Thrombin Inhibition in discordant xenograft rejection

Abstract: Microvascular thrombosis and the associated platelet and endothelial cell activation are prominent observations in xenograft rejection. This pathological picture could be related to the excessive generation of thrombin in the context of either inflammation or putative inter-species molecular incompatibilities between activated coagulation factors and their natural anticoagulants. Relatively selective thrombin Inhibition with the serine protease inhibitor SDZ MTH 958 (MTH-958) are independent of heparinoids and anti-thrombin III. MTH-958 has been shown to significantly prolong porcine cardiac function during perfusion with human blood in an ex vivo model. The aim of this study was to validate the role of thrombin generation in a rodent model of discordant xenograft rejection in vivo. The effect of thrombin inhibition with MTH-958 was tested in both hyperacute rejection (HAR) and delayed xenograft rejection (DXR) after decomplementation with cobra venom factor (CVF) in normal Lewis (Lew) rats and Intrinsic C6 deficiency In PVG (C6-/PVG) recipient rats. Recipient rats received heterotopic guinea pig cardiac xenografts and were treated with titrated doses of MTH-958 until the time of graft rejection. Plasma samples at selected time points were examined to confirm effective thrombin inhibition, and rejected grafts were analyzed by immunohistology. MTH-958 significantly improved graft survival in HAR albeit the extent of prolongation was not marked, but the agent failed to prolong survival In CVF-treated Lew rats. In C6-/PVG rats receiving MTH-958, a significantly reduced graft survival time was observed when compared with C6-/PVG controls. The grafts from MTH-958-treated animals showed dense deposits of C3, IgM, and IgG with fibrin levels similar to controls. The thrombin antagonist tested could prolong xenograft survival during HAR but had no benefit in DXR. The relative non-specificity of the serine protease inhibitor MTH-958 with the potential activation of alternative pathway of complement via the inhibition of factor I could account for the failure to prolong xenograft survival in DXR. The pathogenetic significance of thrombin generation in this situation remains to be determined by the use of more selective and pharmacologically acceptable I anti-thrombin agents.     

Transfer of clonidine and dexmedetomidine across the isolated perfused human placenta

Background: The placental transfer of the a₂ receptor agonist clonidine, earlier used as an adjuvant in obstetric epidural analgesia, was compared with the transfer of the newer and more %-selective agonist dexmedetomidine.
Methods: Term placentas were obtained immediately after delivery with maternal consent and a 2-hour recycling perfusion of a single placental cotyledon was performed. Disappearance from the maternal circulation, accumulation in placental tissue and appearance in the fetal circulation of clonidine or dexmedetomidine with the reference compound antipyrine were followed in 4 experiments for both drugs.
Results: At 2 hours the percent dexmedetomidine found in the fetal circulation was 12.5 (SD 5.1)%, while 48.1 (SD 20.3)% was found in the perfused placental cotyledon. A higher mean clonidine than dexmedetomidine concentration was achieved in the fetal circulation (1.90 vs. 0.56 nmol/l, P <0.05). At 2 hours the percent clonidine found in the fetal circulation was 22.1 (SD 2.4)% ( P <0.05), while 11.3 (SD 3.3)% ( P <0.05) was re tained in the perfused placental cotyledon. The transfer indexes, describing maternal-to-fetal transfer of dexmedetomidine and clonidine normalized with the transfer of antipyrine, were 0.88 (SD 0.07) and 1.04 (SD 0.08) respectively ( P <0.05).
Conclusions: Dexmedetomidine disappeared faster than clonidine from the maternal circulation, while even less dexmedetomidine was transported into the fetal circulation. This was due to its greater placental tissue retention, the basis for which probably is the higher lipophilicity of dexmedetomidine.     

Prognosis of Childhood Seizure Disorders: Present and Future

Summary: The prognoses for seizure disorders have been examined since the beginnings of epileptology, and only recently has the realization emerged that, ultimately, prognosis depends on causation, which, in turn, determines whether a condition is self-limited or progressive. This factor is more important than either mode or alacrity of therapeutic intervention. The epilepsies are a series of conditions that have the final common path of either increasing cerebral irritability or synchronizing normally occurring electrical activity in such a manner that seizures result. In turn, some seizure disorders are characterized by secondary changes in neuronal synaptogenesis, leading to the development of circuits of predilection, which then render the process autonomous. Epilepto-genesis has then become epilepsy, which is the norm in acquired rather than genetic epileptogenesis. An understanding of the basic differences between the primary (idiopathic) epilepsies and the secondary (acquired or symptomatic) epilepsies is basic to a discussion concerning prognosis and to the development of a definitive individualized treatment plan. An elucidation of the genetic factors in idiopathic epilepsy and their neurochemical consequences represents a major frontier in epileptology.     

