Severe and rapid population declines in exotic birds

A particularly vexing phenomenon within invasion ecology is the occurrence of spontaneous collapses within seemingly well-established exotic populations. Here, we assess the frequency of collapses among 68 exotic bird populations established in Hawaii, Puerto Rico, Los Angeles and Miami. Following other published definitions, we define a ‘collapse’ as a decline in abundance of ≥90 % within ≤10 years that lasts for at least 3 years. We show that 44 of the 68 exotic bird populations have exhibited declines at some point within their time series. Sixteen of the populations declined sufficiently to be defined as collapsed. It took on average 3.8 ± 1.8 years for populations to decline into a collapsed state, and this state persisted on average for 7.1 ± 6.3 years across (collapsed) populations. We compared the severity and duration of declines across all 44 declining populations according to taxonomic Order and geographic region. Neither variable explained substantial variation in the metrics of collapse. Our results indicate that severe, rapid, and persistent population declines may be common among exotic populations. We suggest that incorporating the probability and persistence of collapses into management decisions can inform efforts to enact control or eradication measures. We also suggest that applying our approach to other taxa and locations is crucial for improving our understanding of when and where collapses are likely to occur.     

''Cross-talk'' between phospholipase C and adenylyl cyclase involves regulation of G-protein levels in GH3 rat pituitary cells.

We have investigated the possibility that adenylyl cyclase (AC) activity and membrane protein levels of the -subunits of the stimulatory and inhibitory G-proteins of AC (G_s and G_i−2) in cultured prolactin-producing rat pituitary adenoma cells (GH₃ cells) are modulated by phospholipase C (PLC)-generated second messengers. Pretreatment of cells (6–48 h) with ionomycin (1 μM) or 1-oleoyl-2-acetylglycerol (OAG; 1μM) showed that ionomycin regulated G_s levels in a time-dependent, biphasic manner; a two-fold increase followed a 40% initial reduction, while OAG lowered G_s levels by more than 50% at all time-points. G_i−2 levels remained unchanged by both pretreatments. OAG, but not ionomycin, increased basal AC activity without increasing enzyme protein levels. Alterations in AC responsiveness to peptide hormones (e.g. thyroliberin and vasoactive intestinal peptide) correlated to membrane G_s protein -subunit content. These results demonstrate the involvement of G-protein translation regulation as one mechanism of ‘cross-talk’ between the PLC- and AC-dependent signalling pathways.     

Sequential Entry of Transforming Markers into Neisseria meningitidis After Chromosome Alignment

The kinetics of appearance of transformants as a function of time of exposure to deoxyribonucleic acid (DNA) was examined in Neisseria meningitidis. Incubation with chloramphenicol for as long as 2 hr, which probably leads to chromosome alignment, resulted in augmentation of the lag period before the appearance of the first transformants. The lag periods thus found were dependent upon the marker tested. This permitted the construction of a time map according to the lag periods observed for individual markers. This map was in general agreement with the chromosome map of the recipient strain as determined by marker frequency analysis. Transformation of recipient cells with chromosomes aligned by growth to the stationary phase showed the same type of increased lag in the appearance of transformants before the logarithmic phase of growth had again been reached. These results support the assumption that the nature of the marker accepted by a recipient cell corresponds to the marker present at the replication point of the chromosome. In the absence of DNA and protein synthesis, the uptake of one marker seems to be successively followed by other markers in a linear order determined by the chromosome of the recipient cell.     

Stroke research in GenomEUtwin.

Stroke is one of the leading causes of severe disability and death in the world. In the present article we outline possibilities and limitations for future stroke research within the GenomEUtwin. The combined sample of twins born before 1958 from Denmark, Finland, and Sweden, and available for follow-up into the second millennium for non-fatal and fatal stroke events through national inpatient and death registers exceeds 70,000 twin pairs. This sample size will enable the study of genetic influences on stroke and major stroke subtypes. Large samples of twins in GenomEUtwin have been followed up repeatedly through interviews and questionnaires concerning a variety of exposures and potential risk factors for stroke. We briefly outline how this information can be combined with the health register information for epidemiologic and genetic epidemiologic studies of stroke. We also present the number of twin pairs concordant and discordant for stroke in Denmark, Finland and Sweden, and time lags between events for twins concordant for stroke. This information illustrates that the number of affected sib pairs for linkage studies is relatively limited, but the sample sizes are promising for association studies.     

