Publications by authors named "Ricardo Martin"

25 Publications

  • Page 1 of 1

Endocannabinoid signalling in stem cells and cerebral organoids drives differentiation to deep layer projection neurons via CB receptors.

Development 2020 12 23;147(24). Epub 2020 Dec 23.

Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 28049 Madrid, Spain

The endocannabinoid (eCB) system, via the cannabinoid CB receptor, regulates neurodevelopment by controlling neural progenitor proliferation and neurogenesis. CB receptor signalling drives corticofugal deep layer projection neuron development through the regulation of BCL11B and SATB2 transcription factors. Here, we investigated the role of eCB signalling in mouse pluripotent embryonic stem cell-derived neuronal differentiation. Characterization of the eCB system revealed increased expression of eCB-metabolizing enzymes, eCB ligands and CB receptors during neuronal differentiation. CB receptor knockdown inhibited neuronal differentiation of deep layer neurons and increased upper layer neuron generation, and this phenotype was rescued by CB re-expression. Pharmacological regulation with CB receptor agonists or elevation of eCB tone with a monoacylglycerol lipase inhibitor promoted neuronal differentiation of deep layer neurons at the expense of upper layer neurons. Patch-clamp analyses revealed that enhancing cannabinoid signalling facilitated neuronal differentiation and functionality. Noteworthy, incubation with CB receptor agonists during human iPSC-derived cerebral organoid formation also promoted the expansion of BCL11B neurons. These findings unveil a cell-autonomous role of eCB signalling that, via the CB receptor, promotes mouse and human deep layer cortical neuron development.
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http://dx.doi.org/10.1242/dev.192161DOI Listing
December 2020

β-Adrenergic Receptors/Epac Signaling Increases the Size of the Readily Releasable Pool of Synaptic Vesicles Required for Parallel Fiber LTP.

J Neurosci 2020 11 12;40(45):8604-8617. Epub 2020 Oct 12.

Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Instituto Universitario de Investigación en Neuroquímica, Universidad Complutense, 28040 Madrid, Spain

The second messenger cAMP is an important determinant of synaptic plasticity that is associated with enhanced neurotransmitter release. Long-term potentiation (LTP) at parallel fiber (PF)-Purkinje cell (PC) synapses depends on a Ca-induced increase in presynaptic cAMP that is mediated by Ca-sensitive adenylyl cyclases. However, the upstream signaling and the downstream targets of cAMP involved in these events remain poorly understood. It is unclear whether cAMP generated by β-adrenergic receptors (βARs) is required for PF-PC LTP, although noradrenergic varicosities are apposed in PF-PC contacts. Guanine nucleotide exchange proteins directly activated by cAMP [Epac proteins (Epac 1-2)] are alternative cAMP targets to protein kinase A (PKA) and Epac2 is abundant in the cerebellum. However, whether Epac proteins participate in PF-PC LTP is not known. Immunoelectron microscopy demonstrated that βARs are expressed in PF boutons. Moreover, activation of these receptors through their agonist isoproterenol potentiated synaptic transmission in cerebellar slices from mice of either sex, an effect that was insensitive to the PKA inhibitors (H-89, KT270) but that was blocked by the Epac inhibitor ESI 05. Interestingly, prior activation of these βARs occluded PF-PC LTP, while the β1AR antagonist metoprolol blocked PF-PC LTP, which was also absent in mice. PF-PC LTP is associated with an increase in the size of the readily releasable pool (RRP) of synaptic vesicles, consistent with the isoproterenol-induced increase in vesicle docking in cerebellar slices. Thus, the βAR-mediated modulation of the release machinery and the subsequent increase in the size of the RRP contributes to PF-PC LTP. G-protein-coupled receptors modulate the release machinery, causing long-lasting changes in synaptic transmission that influence synaptic plasticity. Nevertheless, the mechanisms underlying synaptic responses to β-adrenergic receptor (βAR) activation remain poorly understood. An increase in the number of synaptic vesicles primed for exocytosis accounts for the potentiation of neurotransmitter release driven by βARs. This effect is not mediated by the canonical protein kinase A pathway but rather, through direct activation of the guanine nucleotide exchange protein Epac by cAMP. Interestingly, this βAR signaling via Epac is involved in long term potentiation at cerebellar granule cell-to-Purkinje cell synapses. Thus, the pharmacological activation of βARs modulates synaptic plasticity and opens therapeutic opportunities to control this phenomenon.
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http://dx.doi.org/10.1523/JNEUROSCI.0716-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7643300PMC
November 2020

Comparison of Growth Patterns of COVID-19 Cases through the ARIMA and Gompertz Models. Case Studies: Austria, Switzerland, and Israel.

Rambam Maimonides Med J 2020 Jul 31;11(3). Epub 2020 Jul 31.

Faculty of Health Sciences, University San Jorge, Zaragoza, Spain.

