Genetic variation and structure of house sparrow populations: is there an island effect?

Population genetic structure and intrapopulation levels of genetic variation have important implications for population dynamics and evolutionary processes. Habitat fragmentation is one of the major threats to biodiversity. It leads to smaller population sizes and reduced gene flow between populations and will thus also affect genetic structure. We use a natural system of island and mainland populations of house sparrows along the coast of Norway to characterize the different population genetic properties of fragmented populations. We genotyped 636 individuals distributed across 14 populations at 15 microsatellite loci. The level of genetic differentiation was estimated using F‐statistics and specially designed Mantel tests were conducted to study the influence of population type (i.e. mainland or island) and geographic distance on the genetic population structure. Furthermore, the effects of population type, population size and latitude on the level of genetic variation within populations were examined. Our results suggest that genetic processes on islands and mainland differed in two important ways. First, the intrapopulation level of genetic variation tended to be lower and the occurrence of population bottlenecks more frequent on islands than the mainland. Second, although the general level of genetic differentiation was low to moderate, it was higher between island populations than between mainland populations. However, differentiation increased in mainland populations somewhat faster with geographical distance. These results suggest that population bottleneck events and genetic drift have been more important in shaping the genetic composition of island populations compared with populations on the mainland. Such knowledge is relevant for a better understanding of evolutionary processes and conservation of threatened populations.     

RH blood groups and diabetic disorders: is there an effect on glycosylated hemoglobin level?

Recent cloning of RH genes has elucidated their structure, suggesting that RH proteins are part of an oligomeric complex with transport function in the erythrocyte. This observation prompted us to investigate a possible relationship between the RH system and the glycosylated hemoglobin level (Hb A(1c)) in diabetes. This compound is considered an important indicator- of glycemic control in diabetic disorders. We studied 278 subjects with non-insulin-dependent diabetes mellitus (NIDDM) from the population of Penne, Italy. Glycemic and glycosylated hemoglobin (Hb A(1c)) levels are associated with RH phenotype. Glucose and Hb A(1c) levels are increased in DCcEe subjects and decreased in ddccee subjects as compared to the mean values for other genotypes. Sex, age at onset of disease, duration of disease, and age of patients were also considered. Correlation analysis suggests that these variables influence glycemia directly and Hb A(1c) indirectly. The RH system, on the other hand, seems to influence the Hb A(1c) level directly. Preliminary data on 53 children with insulin-dependent diabetes mellitus (IDDM) from Sardinia seem to confirm the relationship between RH and Hb A(1c) observed in NIDDM. Since glycosylated hemoglobin is found inside red blood cells, the relationship between RH genetic variability and Hb A(1c) level suggests that RH proteins may influence glucose transport through red cell membrane and/or hemoglobin glycation.     

Song learning from playback in zebra finches: is there an effect of operant contingency?

Social interaction is often regarded as crucial for song copying in zebra finches, Taeniopygia guttata. Contingencies in the interaction between pupil and tutor might be essential for the song-copying process. The effect of contingency between a pupil's operant behaviour and tutor song has been studied previously, but with contradictory results. Our aim in this experiment was to provide a more rigorous test of the effect of operant contingent exposure to song playback in zebra finches. Eight experimental males were trained to expose themselves to tutor song by operant key pecking during their sensitive phase for song learning. Each bird had a yoked control, which heard the same tutor song at the same time. All birds were acoustically isolated. The results were surprising in two ways: (1) the control birds copied song to which they were passively exposed; and (2) the experimental birds did not copy more than the controls did. So, we found no effect of operant contingency on song learning. Furthermore, when tested as adults all but one male preferred the tutor song to an unfamiliar one. We conclude that zebra finches can copy playback song, and that social interaction is not crucial for song copying, although it might still be facilitating. Copyright 1999 The Association for the Study of Animal Behaviour.     

The mid-domain effect and diversity gradients: is there anything to learn?

