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PubMed1995

Extracellular ATP inhibits agonist-induced mobilization of internal calcium in human platelets.

Our previous studies have demonstrated that platelets possess ATP purinergic receptors in addition to the ADP, P2T, receptor. Occupancy of the P2 receptor by ATP inhibited agonist-induced platelet aggregation. This study demonstrated that the mechanism of inhibition may involve ATP inhibition of agonist-induced mobilization of internal calcium. Within the cardiovascular system, the ATP inhibition of calcium mobilization is unique to platelets. All other cell types in the cardiovascular system, where calcium mobilization is affected by extracellular ATP, responded with an increased mobilization as opposed to inhibition. The platelet inhibitory response to ATP was enhanced by the addition of an ATP generating system, creatine phosphate/phosphocreatine kinase. ATP and ATP analogues were found to inhibit calcium mobilization with a rank order of alpha beta-methylene ATP, beta gamma-methylene ATP approximately ATP > benzoyl ATP > 2 methylthio ATP which is a characteristic of P2x-like receptors. The inhibitory effect of ATP could be abrogated by prolonged treatment of platelets with the P2x desensitizing agent, alpha beta-methylene ATP. Also, UTP and CTP were approximately as effective inhibitors as ATP while GTP was not. ATP competition with ADP for the P2T receptor was excluded in studies with platelets derived from an aspirin-treated individual which were essentially insensitive to ADP. The agonist-induced calcium mobilization and inhibition by ATP occurred with the thromboxane A2 mimetic, U46619, collagen and thrombin; however, the kinetics of mobilization varied somewhat with the different agonists. The responses to extracellular ATP were independent of extracellular Ca2+, where 1 mM calcium or 0.3 mM EGTA was added to the reaction mixture. The inhibition of calcium mobilization coupled to inhibition of platelet aggregation by extracellular ATP may serve an important physiologic role. ATP, released from activated platelets at localized sites of vascular injury, may help to limit the size of the platelet plug-clot that, if left unregulated, could occlude the injured blood vessel.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1985

Patient mobility for elective surgical interventions.

In this study, we address the question of patient mobility by defining three types of mobility and testing them with a Probit model. First, we have forced mobility (shortage of resources), second, physician-induced mobility (hospital affiliations) and finally, the mobility chosen by patients. We isolate explanatory variables for observed patient mobility for the year 1977-1978 in Quebec, Canada, and present the results for two specific surgical interventions. We found that forced and induced mobility are statistically significant in explaining the movements of patients in search of specific medical services. However, the mobility chosen by patients requires further investigation.

Adolescent↗

PubMedDate not supplied

Effects of ethanol exposure on neuropeptide-stimulated calcium mobilization in N1E-115 neuroblastoma.

The effects of acute and chronic (100 mM for 7 days) ethanol exposures on resting intracellular free calcium, [Ca2+]i as well as bradykinin and neurotensin mediated [Ca2+]i mobilization were determined in intact N1E-115 neuroblastoma. [Ca2+]i was monitored fluorometrically with the calcium indicator, fluo-3/AM. Acute exposure to ethanol resulted in an inhibition of bradykinin mediated [Ca2+]i mobilization with significant effects observed only at 400 mM ethanol. Neurotensin mediated [Ca2+]i mobilization was not significantly affected by any of the ethanol concentrations tested. Similarly, resting [Ca2+]i (64 +/- 2 nM) was unaffected by either chronic or acute ethanol as high as 400 mM. However, chronic exposure to ethanol significantly reduced the magnitude of bradykinin mediated [Ca2+]i mobilization both in the absence and presence of extracellular [Ca2+]. In contrast, [Ca2+]i mobilization in the presence of various concentrations of neurotensin was not significantly affected by chronic ethanol exposure. The results suggest that neuropeptide mediated [Ca2+]i mobilization is relatively insensitive to the acute presence of ethanol. In addition, chronic ethanol exposure appears to have selective effects on receptor mediated [Ca2+]i mobilization because this response to bradykinin, but not neurotensin, was significantly reduced in cells exposed to ethanol. The results also suggest that the reduction in bradykinin stimulated [Ca2+]i mobilization in chronically exposed cells is due in part to an inhibition of the release of intracellularly bound [Ca2+].

