Insect Herbivory Caused Plant Stress Emissions Increases the Negative Radiative Forcing of Aerosols

Plant stress in a changing climate is predicted to increase plant volatile organic compound (VOC) emissions and thus can affect the formed secondary organic aerosol (SOA) concentrations, which in turn affect the radiative properties of clouds and aerosol. However, global aerosol-climate models do not usually consider plant stress induced VOCs in their emission schemes. In this study, we modified the monoterpene emission factors in biogenic emission model to simulate biotic stress caused by insect herbivory on needleleaf evergreen boreal and broadleaf deciduous boreal trees and studied the consequent effects on SOA formation, aerosol-cloud interactions as well as direct radiative effects of formed SOA. Simulations were done altering the fraction of stressed and healthy trees in the latest version of ECHAM-HAMMOZ (ECHAM6.3-HAM2.3-MOZ1.0) global aerosol-climate model. Our simulations showed that increasing the extent of stress to the aforementioned tree types, substantially increased the SOA burden especially over the areas where these trees are located. This indicates that increased VOC emissions due to increasing stress enhance the SOA formation via oxidation of VOCs to low VOCs. In addition, cloud droplet number concentration at the cloud top increased with increasing extent of biotic stress. This indicates that as SOA formation increases, it further enhances the number of particles acting as cloud condensation nuclei. The increase in SOA formation also decreased both all-sky and clear-sky radiative forcing. This was due to a shift in particle size distributions that enhanced aerosol reflecting and scattering of incoming solar radiation.

High-gain 1.3 μm GaInNAs semiconductor optical amplifier with enhanced temperature stability for all-optical signal processing at 10 Gb/s

We report on the complete experimental evaluation of a GaInNAs/GaAs (dilute nitride) semiconductor optical amplifier that operates at 1.3 μm and exhibits 28 dB gain and a gain recovery time of 100 ps. Successful wavelength conversion operation is demonstrated using pseudorandom bit sequence 2⁷-1 non-return-to-zero bit streams at 5 and 10  Gb/s, yielding error-free performance and showing feasibility for implementation in various signal processing functionalities. The operational credentials of the device are analyzed in various operational regimes, while its nonlinear performance is examined in terms of four-wave mixing. Moreover, characterization results reveal enhanced temperature stability with almost no gain variation around the 1320 nm region for a temperature range from 20°C to 50°C. The operational characteristics of the device, along with the cost and energy benefits of dilute nitride technology, make it very attractive for application in optical access networks and dense photonic integrated circuits.

Microsurgical technique for previously coiled aneurysms

Since the introduction of Guglielmi detachable coils to treat intracranial aneurysms in 1991, the number of patients undergoing endovascular coiling has continuously risen as well as the number of those residual and recurrent previously coiled aneurysms that necessitate a microsurgical occlusion. Between July 1995 and August 2009 we retrospectively analyzed 81 patients with 82 previously coiled aneurysms treated microsurgically at two Finnish Neurosurgical University Hospitals, Helsinki and Kuopio. Fifty-eight aneurysms (71%) were located at anterior circulation and 24 (29%) at posterior circulation. Fifteen patients were operated on within the first month (early surgery) after coiling, whereas 66 were treated later (late surgery). Complete or partial removal of coils during surgery may facilitate clipping, but is significantly (P<0.001) more difficult to accomplish in late surgery. Removal of coils may also increase the chance for poor outcome. Chance of poor outcome increased also with intraoperative aneurysm rupture, size of the aneurysm and posterior circulation location. Good clinical outcome, three months after surgery, was achieved in 71 patients (88%); four patients were severely disabled, and six patients died (three of them due to poor clinical condition). Complete microsurgical occlusion of the residual previously coiled aneurysm is a high-risk procedure in large and giant aneurysms, and these patients should be referred to a dedicated neurovascular center to minimize surgical complications. Bypass procedures may be the best option for demanding growing lesions, especially those in posterior circulation.

