Urinary testosterone-metabolite levels and dominance rank in male and female bonobos (<Emphasis Type="Italic">Pan paniscus</Emphasis>)

The correlation between testosterone (T) and dominance rank may vary among species, and is expected to become stronger as the importance of aggressive competition for rank increases. However, it may also vary among social situations within a species, showing a stronger correlation during socially unstable periods. Knowledge on this topic in great apes, especially in females, is scant. This study presents the first data on the relationship between T and dominance rank in both sexes of the bonobo (Pan paniscus). For each period (four socially unstable and two stable ones), linear rank orders were determined and subsequently correlated with the accompanying mean urinary T-metabolite concentrations (measured as immunoreactive 5-androstan-17-ol-3-one). No correlation between these two variables was found for either sex among individuals during socially unstable or stable periods. Also, within an individual over the six periods, no relationship of T with rank could be demonstrated. These results suggest that either the outcomes of aggressions have no influence on T levels, or such clear outcomes appear insufficiently frequent to affect T levels over longer periods. Even during the unstable periods, the rate of aggressions was not higher than during stable periods, suggesting that frequencies of aggression have little effect on rank. Further analyses indeed demonstrated no correlation between frequencies of overall aggressions or any type of aggressive behavior separately, or rank. Perhaps factors other than the frequency of displayed aggressions alone have a marked influence on a bonobos rank, for example, coalition partners. Overall, in bonobos, T apparently does not form a physiological reflection of social status.     

Highly efficient production of laccase by the basidiomycete Pycnoporus cinnabarinus

An efficient transformation and expression system was developed for the industrially relevant basidiomycete Pycnoporus cinnabarinus. This was used to transform a laccase-deficient monokaryotic strain with the homologous lac1 laccase gene placed under the regulation of its own promoter or that of the SC3 hydrophobin gene or the glyceraldehyde-3-phosphate dehydrogenase (GPD) gene of Schizophyllum commune. SC3-driven expression resulted in a maximal laccase activity of 107 nkat ml(-1) in liquid shaken cultures. This value was about 1.4 and 1.6 times higher in the cases of the GPD and lac1 promoters, respectively. lac1-driven expression strongly increased when 25 g of ethanol liter(-1) was added to the medium. Accordingly, laccase activity increased to 1,223 nkat ml(-1). These findings agree with the fact that ethanol induces laccase gene expression in some fungi. Remarkably, lac1 mRNA accumulation and laccase activity also strongly increased in the presence of 25 g of ethanol liter(-1) when lac1 was expressed behind the SC3 or GPD promoter. In the latter case, a maximal laccase activity of 1,393 nkat ml(-1) (i.e., 360 mg liter(-1)) was obtained. Laccase production was further increased in transformants expressing lac1 behind its own promoter or that of GPD by growth in the presence of 40 g of ethanol liter(-1). In this case, maximal activities were 3,900 and 4,660 nkat ml(-1), respectively, corresponding to 1 and 1.2 g of laccase per liter and thus representing the highest laccase activities reported for recombinant fungal strains. These results suggest that P. cinnabarinus may be a host of choice for the production of other proteins as well.     

δ15N as an indicator of N2-fixation by cyanobacterial mats in tropical marshes

Cyanobacterial mats (CBM) are important components of wetland ecosystems in limestone-based regions of the Caribbean. During two sampling periods (July 1999 and January 2000) we measured N₂-fixation in samples from 23 different marshes simultaneously with measurements of relevant environmental factors. Samples were evaluated for abundance of five groups of cyanobacteria: (1) Leptolyngbya, (2) Oscillatoria, (3) Chroococcales, (4) Nostoc-& Stigonematales, and (5) dead sheaths. Differences in nitrogen fixation, expressed as nitrogenase activity in nmol C₂H₄ cm^–2 h^–1, were best explained by the proportion of heterocyst-forming cyanobacteria. The samples were analyzed for the natural abundance of ¹⁵N. ¹⁵N values ranged from –1.99 to 11.44 and were strongly negatively correlated with N₂-fixation. With all data included, ¹⁵N was also strongly correlated with nitrates in water. With the samples from Little Belize (high nitrate content marshes) excluded, the effect of nitrate became insignificant. N₂-fixation predicted from ¹⁵N measured on an independent data set from September 2000 was moderately accurate (r² = 0.68, 0.52 and 0.54 for predictions based on July 1999, January 2000 and combined data sets, respectively). When individual sample sets were divided into two groups with ¹⁵N < 2 and ¹⁵N > 2, the two groups were always highly significantly different in terms of their N₂-fixation. The presented evidence suggests that ¹⁵N can be used as a reliable indicator of N₂-fixation by CBM.     

