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Results for “Enhancer mapping”

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At least 109 records · Page 6Linked to original sources
PubMed1987

Enhancement of ambulation-increasing effect produced by repeated administration of methamphetamine in rats and neurochemical changes in catecholaminergic neurons.

Male rats of the Wistar strain were repeatedly given methamphetamine (MAP) at 0.5 mg/kg, s.c., 10 times at a fixed interval of 4 days in different environmental situations. The effects of MAP administration on ambulatory activity and neurochemical parameters in the brain were investigated. MAP (0.5 mg/kg) markedly increased ambulatory activity. The ambulation-increasing effect of MAP was progressively enhanced without accompanying stereotyped behaviors when the drug was repeatedly given in the activity cage. The once enhanced effect was considered to be irreversible. In addition, the pretreatment with MAP in the activity cage produced a decrease in the maximum density of 3H-spiperone binding sites in the striatum and that of 3H-WB4101 binding sites in the cortex and hippocampus, with decreases in catecholamine and increases in its metabolites. However, the enhancement of the ambulation-increasing effect of MAP and changes in the binding sites or catecholamine metabolism were scarcely observed when the drug was repeatedly given to the rats in the narrow cage where horizontal ambulation of the animals was strongly impaired. These results suggest that the enhancing effect of MAP is closely related to the environmental situations to which the animals have been exposed to under the drug effect. Moreover, it is indicated that there is a correlation between the enhancement of the ambulation-increasing effect of MAP and changes in the neurochemical parameters. The enhancing effect of MAP is supposed to have been partially caused by changes in cerebral catecholaminergic systems, in particular an increase in catecholamine turnover.

Animals↗
PubMed1995

The Wnt-1 proto-oncogene regulates MAP kinase activation by multiple growth factors in PC12 cells.

PC12/Wnt-1 cells display morphological changes in response to stimulation by select growth factors but do not respond to NGF. Furthermore, stimulation by EGF can induce neuronal differentiation in these cells but not in wild type cells. We have found that in these cells, compared to wild type PC12 cells, FGF and EGF stimulation of MAP kinase activity is enhanced, while NGF stimulation of MAP kinase in diminished. Finally, in cells expressing Wnt-1, the effect of cyclic adenosine monophosphate (cAMP) on MAP kinase activation is reversed; cAMP stimulates MAP kinase in wild type PC12 cells but inhibits MAP kinase in PC12/Wnt-1 cells. These data suggest that Wnt-1 expression alters the specificity of growth factor signaling in neuronal cells.

Animals↗
PubMed1989

Cerebral blood flow determination within the first 8 hours of cerebral infarction using stable xenon-enhanced computed tomography.

Cerebral blood flow mapping with stable xenon-enhanced computed tomography (Xe/CT) was performed in conjunction with conventional computed tomography (CT) within the first 8 hours after the onset of symptoms in seven patients with cerebral infarction. Six patients had hemispheric infarctions, and one had a progressive brainstem infarction. Three patients with very low (less than 10 ml/100 g/min) blood flow in an anatomic area appropriate for the neurologic deficit had no clinical improvement by the time of discharge from the hospital; follow-up CT scans of these three patients confirmed infarction in the area of very low blood flow. Three patients with moderate blood flow reductions (15-45 ml/100 g/min) in the appropriate anatomic area had significant clinical improvement from their initial deficits and had normal follow-up CT scans. One patient studied 8 hours after stroke had increased blood flow (hyperemia) in the appropriate anatomic area and made no clinical recovery.

Aged↗
PubMed1995

Signaling functions of L-selectin. Enhancement of tyrosine phosphorylation and activation of MAP kinase.

