Antitumor and antiangiogenic effects of Tonantzitlolone B, an uncommon diterpene from Stillingia loranthacea.

Natural products have played a pivotal role for the discovery of anticancer drugs. Tonantzitlolones are flexibilan-type diterpenes rare in nature; therefore, few reports have shown antiviral and cytotoxic activities. This study aimed to investigate the in vivo antitumor action of Tonantzitlolone B (TNZ-B) and its toxicity. Toxicity was evaluated in mice (acute and micronucleus assays). Antitumor activity of TNZ-B (1.5 or 3 mg/kg intraperitoneally - i.p.) was assessed in Ehrlich ascites carcinoma model. Angiogenesis and reactive oxygen species (ROS) and nitric oxide (NO) production were also investigated, in addition to toxicological effects after 7-day treatment. The LD50 (lethal dose 50%) was estimated at around 25 mg/kg (i.p.), and no genotoxicity was recorded. TNZ-B reduced the Ehrlich tumor's volume and total viable cancer cell count (p < 0.001 for both). Additionally, TNZ-B reduced peritumoral microvessel density (p < 0.01), suggesting antiangiogenic action. Moreover, a decrease was observed on ROS (p < 0.05) and nitric oxide (p < 0.001) levels. No significant clinical findings were observed in the analysis of biochemical, hematological, and histological (liver and kidney) parameters. In conclusion, TNZ-B exerts antitumor and antiangiogenic effects by reducing ROS and NO levels and has weak in vivo dose-repeated toxicity. These data contribute to elucidate the antitumor action of TNZ-B and point the way for further studies with this natural compound as an anticancer drug.

Inhibition of InsP3R with Xestospongin B Reduces Mitochondrial Respiration and Induces Selective Cell Death in T Cell Acute Lymphoblastic Leukemia Cells.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy whose chemoresistance and relapse persist as a problem despite significant advances in its chemotherapeutic treatments. Mitochondrial metabolism has emerged as an interesting therapeutic target given its essential role in maintaining bioenergetic and metabolic homeostasis. T-ALL cells are characterized by high levels of mitochondrial respiration, making them suitable for this type of intervention. Mitochondrial function is sustained by a constitutive transfer of calcium from the endoplasmic reticulum to mitochondria through the inositol 1,4,5-trisphosphate receptor (InsP3R), making T-ALL cells vulnerable to its inhibition. Here, we determine the bioenergetic profile of the T-ALL cell lines CCRF-CEM and Jurkat and evaluate their sensitivity to InsP3R inhibition with the specific inhibitor, Xestospongin B (XeB). Our results show that T-ALL cell lines exhibit higher mitochondrial respiration than non-malignant cells, which is blunted by the inhibition of the InsP3R. Prolonged treatment with XeB causes T-ALL cell death without affecting the normal counterpart. Moreover, the combination of XeB and glucocorticoids significantly enhanced cell death in the CCRF-CEM cells. The inhibition of InsP3R with XeB rises as a potential therapeutic alternative for the treatment of T-ALL.

Synthesis of diphenylamine macrocycles and their anti-inflammatory effects.

A collection of fourteen diphenylamine macrocyclic derivatives containing a peptide chain with different substituents was synthesized using a protocol of two Ugi four component reactions (Ugi-4CR) and a Buchwald-Hartwig macrocyclization. Their anti-inflammatory effects were assayed with an ear edema model using 12-O-tetradecanoylphorbol-13-acetate, while the activity of myeloperoxidase was determined to evaluate the index of leukocyte infiltration. Compound 5e had an ID50 of 0.18 µM per ear with a potency higher than that of the reference drugs indomethacin and celecoxib (0.24 and 0.91 µM per ear, respectively). Moreover, the cytotoxicity of the macrocycles was determined in two healthy cell lines, showing a low percentage of toxicity.

Can P-glycoprotein and ß-tubulin polymorphisms be used as genetic markers of resistance in Dirofilaria immitis from Rio de Janeiro, Brazil?

