Endothelial remodelling and intracellular calcium machinery.

Rather being an inert barrier between vessel lumen and surrounding tissues, vascular endothelium plays a key role in the maintenance of cardiovascular homeostasis. The de-endothelialization of blood vessels is regarded as the early event that results in the onset of severe vascular disorders, including atherosclerosis, acute myocardial infarction, brain stroke, and aortic aneurysm. Restoration of the endothelial lining may be accomplished by the activation of neighbouring endothelial cells (ECs) freed by contact inhibition and by circulating endothelial progenitor cells (EPCs). Intracellular Ca(2+) signalling is essential to promote wound healing: however, the molecular underpinnings of the Ca(2+) response to injury are yet to be fully elucidated. Similarly, the components of the Ca(2+) toolkit that drive EPC incorporation into denuded vessels are far from being fully elucidated. The present review will survey the current knowledge on the role of Ca(2+) signalling in endothelial repair and in EPC activation. We propose that endothelial regeneration might be boosted by intraluminal release of specific Ca(2+) channel agonists or by gene transfer strategies aiming to enhance the expression of the most suitable Ca(2+) channels at the wound site. In this view, connexin (Cx) channels/hemichannels and store-operated Ca(2+) entry (SOCE) stand amid the most proper routes to therapeutically induce the regrowth of denuded vessels. Cx stimulation might trigger the proliferative and migratory behaviour of ECs facing the lesion site, whereas activation of SOCE is likely to favour EPC homing to the wounded vessel.

Store-dependent Ca(2+) entry in endothelial progenitor cells as a perspective tool to enhance cell-based therapy and adverse tumour vascularization.

Endothelial progenitor cells (EPCs) have recently been employed in cell-based therapy (CBT) to promote neovascularization and regeneration of ischemic organs, such as heart and limbs. Furthermore, EPCs may be recruited from bone marrow by growing tumors to drive the angiogenic switch through physical engrafting into the lumen of nascent vessels or paracrine release of pro-angiogenic factors. CBT is hampered by the paucity of EPCs harvested from peripheral blood and suffered from several pitfalls, including the differentiation outcome of transplanted cells and low percentage of engrafted cells. Therefore, CBT will benefit from a better understanding of the signal transduction pathway(s) which govern(s) EPC homing, proliferation and incorporation into injured tissues. At the same time, this information might outline alternative molecular targets to combat tumoral neovascularization. We have recently found that store-operated Ca(2+) entry, a Ca(2+)-permeable membrane pathway that is activated upon depletion of the inositol-1,4,5-trisphosphate-sensitive Ca(2+) pool, is recruited by vascular endothelial growth factor to support proliferation and tubulogenesis in human circulating endothelial colony forming cells (ECFCs). ECFCs are a subgroup of EPCs that circulate in the peripheral blood of adult individuals and are able to proliferate and differentiate into endothelial cells and form capillary networks in vitro and contribute to neovessel formation in vivo. The present review will discuss the relevance of SOCE to ECFC-based cell therapy and will address the pharmacological inhibition of store-dependent Ca(2+) channels as a promising target for anti-angiogenic treatments.

Extracellular ATP induces fast and transient non-selective cationic currents and cytosolic Ca2+ changes in human umbilical artery smooth muscle cells.

Ionotropic purinergic receptors (P2X) are expressed in endothelial and smooth muscle cells of blood vessels. ATP acting on smooth muscle P2X receptors is able to induce vasoconstriction in different kind of vessels. However, to our knowledge, there are no reports that directly show the activity of these purinergic receptors in native human vascular smooth muscle cells. In this work, we describe for the first time an ATP-induced current in freshly isolated human umbilical artery (HUA) smooth muscle cells. The current was measured by patch-clamp technique in whole-cell condition on cells clamped at -50 mV. At 100 µM of ATP the current showed a rapid activation and desensitization, and was carried by both Na(+) and Ca(2+). The current was completely blocked by suramin (300 µM) and partially blocked by 100 µM of Zn(2+) without affecting the kinetic of desensitization. All these properties suggest that the ATP-induced ionic currents are mediated through P2X(1)-like receptors. Moreover, we show that ATP transiently increased cytosolic Ca(2+) in "in situ" smooth muscle cells of intact HUA segments and that this response is dependent of extracellular and intracellular Ca(2+). These data expand the knowledge of purinergic receptors properties in vascular smooth muscle cells and the probable role of ATP as a paracrine modulator of contractile tone in a human artery which is fundamental for feto-placental blood flow.

