The effect of various forms of selenium supplied to pregnant goats on the levels of selenium in the body of their kids at the time of weaning.

The aim of this trial was to compare the effect of long-term supplementation of goats with different forms of selenium on body reserves of selenium in their kids at the time of weaning. Thirty-three pregnant goats were divided into five groups. Group C was control while the other four groups were supplemented with selenium (Se) for 6 weeks before parturition (0.3 mg/goat/day) and after parturition (0.9 mg/goat/day). Group "Se-I" received sodium selenite and three other groups received organic forms: "Se-L," lactate-protein complex; "Se-P," Se-proteinate; and "Se-Y," Se-yeast. The kids were weaned at 3 months of age and samples of tissues (liver, pancreas, myocardium, lungs, kidneys, spleen, thigh, tongue, and diaphragm) were taken after slaughtering. The long-term supplementation of goats with Se influenced Se concentration in all examined tissues of kids. Significant differences (p≤0.01) were found between the control and all experimental groups, except for the renal cortex and pancreas (Se-I). The average increase of Se concentration in overall examined tissues in comparison with the control (100%) was as follows: Se-Y, 192%; Se-P, 167%; Se-L, 161%; Se-I, 144%. The highest efficiency was found in the group supplemented with Se-yeast with a high content of selenomethionine, also the other two organic forms of Se were more efficient than the inorganic form.

Effect of mitogen lectin on lymphocyte or brain cortex cell activation.

OBJECTIVES: We studied a) mitogen lectin (PHA) evoked changes of Na+/K+-ATPase activity in functionally different lymphocytes or brain cortex cells and b) quantitative relationship between PHA- evoked early enzyme activation and late lymphocyte proliferation were analyzed. MATERIALS AND METHODS: We performed biochemical analyses of Pi released from ATP by Na+/K+-ATPase activity. Lymphocyte proliferation was assayed by 3H-thymidine incorporation. RESULTS: We demonstrated PHA stimulated Na+/K+-ATPase activity of mouse spleen lymphocytes or freshly isolated brain cortex cells. Besides this, we estimated high stimulation of Na+/K+-ATPase activity and subsequent late 3H-thymidine incorporation into pig lymphocytes as both PHA dose and K+ ion concentration dependent. CONCLUSIONS: Thus, early PHA dose-dependent stimulation of Na+/K+-ATPase activity is a more general response in different animal species and functionally different cells. We measured both cell type- and PHA-dose dependent enzyme activity stimulation. We can suggest that intensity of early PHA induced Na+/K+-ATPase activation could be in relationship to subsequent elevated level of T lymphocyte proliferation. The Na+/K+-ATPase can be a part of mitogen lectin evoked signal transduction mechanisms.

Dynamical habitability of planetary systems.

The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries).

Monitoring of changes in selenium concentration in goat milk during short-term supplementation of various forms of selenium.

The goal of the experiment was to monitor the changes in the selenium concentration in goat milk during short-term oral supplementation of three different forms of selenium. The experiment involved 24 lactating goats of white shorthaired breed. Group C was the control; group S received selenium in the form of selenium-enriched yeast, group L in the form of lactate, and group B in the form of proteinate. Individual selenium preparations were administered individually orally in 250 microg Se dose per animal for 20 days. After the beginning of selenium supplementation, the selenium concentration in milk during the first 5 days grew gradually in group S. Between days 7 and 20 of Se supplementation, the mean Se concentrations in milk in groups were 12.53 +/- 3.69 microg l(-1) (C), 25.90 +/- 6.30 microg l(-1) (S), 13.14 +/- 3.54 microg l(-1) (L), 11.70 +/- 3.69 microg l(-1) (B). Differences between group S and other groups (C, B, L) were highly significant (p < 0.0001). Based on our results, selenium in the form of lactate and proteinate was excreted into the milk similarly, but selenium in the form of yeast, which contains high amount of selenomethionine, was excreted by milk in the highest amounts.

Trojans in habitable zones.

With the aid of numerical experiments we examined the dynamical stability of fictitious terrestrial planets in 1:1 mean motion resonance with Jovian-like planets of extrasolar planetary systems. In our stability study of the so-called "Trojan" planets in the habitable zone, we used the restricted three-body problem with different mass ratios of the primary bodies. The application of the three-body problem showed that even massive Trojan planets can be stable in the 1:1 mean motion resonance. From the 117 extrasolar planetary systems only 11 systems were found with one giant planet in the habitable zone. Out of this sample set we chose four planetary systems--HD17051, HD27442, HD28185, and HD108874--for further investigation. To study the orbital behavior of the stable zone in the different systems, we used direct numerical computations (Lie Integration Method) that allowed us to determine the escape times and the maximum eccentricity of the fictitious "Trojan planets."

Diffusion and scaling in escapes from two-degrees-of-freedom Hamiltonian systems.

This paper summarizes an investigation of the statistical properties of orbits escaping from three different two-degrees-of-freedom Hamiltonian systems which exhibit global stochasticity. Each time-independent H=H(0)+ varepsilon H('), with H(0) an integrable Hamiltonian and varepsilon H(') a nonintegrable correction, not necessarily small. Despite possessing very different symmetries, ensembles of orbits in all three potentials exhibit similar behavior. For varepsilon below a critical varepsilon (0), escapes are impossible energetically. For somewhat higher values, escape is allowed energetically but still many orbits never escape. The escape probability P computed for an arbitrary orbit ensemble decays toward zero exponentially. At or near a critical value varepsilon (1)> varepsilon (0) there is a rather abrupt qualitative change in behavior. Above varepsilon (1), P typically exhibits (1) an initial rapid evolution toward a nonzero P(0)( varepsilon ), the value of which is independent of the detailed choice of initial conditions, followed by (2) a much slower subsequent decay toward zero which, in at least one case, is well fit by a power law P(t) proportional, variant t(-&mgr;), with &mgr; approximately 0.35-0.40. In all three cases, P(0) and the time T required to converge toward P(0) scale as powers of varepsilon - varepsilon (1), i.e., P(0) proportional, variant ( varepsilon - varepsilon (1))(alpha) and T proportional, variant ( varepsilon - varepsilon (1))(beta), and T also scales in the linear size r of the region sampled for initial conditions, i.e., T proportional, variant r(-delta). To within statistical uncertainties, the best fit values of the critical exponents alpha, beta, and delta appear to be the same for all three potentials, namely alpha approximately 0.5, beta approximately 0.4, and delta approximately 0.1, and satisfy alpha-beta-delta approximately 0. The transitional behavior observed near varepsilon (1) is attributed to the breakdown of some especially significant KAM tori or cantori. The power law behavior at late times is interpreted as reflecting intrinsic diffusion of chaotic orbits through cantori surrounding islands of regular orbits. (c) 1999 American Institute of Physics.