Sesquiterpene lactone from Wunderlichia crulsiana inhibits the respiratory burst of leukocytes triggered by distinct biochemical pathways

The sesquiterpene lactone tubiferin was chemically purified from the brazilian native plant Wunderlichia crulsiana and identified by NMR and GC/MS data. Its ability to inhibit the respiratory burst of peritoneal inflammatory polymorphonuclear leukocytes (PMN) stimulated upon addition of phorbol miristate acetate (PMA), opsonized zymosan (OZ), and N-formyl-methionyl-leucyl-phenylalanine (fMLP) was evaluated. The tubiferin inhibition was more pronounced when PMN were stimulated through the protein kinase C pathway (PMA) compared to the alternative complement pathway (OZ). The inhibition when PMN were triggered by a chemoattractant stimulus (fMLP) was similar to that achieved with OZ-stimulated phagocytes. Tubiferin showed dose-dependent effects on the PMN respiratory burst triggered by the three different substances, and also decreased substantially the carrageenan-induced mice paw edema.

Chemical composition and antifungal activity of the essential oil of Origanum virens on Candida species

The composition and the antifungal activity of the essential oil of Origanum virens on Candida species were studied. The essential oil was obtained from the aerial parts of the plant by hydrodistillation and analyzed by GC and GC-MS. The oil was characterized by its high content of carvacrol (68.1 %) and its biogenetic precursors, gamma-terpinene (9.9 %) and p-cymene (4.5 %). The minimal inhibitory concentration (MIC) and the minimal lethal concentration (MLC) were used to evaluate the antifungal activity against Candida strains (7 clinical isolates and 3 ATCC type strains). The inhibition of germ tube formation and flow cytometry, using the fluorescent probe propidium iodide (PI), were used to evaluate their mechanisms of action. MIC and MLC values were similar for most tested strains, ranging from 0.16 to 0.32 microL/mL. Concentrations lower than MIC values strongly prevent germ tube formation. The fungicidal effect is primarily due to an extensive lesion of the membrane.

A novel biweekly pancreatic cancer treatment schedule with gemcitabine, 5-fluorouracil and folinic acid

Pancreatic adenocarcinoma is a common disease considered to be poorly responsive to antiblastic treatment. Recent clinical and preclinical results suggest that a combined treatment of gemcitabine (GEM), 5-flurouracil (5-FU) and folinic acid (FA) offers a clinical benefit in patients with advanced pancreas adenocarcinoma. The aim of this phase II clinical trial was to evaluate the antitumour activity and toxicity of a novel biweekly schedule of this combination in patients with pancreatic adenocarcinoma. A total of 42 patients received a 30 min infusion of FA (100 mg m(-2)) and 5-FU (400 mg m(-2)) (FUFA) on days 1-3, and GEM 1000 mg m(-2) on day 1 every 15 days. We observed 13 objective responses (two complete, 11 partial) and 23 stable diseases. The median time to progression was 9.75 months (95% Confidence Interval (CI), 6.88-12.62) and the median overall survival was 13.10 months (95% CI 9.64-16.56). There were seven cases of each grade III gastroenteric and haematological toxicity. The GEM plus FUFA combination appears to be well tolerated and very active in patients with pancreatic carcinoma.

Gemcitabine increases systemic 5-fluorouracil exposure in advanced cancer patients

A number of recent clinical trials testing the combination of 5-fluorouracil (5-FU) and gemcitabine in patients with advanced pancreatic adenocarcinoma have shown a significant clinical response rate, but also significant toxicity. As the two antimetabolites may interact at several biochemical levels along their pathways of activation, we investigated whether gemcitabine (GEM) affects 5-FU pharmacokinetics in cancer patients. Thus, we compared 5-FU pharmacokinetics in two groups of patients with various cancers who received the same schedule of 5-FU and folinic acid (FUFA), with or without GEM. There was a significant increase in systemic (5-FU) exposure and toxicity in the FUFA plus GEM group. Our finding may be useful in designing future studies of the combination in order to reduce the occurrence of side-effects and to maximise the antitumour activity.