OBJECTIVE: Dirofilaria immitis, the causative agent of canine heartworm infection, is worldwide the most important filarid to affect domestic dogs. Prevention of this infection is done by macrocyclic lactones, but some reports on the lack of efficacy have been published. Although the actual cause of resistance is unknown, single nucleotide polymorphisms (SNPs) on a P-glycoprotein ABC transporter and ß-tubulin genes have been pointed out as candidates for genetic markers of resistance. We conducted a survey to verify the presence of these suggested genetic markers in microfilariae from 30 naturally infected dogs under macrocyclic lactones treatment living in an endemic area in the state of Rio de Janeiro. RESULTS: The analysis of these specific SNPs demonstrated no sign of polymorphism on the P-glycoprotein loci, while 72 and 48% of the samples were polymorphic to the first and second SNPs on ß-tubulin loci, respectively. This work demonstrates that the P-glycoprotein position 11 and 618 were not polymorphic and, therefore, not suitable as a genetic marker of resistance in Rio de Janeiro whereas both ß-tubulin loci were polimorphic. This work points out the difficulty of finding a universal genetic marker for resistance.

Synthesis, spectroscopic, physicochemical and structural characterization of tetrandrine-based macrocycles functionalized with acridine and anthracene groups: DNA binding and anti-proliferative activity.

In this work, we report on the synthesis of two new mono-alkylated tetrandrine derivatives with acridine and anthracene units, MAcT and MAnT. The compounds were fully characterized by physicochemical techniques and single-crystal X-ray diffraction analysis. In addition, both derivatives were studied as nucleotide receptors and double-stranded DNA binders in aqueous phosphate buffer at pH = 7.2 using UV-vis and fluorescence spectroscopy. According to the molecular recognition studies, MAcT and MAnT exhibit high affinity (K ∼ 105 M-1) and selectivity for ds-DNA, presumably in an intercalation mode. Finally, the anti-proliferative effects of the tetrandrine derivatives on different cancer cell lines were explored, revealing promising activities. Particularly, the mono-anthracene tetrandrine derivative MAnT showed an IC50 of 2.74 µg/mL on the HeLa cervical cancer cell line, representing a value 3.3 times smaller than that obtained for unsubstituted tetrandrine. Examination of the cytotoxic effects on the HeLa cell line by inverted microscopy suggests that the cell death mechanism consists basically in apoptosis. The molecular modelling of three ds-DNA-MAcT complexes, suggested that the macrocycles may use an intercalation binding mode towards DNA. MAcT is predicted to bind into the major groove of the ds-DNA providing non-covalent interactions such as electrostatic, van der Waals and hydrophobic interactions that lead to selectivity. Overall experimental data supports the mode of action of MAnT and MAcT as cytotoxic compounds against cancer cell lines via a DNA interaction mechanism.

Diversity-oriented synthesis and cytotoxic activity evaluation of biaryl-containing macrocycles.

Synthesis of biaryl-containing macrocycles has been carried out through a four-step approach comprising two Ugi four component reactions and a Suzuki-Miyaura macrocyclization. This protocol allowed the synthesis of 12- and 14-membered macrocycles. Cytotoxic activity evaluation showed that some of the molecules were effective against leukemia, glioblastoma and lung cancer cell lines (IC50 = 4.0, 5.9 and 7.6, respectively).

