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Partial Reversal (partial + reversal)
Selected AbstractsPartial reversal of conduction slowing during repetitive stimulation of single sympathetic efferents in human skinACTA PHYSIOLOGICA, Issue 3 2004M. Campero Abstract Aims:, To describe and identify the function of a class of human C fibre with an unusual response to repetitive electrical stimulation. Other C fibres slow progressively at 2 Hz (type 1), reach a latency plateau (type 2) or hardly slow at all (type 3). Methods:, C fibres innervating hairy skin were recorded by microneurography in the superficial peroneal nerves of 19 healthy volunteers. Baseline electrical stimulation of the skin was at 0.25 Hz, and activity-dependent slowing recorded during stimulation at 2 Hz for 3 min and after a 3-min pause in stimulation. Results:, In 41 units, there was a partial recovery of latency during repetitive stimulation. These were classified as ,type-4' units, and identified as sympathetic efferents, since they exhibited spontaneously activity, which was enhanced by manoeuvres that increase sympathetic outflow (15 of 16 cases) and/or suppressed by a proximal anaesthetic block (eight of eight cases). The peak slowing during 2 Hz trains averaged 6.47 ± 2.06% (mean ± SD, n = 41), but after 3 min the slowing had reduced to 4.90 ± 2.20%, which was less than in all type 1 (nociceptor) fibres but similar to that in type 2 (cold) fibres. Compared with cold fibres, type-4 sympathetic fibres slowed more after the first 10 impulses at 2 Hz (2.57 ± 0.45%) and also after a pause in stimulation (1.66 ± 0.51%). Conclusions:, The distinctive activity-dependent slowing profiles of these type-4 sympathetic C units may help identification in vitro, and suggest that hyperpolarization-activated channels have a particularly prominent role in the axonal membrane. [source] Changes associated with the development of resistance to imatinib (STI571) in two leukemia cell lines expressing p210 Bcr/Abl protein,CANCER, Issue 7 2004Barbara Scappini M.D. Abstract BACKGROUND Although various mechanisms have been recognized as being associated with the development of resistance to imatinib mesylate in vitro and in clinical situations, their relative significance and contributions remain poorly understood, as is the sequence of events leading to the selection of the resistant phenotype. Experimental in vitro systems involving well defined cell lines and conditions can be used to some advantage to answer specific questions and to develop in vitro models of imatinib resistance that would reflect its potential heterogeneity. METHODS Two cell lines, KBM5 and KBM7, which expressed p210 Bcr/Abl and which differed in their inherent sensitivity to imatinib, the number of copies of the BCR/ABL fusion gene, and the activation of apoptotic pathways, were grown in vitro in the presence of increasing concentrations of imatinib. The resistant cells were analyzed for cell cycle progression, apoptotic response after exposure to imatinib, expression of Bcr/Abl, tyrosine kinase activity, and the presence of mutations within the adenosine triphosphate (ATP) coding domain of BCR/ABL. At various levels of resistance, the cells were transferred into drug-free media, and the stability of the resistant phenotype was determined in the absence of the drug. RESULTS In KBM7 cells, the development of resistance was characterized by loss of apoptotic response to the drug, amplification of BCR/ABL, increased levels of expression of p210 Bcr/Abl, and decreased inhibition of Bcr/Abl tyrosine kinase (TK) activity by imatinib. No mutations within the ATP-binding domain of Bcr/Abl were identified, and resistance remained stable in the absence of the drug. In KBM5 cells, which previously were found to be characterized by the acquisition of a single C-T mutation at ABL nucleotide 944 (T315I) at high levels of resistance, this same mutation was detected at an intermediate level, but not at a low level, of resistance. The response of KBM5 cells to imatinib was characterized by a low level of apoptotic response, a marginal increase in BCR/ABL copy number, a modest increase in p210 expression, and a highly imatinib-resistant Bcr/Abl TK. Partial reversal of resistance was observed in highly resistant KBM5-STI571R1.0 cells, which continued to display the C-T mutation. In KBM5 cells with an intermediate level of