Contrasted resistance and resilience of two mangrove forests after exposure to long-term and short-term anthropic disturbances.

Mangroves, coastal forests under the influence of tides, are known to be very resilient when they face natural disturbances such as storms or tsunami. While they provide several ecological services, they are threatened by many anthropic pressures. The aim of this study was to assess and to compare the stability of two mangrove fringes defined by contrasted set of natural constraints and exposed to pretreated domestic wastewaters discharges. The in situ experimental system set up in Mayotte Island (Indian Ocean) allowed us to determine both the short-term (2 years) and the long-term (9 years) resistance and the resilience. We focused on vegetation and crabs, an essential component of mangroves fauna. Wastewater discharges induced increases in tree coverage, leaves productivity and pigment content, and a decrease in crab diversity and density. Within 2 years after the release of the disturbance, several parameters reach back control values indicating fast resilience. Our results notably emphasized the high stability of the mangrove fringe dominated by Rhizophora mucronata trees, which was both more resistant and more resilient. This makes this fringe more suitable for application purposes, such as outfall for domestic wastewaters treatment plants.

Limited impact of several years of pretreated wastewater discharge on fauna and vegetation in a mangrove ecosystem.

It was hypothesized that mangroves, tropical wetlands, could be used for the finishing treatment of domestic wastewaters. Our aim was to determine if a nutrient-stressed mangrove could tolerate long-term discharges of pretreated wastewater (PW). Since 2008, in an in situ experimental system set up in Mayotte Island (Indian Ocean), domestic PW are discharged into two impacted areas (675 m2) dominated by different species of mangrove trees. Anthropogenic inputs during > 4.5 years led to an increase in vegetation growth associated with an increase in leaf pigment content, leaf surface and tree productivity. A marked increase in tree mortality was observed. There was no effect on crabs and meiofauna densities, but significant modifications of community structures. These effects may be directly linked to PW inputs, or indirectly to the modifications of the environment associated with higher tree growth. However, our results indicate that there was no major dysfunction the ecosystem.

Effects of the angiotensin I converting enzyme inhibitor perindopril on cerebral blood flow in awake hypertensive rats.

As chronic hypertension shifts the lower limit of cerebral blood flow (CBF) autoregulation to higher pressure levels, we studied the effects of the angiotensin converting enzyme (ACE) inhibitor, perindopril on mean arterial pressure (mean BP), basal CBF, and CBF autoregulation in awake renovascular hypertensive (2 kidneys, 1 clip model) and spontaneously hypertensive rats (SHR). Blood pressure was measured via a chronically implanted arterial cannula and CBF by hydrogen clearance. Chronic renovascular hypertension, like spontaneous hypertension, caused a marked shift in the lower limit of CBF autoregulation but did not alter basal CBF. In SHR, acute administration of perindopril did not diminish CBF in spite of the fact that BP fell to a level below the lower limit of CBF autoregulation (determined by hypotensive hemorrhage). Chronic treatment of renovascular hypertensive rats with perindopril normalized BP and restored CBF autoregulation.

Differences between the in vitro vasoconstrictor responses of the tail artery to potassium and norepinephrine between spontaneously hypertensive, renovascular hypertensive, and various strains of normotensive rats.

Isolated tail arteries removed from spontaneously hypertensive, renovascular hypertensive, or various strains of normotensive rats were perfused/superfused with norepinephrine or potassium, or subjected to electrical field stimulation. Responses in spontaneously hypertensive and outbred normotensive rat tail artery preparations were similar. Tail artery segments from renovascular hypertensive or normotensive rats of the inbred Wistar-Kyoto strain showed smaller responses to all three stimuli. Thus, in certain in vitro arterial preparations, the apparent increase in vascular reactivity observed when comparing spontaneously hypertensive rats with inbred Wistar-Kyoto rats may be due to a decrease in vascular reactivity in the Wistar-Kyoto rat strain.

Protective effects of antihypertensive treatment with isradipine on the consequences of cerebral ischaemia in the spontaneously hypertensive rat.

Brief bilateral carotid artery ligation in adult spontaneously hypertensive rats (SHR) induced locomotor hyperactivity and lesions of the CA1 region of the hippocampus but had no effect in Wistar normotensive rats. This result suggests that high blood pressure amplifies the consequences of cerebral ischaemia. Treatment for 7 weeks with the calcium entry-blocker isradipine (5 mg/kg per day, subcutaneously) normalized blood pressure and attenuated the behavioural and histological consequences of cerebral ischaemia. Chronic treatment with hydralazine (25 mg/kg per day, subcutaneously) also normalized blood pressure but afforded no protection against the consequences of cerebral ischaemia. This suggests that the protective effect of antihypertensive treatment depends not only on the blood pressure-lowering action but may also be linked to the mechanism of action of the drug used.

