Mitochondrial matrix granules in soft tissues : I. Elemental composition by X-ray microanalysis

The elemental composition of individual matrix granules in mitochondria of rat brown fat, mouse gall bladder and guinea pig kidney has been examined by X-ray microanalysis. The matrix granules showed a similar elemental composition that was strongly dependent upon the method of sample preparation. Low-temperature oxygen plasma microincineration or wavelength-dispersive X-ray spectrometers were used to demonstrate the presence of phosphorus in matrix granules of osmium tetroxide-fixed specimens. Matrix granule osmiophilia was retained in glutaraldehyde-fixed brown fat only if exposure to polar organic solvents was avoided during subsequent steps, e.g. by cryosectioning. As normally prepared, matrix granules lack detectable calcium but had bound this at detectable levels after fixation in osmium tetroxide, but not glutaraldehyde, supplemented with 5 mM Ca²⁺. The results demonstrate that mitochondrial matrix granules of normal soft tissues are not calcium phosphate deposits and contain phospholipids, apparently as a major constituent. Thus they provide evidence against the hypothesis that matrix granules are primarily involved in mitochondrial calcium sequestration and, indirectly, for the hypothesis that the granules may be related to inner membrane assembly.     

Partitioning of carbohydrates and biomass of needles in Scots pine canopy

The study was aimed at the quantitative evaluation of the temporal and spatial partitioning of non-structural carbohydrates and needle biomass in a canopy of Scots pine (Pinus sylvestris L.) growing in a Myrtillus site type forest stand (predominant in Estonia). The tree canopy was divided into ten equal layers and the material for the spatial partitioning of the investigated characteristics was sampled from all layers. Our findings revealed a significant variation in morphology and in the partitioning of carbohydrates in needles in different layers of the canopy. The study of the temporal dynamics of carbohydrates showed that starch content in needles started to increase in early spring before budbreak, which was accompanied by a decline in soluble carbohydrates. In October, the starch content of needles was low, but the concentration of soluble sugars started to increase attaining a maximum in winter. Regression analysis indicated that before budbreak, the partitioning of soluble sugars in different canopy layers was relatively weakly correlated with the height of the layer; however, a strong correlation was observed for starch. In autumn, when the growth of trees stopped and daily temperatures decreased, the allocation of soluble sugars was correlated with the height of the canopy layer.     

Description of Crypsiphona tasmanica sp. nov. (Lepidoptera: Geometridae: Geometrinae), with notes on limitations in using DNA barcodes for delimiting species

External morphological differences were found between Tasmanian and mainland Australian specimens of what was previously considered a single species, the Redlined Geometrid, Crypsiphona ocultaria (Donovan). Examination of genitalia showed constant differences, suggesting that Tasmanian and mainland Australian populations represent distinct species. This hypothesis was tested using DNA sequences from the mitochondrial cytochrome oxidase subunit I (COI) gene and nuclear elongation factor 1-alpha (EF-1α) gene. Tasmanian Crypsiphona Meyrick populations were found to represent a distinct species, described here as C. tasmanica sp. nov. The results show that a phylogeny-based approach allows the delimitation of C. ocultaria (Donovan) and C. tasmanica sp. nov., but distance-based delimitation is problematic due to substantial overlap in intra- and interspecific genetic distances. Using nucleotide data in character-based species delimitations might be possible for discriminating between C. ocultaria and C. tasmanica , but our current knowledge does not allow the assignment of characters required for this purpose.     

A Novel Feeder-Free Culture System for Human Pluripotent Stem Cell Culture and Induced Pluripotent Stem Cell Derivation

Correct interactions with extracellular matrix are essential to human pluripotent stem cells (hPSC) to maintain their pluripotent self-renewal capacity during in vitro culture. hPSCs secrete laminin 511/521, one of the most important functional basement membrane components, and they can be maintained on human laminin 511 and 521 in defined culture conditions. However, large-scale production of purified or recombinant laminin 511 and 521 is difficult and expensive. Here we have tested whether a commonly available human choriocarcinoma cell line, JAR, which produces high quantities of laminins, supports the growth of undifferentiated hPSCs. We were able to maintain several human pluripotent stem cell lines on decellularized matrix produced by JAR cells using a defined culture medium. The JAR matrix also supported targeted differentiation of the cells into neuronal and hepatic directions. Importantly, we were able to derive new human induced pluripotent stem cell (hiPSC) lines on JAR matrix and show that adhesion of the early hiPSC colonies to JAR matrix is more efficient than to matrigel. In summary, JAR matrix provides a cost-effective and easy-to-prepare alternative for human pluripotent stem cell culture and differentiation. In addition, this matrix is ideal for the efficient generation of new hiPSC lines.     

