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.     

Micropropagation of Calluna vulgaris cv. ‘H.E. Beale’

Axillary shoot producing cultures were obtained from microcuttings and shoot tips of Calluna vulgaris cv. H.E. Beale. For cultures derived from microcuttings the highest multiplication rate of 38 shoots (5 mm or longer) was obtained on a reduced salt medium with the addition of 0.5 mgl^-1 2-isopentenyladenine (2iP) during an 8 week subculture. For shoot tip derived cultures 0.2 mgl^-1 6-benzyladenine (BA) was the best cytokinin and led to a multiplication rate of 26 for a 6 week subculture. The addition of 1 g/l casein hydrolysate to a multiplication medium enhanced shoot proliferation in presence of 0.5 mgl^-1 BA.Despite various auxin treatments shoots formed no roots in vitro but rooted readily if transferred to a peat substrate ex vitro. A high rooting percentage (80%) was also obtained with shoots taken from the end of a multiplication phase and rooted directly. An additional subculture on low auxin containing media before transfer to peat substrate is recommended because the shoot condition can be improved in this way. A high number of rooted plantlets was produced, so the methods described will allow mass propagation.     

Induction and floral determination in the terminal bud of Nicotiana tabacum L. cv. Maryland Mammoth,a short-day plant

Floral determination in the terminal bud of the short-day plant Nicotiana tabacum cv. Maryland Mammoth has been investigated. Plants grown continuously in short days flowered after producing 31.4±1.6 (SD) nodes while plants grown continuously in long days did not flower and produced 172.5±9.5 nodes after one year. At various ages, expressed as number of leaves that were at least 1.0 cm in length above the most basal 10-cm leaf, one of three treatments was performed on plants grown from seed in short days: 1) whole plants were shifted from short days to long days, 2) the terminal bud was removed and then rooted and grown in long days, and 3) the terminal bud was removed and then rooted and grown in short days. Whole plants flowered only when shifted from short days to long days at age 15 or later. Only rooted terminal buds from plants at age 15 or older produced plants that flowered when grown in long days. Only terminal buds from plants at age 15 or older that were rooted and grown in short days produced the same number of nodes as they would have produced in their original locations while buds from younger plants produced more nodes than they would have in their original locations. Thus, determination for floral development in the terminal bud, as assayed by rooting, is simultaneous with the commitment to flowering as assayed by shifting whole plants to non-inductive conditions.Abbreviations LD long day(s) - SD short day(s) - DN dayneutral     

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.     

RFLP maps of potato and their alignment with the homoeologous tomato genome

Summary An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.     

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.     

Different structure of polytene chromosomes ofPhaseolus coccineus suspensors during early embryogenesis

Summary The pattern of DNA and RNA puffs in pair VII of polytene chromosomes has been investigated in the suspensor ofPhaseolus coccineus during early embryo development. The pattern of³H-TdR and³H-U incorporation has been also detected. Collected data indicate that: 1. both heterochromatic regions, p₁₁ and q_(111+112), of chromosome pair VII, organize large DNA puffs; 2. DNA puffs of both regions are specific of different embryo differentiation steps; 3. a seasonal influence on the DNA puffing seems also to be present, as demonstrated by the comparison of the results collected in two different crops; 4. the incorporation experiment by³H-TdR evidences that not all DNA puffs show clustered labeling; 5. the RNA puffing of the two regions seems also to be specific of determined embryo stages.