Increase in levels of total free fatty acids in rat brain regions following 3-nitropropionic acid administration

Acute exposure to a neurotoxin, 3-nitropropionic acid (3-NPA), in rats results in an increase in total free fatty acid (FFA) concentration in selective brain regions. We investigated the effect of 3-NPA administration on the cerebral concentrations of FFA used as a marker of oxidative stress. Rats (n=3/group) were dosed subcutaneously (s.c.) either with a vehicle (phosphate buffer) or 3-NPA in phosphate buffer at 30 mg/kg body weight. Animals were sacrificed after 1, 2, 3, and 6 h of injection. Brains were then dissected into frontal cortex (FC), caudate nucleus (CN), and hippocampus (HIP). The concentration of total FFA increased from 130 to 300% within 1–2 h after 3-NPA injection in all brain regions when compared with the baseline level obtained from the control rats and taken as 100%. In CN, FFA returned to the baseline level within 3 h of treatment. However, in FC and HIP the concentration of FFA remained significantly elevated above the baseline until 6 h. The released FFA provide a substrate for free radicals formation. The results of this study suggest a role of oxidative stress in the mechanism of 3-NPA toxicity.     

In vitro effect of zinc on oxidative changes in human semen

Summary The in vitro effect of zinc on superoxide anion (O₂^?) generation and on experimentally induced lipid peroxidation (LPO) in spermatozoa of infertile men was investigated. Washed spermatozoa pre-incubated for 30 min at 37°C in the presence of 1 or 3 mmol l^-1 zinc, released less superoxide anions (P<0.03 and P<0.02, respectively; n=9) than the untreated spermatozoa. Similar results were obtained using activated polymorphonuclear leukocytes (1 times 10⁶ cells ml^-1) in the presence of 1 or 3 mmol l^-1 Zn (P<0.001 and P<0.0002, respectively; n=9). The in vitro evidence of the inhibitory effect of zinc on O₂^? generation by human spermatozoa and leukocytes indicates that zinc may act in vivo as a scavenger of excessive O₂^? production by defective spermatozoa and/or leukocytes in semen after ejaculation. A significant stimulatory effect of Zn (3 mmol l^-1) on iron-induced lipid peroxidation, measured by the formation of thiobarbituric acid reactive substances (TBARS), was detected in the spermatozoa of 16 normo- and 17 asthenozoospermic males (P<0.0001 and P<0.001, respectively). In 11 samples with sperm concentration 20.3±2.1 times 10⁶ ml^-1, exhibiting initial TBARS concentration two times higher than in normo-and asthenozoospermic samples (40.5±2.4 vs. 17.1±1.1 and 28.5±4.1 nmoles TBARS 10^-8 spermatozoa), no effect of zinc on the LPO rate was found. The observed inhibitory effect of zinc on superoxide anion regardless of the initial O₂^? level and stimulatory effect of zinc depending on the initial LPO rate in human spermatozoa suggests that this metal ion participates in the oxidative changes occurring after ejaculation and thus may modulate the properties of germ cells.     

FIA—fluorimetric determination of thiamine

A flow injection-fluorimetric determination of thiamine is reported. The procedure is based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anionic exchange resin; the fluorescence is monitored in aqueous basic solution. Concentrations of the vitamin of 0.1–4 ppm have been determined; the relative standard deviation was 1.8%. The injection rate was 28 samples/h. The influence of other substances and the determination of the drug in a pharmaceutical formulation are also reported.     

The heat shock/oxidative stress connection

Involvement of free-radical oxidations in the aging process has been a topic of interest since Harman's original contribution. Because of the close association between aging and Alzheimer disease (AD) and the qualitative similarity in the neuropathology of both conditions, it has been proposed by many investigators that oxidative stress may be important in AD. If such modality of injury was indeed involved, one should expect to find markers of oxidation and heat shock (since free radicals are key mediators of heat-shock induction) in brains of patients with AD. In fact, several studies documented abnormal expression of antioxidant enzymes and heat-shock proteins (HSP) along with other markers of oxidation in AD brains. We showed that abnormally expressed antioxidant enzymes are topographically associated with senile plaques and neurofibrillary tangles, and that the activity of these enzymes is (contrary to what one would expect) markedly reduced. These findings have recently been confirmed by other investigators. Despite a large amount of evidence that suggests an association between oxidative stress and the pathogenesis of AD, it is not yet known whether oxidative stress is a cause or consequence of the disorder. Future research efforts regarding the oxidative stress hypothesis of AD should include attempts, at generating AD pathology by oxidative means in laboratory animals, determining the role and integrity of the heat-shock response in AD, as well as that of various antioxidant systems, growth factors, and hormones with antioxidant and neuroprotective properties.     

