibitor of the cardiac sodium channel. Together, these results demonstrate that WIN 17317-3 is a new, high-affinity, subtype-selective ligand for sodium channels and is a potent blocker of brain IIA sodium channels.
Animals↗
Purchasing. What the doctors ordered.
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Clinical Protocols↗
Ceftriaxone (Rocephin) in abdominal trauma.
A prospective study was undertaken to evaluate the use of ceftriaxone in patients with abdominal trauma admitted to our hospital over a period of 6 months. Because of the large trauma load and an unacceptable waiting period before surgery combined with the fact that many patients on 6-hourly antibiotic regimes often did not receive their second and third doses, it was decided to use ceftriaxone because of its long half-life with maintenance of fluid and tissue concentrations for 24-48 hours. Because ceftriaxone is not reliably effective against anaerobic organisms such as Bacteroides fragilis, it was decided to add metronidazole as a combined initial dose. Two hundred ninety patients were entered in this trial, of which there were 259 stab wounds (89.3%), 20 missile injuries (6.9%), and 11 blunt injuries (3.8%). It was found that the mean delay between injury and initial dosage of ceftriaxone was 9.1 hours, with a range of 1-126 hours, and the mean delay between antibiotic therapy and operation 6.3 hours, with a range of 0-39 hours. The organs most frequently injured were the small bowel, the large bowel, the stomach, and the liver. Wound infection developed in only 4 patients (1.4%); intra-abdominal sepsis did not occur; and 35 patients (12%) developed respiratory infections. There were no deaths. We conclude that ceftriaxone, because of its 24-hour dosage was not only convenient but also adequate to prevent intra-abdominal sepsis and there was no difference in cost between this product and our previous protocol of 6-hourly antibiotic regime.
Abdominal Injuries↗
Identification of an actin-binding protein from Dictyostelium as elongation factor 1a.
Indirect evidence has implicated an interaction between the cytoskeleton and the protein synthetic machinery. Two recent reports have linked the elongation factor 1a (EF-1a) which is involved in protein synthesis, with the microtubular cytoskeleton. In situ hybridization has, however, revealed that the messages for certain cytoskeletal proteins are preferentially associated with actin filaments. ABP-50 is an abundant actin filament bundling protein of native relative molecular mass 50,000 (50K) isolated from Dictyostelium discoideum. Immunofluorescence studies show that ABP-50 is present in filopodia and other cortical regions that contain actin filament bundles. In addition, ABP-50 binds to monomeric actin in the cytosol of unstimulated cells and the association of ABP-50 with the actin cytoskeleton is regulated during chemotaxis. Through complementary DNA sequencing and subsequent functional analysis, we have identified ABP-50 as D. discoideum EF-1a. The ability of EF-1a to bind reversibly to the actin cytoskeleton upon stimulation could provide a mechanism for spatially and temporally regulated protein synthesis in eukaryotic cells.
Amino Acid Sequence↗
Identification of a short sequence essential for actin binding by Dictyostelium ABP-120.
Tryptic digestion of ABP-120, an actin cross-linking protein from Dictyostelium discoideum, generates a ladder of peptides differing in molecular mass by 13,000 daltons, indicating a structural repeat within the molecule. A number of peptides bind actin with the smallest having a molecular mass of 17,000 daltons (T17). Our sedimentation assays also show that a peptide of 14,000 daltons does not bind actin. Using the full-length cDNA sequence (Noegel, A., Rapp, S., Lottspeich, F., Schleicher, M., and Stewart, M. (1989) J. Cell Biol. 109, 607-618) and protein sequencing techniques, we have determined that T17 begins at residue 89 while T14 begins at residue 116. Therefore we have localized 27 amino acids which are essential for actin binding activity. This region is at the end of the molecule, distal from the repetitive beta-sheet region predicted from the cDNA sequence, and displays high sequence identity with regions in the N termini of ABP/filamin, dystrophin, beta-spectrin, and alpha-actinin.
