A specific,sensitive and high-capacity immunoassay for PAF

A specific radioimmunoassay for platelet-activating factor (PAF) sensitive in the range 10–1000 pg (0.02–2 pmoles) has been developed. Detailed quantitative hapten inhibition studies showed specificity for the acetyl group at C-2 of PAF, a requirement for the ether linkage at C-1 and some tolerance for substituents on the choline nitrogen. No significant cross-reactivity was found with phosphatidylcholine and lysophosphatidylcholine or with lysoPAF. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Chromosome 1p36 deletions: the clinical phenotype and molecular characterization of a common newly delineated syndrome

Deletions of the distal short arm of chromosome 1 (1p36) represent a common, newly delineated deletion syndrome, characterized by moderate to severe psychomotor retardation, seizures, growth delay, and dysmorphic features. Previous cytogenetic underascertainment of this chromosomal deletion has made it difficult to characterize the clinical and molecular aspects of the syndrome. Recent advances in cytogenetic technology, particularly FISH, have greatly improved the ability to identify 1p36 deletions and have allowed a clearer definition of the clinical phenotype and molecular characteristics of this syndrome. We have identified 14 patients with chromosome 1p36 deletions and have assessed the frequency of each phenotypic feature and clinical manifestation in the 13 patients with pure 1p36 deletions. The physical extent and parental origin of each deletion were determined by use of FISH probes on cytogenetic preparations and by analysis of polymorphic DNA markers in the patients and their available parents. Clinical examinations revealed that the most common features and medical problems in patients with this deletion syndrome include large anterior fontanelle (100%), motor delay/hypotonia (92%), moderate to severe mental retardation (92%), growth delay (85%), pointed chin (80%), eye/vision problems (75%), seizures (72%), flat nasal bridge (65%), clinodactyly and/or short fifth finger(s) (64%), low-set ear(s) (59%), ear asymmetry (57%), hearing deficits (56%), abusive behavior (56%), thickened ear helices (53%), and deep-set eyes (50%). FISH and DNA polymorphism analysis showed that there is no uniform region of deletion but, rather, a spectrum of different deletion sizes with a common minimal region of deletion overlap.     

A model for the release of sulfur from elemental S and superphosphate

A mathematical model was developed to predict the release of sulfate from elemental S (S⁰) and gypsum in single superphosphate. The release algorithm is based on the observation that release is linearly related to particle surface area. Release rates under various conditions could then be described by the change in radius for each time increment, which allows easier comparison of release rates between different particle sizes. A model based on spherical particles was found to be adequate in accounting for the range of particle shapes found in crushed agricultural S⁰. Release rates calculated from experimental data range from 0.07 to 0.45µm/d depending on environmental conditions.Equations for incorporating the effects of environmental variables and the release of S from S⁰ and from the gypsum component of single superphosphate (SSP) were developed from the literature, and were incorporated within a larger model of S cycling. The model predicted that after 72 days, 99% of the S in SSP would have been released, compared to a release after one year of 54% of the S in sulfur-fortified superphosphate, and 23% of that in crushed agricultural grade S⁰. The model provides a means of assessing the effect of the particle size of S⁰ on release rates and should allow the formulation of fertilizers that supply S at a rate closer to the rate of plant uptake.     

Monitoring the amplification of CATCH, a 3SR based cooperatively coupled isothermal amplification system, by fluorimetric methods

Three different types of fluorescence detection methods were employed to monitor amplification of a previously established isothermal cooperatively coupled amplification system as it can serve as a tool for the investigation of fundamental issues in evolutionary optimization. By using 5'IRD-41 fluorescent labeled primers, the intercalating dye TOPRO-1 and a 5'fluorescin/3'DABCYL 4-(4-dimethylamino-phenylazo)benzoic acid labeled ss 24 nt DNA, evolving molecular cooperation is accessible, sequence specifically as well as non-sequence-specifically without using radioactivity.     

