A serotonergic system in the brain of the Antarctic fish, Trematomus bernacchii

The immunohistochemical distribution of serotonin-containing nerve fibres and cells has been described in the brain of the Antarctic fish, Trematomus bernacchii. The largest serotonergic system was associated with the diencephalic and rhombencephalic ventricles. In particular, serotonin-positive cells have been found in the lateral recess and neuropile zone of the diencephalic ventricle, where we have identified the serotonergic portion of the paraventricular organ. Numerous serotonin cells were localized in the dorsal nucleus of the raphe, the dorsal tegmental nucleus and the central gray. Two large cell groups, arranged in a pair of well-defined columns and connecting the central gray with the dorsal reticular formation, were immunostained in the region of the trigeminal nuclei. In addition, few positive cells have been found in the preoptic area and the cerebellar valvula, and few serotonergic nerve fibres, probably belonging to the lateral lemniscus, have been identified. The distribution of serotonin elements in the brain of T. bernacchii has been compared with that described in other fish, where it showed some modifications in the immunoreactive pattern. Finally, the lack of a serotonergic system at the level of the reticular superior formation has been reported; however, it was not possible to rule out a phylogenetic or environmental explanation.     

Neuronal Basis of Innate Olfactory Attraction to Ethanol in Drosophila

The decision to move towards a mating partner or a food source is essential for life. The mechanisms underlying these behaviors are not well understood. Here, we investigated the role of octopamine – the invertebrate analogue of noradrenaline – in innate olfactory attraction to ethanol. We confirmed that preference is caused via an olfactory stimulus by dissecting the function of the olfactory co-receptor Orco (formally known as OR83b). Orco function is not required for ethanol recognition per se, however it plays a role in context dependent recognition of ethanol. Odor-evoked ethanol preference requires the function of Tbh (Tyramine β hydroxalyse), the rate-limiting enzyme of octopamine synthesis. In addition, neuronal activity in a subset of octopaminergic neurons is necessary for olfactory ethanol preference. Notably, a specific neuronal activation pattern of tyraminergic/octopaminergic neurons elicit preference and is therefore sufficient to induce preference. In contrast, dopamine dependent increase in locomotor activity is not sufficient for olfactory ethanol preference. Consistent with the role of noradrenaline in mammalian drug induced rewards, we provide evidence that in adult Drosophila the octopaminergic neurotransmitter functions as a reinforcer and that the molecular dissection of the innate attraction to ethanol uncovers the basic properties of a response selection system.     

Solid-Supported Oligonucleotide Systems for Special Biomedical Applications

Abstract

The use of composite beads consisting of a 6 μm polystyrene core with 30 nm surface-bound silica particles to routine automatic oligodeoxynucleotide (ODN) synthesis is described.     

Transport of l(-)malic acid and other dicarboxylic acids in the yeast Candida sphaerica

Summary dl-Malic acid grown cells of Candida sphaerica (anamorph of Kluyveromyces marxianus) formed a saturable transport system that mediated accumulative transport of l(-)malic acid with the following kinetic parameters at pH 5.0: V _max, 0.44 nmol l(-)malate·s^-1 per milligram dry weight; K _m ,0.1 mM l(-)malate. Initial uptake of the acid was accompanied by disappearance of extracellular protons, the rates of which followed Michaelis-Menten kinetics as a function of the acid concentration. Variation with extracellular pH of the K _m values, calculated either as the concentrations of anions or of undissociated acid, pointed to anions as the transported form. Furthermore, accumulated free acid suffered rapid efflux after the addition of the protonophore carbonylcyanide-M-chlorophenyl-hydrazone (CCCP). These results suggested that the transport system was a dicarboxylate-proton symporter. The system was inducible and was subject to glucose repression. Succinic, fumaric, -ketoglutaric, oxaloacetic and d-malic acid, but not maleic, malonic, oxalic nor l(+)-tartaric acid, apparently used the same transport system since they acted as competitive inhibitors of l(-)malic acid transport and induced proton movements that followed Michaelis-Menten kinetics. Experiments with glucose-repressed cells showed that undissociated dicarboxylic acid (measured with labelled succinic acid) entered the cells slowly by simple diffusion. The permeability of the cells for undissociated acid increased exponentially with pH, the diffusion constant increasing 100-fold between pH 3.5 and 6.0.     

High-level expression of a tobacco chitinase gene in Nicotiana sylvestris. Susceptibility of transgenic plants to Cercospora nicotianae infection

Endochitinases (E.C. 3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen.     

