New feather mite species of Aralichus (Acarina, Pterolichidae) from the white-capped parrot, Pionus senilis (Spix)

Two new feather mite species of Aralichus Gaud (Pterolichoidea, Pterolichidae) are described from the white-capped parrot Pionus senilis (Spix): Aralichus elongatus and Aralichus menchacai. Immature instars and host-parasite associations are discussed.     

The impact of extremely low frequency electromagnetic fields on stream periphyton: an eleven-year study

Potential effects of extremely low frequency (ELF) electromagnetic fields on periphyton were studied from 1983 to 1993 using a Before, After, Control and Impact design. The study was conducted at two sites on the Ford River, a fourth-order brown water trout stream in Dickinson County, Michigan. The Reference site received 4.9–6.5 times less exposure to ground electric fields and from 300 to 334 times less exposure to magnetic flux from 1989 to 1993 when the antenna was operational at 76 Hz than did the Antenna site. The objective of the study was to determine if ELF electromagnetic fields had caused changes in structure and/or function of algal communities in the Ford River. Significant differences in chlorophyll a standing crop and daily accumulation rate (a surrogate for primary productivity), and organic matter standing crop and daily accumulation rate were observed between the Reference and Antenna site after the antenna became operational. These four related community function variables all increased at the Antenna site with largest and most consistent increases occurring for chlorophyll measures. Compared to pre-operational data, the increase in chlorophyll at the Antenna site also occurred during a period of low amperage testing in 1986–1988, and did not increase further when the antenna became fully operational in 1989, indicating a low threshold for response. There was no significant differences between the Antenna and Reference sites in community structure variables such as diversity, evenness and the relative abundance of dominant diatoms. Thus, 76 Hz ELF electromagnetic radiation apparently did not change the basic makeup of the diatom community but did increase accumulation rates and standing crops of chlorophyll a and organic matter.     

(Glyco)sphingolipidology: an amazing challenge and opportunity for systems biology

Sphingolipids are found in essentially all eukaryotes and in some prokaryotes and viruses, where they influence cell structure, signaling and interactions with the extracellular environment. Because of the combinatorial nature of their biosynthesis, the sphingolipidome comprises untold thousands of species that encompass bioactive backbones and complex phospho- and glycolipids. Mass spectrometry is able to analyze a growing fraction of the sphingolipidome and is beginning to provide information about localization. Use of these structure specific, quantitative methods is producing insights, and surprises, regarding sphingolipid structure, metabolism, function and disease. Dealing with such large data sets poses special challenges for systems biology, but the intrinsic and elegant interrelationships among these compounds might provide a key to dealing with the complexity of the sphingolipidome.     

(Z)-1,1-dichloro-2-(4-benzyloxyphenyl)-2,3-bis(4-methoxyphenyl)cyclopropane: The synthesis and enantiomeric separation of an antitumor agent

(Z)-1,1-Dichloro-2-(4-benzyloxyphenyl)-2,3-bis(4-methoxyphenyl)cyclopropane ( 5 ), a potential antitumor agent designed to treat breast cancer, was prepared in three steps. A stereospecific palladium-catalyzed cross coupling reaction which provided the intermediate (Z)-triaryl alkene 4 was a crucial step in the synthesis. Makosza phase transfer reaction on 4 gave the enantiomeric (Z)-dichlorocyclopropane derivatives 5 which were resolved by semipreparative HPLC on a chiral stationary phase consisting of amylose tris-3,5-dimethylphenyl carbamate coated on silica gel. © 1994 Wiley-Liss, Inc.     

X-ray study of an antiviral agent (S)-9-(2,3-dihydroxypropyl)adenine

The molecular and crystal structures of the antiviral compound, (S)-9-(2,3-dihydroxypropyl)adenine, was established. The space group is P21, unit-cell parameters a 5,546(1), b 8,381(1), c 10,119(1), beta 91,979(9) degrees, Z2. The structure was solved by the direct method and refined by a full-matrix least-squares procedure to R 4,2%. All non-hydrogen atoms of this compound are concentrated in two planes. The first one involves the atoms of the purine moiety and N(6) and C(1'), while the second one accommodates C(2'), C(3'), O(2') and O(3'). The angle between these planes is 54,3 degrees. The conformation of the compound in crystal was compared with that deduced from theoretical analysis.     