[Tolerability of tianeptine in 170 patients with depression treated during one year]. / Acceptabilité de la tianeptine chez 170 patients déprimés traités un an.

Tianeptine, a new antidepressant, has a tricyclic molecular structure. Its main biochemical activity consists of an increase in the reuptake of 5 HT both in men and animals, after acute and chronic administration. Tianeptine demonstrated its antidepressive clinical efficacy in several double-blind versus reference drug trials. A multicentre open trial, including depressed patients enabled us to evaluate the safety of tianeptine and to control the maintenance of the therapeutic efficacy in the course of its long-term prescription. Depressed patients included showed a major depressive episode, single (296.22) or recurrent (296.32) without melancholia or psychotic features, or a dysthymic disorder (300.40), according to DSM III criteria. A minimum MADRS score of a least 25, and the informed consent of the patients were required. The dose of tianeptine was 3 tablets per day (12.5 mg/tablet) with the possibility of increasing to 4 or decreasing to 2 tablets per day, depending on the symptomatology. Therapeutic efficacy was evaluated by item 1 and 2 of the Global Clinical Impression (CGI), the Montgomery and Asberg Depression Rating Scale (MADRS), the Hamilton Anxiety Rating Scale (HARS) and the Hopkins Symptom Check-List (HSCL). Clinical and paraclinical safety were evaluated by CGI item 3, standardized ratings of patients' complaints (CHESS 84), interruption for side effects, evaluation of blood pressure, weight, biological parameters, EKGs. This intermediate evaluation concerns the first 170 depressed patients treated over a one-year period as well as the total group of patients included (n = 447).(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic treatment with the angiotensin I converting enzyme inhibitor, perindopril, restores the lower limit of autoregulation of cerebral blood flow in the awake renovascular hypertensive rat.

Chronic hypertension shifts the lower limit of cerebral blood flow autoregulation to a higher pressure level. Although acute administration of angiotensin converting enzyme inhibitors restores the lower limit of cerebral blood flow autoregulation the chronic effects have not received much attention. We studied the effect of the angiotensin converting enzyme inhibitor, perindopril, on mean arterial pressure, basal cerebral blood flow and cerebral blood flow autoregulation in renovascular hypertensive (two-kidney, one clip model) and normotensive male Wistar rats. Seven weeks after renal artery clipping or sham operation rats received daily intraperitoneal injections of perindopril. The dose was increased from 1 to 8 mg/kg over the first 4 weeks until blood pressure was normalized. Chronic renovascular hypertension caused a marked shift in the lower limit of cerebral blood flow autoregulation but did not alter basal cerebral blood flow. Treatment of hypertensive rats with perindopril normalized blood pressure and restored cerebral blood flow autoregulation. Chronic treatment of normotensive rats with perindopril increased basal cerebral blood flow. In conclusion, chronic treatment of renovascular hypertensive rats with perindopril causes a shift in the lower limit of cerebral blood flow autoregulation towards the value observed in normotensive rats.

Vascular calcium overload produced by administration of vitamin D3 and nicotine in rats. Changes in tissue calcium levels, blood pressure, and pressor responses to electrical stimulation or norepinephrine in vivo.

Increased calcium content of cardiovascular tissues is a phenomenon common to natural aging and various pathological conditions such as hypertension and arteriosclerosis. We investigated an accelerated cardiovascular calcium overload model in young rats produced by treatment with a single dose of vitamin D3 (300,000 IU/kg, i.m.) followed by up to 4 days of twice daily doses of nicotine (25 mg/kg, p.o.). Large increases in the calcium content of the aorta, kidneys, and myocardium but not in the liver or brain were seen. The magnesium content of these tissues was not modified. On the day following the last nicotine injection, there was marked cardiovascular calcium overloading, the aortic calcium level increasing by up to nine times that of controls. The animals had lower body weights, however, and there was a significant degree of mortality (up to 42%). Signs of kidney failure were evident; the blood urea level, for instance, was doubled. If rats were allowed 13 or 180 days to recover, they showed normal growth and kidney function; aortic calcium overload was still pronounced: 16- and 7-fold increases, respectively. Cardiovascular function in recovery animals was characterized by a doubling of pulse pressure. Dose-response curves following noradrenergic stimulation were shifted to the right after 13 (but not after 180) days recovery. Arterial norepinephrine content doubled. The chronic effects of hypervitaminosis D plus nicotine may produce a useful model for the study of the physiological and/or pharmacological consequences of calcium overload.

The quantification of brain lesions with an omega 3 site ligand: a critical analysis of animal models of cerebral ischaemia and neurodegeneration.

Previous investigations have indicated that the detection and quantification of omega 3 (peripheral type benzodiazepine) binding site densities that are associated with reactive astroglia and macrophages could be of widespread applicability in the localization and indirect assessment of neural tissue damage in the central nervous system. In the present study, we analyze the usefulness of this approach in a number of experimental models that are characterized by (or putatively involve) neuronal degeneration. One week after the systemic administration of the excitotoxin, kainate, a marked increase in omega 3 site densities (as assessed by [3H]PK 11195 binding) was noted, an increase that was most prominent in known regions of selective vulnerability (hippocampus and septum). However, the kainate-induced omega 3 site proliferation was not a function of the dose administered, a marked interstudy variation was observed, and the binding increase was prevented by the administration of the anticonvulsant, clonazepam. The densities of omega 3 sites were studied, by autoradiography (using [3H]PK 11195 or [3H]PK 14105 as ligands), in 4 groups of Fischer 344 rats aged 3, 12, 22 and 30 months. No age-related changes were noted except in the 30-month-old group in which discrete and focal increases (reflecting tumoral processes) were observed in various brain regions. In spontaneously hypertensive, stroke-prone rats, omega 3 binding increases were observed concomitant with the development of stroke-related neurological signs. With autoradiography, the omega 3 site increase was localized to focal increases in the boundary zones between major cerebral arteries (and corresponding to regions of ischaemic or haemorrhagic infarction). Focal cerebral ischaemia was studied in rats and mice. Subsequent to middle cerebral artery occlusion in normotensive (Wistar/Kyoto) and spontaneously hypertensive rats, the density of omega 3 sites in the ipsilateral hemisphere was markedly elevated, the increase being greater in the spontaneously hypertensive rats. The increases in omega 3 labelling in these two strains matched the absolute volumes of infarctions, determined previously. Middle cerebral artery occlusion in the mouse also increased hemispheric levels of omega 3 sites; the maximum values were obtained between 4 and 8 days following the induction of focal ischaemia. These results demonstrate the feasibility of using omega 3 sites as a marker of excitotoxic, ischaemic and proliferative damage in the rodent brain. Binding measurement in tissue homogenates is an economic and time-efficient approach, whereas the autoradiographic detection of omega 3 sites allows the localization of brain lesions with a macroscopic or microscopic level of anatomical resolution.(ABSTRACT TRUNCATED AT 400 WORDS)

Norepinephrine and serotonin increase the vasoconstrictor response of the perfused rat tail artery to changes in cytosolic Ca2+.

Vasoconstriction and changes in cytosolic free Ca2+ concentrations (fura 2 with dual wavelength excitation) were measured simultaneously in the perfused tail artery of the rat. Vasoconstrictors (norepinephrine and 5-HT) appear to modulate contraction not only by changing the cytosolic free Ca2+ concentration but also by modifying the sensitivity of the contractile proteins to Ca2+.

In vitro vasoconstriction induced by calcium in renovascular hypertensive or old rats.

We studied the changes in calcium-induced vasoconstriction in isolated tail arteries from young (2 months) and old (12 months) normotensive, and young renovascular hypertensive rats (3 months old, with unilateral renal artery clipping at 6 weeks), pretreated with reserpine. The tail artery was removed and perfused/superfused with either a high potassium Krebs depolarizing solution or Krebs solution plus phenylephrine. Concentration-response curves to calcium were produced. Old rats had a low plasma renin activity and their depolarized tail arteries showed a weak vasoconstrictor response to calcium. Renovascular hypertensive rats had a high mean blood pressure and plasma renin activity. Responses of their depolarized tail arteries to calcium were greater. Responses to calcium in tail arteries perfused with phenylephrine were similar in all groups. We conclude that age and renovascular hypertension produce opposite changes in vasoconstriction induced by calcium in depolarized tail arteries.

The angiotensin I converting enzyme inhibitors, captopril and Wy-44,655 attenuate the consequences of cerebral ischemia in renovascular hypertensive rats.

Global cerebral ischemia (four vessel model) was induced in renovascular hypertensive rats (two kidney, one clip model) chronically treated with intraperitoneal administration of angiotensin I converting enzyme inhibitors, either captopril (100 mg/kg per day) or Wy-44,655 (10 mg/kg per day). Mortality following cerebral ischemia was higher in renovascular hypertensive rats than in normotensive controls. Reduction of blood pressure with captopril or Wy-44,655, lowered mortality. In surviving renovascular hypertensive and normotensive rats cerebral ischemia induced hyperactivity and lesions of the CA1 area of the hippocampus. Prolonged treatment with captopril--but not with Wy-44,655--reduced hyperactivity and the extent of the CA1 lesions. In conclusion, hypertension increases mortality following cerebral ischemia but does not affect the extent of brain injury in survivors. Prior treatment with converting enzyme inhibitors lowers mortality. Treatment with captopril attenuates brain injury in survivors.

Chronic treatment with naftidrofuryl attenuates the development of vascular hypersensitivity to serotonin in the spontaneously hypertensive rat.

Three-month-old spontaneously hypertensive rats were treated for 1, 2, or 3 months with daily intraperitoneal injections of naftidrofuryl (30 mg/kg). Systolic arterial pressure was measured. Tail arteries were removed and perfused at a constant flow rate of 2 ml/min. A concentration-response curve for serotonin was prepared. A second curve was then constructed in the presence of naftidrofuryl. Chronic treatment with naftidrofuryl had no effect on blood pressure but produced a decrease in the maximal vasoconstrictor response and the sensitivity to serotonin in vitro. The in vitro sensitivity to naftidrofuryl was unchanged. These studies suggest that chronic treatment with a dose of naftidrofuryl that does not modify blood pressure attenuates the in vitro vascular sensitivity to serotonin.

Electrically induced arterial thrombosis model in the conscious rat.

Thrombus formation was electrically induced in the left common carotid artery of rats with preoccluded both vertebral and right carotid arteries. Following thrombus induction, animals became unresponsive and lost their righting reflex. The loss of righting reflex was observed when cortical tissular pO2 reached 55 +/- 9% of its initial value. A similar decrease in pO2 was induced by mechanical occlusion of the left carotid artery. The delay between discontinuation of current and the loss of righting reflex was measured to indirectly evaluate occlusive thrombus formation. The capacity of various antithrombotic agents to delay the righting reflex loss was studied. Heparin, ticlopidine and the thromboxane-endoperoxides receptor blocker, BM 13177, exerted a significant activity, whereas acetylsalicylic acid and the thromboxane synthetase inhibitors, OKY O46 and dazmegrel, were inefficient.

Model of global forebrain ischemia in the unanesthetized rat.

Global forebrain ischemia was induced in unanesthetized rats by electrocauterization of the vertebral arteries and transient occlusion of the common carotid arteries for 30 minutes. Local cerebral blood flow (l-CBF), cortical tissular pO2 (tpO2), electrocorticogram (ECoG), mean arterial pressure, pH and blood gas determinations and neurologic deficit were evaluated during and after ischemia. Cerebral ischemia induced a substantial decrease in l-CBF and tpO2 and the ECoG was flattened. One hour after ischemia, the neurologic deficit was at its maximum, l-CBF was still decreased and ECoG depressed. Twenty-four hours later, the neurologic deficit was still present but ECoG, l-CBF and tpO2 had returned to their preischemic values. Treatments with naloxone were performed during, after or during and after ischemia. When naloxone was administered during or after ischemia, postischemic neurologic deficit was not influenced by the treatment. A slight but significant improvement of the neurologic score was observed when naloxone was injected during ischemia and infused thereafter. Our results show that this experimental model of cerebral ischemia is suitable for quantification of neurologic alterations during the postischemic period. The slight improvement observed with naloxone suggests that endogenous opioids may have a minor role in the neurologic consequences of ischemia.

Effect of indomethacin on the coupling of cerebral blood flow to brain metabolism.

The effect of indomethacin (10 mg.kg-1 i.p.) on frontal cerebral blood flow has been investigated in male Sprague Dawley rats using the hydrogen clearance technique. Indomethacin elicited a marked reduction in cerebral blood flow in awake free-moving animals. The response to indomethacin was prevented by pretreatment with pentobarbital (50 mg X kg-1, i.p.). On the other hand, indomethacin was able to antagonize the cerebral vasodilation due to apomorphine chlorhydrate (2 mg X kg-1, i.p.), dexamphetamine tartrate (3 mg X kg-1, i.p.) or immobilization stress. Taken together, the above results lead to the suggestion that indomethacin can suppress the coupling of cerebral blood flow to brain metabolism. Further investigations are needed to ascertain whether this uncoupling influence is related to brain cyclooxygenase inhibition.