Light-induced decrease in DCF fluorescence of wheat leaves in the presence of salicyl hydroxamate

5-(and-6)-Carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCF-DA), a permeative indicator of oxidative stress, was loaded into dissected leaves of wheat in order to monitor the temporal development of reactive oxygen species. DCF fluorescence was found to be constant under dark conditions. Upon loading the leaves with salicyl hydroxamate, a blocker of the alternative oxidase, DCF fluorescence linearly increased in the dark. This indicates a function of alternative oxidase in preventing reactive oxygen radicals in the mitochondria. Upon illumination, the DCF signal decreased within 5 min. As illuminated chloroplasts would increase the load of reactive oxygen species, the observed decrease cannot be assigned to the production of reactive oxygen species in the chloroplasts. Three different putative mechanisms are considered which all assign an important role to light-induced delivery of NAD(P)H: (1) direct quenching of DCF fluorescence by light-generated NAD(P)H, (2) light-stimulated activation of scavenging enzymes, or (3) redirection of mitochondrial electron fluxes as caused by the delivery of excess redox equivalents (NADH) from the chloroplasts.

Effect of CO2 supply on formation of reactive oxygen species in Arabidopsis thaliana

Light-induced generation of reactive oxygen species (ROS) in 2-week-old leaves of Arabidopsis thaliana was studied by means of the ROS-sensitive dyes nitroblue tetrazolium (NBT) and 5-(and-6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCF-DA). Superposition of pictures of chlorophyll fluorescence and DCF fluorescence indicated that the origin of ROS was in the chloroplasts. Experiments were done with zero, 0.1, or 10 mM NaHCO3 in the infiltration medium. Energy quenching in photosystem II was higher under low CO2 concentrations as measured by chlorophyll fluorescence. DCF fluorescence showed that CO2 deficiency led to an increase of ROS generation. In contrast, the photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea reduced the light-induced increase of DCF fluorescence. This indicates that ROS production does not primarily result from over-reduction of photosystem II as caused by impeding electron flow in the electron transfer chain. More likely, it is an effect of diverting electron flux normally aimed at carboxylation in the Calvin cycle to other sinks more prone to the generation of toxic radicals. There was no significant effect of salicyl hydroxamate (a blocker of the alternative oxidase), showing that the mitochondrial electron transfer chain seems to play a minor role as already indicated by the superposition of chlorophyll and DCF fluorescence.

Serum concentrations of fluvoxamine and clinical effects. A prospective open clinical trial

This pilot study examined prospectively blood serum concentrations of fluvoxamine, side effects and therapeutic response after a fixed dosage of 100 mg fluvoxamine/day for 14 days. Twenty male and female patients who met the DSM-IV criteria of a major depression received 50 mg fluvoxamine b.i.d. for two weeks. On days 7 and 14 side effects and therapeutic response were registered and serum concentrations of fluvoxamine were determined. A Receiver Operating Characteristic (ROC) curve was constructed to determine a possible relationship between serum concentrations and clinical effects. The serum concentrations of fluvoxamine were highly variable, even when dosages were corrected for body weight, ranging between 23 to 227 microg/l. No relationship between serum concentrations and side effects was detectable. On the other hand, ROC analysis, conducted on day 14, revealed a significant upper concentration threshold of 85 microg/l (p < 0.01) with no responder above this threshold. The results of this pilot study should be regarded as a hint at the possible therapeutic benefits of lower fluvoxamine serum concentrations by means of lower fluvoxamine dosages. Furthermore, this indicates for the first time that therapeutic drug monitoring might be useful for patients under antidepressant therapy with fluvoxamine.

Nonlinear pharmacokinetics of fluvoxamine and gender differences

This prospective study assessed fluvoxamine serum concentrations under two different fixed doses. The study included 15 male and female patients who met the DSM-III-R criteria for major depression. They were prescribed 50 mg fluvoxamine twice a day for 2 weeks and 100 mg twice a day thereafter. Drug monitoring was carried out on days 14 and 28. Fluvoxamine serum concentrations were highly variable between patients. After the dose was doubled, the serum concentrations of fluvoxamine increased disproportionately (mean, 3.4-fold), and there was a significantly (p < 0.05) more pronounced increase in men (4.6-fold) than in women (2.4-fold). These results provide evidence of nonlinear, sex-dependent pharmacokinetics of fluvoxamine.

Circadian variations in antigen-specific proliferation of human T lymphocytes and correlation to cortisol production

Cortisol is a well-known immunosuppressant when used therapeutically. The present investigation was set out to study if diurnal variations in endogenous cortisol production are reflected by changes in proliferative responses of human lymphocytes to either a mitogen (phytohemagglutinin-A, PHA) or an antigen (tetanus toxoid, TT) stimulus. The study included eight healthy volunteers. Blood was withdrawn at 0200, 0600, 1000, and 1800h for preparation of lymphocytes and determination of cortisol in plasma. Isolated cells were incubated without (baseline activity) or with inclusion of either 1 micrograms PHA or 10 micrograms TT. Proliferation was measured by labelling with 3H-thymidine for 16 h of culture. The cortisol plasma levels exhibited the well known diurnal variations with highest concentrations at 1000h and lowest levels at 0200h. Baseline activity or PHA stimulated cell proliferation did not show significant diurnal fluctuations. The response to TT, however, decreased by 38% between 0600 and 1000h (p = .01). Correlation analyses revealed that the reduction of the proliferative responses to TT correlated significantly (p < .05) with increases in cortisol plasma levels. It was concluded that diurnal fluctuations in the production of endogenous cortisol might be relevant for daytime dependent variations in immune responsiveness.

