Comparisons of polybrominated diphenyl ether and hexabromocyclododecane concentrations in dust collected with two sampling methods and matched breast milk samples.

UNLABELLED: Household dust from 19 Swedish homes was collected using two different sampling methods: from the occupant's own home vacuum cleaner after insertion of a new bag and using a researcher-collected method where settled house dust was collected from surfaces above floor level. The samples were analyzed for 16 polybrominated diphenyl ether (PBDE) congeners and total hexabromocyclododecane (HBCD). Significant correlations (r = 0.60-0.65, Spearman r = 0.47-0.54, P < 0.05) were found between matched dust samples collected with the two sampling methods for ∑OctaBDE and ∑DecaBDE but not for ∑PentaBDE or HBCD. Statistically significantly higher concentrations of all PBDE congeners were found in the researcher-collected dust than in the home vacuum cleaner bag dust (VCBD). For HBCD, however, the concentrations were significantly higher in the home VCBD samples. Analysis of the bags themselves indicated no or very low levels of PBDEs and HBCD. This indicates that there may be specific HBCD sources to the floor and/or that it may be present in the vacuum cleaners themselves. The BDE-47 concentrations in matched pairs of VCBD and breast milk samples were significantly correlated (r = 0.514, P = 0.029), indicating that one possible exposure route for this congener may be via dust ingestion. PRACTICAL IMPLICATIONS: The statistically significant correlations found for several individual polybrominated diphenyl ether (PBDE) congeners, ∑OctaBDE and ∑DecaBDE between the two dust sampling methods in this study indicate that the same indoor sources contaminate both types of dust or that common processes govern the distribution of these compounds in the indoor environment. Therefore, either method is adequate for screening ∑OctaBDE and ∑DecaBDE in dust. The high variability seen between dust samples confirms results seen in other studies. For hexabromocyclododecane (HBCD), divergent results in the two dust types indicate differences in contamination sources to the floor than to above-floor surfaces. Thus, it is still unclear which dust sampling method is most relevant for HBCD as well as for ∑PentaBDE in dust and, further, which is most relevant for determining human exposure to PBDEs and HBCD.

Endothelial-specific deletion of connexin40 promotes atherosclerosis by increasing CD73-dependent leukocyte adhesion.

BACKGROUND: Endothelial dysfunction is the initiating event of atherosclerosis. The expression of connexin40 (Cx40), an endothelial gap junction protein, is decreased during atherogenesis. In the present report, we sought to determine whether Cx40 contributes to the development of the disease. METHODS AND RESULTS: Mice with ubiquitous deletion of Cx40 are hypertensive, a risk factor for atherosclerosis. Consequently, we generated atherosclerosis-susceptible mice with endothelial-specific deletion of Cx40 (Cx40del mice). Cx40del mice were indeed not hypertensive. The progression of atherosclerosis was increased in Cx40del mice after 5 and 10 weeks of a high-cholesterol diet, and spontaneous lesions were observed in the aortic sinuses of young mice without such a diet. These lesions showed monocyte infiltration into the intima, increased expression of vascular cell adhesion molecule-1, and decreased expression of the ecto-enzyme CD73 in the endothelium. The proinflammatory phenotype of Cx40del mice was confirmed in another model of induced leukocyte recruitment from the lung microcirculation. Endothelial CD73 is known to induce antiadhesion signaling via the production of adenosine. We found that reducing Cx40 expression in vitro with small interfering RNA or antisense decreased CD73 expression and activity and increased leukocyte adhesion to mouse endothelial cells. These effects were reversed by an adenosine receptor agonist. CONCLUSIONS: Cx40-mediated gap junctional communication contributes to a quiescent nonactivated endothelium by propagating adenosine-evoked antiinflammatory signals between endothelial cells. Alteration in this mechanism by targeting Cx40 promotes leukocyte adhesion to the endothelium, thus accelerating atherosclerosis.

Charge separation is virtually irreversible in photosystem II core complexes with oxidized primary quinone acceptor.

