The second life of terrestrial and plastic carbon as nutritionally valuable food for aquatic consumers.

Primary production is the basis for energy and biomolecule flow in food webs. Nutritional importance of terrestrial and plastic carbon via mixotrophic algae to upper trophic level is poorly studied. We explored this question by analysing the contribution of osmo- and phagomixotrophic species in boreal lakes and used 13 C-labelled materials and compound-specific isotopes to determine biochemical fate of carbon backbone of leaves, lignin-hemicellulose and polystyrene at four-trophic level experiment. Microbes prepared similar amounts of amino acids from leaves and lignin, but four times more membrane lipids from lignin than leaves, and much less from polystyrene. Mixotrophic algae (Cryptomonas sp.) upgraded simple fatty acids to essential omega-3 and omega-6 polyunsaturated fatty acids. Labelled amino and fatty acids became integral parts of cell membranes of zooplankton (Daphnia magna) and fish (Danio rerio). These results show that terrestrial and plastic carbon can provide backbones for essential biomolecules of mixotrophic algae and consumers at higher trophic levels.

Lake eutrophication and brownification downgrade availability and transfer of essential fatty acids for human consumption.

Fish are an important source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for birds, mammals and humans. In aquatic food webs, these highly unsaturated fatty acids (HUFA) are essential for many physiological processes and mainly synthetized by distinct phytoplankton taxa. Consumers at different trophic levels obtain essential fatty acids from their diet because they cannot produce these sufficiently de novo. Here, we evaluated how the increase in phosphorus concentration (eutrophication) or terrestrial organic matter inputs (brownification) change EPA and DHA content in the phytoplankton. Then, we evaluated whether these changes can be seen in the EPA and DHA content of piscivorous European perch (Perca fluviatilis), which is a widely distributed species and commonly consumed by humans. Data from 713 lakes showed statistically significant differences in the abundance of EPA- and DHA-synthesizing phytoplankton as well as in the concentrations and content of these essential fatty acids among oligo-mesotrophic, eutrophic and dystrophic lakes. The EPA and DHA content of phytoplankton biomass (mgHUFAg-1) was significantly lower in the eutrophic lakes than in the oligo-mesotrophic or dystrophic lakes. We found a strong significant correlation between the DHA content in the muscle of piscivorous perch and phytoplankton DHA content (r=0.85) as well with the contribution of DHA-synthesizing phytoplankton taxa (r=0.83). Among all DHA-synthesizing phytoplankton this correlation was the strongest with the dinoflagellates (r=0.74) and chrysophytes (r=0.70). Accordingly, the EPA+DHA content of perch muscle decreased with increasing total phosphorus (r2=0.80) and dissolved organic carbon concentration (r2=0.83) in the lakes. Our results suggest that although eutrophication generally increase biomass production across different trophic levels, the high proportion of low-quality primary producers reduce EPA and DHA content in the food web up to predatory fish. Ultimately, it seems that lake eutrophication and brownification decrease the nutritional quality of fish for human consumers.

Depressive symptoms and presynaptic dopamine function in neuroleptic-naive schizophrenia.

We have previously reported aberrations in the striatal presynaptic dopamine function in neuroleptic-naive schizophrenic patients compared to healthy controls (Hietala, J., Syvälahti, E., Vuorio, K. et al., 1995. Lancet 346, 1130-1131). In this extended study we explore whether the altered presynaptic dopamine function correlates with the clinical symptomatology in schizophrenia. Striatal dopamine synthesis capacity (6-[18F]fluorodopa (FDOPA) uptake, Ki values) was studied with positron emission tomography in 10 neuroleptic-naive schizophrenic patients and 13 healthy controls. The clinical symptomatology was characterized with the Positive and Negative Symptom Scale (PANSS). The patients had an increased FDOPA uptake in striatum and lacked the asymmetry in caudate FDOPA uptake (p = 0.0005), confirming our earlier results. Left striatal FDOPA uptake (Ki) values correlated negatively with depressive symptoms in a highly significant manner. On the other hand, paranoid symptomatology correlated positively with right putamen FDOPA uptake at a trend level (rho = 0.73, p < 0.02). The lack of asymmetry in caudate Ki values did not associate with any dimension of psychopathology. The major finding in this study is that depressive symptoms in neuroleptic-naive first-admission schizophrenia are associated with low presynaptic dopamine function. This link appears to be hemisphere-related and may have drug-treatment implications, e.g., in prediction of response to D2 receptor blocking antipsychotic drugs. A possible connection between paranoid symptomatology and subcortical hyperdopaminergia is suggested, but this remains to be further verified.