On May 19, 2020, data confirmed that coronavirus 2019 disease (COVID-19) had spread worldwide, with more than 4.7 million infected people and more than 316,000 deaths. In this article, we carry out a comparison of the methods to calculate and forecast the growth of the pandemic using two statistical models: the autoregressive integrated moving average (ARIMA) and the Gompertz function growth model. The countries that have been chosen to verify the usefulness of these models are Austria, Switzerland, and Israel, which have a similar number of habitants. The investigation to check the accuracy of the models was carried out using data on confirmed, non-asymptomatic cases and confirmed deaths from the period February 21-May 19, 2020. We use the root mean squared error (RMSE), the mean absolute percentage error (MAPE), and the regression coefficient index R to check the accuracy of the models. The experimental results provide promising adjustment errors for both models (R>0.99), with the ARIMA model being the best for infections and the Gompertz best for mortality. It has also been verified that countries are affected differently, which may be due to external factors that are difficult to measure quantitatively. These models provide a fast and effective system to check the growth of pandemics that can be useful for health systems and politicians so that appropriate measures are taken and countries' health care systems do not collapse.
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http://dx.doi.org/10.5041/RMMJ.10413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7426552PMC
July 2020

The loss of β adrenergic receptor mediated release potentiation in a mouse model of fragile X syndrome.

Neurobiol Dis 2019 10 23;130:104482. Epub 2019 May 23.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain; Instituto Universitario de Investigación en Neuroquímica (IUIN), Universidad Complutense, 28040 Madrid, Spain; Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040 Madrid, Spain. Electronic address:

In fragile X syndrome, the absence of Fragile X Mental Retardation Protein (FMRP) is known to alter postsynaptic function, although alterations in presynaptic function also occur. We found that the potentiation of glutamate release induced by the β adrenergic receptor (βAR) agonist isoproterenol is absent in cerebrocortical nerve terminals (synaptosomes) from mice lacking FMRP (Fmr1 KO), despite the normal cAMP generation. The glutamate release induced by moderate stimulation of synaptosomes with 5 mM KCl was not potentiated in Fmr1 KO synaptosomes by isoproterenol, nor by stimulating the receptor associated signaling pathway with the adenylyl cyclase activator forskolin or with the Epac activator 8-pCPT. Hence, the impairment in the pathway potentiating release is distal to βARs. Electron microscopy shows that Fmr1 KO cortical synapses have more docked vesicles than WT synapses, consequently occluding the isoproterenol response through which more SVs approach the active zone (AZ) of the plasma membrane. Weak stimulation of synaptosomes with the Ca ionophore ionomycin recovered the release potentiation driven by forskolin and 8-pCPT but not with isoproterenol, revealing an impairment in the efficiency of receptor generated cAMP to activate the release potentiation pathway. Indeed, inhibiting cyclic nucleotide phosphodiesterase PDE2A with BAY 60-7550 reestablished isoproterenol mediated potentiation in Fmr1 KO synaptosomes. Thus, the lack of β-AR mediated potentiation of glutamate release appears to be the consequence of an impaired capability of the receptor to mobilize SVs to the AZ and because of a decreased efficiency of cAMP to activate the signaling pathway that enhances neurotransmitter release.
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http://dx.doi.org/10.1016/j.nbd.2019.104482DOI Listing
October 2019

AhR Deletion Promotes Aberrant Morphogenesis and Synaptic Activity of Adult-Generated Granule Neurons and Impairs Hippocampus-Dependent Memory.

eNeuro 2018 Jul-Aug;5(4). Epub 2018 Aug 22.

Unidad De Investigación Neurovascular, Dpto. Farmacología y Toxicología, Facultad De Medicina, and Instituto Universitario De Investigación En Neuroquímica (IUIN), Universidad Complutense De Madrid (UCM); Instituto De Investigación Hospital 12 De Octubre (i+12), Madrid, Spain.

Newborn granule cells are continuously produced in the subgranular zone of dentate gyrus throughout life. Once these cells mature, they integrate into pre-existing circuits modulating hippocampus-dependent memory. Subsequently, mechanisms controlling generation and maturation of newborn cells are essential for proper hippocampal function. Therefore, we have studied the role of aryl hydrocarbon receptor (AhR), a ligand-activated bHLH-PAS transcription factor, in hippocampus-dependent memory and granule neuronal morphology and function using genetic loss-of-function approaches based on constitutive and inducible-nestin AhR mice. The results presented here show that the impaired hippocampus-dependent memory in AhR absence is not due to its effects on neurogenesis but to aberrant dendritic arborization and an increased spine density, albeit with a lower number of mature mushrooms spines in newborn granule cells, a finding that is associated with an immature electrophysiological phenotype. Together, our data strongly suggest that AhR plays a pivotal role in the regulation of hippocampal function, by controlling hippocampal granule neuron morphology and synaptic maturation.
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http://dx.doi.org/10.1523/ENEURO.0370-17.2018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140122PMC
March 2019

Bidirectional modulation of glutamatergic synaptic transmission by metabotropic glutamate type 7 receptors at Schaffer collateral-CA1 hippocampal synapses.

J Physiol 2018 03 25;596(5):921-940. Epub 2018 Jan 25.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.

Key Points: Neurotransmitter release is inhibited by metabotropic glutamate type 7 (mGlu ) receptors that reduce Ca influx, yet synapses lacking this receptor also produce weaker release, suggesting that mGlu receptors may also prime synaptic vesicles for release. Prolonged activation of mGlu receptors with the agonist l-AP4 first reduces and then enhances the amplitude of EPSCs through a presynaptic effect. The inhibitory response is blocked by pertussis toxin, while the potentiating response is prevented by a phospholipase C inhibitor (U73122) and an inhibitor of diacylglycerol (DAG) binding (calphostin C), suggesting that this receptor also couples to pathways that generate DAG. Release potentiation is associated with an increase in the number of synaptic vesicles close to the plasma membrane, which was dependent on the Munc13-2 and RIM1α proteins. The Glu7 receptors activated by the glutamate released following high frequency stimulation provoke a bidirectional modulation of synaptic transmission.

