Population changes of Antarctic fur seals at Nyrøysa, Bouvetøya

Antarctic fur seal Arctocephalus gazella pup production at Nyrøysa, Bouvetøya was estimated to be approximately 15,000 per annum during each of four summers from 1996 to 2002, indicating a total population of about 66,000. While the Bouvetøya population is the second largest for this species, pup production at this site still accounts for only 2.4% of the global total. This population experienced a mean annual rate of increase of 30.6% for the period 1989–1996, perhaps due, in part, to significant immigration, but has been stable since 1996. Historical accounts of significant numbers of animals being present towards the end of the period of sealing (C.1800–1930), indicate that the geographic isolation and inaccessibility of this site may have resulted in the Bouvetøya population being one of three populations that survived a series of periods of extreme exploitation of this species.     

Simulation of stent deployment in a realistic human coronary artery

Background  

The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis.     

Counts of southern elephant seals, Mirounga leonina, at Bouvet Island

Southern elephant seals were counted and classified into subjective sex-age classes on a weekly basis during expeditions to Bouvet Island in the austral summers of 1996/1997 and 1998/1999. The expeditions coincided with the moulting period of elephant seals aged one?year and older. The presence of weaned pups at the principal haulout site, Nyrøysa/Westwindstranda, during the latter expedition, indicates that breeding took place here during 1998. Elephant seal counts from previous expeditions are summarised.     

Trehalose Increases Freeze-Thaw Damage in Liposomes Containing Chloroplast Glycolipids

Chloroplast thylakoids contain three classes of glycolipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG). We have investigated the stability of large unilamellar vesicles made from egg phosphatidylcholine (EPC) and different chloroplast glycolipids during freezing to -18 degreesC, as a function of the presence of three sugars: glucose, sucrose, or trehalose. Contrary to the situation in thylakoids, where cryoprotection increases from glucose < sucrose < trehalose, liposomes containing 50% DGDG showed the opposite behavior. In fact, carboxyfluorescein leakage increased over the control values (freezing in the absence of sugar) in the presence of trehalose. This effect was not seen in vesicles made from pure EPC, or a mixture of EPC and MGDG, or EPC and SQDG. Liposomes made from mixtures of all three glycolipids, however, showed even more leakage in the presence of trehalose than liposomes containing only DGDG and EPC. Copyright 1998 Academic Press.     

ESTABLISHMENT,GROWTH AND CONSERVATION OF A MAINLAND COLONY OF JACKASS PENGUINS SPHENISCUS DEMERSUS AT STONY POINT,BETTY'S BAY,SOUTH AFRICA

Whittington, P.A., Hofmeyr, J.H. & Cooper, J. 1996. Establishment, growth and conservation of a mainland colony of Jackass Penguins Spheniscus demersus at Stony Point, Betty's Bay, South Africa. Ostrich 67: 144–150.

Following the discovery of a single pair of Jackass Penguins Spheniscus demersus nesting on the mainland at Stony Point, Western Cape Province, South Africa (34 22S 18 53E) in 1982, a colony developed and has since been regularly monitored. Numbers of nests increased to 35 in 1986, until a leopard Panthera pardus severely reduced the size of the colony. Numbers subsequently rose again to a total of 139 nests in 1990, but fell to 57 in 1993. This decrease was probably due to predation by mammals. Following the use of a trap and translocation of the animals caught, the colony increased again in 1995 and 1996. Productivity of the colony was insufficient for it to be self-sustaining, and it therefore presently represents a population sink.     

Experimental evidence for allosteric modifier saturation as predicted by the bi-substrate Hill equation

The cooperative enzyme reaction rates predicted by the bi-substrate Hill equation and the bi-substrate Monod-Wyman-Changeux (MWC) equation when allosterically inhibited are compared in silico. Theoretically, the Hill equation predicts that when the maximum inhibitory effect at a certain substrate condition has been reached, an increase in allosteric inhibitor concentration will have no effect on reaction rate, that is the Hill equation shows allosteric inhibitor saturation. This saturating inhibitory effect is not present in the MWC equation. Experimental in vitro data for pyruvate kinase, a bi-substrate cooperative enzyme that is allosterically inhibited, are presented. This enzyme also shows inhibitor saturation, and therefore serves as experimental evidence that the bi-substrate Hill equation predicts more realistic allosteric inhibitor behaviour than the bi-substrate MWC equation.     

Molecular phylogeny of African hinge‐back tortoises (Kinixys): implications for phylogeography and taxonomy (Testudines: Testudinidae)

We examine the phylogeography, phylogeny and taxonomy of hinge‐back tortoises using a comprehensive sampling of all currently recognized Kinixys species and subspecies and sequence data of three mitochondrial DNA fragments (2273 bp: 12S rRNA, ND4 + adjacent DNA coding for tRNAs, cytb) and three nuclear loci (2569 bp: C‐mos, ODC, R35). Combined and individual analyses of the two data sets using Bayesian and Maximum Likelihood methods suggest that the savannah species of Kinixys are paraphyletic with respect to the rainforest species K. homeana and K. erosa, and that the rainforest species may be derived from a savannah‐living ancestor. The previously recognized savannah species K. belliana was a conglomerate of three deeply divergent clades that we treat here as distinct species. We restrict the name K. belliana (Gray, 1830) to hinge‐back tortoises ranging from Angola to Burundi, while five‐clawed hinge‐back tortoises from the northernmost part of the formerly recognized range of K. belliana, together with four‐clawed tortoises from West Africa, are assigned to the species K. nogueyi (Lataste, 1886). These two species are allied to K. spekii, whereas Southeast African and Malagasy hinge‐back tortoises formerly lumped together with K. belliana represent the distinct species K. zombensis Hewitt, 1931, which is sister to K. lobatsiana. The latter two species together constitute the sister group of the rainforest species K. homeana and K. erosa. Mitochondrial data suggest that K. natalensis has a basal phylogenetic position in a clade embracing K. belliana sensu stricto, K. nogueyi and K. spekii, while nuclear data and the two data sets combined favour a sister group relationship of K. natalensis to all other hinge‐back tortoises. Phylogeographic structure is present in all wide‐ranging species and correlates in K. homeana and K. erosa with the Dahomey Gap and former rainforest refugia. The Malagasy population of K. zombensis is weakly differentiated from its South African conspecifics and further sampling is needed to determine whether there is support for the subspecific distinctness of Malagasy tortoises.