Biomedical subjects

S Winberg

Publications and source records attributed to S Winberg.

23 records · Page 2Linked to original sources

PubMed1993

Changes in the brain levels of GABA and related amino acids in anoxic shore crab (Carcinus maenas).

The effects of anoxia on the brain concentrations of gamma-aminobutyric acid (GABA), glutamate, aspartate, glutamine, alanine, and taurine were measured in the shore crab (Carcinus maenas) and compared with data previously obtained from anoxia-tolerant vertebrates. C. maenas was found to survive 12 h in nitrogen-bubbled water. The changes found in brain amino acid levels were strikingly similar to those seen in anoxia-tolerant vertebrates. Thus, during anoxia, the brain of C. maenas displayed considerable increases in the concentrations of GABA (2.4-fold increase after 12 h) and alanine (8-fold increase after 12 h). By contrast, the brain levels of glutamate, aspartate, and glutamine fell significantly during anoxia, whereas the taurine level remained unchanged. Because GABA is a major inhibitory neurotransmitter in arthropods (as well as in most animal phyla), it is suggested that the increased level of GABA could promote the anoxic metabolic depression displayed by C. maenas and thus prolong anoxic survival. It is also possible that the decreases in glutamate and aspartate levels could play similar roles.

Alanine↗

PubMed1992

Changes in brain serotonergic activity during hierarchic behavior in Arctic charr (Salvelinus alpinus L.) are socially induced.

The experiment was performed in two phases. During the first phase (phase 1) the dominance hierarchy was determined in 4 groups of Arctic charr (Salvelinus alpinus L.), each group consisting of 4 fish. Phase 2 was started by rearranging phase 1 fish into 4 new groups. Group 1 consisted of previously dominant fish and groups 2, 3 and 4 of fish that previously held rank 2, 3 and 4, respectively. After phase 2 telencephalon and brain stem were analyzed with regard to their contents of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), the principle metabolite of 5-HT. No correlation was found between the social rank (measured as dominance index) during phase 1 and the brain serotonergic activity (measured as the ratio 5-HIAA/5-HT) determined after phase 2. However, most important, the 5-HIAA/5-HT ratio was significantly correlated with the last experienced social rank, i.e. that acquired during phase 2. These results shows that the difference in brain serotonergic activity between dominant and subordinate fish develops through social interactions. Further, we found that previous subordinate experience inhibited aggressive behavior, an effect which, in the light of available information on stress and 5-HT, could be related to the increase in brain serotonergic activity. We hypothesize that stress induces an increased serotonergic activity which in turn inhibits the neuronal circuitry which mediates aggressive behavior.

Aggression↗

PubMed1992

The effect of Cu (II) on the electro-olfactogram (EOG) of the Atlantic salmon (Salmo salar L) in artificial freshwater of varying inorganic carbon concentrations.

The effect of inorganic copper species was studied by recording the receptor potential, electro-olfactogram (EOG), from the olfactory epithelium of Atlantic salmon (Salmo salar L). In a series of experiments, the olfactory organ was irrigated with aqueous copper solutions with concentrations of the free cupric ion (Cu2+) ranging from 0.2 to 9.7 microM. The diverse copper species were created by varying the amount of bicarbonate (NaHCO3) in artificial freshwater solutions of equal total copper concentrations. In general, these copper solutions induced a slow depolarization of the baseline followed by a hyperpolarization. The amplitudes of these variations in baseline potentials increased with increasing concentrations of Cu2+ ion, i.e., decreasing concentrations of NaHCO3. Stimulating the olfactory epithelium with L-alanine during the copper exposure evoked atypical EOG responses. The amplitudes and form of the EOGs changed drastically with increasing Cu2+ concentrations, with significant correlation between the reduction in EOG amplitudes and the Cu2+ concentration. The results indicate that among the copper species tested the toxic effect is caused mainly by the dissolved Cu2+ ion. The results also suggest that the Cu2+ ion exerts its toxic effects on the transduction mechanisms of the olfactory receptor cells. The different EOG profiles obtained in response to varying Cu2+ concentrations indicate that this ion affects the transduction mechanisms at different stages.

Animals↗

PubMed1992

Induction of social dominance by L-dopa treatment in Arctic charr.

The effect of L-dopa on social dominance was studied in the juvenile Arctic charr (Salvelinus alpinus). L-dopa is the immediate precursor of dopamine, a neurotransmitter that has been connected with aggressive behaviour in fish as well as mammals. Arctic charr were placed in pairs. One individual in each pair was given L-dopa orally, while the other was given vehicle. The results showed that 18 out of 22 fish given 10 mg L-dopa kg-1 became dominant (p = 0.004, binomial test). A higher dose of L-dopa (200 mg kg-1) induced dyskinesia. L-dopa was found to cause a dose-dependent increase in the brain levels of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC, a major dopamine metabolite), as well as an increase in the DOPAC/dopamine ratio (an index of dopaminergic activity).

Aggression↗

PubMed1990

Differential effects of mercurial compounds on the electroolfactogram (EOG) of salmon (Salmo salar L.).

The effects on the salmon (Salmo salar L.) electroolfactogram (EOG) of the two mercurials, mercuric chloride (HgCl2) and methylmercuric chloride (CH3HgCl), were studied. The EOG responses were evoked by stimulating the olfactory epithelium with 340 microM L-alanine for 10 sec every second minute during a 1-hr period. Each EOG response consisted of an initial peak component followed by a sustained component with an amplitude about 40% below the peak value. Three experimental series, each comprising six fish, were carried out. In the first series, the rosette was irrigated solely with artificial "fresh water." In the two other series, a 5-min exposure to mercury (HgCl2 or CH3HgCl, at 10(-5) M) was included after 10 min and a 15-min exposure after 45 min. The mercuric ion (Hg2+) eliminated the peak response within 2 min and suppressed the sustained response to about 35%. During the subsequent irrigation with mercury-free fresh water, both EOG components regained about 50% of their initial amplitudes. In contrast, methylmercury induced a steady and parallel decline of both the peak and the sustained responses, which were not reversed by rinsing the epithelium with fresh water. The results of this study demonstrate the vulnerability of the olfactory receptor function in fish to mercury exposure. Also, they show the very different effects of inorganic and organic mercurials upon the EOG.

Animals↗