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Membrane Level (membrane + level)
Kinds of Membrane Level Selected AbstractsPotassium Channels in the Human MyometriumEXPERIMENTAL PHYSIOLOGY, Issue 2 2001Raheela N. Khan The contractility of the human uterus is under the fine control of a variety of interacting bioactive agents. During labour, the excitability of the uterus is drastically transformed in comparison with the non-labour state and is manifest at the membrane level via the acivity of uterine ion channels. This article reviews the contribution of potassium (K+) channels to human uterine excitability. [source] Calcium and magnesium competitively influence the growth of a PMR1 deficient Saccharomyces cerevisiae strainFEMS MICROBIOLOGY LETTERS, Issue 2 2005Réka Szigeti Abstract PMR1, the Ca2+/Mn2+ ATPase of the secretory pathway in Saccharomyces cerevisiae was the first member of the secretory pathway Ca2+ ATPases (SPCA) to be characterized. In the past few years, pmr1, yeast have received more attention due to the recognition that the human homologue of this protein, hSPCA1 is defective in chronic benign pemphigus or Hailey,Hailey disease (HHD). Recent publications have described pmr1, S. cerevisiae as a useful model organism for studying the molecular pathology of HHD. Some observations indicated that the high Ca2+ sensitive phenotype of PMR1 defective yeast strains may be the most relevant in this respect. Here we show that the total cellular calcium response of a pmr1, S. cerevisiae upon extracellular Ca2+ challenge is decreased compared to the wild type strain similarly as observed in keratinocytes. Additionally, the novel magnesium sensitivity of PMR1 defective yeast is revealed, which appears to be a result of competition for uptake between Ca2+ and Mg2+ at the plasma membrane level. Our findings indicate that extracellular Ca2+ and Mg2+ competitively influence the intracellular Ca2+ homeostasis of S. cerevisiae. These observations may further our understanding of HHD. [source] Characterization of human sperm N -acetylglucosaminidaseINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 3 2008S. L. Perez Martinez Summary N -acetylglucosaminidase (NAG) is particularly active in mammalian spermatozoa and appears to be involved in fertilization. Although it is assumed that this enzyme is acrosomal, previous results from our laboratory suggest the presence of NAG at the sperm plasma membrane level. The present study attempted to analyse the subcellular distribution of this enzyme in human spermatozoa. Sperm were incubated under different conditions and NAG activity measured in the soluble extracts and cell pellets using a specific fluorometric substrate. A significant proportion of NAG activity was released when sperm were incubated in culture medium, suggesting a weak association with the plasma membrane. This location was confirmed by western blot analysis of plasma membrane fractions and immunofluorescence on non-permeabilized sperm, which showed a positive signal mainly on the acrosomal domain. The distribution of NAG activity between plasma membrane and acrosome was analysed after cell disruption by freezing and thawing. Triton X-100 stimulated sperm and epididymal NAG activity but not the enzyme obtained from other sources. In addition, biotinylated human recombinant NAG was able to bind to human sperm. Finally, after sperm incubation under capacitating conditions, NAG total activity increased and the sperm enzyme lost its ability to be stimulated by Triton X-100. The possible connection of these results with sperm maturation, capacitation and NAG participation in primary binding to the zona pellucida, was discussed. [source] Volume recovery, surface properties and membrane integrity of Lactobacillus delbrueckii subsp. bulgaricus dehydrated in the presence of trehalose or sucroseJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007E.E. Tymczyszyn Abstract Aims:, Although the practical importance of adding sugars before drying is well known, the mechanism of protection of bacteria by sugars is not clear. The response of the dehydrated micro-organisms to rehydration is analysed in terms of structural and functional changes, and correlated with their potentiality to grow in rich media. These aspects are related with the membrane integrity and the metabolic state of the rehydrated bacteria, measured by means of surface properties and permeability. To attain this objective, Lactobacillus delbrueckii subsp. bulgaricus was dehydrated in the presence and in the absence of sucrose and trehalose. The bacterial response upon rehydration was investigated by determining: (i) the lag time of the bacterial growing in rich media, (ii) the restoration of the surface properties and the cellular volume and (iii) the membrane integrity. Methods and Results:,Lactobacillus delbrueckii subsp. bulgaricus was grown in MRS at 37°C overnight [De Man et al. (1960)J Appl Bacteriol 23, 130] and then dehydrated for 10, 20 and 30 min at 70°C in a vacuum centrifuge. The lag time of micro-organisms was determined by optical density changes after rehydration. The surface properties