Subtle but ubiquitous selection on body size in a natural population of collared flycatchers over 33 years

Understanding the magnitude and long-term patterns of selection in natural populations is of importance, for example, when analysing the evolutionary impact of climate change. We estimated univariate and multivariate directional, quadratic and correlational selection on four morphological traits (adult wing, tarsus and tail length, body mass) over a time period of 33 years (≈ 19 000 observations) in a nest-box breeding population of collared flycatchers (Ficedula albicollis). In general, selection was weak in both males and females over the years regardless of fitness measure (fledged young, recruits and survival) with only few cases with statistically significant selection. When data were analysed in a multivariate context and as time series, a number of patterns emerged; there was a consistent, but weak, selection for longer wings in both sexes, selection was stronger on females when the number of fledged young was used as a fitness measure, there were no indications of sexually antagonistic selection, and we found a negative correlation between selection on tarsus and wing length in both sexes but using different fitness measures. Uni- and multivariate selection gradients were correlated only for wing length and mass. Multivariate selection gradient vectors were longer than corresponding vector of univariate gradients and had more constrained direction. Correlational selection had little importance. Overall, the fitness surface was more or less flat with few cases of significant curvature, indicating that the adaptive peak with regard to body size in this species is broader than the phenotypic distribution, which has resulted in weak estimates of selection.

Systemic differences in serum metabolome: a cross sectional comparison of women with localised and widespread pain and controls

Chronic musculoskeletal pain exists either as localised to a single region or as widespread to multiple sites in several quadrants of the body. Prospective studies indicate that widespread pain could act as a far end of a continuum of musculoskeletal pain that started with chronic localised pain. The mechanism by which the transition from localised pain to widespread occurs is not clear, although many studies suggest it to be an altered metabolism. In this study, systemic metabolic differences between women with chronic localised neck-shoulder pain (NP), women with chronic widespread pain (CWP) and women who were healthy (CON) were assessed. Blood samples were analysed taking a metabolomics approach using gas chromatography mass spectrometry (GC-MS) and orthogonal partial least square discriminant analysis (OPLS-DA). The metabolomics analysis showed a clear systematic difference in the metabolic profiles between the subjects with NP and the CON but only a weak systematic difference between the subjects with CWP and the CON. This most likely reflects a difference in the portion of the metabolome influenced by the two pain conditions. In the NP group, the overall metabolic profile suggests that processes related to energy utilisation and lipid metabolism could be central aspects of mechanisms maintaining disorder.

Rapid and unpredictable changes of the G-matrix in a natural bird population over 25 years

Knowledge of the genetic variances and covariances of traits (the G-matrix) is fundamental for the understanding of evolutionary dynamics of populations. Despite its essential importance in evolutionary studies, empirical tests of the temporal stability of the G-matrix in natural populations are few. We used a 25-year-long individual-based field study on almost 7000 breeding attempts of the collared flycatcher (Ficedula albicollis) to estimate the stability of the G-matrix over time. Using animal models to estimate G for several time periods, we show that the structure of the time-specific G-matrices changed significantly over time. The temporal changes in the G-matrix were unpredictable, and the structure at one time period was not indicative of the structure at the next time period. Moreover, we show that the changes in the time-specific G-matrices were not related to changes in mean trait values or due to genetic drift. Selection, differences in acquisition/allocation patterns or environment-dependent allelic effects are therefore likely explanations for the patterns observed, probably in combination. Our result cautions against assuming constancy of the G-matrix and indicates that even short-term evolutionary predictions in natural populations can be very challenging.

Selection in a fluctuating environment and the evolution of sexual dimorphism in the seed beetle Callosobruchus maculatus

Temperature changes in the environment, which realistically include environmental fluctuations, can create both plastic and evolutionary responses of traits. Sexes might differ in either or both of these responses for homologous traits, which in turn has consequences for sexual dimorphism and its evolution. Here, we investigate both immediate changes in and the evolution of sexual dimorphism in response to a changing environment (with and without fluctuations) using the seed beetle Callosobruchus maculatus. We investigate sex differences in plasticity and also the genetic architecture of body mass and developmental time dimorphism to test two existing hypotheses on sex differences in plasticity (adaptive canalization hypothesis and condition dependence hypothesis). We found a decreased sexual size dimorphism in higher temperature and that females responded more plastically than males, supporting the condition dependence hypothesis. However, selection in a fluctuating environment altered sex-specific patterns of genetic and environmental variation, indicating support for the adaptive canalization hypothesis. Genetic correlations between sexes (r(MF) ) were affected by fluctuating selection, suggesting facilitated independent evolution of the sexes. Thus, the selective past of a population is highly important for the understanding of the evolutionary dynamics of sexual dimorphism.

Environmental fluctuations and level of density-compensation strongly affects the probability of fixation and fixation times

The probability of, and time to, fixation of a mutation in a population has traditionally been studied by the classic Wright-Fisher model where population size is constant. Recent theoretical expansions have covered fluctuating populations in various ways but have not incorporated models of how the environment fluctuates in combination with different levels of density-compensation affecting fecundity. We tested the hypothesis that the probability of, and time to, fixation of neutral, advantageous and deleterious mutations is dependent on how the environment fluctuates over time, and on the level of density-compensation. We found that fixation probabilities and times were dependent on the pattern of autocorrelation of carrying capacity over time and interacted with density-compensation. The pattern found was most pronounced at small population sizes. The patterns differed greatly depending on whether the mutation was neutral, advantageous, or disadvantageous. The results indicate that the degree of mismatch between carrying capacity and population size is a key factor, rather than population size per se, and that effective population sizes can be very low also when the census population size is far above the carrying capacity. This study highlights the need for explicit population dynamic models and models for environmental fluctuations for the understanding of the dynamics of genes in populations.