X-ray structures of the Photosystem II (PSII) core revealed relatively large interpigment distances between the CP43 and CP47 antenna complexes and the reaction center (RC) with respect to the interpigment distances in a single unit. This finding questions the possibility of fast energy equilibration among the antenna and the RC, which has been the basic explanation for the measured PSII fluorescence kinetics for more than two decades. In this study, we present time-resolved fluorescence measurements obtained with a streak-camera setup on PSII core complexes from Thermosynechococcus elongatus at room temperature (RT) and at 77 K. Kinetic modeling of the RT data obtained with oxidized quinone acceptor Q(A), reveals that the kinetics are best described by fast primary charge separation at a time scale of 1.5 ps and slow energy transfer from the antenna into the RC, which results in an energy equilibration time between the antenna and the RC of about 44 ps. This model is consistent with structure-based computations. Primary radical pair formation was found to be a virtually irreversible process. Energy equilibration within the CP43 and CP47 complexes is shown to occur at a time scale of 8 ps. Kinetic modeling of the 77 K data reveals similar energy transfer time scales in the antenna units and among the antenna and the RC as at RT, respectively, 7 and 37 ps. We conclude that the energy transfer from the CP43/CP47 antenna to the RC is the dominant factor in the total charge separation kinetics in intact PSII cores.

The Baltic Sea: An ecosystem with multiple stressors.

This introductory chapter to our Environment International VSI does not need an abstract and therefore we just include our recommendations below in order to proceed with the resubmission. Future work should examine waterbirds as food web sentinels of multiple stressors as well as Baltic Sea food web dynamics of hazardous substances and how climate change may modify it. Also, future work should aim at further extending the new frameworks developed within BALTHEALTH for energy and contaminant transfer at the population level (Desforges et al., 2018, Cervin et al., 2020/this issue Silva et al., 2020/this issue) and their long term effects on Baltic Sea top predators, such as harbour porpoises, grey seals ringed seals, and white-tailed eagles. Likewise, the risk evaluation conducted for PCB in connection with mercury on Arctic wildlife (Dietz et al., 2019, not a BONUS BALTHEALTH product) could be planned for Baltic Sea molluscs, fish, bird and marine mammals in the future. Finally, future efforts could include stressors not covered by the BONUS BALTHEALTH project, such as food web fluxes, overexploitation, bycatches, eutrophication and underwater noise.

Rangeland productivity and exploitation in the sahel.

Results of a Malian-Dutch research project on the Sahelian pastures and their utilization suggest reasons why some efforts to develop traditional livestock farming in this area have been unsuccessful. Failure to appreciate the effects of low soil fertility as well as low rainfall on pasture production has resulted in underestimation of the productivity of the nomadic and seminomadic livestock farming system and overestimation of the possibilities for increasing production by better management and by modernization.

Photosynthate and nitrogen requirements for seed production by various crops.

Seed biochemical composition was the basis for segregating 24 crops into four distinct groups. Nitrogen requirements of pulses and soybeans were so great that sustained seed growth demanded continued nitrogen translocation from vegetative tissues. This translocation must eventually induce senescence in these tissues, restrict the duration of the seed-fill period, and limit seed yield.

Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.

OBJECTIVE: To determine the risk factors for anal sphincter injuries during operative vaginal delivery. SETTING AND DESIGN: A population-based observational study. POPULATION: All 21 254 women delivered with vacuum extraction and 7478 women delivered with forceps, derived from the previously validated Dutch National Obstetric Database from the years 1994 to 1995. METHODS: Anal sphincter injury was defined as any injury, partial or complete, of the anal sphincters. Risk factors were determined with multivariate logistic regression analysis. MAIN OUTCOME MEASURES: Individual obstetric factors, e.g. fetal birthweights, duration of second stage, etc. RESULTS: Anal sphincter injury occurred in 3.0% of vacuum extractions and in 4.7% of forceps deliveries. Primiparity, occipitoposterior position and fetal birthweight were associated with an increased risk for anal sphincter injury in both types of operative vaginal delivery, whereas duration of second stage was associated with an increased risk only in vacuum extractions. Mediolateral episiotomy protected significantly for anal sphincter damage in both vacuum extraction (OR 0.11, 95% CI 0.09-0.13) and forceps delivery (OR 0.08, 95% CI 0.07-0.11). The number of mediolateral episiotomies needed to prevent one sphincter injury in vacuum extractions was 12, whereas 5 mediolateral episiotomies could prevent one sphincter injury in forceps deliveries. CONCLUSIONS: Primiparity and occipitoposterior presentation are strong risk factors for the occurrence of anal sphincter injury during operative vaginal delivery. The highly significant protective effect of mediolateral episiotomies in both types of operative vaginal delivery warrants the conclusions that this type of episiotomy should be used routinely during these interventions to protect the anal sphincters.

