Hydrophobic Mismatch in the Thylakoid Membrane Regulates Photosynthetic Light Harvesting.

The ability to harvest light effectively in a changing environment is necessary to ensure efficient photosynthesis and crop growth. One mechanism, known as qE, protects photosystem II (PSII) and regulates electron transfer through the harmless dissipation of excess absorbed photons as heat. This process involves reversible clustering of the major light-harvesting complexes of PSII (LHCII) in the thylakoid membrane and relies upon the ΔpH gradient and the allosteric modulator protein PsbS. To date, the exact role of PsbS in the qE mechanism has remained elusive. Here, we show that PsbS induces hydrophobic mismatch in the thylakoid membrane through dynamic rearrangement of lipids around LHCII leading to observed membrane thinning. We found that upon illumination, the thylakoid membrane reversibly shrinks from around 4.3 to 3.2 nm, without PsbS, this response is eliminated. Furthermore, we show that the lipid digalactosyldiacylglycerol (DGDG) is repelled from the LHCII-PsbS complex due to an increase in both the pKa of lumenal residues and in the dipole moment of LHCII, which allows for further conformational change and clustering in the membrane. Our results suggest a mechanistic role for PsbS as a facilitator of a hydrophobic mismatch-mediated phase transition between LHCII-PsbS and its environment. This could act as the driving force to sort LHCII into photoprotective nanodomains in the thylakoid membrane. This work shows an example of the key role of the hydrophobic mismatch process in regulating membrane protein function in plants.

Characterising the chemical and physical properties of phase-change nanodroplets.

Phase-change nanodroplets have attracted increasing interest in recent years as ultrasound theranostic nanoparticles. They are smaller compared to microbubbles and they may distribute better in tissues (e.g. in tumours). They are composed of a stabilising shell and a perfluorocarbon core. Nanodroplets can vaporise into echogenic microbubbles forming cavitation nuclei when exposed to ultrasound. Their perfluorocarbon core phase-change is responsible for the acoustic droplet vaporisation. However, methods to quantify the perfluorocarbon core in nanodroplets are lacking. This is an important feature that can help explain nanodroplet phase change characteristics. In this study, we fabricated nanodroplets using lipids shell and perfluorocarbons. To assess the amount of perfluorocarbon in the core we used two methods, 19F NMR and FTIR. To assess the cavitation after vaporisation we used an ultrasound transducer (1.1 MHz) and a high-speed camera. The 19F NMR based method showed that the fluorine signal correlated accurately with the perfluorocarbon concentration. Using this correlation, we were able to quantify the perfluorocarbon core of nanodroplets. This method was used to assess the content of the perfluorocarbon of the nanodroplets in solutions over time. It was found that perfluoropentane nanodroplets lost their content faster and at higher ratio compared to perfluorohexane nanodroplets. The high-speed imaging indicates that the nanodroplets generate cavitation comparable to that from commercial contrast agent microbubbles. Nanodroplet characterisation should include perfluorocarbon concentration assessment as critical information for their development.

The ESCRT machinery counteracts Nesprin-2G-mediated mechanical forces during nuclear envelope repair.

Transient nuclear envelope ruptures during interphase (NERDI) occur due to cytoskeletal compressive forces at sites of weakened lamina, and delayed NERDI repair results in genomic instability. Nuclear envelope (NE) sealing is completed by endosomal sorting complex required for transport (ESCRT) machinery. A key unanswered question is how local compressive forces are counteracted to allow efficient membrane resealing. Here, we identify the ESCRT-associated protein BROX as a crucial factor required to accelerate repair of the NE. Critically, BROX binds Nesprin-2G, a component of the linker of nucleoskeleton and cytoskeleton complex (LINC). This interaction promotes Nesprin-2G ubiquitination and facilitates the relaxation of mechanical stress imposed by compressive actin fibers at the rupture site. Thus, BROX rebalances excessive cytoskeletal forces in cells experiencing NE instability to promote effective NERDI repair. Our results demonstrate that BROX coordinates mechanoregulation with membrane remodeling to ensure the maintenance of nuclear-cytoplasmic compartmentalization and genomic stability.

Preparing Lamellae from Vitreous Biological Samples using a Dual-Beam Scanning Electron Microscope for Cryo-Electron Tomography.

