The effects of maturation on self-induced dynamic body sway frequencies of girls performing acrobatics or classical dance

We investigated the effects of maturation on the dynamic body sways of healthy girls. Prepubertal and postpubertal girls practising professional physical activities requiring a good ability to maintain equilibrium (acrobats and dancers) were asked to stand on a free seesaw platform and the results compared to those for untrained age-matched girls. This platform (stabilometer) allows self-induced body sways. Stabilograms were obtained by a double integration of the angular acceleration from the recordings of the platform sways made with an accelerometer. Fast Fourier transform processing of stabilograms allowed spectral frequency analysis. The total spectrum energy and the energies of three frequency bands (0–0.5 Hz, 0.5–2 Hz, 2–20 Hz) were determined. ANOVA showed that, for all groups of different equilibrium activity and independent of visual input, prepubertal girls had higher energy values than postpubertal girls in the 0- to 0.5-Hz band whereas the opposite was true for 0.5- to 2-Hz band. Ballet dancers were more dependent than acrobats on visual inputs for the regulation of their postural control but were less dependent than untrained girls at both ages. Maturation seemed to shift body sways towards higher frequencies and the utilization of the cues of postural control was different according to the type of equilibrium activity practised by the subjects. Accepted: 7 February 1997     

Between‐year variation of MHC allele frequencies in great reed warblers: selection or drift?

The major histocompatibility complex (MHC) genes are extremely polymorphic and this variation is assumed to be maintained by balancing selection. Cyclic interactions between pathogens and their hosts could generate such selection, and specific MHC alleles or heterozygosity at certain MHC loci have been shown to confer resistance against particular pathogens. Here we compare the temporal variation in allele frequencies of 23 MHC class I alleles with that of 23 neutral microsatellite markers in adult great reed warblers (a passerine bird) in nine successive cohorts. Overall, the MHC alleles showed a significantly higher variation in allele frequencies between cohorts than the microsatellite alleles, using a multi-variate genetic analysis (amova). The frequency of two specific MHC alleles, A3e (P = 0.046) and B4b (P = 0.0018), varied more between cohorts than expected from random, whereas none of the microsatellite alleles showed fluctuations exceeding the expectation from stochastic variation. These results imply that the variation in MHC allele frequencies between cohorts is not a result of demographic events, but rather an effect of selection favouring different MHC alleles in different years.     

High transformation frequencies obtained from a commercial wheat (Triticum aestivum L. cv. ‘Combi’) by microbombardment of immature embryos followed by GFP screening combined with PPT selection

Improved gene transfer techniques are necessary to obtain adequatenumbers of stable transgenic wheat plants needed for practical purposes.Considering that wheat transformation is genotype-dependent, we used cv. Combiin all experiments, which had been selected from agronomically important Germanspring wheat cultivars because of its high transformation ability. In mostwheatgene transfer attempts, immature embryos or embryogenic scutellar calli weremicrobombarded. We compared both methods under optimised conditions, usingbar, uidA, andgfp as markers in co-transformation attempts. Integrationof the genes mentioned above was proven by Southern blotting, expression levelswere measured by assays on phosphinothricin acetyltransferase and-glucuronidase activities, and by monitoring for green fluorescentproteinin most developmental stages. Following bombardment of scutellar calli, anaverage transformation frequency of 0.13% was attained. Using immature embryos,mean transformation frequency (1.06%) was 8-fold higher. In addition, embryotechniques were over 2 weeks faster than scutellar callus procedures.Introducing gfp as a vital marker led to an improvement ofembryo-based techniques. In a first screening, transientgfp-expressing embryos were transferred tophosphinothricincontaining callus medium. Only gfp-expressing calli whichdeveloped on it were cultured further on phosphinothricin containingregeneration medium. Shoots obtained from gfp-expressingcalli were rooted on phosphinothricin-free medium, and cultured exvitro. Average transformation frequency (4.93%) was 38-fold higherthan with scutellar callus techniques. Differences between the transformationstrategies used were of high statistical significance. Combining greenfluorescent protein screening with phosphinothricin selection in embryo-basedtechniques offers a promising system to obtain high wheat transformationfrequencies.     

