Pregnancy suppression by an antiserum to the sperm specific lactate dehydrogenase

An antiserum induced against the isozyme of lactate dehydrogenase (LDH-X) that is unique to spermatozoa reduced significantly the number of pregnancies in mice treated at varying times after they had mated. This effect of the antiserum occurred both prior to and following implantation. The fecundity of treated animals appeared to be normal in subsequent matings.     

N2O and NO fluxes between a Norway spruce forest soil and atmosphere as affected by prolonged summer drought

Global change scenarios predict an increasing frequency and duration of summer drought periods in Central Europe especially for higher elevation areas. Our current knowledge about the effects of soil drought on nitrogen trace gas fluxes from temperate forest soils is scarce. In this study, the effects of experimentally induced drought on soil N₂O and NO emissions were investigated in a mature Norway spruce forest in the Fichtelgebirge (northeastern Bavaria, Germany) in two consecutive years. Drought was induced by roof constructions over a period of 46 days. The experiment was run in three replicates and three non-manipulated plots served as controls. Additionally to the N₂O and NO flux measurements in weekly to monthly intervals, soil gas samples from six different soil depths were analysed in time series for N₂O concentration as well as isotope abundances to investigate N₂O dynamics within the soil. N₂O fluxes from soil to the atmosphere at the experimental plots decreased gradually during the drought period from 0.2 to −0.0 μmol m⁻² h⁻¹, respectively, and mean cumulative N₂O emissions from the manipulated plots were reduced by 43% during experimental drought compared to the controls in 2007. N₂O concentration as well as isotope abundance analysis along the soil profiles revealed that a major part of the soil acted as a net sink for N₂O, even during drought. This N₂O sink, together with diminished N₂O production in the organic layers, resulted in successively decreased N₂O fluxes during drought, and may even turn this forest soil into a net sink of atmospheric N₂O as observed in the first year of the experiment. Enhanced N₂O fluxes observed after rewetting up to 0.1 μmol m⁻² h⁻¹ were not able to compensate for the preceding drought effect. During the experiment in 2006, with soil matric potentials in 20 cm depth down to −630 hPa, cumulative NO emissions from the throughfall exclusion plots were reduced by 69% compared to the controls, whereas cumulative NO emissions from the experimental plots in 2007, with minimum soil matric potentials of −210 hPa, were 180% of those of the controls. Following wetting, the soil of the throughfall exclusion plots showed significantly larger NO fluxes compared to the controls (up to 9 μmol m⁻² h⁻¹ versus 2 μmol m⁻² h⁻¹). These fluxes were responsible for 44% of the total emission of NO throughout the whole course of the experiment. NO emissions from this forest soil usually exceeded N₂O emissions by one order of magnitude or more except during wintertime.     

Fluxes of climate‐relevant trace gases between a Norway spruce forest soil and atmosphere during repeated freeze–thaw cycles in mesocosms

For this century, an increasing frequency of extreme meteorological boundary conditions is expected, presumably resulting in a changing frequency of freezing and thawing of soils in higher‐elevation areas. Our current knowledge about the effects of these events on trace‐gas emissions from soils is scarce. In this study, the effects of freeze–thaw events on the fluxes of the trace gases CO₂, N₂O, and NO between soil and atmosphere were investigated in a laboratory experiment. Undisturbed soil columns were collected from a mature Norway spruce forest in the “Fichtelgebirge”, SE Germany. The influence of freezing temperatures (–3°C, –8°C, –13°C) on gas fluxes was studied during the thawing periods (+5°C) in three freeze–thaw cycles (FTCs) and compared to unfrozen controls (+5°C). Two different types of soil columns were examined in parallel—one consisting of O layer only (O columns) and one composed of O layer and mineral soil horizons (O+M columns)—to quantify the contribution of the organic layer and the top mineral soil to the production or consumption of these trace gases. During the thawing period, we observed increasing emissions of CO₂, N₂O, and NO from the spruce forest soil, but the cumulative emissions of these gases did mostly not exceed the level of the controls. The results show that the O layers were mainly involved in the gas production. Severe soil frost increased CO₂ fluxes during soil thawing, whereas repetition of the freeze–thaw events decreased CO₂ fluxes from the thawing soil. Fluxes of N₂O and NO were neither influenced by freezing temperature nor by freeze–thaw repetition. Stable‐isotope analysis indicated that denitrification was mostly responsible for the N₂O production in the FTC columns. Furthermore, isotope data demonstrated a consumption of N₂O through microbial denitrification to N₂. It was further shown, that production of N₂O also occurred in the mineral horizons. The NO emissions were mainly driven by increasing soil temperature during thawing. In this freeze–thaw experiment up to 20 times higher NO than N₂O fluxes were recorded. Our results suggest that topsoil thawing has little potential to increase the emissions of CO₂, N₂O, and NO in spruce forest soils.     

