Über den Feinbau des Nervensystems des Seesterns (Asterias rubens L.)

Ohne ZusammenfassungDurchgeführt mit Unterstützung durch die Deutsche Forschungsgemeinschaft.Herrn Prof. Dr. Kurt Goerttler, Freiburg i. Br., zum 65. Geburtstag gewidmet.     

The genetic control of alkaline phosphatase activity in the duodenum of the mouse

The inheritance of duodenal alkaline phosphatase activity has been studied in two inbred strains of Swiss mice. These two strains consistently maintained a three- to fourfold difference in duodenal phosphatase activity for six generations before the start of the genetic studies. Males of both the high-activity strain (HAS) and the low-activity strain (LAS) were mated to females of the other strain to produce an F₁ generation, members of which were sib-mated to produce an F₂ generation. The frequency distributions of the parental, F₁, and F₂ generations reveal that the activity of the enzyme is under polygenic control. Distribution of activities in the F₂'s derived from HAS grandmothers differs from that of the F₂'s from LAS grandmothers, indicating that a maternally inherited factor, probably contained in the milk of one strain, influences the activity. Heritability estimates based on half-sib correlation coefficients show that additive genetic variance makes up about 50–70% of the total variance of duodenal phosphatase activity in LAS, and approximately 30–45% in HAS. The latter strain is the more variable, both within generations and within litters; its activity is also more strongly enhanced by injection of substrate into the stomach, and is more severely reduced by starvation. Chromatographic analysis of butanol extracts of phosphatase from 11-day-old mice of the two strains reveals that both contain the same two isozymes. HAS does, however, appear to have 6–8 times as much as LAS of an isozymic form of phosphatase having a relatively high phenylphosphate/-glycerophosphate ratio, and only about twice as much of a low PhP/bGP ratio form.Supported by Research Grant GM 03937 from the National Institutes of Health, U.S. Public Health Service.     

Genetic diversity of six arable plants in relation to their Red List status

In Central Germany and throughout Europe, arable plants count among some of the most endangered plant species. Over the last few decades, the number and size of populations have been in sharp decline due to modern land use techniques, including the application of fertilizers, herbicide use and seed cleaning procedures. As arable plant species are underrepresented in population genetic studies, it is unknown whether agricultural intensification has affected the extant populations, and whether genetic structure varies among species with differing vulnerability in respect of their Red List status. We sampled 53 populations from 6 arable plant species throughout Central Germany. Random amplified polymorphic DNA analyses (RAPD) were applied to calculate measures of genetic diversity at the population level and genetic differentiation. Genetic diversity was found to be lowest in Bupleurum rotundifolium and Anagallis foemina, and highest in Consolida regalis and Nigella arvensis. The highest levels of genetic differentiation were observed among populations of An. foemina and B. rotundifolium but within populations in all other species. Φ_ST values differed strongly ranging between 0.116 for C. regalis and 0.679 for An. foemina. Patterns of genetic structure were related to the Red List status for all the species studied except An. foemina, for which it should consequently be raised. Our data confirm that even relatively recent threats are accompanied by detrimental genetic structure. As losses of populations and increased fragmentation have occurred in all common and uncommon species, the situation for arable plants could change for the worse in the following decades, highlighting the need for consistent monitoring.     

Association of enkephalin catabolism inhibitors and CCKB antagonists: A potential use in the management of pain and opioid addiction

The overlapping distribution of opioid and cholecystokinin (CCK) peptides and their receptors (μ and δ opioid receptors; CCK-A and CCK-B receptors) in the central nervous system have led to a large number of studies aimed at clarifying the functional relationships between these two neuropeptides. Most of the pharmacological studies devoted to the role of CCK and enkephalins have been focused on the control of pain. Recently the existence of regulatory mechanisms between both systems have been proposed, and the physiological antagonism between CCK and endogenous opioid systems has been definitely demonstrated by coadministration of CCK-B selective antagonists with RB 101, a systemically active inhibitor, which fully protects enkephalins from their degradation. Several studies have also been done to investigate the functional relationships between both systems in development of opioid side-effects and in behavioral responses. This article will review the experimental pharmacology of association of enkephalin-degrading enzyme inhibitors and CCK-B antagonists to demonstrate the interest of these molecules in the management of both pain and opioid addiction. Special issue dedicated to Dr. Eric J. Simon.     

Exploration of disorder in protein structures by X-ray restrained molecular dynamics

Conformational disorder in crystal structures of ribonuclease-A and crambin is studied by including two independent structures in least-squares optimizations against X-ray data. The optimizations are carried out by X-ray restrained molecular dynamics (simulated annealing refinement) and by conventional least-squares optimization. Starting from two identical structures, the optimizations against X-ray data lead to significant deviations between the two, with rms backbone displacements of 0.45 A for refinement of ribonuclease at 1.53 A resolution, and 0.31 A for crambin at 0.945 A. More than 15 independent X-ray restrained molecular dynamics runs have been carried out for ribonuclease, and the displacements between the resulting structures are highly reproducible for most atoms. These include residues with two or more conformations with significant dihedral angle differences and alternative hydrogen bonding, as well as groups of residues that undergo displacements that are suggestive of rigid-body librations. The crystallographic R-values obtained are approximately 13%, as compared to 15.3% for a comparable refinement with a single structure. Least-squares optimization without an intervening restrained molecular dynamics stage is sufficient to reproduce most of the observed displacements. Similar results are obtained for crambin, where the higher resolution of the X-ray data allows for refinement of unconstrained individual anisotropic temperature factors. These are shown to be correlated with the displacements in the two-structure refinements.     

