Responses of the Asian citrus psyllid to volatiles emitted by the flushing shoots of its rutaceous host plants.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) carries Candidatus liberibacter spp., the putative causal agents of Huanglongbing. D. citri reproduces and develops only on the flushing shoots of its rutaceous host plants. Here we examined whether D. citri is attracted to host plant odors and a mixture of synthetic terpenes. Tests conducted in a vertically oriented Y-tube olfactometer showed that both males and females preferentially entered the Y-tube arm containing the odor from the young shoots of Murraya paniculata (L.) Jack and Citrus limon L. Burm. f. cultivar Eureka. Only males exhibited a preference for the odor of C. sinensis L., whereas the odor of C. x paradisi MacFadyen cultivar Rio Red was not attractive to both sexes. The volatiles emitted by young shoots of grapefruit cultivar Rio Red, Meyer lemon (Citrus x limon L. Burm.f.), and M. paniculata were analyzed by gas chromatograph-mass spectrometry. The samples were comprised of monoterpenes, monoterpene esters, and sesquiterpenes. The number of compounds present varied from 2 to 17, whereas the total amount of sample collected over 6 h ranged from 5.6 to 119.8 ng. The quantitatively dominant constituents were (E)-beta-ocimene, linalool, linalyl acetate, and beta-caryophyllene. The attractiveness of a mixture of synthetic terpenes, modeled on the volatiles collected from M. paniculata, was evaluated in screened cages in a no-choice test. At three observation intervals, significantly more individuals were trapped on white targets scented with the mixture than on unscented targets. These results indicate the feasibility of developing D. citri attractants patterned on actual host plant volatiles.

Investigations to the synthesis of n.c.a. [18F]FClO3 as electrophilic fluorinating agent.

An approach to synthesize the electrophilic fluorinating agent no-carrier-added (n.c.a.) [18F]perchloryl fluoride ([18F]FClO3) in superacidic media in the presence of KClO4 or anhydrous perchloric acid starting from [18F]fluoride was demonstrated in this study. However, the radiochemical yields were low (1-6%) and poorly reproducible. Fluorosulphonic acid proved to be an essential intermediate as revealed by non-radioactive experiments. A key problem in the preparation of [18F]FClO3 is the assumed kinetic inhibition due to the unfavourable stoichiometric ratio of the ClO4 moiety to [18F]HSO3F.

Norchloro-fluoro-homoepibatidine (NCFHEB) - a promising radioligand for neuroimaging nicotinic acetylcholine receptors with PET.

Cholinergic neurotransmission depends on the integrity of nicotinic acetylcholine receptors (nAChRs), and impairment of both is characteristic for various neurodegenerative diseases. Visualization of specific receptor subtypes by positron emission tomography (PET) has potential to assist with diagnosis of such neurodegenerative diseases and with design of suitable therapeutic approaches. The goal of our study was to evaluate in vivo the potential of (18)F-labelled (+)- and (-)-norchloro-fluoro-homoepibatidine ([(18)F]NCFHEB) in comparison to 2-[(18)F]F-A-85380 as PET tracers. In the brains of NMRI mice, highest levels of radioactivity were detected at 20 min post-injection of (+)-[(18)F]NCFHEB, (-)-[(18)F]NCFHEB, and 2-F-[(18)F]-A-85380 (7.45, 5.60, and 3.2% ID/g tissue, respectively). No marked pharmacological adverse effects were observed at 25 mug NCFHEB/kg. Uptake studies in RBE4 cells and in situ perfusion studies suggest an interaction of epibatidine and NCFHEB with the carrier-mediated choline transport at the blood-brain barrier. The data indicate that (+)- and (-)-[(18)F]NCFHEB have potential for further development as PET tracers.

Olfactory and visual stimuli affecting host plant detection in Homalodisca coagulata (Hemiptera: Cicadellidae).