L-selectin is a leukocyte cell surface glycoprotein involved in carbohydrate-specific ligand binding which mediates rolling of leukocytes along endothelial surfaces. In addition to its role in adhesion, an intracellular signaling role for L-selectin has recently been recognized. In particular, cross-linking L-selectin leads to increased cytosolic Ca2+ levels and potentiation of the oxidative burst. As several cell surface glycoproteins have been shown to be linked to tyrosine kinases, we examined the hypothesis that L-selectin may be linked to pathways involving tyrosine phosphorylation in human neutrophils. Ligation of L-selectin by three different antibodies recognizing separate epitopes led to increased tyrosine phosphorylation of several cellular proteins as judged by anti-phosphotyrosine immunoblots of whole cell lysates with prominent bands at 40-42, 55-60, 70-72, and 105-120 kDa. The 42-kDa band comigrated with mitogen-activated protein (MAP) kinase as determined by immunoblotting with anti-MAP kinase antibody. This effect was specific for L-selectin, because antibodies against CD18, CD45, and CD10 did not increase tyrosine phosphorylation. Phosphorylation was not due to Fc binding, since F(ab')2 fragments of the anti-L-selectin antibodies were similarly effective, and the response was unaffected by Fc receptor blockade. Cross-linking of L-selectin was not required for enhanced tyrosine phosphorylation, because monovalent Fab fragments also increased tyrosine phosphorylation. The response to L-selectin antibodies was not inhibited by cytochalasin, suggesting that reorganization of the actin cytoskeleton was not required for this response. Sulfatides, sulfated glycolipids which may be natural ligands for L-selectin, also induced a rapid, dose-dependent increase in tyrosine phosphorylation. In addition, sulfatides, but not control glycolipids, resulted in enhanced tyrosine phosphorylation of MAP kinase. Both sulfatides and anti-L-selectin antibodies increased kinase activity of MAP kinase as determined by gel renaturation assay. The tyrosine kinase inhibitor, genistein, blocked the transient increase in intracellular Ca2+ and the oxidative burst induced by sulfatides, suggesting that this tyrosine phosphorylation is functionally important. We conclude that L-selectin is able to transmit intracellular signals, including increased tyrosine phosphorylation and activation of MAP kinase in neutrophils. We speculate that these events may contribute to the activation of neutrophils during adhesion.

Animals↗
PubMed1992

Recombinant human interleukin-9 induces protein tyrosine phosphorylation and synergizes with steel factor to stimulate proliferation of the human factor-dependent cell line, M07e.

Human interleukin-9 (IL-9) was originally identified and cloned based on its stimulatory effect on proliferation of human myeloid cell line, M07e. IL-9 synergized with Steel factor, the ligand for the c-kit product, to stimulate M07e cell proliferation. To investigate potential mechanisms for this, IL-9 was assessed for effects on protein tyrosine kinase activities in M07e cells by immunoblotting with anti-phosphotyrosine monoclonal antibody; results were compared with those of Steel factor alone and in combination with IL-9, and those of 12-0-tetradecanoyl phorbol-13-acetate (TPA). Recombinant human IL-9 (10 ng/mL) rapidly and transiently induced or enhanced at least four tyrosine phosphorylated protein bands with molecular weights of 105, 97, 85, and 81 Kd. This tyrosine phosphorylation pattern was different from that generated by recombinant murine Steel factor or TPA stimulation and the combination of IL-9 and Steel factor did not change the IL-9-induced pattern. IL-9-induced tyrosine phosphorylated bands were completely blocked by treatment of IL-9 with anti-IL-9 antibody under conditions that also neutralized the synergistic effect of IL-9 with Steel factor on M07e cell proliferation. Genistein, a tyrosine kinase inhibitor, blocked phosphorylation of IL-9 and Steel factor-induced bands. Unlike Steel factor or TPA, IL-9 did not appear to stimulate phosphorylation of 42-Kd mitogen-activated protein (MAP) kinase or Raf-1, or enhance MAP kinase activity. MAP kinase and Raf-1 are serine/threonine kinases that are phosphorylated and activated by many growth factors and by agonists for protein kinase C. While the combination of IL-9 plus SLF did not appear to induce phosphorylation of new bands not already seen with either IL-9 or SLF alone, or enhance the phosphorylation of those bands seen with either cytokine alone, the results suggest that IL-9 activates specific and unique signal transduction pathways.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1980

Inhibition of amygdaloid kindling by chronic pretreatment with cocaine or methamphetamine.

Amygdaloid kindling was induced by daily electrical stimulation in the left amygdala in five groups of cats: a chronic cocaine pretreatment group; a chronic methamphetamine (MAP) pretreatment group; two treatment groups, one using pimozide and the other haloperidol during the period when kindling was being induced; and a drug-free control group. The number of left amygdaloid stimulations required for generalized convulsions was significantly greater in the two chronic pretreatment groups and significantly less in the two treatment groups, compared to the control group. All animals in the chronic cocaine and MAP pretreatment groups showed hemiconvulsions instead of symmetrical generalized convulsions and lateralized interictal discharges in the stimulated hemisphere. In rekindling to the right amygdala, seizure development was significantly suppressed compared to the control group. In the two chronic pretreatment groups, chronic administration of cocaine or MAP was followed by enhancement of behavioral responses to cocaine, MAP, and apomorphine. The association of such "sensitization" with impairment of the kindling process suggests that dopamine receptor sensitivity is an important factor in this form of epileptogenesis.

Amygdala↗
PubMed1995

Effects of fentanyl on sympathetic activation associated with the administration of desflurane.