Regioselective sulfonylation at O-2 of cyclomaltoheptaose with 1-(p-tolylsulfonyl)-(1H)-1,2,4-triazole

2(I)-O-p-Tolylsulfonylcyclomaltoheptaose was obtained in 42% yield by reaction of 1-(p-tolylsulfonyl)-(1H)-1,2,4-triazole on NaH-deprotonated cyclomaltoheptaose in DMF and further converted into the corresponding mono-2(I),3(I)-manno-epoxide.     

Synthesis of (-)-5,8-dihydroxy-3R-methyl-2R-(dipropylamino)-1,2,3,4-tetrahydronaphthalene: an inhibitor of beta-amyloid(1-42) aggregation

A concise synthesis of the beta-amyloid(1-42 )aggregation inhibitor (-)-5,8-dihydroxy-3R-methyl-2R-(dipropylamino)-1,2,3,4-tetrahydronaphthalene [(-)-2] has been developed. The key step is a regio- and diastereoselective hydroboration-amination sequence to convert alkene into amine. Enantiomeric resolution was achieved by recrystallization of amine as the dibenzoyl-D-tartaric acid salt. Hydroquinone is a potent inhibitor of the fibrillar aggregation of beta-amyloid as determined in two different assay systems.     

Further notes on the natural history of the South American pepper frog, Leptodactylus labyrinthicus (Spix, 1824) (Anura, Leptodactylidae)

Leptodactylus labyrinthicus tadpoles reach a large size in the nest through consumption of trophic eggs. We previously suggested that the trophic eggs are laid just after amplexus has finished, but our new data do not support this hypothesis. We also present further details on the natural history of the species with regard to breeding activity, spawning site, retreats and the ability of tadpoles in preying upon fully-growth heterospecific tadpoles. We also show that the tadpoles are mainly nocturnal and take diurnal refuges. We collected the data in Brazil in three localities within the Cerrado Biome. We examined burrows used by L. labyrinthicus males, verified if females still contained mature eggs just after released from amplexus, and tested the ability of tadpoles in preying fully-growth heterospecific tadpoles. Field observations and experiments were conducted on tadpole activity time, hiding behaviour and level of susceptibility to predation by the bird leaf-scrapers in four sheltering situations. Reproduction could start before the first rains; this may be advantageous by allowing the tadpoles to exploit eggs of other frogs. We found one floating nest built in a temporary pool. The nest of the species is normally circumscribed in an excavated basin beside the water body. Adult males were found during the day with their head-out of the entrance of underwater burrows, which were perforations through dense root mats beside calling/spawning sites. Probably, these burrows in permanently water-filled soil are actively excavated by males. Females released all their eggs during the amplexus, so trophic eggs are not produced by the currently-accepted mechanism. Fully-grown heterospecific tadpoles were not preyed upon by L. labyrinthicus tadpoles, which can prey only slow-moving newly hatched ones. Field tadpoles took shelter under mud/dead leaves during daylight and became exposed on the bottom at night. Free-ranging leaf-scrapers removed dead leaves from a pool with their beaks and preyed upon tadpoles. In the experiments, the tadpoles sheltered under gravel/leaves during daylight, but they were exposed at night. Leaf-scrapers ate all exposed tadpoles, but no tadpole of the gravel/leaves trays was consumed. Hence the nocturnal habits and use of diurnal refuges may protect the tadpoles from visual predators, such as the leaf-scrapers.     