The relative effects of visual and olfactory stimuli on host plant detection in immature and adult Homalodisca coagulata Say (Homoptera: Cicadellidae) were studied using a novel olfactometer and factorial experimental designs. Colored, gray, and white cards were used as visual targets. Each card was attached to a glass thistle tube from which host-plant odor (from Vigna unguiculata L.) or blank, humidified air was dispensed. Visual + odor stimuli combinations were presented in no-choice tests. Nymphs were released onto a perch stick downwind from the target. Nymph response to color + odor treatments was measured by the duration of orientation behavior, residence time on the perch, and percentage of individuals that jumped to the target. The assay was modified so that adults crawled from the perch onto the target. Adult response was measured by the duration of individual behaviors (e.g., foraging) and by their position and residence time on the target. Both main effects and interactive effects of the stimuli were observed. Nymphs showed a decrease in orientation and residence times in the colored target + host odor treatments and increased jumping response in the gray + host odor treatment. When adults were exposed to host odor, the duration of foraging behavior increased, whereas crawling and phototactic behaviors decreased. Although nymphs and adults responded to visual stimuli + blank air treatments, host odor enhanced their responses. The primary effect of host odor on host detection behavior may be to enhance H. coagulata responsiveness to visual cues.

Synthesis and in vivo studies of the stereoisomers of N-[11C]methyl-homoepibatidine.

The carbon-11 labeled enantiomers of nicotinic acetylcholine receptor (nAChR) ligand N-[11C]methyl-homoepibatidine have been synthesized to study the neuronal nicotinic acetylcholine receptors (nAChRs). In vivo evaluations were performed in mice and pig using positron emission tomography (PET). The radioligands displayed a strong enantioselectivity. The (-)-enantiomer showed high uptake in the brain while the (+)-enantiomer was rapidly washed out. In metabolite studies in mice >65% unchanged ligand was found in the blood after 60 minutes. No metabolites were found in the brain. After intravenous application of N-[11C]methyl-(-)-homoepibatidine in the pig specific accumulation in the thalamus was seen. Blocking experiments with cytisine showed specific binding consistent with labeling of the alpha4beta2-nAChR-subtype in the brain. Quantitative kinetic modeling of radiotracers in the pig brain was performed using the arterial input function. The brain uptake of the (-)-isomer was best fitted by a three-compartment model. High distribution volumes were found in the thalamus (DV(TOT) = 66.617, DV(S) = 59.910) versus a low uptake in the cerebellum (DV(TOT) = 8.605m, DV(S) = 1.898). The binding characteristics suggest N-[11C]methyl-(-)-homoepibatidine to be suited for PET imaging studies, but high toxicity prevents routine use in humans.

Comparison of in vivo dopamine D2 receptor binding of [(123)I]AIBZM and [(123)I]IBZM in rat brain.

[(123)I]AIBZM, (S)-5-[(123)I]-Iodo-N-[(1-ethyl-2-pyrrolidinyl)]methyl-4-amine-2-methoxybenzamide is a derivative with high affinity for the D2 receptor. Labeling was achieved by the Iodogen method. The in vivo affinity for the D2 receptor and the biological characteristics were performed in rats. The brain uptake of [(123)I]AIBZM was significantly lower, however the striatum/cerebellum ratio (2h p.i.) was higher than that of [(123)I]IBZM. Because of the high affinity and its possibly lower unspecific binding compared to [(123)I]IBZM, [(123)I]AIBZM may be a potential imaging agent for the D2 dopamine receptor.

Chemical modification of epibatidine causes a switch from agonist to antagonist and modifies its selectivity for neuronal nicotinic acetylcholine receptors.

BACKGROUND: Studies of ligand gated channels strongly rely on the availability of compounds that can activate or inhibit with high selectivity one set or a subset of defined receptors. The alkaloid epibatidine (EPB), originally isolated from the skin of an Ecuadorian poison frog, is a very specific agonist for the neuronal nicotinic acetylcholine receptors (nAChRs). We used EPB derivatives to investigate the pharmacophore of nAChR subtypes. RESULTS: Optically pure enantiomers of EPB analogues were synthesised. Analogues were obtained altered in the aromatic part: the chlorine was eliminated and the relative position of the pyridyl nitrogen changed. Voltage clamp electrophysiology was performed with these compounds on neuronal nAChRs reconstituted in Xenopus oocytes. The EPB derivatives show different activities towards the various nAChR subtypes. CONCLUSIONS: Small changes in the molecular structure of EPB produce marked changes in its capacity to activate the nAChRs. Subtype specificity can be obtained by changing the position of or by eliminating the pyridyl nitrogen.

