The structure of sterile cytoplasm types within a maize genebank collection

Maize Research Institute (MRI) gene bank maintains a collection of 6000 maize accessions. Within this collection over 100 sources of cytoplasmic male sterility (CMS) were found in field trials, i.e. more than 2% of the total accession numbers. These sources are distributed among Yugoslav open-pollinated varieties (4.56% of them contain CMS), as well as introduced heterozygous genotypes and inbred lines. In order to identify cytoplasm types the gene-bank sources of CMS were screened using a PCR assay with specific primers for C, T and S cytoplasms. Predominant cytoplasmic male sterility type among the analyzed accessions was CMS-S. Results were inconclusive for three accessions, i.e. different results for the progenies of two ears per accession were obtained. For another two accessions a new PCR product profile was identified, consisting of one band characteristic for CMS-S and one unspecific for any of the three CMS types. The PCR approach enabled a simple, fast and reliable large scale screening of maize cytoplasm among MRI gene bank accessions, significantly reducing time for cytoplasm characterizations compared to classical method of testing with restorers for each known type of CMS.     

Photochemical and photophosphorylation activities of chloroplasts and leaf mesostructure in Chinese cabbage plants grown under illumination with light-emitting diodes

Leaf mesostructure, photochemical activity, and chloroplast photophosphorylation (PP) in the fourth true leaf of 28-day-old Chinese cabbage (Brassica chinensis L.) plants were investigated. Plants were grown under a light source based on red (650 nm) and blue (470 nm) light-emitting diodes (LED) with red/blue photon flux ratio of 7: 1 and under illumination with high-pressure sodium lamp (HPSL) at photon flux densities of 391 ± 24 μmol/(m² s) (“normal irradiance”) and 107 ± 9 μmol/(m² s) (“low irradiance”) in photosynthetically active range. At normal irradiance, the leaf area in plants grown under HPSL was twofold higher than in LED-illuminated plants; other parameters of leaf mesostructure were little affected by spectral quality of incident light. The lowering of growth irradiance reduced the majority of leaf mesostructure parameters in plants grown under illumination with HPSL, whereas in LED-illuminated plants the lowered irradiance reduced only specific leaf weight but increased the leaf thickness and dimensions of mesophyll cells and chloroplasts. The photochemical activity of isolated chloroplasts was almost independent of growth irradiance and light spectral quality. Light quality and intensity used for plant growing had a considerable impact on PP in chloroplasts. At normal light intensity, the highest activity of noncyclic PP in chloroplasts was observed for plants grown under HPSL; at low light intensity the highest rates of PP were noted for plants grown under LED. The P/2e⁻ ratio, which characterizes the degree of PP coupling to electron transport in the chloroplast electron transport chain, showed a similar pattern. Thus, the narrow-band spectrum of the light source had little influence on leaf mesostructure and electron transport rates. However, this spectrum significantly affected the chloroplast PP activity. The PP patterns at low and normal light intensities were opposite for plants grown under LED and HPSL light sources. We suppose that growing plants under LED array at normal light intensity disturbed the chloroplast coupling system, thus preventing the effective use of light energy for ATP synthesis. At low light intensity, chloroplast PP activity was significantly higher under LED illumination, but plant growth was suppressed because of impaired adaptation to low light intensity.     

Neuro-endocrine basis for altered plasma glucose homeostasis in the Fragile X mouse

Background

The fragile X mouse model shows an increase in seizure susceptibility, indicating an involvement of the GABAergic system via an alteration in cellular excitability. In the brain, we have previously described a reduction in GABA_A receptor expression as a likely basis for this susceptibility. In the brains of fragile X mice, this reduction in receptor expression culminates with a concomitant increase in the expression of glutamic acid decarboxylase (GAD), the enzyme responsible for GABA synthesis. Further, voltage-sensitive calcium channel expression is reduced in the pancreas of the fragile X mouse. Since there are considerable similarities in the GABAergic system in the brain and pancreas, we evaluated the protective role of taurine in pancreatic islet development in both wild type (WT) and fragile X mice (KO).

Methods

One-month-old FVB/NJ males or age-matched fmr1-knockout (KO) mice were supplemented with taurine in drinking water (0.05% w/v) for four weeks. Age-matched controls were fed water only for the same duration. At four weeks, mice were sacrificed and pancreases processed for histology and immunohistochemical studies on changes of insulin, glucagon and somatostatin expression. Additional mice were subjected to a glucose tolerance test.