were determined by measuring the zeta potential of the bacteria suspended in aqueous solution. The cellular volume recovery was measured, after stabilization in saline solution, by light scattering and by the haematocrit method [Alemohammad and Knowles (1974)J Gen Microbiol 82, 125]. Finally, the membrane integrity has been determined by using specific fluorescent probes [SYTO 9 and propidium iodide, (PI)] that bind differentially depending on the integrity of the bacterial membrane. The lag time of Lact. delbrueckii subsp bulgaricus, dehydrated by heat in the presence of sucrose or trehalose and after that rehydrated, was significantly shortened, when compared with that obtained for bacteria dried in the absence of sugars. In these conditions, trehalose and sucrose maintained the zeta potential and the cell volume close to the control (nondried) cells. However, the membrane integrity, measured with fluorescent probes, was maintained only when cells were dehydrated for 10 min in the presence of sugars. For larger times of dehydration, the membrane integrity was not preserved, even in the presence of sugars. Conclusions:, When the micro-organisms are dehydrated in the absence of protectants, the membrane damage occurs with a decrease in the absolute value of the zeta potential and a decrease in the cellular volume recovered after rehydration. In contrast, when the zeta potential and the cellular volume are restored after rehydration to that corresponding to nondried cells, the micro-organisms are able to recover and grow with a reduced lag time. This can only be achieved when the dehydration is carried out in the presence of sugars. At short dehydration times, the response is associated with the preservation of the membrane integrity. However, for longer times of dehydration the zeta potential and volume recovery occurs in the presence of sugars in spite of a severe damage at membrane level. In this condition, cells are also recovered. In conclusion, to predict the ability of growing after dehydration, other bacterial structural parameters besides membrane integrity, such as zeta potential and cellular volume, should be taken into account. Significance and Impact of the Study:, The correlation of the lag time with the surface and permeability properties is of practical importance because the correlation of these two parameters with cell viability, allow to determine the potential bacterial capacity to grow in a rich medium after the preservation procedure, without necessity of performing a kinetic curve of growth, which is certainly time-consuming. [source] A Mechanism of Vasodilatory Action of Polyamines and Acetylpolyamines: Possible Involvement of their Ca2+ Antagonistic PropertiesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2000CHANG-SEON MYUNG Polyamines, a class of low-molecular weight organic polycations, have been shown to produce relaxing effects in vascular smooth muscles, although the mechanism has not been carefully examined. In this study, the mechanism of vascular action of polyamines and their metabolites, acetylpolyamines, was pharmacologically examined in the rabbit isolated thoracic aorta focusing on an endothelium-dependent component of vasodilatation and Ca2+ influx through plasma membrane channels. Both polyamines and acetylpolyamines (except N1 -acetylputrescine, which produced no response or very slight contraction) caused concentration-dependent relaxation in pre-constricted aortic rings containing an intact endothelium. Aortic rings denuded of endothelium were also responsive to both polyamines and acetylpolyamines. Inhibitors of nitric oxide (reduced haemoglobin and N, -nitro- l -arginine methyl ester), vasodilator prostaglandins (indomethacin) and guanylyl cyclase (methylene blue) did not affect the relaxation induced by both polyamines and acetylpolyamines in either endothelium-intact or -denuded aortic rings. Both polyamines and acetylpolyamines inhibited the concentration-dependent contraction for phenylephrine and K+. The Ca2+ agonist Bay K 8644 induced concentration-dependent contraction in segments of rabbit aorta partially depolarized with 15 mm KCl, and both polyamines and acetylpolyamines relaxed the Bay K 8644-induced contraction in a concentration-dependent manner. Interestingly, both polyamines and acetylpolyamines also decreased contractions evoked by the Ca2+ ionophore A23187. The concentration-response curve to exogenous Ca2+ in K+ -depolarization medium (K+ = 120 mm) was shifted to the right by both polyamines and acetylpolyamines. The response elicited by Ca2+ was increased by Bay K 8644 (10,6m), and this potentiation was also inhibited by both polyamines and acetylpolyamines. The results indicate that both polyamines and acetylpolyamines can induce vasorelaxation of rabbit thoracic aorta by an endothelium-independent mechanism in-vitro and relax vascular smooth muscle by acting at the plasma membrane level, decreasing the influx of Ca2+. Therefore, polyamines and acetylpolyamines may have Ca2+ antagonistic properties which may, in part, be involved in the mechanism of rabbit aortic vascular smooth muscle relaxation. [source] RET