Abstract: Neurotransmitter release is driven by Ca influx at synaptic boutons that acts on synaptic vesicles ready to undergo exocytosis. Neurotransmitter release is inhibited when metabotropic glutamate type 7 (mGlu ) receptors provoke a reduction in Ca influx, although the reduced release from synapses lacking this receptor suggests that they may also prime synaptic vesicles for release. These mGlu receptors activate phospholipase C (PLC) and generate inositol trisphosphate, which in turn releases Ca from intracellular stores and produces diacylglycerol (DAG), an activator of proteins containing DAG-binding domains such as Munc13 and protein kinase C (PKC). However, the full effects of mGlu receptor signalling on synaptic transmission are unclear. We found that prolonged activation of mGlu receptors with the agonist l-AP4 first reduces and then enhances the amplitude of EPSCs, a presynaptic effect that changes the frequency but not the amplitude of the mEPSCs and the paired pulse ratio. Pertussis toxin blocks the inhibitory response, while the PLC inhibitor U73122, and the inhibitor of DAG binding calphostin C, prevent receptor mediated potentiation. Moreover, this DAG-dependent potentiation of the release machinery brings more synaptic vesicles closer to the active zone plasma membrane in a Munc13-2- and RIM1α-dependent manner. Electrically evoked release of glutamate that activates mGlu receptors also bidirectionally modulates synaptic transmission. In these conditions, potentiation now occurs rapidly and it overcomes any inhibition, such that potentiation prevails unless it is suppressed with the PLC inhibitor U73122.
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http://dx.doi.org/10.1113/JP275371DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830420PMC
March 2018

Targeting factors for change: contraceptive counselling and care of female adolescents.

Eur J Contracept Reprod Health Care 2016 Dec 5;21(6):417-430. Epub 2016 Oct 5.

e The Ottawa Hospital , Ottawa , Canada.

Introduction: Sexual and reproductive health care should empower and enable all individuals to have a sex life that is as safe and pleasurable as possible. Achievement of this goal for adolescents is often impeded by regional and sociocultural barriers.

Objectives: To review global barriers to provision of effective counselling and care of adolescents seeking advice on contraception and sexual and reproductive health and identify elements of best practice that can be adapted to meet their needs at regional level.

Methods: Experts with clinical experience and a scholarly background in the provision of contraceptive services to adolescents participated in a stepwise process of literature review and discussion according to the agreed objectives.

Results: The Global CARE (Contraception: Access, Resources, Education) group identified barriers to the access, availability and acceptance of contraception by adolescents, not only at the political and sociocultural level but also within health care practice. The group collected and summarized successful local strategies and tools suitable for adaptation in other regions. Elements of best practice for providing contraception regardless of setting or regional constraints, including required skills, knowledge, and attitudes, were also proposed.

Conclusion: Sharing of evidence-based best practice in delivering contraceptive services, improvements in health care provider education, and sharing of experience between countries will hopefully help to overcome the barriers to appropriate and effective counselling and care of adolescents.
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http://dx.doi.org/10.1080/13625187.2016.1237629DOI Listing
December 2016

Mammalian Innate Immune Response to a Leishmania-Resident RNA Virus Increases Macrophage Survival to Promote Parasite Persistence.

Cell Host Microbe 2016 Sep 1;20(3):318-328. Epub 2016 Sep 1.

Department of Biochemistry, University of Lausanne, 1066 Epalinges, Switzerland. Electronic address:

Some strains of the protozoan parasite Leishmania guyanensis (L.g) harbor a viral endosymbiont called Leishmania RNA virus 1 (LRV1). LRV1 recognition by TLR-3 increases parasite burden and lesion swelling in vivo. However, the mechanisms by which anti-viral innate immune responses affect parasitic infection are largely unknown. Upon investigating the mammalian host's response to LRV1, we found that miR-155 was singularly and strongly upregulated in macrophages infected with LRV1+ L.g when compared to LRV1- L.g. LRV1-driven miR-155 expression was dependent on TLR-3/TRIF signaling. Furthermore, LRV1-induced TLR-3 activation promoted parasite persistence by enhancing macrophage survival through Akt activation in a manner partially dependent on miR-155. Pharmacological inhibition of Akt resulted in a decrease in LRV1-mediated macrophage survival and consequently decreased parasite persistence. Consistent with these data, miR-155-deficient mice showed a drastic decrease in LRV1-induced disease severity, and lesional macrophages from these mice displayed reduced levels of Akt phosphorylation.
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http://dx.doi.org/10.1016/j.chom.2016.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493041PMC
September 2016

Cross-talk between metabotropic glutamate receptor 7 and beta adrenergic receptor signaling at cerebrocortical nerve terminals.