Results

Taurine treatment resulted in a significant increase in the number and size of islets. WT taurine-fed mice, slightly hypoglycemic prior to glucose injection, showed significantly reduced plasma glucose at 30 min post-injection when compared to control mice. KO mice had normal baseline plasma glucose concentration; however, following glucose injection they had higher plasma glucose levels at 30 min when compared to controls. Supplementation of taurine to KO mice resulted in reduced baseline levels of plasma glucose. After glucose injection, the taurine-fed KO mice had reduced plasma glucose at 30 min compared to KO. Concomitant with the increased islets size and glucose tolerance observed in taurine-fed mice there was an increase in insulin, glucagon and somatostatin immunoreactivity in the islets of WT mice. In the KO mice however, insulin levels were not affected whereas glucagon and somatostatin levels were reduced. Exocytosis of these hormones is calcium-dependent, therefore any exacerbation of calcium homeostasis could affect hormone release. We found the expression of the voltage sensitive calcium channels (VSCC) is drastically reduced in the pancreas of fragile X mice.

Conclusions

During early development, the VSCC play an important role in calcium-dependent gene expression. Since these channels are also involved in depolarization and calcium-mediated vesicular release of neurotransmitters and pancreatic hormones, alterations in the expression of VSCC not only will affect calcium-mediated gene expression but also hormonal and neurotransmitter release creating therefore a neuroendocrine perturbation in the fragile X that may potentially affect other organ systems. We find that in the fragile X mouse, taurine treatment may partially restore functionality of the neuro-endocrine pancreas.

     

Shoulder demands in manual wheelchair users across a spectrum of activities

ObjectiveInvestigate shoulder joint kinetics over a range of daily activity and mobility tasks associated with manual wheelchair propulsion to characterize demands placed on the shoulder during the daily activity of manual wheelchair users.DesignCase series.SubjectsTwelve individuals who were experienced manual wheelchair users.MethodsUpper extremity kinematics and handrim wheelchair kinetics were measured over level propulsion, ramp propulsion, start and stop over level terrain, and a weight relief maneuver. Shoulder intersegmental forces and moments were calculated from inverse dynamics for all conditions.ResultsWeight relief resulted in significantly higher forces and ramp propulsion resulted in significantly higher moments than the other conditions. Surprisingly, the start condition resulted in large intersegmental moments about the shoulder equivalent with that of the ramp propulsion, while the demand imparted by the stop condition was shown to be equivalent to level propulsion across all forces and moments.ConclusionsThis study provides characterization of daily living and mobility activities associated with manual wheelchair propulsion not previously reported and identifies activities that result in higher shoulder kinetics when compared to standard level propulsion.     

Automatic detection of surface EMG activation timing using a wavelet transform based method

The problem of the identification of the muscle contraction timing by using surface electromyographic signal is addressed. The timing detection of the muscular activation in dynamic conditions has a real clinical diagnostic impact. Widely used single threshold methods still rely on the experience of the operator in manually setting that threshold. A new approach to detect the muscular activation intervals, that is based on discontinuities detection in the wavelet domain, is proposed. Accuracy and precision of the algorithm were assessed by using a set of simulated signals obtaining values lower than 11.0 and 8.7 ms for biases and standard deviations of the estimation, respectively. Moreover an experimental application of the algorithm was carried out recruiting a population of 10 able-bodied subjects and processing the myoelectric signals recorded from the lower limb during an isokinetic exercise. The algorithm was able to reveal correctly the timing of muscular activation with performance comparable to the state-of-the-art methods. The detection algorithm is automatic and user-independent, it manages the detection of both onset and offset activation, it can be fruitfully applied even in presence of noise and, therefore, it can be used also by unskilled operators.     

Speciation and phylogeography of giant petrels Macronectes

We examine global phylogeography of the two forms of giant petrel Macronectes spp. Although previously considered to be a single taxon, and despite debate over the status of some populations and the existence of minimal genetic data (one mitochondrial cytochrome b sequence per form), the current consensus based on morphology is that there are two species, Northern Giant Petrel M. halli and Southern Giant Petrel M. giganteus. This study examined genetic variation at cytochrome b as well as six microsatellite loci in giant petrels from 22 islands, representing most island groups at which the two species breed. Both markers support separate species status, although sequence divergence in cytochrome b was only 0.42% (corrected). Divergence was estimated to have occurred approximately 0.2 mya, but with some colonies apparently separated for longer (up to 0.5 my). Three clades were found within giant petrels, which separated approximately 0.7 mya, with the Southern Giant Petrel paraphyletic to a monophyletic Northern Giant Petrel. There was evidence of past fragmentation during the Pleistocene, with subsequent secondary contact within Southern Giant Petrels. The analysis also suggested a period of past population expansion that corresponded roughly to the timing of speciation and the separation of an ancestral giant petrel population from the fulmar Fulmarus clade.     