Presented here is a protocol for preparing cryo-lamellae from plunge-frozen grids of Plasmodium falciparum-infected human erythrocytes, which could easily be adapted for other biological samples. The basic principles for preparing samples, milling, and viewing lamellae are common to all instruments and the protocol can be followed as a general guide to on-grid cryo-lamella preparation for cryo-electron microscopy (cryoEM) and cryo-electron tomography (cryoET). Electron microscopy grids supporting the cells are plunge-frozen into liquid nitrogen-cooled liquid ethane using a manual or automated plunge freezer, then screened on a light microscope equipped with a cryo-stage. Frozen grids are transferred into a cryo-scanning electron microscope equipped with a focused ion beam (cryoFIB-SEM). Grids are routinely sputter coated prior to milling, which aids dispersal of charge build-up during milling. Alternatively, an e-beam rotary coater can be used to apply a layer of carbon-platinum to the grids, the exact thickness of which can be more precisely controlled. Once inside the cryoFIB-SEM an additional coating of an organoplatinum compound is applied to the surface of the grid via a gas injection system (GIS). This layer protects the front edge of the lamella as it is milled, the integrity of which is critical for achieving uniformly thin lamellae. Regions of interest are identified via SEM and milling is carried out in a step-wise fashion, reducing the current of the ion beam as the lamella reaches electron transparency, in order to avoid excessive heat generation. A grid with multiple lamellae is then transferred to a transmission electron microscope (TEM) under cryogenic conditions for tilt-series acquisition. A robust and contamination-free workflow for lamella preparation is an essential step for downstream techniques, including cellular cryoEM, cryoET, and sub-tomogram averaging. Development of these techniques, especially for lift-out and milling of high-pressure frozen samples, is of high-priority in the field.

Maternal Larp6 controls oocyte development, chorion formation and elevation.

La-related protein 6 (Larp6) is a conserved RNA-binding protein found across eukaryotes that has been suggested to regulate collagen biogenesis, muscle development, ciliogenesis, and various aspects of cell proliferation and migration. Zebrafish have two Larp6 family genes: larp6a and larp6b Viable and fertile single and double homozygous larp6a and larp6b zygotic mutants revealed no defects in muscle structure, and were indistinguishable from heterozygous or wild-type siblings. However, larp6a mutant females produced eggs with chorions that failed to elevate fully and were fragile. Eggs from larp6b single mutant females showed minor chorion defects, but chorions from eggs laid by larp6a;larp6b double mutant females were more defective than those from larp6a single mutants. Electron microscopy revealed defective chorionogenesis during oocyte development. Despite this, maternal zygotic single and double mutants were viable and fertile. Mass spectrometry analysis provided a description of chorion protein composition and revealed significant reductions in a subset of zona pellucida and lectin-type proteins between wild-type and mutant chorions that paralleled the severity of the phenotype. We conclude that Larp6 proteins are required for normal oocyte development, chorion formation and egg activation.

Abrupt changes of hydrothermal activity in a lava dome detected by combined seismic and muon monitoring.

The recent 2014 eruption of the Ontake volcano in Japan recalled that hydrothermal fields of moderately active volcanoes have an unpredictable and hazardous behavior that may endanger human beings. Steam blasts can expel devastating ejecta and create craters of several tens of meters. The management of such hydrothermal events in populated areas is problematic because of their very short time of occurrence. At present no precursory signal is clearly identified as a potential warning of imminent danger. Here we show how the combination of seismic noise monitoring and muon density tomography allows to detect, with an unprecedented space and time resolution, the increase of activity (at timescales of few hours to few days) of a hydrothermal spot located 50 to 100 m below the summit of an active volcano, the La Soufrière of Guadeloupe, in the Lesser Antilles. We show how the combination of those two methods improves the risk evaluation of short-term hazards and the localization of the involved volumes in the volcano. We anticipate that the deployment of networks of various sensors including temperature probes, seismic antennas and cosmic muon telescopes around such volcanoes could valuably contribute to early warning decisions.

Correspondence between the CYP2C19 and CYP3A4 genotypes with the inferred metabolizer phenotype by omeprazole administration in Mexican healthy children.