Multiscale imaging characterization of dopamine transporter knockout mice reveals regional alterations in spine density of medium spiny neurons

The dopamine transporter knockout (DAT KO) mouse is a model of chronic hyperdopaminergia used to study a wide range of neuropsychiatric disorders such as schizophrenia, attention deficit hyperactivity disorder (ADHD), drug abuse, depression, and Parkinson's disease (PD). Early studies characterizing this mouse model revealed a subtle, but significant, decrease in the anterior striatal volume of DAT KO mice accompanied by a decrease in neuronal cell body numbers (Cyr et al., 2005). The present studies were conducted to examine medium spiny neuron (MSN) morphology by extending these earlier reports to include multiscale imaging studies using correlated light microscopy (LM) and electron microscopy (EM) techniques. Specifically, we set out to determine if chronic hyperdopaminergia results in quantifiable or qualitative changes in DAT KO mouse MSNs relative to wild-type (WT) littermates. Using Neurolucida Explorer's morphometric analysis, we measured spine density, dendritic length and synapse number at ages that correspond with the previously reported changes in striatal volume and progressive cell loss. Light microscopic analysis using Neurolucida tracings of photoconverted striatal MSNs revealed a highly localized loss of dendritic spines on the proximal portion of the dendrite (30 μm from the soma) in the DAT KO group. Next, thick sections containing MSN dendritic segments located at a distance of 20-60 μm from the cell soma, a region of the dendrite where spine density is reported to be the highest, were analyzed using electron microscope tomography (EMT). Because of the resolution limits of LM, the EM analysis was an extra measure taken to assure that our analysis included nearly all spines. Spine density measurements collected from the EMT data revealed only a modest decrease in the DAT KO group (n=3 mice) compared to age-matched WT controls (n=3 mice), a trend that supports the LM findings. Finally, a synaptic quantification using unbiased stereology did not detect a difference between DAT KO mice (n=6 mice) and WT controls (n=7 mice) at the EM level, supporting the focal nature of the early synaptic loss. These findings suggest that DAT KO mice have MSNs with highly localized spine loss and not an overall morphologically distinct cell shape. The characterization of morphological changes in DAT KO mice may provide information about the neural substrates underlying altered behaviors in these mice, with relevance for human neurological disorders thought to involve altered dopaminergic homeostasis. Results from this study also indicate the difficulty in correlating structural changes across scales, as the results on fine structure revealed thus far are subtle and non-uniform across striatal MSNs. The complexities associated with multiscale studies are driving the development of shared online informatics resources by gaining access to data where it is being analyzed.

Management of dural arteriovenous fistulas - Helsinki and Kuopio experience

Dural arteriovenous fistulas (DAVFs) are complex disorders, some of them with aggressive clinical behaviour. During past decades their treatment strategy has changed due to increased knowledge of their pathophysiology and natural history, and advances in treatment modalities. In asymptomatic cases or cases with mild symptoms in the absence of cortical venous drainage (CVD) no treatment is necessarily required, whereas aggressive DAVFs should be treated promptly by endovascular or microsurgical means.In our series of 323 patients with 333 fistulas, treated in two neurosurgical units in Finland since 1944, there were 265 true DAVFs and 68 Barrow type A caroticocavernous fistulas. Among the DAVFs there was a slight female predominance, 140 women (55%) and 115 men (45%), and the majority of the cases were located in the area of transverse and sigmoid sinuses. Mode of treatment in the early series was proximal ligation of feeding artery, and later craniotomy, endovascular treatment and radiosurgery, or combination of these treatments, with total occlusion rate being 53%.

Combined Treatment with Citalopram and Buspirone: Effects on Serotonin 5-HT2Aand 5-HT2CReceptors in the Rat Brain

INTRODUCTION

We wanted to elucidate whether the proposed advantages of citalopram-buspirone combination treatment are related to changes in 5-HT(2A/C) receptor-mediated neurotransmission.

METHODS

The affinity of buspirone to 5-HT2A and 5-HT2C receptors was measured in vitro, and the influence of buspirone on 5-HT2C receptor-mediated phosphoinositide hydrolysis was estimated. Four groups of rats received citalopram (10 mg/kg), buspirone (6 mg/kg), citalopram-buspirone combination, or saline once a day s.c. for 14 days. Treatment effects on 5-HT2A and 5-HT2C receptors were investigated by receptor autoradiography with antagonist and agonist radioligands.

