The placement, recovery, and loss of scatter hoards by eastern chipmunks,Tamias striatus

Although eastern chipmunks typically larder hoard food in theirburrows, some scatter hoarding occurs, especially by newly emergedjuveniles and by females with young. To examine patterns ofscatter hoard placement and their adaptive significance, weused standard food provisioning tests followed by continuousmonitoring to determine the longevity and fate of scatter hoards.Longevity of scatter hoards was low (median 74 min) and pilferagewas high (46%). Chipmunks placed scatter hoards away from thepatch, closer to their burrow and within the defended area ofprimary use. Scatter hoard placement was affected by the numberof competitors at the patch. However, juveniles and femaleswith young differed slightly in their responses. competitorsthat approached scatteihoards were sometimes chased away bythe scatter hoard's owner, and the scatter hoard was moved toanother location by the owner. Females with young recoveredtheir largest scatter hoards first, but there was little additionalpattern in scatter hoard recovery. An experiment using simulatedscatter hoards showed that scatter hoards farther from a patchof food lasted longer and that disturbing and marking scatterhoards reduced their longevity. These observations indicate:(1) that scatter hoard placement is more related to avoidingpilferage of completed caches than to rapidly sequestering fooditems from an ephemeral patch and (2) that optimal cache distributionmay be affected by the cache-defense ability of individuals,by the relationship between competitor density and cache securitynear the patch, and by the territorial behavior of neighboringconspecifics.     

Altered free calcium transients in pig kidney cells (LLC-PK1) cultured with penicillin/streptomycin

Summary The effect of a conventional antibiotic (penicillin/streptomycin) mixture on the widely used kidney epithelial cell line, LLC-PK₁, was investigated by measuring growth and intracellular free calcium. Free calcium concentration was the same in cells cultured for 3 to 7 wk with (“plus”) and without (“minus”) antibiotics both at rest and when challenged with high (14 mM) external calcium. When exposed to vasopressin, minus cells exhibited significantly smaller calcium transients than plus cells. A similar difference existed for transients elicited by a calcium ionophore, 4-br-A23187. After longer periods of culture (>20 wk), minus cells grew slower than plus cells but on reaching confluence (minus cells took 1 day longer) the morphologies and viabilities were indistinguishable. The finding that culture with penicillin/streptomycin reversibly modified some properties of LLC-PK₁ cells, at least partly through altered calcium homeostasis, is of importance for workers using this cell model to study drug effects and raises the general possibility of similar effects on other cultured cells.     

A Hydrogen-Donating Monohydroxamate Scavenges Ferryl Myoglobin Radicals

The addition of 25μM hydrogen peroxide to 20μM metmyoglobin produces ferryl (Fe^IV = O) myoglobin. Optical spectroscopy shows that the ferryl species reaches a maximum concentration (60-70% of total haem) after 10 minutes and decays slowly (hours). Low temperature EPR spectroscopy of the high spin metmyoglobin (g = 6) signal is consistent with these findings. At this low peroxide concentration there is no evidence for iron release from the haem. At least two free radicals are detectable by EPR immediately after H₂O₂ addition, but decay completely after ten minutes. However, a longer-lived radical is observed at lower concentrations that is still present after 90 minutes. The monohydroxamate N-methylbutyro-hydroxamic acid (NMBH) increases the rate of decay of the fenyl species. In the presence of NMBH, none of the protein-bound free radicals are detectable; instead nitroxide radicals produced by oxidation of the hydroxamate group are observed. Similar results are observed with the trihydroxamate, desferoxamine. “Ferryl myoglobin” is still able to initiate lipid peroxidation even after the short-lived protein free radicals are no longer detectable (E.S.R. Newman, C.A. Rice-Evans and M.J. Davies (1991) Biochemical and Biophysical Research Communications 179, 1414-1419). It is suggested that the longer-lived protein radicals described here may be partly responsible for this effect. The mechanism of inhibition of initiation of lipid peroxidation by hydroxamate drugs, such as NMBH, may therefore be due to reduction of the protein-derived radicals, rather than reduction of ferryl haem.     