Peroxisomal oxidases and catalase in liver and kidney homogenates of normal and di(ethylhexyl)phthalate-fed rats.

1. Activities of peroxisomal oxidases and catalase were assayed at neutral and alkaline pH in liver and kidney homogenates from male rats fed a diet with or without 2% di(2-ethylhexyl)phthalate (DEHP) for 12 days. 2. All enzyme activities were higher at alkaline than at neutral pH in both groups. 3. The effect of the DEHP-diet on the peroxisomal enzymes was different in kidney and liver. Acyl-CoA oxidase activity was raised three- and sixfold in kidney and liver homogenates, respectively. The activity of D-amino acid oxidase decrease in liver, but increased in kidney homogenates. In liver homogenates, urate oxidase activity was not affected by the DEHP diet. The catalase activity was twofold induced in liver, but not in kidney. 4. The differences suggest that the changes of peroxisomal enzyme activities by DEHP treatment are not directly related to peroxisome proliferation. 5. DEHP treatment caused a marked increase of total and peroxisomal fatty acid oxidation in rat liver homogenates. 6. In the control group the rate of peroxisomal fatty acid oxidation was higher at alkaline pH than at neutral pH. 7. This rate was equal at both pH values in the DEHP-fed group, in contrast to the acyl-CoA oxidase activity. These results indicate that after DEHP treatment other parameters than acyl-CoA oxidase activity become limiting for peroxisomal beta-oxidation.     

Interactions of Schwann cells with neurites and with other Schwann cells involve the calcium-dependent adhesion molecule,N-cadherin

During embryogenesis, Schwann cells interact with axons and other Schwann cells, as they migrate, ensheath axons, and participate in organizing peripheral nervous tissues. The experiments reported here indicate that the calcium-dependent molecule, N-cadherin, mediates adhesion of Schwann cells to neurites and to other Schwann cells. Cell cultures from chick dorsal root ganglia and sciatic nerves were maintained in media containing either 2mM Ca⁺⁺ or 0.2 mM Ca⁺⁺, a concentration that inactivates calcium-dependent cadherins. When the leading lamellae of Schwann cells encountered migrating growth cones in medium with 2 mM Ca⁺⁺, they usually remained extended, and the growth cones often advanced onto the Schwann cell upper surface. In the low Ca⁺⁺ medium, the frequency of withdrawal of the Schwann cell lamella after contact with a growth cone was much greater, and withdrawal was the most common reaction to growth cone contact in medium with 2 mM Ca⁺⁺ and anti-N-cadherin. Similarly, when motile leading margins of two Schwann cells touched in normal Ca⁺⁺ medium, they often formed stable areas of contact. N-cadherin and vinculin were co-concentrated at these contact sites between Schwann cells. However, in low Ca⁺⁺ medium or in the presence of anti-N-cadherin, interacting Schwann cells usually pulled away from each other in a behavior reminiscent of contact inhibition between fibroblasts. In cultures of dissociated cells in normal media, Schwann cells frequently were aligned along neurites, and ultrastructural examination showed extensive close apposition between plasma membranes of neurites and Schwann cells. When dorsal root ganglia explants were cultured with normal Ca⁺⁺, Schwann cells migrated away from the explants in close association with extending neurites. All these interactions were disrupted in media with 0.2 mM Ca⁺⁺. Alignment of Schwann cells along neurites was infrequent, as were extended close apposition between axonal and Schwann cell plasma membranes. Finally, migration of Schwann cells from ganglionic explants was reduced by disruption of adhesive contact with neurites. The addition of antibodies against N-cadherin to medium with normal Ca⁺⁺ levels had similar effects as lowering the Ca⁺⁺ concentration, but antibodies against the neuronal adhesive molecule, L1, had no effects on interactions between Schwann cells and neurites.     

Aggrecan: Beyond cartilage and into the brain

Aggrecan is well-studied in cartilage but its expression and function in the central nervous system has only recently begun to be appreciated. Aggrecan plays an important role in the organization of the neural extracellular space by binding and organizing hyaluronan to the cell surface through interactions with link protein and tenascins forming a large aggregated quaternary complex. While all members of the lectican family to which aggrecan belongs are thought to mediate similar roles in organizing the neural matrix, aggrecan is unique in that it is the only family member found almost exclusively in an enigmatic matrix substructure called the perineuronal net. Current work has established a critical role for perineuronal nets and aggrecan in regulating developmental neural plasticity and in the recover from injury. In this review we focus on the structure, expression and function of aggrecan in the central nervous system.