Actins↗
Isolation of an abundant 50,000-dalton actin filament bundling protein from Dictyostelium amoebae.
A monomeric actin bundling protein with a native molecular weight of approximately 50,000 (ABP-50) has been isolated from amoebae of Dictyostelium discoideum. ABP-50 cross-links F-actin to form tightly packed bundles, some of which are highly ordered. It exhibits a Kd of 2.1 microM and a molar ratio to actin of 1:1 in bundles. Calcium and ATP at physiological concentrations have no effect on these activities. ABP-50 is immunologically unrelated to 30-kDa protein, a previously described bundling protein from Dictyostelium. Immunofluorescence with affinity-purified polyclonal antibodies indicates that ABP-50 is localized in regions of the amoeboid cell cortex containing actin bundles. The molar ratio of ABP-50 to actin is approximately 1:5 in vivo. Therefore, the abundance of ABP-50 suggests that it may be responsible for the majority of the bundling activity in these cells.
Actins↗
Mechanisms of amoeboid chemotaxis: an evaluation of the cortical expansion model.
In this work we evaluate the cortical expansion model for amoeboid chemotaxis with regard to new information about molecular events in the cytoskeleton following chemotactic stimulation of Dictyostelium amoebae. A rapid upshift in the concentration of chemoattractant can be used to synchronize the motile behavior of a large population of cells. This synchrony presents an opportunity to study the biochemical basis of morphological changes such as pseudopod extension that are required for amoeboid chemotaxis. Changes in the composition and activity of the cytoskeleton following stimulation can be measured with precision and correlated with important morphological changes. Such studies demonstrate that activation of actin nucleation is one of the first and most crucial events in the actin cytoskeleton following stimulation. This activation is followed by incorporation of specific actin cross-linking proteins into the cytoskeleton, which are implicated in the extension of pseudopods and filopods. These results, as well as those from studies with mutants deficient in myosin, indicate that cortical expansion, driven by focal actin polymerization, cross-linking and gel osmotic swelling, is an important force for pseudopod extension. It is concluded that whereas three forces, frontal sliding, tail contraction, and cortical expansion may cooperate to produce amoeboid movement, the cortical expansion model offers the simplest explanation of how focal stimulation with a chemoattractant causes polarized pseudopod extension.
Actins↗
Ethical obligation arising from routine screening.
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Ethics, Medical↗
Changes in the association of actin-binding proteins with the actin cytoskeleton during chemotactic stimulation of Dictyostelium discoideum.
Triton-insoluble cytoskeletons were isolated from Dictyostelium discoideum AX3 cells prior to and following stimulation with 2'deoxy cyclic adenosine monophosphate (cAMP). Temporal changes in the content of actin and a 120,000 dalton actin-binding protein (ABP-120) in cytoskeletons following stimulation were monitored. Both actin and ABP-120 were incorporated into the cytoskeleton at 30-40 seconds following stimulation, which is cotemporal with the onset of pseudopod extension during stimulation of amoebae with chemoattractants. Changes in the content of total cytoskeletal protein and cytoskeletal myosin were determined under the same experimental conditions as controls. These proteins exhibited different kinetics from those of cytoskeletal ABP-120 and actin following the addition of 2'deoxy cAMP. The authors concluded that the association of ABP-120 with the cytoskeleton is regulated during cAMP signalling. Furthermore, these results indicate that ABP-120 is involved in cross-linking newly assembled actin filaments into the cytoskeleton during chemoattractant-stimulated pseudopod extension.
Actins↗
Transduction of the chemotactic signal to the actin cytoskeleton of Dictyostelium discoideum.