Animals↗

PubMed2005

Extent and variations in mobile phone use among drivers of heavy vehicles in Denmark.

A substantial body of research has shown that use of mobile phones while driving can impair driving performance and increase the risk of being involved in accidents. Similarly, mobile phone use seems to be an increasing activity thus representing a relevant traffic safety issue. This paper investigates the extent and variations in mobile phone use among drivers of heavy vehicles in Denmark. The data was collected through written questionnaires and had a response rate of 58%. It was found that more than 99% of the drivers used mobile phones while driving. Despite a prohibition of hand-held mobile phone use while driving 31% of the drivers reported to do so. Analysis of the variations in usage found a positive significant relationship between driving hours and phone use. A negative linear effect was found between age and phone use. Similarly, a positive significant association was found between the number of stops and the amount of phone use. 0.5% reported that their use of mobile phones had contributed to an accident, while 6% had experienced their mobile phone use causing a dangerous situation. However, 66% reported experiencing dangerous situations because of others road users' mobile phone use. Various implications of the findings are discussed particularly in relation to the drivers with high exposure.

Accidents, Occupational↗

PubMed2006

Change in mobility activity in the second year after stroke in a rehabilitation population: who is at risk for decline?

OBJECTIVES: To investigate the development of mobility status during the second year after stroke in patients who had had inpatient rehabilitation, and to evaluate risk factors for mobility decline. DESIGN: Evaluation of change in Rivermead Mobility Index (RMI) score over the second year after stroke in an inception cohort of first-ever stroke patients eligible for inpatient rehabilitation. Logistic regression techniques were used to predict decline. Independent variables were measured with standardized instruments 1 year after stroke. SETTING: Home or institution, after discharge from rehabilitation center. PARTICIPANTS: Patients (N=148) with single first-ever stroke (supratentorial), age more than 18 years. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Decline of 2 or more points on the RMI and the percentages and odds ratios (ORs) for decline. RESULTS: The mean RMI score did not significantly change over time. Mobility declined in 12% of the patients. Mobility decline was found more often in patients with depression (25%) than without (7%), with right-sided weakness (17% vs 8%), with ischemic stroke (13% vs 8%), with aphasia (22% vs 11%), with cognitive dysfunction (17% vs 11%), with comorbidity interfering with locomotion (25% vs 12%), with poor social functioning (15% vs 10%), and with mobility disability (16% vs 8%). Statistical significance was found only for depression (OR=4.2; 95% confidence interval, 1.3-13.2). CONCLUSIONS: Most patients maintained the level of mobility they achieved during inpatient rehabilitation over the second year after stroke. Only 12% had a decline in mobility, and depression was the only statistically significant predictor for decline.

Activities of Daily Living↗

PubMed2005

Antigen-induced Ca2+ mobilization in RBL-2H3 cells: role of I(1,4,5)P3 and S1P and necessity of I(1,4,5)P3 production.

Inositol 1,4,5-trisphosphate (IP3) has long been recognized as a second messenger for intracellular Ca2+ mobilization. Recently, sphingosine 1-phosphate (S1P) has been shown to be involved in Ca2+ release from the endoplasmic reticulum (ER). Here, we investigated the role of S1P and IP3 in antigen (Ag)-induced intracellular Ca2+ mobilization in RBL-2H3 mast cells. Antigen-induced intracellular Ca2+ mobilization was only partially inhibited by the sphingosine kinase inhibitor dl-threo-dihydrosphingosine (DHS) or the IP3 receptor inhibitor 2-aminoethoxydiphenyl borate (2-APB), whereas preincubation with both inhibitors led to complete inhibition. In contrast, stimulation of A3 adenosine receptors with N5-ethylcarboxamidoadenosine (NECA) caused intracellular Ca2+ mobilization that was completely abolished by 2-APB but not by DHS, suggesting that NECA required only the IP3 pathway, while antigen used both the IP3 and S1P pathways. Interestingly, however, inhibition of IP3 production with the phospholipase C inhibitor U73122 completely abolished Ca2+ release from the ER induced by either stimulant. This suggested that S1P alone, without concomitant production of IP3, would not cause intracellular Ca2+ mobilization. This was further demonstrated in some clones of RBL-2H3 cells excessively overexpressing a beta isoform of Class II phosphatidylinositol 3-kinase (PI3KC2beta). In such clones including clone 5A4C, PI3KC2beta was overexpressed throughout the cell, although endogenous PI3KC2beta was normally expressed only in the ER. Overexpression of PI3KC2beta in the cytosol and the PM led to depletion of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), resulting in a marked reduction in IP3 production. This could explain the abolishment of intracellular Ca2+ mobilization in clone 5A4C. Supporting this hypothesis, the Ca2+ mobilization was reconstituted by the addition of exogenous PI(4,5)P2 in these cells. Our results suggest that both IP3 and S1P contribute to FcvarepsilonRI-induced Ca2+ release from the ER and production of IP3 is necessary for S1P to cause Ca2+ mobilization from the ER.

