Toward the improvement of total nitrogen deposition budgets in the United States.

Frameworks for limiting ecosystem exposure to excess nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). While much progress has been made in developing total Nr deposition budgets for the U.S., current budgets remain limited by key data and knowledge gaps. Analysis of National Atmospheric Deposition Program Total Deposition (NADP/TDep) data illustrates several aspects of current Nr deposition that motivate additional research. Averaged across the continental U.S., dry deposition contributes slightly more (55%) to total deposition than wet deposition and is the dominant process (>90%) over broad areas of the Southwest and other arid regions of the West. Lack of dry deposition measurements imposes a reliance on models, resulting in a much higher degree of uncertainty relative to wet deposition which is routinely measured. As nitrogen oxide (NOx) emissions continue to decline, reduced forms of inorganic nitrogen (NHx = NH3 + NH4+) now contribute >50% of total Nr deposition over large areas of the U.S. Expanded monitoring and additional process-level research are needed to better understand NHx deposition, its contribution to total Nr deposition budgets, and the processes by which reduced N deposits to ecosystems. Urban and suburban areas are hotspots where routine monitoring of oxidized and reduced Nr deposition is needed. Finally, deposition budgets have incomplete information about the speciation of atmospheric nitrogen; monitoring networks do not capture important forms of Nr such as organic nitrogen. Building on these themes, we detail the state of the science of Nr deposition budgets in the U.S. and highlight research priorities to improve deposition budgets in terms of monitoring and flux measurements, leaf- to regional-scale modeling, source apportionment, and characterization of deposition trends and patterns.

Linkage disequilibrium in the human genome.

With the availability of a dense genome-wide map of single nucleotide polymorphisms (SNPs), a central issue in human genetics is whether it is now possible to use linkage disequilibrium (LD) to map genes that cause disease. LD refers to correlations among neighbouring alleles, reflecting 'haplotypes' descended from single, ancestral chromosomes. The size of LD blocks has been the subject of considerable debate. Computer simulations and empirical data have suggested that LD extends only a few kilobases (kb) around common SNPs, whereas other data have suggested that it can extend much further, in some cases greater than 100 kb. It has been difficult to obtain a systematic picture of LD because past studies have been based on only a few (1-3) loci and different populations. Here, we report a large-scale experiment using a uniform protocol to examine 19 randomly selected genomic regions. LD in a United States population of north-European descent typically extends 60 kb from common alleles, implying that LD mapping is likely to be practical in this population. By contrast, LD in a Nigerian population extends markedly less far. The results illuminate human history, suggesting that LD in northern Europeans is shaped by a marked demographic event about 27,000-53,000 years ago.

Immune recognition of swine vesicular disease virus structural proteins: novel antigenic regions that are not exposed in the capsid.

Swine vesicular disease virus (SVDV) is an enterovirus of the Picornaviridae family that belongs to the coxsackievirus B group. A number of antigenic sites have been identified in SVDV by analysis of neutralizing monoclonal antibody-resistant mutants and shown to be exposed on the surface of the capsid. In this paper we have identified seven new immunodominant antigenic regions in SVDV capsid proteins by a peptide scanning method, using a panel of sera from infected pigs. When these antigenic regions were located in the capsid by using a computer-generated three-dimensional model of the virion, one was readily exposed on the surface of the virus and the remaining sites were located facing the inner side of the capsid shell, at subunit contacts, or in the interior of the subunit structure.

Toward a more accurate quantitation of the activity of recombinant retroviruses: alternatives to titer and multiplicity of infection.

In this paper, we present a mathematical model with experimental support of how several key parameters govern the adsorption of active retrovirus particles onto the surface of adherent cells. These parameters, including time of adsorption, volume of virus, and the number, size, and type of target cells, as well as the intrinsic properties of the virus, diffusion coefficient, and half-life (t(1/2)), have been incorporated into a mathematical expression that describes the rate at which active virus particles adsorb to the cell surface. From this expression, we have obtained estimates of C(vo), the starting concentration of active retrovirus particles. In contrast to titer, C(vo) is independent of the specific conditions of the assay. The relatively slow diffusion (D = 2 x 10(-8) cm(2)/s) and rapid decay (t(1/2) = 6 to 7 h) of retrovirus particles explain why C(vo) values are significantly higher than titer values. Values of C(vo) also indicate that the number of defective particles in a retrovirus stock is much lower than previously thought, which has implications especially for the use of retroviruses for in vivo gene therapy. With this expression, we have also computed AVC (active viruses/cell), the number of active retrovirus particles that would adsorb per cell during a given adsorption time. In contrast to multiplicity of infection, which is based on titer and is subject to the same inaccuracies, AVC is based on the physicochemical parameters of the transduction assay and so is a more reliable alternative.