WHAT IS KNOWN AND OBJECTIVE: CYP2C19 genotypes presumably allow the prediction of the metabolizer phenotypes: poor (PMs), extensive (EMs) and ultra-rapid (UMs). However, evidence from previous studies regarding this predictive power is unclear, which is important because the benefits expected by healthcare institutions and patients are based on this premise. Therefore, we aimed to complete a formal evaluation of the diagnostic value of CYP2C19 and CYP3A4 genes for predicting metabolizer phenotypes established by omeprazole (OME) administration in 118 healthy children from Jalisco (western Mexico). METHODS: The genotypes for CYP3A4*1B and CYP2C19*2, *3, *4, *5 and *17 alleles were determined. CYP2C19 and CYP3A4 phenotypes were obtained after 20 mg OME administration and HPLC quantification in plasma to estimate the Hydroxylation Index (HI = OME/HOME) and Sulfonation Index (SI = OME/SOME), respectively. RESULTS AND DISCUSSION: The distribution of genotypes and phenotypes for CYP2C19 and CYP3A4 was similar to previous studies in Mexico and Latin America. We estimated the CYP2C19 UM, EM and PM phenotype frequency in 0.84%, 96.61% and 2.54%, respectively. Although differences in the HI distribution were observed between CYP2C19 genotypes, they showed a poor diagnostic ability to predict the CYP2C19 metabolizer phenotype. Similarly, the number of CYP2C19 and CYP3A4 functional alleles was correlated with the HI distribution, but also their diagnostic ability to predict the CYP2C19 phenotype was poor. WHAT IS NEW AND CONCLUSION: The CYP2C19 phenotype is not predicted by the number of functional alleles of CYP2C19 and CYP3A4 genes. Phenotyping is still the most valuable alternative to dose individualization for CYP2C19 substrate drugs.

A novel form of perceptual attunement: Context-dependent perception of a native contrast in 14-month-old infants.

By the end of their first year of life, infants have become experts in discriminating the sounds of their native language, while they have lost the ability to discriminate non-native contrasts. This type of phonetic learning is referred to as perceptual attunement. In the present study, we investigated the emergence of a context-dependent form of perceptual attunement in infancy. Indeed, some native contrasts are not discriminated in certain phonological contexts by adults, due to the presence of a language-specific process that neutralizes the contrasts in those contexts. We used a mismatch design and recorded high-density Electroencephalography (EEG) in French-learning 14-month-olds. Our results show that similarly to French adults, infants fail to discriminate a native voicing contrast (e.g., [f] vs. [v]) when it occurs in a specific phonological context (e.g. [ofbe] vs. [ovbe], no mismatch response), while they successfully detected it in other phonological contexts (e.g., [ofne] vs. [ovne], mismatch response). The present results demonstrate for the first time that by the age of 14 months, infants' phonetic learning does not only rely on the processing of individual sounds, but also takes into account in a language-specific manner the phonological contexts in which these sounds occur.

Multifractal Downscaling of Rainfall Using Normalized Difference Vegetation Index (NDVI) in the Andes Plateau.

In this paper, a multifractal downscaling technique is applied to adequately transformed and lag corrected normalized difference vegetation index (NDVI) in order to obtain daily estimates of rainfall in an area of the Peruvian Andean high plateau. This downscaling procedure is temporal in nature since the original NDVI information is provided at an irregular temporal sampling period between 8 and 11 days, and the desired final scale is 1 day. The spatial resolution of approximately 1 km remains the same throughout the downscaling process. The results were validated against on-site measurements of meteorological stations distributed in the area under study.

Preparedness of pediatric residents for fellowship: a survey of US neonatal-perinatal fellowship program directors.