resistance, the T315I mutation was no longer detectable upon their reversal to the sensitive phenotype. CONCLUSIONS BCR/ABL amplification with subsequent overexpression of Bcr/Abl protein, loss of apoptotic response, or point mutation of the ATP-binding site of BCR/ABL was associated alternatively with the acquisition of the resistant phenotype, supporting the notion that multiple mechanisms are involved in the induction of resistance to imatinib. The initial number of BCR/ABL copies itself was not related directly to the degree of resistance. The reversibility of the resistance may be complete, partial, or irreversible, depending on the mechanism(s) involved and the degree of resistance. Both cell lines serve as models for further elucidation of various aspects of imatinib-resistance mechanisms. Cancer 2004;100:1459,71. © 2004 American Cancer Society. [source] Loss of RD1 contributed to the attenuation of the live tuberculosis vaccines Mycobacterium bovis BCG and Mycobacterium microtiMOLECULAR MICROBIOLOGY, Issue 3 2002Alexander S. Pym Summary Although large human populations have been safely immunized against tuberculosis with two live vaccines, Mycobacterium bovis BCG or Mycobacterium microti, the vole bacillus, the molecular basis for the avirulence of these vaccine strains remains unknown. Comparative genomics has identified a series of chromosomal deletions common to both virulent and avirulent species but only a single locus, RD1, that has been deleted from M. bovis BCG and M. microti. Restoration of RD1, by gene knock-in, resulted in a marked change in colonial morphology towards that of virulent tubercle bacilli. Three RD1-encoded proteins were localized in the cell wall, and two of them, the immunodominant T-cell antigens ESAT-6 and CFP-10, were also found in culture supernatants. The BCG::RD1 and M. microti::RD1 knock-ins grew more vigorously than controls in immunodeficient mice, inducing extensive splenomegaly and granuloma formation. Increased persistence and partial reversal of attenuation were observed when immunocompetent mice were infected with the BCG::RD1 knock-in, whereas BCG controls were cleared. Knocking-in five other RD loci did not affect the virulence of BCG. This study describes a genetic lesion that contributes to safety and opens new avenues for vaccine development. [source] Heterologous desensitization of the sphingosine-1-phosphate receptors by purinoceptor activation in renal mesangial cellsBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2004Cuiyan Xin Sphingosine-1-phosphate (S1P) is considered a potent mitogen for mesangial cells and activates the classical mitogen-activated protein kinase (MAPK) cascade via S1P receptors. In this study, we show that S1P signalling is rapidly desensitized upon S1P receptor activation. A complete loss of S1P sensitivity occurs after 10 min of S1P pretreatment and remains for at least 8 h. A similar desensitization is also seen with the S1P mimetic FTY720-phosphate, but not with the nonphosphorylated FTY720, nor with sphingosine or ceramide. Prestimulating the cells with extracellular ATP or UTP, which bind to and activate P2Y receptors on mesangial cells, a similar rapid desensitization of the S1P receptor occurs, suggesting a heterologous desensitization of S1P receptors by P2Y receptor activation. Furthermore, adenosine binding to P1 receptors triggers a similar desensitization. In contrast, two other growth factors, PDGF-BB and TGF,2, have no significant effect on S1P-induced MAPK activation. S1P also triggers increased inositol trisphosphate (IP3) formation, which is completely abolished by S1P pretreatment but only partially by ATP pretreatment, suggesting that IP3 formation and MAPK activation stimulated by S1P involve different receptor subtypes. Increasing intracellular cAMP levels by forskolin pretreatment has a similar effect on desensitization as adenosine. Moreover, a selective A3 adenosine receptor agonist, which couples to phospholipase C and increases IP3 formation, exerted a similar effect. Pretreatment of cells with various protein kinase C (PKC) inhibitors prior to ATP prestimulation and subsequent S1P stimulation leads to a differential reversal of the ATP effect. Whereas the broad-spectrum protein kinase inhibitor staurosporine potently reverses the effect, the PKC- , inhibitor CGP41251, the PKC- , inhibitor rottlerin and calphostin C show only