The mid-domain effect (MDE) has been proposed as a null model for diversity gradients and an explanation for observed patterns. Here we respond to a recent defense of the concept, explaining that it cannot represent a viable model in either real or null worlds. First, the MDE misrepresents the nature of species ranges. There is also an internal logical inconsistency underlying the MDE because the range size frequency distribution, necessary to generate a hump-shaped pattern under randomization, cannot exist in the absence of environmental gradients and is generated by the ecological and historical processes that the MDE claims to exclude.     

Cognitive mechanisms of risky choice: is there an evaluation cost?

We contrast two classes of choice processes, those assuming time-consuming comparisons and those where stimuli for each option act independently, competing for expression by cross censorship. The Sequential Choice Model (SCM) belongs in the latter category, and has received empirical support in several procedures involving deterministic alternatives. Here we test this model in risky choices. In two treatments, each with five conditions, European starlings (Sturnus vulgaris) faced choices between options with unpredictable outcomes and risk-free alternatives. In the delay treatment the five conditions involved choices between a variable option offering two equiprobable delays to reward and a fixed option with delay differing between conditions. The amount treatment was structurally similar, but amount of reward rather than delay was manipulated. As assumed (and required) by the SCM, latency to respond in no-choice trials reflected each option's richness with respect to the background alternatives, and, crucially, preferences in simultaneous choices were predictable from latencies to each option in forced trials. However, we did not detect reliable differences in response times between forced and choice trials, neither the lengthening expected from evaluation models nor the shortening expected from the SCM.     

Managing feral cats on a university's campuses: how many are there and is sterilization having an effect?

Worldwide domestic and feral cat (Felis catus) numbers have increased. Concerns regarding high populations of feral cats in urban areas include wildlife predation, public nuisance, and disease. This study aimed to estimate the size of the feral cat population on 5 campuses of the University of KwaZulu-Natal, South Africa, to determine whether sterilization has an effect and to make management recommendations. The study used both the total count and mark-recapture methods to estimate the feral cat population on each campus. The study chose a noninvasive method of taking photographs to "mark" individuals and record those who were sterilized. The study estimated a total of 186 cats on all campuses and density at 161 cats km(-2). There was a negative relationship between sterilization and numbers. Sites with higher sterilization showed a lower proportion of younger cats. At the average sterilization of 55%, the population, according to predictions, would remain stable at fecundity, survival, and immigration rates reported by cat caretakers. However, caretakers underestimated cat abundance by 7 ± 37 SD%. Caretakers' feral cat sterilization and feeding programs appear to provide a service to the university community. Key management recommendations were to increase sterilization to 90% to reduce the population over the long term and to raise funds to support the costs incurred by voluntary cat caretakers.     

Cell cycle control and plant morphogenesis: is there an essential link?

Plant morphogenesis has some interesting features that may have consequences for the regulation of cell division. In particular, the immobility of plant cells implies the necessity for highly accurate controls, in contrast with the flexibility of many developmental processes in animals. An important question in plant development concerns the status of the relationship between plant morphogenesis and cell division. In this review, we discuss the current knowledge of the molecular mechanisms controlling the plant cell cycle and how this could be differentially regulated during plant morphogenesis. The plant genes involved are homologous to those of other higher eukaryotes, suggesting a similar cell cycle machinery. A variety of mechanisms control these genes, reflecting the complexity of internal and environmental signals to which plants should respond. This intricate network requires an upstream control mechanism to function as a failsafe system and to govern cell division and growth to produce the correct plant shape. BioEssays 21:29–37, 1999. © 1999 John Wiley & Sons, Inc.     

Phosphorylation-specific prolyl isomerization: is there an underlying theme?

The prolyl isomerase Pin1 is a conserved enzyme that is intimately involved in diverse biological processes and pathological conditions such as cancer and Alzheimer's disease. By catalysing cis-trans interconversion of certain motifs containing phosphorylated serine or threonine residues followed by a proline residue (pSer/Thr-Pro), Pin1 can have profound effects on phosphorylation signalling. The structural and functional differences that result from cis-trans isomerization of specific pSer/Thr-Pro motifs probably underlie most, if not all, Pin1-dependent actions. Phosphorylation-dependent prolyl isomerization by Pin1 remains a unique mode for the modulation of signal transduction. Here, we provide an overview of the plethora of regulatory events that involve this unique enzyme, with a particular focus on oncogenic signalling and neurodegeneration.     