Interference of the galactose-dependent binding of lectins by novel pentapeptide ligands

A library of pentapeptides containing the sequence -Y-X-Y- based on rational design was screened with six different lectins. Sequences were identified that modulate galectin binding to its natural carbohydrate ligand. SPR showed inhibition values 2-3 times stronger than galactose and NMR studies suggested real carbohydrate mimicry.     

Polo-like kinase-1 controls recovery from a G2 DNA damage-induced arrest in mammalian cells

DNA damage triggers multiple checkpoint pathways to arrest cell cycle progression. Less is known about the mechanisms that allow resumption of the cell cycle once checkpoint signaling is silenced. Here we show that while in undamaged cells several redundant pathways can promote the onset of mitosis, this redundancy is lost in cells recovering from a DNA damage-induced arrest. We demonstrate that Plk1 is crucial for mitotic entry following recovery from DNA damage. However, Plk1 is no longer required in cells depleted of Wee1, and we could show that Plk1 is involved in the degradation of Wee1 at the onset of mitosis. Thus, our data show that the cell cycle machinery is reset in response to DNA damage and that cells become critically dependent on Plk1-mediated degradation of Wee1 for their recovery.     

Genetic characterization of the Guinea-Bissau family of Mycobacterium tuberculosis complex strains

In a previous study of Mycobacterium tuberculosis complex isolates from Guinea-Bissau in West Africa, we identified a unique group of strains, designated here as the Guinea-Bissau family of strains, which, although genotypically closely related, phenotypically demonstrated a considerable heterogeneity. We conducted here a detailed genotypic analysis of a subset (n = 35) of these isolates. Based on the data obtained, and by comparison of known corresponding genes in mycobacteria outside the M. tuberculosis complex, we propose that the Guinea-Bissau strains belong to a unique branch of the M. tuberculosis complex tree in between classical M. tuberculosis and classical M. bovis. These observations are discussed in their significance in M. tuberculosis complex classification.     

Central assumptions of predator-prey models fail in a semi-natural experimental system

The relationship between the encounter rate of predators with prey and the density of this prey is fundamental to models of predator-prey interactions. The relationship determines, among other variables, the rate at which prey patches are depleted, and hence the impact of predator populations on their prey, and the optimal spatial distribution of foraging effort. Two central assumptions that are made in many models are that encounter rate is directly proportional to prey density and that it is independent of the proportion of prey already removed, other than via the decreased density. We show here, using captive great tits searching for winter moth caterpillars in their natural hiding positions, that neither of these assumptions hold. Encounter rate increased less than directly in proportion to prey density, and it depended not only on the current density of prey, but also on the proportion of prey already removed by previous foragers. Both of these effects are likely to have major consequences for the outcome of predator-prey interactions.     

Fluorescent ligands for the histamine H2 receptor: synthesis and preliminary characterization

3-[3-(Piperidinomethyl)phenoxy]alkyl, N-cyano-N′-[ω-[3-(1-piperidinylmethyl)phenoxy]alkyl]guanidine and 2-(5-methyl-4-imidazolyl)methyl thioethyl derivatives containing fluorescent functionalities were synthesized and the histamine H₂ receptor affinity was evaluated using the H₂ antagonist [¹²⁵I]-aminopotentidine. The compounds exhibited weak to potent H₂ receptor affinity with pK_i values ranging from <4 to 8.85. The highest H₂ receptor affinity was observed for N-cyano-N′-[ω-[3-(1-piperidinylmethyl)phenoxy]alkyl]guanidines substituted with methylanthranilate (13), cyanoindolizine (6) and cyanoisoindole (11) moieties via an ethyl or propyl linker.     

Calendar

Telomeres cap the ends of chromosomes and are essential for the protection of chromosomes, as well as restricting the replicative potential of a cell. These functions are achieved by the regulation of telomeric repeat length, making the measurement of telomere length a useful aid in the elucidation of the replicative history and potential of cells. Previously published techniques employed either hybridization or flow cytometry methods, which are technically demanding and time-consuming. In 2002, R. M. Cawthon published a real-time polymerase chain reaction (PCR)-based method for telomere length measurement using the Applied Biosystems Prism 7700 sequence detection system. The technique measures the factor by which the ratio of telomere repeat copy number to single-gene copy number differs between a sample and that of a reference deoxyribonucleic acid sample. In many laboratories worldwide, including ours, real-time PCR is carried out using the Roche LightCycler, as opposed to the AB Prism 7700 system. This benchmark details the modifications to Cawthon’s method and describes the parameters and reagents required to measure telomere length using the Roche LightCycler.