Effect of acute pH depression on the survival of the freshwater amphipod Hyalella azteca at variable temperatures: field and laboratory studies

Field observations on temperature and pH of a small pond showed that a amphipod population of Hyalella azteca was exposed to variable seasonal pH between 5.10–5.85, and water temperatures between 2–21 °C. Laboratory experiments were designed to simulate seasonal temperatures and field pHs of a small pond habitat. Laboratory bioassay experiments were conducted to determine the survival of Hyalella azteca at pHs 4, 5, 6 and 7, and varying temperatures of 5°, 10°, 15°, 20° and 25 °C.The LT₁₀₀ at pH 4 and 25 °C was 5.7 ± 0.47 days, compared to 47.3 ± 2.49 days at 5 °C. An Analysis of Variance (ANOVA) showed temperature was a significant (p > 0.0001) source of variation in the acute lethality of pH to H. azteca. A Duncans Multiple Range Test (DMRT) further showed that in laboratory experiments at pH 4, there was a significant difference ( = 0.01) between the LT_100s at 5°, 10°, 15° and 20 °C, but not between temperatures 20° and 25 °C.     

Life history and reproductive potential of the agarophyte Gelidium robustum in California

The reproductive potential of the tetrasporangial phase of Gelidium robustum was studied for 16 months at two sites off Santa Barbara, California. In all samples tetrasporangial thalli were always more abundant than gametangial ones. Tetratrasporangial sori were present throughout the duration of the study but relative fecundity was highest [300–400 sori g^–1 (w. wt)] in spring/summer samples of consecutive years, as a result of increasing numbers both of tetrasporangial branchlets per plant and of sori per branchlet. On the other hand, laboratory experiments showed that tetraspore release per sorus was highest (150–250 spores sorus^–1 d^–1) in winter. Inferring from these field and laboratory data plants released up to ± 34 000 tetraspores g^–1 (w. wt) d^–1 in the spring/summer of the second study year. Tetraspore germination, under defined culture conditions, also showed a marked seasonality increasing sharply from less than 10% in winter up to almost 60% in spring/summer, thus coinciding with the period of maximal spore output per plant. These results suggest that although relatively high numbers of tetraspores may be released by G. robustum plants all year round these might not always have the potential to germinate and recruit.     

Male-male pairs in Greylag Geese (Anser anser)

Summary For almost two decades a flock of 130 free-flying Greylag Geese (Anser anser) has been the focus of detailed ethological investigations at the Konrad Lorenz Institut in Grünau im Almtal, Austria. Gander pairs, i. e. male-male pairs, represent a prominent social unit in this flock and were the subject of a detailed behavioral investigation. Analysis of the composition and dynamics of the flock over a 15 year period indicated that the incidence of homosexual pairings closely paralleled the male bias of the sex ratio. The behavior of ganders in gander pairs was investigated and compared to that of gander and goose in heterosexual pairs. The behavior of the two males in a gander pair (1) was comparable in most aspects, (2) was similar to the behavior of the gander in heterosexual pairs, and (3) differed greatly from that of the heterosexually paired goose. Therefore, pseudo-female behavior in one partner cannot account for the formation of a pairbond between two males. As a unit, gander pairs were characterized by a higher frequency of offensive agonistic behavior compared to heterosexual pairs and spent significantly more time peripheral to, and away from the flock than did heterosexual pairs.