Presynaptic dopamine function in striatum of neuroleptic-naive schizophrenic patients.

Presynaptic dopamine function (6-[18F]-fluorodopa uptake) in the brains of seven neuroleptic-naive first-admission schizophrenic patients and eight healthy controls was studied with positron emission tomography. The fluorodopa influx constant (Ki) in putamen was higher in the patients than in controls (average mean: 0.0149 vs 0.0129, p = 0.034). The changes in caudate were smaller but significantly lateralised to the left caudate. There was one catatonic schizophrenic patient in our sample. This patient had lower striatal Ki than any control. Alterations in striatal presynaptic dopamine function may constitute a part of disrupted neural circuits that predispose to schizophrenic psychosis.

Striatal D2 dopamine receptor characteristics in neuroleptic-naive schizophrenic patients studied with positron emission tomography.

BACKGROUND: According to the D2 dopamine receptor hypothesis of schizophrenia, there is an increased number of D2 receptors in the brains of schizophrenic patients than in those of healthy controls. We tested this hypothesis in 13 newly admitted neuroleptic-naive schizophrenic patients and 10 healthy volunteers using positron emission tomography. METHOD: The quantification of striatal D2 dopamine receptor density (Bmax) and affinity (Kd) was done using an equilibrium model described for raclopride labeled with carbon 11. RESULTS: No statistically significant alterations were found in D2 receptor densities or affinities between the patient and control groups. However, a subgroup of four patients with a relatively high striatal D2 dopamine density was identified. Two patients, especially, had D2 dopamine densities almost twice as high as the mean control Bmax value. The Kd values also tended to be higher in this subset of patients than in the controls. No consistent striatal D2 dopamine receptor laterality was observed in schizophrenic patients or controls. However, an association of high D2 dopamine density in the left striatum and the mass of raclopride injected in the scan with low-specific radioactivity was observed in patients but not in controls. CONCLUSIONS: There are no general changes in D2 dopamine receptor Bmax or Kd values in neuroleptic-naive schizophrenics, but there may be a subgroup of patients with aberrant striatal D2 dopamine receptor characteristics in vivo.

Eight cases of patients with unfounded fear of AIDS.

This article describes eight cases of patients treated at the Psychiatric Department of the University Central Hospital of Turku (UCHT) Finland who all had as a common feature an unfounded fear of AIDS. Three of the patients committed suicide and one of them had overt suicidal tendencies. An unfounded fear of AIDS may be a sign of psychiatric disturbance with increased suicidal risk. Increased fear of AIDS seems to have correlation with media and counselling services. Owing to the fact that these patients primarily seek medical help from other fields of medicine than psychiatry, they are a new problem especially for general hospital psychiatry.

Determination of IgG, IgM and IgA antibody responses in human toxoplasmosis by enzyme-linked immunosorbent assay (ELISA).

A 4-layer modification of ELISA for the determination of toxoplasma antibodies is described. In 103 Finnish blood donors 27 had antibodies against Toxoplasma gondii. One donor had IgM antibodies and IgA antibodies were found in 9. In patients with acute toxoplasmosis a vigorous IgG antibody response resulted in high antibody levels soon after infection, declining gradually to mean adult levels in approximately 2 yr. IgM antibodies appeared during the earliest phases of infection and disappeared as early as in 1 or 2 months in some cases and in most cases by the 6th month after infection. An IgA antibody response was also always seen. It was slower than the IgM response and could therefore be used to improve the laboratory diagnosis especially in cases where IgM antibodies had already disappeared and no further increase in IgG antibodies could be detected.