Genistein effects on Ca2+ handling in human umbilical artery: inhibition of sarcoplasmic reticulum Ca2+ release and of voltage-operated Ca2+ channels.

Isoflavones are a group of natural phytoestrogens including the compound genistein. Health beneficial effects have been attributed to the consumption of this compound, but the fact that it has estrogen-like activity has raised doubts regarding its potential risk in infants, newborns, or in the fetus and placenta during pregnancy. This work is aimed at studying genistein effects on Ca2+ handling by smooth muscle cells of the human umbilical artery (HUA). Using fluorometric techniques, we found that in these cells genistein reduces the intracellular Ca2+ peak produced by serotonin. The same result could be demonstrated in absence of extracellular Ca2+, suggesting that the isoflavone reduces Ca2+ release from the sarcoplasmic reticulum. Force measurement experiments strengthen these results, since genistein reduced the peak force attained by intact HUA rings stimulated by serotonin in a Ca2+-free solution. Moreover, genistein induced the relaxation of HUA rings precontracted either with serotonin or a depolarizing high-extracellular K+ solution, hinting at a reduction of extracellular Ca2+ entry to the cell. This was confirmed by whole-cell patch-clamp experiments where it was shown that the isoflavone inhibits ionic currents through voltage-operated Ca2+ channels. In summary, we show that genistein inhibits two mechanisms that could increase intracellular Ca2+ in human umbilical smooth muscle cells, behaving in this way as a potential vasorelaxing substance of fetal vessels. Taking into account that genistein is able to cross the placental barrier, these data show that isoflavones may have important implications in the regulation of feto-maternal blood flow in pregnant women who consume soy-derived products as part of their meals.

Efectos de la genisteína en los niveles del Ca2+ citosólico en células musculares de arteria umbilical humana / Genistein effects on Ca2+ handling in human umbilical artery: inhibition of sarcoplasmic reticulum Ca2+ release and of voltage-operated Ca2+ channels

Isoflavones are a group of natural phytoestrogens including the compound genistein.Health beneficial effects have been attributed to the consumption of this compound,but the fact that it has estrogen-like activity has raised doubts regarding itspotential risk in infants, newborns, or in the fetus and placenta during pregnancy.This work is aimed at studying genistein effects on Ca2+ handling by smooth musclecells of the human umbilical artery (HUA). Using fluorometric techniques, we foundthat in these cells genistein reduces the intracellular Ca2+ peak produced by serotonin.The same result could be demonstrated in absence of extracellular Ca2+, suggestingthat the isoflavone reduces Ca2+ release from the sarcoplasmic reticulum.Force measurement experiments strengthen these results, since genistein reduced thepeak force attained by intact HUA rings stimulated by serotonin in a Ca2+-free solution.Moreover, genistein induced the relaxation of HUA rings precontracted eitherwith serotonin or a depolarizing high-extracellular K+ solution, hinting at a reductionof extracellular Ca2+ entry to the cell. This was confirmed by whole-cell patchclampexperiments where it was shown that the isoflavone inhibits ionic currentsthrough voltage-operated Ca2+ channels. In summary, we show that genisteininhibits two mechanisms that could increase intracellular Ca2+ in human umbilical smooth muscle cells, behaving in this way as a potential vasorelaxing substance offetal vessels. Taking into account that genistein is able to cross the placental barrier,these data show that isoflavones may have important implications in the regulationof feto-maternal blood flow in pregnant women who consume soy-derived productsas part of their meals(AU)