Evo-devo and the I.I. Schmalhausen concept of the evolution of ontogeny

Evo-devo is considered a special field of knowledge emphasizing the role of developmental processes and mechanisms in evolution and integrating the data of many disciplines studying various structural levels of biosphere organization. A mechanical approach to estimation of events is regarded as a specific feature of the evo-devo concept. In our opinion, the I.I. Schmalhausen concept of the evolution of ontogeny, opposing the reductionist approach of many contemporary evo-devo adherents, can be regarded as the fundamental basis of evo-devo.     

Fibrinolytic and hypoglycemic effects of the Pro-Gly-Pro-Leu peptide during development of insulin-dependent diabetes in rats

Repeated (over 7 days) intranasal introduction of the Pro-Gly-Pro-Leu peptide into animals at a dose of 1 mg/kg before injection of the diabetogenic metabolite alloxan provided effective protection of an organism against development of insulin-dependent diabetes mellitus and prevented development of hyper-coagulating alterations in the system of hemostasis. An increasing in the anticoagulating and fibrinolytic activities in rat blood plasma was detected. The peptide under study also showed antidiabetogenic action: repeated intranasal introduction of the Pro-Gly-Pro-Leu peptide into animals for 7 days inhibited development of diabetes symptoms in rats pretreated with alloxan.     

Morphogenetic bases and parametric system of trichome evolution in plants of the genus <Emphasis Type="Italic">Draba</Emphasis> L.

Using quantitative morphological analysis of light microscopy data, the normal variation of trichome morphogenesis is studied in six whitlow grass species (Draba L.) and the morphological variation of adult trichomes in 11 species. The evolution consists in the transition from a radial morphogenesis pattern to bilateral and replacement of complex (branched) trichome rays with simple (unbranched) rays. A parametric system is constructed for classification of the ray morphology; this system includes two parameters—the ratio of the numbers of complex to simple rays, characterizing the probability of secondary branching of primary buds, and the number of primary buds, characterizing the probability of primary branching on the surface of the trichome cell. In this parametric space, all of the studied species fit well a third-order curve consisting of two ascending branches displaying a positive correlation between the primary and secondary branchings and a descending branch, located between them, where the primary and secondary branches are negatively correlated. The deduced evolutionary direction is almost independent of the size of the trichome cells and is explained exclusively by the mechanics of morphogenesis: acceleration in the development of the primary bud of the ray decreases the probability of its own branching and creates additional elastic extension of the cell surface, preventing other buds from branching. The morphogenesis itself appears to be a mechanically nonholonomic system, filtering in a selective manner the fluctuations of the same sign, which explains the directed pattern of its evolution. In the evolutionarily initial state, trichome ontogenesis is absent because its modules (primary buds) are formed by a mirror duplication. The ontogenesis commences when mirror symmetry in the formation of modules is lost and replaced with an axial pattern; thus, the change in the morphological type of buds is a direct consequence of the emergence of ontogenesis and its further evolution. Its main material is intraindividual variation, the only source of which is the mechanics of morphogenesis itself. It is found that morphological evolution can take place at an initially zero heritability and zero adaptive value of morphological differences.     

Effect of lectins from <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> to peroxidase and oxalate oxidase activity regulation in wheat roots

Lectins were extracted from the surface of nitrogen-fixing soil bacteria Azospirillum brasilense Sp7 and from its mutant A. brasilense Sp7.2.3 defective in lectin activity. The ability of lectins to stimulate the rapid formation of hydrogen peroxide related to increase of oxalate oxidase and peroxidase activity in the roots of wheat seedlings has been demonstrated. The most rapid induced pathway of hydrogen peroxide formation in the roots of wheat seedlings was the oxalic acid oxidation by oxalate oxidase which is the effect of lectin in under 10 min in a concentration of 10 μg/ml. The obtained results show that lectins from Azospirillum are capable of inducing the adaptation processes in the roots of wheat seedlings.