Effects of long-term selenium yeast supplementation on selenium status studied in the rat

To investigate the selenium status during long-term dietary supply of selenium yeast, 30-day-old male rats were fed for 379 days a methionine-adequate low-selenium diet supplemented with 0.2 mg Se/kg (selenium-adequate diet) or 1.5 mg Se/kg (high-selenium diet) in the form of selenium yeast that contained 60% of the element as l-selenomethionine. Their selenium load was determined at several intervals by neutron activation analysis of the selenium concentrations in the main selenium body pools, skeletal muscle and liver. After 64 days the tissue selenium concentrations plateaued in both groups and then stayed at that level. Compared with the selenium-adequate group, elevated tissue selenium concentrations were found in the high-selenium group, but the increase by a factor of 3.5 in the muscle and by a factor of 2.3 in the liver was smaller than the 7.5-fold increase in the selenium intake. In the selenium-adequate group about 50% of the muscle selenium and 30% of the liver selenium and in the high-selenium group about 85% of the muscle selenium and 70% of the liver selenium were estimated to be present in non-selenoprotein forms. During selenium depletion the liver glutathione peroxidase activity in the high-selenium group remained unaffected for 4 weeks and then decreased more slowly than that in the selenium-adequate group. From these results it can be concluded that selenium incorporated from the selenium yeast diet into non-selenoprotein forms can serve as an endogenous selenium source to maintain selenoprotein levels in periods of insufficient selenium supply.     

Cytochrome P450 monooxygenase from Clostridium acetobutylicum: a new alpha-fatty acid hydroxylase

Cytochrome P450 monooxygenase from the anaerobic microorganism Clostridium acetobutylicum (CYP152A2) has been produced in Escherichia coli. CYP152A2 was shown to bind a broad range of saturated and unsaturated fatty acids and corresponding methyl esters and demonstrated a high peroxygenase activity of up to 200min(-1) with myristic acid. Although a high concentration of hydrogen peroxide of 200microM was necessary for high activities of the enzyme, it led to a fast enzyme inactivation within 2-4min. This might reflect the natural function of CYP152A2 as a rapid hydrogen peroxide scavenging enzyme. In two different reconstituted systems with NADPH, CYP152A2 was able to convert 10 times more substrate, if provided with flavodoxin and flavodoxin reductase from E. coli and even 30-40 times more substrate with the CYP102A1-reductase from Bacillus megaterium. According to the clear preference for hydroxylation at alpha-position, CYP152A2 can be referred to as fatty acid alpha-hydroxylase.     

Complementarity of particles and pits in freeze-fractured hepatic and cardiac gap junctions

Summary Particles and pits of freeze-fractured gap junctions are considered as complementary structures despite the frequent observations of more regular and closer spacings of pits, ascribed to plastic deformation of particle arrays. Recently, however, the noncomplementarity of pits and particles in Purkinje fibers has been reported. To ascertain the relationship between both structures, gap junctions from fixed, cryoprotected liver and myocardium were investigated using spacing and density measurements and complementary replicas.In hepatocyte gap junctions, the center-to-center distances (mean±sd) among pits, 9.57±1.49 nm, and particles, 9.70±1.77 nm, are not significantly different. Density determinations yielded a slightly higher value for the pits, (11,510±830)/m², than for the particles, (11,230±950)/m². In the myocardium, the spacing of the regularly arrayed pits, 9.55±1.33 nm barely exceeds the value of 9.44±1.62 nm for the particles, which show some clustering. However, the packing density for the pits, (10,090±740)/m², appears a little higher than that of the particles (9,890±920)/m². As density and spacing measurements provided no decisive answers, the positions of individual pits and particles of complementary junctional faces were recorded on transparent sheets and compared. In this fashion, a one-to-one correspondence between particles and pits could be established, while small discrepancies may be attributed to plastic deformation. Moreover, the collinearity of pits and particles may be suggested by the observation of a platinum grain in the center of many pits.     

A relationship between the inhibition of heparan sulfate and chondroitin sulfate synthesis and the inhibition of molting by selenate in the hemipteran Rhodnius prolixus

The insect Rhodnius prolixus synthesizes heparan sulfate and chondroitin sulfate after a blood meal containing [35S]-inorganic sulfate. A 40 to 80% inhibition of heparan sulfate synthesis was obtained when the meal was supplemented with 10(-5) and 10(-4) M sodium selenate respectively. Likewise an inhibition of the molting in the order of 30 to 60% was observed when the insects were fed with blood containing 10(-5) and 10(-4) M selenate respectively. The insects after a subsequent meal without selenate molted normally. Except for the inhibition of the ecdysis no gross physiological or morphological changes could be observed in the insects. Based on these and other findings the possible role of sulfated glycosaminoglycans in the control of cell growth is discussed.     

Chemotaxis and nod Gene Activity of Bradyrhizobium japonicum in Response to Hydroxycinnamic Acids and Isoflavonoids

For Bradyrhizobium japonicum, the chemotactic and the nod gene-inducing effects of hydroxycinnamic acids and two of their derivatives were compared with those of isoflavonoids. Only the hydroxycinnamic acids were strong chemoattractants, while the other substances tested were chemotactically inactive. Besides the known nod gene induction by isoflavonoids, a weak nod gene induction by coniferyl alcohol, chlorogenic acid, and ferulic acid was found.     