Las isoflavonas son un grupo de fitoestrógenosnaturales que incluyen la genisteína. Alconsumo de este compuesto se le han atribuidoefectos beneficiosos para la salud, pero su actividadsimilar a los estrógenos permite pensaren efectos indeseados en niños o en el feto o laplacenta durante el embarazo. En este trabajose estudian los efectos de la genisteína sobre elmanejo de Ca2+ por las células de músculo lisode la arteria umbilical humana (AUH).Mediante la utilización de técnicas fluorométricasse observó que la genisteína reduce elpico de Ca2+ intracelular producido por la serotonina en estas células incluso en ausenciade Ca2+ extracelular, lo que sugiere que la isoflavonareduce la liberación de Ca2+ a partir delretículo sarcoplásmico. Los experimentos demedida de fuerza refuerzan estos resultados, yaque la genisteína redujo la fuerza pico desarrolladapor serotonina en anillos intactos deAUH en una solución libre de Ca2+. Además,la genisteína indujo la relajación de anillos deAUH precontraídos con serotonina o con unasolución despolarizante de alto K+ extracelular,lo que apunta a una reducción de la entradade Ca2+ desde el exterior de la célula. Con latécnica de “patch-clamp” en configuración decélula entera, los resultados confirmaron que laisoflavona inhibe corrientes iónicas a través decanales de Ca2+ operados por el voltaje. Enresumen, mostramos que la genisteína inhibedos mecanismos que incrementan el Ca2+intracelular en células de músculo liso deAUH, comportándose de esta manera comoun potencial vasorrelajante de los vasos fetales.Dado que la genisteína atraviesa la barrera placentaria,estos datos muestran que las isoflavonaspodrían tener consecuencias en la regulacióndel flujo materno-fetal en mujeres embarazadasque incluyan productos derivados de lasoja como parte de sus dietas(AU)

The use of photostimulable phosphor systems for periodic quality assurance in radiotherapy.

The fusion of radiological and optical images can be achieved through charging a photostimulable phosphor plate (PSP) with an exposure to a field of X- or gamma-rays, followed by exposure to an optical image which discharges the plate in relation to the amount of incident light. According to this PSP characteristic, we developed a simple method for periodic quality assurance (QA) of light/radiation field coincidence, distance indicator, field size indicators, crosshair centering, coincidence of radiation and mechanical isocenter for linear accelerators. The geometrical accuracy of radiological units can be subjected to the same QA method. Further, the source position accuracy for an HDR remote afterloader can be checked by taking an autoradiography of the radioactive source and simultaneously an optical image of a reference geometrical system.

Genistein inhibits contractile force, intracellular Ca2+ increase and Ca2+ oscillations induced by serotonin in rat aortic smooth muscle.

The soy-derived isoflavones genistein and daidzein affect the contractile state of different kinds of smooth muscle. We describe acute effects of genistein and daidzein on contractile force and intracellular Ca2+ concentration ([Ca2+]i) in in situ smooth muscle of rat aorta. Serotonin (5-HT) (2 microM) or a depolarizing high K+ solution produced the contraction of aortic rings, which were immediately relaxed by 20 microM genistein and by 20 microM daidzein. Accordingly, both 5-HT and a high K+ solution increased the [Ca2+]i in in situ smooth muscle cells. Genistein strongly inhibited the [Ca2+]i increase evoked by 5-HT (74.0 +/- 7.3%, n = 11, p < 0.05), and had a smaller effect on high K+ induced [Ca2+]i increase (19.9 +/- 4.0%, n = 7, p < 0.05). The K+ channels blocker tetraethylammonium (TEA) (0.5 mM) diminished genistein effects on 5-HT-induced [Ca2+]i increase. Interestingly, during prolonged application of 5-HT, the [Ca2+]i oscillated and a short (90 s) preincubation with genistein (20 microM) significantly diminished the frequency of the oscillations. This effect was totally abolished by TEA. In conclusion, in rat aortic smooth muscle, genistein is capable of diminishing the increase in [Ca2+]i and in force evoked by 5-HT and high K+ solution, and of decreasing the frequency of [Ca2+]i oscillations induced by 5-HT. The short time required by genistein, and the relaxing effect of daidzein suggest that tyrosine kinases inhibition is not involved. The small inhibiting effect of genistein on the [Ca2+]i increase evoked by high K+ and the effect of TEA point to the activation by genistein of calcium-activated K+ channels.