Dung removal by dung beetles (Coleoptera: Scarabaeidae) and macrocyclic lactone use on cattle ranches of Yucatan, Mexico / Remoción de estiércol por escarabajos estercoleros (Coleoptera: Scarabaeinae) y uso de lactonas macrocíclicas en ranchos ganaderos de Yucatán, México

Abstract:The expanded use of macrocyclic lactones (ML) to treat endo- and ectoparasites in cattle in tropical regions, can reduce dung beetle populations, and thus interrupt the dung removal process in cattle pasture ecosystems. During the reproductive period (the rainy season) of two functional groups of dung beetles (paracoprid and telocoprid Scarabaeinae), we compared dung removal amount in ranches where ML are and are not used in Yucatan, Mexico, through exclusion traps baited with 500 g of ML-free cow dung. On each ranch, two transects (separated by 500 m) with six traps each, were set up for 24 hours. After this time, all the dung remnants in each trap were obtained and weighed in order to record the dung removal. Results showed that dung removal amounts were similar in ranches with and without ML use. Dung beetles removed 40.1 % of all cow dung weighed. Paracoprids removed 87.46 % and telocoprids 12.54 % of all the dung that was removed. Our results indicated that the ecological function of dung beetles in the pastures studied, does not seem to be affected by the ML use, and that paracoprid species removed most of the dung. For both types of ranch, further studies that take into account the population dynamics and movement of the most important dung beetle species in the region are required, coupled with laboratory studies evaluating the effect of ML on their reproductive success. This could give some light on the effect of ML on the ecological function of this important insect group in the sustainability of cattle production systems. Rev. Biol. Trop. 64 (3): 945-954. Epub 2016 September 01.

ResumenLa expansión en el uso de lactonas macrocíclicas (LM) para el tratamiento de endo y ectoparásitos del ganado en las regiones tropicales puede reducir las poblaciones de escarabajos del estiércol, interrumpiendo así el proceso de eliminación de estiércol de ganado en los pastizales. Durante el período reproductivo (época de lluvias) de dos grupos funcionales de escarabajos coprófagos (paracópridos y telecópridos), se comparó la cantidad removida de estiércol usando trampas de exclusión cebadas con 500 g de estiércol de vaca libre de LM en dos ranchos donde se usan y en dos donde no se usan LM, en la península de Yucatán, México. En cada rancho se establecieron dos transectos (separados por 500 m) con seis trampas cada uno, las cuales estuvieron activas durante 24 horas. Después de este tiempo, todos los restos de estiércol en cada trampa se pesaron para registrar la remoción. Los resultados mostraron que las cantidades de remoción fueron similares en ranchos con y sin uso de LM. Los escarabajos estercoleros removieron 40.1 % del peso total del excremento. Los paracópridos removieron 87.46 % y los telecópridos 12.54 % del total de excremento removido. Los resultados indican que la función ecológica de los escarabajos estercoleros en los potreros estudiados no parece verse afectada por el uso de LM y que las especies paracórpidas remueven la mayor parte del excremento. Se requiere hacer más estudios en ambos tipos de ranchos, en los que se tome en cuenta la dinámica poblacional y el movimiento de las especies más importantes de la región, acoplados a estudios de laboratorio que evalúen el efecto de las LM sobre el éxito reproductivo, y de esta manera esclarecer el efecto de las LM sobre la función ecológica de este grupo de insectos tan importante para la sustentabilidad de los sistemas ganaderos.

GS-9857 in patients with chronic hepatitis C virus genotype 1-4 infection: a randomized, double-blind, dose-ranging phase 1 study.

GS-9857, an inhibitor of the hepatitis C virus (HCV) nonstructural protein (NS) 3/4A, demonstrates potent activity against HCV genotypes 1-6 and improved coverage against commonly encountered NS3 resistance-associated variants (RAVs). In this study, the safety, tolerability, antiviral activity and pharmacokinetics (PK) of GS-9857 were evaluated in patients with chronic HCV genotype 1-4 infection. Patients with genotype 1-4 infection received placebo or once-daily GS-9857 at doses ranging from 50 to 300 mg for 3 days under fasting conditions. GS-9857 was well tolerated; all reported adverse events (AEs) were mild or moderate in severity. Diarrhoea and headache were the most commonly reported AEs. Grade 3 or 4 laboratory abnormalities were observed in 17% of patients receiving GS-9857; there were no Grade 3 or 4 abnormalities in alanine aminotransferase, aspartate aminotransferase or alkaline phosphatase levels. GS-9857 demonstrated potent antiviral activity in patients with chronic HCV infection, achieving mean and median maximum reductions in HCV RNA of ≥3 log10 IU/mL following administration of a 100-mg dose in patients with HCV genotype 1a, 1b, 2, 3 or 4 infection. The antiviral activity of GS-9857 was unaffected by the presence of pretreatment NS3 RAVs. In patients with genotype 1-4 infection, GS-9857 exhibited linear PK and was associated with a median half-life of 29-42 h, supporting once-daily dosing. Thus, the tolerability, efficacy and pharmacokinetic profile of GS-9857 support its further evaluation for treatment of patients with chronic HCV infection.