Animals↗

PubMed2006

Effect of monascus pigment derivatives on the electrophoretic mobility of bacteria, and the cell adsorption and antibacterial activities of pigments.

Various amino acid derivatives of monascus pigments were synthesized. The effects of pigment derivatives on the pigment adsorption ratio, electrophoretic mobility (EPM) of bacterial cells, and antibacterial activity were investigated under varying conditions of pigment type, pigment concentration, pH, and ionic strength. Two hydrophobic and two hydrophilic derivatives were selected as model pigments. There was a close relationship between the antimicrobial activity and the pigment adsorption ratio. Against Escherichia coli, the hydrophobic L-Tyr and L-Phe derivatives (log P = 3.18 and 3.57) exhibited high antimicrobial activities (MIC = 8 and 16 mg/L) and high cellular adsorption ratios (9.6 and 10.9 mg/L). The hydrophilic L-Glu and L-Asn derivatives (log P = 1.40 and 0.47) exhibited low activities (MIC = 64 and 128 mg/L) and low adsorption ratios (4.7 and 4.0 mg/L). The electrophoretic mobility of 11 different bacteria varied between -1.93 x 10(-8) and -1.19 x 10(-8) m(2) V(-1) s(-1) regardless of Gram(+) or Gram(-). The L-Phe derivative showed low MIC values (high antimicrobial activities) against bacteria with a high electrophoretic mobility. A positive linearity between the pigment adsorption ratio and the electrophoretic mobility was established. When the four pigment derivatives were added to E. coli solutions, the electrophoretic mobility of cells in all cases sharply increased with an increasing pigment concentration. The mobility value was high for hydrophobic pigment derivatives in descending order of L-Phe (0.8 x 10(-8) m(2) V(-1) s(-1)), L-Tyr (0.68 x 10(-8) m(2) V(-1) s(-1)), L-Glu (0.46 x 10(-8) m(2) V(-1) s(-1)), and L-Asn (0.44 x 10(-8) m(2) V(-1) s(-1)). Additional adsorption of the hydrophobic derivatives probably occurred due to a hydrophobic interaction between the pigment and the pigment-coated cells. The electrophoretic mobility decreased gradually with an increasing pH and/or ionic strength with both addition and no addition of the pigment derivatives. The pattern of change of the pigment adsorption ratio under varying pH and/or ionic strength values was similar to the pattern for electrophoretic mobility.

Adsorption↗

PubMed2004

GSM-PKI solution enabling secure mobile communications.

Because of its wide distribution and ease of use, the mobile phone, as a reliable personal communications channel, offers an excellent basis for the provision of reliable electronic communications services. In Finland, ca. 75% of the citizens have a mobile phone and, at present and most likely also in the future, it is the most widely spread service channel allowing reliable electronic communications. Despite the restricted functions of the mobile phone, the citizens can use the phone also as a communications medium. In 2001, the Finns sent over 1 billion SMS messages. In Finland, TeliaSonera Finland Oyi and the Population Register Centre (PRC) have closed a co-operation agreement with the aim of creating a mobile phone service for the electronic identification of a person. The co-operation launched is a significant development project from the perspective of the citizens. As a result, the consumers will have a new alternative for reliable electronic communications and commerce in data networks in addition to the electronic identification card. In the future, it will be possible to use the services of both public administration and the private sector by means of a mobile phone more reliably than before, without a physical visit, e.g. to a health centre or to another provider of healthcare services. The possibility of identification and signature by a mobile phone allows an easier provision of versatile services irrespective of time and place, because, in addition to voice, text message, and WAP functions, the service can be utilised also in communications services through the Internet, in which case, the mobile phone acts like a card reader. From the perspective of reliable personal mobile communications, the healthcare sector is one of the most significant and challenging application areas.