Genistein inhibits contractile force, intracellular Ca2+ increase and Ca2+ oscillations induced by serotonin in rat aortic smooth muscle

The soy-derived isoflavones genistein and daidzein affect the contractile state ofdifferent kinds of smooth muscle. We describe acute effects of genistein and daidzeinon contractile force and intracellular Ca2+ concentration ([Ca2+]i) in in situ smoothmuscle of rat aorta. Serotonin (5-HT) (2 ìM) or a depolarizing high K+ solution producedthe contraction of aortic rings, which were immediately relaxed by 20 ìMgenistein and by 20 ìM daidzein. Accordingly, both 5-HT and a high K+ solutionincreased the [Ca2+]i in in situ smooth muscle cells. Genistein strongly inhibited the[Ca2+]i increase evoked by 5-HT (74.0 ± 7.3%, n=11, p<0.05), and had a smallereffect on high K+ induced [Ca2+]i increase (19.9 ± 4.0%, n=7, p<0.05). The K+ channelsblocker tetraethylammonium (TEA) (0.5 mM) diminished genistein effects on 5-HT-induced [Ca2+]i increase. Interestingly, during prolonged application of 5-HT,the [Ca2+]i oscillated and a short (90 s) preincubation with genistein (20 ìM) significantlydiminished the frequency of the oscillations. This effect was totally abolishedby TEA. In conclusion, in rat aortic smooth muscle, genistein is capable of diminishingthe increase in [Ca2+]i and in force evoked by 5-HT and high K+ solution, andof decreasing the frequency of [Ca2+]i oscillations induced by 5-HT. The short timerequired by genistein, and the relaxing effect of daidzein suggest that tyrosine kinasesinhibition is not involved. The small inhibiting effect of genistein on the [Ca2+]iincrease evoked by high K+ and the effect of TEA point to the activation by genisteinof calcium-activated K+ channels (AU)

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Genistein inhibits contractile force, intracellularCa2+ increase and Ca2+ oscillations induced byserotonin in rat aortic smooth muscle

The soy-derived isoflavones genistein and daidzein affect the contractile state ofdifferent kinds of smooth muscle. We describe acute effects of genistein and daidzeinon contractile force and intracellular Ca2+ concentration ([Ca2+]i) in in situ smoothmuscle of rat aorta. Serotonin (5-HT) (2 ìM) or a depolarizing high K+ solution producedthe contraction of aortic rings, which were immediately relaxed by 20 ìMgenistein and by 20 ìM daidzein. Accordingly, both 5-HT and a high K+ solutionincreased the [Ca2+]i in in situ smooth muscle cells. Genistein strongly inhibited the[Ca2+]i increase evoked by 5-HT (74.0 ± 7.3%, n=11, p<0.05), and had a smallereffect on high K+ induced [Ca2+]i increase (19.9 ± 4.0%, n=7, p<0.05). The K+ channelsblocker tetraethylammonium (TEA) (0.5 mM) diminished genistein effects on 5-HT-induced [Ca2+]i increase. Interestingly, during prolonged application of 5-HT,the [Ca2+]i oscillated and a short (90 s) preincubation with genistein (20 ìM) significantlydiminished the frequency of the oscillations. This effect was totally abolishedby TEA. In conclusion, in rat aortic smooth muscle, genistein is capable of diminishingthe increase in [Ca2+]i and in force evoked by 5-HT and high K+ solution, andof decreasing the frequency of [Ca2+]i oscillations induced by 5-HT. The short timerequired by genistein, and the relaxing effect of daidzein suggest that tyrosine kinasesinhibition is not involved. The small inhibiting effect of genistein on the [Ca2+]iincrease evoked by high K+ and the effect of TEA point to the activation by genisteinof calcium-activated K+ channels (AU)

No disponible

The Na+/Ca2+ exchanger is active and working in the reverse mode in human umbilical artery smooth muscle cells.

The data presented in this work suggest that in human umbilical artery (HUA) smooth muscle cells, the Na(+)/Ca(2+) exchanger (NCX) is active and working in the reverse mode. This supposition is based on the following results: (i) microfluorimetry in HUA smooth muscle cells in situ showed that a Ca(2+)-free extracellular solution diminished intracellular Ca(2+) ([Ca(2+)](i)), and KB-R7943 (5microM), a specific inhibitor of the Ca(2+) entry mode of the exchanger, also decreased [Ca(2+)](i) (40.6+/-4.5% of Ca(2+)-free effect); (ii) KB-R7943 produced the relaxation of HUA rings (-24.7+/-7.3gF/gW, n=8, p<0.05); (iii) stimulation of the NCX by lowering extracellular Na(+) increases basal [Ca(2+)](i) proportionally to Na(+) reduction (Delta fluorescence ratio=0.593+/-0.141 for Na(+)-free solution, n=8) and HUA rings' contraction (peak force=181.5+/-39.7 for 130mM reduction, n=8), both inhibited by KB-R7943 and a Ca(2+)-free extracellular solution. In conclusion, the NCX represents an important Ca(2+) entry route in HUA smooth muscle cells.