PCB-induced oxidative stress in the unicellular marine dinoflagellate Lingulodinium polyedrum

The susceptibility of the dinoflagellate Lingulodinium polyedrum to Arochlor 1254, a commercial mixture of polychlorinated biphenyl (PCB) congeners was examined through toxicity bioassays based on cell survival and measures of oxidative balance and adaptive response to PCB stress. The highest Arochlor 1254 concentration that did not cause observed effects (NOEC) on cell growth was 100 (48 h) and 25 ppb (96 h). The concentration that caused maximum effect (MEC) was 300 ppb (48 h) and 250 ppb (microl L(-1)) (96 h). The concentrations that promoted 50% cell death (LC50) were 146 and 122 ppb after 48 and 96 h, respectively. The cell numbers were lower after 96 h of exposure than after 48 h, suggesting that neither recovery nor growth occurred. Under exposure to 120 ppb Arochlor 1254 for 48 h the oxidative damage in proteins was 121% higher than the control, as measured by reactive carbonyl levels, but no oxidative damage was found in lipids measured as malondialdehyde contents. Total superoxide dismutase (SOD) activity increased to plateau levels 146% greater than control values. The cells also exhibited increased ascorbate peroxidase (APx) activity (50%) and peridinin content (27%). No changes were observed in beta-carotene under these experimental conditions. Therefore, SOD and APx induction and increased peridinin content may be principal primary adaptive responses to an increase of reactive oxygen species in Arochlor 1254 stress as indicated by protein oxidative damage and are an early marker of Arochlor 1254 contamination.

Density-dependent patterns of thiamine and pigment production in the diatom Nitzschia microcephala

In the present study we investigate how intraspecific (density-dependent) competition for nutrients by the diatom Nitzschia microcephala affects the level of oxidative stress in the algal cells as well as their production of pigments and thiamine. N. microcephala was grown in three different densities until the stationary growth phase was reached. Throughout the experiment, growth rate was negatively related to cell density. Superoxide dismutase activity, protein thiol, and diatoxanthin concentrations indicated increasing oxidative stress with increasing cell density, which was most probably caused by nutrient depletion of the medium. Pigment contents per cell (except for diatoxanthin) decreased with increasing cell density. N. microcephala was able to synthesize thiamine and its thiamine content per cell increased in concert with cell density. In comparison, the dinoflagellate Amphidinium carterae was unable to synthesize thiamine. These results suggest that cells of N. microcephala subjected to higher competition and lower growth rates have a lower carotenoid content and a higher thiamine content. If such responses would occur in nature as well, eutrophication (higher cell densities) may alter the quality of microalgae as food items for higher trophic levels not only by species shifts in the phytoplankton, but also by changes in the cellular nutritional value within species.

Alcohol and withdrawal: from animal research to clinical issues

The withdrawal syndrome in alcohol-dependent patients appears to be a major stressful event whose intensity increases with repetition of detoxifications according to a kindling process. Disturbances in the balance between excitatory and inhibitory neural processes are reflected in a perturbed physical state while disturbances in the balance between positive and negative reinforcements are reflected in a perturbed mood state. Our purpose is to link the different behavioral outcomes occurring during withdrawal with specific biological brain mechanisms from the animal to the human being. Better understanding of the various biological mechanisms underlying withdrawal from alcohol will be the key to design and to apply appropriate pharmaceutical management, together with appropriate therapy aimed at inducing protracted abstinence.

Catechols from abietic acid synthesis and evaluation as bioactive compounds

Catechols from abietic acid were prepared by a short and good yielding chemical process and further evaluated for several biological activities namely, antifungal, antitumoral, antimutagenic, antiviral, antiproliferative and inhibition of nitric oxide. Their properties were compared with those of carnosic acid (6), a naturally occurring catechol with an abietane skeleton and known to possess potent antioxidant activity, as well as anticancer and antiviral properties. From all the synthetic catechols tested compound 2 showed the best activities, stronger than carnosic acid.

