Toxicity of Dopamine to Striatal Neurons In Vitro and Potentiation of Cell Death by a Mitochondrial Inhibitor

Abstract: Intrastriatal injections of the mitochondrial toxins malonate and 3-nitropropionic acid produce selective cell death similar to that seen in transient ischemia and Huntington's disease. The extent of cell death can be attenuated by pharmacological or surgical blockade of cortical glutamatergic input. It is not known, however, if dopamine contributes to toxicity caused by inhibition of mitochondrial function. Exposure of primary striatal cultures to dopamine resulted in dose-dependent death of neurons. Addition of medium supplement containing free radical scavengers and antioxidants decreased neuronal loss. At high concentrations of the amine, cell death was predominantly apoptotic. Methyl malonate was used to inhibit activity of the mitochondrial respiratory chain. Neither methyl malonate (50 µ M ) nor dopamine (2.5 µ M ) caused significant toxicity when added individually to cultures, whereas simultaneous addition of both compounds killed 60% of neurons. Addition of antioxidants and free radical scavengers to the incubation medium prevented this cell death. Dopamine (up to 250 µ M ) did not alter the ATP/ADP ratio after a 6-h incubation. Methyl malonate, at 500 µ M , reduced the ATP/ADP ratio by ∼30% after 6 h; this decrease was not augmented by coincubation with 25 µ M dopamine. Our results suggest that dopamine causes primarily apoptotic death of striatal neurons in culture without damaging cells by an early adverse action on oxidative phosphorylation. However, when combined with minimal inhibition of mitochondrial function, dopamine neurotoxicity is markedly enhanced.     

An Efficient Regression Type Estimator in Survey Sampling

For the estimation of population mean in simple random sampling, an efficient regression-type estimator is proposed which is more efficient than the conventional regression estimator and hence than mean per unit estimator, ratio and product estimators and many other estimators proposed by various authors. Some numerical examples are included for illustration.     

Fluorescent analysis of alpha-keto acids in serum and urine by high-performance liquid chromatography

A selective procedure using synthetic substrates for determination of exo-1,4,-beta-glucanases in a mixture of exoglucanases , endoglucanases , and beta-glucosidases is formulated. The heterobiosides , p- nithrophenyl -beta-D- cellobioside ( pNPC ) or p-nitrophenyl-beta-D-lactoside ( pNPL ), were used as selective substrates for the measurement of exoglucanase activity. The exoglucanases (especially cellobiohydrolases , which split off cellobiose units from the nonreducing end of the cellulose chain) specifically act on the agluconic bond (between p-nitrophenyl and the disaccharide moiety) and not on the holosidic bond (between the two glucose units of cellobiose). The interfering effect of beta-glucosidase, which acts on both agluconic and holosidic bonds, is overcome by the addition of D-glucono-1,5-delta-lactone, a specific inhibitor of beta-glucosidases. The interference of endoglucanases , which also act on both agluconic and holosidic bonds, can be compensated for by prior standardization of the assay procedure with a purified endoglucanase from the studied mixture of cellulases.     

Dimeric chromenes and mixed dimers of a chromene with euparin from Encelia canescens

The investigation of Encelia canescens afforded, in addition to several known compounds, four new dimeric p-hydroxyacetophenone derivatives, two epimeric chromene dimers and two epimeric mixed dimers of euparin and encecalin. Furthermore, derivatives of tremetone and of encecalin were present. The structures were elucidated hy high field ¹H NMR spectroscopy.     

Sexual dimorphism in the pyrgomorphid grasshopper Phymateus morbillosus: from wing morphometry and flight behaviour to flight physiology and endocrinology

Abstract In the field, adult males of the grasshopper Phymateus morbillosus are able to fly for up to 1 min and cover up to c. 100 m, whereas females, although fully winged, are apparently unable to get airborne. Morphometric data indicate that the males are lighter, have longer wings, a higher ratio of flight muscles to body mass, and a lower wing load value than females. It was investigated whether this inability of females to fly is related to fuel storage, flight muscle enzymatic design and/or the presence and quantitative capacity of the endocrine system to mobilize fuels. In both sexes, readily available potential energy substrates are present in the haemolymph in similar concentrations, and the amount of glycogen in flight muscles and fat bodies does not differ significantly between males and females. Mass-specific activities of the enzymes GAPDH (glycolysis), HOAD (fatty acid oxidation) and MDH (citric acid cycle) in flight muscles are significantly lower in females compared with males, and mitochondria are less abundant in the flight muscles of females. There is no significant difference between the ability of the two sexes to oxidize various important substrates. Both sexes contain three adipokinetic peptides in their corpora cardiaca; the amount of each peptide in female grasshoppers is higher than in males.
Thus, despite some differences listed above, both sexes appear to have sufficient substrates and the necessary endocrine complement to engage in flight. It seems more likely, from the morphometric data above, that the chief reason for flightlessness is that P. morbillosus females cannot produce sufficient lift for flight; alternatively, the neuronal functioning associated with the flight muscles may be impaired in females.     

