Hedbergia, a new genus of Scrophulariaceae from Africa

Hedbergia is described as a new, monotypic genus in the Scrophulariaceae, subfamily Rhinanthoideae, tribe Rhinantheae. The species H. abyssinica is transferred from Bartsia. Hedbergia abyssinica is the most primitive taxon so far known in the subtribe Euphrasineae.     

A glia-derived neurite-promoting factor with protease inhibitory activity.

Brain cells and glioma cells in culture release a protein which induces neurite outgrowth in neuroblastoma cells. This neurite-promoting factor (NPF), which has been purified from serum-free glioma conditioned medium, has an apparent mol. wt. of 43 000. NPF inhibits urokinase as well as plasminogen activator-dependent caseinolysis or fibrinolysis. NPF and urokinase form an SDS-resistant complex. The fact that this glia-derived NPF is a potent protease inhibitor indicates that glial cells modulate the proteolytic activity associated with neuronal cells and suggests that this phenomenon is one of the biochemical events involved in the regulation of neurite growth.     

The incorporation of selenium and alterations of macro- and trace element levels in individual blood cells following supplementation with sodium selenite and vitamin E

Significant alterations in the selenium content of erythrocytes, thrombocytes, and neutrophil granulocytes were observed following a daily supplementation of 200 μg Se + 100 mg vitamin E during a period of 2 months. The neutrophil granulocytes incorporated more selenium than the thrombocytes. The iron content of the thrombocytes decreased on selenium supplementation, while the opposite was noted for the neutrophil granulocytes. The glutathione peroxidase activity was not significantly changed during the period of observation.     

Haemolysis of rabbit erythrocytes by a lectin from the seeds of<Emphasis Type="Italic">Croton tiglium</Emphasis>

The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K⁺, Ca²⁺ and Mg²⁺ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed.     

Plant lectins specific for N-acetyl-β-D-galactosamine

N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus).     

Demonstration of an “Excitation-Contraction Recoupling” Mechanism in Mammalian Ventricular Myocardium

A PROCESS called “excitation-contraction coupling” has been generally accepted to take place only in the direction of excitation to contraction. Through this mechanism a propagated action potential initiates an active state in skeletal or cardiac muscle and the muscle contracts. We propose that, in the mammalian ventricular myocardium at least, the process is not unidirectional and an important reverse coupling between the contractile system and the excitable plasma membrane has been overlooked. Through this feedback interaction the mode of contraction (that is, isotonic or isometric) not only determines the instantaneous electrical state of the plasma membrane, but also influences the mechanical events of the subsequent beats. Thus when Kaufmann et al.¹ recorded intracellular action potentials from cat papillary muscle, the time course of the repolarization was altered depending on the mode of contraction. Some kind of contraction-excitation feedback has also been suggested by Stauch² and Lab^3,4. They showed a difference in the shape of the monophasic action potential, as recorded by a suction electrode, when comparing isotonic and isovolumic contraction of the intact ventricle. But their experimental conditions did not allow satisfactory analysis of the phenomenon.