Kynurenic acid, an aryl hydrocarbon receptor ligand, is elevated in serum of Zucker fatty rats

Obesity is an increasingly urgent global problem and the molecular mechanisms of obesity are not fully understood. Dysregulation of the tryptophan (Trp) - kynurenine (Kyn) metabolic pathway (TKP) have been suggested as a mechanism of obesity and described in obese humans and in animal models of obesity. However, to the best of our knowledge, TKP metabolism has not been studied in leptin-receptor-deficient Zucker fatty rats (ZFR) (fa/fa), the best-known and most widely used rat model of obesity. We were interested to determine if there are any deviations of TKP in ZFR. Concentrations of major TKP metabolites were evaluated (HPLC- MS method) in serum of ZFR (fa/fa) and age-matched lean rats (FA/-). Concentrations of kynurenic acid (KYNA) were 50% higher in ZFR than in lean rats (p<0.004, Mann-Whitney two-tailed test). Anthranilic acid (AA) concentrations, while elevated by 33%, did not reach statistical significance (p<0.04, one-tailed test). Elevated KYNA serum concentrations might contribute to development of obesity via KYNA-induced activation of aryl hydrocarbon receptor. Present results warrant further studies of KYNA and AA in ZFR and other animal models of obesity.

Dynamic changes in extracellular release of GABA and glutamate in the lateral septum during social play behavior in juvenile rats: Implications for sex-specific regulation of social play behavior

Social play is a motivated and rewarding behavior that is displayed by nearly all mammals and peaks in the juvenile period. Moreover, social play is essential for the development of social skills and is impaired in social disorders like autism. We recently showed that the lateral septum (LS) is involved in the regulation of social play behavior in juvenile male and female rats. The LS is largely modulated by GABA and glutamate neurotransmission, but their role in social play behavior is unknown. Here, we determined whether social play behavior is associated with changes in the extracellular release of GABA and glutamate in the LS and to what extent such changes modulate social play behavior in male and female juvenile rats. Using intracerebral microdialysis in freely behaving rats, we found no sex difference in extracellular GABA concentrations, but extracellular glutamate concentrations are higher in males than in females under baseline conditions and during social play. This resulted in a higher glutamate/GABA concentration ratio in males vs. females and thus, an excitatory predominance in the LS of males. Furthermore, social play behavior in both sexes is associated with significant increases in extracellular release of GABA and glutamate in the LS. Pharmacological blockade of GABA-A receptors in the LS with bicuculline (100 ng/0.5 μl, 250 ng/0.5 μl) dose-dependently decreased the duration of social play behavior in both sexes. In contrast, pharmacological blockade of ionotropic glutamate receptors (NMDA and AMPA/kainate receptors) in the LS with AP-5+CNQX (2mM+0.4mM/0.5 μl, 30 mM+3mM/0.5 μl) dose-dependently decreased the duration of social play behavior in females, but did not alter social play behavior in males. Together, these data suggest a role for GABA neurotransmission in the LS in the regulation of juvenile social play behavior in both sexes, while glutamate neurotransmission in the LS is involved in the sex-specific regulation of juvenile social play behavior.

The role of adherence to human mononuclear phagocytes in the destruction of red cells sensitized with non-complement binding IgG antibodies

In patients with IgG incomplete non-complement binding warm autoantibodies, the subclass composition of the antibodies was studied in relation to the occurrence of increased haemolysis in vivo and the adherence of the patients red cells to peripheral blood monocytes (PBM) in vitro. The presence of IgG3 autoantibodies was almost always accompanied by haemolytic anaemia, but the presence of IgG1 autoantibodies only in some patients but not in others. IgG2 and IgG4 autoantibodies were not associated with increased red cell destruction. A relation identical to that between subclass composition and increased haemolysis was found between subclass composition and adherence of the patients erythrocytes to PBM and thus a strong correlation between positive adherence in vitro and increased red cell destruction in vivo. These results support an important role of adherence to mononuclear phagocytic cells in the destruction of red cells sensitized with non-complement binding IgG antibodies. Strong indications were found that IgG1 autoantibodies are of two kinds, only one of which causes adherence to phagocytes and thus increased red cell destruction.

Correlation of PPD and BCG-induced leukocyte migration inhibition, delayed cutaneous hypersensitivity, lymphocyte transformation in vitro and humoral antibodies to PPD in man

In a study of healthy human individuals a complete lack of correlation between the results of the agarose leukocyte migration inhibition (LMI) test, using purified protein derivative (of tuberculin) (PPD) and Bacillus Calmette Guérin (BCG) as antigens, and delayed cutaneous hypersensitivity and lymphocyte transformation in vitro to PPD was found. There was a reasonable correlation between PPD- and BCG-induced LMI. Antibodies to PPD proved to have no influence on PPD-induced LMI. Purified polymorphonuclear leukocytes, whether derived from donors sensitive to PPD in the agarose LMI test or from nonsensitive donors, did not show migration inhibition to PPD. It was concluded that polymorphonuclear leukocytes and lymphocytes need to be present simultaneously for migration inhibition of peripheral blood leukocytes by PPD. Furthermore, because a consistent relation with conventional parameters of cell-mediated immunity was lacking, it is doubtful whether the agarose LMI test can be considered as an alternative parameter of this kind of immunity.

Studies on glycoproteins and glycopeptides from Tn-polyagglutinable erythrocytes

Direct evidence for the theory that Tn-polyagglutinable erythrocytes have a deficiency of alkali-labile sialic acid and galactose is gained by analysing the carbohydrate moiety of the tryptic glycopeptides with spectrophotometric methods and gas-liquid chromatography. Alkaline borohydride treatment of these glycopeptides specifically releases N-acetylgalactosaminitol. In addition it is shown that mainly the third and the first membrane glycoprotein are affected by the defect.

Antigenic differences between macrophages and lymphocytes

Antisera against guinea-pig lymphocytes and guinea-pig macrophages were prepared by injecting rabbits with purified blood lymphocytes or peritoneal macrophages. Both antisera contained antibodies of at least two different specificities, one reacting with an antigen common to lymphocytes and macrophages and one specific for either lymphocytes or macrophages.

Opsonic adherence and phagocytosis of sensitized red cells by macrophages were inhibited by the anti-macrophage serum. The anti-lymphocyte serum showed no such inhibition, when previously absorbed with macrophages.