Cyclo(His-Pro) up-regulates heme oxygenase 1 via activation of Nrf2-ARE signalling

Paraquat (1,1'-dimethyl-4,4'-bipyridinium), a widely used non-selective herbicide, is a redox cycling agent with adverse effects on dopamine systems. Epidemiological data have shown that exposure to paraquat is one of the several risk factors for Parkinson's disease. We have already shown that cyclo(His-Pro), an endogenous cyclic dipeptide produced by the cleavage of the thyrotropin releasing hormone, has a cytoprotective effect through a mechanism involving Nrf2 activation that decreases production of reactive oxygen species and increases glutathione synthesis. Using primary neuronal cultures and PC12 cells as targets of paraquat neurotoxicity, we addressed whether and how cyclo(His-Pro) causes cellular protective response against paraquat-mediated cell death. We found that cyclo(His-Pro) attenuated reactive oxygen species production, and prevented glutathione depletion by up-regulating Nrf2 gene expression, triggering its nuclear accumulation and activating the expression of heme oxygenase1. These protective effects were abolished by RNA interference-mediated Nrf2 knock down whereas were unaffected by RNA interference-mediated Keap1 knock down. Inhibition of heme oxygenase activity decreased cyclo(His-Pro)-induced neuroprotection. These results suggest that cyclo(His-Pro), acting as a selective activator of the brain modulable Nrf2 pathway, may be a promising candidate as neuroprotective agent that act through induction of phase II genes.     

Disease resistance, stress response and effects of triploidy in growth hormone transgenic coho salmon

Diploid and triploid coho salmon Oncorhynchus kisutch transgenic for growth hormone (GH) and control coho salmon were compared for differences in disease resistance and stress response. Resistance to the bacterial pathogen Vibrio anguillarum was not affected in transgenic fish relative to their non‐transgenic counterparts when they were infected at the fry stage, but was lower in transgenic fish when infected near smolting. Vaccination against vibriosis provided equal protection to both transgenic and non‐transgenic fish. Triploid fish showed a lower resistance to vibriosis than their diploid counterparts. Diploid transgenic fish and non‐transgenic fish appeared to show similar physiological and cellular stress responses to a heat shock. These studies provide information useful for both performance and ecological risk assessments of growth‐accelerated coho salmon.     

Studies on the frequency and associations of equine leucocyte antigens in sarcoid and summer dermatitis

The equine leucocyte antigen (ELA) types and the clinical diagnosis for equine sarcoid and summer dermatitis were evaluated in 2026 horses representing five breeds. Data were analysed in unrelated animals and in family material. In the case of equine sarcoid, a strong association was observed between the ELA class II DW13 antigen and its effect on Swiss (cP < 0·001), French (cP < 0·0001) and Irish (cP < 0·01) Warmblood horses. The class I antigen A3 occurred more frequently in sarcoid-affected French horses (cP < 0·001). These results confirm our earlier findings (Gerber et al. 1988). Among Freiberger horses, which lack the ELA DW13 and A3 specificities, a breed-specific class I antigen, ABe108, displayed an increased frequency (cP < 0·05) in the affected group. Among Arabian horses, a tendency for increased frequency of the A1 antigen was observed in the affected animals, but the number of affected horses is too small for statistical significance. The Mendelian segregation in diseased half-siblings by ELA DW13 heterozygous stallions showed a strong association (P < 0·0001) between the inherited DW13 antigen and susceptibility to the sarcoid effect. In the case of summer dermatitis, previously published data (Marti et al. 1992) have been extended. The ELA types in four multiple-case families, founded by the same stallion, were analysed for an association with the effect of sarcoid. Eight out of nine ELA-typed affected offspring inherited the paternal haplotype A15, DW23 in contrast to nonaffected offspring where three out of 12 displayed these antigens (P < 0·005). Moreover, the ELA haplotypes of 11 out of 12 informative affected half-siblings sired by another stallion inherited the paternal haplotype A3, W12, DW23 (P < 0·05). Our findings demonstrate statistically significant associations between certain ELA antigens and two equine diseases. It is still unknown if the major histocompatibility complex (MHC) molecules themselves or another linked gene(s) play a role in the pathogenesis of these conditions.     

Photoproduction of hydrogen, nitrogenase and hydrogenase activities of free and immobilized whole cells of Rhodobacter sphaeroides O.U. 001

Abstract Photoproduction of hydrogen, nitrogenase activity (acetylene reduction) and hydrogenase activity (methylene blue dye reduction) were studied in free and alginate immobilized whole cells of a purple non-sulfur photosynthetic bacterium Rhodobacter sphaeroides O.U. 001. Four-fold increase in hydrogen production, two-fold increase in nitrogenase activity and 1.2-fold increase in the hydrogenase activity were observed in immobilized cells compared to free cells. Effect of various inhibitors (CO and C₂H₂) and electron donor (H₂) on the above three functions by free and immobilized cells has also been studied.