Mismatch negativity is not correlated with neuroendocrine indicators of catecholaminergic activity in healthy subjects

The identification of the brain structures and neurotransmitters responsible for the generation and/or modulation of the mismatch negativity (MMN) may contribute to a clearer understanding of its functional significance, and may have clinical implications. In this context, some findings suggest that the scalp-recorded MMN reflects activity from multiple neuronal ensembles within or in the immediate vicinity of the primary auditory cortex and with possible contribution from the frontal cortex. However, few data are available concerning the influence of neurotransmitter systems on the MMN. In this study, the relationship between both noradrenergic and dopaminergic systems and the MMN were investigated in 34 healthy volunteers. Noradrenergic and dopaminergic activities were assessed with the apomorphine and clonidine challenge tests. The results showed no significant relationship between either growth hormone (GH) responses to apomorphine or clonidine and the MMN amplitude or latency. Therefore, this study does not demonstrate the implication of dopaminergic and noradrenergic activities as assessed by GH response to apomorphine and clonidine for the generation and/or the modulation of the MMN. However, given the complexity of the central neurotransmitter systems, these results cannot be considered as definitive evidence against a relationship between dopaminergic and noradrenergic activity and the MMN.

The response of macrophages to particles of resorbable polymers and their degradation products

Alpha polyesters such as poly(L-lactide) and poly(glycolide) are biodegradable materials used in fracture fixation and they need to be assessed for problems associated with their degradation products. This study has compared cell responses to low molecular weight poly(L-lactide) particles, lactate monomer, poly(glycolide) particles and glycolic acid at cytotoxic and sub-cytotoxic concentrations. Murine macrophages were cultured in vitro and the release of lactate dehydrogenase (LDH), prostaglandin E(2) (PGE(2) and interleukin-1 alpha IL-1alpha was measured following the addition of particles or monomer. Experiments revealed that both the poly(L-lactide) and poly(glycolide) particles gave rise to dose dependent increases in LDH release and an increase in IL-1alpha and PGE(2) release. Comparisons of the poly(L-lactide) particles to the poly(glycolide) particles did not reveal any differences in their stimulation of LDH, IL-1alpha and PGE(2) release. The lactate and glycolate monomers did not increase PGE(2) or IL-1alpha release above control levels. There was no difference in biocompatibility between the poly(L-lactide) and poly(glycolide) degradation products both in particulate and monomeric form.

Venlafaxine: the relationship between dose, plasma concentration and clinical response in depressive patients

The relationship between plasma drug level of venlafaxine and daily intake was studied in 89 major depressive inpatients. In addition, changes over time in severity were assessed weekly in a subgroup of 22 depressed patients using the Montgomery and Asberg Depression Rating Scale (MADRS) and the Clinical Global Impression improvement scale. The results indicate a moderate correlation between daily doses and plasma concentrations, together with a higher relationship between improvement on the MADRS scale and concentration. Moreover, plasma concentrations (for venlafaxine and its predominant metabolite, O-desmethylvenlafaxine) up to 400 microg/l can be considered as effective, as already suggested in a previous study. No case of venlafaxine discontinuation occurred during the longitudinal study, and the incidence of adverse event, as estimated by the Target Emergent Symptoms and Side-effects scale, was low, suggesting that the drug is well tolerated for such plasma concentrations.

Neuroendocrine evaluation of 5-HT1A function in male alcoholic patients

BACKGROUND

Preclinical evidences support the hypothesis of a serotonergic dysfunction in alcohol preference. In human, studies have demonstrated a serotonergic hypoactivity in alcoholism. However, little is known about the role of 5-HT1A receptors.

METHODS

We assessed the hormonal (prolactin and cortisol) responses to flesinoxan (a highly potent and selective 5-HT1A agonist) in 12 male inpatients meeting DSM-IV criteria for alcohol dependence, 3 weeks after the last reported use of alcohol and antidepressants. These patients were compared to 10 male controls.