Toward a more accurate quantitation of the activity of recombinant retroviruses: alternatives to titer and multiplicity of infection.

In this paper, we present a mathematical model with experimental support of how several key parameters govern the adsorption of active retrovirus particles onto the surface of adherent cells. These parameters, including time of adsorption, volume of virus, and the number, size, and type of target cells, as well as the intrinsic properties of the virus, diffusion coefficient, and half-life (t1/2), have been incorporated into a mathematical expression that describes the rate at which active virus particles adsorb to the cell surface. From this expression, we have obtained estimates of Cvo, the starting concentration of active retrovirus particles. In contrast to titer, Cvo is independent of the specific conditions of the assay. The relatively slow diffusion (D = 2 x 10(-8) cm2/s) and rapid decay (t1/2 = 6 to 7 h) of retrovirus particles explain why Cvo values are significantly higher than titer values. Values of Cvo also indicate that the number of defective particles in a retrovirus stock is much lower than previously thought, which has implications especially for the use of retroviruses for in vivo gene therapy. With this expression, we have also computed AVC (active viruses/cell), the number of active retrovirus particles that would adsorb per cell during a given adsorption time. In contrast to multiplicity of infection, which is based on titer and is subject to the same inaccuracies, AVC is based on the physicochemical parameters of the transduction assay and so is a more reliable alternative.

Secretion of phospholipid transfer protein by human hepatoma cell line, Hep G2, is enhanced by sodium butyrate.

Hep G2 cells were used to study the synthesis and secretion of phospholipid transfer protein (PLTP). Upon incubation of the cells at confluence with serum-free Dulbecco's modified Eagle's medium (DMEM), phosphatidylcholine (PC) transfer activity was found to accumulate in the culture media. The PC transfer activity in the media was effectively inhibited by rabbit anti-human PLTP immunoglobulin (Ig)G, thus indicating that the PC transfer activity was due to secreted PLTP. The molecular weight of Hep G2 PLTP was approximately 78 kDa by Western blot analysis, in agreement with the molecular weight obtained for purified human plasma PLTP. The PLTP secreted by Hep G2 also possessed an HDL conversion activity similar to that of human plasma PLTP. The addition of butyrate to the cell culture media resulted in a marked increase in the secretion of PLTP. After 24 h incubation with 4 mmol/L sodium butyrate, a more than twofold increase (P < 0.01) of PC transfer activity in the cell-conditioned media was obtained. The dose-dependent increase in the PC transfer activity in the media upon butyrate treatment was well correlated (r = 0.80, P < 0.01) with that of PLTP mass as determined by immuno-slot blot analysis of cell-conditioned media. The increased secretion of PLTP by Hep G2 treated with sodium butyrate was accompanied by a greater increase in the level of PLTP mRNA in the cells as determined by ribonuclease protection assay. In the presence of 4 mmol/L sodium butyrate, a fourfold increase (P < 0. 01) in mRNA level was obtained at 24 h. No stabilizing effect of butyrate on PLTP mRNA was apparent upon treatment of the cultured cells with the RNA synthesis inhibitor, actinomycin D. Thus, the up-regulatory effect of butyrate on PLTP gene expression seemed to have occurred at the transcriptional level.

Preliminary data from the USEPA dry deposition network: 1989.

The objective of the National Dry Deposition Network is to determine patterns and trends of dry deposition for various sulfur and nitrogen species at roughly 50 locations throughout the continental USA. Each site is equipped for collection of continuous meteorological and ozone data and weekly average concentrations of SO4(2-), NO3-, SO2 and HNO3, using a three-stage filter pack. Results from 40 eastern US sites operational throughout 1989 show species-dependent variability from site to site, season to season, and day to night. Annual average concentrations of atmospheric SO4(2-), NO3-, SO2 and HNO3 ranged from 2.7 to 7.9, 0.2 to 3.9, 2.4 to 23.2 and 0.7 to 3.6 microg/m(-3), respectively. Seasonal variability was considerable for all constituents. Day/night data indicate that SO2 and HNO3, but not SO4(2-) and NO3-, are typically found at moderately to substantially lower concentrations at night, especially during spring and summer. Estimated dry deposition for SO2 and HNO3 appear to be much greater than for SO4(2-) and NO3-, respectively. Comparison of measured wet deposition and estimated dry deposition at numerous sites suggests that the two are similar in magnitude over much of the eastern USA.

