Three-dimensional gas exchange pathways in pome fruit characterized by synchrotron x-ray computed tomography

Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-microm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 microm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit.     

越南苦苣苔科石蝴蝶属植物随记暨国家级分布新记录

石蝴蝶属(Petrocosmea Oliv.)植物的现代分布与分化中心位于中国的西南山地以及周边国家和地区,如印度(阿萨姆邦)、缅甸、泰国、越南等也有分布。近年来,中国和中南半岛上各个国家和地区的新分类群和国家级新记录层出不穷,进一步加深了研究人员对中国和中南半岛植物区系以及该属植物在上述区域的多样性的理解。例如,滇黔石蝴蝶[Petrocosmea martinii (H. Léveillé)H. Léveillé]和丝毛石蝴蝶(P. sericea C.Y. Wu ex H. W. Li)曾被认为是中国的特有种,前者分布于贵州、广西北部和云南东南部,而后者仅见于云南东南部。该文报道了这两种石蝴蝶属植物的越南国家级分布新记录。这两个新记录种的发现,使得越南分布的石蝴蝶属植物种的数量上升到了5 种,这些新记录种的报道或暗示未来在与中国西南山地邻近的地区还将会有更多该属的新分类群或新记录有待发现。该文还同时提供了这两个国家级分布新记录物种的描述、图示、濒危等级现状评价以及目前所有越南已知分布的石蝴蝶属植物的检索表以备检索和核对。     

Peridinin-Chlorophyll a-Protein Is not Implicated in the Photosynthesis Rhythm of the Dinoflagellate Gonyaulax despite Circadian Regulation of its Translation

The levels of peridinin-chlorophyll a -protein (PCP) mRNA, apoprotein and protein bound with peridinin (holoprotein) were measured as a function of circadian time in the dinoflagellate Gonyaulax polyedra to test involvement of this protein in the circadian oxygen evolution rhythm. This involvement was suggested by previous work showing that synthesis of PCP was rhythmic in vivo and in phase with the three-fold rhythm of oxygen evolution. However, Gonyaulax contains six PCP isoforms, only one of which was previously examined. In this report, we extend our analysis to two additional isoforms to encompass roughly 90% of the total cellular PCP. We confirm that synthesis of two additional PCP isoforms is rhythmic in vivo and show that this regulation appears to occur at a translational level as found for two other regulated proteins in this organism. However, PCP is unlikely to be implicated in the oxygen evolution rhythm since both PCP protein levels and the amount of chromophore (OD⁴⁸⁰) bound to protein (OD²⁸⁰) are constant over a circadian period.     

Analyzing surface EMG signals to determine relationship between jaw imbalance and arm strength loss

ABSTRACT: BACKGROUND: This study investigated the relationship between dental occlusion and arm strength; in particular, the imbalance in the jaw can cause loss in arm strength phenomenon. One of the goals of this study was to record the maximum forces that the subjects can resist against the pull-down force on their hands while biting a spacer of adjustable height on the right or left side of the jaw. Then EMG measurement was used to determine the EMG-Force relationship of the jaw, neck and arms muscles. This gave us useful insights on the arms strength loss due to the biomechanical effects of the imbalance in the jaw mechanism. METHODS: In this study to determine the effects of the imbalance in the jaw to the strength of the arms, we conducted experiments with a pool of 20 healthy subjects of both genders. The subjects were asked to resist a pull down force applied on the contralateral arm while biting on a firm spacer using one side of the jaw. Four different muscles -- masseter muscles, deltoid muscles, bicep muscles and trapezoid muscles -- were involved. Integrated EMG (iEMG) and Higuchi fractal dimension (HFD) were used to analyze the EMG signals. RESULTS: The results showed that (1) Imbalance in the jaw causes loss of arm strength contra-laterally; (2) The loss is approximately a linear function of the height of the spacers. Moreover, the iEMG showed the intensity of muscle activities decreased when the degrees of jaw imbalance increased (spacer thickness increased). In addition, the tendency of Higuchi fractal dimension decreased for all muscles. CONCLUSIONS: This finding indicates that muscle fatigue and the decrease in muscle contraction level leads to the loss of arm strength.     

Rapidly diminishing mangrove forests in Myanmar (Burma): a review

IPCC predictions indicate an increase in temperatures by 1.5–7°C in some Amazonian regions during the twenty-first century. These changes could disrupt the present distribution patterns of organisms, including wetland plant species. In this work, we determined in microcosms the effects of scenarios combining elevated temperature and atmospheric CO₂ concentration on the germination and initial growth of the arborescent Amazonian aquatic macrophyte Montrichardia arborescens. Seeds were germinated, and seedlings produced were monitored over a 5-month period in four microcosms: Control: ambient temperature and CO₂ level; Mild: Control + 1.5°C and + 200 ppm CO₂; intermediate: control + 2.5°C and + 400 ppm CO₂; Extreme: Control + 4.5°C and + 850 ppm of CO₂. Rapid light response curves and Fv/Fm values taken in seedlings showed a decrease in electron transportation rate with CO₂ and temperature elevation. Mild and Intermediate treatments stimulated biomass production; Extreme treatment and Control produced similar results. The severe climatic changes expected in the future may negatively influence carbon accumulation in M. arborescens. Since aquatic macrophytes in Amazonian wetlands and wetlands worldwide are key plant species, further studies are needed to predict their fate in a global change perspective.     

Silvorchis vietnamica (Orchidaceae,Orchidoideae, Vietorchidinae), a new miniature mycotrophic species from southern Vietnam

A second species of Silvorchis, until now considered to be a presumably extinct monotypic genus endemic to western Java has been discovered in southern Vietnam. The species, here named as S. vietnamica, is described and illustrated, with data on its distribution, ecology, phenology and estimated conservation status. A key for identification of the two known species of the genus is also provided. The taxonomic affinities and phylogenetic placement of the newly discovered plant are briefly discussed.     

A Balance between Nuclear and Cytoplasmic Volumes Controls Spindle Length

Proper assembly of the spindle apparatus is crucially important for faithful chromosome segregation during anaphase. Thanks to the effort over the last decades, we have very detailed information about many events leading to spindle assembly and chromosome segregation, however we still do not understand certain aspects, including, for example, spindle length control. When tight regulation of spindle size is lost, chromosome segregation errors emerge. Currently, there are several hypotheses trying to explain the molecular mechanism of spindle length control. The number of kinetochores, activity of molecular rulers, intracellular gradients, cell size, limiting spindle components, and the balance of the spindle forces seem to contribute to spindle size regulation, however some of these mechanisms are likely specific to a particular cell type. In search for a general regulatory mechanism, in our study we focused on the role of cell size and nuclear to cytoplasmic ratio in this process. To this end, we used relatively large cells isolated from 2-cell mouse embryos. Our results showed that the spindle size upper limit is not reached in these cells and suggest that accurate control of spindle length requires balanced ratio between nuclear and cytoplasmic volumes.     

Gas chromatography profile of estrogens: Application to pregnancy urine

A method for the simultaneous quantitation of 7 estrogens in pregnancy urine is described. It involves enzymatic hydrolysis, extraction of free steroids, ion-exchange column chromatography and quantitation of the trimethylsilyl derivatives by gas chromatography on OV 1. Data obtained from normal and twin pregnancies and from women with anencephalic fetus or intra uterine fetal death are analysed. The sensibility of the method is about 40 μg of each estrogen by liter of urine.