Population-level performance of Arabidopsis thaliana (L.) Heynh in dense monocultures

尽管几乎所有的农业物种在育种过程中都经历了从多物种环境向密集单种农田的过渡,但对非农业植物物种在单一栽培条件下的表现知之甚少。鉴于最近的研究成果突出杂草物种拟南芥为作物育种提供新视角的可能性,本研究的目的是了解播种密度对拟南芥在不同光周期环境下群体和个体表现的影响。我们研究了拟南芥Cvi-0生态型的表现。Cvi-0的选择基于一项初步实验,发现Cvi-0生态型植物表现出强烈的竞争性能。播种密度处理设置为每株17.6、8.8、4.4、2.2和1.1 cm²,光周期环境为日照12小时或16小时。结果表明,植物在所有密度处理下均获得了恒定的总种子产量。播种密度和日照时间处理会有一些相互作用：在高播种密度和长日照时间的处理下,种子重量更大,而日照时间短的处理下种子重量与密度呈负相关。这些结果阐明了一年生植物在面对激烈的种内竞争时能够采取不同的策略,并有助于为提高群体表现的作物育种提供新的前景。     

miR669a and miR669q prevent skeletal muscle differentiation in postnatal cardiac progenitors

Postnatal heart stem and progenitor cells are a potential therapeutic tool for cardiomyopathies, but little is known about the mechanisms that control cardiac differentiation. Recent work has highlighted an important role for microribonucleic acids (miRNAs) as regulators of cardiac and skeletal myogenesis. In this paper, we isolated cardiac progenitors from neonatal β-sarcoglycan (Sgcb)-null mouse hearts affected by dilated cardiomyopathy. Unexpectedly, Sgcb-null cardiac progenitors spontaneously differentiated into skeletal muscle fibers both in vitro and when transplanted into regenerating muscles or infarcted hearts. Differentiation potential correlated with the absence of expression of a novel miRNA, miR669q, and with down-regulation of miR669a. Other miRNAs are known to promote myogenesis, but only miR669a and miR669q act upstream of myogenic regulatory factors to prevent myogenesis by directly targeting the MyoD 3' untranslated region. This finding reveals an added level of complexity in the mechanism of the fate choice of mesoderm progenitors and suggests that using endogenous cardiac stem cells therapeutically will require specially tailored procedures for certain genetic diseases.     

Do forest plants conform to the theory of island biogeography: the case study of bog islands

Biodiversity conservation is confronted with increasing risk of extinction in isolated small-area remnants and the limitation of species to colonize recently formed habitats. We hypothesized that the equilibrium pattern of forest herb layer in long-term fragmented landscape should comply with the theory of island biogeography. Forests on mineral soil islands located in large mires of western Estonia were considered as dispersal target habitats, and forests on mainland and peninsulas in mires as sources. Species richness was the lowest in mainland forests and the effect was confounded by habitat structure, suggesting a negative effect of silvicultural management in easily accessible forests. We observed the ‘small island effect’, i.e. greater overall species richness in small-area habitats, which was determined by the habitat preference of shade tolerant generalists. The average species richness of common mainland forest specialists varied little, but capitalizing on the traditional approach and analyzing only island data, weak effects of distance and habitat quality were detected. At single species level, unexpectedly, many habitat specialists were observed to have successfully dispersed to islands, indicating insufficient knowledge of the long-distance dispersal mechanisms of forest-dwelling plants. In fragmented forest landscapes the theory of island biogeography can be applied to habitat specialist plant species, but only regarding the effect of isolation and in conditions of persistent forest structural quality. In the light of global changes, optimized conservation planning should primarily target on (i) the conservation of ancient habitat fragments independent of their current area, and (ii) the promotion of diversity of potential dispersal vectors in the landscape.     

A Novel Surgical Approach for Intratracheal Administration of Bioactive Agents in a Fetal Mouse Model

Prenatal pulmonary delivery of cells, genes or pharmacologic agents could provide the basis for new therapeutic strategies for a variety of genetic and acquired diseases. Apart from congenital or inherited abnormalities with the requirement for long-term expression of the delivered gene, several non-inherited perinatal conditions, where short-term gene expression or pharmacological intervention is sufficient to achieve therapeutic effects, are considered as potential future indications for this kind of approach. Candidate diseases for the application of short-term prenatal therapy could be the transient neonatal deficiency of surfactant protein B causing neonatal respiratory distress syndrome^1,2 or hyperoxic injuries of the neonatal lung³. Candidate diseases for permanent therapeutic correction are Cystic Fibrosis (CF)⁴, genetic variants of surfactant deficiencies⁵ and α1-antitrypsin deficiency⁶.Generally, an important advantage of prenatal gene therapy is the ability to start therapeutic intervention early in development, at or even prior to clinical manifestations in the patient, thus preventing irreparable damage to the individual. In addition, fetal organs have an increased cell proliferation rate as compared to adult organs, which could allow a more efficient gene or stem cell transfer into the fetus. Furthermore, in utero gene delivery is performed when the individual''s immune system is not completely mature. Therefore, transplantation of heterologous cells or supplementation of a non-functional or absent protein with a correct version should not cause immune sensitization to the cell, vector or transgene product, which has recently been proven to be the case with both cellular and genetic therapies⁷.In the present study, we investigated the potential to directly target the fetal trachea in a mouse model. This procedure is in use in larger animal models such as rabbits and sheep⁸, and even in a clinical setting⁹, but has to date not been performed before in a mouse model. When studying the potential of fetal gene therapy for genetic diseases such as CF, the mouse model is very useful as a first proof-of-concept because of the wide availability of different transgenic mouse strains, the well documented embryogenesis and fetal development, less stringent ethical regulations, short gestation and the large litter size.Different access routes have been described to target the fetal rodent lung, including intra-amniotic injection^10-12, (ultrasound-guided) intrapulmonary injection^13,14 and intravenous administration into the yolk sac vessels^15,16 or umbilical vein¹⁷. Our novel surgical procedure enables researchers to inject the agent of choice directly into the fetal mouse trachea which allows for a more efficient delivery to the airways than existing techniques¹⁸.