Growth of preterm born children.

BACKGROUND: In this review, we describe the growth of (very) preterm infants or (very) low-birth-weight infants from birth until adulthood. METHODS: A systematic analysis of growth of these infants is thwarted by different definitions (classification by gestational age or birth weight) used in the literature. RESULTS: The early postnatal period of these individuals is almost invariably characterized by substantial growth failure. In the majority of preterm infants this is followed by a period of catch-up growth, which starts in early infancy and usually stops at 2-3 years of age, although in some cases it may continue into adolescence. Catch-up growth is usually incomplete, so that infants born preterm remain shorter and lighter than term-born peers during childhood, adolescence, and adulthood. Disproportionate catch-up growth in height and weight may lead to an altered body composition in adulthood, especially in females. CONCLUSION: Though early catch-up growth has shown to be beneficial for neurodevelopmental outcome, it is also associated with adverse metabolic consequences in adulthood. As the first generation of (very) preterm infants is now reaching young adulthood, future follow-up studies on these effects are warranted.

Myomatous erythrocytosis syndrome: further proof for the pathogenic role of erythropoietin.

BACKGROUND: Myomatous erythrocytosis syndrome is defined by the combination of erythrocytosis, myomatous uterus and persistent restoration of normal haematological values after hysterectomy. A pathogenic role of erythropoietin is suggested by clinical and experimental data. CASE REPORT: A postmenopausal patient is described with the classical clinical signs of the myomatous erythrocytosis syndrome. During hysterectomy we demonstrated a large gradient between the erythropoietin levels in the uterine vein and artery, providing direct evidence for in vivo erythropoietin production by the myomatous uterus. CONCLUSION: While erythropoietin and its receptor are consecutively expressed in normal and myomatous uterine tissue, it is amazing that erythrocytosis occurs so rarely in such a frequent disorder as uterine myomatous. We strongly advocate cytogenetic examination of the myomatous tissue of subsequent patients with this entity.

Enantiomer-specific accumulation of hexabromocyclododecanes in eggs of predatory birds.

The diastereomeric composition of hexabromocyclododecane (HBCD) in eggs of peregrine falcon (Falco peregrinus), white-tailed sea eagle (Haliaeetus albicilla), guillemot (Uria aalge) and common tern (Sterna hirundo) as well as the guillemots' main prey, herring (Clupea harengus) was determined by reversed-phase chromatography with triple-stage quadrupole mass spectrometric detection (LC-MS-MS). alpha-HBCD was the predominant diastereomer in all bird species, while in herring, gamma-HBCD made a substantial contribution. Two, as yet unidentified diastereomers, were detected in common tern egg. The alpha-, beta- and gamma-HBCD (+) and (-) enantiomers were separated using a chiral stationary phase. The enantiomer fractions for alpha-HBCD differed substantially between different bird species as well as between guillemot and its prey, herring. Total HBCD levels determined by LC-MS-MS were comparable to those previously obtained by GC-MS.

Myoendothelial coupling through Cx40 contributes to EDH-induced vasodilation in murine renal arteries: evidence from experiments and modelling.