The macrobenthos of the pristine stream, Skiftesåa, Høylandet, Norway

The species composition of aquatic insects in theboreal stream, Skiftesåa, was investigated usingemergence traps, Malaise traps and kick samples. Atleast 13 Ephemeroptera, 16 Plecoptera, 25 Trichopteraand 120 Chironomidae species were recorded. This faunais representative for non-polluted, northern streams.The production of macrobenthos was estimated to beonly about 1 g dry weight per year and m²,possibly due to the fluctuating flow of water.     

Intracellular transport and degradation of 125I-labelled denatured serum albumin in isolated nonparenchymal rat liver cells

The intracellular movement, following uptake of ¹²⁵I-labelled denatured serum albumin into nonparenchymal liver cells, was followed by means of subcellular fractionation. Isolated nonparenchymal rat liver cells were prepared by means of differential centrifugation. The cells were homogenized in a sonifier and the cytoplasmic extract subjected to isopycnic centrifugation in a sucrose gradient. The intracellular movement of the labelled albumin was followed by comparing the distribution profile of radioactivity in the sucrose gradient with those of marker enzymes for plasma membrane and lysosomes. The distribution profiles for radioactivity after the cells had been exposed to the labelled denatured albumin for different time periods indicated that the radioactivity was first associated with subcellular fractions of lower modal densities than the lysosomes. With time of incubation the radioactivity moved towards higher densities. After prolonged incubations in the absence of extracellular labelled denatured albumin the radioactivity peak coincided with that of the lysosomal marker β-acetylglucosaminidase. When the cells were treated with the lysosomal inhibitor leupeptin, degradation of the labelled albumin was decreased, resulting in a massive intracellular accumulation of radioactivity. The radioactivity peak coincided with the peak of activity for the lysosomal marker β-acetylglucosaminidase, suggesting lysosomal degradation.     

Behaviour and dispersal in adult Taeniopteryx nebulosa (Linnaeus, 1758) and Perlodes microcephalus (Pictet, 1833) (Plecoptera) in Denmark

Adult Taeniopteryx nebulosa (Linnaeus, 1758 Linnaeus, C. (1758), Systema Naturae (10th ed.), Tom 1, Holmiae. [Google Scholar]) and Perlodes microcephalus (Pictet, 1833 Pictet, J., (1833), ‘Memoire sur la Metamorphoses des Perles’, Annales des Sciences Naturelles, XXVII, 44–55. [Google Scholar]) emerge late winter to early spring in Danish streams. Based on 13 years of study, we have provided new data and discussed little-known aspects of biology of these two species. Taeniopteryx nebulosa male deposits a spermatophore on the female gonopore. Both species are poor fliers and seek high posts for take-off, where they thermoregulate by basking in a pre-flight sun posture for heating flight muscles. Oviposition flight is erratic and short. The females skim back to land. Taeniopteryx nebulosa eggs drift a long distance as single eggs before adhering to vegetation. Perlodes microcephalus eggs drift a short distance as intact eggpackets before they fasten and disintegrate on the bottom. Perlodes microcephalus females select oviposition sites on or close to upstream a riffle. This is critical in ensuring that eggs fasten on stable gravel and stone bottoms. The fast recolonisation of P. microcephalus in Danish streams following restoration measures indicates efficient dispersal ability despite poor flight performance. Adults of both species adhere to clothes, feather and fur. Taeniopteryx nebulosa tarsomeres have many hooked setae, P. microcephalus tarsomeres have some hooked setae and a dense cover of microtrichia. They may disperse by hitchhiking on birds and mammals.     

Zinc ions inhibit oxidation of cytochrome c oxidase by oxygen

Cytochrome c oxidase is a membrane-bound enzyme that catalyses the reduction of O2 to H2O and uses part of the energy released in this reaction to pump protons across the membrane. We have investigated the effect of addition of Zn2+ on the kinetics of two reaction steps in cytochrome c oxidase that are associated with proton pumping; the peroxy to oxo-ferryl (P(r)-->F) and the oxo-ferryl to oxidised (F-->O) transitions. The Zn2+ binding resulted in a decrease of the F-->O rate from 820 s(-1) (no Zn2+) to a saturating value of approximately 360 s(-1) with an apparent K(D) of approximately 2.6 microM. The P(r)-->F rate (approximately 10[(4) s(-1)] before addition of Zn2+) decreased more slowly with increasing Zn2+ concentration and a K(D) of approximately 120 microM was observed. The effects on both kinetic phases were fully reversible upon addition of EDTA. Since both the P(r)-->F and F-->O transitions are associated with proton uptake through the D-pathway, a Zn2+-binding site is likely to be located at the entry point of this pathway, where several carboxylates and histidine residues are found that may co-ordinate Zn2+.