Understanding the Mechanisms of Gravity Resistance in Plants.

To understand gravity resistance in plants, it is necessary to analyze the changes induced when the magnitude of gravity in a growth environment is modified. Microgravity in space provides appropriate conditions for analyzing gravity resistance mechanisms. Experiments carried out in space involve a large number of constraints and are quite different from ground-based experiments. Here, we describe basic procedures for space-based experiments to study gravity resistance in plants. An appropriate cultivation chamber must be selected according to the growing period of the plants and the purpose of the experiment. After cultivation, the plant material is fixed with suitable fixatives in appropriate sample storage containers such as the Chemical Fixation Bag. The material is then analyzed with a variety of methods, depending on the purpose of the experiment. Plant material fixed with the RNAlater® solution can be used sequentially to determine the mechanical properties of the cell wall, RNA extraction (which is necessary for gene-expression analysis), estimate the enzyme activity of cell wall proteins, and measure the levels and compositions of cell wall polysaccharides. The plant material can also be used directly for microscopic observation of cellular components such as cortical microtubules.

Hypergravity experiments to evaluate gravity resistance mechanisms in plants.

Hypergravity generated by centrifugal acceleration is the only practical method to modify the magnitude of gravitational acceleration for a sufficient duration on Earth and has been used to analyze the nature and mechanism of graviresponse, particularly gravity resistance, in plants. Plant organs are generally resistant to gravitational acceleration. Hypergravity produced from centrifugation speeds in the range of 10-300 × g, which is easily produced by a benchtop centrifuge, is often used during plant experiments. After centrifugation, the plant material is fixed with suitable fixatives in appropriate sample storage containers such as the Chemical Fixation Bag. The material is then analyzed with a variety of methods, depending on the purpose of the experiment. Plant material fixed with the RNAlater(®) solution can be sequentially used for determining the mechanical properties of the cell wall, for RNA extraction (which is necessary for gene expression analysis), for estimating the enzyme activity of the cell wall proteins, and for determining the levels as well as the compositions of cell wall polysaccharides. The plant material can also be used directly for microscopic observation of cellular components such as cortical microtubules.

Cortical microtubules are responsible for gravity resistance in plants.

Mechanical resistance to the gravitational force is a principal gravity response in plants distinct from gravitropism. In the final step of gravity resistance, plants increase the rigidity of their cell walls. Here we discuss the role of cortical microtubules, which sustain the function of the cell wall, in gravity resistance. Hypocotyls of Arabidopsis tubulin mutants were shorter and thicker than the wild-type, and showed either left-handed or right-handed helical growth at 1 g. The degree of twisting phenotype was intensified under hypergravity conditions. Hypergravity also induces reorientation of cortical microtubules from transverse to longitudinal directions in epidermal cells. In tubulin mutants, the percentage of cells with longitudinal microtubules was high even at 1 g, and it was further increased by hypergravity. The left-handed helical growth mutants had right-handed microtubule arrays, whereas the right-handed mutant had left-handed arrays. Moreover, blockers of mechanoreceptors suppressed both the twisting phenotype and reorientation of microtubules in tubulin mutants. These results support the hypothesis that cortical microtubules play an essential role in maintenance of normal growth phenotype against the gravitational force, and suggest that mechanoreceptors are involved in signal perception in gravity resistance. Space experiments will confirm whether this view is applicable to plant resistance to 1 g gravity, as to the resistance to hypergravity.

[Anesthetic management for robot assisted off-pump construction of composite graft using the da Vinci surgical system].

Robot-assisted minimally invasive surgery has become common in recent years. We used the da Vinci surgical system and managed anesthesia in 6 cases of bilateral internal mammary artery dissection and construction of a composite graft using the radial artery. To ensure vision inside the thoracic cavity, endoscopic robotic surgery employs the inflation of the thoracic cavity with carbon dioxide, producing a pneumothorax and turning the thoracic cavity into a positive pressure chamber. Thus, marked acidosis and circulatory changes manifest during anesthetic management. Although robotic surgery is considered "minimally invasive, such surgery involves a number of problems in terms of anesthetic management, and these problems must be examined.