Competitive environments induce shifts in host fidelity

Recent models support the idea of sympatric speciation as a result of the joint effects of disruptive selection and assortative mating. We present experimental data, testing models of speciation through frequency-dependent selection. We show that under high competition on a mixture of resources/hosts, strains of the Seed beetle, Callosobruchus maculatus, change their host fidelity and evolve a more generalistic behaviour in resource utilization among females. The change in host fidelity did not result in disruptive selection and was not followed by assortative mating. This means that only one of three fundamental prerequisites for sympatric speciation evolved as a result of the frequency-dependent selection. We conclude that for this process to work, a shift to a novel food resource as a result of selection must also lead to a loss of preference for the original resource such that individuals are only able to use either one of the two.

Population differentiation in perch Perca fluviatilis: environmental effects on gene flow?

Environmental parameters were used to investigate barriers to gene flow and genetic differentiation in the Eurasian perch (Perca fluviatilis L.) at a small geographical scale in an archipelago system. Significant genetic differentiation was found among locations. Distance per se did not play a major role in the reduction of gene flow. Instead, the largest genetic differences between populations correlated with major changes in environmental conditions, such as temperature at time of spawning. The results show that genetic divergence can arise between populations in habitats thought to be highly connected, and that environmental variables can influence the level of gene flow between populations, including those that are at small spatial scales (tens of kilometres). The importance of a landscape approach when investigating genetic differentiation and defining barriers to gene flow is highlighted.

Effects of temperature and growth hormone on individual growth trajectories of wild-type and transgenic coho salmon Oncorhynchus kisutch

In this study, individual growth patterns of wild-type and growth-enhanced coho salmon Oncorhynchus kisutch at 8, 12 and 16 degrees C water temperature were followed. Despite large differences among individuals in growth rates, there was generally little variation in the shape of the growth curves among O. kisutch individuals of both genotypes and at all temperatures. Typically, individuals that were relatively large initially were also relatively large at the end of the growth period. The limitation in variation was more pronounced in the growth-enhanced O. kisutch than in the wild type, where the relative size of some individuals reared at 12 and 8 degrees C changed by the end of the trial. As a warmer temperature seems to decrease the plasticity of growth trajectories in wild-type fish, it is possible that global warming will influence the ability of wild fish to adapt their growth to changing conditions.

Cryptic barriers to dispersal within a lake allow genetic differentiation of Eurasian perch

Gene flow between coexisting or nearby populations normally prevents genetic divergence and local adaptation. Despite this, there are an increasing number of reports of sympatric sister taxa, indicating potential divergence and speciation in the face of gene flow. A large number of such reported cases involve lake-dwelling fish, which are expected to run into few physical barriers to dispersal within their aquatic habitat. However, such cases may not necessarily reflect sympatric speciation if cryptic dispersal barriers are common in lakes and other aquatic systems. In this study, we examined genetic differentiation in perch (Perca fluviatilis L.) from nine locations in a single, small lake (24 km(2)), using microsatellites. We detected significant genetic differentiation in all but two pairwise comparisons. These patterns were not consistent with divergence by distance or the existence of kin groups. Instead, they suggest that cryptic barriers to dispersal exist within the lake, allowing small-scale genetic divergence. Such an observation suggests that allopatric (or parapatric) divergence may be possible, even in small, apparently homogenous environments such as lakes. This has important consequences for how we currently view evidence from nature for sympatric speciation.

Testing biennialism in the butterfly Erebia palarica (Nymphalidae: Satyrinae) by mtDNA sequencing

Abstract The montane butterfly Erebia palarica has an unconfirmed life-cycle length. The genus Erebia shows variability in length of diapause depending on latitude and altitude, which may lead to allochronic differentiation. To test for biennialism and possible asynchronous differentiation, we sequenced the most variable fragments of the mitochondrial control region and the cytochrome oxidase I in forty individuals from the same population, from two consecutive years. No differentiation between cohorts could be detected and therefore the idea of a current annual cycle is supported. We conclude that a biennial cycle may never have been important in this population and we further discuss adaptive strategies this species may have used to confront colder climates.

Muscle stretch-induced modulation of noxiously activated dorsal horn neurons of feline spinal cord

The present work was designed to check for the possibility of interactions between mechanical innocuous and chemically induced noxious muscle afferent inputs on discharge behavior of nociceptive superficial dorsal horn neurons (SDHNs) of the spinal cord in decerebrated cats. The innocuous and noxious stimuli were applied separately and in combination, so that the effects of the innocuous stimulus on nociceptive processing could be evaluated. The innocuous stimulus consisted of ramp-and-hold stretches of the gastrocnemius muscles, whereas the noxious stimulus consisted of i.a. injections of bradykinin (BK; 0.5-1 ml, 50 microg/ml) into the arterial circulation of same muscles. Only neurons up to approximately 1mm depth and those that responded to noxious pinch of the gastrocnemius muscles were selected for further analysis. The activity of 16 dorsal horn neurons was recorded extracellularly with high-impedance glass microelectrodes, out of which seven responded to stretch, while 12 neurons responded to bradykinin injections. The bradykinin injections induced three types of responses: excitatory, inhibitory and mixed. The majority of the neurons that showed excitatory and mixed responses to bradykinin were also influenced by stretches applied directly after the bradykinin injection. In these neurons, the stretch usually counteracted the bradykinin-induced response, i.e. shortening and reducing bradykinin-induced excitation and re-exciting the cells after bradykinin-induced inhibition. The mechanism of the stretch modulation is proposed to reside in a segmental spinal control of the nociceptive transmission.

