Improved red cell quality after erythroplasmapheresis with MCS-3P

The cell separator MCS-3P is an apheresis system offering the flexibility to collect standardized red blood cells, plasma, and/or platelets from one donor. Two different programs were used for the red cell apheresis'RBCP (collection of one unit of red cells and two units of plasma) and RBCPS (one unit of red cells and one unit of plasma). The quality of the red cell concentrates (RCC resuspended in SAG-Mannitol) during the storage time of 42 days was measured by biochemical (ATP, 2,3-DPG, pH, free Hb, free potassium, glucose, lactose, p⁵⁰, hemoglobin derivatives) and Theological (morphological index, filtration/rigidity index) parameters. The donation time with 53 donors was 20 min for 355 ml RCC-SAGM and 440 ml plasma and 7 min for 335 ml RCC-SAGM and 239 ml plasma. The donor tolerance was analogous to plateletpheresis or plasmapheresis. Twenty units of the RCC-SAGM were in-line filtered within 6 or 24 hours after donation. The results obtained for red blood cell storage are at least as good as with standard collection (free hemoglobin, free potassium, glucose, lactose, hemolysis) or better (ATP, 2,3-DPG, p⁵⁰, hemoglobin derivatives, filtration/rigidity index) owing to prevention of collection lesion. All blood preparations were sterile after storage (red cells 42 days, plasma after freezing). The erythroplasmapheresis with MCS-3P can be especially recommended for application in an autologous blood program because the application of autologous blood donation in hospitals is often limited by the preconditions of component separation. The erythroplasmapheresis data with MCS-3P are encouraging for the development of a new blood collection methodology.     

Action of rHuEpo on mechanical membrane properties of red blood cells in children with end-stage renal disease.

By means of a micropipette aspiration technique mechanical membrane properties of RBC in ten uraemic children undergoing haemodialysis were compared to those of nine healthy children. In contrast to the healthy reference group (mu = 4.01 +/- 0.71 microN/m), the mean apparent elastic shear modulus of RBC membrane mu as a parameter of static deformability was significantly increased to 9.05 +/- 1.61 microN/m in children with chronic renal failure measured in the pre-study period. At the 7th week of the correction period of rHuEpo therapy, the haematocrit of treated patients is enhanced to a mean of 0.30 +/- 0.03, whereas mean mu is decreased to 5.41 +/- 0.63 microN/m. Within the maintenance period of rHuEpo treatment (30th week), the parameter mu did not show significant differences to the reference value 3.78 +/- 0.31 microN/m. Additionally, a significant increase in red cell mean corpuscular volume was obtained during rHuEpo therapy. Improved deformability of uraemic RBC induced by the rHuEpo therapy can only be explained by the assumption that in the course of this therapy an increasing number of cells with normalised viscoelastic properties have been formed by stimulated erythropoiesis.     

Effects of temperature and mexiletine on the F1473S Na+ channel mutation causing paramyotonia congenita

 The F1473S mutation of the adult human skeletal muscle Na⁺ channel causes paramyotonia congenita, a disease characterized by muscle stiffness sometimes followed by weakness in a cold environment. The symptoms are relieved by the local anaesthetic mexiletine. This mutation, which resides in the cytoplasmic S4-S5 loop in domain IV of the α-subunit, was studied by heterologous expression in HEK293 cells using standard patch-clamp techniques. Compared to wild-type (WT) channels, those with the F1473S mutation exhibit a twofold slowing of fast inactivation, an increased persistent Na⁺ current, a +18-mV shift in steady-state inactivation and a fivefold acceleration of recovery from fast inactivation; slow inactivation was similar for both clones. Single-channel recordings for the F1473S mutation revealed a prolonged mean open time and an increased number of channel reopenings that increased further upon cooling. The pharmacological effects of mexiletine on cells expressing either WT, F1473S or G1306E channels were studied. G1306E is a myotonia-causing mutation located within the inactivation gate that displays similar but stronger inactivation defects than F1473S. The hyperpolarizing shift in steady-state inactivation induced by mexiletine was almost identical for all three clones. In contrast, this agent had a reduced effectiveness on the phasic (use-dependent) block of Na⁺ currents recorded from the mutants: the relative order of block was WT>F1473S>G1306E. We suggest that the relative effectiveness of mexiletine is associated with the degree of abnormal channel inactivation and that the relative binding affinity of mexiletine is not substantially different between the mutations or the WT. Received: 13 January 1998 / Received after revision: 11 May 1998 / Accepted: 19 May 1998     