RESULTS

Buspirone was found to be a weak 5-HT2C receptor antagonist, with a low affinity for 5-HT2A and 5-HT2C receptors. Repeated buspirone-citalopram combination treatment markedly decreased [3H]ketanserin and [125I]DOI binding to 5-HT2A receptors. Repeated administration of buspirone and buspirone-citalopram combination increased the affinity of [3H]mesulergine toward 5-HT2C receptors, and buspirone-citalopram combination also decreased [125I]DOI binding to 5-HT2C receptors.

DISCUSSION

We suggest that downregulation of brain 5-HT2A receptors and possibly of 5-HT2C receptor agonist sites is involved in the beneficial clinical effects of buspirone-SSRI augmentation treatment. Furthermore, a conversion of brain 5-HT2C receptors from high- to low-affinity state may provide an additional mechanism for the anti-anxiety effects of buspirone.

Decreased striatal dopamine transporter binding in vivo in chronic schizophrenia

We have previously reported that average striatal dopamine transporter (DAT) binding in vivo is unaltered in neuroleptic-naive first-episode schizophrenic patients [Laakso et al., Am. J. Psychiatry 157 (2000) 269]. However, as it has been suggested that some of the brain changes in schizophrenia may vary depending on the illness phase, we studied DAT density in eight stable, medicated chronic schizophrenic patients and eight matched controls using positron emission tomography and [18F]CFT, a marker of dopamine nerve terminals. [18F]CFT binding potentials were significantly lower in chronic schizophrenic patients than in controls, both in the caudate and the putamen (-9 to -16%). Together with the finding of unchanged average striatal DAT levels in first-episode patients and relative insensitivity of striatal [18F]CFT binding to endogenous dopamine and neuroleptic drugs, the result is in line with a relative loss of striatal dopaminergic nerve terminals and/or decreased expression of DAT in a subset of chronic schizophrenic patients.

Sertindole is a serotonin 5-HT2c inverse agonist and decreases agonist but not antagonist binding to 5-HT2c receptors after chronic treatment

RATIONALE

Sertindole is a novel antipsychotic drug with high affinity for dopamine D2, alpha-1-adrenoceptors and serotonin 5-HT2A and 5-HT2c receptors. The 5-HT2c receptor component of sertindole may be clinically relevant as this receptor subtype is implicated in regulation of anxiety, cognition/memory and brain plasticity.

OBJECTIVE

To characterise the interaction of sertindole with the 5-HT2C receptor using rat choroid plexus as a physiological receptor source.

RESULTS

Sertindole had nanomolar affinity for the 5-HT2c receptor in vitro. Sertindole antagonised 5-HT-stimulated phosphoinositide (PI) hydrolysis and, like clozapine, also inhibited basal PI hydrolysis suggesting that sertindole is a 5-HT2C receptor inverse agonist. The effect of repeated sertindole dosing on 5-HT2C receptors was studied in rats treated for 21 days with sertindole (20, 300 and 1250 microg/kg/day). Clozapine (25 mg/kg/day) was used as a comparison drug. 5-HT2C receptor binding in the choroid plexus was measured with antagonist and agonist ligands ([3H]mesulergine and [125I]DOI) using quantitative autoradiography 8 days after withdrawal. Clozapine decreased 5-HT2C receptor antagonist and agonist binding sites equally by 36% and 32%, respectively. Sertindole did not induce significant changes in the total number of 5-HT2C receptors, but the highest dose of sertindole lowered the affinity of [3H]mesulergine for 5-HT2C receptors. This was most likely due to residual sertindole levels in the brain which was supported by direct concentration measurements. In contrast, sertindole induced a highly significant and dose-related decrease in 5-HT2C agonist binding (up to 77%). Neither drug affected striatal D2 receptor binding.

CONCLUSIONS

Sertindole, like clozapine, was found to be a serotonin 5-HT2C receptor inverse agonist. The preferential downregulation of 5-HT2C receptor agonist (G-protein-coupled) sites by chronic administration seemed to differentiate sertindole from clozapine at these dose regimens. The 5-HT2c receptor downregulation during repeated dosing may contribute to therapeutic efficacy and/or side effects of sertindole treatment.