Human xenoreactive natural antibodies of the IgM isotype activate pig endothelial cells

Abstract: Preformed, xenoreactive natural antibodies (XNA) and complement (C) are involved in the initiation of vascular rejection of organs transplanted between discordant species, presumably by stimulating donor organ endothelial cells (EC). Although C is known to play a role in the activation of EC, it has not been clear whether the antibodies serve only to anchor the initial components of C, and thus permit the C cascade to proceed, or whether the antibodies themselves deliver a signal to the EC. We have tested affinity-purified human IgM containing XNA (IgM-XNA) for its ability to stimulate in vitro the up-regulation of genes in pig EC. Northern blot analysis shows that IgM, which contains XNA, stimulates mRNA accumulation for certain genes (including IL-8, PAI-1, and ECI-7, a new gene that we have found is associated with EC activation), but not others known to be up-regulated in response to TNF, IL-1 or LPS. Our results show that XNA provide a signal to EC, and thus may themselves participate in activation of EC and consequent vascular rejection.     

Die thermoelastischen Eigenschaften der Herzmuskulatur

Zusammenfassung Bei der Messung der thermischen Ausdehnung von ungedehnten oder nur wenig gedehnten tierischen Geweben mit Faserstruktur machte sich bisher die thermische Änderung des Auftriebes der Versuchsobjekte in der sie umgebendenRinger-Lösung störend bemerkbar. Um diesen Auftriebsfehler auszuschalten und somit auch an ungedehnten Geweben quantitative Versuche über thermische Ausdehnung anstellen zu können, wurde das optische Lineardilatometer vonWöhlisch dadurch verbessert, daß die Versuchsobjekte durch eine an dem festen Dilatometerarm angebrachte Quarzplatte unterstützt wurden. Die Auswirkung der scheinbaren Gewichtsänderungen auf den Dilatometerzeiger wird hierdurch aufgehoben. Eine Störung des Versuches durch die Platte findet infolge der außerordentlich geringen thermischen Ausdehnung des Quarzes nicht statt.Mit dieser Apparatur wurden erstmalig Versuche zur direkten Bestimmung der thermischen Ausdehnung der Herzmuskulatur vorgenommen. Als Versuchsobjekt dienten Streifenpräparate aus dem Ventrikel von R. esculenta. Die Versuche wurden in einem weiten Bereiche der Dehnungen (0% bis über 50%) angestellt. Es ergab sich eine weitgehende Übereinstimmung im Verhalten des Herzmuskels und des Skeletmuskels: Im Bereiche kleiner Dehnungen ist der lineare thermische Ausdehnungskoeffizient (l. th. A.K.) des erregbaren Herzmuskels negativ; an völlig ungedehnten Streifen ergab sich der Mittelwert =–(3,47±0,78) · 10^–5. Durch stärkere Dehnung kommt es wie beim Skeletmuskel und beim Nackenband zu einem Umschlagen des l. th. A.K. zu positiven Werten. Beim toten Herzmuskel ist derl. th. A.K. stets positiv.D 20.     

Effect of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of adhesion molecules on human neutrophils

The effects of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of CD11b/CD18, CD11c/CD18 integrins and l-selectin on human neutrophils were studied by flow cytometry in a whole blood assay. None of these compounds had any effect on the basal expression of CD11b, CD11c, or l-selectin in the concentration range of 20–100 μM. However, linoleic acid at a concentration of 1000 μM slightly up-regulated CD11b and CD11c by a factor of 2.1 and 1.7, respectively. Linoleic acid, linoleic acid anilide, and arachidonic acid did not affect the formyl-methionyl-leucyl-phenylalanine induced up-regulation of CD11b or CD11c. However, linoleic acid and linoleic acid anilide slightly inhibited the phorbol myristate acetate (PMA)-induced expression of CD11b, which was decreased by 27 and 21% at concentrations of 100 and 1000 μM, respectively. Likewise, arachidonic acid at 40 μM inhibited the PMA-induced expression of CD11b by 19%. Our results suggest that linoleic acid, linoleic acid anilide, and arachidonic acid do not dramatically affect the expression of leukocyte adhesion molecules in a whole blood assay. Received: 17 February 1997  / Accepted: 5 May 1997