genotypes in sporadic medullary thyroid cancer: studies in a large Italian seriesCLINICAL ENDOCRINOLOGY, Issue 3 2008Laura Fugazzola Summary Background, Highly discrepant data about the different distribution of RET germline single nucleotide polymorphisms (SNPs) among patients with sporadic medullary thyroid cancer (sMTC) and controls are available. Design and patients, In the present case-control study, a wide panel of seven RET SNPs has been tested in the largest sMTC series and in a matched control group. Results, None of the investigated polymorphisms show a significantly different distribution in patients with sMTC when compared to controls. Twenty haplotypes and 57 genotypes were generated, and their association with the disease and with the clinical features were statistically evaluated. Interestingly, 14 genotypes were found to be unique to sMTC patients and 25 to controls. Two haplotypes and three genotypes, all including the intronic variants IVS1-126 and IVS14-24, were significantly associated with sMTC patients and with a higher tumour aggression. The functional activity of the only nonsynonymous RET variant (c.2071C > A, G691S) was tested for the first time. Interestingly, Western blot analyses showed that the fraction of Ret9-G691S protein located at the plasma membrane level was overrepresented when compared to Ret9-WT, suggesting facilitated targeting at the cell membrane for this variant. However, no transforming activity was shown in a focus formation assay on cells carrying the Ret9-G691S, against a possible oncogenic role of G691S variant. Conclusions,RET genotypes including two intronic RET variants were associated with the risk of developing sMTC and to more aggressive behaviour. Further studies are warranted to elucidate whether these RET genotypes are in linkage disequilibrium with another susceptibility gene or whether these variants could play a role in the genesis of sMTC per se. [source] Remission induction chemotherapy induces in vivo caspase-dependent apoptosis in bone marrow acute myeloid leukemia blast cells and spares lymphocytesCYTOMETRY, Issue 3 2006J.-P. Vial Abstract Background The goal of new therapeutic strategies is to adapt the treatment of acute myeloid leukemia (AML) patients to the prognostic and/or to the hematological response. Methods We analyzed in vivo apoptosis induction in blast cells and in lymphocytes of AML patients receiving remission induction treatment. Results We show, on 12 peripheral blood samples, that the increase of peripheral apoptotic blast cells cannot be considered as the earliest marker of the treatment efficiency, because the significant increase of apoptosis followed the white blood cell and the peripheral blast cell count reductions, probably due to an efficient clearance of circulating apoptotic cells. Furthermore, the study of 65 bone marrow samples at d15 showed that the treatment induced apoptosis of blast cells while sparing the lymphocytes. This apoptosis was evidenced both at the caspase and at the membrane levels using respectively fmk-VAD-FITC and Annexin V binding assays. We found that less than 50% of apoptosis, measured with the fmk-VAD-FITC, in the d15 residual bone marrow blast cells, correlated with lower disease-free survival probability. Conclusion More studies are needed in larger series and earlier during the remission induction treatment to confirm the possible prognostic significance of in vivo apoptosis induction. © 2006 International Society for Analytical Cytology [source] A case,control study of dietary and erythrocyte membrane fatty acids in asthmaCLINICAL & EXPERIMENTAL ALLERGY, Issue 8 2004E. C. Broadfield Summary Background Epidemiological evidence suggests that increased dietary ,-6 and reduced ,-3 fatty acid intake, may have contributed to the rising prevalence of asthma, but these hypotheses have not been tested in studies comparing both dietary intake and objective measures of polyunsaturated fatty acids. Objective To assess whether a higher intake of ,-6 or a lower intake of ,-3 fatty acids increases the risk of asthma, by measuring dietary fatty acid intake by a food frequency questionnaire (FFQ) and erythrocyte membrane fatty acids, as an objective biomarker of intake. Methods We have compared individual fatty acid intake estimated by FFQ and by mass spectrometry of fasting erythrocyte cell membranes in 89 cases of asthma and 89 community-matched controls. Results The odds of asthma were increased in relation to intake of the ,-3 fatty acids eicosapentaenoic acid (odds ratio (OR) for difference between the 25th and 75th centiles of intake=1.89, 95% CI 1.15,3.11) and docosahexaenoic acid (OR=2.11, 95% CI 1.19,3.74). There was no evidence of any difference in erythrocyte membrane levels of ,-3 fatty acids, while the odds of asthma were reduced in relation to linoleic acid (,-6) membrane levels (OR=0.45, 95% CI 0.21,0.95). Conclusion These findings suggest that dietary ,-3 fatty acids do not play a major role in protecting against asthma, and that higher levels of erythrocyte membrane linoleic acid are associated with a lower risk of asthma. [source] | |||||||||||||