A morphometric MRI study of the hippocampus in first-episode, neuroleptic-naïve schizophrenia

Magnetic resonance imaging (MRI) studies have frequently, although not unambiguously, reported hippocampal volume deficit in schizophrenia. Data on the hippocampal volumes in first-episode schizophrenia, however, are sparse. In addition, a recent topographic MRI study proposed a regionally specific volume loss in the hippocampus of chronic schizophrenics, but to date no reports have replicated this finding. In this study two-dimensional MRI-based topographic brain mapping was used to study the possibility of regional changes in the hippocampus of 22 controls and 18 patients with first-episode, neuroleptic-naïve schizophrenia. Compared to controls, there were no significant differences between hippocampal volumes, regional volumes, or length of the hippocampus in the patients with schizophrenia. These data are at odds with the previous reports on hippocampal volume loss in first-episode schizophrenia, and with the hypothesis of regionally specific hippocampal volume deficit in schizophrenia.

PET studies of brain monoamine transporters

Monoamine transporters are proteins mainly located on nerve terminals of dopaminergic, noradrenergic and serotonergic neurons. They are members of a larger sodium dependent transporter family and represent a major mechanism terminating the action of released neurotransmitter in the synaptic cleft. In addition to being important target molecules for many antidepressive drugs and substances of abuse, transporter proteins are good markers for the integrity of monoaminergic innervation. Therefore, there is a growing interest for in vivo imaging studies using positron emission tomography (PET) or single photon emission computed tomography (SPECT) and ligands selective for monoamine transporters. In this review, the use of monoamine transporter ligands (or tracers) for imaging studies of cocaine dependence, neurodegenerative diseases and mechanism of antidepressant drug action is discussed, with special focus on the use of PET for evaluating possible new pharmacological innovations.

Prediction of detached personality in healthy subjects by low dopamine transporter binding

OBJECTIVE

Low striatal dopamine D(2) receptor binding in healthy human subjects has been associated with detached personality in studies using positron emission tomography (PET) and the Karolinska Scales of Personality questionnaire. The authors investigated whether a similar correlation exists between striatal dopamine transporter binding and detached personality.

METHOD

Eighteen healthy volunteers participated in a PET study with the specific dopamine transporter ligand [(18)F]CFT ([(18)F]WIN 35,428) and completed the Karolinska Scales of Personality questionnaire form.

RESULTS

Age-corrected dopamine transporter binding in the putamen, but not in the caudate, correlated negatively with detachment personality scores, especially in the right hemisphere.

CONCLUSIONS

This finding supports the hypothesis that low dopaminergic neurotransmission is associated with detached personality. Furthermore, since [(18)F]CFT binding is thought to reflect the density of dopaminergic nerve terminals in the brain, the authors suggest that the neurodevelopmental formation of the brain dopaminergic system may influence adult personality traits.

Striatal dopamine transporter binding in neuroleptic-naive patients with schizophrenia studied with positron emission tomography

OBJECTIVE

Recent in vivo imaging studies indicate a dysregulated presynaptic function of the striatal dopaminergic system in patients with schizophrenia. To further explore the basis of this phenomenon, the authors studied brain dopamine transporter binding in vivo in patients with first-episode, never-medicated schizophrenia.

METHOD

Nine patients with schizophrenia and nine healthy matched comparison subjects were recruited. Striatal dopamine transporter binding was measured with positron emission tomography and a specific dopamine transporter ligand, [(18)F]CFT, a radiolabeled form of 2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane.

RESULTS

Average caudate and putamen dopamine transporter binding potentials were almost identical in the patients and comparison subjects, but the patients lacked the right-left asymmetry of the caudate dopamine transporter binding seen in the comparison group.

CONCLUSIONS

Average striatal dopamine transporter density is unaltered in neuroleptic-naive patients with schizophrenia. However, patients lack asymmetry in caudate dopamine transporter binding, which conforms with disrupted brain lateralization in this disorder.