RESULTS

There was a highly significant difference between alcoholic patients and controls for the area under the curve relative (AUCr) values of prolactin responses. AUCr values of cortisol responses to flesinoxan showed a trend towards lower values in alcoholics compared to controls.

CONCLUSION

These results support the implication of the serotonergic system, and particularly a decreased sensitivity of post-synaptic 5-HT1A receptors, in alcoholism.

5-HT1A dysfunction in borderline personality disorder

BACKGROUND

A number of challenge studies have reported abnormalities of serotonergic function in borderline personality disorder (BPD). There are, however, problems with the pharmacological probes used in these studies since fenfluramine and m-CPP are not only serotonergic agents but also induce release of catecholamines, particularly dopamine. Therefore, we tested whether subjects with BPD showed a blunted prolactin (PRL) response to flesinoxan, a highly potent and selective 5-HT1A agonist.

METHODS

Flesinoxan challenge test was carried out in 20 BPD in-patients and 20 healthy controls matched for gender but not for age. Since 16 BPD in-patients exhibited major depressive co-morbidity, a group of 20 depressed in-patients matched for gender but not for age was also included.

RESULTS

BPD in-patients exhibited blunted PRL responses as compared to controls, whereas depressed in-patients did not differ from controls. Moreover, PRL responses were lower among BPD in-patients than among depressed in-patients. Among the BPD in-patients, PRL responses to flesinoxan were lower in patients with past history of suicide attempts (N = 8) than in those with a negative history.

CONCLUSIONS

The results show major involvement of serotonergic function in BPD and are consistent with previous studies linking lower serotonergic activity with impulsivity. More particularly, our data suggest that BPD is characterized by lower 5-HT1A receptor sensitivity. Moreover, the data support the involvement of 5-HT1A activity in suicidal behaviour. However, this conclusion is limited because other hormonal responses such as ACTH and cortisol were not assessed, and because BPD was assessed by a self-report questionnaire and not a structured clinical interview.

Changes in superoxide dismutase activity and photosynthetic pigment content during growth of marine phytoplankters in batch-cultures

The ability of phytoplankton to cope with oxidative stress is one of the main factors that influence its survival in the marine environment, when senescence conditions prevail. In a first attempt to investigate the antioxidant strategies of different phytoplanktonic groups face to oxidative stress, the superoxide dismutase (SOD; EC 1.15.1.1) activity and photosynthetic pigment content along the growth curves of the dinoflagellate Lingulodinium polyedrum (Stein) Dodge, the prasinophycean Tetraselmis gracilis (Kylin) Butcher and the diatom Minutocellus polymorphus (Hargraves and Guillard) Hasle, von Stosch and Syvertsen were evaluated in batch-cultures. Total SOD activity was determined by an indirect method involving the inhibition of cytochrome c reduction. The contents of photosynthetic pigments were analysed by HPLC using a reverse phase column (RP-18), based on a ternary gradient. A peak of total SOD activity was detected at the beginning of the T. gracilis and M. polymorphus exponential growth. In L. polyedrum and M. polymorphus, SOD activity increased approximately three times by day 17 of growth, compared to the values obtained on day 3 (exponential phase) of the growth curve. All three species of microalgae had reduced SOD activity at the end of their growth. The levels of peridinin in L. polyedrum increased about 60% by day 17 of growth compared to the values obtained at exponential phase. Tetraselmis gracilis exhibited a remarkable increase (approximately 85%) in beta-carotene concentration after 10-14 days of growth whereas the beta-carotene levels in M. polymorphus decreased about 85% along its growth curve. These findings suggest that the antioxidant response during senescence in batch-cultures differ according to the species. Induction of SOD activity may occur either in the early exponential or stationary growth phases, which is important to prevent oxidative stress triggered by a number of factors that affects growth, such as nutrient and light availability.