OBJECTIVE: To evaluate the preparedness of pediatric residents entering accredited neonatal-perinatal medicine (NPM) fellowships in the United States. STUDY DESIGN: A multi-domain, validated survey was distributed to Program Directors (PDs) of US NPM fellowship programs. The 47-item survey explored 5 domains: professionalism, independent practice, psychomotor ability, clinical evaluation, and academia. A systematic, qualitative analysis on free-text comments was also performed. RESULTS: Sixty-one PDs completed the survey, for a response rate of 62% (61/98). For entering fellows, PDs assessed performance in professionalism positively, including 76% as communicating effectively with parents and 90% treating residents/house-staff with respect. In contrast, most PDs rated performance in psychomotor abilities negatively, including 59% and 79% as deficient in bag-and-mask ventilation and neonatal endotracheal intubation, respectively. Although 62% of PDs assessed entering fellows positively for genuine interest in academic projects, fewer than 10% responded positively that entering fellows understood research protocol design, basic statistics, or were capable of writing a cohesive manuscript well. Thematic clustering of qualitative data revealed deficits in psychomotor ability and academia/scholarship. CONCLUSIONS: On the basis of the perspective of front line educators, graduating pediatric residents are underprepared for subspecialty fellowship training in NPM. To provide the best preparation for pediatric graduates who pursue advanced training, changes to residency education to address deficiencies in these important competencies are warranted.

Proprioceptive body illusions modulate the visual perception of reaching distance.

The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

Capacitation and Ca(2+) influx in spermatozoa: role of CNG channels and protein kinase G.

Cyclic guanosine monophosphate (cGMP) has been recently shown to modulate in vitro capacitation of mammalian spermatozoa, but the mechanisms through which it influences sperm functions have not been clarified. There are at least two targets of cGMP, cyclic nucleotide-gated (CNG) channels and cGMP-dependent protein kinase (PKG), involved in several physiological events in mammalian spermatozoa. It has been suggested that CNG channels allow the influx of Ca(2+) to cytoplasm during capacitation, whereas PKG could trigger a phosphorylation pathway which might also, indirectly, mediate calcium entry. Using the patch-clamp technique in whole-cell configuration, we showed how l-cis-Diltiazem (a CNG-channel inhibitor) and KT5823 (a PKG inhibitor) decreased significantly the amplitude of macroscopic ion currents in a dose-response manner, and decreased in vitro capacitation. The inhibition of CNG channels completely abolishes the Ca(2+) influx induced by cyclic nucleotides in mouse spermatozoa. This work suggests that the downstream cGMP pathway is required in mammalian sperm capacitation and the mechanisms involved include CNG channels and PKG, highlighting these molecules as important therapeutic targets for infertility treatments or to develop new male contraceptives.

Effects of dietary Spirulina on vascular reactivity.

There are several reports suggesting that Spirulina (Arthrospira) may have a beneficial effect in the prevention of cardiovascular diseases. Here we review the results of studies on the effects of dietary Spirulina on the vasomotor reactivity of aortic rings excised from either lean or obese Wistar rats. We also review preliminary results on the effects of Spirulina intake on plasma lipids and blood pressure in humans. The results of the former studies strongly suggest that Spirulina induces a tone-related increase in the synthesis/release of nitric oxide by the endothelium as well as an increase in the synthesis/release of a vasodilating cyclooxygenase-dependent metabolite of arachidonic acid and/or a decrease in the synthesis/release of a vasoconstricting eicosanoid by the endothelium. In humans, Spirulina maxima intake decreases blood pressure and plasma lipid concentrations, especially triacylglycerols and low-density lipoprotein-cholesterol, and indirectly modifies the total cholesterol and high-density lipoprotein-cholesterol values.

Nitric oxide synthases inhibition results in renal failure improvement in cirrhotic rats.

UNLABELLED: Nitric oxide (NO) has been implicated in cirrhosis and might be implicated in renal failure end-stage cirrhosis. AIM: Our aim was to evaluate NO role in renal failure induced during decompensated cirrhosis, using the following inhibitors: aminoguanidine (AG), a specific inducible nitric oxide synthase (iNOS) inhibitor and NG-nitro-l-arginine methyl ester (L-NAME), a nonselective blocker of NOS isoforms. METHODS: Endothelial (eNOS) and iNOS gene expression was analyzed by reverse transcriptase-polymerase chain reaction. Cirrhotic rats received a single intragastric dose of CCl(4) to induce acute liver damage (ALD). RESULTS: After ALD, aspartate aminotransferase highest levels were observed in rats treated with AG and ALT in rats treated with L-NAME. Inhibitors decreased creatinine serum levels to normal values and serum sodium levels re-established after the third day of ALD. L-NAME diminished (P<0.05) eNOS RNA renal expression. Renal iNOS with no inhibitor was overexpressed but was down-regulated by AG treatment. Liver eNOS RNA expression had a decreased expression before ALD in cirrhotic rats, but L-NAME treatment down-regulated eNOS after ALD. AG induced an important iNOS liver decrease. CONCLUSION: Both inhibitors improved renal function, although AG displayed a better effect and did not aggravate liver function. We concluded that NOS isoforms are implicated in the renal pathophysiologic events induced by ALD.