Test for a population expansion after a drastic reduction in population size using DNA sequence data

Populations may, during their evolutionary history, go through drastic changes in population size due to bottlenecks or founder events upon colonization of new areas. This involves a subsample of haplotypes, causing the allele frequencies to be different from the original population. In addition, the period of recovery after a bottleneck can be of considerable length. If reproduction is unequal among individuals but random with regard to haplotype, large deviations from the patterns expected in a stable population may result. By means of computer simulation, I have analysed the patterns arising when populations undergo bottlenecks and then slowly recover, and used two new statistical tests for the detection of the bottleneck. A test based on the variance of the relative frequency of haplotypes had generally high power even at low sample size (n=25). This statistic was most powerful after very strong bottlenecks and lost power with increasing propagule size. A test based on the variance of the pairwise differences shows slightly less power. As expected, power was reduced when migration into the founder population was allowed from the source population. This suggests that the test is particularly suited for detecting relatively recent and strong bottlenecks, and thus may be a valuable tool for identifying population events on a fine temporal scale, such as colonisations after the last glaciation.

Dynamics in the evolution of sexual traits: losses and gains, radiation and convergence in yellow wagtails (Motacilla flava)

We analyse patterns of genetic diversity and song complexity in the Palaearctic yellow wagtail (Motacilla flava), a highly polytypic species complex. Mitochondrial and nuclear DNA show that the complex is polyphyletic, despite parallel plumage variation in western and eastern clades. In the western clade there is genetic structure among southern subspecies, haplotype diversity decreases with latitude, and northern subspecies show evidence of bottlenecking and rapid expansions, as expected from isolation in glacial refugia followed by postglacial colonization. However, northern subspecies, which have more divergent male plumages, lack genetic structure and sing simpler songs. Loss of song complexity and evolution of plumage in founder populations are consistent with the Kaneshiro model, which posits that variation among species is a consequence of founder-induced shifts in female preference leading to loss of ancestral male sexual traits. Our results suggest possible postglacial founder-effect mechanisms for the morhological diversification of the yellow wagtail complex.

Phenotypic variation in growth trajectories in the Arctic charr Salvelinus alpinus

Animals with determinate growth have shown little variation in individual growth patterns, but similar analyses for animals with indeterminate growth have been lacking. We analysed the amount of phenotypic variation in growth patterns across ages among individuals of a hatchery-based population of Arctic charr, Salvelinus alpinus, Salmonidae, using the infinite-dimensional model and including the effects of group size structure. There was little phenotypic variation in growth trajectories: individuals that were small (in relation to the mean) early in life were among the smallest 2.5 years later. If the genetic variation reflects phenotypic variation, not much evolutionary change can be expected. Our results show that there are ecological conditions that determine the strong covariation of size across ages, most likely size-related dominance behaviour, which can mask the true variation of growth patterns. Thus, social interactions can have strong evolutionary effects on traits not directly involved in the behavioural interactions.

Delayed prezygotic isolating mechanisms: evolution with a twist

Assortative mating characterizes the situation wherein reproducing individuals pair according to similarity. Usually, the impetus for this bias is attributed to some type of mate choice conferring benefits (e.g., increased fitness or genetic compatibility) and, thereby, promoting speciation and phenotypic evolution. We investigate, by computer simulation of an evolving deme-structured snail population, the ramifications ensuing from passive assortative mating wherein couples exhibiting opposite shell coil direction phenotypes experience a physical constraint on mating success: putative mating partners inhabiting stout dextral and sinistral shells are unable to exchange sperm. Because shell coil chirality genotype is encoded at a single locus by shell coil alleles that are inherited maternally, snails containing sinistral alleles can present the typical dextral phenotype. Consequently, the incidence of a sinistral allele in as few as one snail can be manifested as prezygotic reproductive isolation within a deme in a subsequent generation. However, because the efficacy of achieving this type of prezygotic reproductive isolation is affected by shell form, the likelihood and product of single-gene speciation should be determined by deme interaction (migration) and composition (morphological distribution). We test this hypothesis and show how stochastic migration interacts with passive assortative mating yielding morphologically induced prezygotic reproductive isolation to produce new species phenotypes. The results show that demes can achieve rapid macroscopic phenotypic transformation and indicate that sympatric speciation might be more plausible than naturalists recognize conventionally.

Spatial working memory improvement by an alpha2-adrenoceptor agonist dexmedetomidine is not mediated through alpha2C-adrenoceptor

1. Aged alpha2C-adrenoceptor knockout and wild type mice were used to investigate whether alpha2C-adrenoceptors are involved in mediating the beneficial effects of alpha2-adrenoceptor agonist, dexmedetomidine, on spatial working memory. 2. A win-stay task in the radial arm maze was used to dissociate the effects of dexmedetomidine on working vs. reference memory. In addition, the animals were tested in simple response habit learning in the T-maze. 3. Knockout mice made more working memory errors after the change of the baited arm in radial arm maze, but after training reached again as accurate level of performance as wild type controls. Dexmedetomidine 5 and 10 microg/kg alleviated the increase in spatial working memory errors after the change of the baited arm in knockout mice. Knockout and wild type mice performed equally well in T-maze, and dexmedetomidine had no effect on this simple response learning. 4. The present results indicate that alpha2-adrenoceptor agonists have a selective effect on spatial working memory not only in monkeys but also in mice. Further, this study confirms our earlier finding that the presence of alpha2C-adrenoceptors is not necessary for the spatial working memory enhancing effect of alpha2-adrenoceptor agonists.

Sensory adaptation after a 2-week stretching regimen of the rectus femoris muscle

OBJECTIVE

To study the effects of a muscle stretching regimen for the rectus femoris muscle on subjective stretch sensation and range of motion (ROM).

DESIGN

A 2 x 2 crossover design comprising 2 treatments and 2 intervention periods.

SETTING

A military base in Sweden.

PARTICIPANTS

A volunteer sample of 29 male military conscripts divided into 2 groups, with each group subjected to both experimental and control treatments at different time periods.

INTERVENTION

Two weeks of supervised stretching (4 times/wk) of the rectus femoris muscle (experimental treatment) and the calf muscles (control treatment).