Cell Phone↗

PubMed2005

Renal mobility during uncoached quiet respiration: an analysis of 4DCT scans.

PURPOSE: Data on organ mobility is required for optimizing radiotherapy. Renal mobility was studied in four-dimensional computed tomography (4DCT) scans acquired during uncoached respiration. METHODS AND MATERIALS: The 4DCT scans of 54 patients, in whom at least the upper pole of both kidneys were visualized in all 10 respiratory phases, were analyzed. Scans were performed on a 16-slice CT scanner (slice index and reconstruction, 2.5 mm) during quiet, uncoached respiration. Mobility of the renal apex was evaluated in all patients by use of the z-position on CT slices. Reproducibility of mobility was studied in 8 patients who underwent 1 or 2 repeat 4DCT scans. RESULTS: Mobility was predominantly craniocaudal, with a mean of 9.8 mm for the left kidney and 9.0 mm for the right kidney. Large interpatient variations were observed that ranged from 2.5 to 30 mm (left) and 2.5 to 20 mm (right), and mobility of 1 kidney did not predict for mobility of the contralateral organ. Reproducibility of renal mobility and position at end-expiration was poor, with positional variations in repeat scans appearing to correlate with changes in the amplitude of respiratory waveform and total lung volume. CONCLUSIONS: Large interpatient variations in renal movement occur during uncoached respiration, which indicates that respiratory coaching is useful for 4DCT imaging and treatment delivery.

Abdominal Neoplasms↗

PubMed2003

Hyper-mobile water is induced around actin filaments.

When introduced into water, some molecules and ions (solutes) enforce the hydrogen-bonded network of neighboring water molecules that are thus restrained from thermal motions and are less mobile than those in the bulk phase (structure-making or positive hydration effect), and other solutes cause the opposite effect (structure-breaking or negative hydration effect). Using a method of microwave dielectric spectroscopy recently developed to measure the rotational mobility (dielectric relaxation frequency) of water hydrating proteins and the volume of hydration shells, the hydration of actin filament (F-actin) has been studied. The results indicate that F-actin exhibits both the structure-making and structure-breaking effects. Thus, apart from the water molecules with lowered rotational mobility that make up a typical hydration shell, there are other water molecules around the F-actin which have a much higher mobility than that of bulk water. No such dual hydration has been observed for myoglobin studied as the representative example of globular proteins which all showed qualitatively similar dielectric spectra. The volume fraction of the mobilized (hyper-mobile) water is roughly equal to that of the restrained water, which is two-thirds of the molecular volume of G-actin in size. The dielectric spectra of aqueous solutions of urea and potassium-halide salts have also been studied. The results suggest that urea and I(-) induce the hyper-mobile states of water, which is consistent with their well-known structure-breaking effect. The molecular surface of actin is rich in negative charges, which along with its filamentous structure provides a structural basis for the induction of a hyper-mobile state of water. A possible implication of the findings of the present study is discussed in relation to the chemomechanical energy transduction through interaction with myosin in the presence of ATP.

Actin Cytoskeleton↗

PubMed2001

Reviewing mobile phases used on Chiralcel OD through an application of data mining tools to CHIRBASE database.

During the past decade, thousands of compounds have been resolved on Chiralcel OD (a cellulose-based chiral stationary phase) under diverse eluting conditions. Many researches have documented the effects of mobile phase on enantioselectivity for a given family of samples but today no comprehensive study aimed at identifying the associations between the structural features present on solute and appropriate mobile phase conditions has yet been proposed. In this review of mobile phases used on Chiralcel OD, we try to go far beyond a simple enumeration of eluting conditions and an effort is made to explore the utility of data mining tools for assessing the knowledge contained in CHIRBASE database. We have extracted from CHIRBASE the chemical features of 2363 chiral compounds separated on Chiralcel OD and their corresponding mobile phases. This data set was submitted to data mining programs for molecular pattern recognition and mobile phase predictions for new cases. Some substructural characteristics of solutes were related to the efficient use of some specific mobile phases. For example, the application of CH3CN/salt buffer at pH 6-7 was found convenient for reversed-phase separation of compounds bearing a tertiary amine functional group. Furthermore, a cluster analysis allowed the arrangement of the mobile phases according to similarity found in molecular patterns of solutes. A decision tree, which may lead to a more rational choice of the mobile phase under reversed-phase conditions, is also proposed.