Involvement of myosin II in dopamine-induced reorganization of the lactotroph cell's actin cytoskeleton.

We have shown that dopamine (DA), an inhibitor of prolactin secretion from anterior pituitary lactotrophs, stabilizes the cortical actin cytoskeleton. DA-induced cortical actin stabilization is accompanied by cytoplasmic actin cable disassembly and cell rounding up. Our aim was to identify the mechanisms involved in DA-induced stabilization of the lactotroph's actin cytoskeleton. Here we show that DA increased the association of myosin II with the cell cortex, suggesting that DA facilitates actin-myosin interaction to stabilize cortical actin filaments. This notion was supported by the finding that inhibitors of actin-myosin interaction blocked DA-evoked morphological responses. In addition, our results showed that DA-induced myosin association with the cell periphery may be mediated by inhibition of Rac1/Cdc42-dependent pathways, whereas, DA-induced cytoplasmic actin filament disassembly may be mediated by the inhibition of MLCK- and RhoA-dependent pathways. In conclusion, the present results provide evidence that myosin II is involved in the DA-induced remodeling of actin filaments in lactotrophs, and that DA-induced cortical actin filament assembly and stabilization involve the translocation of myosin II to the cell cortex. This effect requires, among other things, inhibition of the Rac1/Cdc42-dependent signaling pathway.

Endothelium-dependent effects of the ethanolic extract of the mistletoe Psittacanthus calyculatus on the vasomotor responses of rat aortic rings.

The mistletoe Psittacanthus calyculatus (Loranthaceae) is used in Mexican traditional medicine for the treatment of hypertension. In the present study the effects of a crude ethanolic extract of this mistletoe, on the vasomotor reactivity of superfused rat aortic rings (with or without a functional endothelium) were analyzed. Either in the absence or in the presence of L-NAME or indomethacin, the extract (12.5-800 microg/ml) had no effect on the basal tone of both types of rings. In phenylephrine-precontracted rings, low concentrations of the extract (up to 300 microg/ml) induced a small additional tension development in both types of rings; however, the tension increase was slightly larger in rings having an intact endothelium. At higher concentrations (400-800 microg/ml), the extract relaxed, concentration-dependently, phenylephrine-precontracted rings with an intact endothelium. This relaxation was completely reverted by the addition of L-NAME. When the extract was applied in the continuous presence of L-NAME to phenylephrine-precontracted rings, instead of a relaxation a marked additional tension development occurred. Indomethacin did not modify the relaxation induced by the extract. The results indicate that the ethanolic extract of this mistletoe induces, predominantly, an endothelium-dependent relaxation which seems to be mediated by the synthesis/release of nitric oxide.

[Monitoring dermatomal somatosensory evoked potentials at the ERB point, the cervical spinal cord and the cerebral cortex in the diagnosis of cervical radiculopathy]. / Registro de potenciales evocados somatosensoriales dermatómicos en punto de Erb, médula cervical y corteza cerebral en el diagnóstico de la radiculopatía cervical.