Comparison of N-[(11)C]methyl-norchloroepibatidine and N-[(11)C]methyl-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane with N-[(11)C]methyl-epibatidine in small animal PET studies.

Structural variations of the nicotinic acetylcholine receptor radioligand N-[(11)C]methyl-epibatidine were made to form (11)C-labeled N-methyl-norchloroepibatidine (N-methyl-NorchloroEPB) and N-methyl-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane (N-methyl-2PABH). Radiosyntheses were performed by methylation with high radiochemical purities (>98%) and with specific activities between 140 and 500 GBq/micromol at the end of synthesis. The radiochemical yield (decay-corrected, related to [(11)C]CH(3)I) was between 5 and 10%. Positively and negatively radiolabeled enantiomers were prepared in high optical purity (>98%ee) by labeling of the appropriate optically active substrates, which were obtained via chiral high performance liquid chromatography. For in vivo studies radioligands were administered intravenously in rats. Brain uptake curves were acquired and combined with blocking experiments. Brain uptake of N-[(11)C]methyl-NorchloroEPB was similar to that of N-[(11)C]methyl-EPB whereas N-[(11)C]methyl-2PABH with the modified pyridine ring had a significantly lower uptake.

A new look at the neuronal nicotinic acetylcholine receptor pharmacophore.

Interest in the field of nicotinic receptors has been recently stimulated both by the discovery of the potential therapeutic effects of new agonists, and by the discovery of an association between nicotinic receptor mutations and human neurological diseases. Expression of human receptors in an exogenous system allows their study in isolation. Receptors reconstituted by pairwise injection of either alpha4 or alpha3 with beta2 or beta4 subunits displayed important differences between the resulting receptor subtypes. These results were further compared with those obtained with alpha3:alpha4 fusion proteins. The modifications of either the ligand-binding site in the N-terminal domain or in the ionic pore domain were found to affect the pharmacological properties of the receptors. Finally, the analysis of non-natural derivatives of epibatidine demonstrates how an agonist can be modified to be selective at one receptor subtype or to become an antagonist. These data are well explained on the basis of a three-state allosteric model.

Neuronal nAChR stereoselectivity to non-natural epibatidine derivatives.

The frog toxin epibatidine is one of the most powerful ligands of the neuronal nicotinic receptors and derivatives show promising possibilities for labeling in positron emission tomography studies. In an attempt to reduce epibatidine toxicity, new methyl derivatives were synthesized, tested in positron emission tomography imaging and in electrophysiology. labeling as well as physiological experiments highlighted the differences in sensitivity of the neuronal nicotinic acetylcholine receptors between two methyl enantiomers and the reduction in sensitivity caused by introducing the methyl group. At present, epibatidine derivatives seem the most promising compounds for in vivo labeling of neuronal nicotinic acetylcholine receptors.

Synthesis and in Vivo studies of [C-11]N-methylepibatidine: comparison of the stereoisomers.

The carbon-11-labelled nicotinic acetylcholine receptor (nAChR) agonist N-methylepibatidine was evaluated in vitro and in vivo as a possible positron emission tomography (PET)-tracer for nicotinic receptors in the central nervous system (CNS). The racemic mixture and both enantiomers of N-methylepibatidine were compared. Biodistribution and metabolites for blood and brain of [C-11]N-methylepibatidine were determined in mice. Whole body rat PET data were acquired for both stereoisomers. The regional distribution of the N-methyl-(-)-epibatidine in the brain was determined by a PET scan in a pig. Characteristic differences were found for the in vivo behavior of the stereoisomers of [C-11]N-methylepibatidine.