Carbamates↗

PubMed1979

Mobilization of iron from specifically labeled reticulocyte ghosts.

Specifically labeled 59Fe ghosts have been prepared by incubation of whole reticulocytes with 59Fe3+-transferrin-CO3(2)-- followed by washing and ghost isolation. The binding of 59Fe by the membrane fraction is quite stable over a wide range of conditions, but iron mobilization occurs on incubation with chelating agents or cell lysate. The time course of 59Fe mobilization by unlabeled reticulocyte lysate exhibits five apparently zero-order phases. The rate of iron mobilization is linearly dependent on the concentration of 59Fe ghosts present in the incubation mixture. In contrast, the relative concentration of lysate appears to exhibit a saturation dependence with regard to membrane iron mobilization. Bathophenanthroline sulfonate follows a multiphasic time course of iron mobilization similar to that found with the lysate. Lysate from mature erythrocytes was found to mobilize iron with kinetics that are identical to reticulocyte lysate. The number and duration of the phases is independent of the mobilizing agent. The role of the membrane fraction in regulating the rate of iron release to cytosol was also investigated by the repetitive incubation of 59Fe ghosts with fresh lysate. The rate of 59Fe mobilization depended on the condition of the ghost with regard to prior 59Fe depletion. This publication emphasizes the active role of the membrane fraction in determining the rate at which iron will become available to the cytosol and the possibility that cytosol factors modulate the action of membrane bound components.

Animals↗

PubMedDate not supplied

[Prevalence of mobile phone use while driving vehicles].

OBJECTIVE: To estimate the prevalence of mobile telephone use while driving vehicles in the city of Lleida (Spain). METHODS: A random sample of 1536 cars passing through six intersections regulated by traffic lights in Lleida were selected (three with urban traffic and three with interurban traffic). Cyclists, motorcyclists and driving school cars were excluded. The variables studied were mobile telephone use, age, (18-40; 41-60; >61), sex, the presence of passengers, type of intersection (urban traffic/interurban traffic), day of the week (working day/weekend or holiday) and hour of the day (rush hour/non-rush hour). The prevalence of mobile telephone use was calculated in percentages with a 95% CI. The relationship among the dependent variable (mobile telephone use) and the other independent variables was studied using odds radios (OR) and 95% CI. RESULTS: A total of 1536 direct observations were made and mobile telephone use was detected in 50 drivers. The prevalence was 3.3 (95% CI, 2.4-4.3). The prevalence was higher in men (OR = 2.2; 95% CI, 1.0-5.7), in drivers aged more than 60 years old (OR = 2.2; 95% CI, 0.5-8,4) and in those aged 18-40 years old (OR =1.5; 95% CI, 0.8-3.0), in unaccompanied drivers (OR = 3.0; 95% CI, 1.5-6.3), in urban intersections (OR = 2.7; 95% CI, 1.2-5.9), on workdays (OR = 2.0; 95% CI, 0.9-4.4) and at the rush hour (OR =1.4; 95% CI, 0.8-2.4). CONCLUSIONS: The prevalence of mobile telephone use while driving vehicles can be considered high, because of the increase in car accidents. The profile of drivers using mobile telephones corresponds to men aged 18-40 years or more than 61 years, in urban intersections, without passengers, during workdays and at the rush hour. We recommend the implementation of measures to decrease the use of mobile telephones while driving.

Adolescent↗

PubMed1999

A computer study of fracture mobility and strain on biodegradable plates used for fixation of mandibular fractures.

