Deacetylation of N8-acetylspermidine by subcellular fractions of rat tissue

The in vitro deacetylation of N⁸-acetylspermidine by an enzyme activity in rat tissues is described. This deacetylase activity occurs as a soluble, cytoplasmic enzyme in rat liver and was detected in the 100,000g supernatant fraction of all tissues examined. The highest specific activity was found in liver. Spleen, kidney, and lung were found to contain 20–50% of the activity in liver, while heart, brain, and skeletal muscle exhibited from 2 to 10% of the activity in liver. Serum contained only barely detectable levels of activity, much lower than any of the tissues studied. The in vitro metabolism of N¹-acetylspermidine differed from that observed for N⁸-acetylspermidine and does not appear to involve a simple deacetylation reaction.     

Studies on the mode of action of hygromycin B, an inhibitor of translocation in eukaryotes.

Hygromycin B is an unusual aminoglycoside antibiotic active against both prokaryotic and eukaryotic cells. Hygromycin B at 0.38 mM concentration completely halts yeast cell growth in rich media, presumably by preventing protein synthesis by cytoplasmic ribosomes. Polypeptide synthesis in cell-free extracts from rabbit reticulocytes, wheat germ and yeast is strongly blocked by low concentrations of hygromycin B. The antibiotic inhibits peptide chain elongation by yeast polysomes by preventing elongation factor EF-2-dependent translocation, although it does not affect either the formation of the EF-2-GTP-ribosome complex or the EF-2- and ribosome-dependent GTP hydrolysis which takes place uncoupled from translocation. The inhibition of translocation by hygromycin B might result from the stabilization of peptidyl-tRNA bound to the ribosomal acceptor site, since the stability of [3H]Phe-tRNA-EF-1-poly(U)-ribosome and [3H]Phe-tRNA-poly(U)-ribosome complexes is increased in the presence of hygromycin B. The inhibition of polyphenylalanine synthesis by reticulocyte ribosomes and enzymic translocation of peptidyl-tRNA by yeast polysomes can be reversed by increasing concentrations of EF-2 suggesting a relationship between the binding sites of EF-2 and hygromycin B on the ribosome. Neither non-enzymic translocation, that takes place in the presence of high potassium concentrations, nor the peptide bondforming step are affected by hygromycin B.     

Effect of fasting and insulin on the glucagon-induced orthophosphate incorporation to the isolated perfused rat liver.

Isolated perfused fed rat livers spontaneously liberated glucose and orthophosphate to the medium; 24-hr fasted rat livers did not exhibit these phenomena. In perfused fed rat livers, glucagon (2 mug) increased glucose output and promoted orthophosphate incorporation. In perfused fed rat livers, insulin (250 or 500 mU) inhibited the spontaneous liberation of glucose and orthophosphate. Comparable doses of insulin significantly reduced the glucagon (2 mug)-induced increase in glucose output from perfused fed rat liver, but did not affect orthophosphate uptake by the organ.     

Effect of p-chlorophenylalanine on the reproduction of the rat (author's transl)]

The effect of p-chlorophenylalanie (p-CPA) --300 mg/kg-- on reproduction has been studied in the female rat. Groups of animals were injected with a dose of 300 mg/kg of p-CPA 48 hours before proper copulation conditions at different moments along the ovarian cycle. Presence of spermatozoa in the vaginal frotis was negative in treated rats; in the control groups however, positivity was found in variable proportions according to the phase of the ovarian cycle: 30 ad 90% in diestrus and proestrus respectively. Treated animals showed continuous diestrus phases and diffuse luteinitation of the ovary. The results may indicate that a decrease of cerebral 5-HT, caused by p-CPA, lessens the reproductive behaviour of the female rat through mechanisms depending probably on the liberation of gonadrotrophins.     

Winter locations of red‐throated divers from geolocation and feather isotope signatures

Migratory species have geographically separate distributions during their annual cycle, and these areas can vary between populations and individuals. This can lead to differential stress levels being experienced across a species range. Gathering information on the areas used during the annual cycle of red‐throated divers (RTDs; Gavia stellata) has become an increasingly pressing issue, as they are a species of concern when considering the effects of disturbance from offshore wind farms and the associated ship traffic. Here, we use light‐based geolocator tags, deployed during the summer breeding season, to determine the non‐breeding winter location of RTDs from breeding locations in Scotland, Finland, and Iceland. We also use δ¹⁵N and δ¹³C isotope signatures, from feather samples, to link population‐level differences in areas used in the molt period to population‐level differences in isotope signatures. We found from geolocator data that RTDs from the three different breeding locations did not overlap in their winter distributions. Differences in isotope signatures suggested this spatial separation was also evident in the molting period, when geolocation data were unavailable. We also found that of the three populations, RTDs breeding in Iceland moved the shortest distance from their breeding grounds to their wintering grounds. In contrast, RTDs breeding in Finland moved the furthest, with a westward migration from the Baltic into the southern North Sea. Overall, these results suggest that RTDs breeding in Finland are likely to encounter anthropogenic activity during the winter period, where they currently overlap with areas of future planned developments. Icelandic and Scottish birds are less likely to be affected, due to less ship activity and few or no offshore wind farms in their wintering distributions. We also demonstrate that separating the three populations isotopically is possible and suggest further work to allocate breeding individuals to wintering areas based solely on feather samples.     

Hypotensive effect of naloxone on high blood pressure induced by stress in the rat

A naloxone-reversible enhancement of systolic blood pressure (BP) was induced in rats by application of three different types of stressor, i.e. intense light and sound, cold and foot-shock. In the case of labile high BP provoked by short-term isolation, the opiate antagonist naloxone (1 mg/Kg, i.p.) was also found to reverse hypertension. Naltrexone (2.5 mg/Kg, i.p.) also diminished high BP readings of briefly isolated rats. Conversely, blockade of the opiate receptor with naloxone did not alter elevated BP in cases of established hypertension (spontaneously hypertensive rats, deoxycorticosterone (DOCA)-salt rats and long-term isolated rats). These data can be taken as an evidence of opioid involvement at the onset of high BP readings induced by stress. However, once hypertension becomes established, the opioid system appears to recover its silent features.