Measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography

A rapid procedure for the isolation, separation, identification and measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography (HPLC) is presented. The initial isolation of these compounds from urine was accomplished with small disposable ion-exchange columns. HPLC was performed on a silica gel column with a mobile phase composed of methylene chloride, methanol and 1 M aqueous ammonium formate buffer. Peaks were recorded at both 254 nm and 280 nm and the response ratio was used in conjunction with the elution volume for compound identification. The minimum detectable amount (signal-to-noise ratio = 2) ranged from 0.2 ng for uracil to 2.2 ng for cytidine. Linearity and recovery for thymine, uracil, uridine, pseudouridine, orotic acid and orotidine added to urine was demonstrated over almost a 10³ concentration range. The potential application of this method for the study of inborn errors in the urea cycle is discussed.     

C8- and C9-Alkylphenols and Ethoxylates: II. Assessment of Environmental Persistence and Bioaccumulation Potential

C8- and C9-alkylphenols and their ethoxylates (APE) are widely used commercial products mainly used in industrial applications, in the formulation of crop protection chemicals, and in industrial and household cleaners. Recent regulatory focus on these compounds has included an assessment of their potential to meet criteria for persistent, bioaccumulative, and toxic compounds (PBT). To fully evaluate either the relative persistence or bioaccumulation potential of any APE, degradation intermediates and metabolic by-products of these compounds should also be considered. To facilitate the evaluation of the ultimate fate of APE in the environment, a review of the degradation pathways and identification of degradation intermediates was performed (part I of a two-part series). In part II of this series, the relative persistence of APE as indicated by degradation half-lives was examined based on a review of abiotic and biological degradation data. To assess the bioaccumulation potential of APE, the relevant literature was also reviewed. The available data for C8- and C9-APE show that the commercial products and their degradation intermediates do not meet any national or international criteria for identifying these compounds as PBT substances.     

Curschmann's spirals in pleural and peritoneal effusions

Curschmann's spirals were found in smears and cell block preparations of five spontaneously occurring pleural and peritoneal fluids. The spirals were similar to those seen in the respiratory tract, although generally much smaller. In three of the five cases, the fluids also contained mucus-secreting adenocarcinoma cells; it is postulated that the spirals formed from mucus secreted by these cells. In the other two cases, there was evidence of serosal inflammation; it is suggested that the spirals in these cases developed from submesothelial connective tissue mucosubstances that entered the serosal cavity through a mesothelium of increased permeability due to the inflammation. No simple explanation can be accepted as to the exact mode of spiral formation, which is presumed to be a complex physical and biochemical phenomenon.     

Calibration and use of a Clark-type oxygen electrode from 5 to 45 degrees C

A calibration procedure for a Clark-type oxygen electrode over a wide range of temperatures is described. The autoxidation of duroquinol (2,3,5,6-tetramethyl-1,4-benzenediol) was used to verify the electrode's ability to accurately sense the total amount of dissolved O2 in an aqueous buffer. Electrode response time was measured by using oxygenated ethanol to deliver a rapid increase in O2 concentration to the reaction medium. An oxygen-producing system (spinach thylakoids) was utilized to test the range of O2-evolution rates able to be sensed. It was concluded that a Clark-type oxygen electrode has the absolute sensitivity, rapidity, and range necessary to accurately track rates of O2 production or consumption from 5 to 45 degrees C.     

Variation in sex determination in natural populations of a shrimp

Strategies of sex determination were studied in Gammarus duebeni, a brackish water shrimp (Crustacea, Amphipoda). Animals from Budle Bay, northern England, have environmental sex determination (e. s. d.), in accord with a population studied in Germany. Males are produced in long day photoperiods and females in short days. By contrast, animals from southern England show no significant sex ratio variation with daylength. This is the first report of such variation in sex determination for an invertebrate. Detailed studies of Budle Bay animals show that sex is determined several weeks after young are released by the mother; that the critical daylength is longer at Budle Bay than in Germany; and that the critical response is cued at the onset of a photophase. The nature of sex determination in G. duebeni may be associated with population dynamics. Males gain greater relative fitness by large size than females. E. s. d. is then adaptive where the breeding season produces significant growth differences between early and late animals, but where generations do not overlap. Comparisons are drawn with the flexible sex determining system in Menidia menidia (Pisces).     

The small-subunit ribosomal RNA gene sequences from the hypotrichous ciliates Oxytricha nova and Stylonychia pustulata

We have determined the complete nucleotide sequence of the small- subunit ribosomal RNA genes for the ciliate protozoans Stylonychia pustulata and Oxytricha nova. The sequences are homologous and sufficiently similar that these organisms must be closely related. In a phylogeny inferred from comparisons of several eukaryotic small-subunit ribosomal RNAs, the divergence of the ciliates from the eukaryotic line of descent is seen to coincide with the radiation of the plants, the animals, and the fungi. This radiation is preceded by the divergence of the slime mold, Dictyostelium discoideum.      

Livestock Disease Management for Trading Across Different Regulatory Regimes

The maintenance of livestock health depends on the combined actions of many different actors, both within and across different regulatory frameworks. Prior work recognised that private risk management choices have the ability to reduce the spread of infection to trading partners. We evaluate the efficiency of farmers’ alternative biosecurity choices in terms of their own-benefits from unilateral strategies and quantify the impact they may have in filtering the disease externality of trade. We use bovine viral diarrhoea (BVD) in England and Scotland as a case study, since this provides an example of a situation where contrasting strategies for BVD management occur between selling and purchasing farms. We use an agent-based bioeconomic model to assess the payoff dependence of farmers connected by trade but using different BVD management strategies. We compare three disease management actions: test-cull, test-cull with vaccination and vaccination alone. For a two-farm trading situation, all actions carried out by the selling farm provide substantial benefits to the purchasing farm in terms of disease avoided, with the greatest benefit resulting from test-culling with vaccination on the selling farm. Likewise, unilateral disease strategies by purchasers can be effective in reducing disease risks created through trade. We conclude that regulation needs to balance the trade-off between private gains from those bearing the disease management costs and the positive spillover effects on others.