PURPOSE: This computer-based study was done to determine whether a small biodegradable plate system was suitable for internal fixation of mandibular fractures. MATERIALS AND METHODS: In a three-dimensional computer model of the mandible, fracture mobility and plate strain were calculated for bite forces applied on 13 bite points on the dental arch. Simulated solitary angle, body, and symphysis fractures were fixed with one titanium miniplate, one polylactide (PLA) midiplate, one PLA maxiplate, or two PLA midiplates. Fractures with and without interfragmentary bone contact were studied. In the case of fractures with bone contact, the loads were transmitted through the fracture surfaces and the plate; when there was no contact, the loads were transmitted only through the plate. Maximum fracture mobility was set at 150 microm. Maximum plate strain was set at the yield strain of PLA and titanium. RESULTS: For fractures without interfragmentary bone contact, all plate fixations resulted in a fracture mobility and plate strain higher than the limits set, except for the symphysis fracture fixed with two PLA midiplates. Interfragmentary bone contact significantly reduced fracture mobility and plate strain. For the angle fracture with bone contact, all PLA plate fixations resulted in a fracture mobility above the limit, whereas the titanium miniplate fixation had a fracture mobility below the limit. For the body and symphysis fracture with bone contact, only double PLA midiplate fixation resulted in a fracture mobility below the limit. CONCLUSIONS: From a mechanical point of view, based on the computer model, small PLA plates are only suitable for symphysis fractures with and without interfragmentary bone contact and for body fractures with interfragmentary contact. However, fixation with two PLA plates is always necessary to provide sufficient reduction of fracture mobility and plate strain.

Absorbable Implants↗

PubMed2001

Health risks from the use of mobile phones.

Widespread concerns have been raised about the possibility that exposure to the radiofrequency (RF) fields from mobile telephones or their base stations could affect people's health. Such has been the rapid growth of mobile telecommunications that there will be about one billion mobile phone users before 2005. Already there are more mobile than fixed-line users. Developing countries are establishing mobile telecommunications rather than the more expensive fixed-line systems. Thus, if there is any impact on health from mobile telephones, it will affect everyone in the world. The World Health Organization (WHO) established the International EMF Project in 1996 to evaluate the science, recommend research to fill any gaps in knowledge and to conduct formal health risk assessments of RF exposure once recommended research had been completed. In addition, the UK government established an independent expert group to review all the issues concerning health effects of mobile telephones and siting of base stations. Cancer has been suggested as an outcome of exposure to mobile telephones by some scientific reports. This paper reviews the status of the science and WHO's programme to address the key issues. In addition, the main conclusions and recommendations of the UK expert group will be summarised.

Brain↗

PubMed1997

Inhibition of muscarinic-stimulated polyphosphoinositide hydrolysis and Ca2+ mobilization in cat iris sphincter smooth muscle cells by cAMP-elevating agents.

The effects of carbachol (CCh) on inositol 1,4,5-trisphosphate (IP3) production and intracellular calcium ([Ca2+]i) mobilization, and their regulation by cAMP-elevating agents were investigated in SV-40 transformed cat iris sphincter smooth muscle (SV-CISM-2) cells. CCh produced time- and dose-dependent increases in IP3 production; the t1/2 and EC50 values were 68 s and 0.5 microM, respectively. The muscarinic agonist provoked a transient increase in [Ca2+]i which reached maximum within 77 s, and increased [Ca2+]i mobilization in a concentration-dependent manner with an EC50 of 1.4 microM. Thapsigargin, a Ca(2+)-pump inhibitor, caused a rapid rise in [Ca2+]i and subsequent addition of CCh was without effect. Both CCh-induced IP3 production and CCh-induced [Ca2+]i mobilization were more potently antagonized by 4-DAMP, an M3 muscarinic receptor antagonist, than by pirenzepine, an M1 receptor antagonist, suggesting that both responses are mediated through the M3 receptor subtype. Treatment of the cells with U73122, a phospholipase C (PLC) inhibitor, resulted in a concentration-dependent decrease in both CCh-stimulated IP3 production and [Ca2+]i mobilization. These data indicate close correlation between enhanced IP3 production and [Ca2+]i mobilization in these smooth muscle cells and suggest that the CCh-stimulated increase in [Ca2+]i could be mediated through increased IP3 production. Isoproterenol (ISO) inhibited CCh-induced IP3 production (IC50 = 80 nM) and [Ca2+]i mobilization (IC50 = 0.17 microM) in a concentration-dependent manner. Microsomal fractions isolated from SV-CISM-2 cells contained phospholipase C (PLC) which was stimulated by CCh (10 microM) and GTP gamma S (0.1 microM). Pretreatment of the cells with ISO or forskolin, 5 microM each, produced membrane fractions in which CCh-stimulated PLC activity was significantly attenuated. Furthermore, when microsomal fractions isolated from SV-CISM-2 cells were phosphorylated with Protein kinase A (PKA), the CCh- and GTP gamma S-stimulated IP3 production were significantly inhibited. It can be concluded from these studies that in SV-CISM-2 cells, activation of M3 muscarinic receptors results in stimulation of PLC-mediated PIP2 hydrolysis, generating IP3 which mobilizes [Ca2+]i. Furthermore, elevation of cAMP may inhibit IP3 production and [Ca2+]i mobilization through mechanisms involving PKA-dependent phosphorylation of PLC, G-proteins, IP3 receptor and/or IP3 metabolizing enzymes.