Expression and function of neuronal nicotinic ACh receptors in rat microvascular endothelial cells.

The expression and function of nicotinic ACh receptors (nAChRs) in rat coronary microvascular endothelial cells (CMECs) were examined using RT-PCR and whole cell patch-clamp recording methods. RT-PCR revealed expression of mRNA encoding for the subunits alpha(2), alpha(3), alpha(4), alpha(5), alpha(7), beta(2), and beta(4) but not beta(3). Focal application of ACh evoked an inward current in isolated CMECs voltage clamped at negative membrane potentials. The current-voltage relationship of the ACh-induced current exhibited marked inward rectification and a reversal potential (E(rev)) close to 0 mV. The cholinergic agonists nicotine, epibatidine, and cytisine activated membrane currents similar to those evoked by ACh. The nicotine-induced current was abolished by the neuronal nAChR antagonist mecamylamine. The direction and magnitude of the shift in E(rev) of nicotine-induced current as a function of extracellular Na(+) concentration indicate that the nAChR channel is cation selective and follows that predicted by the Goldman-Hodgkin-Katz equation assuming K(+)/Na(+) permeability ratio of 1.11. In fura-2-loaded CMECs, application of ACh, but not of nicotine, elicited a transient increase in intracellular free Ca(2+) concentration. Taken together, these results demonstrate that neuronal nAChR activation by cholinergic agonists evokes an inward current in CMECs carried primarily by Na(+), which may contribute to the plasma nicotine-induced changes in microvascular permeability and reactivity induced by elevations in plasma nicotine.

Comparison of three bone ultrasounds for the discrimination of subjects with and without osteoporotic fractures among 7562 elderly women.

UNLABELLED: Bone ultrasound measures (QUSs) can assess fracture risk in the elderly. We compared three QUSs and their association with nonvertebral fracture history in 7562 Swiss women 70-80 years of age. The association between nonvertebral fracture was higher for heel than phalangeal QUS. INTRODUCTION: Because of the high morbidity and mortality associated with osteoporotic fractures, it is essential to detect subjects at risk for such fractures with screening methods. Because quantitative bone ultrasound (QUS) discriminated subjects with osteoporotic fractures from controls in several cross-sectional studies and predicted fractures in prospective studies, QUS could be more practical than DXA for screening. MATERIAL AND METHODS: This cross-sectional and retrospective multicenter (10 centers) study was performed to compare three QUSs (two heel ultrasounds: Achilles+ [GE-Lunar] and Sahara [Hologic]; the phalanges: ultrasound DBM sonic 1200 [IGEA]) for determining by logistic regression nonvertebral fracture odds ratio (OR) in a sample of 7562 Swiss women, 75.3 +/- 3.1 years of age. The two heel QUSs measured the broadband ultrasound attenuation (BUA) and the speed of sound (SOS). In addition, Achilles+ calculated the stiffness index (SI) and the Sahara calculated the quantitative ultrasound index (QUI) from BUA and SOS. The DBM sonic 1200 measured the amplitude-dependent SOS (AD-SOS). RESULTS: Eighty-six women had a history of a traumatic hip fracture after the age of 50, 1594 had a history of forearm fracture, and 2016 had other nonvertebral fractures. No fracture history was reported by 3866 women. Discrimination for hip fracture was higher than for the other nonvertebral fractures. The two heel QUSs had a significantly higher discrimination power than the QUSs of the phalanges, with standardized ORs, adjusted for age and body mass index, ranging from 2.1 to 2.7 (95% CI = 1.6, 3.5) compared with 1.4 (95% CI = 1.1, 1.7) for the AD-SOS of DBM sonic 1200. CONCLUSION: This study showed a high association between heel QUS and hip fracture history in elderly Swiss women. This could justify integration of QUS among screening strategies for identifying elderly women at risk for osteoporotic fractures.

Dual effect of Zn2+ on multiple types of voltage-dependent Ca2+ currents in rat palaeocortical neurons.

