Quantifying Irrigated Winter Wheat LAI in Argentina Using Multiple Sentinel-1 Incidence Angles

Synthetic aperture radar (SAR) data provides an appealing opportunity for all-weather day or night Earth surface monitoring. The European constellation Sentinel-1 (S1) consisting of S1-A and S1-B satellites offers a suitable revisit time and spatial resolution for the observation of croplands from space. The C-band radar backscatter is sensitive to vegetation structure changes and phenology as well as soil moisture and roughness. It also varies depending on the local incidence angle (LIA) of the SAR acquisition's geometry. The LIA backscatter dependency could therefore be exploited to improve the retrieval of the crop biophysical variables. The availability of S1 radar time-series data at distinct observation angles holds the feasibility to retrieve leaf area index (LAI) evolution considering spatiotemporal coverage of intensively cultivated areas. Accordingly, this research presents a workflow merging multi-date S1 smoothed data acquired at distinct LIA with a Gaussian processes regression (GPR) and a cross-validation (CV) strategy to estimate cropland LAI of irrigated winter wheat. The GPR-S1-LAI model was tested against in situ data of the 2020 winter wheat campaign in the irrigated valley of Colorador river, South of Buenos Aires Province, Argentina. We achieved adequate validation results for LAI with R C V 2 = 0.67 and RMSE _CV = 0.88 m² m^-2. The trained model was further applied to a series of S1 stacked images, generating temporal LAI maps that well reflect the crop growth cycle. The robustness of the retrieval workflow is supported by the associated uncertainties along with the obtained maps. We found that processing S1 smoothed imagery with distinct acquisition geometries permits accurate radar-based LAI modeling throughout large irrigated areas and in consequence can support agricultural management practices in cloudprone agri-environments.

Seasonal Mapping of Irrigated Winter Wheat Traits in Argentina with a Hybrid Retrieval Workflow Using Sentinel-2 Imagery

Earth observation offers an unprecedented opportunity to monitor intensively cultivated areas providing key support to assess fertilizer needs and crop water uptake. Routinely, vegetation traits mapping can help farmers to monitor plant development along the crop's phenological cycle, which is particularly relevant for irrigated agricultural areas. The high spatial and temporal resolution of the Sentinel-2 (S2) multispectral instrument leverages the possibility to estimate leaf area index (LAI), canopy chlorophyll content (CCC), and vegetation water content (VWC) from space. Therefore, our study presents a hybrid retrieval workflow combining a physically-based strategy with a machine learning regression algorithm, i.e., Gaussian processes regression, and an active learning technique to estimate LAI, CCC and VWC of irrigated winter wheat. The established hybrid models of the three traits were validated against in-situ data of a wheat campaign in the Bonaerense valley, South of the Buenos Aires Province, Argentina, in the year 2020. We obtained good to highly accurate validation results with LAI: R² = 0.92, RMSE = 0.43 m² m^-2, CCC: R² = 0.80, RMSE = 0.27 g m^-2 and VWC: R² = 0.75, RMSE = 416 g m^-2. The retrieval models were also applied to a series of S2 images, producing time series along the seasonal cycle, which reflected the effects of fertilizer and irrigation on crop growth. The associated uncertainties along with the obtained maps underlined the robustness of the hybrid retrieval workflow. We conclude that processing S2 imagery with optimised hybrid models allows accurate space-based crop traits mapping over large irrigated areas and thus can support agricultural management decisions.

Quinolinic acid induced neurodegeneration in the striatum: a combined in vivo and in vitro analysis of receptor changes and microglia activation

PURPOSE

Huntington's disease (HD) is a progressive neurodegenerative disorder, which is characterised by prominent neuronal cell loss in the basal ganglia with motor and cognitive disturbances. One of the most well-studied pharmacological models of HD is produced by local injection in the rat brain striatum of the excitotoxin quinolinic acid (QA), which produces many of the distinctive features of this human neurodegenerative disorder. Here, we report a detailed analysis, obtained both in vivo and in vitro of this pharmacological model of HD.

MATERIALS AND METHODS

By combining emission tomography (PET) with autoradiographic and immunocytochemical confocal laser techniques, we quantified in the QA-injected striatum the temporal behavior (from 1 to 60 days from the excitotoxic insult) of neuronal cell density and receptor availability (adenosine A(2A) and dopamine D(2) receptors) together with the degree of microglia activation.

RESULTS

Both approaches showed a loss of adenosine A(2A) and dopamine D(2) receptors paralleled by an increase of microglial activation.