MAIN OUTCOME MEASURES

Subjective rating of the stretch sensation for the anterior aspect of the thigh determined on a category ratio scale. Passive knee flexion ROM determined on each test with the same applied torque, specific for each subject.

RESULTS

An additive analysis of variance revealed that the stretch sensation after the experimental treatment was decreased, compared with the control treatment (p <.01). The knee flexion, however, remained the same regardless of the treatment.

CONCLUSION

Sensory adaptation seems to be an important mechanistic factor in the effect stretching has on ROM changes. The lack of change in knee flexion suggests that the stretching, as performed in this study, did not influence stiffness of the rectus femoris muscle. Sensory adaptation may also be an underlying mechanism in the alleviating effect of stretching when applied to tired, tender, and painful muscles.

Purification and characterization of a novel bromoperoxidase-catalase isolated from bacteria found in recycled pulp white water

A bacterial strain, Pseudomonad EF group 70B, containing a high catalase-like activity was found in process water (white water) from pulp using recycled fibers. The enzyme was purified and characterized, and found to be a hydroperoxidase. The active enzyme has an apparent molecular mass of about 153 kDa with two identical subunits and a pI value of 4.7. It has a rather sharp pH optimum for catalase activity at 6.0 but exhibits catalase, peroxidase and brominating activities over a broad pH range from 4 to 8. It was not inhibited by 3-amino-1,2,4-triazole. Peroxidase-like activity was found when adding o-dianisidine, pyrogallol, guaiacol and 4-aminoantipyrine. Brominating activity was noticed using monochlorodimedone as a substrate. The absorption spectrum exhibited a Soret band at 404 nm. Upon reduction with dithionite the Soret peak decreased and shifted to 436 nm. Pyridine hemochrome spectra indicated the presence of a protophorfyrin IX heme group and the enzyme was inhibited by the known heme ligands cyanide and azide. N-terminal amino acid analysis gave the sequence STEVKLPYAVAGGGTTILDAFPGE, which showed no homology with those of known catalases or peroxidases. It is concluded that the enzyme is a novel type of catalase-peroxidase or, more specifically, a bromoperoxidase-catalase, and that future developments of inhibitors of hydrogen peroxide-degrading activities in white water may be based on this enzyme and other catalase-peroxidases.

Lack of relationship between thalamic oscillations and attention in rats: differential modulation by an alpha-2 antagonist

A five-choice serial reaction time (5-CSRT) task was used to assess attention in rats. In this behavioral paradigm, the rats are required to spatially discriminate a short visual stimulus that will occur randomly in one of five locations while maintaining a sufficient activity level. The ability of a rat to maintain attention on the task can be measured by counting the choice accuracy (percent correct responses), whereas the probability of premature responses indicates the level of impulsivity. According to previous results [24], rats performing poorly in the task have a lower choice accuracy and make more premature responses than normally behaving individuals, i.e., a clear, inverse correlation was observed between choice accuracy and impulsiveness of rats. Methylphenidate, a psychostimulant that has been shown to alleviate the symptoms in attention deficit-hyperactivity disorder (ADHD), improved the choice accuracy of poor performing rats in this task [24]. The present results show that the correlation between choice accuracy and impulsivity exists also when the rats are tested using a reduced stimulus intensity or curtailed stimulus duration. The results of a pharmacological experiment suggested that atipamezole (30, 300, or 1000 micrograms/kg), a potent and specific alpha-2 antagonist that is known to increase the activity of monoaminergic systems in the brain, did not affect the percent correct responses in poor performers or in controls tested either at the baseline conditions or at a curtailed stimulus duration (which impaired their choice accuracy). At the doses of 300 and 1000 micrograms/kg, however, atipamezole slightly increased the probability of premature responses in all group of rats. The results of an electrophysiological study indicated that the poor choice accuracy or impulsiveness of rats is not related to the amount of cortically recorded spike-wave discharges/high voltage spindle (HVS) activity, which reflect thalamo-cortical oscillation. Atipamezole dose-dependently reduced the incidence and duration of HVSs. The present data, therefore, indicate that (a) alpha-2 antagonist treatment is not superior to methylphenidate treatment when investigated using acute administrations of the agents in poor performers of the 5-CSRT task, and (b) thalamic oscillations are not the reason for the attention deficit of rats in this model of ADHD. The relationship between choice accuracy and impulsivity is discussed.

Alpha2C-adrenoceptor overexpression disrupts execution of spatial and non-spatial search patterns

We investigated the role of alpha2C-adrenoceptors in the modulation of spatial and non-spatial navigation behaviour. Alpha2C-adrenoceptor overexpressing mice developed an ineffective thigmotaxic search pattern characterized by swimming close to the pool walls during both spatial and non-spatial water maze training. A subtype-non-selective alpha2-adrenoceptor antagonist, atipamezole (1000 microg/kg, s.c.), fully reversed this impairment in their search strategy. Withdrawal of atipamezole at the end of spatial training resulted in an immediate disruption of the search pattern in alpha2C-adrenoceptor overexpressing mice. The swimming pattern of alpha2C-adrenoceptor overexpressing mice during a five day free swimming period was normal, when no cognitive component was required. Diazepam (0.3 and 1.0 mg/kg, i.p.), neither improved the accuracy in finding the platform nor decreased thigmotaxis. These results suggest that alpha2C-adrenoceptors may modulate the execution of complex navigation patterns.