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Zusammenfassung Das Sozialgefüge einer Schar Graugänse ist weitaus komplizierter, als es das monogame Fortpflanzungssystem erwarten ließe (Collias &Jahn 1959,Fischer 1965,Kalas 1979,Rutschke 1982). Ganterpaare, die häufig über Jahre hinweg bestehen bleiben, sind für tiersoziologische Untersuchungen interessant, weil ihre Funktion nicht im Rahmen der Fortpflanzung gesehen werden kann. Welche Bedingung begünstigen die Bildung von Ganterpaaren, und welche Verhaltensmechanismen tragen zum Entstehen und zur Aufrechterhaltung dieser Verbindung bei? Die Zusammensetzung der Grünauer Graugansschar 1973–1988 zeigt, daß die Anzahl der Ganterpaare von einem Überschuß von Männchen in der Schar abhängt. Das Verhalten von 6 Ganterpaaren wurde untersucht und mit dem von heterosexuellen Paaren verglichen. Innerhalb eines Ganterpaares entsprachen sich die Partner in der Häufigkeit von agonistischem sowie sozial-bindendem Verhalten. Homo- und heterosexuell verpaarte Ganter zeigten sich im Verhalten vergleichbar. Der Ganter eines Ganterpaares unterschied sich jedoch in der Häufigkeit aller untersuchten Verhaltensweisen von dem der heterosexuell verpaarten Gans. Folgende Schlußfolgerungen und Hypothesen bieten sich an: (1) Pseudo-weibliches Verhalten bei einem der Ganter scheint nicht die Bildung von Ganterpaaren erklären zu können. Beide Ganter verhalten sich rein männlich und behandeln den Partner so, als ob dieser ein Weibchen wäre. (2) Ein Mangel an gegengeschlechtlichen Schargenossen fördert die Bildung von homosexuellen Paaren und aufzuchtsbekannte Vögel werden dabei vorgezogen. (3) Ein Zusammenschluß mit einem gleichgeschlechtlichen Artgenossen sollte, verglichen mit der Möglichkeit alleine zu bleiben, eine überlegene Strategie darstellen, da unverpaarte Gänse geringeren Zugang zu Futterquellen haben und eher Raubtieren zum Opfer fallen. (4) Homosexuelle Paare könnten als ein Puffersystem für Ganter angesehen werden, vor allem zu Zeiten in denen das Geschlechtsverhältnis in Richtung der Männchen verschoben ist. (5) Aggression des Ganters richtet sich generell gegen andere männliche Schargenossen. Die Bildung von Ganterpaaren, also besonders aggressiven Paaren, könnte daher dazu beitragen, Ganter aus der Schar zu vertreiben und ein Übermaß von Männchen in der Schar zu verhindern. (6) Da wir zeigen konnten, daß sich homosexuelle Paare oft am Rande der Schar aufhalten und dabei häufig sichern, könnte solchen Paaren eine Art Wächterfunktion zukommen. (7) Andererseits ist es durchaus möglich, daß Ganterpaare bloß ein Epiphenomen einer Graugansschar mit einem Überschuß an Männchen darstellen.

     

Neutral adaptation of the genetic code to double-strand coding

Summary We lay new foundations to the hypothesis that the genetic code is adapted to evolutionary retention of information in the antisense strands of natural DNA/RNA sequences. In particular, we show that the genetic code exhibits, beyond the neutral replacement patterns of amino acid substitutions, optimal properties by favoring simultaneous evolution of proteins encoded in DNA/RNA sense-antisense strands. This is borne out in the sense-antisense transformations of the codons of every amino acid which target amino acids physicochemically similar to each other. Moreover, silent mutations in the sense strand generate conservative ones in its antisense counterpart and vice versa. Coevolution of proteins coded by complementary strands is shown to be a definite possibility, a result which does not depend on any physical interaction between the coevolving proteins. Likewise, the degree to which the present genetic code is dedicated to evolutionary sense-antisense tolerance is demonstrated by comparison with many randomized codes. Double-strand coding is quantified from an information-theoretical point of view.     