Regulation of renal vascular resistance plays a major role in controlling arterial blood pressure. The endothelium participates in this regulation as endothelial derived hyperpolarization plays a significant role in smaller renal arteries and arterioles, but the exact mechanisms are still unknown. AIM: To investigate the role of vascular gap junctions and potassium channels in the renal endothelial derived hyperpolarization. METHODS: In interlobar arteries from wild-type and connexin40 knockout mice, we assessed the role of calcium-activated small (SK) and intermediate (IK) conductance potassium channels. The role of inward rectifier potassium channels (Kir) and Na+ /K+ -ATPases was evaluated as was the contribution from gap junctions. Mathematical models estimating diffusion of ions and electrical coupling in myoendothelial gap junctions were used to interpret the results. RESULTS: Lack of connexin40 significantly reduces renal endothelial hyperpolarization. Inhibition of SK and IK channels significantly attenuated renal EDH to a similar degree in wild-type and knockout mice. Inhibition of Kir and Na+ /K+ -ATPases affected the response in wild-type and knockout mice but at different levels of stimulation. The model confirms that activation of endothelial SK and IK channels generates a hyperpolarizing current that enters the vascular smooth muscle cells. Also, extracellular potassium increases sufficiently to activate Kir and Na+ /K+ -ATPases. CONCLUSION: Renal endothelial hyperpolarization is mainly initiated by activation of IK and SK channels. The model shows that hyperpolarization can spread through myoendothelial gap junctions but enough potassium is released to activate Kir and Na+ /K+ -ATPases. Reduced coupling seems to shift the signalling pathway towards release of potassium. However, an alternative pathway also exists and needs to be investigated.

Risk stratification for the development of venous thromboembolism in hospitalized patients with cancer.

Essentials The Khorana score is validated for risk of venous thromboembolism (VTE) in cancer outpatients. We conducted a multicenter analysis of medically hospitalized cancer patients. Patients with a higher Khorana score on admission were more likely to develop VTE. The Khorana score is predictive of in-hospital, symptomatic VTE development. SUMMARY: Introduction The Khorana score is a validated risk assessment score for estimating the risk of symptomatic venous thromboembolism (VTE) in outpatients with cancer. The objective of this study was to assess the Khorana score for predicting the development of VTE in cancer patients during hospital admission. Methods We conducted an analysis of consecutive, adult cancer patients hospitalized for medical reasons between January and June 2010 in three academic medical centers. Information on objectively diagnosed, symptomatic VTE during hospitalization, use of anticoagulant thromboprophylaxis (TP) and Khorana score variables at the time of admission was collected. Results A total of 1398 patients were included. Mean age was 62 years, 51.2% were male, and mean BMI was 25.9 kg m-2 . The most frequent reasons for hospitalization were chemotherapy administration (22.3%), followed by pain control and palliation (21.4%). The overall incidence of VTE was 2.9% (95% CI, 2.0-3.8%), occurring in 5.4% (95% CI, 1.9-8.9%) of the high-, 3.2% (95% CI, 2.0-4.4%) of the intermediate- and 1.4% (95% CI, 0.3-2.6%), of the low-risk groups. High-risk patients were more likely than low-risk patients to have VTE (OR, 3.9; 95% CI, 1.4-11.2). Conclusion The Khorana score is predictive of in-hospital, symptomatic VTE development in cancer patients who are hospitalized for medical reasons and may be a useful tool for tailoring inpatient anticoagulant thromboprophylaxis.

Poly(A) tail shortening is the translation-dependent step in c-myc mRNA degradation.

The highly unstable c-myc mRNA has been shown to be stabilized in cells treated with protein synthesis inhibitors. We have studied this phenomenon in an effort to gain more insight into the degradation pathway of this mRNA. Our results indicate that the stabilization of c-myc mRNA in the absence of translation can be fully explained by the inhibition of translation-dependent poly(A) tail shortening. This view is based on the following observations. First, the normally rapid shortening of the c-myc poly(A) tail was slowed down by a translation block. Second, c-myc messengers which carry a short poly(A) tail, as a result of prolonged actinomycin D or 3'-deoxyadenosine treatment, were not stabilized by the inhibition of translation. We propose that c-myc mRNA degradation proceeds in at least two steps. The first step is the shortening of long poly(A) tails. This step requires ongoing translation and thus is responsible for the delay in mRNA degradation observed in the presence of protein synthesis inhibitors. The second step involves rapid degradation of the body of the mRNA, possibly preceded by the removal of the short remainder of the poly(A) tail. This last step is independent of translation.

Thrombotic and bleeding outcomes following perioperative interruption of direct oral anticoagulants in patients with venous thromboembolic disease.