High genetic variation in leopards indicates large and long-term stable effective population size

In this paper we employ recently developed statistical and molecular tools to analyse the population history of the Tanzanian leopard (Panthera pardus), a large solitary felid. Because of their solitary lifestyle little is known of their past or present population dynamics. Eighty-one individuals were scored at 18 microsatellite loci. Overall, levels of heterozygosity were high (0.77 +/- 0.03), with a small heterozygote deficiency (0.06 +/- 0.03). Effective population size (Ne) was calculated to be 38 000-48 000. A Ne:N ratio of 0.42 (average from four cat studies) gives a present population size of about 100 000 leopards in Tanzania. Four different bottleneck tests indicated that this population has been large and stable for a minimum of several thousand years. FST values were low and no significant genetic structuring of the population could be detected. This concurs well with the large migration values (Nm) obtained (>3.3 individuals/generation). Our analysis reveals that ecological factors (e.g. disease), which are known to have had major impact on other carnivore populations, are unlikely to have impacted strongly on the population dynamics of Tanzanian leopards. The explanation may be found in their solitary life-style, their often nonconfrontational behaviour toward interspecific competitors, or that any bottlenecks have been of limited size, localized, or too short to have affected genetic variation to any measurable degree. Since the genetic structuring is weak, gene flow is not restricted to within protected areas. Local loss of genetic variation is therefore not of immediate concern.

Overexpression of alpha2C-adrenoceptors impairs water maze navigation

We investigated the role of overexpression of alpha2C-adrenoceptors in water maze navigation in mice transgenically manipulated to have a threefold overexpression of the alpha2C-adrenoreceptors. Alpha2C-adrenoreceptors overexpressing mice swam more in the peripheral annulus of the pool and did not find the hidden escape platform as well as the wild type control mice. A subtype-nonselective alpha2-adrenoreceptor antagonist, atipamezole (ATI, 1000 microg/kg, s.c.), fully reversed the deficit in platform finding and search strategy in overexpressing mice. Noradrenaline depletion (-95%) induced by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) did not impair platform finding of wild type or overexpressing mice. The DSP-4 lesion slightly increased swimming in the peripheral annulus in wild type mice, but not in overexpressing mice. The DSP-4 lesion produced a dissociable effect on the action of atipamezole to improve platform finding and search strategy in overexpressing mice: atipamezole did not alleviate the platform finding deficit in DSP-4 lesioned overexpressing mice, but normalized their abnormal search strategy. These results suggest that the abnormal search pattern and deficit in the accuracy of platform finding are mediated by constitutive activity of overexpressed alpha2C-adrenoreceptors.

Position sense acuity is diminished following repetitive low-intensity work to fatigue in a simulated occupational setting

Repetitive work to fatigue is soundly associated with work-related musculoskeletal disorders (WMSD), although the underlying mechanisms are poorly understood. In the present study, we tested the hypothesis that fatiguing work leads to proprioceptive deficits, which can be an initiating factor for the occurrence of WMSD. Thus, the position sense of the shoulder was determined for 13 males and 13 females before and after performing repetitive low-intensity arm work to fatigue in a simulated occupational setting. From a starting position of 45 degrees to the sagittal plane, position sense tests consisted of subjects attempting to actively reproduce target positions of horizontal movements to 15 degrees and 30 degrees (shoulder adduction) and to 60 degrees and 75 degrees (shoulder abduction). An analysis of variance revealed that the absolute error was significantly increased following fatigue for the subjects as a group (P < 0.001). Furthermore, females had an overall higher error than males (P < 0.01). No difference in error was detected for the shorter movements versus the longer movements. However, the overall absolute error for adduction was significantly higher than for abduction (P < 0.001). The results of the present study support the hypothesis of diminished proprioceptive acuity following low-intensity work to fatigue. A reduction in position sense acuity could lead to impairment in motor control, which would further impact on position sense. Thus, a vicious cycle may be activated that might result in WMSD. The poorer position sense acuity observed for females may contribute to the explanation of why females demonstrate a higher incidence of WMSD than males.

Cancer patients' experiences of nurses' behaviour and health promotion activities: a critical incident analysis

Patients with head and neck cancer report several disease- and health-related problems before, during and a long time after completed treatment. Nurses have an important role in educating/supporting these patients about/through the disease and treatment so that they can attain well-being. This study describes the cancer patients' experiences of nurses' behaviour in terms of critical incidents after nurses had given them care to promote health. The study had a qualitative, descriptive design and the method used was the critical incident technique. Twenty-one informants from the Nordic countries diagnosed with head and neck cancer were strategically selected. It was explained to the informants what a critical incident implies before the interviews took place; this was defined as a major event of great importance, an incident, which the informants still remember, due to its great importance for the outcome of their health and well-being. The nurses' behaviour was examined, and critical incidents were involved in 208 cases-150 positive and 58 negative ones-the number of incidents varying between three and 20 per informant. The nurses' health promotion activities or lack of such activities based on the patients' disease, treatment and symptoms, consisted of informing and instructing the patients as well as enabling their participation. Personal consideration and the nurses' cognisance, knowledge, competence, solicitude, demeanour and statements of understanding were found to be important. Continuous health promotion nursing interventions were of considerable value for the majority of this group of cancer patients. Oncology nurses could reconfirm and update the care of head and neck cancer patients by including health promotion activities in individual care plans. By more frequent use of health promotion models, such as the empowerment model, the nurses could identify and focus on those individuals who needed to alter their life-style as well as tailor their approach towards these patient by setting goals for well-being and a healthy life-style.

Nanobacteria: an infectious cause for kidney stone formation

BACKGROUND

Nanobacteria are cytotoxic, sterile-filterable, gram-negative, atypical bacteria detected in bovine and human blood. Nanobacteria produce carbonate apatite on their cell walls. Data on Randall's plaques suggest that apatite may initiate kidney stone formation. We assessed nanobacteria in 72 consecutively collected kidney stones from Finnish patients.

METHODS

Nanobacteria and kidney stone units were compared using scanning electron microscopy (SEM). Demineralized kidney stones were screened for nanobacteria using a double-staining method and a specific culture method. Isolated nanobacteria were analyzed for mineral formation in vitro with Ca and 85Sr incorporation tests.

