Model of ammonia volatilization from calcareous soils

A quantitative model of ammonia volatilization from the calcareous soil uppermost 1-cm layer was developed and tested. The model accounts for the following processes: ammonium-ammonia equilibration in the soil solution, cation exchange between calcium and ammonium which results in ammonium distribution between soil liquid and solid phases, nitrification of dissolved ammonium, distribution of ammonia between liquid and gaseous phases and diffusion of gaseous ammonia in the soil air. The combined effect of various characteristics such as soil pH, cation exchange capacity, water capacity and nitrification rate on ammonia losses from various soil types have been studied. The model was validated against experimental results of ammonia losses from different soils for its use as a predicting tool. The model shows that most of ammonia losses can be explained by the interactive effect of high soil pH and low cation exchange capacity. Computations show increased ammonia volatilization with decreasing soil water capacity. Increasing fertilizer application rate has a small effect on percentage of ammonia losses. Increased nitrification rate and shorter “lag” period of nitrification reduce ammonia losses considerably. Good agreement was obtained between model calculations and experimental results of ammonia volatilization from 13 soils.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Two-color flow cytometric analysis of monocyte depleted human blood lymphocyte subsets

Peripheral blood mononuclear cells (PBMC) from normal individuals were examined using 16 pairs of FITC and phycoerythrin (PE) directly conjugated monoclonal antibodies. Each pair of reagents was used to evaluate a conventional lymphocyte gate as well as open (non) gate of monocyte depleted PBMC. Parallel studies using the same panel of monoclonal antibodies were carried out on selected, nonmonocyte depleted samples. The major findings of this analysis were that 1,000-1,200 lymphocytes in a 10,000 cell analysis are found outside the lymphocyte gate and of these approximately 2/5 are CD16 positive LGL/NK cells, 2/5 are CD3 positive T cells, and 1/5 are CD19/CD20 positive B cells. Thus, it appears that 10-15% of the lymphoid cells fall outside of the conventional lymphocyte gate, and in certain settings monocyte depletion may be useful to perform more complete evaluation of the total lymphoid cell population obtained after ficoll-hypaque separation.     

Dexamethasone blocks increased leukotriene B4 production during endotoxin-induced lung injury

We hypothesized that leukotriene B4 (LTB4) might be produced during endotoxemia in pigs and, if so, might play a role in the pathophysiology of acute respiratory failure. Escherichia coli endotoxin (055-B5) was infused intravenously into anesthetized pigs at 5 micrograms/kg the 1st h, followed by 2 micrograms.kg-1.h-1 for 3 h. Endotoxemic pigs were treated with dexamethasone (DEX, iv) 18 h (5 mg/kg) and 1 h (5 mg/kg) before onset of endotoxemia. During phases I (i.e., 0-2 h) and II (i.e., 2-4 h), endotoxin decreased cardiac index, caused granulocytopenia, and increased mean pulmonary arterial pressure, pulmonary vascular resistance, alveolar-arterial O2 gradient, and hematocrit. During phase II, plasma LTB4 levels were increased (as determined by radioimmunoassay, reverse-phase high-performance liquid chromatography, and ultraviolet spectroscopy). Endotoxin increased the levels of LTB4 and albumin in bronchoalveolar lavage fluid (BALF). DEX blocked or greatly attenuated the endotoxin-induced hemodynamic abnormalities and blocked the increases in plasma and BALF LTB4 levels. We conclude that LTB4 is produced during porcine endotoxemia and could possibly play a role in the pathophysiology of endotoxin-induced lung injury in anesthetized pigs.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Argininosuccinic aciduria: prenatal studies in a family at risk.

We have monitored two successive pregnancies in a family which we found to be at risk for argininosuccinic aciduria. We measured argininosuccinic acid (ASA) concentrations in amniotic fluid and utilized an indirect assay of ASA lyase activity in cultured amniotic fluid cells. The assay procedure is based on the uptake of 14C from [14C]citrulline and of [3H]leucine into protein. ASA was easily measured in amniotic fluid from the first fetus at risk, whereas none was detectable in control fluids. Amniotic fluid cells cultured from this fetus had only 5.5% of control ASA lyase activity. The pregnancy was terminated, and hepatic ASA lyase activity in the fetus was shown to be about 1.3% of control values. In addition, eight fetal tissues were analyzed for ASA, and all had significant accumulation. ASA was not detected in amniotic fluid from the second fetus at risk, and ASA lyase activity in cultured cells was 80% of control activity. Enzymatic analysis of erythrocyte lysate confirmed the diagnosis of an unaffected child (ASA lyase = 46% of control) and indicated heterozygosity. Thus, we provide further evidence that argininosuccinic aciduria can be diagnosed successfully in utero by indirect assay of ASA lyase activity in cultured amniotic fluid cells. In addition, high amniotic fluid ASA concentrations provide strong adjunctive evidence for such a prenatal determination, and may prove to be sufficient for diagnosis.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Thin-layer chromatography of β-aminopropionitrile

Thin-layer chromatography of β-aminopropionitrile (BAPN) in acetone and 1 m ammonium hydroxide (9:1) allowed separation of that compound from amino acids present in rat-liver perfusion fluid without prior solvent extraction. Direct densitometry of the spots obtained with ninhydrin yielded satisfactory quantitation of β-aminopropionitrile present. Utilization of [¹⁴C]nitrile-labeled β-aminopropionitrile and concurrent analysis of cyanoacetic acid allowed almost complete accountability of BAPN added to isolated rat liver.