Simultaneous detection of thiamine and its phosphate esters from microalgae by HPLC

We present an easy and sensitive method for measuring thiamine and its phosphate esters in small biological samples of microalgae (Amphidinium carterae Hulburt and Nitzschia microcephala Grun). The method consists of extraction of thiamine and its derivatives in acid solution, followed by liquid chromatography with fluorescence detection. The detection limit is as low as 15 fmol of thiamine. For comparison to microalgae, the method has been applied to evaluate thiamine levels in the crustacean Artemia salina Leach and is suitable for nutritional studies of the food web of the Baltic salmon, which suffers from thiamine deficiency. This method of HPLC analysis can be readily utilized to follow uptake and interconversion of thiamine and its phosphate esters in many micro- and macroalgae.

Preoperative positivity of serum tumor markers is a strong predictor of hematogenous recurrence of gastric cancer

BACKGROUND AND OBJECTIVES

Preoperative positivity of serum tumor markers has been reported to be a prognostic factor in several neoplasms. The aim of this longitudinal study was to evaluate the correlation between CEA, CA 19-9, and CA 72-4 preoperative serum levels and the site of recurrence after curative surgery for gastric cancer.

METHODS

One hundred sixty-seven patients resected for primary gastric cancer between January 1988 and June 1996 were considered. All patients were followed-up according to the same protocol, with a mean follow-up time of 45 +/- 39 months (range: 2-130). The correlation between marker positivity and the incidence of recurrence was studied by means of univariate and multivariate analyses.

RESULTS

A tumor recurrence was found in 92 patients (55.1%). For each of the three markers, preoperative positivity was related to a higher incidence of hematogenous recurrences with respect to negative cases; univariate analysis also revealed a higher incidence of locoregional recurrences in CA 72-4-positive cases. At multivariate analysis, preoperative positivity for one or more tumor markers proved to be an independent predictor of hematogenous recurrences (P < 0.005, relative risk [RR] 4.82), in addition to lymph node involvement (P < 0.05, RR 3.82); no correlation between marker positivity and the onset of locoregional or peritoneal recurrences was found.

CONCLUSIONS

Preoperative positivity for CEA, CA 19-9 or CA 72-4 is an independent risk factor for hematogenous recurrences of gastric carcinoma; this aspect should be considered in the option of using adjuvant chemotherapy after surgery for gastric cancer.

Differential activation by daphnetoxin and mezerein of PKC-isotypes alpha, beta I, delta and zeta

Daphnetoxin, a mezerein derivative, was isolated from the stem bark of Daphne gnidium. Mezerein is a PKC activator that exhibits antileukemic properties. However, daphnetoxin and its analogue 12-hydroxydaphnetoxin were described as being devoid of this effect. In the present study daphnetoxin and mezerein were compared as PKC activators on classical (alpha and beta I), novel (delta) and atypical (zeta) isoforms, using an alternative in vivo yeast phenotypic assay. The aim was to clarify if daphnetoxin is a PKC activator and if the differences between the antiproliferative effect of mezerein and of its analogue daphnetoxin may be ascribed to differences on their potency or selectivity as PKC activators. Yeast samples expressing each of the mammalian PKC isoforms tested were incubated with daphnetoxin or mezerein. Growth inhibition caused by these drugs was assumed to be due to PKC activation since it did not occur when expression was not induced. Mezerein inhibited the growth of yeast expressing PKC alpha (IC(50) = 1190 +/- 237 nM; n = 20), PKC beta I (IC(50) = 908 +/- 46 nM; n = 20), and PKC delta (IC(50) = 141 +/- 25 nM; n = 20) but not of yeast expressing PKC zeta. Daphnetoxin also inhibited the growth of yeast expressing isoforms alpha, beta I and delta, being more potent than mezerein on PKC alpha (IC(50) = 536 +/- 183 nM; n = 20; P < 0.05), as potent as mezerein on PKC beta I (IC(50) = 902 +/- 129 nM; n = 20) and less potent than mezerein upon PKC delta (IC(50) = 3370 +/- 492 nM; n = 20; P < 0.05). These results show that daphnetoxin is a potent PKC activator but with a selectivity different from that of mezerein. It is suggested that the lack of antileukemic and antiproliferative effects of daphnetoxin may be due to its lower potency to activate PKC delta.