Gravity-induced modifications to development in hypocotyls of Arabidopsis tubulin mutants.

We investigated the roles of cortical microtubules in gravity-induced modifications to the development of stem organs by analyzing morphology and orientation of cortical microtubule arrays in hypocotyls of Arabidopsis (Arabidopsis thaliana) tubulin mutants, tua3(D205N), tua4(S178Delta), and tua6(A281T), cultivated under 1g and hypergravity (300g) conditions. Hypocotyls of tubulin mutants were shorter and thicker than the wild type even at 1g, and hypergravity further suppressed elongation and stimulated expansion. The degree of such changes was clearly smaller in tubulin mutants, in particular in tua6. Hypocotyls of tubulin mutants also showed either left-handed or right-handed helical growth at 1g, and the degree of twisting phenotype was intensified under hypergravity conditions, especially in tua6. Hypergravity induced reorientation of cortical microtubules from transverse to longitudinal directions in epidermal cells of wild-type hypocotyls. In tubulin mutants, especially in tua6, the percentage of cells with longitudinal microtubules was high even at 1g, and it was further increased by hypergravity. The twisting phenotype was most obvious at cells 10 to 12 from the top, where reorientation of cortical microtubules from transverse to longitudinal directions occurred. Moreover, the left-handed helical growth mutants (tua3 and tua4) had right-handed microtubule arrays, whereas the right-handed mutant (tua6) had left-handed arrays. There was a close correlation between the alignment angle of epidermal cell files and the alignment of cortical microtubules. Gadolinium ions, blockers of mechanosensitive ion channels (mechanoreceptors), suppressed the twisting phenotype in tubulin mutants under both 1g and 300 g conditions. Microtubule arrays in tubulin mutants were oriented more transversely by gadolinium treatment, irrespective of gravity conditions. These results support the hypothesis that cortical microtubules play an essential role in maintenance of normal growth phenotype against the gravitational force, and suggest that mechanoreceptors are involved in modifications to morphology and orientation of microtubule arrays by 1g gravity and hypergravity in tubulin mutants.

Cerebrospinal fluid analysis in children with seizures from respiratory syncytial virus infection.

We report 3 cases of respiratory syncytial virus infection-associated seizures; their abnormalities of cerebrospinal fluid (increased interleukin-6 and positive for virus by highly sensitive assay) were documented. These data revealed that neurological involvement might be caused by a direct invasion.

[Effects of intravenous anesthetics on acidosis induced apoptosis in primary brain cell culture].

BACKGROUND: We have reported protective effects of intravenous anesthetics on the brain cell. This study examined the effects of extracellular Ca2+ on acidosis-induced apoptosis and the protective effects of intravenous anesthetics on such appearance of apoptosis. METHODS: Using the primary culture of rat cerebellular granule cells, extracellular acidosis was produced at pH 6.7 and pH 6.3 and the extracellular Ca2+ free condition was produced by 1 mM EGTA instead of 1.2 mM CaCl2. The cell death was determined by the calcein method and the measurement of apoptosis was done using the screening kit for apoptosis with TUNEL method. Bcl-2 mRNA was detected using quantified RT-PCR method. Midazolam, pentobarbital and propofol were used as typical intravenous anesthetics. RESULTS: Under extracellular acidosis, the significant cell death was detected 6 hr after exposure to acidosis. Moreover, in case of extracellular Ca2+ free/acidosis condition, there was a greater incidence of cell death. Such cell death was much enhanced 20 hr after exposure to acidosis. Furthermore, in case of extracellular acidosis and Ca2+ free condition, there were a significant increase of apoptosis and significant changes of bcl-2. By treatment with intravenous anesthetics, the significant inhibition of cell death and appearance of apoptosis were observed. In these protections by intravenous anesthetics, midazolam and pentobarbital significantly increased the bcl-2 levels. CONCLUSIONS: We demonstrated that intracellular Ca2+ modulates the appearance of apoptosis under acidosis. Moreover it seems that the inhibitory effects of midazolam and pentobarbital on acidosis-induced apoptosis are different from that of propofol.