Prostanoid receptors of the EP3 subtype mediate the inhibitory effect of prostaglandin E2 on noradrenaline release in the mouse brain cortex

Mouse or rat brain cortex slices were preincubated with ³H-noradrenaline and superfused with physiological salt solution containing desipramine. We studied the effects of prostaglandin E₂ (PGE₂), prostaglandin D₂ (PGD₂) and related drugs on the electrically evoked (50 mA, 2 ms, 0.3 Hz) tritium overflow.PGE₂ inhibited the electrically evoked tritium overflow from mouse brain cortex slices; the maximum effect of PGE₂ (79010) was attenuated by the ₂-adrenoceptor agonist talipexole (to 52010) and enhanced by the ₂-adrenoceptor antagonist rauwolscine (to 92%). Rauwolscine was added to the superfusion medium in all subsequent experiments. The effect of PGE₂ was readily reversible upon withdrawal from the medium and remained constant upon prolonged exposure of the tissue to the prostanoid. Studies with EP receptor agonists, mimicking the inhibitory effect of PGE₂, showed the following potencies (pIC₅₀): sulprostone (8.22); misoprostol (8.00); PGE₂ (7.74); PGEZ (7.61); iloprost (5.86). The concentration-response curve of PGE₂ was marginally shifted to the right by the EP₁ receptor antagonist AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid; apparent pA₂ 3.97) and by the TP receptor antagonist vapiprost (4.50). AH 6809, by itself, did not affect the evoked overflow whereas vapiprost increased it. PGD2 inhibited the evoked overflow at high concentrations (pIC₅₀ 4.90); this effect was not altered by the DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexyl-2hydroxyethylamino)hydantoin), which, by itself, did not affect the evoked overflow. Indometacin slightly increased the evoked overflow and tended to increase the inhibitory effect of PGE₂. PGE₂ inhibited the electrically evoked tritium overflow also in rat brain cortex slices. The maximum effect (obtained in the presence of rauwolscine) was 61%; the pIC₃₀ value was 7.67.The present study suggests that PGE₂ inhibits noradrenaline release from mouse brain cortex via EP₃ receptors and that its maximum effect is more marked in the mouse than in the rat. The inhibitory effect of PGD₂ (in the mouse brain) does not involve DP receptors and may also be related to EP₃ receptors. The EP₃ receptors interact with a2-adrenoceptors and may be activated by endogenous prostanoids.     

A multinational study of the relationships between nighttime urinary melatonin production, age, gender, body size, and latitude

Overnight urines were collected each month for 12–16 months from 321 normal subjects at 19 medical centers in 14 countries distributed on 5 continents at latitudes from 31 01 South to 77 00 North. Mean melatonin concentration was found to negatively correlate with age, weight, and height. When the sexes were considered separately melatonin only correlated with age for female and with age and weight for males. A weak correlation with latitude, but not longitude, was also found. Received: 26 February 1998 / Accepted: 9 September 1999     

Effects of the novel H1 agonists 2-(3-trifluoromethylphenyl)- and 2-(3-bromophenyl)histamine and of 2-(2-thiazolyl)ethylamine on cardiovascular paramenters in the pithed rat

The effect of the newly synthetized H₁ agonists 2-(3-trifluoromethylphenyl)histamine (2-TFMPH) and 2-(3-bromophenyl)histamine (2-BPH) and of the reference compound 2-(2-thiazolyl)ethylamine (2-TEA) on diastolic blood pressure and heart rate was studied in pithed and vagotomized rats. 2-TFMPH and 2-BPH were at least equipotent with 2-TEA in producinga dimethindene-sensitive, short-lasting vasodepressor response. At the highest dose, 2-TFMPH and 2-BPH produced an additional small vasopressor response, which was followed by a long-lasting vasodepressor effect not counteracted by dimethindene and ranitidine 2-TEA, at the highest dose, induced an additional vasopressor response abolished by prazosin plus rauwolscine. Basal heart rate was increased by 2-TEA (in a desipramine-sensitive manner) but not affected by 2-TFMPH or 2-BPH. In conclusion, 2-TFMPH and 2-BPH are potent H₁ agonists, devoid of an indirect sympathomimetic effect; at high doses, they produce a vasodepressor response not mediated via histamine receptors.Recipient of a fellowship provided by the Alexander von Humboldt-Stiftung (Bonn, Germany)     

Inhibition of noradrenaline release from the sympathetic nerves of the human saphenous vein by presynaptic histamine H3 receptors

Summary The human saphenous vein was used to examine whether presynaptic histamine receptors can modulate noradrenaline release and, if so, to determine their pharmacological characteristics. Strips of this blood vessel were incubated with [³H]noradrenaline and subsequently superfused with physiological salt solution containing desipramine and corticosterone. Electrically (2 Hz) evoked ³H overflow was inhibited by histamine and the H₃ receptor agonist R-(–)--methylhistamine. Histamine-induced inhibition of electrically evoked tritium overflow was not affected by ₂-adrenoceptor blockade by rauwolscine. S-(+)--methylhistamine (up to 10 mol/l) as well as the histamine H₁ and H₂ receptor agonists 2-(2-thiazolyl)ethylamine (up to 3 mol/l) and dimaprit (up to 30 mol/l), respectively, were ineffective. The selective histamine H₃ receptor antagonist thioperamide abolished the inhibitory effect of histamine. The histamine H₂ and H₁ receptor antagonists ranitidine and pheniramine, respectively, did not affect the histamine-induced inhibition of evoked tritium overflow. The present results are compatible with the suggestion that the sympathetic nerves of the human saphenous vein are endowed with inhibitory presynaptic histamine receptors of the H₃ class. Send offprint requests to M. Gothert at the above address     

