Influence of training on the response to exercise of adrenocorticotropin and growth hormone plasma concentrations in human swimmers

The aim of the present study was to evaluate the response of adrenocorticotropin ([ACTH]) and growth hormone ([GH]) concentrations to a typical aerobic swimming set during a training season. Nine top-level male endurance swimmers (age range 17–23 years) were tested during three training sessions occurring 6, 12 and 18 weeks after the beginning of the season. During each session, after a standard warm-up, the swimmers performed a training set of 15 × 200-m freestyle, with 20 s of rest between repetitions, at a predetermined individual speed. Blood samples were collected before warm-up and at the end of the training set. A few days before each session, the individual swimming velocity corresponding to the 4 mmol · l⁻¹ blood lactate concentration (v ₄) was assessed as a standard of aerobic performance. Aerobic training affected v ₄ levels, which were highest 18 weeks after the beginning of the season; at the same time, while [ACTH] response was attenuated, [GH] response was enhanced. These results could be considered as adaptations to the exercise intensity. In our training programme, these adaptations seemed to have occurred between the 12th and 18th weeks of the training season. Accepted: 21 April 1998     

Micropropagation and molecular characterization of Thymus sibthorpii Benth. (Lamiaceae), an aromatic-medicinal thyme with ornamental value and conservation concern

Thymus sibthorpii Benth. (Lamiaceae), with accession number 01,1796-22, is a biotype of native Greek thyme with ascending stems and potential use as a new medicinal-aromatic crop and ornamental plant. An efficient and reliable protocol for in vitro clonal propagation of T. sibthorpii from nodes and meristem tip explants was developed. Shoot proliferation succeeded on a new basal medium (BB) without plant growth regulators, as prior experiments with 6-benzyladenine generated hyperhydricity. Eight different basal media were compared; on two formulations using the new BB 5.9 and 5.6 shoots per explant were produced. Regenerated single shoots were rooted in the BB medium, supplemented with 5 μM of indole-3-butyric acid, and produced 3.1 roots along with 2.5 adventitious shoots. Three types of acclimatization were assessed: in vitro, using two different systems (no significant differences); ex vitro, using eight soil substrates under greenhouse and outdoor nursery conditions (in two of them, 100% of plantlets survived); and in field cultivations, established at eight geographically distant areas of Greece (100% survival rate at all locations). Molecular characterization of T. sibthorpii was evaluated with one nuclear ribosomal DNA and seven chloroplast DNA markers, followed by DNA sequence comparisons with a total of 30 different Thymus species, subspecies, and varieties. The trnH/psbA, trnL/trnF, and matK genes were the most efficient markers for molecular characterization of T. sibthorpii. The molecular markers rpoC1 and petB/petD did not match to any Thymus species and therefore, these DNA sequences provide new sequence information for entire Thymus taxa.

     

Measuring Symmetry,Asymmetry and Randomness in Neural Network Connectivity

Cognitive functions are stored in the connectome, the wiring diagram of the brain, which exhibits non-random features, so-called motifs. In this work, we focus on bidirectional, symmetric motifs, i.e. two neurons that project to each other via connections of equal strength, and unidirectional, non-symmetric motifs, i.e. within a pair of neurons only one neuron projects to the other. We hypothesise that such motifs have been shaped via activity dependent synaptic plasticity processes. As a consequence, learning moves the distribution of the synaptic connections away from randomness. Our aim is to provide a global, macroscopic, single parameter characterisation of the statistical occurrence of bidirectional and unidirectional motifs. To this end we define a symmetry measure that does not require any a priori thresholding of the weights or knowledge of their maximal value. We calculate its mean and variance for random uniform or Gaussian distributions, which allows us to introduce a confidence measure of how significantly symmetric or asymmetric a specific configuration is, i.e. how likely it is that the configuration is the result of chance. We demonstrate the discriminatory power of our symmetry measure by inspecting the eigenvalues of different types of connectivity matrices. We show that a Gaussian weight distribution biases the connectivity motifs to more symmetric configurations than a uniform distribution and that introducing a random synaptic pruning, mimicking developmental regulation in synaptogenesis, biases the connectivity motifs to more asymmetric configurations, regardless of the distribution. We expect that our work will benefit the computational modelling community, by providing a systematic way to characterise symmetry and asymmetry in network structures. Further, our symmetry measure will be of use to electrophysiologists that investigate symmetry of network connectivity.     

A novel improved method for Aspergillus nidulans transformation

We systematically investigated the efficiency of Aspergillus nidulans transformation using protoplasts prepared from different stages of conidiospore germination and young mycelium. Using standard integrative plasmids, increased transformation yields were obtained with protoplasts isolated from a specific stage coincident with germ tube emergence. This increase ranged, on the average, from two- to eightfold depending on different plasmids used. Transformation efficiencies with a replicative plasmid were similar to those obtained using previously described methods. Although this observation suggests that elevated transformation efficiencies might be due to increased efficiency of recombination between plasmid and genomic sequences, we cannot exclude other factors associated with the particular developmental stage used. In the course of this study, we also examined the effect of other parameters that might enhance transformation yields. The method described is also significantly easier and faster than other current methods.     

