Stimulation of ribose-5-phosphate and 5-phosphoribosyl-1-pyrophosphate generation by pyrroline-5-carboxylate in mouse liver in vivo: evidence for a regulatory role of ribose-5-phosphate availability in nucleotide synthesis.

Pyrroline-5-carboxylase (P5C), a physiological stimulator of hexose-monophosphate-pentose pathway activity, was found before to increase 5-phosphoribosyl-1-pyrophosphate (PRPP) generation and nucleotide synthesis in human erythrocytes and cultured fibroblasts. We now report the stimulation of PRPP generation by P5C also in mouse liver in vivo. In addition we demonstrated a simultaneous elevation in ribose-5-phosphate (R5P) concentration, which was relatively smaller and transient. The demonstrated effect of P5C on liver R5P and PRPP content in vivo provides strong evidence for the physiological role of R5P availability in the regulation of PRPP and purine production.     

Co-existence of immunoreactivity to anti-dopamine,anti-serotonin and anti-vasotocin in the cerebral giant neuron of the pond snail Lymnaea stagnalis

Summary Consecutive sections of certain neurons in the central ganglia of the pond snail Lymnaea stagnalis appear to be immunoreactive to anti-dopamine and anti-serotonin. The Cerebral Giant Neurons stain in addition with antivasotocin. The observations indicate the presence of two biogenic amines within the same neuron and in addition their co-existence with a biologically active peptide.     

Protamine amount and cross linking in mouse teratospermatozoa and aneuploid spermatozoa

The level of SH-group oxidation in spermatozoa from the cauda epididymis was measured by a cytofluorometric method in chromosomally normal mice and two chromosome mutants. The first one, a tertiary trisomic karyotype (Ts(1(13]7OH), is characterized by severe oligospermia and high levels (approximately 75%) of malformed spermatozoa. The second, a hybrid between two European feral mouse stocks, is heterozygous for multiple Robertsonian translocations and produces exclusively aneuploid spermatozoa. Neither the severe teratospermiogenesis nor the severe aneuploidy was reflected in total SH-group fluorescence values nor in free SH-group fluorescence. It is concluded that both the production of protamines and protamine cross linking by S-S bridge formation are rather autonomous processes during spermatogenesis because 1) the increased DNA variance of the aneuploid spermatozoa is not reflected in an increased variance of the total and free SH-groups, 2) aneuploidy for the protamine gene carrying chromosome 16 is not reflected by the SH-group values for individual spermatozoa, and 3) protamine production and cross linking are independent of the mild to severe terataspermiogenesis in the tertiary trisomic karyotype.     

The alpha-amylase gene in Drosophila melanogaster: nucleotide sequence, gene structure and expression motifs.

We present the complete nucleotide sequence of a Drosophila alpha-amylase gene and its flanking regions, as determined by cDNA and genomic sequence analysis. This gene, unlike its mammalian counterparts, contains no introns. Nevertheless the insect and mammalian genes share extensive nucleotide similarity and the insect protein contains the four amino acid sequence blocks common to all alpha-amylases. In Drosophila melanogaster, there are two closely-linked copies of the alpha-amylase gene and they are divergently transcribed. In the 5'-regions of the two gene-copies we find high sequence divergence, yet the typical eukaryotic gene expression motifs have been maintained. The 5'-terminus of the alpha-amylase mRNA, as determined by primer extension analysis, maps to a characteristic Drosophila sequence motif. Additional conserved elements upstream of both genes may also be involved in amylase gene expression which is known to be under complex controls that include glucose repression.     

Predicting Effects of Water Regime Changes on Waterbirds: Insights from Staging Swans

Predicting the environmental impact of a proposed development is notoriously difficult, especially when future conditions fall outside the current range of conditions. Individual-based approaches have been developed and applied to predict the impact of environmental changes on wintering and staging coastal bird populations. How many birds make use of staging sites is mostly determined by food availability and accessibility, which in the case of many waterbirds in turn is affected by water level. Many water systems are regulated and water levels are maintained at target levels, set by management authorities. We used an individual-based modelling framework (MORPH) to analyse how different target water levels affect the number of migratory Bewick’s swans Cygnus columbianus bewickii staging at a shallow freshwater lake (Lauwersmeer, the Netherlands) in autumn. As an emerging property of the model, we found strong non-linear responses of swan usage to changes in water level, with a sudden drop in peak numbers as well as bird-days with a 0.20 m rise above the current target water level. Such strong non-linear responses are probably common and should be taken into account in environmental impact assessments.     

Selecting high-dimensional mixed graphical models using minimal AIC or BIC forests

Background  

Chow and Liu showed that the maximum likelihood tree for multivariate discrete distributions may be found using a maximum weight spanning tree algorithm, for example Kruskal's algorithm. The efficiency of the algorithm makes it tractable for high-dimensional problems.