Mechanisms of changes in human hemodynamics under the conditions of microgravity and prognosis of postflight orthostatic stability

The mechanisms of hemodynamic responses to orthostatic stresses and orthostatic stability (OS) of cosmonauts were studied before and after short-and long-term spaceflights (SFs) using orthostatic tests, as well as before, during, and after SFs using ultrasonic methods in tests with exposure to lower body negative pressure (LBNP). The capacitance and distensibility of the veins of the lower extremities were studied using occlusive air plethysmography before, during, and after SFs of different durations. A stay in microgravity has been proved to result in detraining of, mainly, the vascular mechanisms of compensating orthostatic perturbations. It has been established that the decrease in OS under the influence of microgravity is determined by a reduction of the vasoconstrictive ability of large blood vessels of the lower extremities; an increase in venous distensibility and capacitance of the legs; and an impairment of blood flow regulation, which leads to a cerebral blood flow deficit in orthostatic stresses, and of the initial individual OS before the flight. The results of preflight studies of hemodynamics by ultrasonic methods at LBNP and the data of orthostatic tests before SFs make it possible to predict the degree of decrease of OS after an SF proceeding in the normal mode. At the same time, the data of ultrasonic blood flow examination provide more a accurate estimation of OS and make it possible to assess the physiological reserves of hemodynamic regulation and to reveal the loss of regulation capacity even in cases where integrated indices (heart rate and blood pressure) are within the normal ranges.     

Alpine SteinadlerAquila chrysaetos durch Bleivergiftung gef?hrdet?

In 1990 and 1994, two males of Golden Eagles were found with small lead particles in their stomachs. Both individuals died soon after they had been taken sitting on the soil in bad condition. There are some findings of dead eagles in the same area which showed no sign of having been injured. The two cases of presumed lead poisoning coincide with intense efforts to reduce the number of ChamoixRupicapra rupicapra by hunting. The bullets used contain a nucleus of lead and eagles were seen taking the entrails of the shot chamoix.     

Synaptonemal complexes and meiosis in myxomycetes

Synaptonemal complexes (SC) have been observed in spores 18–24 hr past cleavage in natural fruitings of Physarum cinereum, P. bogoriense, Hemitrichia stipitata, Tubifera ferruginosa, and Arcyria incarnata. Laboratory fruitings of Arcyria cinerea, Stemonitis herbatica, and a homothallic isolate of Physarum pusillum also have SC's present in spores during the same postcleavage period. The presence of these paired chromosomes of meiotic prophase in spores of species collected in nature and in a diversity of taxa suggests that the usual position of meiosis in Myxomycetes is inside the postcleavage spore. Criteria are proposed for evaluating the validity of the SC as an indicator of meiosis.     

Community persistence in Broadstone Stream (U.K.) over three decades

1. Few detailed long-term data sets exist for fresh waters with which to examine large-scale temporal changes in community composition. Consequently, insight into community persistence has been restricted to a few, contingent case studies. We collated and analysed data for the aquatic macroinvertebrate community of Broadstone Stream in south-east England, spanning three decades. The pH of this naturally acid stream has risen progressively since the 1970s, and we sought to examine the potential effects of this environmental change upon the community.
2. Persistence within Broadstone was high when compared with other systems that have been analysed using similar methods. The stream was characterised by a `core' community of eight taxa that were always present, and contributed 75–97% of total invertebrate abundance, with a trailing limb of progressively rarer and more acid-sensitive taxa. There was little species turnover, although the time-series exceeded 20 generations for most species.
3. Despite this high persistence, a long-term response to rising pH was detected: species indicating profound acidity (identified a priori from independent studies) have declined since the 1970s, whereas indicators of moderate acidity increased. The structure of the community food web has also changed since the 1970s, with increased predator diversity and abundance, and a lengthening of food chains following the invasion of a new top predator.
4. These changes in the community appeared to be driven by an interaction between pH and climate. The unusually hot, dry summers characteristic of the 1990s may have raised pH during the more sensitive (i.e. early) stages of the life-cycle, and thus provided a window of opportunity for less acid-tolerant taxa to colonise and become established. Changes in pH appeared to set the boundaries of the available local species pool, within which biotic interactions ultimately shaped the community.     

Molecular Mechanisms of Translation Initiation in Mammals Studied by in vitroReconstruction of Initiation Complexes

Papers on the mechanisms of translation initiation in mammals studied by reconstruction of initiation complexes from individual components are reviewed. The author points to the constraints of this approach and to the pitfalls ignoring which one might come to erroneous conclusions and even artifacts. In addition, some methods employed in the field as well as some technical problems are discussed in the paper, together with the means of obviating them. The review could be a guidebook for newcomers into this quite labor-consuming field.     

Systematic analysis of the long-chain components of Eubacterium lentum

The cellular long-chain component patterns of 33 strains of Eubacterium lentum were determined by gas chromatography. Two main types of long-chain component patterns were distinguished. The first (26 strains) was characterized by saturated branched-chain fatty acids (br14:0, br15:0, br16:0 and br17:0). The second (7 strains) did not contain branched-chain fatty acids and was characterized by saturated straight-chain fatty acids (11:0, 12:0, 14:0 and 16:0). Both types contained fatty aldehydes and their respective dimethyl acetals (14ald and 14dma, 16ald and 16dma). br16dma was only found in the first type. The G + C content of the DNA (Tm) of the 33 strains varied between 63.7 and 69.1 mol %. Canonical correlation analysis distinguished three subtypes within the first main type.