Low temperature-acclimation impairs cellular migration in the adult cerebral cortex of the tropical lizard, Tropidurus hispidus (Spix, 1825) (Squamata: Tropiduridae)

The effects of different temperature-acclimations on cellular proliferation and migration were studied in the cerebral cortex of the tropical lizard, Tropidurus hispidus. Lizards were divided in two groups: warm-acclimated lizards (WALs), maintained at the temperature and photoperiod conditions of their natural habitat (mean temperature 26°C; 12:12 light:dark) and the cold-acclimated lizards (CALs), maintained at the same cycle of illumination and a mean temperature of 16°C. Animals were injected with the proliferative marker 5-bromodeoxyuridine (BrdU) and euthanized fifteen or thirty days later for the immunostaining. There was no difference in the number of BrdU-positive nuclei between the experimental groups in any of the cortical layers. In CALs, the positive nuclei were found mostly close to the ependyma, whereas in WALs many positive nuclei were also found in the plexiform and cellular layers of the cortex. In CALs, BrdU-positive nuclei appeared grouped (of 2-3 nuclei), a characteristic not seen in the other group. These data suggest that temperature affects the migrating capability of the newly generated neurons in the lizard cortex, but appears not to interfere with its generation.     

(-)-(S)-flunoxaprofen and (-)-(S)-naproxen isocyanate: two new fluorescent chiral derivatizing agents for an enantiospecific determination of primary and secondary amines

The synthesis and analytical testing of two new fluorescent chiral derivatizing agents (-)-(S)-flunoxaprofen and (-)-(S)-naproxen isocyanate, is described. In a few simple steps the free carboxylic acids [(S)-flunoxaprofen and (S)-naproxen] are activated with ethyl chloroformate/sodium azide and transformed to the corresponding isocyanates. The crystalline reaction products display high enantiomeric and chemical purity and stability. The direction of the optical rotation of both substances is inverse to that of the corresponding carboxylic acids. At ambient temperature the reagents swiftly react with primary and secondary amines, yielding highly fluorescent ureas. The applicability of the two reagents for the resolution of racemic amines was tested with a number of pharmaceuticals (antiarrhythmics, beta-adrenergic antagonists, calcium channel blockers, centrally acting antidepressants). The diastereoisomeric derivatives were efficiently resolved and separated from side-products by means of normal and reversed-phase high-performance liquid chromatography (HPLC). The use and sufficient sensitivity of the two reagents for pharmacokinetic studies were demonstrated with a determination of plasma levels of propranolol enantiomers after oral administration of the racemic drug [80 mg (R,S)-propranolol-HCl] to two volunteers.     

The absolute configuration of (-)-3-hydroxy-alpha-calacorene

3-Hydroxy-alpha-calacorene was identified in extracts from cold-shocked seedlings of cotton (Gossypium hirsutum L.) and kenaf (Hibiscus cannabinus L.), both of which are members of the Malvaceae family. (-)-3-Hydroxy-alpha-calacorene was isolated from Heterotheca inuloides Cass. (Asteraceae). HPLC on a chiral stationary phase column showed that the 3-hydroxy-alpha- calacorene from cotton and kenaf had the same relative configuration, while that from H. inuloides was of the opposite configuration. X-ray crystallographic analysis established the absolute configuration of the compound in H. inuloides as (8R)-(-)-3-hydroxy-alpha-calacorene.     

Preparation of alkyl (R)-(-)-3-hydroxybutyrate by acidic alcoholysis of poly-(R)-(-)-3-hydroxybutyrate

An efficient method for the preparation of optically active alkyl (R)-(-)-3-hydroxybutyrates by chemical depolymerization of biopolymer, poly-(R)-(-)-(3-hydroxybutyrate), was established. This method consists of simple recovery of poly-(R)-(-)-(3-hydroxybutyrate) from bacterial cells followed by acidic alcoholysis. When poly-(R)-(-)-(3-hydroxybutyrate) was purified by a simple digestion method that used 0.2 N sodium hydroxide, alkyl (R)-(-)-hydroxybutyrates were most efficiently produced by alcoholysis with anhydrous hydrochloric acid.     

Chemical Synthesis of Oligonucleotides Containing The (6-4) Photoproduct at the Thymine-Cytosine Site and Its Repair By (6-4) Photolyase

Abstract

A phosphoramidite building block of the T(6-4)C photoproduct was synthesized. One of the differences from T(6-4)T was formation of cytosine hydrates by UV irradiation, and the other was acylation of the amino function with the capping reagent. The capping step was omitted to improve the yield of the desired oligonucleotides. Characterization of the (6-4) photolyase using one of the oligonucleotides revealed that this enzyme restores the pyrimidines in T(6-4)C to their original structures.