[18F]CFT [(18F)WIN 35,428], a radioligand to study the dopamine transporter with PET: characterization in human subjects

We have characterized the usage of [18F]CFT (also known as [18F]WIN 35,428) as a radioligand for in vivo studies of human dopamine transporter by PET. CFT was labeled with 18F to a high specific activity, and dynamic PET scans were conducted in healthy volunteers at various time points up to 5 h from [18F]CFT injection. The regional distribution of [18F]CFT uptake correlated well with the known distribution of dopaminergic nerve terminals in the human brain and also with that of other dopamine transporter radioligands. Striatal binding peaked at 225 min after injection and declined thereafter, demonstrating the reversible nature of the binding to the dopamine transporter. Therefore, due to the relatively long half-life of 18F (109.8 min), PET scans with [18F]CFT could easily be conducted during the binding equilibrium, allowing estimation of Bmax/Kd values (i.e., binding potential). Binding potentials for putamen and caudate measured at equilibrium were 4.79+/-0.11 and 4.50+/-0.23, respectively. We were able to also visualize midbrain dopaminergic neurons (substantia nigra) with [18F]CFT in some subjects. In conclusion, the labeling of CFT with 18F allows PET scans to be conducted at binding equilibrium, and therefore a high signal-to-noise ratio and reliable quantification of binding potential can be achieved. With a high resolution 3D PET scanner, the quantification of extrastriatal dopamine transporters should become possible.

Striatal presynaptic dopamine function in type 1 alcoholics measured with positron emission tomography

Recent in vivo studies have shown low dopamine D2 receptor and dopamine transporter densities among late onset (type 1) alcoholics. We have now studied 6-[18F]-FDOPA (FDOPA) uptake in 10 type 1 alcoholics and eight matched controls to test the hypothesis that striatal presynaptic dopamine function is lower among alcoholics. Markedly low FDOPA uptake (Ki) was observed in the left caudate of two alcoholic patients, but the mean striatal uptake values of the patient group were higher than those of the control group. The greatest difference was observed in the mean FDOPA intake in the left putamen, which was 28% higher in the patient group (t = 3.00, P = 0.008, d.f. = 16, independent samples t-test), and in the right caudate (difference 36%, t = 2.87, P = 0.01). The elevated FDOPA uptake in putamen and caudate correlated with poor Wisconsin Card Sorting Test (WCST) performance (error %) among alcoholics (correlation coefficients from 0.49 to 0.56), which suggests that the magnitude of presynaptic dopamine function alteration correlates with the degree of disability to modify one's behavior. The results do not give support to the hypothesis of generally decreased striatal dopamine turnover in type 1 alcoholism, but on the contrary indicate an increased presynaptic dopamine function. This may represent a compensatory mechanism to low postsynaptic DA function. The low presynaptic DA function observed in the left caudate of two patients suggests that type 1 alcoholism may be a heterogeneous disorder.

Interactions of selective serotonin reuptake inhibitors with the serotonin 5-HT2c receptor

Interactions of the selective serotonin reuptake inhibitors (SSRIs) citalopram, fluoxetine and its main metabolite norfluoxetine, and the tricyclic antidepressant (TCA) imipramine with the rat serotonin 5-HT2C receptor in a clonal cell line and in the rat choroid plexus were investigated by radioligand binding and phosphoinositide (PI) hydrolysis assays. For comparison, the affinities of a variety of other antidepressants of different chemical classes for the cloned rat 5-HT2C and 5-HT2A receptors were also determined by radioligand binding assays. Fluoxetine displayed relatively high affinity for the 5-HT2C receptor in the choroid plexus, with a Ki value for inhibition of [3H]mesulergine binding of 55.4 nM. The Ki values for imipramine, norfluoxetine and citalopram were 136 nM, 203 nM, and 298 nM, respectively. Similar rank order of potency was detected in PI hydrolysis assays, which showed that these drugs are antagonists at the 5-HT2C receptor without exhibiting inverse agonist activity. [3H]Ketanserin (5-HT2A) binding assays revealed that the SSRIs fluoxetine, norfluoxetine and citalopram show 10- to 23-fold selectivity for the 5-HT2C receptor in vitro, whereas the TCA imipramine does not. Many other TCAs also had high to intermediate affinity for both 5-HT2A and 5-HT2C receptors. The present data provide evidence that fluoxetine, norfluoxetine and citalopram, along with many other antidepressant compounds, interact directly with the 5-HT2C receptor.