CONCLUSION

This combined longitudinal analysis of the disease progression, which suggested an impairment of neurotransmission, neuronal integrity and a reversible activation of brain inflammatory processes, might represent a more quantitative approach to compare the differential effects of treatments in slowing down or reversing HD in rodent models with potential applications to human patients.

Metabotropic glutamate receptor agonist (1S,3R-ACPD) increased frontal cortex dopamine release in aged but not in young rats

The effects of the metabotropic glutamate (mGlu) receptor agonist (1S,3R)-1-Amino cyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) infusion on frontal cortex dopamine extracellular levels were studied by microdialysis in young (3 months) and aged (24 months) rats. Basal dopamine levels were significantly higher in young than in aged rats. (1S,3R)-ACPD (1 mM) significantly increased dopamine efflux in aged rats, an effect which was antagonized by the mGlu receptor antagonist, (S)-alpha-methyl-4-carboxypheniylglycine (MCPG) (2 mM). On the contrary, (IS,3R)-ACPD up to the concentration of 2 mM failed to influence dopamine extracellular levels in young rats. These results suggest that the agonist of mGlu receptor group I and/or II can improve dopamine release under conditions of deficiency of extracellular dopamine concentration as observed in aging.

Adenosine A1 receptor blockade selectively potentiates the motor effects induced by dopamine D1 receptor stimulation in rodents

An antagonistic interaction between adenosine A1 and dopamine D1 receptors has previously been found in the basal ganglia. However, direct evidence for a selective adenosine A1 antagonist-induced potentiation of dopamine D1-mediated motor activation is lacking. The systemic administration of the adenosine A1 antagonist 8-cyclopentyl-1,3-dimethylxanthine significantly potentiated the motor activating properties of the systemically administered dopamine D1 agonist SKF 38393 in both reserpinized mice and unilaterally 6-hydroxy-dopamine-lesioned rats. However, 8-cyclopentyl-1, 3-dimethylxanthine did not modify the motor effects of the dopamine D2 agonist quinpirole. The present work shows that an antagonistic interaction between adenosine A1 and dopamine D1 receptors may be involved in the motor activating effects of adenosine antagonists, like caffeine.

Non-opioid antitussives potentiate some behavioural and EEG effects of N-methyl-D-aspartate channel blockers

The effects of the non-opioid oral antitussives dextromethorphan (DM) and caramiphen (CP) were tested against the behavioural and EEG effects elicited by the N-methyl-D-aspartate (NMDA) antagonists dizocilpine (MK 801) and phencyclidine (PCP) in rats and mice. PCP (1.25-10 mg/kg i.p.) induced a dose-dependent increase/decrease of the locomotor/exploratory activity of mice. DM (25-50 mg/kg i.p.) and MK 801 (0.125-0.250 mg/kg i.p.) induced an increase of the locomotor/exploratory activity of mice, while CP (25-50 mg/kg i.p.) did not produce such an effect. CP (12.5 mg/kg i.p.) and DM (12.5 mg/kg i.p.) significantly potentiated the effects of PCP (1.25 mg/kg i.p.) and MK 801 (0.062 mg/kg i.p.) in the open field test in mice. In rats, PCP (1.25-10 mg/kg i.p.) induced three dose-dependent EEG stages: 1) increase of the cortical desynchronization periods; 2) increase of the amplitude of cortical background activity; 3) appearance of cortical slow wave-spike complexes. Even though DM (up to 100 mg/kg i.p.) only induced PCP-like EEG stage 1 by itself, and CP (up to 50 mg/kg i.p.) did not affect basal cortical EEG activity, these drugs, at the doses of 30-50 mg/kg i.p., potentiated all the EEG effects induced by PCP. These data support the view of an interaction between non-opioid antitussives and non-competitive NMDA antagonists.

Verapamil and flunarizine inhibit phencyclidine-induced effects: an EEG and behavioural study in rats

The influence of verapamil and flunarizine on phencyclidine-induced effects has been studied in adult male rats. Both verapamil (25 and 100 micrograms/10 microliters, i.c.v.) and flunarizine (40 and 60 mg/kg, i.p.) significantly reduced behavioural (mean intensity of ataxia, mean duration of head weaving) and the EEG (increase in the mean voltage of background activity of the EEG) effects induced by phencyclidine 5 mg/kg (i.p.). It was reported previously that nimodipine and diltiazem significantly potentiate effects induced by phencyclidine. The contrasting results obtained with verapamil and flunarizine, suggest that these drugs may modulate effects induced by phencyclidine by acting at sites other than NMDA receptor-coupled "L"-type calcium channel.