Neuropharmacology 2016 Feb 23;101:412-25. Epub 2015 Jul 23.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain; Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Hospital Clínico San Carlos, C/Profesor Martín Lagos s/n, Madrid 28040, Spain. Electronic address:

The co-existence of presynaptic G protein coupled receptors, GPCRs, has received little attention, despite the fact that interplay between the signaling pathways activated by such receptors may affect the neurotransmitter release. Using immunocytochemistry and immuhistochemistry we show that mGlu7 and β-adrenergic receptors are co-expressed in a sub-population of cerebrocortical nerve terminals. mGlu7 receptors readily couple to pathways that inhibit glutamate release. We found that when mGlu7 receptors are also coupled to pathways that enhance glutamate release by prolonged exposure to agonist, and β-adrenergic receptors are also activated, a cross-talk between their signaling pathways occurs that affect the overall release response. This interaction is the result of mGlu7 receptors inhibiting the adenylyl cyclase activated by β adrenergic receptors. Thus, blocking Gi/o proteins with pertussis toxin provokes a further increase in release after receptor co-activation which is also observed after activating β-adrenergic receptor signaling pathways downstream of adenylyl cyclase with the cAMP analog Sp8Br or 8pCPT-2-OMe-cAMP (a specific activator of the guanine nucleotide exchange protein directly activated by cAMP, EPAC). Co-activation of mGlu7 and β-adrenergic receptors also enhances PLC-dependent accumulation of IP1 and the translocation of the active zone protein Munc13-1 to the membrane, indicating that release potentiation by these receptors involves the modulation of the release machinery.
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http://dx.doi.org/10.1016/j.neuropharm.2015.07.025DOI Listing
February 2016

Comparison of industrially viable pretreatments to enhance soybean straw biodegradability.

Bioresour Technol 2015 Oct 30;194:1-6. Epub 2015 Jun 30.

Departamento de Ingeniería Química y Tecnología de Alimentos, Universidad de Cádiz, Campus Río San Pedro, s/n, Puerto Real, 11510 Cádiz, Spain.

This study explores acid and alkaline pretreatments in order to enhance soybean straw biodegradability. The effects of sulfuric acid and sodium hydroxide for different pretreatment times at 30°C and 121°C on biomass dissolution and the subsequent enzymatic hydrolysis were investigated. The highest total conversion to reducing sugars of 93.9% was attained when soybean straw was pretreated with acid (4% H2SO4, 121°C, 1 h) and subsequently subjected to the enzymatic process. However, conversion of 86.5%, were reached only with the hydrolysis of the pretreated residue using mild conditions, (0.5% NaOH, 30°C, 48 h), involving the reduction cost of the process. In addition to this, this result was dramatically decreased when pectinase was removed from the enzyme cocktail. It has been also demonstrated that the reduction of the enzyme loading to less than half allowed obtaining about 96% of the reducing sugars attained with the highest enzyme dose.
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http://dx.doi.org/10.1016/j.biortech.2015.06.090DOI Listing
October 2015

Presence of Leishmania RNA Virus 1 in Leishmania guyanensis Increases the Risk of First-Line Treatment Failure and Symptomatic Relapse.

J Infect Dis 2016 Jan 29;213(1):105-11. Epub 2015 Jun 29.

Department of Biochemistry, University of Lausanne, Epalinges.

Treatment failure and symptomatic relapse are major concerns in American tegumentary leishmaniasis (TL). Such complications are seen frequently in Leishmania guyanensis infections, in which patients respond variously to first-line antileishmanials and are more prone to develop chronic cutaneous leishmaniasis. The factors underlying this pathology, however, are unknown. Recently, we reported that a double-stranded RNA virus, Leishmania RNA virus 1 (LRV1), nested within L. guyanensis parasites is able to exacerbate experimental murine leishmaniasis by inducing a hyperinflammatory response. This report investigates the prevalence of LRV1 in human L. guyanensis infection and its effect on treatment efficacy, as well as its correlation to symptomatic relapses after the completion of first-line treatment. In our cohort of 75 patients with a diagnosis of primary localized American TL, the prevalence of LRV1-positive L. guyanensis infection was elevated to 58%. All patients infected with LRV1-negative L. guyanensis were cured after 1 dose (22 of 31 [71%]) or 2 doses (31 of 31 [100%]) of pentamidine. In contrast, 12 of 44 LRV1-positive patients (27%) presented with persistent infection and symptomatic relapse that required extended therapy and the use of second-line drugs. Finally, LRV1 presence was associated with a significant increase in levels of intra-lesional inflammatory markers. In conclusion, LRV1 status in L. guyanensis infection is significantly predictive (P = .0009) of first-line treatment failure and symptomatic relapse and has the potential to guide therapeutic choices in American TL.
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http://dx.doi.org/10.1093/infdis/jiv355DOI Listing
January 2016

Knowledge and attitudes of Latin American gynecologists regarding unplanned pregnancy and use of combined oral contraceptives.

Int J Womens Health 2015 4;7:485-91. Epub 2015 May 4.

Department of Obstetrics and Gynecology, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, Brazil.

Background: Unintended pregnancy is a public health problem and unmet medical need worldwide. It is estimated that in the year 2012, almost 213 million pregnancies occurred, and the global pregnancy rate decreased only slightly from 2008 to 2012. It was also estimated that 85 million pregnancies (40% of all pregnancies) were unintended and that 38% ended in an unintended birth.

Objectives: To assess knowledge and attitudes of Latin American (LA) obstetricians and gynecologists (OBGYNs) regarding unintended pregnancies and aspects of combined oral contraceptive (COC) use.