RESULTS

SEM highlighted the resemblance in size and morphology of nanobacteria and the smallest apatite units in the kidney stones. Nanobacterial antigens could be detected after the demineralization of the stones in 1 N HCl. Nanobacteria were surprisingly resistant to this treatment, and cultures could be established from 93.1% of the stones. Only struvite stones had common bacteria, in addition to the nanobacteria. When the results of all of the assays were combined, 70 of the 72 stones (that is, 97.2%) were nanobacteria positive. Although apatite stones indicated highest nanobacteria antigen signals, the overall nanobacteria positivity did not depend on the stone type. The isolated nanobacteria produced apatite stones in vitro, measured by Ca and 85Sr incorporation.

CONCLUSIONS

We propose that kidney stone formation is a nanobacterial disease analogous to Helicobacter pylori infection and peptic ulcer disease. Both diseases are initiated by bacterial infection and subsequently endogenous and dietary factors influence their progression.

Nucleotide substitution models and estimation of phylogeny

The nucleotide substitution matrix inferred from avian data sets using cytochrome b differs considerably from the models commonly used in phylogenetic analyses. To analyze the possible effects of this particular pattern of change in phylogeny estimation we performed a computer simulation in which we started with a real sequence and used the inferred model of change to produce a tree of 10 species. Maximum parsimony (MP), maximum likelihood (ML), and various distance methods were then used to recover the topology and the branch lengths. We used two kinds of data with varying levels of variation. In addition, we tested with the removal of third positions and different weighting schemes. At low levels of variation, MP was outstanding in recovering the topology (90% correct), while unweighted pair-group method, arithmetic average (UPGMA), regardless of distances used, was poor (40%). At the higher level, most methods had a chance of around 40%-58% of finding the true tree. However, in most cases, the trees found were only slightly wrong, with only one or a few branches misplaced. On the other hand, the use of a "wrong" model had serious effects on the estimation of branch lengths (distances). Although precision was high, accuracy was poor with most methods, giving branch lengths that were biased downward. When seeded with the true distance matrix, Fitch and NJ always found the true tree, while UPGMA frequently failed to do so. The effect of removing third positions was dramatic at low levels of variation, because only one MP program was able to find a true tree at all, albeit rarely, while none of the others ever did so. At higher levels, the situation was better, but still much worse than with the whole data set.

Alpha2C-adrenoceptor-overexpressing mice are impaired in executing nonspatial and spatial escape strategies

Drugs acting via alpha2-adrenoceptors modulate cognitive functions mediated via frontostriatothalamic feedback loops. The alpha2C-adrenoceptor subtype is expressed in the basal ganglia, hippocampus, and neocortex, areas that are involved in memory and other cognitive functions. alpha2C-Overexpressing (OE) mice were impaired in spatial or nonspatial water maze (WM) tests, and alpha2 antagonist treatment fully reversed the WM escape defect in OE mice. However, alpha2C-overexpression did not influence open field and passive avoidance behaviors or cortical EEG arousal or the actions of alpha2 agonist or antagonist drugs on these functions. Our results suggest that alpha2C-adrenoceptors can modulate navigation to a hidden or visible escape platform, whereas many other actions of alpha2-adrenergic agents, such as sedation, are not mediated via alpha2C-adrenoceptors. Therefore, alpha2-agonists lacking alpha2C-AR affinity or alpha2C-AR subtype-selective alpha2 antagonists could modulate functioning of frontostriatothalamic feedback loops more effectively than the current subtype-nonselective drugs.

Cognitive changes in mice following moderate MPTP exposure

We evaluated the cognitive effects of two moderate doses (30 mg/kg x 3 every 12 h and 20 mg/kg x 6 every 8 h, i.p.) of 1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP) in mice. The dose of 30 mg/kg x 3 caused about 60% depletion of striatal dopamine but did not reduce the levels of its metabolites. Mice treated with MPTP did not differ from controls in their motor behavior in the open field. Mice treated with MPTP were comparable to controls in T-maze delayed alternation with fixed delays but were impaired when trials with mixed 20 s and 120 s delays were presented, indicative of a spatial working memory impairment. Dexmedetomidine at 10 microg/kg (s.c.) slightly improved delayed alternation performance in all groups but also slowed initiation of the motor response. Mice treated with MPTP at the dose of 30 mg/kg x 3 were less sensitive to this adverse effect of dexmedetomidine. The impairment in spatial working memory after MPTP exposure in mice parallels the findings in monkeys, but the deficit is much less severe.

Activation of acetylcholine receptors and 5-HT2 receptors have additive effects in the suppression of neocortical high-voltage spindles in aged rats

We investigated if activation of the muscarinic or nicotinic acetylcholine receptors and serotonin (5-hydroxytryptamine; 5-HT) subtype 2 receptors would have additive or synergistic effects on the suppression of thalamocortically generated rhythmic neocortical high-voltage spindles (HVSs) in aged rats. The 5-HT2 receptor antagonist, ketanserin, at a moderate dose (5 mg/kg) prevented the ability of a muscarinic acetylcholine receptor agonist, (oxotremorine 0.1 mg/kg), and a nicotinic acetylcholine receptor agonist (nicotine 0.1 mg/kg), to decrease HVSs. At a higher dose (20 mg/kg), ketanserin completely blocked the decrease in HVSs produced by moderate doses of muscarinic acetylcholine receptor agonists (pilocarpine 1 mg/kg and oxotremorine 0.1 mg/kg), and by a high dose of nicotine (0.3 mg/kg), though not that produced by high doses of pilocarpine (3 mg/kg) and oxotremorine (0.9 mg/kg). The ability of a 5-HT2 receptor agonist, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.1-1.0 mg/kg), to suppress HVSs was non-significantly modulated by the nicotinic acetylcholine receptor antagonist, mecamylamine (1-15 mg/kg), and the muscarinic acetylcholine receptor antagonist, scopolamine (0.03-0.3 mg/kg). The effects of the drugs on behavioral activity could be separated from their effects on HVSs. The results suggest that activation of the muscarinic or nicotinic acetylcholine receptors plus 5-HT2 receptors has additive effects in the suppression of thalamocortical oscillations in aged rats.

