Adrenergic and cholinergic components of the innervation of the arteries of the base of the bird brain

By means of Falck's and Koelle's methods adrenergic and cholinergic structures were studied in the arteries in the cerebral basis of blue rock pigeons and of hens, white leghorn stock. The number of nerve transmitters was estimated per 1 mm2 of the vessel surface. The arteries of the basis in pigeon brain are surrounded with developed adrenergic and cholinergic nerve plexuses, their density decreasing in the following order: nasal branch of the internal carotid artery, middle, nasal cerebral and basilar arteries. A little more cholinergic transmitters occur on the middle cerebral artery, while on the other vessels, concentration of cholinergic and adrenergic fibers is equal. In hens, the density in the arrangement of adrenergic nerve transmitters is higher in the nasal branch of the internal carotid and in the nasal cerebral arteries than in the basilar artery. At the same time, chromaffin cells forming numerous conglomerations in some places are found on the latter. In pigeons, the density of adrenergic fibers arrangement on the arteries of the cerebral basis is higher than in hens.     

Rapid simulation and analysis of isotopomer distributions using constraints based on enzyme mechanisms: an example from HT29 cancer cells

MOTIVATION: Addition of labeled substrates and the measurement of the subsequent distribution of the labels in isotopomers in reaction networks provide a unique method for assessing metabolic fluxes in whole cells. However, owing to insufficiency of information, attempts to quantify the fluxes often yield multiple possible sets of solutions that are consistent with a given experimental pattern of isotopomers. In the study of the pentose phosphate pathways, the need to consider isotope exchange reactions of transketolase (TK) and transaldolase (TA) (which in past analyses have often been ignored) magnifies this problem; but accounting for the interrelation between the fluxes known from biochemical studies and kinetic modeling solves it. The mathematical relationships between kinetic and equilibrium constants restrict the domain of estimated fluxes to the ones compatible not only with a given set of experimental data, but also with other biochemical information. METHOD: We present software that integrates kinetic modeling with isotopomer distribution analysis. It solves the ordinary differential equations for total concentrations (accounting for the kinetic mechanisms) as well as for all isotopomers in glycolysis and the pentose phosphate pathway (PPP). In the PPP the fluxes created in the TK and TA reactions are expressed through unitary rate constants. The algorithms that account for all the kinetic and equilbrium constant constraints are integrated with the previously developed algorithms, which have been further optimized. The most time-consuming calculations were programmed directly in assembly language; this gave an order of magnitude decrease in the computation time, thus allowing analysis of more complex systems. The software was developed as C-code linked to a program written in Mathematica (Wolfram Research, Champaign, IL), and also as a C++ program independent from Mathematica. RESULTS: Implementing constraints imposed by kinetic and equilibrium constants in the isotopomer distribution analysis in the data from the cancer cells eliminated estimates of fluxes that were inconsistent with the kinetic mechanisms of TK and TA. Fluxes measured experimentally in cells can be used to estimate better the kinetics of TK and TA as they operate in situ. Thus, our approach of integrating various methods for in situ flux analysis opens up the possibility of designing new types of experiments to probe metabolic interrelationships, including the incorporation of additional biochemical information. AVAILABILITY: Software is available freely at: http://www.bq.ub.es/bioqint/selivanov.htm CONTACT: martacascante@ub.edu     

Nucleotide-gated KATP channels integrated with creatine and adenylate kinases: Amplification,tuning and sensing of energetic signals in the compartmentalized cellular environment

Transmission of energetic signals to membrane sensors, such as the ATP-sensitive K+ (KATP) channel, is vital for cellular adaptation to stress. Yet, cell compartmentation implies diffusional hindrances that hamper direct reception of cytosolic energetic signals. With high intracellular ATP levels, KATP channels may sense not bulk cytosolic, but rather local submembrane nucleotide concentrations set by membrane ATPases and phosphotransfer enzymes. Here, we analyzed the role of adenylate kinase and creatine kinase phosphotransfer reactions in energetic signal transmission over the strong diffusional barrier in the submembrane compartment, and translation of such signals into a nucleotide response detectable by KATP channels. Facilitated diffusion provided by creatine kinase and adenylate kinase phosphotransfer dissipated nucleotide gradients imposed by membrane ATPases, and shunted diffusional restrictions. Energetic signals, simulated as deviation of bulk ATP from its basal level, were amplified into an augmented nucleotide response in the submembrane space due to failure under stress of creatine kinase to facilitate nucleotide diffusion. Tuning of creatine kinase-dependent amplification of the nucleotide response was provided by adenylate kinase capable of adjusting the ATP/ADP ratio in the submembrane compartment securing adequate KATP channel response in accord with cellular metabolic demand. Thus, complementation between creatine kinase and adenylate kinase systems, here predicted by modeling and further supported experimentally, provides a mechanistic basis for metabolic sensor function governed by alterations in intracellular phosphotransfer fluxes.     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Transgenic sorghum with improved digestibility of storage proteins obtained by <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation

Development of transgenic plants with modified seed storage protein composition and increased nutritive value is one of the most promising areas of genetic engineering. This task is especially important for sorghum—a unique drought tolerant cereal crop that is characterized, however, by a relatively poor nutritive value in comparison with other cereals. It is considered that one of the reasons of the low nutritive value of the sorghum grain is the resistance of one of its seed storage proteins, γ-kafirin, located in the outer layer of endosperm protein bodies, to protease digestion. Using Agrobacterium-mediated genetic transformation, we obtained transgenic sorghum plants (Sorghum bicolor (L.) Moench) harboring a genetic construct for RNAi silencing of the γ-kafirin gene. In the T₁ generation, the plants with almost floury or modified endosperm texture of kernels were found. In these kernels, the vitreous endosperm layer has been reduced and/or covered by a thin layer of floury endosperm. In vitro protein digestibility (IVPD) analysis showed that the amount of undigested protein in transgenic plants from the T₃ generation was reduced by 2.9–3.2 times, in comparison with the original non-transgenic line, and the digestibility index reached 85–88% (in comparison with 59% in the original line). In T₂ families, the plants combining high IVPD with vitreous endosperm type were found. In the electrophoretic spectra of endosperm proteins of transgenic plants with increased digestibility, the proportion of 20 kD protein that is encoded by the γ-kafirin gene, was significantly reduced, in comparison with the original non-transgenic line. HPLC analysis showed total amino acid content in two out of the three studied transgenic plants from the T₂ generation was reduced in comparison with the original non-transgenic line, while the lysine proportion increased by 1.6–1.7 times. The mechanisms conditioning improved digestibility of storage proteins in transgenic plants are discussed. The results of experiments demonstrate that it is feasible to develop sorghum lines combining high protein digestibility and vitreous endosperm that has a high breeding value.     

Activities of antioxidant enzymes of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> plants during cold hardening to hypothermia

Changes in activities of the enzymes performing direct antioxidant functions were studied in 7–8-week-old plants Arabidopsis thaliana Heinh (L.) of Columbia (Col-0) ecotype. It was found that 5-day cold hardening at 2°C increased plant cold resistance to the subsequent stronger cooling. Under these conditions, the marked changes occurred in activities of superoxide dismutase and III type (guaiacol) peroxidses but not in that of catalase. The total peroxidase activity exceeded the catalase activity before cold hardening. Therefore, peroxidases are able to decompose more H₂O₂ than catalases and appear to make the dominant contribution to the protection from the cold damage.     

Synthesis,structure, and biological properties of some 8α analogues of steroid estrogens with fluorine in position 2

A total synthesis of 8α analogues of steroid estrogens with fluorine in position 2 was achieved. Structural features of these compounds were studied by the example of 17β-acetoxy-2-fluoro-3-methoxy-8α-estra-1,3,5(10)-triene. It was shown that the 8α analogues of 2-fluorosubstituted steroid estrogens have a low uterotropic activity and retain the osteoprotective and hypocholesterolemic activities.     

Changes in the activity of superoxide dismutase isoforms in the course of low-temperature adaptation in potato plants of wild type and transformed with Δ12-acyl-lipid desaturase gene

We investigated the changes in the total activity of superoxide dismutase (SOD) and the role of its isoforms in hardening potato (Solanum tuberosum L., cv. Desnitsa) plants of wild type and transformed with desA gene of Δ12-acyl-lipid desaturase from Synechocystis sp. PCC 6803. Hydroponically grown 8-week-old plants were exposed for six days to hardening temperature of 5°C. Before chilling, the total SOD activity in the transformed plants was somewhat greater than in the control plants. By the first day of hardening, SOD activity in both potato genotypes rose almost 1.5 times; however, the absolute value of SOD activity was considerably greater in the transformed plants. Subsequently, the total SOD activity in both genotypes decreased and by the end of the 6th day, it almost returned to the initial level. Electrophoretic and inhibitor analyses of potato plants revealed three types of SOD with one isoform of Mn-SOD, four isoforms of Fe-SOD, and two isoforms of Cu/Zn-SOD. In both genotypes, Fe-SOD3 manifested the greatest activity before chilling and in the course of hardening. Such changes in SOD activity corresponded to the rate of generation of superoxide anion radical and elevation of the content of products of peroxide oxidation of lipids (POL). Our data suggest that in the course of hardening of cold-resistant potato plants, the total SOD activity changed mostly due to Fe-SOD3 and to some extent as a result of elevated Cu/Zn-SOD2 activity, which was particularly evident at the beginning of hardening and more pronounced in the transformed plants. We assume that such temporal pattern is related to a greater rate of superoxide anion generation in the transformed plants as compared with control plants.     

Strong coupling of plant and fungal community structure across western Amazonian rainforests

The Amazon basin harbors a diverse ecological community that has a critical role in the maintenance of the biosphere. Although plant and animal communities have received much attention, basic information is lacking for fungal or prokaryotic communities. This is despite the fact that recent ecological studies have suggested a prominent role for interactions with soil fungi in structuring the diversity and abundance of tropical rainforest trees. In this study, we characterize soil fungal communities across three major tropical forest types in the western Amazon basin (terra firme, seasonally flooded and white sand) using 454 pyrosequencing. Using these data, we examine the relationship between fungal diversity and tree species richness, and between fungal community composition and tree species composition, soil environment and spatial proximity. We find that the fungal community in these ecosystems is diverse, with high degrees of spatial variability related to forest type. We also find strong correlations between α- and β-diversity of soil fungi and trees. Both fungal and plant community β-diversity were also correlated with differences in environmental conditions. The correlation between plant and fungal richness was stronger in fungal lineages known for biotrophic strategies (for example, pathogens, mycorrhizas) compared with a lineage known primarily for saprotrophy (yeasts), suggesting that this coupling is, at least in part, due to direct plant–fungal interactions. These data provide a much-needed look at an understudied dimension of the biota in an important ecosystem and supports the hypothesis that fungal communities are involved in the regulation of tropical tree diversity.