Effects of temperature and photoperiod on flowering in Hyptis brevipes

Few tropical species have been tested for their flowering response under controlled conditions. Hyptis brevipes Poit, is an annual herb, commonly found in wet margins of streams and ponds, being considered a weed for some perennial plantations in Brazil. Under experimental glasshouse conditions, this species proved to be an obligate short-day plant. Flowering was delayed when photoperiods longer than 8 h were given, the critical photoperiod being between 12 and 13 h. When both temperature and photoperiod were controlled, at 20°C a longer protoperiod (by almost 1 h) is still inductive compared to 25 and 30°C. The number of short-day cycles required for full induction is relatively high and dependent upon temperature; at 20°C or above, 10 cycles are adequate, but at 15°C, more short-day cycles are needed. The number of inflorescences formed as well as the floral index vary according to daylength × temperature × inductive cycle number, allowing flowering to be assessed quantitatively. Long days are inhibitory to flowering, either suppressing it completely (when symmetrically intercalated among 24 inductive cycles) or preventing the floral index from increasing.     

Comparing survival among species with imperfect detection using multilevel analysis of mark—recapture data: a case study on bats

For comparative demography studies, 2 prerequisites are usually needed: 1) using typical parameter values for species, 2) correctly accounting for the uncertainty in the species specific estimates. However, although within‐species variability may be essential, it is typically not considered in analytical procedures, resulting in parameter estimates that may not be representative of the species. Further, data are analysed in 2 steps, first separately for each species, then estimates are compared among species. Accounting for the uncertainty in the species specific estimates is then difficult. Here we propose the application of multilevel Bayesian models on mark—recapture (MR) data for comparative studies on survival probabilities that solves these problems. Our models account for within‐species variability in space and time in the form of random effects. Models reflecting different biological predictions related to the species’ ecology and life‐history traits may further be contrasted. To illustrate our approach, we used long‐term data from 5 temperate tree‐roosting bat species and compared their survival probabilities. Results suggest that species foraging in open space, high reproductive output and short longevity records have lower survival than species foraging at short distances, with low reproductive output and high longevity records. Multilevel models provided relatively precise estimates, away from the edges of the parameter space, even for species with low encounter rates and short study duration. This is particularly valuable for less studied taxa such as bats for which available data are often more sparse. Our approach can be easily extended to include additional groups or levels of interest and effects at the individual level (e.g. sex or age). Different hypotheses regarding differences or similarities in parameters among species can be tested through the application of different models. Overall, it offers a flexible tool to ecologists, and population and evolutionary biologists for comparative studies, explicitly accounting for multilevel structures often encountered in MR data.     

Nimodipine confers clinical improvement in two models of experimental autoimmune encephalomyelitis

Multiple sclerosis is characterised by inflammatory neurodegeneration, with axonal injury and neuronal cell death occurring in parallel to demyelination. Regarding the molecular mechanisms responsible for demyelination and axonopathy, energy failure, aberrant expression of ion channels and excitotoxicity have been suggested to lead to Ca²⁺ overload and subsequent activation of calcium‐dependent damage pathways. Thus, the inhibition of Ca²⁺ influx by pharmacological modulation of Ca²⁺ channels may represent a novel neuroprotective strategy in the treatment of secondary axonopathy. We therefore investigated the effects of the L‐type voltage‐gated calcium channel blocker nimodipine in two different models of mouse experimental autoimmune encephalomyelitis (EAE ), an established experimental paradigm for multiple sclerosis. We show that preventive application of nimodipine (10 mg/kg per day) starting on the day of induction had ameliorating effects on EAE in SJL /J mice immunised with encephalitic myelin peptide PLP _139–151, specifically in late‐stage disease. Furthermore, supporting these data, administration of nimodipine to MOG _35–55‐immunised C57BL /6 mice starting at the peak of pre‐established disease, also led to a significant decrease in disease score, indicating a protective effect on secondary CNS damage. Histological analysis confirmed that nimodipine attenuated demyelination, axonal loss and pathological axonal β‐amyloid precursor protein accumulation in the cerebellum and spinal cord in the chronic phase of disease. Of note, we observed no effects of nimodipine on the peripheral immune response in EAE mice with regard to distribution, antigen‐specific proliferation or activation patterns of lymphocytes. Taken together, our data suggest a CNS ‐specific effect of L‐type voltage‐gated calcium channel blockade to inflammation‐induced neurodegeneration.

     

A sequential analysis of the development of the synaptonemal complex in spermatocytes of the mouse by electron microscopy using hydroxyurea and agar filtration

A method is presented for sequential analysis of the development and behaviour of the Synaptonemal Complex (SC) in primary spermatocytes of male mice, using agar filtration for electron microscope grid preparation. The mice were treated with hydroxyurea (HU) to produce a gap in the spermatogenic line. The front of surviving cells behind the gap was examined day by day. The first visible parts of unpaired axial elements, with some barely recognizable paired regions were found 9 days after the last HU injection i.e. directly after the last S-phase before meiosis. During mid zygotene and late zygotene the axes of the autosomes had a fuzzy ill-defined appearance with irregular regions of apparent thickening. The axes of the XY pair could be recognized only at late zygotene. During pachytene the SCs of the autosomal pairs did not show a significant change except for a slight increase in size of the attachment points of the axial elements. On the first day of pachytene the axes of the XY pair appeared thin and long. On the second day the axes of the XY pair showed maximal pairing of about 50% of the axis of the Y chromosome. From the third to the fifth day a decrease of the paired region of the sex chromosomes was found together with an increase in thickness of the axes, which reached its maximum on the fourth day. Diplotene could be easily recognized: the autosomal axes showed a sharp, well-defined outline with thick attachment points with deltoid structure, and desynapsis was very clear. The axes of the XY pair showed variation during diplotene but on the third day of diplotene a characteristic bulging could be seen. The axes of the autosomes disappeared at this time and in most cases only the attachment points remained visible. The duration of the prophase classes of meiosis I was found to be: zygotene approximately 2 days; pachytene a little more than 5 days and diplotene approximately 3 days. Leptotene could not be traced by the method used. If it exists at all, it must be a stage of very short duration.