The effects of Zn(2+) were evaluated on high-voltage-activated Ca(2+) currents expressed by pyramidal neurons acutely dissociated from rat piriform cortex. Whole-cell, patch-clamp experiments were carried out using Ba(2+) (5 mM) as the charge carrier. Zn(2+) blocked total high-voltage-activated Ba(2+) currents with an IC(50) of approximately 21 microM. In addition, after application of non-saturating Zn(2+) concentrations, residual currents activated with substantially slower kinetics than control Ba(2+) currents. Both of the above-mentioned effects of Zn(2+) were also observed in high-voltage-activated currents recorded in the presence of nearly-physiological concentrations of extracellular Ca(2+) (1 and 2 mM) rather than Ba(2+). Under the latter conditions, 30 microM Zn(2+) inhibited high-voltage-activated currents somewhat less than observed in extracellular Ba(2+) (approximately 47% and approximately 41%, respectively, vs. approximately 59%), but slowed Ca(2+)-current activation to very similar degrees. All of the pharmacological components in which Ba(2+) currents could be dissected (L-, N-, P/Q-, and R-type) were inhibited by Zn(2+), the percentage of current blocked by 30 microM Zn(2+) ranging from 34 to 57%. Moreover, the activation kinetics of all pharmacological Ba(2+) current components were slowed by Zn(2+). Hence, the lower activation speed observed in residual Ba(2+) currents after Zn(2+) block is due to a true slowing of macroscopic Ca(2+)-current activation kinetics and not to the preferential inhibition of a fast-activating current component. The inhibitory effect of Zn(2+) on Ba(2+) current amplitude was voltage-independent over the whole voltage range explored (-60 to +30 mV), hence the Zn(2+)-dependent decrease of Ba(2+) current activation speed is not the consequence of a voltage- and time-dependent relief from block. Zn(2+) also caused a slight, but significant, reduction of Ba(2+) current deactivation speed upon repolarization, which is further evidence against a depolarization-dependent unblocking mechanism. Finally, the slowing effect of Zn(2+) on Ca(2+)-channel activation kinetics was found to result in a significant, extra reduction of Ba(2+) current amplitude when action-potential-like waveforms, rather than step pulses, were used as depolarizing stimuli. We conclude that Zn(2+) exerts a dual action on multiple types of voltage-gated Ca(2+) channels, causing a blocking effect and altering the speed at which channels are delivered to conducting states, with mechanism(s) that could be distinct.

Cu2+, Co2+, and Mn2+ modify the gating kinetics of high-voltage-activated Ca2+ channels in rat palaeocortical neurons.

The effects of three divalent metal cations (Mn2+, Co2+, and Cu2+) on high-voltage-activated (HVA) Ca2+ currents were studied in acutely dissociated pyramidal neurons of rat piriform cortex using the patch-clamp technique. Cu2+, Mn2+, and Co2+ blocked HVA currents conducted by Ba2+ ( IBa) with IC50 of approximately 920 nM, approximately 58 micro M, and approximately 65 micro M, respectively. Additionally, after application of non-saturating concentrations of the three cations, residual currents activated with substantially slower kinetics than control IBa. As a consequence, the current fraction abolished by the blocking cations typically displayed, in its early phase, an unusually fast-decaying transient. The latter phenomenon turned out to be a subtraction artifact, since none of the pharmacological components (L-, N-, P/Q-, and R-type) that constitute the total HVA currents under study showed a similarly fast early decay: hence, the slow activation kinetics of residual currents was not due to the preferential inhibition of a fast-activating/inactivating component, but rather to a true slowing effect of the blocker cations. The percent IBa-amplitude inhibition caused by Mn2+, Co2+, and Cu2+ was voltage-independent over the whole potential range explored (up to +30 mV), hence the slowing of IBa activation kinetics was not due to a mechanism of voltage- and time-dependent relief from block. Moreover, Mn2+, Co2+, and Cu2+ significantly reduced I(Ba) deactivation speed upon repolarization, which also is not compatible with a depolarization-dependent unblocking mechanism. The above results show that 1) Cu2+ is a particularly potent HVA Ca2+-channel blocker in rat palaeocortical neurons; and 2) Mn2+, Co2+, and Cu2+, besides exerting a blocking action on HVA Ca2+-channels, also modify Ca2+-current activation and deactivation kinetics, most probably by directly interfering with channel-state transitions.