Dung removal by dung beetles (Coleoptera: Scarabaeidae) and macrocyclic lactone use on cattle ranches of Yucatan, Mexico.

The expanded use of macrocyclic lactones (ML) to treat endo- and ectoparasites in cattle in tropical regions, can reduce dung beetle populations, and thus interrupt the dung removal process in cattle pasture ecosystems. During the reproductive period (the rainy season) of two functional groups of dung beetles (paracoprid and telocoprid Scarabaeinae), we compared dung removal amount in ranches where ML are and are not used in Yucatan, Mexico, through exclusion traps baited with 500 g of ML-free cow dung. On each ranch, two transects (separated by 500 m) with six traps each, were set up for 24 hours. After this time, all the dung remnants in each trap were obtained and weighed in order to record the dung removal. Results showed that dung removal amounts were similar in ranches with and without ML use. Dung beetles removed 40.1 % of all cow dung weighed. Paracoprids removed 87.46 % and telocoprids 12.54 % of all the dung that was removed. Our results indicated that the ecological function of dung beetles in the pastures studied, does not seem to be affected by the ML use, and that paracoprid species removed most of the dung. For both types of ranch, further studies that take into account the population dynamics and movement of the most important dung beetle species in the region are required, coupled with laboratory studies evaluating the effect of ML on their reproductive success. This could give some light on the effect of ML on the ecological function of this important insect group in the sustainability of cattle production systems.

Mechanisms of cytotoxicity induced by the anesthetic isoflurane: the role of inositol 1,4,5-trisphosphate receptors.

Isoflurane can induce widespread cytotoxicity. We hypothesized that isoflurane induces apoptosis partly by causing excessive calcium release from the endoplasmic reticulum (ER) via direct activation of inositol 1,4,5-trisphosphate receptors (IP3R). Rat pheochromocytoma cells cultured for seven days with nerve growth factor were divided into four groups: control group (C), IP3R antagonist group (X), isoflurane group (I) and isoflurane + IP3R antagonist group (I+X). Groups I and I+X were treated with 1 MAC isoflurane for 12 h. Groups X and I+X were pretreated with IP3R antagonist. Annexin V/PI apoptosis and TUNEL assays were performed to evaluate cell apoptosis. TEM was used to observe changes in cell ultrastructure. Changes in calcium concentration ([Ca(2+)]i) in the cytoplasm were measured by flow cytometry. RT-PCR was performed to evaluate IP3R mRNA expression. TEM showed that isoflurane treatment altered cell ultrastructure. Compared to group C, cell apoptosis rate and [Ca(2+)]i increased in groups I and I+X (P < 0.05). Compared to group C, IP3R mRNA expression was lower in group X and higher in group I (P < 0.05). Compared to group X, cell apoptosis rate, [Ca(2+)]i and IP3R mRNA expression increased in groups I and I+X (P < 0.05). Compared to group I, cell apoptosis rate, [Ca(2+)]i and IP3R mRNA expression decreased in group I+X (P < 0.05). These results suggest that exposure to 1 MAC isoflurane for 12 h causes excessive calcium release partly by direct activation of IP3R on the ER membrane and triggers cell apoptosis.