Migration Behavior of Rodent Granule Neurons in the Presence of Antibody to the 4C5 Antigen

Abstract: We have reported the production of monoclonal antibody 4C5, which recognizes a cell surface antigen, the 4C5 antigen, involved in granule cell migration processes. In the present study, we investigated in a more precise manner the role of the 4C5 antigen in the different types of granule cell migrations that take place during cerebellar development. When cerebellar explant cultures derived from 10-day-old rats were performed for 2 days in the presence of monoclonal antibody 4C5, vertical granule cell migration, occurring in the presence of glia, was not significantly inhibited. In contrast, when monoclonal antibody 4C5 was included in the medium of microexplant cultures derived from 4-day-old mice and maintained for 4 days in vitro, granule cell migrations that occurred both parallel and perpendicular to the neurite bundles that were free of glia were inhibited. Moreover, a stronger inhibitory effect of the antibody was observed on migration perpendicular to the neurite bundles compared with the parallel type of migration. Our results indicate that the 4C5 antigen differentially affects the different developmental stages and types of granule cell migration during rodent cerebellar development.     

Environmental symbiont acquisition may not be the solution to warming seas for reef-building corals

Background

Coral reefs worldwide are in decline. Much of the mortality can be attributed to coral bleaching (loss of the coral''s intracellular photosynthetic algal symbiont) associated with global warming. How corals will respond to increasing oceanic temperatures has been an area of extensive study and debate. Recovery after a bleaching event is dependent on regaining symbionts, but the source of repopulating symbionts is poorly understood. Possibilities include recovery from the proliferation of endogenous symbionts or recovery by uptake of exogenous stress-tolerant symbionts.

Methodology/Principal Findings

To test one of these possibilities, the ability of corals to acquire exogenous symbionts, bleached colonies of Porites divaricata were exposed to symbiont types not normally found within this coral and symbiont acquisition was monitored. After three weeks exposure to exogenous symbionts, these novel symbionts were detected in some of the recovering corals, providing the first experimental evidence that scleractinian corals are capable of temporarily acquiring symbionts from the water column after bleaching. However, the acquisition was transient, indicating that the new symbioses were unstable. Only those symbiont types present before bleaching were stable upon recovery, demonstrating that recovery was from the resident in situ symbiont populations.

Conclusions/Significance

These findings suggest that some corals do not have the ability to adjust to climate warming by acquiring and maintaining exogenous, more stress-tolerant symbionts. This has serious ramifications for the success of coral reefs and surrounding ecosystems and suggests that unless actions are taken to reverse it, climate change will lead to decreases in biodiversity and a loss of coral reefs.     

Adaptive divergence in experimental populations of Pseudomonas fluorescens. III. Mutational origins of wrinkly spreader diversity

Understanding the connections among genotype, phenotype, and fitness through evolutionary time is a central goal of evolutionary genetics. Wrinkly spreader (WS) genotypes evolve repeatedly in model Pseudomonas populations and show substantial morphological and fitness differences. Previous work identified genes contributing to the evolutionary success of WS, in particular the di-guanylate cyclase response regulator, WspR. Here we scrutinize the Wsp signal transduction pathway of which WspR is the primary output component. The pathway has the hallmarks of a chemosensory pathway and genetic analyses show that regulation and function of Wsp is analogous to the Che chemotaxis pathway from Escherichia coli. Of significance is the methyltransferase (WspC) and methylesterase (WspF) whose opposing activities form an integral feedback loop that controls the activity of the kinase (WspE). Deductions based on the regulatory model suggested that mutations within wspF were a likely cause of WS. Analyses of independent WS genotypes revealed numerous simple mutations in this single open reading frame. Remarkably, different mutations have different phenotypic and fitness effects. We suggest that the negative feedback loop inherent in Wsp regulation allows the pathway to be tuned by mutation in a rheostat-like manner.     

Postprandial hepatic protein expression in trout Oncorhynchus mykiss a proteomics examination

Following a meal, a series of physiological changes occurs in animals as they digest, absorb and assimilate ingested nutrients, the kinetics of these responses depends on metabolic rate and nutrient quality. Here we investigated the hepatic proteome in the ectothermic teleost, the rainbow trout, following a single meal to define the postprandial expression of hepatic proteins. The fish were fed a high marine fishmeal/fish oil single meal following a period of 24 h without feeding. Liver protein profiles were examined by 2D gel electrophoresis just before feeding (time 0 h) and at 6 and 12 h after feeding. Of a total of 588 protein spots analysed in a temporal fashion, 49 differed significantly in abundance between the three time groups (ANOVA, p<0.05), before and after feeding, 15 were increased and 34 were decreased in abundance after feeding. Amino acid metabolism-regulated proteins such as phenylalanine-4-hydroxylase and proliferating cell antigen were increased in abundance 12 and 6 h following the meal, suggesting by this time that the fish were increasing their protein turnover to utilize efficiently their dietary protein consumption. Overall, these results highlight some specificity of the trout metabolism and identify postprandial response of metabolism-related proteins 6–12 h after feeding a single meal.