Characterisation of silica-based heparin affinity sorbents from equilibrium binding studies on plasma fractions containing thrombin

The binding properties of rigid heparin sorbents, synthesised by end-point-attachment of heparin onto aminopropylderivatised silica through reductive amination, were characterised through batch-adsorption studies employing human plasma fractions containing thrombin. Thrombin was quantified using a chromogenic assay that had been specially modified for these studies. These investigations yielded information regarding the maximum adsorption capacities/stoichiometries and binding affinities for thrombin present in complex protein mixtures. Of the two types of heparin-silica evaluated, heparin-Fractosil 1000, with a pore size of 1000 A, displayed a capacity of 2.4 mol of thrombin/mol of heparin (mol T-mol H). This stoichiometry was significantly higher than the value of 1.8 mol T-mol H obtained for the commercial soft gel heparin-Sepharose CL-6B. Furthermore, the heparin-Fractosil 1000 sorbents were superior in capacity and binding site accessibility to heparin-LiChroprep Si60 sorbents, where the smaller pore size of 60 A largely restricts the ligand-protein interactions to the outer surface of the sorbent particles. Nevertheless, heparin-LiChroprep Si60 sorbents were useful, in that they simulated a non-porous particle system, in which intra-pore diffusion effects are eliminated. The batch adsorption results with these sorbents indicated that the adsorption involved both high and low binding affinity characteristics. This bimodal binding mechanism was also evident with the commercial heparin-Sepharose sorbent. Binding stoichiometries and affinities in the high concentration range were similar to values reported for a largely non-specific electrostatic thrombin-heparin interaction. Dissociation constants in the nanomolar range were observed in the low concentrations range. This stronger binding affinity is more similar to highly specific bio-affinity interactions. Thus, the results indicated that heparin-thrombin interactions with these systems involve both a weak electrostatic and a strong biospecific interaction component.

Chronic nimodipine and acute metrifonate treatment decreases age-related cortical high voltage spindles in rats

We studied the effect of nimodipine (1000 ppm mixed in food), an L-type calcium-channel antagonist, administered for 4 months, on the cortical EEG activity in young and aged rats. Nimodipine treatment decreased cortical high voltage spindles (HVSs) in aged rats, but did not prevent the diminution of spontaneous locomotor activity. The threshold dose of metrifonate, a cholinesterase inhibitor, for suppression of HVSs was lower in nimodipine compared to placebo treated aged rats (30 mg/kg versus 60 mg/kg; p.o.). In young rats, nimodipine did not decrease HVSs, protect from scopolamine (0.1 or 0.8 mg/kg, i.p.) induced EEG slowing or augment the effect of metrifonate to suppress slow waves induced by scopolamine. The present results suggest that a chronic nimodipine treatment modulates thalamocortical arousal and thereby adds to the therapeutic effects of metrifonate to restore normal cortical electrical arousal in aged rats.

Effects of combined nimodipine and metrifonate on rat cognition and cortical EEG

The present study investigated if short-term treatment with an L-type Ca2+-channel inhibitor, nimodipine, can stimulate cognitive functioning and cortical electroencephalograph (EEG) arousal, and potentiate the effect of a cholinesterase inhibitor, metrifonate. Pretraining administration of nimodipine (3, 10 and 30 mg/kg, p.o.) had no effect on water maze and passive avoidance behavior of young neurologically intact controls, or water maze and passive avoidance performance failure induced by scopolamine pretreatment (i.p.; 0.4 mg/kg during the water maze and 2.0 mg/kg during the passive avoidance study), medial septal lesioning, or aging. Furthermore, nimodipine (3, 10 and 30 mg/kg, p.o.) had no effect on the improvement by metrifonate (10 mg/kg, p.o.) of the water maze and passive avoidance failure induced by scopolamine pretreatment or medial septal lesioning, nor did it affect the potential of metrifonate (30 mg/kg. p.o.) to improve the water maze or passive avoidance behavior of aged rats. Finally, nimodipine (3, 10 and 30 mg/kg, p.o.) had no effect on spontaneously occurring thalamically generated neocortical high-voltage spindles or spectral EEG activity of young controls, nor did it alleviate the spectral EEG abnormality induced by scopolamine (0.2 mg/kg, i.p.) administration. Also, the combination of nimodipine 3 or 10 mg/kg and a subthreshold dose of metrifonate 10 mg/kg could not suppress high-voltage spindles or scopolamine treatment-induced spectral EEG activity abnormalities. According to the present results, short-term treatment with nimodipine does not stimulate cognitive functions or increase cortical EEG arousal, and does not block or potentiate the propensity of metrifonate to improve cognitive performance of rats.

The effects of cholinergic drugs on rat neocortical high-voltage spindles in ketanserin-treated rats

To investigate the roles of the cholinergic system and 5-HT2 receptors in the modulation of thalamocortical oscillations, we studied the effects of systemic (s.c.) administration of anticholinesterases (physostigmine, tetrahydroaminoacridine) and muscarinic acetylcholine receptor agonists (pilocarpine, oxotremorine) on spontaneous thalamically generated rhythmic neocortical high-voltage spindles in adult rats pretreated with either saline or ketanserin, a 5-HT2 receptor antagonist. Ketanserin at 20.0 mg/kg increased the number of high-voltage spindles. In saline-treated rats, tetrahydroaminoacridine 3.0 and 9.0 mg/kg was able to decrease high-voltage spindles, whereas in ketanserin 20.0 mg/kg-treated rats only the highest dose of tetrahydroaminoacridine (9.0 mg/kg) decreased high-voltage spindles. Both doses of physostigmine, 0.12 and 0.36 mg/kg, decreased high-voltage spindles in both saline and ketanserin 20.0 mg/kg-treated rats. Lower doses of tetrahydroaminoacridine (1.0 mg/kg) and physostigmine (0.06 mg/kg) were ineffective in both saline- and ketanserin 20.0 mg/kg-treated rats. Pilocarpine 3.0 mg/kg and oxotremorine 0.1 and 0.9 mg/kg decreased high-voltage spindles in saline-treated rats. However, in rats treated with ketanserin 20.0 mg/kg, only the lower doses of pilocarpine (0.3 and 1.0 mg/kg) and oxotremorine (0.03 mg/kg) were able to decrease the high-voltage spindles. The results suggest that activation of the cholinergic system and activation of 5-HT2 receptors have additive effects in the suppression of thalamocortical oscillations and related neocortical high-voltage spindles in rats, thus maintaining effective information processing in thalamocortical networks.