Tumor size and prognosis in patients with Wilms tumor / Tamanho tumoral e prognóstico em pacientes portadores de tumor de Wilms

OBJECTIVE: Investigate the relationship of the tumor volume after preoperative chemotherapy (TVAPQ) and before preoperative chemotherapy (TVBPQ) with overall survival at two and at five years, and lifetime. METHODS: Our sample consisted of consecutive patients evaluated in the period from 1989 to 2009 in an Onco-Hematology Service. Clinical, histological and volumetric data were collected from the medical records. For analysis, chi-square, Kaplan-Meier, log-rank and Cox regression tests were used. RESULTS: The sample consisted of 32 patients, 53.1% were male with a median age at diagnosis of 43 months. There was a significant association between TVAPQ>500mL and the difference between the TVBPQ and TVAPQ (p=0.015) and histologic types of risk (p=0.008). It was also verified an association between the difference between the TVBPQ and TVAPQ and the predominant stromal tumor (p=0.037). When assessing the TVAPQ of all patients, without a cutoff, there was an association of the variable with lifetime (p=0.013), i.e., for each increase of 10mL in TVAPQ there was an average increase of 2% in the risk of death. CONCLUSIONS: Although our results indicate that the TVAPQ could be considered alone as a predictor of poor prognosis regardless of the cutoff suggested in the literature, more studies are needed to replace the histology and staging by tumor size as best prognostic variable. .

OBJETIVO: Investigar a relação entre o volume do tumor após a quimioterapia pré-operatória (VTPOS) e antes da quimioterapia pré-operatória (VTPRE) com sobrevida geral aos dois e cinco anos e tempo de vida. MÉTODOS: A amostra foi composta por pacientes consecutivos avaliados de 1989 a 2009, em um serviço de onco-hematologia. Os dados clínicos, histológicos e volumétricos foram coletados a partir dos registros médicos. Para análise, usaram-se os testes qui-quadrado, Kaplan-Meier, log-rank e regressão de Cox. RESULTADOS: A amostra foi composta de 32 pacientes, 53,1% do sexo masculino, com mediana de idade ao diagnóstico de 43 meses. Houve associação significativa entre VTPOS >500 mL e a diferença entre o VTPRE e VTPOS (p=0,015) e os tipos histológicos de risco (p=0,008). Verificou-se também uma associação entre a diferença entre o VTPRE e VTPOS e o tumor de predomínio estromal (p=0,037). Quando se avaliou o VTPOS de todos os pacientes, sem um ponto de corte definido, observou-se associação dessa variável com o tempo de vida (p=0,013), isto é, para cada aumento de 10 mL no VTPOS houve um aumento médio de 2% no risco de morte. CONCLUSÕES: Embora os resultados indiquem que o VTPOS poderia ser considerado um preditor isolado de mau prognóstico, independentemente do ponto de corte sugerido na literatura, mais estudos são necessários para substituir a histologia e estadiamento pelo tamanho do tumor como melhor variável prognóstica. .

In vitro leishmanicidal activity of pyrazole-containing polyamine macrocycles which inhibit the Fe-SOD enzyme of Leishmania infantum and Leishmania braziliensis species.

The in vitro leishmanicidal activity and cytotoxicity of pyrazole-containing macrocyclic polyamines 1-4 was assayed on Leishmania infantum and Leishmania braziliensis species. Compounds 1-4 were more active and less toxic than glucantime and both infection rates and ultrastructural alterations confirmed that 1 and 2 were highly leishmanicidal and induced extensive parasite cell damage. Modifications in the excretion products of parasites treated with 1-3 were also consistent with substantial cytoplasm alterations. Compound 2 was highlighted as a potent inhibitor of Fe-SOD in both species, whereas its effect on human CuZn-SOD was poor. Molecular modelling suggested that 2 could deactivate Fe-SOD due to a sterically favoured enhanced ability to interact with the H-bonding net that supports the enzyme`s antioxidant features.

