Molecular Biology of Serotonin Receptors

Over the last several years the use of molecular cloning technology has revealed a vast diversity among serotonin (5-HT)receptors, where by what was previously thought to be a family of three pharmacologically defined classes of 5-HT receptors is actually composed of seven distinct subfamilies designated 5-HT_1–7. The 5-HT₁, 5-HT₂, and 5-HT₅ subfamilies currently consist of five, three and two subtypes respectively while the 5-HT₃,5-HT₄, 5-HT₆, and 5-HT₇ “subfamilies” have at present one subtype each. Fourteen separate genes encode 13 receptors which fall in the superfamily of G protein-coupled receptors and one ligand-gated ion channel receptor. Our lab has contributed to the elucidation of this subtype diversity by cloning the cDNAs from both rat and human encoding the 5-HT_2B receptor. This receptor subtype is equally homologous (approximately 70%) to the 5-HT_2A and 5-HT_2C receptors when amino acids comprising the transmembrane domains are compared and is clearly the third member of the 5-HT₂ subfamily. The 5-HT_2B receptor has been shown to couple to phosphoinositide hydrolysis as do the other two members of this subfamily when expressed in AV12-664 cells. Limited pharmacological analyses indicated that both rat and human 5-HT_2B receptors are similar but distinguishable. With one tantalizing exception, the mRNAs for these receptors appear to be similarly distributed within rat and human. The 5-HT_2B receptor mRNA is not found in rat brain, whereas in human brain it has been identified in multiple regions. This later finding suggests that the 5-HT_2B receptor may be serving a unique CNS function in man that is absent in rat.     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Testing time–place learning in the cichlid fish Nile tilapia

Time–place learning based on food association was investigated in the fish Nile tilapia. During a 30-day period, food was placed at one side of the aquarium (containing three compartments) in the morning and at the opposite side in the afternoon. Learning was inferred by the number of correct side choices of all fish in each day of test (15th, 30th). During the test day, fish were not fed. The Nile tilapia did not learn to switch sides at the correct day period in order to get food, suggesting thus that this species does not have time–place learning ability.     

Calycine colleters of seven species of Apocynaceae (Apocynoideae) from Brazil

The structure and organization of calycine colleters belonging to four genera of Apocynaceae are described. Calycine colleters were found in all species. All colleters had the same histological composition, but morphological differences were observed in four species. Most colleters were of the standard type, and possible deviations resulted in three morphological types: bifurcated, laminar, and sessile. Mechanisms of cell separation, proliferation, and elongation may explain the origin of the new types. As a consequence of morphological changes, the secretory surface was expanded in the bifurcated, laminar, and sessile glands. Most colleters were in a post-secretory phase, but a hydrophilic secretion was observed in Mandevilla pycnantha and Mesechites mansoana . A larger secretory surface, together with the extension of the secretory phase in adult flowers, were major shifts in the calycine colleters of Apocynaceae, and are possibly correlated with the functional and ecological aspects of these organs. Three patterns of distribution of calycine colleters were observed: alternate, opposite, or indefinitely distributed. The alternate pattern was not homogeneous, and three subtypes were recognized: four-, five-, and ten-grouped colleters. The number of calycine colleters was variable between taxa and even within the same species.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 387–398.     

Crystal structure of the lectin of Camptosema pedicellatum: implications of a conservative substitution at the hydrophobic subsite

Lectins have been used as models for studies of the molecular basis of protein-carbohydrate interaction and specificity by deciphering codes present in the glycan structures. The purpose of the present study was to purify and solve the complete primary and crystal structure of the lectin of Camptosema pedicellatum (CPL) complexed with 5-bromo-4-chloro-3-indolyl-α-d-mannose (X-Man) using tandem mass spectrometry. CPL was purified by single-step affinity chromatography. Mass spectrometry findings revealed that purified CPL features a combination of chains weighing 25,298 ± 2 (α-chain), 12,835 ± 2 (β-chain) and 12,481 ± 2 Da (γ-chain). The solved crystal structure of CPL features a conservative mutation in the hydrophobic subsite, a constituent of the carbohydrate recognition domain (CRD), indicating the relevance of hydrophobic interactions in the establishment of interactions with carbohydrates. The substitution and the analysis of the interactions with X-Man also revealed that the hydrophobic effect caused by a minor change in the hydrophobic subsite interferes in the formation of H-bonds due to the reorientation of the indolyl group in the CRD.     

An optimum environment for the culturing of Cytospora isolates from stone fruits. IV. Hydrogen-ion concentration

Summary SixCytospora isolates were cultured on laboratory media over an initial pH range of 8.0 to 4.0.The optimum pH was found to be approximately 4.2. However, since the autoclaving process shifts pH values in the acid direction, adjustment of media to pH 4.8 is necessary prior to sterilization.Growth processes of the isolates were demonstrated to have a similar acidifying effect on the medium, but this effect was much reduced at 5.5 and lower pH levels.In summarizing the results of the series of investigations dealing with optimum conditions of laboratory environment; the authors recommend culturingCytopora fungi at 28° C, on modified Lilly and Barnett media containing maltose and potassium nitrate as carbon and nitrogen sources, at a pH level of 4.2.Approved by the Director of the Idaho Agricultural Experiment Station as Research Paper No. 520.