a partial reversal at maximal concentrations. Suramin, which is reported as a selective S1P3 receptor antagonist compared to the other S1P receptor subtypes, has no effect on the S1P-induced MAPK activation, thus excluding the involvement of S1P3 in this response. In summary, these data document a rapid homologous and also heterologous desensitization of S1P signalling in mesangial cells, which is mechanistically triggered by PKC activation and eventually another staurosporine-sensitive protein kinase, as well as by increased cAMP formation. British Journal of Pharmacology (2004) 143, 581,589. doi:10.1038/sj.bjp.0705980 [source] Off-Target Effects Related to the Phosphorothioate Modification of Nucleic AcidsCHEMMEDCHEM, Issue 8 2010Johannes Winkler Dr. Abstract Phosphorothioate antisense oligonucleotides have been widely used in clinical studies for rational sequence-specific gene silencing. However, several sequence-unspecific off-target effects have been recently described for this compound class. In contrast to siRNA-mediated knockdown of the same gene, the bcl-2 -targeted oblimersen (Genasense, G3139) downregulates a number of proteins involved in apoptotic resistance and several glycolytic enzymes in 607B human melanoma cells. Regardless of their target, phosphorothioate-modified antisense and siRNA compounds, but not oligonucleotides with a phosphodiester backbone, resulted in a similar impact on the proteome. Unspecifically downregulated proteins include cancer markers involved in apoptotic resistance and endoplasmatic reticulum (ER) stress such as the 78,kDa glucose regulated protein (GRP,78), protein disulfide isomerase,A3 (PDIA3, GRP,58), calumenin, and galectin-1, as well as the glycolytic enzymes triose phosphate isomerase, glyceraldehyde phosphodehydrogenase, and phosphoglycerate mutase. The depletion of the glycolytic enzymes is reflected by a decrease in L -lactate production, indicating a partial reversal of the Warburg effect. Compared with other phosphorothioate oligonucleotides, oblimersen generally led to a more pronounced effect both in terms of the number of influenced proteins and the extent of downregulation, suggesting a synergistic effect of Bcl-2 downregulation. [source] CYTIDINE 5,-DIPHOSPHOCHOLINE RESTORES BLOOD FLOW OF SUPERIOR MESENTERIC AND RENAL ARTERIES AND PROLONGS SURVIVAL TIME IN HAEMORRHAGED ANAESTHETIZED RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2006M Sertac Yilmaz SUMMARY 1The aim of the present study was to investigate the effect of the intracerebroventricular (i.c.v.) or intravenous (i.v.) administration of cytidine 5¢-diphosphocholine (CDP-choline) on superior mesenteric artery (SMA) and renal artery (RA) blood flow, along with the cardiovascular parameters and survival time of anaesthetized rats under conditions of haemorrhagic shock. 2Rats were anaesthetized with urethane (1.25 g/kg, i.p.) and acute haemorrhage was mimicked by the withdrawal of a total volume of 2,2.1 mL blood/100 g bodyweight over a period of 20 min. The CDP-choline was injected i.c.v. (1.0, 1.5 and 2.0 mmol) or i.v. (250 mg/kg) after the end of haemorrhage. Blood pressure, heart rate, SMA and RA flow values and the survival time of rats were recorded. Changes in blood flow were estimated by laser-Doppler flowmetry. 3The haemorrhage procedure decreased the blood pressures of rats by 60% and limited their survival time to 22 ± 2 min. Both SMA and RA flow decreased to approximately 25% of initial values at the end of the haemorrhage procedure. 4The i.c.v. administration of CDP-choline (1.0, 1.5 and 2.0 mmol) increased blood pressure and partially reversed the hypotension in a dose- and time-dependent manner. At 1.5 and 2.0 mmol, i.c.v., CDP-choline completely restored the decreased flow of the RA and transiently reversed hypoperfusion of the SMA. It also produced an almost fourfold increase in the survival time of rats. 5The i.v. administration of CDP-choline (250 mg/kg) also completely, but transiently, restored SMA and RA flow, whereas it increased blood pressure by only 40% compared with control values. The survival time of rats in the i.v. CDP-choline group was doubled that of control. 6These results indicate that both centrally and peripherally injected CDP-choline can restore SMA and RA flow, together with a partial reversal of hypotension and an increase in the survival time of rats. [source] | |||||||||||||