Divalent Cations Modulate the Inhibitory Substrate Properties of Murine Glia-derived J1-160 and J1-180 Extracellular Matrix Glycoproteins for Neuronal Adhesion

J1-160 and J1-180 are developmentally late appearing J1 extracellular matrix glycoproteins derived from oligodendrocytes. They prevent adhesion of neurons (but not of astrocytes or fibroblasts) when offered as a substrate in mixture with laminin (Pesheva et al., J. Cell Biol., 109, 1765 - 1778, 1989). In the present study we have examined the influence of divalent cations on the inhibitory substrate properties of J1-160/180 glycoproteins towards adhesion of neurons. By metal chelate affinity chromatography, we show that J1-180, but not J1-160, binds Ca2+, while both J1 components are capable of binding Zn2+ and other divalent metal ions. Divalent cation binding was observed by gel filtration, aggregation assays with coated latex beads and electron microscopic examination to elicit aggregation of the molecules. Divalent cation binding also affects their non-permissive substrate properties towards neurons from early postnatal mouse cerebellum. Without divalent cations, J1-160 and J1-180 are inhibitory for substrate adhesion of neurons independently of the adhesive substrate present (laminin or poly-l-lysine). This effect is neutralized when J1-180 is preincubated with Ca2+ or Zn2+ prior to coating as substrate. In contrast, preincubation with Ca2+ ions does not affect the inhibitory substrate properties of J1-160 under these conditions. These observations show that J1-160/180 molecules may undergo self-aggregation in a divalent cation-dependent mechanism, which correlates with the neutralization of their inhibitory effect on neuronal adhesion. The aggregation state of the molecules may thus influence the process of myelination by a homophilic binding mechanism and determine the effectiveness of neurite extension during central nervous system development and under traumatic conditions in the adult.     

Interaction of phenylbutazone with racemic phenprocoumon and its enantiomers in rats

The interaction of phenylbutazone with the enantiomers and racemic [ ³ H]phenprocoumon was studied in male inbred Wistar-Lewis rats following a single i.v. dose of the three forms of phenprocoumon and chronic oral treatment with phenylbutazone (average plasma concentration of about 60 g/ml). Phenylbutazone augmented the anticoagulant effect of R(+), S(–), and R, S (±) phenprocoumon to a similar extent. The free fraction of drug in the plasma of the enantiomers and racemic phenprocoumon increased in the presence of phenylbutazone. However, the rate of elimination of total drug from plasma and liver and the distribution between liver and plasma of all three forms of phenprocoumon remained nearly unaffected by phenylbutazone. Thus there is no evidence for a stereoselective drug interaction between phenprocoumon and phenyl-butazone. For racemic [ ³ H]phenprocoumon it was possible to follow the kinetics of free drug in plasma and liver along with the time course of anticoagulant activity. In these studies, free drug concentrations in plasma and liver increased during treatment with phenylbutazone, but the elimination rate constant of free racemic phenprocoumon in plasma and liver remained essentially unchanged. Phenylbutazone markedly decreased the volume of distribution referenced to free drug and the clearance of free phenprocoumon (i.e., intrinsic metabolic clearance). Whereas the total (bound and unbound) drug concentration-effect relationship in plasma and liver was shifted to the left in rats treated with phenylbutazone, such shift was not seen in the free drug concentration-response relationship. In conclusion, the increase in the free concentration of phenprocoumon in plasma and liver and the concomitant decrease in the clearance of free drug are the mechanisms responsible for the marked and sustained enhancement of the anticoagulant effect which follows treatment with phenbutazone.This work was supported by the Deutsche Forschungsgemeinschaft.     

Management of soft tissue sarcomas (STS) in first isolated local recurrence: a retrospective study of 83 cases.