BACKGROUND: Activation of the sympathetic nervous system occurs when desflurane is inspired shortly after anesthetic induction and when the inspired concentration of desflurane is rapidly increased during steady-state periods of anesthesia. The purpose of this study was to determine the effectiveness and dose response of fentanyl pretreatment in attenuating the neurocirculatory responses to desflurane in healthy human volunteers. METHODS: After Institutional Research Review Board approval, three study groups were selected and, in random order, received either placebo (n = 10), a 2.5-micrograms.kg-1 intravenous bolus of fentanyl citrate followed by a continuous infusion of 1 microgram.kg-1.h-1 (n = 9), or a 5.0-micrograms.kg-1 intravenous bolus followed by an infusion of 2 micrograms.kg-1.h-1 (n = 11) before the administration of desflurane. Arterial (MAP) and central venous (CVP) pressures were measured directly, and heart rate (HR) was determined indirectly. Efferent muscle sympathetic nerve activity (SNA) was recorded from the peroneal nerve by microneurography. After neurocirculatory recordings at conscious unmedicated baseline and 12 min after fentanyl administration, anesthetic induction was carried out with 2.0 mg.kg-1 propofol and 0.2 mg.kg-1 vecuronium. Neurocirculatory measurements were repeated beginning 2 min after induction when desflurane was given via mask (semiclosed circle system, 61/min fresh gas flow, 100% O2) in three incremental 1-min steps (3.6%, 7.2%, and 11%). Intubation occurred 10 min after propofol administration. Twenty minutes after intubation, recordings were obtained during two steady-state periods during which end-tidal concentrations had achieved 5.4% (0.75 MAC) and 11% (1.5 MAC) desflurane for at least 10 min. Data also were obtained during the rapid increase in the inspired gas concentration from 5.4% to 11% ("transition"). RESULTS: Neurocirculatory variables did not differ between the three groups at conscious baseline, after fentanyl, and during steady-state periods of anesthesia. Propofol administration significantly reduced SNA and MAP. The MAP reduction was enhanced in the fentanyl-treated groups. After induction, the increases in SNA and MAP associated with the administration of desflurane by mask were not significantly reduced by fentanyl. The transition from 5.4% to 11% desflurane resulted in increases in SNA, HR, MAP, and fentanyl administration significantly attenuated the HR and MAP components. At the 11% steady-state measurement period, CVP was increased and MAP was decreased from conscious baseline, and these changes were not modified by fentanyl. CONCLUSIONS: The administration of desflurane was associated with increases in SNA, HR, MAP, and CVP. Maximum sympathetic activation and hemodynamic responses occurred 4-5 min after initiating desflurane during induction and 2-3 min after increasing the inspired concentration of desflurane during the "transition" period. Although fentanyl partially attenuated the hemodynamic component in a dose-dependent fashion during the "transition" period, it did not significantly diminish the response during induction.

Adult↗
PubMedDate not supplied

Simian virus 40 enhancer increases RNA polymerase density within the linked gene.

Enhancers are regulatory DNA elements, usually about 200 base pairs (bp) long, which are able to stimulate transcription of linked genes in eukaryotic cells. This activation can be exerted over large distances, and from a position 5' or 3' to the gene. Enhancers have been identified in viral genomes and cellular genes. Using a transient expression assay, we have analysed transcription of the rabbit beta-globin gene and the thymidine kinase gene from herpes simplex virus with and without a simian virus 40 (SV40) enhancer. S1 nuclease mapping shows a high level of specific transcripts when the genes are linked to the enhancer. To determine whether this increased number of transcripts is due to a higher transcription rate, or perhaps to a shift from nonspecific to specific initiation, we have performed run-on transcription assays with isolated nuclei. Our results, presented here, demonstrate that the SV40 enhancer increases the RNA polymerase density within the linked gene. Therefore, enhancers apparently increase the rate of transcription initiation without influencing the specificity of initiation.

Cell Nucleus↗
PubMed1988

DNase I hypersensitivity is independent of endogenous topoisomerase II activity during chicken erythrocyte differentiation.