Zur Frage der hydrostatischen Druckwirkung des Bades auf die Blutzirkulation

Zusammenfassung An narkotisierten Hunden wird die Carotisdurchblutung im thermoindifferenten Sü?wasserbade und im Sandbade mittels der Reinschen Thermostromuhr registriert. Dabei wird die ?nderung der Carotisdurchblutung als relatives Ma? einer Herzminutenvolum?nderung angesehen. In Wasserb?dern steigt die H?he des Minutenvolumens ungef?hr proportional der Badewasserh?he an. In Sandb?dern von Zimmertemperatur ist entweder keine oder eine nur geringe Kreislaufwirkung nachweisbar, was auf die eigenartigen Druckverh?ltnisse im Sandbade, die zum Teil durch einen Modellversuch gekl?rt werden, zurückgeführt wird. Eine isolierte Bauchkompression au?erhalb des Bades führt meist zu einer geringen Erh?hung des Herzminutenvolumens, eine Thoraxkompression zur Verminderung. Im üblichen Vollbade wird die Thoraxkompression nicht in dieser Weise wirksam, da die st?rkere hydrostatische Druckwirkung auf das Abdomen und die hinteren Extremit?ten eine Abnahme des ven?sen Druckgef?lles verhindert. Eine Beteiligung der im Bade vorhandenen Bauchkompression an der Rückflu?f?rderung kann als gesichert gelten. Mit 5 Textabbildungen.     

Evaluation of recombinant vaccinia virus--measles vaccines in infant rhesus macaques with preexisting measles antibody

Immunization of newborn infants with standard measles vaccines is not effective because of the presence of maternal antibody. In this study, newborn rhesus macaques were immunized with recombinant vaccinia viruses expressing measles virus hemagglutinin (H) and fusion (F) proteins, using the replication-competent WR strain of vaccinia virus or the replication-defective MVA strain. The infants were boosted at 2 months and then challenged intranasally with measles virus at 5 months of age. Some of the newborn monkeys received measles immune globulin (MIG) prior to the first immunization, and these infants were compared to additional infants that had maternal measles-neutralizing antibody. In the absence of measles antibody, vaccination with either vector induced neutralizing antibody, cytotoxic T cell (CTL) responses to measles virus and protection from systemic measles infection and skin rash. The infants vaccinated with the MVA vector developed lower measles-neutralizing antibody titers than those vaccinated with the WR vector, and they sustained a transient measles viremia upon challenge. Either maternal antibody or passively transferred MIG blocked the humoral response to vaccination with both WR and MVA, and the frequency of positive CTL responses was reduced. Despite this inhibition of vaccine-induced immunity, there was a reduction in peak viral loads and skin rash after measles virus challenge in many of the infants with preexisting measles antibody. Therefore, vaccination using recombinant vectors such as poxviruses may be able to prevent the severe disease that often accompanies measles in infants.     

The new anticonvulsant retigabine favors voltage-dependent opening of the Kv7.2 (KCNQ2) channel by binding to its activation gate

Retigabine (RTG) is an anticonvulsant drug with a novel mechanism of action. It activates neuronal KCNQ-type K(+) channels by inducing a large hyperpolarizing shift of steady-state activation. To identify the structural determinants of KCNQ channel activation by RTG, we constructed a set of chimeras using the neuronal K(v)7.2 (KCNQ2) channel, which is activated by RTG, and the cardiac K(v)7.1 (KCNQ1) channel, which is not affected by this drug. Substitution of either the S5 or the S6 segment in K(v)7.2 by the respective parts of K(v)7.1 led to a complete loss of activation by RTG. Trp236 in the cytoplasmic part of S5 and the conserved Gly301 in S6 (K(v)7.2), considered as the gating hinge (Ala336 in K(v)7.1), were found to be crucial for the RTG effect: mutation of these residues could either knockout the effect in K(v)7.2 or restore it partially in K(v)7.1/K(v)7.2 chimeras. We propose that RTG binds to a hydrophobic pocket formed upon channel opening between the cytoplasmic parts of S5 and S6 involving Trp236 and the channel's gate, which could well explain the strong shift in voltage-dependent activation.