Linkage data suggesting allelic heterogeneity for paramyotonia congenita and hyperkalemic periodic paralysis on chromosome 17

Summary Paramyotonia congenita (PC), an autosomal dominant non-progressive muscle disorder, is characterised by cold-induced stiffness followed by muscle weakness. The weakness is caused by a dysfunction of the sodium channel in muscle fibre. Parts of the gene coding for the -subunit of the sodium channel of the adult human skeletal muscle (SCN4A) have been localised on chromosome 17. To investigate the role of this gene in the etiology of PC, a linkage analysis in 17 well-defined families was carried out. The results (z=20.61, =0.001) show that the mutant gene responsible for the disorder is indeed tightly linked to the SCN4A gene. The mutation causing hyperkalemic periodic paralysis (HyperPP) with myotonia has previously been mapped to this gene locus by the same candidate gene approach. Thus, our data suggest that PC and HyperPP are caused by allelic mutations at a single locus on chromosome 17.Dedicated to Professor P. E. Becker on the occasion of his 83rd birthday.     

Phosphorylation of a 51-kDa envelope membrane polypeptide involved in protein translocation into chloroplasts

In this report we demonstrate that a 51-kDa outer-envelope membrane protein (P51) is involved in protein translocation into chloroplasts. Furthermore it is shown that phosphorylation of P51 is functionally related to the process of binding and/or importing precursor proteins into chloroplasts. Several lines of evidence have been obtained supporting this suggestion. First, protein import into chloroplasts was inhibited by the membrane-impermeable agent pyridoxal 5'-phosphate, which has been shown to react with a component of the protein-import apparatus. Phosphorylation of envelope membrane polypeptides using [gamma-32P]ATP in the presence of pyridoxal 5'-phosphate resulted in an increased incorporation of 32P radiolabel into a 51-kDa membrane polypeptide (P51). A close correlation between the inhibition of protein import and the increase in the phosphorylation state of P51, both as a function of PLP concentration, was observed. Second, binding of purified precursor proteins to chloroplasts resulted in a specific increase in the phosphorylation state of P51. This effect was not exerted by the mature form of the precursor protein lacking the presequence. Third, internally generated ATP was able to compete specifically with externally added [gamma-32P]ATP for the phosphorylation of P51. Fourth, digestion of the outer-envelope membrane with low amounts of thermolysin resulted in a loss of protein import activity, which was associated with the removal of the phosphorylation site of P51. Phosphorylation of P51 proceeds with an apparent Km (ATP) of about 5 microM, which is much lower than the ATP concentration required for the protein translocation itself. We suggest that two different ATP-dependent processes are involved in protein translocation into chloroplasts. P51 represent presumably a regulatory component of the protein-import apparatus or the protein receptor itself.     

Energy dependence of protein translocation into chloroplasts

The translocation of in vitro synthesized precursor proteins into intact spinach chloroplasts was investigated with respect to its energy requirement. It was demonstrated that MgATP itself, and not a transmembrane electrochemical gradient across the envelope membrane, promotes protein import. By manipulating the external and the stromal level of MgATP, we provided evidence that MgATP energized the protein import not within the chloroplast but at the outside of the envelope membrane. It is postulated that an MgATP-dependent phosphorylation/dephosphorylation cycle at the outer membrane face was involved in the course of protein translocation into the chloroplast.     

Head-group contributions to bilayer stability: monolayer and calorimetric studies on synthetic, stereochemically uniform glucolipids

Monolayer and differential scanning calorimetry studies have been performed on synthetic, stereochemically uniform glyceroglucolipids having saturated, ether-linked alkyl chains. The limiting area, A0 = 40 A2 X molecule-1, resulting from the monolayer measurements of the glucolipids is comparable to the A0 value found for phosphatidylethanolamine lipids. The area corresponds to twice the value observed with saturated straight chain fatty acids, which indicates that at high surface pressure the space requirement of the glucose head group does not exceed that of the two alkyl chains. The apparent specific heat capacities of the glucolipid dispersions have been found to be higher than those of corresponding phospholipids. They can be approximated from group parameters with the additional assumption that the experimental partial molar heat capacity of glucose is valid for the glucose head groups of the lipids. The transition enthalpies of the C16 and C18 glyceroglucolipids are clearly larger than the delta H values of corresponding phospholipids, while the C14 glyceroglucolipid has the same transition enthalpy as dimyristoylphosphatidylethanolamine or ditetradecylphosphatidylethanolamine. Glucolipids exhibit gel to liquid-crystalline phase transition temperatures which are only slightly lower than those of their phosphatidylethanolamine analogues, although they are uncharged molecules. Like phosphatidylethanolamine the glucolipids do not show a pretransition; however, with the C14 glucolipid a highly cooperative posttransition, approximately 5 deg above the main transition, has been found. Calorimetric experiments with a C14 glucolipid, in which the hydroxyl protons of the glucose moiety have been exchanged by deuterium, suggest that the posttransition might reflect structural changes of the head group.(ABSTRACT TRUNCATED AT 250 WORDS)