In vitro activity of scorpiand-like azamacrocycle derivatives in promastigotes and intracellular amastigotes of Leishmania infantum and Leishmania braziliensis.

The activity of a family scorpiand-like azamacrocycles against Leishmania infantum and Leishmania braziliensis was studied using promastigotes, axenic and intracellular amastigotes forms. All the compounds are more active and less toxic than meglumine antimoniate (Glucantime). Moreover, the data on infection rates and amastigotes showed that compounds P2Py, PN and P3Py are the most active against both species of Leishmania. On the other hand, studies on the inhibitory effect of these compounds on SOD enzymes showed that while the inhibition of the Fe-SOD enzyme of the promastigote forms of the parasites is remarkable, the inhibition of human CuZn-SOD and Mn-SOD from Escherichia coli is negligible. The ultrastructural alterations observed in treated promastigote forms confirmed that the compounds having the highest activity were those causing the largest cell damage. The modifications observed by (1)H NMR, and the amounts of catabolites excreted by the parasites after treatment with the compounds, suggested that the catabolic mechanism could depend on the structure of the side chains linked to the aza-scorpiand macrocycles.

Ivermectin resistance status and factors associated in Rhipicephalus microplus (Acari: Ixodidae) populations from Veracruz, Mexico.

The objectives of the present study were to (1) determine the status of resistance or susceptibility to ivermectin (IVM) in Rhipicephalus microplus tick populations in Veracruz, Mexico, (2) determine the level of resistance (resistance ratios [RR] and lethal concentrations for 50% [LC(50)] and 99% [LC(99)]) mortality in each R. microplus population, and (3) identify factors associated with resistance. Populations of R. microplus were sampled from 53 cattle farms to evaluate their resistance using the larval immersion test. Mortality data were subjected to probit analysis to calculate LC(50) and LC(99). Resistance ratios were calculated in relation to a susceptible reference strain. A logistic regression model was used to evaluate the relation between resistance and possible associated factors. Thirteen tick populations were susceptible to ivermectin, eighteen had incipient resistance and twenty-two had significant resistance. RR(50) of the susceptible tick populations varied from 0.59 to 1.07. The populations that showed the highest level of resistance were: ANTE (RR(50)=8.21; RR(99)=46.0), PALO (RR(50)=6.25; RR(99)=35.47), P.VIE (RR(50)=5.89; RR(99)=180.3), AURO (RR(50)=5.36; RR(99)=13.82 and CEDR (RR(50)=4.11; RR(99)=26.47). Cattle farms that used macrocyclic lactones ≥ 4 times per year were more likely to develop R. microplus resistant to ivermectin (OR=13.0; p=0.0028). In conclusion, more than two-thirds of the farms sampled in Veracruz, Mexico, showed some level of ivermectin-resistant R. microplus populations and the number of ML applications per year is factor associated with the resistance of R. microplus to IVM.

Geographic variability and anti-staphylococcal activity of the chrysophaentins and their synthetic fragments.

Drug-resistant Staphylococcus aureus is a continuing public health concern, both in the hospital and community settings. Antibacterial compounds that possess novel structural scaffolds and are effective against multiple S. aureus strains, including current drug-resistant ones, are needed. Previously, we have described the chrysophaentins, a family of bisdiarylbutene macrocycles from the chrysophyte alga Chrysophaeum taylori that inhibit the growth of S. aureus and methicillin-resistant S. aureus (MRSA). In this study we have analyzed the geographic variability of chrysophaentin production in C. taylori located at different sites on the island of St. John, U.S. Virgin Islands, and identified two new linear chrysophaentin analogs, E2 and E3. In addition, we have expanded the structure activity relationship through synthesis of fragments comprising conserved portions of the chrysophaentins, and determined the antimicrobial activity of natural chrysophaentins and their synthetic analogs against five diverse S. aureus strains. We find that the chrysophaentins show similar activity against all S. aureus strains, regardless of their drug sensitivity profiles. The synthetic chrysophaentin fragments indeed mimic the natural compounds in their spectrum of antibacterial activity, and therefore represent logical starting points for future medicinal chemistry studies of the natural products and their analogs.

