Beta-adrenergic inhibition of cardiac sodium channels by dual G-protein pathways

The signaling pathways by which beta-adrenergic agonists modulate voltage-dependent cardiac sodium currents are unknown, although it is likely that adenosine 3'5'-monophosphate (cAMP) is involved. Single-channel and whole-cell sodium currents were measured in cardiac myocytes and the signal transducing G protein Gs was found to couple beta-adrenergic receptors to sodium channels by both cytoplasmic (indirect) and membrane-delimited (direct) pathways. Hence, Gs can act on at least three effectors in the heart: sodium channels, calcium channels, and adenylyl cyclase. The effect on sodium currents was inhibitory and was enhanced by membrane depolarization. During myocardial ischemia the sodium currents of depolarized cells may be further inhibited by the accompanying increase in catecholamine levels.     

Saturn's gravitational field, internal rotation, and interior structure

Saturn's internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft's gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and 35 +/- 13 seconds. This more rapid spin implies slower equatorial wind speeds on Saturn than previously assumed, and the winds at higher latitudes flow both east and west, as on Jupiter. Our related Saturn interior model has a molecular-to-metallic hydrogen transition about halfway to the planet's center.     

Polyacetylenes from the Apiaceae vegetables carrot, celery, fennel, parsley, and parsnip and their cytotoxic activities

A dichloromethane extract of root celery yielded falcarinol, falcarindiol, panaxydiol, and the new polyacetylene 8-O-methylfalcarindiol. The structure of the new compound was established by one- and two-dimensional (1D and 2D) NMR, mass spectrometry, and optical rotation data. Nonpolar extracts of roots and bulbs of carrots, celery, fennel, parsley, and parsnip were investigated for their content of polyacetylenes by high-performance liquid chromatography with diode array detection (HPLC-DAD). All five species contained polyacetylenes, although carrots and fennel only in minor amounts. Additionally, the cytotoxicity of the four polyacetylenes against five different cell lines was evaluated by the annexin V-PI assay. Falcarinol proved to be the most active compound with a pronounced toxicity against acute lymphoblastic leukemia cell line CEM-C7H2, with an IC(50) of 3.5 micromol/L. The possible chemopreventive impact of the presented findings is discussed briefly.     

Consequences of sodium exclusion for the osmotic potential in the rhizosphere – Comparison of two maize cultivars differing in Na+ uptake

According to the biphasic model of growth response to salinity, growth is first reduced by a decrease in the soil osmotic potential (Ψ_o), i.e., growth reduction is an effect of salt outside rather than inside the plant, and genotypes differing in salt resistance respond identically in this first phase. However, if genotypes differ in Na⁺ uptake as it has been described for the two maize cultivars Pioneer 3906 and Across 8023, this should result in differences in Na⁺ concentrations in the rhizosphere soil solution and thus in the concentration of salt outside the plant. It was the aim of the present investigation to test this hypothesis and to investigate the effect of such potential differences in soil Ψ_o caused by Na⁺ exclusion on plant water relations. Sodium exclusion at the root surface of intact plants growing in soil was investigated by sampling soil solution from the rhizosphere of two maize cultivars (Across 8023, Pioneer 3906). Plants were grown in a model system, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). Across 8023 accumulated higher amounts of sodium in the shoot compared to the excluder (Pioneer 3906). The lower Na⁺ uptake in the excluder was partly compensated by higher K⁺ uptake. Pioneer 3906 not only excluded sodium from the shoot but also restricted sodium uptake more efficiently from roots relative to Across 8023. This was reflected by higher Na⁺ concentrations in the rhizosphere soil solution of the excluder 34 days after planting (DAP). The difference in Na⁺ concentration in rhizosphere soil solution between cultivars was neither due to differences in transpiration and thus in mass flow, nor due to differences in actual soil water content. As the lower Na⁺ uptake of the excluder (Pioneer 3906) was only partly compensated by increased uptake of K⁺, soil Ψ_o in the rhizosphere of the excluder was more negative compared to Across 8023. However, no significant negative effect of decreased soil Ψ_o on plant water relations (transpiration rate, leaf Ψ_o, leaf water potential, leaf area) could be detected. This may be explained by the fact that significant differences in soil Ψ_o between the two cultivars occurred only towards the end of the experiment (27 DAP, 34 DAP).     

Differential staining of mitotic chromosomes from inbred lines and hybrids ofZea mays L.

Summary The Giemsa banding patterns of four inbred lines (DB1113, DB1116, WIR44 and WIR27) ofZea mays and their hybrids have been compared. The polymorphism of knob heterochromatin of 4 chromosome pairs allowed to distinguish the 4 inbred lines on the basis of their banding patterns, reflected the evolutionary distance of the inbred lines and provided evidence as to the origin of these chromosomes in hybrids.Sister chromatid differentiation by means of BrdUrd incorporation prior to fluorescence plus Giemsa(FPG)-technique revealed 3.7 SCEs per cell for the hybrid BEKOS 251. Individualization of chromosomes on the basis of their replication patterns or asymmetric bands after application of the same technique was impossible.

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Differentialfärbung mitotischer Chromosomen von Inzuchtlinien und deren Hybriden beiZea mays L.

Zusammenfassung Die Giemsabandenmuster der vier Inzuchtlinien des Maises DB1113, DB1116 (convar.vulgaris) und WIR27, WIR44 (convar.dentiformis) sowie der daraus entstandenen Hybriden SU 10, Kappa und BEKOS 251 wurden untereinander verglichen. Polymorphismen des Knob-Heterochromatins auf vier Chromosomenpaaren (I, VI, VII, VIII) erlaubten die Unterscheidung der vier Inzuchtlinien anhand ihrer Bandenmuster, widerspiegelten den jeweiligen Verwandtschaftsgrad zwischen den Inzuchtlinien und ermöglichten für einige Chromosomen der Hybriden den Herkunftsnachweis.Schwesterchromatidendifferenzierung nach BrdUrd-Einbau und FPG-Färbung ergaben für die Doppelhybride BEKOS 251 3.7 SCEs/Zelle. Die Erfassung von Replikationsmustern oder asymmetrischen Banden zur Charakterisierung individueller Chromosomen war mit dieser Methode nicht möglich.

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Zea mays L.

, , DB1113, DB1116 (convar.vulgaris) WIR27, WIR44 (convar.dentiformis), SU 10, Kappa BEKOS 251. - (I, VI, VII, VIII) , . BrdUrd FPG BEKOS 251 3,7 . .

     

Genetic diversity and cytogenetic analyses in <Emphasis Type="Italic">Curcuma zedoaria</Emphasis> (Christm.) Roscoe from Bangladesh

Curcuma zedoaria populations comprise 2n = 63 chromosomes with three satellite chromosomes showing elongated secondary constrictions. Flow cytometry results inferred that the 2C nuclear DNA values varied between the populations. The largest genome size was found in the population Chittagong (mean 3.37 pg) and the lowest in the Birganj population (mean 3.15 pg). RAPD based estimations of genetic diversity revealed that hilly populations maintain higher genetic diversity, which was also found to be distinct from plainland and plateauland populations. Genome sizes and genetic diversity values of the populations were positively correlated.     

奶牛隐性乳房炎的研究进展

奶牛乳房炎是奶牛常见、多发的疾病之一,严重制约着奶牛养殖业的发展,文章对奶牛乳房炎的病因、发病机理、临床症状、诊断方法及防治措施等进行了综述,这将对内蒙古自治区奶牛养殖业的发展产生积极影响.