PURPOSE: To analyze the management and clinical outcome of patients treated for a first isolated local recurrence of soft tissue sarcomas (trunk or extremities) and to identify prognosis factors. METHODS AND MATERIAL: Between 1980 and 1999, 83 adult patients were included in the study. Mean age was 61 years. Mean tumor size was 6 cm. Most sarcomas were located in extremities (n=74), were deep (n=60), and proximal (n=53); 30 involved nerves or vessels. Histologic subtypes were mainly grade 2 (42%) or 3 (36%) histiocytofibrosarcomas (49%) and liposarcomas (20%). Surgical treatment of recurrences consisted in wide excision (29 cases), marginal resection (43 cases), 5 patients requiring amputation. Final results were R0 (n=33), R1 (n=47) or R2 (n=3) resection. Besides surgery, 6 patients received neo-adjuvant and 7 others adjuvant chemotherapy. Twenty three patients received post-operative external beam radiotherapy (EBRT) (mean dose 55 Gy) and 26 interstitial 192Ir low dose rate brachytherapy (BCT) (mean dose 45 Gy for BCT alone, 22 Gy when associated with EBRT), 19 patients being re-irradiated. RESULTS: Mean follow up was 13 years. Thirty-seven (45%) patients relapsed, 62% of whom presenting an isolated local recurrence. Nineteen patients developed distant metastases. Multivariate analysis showed only tumor depth (P=0.05) and re-resection for primary R1 resection (P=0.018) being independent prognosis factors for tumor control, radiotherapy (EBRT and/or BCT) being significant in univariate analysis (P=0.05). Overall survival rate was 73%, 54%, and 47% at, respectively, 3.5 and 10 years, and was 65%, 35% and 32% after a further local recurrence. Multivariate analysis showed trunk (P=0.0001) or inferior extremity locations (P=0.023), symptomatic (P=0.001), high grade (P=0.01), deep (P=0.01) tumors, and the occurrence of a further local failure (P=0.004) as unfavorable characteristics for overall survival. CONCLUSIONS: A first isolated local recurrence of STS increases mainly the risk of a subsequent local relapse. Quality of local treatment is decisive. When a conservative treatment is feasible, it should combine surgical resection and radiotherapy, BCT being the best suited in previously irradiated patients. Efforts have to be pursued to increase quality of the treatment of primary tumors, at best performed in centers that have expertise in this field.     

Increase of regulatory T cells in the peripheral blood of cancer patients.

PURPOSE: T cells constitutively expressing both CD4 and CD25are essential for maintenance of self-tolerance and therefore have been referred to as regulatory T cells (Treg). Experimental tumor models in mice revealed that Tregs are potent inhibitors of an antitumor immune response. The current study was designed to determine whether cancer patients exhibit an expanded Treg pool. EXPERIMENTAL DESIGN: The frequency of Tregs in the peripheral blood of 42 patients suffering from epithelial malignancies and from 34 healthy controls was determined by flow cytometry. The immunoregulatory properties of CD4(+)CD25(+) and CD4(+)CD25(-) T cells were characterized by proliferation and suppression assays. Cocultures with natural killer (NK) cells were performed to determine the impact of Tregs on NK-mediated cytotoxicity. RESULTS: Patients with epithelial malignancies show an increase of CD4(+)CD25(+) T cells in the peripheral blood with characteristics of Tregs, i.e., they are CD45RA(-), CTLA-4(+), and transforming growth factor beta(+). Notably, CD4(+) T cells from cancer patients are characterized by an impaired proliferative capacity, which is restored to the extend of CD25-depleted CD4(+) T cells from control persons by prior removal of CD25(+) T cells. In contrast to CD4(+)CD25(-) T cells, isolated CD4(+)CD25(+) T cells from cancer patients were anergic towards T cell receptor stimulation. In addition, CD4(+)CD25(+) T cells suppressed the proliferation of CD4(+)CD25(-) T cells. When cultured together with CD56(+) NK-cells, CD4(+)CD25(+) T cells from cancer patients effectively inhibited NK-cell-mediated cytotoxicity. CONCLUSIONS: Thus, we provide evidence of an increased pool of CD4(+)CD25(+) regulatory T cells in the peripheral blood of cancer patients with potent immunosuppressive features. These findings should be considered for the design of immunomodulatory therapies such as dendritic cell vaccination.     

Total versus tube-related additional work of breathing in ventilator-dependent patients

BACKGROUND: In tracheally intubated or tracheostomized spontaneously breathing patients, tube resistance can highly increase the patient's work of breathing. In this study we focused upon the relationship between total (WOBtot) and tube-related additional inspiratory work of breathing (WOBadd) and compared different ventilatory modalities for proper tube compensation. METHODS: In ten tracheostomized spontaneously breathing patients we measured WOBtot and WOBadd in the continuous positive airway pressure (CPAP) mode, under inspiratory pressure support of 5, 10, and 15 cmH2O in the pressure support ventilation (PSV) mode, and under flow-adjusted pressure support in the automatic tube compensation (ATC) mode. WOBadd and WOBtot were calculated on the basis of measured tracheal pressure and esophageal pressure, respectively. Inspiratory peak tracheal pressure above PEEP was taken as an estimate of pressure support beyond mere tube compensation (i.e., overcompensation). RESULTS: The percentage of the tube-related WOBadd on WOBtot in the CPAP mode was 52%. It decreased with increasing pressure support in the PSV mode from 32% (PSV 5 cmH2O) to 17% (PSV 15 cmH2O). WOBadd was only 15% of WOBtot in the ATC mode. In contrast to the other ventilatory modes, reduction of WOBadd in the ATC mode was achieved with the smallest amount of overcompensation, i.e. with minimal pressure assist beyond mere tube compensation. CONCLUSION: In tracheally intubated or tracheostomized spontaneously breathing patients, adequate compensation of tube resistance (i.e. with minimal overcompensation and minimal undercompensation) is best done by the ATC mode.