Endogenous topoisomerase II cleavage sites were mapped in the chicken beta A-globin gene of 12- to 14-day embryonic erythrocytes. A major topoisomerase II catalytic site was mapped to the 5' end of the globin gene which contained a nucleosome-free and DNase I-hypersensitive site and additional but minor sites were mapped to the second intron and 3' of the gene to a tissue-specific enhancer. Cleavage sites, mapped in situ by indirect end labeling, were aligned to single-base-pair resolution by comparison to a consensus sequence derived for vertebrate topoisomerase II catalytic sites. In contrast to embryonic erythrocytes, endogenous topoisomerase II cleavages were not detected in erythrocytes from peripheral blood of adult chickens; therefore, as the transcriptional activity of the beta A-globin gene declines during terminal differentiation of erythrocytes, the activity of topoisomerase II in situ declines as well, despite the fact that DNase I hypersensitivity persists. The results showed that DNase I-hypersensitive chromatin can be maintained in the absence of topoisomerase II activity and suggested that topoisomerase II acts at hypersensitive sites because of an inherent attraction to some preexisting combination of DNA sequence or chromatin structure associated with DNase I-hypersensitive regions.

Animals↗
PubMedDate not supplied

Automatic enhancement, animation, and segmentation of flow in peripheral arteries from MR phase-shift velocity mapping.

The authors describe a technique for automatic enhancement, segmentation, and analysis of flow from MR phase shift velocity mapping. This method uses a specific flow related enhancement process to extract and localize the flow field within the image, followed by global flow analysis. By animation on low cost equipment (personal computers), this method can provide various ways of visualizing flow in vivo and its variation in different structures and lesions. Our preliminary results using this method for analyzing flow data in the aortic bifurcation of healthy volunteers are encouraging.

Aorta, Abdominal↗
PubMed1992

Brain ouabain and central effects of dietary sodium in spontaneously hypertensive rats.

High sodium intake (HNa) increases brain ouabainlike activity (OLA) in rats. In spontaneously hypertensive rats (SHR), HNa exaggerates development of hypertension and pressor and sympathoexcitatory responses to stress. To investigate whether dietary sodium-induced changes in brain OLA play a functional role, responses of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) to intracerebroventricular ouabain and to mental stress and intracerebroventricular alpha 2-adrenoceptor agonist guanabenz alone or preceded by intracerebroventricular ouabain were recorded in conscious SHR and Wistar-Kyoto (WKY) rats maintained from 4 to 8 weeks of age on different sodium diets: 1) low sodium intake (LNa, 17 mumol), 2) normal sodium intake (NNa, 101 mumol), and 3) HNa (1,370 mumol). SHR on NNa showed significantly higher MAP and RSNA compared with WKY rats on NNa. HNa or LNa significantly increased or decreased MAP but had no effects on resting RSNA in SHR and had no effects on resting MAP and RSNA in WKY rats. Intracerebroventricular ouabain induced dose-dependent increases in MAP, RSNA, and HR. In both SHR and WKY rats, LNa significantly enhanced these responses. In contrast, HNa significantly attenuated these responses only in SHR. Air stress increased and intracerebroventricular guanabenz decreased MAP, HR, and RSNA. The magnitudes of increases and decreases were significantly larger in SHR than in WKY rats. In WKY rats, dietary sodium did not change these responses. In contrast, in SHR, HNa significantly enhanced MAP, HR, and RSNA responses to air stress or intracerebroventricular guanabenz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

G protein beta gamma subunit activates Ras, Raf, and MAP kinase in HEK 293 cells.

Using transient transfection of HEK 293 cells, we have studied the activation of Ras, c-Raf, and MAP kinase by G protein-coupled receptors, activated G protein alpha subunit (G alpha), and beta gamma subunits (G beta gamma). The expression of constitutively activated Gs alpha, Gi alpha, and G11 alpha did not have any effect on MAP kinase phosphorylation. In contrast, overexpression of G beta gamma could stimulate the phosphorylation of MAP kinase and enhance the MEK kinase activity of c-Raf. Coexpression of dominant negative Ras inhibited G beta gamma-induced phosphorylation of MAP kinase. Furthermore, the GTP-bound form of Ras was increased by overexpression of G beta gamma. These results strongly suggest that the G beta gamma may play an important role in signaling from G protein-coupled receptors to the MAP kinase pathway, and the activation of Ras and c-Raf may be involved in this signaling cascade in HEK 293 cells.

Cell Line↗
PubMed1992

Rapid attachment of a helper T cell epitope to branched peptides by fragment condensation to give enhanced immunogenicity.

We describe a rapid method of fragment condensation to couple a helper T cell epitope, active in BALB/c mice, to the amino terminus of branched peptides (or 'multiple antigenic peptides', MAPs). The helper T cell epitope-MAP conjugate considerably enhanced the immunogenicity in BALB/c mice of branched peptides. The method of fragment condensation, whereby the helper T cell epitope portion of the immunogen is added as a 'cassette' in a one step addition process, is both faster and more convenient than continuous step-by-step addition of individual amino acids and is likely to be generally applicable. The method should be advantageous in the development of peptide based vaccines.