Adrenergic beta-Agonists↗

PubMed2001

Dielectric friction in capillary electrophoresis: mobility of organic anions in mixed methanol-water media.

The mobilities of a series of organic carboxylates and sulfonates, ranging in charge from -1 to -4, were investigated by capillary electrophoresis using buffers containing 0 to 75% (v/v) methanol. Effective mobilities were measured at a series of ionic strengths, and were extrapolated to zero ionic strength using Pitts' equation to yield absolute mobilities. Generally, higher-charged ions were more strongly influenced by ionic strength, as predicted by the Pitts' equation. Some differences in the ionic strength effects for anions of like charge were observed and were consistent with the relaxation effect. The absolute mobilities of anions were altered by the addition of methanol to the buffer. Analytes with higher charge-to-size ratios were slowed to a greater extent than were ions with lower charge-to-size. As a result, dramatic changes in relative mobility were observed, such as a reversal in migration order between anions of -1 and -4 charge at 75% methanol and 20 mM ionic strength. The mobility changes caused by the addition of methanol are attributed to dielectric friction. Mobilities in the methanol-water solutions were found to depend on analyte charge-to-size and solvent dielectric relaxation time (tau) and were inversely dependent upon solvent dielectric constant (epsilon), as predicted by the Hubbard-Onsager mobility model.

Journal Article↗

PubMed1992

Kinetic characterization of reductant dependent processes of iron mobilization from endocytic vesicles.

The reductant dependence of iron mobilization from isolated rabbit reticulocyte endosomes containing diferric transferrin is reported. The kinetic effects of acidification by a H(+)-ATPase are eliminated by incubating the endosomes at pH 6.0 in the presence of 15 microM FCCP to acidify the intravesicular milieu and to dissociate 59Fe(III) from transferrin. In the absence of reductants, iron is not released from the vesicles, and iron leakage is negligible. The second-order dependence of rate constants and amounts of 59Fe mobilized from endosomes using ascorbate, ferrocyanide, or NADH are consistent with reversible mechanisms. The estimated apparent first-order rate constant for mobilization by ascorbate is (2.7 +/- 0.4) x 10(-3) s-1 in contrast to (3.2 +/- 0.1) x 10(-4) s-1 for NADH and (3.5 +/- 0.6) x 10(-4) s-1 for ferrocyanide. These results support models where multiple reactions are involved in complex processes leading to iron transfer and membrane translocation. A type II NADH dehydrogenase (diaphorase) is present on the endosome outer membrane. The kinetics of extravesicular ferricyanide reduction indicate a bimolecular-bimolecular steady-state mechanism with substrate inhibition. Ferricyanide inhibition of 59Fe mobilization is not detected. Significant differences between mobilization and ferricyanide reduction kinetics indicate that the diaphorase is not involved in 59Fe(III) reduction. Sequential additions of NADH followed by ascorbate or vice versa indicate a minimum of two sites of 59Fe(III) residence; one site available to reducing equivalents from ascorbate and a different site available to NADH. Sequential additions using ferrocyanide and the other reductants suggest interactions among sites available for reduction. Inhibition of ascorbate-mediated mobilization by DCCD and enhancement of ferrocyanide and NADH-mediated mobilization suggest a role for a moiety with characteristics of a proton pore similar to that of the H(+)-ATPase. These data provide significant constraints on models of iron reduction, translocation, and mobilization by endocytic vesicles.

Animals↗