Patient effective dose from endovascular brachytherapy with 192Ir sources.

The growing use of endovascular brachytherapy has been accompanied by the publication of a large number of studies in several fields, but few studies on patient dose have been found in the literature. Moreover, these studies were carried out on the basis of Monte Carlo simulation. The aim of the present study was to estimate the effective dose to the patient undergoing endovascular brachytherapy treatment with 112Ir sources, by means of experimental measurements. Two standard treatments were taken into account: an endovascular brachytherapy of the coronary artery corresponding to the activity x time product of 184 GBq.min and an endovascular brachytherapy of the renal artery (898 GBq.min). Experimental assessment was accomplished by thermoluminescence dosemeters positioned in more than 300 measurement points in a properly adapted Rqndo phantom. A method has been developed to estimate the mean organ doses for all tissues and organs concerned in order to calculate the effective dose associated with intravascular brachytherapy. The normalised organ doses resulting from cronary treatment were 2.4 x 10(-2) mSv.GBq(-1).min(-1) for lung, 0.9 x 10(-2) mSv.GBSq(-1).min(-1) for oesophagus and 0.48 x 10(-2) mS.GBq(-1).min(-1) for bone marrow. During brachytherapy of the renal artery, the corresponding normalised doses were 4.2 x 10(-2) mS.GBq(-1).min(-1) for colon, 7.8 x 10(-2) mSv.GBq(-1).min(-1) for stomach and 1.7 x 10(-2) mSv.GBq(-1).min(-1) for liver. Coronary treatment iJnvlled an efl'fective dose of (0.046 mSv.GBq(-1).min(-1), whereas the treatment of the renal artery resulted in an effective dose of 0.15 mSv.GBq(-1).min(-1); there were many similarities with data from former studies. Based on these results it can be concluded that the dose level of patients exposed during brachytherapy treatment is low.

A new method to assess the fluidodynamic behaviour of an angiographic contrast agent.

PURPOSE: To propose a new method for the assessment of the fluidodynamic behaviour of angiographic contrast agents. The method enables measurement of the spatial distribution and time dependence of the contrast agent along a pseudo-vessel on images obtained with an X-ray image intensifier. MATERIAL AND METHODS: A particular phantom was devised consisting of a plexiglas box with an insert into which a latex tube with a 0.4 cm in diameter was placed in order to simulate the tortuous flow of a blood vessel. The box, which is filled with water to simulate the thickness of a normal patient, is connected to an injection and pumping system which serve to keep the contrast agent flowing in the pseudo-vessel tube. The pseudo-vessel tube was filled with plain water in one case and with saline solution in another case to assess their different dilution capabilities. The phantom and the flow of contrast agent were imaged with a conventional X-ray image intensifier system and the images were stored in digital format during 35 second acquisitions at a speed of 4 frames per second; for any frame it is possible to measure the mathematical contrast in any position in the image. Further, a diagram showing the time dependence of the spatial distribution of the mathematical contrast is proposed. The X axis shows the spatial distribution of the mathematical contrast, whereas the Y axis shows its temporal variation with a gray level proportional to the mathematical contrast value. By building an horizontal profile of this diagram one can obtain the spatial distribution at a fixed time, while by building a vertical profile one can obtain the temporal variation at a fixed point. Several different contrast agents were so tested. RESULTS: The proposed method allows different fluido-dynamic behaviour patterns of contrast agents and flowing media to be shown. Owing to the different chemical characteristics of water and saline solution these media have different dilution capabilities (higher for water) and this is well demonstrated by the diagram profiles obtained for each. The system has also allowed the detection of a particular behaviour of some contrast agents, whose spatial distribution was non uniform even in the last frames, thus showing a tendency to maintain their bolus-nature over time. An interesting feature which can be noticed in all the temporal profiles is the presence of a "pre-bolus", i.e. the contrast is higher at the very beginning of the flow, then decreases and after some time starts to increase again. Though the initial contrast value obviously depends on the iodine concentration employed, the method shows the contrast variation as a function of time is different for different contrast agents. CONCLUSIONS: The method and the equipment proposed provide a good description of the fluidodynamic behaviour of different contrast agents, but do not constitute a reference method for testing haemodynamic behaviour which, "in vivo", is obviously affected by several other chemical and metabolic factors. However, the method allows evaluation of the contrast agents from a physical and fluidodynamic point of view, showing that the iodine content is not the only feature affecting their behaviour. The method can be used in quality control to test the constancy of the physical behaviour of different contrast agents.