Synthesis and electrophysiological studies of a novel epibatidine analogue.

The new epibatidine analogue exo-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane (2PABH) was synthesised. Separation of enantiomers was performed on chiral HPLC chromatography in polar-organic phase mode at 0 degree C. Enantiomeric purity was greater than 99.8%ee for the (-)- and 90.5%ee for the (+)-enantiomer respectively. Optical rotation was determined to be [alpha]23D = +/- 13 degrees. Electrophysiological studies of 2PABH were carried out on alpha 4 beta 2, alpha 3 beta 4 and alpha 7 nAChR subtypes cloned from rat and reconstituted in Xenopus oocytes. Both enantiomers could not significantly activate the heteromeric subtypes. The homomeric alpha 7 nAChR displays a high sensitivity only towards (-)-2PABH. The EC50 for (-)-2PABH and ACh were determined (32.5 +/- 9.5 microM, 137.3 +/- 16.5 microM). (-)-2PABH was shown to be a partial agonist (80% of ACh). Thus the efficacy of 2PABH differs markedly from that of epibatidine. The intramolecular N-N-distance and the spatial pyridine nitrogen orientation play a central role in nAChR recognition.

Pathway of terpene excretion by the appendix of Sauromatum guttatum.

Electron microscopy of the cells of the thermogenic appendix of Sauromatum guttatum has revealed a fusion event between pocket-like structures of the rough endoplasmic reticulum (rER) and the plasma membrane. As a result of the fusion event, many regions of the plasma membrane have paired unit membranes (four leaflets instead of two). The fusion allows the transfer of osmiophilic material from the rER pockets to the plasma membrane, where the osmiophilic material is confined to bilayer, pocket-like structures. A clear correlation is found between the presence of the osmiophilic compound and sesquiterpenes. Prior to heat production, the rER- and plasma-membrane pockets are electron dense, and sesquiterpenes are detectable only in tissue extracts. On the day of heat production, electron-translucent pockets are subsequently found and the stored sesquiterpenes are released to the atmosphere. Three sesquiterpenes have been identified by gas chromatography-mass spectrometry as alpha-copaene and beta- and alpha-caryophyllene.

Preoperative embolization of hypervascular head and neck neoplasms using microfibrillar collagen.

Microfibrillar collagen is a bovine collagen material that promotes hemostasis. When mixed with contrast material it makes a fine slurry that is easily injected through small catheters. Experience with preoperative embolization of head and neck neoplasms in six patients indicates that microfibrillar collagen slurry is a highly effective, easy to use embolic material for occlusion of highly vascular neoplasms.

Effects of metyrapone and ACTH on intestinal absorption of immunoreactive bovine IgG in cesarean-derived pigs.

Newborn cesarean-derived pigs were injected with 5.0 mg of metyrapone/kg, or 1 USP U of ACTH/kg, or the vehicle 1.0 ml of 44 mM sodium tartrate and 88 mM NaCl soon after delivery (0 hour) and again 4, 8, and 12 hours later. Beginning at 2 hours, each pig in the 3 groups was given 40 ml of pooled bovine colostrum/kg by stomach tube every 8 hours for the duration of the experiment. Four hours after each feeding, pigs were killed; plasma and serum were collected and assayed for cortisol and bovine immunoglobulin (IgG), respectively. Some nonfed, nontreated pigs were killed at 0 hour also. Metyrapone significantly decreased plasma cortisol (hydrocortisone) concentrations at all times tested, whereas ACTH-treated pigs demonstrated a biphasic increase of plasma cortisol. Immunoreactive serum bovine IgG was not detected in nonfed, nontreated pigs. In vehicle-injected control pigs, bovine IgG was present in the serum at 6 hours; the concentration increases consistently to 22 hours, but not significantly thereafter. The concentration of bovine IgG in the serum of metyrapone-treated pigs also increased steadily before plateauing at 22 hours, but the values were significantly less than those of the controls at 14, 22, 30, and 38 hours. The concentration of bovine IgG in the serum of ACTH-treated pigs did not differ significantly from the control values at any of the times tested.