Astaxanthin and peridinin inhibit oxidative damage in Fe(2+)-loaded liposomes: scavenging oxyradicals or changing membrane permeability?

Astaxanthin and peridinin, two typical carotenoids of marine microalgae, and lycopene were incorporated in phosphatidylcholine multilamellar liposomes and tested as inhibitors of lipid oxidation. Contrarily to peridinin results, astaxanthin strongly reduced lipid damage when the lipoperoxidation promoters-H(2)O(2), tert-butyl hydroperoxide (t-ButOOH) or ascorbate-and Fe(2+):EDTA were added simultaneously to the liposomes. In order to check if the antioxidant activity of carotenoids was also related to their effect on membrane permeability, the peroxidation processes were initiated by adding the promoters to Fe(2+)-loaded liposomes (encapsulated in the inner aqueous solution). Despite that the rigidifying effect of carotenoids in membranes was not directly measured here, peridinin probably has decreased membrane permeability to initiators (t-ButOOH > ascorbate > H(2)O(2)) since its incorporation limited oxidative damage on iron-liposomes. On the other hand, the antioxidant activity of astaxanthin in iron-containing vesicles might be derived from its known rigidifying effect and the inherent scavenging ability.

Alpha-2-adrenoreceptors in depressed suicide attempters: relationship with medical lethality of the attempt

Several lines of evidence tend to suggest a role for noradrenaline, and more specifically alpha-2-adrenoreceptors, in the biology of suicidal behavior. The purpose of this study was to assess the growth hormone (GH) response to clonidine, an alpha-2-adrenergic agonist, in majorly depressed inpatients with a history of highly lethal suicide attempt compared to depressed patients with a history of low lethal suicide attempt and nonattempters. Our sample included 20 male depressed inpatients with a history of suicide attempt compared to 20 male depressed nonattempters. We did not observe any significant difference between suicide attempters and nonattempters for GH peak values (2.4 +/- 2.9 vs. 4.1 +/- 3.7 ng/ml; F = 2.52, d.f. = 1, 38, p = 0.12). Moreover, GH peak responses to clonidine were not related to the degree of lethality of the attempt. The results of the present study do not support a major role for noradrenaline in the biology of suicidal behavior.

Reduced dopamine function in depressed patients is related to suicidal behavior but not its lethality

Several lines of evidence suggest a role for dopamine in the control of suicidal behaviour. Previously, we suggested an involvement of D2-dopaminergic function in the biology of suicide by demonstrating a smaller growth hormone (GH) response to apomorphine, a dopaminergic agonist, in depressed patients who later died by suicide. The purpose of the present study was to assess GH response to apomorphine in major depressed in-patients with a history of highly lethal suicide attempt compared to depressed patients with a low lethal lifetime suicide attempt history and non-attempters. The study was performed in a sample of 26 male depressed in-patients with a history of suicide attempt compared to 26 male depressed non-attempters. We observed a significant difference between suicide attempters and non-attempters (for GH peak, 6.3+/-5.1 ng/ml vs 15.8+/-14.2 ng/ml, F=10.3, df=1, 50, P=0.002). Moreover, GH peak responses to apomorphine did not differ between depressed patients with a high lethal lifetime suicide attempt history and patients who made low lethal lifetime suicide attempt. In conclusion, the results of the present study support a role for dopamine in the biology of suicidal behaviour. More specifically, an impaired GH response to apomorphine could be a marker of suicide risk.