Essentials Studies evaluating the procedural interruption of direct oral anticoagulants (DOACs) are lacking. We conducted a study of the interruption of DOACs for prior venous thromboembolic disease (VTE). The post-operative risks of recurrent VTE and major bleeding are low in this patient population. A scheme based on half-life and procedure-related bleeding appears safe and efficacious. SUMMARY: Background Direct oral anticoagulants (DOACs) are increasingly being used in the setting of venous thromboembolic disease (VTE). There is little evidence to guide the peri-procedural interruption of DOACs in this patient population. A number of studies have evaluated the perioperative interruption of DOACs based on half-life of the anticoagulant and the underlying procedural bleeding risk in patient with atrial fibrillation, but it remains unclear whether these findings can be extended to patients with VTE. Objective Evaluate thrombotic and bleeding outcomes following the perioperative interruption of direct oral anticoagulation in patients with prior VTE. Methods We conducted a retrospective analysis of consecutive patients on a DOAC for prior VTE requiring temporary interruption of anticoagulation for an invasive procedure. The primary efficacy outcome was the 30-day symptomatic VTE rate, and the primary safety outcome was the 30-day major bleeding rate. Secondary outcomes included overall mortality and the rate of clinically relevant non-major bleeding. Results A total of 190 patients were included in the analysis. The 30-day VTE rate was 1.05% (95% CI, 0.29-3.8%) and the 30-day major bleeding rate was 0.53% (95% CI, 0.09-2.93%). There were no deaths during the 30-day follow-up period. The rate of clinically relevant non-major bleeding was 3.16% (95%CI , 1.46-6.72%). Conclusions The perioperative interruption of DOACs in the setting of VTE, using a strategy that considers the half-life of the DOAC and the underlying procedural bleeding risk, appears to be both safe and effective.

Net clinical benefit of hospitalization versus outpatient management of patients with acute pulmonary embolism.

Essentials Clinical benefit of hospitalization vs. outpatient treatment in pulmonary embolism (PE) is unknown. We performed a propensity matched cohort study of hemodynamically stable PE patients. Regardless of the risk assessment, hospitalized patients had the highest rate of adverse event. If confirmed, ambulatory care of normotensive PE patients may be preferred whenever possible. SUMMARY: Background The decision to hospitalize or not patients with acute pulmonary embolism (PE) is controversial. Despite the advantages of close monitoring, hospitalization by itself may lead to in-hospital complications and potentially worsen the prognosis of PE patients. Objectives To determine the net clinical benefit of hospitalization vs. outpatient management of normotensive patients with acute pulmonary embolism (PE). Methods Retrospective cohort propensity score analysis (radius marching with replacement). Hemodynamically stable PE patients treated as outpatients or inpatients were matched to balance out differences for 28 patient characteristics and known risk factors for adverse events. The primary outcome was the rate of adverse events at 14 days, including recurrent venous thromboembolism, major bleeding or death. Results Among 1127 eligible patients, 1081 were included in the matched cohort, 576 treated as inpatients and 505 as outpatients. The 14-day rate of adverse events was 13.0% for inpatients and 3.3% for outpatients (adjusted OR, 5.07; 95% CI, 1.68-15.28). The 3-month rate was 21.7% for inpatients and 6.9% for outpatients (OR, 4.90; 95% CI, 2.62-9.17). In the high-risk subgroup (Pulmonary Embolism Severity Index class III-V; n = 597), the 14-day rate of adverse events was 16.5% for hospitalized patients vs. 4.5% for outpatients (OR, 4.16; 95% CI, 1.2-14.35). Conclusion Outpatient treatment of hemodynamically stable PE patients seems to be associated with a lower rate of adverse events than hospitalization and, if confirmed, may be considered as first-line management in patients not requiring specific in-hospital care, regardless of their initial risk stratification, if proper outpatient care can be provided.

Communication Through Gap Junctions in the Endothelium.