Dictyostelium discoideum amebae chemotax toward folate during vegetative growth and toward extracellular cAMP during the aggregation phase that follows starvation. Stimulation of starving amebae with extracellular cAMP leads to both actin polymerization and pseudopod extension (Hall et al., 1988, J. Cell. Biochem. 37, 285-299). We have identified an actin nucleation activity (NA) from starving amebae that is regulated by cAMP receptors and controls actin polymerization (Hall et al., 1989, J. Cell Biol., in press). We show here that NA from vegetative cells is also regulated by chemotactic receptors for folate. Our studies indicate that NA is an essential effector in control of the actin cytoskeleton by chemotactic receptors. Guided by a recently proposed model for signal transduction from the cAMP receptor (Snaar-Jagalska et al., 1988, Dev. Genet. 9, 215-225), we investigated which of three signaling pathways activates the NA effector. Treatment of whole cells with a commercial pertussis toxin preparation (PT) inhibited cAMP-stimulated NA. However, endotoxin contamination of the PT appears to account for this effect. The synag7 mutation and caffeine treatment do not inhibit activation of NA by cAMP. Thus, neither activation of adenylate cyclase nor a G protein sensitive to PT treatment of whole cells is necessary for the NA response. Actin nucleation activity stimulated with folate is normal in vegetative fgdA cells. However, cAMP suppresses rather than activates NA in starving fgdA cells. This indicates that the components of the actin nucleation effector are present and that a pathway regulating the inhibitor(s) of nucleation remains functional in starving fgdA cells. The locus of the fgdA defect, a G protein implicated in phospholipase C activation, is directly or indirectly responsible for transduction of the stimulatory chemotactic signal from cAMP receptors to the nucleation effector in Dictyostelium.
Actins↗
Identification of actin nucleation activity and polymerization inhibitor in ameboid cells: their regulation by chemotactic stimulation.
Actin polymerization occurs in amebae of Dictyostelium discoideum after chemotactic stimulation (Hall, A. L., A. Schlein, and J. Condeelis. 1988. J. Cell. Biochem. 37:285-299). When cells are lysed with Triton X-100 during stimulation, an actin nucleation activity is detected in lysates by measuring the rate of pyrene-labeled actin polymerization. This stimulated nucleation activity is closely correlated with actin polymerization observed in vivo in its kinetics, developmental regulation, and cytochalasin D sensitivity. Actin polymerization is coordinate with pseudopod extension in synchronized populations of cells and is correlated with the accumulation of F actin in pseudopods. The stimulated actin nucleation activity is present in low-speed pellets from Triton lysates (cytoskeletons) within 3 s of stimulation and is stable compared with the nucleation activity of whole cell lysates. Low-speed supernatants contain a reversible inhibitor of the actin nucleation activity that is itself regulated by chemotactic stimulation. Neither activity requires Ca2+ and both are fully expressed in 10 mM EGTA. Fractions containing the inhibitor do not sever actin filaments but do inhibit actin polymerization that is seeded by fragments of purified F actin. These results indicate that chemotactic stimulation of Dictyostelium discoideum generates both an actin-nucleating activity and an actin-polymerization inhibitor, and suggest that the parallel regulation of these two activities leads to the transient phases of actin polymerization observed in vivo. The different compartmentation of these two activities may account for polarized pseudopod extension in gradients of chemoattractant.
Actins↗
Actin polymerization and pseudopod extension during amoeboid chemotaxis.
Amoebae of the cellular slime mold Dictyostelium discoideum are an excellent model system for the study of amoeboid chemotaxis. These cells can be studied as a homogeneous population whose response to chemotactic stimulation is sufficiently synchronous to permit the correlation of the changes in cell shape and biochemical events during chemotaxis. Having demonstrated this synchrony of response, we show that actin polymerization occurs in two stages during stimulation with chemoattractants. The assembly of F-actin that peaks between 40 and 60 sec after the onset of stimulation is temporally correlated with the growth of new pseudopods. F-actin, which is assembled by 60 sec after stimulation begins, is localized in the new pseudopods that are extended at this time. Both stages of actin polymerization during chemotactic stimulation involve polymerization at the barbed ends of actin filaments based on the cytochalasin sensitivity of this response. We present a hypothesis in which actin polymerization is one of the major driving forces for pseudopod extension during chemotaxis. The predictions of this model, that localized regulation of actin nucleation activity and actin filament cross-linking must occur, are discussed in the context of current models for signal transduction and of recent information regarding the types of actin-binding proteins that are present in the cell cortex.