[Ultra-fast opiate detoxification under general anesthesia: preliminary results of the Liege protocol]

Many studies support the hypothesis of a substantial benefit in inducing an Opiate Receptor Blockade through a Rapid Opiate Detoxification under general Anaesthesia (RODA) in opiate dependent patients. However, prospective studies and long term evaluation of the technique are lacking. In order to evaluate long-term abstinence rates after a RODA among a sample of opiate addicts, a study was started in March 1999 at the University of Liège. To date, 45 patients were evaluated (mean age: 29 +/- 5 years) with a mean opiate dependence duration of 8 +/- 4 years. Most of them were both heroin and methadone dependent; 42.2% of them were included while 31.1% did not complete the whole inclusion procedure and 26.7% were excluded. None experienced severe withdrawal symptoms. At six months, abstinence rate was 67% and 46% at one year. These preliminary results suggest the interest of the procedure in carefully selected patients.

[Malignant localized fibrous tumor of the pleura]

The authors report a case of a localized fibrous tumour of the pleura with huge proportions of 26 x 14 x 12 cm and 1.25 Kgr of weight, in a 56 year old female patient. The tumour occupied practically the inferior 2/3 of the right pulmonary field and had an unusual insertion in the diaphragmatic parietal pleura. It was non pediculous and had histological features of malignancy. The diagnosis of localized fibrous tumour of the pleura was achieved through observation of the sample obtained by fine needle aspiration. The immunohistochemical study subsequently done on the surgical specimen, confirmed the previous diagnosis. The evaluation of malignancy was based ou the following histological criteria: high cellularity, cellular pleomorphism, mitotic activity (more than four mitotic figures per 10 high power fields), hemorrhagic areas and necrosis.

Reduced dopaminergic activity in depressed suicides

Several data are available about the implication of the dopaminergic system in the control of inward-directed aggression. Previously, we suggested an involvement of D2-dopaminergic function in the expression of suicidal behavior by demonstrating a smaller growth hormone (GH) response to apomorphine, a dopaminergic agonist, in depressed patients with a history of suicide attempts in comparison to nonattempters. In the present study, the purpose was to analyze GH responses to apomorphine in depressive patients who later died by suicide. Our sample comprised eight male depressive inpatients who died by suicide within one year after hospitalisation. These patients were compared to 18 male major depressed inpatients who never attempted suicide. Mean GH peak responses to apomorphine differed significantly between suicide completers and controls (mean +/- SD): for GH peak, 7.6 +/- 4.1 ng/ml vs 18.9 +/- 14.2 ng/ml, U = 30, Z = -2.33, P = 0.02. Our results tend to confirm the role of dopamine in the biology of suicide in depression.

Antioxidant modulation in response to metal-induced oxidative stress in algal chloroplasts

To investigate adaptive responses to metal stress at the subcellular level, the oxidative balance in isolated chloroplasts was evaluated for the first time in the unicellular alga Gonyaulax polyedra exposed to the toxic metals Hg(2+), Cd(2+), Pb(2+), and Cu(2+). Different antioxidant responses were verified according to the metal and model of stress applied. Cells chronically exposed to metals exhibited high activity of the antioxidant enzymes superoxide dismutase and ascorbate peroxidase, high glutathione content, and decrease of peridinin levels, whereas no significant changes were detected for beta-carotene levels. In contrast, cells subjected to acute metal stress displayed twice as much beta-carotene but only a slight increase in superoxide dismutase and ascorbate peroxidase activities. The correlation of acute metal treatment and oxidative stress was inferred from the higher oxygen uptake and decreased reduced glutathione pool found in treated cells. In addition, increased oxidative damage to proteins and lipids occurred mainly in cells under acute stress. Pb(2+) was the most damaging toxicant, causing protein oxidation and lipid peroxidation even at chronic treatment. These results indicate that heavy metals are able to induce oxidative stress in chloroplasts of G. polyedra, particularly under acute conditions. Nevertheless, the maintenance of a high antioxidant capacity within chloroplasts seems to be an important strategy during acclimation of G. polyedra to chronic metal stress. By acting at the subcellular site, where oxidative stress is triggered, induction of such chloroplast antioxidants might be crucial for cell survival during exposure to heavy metals.