Chronic citalopram and fluoxetine treatments upregulate 5-HT2c receptors in the rat choroid plexus

The effects of chronic (for 14 days) citalopram and fluoxetine treatments with three doses (2.5, 10, and 20 mg/kg) and withdrawal times (24 hours, 68 hours, and 14 days) on 5-HT2C (formerly 5-HT1C) receptors in the rat brain choroid plexus were studied with quantitative receptor autoradiography in two separate experiments. Chronic citalopram treatment caused a consistent and dose-related increase in the density of 5-HT2C receptors (up to 90%). This effect was slightly more pronounced when measured with an antagonist ligand ([3H]mesulergine) than with an agonist ligand [(+/-)-1-(2,5-dimethoxy-4-[125I]iodophenyl)-2-aminopropane ([125I]DOI)]. The upregulation was most evident 24 hours after the last dose and disappeared thereafter rather rapidly. Chronic fluoxetine treatment also increased the density of 5-HT2C receptors 24 hours from the last dose, but the increase was accompanied by a reduced affinity and was less marked than that observed with citalopram. The changes in receptor characteristics were not observed consistently after the 68-hour withdrawal from fluoxetine. Furthermore, the upregulation of fluoxetine appeared not to be dose related or reflected by an increase in agonist binding. In conclusion, the results show that chronic citalopram and fluoxetine treatments induce an increase of choroid plexus 5-HT2C receptor density, but the effect is more marked with citalopram. These differences in the regulation of the 5-HT2C receptors may lead to pharmacodynamic differences between chronic citalopram and fluoxetine treatments.

[18F]CFT ([18F]WIN 35,428), a radioligand to study the dopamine transporter with PET: biodistribution in rats

We describe the 18F-radiolabelling synthesis (18F; T(1/2) = 109.8 min) of 2-beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (also known as CFT or WIN 35,428) and the biodistribution of this compound in rats. 18F-labelled CFT has high chemical and radiochemical purity and relatively high specific radioactivity [specific radioactivity up to 14.8 GBq/mumol (400 mCi/mumol) at end of synthesis]. Striatum to cerebellum radioactivity uptake ratios were calculated from digitised images of rat brain slices recorded with a phosphoimaging device, the maximum ratio of about 10 was obtained at 2 h postinjection. Pretreatment of the rats with a specific dopamine transport inhibitor, GBR 12909, showed that CFT binding is specific in striatum. The highest accumulation of 18F-radioactivity was found in the liver, urine, striatum, and kidney of the rat. Clearance from blood was rapid. The uptake in bone was low, indicating that [18F]CFT is not defluorinated. The relatively long half-life of 18F makes it possible to study the uptake of [18F]CFT in the brain, as equilibrium between specific and non-specific binding is reached. This will improve the signal to noise ratio as compared to positron emission tomography (PET) studies with [11C]CFT (11C; T(1/2) = 20.4 min). CFT labelled with 18F is clearly a promising radioligand for PET studies of the dopamine transporter system in humans.

Up-regulation of beta 1-adrenergic receptors in rat brain after chronic citalopram and fluoxetine treatments

Quantitative receptor autoradiography was used to study the effects of the selective serotonin reuptake inhibitors citalopram and fluoxetine and the tricyclic antidepressant imipramine on the regulation of beta 1-adrenergic receptors in the rat brain. Rats were treated with saline, citalopram (10 mg kg-1), fluoxetine (10 mg kg-1), or imipramine (15 mg kg-1) SC once daily for 14 days. [125I]Iodocyanopindolol binding to beta 1-adrenergic receptors was found to increase significantly in the caudate-putamen and the somatosensory areas of the frontal cortex after both citalopram and fluoxetine treatments. Imipramine treatment elicited a marked decrease in beta 1 binding in the outer laminae of the cingulate cortex, as well as in the motor and somatosensory areas of the frontal cortex. In a separate experiment, rats were treated with saline, citalopram (2.5, 10 and 20 mg kg-1) or fluoxetine (2.5, 10 and 20 mg kg-1) SC once daily for 14 days. The effects of citalopram and fluoxetine on beta 1 receptors in the somatosensory cortex and caudate-putamen were replicated. These results demonstrate that chronic administration of selective serotonin reuptake inhibitors, in contrast to imipramine, can cause a regional up-regulation of beta 1-adrenergic receptors in the rat brain.