Effect of broadcast and precise ephemerides on estimates of the frequency stability of GPS Navstar clocks

Frequency stability analysis of on-orbit Navstar clocks is performed by the Naval Research Laboratory using both the broadcast and the precise post-processed ephemerides. The phase offset between the Navstar clock and the reference clock is computed from pseudorange measurements obtained by dual-frequency GPS receivers at the five GPS monitor sites and at the U.S. Naval Observatory precise-time site. The broadcast ephemerides are generated at the GPS master control station by a Kalman filter using data collected from the five GPS monitor stations. The precise post-processed ephemerides are generated by the Defense Mapping Agency (DMA) using data collected from the GPS monitor sites and from five additional DMA monitor sites. In this paper the frequency stability is estimated for two Navstar caesium clocks–a Block I caesium clock (Navstar 9) and a Block II caesium clock (Navstar 23)–using both the broadcast and the precise ephemerides. A significant improvement in the estimate of the frequency stability of the Block II clocks has been achieved using the precise ephemeris.     

In vitro evolution of molecular cooperation in CATCH, a cooperatively coupled amplification system

BACKGROUND: One of the key issues in the investigation of evolution is how complex systems evolved from simple chemical replicators. Theoretical work proposed several models in which complex replicating systems are kinetically stabilized. The development of powerful isothermal amplification technique allows complex nucleic acid based evolving in vitro systems to be set up, which may then serve to verify experimentally current theories of evolution. Recently such a system based on the 3SR (self-sustained sequence replication) reaction has been established to investigate the evolution of cooperation: the trans-cooperatively coupled CATCH (cooperative amplification by cross hybridization). RESULTS: Over four rounds of serial transfer, the cooperatively coupled two species CATCH system evolved into a more complex cooperative four species system, which then was overgrown by CATCH-derived RNA-Z-like hairpin species. In contrast to the classical RNA-Z species, these molecules have complementary loop sequences and self-amplify using a dual mechanism that includes concentration-dependent phases of noncooperative and cooperative amplification. CONCLUSIONS: The evolution of a cooperative system, under conditions that were alternately unfavorable and favorable for cooperative amplification, led to a system showing facultative cooperation. This principle of facultative cooperation preserves the complexity of the system investigated and could have general implications for the evolution and stabilization of cooperation under oscillating reaction conditions.     

A model of S,P and N uptake by a perennial pasture

Phosphate sorption curves give useful information about the management of the P fertility in soils. This study was conducted to examine how P sorption characteristics were influenced, and could be predicted from the properties of Mediterranean soils of Spain. The 114 soils studied differed widely in origin and properties and were grouped as calcareous (43) and noncalcareous (71). Citrate-bicarbonate-dithionite extractable Fe (Fe_d) and Al (Al_d) and clay were the properties best correlated with the P sorbed and the P buffer capacity at an equilibrium concentration of 0.2 mg P l^–1. This suggests that Fe oxides and silicate clays play a significant role in P sorption. Stepwise regression analysis showed, however, that clay was not a significant variable in the calcareous group, but active CaCO₃ was. Prediction of the P sorption parameters was better for the noncalcareous than for the calcareous group. This reduced ability to predict P sorption in calcareous soils may be due to the inability of total or active CaCO₃ to adequately measure the reactivity of carbonates towards P sorption. From 53 to 75% of the variation in P sorption parameters could be explained by regression equations including all or several of the following routinely-determined soil properties: clay, pH, Fe_d, and active CaCO₃. These equations could, therefore, provide a simple and rapid estimation of P sorption in soils of Mediterranean regions.     

Soil phosphorus pools with addition of fertiliser phosphorus in a long-term grazing experiment

Nutrient Cycling in Agroecosystems - Grasslands are a globally important use of land for food and fibre production, which often require the addition of phosphorus (P) fertiliser to maximise plant...     

Evaluation of low-temperature coal tars by a rapid,detailed assay based on chromatography

A rapid, detailed assay, based largely on both liquid and gas chromatography, was developed for low-temperature coal tars. With the use of this assay, the pounds per ton of coal of various compounds of commercial interest could be determined, thus supplying the information needed for an economic evaluation of the tars and the carbonisation processes. The amounts of about 100 individual compounds of several classes were involved, including light oil components, tar acids and bases, and neutral-oil components such as naphthalenes and straight-chain paraffins and olefins, and the total amounts of these classes in the entire tar. The results for six different tars from the same coal were chosen as examples.