Aurintricarboxylic Acid Protects Hippocampal Neurons from NMDA-and Ischemia-Induced Toxicity In Vivo

Abstract: The polymeric dye aurintricarboxylic acid (ATA) has been shown to protect various cell types from apoptotic cell death, reportedly through inhibition of a calcium-dependent endonuclease activity. Recent studies have indicated that there may be some commonalities among apoptosis, programmed cell death, and certain other forms of neuronal death. To begin to explore the possibility of common biochemical mechanisms underlying ischemia-or excitotoxin-induced neuronal death and apoptosis in vivo, gerbils or rats subjected to transient global ischemia or NMDA microinjection, respectively, received a simultaneous intracerebral infusion of ATA or vehicle. As a biochemical marker of neuronal death, spectrin proteolysis, which is mediated by activation of calpain I, was measured in hippocampus after 24 h. ATA treatment resulted in a profound reduction of both NMDA-and ischemia-induced spectrin proteolysis, consistent with the possibility of some common mechanism in apoptosis and other forms of neuronal death in vivo.     

Ecto-Protein Kinase and Surface Protein Phosphorylation in PC12 Cells: Interactions with Nerve Growth Factor

Abstract: The phosphorylation of surface proteins by ectoprotein kinase has been proposed to play a role in mechanisms underlying neuronal differentiation and their responsiveness to nerve growth factor (NGF). PC 12 clones represent an optimal model for investigating the mode of action of NGF in a homogeneous cell population. In the present study we obtained evidence that PC12 cells possess ectoprotein kinase and characterized the endogenous phosphorylation of its surface protein substrates. PC12 cells maintained in a chemically defined medium exhibited phosphorylation of proteins by [γ-³²P]ATP added to the medium at time points preceding the intracellular phosphorylation of proteins in cells labeled with ³²P_i. This activity was abolished by adding apyrase or trypsin to the medium but was not sensitive to addition of an excess of unlabeled P_i. As also expected from ecto-protein kinase activity, PC12 cells catalyzed the phosphorylation of an exogenous protein substrate added to the medium, dephospho-α-casein, and this activity competed with the endogenous phosphorylation for extracellular ATP. Based on these criteria, three protein components migrating in sodium dodecyl sulfate gels with apparent molecular weights of 105K, 39K, and 20K were identified as exclusive substrates of ecto-protein kinase in PC12 cells. Of the phosphate incorporated into these proteins from extracellular ATP, 75–87% was found in phosphothreonine. The phosphorylation of the 39K protein by ecto-protein kinase did not require Mg²⁺, implicating this activity in the previously demonstrated regulation of Ca²⁺-dependent, high-affinity norepinephrine uptake in PC12 cells by extracellular ATP. The protein kinase inhibitor K-252a inhibited both intra- and extracellular protein phosphorylation in intact PC12 cells. Its hydrophilic analogue K-252b, had only minimal effects on intracellular protein phosphorylation but readily inhibited the phosphorylation of specific substrates of ecto-protein kinase in PC12 cells incubated with extracellular ATP, suggesting the involvement of ecto-protein kinase in the reported inhibition of NGF-induced neurite extension by K-252b. Preincubation of PC12 cells with 50 ng/ml of NGF for 5 min stimulated the activity of ecto-protein kinase toward all its endogenous substrates. Exposure of PC12 cells to the same NGF concentration for 3 days revealed another substrate of ecto-protein kinase, a 53K protein, whose surface phosphorylation is expressed only after NGF-induced neuronal differentiation. In the concentration range (10–100 μM) at which 6-thioguanine blocked NGF-promoted neurite outgrowth in PC12 cells, 6-thioguanine effectively inhibited the phosphorylation of specific proteins by ecto-protein kinase. This study provides the basis for continued investigation of the involvement of ecto-protein kinase and its surface protein substrates in neuronal differentiation, neuritogenesis, and synaptogenesis.     

ANTIVIRAL ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

Lipophilic and hydrophilic extracts from approximately 600 strains of cultured cyanophytes, representing some 300 species, were examined for antiviral activity against three pathogenic viruses. Approximately 10% of the cultures produced substances that caused significant reduction in cytopathic effect normally associated with viral infection. The screening program identified the order Chroococcales as commonly producing antiviral agents.