Quality controls for two heel bone ultrasounds used in the Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture Risk Study.

Because of the important morbidity and mortality associated with osteoporosis, it is essential to detect subjects at risk by screening methods, such as bone quantitative ultrasounds (QUSs). Several studies showed that QUS could predict fractures. None, however, compared prospectively different QUS devices, and few data of quality controls (QCs) have been published. The Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture Risk is a prospective multicenter study that compared three QUSs for the assessment of hip fracture risk in a population of 7609 women age >/=70 yr. Because the inclusion phase lasted 20 mo, and because 10 centers participated in this study, QC became a major issue. We therefore developed a QC procedure to assess the stability and precision of the devices, and for their cross-calibration. Our study focuses on the two heel QUSs. The water bath system (Achilles+) had a higher precision than the dry system (Sahara). The QC results were highly dependent on temperature. QUS stability was acceptable, but Sahara must be calibrated regularly. A sufficient homogeneity among all the Sahara devices could be demonstrated, whereas significant differences were found among the Achilles+ devices. For speed of sound, 52% of the differences among the Achilles+ was explained by the water s temperature. However, for broadband ultrasound attenuation, a maximal difference of 23% persisted after adjustment for temperature. Because such differences could influence measurements in vivo, it is crucial to develop standardized phantoms to be used in prospective multicenter studies.

P2y1 and P2y2 receptor-operated Ca2+ signals in primary cultures of cardiac microvascular endothelial cells.

Intracellular Ca2+ signals elicited by nucleotide agonists were investigated in primary cultures of rat cardiac microvascular endothelial cells using the fura-2 technique. UTP increased the intracellular [Ca2+] in 94% of the cells, whereas 2MeSATP was active in 32%. The rank order of potency was ATP = UTP > 2MeSATP and the maximal response to 2MeSATP was lower compared to UTP and ATP. ATP and UTP showed strong homologous and heterologous desensitization. ATP fully inhibited the 2MeSATP response, while UTP abolished 2MeSATP-elicited transients in 25% of cells. 2MeSATP did not desensitize the UTP or ATP response. Adenosine 2',5'-diphosphate inhibited the response to 2MeSATP, while it did not modify the response to ATP and UTP. 2MeSATP was more sensitive to suramin than UTP and ATP. These results indicate that P(2Y1) and P(2Y2) receptors may be coexpressed in CMEC. Nucleotide-induced Ca2+ signals lacked a sustained plateau and were almost independent from extracellular Ca2+. ATP and UTP elicited Ca2+ transients longer than 2MeSATP-evoked transients. The kinetics of Ca2+ responses was not affected by bath solution stirring or ectonucleotidase inhibition. Furthermore, the nonhydrolyzable ATP analogue AMP-PNP induced Ca2+ signals similar to those elicited by ATP and UTP. These results suggest that the distinct kinetics of nucleotide-evoked Ca2+ responses do not depend on the activity of ectonucleotidases or ATP autocrine stimulation. The possibility that Ca2+ signals with different time courses may modulate different cellular responses is discussed.

Flow-activated Na(+)and K(+)Current in cardiac microvascular endothelial cells.

The patch-clamp technique was used to investigate the electrical response of cardiac microvascular endothelial cells to fluid stream applied through a microtube. The fluid stream induced a membrane current whose amplitude was dependent on flow rate. The I-V relationship of the flow-activated current showed a strong inward rectification and a reversal potential close to +30 mV, which gave a P(Na)/P(k)=3.47. The inward and outward components of the current nearly disappeared when extracellular Na(+)and internal K(+), respectively, were replaced by NMDG(+). Finally, the flow-activated current was fully blocked by 50 microM Gd(3+)and La(3+). These results show that cardiac microvascular endothelial cells respond to mechanical stimulation associated with flow by increasing their permeability to Na(+)and K(+). This mechanism is suggested to contribute to ionic homeostasis at high heart rates and during post-ischaemic reperfusion.