A swarm of fish displays a collective behavior (swarm behavior) and moves "en masse" despite the huge number of individual animals. In analogy, organ function is supported by a huge number of cells that act in an orchestrated fashion and this applies also to vascular cells along the vessel length. It is obvious that communication is required to achieve this vital goal. Gap junctions with their modular bricks, connexins (Cxs), provide channels that interlink the cytosol of adjacent cells by a pore sealed against the extracellular space. This allows the transfer of ions and charge and thereby the travel of membrane potential changes along the vascular wall. The endothelium provides a low-resistance pathway that depends crucially on connexin40 which is required for long-distance conduction of dilator signals in the microcirculation. The experimental evidence for membrane potential changes synchronizing vascular behavior is manifold but the functional verification of a physiologic role is still open. Other molecules may also be exchanged that possibly contribute to the synchronization (eg, Ca(2+)). Recent data suggest that vascular Cxs have more functions than just facilitating communication. As pharmacological tools to modulate gap junctions are lacking, Cx-deficient mice provide currently the standard to unravel their vascular functions. These include arteriolar dilation during functional hyperemia, hypoxic pulmonary vasoconstriction, vascular collateralization after ischemia, and feedback inhibition on renin secretion in the kidney.

Oxidized LDL increases the sensitivity of the contractile apparatus in isolated resistance arteries for Ca(2+) via a rho- and rho kinase-dependent mechanism.

BACKGROUND: Oxidized LDL reduces NO-mediated and endothelium-derived hyperpolarizing factor-mediated dilations. We studied, in hamster skeletal muscle resistance arteries (213+/-8 micrometer n=51), whether an altered vascular smooth muscle (VSM) response, particularly sensitization of the VSM contractile apparatus to Ca(2+), is involved in this oxLDL effect. Methods and Results-VSM or endothelial [Ca(2+)](i) and vascular diameter were measured in response to norepinephrine (0.3 micromol/L), sodium nitroprusside (10 micromol/L), C-type natriuretic peptide (1 to 100 nmol/L), papaverine (0.1 to 10 micromol/L), or the endothelial agonist acetylcholine (ACh, 0.01 to 1 micromol/L). OxLDL significantly increased resting VSM [Ca(2+)](i) (11+/-3%), decreased diameter (8+/-2%), and enhanced norepinephrine-induced constrictions. Dilations to sodium nitroprusside and C-type natriuretic peptide were significantly reduced (by 10+/-2% and 35+/-6%), whereas dose-response curves for papaverine and ACh were shifted to the right, despite unchanged increases in endothelial Ca(2+) after ACh. OxLDL significantly shifted the Ca(2+)-diameter relation to the left, as assessed by stepwise increasing extracellular Ca(2+) (0 to 3 mmol/L) in depolarized skeletal muscle resistance arteries. This sensitization to Ca(2+) by oxLDL was abolished after inhibition of Rho (C3 transferase) or Rho kinase (Y27632). CONCLUSIONS: OxLDL reduces VSM responsiveness to vasodilators by increasing VSM Ca(2+) but preferentially by sensitizing VSM to Ca(2+) via a Rho- and Rho kinase-dependent pathway.

Synergistic action of vasodilators that increase cGMP and cAMP in the hamster cremaster microcirculation.

OBJECTIVE: Compounds such as endothelium derived nitric oxide (NO) and prostacyclin (prostaglandin I2) which increase cGMP and cAMP inhibit platelet activation in a synergistic manner. The aim of this study was to examine whether these compounds also interact synergistically in the control of smooth muscle tone. METHODS: Vascular diameters in the cremaster of 49 anaesthetised hamsters (465 arterioles) were studied during superfusion with compounds raising cAMP (isoprenaline and prostacyclin) and cGMP (sodium nitroprusside) alone or in combination. RESULTS: (1) The isoprenaline induced maximum dilator response was significantly attenuated, from 86.1(SEM 0.7)% to 37.1(0.2)%, after inhibition of NO-synthase with NG-nitro-L-arginine (L-NNA, 30 microM). Superfusion with sodium nitroprusside (30 nM, dilatation alone: 6.7%), which was used to substitute for endothelium derived NO, restored the attenuated isoprenaline response. The combined effects of isoprenaline and sodium nitroprusside were supra-additive. Virtually identical results were obtained when prostacyclin, another cAMP raising compound, was used instead of isoprenaline. The K+ channel opener cromakalim (100 nM) which acts cGMP independently was without effect on the prostacyclin induced dilator response. (2) The sodium nitroprusside induced maximum dilator response was attenuated from 80.9(0.25)% to 70.1(0.4)%, after indomethacin (3 microM) and restored by simultaneous application of prostacyclin (1 nM, dilatation alone: 1.4%) but not of cromakalim. Again, the combined effects were supra-additive, suggesting a synergistic action of these compounds. (3) Although indomethacin or L-NNA alone decreased the resting diameter by approximately 9.5%, the simultaneous application of both inhibitors failed to decrease the resting diameter further (10.0%, p = 0.97). CONCLUSIONS: Vasodilators increasing cGMP and cAMP act synergistically in vivo. Continuous release of NO and prostaglandins by the endothelium may therefore not only modulate the efficacy of such cyclic nucleotide increasing vasodilators but also interact synergistically in controlling basal vascular tone.