Inhibition of antidepressant demethylation and hydroxylation by fluvoxamine in depressed patients

Bidirectional drug interactions between fluvoxamine and classical antidepressants were studied in depressed patients. A column switching technique combined with high performance liquid chromatography (HPLC) enabled automated analyses of plasma for simultaneous determination of fluvoxamine, tricyclic and tetracyclic antidepressants and demethylated and major hydroxylated metabolites in a single HPLC run. The measurements revealed that fluvoxamine inhibited N-demethylation of imipramine, clomipramine, amitriptyline and maprotiline whereas interferences with hydroxylation reactions were restricted to aromatic 8-hydroxylation of clomipramine. In patients under fluvoxamine monotherapy before comedication, plasma concentrations of fluvoxamine increased after administration of a tricyclic antidepressant, thus indicating bidirectional drug interactions. The inhibitory effects of fluvoxamine on the metabolism of classical antidepressants disappeared after discontinuation of concomitant fluvoxamine treatment within at least 1-2 weeks. The reported alterations in drug metabolism observed in depressed patients who were under fluvoxamine/tricyclic antidepressant comedication suggested that careful supervision and regular drug monitoring are necessary in such patients.

Roxindole, a dopamine autoreceptor agonist, in the treatment of major depression

Roxindole is a potent autoreceptor-"selective" dopamine agonist originally developed for the treatment of schizophrenic syndromes. The drug also inhibits 5-HT uptake and has 5-HT1A agonistic actions. In this open clinical trial 12 in-patients suffering from a major depressive episode (DSM-III-R) were treated with roxindole for 28 days in a fixed dosage of 15 mg per day. A reduction of at least 50% in HAMD-17 total scores was observed in 8 out of 12 patients after 4 weeks (mean HAMD-17 reduction of 56% in all patients), while 4 patients did not respond to roxindole treatment. Half of the patients showed a complete psychopathological remission (HAMD-17 < 8). Roxindole's onset of antidepressant action was remarkably rapid. Seven out of eight responders improved within the first 2 weeks of treatment (at least 50% decrease in HAMD-17 total score), and four patients were nearly asymptomatic within 1 week. Our results indicate that roxindole may possess potent antidepressant properties and that its efficacy should be further evaluated by double-blind controlled studies against reference drugs.

Sub-acute effects of interferon-alpha 2 on adrenocorticotrophic hormone, cortisol, growth hormone and prolactin in humans

This study investigated the chronic effects of interferon-alpha 2 (IFN-alpha 2) on hormonal secretion in humans. Six patients suffering from chronic hepatitis B or C infection received SC doses of 3 million IU IFN-alpha 2 three times a week for 4 mo. Each patient was examined for hormone secretion four times: the day before initial IFN-alpha 2 administration (day 0), the day of the first injection (day 1), and 4 wk after start of IFN therapy on days 27 (without IFN administration) and 28 (with IFN administration). Adrenocorticotrophic hormone (ACTH), cortisol, growth hormone (hGH), and prolactin (PRL) were measured in plasma samples drawn at 30-min intervals between 1600h and 2400h. Acute administration of IFN-alpha 2 stimulated the release of ACTH to 423% (p = 0.02 vs. day 0) and cortisol to 393% (p = 0.01 vs. day 0) of control values in each patient. In five of the six patients, the plasma levels of hGH were higher on day 1 than on day 0. IFN-alpha 2 did not affect the secretion of prolactin. On day 27, the plasma levels of the four hormones were similar to the baseline levels on day 0. When IFN-alpha 2 was given on day 28, there were no significant differences in the release of ACTH (135% of control, p = 0.4) or cortisol (124% of control, p = 0.5) in comparison to day 27. These findings indicate that IFN-alpha 2 stimulation of hormone release is restricted to specific hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-alpha-2-induced stimulation of ACTH and cortisol secretion in man

Short-term effects of interferon-alpha 2 on plasma concentrations of adrenocorticotrophic hormone (ACTH) and cortisol were measured in man in relation to interferon absorption. Interferon-alpha 2 was given subcutaneously at a dose of 3 x 10(6) IU at 17.00 h to 2 female and 5 male patients who suffered from chronic hepatitis B infection and who had not previously been treated with interferon. Plasma levels of ACTH, cortisol and interferon-alpha were determined at 30-min intervals between 16.00 and 24.00 h. In each patient a similar cortisol, ACTH and interferon-alpha profile was determined on a day, when no interferon-alpha treatment was given. Interferon-alpha plasma levels peaked around 21.30 h, i.e. 4.7 h after injection. In each patient ACTH and cortisol levels were increased. As calculated from the areas under the curves, ACTH release was increased by an average of 332% (maxima at about 22.00 h, i.e. 5.2 h post injection); cortisol release was increased by an average of 311% (maxima at about 23.00 h, 5.8 h post injection). These actions were not related to side effects like fever or other flu-like symptoms. Our findings confirm that in man as in animals interferon-alpha 2 can act as a mediator between the immune and endocrine system.