UVB radiation induces phosphorylation of the epidermal growth factor receptor, decreases EGF binding and blocks EGF induction of ornithine decarboxylase gene expression in SV40-transformed human keratinocytes

Abstract We previously demonstrated that epidermal growth factor (EGF) induces a several-fold increase in ornithine decarboxylase (ODC) activity and the steady-state level of ODC mRNA in cultured SV40-transformed human keratinocytes (1). Pretreatment of cell cultures with ultraviolet B (UVB) radiation resulted in a reduction of EGF-induced ODC activity. To determine whether UVB inhibits the accumulation of ODC mRNA by EGF, cells were pretreated with 20 mJ/cm² UVB or sham-irradiated and then incubated with 100 ng/ml EGF. Northern blot analysis revealed that UVB irradiation entirely blocked the EGF induction of ODC mRNA. Since the binding of EGF to its plasma membrane receptor is the first step in initiating a biological response, the effect of UVB on EGF binding was evaluated. UVB treatment of cultured keratinocytes resulted in an immediate and dose-dependent reduction of EGF binding. Scatchard analysis revealed thai the reduction of EGF binding was due to a 52% decrease in the number of available receptors, from 6.2 × 10⁴/cell to 3.0 × 10⁴/cell. However, UVB decreased the EGF-binding affinity very little (Kd = 0.60 nM in control and Kd=0.75 nM in UVB-treated Z114 cells). In addition, UVB did not alter the rate of EGF internalization. These data suggest that UVB blocks the signal transduction pathway of EGF that is involved in regulation of ODC gene expression. Immunoblot analysis of extracts from irradiated cells showed that UVB induced tyro-sine phosphorylation of EGFR and that the quantity of EGFR protein was unaffected by UVB treatment. Phosphorylation of EGFR may be responsible for decreased binding of EGF to its receptor.     

The Drosophila Mutant tetanic Interacts with a Gene Complex Including the Structural Locus of K+ Channels and Shows Altered Dephosphorylation and Learning

The tetanic (tta; X.-52.6) mutation has been isolated on the basis of its sensitivity to extradoses of the normal Shaker gene complex (ShC) where the K+ channel la is encoded. The mutant shows up to threefold elevation of the membrane bound protein phosphatase type 1 (PP1) activity in body extracts, probably due to reduced levels of the PP1 specific inhibitor 2 (I-2). By contrast, PP1 activity in the head is only half of the normal value. In addition, tta fails to perform normally in a negative reinforcement olfactory paradigm. The functional relationships between phosphorylation, K+ currents, phosphatase activity and modulation of synaptic activity during learning and memory are discussed in the light of their possible genetic links.     

Genetically determined N-acetylation and oxidation capacities in Japanese patients with non-occupational urinary bladder cancer

Summary Genetically determined polymorphisms of N-acetylation and oxidative capacity have been studied using dapsone and metoprolol in 51 Japanese patients with spontaneous bladder cancer and 203 healthy control subjects.The results for N-acetylation pharmacogenetics were against the initial expectation that there would be a preponderance of slow acetylators in the cancer group, as 3 such patients (5.9%) were found as compared to 13 (6.4%) in the healthy group. There was no poor metabolizer (PM) of metoprolol in the cancer group, whereas in the healthy group one (0.5%) was a PM. There were no significant differences between the groups in the frequency of slow acetylator and poor oxidiser phenotypes, or in the frequency distribution profiles of acetylation (monoacetyldapsone/dapsone) and oxidative metabolic ratio (log metoprolol/-hydroxymetoprolol).The results indicate that neither N-acetylation nor the debrisoquine/sparteine-type oxidative phenotype and/or capacity represent a genetic predisposition to spontaneous bladder carcinogenesis in Japanese patients. In the normal Japanese population there is a great predominance of rapid acetylators and extensive oxidisers.     

Hypoxia,energy state and pulmonary vasomotor tone

Vasomotor responses to hypoxia constitute a fundamental adaptation to a commonly encountered stress. It has long been suspected that changes in cellular energetics may modulate both hypoxic systemic artery vasodilatation (HSV) and hypoxic pulmonary artery vasoconstriction (HPV). Although limitation of energy has been shown to underlie hypoxic relaxation in some smooth muscles, the response to hypoxia in vascular smooth muscle does not appear to be a simple function of energy stores, but instead may involve perturbations of ATP or energy delivery to mechanisms controlling muscle force, and/or changes associated with anaerobic metabolism. Recent work in pulmonary vascular smooth muscle has demonstrated that energy stores are maintained during hypoxic pulmonary vasoconstriction, and that this is dependent on glucose availability and up-regulation of glycolysis. There is increasing evidence that glycolysis is preferentially coupled to a variety of membrane associated ATP dependent processes, including the Na(+) pump, Ca(2+)-ATPase, and possibly some protein kinases. These and other mechanisms may influence excitation-contraction coupling in both systemic and pulmonary arteries by effects on intracellular Ca(2+) and/or Ca(2+) sensitivity. Hypoxia has also been postulated to have major effects on other cytosolic second messenger systems including phosphatidylinositol pathways, cell redox state and mitochondrial reactive oxygen species production. This review examines the relationship between energy state, anaerobic respiration and hypoxic vasomotor tone, with a particular emphasis on hypoxic pulmonary vasoconstriction.