Oxygen isotope ratios of juice water in Australian oranges and concentrates.

Australian orange juices from major growing regions have been surveyed over a 5 year period with a view to establishing a database of (18)O/(16)O isotope ratios against which retail samples can be tested for authenticity. The (18)O/(16)O ratios were found to follow a consistent pattern that had both a cyclic seasonal and a regional influence. Oxygen delta values ranged from a summer maximum of >+15 per thousand for oranges from inland regions to a winter minimum of approximately +1 per thousand for oranges grown in coastal areas. However, over a shorter time period, the range of values was markedly less than this. Concentrated orange juices, pulpwashes, and peel extracts, as well as other citrus types, were also tested. The effect of some industry practices that have an effect on (18)O/(16)O ratios was also investigated.     

Soil and plant water status under sprinkling and trickling

In a comparison of methods of irrigating tomatoes on the sand dunes of northern Sinai (El-Arish region), yields obtained by trickling were higher than those by sprinkling. The present study attempts to explain these results from a physical point of view. Before each irrigation and during a complete irrigation cycle measurements were made of soil moisture content, moisture tension in the root zone, and plant water potential. The amount of water applied was based on Class A pan evaporation. At 24 h after the end of an irrigation the soil moisture content was 4% by weight, regardless of the quantity of water applied. The soil moisture tension and the plant water potential were similar for both methods during the first 24 h after irrigation, but the values rose gradually and were higher at the end of the sprinkle irrigation cycle which lasted 3 days, than at the end of the daily trickle irrigation cycle. These differences in soil moisture tension affected the plant water potential and in turn plant development and yield.     

Generation and in vitro differentiation of a spermatogonial cell line

Spermatogenesis is the process by which spermatogonial stem cells divide and differentiate to produce sperm. In vitro sperm production has been difficult to achieve because of the lack of a culture system to maintain viable spermatogonia for long periods of time. Here we report the in vitro generation of spermatocytes and spermatids from telomerase-immortalized mouse type A spermatogonial cells in the presence of stem cell factor. This differentiation can occur in the absence of supportive cells. The immortalized spermatogonial cell line may serve as a powerful tool in elucidating the molecular mechanisms of spermatogenesis. Furthermore, through genomic modification and transplantation techniques, this male germ cell line may be used to generate transgenic mice and to develop germ cell gene therapy.     

Plant embryogenesis: zygote to seed

Most differentiation events in higher plants occur continuously in the postembryonic adult phase of the life cycle. Embryogenesis in plants, therefore, is concerned primarily with establishing the basic shoot-root body pattern of the plant and accumulating food reserves that will be used by the germinating seedling after a period of embryonic dormancy within the seed. Recent genetics studies in Arabidopsis have identified genes that provide new insight into how embryos form during plant development. These studies, and others using molecular approaches, are beginning to reveal the underlying processes that control plant embryogenesis.     

Antibodies to a precursor of human collagen

Antiserum prepared against serum-free medium from human fibroblast cultures reacted specifically with protropocollagen, an assembled, soluble precursor of tropocollagen. The antibodies were directed to antigenic determinants in the nonhelical, amino terminal peptide extensions (propeptides). Amino acid sequences in the precursor molecule corresponding to the telopeptides and helical alpha chains of tropocollagen were not recognized by the antiserum.     

Free Radicals and Reactive Molecules in Clathrate Cavities

Reactive molecules and free radicals, when located in the cavities of the water clathrate lattice, can be prevented from recombining at temperatures almost up to the decomposition point of the lattice. The active species are produced by selective photochemical dissociation of the guest molecules in the clathrate compounds. Data taken from water clathrates of H(2)S, CH(3)SH, and C(2)H(5)SH suggest that S(2), CH(3)S and C(2)H(5)S can be preserved in this way.