Endogenous Retroviruses in Domestic Animals

Endogenous retroviruses (ERVs) are genomic elements that are present in a wide range of vertebrates. Although the study of ERVs has been carried out mainly in humans and model organisms, recently, domestic animals have become important, and some species have begun to be analyzed to gain further insight into ERVs. Due to the availability of complete genomes and the development of new computer tools, ERVs can now be analyzed from a genome-wide viewpoint. In addition, more experimental work is being carried out to analyze the distribution, expression and interplay of ERVs within a host genome. Cats, cattle, chicken, dogs, horses, pigs and sheep have been scrutinized in this manner, all of which are interesting species in health and economic terms. Furthermore, several studies have noted differences in the number of endogenous retroviruses and in the variability of these elements among different breeds, as well as their expression in different tissues and the effects of their locations, which, in some cases, are near genes. These findings suggest a complex, intriguing relationship between ERVs and host genomes. In this review, we summarize the most important in silico and experimental findings, discuss their implications and attempt to predict future directions for the study of these genomic elements.     

Morphine metabolism and normorphine in Papaver somniferum

Normorphine has been established as an active metabolite of morphine in P. somniferum. This was done by, (a) demonstrating the presence of normorphine throughout the life cycle of the plant, (b) finding normorphine-¹⁴C after feeding morphine-¹⁴C via the roots, and (c) exposing opium poppies to ¹⁴CO₂ under steady state conditions which led to morphine and normorphine of the same specific activity. Feeding normorphine-¹⁴C showed that the N-demethylation step is irreversible. A sensitive procedure was developed for the detection of normorphine in the presence of large amounts of morphine; using this procedure, normorphine was found in raw opium. These results indicate that the major, if not the sole, morphine degradative pathway involves an initial demethylation to normorphine, which is subsequently degraded to non-alkaloidal metabolites. The high rates of turnover observed led to the conclusion that the morphine alkaloids do play an active metabolic role, perhaps as specific methylating agents.     

Fusicoccin receptors. Evidence for endogenous ligand

The binding of fusicoccin to the microsomal preparations of maize roots in vitro is increased several-fold when segments of the tissue are washed for 2 h in distilled water before homogenization. Addition of freeze-dried wash solution to microsomal preparations of spinach leaves or fresh roots, washed roots, or coleoptiles of maize inhibited the binding of fusicoccin to particulate fractions. The freeze-dried material also blocked fusicoccin-promoted H⁺ extrusion from maize root segments. Roots may contain one or more water-soluble compounds competing with fusicoccin at the receptor level; such ligands might play a physiological role as modulators of the H⁺/K⁺ exchange system in higher plants.Abbreviation FC Fusicoccin     

Release of Endogenous and Newly Synthesized Glutamate and of Other Amino Acids Induced by Non-N-Methyl-D-Aspartate Receptor Activation in Cerebellar Granule Cell Cultures

Amino acid release studies were performed by an HPLC procedure using differentiated rat cerebellar granule cell cultures. Kainic acid (KA; 50 microM) caused an increase (about threefold) in the release of endogenous glutamate and a lesser, but statistically significant, increase in the release of glutamine, glycine, threonine, taurine, and alanine. Quisqualic acid (QA) and, to a lesser degree, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) (both 50 microM) enhanced the release of the following amino acids in the order glutamate greater than aspartate greater than or equal to taurine, whereas the release of other amino acids was either unaffected or affected in a statistically nonsignificant way. The release of glutamate induced by KA was partially (43%) Ca2+ dependent. The other release-inducing effects of KA and QA were not Ca2+ dependent. In all cases, the evoked release could be prevented by the non-N-methyl-D-aspartate (non-NMDA) receptor antagonist 6-cyano-2,3-hydroxy-7-nitroquinoxaline, and thus appeared to be receptor mediated. NMDA (5 and 50 microM) had no release-inducing activity. The KA-, QA-, and AMPA-evoked release of newly synthesized [3H]glutamate and [3H]aspartate (formed in the cells exposed to [3H]glutamine) was very similar to the evoked release of endogenous glutamate and aspartate. On the other hand, the release of preloaded D-[3H]aspartate (purified by HPLC in the various fractions analyzed, before radioactivity determination) induced by 50 microM KA was twice as high as that of endogenous glutamate. In the case of high [K+] depolarization, in contrast, the release of preloaded D-[3H]aspartate was approximately 30% lower than that of endogenous glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)