Methods: A survey was conducted during a scientific meeting about contraception in 2014, in which OBGYNs from 12 LA countries who provide attention in contraception were invited to respond to a multiple-choice questionnaire to assess their knowledge and attitudes regarding unplanned pregnancy and some aspects regarding COC use.

Results: A total of 210 OBGYNs participated in the study. Their knowledge regarding COC failure was low. The participants reported they believed that their patients habitually forgot to take a pill and that their patients did not know what to do in these situations. They were aware of the benefits of COC use; however, they were less prone to prescribe COCs for the purpose of protecting against ovarian and endometrial cancer, and one-quarter of them had doubts about the association between COC use and cancer risk.

Conclusion: The interviewed LA OBGYNs showed some flaws in terms of knowledge of COC failure rates and the non-contraceptive benefits and risks of COCs. To adequately counsel their patients regarding COC intake, OBGYNs must be updated regarding all aspects of COC use.
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http://dx.doi.org/10.2147/IJWH.S78874DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4427065PMC
May 2015

Alkaline and alkaline peroxide pretreatments at mild temperature to enhance enzymatic hydrolysis of rice hulls and straw.

Bioresour Technol 2014 Sep 4;167:1-7. Epub 2014 Jun 4.

Departamento de Ingeniería Química y Tecnología de Alimentos, Universidad de Cádiz, Campus Río San Pedro, s/n, Puerto Real 11510, Cádiz, Spain.

The current study explores alkaline and alkaline peroxide pretreatments in order to achieve a method to improve saccharification of agricultural residues for ethanol production. The effects of reagent concentration and pretreatment time at 30°C and atmospheric pressure on biomass dissolution after the pretreatment and enzymatic hydrolysis of the pretreated biomass were investigated. In fact, although all pretreatments tested improved enzymatic hydrolysis of native residues, the best results were not achieved for the highest biomass loss. The maximum conversions to reducing sugars in the hydrolysis stage of 77.5% and 92.6% were obtained for rice hulls and straw pretreated by alkaline peroxide (4%, 24h) and alkaline (1%, 48 h) methods, respectively. For both pretreated residues, the reduction to more than half the recommended enzyme loading allowed obtaining more than 94% the reducing sugars attained with the recommended dose.
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http://dx.doi.org/10.1016/j.biortech.2014.05.103DOI Listing
September 2014

Leishmania metacaspase: an arginine-specific peptidase.

Methods Mol Biol 2014 ;1133:189-202

Department of Biochemistry, University of Lausanne, Lausanne, Switzerland.

The purpose of this chapter is to give insights into metacaspase of Leishmania protozoan parasites as arginine-specific cysteine peptidase. The physiological role of metacaspase in Leishmania is still a matter of debate, whereas its peptidase enzymatic activity has been well characterized. Among the different possible expression systems, metacaspase-deficient yeast cells (Δyca1) have been instrumental in studying the activity of Leishmania major metacaspase (LmjMCA). Here, we describe techniques for purification of LmjMCA and its activity measurement, providing a platform for further identification of LmjMCA substrates.
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http://dx.doi.org/10.1007/978-1-4939-0357-3_12DOI Listing
October 2014

The number of Toll-like receptor 9-agonist motifs in the adenovirus genome correlates with induction of dendritic cell maturation by adenovirus immune complexes.

J Virol 2012 Jun 4;86(11):6279-85. Epub 2012 Apr 4.

Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland.

Adenovirus serotype 5 (Ad5) vectors and specific neutralizing antibodies (NAbs) generate immune complexes (ICs) which are potent inducers of dendritic cell (DC) maturation. Here we show that ICs generated with rare Ad vector serotypes, such as Ad26 and Ad35, which are lead candidates in HIV vaccine development, are poor inducers of DC maturation and that their potency in inducing DC maturation strongly correlated with the number of Toll-like receptor 9 (TLR9)-agonist motifs present in the Ad vector's genome. In addition, we showed that antihexon but not antifiber antibodies are responsible for the induction of Ad IC-mediated DC maturation.
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http://dx.doi.org/10.1128/JVI.00123-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372176PMC
June 2012

[Spatial and temporal variation in diet composition of invertivore fishes in a tropical stream, Venezuela].

Rev Biol Trop 2011 Sep;59(3):1217-31

Instituto de Biología Experimental, Universidad Central de Venezuela, Apartado postal 48170, Caracas 1041A, Venezuela.

Invertivores fishes are an important component of neotropical streams and they represent a link between aquatic invertebrates and piscivorous species. This study evaluated the breadth diet and interspecific food overlap of nine invertivores fish species during three consecutive hydrological phases: falling (December/07, January/08, February/08 and March/08), low (April/08) and rising waters (June/08), in two sections of a Venezuelan neotropical stream, which were located at different elevation, high watershed (HW) and low watershed (LW). The fishes were collected with a beach seine (5mm mesh) between 8:00 and 11:00 hours. The diet of each species was evaluated using an index of relative importance (IRI), which includes as variables the number, weight and occurrence frequency of food items consumed. The Levin' index (B ) and Morisita (IM) were used to estimate the breadth diet and interspecific food overlap, respectively. All estimations were made using the numeric proportion of preys. Nine fish species were captured, eight Characiformes, of which three were captured in HW (Knodus deuteronoides, Creagrutus bolivari and C. melasma) and five in LW (Thoracocharax stellatus, Moenkhausia lepidura, Cheirodon pulcher, Ctenobrycon spilurus and Aphyocharax alburnus), and one Cyprinodontiformes (Poecilia reticulata), which was also found in HW. In HW aquatic insects were the main resource consumed by fishes while plant material and terrestrial arthropods were secondary resources. In LW the fishes ingested all of these items in addition to zooplankton (Copepoda, Cladocera and larval stages of Decapoda). However, there was a temporal replacement with a predominance of zooplankton in falling and low water. In general, the breadth diet decreased during the falling water in both sections and increased in rising water. However, the average breadth diet was higher in HW. The interspecific food overlap was high in HW while low values were more frequent in LW and its temporal variation was opposed in both sections during almost all the sampling period.
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September 2011