Comparison of the CopB systems of plasmids R1 and Co1V2-K94: A single base alteration in CopB gene is responsible for the increased copy number of the low copy number plasmid CoIV2-K94

Summary We have isolated a deletion mutation and a point mutation in the copB gene of the replication region Repl of the IncFI plasmid Co1V2-K94. Subsequently, this copB gene with and without point mutation was cloned and sequenced, and the point mutation was mapped in the coding region of copB with a change of one amino acid from arginine to serine. Furthermore, this copB mutant had an approximately 10-fold increase in copy number. The CopB-phenotype of Co1V2-K94 could be complemented in trans by the copB gene of coresident IncFII plasmids such as R1 and R538, but not R100, suggesting that ColV2-K94 and R1 or R538 contain the same copB allele.     

Microsatellites: consensus and controversy

Microsatellite DNA loci have recently been adopted for many biological applications. Comparative studies across a wide range of species has revealed many details of their mutational properties and evolutionary life cycles. Experience shows that a full understanding of these processes is essential to ensure the effective use of microsatellites as analytical tools. In this article, we review the controversies that have arisen as biologists have taken up this new technology and the emerging consensus that has resulted from their debates. We point to the need for comparative DNA sequencing studies to produce input data for a new generation of theoretical models of microsatellite behaviour. We conclude by presenting our own conceptual model, ‘Snakes and Ladders’, as an aid to theory development.     

Temporal changes in allele frequencies in two European F2 flint maize populations under modified recurrent full-sib selection

Selection and random genetic drift are the two main forces affecting the selection response of recurrent selection (RS) programs by changes in allele frequencies. Therefore, detailed knowledge on allele frequency changes attributable to these forces is of fundamental importance for assessing RS programs. The objectives of our study were to (1) estimate the number, position, and genetic effect of quantitative trait loci (QTL) for selection index and its components in the base populations, (2) determine changes in allele frequencies of QTL regions due to the effects of random genetic drift and selection, and (3) predict allele frequency changes by using QTL results and compare these predictions with observed values. We performed QTL analyses, based on restriction fragment length polymorphisms (RFLPs) and simple sequence repeats (SSRs), in 274 F_2:3 lines of cross KW1265 × D146 (A × B) and 133 F_3:4 lines of cross D145 × KW1292 (C × D) originating from two European flint maize populations. Four (A × B) and seven (C × D) cycles of RS were analyzed with SSRs for significant allele frequency changes due to selection. Several QTL regions for selection index were detected with simple and composite interval mapping. In some of them, flanking markers showed a significant allele frequency change after the first and the final selection cycles. The correlation between observed and predicted allele frequencies was significant only in A × B. We attribute these observations mainly to (1) the high dependence of the power of QTL detection on the population size and (2) the occurrence of undetectable QTL in repulsion phase. Assessment of allele frequency changes in RS programs can be used to detect marker alleles linked to QTL regions under selection pressure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Proportions of different habitat types are critical to the fate of a resistance allele

We describe a simple deterministic theoretical framework for analysing the gene frequency evolution of two alternative alleles at a single genetic locus in a habitat comprising two environments in which the genotypes have different relative fitnesses. We illustrate this for adaptation of pest insects, where one allele (resistance to toxins expressed in transgenic crops) is favoured in one environment (transgenic plants) and the other allele (susceptibility to toxins) is favoured in the other environment (‘refuges’ of non-transgenic plants). The evolution of allele frequencies depends on selection pressure because of relative sizes of the environments and relative fitnesses of the genotypes in each environment. We demonstrate that there are critical threshold proportions for habitat division that determine equilibrium allele frequencies. The stability of the system depends on relationships between the relative genotype fitnesses. In some cases, the division of the habitat in exactly the threshold proportions removes selection pressure and maintains polymorphism at all allele frequencies.     

Acoustic structure of vocalization and stapedius muscle activity during vocal development in chickens (Gallus gallus)

The link between stapedius muscle activity and acoustic structure of vocalization was analysed in cocks of age 20–30 to 90–100 days old. The results show that stapedius muscle activation depends on the acoustic structure of vocalization and changes during vocal development. This dependence was observed in spontaneous calls and in vocalizations elicited by stimulating the mesencephalic calling area. In 30-day-old cocks stapedius muscle EMG response is never associated with vocalizations with an acoustic energy content which is always distributed at frequencies higher than 2000 Hz. The coupling between vocalization and stapedius muscle activity begins later, when birds produce vocalizations with acoustic energy shifted towards lower frequencies. Overall, stapedius muscle activity is related to a bird's production of high amplitude low frequencies. These results support the hypothesis that the primary role of the stapedius muscle during normal vocal development is to dampen the amplitude of low frequency energy that reaches the cochlea during vocalization.