Inhibitory influence of morphinans on ictal and interictal EEG changes induced by cortical application of penicillin in rabbits: a comparative study with NMDA antagonists and pentobarbitone

The effects of dextrorphan (DX) and dextromethorphan (DM) were tested using the electroencephalogram (EEG) and behavioral effects induced by topical cortical application of penicillin in rabbits. For comparison, the influence of the NMDA antagonists, dizocilpine (MK 801) and 3-((+-(-)2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP), and of pentobarbitone was investigated. Intracortical injection of 500 IU of penicillin produced an EEG spiking followed by a repeated generalization of the electrical and behavioral symptoms. Within a few minutes, DX (5-15 mg/kg, IV) or pentobarbitone (5-10 mg/kg, IV) reduced dose dependently and significantly (p less than 0.01) the interictal and ictal EEG and behavioral effects elicited by cortical injection of 500 IU of penicillin. Higher doses of pentobarbitone (20 mg/kg, IV) but not of DX (20 mg/kg, IV) completely blocked the ictal behavioral and EEG effects elicited by cortical injection of 500 IU of penicillin. Within a few minutes, MK 801 (0.1-0.2 mg/kg, IV) or CPP (10-20 mg/kg, IV) reduced dose dependently and significantly (p less than 0.01) the ictal EEG and behavioral effects elicited by cortical injection of 500 IU of penicillin, while they did not affect the penicillin-induced interictal EEG changes. Higher doses of MK 801 (0.3 mg/kg, IV) completely blocked the ictal behavioral and EEG effects elicited by cortical injection of 500 IU of penicillin. Within a few minutes, DM (10-20 mg/kg, IV) blocked the behavioral effects, but failed to affect either the interictal or the ictal EEG effects induced by cortical injection of 500 IU of penicillin.(ABSTRACT TRUNCATED AT 250 WORDS)

Different capability of N-methyl-D-aspartate antagonists to elicit EEG and behavioural phencyclidine-like effects in rats

Phencyclidine (PCP), a drug inducing schizophrenia-like symptoms in humans, is reported to be a non-competitive antagonist at the N-methyl-D-aspartate (NMDA) subtype of excitatory amino acid receptors. In rats, PCP produces three dose-dependent stages of EEG patterns: 1) increase of cortical desynchronization duration; 2) increase of the amplitude of the high-frequency (20-30 Hz) low-voltage (30-50 microV) cortical background activity; 3) appearance of cortical slow (2-3 Hz) wave-sharp wave complexes. These EEG changes are accompanied by stimulatory-depressive effects such as stereotypy (circling, head weaving) and ataxia. In the present study, the EEG and behavioural effects induced by systemic administration of the NMDA antagonists dizocilpine (MK 801), dextromethorphan (DM), [(+)-alpha-(4-chlorophenyl)-4- [(phenyl)methyl-1-piperidine ethanol] (SL 82.0715), (+)3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), cis-4-phosphonomethyl-2-piperidine-carboxylic acid (CGS 19755) have been compared to those of PCP in rats. The rank of potency for inducing PCP-like EEG stages 1-3 was as follows: MK 801 > PCP > CGS 19755 > CPP. These drugs also induced PCP-like behavioural effects. On the contrary, DM and SL 82.0715, administered up to the dose of 100 mg/kg IP, failed to induce PCP-like behavioural effects and elicited only the stage 1 of PCP-like EEG. These results strongly suggest the involvement of NMDA neurotransmission in the behavioral and EEG effects of PCP.

Cromakalim (BRL 34915) counteracts the epileptiform activity elicited by diltiazem and verapamil in rats

