N1-Methyl-2-125I-Lysergic Acid Diethylamide, a Preferred Ligand for In Vitro and In Vivo Characterization of Serotonin Receptors

Methylation of 2-125I-lysergic acid diethylamide (125I-LSD) at the N1 position produces a new derivative, N1-methyl-2-125I-lysergic acid diethylamide (125I-MIL), with improved selectivity and higher affinity for serotonin 5-HT2 receptors. In rat frontal cortex homogenates, specific binding of 125I-MIL represents 80-90% of total binding, and the apparent dissociation constant (KD) for serotonin 5-HT2 receptors is 0.14 nM (using 2 mg of tissue/ml). 125I-MIL also displays a high affinity for serotonin 5-HT1C receptors, with an apparent dissociation constant of 0.41 nM at this site. 125I-MIL exhibits at least 60-fold higher affinity for serotonin 5-HT2 receptors than for other classes of neurotransmitter receptors, with the dopamine D2 receptor as its most potent secondary binding site. Studies of the association and dissociation kinetics of 125I-MIL reveal a strong temperature dependence, with very slow association and dissociation rates at 0 degree C. Autoradiographic experiments confirm the improved specificity of 125I-MIL. Selective labeling of serotonin receptors was observed in all brain areas examined. In vivo binding studies in mice indicate that 125I-MIL is the best serotonin receptor label yet described, with the highest frontal cortex to cerebellum ratio of any serotonergic radioligand. 125I-MIL is a promising ligand for both in vitro and in vivo labeling of serotonin receptors in the mammalian brain.     

Taste sorting and naming: can taste concepts be misrepresented by traditional psychophysical labelling systems?

Japanese and American subjects were required to sort filterpapers, soaked in taste stimuli, into categories that had conceptuallythe same taste. Both Japanese and Americans sorted in the samemanner, indicating similar conceptualization. Taste names weregiven to the taste categories obtained by using the traditional‘four basic taste’ naming system, common in tastepsychophysics. This method was seen to underestimate the numberof categories actually present. This suggests a re-assessmentof current psychophysical taste-naming techniques.     

A light and electron microscopic study of the quadriflagellate green algaSpermatozopsis exsultans

The green flagellateSpermatozopsis exsultans Korshikov has been studied in culture by light and electron microscopy. The organism is naked, bears four flagella and is conspicuously spirally twisted. The ultrastructure and location of cell organelles (except the flagellar apparatus) has been investigated in detail using an absolute configuration analysis. With the exception of a doubling of the flagella and of the secondary cytoskeletal microtubule system,S. exsultans has the exact same complement of organelles occupying the same relative positions as has been described forS. similis. The two species are therefore correctly placed in the same genus. The usefulness of absolute orientations of cell organelles for green algal taxonomy and phylogeny is stressed.Dedicated to Prof.M. Mix on the occasion of her 60th birthday.     

Influence of leaf surfaces on movements by the hymenopterous parasitoid Trichogramma exiguum

Walking speeds of female Trichogramma exiguum Pinto & Platner were fastest on maize and soybean (12 cm/min), intermediate on tomato (8 cm/min), and slowest on woolly mullein, Verbascum thapsus (3 cm/min). Similarly, rates of turning along the paths of walking T. exiguum were smallest on maize (median angle=0°±15°), intermediate on soybean and tomato, and greatest on V. thapsus (median angle=30°±15°). Leaf trichome density and morphology influenced walking behavior. Walking was slowed and flight initiation delayed for T. exiguum walking on Amaranthus hybridus leaves compared to either maize or filter paper. When inundative releases are conducted, the effects of plant surfaces on searching rates and arrestment should be considered in determining release rates of Trichogramma spp.

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Résumé La vitesse de marche a été déterminée en lâchant des individus sur chaque substrat végétal et en traçant leur parcours sur une plaque de verre placée à 9 mm au dessus du sujet. Les déviations angulaires de portions successives des tracés, longues de 1 mm, ont été utilisées pour mesurer les taux de changement de direction. Dans une deuxième expérience, des individus ont été lâchés au milieu d'une cercle de 40 mm de diamètre sur chaque substrat et les temps écoulés avant l'envol ou pour atteindre le bord du cercle à la marche ont servi à évaluer respectivement la propension au vol et la vitesse de déambulation.Les vitesses de marche ont été plus rapides sur maïs et soja (12 cm/min), moyennes sur tomate (8 cm/min) et les plus lentes sur Verbascum thapsus (Scrophulariaceae) (3 cm/min). De le même façon, les angles de changement de direction au cours des marches effectuées par T. exiguum ont été plus petits sur maïs, moyens sur soja et tomate, et plus grands sur V. thapsus. Chez T. exiguum marchant sur des feuilles d'Amaranthus hybridus L. (Amaranthaceae), la marche a été plus lente et l'envol plus tardif que sur maîs ou papier filtre.Lors de lâchers inondatifs, les effets des surfaces végétales sur les vitesses d'exploration et d'arrêt devraient être pris en compte pour déterminer les vitesses de lâcher des Trichogramma spp.

     

The Influence of Nonautonomous P Elements on Hybrid Dysgenesis in Drosophila melanogaster

An inbred line of the M' strain Muller-5 Birmingham was studied for its abilities to affect P-M hybrid dysgenesis. This strain possesses 57 P elements, all of which are apparently defective in the production of the P transposase. In combination with transposase-producing elements, these nonautonomous elements can enhance or diminish the incidence of hybrid dysgenesis, depending on the trait that is studied. Dysgenic flies that have one or more paternally-derived chromosomes with these elements partially repress the instability of the P element insertion mutation, snw; however, such flies have elevated frequencies of another dysgenic trait, GD sterility, and also show distorted segregation ratios. An explanation is presented in which all of these phenomena are unified as manifestations of the kinetics of P element activation in the germ line. The progeny of Muller-5 Birmingham females exhibit partial repression of both snw instability and GD sterility. This repression appears to involve a factor that can be transmitted maternally through at least two generations. This mode of repression therefore conforms to the pattern of inheritance of the P cytotype, the condition that brings about nearly total repression of P element activity in some strains. Models in which this repression could arise from the nonautonomous P elements of Muller-5 Birmingham are discussed.     

Estimating the number of genetic elements that defer senescence inDrosophila

Summary Although many different physiological and biochemical changes characterize the process of senescence, little is understood of the genetic elements that determine its age of onset. We provide here the first estimates of the number of genetic factors that extend longevity inDrosophila melanogaster. Life span was measured in F₁, F₂ and backcrosses of true-breeding long and short-lived stocks ofD. melanogaster, established by selection. Estimates of the number of effective factors delaying senescence range from about 0.3 to 1.5, indicating control by a single factor. The distribution of longevity shows this to arise as selection acts on the short-lived parental stock. Life span is extended at the cost of early fecundity.     

Aging alterations in the modulation of central dopaminergic cilioinhibition by etorphine in the marine mussel,Mytilus edulis: Decrease in the inhibition of presynaptic dopamine release

1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress.