Superexchange coupling and slow magnetic relaxation in a transuranium polymetallic complex.

{Np(VI)O2Cl2}{Np(V)O2Cl(thf)3}2 is the first studied example of a polymetallic transuranic complex displaying both slow relaxation of the magnetization and effective superexchange interactions between 5f centers. The coupling constant for Np(V)-Np(VI) pairs is 10.8 K, more than 1 order of magnitude larger than the common values found for rare-earth ions in similar environments. The dynamic magnetic behavior displays slow relaxation of magnetization of molecular origin with an energy barrier of 140 K, which is nearly twice the size of the highest barrier found in polymetallic clusters of the d block. Our observations also suggest that future actinide-based molecular magnets will have very different behavior to lanthanide-based clusters.

Co-variation between the intensity of behavioural manipulation and parasite development time in an acanthocephalan-amphipod system.

Pomphorhynchus laevis, a fish acanthocephalan parasite, manipulates the behaviour of its gammarid intermediate host to increase its trophic transmission to the definitive host. However, the intensity of behavioural manipulation is variable between individual gammarids and between parasite populations. To elucidate causes of this variability, we compared the level of phototaxis alteration induced by different parasite sibships from one population, using experimental infections of Gammarus pulex by P. laevis. We used a naive gammarid population, and we carried out our experiments in two steps, during spring and winter. Moreover, we also investigated co-variation between phototaxis (at different stages of infection, 'young' and 'old cystacanth stage') and two other fitness-related traits, infectivity and development time. Three main parameters could explain the parasite intra-population variation in behavioural manipulation. The genetic variation, suggested by the differences between parasite families, was lower than the variation owing to an (unidentified) environmental factor. Moreover, a correlation was found between development rate and the intensity of behavioural change, the fastest growing parasites being unable to induce rapid phototaxis reversal. This suggests that parasites cannot optimize at the same time these two important parameters of their fitness, and this could explain a part of the variation observed in the wild.

Biological invasion and parasitism: invaders do not suffer from physiological alterations of the acanthocephalan Pomphorhynchus laevis.

Biological invasions expose parasites to new invasive hosts in addition to their local hosts. However, local parasites are often less successful in infecting and exploiting their new hosts. This may have major consequences for the competitive ability of hosts, and finally on the fate of the parasite-host community. In Burgundy (Eastern France), the acanthocephalan parasite, Pomphorhynchus laevis, infects 2 amphipod species living in sympatry: the native Gammarus pulex and the invasive Gammarus roeseli. While P. laevis affects the behaviour and the immunity of G. pulex, G. roeseli seems unaffected by the infection. In this study, we examined in detail the ability of the parasite to affect the immune system and resource storage of both gammarid species. We found that the infection was associated with a general decrease of the prophenoloxidase activity, haemocyte density, resistance to an artificial bacterial infection and level of sugar reserves in G. pulex, but not in G. roeseli. These results demonstrate a differential ability of P. laevis to exploit its local and its invasive gammarid hosts. Potential mechanisms of these differential physiological alterations and their potential consequences on the coexistence of both gammarid species in sympatry are discussed.

Involvement of endothelin in renal processes.

This study examined the effect of various doses of endothelin (from 0.2 to 2 nmol/kg body wt) on regional hemodynamics in conscious unrestrained rats. Normal rats were instrumented chronically with femoral artery and vein catheters and pulsed Doppler flow probes simultaneously on the renal and superior mesenteric arteries and the abdominal aorta. Endothelin induced a biphasic response of mean arterial pressure. First, endothelin provoked a sharp hypotension with tachycardia, vasodilation of the hindquarter, and a pronounced decrease in renal and mesenteric blood flows. After this initial response, endothelin induced a dose-dependent increase of mean arterial pressure. Changes in the hindquarter vascular resistance were less pronounced than those in renal and mesenteric vascular resistances. Endothelin (2 nmol/kg) reduced renal flow (-86%) resulting from a vasoconstriction (+1,818%) significantly more pronounced than for the mesenteric vascular bed. In another set of experiments, endothelin (2 nmol/kg) induced an increase in proteinuria, characterized by an increase in excreted albumin and by the appearance of proteins with molecular weights of 20,000-280,000. Renal vascular bed exhibited a pronounced sensitivity to the vasoconstrictive effect of endothelin associated with changes in renal function.

Synergistic protective effects of antioxidant and nitric oxide synthase inhibitor in transient focal ischemia.

Both nitric oxide synthase (NOS) inhibitors and free radical scavengers have been shown to protect brain tissue in ischemia-reperfusion injury. Nitric oxide and superoxide anion act via distinct mechanisms and react together to form the highly deleterious peroxynitrite. Therefore the authors examined the effects and the interaction between the NOS inhibitor, NG nitro-L-arginine (LNA) and the antioxidant/superoxide scavenger, di-tert-butyl-hydroxybenzoic acid (DtBHB) in the rat submitted to 2 hours of middle cerebral artery occlusion. Posttreatment was initiated 4 hours after the onset of ischemia and infarct volume was measured at 48 hours. The dose-related effect of LNA resulted in a bell-shaped curve: 15, 56, 65, and 33% reduction of total infarct for 0.03, 0.1, 0.3, and 1 mg/kg (intravenously [IV]) respectively and 11% increase in infarct volume for 3 mg/kg (IV). Whereas DtBHB (20 mg/kg; intraperitoneally [IP]) was ineffective, the dose of 60 mg/kg produced 65% protection in infarct volume. The combination of a subthreshold dose of LNA (0.03 mg/kg; IV) and DtBHB (20 mg/kg; IP) resulted in significant reduction (49%) in infarct volume. These results show that LNA and DtBHB act synergistically to provide a consistent neuroprotection against ischemic injury when administered 4 hours after ischemia. This suggests that nitric oxide and free radicals are involved and interact in synergy in ischemia-reperfusion injury.

BN 80933 inhibits F2-isoprostane elevation in focal cerebral ischaemia and hypoxic neuronal cultures.

Formation of the lipid peroxidation product 8-epi-prostaglandin2alpha (8-epi-PGF2alpha) a bioactive marker of oxidative stress, was quantified in in vitro and in vivo models of neuronal death. In culture media of primary rat cortical neurones exposed to hypoxia followed by reoxygenation, a 3.7-fold increase of 8-epi-PGF2alpha concentration was observed in comparison to control cells. In rats submitted to 2h middle cerebral artery occlusion followed by a 22h reperfusion period, a 27-fold increase of 8-epi-PGF2alpha was observed in the ischaemic hemisphere compared with the corresponding hemisphere of sham-operated rats. Treatment with the neuroprotective agent BN 80933 significantly reduced both 8-epi-PGF2alpha elevations in vitro and in vivo. These data suggest that 8-epi-PGF2alpha elevations might reflect the damaging free radical overproduction and subsequent lipid peroxidation during neuronal injury induced by hypoxia and ischaemia. Inhibition of 8-epi-PGF2alpha elevations participates to the neuroprotective effects of BN 80933.

Basement membrane proteoglycans and anionic sites in the fetal rat kidney during late gestation.

Proteoglycans were studied in developing rat fetal kidney using cytological and biochemical techniques. These compounds were detected with immunoperoxidase in the nephron basement membranes from the earliest stages of differentiation. In the glomerular basement membrane, immunostaining appeared as both diffuse and granular deposits, as long as this membrane consisted of loose material; however, as soon as a three-layered membrane had formed, staining was confined to the laminae rarae as regularly arranged granules. The same pattern of staining was observed during differentiation of the basement membrane of the proximal tubule. In Bowman's capsule, immunostaining appeared as granules, which were sparsely distributed in the developing glomerulus and then regularly lined the stacked laminae when differentiation was complete. In all basement membranes, anionic sites (disclosed by polyethyleneimine) were colocated with immunostained granular deposits. Total glycosaminoglycan content gradually increased from the beginning of metanephros development to birth. During this period, the relative proportions of glycosaminoglycans changed: heparan sulfate increased and hyaluronic acid decreased as differentiation proceeded. The possible relationship between morphological observations and biochemical changes in glycosaminoglycan content is discussed.

[The impact of endothelin on renal hemodynamics in conscious rats]. / Impact de l'endothéline sur l'hémodynamique rénale chez le rat vigile.

Endothelin (ET), a peptide recently isolated from the supernatant of cultured endothelial cells, is the most potent vasoconstrictive and hypertensive agent known up till now. We have examined the effect of ET-1 intravenous injection on regional hemodynamics in conscious unrestrained rats. Normal rats are instrumented with an arterial catheter for measurement of mean arterial pressure (MAP) and with pulsed Doppler flow probes on renal and mesenteric arteries and the abdominal aorta for simultaneous recording of blood flow velocities (V). These parameters allow calculation of vascular resistance (R) (R = MAP/V). Thus, ET-1 induces an initial and sharp hypotension, concomitant with tachycardia and a marked vasoconstriction of renal and mesenteric arteries, but a vasodilatation of aorta. This response is followed by a dose-dependent and long-lasting increase of MAP and of renal, mesenteric and aortic vascular resistances accompanied by a decrease of heart rate. The greatest impact of ET-1 constrictive effects is seen on the renal vascular bed whereas the abdominal aorta appears to be far less sensitive. In fact, the dose of 2 nmol/kg of ET-1 induces a dramatic and long-lasting fall of renal blood flow (-86%) resulting from an important vasoconstriction (+1818%). Finally, an elevation of proteinuria is revealed in ET-1 (2 nmol/kg) treated rats, but not in those treated with the same dose of Angiotensin II. This proteinuria is characterized by the appearance of proteins with a molecular weight from 20,000 to 140,000 and sometimes 280,000, and an increase of excreted albumin, seeming to reflect an alteration of glomerular permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

A phase I study of the optimized cryptic peptide TERT(572y) in patients with advanced malignancies.

OBJECTIVE: It was the aim of this study to evaluate the safety of the optimized cryptic peptide TERT(572Y) in pretreated patients with advanced cancer. METHODS: Nineteen patients with progressive and chemotherapy-refractory tumors received escalated doses (2-6 mg) of 2 subcutaneous injections of the optimized TERT(572Y) peptide followed by 4 subcutaneous injections of the native TERT(572) peptide every 3 weeks. Both TERT peptides were coinjected with adjuvant Montanide ISA51. Toxicity was evaluated every 3 weeks and peptide-specific CD8+ cells were detected by flow cytometry using TERT(572Y) tetramers. RESULTS: Fourteen out of 19 patients completed the vaccination program. No grade III/IV toxicity was observed. Grade I anemia was observed in 4 patients and local skin reaction at the injection site in 11 patients. Other nonhematologic toxicities were mild, and no late toxicity was observed after a median postvaccination follow-up period of 10.7 months. There was no dose-limiting toxicity. Peripheral blood TERT(572Y)-specific CD8+ lymphocytes were detected in 13 out of 14 evaluable patients after 2 injections with the optimized TERT(572Y) peptide. There was no complete or partial response, but 4 patients (21%) with persistent TERT(572Y)-specific CD8+ experienced stable disease for a median of 10.5 months. CONCLUSION: TERT(572Y) peptide vaccine is well tolerated and effective in eliciting specific TERT(572Y) CD8+ lymphocytes in pretreated cancer patients, demonstrating that cryptic peptides could be used in cancer immunotherapy.

Implication of different endothelin receptors in the vascular action of a hypertensive dose of ET-1 in rat.

The role of different endothelin (ET) receptors in the hemodynamic action of ET-1 was investigated with an ETA-receptor antagonist, BQ-123, in anesthetized Wistar rat. BQ-123 (10 mg/kg/0.1 ml) was injected 5 min before ET-1 injection (1 nmol/kg). IV injection of ET-1 induced a short period of hypotension associated with aortic vasodilation, followed by long-lasting hypertension and aortic vasoconstriction. These effects were concomitant with immediate renal and mesenteric vasoconstriction. In the presence of BQ-123, the hypotension and aortic vasodilation induced by ET-1 were prolonged and the subsequent hypertension and aortic constriction were prevented. In the renal vascular bed, BQ-123 did not significantly affect the initial ET-1-induced constriction but markedly shortened its duration. In contrast, in the mesenteric vascular bed, BQ-123 seemed initially to amplify the ET-1-induced constriction, but afterwards slightly reduced it. The hemodynamic response to ET-1 may be mediated at first by ETB receptors, which induce a reduction of systemic blood pressure and regional vasoconstriction. In a second phase, ETA receptors operate to induce a systemic pressor effect and participate with ETB receptors in regional vasoconstriction. Therefore, ETA and ETB receptors may exist in various proportions in different vessels, the renal vascular bed appearing to be richer in ETA receptors than the mesenteric bed. The results, which demonstrate that ETB receptors mediate aortic dilation and regional constriction, are unexpected and suggest the existence of another non-ETA-type receptor and/or a different localization of non-ETA receptors in the vascular wall.

Cicletanine modulates endothelin-induced renal vasoconstriction in the rat.

Endothelin (ET-1), a recently discovered endothelium-derived peptide, has been reported to produce potent vasoconstriction in various isolated vessels of experimental animals. Cicletanine (CIC) is a novel antihypertensive agent. This study concerns the effect of CIC on the vascular actions of ET-1 (0.2 nM/kg) and epinephrine (1 microgram/kg) in normotensive Wistar rats. The hemodynamic effects of ET-1 and epinephrine were also tested in the presence of molsidomine (MOL), a vasodilator that releases nitric oxide. Rats were treated for 15 days with CIC (10 mg/kg/day) or gum arabic p.o. Subsequently, the animals were anesthetized and renal and aortic blood flow (BF) determined by pulsed Doppler flowmetry. ET-1 or epinephrine was injected. After return to the basal level, MOL (5 mg/kg) was injected; 10 min later, the mean arterial pressure (MAP) was decreased and then ET-1 or epinephrine was administered. The vascular resistance was calculated by the MAP/BF ratio and expressed as a percentage. In CIC-treated rats, ET-1 induced a renal vasoconstriction smaller than in control rats (+27.2 +/- 5.95 and +60.4 +/- 11.95%, respectively, p less than 0.01). In the presence of MOL, ET-1 produced a smaller increase in MAP (+9.7 +/- 1.34 and +16.9 +/- 2.49 mm Hg, p less than 0.05). Epinephrine injected after MOL in CIC-treated rats induced a smaller renal vasoconstriction than in control rats (+98.8 +/- 29.83 and 185 +/- 30.33%, p less than 0.05). Thus, CIC partially reduced the hypertensive and renal vasoconstrictor effects of ET-1. A combination of CIC and MOL diminished the renal effects of epinephrine. In conclusion, CIC could be used to attenuate the hypertensive status or renal ischemia disorders where ET-1 seems to be implicated.

Localization of basement membrane glycoproteins in rat kidney during foetal development.

The distribution of basement membrane glycoproteins (type IV collagen, laminin, fibronectin, and proteoglycans) was studied in foetal rat kidney by immunohistochemical techniques using polyclonal antibodies. From the first stages of nephron differentiation, all these glycoproteins were detectable by immunofluorescence in the tubular and glomerular basement membranes and in the mesangial matrix. As differentiation proceeded, labelling of glycoproteins progressively intensified, except for that of fibronectin, which gradually decreased in the glomerular basement membrane (GBM) and was barely observable at full differentiation. With immunoperoxidase staining in electron microscopy, all glycoproteins were seen to be widely dispersed in the spaces between the epithelial and endothelial glomerular cells so long as the GBM remained a loose structure. However, after it became a compact, 3-layered formation, type IV collagen and laminin were distributed throughout the GBM, whereas proteoglycans and anionic sites appeared as 2 rows of granules confined to the laminae rarae.

Upregulation of renal endothelin receptors in glycerol-induced acute renal failure in the rat.

Acute renal failure was induced in rat with a hypertonic glycerol solution and endothelin-1 (ET-1) binding was measured in kidney membrane preparations. In control animals, [125I]-ET-1 bound to specific recognition sites in kidney cortex (Bmax = 134 +/- 11 fmol/mg protein) and medulla (Bmax = 300 +/- 9 fmol/mg protein) with an apparent dissociation constant (Kd) of 0.16 +/- 0.06 nM and 0.39 +/- 0.07 nM for cortex and medulla, respectively. A single i.m. dose of 10 ml/kg glycerol (50% w/v) resulted in alterations of renal function that were maximal 48 h after glycerol administration. After this 48-h period, serum urea was increased from 0.20 +/- 0.01 g/L to 1.16 +/- 0.20 g/L (p < 0.001) and creatinine clearance was reduced from 1.04 +/- 0.15 ml/min to 0.23 +/- 0.06 ml/min (p < 0.001). Renal ET-1 receptor density was significantly increased in glycerol-treated rats to 255 +/- 14 fmol/mg protein in renal cortex (p < 0.01), and 576 +/- 55 fmol/mg protein in renal medulla (p < 0.01), with no significant modification of the Kd values. These results suggest that upregulation of ET-1 receptors is involved in renal hemodynamic impairment induced by glycerol.

Endothelin receptor subtypes A and B are up-regulated in an experimental model of acute renal failure.

The two endothelin (ET) receptor subtypes (ETA and ETB) have been characterized in rat kidney from normal rats and rats with acute renal failure induced by hypertonic glycerol administration. In control rats, the total number of ET receptors in kidney cortex and medulla was 155 and 386 fmol/mg of protein, respectively. The ratio of ETA to ETB receptors was 54:46 in renal cortex and 35:65 in renal medulla. Treatment of rats with 10 ml/kg glycerol (50%, w/v) intramuscularly resulted in severe renal dysfunction; the serum urea concentration increased from 0.46 to 2.65 g/liter and the creatinine clearance decreased from 1.06 to 0.30 ml/min. Ligand binding studies showed that glycerol-induced acute renal failure was associated with a marked up-regulation of ETA and ETB receptor subtypes in both cortex and medulla. In glycerol-treated rats, the total ET receptor density in kidney cortex and medulla was increased to 294 and 1172 fmol/mg of protein, with ETA/ETB ratios of 52:48 and 31:69, respectively. The upregulatory effect of glycerol treatment was significantly more pronounced in renal medulla than renal cortex and affected ETB receptors preferentially, compared with ETA receptors. Subsequently, ETA and ETB receptor mRNA levels were markedly increased by glycerol administration in both kidney cortex and medulla, as assessed by polymerase chain reaction coupled to reverse transcription. These results suggest that up-regulation of renal ET receptors, particularly ETB receptors in kidney medulla, may account for or contribute to renal function impairment induced by glycerol, and they support a pathophysiological role for ET in acute renal failure.

BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation: a promising neuroprotective strategy.

Nitric oxide (NO) and reactive oxygen species (ROS) act independently as well as cooperatively to induce neuronal death in acute neurological disorders. Inhibition of neuronal nitric oxide synthase (nNOS) and inhibition of lipid peroxidation induced by ROS have both been proposed as neuroprotective strategies in stroke and trauma. Recently, in our laboratory, the combination of the two strategies was found to be synergistic in reducing neuronal damage. Here, we report that BN 80933 [(S)-N-[4-[4-[(3,4-dihydro-6-hydroxy-2, 5,7, 8-tetramethyl-2H-1-benzopyran-2-yl)carbonyl]-1-piperazinyl]phenyl]-2- thiophenecarboximidamide], a compound that combines potent antioxidant and selective nNOS inhibitory properties in vitro, affords remarkable neuronal protection in vivo. Intravenous administration of BN 80933 significantly reduced brain damage induced by head trauma in mice, global ischemia in gerbils, and transient focal ischemia in rats. Treatment with BN 80933 (0.3-10 mg/kg) significantly reduced infarct volume (>60% protection) and enhanced behavioral recovery in rats subjected to transient (2-h) middle cerebral artery occlusion and 48-h or 7-day reperfusion. Furthermore, treatment with BN 80933 commencing up to 8 h after the onset of ischemia resulted in a significant improvement of neurological outcome. All these results indicate that BN 80933 represents a class of potentially useful therapeutic agents for the treatment of stroke or trauma and possibly neurodegenerative disorders that involve both NO and ROS.