Erythropoietic protoporphyria. The problem of a suitable screening test.

Erythropoietic protoporphyria (EPP) is characterized by increased red cell protoporphyrins and is included in the differential diagnosis of children presenting with photosensitivity. In the past 20 years, using the traditional solvent extraction qualitative screening test for blood porphyrins, the diagnosis of EPP had been missed in 9 out of 10 patients but recently, using fluorescence microscopy of erythrocytes, no patients with EPP have been missed. All 14 patients in Northern Ireland known to have EPP were recalled and it was found that fluorescence microscopic determination was positive in all cases. We recommend fluorescence microscopy as the screening test of choice for the detection of increased red cell porphyrins.

Plasma cholinesterase activity and the duration of suxamethonium apnoea in children.

Plasma cholinesterase activity and the duration of suxamethonium apnoea were studied in 89 children and in 15 adults for comparison. Whereas the level of cholinesterase activity was not different in the two groups, children showed a significantly shorter duration of apnoea. There was poor correlation between the enzyme activity and duration of apnoea. The shorter duration of action of suxamethonium may be due to the larger volume of extracellular fluid in children.

Plasma cholinesterase levels following pancuronium and vecuronium.

Plasma cholinesterase levels were measured in 52 patients following administration of pancuronium 1 mg/70 kg (10 patients) and 0.1 mg/kg (10 patients) and vecuronium in doses of 1 mg/70 kg (10 patients), 0.1 mg/kg (10 patients) and 0.2 mg/kg (12 patients). Both doses of pancuronium produced a significant (P less than 0.05 - less than 0.005) reduction in the enzyme levels. Vecuronium in a dose of 1 mg/70 kg was without any significant effects but the two higher doses produced a dose-related reduction of about 8 and 16% in the enzyme levels, respectively, which was statistically significant (P less than 0.05 - less than 0.001).

Effects of neostigmine and pyridostigmine on serum cholinesterase activity.

Serum cholinesterase activities were measured from 270 minutes in patients following administration of neostigmine or pyridostigmine for the reversal of pancuronium block in groups of seven patients each. The enzyme activities were significantly depressed by neostigmine for four hours and by pyridostigmine throughout the whole period of study. Whereas the immediate effects of neostigmine were more intense, the effects of pyridostigmine beyond the first 30 minutes were more profound. The clinical relevance of these findings is discussed.

Relation of high-density lipoprotein cholesterol concentration to type of diabetes and its control.

Serum cholesterol and high-density lipoprotein (HDL) cholesterol concentrations were measured in 192 diabetics (94 with juvenile-onset and 98 with maturity-onset diabetes) and 177 non-diabetic controls. Hb A1C, an index of blood sugar control, was also measured in the diabetics. Serum cholesterol concentrations were similar in all the diabetics and controls, but HDL cholesterol concentrations were lower in patients with maturity-onset diabetes than in those with juvenile-onset diabetes and controls. There was no correlation in diabetics between HDL cholesterol and Hb A1C. We conclude that HDL cholesterol concentrations are abnormally low in patients with maturity-onset diabetes but essentially normal in those with juvenile-onset diabetes. They are not related to diabetic control.

Changes in liver function after different types of surgery.

Liver function tests carried out after minor surgical procedures, under anaesthesia lasting for 1 hr, showed no abnormalities. Tests after body surface operations under the same anaesthetic techniques showed transient derangements. After intra-abdominal procedures, liver dysfunction was more marked, although no patients with evidence of preoperative liver dysfunction or postoperative surgical complications were studied and none received blood transfusions. Measurements of the serum bilirubin concentration showed the most frequent abnormalities, but the pseudocholinesterase concentration decreased progressively after intra-abdominal surgery and b.s.p. retention increased significantly. Serum concentration of intracellular enzymes (LDH, s.g.o.t. and s.g.p.t.) increased within an hour of starting surgery, changes which were probably not related to liver function.