Catecholaminergic contributions to the neuronal machinery of the olfactory bulb: aftoradiographic, immunohistochemical and evoked feild potential studies

aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons.     

Foraging interactions between Wandering Albatrosses Diomedea exulans breeding on Marion Island and long-line fisheries in the southern Indian Ocean

Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.     

The ultrastructure of the so-called olfactory setae on the antennula ofDaphnia magna Straus (Crustacea,Cladocera)

A group of nine sensory setae is found on the tip of the antennula ofDaphnia magna in both sexes. Inside a seta four dendrites are situated, each with one receptor cilium. The receptor cilia extend through a liquor space into the exterior part of the seta. The exterior part of the liquor space is divided from the interior part by a knob-like thickening of the innermost layer of the epicuticle, the basal bead. The basal bead narrows the liquor space and the receptor cilia. The interior part of the liquor space is surrounded by five sheath cells, the exterior part by a thin cuticle. In the exterior part the receptor cilia branch partly and reach a terminal pellet on the tip of the seta. The terminal pellet is a thickened part of the epicuticle. It is permeable to several dissolved substances. It is the exterior part of the receptor that projects over the tip of the antennula and seems to be the entire seta. During the premoult the fifth sheath cell builds up the articulation of the seta, the fourth the basal bead, and the third the shaft of the seta. The first sheath cell forms the cuticular sheath. The organ seems to be a chemoreceptor, but the adequate stimulus is as yet unknown.     

High-affinity uptake of γ-[3H]aminobutyric acid by isolated mouse oligodendrocytes in culture

Oligodendrocytes were isolated from mixed glial cultures of neonatal mouse forebrain and further grown in serum-free hormone supplemented culture medium. Cell populations were identified by indirect immunofluorescence using a range of specific antibodies, revealing a predominantly immature population of oligodendrocytes, the majority expressing the myelin glycolipids galactocerebroside and sulfatide on their plasma membrane. Astroglial contamination was found to be minimal. Simultaneous autoradiography and immunofluorescence demonstrated the presence of a transport system for the major inhibitory neurotransmitter GABA in the oligodendrocytes. The transport system was found to be energy, sodium and temperature dependent. Kinetic analysis revealed a high affinity system, with aK _m of 6.27 M and aV _max of 0.714 nmol/min/mg protein, which is comparable to that found previously for CNS neurons and astrocytes.Special Issue dedicated to Dr. E. M. Shooter and Dr. S. Varon.     

Pelodictyon phaeoclathratiforme sp. nov., a new brown-colored member of the Chlorobiaceae forming net-like colonies

A new strain of the green sulfur bacteria was isolated from the monimolimnion of Buchensee (near Radolfzell, Lake Constance region, FRG). Single cells were rod-shaped, nonmotile and contained gas vacuoles. Typical net-like colonies were formed by ternary fission of the cells. As photosynthetic pigments bacteriochlorophylls a, e, isorenieratene and -isorenieratene were present. Sulfide, sulfur and thiosulfate were used as electron donors during anaerobic phototrophic growth. Besides carbon dioxide, acetate and propionate could serve as carbon sources under mixotrophic conditions in the light. Like all other members of the green sulfur bacteria, the new bacterium is strictly anaerobic and obligately phototrophic. The possession of gas vacuoles and the formation of net-like colonies and the guanine plus cytosine content of the DNA (47.9 mol% G+C) are typical characteristics of the genus Pelodictyon. Because of its photosynthetic pigments which differ from those of Pelodictyon clathratiforme, strain BU 1 represents a new species, P. Phaeoclathratiforme sp. nov.     

Genetic and Molecular Characterization of Suppressors of Sir4 Mutations in Saccharomyces Cerevisiae

In order to learn more about other proteins that may be involved in repression of HML and HMR in Saccharomyces cerevisiae, extragenic suppressor mutations were identified that could restore repression in cells defective in SIR4, a gene required for function of the silencer elements flanking HML and HMR. These suppressor mutations, which define at least three new genes, SAN1, SAN2 and SAN3, arose at the frequency expected for loss-of-function mutations following mutagenesis. All san mutations were recessive. Suppression by san1 was allele-nonspecific, since san1 could suppress two very different alleles of SIR4, and was locus-specific since san1 was unable to suppress a SIR3 mutation or a variety of mutations conferring auxotrophies. The SAN1 gene was cloned, sequenced, and used to construct a null allele. The null allele had the same phenotype as the EMS-induced mutations and exhibited no pleiotropies of its own. Thus, the SAN1 gene was not essential. SAN1-mediated suppression was neither due to compensatory mutations in interacting proteins, nor to translational missense suppression. SAN1 may act posttranslationally to control the stability or activity of the SIR4 protein.