DNA/NYVAC vaccine regimen induces HIV-specific CD4 and CD8 T-cell responses in intestinal mucosa.

J Virol 2011 Oct 20;85(19):9854-62. Epub 2011 Jul 20.

Department of Medicine, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland.

In the present study, we have investigated the anatomic distribution in blood and gut mucosal tissues of memory poxvirus-specific CD4 and CD8 T cells in subjects vaccinated with smallpox and compared it with vector (NYVAC)-specific and HIV insert-specific T-cell responses induced by an experimental DNA-C/ NYVAC-C vaccine regimen. Smallpox-specific CD4 T-cell responses were present in the blood of 52% of the subjects studied, while smallpox-specific CD8 T cells were rarely detected (12%). With one exception, smallpox-specific T cells were not measurable in gut tissues. Interestingly, NYVAC vector-specific and HIV-specific CD4 and CD8 T-cell responses were detected in almost 100% of the subjects immunized with DNA-C/NYVAC-C in blood and gut tissues. The large majority (83%) of NYVAC-specific CD4 T cells expressed α4β7 integrins and the HIV coreceptor CCR5. These results demonstrate that the experimental DNA-C/NYVAC-C HIV vaccine regimen induces the homing of potentially protective HIV-specific CD4 and CD8 T cells in the gut, the port of entry of HIV and one of the major sites for HIV spreading and the depletion of CD4 T cells.
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http://dx.doi.org/10.1128/JVI.00788-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3196391PMC
October 2011

Non-additive potentiation of glutamate release by phorbol esters and metabotropic mGlu7 receptor in cerebrocortical nerve terminals.

J Neurochem 2011 Feb 19;116(4):476-85. Epub 2011 Jan 19.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.

We recently showed that prolonged activation of metabotropic glutamate receptor 7 (mGlu7) potentiates glutamate release. This signalling involves phospholipase C activation via a pertussis toxin insensitive G protein and the subsequent hydrolysis of phosphatidylinositol (4,5)-bisphosphate. Release potentiation is independent of protein kinase C activation but it is dependent on the downstream release machinery, as reflected by the concomitant translocation of active zone Munc13-1 protein from the soluble to particulate fractions. Here we show that phorbol ester and mGlu7 receptor-dependent facilitation of neurotransmitter release is not additive, suggesting they share a common signalling mechanism. However, release potentiation is restricted to release sites that express N-type Ca(2+) channels, because phorbol ester and mGlu7 receptor-mediated release potentiation are absent in nerve terminals from mice lacking N-type Ca(2+) channels. In addition, phorbol esters but not mGlu7 receptors potentiate release at nerve terminals with P/Q-type Ca(2+) channels, although only under restricted conditions of Ca(2+) influx. The differential effect of phorbol esters at nerve terminals with either N- or P/Q-type Ca(2+) channels seems to be unrelated to the type Munc13 isoform expressed, and it is more likely dependent on other properties of the release machinery.
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http://dx.doi.org/10.1111/j.1471-4159.2010.07134.xDOI Listing
February 2011

Idiopathic sclerosing orbital inflammation with intranasal extension.

Orbit 2010 Apr;29(2):106-9

Oculoplastic and Orbital Service, University Hospital La Paz, Madrid, Spain.

Introduction: To report a case of idiopathic orbital sclerosing inflammation (ISOI) with intranasal extension.

Material And Methods: The patient presented with a 6-month history of epiphora, upper eyelid swelling, ptosis and mild orbital pain. Ophthalmologic examination, CT, MRI and biopsy with surgical debulking were performed.

Results: MRI revealed a homogeneously enhancing diffuse right orbital mass in the inferonasal quadrant of the orbit, which extended to the nasal cavity up to inferior nasal concha, maxillary and ethmoid sinuses. Histological analysis showed dense collagenous tissue with sparse infiltration of mixed inflammatory cells. Inmunohistochemical analysis confirmed polyclonality. The diagnosis of idiopathic sclerosing orbital inflammation was made and 80 mg/day of oral prednisolone was prescribed. At last follow up, one year later, there was no clinical evidence of recurrent orbital disease.

Conclusion: ISOI can present with extraorbital extension. Corticosteroids are a reasonable first-line treatment, until the pathogenesis is better understood.
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http://dx.doi.org/10.3109/01676830903486401DOI Listing
April 2010

The metabotropic glutamate receptor mGlu7 activates phospholipase C, translocates munc-13-1 protein, and potentiates glutamate release at cerebrocortical nerve terminals.