Unique properties of the capacitative Ca(2+)-entry antagonist LU 52396: its inhibitory activity depends on the activation state of the cells.

The pharmacological properties of the recently described antagonist for capacitative Ca2+ entry LU 52396 were investigated and compared to known Ca2+ antagonists in Jurkat T-lymphocytes. In the first set of experiments, cells were stimulated with the anti-CD3 monoclonal antibody OKT3 and, subsequently, Ca2+ antagonists were added. Under such conditions SK-F 96365, econazole, nitrendipine and ZnCl2 dose-dependently antagonized Ca2+ signaling, whereas LU 52396 in concentrations up to 100 microM did not. In contrast, when LU 52396 was added a few minutes before OKT3, a dose-dependent inhibition of the OKT3-stimulated Ca2+ signals by LU 52396 was observed. Likewise, by prior addition of LU 52396 to thapsigargin-stimulated Jurkat T cells, a dose-dependent inhibition of Ca2+ signals was achieved. The IC50 value of LU 52396 for both agonists was about 5 microM. LU 52396 also inhibited Jurkat T cell proliferation, but showed cytotoxic effects at concentrations > 50 microM. Our data indicate that, in contrast to the other Ca2+ antagonists SK-F 96365, econazole, nitrendipine and ZnCl2, LU 52396 recognized the channel for capacitative Ca2+ entry only when intracellular Ca2+ was low and the channel was in its closed state.

Nitric oxide opposes myogenic pressure responses predominantly in large arterioles in vivo.

A myogenic vasoconstriction may amplify the effects of circulating vasoconstrictors. In cremaster arterioles, the contribution of a myogenic component to the constriction on intravenous infusion of norepinephrine (NE) or angiotensin II (Ang II) was studied. Second, the role of endothelium-derived nitric oxide (NO) in the control of these myogenic constrictions and its site of action in the resistance vascular bed was investigated. In 30 anesthetized (pentobarbital) hamsters, the cremaster was prepared for intravital microscopy, and a pneumatic vessel occluder was placed around the aorta to vary blood pressure in the hindquarter of the animal. Intravenous infusion of NE (0.5 nmol/min) increased the systemic blood pressure by 52+/-2 mm Hg. Simultaneously, constrictions of up to 33+/-6% were observed in the small arterioles (SAs; maximal inner diameter, 36 to 65 microm). The constrictions were not significantly altered by a local adrenergic blockade but were abolished when the pressure elevation in the cremaster arterioles was blocked by partial occlusion of the abdominal aorta. Diameters in large arterioles (LAs; maximal inner diameter, 65 to 127 microm), however, did not change significantly on NE infusion. Similar responses in the arterioles were observed when the local pressure was increased stepwise from 60 to 120 mm Hg by partial opening of the aortic occluder. However, after treatment of the cremaster tissue with the inhibitor of the NO synthase, N(G)-nitro-L-arginine (L-NNA, 30 micromol/L), a significant pressure-induced constriction of up to 16+/-3% occurred in LAs, whereas the magnitude of the constriction in SAs remained unchanged. L-NNA also abolished the increases in blood flow that were observed with increments in pressure in control animals. Similar results were obtained when Ang II was used to increase blood pressure. We conclude that a myogenic constriction of SAs contributes markedly to the overall response of cremaster arterioles to circulating vasoconstrictors. NO effectively opposes the myogenic response in LAs, thus preventing myogenic constrictions in a vascular region where constriction cannot be fully controlled by metabolic dilation. If this attenuating effect of NO on myogenic constriction also takes place in other organs, it might be a decisive mechanism in controlling changes of total peripheral vascular resistance elicited by vasoconstrictors.