Characterisation of silica-based heparin-affinity adsorbents through column chromatography of plasma fractions containing thrombin

Different heparin-silicas, synthesised in this laboratory via directional end-point attachment of heparin (H) onto various amino-derivatised silicas, have been evaluated in packed-bed and expanded-bed column chromatographic experiments using crude preparations of the therapeutic protein, thrombin (T). Adsorbent capacities, determined through batch adsorption experiments, were verified by employing frontal analysis in packed-bed systems. The performance of these adsorbents was also investigated in terms of thrombin purification factors and recoveries. The potential of the heparin-silicas was further examined in the expanded-bed column chromatographic mode using a scaled-up procedure. With heparin-Fractosil 1000 adsorbents, capacities of around 100,000 U thrombin/ml adsorbent could be achieved. Heparin-Fractosil 1000 adsorbents of intermediate heparin content (around 4 mg heparin/ml sorbent) displayed binding stoichiometries similar to that of the commercial heparin-Sepharose (2.6-2.7 mol T/mol H). Furthermore, binding stoichiometries were largely unaffected by increasing the heparin content on the heparin-Fractosil 1000 adsorbents from 0.8 to 4.6 mg of heparin/ml of sorbent. This result suggests that optimal binding site accessibilities for the thrombin-heparin interaction occurs at lower ligand density values. The binding capacity values determined from frontal analysis were confirmed by the recovery data, thus indicating minimal irreversible adsorption. Specific activities of ca. 2100 U/mg were obtained for thrombin when affinity-purified on these heparin-LiChroprep Si60 or heparin-Fractosil 1000 adsorbents. These values were higher than the maximum achievable purity obtained through alternative, multi-step chromatographic purification procedures reported by other investigators. These results indicated that the packed-bed performances with these silica-based adsorbents were superior to currently available commercial soft gel adsorbents, with the more dense heparin-silicas exhibiting very good potential for use in expanded-bed applications.

An indirect cholinesterase inhibitor, metrifonate, increases neocortical EEG arousal in rats

We investigated the ability of a cholinesterase inhibitor, metrifonate, to desynchronize cortical EEG activity. Metrifonate suppressed immobility-related high voltage spindling activity in young and aged rats at doses of 30 and 60 mg kg-1, p.o., and 10, 30 and 60 mg kg-1, p.o., respectively. The increase in EEG 1-20 Hz amplitude induced by scopolamine (0.2 mg kg-1, i.p.) was fully alleviated by metrifonate (30 and 100 mg kg-1, p.o.) and partially alleviated by a reference cholinesterase inhibitor, THA (3 and 6 mg kg-1, i.p.). Nucleus basalis (NB) lesions induced by quisqualic acid decreased frontal cortical choline acetyltransferase activity by 80% and increased cortical EEG slow waves. Metrifonate and THA did not reverse NB lesion-induced EEG abnormality. We conclude that metrifonate enhances cholinergic desynchronization of cortical EEG waves and that a severe defect of presynaptic NB cholinergic fibres limits the therapeutic effects of metrifonate.

Suppression of neocortical high-voltage spindles by nicotinic acetylcholine and 5-HT2 receptor stimulation

To investigate the roles of the nicotinic acetylcholine receptor and the serotonin (5-hydroxytryptamine; 5-HT) subtype 2 receptor in the modulation of rat thalamocortical oscillations, the effects of systemic (s.c.) administration of nicotine, a nicotinic acetylcholine receptor agonist, and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT2 receptor agonist, on neocortical high-voltage spindle activity occurring during quiet waking-immobility behavior in aged (28 months of age) and adult (7 months of age) rats were studied. Nicotine 0.1 and 0.3 mg/kg alleviated the age-related increase of neocortical high-voltage spindles, whereas in adult rats only nicotine 0.3 mg/kg was effective. DOI 0.3, 1.0 and 2.0 mg/kg suppressed high-voltage spindles in both aged and adult rats. In aged rats, a combination of subthreshold doses of nicotine (0.03 mg/kg) and DOI (0.1 mg/kg) decreased neocortical high-voltage spindles, whereas in adult rats two different subthreshold dose combinations (nicotine 0.03 or 0.1 mg/kg+DOI 0.1 mg/kg) had no effect. p-Chlorophenylalanine (400 mg/kg/day i.p. for 3 consecutive days) treatment decreased brain serotonin concentration (> 80% reduction), but did not affect high-voltage spindles. However, in both aged and adult rats, p-chlorophenylalanine treatment blocked the decrease in high-voltage spindle activity produced by DOI 0.3 mg/kg, though not the decrease produced by higher doses of DOI (1.0 and 2.0 mg/kg). It is important that, in adult rats, p-chlorophenylalanine treatment was able to abolish the decrease in high-voltage spindle activity seen after a relatively high dose of nicotine (0.3 mg/kg). The results suggest that nicotinic acetylcholine and 5-HT2 receptors may act in concert to suppress neocortical high-voltage spindling in rats, and that intact brain serotonergic systems may be important for some of the therapeutic effects of nicotine.