J Biol Chem 2010 Jun 7;285(23):17907-17. Epub 2010 Apr 7.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.

At synaptic boutons, metabotropic glutamate receptor 7 (mGlu7 receptor) serves as an autoreceptor, inhibiting glutamate release. In this response, mGlu7 receptor triggers pertussis toxin-sensitive G protein activation, reducing presynaptic Ca(2+) influx and the subsequent depolarization evoked release. Here we report that receptor coupling to signaling pathways that potentiate release can be seen following prolonged exposure of nerve terminals to the agonist l-(+)-phosphonobutyrate, l-AP4. This novel mGlu7 receptor response involves an increase in the release induced by the Ca(2+) ionophore ionomycin, suggesting a mechanism that is independent of Ca(2+) channel activity, but dependent on the downstream exocytotic release machinery. The mGlu7 receptor-mediated potentiation resists exposure to pertussis toxin, but is dependent on phospholipase C, and increased phosphatidylinositol (4,5)-bisphosphate hydrolysis. Furthermore, the potentiation of release does not depend on protein kinase C, although it is blocked by the diacylglycerol-binding site antagonist calphostin C. We also found that activation of mGlu7 receptors translocate the active zone protein essential for synaptic vesicle priming, munc13-1, from soluble to particulate fractions. We propose that the mGlu7 receptor can facilitate or inhibit glutamate release through multiple pathways, thereby exerting homeostatic control of presynaptic function.
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http://dx.doi.org/10.1074/jbc.M109.080838DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2878553PMC
June 2010

Subcellular compartment-specific molecular diversity of pre- and post-synaptic GABA-activated GIRK channels in Purkinje cells.

J Neurochem 2009 Aug 22;110(4):1363-76. Epub 2009 Jun 22.

Departamento de Ciencias Médicas, CRIB-Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain.

Activation of G protein-gated inwardly-rectifying K(+) (GIRK or Kir3) channels by metabotropic gamma-aminobutyric acid (B) (GABA(B)) receptors is an essential signalling pathway controlling neuronal excitability and synaptic transmission in the brain. To investigate the relationship between GIRK channel subunits and GABA(B) receptors in cerebellar Purkinje cells at post- and pre-synaptic sites, we used biochemical, functional and immunohistochemical techniques. Co-immunoprecipitation analysis demonstrated that GIRK subunits are co-assembled with GABA(B) receptors in the cerebellum. Immunoelectron microscopy showed that the subunit composition of GIRK channels in Purkinje cell spines is compartment-dependent. Thus, at extrasynaptic sites GIRK channels are formed by GIRK1/GIRK2/GIRK3, post-synaptic densities contain GIRK2/GIRK3 and dendritic shafts contain GIRK1/GIRK3. The post-synaptic association of GIRK subunits with GABA(B) receptors in Purkinje cells is supported by the subcellular regulation of the ion channel and the receptor in mutant mice. At pre-synaptic sites, GIRK channels localized to parallel fibre terminals are formed by GIRK1/GIRK2/GIRK3 and co-localize with GABA(B) receptors. Consistent with this morphological evidence we demonstrate their functional interaction at axon terminals in the cerebellum by showing that GIRK channels play a role in the inhibition of glutamate release by GABA(B) receptors. The association of GIRK channels and GABA(B) receptors with excitatory synapses at both post- and pre-synaptic sites indicates their intimate involvement in the modulation of glutamatergic neurotransmission in the cerebellum.
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http://dx.doi.org/10.1111/j.1471-4159.2009.06229.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774143PMC
August 2009

Partial compensation for N-type Ca(2+) channel loss by P/Q-type Ca(2+) channels underlines the differential release properties supported by these channels at cerebrocortical nerve terminals.

Eur J Neurosci 2009 Mar;29(6):1131-40

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.

N-type and P/Q-type Ca(2+) channels support glutamate release at central synapses. To determine whether the glutamate release mediated by these channels exhibits distinct properties, we have isolated each release component in cerebrocortical nerve terminals from wild-type mice by specifically blocking N-type Ca(2+) channels with omega-conotoxin-GVIA and P/Q-type Ca(2+) channels with omega-agatoxin-IVA. In addition, we have determined the release properties at terminals from mice lacking the alpha(1B) subunit of N-type channels (Ca(v) 2.2) to test the possibility that P/Q-type channels can compensate for the loss of N-type Ca(2+) channels. We recently demonstrated that, while evoked glutamate release depends on P/Q- and N-type channels in wild-type nerve terminals, only P/Q-type channels participate in these knockout mice. Moreover, in nerve terminals expressing solely P/Q-type channels, metabotropic glutamate receptor 7 (mGluR7) fails to inhibit the evoked Ca(2+) influx and glutamate release. Here, we show that the failure of mGluR7 to modulate evoked glutamate release is not due to a lack of receptors, as nerve terminals from mice lacking N-type Ca(2+) channels express mGluR7. Indeed, we show that other receptor responses, such as the inhibition of forskolin-induced release, are preserved in these knockout mice. N-type channels are more loosely coupled to release than P/Q-type channels in nerve terminals from wild-type mice, as reflected by the tighter coupling of release in knockout nerve terminals. We conclude that the glutamate release supported by N- and P/Q-type channels exhibits distinct properties, and that P/Q-type channels cannot fully compensate for the loss of N-type channels.
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http://dx.doi.org/10.1111/j.1460-9568.2009.06675.xDOI Listing
March 2009

The inhibition of release by mGlu7 receptors is independent of the Ca2+ channel type but associated to GABAB and adenosine A1 receptors.

