Involvement of thalamic nuclei in the formation of conditional avoidance reflexes in rats. II. Lesions of the midline nuclei

Lesions of the habenular-paraventricularis-anterior complex of the thalamus caused a total impairment of conditioned avoidance response of hooded rats (Long-Evans-strain) in a jumping test, but not in a simple runway. The change of stereotyped avoidance reactions could be attained very slowly. Running speed was lower and the number of errors much higher using an alternation schedule. Lesions of the nucleus centralis medialis and partly of its surrounding caused less deficits. From the results may be suggested that regulatory interactions between general behavioural activation originating from the brain stem, motivational processes and the analyzer systems are disrupted.     

IgG antibodies to Lewis type 2 antigens in serum of H. pylori-infected and noninfected blood donors of different Lewis(a,b) blood-group phenotype

Individuals of the Le(b+)/secretor phenotype revealed a stronger natural immune response to Le(x) and Le(y) epitopes irrespective of Helicobacter pylori serologic status. In contrast, H. pylori-infected Le(b-) type individuals showed a significantly higher proportion of strong responders to Le(x) antigen compared with the H. pylori-uninfected subgroup. The data suggest that the immune response to Lewis type 2 determinants is related to both the H. pylori serologic status and the Le(a,b) phenotype of the host.     

Reversible structural changes in a hydrophobic protein,elastin, as indicated by fluorescence probe analysis

Fluorescent probe analysis of purified elastin using 1-anilinonaphthalene-8-sulfonate has been used to investigate reversible structural changes that accompany stretching of this rubberlike protein. There is a specific binding of 1-anilinonaphthalene-8-sulfonate to elastin with a single dye molecule attached per 74,000 molecular-weight protein subunit. When labeled elastin is stretched, the intensity of the 1-anilinonaphthalene-8-sulfonate fluorescence decreases reversibly, and this decrease appears to be linked to an increase in the environmental polarity in the immediate vicinity of the bound dye molecule. The results of experiments carried out in H₂O and D₂O indicate that this polarity change is due to an increase in the exposure of the 1-anilinonaphthalene-8-sulfonate to water as the hydrophobic interior of the protein subunit is unfolded during stretching. The data are consistent with the proposal that the elastin network is a two-phase system of hydrophobic protein globules surrounded by free solvent spaces.     

Production of Bacterial Substrate by Marine Copepods: Effect of Phytoplankton Biomass and Cell Size

Laboratory experiments were performed to evaluate the importanceof grazing activity of the marine copepod Acartia tonsa forproduction of substrate for bacteria. Acartia tonsa were feda range of concentrations of the nanoflagellate Rhodomonas baltica,the diatom Ditylum brightwelli and the dinoflagellate Ceratiumlineatum. Regardless of the concentration of R. baltica, nodetectable response in bacterial biomass was observed due tograzing. However, when A. tonsa grazed the larger phytoplanktoncells of D. brightwelli and C. lineatum, responses in bacterioplanktonwere observed. It was estimated that approximately 54–69%of the grazed carbon was lost to the surroundings when A. tonsawas feeding on these large phytoplankton species. The laboratoryresults were applied to a dataset from a coastal temperate ecosystem.This analysis showed that the copepod contribution to the DOCpool was as important as the leakage from the primary producers.It is concluded, that the DOM contribution from copepods willbe largest when grazing plankton communities are composed oflarge species.