Actins↗
Structure-activity profile of a series of novel triazoloquinazoline adenosine antagonists.
During a search for benzodiazepine receptor modulators, a highly potent adenosine antagonist (CGS 15943) was discovered. The compound was defined as a resonance-stabilized hybrid of the canonical structures 9-chloro-2-(2-furyl)[1,2,4]triazolo[1,5-c]quinazolin-5-amine (2a) and 9-chloro-2-(2-furyl)-5,6-dihydro[1,2,4]triazolo[1,5-c]-quinazolin- 5-imine (2b). Spectroscopic evidence and chemical reactivity in polar media favor the amine form 2a as the major contributor of the two canonical structures. The synthesis of 2 and some of its analogues and the structure-activity relationships in four biological test systems are described. Replacement of the 9-chloro group by hydrogen, hydroxyl, or methoxyl gave compounds with comparable binding potency at the A1 and A2 receptors but much less activity as antagonists of 2-chloroadenosine in guinea pig tracheal strips. Alkylation of the 5-amino group caused, in general, a loss of binding activity, particularly at the A2 receptor, as well as complete loss of activity in the tracheal model. Modification of the 2-furyl group caused a pronounced loss of activity in all of the test systems.
Adenosine↗
Effects of rise-fall time, frequency, and intensity on the early/middle evoked response.
Auditory evoked responses to tone pips were recorded on 10 normally hearing adults. Tone pips centered at 500 and 2000 Hz with 1, 2, and 4 ms rise-fall times were presented at intensities of 40, 30, 20, and 10 dB nHL. The band-pass of the recording-amplifier system was set to 55 and 3000 Hz. Responses were measured during the first 25 ms following the onset of the stimulus and the first three prominent waves were labeled P10, N15, and P20. The results indicated that varying rise-fall times from 1 to 4 ms had little effect on the detectability of these waves. Consequently, the 4-ms rise-fall time was recommended because of its greater frequency specificity. The number of identifiable responses was similar for both 500 and 2000 Hz for waves P10, N15, and P20. The similarity in the number of detectable responses suggests that any of these waves may be used as a threshold indicator. The acoustic/physiologic mechanisms underlying the latency changes are discussed.
Acoustic Stimulation↗
Slope characteristics of CID W-22 word functions in elderly hearing-impaired listeners.
Some variables affecting the slope of monosyllabic word functions were investigated among subjects having mild-to-moderate sensorineural hearing loss. Slope is an important variable because it determines the intensity range and the step size that is likely to accurately and efficiently describe the function. Eighty-one ears from 60 elderly subjects were tested with the Auditec recordings of the CID W-22 words. Slopes were computed between the 20 and 80% intelligibility points from the individual functions. The results indicated that the magnitude of hearing loss did not affect the slope of the intelligibility function. That is, slopes remained at approximately 3% per dB even though spondaic thresholds varied over a 45-dB range (15-60 dB HTL). The audiometric configuration was found to affect slope, although this relationship was weak (r = .30). As the audiogram progressed from flat to steeply falling, the slope decreased from about 3.5% per dB to 2.5% per dB. With subjects having flat and falling audiograms, slope was steeper for the 20-50% intelligibility segment (4.3% per dB) than for the 50-80% interval (2.9% per dB). These subjects also exhibited substantial differences in mean slope, depending on the procedure selected for computations. The mean of individual slopes was steepest (3.3% pr dB), whereas the mean slope was only 2.4% per dB when computed from the function derived in the conventional manner by averaging intelligibility scores at fixed intensities.
Aged↗
Intractable angina pectoris. Combined therapy with propranolol and permanent pervenous pacemaker.
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Aged↗