1. The effects of BRL 34915 (cromakalim), a potassium channel opener, have been tested on the epileptiform activity elicited by high dose/concentrations of some calcium antagonists in in vivo (diltiazem) and in vitro (diltiazem and verapamil) experiments in rats. 2. Diltiazem (150-300 mg kg-1, i.p.) induced behavioural and electroencephalographic (EEG) seizures that were completely prevented by cromakalim (10 nmol/10 microliters, i.c.v.). Whereas, pentobarbitone (5-10 mg kg-1, i.p.) only prevented the behavioural component of the seizures. 3. In hippocampal slices, verapamil (1.5-2.0 mM) produced, within 30-60 min of perfusion, a CA1 epileptiform bursting in 80% of the experiments. This epileptiform activity was prevented by the cromakalim concentration (50 microM) that did not affect the control CA1 synaptic transmission per se. Pentobarbitone also prevented verapamil-induced epileptiform bursting only at the concentration (100 microM) that also reduced control CA1 synaptic transmission. 4. Diltiazem (1.5 mM) produced a biphasic excitatory-depressant effect within 60 min of perfusion. A CA1 epileptiform bursting appeared in 100% of the experiments within 30 min of perfusion. These excitatory effects were followed by a depression phase, characterized by a reduction of the magnitude of CA1 excitatory postsynaptic potentials (e.p.s.ps) and population spike. 5. The diltiazem-induced epileptiform bursting was prevented by cromakalim at a concentration (50 microM) that did not affect the control CA1 synaptic transmission per se. Pentobarbitone also prevented the diltiazem-induced epileptiform bursting only at a concentration (100 microM) that also reduced the control CA1 synaptic transmission. Both cromakalim (50 microM) and pentobarbitone (100 microM) failed to affect the depressant effects of diltiazem on CA1 hippocampal area. On the contrary, high (3.3mM) calcium solutions prevented both the excitatory and the depressant effects of 1.5 mm diltiazem within 60 min.6. These data indicate an involvement of potassium currents in the epileptiform activity elicited by high doses of diltiazem and verapamil.

Differential effects of morphinan drugs on haloperidol-induced catalepsy in rats: a comparative study with an N-methyl-D-aspartate antagonist

The effects of the morphinan drugs dextrorphan, dextromethorphan and levorphanol were tested towards the cataleptic activity induced by 1 mg/kg of haloperidol i.p. in rats. The influence of the morphinans was compared to that of the N-methyl-D-aspartate competitive antagonist, 2-amino-5-phosphonovaleric acid. 2-Amino-5-phosphonovaleric acid (0.5 mumoles, i.c.v.), dextrorphan (7.5-15 mg/kg, i.p.) and dextromethorphan (15-30 mg/kg, i.p.) significantly reduced the degree of catalepsy in the haloperidol-treated rats within 15 min. Conversely, levorphanol (15-30 mg/kg, i.p.) significantly increased the degree of catalepsy in the haloperidol-treated rats within 15 min. Naloxone (2 mg/kg, i.p.) counteracted the potentiating effects of levorphanol. These findings demonstrate a differential influence of the morphinan stereoisomers dextrorphan and levorphanol on experimental catalepsy, and suggest a potential use of dextromethorphan in the treatment of Parkinson's disease.

An EEG and behavioural study on the interactions of clonidine with phencyclidine and ketamine in rats

1. Clonidine, an alpha-2 adrenergic agonist, induced in rats a synchronization of the electrical activity of the brain (EEG) accompanied by sedation starting from the dose of 0.05 mg/kg, i.p. 2. This drug (0.05 mg/kg, i.p.) was also able to influence both the EEG and behavioural effects elicited by two "dissociative anaesthetics", PCP and KT. 3. At low and moderate doses of these two drugs, clonidine fully inhibited the EEG and behavioural effects, whereas at high doses of both drugs clonidine potentiated these effects. 4. Yohimbine was able to revert the inhibitory and potentiating effects produced by clonidine. It was also able to revert sedation accompanied by EEG synchronization. 5. Prazosin, on the other hand, was not able to produce such effects. This fact suggests that the alpha-2 adrenoceptors are involved in these effects. 6. Based on our findings, the interaction of the dissociative anaesthetics (PCP-KT) with the central adrenergic receptors seems to be very complex. The possible relevance of clonidine on both the improvement of KT-induced anaesthesia and the treatment of PCP-intoxication is also discussed.

Study on the anticonvulsant activity of clonidine against pentylenetetrazol-induced seizures in rats: pharmacological evidence of alpha 2-adrenoceptors mediation

The present work deals with an EEG and behavioral study of the interaction of alpha-adrenoceptor antagonists on the anticonvulsant activity of clonidine against the convulsions due to pentylenetetrazol (PTZ) in rats. Clonidine's ability (0.5 mg/kg, i.p.) to inhibit the tonic seizures and mortality induced by PTZ (75 mg/kg, i.p.) was counteracted by pretreatment with yohimbine and mianserine (10 mg/kg, i.p.). On the contrary, prazosin (10 mg/kg, i.p.) did not influence the anticonvulsant effect of clonidine. The results suggest that central alpha 2-adrenoceptors play an important role in the control of motor and EEG convulsions elicited by PTZ.