Effect of low level laser therapy on bronchial hyper-responsiveness.

The objective of this study was to investigate whether low level laser therapy (LLLT) could reduce bronchial hyper-responsiveness (BHR) induced by tumour necrosis factor-alpha (TNF-alpha) modulating the metabolism of inositol phosphate (IP) in bronchial smooth muscle cells (BSMCs). The study was on 28 Wistar rats, randomly divided into four groups. Irradiation (1.3 J/cm(2)) was administered 5 min and 4 h after bronchial smooth muscle (BSM) had been suspended in TNF-alpha baths, and the contractile response-induced calcium ion (Ca(2+)) sensitization was measured. The BSMCs were isolated, and the IP accumulation was measured before and after TNF-alpha immersion in the groups that had been irradiated or not irradiated. BSM segments significantly increased contraction 24 h after TNF-alpha immersion when exposed to carbachol (CCh) as Ca(2+), but it was significantly reduced by 64% and 30%, respectively, after laser treatment. The increase in IP accumulation induced by CCh after TNF-alpha immersion was reduced in the BSMCs by LLLT. The dose of 2.6 J/cm(2) reduced BHR and IP accumulation in the rats' inflammatory BSMCs.

Differential contribution of extracellular and intracellular calcium sources to basal transmission and long-term potentiation in the sympathetic ganglion of the rat.

Calcium involved in basal ganglionic transmission and long-term potentiation (LTP) can arise either by influx from the extracellular medium or release from intracellular stores. No attempts have yet been made to concurrently explore the contributions of extracellular and intracellular Ca2+ to basal ganglionic transmission or LTP. Here, we investigate this subject using the superior cervical ganglion of the rat. To explore the extracellular Ca2+ contribution, we evaluated basal transmission and LTP at different extracellular Ca2+ concentrations. To assess intracellular Ca2+ release, we explored the contribution of the calcium-induced calcium release process by overactivation or blockade of ryanodine-sensitive Ca2+ receptor channel with caffeine, and also by blocking either IP3R with Xestospongin C or the sarco(endo)plasmic reticulum Ca2+-ATPase pump with thapsigargin. Extracellular Ca2+ affected ganglionic basal transmission and LTP to different extents. While 25% of the physiological Ca2+ concentration supported 80% of basal transmission, 50% of normal Ca2+ was required to achieve 80% of LTP. Notably, disruption of intracellular Ca2+ release by all the drugs tested apparently did not affect basal ganglionic transmission but impaired LTP. We conclude that basal transmission requires only a small level of Ca2+ entry, while LTP expression not only requires more Ca2+ entry but is also dependent on Ca2+ release from intracellular stores.

A macrocyclic nitrosyl ruthenium complex is a NO donor that induces rat aorta relaxation.

The vasorelaxation induced by a nitrosyl macrocyclic ruthenium complex, proposed as a new nitric oxide (NO) carrier, was studied in rat isolated aorta. The compound trans-[RuCl([15]aneN4)NO]2+ was characterized by elemental analysis, UV-visible spectrum, and infrared spectrum. Based on the electrochemical process, the reduction of the compound was followed by NO release, which was also observed using norepinephrine as a reducing agent and NO released was analyzed by a sensor. Vasorelaxation induced by this NO donor was studied and compared to those obtained with sodium nitroprusside (SNP). The relaxation induced by the compound was concentration-dependent in denuded rat aortas and occurred only in pre-contracted arteries with norepinephrine. The macrocyclic compound induced relaxation with a similar efficacy as SNP, although the potency of SNP was slightly greater. The time to reach maximum relaxation (595 s) was longer than that of SNP (195 s). Relaxation was completely abolished by oxyhemoglobin, a known NO scavenger.