Studien an einer farbig beringten Population des Braunkehlchens (Saxicola rubetra)

Ohne ZusammenfassungMrs. Margaret M. Nice gewidmet zum 70. Geburtstag am 6. Dezember 1953In verkürzter Form vorgetragen vonK. Schmidt auf der 67. Tagung der D. O.-G. am 16. August 1953 in Köln. — 291. Ringfundmitteilung der Vogelwarte Radolfzell.     

Indo-Pacific and Atlantic spurs and grooves revisited: the possible effects of different Holocene sea-level history,exposure, and reef accretion rate in the shallow fore reef

Shallow fore-reef areas worldwide are usually characterized by spurs and grooves. A comparison of examples from the three world oceans suggests that Indo-Pacific spurs and grooves are shaped predominantly by erosion, whereas western Atlantic spur and groove systems are largely a product of constructive processes. I propose that this difference is caused by regional differences in Holocene sea-level change, which controlled exposure to waves and currents, and reef-accretion rates. The transgressive–regressive sea-level curve in the Indo-Pacific realm, i.e., the Mid-to-Late Holocene sea-level fall in these areas has maintained high-energy conditions in the shallow fore reef. Higher exposure to waves and currents favors erosion and leads to a dominance of crustose coralline algae that have relatively slow growth rates. In the western Atlantic, the transgressive Holocene sea level has caused Mid-to-Late Holocene deepening and has maintained accommodation space for reef accretion. Fast-growing acroporid corals thrive under lower exposure and are more common than coralline algae. The fossil record of the spur and groove system is rather poor, which is probably a consequence of the need of excellent, three-dimensional outcrops for identification.     

Effect of pathogenic mutations on the structure and dynamics of Alzheimer’s Aβ42-amyloid oligomers

Converging lines of evidence suggest that soluble Aβ-amyloid oligomers play a pivotal role in the pathogenesis of Alzheimer’s disease, and present direct effectors of synaptic and cognitive dysfunction. Three pathological E22-Aβ-amyloid point mutants (E22G, E22K, E22Q) and the deletion mutant E22Δ exhibit an enhanced tendency to form prefibrillar aggregates. The present study assessed the effect of these four mutations using molecular dynamics simulations and subsequent structural and energetic analyses. Our data shows that E22 plays a unique role in wild type Aβ, since it has a destabilising effect on the oligomer structure due to electrostatic repulsion between adjacent E22 side chains. Mutations in which E22 is replaced by an uncharged residue result in higher oligomer stability. This effect is also observed to a lesser extent for the E22K mutation and is consistent with its lower pathogenicity compared to other mutants. Interestingly, deletion of E22 does not destroy the amyloid fold but is compensated by local changes in the backbone geometry that allow the preservation of a structurally important salt bridge. The finding that all mutant oligomers investigated exhibit higher internal stability than the wild type offers an explanation for the experimentally observed enhanced oligomer formation and stability.     

A survey for Cyclospora spp. in Kenyan primates, with some notes on its biology.

From March 1999 through August 2000, 511 stool samples collected from 11 different primate species in 10 geographically distinct locations in Kenya, East Africa, were screened for the presence of Cyclospora spp. oocysts. Positive samples (43/102, 42%) were identified in vervet monkeys (Cercopithecus aethiops) in 4 of 4 locations; 19/206 (9%) in yellow and olive baboons (Papio cynocephalus, P. anubis, respectively) in 5 of 5 locations; and 19/76 (25%) in black and white colobus monkeys (Colobus angolensis, C. guereza, respectively) from 2 of 3 locations. DNA sequences obtained from 18 S rRNA coding regions from respective subsets of these positive samples were typed as Cyclospora cercopitheci (samples from Cercopithecus aethiops). Cyclospora papionis (samples from Papio cynocephalus and P. anubis), and Cyclospora colobi (samples from Colobus angolensis and C. guereza). Cyclospora oocysts were not detected in samples collected from patas, highland sykes, lowland sykes, blue sykes, DeBrazza, or red-tailed monkeys. A coded map showing the geographic location of the collected samples is given. Stool samples from 1 troop of vervet monkeys were collected over a 12-mo period. Positive samples ranged between 21 and 63%. These results suggest that there is no strongly marked seasonality evident in Cyclospora infection in monkeys as has been noted in human infection. This is further confirmed by the recovery of positive samples collected from vervet monkeys, baboons, and colobus monkeys at all times of the year during this survey. This absence of seasonality in infection is especially notable because of the extreme weather patterns typical of Kenya, where marked rainy and dry seasons occur. A second noteworthy observation is that the striking host specificity of the Cyclospora species initially described was confirmed in this survey. Baboons were only infected with C. papionis, vervet monkeys with C. cercopitheci, and colobus monkeys with C. colobi, despite geographic overlaps of both the monkey and parasite species and wide geographic distribution of each parasite and monkey host.     

Exposure of Dunnocks (Prunella modularis) to their Previous Wintering Site Modifies Autumnal Activity Pattern: Evidence for Site Recognition?

We caught dunnocks at a wintering site near Pisa/Italy prior to their departure for breeding territories and held them indoors north of this site (Andechs/Germany) on a simulated photoperiod of 52.5 °N. After birds had gone through a reproductive cycle and postnuptial moult they developed migratory restlessness in autumn. At this time one group was transferred back to the previous wintering site (Pisa) where birds were held in individual activity cages in an outdoor aviary, allowing them to perceive as much environmental information as possible. A second group was transferred to a control site near Tour du Valat/France of approximately the same latitude and climate, but different longitude and held in an identical aviary. The diurnal activity pattern changed after transfer back to the previous wintering site, but not after transfer to the control site. Specifically, the amount of morning activity was reduced while afternoon activity was increased. This effect was restricted to those individuals that had been developing nocturnal migratory restlessness the previous spring. It was absent in individuals without migratory restlessness in spring, indicating that the different patterns were not due to unspecific effects from the testing sites. These results are consistent with the hypothesis that birds were able to derive information about their locality and to recognize their previous wintering site, resulting in suppression of migratory state by experience. The results are not definitely conclusive, however, because of several difficulties in the interpretation of perch-hopping activity, which are discussed in detail.