Amino Acid Sequence↗
PubMed1985

[Chronological change in abnormal behavior produced by long-term methamphetamine administration in the rat].

Rats received once daily injections of methamphetamine (MAP; 4 mg/kg/day) intraperitoneally, at most 100 times. Enhanced ambulatory activity by MAP reduced during the long-term administration of MAP. The mean rating score of MAP-induced abnormal behavior, including locomotion, stereotyped behavior, motor inhibition and the response to acoustic stimulation, increased until 56th injection of MAP. But after that, the score tended to decrease mainly because the injected MAP failed to keep the movement of rats reduced under acoustic stimulation. Neither the time course of these rating score nor the decrease in [3H] spiperone binding sites, examined after the injection of MAP 100 times, seemed to develop along with the repeated MAP administration. Thus, the changes in both behavior and [3H] spiperone binding sites produced by repeated MAP would not necessarily indicate the symptoms of MAP-induced psychosis in man, because the susceptibility to psychosis in man increases along with the time of MAP injection. It is presumed that the animal model of psychosis produced by administration of MAP is important not as a model of psychotic symptoms, but as a model of increased susceptibility to psychosis induced by MAP.

Animals↗
PubMed1995

Purification of a 12,020-dalton protein that enhances the activation of mitogen-activated protein (MAP) kinase by MAP kinase kinase.

We have purified 3500-fold from rabbit skeletal muscle a 12,020-Da mitogen-activated protein kinase kinase (MEK)-enhancing factor (MEF) that stimulates both mitogen-activated protein kinase (MAPK) autophosphorylation and the rate (24-fold) at which the enzyme is phosphorylated by MEK in vitro. This was manifest by the finding that in the presence of MEF, molar equivalents of MEK to MAPK were sufficient to produce fully phosphorylated (2.1 +/- 0.4 mol/mol; S.D., n = 3) and activated MAPK. This contrasted with the 40:1 molar excess ratio of MEK to MAPK required to produce fully phosphorylated and activated MAPK in the absence of MEF. Phosphoamino acid analysis revealed that in the presence of MEF, phosphorylation of MAPK by MEK was ordered, with Tyr-185 phosphorylation preceding Thr-183 phosphorylation. However, the rate at which Thr-183 was phosphorylated relative to Tyr-185 was greatly increased. The finding that MEF stimulated MAPK autophosphorylation and increased its ability to be phosphorylated by MEK suggests a mechanism of action in which MEF interacts with MAPK to alter its conformation.

Amino Acid Sequence↗
PubMed1990

Tandem AP-1-binding sites within the human beta-globin dominant control region function as an inducible enhancer in erythroid cells.

A powerful enhancer has been mapped to an 18-bp DNA segment located 11 kb 5' to the human epsilon-globin gene within the dominant control or locus-activating region. This enhancer is inducible in K562 human erythroleukemia cells, increasing linked gamma-globin promoter/luciferase gene expression to 170-fold over an enhancerless construct. The enhancer consists of tandem AP-1-binding sites, phased 10 bp apart, which are both required for full activity. DNA-protein binding assays with nuclear extracts from induced cells demonstrate a high molecular weight complex on the enhancer. The formation of this complex also requires both AP-1 sites and correlates with maximal enhancer activity. Induction of the enhancer may have a role in the increase in globin gene transcription that characterizes erythroid maturation. Enhancer activity appears to be mediated by the binding of a complex of proteins from the jun and fos families to tandem AP-1 consensus sequences.

Base Sequence↗
PubMed1989

Locations of nucleosomes on the regulatory region of simian virus 40 chromatin.

We have asked where the nucleosomes are located with respect to the replication origin and regulatory region of simian virus 40 DNA, what would be the possible functional consequences of the identified locations, and to what extent these locations correlate with the current views on mechanisms involved in establishing nucleosome-free regions in chromatin. To identify the precise location of nucleosomes, we have shot-gun cloned and sequenced nucleosomal DNA obtained from micrococcal nuclease digestion of wt776 chromatin prepared late in infection. Our results indicate that nucleosomes do not occupy unique positions over the replication origin or the elements involved in transcriptional control. However, it appears that the nucleosome distribution is not random, since several nucleosomes are represented by two or more independently generated clones. Two nearly identical cloned fragments map over the replication origin; five include 1.5 copies of the 72 base-pair enhancer sequences; and eight map to a region that spans a DNA bending locus and the major transcription initiation site of the late genes. The complex nucleosome distribution pattern observed in our direct analysis suggests that disparate nucleosome-free regions may be involved in controlling replication, and selective expression of the viral early or late genes.

Cell Line↗