INTRODUCTION: Recording at various levels of the somatosensory pathway is often used in somatosensory evoked potentials to mixed nerve stimulation (SEP), but not in dermatomal somatosensory evoked potentials (DSEP) in which only the cortical potential is usually recorded. The aim of our study was to compare the recordings of upper limb DSEP at Erb point, cervical cord, and subcortical and cortical levels with SEP recordings in healthy subjects and patients with cervical radiculopathy. PATIENTS AND METHODS: 17 patients with clinical history, MRI and electromyography consistent with cervical radiculopathy and 17 healthy subjects were included. Median and ulnar nerves were stimulated at the wrist; and C6, C7 and C8 dermatomes at the 1st, 3rd and 5th fingers respectively. All the potentials obtained with SEP and DSEP were compared between controls and patients by t test for independent samples. We also used Pearson s correlation for height/latencies, weight/amplitude and age/peripheral nerve conduction velocity (PNCV). RESULTS: DSEP potentials were of similar morphology of those observed in SEP but had longer latencies and smaller amplitudes. We found a positive correlation between height and latencies, and a negative association of weight with amplitude of peripheral potential, and age/PNCV. No difference between controls and the neurological intact segments of patients was found. 13 patient had DSEP altered while only 5 of them had altered SEP recorded. The most common finding was prolongation of the conduction time of the segment N9 N13 on DSEP recordings. CONCLUSION: We found that it is possible to record and to identify all the potentials in DSEP as observed in the SEP. On cervical radiculopathy, DSEP with the present technique increase the sensitivity and give some additional and useful information regarding the extension and localization of the pathology. Besides, DSEP recording is a non invasive technique, non traumatic and well tolerated for our patients.

Design, synthesis, and modeling of novel cyclic thrombin receptor-derived peptide analogues of the Ser42-Phe-Leu-Leu-Arg46 motif sequence with fixed conformations of pharmacophoric groups: importance of a Phe/Arg/NH2 cluster for receptor activation and implications in the design of nonpeptide thrombin receptor mimetics.

The novel cyclic analogues cyclo(Phe-Leu-Leu-Arg-epsilonLys-Dap) (1) and cyclo(D-Phe-Leu-Leu-Arg-epsilonLys-Dap) (2), which differ only in the absolute conformation of Phe, have been designed and synthesized based upon the minimal peptide sequence Phe-Leu-Leu-Arg which has been found to exhibit biological activity for the thrombin receptor. Compound 1, in which all amino acids have the L-configuration, exhibited higher activity in the rat aorta relaxation and rat longitudinal muscle bioassays compared to compound 2, in which the Phe residue is in the D-configuration. This is attributed to the spatial proximity of the Phe and Arg in compound 1 which does not exist in its diastereomeric compound 2, as is depicted from a combination of NMR studies and computational analysis. Structure-activity studies (SAR) showed that the Phe and Arg side chains along with a primary amino group form an active recognition motif that is augmented by the presence of a second primary amino group in the cyclic peptide. We suggest that a comparable cyclic conformation may be responsible for the interaction of linear TRAPs with the thrombin receptor. The validity of this proposition was tested by the synthesis of four active nonpeptide thrombin receptor mimetics. Substance (S)-N-(6-guanidohexanoyl)-N'-(2-amino-3-phenylpropionyl)piperazine (3), in which the pharmacophoric phenyl, guanidino, and amino groups were incorporated onto a piperazine template, was found to be the most active compared to the other synthesized compounds which lack the amino pharmacophoric group.

Effects of the ethanolic extract of Spirulina maxima on endothelium dependent vasomotor responses of rat aortic rings.

Dietary Spirulina decreases, endothelium-dependently, the responses to vasoconstrictor agonists and increases the endothelium-dependent, agonist-induced, vasodilator responses of rat aorta rings. The aim of this study was to analyze, in vitro, the effects of a raw ethanolic extract of Spirulina maxima on the vasomotor responses of rat aortic rings to phenylephrine and to carbachol. On rings with endothelium, the extract produced the following effects: (a) a concentration-dependent (60-1000 microg/ml) decrease of the contractile response to phenylephrine; (b) a rightward shift and a decrease in maximal developed tension, of the concentration--response curve to phenylephrine; (c) a concentration dependent relaxation of phenylephrine-precontracted rings. These effects were blocked by L-NAME, and not modified by indomethacin. The extract had no effect on the concentration-response curve to carbachol of rings with endothelium. On endothelium-denuded rings the extract caused a significant rightward shift of the concentration response curve to phenylephrine without any effect on maximal tension development. In the presence of the extract, indomethacin induced a marked decrease in the maximal phenylephrine-induced tension of endothelium-denuded rings. These results suggest that the extract increases the basal synthesis/release of NO by the endothelium and, also, the synthesis/release of a cyclooxygenase-dependent vasoconstricting prostanoid by vascular smooth muscle cells.