Cholesterol's decoupling effect on membrane partitioning and permeability revisited: is there anything beyond Fick's law of diffusion?

In general, Fick's law of diffusion describes membrane permeation of hydrophobic or amphiphilic molecules. In contrast to this, Thomae et al. recently identified the volume ratio between barrier and aqueous compartments as important additional determinants of membrane permeability (Pm) [A.V. Thomae, T. Koch, C. Panse, H. Wunderli-Allenspach, and S.D. Kramer, Comparing the lipid membrane affinity and permeation of drug-like acids: the intriguing effects of cholesterol and charged lipids, Pharm. Res. 24 (2007) 1457-1472.]. This new theory was supported by the striking observation that low concentrations of cholesterol increased Pm of salicylic acid. As Fick's law is of fundamental importance to all membrane transport processes, we reinvestigated this phenomenon. We measured the electrophoretic mobility of vesicles and used electrochemical scanning microscopy to study the adsorption of the SA anion to lipid vesicular bilayers and SA transport through planar lipid bilayers, respectively. As predicted by Fick's law, Pm of SA decreased continuously with increasing cholesterol content. Thomae et al. made the contrasting artifactual observation because their kinetic approach lacked the required time resolution and led to an underestimation of Pm by five orders of magnitude. We conclude that there is nothing beyond Fick's law of diffusion. It is still valid.     

Steric aspects of formoterol and terbutaline: Is there an adverse effect of the distomer on airway smooth muscle function?

Experiments were made on isolated tissues from guinea-pig to test the hypothesis that the distomers of rac-β₂-adrenoceptor agonists induce airway hyperreactivity. Tracheal strip preparations were contracted with carbachol. Both rac- and (R;R)-formoterol (2 and 1 μmol/1, respectively) produced an immediate relaxation, followed by a slow recovery of tone. (S;S)-Formoterol (2 μmol/1) had no effect on smooth muscle tone. Similar results were obtained with the enantiomers of terbutaline. In other strip preparations of the trachea or the main bronchi, cholinergic or nonadrenergic/noncholinergic (NANC) excitatory responses were evoked by electrical field-stimulation. The eutomers, (R;R)-formoterol and (R)-terbutaline, inhibited concentration-dependently both cholinergic and NANC-induced contractions. The distomers, (S;S)-formoterol and (S)-terbutaline, showed qualitatively the same effects but were about 1,000 times less potent than the corresponding eutomer. In a third series of experiments, either enantiomer of formoterol was administered to an electrically stimulated vagus nerve-trachea tube preparation. The nerve-induced contractions were inhibited by both enantiomers, but (S;S)-formoterol was about 1,000 times less potent than (R;R)-formoterol. For both enantiomers of formoterol, about tenfold higher concentration was required to obtain the same degree of inhibition when given intratracheally as compared with administration in the external medium. There was no indication in any of the experimental approaches that (S;S)-formoterol or (S)-terbutaline might enhance the response to cholinergic or NANC-related stimuli. Chirality 8:567–573, 1996. © 1997 Wiley-Liss, Inc.     

Obesity and the rate of time preference: is there a connection?

It is hypothesized that recent trends in US and worldwide obesity are, in part, related to an increase in the marginal rate of time preference, where time preference refers to the rate at which people are willing to trade current benefit for future benefit. The higher the rate of time preference, the larger is the factor by which individuals discount the future health risks associated with current consumption. Data from the United States, as well as international evidence, suggest that a relationship between these two variables is plausible. The authors encourage researchers to explore the possible link between obesity and time preference, as important insights are likely to result.     

Ethics and evidence-based medicine: is there a conflict?

This article addresses the advantages, disadvantages, and traps to which evidence-based medicine (EBM) may lead and suggests that, to be ethically valid, EBM must be aimed at the patient's best interests and not at the financial interests of others. While financial considerations are by no means trivial, it is hypocritical - if not dangerous - to hide them behind words like "evidence" or "quality."