Neuropharmacology 2008 Sep 23;55(4):464-73. Epub 2008 Apr 23.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Avda Puerta de Hierro s/n, 28040 Madrid, Spain.

Neurotransmitter release is inhibited by G-protein coupled receptors (GPCRs) through signalling pathways that are negatively coupled to Ca2+ channels and adenylyl cyclase. Through Ca2+ imaging and immunocytochemistry, we have recently shown that adenosine A1, GABAB and the metabotropic glutamate type 7 receptors coexist in a subset of cerebrocortical nerve terminals. As these receptors inhibit glutamate release through common intracellular signalling pathways, their co-activation occluded each other responses. Here we have addressed whether the occlusion of receptor responses is restricted to the glutamate release mediated by N-type Ca2+ channels by analysing this process in nerve terminals from mice lacking the alpha1B subunit (Cav 2.2) of these channels. We found that glutamate release from cerebrocortical nerve terminals without these channels, in which release relies exclusively on P/Q type Ca2+ channels, is not modulated by mGlu7 receptors. Furthermore, there is no occlusion of the release inhibition by GABAB and adenosine A1. Hence, in the cerebrocortical preparation, these three receptors only appear to coexist in N-type channel containing nerve terminals. In contrast, in hippocampal nerve terminals lacking this subunit, where mGlu7 receptors modulate glutamate release via P/Q type channels, the occlusion of inhibitory responses by co-stimulation of adenosine A1, GABAB and mGlu7 receptors was observed. Thus, occlusion of the responses by the three GPCRs is independent of the Ca2+ channel type but rather, it is associated to functional mGlu7 receptors.
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http://dx.doi.org/10.1016/j.neuropharm.2008.04.011DOI Listing
September 2008

The coexistence of multiple receptors in a single nerve terminal provides evidence for pre-synaptic integration.

J Neurochem 2007 Dec 18;103(6):2314-26. Epub 2007 Oct 18.

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.

Excitatory synaptic transmission is inhibited by G protein coupled receptors, including the adenosine A(1), GABA(B), and metabotropic glutamate receptor 7. These receptors are present in nerve terminals where they reduce the release of glutamate through activating signaling pathways negatively coupled to Ca(2+) channels and adenylyl cyclase. However, it is not clear whether these receptors operate in distinct subpopulations of nerve terminals or if they are co-expressed in the same nerve terminals, despite the functional consequences that such distributions may have on synaptic transmission. Applying Ca(2+) imaging and immunocytochemistry, we show that these three G protein coupled receptors coexist in a subpopulation of cerebrocortical nerve terminals. The three receptors share an intracellular signaling pathway through which their inhibitory responses are integrated and coactivation of these receptors produced an integrated response. Indeed, this response was highly variable, from a synergistic response at subthreshold agonist concentrations to an occluded response at high agonist concentrations. The presence of multiple receptors in a nerve terminal could be responsible for the physiological effects of neurotransmitter spillover from neighboring synapses or alternatively, the co-release of transmitters by the same nerve terminal.
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http://dx.doi.org/10.1111/j.1471-4159.2007.04964.xDOI Listing
December 2007

mGluR7 inhibits glutamate release through a PKC-independent decrease in the activity of P/Q-type Ca2+ channels and by diminishing cAMP in hippocampal nerve terminals.

Eur J Neurosci 2007 Jul;26(2):312-22

Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid 28040, Spain.

The modulation of calcium channels by metabotropic glutamate receptors (mGluRs) is a key event in the fine-tuning of neurotransmitter release. Here we report that, in hippocampal nerve terminals from adult rats, the inhibition of glutamate release by the group III mGluR agonist L-2-amino-4-phosphonobutyrate (L-AP4) is largely mediated by mGluR7. In this preparation, P/Q-type Ca(2+) channels support the major component of glutamate release while the remaining release is supported by N-type Ca(2+) channels. The release associated with P/Q channels was modulated by mGluR7, either in the presence of omega-conotoxin-GVIA or after decreasing the extracellular Ca(2+) concentration [Ca(2+)](o) to abolish the contribution of N-type Ca(2+) channels. Under these conditions, L-AP4 (1 mm) reduced the evoked glutamate release by 35 +/- 2%. This inhibition was largely prevented by pertussis toxin, but it was insensitive to inhibitors of protein kinase C (bisindolylmaleimide) and protein kinase A (H-89). Furthermore, this inhibition was associated with a reduction in the Ca(2+) influx mediated by P/Q channels in the absence of any detectable change in cAMP levels. However, L-AP4 decreased the levels of cAMP in the presence of forskolin. The activation of this additional signalling pathway was very efficient in counteracting the facilitation of glutamate release induced by forskolin. Thus, mGluR7 mediates the inhibition of glutamate release at hippocampal nerve terminals primarily by inhibiting P/Q-type Ca(2+) channels, although augmenting the levels of cAMP reveals the ability of the receptor to decrease cAMP.
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http://dx.doi.org/10.1111/j.1460-9568.2007.05660.xDOI Listing
July 2007