Response latency of conditioned avoidance responses during generalization experiments in self-stimulated rats

Rats exhibiting steady self-stimulation behavior were trained to avoid a footshock after presentation of a unique brain rewarding stimulation of the postero-lateral part of the hypothalamus. Fifty percent of the animals tested were able to learn this conditioning paradigm. An hypothesis based upon modified internal physiological state elicited by the hypothalamic stimulation is discussed to explain the remaining half of the sample which failed to be conditioned. In the conditioned rats it seems that the time-dependent variable, the latency of response, can be used as a valid index for other experiments in which it is wished to study the internal decision process used to discriminate different hypothalamic stimulations in terms of their rewarding value.     

A serologic comparison of Moloney lymphoma cell surface and Moloney oncornavirus antigens.

Moloney lymphomas and Moloney sarcomas share strong tumor antigens. In this report we analyze the cell-surface antigens on a Balb/c Moloney lymphoma, LSTRA, using hyperimmune sarcoma regressor sera (alphaMo) as a primary reagent. We also use heterologous anti-viral p30 and gp70 sera for a direct analysis of virion protein antigens on the LSTRA surface. Using radiolabeled alphaMo-binding assays, we demonstrate that LSTRA tumor antigens detected by these sera are all Moloney viral antigens; approximately 1/3 of these antigenic determinants are expressed on the intact virus, and the other determinants are revealed by detergent lysis of the virus. The major viral antigens expressed on the LSTRA cell surface are viral env gene products, whereas gag gene products are only sparsely represented. We conclude that alphaMo sera detect almost exclusively viral antigens on LSTRA cells, and these antigens are almost exclusively virion env gene products.     

Acoustic phenomena related to an enriched benthic zone in the North Sea

In late summer and autumn 1985 and 1986, acoustic recordingswere made with a 38 kHz echo-sounder in a series of transectsoverlying the hydrographical front area south of the OysterGrounds (North Sea). The echograms revealed a narrow band ofincreased backscattering, which seemed related to an enrichedbenthic zone, located underneath this band at depths of 30–40m below the sea surface. This phenomenon is a permanent featureat this time of year, caused by locally high concentrationsof larger zooplanktonic and nektonic organisms. The peak inbackscattering showed a 6 h periodical shift in a north-southdirection as a result of tidal movements. ³Present address: University of Amsterdam, Institute of TaxonomicZoology, Department of Marine Invertebrates, P.O. Box 4766,1009 AT Amsterdam, The Netherlands     

Cover‐weighted averaging of indicator values in vegetation analyses

Question: How should species cover be weighted when calculating average indicator values of vegetation relevés? Location: The Netherlands. Method: Various weighting methods were statistically investigated with 188 relevés from The Netherlands for which accurate groundwater levels were available. For each method the correlation between average Ellenberg indicator value for moisture and mean spring groundwater level was calculated. A permutation test on correlation coefficients revealed whether differences between methods were significant or not. Results: Optimization of a general weighting function did not produce a significantly higher correlation than disregarding cover and calculating the average as the arithmetical mean of indicator values. Giving a higher weight to species at both ends of the indicator scale and using indifferent species as indicators of mediocre conditions did improve the correlation significantly. Weighting species proportionate to their cover yielded a significantly lower correlation than the correlation obtained with the method that disregards cover. A significantly lower correlation was also established when taking into account the fact that cover is related to the growth strategy of species.     

The diagnostic significance of nuclear deoxyribonucleic acid measurement in automated cytology.

Flow cytometric analysis of cytologic samples from four different organs shows that nuclear DNA content of malignant cell populations depends to a large extent on organ of origin of the tumor. This fact must be considered in planning screening systems.     

Technique for the quantification of transient quadratic phase couplings between heart rate components.

A technique for the time-variant analysis of quadratic phase coupling (QPC) in heart rate data is introduced and tested in 6 human neonates during quiet sleep. The set up of the approach is based up on the assumption that QPCs in the heart rate variability (HRV) are related to amplitude modulation effects. The application of the biamplitude deals with the detection of the coupling pattern and the bicoherence is used for the statistical quantification of coupling. By means of the results of bispectral analysis the time-variant processing has been adapted. The frequency-selective complex demodulation of the HRV leads to the envelope of the respiratory sinus arrhythmia (RSA), this has been used as one input for a time-variant coherence analysis. The other input is the low-pass filtered 10-second-rhythm of the HRV. A time-continuous quantification of the QPC, caused by amplitude modulation (10-second-rhythm modulates the RSA), is possible using this approach. According to our observed results in neonatal HRV both a phase co-ordination between the 10-second-rhythm and RSA as well as a non-linear coupling (amplitude modulation) between these HRV components can be seen.     

Structural basis for the substrate specificity and catalytic features of pseudouridine kinase from Arabidopsis thaliana

RNA modifications can regulate the stability of RNAs, mRNA–protein interactions, and translation efficiency. Pseudouridine is a prevalent RNA modification, and its metabolic fate after RNA turnover was recently characterized in eukaryotes, in the plant Arabidopsis thaliana. Here, we present structural and biochemical analyses of PSEUDOURIDINE KINASE from Arabidopsis (AtPUKI), the enzyme catalyzing the first step in pseudouridine degradation. AtPUKI, a member of the PfkB family of carbohydrate kinases, is a homodimeric α/β protein with a protruding small β-strand domain, which serves simultaneously as dimerization interface and dynamic substrate specificity determinant. AtPUKI has a unique nucleoside binding site specifying the binding of pseudourine, in particular at the nucleobase, by multiple hydrophilic interactions, of which one is mediated by a loop from the small β-strand domain of the adjacent monomer. Conformational transition of the dimerized small β-strand domains containing active site residues is required for substrate specificity. These dynamic features explain the higher catalytic efficiency for pseudouridine over uridine. Both substrates bind well (similar K_m), but only pseudouridine is turned over efficiently. Our studies provide an example for structural and functional divergence in the PfkB family and highlight how AtPUKI avoids futile uridine phosphorylation which in vivo would disturb pyrimidine homeostasis.     

Electrochemical removal of metallic implants from Technovit 9100 New embedded hard and soft tissues prior to histological sectioning

Solid metallic implants in soft or hard tissues are serious challenges for histological processing. However, metallic implants are more frequently used in e.g. cardiovascular or orthopaedic therapies. Before clinical use, these devices need to be tested thoroughly in a biological environment and histological analysis of their biocompatibility is a major requirement. To allow the histological analysis of metallic implants in tissues especially in calcified hard tissues, we describe a method for embedding these tissues in the resin Technovit 9100 New and removing the metallic implants by electrochemical dissolution. With the combination of these two processes, we are able to achieve 5 μm thick sections from soft or hard tissues with a superior preservation of tissue architecture and especially the implant-tissue interface. These sections can be stained by classical stainings, immunohistochemical and enzymehistochemical as well as DNA-based staining methods.     

A model to predict and assess the impacts of hydrologic changes on terrestrial ecosystems in The Netherlands,and its use in a climate scenario

Current water management policy in The Netherlands aims to serve a multitude of land use functions, such as agriculture, industry, shipping, and drinking water supply. To attune this policy to the diversity of functions, computer models are used to predict the consequences of various policy options as a part of PAWN: the government's Policy Analysis of Water management for The Netherlands.Nature conservation and development is a relatively new aspect of water management policy. This article describes the PAWN model DEMNAT, which is designed to predict the impact of hydrologic changes on terrestrial ecosystems in The Netherlands. The main components of the model are explained and the predicted effects of an assumed climatic change are discussed.